WO2012042239A1 - Process for preparing curable polymers and membranes - Google Patents

Abstract

A process for preparing a curable polymer comprising the steps: (I)providing a pre-polymer comprising a backbone and, pendant thereon, side chains (a) comprising a poly(ethylene oxide) group and side chains (b) comprising a reactive group A which is capable of reacting with reactive group B mentioned in (II) below, wherein said side chains are free from ethylenically unsaturated groups; (II)providing a compound having an ethylenically unsaturated group and a reactive group B; and (III) reacting said reactive groups A and B together thereby forming a covalent bond between the said pre-polymer side chains (b) and the compound to give the curable polymer. The curable polymers have an ethylene oxide content of at least 50wt% and are useful for preparing membranes e.g. for gas separation.

Description

PROCESS FOR PREPARING CURABLE POLYMERS AND MEMBRANES

This invention relates to a process for preparing curable polymers and to membranes. The membranes may be used for separating mixtures of polar and non-polar gases.

In recent years there has been an increasing interest in the separation of gases. Usually non-porous membranes are used and the chemical and physical properties of the membranes influence the selectivity of the membrane and the flux of gases. Ideally membranes have a good durability while at the same time discriminate between polar and non-polar gases to provide efficient gas separation. There is a particular need for membranes suitable for separating methane and carbon dioxide.

WO 2008/143516 describes the preparation of gas separation membranes by polymerizing a composition comprising a compound having a molecular weight of at least 1500 Da, at least 75 weight% of oxyethylene groups and at least two polymerisable groups, each comprising a non-substituted vinyl group.

WO 2008/143515 describes membranes obtainable by polymerizing a compound comprising at least 70 oxyethylene groups and at least two polymerisable groups, e.g. poly(ethylene glycol) 4000 diacrylate. In comparative Example 3, a 50:50 mixture of poly(ethylene glycol) 600 diacrylate and poly(ethylene glycol) methyl ether acrylate (Mn ~ 454) was polymerised to give a membrane having an ethylene oxide content reported to be 80.7%.

There is a need for further membranes capable of discriminating between gases and having even better fluxes. Ideally such membranes can be produced efficiently at high speeds using toxicologically and environmentally acceptable liquids (particularly water). Furthermore, there is a need for polymers which can be used to make such membranes.

This specification describes the preparation of curable polymers which can be used to prepare membranes having excellent flux and selectivity performance and can be produced in a safe and environmentally friendly manner.

According to a first aspect of the present invention there is provided a process for preparing a curable polymer comprising the steps:

(I) providing a pre-polymer comprising a backbone and, pendant thereon, side chains (a) comprising a poly(ethylene oxide) group and side chains (b) comprising a reactive group A which is capable of reacting with reactive group B mentioned in (II) below, wherein said side chains are free from ethylenically unsaturated groups;

(II) providing a compound having an ethylenically unsaturated group and a reactive group B; and (III) reacting said reactive groups A and B together thereby forming a covalent bond between the said pre-polymer side chains (b) and the compound to give the curable polymer wherein the curable polymer has an ethylene oxide content of at least 50wt%.

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".

In one embodiment the backbone is free from ethylenically unsaturated groups.

Preferably the combined molecular weight of the side chains (a) and (b) is at least twice the molecular weight of the backbone. Preferably the pre-polymer is free from fluorine. Preferably the pre-polymer has one (and only one) backbone.

Preferably the pre-polymer is free from poly(ethylene oxide) groups comprising more than 22 consecutive ethylene oxide units.

Preferably the curable polymer and/or the pre-polymer have an ethylene oxide content above 55wt%, more preferably above 60wt%, especially above 65wt%, more especially above 70wt% and even more especially above 75wt%, particularly above 80wt%, e.g. around 85wt% (between 82 and 88wt%).

Preferably the curable polymer and/or the pre-polymer has an ethylene oxide content below 98wt%, more preferably below 96wt%, especially below 94wt%.

The pre-polymer comprises alkylene oxide groups. Preferably at least 85wt%, more preferably at least at least 92wt% and especially 100wt% of the alkylene oxide groups are ethylene oxide groups. Any alkylene oxide groups which are not ethylene oxide groups are preferably propylene oxide groups.

In the majority of the chains the ethylene oxide groups are preferably present in poly(ethylene) oxide chains comprising at least two, more preferably at least three consecutive ethylene oxide units (e.g. as in -(CH₂ CH₂O)_N- wherein n is at least 2, preferably at least 3). Even more preferably the poly(ethylene) oxide chains comprise at least 5 consecutive ethylene oxide units, especially 8 to 15, e.g. about 10 or about 13 consecutive ethylene oxide units.

The ethylene oxide units in the pre-polymer may form an uninterrupted poly(ethylene oxide) chain (e.g. as in -(CH₂ CH₂O)_N- wherein n is preferably 3 to 22) or the chain may contain interruptions (e.g. as in -(CH₂CH₂O) N-R-(OCH₂CH₂) M- wherein N and M are each at most 22). Examples of such interruptions represented by R include -CH₂-, -(CH₂)_X- wherein x>2, -CH(CH₃)-, -C(CH₃)₂-, - CH₂CH(CH₃)-, -CH₂-C(CH₃)₂-CH₂-,-C₆H₄-, -C₆H₄-C(CH₃)₂-C₆H₄- (bisphenol A), -C₆H₄-CH₂-C₆H₄- (bisphenol F), cycloalkyl and -(C=O)-. Preferably the poly(ethylene oxide) groups comprise up to 22 consecutive ethylene oxide (-(CH₂ CH₂O)-) repeat units. These poly(ethylene oxide) groups are preferably present in one or more of the side chains (a) and (b). The backbone may contain ethylene oxide units, however this is not necessarily required to produce a membrane having superior properties.

A high ethylene oxide content for the pre-polymer is preferred because this can enhance the permeability of membranes formed from the resultant curable polymer to polar gases such as carbon dioxide and hydrogen sulphide.

The poly(ethylene oxide) groups in the pre-polymer preferably all comprise less than or equal to 22 consecutive ethylene oxide units (e.g. n, N and M are positive integers less than or equal to 22) because this can reduce the tendency of membranes made therefrom to crystallize. However when operating at temperatures higher than the crystallization temperature, crystallisation does not occur and the curable polymer may contain more than 22 consecutive ethylene oxide units.

Preferably side chains (a) are terminated by an alkoxy or aryloxy group, especially by a Ci_-4-alkoxy or C6-io-aryloxy group.

Preferably side chain (b) further comprises a poly(ethylene oxide) group. Preferably side chains (a) comprise, on average, at least eight ethylene oxide groups.

