Cold Pad Batch Dyeing: Eco-friendly Dye Application on Cotton
Over the last few decades, the environmental impact of dyes and processes has become an increasingly large part of the dyer’s task. In recent years, the “default” choice is reactive dyes because of their generally good fastness to wet treatments and good
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Abstract Over the last few decades, the environmental impact of dyes and processes has become an increasingly large part of the dyer’s task. In recent years, the “default” choice is reactive dyes because of their generally good fastness to wet treatments and good range/brightness of shades. In seeking to achieve eco-friendly responsibility in dye application, there is no single solution since there is no single definition of what is green or environmentally responsible. Environmental responsibility is best achieved in cold pad batch application since little or no electrolyte is required, dye fixation is at ambient temperature, and fixation is high. This chapter represents general methodology of cold pad batch dyeing (CPB) of cotton fabric with reactive dyes and gives approach to eco-friendliness of this process. Keywords Bath stability • Cotton dyeing • CPB • Eco-friendly dyeing • Energy efficient • Environmental responsible dyeing • Reactive dyeing
1 Introduction Cold pad batch dyeing dates back, soon after the introduction of reactive dyes in 1956. Over the decades, several innovative changes have taken place in the process from the point of view of the dyestuff selection and chemicals used for the process. Pad batch dyeing is a cold method used for dyeing cellulosics (mainly low-percent cotton and polyester/cotton blends) that can achieve large reductions in pollution, energy requirements, and costs. The basic technique is to saturate the prepared fabric with premixed dye liquor (Table 1) and pass it through a padder, which forces the dyestuff inside the fabric
Z. Khatri (*) Department of Textile Engineering, Mehran University of Engineering and Technology, Jamshoro, Pakistan e-mail: [email protected] M.A. Uqaili and K. Harijan (eds.), Energy, Environment and Sustainable Development, DOI 10.1007/978-3-7091-0109-4_29, # Springer-Verlag/Wien 2012
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Table 1 Dyeing recipe for cold pad batch
Dyes and auxiliaries Reactive dye Antimigrating agent Wetting agent Caustic soda 36 Be´ Sodium silicate 38 Be´ Soda ash
Quantity x g/l 1 g/l 2 g/l 15–33 ml/l 70 ml/l 10–20 g/l
for greater penetration while removing the excess dye solution. The fabric is then stored, or batched, on rolls or in boxes for 4–12 h. Typically, the batches are covered with a plastic film to prevent carbon dioxide absorption and water evaporation. While in batching, the dyestuff reacts with and penetrates the fabric, resulting in even, consistent color. After the reaction is completed, the fabric is washed [1]. The dyeing ecology is also discussed [2].
2 Materials and Methods 2.1
Fabric Requirement
Pad batch dyeing can be used on wovens or knits in many constructions. Certain tubular knit styles may develop edge marks at the fold, but new methods in development will reduce this problem in heavyweight styles [3].
2.2
Dyeing Equipment
The equipment needed for pad batch dyeing includes a padding unit; a batcher or material handling system; a dye/alkali mixing device (dosing pump); A-frames, storage racks, and
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