Hydrolysis of Sugar for Dyeing of Cotton Fabric with Sulphur Black

Abstract

The importance of sulfur dyeing of cellulosic fibers, particularly cotton, is realized economically throughout the dyeing industry. At the present time, dyeing with sulfur dyes requires the use of various auxiliaries, many of which have adverse effects on the environment. The most damaging of these is the reducing agent sodium sulfide, required to reduce the dye molecules to a water-soluble leuco form to enable adsorption and diffusion into the fiber. Different researchers have made attempts to replace the sodium sulfide used within the sulfur dyeing process with a variety of environmentally friendly reducing sugars. But most of the researchers did not mention the waiting time of the hydrolyzed sugars. So, this papers mainly concentrates the impact of the hydrolyzed sugar waiting time on dyeing of cotton fabric with sulphur black and subsequently, cotton was dyed with the world's most important sulfur dye, using hydrolyzed sugars under alkaline conditions, and compared to dyeing secured by employing commercial sulfide reducing agents. It was observed that reducing sugars gave comparable, and in many cases superior, color strength and wash fastness results, with respect to the commercial sulfide-based reducing agents, which still account for the vast majority of sulfur dyeing processes and that pose significant environmental concern. Employment of reducing sugars in sulfur dyeing could provide a sustainable, nontoxic, biodegradable, cost-effective alternative to sodium polysulfide and sodium hydrogen sulfide.

Keywords: Waiting time, Hydrolysis, Dyeing sodium sulphide and sugar