| 摘要 |
A granular, cyanoethyl ether of acid-hydrolysed starch is gelatinizable in water at pH 6 to 8. The starch may be hydrolysed by acid to a fluidity of 18-97 c.c. and, before or after hydrolysis, cyanoethylated to DS 0.01-0.09 in aqueous medium at alkaline pH. In one embodiment, an aqueous suspension containing 10-60% by weight of starch is heated to a temperature less than the gelatinization temperature with 0.1-10% by weight, based on dry weight of starch, of sulphuric or hydrochloric acid. When the desired fluidity has been obtained, the slurry is neutralized by a strong base. Acrylonitrile (e.g. 0.03-0.12 moles/ mole of starch) is added to an aqueous alkaline (pH 7-12) suspension of the acid-hydrolysed, granular starch and the mixture is heated until a DS of 0.01-0.09 is obtained. The reaction mixture is neutralized to pH 6-8, washed and dried. The product may then be bleached. A slurry of the granular cyanoethyl starch ether in water (pH 4-8) is used to surface-size paper webs. (Divisions D1-D2).ALSO:Paper is surface-sized by applying to the web an aqueous paste of a cyanoethyl ether of acid-hydrolysed starch at pH 4 to 8, and drying the web. The starch ether may have a cyanoethyl D.S. of 0.01-0.09, and the aqueous paste of the ether may be acid-hydrolysed to a fluidity of 18-97 cc. The paste may be applied to the paper as it passes between two rolls, e.g. the nip of a vertical size press. |
