• Technical

e-Sulfonated Fatty Acids and Esters: Manufacturing

Process, Properties, and Applications
W. STEIN and H. BAUMANN, Henkel & Cie GmbH, D-4 DUsseldorf,West Germany

ABSTRACT same time, Knaggs and co-workers at the Stephan Chemical

a-Sulfonated fatty acid esters, because of their Company (2) carried out a study concerned with ES which
wide-range of application and biological properties, was primarily concerned with the range of application and
represent an interesting class of surfactants. A techni- biological properties of these substances.
cal method for the preparation of a-sulfonated fatty The problem concerning the direct sulfonation of fatty
acid esters is described. By using special reaction con- esters was that the a-hydrogen atoms, due to the neighbor-
ditions it is possible to a-sulfonate saturated fatty ing ester group, were only weakly activated. Therefore, to
esters directly without the use of solvents. The use of achieve sulfonation, stronger sulfonating agents and more
gaseous SO3 gives the product in greater than 97% drastic reaction conditions were required. However, under
yield. A process for the bleaching of the a-sulfonated these conditions the side reactions which normally occurred
fatty esters has been developed, whereby a product of during sulfonation became more pronounced, leading to the
faultless color is produced without the necessity of formation of darkly colored decomposition products. Up to
further purification or separation techniques. The sul- the beginning of the 1960's, a technically useful manu-
fonation and bleaching processes operate continuous- facturing process was unknown for ES of an acceptable
ly. The process has been tried successfully on a com- quality without the necessity of further purification steps.
mercial scale using the methyl esters of technical The only method by which it was possible to obtain ES of
fatty acids. Methods for the preparation of a- satisfactory quality was by esterification of pre-formed and
sulfonated fatty acids are given. The chemical, techni- purified FAS using the appropriate alcohols (3). However,
cal, and biological properties of the a-sulfonated fatty this method was too troublesome to achieve practical im-
acids and their esters are discussed, a-Sulfonated fatty portance.
esters possess good washing and foaming properties,
have good biological degradability, possess good skin PROCEDURES
compatibility and low acute toxicity. They can be
considered as surfactant components for phosphate- Starting Materials
free or low-phosphate detergents, a-Sulfonated fatty Esters were derived from unbranched C8-C22 car-
acids and esters also possess other favorable technical boxylic acids and from C1-C3 alcohols. On economic
properties which allow them to be used in cosmetics, grounds, the methyl esters of commercial fatty acids
as auxiliary agents in the production o f fibers, plas- were preferred. In particular, we have used the methyl
tics, and rubber, and in leather manufacture. esters (in some cases ethyl esters) from palm kernel oil,
coconut oil or tallow. As will be shown later, to produce
INTRODUCTION sulfonated products which can be readily bleached, it was
necessary that the original fatty acid esters be hydrogenated
Salts of a-sulfonated fatty acids (abbreviated as fatty to such an extent that their iodine number was less than
acid sulfonates [FAS] ) and salts of a-sulfonated fatty esters 0.5. Analytical data for the starting materials are given in
(abbreviated as ester sulfonates [ E S ] ) h a v e been known for Table I. The esters were practically colorless, and SO3 was
a considerable period of time. Their chemical formulas are: used as ca. 5 volume-% mixture with air, dried over Silica
0 gel.
II
R-CH-C-OH Sulfonation Apparatus
I
The sulfonation was carried out in various pieces of ap-
S03H paratus in the laboratory, on a pilot plant scale, and on a
tx-sulfonated fatty acids manufacturing scale. F o r batch sulfonation in the labora-
tory, a cylindrical glass vessel of 4 cm inner diameter (ID)
0 and 45 cm ht was used. It was fitted with a cooling jacket,
II
R-CH-C-OR
I
gas inlet tube, gas outlet tube, and an inner thermometer. A
gas inlet tube of 8 mm ID led from the top of the apparatus
to the b o t t o m o f the container. Continuous sulfonation
S03H experiments on a laboratory scale were carried out using a
ce-sulfonated fatty acid esters thin film reactor. This consisted of a glass tube 1 m long
Because of their superior properties, the ES are of great- and 6 mm ID fitted with a cooling jacket. The ester was
er practical importance than are FAS. However, because of injected into the reactor through a nozzle, thereby forming
the lack of a simple, economical manufacturing process, a film on the inner surface of the glass tube. The ester film
they have received little attention. Therefore, at the end of reacted with an SO 3 :air mixture also introduced at the t o p
the 1950's we began to develop a technically practical of the apparatus. Also connected to this apparatus were a
method for preparing ES of exceptional quality (1). On gas separator which served to separate the gaseous and
economic grounds, this could only proceed by direct sul- liquid phases, and a heated, extended residence time coil.
fonation of fatty esters, especially methyl esters. At ca. the This apparatus had the function o f ensuring that the re-
action went to completion. The ester throughput was ca.
1presented at the AOCS Meeting, Mexico City, Mexico, April 600 g/hr, and the SOa concentration in the SO3:air mix-
t974. ture was ca. 5 volume-%.
323
324 J O U R N A L OF THE A M E R I C A N O IL CHEMISTS' SOCIETY VOL. 52

