IJARET Eco-Friendly Dyeing of Viscose Fabric

International Journal of Advanced Research in and Technology (IJARET)
International Journal of Advanced Research in Engineering Engineering
and Technology (IJARET), ISSN 0976 – 6480(Print)
ISSN 0976 – 6499(Online) Volume 1
IJARET
ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 1, Number 1, May - June (2010), © IAEME

Number 1, May - June (2010), pp. 25-37 © IAEME
© IAEME, http://www.iaeme.com/ijaret.html

ECO-FRIENDLY DYEING OF VISCOSE FABRIC WITH
REACTIVE DYES
B. J. Agarwal
Department of Textile Chemistry
Faculty of Technology and Engineering
The Maharaja Sayajirao University of Baroda, Vadodara
E-Mail: bjagarwal@yahoo.com

ABSTRACT
Water-soluble polymers have versatile applications but they are hardly used in
wet processing of cellulosic substrates (cotton, viscose, jute, etc.), particularly in dyeing.
In this paper, one such water-soluble polymer, polyacrylic acid has been synthesized,
characterized and applied to viscose fabric in conjunction with various types of reactive
dyes, namely triazinyl, vinyl sulphone, high exhaustion and bi-functional, along with
cross-linking agents, namely Glycerol-1,3-dichlorohydrin and hexamethylene tetramine-
hydroquinone respectively. One of the cross-linking agents (the former one) has been
synthesized in the laboratory and characterized. Cross-linking agent is necessary to
adhere the dye onto the cellulose macromolecule. Different process sequences have been
formulated for dyeing purpose. The dyed samples were assessed by Computer Colour
Matching system for colour strength in terms of K/S values and their fastness properties
were assessed by standard methods. All such dyeings were compared with conventional
dyed samples.
Key words: Polyacrylic acid, cross-linking agent, viscose, reactive dyes
1. INTRODUCTION
In the textile industry, ecology and economy are the two most important aspects
in the present worldwide scenario and their significance is of great importance for the
survival of the textile industry. There is an increasing demand for the minimization of
pollution load during wet processing of textiles, particularly in dyeing.

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International Journal of Advanced Research in Engineering and Technology (IJARET)

For dyeing of cellulosic substrates, the most widely used dyes are Reactive dyes.
Their popularity on the commercial scale is mainly due to their acceptable price,
brilliancy of shades, good tinctorial value and reasonably good fastness properties.
However, they suffer from several drawbacks – one of which is environmental hazards
due to the utilization of very high concentrations of exhausting agents, viz. sodium
chloride or sodium sulphate (up to 100 gpl) as well as alkali (up to 20 gpl) in its dyeing
process, which ultimately cause tremendous effluent problems. Together with this,
commercial reactive dyes give only 65-70% exhaustion of the dyebath liquor. Further, to
remove the unfixed dye, time-consuming, energy intensive and expensive washing-off
procedures are required.
Unfixed reactive dye and/or hydrolyzed dye, along with alkali used for fixation,
may also pose an environmental hazard because the hydrolyzed dye will pass in the
effluent thereby increasing the pollution load. Certain reactive dyes, like mono- and di-
chlorotriazine, or flourotriazine type of reactive dyes may cause the passage of organo-
halogen in the discharge effluent, which may by-pass the permissible discharge limit
fixed by certain countries.
The achievement of high dye fixation in a non-polluting dyeing procedure would
be of great benefit. This can be attained either by the modification of the dyeing
procedure or the substrate itself, or by the development of dyes with high fixation yields.
Treatment of cotton, viscose and other cellulosic substrates with various
chemicals prior to its dyeing has been reported in literature to improve their dyeability
with reactive dyes [1-4]. Dyeing of such pretreated fabric(s) was followed by treatment
with an alkali for the fixation of these dyes. Other approaches reported [5-11] where
some chemicals have been devised, namely Glytac A, etc. for improving the dyeability of
such cellulosic materials with reactive dyes, which is due to increased dyebath
exhaustion. In all these cases, alkaline conditions have been used for dyeing. In spite of
extensive search, very little information has been received for dyeing cotton, viscose, etc.
with reactive dyes at neutral pH. Burkinshaw et. al. [12-13] recently reported a method of
dyeing cotton using Hercosett resin pretreatments, thereby improving the substantivity
and reactivity of cotton. This facilitates dyeing process at neutral pH but lowers the light
fastness. Thus, it would be a great achievement if reactive dyes can be applied to

