Introduction to Textile Dyeing

Basic Textile Terms and Definitions

Dyestuff is organic or inorganic substances

which can absorb light and reflect some lights
to show color.

Pigment is a substance that can absorb light

and reflect some lights to show color but it is
water insoluble substances. Normally it is
used for printing (with the presence of binder)

Staining is an unpleasant of dyeing in the

area that we do not want. 2
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 Theory of Dyeing

Forces responsible
1. Force of repulsion which are developed
between the dye molecules and water.

2. Force of attraction which are developed

between the dye molecules and fibres.

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 Phases of Dyeing process

1. Attachment of the dye molecule to the

surface of the fiber

2. Penetration into the intermolecular spaces

as well as diffusion through the fiber

3. Orientation (and fixation) along the long

chain molecules

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Rate Of Dyeing:
1. concentration of dye
2. Temperature
3. presence of electrolytes
4. Material to liquor ratio(The rate of dyeing decreases with
increasing ratio of goods to liquor)

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 Classification of Dyestuffs
Dyestuffs can be classified by many methods
as follows:
1. by their ionic (e.g. cationic, anionic and
non-ionic)
2. by their fiber dyeabilities (e.g. on
cellulosic, protein, polyester, polyamide etc.)
3. by their names (e.g. acid, direct, disperse,
reactive, basic etc.)
4. by their chemical structures (e.g. azo,
anthraquinone
5. by their origins (e.g. natural, synthetic)
6. by their colors (e.g. red, green, black etc.)
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 Choice of dye

??
1. Cost
2. Non-toxic
3. Compatible to other dyes and chemicals
4. High color strength
5. Better brightness
6. Better fastness
7. Good levelness on the materials

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 Dyeing Methods

1. Mass-coloration

Advantage &
Disadvantage?

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2. Fiber Dyeing
dyeing fibers before blending with other
colors to give fancy yarns or fabrics.

Advantage &
Disadvantage? 15
3. Yarn Dyeing
Dyeing yarns in forms of hanks or packages
dyeing. This will give Scottish’s style
fabrics, carpet with many colors and styles.

Advantage &
Disadvantage? 16
4. Fabric Dyeing
Dyeing after weaving, knitting, or non-woven to
make fabrics. This is very popular method of
dyeing as the dyed fabrics will be processed
further to garment industries very easily.

fabric dyeing can be used in 2 ways:

a. Open width form using the fabrics to spread

without any creases and dye them.

b. Rope form using the fabrics with the form like

a rope (many creases and look like “a rope”) 17
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 5.Garment Dyeing
The types of apparel that can be dyed are
mostly non-tailored and simpler forms, such
as sweaters, sweatshirts,T-shirts,hosiery, and
panty hose.

Advantage &
Disadvantage? 19
Garment dyeing is done by placing a suitable number of garments (usually
about24 sweaters or the equivalent, depending on the weight) into large
nylon net bag. The garments are loosely packed. From 10 to 50 of the bags
are placed in large tubs containing the dye bath and kept agitated by a
motor– driven paddle in the dye tub. The machine is appropriately called a
paddle dryer

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 Exhaustion Dyeing Process
This method is using lot of water as shown
in “Liquor Ratio This should immerse the
goods into dye solution for a long time in
order to let the dye penetrate into the goods.

Advantage: inexpensive, no need to train the

worker to look after and run them properly.

Disadvantage: lots of water needed, very

slow process (60-120 min/batch.),More
waste water
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Continuous Process
This method is designed by putting different
machinery into a sequence so that it can
produce the dyed fabric in one pass.

Advantage: very fast process (10-100

m/min), small amount of water in the
process.

Disadvantage: very expensive, need to train

the worker to look after and run them
properly.
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Name of Dyestuffs Fibers that can be dyed
Acid Silk, wool, polyamide,
Azoic Cotton
Basic Acrylic
Direct Cellulosic, viscose
Disperse Acetate, triacetate,
polyamide, polyester,
acrylic
Reactive Cellulosic, viscose,
protein
Vat Cellulosic
Sulphur Cellulosic
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 Direct Dyes (Anionic)

They can be dyed directly on cellulosic

fibers. When the fibers are immersed in
water, it will show anionic charge which
repel the dyes.

