SINGLE BATH FULL BLEACHING OF WOOL USING SODIUM TRITHIOCYANURATE IN-PLACE OF THIOUREA

A single bath full bleaching procedure for textile materials has been developed. In this procedure, following oxidative bleaching using hydr ogen peroxide, the peroxide bath is converted to a reductive bath by a ddition of thiourea and bleaching continues without the need for a fre sh bath for the reductive step. Such full bleaching is easy, economica l and very effective in inducing improved whiteness. One drawback is t he toxic nature of thiourea. Thiourea, though easily handled and thoro ughly consumed in this procedure, is classified as a carcinogen unlike its oxidized counterpart, thiourea dioxide (formamidinesulfinic acid) . This work presents how thiourea may be replaced by sodium trithiocya nurate (Na(3)TTCA), which is not classified as a carcinogen. Full blea ching with the modified protocol is just as effective as the procedure using thiourea, but Na(3)TTCA was found to be most effective at 90% o f the stoichiometric weight to peroxide, as opposed to 70% for thioure a; the Na(3)TTCA process was more sensitive to the pH of the rinse bat h than the thiourea process; and the Na(3)TTCA reagent is more expensi ve than thiourea. Nevertheless, the attractiveness of using Na(3)TTCA is the avoidance of a potential carcinogen and achievement of exceptio nal whiteness over conventional peroxide bleaching.