In one embodiment the backbone is substantially free from pendant side chains other than side chains (a) and (b). Optionally a low amount of other side chains (e.g. side chains which are free from poly(ethylene oxide) groups and nucleophilic groups) are present. When such other side chains are present, they are preferably present in a molar ratio of less than 1 :10, more preferably less than 1 :20, relative to the total number of moles of side chains (a) and (b). Preferably at least 80 mole% of the side chains (including optional other side chains) comprise a poly(ethylene oxide) group. More preferably at least 90 to 100mole% of the side chains comprise a poly(ethylene oxide) group. Preferably both of side chains (a) and (b) comprise a poly(ethylene oxide) group.

Preferably, the backbone is an aliphatic backbone, or, the backbone comprises aliphatic and alkylene oxide (e.g. ethylene oxide) groups. If desired, the backbone may comprise aromatic groups, preferably in a low amount, as this can be useful to modify the properties of the resultant curable polymer.

The preferred weight average molecular weight for the curable polymer depends to some extent on the pore size of the support (if any), with lower weight average molecular weights being allowed for supports having smaller pore sizes. Generally speaking, however, the curable polymer preferably has a weight average molecular weight above 105,000, more preferably above 125,000, especially above 150,000, more especially above 160,000, particularly above 170,000 Daltons.

Preferably the curable polymer has a weight average molecular weight below 10 million Daltons, more preferably below 9 million Daltons, especially below 5 million, more especially below 3 million Daltons. The latter preference arises from practical considerations such as the viscosity of a solution of the curable polymer in relation to handleability, e.g. in terms of chemical functionalisation and coating behaviour.

Preferably the curable polymer is in isolated form, i.e. in a form which substantially free from the monomers used to produce it.

The mole ratio of side chains (b):(a) is preferably from 0.001 to 0.95, more preferably 0.01 to 0.8, more preferably 0.02 to 0.6, especially 0.05 to 0.5, and more especially 0.07 to 0.3, e.g. between 0.10 and 0.20. The mole ratio of side chains (b):(a) may be calculated according to the formula [(number of moles of side chain (b))/(number of moles of side chain (a))]. For example, if a curable- polymer has 1 mole of side chain (b) and 2 moles of side chain (a) the mole ratio of side chains (b):(a) is 1/2 = 0.5. By controlling the number of ethylenically unsaturated groups present in the curable polymer (e.g. in the side chains (b)) the crosslink density of membranes derived from the curable polymer can be tuned to the desired value.

The curable polymers of the present invention may be used to prepare membranes having a high permeability to polar gases (e.g. CO2, H₂S, NH₃, SO_x, and nitrogen oxides, especially NO_x) and selectivity for polar gases over non-polar gases, vapors and liquids(e.g. methane and other hydrocarbons and nitrogen). The gases may comprise vapors, for example water vapor.

In one embodiment the membrane has low permeability to liquids, e.g. water and aqueous solutions.

The membranes are particularly suitable for purifying natural gas (a mixture which comprises methane) by removing polar gases (CO2, H₂S), and for removing CO2 from hydrogen and from flue gases or biogas. Flue gas is typically a gas that exits to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from e.g. a fireplace, oven, furnace, boiler, combustion engine or steam generator. Flue gases also include the exhaust gases produced at power plants. Its composition depends on what is being burned, but it will usually contain mostly nitrogen (typically more than two-thirds) derived from the combustion air, carbon dioxide (CO2) and water vapour as well as oxygen (also derived from the combustion air). It further contains a small percentage of pollutants such as particulate matter, carbon monoxide, nitrogen oxides and sulphur oxides. Biogas is emitted from landfills, digesters, etc. and comprises primarily methane and CO2 resulting from the anaerobic decomposition of waste materials, for example domestic and industrial waste and agricultural sewage. Recently the separation and capture of CO2 has attracted attention in relation to environmental issues (global warming). For most applications the cost of the membranes and their environmental friendly production are important considerations.

The membranes derived from the curable polymers of the invention have a high flux in combination with a good selectivity.

Membranes may be prepared by performing the process of the first aspect of the present invention to give a curable polymer and then curing the curable polymer, preferably on a support.

In one embodiment the support is a non-porous support. In this embodiment the resultant membrane preferably is removed from the support after curing. In another embodiment the support is porous and the resultant membrane and porous support preferably are in contact to provide a composite membrane.

The curable polymer may be applied to the support by any suitable methods, preferably by curtain coating, extrusion coating, air-knife coating, knife- over-roll coating, slide coating, nip roll coating, forward roll coating, reverse roll coating, dip coating, foulard coating, kiss coating, rod bar coating and/or spray coating. The coating of multiple layers, if desired, can be done simultaneously or consecutively, depending on the embodiments used.

In order to produce a sufficiently flowable composition for use in a high speed coating machine, it is preferred that a composition comprising an inert liquid and the curable polymer is applied to the support. The viscosity of the composition is preferably below 4000 mPa-s (all viscosities mentioned herein are measured at 35°C, unless indicated otherwise) more preferably below 1000 mPa s at 35°C. For coating methods such as slide bead coating the preferred viscosity is preferably 1 to 100 mPa s. The desired viscosity is preferably achieved by controlling the amount and/or identity of the inert liquid vehicle (e.g. water and/or organic solvent) present in the composition. With suitable coating techniques, coating speeds of at least 5 m/min, e.g. 15 m/min or higher can be achieved. For example coating speeds as high as 200 m/min can be reached, although speeds of up to 60 m/min or 120 m/min are more usual.

After application of the curable polymer (e.g. in the form of a composition further comprising an inert liquid) it may partly or even totally penetrate the porous support to achieve a good adhesion thereto. The latter alternative can be very useful for providing membranes with greater mechanical strength and durability having a high flux and the process for making such supported membranes is particularly efficient and convenient.

Optionally the process further comprises the step of washing and/or drying the membrane after curing.

A further advantage of curable polymers obtained by the presently claimed process is that their water-solubility is often good, reducing or removing the need to use organic solvents when the curable polymers are used for the manufacture of composite membranes. Reducing or avoiding organic solvents is advantageous for environmental, safety and health reasons.

Suitable ethylenically unsaturated groups are preferably of the formula

CH₂=CH- (i.e. a non-substituted vinyl group) or CH₂=C(CH₃)-, CH₃CH=CH- or aryl- CH=CH- (i.e. a substituted vinyl group). For making a network structure at least two ethylenically unsaturated groups per molecule of curable polymer should be present.

