Zeitschrift für Textilwissenschaft und -technik

Eco-friendly, Salt-Free Reactive Dyeing by Cationization of Cotton with Amino Acids Obtained from Soya Bean Hull

Abstract

Dessiea A and Govindanb N

Cotton acquires negative charge in aqueous medium and thus repels negatively charged dye anion during dyeing. Such repulsion between fibre and dye is offset by using large quantity of salt in dye bath, particularly for reactive dyes. A low dye bath exhaustion also leads to low dye fixation of reactive dyes on cotton. Thus, the use of high salt concentration and low reactive dye fixation lead to environmental problems related to highly coloured effluent with high salt content. Hence, modifying the cotton fibre to increase dye-fibre interaction is therefore the best route to overcome the lack of affinity for cotton to reactive dyes making salt-free reactive dyeing. However, majority of the chemicals used for imparting cationic sites in cotton are themselves not eco-friendly. This paper presents the possibility of salt-free reactive dyeing of cotton by modifying the surface of cotton fabric using soya bean hull. The cationization of cotton was carried out with natural amino acid extract obtained by acid hydrolysis from soya bean hull and cationized in the pad-dry-curing process to investigate its dyeability with reactive dye in both a conventional alkaline dye bath and salt-free acidic dye bath. FTIR spectroscopy confirmed that there was a change in chemical composition after cationization by pad-dry-cure technique. The color strength of modified cotton was better than that of conventional sample which is 3.9865 and 3.7135 respectively. The extent of improvement was 4% in dye exhaustion, 3.34% in dye fixation and 7.12% in the total dye utilization was achieved in this study. The wash, dry rubbing and perspiration fastness of the cationized cotton was found almost similar to that of the normal dyeing. There was a slight increase in flexural rigidity and crease recovery angle in the cationized cotton. The tensile strength of cationized and the conventional dyed cotton were found almost the same. The cationized cotton dyeing technique reduced the BOD, COD and TDS by around 32.4%, 27.3% and 75.4% respectively. It was revealed that soya bean hull was found to be effective for cationization in salt-free dyeing of cotton.