An oxidative batchwise shrink-resist treatment for wool using monoperoxyphthalic acid

The effectiveness of three oxidising agents have been compared in a batchwise process for conferring wash fastness to wool in the form of tops, knitting yarn and knitted and woven cloth. The three were dichloroisocyanuric acid (DCCA), peroxymonosulphuric acid (PSA) and monoperoxyphthalic acid. DCCA, the commonly used agent for batch shrink-resist treatments, reacts so rapidly as to cause unevenness. It also tends to harden and yellow the fibres and so is usually used at low application rates, as a pretreatment before the application of a resin. It contributes to the presence of organic halides in effluent (AOX). Neither PSA nor monoperoxyphthalic acid suffered from these deficiencies, but PSA could only be used successfully for woven cloth, unless applied with resins. Monoperoxyphthalic acid was effective for wool in all its forms, without subsequent resin treatment However, it is not available in commercial quantities, so a simple process for preparing it cheaply from phthalic anhydride and hydrogen peroxide has been developed. It can be applied after dyeing with Lanaset dyes without significant shade change.