WO2012042238A1 - Curable polymers and their uses - Google Patents

Abstract

A curable polymer having an ethylene oxide content above 50wt% comprising a backbone and, pendant thereon, the following side chains (a) and (b): (a)side chains which comprise a poly(ethylene oxide) group and are free from ethylenically unsaturated groups; and (b)side chains which comprise an ethylenically unsaturated group; wherein the mole ratio of side chains (b):(a) is from 0.001 to 0.95.

Description

CURABLE POLYMERS AND THEIR USES

This invention relates to curable polymers and to their preparation and uses, e.g. for making membranes suitable 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.

We have found that certain curable polymers having a ratio of certain side chains of from 0.001 to 0.95 can be used to make membranes having good selectivity and flux.

According to the present invention there is provided a curable polymer having an ethylene oxide content above 50wt% comprising a backbone and, pendant thereon, the following side chains (a) and (b):

(a) side chains which comprise a poly(ethylene oxide) group and are free from ethylenically unsaturated groups; and

(b) side chains which comprise an ethylenically unsaturated group;

wherein the mole ratio of side chains (b):(a) is from 0.001 to 0.95. 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".

Preferably the curable polymer is UV curable. Preferably 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 curable polymer is free from fluorine. Preferably the curable polymer has one (and only one) backbone.

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

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

The curable 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 curable 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 curable polymer is preferred because this can enhance the permeability of membranes formed therefrom to polar gases such as carbon dioxide and hydrogen sulphide.

The poly(ethylene oxide) groups in the curable 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 the curable polymer and 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. In one embodiment, the curable polymer is obtained entirely from the copolymerisation of compounds having one (i.e. only one) ethylenically unsaturated group.

Preferably side chains (a) are terminated by Ci_-4-alkoxy groups and side chains (b) are terminated by ethylenically unsaturated groups, for example (meth)acryl groups or other unsaturated acyl groups, e.g. cinnamoyl groups.

Preferably side chains (a) comprise, on average, at least eight ethylene oxide groups.

Preferably side chain (b) further comprises a poly(ethylene oxide) group. Preferably side chain (b) comprises one (and only one) ethylenically unsaturated group.

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 ethylenically unsaturated 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 100 mole% 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 is substantially free from the monomers used to produce it.

The mole ratio of side chains (b):(a) is preferably from 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 0.1 and 0.2. 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 cured polymers can be tuned to the desired value.

The curable polymers of this 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 of the present invention 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 of the invention comprising the cured polymer have a remarkably high flux in combination with a good selectivity.

The crosslink density of membranes obtained from curing the curable polymer may be further influenced by the presence of monomers having two or more ethylenically unsaturated groups. Such monomers may be copolymerized with the curable polymer and/or they may be included in the formulation used to prepare a pre-polymer from which the curable polymer has been obtained, although the latter is not preferred. Generally speaking, as the amount of monomers having two or more ethylenically unsaturated groups is increased so will the crosslink density. High crosslink density improves durability for resultant membranes, although this may be at the expense of flux rate. On the other hand, lower crosslink density will improve flux rate, but this may be at the expense of membrane durability, e.g. under mechanical stress, in the presence of solvents or under humid conditions. Membranes of the present invention obtained from the curable polymers are often durable even under humid conditions, providing an advantage that dehumidification of gas streams is often not needed.

When the curable polymer has a weight average molecular weight above the molecular weight cut-off value of the porous support, penetration of the curable polymer into the pores of a porous support may be prevented or reduced, resulting in a composite membrane wherein the cured polymer forms a thin layer on top of the porous support and/or only partly within the pores of the support. Preferably the cured polymer forms a non-porous thin layer. This has the advantage of reducing defects which might otherwise reduce selectivity of the resultant composite membrane.

A further advantage of the presently claimed curable polymers having an ethylene oxide content above 50wt% is that their water-solubility is often very good, reducing or removing the need to use organic solvents when the curable polymers are used for the manufacture of membranes. Reducing or avoiding organic solvents is advantageous for environmental, safety and health reasons.

