Green Technology in Textile Processing: Part IV-Eco-Friendly Dyeing of Polyester/Cotton Fabric
Indian Journal of Fibre & Textile Research Vol. 24, March 1999,-pp. 64-69
Green technology in textile processing: Part IV-Eco-friendly dyeing of polyester/cotton fabric
H T Deo', A I Wasif, B K Desai & Arindam Chakraborty Division of Technology of Fibres and Textile Processing, Department of Chemical Technology, University ofMumbai, Matunga, Mumbai 400 019, India Received 31 March 1998; accepted 3 June 1998
New eco-friendly dyeing processes are described for dyeing of polyester/cotton blend fabrics with disperselreactive and di sperse/vat dyes. By process modifications (Eco-Dyeing I and Eco-Dyeing II) and by substituting the non-ecofriendly chemicals with the eco-friendly ones, a significant reduction in pollution load in terms of Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand'(COD) has been achieved. The reductions achieved in BOD and COD respectively are 10.47% and 14.38% for dyeing with disperse/reactive dyes and 7.56% and 12.82% for dyeing with disperse/vat dyes. A substantial saving in water consumption has also been achieved in both the methods of dyeing. Eco-Dyeing II , in particular, results in 85 % saving in water consumption.
Keywords : Disperse dye, Dyeing, Eco-dyeing, Polyester/cotton fabric, Reactive dye, Vat dye, Water recycl in g
I Introduction Kenyon4 reported that polyester/cotton blends can In recent years, the production capacity of polyes be dyed by reverse dyeing technique with vinyl sul ter has increased tremendously in India. Due to the phone colours. leI reported a process for batch col existing tropical conditions, a large proportion of the ouration of polyester/cotton blends, wherein alkali polyester produced is blended with cotton, viscose stable disperse dyes and high-exhaust reactive dyes and . polynosic fibres. The popularity of polyes (Procion HE) are used. The high stability of HE reac ter/cotton blend is due to its reasonable price, excel tive dyes up to 1100 e allows the application of both lent combination of aesthetic properties and superior disperse and reactive dyes in a single bath at boil. easy care performance I . Hildebrand and Fiegel5 reported a pH sliding In general, the polyester/cotton b~ends are dyed with two classes of dyes by batchwise or continuous method (a one-bath process) in which the pH of the 2 dyebath containing disperse and reactive dyes is al- methods . In India, thtse ble~ds are dyed by the batc hwise methods. The most common process is the 10wed to change slowly from alkali:1e to acidic. The two-bath dyeing process, wher:ein polyester compo reactive dyes are fixed first in the alkaline medium, nent is dyed with di sperse dye foilowed by the dyeing followed by disperse dyes in acidic medium. 6 of cotton component with· reactive, vat or sulphur Marschner and Hildebrand developed AT process dye. Although the two-bath dyeing involves addi (acid fixation) for continuous dyeing of polyes tional labour and is hme consllming, it often produces ter/cellulosic blend fabrics, wherein Levafix EA and shades' of good fastness. For dyeing polyester/cotton Levafix PA dyes react with cellulose in the presence blends, disperse/reactive combination is, at times, of dicyandiamide without alkali. Saus et aC reported preferred to disperse/vat combination, because it is a novel dyeing process using supercritical carbon di oxide medium that completely avoids water pollution. comparatively cheap~r. and i's known · for its brilliant 8 shades with good 'fastness properties). Vlyssides an d Israilides characterized the effluent generated during the dyeing of polyester/cellulose blend fabrics . • The author,hoschanged hi s name from H T Lokhande to H T Deo. In the present work, an attempt has been made to To wh om all th e correspo ndence