Examples of suitable vinyl groups are (meth)acrylate groups, unsaturated acyl groups (e.g. cinnamoyl and crotonoyl groups), (meth)acrylamide groups, vinyl ether groups, vinyl ester groups, vinyl amide groups, allyl ether groups, allyl ester groups, allyl amine groups, allyl amide groups, styryl groups, and combinations thereof.

The preferred ethylenically unsaturated groups are acrylic (CH₂=CHC(O)-) groups, especially acrylate (CH₂=CHC(O)O-) groups or methacrylic (CH₂=C(CH₃)C(O)-) groups, especially methacrylate (CH₂=C(CH₃)C(O)O-) groups. Acrylate groups are preferred because of their fast polymerization rates, especially when using UV light to effect the curing, and good commercial availability.

Preferably the vinyl group is a non-substituted vinyl group, especially for high speed membrane production methods where fast curing is desired. When substituted vinyl groups are used, a high energy curing method is preferred such as electron beam irradiation or plasma treatment. Even with these methods unsubstituted vinyl groups are preferred.

When radiation is used to convert the curable polymer into a membrane, in principle (electromagnetic) radiation of any suitable wavelength can be used, such as for example ultraviolet, visible or infrared radiation, as long as it matches the absorption spectrum of the photo-initiator, if present, or as long as enough energy is provided to directly cure the curable polymer without the need of a photo- initiator. Electron beam radiation may also be used.

Curing by infrared radiation is also known as thermal curing. Thus curing may be effectuated by combining the curable polymer having ethylenically unsaturated groups on side chains (b) with a thermally reactive free radical initiator and heating the mixture, for example by using infrared radiation, microwave radiation, hot air convection and/or conduction heating. Examples of thermally reactive free radical initiators include organic peroxides, e.g. ethyl peroxide and benzoyl peroxide; hydroperoxides, e.g. methyl hydroperoxide; acyloins, e.g. benzoin; certain azo compounds, e.g. α,α'-azobisisobutyronitrile and y,y'-azobis(y- cyanovaleric acid); persulfates; peroxyesters, e.g. methyl peracetate and tert-butyl peracetate; peroxalates, e.g. dimethyl peroxalate and di(tert-butyl) peroxalate; disulfides, e.g. dimethyl thiuram disulfide; and ketone peroxides, e.g. methyl ethyl ketone peroxide. Temperatures in the range of from about 30°C to about 150°C are generally employed. More often, temperatures in the range of from about 40°C to about 1 10°C are used.

Of all the abovementioned methods of curing, the use of ultraviolet light is preferred. Suitable wavelengths are for instance UV-A (400-320 nm), UV-B (320- 280 nm), UV-C (280-200 nm), provided the wavelength matches with the absorbing wavelength of the photo-initiator, if present.

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 vapor type. In addition, additives such as metal halides may be present to modify the emission spectrum of the lamp. In most cases lamps with emission maxima between 200 and 450 nm are most suitable.

The energy output of the exposing device may be between 20 and 1000 W/cm, preferably between 40 and 500 W/cm but may be higher or lower as long as the desired exposure dose can be realized. The exposure intensity is one of the parameters that can be used to control the extent of curing which influences the final structure of the membrane. Preferably the exposure dose is at least 40 mJ/cm², more preferably between 40 and 1500 mJ/cm², most preferably between 70 and 900 mJ/cm² as measured by an High Energy UV Radiometer (UV PowerMap™ from EIT, Inc) in the UV-A and UV-B range indicated by the apparatus. Exposure times can be chosen freely but preferably are short and are typically less than 10 seconds, preferably less than 5 seconds, more especially less than 2 seconds, e.g. between 0.1 and 1 second. For determining exposure time only the direct radiation including the radiation reflected by the mirror of the exposure unit is taken into account, not the indirect stray light.

When radiation is used to prepare a membrane, a free radical initiator, e.g. photo-initiator, may be used. Photo-initiators are usually required when the curable polymer is reacted with a compound comprising an electrophilic group and an ethylenically unsaturated group to give a thermal or radiation curable polymer having ethylenically unsaturated groups on side chains (b) which is to be cured by UV or visible light radiation. Suitable photo-initiators are those known in the art such as radical type, cation type or anion type photo-initiators.

Examples of radical type I photo-initiators are disclosed in WO2008/143515, page 14, line 23 to page 15, line 28, which are incorporated herein by reference thereto.

Examples of type II photo-initiators are disclosed in WO2008/143515, page 15, line 29 to page 16, line 28, which are incorporated herein by reference thereto. If desired combinations of photo-initiators may also be used.

Type I photo-initiators are preferred.

Preferably the weight ratio of photo-initiator to curable polymer is from 0.001 to 0.1 , more preferably from 0.005 to 0.05. A single type of photo-initiator may be used or a combination of several different types.

The curing is preferably effected using UV radiation. When UV radiation is used, a UV light source can be selected having emissions at several wavelengths. The combination of UV light source and photo-initiator(s) can be optimized so that sufficient radiation penetrates deep into the layer(s) to activate the photo-initiators. A typical example is an H-bulb with an output of 600 Watt/inch (240 W/cm) as supplied by Fusion UV Systems. Alternatives are the V-bulb and the D-bulb which have a different emission spectrum. Also combinations of different types of light sources may be used. Preferably the UV light source(s) and the photo-initiators are chosen such that the wavelength of the UV light provided corresponds to the absorption of the photo initiator(s).

When no photo-initiator is added, the curable polymer can be advantageously cured by electron-beam exposure. Curing can also be achieved by beta or gamma irradiation or by plasma or corona exposure.

To reach the desired dose at high coating speeds, more than one UV lamp may be used such that the coated layer is exposed to more than one lamp.

If desired the support is a support which has been subjected to a chemical treatment, corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet light irradiation treatment or the like. Such treatments can improve the wettability and the adhesiveness of the support.

While it is possible to produce the membrane on a batch basis using a stationary support, to gain full advantage of the invention, it is much preferred to perform the process on a continuous basis using a moving support. A moving support may be provided by using a roll-driven continuous web or belt.

Examples of suitable supports include woven materials, non-woven materials, porous polymeric membranes and porous inorganic membranes. The support may be made from any suitable material, for example polysulfone, polyethersulfone, polyimide, polyethermide, polyamide, polyamideimide, polyacrylonitrile, polycarbonate, polyacrylate, cellulose acetate, polypropylene and/or poly(4-methyl 1 -pentene). In a preferred embodiment the membrane is not separated from the support, in which case the support is preferably sufficiently porous to enable a high flux through the membrane. Preferably the support has an air flux of more than 18, more preferably 25 to 540, even more preferably 36 to 290 m³(STP)/m² bar h, at a feed pressure of 2.07kPa and a temperature of 298 K, as measured prior to application of the curable polymer thereto.

