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By: Sankar Ray Maulik Dyeing of Cotton Fabric with Pigment Colour

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Dyeing of Cotton Fabric with Pigment Colour

By: Sankar Ray Maulik

Dyeing of Cotton Fabric with Pigment ColourBy: Sankar Ray Maulik1. Introduction Cotton fibre can chiefly be dyed with direct, reactive, vat, sulphur and azoic classes of dyestuffs. In textile applications this environment friendly fibre has some distinct advantages like moderate dry and wet tensile strength, appreciable moisture regain, moderate extensibility and soft feel, which makes it suitable for apparel and diversified applications. Chemical modification of cotton to improve its affinity for acid and reactive classes of dyestuffs and as well as natural colourants has received considerable attention in recent years [1-4]. Most of these modifications were based on the introduction of cationic groups in the form of quaternary, tertiary or secondary amino residues in the molecular structure of cotton cellulose. Unlike this, research works related to the application of pigment on cotton cellulose through an exhaust technique was scanty [5-7]. Pigments are insoluble in water and have no affinity for textile. Use of pigments for printing of textile by ancient Chinese in the eighteenth century by using blocks had been reported in the literature determining the aesthetic appeal and acceptability of the products made from them. The main attention of the study embodied in the present paper centers round the modification of cotton cellulose by different aminating agents to impart pigment affinity and to compare the results with the conventional pigment dyeing process. Optimisation of dose level of those aminating agents in terms of depth of shade, mechanical parameters and assessment of different colourfastness properties of those pigment dyed fabrics were also carried out and the results are reported in the present work.[8]

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Colouration of cotton cellulose with pigment emulsion has always played a key role in

2. EXPERIMENTAL

2.1 Materials Loom state cotton fabric having 20 tex warp count and 20 tex weft count and 360 ends/dm and 320 picks/dm with 120 gm/m2 in weight were used in this study. Acramin Red FGR (pigment), commercial polyamine compound (Solidogen CPD), binder, acrylamide and citric acid were used

as and when required. All other chemicals used in this study were of laboratory reagent grade supplied by M/s Loba Chemie Pvt. Ltd., Mumbai, India.

2.2 Methods

2.2.1 Desizing, scouring and bleaching of cotton fabric In order to remove size and other chemicals from the cotton fabric, the latter was desized, scoured and bleached prior to dyeing in the manner as described below: Desizing of cotton fabric was performed using a 0.25(N) hydrochloric acid solution at the temperature of 500C for duration of 2 hours, at a fabric-to-liquor ratio of 1:20 (w/v), in a laboratory winch machine. The desized cloth was washed thoroughly using hot water, which was followed by a cold wash prior to scouring treatment. Scouring treatment of the desized cotton fabric was performed by pad-steam technique[9-11]

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Application of sodium hydroxide was made by padding the fabric with 10% sodium hydroxide solution containing 2% of an anionic wetting agent (sulphonated caster oil) in a two bowl padding mangle and the squeezing pressure for the padding operation was adjusted to enable a wet pick up 100%. The caustic padded fabric was subsequently steamed in a laboratory steamer at 1000C for 10 minutes. After steaming, the cotton fabric was washed thoroughly with cold water, neutralised with dilute acetic acid, washed again with water and finally dried in air. Bleaching of the scoured fabric was performed using a solution containing hydrogen peroxide (0.1%), sodium meta-silicate (0.08%) and sodium hydroxide (0.05%) at a temperature of 800C for a period of 1 hour in the laboratory winch machine. The bleached fabric was washed thoroughly with cold water, neutralised with dilute acetic acid, washed again with water and dried in air.

2.2.2 Conventional pigment dyeing process Application of pigment emulsion was done at different specified conditions following a pad-drycure technique. For the above purpose, the impregnation of the cotton fabrics in a solution containing pigment emulsion, binder, acetic acid and different specified catalysts was performed separately at nearly 100% wet pick up in a miniature laboratory model two bowl padding mangle. The impregnated and padded fabrics were then dried and finally cured at a temperature of 1400C for 5 minutes using a dry heat in a laboratory drying and curing chamber. Soaping of all the dyed

fabric samples was performed employing 2 g/l non-ionic detergent at 600C for 10 minutes. Finally, the fabric samples were cold washed and dried.

