This invention relates to films and to their preparation and use, e.g. for water purification, for detecting, filtering and/or purifying biomolecules and for detecting or removing metal ions.

The present invention seeks to provide films (including but not limited to ion exchange membranes) which have good tolerance to high and low pH and are porous and have a good ion exchange capacity and water flux e.g. for water purification and the generation of electricity. The films can also be used, for example, for the detection of metal ions, for the filtration and/or purification of compositions comprising metal ions, for the detection, filtration and purification of biomolecules.

According to a first aspect of the present invention there is provided a porous film obtainable by curing a composition comprising the following components:

(a) 20 to 70wt% styrenic monomer comprising a group of the formula -SO ₂ X;

(b) 5 to 30wt% crosslinking agent; wherein:

X is of the formula -N(M)SO ₂ R or OM;

R is a C _1-12 -alkyl group or a C _1-12 -aryl group; and

M is H, a cation or a C _1-6 -alkyl group.

In this document (including its claims), the verb “comprise” and its conjugations is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. In addition, reference to an element by the indefinite article “a” or “an” does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article “a” or “an” thus usually mean “at least one”.

A styrenic monomer is a compound comprising the group CH2=CH-C6H6, wherein the phenyl ring may be substituted.

In one embodiment component (a) comprises one and only one ethylenically unsaturated group.

Component (a) may consist of one or more than one styrenic monomer comprising a group of the formula -SO ₂ X wherein X is as defined above.

Similarly component (b) may comprise one or more than one crosslinking agent, e.g. 2 to 5 crosslinking agents.

The cation represented by M is preferably Li ⁺ , Na ⁺ , K ⁺ , NH ₄ ⁺ , or a positively charged organic ion or a combination of two or more of the foregoing. Preferred positively charged organic ions are each independently of the formula ⁺ N(R ¹ )4 wherein at least one (e.g. 1 , 2, 3 or all 4) of the groups represented by R ¹ are of the formula C _1-4 -alkyl or C _1-4 -alkyl-OH and any of the groups not of the formula C-M-alkyl or C _1-4 - alkyl-OH are H. Preferably the composition further comprises an inert solvent as component (c).

Component (c) may comprise one or more than one inert solvent.

Optionally the composition further comprises (d) a rheology modifier.

Component (a) is preferably of Formula (1 ):

Formula (1 ) wherein: m has a value of 1 or 2; and X is as hereinbefore defined.

In the compound of Formula (1 ), preferably X is of the formula -N(M)SO ₂ R or OM wherein M is H, a cation or a C _1-6 —alkyl group, m has a value of 1 or 2 and R is a C _1-12 - alkyl group or a C _1-12 -aryl group.

Preferably the composition comprises component (a) in an amount of 10 to 70wt%, more preferably 15 to 60 wt% and especially 20 to 55wt%.

The crosslinking agent(s) (b) preferably each independently have two to six ethylenically unsaturated groups, more preferably two or three, especially two ethylenically unsaturated groups. The preferred ethylenically unsaturated groups which may be present in component (a) and (b) are vinyl groups, including (meth)acrylic groups, such as (meth)acrylate or (meth)acrylamide groups, more preferably acrylic groups such as acrylate or acrylamide groups, and especially aromatic vinyl groups.

Examples of crosslinking agents having from two to six acrylamide groups include N,N'-methylene bis(meth) acrylamide, N,N'-ethylene bis(meth)acrylamide, N,N'-propylene bis(meth)acrylamide, N,N'-butylene bis(meth)acrylamide, N,N'-(1 ,2- dihydroxyethylene) bis-(meth)acrylamide, 1 ,4-diacryloyl piperazine, 1 ,4- bis(acryloyl)homopiperazine, triacryloyl-tris(2-aminoethyl)amine, triacroyl diethylene triamine, tetra acryloyl triethylene tetramine, 1 ,3,5-triacryloylhexahydro-1 ,3,5-triazine and/or 1 ,3, 5-trimethacryloylhexahydro-1 ,3,5-triazine. The term ‘(meth)’ is an abbreviation meaning that the ‘meth’ is optional, e.g. N,N'-methylene bis(meth) acrylamide is an abbreviation for N,N'-methylene bisacrylamide and N,N'-methylene bismethacrylamide.

Examples of crosslinking agents comprising at least two vinyl groups include for example, isoprene, polybutadiene and the following compounds:

In a preferred embodiment component (b) is free from ester and amide groups. This preference arises because the pH stability of the resultant film can be improved by the absence of such groups. Typically the component (b) is free from SO ₂ X groups (wherein X is as hereinbefore defined).

Crosslinking agents which may be used as component (b) can be synthesised or obtained from commercial sources, e.g. from Sigma-Aldrich. It is especially preferred that component (b) is or comprises divinylbenzene or a polybutadiene because these compounds are widely available at low cost. Divinylbenzene is often a mixture of isomers.