Examples of commercially available materials possessing an air flux of more than 18 m³(STP)/m² bar h include: GMT-L-6, GMT-L-10 and GMT-NC-5 ultrafiltration polyacrylonitrile membranes from GMT Membrantechnik GmbH, Germany; OMEGA ultrafiltration (300kD) polyethersulfone membrane from Pall; PAN200 ultrafiltration polyacrylonitrile membrane from Sepro; MP005 microfiltration polyethersulfone membrane from Microdyn-Nadir; and UV150T ultrafiltration PVDF membrane from Microdyn-Nadir. The support is not limited to sheet form, as supports in tubular form like hollow fibers can also be used.

Removal of any solvent from the composition is preferably performed before any re-rolling the support with the membrane thereon, although it may also be done at a later stage.

Preferably the pre-polymer may be prepared by a process comprising the polymerisation of a composition comprising monomers (i) and (ii):

(i) a monomer comprising an ethylenically unsaturated group and a poly(ethylene oxide) group and being free from reactive groups A capable of reacting with reactive group B; and

(ii) a monomer comprising an ethylenically unsaturated group and a reactive group A which is capable of reacting with reactive group B.

This polymerisation process for making the pre-polymer may be performed using any polymerisation technique, for example polymerisation may be induced thermally or using light.

Inducing polymerisation using light may be performed in an analogous manner to the conditions described above (e.g. using an inert liquid medium, photo-initiators, synergists and irradiation conditions as discussed above)

Thermally induced polymerisation is preferred for preparation of the pre- polymer, typically by a process comprising heating of the composition comprising monomers (i) and (ii) with a thermally reactive free radical initiator.

Preferred thermally reactive free radical initiators include organic peroxides (e.g. ethyl peroxide and benzyl peroxide); hydroperoxides (e.g. methyl hydroperoxide); acyloins (e.g. benzoin); certain azo compounds (e.g. [alpha], [alpha]'-azobisisobutyronitrile and [gamma], [gamma]'-azobis([gamma]- cyanovaleric acid); peroxyesters (e.g. methyl peracetate and tert- butyl peracetate); peroxalates (e.g. dimethyl peroxalate and di(tert-butyl) peroxalate); disulfide (e.g. dimethyl thiuram disulfide); and ketone peroxides (e.g. methyl ethyl ketone peroxide); inorganic peroxides (e.g. hydrogen peroxide); persulphates (e.g. potassium persulphate, ammonium persulphate and sodium persulphate); redox initiators (e.g. redox systems derived from a peroxide and a transition metal ion or complex).

Additionally, the polymerisation can be performed by a controlled polymerization technique, e.g. atom transfer radical polymerization, nitroxide- mediated polymerization or reversible addition fragmentation chain transfer polymerization.

The process for preparing the pre-polymer is preferably performed at a temperature in the range of from 30 to 150°C, more preferably 40 to 90°C.

Typically the composition comprises an inert liquid medium. Examples of suitable liquid media include water, organic solvents and mixtures thereof. Organic solvents include esters (e.g. ethylacetate, butyl acetate and di-methyl carbonate), ethers (e.g. tetrahydrofuran and 1 ,4-dioxane), aromatic solvents (e.g. benzene and toluene) and alcohols (e.g. methanol and ethanol).

Preferably monomer (i) is terminated at one end by a Ci_-4-alkoxy group and at another end by a (meth)acrylate or (meth)acrylamide group. Monomer (i) preferably comprises a poly(ethylene oxide) group.

Monomer (ii) preferably is terminated at one end by a hydroxyl, thiol or amino group and at another end by a (meth)acrylate or (meth)acrylamide group. Monomer (ii) preferably comprises a poly(ethylene oxide) group.

Examples of specific compounds suitable for use as monomer (i) include CD550 (methoxy polyethylene glycol (350) monomethacrylate), CD552 (methoxy polyethylene glycol (550) monomethacrylate), CD553 (methoxy polyethylene glycol (550) monoacrylate), AM-130G (methoxy poly(ethylene glycol) mono acrylate having an approximate MWT of 600), AM-230G (methoxy poly(ethylene glycol) mono acrylate having an approximate MWT of 1000), methoxy poly(ethylene glycol) acrylate 350, methoxy poly(ethylene glycol) acrylate 500, methoxy poly(ethylene glycol) acrylate 1 K and methoxy poly(ethylene glycol) acrylate 2K. The methacrylate analogues of the foregoing acrylates may also be used.

Examples of specific compounds suitable for use as monomer (ii) include SR604 (polypropylene glycol monomethacrylate), AE-400 (poly(ethylene glycol) mono acrylate of average molecular weight 468), poly(ethylene glycol) acrylate 1 K, poly(ethylene glycol) acrylate 2K, poly(ethylene glycol) acrylate 5K, poly(ethylene glycol) acrylate 10K, poly(ethylene glycol) acrylate 20K and poly(ethylene glycol) acrylate 30K polypropylene glycol monomethacrylate (e.g. SR-604 from Sartomer). The methacrylate analogues of the foregoing acrylates may also be used.

In general, the preferred pre-polymers comprise copolymerization of a composition wherein all of the polymerisable components therein have one (and only one) ethylenically unsaturated group. Preferably all of the polymerisable components of the composition comprise a plurality of ethylene oxide units, e.g. at least two, preferably at least three. Higher functional monomers may be used but usually in low amounts (e.g. less than 5wt%) to prevent a too high crosslink density.

In one embodiment, monomer (i) and monomer (ii) each independently are of Formula I:

Formula I

wherein:

Ri is H or methyl;

R₂ is H or methyl whereby at least 90% of the R2 groups in the monomer is H and up to 10% of the R2 groups in the monomer is methyl;

R3 is C1-4 alkoxy or C-6-12 aryloxy for monomer (i) and hydroxyl, amine, carboxyl or thiol for monomer (ii); and

n is 1 to 100.

Preferably all of the R2 groups in the monomer are H. Preferably n is 1 to 22. For monomer (i), n is more preferably 8 to 18. For monomer (ii), n is more preferably 3 to 100. The value of n quoted above is an average value.

The compound having an ethylenically unsaturated group and a reactive group B preferably has one (and only one) ethylenically unsaturated group. The reactive group B is preferably an electrophilic group. Optionally the compound is preferably provided in the form of a solution in an inert solvent. Step (III) is preferably performed in the absence of free radicals. This preference arises because free radicals are not necessary for the covalent bond formation. Free radicals may also cause premature polymerization leading to crosslinking and/or formation of homopolymer of the compound B, therefore Step (III) is preferably performed in the absence of free radical initiators (e.g. photo-initiators).