TABLE I

Analytical Data of Starting Materials

Acid Iodine Hydroxyl Saponification

Starting material no. no. no. no. CIO C12 C14 C16 C18 C20 Average chain length

H y d r o g e n a t e d palm kernel
fatty acid m e t h y l ester 1.2 0.1 2.4 240 1.2 59.1 21.9 8.8 9.0 --- C13.1
H y d r o g e n a t e d t a l l o w fatty
acid m e t h y l ester 0.6 0.3 0 196 --- 0.7 4.0 29.8 64.6 0,9 C17.6

Pilot plant sulfonations were carried out continuously as a function of reaction temperature (in the case of the
either in a 2 in. Chemithon reactor or a Cascade apparatus discontinuous laboratory sulfonation of palm kernel fatty
with 5 reactors connected together. The 2 in. Chemithon acid methyl ester) with a mole ratio of ester:SO3 of 1: 1.3.
reactor, which is an annular space reactor fitted with a cylin- Temperatures of 70-90 C were required to achieve an ade-
drical rotor (4), had a throughput of ca. 45 kg ester/hr. The quate degree of sulfonation. The SO3 reacted exothermical-
standard apparatus was connected to a heated, extended ly and rapidly with the fatty acid ester at lower tempera-
residence time reactor. tures (apparently by adduct formation at the carbonyl
The cascade apparatus consisted of 5 cylindrical vessels oxygen atom of the ester group) without resulting in a large
(each of ca. 7 liter capacity) connected in series. Each was degree of sulfonation. Only at increased temperature can an
fitted with a cooling jacket, a product and gas inlet tube, a increased amount of sulfonation take place at the a-C-atom.
gas outlet tube, and a product outflow tube. The vessels The use of temperatures of 70-90 C, however, lead to
were arranged so that a flow of product from one vessel to the unavoidable formation of darkly colored side products.
the next occurred automatically. An SO3:air mixture was It was shown that lightly colored ES could be obtained by
led into the first four vessels, the fifth vessel serving as an means o f a special bleaching process when the side products
extended residence time reactor. The cascade apparatus had formation could be held in check by a suitable choice of
a throughput of ca. 20 kg ester/hr. The sulfonation of fatty sulfonation conditions.
acid esters on a production scale was carried out in a 12 in. To achieve a practical, quantitative sulfonation o f the
Chemithon reactor with a throughput of ca. 800 kg ester/ fatty esters, an excess of SO 3 must be used. The amount of
hr. SO 3 used has a decisive factor in side product formation,
and was dependent upon the sulfonation process used. In
RESULTS AND DISCUSSION the case of discontinuous sulfonation on a laboratory scale,
the degree of sulfonation of palm kernel methyl ester as a
Sulfonation of Fatty Acid Esters function of the amount of SO3 is shown in Figure 2. The
Because of its commercial availability and quality, the necessary excess SO3 was ca. 30 mole-%. In the case o f
most favorable sulfonating agent has been gaseous SO 3 continuous sulfonations using continuous short time sul-
mixed with an inert gas, (preferably 90-95 volume-% air). fonation reactors, a smaller excess of SO3 was used. A
Figure 1 shows the dependency o f the degree of sulfonation laboratory thin film reactor required ca. 20 mole-%, and a
Chemithon reactor ca. 10-20 mote-% excess. The degree of
sulfonation was greater than 97%.
% Sulfonated As already mentioned, the sulfonation of fatty esters
100 - proceeded in two stages. The first stage was rapid adduct
formation between the SO3 and the ester group. The
second stage was the slow, temperature dependent sulfona-
tion in the a-position. Total reaction time to achieve 95%
reaction in the case of discontinuous sulfonation was of the
order of 50-60 min with a 30 mole-% SO3 excess at 80 C.
In continuous short time sulfonation reactors, the residence
©
°/,Sulfonated
100
©
80
90
j
70 80-

© 70

60 ~ 1 I I I I I T T I
9O 80 70 60 50 40 C 1,0 1,1 1,2 1,3
Reaction temperature Mole SO3/Mole Ester
FIG. l. Sulfonation of palm kernet methyl ester-degree of sul- FIG. 2. Sulfonation of palm kernel methyl ester-degree of sul-
fonation vs reaction temperature. Reaction time = 60 + 10 min; fonation vs SO3:ester mole ratio. Reaction time = 60 + 10 min;
mole ratio = ester: SO3 = 1:1.3; 5 % by volume SO 3 in air. reaction temperature = 80 C; 5 % by volume SO 3 in air.
SEPTEMBER, 1975 STEIN AND BAUMANN: a -S U LEO N A TED FATTY ACIDS AND ESTERS 325

