ARS | Publication request: Preparation and Properties of Sorbitol Citrate Polyesters

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: April 17, 2006
Publication Date: June 15, 2006
Citation: Shogren, R.L., Doll, K.M., Gonzalez, S.O., Willett, J.L., Swift, G. 2006. Preparation and properties of sorbitol citrate polyesters [abstract]. BioEnvironmental Polymer Society Meeting. p.93.

Technical Abstract: There is much current interest in developing biodegradable water soluble and swellable polycarboxylates to replace non-degradable petroleum based polymers such as polyacrylic acid (PAA). PAA enjoys wide use as an antiscalant, flocculant and superabsorbant. Although sorbitol and starch citrates have been prepared previously, these procedures required large amounts of solvent and products were often highly cross-linked. The goal of this research was to develop an economical, solvent-free method to prepare polysaccharide citrates which can replace PAA but also be biodegradable and renewable. Sorbitol was selected initially as a polysaccharide model since it melts at 99 deg C and thus can be easily processed. Sorbitol citrate polyesters were prepared by melting mixtures of sorbitol and citric acid, mono- or di-sodium citrate at 110-200 deg C then removing water of esterification in a vacuum oven, mixer or twin screw extruder. Esterification was confirmed by FTIR bands at 1735 and 1188 cm-1 and decreases in acid value of 20-80%. Reaction rates increased with increasing temperature, sodium (for Na/citrate less than 0.5) and sorbitol concentrations. With citric acid, the resulting polyesters were partially water insoluble and had water absorbencies at pH 7 of about 16 g/g polymer and 60 g/g insoluble polymer. With mono-sodium citrate, polyesters were water soluble and had molecular weight components ranging from monomeric to 4000 by GPC. Sorbitol citrates had significant activity in preventing CaCO3 crystallization, although more was required than for PAA.