Cotton dyebath reuse

Figure 1. Dyebath reuse 100% cotton/low-temperature reactive dyes...

Table XXVII. Dyebath Reuse Color Difference Calculations 100% Cotton/One Low-Temperature Reactive Dye...

Figure 2. Dyebath reuse 50/50 cotton/polyester, high energy reactive/base-...

Table XXXII. Direct Savings in Two-Step Dyebath Reuse Coloration of Cotton/Polyester Knits Based on 3.6 x 10 Lb./Yr. Production...

Chlorination was found (172) to be the most suitable and effective method for decolori2ing and reducing the COD of waste dyebaths containing a2o dyes. These findings have been substantiated for chlorination and biochemical purification (173). A study (174) has been done on the technical and economic feasibiUty of a chlorination dye wastewater reclamation system for treating effluent that is suitable for reuse in dyeing of polyester/cotton blends with disperse and direct dyes. 

The initial reuse research dealt with dyeing of 100% cotton knit underwear fabrics. The approach was to dye 100% cotton with a single reactive dye (low-temperature) in order to determine the initial problems in adapting reuse to reactive dye systems. The analysis of the reactive dyebath was similar to that described for disperse dyes in the general discussion section of this chapter. Since the reactive dye was water soluble, no organic extraction was necessary before analysis. The problems encountered and the solutions derived in this stage were ... 

Savings and Cost/Benefit Analysis. The bench scale experiments were successful Tn overcoming major technical problems while demonstrating that dyebath/auxiliary bath reuse is indeed feasible with reactive dyes on cotton-containing fabrics. In addition, a shortened-cycle dyeing procedure coupled with reuse for cotton/polyester blends was shown to further increase energy, mass, and time savings (Table XXX). 

To construct a model plant for incorporation of the two-step dyebath/fixation bath reuse technique to the coloration of cotton/ polyester knits, several assumptions were made ... 

Good lot-to-lot shade correlations were also obtained with reuse of low-temperature reactive dyebaths and fixation baths on 100% cotton, and with reuse of combined high-energy reactive/disperse dyebaths and fixation baths on cotton/polyester knit fabrics. Further computer program development is required, however, before industrial shades can be matched with the reactive dye reuse system. 

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