Abstract: 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.

Abstract: An electrolyte permeable asbestos diaphragm is prepared by depositing asbestos and a particulate thermoplastic polymeric material from an aqueous slurry including alkali metal hydroxide onto a porous substrate, and heating the deposited asbestos, particulate thermoplastic polymeric material, and alkali metal hydroxide for a period of time, e.g., at least 2 hours, and at temperatures sufficient to react the asbestos and alkali metal hydroxide but temperatures insufficient to melt or sinter the particulate thermoplastic polymeric material, whereby the particulate thermoplastic polymeric material functions to provide permeability for the diaphragm.

Abstract: An electrolyte permeable diaphragm consisting essentially of asbestos is prepared by depositing asbestos and a porosity control agent selected from the group of cellulosic-type materials, e.g., starch, cellulose or rayon, infusible thermoset polymer materials, e.g., phenol-formaldehyde resin, urea-formaldehyde resin or melamine-formaldehyde resin, and inorganic materials, e.g., fiberglass, graphite, titania, silica, talc, vermiculite or potassium-containing mica from an aqueous slurry including alkali metal hydroxide onto a porous substrate, the porosity control agent being substantially stable and insoluble in the aqueous alkali metal hydroxide-containing slurry, followed by heating the deposited asbestos, porosity control agent and alkali metal hydroxide at temperatures between about 110.degree. C. and 280.degree. C. for a period of time sufficient to react the asbestos and alkali metal hydroxide whereby the porosity control agent provides the permeability for the diaphragm.

Abstract: An electrolyte permeable asbestos diaphragm is prepared by depositing asbestos and a particulate thermoplastic polymeric material from an aqueous slurry including alkali metal hydroxide onto a porous substrate, and heating the deposited asbestos, particulate thermoplastic polymeric material, and alkali metal hydroxide for a period of time, e.g., at least 2 hours, and at temperatures sufficient to react the asbestos and alkali metal hydroxide but temperatures insufficient to melt or sinter the particulate thermoplastic polymeric material, whereby the particulate thermoplastic polymeric material functions to provide permeability for the diaphragm.