The use of ultraviolet radiation in an adsorbable organohalogen‐free print preparation for wool and in wool dyeing: the Siroflash process

Abstract

German legislation controlling the discharge of adsorbable organohalogens (AOX) in process effluents has focused attention on the need for environmentally acceptable alternatives to chlorination as a prepare‐for‐print (PFP) treatment for wool. The Siroflash process is a novel AOX‐free approach which involves continuous UV irradiation of dry wool fabric, followed by conventional wet oxidation using hydrogen peroxide or permonosulphuric acid. Although permonosulphuric acid or peroxide treatments alone are ineffective as a PFP, the colour yields of prints on Siroflash‐treated fabric are similar to those on chlorinated wool. The synergistic interaction between UV exposure and wet oxidation results in high levels of cystine oxidation, cuticle damage and loss of soluble protein, all of which are highly specific to irradiated surface fibres. UV irradiation of wool can significantly increase dyeing colour yields. The use of 1:1 metal‐complex dyes is particularly effective, and a 3% o. w. f. dyeing on UV‐treated fabric can produce a better depth of shade than a 5% dyeing on untreated fabric.