Electrolytic cell membrane and method of preparation by plasma polymerization of polyamide or polytetrafluoroethylene thin films onto polymeric substrates

Claim 1

An improved hydraulically impermeable cation exchange membrane consisting essentially of: a substrate selected from the group of a film of copolymer having the repeating structural units of the formula ##STR4## in which R' is fluorine, or perfluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1, 2 or 3; n is 0 or 1; x is fluorine, chlorine or trifluoromethyl; and x' is x or CF 3 --CF 2 -- a O--; wherein a is 0 or an integer from 1 to 5; the units of formula (I) being present in an amount to provide a copolymer having an --SO 3 H equivalent weight of about 1000 to 1400; copolymers of tetrafluoroethylene and hexafluoropropylene having grafted thereon a 50-50 mixture of styrene and alpha methylstyrene which has been sulfonated; or an insoluble, infusible copolymeric matrix formed from at least 20 percent by weight of a polyvinyl aromatic compound and not more than 80 percent of a monovinyl aromatic compound with a reinforcing material therein and no more than 70 percent by weight of a monovinyl aromatic compound without a reinforcing material therein, sulfonate groups chemically bonded to the aromatic nuclei of the matrix and a solvating liquid in gel relationship with the matrix, the sulfonate groups being present in an amount no more than four equivalents or sulfonate groups for each mole of polyvinyl aromatic compound and not less than one equivalent of sulfonate groups for each 10 moles of poly- and monovinyl aromatic compound the solvating liquid being at least 25 percent by volume of the resin; and a top coating deposited upon the surface of at least one side of said substrate by plasma polymerization to produce a thin pinhole free coating in the range of 50 to 2000 Angstroms having a chemical makeup selected from the group of polyamide or polytetrafluoroethylene.

Claim 4

A method for the preparation of an improved hydraulically impermeable cation exchange membrane comprising the steps of: selecting a substrate material from a group of copolymers having the repeating structural units of the formula ##STR5## in which R 1 is fluorine, or perfluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1, 2 or 3; n is 0 or 1; x is fluorine, chlorine or trifluoromethyl; and x 1 is x or CF 3 --CF 2 -- a O--, wherein a is 0 or an integer from 1 to 5; the units of formula (I) being present in an amount to provide a copolymer having an --SO 3 H equivalent weight of about 1000 to 1400; copolymers of tetrafluoroethylene and hexafluoropropylene having grafted thereon a 50-50 mixture of styrene and alpha methylsytrene which has been sulfonated; or an insoluble, infusible copolymeric matrix formed from at least 20 percent by weight of a polyvinyl aromatic compound and not more than 80 percent of a monovinyl aromatic compound with a reinforcing material therein and no more than 70 weight percent by weight of a monovinyl aromatic compound without a reinforcing material therein, sulfonate groups chemically bonded to the aromatic nuclei of the matrix and a solvating liquid in gel relationship with the matrix, the sulfonate groups being present in an amount no more than four equivalents or sulfonate groups for each mole of polyvinyl aromatic compound and not less than one equivalent of sulfonate groups for each 10 moles of poly- and monovinyl aromatic compound the solvating liquid being at least 25 percent by volume of the resin; and applying a top coating selected from the group of polyamide or polytetrafluoroethylene to the surface of at least one side of said substrate by means of plasma polymerization to produce a thin pinhole free coating in the range of 100 to 2000 Angstroms.

Claim 5

A method for the preparation of an improved hydraulically impermeable cation exchange membrane comprising the steps of: selecting a substrate material from a group of copolymers having the repeating structural units of the formula ##STR5## in which R 1 is fluorine, or perfluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1, 2 or 3; n is 0 or 1; x is fluorine, chlorine or trifluoromethyl; and x 1 is x or CF 3 --CF 2 -- a O--, wherein a is 0 or an integer from 1 to 5; the units of formula (I) being present in an amount to provide a copolymer having an --SO 3 H equivalent weight of about 1000 to 1400; copolymers of tetrafluoroethylene and hexafluoropropylene having grafted thereon a 50-50 mixture of styrene and alpha methylsytrene which has been sulfonated; or an insoluble, infusible copolymeric matrix formed from at least 20 percent by weight of a polyvinyl aromatic compound and not more than 80 percent of a monovinyl aromatic compound with a reinforcing material therein and no more than 70 weight percent by weight of a monovinyl aromatic compound without a reinforcing material therein, sulfonate groups chemically bonded to the aromatic nuclei of the matrix and a solvating liquid in gel relationship with the matrix, the sulfonate groups being present in an amount no more than four equivalents or sulfonate groups for each mole of polyvinyl aromatic compound and not less than one equivalent of sulfonate groups for each 10 moles of poly- and monovinyl aromatic compound the solvating liquid being at least 25 percent by volume of the resin; and applying a top coating selected from the group of polyamide or polytetrafluoroethylene to the surface of at least one side of said substrate by means of plasma polymerization to produce a thin pinhole free coating in the range of 100 to 2000 Angstroms.