2.2.3 Application of pigment in presence of citric acid Scoured and bleached cotton fabric was padded in a solution containing pigment emulsion, binder, acetic acid, citric acid and sodium di-hydrogen phosphate at nearly 100% wet pick-up in a laboratory model two bowl padding mangle. The padded fabric was then dried and finally cured at a temperature of 1400C for 5 minutes. Soaping of the dyed fabric sample was done at a temperature of 600C for 10 minutes employing 2 g/l non-ionic detergent.

2.2.4 Cotton fabric modified with acrylamide and dyeing with pigment emulsion Pre-soaking of scoured and bleached cotton fabric with potassium peroxodisulphate (K2S2O8) solution of 5 g/l concentration at room temperature for 15 minutes and subsequent application of aqueous acrylamide monomer on the pre-soaked cotton under different specified concentration were performed separately by padding technique in a laboratory two bowl padding mangle. Squeezing pressure for the padding operation was adjusted in each case to enable a wet pick up of 100%. The padded fabrics were then subjected to drying in a drying oven at 950C for 5 minutes. The dried fabrics were then allowed to get cured in a laboratory curing chamber at a temperature of 1400C over a period of 5 minutes. The aminated cotton fabrics were then subsequently dyed with pigment emulsion following an exhaust technique keeping a fabric-to-liquor ratio of 1:20 at 700C for 10 minutes. Fixation of pigment was carried out by treating those fabrics in acetic acid solution for 5 minutes at room temperature followed by treatment with binder for another 15 minutes at a temperature of 500C. Soaping of all the dyed fabric samples was done employing 2 g/l non-ionic detergent at 600C for 10 minutes. Finally, the fabric samples were cold washed and dried.

2.2.5 Cotton fabric modified with polyamine compound and dyeing with pigment emulsion Cotton fabrics were first treated with non-ionic wetting agent at room temperature for 10 minutes. These pre-wetted fabrics were then treated with different specified dose level of polyamine compounds in presence of acetic acid following an exhaust technique for 5 minutes at room temperature. This process was further continued for another 10 minutes at 700C temperature.

Those pre-treated (aminated) fabrics were then separately dyed with pigment emulsion following an exhaust technique at 700C for 10 minutes. Both the pre-treatment and dyeing process were performed at a fabric-to-liquor ratio of 1:20 keeping the dye bath pH ~5. The fixation of the pigment was carried out by treating those dyed fabrics with acetic acid at room temperature for 5 minutes, followed by the application of binder at 500C for 15 minutes. The dyed fabrics were then washed with 2g/l non-ionic detergent at 600C for 10 minutes, followed by cold washed and finally dried.

2.2.6 Measurement of K/S value Dye receptivity of fabric samples dyed with pigment emulsion under different specified conditions as estimated in terms of K/S (Kubelka-Munk function) [12] was determined. The value is based on measuring the reflectance of each dyed fabric samples at the respective wavelength of maximum absorption (max) in a Macbeth 2020- plus reflectance spectrophotometer and converting the reflectance value to (Kubelka-Munk function) K/S as detailed below using the appropriate formula and relevant software attached to the computer aided equipment following the standard procedure: [K/S = (1-R) 2 / (2R)], where K is the coefficient of absorption, S is the coefficient of scattering and R is the reflectance of the substrate at wavelength .

2.2.7 Determination of stiffness Fabric stiffness as expressed by the bending length, was measured in accordance with IS: 6490 1971 (cantilever test) in a SASMIRA Stiffness Tester with a specimen size of 25 x 200 mm [13].

2.2.8 Measurement of wrinkle recovery angle The wrinkle recovery angle of the fabric samples was measured using a SASMIRA Crease Recovery Tester in accordance with IS: 4681 1972 [14]. Average crease recovery in each of warp and weft direction was computed.

2.2.9 Determination of tear strength Tear strength measurement of all the fabric samples were done in accordance with the method prescribed in IS: 6489 1971 in an Elmendorf Tear Strength Tester with a sample size of (100 2 mm) x (63mm 0.15 mm) [15].

2.2.10 Measurement of tensile properties Breaking strength and elongation at break of fabric samples were measured according to a method prescribed in IS: 1969 1968 in a ZWICK/ROELL ZOI0 CRT Tensile Strength Testing Machine [16].

