STUDIES ON THE DYEING OF ACRYLONITRILE FIBER

(PART II) MECHANISM OF REDUCTION ON CUPRIC SULPHATE

Abstract

The constituion of poly-acrylonitrile fibre contains no cationic groups, which give absorption site for anionic acid dyes. But nitrile group co-ordinates with cuprous ion, introducing new positively charged sites in the fibre on which absorption of dye anions occurs. Cuprous ion is produced by cupric sulphate with reducing agents at high temperatures. Reduction and co-ordinate absorption must take place on the fibre simultaneously, so that under such conditions, redox potential, rate and extent of cuprous ion may become decisive factors in determing its suitablity for acid dyes.
From such considerations, our results suggest that hydroxylamine sulphate is more satisfactory reducing properties than other agents, as it reduces cupric sulphate slowly and moreover can show almost theoretical redox potential. However even this agent does not seem satisfactory for decrease less than 3 percent(o. w. f.).