Handbook of Surfactants

To Betty
 Handbook of Surfactants

M.R. PORTER, BSc, PhD, CChem, MRSC

Maurice R. Porter & Associates
Consultants in Speciality Chemicals
Cardiff

Springer Science+Business Media, LLC

First edition 1991
Reprinted 1993
@ 1991 Springer Science+Business Media New York
Originally published byBlackie &. Son Ltd in 1991
Softcover reprint of the hardcover 1st edition 1991
Typeset by Thomson Press (India) Limited, New Delhi
ISBN 978-1-4757-1295-7 ISBN 978-1-4757-1293-3 (eBook)
DOI 10.1007/978-1-4757-1293-3
Apart from any fair dealing for the purposes of research or private
study, or criticism or review, as permitted under the UK Copyright
Designs and Patents Act, 1988, this publication may not be
reproduced, stored, or transmitted, in any form or by any means,
without the prior permission in writing of the publishers, or in the case
of reprographic reproduction only in accordance with the terms of the
licences issued by the Copyright Licensing Agency in the UK, or in
accordance with the terms of licences issued by the appropriate
Reproduction Rights Organization outside the UK. Enquiries concerning
reproduction outside the terms stated here should be sent to the
publishers at the Glasgow address printed on this page.
The publisher makes no representation, express or implied, with
regard to the accuracy of the information contained in this book and
cannot accept any legal responsibility or liability for any errors or
omissions that may be made.
A catalogue record for this book is available from the British Library
Library of Congress Cataloging-in-Publication Data available
Preface

The worldwide consumption of surfactants now exceeds several million tonnes

per annum. Six ofthe major types represent approximately 80% ofthe volume
consumed, whereas the remaining 20% is made up of approximately 40
different chemical types.
Commercially produced surface active agents are not pure chemicals, and
within each chemical type there can be tremendous variation. Technical staff
who are not familiar with surfactants are frequently bewildered by the
enormous variety of different products on the market and the vast body of
literature which exists on the composition and properties of surfactants. The
selection of the best surfactant for any given use therefore becomes a major
problem.
This volume arose from the clear need to have available a simple reference
book summarising the different types of surfactants on the market and their
properties. The concept and structure of the book evolved from early attempts
to define chemical structure/property relationships of all the different types
of surfactants commercially available, into a simple handbook providing
essential background information for the surfactant user. It is realised that
most users will be developing their own data bank of structure/end use
property relationships and they will therefore be the experts on end use.
What most users seem to lack is an appreciation of the chemical structures
of commercial surfactants. They will be purchasing a surfactant which is a
mixture of surface active molecules (and possibly also non surface active
molecules) from sales people who may have little or no knowledge of the
exact composition. The book will also be of value to those who need a clear
and straightforward account of the constitution of commercial surfactants,
their general properties, and their surface active properties.
Because of the need to discuss broad principles and keep statements simple
I have had to make many generalisations. Although there may be instances
where these generalisations may not be entirely accurate for every surfactant,
overall they will serve the purpose of enabling readers rapidly to improve
their knowledge of surfactants and surfactant technology.
I would like this opportunity to thank the very large number of people in
the surfactant industry who have willingly supplied data, and who have made
many helpful comments and suggestions. Particular thanks are due to David
Karsa, who played a key role in the formative thinking which preceded the
actual writing of this book, and Enc Lomax who checked the draft on
amphoterics.

M.R.P.
Abbreviations

Ac Acetyl group - CH 3 CO
AE Alcohol ethoxylate
AES Alcohol ether sulphate
AOS Alpha-olefin sulphonate
APE Alkyl phenol ethoxylate
APG Alkyl polyglycoside
AS Alcohol sulphate
CD Coconut diethanolamide
CMC Critical micelle concentration
DEA Diethanolamine
EO Ethylene oxide
EO/PO Ethylene oxide/propylene oxide co-polymer
Et Ethyl- C2HS
EtOH Ethanol (ethyl alcohol) - C 2H sOH
FES Fatty ester sulphonate
HLB Hydrophilic lyophilic balance
LABS Linear alkyl benzene sulphonate
Me Methyl- CH 3
MEA Monoethanolamine
MeOH Methanol (methyl alcohol) - CH 3 0H
NPE Nonyl phenol ethoxylate
O/W Oil in water emulsion
PE Phosphate ester
PEG esters Polyoxyethyleneglycol esters of fatty acids
PO Propylene oxide
QAC Quaternary ammonium compound
RT Room temperature
SAS Secondary alkane sulphonate (paraffin sulphonate)
ST Surface tension
TEA Triethanolamine
W/O Water in oil emulsion
Contents

1 General introduction 1
2 General approach to using surfactants in formulations 6
2.1 Introduction 6
2.2 Systematic approach 8
2.3 Practical formulation 9
2.4 Understanding formulations and end effects 10
2.5 Properties of the hydrophilic and hydrophobic groups 10
2.5.1 The hydrophilic group 11
2.5.2 The hydrophobic group 11

3 Information sources 13
3.1 Introduction 13
3.2 Manufacturer's literature 14
3.3 Published books 15
3.4 Journals and periodicals 18
3.5 Patents 20
3.6 Symposia and meetings 21
3.7 Government publications 22
3.8 Data bases 22

4 Use of surfactant theory 24

4.1 Introduction 24
4.2 Adsorption 25
4.3 Micelles 29
4.3.1 CMC and chemical structure 32
4.4 Solubility 33
4.5 Wetting 34
4.6 Dispersing 36
4.6.1 Non-polar solids in water 37
4.6.2 Polar solids in water 37
4.7 F oaming/defoaming 38
4.8 Solubilisation, emulsions, microemulsions and HLB 40
4.8.1 Solubilisation and emulsions 41
4.8.2 Formation of oil in water (OfW) and water in oil (WjO) emulsions 41
4.8.3 Solubilisation 43
4.8.4 Microemulsions 43
References 47

5 Surfactants commercially available 49

Reference 53
Vlll CONTENTS

6 Anionics 54
6.1 Carboxylates 55
6.1.1 Soaps 55
6.1.2 Ethoxy carboxylates 59
6.1.3 Ester carboxylates 61
6.2 Isethionates 63
6.3 Phosphate esters 64
6.4 Sarcosinates 67
6.5 Sulphates (general) 68
6.5.1 Alcohol sulphates 70
6.5.2 Alcohol ether sulphates 73
6.5.3 Sulphated alkanolamide ethoxylates 77
6.5.4 Sulphated oils and glycerides 7X
6.5.5 Nonyl phenol ether sulphates RO
6.6 SuI phonates (general) 81
6.6.1 Ethane suI phonates 85
6.6.2 Paraffin sulphonates 86
6.6.3 Alkyl benzene suI phonates 88
6.6.4 Fatty acid and ester sulphonates 93
6.6.5 Alkyl naphthalene sulphonates 97
6.6.6 Olefin suI phonates 100
6.6.7 Petroleum sulphonates 103
6.7 Sulphosuccinates and sulphosuccinamates 107
6.7.1 Sulphosuccinates 1m
6.7.2 Sulphocussinamates 112
6.8 Taurates 113
References 115

7 Non-ionics 116
7.1 General introduction 116
7.1.1 The chemistry of ethoxylation 117
7.1.2 General properties of non-ionics 119
7.1·.3 Surface active properties of non-ionics 123
7.2 Acetylenic surfactants 128
7.3 Alcohol ethoxylates 130
7.4 Alkanolamides 135
7.5 Amine oxides 139
7.6 Surfactants derived from carbohydrates 142
7.7 Ethoxylated alkanolamides 145
7.8 Ethoxylated long chain amines 147
7.9 Ethylene oxide/propylene oxide (EO/PO) co-polymers 150
7.10 Fatty acid ethoxylates 155
7.11 Sorbitan derivatives 159
7.12 Ethylene glucol. propylene glycol, glycerol and polyglyceryl esters plus
their ethoxylated derivates 163
7.13 Alkyl amines and alkyl imidazolines 168
7.14 Ethoxylated oil~ and facts 173
7.15 Alkyl phenol ethoxylates 174
References 178

8 Cationics 179
8.1 Cationics general 179
8.2 Quaternary ammonium 180
8.3 Amine and imidazoline salts 185
 CONTENTS IX

9 Amphoterics 189
9.1 Amphoterics general 189
9.2 Betaines 193
9.3 Glycinates and aminopropionates 196
9.4 Imidazoline-based amphoterics 199
References 202

10 Speciality surfactants 203

10.1 General 203
10.2 Silicones 204
10.3 Fluorocarbons 206

11 Polymeric surfactants 209

Appendices 212
Appendix I: Names of hydrophobes and average composition of fats and oils 212
Appendix II: Ecological and toxicity requirements 213

Index 223
1 General introduction

The basic aim of the book is to give practical help to users of surfactants and
those people who make formulations with surfactants. The choice of a cost-
effective surfactant, although essential, is not easy due to: the bewildering
number of surfactants available on the market; insufficient data given by the
manufacturers; poorly defined chemical structure/effect relationships. This
book attempts to provide some practical help with these problems but also to
explain the basic properties of particular types of commercially available
surfactants.
The practical help consists of describing the various types of surfactants in
terms of their chemical structure, the principal physical properties of that type,
the functional properties, the principal end uses and some comments on the
requirements for quality control. There are chapters on using surfactants in
formulations, the use of surfactant theory, how and where to find information
concerning surfactants and their applications, and a broad description of test
methods for biodegradation and toxicity. However, the bulk of the book is
about the surfactants themselves in a concise, consistent format.
Surfactants are generally described as anionic, non-ionic, cationic or
amphoteric. However, these are physical properties of particular chemical
structures. To describe a surfactant in these terms gives some very general
properties which may, but usually do not, help a user to choose a surfactant.
The more important factors in the choice of a surfactant are:
• Is it commercially available?
• Does it perform the function required?
• Is it expensive to use?
• Is the physical form convenient for manufacture and use?
• Is the surfactant stable to storage in its end use?
• Is it safe in manufacture and transport?
• Is it safe to use in the required end use?
• Does it pose any dangers to the ecology?
The last three requirements are becoming the most important. No matter how
good or cheap the finished product, if the surfactant (or any other component
for that matter) gives a danger, real or imagined, to the end user or the ecology
then the product is not saleable. There are no safety or toxicity data given on
the various types of surfactants described, the reason being that it is impossible
to generalise on toxicity. This is because small changes in the hydrophobic
2 HANDBOOK OF SURFACTANTS

group can affect the toxicity of products. On environmental grounds, the

requirements change so rapidly that statements on environmental safety could
be misleading. Factual data such as toxicity tests and biodegradation tests are
not useful unless full details of the test protocols are given. Instead a short
chapter on this subject has been included to give some background on the
various tests for those new to this area. At least the readers may then have a
better understanding of the data and statements made by the surfactant
manufacturer or supplier who should be the major source of data and advice.
When picking surfactants for a particular end use, a user must bear in mind
all these requirements in order to make cost-effective, saleable products, or to
use surfactants without problems within his factory. It is only sensible to use
those surfactants which will cover all the requirements above. Although there
are hundreds of surfactants commercially available, only a small number of
chemical types are commercially produced, in large volumes, world-wide. It is
obviously preferable to select one or more of these types if possible. However,
there can be problems in picking one chemical type. The great majority of
surfactants available on the market are not pure but consist of mixtures of
chemicals. It is these mixtures which often give the end effect required. This is
why there can be variations in performance of surfactants from one manu-
facturer to another. Although manufacturers may give as full a chemical
description as possible, the relationship between chemical structure and
performance remains poorly documented and not well understood.
A very large amount of information is available on surfactants in published
papers and conference proceedings. The surfactant manufacturer will also
have a considerable amount of information on the properties, end use and
safety of his products. The majority of published scientific information relates
to the properties of the surfactants, whereas details of the use of surfactants in
formulations tend to be in the patent literature. Patent literature can often be
more confusing than helpful if one is seeking the reason behind the choice of a
particular surfactant in a specific end use.
The theoretical basis of surfactants is well-established but is usually
insufficient to help formulators in fine detail. Some understanding is therefore
necessary. Although the concept of adsorption at a surface need not be
mathematically understood, a visualisation does help. The simple concept of
McBain for the formation of micelles has been shown to be much more
complex with spherical, disc, lamellar and hexagonal micelles in practice. This
can explain many ofthecomplex solubility and phase changes encountered in
surfactant solutions.
The present tendency to stricter quality control emphasises the need for the
routine analysis of the surfactant, plus the analysis of the surfactant in the
formulation. Users need to know which tests must be carried out in order to
identify significant variations in the composition of the surfactant.
There is now a strong move by consumer groups and some sections of the
surfactant producers to move away from petrochemical-based feedstocks.
 GENERAL INTRODUCTION 3
Surfactants made from natural materials other than petroleum have been
neglected but are now making a comeback. It is for this reason that possibly a
disproportionate amount of space has been devoted to products whose major
raw materials are derived from animal fats, vegetable oils or carbohydrates.
The use of surfactants is extremely widespread both in industry and in the
home. There are three major reasons for this:
• The increasing use of water rather than organic solvents in industrial
products
• Most mixtures and formulations are applied to solid substrates
• Cleaning is a very common requirement
Most industrial and domestic processes using chemicals involve contact
between a liquid and a solid where the solid needs wetting. This is exactly the
function ofthe surfactant. However, there are many products which can easily
wet substrates better than water, for example alcohol, hydrocarbons, etc. It is
the particular property of surfactants to decrease the surface tension of water
using very low concentrations that is so valuable. In practical terms it means
that most of the properties of water can be retained and the wetting improved
at a very small additional cost. The function of cleaning is extremely common
both in consumer use, and in industry. There is no other end use offormulated
products which approaches the volume and number of applications involving
cleaning or the scientific term 'detergency'. Water is by far the most common
medium and all aqueous-based detergents (formulations for cleaning pur-
poses) contain surfactants.
Surfactant is an abbreviation for surface active agent which literally means
active at a surface. The surface can be between solid and liquid, between air
and liquid or between liquid and a different, immiscible, liquid. The primary
property of a surfactant in a solution is that the concentration ofthe surfactant
is higher at the surface than in the bulk of the liquid. Thus the surfactant
concentrates at the surface. As this is the point where they are doing a useful
function, it is therefore not surprising to find that surfactants can be very
economically used. This may be an elementary concept but it does explain the
effectiveness of surfactants in many applications, compared to other products
which do not show any marked surface active properties. The user is always
concerned with the economics of the product which is often dependent upon
the basic surface active properties.
What do we mean by a formulated product? Manufacturing industry makes
a wide variety of formulations for use both within industry, and as the
manufactured product for use in industry or in the home and institutions.
Detergents, paints, inks, adhesives, cosmetics, dyes, weedkillers, insecticides,
ice cream, are all examples of common formulations. However,· inside the
manufacturing industry there are many formulations which are not seen by the
end consumer, but are essential as processing aids. The textile industry uses
scouring aids to clean fibres, aqueous-based lubricants for spinning synthetic
4 HANDBOOK OF SURFACTANTS

fibres, warp sizes to protect fibres in weaving, defoamers to suppress foam

during dyeing, and softening agents to treat fabrics in order to give a soft
'handle'. The paper industry uses defoamers, dispersing aids and release
agents. The engineering industry uses lubricants, anticorrosive treatments and
metal working lubricants. Practically all these formulations are composed of
mixtures of chemicals. Surface active agents are present in all the formulations
mentioned so far, and in numerous others.
Although formulations differ from one application to another, there are
some factors which are common to every formulation.
1. An active ingredient which carries out the primary function desired by
the end user.
2. A medium by which the active ingredient is carried.
3. At least one secondary function which will usually, but not always, be
achieved by at least one other ingredient.
It is possible to provide all functions with one chemical product. A good
example is soap, which in the bar form provides the active ingredient which
washes, the solid medium which is convenient for washing hands, and the good
dispersion of the dirt in water for easy disposal. Modern synthetic detergents
now contain active washing ingredients which can wash at much lower
temperatures, are liquid in form by virtue of their solubility in water (which is
now the medium) and provide better dispersion of dirt particularly in hard
waters. Although new synthetic organic chemicals have been produced which
can give all these improvements in one chemical species, they are very rarely
used. The reason is that mixtures of chemicals are easier and cheaper to
produce than new molecules, particularly on a large scale. Although soap has
not disappeared from the market place, the soap tablet of today is not one
chemical, but a carefully formulated product.
Another example is lubricating oils which were at one time a refined fraction
of crude petroleum. The oil would provide the essential function oflubricating,
it would be its own medium (being liquid and easily handled) and it had
secondary functions such as dispersing solids and giving some corrosion
resistance. However, modern lubricants are complex mixtures with chemical
additives, some giving improved lubrication and others giving improved
corrosion resistance and improved dispersibility of solids. It is very much
easier and cheaper to provide improved products by mixing rather than by
synthesising new chemical molecules with the desired properties. New
synthetic organic chemicals (esters, synthetic hydrocarbons, phosphate esters)
have been produced which are superior to petroleum-based lubricating oils as
lubricants. However, even these synthetic products are now being formulated
by the addition of additives to improve their basic properties.
These two examples illustrate the practical effect of using mixtures of
chemicals to solve problems. In the great majority of formulations used by
industry and in the home, a surfactant or a mixture of surfactants will be used.
 GENERAL INTRODUCTION 5
The information presented in this book has been obtained from a
combination of personal experience, manufacturers' technical information
and the patent and scientific literature. There are very few references but a
considerable number of generalisations in order to make the book easy to
read. If there is no reference it means that there are at least two sources of
information which agree, plus the author's own experience. If a reference is
given it generally means that the statement is reasonable within the author's
knowledge but a secondary independent source cannot be found. The
number of generalisations means that exceptions can probably be found,
particularly those relating chemical structure and physical/chemical pro-
perties. The end uses given, with very few exceptions, have been positively
identified as those actually used in practice rather than quotations from patent
literature. There will be many uses of particular surfactants which are not
mentioned but the author believes that he has identified the major uses of
particular types of surfactant. If he is wrong in statements on data or end uses
he would be most interested to be provided with appropriate data confirming
the error.
 2 General approach to using surfactants in
formulations

2.1 Introduction

There can be two quite different approaches to formulation because of the very
different requirements of the market. There are basically two different market
conditions:
1. Where there is a large volume market and the formulation will be sold for
several years without significant change, e.g. a household detergent
2. Where the market is small and subject to change
In the first situation the potential profit on a single product can be very large
and hence a detailed technical program can be initiated. Planned experiments
on end effect, storage stability and environmental acceptability with compre-
hensive testing of various surfactants and of hundreds of formulations is
feasible. Detailed examination of the properties of the surfactant is possible,
new methods of analysis can be devised and more information is often
obtained than that possessed by the supplier. The formulator then becomes to
a large degree independent of the technical help from the supplier.
The picture is very different in the second situation. The potential profit is so
much smaller that technical work has to be limited. The formulation is always
required quickly, if not by the customer then at least by one's own sales staff.
The resources are generally very much more limited. The overall result is that
the formulator becomes very dependent upon the supplier. His main contact
from the supplier comes via a sales representative and the technical literature
published by the company. The formulator will be hoping that someone can
tell him all that the formulation requires together with all safety data and
environmental acceptability. However in the case of surfactants, the
formulator's major problem is finding and choosing the supplier. As
surfactants are often siPlilar in effect, most suppliers will be promoting a
particular surfactant. This product might well be the best product in that
supplier's range but is it the most cost effective product available on the
market? In the first situation above, the technical department have the time
and resources to search for the best surfactant. In the second situation, the
formulator is dependent upon his own (sometimes literally) knowledge and in
extreme circumstances has to make decisions in a matter of days.
The information in this book will not enable formulations to be quickly
 GENERAL APPROACH TO USING SURFACTANTS IN FORMULATIONS 7
made up but should help the formulator in choosing the right family of
surfactants and posing the right questions to suppliers in order to identify the
best surfactant to use.
There will be a reason for a new or modified form ulation. This reason should
be firmly established with other members of the company, e.g. the marketing
department before commencing work as this reason can and does restrict the
choice of surfactant. The most common reasons are:
• Meeting a new market requirement in terms of a completely new product
• Changing the physical characteristics of the formulation
• Improving the functional efficiency of a product
• Reducing costs of a formulation to meet competition
• Avoiding problems of human toxicity
• Avoiding problems of environmental acceptability
• Avoiding a patent
However the exact reason for the need of a new formulation may not be clear
in detail or quantifiable. 'It dosen't work' or 'it's too expensive' are often the
reasons given by the marketing department. They, however, have their
problems and it is likely that the customer has been vague with them. There is
no substitute for a meeting with the end user, even if the need is for a cheaper
product, in order to identify the critical requirements of the product as seen
by the user. Thus after the reason, i.e. the overall objective, is established,
there is the need to establish the technical and economic target. The main
factors are:
• The end effect (or function) desired and the conditions of use
• The costs to be met
• The physical form
• Restriction on safety in manufacture, handling, transport and use
The end effect and costs are generally related, a high cost product can be
sold if it is very efficient, i.e. used in smaller quantities than the cheaper
formulation.
In the case of changing an existing formulation, the situation can often arise
that the original formulation has been unchanged for many years, the original
formulator has retired and there are no detailed records of the development
work leading to the formulation. This situation often arises where a company
places great importance on the confidentiality of the formulations. Particular-
ly where a formulation contains more than one surfactant, the functions
performed by each individual surfactant may not be at all clear. There is now
considerable evidence to show that mixtures of different surfactants do show
synergistic properties so, if mixtures are present, not only must the properties
of each surfactant be identified but also the interaction between them. When
there is a need to change a complex formula, it may be simpler to start from
basics rather than modify by trial and error.
8 HANDBOOK OF SURFACTANTS

2.2 Systematic approach

The first essential in a systematic approach is to draw up a detailed

requirement for the product:
• Identify the end user's requirement in terms of the function of the finished
formulation and how to test for that requirement (if possible)
• Identify the physical properties required by the product and user
• Identify toxicity and ecological requirements
• Identify cost limitations
• Identify time limitations, i.e. when is the new formulation required
Experienced formulators will find that this target requirement can often be
determined very quickly but the author strongly urges time to be spent on this
analysis in order to avoid wasted time and effort. It must also be realised that
one or more of these requirements can change during the course of the
developmen.t of a formulation. Therefore there is a need to update these
requirements if there is a time delay in producing a new formulation. An
update should be made at a maximum of 3 months.
These targets can be quickly identified but the problems arise in translating
the properties required into the type of surfactant which will satisfy the targets.
The following approach is suggested:
1. Consider the cost of the formulation and the quantity of surfactant in the
formula; ifthere is a high proportion of surfactant in the formulation then
this can often eliminate high priced surfactants.
2. Identify the physical properties required, e.g. solubility, viscosity, pH
range stability, chemical stability, compatibility with other components,
hard water tolerance. Again this can often eliminate many surfactants.
3. Try to identify the basic functions provided by the surfactant, namely
wetting, foaming, emulsifying, solubilisation, dispersing and cleaning.
Cleaning is not a basic property but it is included in this category because
it demands the right combination of wetting, foaming, emulsifying and
dispersing properties. It is also a very common requirement of household
and industrial formulations.
The chapters on the different classes of surfactants have been written in such a
way that it is easy to determine the physical and functional properties of the
various classes of surfactants.
Cost and availability are probably the most important considerations and
the next step should be to see if the properties specified so far would be satisfied
with those surfactants which are produced in large volume world-wide.
Examine whether the following chemical types can satisfy these criteria:
soaps; linear alkylbenzene sui phonates (LABS); alcohol ethoxy sulphates
(AES); alcohol sulphates (AS); alkane or paraffin sulphonates (SAS); alcohol
ethoxylates (AE). There are many other surfactants availaole in volume but the
above families probably represent the cheapest and most commonly available
 GENERAL APPROACH TO USING SURFACTANTS IN FORMULATIONS 9
products world-wide. There is also the added benefit that safety information
on these surfactants is available in great detail.
Once a detailed target and also some idea of the surfactant's requirements
have been established then it is much easier to search the technical literature
and to put the right questions to potential suppliers. Of major help in creating
a new formulation is to find internal reports or personal knowledge from
someone who has formulated a similar kind of product. Lacking that help,
external sources must be used (see Chapter 3). The five main sources of
information are: internal reports or verbal help; manufacturers' literature or
advice from their technical departments; specialist books; Chemical Abstracts
as an index to published articles; patents.

2.3 Practical formulation

In nearly all cases, a meaningful test for the functional use of a formulation is
the most difficult to devise. There are laboratory tests for detergents, wetting
agents, lubricants, defoamers, dispersing agents etc. but no one laboratory test
can simulate the many different end user requirements. Therefore it is
preferable to eliminate as many surfactants/formulations as possible with
simple, quick and cheap tests which do not attempt to test for functional use.
Requirements such as flash point, viscosity, minimum solids content etc. can
be quickly checked. As described in Section 2.2 many products can also be
eliminated on cost and safety considerations.
With the use of this handbook, the chemical type of surfactant to give
the required end effect can usually be identified. However the exact choice of
surfactant can only be made following tests for the end use. Such testing is most
easily carried out in the laboratory but the essential need is to correlate
laboratory tests with actual practice. With many variables, statistically
designed experiments are more efficient but rarely carried out in practice.
When a finished formulation is ready for outside testing it is wise to carry
out some simple stability tests because surfactants are usually in a state of
semi-solution giving separation of phases, thickening, thinning and sometimes
loss of activity. Stability tests at higher (40°C) or lower (freezing) temperatures
can often quickly identify unsatisfactory formulations. Visual examination is
generally adequate for shelf stability tests. When such tests have been carried
out, the products can be released for commercial evaluation. Often a
considerable length of time will elapse before results are available from outside
customers. Such time should not be wasted. Extended storage trials do not
involve much extra effort in visual examination once a week. Additional
information can be obtained from suppliers on methods of analysis for quality
control, which will be needed if the product is successful commercially.
The quantitative analysis of a surfactant in a formulation is often needed for
quality control. Analysis of a single surfactant species is relatively easy and
well documented but analysis of small quantities of surfactants in mixtures is
10 HANDBOOK OF SURFACTANTS

not. The manufacturer of the surfactant can usually supply methods of

analysis.
There is a need to check on published toxicity and environmental
information. Check that it is in EINECS and EPA regulations. All the large
volume surfactants are registered in EINECS and the surfactant manufacturer
should provide help in other cases.
At all stages of the work keep neat detailed records of all results particularly
negative results. There is a need to keep such results confidential but accessible
to future workers.
The problem oftrying to improve a present formulation is quite different, as.
one way of improving performance will be identifying a synergistic effect of
mixture of surfactants or identifying a new surfactant to solve the problem. A
detailed literature survey is advisable, whilst some theoretical basis often helps
in designing the experiments since the number of possible combinations of
mixtures of surfactants will run into thousands.

2.4 Understanding formulations and end effects

To understand the interrelationship between surfactant structure and the end

effects caused by the surfactant is the goal of every formulator. Unfortunately
surfactant theory is not yet advanced enough to give more than guidelines.
Empirical data is comprehensive but scattered throughout the literature, or
more often than not never published but filed away in industrial files or in
someone's mind. This book attempts to give basic data on different surfactant
types which can be used for reference. However, it is also hoped that the data are
presented in such a way that the reader begins to build a relationship of the
properties given by a particular chemical structure. What is so confusing is
that small variations in hydrophobic and hydrophilic groups give so many
different properties. To obtain a simplified view of these relationships it is best
to distinguish between the properties conferred by the hydrophobic and the
hydrophilic groups. Whilst Chapters 6-11 give detailed data on the individual
surfactants the following section attempts to give an overall view of the
main properties of the hydroph0bic and hydrophilic groups.
As pointed out in Chapter 1, any attempt to summarise the properties of
surfactants will fail to be entirely accurate and examples will be found which
do not agree precisely with the statements below. Thus the general comments
presented here must only be used as a guide.

2.5 Properties of the hydrophilic and hydrophobic groups

Since the major applications of surfactants are in aqueous media, this

summary is confined to applications where water is the continuous phase.
 GENERAL APPROACH TO USING SURFACTANTS IN FORMULATIONS II
2.5.1 The hydrophilic group

The data have been organised on differences in the hydrophilic group because
this group determines the main differences between the majority of surfactants
on the market. Thus it is important to bear in mind the major properties, i.e.
end effects of the main surfactant types, namely:
• Anionics detergents, adsorption on polar surfaces
• Non-ionics stability in varying pH
• Cationics adsorption on surfaces
• Sulphonates stable in solution
• Sulphates unstable in solution
• Ethoxylates stable in hard water
Other generalisations on the hydrophilic groups are given in Chapter 5.

2.5.2 The hydrophobic group

The hydrophobic group for 99% of surfactants is made up of hydrocarbon

chains and the majority of these are linear due to the demands for
biodegradability. As the major application of surfactants is detergency and as
detergency is generally in the C I O-C 16 range, the majority of surfactants on
the market have these groups. Also, detergency tends to be a combined
adsorption, wetting, emulsifying action so the majority of other surfactant
applications will either be in this region, i.e. C lO-C 16, or at least close to it. The
hydrophobic group will constitute the largest part of the molecule except for
high ethylene oxide non-ionics and thus is the major cost of a surfactant
molecule. The commercial history of surfactants is the availability of
hydrophobic groups at costs which the application can carry. A good example
is the use of the silicone chain in place of the hydrocarbon chain as the
hydrophobe. The silicone chain has some advantageous properties compared
to the hydrocarbon chain but the cost is so much greater that silicone-based
surfactants are only used where they have special properties and can carry a
higher cost.
The hydrophobic group based on hydrocarbons is basically available from
three sources:
1. Petrochemicals
2. Natural vegetable oils
3. Natural animal fats
It is important to appreciate that in every case the hydrophobic group exists as
a mixture of chains of different length whether manufactured or found in
nature. It is fortunate for the surfactant users that mixtures of varying chain
length are normally better surfactants in practice than pure compounds. If this
were not the case then the separation and purification costs would be higher
12 HANDBOOK OF SURFACTANTS

and the resulting costs would be higher. Even more important, the choice of
hydrophobes would be more limited.

2.5.2.1 Petrochemicals. There is a comprehensive literature on the chemistry

and production of hydrocarbons as raw materials for surfactants but this
information is not very relevant. How these raw materials are converted into
the surfactants is covered in Chapters 6-9 which describe the manufacture
of all the major types of surfactants. However the hydrophobe of the finished
surfactant will be entirely dependent upon the starting hydrocarbon in the
majority of cases. Thus if the hydrocarbon used in the surfactant manufacture
has a distribution of chain lengths of 25% C 10, 50% C 12 and 25% C 14, then the
resulting surfactant will have exactly the same distribution of chain lengths in
the hydrophobe. The resulting surfactant properties of solubility, viscosity,
wetting etc. will depend upon this carbon chain distribution. Thus the
surfactant properties will be dependent upon the starting hydrocarbon chain
distribution.
All this seems very obvious but in many cases the formulator will not know
the carbon chain distribution because the surfactant manufacturer will not
include this in his specification. However, demand for the specification of
carbon chain distribution is becoming more common particularly by the big
detergent manufacturers. Specification of carbon chain distribution to a large
degree can specify surfactant performance but not entirely; Chapters 6-10 give
some details where specification of carbon chain distribution is desirable.
Surfactant performance can be critically dependent upon carbon chain
distribution, yet there are surfactant types where it may be less significant than
the variations in the hydrophilic group (e.g. ethoxylates).
Hydrocarbons from petrochemicals can have the following variations:
1. Length of the hydrocarbon chain
2. Degree of branching
3. Odd or even carbon atoms
Note that variations in alkyl benzenes are a special case and are described in
Section 6.1.6.3.
The odd or even carbon atoms arise due to the method of manufacture.
Mixtures of odd and even carbon chains are obtained by 'cracking' higher
hydrocarbons, whilst even-numbered chains are derived by building up chains
from ethylene. Hydroc.arbons from natural sources invariably contain only
even numbers of hydrocarbon chains, and thus products derived from ethylene
are said to match 'natural' products more closely than do those derived by
cracking. At carbon chain lengths of CI0 and greater, the difference in
surfactant properties between surfactants made from even carbon chain
lengths, and mixtures of odd and even chain lengths is minimal.
3 Information sources

3.1 Introduction

Information on the properties of surfactants and their use in formulations is

not neatly collected together in anyone type of publication. Although surface
active agents are chemicals they are not pure, and the products of commerce
are mixtures of chemicals of very similar but not identical properties. Thus
publications such as Beilstein and the Registry file of Chemical Abstracts are of
very limited use. The major source of information on surfactants are the
manufacturers. Their information is generally inadequate because they will
concentrate on that information relevant to the manufacture and safety of the
surfactants rather than their use. The larger manufacturers will have available
considerable information on the use of their products as a sales aid, but this
will inevitably be limited to the larger end uses.
The surfactant manufacturer will have a reasonable idea of the composition
of his raw materials (which are generally mixtures) and a reasonable
knowledge of the chemistry he uses but that is all unless he undertakes
considerable research to find out more. The profit margin on most surfactants
is such that he will not carry out that research unless motivated by legal or
economic reasons. The profit margin per tonne on speciality surfactants may
be good but the volume is small, so again there is a reluctance to determine
exactly what is being made and sold. All surfactants, without exception will
contain by-products not described by the general chemical description of the
particular surfactant. In the majority of products the by-products are not
relevant to the end use ofthe surfactant and may be disregarded. Occasionally
a by-product can become so undesirable in the finished formulations that
great care must be taken in the choice of surfactant to minimise the presence of
the by-product. A knowledge of the chemical constitution of the surfactant is
becoming more important as consumer standards rise ever higher. Fortu-
nately there has been a lot of information published on the composition of
surface active agents but it is scattered throughout the technical literature.
In addition to the actual composition of the surfactant the effect of
surfactant composition on the physical properties and functional character-
istics will be of prime importance to the end user. Manufacturers provide
considerable data in this respect but generally only on their own products.
Independent information on the relationship between the chemical structure
of the surfactant and its functional properties will be of significant help to a
14 HANDBOOK OF SURFACTANTS

user in choosing the most cost effective surfactant. To the author's knowledge
there is no one single source of information which gives an in depth account of
such relationships. The majority of the information is given in scientific
conferences and meetings, not all of which have the proceedings published or
easily obtained.
Most surfactant users only deal with a limited number of surfactants and are
only interested in a limited number of applications. They will undoubtedly be
building a data base on raw materials (surfactants plus other chemicals) and
also the functional properties obtained by these raw materials. This private
data base will be the technology for their products and it is essential to have a
systematic method of keeping and retrieving such information. Very few
companies do this job very well and considerable knowledge resides in a few
individuals, which is lost if they leave for any reason. Computer-based
information systems are becoming common but for the type of information
required, a computer-based information system will not be satisfactory unless
a good paper-based filing system already exists.
The sources of information on surfactants and their applications in
approximate order of importance are:
I. Manufacturer's literature
2. Published books
3. Patents
4. Specific meetings and symposia
5. Published scientific papers
6. Government publications
Each of these will be described in more detail. It is worth pointing out at this
stage that computer on-line data bases or Chemical Abstracts are not primary
sources but are methods of searching the primary sources. Generally they are
the quickest method of searching and identifying particular sources.

3.2 Manufacturer's literature

The quality of manufacturer's literature ranges from the very good to the very
bad. That published by the very large surfactant manufacturers is extremely
good and represents very significant research and development work parti-
cularly on the chemical properties, physical properties and safety data.
Suggested formulations using the surfactants can be useful but such formul-
ations may be out of date.
However every surfactant manufacturer will have considerably more data
than that printed in glossy brochures, and it is worth writing to or contacting
the technical departments who have generated the data. Very often they are
only too anxious to give such data when asked. If the primary contact is via a
salesman it is not always realised that salesman may not be chemists and
 INFORMA TlON SOURCES 15
therefore requests for data should be very specific. The information required
from the manufacturer will fall into several categories:
1. Suitability of the surfactant to do the job. A surfactant manufacturer can
only recommend a particular surfactant if he knows its exact use. Often
this is confidential so one must then define the requirements in terms of
detergency, foaming, wetting etc. and of course price. Many manu-
facturers produce application booklets on specific applications.
2. Physical properties such as specific gravity, colour, flash point etc. which
are generally contained in sales leaflets on the product.
3. Safety data. Recommendations on safe handling and storage will be
available from all surfactant manufacturers. In addition most manu-
facturers will give simple toxicity data and biodegradation character-
istics for the type of chemicals which they sell. The great majority of this
information is obtained from the literature and therefore the results
obtained are not for the actual surfactant being sold, but for a chemical
which has a similar composition. Only a few surfactant manufacturers
can give toxicity and biodegradation data obtained from testing the
products as sold.
4. Specification for a check on quality. Most glossy data sheets will have a
'manufacturer's specification' which may well fully characterise the
surfactant, but more often the measurements on the specification will
give very little in the way of guarantee of reproducible material. In
Chapters 6-10 there are short sections which give for each surfactant,
some suggested chemical or physical tests likely to reveal any batch to
batch variation. It is not suggested that these tests are the only ones, or
are even required in every case for checking quality. Each end use of a
surfactant can demand a different requirement which should be agreed as
a specification between the supplier and the user. In this book the tests for
specification are suggestions, as a basis for discussion between the
supplier and user.
Collecting manufacturers literature is easy, as such literature is freely
available. Writing to the manufacturer and visiting trade fairs and exhibitions
is the quickest way. Filing the information by name of manufacturer is
convenient but, if such a data bank is to be useful, cross references to type of
surfactant and application are also needed. Names and addresses of manu-
facturers can be obtained from Directories of surfactants; a list of Directories is
given in Section 3.3.

3.3 Published books

There are now many books on surfactants but by far the majority are
concerned with academic research. The following books all contain useful
16 HANDBOOK OF SURFACTANTS

information for the practical chemist using surfactants, together with a brief
note on the principal features of the book.

General

Encyclopedia of Shampoo Ingredients, A.L. Hunting, Micelle Press, 1983,

479 pp. Gives quite good descriptions of some surfactants and LDso data.
Industrial Applications of Surfactants, ed. D.R. Karsa, Royal Society of
Chemistry, Special Publication No. 59, 1987, 360pp. Proceedings of a
Symposium organised by the Industrial Division of the Royal Society of
Chemistry, held at the University of Salford, 15-17 April 1986. Good review
of industrial applications.
Industrial Applications of Surfactants II, ed. D.R. Karsa, Royal Society of
Chemistry, Special Publication No. 77, 1990, 402pp. Proceedings of a
Symposium organised by the Industrial Division of the Royal Society of
Chemistry, held at the University of Salford, 19-20 April 1989. Excellent
account of speciality surfactants.
Surface Active Agents: Their Chemistry and Technology, Vol. 1, A.M. Schwarz
et al., Wiley, 1949, reprinted Krieger 1978,592 pp. Rather old and academic
but comprehensive.
Surfactants in Consumer Products- Theory ant! Applications, ed. J. Falbe,
Springer-Verlag, 1987. 547pp. Good but brief summary of commodity
surfactants. Good review of publications on household detergents.
Surfactants and interfacial phenomena, 2nd edn., MJ. Rosen, Wiley, 1989,
448 pp. Good general account of surface active properties.

Anionic surfactants

Anionic Surfactants, ed. W.M. Linfield, Parts 1 and 2, Marcel Dekker, 1976,
376 pp. Probably the best book on anionics.
Anionic Surfactants Biochemistry, Toxicology and Dermatology, ed. C.
Gloxhuber, Marcel Dekker, 1980, 456 pp.
Anionic Surfactants-Physical Chemistry of Surfactant Action, ed. E.H.
Lucassen-Reynders, Marcel Dekker, 1981,413 pp., Somewhat theoretical.

Non-ionic surfactants

Nonionic Surfactants, ed. M.J. Schick, Marcel Dekker, 1966, 1120pp. Out of
date on applications but excellent for the chemistry of ethoxylation and the
physical properties of non-ionics.
Nonionic Surfactants: Physical Chemistry, ed. MJ. Schick, Marcel Dekker,
1987, 1160pp.
 INFORMA nON SOURCES 17
Surface Active Ethylene Oxide Adducts, N. Schonfeldt, Pergamon, 1970, 964pp.
£169 reprint made to order by Micelle Press. Same comments as Nonionic
Surfactants ed. by Schick above.

Cationic suifactants

Cationic Surfactants, E. Jungermann, Marcel Dekker, 1970,672 pp. Good but

out of date.

Amphoteric surfactants

Amphoteric Surfactants, B.R. Buestein and c.L. Hilton, Marcel Dekker, 1982,
352 pp. Not good or up to date but the only book available. Amphoterics is
a rapidly changing field.

Analysis

The Analysis of Detergents and Detergent Products, G.F. Longman, Wiley

1975, 625 pp.
Analysis of Oils and Fats, R.J. Hamilton and J.B. Rossell, Elsevier Applied
Science, 1986, 440 pp.
Anionic Surfactants-Chemical Analysis, J. Cross, Marcel Dekker, 1977,
272pp.
Nonionic SurJactants: Chemical Analysis, 1. Cross, Marcel Dekker, 1987,
432pp.
Systematic Analysis of Surface Active Agents, MJ. Rosen and H. A. Gold-
smith, 2nd edn., Wiley, 1972.

Applications

Detergents and Textile Washing, G. Jacobi and A. Lohr, VCH Verlagsgesell-

schaft, 1987. Excellent plus many non-surfactant aspects.
Emulsions and Solubilisation, K. Shinoda and S. Friberg Wiley, 1986, 172 pp.
ISBN 0-471-03646-3. Quite a short book, good but more theoretical than
practical.
Encyclopedia of Emulsion Technology, P. Becher, Marcel Dekker, Vol. 1, Basic
Theory, 1983, 752pp., Vol. 2, Applications, 1985, 536pp., Vol. 3, Basic
Theory/ M easurement/ Applications.
Microemulsions- Theory and Practice, L.M. Prince, Academic Press, 1977,
173 pp.
Synthetic Detergents, A. Davidson and B.M. Milwidsky 7th edn., G. Godwin,
1987, 228 pp. The best practical book but limited.
18 HANDB(X)K OF SURFACTANTS

Environment and safety

Surfactant Biodegradation, 2nd rev. edn., R.D. Swisher, Marcel Dekker, 1987,
1120pp.

Theoretical

Structure/Performance Relationships in Surjactants, ed. Mol. Rosen, American

Chemical Society, 1984, 356 pp. Does not quite live up to title.
Surfactant Science and Technology, D.Y. Myers, VCH, 1988, 419 pp. An
attempt to explain the properties of surfactants from their chemical
structure and micellear structure. Not completely successful but worth
reading.

Directories of surfactant manufacturers

Surfactants Applications Directory, directory of the applications of surface

active agents available in Europe, eds. D.R. Karsa, J.M. Goode and Pol.
Donnelly, Blackie & Son Ltd., UK 1991.
Surfactants UK, Directory of surface active agents available in UK 1979, ed.
G.L. Hollis, Tergo-Data, Darlington, UK, 1979.
Surfactants Europa, Directory of surface active agents available in Europe, ed.
G.L. Hollis, Tergo-Data, Darlington, UK 1989.
Surveys on Surfactants Commercialized in Europe, D.T.A., 3, rue Lavoisier,
BP 72, 77330 Ozoir-Ia-Ferriere, France.
McCutcheons's Emulsifiers and Detergents, North American and International
editions. Published annually by the McCutcheon Division of MC Publishing
Company, 175 Rock Road, Glen Rock, New Jersey, USA.

3.4 Journals and periodicals

There is a considerable amount of technology and scientific literature

published regularly on surfactants. Probably the best way to keep abreast of
most of this literature is to read Chemical Abstracts Selects. This is a regular
(every two weeks) publication of Chemical Abstracts on specific subjects. The
most relevant are:
• Number SVC 089 Detergents, Soaps and Surfactants
Preparation, properties and uses of soaps and synthetic detergents
Formulations
Dry-cleaning solvents
Use of surfactants in petroleum recovery
 INFORMATION SOURCES 19
Not routinely covered: detergent additives for fuels and lubricants
• Number SVC 041 Colloids (Applied Aspects)
Emulsions, gels, latexes, micellar solutions, sols, other forms of
colloidal dispersions
Uses of these materials in cosmetics, foods, fuels, metals, other
products
Excludes: routine application of silica gel, emulsions and suspensions.
• Number SVC 04A Emulsifiers and Demulsifiers
Preparation, properties, uses of surface-active agents in formation,
stabilisation and destabilisation of emulsions
Aqueous and nonaqueous emulsions
Applications in cosmetics, food, petroleum, polymer industries
Others of more specific interest which do contain some references to surfactants
are:

• Number SVC 082 Adhesives

• Number SVC 042 Colloids (Physicochemical aspects)
• Number SVC 03J Cosmetic Chemicals
• Number SVC 05M Drilling Muds
• Number SVC 02G Emulsion Polymerisation
• Number SVC 04M Enhanced Petroleum Recovery
• Number SVC 03N Fats and Oils
• Number SVC 04H Lubricants, Greases and Lubrication
• Number SVC 04R Paint Additives
• Number SVC 070 Quaternary Ammonium Compounds
• Number SVC 05T Water-Based Coatings

They can be obtained from the Chemical Abstracts Service, 2540 Olentangy
Road, PO Box 3012, Columbus, OH 43210, USA.
For a formulator or surfactant chemist the other journals which are useful
are:
Tenside Surfactants Detergents, Carl Hanser Verlag, 8000 Munchen 86,
Postfach 860420, Germany. Although this is mainly in German, many
articles are in English. Probably the best journal for surfactants.
Journal of the American Oil Chemists Society, American Oil Chemists Society,
PO box 3489, Champaign, IL 61826-3489, USA. Practical articles on
surfactants and applications.
Soap. Cosmetics and Chemical Specialities (USA), MacNair-Dorland Co., 101
West 31st, Street, New York, NY 100001, USA. Occasional good articles on
surfactants and applications.
SPC (Soap. Perfumery and Cosmetics), Maxwell Business Communications
Ltd., 33-35 Bowling Green Lane, London ECI R ODA, UK.
Performance Chemicals, Reed Business Publishing, Quadrant House, The
Quadrant, Sutton, Surrey SM2 5AS, UK.
20 HANDBOOK OF SURFACTANTS

3.5 Patents

Patents are an enormous source of information on surfactants and their

applications. The type of information which can be found in patents is:

1. Processes for the manufacture of surfactants

2. Formulations for many different end uses with details of the surfactant
which is used in the formulation; often comparisons are given between
one surfactant and another in the formulation

To use patents as a source it is essential to have a clear objective, as reading

patents randomly is probably the most efficient way of wasting time, money
and effort. There are technical and business objectives in the use of patents.
The business objectives of avoiding patents, licensing and taking out new
patents will not be covered in this book. The technical objectives resolve
themselves into either a broad objective of using patents to keep up to date
with technology or a specific objective of requiring information on a particular
surfactant or a particular application.
Taking the broad objective, the best method is to have a librarian or
information expert who is conversant with patents produce regular monthly
abstracts of relevant patents. He will however need a better definition than
'surfactants'. Two typical broad objectives would be:

1. Anionic surfactants-particularly sulphonated, and especially sulphur

trioxide sui phonation; methods of manufacture, details of plants and
materials of construction
2. Surface.coating antifoams and/or defoamers-particularly for emulsion
paints and water-based industrial paints; details offormulations and test
methods for measuring efficiency of the antifoam/defoamer

In the absence of a librarian there are several abstract services for patents
which can be expensive and time-consuming to wade through as you cannot
specify the area of search, except in some on-line data bases (see Section 3.8).
The easiest, cheapest and most accessible is the CA Selects Number 089 (see
Section 3.4) which includes world-wide patents. The most comprehensive is
the Derwent Patent Abstracts (Derwent Inc (USA), Suite 500, 6845 Elm Street,
McLean, VA 22101, USA or Derwent Publications Ltd., Rochdale House, 128
Theobalds Road, London WCIX 8RP).
Taking a narrow objective the two best ways of identifying the right patents
are Chemical Abstracts or on-line data bases. The latter is the quickest but it is
also very easy to miss the relevant patents (see Section 3.8). The Chemical
Abstract Decenniel Indexes in a library are really the most efficient and, in the
author's experience, superior to on-line searching of Chemical Abstracts. Thus
go to Chemical Abstracts Decenniel indexes, find the Chemical Abstract
number, look that number up, read the Chemical Abstract, decide if the patent
 INFORMA nON SOURCES 21
is worth reading, obtain the patent and read it. The only short cut in this
procedure is to use an on-line data base when you have the Chemical Abstract
number, as it is quick and easy to find and print out a Chemical Abstract using
an on-line data base. The newer technology of CD-ROM will make this
procedure easier but it is likely that searching the CD-ROM records will have
similar limitations to on-line data bases (see Section 3.8). The reason for the
superiority in using Chemical Abstracts Indexes is that 'browsing' is much
easier. Browsing means noticing a word or phrase in the text which had not
been visualised at the beginning of search. Browsing is possible but expensive
using computer data bases.
On-line data bases are very rapidly increasing in number and quality, each
ofthe host data bases will have their own patent files. US patents are very well
covered by on-line data bases but there are no specific European patent data
bases and one has to use world-wide patent data bases or Chemical Abstracts
data base.
Thus patents, whilst possibly the largest source of information, are not the
easiest source to use, particularly for the unskilled.

3.6 Symposia and meetings

Surfactants are well covered by meetings and symposia. The large symposia
publish the proceedings and there are many useful papers given and published
on new surfactants and new applications. There are currently three regular
symposia which attract all the surfactant industry and the main users, the
detergent industry; these are:

1. The CESIO (Comite Europeen des Agents de Surface et leurs Inter-

mediaires Organiques) conference every four years; the last one was in
Paris in 1988 and the next one will be in the United Kingdom in
1992.
2. The Soap and Detergent Association (USA) holds regular meetings.
3. Organizados por la Asociation de Investigacion de la Industria Espanola
de Detergentes, Tensioactivos y Afines (A.I.D) y el Comite Espanol de
La Detergencia (C.E.D) holds an annual meeting generally in Barcelona
in March. Some papers are in Spanish but there are usually some
interesting papers in English. The address for correspondence is
Secretaria General, Association de Investigacion de Detergentes (AID),
Jorge Girona Salgado, 18-26, 08034 Barcelona, Spain.
In addition the British Association for Chemical Specialities has a
Surfactants Section which holds regular meetings covering various applic-
ations of surfactants. All the meetings are well publicised with the exception of
the Spanish Conference.
 22 HANDBOOK OF SURFACTANTS

3.7 Government publications

Legislation concerning chemicals is quickly becoming more complex on issues

such as labelling, packing and transport. However there is some specific
legislation which gives considerable information on the application of
surfactants. FDA Regulations of the United States give many specific
references to the use of specific surfactants in applications which may come
into contact with food, e.g. antifoam in sugar beet processing. UK Food
Regulations cover emulsifiers permitted for use in food.

3.8 Data bases

On-line data bases have been mentioned several times as they are a convenient
source of technical information. Undoubtedly computer data bases will slowly
become the means of storing the technical data of the future. However, at the
present time they certainly have not completely replaced paper. The output of
a computer data base of technical information is always a printout on paper
because it is so much more convenient to read a piece of paper. What then are
the advantages of on-line data bases.
t. Accessibility: Connection to anyon-line system world-wide is possible if
there is a public telephone line. It is best to use a specific connection for
computers (in the United Kingdom it is called Packet Switch Stream,
PSS) but that is not absolutely necessary. Good accessibility is of great
advantage if you have no library of your own or are very distant from a
large technical library.
2. Low cost to set up: a personal computer and a telephone line are all that
are needed to access on-line data bases. To set up a system with new
equipment can be quite inexpensive if care is taken over the choice of
hardware. Libraries are very costly to build, maintain and run and also
costly to use if they are very distant.
3. Rapid searching: A typical search for a subject can last seconds. The
printout of the information will only take minutes so within a very short
time of requesting the information you can be reading it.
4. Up to date i1iformation: Unlike books, all data bases are continually
updated.
With these advantages, what are the disadvantages and why can we not rely
on such data bases for our information:
1. Abstracts only: With few exceptions, technical data bases only contain an
abstract of the primary information which is in the form of printed
material, e.g. a patent. Thus the on-line data search will only give a
reference to the full information which must then be obtained separately.
 INFORMA TION SOURCES 23
However, a few technical journals have the full text available and this is
the area where computer data bases are probably going to develop.
2. Complex to use: You need to know which data base to use. There are now
so many data bases available, it needs an expert to pick out the best one.
The commands for searching are not uniform; the 'language' can be
different from one data base to another. The user must be a frequent user
of on-line bases in order to be economic and efficient. Occasional users
find the language difficult to remember although there are now improved
computer programs.
3. Expensive to use: Once you get to a library the only cost is your own time.
On-line data bases are expensive to use, you pay for the time and/or the
information received. It is very easy to spend a great deal of time and
money on a single query if you have difficulty in finding the right key
words, so careful planning and preparation beforehand are vital.
The on-line data bases could well become obsolete if CD-ROM develops
quickly and cheaply to take their place. However, for the present, on-line data
bases are a very valuable source of information and should not be neglected. If
you have not had the experience then the best way to start is to contact a data
base host. This is a company which offers a number of data bases which can be
searched for payment to the host. This host company will give full details on
setting up and tuition in searching and accessing the system. Unfortunately
there is no common language between data based hosts, the languages used
are very similar but not identical. At the time of writing two useful data base
hosts for chemicals (Le. surfactants) are:
1. STN International. Headquarters: Postfach 2465, 0-7500 Karlsruhe 1,
Germany. USA: 2540 Olen tangy River Road, PO Box 02228, Columbus,
OH 43202, USA.
2. Pergamon/Orbit Infoline. Headquarters: 8000 Westpark Drive,
McLean, VA 22102, USA. Europe: 12 Vandy Street, London EC2A 2DE,
UK.
Undoubtedly there are others which are wider in scope, but these two data
base hosts specialise in scientific, and particularly chemical data bases. Each
host contains data bases covering Chemical Abstracts and a number of patent
data bases.
4 Use of surfactant theory

4.1 Introduction

Formulations using surfactants, particularly mixtures of surfactants, have

been devised by trial and error, and theory has followed to explain the
observed results. The application of theory will not lead to quick, easy
solutions of practical problems. However there is a need to have a grasp of
theory for a better understanding of the mode of action of a surfactant. This
helps in the more rapid and efficient selection of the correct surfactant, and
possibly other components.
The approach presented describes the theoretical basis of surfactant
behaviour in a pictorial form rather than mathematical, on the ground that
such pictures are more easily remembered and used. The principal properties
which characterise surfactants are described:
• Adsorption
• Surface tension and interfacial tension
• Micelles
• Wetting of solids
• Dispersing/aggregation of solids
• Foaming/defoaming
• Emulsifying/demulsifying (including microemulsions, HLB, PIT and
CER methods)
There have been numerous studies published on the correlation between the
chemical structure of a surfactant and its properties. The purpose of this
chapter is to show how a particular chemical structure produces specific
properties. In other chapters there will be frequent reference to empirical
relationships between structure and properties. The good formulator gradu-
ally builds up a mental picture of such relationships by experimental trial and
error over a period of time. The theoretical approach enables one to
understand and use such relationships in a more systematic manner but it will
not solve every problem or eliminate the need to do experimental work.
The theory of surfactant behaviour is now an extensive branch of physical
chemistry and considerable basic research has been carried out in the last 20
years. The major reason for this work has been the possible shortage of oil in
the 1970s leading to the use of surfactants in enhanced oil recovery. It was
found that the theoretical knowledge of the day was inadequate to explain the
complex behaviour of surfactants in microemulsions. In addition, the
 USE OF SURFACTANT THEORY 25
importance of the physical chemistry of surfactant behaviour is now being
recognised in biochemistry, and in the study of cell behaviour. A further
impetus to surfactant research has been the development of thin film
technology in the production of microelectronics by the use of Langmuir-
Blodgett films. However, for the practical user and formulator, the basic ideas
covered in this chapter will prove adequate.
There are two basic concepts which need to be well understood in order to
explain the majority of observed phenomena: these are adsorption of a
surfactant at a surface and the formation of micelles in solution. These two
phenomena differentiate a surfactant from other chemical entities. It is
adsorption at surfaces which gives the surface active effects of foaming,
wetting, emulsification, dispersing of solids and detergency. It is the micelle
properties which give the solution and bulk properties of surfactants such as
viscosity and solubility.

