GB935339A - Hydroxyalkyl amylose - Google Patents

Abstract

Hydroxyalkyl amylose, defined as a reaction product between amylose or chemically modified amylose and a vic-epoxy compound, is obtained in a form which is substantially water-insoluble at temperatures up to 100 DEG C., and forms at temperatures above 100 DEG C., an aqueous solution which neither gels nor retrogrades on subsequent cooling to room temperature. The hydroxyalkyl amylose has a molar substitution of at least 0,15 and is prepared by treating a suspension of amylose at 30 DEG to 90 DEG C. with at least 0,2 moles of a vic-epoxy compound and at least 0,04 moles of an alkaline catalyst per mole of amylose and neutralizing the suspension. The suspending liquid is a polar solvent for the vic-epoxy compound and may be, e.g. water, alcohols or ethers. The resulting coldwater insoluble hydroxyalkyl amylose may bee solubilized by heating the neutralized suspension to above 100 DEG C., and subsequently cooling. Alternatively the cold water-insoluble product may be separated from the suspending liquid, dispersed in water, heated to above 100 DEG C. until the hydroxyalkyl amylose is dissolved, and cold water-soluble product isolated from the cooled solution. The solution may be dispersed on a surface to form, on evaporation of the liquid, a self-supporting flexible film of hydroxyalkyl amylose assaying at least 0,15 moles of alkylene oxide per mole of amylose. Alternatively, cold water-soluble hydroxyalkyl amylose may be isolated from solution by precipitation with an organic material, or by spray-drying. The hydroxyalkyl amylose of the invention ,ay be separated from that having a molar substitution of at least 0,40 and which is immediately cold water-soluble, by filtration or centrifugation, when water is the suspending liquid. If an organic suspending liquid is used, the solid hydroxyalkyl amylose is separated therefrom, re-suspended in water and again separated. The amylose used may be a crystalline, amorphous or spray-dried form, prepared from any native starch modified by, e.g. hypochlorite oxidation, acid hydrolysis, or enzymic degradation. The vic-epoxy compounds may be alkylene oxides such as ethylene, propylene, and 1,2-butylene oxides, or substituted alkylene oxides such as 9,10-epoxystearic acid, 3-diethylamino-1,2-epoxy-propane and epoxidized soybean oil acids. The alkaline catalysts may be any alkaline material soluble in the suspending liquid, e.g. alkali and alkaline earth metal hydroxides, tetra-alkylammonium hydroxide, tetra-alkylphosphnium hydroxides, pyridine or alkali metal alcoholates. Specifications 895,215 and 895,429 are referred to.