GB506875A - Two-stage process for decomposing plants containing silicon, especially grain straw, to form highly refined cellulose - Google Patents

Abstract

506,875. Refining cellulosic materials. EGGERT, J. W. June 8, 1938, No. 16978. Convention date, Sept. 11, 1937. [Class 2 (ii)] Straw, e.g..grain straw, and other plant materials containing silica are first subjected to treatment with an aqueous solution of a salt having a reducing action, e.g. sodium or potassium sulphite, at a temperature of 120- 130‹ C. so. as to remove all water-soluble constituents. The extraction liquid may also contain a phosphorous salt. The materials are then subjected to treatment with a solution of caustic soda containing a reducing salt at a temperature of 140-160‹ C. The lye is subsequently removed from the treated cellulose rapidly and completely whilst in a hot state. The cellulose material may then be subjected to the action of chlorine in a concentration of 0À43-1 per cent in aqueous solution at a temperature not exceeding 17‹ C. Buffer substances are present during the chlorination treatment so as to prevent acid formation. The material may then be subjected to a further treatment with alkalies, alkaline earths; or alkaline salts. The final alkaline treatment may be effected with concentrated alkalies or alkaline-earth hydroxides at low temperature. An anti-chlor, e.g. sodium sulphite may be added to the solution, and the alkali may then be washed out by means of low-pressure wet steam. The cellulose pulp may be acidified before the last washing process. The cellulose pulp may be used for making cellulosic solutions.