4.2 Adsorption

Many chemicals produce foams and wet surfaces but are not considered
surfactants, e.g., methyl alcohol in aqueous solution. The major characteristic
of a surfactant is that it is at higher concentration at the surface than in the
bulk of a liquid. This phenomenon is known as adsorption and occurs at a
liquid/solid interface, at a liquid/liquid interface and at an air/liquid interface
as shown in Figure 4.1.
In Figure 4.1 the surfactant molecule is pictured as a long straight
hydrophobic group and a small round hydrophilic group. The surfactant
molecule can be oriented in various ways. As we shall see later (Section 4.8) this
is a gross over-simplification, and it is the relative sizes and shapes of the
hydrophobic and hydrophilic parts of the surfactant molecule which deter-

Jromrn L
"'"
Hydrophobic
solid

Figure 4.1 Adsorption at interfaces.

26 HANDBOOK OF SURF ACT ANTS

mine many of its properties. For now we will stay with the simple structure.
The adsorption of a surfactant at an air/water surface will result in
pronounced physical changes to the liquid; the more surfactant there is at the
surface up to complete coverage of the surface, the more the change.
The effect of surface tension has been used to study and measure adsorption.
An example is given of two surfactants where the surface tension is plotted
against concentration (see Figuft. 4.2). Two features are notable. Firstly, for
both surfactants the graph is discontinuous, with the surface tension falling
rapidly as the concentration increases until a point is reached where the surface
tension falls only very slowly. This point is where the surface is covered by a
monolayer ofthe surfactant. The second feature is that surfactant I behaves in
qualitatively similar way to surfactant 2 but not quantitatively, the fall is
different and the change in slope in the graph is at quite a different
concentration. The reason is that both surfactants have formed a monolayer
on the solid but the concentration of each surfactant is different at the point
when the monolayer is formed. In addition, the minimum surface tension
obtained after the monolayer is formed is different for the two surfactants.
These differences are due to the different sizes and shapes of the hydrophobic
and hydrophilic groups on the surfactants giving a different packing at the
surface. This concept is described in more detail in Section 4.8.
As adsorption is the amount of surfactant at a surface compared to that in
the bulk of the liquid, one would assume it is easy to measure. Unfortunately in
the case of liquidjIiquid interphases and also air/liquid interphases, it is not
easy and so indirect means must be found. In the case of adsorption at a

1
Surlace
tension

----------------surlactant1
'-~-----------------surlactant2

\monolayer
f surlactant
•
concentration
of
surlactant

Figure 4.2 Surface tension versus concentration.

 USE OF SURFACTANT THEORY 27
liquid/solid surface, the concentration of the surfactant can be measured
before and after introducing a surface and hence the amount adsorbed can be
measured. The exact area of the surface of a solid in a liquid can be difficult to
determine so that the amount adsorbed per unit area is still not easy to
determine. The extent of adsorption and the area per adsorbed molecule can
be calculated from the Gibbs isotherm but these relationships do not apply
above the critical micelle concentration (CMC) where most surfactant
formulations are made and generally, but not always, used. The Gibbs
isotherm relates the change in surface tension to the concentration of
surfactant in excess to that in the bulk phase.
The adsorption of the surfactant at the surface is a consequence of the
molecular structure of the surfactant. The hydrophilic group wishes to dissolve
in the aqueous phase whilst the hydrophobic group has only a slight affinity
for water. The water molecules have a strong affinity for one another, stronger
than the hydrocarbon chains making up the hydrophobic group and thus the
hydrophobic groups are withdrawn from the surrounding water. The eventual
fate of the hydrocarbon group will be dependent upon the properties of the
surface with which it is in contact. If the surface is air then it will orient
away from the water (Figure 4.1), if a hydrophobic solid it will orient towards
the solid, but if the solid is highly polar it could orient away from the solid.
Adsorption of surfactant on solid surfaces will depend upon the nature of
the surface, whether hydrophilic (polar) or hydrophobic (non-polar). The
adsorption mechanisms are still not known in detail but for details of the
complexity see Myers (1988). A summary from Myers (1988) follows:

Polar or hydrophilic surfaces

1. The chemical nature of the surface can play an important role, e.g. metal
oxides can form salts on the surface (chemisorption) with anionics.
2. With polar surfactants, adsorption can be high; the polar groups can
orient towards the surface and the hydrophobic chain then makes the
particle hydrophobic. A second layer can be formed with hydrophilic
groups on the outside.

Non-polar or hydrophobic surfaces

1. The amount of adsorption is extremely small with polar surfactants;
1 x 10 - 4 moljg on activated carbon in 0.05% sodium dodecyl sulphate.
2. The adsorption of polar surfactants can be increased by addition of
electrolytes which reduces the electrical double layer.
3. Non-ionics adsorb appreciably higher amounts (10 x) than polar
surfactants.
4. The effect of electrolyte addition on adsorption of non-ionics does not
significantly affect the amount of adsorption.
28 HANDBOOK OF SURFACTANTS

5. Effect of temperature: polar surfactants adsorb less with increase in

temperature. Ethoxylates increase adsorption with increasing tempera-
ture (because they hydrate with increasing temperature thereby becom-
ing more hydrophobic).
6. Increase in the length of the hydrocarbon chain increases adsorption.
7. Branching in the hydrocarbon chain decreases adsorption.
The adsorbed molecules are not stationary, they are in dynamic equilibrium
with neighbouring molecules. They also need a finite time to adsorb which will
be dependent upon the shape and size of the surfactant and the adsorption
mechanism. Most practical applications of surfactants, detergency, wetting,
foaming, etc. are a dynamic process and the systems are not at equilibrium. If a

Liquid

~~I~SOlid
I liquid I
I interface I

Figure 4.3 Creation of new surfaces.

 USE OF SURFACTANT THEORY 29
thin film of liquid containing surfactant is expanded, a new surface is created.
However, the surfactant cannot move as fast as the surface is created and the
amount of adsorption per unit area decreases (see Figure 4.3). There is then
less surfactant adsorbed and the surface tension increases in the new surface.
The overall result is a force at right angles to the surface which helps to restore
the equilibrium. This is known as the Gibbs film elasticity and the Marangoni
effect (for the difference see Lunkenheimer et al., 1981) and is used to explain
foam stability (see also Section 4.7).

4.3 Micelles

Picture a low concentration of surfactant molecules in dilute solution such

that the majority are adsorbed on to the air/water interface. If additional
surfactant is added then the surfactant will be adsorbed at the surface until
saturation is reached and the surface tension then becdmes constant (or nearly
constant) with increasing concentration (see Figure 4.2). If further surfactant is
added to the solution, the surfactant molecules remain in the bulk of the
solution but these hydrophobic heads will still be repelled from the water.
They can form spherical assemblies known as micelles where the interior of the
micelle resembles a hydrocarbon separate phase (see Figure 4.4). The con-

Figure 4.4 Micelles.

30 HANDB(X)K OF SURFACTANTS

centration at which micelles first form is known as the critical micelle

concentration (CMC).
These micelles behave as large molecules and influence two important
properties:
1. Solubility of organic hydrocarbons and oils in aqueous solution
2. Viscosity
The size of the micelle is measured by the aggregation number which is the
number of surfactant molecules associated with a micelle (see Table 4.1).
Several things are of interest from this table; firstly the very large micelle
size for non-ionics against the anionics or cations. This would suggest that any
properties such as viscosity or solubilisation which are dependent upon the
size of the micelle will be much more evident for non-ionics than anionics or
cationics. This is in fact the case in practice and non-ionics are very good in
solubilising hydrocarbon oils.
A second point of interest is the abnormal behaviour of the non-ionic with
respect to a change of temperature. For polar surfactants an increase in
temperature will reduce the tendency to aggregate because of the increased
kinetic energy of the molecules. In the case of non-ionics the same effect is
there, but is far outweighed by the loss of water from the EO group making the
product less soluble and hence increasing the tendency to aggregate. Non-
ionics will continue to aggregate up until they become insoluble, i.e. complete
aggregation or a micelle of infinite size.
Why should the micelle be spherical? It would seem that for the majority of
surfactants this is the most stable thermodynamic state, being dependent upon
the relative sizes of the hydrophobe and hydrophilic group. Spheres are the
common shape ofthe micelle at concentrationsjust above the CMC which will
be less than 1%for most surfactants. Less than 1% is where many surfactants
are actually used, so a spherical micelle, just near the CMC would be the
correct picture of a surfactant. However as the concentration increases to

Table 4.1 Aggregation numbers

Surfactant Temperature Aggregation

(0C) No.

Sodium dodecyl sulp'hate 23 71

54 40
Dodecyl alcohol + 6EO 25 400
35 1400
45 4000
Decyltrimethyl ammonium bromide 23 36
Barium dinonylnaphthalene sulphonate 20 15
(in benzene)
 USE OF SURFACTANT THEORY 31
those levels at which many surfactant solutions are made and sold, e.g. 25%
active washing up liquids, 15% active shampoos, then the solution properties
show strange behaviour in solubility and viscosity. The reason for this is that
the micelles change shape as the available free space decreases. The first change
is to lamellar micelles where they can form lamellar sheets or take the form of
long cylinders (see Figure 4.5). Similar non-spherical cylinder shaped micelles
are formed in more dilute solution with certain surfactants which have very
long hydrophobic chains, or strongly associating counter ions.
Surfactant solutions with spherical micelles behave like Newtonian liquids,
i.e. the viscosity is independent of shear rate and not very different from water.
The transition from spherical to cylindrical or lamellar micelles results in a
large viscosity increase which changes to non-Newtonian, i.e. dependent upon
shear rate. At a certain concentration, the solutions are so viscous that a gel
forms. The cylindrical micelles are usually formed at medium concentrations
and usually represent the maximum viscosity. At higher concentrations of
surfactant, the lamellar phase is formed with water trapped between the
surfactant double layers. Thus, in aqueous solution, many surfactants will be
soluble at low concentrations (up to 25-35%), then give very viscous solutions
or gels at concentrations in the range 60-80%, followed by viscous solutions at
70-90% concentrations. The molecules in the micelles are not fixed but are in
dynamic equilibria. Micelle formation and micelle disintegration can occur in
fractions of a second in spherical micelles, i.e. in dilute solutions. In the case of

Figure 4.5 Micelles in concentrated solution.

32 HANDBOOK OF SURFACTANTS

Table 4.2 CMCs of various surfactants

Surfactant CMC (Molar) CMC(%)

Anionic
Sodium dodecyl sulphate 8.6 x 10- 3 0.19
Sodium dodecyl benzene sulphonate 1.2 x 10- 3 0.04
Non-ionic
Dodecyl alcohol + 4EO 4.0 x 10-5 0.0014
Dodecyl alcohol + 7EO 5.0 x 10-5 0.0025
Cationic
Dodecyltrimethyl ammonium bromide 2.0 x 10- 2 0.45
Amphoteric
N-Dodecyl aminopropionic acid I.3xlO-.l 0.033

the formation of lamellar or cylinder shaped micelles the formation of micelles

is much slower and can take hours or days (Falbe, t 987).
There are many examples in formulations where a mixture of two or more
surfactants is more efficient than a single surfactant. The idea of mixed
micelles where two or more surfactants will form one type of micelle has been
put forward to explain some surfactant phenomena (see microemulsions,
Section 4.8.1).
Some typical CMC values are shown in Table 4.2.

4.3.1 CMC and chemical structure

The hydrophobic group

1. The CMC decreases as the number of carbons in the hydrophobic chain
increases.
2. The CMC increases as the head moves away from the end of the
hydrophobe towards the middle.
3. The CMC increases if polar atoms (e.g. N or 0) are included in the
hydrophobic group.
4. The CMC decreases if fluorine atoms replace carbon atoms in the
hydrophobic group.

The hydrophilic group.'

1. Charged hydrophilic groups have CMCs much higher than ethoxylated
non-ionics.
2. The nature of the hydrophilic group, if charged, has little effect on the
CMC.
3. Addition of an ethylene oxide unil to a non-ionic gives an increase in
CMC.
 USE OF SURFACTANT THEORY 33
4. Addition of an ethylene oxide unit to an ether sulphate gives a decrease in
CMC (the EO unit is acting as a hydrophobe not a hydrophilic unit).
5. The CMC increases if an extra hydrophilic head is introduced (but not
EO, see 4).
6. In an anionic salt the CMC decreases in the order Li + > Na +
> K + > Ca 2+ = Mg2 +.

Effect of added electrolyte

1. The CMC decreases when electrolyte is added to ionic surfactants.
2. The CMC of non-ionics and amphoterics is not much affected by
electrolyte addition.
Effects of added organics are discussed under solubilisation.
Micelles can also be formed in non-aqueous solution. There has not been
very much work carried out in this area but the micelles that are formed in
hydrocarbon and aromatic solvents would seem to be much smaller in size
than those found in aqueous solution.

4.4 Solubility

The solubility of a surfactant in aqueous solution increases with increasing

temperature in a similar way to most organic molecules (for the exception see
Chapter 8 on ethoxylated non-ionic surfactants). Figure 4.6 shows the effect of

f
Concentration
Micellar solution

--
Molecular

-- --
solution

--- --
and
crystals

Molecular solution

The Kraft point

Temperature
Figw-e 4.6 The Kraft point.
34 HANDBOOK OF SURFACTANTS

temperature on the solubility of sodium dodecyl sulphate. At a particular

temperature the solubility rises dramatically, this temperature is known as the
Kraft point. This has significance to the practical user because much more
concentrated solutions are possible above the Kraft point than below it,
making a Kraft point below room temperature desirable. The Kraft point is
that temperature above which micelles are formed. Non-ionics based on
ethylene oxide show a decrease in solubility with increase in temperature. The
Kraft points for most common ethoxylates have a hypothetical Kraft point
below O°e. Ethoxylated non-ionies with a large hydrophobe have Kraft points
above o°e.
The Kraft point and solubility of ionic surfactants is determined by the
counter ion. Sodium salts of fatty acids have higher Kraft f>oints than the
potassium salts yet this is reversed for dodecyl sulphates. Kraft points of
calcium salts of fatty acids are usually significantly higher than the sodium
salts, i.e. calcium salts tend to form micelles less readily than sodium salts.
Thus hard water (containing calcium ions) can reduce the solubility of soaps in
aqueous solution. On the other hand calcium salts of most anionic surfactants
will be more soluble in hydrocarbon solutions.
The reduction of the Kraft point, i.e. to increase micelle formation, can be
brought about by increasing the hydrophilic character of the surfactant or by
reducing the hydrophobic character; thus:
1. Inclusion of ethoxy groups in dodecyl sulphate increases solubility (but
increase in the number of EO groups does not reduce CMC, see
Section 4.3).
2. Reduction in the length of a hydrophobic chain may result in loss of other
properties.
3. Increase in branching may result in the surfactant becoming non-
biodegradable.
4. Addition of electrolyte usually results in an increase in the Kraft point.
S. Addition of low molecular weight alcohols results in a reduction in the
Kraft point.
The solubility of ethoxylated surfactants is discussed in more detail in
Section 7.1

4.5 Wetting

When a drop of water is placed on a surface it can either spread over the
surface, i.e. it 'wets' or form a stable drop, i.e. it does not 'wet'. Reduction in
surface tension of water by a surfactant can make a non-wetting solution into a
wetting solution on particular substrates. The ability to wet depends upon the
surface tension ofthe solution and the critical solid tension (CST) ofthe solid.
 USE OF SURFACTANT THEORY 35
The CST is the surface tension of a liquid which will form a contact angle of
zero measured through the film on that solid, i.e. the liquid spreads over the
solid.
Grass, with a CST of more than 70 dynes/cm can be wet with water.
Polypropylene with a CST of 28 cannot be wet with water but can be by
aqueous solutions of surfactants. Teflon with a CST of 18 cannot be wet with
most common surfactants although there are now silicone and fluorochemical
surfactants which can achieve this very low surface tension.
Although wetting is often described in terms of the spreading coefficient and
Young's equation, such mathematical relations are only true at equilibrium. In
most practical applications of wetting, e.g. a detergent or removing water from
a metal surface, the process is only in one direction and it is the kinetics of the
wetting process which is more important. In addition very few materials have
smooth surfaces, e.g. textiles, powders, chalk, and there are considerable
capillary effects. Most practical tests (e.g. the Draves wetting test for fabrics
using tape (Shapiro, 1950)) are dynamic rather than at equilibrium.
An important concept is the rate of surface tension lowering. Imagine a drop
ofliquid placed on a surface with a zero contact angle. In order to spread, the
surface of the liquid must expand and the surface tension increases as the
spreading pressure decreases. However surfactant molecules will diffuse from
the interior back to the surface in order to lower the surface tension. Thus if the
diffusion is slow (see Figure 4.3) then the rate of wetting is poor. Correlation
between the rate at which the surface tension is lowered and wetting has been
observed (Gruntfest, 1951) but it is not the only factor. Nevertheless it gives an
easily understood phenomenon that the faster a surfactant molecule diffuses to
a freshly formed surface, then the better (faster) the wetting. In practice this very
general rule is borne out as smaller surfactants are generally better wetters
than large molecules. This is due to smaller molecules diffusing faster through
the solution than larger molecules.
The relationship between chemical structure and wetting (as measured by
practical tests, e.g. Draves) can be listed as follows:

• The shorter the hydrophobic chain the better the wetting.

• The optimum wetting characteristics are shown around the C12 carbon
chain.
• Symmetrically located internal head group substitution and ortho-
substituted alkyl benzene sui phonates are better wetters than straight
chain or para-substituted (Gray et al., 1965).
• Additional polar groups in the molecules (ester, amide, EO) usually
result in loss of wetting power.
• Draves wetting times increase with each added EO group in ether
sulphates.
• Ethoxylated non-ionics will pass through a minimum of wetting
36 HANDBOOK OF SURFACTANTS

performance as the EO content increases; this minimum is where the

cloud point is just above the test temperature (Komor and Beiswanger,
1966).
• Ethoxylated fatty alcohols are better wetters than similar ethoxylated
fatty acids (Wrigley et aI., 1957).

Conditions which affect wetting are as follows:

• Increase in temperature reduces wetting power due to the better

solubility and reduced adsorption but not with ethoxylated non-ionics.
• Addition of electrolyte which causes a reduction in surface tension will
improve wetting.
• Addition of long chain alcohols and non-ionic co-surfactants improves
the wetting properties of anionics (Biswas and Mukherji, 1960; Bland
and Winchester, 1968).
• pH is important when weak basic and/or acidic groups are present;
sulphocarboxylic acids show better wetting at low pH where the carboxyl
group is not ionised.

4.6 Dispersing

The suspension of a solid particle in a liquid medium, particularly water, is an

important technological process. Surfactants playa role in preparing suspen-
sions of the right particle size which will be stable on storage for an extended
period of time. The usual step in preparing a suspension is to add a solid to a
small amoun·t of liquid, grind to the required particle size then disperse the
concentrate into a larger volume of the liquid. Surfactants also play an
important role in the wetting out of the solid (see Section 4.5). In dispersion
processes, new solidjliquid interfaces are formed and a surfactant will reduce
the interfacial energy at the solidjliquid interface and thereby facilitate the
formation of new interfaces. In practice it is found that such surfactants
are very different to those giving good wetting. Instead of being small
molecules, one finds that the surfactants which stabilise solid suspensions
are large.
The best known theory explaining this stabilisation is the DLVO theory
(Derjaguin, Landau, Ve~wy and Overbeek) which only covers lyophobic solids.
However, this theory has shortcomings and as yet there is no simple theory to
explain the stability oflyophilic (or hydrophilic) solids. Nevertheless the initial
mechanism is probably adsorption by the surfactant on to the solid as shown in
Figure 4.1. When adsorbed, the surfactant then produces a barrier to prevent
re-aggregation of the particle. The type of surfactant which will give efficient
dispersing properties will depend upon the nature of the solid to be
dispersed.
 USE OF SURFACTANT THEORY 37
4.6.1 Non-polar solids in water

Adsorption of the hydrophobic tail of an ionic surfactant on to the surface will

cause the particles to acquire a charge of the same sign and hence repel one
another (see Figure 4.7).

4.6.2 Polar solids in water

These will already have a charge. If a surfactant of the opposite charge is used
then flocculation may occur. If a surfactant of the same charge is used then
there is no improvement until a relatively high concentration of surfactant is
added so that adsorption is sufficiently high to stabilise the particle. As the
majority of polar solids are negatively charged, one finds that anionic type
surfactants are the most efficient stabilisers. Such surfactants are those of high
molecular weight with a multiplicity of ionic groups; these products are now
becoming known as polymeric surfactants. The multiple ionic groups serve a
number of purposes. They can also adsorb and yet still give an electrical
barrier on oppositely charged particles. They can give a steric barrier to
coalescence. Examples of commonly used dispersing agents are naphthalene

\ r;-

Anionic surfactant
Figure 4.7 Non-polar solids in water.
38 HANDBOOK OF SURFACTANTS

sulphonates condensed with formaldehyde and low molecular weight

polyacrylic acid (also see Chapter II).

4.7 Foaming/defoaming

Most surfactants give rise to foam which can be desirable or undesirable

depending upon the application. Whether the requirement is copious foam,
little foam or no foam, the user will wish to control the level of foam and to
know what external effects can affect it e.g. foam increase or foam collapse. As a
general rule a foam is not generated in a pure liquid phase. A surfactant which
strongly adsorbs at the air/interface is necessary in oider to produce a foam in
aqueous solution.
Foams consist of bubbles of gas, with the bubble walls comprising thin
liquid films forming three-dimensional structures. There is a junction where
the gas bubbles meet (see Figure 4.8). The liquid will drain from the walls (W)
into the junction by gravity. In very thin films the pressure in the thin walls is
higher than that in the thicker junctions giving a flow of liquid from the thin
wall to the junction. If the drainage and flow continue, the walls will continue
to shrink and the foam will collapse. If the liquid is prevented from moving into
this junction then the foam will be stable unless a rupture appears in one of the
walls by mechanical or physico-chemical means, i.e a defoaming agent.
The effects which surfactants produce to prevent the flow of liquid are as
follows:
1. Electrostatic effects. These are only applicable to ionic surfactants when
the film .thickness is less than 1000 A. The charged monolayers repulse
each other and stabilise the foam. Such films are very thin and appear

FIgure 4.8 Gas bubble.

 USE OF SURFACTANT THEORY 39
transparent so that they are of very little interest in applications where
the appearance of the foam is important, e.g. shampoos.
2. Surface viscosity. Surfactants oriented or packed together in multilayers
can give very different and generally higher viscosity at the interface
between the air and liquid. The interactions between alkanolamides and
anionics have been suggested as explaining the stabilisation of anionic
foams and the different foam appearances (Wingrave, 1981).
3. Bulk viscosity. Polymeric additives enhance foam stability by increasing
the bulk viscosity and slowing down the drainage.
4. A second liquid or solid phase. When an immiscible phase is present then
the stability ofthe foam can be changed significantly, either increasing or
decreasing the stability. Possibly the most important effect will be the
change in the distribution of the stabilising surfactant molecules which
can be adsorbed at the new liquid/liquid or solid/liquid interfaces and
lost to the air/water interface. Soil is one such possible interface, and
therefore during shampooing or cleaning of clothes the solution loses
surfactant to the soil and destabilises the foam. In addition, the effect of
added particles can induce the Marangoni effect (see below).
5. Film elasticity. In any of the changes referred to above the concentration
of surfactants can change at the interface. This can lead to changes in the
interfacial elasticity, known as the Gibbs elasticity and dynamic
Marangoni elasticity. The essential features of these two effects are
shown in Figure 4.9.
Gibbs introduced the concept of film elasticity, where the stretching of the
film produced fewer adsorbed molecules of surfactant per unit area and

Gibbs effect

Initial state
ST
liquid lamellar

Marangoni

66 6 6 66
- - - - I..
~ .....
~I---

Flow of liquid
and surfactant

Figure 4.9 Gibbs and Marangoni film elasticity.

40 HANDBOOK OF SURFACTANTS

therefore a higher surface tension in the thin area which gave the effect of
elasticity. This effect only relates to lamellae. The Marangoni effect is where
the surface tension of a newly formed surface is higher than the unchanged
surface and the resulting force will transport surfactant and liquid into the
newly formed surface area. The Marangoni effect operates on surfaces. The
combined effect of a sudden thinning in one part of the film is the transport of
liquid and surfactant back into this thin area.
Some very general rules on the relationship between foaming and chemical
structure are as follows:

1. There is no direct relationship between the ability to produce foam and

the ability to stabilise foam.
2. Foam volume formed increases with an increase in the concentration of
the surfactant up to the CMC. Above that the amount of foam is
relatively constant. There is no similar rule with respect to the stability of
the foam.
3. Ionic surfactants produce more foam, and more stable foam than non-
ionics.
4. Straight chain hydrophobes show better foaming than the corresponding
similar length branched chain hydrophobes.
5. The amount offoam goes through a maximum as the chain length ofthe
hydrophobe increases in a homologous series. The longer the hydro-
phobe, the lower the surface tension and hence more foam. However, as
the chain length grows, the solubility of the surfactant rapidly decreases.
6. If the hydrophilic group is moved from a terminal position to an internal
position along the chain, higher foam heights but lower foam stability is
the general rule (at concentrations above the CMC)
7. The effect of temperature on foaming ability will be similar to the effect of
temperature on solubility. Thus ionic surfactants will foam better on
increasing temperature whilst non-ionics will either show a decrease or
go through a maximum in foam production on increasing temperature.
8. Polar organic additives (other surfactants) which lower the CMC of a
surfactant can improve the stability of foam. The most effective have a
similar chain length to that of the surfactant. Examples are alkyl alcohols
and fatty alkanolamides.

4.8 Solubilisation, emulsions, microemulsions and HLD

One of the widest applications of surfactants is to solubilise or disperse water

insoluble substances (generally organic compounds) in water. Paint, adhes-
ives, textile finishes, paper coatings, leather finishes, hand cleaners, etc. have in
the past been formulated with organic compounds which would not dissolve
in water. In recent years there has been an accelerating trend to replace
 USE OF SURFACTANT THEORY 41
solvents either entirely, or partly with water. The main reason for this change
has been due to the increasing realisation of the toxicity of many of the cheap
solvents employed. In addition water-based products are favoured by
customers because of the ease of handling and of cleaning up spillages. A
further compelling reason has been the fact that water is cheap compared to
organic solvents and not subject to the fluctuations of price and supply of
petrochemical-based products. All these reasons have resulted in a large
number of applications where the intention is to dissolve or disperse a water
insoluble compound in water.

4.8.1 Solubilisation and emulsions

If a water insoluble compound (e.g. a hydrocarbon oil) is added to an aqueous

solution of a surfactant there is the possibility of:
1. An oil in water emulsion (OfW): this consists of two liquid phases, the oil
phase dispersed as globules in the continuous water phase. The
appearance of such a system is opaque and white in colour. Such systems
are unstable and separate on standing. They show high electrical
conductivity.
2. A water in oil emulsion (W/0): this consists of two liquid phases, the
water phase dispersed as globules in the continuous oil phase. The
appearance of such a system is opaque and white in colour. Such systems
are unstable and separate on standing. They show low electrical
conductivity.
3. Solubilisation of the oil in the water/surfactant: the oil apparently
dissolves in the aqueous solution. The appearance of the solution is the
same as before the oil was added. Such systems are stable and do not
separate on standing. They show high electrical conductivity.
4. The formation of a microemulsion: the oil dissolves or disperses in the
aqueous solution. The appearance is a transparent or translucent
solution which often gives a coloured solution (reddish orange to blue).
Such systems are stable and do not separate on standing. They show high
electrical conductivity.
In practice these different systems can be formed by varying the type of
surfactant, the ratio of oil/water/surfactant and the addition of non-
surfactants.

4.8.2 Formation of oil in water (O/W) and water in oil (W/O) emulsions

Surfactants will adsorb on the oil/water interphase depending upon their

structure (see Figure 4.10). Adsorption and stabilisation are found to be most
efficient when the surfactant is more soluble in the continuous phase, i.e. for
42 HANDBOOK OF SURFACTANTS

oil in water

water

water in oil

oil

Figw-e 4.10 Adsorption.

W/0 emulsions a water soluble surfactant is most efficient; for OjW emulsions
an oil soluble surfactant is most efficient. In practice it is found that a mixture
of surfactants with differing solubility properties will produce emulsions with
enhanced stability. The discussion on microemulsions in Section 4.8.4 gives
some indication why this is so.
Many attempts have been made to correlate surfactant structures with their
effectiveness as emulsifiers. The most successful and still used is the
hydrophilic/lypophilic balance (HLB) first developed by Griffin (1949). This
has prove.d very successful with alkoxylated non-ionic surfactants but less
successful with ionic surfactants. Griffin proposed to calculate the HLB
number from its chemical structure, i.e. HLB = % of the hydrophilic group
(molar) divided by 5. Thus the maximum HLB number was 20 and represented
a completely water soluble surfactant. An HLB of zero represented a
completely water insoluble product. An approximate HLB number can be
obtained by adding a small quantity of a surfactant to water and shaking.

HLB number Appearance on adding surfactant to water

1-4 Insoluble
4-7 Poor dispersion unstable
7-9 Stable opaque dispersion
10-13 Hazy solution
13-20 Clear solution
 USE OF SURFACTANT THEORY 43
Thus low HLB number surfactants will be used for O/W emulsions and high
HLB numbers used for W/0 emulsions.
Temperature has a big effect on emulsion systems made with non-ionic
(ethoxylated) surfactants. Increase in temperature will bring about a phase
inversion from O/W to W/0 due to the non-ionic becoming less water soluble
as the temperature increases. The temperature at which the inversion takes
place is known as the phase inversion temperature (PIT). The PIT can be used
as a method for emulsion preparation. An emulsion is prepared near its PIT
where the minimum droplet size is obtained. Then it is cooled to its normal use
or storage temperature.

4.8.3 Solubilisation

The increasing solubility of water insoluble organic materials in aqueous

solutions of surfactants is due to the organic compound 'dissolving' in the
micelle. Whether this is in the interior, the interface or the micellar surface, will
depend upon the chemical structures of both the surfactant, and the organic
material. The presence of associated molecules of surfactants is essential,
although the observation of solubilisation effects below the normal CM C also
suggests the presence of submicellar species. However, most practical uses of
solubilisation are well above the CMC. The amount of hydrocarbons and other
water insoluble organic compounds solubilised increases as the size of the
micelle increases. Thus non-ionics will give higher degrees of solubilisation
than ionic species. Increase in the length of the hydrophobic chain of the
surfactant generally gives a higher degree of solubilisation. With additives of a
more polar character, e.g. long chain alcohols, the picture is less clear, with the
relative shapes and sizes of surfactant and additive being more significant
(see Section 4.8.4).

4.8.4 M icroemulsions

The distinction between simple emulsions and microemulsions is fairly clear.

Simple emulsions are fundamentally unstable whilst microemulsions appear
infinitely stable. On the other hand, the difference between solubilisation and
microemulsions is not possible by simple observation and there is a current
view that microemulsions are really swollen micelles. However, not all
authorities agree with this view and argue that there is a difference between
solubilisation and microemulsions.
Sodium dodecylbenzene sulphonate (SLABS) in aqueous solution will
solubilise only very small amounts of heptane but if SLABS is dissolved in
0.1 M sodium chloride and octanol is then added at 1:8 mole ratio of SLABS,
the resulting mixture will dissolve appreciable quantities of heptane and form
a clear aqueous solution, i.e. a microemulsion.
44 HANDBOOK OF SURFAC'TANTS

The SLABS first exists in the form of a spherical micelle (see Figure 4.11).
The addition of sodium chloride alters the effective charge on the polar group
and together with the addition of the octanol into the micelle, changes the
spherical micelle into a rod shaped micelle which is a mixed micelle. This rod
can take up a considerably greater volume than the spherical micelle. The
greater volume of the rod micelle can now solubilise a larger volume of
heptane to form the microemulsion. The reason for this change is due to the
reduced polar charge of the SLABS molecules which enables them to pack
together in a different manner.
The packing must depend upon the relative sizes ofthe hydrophilic, and the
hydrophobic group. The 'effective' hydrophilic group is not the size of the
molecule, but rather the effect in surfactant solutions of the charge if ionic, and
the effect of solvation if a polyethylene glycol chain. The effective size of the
hydrophobic group will depend on whether the alkyl chain is linear or
branched, or whether there are one, two or more hydrophobic chains. It is well

"',,
,
\
\
\
I spherical
I micelle
I

,
I
I

--~~ ... ",

x X X
0 0 0 0
0 0 0

Q=SLABS

X =Octanol

Figure 4.11 SLABS as a micelle.

 USE OF SURFACTANT THEORY 45
known that such variations in the alkyl chain can give practical differences in
the use of the surfactant. If we now visualise a surfactant as an effective head
group (with a cross-sectional area ah ) and an effective chain group (with cross-
sectional area ac) (see Figure 4.l2), these molecules are adsorbed at an oil/water
interface to give a unimolecular layer.
A function known as the packing ratio P can be defined as
P = aja h
If the groups are of relatively equal cross-section, i.e. P = 1, they will pack
together easily provided the surface is planar (see Figure 4.13a). If the groups
are of very different cross-sections such that the hydrophilic group is larger
than the hydrophobic group (Figure 4.13b), i.e. P < 1, then for best packing the
surface will curve towards the smaller group and there will be a tendency to oil
in water emulsions. If the groups are of very different size such that the
hydrophilic group is smaller than the hydrophobic group (Figure 4.13c), i.e.
P> 1, then for best packing the surface will curve towards the smaller group
and there will be a tendency to water in oil emulsions.
There will be similar tendencies in forming micelles, and therefore to form
small, tightly-packed micelles in water the best packing will be as in

...........
,- - ~t----
....., ... area ac
........ --

oil

water

_III ........... _.
C : ....- - area ah
...................
Figure 4.12 Surfactant with head and chain.
46 HANDBOOK OF SURFACTANTS

(a)

oil
Planar
water

(b)

OiVwatcr
emulsion

(c)

Water/ oil
emulsion

Figure 4.13 Packing on surfaces.

Figure 4.13b, i.e. where the hydrophilic group is very much larger than the
hydrophobic group. In order to form larger micelles of different shape with less
well-ordered structure, then a reduction of the size of the effective hydrophilic
group is required and a possible disruption of the packing of the hydrophobic
groups. The addition of sodium chloride will reduce the size of the hydrophilic
group, whilst the octanol may disrupt the packing by penetrating the alkyl
chains and taking part in micelle formation. Although this idea of disrupted
packing may be wrong, the final result is likely to affect the overall packing to
make a stable structure. The resulting micelle can then absorb considerably
more heptane but, more importantly, the removal of the chain packing
restraints can lead to a liquid heptane core and the swollen micelles are
transformed into microemulsions. Why does this not happen with SLABS
alone? Because the packing of the molecules into the spherical micelle gives a
structure which is too stable to be increased. This situation persists until the
relative sizes of the chain and polar head can be changed e.g. salt addition.
For packing ratios less than 1/3, spherical aggregates are formed in aqueous
 USE OF SURFACTANT THEORY 47
solution but when P is between 1/3 and 1/2 then rod shaped micelles form. As P
increases beyond 1/2 towards 1, microemulsions form. If P is greater than 1
then water in oil emulsions form, with microemulsions from P just greater than
1, and coarse emulsions with low solubilisation at P greater than 2.
One prediction from this idea is that microemulsions can readily change
from O/W to W/O as there is the least change in P for this process. Therefore
addition of electrolyte, temperature change, co-surfactant addition and
co-solvent addition will all be expected to give the most significant changes
in properties to surfactants which have P close to l.
The most common surfactants used for detergents must have P very much
less than I because they readily form O/W emulsions not susceptible to
change by electrolyte, do not easily form microemulsions and do not solubilise
high volumes of solvents.
Note that there is no actual need for the sodium chloride and octanol if a
surfactant can be found with the required relative sizes of hydrophilic and
hydrophobic groups. Such a product is diisooctyl sulphosuccinate (DIOS)
where there are two alkyl chains and where the hydrophilic group could be less
than the hydrophobic group. DIOS will dissolve in heptane and can solubilise
water to form water in oil microemulsions.
Non-ionics are different to the ionic surfactants in having very large
hydrophilic groupings. From the postulates proposed above, they would
therefore be expected to form very small spherical micelles. However, although
they form micelles at much lower concentration than ionics the micelles are
considerably larger. If we assume the ideas above are correct then we must
assume the effective hydrophilic group is much smaller for the polyethylenegly-
col group than for ionic groups. There is some evidence to suggest this may be
true (Baglioni et aI., 1989). As the EO content increases the packing ratio
should decrease making the non-ionic more akin to the ionic. One should not
attempt to use this picture of the packing as being solely dependent upon the
effective cross-sectional area, since the chain lengths must play some part in
both the packing, and the size of the micelle which is formed.
This concept does explain the cloud point of non-ionics. Increase of
temperature reduces the effective head area due to the loss of solvation on the
EO chain. P will then increase to give a more planar surface, i.e. larger
aggregates, which is what happens. They should also become more asym-
metric and influence viscosity appreciably.
These concepts can be extended to explain the relationship between the
formation of microemulsions and very low interfacial tensions. A good
account is given by Aveyard (1987).

References

Aveyard, R. (1987) Chern. Ind. 20, 474.

Baglioni, P., Bengiovanni, R., Rivara-Minten, E. and Kevan, L. (1989) J. Phys. Chern. 93(14)
5574-5578.
48 HANDBOOK OF SURFACTANTS

Biswas, A.K. and Mukherji, B.K. (1960) J. App/. Chem. 10, 73.
Bland P. and Winchester, J.M. (1968) Proceedings of the fifth International Congress on Surface
Activity, Barcelona, Ill, 325.
Falbe, J., ed. (1987) Surfactants in Consumer Products, Springer-Verlag, New York, p. 165.
Gray, F.W., Krems, I.G. and Gerecht, J.F. (1965) J. Am. Oil. Chem. Soc. 42, 298.
Griffin, W.e. (1949) J. Soc. Cosmet. Chem. 1, 311.
Gruntfest, I.J. (1951) Textile Res. J. 21, 861-966.
Komor, lA. and Beiswanger, I.P.G. (1966) J. Am. Oil Chem. Soc. 43, 435.
Lunkenheimer K., Miller, R. and Hartenstein, e. (1981) Colloids Surfaces 3,329.
Myers, D. (\988) Surfactant Science and Technology, VCH, New York, Chap. 3.
Shapiro, L. (1950) Am. Dyestuff Report 39, no. 2, Proc. Am. Assoc. Textile Chemists Colorists,
pp. 38-45, 62.
Wingrave, lA. (\981) Soap/Cosmetics/Chemical Specialties Nov, 33-40.
Wrigley, A.N., Smith, F.D. and Stirton, A. (1957) J. Am. Oil Chem. Soc. 34, 39.
5 Surfactants commercially available

The first requirement of any practical user of surfactants is to find out if a

particular surfactant is available commercially in the required quantities, and
in the right price range. Directories giving details of which specific products
are available do exist (see Chapter 3); Chapters 6-11 do not attempt to replace
these sources of information. Most directories will have considerable detail on
where to find products, trade names, approximate compositions and sug-
gested applications but lack details of the composition and properties of
different classes of surfactant. Chapters 6-11 attempt to classify products,
describe their composition, give a description of the physical and chemical
properties, the applications in which they are used and some suggested tests on
which to base a specification for quality and reproducibility. There are
speciality books dealing with all these aspects but these chapters summarise
these features to enable the user to obtain an initial choice of the surfactant.
They should also give a quick easy summary ofthe principal properties ofthose
surfactant types which are unfamiliar. All the types of surfactants described are
commercially available at the time of writing.
Although considerable work and care has been taken in drawing up this
information, the reader must beware of the limitations in summarising
information on surfactants. These are:
• Quantitative data is difficult to provide in every case.
• Generalisations will always have exceptions.
• Commercial surfactants are not pure compounds, therefore samples of
apparently the same product from different manufacturers may have
slightly different properties.
Nevertheless the type of information given is that information which
accumulates in a formulator's mind over a period oftime. These summaries are
to try and give the beginner the benefit of experience. Every statement should
be checked off against practical experience and, if differing, then a note to that
effect should be made. However do not let one exception make a new
generalisation which is equally misleading.
The information presented does not generally have references as it is a
combination of the writer's experience, information from trade literature and
information from published sources. Giving numerous references to justify
every statement would not be helpful. However, there are occasions where
information is available which is useful and seems logical, but the writer has
50 HANDBOOK OF SURFACTANTS

not been able to find corrobatory evidence or has no personal experience. In

this case a reference is given to the original information.
The information is presented in a standard format. The standard sections
are as follows.
1. Nomenclature. The various technical names and abbreviations are given
to the appropriate surfactant. Common names and chemical names are
given but not trade names except where these have achieved common
name status. The names given are under two headings: (i) Generic, which
decribes the class of surfactants covered by the section; (ii) Examples,
gives specific examples of the most common surfactants in that generic
class. In some cases a chemical formula is given but readers must keep in
mind that practically no commercial surfactant is a pure product.
2. Description. Identifies the major chemical constituents in the named
class. All surfactants are mixtures, some more than others, and it is
important to realise this fact when comparing the end effect of one
product with another. A very brief description of the method of
manufacture of the surfactant type is given. This is often useful in
appreciating the composition of the surfactant and how products can
differ in composition and hence properties. Chemical impurities are
described which might be important. Impurities are defined as those
chemicals which are not normally described by the chemical name of the
class. This feature is becoming more important due to more attention
being paid by legislation and the public's attitude towards chemicals. In
most cases the impurities are no more harmful than the major
component but it is well to know of their existence, their properties and
how to .detect them.
3. General properties. The general physical and chemical properties and end
uses are summarised rather than giving tables of detailed information.
An attempt has been made to emphasise that particular property which
makes that particular surfactant different from other surfactants. Com-
parisons are made between the type described and very similar types. The
properties covered are:
• Solubility. Of primary importance to a user because most formul-
ations are liquids in solvent, the most common being water. The
information presented is for the surfactant alone but the solubility can
be changed wit~ mixtures of surfactants and other non-surfactants,
e.g. hydrotropes.
• Chemical stability. Surfactants will need to be stable in the formul-
ation in which they are used for two reasons, storage stability of the
formulation and chemical stability under the conditions of use. In
aqueous solution hydrolysis is of paramount importance particularly
if the pH of the solution is far removed from 7, as is often the case for
detergents. Other components such as oxidising (bleach) or reducing
 SURFACTANTS COMMERCIALLY AVAILABLE 51
agents can attack the organic-based surfactant. In actual use, tempera-
tures can often be 10(rC or higher for aqueous solutions, e.g. deep oil
wells and so hydrolysis at high temperatures can be a determining
factor on whether or not a surfactant is used.
• Compatibility with aqueous ions. This is quite different to chemical
stability but refers principally to the effect of hard water or inorganic
ions on solubility. Most formulations used in the aqueous phase are
diluted with water which may be hard or soft. Many formulations also
contain added polyvalent ions, e.g. polyphosphates and such ions can
often cause considerable solubility changes in the surfactant. Such
solubility changes can affect storage stability and performance as
solubility is related to surface activity.
• Compatibility with other surfactants. Where there are exceptions to
the general rules (see below) mention is made of this fact, particularly
where surfactants cannot be so easily classified.
• Surface active properties. Very basic surface active properties such as
the critical micelle concentration and the surface tension in water are
generally available for most major surfactant types. Such information
is interesting but should not be used as the only criterion for the
selection of surfactants. Most of the information on critical micelle
concentrations was obtained from Makurejie and Mysels (1971). Most
of this data is on purified compounds and can differ significantly from
measurements on commercial samples.
• Functional properties. The properties covered in this section are
wetting, dewetting, foaming, defoaming, dispersing, antistatic and
detergency. These are the most important sections in the general
properties and are a guide to surfactant selection once the connection
between the functional properties and the applications can be
correlated.

4. Applications. The most significant applications are given and these will
often be detergents and cleaning as these are the ma~:)r uses of surfactants
by volume. However, industrial uses will be mentioned where particular-
ly relevant and also the principal characteristic of the surfactant which
determines its use, e.g. wetting property in a paint for difficult to wet
surfaces.
5. Specification. In most cases the surfactant manufacturer will assist in the
analysis of his product. The user's main concern will be in the
specification of the material which will help him in checking product
variability. This section contains the most useful tests found in specific-
ations and has a two-fold use: (i) To help the user in checking the
surfactant for batch to batch variation in chemical constitution. In most
cases the surfactant manufacturer will give this information and a lot
more. However the list of specifications given are the most important. In
52 HANDBOOK OF SURFACTANTS

some cases there is reference to the amount of impurities, this mayor may
not be important depending upon the end use. (ii) To help in
identification.
6. Safety. No statements are made on safety other than in a few special
cases. The main reason is that it is impossible to make a general
statement on safety on a group of surfactants. The primary source on
safety data is the surfactant manufacturer or supplier.
The classification given is based on chemical structure of the hydrophilic
group:
• Anionic: The surface active part ofthe molecule carries a negative charge,
e.g. C12H25~CO~O- Na +, has a long chain hydrophobe carrying the
negative charge
• Non-ionic: The surface active part of the molecule apparently carries no
charge, e.g. C12H25~O~(CH2CH20h~H
• Cationic: the surface active part ofthe molecule carries a positive charge,
e.g. C 12 H 25 N(CH 3h + CI-
• Amphoteric: The surface active part of the molecule can carry a positive or
a negative charge or both depending upon the conditions, e.g. C12H25~
N+(CH3}z~CH2COO-

Speciality surfactants which are chemically quite dissimilar, e.g. silicones,

fluorocarbons, have been described quite separately although they are strictly
examples of a particular hydrophobe. There are anionic, cationic, non-ionic
and amphoteric silicones but they are all included under silicones. The
classification adopted is not strictly scientific but more based on common
usage in industry. Every series of classification has merits and demerits but the
comprehensive index should enable the reader to quickly find the product
group required.
Some generalisations are as follows but note that exceptions can always be
found.
1. Anionic surfactants are generally not compatible with cationics and also
vice versa.
2. Non-ionics and true amphoterics are compatible with each other and
with anionics or cationics.
3. If the hydrophobic group is an alkyl paraffin chain then maximum
surfactant properties in aqueous solution are in the region ofClO~C18
length of the hydrocarbon chain. Straight chain alkyl groups show
increased viscosity, better biodegradability and inferior solubility com-
pared to branched chain or ring-containing similar surfactants.
4. More than one hydrophilic group in the surfactant molecule will
increase solubility and shift the optimum chain length ofthe hydrophobe
to higher carbon numbers.
5. If the surfactant can react with ethylene oxide then the products are more
 SURFACTANTS COMMERCIALLY A V AIL ABLE 53
water soluble than the starting material. The larger the amount of
ethylene oxide the better the water solubility.
6. Organic sulphates are readily hydrolysed by hot acids. Organic esters are
hydrolysed by acids or, more readily, by alkalis. Organic amides are
more resistant to hydrolysis than esters or sulphates. Organic
sui phonates are resistant to hydrolysis by hot acid or hot alkali.

Reference

Makurejie, P. and Mysels, K.1. (\971) Critical micelle concentration of aqueous surfactant
systems, National Bureau of Standards (US), 36, 227.
6 Anionics

Anionics are manufactured and used in greater volume than all other types of
surfactants. The reason is the ease and low cost of manufacture. and they are
used in practically every type of detergent. the main application of surfactants.
For optimum detergency the hydrophobic group is a linear paraffin chain in
the range C12-C16 and the polar group should be at one end of the chain.
Hence the majority of water soluble anionc surfactants available on a large
scale are of the type
cccccccccccccccccc-x
X is the hydrophilic group which is ionised and can be:
• Carboxylate (soap) RCOO-
• Sulphonate RSO;
• Sulphate ROSO;
• Phosphate ROPO(OH)O- (monophosphate)
The main types of anionics commercially available are:
1. Carboxylates: soaps; ethoxy carboxylates; ester carboxylates
2. Isethionates and taurates
3. Phosphates (ethoxylates, alcohols, amides)
4. Sarcosinates (amide sarcosinates)
5. Sulphates: alcohol; alcohol ether; alkanolamides ethoxylates; natural
oils; nonyl phenol ether
6. Sulphonates: alcohol ether (ethane) or alkyl phenyl ether; paraffin; alkyl
benzene; fatty acids and esters; naphthalene derivatives; olefin
sulphonates; petroleum sulphonates
7. Sulphosuccinates and sulphosuccinamates
8. Taurates
Note that soap is a generic name being the alkali metal salt of a carboxylic
acid derived from animal fats or vegetable oils. Whether to classify sulpho fatty
acid esters as sui phonates or carboxylic acid derivatives can be argued either
way. They have been classified here as sulphonates as their properties are
more similar to sulphonates than carboxylates.
The cations most commonly used are sodium, potassium, ammonium,
calcium and various amines principally isopropyl amine, monoethanolamine,
diethanolamine and triethanolamine. The triethanolamine salts give impro-
 ANIONICS 55
ved solubility in water over the sodium salts. Products containing ethylene
oxide in the molecule have superior aqueous solubility, compared to similar
molecules without the ethylene oxide. The calcium salts and the
aminejalkanolamine salts generally give better solubility in non-aqueous
solvents. The magnesium salts, formerly hardly used at all, are now becoming
more common.
Regarding solubility, carboxylic acid salts are more sensitive to low pH,
polyvalent cations and inert electrolyte in the aqueous phase than are the
corresponding salts of phosphorus, sulphate or sulphonate.
Regarding chemical stability, sulphonates contain the C-S bond, which is
more stable chemically than the C-O-S bond of the sulphates or the C-O- P
bond of the phosphates. Both sulphates and phosphates are esters and capable
of being hydrolysed back to the free acid and alcohol. Thus sui phonates and
carboxylates are more stable to hydrolysis and extremes of pH than are
sulphates or phosphates.
The decreased use of the carboxylates (soaps) is due to the superior
detergent performance of sulphonates and sulphates in hard water when
properly formulated.

6.1 Carboxylates

Carboxylates are those surfactants with the hydrophilic (ionic) group being a
carboxyl group, -COOH. Soaps are the alkaline earth salts of the carboxylic
acids of fatty acids, i.e. C 17 H 3S COONa is the sodium salt of stearic acid and
is a soap. There are now commercially available modified carboxylates
with additional functional groups. These have improved solubility in hard
water.
1. Ethoxy carboxylates: addition of the polyoxyethylene chain (see
Section 6.1.2). General structure is RO(CH 2 CH 2 0).CH 2 COO-
2. Ester carboxylates: addition of a hydroxyl or multi-COOH groups (see
Section 6.1.3).
3. Sarcosinates: addition of an amide group (see Section 6.1.4). Products
with the general structure RCON(R')COO-.
4. Half ester sulphosuccinates: addition of a sulphate group (see
Section 6.7.1).
5. Betaines: addition of an amine group (see Section 9.2).

6.1.1 Soaps

The most important soap-forming fatty acids are, from a practical point of
view: CI2 (dodecyl) straight chain saturated acid; C14 (myristyl) straight
chain saturated acid; ClS (stearic) straight chain saturated acid; ClS (oleic)
56 HANDBOOK OF SURFACTANTS

straight chain, singly unsaturated acid. It is no coincidence that below

C8 the products are very soluble in water, between C8 and C18 sparingly
soluble, and above C20 insoluble in water. Optimum surface active properties
are obtained with the sparingly soluble products. Most commercial soaps, e.g.
the tablet of soap with which you wash your hands, will be a, mixture of fatty
acids obtained from tallow, coconut oil, palm oil, etc.
Soap has the following attractive features:
1. Widely produced and used in very large volume
2. It is an excellent detergent
3. The raw materials are independent of the price and availability of
petroleum
4. Biodegrades very readily
5. Toxicology well known
Why then has it been replaced on such a large scale? The big disadvantage of
soaps is their instability towards heavy metal ions, particularly the calcium
and magnesium salts found in hard water, and also their instability towards
acids. In both cases the end result is the same, the soap comes out of aqueous
solution because of the low aqueous solubility of either the calcium and
magnesium salt, or the free fatty acid. This shortcoming was possibly the most
important single factor in stimulating the development of the newer synthetic
surface active agents.
It is well to bear in mind that in the absence of these conditions soaps can
give excellent performance. Also, there has been considerable effort to use
additives (known as lime soap dispersing agents) to reduce these adverse
effects. Soap is of considerable interest particularly in countries with a plentiful
supply of fats and oils and without petroleum.

Nomenclature

Generic:
Soap
Carboxylic acid salts
Examples:
Tallow soap, sodium salt of a mixture of carboxylic acids made from tallow
Tall oil soap, sodium·salt of a mixture of carboxylic acids made from tall oil
For the names of all the commonly occurring fatty acids see Appendix 1.

Description

Soaps are produced on a very large scale by a very small number of

manufactures (Proctor and Gamble, Unilever, Henkel and Colgate) by the
 ANIONICS 57
saponification of natural oils and fats. The most common carboxylates
produced are:
• Tallow soaps, i.e. soaps produced from tallow (oleic 40-45%, palmitic
25-30%, stearic 15-20%)
• Coconut soaps, i.e. soaps produced from coconut oil (C12 48%, C14
17-20%, C16 8-10%, oleic 5-6%)
• Oleic soaps, i.e. soaps produced from olein
• Tall oil soaps, i.e. soaps produced from tall oil (mixture of fatty acids and
rosin acids from wood). Distilled tall oil (DTO) usually consists of
25-30% rosin acids, 70-75% fatty acids (composition: saturated 5%; oleic
acid 25%; linoleic acid and other unsaturates 70%). Tall oil fatty acids are
acids of similar composition but with rosin contents of 1-10%.
• Coconut acid (the starting material for many surfactants) has the
following composition
C12 (lauric acid) 46-50%
C14 (myristic) 17-20%
Cl6(palmitic acid) 8-10%
C8 (caprylic acid) small amounts
CIO (capric acid) small amounts
Cl8(0leic acid) small amounts
Stripped coconut fatty acids are often described as lauric acid.
• Naphthenates occur in crude petroleum and are complex mixtures of
linear C6 and C7 acids plus alkyl and alkyl carboxyl substituted cyclic
pentanes. Products used as surfactantshave molecular weight 250-350.
Once widely used but now being phased out of surfactant applications.

