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Wood pulp

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  • Title:
    Wood pulp
  • Subjects: APPARATUS THEREFOR ; PAPER-MAKING ; PRODUCTION OF CELLULOSE ; PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCESFROM CELLULOSE-CONTAINING MATERIALS ; REGENERATION OF PULPING LIQUORS ; TEXTILES
  • Description: Cellulose pulp is obtained by impregnating wood with an acid sulphite digesting liquor at a temperature not exceeding 120 DEG C. and then heating the impregnated wood to a temperature between 190 DEG C. and 205 DEG C. and maintaining the temperature within this range until the digestion is substantially complete. Cellulose pulp of high quality suitable for acetylation, with little or no further purification, is obtained. Following the impregnation, part or all of the excess sulphite liquor may be drained from the wood chips. The sulphite liquor may be a solution of sodium or calcium bisulphite. During the digestion at 190-205 DEG C. the pressure may be maintained at 225-260 p.s.i.g. by relieving the pressure in the digestion vessel continuously or intermittently. After the digestion, the pulp may be given a simple bleaching and a light purification with dilute alkali solution. The impregnation and subsequent digestion of the wood may be carried out as a single continuous operation. The process may be carried out in apparatus such as is described in Specification 710,330. In an example, hemlock chips are immersed for two hours in an excess of a calcium sulphite cooking liquor containing 5.5 per cent. of free SO2 and 2.33 per cent. of combined SO2, at a temperature of 110 DEG C. and a pressure of 70 p.s.i.g. The chips are drained and then heated with steam for seven minutes to raise the temperature to 195 DEG C., the pressure being maintained at a maximum of 225 p.s.i.g. The cellulosic material is kept at 195 DEG C. for one minute and then cooled rapidly. The pulp obtained is bleached with dilute sodium chlorite solution and washed. It may then be acetylated and the cellulose acetate may be dissolved, e.g. in acetone, and formed into filaments or films.
  • Creation Date: 1954
  • Language: English
  • Source: esp@cenet
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