should be addressed. dye the polyester/cotton blend fabric with safe dyes, DEO e( al.: GREEN TECHNOLOGY IN TEXTILE PROCESSING: PART IV 65 eco-friendly auxiliaries and chemicals, and to reduce adjusted to 5 with formic acid. The sample was then effluent volume and waste concentration in effluents. put into the dyebath and temperature was raised to Attempts have also been made to achieve savings in 130°C in 60 min. Dyeing was carried out at this tem water consumption, reuse the low load effluent after perature for 60 min. The dyebath was then cooled to suitable treatment and to increase productivity. 85°C and pH was brought to neutral by adding small quantity of soda ash. 2 Materials and Methods 2.1 Materials Reactive Dyeing Polyester/cotton (70:30) blend fabric having the In the above bath, pre-dissolved salt (20 gil) was following specifications was used: warp count, 2/40s; added and dyeing was continued for 20 min. Further, weft count, 20s; pickslin, 62; and endslin,52. 25 gil of pre-dissolved salt was added and dyeing was Serene Red RGLS ( c.1. Disperse Red 202), Navi continued for 25 min. Pre-dissolved sodium carbon non Red 6B-90 (C.1. Vat Red 13) and Procion Bril ate (7.5 gil) was added into the bath and dyeing was liant Red H-8B (C.1. Reactive Red 31) were used. carried out for 10 min. Remainder sodium carbonate S~dium hydrosulphite (GR grade), common salt, (7.5 gil) was then added and dyeing was continued sodium hydroxide, sodium carbpnate, acetic acid, for 45 min, maintaining the temperature at 85°C. The formic acid, calcium chloride, magnesium sulphate, bath was drained and the sample was rinsed with cold ferric chloride, mercuric sulphate, silver sulphate, water followed by soaping with 2 gil non-ionic deter potassium dichromate and ferrous sulphate, all of gent Ultra NC at boil for 15 min. Again after draining AnaiaR grade, were used as such. the bath, the sample was given hot wash followed by Product CD and Ultra NC ( both from C.D. Corpo a cold wash. The dye fixing treatment was given in ration, Mumbai) and Sando fix WEI (Clariant India the same bath at room temperature (30°C) with dye Ltd, Mumbai) were used. fixing agent Sandofix WEI (2 gil) after adjusting the pH to 9 with a little quantity of soda ash. The dyebath 2.2 Methods was drained. Finally, the sample was rinsed with cold 2.2.1 Dyeing water. The polyester/cotton fabric was desized, scoured, bleached and mercerized by the conventional meth Vat Dyeing ods. The fabric was then dyed with disperse/reactive In the same bath used for disperse dyeing, the and di sperse/vat dyes by the conventional method as blank vat (5 gil caustic soda and 5 gil sodium hydro well as Eco-Dyeing I and Eco-Dyeing II processes. sulphite) was added followed by the addition of vat ted dyestuff. Dyeing was continued for 75 min while 2.2.1.1 Conventional Dyeing allowing the bath temperature to drop to 60°C. The The two-bath HTHP method was used for dyeing bath was then drained and the fabric sample was polyester/cotton blend fabric. The cotton component squeezed and rinsed. Oxidation was carried out with was dyed with reactive and vat dyes using the stan 3mlll hydrogen peroxide (130 vol ) at 60°C for 30 dard ·methods of dyeing. min. The soaping was carried out in the same bath 2.2.1.2 Eco-Dyeing I with 2 gil soap and 2 gil soda ash at boil for 15 min. In thi~ process, the polyester component of poly Finally, the sample was given a hot rinse followed by ester/cotton fabric (5 g ) was dyed first with a dis a cold rinse. perse dye in 1% shade in a laboratory HTHP beaker dyeing machine and then the cotton component was 2.2.1.3 Eco-Dyeing II dyed with a reactive or vat dye in 1% shade in the In the Eco-Dyeing II, the procedure adopted was same respective bath. The material-to-liquor ratio was similar to the one followed in the conventional dye kept at I :40. The following sequence was used for the ing. However, instead of using fresh water, the total dyeing: wash liquors generated in dyeing of polyester with disperse dye and of cotton with reactive or vat dye Disperse Dyeing were reused after giving the following treatment. The The dyebath was set at 60°C with a disperse dye wash liquors generated in polyester dyeing and cotton and dispersing agent Product CD (lg/l). The pH was dyeing were mixed and the pH was brought to 8.5 66 INDIAN 1. FIBRE TEXT. RES., MARCH 1999
