GB465554A - Process for obtaining cellulose from liquified cellulosic matter - Google Patents

Abstract

In a process for obtaining from lignified cellulosic matter a cellulose which can be bleached in an exceedingly easy manner, the matter is treated for 8--18 hours at 105--106 DEG C. with a lye containing, with respect to its total quantity about 6 per cent free SO2 and sodium bisulphite corresponding to 0,13--0,15 per cent sodium oxide, is thereafter mechanically transformed into pulp and subjected, while circulating through the stamp mill at a density of 5--8 per cent, to a current of gaseous chlorine conveyed into the pulp at the point where the latter receives the thrust of the propeller, chlorine being introduced until it is no longer absorbed by the cellulosic matter. The material in suitable size is introduced into an insulated lixiviator, preferably adapted for circulation, submitted to the action of a current of steam and then rapidly cooled by circulation of cold water. The water is pumped off and lye introduced. The lye contains about 9 per cent SO2 together with the necessary amount of sodium carbonate so that with the water in the material, a composition of 6 per cent SO2 and 0,13--0,15 per cent sodium oxide is attained. The temperature is maintained at 105--106 DEG C., the pressure being then reduced, the SO2 being recovered. The material after washing is reduced to pulp by usual mechanical treatment and treated at a density of 5--8 per cent while being circulated in a stamp mill with gaseous chlorine supplied by a blower within the pulp at the point where the latter receives the thrust of the propeller. The product is washed in the stamp mill or washer, and heated for about 1 hour at 65--75 DEG C., in a liquid containing sodium carbonate and sodium sulphite in a total concentration of about 0,25 per cent. It is then washed until neutral and may be bleached with a hypochlorite.