time of only a few seconds at 80-90 C was not sufficient to TABLE II

achieve a quantitative sulfonation. Therefore, a second re-
Bleaching of a-Sulfonated Palm Kernel Et hyl ESter:Color at
action stage was used whereby the sulfonated products re- Various Hydrogen Peroxide Quantitiesa
mained at 80-90 C for 10-20 rain.
The most advantageous sulfonation process with respect Color c
Hydrogen peroxide
to color of the sulfonated products and their bleachability, quantity
has been shown to be the continuous cascade process. The (wt %)b Yellow Red Blue
temperatures during sulfonation were increased from 50 C
0 NM d NM NM
in the first reactor to 60 C in the second, 70 C in the third, 0.5 18.6 3.4 0.5
and 80-85 C in the fourth reactor. The SO3 was distributed 1.0 7.3 1.0 0.4
in the ratio of 40:20:20:20 in the individual reactors (5). In 1.5 2.5 0.7 0.3
the case of shorter chain fatty esters, the cascade principle 2.0 2.5 0.4 0
2.5 1.9 0.2 0
can be altered so that necessary uptake of SO 3 occurs in 3.0 1.5 0.I 0
the first reactor at a temperature of 30-40 C, and the actual
sulfonation occurs at 80-90 C in a second reaction step (6). a R e a c t i o n conditions: bleaching time-2 hrs; t e m p e r a t u r e = 6 0 C
By this means, losses of low boiling, short chain fatty esters H 2 0 2 c onc e nt ra t i on = 40 wt-%.
by evaporation are avoided. bCalculated on the basis of s ul fona t e d product.
The preparation of bleachable sulfonated products by c5 wt-% solution; measured by Lovibond 4 in.cell.
continuous sulfonation under optimal reaction conditions dNM = not measureable.

TABLE III
Bleaching of a-Sulfonated Palm Kernel Et hyl Ester: Degree of Hydrolysis and
Color at Various Hydrogen Peroxide ( H 2 0 2 ) C onc e nt ra t i ons a

Color b
Hydrogen peroxide concentration Sulfuric acid concentration Degree of hydrolysis
(wt %) (wt %) (%) Y e l l ow Red Blue

80 94 5 7.0 1.7 0
60 83 8 2.7 0.7 0
40 68 10 2.0 0.3 0
20 44 17 3.1 0.8 0
10 26 36 7.0 1.3 0

aReaction conditions: bleaching time = 2 hr; t e mpe ra t ure = 60 C; H 2 0 2 q u a n t i t y = 3 wt-%, calculated on the
basis of sulfonated product.
b5 wt-% s o l u t i o n ; measured by Lovibond 4 in. cell.

has been described above. The following technical possi- Color

bilities were available: (A) Multiple step working conditions yellow
such that the reaction vessels are arranged in a cascade se-
25-
quence with stepwise controlled temperatures and con-
trolled SO a additions. This type of reaction procedure is
used, for example, in the Ballestra sulfonation plant (7,8).
(B) Use of short time sulfonation reactors which operate
according to the falling film, thin film, annular space, or 20-
injection principle with an additional stage for an extended
residence time reactor. In these reactors extensive mixing of
reaction components and simultaneous rapid removal of the
heat of reaction at the reaction site takes place. This has the
effect of reducing the required excess of SO3, thus keeping
the formation of difficultly bleachable side products to a 15-
minimum.
Reactors other than the Cemithon reactor (4), which has
been successfully used by us, may also be suitable, e.g. the
Allied Chemical Co. and the Stepan reactors (7). The qual- red
ity of the resultant products would be especially good when
10-
approaches A and B are combined, i.e. two or three short
time reactors connected together.
Fats, i.e. fatty acid triglycerides, after hardening can also
be sulfonated under the reaction conditions given. Because
the high viscosity of the sulfonated fats caused difficulties
in sulfonation, at least 10-25% by wt of fatty acid esters of _
short chain alcohols, e.g. methyl esters, must be added (9).
The esters of alchohols having chains of more than three
carbon atoms, and ether alcohols, are cleaved to a large
extent during the sulfonation, resulting in a poor yield of
ester sulfonates. For the preparation of these types of ester
sulfonates in good yields, ca. 50% neutralized a-sulfonated 0 I I i ! t ! 't ................
t ..............
I ....... i
fatty methyl esters are subjected to exchange of ester 20 40 60 80 100 C
groups with the desired long chain alcohols or ether alco- Temperature
hols.
Bleaching of a-Sulfonated Fatty Acid Esters FIG. 3. Bleaching of a-sttlfonated palm kernel methyl ester.
Bleaching time = 2 hr; 2 wt-% H202 (40 wt-% solution); Lovibond
Even when the fatty esters have been sulfonated under color; 4 in. cell; 5 wt-% solution.
326 JOURNAL OF THE AMERICAN OIL CHEMISTS' SOCIETY VOL. 52

TABLE IV
Typical Composition and Color Numbers of Ester Sulfonates
Color a Unsulfonated
Sulfonate matter Disodium sulfate
Sulfonation.method Ester sulfonate Yellow Red Blue (%) (%) (%)
L a b o r a t o r y scale,
batchwise PMS b 4.1 0.5 0 39 2.1 4.8
Laboratory scale,
batchwise TMS c 9.4 1.8 0 24.5 1.4 2.6
L a b o r a t o r y scale,
continuous PMS 2.3 0.3 0 40 1.4 2.9
Laborato ry scale,
co ntinuous TMS 6.6 1.3 0 24.5 1.0 1.9
Pilot plant, multistep
sulfonation PMS 1.1 0.1 0 39 1.3 4.4
Pilot plant, multistep
sulfonation TMS 4.9 0.9 0 24 0.9 2.4
Pilot plant, 2 in
Chemith on reactor PMS 1.2 0.2 0 39.5 0.8 2.8
Pilot plant, 2 in
C h e m i t h o n reactor TMS 5.6 1.0 0 25 0.6 1.8
Production plant, 12
in C h e m i t h o n reactor PMS 2.0 0.2 0 39.6 0.8 2.2

a5 wt -% solution; measured by Lovibond 4 in.cell.

