Single stage process for desizing, scouring, and bleaching of cotton fabric

Abstract

AbstractThe efficiency of a treating bath formulation consisting of H2O2, sodium hydroxide, chelating agents, wetting agent, metal ions, and MgSO4 · 7H2O in effecting combined desizing, scouring, and bleaching of cotton fabric using a winch beck system was investigated under different conditions. Presence of MgSO4 · 7H2O at a concentration of up to 3 g/l was essential for stabilization of the strongly alkaline H2O2 solutions (containing 10 g/l NaOH) at 95°C for 90 min to achieve complete starch removal and to bring about fabric with satisfactory whiteness and absorbency without seriously degrading the fibre substance. Chelating agents, namely EDTA and gluconic acid (2 g/l, each) assisted in stabilization of H2O2 even in presence of Fe3+, Cu2+ or both ions and resulted in improved whiteness and lower fibre degradation but had no effect on residual starch or on wettability of the fabric. The wetting agent used had no significant effect on stabilization of H2O2 and fibre degradation, but it helped starch removal and improved the wettability of the fabric. The decomposition of H2O2 increased by increasing its own concentration from 2 to 12 ml/l as well as the concentration of sodium hydroxide from 5 to 17.5 g/l. The same hold true for temperature (60 to 98°C) and duration (30 to 150 minutes). Combined desizing, scouring, and bleaching of loomstate cotton fabric could successfully be effected by using a treating bath consisting of sodium hydroxide (10 g/l), H2O2 (4 ml/l), MgSO4 · 7H2O (3 g/l), EDTA (2 g/l), gluconic acid (2 g/l), anionic/nonionic wetting agent (1.5 g/l) at 95°C for 90 min, and a material : liquor ratio of 1 : 25.