26


cellulosic substrates without utilization of any alkali or salt in the dyebath. In this paper,
an attempt has been made to study the modification of viscose material in order to
perform reactive dyeing even at neutral pH conditions, i.e. without utilizing salt, alkali or
any other chemical in the dyebath. For this purpose, a treatment with a highly reactive
polymer has been suggested.
2. MATERIALS & EXPERIMENTAL PROCEDURES
2.1 Materials
Plain weave viscose fabric (prepared from high twist yarn without lustre), having
following specifications, was used for the study:
Warp: 98 ends/inch
Weft: 64picks/inch
Weight: 94 g/m2
The fabric was scoured with 5 gpl non-ionic detergent (Lissapol N) and 5 gpl soda
ash at boil for 90 min. The scoured fabric was then bleached with sodium hypochlorite (3
gpl available chlorine) using pH 10 at room temperature for 1 hour and subsequently
washed thoroughly till it became neutral.
Acrylic acid monomer (A. R. grade) was used for the present investigation. Two
cross-linking agents, namely Glycerol-1,3-dichlorohydrin (CA) and hexamethylene
tetramine-hydroquinone (CB) utilized were based on non-nitrogenous and nitrogenous
type products respectively. The former cross-linking agent, Glycerol-1, 3-dichlorohydrin
has been synthesized in the laboratory. For the synthesis, Epichlorohydrin (mol. wt. 92.53
and purity 98%) and other chemicals used were of laboratory grade. Hexamethylene
tetramine-hydroquinone (HMTA-HQ) cross-linking agent used was of Analytical
Reagent grade.
Ten commercial reactive dyes, comprising of various reactive systems, viz.
monochlorotriazine (MCT), dichlorotriazine (DCT), vinyl sulphone (VS), bis-
monochlorotriazine (high exhaustion, HE) and bifunctional (ME) dyes were used without
any further purification. The reactive dyes used for the work are represented in Table 1.

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Table 1Reactive dyes used with their reactive systems and Colour Index numbers
DYE CI Reactive

Monochloro-triazine (MCT) dye
D1 Procion Brill. Red H7B Red 4
D2 Procion Blue H5R Blue 13

Dichlorotriazine (DCT) dye
D3 Procion Brilliant Red M5B Red 2
D4 Procion Brilliant Yellow MGR Yellow 7

Vinyl Sulphone (VS) dye
D5 Remazol Brilliant Violet 5R Violet 5
D6 Remazol Brilliant Red 3B Red 23

High Exhaustion (HE) Reactive dye
D7 Procion Red HE-3B Red 120
D8 Procion Orange HE-R Orange 84

Bifunctional (ME) Reactive dyes
Red 195
D9 Reactofix Red ME4BL
D10 Reactofix Blue ME2RL Blue 248
2.2 Methods
2.2.1 Polymer preparation
Polyacrylic acid was synthesized from its monomer acrylic acid by standard
polymerization process. The polymer thus formed was with viscosity average molecular
weight 3,416 and the solid content of the synthesized polymer was 48%.
2.2.2 Preparation of Glycerol-1,3-dichlorohydrin
Glycerol-1,3-dichlorohydrin was prepared by interaction of Epichlorohydrin and
Hydrochloric acid. Epichlorohydrin was gradually added to a mixture of 1 part conc. HCl
and 3 parts of 13% by weight NaCl solution at 30o C over a period of 2 hours.
2.2.3 Pretreatment
Viscose fabric was treated in liquor containing polyacrylic acid (50 gpl) and
cross-linking agent (25 gpl) and then immediately padded (to minimize the reaction
between polyacrylic acid and the individual cross-linking agent) by 2-dip-2-nip technique
(using 65% expression). After padding, the fabric was dried at an ambient temperature