Adding salt into the dye bath, it will reduce

anionic on the fibers so the dyes can get
closer and adsorb into the fibers.

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 Direct Dyes (Anionic)
Properties:

1. Direct application(readily water soluble) mainly

on cellulosic fibres to get bright deep colors
having a complete color range.
2. Common salt or Glauber‟s salt (Sodium
sulphate) added to improve dye exhaustion
3. Have moderate washing fastness and light
fastness
4. Mainly used to dye products going with fewer
washes. T-shirts,curtains

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Yellow Pink Brown Turquoise

Orange Red Violet Black

Forrest
Fushia Grey Green
Green

Scarlet Blue Wine China Blue

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 Direct Dyes (Anionic)
The Effected factors :

 Electrolytes → to promote exhaustion of direct dyes

 Temperature → Gradual Increase of temperature
improves dye migration
 liquor ratio → Dyeing in short-liquor ratio
 pH value → applied from a neutral solution

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 Direct Dyes (Anionic)
After treatments:
1. Diazotisation
Certain direct dyes having a base structure that
chemically combines with “Napthol” to form an
insoluble Azoic dyes

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 Direct Dyes (Anionic)
After treatments:
2. Copper treatment
Treatment with CuSo4 and HAC,will form a copper
metal complex having a larger size dye molecules within
the fibre
Mainly to navy and balck shades

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 Direct Dyes (Anionic)
After treatments:
3. Cationic agents
involves precipitation of anionic dyes in the cotton with
a cationic surfactant or polymer in warm water.

It tends to reduce the fastness to light of the dyeing.

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 Acid Dyes(Anionic)

Needs acidic dyeing condition.

It can be dyed on protein fibres (silk, wool,
other animal fibres) and on polyamide fibres.

Acidic condition will give the fibers a

positive charge. As the negative charge will
attach directly to positive charge, and
penetrate into the fibers.

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 Acid Dyes (Anionic)
Properties:

1. Acid dyestuff is soluble in water and easily

applied on wool, silk and nylon fibres

2. These dyes are generally applied in the presence

of acids like sulphuric, acetic orformic acid

3. The dyed acid colors have good light fastness

and moderate washing fastness.And leveling
characteristic

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 Acid Dyes (Anionic)
Sub Classes:

a) Simple Acid Dyes

b) Metal Complex Acid Dyes

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 Acid Dyes (Anionic)
a. Simple Acid Dyes

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 Acid Dyes (Anionic)
Simple Acid Dyes Properties

Wash Fastness 2-3 for good levelling acid dyes

3-4 with average levelling acid dyes
4-5 with poor levelling acid dyes

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 Acid Dyes (Anionic)
b. Metal complex(pre-metallised) Acid Dyes

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 Acid Dyes (Anionic)
Metal complex(pre-metallised) Acid Dyes Properties

Excellent light-fastness even in the pale shades

Medium washing fastness.
Shows very good level dyeing and penetration characteristics.

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 Acid Dyes (Anionic)
The Effected factors :

 Strong acidic condition → to promote dye exhaustion

 Temperature → Gradual Increase of temperature
improves dye migration
 Glauber’s salt(Na2SO4.10H2O) → retarding/leveling
agent

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 Basic Dyes(Cationic)

Basic dyes(cationic dyes)) are salts of organic bases. Basic

dye molecules become positively charged when it is ionized
in a solution.

Basic dyes are used for dyeing wool, silk, and acrylic and
modacrylic fibre

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 Basic Dyes (Cationic)
Properties:
1. Brilliant colors can be obtained than any other dye class

2. Sparingly soluble in water.(HAC used to improve solubility)

3. The basic dyes are poor fastness to light and vary with regard to
washing fastness from poor to moderate-Do back Tanning

4. The basic dyestuff will combine with direct or sulphur or some acid
dyestuffs. Sothey cannot be used together in the same bath.

