Ppg Industries Ohio, Inc.

Jerry N Kinney

Donald W DuBois

Bernard A Maloney

A method of forming a liquid-permeable asbestos-free diaphragm on a cathode structure is described. The method comprises forming a liquid-permeable diaphragm base mat comprising fibrous synthetic polymeric material, e.g., polytetrafluoroethylene, on a cathode structure, e.g., a foraminous cathode; drawing a liquid slurry comprising an aqueous medium containing a wetting amount of surfactant and water-insoluble inorganic particulate material through the base mat, thereby to deposit said inorganic particulate material on and within the pre-formed base mat; and drying the resultant diaphragm at temperatures less than the temperature at which decomposition by-products of the surfactant are formed. The liquid slurry is substantially free of alkali metal halide and alkali metal hydroxide; and the inorganic particulate material comprises at least one oxide or silicate of a valve metal, e.g., zirconium oxide, having a median diameter of 0.1 to 5 micrometers, and optionally clay mineral and/or hydrous oxide of zirconium and/or magnesium. In a further embodiment of the present invention, the base mat is dried prior to deposition of the inorganic particulate material.

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Harrison City, PA, United States of America

Jerry N Kinney