28


and cured at 150o C for 4 min. The curing conditions were so chosen as these are
commercially practiced in wet processing of textiles, e.g. in wash-n-wear and pigment
dyeing/printing for cellulosic materials. The pretreated sample was rinsed with water and
dried. The mass add-on of the polyacrylic acid-CA treated sample was found to be 6.7%
and that of polyacrylic acid-CB treated sample was 8.2%.
The concentrations of polyacrylic acid and each individual cross-linking agent
CA and CB were optimized followed by the assessment of their dyeability (K/S values)
with two commercial reactive dyes, viz. CI Reactive Red 4 (MCT) and CI Reactive Red 2
(DCT) at 2% depth of shades on the pretreated samples by exhaust dyeing for 90 min at
boil (for MCT dye) and at 50o C (for DCT dye), as well as by pad-dry-cure dyeing
(curing conditions: 150o C/4 min for MCT dye and 150o C/1min for DCT dye)
techniques. In above dyeings, no alkali/salt was used. The pH of the dyebath was
maintained at 7.0 ± 0.1. After dyeing, the dyed sample was washed, soaped with a non-
ionic detergent, Lissapol N (2 gpl) and soda ash (1 gpl) at 60o C for 30 min using a liquor
ratio of 30:1, followed by thorough rinsing and drying.
2.2.4 Dyeing Procedures
After optimization, dyeing was performed with pad-dry-cure method at different
depth of shades, viz. 0.5, 1, 2, 3, and 5% respectively. Subsequently, different process
sequences were formulated and ten commercial reactive dyes containing various reactive
systems were applied on pretreated samples at 2% shade. Various dyeing sequences
adopted were:
S I – Exhaust dyeing: Pretreated sample was dyed for 90 min. at boil (for MCT, VS &
HE dyes) and at 50o C (for DCT & ME dyes)
S II – Pretreatment followed by pad-dry-cure dyeing: Pretreated sample was padded
with requisite amount of dye solution using 2-dip-2-nip technique (65 % expression),
dried and cured.
S III – Simultaneous dyeing: Sample was padded with optimized concentrations of
polyacrylic acid, cross-linking agent and dye, dried and cured.
For sequences S II and S III, curing conditions chosen were 150o C & 4 min for
MCT, VS, & HE dyes and 150o C & 1min for DCT & ME dyes, while the washing and
soaping procedures were kept same as mentioned earlier. Various dyeings were also

29


compared with conventionally dyed samples [14].
2.3 Testing and Analysis
2.3.1 Mechanical Properties
Tensile properties, namely breaking strength and elongation at break, of the
treated and untreated samples were determined on the Instron 1121 tensile tester. An
average of 10 readings was taken.
2.3.2 Determination of Nitrogen Content
Nitrogen content of the treated and untreated samples was determined on C, H, N
Analyzer (Perkin Elmer Model 240 Elemental Analyzer).
2.3.3 Evaluation of Colour Strength
The dyeing performance of various dyed samples was assessed on Data Spectra
flash SF 600 Spectrophotometer by measuring the relative colour strength (K/S value)
spectrophotometrically. These values are computer calculated from reflectance data
according to Kubelka-Munk equation [15].
2.3.4 Assessment of Fastness Properties [16]
Wash fastness was evaluated according to ISO Standard Test No.3 on Launder-O-
meter; light fastness on fade-O-meter using carbon-arc continuous illumination (BS 1006:
1987) and rub fastness (both dry as well as wet) on Crockmeter (BS 1006: No.X12;
1978).
2.3.5 Determination of Wrinkle Resistance
Wrinkle resistance (crease recovery) of the untreated and treated samples was
measured on crease recovery tester (Model: Sasmira) using standard method [16].
3. RESULTS AND DISCUSSION
Viscose fabric, treated with polyacrylic acid and cross-linking agent, was dyed
with reactive dyes (CI Reactive Red 4 and CI Reactive Red 2) without using alkali/salt,
i.e. at neutral pH (7.0 ± 0.1). Uniform dyeing was obtained. Therefore, the concentrations
of polyacrylic acid and cross-linking agents were optimized. This was carried out by
using various concentrations of polyacrylic acid (50, 100, 150, 200 and 250 gpl) and
cross-linking agent (25, 50, 75, 100 and 150 gpl) for both exhaust as well as pad-dry-cure
dyeing methods. Optimized concentrations of these three were found out individually by