with,hydrochloric acid or lime. The solution was then were assigned. treated with ferrous sulphate (300 mg/l), stirred and kept stagnant for 3 h. The sludge formed was allowed 3 Results and Discussion to settle down and the clear liquor was passed Waste water generated in dyeing of polyes through an activated carbon column. This colourless ter/cotton fabric with disperse/reactive and dis liquor was reused in Eco-Dyeing II. perse/vat dye combinations by conventional, Eco Dyeing I and Eco-Dyeing II methods was analyzed 2.2.2 Tests for pH, total solids, total dissolved solids, suspended Total solids, suspended solids, total dissolved sol solids, BOD and COD. The results are shown in Ta ids, BOD. COD, pH, KlS values, colour difference ble 1. (by CCM), and colour fastness to washing and day The effluent generated in dyeing of polyes light were determined as reported earlier. ter/cotton fabric with disperse/reactive dye combina tion by the conventional method shows alkaline pH 2.2.3 Assessment of Fastness to Rubbing and high total dissolved solids, which may be due to Two pieces of fabric (14 cm x 5 cm) drawn from the usage of J. arge quantity of salt and · various other the dyed sample, one having the le~gth direction par chemicals. Since the values of BOD and COD are allel to warp yams and th~ other parallel to weft, were higher in conventional dyeing, certain modifications used for dry rubbing. Similarly, two more fabric become essential to reduce the pollution load. In Eco pieces were drawn for wet rubbing. Both the tests Dyeing I, which is a single bath modified dyeing pro were carried out on a crockmeter (World Traders & lO cess, the high BOD generating acetic acid, which is Co, Mumbai) according to IS: 766(1956) method • normally used in the conventional dyeing, has been 2.2.3.1 Dry Rubbing substituted with a low BOD generating formic acid. One test piece was fixed to the crockmeter. An Besides various steps, such as rinsing after disperse other piece of the dry undyed bleached cotton cloth dyeing and reduction clearing followed by two rinses, was fixed in a place over the end of the finger of the have been avoided in Eco-Dyeing I. Therefore, Eco crockmeter and then rubbed to and fro on the dry test Dyeing I effluent shows lower values of total solids, piece 10 times in lOs with a downward force of 900 BOD and COD as compared to that shown by the g on the finger. conventional method. The reduction in pollution load in terms of BOD and COD in case of Eco-Dyeing I is 2.2.3.2 Wet Rubbing 10.47% and 14.38% respectively. In Eco-Dyeing II, The procedure was similar to that used in dry rub the total effluent generated in the conventional bing except that a wet undyed bleached cotton cloth method has been put to reuse after giving suitable was taken in the place of dry cloth. Degree of staining treatment. The Eco-Dyeing II effluent shows higher of the piece of undyed cloth was evaluated with the values of total dissolved solids, which indicate that help of Geometric Grey Scale (Staining) and ratings dissolved solids from the conventional dyeing are not
Table I-Analysis of waste water generated during dyeing of polyester/cotton fabric with disperse/reactive and disperse/vat dyes Dyeing pH Total solids Total dissolved Suspended solids BOD COD process mg/l solids mg/I (5 days at 20°C) mg/I mg/I mg/I