A second feature of the present invention provides a membrane comprising a cured polymer according to the first aspect of the present invention. The membrane may be prepared by curing the curable polymer of the first aspect of the present invention, e.g. using radiation, for example UV light, or by a thermal method.

Preferably the curing is performed by a process comprising application of the composition to a support, e.g. to form a thin layer thereon, and curing the curable polymer to provide the membrane. In this way a membrane may be produced at low cost and at a high production rate (high application/coating speeds). 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 non-porous membrane and porous support preferably are in contact to provide a composite membrane. After application of the composition to the support it may partly or even totally penetrate the porous support to achieve a good adhesion. 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.

For a membrane to be effective as a separation membrane the size of the pores should in general be smaller than the dimensions of at least one of the chemicals to be separated. Preferably the membranes of the present invention are substantially non-porous.

A suitable method to determine the pore size is observation by scanning electron microscope (SEM). Substantially non-porous means that no pores are detected by SEM (using a Jeol JSM-6335F Field Emission SEM, applying an accelerating voltage of 2 kV, working distance 4 mm, aperture 4, sample coated with Pt with a thickness of 1 .5 nm, magnification 100 000 x, 3° tilted view).

Preferably the membrane has an average pore size of below 10 nm, more preferably below 5 nm, especially below 2 nm, e.g. below 0.5 nm. The maximum preferred pore size depends on the application e.g. on the chemicals to be separated.

Another method to obtain an indication of the actual porosity is the permeance to liquids such as water. Preferably the permeance of the membrane to liquids is very low, i.e. the average pore size of the membrane is such that the pure water permeance at 20°C is less than 6x10^"8 m³/m² s kPa, more preferably less than 3x10^"8 m³/m² s kPa.

In the case of a composite membrane the porous support preferably has an average pore size of 5 to 50nm, more preferably 10 to 40nm, especially of 15 to 30nm, e.g. about 20nm. For pore sizes in the range of 10 to 25nm the curable polymer preferably has a weight average molecular weight of 105 to 1000kDa. However, for pore sizes in the range of 18 to 40nm the curable polymer preferably has a weight average molecular weight of 200 to 3000kDa.

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.

If desired, monomers comprising ethylenically unsaturated groups may be mixed with the curable polymer before curing in order to modify the properties of the resultant membrane. Examples of other monomers comprising ethylenically unsaturated groups include e.g. alkyl (meth)acrylates that can be included to modify the (a)polar character of the curable polymer and glycidyl (meth)acrylate and/or allyl (meth)acrylate that can be included to modify the crosslink density of polymers obtained from curing the curable polymer.

In one embodiment the curable polymer is cured in the presence of a crosslinking agent comprising two or more ethylenically unsaturated groups. Examples of such crosslinking agents include aliphatic diol di(meth)acrylates (e.g. 1 ,4-butanediol diacrylate, 1 ,6-hexanediol diacrylate, hydroxypivalic acid neopentylglycol diacrylate, neopentylglycol diacrylate and/or tricyclodecannedimethanol diacrylate), trimethylolpropane triacrylate, glyceryl triacrylate, pentaerythitol triacrylate, pentaerythitol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate and/or divinylbenzene. In general the dry thickness of the membrane of this invention when used without a porous support may typically be between 20 μιτι and 300 μιτι, more preferably between 30 and 200 μιτι. When joined to a support to give a composite membrane, thinner membranes can be used because the support provides mechanical strength and the optimal thickness is then based on the desired permeability and the ability to provide a uniform, defect-free membrane. In the case of composite membranes, the membrane derived from the curable polymer preferably has a dry thickness of 0.05 to about 20 μιτι, more preferably 0.05 to 10 μιτι. Even more preferably the dry thickness of composite membranes according to the present invention is less than 4μηη, especially less than 2μηη, e.g. about 1 μηη, most preferably less than 1 μηη, e.g. of 0.05 to Ο.δμιτι. The flux of gases and vapors is directly related to the thickness of the membrane layer derived from the curable polymer, so a layer as thin as possible is preferred. On the other hand the layer should be uniform without defects such as pinholes that would reduce its selectivity.

