Patent GB-752518-A (GB)
Title: An improved method of removing cellulose fibres from scrap rubber or other acid resistant material
Inventor: DASHER PAUL JAMES
IPC: C08J11/04
Filed: 1954-07-06
Abstract: <PICT:0752518/IV(a)/1> In a method for removing cellulosic fibres from scrap rubber or other acid-resistant material containing such fibres, the scrap material is treated with a mineral acid vapour while maintaining a temperature differential between the vapour and the scrap so that the vapour will condense on the scrap, and the treatment is continued for a period sufficient to effect substantially a maximum of depolymerization of the cellulose while preventing actual hydrolysis thereof.  As shown, the scrap is fed from storage bins 10, Fig. 1, through a system comprising a bale cutter 12, cracker mills 14, rotary cutters 16, a cyclone storage bin 20, a tube 22 in which it is treated with hydrochloric acid vapour, a hammer mill 24 for mechanically separating the depolymerized fibres from the scrap, a vibrating screen 26, and a centrifugal separator 30 having separate outlets for the refined scrap and the depolymerized fibrous material.  The scrap is cut by the rotary cutters 16 into pieces small enough to pass a 3/8 -inch screen, any fibres removed by the cutting process being separated in the cyclone storage bin 20. The hydrochloric acid vapour, which is passed through the processing tube 22, preferably in a direction opposite to the flow of scrap, is supplied from a vaporizer 40 fed by a pump 34 with acid from a storage tank 32 via a specific gravity indicator 36 and a flow-meter 38.  The acid vapour is withdrawn by suction from the tube 22 through a conduit 41 to a condenser 42, from which condensed hydrochloric acid solution flows back through a conduit 43 to the tank 32. Uncondensed vapour passes to a cyclone separator 44, which removes any fibrous material, and to jet-type fume scrubbers 48 which draw the remaining acid vapour into condensers 50, from which the condensed liquid is returned to the storage tank 32.  The scrubbers 48 are operated by jets of liquid acid supplied by a pump 49 from the tank 32.  The relative proportions of hydrochloric acid and water vapour in the tube 22 are preferably those of a constant boiling point solution of hydrochloric acid, viz. 20.2 per cent acid, the hydrochloric acid solution supplied to the vaporizer 40 having a concentration of 21 to 28 per cent acid, dependent upon the amount of water in the scrap.  In order to assist the condensation of the acid on the scrap, the latter may be sprayed with a wetting agent prior to entry into the tube 22, e.g. in the cracker mills 14.  The tube 22 is heated and rotated during the treating operation, and has longitudinal internal blades 82, Fig. 3, for agitating the scrap. Independently-controlled electric heaters 124, Fig. 3, are provided in each of eight zones extending along the length of the tube 22, and the temperature in each zone is regulated by a thermostat 126 so that the temperature immediately adjacent the tube 22 varies along the length thereof.  The method is stated to be applicable also to the removal of cotton fibres from wool or nylon.ALSO:<PICT:0752518/IV(c)/1> <PICT:0752518/IV(c)/2> In a method for removing cellulosic fibres from acidresistant material containing such fibres such as a mixture of cotton with wool or nylon, the material is treated with a mineral acid vapour while maintaining a temperature differential between the vapour and the material so that the vapour will condense on the material, and the treatment is continued for a period sufficient to effect substantially a maximum of depolymerization of the cellulose while preventing actual hydrolysis thereof.  As shown, the material is fed from storage bins 10, Fig. 1, through a system comprising a bale cutter 12, cracker mills 14, rotary cutters 16, a cyclone storage bin 20, a tube 22 in which it is treated with hydrochloric acid vapour, a hammer mill 24 for mechanically separating the depolymerized fibres from the material, a vibrating screen 26, and a centrifugal separator 30 having separate outlets for the refined material and the depolymerized fibrous material.  The material is cut by the rotary cutters 16 into pieces small enough to pass a 3/8 inch screen, any fibres removed by the cutting process being separated in the cyclone storage bin 20.  The hydrochloric acid vapour, which is passed through the processing tube 22, preferably in a direction opposite to the flow of material, is supplied from a vaporizer 40 fed by a pump 34 with acid from a storage tank 32 via a specific gravity indicator 36 and a flow meter 38.  The acid vapour is withdrawn by suction from the tube 22 through a conduit 41 to a condenser 42, from which condensed hydrochloric acid solution flows back through a conduit 43 to the tank 32.  Uncondensed vapour passes to a cyclone separator 44, which removes any fibrous material, and to jet type fume scrubbers 48 which draw the remaining acid vapour into condensers 50, from which the condensed liquid is returned to the storage tank 32.  The scrubbers 48 are operated by jets of liquid acid supplied by a pump 49 from the tank 32.  The relative proportions of hydrochloric acid and water vapour in the tube 22 are preferably those of a constant boiling point solution of hydrochloric acid, viz. 20.2 per cent acid, the hydrochloric acid solution supplied to the vaporizer 40 having a concentration of 21 to 28 per cent acid dependent upon the amount of water in the material.  In order to assist the condensation of the acid on the material, the latter may be sprayed with a wetting agent prior to entry into the tube 22, e.g. in the cracker mills 14.  The tube 22 is heated and rotated during the treating operation, and has longitudinal internal blades 82, Fig. 3, for agitating the material. Independently controlled electric heaters 124, Fig. 3, are provided in each of eight zones extending along the length of the tube 22, and the temperature in each zone is regulated by a thermostat 126 so that the temperature immediately adjacent the tube 22 varies along the length thereof.