| abstract |
Describes a liquid-permeable diaphragm assembly for use in electrolytic cells, e.g., chlor-alkali electrolytic cells. The diaphragm assembly includes a foraminous cathode, a liquid permeable base mat comprising synthetic polymeric material that is at least partially resistant to the environment within the electrolytic cell on the foraminous cathode, and a topcoat of water-insoluble particulate material on the base mat. The topcoat is deposited on the base mat from an aqueous slurry comprising (i) at least one oxide, boride, carbide, nitride or silicate of a valve metal, (ii) clay mineral, (iii) hydrous metal oxide chosen from the hydrous oxides of magnesium, the hydrous oxides of zirconium, and mixtures of such hydrous metal oxides, and (iv) alkali metal polyphosphate. |