GB388656A - Improvements in processes for producing practically pure cellulose ("alpha-cellulose") from raw celluloses of any origin - Google Patents

Abstract

388,656. Preparation of cellulose. PALAZZO, F. C. and PALAZZO, F., 34, Via Montebello, Florence, Italy. July 19, 1932, No. 20462. Convention date, Aug. 4, 1931. [Class 96.] Cellulose containing 96-99 per cent alphacellulose is obtained from raw cellulose of any origin by treating with an alkaline sulphite liquor containing 1-1À5 per cent NaOH and 0À5-À75 per cent Na2SO3 under a pressure of À5-2 atmospheres for 1-3 hours. The pulp at a concentration of 5-6 per cent may be bleached with a slightly alkaline sodium hypochlorite solution, containing 1-2 per cent active chlorine, or with a slightly acid potassium permanganate solution, or with both systems successively. Any remaining impurities are removed by a treatment with dilute sulphurous acid, e.g. À5-1 per cent solution, or with dilute hydrochloric acid followed by a thorough washing. To obtain a very pure product, the pulp may be subjected to a second treatment with the soda-sulphite solution at a pressure of À5-1 atmosphere for a period up to 1 hour. The percentage of chemicals added is calculated to allow for the moisture content of the raw material, and for the amount of condensate if the heating is effected by steam injection. The proportion of raw cellulose to liquor varies from 1 : 4 for air-dried raw material to 1 : 10 for watery material. The product may be shaped according to its ultimate use, either as a mass resembling cotton wool obtained by drying the product with hot air and then carding or treating in a centrifugal disintegrator, or as thin leaves or foils, which may be cut into ribbons, or as felt, prepared on a rotary suction filter.