Novel membranes and process for making them

Claim 2

A process for preparing a microporous membrane which comprises casting the membrane from a solution comprising (i) a mixture of at least one pore-forming polymer and at least one film-forming polymer, (ii) a solvent for the mixture of polymers, and optionally (iii) at least one salt, wherein the at least one pore-forming polymer is one which if cast alone would contract to form either large pores or a non-uniform distribution of material.

Claim 3

Process according to claim 1, wherein the solution comprises a water-miscible solvent and the membrane is cast in water, or in an aqueous solution or mixture.

Claim 4

Process according to either claim 1 or claim 2, wherein the solution comprises additionally (a) a liquid which is a non-­solvent for the mixture of polymers, such as one selected from the group consisting of acetone, ethanol, methanol, butanol, ethyl acetate, water, formamide and ethylene glycol, and/or (b) at least one hydrophilic polymer.

Claim 5

Process according to any of the preceding claims, wherein at least one polymer used in forming the membrane comprises reactive functions, such as those selected from the group consisting of reactive halogens, glycidyl, isocyanato and isothiocyanato, which are incorporated in the membrane structure, and are thereafter optionally replaced by cationic, anionic or hydrophilic neutral groups.

Claim 6

Process according to claim 4, wherein the reactive functions are reactive halogens in the form of haloalkyl groups.

Claim 7

Process according to either claim 4 or claim 5, wherein subsequently to membrane formation, the reactive functions are replaced by reaction with a monomeric or polymeric substance containing one or more groups selected from reactive primary amino, secondary amino, tertiary amino, OH and SH groups.

Claim 8

Process according to claim 6, wherein the said substance is a tertiary amine, and the reaction product is a membrane containing quaternary ammonium groups.

Claim 9

Process according to claim 6, wherein the said substance is at least one polymer containing -NH- groups, and the reaction product is a cross-linked membrane, and wherein in said -NH-groups one free valency is attached to said at least one polymer, and the other free valency is attached to a hydrogen atom, a substituent group, or said at least one polymer.

Claim 10

Process according to claim 6, wherein said substance is a monomeric, oligomeric or polymeric biologically active material.

Claim 11

Process according to any of the preceding claims, wherein the membrane is cast without the use of a support.

Claim 12

Process according to any of claims 1 to 9, wherein the membrane is cast onto a discrete support, such as one selected from the group consisting of woven and nonwoven polyesters, polyolefins, poly(fluorinated alkenes), cellulosics, nylons, vinyl chloride homo- and co-polymers, polystyrene, glass fibers, ceramics and porous metals, and the case membrane is optionally subsequently removed from said support.

Claim 13

Process according to any of the preceding claims, wherein the pore-forming polymer is selected from the group consisting of halomethylated polyphenyleneoxide, brominated polyphenyleneoxide, polystyrene derivatives, nitropolystyrene, perfluoro polymers, silicone polymers, nitrated polyphenyleneoxide, nitrated polysulfones, polyisobutylenes, polyisoprenes, and halogenated polysulfones, and/or the film-­forming polymer is selected from the group consisting of polysulfones, sulfonated polysulfones, chloromethylated polysulfones, polytetrafluoroethylene-based copolymers, polychloro-trifluoroethylene, vinylidene fluoride homopolymer, vinylidene fluoride copolymers with hexafluoropropylene or chlorotrifluoroethylene, polyacrylonitrile, copolymers of acrylonitrile with vinyl acetate or with acrylic or methacrylic acid, nylon 6, nylon 6,6, polyether sulfones, polysulfones made with Bisphenol A, polyimideamides, polyamides, polyetherphenylketones, polyimides, polyepoxy compounds, polycarbonates and oxidation polymers.

Claim 14

Process according to any of claims 1 to 11, wherein the pore-forming polymer is selected from the group consisting of halomethylated polyphenyleneoxide, brominated polyphenyleneoxide, polystyrene derivatives, halomethylated polystyrene, nitropolystyrene, perfluoro polymers, silicone polymers, nitrated polyphenyleneoxide, nitrated polysulfones, polyisobutylenes, polyisoprenes, and halogenated polysulfones, and/or the film-­forming polymer is selected from the group consisting of polysulfones, sulfonated polysulfones, chloromethylated polysulfones, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene-based copolymers, polychloro­trifluoroethylene, vinylidene fluoride homopolymer, vinylidene fluoride copolymers with hexafluoropropylene or chlorotrifluoroethylene, cellulosic esters and ethers, polyacrylonitrile, copolymers of acrylonitrile with vinyl acetate or with acrylic or methacrylic acid, nylon 6, nylon 6,6, polyether sulfones, polysulfones made with Bisphenol A, polyimideamides, polyamides, polyetherphenylketones, polyimides, polyepoxy compounds, polycarbonates and oxidation polymers.

Claim 15

Process according to any of claims 1 to 13, wherein the solvent for the polymers is selected from the group consisting of N-methypyrrolidone, pyrrolidone, dimethylsulfoxide, dimethylacetamide, and dimethylformamide.

Claim 16

Process according to any of the preceding claims, wherein said salt is present and is selected from the group consisting of LiHCO₃, LiCl, MgCl₂, MgClO₄, ZnCl₂, ZnBr₂ and ZnI₂.

Claim 17

Process according to any of the preceding claims, wherein the membrane is formed into a tubular configuration.

Claim 18

A membrane which is composed of at least two different polymers, at least one of which is a film former, and at least another of which is a pore former which if cast alone would form large pores or a non-uniform distribution of material; said membrane comprising a microporous surface of well defined pore shapes, which surface is integrally and continuously connected to a pore support of the same material as said surface, in which pore support there exists a non-exact distribution of materials and preferably a structure which approximates to that of an array of sintered particles.

Claim 19

A membrane which is composed of at least two different polymers, at least one of which is a film former, and at least another of which is a pore former which if cast alone would form large pores or a non-uniform distribution of material; said membrane comprising a microporous surface of well defined pore shapes, which surface is integrally and continuously connected to a pore support of the same material as said surface, in which pore support there exists a non-exact distribution of materials and preferably a structure which approximates to that of an array of sintered particles.

Claim 20

A membrane according to claim 17, wherein at least the majority of the pores are characterized by one or more of the following characteristics, namely: relatively larger cross-sectional area on the microporous surface and tapering to a relatively smaller cross-­section towards the interior of the membrane; and/or a cross-sectional shape at said surface approximating to circles or ellipses, or to segments, crescents or annuli derived from such circles or ellipses; and/or diameters which lie within the range of from 0.01 to 20 microns, preferably from 0.01 to 10 microns.

Claim 21

A membrane according to either claim 17 or claim 18, wherein said pores occupy not less than about 10%, and preferably not less than about 50%, of the area of said microporous surface.

Claim 22

A membrane according to any of claims 17 to 19, and mounted upon a discrete support layer.

Claim 23

A membrane according to any of claims 17 to 20, which contains monomeric or polymeric anionic and/or cationic groups and/or neutral hydrophilic groups on its external and internal surfaces.

Claim 24

A membrane according to any of claims 17 to 21, wherein at least one polymeric constituent of the membrane contains chemically incorporated therein a monomeric, oligomeric or polymeric biologically active material.

Claim 25

A membrane according to any of claims 17 to 22, which has been prepared according to the process claimed in any of claims 1 to 16.