Process for preparing cellulose ether

Abstract

A process for preparing a cellulose ether which comprises reacting celluloses untreated or treated with an aqueous solution of alkali hydroxide with an etherifying agent in the presence of an aqueous solution of alkali hydroxide, an organic solvent being substantially immiscible with water and capable of dissolving the etherifying agent and a quaternary salt having the following general formula: ##STR1## wherein M is nitrogen atom or phosphorus atom, R.sup.1, R.sup.2, R.sub.3 and R.sub.4 are independently an organic group and X.sup.- is an anion. According to the process, the etherification is carried out uniformly to give a cellulose ether of a high quality in which the substituents are uniformly distributed. The process includes two processes for preparing a low viscosity carboxymethyl ethyl cellulose: One is a process in which carboxymethyl cellulose is mercerized in the presence of hydrogen peroxide to give a mercerized carboxymethyl cellulose having a low molecular weight and it is etherified according to the above process. The other is a process in which the carboxymethyl ethyl cellulose prepared according to the above process is depolymerized in the presence of hydrogen peroxide. The low viscosity carboxymethyl ethyl cellulose obtained has a uniform quality and give a completely continuous coating film.