Patent ID: 9359450
Filing Date: 2016-06-07
CPC Classification: C08B

Claim Text:
1. A process for reducing the amount of water-insoluble fibers in a water-soluble cellulose derivative comprising the steps of ai) treating cellulose with an alkali metal hydroxide to produce alkali cellulose, aii) reacting the alkali cellulose with a derivatizing agent to produce a water-soluble cellulose derivative, and aiii) washing the water-soluble cellulose derivative with a washing liquor having a temperature of 65 to 95° C. to remove by-products with or without a subsequent drying step but in the absence of a grinding step, to provide a water-soluble cellulose derivative having a residual amount of at least 20 ppm by weight of water-insoluble fibers in a 2 weight percent aqueous solution of the water-soluble cellulose derivative; b) mixing the water-soluble cellulose derivative of step a) with a liquid in a compounder to provide a moist water-soluble cellulose derivative having a temperature of at least 55° C. and up to 75° C. and a moisture content of from 50 to 75 percent, based on the total weight of the moist cellulose derivative; and c) drying-grinding the mixture of step b) having a temperature of at least 55° C. and up to 75° C. in a gas-swept impact mill to obtain a dried and ground cellulose derivative, wherein the water-soluble cellulose derivative is a methylcellulose or a hydroxypropyl methylcellulose.