Preferably 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.

According to a third aspect of the present invention there is provided a process for preparing a membrane comprising curing a curable polymer according to the first aspect of the present invention. This process preferably comprises the following steps:

(i) providing a composition comprising the curable polymer according to the first aspect of the present invention;

(ii) applying the composition to a support;

(iii) curing said composition thereby forming a membrane comprising a cured polymer;

(iv) optionally washing and/or drying the membrane; and

(v) optionally removing the membrane from the support.

The cured polymer is preferably used as a gas separation membrane.

When the cured polymer is not removed from the support it is preferred that the support is porous and, as a result, a composite membrane is formed. The support itself may comprise more than one layer, e.g. an ultrafiltration membrane comprising a woven or nonwoven and a polymeric layer.

The composition referred to in step (i) generally comprises the curable polymer according to the first aspect of the present invention and preferably an inert liquid medium and optionally a photoinitiator. An inert liquid medium is a medium that does not react with the curable polymer during step (iii).

The curable polymer preferably has good solubility in the inert liquid medium. The main function of the inert liquid medium is to provide the curable polymer in a dilute, low viscosity form which can easily be applied to a support at high speed. Suitable inert liquid media include organic solvents, water and combinations thereof. For reasons of safety, health and the environment, as well as from economic viewpoint, the inert liquid medium preferably comprises water as the only or predominant solvent.

The inert liquid medium therefore preferably comprises water and optionally one or more organic solvents, especially water-miscible organic solvent(s). As examples of organic solvents there may be mentioned: Ci-6-alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n- pentanol, cyclopentanol and cyclohexanol; linear amides, preferably dimethylformamide or dimethylacetamide; ketones and ketone-alcohols, preferably acetone, methyl ether ketone, cyclohexanone and diacetone alcohol; ethers, preferably tetrahydrofuran and dioxane; diols, preferably diols having from 2 to 12 carbon atoms, for example pentane-1 ,5-diol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferably diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol; triols, preferably glycerol and 1 ,2,6-hexanetriol; mono-Ci_-4-alkyl ethers of diols, preferably mono-Ci_-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-[2-(2- ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether; cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, caprolactam and 1 ,3-dimethylimidazolidone; cyclic esters, preferably caprolactone; sulphoxides, preferably dimethyl sulphoxide and sulpholane.

When an organic solvent is used in the composition, the solvent is preferably chosen so that a stable and homogeneous solution is formed which does not phase separate upon curing of the curable polymer.

Free radical initiators, e.g. photo-initiators, may be included in the composition. Photo-initiators are usually required when the curable polymer 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).

Curing rates may be increased by adding amine synergists to the composition. The amount of amine synergists is preferably from 0.1 -10 wt.% based on the weight of curable polymer in the composition, more preferably from 0.3-3 wt.% based on the weight of curable polymer in the composition. Examples of suitable amine synergists are disclosed in WO2008/143515, page 18, lines 8 to

16, which are incorporated herein by reference thereto.

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.

Where desired, a surfactant or combination of surfactants may be included in the composition as a wetting agent or to adjust surface tension. Examples of suitable surfactants are disclosed in WO2008/143515, page 18, line 22 to page 20, line 13, which are incorporated herein by reference thereto.

Optional further additives may be included in the composition, for example as disclosed in WO2008/143515, page 21 , line 4 to page 22, line 4, which are incorporated herein by reference thereto.

