Dye-Fiber Bond Stabilities of Some Reactive Dyes with Wool

Abstract

Wool was dyed with seven reactive dyes having the same chromophoric group (1-amino-4-anilino-anthraquinone-2- sulfonic acid) but different reactive groups and then thoroughly extracted so that all noncovalently bound dye was re moved. The wool was treated with buffer solutions in the pH range of 1.6-10.6 at 70°C. The hydrolysis rate of the dye-fiber bonds was estimated by colorimetric measurement of the buffer solution. Reactive dyes containing the α-bromoacrylamide or the difluoromonochloropyrimidyl system gave the highest fixation on wool, whereas those containing a mono- or di-chloro-s-triazine, trichloropyrimidine, or vinylsulfone group gave lower values. Poor fixation was obtained with the β-hydroxyethylsulfone sulfuric acid ester and the β-hydroxyethylsulfona mide reactive group. Since only 2-10% dye-fiber bond hydrolysis was observed after 24 hr at 70°C, it must be concluded that the dye-fiber bond stability of all the reactive groups now available is sufficient for wool dyeing. The washfastness of reactively dyed wool is, therefore, not dependent on the nature or stability of the dye-fiber bond but on the fixation ratio, (i.e., the fraction of covalently bonded dye relative to all dye on the fiber) obtained during dyeing.