In a preferred embodiment the crosslinking agent (b) is free from ionic groups (e.g. free from sulfonic acid and sulfonate groups).

Preferably the composition comprises component (b) in an amount of 5 to 30 wt%, more preferably 6 to 25 wt%, and especially 8 to 25wt%.

Preferably the molar ratio of component (a):(b) is >1 , e.g. in the range 1 to 200, more preferably 1.2 to 100 and especially 1.5 to 50, more especially 1.6 to 5.

Preferably the composition comprises 40 to 95 wt% of component (a) relative to the total amount of curable components and 8 to 55wt% of component (b) relative to the total amount of curable components present in the composition.

The inert solvent (c) may be any solvent which does not copolymerise with component (a) or (b). An inert solvent comprising an inert organic solvent and water is advantageous, especially where some or all of the inert organic solvent is water- miscible. The water can be useful for dissolving component (a) when it comprises a water-solubilising group and the inert organic solvent is useful for dissolving any water- insoluble organic components of the composition.

The inclusion of an inert solvent can be useful for reducing the viscosity and/or surface tension of the composition, making the manufacturing process for the films of the present invention easier in some respects. Suitable solvents include water and non-aqueous solvents. As examples of non-aqueous solvents which may be used as component (c) there may be mentioned alcohol-based solvents, ether-based solvents, amide-based solvents, ketone-based solvents, sulfoxide-based solvents, sulfone-based solvents, nitrile-based solvents and organic phosphorus based solvents. Examples of alcohol-based solvents which may be used as or in component (c) include methanol, ethanol, isopropanol, n-butanol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol and mixtures comprising two or more thereof. In addition, preferred inert, organic solvents which may be used in component (c) include dimethyl sulfoxide, dimethyl imidazolidinone, sulfolane, N-methyl pyrrolidone, dimethyl formamide, acetonitrile, acetone, 1 ,4- dioxane, 1 ,3-dioxolane, tetramethyl urea, hexamethyl phosphoramide, hexamethyl phosphorotriamide, pyridine, propionitrile, butanone, cyclohexanone, tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, ethylene glycol diacetate, cyclopentylmethylether, methylethylketone, ethyl acetate, y-butyrolactone and mixtures comprising two or more thereof. Dimethyl sulfoxide, N-methyl pyrrolidone, , dimethyl formamide, dimethyl imidazolidinone, sulfolane, acetone, cyclopentylmethylether, methylethylketone, acetonitrile, tetrahydrofuran, 2- methyltetrahydrofuran and mixtures comprising two or more of the foregoing.

In some embodiments, the composition comprises less than 5wt% of water, e.g. less than 1 wt% water.

In one embodiment the inert organic solvent has a low boiling point, e.g. a boiling point below 100°C. Inert solvents having a low boiling point can be easily removed by evaporation, avoiding the need for a washing step for removal of the solvent.

The curable composition may comprise one or more than one solvent as component (c).

Preferably component (c) comprises water, or a mixture of water and an inert, organic solvent (preferably a water-miscible, inert organic solvent) having a water- solubility of at least 5wt%.

Examples of inert solvents which may be used as or in component (c) include alcohol-based solvents, ether-based solvents, amide-based solvents, ketone-based solvents, sulfoxide-based solvents, sulfone-based solvents, nitrile-based solvents and organic phosphorus-based solvents, of which inert, aprotic, polar solvents are preferred.

Examples of alcohol-based solvents which may be used as or in component (ii) (especially in combination with water) include methanol, ethanol, isopropanol, n- butanol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol and mixtures comprising two or more thereof. Isopropanol is particularly preferred.

In addition, preferred inert, organic solvents which may be used as or in component (c) include dimethyl sulfoxide, dimethyl imidazolidinone, sulfolane, N- methyl pyrrolidone, dimethyl formamide, acetonitrile, acetone, 1 ,4-dioxane, 1 ,3- dioxolane, tetramethyl urea, hexamethyl phosphoramide, hexamethyl phosphorotriamide, pyridine, propionitrile, butanone, cyclohexanone, tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, ethylene glycol diacetate, cyclopentylmethylether, methylethylketone, ethyl acetate, y-butyrolactone and mixtures comprising two or more thereof. Dimethyl sulfoxide, N-methyl pyrrolidone, dimethyl formamide, dimethyl imidazolidinone, sulfolane, acetone, cyclopentylmethylether, methylethylketone, acetonitrile, tetrahydrofuran, 2- methyltetrahydrofuran and mixtures comprising two or more thereof are preferable.