2.2.11 Assessment of colourfastness to washing Colourfastness to washing of cotton fabric samples dyed with pigment emulsion under specified conditions was assessed in a launder-o-meter in accordance with a method prescribed in IS: 3361 1984 (ISO II) [17].

2.2.12 Assessment of colourfastness to light Colourfastness to light of cotton fabric samples dyed with pigment colour was assessed on a Mercury Bulb Tungsten Filament (MBTF) lightfastness tester following a method prescribed in IS: 2454-1984 [18].

2.2.13 Assessment of colourfastness to rubbing This was determined employing a Crockmeter following the method prescribed in IS: 766 1984[19]

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3. RESULTS AND DISCUSSION

3.1 Effect of catalyst on depth of shade Studies on effect of different catalysts on depth of shade (measured in terms of K/S) for colouration of cotton fabric with pigment emulsion following a pad-dry-cure technique was performed and the results of such studies are given in table 1. From the table it is observed that, there is an increase in depth of shade of the pigment dyed fabric in presence of those acid catalysts. Under acidic condition binder gets cross-linked with the hydroxyl group of cellulose, as well as self cross-linking of the binder also takes place. The reaction was catalyzed under acidic condition and reversible in nature, hence elimination of bi-product i.e. water or methanol leads to the fixation of the binder onto the fibre.

3.2 Effect of catalyst on mechanical and colourfastness properties Studies on the effect of different catalysts on mechanical and colourfastness properties for colouration of cotton fabric with pigment emulsion following a pad-dry-cure technique were done and the results of such studies are shown in table 1 and table 2 respectively. From table 1 it is noticed that for all those catalysts used, there is a common increase in bending length value i.e. stiffness of the fabric increases. This fact may be viewed as the consequence of the deposition of the pigments along with the binder onto the fabric surface. Application of pigment in presence of ammonium chloride as an acid liberating catalyst produced minimum retention of tensile and tearing strength as compared to the other two catalysts. Under curing condition ammonium chloride decomposed and produced hydrochloric acid which gives the desired pH for crosslinking of the binder along with the hydroxyl group of cellulose. During the curing condition cotton cellulose was also converted into hydro-cellulose in presence of excess of hydrochloric acid, resulting into loss of tensile strength. There is also a marginal improvement in wrinkle recovery angle of the dyed fabric by the use of those catalysts. From table 2 it is observed that, cotton fabrics coloured with pigment emulsion in presence of all the catalysts commonly produced good to excellent washfastness, good lightfastness and good dry rubbing fastness properties, whereas in all the cases wet rubbing was found to be poor.

3.3 Effect of variation in dose level of different aminating agents on K/S value Cotton fabric was separately modified with different dose level of acrylamide and commercial polyamine compounds. Those modified fabrics were then dyed with pigment emulsion following an exhaust technique and the results of such studies in terms of K/S value are enlisted in table 3 and table 4 respectively. From those two tables it is observed that with the increasing dose level of both the aminating agents, depth of shade (measured in terms of K/S value) of the cotton fabric dyed with pigment emulsion followed a common increasing trend up to a dose level of 2g/l and decreases thereafter. Generally pigments are anionic in nature when dispersed in water and have no affinity towards cellulosic fibre. The presence of cationic charges on or in the fibre causes pigments to be strongly attracted to the fibre and to be held much more tightly on the fibre. Higher doses than the optimum level reduce the pigment build up ability and level dyeing property. Above modifying agents act as a physical barrier for the pigment molecule to attach on to the fibre surface, resulting loss in depth of shade. Excessive build up of polymer on the interior surface of the machine can also occur which cannot be removed easily and will give patchy dyeing/dye spot etc.

3.4 Effect of aminating agents on mechanical properties Studies on modification of cotton fabric with different application level of aminating agents followed by dyeing with pigment emulsion were done and the results of such studies in terms of bending length, tear strength, wrinkle recovery angle, tensile strength and elongation at break are given in table 3 and table 4 respectively. Prior modification of cotton with different dose level of aminating agents commonly produces higher bending length without much loss in tensile and tear strength property. Increase in stiffness of the fabric may be due to the deposition of pigment along with the binder onto the fabric surface. There is an improvement in breaking elongation property of the dyed fabric with the increasing dose level (upto 2 g/l) of both the aminating agents without further improvement in wrinkle recovery angle.