Heating and/or basification and/or the addition of a catalyst may be used as triggers for causing reactive groups A and B to react together thereby forming a covalent bond between the said pre-polymer side chains and the compound to give the curable polymer having ethylenically unsaturated groups. The preferred reaction temperatures for the covalent bond formation depend on the type of reaction applied.

Preferably step (III) is performed under anhydrous conditions.

Preferably one of A and B is a nucleophilic group and the other is an electrophilic group capable of reacting with the nucleophilic group to form a covalent bond between the pre-polymer side chains and the compound. A is preferably the nucleophilic group.

The amounts of pre-polymer and compound having an ethylenically unsaturated group and a reactive group B are preferably selected such that the number of moles of reactive group A and B are approximately equal or the number of moles of reactive group B are in excess. For example, the molar ratio of pre- polymer to compound having an ethylenically unsaturated group and a reactive group B is preferably from 0.3:1 to 1 .2:1 , preferably 0.5:1 to 1 .1 :1 , especially 0.7:1 to 1 :1 .

Typically the nucleophilic group comprises an electron rich group, for example a group containing a negative charge or a lone pair of electrons.

Groups containing a negative charge preferably comprise a sulphur anion (i.e. -S-), oxygen anion (i.e. -O-) or a nitrogen or carbon anion (i.e. a nitrogen or carbon atom having a negative charge), especially -S- which works particularly well, provided that the group containing a negative charge is capable of forming a covalent bond between the pre-polymer and compound, e.g. when the two are reacted together.

Groups containing a lone pair of electrons preferably comprise an -NH-, - NH₂, -N=, -S-, -SH, =S, -PR2 (wherein each R independently is alkyl or alkoxy, especially -C i_-4-alkyl or -O-Ci_-4-alkyl) or -OH group or a combination thereof, (for example -NHNH₂, -NHOH, -N=N=N or -CO-NHOH), preferably a combination which contains at least or -SH group (for example C=S, a thiourea, -CS- OH, -CO-SH, -NH-CS-NH-IMH2, -NH-CO-SH, -CS-NH₂, -NH-CS-OH, -PS(-OH)₂ or -O-PS(-OH)₂) provided that the group containing a lone pair of electrons is capable of forming a covalent bond with the electrophilic group e.g. when reacted.

When the group comprising a lone pair of electrons comprises an amine (-NH2 group) it is preferred that the -NH₂ group is directly attached to an alkyl group to give an aminoalkyl group. Preferred aminoalkyl groups are or comprise a group of the formula -CH(CH₃)NH₂, -C(CH₃)₂-NH₂, CH₂-NH₂ and homologues thereof.

The most preferred nucleophilic group is a hydroxyl group.

The electrophilic group may be any group capable of reacting with the nucleophilic group to form a covalent bond between the pre-polymer side chains and the compound, e.g. when the two are reacted together. Preferably said electrophilic group is a group capable of undergoing 1 ) a substitution reaction, 2) an addition reaction or 3) an addition- elimination reaction with the aforementioned nucleophilic group.

Groups which are capable of undergoing a substitution reaction preferably comprise a carbon or sulphur atom having an electron withdrawing displaceable atom or group attached thereto, for example in the case of carbon a halide, sulpho, quaternary ammonium or a mesylate, tosylate or acetate group and in the case of sulphur or oxygen an acyl group or -SO3^" group.

As examples of groups which are capable of undergoing a substitution reaction there may be mentioned halides, anhydrides of acids and heterocyclic compounds which contain at least one or preferably 2 or 3 nitrogen atoms in the heterocyclic ring and a substituent which is sufficiently labile to be removed by nucleophilic substitution by the nucleophilic group.

Preferred groups capable of undergoing a substitution reaction include groups of the formula -CO-X¹, -COCH2-X¹, -COCHR⁴CH₂-X¹,

-COCHX¹CHX¹CO₂R⁵, -COCHX¹CHX¹COR⁴, -CH₂-X¹ and -NHCOCH2-X¹ wherein:

X¹ is a labile group;

R⁴ is H or a labile group; and

R⁵ is H or optionally substituted alkyl, aryl or heteroaryl.

A labile group is a group displaceable by the aforementioned nucleophilic group. Preferred labile groups are halides (especially chloro, bromo or iodo), mesylate and tosylate.

When R⁴ is a labile group it is preferably halide, especially chloro or bromo.

R⁵ is preferably H, phenyl or Ci_-4-alkyl, especially methyl or ethyl.

Groups which are capable of undergoing an addition reaction preferably comprise an epoxide group, an aziridine, aziridinium, azetidine, azide, cyclopropane group or isocyanate group, more preferably, an activated alkene (e.g. alkenyl sulphone) or alkyne capable of undergoing a Michael -type addition with the aforementioned nucleophilic group.

The meaning of terms such as nucleophilic, electrophilic, substitution, addition, elimination and Michael-type addition are clear to organic chemists of ordinary skill and are commonly used in standard chemical textbooks, for example "Advanced Organic Chemistry", Fourth Edition by Jerry March, in particular pages 742 and 767 thereof.

Reactive group A is preferably a nucleophilic group, especially a hydroxyl, thiol or amino group, more especially a hydroxyl group. Reactive group B is preferably an electrophilic group capable of undergoing a substitution reaction, an addition reaction or an addition-elimination reaction with a nucleophilic group, more preferably an electrophilic group capable of undergoing a substitution reaction with a nucleophilic group.

It is especially preferred that reactive group A is a hydroxyl group and reactive group B is an acyl halide group.

In a particularly preferred embodiment the compound is a (meth)acryloyl compound having a labile atom or group (e.g. a halo or labile ester group) and this is condensed with nucleophilic groups present in the pre-polymer defined above (e.g. hydroxyl groups present on a side chain comprising a poly(ethylene oxide) group). Such a condensation is preferably performed in the presence of base, e.g. pyridine or triethylamine. Preferably the number of moles of base used is greater than the number of moles of the compound having an ethylenically unsaturated group and a reactive group B, e.g. 1 .05 to 2 moles of base per mole of compound having an ethylenically unsaturated group and a reactive group B.

As examples of compounds having an ethylenically unsaturated group and an electrophilic group capable of reacting with a nucleophilic group in side chain (b) there may be mentioned (meth)acryloyl halide, e.g. acryloyl chloride, acryloyl bromide, methacryloyl chloride and methacryloyl bromide; cinnamoyl halide; crotonoyl halide; and other unsaturated halides and 2-isocyanato-ethyl (meth)acrylate.

A further feature of the present invention provides a membrane comprising a cured curable polymer according to the invention.