In a preferred embodiment component (c) comprises a composition comprising one of inert solvents selected from list (c _a ) and one or more inert solvents selected from list (C _b ): list (c _a ): iso-propanol, methanol, ethanol, acetone, tetramethyl urea, hexamethyl phosphoramide, hexamethyl phosphorotriamide, butanone, cyclohexanone, methylethylketone, tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, cyclopentylmethylether, propionitrile, acetonitrile, 1 ,4-dioxane, 1 ,3- dioxolane, ethyl acetate, y-butyrolactone, ethanolamine or a mixture comprising two or more thereof; list (C _b ): water, glycerol, ethylene glycol, dimethyl sulfoxide, sulpholane, dimethyl imidazolidinone, sulfolane, N-methyl pyrrolidone, dimethyl formamide, acetonitrile, acetone, 1 ,4-dioxane, 1 ,3-dioxolane, tetramethyl urea, hexamethyl phosphoramide, hexamethyl phosphorotriamide, pyridine, propionitrile, butanone, cyclohexanone, tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, ethylene glycol diacetate, cyclopentylmethylether, methylethylketone, ethyl acetate and y-butyrolactone, and among these, dimethyl sulfoxide, N- methyl pyrrolidone, N,N-dimethyl formamide, dimethyl imidazolidinone, N-methyl morpholine, acetone, cyclopentylmethylether, methylethylketone, acetonitrile, tetrahydrofuran, 2- methyltetrahydrofuran and mixtures comprising two or more thereof.

In one embodiment the composition comprises water and one or other more solvents from list (c _a ) and/or list (C _b ).

In one embodiment component (c) comprises an organic amine (especially an C _2-6 -alcoholamine), for example methylamine, ethylamine, diethylamine, triethylamine and especially ethanolamine. The amount of organic amine present in the composition is preferably sufficient to neutralize at least 50%, more preferably at least 75% and especially all of the anionic groups present in component (a) and (b) (when present).

In one embodiment component (c) comprises 40 to 70wt% of isopropanol, 10 to 40wt% of water and optionally 0.01 to 10wt% of organic amine.

Optionally the composition further comprises a monomer which is reactive with component (b), for example a monomer which comprises one polymerisable group (e.g. an ethylenically unsaturated group) and optionally one or more anionic groups. Preferred polymerisable groups are ethylenically unsaturated groups and especially (meth)acrylic or aromatic vinyl groups, as described above in relation to component (b)].

Preferably the composition comprises component (c) in an amount of 10 to 85 wt%, more preferably 20 to 80 wt%, especially 30 to 75 wt%.

In order to control the coatability of the composition and the pore size in the resultant film, the composition preferably further comprises a rheology modifier (d). Examples of rheology modifiers Include poly(ethylene glycol), poly(acrylic acid), polyamide, silica particles, polyethylene particles, olefin copolymers, clays, fumed silica (e.g. Aerosil™ 380), cellulosics, polypropylene, poly(propyleneglycol), polyurethane, polyester, poly(vinylalcohol), poly(methacrylic acid), poly(methylmethacrylate), poly(ethyleneimine), polystyrene and polystyrene sulfonate.

Preferably the composition comprises component (d) in an amount of 0 to 10 wt%, more preferably 0 to 8 wt%, especially 0 to 5 wt%,

In one embodiment the composition is free from free radical initiators. When the composition is free from free radical initiators the film may be formed by a process comprising irradiating the composition with electron beam radiation.

Preferably the curable composition comprises one or more than one free radical initiator (component (e)).

The composition is preferably thermally curable (e.g. by irradiating the composition with infrared light or by heating) or photocurable (e.g. by irradiating the composition with ultraviolet or visible light).

Preferably the composition comprises component (e) (an initiator) in an amount of 0 to 10 wt%, more preferably 0 to 5 wt%, especially 0 to 2 wt%. When it is intended to cure the composition thermally or using light (e.g. UV or visible light) the composition preferably comprises 0.001 to 2 wt%, especially 0.005 to 0.9wt%, of a photoinitiator as component (e).

Examples of suitable thermal initiators which may be used as component (e) include 2,2’-azobis(2-methylpropionitrile) (AIBN), 4,4’-azobis(4-cyanovaleric acid), 2,2’-azobis(2,4-dimethyl valeronitrile), 2,2’-azobis(2-methylbutyronitrile), 1 ,1’- azobis(cyclohexane-1 -carbonitrile), 2,2’-azobis(4-methoxy-2,4-dimethyl valeronitrile), dimethyl 2,2’-azobis(2-methylpropionate), 2,2’-azobis[N-(2-propenyl)-2- methylpropionamide, 1 -[(1 -cyano-1 -methylethyl)azo]formamide, 2,2'-Azobis(N-butyl- 2-methylpropionamide), 2,2'-Azobis(N-cyclohexyl-2-methylpropionamide), 2,2'- Azobis(2-methylpropionamidine) dihydrochloride, 2,2'-Azobis[2-(2-imidazolin-2- yl)propane]dihydrochloride, 2,2'-Azobis[2-(2-imidazolin-2-yl)propane]disulfate dihydrate, 2,2'-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate, 2,2'- Azobis{2-[1 -(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'- Azobis[2-(2-imidazolin-2-yl)propane], 2,2'-Azobis(1 -imino-1 -pyrrolidino-2- ethylpropane) dihydrochloride, 2,2'-Azobis{2-methyl-N-[1 , 1 -bis(hydroxymethyl)-2- hydroxyethl] propionamide} and 2,2'-Azobis[2-methyl-N-(2-hydroxyethyl) propionamide].