30


assessing the dyeing performance in terms of K/S values (not mentioned here) of the
respective sample. It was found that optimum concentration of polyacrylic acid was 100
gpl (for exhaust dyeing process) and 150 gpl (for pad-dry-cure process), while the
optimum concentration of cross linking agent CA was 25 gpl (for both the dyeing
processes) and the respective values of cross-linking agent CB were 25 gpl (for exhaust
dyeing) and 50 gpl (for pad-dry-cure dyeing).
The morphological changes incurred in the cellulosic substrate due to such
treatment were investigated through nitrogen content determination and tensile properties
of the pretreated sample. The nitrogen content value of only polyacrylic acid treated (150
gpl/pad-dry-cure process) sample was 0.139% and those treated along with cross-linking
agent CA or CB (50 gpl) sample were 0.214% and 0.795% respectively. This higher value
of nitrogen content, particularly in case of polyacrylic acid and cross-linking agent CB
treated sample manifests the possibility of cross-linking reaction being taken place with
cellulose macromolecule.
The sample pretreated with polyacrylic acid and cross-linking agent CA (at
optimized concentration) showed 14.7 kg breaking strength and 13.6% elongation-at-
break. The respective values for polyacrylic acid and cross-linking agent CB treated
sample (at optimized concentration) are 13.3 kg and 14.2% as compared with 16.28 kg
and 12.3% breaking strength and elongation-at-break respectively for untreated sample.
The decrease in breaking strength, viz. 9.7% (in case of cross-linking agent CA) and
18.3% (in case of cross-linking agent CB) is also an indicative of cross-linking reaction
being taken place.
The optimized concentrations of polyacrylic acid and the two cross-linking agent
have been used to study their various dyeing behaviour at neutral pH. It has been
observed that pretreated fabric offered very good dyeing with pad-dry-cure dyeing
technique as compared with exhaust dyeing. Therefore, viscose fabric was subsequently
dyed by pad-dry-cure process at different depth of shades with three reactive dyes, one
each of MCT, DCT and VS groups. The results are represented in Table 2. It can be seen
that satisfactory dyeing is achieved on pretreated samples at all levels of dyeing. The dye
uptake increases with the increase in the concentration of the dye in the dyebath.
Dichlorotriazine (DCT) based dye gave best dyeing performance followed by vinyl

31


sulphone (VS) and monochlorotriazine (MCT) dyes. This in good agreement with the
observations reported in literature [14].
Table 2 Colour strength (in terms of K/S values) of viscose fabric dyed by pad-dry-cure
(S II) technique with various percent shades using different reactive dyes
Dye K/S values
Dye CI conc. Conventional Polymer-aided dyeing by S II process
Reactive (%) dyeing
P + CA P + CA
Procion Blue H5R Blue 13 0.5 2.19 1.65 (-24.65) 1.98 (-9.59)
(MCT dye) 1.0 5.86 5.11 (-12.79) 5.63 (-3.92)
2.0 12.56 11.98 (-4.61) 12.15 (-3.26)
3.0 16.29 14.25 (-12.52) 15.23 (-6.50)
5.0 22.35 20.81 (-6.89) 21.96 (-1.74)
Procion Brill. Red M5B Red 2 0.5 5.26 4.36 (-17.11) 5.12 (-2.66)
(DCT dye) 1.0 11.51 9.88 (-14.16) 10.29 (-10.59)
2.0 19.63 18.62 (-5.14) 19.11 (-2.65)
3.0 24.96 22.15 (-11.26) 24.35 (-2.44)
5.0 32.33 29.63 (-8.35) 32.68 (+1.08)
Remazol Brill. Violet 5R Violet 5 0.5 3.21 2.65 (-17.44) 3.11 (-3.11)
(VS dye) 1.0 6.89 5.86 (-14.95) 7.02 (+1.88)
2.0 12.39 11.59 (-6.45) 12.98 (+4.76)
3.0 17.86 15.66 (-12.32) 18.15 (+1.62)
5.0 25.28 21.29 (-15.78) 27.26 (-7.83)
Note: Data in parenthesis indicates percentage loss/gain over conventional dyeing.
P - Polyacrylic acid,
CA - Glycerol-1, 3-dichlorohydrin
CB - Hexamethylene tetramine-hydroquinone
The probable mechanism for fixation of reactive dyes on polyacrylic acid treated
and partially cross-linked viscose fabric may be explained as:
Viscose fabric treated with polyacrylic acid and cross-linking agents (particularly
CB type) demonstrate the introduction of a highly nucleophilic amino group (-NH2) in the
cellulosic chain. The cationic charged amino groups may be involved in the adsorption of
anionic chromophore of reactive dyes. The attachment of dye molecules onto the partially
modified cellulosic substrate is found to be through covalent bonding as no dye strips out
from dyed sample in pyridine (100%) as well as in its mixture with water (50:50).
An attempt has been made in the present investigation to commercialize this
neutral dyeing of reactive dyes on viscose. For this, ten commercial reactive dyes,
comprising of MCT, DCT, VS, bis-MCT and bifunctional groups were dyed by different
dyeing sequences as mentioned. The results are given in Table 3. Such dyeings were also

