Amylopectin was partially dicarboxylated so as to retain the unreacted glucopyranose groups as biodegradable segments in the polymer chain; and the bioenzymatic degradability, as well as builder performance in detergent formulations, was evaluated and compared with data obtained from amylose. Dicarboxylation of amylopectin was carried out by conversion of the vicinal diols of the glucopyranose groups of amylopectin into the corresponding dicarboxylates via dialdehydes. The aerobic biodegradability of sodium dicarboxyamylopectin (DCAp) was evaluated by measuring the biological oxygen demand (BOD) with activated sludge. The biodegradability, of DCAp depended on the content of unreacted glucopyranose groups in the polymer chain. DCAp containing more than 80 mol% glucopyranose groups showed excellent biodegradability. The biodegradability, obtained by the BOD test, and the enzymatic degradability also correlated well, suggesting that these polymers are first cleaved at the unreacted glucopyranose units with subsequent assimilation of the resultant oligomeric fractions. DCAp, which was biodegradable under aerobic conditions, also biodegraded under anaerobic conditions. Detergency tests were carried out with heavy-duty detergent formulations. The detergency was determined by the content of dicarboxylate groups in the polymer when compared on an equal weight basis. The polymers with high dicarboxylate contents showed better builder performance. DCAp showed better builder performance than the corresponding amylose derivatives. This excellent builder performance is ascribed to the cluster-type structure of amylopectin, in which calcium ion is effectively sequestered. Builder performance in detergent formulation improved greatly with increasing amounts of DCAp used in the detergent formulation.
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