5. Basic dyes are used for woolen goods when particularly bright
shades are requiredwhich cannot be obtained with an acid dyes

6. Special cationic dyes are available for dyeing acrylic fibre

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 Reactive Dyes (Anionic)

They can be dyed on mainly on cellulosic fibers. It can also be used in

printing due to high fastness properties. The mechanism is nearly the
same as described in Direct dyes.

Advantage: high wet fastness due to covalent bonding (Chemical

Bonding) between fibers and dyes, easily dyed on fibers
Disadvantage: Expensive

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 Reactive Dyes (Anionic)
Properties:

1. Excellent Wash and good Light fastness

2. Negative effect for acids
3. Wide range of colors
4. Easy to hydrolysis

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Reason of Popularity
 Ability to produce bright shades of wide
range.
 High leveling quality.
 Good washing fastness.
 Good light fastness.
 Simple dyeing method therefore one stage
dyeing.
 Low temperature dyeing (below 1000C)
 Lower cost, i.e. cheaper.

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• A dye, which is capable of reacting chemically
with a substrate to form a covalent dye substrate
linkage, is known as reactive dye.
• Here the dye contains a reactive group and this
reactive group makes covalent bond with the
fiber polymer and act as an integral part of fiber.
• Reactive dyes are so called because this is the
only type of dye, which has reactive group, and
that reactive group reacts chemically with fiber
polymer molecules and form covalent bond.
 Full Colour Gamut
 Brilliant, bright colours
 Colvalent fixation → high WashFastness (WF)
 Varying reactivities
◦ Various temperatures
including low energy (cold dyeing)
 Various methods of application
 Inexpensive to apply (but dyes expensive)
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 Exhaustion of dye in presence of electrolyte
or dye absorption.
 Fixation under the influence of alkali.
 wash-off the unfixed dye from material
surface.
1) pH of the dye bath
2) Amount of alkali
3) Dyeing temperature
4) Electrolyte concentration
5) Time of dyeing
6) Liquor ratio
On the basis of dyeing temperature:

a) Cold brand:
These types of dyes contain reactive group of
high reactivity. So dyeing can be done in
lower temperature i.e. 30-400C.

For example: PROCION M, LIVAFIX E.

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 b) Medium brand:
This type of dyes contains reactive groups of
moderate reactivity. So dyeing is done in
higher temperature than that of cold brand
dyes i.e. in between 60-70 0C temperatures.

For example, Remazol, Livafix are medium

brand dyes.

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 c) Hot brand:
This type of dye contains reactive groups of
least reactivity. So high temperature is
required for dyeing i.e. 70-900 C temperature
is required for dyeing.

For example PRICION H, CIBACRON are hot

brand dyes.

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Typical dyeing conditions for a bifunctional
monochlorotriazine dye
(Procion Red H-3B, C.I. Reactive Red 3) -
Hot Brand dye

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 Continuous
◦ eg. Pad - Thermofix
 Semi-Continuous
◦ eg. Pad - Batch
 Batchwise Exhaustion *
◦ eg. Winch, Jet, Package and Beam Dyeing
 Printing
◦ eg. Print - Thermofix
 Uneven Dyeing
 Batch to Batch Shade variation
 Patchy dyeing effect
 Roll to roll variation or Meter to Meter
variation
 Crease mark
 Dye spot
 Wrinkle mark
 Softener Mark
 VAT Dyes(Anionic when soluble)

The dye is named from the container (Vat)

that used for rotting the dye with alkali
solution. This crucial process will reduce the
dye from insoluble to soluble dye.

The fiber most readily colored with Vat dyes

are the natural and man made cellulose fibres
of cotton, viscose rayon of high quality
goods

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 VAT Dyes(Anionic when soluble)
Properties:

1. insoluble in water .
2. excellent washing and light fastness
3. expensive compared to other dye classes

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 VAT Dyes(Anionic when soluble)
Vat dyes being insoluble in water, cannot be directly
applied to textile materials. They have to be
converted into water soluble form having affinity
for textile fibres such as cellulose fibres.

