GB1263172A - Preparation of mixed cellulose ethers - Google Patents

Abstract

1,263,172. Preparation of mixed cellulose ethers. DOW CHEMICAL CO. 12 Feb., 1969, No. 7579/69. Heading C3A. [Also in Division E1] Mixed carboxyalkylhydroxyalkyl cellulose ethers, wherein the carboxyalkyl and hydroxyalkyl groups each contain from 2 to 3 carbon atoms, having a carboxyalkyl M.S. (i.e. the average number of moles of that substituent attached, directly or indirectly through a side chain, to each anhydro-glucose residue unit of the ether) of 0À2 to 1À2 and a hydroxyalkyl M.S. of 1À5 to 5, are prepared by reacting cellulose with, in order of addition, an alkali hydroxide (i.e. an alkali metal hydroxide or quaternary ammonium base), a chlorinated carboxylic acid having from 2 to 3 carbon atoms and an alkylene oxide having from 2 to 3 carbon atoms to form the cellulose ether, which is dried in the presence of from 0À1 to 3% of base, based on the weight of the reaction mass, at a temperature less than 200‹ F. A portion of the total chlorinated carboxylic acid used may be reacted with the alkalized cellulose prior to the addition of the alkylene oxide to provide an intermediate carboxymethyl cellulose with a carboxymethyl M.S. of 0À05 to 0À2. The alkali hydroxide used may be sodium or potassium hydroxide or trimethyl benzyl ammonium hydroxide. When too little base remains in the reaction mass, additional base (e.g. an alkali metal hydroxide or carbonate or quaternary ammonium compound) is incorporated at the end of the reaction. A preferred product is a carboxymethyl hydroxyethyl cellulose having a carboxymethyl M.S. of 0À3 to 0À5 and a hydroxyethyl M.S. of 1À8 to 3. The ethers are soluble in water and brine and are non-thermogelling.