Cationization of cotton for low-salt or salt-free dyeing

Abstract

Cotton acquires negative charge in aqueous med ium and thus repels negati vely charged dye ani on during dyeing. Such repul sion between fibre and dye is offset by using large quantity of salt in dye bath. particularly for reacti ve dyes. A low dye bath ex haustion also leads to low dye fixation of reactive dyes on cotton. Thus. the use of hi gh salt concentration and low reactive dye fixation lead to environmental problems related to hi ghly coloured efnu ent with high salt content. These problems can be overcome by improving the dye substantivity of cotton in the absence of salt or with low salt additions. One such approach is cation ization of cotton which is criti ca lly reviewed in the present paper. Majori ty of the chemica ls used for in troducing cat ionic si tes in cotton are themselves not sa fe environmentall y. Therefore. there is a need to explore the potentiality of the cationi za ti on route using eco fri endly chemicals. The use of chitosan. a polymer derived from chitin . is a step forward in this direc tion.