The above-mentioned additives (photo-initiators, amine synergists, surfactants, chain transfer agents, plasticizers, conventional additives) may be added in a range of preferably from 0 to 10 weight% based on the weight of the curable polymer. Any of the components mentioned above may be employed alone or in combination with each other. They may be added after being solubilised in water, dispersed, polymer-dispersed, emulsified or may be converted into oil droplets.

In view of the foregoing, the composition (which forms a further feature of the present invention) used to form the membrane preferably comprises:

(a) 1 to 60 parts of the curable polymer according to the first aspect of the present invention;

(b) 0 to 2 parts photo-initiator;

(c) 40 to 99 parts inert liquid medium; and

(d) 0 to 3 parts surfactant;

wherein all parts are by weight.

Component (a) is preferably present in an amount of 2 to 50 parts, more preferably 4 to 35 parts.

Component (b) is preferably present in an amount of 0.001 to 1 parts, more preferably 0.01 to 0.8 parts.

Component (c) is preferably present in an amount of 50 to 98 parts, more preferably 65 to 96 parts.

Component (d) is preferably present in an amount of 0 to 2 parts, more preferably 0 to 1 parts.

The application mentioned in step (ii) preferably comprises 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 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 the viscosity of the composition used to form the membrane is 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 of solvent, preferably water, 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.

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.

The curable composition can be made on a continuous basis or it can be made on a large batch basis. The composition may be applied continuously onto the upstream end of the driven continuous belt or web support using a composition application station, the polymerization effecting means (such as an irradiation source) being located above the belt or web downstream of a composition application station. A membrane removal station is optionally included further downstream of the belt in order to remove the membrane from the belt in the form of a lengthy sheet.

Removal of any water or solvent from the membrane can be accomplished either before or after the membrane is removed from the belt.

When it is desired to remove the membrane from the support, it is, of course, preferable that the support be such as to facilitate as much as possible the removal of the membrane therefrom. Typical of the supports useful for the practice of such embodiments have a low surface energy and are smooth, stainless steel sheet or, better still, Teflon™ or Teflon™-coated metal sheet.

Instead of using a continuous belt, the support can be of an expendable material, such as release paper, resin coated paper, plastic film, or the like (but not soluble in the solvent when present), in the form of a roll thereof such that it can be continuously unrolled from the roll, upstream of the composition application station, as a continuous driven length and then re-rolled, with the membrane thereon, downstream of the polymerization effecting means (e.g. irradiation source).

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 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, polyetherimide, polyamide, polyamideimide, polyacrylonitrile, polycarbonate, polyacrylate, cellulose acetate, polypropylene and/or poly(4-methyl 1 -pentene).

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.

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 membranes (and composite membranes) of the present invention may be used for separating gases by contacting a mixture of gases with the membrane, allowing at least one of the gases to pass through the membrane to give a permeate gas and a retentate gas, wherein the retentate gas is deficient in the gas which passed through the membrane and the permeate gas is enriched in the gas which passed through the membrane, and collecting the permeate and/or retentate gas.

Since gases often comprise water vapour and/or organic solvents the membrane is preferably resistant to water and organic solvents. Therefore the main component of the membrane is preferably a cured polymer according to the first aspect of the present invention.

While we have emphasised the usefulness of the membranes and composite membranes of the present invention for separating gases (especially mixtures comprising polar gas and non-polar gas) it will be understood that the membranes may also be used for other purposes. The curable polymers may be prepared by a process 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 and the compound to give the curable polymer wherein the curable polymer has an ethylene oxide content of at least 50wt%.

Preferably the pre-polymer may be prepared by a process comprising the polymerisation of a composition comprising monomer (ii) and optionally monomer

(i):

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

(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 herein for curing the curable polymer (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 monomer (ii) and optionally monomer (i) 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.

The composition used to prepare the pre-polymer preferably comprises both monomers (i) and (ii) such that the resultant pre-polymer comprises a backbone and, pendant thereon, the following side chains (a) and (b):

(a) side chains which comprise poly(ethylene oxide) groups and are free from reactive groups A which are capable of reacting with reactive group B; and

(b) side chains which comprise a reactive group A capable of reacting with reactive group B;

wherein side chains (a) and (b) are free from ethylenically unsaturated groups and the mole ratio of side chains (b):(a) is 0.001 to 0.95.