32


compared with conventionally dyed sample. No clear trend is observed from the results.
The nature as well as chemical constitution of the dye and the dyeing process utilized
also influences the dyeing performances.
Table 3 Colour strength (in terms of K/S values) of viscose fabric dyed with different
reactive dyes
K/S values for Polymer-aided dyeing
Dye CI Exhaustion (S I) Pad-dry-cure (S II) Pad-dry-cure (S III)
Reactive P + CA P + CB P+ P + CB P + CA P + CB
CA

Monochlorotriazine
dye
D1 Procion Brill. Red Red 4 4.11 4.36 10.21 10.98(-1.34) 11.26(+1.17)11.53(-3.59)
H7B (-17.47) (-12.45) (-8.26)
D2 Procion Blue H5R Blue 13 3.29 3.98 11.63 12.05(-2.90) 12.12(-2.33) 13.08(-5.39)
(-20.14) (-3.39) (-6.28)

Dichlorotriazine dye
D3 Procion Brill. Red Red 2 4.19 4.88 12.63 15.69 19.99 25.23(+28.20)
M5B (-19.73) (-6.50) (-35.82) (-20.27) (+1.57)
D4 Procion Brill. Yellow 7 4.98 5.08 7.26 8.15(-4.56) 9.25(+8.31) 12.59(+47.42)
Yellow MGR (-11.38) (-9.61) (-14.98)

Vinyl Sulphone dye
D5 Remazol Brill. Violet 5 4.63 5.13 9.23 11.54 13.63 19.86(+62.92)
Violet 5R (-11.47) (-1.91) (-25.28) (-5.33) (+11.81)
D6 Remazol Brill. Red 23 4.01 4.29 11.63 13.21 14.11 25.81(+95.67)
Red 3B (-5.64) (+0.94) (-11.82) (+0.15) (+6.97)

High Exhaustion
Reactive dye
D7 Procion Red HE- Red 120 11.96 12.92 6.12 6.48 7.23(-5.12) 7.98(+4.72)
3B (-6.56) (+0.93) (-19.68) (-14.96)
D8 Procion Orange Orange 12.15 13.66 5.86 6.23 6.98(+7.05) 7.11(+9.05)
HE-R 84 (-6.03) (+5.64) (-10.12) (-4.47)

Bifunctional Reactive
dyes
D9 Reactofix Red Red 195 13.15 14.98 8.21 9.15 10.25 12.63
ME4BL (-10.36) (+2.11) (-16.73) (-7.20) (+3.95) (+28.09)
D10 Reactofix Blue Blue 248 16.28 17.26 10.33 11.36 12.15(8.19) 15.23
ME2RL (-3.26) (+2.55) (-8.01) (+1.15) (+35.62)
It can be observed that in case of MCT, DCT and VS dyes, the colour strength of
treated sample dyed by either S I or S II are only slightly lower in comparison with the
respective conventionally dyed samples. This is due to slight lower fixation of the dye in