Dlsperse/Reactive Combination Conyentional 8.0 4794 4353 441 296 751 Eco-Dyeing I 8.4 4398 3986 412 265 643 Eco-Dyeing II 8.0 5802 5326 476 340 885
Disperse! Vat Combination Conventional 9.7 5317 4733 584 357 928 Eco·Dyeing I 10.0 4969 4437 532 330 809 Eco-Dyeing " 9.7 5986 5378 608 379 1023
BOD-Biochemical oxygen dem~d; COD-Chemical oxygen demand DEO et al. : GREEN TECHNOLOGY IN TEXTILE PROCESSING: PART IV 67 removed during the treatment. Only marginal in dyes. In Eco-Dyeing I, reduction in BOD and COD crease in the BOD and COD values of Eco-Dyeing II values is 7.56% and 12.82% respectively. In Eco effluent indicates that substantial amount of dyes and Dyeing II, the total effluent of the conventional dye various chemicals are removed from the conventional ing has been reused after giving suitable treatment. dyeing effluent by the treatment. Thus, not only the Therefore, the effluent of Eco-Dyeing II shows higher saving in water consumption is achieved but also re values of total dissolved solids. However, BOD and duction in pollutio!1 load of effluent has been ef COD values increase only marginally in Eco-Dyeing fecteli, improving the quality of effluents to be reused II effluent. in Eco-Dyeing II. Table 2 shows the KJS values of polyester/cotton The effluent from the conventional dyeing of poly fabric dyed with disperse/reactive and disperse/vat ester/cotton fabric with disperse/vat dye combination dye combinations. It is observed that the sample dyed shows alkaline pH and much higher values of total by Eco-Dyeing I shows higher KJS value as compared solids, total dissolved solids, suspend~d solids, BOD to the conventionally dyed sample in case of dis and COD. In Eco-Dyeing I, chemical oxidation with perse/reactive dyes. This indicates that the single bath non-ecofriendly potassium dichromate and acetic acid dyeing process as adopted in Eco-Dyeing I achieves has been avoided and instead oxidation with eco higher dye uptake. However, the sample dyed by friendly hydrogen peroxide carried out. Besides, a Eco-Dyeing II shows somewhat lower KJS values number of steps being followed in conventional dye than the conventionally dyed sample. The lower dye ing have been eliminated in Eco-Dyeing I. Thu"s, hot uptake for the sample dyed by Eco-Dyeing II may be rinse after disperse dyeing, reduction clearing, and attributed to much higher amount of total dissolved hot and cold rinse after reduction clearing have been solids present in the recycled water which may be eliminated. Oxidation and soaping are carried out in interfering with the di ssolution of dyestuffs. In case the same bath. Therefore, the effluent generated in of dyeing with di sperse/vat dyes, it is observed that Eco-Dyeing I shows much lower values of total dis conventional dyeing and Eco-Dyeing I do not show solved solids, BOD and COD as compared to that any significant difference in terms of KJS values. shown by the effluent in conventional dyeing with vat However, the sample dyed by Eco-Dyeing II shows lower KJS value in comparison to those dyed by con ventional and Eco-Dyeing I methods, indicating low Table 2- KlS values of polyester/cotton fabric dyed with dye uptake in Eco-Dyeing II method. disperse/reactive and disperse/vat dyes Table 3 shows that both "dry and wet rubbing fast Dyeing process KlS value ness of samples dyed with di sperse/reactive combi DisperselReactive DisperseN at nation by conventional dyeing and Eco-Dyeing I re main unaltered. However, for Eco~Dyeing II, slight ConventIOnal 6.9607 5.4032 lowering of ratings of dry and wet rubbing fastness is Eco-Dyeing I 7.2374 5.3917 observed for disperse/reactive combination. In case of Eco-Dyei ng II 6.2058 4.9435 disperse/vat combination, however, the ratings re-
