This document summarizes a study on dyeing cotton with reactive dyes without the use of salt or alkali. Conventionally, reactive dyeing of cotton requires alkali and salt. The study explores pretreating cotton with polyacrylamide, which introduces amide groups to the cotton's cellulose structure. This allows the cotton to behave similarly to wool and take up reactive dyes at neutral pH without salt or alkali. The pretreated cotton was dyed with various reactive dyes and showed good color fastness properties comparable to conventional dyeing. Dye exhaustion and color strength were also improved with the polyacrylamide pretreatment compared to untreated cotton.

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Salt & Alkali Free Reactive
Dyeing On Cotton
By: R. Nithyanandan and M. Subramanian
Senthil Kannan

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Salt & Alkali Free Reactive
Dyeing On Cotton
By: R. Nithyanandan and M. Subramanian Senthil Kannan
ABSTRACT
In conventional Method of dyeing of cotton with reactive dyes, alkali P
H
is should maintain in
the dye bath. This method requires more electrolytes for exhaustion and alkali for fixation. In
this paper the fibre modification technique based on polyacrylamide was discussed. When the
fabric is treated with polyacrylamide, the primary hydroxyl groups of cellulose is (partially)
modified into a amide groups, which intern leads the cellulose to act like as wool fibre and
hence reactive dyes can be dyed on cotton at neutral PH
in the absence of electrolyte and
alkali.
INTRODUCTION
In current practice, cellulosic fibres are predominantly dyed with reactive dyes in the presence
of a considerable amount of salt and fixed under alkaline conditions. However, dye fixation
efficiency on cellulosic fibres is generally low (varying from 50 – 90%). This, results in a highly
coloured dye effluent, which is unfavorable on environmental grounds. Furthermore, the high
concentrations (40 – 100g/I) of electrolyte and alkali (5 – 20 g/I) required in cellulose fiber
dyeing may pose additional effluent problems.
In this work, a new fiber –modification technique based on cationic acrylic copolymer.
Pretreatment of cellulosic fiber with Polymer is believed to offer an opportunity for increasing
both the substantivity and reactivity of fibers towards reactive dyes under neutral conditions.
The nature of a reactive polymer resin is such that it may react with nucleophilic sites in
cellulosic fibers or in the polymer itself, thus fixing the polymer to the substrate. During
subsequent dyeing, further reactions between the polymer and the dyestuff, the fiber and the
dyestuff, and the fibre and the polymer and can be expected to take place, forming crosslink
within the fibers.
MATERIALS AND METHODS:
MATERIALS:
Plain fabric of count 32 of warp and weft is used throughout the process. The weight of the
fabric is 123 GSM, its cover factor is 21.63, and Ends/inch is 98, Picks/ inch is 64.
Were Polyacrylamide resin, reactive dyes, Remazol Brill.Orange 3 R, Remazol Brill.Red 5B,
Remazol Brill.Violet 5R, Remazol Turquiose Blue G, Procion Red M5B, Cibacron Green LS –
3 B, Cibacron Navy LS – G, Cibacron Red FN – R Cibacron Yellow FN – R are used.
METHODS:
The material is first Desized using enzyme, scoured with caustic soda and then bleached with
hydrogen peroxide. The fabric neutralized and goes for dyeing.
DYEING
CONVENTIONAL METHOD:
The dye bath is set with calculated amount of dye solution and water using MLR 1:20. Enter
the wetted well bleached fabric into the bath, raise the temperature to 40o
c and work for 10
min then add the calculated quantity of salt in three portions at regular intervals (10 min).
Raise the temperature to 50 o
c and continue dyeing for 30 min, add the calculated quantity of
soda ash and continue the dyeing for further 30 min. Finally take the material out, wash the
material with cold water and then give soaping treatment to remove the unfixed dyestuffs and
chemicals. The dyeing temperature and recipe of various reactive dyes are shown in table 1

