Factors influencing production of cationic starches

Abstract

The main factors – the amount of catalyst NaOH, the temperature and composition of reaction mixture – influencing the effectiveness of starch cationization with glycidyltrimethylammonium chloride (GTAC) were investigated. It was found that cationic or cross-linked cationic starches with preserved microgranules, a degree of substitution from 0.2 to 0.85 and reaction efficiency from 82% to 93% could be obtained during etherification of starch or cross-linked starch with a mixture containing GTAC, “free” water and 0.04–0.08mol/AGU sodium hydroxide in heterogeneous condition. The activation energy of the GTAC main reaction is lower than that of the side reactions, thus starch cationization at a lower temperature proceeds with higher reaction efficiency.The amount of NaOH in the cationization mixture has a great influence on the rate of the main and side reactions of GTAC. Only the main reaction – cationization of starch – proceeds when all the NaOH present in the reaction mixture is adsorbed from the liquid phase by the starch. The duration of this “first reaction stage” decreases with increasing reaction temperature and the amount of NaOH in the reaction mixture. NaOH present in the liquid phase of the reaction mixture catalyzes the side reactions of GTAC and changes their character.