Sulphur dyes on nylon 6,6—part 2: the effects of reductant, oxidant and wash-off

Abstract

Nylon 6.6 was dyed with five commercial suphur dyes using seven different reducing systems and three oxidation systems and the dyeings were subected to repeated wash testing and to light fastness assessment. It was found that the different reductants effected not only the colour strength of the dyeings but also influenced the colour of the dyeings. Two of the reducing systems studied had a deleterious effect on colour strength achieved for some of the dyes. From a wash fastness viewpoint, while the same two reducing systems had a deliterious effect on both the extent of shade change and staining of adjacent multifibres, overall, the dyeings displayed very good fastness to the five repeated wash tests. There was very little difference between the three oxidising systems examined in terms of the colour strength of the dyeings, with the f( k) values obtained for the five dyes being virtually identical for each of the three oxidation systems used. However, the colour of the dyeings differed for the three oxidation systems studied. The wash fastness of the dyeings was little effected by the type of oxidant used. The wash-off of dyeings markedly reduced the extent of staining of adjacent multifibre strip but did not improve the colour change that occurred upon repeated washing. With the exception of the black dye, the dyes displayed poor fastness to light and this was, in general, little influenced by reductant, oxidant and wash-off.