33


absence of alkali in S I and S II sequences. However, sample dyed by S III sequence gave
better dyeing performance (colour strength enhanced up to 63% and 96% with D5 and D6
dyes respectively for polyacrylic acid and cross-linking agent CB, and by 1% to 48% with
various other reactive dyes, with a few exceptions) over conventionally dyed samples.
The overall dyeing performance of these three dyeing sequences with MCT, DCT, VS
and ME reactive dyes can be represented as S III > S II > S I. On the other hand, a
reverse trend is observed with high exhaust (bis-monochlorotriazine/HE type) and
bifunctional (ME type) reactive dyes for obvious reason of their high reactivity as well as
the nature of the dye. With these dyes, the observed dyeing performance is represented as
S I > S III > S II. The reason for such behaviour may be attributed to the fact that in S III
sequence, the dye molecule and cross-linking agent molecule compete with each other to
combine with either cellulosic hydroxyl group or with the groups on the polymeric chain.
The reactive dye is capable of combining with hydroxyl group of cellulose via covalent
bond formation, which varies from dye to dye depending upon their reactivity. The
unfixed reactive dye molecules also get linked with the polymeric chain at the curing
stage. This results in increased colour strength during S III sequence.
The fastness properties of all such dyed sample are quite satisfactory and
comparable with conventionally dyed sample (Table 4). However, in polymer-aided
exhaust dyeing process (S I), there is slight impairment in the light fastness for some of
the dyes, particularly DCT dyes.
Improved wrinkle recovery is expected due to occurrence of cross-linking
reactions as manifested earlier. The dry crease recovery angle (DCRA) values of the
polymer-aided dyed samples were 133o (S I), 135o (S II) and 129o (S III) for Glycerol-1,3-
dichlorohydrin (CA) cross linking agent and 131o (S I), 132o (S II) and 130o (S III) for
hexamethylene tetramine-hydroquinone (CB) cross-linking agent, while that of bleached
(untreated) and treated (undyed) samples are 95o and 109o respectively. The DCRA for
conventionally dyed sample were 115o (exhaust dyeing) and 117o (pad-dry-cure)
respectively. Therefore, the polymer-aided dyed samples indicate an improvement in the
wrinkle recovery for obvious reason. In sequence S III, the extent of cross-linking is
restricted because of the process involved, thereby offering comparatively less DCRA
values.

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Table 4 Fastness properties of viscose fabric dyed with various reactive dyes
Fastness grades for Polymer-aided dyeing
Exhaustion (SI) Pad-dry-cure (SII) Pad-dry-cure (SIII)
CI
Dye Reac P + CA P + CB P + CA P + CB P + CA P + CB
tive W L R WL R WL R WL R WL R W L R
Dr We Dr We Dr We Dr We Dr We Dr We
y t y t y t y t y t y t
Monochloro-
triazine dye
D1 Procion Brill. Red 4 4-5 5 5 4-5 4- 5 5 7 5 7 4 3-4 5 7 4 3-4 4 7 4-5 4-5 5 7 4-5 4-5
Red H7B - 5 -
6 6
D3 Procion Blue Blue 4-5 5 5 4-5 4- 5 4-5 7 4- 7 4 4 4- 7 4 4 4 7 4 4 4-5 7 4 4
H5R 13 - 5 - 5 5
6 6

Dichlorotriazin
e dye
D3 Procion Brill. Red 2 5 4 5 4-5 5 4 5 7 5 7 4 4 5 7 4 4 5 7 4-5 4-5 5 7 4-5 4-5
Red M5B - -
5 5
D4 Procion Brill. Yello 4-5 4 5 4-5 4- 4 4-5 6-7 4- 6 4 4 4- 6 4 4 5 7 4-5 4-5 5 7 4-5 4-5
Yellow MGR w7 5 - 5 - 5 -
5 7 7

