Process for the preparation of watersoluble methyl hydroxypropyl ethers of cellulose

Abstract

Abstract Water-soluble hydroxypropyl-methyl cellulose is produced by treating soda cellulose having a weight ratio of air-dry cellulose to NaOH between 1:0.5 and 1:0.9 simultaneously with 0.02 to 0.15 part by weight of propylene oxide and at least 4 parts by weight of liquid methyl chloride per 1 part by weight of air-dry cellulose under pressure at temperatures from 40 DEG to 100 DEG C., and subsequently, after removal of the excess methyl chloride, the crude product is purified in a known manner, e.g. washed with water at about 85 DEG to 95 DEG C. to remove any sodium chloride and methanol formed, and centrifuged or filtered to remove excess water. The washed product may then be homogenized in an extrusion press from which it is extruded in the form of strands, dried and ground, e.g. in a hammer mill, to a grain size of 0.1 to 0.6 mm. The product may then be dried in a current of hot air to a water content of about 5 to 12%. A small proportion of a wetting agent may be added to the purified product before the homogenizing step. "Air-dry" cellulose is defined as common cellulose having a water content of 4.5 to 6.5% by weight.

Inventors

• 👤 Werner Scherff

Bibliographic Details