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Table no: 1
Note:
Incase of vinylsulphone reactive dyes neutralization is very important before soaping.
Neutralization is carried out with 0.5% Hcl at room temperature.
FIBRE MODIFICATION TECHNIQUE
Treatment with polyacrylamide:
Pad the material with calculated quantity of polyacrylamide and water with 70% expression.
After padding the material is dried at ambient temperature and then cured at 120o
c for 7 min.
Dyeing of pretreated fabric:
Set the bath with calculated amount of dye solution and water. Enter the pretreated fabric into
the bath. Raise the temperature to a specified level at 1.5o
c / min, and dyeing continue at the
set temperature for the further 60 min. Finally take out the material, soaped thoroughly and
washed with cold water and dried.
RESULTS:
Determination of fastness to washing:
The wash fastness was tested following ISO (standards) test no: 2
Table 2: Wash fastness values.
Determination of fastness to light:
The light fastness was tested following ISO (standards) test no: 2
Table 3: Light fastness values.
S.No Dyes Salt Dyeing Temperature Soda ash
1
2
3
4
DCT
Vinylsulphone
Cibacron Ls
Cibacron Fn
50 g/l
50 g/l
25 g/l
50 g/l
Room temperature
60o
c
70o
c
60o
c
15 g/l
15 g/l
7 g/l
15 g/l
Dye stuff C.I
Reactive
Untreated Treated
Remazol Brill.Orange 3 R
Remazol Brill.Red 5B
Remazol Brill.Violet 5R
Remazol Turquiose Blue G
Procion Red M5B
Cibacron Green LS – 3 B
Cibacron Navy LS - G
Cibacron Red FN – R
Cibacron Yellow FN – R
Orange 7
Red 21
Violet 5
Blue 21
Red 2
-
-
-
-
5
5
5
5
5
5
5
5
5
5
5
4 - 5
4 -5
4 - 5
5
5
5
5

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Determination of colour strength (k/s):
The colour strength which is a measure using spectrophotometer using KUBELKA – MUNK
FUNCTION. K/S = (1 – R)2
/2R
Where, R = Reflectance value at wave length of maximum absorption.
K =Absorption co – efficient
S = Scattering co – efficient
Table 4: The colour strength values
Dye stuff C.I
Reactive
Untreated Treated
Remazol Brill.Orange 3 R
Remazol Brill.Red 5B
Remazol Brill.Violet 5R
Remazol Turquiose Blue G
Procion Red M5B
Cibacron Green LS – 3 B
Cibacron Navy LS - G
Cibacron Red FN – R
Cibacron Yellow FN – R
Orange 7
Red 21
Violet 5
Blue 21
Red 2
__
__
__
__
7 - 8
8
8
8
8
7 – 8
8
8
7 - 8
7 – 8
7 – 8
7
7 –8
8
7 – 8
8
8
7 - 8
Dye stuff
C.I
Reactive
Dye
conc.
%
Untreate
d
Treated
Remazol Brill.Orange 3 R
Remazol Brill.Red 5B
Remazol Brill.Violet 5R
Remazol Turquiose Blue G
Procion Red M5B
Cibacron Green LS – 3 B
Cibacron Navy LS - G
Cibacron Red FN – R
Cibacron Yellow FN – R
Orange 7
Red 21
Violet 5
Blue 21
Red 2
__
__
__
__
1.0
2.0
3.0
1.0
2.0
3.0
1.0
2.0
3.0
1.0
2.0
3.0
1.0
2.0
3.0
1.0
2.0
3.0
1.0
2.0
3.0
1.0
2.0
3.0
1.0
2.0
3.0
7.76
11.56
14.86
8.69
13.98
21.45
6.89
12.52
15.93
6.96
14.12
17.86
15.06
19.77
20.25
14.78
19.06
23.06
11.79
15.86
18.95
15.06
20.03
24.12
13.93
18.79
20.03
8.03
12.11
15.12
9.82
15.03
24.03
7.79
13.97
16.03
7.72
14.98
17.98
16.77
20.80
21.03
15.62
19.98
24.02
12.34
16.04
20.01
15.94
21.12
25.98
13.98
19.56
20.68

