Studies on the Shrink-Resist Treatment of Wool with Potassium Permanganate

Abstract

A detailed investigation of the shrink-resist effect imparted to wool by potassium permanganate solution is described. The KMnO4 consumed by the wool increased with time, temperature, and concentration of the treating bath. The addi tion of a relatively small amount of sodium chloride in the range of 10 g/l. to the KMnO4 treatment bath incrased to some extent the KMnO4 consumed by the wool. The acidic KMnO4 treatment imparted better shrink resist properties to the wool, as well as less yellowing when compared with an alkaline treatment. The treatment produced some bleach ing effects to wool that makes it possible to use milder bleaching conditions subsequently without effecting the level of whiteness. Amino acids cystine, tyrosine, and tryptophan were greatly affected by the KMnO4 treatment. This observation may be compared with the changes associated with chlorinated or H2O2 treated wool. Nitrogen and sulfur contents decreased with increased extent of KMnO4 treatment. Alkali and urea bisulfite solubilities of the treated wool increased and were favored by increase in pH, temperature, and concentration of the KMnO4 solution. Tensile strength and elongation of the treated wool were decreased slightly by the KMnO4 treatment. The affinity of treated wool to dyeing increased, and brighter colors were imparted to dyed wool in the case of pale and medium shades as compared to untreated wool. No change in the color of the treated wool after suitable KMnO4 treat ment was observed.