Examples of suitable photoinitiators which may be included in the compositions as component (e) include aromatic ketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thio compounds, hexa-arylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon halogen bond, and an alkyl amine compounds. Preferred examples of the aromatic ketones, the acylphosphine oxide compound, and the thio-compound include compounds having a benzophenone skeleton or a thioxanthone skeleton described in "RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY", pp.77-117 (1993). More preferred examples thereof include an alpha-thiobenzophenone compound described in JP1972-6416B (JP-S47-6416B), a benzoin ether compound described in JP1972-3981 B (JP-S47-3981 B), an alpha-substituted benzoin compound described in JP1972-22326B (JP-S47-22326B), a benzoin derivative described in JP1972-23664B (JP-S47-23664B), an aroylphosphonic acid ester described in JP1982-30704A (JP-S57-30704A), dialkoxybenzophenone described in JP1985- 26483B (JP-S60-26483B), benzoin ethers described in JP1985-26403B (JP-S60- 26403B) and JP1987-81345A (JPS62-81345A), alpha-amino benzophenones described in JP1989-34242B (JP H01 -34242B), U.S. Pat. No. 4,318, 791 A, and EP0284561A1 , p-di(dimethylaminobenzoyl)benzene described in JP1990-211452A (JP-H02- 211452A), a thio substituted aromatic ketone described in JP1986-194062 A (JPS61 -194062A), an acylphosphine sulfide described in JP1990-9597B (JP-H02- 9597B), an acylphosphine described in JP1990-9596B (JP-H02-9596B), thioxanthones described in JP1988-61950B (JP-S63-61950B), and coumarins described in JP1984-42864B (JP-S59-42864B). In addition, the photoinitiators described in JP2008-105379A and JP2009-114290A are also preferable. In addition, photoinitiators described in pp. 65 to 148 of "Ultraviolet Curing System" written by Kato Kiyomi (published by Research Center Co., Ltd., 1989) may be used.

Especially preferred photoinitiators include Norrish Type II photoinitiators having an absorption maximum at a wavelength longer than 380nm, when measured in one or more of the following solvents at a temperature of 23°C: water, ethanol and toluene. Examples include a xanthene, flavin, curcumin, porphyrin, anthraquinone, phenoxazine, camphorquinone, phenazine, acridine, phenothiazine, xanthone, thioxanthone, thioxanthene, acridone, flavone, coumarin, fluorenone, quinoline, quinolone, naphtaquinone, quinolinone, arylmethane, azo, benzophenone, carotenoid, cyanine, phtalocyanine, dipyrrin, squarine, stilbene, styryl, triazine or anthocyanin-derived photoinitiator.

Where desired, a surfactant or combination of surfactants may be included in the composition as component (f), e.g. as a wetting agent or to adjust surface tension. Commercially available surfactants may be utilized, including radiation-curable surfactants. Surfactants suitable for use in the composition include non-ionic surfactants, ionic surfactants, amphoteric surfactants and combinations thereof.

Preferred surfactants are as described in WO 2007/018425, page 20, line 15 to page 22, line 6, which are incorporated herein by reference thereto. Fluorosurfactants are particularly preferred, especially Zonyl® FSN and Capstone® fluorosurfactants (produced by E.l. Du Pont). Also preferred are polysiloxane based surfactants, especially Surfynol from Air Products, Xiameter surfactants from DowCorning, TegoPren™ and TegoGlide™ surfactants from Evonik, Siltech and Silsurf™ surfactants from Siltech, and Maxx™ organosilicone surfactant from Sumitomo Chemical.

Preferably the composition comprises component (f) in an amount of 0 to 3 wt%, more preferably 0 to 2.5 wt%, especially 0 to 2 wt%

In a preferred embodiment the porous film is obtainable by curing a composition comprising the following components:

(i) the styrenic monomer comprising a group of the formula -SO ₂ X (a), e.g. the compound of Formula (1 ) as hereinbefore defined;

(ii) the crosslinking agent (b);

(iii) a solvent (c);

(iv) optionally (d) a rheology or viscosity modifier;

(v) optionally (e) a radical initiator; and

(vi) optionally (f) a surfactant.

In an especially preferred embodiment the porous film is obtainable by curing a composition comprising the following components:

(i) 20 to 55 wt% of component (a);

(ii) 5 to 30 wt% of component (b);

(iii) 30 to 65 wt% of component (c);

(iv) 0 to 5 wt% of component (d);

(v) 0 to 2 wt% of component (e); and

(vi) 0 to 2 wt% of component (f).

Preferably the total wt% of components (b) which contain ester or amide groups is less than 5 wt%.

