GB733364A - An improved physico-chemical process for the extraction of celluloses from vegetablematerials in general, and a product obtained thereby - Google Patents

Abstract

Cellulose is obtained from fibrous vegetable material by crushing the material and then treating it with a dilute solution of an oxidizing agent in the presence of caustic soda, sodium carbonate or the like so that non-cellulosic constituents of the material undergo hydrolysis and are removed. The hydrolysis may be carried out at 30-50 DEG C. The oxidizing agent may be sodium, potassium or calcium hypochlorite; sodium or hydrogen peroxide; ammonium persulphate or sodium meta-perborate. Mixtures of oxidizing agents may be used if desired. Non-woody material such as straw, broom-corn, stems and cobs of maize, or genista is washed with water, ground and selected in lengths of 3-5 cm. The material is washed and then passed through crushing machines to break knots and crush the fibres, and to expel moisture and air. Small quantities of oxidizing agents may be present during the crushing. Woody material is washed and reduced to pieces of 2-5 cm. in length and then passed through crushing machines, preferably after being moistened with a dilute oxidizing solution. The crushed material may then be treated with a solution of sodium hypochlorite of specific gravity 1.15-1.18, together with caustic soda, sodium carbonate or the like to obtain an alkaline medium up to a pH of 9-12. During the reaction, chlorine is liberated. This is collected and returned to the liquid, through which it is bubbled. The heat liberated during the reaction may raise the temperature to 65 DEG C. The time of treatment may range from 1-6 hours. The treatment time may be reduced by projecting light on to the material undergoing treatment. At the end of the treatment the mass is filtered and the liquid is treated for the recovery of salts and chlorinated compounds formed during the reaction. The liquid may then be re-used for treating a subsequent quantity of the crushed vegetable material. The crude cellulose, freed from the bulk of treatment liquid, is washed with water at 40 DEG C. in a tank provided with a stirrer to dissolve salts and chlorinated compounds, and it is further washed in Hollanders. It is then subjected to an anti-chlor treatment with sodium thiosulphate solution, washed with water, treated with dilute sodium carbonate solution, washed again, filtered and dried.