Table 3-Fastness properties of polyester/cotton fabric dyed with di sperse/reactive and disperse/vat dyes
Dyeing process Fastness to Rubbing Washing Light Dry Wet Colour change Staining on white
Disperse/Reactive Combination Conventional 4-5 4 4 4 5 Eco-Dyeing I 4-5 4 4 4 5 Eco-Dyeing II 4 3-4 4 3-4 4-5
Disperse/Vat Combination Conventional 5 4-5 4-5 5 6 Eco..oyeing I 5 4 4-5 5 6 Eco-Dyeing " 5 4-5 4-5 5 6 68 INDIAN J. FIBRE TEXT. RES., MARCH 1999
Table 4-Water consumption in dyeing of polyester/cotton fabric with disperse/reactive and disperse/vat dyes
Amount of water, litre Step. Conventional JEco-Dyeing I Eco-Dyeing II
Disperse/Reactive Combination. Disperse dyeing 600 600 600" Hot rinse after dyeing 600 Nil 600" Reduction clear 400 Nil 400· Rinse 400 Nil 400" Rinse (after acidification) 400 Nil 400" Reactive dyeing 150 150 150" Cold rinse after dyeing 400 600 400" Soaping 400 600 400· Hot wash after soaping 400 600 400" Cold wash 400 600 400 Rinsing after dye fixing Nil 600 Nil Total water consumption 4150 3750 400 Total savings per batch of 100 kg fabric 400 3750b Saving in monetary terms 9.63% 82.41%
DisperseNat Combination Disperse dyeing 600 600 600· Hot rinse after dyeing 600 Nil 600· Reduction clear. 400 Nil 400· Hot rinse 400 Nil 400· Cold rinse 400 Nil 400· Vat dyeing 150 150 1.50· Rinse 400 600 400· Oxidation 400 600 400· Rinse 400 Nil 400· Soaping 400 Nil 400" Hot rinse 400 600 400· Cold rinse 400 600 400 Total water consumption 4950 3150 400 Total savings per batch of 100 kg fabric 1800 4550b Saving in monetary terms 36.36% 85.04%
• Recycled water, b For two batches (one each by conventional dyeing and Eco-Dyeing II) main, unchanged in both Eco-Dyeing I and II, except 82.41 % respectively. The dyeing of polyester/cotton a slight lowering in Eco-Dyeing I for wet rubbing fabric with disperse/vat dye combination by Eco fastness (4-5 to 4). Similarly, the wash fastness and Dyeing I and II results in savin~s of 1800 and 4550 light fastness ratings for conventionally dyed and litres water respectively per batch of 100 kg fabric. In Eco-Dyeing I dyed samples are identical. These re monetary terms, the savings obtained per batch in sults indicate that the fastness properties are not ad Eco-Dyeing I and Eco-Dyeing II are 36.36% and versely affected in Eco-Dyeing I, in spite that it is a 85 .04% respectively. one-bath dye'jng process. Table 4 shows the water consumption in dyeing of References I Chavan R B & Jain A K, Dyeing ofpolyester and its blends, polyester/cotton fabric with disperse/reactive and dis edite'(j by M L Gulrajani (lIT, New Delhi), 1987,205. perse/vat dye combinations. It is observed that in case 2 Mehra R H, Jhangiani S B, Tolia A H & Mehra A R, in of disperse/reactive dye combination, Eco-Dyeing I Blended textiles, edited by M L Gulrajani [The Textile Asso and Eco-Dyeing II result in savings of 400 and 3750 ciation (India)], 1981, 277. 3 Basu A K, Deb T K, Gandhi R B & Shroff J J, in Blended litres water respectively per batch of 100 kg fabric. In textiles, edited by M L Gulrajani [The Textile Association monetary terms, the savings obtained per batch in (India)], 1981 , 282. Eco-Dyeing I and Eco-Dyeing II are 9.63% and 4 Kenyon G H, Am Dyest Rep, 68(3) (1979) 19. DEO £'1 a/. . GREEN TECHNOLOGY IN TEXTILE PROCESSING: PART IV 69
5 Hildebrand D & Fiegel J, Bayer Farbel/ Review, (34) (1983) 8 Vlyssides A G & Israilides C J , Fresenius Environ Bull, 6 3 1; World Texl Abslr, 17 (1985) 1828, 174. (11112) (lCl 97) 705; (,helll Abstr, 127 (1997) 282930. (j Marschner W & Hildebrand D, in Blel/ded lextiles. edited by 9 Deo H T & Wasif A I, Indian J Fibre Text Res. 24 (1999) 58. M L Gulrajani [The Textile Association (India»), 1981 ,269. 7 Saus W. Knittel D & Schollmeyer E, Text Res J, 63(3) lOIS: 766-1956, lSI handbook of textile testing (Bureau of (199.1) 135 . Indian Standards, New Delhi), 1982.