General properties

1. Solubility. C12 saturated soaps soluble in water, C18 soaps very slow to
dissolve. C16-C18 unsaturated soaps soluble in water. The potassium
salts of soaps are more soluble than the sodium (this is the opposite to
sulphates where the potassium salt is more insoluble). The alkanolamine
salts (MEA, DEA and TEA) have better solubility. The TEA salts of
lauric acid and oleic acid are milder than the sodium salts, more soluble
and have better foaming properties. Tall oil fatty acids (i.e. made with
unsaturated acids) are more water soluble and give lower viscosity
solutions than those from tallow.
2. Chemical properties. Insoluble in aqueous solution below pH 7 due to
the formation of the water insoluble free fatty acid.
3. Compatibility with aqueous ions. All the soluble salts are readily
insolubilised by electrolytes and salted out, e.g. by NaCI, etc. Soaps do
not perform well in hard water (reduction in solubility and foaming
5S HANDBOOK OF SURFACTANTS

ability) because of the insolubility of the calcium and other divalent and
trivalent salts. Acts as builders in conjunction with anionic/non-ionics.
4. Surface active properties. CMC C12(saturated) sodium salt molecular
weight 222.3 = 2.6 x 10- 2 M (0.57%); CMC ClS(saturated) sodium salt
molecular weight 306.5 = l.S x 10- 3 M (0.055%); CMC CIS (unsat.
oleate) sodium salt molecular weight 304.4 = 2 x 10- 3 M (0.06%).
5. Functional properties
• Foaming: Sodium stearate gives rich creamy foam but oleate,
laurates and tallates give more open foam; oleates give thick creamy
foam but with less total foam so a mixture of coco and oleic gives
copious foam with excellent stability (e.g for shampoos).
• Defoaming: CIS soaps give defoaming of other surfactants in the
presence of calcium.
• Emulsifying properties: can be made in situ (e.g. for use as an
emulsifier by adding fatty acid to the oil phase and alkali to the
aqueous phase).

Applications

1. Personal care. The main application is soap bars for washing (standard
bar is SO% beef tallow/20% nut oil (either coconut or palm kernel).
Soap for washing in sea water and liquid soaps are made from
sodium/potassium salts of coconut oil fatty acids (CI2-CI6).
2. Household detergents. Used in 1: 1: 1 sulphonate:soap:non-ionic liquid
phosphate-free liquid heavy duty detergents; foam depressant in heavy
duty detergents (ClS-C22).
3. Industrial laundries. Soap can be used on its own as most industrial
laundries have water softeners. Blends with LABS and non-ionics are
also used with very similar formulations to those used in household
heavy duty detergents.
4. Pine oil disirifectants. Castor oil soaps were used very widely, but their
use is now diminishing. A typical formula is: chlorinated phenols, 3-5%;
pine oil, 5-lO%; industrial alcohol, 10-20%; 25% castor oil Na salt,
20-25%; water, to 100%.
5. Cosmetics and shampoos. In soft water, soaps have most of the
properties desirable in a shampoo but to obtain clear soap solutions the
pH must be alkaline. The alkalinity causes roughening of the scales of
the hair cuticle thereby giving a dull appearance. These disadvantages
can be overcome by a mild acid rinse or by using the less alkaline
alkanolamine salts. In hard water, soaps also cause dullness by the
deposition of calcium and magnesium soaps on the hair. This can be
prevented by the addition of a lime soap dispersant or of sequestering
agents for calcium and magnesium ions, e.g. EDT A or polyphosphates
but these agents have no effect on the alkalinity of the soap. Free fatty
 ANIONICS 59
acids give conditioning in shampoos below pH 8; CI8 thickener for
surfactant solutions and opacifier.
6. Textile industry. Scouring; potassium oleate used in gel foam for carpet
backing latices.
7. Paper industry. Dispersing agent in paper coating mixtures.
8. Emulsion polymerisation. 20% potassium oleate used as the main
emulsifier for crumb SBR rubber.
9. Oil field chemicals. Emulsifier for drilling muds.
to. Polishes. Water resistant film from aqueous solutions; ammonia, mor-
pholine or other volatile amine salts are used in polishes where the
evaporation of the amine leaves only the free acid which is then
insoluble in water, thus preventing re-emulsification. The same
principle has been used in waterproofing textiles.

Specification

Saturated acid Oleic acid

Titre ("C) 54-67 Flow point 5-7

Iodine value (unsaturation) 1-4 90
Acid value (mg KOH/g) 196 for C18 197-203
242 for C14
Sap value 197 for C18 198-205
Unsap material 0.2-1.2 0.2-0.5

6.1.2 Ethoxy carboxylates

Nomenclature

Generic:
Alkyl (poly-I-oxapropene) oxaethane carboxylic acids
Alkyl (e.g. lauryl) polyglycol ether carboxylic acids
Alkylphenol polyglycol ether carboxylic acids
Carboxymethylated alcohols
Ethoxy carboxylates
Ether carboxylates
Polyalkoxylated ether glycollates
Example:
Lauryl alcohol + 3EO carboxylate, sodium salt: C12HzsO(CHzCHzOh-
CH 2 COO- Na+.

. Description

These products are the ethers of glycolic acid, HO-CH 2 -COOH, prepared
60 HANDBOOK OF SURFACTANTS

by the reaction of chloracetic acid with the corresponding ethoxylate.

RO(CH 2 CH 2 0)n H + CICH 2 COOH ---. RO(CH2CHzO)nCH2COOH + HCI
A very large number of products are possible but, if prepared by the above
route, they will all contain chloride ions, unless purified. The ethoxylate can
have an alcohol, nonyl phenol, a fatty amine or an acid as starting material but
the ethoxylated alcohols (as shown above) are the most common.
The reaction above does not go to completion and therefore the starting
non-ionic can remain as an impurity. Salt is present, e.g. NaCI in the sodium
salts, unless it is deliberately removed.

General properties

1. Solubility. The addition of the ethoxylated grouping results in increased

water solubility in the products. HLB values vary from approx. 8 with
excellent solubility in organic solvents, to 20 where the products are only
soluble in polar solvents. Generally good lime soap dispersant. Good
alkali solubility.
2. Chemical stability. Does not hydrolyse in alkali or acid.
3. Compatibility with aqueous ions. Stable to addition of electrolyte;
improvement of properties in hard water compared to soap.
4. Compatibility with other surfactants. Compatible with non-ionics and
amphoterics; compatible with some cationics; good lime soap dispersant.
5. Surface active properties. The CMC is reached at lower values for the
acid than for the salt. Also the micelles formed in acid solution are smaller
than for the salt. Thus it is possible to adjust the micelle size which is an
important feature of emulsification. The surface tension increases with
increasing pH. Moderate surface tension reduction, C12 acid + 2.5 EO
methyl carboxylate = 33, dynjcm at 1 gjlitre.
6. Functional properties. Retains the best properties of non-ionic surfact-
ants, i.e, wetting without the inverse solubility with temperature (no
cloud point); good dispersing properties (e.g. pigments in paint); good
foam stability; good anticorrosive action; very mild and non-aggressive
action on hair and skin and reduces the skin irritation of LES.

Applications

1. Household products. Stable to hydrochloric acid and used in toilet

cleaners; thickener for bleach, high EO content; soap additive to give
liquid fatty acid soaps.
2. Textiles. Detergent, cloud point elevated to more than 100°C; kier
boiling in caustic. (Fr. Patent 848, 529 (Sandoz)) dye bath auxiliaries;
fabric softeners particularly for woollens (i.e. dialkyl adducts as base);
spin finish antistatic agents particularly if amine-based.
 ANIONICS 61
3. Shampoos. (Gerstein T. USP 3,990,991 (Revlon 1976)) mild and some
conditioning properties are claimed particularly at low pH. Gives
creamy foam, particularly in hard water and improves lubricity. Used in
conjunction with ether sulphates to improve foam and reduce irritation.
Compatible with cationics (including cationic polymers). The ether
carboxylate can be used for the cleaning part of the formulation with the
cationics giving excellent conditioning.
4. Paint. Dispersing agents.
5. Aerosols. Carpet shampoos.
6. Metal treatments. Boring and cutting oils, de-oiling baths.

Specification

Solids content, 90%

Active content, 70-80%
Sodium chloride, 1-15%

6.1.3 Ester carboxylates

Nomenclature

Generic:
Ester carboxylates
Long chain esters of 0 H acids
COO(CH2CH20hC12H2S -
I
CH 2
I
HOCCOO Na+
I
CH 2
I
COO(CH2CH20hC12H2S

Sodium di (lauryl alcohol + 7EO) citrate

Sodium lauryl alcohol + 7EO tartrate

Figure 6.1 Examples of ester carboxylates.
62 HANDBOOK OF SURFACTANTS

/(COOH)n-l
R-OH + HO-X-(COOH)n---HO-X~COOR + H20
Figure 6.2 Preparation or ester carboxylatcs.

Example:
Sodium di(lauryl alcohol + 7EO) citrate (see Figure 6.1) or sodium
dilaureth-7 citrate
Sodium lauryl alcohol + 7EO tartrate (see Figure 6.1) or sodium laureth-7
tartrate

Description

The reaction of a long chain fatty alcohol (or ethoxylate) with a multi-
functional carboxylic acid (esterification). The multifunctional fatty acid
usually contains hydroxyl groups (see Figure 6.2). These products do not
contain the same large amounts of chloride ions as the ethoxy carboxylates
(Section 6.1.2) but they do have the disadvantage of containing an ester group
R-COO which can hydrolyse in solution whereas products such as the
ethoxy carboxylates have ether groups which are stable to hydrolysis. Typical
products would be made with citric or tartaric acid as the multifunctional
carboxylic acid and lauryl alcohol + 5-7EO.

General properties

1. Solubility. Products are usually very soluble in water in the C12-C16

range.
2. Chemical stability. About 80°C maximum in aqueous solution.
3. Surfactant properties. The lowest surface tension is found with sodium
dicoco + 7EO citrate at 31.5 dyn/cm and similar to ether sulphates.
4. Functional properties. Moderate wetter (Draves 2 gllitre 50-1 JO ms
(NaLABS is 10 s)); good foaming, Ross Miles for Na CI2 + 7EO tartrate
1 gil = 145 ml; good detergency; solutions can be thickened with
viscosity modifiers, e.g. PEG 6000 distearate.

Applications

1. Cosmetics. Sodium lauryl alcohol + 7EO tartrate or sodium di(lauryl

alcohol + 7EO) citrate can be used as a shampoo detergent but gives
a more economical formulation mixed with AES. Such mixtures show
considerably reduced skin irritation with AES when only small
quantities of the citrate are added.
 ANIONICS 63
2. Liquid detergents.
3. Institutional surface cleaners.

Specification

Activity, 25% aqueous soln. typical

Alkalinity value 10-30mg KOH/g
Sap value 15-18mg KOH/g

6.2 Isethionates

Nomenclature

Generic:
Acyl oxyalkane sulphonates
Esters of isethionic acid HOCH 2 CH 2 S0 3 H (note, the taurates (see
Section 6.8) are amides of methyl taurine CH 3 NHCH 2 CH 2 S0 3 .)
Isethionates
Sulphoalkyl esters
Examples:
Coconut fatty acid, 2-sulpho ethyl-I-ester, sodium salt formula,
CocoCOOCH 2 CH 2 SO; Na+

Description

Preparation by reaction of acid chloride (of the fatty acid) with sodium
isethionate.
RCOCI + HOCH 2 CH 2 S0 3 Na ----4 RCOOCH 2 CH 2 S0 3 Na + HCl
sodium isethionate
The sodium isethionate is prepared from ethylene oxide and sodium sulphite.
Some typical impurities are salt 8-10% but some products very low ( < 1%);
soap; fatty acid; unreacted sodium isethionate.

General properties

1. General. The esters were originally known as Igepon A (now Hostapon,

Hoechst trade name) and have properties similar to those of alkyl
sulphates with similar chain length although the foaming properties may
be slightly inferior.
2. Solubility. Sodium salt ofC12-14 soluble in hot water (50~<) soln at 70°C)
but very low solubility in cold water (0.01% at 25°C); sodium salt of oleic
acid 11 '!~ soluble at 70°C, 2.5~1., at 25°C.
64 HANDBOOK OF SURFACTANTS

3. Compatibility with aqueous ions. Practically unaffected by calcium ions;

50% mixture with soap considerably reduces scum and precipitation in
hard water.
4. Chemical stability. Suitable for use at pH 6-8 but hydrolyses outside this
range in hot water. This limits their usefulness to solids and powders.
5. Surface active properties. Coconut derivative, surface tension at
0.1 % = 27 dyn/cm; oleic derivative, 28 dyn/cm.
6. Functional properties. Good foaming properties (0.05% Ross and Mile
initial foam coco derivative 93 ml, oleic derivative 145 m!) not as good
as alkyl sulphates; gives excellent foaming properties when used as a
mixture with soap; excellent detergent for grease and oil; good lime soap
dispersant (coco derivative 15-20 index, oleic acid derivative 15-20
index).
7. Disadvantages. Unstable in aqueous solution at high temperatures and
high and low pH.

Applications

1. Household products. Synthetic bar soap, excellent for removing grease

and oily dirt and good foam in hard water. Typical formula: 78% active
powder (coco derivative), 20 parts; water, 12 parts; tallow soap/coco soap
(80/20), 68 parts.

Specification

Appearance, powder
Active, 70-80%
Sodium chloride, 1-10%
Free acid, 1-10%

6.3 Phosphate esters

Nomenclature

Abbreviations: PE, phosphate esters, used in this book.

Generic:
Alkyl acid phosphates
Alkyl ether phosphates
Alkyl phosphates
Dialkyl pyrophosphates
Monoalkyl phosphates
Phosphate esters
Phosphated alcohols (or ethoxylated alcohols)
 ANIONICS 65

Examples:
Lauryl alcohol + 7EO phosphate or lauryl polyethyleneglycol phosphate.

OH OR OR
I I I
R-OH+HO-P=O~HO-P=O+HO-P=O
I I I
OH OH OR
monoester diester
Figure 6.3 Reaction between an aleohol and phosphoric acid.

Description

The reaction between an alcohol group and phosphoric acid is shown in

Figure 6.3. This equation is an over simplification as a mixture of mono-, di-
and triesters plus polymeric esters are formed together with some of the
original phosphoric acid. There are two phosphorylating agents in use,
tetraphosphoric acid (TPA) and phosphorous pent oxide (P 2 0 S )' The reac-
tions involving TPA are now well understood, and the major product is the
monoester. The reactions involving P2 0 S are more complex but the major
product is diester. The majority of commercial products are made with P 20 S
and are therefore predominantly diesters, but with significant amounts of
monoester and polymeric esters present.

General properties

1. General. The phosphate esters have properties intermediate between the

ethoxylated non-ionics and the sulphated derivatives. Thus they have
good compatibility with inorganic builders. good emulsifying properties
and a foaming capacity intermediate between the low-foaming non-ionics
and the high-foaming ether sulphates. Properties compared to the
parent ethoxylate after reaction with TPA are:

C12 ale. + 7EO C12 ale. +7EO+TPA

In 5% or 10% NaOH Insoluble Soluble

ST of 0.1 % solution at 25°C (dyn/cm) 30.3 37.0
ST of 0.1% solution at 60°C (dyn/cm) 33.7 34.2
Draves wetting times at 25°C (s) 7.5 26
Draves wetting times at 60°C(s) 31.5 21.5
Ross-Miles initial foam (ml) 104 152
Ross-Miles foam after 5 min (ml) 20 133
66 HANDBOOK OF SURFACTANTS

2. Solubility. Free acids have good solubility in both water and organic
solvents with the acidity comparable to phosphoric acid. However,
depending upon the hydrophobe, some phosphated non-ionic surfac-
tants are insoluble in water whilst the alkali metal salts are soluble.
Sodium salts of mono esters with long alkyl chains have poor solubility in
water. Alkali metal salts of products made from ethoxylated surfactants
by reaction with P 2 0 S (high diester content) are usually quite soluble.
However many commercial products are the potassium salts which have
better solubility than the sodium salts.
3. Chemical stability. Resistant to hydrolysis by hot alkali and colour not
affected, stable to acid solution and high temperatures.
4. Compatibility with aqueous ions. TPA phosphat ion gives products with
better electrolytic compatibility than with P 2 0 S ; can sequester iron and
other metal ions; polyoxyethylation gives good resistance to hard water
and concentrated electrolyte.
5. Surface active properties. Surface tension of the diesters decreases with
increasing alkyl chain length; branching of the alkyl chain gives lower
values than straight chain alkyl groups.
6. Functional properties. Efficient oil emulsification (better with P 2 0 S
products); good detergency on fibres; diesters have good wetting
properties with low molecular weight giving the best wetting properties;
excellent rinsability; lower foam than the corresponding sulphate or
sulphonate; corrosion inhibition; antistatic properties; good dispersing
agents (better with P 2 0 S products); hydrotrope properties (particularly
with short alkyl chains).
7. Disadvantages. Only moderate reduction in surface tension of aqueous
solution; more expensive than sui phonates; sodium salts not always
water soluble so the more expensive potassium and alkanolamine salts
are needed for aqueous solubility of a neutral phosphate ester; the
compositions of most phosphate esters are complex and difficult to
analyse.

Applications

1. Textiles. Lubricant and/or emulsifier with anticorrosive properties;

wetting agent in the presence of alkali, e.g. kier boiling (nonyl phenol
+ 13EO + P 2 0 s);"dye bath additive for even dying and better penetra-
tion; short chain alkyl esters are efficient antistatic agents in spin finishes
for sythetic fibres (C8 alcohol + P 2 0 s).
2. Detergents. Solubilisation of non-ionics in high concentrations of
electrolyte; dry cleaning soaps for antistatic effect.
3. Agriculture. Emulsifying agents in herbicides especially when blended
with concentrated liquid fertilisers; dispersing agents for aqueous
 ANIONICS 67
dispersions of insoluble herbicides or insecticides to give better storage
stability of the concentrated dispersion plus better flow properties;
lubricant additive and metal working; Cl2 alcohol + 6EO + P20S gives
good emulsifier for mineral oil but also good load carrying properties.
4. Antifoams. Cl8 alkyl monoester products are good antifoams for
anionic surfactants.

Specification

Difficult but essential as the product being used is a mixture. A test of

surfactant properties is often the best method of quality control. However
most of the chemical tests are adequate for showing batch to batch variation.
% Active, 100% for acids, 30-45% for potassium salts.
mg KOH/g to pH 5.2,85-110, an indication of high monoester concentration.
mg KOH/g to pH 9.3,160-220, an indication of high diester concentration.
Titration with KOH to two particular pH points is more useful than a
normal acid number.

6.4 Sarcosinates

Nomenclature

Generic:
Sarcosinates
N-Acyl derivatives of sarcosine (N-methyl glycine CH 3 NHCH 2 COOH)
Examples:
Lauryl sarcosine, C 12 H 2S CON(CH 3) CH 2 COOH

Description

Made from a fatty acid chloride and N-methyl glycine

RCOCI + CH 3 NHCH 2 COOH --+ RCON(CH 3 ) CH 2 COOH (catalysed by
alkali) + NaCl
The product as made contains sodium chloride which can be removed. Most
commercial products contain considerable amounts of sodium chloride.

General properties

1. General. More acidic than fatty acids and therefore there is less need to
avoid free acid and pH control is easier; similar properties to isethionates.
2. Solubility. Sodium salt not very soluble in acid or neutral pH but quite
soluble in alkali; TEA salt more soluble at neutral pH.
68 HANDBOOK OF SURF ACT ANTS

3. Compatibility with other surJactants. Good compatibility with anionic,

non-ionic and cationics where they do not adversely affect the bacter-
icidal properties; compatible with quaternaries and phenolic biocides.
4. Compatibility with aqueous ions. Excellent, e.g. good foam with TEA
salt in hard water.
5. Chemical stability. Stable in acid and moderate acid at normal tempera-
tures; unstable in strong acid or acid at high temperatures, loses foaming
characteristics and thickens appreciably.
6. Functional properties. Foams well even in presence of sebum and oils;
foams better in hard water than soft water; good lime soap dispersant;
some bacteriostatic activity claimed.

Applications

1. Household products. Toothpaste ingredient, enzyme inhibiting, strong

foamer, good detergent; liquid soaps.
2. Personal care. Foaming agent in shampoos, boosts lather of alkyl
sulphates in presence of sebum and good foaming in the presence of
soaps; detoxifying agent in shampoos; addition to anionics improves
mildness, conditioning and foaming; shaving preparations; foam baths;
facial cleaners.
3. Surgical scrubs.
4. Corrosion inhibitor.

Specification

Activity, 30% for Na salt, 40% for TEA salt

Acid value, 50-60 mg KOH/g
Sodium chloride, 1-5%

6.5 Sulphates (general)

At one time the sulphates were the largest and most important class of
synthetic surfactants but have now been overtaken by the sulphonates in terms
of volume consumption. Organic sulphates are the esters of sulphuric acid, i.e.
"ROH + H 2 S0 4 -- ROS0 3 H
The sulphur atom is joined to the carbon atom of the hydrophobic chain via an
oxygen atom. The acid ester is unstable and can revert back readily to the
alcohol and sulphuric acid (particularly in acid conditions) whereas the
neutralised salts are stable at neutral pH. In !he case of a sulphonate (see
Section 6.6) the sulphur is joined directly to the carbon chain of the hydro-
phobe. In the manufacture of sulphates the neutralisation must be carried out
 ANIONICS 69
quickly to avoid the breakdown of the acid ester. In practice sulphuric acid is
very seldom used and chlorsulphonic or sulphur trioxide/air mixtures (in
continuous reactors) tend to be the most common methods of sulphating
alcohols (a fuller description is given in Section 6.6). The neutralisation is
usually carried out continuously with the sulphation.
Commercial products available with the R group on the alcohol can be:
1. A saturated linear hydrocarbon from natural or synthetic (oxo or Ziegler
alcohols) sources, CH 3 (CH 2).OH, with n usually in the range 8-13 and
usually linear. The products are then known as the fatty alcohol sul-
phates, e.g. sodium dodecyl sulphate from dodecanol (see Section 6.5.1).
2. Unsaturated alcohols, although sulphation/sulphonation can take
place on the unsaturated bond.
3. A long chain alcohol with ethylene oxide, RO(CH2CH20)nH, with
R = C12-CI5 and either natural or synthetic but usually linear and
with n commonly 2 or 3 but sometimes up to 10. The products are
commonly known as ether sulphates, e.g. sodium dodecyl ether sulphate
(see Section 6.5.2).
4. An alkylated phenol ethoxylate, RC 6 H 4 0 (CH 2CH 20).H, with R
commonly C9 based on tripropylene(nonyl) and therefore branched with
n commonly 4-20. The products are commonly known as nonyl phenol
ether sulphates (see Section 6.5.5).
5. A monoethanolamide ethoxylate, RCONHCH 2CH 20(CH 2CH 20).H,
with R commonly derived from a natural oil (e.g. coconut oil) with n
commonly in the range 3-6. The products are known as fatty acid
alkanolamide ether sulphates (see Section 6.5.3).
The properties of the sulphates depend upon the properties of the
hydrocarbon chain and that of the sulphate group. The properties of the
hydrocarbon chain are common to those of all other surfactants.
It is worth mentioning the secondary alkyl sulphates which were produced
by reacting oleum with alpha-olefins from cracked waxes. These products had
typical detergent sulphate properties but tended to have disagreeable odours
and dark colours. These products are no longer available in Western Europe
but they are relatively easy to make with simple equipment and may be
available in other parts of the world.

Properties of the sulphate group

1. Solubility. The alkali metal salts show good solubility in water.

2. Physical properties of aqueous solutions. Most surfactant sulphates show
what is known as the salt effect. The addition of inorganic salts (sodium
chloride, sodium sulphate) to dilute solutions (below about 30%) increases
the viscosity, whilst addition to concentrated solutions decreases the
70 HANDBOOK OF SURFACTANTS

viscosity. Any salts formed during the sulphation and/or neutralisation

can lead to viscosity changes. Sources of salts are moisture during
sulphation, hydrolysis of the acid prior to and during neutralisation and
the addition of hypochlorite bleach (by the surfactant manufacturer).
3. Chemical stability. Sulphates are easily hydrolysed particularly by acids
(below pH 3.5). The acid hydrolysis releases sulphuric acid which
catalyses the hydrolysis.
Acid conditions:
Alkali conditions: ROS0 3 Na + NaOH~ROH + Na 2 S0 4
The alcohol sulphates are therefore more stable in alkali than acid.
The stability depends upon a number of factors but for aqueous
formulations to give long-term shelf stability at room temperature, pH
range 5-9.5 is preferred. At elevated temperatures (> 50°C) sulphates are
unstable. The ammonia salts on the alkaline side (> pH 7) give off
ammonia which can be irritating in household products or give odours in
industrial products. The ammonium salts are also slightly superior to the
sodium or triethanolamine salts with regard to resistance to acid
hydrolysis.
4. Impurities. Hypochlorite bleach is very often added by the surfactant
manufacturer to produce better coloured material. Residues can often be
detected.

6.5.1 Alcohol sulphates

Nomenclature

Abbreviations: AS, alcohol sulphates, used in this book; ALS, ammonium

lauryl sulphate; F AS, fatty alcohol sulphate; LAS, sometimes used but it is
more often used for linear alkyl benzene sulphonates or linear alkane
sulphonates (paraffin sulphonates) and thus can lead to confusion.
Generic:
Alcohol sulphates
Examples:
Sodium lauryl sulphate C 12 H 2s S0 4 Na

..Description
'

Alcohol sulphates are now only available from primary linear alcohols which
can be natural or synthetic. Alcohol sulphates are not stable as the free acids, so
only the salts are commercially available. The most common form is the sodium
salt. Amine salts based on mono-, di- or triethanolamine and ammonia are also
offered by most manufacturers; these are usually 30-40% active. Solutions of
 ANIONICS 71
60-70% can be made and are sometimes offered by manufacturers. Alcohol
sulphates are now made by sulphonation of the alcohol with sulphur trioxide
(see Section 6.6).

General properties

1. Solubility. The common sodium salts of C12-C14 (dodecyl) alcohol

sulphates give gels at active concentrations above 30%. Below 30%
active, they will be liquid at normal temperatures but set to a soft paste
when the temperature falls below 25°C (the Kraft point, see Chapter 4).
Amine salts (MEA, DEA or TEA) improve solubility, DEA less soluble
than TEA but gives a lower viscosity solution. The amine salts darken on
storage particularly on exposure to light. The Kraft point depends upon
the distribution of carbon chains in the parent alcohol with a wide
distribution giving a lower Kraft point (around 10°C) and resulting
flowable solutions at room temperature. The solutions of fatty alcohol
sulphates show cloud points below room temperature which can vary
from one manufacturer to another. The main reason for the variation is
the amount of electrolyte and free alcohol remaining in the product.
2. Chemical stability. Both primary and secondary alcohol sulphate salts are
unstable to acid as described under Sulphates (general) (see Section 6.5).
3. Viscosity of aqueous solutions. The viscosity increases very rapidly
around 30-40% to give a gel, but then falls at about 60-70% to give a
pourable liquid, after which it increases again to a gel. The concentration
at which the minimum occurs varies according to the alcohol sulphate
used, and also the presence of impurities, e.g. unsulphated alcohol. The
position of the minimum can also be affected by temperature. Viscosity of
aqueous solutions can be reduced by the addition of short chain alcohols
and glycols. Easily thickened with alkanolamides (and salt). The viscosity
can be increased by addition of electrolyte (e.g. Cl- and SO~ -). The
MEA salt IS more sensitive to added inorganic salt (particularly the Cl
ion) than is the TEA salt. The effect of salt on the viscosity is also
dependent upon the concentration of unreacted fatty alcohol in the
alcohol sulphate. To thicken TEA salt, use alkanolamides or
cocoamidopropyl betaine.
4. Compatibility with aqueous ions. Stable to hard water at low alkyl chain
lengths (C 10) but sensitivity to hard water increases with increasing chain
length. Magnesium salts have improved stability over the sodium salts in
hard water and have higher alkali tolerance.
5. Surface active properties. CMC of sodium dodecyl sulphate molecular
weight 288.3 = 8 x 10- 3 M (0.24%). CMC of sodium octadecyl sulphate
molecular weight 372.5 = 2 x 10- 4 M (0.007%).
6. Functional properties. Foaming properties: foam volume and stability
72 HANDBOOK OF SURFACTANTS

increases in hard water compared to soft water; optimum foaming is with

C12-C14 mixture (especially if some free alcohol left) in hard water for
quantity and quality (forms small bubbles and a rich creamy foam); C8-
ClO is a foam depressant; ClO increases the flash foam; C14 lower
volume and less stable foam than C12-C14 mixture; C16-C18, less foam.
Wetting properties: good wetting agents but sulphation along the chain
(secondary alcohol) rather than at the of the chain will give a smaller
branched molecule (USP 2422613 and USP 2423692) with better
wetting but reduced detergency. Wetting also improves as the chain
le~gth of the hydrophobe is reduced. Excellent emulsifiers (particularly
for sebum); excellent detergency.
7. Disadvantages. Poor hydrolytic stability.

Applications

1. Household detergents. Tallow alcohol sulphate can be substituted for

LABS in heavy duty detergents to give lower foaming products but with
slightly superior detergency. Tallow is:

Beef Mutton

Oleic acid (%) 40-50 35-40

Palmitic acid (%) 25-35 25-35
Stearic acid (%) 19 30

Heavy duty liquids in conjunction with non-ionics.

2. Cosmetics and shampoos. DEA lauryl sulphate often used with lauro-
aminopropionates (amphoterics, see Chapter 9) to improve detergency
in shampoos. Sodium lauryl sulphate was once the main surfactant for
shampoos but had poor solubility (due to inorganic content from
chlorsulphonic acid manufacture) and needed alkanolamides
(cocomonoethanolamide at 10-15%) on the sulphate or glycols to give
clear solutions. It was, however, excellent for creams and pastes. Modern
manufacturing methods (S03) give AS with low amounts of electrolyte
and low alcohol, and thus a low cloud point. For pastes or creams it may
be necessary to add alcohol or salt to give the instability required.
Alternatively, addition of some C14-C18 alcohol will thicken/opacify.
The triethanoalmine salt gives clear products due to better solubility.
The addition of sarcosinate has been recommended with TEA sulphate
to improve lather. TEA sulphate has lost ground to the ammonium salt
(which is cheaper and avoids the nitroso problem), amphoterics or
monoester sulphosuccinates. At the present time, ammonium lauryl
sulphate is probably used in more shampoos than any other anionic
 ANIONICS 73
surfactant. The ammonium salt is claimed to be less irritant than the
sodium salt. Optimum alcohol blend for shampoos is: 70-75% C12;
25-30% C14.
3. Textiles. Low temperature detergent for delicate fabrics; dye retarder
when amine groups are present on the fibre; dyestuff dispersant in
aqueous media.

Specification

Active material, usually 30-40% for aqueous solutions

Mean molecular weight, 290-310 for sodium salt of C12-C14 alcohol
Carbon chain distribution:
Free MEA, DEA or TEA, < 3%
Unsulphated matter, up to 5% but most products now < 1%
Sodium sulphate, up to 2%
Sodium chloride, should be below 0.1 %
Cloud point (Kraft point) 1O-25°C
Viscosity, can vary over a very wide range.

6.5.2 Alcohol ether sulphates

Nomenclature

Abbreviation: AES, alcohol ether sulphates, used in this book.

Generic:
Alcohol ether sulphates
Ether sulphates
Ethoxy sulphates
Polyoxyethylene alcohol sulphates
Sulphated polyoxyethylated aliphatic alcohols
Examples:
Sodium C12-C14 3-mole ether sulphate (short hand description) means
that an alcohol consisting predominantly of C12-C14 hydrocarbon
chains has been reacted with 3 moles of ethylene oxide, then sulphated
and then neutralised with sodium hydroxide.
C12-C14 alcohol + 3EO sulphate sodium salt, same as above
Sodium laureth-3 sulphate, Cl2 alcohol + 3EO sulphate sodium salt
Sodium dodecane/oxyethylene/3 sulphate, nomenclature used by US Bureau
of Standards, this is the same as Cl2 alcohol + 3EO sulphate sodium
salt
Sodium lauryl ether sulphate (the amount of ethylene oxide is not defined);
very often used to describe sodium C12-C14 alcohol + 3EO sulphate
particularly in dishwashing detergents, shampoo and cosmetic formu-
lations
74 HANDBOOK OF SURFACTANTS

Description

These products are made by the sulphation of ethoxylated alcohols using

sulphur trioxide/air on continuous plants (see Section 6.6). It is possible to
make AES in batch reactors with sulphur trioxide injection but colours are
generally very poor. Generic formula is RO(CH2CH20)nS04 where R is a
hydrocarbon radical, usually linear and n is 2 or 3, although there are a few
speciality products with n in the range 4-10.
The sodium, magnesium, and ammonium salts are readily available from a
large number of manufacturers where n is 2 or 3. Practically all products are
based on natural or synthetic alcohols with 10-15 carbon atoms. The ranges
available are: 27-29% active, aqueous, based on the sodium or ammonium
salts, viscous liquids; 60% active, aqueous/alcoholic, based on the ammonium
salts, liquids; 65-70% active, aqueous, based on the sodium salts, mobile gels.
The hydrophobic alcohols used are similar to those described under alkyl
sulphates (see Section 6.5.1) but oxo alcohols with odd numbered carbon
chains are used to a greater degree than with alcohol sulphates. The free acid
is unstable (similar to the alcohoi sulphate (see Section 6.5.1)) and must be
neutralised as soon as it is made; 90% + active blends can be made by
neutralising the ether sulphate acid with a 2: I dialkanolamide. The high active
materials (65-70%) have several advantages. Reduction in transport and
storage costs are fairly obvious but high active materials exhibit increased
resistance to microbiological attack even if unpreserved. Also the level of
impurities tends to be somewhat lower in the high active materials.
Minor components and impurities include: (i) alcohol sulphate. This is
formed from the free alcohol which remains after the ethoxylation. Ethoxyl-
ation of alcohols under normal alkaline catalysis gives a broad range of
products (see Chapter 7). In the case of the 2 mole ethoxylate there can be as
much as 20-25% of free alcohol remaining which on sulphation gives an
alcohol sulphate. (ii) Alcohol ethoxylate. Unsulphated material when sulpha-
tion is carried out in a manner to avoid formation of lA-dioxane. (iii) 104-
Dioxane is formed by the breaking of the ethoxylate chain under the
conditions of sulphation. The amount is relatively small ( < 100 ppm on active
solids) but there has been considerable concern in Europe mainly due to the
low level required in the EEC Cosmetic Directory. The amount of 1A-dioxane
found is mainly due to the sulphation conditions, oversulphation giving higher
levels. The amount of ethylene oxide in the molecule is also a critical factor and
high EO (> 4 mole) cari contain considerable amounts of 1A-dioxane. High
levels can be reduced by steam distillation.

General properties

1. Solubility. The presence of polyethylene oxide (a water soluble group)

confers improved solubility on ether sulphates, compared to alcohol
 ANIONICS 75
sulphates. When mixed with alcohol sulphates. ether sulphates improve
the solubility. Unlike alkyl sulphates, the ether sulphates have cloud
and clear points below O°e.
2. Compatibility with aqueous ions. Stable to hard water; both the 2-mole
and 3-mole ethoxy sulphate have excellent lime-soap dispersing pro-
perties due to the calcium salt being soluble (calcium lauryl sulphate is
insoluble).
3. Chemical stability. Hydrolyses in aqueous solution at acid pH and high
temperatures (not suitable for use above 50°C) but less so than alcohol
sulphates; ammonium salts more stable than sodium at pH just less than
7 but needs to be kept at below pH 7 at all times during processing; even
at neutral pH, hydrolysis may be initiated by autocatalytic acidification;
this can be prevented using phosphate or citrate buffers.
4. Viscosity behaviour of aqueous solution. Very similar to alcohol sul-
phates in giving gels in the 30-60% concentration range, whilst being
liquid above and below that concentration; thus, diluting a concentrated
solution of say 65% can first lead to very large increases in viscosity, and
hence to gels; where minimum formulation viscosity is required at
maximum activity, then selection of a higher degree of ethoxylation is
preferable.
5. Thickening aqueous solutions, the salt effect. Ether sulphates show a
pronounced salt effect, i.e. addition of sodium chloride to a dilute
solution will give an increase in viscosity; the quantitative increase in
viscosity is different for each ether sulphate and can even vary from batch
to batch of apparently the same product; the largest changes in viscosity
on salt addition are shown by ether sulphates with low ethylene oxide
content, i.e. the 2-mole ethylene oxide derivative; ether sulphates can also
be thickened with dialkanolamides, betaines, polyethylene glycol esters
and amine oxides (see relevant sections); however, the foaming perfor-
mance can be affected by such additives, the PEG esters tending to give
lower foaming performance.
6. Thinning aqueous solutions. Alcohols, normally ethanol can reduce the
viscosity of ether SUlphate solutions; isopropanol is very effective but can
give odours in the final products.
7. Surface active properties. CMC of sodium dodecyl alcohol + 2EO
sulphate molecular weight 376.5 = 3 x 10- 3 M (0.11%); CMC of sodium
dodecyl alcohol + 3EO sulphate molecular weight 420.5 has figures
quoted in the literature from 0.008 to 0.03%. Surface tension of
C13-C15 + 3EO sulphate, sodium salt:
0.01%,40.0dyne/cm
0.1 %, 36 dyne/cm (data from ICI Synperonic data sheet).
8. Functional properties. Excellent detergents, do not show loss of deter-
gency in brine or hard water (unlike AS or LABS) and therefore can be
used unbuilt (no polyphosphates); detergency is enhanced by addition of
76 HANDBOOK OF SURF ACT ANTS

magnesium salts; the good solubility characteristics make them specially

useful for use in alkaline and phosphate built liquid formulations, where
they can improve the aqueous solubility of other less polar surfactants;
excellent emulsifiers (particularly for sebum); excellent foaming agents
particularly in the presence of electrolytes, the foam is lighter compared
to alkyl sulphates, more open and collapses more readily in the presence
of grease and oils; in general, ether sulphates do not give stable foams in
the presence of sebum (unlike alkyl sulphates which do give stable foam
in the presence of sebum), but the addition of sarcosinates, betaines or
alkanolamides can stabilise the foam in the presence of sebum; the C12
hydrophobe is claimed to give better foaming properties than the C14
(Adam and Neumann, 1980); products from different manufacturers with
apparently very similar compositions can often vary significantly in
foaming performance; This is mainly due to differences in the ethoxylated
alcohol feedstocks; the presence ofC9, CIO and Cll as alcohol sulphates
are likely to depress foaming performance.
9. Disadvantages. Hydrolytically unstable.

Applications

1. General. The sulphated ethoxylated alcohols began to replace alcohol

sulphates in hand dish washing and as shampoos in the 1950s on the
basis of improved solubility, foaming, hard water tolerance of foam,
better build of viscosity with salt and decreased irritation to eyes and
skin.
2. Household products. Three-mole ether sulphate used as foam
stabiliser/detergent in dish washing liquid; major component of low
temperature or low phosphate content heavy duty fabric laundry liquids
and powders; carpet shampoos; hard surface cleaners; chlorphenolic
disinfectant concentrates.
3. Shampoos and cosmetics. Shampoos, bubble baths, liquid soaps and
shower gels are the main applications; the 2-mole ether sulphate is
usually used in shampoos to give a stable voluminous foam (without
alkanolamide) when the level of sebum is not high; 3-mole ether sulphates
produce excellent 'flash' foam, less stable and more open than the 2-mole
ether sulphates and more suitable for foam baths and washing up liquids;
cleansing properti~s and vicosity building abilities fall off as the amount
of ethylene oxide increases. On the other hand, increasing ethoxylation
gives reduced eye and skin irritation; products with EO up to 12 are used
in shampoos as a mild foaming and cleansing agent and also as a
detoxifying agent; also have good solubilising properties.
4. Oil field chemicals. Three-mole ether sulphates used as foaming agent
in foam drilling where tolerance to salt and hard water is important
but has limited temperature stability (see Section 9.2).
 ANIONICS 77
5. Gypsum board production. Foaming agent with tolerance .to high con-
centrations of calcium ions.
6. Emulsion polymerisation. Emulsifying agent for rubber latices.

Specification

Active content, 27-28% or 60-70%

Carbon chain distribution
Amount of ethylene oxide
Unsulphated material, typically 3-8% (on 100% active)
Colour, high sulphated material gives good colours whilst low un sulphated
material gives poor colours
pH, can show pH drift, i.e. pH changes with time
Sodium sulphate, 0.5-3%
Sodium chloride, up to 0.05%
Flash point, some products contain alcohol
Ethyl alcohol, 10-15% (on 60% active ammonium salt)
l,4-dioxane, 500 ppm (on 100% active) would be high at time of writing
Viscosity, viscosity figures, particularly on high actives should be treated
with caution as the viscosity is extremely dependent upon the rate of shear
and thus the method of measurement.

6.5.3 Sulphated alkanolamide ethoxylates

Nomenclature

Generic:
Sulphated alkanolamide ethoxylates
Sulphated ethoxylated alkanolamides
Sulphated polyoxyethylene amides
Example:
Sodium salt of coco monoethanolamide + 2EO sulphate

Description

These products are prepared by sulphation of the ethoxylated monoalkanola-

mides. Complete sulphation gives very high viscosity products, so sulphation
is only carried out to approx. 50-70% of the theoretical value. Products
described as sulphated alkanolamide sulphates are therefore mixtures of
sulphated ethoxylated alkanolamides and ethoxylated alkanolamides. Sui ph-
ation is normally carried out as if the starting materials were ethoxylated
alcohols.
78 HANDBOOK OF SURFACTANTS

General properties
I. Solubility. Very soluble in water.
2. Chemical properties. Similar chemical stability to the ether sulphates (see
Section 6.5.2).

Applications

The products are excellent detergents, particularly for dish washing but are
too costly and therefore not used. The only known application is in shampoos,
and this is now probably being replaced by betaines.

Specification

Anionic content, typically \5-20;;,

Unsulphated content, typically 10-\5%
Viscosity, generally high and can be variable.

6.5.4 Sulphated oils and glycerides

Nomenclature

Generic:
Fatty monoglyceride sulphates
Mono-, di- or triglyceride sulphates
Sulphated mono-, di- or triglycerides
Sulphated 'oils
Examples:
Lauryl monoglyceryl sulphate, C"HZ3COOCHzCH(OH)CHzOS03 -M+
Turkey red oil (sulphated castor oil)

Description

Produced by sulphation (usually with oleum) of the glyceride of a fatty acid, i.e.
an animal fat or vegetable oil. There are three possible reactions:
I. Reaction with the OH group in the hydrocarbon chain, if it contains a
hydroxyl group (e.g. castor oil).
2. Reaction with a double bond in the hydrocarbon chain of the fatty acid
(e.g. oleic acid)
3. Hydrolysis of the ester group to give a free hydroxyl group on the
glyceride portion and subsequent sulphation of the hydroxyl group. Or
sulphation of a previously prepared fatty monoglyceride. Alternatively
the formation of the monoglyceride and the sulphate may be combined
by reaction with oleum in the presence of the appropriate amount of
glycerol. There are numerous patents on these types of preparations.
 ANIONICS 79
Sui phonation of the saturated hydrocarbon chain is possible when sulphur
trioxide is used (see Section 6.6.4).
Even with one specific oil, a large number of products with different
properties can be made. The degree of sulphation can be altered, thus resulting
in varying mixtures of sulphated products, soap and free oil. It is probably
this varying composition of the products which has been a factor in their
declining use.
The most common sulphated oils are: Turkey red oil (ricinoleic acid
triglyceride) made from castor oil; sulphated methyl and ethyl ricinoleate;
sulphated methyl esters, e.g. butyl oleate; fish oil, lard oil, tallow, palm kernel,
tall oil and rape seed oil sulphates.

General properties

Although the products are complex mixtures, they are all sulphate esters, and
subject to acid and alkaline hydrolysis (see Section 6.5). In addition, any ester
groups from the glyceride portion of the molecule will also be susceptible to
hydrolysis.
The sulphated monoglycerides are excellent detergents. Partial glycerides
containing unsaturated acids or hydroxy acids have more than one site
available for sulphation and possess specific properties such as wetting and
emulsification. Taking sulphated castor oils (Turkey red oil) as an example, the
main properties can be grouped under two headings:
1. Good wetting, penetrating and emulsifying; obtained by a high degree of
sulphation
2. Plasticising or softening properties of the oil; obtained by a low degree of
sulphation
Group 1 products are used as surfactants, products of Group 2 are unlikely to
be very useful as surfactants.
Sulphated methyl esters have good wetting properties, but usually with low
foam. This is rare in anionic surfactants.

Applications

1. Household products. Detergents, the sulphated monoglycerides of

coconut fatty acids were once made on a very large scale for use in
household detergents; they have been replaced by petrochemical based
surfactants. Disinfectants, sulphated castor oil was used as emulsifier for
pine oil, and creosote for pine and block type disinfectants (superseded by
synthetics mainly due to the price volatility of castor oil).
2. Shampoos and cosmetics. Ammonium salt of coco acid monoglyceride
sulphate was used as the basis for a popular US shampoo. The product is
very similar to the equivalent lauryl sulphate but due to the additional
hydroxyl groups it has slightly better water solubility. Deodorants,
sulphated castor oil.
80 HANDBOOK OF SURFACTANTS

3. Textiles. Emulsifying and wetting agents in dyeing and printing (Turkey

red oil); detergent, kier boiling.
4. Metal working. Emulsifying agent for kerosene in hand gel cleaners
(sulphated castor oil); emulsifying agents in cutting oils (sulphated butyl
oleate).
5. Leather manufacture. Fat liquoring.
6. Printing inks. Pigment dispering agents and wetting agents.
7. Mineral processing. Until recently, the sulphated monoglycerides were
used in ore flotation.

Specification

It is difficult to give representative figures as products vary so widely in

composition, but active anionic content, free fatty acid, total alkali, combined
sulphate, inorganic sulphate, solubility in water and solubility in white spirit
should all be tested.

6.5.5 Nonylphenol ether sulphates

Nomenclature

Generic:
Alkylphenol ether sulphates
Nonylphenol ether sulphates
Polyoxethylene nonyl phenol sulphates
Sulphated .nonyl ethoxylates
Examples:
Nonyl phenol + 7EO sulphate ammonium salt,
C9HI9C6H4(OCH2CH2)S04 -NH 4+

Description

Very similar to the alcohol ether sulphates but have been produced by two
different routes: (i) reaction with sulphamic acid gives the ammonium salt and
the product contains equimolar quantities of ammonium sulphate; (ii) reaction
with sulphur trioxide ~nd neutralisation with sodium hydroxide gives the
sodium salt; the products are relatively free from inorganics.
The products based on nonyl phenol + 4-9EO and, using sulphamic acid,
were at one time common in washing up liquids but are now too expensive.
However, products made from nonyl phenol + 4-15EO sulphated with
sulphur trioxide, do find speciality uses. The products with high amounts of
EO contain high quantities of 1,4-dioxane after sulphation, which is normally
stripped off before sale.
 ANIONICS 81
Typical impurities are: ammonium chloride (from sulphamic acid made
material); l,4-dioxane (from high ethylene oxide raw materials and sulphur
trioxide sulphation).

General properties

Similar to ether sulphates, but special properties possibly due to ring

sui phonation as well as sulphation of the hydroxyl group.
1. Disadvantages. Doubts on biodegradability of the alkyl phenol residue.
The ammonium salt (made via sulphamic acid) gives off ammonia in
alkaline solutions and therefore restricts their use in detergents.

Applications

1. Household products. The largest use of sulphated nonyl phenol ethoxy-

lates (4EO) made with sulphamic acid was in blends with LABS for use in
hand dish washing liquids where they gave high foam, low skin irritation
and low cost; they have now been superseded by the more cost effective
LABSjAES formulations.
2. Emulsion polymerisation.
3. Agricultural emulsifiers.

Specification

Active matter, 30-40%

Unsulphated, 1-5% (can be high if manufacturer wishes to avoid ring
sui phonation)
Inorganic sulphate, < 1% for sulphur trioxide production, 6-8% for
ammonium salt made from sulphamic acid
1,4-dioxane, should be below 500 ppm for stripped material.

6.6 Sulphonates (general)

As explained in Section 6.5, the sulphate has the sulphur atom indirectly
linked to the carbon of the hydrophobe via an oxygen atom. In the case of
sui phonates, the sulphur atom is linked directly to the carbon atom which
is usually, but not always, in an aromatic ring (Figure 6.4). This difference
in structure gives significant differences in properties between the sulphonate
and sulphate group. The most practical difference is that the ester link in
sulphates is very readily hydrolysed under acidic conditions, which means
that the free acids are not stable (see Section 6.5). On the other hand, the
82 HANDBOOK OF SURFACTANTS

o
I
R- S,,=O
I
0-
Figure 6.4 The sulphonate group.

R-OH + SO) -----+ R-O-SO) -

a sulphate

R---H + SO] ----> R SO)-

a sulphonate
Figure 6.5 Sulphation and sui phonation.

sui phonic acids are quite stable and therefore the surfactant sui phonic acids
are available commercially. This means that the user can carry out his own
neutralisation and make a variety of salts with only one surfactant raw
material.
The preparation of sulphates and suI phonates is carried out using the
same sulphating/sulphonating agents; the difference being the chemical
structure of the material to be reacted. If the reaction occurs with hydrogen
attached to oxygen (an alcohol) then a sulphate is produced, whilst if the
reaction occurs with a hydrogen attached to carbon then a sulphonate is
produced (see Figure 6.5).
The main sulphating/sulphonating agents are:
1. Using chlorsulphonic acid. Chlorsulphonic acid will react with long
chain alcohol groups to produce sulphates but inorganic chloride is
produced as a by-product. Chlorsulphonic acid is not suitable for
sulphonating aromatic rings because chlorination of the aromatic
nucleus is likely to occur.
2. Using oleum (fuming sulphuric acid). Liquid sulphuric acid or oleum is
used to sulphonate alkyl aryl hydrocarbons, e.g. xylene, toluene, dodecyl
benzene, naphthalene, alkyl naphthalene.
3. Using gaseous sulphur trioxide. Diluted with air or otherwise, gaseous
sulphur trioxide can be used for most sulphonations and sulphations, but
needs special reactors due to the very fast and exothermic reaction.
Reaction with alcohols give sulphates, whilst reaction with hydro-
carbons (aliphatic or aromatic) gives sui phonates. Methods using
gaseous sulphur trioxide are now dominant for most raw materials,
because they are both more economic and produce better quality
materials, compared to using oleum. The major difference in quality to
oleum sulphonation (or sulphation) is the low inorganic levels Gnd paler
colours obtained using the sulphur trioxide/air on a continuous plant.
 ANIONICS 83
However sulphur trioxide is also a powerful dehydrating and oxidising
agent, and side reactions can occur, e.g. formation of l,4-dioxane in sulphating
ethoxylates (see Section 6.5.2). Processes have been developed using sulphur
trioxide in liquid sulphur dioxide, but most processes use sulphur dioxide
diluted with air in a continuous plant. The major sulphonation processes
are known by the name of the sui phonation plant manufacturers; some of
the best known are Chemithon, Ballestra, Mazzoni, Stephan and Meccaniche
Moderene. Some of the sulphonators produced their own plant designs, e.g.
Albright and Wilson, Stephan, Berol, Unilever. These plants are invariably
continuous, and basically consist of a sulphur trioxide generator, the
sui phonation reactor and a continuous neutraliser. A diagrammatic view of
a typical sulphonation/sulphation plant is shown in Figure 6.6. The products
will differ more in raw material variation than from different plants, with
the exception of colour. Dark colours occur when the product is over
sulphonated/sulphated and/or the sulphonation/sulphation rate is not
controlled.
The aim of the sulphonator is to react equimolar quantities of the raw
material and sulphur trioxide and to obtain 100% conversion. In practice this
is not possible, so a slight excess of sulphur trioxide is used (4-10%), the excess
gaseous sulphur trioxide being taken off with the air leaving the sulphonic
acid. Excess sulphur trioxide gives oxidation which gives dark coloured
material. If poor colour is to be avoided, then the degree of sulpho-
nation/sulphation must be kept below 100%. Consequently there is a conflict
between low sulphonation/sulphation giving good colour but high
unsulphonated/unsulphated material, and high sulphonation/sulphation giv-
ing poor colour but low unsulphonated/unsulphated material. In modern
plants extremely good colour can now be obtained with up to 99%
conversion.
These plants have been designed to give optimum conditions with the major
surfactants commercially produced, i.e. alkylbenzene sulphonates with the
alkyl group in the region ofClO-CI4. Such continuous plants have limitations
on the type of raw material which they can handle:
I. There is a lower limit of molecular weight where the exotherm volatilises
the material being sulphonated. Thus benzene, toluene, xylene, cumene
and naphthalene are not usually sulphonated on the large scale
continuous plants used for LABS.
2. There is an upper limit of molecular weight where the raw material is too
viscous to flow in the sulphonation area ofthe plant and severe oxidation
occurs. This limit is plant variable but is in the region of 500 molecular
weight.
Thus there are still many produced with oleum, such as: benzene
sui phonates; toluene sulphonates; cumene sulphonates; xylene sui phonates;
naphthalene sulphonates; alkyl naphthalene sulphonates; petroleum sulpho-
nates; heavy alkylate sulphonates.
 00
~

to vents

demister
S03
:t
dry air ;I>
z
I:)
t:O
8
~
o.."
C
gas .."
product ;I>
'"
n
-l
;I>
Z
-l
rJ>
1 II .. water

heat exchanger

alkyl
benzene liquid aging hydrolysis

Figure 6.6 Continuous sulphonation/sulphation plant.

 ANIONICS 85
6.6.1 Ethane sulphonates

Nomenclature

Generic:
Alcohol ether (or ethoxy) sulphonates
Alkyl phenol ether (or ethoxy) sulphonates
Ethane sulphonates
Ether sui phonates .
Example:
Sodium nonyl phenol2-mole ethoxylate ethane sulphonate has the formula
C9H17C6H40CH2CH20CH2CH2S03 - Na+.
Note that some authors give the name of ether sulphonates to the reaction
product of unsaturated polyglycol ethers with sulphur trioxide. These are
mixtures of hydroxyalkane alkyl polyglycol ether sui phonates and alkenyl
alkyl polyglycol ether sulphonates. In such products, the sulphonate groups
are along the hydrophobic chain, whereas in the ethane sulphonates, the
sulphonate group is at the end of the polyglycol chain (see Figure 6.7).

Description

At the time of writing the author does not know of any large scale producer of
ethane sulphonates, although several companies are offering them on the
market. There has been a small specialist use for many years, but the products
have recently (1985-1990) aroused considerable interest due to their potential
use in enhanced oil recovery. The products cannot be made by conventional
methods of sui phonation (oleum, chlorsulphonic acid or sulphur trioxide).
Published methods of preparation are:
1. The Strecker reaction:
RCI + Na 2S0 3 ---+ RS0 3- Na +
The usual method of preparing the chloride is by reaction of phosphor-
ous pentachloride with an alcohol, ethoxylated alcohol or ethoxylated
nonyl phenol. The products from the Strecker reaction contain a number

I
RO(CH2CH20)12H + CI·CH 2CH-CH 2 + Na2S03
'0/

RO(CH2CH20)12CH2-CH-CH2S03 -Na+
I
OH
FIpre 6.7 Preparation of ethane sulphonates.
86 HANDBOOK OF SURFACTANTS

of impurities: fatty alcohol; fatty chloride; sodium sulphate and sodium

sulphite.
2. Using epichlorhydrin. This is the reaction between fatty alcohol,
epichlorhydrin and sodium sulphite (see Figure 6.7). Described in a
number of patents (Bruson, 1937, 1938).

