GB774004A - Improvements in and relating to the production of cellulose xanthate - Google Patents

Abstract

Cellulose xanthate is made by immersing alkali cellulose in a pool of carbon disulphide, withdrawing the impregnated alkali cellulose from the pool and pressing it to remove carbon disulphide in excess of a predetermined amount, and then passing it to a xanthation chamber and, after the xanthation period, removing the cellulose xanthate from the xanthation chamber. As shown, particles of an alkali cellulose containing 30 per cent by weight cellulose, 15 per cent sodium hydroxide and 55 per cent water, obtained by shredding sheets of wood pulp which have been steeped in aqueous sodium hydroxide are, after ageing, fed at a constant rate to an impregnation chamber 2 by means of a rotating star-wheel 3. The particles fall upon a conveyer belt 4 and are carried thereby beneath the surface of a pool 6 of carbon disulphide, complete immersion being ensured by a baffle 9. Carbon disulphide is supplied through a pipe 10 at a rate calculated to give a carbon disulphide/cellulose ratio by weight of <PICT:0774004/IV(a)/1> 34/100 . Nitrogen is introduced into the chamber 2 through a pipe 11. The particles are conveyed to a xanthation chamber 15 between the nip of a pair of rollers 7, 8, the pressure between which is maintained by a spring 12 and is adjusted by a screw 13 to an extent whereby the amount of carbon disulphide expressed maintains the level of the pool 6 constant. The particles are conveyed through the chamber 15 on a conveyer belt 14 and are delivered to a hopper 17 from which they are removed by a screw 18. Passage through the xanthation chamber may take about 90 minutes. Gaseous ammonia may be supplied to the chamber 15 through a pipe 19. The alkali cellulose particles may also be prepared by a slurry steeping process.