For the avoidance of doubt, the wt% refer to the weight of the relevant component relative to the total weight of components (a) to (f) present in the composition.

In order to maximize the -SO ₂ X functionality density in the membranes, the composition preferably contains a higher wt% of component (a) than the wt% of component (b): i.e. wt% (a)/wt% (b) > 1 , e.g. 1.2 to 10.

Preferably the film further comprises a porous support. As examples of porous supports there may be mentioned woven and non-woven synthetic fabrics and extruded films. Examples include wetlaid and drylaid non-woven materials, spunbond and meltblown fabrics and nanofiber webs made from, e.g. polyethylene, polypropylene, polyacrylonitrile, polyvinyl chloride, polyester, polyamide, and copolymers thereof. Porous supports may also be porous membranes, e.g. polysulfone, polyethersulfone, polyphenylenesulfone, polyphenylenesulfide, polyimide, polyethermide, polyamide, polyamideimide, polyacrylonitrile, polycarbonate, polyacrylate, cellulose acetate, polypropylene, poly(4-methyl 1- pentene), polyinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene and polychlorotrifluoroethylene membranes.

The porous support, when present, may be treated to modify its surface energy, e.g. to values above 45 mN/m, preferably above 55mN/m. Suitable treatments include corona discharge treatment, plasma glow discharge treatment, flame treatment, ultraviolet light irradiation treatment, chemical treatment or the like, e.g. for the purpose of improving the wettability of and the adhesiveness to the porous support to the polymer film.

Commercially available porous supports are available from a number of sources, e.g. from Freudenberg Filtration Technologies (Novatexx materials), Lydall Performance Materials, Celgard LLC, APorous Inc., SWM (Conwed Plastics, DelStar Technologies), Teijin, Hirose, Mitsubishi Paper Mills Ltd and Sefar AG.

Preferably the support is a polymeric support. Preferably the support is a woven or non-woven synthetic fabric or an extruded film without covalently bound ionic groups.

The porous support preferably has an average thickness in the range 10 and 800 pm, more preferably in the range 15 and 300 pm, especially in the range 20 and 150 pm.

Preferably the porous support has an average porosity in the range 30 to 95%. The porosity of the support may be determined by a porometer, e.g. a Porolux™ 1000 from IB-FT GmbH, Germany.

The average thickness of the film, including porous support when present, is preferably within the range 10 to 1000, more preferably within the range 20 to 800 pm, especially within the range 30 to 500.

Preferably the porosity of the porous film of the present invention is in the range 10% to 60%, more preferably 15% to 50%, especially 20% to 40%.

Preferably the porous film has a mean flow pore size (“MFP”) in the range 5 to 10,000 nm, more preferably 10 to 5,000 nm and especially 10 to 1 ,000 nm. The MFP of the membrane is preferably the MFP as determined by capillary flow porometry (also known as porometry). In capillary flow porometry an inert gas is used to displace a liquid from the pores of the film under evaluation. The pressure required to empty the pores corresponds to the pressure necessary to evacuate the liquid from the most constricted part of the pore. This most constricted part is the most challenging one and it offers the highest resistance to remove the liquid. Equipment for measuring MFP is commercially available, e.g. the Porolux™ 1000 from IB-FT GmbH, Germany. Suitable conditions for measuring MFP are as described below in the Examples.

The films of the present invention preferably have an ion-exchange capacity (IEC) of at least 1 meq/g, more preferably of at least 1.2 meq/g, especially more than 1 .4 meq/g, more especially more than 1 .5 meq/g, based on the total dry weight of the membrane (including the porous support when present), e.g. in the range 1 meq/g to 8.00 meq/g, more preferably 1 .2 meq/g to 6.00 meq/g and especially 1 .4 meq/g to 4.00 meq/g. The ion-exchange capacity (IEC) of the films according to the present invention may be determined as described below.

The films of the present invention preferably have a water flux of more than 100 L/m ² /bar/hr, more preferably more than 150 L/m ² /bar/hr, especially more than 500 L/m ² /bar/hr. The water flux of the films according to the present invention may be determined as described below.

The films of the present invention have an average sulphur amount between 5 to 20 wt%, more preferably between 6 to 20 wt%, more preferably 6 to 17 wt% and most preferred between 6 to 9 wt%. A technique to analyze the sulphur content of the porous film is to break down the material and analyze the product by size-exclusion chromatography, mass spectrometry, Inductively coupled plasma - optical emission spectrometry (ICP-OES) or Inductively coupled plasma - mass spectrometry (ICP- MS). A suitable pyrolysis and gas chromatography technique which may be used to determine the composition of Sulfur content in a layer is described in the paper by H. Matsubara and H. Ohtani entitled “Rapid and Sensitive Determination of the Conversion of UV-cured Acrylic Ester Resins by Pyrolysis-Gas Chromatography in the Presence of an Organic Alkali” in Analytical Sciences, 2007, 23(5), 513.