A still further feature of the present invention provides a gas separation cartridge comprising a membrane according to the present invention. The membrane geometry influences the manner in which the membrane is packaged. The preferred cartridge geometries is in spiral-wound, plate-and-frame or envelope form.

The present invention also provides a gas separation module for separating a feed gas containing a target gas into a gas stream rich in the target gas and a gas stream depleted in the target gas, the module comprising a housing and a cartridge as described above.

The present invention will be illustrated in more detail by the following non- limiting examples. Unless stated otherwise, all given ratios and amounts are based on weight.

Tables 1 and 2 describe the ingredients used in the Examples. Table 1

^* EO chain length was determined by combined liquid chromatography and mass spectroscopy (Waters Acquity UPLC equipped with Waters QTOF premier mass spectroscopy detector; sample concentration 1 mg/L in methanol). The EO content (wt%) stated in the examples below was calculated using these chain lengths.

Table 2 : other ingredients

GMT-L-10 support is a ultra-filtration poly(acrylonitrile) membrane from GMT Membrantechnik GmbH. Water used in the Examples was demineralised. All other raw materials and organic solvents were used without purification. Monomers were mostly used as received without removal of inhibitor. Examples 1 to 17 and Comparative Example

Step (i) - Preparing Pre-Polvmer 1 ("PP1 ")

AM130G (a monomer comprising an ethylenically unsaturated group, a poly(ethylene oxide) group and a terminal methoxy group, 340g), AE400 (a monomer comprising an ethylenically unsaturated group and a nudeophilic hydroxyl group, 24.18g) and water (1278g) were charged into a 2 litre round bottom flask equipped with a condenser, nitrogen in- and outlet and stirrer. The mixture was heated at 80°C under a blanket of nitrogen gas. A solution of VAZO56 (0.193g) dissolved in water (10cm³) was purged with nitrogen for 30 minutes before this solution was added to the flask. The mixture was stirred at 80°C for 6 hours, maintaining the blanket of nitrogen gas, following which polymerization was essentially complete and an aqueous polymer was obtained. The WAMW of the resultant pre-polymer 1 was measured as described below.

Measurement of polymer weight average molecular weight (WAMW) by Gel Permeation Chromatography:

The pre-polymer (1 g) and water (250 cm³) were mixed at room temperature and then stored for 1 hour at 80°C. After cooling to room temperature, the solution was passed through a 0.45 μιτι filter. The filtrate (20 μΙ_) was injected into gel permeation chromatography equipment (Waters 2690 instrument equipped with Waters 2410 Rl detector and ShodexSB-8O6MHQOhpak column at 30°C) and eluted with an aqueous solution of 0.1 mol/L NaCI at a flow rate of 0.5 ml/min.

For calculating the WAMW of the pre-polymer based on the Rl trace, a first order calibration curve was used. This calibration curve was prepared using polyethylene glycol) calibration samples (1 .9, 20.36, 82.25, 167.7, 300.4 and 791 .5 kDaltons) using the same gel permeation equipment and conditions.

The pre-polymer 1 was found to have a WAMW of 351 .5 kDaltons.

Step (i) - Preparing Pre-Polymers 2 to 17 and Comparative Pre-polymer 1

The method used for pre-polymer 1 was repeated except that the modifications described in Table 3 below were made to give pre-polymers PP2 to PP17 and comparative pre-polymer CPP1 . The WAMW of the resultant pre- polymers is shown in the right hand column. Table 3

Example Modification relative to Example 1 WAMW

(KDa)

2 AM130G (50g), AE400 (3.9g) and water (249.6g) were 150.1 charged into a 500cm³ round bottom flask equipped with a condenser, nitrogen in- and outlet and stirrer. The mixture was heated at 80°C under a blanket of nitrogen gas. A solution of VAZO56 (3g) in water (100cm³) was purged with nitrogen for 30 minutes beforel cm³ of this solution was added to the flask. The mixture was kept at 80°C for 6 hours, maintaining the blanket of nitrogen gas, following which polymerization was essentially complete. The resultant pre-polymer was called PP2.

3 The amounts of ingredients were changed as follows: 182.4

AM130G (1830.2g), AE400 (130.3g), VAZO56 (2.21 g in

10cm³ of water), water (5518.5 g). The flask was a 10 litre jacketed flask. The resultant pre-polymer was called PP3.

4 Instead of 80°C, temperatures of 65°C were used. The 659 resultant pre-polymer was called PP4.

5 Instead of 80°C, temperatures of 65°C were used. 1608

Furthermore, in place of 249.6g of water there was used

174g of water. The resultant pre-polymer was called PP5.

6 CD552 (42.1 g) and PEG-MA 409529 (3.2g) were used in 2983 place of AM130G and AE400 and 600g of water was used in place of 249.6g. 1 cm³ of VAZO56 solution (0.45g in 10cm³ of water) was used as initiator. Instead of 80°C, temperatures of 75°C were used. The resultant pre-polymer was called PP6.

7 Instead of a 500ml flask, there was used a 200 litre reaction 530 vessel. The amount of each ingredient was changed as follows: AM130G (12.35Kg), AE400 (878.2g) in 46.77Kg of water. VAZO56 (7.0g in 100cm³ of water) was used as initiator. The reaction temperature was 65°C. The resultant pre-polymer was called PP7. Instead of a 500ml flask, there was used a 1 litre flask. The 502 amount of each ingredient was changed as follows: AM130G (49.5g), AE400 (15.3g) in 434.2g of water. 1 cm3 of VAZO56 solution (0.731 g in 10cm3 of water) was used as initiator. The reaction temperature was 65°C. The resultant pre- polymer was called PP8.

Instead of a 500ml flask, there was used a 1 litre flask. The 368 amount of each ingredient was changed as follows: AM130G (29.0g), AE400 (20.34g) in 429.2g of water. 1 cm³ of VAZO56 solution (0.598g in 10cm³ of water) was used as initiator. The reaction temperature was 65°C. The resultant pre- polymer was called PP9.

Instead of AM130G and AE400 in 249.6g of water there was 326 used CD553 (50.0g) and SA X93422 (0.32g) in 248.6g of water; 1 cm³ of VAZO56 solution (0.630g in 10cm³ of water) was used as initiator. Mol ratio (b):(a) was 0.010. The resultant pre-polymer was called PP10.

The same as Example 10 except that 1 .06g of SA X93422 345 were used. Mol ratio (b):(a) was 0.033. The resultant pre- polymer was called PP1 1 .

The same as Example 10 except that 2.03g of SA X93422 350 were used. Mol ratio (b):(a) was 0.063. The resultant pre- polymer was called PP12.

