Compensation for Hydrolysis in the Reuse of Reactive Dyes

Abstract

In conventional exhaust processes for applying reactive dyes, the alkali accelerates dye hydrolysis, restricting subsequent reuse. Step-up and chemical build-up can complicate accurate color duplication with reused dyes as well. A two-bath method of first applying the dye from a salt and dye bath followed by treatment in a separate alkali bath eliminates the possibility of alkali-induced hydrolysis, step-up, and chemical build-up effects. In this study, four reactive dyes differing in reactive group and dyeing temperatures are applied to cotton poplin fabric from original and reused dyebaths by one- and two-bath application methods, and the percent fixation of adsorbed dyes and the K/S values are determined. Dye hydrolysis and step-up and wash-off effects that occur in the one-bath method interfere with reuse. These complications are eliminated when the reactive dyes are reused by the two-bath method.