General properties

The sulphonate group has better chemical stability than the corresponding
sulphate groups on alcohols or ethoxylated alcohols. Sulphonating ethoxy-
lated alcohols gives products with excellent water solubility and chemical
stability, particularly at high temperatures.
1. Disadvantages. High price, at the present time, compared to sui phonates
or ether su1phates; the high cost of manufacture by the Strecker route is
due to the low yields obtained.

Applications

1. Industrial detergents. Used for many years in surgical scrubs.

2. Oil field chemicals. Enhanced oil recovery (Shupe, 1977).

6.6.2 Paraffin sulphonates

Nomenclature

Abbreviations: SAS, secondary alkane sulphonates, used in this book; LAS,

occasionally used, more often used for LABS; PAS; PS.
Generic:
Alkane sulphonates
Paraffin sulphonates, should not be confused with petroleum sui phonates
(see Section 6.6.7)
Secondary n-alkane sulphonates
Examples:
There are very few manufacturers and these give trade names rather than
chemical descriptions, e.g. Hostapur SAS 60 (Hoechst)

Description

Produced by sulphoxidation of normal linear paraffins with sulphur dioxide

and oxygen and catalysed with ultraviolet light or gamma radiation (see
Figure 6.8). There are very few plants world-wide as the plants are specific to

Paraffin + S02 + UV light ---> Paraffin-S03H + unreacted paraffin

Figure 6.8 Sulphonation of paraffins.
 ANIONICS 87
SAS and capital intensive. The conversion after sulphoxidation is poor so
unreacted paraffin must be removed and recycled. The alkane sulphonic acid is
neutralised with sodium hydroxide solution, after which the excess water and
any remaining paraffin are removed by distillation leaving an alkane
sulphonate melt. This can be processed to make flake, or diluted with water to
obtain a paste of approximately 60% concentration.
The paraffin used is usually a mixture with a carbon chain distribution C14
to C17 which is the optimum chain length for heavy duty detergents in SAS.
Available as 30% aqueous solution, 60-65% paste or 90% prills. Impurities
include disulphonate and sodium sulphate.

General properties

1. General. Excellent aqueous solubility and excellent biodegradability.

2. Solubility. The C14-C17 mixture has 31% solubility at 20°C which is
superior to LABS or lauryl ether sulphate (28%); synergistic solubility
with lauryl ether sulphate of 40% (80 SAS/20AES) at 20°C; this means
that the mixture exhibits better solubility than either of the components;
solubility not affected by addition of amine oxides (unlike LABS where
the solubility decreases with addition of amine oxides).
3. Compatibility with aqueous ions. Excellent with calcium and magnesium;
if high concentrations of alkali are added, surface activity and solubility
can be improved by adding non-ionic surfactants (alcohol ethoxylates)
4. Functional properties. Wetting optimum at C15 with C12 and C14
inferior (Trautman and Jurges, 1984); this is quite unusual as wetting is
usually at an optimum chain length well below the detergency chain
length optimum; wetting time 5-10 s at 0.1 % at 20°C (DIN 53 901);
foaming 600 ml foam for 0.1 % in demineralised water, 150 ml of foam for
0.1% in 220 ppm CaC0 3 (foaming measured by DIN 53 902/1).
5. Surfactant properties. CM C = 0.06% (for the C 15); surface tension of
0.1 % aqueous soln = 36 dyn/cm.
6. Biodegradability. Faster and more complete than LABS.
7. Disadvantages. Difficult to thicken by addition of electrolyte unless ether
sulphates are present.

Applications

1. Household products. Powdered heavy duty detergents; liquid heavy duty

detergents; washing up liquids, the SAS products are used in highly
concentrated formulations where the overall formulation is cheaper
using SAS rather than LABS which needs the addition of hydrotropes
and alcohol; hard surface cleaners (general purpose) with builders but
without the need for hydrotropes due to the good solubility.
2. Industrial cleaning. High electrolyte containing formulations, e.g. with
caustic soda, phosphoric acid, sulphuric acid.
88 HANDBOOK OF SURFACTANTS

3. Emulsion polymerisation. Emulsifier in the polymerisation of vinyl

chloride and as a post stabiliser after pulymerisation; in the production of
carboxylated butadiene-styrene copolymers.
4. Leather processing. Used in fat liquoring to replace the older sulpho-
nated/sulphated natural oils.
5. Mineral separation. Ore flotation agent.
6. Petroleum industry. Enhanced oil recovery.

Specification
Active content, 60
Appearance, pale yellow paste
Di- and polysulphonates, 6-7%
Sodium sulphate, 2-4%
Unsulphonated material, less than 1%.

6.6.3 Alkyl benzene sulphonates

Nomenclature

Abbreviations: LABS, linear alkyl benzene sui phonates, used in this book;
ABS, alkylbenzene sui phonates; DDBS, dodecyl benzene sulphonic acid or
sulphonate; DOBS, dodecyl benzene sulphonic acid or sulphonate derived
using Dobanes (alkyl benzene made by Shell Chemicals); LAS, not often used
but occurs in old literature, not to be confused with paraffin sulphonates or
alcohol sulphates.

Generic:
Acid, alkyl (usually linear C12-C14) benzene sulphonic acid
Alkylbenzene sulphonates
Broad cut acid, alkyl (usually linear, wide distribution of alkyl chain length)
benzene sulphonic acid
Dodecylbenzene sulphonates
Hard acid, alkyl (branched chain) benzene sui phonic acid, non-biodegradable
Narrow cut acid, alkyl (usually linear C12-CI4, narrow distribution of alkyl
chain length) benzene sulphonic acid
Soft acid, alkyl (linear) benzene sui phonic acid, biodegradable
Examples:
Sodium dodecylbenzene sulphonate
Dodecyl diphenyl oxide disulphonate

Description

The empirical formula of a sulphonate can be expressed as RC 6 H 4 S0 3 - M +

where Ris a linear hydrocarbon in the range C9·-C15 and M is an alkaline
 ANIONICS 89
metal ion or an amine derivative. The two major products produced world-
wide are where R = C9-CI4, known as broad cut alkyl benzene sulphonic
acid, and R = ClO-C13, known as narrow cut alkyl benzene sulphonic acid.
The free acid is quite stable and also freely available, it has the advantage of
reduced transport costs (as it is 100% active) and reduced storage as the salts
can easily be made in situ. The most common salt is the sodium. It is usually
used as a 30% aqueous solution. The 95% flake form is available.
There are the following variations in alkyl groups and isomers:
1. Variation in the length of the chain, C8 up to CI5.
2. Substitution ofthe benzene ring in different positions, 2-phenyl, 3-phenyl
and 4-phenyl; 25-30% of the 2-phenyl alkane is produced using alu-
minium chloride as catalyst with the amounts of 3-, 4-, 5- an~-phenYL
isomers decreasing steadily from about 22% to 15%, respectively; 15-
20% of 2-phenyl alkane is produced using hydrogen fluoride as catalyst
with the rest of the isomers distributed fairly evenly. On sulphonation
these isomers are retained and the two different alkylation catalysts give
what is now known as high 2-phenyl content and low 2-phenyl content
sulphonates.
3. Variation in chain branching. Branched hydrocarbons are now very
rarely used in Europe, United States and Japan because of poor
biodegradability.
4. Linear narrow or broad cut (based on linear narrow or broad cut
alkylate derived from linear cracked olefins (wax cracking) or from linear
olefins by polymerisation of ethylene)
These variations can affect physical properties, e.g. solubility and functional
properties to varying degrees. The sulphonation is usually shown as
RC 6 H 5 + S03 -+ RC 6 H 4 S0 3H
However it is more complex, and side reactions occur. These side reactions
give by-products which can affect the properties of the finished product. The
literature gives various differing mechanisms. The following description gives
the overall effects and is not intended to describe the mechanism.
Excess S03 is invariably used in practice to reduce the unreacted alkylate to
a minimum. This excess S03 forms a disulphonic acid and an anhydride:
RC 6 H 5 + excess S03 -+ RC 6 H 4 S0 3S0 3H -+(RC 6 H 4 S0 2 }z0
Disulphonic acid Anhydride
or pyrosulphonic acid
These products can be removed by:
1. Ageing. The disulphonic acid reacts with unreacted alkylate
RC 6 H 4 S0 3S0 3H + RC 6 H 5 -+2RC 6 H 4 S0 3H
LABS
90 HANDBOOK OF SURFACTANTS

2. Hydrolysis. The presence of water will hydrolyse the disulphonic acid,

the anydride and any oleum.
RC 6 H 4 S0 3S0 3H + H 2 0 -----+RC 6 H 4 S0 3H
Disulphonic acid LABS
(RC 6 H 4 S0 2 hO + H 2 0 -----+ RC 6 H 4 S0 3H
Anhydride LABS
H 2 S0 4 nS0 3 + nH 2 0 -----+(1 + n)H 2 S0 4
Thus sulphonation plants will have an ageing stage, and also the addition of
approx. 0.5% water to eliminate the anhydride. As the great majority of
sulphonic acids are used as the aqueous salts, these side reactions should give
no problems, but it is best to be aware of them as the by-products can affect
analyses of active contents, and some physical properties such as sodium salt
slurry viscosity (Moreno et ai., 1988). These side reactions are not only
dependent upon the raw materials but also on the running of the sulphonation
plant, e.g. variation in the S03 excess.
There can also be small quantities of sui phones, tetralin and indanes which
will be found in the unsulphated material (or free oil). The amount oftetralin in
the alkylate is determined by the catalyst used for its manufacture. Aluminium
chloride gives considerably higher tetralin concentrations than does hydrogen
fluoride. .

General properties

1. Genera/, The surfactant properties are mainly influenced by the average

molecular weight and the spread of carbon number of the alkyl side
chain.
2. Solubility. The acids are soluble in water and soluble/dispersable in
organic solvents. However, on dilution with water the acid will form a
high viscosity liquid or a gel between 30 and 80% acid in water. For salts,
see Table 6.1. As broad cut acids give better sodium salt solubility, higher
active concentrations can be made (typically 32%), with lower viscosities

Table 6.1 Solubility of salts of LABS; S = soluble. o = dispersable. 1=

insoluble

Sodium Isopropylamine Calcium TEA

10% in water S 0 0 S
10% in ethanol S S S S
10% in mineral oil I S S I
10% in white spirit I S S I
10% in aromatic solvent I S S I
10% in perchlorethylene I S S I
 ANIONICS 91
than when using narrow cut acid (typically 25%). TEA salts are more
soluble in water (50-60% active) than sodium (30% soln max). Calcium
and isopropylamine salts have better solubility in hydrocarbon solvents
than the sodium salts. Increased solubility results in lower cloud points
and less response to salt. The cloud point can be lowered by addition of
urea, sodium xylene sulphonate or alcohol. Solubility and cloud points of
the aqueous salts depend upon the solubility of the sulphonate and hence
upon the hydrophobic group, i.e. length of chain, solubility decreases
with increasing chain length; 2-phenyl content, the higher the 2-phenyl
content the more soluble the LABS.
3. Chemical stability. Resistant to hydrolysis in hot acid or alkali. The acids
evolve heat on dilution with water and generate hydrogen on contact
with some metals (e.g. zinc).
4. Compatibility ofaqueous solution to ions. Completely ionised and the free
sulphuric acid is water soluble so the solubility is not affected at low pH;
calcium salts are precipitated from solution but in the presence of non-
ionics the active content is not reduced even at high hardness levels;
sodium salts are reasonably soluble in the presence of electrolyte (salt
and/or sodium sulphate).
5. Functional properties. Wetting: CII-CI3 is optimum; good wetting is
dependent upon concentration; 0.5% solution of sodium salt necessary
to obtain less than lOs on Draves test. Foaming: in blends with AES,
optimum foam stability (not Ross-Miles which measures flash foam) is
at CII-CI2. Detergency: C13-CI4 is optimum.
6. Surfactant properties. CMC of sodium dodecylbenzene sulphonate
(molecular weight 348.4) = 5 x 10- 3 M = 0.018%; surface tension of a
1% solution of sodium dodecylbenzene sulphonate = 47 dyn/cm.
7. Disadvantages of LABS. LABS used on its own for personal care gives
severe defatting action on skin; sodium salts need builders or
sequestrants in hard water for stability.

Applications

1. General. Used in practically all detergents, domestic and industrial,

where heavy duty performance is required.
2. Heavy duty clothes washing detergents. Powdered detergents both high
and low foam; C13-C14 used in free flowing powders; liquid detergents
both high and low foam; C9-Cll gives best solubility; also high 2-
phenyl content.
3. Light duty detergents (washing up liquids, hard surface cleaners). Broad
cut acids give better solubility so give high actives with lower viscosities
than narrow cut; narrow cut, low active detergents with high viscosity;
broad cut, high active detergents with low viscosities, high 2-phenyl
92 HANDBOOK OF SURFACTANTS

content, medium to high active detergents (due to better solubility); low

2-phenyl content, low active detergents (poorer solubility than high 2-
phenyl).
4. Industrial detergents. Commercial laundries, vehicle washing where
considerable foam is required.
5. Plaster board manufacture. Foaming agent for plaster board due to
stability to calcium ions.
6. Emulsifying organic non-water soluble materials. Isopropylamine salt
used as oil soluble emulsifier for solvent degreasers, hand gels, emulsion
cleaners and dry cleaning charge soaps.
7. Agriculture. In conjunction with non-ionics, the calcium salt is
used for agricultural herbicide formulations with self-emulsifying
properties.
8. Cellulose and paper industry. Pulp washing agents; dispersing agent for
dyes.
9. Textiles. Washing of fabrics; dye dispersing agents.
10. Solubiliser. Isopropylamine derivative added to fuel oil to solubilise
traces of water.
11. Emulsion polymerisation. Emulsifying agent for vinyl acetate/acrylate
copolymerisation.
12. Detoxifying action of other surfactants. Improved skin irritation by
addition of sulphosuccinates, sarcosinates or amphoterics.

Specification

Acid (typical narrow cut)

Appearance, brown viscous liquid with acidic odour
Active material, 97-98%
Free oil (neutral material), 1- 3%
Free sulphuric acid, 1-3%
Molecular weight, 315-340
2-phenyl isomer, 15% (low) to 30% (high).
Sodium salt (from narrow cut acid)
Active material, 25%
Unsulphated organic material, 0.5-~2%
Inorganic sulphate, 0.3-\ %
Cloud point, 19-40°C
Molecular weight, 337-362
2-phenyl isomer, 15% (low) to 30% (high).
Sulphones are found in the free oil of the acid. They are supposed to be
hydrolysed when salts are formed but Moreno et al. (1988) reports them as
being found in the free oil.
The above figures are for products made by sui phonation with sulphur
trioxide, which represents the majority of LABS on the market. If oleum is
used then the inorganic content will be very much higher.
 ANIONICS 93
6.6.4 Fatty acid and ester sulphonates

Nomenclature
Type 1. Sulphonated unsaturated acids where the sulphonate group is not
near the end of the chain.
Generic:
Sulphonated acids
Example:
Sulphonated oleate potassium salt
Type 2. Salts of alpha-sulphonated fatty esters (or acids). Abbreviations: FES,
fatty ester sulphonates, used in this book; F AS, salts of alpha-sulphonated
fatty acids; ES, ester sulphonates.
Generic:
Alpha sulphonated fatty acids (or esters)
Ester sulphonates
Fatty acid sulphonates
Example:
Sodium tallow methyl ester alpha-sulphonate
Type 3. Omega sulphonated fatty acids (or esters). Not commercially avail-
able but may be in the future.

Description

There are two quite distinct types of sulphonated fatty acids/esters on the
market.
Type 1. Sulphonated unsatumted acids. These are produced by the sul-
phonation of unsaturated fatty <"cids (or esters). There are not many products
of this type available, an example being sulphonated oleic acid (see Figure 6.9).
These should not be confused with the sulphated oils and esters (see
Section 6.5.4) which have very different properties, The sulphonic acid group is
in the middle of the chain, The acid is quite stable but the potassium salt is the
normal salt offered for sale due to its higher solubility than the sodium salt.
Type 2, Alpha sulphonated acids or esters. First produced commercially in
Japan and then in Europe in the early 1980s, at the present time (1989), there
are very few large scale producers in the world but the potential of this type of
sulphonate is likely to be very large. The products are available as high active
pastes (50-60% active) but such products often contain added ether sulphates
or the salts of short chain carboxylic acids to facilitate handling,

Figure 6.9 Sulphonated oleic acid.

94 HANDBOOK OF SURFACTANTS

The chemistry and properties of the products were fully described by the US
Department of Agriculture in the 1950s but practical large scale production on
continuous sulphonation plants has only been realised in the 1980s. Sulpho-
nation at the alpha position of the fatty acids does not occur readily due to the
weak activation of the carbon atom. Strong sulphonating agents (sulphur
trioxide) must be used leading to problems of poor colour, particularly if the
starting esters have unsaturated groups. The sulphonation reaction is complex
(see Figure 6.10).
The above reaction does not fully describe the published work but indicates
the complexity of the reaction and the formation of the disulphonates. At the
end of the reaction there is a mixture of sulphoester acid and disulphonate.
Neutralisation with sodium hydroxide gives the result shown in Figure 6.11.
Thus the sodium salt will be a mixture of:
1. The monosodium sulphonate salt of the ester, approx. 80% of the active
2. The disodium salt of the alphasulphonated carboxylate, approx. 20%
of the active
3. The sodium salt of the fatty acid produced by hydrolysis of the starting
ester which was not sulphonated, i.e. soap approx. 3% of the active
The properties of these three products are different in solubility, physical
properties and surfactant behaviour and therefore users should expect
differences from one manufacturer to another. However consistent manu-
facturing conditions should give a consistent material but it would be
advisable to check for reproducibility from any manufacturer until confidence
in batch to batch variation can be established.
The majority of data have been obtained using distilled methyl esters offatty
acids, e.g. tallow fatty acid. However the presence of some unsaturated
triglycerides in the methyl ester seems to have a surprisingly low effect on

Fast Step 1
R 1CH 2COOR z + 2S0 3 ---+R1CHCOOSOzOR z
I
S03H
disulphonate (or anhydride
or sulphoanhydride)
Slow step 2.
R 1CHCOOSO zOR 2 + R1CHzCOOR z --+2R 1CHCOOR z
I I
S03H S03H
alpha sulphonated methyl
ester (R2 = CH 3)
Figure 6.10 Sui phonation of fatty esters.
 ANIONICS 95
1. With the alpha sulphonated ester

monosodium disodium
salt salt

2. With the disulphonate

R1CH COO S020R2 NaOH I RCH COO Na

I
S03H
I
S03Na
disodium salt
Figure 6.11 Neutralisation of sulphonated esters.

colour and this could well permit the use of undistilled saturated methyl ester
for sulphonation in order to reduce costs. Even under optimum sulphonation
dark coloured products are reported in the literature and special bleaching of
the acid and also of the salts is often needed.
Impurities/by-products include disulphonate, soaps and bleaching by-
products.
Type 3. Omega ester sulphonates. These products are different in chemical
structure to Types 1 and 2. They are products made by sulphonation of
saturated fatty esters using UV radiation as catalyst. The sulphonic acid group
is statistically distributed at random along the chain. Such products are not
made on a large scale but are included as they may well be commercialised in
the future. They will not be discussed any further.

General properties

1. General. Type 1: excellent wetting; good stability and solubility in high

concentrations of electrolytes. Type 2: excellent cold and hot water
detergency in hard water; FES behave in a similar manner to fatty
alcohol sulphates with similar chain length but with better hydrolytic
stability.
2. Solubility. Type 1 (sulphonated oleic acid): poor aqueous solubility of
acid and sodium salt; potassium salt more soluble. Type 2: solubility of
the salts of C12-C14 FES is excellent but the solubility of the salts of
96 HANDBOOK OF SURFACTANTS

C16-C18 FES is poor compared to other detergent sulphonates:

Kraft point ("C)

LABS (ClO-C\3) <0

AOS (CIS-CI8) <0
SAS (C14-C17) <0
FES (CI2-C14) <0
FES (C16-C18) 39

Salts of the disulphonate will tend to crystallise out of solution. The

commercial products can be solubilised with hydrotropes.
3. Chemical stability. Type2: The principal active product is the
sulphonate of a methyl ester of a fatty acid which would be expected
to be hydrolytically unstable. However it is claimed that the methyl
ester is stable between pH 3 and 9.S at 80 a e. The product is stable in
a neutral detergent and minimal hydrolysis occurs in spray drying of
a slurry containing FES and storing at 60°C for some months (Knaggs
et al., 1965).
4. Compatibility with aqueous ions. Type2: Shows excellent sequestration
of hard water in the presence of soap, i.e. lime soap dispersion; thus
soap as an impurity could be beneficial.
S. Viscosity behaviour. Type2: The addition of the disodium salts of FES
(acid), particularly ClO-CI2, can lower the viscosity of LABS, soap,
alkyl sulphates, ether sulphates and FES; this can be utilised in reducing
the viscosity of slurries for spray drying.
6. Functional properties. Type2: Foaming properties are better with
C12-C14 than with C16-C18 fatty acids; thus alpha-sulpho methyl
tallow ate gives low foam. C16-C18 based detergents showed superior
detergency to LABS in the absence of polyphosphates at low
concentration and at high water hardnesses. Soil suspending power is
good, but foam is too high in horizontal washing machines although
foam problems are not encountered with C12-C14 which is unexpected.
Some doubt on fabric incrustation in the complete absence of
polyphosphates.

Applications

Type 1. Wetting agent particularly in high pH solutions and high con-

centrations of electrolyte; gives very low foam compared to most other
anionics of similar wetting properties; applications in textile processing, metal
cleaning, industrial detergents, emulsion polymerisation.
Type 2. Excellent detergency with good lime soap dispersability, parti-
cularly phosphate free detergents can be manufactured to give excellent
performance if soap is included; optimum detergency found at C16-C18 fatty
acids (with the methyl ester); used in synthetic soap bars with cocomono-
 ANIONICS 97
ethanolamide and inorganic builders and as an emulsifier for emulsion
polymerisation (pvc).

Specifications (Type 2 only)

Active, pastes at 40% or 60-65% concentration

Disodium salt, 20% (of active content)
Soap, 2-5% of the active content
The viscosity/active curve for the C16/C18 FES shows two pronounced
minima at 40~~ and 60-65% active.

6.6.5 Alkyl naphthalene sulphonates

Nomenclature

Generic:
Alkyl naphthalene sui phonates
Phenol formaldehyde sulphonic acid condensates, see polymeric surfactants
(Chapter 11)
Naphthalene sui phonic acid-formaldehyde condensates, see polymeric
surfactants (Chapter 11)
Dinonylnaphthalene sulphonates, see petroleum sulphonates (Section
6.6.7)
Examples:
Sodium isopropyl naphthalene sulphonate
Sodium dibutylnaphthalene sulphonate

Description

Alkylation of naphthalene followed by sulphonation gives a wide variety of

products depending upon the size of the alkyl group and the amount of
sulphonation. If the alkyl group contains less than five carbon atoms the
products are water soluble and show surfactant properties depending on the
size and number of alkyl groups. If the products have alkyl groups of nine
carbon atoms and above the products are not water soluble (with one
sulphonic acid group) but begin to show solubility in mineral oil. These latter
products therefore show properties more similar to the petroleum sulphonates
and are included in Section 6.6.7. The remainder of this section is therefore
devoted to the water soluble alkyl naphthalene sulphonates.
The water soluble alkyl naphthalene sulphonates are made on simple batch
reactors (glass lined) by reaction of a short chain alcohol with naphthalene in
the presence of oleum. The oleum acts as a catalyst for the alkylation of the
naphthalene by the alcohol as well as sulphonating the naphthalene (see
Figure 6.12). The degree of alkylation and the degree of sulphonation can be
98 HANDBOOK OF SURFACTANTS

("]1 ,"0
C

~ S03H
Figure 6.12 Alkylation of naphthalene.

controlled by the proportion of starting ingredients. The position of sulpho-

nation on the naphthalene ring will depend upon the temperature of sulpho-
nation, the sulphonate group being in both the 1 and 2 positions with low
temperatures favouring the 1 position and high temperatures (> lOO°C) the 2
position. There will also be some disulphonation and the alkyl groups can be
anywhere on the naphthalene ring. Thus the reaction products are complex
mixtures. One way of characterisation is by molecular weight:

Alkyl derivative of Molecular weight of

monosulphonate sodium salt

Methyl 244
Ethyl 258
Isopropyl 272
Butyl 286
Diisopropyl 313
Dibutyl 351

Note that all kinds of mixtures are possible so a molecular weight of 272 could
mean alkylation with isopropyl alcohol or with a mixture of methanol and
butanol. The two main commercial products are butyl naphthalene sulpho-
nate and isopropyl naphthalene sulphonate, both available in powder form as
the sodium salt, but most products contain large quantities (5-\5%) of sodium
sulphate. However some manufacturers offer products with low sodium
sulphate content.

General properties

l. Solubility. Excellent solubility in water depending upon the type and

amount of alkyl substitution; most products can be made at 40% active
aqueous solutions; the dibutyl derivative is less soluble than the
monobutyl or diisopropyl but has better wetting and emulsifying
properties.
2. Compatibility with aqueous ions. Tolerant to hard water; good lime soap
dispersability; compatible with strong alkalis, strong acids and high
concentrations of electrolytes.
 ANIONICS 99
3. Chemical stability. Stable to acids and alkalis; aqueous solutions stable
up to lOODC; unstable above (e.g. disperse dying under pressure); stable in
oxidising and reducing agents.
4. Functional properties. Excellent wetting properties with the higher
molecular weight (diisopropyl and dibutyl) derivatives, best detergent
properties with dibutyl derivative; low foam with low molecular weight
products 250-260 (methyl, ethyl) but high foam with molecular weight
280-300; hydrotrope properties claimed for low-medium molecular
weight products.
5. Disadvantages. Doubts on biodegradability but lack of information.

Applications

1. General. The alkyl naphthalene sulphonates were developed as soap

substitutes before and during the 1914-1918 war and were mainly used in
textile processing. They were extensively used during the 1930s and up to
1950 as general purpose surfactants and detergents but were replaced by
petrochemical-based anionics (LABS). The present uses are restricted to
their excellent wetting and dispersing properties rather than the deter-
gent properties.
2. Household products. Products with molecular weight 280-290 have been
recommended for use with lauryl sulphate in rug shampoos in order to
depress the cloud point and improve the friability of the residue on
drying.
3. Textiles. Wetting agent and dispersing agent for disperse dyes but
limited to dying temperatures of lOODC maximum.
4. Industrial detergents. Used as a wetting agent in cheap acid cleaners, e.g.
brick cleaning, metal cleaning and metal pickling; stable to 5% hydroch-
loric acid.
5. Agricultural. Act as combined wetting and dispersing agent for wettable
powder pesticides; use in fertilisers where an alkyl naphthalene sulpho-
nate is incorporated into a urea melt to give protection against caking.
6. Paints. Wetting agent in water-based paints.
7. Electroplating. Wetting agent for acid electroplating baths.

Specification

Active content, 80-95% powder

Sodium sulphate, 3-20%
Unsulphonated material, 1-3%
Molecular weight, 240-290
Occasionally sold as a liquid with active content 20-40%
Compare with molecular weight of LABS of 340-360.
100 HANDBOOK OF SURFACTANTS

6.6.6 Olefin sulphonates

Nomenclature

Abbreviations: AOS, alpha-olefin sulphonates, used in this book.

Generic
Alkene sulphonates/hydroxy alkane sulphonates
Alpha-olefin sulphonates
Examples:
Sodium olefin (C14~C16) sulphonate
Sodium (C14~C16) olefin sulphonate

Description

The products are manufactured by the sui phonation of alpha-olefins using

sulphur trioxide on continuous plants similar to those producing LABS. There
are usually two ranges offered, the most common based on C14~C16 olefin
and the other based on C16~C18 olefin. The olefins made from ethylene are
preferred raw materials, giving better colour and less impurities than olefins
from paraffins by wax cracking. The sodium salts are available as 40% liquids,
high active slurries (60~ 70%) and > 90% spray dried powders or flake.
The immediate products after sui phonation are shown in Figure 6.13. These
products are hydrolysed by alkali to give mixtures of two types of chemical
structures as shown in Figure 6.14. A typical commercial product could be
70% alkene sui phonates and 30% hydroxy alkane sulphonates. If a C 14~C 16
olefin is used as the starting material then R = CI0~C12. If a C16~C18 olefin is
used as the starting material then R = C12~C14.
The properties of the hydroxy alkane sulphonate and the alkene sulpho-
nates differ.

100% alkene sulphonates lOO~, hydroxy compound

Viscosity of 35% solution (cS) 11 22000

Solubility More soluble
On cooling the solution Crystallises Thickens
Foaming ability Better
Detergency Better

Sulphonation is carried out on a conventional continuous plant using sulphur

trioxide/air mixtures. The reaction is extremely exothermic and more care has
to be taken to prevent over sulphonation than in the case of alkyl benzene
sui phonation. Colour degradation occurs very easily and bleaching is often
necessary. This, together with the fact that the products are mixtures, could
 ANIONICS 101
RCH=CH 2 + S03 ~ RICH=CH(CH2)nS03H
alkene sulphonic acid
+ R 2CH -(CH 2)m
I I
0--S02
alkane sultone
Figure 6.13 Sui phonation of alpha olefins.

1. Alkene sulphonic acid

RICH=CH(CH2)nS03H ~R2CH2CH=CHCH2S03Na
2-alkenyl sulphonate
+
R2CH=CHCH 2CH 2S0 3 Na
3-alkenyl sulphonate

2. Alkane sultone

RCH-(CH 2)n ---+.

NaOH
R2CH2CHCH2CH2S03Na
I
0-S02
I OH
I
3-hydroxy alkane sulphonate
+
R1CHCH2CH1CH1S03Na
I
OH
4-hydroxy alkane sulphonate
Figure 6.14 Hydrolysis of alpha olefin sulphonates.

well lead to considerable differences between manufa9turers, and also between

deliveries. Analysis is complex and it is recommended that some simple
functional tests (e.g. foaming, solubility, wetting) be carried out on any new
materials and also on every batch from new suppliers until confidence in
reproducible properties can be obtained.
Impurities/by-products include disulphonates (these can be up 1-5% on
actives), suitones, breakdown products of bleach (hydrogen peroxide) and
olefins.
 102 HANDBOOK OF SURFACTANTS

General properties

1. General. The C 16-C 18 products are similar in properties to the

C14-C16 but they foam less, have lower solubility, better detergency and
better emulsifying properties.
2. Solubility. AOS are more soluble than LABS or AS due to the hydroxyl
group in the hydroxy derivative and the unsaturated links in the alkenyl
derivatives.
3. Compatibility with aqueous ions. Calcium salts have low solubility; small
degrees of hardness (50 ppm CaCO 3) improved dish-washing
performance but higher degrees of hardness reduce performance.
4. Chemical stability. Good chemical stability similar to other sulphonates
(see Section 6.6); good hydrolytic stability, can be used in strong acid
or alkaline formulations.
5. Viscosity behaviour. The viscosity of the hydroxy alkane and alkenes
differ markedly (see above). It is difficult to obtain a high viscosity with
salt at low actives (expected due to the excellent solubility). Addition of
ammonium chloride will give higher viscosity than sodium chloride and
oleamide diethanolamide will give higher viscosity than cocodieth-
anolamide. Partial replacement of cocodiethanolamide with cocoami-
do propylbetaine will increase viscosity significantly. Viscosity can also be
increased by the addition of hydroxyethyl cellulose but only low levels
( < 1.5%) of hydroxyethyl cellulose can be used as high concentrations
are incompatible.
6. Surfactant properties. CM C for C 15-C 18 is at 0.03%. Surface tension
decreases with increasing chain length up to C 14 but is constant
thereafter. Lowest surface tension for C 14-C 16 = 33 dyn/cm in water but
drops to 28 dyn/cm in hard water (125 ppm CaCO 3)'
7. Functional properties. The C14-C16 give excellent cleaning and excel-
lent foaming in hard water; it foams better in hard water than in soft water
(Hart and DeGeorge, 1982); foams well in the presence of sebum; flash
foaming increases rapidly with length of alkyl chain up to C15 then more
slowly; wetting optimum is at C16 alkyl chain.

Applications

1. General. AOS based on C16-C18 olefins were first commercialised by

Lion Fat and Oil in heavy duty powders in Japan in 1968 and were
claimed to be superior in detergent ability in hard water. The main use in
the United States has been as a partial replacement of ether sulphates in
household products particularly in bath additives and liquid soaps due
to the foam stability in the presence of soap. The alpha olefins have found
a market in synthetic soaps, both toilet and household, in South East
Asia due to the cold water conditions of use in that geographical area.
 ANIONICS 103
AOS has not found significant applications (at the time of writing) in
Europe.
2. Household products. Dish washing detergents (good solubility for high
active).
3. Personal care. Use in bubble bath (foam stability good in the presence of
soap); use in shampoos (problems in low actives, see viscosity behaviour
above); claims that sodium C14-C16 alpha-olefin sulphonate will not
strip the hair of natural oils; when combined with alkanolamides,
betaines or amine oxides, performance equivalent to an alcohol sulphate
can readily be achieved; used in liquid soaps (foam stability good in
presence of soap) for cold water washing; used in synthetic detergent bar
soaps for cold water washing.

Specification

Active matter, 35-40%

Free oil, 1-2%
Sodium sulphate, 0.5-2.0%
Sodium chloride, up to 1%.

6.6.7 Petroleum sulphonates

Nomenclature

Generic:
Alkyl benzene bottom sulphonates
Dialkyl benzene sui phonates
Heavy alkylate sulphonates
Overbased sui phonates or overbasified suI phonates
Petrolum sui phonates
SuI phonates
Synthetic petroleum sui phonates
Synthetic long chain alkyl benzenes sulphonates

Figure 6.15 Sodium salt of dialkyl (CIO--CI4) benzene sulphonate.

104 HANDBOOK OF SURFACTANTS

Figure 6.16 Barium dinonylnaphthalene sulphonate.

Examples:
Calcium petroleum sulphonate (molecular weight 470), no defined chemical
structure
Sodium salt of dialkyl (CI0-CI4) benzene sUlphonate (see Figure 6.15)
Barium dinonylnaphthalene sulphonate (see Figure 6.16)

Description

There is a group of sulphonates whose common characteristic is their

molecular weight and oil solubility. The molecular weight is higher than that
of the normal detergent sulphates and sui phonates making the acids and salts
generally insoluble in water but soluble in mineral oil. The various types of
sulphonates are characterised by different molecular weight, the particular salt
and the alkalinity. These products originated as a by-product in the refining of
petroleum and were thus referred to as petroleum sui phonates. Petroleum
sulphonates are sulphonated extracts from lubricating oil fractions. The
products are sui phonates of fused ring compounds and there are usually two
fractions, the green acids which are water soluble and the mahogany acids
which are water insoluble but soluble in mineral and natural oils. However due
to shortages of the natural sulphonates, plus certain disadvantages, chemical
manufacturers have attempted to find synthetic replacements for these natural
petroleum sui phonates. Such products have become known as synthetic
petroleum sui phonates.
Synthetic petroleum sulphonates are sulphonated alkyl and dialkyl deriva-
tives of benzene, xylene or naphthalene and offered by suppliers as a substitute
for the petroleum sulphonates, the main types available are:
I. Alkyl benzene bottom sui phonates: these are the sulphonates of the
residues from the distillation of the alkylation of benzene to make
detergent alkylate. The composition of such residues is a mixture of
dialkyl (averaging C12) benzene and diphenyl alkane (the alkane having
an average ofC12 and the phenyl groups being at both ends of the alkyl
 ANIONICS 105
chain). On sulphonation the diphenyl alkane gives a very water soluble
sulphonate which is washed out in the processing. Thus the sulphonate is
principally dialkyl benzene sulphonate with the length of the alkyl group
dependent upon the distribution of chain length used in the alkylation
reaction.
2. Dialkyl benzene sulphonates: the crude alkyl benzene bottoms (see
above) can be fractionated and the dialkyl benzene separated and then
sulphonated. The products are similar to the sulphonates in (1) above.
3. Synthetic long chain alkyl benzenes: the long alkyl chain is synthetically
produced at C20-C26 and then reacted with benzene.
4. Synthetic long chain alkyl xylenes: 'the alkyl chain is similar to that in (3)
but is generally shorter to obtain oil solubility.
5. Synthetic dialkyl (normally C9) naphthalenes. Oil solubility can be
achieved at lower alkyl chain length when naphthalene is the nucleus for
sui phonation.
The products are all made by conventional sui phonation reagents, either
oleum or sulphur trioxide. Oleum has been the major reagent used in batch
reactors but the production is difficult in removing the unreacted acid or
sodium sulphate. After neutralisation the product becomes water insoluble
and washing can give considerable problems in emulsification. In recent years
considerable efforts have been made to sulphonate the various alkylates using
continuous sulphur trioxide reactors which have been designed to manufac-
ture water soluble detergent sulphonates. This method has the advantage of
reducing problems of unreacted acid but the high viscosity of the starting
alkylates (much higher than conventional dodecyl benzene) can give severe
oxidation, poor conversions and considerable sludge formation.
All products are normaliy produced and sold as 40-60% solutions in a
mineral oil. The sodium, calcium and barium salts are the most common
although zinc and magnesium salts are available for special applications. The
divalent salts, e.g. calcium, can also be found with high levels of alkalinity from
finely dispersed calcium hydroxide or calcium carbonate; such products are
known as overbased or overbasified salts.

General properties

1. Solubility. Soluble in mineral oil particularly mineral oil which is

predominantly paraffinic with low aromatic content.
2. Chemical properties. In general have the properties of sulphonates, i.e.
stable to acid/alkali and good heat stability; overbasified salts will
combat acidic conditions, e.g. automotive crank case oils.
3. Functional properties. Emulsifying mineral oil in water; also the ability
to form microemulsions in the presence oflow molecular weight alcohols
and/or soap and alkanolamides; wetting, ability to replace water on a
106 HANDBOOK OF SURFACTANTS

metallic surface and adhere to that surface to give a degree of protection

against rust; excellent dispersing agents for insoluble dispersions in
mineral oils.
4. Disadvantages. The natural petroleum sui phonates are chemically very
ill-defined and subject to variability in some functional uses. This is not
easily detected using chemical tests. All the synthetic petroleum sulpho-
nates (groups (1)-(5) in the description above) do not exactly replace the
natural products and each group has its specific properties. Many of the
technically best products for use in lubricating oils and as rust
preventives are the barium salts, however at the time of writing there is
growing concern over the use of barium products in industry within
Europe.

Applications

1. Lubricating oil additives. Ammonium and sodium salts as detergents,

dispersants and rust inhibitors; overbasified salts of barium, calcium and
magnesium in conditions of high acidity, e.g. crank case oils for large
marine diesels.
2. Metal working. Oil in water emulsifying agents (sodium salts) for
mineral oil in producing soluble cutting oils; they also give some degree
of rust protection; they are usually used in admixture with other
surfactants with emulsifying properties such as fatty acid soaps, fatty
alkanolamides and ethoxylated alcohols or alkyl phenols; degreasing of
metal surfaces is possible using petroleum sulphonates modified with
fatty acid soaps and coupling agents to make emulsion or emulsifiable
cleaners.
3. Rust inhibitors. Calcium or barium salts for temporary metal protection;
the higher equivalent weight sulphonates ( > 500) are the most efficient.
4. Fuel oils and petrol. Rust inhibitors and sludge dispersant (ammonium,
calcium, barium and magnesium salts).
5. Pigment dispersants. Dispersing aids for pigments in organic solvents.
6. Petroleum production. Oil field drilling emulsifiers; crude oil demul-
sifiers; emulsifier for microemulsions in enhanced oil recovery (tertiary
recovery).
7. Mining. Petroleum sulphonates function as promoters or collectors and
lower molecular weight products act as frothing agents; main ores
processed with sulphonates are iron and silica sand.
8. Textiles. The type of formulations used in metal working are used in
textile processing oils to give fibre-metal and fibre-fibre lubrication.

Specification

Appearance, dark red brown viscous liquids

Active material, 50-60%
Equivalent weight of acid, 400-600
 ANIONICS 107
Molecular weight distribution, critical for some uses
Water, 0.5-5%
Acid number, 0.1-1 % (as sulphuric acid)
Inorganic salts (sodium sulphate), 0.1-1 %
Total base number, 0-400 mg KOH/g
Metal content (calcium and barium), 2-3% normal salts, 8-13% overbased
Inorganic chloride content, should be very low ( < 100 ppm) for rust inhibitors.
Equivalent weight equals molecular weight for monovalent salts, e.g.
sodium, but equal to half the molecular weight for the divalent salts, e.g.
calcium. The equivalent weight of the sulphonic acid before neutralisation is
nearly always in the range 400-600.
High molecular weight material gives good rust preventive properties whilst
lower molecular weight material gives good emulsifying properties. If both
emulsifying and rust preventative properties are required, the molecular
weight distribution must be carefully controlled.
The normal salts have total base numbers usually 0-20mg KOH/g but
overbased products have typically barium 70, calcium 300 and magnesium
400mg KOH/g. However 500-600 total base numbers are now probably
available.

6.7 Sulphosuccinates and sulphosuccinamates

6.7.1 Sulphosuccinates

Nomenclature

These products are esters of sulphosuccinic acid (see Figure 6.17). The acid
groups can be either the monoester (Figure 6.18) or the diester (Figure 6.19).
The monoesters are often called half esters.

Figure 6.17 Sulphosuccinic acid.

Figure 6.18 Monoesters.

Figure 6.19 Diesters.

108 HANDBOOK OF SURFACTANTS

Figure 6.20 Disodium coco alcohol ethoxylate (3) monosulphosuccinate.

Generic:
Dialkylsulphosuccinate, a diester
Fatty alcohol ether sulphosuccinate, could be mono- or diester but almost
always mono- if alcohol is ethoxylated
Half ester sulphosuccinate, a monoester
Sulphosuccinates, could be mono-or diester
Examples:
Sodium di(2-ethylhexyl)sulphosuccinate, a diester
Disodium coco alcohol ethoxylate(3) monosulphosuccinate, a monoester
formed from coconut alcohol (average Cl2 alkyl chain) ethoxylated with
3 moles of ethylene oxide (see Figure 6.20)

Description

Made by esterification of maleic anhydride and then reacting with sodium

bisulphite. The diester is made using 2 moles alcohol/mole of maleic anhydride
and the monoester using I mole alcohol/mole of maleic anhydride (see
Figure 6.21). The most common diesters are made with C8 and C9 alcohols
(which are readily available in bulk as they are used on a large scale for the
production of phthalate plasticisers for pvc). These alcohols can be isomeric
mixtures, e.g. isooctanol, or fairly pure products, e.g. 2-ethylhexanol.
There is a bigger variety of alcohols used in the preparation of monoesters
as the normal chain length ofthe alcohol is C12-C18 thus detergent alcohols,
ethoxylated alcohols or ethoxylated monoalkanolamides have all been used to
make the half ester. Practically any ethoxylate or propoxylate with a primary
hydroxyl end group can be used in the esterification. The most common
monoesters are based on ethoxylated coconut fatty alcohols or ethoxylated
alkanolamides.
The sulphation is carried out after esterification using sodium bisulphite
(usually a solution of sodium metabisulphite) in aqueous solution in the
presence of alcohol. Sulphation is very easy with the monoester because the
starting materials (due to the free carboxyl group) have some degree of water
solubility. Sulphation of the diester is not easy because the starting esters are
generally insoluble in water and the reaction is difficult to start. Once product
is formed, the reaction proceeds rapidly due to the sulphosuccinate acting as
solubiliser for the ester. The exotherm can be very violent and care must be
taken in large scale production.
 ANIONICS 109

1 mole ROH - CHCOOR

II
CHCOOH
CH-CO
II
CH-Cu
":::0 + or

2 moles ROH -CHCOOR

II
CHCOOR

CHCOOR CH 2 COOR
I + Na 2 S0 3 - I
CHCOOH CHCOONa
I
S03 Na
monoester
CHCOOR CH 2 COOR
II +Na 2 S0 3 - I
CHCOOR CHCOOR
I
S03 Na
diester
Figure 6.21 Production of sulphosuccinates.

Excess sulphite (present in metabisulphite) or bisulphite can be removed by

oxidation with hydrogen peroxide but the bisulphite oxidation product is
sodium bisulphate which is a strong acid. This strong acid or excess alkali can
give hydrolysis resulting in hazy products.
Impurities include unreacted hydrophobe, trisodium sulphosuccinate (from
the reaction of sodium sulphite, maleic anhydride and water), unreacted
sodium sulphite and maleic sulphonate (postulated).

General properties

1. Solubility. Disodium salts of the monoesters are generally insoluble in

organic solvents and very soluble in water. The sodium salts of the
diesters vary in solubility depending upon the chain length of the ester:

Solubility in water Solubility in paraffin

Ester group at 20 we e,~) hydrocarbons

Dicyclohexyl 20 Only soluble when warm

Dihexyl 30 Soluble
Dioctyl 1 Very soluble
Di-tridecyl 0.1 Very soluble
110 HANDBOOK OF SURFACTANTS

These solubilities are those of the diesters but most commercial products
contain alcohol as solvent and therefore commercial dialkylsulphosucci-
nates will be more soluble in small quantities of water than the above
figures would suggest.
2. Chemical stability. Monoesters are hydrolytically unstable at acid pH
and high temperatures; also unstable to alkali but to a more limited
extent; drifts to acid pH with alkanolamides but this tends to increase
viscosity while not affecting the foaming properties, whereas hydrolysis
of alkyl sulphates gives reduced foam and opacity (due to alcohol
released); keep pH between 5 and 9 in formulated products and
preferably pH 6-8. For diesters, the diisooctylsulphosuccinate is stable
between pH 1 and pH 10 at room temperature, i.e. more unstable to
alkali than acid; if long term stability is required in dilute solution then
pH 8 is probably a safe maximum.
3. Compatibility with aqueous ions. Monoesters have excellent mineral
acid and inorganic salt tolerance; calcium tolerance of 0.5% solution
> 2000 ppm CaC0 3 ; good tolerance to Fe, AI and Mg ions. Diesters
have moderate tolerance to hard water; calcium tolerance of 0.25%
solution = 300 ppm CaC0 3 .
4. Compatibility with other surfactants. As anionic, generally incompatible
with cationics but the Cl2 dialkanolamide monoester will tolerate small
amounts of cationics without interference.
5. Surfactant properties. Critical micelle concentration at 0.06% for most
diesters C6-C8 sodium salts but varies for monoester between 0.02 and
0.1 % depending upon the ether group. Minimum surface tension of
26 dyn/cm obtainable with C8 diester sodium salt; minimum surface
tension 'of monoesters is higher at approx. 30 dyn/cm but varies from 28
to 35 dyn/cm depending on ester group.
6. Functional properties. Wetting: diesters are outstanding in having
excellent wetting and penetrating properties; Draves wetting time for
0.025%) solution < 25 s; monoesters are average to poor wetters. Solubilis-
ing and emulsifying: both mono- and diesters are excellent solubilising
agents with the diesters outstanding in their capacity to form microemul-
sions (see Chapter 4).
7. Skin irritation. The monoesters are claimed to irritate the eyes and skin
less than other anionics, and to the same extent as the imidazolines. This is
why the ethoxylated alcohols or ethoxylated alkanolamides are used as
starting materials for these products, although they do give some-
what poorer foaming performance than the non-ethoxylated
alcohols or alkanolamides. In practice the monoesters are often used
as part replacement for ether sulphates in shampoos as they have a
detoxifying action on the ether sulphate.
8. Disadvantages. Poor detergency (although there are patents (USP
4,434,087) on the use of diesters of mixed C6 and C8 chain length which
claim to give excellent dish washing detergents when used with ether
 ANIONICS 111
sulphates); hydrolysis in alkaline conditions; poor solubilisation of
perfumery oils by the monoester.

Applications

Monoesters are used as follows:

1. Shampoos and bath additives. Behave as extremely mild foaming agents
but do not have the detergent power to be the sole ingredient; synergistic
effect with other surfactants, e.g. fatty alcohol sulphates and/or alpha
olefin sulphonates; low irritation is claimed for this mixture (Goldem-
berg, 1979). The longer the alcohol chain and the more EO the better the
irritation reducing properties (Sass, 1974). Alkanolamide based
monoesters have lower irritation than the fatty alcohol monoesters.
Products based on undecylenic acid monoethanolamide as foaming
agents also have fungicidal activity (Hunting, 1981).
2. Rug shampoos. Good detergent, copious foam, when used with lauryl
sulphate gives a dry residue easy to vacuum.
3. Polymer applications. Emulsifier in emulsion polymerisation to give
intermediate particle size in vinyl acetate/acrylate copolymers; emulsifier
for acrylate emulsion polymerisation for small particle size latices;
foaming agents for latices.
Diesters are used as follows:
1. Textiles. Wetting agent to improve dyestuff dispersability and speed up
the wetting and penetration of resin treatments.
2. Dry cleaning. Emulsifier/wetter for charge systems.
3. Paints and printing inks. Dispersing and flushing agents for pigments and
colours into organic media.
4. Metal treatments. Dewatering agent with mineral oil (WD-40 type
products).
5. Agriculture. Dispersing and wetting agent in wettable powders.
6. Polymer applications. Emulsifier and particle size control in both
suspension and emulsion polymerisation; dispersing pigments, colours
and dyes in plastics.

Specification
Monoester (Note 1) Diester (Note 2)
% solids 40-45 65-75
Solvent water water/isopropanol
Acid number (mg KOH/g) 1-3
Flash point Cc) 30-50
Solubility in water v. soluble low (1% at RT)
Note I-disodium sulphosuccinate fatty alcohol ethoxylate (3) ester
Note 2-monosodium sulphosuccinate, bis (2-ethylhexyl) ester
112 HANDBOOK OF SURFACTANTS

6.7.2 Sulphosuccinamates

Nomenclature

Generic:
Sulphosuccinamates
Example:
Sodium N-octadecyl sulphosuccinamate (see Figure 6.22)

Description

The most common commercial products are: N-octadecyl(stearyl), a paste at

35% active; N-oleyl, a liquid at 35% active. The products are manufactured by
reacting a long chain fatty amine with maleic anhydride and then sulphating
with bisulphite (see Figure 6.23).
Impurities include unreacted hydrophobe, unreacted bisulphite and long
chain amino acids by addition of the amine group across the double bond of
the maleic anhydride.

General properties

1. Solubility. Similar to the equivalent monoester sulphosuccinates but the

usual commercial sulphosuccinamates are the N-stearyl and N-oleyl,
whilst the most common monoesters are made from ethoxylated alcohols

Figure 6.22 Sodium N-octadecyl sulphosuccinamate.

RNH2 + CHCO - - RNHCOCH

II:::=::O I
CHCO CHCOOH

[+N"OO,
RNHCOCHS0 3 Na
I
CH 2COONa
Figure 6.23 ProductiQn of sulphosuccinamates.
 ANIONICS 113
or amides. Thus the sulphosuccinamates available are not very soluble in
water but do disperse. They are also insoluble in most organic solvents.
2. Chemical stability. More stable to alkali (due to the amide bond) than the
esters, hence their use in high pH latex compounds.

Applications

1. Textiles. Carpet backing: these products were developed on a large scale

for one specific end use, as the foaming agent for carboxylated styrene
butadiene latex which is applied to the back of tufted carpets. These
aqueous lattices were heavily loaded with chalk and the sulphosuccina-
mates showed outstanding ability to give stable foam in alkaline
conditions.
2. Emulslfiying agent for wax and oil polishes.

Speclfication

Solids content, 35%

Surface active content (S03) 3.5-5.0%
Free sulphite (as S02)' 0%.
Titration using hyamine with mixed indicator (ISO Method 2271) assuming
a molecular weight of 486 for the disodium tallow derivative and 493 for the
disodium oleyl derivative. Conversion rates can be low and therefore the
surface active component must be measured rather than assuming that solids
represent active material.

6.8 Taurates

Nomenclature

Generic:
Derivatives of methyl taurine CH 3-NH-CH 2-CH 2-S0 3
Sulphoalkyl amides
n-Acyl-N-alkyl-taurate has the structure RCON(R') CH 2CH 2S03" M+
Examples:
n-Cocoyl-N-methyl taurine has the structure CocoCON(CH 3 )-
CH 2CH 2SO;Na+

Description

Prepared by reaction offatty acid chloride on methyl taurine (see Figure 6.24).
The methyl taurine is made from sodium isethionate and methylamine
(CH 3 NH 2). Taurine, a similar product but without the methyl group, can be
114 HANDBOOK OF SURFACTANTS

Figure 6.24 Preparation of taurates.

made in the same way but has inferior detergent properties to the methyl
taurine.
Impurities include soap and sodium chloride.

General properties

l. General. Similar to the corresponding fatty acid soaps in soft water but
more effective in hard water and not sensitive to low pH (unlike the
isethionates) and better wetting agents; similar in many properties to the
corresponding isethionate but the taurates are more hydrolytically stable
than the isethionates; the taurates can be looked upon as amide
derivatives of sulphates just as sarcosinates are amide derivatives of soap;
both are milder than their counterparts because of the amide group;
taurates perform better in hard water than sarcosinates.
2. Solubility. Sodium salt ofC12-C14 soluble in hot water and cold water
(> 50% solution at 70°C, > 50% at 25°C); oleic acid derivative > 50%
solution at 70°C, 14~~ at 25°C).
3. Compatibility with aqueous ions. Calcium and magnesium salts are
soluble in high concentrations of electrolyte.
4. Chemical stability. Very stable to hydrolysis under acid and alkaline
conditions, hot or cold.
5. Surface active properties. Coconut derivative surface tension at
0.1 % = 32 dyn/cm, oleic derivative, 32 dyn/cm.
6. Functional properties. Good foaming properties (0.05% cone. Ross and
Miles, initial foam coco derivative 115 ml, oleic derivative 98 ml) but
not as good as alkyl sulphates; does not reduce foam of soap solutions;
excellent detergent for grease and oil; also effective detergent for solid soil
(better than isethionates); excellent wetting agent even under extreme
conditions of temperature and pH; good suspending power for dirt
particles and reduces re-deposition when used in formulated detergents;
good lime soap dispersant; low foam anionic (very few such products)
when alkyl group is cyclohexyl and the palmitoyl derivative is used, i.e.
ClsH31-CO-N(C6Hll)-CH2-CH2-S0; Na+.

Applications

l. General. Mild cleaner, foaming agent foam boost stabiliser, conditioner;

formerly widely used in shampoos but replaced by lauryl sulphates and
ether sulphates.
 ANIONICS 115
2. Household products. Sea water laundering.
3. Shampoos. The cocoyl methyl taurate has been suggested as an ideal
ingredient to blend with AOS in shampoos and it is claimed to be as
effective as alkanolamides in boosting and stabilising the foam height of
AOS; bubble baths and toilet bars, both with soap mixtures; taurates can
be used with soap and not affect the foam unlike ether sulphates which
are defoamed with soap.
4. Agriculture. Pesticide powders; gives good wetting and dispersability.
5. Textiles. Disperses pigments and facilitates removal of loose colour
from dyestuffs and printed goods; oleic derivative used in textile scouring
(kier boiling in alkali) and in dyeing to remove loose colour and give a
levelling effect on acid dyestuffs applied to wool and nylon.

