Patent GB-457171-A (GB)
Title: Improvements in and relating to processes of treating vegetable fibrous material for the production of cellulose fibre or pulp
IPC: D21C3/00
Filed: 1936-06-03
Abstract: <PICT:0457171/IV/1> Vegetable fibrous material, e.g. ramie, flax, jute, sisal, hemp, and including woods, especially coniferous woods is treated for the production of cellulose fibres or pulp by immersion for a suitable length of time in an aqueous weakly alkaline solution comprising a major portion of tribasic sodium phosphate and a minor portion of an aluminium containing substance said solution being capable of dissolving gums and resins but not the waxes within the fibrous material and of precipitating tannic substances contained in said fibrous material without affecting the cellulose of the fibres, the fibrous material being thereafter washed to remove the chemicals and the foreign material which have been released by the action of the solution.  The fibrous material 1 is cut to a desirable staple length and placed in a perforated basket 2 suspended by supports 3 from a cable 4 passing over a pulley 5 depending from a trolley 6 on a track 7 over a series of kiers 8, 9, 10, 11.  The first kier 8 contains a solution of the following composition:--water 1000 galls., tribasic sodium phosphate 719 lbs., soda ash 62,5 lbs., aluminium sulphate 7,8 lbs.  Instead of aluminium sulphate, 23,3 ozs. of finely divided metallic aluminium may be used.  The chemicals may be added to the cold water before introduction of the basket 2 into the kier 8, but preferably, the basket 2 is placed in the water which is raised to boiling point, e.g. by steam from a pipe 13, and the chemicals then added.  Boiling time varies from 15--135 minutes according to the nature and condition of the fibres.  When decortication and degumming is complete, bark and other materials floating on the surface may be skimmed off, and the basket 2 transferred to kier 9 for washing by hot water forced in by pipes 15 and branches 16 and overflowing at 18.  The basket may be transferred successively to similar kiers 10, 11 for further washing.  If desired a bleaching agent may be added to the weakly alkaline solution, e.g. sodium hypochlorite in the proportion of two ounces to one gallon of solution, and in this case between the second and third washing baths, a treatment for five minutes or more in a solution containing one ounce of concentrated sulphuric acid per gallon of water is interposed.  The bleached material may be dried by hot air.  Fibres, e.g. ramie fibres produced by the above process may be treated in usual cotton mixing, and carding machines and spun, woven or otherwise treated either alone or mixed with cotton or silk.  If desired the ramie or other fibrous material may be treated with a solvent for waxes or oils, e.g. naphtha to produce an absorbent cellulose material.  This product is suitable for surgical bandages or wicks.  In treating wood especially coniferous wood to produce pulp for paper making or for the manufacture of cellulose derivatives, e.g. for explosives, the wood is treated in the form of chips for 3--17 hours in the weakly alkaline bath.  If desired the wood may then be washed and the treatment repeated for 2 hours.