Patent GB-683133-A (GB)
Title: Process and apparatus for the concentration of rubber latex
IPC: C08C1/075
Filed: 1949-10-01
Abstract: - 683,133. Concentrating latex. DUNLOP RUBBER CO., Ltd., and PATON, F. J. Aug. 15, 1950 [Oct. 1, 1949], No. 25276/49. Class 70. [Also in Group XXXVI] In concentrating rubber latex by electrodecantation in an apparatus with semi-permeable membranes, the rubber-containing material deposited on the membranes is redispersed by agitating the membranes in an aqueous dispersion medium. Figs. 1 and 2 illustrate an apparatus suitable for carrying out the process. A vessel encloses semi-permeable membranes 29 of regenerated cellulose between ebonite frames 1 clamped in side by side relationship by rods 7; there are electrodes 14 and 18 at the respective ends; on opening a cock 26, latex is fed to compartments between the membranes by way of pipes 25, which extend through holes 5 in lugs on the frames, and from the pipes 25 through channels 6 extending from the holes 5 to the inner peripheries of the frames; rubberenriched latex produced by electro-decantation is delivered from the apparatus by an outlet 10 controlled by a cock 24, and serum is delivered by an outlet 11 controlled by a cock 23; the apparatus is rotatable, circular end plates 15 and 17 and a central circular enlarged ebonite frame 8 being supported in grooves in pairs of driven rollers 27. According to an example of continuous working, the apparatus, of 40-50 gal. capacity, is filled with latex of rubber content 30 per cent, a potential which produces a gradient of 1 volt/cm. across the apparatus is applied to the electrodes, and the current is periodically reversed to slow down the building up of rubber deposit on the membranes; after 3-4 hr. there is rubber-enriched latex above and serum below; latex is then passed into the apparatus at the rate of 10 gal./hr., the rubber-enriched latex, of 60 per cent rubber content, being thus displaced through the pipe 10 at 5 gal./hr. and the serum being displaced through the pipe 11 at slightly more than 5 gal./hr.; these conditions are maintained until rubber begins to appear in the serum (about 24 hr.); the potential is thereupon switched off, the cocks 23, 24 and 26 are closed, and the apparatus is rotated for half an hour to redisperse rubber deposited on the membranes; the apparatus is then emptied, and, after it has again been filled with 30 per cent latex, the cycle of operations is resumed. According to an example of discontinuous working, the apparatus is filled with latex of 60 per cent rubber content, a potential gradient of 1 volt/cm. is applied, and the current is periodically reversed; after 3 hr. the serum, which is about 14 gal., is withdrawn by the pipe 11, the cocks 23 and 24 being opened; the cocks 23 and 24 are then closed, and the potential switched off, and the apparatus is rotated for half an hour to redisperse the membrane deposit in the rubber-rich fraction remaining in the apparatus; the product, which is of 65 per cent rubber content, is withdrawn by the pipe 11 after opening the cocks 23 and 24, and the empty apparatus is then ready for treatment of a further batch of latex in the same manner.