The films of the present invention preferably have a swelling in water of less than 20%, more preferable less than 10% and especially less than 5%. The swelling in water of the films according to the present invention may be determined as described below

The films of the present invention are preferably stable in 1 M HCI and 1 M NaOH solutions for 7 days at 80°C. The pH stability of the films may be expressed as the percentage of ion exchange capacity remaining after the test compared to the ion exchange capacity of the film before the test. When the ion-exchange capacity after the test is at least 80% of the ion-exchange capacity before the test, the film is considered to be pH stable. The pH stability of the films according to the present invention may be determined as described below.

According to a second aspect of the present invention there is provided a process for preparing a porous film comprising polymerisation of a composition comprising a styrenic monomer comprising a group of the formula -SO ₂ X, wherein:

X is of the formula -N(M)SO ₂ R or OM;

R is a C _1-12 - alkyl group or a C _1-12 -aryl group; and M is H, a cation or a C _1-6 — alkyl group;

The styrenic monomer used in the second aspect of the present invention is preferably of Formula (1 ) as defined above in relation to the first aspect of the present invention.

In the second aspect of the present invention, the preferences for the compound of Formula (1 ) are as defined herein in relation to the first aspect of the present invention.

In the second aspect of the present invention, the composition is preferably as described in relation to the first aspect of the present invention. The preferences for the composition used in the process of the second aspect of the present invention are as described herein in relation to the first aspect of the present invention.

The compositions may be cured to prepare films according to the second aspect of the present invention by any suitable process, including thermal curing, photocuring, electron beam (EB) radiation, gamma radiation, and combinations of two or more of the foregoing. Optionally, dual curing - defined as the combination of two of the above mentioned curing techniques - may be used. However the compositions are preferably cured by photocuring, e.g. by irradiating the compositions by ultraviolet of visible light and thereby causing the curable components present in the composition to polymerise, or by thermal curing.

While it is possible to prepare the films of the present invention on a batch basis using a stationary support, it is much preferred to prepare the film on a continuous basis using a moving untreated membrane. The untreated membrane may be in the form of a roll which is unwound continuously or the untreated membrane may rest on a continuously driven belt (or a combination of these methods). Using such techniques the composition can be applied to a porous support or a non-porous support on a continuous basis or it can be applied on a large batch basis.

The curable composition may be applied to a porous support or a non-porous support by any suitable method, for example by curtain coating, blade coating, air- knife coating, knife-over-roll coating, slide coating, nip roll coating, forward roll coating, reverse roll coating, micro-roll coating, dip coating, foulard coating, kiss coating, rod bar coating or spray coating. The curable composition typically forms a continuous film. The coating of multiple layers can be done simultaneously or consecutively. When coating multiple layers, the curable compositions may be the same or different.

Thus the application step may be performed more than once, either with or without curing being performed between each application. When applied to different sides the resultant film may be symmetrical or asymmetrical.

Thus in a preferred process, the composition is applied continuously to a porous support or a non-porous support, preferably by means of a manufacturing unit comprising one or more composition application station(s), one or more curing stations for curing the composition (thermally and/or by photocuring), a film collecting station and a means for moving the a porous support or a non-porous support from the curable composition application station(s) to the curing station(s) and to the film collecting station. The curing station(s) may comprise irradiation source(s) when a composition is photocurable, and heat source(s) when a composition is thermally curable.

The composition application station(s) may be located at an upstream position relative to the curing station(s) and the curing station(s) is/are located at an upstream position relative to the film collecting station.

During polymerisation, components (a) and (b) typically polymerise to form a very thin film layer. The copolymerisation of components (a) and (b) together may be brought about by any suitable means, e.g. by irradiation and/or heating. When using irradiation the polymerisation preferably occurs sufficiently rapidly to form a film within 30 seconds. If desired further curing may be applied subsequently to finish off, although generally this is not necessary.

Preferably curing of the composition begins within 3 minutes, more preferably within 60 seconds, after the composition has been applied to a porous support or a non-porous support.

Photoinitiators may be included in the curable composition, as mentioned above, and are usually required when curing uses UV or visible light radiation.

Photocuring by ultraviolet or visible light is preferably performed at a wavelength between 100 nm and 800 nm, typically using a dose of light of between 40 and 1500 mJ/cm ² , more preferably between 40 and 1500 mJ/cm ² , most preferably between 70 and 900 mJ/cm ² as measured using a High Energy UV Radiometer (UV PowerMap™ from EIT, Inc) in the UV-A and UV-B range indicated by the apparatus. To reach the desired exposure dose at high coating speeds, more than one UV lamp may be used, so that the composition is irradiated more than once Thermal curing is preferably performed at a temperature of between 20°C and 100°C, e.g. for a period of 0.01 hour to 24 hours.

Preferably the curing is achieved by irradiating the composition for less than 30 seconds, more preferably less than 10 seconds, especially less than 3 seconds, more especially less than 2 seconds. In a continuous process the irradiation occurs continuously and the speed at which the composition moves through the beam of irradiation is mainly what determines the time period of curing. The exposure time is determined by the irradiation time by the concentrated beam; stray ‘light’ generally is too weak to have a significant effect.

