Microporous hydrophilic fluoropolymer membranes and method

Claim 2

An hydrophilic fluoropolymeric microporous diaphragm comprising a fluorine-containing polymeric substrate to which has been radiation co-grafted a mixture of monomers comprising at least one functional monomer selected from the group consisting of compounds of formula I CF.sub.2 ═CF(CF.sub.2).sub.n A, and formula II CF.sub.2 ═CF--O--(CFX--CFX).sub.m A wherein A is carboxyl, alkoxycarbonyl, hydroxyalkoxy, carbonyl, cyano, hydroxsulfonyl, fluorosulfonyl, or the group --CO--NR 1 R 2 wherein R 1 and R 2 are independently selected from hydrogen and C 1 to C 6 alkyl, one X is fluorine and the other X is selected from chlorine fluorine and a trifluoromethyl group, n is an integer from 1 to 12, m is an integer from 1 to 3, and unsaturated dicarboxylic acids or derivatives thereof containing the group of formula III ##STR5## wherein R 3 and R 4 are independently selected from hydrogen, fluorine, chlorine, and C 1 to C 6 alkyl or halogenated C 1 to C 6 alkyl or together form a double bond; and at least one non-functional monomer selected from the group consisting of aliphatic vinyl monomers of formula IV and aromatic vinyl monomers of formula V ##STR6## wherein Y is hydrogen or fluorine, Z is hydrogen, fluorine or chlorine, and W is hydrogen, C 1 to C 6 alkyl, C 2 to C 6 alkenyl, halogenated C 1 to C 6 alkyl or halogenated C 2 to C 6 alkenyl; and wherein the molar ratio of co-grafted functional monomer to co-grafted non-functional monomer is in the range of 2:1 to 1:20.

Claim 3

A microporous diaphragm according to claim 1 wherein the molar ratio of said functional monomer to said non-functional monomer is in the range of 2:1 to 1:3.

Claim 4

A microporous diaphragm according to claim 1 or claim 2 wherein the fluorine-containing polymeric substrate is a homopolymer or copolymer of a fluorinated ethylene.

Claim 5

A microporous diaphragm according to claim 3 wherein the fluorinated ethylene is vinylidene fluoride.

Claim 6

A microporous diaphragm according to claim 3 wherein the fluorinated ethylene is tetrafluoroethylene.

Claim 7

A microporous diaphragm according to claim 3 wherein the fluorinated ethylene is chlorotrifluoroethylene.

Claim 8

A microporous diaphragm according to claim 3 wherein the copolymer comprises hexafluoropropylene units.

Claim 9

A microporous diaphragm according to claim 1 wherein the fluorine-containing polymeric substrate is polytetrafluoroethylene.

Claim 10

A microporous diaphragm according to claim 1 wherein the fluorine-containing polymeric substrate is polychlorotrifluoroethylene.

Claim 11

A microporous diaphragm according to claim 1 wherein the fluorine-containing polymeric substrate is a copolymer of tetrafluorethylene and hexafluoropropylene wherein the hexafluoropropylene incorporated in the said copolymer is in the concentration range of 3.5-12.5% w/w.

Claim 12

A microporous diaphragm according to claim 1 wherein the compounds of formula I and II are pentafluorobutenoic acid, C 1 to C 6 alkyl pentafluorobutenoates and trifluorovinylsulfonyl fluoride.

Claim 13

A microporous diaphragm according to claim 11 wherein the said C 1 to C 6 alkyl pentafluorobutenoates are methyl pentafluorobutenoate and ethyl pentafluorobutenoate.

Claim 14

A microporous diaphragm according to claim 1 wherein the compounds of formula III are maleic acid, 1,2-difluoromaleic acid, acetylene dicarboxylic acid and anhydrides, amides and C 1 to C 6 alkyl esters thereof.

Claim 15

A microporous diaphragm according to claim 1 wherein the non-functional monomers of formula IV are tetrafluoroethylene and chlorotrifluoroethylene.

Claim 16

A microporous diaphragm according to claim 1 wherein the non-functional monomers of formula V are styrene, α, β, β-triflurostyrene, divinylbenzene and α, β, β, α', β', β'-hexafluorodivinylbenzene.