3.5 Effect of aminating agents on colourfastness properties Studies on modification of cotton fabrics with different dose level of aminating agents followed by dyeing with pigment emulsion were done and the results of such studies in terms of colourfastness to washing, light and rubbing are given in table 5 and table 6 respectively. From

those tables it is observed that prior modification of cotton with those aminating agents followed by dyeing with pigment emulsion commonly produced good colourfastness to wash, light and dry rubbing properties. Among the two aminating agents used, fabric dyed with pigment emulsion after prior modification with commercial polyamine compound produced much better lightfastness property as compared to the fabric prior modified with acrylamide and subsequently dyed with pigment colour. Increase in lightfastness property of the dyed cotton fabric prior modified with commercial polyamine compound is the consequence of increase in depth of shade as compared to the fabric dyed with pigment colour after prior modification with acrylamide. Higher dye content of the fibre results in higher lightfastness rating of the substrate in view of the fact that photo fading of dye in any polymer media is a surface phenomena and with increase in dye content the surface area per unit volume of the assemblage of the dye molecule decreases with consequent decrease in the fading rate of the dye incorporated in the polymer media [20].

4 Conclusions Pigments can be applied on cotton fabric either following conventional pad-dry-cure technique or by modifying the cotton cellulose with aminating agents, followed by dyeing with pigment emulsion through an exhaust technique. Colouration of cotton with pigment colour has always played a key role in determining the aesthetic appeal and acceptability of the products made from them. Ammonium chloride, di-ammonium phosphate and citric acid can be effectively used as catalysts for colouration of cotton fabric with pigment colour following a paddrycure technique. In presence of these catalysts there is an improvement in depth of shade with marginal improvement in wrinkle recovery angle of the pigment dyed fabrics. These dyed fabrics commonly produced good colourfastness to washing, light and rubbing (dry). Pigments can also be applied on the cotton fabric following an exhaust technique after prior modification of the cotton cellulose with acrylamide and commercial polyamine compounds. With the increasing dose level of both the aminating agents the depth of shade of the cotton fabric followed a common increasing trend up to a dose level of 2g/l and decreases thereafter. Prior modification of cotton with different dose level of these aminating agents commonly produced higher bending length, good light fastness, excellent wash and dry rubbing fastness properties without much loss in tensile and tear strength. Among the two aminating agents used, fabric dyed with pigment colour after prior modification with commercial polyamine compound produce much better lightfastness property as compared to the fabric prior modified with acrylamide and subsequently dyed with pigment colour.

References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 D M Lewis and K A Mcllroy, Rev Prog Col, 27, (1997), pp 5 17. S A Abdel-Hafiz, F F El-Sisi, M Helmy and A Hebeish, J Soc Dyers Col, 112, (1996), p 57. S A Abdel-Hafiz, F F El-Sisi, M Helmy and A Hebeish, J Soc Dyers Col, 112(5-6), (1996), pp 162 - 166. S Eom, D Y Shin and K J Yoon, Indian J Fibre Text Res, 26(4), (2001), pp 425 431. Imperon Dyestuffs in Dyeing with Acramin FKLN/Acramin SBD by Padding process, (Colour Chem Ltd., Mumbai), pp 1-6. Garment Pigment Dyeing, International Textile Bulletin, 5, (2004), pp 72 78. G Cawood and J Scotney, Rev Prog Col, 30 (2000), pp 35-40 V A Shenai, Technology of Textile Processing, Technology of Printing, 3rd edition, (Sevak Publication, India), (1991). V A Senhai, Technology of Textile Processing, Vol III, Technology of Bleaching and Mercerizing, 3rd edn, (Sevak Publication, India), 1991, p101. D Das and R Munsi, J Text Inst, 97(6), (2006), pp 519-520. P Ghosh and D Das, European Polym J, 36, (2000), p 2506. F W Billmeyer and M Saltzman, Principles of Color Technology, 2nd edn, (A Willey Interscience Publication), 1981, p 140. Handbook of Textile Testing, (Bureau of Indian Standard, New Delhi, India), Determination of stiffness of fabrics cantilever test, (SP: 15-1981), IS: 6490-1971, pp 255-256. Handbook of Textile Testing, (Indian Standard Institution, New Delhi), Determination of wrinkle recovery of fabrics, IS: 4681 1968, pp 280-282. Handbook of Textile Testing, (Bureau of Indian Standard, New Delhi, India), Determination of tear strength of woven textile fabrics by Elmendorf tester, (SP: 151981), IS: 6489-1971, pp 257-258. Handbook of Textile Testing, (Bureau of Indian Standard, New Delhi, India), Determination of breaking load and elongation at breaking of woven textile fabrics, (SP: 15-1981), IS: 1969-1968, pp 221-224. Handbook of Textile Testing, (Indian Standard Institution, New Delhi), Determination of colourfastness of textile materials to washing: Test 2, IS:3361-1984, pp 571-572. Handbook of Textile Testing, (Indian Standard Institution, New Delhi), Determination of colourfastness of textile materials to light: IS: 2454-1984, pp 536-537. Handbook of Textile Testing, (Indian Standard Institution, New Delhi), Determination of colourfastness of textile materials to rubbing: IS: 766 1984, p 553. N S Allen, Rev Prog Col, 17, (1987), pp 61-71.