The same as Example 10 except that 3.18g of SA X93422 360 were used. Mol ratio (b):(a) was 0.1 . The resultant pre- polymer was called PP13.

Instead of the mixture described in Example 1 , the flask was 378 charged with ethyl acetate (189.28g), AM30G (50.01 g) and AE400 (10.52g). 1 cm³ of VAZO67 solution (1 .0184g in 25cm³ of ethyl acetate) was used as initiator. The mixture was heated under reflux, with stirring, for 20 hours under a blanket of nitrogen. The formed polymer was precipitated by pouring the reaction mixture into n-heptane. Repeated solution in ethyl acetate followed by precipitation with n- heptane gave the polymer substantially free from unreacted monomers. The resultant pre-polymer was called PP14. 15 Instead of the mixture described in Example 1 , the flask was 477 charged with water (244.42g), mPEG-MA 447943 (40.05g) and HEA (1 .00g) before heating to 80°C under nitrogen.

2cm³ of VAZO56 solution (1 .57g in 25cm³ of water) was used as initiator and the heating at 80°C was maintained for

5.5 hours. The resultant pre-polymer was called PP15.

16 Instead of the mixture described in Example 2, the flask was 1046 charged with water (290.28g), mPEG-MA 447943 (30.05g) and PEG-MA 409529 (3.37g) before heating to 80OC under nitrogen. 10cm³ of VAZO56 solution (0.4684g in 100cm3 of water) was used as initiator and the heating at 80°C was maintained for 5.25 hours. The resultant pre-polymer was called PP16.

17 Instead of he mixture described in Example 2, the flask was 360 charged with water (50.0g), AM230G (50.0g) and SA X93422 (3.37g) before heating to 80°C under nitrogen.

1 cm³ of VAZO56 solution (0.185g in 10cm³ of water) was used as initiator and the heating at 80°C was maintained for

6 hours. The resultant pre-polymer was called PP17.

CPP1 The amount of each ingredient was changed as follows: 531

AM130G (60g), AE400 (Og) in 209.9g of water. 1 cm³ of VAZO56 solution (0.613 in 10cm³ of water) was used as initiator. The reaction temperature was 65°C. To clarify, the reaction mixture contained no AE400 and therefore the polymer had no nucleophilic groups. The resultant pre- polymer was called CPP1 .

Step (iii) - Preparing Curable Polymers CP1 to CP17

Pre-polymers PP1 to PP17 (as described in Table 3 above) were converted into curable polymers CP1 to CP17 by reaction with acryloyi chloride using the following general method:

Water was evaporated from the pre-polymer under vacuum (<50 mbar at 75°C) until the solids content was about 90 wt%. Ethyl acetate (808g) was added and the resultant azeotrope was removed under vacuum (200 mbar at 65°C) to again give a solids content of about 90wt%. The mixture was then diluted with ethyl acetate to give a solids content of about 20 wt%. The water content was then further lowered to about 0.01 wt% by the addition of 3 angstrom molecular sieves. After removing the molecular sieves by filtration, triethylamine (10.40g) was added, followed by slow addition of acryloyi chloride (i.e. a compound having an ethylenically unsaturated group and one electrophilic group, 6.99g) over 10 minutes. The amount of triethylamine was about 1 .33 times the molar amount of acryloyi chloride and the amount of acryloyi chloride was about 1 .2 times the combined molar content of hydroxyl from the AE400 and the trace amount of remaining water. The mixture was kept at room temperature for 2 hours after which excess acryloyi chloride was destroyed by the addition of water (1 cm³). The resultant mixture was centrifuged to remove the formed triethylamine salts. Water (1458g) and n-heptane (1458g) were then added. The resultant two-phase mixture was mixed vigorously for 15 minutes and then allowed to phase separate. The aqueous phase was collected and 4-methoxyphenol (0.364g) was added.

The resultant mixtures had a curable polymer content of 20 wt%.

The WAMW of the curable polymers was measured by the method described above and are shown in tables 4 to 6 below.

Membrane Preparation

A composition was prepared by mixing each of the curable polymers CP1 to CP6 and CP10 to CP17 (142.5g, 20wt% solids content), water (369.36g), HDMAP (1 .14g) and Zonyl™ FSN100 solution (57g of a 3wt% solution of Zonyl™ FSN100 in water) in the dark for 15 minutes at 35°C.

The composition was applied to a porous support using a manufacturing unit consisting of (i) a curable composition application station containing a slide bead coater having 2 slots; (ii) an irradiation source; (iii) a drying means; and (iv) a composite membrane collecting station. The porous support was moved at a speed of 30 m/min from the application station to the irradiation source and then on to the composite membrane collecting station via a drying means. Water and the composition were each applied to the porous support (GMT-L-10 support) using respectively the lower and upper slots of a slide bead coater. The function of the water applied through the lower slot was to limit the extent to which the composition containing the curable polymer permeated into the porous support. The water was applied in an amount of 80 cm³/m² and the composition was applied in an amount of 18.182 cm³/m² (equivalent to a dry, cured coating weight of about 1 .0 g/m²). Curing of the curable polymer was achieved by UV-irradiation using a Light Hammer LH6 from Fusion UV Systems fitted with a D-bulb working at 100% intensity. Then the coated support proceeded further to the drying zone having a temperature of 40 C and 8% relative humidity and the resultant composite membrane was collected at the composite membrane collecting station. The curable polymers CP7 to CP9 were applied to a support (porous poly(acrylonitrile) GMT-L-10) using a slide coater and the resultant coated curable polymer was cured using UV light using the general procedure described above. The polymer CPP1 was coated on the support without curing and dried. The dry coating weight of the membranes after curing was 1 .0 g/m².

Measuring the CO? Gas Flux and CO?/CH₄ Selectivity of the Composite Membranes Derived from CP1 to CP6 and CP10 to CP13

A sample of each composite membrane was set into a Millipore membrane cell with a diameter of 47 mm. A feed gas consisting of a 20:80 or 50:50 mixture by volume of CO2 and CH was applied to one side of each composite membrane each membrane at a feed pressure of 1000kPa. The flow rate of gas permeating through the other side of the membrane (Js) was measured using a digital flow meter. The gas permeating through the composite membrane was analyzed by gas chromatography to determine the ratio of CO2 CH .

The flux of each gas i of each composite membrane (Qs,) in m³(STP)/m² bar h at a feed pressure of 1000 kPa and a temperature of 298 K was then determined by the following calculation: OS, = Js x X_Pi /(A x (p_f x X_fi - Pp x X_pi)) wherein:

Js is the flow rate of permeate gas in m³/s;

Xpi is the volume fraction of each gas i in the permeate gas as determined by gas chromatography;

A is the membrane area in m²;

Pf is the feed pressure in bar;

Xfi is the volume fraction of each gas i in the feed gas; and

PP is the permeate pressure in bar.