Furthermore, the composition is preferably free from monomers comprising two or more ethylenically unsaturated groups because this ensures that the side chains in the resultant pre-polymer are free from ethylenically unsaturated groups and that uncontrolled crosslinking during formation of the pre-polymer is prevented.

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. The hydroxyl, thiol or amino group may subsequently be used as the site for reacting the pre- polymer with, for example, a (meth)acryloyl halide or other unsaturated acyl halide

(e.g. cinnamoyl- or crotonyl halide), or an isocyanate compound (e.g. 2- isocyanatoethyl (meth)acrylate), to provide the side chains (b) in the curable polymer. 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 F¾ 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 values of n quoted above are average values.

Preferably the resultant pre-polymer has a weight average molecular weight of at least 105,000, especially the weight average molecular weight preferences described earlier in this specification for the curable polymer. In general the preferences mentioned earlier in this specification in relation to the curable polymer apply mutatis mutandis to the present processes for preparing the pre- polymer.

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.

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 monomer comprising reactive group B. Step (III) is therefore 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. The preferred reaction temperatures for the covalent bond formation depend on the type of reaction applied.

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.

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 one =S or -SH group (for example C=S, a thiourea, -CS- OH, -CO-SH, -NH-CS-NH-NH2, -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 nudeophilic group.

The meaning of terms such as nudeophilic, 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 nudeophilic 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 elimination and addition reaction with a nudeophilic group, more preferably an electrophilic group capable of undergoing a substitution reaction with a nudeophilic 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 nudeophilic groups present 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.

As examples of compounds having an ethylenically unsaturated group and an electrophilic group capable of reacting with a nudeophilic 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.

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

Chemical Chemical name Supplier name/No.

VAZO56 2,2'-azobis (2-methylpropionamidine) Dupont, VAZO™56 WSP dihydrochloride

VAZO67 2,2'-Azobis(2-methylbutyronitrile) Dupont, VAZO™67

HDMAP 1 -hydroxy-2-methyl-1 -phenylpropanone Cytec, Additol™ HDMAP

Zonyl™ FSN100 Ethoxylated fluorosurfactant Dupont

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.

Example 1 - Preparation of a Curable Polymer

Preparation of the Pre-Polymer for example 1 :

AM130G (340g), AE400 (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 a pre-polymer solution was obtained. The WAMW of the pre-polymer was measured as described below. Measurement of Pre-Polymer weight average molecular weight (WAMW) by Gel Permeation Chromatography:

The pre-polymer solution (1g) 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 for example 1 was found to have a WAMW of 351 .5 kDaltons.

Preparation of the Curable Polymer

Water was evaporated from the aqueous pre-polymer described above 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 dry ethyl acetate to give a solids content of about 20wt%. The water content was then further lowered to about 0.01wt% 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 (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 mixture had a curable polymer content of 20 wt% and contained 4-methoxyphenol as polymerization inhibitor (200 mg/kg). The WAMW of the curable polymer was measured by an analogous method as described above and was found to have a WAMW of 356.2kDaltons.

Preparation of a Membrane from the Curable Polymer of Example 1 :

A composition was prepared by mixing the curable polymer mixture described above (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) for 15 minutes at 35°C in the dark.

The composition was applied to a porous support using a manufacturing unit containing (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 pure water permeance of the resultant composite membrane was 4.8x10^"3 m³/m² bar h.

Example 2

AM130G (50g), AE400 (3.9g) and water (249.6g) were 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 before 1 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 pre-polymer was converted to a curable polymer by reaction with acryloyl chloride using an analogous method to that described in Example 1 . The WAMW of the resultant curable polymer was measured as described in Example 1 and was found to be 151 .OkDa.