Table 1: Effect of catalysts on K/S and other mechanical properties Catalyst used K/S (at wave length 420 nm) 0.17 0.65 0.66 0.75 Bending length (cm) 2.21 3.15 3.17 3.15 Total wrinkle recovery angle (0) 128 162 162 164 (%) Retention of tear strength 100 87.5 73.26 84.67 (%) Retention of tensile strength 100 69.27 52.75 62.69 Elongation at break (%) 11.67 10.91 10.64 12.38

nil Di-ammonium phosphate Ammonium chloride Citric acid

Table 2: Effect of catalysts on colourfastness properties Catalyst used Light fastness 4 4-5 4-5 Change in colour 4-5 4-5 4-5 Washfastness Staining on cotton 5 5 5 Staining on wool 4-5 4-5 4-5 Rubbing fastness Dry Wet 4-5 4-5 4-5 2-3 2-3 2-3

Di-ammonium phosphate Ammonium chloride Citric acid

Table 3: Effect of dose level of acrylamide on K/S and mechanical properties Acrylamide (g/l) K/S (at wave length 420 nm) 0.17 1.14 1.49 1.11 1.10 0.92 Bending length (cm) 2.21 3.10 3.13 3.23 3.35 3.41 Total wrinkle recovery angle (0) 128 134 136 136 136 134 (%) (%) Elongation Retention Retention at break of tear of tensile (%) strength strength 100 70.09 68.43 66.33 64.47 62.45 100 87.32 85.30 82.81 80.58 79.45 11.67 12.28 14.70 13.60 13.31 13.65

0 1 2 5 10 20

Table 4: Effect of dose level of commercial polyamine compound on K/S and mechanical properties Commercial polyamine compound (g/l) 0 1 2 5 10 20 K/S (at wave length 420 nm) 0.17 2.92 4.05 3.62 2.76 2.33 Bending length (cm) 2.21 3.00 3.13 3.00 3.13 3.27 Total wrinkle recovery angle (0) 128 134 134 136 136 136 (%) (%) Elongation Retention Retention at break of tear of tensile (%) strength strength 100 71.00 74.19 67.74 67.74 64.51 100 95.18 94.60 93.35 89.26 89.21 11.67 14.72 15.02 14.31 14.55 14.34

Table 5: Effect of dose level of acrylamide on colourfastness properties Acrylamide (g/l) Light fastness 4 4-5 4-5 4 4 Washfastness Change Staining Staining in colour on cotton on wool 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 Rubbing fastness Dry Wet 3-4 3-4 3-4 3-4 3-4 2 2 2 2 2

1 2 5 10 20

Table 6: Effect of dose level of commercial polyamine compound on colourfastness properties Commercial polyamine compound (g/l) 1 2 5 10 20 Light fastness 5 5-6 5-6 5 5 Wash fastness Staining Staining on cotton on wool 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 Rubbing fastness Dry Wet 4 4 4 4 4 2 2 2 2 2

Change in colour 4-5 4-5 4-5 4-5 4-5

Acramin Red FGR

Texcron Brown GR

Texcron Blue BN

Acramin Golden Yellow FRM

About the Author The author is Lecturer at Visva Bharati University in the Department of Silpa Sadana (Textile section), Sriniketan, Dist. Birbhum, West Bengal