This conversion is usually brought about in two steps:

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 Conversion of CI Vat Red 42

Reduction Na+

Oxidation NaOH
Na+

Dye form(Insoluble) Leuco form(Alkali soluble) Salt form(Water soluble)

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 VAT Dyes(Anionic when soluble)

Principles of application of Vat Dyes

1. Vatting
2. Dyeing
3. Oxidation
4. After Treatments-Soaping off

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 Solubilised vat dyes (indigosols)

Properties:

1. Soluble in Water
2. Vatting operation is not necessary and hence can
be applied directly in the bath
3. Solubilised vat dye have less affinity for the
fibres
4. Suitable for light and medium depths
5. Posses a good coverage and leveling properties

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 Sulfur Dye (Anionic when soluble)

The dyeing process has the same process as described in the

vat dye except that using Sodium sulfide instead of Sodium
hydrosulphite.

Applied on Cellulosic fibres

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 Sulphur Dyes(Anionic when soluble)
Properties:

1. insoluble in water.
2. Moderate wash & light fastness
3. Color range is limited to black,blue,brown
4. Popular for dark sulphur colors of navy and
black due to relatively low cost

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 Non-ionic organic coloring substances which
are insoluble in water.
 Developed for synthetic fibers which are
hydrophobic.
 Disperse dyes were developed because these
fibers were not dyed with any other dye.
 Polyester fibers have more crystalline region
which are closely packed (more compact
structure).
 On the other hand disperse dye molecule size
is smaller, that is why disperse dyes are used
for these fibers.
 Polyester fibers are extremely crystalline and
hydrophobic that is why difficult to dye with
medium or dark shades even by dyeing at the
boil.

 In order to obtain medium to dark shades,

carrier method or high temperature dyeing
techniques are used.
 There are three methods of disperse dyeing

Carrier Method
(at 100°C temp.)

High Temperature Method/HT Method

(at 120-130°C temp. without carrier)

Thermosol or Thermo fixation Method with high

temperature
 Due to extremely crystalline and hydrophobic
nature, it is difficult to obtain dark shades by
conventional dyeing methods, even when the
dyeing is carried out at boil of the dye liquor.

 Then certain organic compounds were

discovered that assisted the disperse dye
molecules to enter the polyester dyes to enter
the polyester fiber polymer resulting in dark
shades.
 Actually carriers enter the polyester fiber and
open (swells which results in easy water
diffusion) its structure so that dye molecules
easily penetrate into it.

 Also gives the transportation to the disperse

dye molecules means accelerates the rate of
dyeing.
 High cost of carrier.

 Difficult to remove carrier completely from the dyed fabric

which creates odor.

 Spotting problems (due to adherence of carrier particles).

 Pollution problems.

 Carrier (if remain in fabric) adversely affect light fastness

properties of dyed fabrics.
 This dyeing is carried out at high temp. (130°C)
and high pressure (0 to 170 kPa) instead of at
boil.
 Also called high pressure dyeing.
 High temp. and pressure causes the polyester
fiber to swell and helps in deep penetration of
the disperse dye molecules into the fiber polymer
system.
 Eliminates the need of carrier and results in lower
cost and unpleasant odor.
 Reduction in dyeing time.

 No carrier cost.

 Complete penetration of dye molecules in polyester.

 Dark and heavy shades easily produced.

 Exhaustion of dye molecules is rapid.

 High temp. is used in dyeing of polyester fiber
under the name of “Thermosol Process”.
 When polyester is heated to high tem. (200-
230°C), it is softened and its internal structure
is opened up.
 The dye molecules can now diffuse into the
fiber very easily.
 The diffusion of the dye molecules takes place
with in few seconds to one minute.
 RC process is simply a washing process in
disperse dyeing for removing unfix dye from
the surface of the textile material after dyeing.
 Three substances are used in this process:
Caustic Soda
Sodium Hydrosulphite
 Detergent/Soap
 Treat the fabric at 60°C for 15 min.
 Washing Fastness:
Disperse dyed textile materials show moderate to
good washing fastness (due to partly insolubility of
disperse dye molecules and partly to the hydrophobic
nature of the fibers to which disperse dye are usually
applied).

 Light Fastness:
Show fair to good light fastness properties (may be
attributed in part to the non-polar nature of the dye
molecule which will not readily attract water
molecules and other polar agents that may have a
degrading effect.