GB631242A - Improvements in making of starch derivatives - Google Patents

Abstract

Ungelatinized starch derivatives are obtained by treating ungelatinized starch with a carboxylic acid anhydride in an aqueous alkaline medium of preferably pH 7 to 11. The derivatives show "non-gel," "increased water absorption" and "inhibited" characteristics depending on the quantity and type of anhydride used. In general, "non-gel" starches are obtained from acetic, propionic, butyric and phthalic anhydrides, "water absorptive" from succinic, maleic, glutaric and citraconic anhydrides these derivatives also having "non-gel" properties and inhibited starches from adipic and azelaic anhydrides. The starch used may be modified as by e.g. acid hydrolysis to yield "fluidity starches." Up to 10 per cent by weight of anhydride is preferred per weight of dry starch and alkalies mentioned are sodium, potassium and calcium hydroxides, sodium carbonate and tri-sodium phosphate. In the preferred method the anhydride is added to an aqueous alkaline suspension of ungelatinized starch. Other methods are the concurrent addition of aqueous alkali and anhydride to a starch milk; concurrent addition to the reaction vessel of aqueous alkali, anhydride and starch milk, heating a mixture of anhydride and commercially dry starch (containing about 5 to 20 per cent moisture) which has been treated with trisodium phosphate. Derivatives of anhydrides such as chloro-maleic anhydride may be used alone or mixed with anhydrides and acids such as citric acid may be used in conjunction with a dehydrating chemical such as acetic anhydride, acetyl chloride and thionyl chloride, in which case the corresponding acid anhydride is produced. The derivatives obtained may be after-treated as by e.g. chlorination with sodium hypochlorite solution. The products may be used as sizes in the textile and paper trades, and in the adhesive and food industries. In examples, "non - gelling" starches are produced by treating corn starch with 2 per cent sodium hydroxide solution and (1) and (2) acetic anhydride, (6) maleic anhydride followed by sodium hypochlorite and (7) phthalic anhydride, (3) by the concurrent addition of propionic anhydride and 3 per cent sodium hydroxide to corn starch milk, (4) and (5) from 20 fluidity starch by treatment with maleic and acetic anhydrides, (8) and (9) from corn starch by treatment with succinic anhydride and 3 per cent sodium hydroxide, sodium succinate formed being removed at the halfway stage because it buffers the reaction, (14) and (15) heating a mixture of corn starch with either acetic or succinic anhydride and trisodium phosphate, "water absorptive" by (7), (8), (9), (14), (15) and (10) from tapioca starch on treatment with chloro-maleic anhydride and 3 per cent sodium hydroxide, and "inhibited" by waxy maize starch and 3 per cent sodium hydroxide and (11) adipic anhydride, (12) mixed succinic and acetic anhydrides, (13) from high-grade tapioca starch with 3 per cent sodium hydroxide and adipic or citric acid in acetic anhydride and (16) by heating waxy-maize starch with adipic anhydride and trisodium phosphate.