Process for the extraction of pure cellulose from annual and biennial plants

摘要

500,204. Obtaining cellulose. CONTARDI, A., and CIOCCA, B. Aug. 3, 1937, Nos. 21419 and 21420. Convention dates, July 31, 1936 and Nov. 3, 1936. [Class 2 (ii)] To obtain cellulose of high a cellulose and low ash content, suitable, e.g. for nitration or for the viscose industry, the stems or leaves of annual or biennial plants such as sorghum, buckwheat, sugar cane, marsh cane, bamboo, alfa, algerian esparto, cotton plant refuse or banana or palm leaves are subjected for 10 hours at 4 atmospheres pressure to treatment with at least 5 times their weight of a 1À5 per cent solution of sodium bisulphite, followed by washing, mechanical disintegration and a further treatment with caustic soda of less than 1 per cent strength. The material is finally washed, bleached and neutralized. In an example, the alkaline treatment is conducted for 5-6 hours at 2-3 atmospheres pressure with a weight of NaOH solution at least 5 times that of the material being treated. For the alkaline treatment, and for preparation of the sodium bisulphite, use may be made of caustic soda recovered in the course of artificial silk manufacture. The Specification as open to inspection under Sect. 91 states that the second treatment with alkali may be performed hot or cold at ordinary pressure but with a more concentrated soda solution. It also includes a claim for treating the material first with dilute soda solution and then with a dilute bisulphite solution. This subject-matter does not appear in the Specification as accepted.