Patent ID: 9534061
Date: 2017-01-03
CPC Classifications: C08B

Claim:
1. A method for preparing a cellulose ether, comprising the steps of: bringing pulp into continuous contact with 35 to 60% by weight aqueous solution of alkali metal hydroxide to generate a contact mixture consisting essentially of alkali cellulose and unreacted alkali metal hydroxide solution, said pulp is in the form of chips; draining the contact mixture using a continuous centrifugal separator to separate a cake comprising the alkali cellulose from an alkali metal hydroxide containing liquid, wherein said centrifugal separator is a continuous centrifugal separator comprising a perforated rotor; and etherifying the alkali cellulose obtained in the draining step with an etherifying agent to produce cellulose ether, wherein the alkali metal hydroxide containing liquid obtained in the draining step is subjected to addition of a new alkali metal hydroxide solution and recycled into said step of bringing pulp into continuous contact in an amount equal to an amount of the alkali metal hydroxide solution contained in the alkali cellulose so as to keep the concentration of the alkali metal hydroxide solution constant in the step of bringing pulp into continuous contact.