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DISCUSSION:
The probable mechanism for the fixation of reactive dye on the polymer treated cotton sustain
may be expressed as follows:
The pretreatment of cotton fabric with polyacrylamide demonstrates the introduction of
functional amino groups which increase the substantivity and also the reactivity of cotton. The
cationic charged amino groups may be involved in the adsorption of anionic chromophore of
reactive dyes.
Structure of polyacrylamide
Reaction
Cellulose Polyacrylamide
The improved dye ability is postulated due to the presence of amide groups (-CONH2)
available from the polyacrylamide which also tents to improve the reactivity of cellulosic
substrate. The attachment of the dye molecules onto the partially-modified cellulosic substrate
is by covalent bonding since no dyes strips out from the dyed sample. This is also indicative
through the fastness properties wash fastness.
The fastness values (given in table 1 and 2) of all such dyed samples are quite satisfactory
and comparable with those of conventional dyed samples. The dry crease recovery angle
values of the polymer treated samples are 80 o
while that of conventional dyed sample is 68 o.
Therefore, as expected, the polymer treated dyed samples indicate an improvement in the
wrinkle recovery.
A high level of dye exhaustion on the treated fabric can be achieve in the absence of salt and
alkali at a temperature as low as (Normally at 60-80o
c) that used in the conventional dyeing
process. Further increases in temperature may improve dye bath exhaustion, but only to a
limited extent. However higher temperatures (90-100
o
c) are generally recommended for
dyeing modified fabrics to obtain better penetration and fixation.
CONCLUSIONS:
Pretreatment of cotton with polyacrylamide enhances the possibility of dyeing cotton at
neutral pH with various commercial reactive dyes. Such pretreatment, as applied through pad
– dry – cure process, brings about some chemical changes in the treated fabric.

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Fastness properties are adequate and quite comparable with conventionally dyed samples.
The wrinkle resistance of the dyed fabric also improves. The dyeing of cotton with reactive
dyes using polyacrylamide in the dye bath improves the dye ability of cellulosic fabrics with
reactive dyes and reducing effluent discharge.
When dyeing the modified substrates, reactive dyes can be much more efficiently exhausted
and fixed onto cellulosic fabrics under neutral conditions in the absence of salt. The
modifications show an overall suitability for different reactive dyes. The modified dyeing do
not suffer either from a significant drop in light fastness, wash fastness or from duller shades.
REFERENCES:
1) Burkinshaw , S.M.,Lei,X .P., and Lewis, D.M. Modification of Cotton to Improve its
Dyebility , Part I : Pretreating Cotton with Reactive Polyamide - epichlorohydrin
Resin. J,Soc.Dyers Colour.105 (11),391 – 398 (1989)
2) Burkinshaw , S.M.,Lei,X .P., Lewis, D.M., Easton, J.R., Parton, B., and Philips,
D.A.s., Modification of Cotton to improve its Dye ability, Part 2: Pretreating Cotton
with a Thiourea Derivative of Polyamide – epichlorohydrin Resins, J.Soc.Dyers and
Colours.106 (10),307 – 315 (1990)
3) Booth J.E, principles of textile testing, [Butterworth scientific publishers, London,
1987.
4) Bhattacharya S.D.& B.J Agarwal , A novel technique of cotton dyeing at reactive dyes
at neutral pH , IJF & TR ,vol 26, Dec 2001, PP 418 - 424
5) Cai.Y, M.T.Pailthorpe and S.K.David , A new method of improving the dye ability of
cotton with reactive dyes, TRJ (440 – 446).
6) Lewis, D.M.. New Possibilities to improve Cellulose Fibre Dyeing Processes with
fibre- reactive systems:J .Soc.Dyers Colour .106 (11), 352 – 357 (1990).
7) Lewis, D.M.,and Lei, X.P., New methods of improving the dye ability of cellulose
Fibres with reactive dyes, J.Soc.Dyers colour . 107 (3), 102- 109 (1991)
8) Texincon,vol 14, No 2, Page no 14.(World Textile Abstract)
About the Author:
M. Subramanian Senthil Kannan is presently working as a KAM Executive
in Consumer Testing Services, SGS India (P) Ltd, Bangalore. He is a
Textile Graduate from Bannari Amman Institute of Technology, Tamilnadu.
He has obtained his master’s degree in Textile Technology from PSG
college of Technology, Coimbatore, Tamilnadu. He is a gold medalist in
both of his UG and PG programmes. He has published around 60 articles
in various national and international journals. He has also presented many
technical papers in various national level symposia and in various national
& international conferences. He has won several prizes in paper & poster presentations and
quiz competitions in both national and international levels. He has got one and half years of
experience in R& D in spinning and weaving and one year in Quality assurance in Spinning.
Email: senthilkannan@gmail.com