Membrane-electrode structure for electrochemical cells

Claim 2

A membrane-electrode structure for use in electrochemical cells which comprises an ion exchange membrane with an electrode layer, and intermediate layers between said membrane and said electrode layer, said intermediate layers comprising at least two layers or zones of inorganic solid particles and an organic binder polymer having a melting point of about 230° F. to 540° F., a first intermediate layer or zone being adjacent to said membrane and comprising more than 50% by weight of inorganic particles, a second intermediate layer or zone being adjacent to said first intermediate layer and the electrode layer and comprising 50% by weight or less of inorganic particles.

Claim 3

The structure of claim 1 wherein said first intermediate layer comprises about 65 to 70% by weight of inorganic particles.

Claim 4

The structure of claim 2 wherein said first intermediate layer comprises about 70% by weight of inorganic particles and about 30% by weight of polymers.

Claim 5

The structure of claim 1 wherein said second intermediate layer comprises about 50% by weight of inorganic particles.

Claim 6

The structure of claim 1 wherein the tortuosity/porosity ratio of said first intermediate layer is in the range of 2-500 and the porosity is in the range of 5%-90%.

Claim 7

The structure of claim 1 including a coating of an organic ionic conductive material free of inorganic particles adjacent to said electrode layer.

Claim 8

The structure of claim 1 wherein said inorganic solid particles comprising at least one of the borides, carbides, and nitrides of metals of Groups IIIB, IVA, IVB, VB, and VIB of the Periodic Table.

Claim 9

The structure of claim 7 wherein said inorganic particles are silicon carbide.

Claim 10

The structure of claim 1 wherein said polymer consists of a copolymer of a monomer of the general formula: CF.sub.2 =CZZ' (I) wherein Z and Z' are independently selected from the group consisting of --H, --Cl, --F, and --CF 3 , and at least one monomer selected from compounds represented by the general formula: Y--(CF.sub.2).sub.a --(CFR.sub.f).sub.b --(CFR.sub.f).sub.c --O--[CF(CF.sub.2 X)--CF.sub.2 O ].sub.n --CF═CF.sub.2(II) wherein Y is --SO 2 Z Z is --I, --Br, --Cl, --F, --OR or --NR 1 R 2 ; wherein R is a branched or linear alkyl radical having from 1 to about 10 carbon atoms or an aryl radical; R 1 and R 2 are independently selected from the group consisting of --H, a branched or linear alkyl radical having from 1 to about 10 carbon atoms and an aryl radical; wherein: a is 0-6; b is 0-7; c is 0 or 1; provided a+b+c is not equal to 0; X is --Cl, --Br, --F, or mixtures thereof when n>1; n is O to 6; and R f and R f are independently selected from the group consisting of --F, --Cl, perfluoroalkyl radicals having from 1 to about 10 carbon atoms and fluorochloroalkyl radicals having from 1 to about 10 carbon atoms.

Claim 11

The structure of claim 9 wherein said copolymer has an equivalent weight of about 550 to 1200.

Claim 12

The structure of claim 9 wherein Y is --SO 2 F, n is O or 1; R f and R f are --F, X is --Cl or F, and a+b+c is 2 or 3.

Claim 13

The structure of claim 9 wherein the ion exchange membrane is a cation exchange membrane comprising a polymer containing sulfonic acid groups and carboxylic acid groups.

Claim 14

The structure of claim 12 wherein said ion exchange membrane comprises a bilayer ion exchange membrane.

Claim 15

The structure of claim 9 wherein said copolymer is blended with a nonionic polymer.

Claim 16

The structure of claim 1 wherein said first and second barrier layers are formed by suspending inorganic particles and non-hydrolyzed polymeric particles in a solvent, spraying said suspension on an ion exchange membrane and then hydrolyzing said polymer.

Claim 17

The structure of claim 1 wherein said electrode layer comprises a platinum group metal oxide and silver.

Claim 18

The structure of claim 16 wherein said one electrode is a cathode.

Claim 19

The structure of claim 1 wherein only one electrode layer is bonded to said membrane.

Claim 20

The structure of claim 1 wherein said intermediate layers comprise an interpenetration polymer network composition.

Claim 21

The structure of claim 19 wherein said interpenetration polymer network composition comprises a mixture of at least one ionic thermoplastic polymer and one nonionic thermoplastic polymer as the binder.

Claim 22

The structure of claim 1 wherein each of said intermediate layers comprises a mixture of at least one ionic thermoplastic polymer and one nonionic thermoplastic polymer as the binder.

Claim 23

The structure of claim 1 wherein each of said intermediate layers or zones contains a nonionic thermoplastic binder.

Claim 24

In an electrochemical cell having an electrode-membrane structure, wherein the improvement comprises said membrane-electrode structure consisting of the structure of claim 1.

Claim 25

The electrochemical cell of claim 23 wherein the intermediate layers of said membrane-electrode structure comprise an interpenetration polymer network composition.

Claim 26

The electrochemical cell of claim 23 wherein said electrochemical cell comprises a chlor alkali cell.