STP means referred data is defined under standard temperature and pressure (i.e. 25°C and 1 atmosphere pressure).

The CO2 CH selectivity a was then determined by the following calculation:

O.C02/CH4 = QSC02 / QScH4

The CH gas flux of each composite membrane was determined in an identical way.

Selectivity a CO2 CH was calculated based on the following equation a CO2 CH₄ = gas fluxco2/gas fluxes- The selectivity and flux (measured with mixed gas of composition 80:20 CH₄/CO₂) of each membrane derived from CP1 to CP6 and CP10 to CP13 is shown in Table 4 below:

Table 4

EO content means wt% ethylene oxide of the curable polymer.

Mole ratio refers to the number of moles (b) divided by the total number of moles of (a) in the curable polymer.

The properties of the resultant membranes derived from CP7 to CP9 and CPP1 , including the selectivity and flux (measured with mixed gas of composition 50:50 CH CO₂) are shown in Table 5 below.

Table 5

Membrane Curable Polymer Used Selectivity CO2 flux

(curable Mole ratio EO content WAMW (kDa) a CO₂/CH₄ (m³(STP)/ m² bar h) polymer) (b):(a) (w/w%)

7 (CP7) 0.091 85.0 534 15.2 0.75

8 (CP8) 0.4 83.3 516 14.5 0.71

9 (CP9) 0.91 81 .6 387 14.1 0.56

CM1 (CPP1 ) 0 85.6 531 14.9 0.67 The comparative membrane (CM1 ) derived from CPP1 had low resistance to water and organic solvents.

Further membranes derived from the CP14 to CP17 were prepared from ethyl acetate solutions as follows.

Under exclusion of light mixtures were prepared containing one of the curable polymers (40 parts) Zonyl FSN (0.09 parts) and HDMAP (0.4 parts) and the balance to 100 parts made up of ethyl acetate. The mixtures were sonicated in the dark for about 10 minutes to remove bubbles, coated on a glass plate using a bar coater (Spiral wound K Bar from R K Print Coat Instruments Ltd.), and cured by exposure to UV light three times using a Light-Hammer™ fitted in a bench-top conveyor LC6E (both supplied by Fusion UV Systems) with 100% UV power (D- bulb) and a conveyer speed of 15 m/min. The resultant membranes were removed from the glass plate and dried at 40°C for 24 hours. The resultant membranes derived from CP14 to CP17 had a thickness of approximately 0.10 ± 0.04 mm.

Evaluation of the gas permeability

Flux of CO2 and CH through membranes derived from CP14 to CP17 was measured at 35°C and a gas feed pressure of 2000 kPa (20 bar) using a gas permeation cell from Millipore with a measurement diameter of 42 mm. Permeability P in m³(STP)-m/m²-bar-h was calculated using the following equation:

P = F x L /( A x p) wherein:

F is gas flow in cm³ per hour under STP conditions;

L is the membrane thickness in micrometers;

A is the membrane area in m² (0.001385 m²); and

p is the feed gas pressure in bar.

The permeability P in m³(STP).m/m² bar h was multiplied by 3.70x10⁸ to provide permeability in barrer units. Selectivity a CO2 CH was calculated based on following equation a CO2 CH₄ = PCO2 PCH4

The properties of the resultant membranes are shown in Table 6 below. Table 6

Membrane Curable Polymer Used Gas separation

(curable Monomer Monomer Mole ratio EO WAM

polymer) (i) (ϋ) (b):(a) w/w% W Pc02 Selectivity

(kDa) (barrer) a CO₂/CH₄

14 (CPU) AM30G AE400 0.1 63.8 381 142 22

15 (CP15) m- HEA 0.1 77.5 485 241 15.3

PEGMA

16 (CP16) m- PEGMA 0.1 79.3 1058 298 16.4

PEGMA

17 (CP17) AM230G SA 0.1 90.7 362 306 16.2

X93422

Claims

1 . A process for preparing a curable polymer comprising the steps:

(I) providing a pre-polymer comprising a backbone and, pendant thereon, side chains (a) comprising a poly(ethylene oxide) group and side chains (b) comprising a reactive group A which is capable of reacting with reactive group B mentioned in (II) below, wherein said side chains are free from ethylenically unsaturated groups;

(II) providing a compound having an ethylenically unsaturated group and a reactive group B; and

(III) reacting said reactive groups A and B together thereby forming a covalent bond between the said pre-polymer side chains (b) and the compound to give the curable polymer and wherein the curable polymer has an ethylene oxide content of at least 50wt%.

2. A process according to claim 1 wherein one of A and B is a nudeophilic group and the other is an electrophilic group capable of reacting with the nudeophilic group to form a covalent bond between the pre-polymer side chains (b) and the compound.

3. A process according to claim 2 wherein the nudeophilic group comprises a sulphur, oxygen or nitrogen atom.

4. A process according claim 2 or 3 wherein the electrophilic group is a group capable of undergoing 1 ) a substitution reaction, 2) an addition reaction or 3) an addition-elimination reaction with the nudeophilic group.

5. A process according to any one of the preceding claims wherein the mole ratio of side chains (b):(a) is from 0.001 to 0.95 and/or the curable polymer has a weight average molecular weight of from 105,000 to 10 million Daltons.

6. A process according to any one of the preceding claims wherein the compound having an ethylenically unsaturated group and a reactive group B is (meth)acryloyl halide, cinnamoyl halide, crotonoyl halide or 2-isocyanato-ethyl (meth)acrylate.

7. A process according to any one of the preceding claims wherein the reactive group A comprises a hydroxyl, thiol or amino group.

8. A process according to any one of the preceding claims which is performed in the presence of a base.

9. A process according to any one of the preceding claims which is performed at a temperature of 30 to 150°C.

10. A process according to any one of the preceding claims wherein the molar ratio of pre-polymer and compound having an ethylenically unsaturated group and a reactive group B is from 0.3:1 and 1 .2:1 .

1 1 . A process according to any one of the preceding claims wherein the side chains (a) comprise at least eight ethylene oxide units.

12. A process according to any one of the preceding claims wherein at least 80 mole% of the side chains comprise a poly(ethylene oxide) group.

13. A process for preparing a membrane comprising performing the process of according to any one of claims 1 to 12 to give a curable polymer and then curing the curable polymer.

14. A process according to claim 13 wherein the curable polymer is cured by irradiation.

15. A process according to claim 13 or 14 wherein the curable polymer is cured on a porous support.

16. A membrane obtained by a process according to any one of claims 13 to 15.