bpMS = Palm-Kernel methyl ester-a-sulfonate.
CTMS = Tallow m e t h y l ester-c~-sulfonate,

influence of the H202 quantity on the bleaching ef-

fect is shown in Table II. A palm kernel ethyl ester pre-
pared by a discontinuous process and containing 28 mole-%
free SO3 was bleached. The color measurement was carried
out in all cases with a Lovibond Tintometer using 5 wt-%
ester sulfonate solutions in 4 in. cuvettes. An unbleached
product, too dark to be measured, was satisfactorily
bleached with 2 wt-% H202 wt basis of sulfonated fatty
Sulfonation Bleaching NeutraWsatk)n ester. The optimum quantity of H202 was dependent upon
the quality of the fatty ester to be bleached. It varied from
FIG. 4. Flow sheet of the manufacturing process for fatty ester
sulfonates.
1.5-3.5%, calculated as percent of the sulfonated product.
The hydrogen peroxide concentration played a decisive
role in the bleaching effect. There was a connection be-
R-CH C-(~ CH--R~R-CH/-C-~ CH-W tween the bleaching effect and the sulfuric acid concentra-
iOI @I
tion in the sulfonated product due to the reaction of the
SO, excess SO3 with the water in the H202. The formation of
I persulfuric acids apparently played an important rote in the
.H_" [ bleaching process. Optimum results were obtained when ca.
~0 S-'O
60-90% concentration of sulfuric acid was present in the
dh
sulfonated product. The a m o u n t and concentration of
H202 was calculated taking into account the excess SO3
o, used. If the concentration of sulfuric acid formed was too
high, attack on the sulfonated product with the concomi-
iN ~ °fi~° ~Na~ tant worsening of color occurred. If, on the other hand, the
? ? concentration was too low, hydrolytic cleavage of the ester
occured. The influence of the H202 concentration on the
s~
bleaching effect is shown in Table III. Three % H 2 02 was
FIG. 5. Reaction mechanism of the a-sulfonation of fatty acid added to an a-sulfonated palm kernel ethyl ester, sulfon-
esters. ~ = Major reaction; - - - ) = minor, side reaction. ated in the laboratory by a discontinuous process. It con-
rained 28 mole-% unreacted SO 3. The best bleaching effect
was reached with 40% H 2 0 2 , which corresponds to a 68%
optimal conditions, the ES were still dark colored. Conven-
sulfuric acid concentration. Ester hydrolysis at this concen-
tional bleaching process by addition of sodium hypochlo-
tration was very low.
ride or hydrogen peroxide to neutralized aqueous solutions
The bleaching effect also was strongly temperature de-
of the ES led to products which were totally unsatisfactory
pendent. Figure 3 shows that the lightest color was attained
because of poor color. Ozone or a bleach under reducing
at temperatures between 60-80 C. In order not to exceed
conditions also gave products which possessed poor color these temperatures, the considerable heat of reaction was
properties. We found that the ES could be satisfactorily removed by efficient cooling. Temperature control was very
bleached with H202 before neutralization attention was critical. If insufficient heat was removed, the reaction rapid-
paid to the amounts and concentration of H 2 0 2 , the ly went out of control, resulting in decomposition of the
bleaching temperature, and the bleaching time (10). The sulfonation products and irreversible darkening of the prod-
H202 was added incrementally as an aqueous solution to uct. The bleaching times required at a temperature of 60 C
the raw sulfonated product. Efficient stirring and efficient were between 10 min and 1 hr. After this time interval,
means of removing the reaction heat were provided. The practically complete bleaching of the sulfonation products
SEPTEMBER, 1975 STEIN AND BAUMANN: c~-SULFONATEDFATTY ACIDS AND ESTERS 327

had occurred. In individual cases where bleaching with °/o Hydrolysis/hr

H202 was insufficient because of the poor quality of the
starting materials, products of satisfactory color were ob- 6- 80C
tained by the addition of 0.5 wt-% sodium hypochlorite
(basis wt of sulfonated product) added as a 13% aqueous 5-
solution to the neutral ester sutfonates at 50 C (11).
Bleaching of a-sulfonated fatty esters was carried out
4
continously in several different ways (12). Thus under the
optimal bleaching conditions a vigorous stirring device for
mixing a-sulfonated esters with H202 was used in conjunc- 3
60C

