Low-temperature dyeing of protein and polyamide fibres using a redox system

Abstract

Dyeing investigations were performed on wool, silk and polyamide-6 fibres with acid dyes having various A-values (ratio of organic to inorganic character) in the presence of a thiourea/hydrogen peroxide redox system and in aqueous and water/n-propanol (9:1). An increase in colour intensity of the substrates dyed in presence of the redox system, as well as rapid exhaustion of the dyebath, were observed. Wool gave the highest relative colour intensity, followed by silk and then polyamide-6. Colour intensity was relatively improved in the case of the water/propanol dyeing medium compared to a purely aqueous medium. Both the time of half-dyeing and the specific dyeing rate constant decreased with increase in the A values of the dyes. Addition ofn-propanol to the bath preferentially lowered the time of half-dyeing, especially in the presence of the redox system. A tendency was also observed for the affinity and heat of dyeing of the substrates with acid dyes to increase with increasing A values of the dyes. The presence of n-propanol during dyeing gave a decrease in entropy due to the increased availability of the fibre structures to dyes of relatively high A value.