Suitable sources of ultraviolet light are mercury arc lamps, carbon arc lamps, low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, swirlflow plasma arc lamps, metal halide lamps, xenon lamps, tungsten lamps, halogen lamps, lasers and ultraviolet light emitting diodes. Particularly preferred are ultraviolet light emitting lamps of the medium or high pressure mercury vapour type. In most cases lamps with emission maxima between 200 and 450 nm are particularly suitable. A typical example of a UV light source for curing is a D-bulb with an output of 600 Watts/inch (240 W/cm) as supplied by Fusion UV Systems. Alternatives are the V-bulb and the H-bulb from the same supplier.

When no initiator is included in the composition, the composition can be cured by electron-beam exposure, e.g. using an exposure of 50 to 300 keV. Reaction can also be achieved by plasma or corona exposure.

In order to produce a sufficiently flowable composition for application by a high speed coating machine, it is preferred that the composition has a viscosity below 5000 mPa s when measured at 35°C, more preferably from 1 to 1500 mPa·s when measured at 35°C. Most preferably the viscosity of the composition is from 2 to 500 mPa s when measured at 35°C. For coating methods such as slide bead coating the preferred viscosity is from 2 to 150 mPa s when measured at 35°C.

With suitable coating techniques, the composition may be applied to a moving a porous support or a non-porous support at a speed of over 1 m/min, e.g. 5 m/min, preferably over 10 m/min, more preferably over 15 m/min, e.g. more than 20 m/min,.

When the film arising from the process of to the second aspect of the present invention films comprises one or more groups of the formula -SO ₂ X in which X is of the formula -OM or -N(M)SO ₂ R wherein M is C _1-6 -alkyl such group(s) may be converted to groups of formula -SO ₂ X in which X is of the formula -OM or -N(M)SO ₂ R respectively wherein M is H or a cation by hydrolysis, e.g. using aqueous acid (e.g. 0.1 M hydrochloric acid) or aqueous alkali (e.g. 0.1 M aqueous LiOH, NaOH or KOH). Optionally the hydrolysing solution comprises a water miscible organic solvent to enhance the reaction speed. Heating may be used (e.g. to a temperature above 50°C, e.g. 60 to 90°C and especially about 80°C). The hydrolysis may be performed for as long as is necessary, e.g. for a period of 1 hr to 8 days, preferably 12 hrs to 6 days, e.g. about 16 hrs or about 4 days.

According to a third aspect of the present invention there is provided use of a film according to the first aspect of the present invention for water purification, for detecting, filtering and/or purifying biomolecules or for detecting or removing metal ions.

The films may be used for the detecting, filtering and purifying biomolecules (e.g. proteins, amino acids, nucleic acids, anti-bodies and endotoxins) by a number of techniques. These techniques include size-exclusion chromatography (where biomolecules are separated and/or purified based on their size (i.e., physical exclusion)) and ion exchange chromatography (where biomolecules are purified or separated according to the strength of their overall ionic interaction with ionic groups in a film).

The films of the present invention are particularly useful for filtering, and/or purifying biomolecules by processes comprising eluting solutions containing biomolecules, especially biomolecules which carry a positive charge. The positive charge on such biomolecules is attracted to the negative charge on the film derived from component (i).

The films of the present invention may be used for detecting biomolecules by techniques involving the detection of colour, especially when the biomolecules comprise a fluorescent of coloured marker.

The films according to the first aspect of the present invention may be used for purifying a biomolecule and/or separating a biomolecule from other biomolecule(s) by processes comprising contacting the biomolecules with a film according to the present invention. Preferably the process for purifying a biomolecule and/or separating a biomolecule from other biomolecule(s) comprises film size-exclusion chromatography or ion exchange chromatography.

The films of the present invention may be used for detecting metal ions by techniques involving the detection of colour.

Compositions comprising metal-ions (e.g. two or more metal ions and optionally contaminants), colloids containing metals or other agglomerates of metal-ions may be separated and/or purified based on their size (i.e., physical exclusion) or by ion exchange chromatography where compositions comprising metal-ions are purified or different metal ions are separated from each other according to the strength of their overall ionic interaction with anionic groups in the films of the present invention.

The films of the present invention may of course be used for other purposes too.

Preferably the films of the present invention are stable at pH 0.0 to pH 14.0 for at least 48 hours, more preferably for at least 96 hours, e.g. at a temperature of 80°C.

The invention will now be illustrated by the following Examples in which all parts and percentages are by weight unless specified otherwise.

In the Examples and Comparative Examples below, each of the compositions was polymerised to form a porous film of thickness 100pm by coating the compositions onto a polypropylene/polyethylene porous support (PE/PP non-woven support) for reinforcement with the aid of a 100pm Meyer bar. The polymerization was carried out at 80°C overnight (16 hours).

