Crosslinking Effects in Reactive Dyeing of Protein Fibers'

Abstract

Dyes featuring two reactive groups or one bifunctional group, when applied to wool and silk, can reduce the solubilities of these fibers in appropriate solvent systems. This is consistent with the formation of crosslinks during dyeing. Of the nine dyes studied, the most effective crosslinker possessed two well separated reactive groups. On wool, dyes with more closely located reactive sites were comparable in effect to formaldehyde. The reduced solubility of wool dyed with dyes containing one α-bromoacrylamide group indicates a bifunctional reaction of this group; this is in agreement with a hy pothesis stating bifunctionality. On silk, α-bromoacrylamide dyes undergo bifunctional reactions to a limited extent only, if at all. With other bifunctional dyes, the number and distribution of cnosslinks on silk depend on the type of reactive group and the method of dyeing. The inhibition of dye penetration after crosslink formation on silk in dyeings with a difluorochlo ropyrimidine dye at 40°C can be greatly alleviated by dyeing at 90°C, and thereby distributing the crosslinks more evenly throughout the fiber. The effectiveness of the highly reactive dichlorotriazine system in crosslinking depends on the method of dyeing used on wool and on silk.