Examples 3 to 6

The method of Example 2 was repeated except that the modifications mentioned in Table 3 below were made:

Table 3

Preparation of Composite Membranes with curable polymer compositions 2-6

Membranes were prepared using the curable polymers obtained in Examples 2 to 6 using the general method described above for Example 1 .

Measuring the CO? Gas Flux and CO?/CH₄ Selectivity of the Composite Membranes

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 at a feed pressure of 10OOkPa. 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 at a temperature of 298 K was then determined by the following calculation:

OS, = Js x Xpi /(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 CH CO2) of each membrane is shown in Table 4 below:

Table 4

EO content means wt% ethylene oxide.

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

N.A. means not applicable.

Examples 7 to 9 and Comparative Examples CE1 and CE2 - Varying Mole ratio mm

Curable Polymers were prepared by the method of Example 2 except that the modifications mentioned in Table 5 below were made: Table 5

Each curable polymer 7 to 9 and CE2 was 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 in Examples 1 -6. The polymer CE1 was coated on the support without curing and dried. The dry coating weight of the curable polymers after curing was 1 .0 g/m². The properties of the resultant membranes, including the selectivity and flux (measured with mixed gas of composition 50:50 CH CO₂) are shown in Table 6 below. Table 6

Comparative example CE1 had very low resistance to water and organic solvents, while the other examples had a good durability in streams containing water and/or organic solvents.

Examples 10 to 13

Curable Polymers were prepared by the method of Example 2 except that the modifications mentioned in the Table 7 below were made:

Table 7

The properties of the resultant membranes including the selectivity and flux (measured with mixed gas of composition 80:20 CH CO₂) are shown in Table 8 below. Table 8

Examples 14 to 17 and Comparative Example CE3 to CE5

Curable Polymers were prepared by the method of Example 2 except that the modifications mentioned in the Table 9 below were made:

Table 9

Example Modification to Example 2

14 Instead of the mixture described in Example 2, the flask was 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 20hr under a blanket of nitrogen. The prepolymer was precipitated by the pouring the reaction mixture into n-heptane. Repeated solution in ethyl acetate followed by precipitation with n-heptane gave the pre-polymer substantially free from unreacted monomers. The prepolymer was then converted to a curable polymer by reaction with acryloyl chloride in an analogous manner to Example 2.

15 Instead of the mixture described in Example 2, the flask was 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 prepolymer was then converted to a curable polymer by reaction with acryloyl chloride in an analogous manner to Example 2.

16 Instead of the mixture described in Example 2, the flask was charged with water (290.28g), mPEG-MA 447943 (30.05g) and PEG-MA 409529 (3.37g) before heating to 80°C 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. Example Modification to Example 2

The prepolymer was then converted to a curable polymer by reaction with acryloyl chloride in an analogous manner to Example 2.

17 Instead of the mixture described in Example 2, the flask was 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 prepolymer was then converted to a curable polymer by reaction with acryloyl chloride in an analogous manner to Example 2.

CE3 (EO Instead of the mixture described in Example 2, the flask was content charged with butyl acetate (109.28g), MOEA (25.23g) and HEA too low) (2.28g). 1 cm³ of VAZO67 solution (1 .035g in 50cm³ of butyl acetate) was used as initiator. The mixture was heated under reflux, with stirring, for 20 hours under a blanket of nitrogen. The prepolymer purification and conversion to a curable polymer by reaction with acryloyl chloride were performed in an analogous manner to Example 14.

CE4 (EO Instead of the mixture described in Example 2, the flask was content charged with ethyl acetate (126.17g), MOEA (14.63g), AM30G too low) (25.03g) and HEA (2.61 g). 1 cm³ of VAZO67 solution (0.7021 g 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 prepolymer purification and conversion to a curable polymer by reaction with acryloyl chloride were performed in an analogous manner to Example 14

Comparative Example CE5 consisted of the ingredient: poly(ethylene glycol) 600 diacrylate from Sigma Aldrich.

