Diaphragm for electrolytic cell
First Claim
1. A liquid-permeable diaphragm for use in a chlor-alkali electrolytic cell comprising:
- (a) a liquid-permeable base mat, said base mat comprising synthetic polymeric material that is at least partially resistant to the environment within said electrolytic cell, and(b) a coating of water-insoluble particulate material on said base mat, the water-insoluble particulate material having been deposited on said base mat from an aqueous slurry of water and particulate material consisting essentially of;
(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 said hydrous metal oxides, and(iv) from 0.01 to 2 weight percent of alkali metal polyphosphate.
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Accused Products
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.
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Citations
20 Claims
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1. A liquid-permeable diaphragm for use in a chlor-alkali electrolytic cell comprising:
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(a) a liquid-permeable base mat, said base mat comprising synthetic polymeric material that is at least partially resistant to the environment within said electrolytic cell, and (b) a coating of water-insoluble particulate material on said base mat, the water-insoluble particulate material having been deposited on said base mat from an aqueous slurry of water and particulate material consisting essentially of; (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 said hydrous metal oxides, and (iv) from 0.01 to 2 weight percent of alkali metal polyphosphate. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A liquid-permeable diaphragm assembly for use in a chlor-alkali electrolytic cell comprising:
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(a) a foraminous cathode, (b) a liquid-permeable base mat on said foraminous cathode, said base mat comprising synthetic polymeric material that is at least partially resistant to the environment within said electrolytic cell, and (c) a coating of water-insoluble particulate material on said base mat, the water-insoluble particulate material having been deposited on said base mat from an aqueous slurry of water and particulate material consisting essentially of; (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 said hydrous metal oxides, and (iv) from 0.01 to 2 weight percent of alkali metal polyphosphate. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. In the method of electrolyzing alkali metal halide brine in an electrolytic diaphragm cell wherein the electrolytic cell comprises an anode compartment containing an anode and alkali metal halide brine, a cathode compartment, and a liquid-permeable diaphragm assembly separating the anode compartment and the cathode compartment, the improvement comprising electrolyzing alkali metal halide brine in an electrolytic diaphragm cell having a liquid-permeable diaphragm assembly comprising:
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(a) a foraminous cathode, (b) a liquid-permeable base mat on said foraminous cathode, said base mat comprising synthetic polymeric material that is at least partially resistant to the environment within said electrolytic cell, and (c) a coating of water-insoluble particulate material on said base mat, the water-insoluble particulate material having been deposited on said base mat from an aqueous slurry of water and particulate material consisting essentially of; (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 said hydrous metal oxides, and (iv) from 0.1 to 1 weight percent of alkali metal polyphosphate, thereby minimizing the amount of chlorate ion produced during electrolysis of alkali metal halide brine. - View Dependent Claims (16, 17, 18)
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19. A method for forming an electrolyte-permeable synthetic diaphragm on a foraminous cathode structure for use in a chlor-alkali electrolytic cell, said method comprising:
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(a) depositing a liquid-permeable base mat on said cathode structure, said base mat comprising synthetic polymeric material chosen from fluorine-containing polymer fibers, fluorine and chlorine-containing polymer fibers, and mixtures of such halogen-containing polymer fibers, said base mat having been deposited from an aqueous slurry of said synthetic polymeric material, (b) coating said deposited base mat with a coating consisting essentially of water-insoluble particulate material of; (i) at least one valve metal oxide, (ii) clay mineral chosen from hydrated aluminum silicates, hydrated magnesium silicates, hydrated aluminum magnesium silicates, and mixtures of such hydrated silicates, (iii) hydrous metal oxide chosen from hydrous oxides of magnesium, the hydrous oxides of zirconium, and mixtures of such hydrous metal oxides, and (iv) from 0.1 to 1 weight percent of tetraalkali metal pyrophosphate, and (c) drying the resultant formed diaphragm. - View Dependent Claims (20)
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Specification