The following methods were applied.

Mean Flow Pore size

The mean flow pore size (MFP) of the films described in the Examples and Comparative Examples was determined using a Porolux™ 1000 porometer from IB- FT GmbH, Germany. The porometer was equipped with a SH-25 sample holder in which samples with 18.5 mm effective diameter were placed. The wetting fluid used was the Porefil™ fluid (16 dyn/cm fluid tension). The Nitrogen pressure was varied from 0 to 2 bar with a slope of 5 sec/bar. Bubble point flow rate was 30 ml/min. The flow and pressure accuracies were set at 0.5% with a 2 sec time. Porosity %

The porosity % of the films was determined from their apparent density (ρ apparent) and the real density as follows. The ρ apparent was measured in air by weighing the film and determining its volume from the dimensions of the film (length, width and thickness). The real density of the film was determined from pycnometer measurements of the film with known weight under helium atmosphere. The Helium occupied the pores of the film with known weight, and therefore the volume of polymer could be determined. From this the porosity could be determined according to Formula below:

The pycnometer used was the AccuPyc™ II 1340 gas displacement pycnometry system from Micromeritics Instrument Corporation.

Ion-exchange capacity (“IEC”)

Prior to measuring a film's IEC, the film was weighed in the dry state. The film was then stored in 1.0 M KCI solution for 24 hours to fully exchange all possible counter-ions of the film for chloride ions and then the film was stored in demineralised water for 24 hours. Subsequently, the film was equilibrated with 0.1 M KBr solution for 24 hours and rinsed with demineralised water for 24 hours. The remainder of KBr solution and the rinsing solution of demineralised water were combined quantitatively; 1.0 g of barium acetate was added and the solution was titrated with 0.1 M AgNO ₃ . The amount of silver ions were measured using an ion selective silver electrode, which resulted in an amount of ions which had been exchanged per unit weight of film.

Water flux

The water flux of the films was measured using a device where the weight of water passing through the film was measured over time. A column of feed solution (pure water) was brought into contact with the film under evaluation and the feed solution was forced through the film by a constant applied air pressure on top of the water column. By achieving a constant flow of water at a constant applied pressure, the water flux could be determined.

Typically the film under evaluation was stored for 12 hours in pure water prior to use. The feed solution (250 ml of pure water) was brought into contact with the film (film contact area of 12.19 cm ² ). The water column was closed and pressurized with air pressure and the film was flushed with one water column (250 ml). The feed solution was refreshed and a constant air pressure of 100 mbar was applied. Finally, the measurements were performed by monitoring the weight by balance at a constant flow. Swelling

The swelling of the films of the present invention was determined by measuring the volume of the film when dry and when wet with water and performing the following calculation: pH stability

To test pH stability, samples of the film were immersed in 1 M HCI or 1 M NaOH solutions for 7 days at 80°C. The pH stability is expressed as the percentage of IEC remaining after the 7 day immersion compared to the IEC of the film before the immersion. When the IEC after the immersion is at least 80% of the original IEC the film is considered to be pH stable.

Average sulphur content of the films determination by ICP method

The average sulphur content can be determined by cutting, weighing and digesting 12.57 cm ² of each film in 10 ml concentrated nitric acid. Digestion was performed by means of microwave digestion (Digestion program 1200W ramp 15', Hold 30', Cool 30'.).

The digested solutions were diluted up to 50ml with milli-Q water and sulphur amount was determined using Thermo ICAP-PRO ICP-OES. A standard concentric nebulizer is used in conjunction with a cyclonic spray chamber. All samples were prepared in duplicate.

Materials

Examples Ex. 1 and Ex, 2 and Comparative Examples CEx. 1 and CEx. 2 Compositions were prepared by mixing the components described in Tables 1 a and 1 b below in the specified amounts.

Table 1a

Recalculated to 100% pure compound

Table 1 b

Recalculated to 100% pure compound

The compositions described in Tables 1 a and 1 b above were coated onto the PE/PP non-woven support and polymerised under the following conditions: heating at 80°C, for 16 hours.

The films arising from Examples 1 and 2 comprised groups of the formula -SO ₂ CH ₂ CH ₃ . These -SO ₂ CH ₂ CH ₃ groups were converted to -SO ₂ OLi groups by hydrolysis. The hydrolysis was performed by immersing the films comprising the groups of the formula -SO ₂ CH ₂ CH ₃ in 0.1 M aqueous LiOH at 80°C for 4 days. The porosity, mean pore size, water flux, swelling, pH stability and IEC of the films resulting from hydrolysis of the films prepared in Examples Ex. 1 , Ex. 2 and Comparative Examples CEx.1 and CEx.2 were measured as described above and the results are shown in Table 2 below: Table 2 - Results

As can be seen from Table 2 above, the films arising from Examples 1 and 2 were porous and had much better pH stability and higher IEC than the films arising from the Comparative Examples.