Polysaccharides substituted with polycarboxylated moieties

Abstract

A derivatized polysaccharide in which at least a portion of the active hydrogens originally present in the polysaccharide are substituted by monovalent aliphatic groups containing at least two carboxylic acid groups to an extent sufficient to provide a degree of substitution of at least about 0.1. The monovalent aliphatic groups contain from 4 to about 10 carbon atoms. The polysaccharide may be cellulose. At least a portion of the carboxylic acid groups present in the derivatized polysaccharide may be crosslinked permanently or reversibly. The monovalent aliphatic groups containing at least two carboxylic acid groups may be derived from 2,3-epoxysuccinic acid; 1,2-epoxypropane-1,2,3-tricarboxylic acid; 2-(epoxyethyl)-succinic acid; or mixtures thereof. Also provided is a method of preparing a derivatized polysaccharide. The method involves providing a polysaccharide; dispersing the polysaccharide in a strongly alkaline aqueous alcohol solution; adding to the dispersion an excess of an aliphatic polycarboxylic acid having an epoxy group, wherein the aliphatic polycarboxylic acid contains from 4 to about 10 carbon atoms; and heating the dispersion at a temperature and for a time sufficient to permit the reaction of epoxy groups of the aliphatic polycarboxylic acid with active hydrogens present in the polysaccharide to an extent sufficient to result in a degree of substitution of at least about 0.1. The present invention further provides a paper containing an amount of the derivatized cellulose described above sufficient to provide improved strength characteristics to the paper, compared with an otherwise identical paper which lacks the derivatized cellulose.