Claim 17

A process of preparing an hydrophilic fluoropolymeric microporous diaphragm which process comprises radiation co-grafting onto a fluorine-containing polymeric diaphragm a mixture of monomers comprising at least one functional monomer selected from the group consisting of compounds of formula I CF.sub.2 ═CF(CF.sub.2).sub.n A, and formula II CF.sub.2 ═CF--O--(CFX--CFX).sub.m A wherein A is carboxyl, alkoxycarbonyl, hydroxyalkoxy, carbonyl, cyano, hydroxysulfonyl, fluorosulfonyl, or the group --CO--NR 1 R 2 wherein R 1 and R 2 are independently selected from hydrogen and C 1 to C 6 alkyl, one X is fluorine and the other X is selected from chlorine fluorine and a trifluoromethyl group, n is an integer from 1 to 12, m is an integer from 1 to 3, and unsaturated dicarboxylic acids or derivatives thereof containing the group of formula III ##STR7## wherein R 3 and R 4 are independently selected from hydrogen, fluorine, chlorine, and C 1 to C 6 alkyl or halogenated C 1 to C 6 alkyl or together form a double bond; and at least one non-functional monomer selected from the group consisting of aliphatic vinyl monomers of formula IV CY.sub.2 ═CYZ and aromatic vinyl monomers of formula V ##STR8## wherein Y is hydrogen or fluorine, Z is hydrogen, fluorine or chlorine, and W is hydrogen, C 1 to C 6 alkyl, C 2 to C 6 alkenyl, halogenated C 1 to C 6 alkyl or halogenated C 2 to C 6 alkenyl; and wherein the molar ratio of functional monomer to non-functional monomer is in the range of 1:20 to 9:1.

Claim 18

A process of preparing an hydrophilic fluoropolymeric microporous diaphragm which process comprises radiation co-grafting onto a fluorine-containing polymeric diaphragm a mixture of monomers comprising at least one functional monomer selected from the group consisting of compounds of formula I CF.sub.2 ═CF(CF.sub.2).sub.n A, and formula II CF.sub.2 ═CF--O--(CFX--CFX).sub.m A wherein A is carboxyl, alkoxycarbonyl, hydroxyalkoxy, carbonyl, cyano, hydroxysulfonyl, fluorosulfonyl, or the group --CO--NR 1 R 2 wherein R 1 and R 2 are independently selected from hydrogen and C 1 to C 6 alkyl, one X is fluorine and the other X is selected from chlorine fluorine and a trifluoromethyl group, n is an integer from 1 to 12, m is an integer from 1 to 3, and unsaturated dicarboxylic acids or derivatives thereof containing the group of formula III ##STR7## wherein R 3 and R 4 are independently selected from hydrogen, fluorine, chlorine, and C 1 to C 6 alkyl or halogenated C 1 to C 6 alkyl or together form a double bond; and at least one non-functional monomer selected from the group consisting of aliphatic vinyl monomers of formula IV CY.sub.2 ═CYZ and aromatic vinyl monomers of formula V ##STR8## wherein Y is hydrogen or fluorine, Z is hydrogen, fluorine or chlorine, and W is hydrogen, C 1 to C 6 alkyl, C 2 to C 6 alkenyl, halogenated C 1 to C 6 alkyl or halogenated C 2 to C 6 alkenyl; and wherein the molar ratio of functional monomer to non-functional monomer is in the range of 1:20 to 9:1.

Claim 19

A process according to claim 16 wherein the molar ratio is in the range of 1:4 to 4:1.

Claim 20

A process according to claim 16 wherein the molar ratio is in the range of 1:2 to 2:1.

Claim 21

A process according to claim 16 wherein the material comprising the diaphragm and the mixture of monomers are subjected together to irradiation by any one form of radiation selected from the group consisting of γ-rays, X-rays and electron beams.

Claim 22

A process according to claim 16 wherein the mixture of monomers is dissolved in a solvent capable of swelling the diaphragm.

Claim 23

A process according to claim 16 wherein before addition of the monomers the diaphragm is treated with a solvent capable of swelling the diaphragm.

Claim 24

A process according to claim 20 wherein the solvent is selected from the group consisting of toluene, xylene, trichlorotrifluoroethane and oligomers of tetrafluoroethylene.

Claim 25

A process according to claim 16 wherein the mixture of monomers additionally comprises at least one polymerization inhibitor and at least one chain transfer agent.

Claim 26

A process according to claim 23 wherein the polymerization inhibitor is selected from the group consisting of p-benzoquinone, naphthaquinone, hydroquinone in the presence of oxygen, copper acetate, 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxide, 2,2,6,6-tetramethylpiperazine-N-oxide, and chloranil.

Claim 27

A process according to claim 23 wherein the polymerization inhibitor is in the concentration range of 0.001 to 2% w/w of the total mixture of monomers and charger transfer agent.

Claim 28

A process according to claim 25 wherein the concentation range is 0.01 to 0.5% w/w.

Claim 29

A process according to claim 24 wherein the chain transfer agent is a solvent selected from the group consisting of chloroform, carbon tetrachloride, dimethylformamide and mixtures thereof.

Claim 30

A process according to claim 24 wherein the concentration of the monomers in the chain transfer solvent is in the range of 10 to 60% w/w.

Claim 31

A process according to claim 28 wherein the said range is 30-50% w/w.