Specification

Appearance, white paste or liquid

Active, 20-25%
Sodium chloride, 1-10%
Free fatty material, 1-5%.

References

Adam, W.E. and Neumann, K. (1980) Fette, Siefen, Anstrichm. 82 (9),367-370.

Bruson, H.A. (1937) US Patent 2,098,203 to Rohm and Haas;(J938) US Patent 2,106,716 to Rohm
and Haas; (1938) US Patent 2,115,192 to Rohm and Haas.
Goldemberg, R.L. (1979) J. Soc. Cosmet. Chem. 30, 415-427.
Hart, lR. and DeGeorge, M.T. (1982) The effect of conditioning ingredients on the lathering
potential of anionic surfactants, presented at the Society of Cosmetic Chemists Annual
Scientific Seminar, Memphis, TN.
Hunting, A.L.L. (1981) Cosmetics and Toiletries 96 (8), 29-34.
Knaggs, E.A., Yeager, J.A., Varenyl, L. and Fischer, E. (1965) J. Am. Oil Chem. Soc. 42, 805.
Moreno, A., Bravo, J. and Berna, lL. (1988) J. Am. Oil Chem. Soc. 65 (6), 1000-1006.
Sass, C. (1974) Sulphosuccinates and the cosmetic types available, presented at the Society of
Cosmetic Chemists Annual Scientific Seminar, Chicago, IL.
Shupe, R.D. (1977) US Patent 4,018,278 to Texaco.
Trautman, T. and Jurges, P. (1984) Tenside Detergents 21(2), 57-61.
7 Non-ionics

7.1 General introduction

Non-ionic surfactants are surfactants which do not have a charged group. The
hydrophilic group is provided by a water soluble group which does not ionise.
The most common are the hydroxyl group (R-OH) and the ether group
(R-O-R'). Other groups are the oxide (amine oxide) and triple unsaturated
bond (acetylenic alcohols).
The water solubilising properties of a hydroxyl group or an ether group are
low compared to the sulphate or sulphonate groups. If only one hydroxyl or
one ether group is present, the chain length of the hydrocarbon R will be only
6-8 before the product becomes insoluble and has poor surfactant properties.
Thus dodecyl alcohol is practically insoluble and aqueous solutions show
poor foaming, poor detergency, poor wetting, etc. Surfactants showing
desirable properties are obtained using multihydroxyl groups or multi-ether
groups to increase water solubility. In practice the most versatile method of
using ether groups is by the addition of ethylene oxide to the hydrophobe.
Ethylene oxide will react with a hydrogen atom attached to a hydrophobic
group (see Figure 7.1). The amount of ethylene oxide in the molecule can be
controlled by varying the amount which is added to the hydrophobe. The
reaction is almost quantitative. Any free ethylene oxide can easily be removed
at the end of the reaction (it is a gas at room temperature). The larger the
amount of ethylene oxide the more water soluble the product. The properties
of the ethoxylates will depend mainly upon the hydrophobe used but can also
be affected in a minor way by the method of ethoxylation because the value of n
is only an average value and the actual number of ethoxy groups will be a
distribution around the average value. The latter can, on occasions, be
important to the formulator so that the empirical formula given above will not
truly reflect the structure of the surfactant.
The alternative method of using multi hydroxyl groups is not utilised to the
same degree in practice because there is no easy cheap method of attaching
multiple hydroxyl groups on to a hydrocarbon. Nevertheless many surfactants

R~H + nCH -CH ~ R--(CH -CH 0) H

~o' 2 2 2 n

Figure 7.1 Ethoxylation.

 NON-IONICS 117
are based on this principle because of the widespread occurrence of
multihydroxyl products in natural products, i.e. the saccharides, multi sac-
charides and carbohydrates. However the chemistry is complex and the
intermediates are often high melting solids which can degrade on heating. A
very large amount of research has been carried out and many surfactants
based on multihydroxyl groups are on the market but they do not offer the
formulator the same variety of properties obtained from the ethoxylated
derivatives. Nevertheless there are significant problems surrounding ethylene
oxide and its derivatives and more efforts will probably be made in the future
to find alternatives to ethylene oxide. Some space is therefore devoted to
various alternatives to ethylene oxide.
Examples of ethoxylates (from ethylene oxide reacting with a hydrophobe)
are:
• Alcohol ethoxylates
• Mono alkanolamide ethoxylates
• Fatty amine ethoxylates
• Fatty acid ethoxylates
• Ethylene oxide/propylene oxide copolymers
• Alkyl phenol ethoxylates
Examples of multihydroxyl products (from reaction of a hydrophobe with a
multihydroxyl product by esterification) are:
• Glucosides
• Glycerides
• Glycol esters
• Glycerol esters
• Polyglycerol esters and polyglycerides
• Polyglycosides
• Sorbitan esters and sorbitan ester ethoxylates
• Sucrose esters
The description of non-ionic surfactants will follow closely that of anionics,
i.e. by describing groups of surfactants which have a similar hydrophilic group.
However, ethoxylated products share many common characteristics which
are independent of the hydrophobe and it is simpler and avoids repetition if
these common characteristics are described in this section.

7.1.1 The chemistry of ethoxylation

An examination of the chemistry of the reaction between ethylene oxide and

the various hydrophobes will give considerable insight into the properties of
the various ethoxylates. The mechanism of ethoxylation depends upon the
catalyst used but most common ethoxylates are made using an alkaline
118 HANDBOOK OF SURFACTANTS

Table 7.1 Ethoxylation of alcohols and phenols with 3 moles

of EO

Dodecyl Nonyl
alcohol phenol
(%) (%)

Free starting material 22 o

Starting material + I EO 10 10
Starting material + 2 EO 14 24
Starting material + 3 EO 16 27
Starting material + 4 EO 15 20
Starting material + 5 EO 12 II
Starting material + 6 EO 7 5

catalyst. Using alkaline catalysts, the rate of ethoxylation is dependent upon

the ionisation of the active hydrogen. The acid ionisation constants in water
are: alcohol, 10 - 15; phenol, 10 - 9; carboxylic acid, 10 - 5.
There are three different situations:
1. Where the active hydrogen on the starting material is equal in reactivity
to that of the ethoxylate which is formed, e.g. starting material is an
alcohol, an amide or water. As more ethylene oxide is added to the
alcohol ethoxylate, the ethylene oxide adds on in a random manner to
any hydroxyl group and therefore free alcohol remains until a very large
amount of ethylene oxide has been added.
2. Where the active hydrogen on the starting material is more acidic than
that of the ethoxylate which is formed, e.g. starting material is a phenol,
mercaptan or carboxylic acid. As ethylene oxide is added to the alkyl
phenol it is preferentially added to the hydroxyl group attached to the
benzene ring, i.e. the starting material. Thus all the phenol group reacts
before any EO goes on to the hydroxyl group on the product. The
difference is shown on comparing the ethoxylation of an alcohol or alkyl
phenol with 3 moles of ethylene oxide (Table 7.1). Table 7.1 illustrates
typical figures. A change in catalyst and/or reaction conditions will affect
these figures although the major difference of high free dodecyl alcohol
will remain.
3. Where the active hydrogen on the starting material is less acidic than that
of the ethoxylate which is formed, e.g. starting material is an amine. Using
basic catalysts, very little reaction with ethylene oxide would take place
because ionisation of the hydrogen on the amine in the presence of a base
does not take place to any practical extent. However, amines will react
readily with ethylene oxide if either water or an acid is present to give an
ethanolamine (Figure 7.2). The ethanolamine formed can then be reacted
with further ethylene oxide using a basic catalyst.
 NON-IONICS 119
water. R_N/CH2CH20H
'---CH 2CH 20H

Figure 7.2 Reaction of ethylene oxide with amines.

The ethoxylation of an alcohol or alkyl phenol gives a distribution of chain

lengths. This distribution is dependent upon the catalyst used and the
conditions of ethoxylation. In the majority of applications the exact distri-
bution is not that critical but there have been specific applications where the
distribution can be critical. The easiest way to change the distribution is by
using a blend of two ethoxylates but this can only broaden the distribution.
There have been attempts to commercialise ethoxylated alcohols with a
narrow distribution.
Impurities in the finished ethoxylate include:
1. Polyglycols. The hydroxyl group on water can take part in all the
reactions as ethylene oxide will react with water, particularly under basic
catalyst conditions, to form polyglycols. Thus it is necessary to remove
water from the starting materials (except for amines where the level must
be controlled) or the formation of polyglycols is inevitable. Polygylcols
can be formed however in the absence of water. Polyglycols are often
insoluble in the non-ionic and show as a haze or even separate out.
Addition of water to the finished non-ionic will often clear the haze so a
clear ethoxylate is no guarantee that it does not contain polyglycols. For the
majority of detergent applications small quantities of poly glycols are not
detrimental, but there are applications where they can affect surfactant
functional performance.
2. Ethylene oxide. Unreacted ethylene oxide is left at the end of the reaction
and is readily removed by vacuum and heating. However, very small traces
(1-25ppm) remain in the ethoxylate and this quantity slowly reduces
with time. Very small levels of EO are demanded for cosmetic use.
3. I,4-Dioxane. Formed in small amounts ( < 50 ppm) in most ethoxylates;
can be removed by steam distillation; very low levels required for
cosmetic use.

7.1.2 General properties ojnon-ionics

7.1.2.1Solubility in water. The solubility of EO derivatives is due to the

hydrogen bond between water and the EO group. Energy of hydrogen bond
120 HANDBOOK OF SURFACTANTS

Table 7.2 Cloud points of ethoxylates

Octyl phenol + 8.5 EO

Cloud
point
(Y" Concentration) ('C)

0.01 > 100

0.015 > 100
0.02 38
0.03 48
0.05 48
0.10 49
0.50 50
5.0 50

is approx. 7 kcaljmol and heating can impart enough energy to destroy the
bond. Dehydration takes place and the product comes out of solution; the
temperature at which this takes place is known as the cloud point. On cooling,
the product dissolves. A 1% solution is usually used for determination of the
cloud point as, at low concentrations, the cloud point is dependent upon the
concentration (Table 7.2). The water solubility increases as the amount of
ethylene oxide increases. There is a simple rule of thumb relating the amount
of ethylene oxide with the number of carbon atoms (N) in the hydrophobe
to achieve water solubility; water solubility just achieved at N /3 moles of
EO; fairly good water solubility at N/2 moles of EO; very good water
solubility at 3N/2 moles of EO.
Non-jonics tend to have maximum surface activity near to the cloud point.
Addition of alkalis and/or inorganic salts generally lowers the cloud point
but there is no consistent pattern on the addition of inorganic acids. Addition of
large quantities of inorganic salts can cause precipitation at room temperature
(salting out). The order of salting out of inorganic anions and cations has
been summarised by Meguro et al. (1987) as: SO/ - > Cl- > Br - > N0 3 - and
Na + > K + > Li +. Addition of mineral acids does not usually cause reduction
in cloud point and solubility. Addition of non-polar liquids generally increases

Table 7.3 Effect of added non-polar liquids to cloud points

Compound added Cloud point of 1%

to saturation nonyl phenol + 9EO ("Cl

None 56
n-Heptane (C 7 H'6l 71
n-Decane (C,oH 22 l 79
n-Dodecane (C 12 H 26 ) 79
n-Hexadecane (C'6H34l 80
Cyclohexane 54
Ethyl benzene 31
Ethylene tetrachloride 31
 NON-IONICS 121

1
Viscosity

50
.. 100
Concentration (%) in water

Figure 7.3 Viscosity of ethoxylates.

the cloud point but there are exceptions (Table 7.3). Addition of aromatic and
polar aliphatic compounds generally reduces cloud point, particularly
aliphatic alcohols, fatty acids and phenols.
Double cloud points are sometimes observed with mixtures of non-ionics
and some EO/PO co-polymers. On increasing the temperature the solution
first becomes turbid then less turbid, hazy and then turbid again. Non-ionics
with hydrophobic groups with two or three side branches have decreased
cloud points compared to linear products and do not form spherical micelles.
Most water soluble ethoxylates form very viscous solutions or even gels at
concentrations of 40-70% in water (see Figure 7.3). In order to prepare dilute
solutions, ethoxylates must be added to well-stirred water. To prepare
concentrated solutions, water must be added to well-stirred ethoxylates.

7.1.2.2 Compatibility with other suifactants. Ethoxylates are compatible with

all other surfactants. This does not mean that they are inert to other
surfactants. In fact synergy is very strong with anionics and mixed micelles
with other surfactants are well known.

7.1.2.3 Chemical stability of the polyoxyethylene chain. Non-ionics show

excellent chemical stability in a very large number of aqueous formulations
particularly household products. Nevertheless the polyethoxy chain shows
behaviour similar to that of the simple ethers and undergoes oxidation very
readily. Oxidation can cleave the polyethoxy chain which will then change the
122 HANDBOOK OF SURFACTANTS

surfactant properties as the degree of hydrophilicity has been reduced. The

chemical stability of products where the polyethoxy chain is attached to the
hydrophobe by an ester or amide group is described in the relevant section
dealing with ethoxylated esters or amides. In the majority of cases, oxidation
will attack the polyethoxy chain before the hydrophobic chain unless
unsaturation is present in the hydrophobic chain.
When free radicals are introduced into a system containing polyethoxy
groups, they initiate oxidation so long as oxygen is present. A chain reaction is
set up which is propagated by the regeneration of new free radicals.
Hydroperoxy groups are intermediates which accumulate as they are more
stable than the free radicals. Catalysts can have a profound influence on the
formation and the decomposition of the hydroperoxides. Transition metal
ions (e.g. copper, cobalt, manganese), even at very low concentrations (a few
parts per million), can induce decomposition of the peroxide. Reducing or
oxidising agents (e.g. ferrous ions, bleach) can accelerate peroxide decompo-
sition. Acid catalysts can accelerate peroxide decomposition to form aldehyde
groups which can give rise to coloured compounds.
On oxidation, the peroxy concentration first increases to a maximum and
then decreases as the peroxy compounds degrade into the final product. A
variety of final product groups can be found which depend upon the
conditions of oxidation, the temperature, the catalyst, etc. The principal
organic groups to be found are: carboxylic acids; aldehydes; alcohols; lactones;
esters. Some of these groups may have a better water solubility than the ether
group but scission of the polyoxyethylene chain commences almost from the
start of the oxidation, whatever the product groups formed. The overall effect
will change the surface active properties, but the interpretation ofthe chemical
effect by the observed physical effect is extremely difficult if not impossible. An
example is viscosity, which should fall if chain scission takes place but nothing
else except the molecular size changes. However, a change in the water
solubility may change the size of the micelle, which will then influence the
viscosity.
As the cloud point is a measure of water solubility of the hydrophilic chain,
oxidation and scission of the chain would be expected to give decreased cloud
points which has been shown to !Je true in practice. Thus the cloud point can
be used as a measure of oxidation, but again care should be taken in
interpretation as there can be many reasons for reduction in cloud point.
The most common methods for determining hydroperoxide are iodine or
arsenite titrations. However in the presence of non-ionic surfactants as much
as 40% of the iodine liberated from the potassium iodide by the hydroper-
oxides was found to be unavailable for titration (Henderson and Newton 1966,
1969; Hugo and Newton, 1963).
Hydroperoxide formation is increased by:
• Decreasing the surfactant concentration
• Increasing exposure to light
 NON-IONICS 123
• Increasing temperature (e.g. sterilisation by autoclaving)
• Bleaching with hydrogen peroxide
• Decrease in pH below 6
• Presence of transition metal ions
Stabilisation of polyoxyalkylene derivatives requires the following:
• Store in the dark
• Minimal air access, store under nitrogen if possible
• Temperature as low as possible
• Buffer aqueous solutions to neutrality
• Low concentrations should be avoided wherever possible
• Add antioxidant, but check that the non-ionic already contains an
antioxidant; get non-ionic manufacturers recommendation on the
antioxidant to use
The great majority of aqueous surfactant formulations containing
polyoxyethylated surfactants will not need any further stabiliser added other
than that added by the non-ionic manufacturer. However, the formulator
should be aware of the tendency of such products to oxidise as many
formulations are used in oxidising conditions.

7.1.3 Surface active properties of non-ionics

7.1.3.1 Surface tension. The surface tension decreases with increasing

concentration in a similar manner to all surfactants but the minimum surface
tension obtained increases as the degree of ethoxy1ation increases, i.e. the
lowest water solubility gives the lowest surface tension (Figure 7.4).

surface
tension

1 NP+18EO
NP+10EO
NP +30 EO

NP+6 EO

0.001 O.Oi 0.1 1.0

log concentration

Figure 7.4 Effect of EO content on surface tension.

124 HANDBOOK OF SURFACTANTS

7.1.3.2 Micelles. The size of the micelle for non-ionics is very much larger
than that for anionics or cationics (see Chapter 4).

7.1.3.3 Critical micelle concentration (CMC). In general the CMCs for

ethoxylated products are much lower than for ionic materials of similar
activity being of the order of 10- 4 moIjlitre. Factors affecting the CMC are:
I. The effect of varying ethylene oxide content. From Figure 7.4, the CMC
obviously increases with increasing degree of ethoxylation, but when
the molar concentration is calculated, the effect is not so pronounced
(see Table 7.4).
2. The effect of temperature. The CMC decreases with increasing tempera-
ture, the molecule becoming more insoluble (dehydration of the
polyoxyethylene chain) and thus becoming more surface active. For
anionics the CMC increases with an increase in temperature because the
molecule becomes more soluble and hence less surface active. What is
more important is that the aggregation number or size of the micelle
increases rapidly with temperatures near the cloud point. Thus the
micelle is considerably larger to solubilise other products. At or near the
cloud point the size ofthe micelle becomes so large that it is visible, i.e. the
non-ionic comes out of solution. Thus non-ionics are most efficient at
solubilisation near the cloud point.
3. The effect of added inorganic salts. In general, added inorganic salts will
result in a decrease in CMC being more dependent on the anion than the
cation.
4. The effect of added polar solvents. If a polar solvent (e.g. ethyl alcohol) is
added to lauryl alcohol ethoxylates, micelle formation no longer occurs
above 25% alcohol (sodium lauryl sulphate micelles vanish at about 40%
ethanol in water).
5. The effect of side groups in the hydrophobic chain. Increases the CMC
compared to linear chain due to inhibition of micelle formation by the
bulky side groups.

Table 7.4 CMC and degree of ethoxylation

Molecular
Product' CMC (mol/litre) weight CMC(%)

NP+4EO 29.5 x 10- 6 380 0.0011

NP+5EO 61 x 10- 6 424 0.0026
NP+6EO 61 x 10- 6 468 0.0028
NP+7EO 70 x 10- 6 512 0.0035
NP+8EO 44 x 10- 6 556 0.0025
NP+9EO 67 x 10- 6 600 0.0046
NP+ 10EO 68 x 10- 6 644 0.0044
NP+20EO 79 x 10- 6 1113 0.0088

, The nonyl phenol ethoxylates were commercial unfractionated materials.

 NON-IONICS 125
7.1.3.4 Functional properties

General. Excellent detergents; poor foaming properties (this does not mean
that they cannot create and/or stabilise foam in the presence of other
surfactants); poor wetting; good emulsification; do not adsorb on charged
surfaces.

Wetting. For aqueous solution, HLB (see Chapter 4) value approx. 7-9 is
the optimum (Table 7.5). The wetting times of the best were in the order
shown in Table 7.5, i.e. C8 + 2 EO the best and C18 + 10 EO the worst.
Addition of electrolytes generally reduces the wetting power.

Foaming. As a class, non-ionics are moderate to low foamers but at the

optimum EO content and at their optimum temperature for foaming they are
nearly as good as LABS (see Table 7.6). The data in Table 7.6 are the result of
experience and looking at various published works. The exact composition of
some samples are not known and the temperature of the test is not always
given. Therefore these results should be treated with caution but they do
illustrate the very different results obtained with different tests for foaming.

Table 7.5 Wetting and EO content

EO content for
Product optimum wetting"

C8 alcohol 2EO
CIO alcohol 6EO
CI6 alcohol 9EO
CI8 alcohol 10EO
" These conclusions were made using a sinking
method with a canvas disk. Different test
methods give slightly different results but there
is no doubt that the smaner hydrophobes give
the better wetting properties.

Table 7.6 Foaming and EO content

EO content for optimum (at 25°q

Product Foam height" Foam stabilityb

C8 saturated alcohol 15 4
CI2 saturated alcohol 8-12 4-10
CI6 saturated alcohol 20 4-8
CI8 saturated alcohol 15-20 4-10
Nonyl phenol 25 5-6
• Ross-Miles method gives flash foam.
b Aeration method to measure dynamic foam stability.
126 HANDBOOK OF SURFACTANTS

Non-ionic surfactants can be d"efoamers when they are practically insoluble

(i.e. at or above their cloud point) in the system but are more often employed as
foam stabilisers for anionics, e.g. alkanolamides (see Section 7.4). Foam
stabilisers are soluble in the system so a foam stabiliser for LABS at room
temperature would be a C 12 alcohol + 8-10 EO. LABS could be defoamed
with a EO/PO co-polymer containing sufficient PO that the product is just
insoluble at the temperature of use.

Solubilisation. Solubilisation is the dissolving of a water insoluble substance

in an aqueous solution of a surfactant to form a clear homogeneous solution.
Solubilisation takes place in the micelles and as non-ionics form micelles at
concentrations appreciably lower than anionics or cationics, it would be
expected that non-ionics would therefore solubilise organic compounds at
lower concentrations than the charged species. In addition, the larger size of
the non-ionic micelles together with the solubilising property of the
polyoxyethlene glycol chain as well as the hydrophobe would suggest that
non-ionics should be very useful for solubilising organic compounds in
aqueous solution.
The solubilisation end point for ionic surfactants can be detected by the
formation of turbidity or an emulsion. This is not the case for non-ionics
because it is difficult to differentiate between the limit of solubilisation and the
haze formed by depression of the cloud point. Thus much published data
should be interpreted with suspicion. From the practical point, whether the
limit of solubility is reached by cloud point or solubilisation would not seem to
matter. However the reason for the incompatibility needs to be understood. In
general maximum solubilisation is of the order of 1-3 moles of solubilisate per
mole of surfactant. Thus, do not expect a 0.1 % solution of a non-ionic to
solubilise 25% of a hydrocarbon.
Some generalisations as a guide for dilution (0.1-1 % surfactant solution)
are:
• n-Hydrocarbons show least solubilisation decreasing with increasing
length of the hydrocarbon chain
• Aromatic hydrocarbons show moderate solubilisation
• Polar compounds, e.g. alcohols, amines, ketones, fatty acids show the
highest solubilisation decreasing with increase in molecular weight
• Mixed surfactant systems can show synergism
• Solubilisation is most effective with high HLB values (> 15) (see
Chapter 4)
For solubilisation with concentrated solutions, the concept of a globular
micelle surrounded by an aqueous phase is no longer valid and thus
solubilisation depends upon the structure of the surfactant in solution (see
Chapter 4).
For solubilisation in non-aqueous solutions, surfactants form micelles in
 NON-IONICS 127
non-aqueous solution. Thus non-ionics which will dissolve in mineral oil can
solubilise water or aqueous solutions in the mineral oil.
Data on solubilisation is not often published but a useful list of early
literature references are given by Nakagawa (1967). References are given for
non-ionics which will solubilise saturated hydrocarbons, unsaturated hydro-
carbons, halogenated hydrocarbons, alcohol, phenol, acids, esters, ethers,
amines, vitamins, steroids, dyes, iodine and water.

Emulsification. Emulsification, in this section, is where the emulsion is an

opaque white liquid with two distinct separate phases. For microemulsions,
see Chapter 4. Non-ionics have found wide use as emulsifying agents. In
practice the most stable emulsions are often made by two or more surfactants
of differing hydrophobic/hydrophilic properties (HLB, see Chapter 4). The
addition of ethylene oxide in various proportions can provide such variations
and the use of emulsification systems based on products with varying ethylene
oxide content is the best practical way of choosing surfactants for any
emulsification problem. The major systems in use are:
• Sorbitan esters and their ethoxylated derivatives (Section 7.11)
• Alkyl phenol ethoxylates (Section 7.15)
• Alcohol ethoxylates (Section 7.3)
• Fatty acid ethoxylates (Section 7.10)
In each of these systems there are products of varying solubility from soluble in
mineral oil to soluble in water, enabling both water in oil (W /0) and oil in
water (O/W) to be made (see Chapter 4). Non-ionics are also less affected by
the presence of electrolytes and pH changes in the water phase. For choice of
emulsifier, see Table 7.7. There are many published lists of HLB values for
non-ionics and the HLB value is an excellent way of indicating the degree of
water or oil solubility of a product. The author considers that knowing the
ethylene oxide content, the hydrophobic structure and chain length are
probably of greater value in assessing the emulsifying properties of a non-ionic
surfactant. Lacking that information, the HLB value is useful. For HLB values
required to emulsify various oil phases, see Schick (1967).

Dispersing properties. Non-ionics help to disperse organic or inorganic

particles in aqueous or non-aqueous systems. They help in wetting out,
reducing the work needed for dispersion, prevent aggregation of the particles

Table 7.7 Emulsification and HLB number

HLB number Application

2-7 Water in oil

7-18 Oil in water
128 HANDBOOK OF SURFACTANTS

and reduce flocculation and settling. Polymeric water soluble compounds (e.g.
starch, polyvinyl alcohol) are used for this purpose and the polyoxyethylene
chain in the non-ionics behaves in a similar manner.

Detergency. There is a very large volume of data on the optimum carbon

chain length of the hydrophobe and the ethylene oxide content of non-ionics
for detergency, much of it contradictory. The main problem is the test method
and the other components in the detergent. Work on distilled fractions of
ethoxylated dodecyl alcohol showed that whiteness retention and soil removal
were optimised at different ethylene oxide levels, i.e. soil removal best at C12
alcohol + 7-8EO but whiteness retention best at CI2 alcohol + 4-5EO. Thus
the wide distribution of the ethoxylated non-ionics may be an advantage for
practical detergency. On examining the published data on nonyl phenol
ethoxylates, the optimum detergency for cotton would seem to be in the area of
8-10 moles of ethylene oxide. HLB (see Chapter 4) values in the range 13-15
have been quoted as the optimum. Comparison of ethoxylated fatty acids,
fatty acid amides, fatty alcohols and mercaptans (Kassem, 1984) showed that
the C12 chain was the optimum hydrophobe chain length for all the products
examined. However other people (Shell Technical Data Sheets) have shown
that optimum detergency is obtained with 50/50 mixtures of C14/C15 with
EO content at 11 moles.
The type of soil has also a big effect on the efficiency of the detergent and
non-ionics, in general, are more efficient in removing oily and organic dirt than
inorganic or polar dirt. The effect of concentration is important with optimum
concentration at 0.1 %or greater (particularly if the non-ionic is well below the
cloud point). Note that this is several orders of magnitude above the CMC.
The temperature is important with the maximum optimum detergency at or
near the cloud point.
In practice non-ionics are usually used in blends with anionics for heavy
duty performance, with the anionics in the larger proportion. More recently
the amount of non-ionics has increased relative to the anionics for lower
temperature washing powder detergents. In liquid detergents, the non-ionics
are used at even higher concentrations.

7.2 Acetylenic surfactants

Nomenclature

Generic:
Acetylenic diols
Acetylenic glycols
Acetylenic surfactants
Surfynols (trade mark of Air Products Inc.)
 NON-IONICS 129
CH 3 CH 3
I I
C2HS -C-C=C-C-C 2H S
I I
OH OH
3,6-dimethyl-4-octyne-3,6 diol
CH 3 CH 3 CH 3 CH 3
I I I I
CH3-CH-CH2-C-O:::==C-C-CH2CH-CH3
I I
OH OH
2,4,7,9 tetramethyl-S decyn-4,7 diol
Figure 7.S Acetylenic surfactants.

Examples:
Dimethyloctynediol or 3,6-dimethyl-4-octyne-3,6-diol (see Figure 7.S)
2,4,7,9-Tetramethyl-S-decyn-4,7-diol (see Figure 7.5)

Description

The products are difficult and expensive to make from acetylene. They are
often in the form of free flowing powders manufactured by adsorption of
active surfactant onto finely divided silica.
The hydroxyl groups may also be reacted with ethylene oxide. Ethoxylation
of hydroxyl groups increases water solubility without loss in surface active
properties, but products become liquid and lose steam volatility.

General properties

1. Crystalline solids (rare with non-ionics). Dimethyl octynediol is a white

odourless crystalline solid, m.p. SO°c.
2. Solubility. Low solubility in water unless ethoxylated; soluble in al-
cohols and glycols; soluble in polar solvents, e.g. ketones, butyl
cellusolve.
3. Functional properties. Low foam, reduces foam of anionic and non-
ionics whilst increasing wetting; excellent wetting agents at low con-
centrations; in combination with other surfactants there is a synergistic
effect giving even better wetting; low molecular weight products are
volatile with steam so can be easily removed from the system; reduces
viscosity of vinyl plastisols and starch solutions.
4. Disadvantages. Expensive on an active basis compared to commodity
surfactants, but in some applications very small quantities of active are
130 HANDBOOK OF SURFACTANTS

needed and therefore can compete on a cost/efficiency basis; very low

solubility in water unless ethoxylated; unstable to acids.

Applications

I. Shampoos. Dimethyl octynediol used as a solubiliser and clarifier for

shampoos.
2. Surface coatings. Wetting agent particularly for aqueous systems of
industrial coatings on oil contaminated steel to give better coverage and
good recoatability; defoamer and pigment dispersing agent.
3. Oil field chemicals. Corrosion inhibitors
4. Agricultural chemicals. Additive to wettable powders to give low foam,
good wetting and increased re-dispersability.

Specification

Appearance, white waxy solid with sharp melting point (usually 100% active),
liquid (SO-7S% active in alcohols or glycols) or free flowing powder (adsorbed
on silica, approx. S% active); cloud point, < 100°C, likely to be an ethylene
oxide adduct.

7.3 Alcohol ethoxylates

Nomenclature

Abbreviations: AE, alcohol ethoxylates, used in this book; AEO.

Generic:
Alkyl polyoxyethylene glycols
Ethoxylated fatty alcohols
Monoalkylpolyethylene glycol ethers
Polyoxyethylene alcohols
Polyoxyethylated fatty alcohols
Polyoxyethylenated straight chain alcohols
Examples:
Coco alcohol + SEO,this represents the alcohol derived from coconut fatty
acid reacted with five molecules of ethylene oxide.

Description

The main commercial products are based on the following alcohols:

Mixed coconut oil fatty acid fractions hydrogenated, C12-C14 chain length
Synthetic straight chain CI2-CI8, various fractions based on Ziegler
 NON-IONICS 131
Table 7.S Dodecanol + 3EO

Component

Free dodecanol 22
Dodecanol + I EO 10
Dodecanol + 2EO 14
Dodecanol + 3EO 16
Dodecanol + 4EO 15
Dodecanol + 5EO 12
Dodecanol + 8EO 3
Dodecanol + 12EO 0.5

alcohols, i.e. even number chain lengths

Synthetic straight chain C12-ClS, various fractions based on oxo alcohols,
i.e. odd and even numbered chain lengths
Natural alcohols, e.g. castor oil
Tallow derived C16-C18, products with high oleyl content are more fluid
than the saturated derivatives
Hardened tallow C16-C18, hydrogenated products with low unsaturation.
The ethoxylation of a primary alcohol gives a different distribution to that
of a nonyl phenol or carboxylate (see Section 7.1.1). The result is that free
alcohol remains in most ethoxylates when the degree of ethoxylation is not
high, thus for the reaction between dodecanol and 3 moles of EO the resulting
ethoxylate has the composition shown in Table 7.8.
In end blocked non-ionics and low foam alcohol ethoxylates, the terminal
OH may be reacted with propylene oxide to give reduced foam but the degree
of biodegradability decreases as the propylene oxide content increases. In
addition the terminal H on the EO or PO chain can be replaced with an alkyl
group or the benzyl group. They are used to chemically stabilise the products.
If the end group is bulky, e.g. benzyl, then foam reduction is also obtained. A
number of newer low foam alcohol ethoxylates are now available:
R-O-(EO)n-(PO)m- R'
R-O-(EO)n-R"
R-O-(EO)n-benzyl
R-O-(EO)n-(BuO)m-H
where R = aliphatic alcohol CIO-C16, R' = alkyl group C 1 -C 3 , R" = alkyl
group C 3 -C S and BuO = butylene oxide.
Minor components and impurities are: free alcohol, polyglycols, free
ethylene oxide (very small quantities) and lA-dioxane (very small quantities).

General properties

1. Solubility. When the EO content increases beyond S moles EO/mole of

alcohol, there will be very little difference in solubility between a C12, a
132 HANDBOOK OF SURFACTANTS

Table 7.9 Solubility of a C12-C14 alcohol etbxylate (S = soluble, 0= dispersable,

I = insoluble)

+IEO +3EO +5EO +7EO + 15EO

HLB 3.5 8 10 12 15
10% in water I 0 0 S S
10% in mineral oil S S 0 0 I
10% in white spirit S 0 D D 0
10% in aromatic solvent S S S S S
10% in perchlorethylene S S S S S

Table 7.10 Solubility of oleyl and tallow ethoxylates (S = soluble, D = dispersable,

I = insoluble)

Oleyl + 2EO Oleyl + IOEO Tallow + IOEO Tallow + 30EO

HLB 5 12 12 17
10% in water I !S D S
10% in mineral oil S 0 I I
10% in white spirit D 0 D I
10% in aromatic solvent S S 0 I
10% in perchlorethylene S D D D

C12-C14 or a C12-C15 alcohol ethoxylate. For solubility of a C12-C14

alcohol ethoxylate, see Table 7.9. For solubility of oleyl and tallow
ethoxylates, see Table 7.10.
2. Cloud point. Highly branched (2 or 3 methyl) alcohols are significantly
more hydrophobic than their more linear counterparts and more EO has
to be added to achieve the equivalent cloud point.
3. Chemical stability. Excellent for acids but the free hydroxyl group is
sensitive to concentrated alkali and turns brown in powdered products,
Unstable with high pH and oxidising agents (e.g. hypochlorite bleach)
(see Section 7.1.2).
4. Compatibility with aqueous ions. Excellent with hard water.
5. Surface active properties. CMC increases as the EO content increases.
For a C12-C14 alcohol mixture, the minimum CMC is at about 0.001-
0.003% at low EO levels rising to 0.02-0.04% at high (15-20) EO. C8-
C181inear alcohols show similar behaviour in that the minimum surface
tension obtainable decreases with decreasing EO content. Lowest surface
tension is 29 dyn/cm at 5-7EO, i.e. where AE is nearly insoluble, rising to
40dyn/cm at 15EO. The branched chain alcohols (C1O-C12) however
have a constant surface tension (29-33 dyn/cm) whilst the EO content
varies from 5EO to 30EO.
6. Functional properties. See Table 7.11. By choosing the appropriate
alcohol and the appropriate degree of ethoxylation the alcohol
ethoxylates can give the following properties.
Excellent wetting: linear alcohol C8-C 14 with 7-12EO; for each
 NON-IONICS 133
Table 7.11 Functional properties

Alcohol Moles EO Applications

Lauryl 3 Viscosity control, emulsifier

Lauryl 12 Foaming agent, emulsifier, solubiliser, detergent
Lauryl 23 Solubiliser
Ceto/stearyl 5 Thickener, opacifier, emulsifier
Oleyl 20 Solubiliser for perfumes

alcohol there is a sharp optimum of EO content with the wetting power

decreasing rapidly with increasing EO content above the optimum;
branched chain alcohol ethoxylates show better wetting than straight
chain alcohols of the same molecular weight. Good flash foam but poor
foam stability: linear alcohols generally give better foam than branched
chain alcohols; most stable foams with ClO-C14 alcohols obtained with
8-12EO content; hard water has only a minor effect on flash foam but
decreases foam stability.
Excellent dispersing power: optimum alkyl chain and EO content
depends upon the material being dispersed but high molecular weight
products are better than low molecular weight.
Excellent emulsifying properties: optimum alkyl chain and EO
content depends upon material being emulsified.
Excellent detergency: optimum linear alcohol C 12-C 15 with 6-15EO;
Higher alcohols, e.g. C18, show excellent detergency but need higher
EO levels (15-20EO).
Note however that the optimum level of EO depends very much on
the temperature.
7. Disadvantages Compared to NPEs, AEs contain free alcohol inappreci-
able quantities at low levels of EO.

Applications

1. Intermediate for sulphation. The 2- and 3-mole EO are sulphated for use
in detergents and cosmetics (see Section 6.5.2).
2. Household products. Heavy duty powder detergents, major component
of low and medium foam detergents, C12-C14 alcohol + 9EO; heavy
duty liquid detergents, more soluble than LABS for use in high active
heavy duty liquid detergents which are free or low in phosphates; used
with LABS as solubiliser and foam stabiliser, usually C12-CI5 + 7-9EO.
3. Industrial detergents. Metal cleaning, low foam products stable to alkali,
e.g. benzyl blocked; machine cleaning of food soils, low foam products,
benzyl or propylene oxide tipped.
4. Textiles. Wide variety of AE used for scouring depending upon the
temperature, e.g. C13 + 5EO (HLB 10.5) for low temperature textile
134 HANDBOOK OF SURFACTANTS

scouring; lubricants and antistatic agents in fibre processing, tallow

+ 20EO, also mineral oil and vegetable oils are used as lubricants with
AEs as emulsifiers; emulsifiers as dye carriers (better emulsifiers than cor-
responding NPEs) and for hydrophobic glycerides in blended fibre lubri-
cants; dyeing assistants for wool/synthetic blends, tallow + 20-40EO;
in cotton processing as penetrants, wetting agents and dyeing assistants.
5. Emuls!fiers. For W/O emulsion in mineral oil, paraffin and chlorinated
solvents, C12-Cl5 + 3EO; for waxes, fats and oils, C12-C15 + 7-SEO;
for solvent emulsifier in dye carriers, C12-Cl5 + 23EO; Cosmetic, the
higher alcohols, oleyl, ceto-stearyl are used as emulsifiers in cosmetics to
emulsify oils and fats, a combination of a lower (2-3EO) and a higher
(1 0-20EO) ethoxylate can give O/W and W/0 emulsions; the presence of
some free alcohol (i.e. oleyl or stearyl alcohol) is not detrimental to odour
as would be the lower alcohols, e.g. lauryl alcohol; castor oil + 5EO
emulsifiers and dispersing agents to give antifoam properties to chlori-
nated solvents.
6. Agriculture. Excellent emulsifiers for pesticide sprays because they are
unaffected by hard water and pH changes; used in emulsifiable concen-
trates, e.g. castor + 30EO; water soluble emulsifiers used in conjunction
with anionics in agricultural herbicides.
7. Paper industry. Re-wetting agents to improve absorbency, e.g. paper
towels; repulping aids for waste paper.
S. Emulsion polymerisation. Excellent emulsifier for emulsion polymeris-
ation due to tolerance to inorganic ions and pH changes.

Specification.

Active content: usually 100% but some solid products have water added and
are sold as low as SO% active. The reason for adding the water is to supply a
liquid product rather than a paste or solid. Small amounts of water are often
added to hide the haze caused by polyglycols.
Water content: see active content
EO content: usually supplied by the manufacturer; difficult to check; see
hydroxyl number and cloud point
Cloud point: room temperature to 90°C indicates EO content (see
Section 7.1.2). If cloud point is indistinct this may be caused by a high
polyglycol content
Polyglycol: very variable, 0.05-5%; low amounts (up to 2%) found in low
EO products and 3-5% found in highly ethoxylated materials
Sap value: 150 (low EO) to 15 (high EO) for castor oil derivatives
Hydroxyl number: for high amounts of ethylene oxide ( < 200H number
mg KOH/g) the hydroxyl number is difficult to measure accurately.
Viscosity: can be used as a rough measure of EO distribution. due to the
viscosity preferentially measuring the high molecular part of the
distribution.
 NON-IONICS 135
7.4 Alkanolamides

Nomenclature

Generic: The products described in this section are the N -acyl derivatives of
monoethanolamine and diethanolamine. The polyethoxylated alkylamides are
described in Section 7.7. The distinction between these groups of products is
shown in Figure 7.6. There are two types of alkanolamides: Type 1: 1, the
superamide which can be mono- or dialkanolamide (see Figure 7.6). The
phrase superamide usually refers to the dialkanolamide. Type 2: 1, the
Kritchevsky alkanolamide which consists of the superamide plus free
alkanolamine.
Abbreviations: Amide, alkyl (usually coconut) diethanolamide; CD,
coconut diethanolamide, used in this book; CE, coconut diethanolamide;
CMEA, coconut monoethanolamide; LDEA, lauric diethanolamide; LMEA,
lauric monoethanolamide; LMP, lauric monopropanolamide (made from
isopropanolamine).
Example:
Lauric monoethanolamide
Note that suppliers often do not differentiate between the superamide and the
Kritchevsky alkanolamide but the difference is shown under Specification.

RCONHCH 2CH 20H monoalkanolamide

/CH 2CH 20H

RCON dialkanolamide
-""""CH 2CH 20H
RCONH(CH2CH20)nH polyethoxylated monoalkanolamide.
Figure 7.6 Alkanolamides.

or

RCOOCH NH/CH2CH20H ------+ RCON/CH2CH20H CH OH

3 + -""""CH 2CH 20H -""""CH 2CH 20H + 3

Formation of ester~amide

ester~amide

Figure 7.7 Superamide or Type 1: I.

136 HANDBOOK OF SURFACTANTS

RCOOH + 2NW,/CH 1CH 10H ------+ RCON/CH1CH10H

~CH1CH10H ~CH2CH10H

+ NH(CH1CH10H
CH1CH10H
Figure 7.8 Kritchevsky or Type 2: I alkanolamides.

Description

The superarnide Type 1: 1. Reaction between one mole of the ester of a fatty
acid and one mole of mono or diethanolamine (see Figure 7.7). R' is usually Me
and MeOH taken off. If R' = glycerol, i.e. the free glyceride is used, then the
glycerol will be left in the alkanolamide.
Impurities include small amounts of free diethanolamine (1-3%), ester-
amide (see Figure 7.7), soap and possibly glycerol (if free oil is used).

Kritchevsky Type 2: 1. Reaction between one mole of the fatty acid or ester
and two molecules of diethanolamine. There is no Kritchevsky monoalkano-
lamide (see Figure 7.8).
Impurities include molar amounts of alkanolamine (25-30% is common),
ester-amide (formed in the same way as for Type I: I, see Figure 7.7), free fatty
acid (at least 5%) and dihydroxy ethyl piperazine (formed when 2 moles of
diethanolamine react and split out 2 moles of water; occurs when reactions are
at high temperature (I60-180°C)).
The reactions indicated in Figures 7.7 and 7.8 are simplifications due to
further reactions involving the ester amide with itself and with fatty acid.

General properties

1. General. The superamides (Type I: 1) have low free alkanolamine and

therefore are more suited for household and personal use. They have
poor water solubility at room temperature. The Kritchevsky dialkanola-
mides have good water solubility at room temperature but high free
diethanolamine, therefore they are more suited to industrial use. The free
fatty acid and free diethanolamine are both necessary to obtain the water
solubility of the product. The reason for this is that the diethanolamine
fatty acid soap forms a co-micelle with the dialkanolamide giving the
high solubility in water.
2. Solubility. Type I: I CI2 monoethanolamides are solid at room
temperature (see Table 7.12). Type \: I CI8 monoethanolamide solid
(m.p. 80°C) disperses in water but is not soluble. Type I: 1 CI2
diethanolamide, is semi-liquid at room temperature (see Table 7.13).
 NON-IONICS 137
Table 7.12 Solubility of cocomonoethanolamide (I = insoluble,
D = dispersable)

1% in water I 10% in water I

1% in mineral oil I 10% in mineral oil I
1% in white spirit I 10% in white spirit I
1% in aromatic solvent D 10% in aromatic solvent D
1% in perchlorethylene I 10% in perchlorethylene D

Table 7.13 Solubility of Type 1: 1 cocodiethanolamide (D =

dispersable, S = soluble)

1% in water D 10% in water D

1% in mineral oil D 10% in mineral oil D
1% in white spirit D 10% in white spirit D
1% in aromatic solvent S 10% in aromatic solvent S
1% in perchlorethylene S 10% in perchlorethylene S

Table 7.14 Solubility of Type 2: 1 cocodiethanolamide (S =

soluble, D = dispersable)

1% in water S 10% in water S

1% in mineral oil D 10% in mineral oil D
1% in white spirit D 10% in white spirit D
1% in aromatic solvent D 10% in aromatic solvent S
1°1. in perchlorethylene S 10% in perchlorethylene S

Blends with unsaturated acids or lower acids are liquid at room

temperature. For Type 2:1 C12-C14 diethanolamide, see Table 7.14.
3. Compatibility with other surJactants. Type 1: 1 dialkanolamide is com-
patible with anionics and cationics over a wide pH range. Type 2: 1 is not
compatible with cationics due to fatty acid.
4. Chemical stability. All alkanolamides are unstable to hydrolysis but
Type 1: 1 monoethanolamide is more stable to hydrolysis than the
corresponding diethanolamide, particularly under alkaline conditions.
The monoethanolamide is preferred for use in acid solutions.
5. Functional properties. Foaming properties: good flash foam and stable
foam with Type 2: 1. Foam stabilisation of alkanolamides: shown with
all the alkanolamides; alkanolamides stabilise foam in anionics when
hard water and sebum or soil is present (if alkanolamide absent then
anionic foam will collapse in hard water/sebum); some alkanolamides
boost or increase the volume of foam of an anionic in the presence of soil;
alkanolamides do not always increase the amount of foam, in fact they
can decrease it because some surfactant is often needed to solubilise the
alkanolamide. Solubiliser: for anionics, monoethanolamide is a good
solubiliser for lauryl sulphate. Emulsification: Both Type 1: 1 and
 138 HANDBOOK OF SURFACTANTS

Type 2: 1 are excellent emulsifiers for O/W; Type 2: 1 C16-C18 are

excellent emulsifiers for mineral oil; lime soap dispersant. Poor wetting
for Type 1: 1 products, excellent wetting for Type 2: 1 products. Poor
detergent properties for Type 1: 1 products but synergistic with other
surfactants which show these properties; excellent detergent properties
for Type 2: 1.
6. Viscosity effects. Addition of alkanolamides to anionic surfactants does
not increase the viscosity. It is only when electrolyte (salt), oils or fatty
alcohols are present that the viscosity increases. Generally monoetha-
nolamides are superior to diethanolamides in increasing viscosity of
anionics. This is called building the viscosity. The viscosity building
effect is inversely proportional to water solubility, i.e. the lower the
water solubility the higher the built viscosity. Type 1: 1 dialkanolamides
prepared via the methyl ester are better viscosity builders than those
prepared from fatty acids (Milwidsky and Holtzmann, 1972). Monoiso-
propanolamides more effective than monoethanolamides or diet hanol-
amides for increasing the viscosity of sodium lauryl sulphate.
7. Disadvantages of Type 1: 1. Low solubility in water.
8. Disadvantages of Type 2: 1 compared to Type 1: 1. High alkanolamine
content; fatty acid makes it incompatible with cationics; complex
mixture, difficult to analyse and check for quality.

Applications

Type 1: 1 applications are:

1. Household products. The most common products available are those
based on coconut oil but some products based on lauric acid are also
available. These products were at one time extensively used in detergents
and household products for their good detergent properties combined
with foam stabilising action on anionics. In Europe they have been
largely replaced by non-ionics based on ethoxylates oflauryl alcohol and
ether sulphates. However monococoalkanolamide is still used as a foam
stabiliser in powder laundry detergents.
2. Shampoos and bubble baths. The most useful property of dialkanola-
mides is their ability to stabilise the foam and thicken solutions of anionic
surfactants, e.g. akohol sulphates and ether sulphates in shampoos and
bath additives. The 1: 1 Type is more effective than the 2: 1 Type. Recently
their use in personal care products has decreased due to problems of
nitroso content (see Specification) and replacements are appearing on the
market as foam stabilisers and thickeners for ether sulphates.
Type 2: 1 applications are:
1. Detergents. The C12-C14 alkanolamides can be used as detergents but
are more often used for formulating built liquid detergent formulations
 NON-IONICS 139
Table 7.15 Analysis of alkanolamides'

Type 1: 1 (superamide) Type 2: 1 (Kritchevsky)

Appearance Liquid-paste Amber or straw liquid

Active (%) (amide content)" 80-90 45-65
Free amine (%)' 1-6 20-30
Free acid (as soap) (%) 0.1-1 5-10
Amine soap (%) 1-2 8-10
pH (1% soln) 8-10 8-11
Nitroso content
Ester-amide (%) 1-3 3-5

aAlkanolamides are difficult to analyse and discrepancies are often obtained between different
laboratories unless the same procedures are followed. The figures for Type I: 1 are via the methyl
ester.
"The active (amide) content is not usually measured directly but obtained by difference.
'Type I: I has lower level of free amine (1%) in monoethanolamide than diethanolamides (5%).
d Nitroso content: there is concern over the use of alkanolamides in cosmetic products. Some
nitrosamines have been shown to be potential carcinogens. N-nitrosodiethanolamine has been
detected in very low concentrations in cosmetics in the United States (Fan et ai., 1977). One
possible source is dialkanolamides. Nitroso compounds have been found at very low levels in
alkanolamides. At the time of writing there is considerable work on developing analytical
techniques for nitroso compounds. Whether there is real danger to humans is difficult to
determine but new additives to shampoos are replacing dialkanolamides, the new additives having
claims that there is no possibility of them being precursors to nitrosamines.

that include hard surface cleaners, floor cleaners and wax strippers. The
addition of dialkanolamides to LABS has a synergistic effect on
detergency.
2. Metal working. The other major range of products available is the 2: 1
based on tall oil fatty acid, soya bean acid or oleins. These products
are oil soluble and are excellent emulsifiers for mineral oil in water
combined with corrosion inhibition from the free alkanolamines. These
products are mainly used in cutting oils and metal working fluids.
Alkanolamides react readily with boric acid to give 'borate esters'. Such
products are used in metal cutting oils as corrosion inhibitors/biocides
but the chemical structure of the 'ester' is now doubtful.

Specification

A typical analysis (for cocodiethanolamide) is shown in Table 7.15.

7.5 Amine oxides

Nomenclature

Generic:
N-Alkyl amidopropyl-dimethyl amine oxides
N-Alkyl bis(2-hydroxyethyl) amine oxides
140 HANDBOOK OF SURFACTANTS

CH 3
I
CocoCONHCH1CHzCH1N --+ 0
I
CH 3
COCO amido propyl-dimethyl amine oxide

CH1CHzOH
I
CocoN -----> 0
I
CH1CHzOH
Coco bis(2-hydroxyethyl) amine oxide

CH 3
I
C 12 H 25 N --+ 0
I
CH 3
Lauryl dimethyl amine oxide
Figure 7.9 Amine oxides.

N-Alkyl dimethyl amine oxides

Amine oxides
Examples:
Coco amido propyl-dimethyl amine oxide (see Figure 7.9)
Coco bis(2-hydroxyethyl) amine oxide (see Figure 7.9)
Lauryl dimethyl amine oxide (see Figure 7.9)

Description

Amine oxides are prepared by oxidising a tertiary nitrogen group with

aqueous hydrogen peroxide at temperatures of approx. 60-80°C.
RR'R"N + HzO z - - RR'R"N -+ 0 + HzO
R can be: (i) an alkyl chain and R' and R" methyl groups to give N-alkyl
dimethyl amine oxides or (ii) an amido propyl alkyl chain;
RCONHCHzCHzCH~N- with R' and R"methyl groups to give N-alkyl
amidopropyl-dimethyl amine oxides. R' and R" are generally CH 3 but can be
any group, e.g. CH 2 CH zOH; thus a primary amine can be reacted with 2 moles
of ethylene oxide and then with hydrogen peroxide to give the bis(2-
hydroxyethyl) amine oxides.
Impurities and by-products include free starting material, e.g. alkyl
dimethyl amine.
 NON-IONICS 141
General properties

1. General. Similar to betaines because the substituted amino group is

protonated and acts as a cationic surfactant in acid solution. In neutral or
alkaline solution the amine oxides are essentially non-ionic in character.
They are sometimes known as quasi-cationic. Thus they are weakly
cationic at acid pH (cationic below pH 3) and non-ionic at alkaline pH
(above pH 7).
2. Solubility. Alkyl dimethyl amine oxides are water soluble up to C16
alkyl chain. Most products are dispersable in mineral oil but insoluble
in white spirit, aromatic solvents and perchlorethylene.
3. Compatibility with other surfactants. With anionics, a 1: 1 salt is formed
that is more surface active than either the anionic or amine oxide thus in
conjunction with anionics amine oxides can replace alkanolamides in
shampoos although claimed to be more efficient foam boosters. They can
increase viscosity, especially the amido-amine oxides. They also detoxify
the effect of anionic surfactants. Above pH 9, amine oxides are
compatible with most anionics. At pH 6.S and below some anionics tend
to interact and form precipitates. A 9: 1 ratio of anionic (alkyl and alkyl
ether sulphates)/amine oxide gives a clear aqueous solution down to
pH 4; 8:2 ratio of anionics/amine oxide (amido-amine oxides) gives a
clear solution to pH 4 but alkyl dimethyl only to pH 6; 7: 3 ratio of
anionics/amine oxide, only amido amines can be used below pH 7 to give
clear aqueous solutions. There is an increase in cloud point when a
small amount of amine oxide is mixed with a non-ionic.
4. Compatibility with aqueous ions. Resistant to hard water; good lime
soap dispersing properties.
S. Chemical stability. Do not show oxidising properties; amine oxides form
peroxides with excess hydrogen peroxide.
6. Surface active properties. Surface active properties lost when the alkyl
chain in alkyl dimethyl amine oxides is less than 10 carbon atoms.
7. Functional properties. Excellent foaming agents; C12-C14 dimethyl-
amine oxide is an excellent foam booster for LABS and superior on a
weight basis to lauric diethanolamide or lauric isopropanolamide; the
foam produced has a creamy feel.
8. Disadvantages. The main problem in conjunction with anionics is a
slight incompatibility at acid pH unless the correct combination of
anionic/amine oxide is chosen.

Applications

1. Shampoos and bath products. C12 or coco products (with anionics gives
conditioning) reduce eye irritation, impart lttbricity, increase viscosity
142 HANDBOOK OF SURFACTANTS

and stabilise foam; replace alkanolamides wholly or partly; used in low

pH or acid balanced shampoos; C 18-dimethyl reduces irritation of zinc
pyrithane in shampoos (Gerstein, 1977).
2. Household products. Liquid detergents ~ C 12 or coco ~ stabilise foam
and increase viscosity. The performance is similar to cocodiethanolamide
but lower concentrations can be used. The foam stabilising properties are
most apparent when the anionic in the formulation is only ether sulphate
with no LABS.
Thickens bleach in conjunction with fatty acid soap (Unilever UK
Patent 1,329,086) or ether sulphate.
3. Textiles. CI2 or coco - antistatic softener
4. Polymers. CI2 or coco gives foam stabilisation in foam rubber (SBR
latex)
5. Metal treatments. CI2 bis(2-hydroxyethyl)~corrosion inhibitor for non-
ferrous metals.
6. Petroleum production. Stabilises foam in foam drilling.

