Synthesis of cationic hydrolyzed starch with high DS by dry process and use in salt-free dyeing

Cationic hydrolyzed starch was prepared by hydrolyzed maize starch with 2,3-epoxypropyltrimethyl ammonium chloride by dry process. Experiments showed that 80 °C, 1 h, 0.1:1 of molar ratio of sodium hydroxide to cationizing reagent were suitable for cationization, and high degree of substitution of cationic hydrolyzed starch was obtained. The structures of the hydrolyzed maize starch and cationic hydrolyzed starch were characterized by IR spectroscopy, scanning electronic microscopy and X-ray diffraction. The synthesized cationic hydrolyzed starch was employed in salt-free dyeing of reactive dyes. It showed that high dye fixation and level dyeing were obtained by pretreating cotton with the cationic hydrolyzed starch with low viscosity and high DS. Besides, wash fastness and rub fastness were not affected. The highest dye fixation in salt-free dyeing is higher than that of conventional dyeing by 20.3%, 0.9% and 18.4% for C.I. Reactive Red 2, C.I. Reactive Blue 19 and C.I. Reactive Yellow 145, respectively.