GB548280A - Improvements in and relating to the production of cellulose - Google Patents

Abstract

548,280. Caustic soda; soap; natural resins. BAKER, A., SALE, G. S., and SALE, C. V. (trading as SALE & CO.). Feb. 28, 1941, No.2725. [Classes 1 (ii), 91 and 95] [Also in Group IV] The liquor resulting from the boiling of cellulosic material in a caustic soda solution is trated with carbon dioxide or alumina in such proportion that precipitation of organic matter takes place and sodium bicarbonate or sodium aluminate is formed. The sodium salt is subsequently converted into caustic soda. When using carbon dioxide, the liquor is saturated with the gas, e.g. 11 pounds of carbon dioxide to each 10 pounds of caustic soda. The organic matter is precipitated without concentration of the liquor and it is separated, e.g. by filtration or centrifuging. The resulting sodium bicarbonate liquor is converted into a caustic soda solution; e.g. by treatment with lime. If alumina is used as precipitating agent, it is intimately mixed in moist freshly precipitated form with the liquor, e.g. 15 pounds calculated as dry aluminium oxide for each 10 pounds of caustic soda. Resins are separated and sodium aluminate remains in the solution. This may readily be converted into caustic soda. Before treating the liquor with carbon dioxide or alumina the free caustic soda may be converted into soap. The liquor may be heated with a saponifiable fat or fatty acid, e.g. 35 pounds of stearic acid for each 10 pounds of caustic soda, to form a soap which separates as a solid on cooling. The remaining liquid containing sodium compounds of resins is then treated with carbon dioxide or alumina to precipitate resins. The cellulosic material may be linseed straw or a hard wood. The Provisional Specification refers also to the use of other weakly acidic or amphoteric substances as precipitants instead of carbon dioxide or alumina.