Green Technology in Textile Processing: Part IV-Eco-Friendly Dyeing of Polyester/Cotton Fabric
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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.