GB469901A - Improvements in or relating to the production of cellulose ethers - Google Patents

Abstract

Cellulose ethers of low ether content suitable for working up into threads, films, plastic masses, and the like, are obtained by steeping cellulose in an aqueous solution of a water-soluble etherifying agent, pressing to remove excess of solution, shredding or otherwise disintegrating the pressed material and then treating it with caustic alkali solution, the etherification being continued until the product is capable of being brought into solution in dilute aqueous solutions of caustic alkali. The etherifying agent may be a water-soluble organic halogen compound such as an alkali metal chloroacetate, or glyceryl mono-chlorohydrin, or it may be an alkylating agent such as an alkali metal methyl sulphate. The cellulose may be loose or in sheets, and steeping may take place in batches or by continuously using it in roll or sheet form. Wetting agents may be used in the steeping process. The pressed mixture of cellulose and etherifying agent is placed in a shredder, and caustic alkali in aqueous or aqueous alcoholic solution is added. Mixing may be continued till the reaction is complete or the product may be removed from the mixer and stored till the reaction is finished. The product may be aged. In examples, wood cellulose sheets are steeped in an aqueous solution of chloracetic acid neutralized by sodium bicarbonate, and containing if desired as wetting-agent a small quantity of sodium salts of acids prepared from primary branched chain alcohols of 6--8 carbon atoms obtained synthetically by the reduction of carbon monoxide under pressure. After steeping for a few hours, the sheets are pressed, shredded, and mixed with sodium hydroxide in water or methanol-water mixture. Mixing is continued for several hours. The product with or without ageing is dissolved in dilute caustic soda in some cases by cooling to a temperature of -10 DEG C. In another example, sulphite wood cellulose sheets are steeped in sodium chloroacetate solution obtained by mixing the acid with crushed ice and neutralizing with caustic soda solution. The pressed sheets are shredded with caustic soda at a temperature at below 30 DEG C. and aged. The product is acidified with dilute sulphuric acid and washed. In other examples, glyceryl monochlorhydrin, or sodium methyl sulphate is used as etherifying agent. The products are soluble in water or caustic alkali solutions, or can be brought into solution in caustic alkali solutions by freezing and subsequent thawing.