t
tion with a good heat exchanger. It was efficient also in the
case of high viscosity liquids and the heat exchanger was 2 40 C
capable of functioning as residence time reactor. 20 C
Neutralization of a-Sulfonated Esters
The bleached c~-sulfonated esters were neutralized with "0 ...... ! / I I i ~l I I i I I i
aqueous sodium hydroxide or other aqueous bases. During 0 2 4 6 8 10 12 14
the neutralization, the temperature did not exceed 45 C to
avoid hydrolysis of the ester groups. An efficient mixing pH
device was used to ensure that rapid mixing occurred to FIG. 6. Rate of hydrolyses of palm kernel methyl ester sul-
give a mixture which was as homogeneous as possible. fonate. Concentration = 3.4 g/liter.
Simultaneously, the heat of reaction was efficiently re-
moved. The danger of ester hydrolysis, in a continuous TABLE V
process was small when the pH was automatically con- Solubility of Sulfonates
trolled between a value of 7.5 and 9. The concentration of
the sodium hydroxide solution was chosen so that after Krafftpoint
neutralization a 40% aqueous slurry of sodium palm kernel Surfactant (C)o
methyl ester a-sulfonate (PMS), or ca. 25% aqueous slurry Alkylbenzenesulfonate (LAS) (C 10-13)a <0.0
of sodium tallow methyl ester a-sulfonate (TMS) was ob- Tallow methyl ester sulfonate (TMS) (C 16-18) 39.0
tained. Such slurries had a low viscosity and were easily Palm kernel methyl ester sulfonate (PMS) (C12-14) <0.0
processed further. Typical compositions of products ob- a-Olefinesulfonate (AOS) (C 15-18) 23.5
tained in the various sulfonation devices are given in Alkanesulfonate (AS) (C 14-17) < 0.0
Table IV.
By combining the three steps described (13), sulfonation, aLength of alkyi chain.
bleaching, and neutralization, it was possible to produce ES bTemperature at which 10 g/liter is soluble.
of perfect quality with degrees of sulfonation greater than
97% when working continuously on a large scale (Fig. 4).
The production of ester sulfonates on the basis of palm % Brightness
kernel and coconut methyl esters has been successfully car-
ried out on a 2000 t o n / m o n t h scale (12 in. Chemithon re- 100 t
actor) over an extended period of time.
90
Preparation of ~-Sulfonatad Fatty Acids
The preparation of c~-sulfonated fatty acids can be car- 80
ried out in two ways: (A) By direct sulfonation of fatty
acids with SOa under the conditions described for the fatty
esters. However, sulfonation temperatures were 10-15 C 70
higher, and 1-2% of additional bleach was necessary to at- TMS
tain yields and color quality comparable to those of the 60
esters. Sttlfonation of fatty acids with SO3 in inert solvents
also lead to t~-sulfonated fatty acids of good quality (14)
("Armosul," Armour Industrial Chemical Co., Chicago, 50 PMS
Ill. [15]). However, the use of solvents makes this
process quite laborious. (B) By hydrolysis of 0t-sulfonated 40
esters. The preparation of ot-sulfonated fatty acids or their
salts was achieved by in process hydrolysis of ester sul-
fonates. One can either acid hydrolyze the unneutralized
30
ct-sulfonated esters by heating them with water, or, prefer-
ably, carry out an alkaline hydrolysis of the alkali salts of 20
an ct-sulfonated ester with an aqueous solution of the cor-
responding base at higher temperatures.
10 LAS
Reaction Mechanism for Sulfonation of Fatty Esters
The primary reaction product, resulting from the re- ..... I I i i

action of fatty acids and SO3 has been described by de 0 4 8 17 33

Boer (16) as a mixed anhydride, which rearranges at higher
temperatures to an ct-sulfo-fatty acid.
Water hardness grains/gallon
(a)
R-CH2-CO-OH+SO(OC) R-CH2-CO-O-SO2-OH ...............> R-CH-CO-OH FIG. 7. Effectiveness of washing wool as a function of the water
I hardness. Temperature = 30 C; washing bath = 1:50; washing time =
SO3H 15 rnin; concentration= 2g product/liter (% surfactant + ¾
On the basis of our experiments, however, we assume the Na2SO4). TMS = Tallow methyl ester sulfonate; PMS = palm kernel
following reaction mechanism for the sulfonation of fatty methyl ester sulfonate; and LAS = alkylbenzenesulfonate.
328 JOURNAL OF THE AMERICAN OIL CHEMISTS' SOCIETY VOL. 52

TABLE VI is stabilized m a r k e d l y b y t h e a - s u l f o n a t e g r o u p . This is

Wool Detergency Tests a of Light Duty Detergent Formulations b s h o w n in F i g u r e 6. T h e h y d r o l y s i s r a t e o f PMS is p l o t t e d as
a f u n c t i o n o f t e m p e r a t u r e a n d p H at a c o n c e n t r a t i o n o f
Concentration (g/liter) 3.4 g PMS/liter, i.e. a c o n c e n t r a t i o n w h i c h c o r r e s p o n d s t o
Surfactant c 2 4 6 concentrations in a washing solution. The hydrolysis rate of
t h e ES is v e r y slow, i n t h e p H r a n g e o f 3-9.5 e v e n at t e m -
TMS 78.5 85.0 83.0 p e r a t u r e s Of 8 0 C. T h e p r o d u c t is s t a b l e in a n e u t r a l d e t e r -
PMS 63.0 73.5 75.0
gent s o l u t i o n , a n d m i n i m a l h y d r o l y s i s h a s b e e n f o u n d dur-
LAS 60.0 84.0 85.0
ing s p r a y d r y i n g o f a PMS c o n t a i n i n g d e t e r g e n t slurry, a n d
aValues expressed as % brightness. a f t e r s t o r i n g n e u t r a l s o l u t i o n s o f t h e ES at 6 0 C f o r several
bFormulation : 26.5% surfactant, 15.0% sodium tripolyphosphate months.
50.0% sodium sulfate, up to 100%with other compounds and water; Physical properties: I n general, o n e c a n say t h a t ES o f
washing bath = 1:50; temperature = 30 C; water hardness = 300 ppm s h o r t c h a i n a l c o h o l s possess e x c e l l e n t w a s h i n g p r o p e r t i e s ,
CaCO3/gallon. w h e r e a s , t h e ES i n w h i c h t h e s u l f o n a t e g r o u p is i n t h e
CTMS = Tallow methyl ester sulfonate; PMS = palm kernel m i d d l e o f t h e m o l e c u l e (as in t h e case o f l o n g c h a i n a l c o h o l
methyl ester sulfonate; LAg = alkylbenzenesulfonate. esters), possess g o o d w e t t i n g , b u t p o o r w a s h i n g p r o p e r t i e s