Vinyl Sulphone
dye
D5 Remazol Viole 4-5 6 5 5 4- 6 4-5 7 5 7 4 5 4- 7 4-5 4 4- 7 4-5 4-5 4-5 7 4-5 4-5
Brill. Violet 5R t 5 5 - 5 5
7
D6 Remazol Red 4-5 6 5 4-5 4 6 5 7 4- 7 4 4-5 5 7 4-5 4 4- 6 4-5 4 4-5 6-7 4-5 4
Brill. Red 3B 23 - 5 5 -
7 7

High
Exhaustion
Reactive dye
D7 Procion Red Red 5 7 5 5 5 7 5 7 5 7 5 4-5 5 7 5 4-5 5 7 5 4-5 5 7 5 4-5
HE-3B 120
D8 Procion Oran 5 7 5 5 5 7 5 7 5 7 5 4-5 5 7 5 4-5 5 7 5 4-5 5 7 5 4-5
Orange HE-R ge 84

Bifunctional
Reactive dyes
D9 Reactofix Red 5 6 5 5 4- 7 5 4-5 5 6 4-5 5 5 6 4 4-5 5 6- 4 4 5 6-7 4 5
Red ME4BL 195 - 5 - - 7
7 7 7
D10 Reactofix Blue 4-5 6 5 4-5 4- 7 5 4-5 5 7 4 5 5 6 4-5 4 5 7 4 5 5 7 4 4
Blue ME2RL 248 5 -
7
W = Washing fastness, L = Light fastness, R = Rubbing fastness.

35


P - Polyacrylic acid, CA - Glycerol-1, 3-dichlorohydrin, CB - Hexamethylene tetramine-
hydroquinone
CONCLUSIONS
Viscose fabric was pretreated with polyacrylic acid and cross-linked with either
CA or CB cross-linking agents by pad-dry-cure (at 150o C for 4 min) technique. The
optimum concentration for polyacrylic acid was found to be 100 gpl (for exhaust dyeing)
and 150 gpl (for pad-dry-cure dyeing) and that for CA cross-linking agent was 25 gpl (for
either dyeing method) and for CB cross-linking agent were 25 gpl and 50gpl respectively
for exhaust and pad-dry-cure dyeing techniques respectively. The morphological changes
indicate cross-linking reaction through higher nitrogen content (0.214% with CA cross-
linking agent and 0.795% with CB cross-linking agent), and also decrease in tensile
strength by 9.7% with CA and 18.3% with CB cross-linking agents respectively.
Such pretreated and partially cross-linked viscose fabric can successfully be dyed
with various types of reactive dyes by different process sequences. The colour strength of
all the dyed samples was adequate and quite comparable with conventionally dyed
samples. The polymer (polyacrylic acid)-aided dyeing was better when hexamethylene
tetramine-hydroquinone (CB) was used as the cross-linking agent as compared to
Glycerol-1,3-dichlorohydrin (CA) cross linking agent. In case of simultaneous dyeing
(SIII), the dye-uptake was about 1 – 96% (in case of DCT, VS and ME dyes) and up to
10% (in case of MCT and HE dyes) higher with respect to their conventionally dyed
samples. The plausible dyeing mechanism revealed covalent bond formation. The
fastness properties of such dyeings were very good. The dyed fabric also exhibited very
encouraging wrinkle recovery, which may replace even the subsequent wash-n-wear
treatment. The fabric so dyed did not utilize any salt or alkali during dyeing. So it may be
considered as Green processing of textiles without any pollution problem.
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13. S. M. Burkinshaw, X. P. Lei and D. M. Lewis (1990), Journal of Society of Dyers &
Colourist, 106, pp. 307.
14. E. R. Trotman (1975), “Dyeing and Chemical Technology of Textile Fibres”, 5th
Edition, Charles Griffin and Company Ltd.; London and High Wycombe, pp.540.
15. F. W. Billmeyer Jr., and M. Saltzman (1981), “Principles of Colour Technology”,
2nd Edition; John Wiley & Sons: New York; pp.140.
16. J. E. Booth (1987), “Principles of Textile Testing”, Butterworth Scientific
Publishers: London.

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