Specification
Amine oxide content, 20~40%
Solvent, water but can sometimes contain isopropanol
Free amine, 1~3% typical but shampoos require lower values
Free peroxide, can be up to 0.2%, can cause problems with colours

7.6 Surfactants derived from carbohydrates

Nomenclature
Products based on sorbitan or sorbitol (see Section 7.2.10). Abbreviations:
APG, alkyl polyglycosides, used in this book.
Generic:
Alkyl glucosides
Alkyl polyglycosides
Fatty acid sugar esters
Glucosyl alkyls (Note I)
Methyl glucoside esters
Sucrose esters
Sugar esters
Do not confuse these products, which are alkyl derivatives of glucose, with
glycerides, which are derivatives of glycerol (see Section 7.12).

Description

There is a considerable literature on attempts to make surfactants from mono

or oligosaccharides, sucrose or carbohydrates. The interest lies in the ready
 NON-IONICS 143
availability of cheap raw materials which are not derived from petrochemicals,
they biodegrade easily and are readily accepted by the consumer. Many useful
products have been made on a small scale, e.g. transesterification between
natural glycerides and methyl glucoside. Two groups of products, the sucrose
esters and alkyl glucosides have achieved commercial status. The former have
been manufactured for many years and have achieved commercial status
world-wide but there are still very few manufacturers. The alkyl glucosides are
relatively new products but there are a number of companies offering these
products.
Sucrose + nRCOOCH 3 ---- Sucrose ester with n fatty residues + MeOH
Sucrose esters are prepared by esterification of sucrose with the methyl
ester of a fatty acid in a solvent (dimethylformamide) or in aqueous dispersion
by emulsion technology. In place of the methyl ester a fatty oil (polyglyceride)
can be used and transesterification occurs leaving glycerol in the product.
The monoesters probably have the composition shown in Figure 7.10. Some
diesters are formed even when high ratios of sucrose to fatty ester are used.
Products made with solvent need the dimethylformamide removed for use
in food. Such purification procedures are costly.

H OH OH H
Figure 7.10 Sucrose esters.

CHpH

j_OR
to
x
H OH H OH

R~C8-C12
x ~ 0 to 4

Figure 7.11 Structure of a commercial alkyl glucoside.

144 HANDBOOK OF SURFACTANTS

Note that impure sucrose esters can be prr-pared by heating a fatty acid with
sucrose in the presence of alkali, some sucrose ester is formed but equal
quantities of soap are also formed. The preparation of this type is much easier
and cheaper than the products mentioned above but they never seem to have
been successful commercially.
Alkyl glucosides are made by the alkylation of monosaccharides (e.g.
glucose) or polysaccharides, they are known as alkyl glucosides or alkyl
polyglycosides. The detailed chemistry is complicated because products
available seem to consist of mixtures of alkyl monoglucoside, alkyl digluco-
side, triglucosides, etc. The structure given for such products is shown in
Figure 7.11. Methods of manufacture have been published but it is not clear
at present which methods are used in large scale manufacture. The raw
material for the hydrophobe portion is almost certainly a linear fatty alcohol.

General properties

1. General. The monoesters of sucrose with the CI2-CI8 fatty acids are
soluble in warm water due to the large number of free hydroxyl groups
remaining. They show general surfactant properties similar to ethoxy-
lated alcohols and alkyl phenols. However, the pure products are solids
which are not that easy to dissolve in water. The alkyl glucosides are
usually dark brownish liquids with 50-70% solids. They are stable in
neutral and alkaline solutions.
2. Solubility ofsucrose esters. Sucrose monolaurate, soluble in warm water;
sucrose monostearate, soluble in warm water; sucrose distearate, insol-
uble in' water; sucrose mono oleate, soluble in warm water; sucrose
dioleate, insoluble in water.
3. Solubility of alkyl polyglycosides. Alkyl polyglycosides have good solu-
bility in water, high cloud point (> 100°C) but increased solubility in
alkali.
4. Chemical stability. The sucrose esters have the typical stability of esters,
i.e. more stable in acid than alkaline solutions. The alkyl glucosides are
stable in neutral and alkaline solutions but unstable in strong acid
solution.
5. Compatibility of aqueous solutions to ions. The alkyl glucosides are
soluble at all levels of water hardness and extremely tolerant to high
concentrations of electrolyte.
6. Surface active properties. I % solution of sucrose monoesters with
C 12 acid is 33.4 dyn/cm and with C 18 fatty acid 33.5 dyn/cm. 1%solution
of alkyl glucosides give surface tension of 27-29 dyn/cm. In the presence
of caustic soda a surface tension of 23 dyn/cm is quoted but some doubt
must be expressed at such a low figure. CMC of 0.09% is quoted for alkyl
(C8-CI0) glycoside.
 NON-IONICS 145
7. Functional properties. Sucrose esters: early investigation showed the
monoesters of sucrose to be good detergents for cotton and superior to
LABS (Osipow et al. 1956). The optimum monoester was the palmitic or
oleic ester. Alkyl glucosides give good wetting and high foam comparable
with LABS and sodium lauryl sulphate. The foam, however, is reduced
by increase of temperature and/or in alkaline solution. Alkyl glucosides
are effective emulsifiers of polar compounds, e.g. triglycerides.

Applications

1. Sucrose esters. Emulsifier for feeding stuff for calves; food additive,
soluble in water and could replace polysorbates but considerably more
expensive than polysorbates.
2. Alkyl glucosides. Alkali stable detergents; shampoo base.

Specification

Alkyl polyglycosides: solids, 50-70%

Cloud point, > lOO°C
Free alcohol, 1-4%

7.7 Ethoxylated alkanolamides

Nomenclature

Generic:
Alkanolamide ethoxylates
Alkyl monoethanolamide ethoxylates
Amide ethoxylates
Ethoxylated alkanolamides
Ethoxylated monoalkanolamides
Fatty amide polyglycol ethers
Polyoxyethylated alkylamides
Example:
Coconut monoethanolamide + 5EO

Description

These products are made by reacting a monoalkanolamide (see Section 7.4)

with ethylene oxide. In the presence of a basic catalyst the ethylene oxide
adds preferentially on to the hydroxyl rather than the hydrogen attached to
the nitrogen (see Figure 7.12). The main commercial products are the coconut
and lauryl derivatives.
146 HANDBOOK OF SURFACTANTS

Figure 7.12 Addition or EO to monoethanolamides.

General properties

1. General. As the amount of ethylene oxide increases, the products change

from typical alkanolamides to typical ethoxylates. The addition of the
ethylene oxide improves dispersability or solubility in water.
2. Solubility. Solubility of cocomonoethanolamide with varying ethylene
oxides is given in Table 7.16.
3. Chemical stability. Addition of ethylene oxide increases stability to
strong alkali. With 6 moles of EO no hydrolysis occurs after refluxing for
2 h with 1 N sodium hydroxide.
4. Compatibility with other surfactants. Improves lime soap dispersability.
5. Surface active properties. Oleyl amide + SEO, surface tension of 1%
solution = 34 dyn/cm; hydrogenated tallow amide + SEO, surface ten-
sion of 1% solution = 37 dyn/cm; hydrogenated tallow amide + SEO,
surface tension of 1% solution = 46 dyn/cm.
6. Functional properties. Foaming and wetting are at the optimum when
3-4 moles of ethylene oxide are added (Tagawa et al., 1962).

Applications.

1. General. The properties are similar to either the alkanolamides or the

ethoxylated alcohols but more expensive than either. Hence the limited
use in practice.
2. Cosmetics. Similar to alkanolamides, i.e. thickening and foam stabilising
but with improved dispersability. Optimum foaming properties at 3-4
moles of EO (Knaggs, 1965).

Table 7.16 Solubility or monoethanolamides (eI2) with

varying EO content (S = soluble, 0 = dispersable, I = insoluble)

Nil EO 2EO SEO

10% in water I 0 S
10% in mineral oil I I I
10% in white spirit I I I
10% in aromatic solvent 0 S S
10% in perchlorethylene 0 S S
 NON-IONICS 147
3. Detergents. Coconut monoethanolamide + 5EO is used in strongly
alkaline cleaners where foam stability is required. Used in car wash and
wax-wash formulations where it is claimed to leave a residual wax-like
finish on the car.

Specification
For appropriate tests similar to ethoxylated alcohols, see Section 7.3.
Solidification temperature is 13°C for 5EO and 20°C for 2EO.

7.8 Ethoxylated long chain amines

Nomenclature

Generic:
Alkyl polyamine ethoxylates
Alkyl polyoxyethylene amines
Ethoxylated amines
Fatty amine ethoxylates
Polyoxyethylated fatty amines
Polyoxyethylene alkylamines
Examples:
Laurylamine ethoxylate, C12H2SN[(CH2CH20hHJ2; usually described as
laurylamine + 6EO
Bis(2-hydroxyethyl)dodecylaminc, C12H2sN[(CH2CH20H)]2
Notc that the imidazolines are described in Section 7.13.

Description
Whether to call these products nonionics or cationics depends upon the
amount of ethylene oxide and the pH at which they are used. At low ethylene
oxide levels they are cationic in nature but at high ethylene oxide levels and
neutral pH they behave very similarly to non-ionics.
Prepared by addition of ethylene oxide to primary or secondary fatty
amines (see Section 7.1, Ethoxylation). The ethylene oxide preferentially reacts
with the amine (like the phenols) so products have only very small quantities of
free amine unlike the ethoxylated alcohols which have considerable quantities
of free alcohol. When ethoxylating a primary amine both hydrogen atoms on
the amine react with ethylene oxide before the ethylene oxide adds to the
hydroxyl to form the polyethoxylate. No catalyst is needed for the replacement
of the hydrogen on the nitrogen but a basic catalyst is then needed for
subsequent reaction of ethylene oxide with the hydroxyl groups (see
Figure 7.2).
148 HANDBOOK OF SURFACTANTS

RNH +nCH -CH ~R __ N/(CH2CH20)xH

2 "- 2 / 2 '-....(CH CH 0) H
"-0 2 2 Y

alkyl amine ethoxylate

x+y=n

RNHCH 2 CH 2CH 2NH 2 + nCH 2 -CH2

~/
o
--->R-N-CH CH CH N/(CH 2 CH 2 0)yH
I 2 2 2 '-....(CH 2CH 20)=H
(CH 2 CH zO)x H
alkyl propanediamine ethoxylate
x+y+z=n

RNH(CH2CH2NH)mH + nCH 2-CH 2

"(/
o
~ R-N~(CH2CH2 N)m-(CH 2CH 20)zH
I I
(CH2CH10)xH (CH 1 CH 2 0)yH
alkyl polyamine ethoxylate
x+y+z=n
Figure 7.13 Common ethoxylated amines.

A wide variety of ethoxylated alkyl amines can be prepared depending upon

the starting amine. The various amines are described in Section 7.13 but the
most common ethoxylated amines are ethoxylated primary amines, ethoxy-
lated propanediamines and ethoxylated polyamines (see Figure 7.13). The
most common of these products are the ethoxylated primary amines.
Minor components and by-products include free amine, ethylene oxide and
lA-dioxane.

General properties

1. Solubility. The products become more similar to the corresponding non-

ionics as the ethylene oxide chain increases and the cationic properties
decrease, i.e. the solubility does not change with pH and the incompati-
bility with anionics diminishes. At low ethylene oxide content, products
are not soluble in water but soluble in acid (mineral or low molecular
weight organic) solution. At high ethylene oxide content the products
based on C 12 amine are soluble in water but those based on C 18 amine
 NON-IONICS 149
Table 7.17 Surface tension of amine ethoxylates

Surface tension
(dyn/cm) of 1%
Product in water

Cocoamine + SEO 33
Cocoamine + tOEO 38
Cocoamine + ISEO 41
Tallowamine + SEO 33
Tallowamine + ISEO 40

are generally insoluble. With the tallow derivatives and low ethylene
oxide content the products are soluble in most organic solvents and
mineral oil. Salts with high molecular weight organic acids are oil soluble
and show inverse solubility with respect to temperature at high ethylene
oxide levels (see Section 7.1, Cloud points).
2. Chemical stability. Comments on the chemical stability of ethoxylates
(Section 8.1) apply but products are tertiary amines and therefore show
properties of that group, i.e. ionisation, quaternisation and oxidation. At
low levels of ethoxylation they show very good thermal stability, e.g.
dodecyl amine + 2EO is thermally stable at temperatures > 200°C
(Humko data sheet).
3. Surface active properties. The length of the ethylene oxide chain
dominates the surface active properties (see Table 7.17).
4. Functional properties. Excellent wetting properties with low EO content
products. Unsaturated alkyl chains having better wetting properties than
saturated alkyl chains. Adsorption on to metal surfaces when ethylene
oxide content is low and/or there are a multiplicity of amine groups.

Applications

1. General. The ethoxylated alkyl amines have very wide applications. It is

the cationic property that has extended the use of these compounds.
Most metal, mineral and fibre surfaces are negatively charged in aqueous
solution and the amine group is strongly adsorbed on to such surfaces.
2. Oilfields and refineries. Act as corrosion inhibitors. By variation in the
alkyl chain of the amine, the ethylene oxide content and the type of
organic acid (see solubility above) a very wide range of water/oil soluble
materials may be made. For cost and logistics reasons, the variations on
alkyl chain and organic acid are limited so that the variation in ethylene
oxide content becomes the main variable used in practice.
3. Emulsifying agents (for similar reasons as corrosion inhibitors). Agro-
chemical emulsions, wax emulsions and two phase emulsion cleaners.
150 HANDBOOK OF SURFACTANTS

4. Textiles. Processing aid in rayon production in the spinning bath;

softener and antistatic agent in processing because they adsorb on the
fibre from aqueous solution; scouring, desizing and dyeing assistants
(levelling aid).
5. Road repairs. Coating of asphalt aggregates for adhesion to wet surfaces;
addition to asphalt or use as emulsifying agent for bitumen emulsions.
6. Paint. Dispersing agents for pigments in oil paints.

Specification

Active content, usually > 99%

Hydroxyl number, can vary over a wide range
PEG and non-amine, 2-5~~
Free amine, usually very low but can be significant
Free ethylene oxide, usually very low
1,4-dioxane, should be very low

7.9 Ethylene oxide/propylene oxide (EO/PO) co-polymers

Nomenclature

In this book the abbreviation EO = ethylene oxide and PO = propylene

oxide. Abbreviations: EO/PO or (EO)x(PO)y are ethylene oxide/propylene
oxide block co-polymers, used in this book; EPE polyols.
Generic:
Ethylene oxide/propylene oxide block co-polymers, (EO)APO)y
Pluronics (Wyandotte trade name)
Polaxamer
Polyalkylene oxide block co-polymers
Polyoxyethylated polyoxypropylene glycols, (EOUPOMEO)x = Pluronics
Polyoxypropylated polyoxyethylene glycols, (PO)AEOMPO)x = Reverse
Pluronics
Examples:
All EO/PO co-polymers are trade names which do not directly give the
composition. Some manufacturers adopt a systematic nomenclature
from which it is possible to derive an approximate composition.

Description

There are many possible variations in this class of products and more appear
every year. However, the major types to achieve significant volume are not so
extensive, these are as follows.

Type 1. EO/PO co-polymers which have been based on the reaction of a

polyoxypropylene glycol (difunctional) with EO or mixed EO/PO
 NON-IONICS 151
(EOln(PO)m(EO)n block co-polymer the Pluronic polyols
(AO)iPO)m(AO)n AO = EO or PO random co-polymer

Type 2. EO/PO block co-polymers based on the reaction of a polyethylene

glycol (difunctional) with PO or mixed EO/PO.

(POln(EO)m(pO)n block co-polymer the reverse Pluronics

(AO)n(EO)m(AO)n AO = EO or PO random co-polymer
A wide range of surfactants can be made using just two basic chemicals (EO
and PO) in differing ratios, rather than by using different hydrophobes, and
therefore logistically this system has great economic attractions for making a
wide range of surfactants. However there are certain disadvantages: the
starting materials are highly toxic and potentially explosive so that very
specialised equipment is needed; the many variations tend to proliferate
product lines; slight differences in manufacture can give different properties
although the ratio of EO/PO may be correct, (this gives problems in quality
control).

Type 3. EO/PO co-polymers, both block and random, can be based on any
starting material (initiator) with an active hydrogen but the most common are
an alcohol ROH (monofunctional)

RO(AO)n(EO)m AO = mixed EO and PO to give a random co-polymer

RO(POln(AO)m AO = EO to give a block co-polymer or
RO = mixed EO and PO to give a random co-polymer
RO(EO)n(AO)m AO = PO to give a block co-polymer or
AO = mixed EO and PO to give a random co-polymer

The products RO(EOln(AO)m where R = e12-CI8 are basically modified

alcohol ethoxylates which have reduced foam by addition of the PO.

Functionality. Types 1 and 2 are difunctional, i.e. have two free hydroxyl
groups and two hydrophilic or hydrophobic chains. Type 3 is monofunc-
tional, i.e. has one hydroxyl group and one hydrophilic chain and one hydro-
phobic chain. Trifunctional products are also available where the starting
polypropylene glycol is based on glycerol (see Figure 7.14). These products
will have three free hydroxyl groups and three chains either of block or
random co-polymers. Tetrafunctional products are available where the
starting material for ethoxylation is ethylene diamine (see Figure 7.15). These
products will have four free hydroxyl groups with four block co-polymer
chains.
The surfactant properties will be influenced by the hydroxyl group on the
end of the chain, the number of chains and the properties of each individual
chain. Thus, characterisation by EO content, PO content and EO/PO ratio is
152 HANDBOOK OF SURFACTANTS

Figure 7.14 Glycerol-based EO/PO co-polymers.

(EO)x"'-... /(EO)x
H 2NCH 2CH 2NH 2 + 4xEO ~ (EO)//NCHJ2CH2N"'-...(EO)X

+4yPO

Figure 7.15 Ethylene diamine-based products.

generally meaningless when comparing one product with another, but is useful
as a quality control on one product.

General properties

The great advantage of the products is that by varying the EO/PO ratio and
molecular weight a wide range of products can be made with properties
varying from:
• Liquids to solids
• Water soluble to water insoluble
• Cloud points from room temperature to > tOO°C; some products show
two cloud points
• High foam to no foam
• Poor wetting to non-wetting
• Excellent dispersing properties to no dispersing properties
 NON-IONICS 153
Some generalisation (for products consisting solely of EO and PO on
difunctional initiators) are as follows.
1. Solubility. Most products are more soluble in cold water than in hot
water but often form gels. The reverse products (PO/EO/PO) have a
faster rate of solubility in water than the normal products (EO/PO/EO)
and rarely form gels. The tetrafunctional products dissolve faster than
the difunctional products. Most products are soluble in aromatic
solvents or other polar organic solvents. Very short PO chains behave
like EO and hydrophobicity only appears when> 5PO units are present.
Increasing EO content increases cloud point, increasing PO content
decreases cloud point.
2. Foaming properties. Maximum foam at PO/EO ratios of 2:3 for
difunctional (EO/PO/EO), 1: 1 for difunctional (PO/EO/PO) and 1:2 for
tetrafunctional. Low EO content products have low foaming properties,
so varying the PO content can control foam. Best antifoam efficiencies
are obtained at PO/EO ratios of 4: 1 to 9: 1. Good defoamers of other
surfactants if the PO content is high and if the molecular weight> 2000.
Reverse products (PO/EO/PO) give the lowest foam.
3. Wetting properties. Wetting time decreases as the molecular weight of the
hydrophobe increases up to an optimum value; above that the wetting
time decreases. Wetting time decreases with a decrease in EO content.
High molecular weight with low EO content have good wetting
properties and better than polyethylene glycol fatty esters.
4. Dispersing properties. High EO content has good dispersing properties.
5. Emulsifying properties. Good emulsifiers are obtained at molecular
weights of the PO portion from 2000 to 4000.

WARNING: there are so many products possible that the above generalis-
ations will have many exceptions. There is considerable information available
from the suppliers and also in the technical literature on the properties of these
products. For detailed information on the basic properties of the EO/PO
block co-polymers (Pluronics Type 1) see Schick (1967, pp. 309-333). A good
summary on the differences between mono-, di-, tri- and tetrafunctional
products is given by Schmolka (1977).
Some specific properties of interest in formulating mixtures are: some
products show an increase in cloud point by addition of anionics, e.g. LABS;
the increase can be up to 20 o e; most products form molecular complexes with
iodine (the iodophors); most water soluble products function as lime soap
dispersants; products based on tetrafunctional initiators (the best known
being ethylene diamine) exhibit excellent cold water detergency when the EO
content is 25-55%; however they are used more for low foam wetting than for
their detergency; they also have the ability to disperse lime soaps in hard water.
6. Disadvantages. High PO products have poor biodegradability; difficult
to characterise chemically and problems of product replacement;
154 HANDBOOK OF SURFACTANTS

suppliers of many of these products do not give a detailed description of

their chemical composition; may contain traces of free EO.

Applications

1. General. The EO/PO co-polymers find many varied applications gener-

ally in small quantities, the main application being foam control. This
can be either as a process defoamer or as an additive to a detergent
solution to control the foam. Other major uses are as wetting agent,
dispersing agent or emulsifying agent.
2. Defoaming. Defoaming agents are used in paper manufacture, industrial
fermentation, emulsion paints, sugar processing, textile processing, oil
field chemicals, etc. Most defoaming agents are formulated products with
the compositions not disclosed. EO/PO co-polymers are widely used in
these formulations but in many cases the products are not standard
EO/PO co-polymers but tailor made for the end application. Also used
for foam control in laundry detergents (low molecular weight with high
PO content).
3. Rinse aids in machine dish washing. Low molecular weight (2000) with low
EO (10%) content as defoamer constituent blended with 2500 molecular
weight diol with EO content 30% as low foam wetter.
4. Disinfectants. Used in the manufacture of iodophores.
5. Textile industry. Defoamer components in defoaming dyeing and
finishing processes. Wetting and emulsifying agents in lubricants and
spin finish formulations.
6. Emulsion polymers. Low molecular weight ( < 2000) products are used as
primary emulsifiers. High molecular weight products with high (> 70%)
EO content are used as post stabilisers.
7. Emulsion paints. Dispersants for pigments in emulsion paints (high
molecular weight with high PO content); defoamer component.
8. Agriculture. Emulsifier for herbicides and insecticides, usually used in
conjunction with other surfactants (mixtures of anionic and non-
ionic); spray additives for herbicides. to give good wetting and improve
penetration but without promoting foam.
9. Water treatment. Scale removal in boilers (high molecular weight with
high EO content).

S peciflcation

Water content: usually low ( < 0.5%) cloud point of 1% aqueous solution; can
obtain double cloud points or indeterminate cloud points as they are
susceptible to small amounts of polyglycol; but cloud point is important as
a small difference in EO level can appreciably affect cloud point; thus it can
be a simple sensitive test for EO content.
 NON-IONICS 155
Viscosity: for high molecular weight products viscosity can be a useful quality
control
EO and PO content: useful to know but difficult to measure and no guarantee
of consistency
Hydroxyl number: useful as quality control but not a guarantee of consistency
Functional test: wetting, foaming, defoaming, solubility etc. can be often
more discerning in checking batch variation or product replacement

7.10 Fatty acid ethoxylates

Nomenclature

Abbreviations: PEG esters, polyethylene glycol esters, used in this book.

Generic:
Fatty acid ethoxylates
Long chain carboxylic acid esters
Polyethylene glycol esters
Polyoxyethylene fatty acid esters
Polyoxyethylene esters
Examples:
PEG (400) monolaurate, this indicates that a polyethylene glycol of
molecular weight 400 has one hydroxyl group replaced with an ester
grouping formed with lauric acid

Description

Monoesters can be made in two ways:

1. Reaction of ethylene oxide with a fatty acid

RCOOH + nEO ------> RCOO-(CH2CH20)nH

2. Reaction of the acid with a polyglycol

The most common fatty acids used are coconut (CI2), tallow (CI8) or oleic
(C 18 unsat.). The usual practice in naming is to give the molecular weight of
the ethylene glycol; 200,400 and 600 are common.
Reaction 2 is basically an esterification and so can be made on simple
equipment, whilst reaction 1 demands specialised equipment to handle
ethylene oxide. The products look identical but reaction 1 will give a spread of
n (see Section 7.2) whilst reaction 2 will give a mixture of the monoester (as
shown above) plus some diester (shown below); also it is an equilibrium reaction
and therefore some free fatty acid and polyglycol are present. Up to 30% of the
156 HANDBOOK OF SURFACTANTS

diester is very common.

RCOO-(CHzCHzO)n-OCOR the diester
In reaction I the carboxyl group is highly ionised (see Section 7.2) and
therefore the first step in the ethoxylation is the reaction of the fatty acid with
one molecule of ethylene oxide. Only when all the carboxyl groups have
disappeared will the ethylene oxide react with the hydroxyl group which is
formed. The result is that ethoxylated fatty acids produced by reaction 1 are
quite free of fatty acid, unlike those produced by reaction 2. However during
the ethoxylation reaction in the presence of an alkaline catalyst, transesterific-
ation occurs.
2RCOO(CHzCHzO)nH --+ RCOO-(CHzCHZO)n-OCOR + HO-
(CHzCHzO)n- H
This gives a mixture of polyglycol, monoester and diester generally in the
proportion of 1:2: 1. The relative proportions of polyglycol, monoester and
diester in reaction 2 will depend upon the ratio of the reactants. An equal
molar ratio of fatty acid and poly glycol results in a mixture which is
predominant in monoester and similar to that produced in reaction 1. In the
preparation of monoesters by reaction 2 an excess of the polyglycol is usually
used to react with the fatty acid to ensure a high conversion to the monoester.
Minor components and impurities depend upon route. For reaction 1 (EO
route) these include: traces of EO; polyglycol (from water); diester; sodium
methoxide (catalyst for ethoxylation); acetic acid (used in the neutralisation of
the sodium methoxide or sodium acetate. For reaction 2 (polyglycol route)
these include: diester; fatty acid; polyglycol.
The diesters are made by the acid/polyglycol route with two moles of acid to
one mole of polyglycol. This reaction is again in equilibrium with fatty acid
and polyglycol present plus some monoester.

General properties

1. Solubility. The longer the chain length of the fatty acid, the less soluble
the product in water. The larger the amount of ethylene oxide, the better
solubility in water. Addition of 1-8 moles of ethylene oxide gives oil
soluble products. At 12-15 moles of EO water dispersability or solubility
occurs; 8 moles of EO = 372 molecular weight; 12 moles of EO = 528
molecular weight. Solubility in water depends upon the product being
monoester or diester. The monoesters are much more soluble in water
than the diesters which are only dispersable in water (at PEG molecular
weight < 1000).
2. Compatibility with aqueous ions. Excellent unless fatty acid is present.
3. Chemical stability. Readily hydrolysed by hot alkali.
 NON-IONICS 157
4. Surface active properties. Lowest surface tension at 10 moles of EO with
most acids at 30-36dyn/cm. Lowest surface tension (30dyn/cm) with
ClO-CI2 acids and 8-10 moles EO. HLB values (see Chapter 4) can be
calculated from the relation, HLB = (ethylene oxide content in %
+ propylene oxide content in %)/5.
5. Functional properties. Outstanding emulsifying properties and better
than AE or NPE. By choice of the fatty acid, the ethylene oxide content
and mono/diester content, a very wide range of HLB values can be
obtained (3-20). Lower flash foam and poorer foam stability than other
non-ionic types and the PEG diesters are often used as defoamer
components. Increase in temperature has no marked effect on the
foaming properties of the majority of the products. Tall oil derivatives
(with rosin) have lower foaming properties than corresponding fatty
acid derivatives. The PEG esters are poor wetting agents compared to
alcohol ethoxylates or alkyl phenol ethoxylates. The best are the lower
chain length acids (CI2) with low amounts of EO (10 moles = PEG
(400) monolaurate. Detergency is not outstanding.
6. Disadvantages. Poor chemical stability to alkali; generally poor wetting
properties.

Applications

1. Emulsifying agents for O/W and W/O emulsions: detergents; cosmetics;

solvent cleaner; degreasers; leather industry; oil industry; textile industry;
agriculture. Monoesters are usually used as blends of different HLBs.
Some typical HLB values are shown in Table 7.18. Diesters are generally
more oil soluble with much lower HLBs; they are used as emulsifiers
for oil particularly where foam has to be low. Typical HLBs are shown
in Table 7. t 9.
2. Shampoos. Ethylene glycol monostearate (EGS) (can be up to 30%
diester) is used as a pearling agent in other surfactants (e.g. shampoos). It

Table 7.18 HLB values of fatty acid PEG

monoesters

HLB

Oleic monoester with EO. = 1 3.5

(ethylene glycol)
PEG (200) monolaurate (CI2) 9.8
PEG (400) monolaurate (CI2) 12.8
PEG (600) monolaurate (CI2) 14.6
PEG (200) monostearate (CI8) 8.0
PEG (400) monostearate (CI8) 11.2
PEG (600) monostearate (CI8) 13.2
158 HANDBOOK OF SURFACTANTS

Table 7.19 HLB values for fatty acid

PEG diesters

HLB
-----------~--

PEG (200) distearate S.O

PEG (400) distearate 7.8
PEG (600) distearate 10.6
PEG (200) dilaurate 7.4
PEG (400) dilaurate 10.0
PEG (600) dilaurate II.S

Table 7.20 Properties of PEG esters

Typical properties
(PEG (400) laurate) Monoester Diester

Appearance Liquid-paste Liquid-paste

Active content 100 100
Acid value (mg KOH/g) O.OS-O.S
Water content e/~) O.5-S' 0.1-1.0
Sap value (mg KOH/g)b 80-90 130-140
Hydroxyl value (mg KOH/g)b 80-90 10-20
Solubility in water (10~;;;) D D
Solubility in white spirit D S

, Some manufacturers add up to 5~> water to keep products liquid. If water is > 5%
then there is danger of corrosion of mild steel drums.
b Sap value will depend upon whether monoester or diester. The diester will always
be higher than the monoester at the same molecular weight of the PEG portion. The
higher the molecular weight of the PEG part of the molecule, the lower the sap
number. The higher the molecular weight of the fatty acid, the lower the sap value.
Sap value should equal the hydroxyl value for monoesters but be higher (approx.
twice) for diesters.

is necessary to add the solid EGS to the heated shampoo then stir and
cool. It is difficult to get the pearling effect with sulphosuccinates but easy
with AOS, LABS, AS and AES.
3. Textiles. Lubricant components and emulsifiers (particularly for fatty
acid esters); also gives antistatic properties with high EO contents; dyeing
assistant.
4. Cutting oils. Emulsifier for both 0/W and W10.
5. Paints. Defoamers and levelling agents in emulsion paints.

Specification

See Table 7.20.

 NON-IONICS 159
7.11 Surbitan derivatives

Nomenclature
Two groups of products are covered in this section, the fatty acid esters of
sorbitan and their ethoxylated derivatives.
Generic: esters
Anhydrohexitol esters
Sorbitan esters
Sorbitan fatty acid esters
Spans (Atlas trade name)
Examples:
Sorbitan monolaurate
Sorbitan trioleate
Generic: ethoxylated esters
Polyoxyethylene sorbitan esters
Sorbitan ester ethoxylates
Tweens (Atlas trade name)
Example:
Polyoxyethylene (20) sorbitan monolaurate, this indicates that 20 moles
of EO have been reacted with sorbitan monolaurate
Atlas were the first company to commercialise these products and as such they
are often called by the Atlas trade names, Spans (the sorbitan esters) and
Tweens (the ethoxylated sorbitan esters)

Description
The two groups of products, the sorbitan esters and the ethoxylated sorbitan
esters have been grouped together because they are so often used together.

The esters. Sorbitol is reacted with a fatty acid at 200°C plus. The sorbitol
dehydrates to l,4-sorbitan and then esterification takes place. The resulting
product is a mixture with esterification taking place primarily on the primary
OH (see Figure 7.16). If one mole of fatty acid is reacted with one mole of
sorbitol then the product is principally the monoester but some diester is
formed.

The ethoxylates. Ethylene oxide can react on any hydroxyl group remaining
on the sorbitan ester group, in addition there can be ester interchange; some
polyoxyethylene groups can get between the sorbitan and the acid radical. If
sorbitol is first reacted with ethylene oxide and then esterified, an ethoxylated
sorbitan ester is obtained which will have different surfactant properties to the
Tweens.
160 HANDBOOK OF SURFACTANTS

CH 2 0H CH?~
H-C-OH
I
H--t~OH I
I I 0
HO-C-H
I HO-b~
H-C-OH
I I
H-C-OH H-C-OH
I I
CH 2 0H CH 2 0H
Sorbitol Sorbitan
+ RCOOH

CH2i
H-?-OH I
HO-C-H 0
tI I
H-C-OH
I
CH 2 0COR
Sorbitan monoester
Figure 7.16 Sorbitan esters.

General properties

1. Solubility. The esters are insoluble in water but soluble in most organic
oils (see Table 7.21). Depending on how much ethylene oxide is added,
ethoxylated derivatives can be made soluble or dispersable in water to
give a high HLB value (see Table 7.22).
2. Surface active properties. See Tables 7.23 and 7.24.
3. Functional properties. Esters give poor wetting, foaming, dispersing,
detergency but are excellent emulsifiers particularly when used in
conjunction with the ethoxylates. They are also excellent lubricants for
fibres. Ethoxylates, depending upon EO content, can be excellent
foamers, dispersing agents, wetting agents and detergents. However in
the majority of cases other non-ionies (ethoxylated alcohols) are more
cost effective.
 NON-IONICS 161
Table 7.21 Solubility of sorbitan esters (1-10% concentration) (S = soluble,
D = dispersable, I = insoluble)

HLB Solubility in Solubility in

Product number water mineral oil

Monolaurate (Span 20) 8.6 D S

Monostearate (Span 60) 4.6 I D(at 50°C)
Monooleate (Span 80) 4.2 I S
Tristearate (Span 65) 2.1 I D(at 50°C)
Trioleate (Span 85) 1.8 I S

Table 7.22 Solubility of sorbitan ester ethoxylates (1- 10% concentration)

(S = soluble, D = dispersable, I = insoluble)

Solubility in Solubility in
Product water mineral oil

Polyoxyethylene (4) sorbitan monostearate D

Polyoxyethylene (20) sorbitan monostearate S
Polyoxyethylene (20) sorbitan tristearate D

Table 7.23 Surface active properties of the esters

Surface tension
of 1% in water
Product (dynjcm)

Monolaurate (Span 20) 28

Monostearate (Span 60) 46
Monooleate (Span 80) 30
Tristearate (Span 65) 48
Trioleate (Span 85) 32

Table 7.24 Surface active properties of the ethoxylates

Surface tension
of 1% solution
in water
Product (dynjcm) CMC(%)

Polyoxyethylene (4) sorbitan monolaurate 0.0013

Polyoxyethylene (4) sorbitan monostearate 38
Polyoxyethylene (20) sorbitan monostearate 43 0.0027
Polyoxyethylene (20) sorbitan tristearate 31
162 HANDBOOK OF SURFACTANTS

Applications

l. General. The sorbitan esters and ethoxylated derivatives have been used
and approved as food additives in most countries throughout the world.
They are, therefore, used in many applications where they may be less
cost-effective than other surfactants, but Governmental Regulations
inhibit the use of the competitive materials. They are also a family of
surfactants where there is long experience of their use as emulsifying
agents.
2. Food. There are many applications where esters are used as oil soluble
emulsifiers which can change the wetting, dispersing and the physical
properties of oil or fat mixtures. This can give improved palatability or
shelf storage properties. They can also function as water in oil emulsifiers
to promote air retention and other physical properties of food mixtures
where the water content is low, e.g. cakes.
Ethoxylates have many applications where they can function in a
similar manner to the esters but acting more as an oil in water emulsifier
for products with a higher water content, e.g. ice creams. Mixtures of
esters and ethoxylates are commonly used in many foods in order to
obtain the benefits of both sets of products.
3. Shampoos. Ethoxylated products are used with anionics (ether sulphates)
for production of baby shampoos (low eye irritation).
4. Cosmetics. Ethoxylates are used as solubilisers for oils and fragrances.
Perfume oils are solubilised for use in products such as colognes, bath oils
and after-shave lotions. Lotions and creams of the oil in water type are
prepared from mixtures of esters and ethoxylates. Creams ofthe water in
oil type; e.g. cold creams are generally prepared with the esters but small
quantities of the ethoxylates makes a more easily prepared cream.
5. Pharmaceuticals. Both esters and ethoxylates are used in pharmaceutical
preparations as solubilisers, emulsifiers and dispersants. Mutually
incompatible ingredients can be used as ointments or lotions by
emulsification or dispersion particularly in aqueous solution. Increased
biological activity is sometimes obtained by administration in solubilised
form.
6. Textiles. Low HLB products are used as lubricants for fibres. The
ethoxylates were commonly used as emulsifying agents for the esters and
mineral oils but are now being replaced by more cost-effective non-
ionics.
7. Metal protectants and metal working. Sorbitan oleates were at one time
extensively used in anticorrosion compositions in lubricating oils.
Removable protective coatings or temporary protective coatings often
incorporate the esters, usually the oleates. The ethoxylates are used as
emulsifying agents in cutting oils and give some degree of corrosion
inhibition as well. However, more cost-effective formulations based on
 NON-IONICS 163
Table 7.25 Analysis of esters

Monoester Triester

Acid value (mg KOH/g) 2-10 2-15

Sap value a 145-170 170-190
Hydroxyl value b 200-350 50-90

aSap values will depend upon the hydrophobe (the lower

the chain length of the hydrophobe the higher the sap
value) but also upon the amount of diester formation. The
difference between mono- and triesters may not be so
large.
bThe hydroxyl value indicates more readily the difference
between mono- and triesters.

Table 7.26 Analysis of ethoxylates

Acid value (mg KOH/g) 1-5

Sap value (mg KOH/g)" 20-120
Hydroxyl value (mg KOH/g)" 40-250

aDepends upon degree of ethoxylation; low values for

high degrees of ethoxylation.

oil soluble sulphonates and fatty acids are replacing the sorbitan-based
products.
8. Oil slick dispersants. The excellent emulsifying properties of the ethoxy-
lates plus the extensive knowledge of their toxicity has led to their use in
oil slick dispersing agents.
9. Explosives. Ethoxylated sorbitan monooleate is used as an emulsifier
for liquid explosives.

Specification

See Tables 7.25 and 7.26. The following combinations of sap value and
hydroxyl value are useful indicators to composition:
high (150-170) sap and high (200 + ) OH value = monoester; high (150 + )
sap and low ( < 80) OH value = triester; low ( < 100) sap and low ( < 60) OH
value = ethoxylated triester.

7.12 Ethylene glycol, propylene glycol, glycerol and polyglyceryl

esters plus their ethoxylated derivatives

The esters are grouped together because they are all formed by a hydrophobic
group or groups which are attached by an ester group to a muitihydroxyl (2 or
more hydroxyl groups) compound. Most products are synthesised but some
164 HANDBOOK OF SURFACTANTS

occur naturally. There are very similar products which are derived from
carbohydrates (Section 7.6). The fatty acid ethoxylates are the esters of
polyethylene glycol but these are described in Section 7.10.
The ester ethoxylates are those esters with free hydroxyl groups remaining
after esterification which have been reacted with ethylene oxide to increase
water solubility. Again the sorbitan ester ethoxylates strictly belong to this
group but they are described in Section 7.11.

Nomenclature

Can be confusing.
Generic: esters (see Figure 7.17 for structural formula)
Ethylene glycol esters or glycol esters
Glycerol esters, mono- or diglycerides

Esters
RCOOCH1CH10H ethylene glycol esters
RCOOCH 1CHCH 20H propylene glycol esters
I
CH 3
CH 20COR
I monoglycerides
CHOH
I
CH 20H
CH 20COR
I 1,3-diglycerides
CHOH
I
CH 20COR
HOCH2CHCH20(CH2-CHCH20)nCH2CHCH20COR
I I I
OH OH OH
polyglyceryl monoester
Ethoxylates
CH 20COR
I
CHO(CH 2CH 2 0)nH polyethoxylated 1,3-diglyceride
I
CH 20COR
Figure 7.17 Structural formula of esters/ethoxylates.
 NON-IONICS 165
Glyceryl esters, same as glycerol esters
Polyethylene glycol esters, not described here, see Section 7.10
Polyglyceryl esters
Polyol monoester, careful, this can mean polyglyceryl or polyoxyethylene
or even a polyoxyethylene polyglyceryl ester; Ask the supplier what it
means
Propylene glycol esters
Example: Esters
Glycerol (or glyceryl) monostearate
I-Monolaurin = glycerol monolaurate
Triglycerol monostearate = a polyglyceride (3 moles of glycerol poly-
merised then esterified with 1 mole of stearic acid)
Decaglycerol tristearate = a polyglyceride (10 moles of glycerol poly-
merised then esterified with 3 moles of stearic acid)
Generic: Ethoxylated esters (see Figure 7.17 for structural formula)
Polyoxyalkylene glycol esters
Polyoxyalkylene propylene glycol esters
Polyoxyalkylene polyol esters = probably ethoxylated polyglyceryl esters
Polyoxyalkylene glyceride esters
Examples: Ethoxylated esters
Polyoxyethyleneglycol(400) triglycerol monostearate; in this case the
number 400 indicates molecular weight of the polyoxyethyleneglycol

Description
1. Glycol esters (ethylene or propylene glycol monoesters). Preparation by
reaction of one mole of glycol with one mole of fatty acid gives a mixture
of mono- .and diesters. Commercial glycol ester surfactants usually
consist of such mixtures. An excess of glycol will give an ester with a high
monoester content. Both hydroxyl groups of ethylene glycol are of equal
reactivity but the two hydroxyl groups of 1,2-propylene glycol have not
the same reactivity with the I-hydroxyl being a primary hydroxyl group
and the 2-hydroxyl group being a secondary hydroxyl group. The
primary esterifies at a faster (about 3 times) rate than the secondary
hydroxyl group.
2. Glyceryl esters (mono- and diesters of glycerol). Method 1: Directly from
animal fats or vegetable oils. When a triglyceride (an animal fat or
vegetable oil) is reacted with glycerol in the presence of an alkaline
catalyst transalcoholysis takes place and mono-, di- and triesters of
glycerol are formed, the proportions depending upon the ratio of starting
materials. Method 2: Partial hydrolysis with alkali gives a mixture of
soap, mono-, di- and triglycerides of varying composition depending
upon the extent of saponification. The products are easy to make in
166 HANDBOOK OF SURFACTANTS

simple equipment, but ill-defined and not easy to reproduce. Method 3:

From purified fatty acids and glycerol.
An alternative method of manufacture is to esterify the fatty acid
(which can be fractionated) with glycerol; much better defined products
are obtained, but they are more expensive. The usual products available
are described as monoesters, e.g. glyceryl monolaurate indicating two
free hydroxyl groups or triesters indicating no free hydroxyl groups.
However, most commercial monoesters will have some diester present.
The number of free hydroxyl groups are important as they can influence
solubility, i.e. the greater the hydroxyl value the more water soluble.
There is considerable complexity in these reactions and most of the
reactions are reversible. The monoesters can be separated from the
mixtures by molecular distillation and can be obtained in a pure stable
state.
3. Polyglycerides. When glycerol is heated in the presence of an alkaline
catalyst, dehydration occurs, with the formation of polyglycerols. The
polyglycerols can be esterified with fatty acids. The degree of polymeris-
ation of the glycerol and the degree of esterification can give a large
number of products with widely varying surfactant properties.
4. Polyoxyalkylene glyceride esters. Formed by reaction of ethylene oxide
with free hydroxyl groups in monoglycerides or diglycerides or polygly-
cerol esters.

General properties

1. Solubility. See Tables 7.27-7.29.

2. Solubility (general). Practically all the esters are insoluble in water unless
there is a high proportion of hydroxyl groups, e.g. polyglceryl esters when
the products can disperse to form hazy solutions. Conversely, most esters
are soluble in mineral oil unless there is a high proportion of hydroxyl or
ether groups. Ethoxylation improves water solubility and decreases
mineral oil solubility.

Table 7.27 Solubility of monoesters (HLB = 3)' (S = soluble. D = dispersablc. I = insoluble)

Monolaurate Monooleatc Monostearate

-,--------- _._----
EG PG G EG PG G EG PG G

1% in water I I I I I I
I% in mineral oil S S S S D S
I % in white spirit S D
1% in aromatic solvent D D D D S D
I% in perchlorethylene D S

'EG = ethylene glycol monoester; PG = propylene glycol monoester; G = glycerol monoester.

 NON-IONICS 167
Table 7.28 Solubility of glyct:rol trioleate (HLB = 0.8) (S = soluble, 1=
insoluble)

1% in water I 10% in water I

1%in mineral oil S 10% in mineral oil S
1% in white spirit S 10% in white spirit S
1% in aromatic solvent S 10% in aromatic solvent S
1% in perchlorethylene S 10% in perchlorethylene S

Table 7.29 Solubility of polyglyceryl esters' (S = soluble, D =

dispersable)

TG/MS DG/MS DG/TS

1% in water D D D
I % in mineral oil D D S
1% in aromatic solvent S S S

'TG/MS = triglycerol monostearate; DG/MS = decaglycerol

monostearate; DG/TS = decaglycerol tristearate.

3. Functional properties. Wetting, foaming, dispersing and detergent pro-

perties are poor compared to the alcohol or alkyl phenol ethoxylates.
This is because the molecular weight has to be high before water
solubility is achieved. Emulsification properties, particularly water in oil,
are excellent and the relatively high molecular weight gives very stable
emulsions. This group of products is one example of polymeric
surfactants (see Chapter 11).

Applications

1. General. Confined to emulsification and/or applications where the low

toxicity properties are utilised, e.g. food additives. The ethoxylated
sorbitan derivatives are used in very similar applications but these are
discussed in Section 7.11.
2. Food. Many foods contain a water in oil emulsion and/or oil in water
emulsion inside a fat or oil. The oil soluble surfactants (often used with
water soluble surfactants, e.g. ethoxylated sorbitan esters, see Section
7.11) play an important role in entrapping air and holding small bubbles
of air. They can also affect both the physical properties of the mixtures,
and the physical stability over a period of time.
For many years glyceryl monostearate (with some distearate) was the
standard anti staling agent in bread products. Addition of approx. 0.35%
surfactant on the weight of flour retards the crytallisation of amylopectin
and the resultant release of moisture, thus delaying the firming of the
bread. Propyleneglycol monoesters are used in conjunction with glyceryl
168 HANDBOOK OF SURFACTANTS

monoesters in high volume cakes and whipped toppings; food emul-

sifiers; ice cream; margarine; synthetic cream.
3. Pharmaceuticals. Emulsifying agents in ointments and lotions, again
often used in combination with the ethoxylated sorbitan derivatives (see
Section 7.11).
4. Defoamer components. The type of esters described in this section are
excellent defoamers for a variety of aqueous systems particularly where
toxicity is an important consideration.
5. Cosmetic emulsifiers. Lotions, creams, gels and other vehicles are used in
cosmetics, many of them being water in oil emulsions. The esters can be
either the oil base for the cmulsion or used as one of the emulsifiers for the
system. Ethylene glycol, propylene glycol and glycerol monoesters
(particularly stearates) are used to thicken creams and lotions and
opacify solutions of soap and more hydrophilic materials.
6. Textiles. Used as emulsifiers and/or lubricants in spinning oils.
7. Polymers. Mono- and diglycerides are applied to the surface of food
packaging to give anti-fogging properties.

Specification
Appearance, usually viscous liquid or pasty solid
Free glycol, can be 5-10% for monoesters but purified products can be as
low as 0.5%
Acid value, 0.2-4mg KOH/g
Soap, 1-6%
Iodine value, check on unsaturation but not applicable to ethoxylates
Hydroxyl value, useful for ethoxylates (see Section 4.2) or polyglyceryl esters
(100-350mg KOH/g)
Safety and toxicity

This group of products is more widely accepted as food additives than any
other group of surfact ants (also see Section 7.1). One reason for this is that the
chemical structures are very similar to naturally occurring oils and fats. Also,
glycerides are prepared from naturally occurring glycerol and fatty acids or
even direct from the naturally occurring glycerides. Members of this group
appear in lists of approved additives in the United States and the EEC.
Suppliers will give full details of whether or not their products comply with
Food Regulations.

7.13 Alkyl amines and alkyl imidazolines

Nomenclature

Generic (see Figure 7.18 for formula):

Alkyl amidopropyl dimethylamine
Alkyl primary amines
 NON-IONICS 169

primary amine

secondary amine

tertiary anine

RNHCH1CH1CH1NH 1 propane diamine

RNHCH1CH1NH 1 ethylene diamine
RNHCH2CH1NHCH2CH2NHl diethylene triamine
RNH(CH1CH2NH)xH alkyl polyamine

Figure7.18 Alkyl amines.

Alkyl secondary amines

Alkyl tertiary amines
Alkyl propanediamines
Alkyl ethylene diamines
Alkyl diethylene triamines
Alkyl triethylene tetramines
Alkyl tetraethylene pentamines
Alkyl polyamines
Diamines
Fatty primary amines
Imidazolines
Alkylimidazoline hydroxyethylamines
Alkylimidazoline ethylenediamine
N, N-Dimethyl-N-(3-alkyl amidopropyl)amines
Polyamines
Examples:
Laurylamine, C 12 H 15 NH 1
N.N'-Dimethyl-N-(3-lauryl amidopropyl)amine = laurylamidopropyl di-
methylamine, C12H15CONHCH1CH2CH1N(CH3)z

Description

The major products, first available commercially, were based on natural fatty
acids which had been converted to primary amines via the amide and
 170 HANDBOOK OF SURFACTANTS

hydrogenation (see Figure 7.19). From the primary amine formed, secondary,
tertiary and alkyl propane diamines can be made (see Figure 7.19). The most
common alkyl groups are derived from coconut oil, tallow or soya bean oil
and may be fractionated or not.
In more recent years, alternative routes to the primary amines and tertiary
amines have been developed, to avoid the costly route shown in Figure 7.19.
The two principal routes are: (i) from the alkyl halide by reaction with
ammonia; (ii) from the olefin by reaction with ammonia.
The importance to the formulator of the three different routes via fatty acid,
via alkyl halide and via the olefin is two-fold (i) the distribution of the alkyl
chain will be different because the fatty acid is from natural sources and the
other route via petrochemicals; even if the petrochemical route is via ethylene
polymerisation, the distribution of chain lengths may be different. (ii) The
minor components will be different which may be very important or not at
all. Thus care should be taken in changing raw materials. Very few amines
are used as such, most being changed into ethoxylated products, betaines,
amine oxides and quaternaries. However, the by-products can sometimes
interfere with the conversion process or even pass through to the finished
derivative.
There is much interest in developing new routes to tertiary amines because
the alkyl dimethyl tertiary amines are the raw materials for amine oxides
(Section 7.5), quaternaries (Section 8.2) or betaines (Section 9.2). The prin-
cipal tertiary amines available are imidazolines, alkylamido dimethyl propyl-
amines and alkyl dimethylamines.

Primary amines .

Propane diamines

Secondary amines

Raney /R
2RNH2 --nic-'ke-'--l-' HN""'R + NH3

Tertiary amines (alkyl dimethyl)

Figure 7.19 Manufacture of amines.

 NON-IONICS 171

R' = CH 2 CH 2 NH 2 = alkyl aminoethyl imidazoline

R' = CH 2 CH 2 0H = alkyl hydroxyethyl imidazoline
Figure 7.20 Manufacture of imidazolines.

Figure 7.21 Alkylamido dimethyl propylamines.

Imidazolines are made by reacting a fatty acid with a substituted ethylene

diamine and then cyclising (heating at 220-240°C) (see Figure 7.20). R is the
hydrophobe usually in the range CI2-CIS derived from a fatty acid. The
group R' can be practically any group although if it contains a reactive group
capable of reacting with a COOH group, e.g. a OH group, then the result-
ing products can be very complex. Typical commercial products are: R' =
CH 2 CH 2 NH 2 , aminoethyl imidazoline; R' = CH 2 CH 2 0H, hydroxyethyl
imidazoline. The imidazoline ring has a tertiary nitrogen group which can be
quaternised. However if the group R' contains amino groups then these can
also act as cationic groups when acidified. The imidazoline ring readily splits
open on hydrolysis (see Section S.3).
Alkylamido dimethyl propylamines (see Figure 7.21) are now available,
principally to make amine oxides or amidopropyl betaines.
In alkyl dimethylamines, the alkyl group most often found is CI2~CI4.
The products are used to make amine oxides (Section 7.5), quaternaries
(Section S.2) and betaines (Section 9.4). There are now several ways of pre-
paring these products (via the primary amine, via olefins or via alkyl alcohols).
There can be small differences in the by-products depending upon the manu-
facturing route.

General properties

1. Solubility. Generally insoluble in water but soluble in strong acid

solutions (see Table 7.30). Solubility of alkyl amino ethyl imidazolines is
172 HANDBOOK OF SURFACTANTS

Table 7.30 Solubility (:%,,) of amines and ~alts (I = insoluble)

In water Ethanol

20"C 40"C 20VC 40"C

C'2 H 2S NH 2 I I 53 87
C'2HZSNH2 + HC! 0.3 36 13 34
C'2H2SNH2 + HOAc 25 28 45 72

Table 7.31 Solubility of amino ethyl imidazolines (S = soluble, D = dis-

persable, I = insoluble)
--~--

Coco Oleic Tall oil Stearic

------
\0% in water D D I I
10% in mineral oil I S D D
\0% in white spirit I S S S
\0% in aromatic solvent I S S S
\0% in perchlorethylene I S S S

shown in Table 7.31. Some salts are compatible with anionics, e.g.
propionic acid salt of cocoamidopropyl dimethylamine is compatible
with lauryl sulphate and lauryl ether sulphate and small amounts (\- 5%)
will actually give an increase in flash foam. Most alkyl polyamines arc
soluble in acid (mineral or low molecular weight organic) solution. Salts
with high molecular weight organic acids are oil soluble.
2. Chemical stability. The amines are all reactive, the principal reactions
being: salt formation with mineral or low molecular weight organic acids
for p-, sec- and t-; forms carbonate salts with carbon dioxide which is
reversible by heating for the p- and sec-; reaction with aldehydes and
ketones, p-; reaction with alkyl halides, p-, sec-, t-; reaction with ethylene
oxide, p-, sec- or t-; p- and sec- decompose on heating above 90°C;
t-amines are more stable; N,N-dimethyl-N-(3-laurylamidopropyl)amine
hydrolyses at temperatures of 90°C but acid hydrolysis will be faster.

Applications

The major applications are as chemical intermediates for amine salts,

quaternary ammonium salts, ethoxylated derivatives or betaines, However
there are a large number of applications of the amines or imidazolines which
have not been chemically reacted.
1. Primary amines. Cationic emulsifying agent below pH 7; corrosion
inhibitor for fuels, lubricating oils and for metal surfaces; anticaking
agents for fertilisers, normally C 1s NH 2 but liquid formulations are used
composed of amine in mineral oil and sometimes in conjunction with a
fatty acid; solid formulations are made by coating kaolin or talc with the
 NON-IONICS 173
amine; adhesion promoter for painting damp surfaces; ore flotation
collector.
2. Diamines, po/yamines and imidazolines. Uses as above but main uses are
as adhesion promoters for bitumen coating of damp road surfaces; textile
softener; pigment coatings; oil field chemicals as corrosion inhibitors; by
variation in the alkyl chain of the amine and the type of organic acid used
to neutralise the amine, a very wide range of water/oil soluble materials
can be prepared.
3. Tertiary amines. For manufacture of quaternaries, amine oxides and
alkyl betaines.
4. Imidazolines. Can function as oil soluble emulsifiers producing cationic
O/W emulsions; if they are neutralised below pH 8 they become
hydrophilic and can act as emulsifiers for polar organic solvents, e.g.
toluene, pine oil or triglycerides; used in water displacing solvents as they
adsorb at metal surfaces in place of water; addition to oils, waxes or
bitumen to improve adhesion to substrates; addition to paints to
improve adhesion.