TABLE VII
Washing-Tests in the Launder-O-Meter With and Without Tripolyphosphate a
Textile Nonfinished cotton Finished cotton Polyester/Finishe d cotton
Washing temperature 90 C 90 C 60 C
Concentration (g/liter) 0.75 b 2c 6c 0.75 b 2c 6e 0.75 b 2c 6c
gurfactant d
LAg 40.4 66.0 76.0 43.6 47.5 73.5 38.4 43.0 60.0
TMg 61.7 72.0 76.0 58.7 51.5 73.0 57.5 45.0 60.0
PMg 46.4 64.0 76.0 53.0 49.0 74.0 50.9 42.5 58.0

aValues expressed as % remission; water hardness = 300 ppm CaCO3/gallon.

bAnionic surfactant only, without tripolyphosphate.
CFormulation: 7.1% anionic surfactant, 2.4% nonionie surfactant, 38.8% tripolyphosphate, up to 100% with
complexing agents, sodium perborate and foam inhibitors.
dLAS = Alkylbenzenesulfonate; TMS = tallow methyl ester sulfonate; PMS = palm kernel methyl ester sul-
fonate.

TABLE VIII ( 1 7 ) . O p t i m u m w a s h i n g p r o p e r t i e s are r e a c h e d i n t h e case

o f t h e m e t h y l ES w i t h C16-C18 f a t t y acids. In t h e follow-
Biological Properties of Fatty Methyl Ester Sulfonates ing t e x t we c o n c e n t r a t e m a i n l y u p o n t h e p r o p e r t i e s o f t h e
and Fatty Acid Sulfonates
t e c h n i c a l l y i m p o r t a n t m e t h y l ES ( s o d i u m salts) o n t h e basis
Surfactant a PMS TMS PAS TAS o f p a l m - k e r n e l oil ( o r c o c o n u t oil) ( P M S ) a n d t a l l o w (TMS).
T h e s o l u b i l i t y o f a series o f s u l f o n a t e s is s h o w n in
Biodegradibility b 94 9S 94 93 T a b l e V a n d e x p r e s s e d as K r a f f t - P o i n t s . TMS was clearly
Acute oral toxicity c 3.8 >2.7 >2.2 >2.3 m u c h less soluble t h a n a l k y l b e n z e n e s u l f o n a t e (LAS). T h e
Skin compatabilityd NR e NR NR NR
ES, especially TMS, in c o n t r a s t t o LAS possess d e t e r g e n c y
apMS = Palm kernel methyl ester sulfonate; TMS = tallow w h i c h was i n d e p e n d e n t o f w a t e r h a r d n e s s . This is s h o w n i n
methyl ester sulfonate; PAS = palm kernel acid sulfonate; TAS = F i g u r e 7 in w h i c h t h e w a s h i n g p o w e r for w o o l in t h e ab-
tallow acid sulfonate. s e n c e o f c o m p l e x i n g agents is s h o w n as a f u n c t i o n of w a t e r
bOrganization for Economic Cooperation and Development-Con- h a r d n e s s . W h e n TMS was used in a light d u t y d e t e r g e n t
firmatory test (% decrease in methylene blue active substance f o r m u l a t i o n its e x c e l l e n t w a s h i n g p r o p e r t i e s b e c o m e ap-
[MBAS] after 30 days).
p a r e n t , especially at l o w c o n c e n t r a t i o n s ( T a b l e VI). TMS
CMale, white mice; LDs0 , g/kg body-wt.
w a s h e d n o t i c e a b l y b e t t e r t h a n PMS, b u t PMS h a d b e t t e r
dHairless mice, treated once daily for 7 days.
eNR= no reaction, f o a m i n g p r o p e r t i e s ( u p t o 4 0 C). L a u n d e r - o - m e t e r w a s h i n g
tests with heavy duty detergent formulations containing
ES, u s i n g f i n i s h e d a n d n o n f i n i s h e d c o t t o n as w e l l as poly-
esters. I n t h e first stage, t h e SO 3 r e a c t s i n t h e e x t r e m e ester-cotton blends, further demonstrate the good washing
c a n o n i c a l f o r m , w h i c h carries a positively c h a r g e d s u l f u r p r o p e r t i e s o f TMS e v e n at l o w c o n c e n t r a t i o n s as s h o w n in
a t o m w i t h t h e free e l e c t r o n p a i r o f t h e c a r b o n y l o x y g e n o f T a b l e VII. I t s h o u l d be n o t e d t h a t TMS possessed good
t h e ester g r o u p . Due t o t h e i n c r e a s e d a c t i v a t i o n o f t h e washing properties for cotton and polyester-cotton blends
0~-hydrogen a t o m s b e c a u s e o f a d d u c t f o r m a t i o n , a re- in t h e a b s e n c e o f t r i p o l y p h o s p h a t e . This was n o t t h e case
a r r a n g e m e n t t h e n occurs, w h e r e b y a n eL-hydrogen a t o m is w i t h L A S . T h e r e a s o n f o r this a n d for t h e g o o d w a s h i n g
s u b s t i t u t e d b y a n SO~ g r o u p f o r m i n g a C-S b o n d (Fig. 5). A p r o p e r t i e s at l o w c o n c e n t r a t i o n s was p r o b a b l y d u e t o t h e
m i n o r side r e a c t i o n o c c u r s w h i c h r e q u i r e s a d d i t i o n a l SO 3. l o w s e n s i t i v i t y o f TMS t o w a t e r h a r d n e s s . T h e r e f o r e , TMS is
This r e a c t i o n is a p p a r e n t l y t h e f o r m a t i o n o f an a n h y d r i d e especially i n t e r e s t i n g f o r t h e d e v e l o p m e n t o f l o w p h o s p h a t e
f r o m s u l f o c a r b o x y l i c acid a n d alkyl sulfuric acid w h i c h is o r p h o s p h a t e - f r e e w a s h i n g a n d cleaning agents. It s h o u l d b e
easily cleaved b y alkali. This side r e a c t i o n b e c o m e s t h e mentioned, however, that problems concerning secondary
m a j o r r e a c t i o n in t h e case o f f a t t y esters o f l o n g e r c h a i n p r o p e r t i e s still exist, s u c h as f a b r i c i n c r u s t a t i o n i n t h e c o m -
alcohols. p l e t e a b s e n c e o f p h o s p h a t e s . T h e soil s u s p e n d i n g p o w e r o f
TMS was also s a t i s f a c t o r y .
Properties of Fatty Acid Sulfonates and Ester Sulfonates
A d i s a d v a n t a g e o f TMS c o n t a i n i n g d e t e r g e n t s , w h e n u s e d
Chemical properties: T h e h y d r o l y t i c s t a b i l i t y o f t h e ES in the normal European horizontal drum type automatic
is o f great p r a c t i c a l i m p o r t a n c e . T h e e s t e r g r o u p a p p a r e n t l y w a s h e r s is t h a t t h e y h a v e a t e n d e n c y t o p r o d u c e t o o m u c h
SEPTEMBER, 1975 STEIN AND BAUMANN: c~-SULFONATED FATTY ACIDS AND ESTERS 329

