GB542204A - Improvements in or relating to the preparation of crude rubber - Google Patents

Abstract

542,204. Preparing rubber from latex. FAIRWEATHER, H. G. C. (Goodrich Co., B. F.). April 14, 1939, No. 11337. [Class 70] Crude rubber of normal nitrogen content and low water absorption capacity is obtained by coagulating fresh or substantially fresh Heavea latex, if desired by first flocculating the dilute latex, heating the wet colgulum to insolubilize the protein constituents, and washing to separate the water-soluble constituents therefrom. Both results may be achieved by treatment with hot water, or the insolubilization may be effected partly by chemical precipitants such as formalin or tannin. In the preferred method latex from a tank 1 is drawn into an ageing tank 2 in which sodium sulphide solution from tank 3 is added to it in the proportion of 20 grammes of crystalline hydrated sulphide to a litre of latex, the mixture being allowed to stand for from two to fourteen days, after which the latex is diluted with an equal volume of water from the main 4 and sufficient 2 per cent. acetic acid from tank 5 is added to make it acid to litmus. The treated latex is then discharged into weakly acid water (.05 per cent. acetic acid) in the flocculating tank 6, the creamed latex passing then to tank 7 from which it flows through a constant-level device 8 to the trough 9 of a drum filter 10, the rubber particles on the surface of the filter being washed by a hot water spray 11. The sheet of coagulum from the filter passes for further washing through almost boiling water in tank 12, through 20 per cent. formalin solution or 1-2 per cent. ammonia in trough 13 to a drier 14 and preferably, if subsequent breaking-down in the factory is to be avoided, through a hot-air softening chamber 15 to a winding device at 16, a spray 17 of talc being applied to prevent the layers from adhering together. Specification 116,324, [ Class 70], and 348,101 are referred to.