GB1253726A - Manufacture of carboxymethyl hydroxyalkyl mixed cellulose ethers - Google Patents

Abstract

1,253,726. Mixed carboxymethyl hydroxyalkyi cellulose ethers. DOW CHEMICAL CO. 18 Feb., 1969, No. 8746/69. Heading C3A. Mixed carboxymethyl hydroxyalkyl cellulose ethers having from 2 to 4 carbon atoms in the hydroxyalkyl groups are prepared by reacting cellulose, an alkali metal chloroaoetate and an alkali metal hydroxide in the presence of water to provide a carboxymethyl cellulose with a carboxymethyl degree of substitution of from 0-2 to 1-0, acidifying the carboxymethyl cellulose with a fluid acid to reduce the pH to less than 7, washing the acidified carboxymethyl cellulose ether with water to remove impurities, drying the washed ether to a moisture content of from 20 to 75% by weight of the ether, reacting the dried ether with an alkylene oxide containing from 2 to 4 carbon atoms, e.g. ethylene or propylene oxide, in the presence of at least 0À01% by weight, based on the weight of the ether, of a basic catalyst to provide a mixed carboxymethyl hydroxyalkyl cellulose ether having a hydroxyalkyl molar substitution from 0-2 to 5-0. The starting material cellulose is preferably in particulate form, which form is retained in the final product. The reaction of the cellulose, alkali metal chloroacetate and alkali metal hydroxide is preferably carried out in the absence of oxygen, at 25‹ to 90‹ C. with vigorous agitation. The fluid acid may be an acidic gas, e.g. gaseous hydrogen chloride, or an aqueous solution of a mineral acid, and the catalyst may be an aqueous alkali metal hydroxide, e.g. NaOH.