GB833834A - Water-soluble thermoplastic cellulose ethers - Google Patents

Abstract

Hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, or hydroxybutyl methyl cellulose, which is both soluble in cold water and thermoplastic is produced by subjecting an alkali cellulose, initially having an alkali to cellulose ratio of 0.7-1.5 and prepared by treating cellulose with a 30-60% aqueous sodium or potassium hydroxide solution, to the action of 0.34-0.6 part by weight of ethylene oxide or 0.45-0.8 part of propylene oxide or 0.15 to 0.8 part of butylene oxide per part of cellulose, p at a temperature not in excess of 40 DEG C., until the olefine oxide is substantially fully reacted, and to the action of 1.1-2.0 parts by weight of methyl chloride per part of cellulose, at a temperature of 40 DEG to 80 DEG C., until all the methyl chloride is fully reacted. Both etherifying agents may be present at the start of the etherification reaction, or the methyl chloride may be added after the reaction with the olefine oxide is substantially complete. The preferred product is a cellulose ether having 10-14% by weight of hydroxypropyl groups and 25-30% by weight of methyl groups. Other products contain 10-14% of hydroxyethyl groups and 25-30% by weight of methyl groups, or 5-7% of hydroxybutyl groups and 27-28.5 of methyl groups. In an example, alkali cellulose having a NaOH/cellulose ratio of 1.35 is heated in a rotating pressure vessel at 40 DEG C. for 3 hours with propylene oxide and methyl chloride in the ratios propylene oxide/cellulose = 0.5 and methyl chloride/cellulose = 1.67. In 4 hours the temperature of the mixture is raised to 60 DEG C. and then maintained for 2 hours at that temperature. The cellulose ether thus obtained is then washed with hot water and dried. Specifications 796,308, 798,448 and 804,749 are referred to.