GB727019A - Process for treating cellulose and for the manufacture of cellulose in the form of powder - Google Patents

Abstract

Cellulose with a reduced degree of polymerization is produced by passing cellulose containing not more than 35 and preferably not more than 10 per cent of moisture one or more times through the nip of one or more pairs of closely spaced hard-surfaced hollow rolls through which cooling water is passed, the nip clearance not exceeding 0.05 mm. and preferably not exceeding 0.02 mm., and the rolls of each pair of rolls rotating at different peripheral speeds with respect to each other, so that the temperature of the cellulose is raised sufficiently to cause the cellulose to become brittle and the rolled product consequently becomes disintegrated into flakes. The flakes may be ground in a mill into a powder free from fibres. Preferably sheets of cellulose 0.5-3 mm. thick are passed singly through the nip of the rolls. In the example sheets of chemical wood pulp containing 9 per cent of moisture, based on dry cellulose, and 0.9-1.2 mm. thick, are passed 4 times through the nip of a pair of rolls each 7 cm. in diameter, rotating at 23 and 18-19 r.p.m. respectively and having a nip clearance of 0.01 mm. The rolls are cooled with water having an inlet temperature of 13 DEG C. After the treatment the D.P. of the cellulose has decreased from 900 to 750. The cellulose to be treated may be in the form of continuous strips, and the nip clearance of successive pairs of rolls may decrease. The cellulose may be in the form of cotton linters or fibres or refined wood pulp flakes. Specification 683,385 and U.S.A. Specification 1,910,406 are referred to.