f o a m due to the extensive mechanical action. In the U.S., REFERENCES

these difficulties may n o t appear, however, due t o the dif-
I. Stein, W., H. Weiss, O. Koch, P. Neuhausen, and H. Baumann,
ferent type o f c o n s t r u c t i o n o f the washing machines and Fette, Seifen, Anstrichm. 72:956 (1970).
the lower washing temperatures. The use o f special f o a m 2. Knaggs, E.A., J.A. Yeager, L. Varenyi, and E. Fischer, JAOCS
inhibitors, or the a d d i t i o n of o t h e r detergents may solve the 42:805 (1965).
p r o b l e m o f t o o m u c h foam with TMS c o n t a i n i n g washing 3. Stirton, A.J., R.G. Bistline, Jr., J.K. Weil, W.C. Ault, and E.W.
Maurer, JAOCS 39:128 (1962).
f o r m u l a t i o n s , even in d r u m t y p e a u t o m a t i c washers. Such 4. Brooks, R.J., and B. Brooks, (The Chemithon Corporation),
p r o b l e m s were n o t e n c o u n t e r e d w i t h PMS. U.S. Pat. No. 3,427,342 (1964).
The disodium salts of sulfonated palm kernel fatty acids 5. Stein, W., H. Weiss, and O. Koch, (Henket & Cie), U.S. Pat. No.
and sulfonated tallow fatty acid possess m a r k e d l y lower 3,256,303 (1961).
solubility than the corresponding ES. F u r t h e r m o r e , t h e y 6. Blaser, B., W. Stein, H. Weiss, and O. Koch, (Henkel & Cie),
U.S. Pat. No. 3,158,632 (1961).
are inferior in their washing p o w e r c o m p a r e d to ES and 7. Schaafsma, B.R., Deterg. Age 1:22 (1965).
LAS. 8. Silvis, S.J., and M. Ballestra, JAOCS 40:618 (1963).
The viscosity of aqueous solutions of o t h e r surfactants, 9. Stein, W., H. Weiss, and O. Koch, (Henkel & Cie), U.S. Pat. No.
e.g. alkylbenzenesulfonates, soaps, alkyl sulfates, alkyl- 3,251,868 (1961).
10. Wulff, C., W. Stein, O. Koch, and H. Weiss, (Henkel & Cie), U.S.
ethersulfates, and ES can be lowered m a r k e d l y by the addi- Pat. No. 3,159,657 (1961).
t i o n o f the d i s o d i u m salts o f F A S (especially C10-C12) 11. Stein, W., O. Koch, and H. Weiss, (Henkel & Cie), U.S. Pat. No.
(18-20). The preparation o f such low viscosity surfactant 3,354,187 (1962).
solutions is i m p o r t a n t in the case o f liquid washing and 12. Stein, W., H. Weiss, and Oo Koch, (Henket & Cie), Brit. Pat. No.
1,063,431 (1964).
cleaning agents, and for the preparation o f detergents slur- 13. Wulff, C., W. Stein, O. Koch, and H. Weiss, (Henkel & Cie),
ries w h i c h are to be spray dried as laundry detergents. Brit. Pat. No. 1,050,534 (1963).
Detergent slurries containing ES can be spray dried t o wash- 14. Well, J.K., A.J. Stirton, R.G. Bistline, Jr., and W.C. Ault,
JAOCS 37:679 (1960).
ing powders possessing a d e q u a t e p o w d e r properties. T h e 15. A r m o u r Industrial Chemical Company, "Alpha-Sulfoalkyl
presence o f disodium salts o f F A S i m p r o v e s t h e p o w d e r Acids," Technical Bulletin G-"/(1956).
properties further. The properties o f detergent powders 16. De Boer, J.H., Recueil 71:814 (1952).
containing o t h e r surfactants, e.g. alkyl benzenesulfonates, 17o Stirton, A.J., JAOCS 39:490 (1962).
