Adsorption of direct cotton dyes by chemically modified celluloses

Abstract

Equilibrium adsorption of two direct cotton dyes on cellulose oxidized with specific oxidizing agents and by the products of reduction of these oxycelluloses, under standard conditions of dyeing has been studied. It is shown that conversion of hydroxyl groups of cellulose to carbonyl groups does not influence dye adsorption, but formation of ioniz able carboxyl groups in cellulose chain molecules brings about an appreciable reduction in dye uptake, the extent of reduction being independent of the position in the glucose units of cellulose at which the carboxyl group is formed. Based on a theoretical treat ment, it is shown that only a fraction of the total carboxyl groups is responsible for the reduction in dye adsorption under specific conditions of dyeing, and with progressive increase in the total carboxyl content of cellulose, the value of this fraction goes on de creasing continuously.