Specification
Amine number of neutralisation equivalent
amine value
determination of p-, sec- and I-amine, p-amines can have 3% sec- and 1% t-
sec-amines can have 7% p- and 6% t-
t-amines can have 0.5% p- and 4% sec-
iodine value
The amine number is the amount of hydrochloric acid (in mg) needed for the
neutralisation of 1 g of sample = amine value x 0.6498. The fatty amines are
insoluble in water so isopropanol is used as solvent and titration carried out
with isopropanolic hydrochloric acid.
The amine value is the amount of KOH (in mg) that would be equal to the
number of milliequivalents of amine present in 1 g of sample = amine number
x 1.539.
Most primary amines contain small amounts of sec- and t-amines. Likewise
secondary amines contain small amounts of p- and t-amines. The impurities
can often be important. The diamines and polyamines however can have equal
quantities of p- and sec-. Thus the relative amount of p-, sec- and t-amine is
a useful identifier for unknown products.

7.14 Ethoxylated oils and fats

Nomenclature
Generic:
Ethoxylated lanolin
Ethoxylated castor oil
174 HANDBOOK OF SURFACTANTS

Description

A number of natural oils or fats have been ethoxylated to give surfactant

properties. The two principal products are wool fat or lanolin and castor oil
ethoxylate.
Raw wool consists of a mixture of fatty acid esters of cholesterol,
isocholesterol, other higher fatty alcohols and terpene derivatives. Normally
the wool fat undergoes chemical fractionation, and the ethoxylation is carried
out on the lanolin alcohol which is still a mixture of aliphatic alcohols and
sterols.
The initial site for ethoxylation of castor oil is the hydroxyl groups on the
ricinoleic acid chain. However, the ester groups may provide additional
reaction sites under the effect of alkaline catalyst and heat. Thus the
composition of the products will depend upon the conditions of ethoxylation.

General properties

The properties follow all the normal ethoxylate properties as the main variable
is the polyoxyethylene content. Specific properties are summarised below.
I. Lanolin ethoxylate. With > 55% ethylene oxide, products are water
soluble and give solubilisation and emulsification properties.
2. Castor oil ethoxylate. With> 60% ethylene oxide, the products make
excellent emulsifiers.

Applications

I. General. The high molecular weight of most products (e.g. castor oil + 40
moles of ethylene oxide = 2800) restricts their use to emulsifiers,
demulsifiers, defoamers and dispersing agents.
2. Cosmetics. Numerous ethoxylated natural products have been made for
the cosmetic industry, mainly to be able to claim that a chemical had a
natural base.

Specifications

Similar to most ethoxylates in cloud point, hydroxyl number and acid number.

7.15 Alkyl phenol ethoxylates

N omenclalure

Abbreviations: APE, alkyl phenol ethoxylates, used in this book; APEO;

APO; NPE, nonyl phenol ethoxylate, used in this book; NPEO; NPO.
 NON-IONICS 175
Generic:
Alkylphenol ethoxylates
Polyoxyethylated alkyl phenols
Polyoxyethlylene alkylphenols
Examples of names for the product, C9H19C6H40(CH2CH20)9H
Nonyl phenol + 9EO
Nonyl phenol ethoxylate (9EO)
Ethoxylated (9EO) nonyl phenol
Nonoxynol9

Description

Prepared by reaction of ethylene oxide with the appropriate alkyl phenol.

Principal products commercially available are ethoxylates of para-
nonylphenol, para-dodecylphenol, dinonylphenol (mixture of isomers) and
para-octylphenol (once the major product).
The most common APEs are the nonyl phenol ethoxylates which are made
using distilled nonyl phenol which is predominantly para, usually> 90%. The
nonyl group is derived from propylene trimer and therefore the alkyl group is a
branched chain. Nonyl phenol ethoxylates (at the time of writing) are the only
large volume surfactants on the international market with a branched
hydrophobic group. The reason is their low price and excellent properties, but
the biodegradability is suspect and therefore their long-term future is in doubt.
However, exactly the same statement has been said for 20 years and they are
still bought and sold, but this is mainly for use in industrial products rather
than domestic detergents. They are likely to be used whilst they are cheaper
than the similar alcohol ethoxylates.
Impurities include polyethylene glycols (often show as a haze) but a small
proportion of water gives clear solutions. The presence of polyglycols can
often increase a product's tendency to gel. Catalyst residues, sodium
hydroxide or sodium methoxide, are usually neutralised with acetic acid. 1,4-
dioxane can be easily removed from APEs. Free ethylene oxide may also be
present.

General properties

I. Solubility. Solubility of NPEs is shown in Table 7.32. In comparison

with the alcohol ethoxylates, NPEs show better solubility in organic
solvents at similar HLB value. Note the improved solubility of dinonyl
phenol ethoxylate + tOEO in white spirit over nonyl phenol + 6EO
although they have the same HLB value of 11. NPEs are more liquid and
have lower viscosities than equivalent AEs. Aqueous solutions of many
NPEs show a very large increase in viscosity, or even gel, at about
 .-
-.J
0\

Table 7.32 Solubility of NPEs· (S = soluble, D = dispersable, I = insoluble) ;:e

>
NP+ lEO NP+4EO NP+6EO NP+8EO NP+ IIEO NP+20EO DNP + 10EO Z
o
HLB 4.5 9 11 12 14 16 11
Cloud point b <room temp <room temp < room temp 20-30 60-70 > 100 ~
10% in water I I I D S S I ~
10% in mineral oil S S I I I I S
10% in white spirit S S S S I I S ~
10% in aromatics S S S S S I S ~
10% in perchlorethylene S S S S S I S n
-l
>
·NP = nonyl phenol; DNP = dinonyl phenol; bIn °C of a 1% solution in water (DIN 53917). For low EO contents a 2~ 0 solution in 25~~ diethylene glycol ~
monobutyl ether can be used. For high EO contents a 1% solution in 10% sodium chloride can be used. en
 NON-IONICS 177
50-60% concentration, with lower viscosities below or above this
concentration. The solubility decreases with increasing temperature,
see cloud point in Section 7.1.
2. Compatibility with aqueous ions. Excellent compatibility with all
aqueous ions. Lime soap dispersion index for most products is in the
range of 4-8% of NPE relative to sodium oleate in 333 ppm hard water.
However at 6EO (optimum surface active activity at room temperature)
the index is 1O-15(GAF Corp. Tech. Bull 7543-002(1965).)
3. Chemical stability. Stable to heat for short periods but show a slow
increase in colour when held for extended periods above 80°C in air.
Addition of antioxidants (e.g. hindered phenols) can improve stability to
well above 100°C. NPEs are stable to hot dilute acid, alkali (except
yellowing in solid powders) but end blocking improves the stability to
alkali. Not entirely stable to oxidising agents, e.g. hypochlorite, peroxide
and perborate (see Section 7.1).
4. Surface active properties. Minimum surface tension in water of
28 dyn/cm occurs with nonyl phenol at the 6EO level where it only
disperses rather than dissolves. Maximum surface activity occurs near
cloud point.
5. Functional properties (for NPEs). Excellent wetting agents with lowest
Draves wetting times near cloud point; thus the optimum EO content
will depend upon the temperature, but higher temperatures and hence
higher cloud points give better wetting. Excellent detergent for oils and
greases, EO = 9 for optimum but depends upon formulation; solubiliser
for oils and perfumes, EO = 3-5 for optimum; foaming agent, EO = 15
for optimum but low foam compared to anionics; depends upon
temperature in a similar way to wetting; Emulsifier, W/O EO = 1-5
for optimum, O/W EO = 8-40 for optimum; for waxes, oils and fats,
EO = 4-6 for optimum; defoaming, EO = 1-3 for optimum.
6. Disadvantages. Doubts on large scale availability in the future due to the
biodegradation properties.

Applications

I. Household products and industrial cleaning. Not used in the western

world because of biodegradation properties but products give excellent
cleaning compounds especially in detergent sanitisers. Most usual
products are NPE with 10-12 EO (compatible with iodophors, quater-
naries and phenolics) but in presence of strong electrolyte and high
temperatures EO = 15 is optimum (particularly for bottle cleaners, metal
cleaners and heavy duty alkaline cleaners). In formulated conveyor
lubricants, gives both good detergency and lubrication (not found with
AE). Make excellent heavy duty solvent type cleaners for floors and
178 HANDBOOK OF SURFACTANTS

general cleaning containing> 25% kerosene with 10% of NPE with

9EO. Now superseded by aqueous dispersions wherever possible.
2. Textiles. Detergents, wetting agents and emulsifiers for processing wool,
cotton and synthetics (scouring, bleaching, kier boiling, warp desizing),
NPE with 8-9EO at low temperatures and 20EO at high temperatures;
anti-static agent; dye retarders.
3. Agriculture. Used as emulsifiers in self-emulsifying herbicides and
insecticides.
4. Concrete. Foam entrainment for frost protection, NPE with EO > 15.
5. Emulsion polymers. Emulsifiers and stabilisers, NPE with EO> 20.

Specification

Water content, can be 0.1-20%

Polyglycol content, 0.1-5%
Melting point, more realistic measure of EO content than cloud point for
high EO content materials
Refractive index, quick method for checking EO content
Cloud point, quick method for checking EO content but can be misleading
if polyglycols are present

References

Fan, T.Y., Goff, V., Song, L., Fine, D.H., Arsenault, G.P. and Biemann, K. (\ 977) N-nitrosamine in
cosmetics,loti.ons and shampoos, presented at the American Chemical Society Meeting, New
Orleans, LA.
Gerstein, T. (\ 977) VS Patent 4,033,895 to Revlon.
Henderson, G. and Newton, 1.M. (\966) Pharm. Acta. Helv. 41, 228.
Henderson, G. and Newton, 1.M. (\969) Pharm. Acta. Helv. 44, 129.
Hugo, W.B. and Newton, 1.M. (1963) J. Pharmacol. 15, 731.
Kassem, T.M. (1984) Tenside Detergents 21(3), 144.
Knaggs, E.A. (1965) Soap Chem. Specia/it;es 41, 64.
Meguro, K., Veno, M. and Esumi, K. (1987) Nonionic Surjactants-Physical Chemistry, Marcel
Dekker, New York, p. 150.
Milwidsky B. and Holtzmann, S. (1972) Effects of regular amides and superamides on the foaming
and viscosity of detergents, presented at the VIth International Congress of Surface Active
Substances, Zurich.
Nakagawa, T. (1967) In Nonionic SurJactants, ed. MJ. Schick, Marcel Dekker, New York, p. 599.
Osipow, 0., Snell, F.D., Marra, D. and York, W.e. (1956) Ind. Eng. Chem. 48, 1462.
Schick, MJ., ed. (1967) Nonionic SurJactants, Marcel Dekker, New York.
Schmolka, I.R. (1977) J. Am. Oil Chem. Soc. 54, 110.
Tagawa, T., lino, S., Sonoda, T. and Oba, N. (1962) Kogyo Kagaku Zasshi 65, 953; Chemical
Abstracts 58, 680 (1963).
8 Cationics

8.1 Cationics general

Nomenclature

The cationics are named after the parent nitrogen, phosphorus or sulphur
starting material. Thus the quaternary ammonium compound, dodecyltri-
methyl ammonium chloride, is formed from the starting material dodecyldi-
methylamine reacted with methyl chloride.

Description

Cationic surfactants are those surfactants where the ionic group on the
hydrophobic group would go to the cathode (negatively charged) and hence
have a positive charge. With very few exceptions, commercially available
cationics are based on the nitrogen atom carrying the positive charge. The
only other products are based on phosphorus and sulphur. C12H2SNH2 is a
primary amine and in neutral solution is uncharged, therefore these surfact-
ants are not strictly cationic. However as a salt of, for example, acetic acid,
C12H2SNH3 +CH 3COO-, the amine is now a cationic surfactant. The largest
volume products are those used for fabric softening in domestic use. These are
quaternary ammonium products based on either distearylmethylamine or
ditallow imidazoline.

General properties

Non-quaternary cations are sensitive to high pH, polyvalent ions and high
concentrations of electrolyte whereas quaternary cations are sensitive to none
of these. Cationics differ from anionic and non-ionic surfactants in their high
degree of substantivity. This term substantivity encompasses the uptake of
surfactant from solution on to the surface of a wide variety of negatively
charged surfaces: fibres, cellulosic such as paper and cotton, protein such as
wool and synthetic fibres such as polyamide and acrylic; plastics, polyvinyl
chloride and polyvinyl acetate; silicates; metals; pigments. Depending upon
the chemical structure of the cationic surfactant, it is possible to make a
hydrophilic solid behave as if it was hydrophobic or less usual make a
180 HANDBOOK OF SURFACTANTS

hydrophobic solid behave as if it were hydrophilic. Thus the surface properties

of solids can be modified using cationic surfactants.
1. Bactericidal action. The long chain fatty amines and their salts, the
quaternaries and the imidazolines have the ability to kill microorganisms
or restrict their growth. The chemical structure for optimum effectiveness
varies depending upon the type of cationic. However the imidazolines do
not appear to be used very often as biocides.
2. Complex formation with anionic surfactants. Cationics will generally
form insoluble complexes with anionic surfactants which are insoluble in
water and may lose their surfactant properties, e.g. the ability to foam or
wet. However, in organic solvents and mineral oil, anionic/cationic
surfactant complexes can show substantivity, wetting and corrosion
resistance suggesting that they are surface active in such an
environment.
3. Disadvantages. More expensive than anionics; poor detergency; poor
suspending power for solids (e.g. carbon).

Applications

Most solid surfaces are negatively charged and thus cations will adsorb on to
solid surfaces. Examples of this application are: textiles, softeners, antistats;
fertilisers, anticaking agents; bitumen coatings, emulsifier for bitumen; oil
field chemicals, corrosion inhibitors in oil production; pigments, dispersing
agents; mineral processing, flotation agents.

8.2 Quaternary ammonium

Nomenclature

These compounds are substituted ammonium salts where none of the four
substituent groups are hydrogen
R'R"R"'R""N + X-
X- is usually the chloride ion Cl- or the ethyl sulphate ion C zH sS0 4 -, e.g.
N-alkyltrimethylammonium chloride, R' = alkyl, R" = R'" = R"" = methyl,
X = chloride; N-ditallowdimethylammonium chloride, R' = R" = alkyl chain
with same length as tallow fatty acid, R'" = R"" = methyl, X = chloride;
bis(hydrogenated tallow alkyl)dimethylammonium chloride, see Figure 8.1;
benzalkonium chloride, see Figure 8.1; quaternised polyoxyethylene fatty
amines, see Figure 8.1.
Abbreviation: QAC, quaternary ammonium compound, used in this
book.
 CATIONICS 181

[
allow (C18)\
N
/CH 3
J+ CI-
Tallow (C18)/ \
CH 3

bis (hydrogenated tallow) dimethylammonium chloride

benzalkonium chloride

dodecyl methylpolyoxyethylene ammonium chloride

Figure 8.1 Quaternary ammonium compounds.

Description

Quaternaries can be made in simple equipment under mild conditions by

reacting an appropriate tertiary amine with an organic halide or organic
sulphate (Figure 8.2). The products made in largest volume are the textile
softeners for household use, where there are usually two long alkyl groups and
two short alkyl groups, the anion can be chloride or sulphate. An example
would be bis(hydrogenated tallow alkyl)dimethylammonium chloride (see
Figure 8.l).
The best known quaternary is benzalkonium chloride. It is alkyl dimethyl
benzyl ammonium chloride where the alkyl group is usually derived from
coconut fatty acid or stripped coconut fatty acid and contains C12, C14 and
C16. It is a white powder soluble in water and alcohol. Aqueous solutions are
also on the market with products containing more than 40% co-solvent.
Imidazolines can form quaternaries, the most common product being the
ditallow derivative quaternised with dimethyl sulphate (see Figure 8.3).
182 HANDBOOK OF SURFACTANTS

Figure 8.2 Preparation of quaternary ammonium compounds.

Figure 8.3 lmidazoline-based quaternary compound.

General properties

1. Solubility. Generally water soluble when there is only one long hydro-
phobe and correspondingly insoluble in mineral oil, white spirit and
perchlorethylene. When there are two or more long chain hydrophobes,
the products become dispersable in water and soluble in organic solvents
such as white spirit and perchloroethylene. The benzyldimethylalkyl
ammonium chorides show excellent solubility in water and isopropanol.
2. Compatibility with aqueous ions. Compatible with most inorganics and
hard water but incompatible with metasilicates and highly condensed
phosphates; incompatible with protein-like organic matter which is
precipitated; incompatible with substituted phenolic ions when the
quaternary molecule is large.
3. Chemical stability. Stable to pH changes, both acid and alkaline,
especially acid (even HF) but hot alkali usually causes separation;
decomposes when heated to over 100°C.
4. Compatibility with other surfactants. Incompatible with anionics; com-
patible with non-ionics except alkanolamides with high soap content,
polyols with high propylene oxide content and hydrophobic ethoxylates
(e.g. nonyl phenol + 4EO).
5. Surface active properties. CMC of benzalkonium chloride (molecular
weight 340) = 5 x 10- 3 M (0.17%); surface tension of 0.1 % solution of
benzalkonium chloride = 34 dyn/cm.
6. Functional properties. The functional properties depend upon the water
solubility with poor water solubility giving high adsorption and
maximum surface activity. This is illustrated by the difunctional products
which show a change in properties as the chain length increases (see
 CATIONICS 183
Table 8.1 Properties of quaternaries and chain length

2 C8 chains Very soluble in water Mild germicide

2 CIO chains Soluble in water Strong germicide
2 Cl2 chains Poor solubility in water Weak germicide
2 CI4 chains Low solubility in water Antistat
2 C16-C18 chains Practically insoluble in water Softener and antis tat

Table 8.1). Substantive to negatively charged surfaces, e.g. conditioner

for hair, corrosion inhibitor for metals; moderate foaming properties;
poor wetting properties; good emulsification properties; detergency poor
to moderate and at best comparable with non-ionics but more expensive;
germicidal properties present at low concentrations therefore cost-
effective germicidal detergents obtained with the maximum amount of
non-ionic, however, small amounts of non-ionics will not adversely affect
germicide properties but a high non-ionic/cationic ratio can have
reduced germicidal activity.
Monoalkyl has more effective germicidal properties than bis(long-
chain alkyl); reaction with ethylene oxide reduces germicide effect;
chlorination of aromatic ring increases germicide effect. The most
common germicides with optimum chain lengths are shown in
Figure 8.4. The general word germicide has been used to describe

R = C12 -C16

R=C12-C16

R = C10

Figure 8.4 Quaternaries as bactericides.

184 HANDBOOK OF SURFACTANTS

quaternaries because of the different properties of the many quaternaries

which can be a bactericide (an agent which kills bacteria) or a bacteriostat
(an agent that prevents growth of bacteria).
Quaternaries are adsorbed on to soil and protein so their performance
can be adversely affected by dirt or blood. Bactericidal properties appear
with the C 12 isomer and continue up to C 16C18. As the cations cannot
differentiate between bacteria and associated protein the strongly
adsorbing higher isomers C16- C 18 are not available to the bacteria. The
performance of the C 12 isomer is inferior to the C 16 isomer in distilled
water but superior in the presence of significant contamination. Quater-
naries are moderate foaming agents.
7. DisadlJantagcs. As a germicide, readily deactivated and cannot kill
spores (certain bacteria and fungi), thus cannot be used for sterilisation.

Applications

I. Biocides. Benzalkonium chloride BP, C6HsCH2N(CH3hR + Cl- where

R = mixture ofalkyls from C 8H 17 to C 18HJ7. There is a differencefor the
alkyl chain distribution for the BP (British Pharmacopoeia) and US
Pharmacopoeia specifications. The USP contains no C8, CIO or C18
alkyl chains. Cetrimide BP, R-N(CH3h + Br- where R = mixture of
CI2-CI6, mainly C14 is a germicidal quaternary which has some detergent
properties; usually used in conjunction with chlorhexidine digluconate.
Benzalkonium chloride and N-benzyl-N-alkyldimethylammonium
halides are used as a bactericide against Gram positive bacteria but less
effective against Gram negative bacteria in hard water. They are used as
germicides, disinfectants and sanitisers; compatible with alkaline
inorganic salts and non-ionics and used with them in alkaline detergent-
sanitisers for dish washing in pubs, restaurants etc.; deactivated by
anionics. Hard water tolerance can be improved by careful selection of
the distribution of the alkyl chain (optimum is at C14).
2. Textiles. The main volume application is the use of bis(hydrogenated
tallow alkyl) dimethylammonium chloride as a textile softener for home
use as the final rinse in the washing machine. Imparts soft fluffy feel to
fabrics by adsorbing them with hydrophobic groups oriented away from
the fibre. Antistatic finish for synthetic fibres; dye retardant and dye
leveller by competing for positive dye sites on the fibre (e.g. benzyl
trimethylammonium chloride).
3. Hair care. Products chemically very similar to the textile softeners are
used as a rinse after shampooing since they absorb on the hair giving
softness and antistatic properties.
4. Emulsifiers. N-Alkyltrimethylammonium chlorides and N-alkyl
imidazoline chlorides used as emulsifiers where adsorption of the
emulsifying agent onto the strata is desirable (e.g. bitumen treatment of
damp roads, insecticide emulsions). Used for the emulsification of polar
compounds (e.g. fatty acids and amines) in O/W emulsions.
 CATIONICS 185
5. Metal working. Addition to acid (hydrochloric and sulphuric) used in
the cleaning and pickling of steel to prevent hydrogen corrosion.
6. Road building. Quaternary fatty ammonium and imidazoline salts used
to make bitumen emulsions which can be used to repair roads in wet
weather.
7. Bentonite treatment. Bentonite can be treated with quaternary am-
monium salts to convert the normally hydrophilic bentonite into a
product with hydrophobic properties. These products can be used as
thickening agents in organic systems, e.g. paint or greases.
8. Oil fields. Alkyl trimethyl ammonium chloride is used as germicide for
sulphur producing bacteria which cause corrosion and hence are known
as corrosion inhibitors.
9. Antistatic. In polymers, e.g. in PVC belting for coal mines.

Specification
Active content can vary very widely, 15-80%
Solvent, usually isopropanol
Free amine, 0.01-2%
Free alkyl chloride or alkyl sulphate, should- be very low

8.3 Amine and imidazoline salts

Nomenclature

See Section 7.13 describing the parent alkyl amines.

Generic: salts with hydrochloric acid
Diamine hydrochlorides
Imidazoline hydrochlorides
Alkylimidazoline hydroxyethylamine hydrochlorides
Alkylimidazoline ethylenediamine hydrochlorides
Polyamine hydrochlorides
Primary amine hydrochlorides
Secondary amine hydrochlorides
Tertiary amine hydrochlorides
Examples:
Dodecyl dimethylamine hydrochloride (or dodecyl dimethylamine am-
monium chloride) C12H25N(CH3hH+ Cl-

Description

The usual method of forming salts is the neutralisation of the amine with an
acid in aqueous solution, .e.g. when hydrochloric acid is used. amine
186 HANDBOOK OF SURFACTANTS

N-CH H 20
R--C<N_tH:' • RCONHCHzCHzNHCHzCHzOH
I
CH1CH10H
Figure 8.5 Hydrolysis of imidazolines.

hydrochlorides are formed. If less than the theoretical amount of acid is used
the amine salt can often act as an emulsifier for the unreacted amine in aqueous
solution. If the amine salt is insoluble in water the salt can be formed by double
decomposition. Of the inorganic salts, those with hydrochloric acid, the
hydrochlorides, are the most frequent although having poor solubility in cold
water. Salts obtained using organic acids are usually more water soluble than
those from inorganic acids but care must be taken to avoid amide formation
with carboxylic acids by keeping temperatures well below 1OO"c. The acetates
are the most common organic salts.
The parent amines and imidazolines have already been described in
Section 7.13. However some comments are needed with reference to the
imidazolines. The imidazoline ring, shown in Figure 8.5 is definitely formed in
the manufacture. However there is now considerable evidence to show that
this ring breaks down in aqueous solution by hydrolysis back to the amide (see
Figure 8.5). Thus if salts ofimidazolines are made in aqueous solution, the ring
may be disappearing on storage. On the other hand, if a salt was made with an
organic acid in an organic medium, the ring may well be stable for a
considerable length of time.

General properties

1. Gen€ral. The positively charged ion adsorbs strongly on metal and fibre
surfaces.
2. Solubility. Inorganic salts particularly sulphates, phosphates and sili-
cates, have poor solubility in cold water. The salts of amidosulphonic
acids are more soluble. Organic salts of acetic acid show good aqueous
solubility for coco amine but not higher amines, e.g. tallow amine. Salts of
hydroxycarboxy acids (e.g. lactic acid, glycolic acid) are readily soluble in
cold water. If high molecular weight carboxylic acids are used (e.g. oleic
acid, stearic acid), the salts are insoluble in water but readily soluble in
fats and oils.
3. Compatibility with other surfactants. Form water insoluble products
with anionic surfactants.
4. Chemical stability. Lower thermal stability than the parent amine, e.g.
amine acetates will break down to substituted amides after only a few
hours at 100°C.
5. Germicidal activity. Salts of fatty amines with a chain length of 12-16
 CATIONICS 187
carbon atoms are the most effective. Salts with acetic acid, glycolic acid,
lactic acid and benzoic acid have all proved successful. To increase
fungicidal action, use acids or phenols which are effective against
fungi for neutralisation, e.g. salicylic acid, o-chlorobenzoic acid,
o-phenylphenol as well as chlorinated phenols (Fatty amines and deriva-
tives, Hoechst data sheets).
6. Emulsifying properties. Cationic emulsions of the oil (or wax) in water
type have the property of allowing a normally hydrophobic oil droplet to
wet and deposit on to a wide variety of surfaces, both polar and non-
polar. They can even be used to treat a water wet surface (a wet road for
instance) with a hydrophobic material (bitumen in the form of a cationic
emulsion). The cationic surfactant acts as a bridge between the solid
substrate which has the polar head attached and the hydrophobic chain
which gives adhesion to the oil or wax. An excess of cationic surfactant
can give multilayers on the substrate and loss of adhesion.

Applications

1. Emulsifiers. Primary amine salts are cationic emulsifying agents below

pH 7. Imidazolines can function as oil soluble emulsifiers producing
cationic O/W emulsions. If they are neutralised below pH 8 they become
hydrophilic and can act as emulsifiers for polar organic solvents, e.g.
toluene, pine oil or triglycerides. Acetate salts are used for emulsifying
waxes although non-ionics need to be added in hard water systems. The
cationic wax emulsions so formed can give antistatic and water repellent
coatings.
2. Lubricants and metal working. Corrosion inhibitor for fuels, greases,
lubricating oils and for metal surfaces using long chain carboxylic acids
for neutralisation to give solubility in oils. Short chain carboxylic acids
(acetic, propionic and benzoic) are used in aqueous systems.
3. Mining. Stearylamine and tallow fatty amine salts have been used in
potassium flotation. Fatty amine acetates are used as collectors for zinc
ores. The fatty amines and salts can be used for both collectors and
frothers for many silicate ores although frothing agents are generally
needed as well.
4. Fertilisers. The free amine (coconut, stearylamine or tallow) or the
acetate salt can be used to treat fertilisers to prevent caking together,
particularly potassium salts.
5. Road repairing. Fatty amines as free bases are used as adhesive agents
for hot bitumen. Fatty amine salts can be used to make cationic bitumen
emulsions which can be used in wet weather.
6. Treatment of pigments. Pigments used in organic coatings need to be
quite dry. Water soluble fatty amine salts will displace the water and
188 HANDBOOK OF SURFACTANTS

produce a water repellent effect, such that the pigment can disperse
readily in an organic medium. Fatty amine oleates are particularly useful
for pigments in paints. The fatty amine oleate can be made in situ by
treatment with a fatty amine water soluble salt (an acetate) followed by
treatment with sodium oleate. The dioleate salt of N-tallow trimethylene
diamine is one specific product used for dispersing inorganic pigments
(0.5% on weight of pigment) and organic pigments (2% on weight of
pigment).
7. Textiles. Antistatic treatment.

Specification

Neutralisation (or non-amine), 98-100%

p-, sec- and t- amine, see Section 7.13
Water content, for many organic salts,e.g.acetates,and oleates the water
content is low (typically 1%).
9 Amphoterics

9.1 Amphoterics general

Nomenclature

The word amphoteric is derived from the Greek amphi meaning both and used
to describe surfactants which have both a positive (cationic) and a negative
(anionic) group. Sometimes the phrase ampholytic is used. The nomenclature
of some amphoterics has been confused in the past, partly due to mistakes in
the original chemical structures, and, more recently, due to retention of the
word betaine for products which are strictly not amphoteric. The main
categories of amphoterics are as follows.

N-alkyl aminopropionates or N-alkyl iminodipropionates. The reaction of

amines with chlorpropionic acid or acrylic acid
R-NH2 + CICH 2CH 2COOH ---+ R-NHCH 2CH 2COOH
an aminopropionate
R-NH2 + CH 2=CH 2COOH ---+ R-NHCH 2CH 2COOH
an aminopropionate
R-NH2 + 2CH 2=CH 2COOH ---+ R-N(CH 2CH 2COOHh
an iminodipropionate
In the case ofthe aminopropionate the NH group is still reactive and will react
with a further molecule of acrylic acid giving an iminodipropionate. This does
not occur with the glycinate (see below).
Example:
Sodium N-coco aminopropionate, CocoNHCH 2CH 2COONa
Disodium N-coco iminodipropionate, CocoN(CH 2CH 2COOHNa)2

N-alkyl betaines. The word betaine originally described the compound

trimethyl glycine, (CH 3 hN+CH 2COOH, which has a quaternary nitrogen.
The word was then extended to N-trialkyl derivatives of amino acids. In the
scientific literature it now means the internal salt of a quaternary ammonium,
oxonium or sulphonium ion. They are formed when chloracetic acid reacts
with a tertiary nitrogen (see Figure 9.1). Note that a quaternary nitrogen
190 HANDB{X)K OF SURFACTANTS

NaOH

Figure 9.1 Preparation or betaines.

group is formed by this reaction but not formed in the case of the glycinate and
aminopropionate. Strictly speaking the betaines are not amphoterics
because they are never anionic. They are more like a quaternary ammonium
compound. Nevertheless, by common usage they have been included in
amphoterics. The tertiary nitrogen may be present in:
an alkyl dimethyl amine ~ an alkyl dimethyl betaine;
an alkyl amidopropyldimethyl amine ~ an alkyl amidopropyldimethyl
betaine;
an alkyl imidazoline, ~ an alkyl imidazoline betaine (but see below);
an alkyl bis(hydroxyethyl) amine ~ an alkyl bis(hydroxyethyl) betaine.
Example:
Laurylamidopropyldimethyl betaine, C12H2SCON(CH3hCH2COOH
Note the alkyl betaines have sometimes been described as alkyl dimethyl
glycinates.

N -alkyl glycinates. These are specific alkyl amino acids with the alkyl group
attached to the nitrogen atom of the amine. They are derivatives of glycine,
NH 2CH 2COOH, called glycinates and formed from chloracetic acid and an
alkyl amine
R-NH2 + CICH 2COOH ~ R-NHCH 2COOH an alkyl glycinate
Example:
Coco glycinate, CocoNHCH 2COOH

Carboxy glycinates. Indicates that there are two carboxyl groups present by
formation with two molecules of chloracetic acid. It does not define the
structure and the products are nearly always mixtures.

Alkyl imidazoline-based products. If made from an alkyl imidazoline and

chloracetic acid they are called: monocarboxylic derivatives or amphoglyci-
nates; dicarboxylic derivatives or amphocarboxy glycinates. The imidazoline
amphoterics were the first amphoterics to be commercialised on a large scale
and it is these products which have given confusion in naming. The products
made from imidazolines and chloracetic acid were once thought to have a ring
structure but are now known to have a linear structure as the imidazoline ring
breaks down during the formation of the amphoteric (see Sectioll 8.3,
Figure 8.5). They are derivatives of glycine acid and do not give betaines. At
 AMPHOTERICS 191

Figure 9.2 An alkyl polyamine carboxylate.

one time, mixtures of imidazoline amphoterics with alkyl sulphates or alkyl

ether sulphates were also described as complexes but no evidence for complex
formation has been found.
If made from an alkyl imidazoline and acrylic acid they are called:
monocarboxylic derivatives (salt free), amphopropionates; dicarboxylic de-
rivative (salt free), amphocarboxypropionates. Again these names give no
indication of the actual chemical structure.
If the name includes the word ampho, e.g. cocoamphocarboxy glycinate
then a number of manufacturers have used this description to indicate the
product is a derivative of an imidazoline. Unfortunately this phraseology has
not been followed universally so no particular significance should be attached
to the inclusion of this word unless indicated by the manufacturer.

Alkyl po/yamino carboxylates or polyamphocarboxy glycinates. These are

products where there is more than one nitrogen capable of reacting with
chloracetic acid. The abbreviation APAC is now becoming increasingly used.
Coco APAC reveals that the alkyl group is derived from coconut oil but does
not give any idea ofthe number of nitrogen groups or the number of carboxyl
groups. A typical product is shown in Figure 9.2. This product would
probably be called sodium carboxymethyl coco poly amino propionate, an
alternative description might be sodium coco polycarboxyaminopropionate.
At the present time there does not seem to be' any agreed nomenclature
between manufacturers, and there is unlikely to be so whilst the exact
compositions are confidential.

Amine oxides. Amine oxides show amphoteric properties but in neutral and
alkaline conditions they are essentially non-ionic and are included in Section
7.2.4.

General properties

1. General. By altering the pH of an aqueous solution the anionic or

cationic character of the amphoteric can be changed. At some intermedi-
ate pH (not necessarily pH 7) both ionic groups show equal ionisation
and this pH is called the isoelectric point or (area). This type of molecule
is often described as a zwitterion (German for mongrel).
N + .• , COO H +------+ N + ••. COO - +------+ NH ... COO-
acid pH < 3 isoelectric pH > 6 alkaline
192 HANDBOOK OF SURFACTANTS

The isoelectric point is not a sharp point but depends upon the nature of
the anionic and cationic groups. The most common anionic group is the
carboxyl group (COOH) and the most common cationic group is the
amine group (NH z). At the isoelcctric point amphoterics generally have
minimum surfactant properties; i.e. minimum foam, minimum wetting,
minimum detergency. An amphoteric which is soluble at the isoelectric
point is soluble across the whole pH range. The ionic nature of an
amphoteric is rarely wholly anionic or cationic above and below the
isoelectric area. What is more important is that it changes the properties,
thus comparing the two surfactants R-CH1CH1CH1COONa and
R-NHCH 2CH 2COONa. The substitution of NH for CH 2 improves
hard water tolerance.
2. Solubility. Excellent solubility in aqueous solution but at a minimum in
the isoelectric area.
3. Compatibility with aqueous ions. Excellent.
4. Compatibility with other surJactants. Amphoterics show excellent com-
patibility with other surfactants. Mixed micelles are frequently formed,
and the mixtures often have functional properties not found in either of
the components. For instance, skin irritation can be reduced below the
level of either of the ingredients. Biocidal activity sometimes found in
amphoterics can be reduced when stable mixed micelles are formed. The
effect of adding an amphoteric to an anionic is to reduce the eye and skin
irritation, increase viscosity in the presence of electrolyte, improve foam
stability and improve detergency. The effect of adding amphoterics to
non-ionics is more specific to the amphoteric than in the case of anionics.
Most amphoterics will act as hydrotropes in solubilising non-ionics in
high electrolyte concentrations particularly at high temperatures. This
ability to solubilise depends upon the structure of the amphoteric.
Amphoterics with polycarboxy groups and non-ionics can show signifi-
cant synergism in detergency depending upon the ratio of non-ionic to
amphoteric (Amphoterics International (1987)).
5. Functional properties. Excellent wetting agent in the presence of high
electrolyte concentration.
6. Biocidal activity. Amphoterics possess biocidal activity but this is
weak for the simpler amphoterics and only becomes pronounced
when the number of amine groups (particularly secondary)
increases. Some amphoterics show synergism with betaines.
C12H25NHCH2CH2NHCH2CH2NHCH1COOH is 10 times more
effective than C12H25NHCH2COOH (Sykes, 1965). Amphoterics have
the advantage over quaternary compounds of being unaffected by hard
water and alcohol.
Imidazoline base amphoterics give the following properties: good lime
soap dispersion properties; mild, detoxify anionics, non-stinging to the
eyes; improve foaming properties of AES in presence of sebum; viscosity
 AMPHOTERICS 193
adjustment difficult because dialkanolamides are ineffective; PEG (150)
distearate usually used as thickener; slight bacteriostatic effect.
Amino propionates, isoelectric area, pH 3 5
imino propionates (two moles of acrylic acid), isoelectric area, 1.75-3.5,
i.e. lower because of the two COOH groups; Because of the lower
isoelectric point, the imino derivatives will have better detergency and
solubility at acid and neutral pH. The wetting properties are inferior.

Applications

Amphoterics are used in amphoteric/anionic mixtures in shampoos, foam

baths, shower gels, liquid soaps, hand cleaners, hand laundry and hand dish
washing. The main products used are: coco ami do propyl betaine; coco
amphocarboxy glycinate (imidazoline base); coco dimethyl betaine; tallow
polyamino carboxylates. Amphoterics will detoxify anionics in shampoo
formulations due to the formation of mixed micelles. However these mixed
micelles may inhibit biocidal behaviour. Amphoterics are used in
amphoteric/non-ionic mixtures in liquid and powdered laundry detergents.
Amphoterics tend to be less deactivated by protein than are quaternary
ammonium compounds and this should make them suitable for use in dairy
cleaning. They are also relatively easily removed from metals, whereas
quaternaries are more tenacious and not so easily removed.

9.2 Betaines

Nomenclature

Generic:
Alkyl amido betaines (nearly always the dimethylamine derivatives)
Alkyl amidopropyl betaines (nearly always the dimethylamine derivatives)
Alkyl amidopropyldimethyl betaines
Alkyl amidopropyldimethyl sulphobetaines
Alkyl amidopropyl hydroxysultaines
Alkyl betaines (nearly always the dimethylamine derivatives)
Alkyl bis(2-hydroxyethyl) betaines
Alkyl dimethyl betaines
Sulpho amido betaines
Sulpho betaines
Examples:
Lauryldimethyl betaine
Coco amidopropyl betaine
194 HANDBOOK OF SURFACTANTS

Oleyl bis(hydroxyethyl) betaine

3-[(3-Coco amidopropyl)dimethylamino] 2-hydroxypropane sulphonate

Description

The betaines are made by reaction of chloracetic acid with a tertiary amine to
form a quaternary N atom and an ionised COO group (see Figure 9.1). R I' R2
and R3 could be any alkyl group. The most common products on the market
are where R2 = R3 = methyl and RI = coco(CI2-CI4), RI = coco amido-
propyl, C II H 23CONHCH 2CH 2CH 2' There are products also available where
R' = R" = CH 2CH 20H, i.e. bis-2-hydroxyethyl and R can be CI2-CI8. The
reaction is usually carried out in aqueous solution with caustic soda to
neutralise the hydrochloric acid. The sodium chloride formed is usually, but
not always, left in the product. Sulphobetaines (or a hydroxysultaine) are
where the COOH has been replaced by S03' e.g. RCONHCH 2CH 2-
CH 2N(Me}zCH 2CH(OH)CH 2S0 3. They can be prepared by the addition of
epichlorhydrin to alkyl dimethylamines and then sulphated using sodium
bisulphite. These products are not new but there is renewed interest.

General properties

1. General. Not really amphoterics because they cannot donate H + in

alkaline solution and therefore are never anionic. They are internal
quaternary ammonium compounds but do not show zwitterionic
properties at pH at and above their isoelectric point (neutral and
alkaline pHs). They thus show cationic properties similar to quaternary
ammonium compounds below their isoelectric point (acid pH).
2. Solubility. Soluble in water, insoluble in mineral oil, white spirits,
aromatic solvents and perchlorethylene; retain good solubility at and
near their isoelectric area (unlike the amino propionates and imino
dipropionates).
3. Compatihility with aqueous ions. Acid and neutral aqueous solutions are
compatible with alkaline earth and other metallic ions (aluminium,
chromium, copper, nickel and zinc). Betaines can act as hydrotropes and
solubilise alkali in non-ionics but the other amphoterics are superior.
Whether they are cost-effective compared to other hydrotropes will
depend upon the overall formulation and relative cost, but 0.7 g of
sodium coco dimethylbetaine can solubilise 2 g of NP + 9EO in 3%
caustic soda at room temperature. Good lime soap dispersants.
4. Compatihility with other surJactants. They are compatible with all classes
of surfactants except at low pH with anionics where they give a
precipitate. Thickens anionics in the presence of salt, ringing gel can be
made with triethanolamine lauryl sulphate. At slightly acid pH, the
 AMPHOTERICS 195
cationic nature of the betaine is neutralised by the anionic and a neutral
salt results. This is also the point of minimum solubility which is the point
of maximum viscosity hence the good thickening properties with
anionics. Alkyl amido betaines will complex and solubilise quaternary
surfactants in anionic formulations (Scher Chemicals, 1983).
5. Chemical stability. Good chemical stability against oxidising agents.
Resistant to hydrolysis (even the amidopropyldimethyl betaines).
6. Surface active properties. CM C of lauryl dimethyl betaine = 2 x 10- 3 M
= 0.06%; surface tension of 1% active lauryl dimethyl betaine
= 33 dyn/cm; CMC of C16 dimethyl betaine = 2 x 10- 5 M = 0.0007%
7. Functional properties. Good foaming agents but not as good as alkyl
sulphates or ether sulphates although better and more stable at alkaline
pH; Hard water has no effect; dimethyl betaines are better than
amidopropyl betaines in soft water in the presence of sebum; increasing
chain length of the alkyl group reduces foaming properties (optimum at
CI2); best foaming properties at alkaline pH but good over a wide pH
range (3-11); unaffected by hard water; alkyl amido betaines give larger
foam volumes than alkyl betaines; good wetting agents with lower
molecular weight products in acid solution; good detergent properties
but not as good as anionics used alone; increasing chain length improves
detergent properties; best detergency at alkaline pH; unaffected by hard
water; emulsification properties, good for slightly polar materials but not
good for paraffins; viscosity increase with anionics, dimethyl betaines
better than amidopropyl betaines; detoxifying of anionics is quoted in the
literature but the imidazoline (glycinates) and the newer polycarboxy
glycinates are superior.

Applications
1. Shampoos. Mild characteristics with anionics, i.e. low eye and skin
irritation; antistatic properties to hair; good conditioning; foam boost
and stabilisation; viscosity increase with anionics (at low pH or with salt);
good foaming and detergency on its own; typically utilised at 3-10% in a
formulation either as a partial or total replacement for conventional
foam boosters (alkanolamides); Coco amidopropyldimethyl betaine is
becoming the main betaine used in shampoos but in conjunction with
ether sulphates and sometimes half ester sulphosuccinates; baby sham-
poo patent, (Verdiccho and Walts, 1976) is an equimolar concentration of
amidobetaine and sulphate with a polysorbate (or EO sorbate ester
+ EO/PO co-polymer). This is aI).alagous to the imidazoline/sulphate
system which is described as tear-free.
2. Foam baths, liquid soaps, shower gels and hand cleaners. Foam boost and
stabilisation with anionics; viscosity increase with anionics; good lime
soap dispersant; good foaming and detergency on its own.
196 HANDBOOK OF SURFACTANTS

3. Household products. Hand textile washing and dishwashing products,

mild characteristics with anionics and excellent foam stability and
increase in viscosity (at lower pH); pH is usually reduced by using citric
acid; car cleaners (high sequestrant levels).
4. Textiles. Cocoamidopropyl betaine used as antistatic agent in spin
finishes.
5. Oilfield applications. Foaming agents in foam drilling, resistant to high
electrolyte concentration.

Specification

The analysis of amphoterics gives significant problems particularly in the

interpretation of the data
Solids, 20-55% (part of the solids may not be surface active, possibly sodium
glycollate derived from the hydrolysis of sodium chloroacetate)
Sodium chloride, 5-15%
Sodium glycollate, 1-4%
Free amine, typically 0.25% for coco-dimethyl betaine, typically 1.5% for
coco-amidopropyl betaine
pH, 6--9

9.3 Glycinates and aminopropionates

Nomenclature

This section describes glycinates, aminopropionates and iminopropionates

where the alkyl hydrophobe is directly attached to the nitrogen.
Generic:
Alkyl glycinates
Alkyl amino propionates
Alkyl amphopolycarboxyglycinates
Alkyl amphopolycarboxypropionates
Alkyl imino diglycfnate
Alkyl imino dipropionates
Alkyl polyaminocarboxylates
Alpha-N-alkylamino acetic acids
Beta-N-alkylamino propionates = alkyl amino propionates
Beta-N-alkylimino propionates = alkyl imino dipropionates
Glycinates
Propionates
Examples:
Monosodium N-lauryl beta-imino dipropionate
Tallow amphopolycarboxy glycinate
Coco imino diglycinate
Tallow imino dipropionate
 AMPHOTERICS 197
The imidazoline glycinates and propionates (see Section 9.4) are probably
the best known and most widely used true amphoterics. They are known as
the alkyl amphoglycinates and alkyl amphocarboxyglycinates. The word
ampho has no specific chemical significance as such but is widely used in
this type of compound. All the products described in Section 9.4 are formed
via the fatty acid.

Description

Made from primary or secondary amines and chloracetic or acrylic acid

(more usual). The major products on the market are as follows.

Alkyl imino dipropionates. Made by reaction of 2 moles of acrylic acid with

a long chain primary amine (see Figure 9.3). The products have two carboxy
groups so that the acid, the monosodium salt or the disodium salt are all
produced. The most common products are the disodium salts.

Complex iminoglycinates or polycarboxyglycinates. Made by reaction of

more than one mole of chloracetic acid with a long chain amine with more
than one nitrogen group. The products are characterised by the number of
amine groups, the number of carboxyl groups and large amounts (8-13%)
of sodium chloride.

Complex iminodipropionates or polycarboxypropionates. Made by reaction of

more than one mole of acrylic acid with a long chain amine with more than one
nitrogen group. The products are characterised by the number of amine
groups, the number of carboxyl groups and very small amounts of sodium
chloride.

General properties

1. General. Disodium N-coco imino dipropionate, isoelectric area pH

2.4-4; disodium N-tallow imino dipropionate, isoelectric area pH
1.3-4.7
2. Solubility. Products with more than one carboxy group are more soluble
in water than the monocarboxy products; very soluble in strong acids
and alkalis (including presence of electrolyte); solubility low in most
organic solvents (including ethanol).

RNH + 2CH =CHCOOH ---+ R_N/CH2CH2COOH

2 2 "'-CH 2CH 2COOH
Figure 9.3 Preparation of alkyl imino dipropionates.
198 HANDBOOK OF SURFACTANTS

3. Compatibility with aqueous ions. Excellent with hard water, e.g. calcium
and magnesium ions; solubilises phenols and poly phosphates.
4. Compatibility with other surfactants. Solubilises quaternary ammonium
salts; the coco iminodipropionates are compatible with high con-
centrations of sulphates, ether sulphates and coco alkanolamides; alkyl
products can solubilise non-ionics in alkaline solution but the efficiency
increases as the number of carboxyl groups increase (at the same
hydrophobe chain length).
5. Chemical stability. Excellent stability to oxidising agents, hydrolysis,
acid and alkali.
6. Surfactant pruperties. N-Lauryl aminopropionic acid, CMC = 2 x
10- 3 M = 0.052%; N-Iauryl iminodipropionic acid, CMC = 1.2 x
1O- 3 M=0.04%; surface tension of C12-C15 dipropionate=
28dyn/cm.
7. Functional properties. Substantive to surfaces to give antistatic effects;
effective emulsifying agents for long chain alcohols and slightly polar
compounds but not for paraffinic oils; detergency rises with increasing
pH; products with several carboxyl groups have synergistic properties,
e.g. detergency particularly with non-ionics; decreased eye and skin
irritation with anionics; beta-N-dodecylamino propionic acid, excellent
wetting agent and foaming agent at alkaline pH, reduced foam at acid
pH.

Applications

1. Personal products (shampoos, bath additives etc.) Polycarboxy products

used with anionics to decrease skin and eye irritation and give
conditioning properties.
2. Household and industrial detergents. Products give good solubility in
high built liquids combined with synergism (with non-ionics) in detergent
properties; used in liquid and powder laundry detergents.
3. Electroplating. The dipropionates give excellent wetting properties in
electroplating baths.
4. Fire fighting. Foaming agent for foams used in fire fighting.

Specification

Solids, 30-40% (active has been often assumed as equal to solids minus
sodium chloride concentration; this is wrong if the sodium glycollate
concentration is high)
Sodium glycollate, 2-9%
Sodium chloride, 7-12% from glycinates 0.05/ typical for propionates.
0

Sodium glycollate is formed by hydrolysis of unreacted chloracetic acid so it

is only found in glycinates. The high levels (6-8%) are found when the
 AMPHOTERICS 199
glycinates have been prepared and when excess chloracetic has been used and
then subsequently hydrolysed.

9.4 Imidazoline-based amphoterics

Nomenclature

The confused nomenclature for this group of products arises from the wrong
chemical structure being assigned to early products.
Generic:
Alkyl-imidazoline betaine
Alkyl-imidazoline sulphobetaine
Amphocarboxyglycinates
Amphoglycinate
Carboxy methyl betaines
Cycloimidates
Oi-carboxyl alkyl imidazoline betaines = amphocarboxyglycinates
Imidazoline betaines
Imidazoline carboxylates
Imidazoline propionates
Monocarboxy alkyl imidazoline betaines = amphoglycinates
Examples:
Coco imidazoline betaine
2-Coco-l-(ethyl betaoxypropionic acid) imidazoline
Coco amphopropionate

Description

A common imidazoline structure is shown in Figure 9.4. The group R comes

from fatty acids and the products are made by reacting aminoethylethano-
lamine, NH2CH2CH2NHCH2CH20H, with a fatty acid (or methyl ester)
to form the amide, following this, there is ring cyclisation to form the
imidazoline ring. When one mole of chloracetic acid reacts with the imidazoline
it was thought that the ring stayed intact and that the chloracetic acid reacted

Figure 9.4 An imidazoline.

200 HANDBOOK OF SURFACTANTS

with the tertiary amine; such products were known as monocarboxy alkyl
imidazoline betaines due to the similarity with the betaine structure. However
the imidazoline ring breaks down (by hydrolysis, see Scction 8.3) during the
reaction with chloracetic acid and an N-derivative of glycine is formed (see
Figure 9.5). The products of the reaction are known as alkyl glycinates
or alkylamphoglycinates or sometimes known as the monocarboxylated
glycinates.
Two molecules of chloracetic can be reacted with an alkyl imidazoline to give
what are known as alkylcarboxyglycinates or alkylamphocarboxyglycinate or
sometimes known as the dicarboxylated glycinates. The composition of such
products is complex and generally contains a mixture of monocarboxylated
and dicarboxylated substances. There would seem to be very little information
given by most producers on the exact constitution. The products of the reaction
depend considerably on the reaction conditions. Thus imidazoline-based
amphoterics may have very little imidazoline ring in them but have often been
described as such in the literature. Manufacturers thus describe such products
in ill-defined chemical terms e.g., coco imidazoline betaine. These remarks
apply to the imidazoline reaction products with chloracetic acid and the
imidazolines, i.e. not reacted with chloracetic acid, may have a much more
stable ring so long as water is absent.
Imidazolines can also be reacted with one or two molecules of acrylic acid to
give substituted propionates (more usually called ampho propionates) or

. N~CH
R~CCN~CH: ------> RCONHCH 2 CH 2 NHCH 2 CH zOH
I
CHzCHzOH +ClCH,COOH

+CICH,COOH

This formula is probably incorrect

Figure 9.5 A glycinate derived from an imidazoline.
 AMPHOTERICS 201
substituted dipropionates (more usually called ampho carboxy propionates).
Once again the compositions of such products are very rarely given in detail.
One manufacturer claims that products can be obtained either with the
imidazoline ring intact or hydrolysed back to the open chain.
To summarise, there are four main groups of imidazoline-based
amphoterics:
1. Monocarboxylated glycinates or glycinates: glycinates made by reaction
with I mole of chloracetic acid with an imidazoline
2. Dicarboxylated glycinates or carboxyglycinates: glycinates made by
reaction with 2 moles of chloracetic acid with an imidazoline
3. Monocarboxylated propionates or propionates: propionates made by
reaction with I mole of acrylic acid with an imidazoline
4. Dicarboxylated propionates or carboxypropionates: propionates made
by reaction with 2 moles of acrylic acid with an imidazoline

General properties

1. General. In aqueous solution most imidazoline-based amphoterics

will show true amphoteric properties and behave as glycinates (one
carboxy group), i.e. cationic properties at low pH, anionic properties at
high pH
2. Solubility. Monocarboxylates are soluble in water with high electrolyte
concentration, acids or alkalis; insoluble in mineral oil, white spirit,
aromatic solvent or perchlorethyelene; soluble in the isoelectric area
(similar to betaines).
3. Compatibility with aqueous ions. Excellent compatibility with high
concentration of inorganic ions; propionates better hydro tropes than
glycinates.
4. Compatibility with other surfactants. Compatible with all other surfact-
ants with the dicarboxy products being superior to the monocarboxy
products; glycinates generally thicken anionics, probably due to the salt
they contain; propionates will decrease viscosity of many (but not all)
anionics; show moderate solubilising properties for non-ionics in
alkaline solution.
5. Surface active properties. Surface tension of caprylamphocarboxy
glycinate is 29 dyn/cm at 1%.
6. Functional properties. Low foaming systems stable to alkali or acid
utilise alkyl chain lengths C8-C 10; high foaming and high tolerance with
inorganic salts; good wetting agent particularly in high strength caustic
soda; emulsifier for soils; dicarboxylates (particularly propionates) will
thicken alkali; when R' contains a second COOH group the products
show very low skin and eye irritation (but also see polyglycinates,
Section 9.3).
202 HANDBOOK OF SURFACTANTS

Applications

1. General. The outstanding property is the retention of surface active

properties in high concentrations of electrolyte and over a wide pH
range.
2. Shampoo and bath additives. Dicarboxylated glycinate derivatives usu-
ally used with anionics, baby shampoos (low eye irritation) have used
coconut oil-based products formulated with lauryl sulphates, ether
sulphates and ethoxylated sorbitan monoesters; conditioning shampoos
can be formulated with tallow-based glycinates.
3. Fabric softener. Particularly efficient in neutral and acid solution (can be
removed from substrate by alkali).
4. Liquid built detergents and industrial cleaners. The propionates are used
in industrial cleaning applications where stability over a wide pH range
and compatibility with high levels of inorganic builders are required;
caprylic acid-based products are used for high pressure washing, e.g.
metal cleaning as they are low roamers.
5. Car cleaners. Used with high levels of sequestering agents; generally the
dicarboxylated glycinates used.