18. Stein, W., I4. Weiss, and P. Neuhausen, (Henkel & Cie), U.S. Pat.
alkane sulfonates, olefin sulfonates, alkylsulfates, alkyl- No. 3,377,289 (1964).
ethersulfates, and alcohol polyglycol ethers, can be opti- 19. Stein, W., O. Koch, and H. Weiss (Henkel & Cie), U.S. Pat. No.
mized similarly b y t h e addition o f the d i s o d i u m salts o f 3,377,290 (1963).
F A S (21-23). However, ES are n o t o n l y o f interest as raw 20. Stein, W., O. Koch, and H. Weiss (Henkel & Cie), U.S. Pat. No.
3,390,096 (1964).
materials for washing products. TMS is described in the 21. Stein, W., H. Weiss, and O. Koch, (Henkel & Cie), U.S. Pat. No.
literature as being a good lime soap dispersing agent (24). 3,351,559 (1963).
ES are suitable for the antistatic finishing o f fibers (25). 22. Stein, W., H. Weiss, and O. Koch, (Henkel & Cie), U.S. Pat. No.
Special ES and FAS can also be used as release agents for 3,345,301 (1963).
23. Stein, W., H. Weiss, and O. Koch, (Henkel & Cie), U.S. Pat. No.
rubber and p o l y u r e t h a n e elastomers (26-28). F A S possess 3,274, t 17 (1962).
good properties as emulsifiers for the emulsion polymeriza- 24. Bistline, R.G., Jr., W.R. Noble, J.K. Weil, and W.M. Linfield,
tion of PVC (29-31). Special ES with alkylpolyglycol ethers JAOCS 49:63 (1972).
have b e e n used as constituents for spin finish agents used 25. Loewenstein, A., W. Stein, H. Weiss, and O. Koch, (Henkel &
Cie), DBP No. 1,174,739 (1962).
with s y n t h e t i c fibers (32). ES and F A S w i t h d o u b l e b o n d s 26. Klement, G., H. Baurnann, H. Scheer, and E. Scheidt, (Henkel
t h a t have been chlorinated, possess g o o d properties as & Cie), DOS No. 2,042,081 (1970).
leather auxiliaries (33). ES can also be used in c o s m e t i c 27. Klement, G., H. Baumann, and E. Scheidt, (Henkel & Cie),
preparations, as surfactants in t o o t h p a s t e s and s h a m p o o s , as Belg. Pat. No. 808,886 (1972).
28. Klement, G., H. Baumann, and E. Scheidt, (Henkel & Cie), DOS
well as in m a n y o t h e r areas of application. No. 2,255,310 (1972).
Biological properties: ES and F A S can be degraded bio- 29. Kuhnen, L., (Chemische Werke Hills AG), DOS No. 1,720,430
logically easily, possess a tow acute oral t o x i c i t y , and g o o d (1968).
skin compatibility. The data for the biological properties 30. Kuhnen, L., (Chemische Werke Hi~ls AG), DOS No. 1,901,493
are s h o w n in Table VIII. (1969).
31. Jadamns, H., (Chemische Werke Hills AG), DOS No. 2,054,103
(1970).
ACKNOWLEDGMENTS 32. Clark, J.E., and M.R. Cusano, (Henkel & Cie), DOS No.
2,002,662 (1970).
Contributions to the sulfonation and bleaching processes were 33. Dieckelmann, G., J. Plapper, H. Baumann, and W. Stein,
made by H. Weiss, O. Koch, and P. Neuhausen. The washing experi- (Henkel & Cie), DOS No. 2,245,007 (1972).
ments were carried out by P. Krings, and the biological results ob-
tained by M. Potokar and R. Schmid. [Received D e c e m b e r 1, 1974]