GB305630A - Improvements in or relating to the electrophoretic deposition of solids from dispersions, for example caoutchouc from latex - Google Patents

Abstract

305,630. Siemens - Elektro - Osmose Ges. Feb. 8, 1928, [Convention date]. Latex, treating.-In the electrophoretic deposition of substances from dispersions thereof, the dispersion is modified by the addition of suitable colloids or compounds comprising multivalent cathions in such a way that particles normally moving to the anode are directed to the cathode. The deposit may take place on the cathode or on a diaphragm or a moulded insulating body disposed in front of it. The reversal of direction is best effected in an electrolyte having a hydrogen ion concentration of 7 or less. When treating commercial rubber latex the ammonia is first partially removed. The reversal may be effected by adding 1 c.c. of a 5 per cent thorium nitrate solution to 36 c.c. of a dialyzed latex solution. Addition agents may be deposited with the rubber. In an example, 8 gms. of colloidal sulphur are stirred with water containing a protective colloid and the dispersion is introduced with stirring into 1 litre of dialyzed latex of 20 per cent caoutchouc content. The pH value is adjusted to about 7 and 28 c.c. of a 5 per cent solution of thorium nitrate is added. Zinc electrodes are employed in the electrophoresis. In another example, 4 gms. of zinc oxide and 6 gms. of sulphur are suspended in 40 c.c. of water containing a protective colloid such as gum arabic. The suspension is introduced with stirring into 1 litre of 20 per cent dialyzed latex and thorium nitrate added as before. Specification 301,100 is referred to. According to the Specification as open to inspection under Sect. 91 (3) (a) a mixture of colloids may be separated by addition of a substance which effects reversal of direction for some of the constituents only. This subject-matter does not appear in the Specification as accepted.