Low-temperature Dyeing Of Wool Processed For Shrinkage Control
Wool fabrics treated for shrinkage control by applying a novel two-step ARS process3 involving an activated peroxide bleach followed by enzyme treatment were dyed at lower temperatures within shorter dyeing times than conventional dyeing with acid dyes which require 90 ° C or higher for 60 minutes or longer. The shrinkage control process involved bleaching pretreatment with dicyandiamide in alkaline hydrogen peroxide and with gluconic acid additive at 30 ° C (86 ° F) for 30 minutes followed by sulfite-assisted serine protease treatment for biopolishing and shrinkage prevention at 45 ° C (113 ° F) for 40 minutes. Dye uptake with time over the temperature range of dyeing showed that untreated fabrics and pretreated fabrics exhibited sigmoidal dyeing behavior with exhaustion within 55–70 minutes at 55–60 ° C. Fabrics pretreated and subsequently treated with enzyme exhibited exponential dyeing behavior with exhaustion within 20–30 minutes at 30–55 ° C. We attributed low temperature dyeing with reduced dyeing times to changes in wool morphology and chemical structure as documented by both scanning electron and confocal fluorescent microscopy. The ARS process provides shrinkage control with greater ease of bleaching and dyeing.