Specification

Solids, 30-55% (active has been often assumed as solids minus sodium
chloride concentration; this can be misleading if the sodium glycollate
concentration is high)
Sodium glycollate, 2-9%
Sodium chloride, 7-12% from glycinates, 0.051:, typical for propionates.
Sodium glycoUate is formed by hydrolysis of unreactcd chloracetic acid
so is only found in glycinates. The high levels (6-8%) are found when the
dicarboxy glycinates have been prepared using 2 moles of chloracetic acid
when excess chloracetic remains at the end of the reaction and is hydrolysed.

References

Amphoterics International (1987) European Patent 0, 214, 868.

Scher Chemicals (1983) The chemistry and applications of amido-amines, presented to the Society
of Cosmetic Chemists Annual Seminar, Cincinatti, OH.
Sykes, G. (1965) Disinfection and Sterilisation, 2nd edn., pp. 377-378.
Verdiccho, RJ. and Walts, J.M. (1976) US Patent 3,950,417 to Johnson & Johnson.
10 Speciality surfactants

10.1 General

The description of surfactants given in Chapters 5-9 concentrated on those

surfactants commercially available from many producers in volume through-
out the world. They have been grouped together on the basis of a common
chemical structure. Within these groupings there are hundreds of speciality
surfactants. What is a speciality surfactant? The author's definition of a
speciality surfactant is one that is different in properties and use to the major
volume surfactants used for domestic detergents. Such surfactants are
characterised by being significantly higher in price, only available from a
limited number of manufacturers and the compositions not so well known, at
least by the user. Phosphate esters, most of the amphoterics, ethane
sulphonates and sulphosuccinates would come under this heading. However
it is not a definition that is clear and distinct, and a product may become a
speciality if its volume declines, e.g. alkyl naphthalene sulphonates.
The speciality surfactants described in this chapter are quite different to
those above. The author has grouped fluorinated surfactants and silicone
surfactants together because these two very high priced product groups have
very special properties in the hydrophobic part of the molecule. All the
surfactants so far described have the hydrophobic part of the molecule made
up of linear or branched paraffinic groups i.e. the CH 2 or CH group. The
minimum surface tension (in the region of 25-27 dyn/cm) is obtained by the
incorporation ofa suitable polar group at the end ofa paraffinic chain 10-18
carbon atoms long. This minimum surface tension is adequate for most
applications involving detergency. There are some applications, however,
where a lower surface tension in aqueous solution is required, e.g. wetting a
polythene film or spreading an aqueous foam on top of a petrol fire. The
fluorinated and silicone surfactants were found to posses the ability to depress
the surface tension of aqueous solutions down as low as 18 dyn/cm.
Many fluorinated and silicone surfactants have been made and tested in the
market. Very few are used in any volume, principally due to their high
price. The silicone surfactants in particular are capable of many variations and
tailoring for specific end products.
204 HANDBOOK OF SURFACTANTS

10.2 Silicones

Nomenclature

Generic:
Dimethicone co-polyol
Dimethylsiloxane glycol co-polymers
Ionic organo-polysiloxanes
Organo-polysiloxane co-polymers
Polyether polysiloxane co-polymers
Polysiloxane glycol co-polymers
Silicone surfactants
Example:
Polysiloxane polyorganobetaine co-polymer

Description

Organosilicones described hereafter are those with a polydimethylsiloxane

backbone. Unmodified they are insoluble in water and show poor compati-
bility with organic media. The incorporation of a water soluble or hydrophilic
group into the silicone structure can give products which exhibit surface

Type 1

Difunctional linear

3 I
CH -Si-CH
3 Polyfunctional - branched
o
I
x m

Type 2

Figure to.l Silicone surfactants.

 SPECIALITY SURFACTANTS 205
active properties in water. In addition, incorporating organic groups of an
organophilic character can give products which exhibit surface active
properties in organic solvents.
The structure of silicone surfactants is mainly of two types, either the
hydrophilic group is at the end of the siloxane chain (type 1) or along the
chain (type 2) (see Figure 10.1). The latter are often called rake or comb
polymers. In Figure 10.1 X can be a polar group which is anionic, non-ionic,
cationic or amphoteric, or an organic group such as an ester, amide, epoxy,
etc.
The most common silicone surfactants which have been used for many years
are where X is a polyalkylene oxide co-polymer, generally a mixed ethylene
oxide and propylene oxide co-polymer. There are a very large number of
variations possible, the main ones being the amount of ethylene oxide, the
amount of propylene oxide, the functionality of the EO/PO attachment to
the siloxane and the size and structure of the polydimethyl siloxane portion.
Manufacturers very rarely reveal the exact structure of the products sold,
sometimes they do not know themselves. The methods of synthesis are of little
interest to the user except for the point of attachment between the siloxane and
EO/PO co-polymer. This can be (i) a Si-O-C link where the silicon atom is
linked to the carbon atom of a EO/PO co-polymer via an oxygen atom. Such
products are unstable to hydrolysis although they may have enough stability
for their end use. Type 1 products are often, but not always, unstable to
hydrolysis and possess the Si-O-C link. (ii) A Si-C link where the silicon
atom is directly linked to the carbon atom of a EO/PO co-polymer. Such
products are stable to hydrolysis. Type 2 products are often, but not always,
stable to hydrolysis.

General properties

1. General. Many of the comments in Section 7.9 (on EO/PO co-polymers)

apply as products can be made of very widely varying properties;
however only a few products have achieved commercial success.
2. Solubility. Ability to vary water and organic solvent solubility over a
very wide range; silicone surfactants with EO/PO co-polymers show
inverse solubility with temperature (cloud points) in a similar manner to
non-ionics (see Section 7.1.2).
3. Surface active properties. Silicone surfactants can decrease the surface
tension of water down to 20dyn/cm.
4. Functional properties. Excellent wetting properties on low energy sur-
faces are obtained by virtue of the low surface tensions. Foaming can be
controlled to give zero foam and silicones with a low EO/PO content are
excellent antifoams for aqueous systems. The unmodified polydimethyl-
siloxanes are good antifoams for some solvents and hydrocarbons.
Emulsifying properties are excellent for O/W emulsions.
206 HANDBOOK OF SURFACTANTS

Applications

I. Foam control ill polyurethane foams. Polysiloxane EO/PO co-polymers

are the major cell control additive for flexible and rigid polyurethane
foam systems.
2. Paint additives. Antifloating of pigments and preventing surface defects
such as crater formation and orange peeling in water- and solvent-based
paints; unmodified silicones and EO/PO co-polymer modified are both
used.
3. Emulsifying agents. Stable O/W emulsions of silicone oils can be formed
using products shown in Figure 10.1, Type 2 with 30 50 silicon atoms
and 6-19 EO/PO blocks.
4. Textiles. Mineral oil surface tension can be decreased so that it will wet
polypropylene for use in lubricants by the use of a difunctional Type I
where X = the nonylphenyl group; gives soft handle and reduced friction
on fabrics.
5. Agriculture. Excellent wetting agents with low foam for herbicides and
increased efficiency of nutrient sprays.

Specification

Normal chemical tests are not applicable. It is suggested that a functional test
(surface tension) or more preferably a simulated performance test is carried out
for quality control. Chemical analysis data is difficult to interpret.

10.3 FluorQcarbons

Nomenclature

Generic:
Fluorinated surfactants
Fluorochemical surfactants
Fluorosurfactant
Organofluorine surfactants
Perfluoroalkyl surfactants
Perfluoropolyether surfactants
Examples:
Amino polyflurosulphonate
Ethoxylated polyfluoroa\Cohol
Fluorinated alkyl polyoxyethyleny ethanol
Perfluoropolymethylisopropyl ether
Polyfluoroalkyl betaine
Polyfluoropyridinium salt
Polyfluorosulphonic acid salt
Potassium fluorinated alkyl carbonylate
 SPECIALITY SURFACTANTS 207
Description

There are two basic types available. The older products are CF 3-(CF 2)n-
hydrocarbon group-X where n is usually 6-10. The hydrocarbon group can
be alkyl, pyridine group, amidopropyl, etc. This group is a link between the
fluorinated chain and the hydrophilic group. -X is the hydrophilic group and
can be -COOH, S03' (CH 2-CH 2-O)x, cationic or amphoteric. These types
of products are supplied by 3M, ATO Chemie and Asahi Glass Company.
Recent products developed by Montedison are known as the perfluro-
polyether surfactants as they are the fluorinated analogues of ethylene oxide
and propylene oxide polymers, CF3-(O-CF2-CF(CF3))n-(O-CF2)m-O-CF3
where n/m = 20-40. There are also modifications to this formula with ionic
groups at the end of the chain, e.g. COOH.

General properties

The fluorochemical-based products are very similar to conventional surfact-

ants, in having a hydrophobic and hydrophilic group. The special properties
are:
1. Solubility. Possible immiscibility with both polar and non-polar solvents.
This means that a solvent phobic group is available in the common
solvents and in mineral oils. In Type 1 above if group X = H then a
surfactant for oils or solvents can be produced. To obtain the necessary
miscibility with water, X must be a water soluble group for surfactants
suitable for aqueous systems.
2. Compatibility with aqueous ions. Perfluorocarboxylic acids are more
ionised than the corresponding fatty acids and therefore are unaffected
in aqueous solution by mineral acids and polyvalent cations.
3. Thermal and chemical stability. The C-F bond is very strong and the size
of a fluorine atom is approx. 1.35 A (hydrogen is 1.2 A). This means that
the fluorine atoms are closely packed around a carbon giving
considerably better thermal and chemical stability than hydrocarbons.
The sulphonate group has good thermal and oxidation stability so the
perfluoroalkyl sulphonates have outstanding thermal and oxidative
stability.
4. Surface active properties. The perfluorocarbons have very low inter-
molecular forces between molecules which gives very low surface
energies to the liquid phase and therefore very low surface tensions (as
low as 15 dyn/cm) in aqueous systems. Using different products they can
also reduce the surface tension of non-aqueous systems (esters, alcohols,
ethers, epoxies, polyesters, urethanes, acrylics) to about 20 dyn/cm.
5. Functional properties. Excellent wetting particularly on low energy
surfaces, e.g. polythene; good foaming and excellent foam stability in very
strong acids and alkalies; defoaming properties of non-aqueous systems;
208 HANDBOOK OF SURF ACT ANTS

Type 1 poor emulsifying agents for oil and water but excellent for
fluorinated monomers in the production of PTFE; Type 2 excellent O/W
emulsifiers.
6. Disadvantages. Very expensive, only use if the properties are really
required; due to their exceptional stability there must be doubts on their
ability to biodegrade.

Applications

Due to the high price of fluorinated surfactants the applications have been
confined to problems which conventional (i.e. lower priced) surfactants cannot
solve. These are generally related to wetting and spreading phenomena where
the conventional surfactants have a limit of approx. 26 dyn/cm in aqueous
solution. Difficult-to-wet surfaces are plastic films of polythene and polypro-
pylene etc. and therefore adhesives, coatings, paints, inks and polishes need to
have surface tensions lowered to wet these surfaces. Other difficult-to-wet
surfaces are surfaces on plants, insects and the very small fissures in rocks.
Specific applications are as follows.
I. Fire fighting. Foaming agent for aqueous-based foam which will spread
on burning hydrocarbons to cut off air.
2. Paint. Reducing orange peel, cissing, cratering and edge crawling in non-
aqueous paints. Improves wetting of low energy surfaces.
3. Polishes. To achieve improved levelling, spreading and gloss.
4. Emulsion polymerisation. Emulsifiers in the emulsion polymerisation of
PTFE.
5. Petrofe"um production. Used in acid fracturing to reduce surface tension
for foam generation to open fissures and improve penetration in oil and
gas stimulation; good thermal stability and low adsorption.
6. Electroplating. Gives antifoam effect in very strong acids, e.g. chromic
acid.
7. Cosmetics and barrier creams. Very stable O/W emulsions.

Specification

The manufacturers, with very few exceptions, do not reveal the exact chemical
constitution of their products. Easily measured chemical properties arc of very
little value in assessing the reproducibility of most fluoro chemical products. A
simple functional test such as the measurement of the surface tension of a
solution would be more suitable. However, such tests are not easy to carry
out. A simple performance test would seem to be the most satisfactory. For
example, if a fluorosurfactant was added to a paint to reduce cissing then a
cissing test would be most appropriate.
11 Polymeric surfactants

Nomenclature

In recent years there has been considerable interest in polymeric surfactants

but there is no clear definition of a polymeric surfactant. EO/PO co-polymers
(see Section 7.9) and silicone surfactants (Section 10.2) could be looked upon
as polymeric surfactants. Poly acrylic acid oflow molecular weight « 15,000),
condensates of naphthalene sulphonate with formaldehyde and sulphonated
styrene/maleic anhydride co-polymers are often included in descriptions of
surfactants. Synthetic resins based on natural fatty acids such as long oil alkyl
resins can be made oil soluble or partially water soluble and show some sur-
factant properties. Natural products such as algi nates, pectins, and protein-
based products could all be looked upon as polymeric surfactants. Most of
these products show only weak surfactant properties with respect to surface
tension reduction in aqueous solution and the formation of micelles. The
word polymeric would suggest high molecular weight with a large number
of repeating molecular units. Most polymeric surfactants have only a few
repeating units and the phrase oligomeric would seem more descriptive.
However the word polymeric has now been firmly established and so is used in
this book.
F or this chapter we will consider only two general types of product: Type 1,
comb or rake polymers where there is an organic polymeric chain with
hydrophobic groups at regular intervals along the chain and hydrophilic
groups at random or regular intervals along that chain (see Figure 11.1); Type
2 block co-polymers where there are blocks of hydrophobic groups (B) and
blocks of hydrophilic groups (A) usually in an A-B-A configuration. Note
that the EO/PO co-polymers are exactly this type of structure but these
products have already been described in Section 7.9.

R R R R R R
I I I I I I
--C-C-C-C-C-C-
I I I
X X X
R = hydrophobic group
X = hydrophilic group
Figure 11.1 Polymeric surfactants.
210 HANDBOOK OF SURFACTANTS

Generic:
Alkoxylated alkyl phenol condensates, Type 1
Polyamine derivatives of polyisobutenylsuccinic anhydride, Type 2
Polyalkylene glycol modified polyester, Type 2
Examples:
All commercial products have trade names with no specific chemical name

Description

Two major types are described

Type J. Alkoxylated alkyl phenol condensates consist of polymer chains

composed of alkyl phenols linked by formaldehyde. The phenol group can
then be reacted with ethylene oxide, or propylene oxide as blocks or a mixture
to give random chains (see Figure 11.2). There is an enormous number of
variations possible with the main variables being the size of the alkyl group
(R), the length of the phenol formaldehyde chain (usually quite low, 4~8
units) and the composition and size of the polyalkylene oxide side group (AO).

Type 2. Consists of polyalkylene glycol modified polyester with fatty acid

hydrophobe, with polyisobutene hydrophobe or with the polyester made by
polymerisation of 12-hydroxystearic acid. The exact molecular structure of
these products has not been released by the manufacturers although there are
now a number of patents describing these products.

General properties

1. Solubility. By the correct choice of side groups and the backbone of the
chain, polymeric surfactants can be made that are soluble in aqueous or
non-aqueous media.

R R R

Y Y
CH 2 CH 2
~ ~

0 0 0
(AO), (AO), (AO),
H H H

R ~ alkyl group
AO ~ EO or EO/PO

Figure 11.2 Alkoxylated alkylphenol-formaldehyde polymer".

 POLYMERIC SURFACTANTS 211
2. Surface active properties. Surface active properties such as lowering of
surface tension disappear quickly as the chain length increases.
3. Functional properties. Excellent emulsification properties, particularly of
W /0 emulsions with the water phase containing inorganic salts or water
soluble organic compounds; excellent demulsification of water/oil
mixtures; excellent dispersing of solids in non-aqueous media and
aqueous media.

Applications

I. Oil field chemicals. Demulsification of crude oil; the alkoxylated alkyl

phenol formaldehyde condensates are one of the principal products used
in the demulsification of crude petroleum. The large number of
permutations make possible the fine control of solubility and hence
distribution between water and organic oils. Oil-based drilling muds;
polymeric surfactants can act as dispersing agents for solids to provide
rheological control and also facilitate the emulsification of the brine
phase up to 70%. Oil slick dispersants made with polyalkylene glycol
modified polyesters (with polyisobutene as hydrophobe).
2. Lubricating oils. Ashless dispersants, use of polyamine derivatives of
polyisobutenylsuccinic anhydride.
3. Emulsion polymerisation. Inverse emulsions, high molecular weight
acrylamide polymers are made by emulsion polymerisation in paraffinic
oils where they give a low viscoity, easily handled W/O emulsion. These
emulsions invert to a O/W emulsion on addition of water and give faster
dissolution of the polymer than the equivalent polymer powder. The use
of polymeric emulsifiers in the polymerisation process gives more
concentrated and stable emulsions than conventional emulsifiers.
4. Coatings. Oil-based coatings with easy brush cleaning properties, i.e.
with aqueous washing up liquid; the products used are polyalkylene
glycol modified polyesters. These have the ability to act as dispersing
agents for the pigment in non-aqueous paint, yet, when added to water, to
act as dispersants for the same pigment in aqueous solution.
5. Fuel emulsions. Macroemulsions of ethanol in diesel oil can be made. The
exact constitution of the polymeric surfactants is not clear.

Specification

Due to the very wide variety of chemical types, it is impossible to give specific
advice except that chemical tests will not be relevant for evaluation of
surfactant performance. Functional tests will almost certainly be necessary for
testing product quality.
Appendix I

Names of hydrophobes

Carbon chain Hydrocarbon Common name Common name of acid

CI CH 4 methane formic
C2 C 1H. ethane acetic
n-C3 CJH S propane propionic
n-C4 C 4H 1O butane butyric
n-C5 C SHll pentane valerie
n-C6 C 6HI4 hexane caproic
n-C7 C 7 H I6 heptane heptoic or oenathic
n-C8 CsHIS octane caprylic
n-C9 C q HI0 nonane pelargonic
n-CIO CIO H l l decane capric
n-ClI C 11 H 24 undecane undecylic
n-C12 C 12H26 dodecane lauric
n-CI3 C 13 H 18 tridecane tridecylic
n-C14 C I4 H JO tetradecane myristic
n-C15 C 1S H J1 pentadecane pentadecylic
n-C16 C I6 H J4 hexadecane palmitic
n-C17 C t7 H J• heptadecane margaric
n-C18 C1SH JS octadecane stearic
cis C18:1 (d9) C 1s H 36 octadecene oleic
trans C18:1 C I8 H 36 octadecene elaidic
C!8:2 C 1s H 34 linoleic
C18:3 C I8 H 31 linolenic
OH-C!8:! C 1S H 37 OH ricinoleic
n-C20 C 10 H 42 eicosane arachidic
n-C22 C l l H 46 docosane behenic
cis C22:1 C l l H 44 erucic
n-C24 C14 H SO tetracosane lignoceric
n-C26 C 26 H s4 hexacosane cerotic
n-C28 C1sHss octacosane montanic

Average composition of fats and oils

Oil Carbon chain

C8-10 CI2 CI4 CI6 CI8 C18:1 C18:2 C18:3

Coconut 15 48 18 8 2 6 2
Corn 12 2 28 57
Olive (California) 8 2 83 6
Palm kernel 6 50 18 9 2 13 I
Saffiower 7 3 13 77
Soyabean II 3 23 53 8
Tallow (beef) 6 29 19 44 2
Tallow (mutton) 5 25 30 36 4
Appendix II: Ecological and toxicity requirements

All industrialised countries have developed legislation and guidelines for the
use and disposal of chemicals. However, for the biodegradation of surfactants,
only the EEC has issued comprehensive directives, and these are presented
in this appendix as examples of guidelines and legislation specific to
surfactants.
Although the United States Environmental Protection Agency (EPA) has
pioneered the development of test guidelines for evaluating the fate of
chemicals in the environment, it does not yet have specific legislation on the
area of biodegradation of surfactants. The EPA does have test guidelines
(published as final rules in the Federal Register) which have biodegradation
tests comparable to those described in this appendix.

Biodegradation

At the time of writing, there is a heightened concern worldwide about

environmental issues. Although concern for surfactants in the environment
has been enshrined in European legislation for nearly 20 years, only more
recently has there been a more general concern over the fate of all synthetic
chemicals in the environment. The pattern of use of the large volume
surfactants is well known and it is possible to calculate the probable
environmental concentration (PEC) in the various parts of the aquatic
environment. Toxicity testing on fish and algae can be carried out and the
concentration having no observed effect (NOEC) can be measured. If PEC is
lower than NOEC by 1-2 orders of magnitude or more, the chemical may be
considered safe in the environment. However if the PEC is of greater or the
same order of magnitude as the NOEC, then the chemical could pose a
problem. Most of the surfactants used in households and in industry go into
the sewers. Surfactants have a relatively high PEC in sewage. The PEC will
give an annual volume which enters the environment but gives no indication of
what happens thereafter. It was hoped that measuring biodegradation would
give a measure of the persistence in the environment.
Biodegradation is a process carried out by bacteria present in nature.
Bacteria are microorganisms which can metabolise an organic chemical and
convert it into less complex chemicals by a series of enzymatic reactions.
Finally, the end products are reached: carbon dioxide; water; oxides of the
other elements. Thus if an organic chemical undergoes biodegradation it is
transformed into its inorganic substituents and in effect disappears from the
environment. If a product does not undergo natural biodegradation then it is
stable and persists in the environment. The study of a surfactant's biodegrad-
ation is therefore important as a measure of its life in the natural environment.
214 HANDBOOK OF SURFACTANTS

Water, oxygen, mineral salts, growth factors and the appropriate species of
bacteria must be available before biodegradation takes place. Biodegradation
takes time, the molecules changing one step at a time in the biochemical
reactions. Biological reactions in aqueous media are also heavily dependent
upon concentration, pH and, in particular, temperature. The rate of bacterial
breakdown of chemicals can vary from a half life (under optimum conditions)
of 1-2 h for fatty acids and sugars, 1- 2 days for linear alkyl benzene
suI phonates and months for branched chain alkyl benzene suI phonates. Note
that, given enough time, even the latter will degrade but the rate of degradation
is very slow and hence it could build up in the environment if it is added at a
rate which is faster than the rate at which it decays. One hundred per cent
conversion of organic carbon into carbon dioxide is not possible because some
of the carbon is utilised in the synthesis of new bacterial cells, and soluble
intractable organic products are often formed as a small proportion of the
original carbon.
Petrochemical-based surfactants have probably been studied in greater
detail than any other group of chemicals and it would be expected that there
would be no problems by now. Such is not the case but the reason is complex
and the explanation partly technical and partly political. It is wise therefore
that the surfactant user should have a grasp of the essential reasons behind this
concern and should have the required data on his products available in order
to answer questions on this subject.
Soap has been used for thousands of years and many synthetic surfactants
have been in use over the last 100 years, but it is only during the last 25 years
that problems have arisen. During the 1950s, persistent foam began to
accumulate on many rivers in the United States and Europe. It was found that
this foam was due to alkyl benzene suI phonates based on tetrapropylene
which seemed to persist in rivers. This surfactant (ABS) was replacing soap in
domestic washing powders and was a constituent of the new liquid washing up
liquids. Testing in the presence of bacteria showed that the ABS was relatively
stable and did not degrade whilst soap was unstable in the presence of bac-
teria, the surfactant properties were destroyed and the foam disappeared.
Substitution of alkyl benzene sulphonates with linear alkyl chains (LABS)
for ABS eliminated the foam present in rivers. This piece of history is very
interesting in that action was taken by all the major surfactant producers and
users, in advance oflegislation. The point at which action was taken was when
a significant proportion of the users (the population) was aware of the
problem and that the problem (foam) was found to be due to the surfactant. In
the case of foam the general population was very aware as they could see it.
But, when the foam disappeared the problem was apparently solved. The
change over from 'hard' ABS to 'soft' LABS was taken by the surfactant
manufacturers before legislation was passed by the EEC. Nevertheless
legislation was passed by the EEC in 1973 to the effect that detergents must be
capable of being degraded by natural bacteria. The first legislation, EEC
Directive 73/404/EEC, stated that the detergents (not surfactants) must be
capable of at least 90% biodegradation. The definition of a detergent is:
 ECOLOGICAL AND TOXICITY REQUIREMENTS 215
For the purposes of this Directive, detergent shall mean the composition of which has been
specially studied with a view to developing its detergent properties, and which is made up of
essential constituents (surfactants) and in general, additional constituents (adjuvants, intensify-
ing agents, fillers, additives and other auxiliary constituents).

This Directive does not give a clear definition of a detergent, and non-
detergent uses are not covered by the legislation. However, as detergents are
the major use of the 'commodity' surfactants, in practice all large volume
surfactants will comply with the requirements of the legislation.
The EEC Directive 73/404/EEC did not define the test methods by which
the standard of 90% should be achieved. Subsequent directives did define tests
methods as follows. Anionics: EEC Directive 73/405/EEC; EEC Directive
82/243/EEC. Non-ionics: EEC Directive 82/242/EEC. Each of the EEC
countries have national legislation covering these directives. Any of four test
methods can be used:
1. The OECD (Organisation for Economic Co-operation and Develop-
ment) method published in the OECD Technical Report of 11 June 1976,
Proposed Method for the Determination of the Biodegradability of
Surfactants used in Synthetic Detergents (anionic and non-ionic).
2. The German method established by the Verodnung tiber die Ab-
baubarkeit anionischer und nichtionischer grenzflachenaktiver Stoffe in
Wasch- und Reinigungsmitteln of 30 January 1977, published in the
Bundesgesetzblatt 1977, Part 1, page 244 as set out in the Regulation
amending that Regulation of 18 June 1980, published in the Bundezgeset-
zblatt 1980 Part 1, page 706 (anionic and non-ionic).
3. The French method approved by the Decree of 28 December 1977
published in the Journal Officiel de la Republique franc;:aise of 18
January 1978, pages 514 and 515 and experimental standard T73-260 of
June 1981 (for anionic surfactants) or T73-270 of March 1974 (for non-
ionic surfactants), published by the Association franc;:aise de normalis-
ation (AFNOR).
4. The United Kingdom method called the Porous Pot Test as described in
the Technical Report No 70/1978 of the Water Research Centre.
In the case of conflict on test methods, an annex in Directive 73/405/EEC has
the confirmatory test method for anionics surfactants and likewise
82/242/EEC for non-ionics. At the present time there is no EEC Directive
defining the test method for cationics or amphoterics. The general principles
behind all the test methods are:
1. A dilute solution of the surfactant is mixed with bacteria taken from
sewage sludge and the solution analysed for the surfactant after a period
oftime. This is compared to the initial concentration of the surfactant.
2. The method of analysis for the anionic is by titration with methylene blue
which will analyse for an anionic showing ~urfactant properties.
3. The method of analysis of the non-ionic is a colorimetric method known
as the Wick bold which measures, however, only non-ionics which show
216 HANDBOOK OF SURFACTANTS

surfactant properties, and is specific to non-ionic surfactants containing

6-30 alkylene oxide groups.
All the surfactants used in household products in Europe will pass the
requirements of these Directives.
However, these test procedures for biodegradability have several unsatis-
factory features and these have led to growing criticism of the results. The tests
were intended to show whether a surfactant was degraded by bacteria in
natural waters and/or a sewage plant. They have proved to be very good tests
in showing whether or not a product persists in giving foam on rivers, but do
not show what actually happens to the surfactant. only that it loses its
surfactant (foaming) properties. The reason is the analytical method used to
estimate the amount of surfactant remaining in the solution measures the
amount of anionic or non-ionic original surfactant remaining. Once the test
substance has lost its surfactant properties it can no longer be measured by the
method of analysis, therefore has disappeared and apparently biodegraded.
This measurement of biodegradability is now known as primary biodegrad-
ation. The material having lost its surfactant properties generally goes on
biodegrading until all the carbon, hydrogen, nitrogen and oxygen atoms in the
original molecule have been transformed into carbon dioxide, nitrogen gas
and water and this is called ultimate (or inherent) biodegradation. There has
been considerable work carried out to show that in the EEC tests as outlined
above, ultimate biodegradation does in fact take place but is not measured.
Thus the test procedures detailed above do not measure the ultimate
bidegradation only the primary biodegradation.
These test procedures have practical problems in giving reproducible results
such as the number and source of bacteria, and the bacterial evolution and
change. Nevertheless it is the problems of measuring ultimate biodegradation
which are of major concern at the time of writing. What are these problems?

Ultimate biodegradation

This is becoming the more important requirement for surfactants for several
reasons.
1. The unsatisfactory nature of the EEC tests described above has led to the
search for better test methods.
2. The EEC Directive for Classification, Packaging and Labelling of
Dangerous Substances (79/831/EEC) includes a notification scheme for
'new substances' requiring information on the potential for biodegrad-
ation to be submitted to the authorities. There is no pass or fail but the
information must be on the ultimate biodegradation if the volume for
sale is greater than 10 tonnes per annum (tpa). Therefore a new surfactant
whilst it may meet the biodegradability requirements of EEC 73/404 (the
detergent directive) may have poor biodegradability under the notific-
ation directive.
 ECOLOGICAL AND TOXICITY REQUIREMENTS 217
3. Due to concern over the inertness of some groups of chemicals (e.g. PCBs,
fluorocarbons) to biodegradation, several national authorities have been
proposing ultimate biodegradability as a better estimate of the life of a
chemical (including surfactants) in the environment.
4. There is discussion at present on the need for a warning label on
chemicals which may be dangerous to the environment.
All this supposes that there is not only a satisfactory test method for ultimate
biodegradation, but also standards of pass and fail using the test method. At
the present time it is the author's opinion that it will be some years before such
a test and pass/fail standards will be developed and EEC legislation passed. In
the meantime there will be considerable confusion on the meaning of test
methods and the standards to be applied particularly if one country lays down
specific requirements. Also it should be noted from the earlier history that
commercial and market requirements are often well in advance oflegislation.
It is not unlikely that certain markets could seize on particular requirements
which have no legislative backing or even scientific reason. All this makes it
more imperative for a user to have a grasp of the requirements particularly if
dealing with customers who themselves are vague as to the exact requirements.

Tests for EEC notification and OECD tests for biodegradation

At the time of writing Table A.l shows the test proposed. Although all tests
are to measure ultimate biodegradability, the practical tests proposed are of
three different levels of severity: ready, inherent and simulation tests.
1. Ready biodegradability. Tests which show the product will degrade to
inorganic and cellular products. They are fail-safe tests as many
Table A.I Tests for biodegradation (ultimate)

OECD EEC test method

Stage 1: 10 tpa, ready biodegradability,

5 different tests
301 A Modified AFNOR test
3018 Modified Sturm test
301C Modified MITI (I)
30m Modified bottle test
301E Modified OECD screening test

Stage 2: l00tpa, inherent biodegradability,

bacteria exposed for a long time
302A Modified SCAS test
3028 Modified Zahn-Wellens test
302C Modified MITI(II)

Stage 3: l000tpa, simulation tests (aerobic sewage)

303A Coupled units test
OECD confirmatory test
Porous pot test
218 HANDBOOK OF SURFACTANTS

compounds do not degrade under these test conditions but are known to
degrade in the environment.
2. Inherent biolieyradation. These tests are intended to assess the products'
intrinsic potential for biodegradation, i.e. their vulnerability to break-
down by the actions of microorganisms under conditions favourable for
biodegradation.
3. Simulation tests. These tests are carried out under conditions as close as
possible to those in the environment (in sewage or natural waters).
However, at the present time, there are no generally acceptable tests for
natural waters.
This table is included to show the complexity of the present situation. It may
become simpler but in the author's opinion this is very unlikely in the next few
years. Practically all queries on the question of biodegradation can be referred
back to the surfactant manufacturer but he can have considerable difficulties
in giving a sensible answer.
The most common question posed will be: Is your product biodegradable?
Before referring the problem back to the surfactant manufacturer it would be
of great help to him if the following questions could be answered:
1. Is primary or ready (ultimate) biodegradation required?
2. Is there any specific legislation, e.g. EEC 73/404?
3. Is there any particular standard required?
4. Is there any particular test method required?

Toxicity

Most of the commodity surfactants have been thoroughly investigated in

respect of their possible toxic effects on humans. Considerable data, much of it
has been published, exists on the testing of surfactants. The majority has been
collected by tests on laboratory animals, but there is also a considerable
amount on accidental ingestion by the public, which has been collected by the
large detergent companies. This is not always published. It would be safe to say
that the present surfactants which nave been used on a large scale for a number
of years are as safe to use as natural soaps. However there are a number of
exceptions to this statement of which users should be aware.
1. Synthetic surfactanis can alter in composition by raw material changes
and/or process changes by the manufacturer.
2. A surfactant which has only been used in small volumes suddenly finds a
new use and is produced and used in considerable volume in consumer
markets. Long-term testing is very seldom carried out until after a
surfactant has been produced in large volume.
3. Most surfactants used for industrial use do not undergo the extent of
testing carried out on surfactants used in consumer markets.
 ECOLOGICAL AND TOXICITY REQUIREMENTS 219
Surfactants are subject to all the regulations governing the general use of
chemicals and there is no intention in this book to cover the general safety of
chemicals. Focus will centre on thc description of those features of toxicity
more relevant to the use of surfactants.The general application of surfactants
in industry is similar to that of other chemicals. However surfactants are
different to most other synthetic organic chemicals when they are used in
personal and household products. Such products are regularly applied by
millions of people to their hair and skin. Accidental ingestion of small
quantities is impossible to avoid, e.g. in toothpaste and dish washing products.
Thus the emphasis is on evaluation of the short- and long-term effects of
ingestion and the short- and long-term effects of exposure to the skin and
mucous membranes.
Considerable research has been carried out, and is still continuing, on the
effects of surfactants on biological membranes due to their ability to adsorb at
interfaces. This research generally uses cultured cells in vitro and the
morphological structure of the cell can be changed. Anionic and cationic
surfactants can adsorb on to proteins, inducing physico-chemical changes that
result in a loss in the biological activity of the protein. There has also been
considerable research on the adsorption of surfactants by the skin. Surfactants
de-fat the skin by emulsification of the lipids and thereby remove some of the
protection offered by the skin against aqueous systems and also can lead to a
loss of water by the skin. However the lipid regenerating factor of the skin is
considerable and it is the result of continuous exposure of skin to surfactants
which results in roughness, scaling and dry skin. Fortunately these effects have
been recognised by users for many years concerning the use of soap in washing,
and most people take sensible precautions.
The practical problem facing users and formulators with surfactants, is the
various labelling regulations now appearing which place upon the manu-
facturer or supplier the need to label his product ifit is dangerous to man or the
environment. This account cannot be up to date on this subject but the
manufacturer or supplier should have the necessary data available on which a
decision can be made. The exact interpretation of toxicity data should be left to
a competent expert but the collection of the appropriate data usually falls on
the formulator/seller. Therefore it is becoming more important for a user of
surfactants to understand the various tests which are carried out for labelling
purposes. The rest of this section is therefore devoted to a simple description of
those tests used for labelling purposes.
There are a number of labelling regulations but the two principal
regulations are:
• EEC Directive 67/548, The classification, packaging and labelling of
dangerous substances
• The Federal Hazardous Substances Act (USA), Code of Federal
Regulations Title 16, Parts 1500.3, 1500.4, 1500.41 National Archives of
the United States, Washington, DC (1973)
220 HANDBOOK OF SURFACTANTS

There have been a considerable number of amendments and additions to these

regulations. EEC members have national regulations to implement Directive
67/548. Non-EEC member countries in Europe have similar legislation in
respect of the toxicity tests required but can be different in the standards
required.
The regulations give standards of results on animal tests whereby the
product may then be classified as dangerous, and is given an appropriate label.
The protocol for the animal tests is standardised. Protocol means the exact
way in which the test is carried out. There is no intention here to describe the
tests in detail, but rather to give the principal features of the tests.

1. Acute toxicity oral. Normally carried out by feeding a number of

animals with varying doses of the surfactant and estimating the dose at
which 50% die. This is known as the LDso value and is usually
expressed in milligrams of surfactant/kilogram of body weight. The
higher the figure the less toxic is the substance. The LDso value of most
common surfactants is high, alkyl sulphates giving figures 1000-
10 000 mg/kg. Tests for labelling only, may be made solely at one level,
i.e. that which is greater than the maximum allowed for a particular
safety label. Therefore if less than 50~~ die, the product does not
require that safety label. A sufficient number of animals must be used
in this type of test, so the number of animals used must be ascertained.
2. Acute toxicity percutaneous (skin toxicity or dermal toxicity). Similar to
oral tests but the test substance is injected under the skin.
3. Acute toxicity by inhalation. Generally not applicable as surfactants are
very rarely in powder or spray form.
4. Chronic toxicity. These are long-term tests carried out in conjunction
with tests for carcinogenicity. Surfactant is added to the food or
drinking water of a group of laboratory animals at a level below the
LDso over periods of up to 2 years. The effects on the test animals are
compared to a similar group of animals with no added surfactant. If
surviving at the end of the test period, all the animals are slaughtered
and post mortems carried out. One criticism of these tests is the very
high level of surfactants fed to the animals ifthe LD so value is high, since
this may not represent anywhere near the levels of surfactants normally
ingested by humans over a period of time.
5. Primary skin irritation. Surfactant is applied to the bare skin of animals
and the skin irritancy is measured by the swelling (oedema) and the
redness (erythema) ofthe skin. This is done visually on a scale (0-4 in the
case of the original Draize test). There are variations possible in this test
such as the concentration of the surfactant and the time of contact with
the skin.
6. Secondary irritation or skin sensitisation. Chemical compounds can
cause allergies in certain individuals. Such allergies result in severe skin
 ECOLOGICAL AND TOXICITY REQUIREMENTS 221
irritation and, possibly, effects on the respiratory system (e.g. bronchial
asthma) following exposure to minute quantities of a chemical com-
pound. Sensitisation is the development of an allergy after renewed
exposure to the compound. The big problem in evaluation is that not
everyone is subject to an allergy produced by a compound and not
everyone is subject to sensitisation. The surfactant industry is now
extremely cautious on possible effects of sensitisation due to the well-
documented effects of very small traces of sui phones in washing up
liquids in Norway in 1965-1966. There are a number of tests used in
evaluation, of which the Magnusson-Kligman and Buehler tests on
guinea pigs are the best known. These consist of injection and/or
application of the test substance to the guinea pig's skin followed by
application of the test substance as in the primary skin irritation test.
Tests on humans are preferable to form the best evaluation, and the
most well-known test procedure is the repeated insult patch test
(Marzulli and Maibach, 1977).
7. Corrosive. In the EEC Directive, a substance is considered to be
corrosive if, when it is applied to healthy intact animal skin, it produces
full thickness destruction of skin tissue. Thus the tests are basically
primary skin irritation tests.
8. Eye irritation. Accidental exposure to the eye is very common, e.g.
shampoos. Tests on the eye, however, also represents the effects on
muscous membranes. Surfactant is injected into the eye of a rabbit, and
irritation first causes reddening through increased blood pressure in the
conjunctivae. This can further lead to destruction of the cell walls
followed by bleeding. Damage to the cornea (which in the case of severe
attack can lead to irreversible clouding) and to the iris can also occur.
The most common test is the Draize test on the rabbit (Draize et at.,
1944).
9. Carcinogenicity. Carried out in a similar manner to the acute toxicity
tests, but in this case the organs of the test animals are compared to
those of the control animals at the end of the test periods. In large
studies it is almost certain that some of the control animals will have
abnormal organs, therefore the effect of the surfactant can only be
determined by the difference between the test and control animals, and
whether this difference is statistically significant.
to. Mutagenicity. Mutagenicity is the danger of genetic damage being
passed on the offspring by mutations affecting the ovum before
fertilisation. The most common test is the Ames test (Ames et at., 1975)
which is easy and relatively cheap to carry out. However, there is a
problem in interpretation ofthe Ames test, as although a negative result
is meaningful, a positive result does not necessarily mean that the
product tested causes mutagenicity.
11. Embryotoxicity (teratogenicity). Embryotoxicity is the effect of chemi-
222 HANDBOOK OF SURFACTANTS

cals on the mother during pregnancy, causing death or a change in the

embryo. Such testing is difficult, particularly in interpretation, and
although there have been reports mainly from Japan, of surfactants
causing some changes, these have not been reproduced elsewhere.

References

Ames. B.N .• McCann. J. and Yamasaki. E. (1975) Mu/al. Res. 31. 347-364.
Draize. J.H .. Woodward. G. and Calvery. H. (1944) J. Pharmacoi. Exp. Ther. 82. 377.
Marzulli. F.N. and Maihach. H.I. (1977) Derma/otosicoio!!.\' (//1(/ Pharmacoioyy. Wiley. New York.
1977.
Index

ABS 88 alkyl amidopropyl dimethylamine 168

abstract services 20, 22 alkyl bis(2-hydroxyethyl) betaines 193
acetylenic alcohols 116 alkyl triethylene tetramines 169
acyl oxyalkane sui phonates 63 alkyl acid phosphates 64
AE(alcohol ethoxylates) 8, 110, 144, 146, alkyl alcohols 40
160, 167, 175, 177 alkyl amido betaines 193
detergency 128 alkyl amidopropyl betaines 193
in alcohol ether sulphates 106 alkyl amidopropyldimethyl sulphobetaines
with paraffin sulphonates 106 193
wetting by 36 alkyl amphopoiycarboxy glycinates 196
AES(alcohol ether sulphates) 8, 33, 77, alkyl amphopolycarboxy propionates 196
80, 87, 102, 114, 195 alkyl benzene bottom sulphonates 103
with alkanolamides 138 alkyl diethanolamide 135
with alkyl amines 172 alkyl ether phosphates 64
with amine oxides 141, 142 alkyl ethylene diamines 169
with amphoterics 191 alkyl glucosides 142
with ester carboxylates 62 alkyl imino diglycinates 196
with ethoxy carboxylates 61 alkyl iminodipropionates 196
with fatty acid ethoxylates 158 alkyl monoethanolamide ethoxylates 145
with fatty ester sulphonates 96 alkyl naphthalene sulphonates 203
with glycinates 202 alkyl phenol ethoxylates 127, 157, 175
with imidazolines 192 alkyl phenol ether sulphonates 84
with LABS 81, 91 alkyl phenolethoxy sulphonates 84
with quaternary ammonium 198 alkyl phosphates 64
with sorbitan ester ethoxylates 162 alkyl polyamine ethoxylates 147
aggregation number 30 alkyl polyamines 169
alcohol ether sulphates see AES alkyl polyamino carboxylates 191
alcohol ether sulphonates 84 alkyl polyaminocarboxylates 196
alcohol ethoxy sui phonates 84 alkyl polyglycolether carboxylic acids 59
alcohol ethoxylates 87, 127, 157 alkyl polyglycosides 142
alcohol sulphates see AS alkyl polyoxyethylene amines 147
alkane sui phonates 86 alkyl polyoxyethylene glycol 130
alkanolamide ethoxylates 145 alkyl primary amines 168
alkanolamides 40,72, 115, 141, 142, 146, 195 alkyl propanediamines 169
with amphoterics 193 alkyl secondary amines 169
with alcohol ether sulphates 75, 77 alkyl sulphates 75, 76, 96
with alcohol sulphates 71 alkyl tertiary amines 169
with anionics 126 alkyl tetraethylene pentamines 169
with glycinates 198 alkyl xylene sulphonates 105
with olefin sulphonates 103 alkyl(poly -1- oxapropene )oxaethane
with paraffin sulphonates 105, 106 carboxylic acid 59
with quaternary ammonium 182 alkyl-imidazoline betaines 199
alkene sulphonates 100 alkyl-imidazoline sulphobetaines 199
alkenyl alkyl polyglycolether sulphonates 85 alkylamidopropyldimethyl betaines 193
224 INDEX

alkylimidazoline hydroxyethylamines 169 data base host 23

alkyl phenol ether sulphates 80 decaglycerol tristearate 165
alpha olefin sulphonates III dialkyl benzene sui phonates 103
alpha sulphonated fatty acids 93 dialkyl naphthalene sulphonates 105
alpha - N - alkylamino acetic acids 196 dialkyl pyrophosphates 64
alpha - olefin sui phonates 100 dialkylsulphosuccinate 108
amide ethoxylates 145 diamine hydrochlorides 185
amine oxides 103 di - carboxyl alkyl imidazoline betaines 199
amine oxides 75, 1I6, no, 171, 191 dicarboxyglycinates 200
amphocarboxy glycinates 190, 199 1,3-diglycerides 16
amphoglycinates 190, 199 diglyceride sulphate 78
amphoteric surfactants 52, 72, 92, 203 dihydroxy ethyl piperazine 136
anhydrohexitol esters 159 dimethicone co-pol yo I 204
anionic surfactants 52, 180, 192, 195 dimethylsiloxane glycol co-polymers 204
AOS(alpha olefin sui phonates lIS, 158 dimethyl octynediol 130
APE(alkyl phenol ethoxylates) 106, 167 dinonylnaphthalene sulphonates 97
AS(alcohol sulphates) 70, 102, 1I4, 195 1,4-dioxane 18, 74, 80, 82, 119, 131
in alcohol ether sulphates 74 directories 18
with alkanolamides 138 disinfectants 184
with alkyl amine salts 172 dispersing agents 37
with glycinates 202 disulphonate 94
with imidazoline amphoterics 191 disulphonic acid 89
with sulphosuccinates 1ll DOBS 88
dodecyitrimethylammonium chloride 179
benzalkonium chloride 181 Draves wetting test 35
benzalkonium chloride BP 184
benzene sui phonates 84 electrostatic effects 38
beta-N-alkylamino propionates 196 end blocked non-ionics 131
beta - N - alkylimino propionates 196 EO/PO copolymers 126, 205, 209
betaines 75, 76. 103. 170. I7I. 172. ES 93
192 ester suiphonates 93
borate esters 139 esters of isethionic acid 63
broad cut acid 88 ethane sulphonates 203
bulk viscosity 39 ether carboxylates 59
by-products 13 ether sulphates see AES
ether sui phonates 84
carbohydrates 117 ethoxy groups 34
carboxy glycinates 190 ethoxy sulphates 73
carboxylic acid salts 56 ethoxylated alcohols see AE
carboxymethyl betaines 199 ethoxylated alkanolamides 77, 108. 110
carboxymethylated alcohols 59 ethoxylated alkyl phenols see APE
castor oil 78 ethoxylated castor oil 173
cationic surfactants 52. 194 ethoxylated coconut fatty alcohol 108
cations 54 ethoxylated dodecyl alcohol 128
Chemical Abstracts 18 ethoxylated fatty acid amides 128
chemical stability 50 ethoxylated fatty acids 128
cloud point 47 ethoxylated fatty alcohols see AE
co-surfactants 40 ethoxylated lanolin 173
cocoamidopropyl betaine 71. 102 ethoxylated mercaptans 128
coconut diethanalamide 102. 135. 142 ethoxylated monoalkanolamides 145
coconut fatty acid 8 ethoxylated non-ionics 35. 36. 65
coconut monoethanolamide 72. 97. ethoxylated nonyl phenols 144
135 ethoxylated polyamines 148
coconut soaps 67 ethoxylated polyglyceryl esters 165
compatibility 51 ethoxylated primary amines 148
critical surface tension 34. 35 ethoxylated propanediamines 148
cumene sui phonates 84 ethoxy1ated sorbitan esters 127. 167. 168,
cycloimidates 199 195, 202
 INDEX 225
ethylene glycol esters 164 with amine oxides 14, 142
ethylene glycol monostearate 157 with fatty acid ethoxylates 158
existing formulations 7 with fatty ester sulphonates 96
with non-ionics 126, 153
FAS 70,93 with sulphated nonyl phenol ethoxylates
fatty acid esters of cholesterol 174· 81
fatty acid ethoxylates 127 lamellar micelles 30
fatty acid sugar esters 142 Langmuir- Blodgett films 25
fatty alcohol ether sulphosuccinate 108 lauric diethanolamide 135, 141
fatty alcohol sulphates see AS lauric isopropanolamide 141
fatty alkanolamides see alkanolamides lauric monoethanolamide 135
fatty amide polyglycol ethers 145 lauric monopropanolamide 135
fatty monoglyceride sulphates 78 lauroaminopropionates 72
fatty primary amines 169 lauryl sarcosinate 67
film elasticity 39 lauryl sulphate 137 see also AS
fluorinated surfactants 203 laurylamine 169
functional properties 51 LAS 70
liquid detergents 58
germicides 183 long chain alcohols 43
Gibbs elasticity 39 long chain carboxylic acid eSters 155
Gibbs film elasticity 29
Gibbs isotherm 27 mahogany acids 104
glucosyl alkyls 142 Marangoni effect 29, 39, 40
glyceryl esters 165 methyl glucoside esters 142
green acids 104 minimum surface tension 203
mixed micelles 31
half ester sulphosuccinate 108, 195 monoalkylpolyethylene glycol 130
hard acid 88 monocarboxy alkylimidazoline betaines 199
heavy alkylate sulphonates 84, 103 monoester sulphosuccinates 72
HLB 42,127 monoglyceride sulphate 78
hydrocarbon chain 12, 28 monoglycerides 164
hydrophilic I-monolaurin 165
group 25, 32, 40, 52 multisaccharides 117
solids 36
surfaces 27 N - alkyl amidopropyl- dimethyl amine
hydrophobic oxides 139
chain 25, 32, 34, 40, 43, 52 N-alkyl aminopropionates 189
solids 37 N-alkyl betaines 189
surfaces 27 N-alkyl bis{2-hydroxyethyl)amine oxides
hydroxy alkane sulphonates 100 139
hydroxyalkane alkyl polyglycolether N-alkyl dimethyl amine oxides 140
sulphonates 85 N-alkyl g1ycinates 190
N-alkyl iminodipropionates 189
imidazoline hydrolysis 186 N,N - dimethyl- N - (3 - alkyl amidopropyl)
imidazolines 110 amines 169
indanes 90 naphthalene sulphonate formaldehyde
industrial laundries 58 condensates 38
instability of soaps 56 naphthalene sulphonates 84
ionic organo-polysiloxanes 204 naphthalene formaldehyde sulphonic acid
ionic surfactants 40, 43 condensates 97
isethionates 114 narrow cut acid 88
new formulations 7
Kraft point 33, 34 nitroso problem 72
Kritchevskyalkanolamide 135. nomenclature 50
non-ionic surfactants 40, 44, 52, 92, 183,
LABS(linear alkyl benzene sulphonates) 8, 192, 198, 201
35, 75, 87, 99, 102, 133, 145 ~PE(nonyl phenol ethoxylates) 128, 133,
with alkanolamides 139 134, 182
226 INDEX

oil soluble emulsifiers 173 polY0xyethyiated fatty alcohols 130

oil soluble sulphonates 163 polyoxyethylenated straight chain alcohols
oleamide diethanolamide 102 130
oleic soaps 57 polyoxyethylene alcohol sulphates 73
omega ester sui phonates 94 polyoxyethylene alcohols 130
omega sulphonated fatty acids 93 polyoxyethylene alkylamines 147
organic amides 53 polyoxyethylene alkylphenols 175
organic esters 53 polyoxyethylene esters 155
organic sulphates 53 polyoxyethylene fatty acid esters 155
organic sui phonates 53 polyoxyethylene nonylphenol sulphates 80
organo-polysiloxane co-polymers 204 polyoxyethylene polyglyceryl ester 165
organofluorine surfactants 206 polyoxyethylene sorbitan esters 159
overbased sui phonates 103 polyoxypropylated polyoxyethylene glycols
overbasified sulphonates 103 150
oxo alcohols 74 polysiloxane glycol co-polymers 204
primary amine hydrochlorides 185
packing of molecules 43 propylene glycol esters 164
packing ratio 45 pyrosulphonic acid 89
paraffin sui phonates 70
PEG(l50)distearate 193 quaternary ammonium surfactants 170,
perfluoroalkyl surfactants 206 171, 172, 179, 190, 192, 194, 198
perfluoroalkyl sui phonates 207
perfluoropolyether surfactants 206
petrochemicals 12 reverse pluronics 150
petroleum sui phonates 84 ricinoleic acid tryglyceride 78
phase inversion temperature 43 rod shaped micelles 47
phenol formaldehyde sulphonic acid
condensates 97 saccharides 117
phosphate esters 55, 203 safety data 15
pine oil disinfectants 58 salt effect 75
pluronics 150 salting out 120
polar groups 35 sanitisers 184
polaxamer 150 sarcosinates 72, 76, 92, 114
polish 59 SAS(paraffin sulphonates) 8
polyacrylic acid 38 secondary alkane sulphonates 86
polyalkoxylated ether glycollates 59 secondary alkyl sulphates 69
polyalkyleneoxide block copolymer 150 secondary amine hydrochlorides 185
polyamine hydrochlorides 185 secondary n - alkane sui phonates 86
polyamines 169 silicone surfactants 203, 209
polyamphocarboxy glycinates 191 soap 64, 68, 96, 105, 106, 114
polyether polysiloxane co-polymers 204 soap bars 58
polyethoxylated 1,3-diglyceride 164 sodium dilaureth - 7 citrate 62
polyethoxylated alkylamides 135 sodium dodecyl benzene sulphonate 43
polyethylene glycol esters 75, 155 sodium dodecyl sulphate 27
polyethylene glycols 175 sodium laureth - 7 tartrate 62
polyglyceryl esters 165 sodium lauryl sulphate 145
polyglyceryl monoester 164 sodium oleate 188
polyglycols 119, 131, 134 sodium xylene sulphonate 91
polyol monoester 165 soft acid 88
polyoxyalkylene glyceride esters 165 sorbitan ester ethoxylates 159
polyoxyalkylene glycol esters 165 sorbitan esters 127, 159
polyoxyalkylene polyol esters 165 sorbitan fatty acid esters 159
polyoxyalkylene propylene glycol esters 165 spans 159
polyoxyethylated alkylamides 145 specifications 15, 51
polyoxyethylated alkylphenols 175 spherical micelles 30
polyoxyethylated fatty amines 147 stability tests 9
polyoxyethylated polyoxypropylene glycols Strecker reaction 85
150 sucrose esters 142
 INDEX 227
sugar esters 142 surface tension 26
sulphated ethoxylated aklanolamides 77 of non-ionics 123
sulphated nonyl ethoxylates 80 surface viscosity 39
sulphated oils 78 surfactant classification 49, 52
sulphated polyoxyethylated alcohols 73 Surfynols 128
sulphated polyoxyethylene amides 77 swollen micelles 46
sulphates 65 synthetic long chain alkyl benzene
sulphating agents 82 sui phonates 103
sulpho amide betaines 193 synthetic petroleum sui phonates 103
sulpho betaines 193
sulphoalkyl amides 113 tall oil soaps 57
sulphoalkyl esters 63 tallow soaps 57
sulphoanhydride 94 tertiary amine hydrochlorides 185
sulphocarboxylic acids 36 tetralin 90
sulphonated fatty acids 93 toluene sulphonates 84
sulphonated oleic acid 94 triethanolamine lauryl sulphate 194
sulphonated unsaturated fatty acids 93 triglyceride sulphate 78
sui phonates 66, 68, 103 triglycerol monostearate 165
sulphonating agents 82 Turkey red oil 78
sulphones 90, 92 Tweens 159
sui phonic acids 81
undecylenic acid monoethanolamide 111
sulphosuccinates 92, 203
sulphoxidation 86 viscosity of surfactants 31
sulphur trioxide 82, 84
sultones 101 wool fat 174
superamide 135
surface active properties 51 xylene sulphonates 84