Preparation of the membranes:

Further membranes derived from the curable polymers of Examples 14 to 17 and Comparative Example CE3 to CE4 were prepared from ethyl acetate solutions as follows.

Mixtures were prepared under exclusion of light consisting of 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 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 membrane was removed from the glass plate and dried at 40°C for 24 hours. The resultant membranes had a thickness of approximately 0.10 ± 0.04 mm.

A further mixture was prepared consisting the curable monomer from Comparative Example CE5 (50 parts), Zonyl™ FSN (0.09 parts), HDMAP (0.5 parts) and water (49.4 parts). This mixture was applied to a glass plate at 200 micrometer wet coating thickness, cured according the procedure mentioned above for Examples 14 to 17 and the properties of the resultant membrane were evaluated as described below. The thickness of the membrane was approximately 0.15 ± 0.03 mm.

Evaluation of the gas permeability

Flux of CO₂ and CH through the membranes derived from the curable polymers of Examples 14 to 17 and CE3 to CE5 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 m³ 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.

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

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

The properties of the resultant membranes are shown in Table 1 1 below. Table 1 1

Monomer(s) (i) Monomer Mole EO Gas separation

(ϋ) ratio w/w Pc02 Selectivity

(b):(a) % (barrer) a CO₂/CH₄

14 AM30G AE400 0.1 63.8 142 22

15 m-PEGMA HEA 0.1 77.5 241 15.3

16 m-PEGMA PEGMA 0.1 79.3 298 16.4

17 AM230G SA X93422 0.1 90.7 306 16.2

CE3 MOEA HEA 0.1 32.2 16 23

CE4 MOEA and AM30G HEA 0.1 49.7 105 22

CE5 PEGDA - 0 82.5 125 19

Claims

1 . A curable polymer having an ethylene oxide content above 50wt% comprising a backbone and, pendant thereon, the following side chains (a) and (b):

(a) side chains which comprise a poly(ethylene oxide) group and are free from ethylenically unsaturated groups; and

(b) side chains which comprise an ethylenically unsaturated group;

wherein the mole ratio of side chains (b):(a) is from 0.001 to 0.95.

2. A polymer according to claim 1 having a weight average molecular weight above 105,000.

3. A polymer according to any one of the preceding claims having a weight average molecular weight above 150,000.

4. A polymer according to any one of the preceding claims having a weight average molecular weight below 10 million.

5. A polymer according to any one of the preceding claims wherein the poly(ethylene oxide) groups comprise up to 22 consecutive ethylene oxide repeat units.

6. A polymer according to any one of the preceding claims wherein the side chains (a) comprise at least 3 ethylene oxide units.

7. A polymer according to any one of the preceding claims wherein the side chains (a) are terminated by Ci_-4-alkoxy groups and side chains (b) are terminated by (meth)acryl groups.

8. A polymer according to any one of the preceding claims wherein the backbone is substantially free from pendant side chains other than side chains (a) and (b).

9. A polymer according to any one of the preceding claims wherein the polymer has an ethylene oxide content above 70wt%.

10. A polymer according to any one of the preceding claims wherein the side chains (a) comprise on average at least 8 ethylene oxide units.

1 1 . A process for preparing a membrane comprising curing a polymer according to any one of claims 1 to 10.

12. A process according to claim 1 1 comprising the following steps:

(i) providing a composition comprising a polymer according to any one of claims 1 to 10;

(ii) applying the composition to a support;

(iii) polymerizing said composition thereby forming a cured polymer;

(iv) optionally washing and/or drying the polymer film; and

(v) optionally removing the polymer film from the support.

13. A process according to claim 12 wherein the composition is applied to the support at a coating speed of at least 5 m/min.

14. A process according to any one of claims 10 to 13 which is performed on a continuous basis using a moving support.

15. A process according to one of claims 10 to 14 wherein the curing is performed by exposing the polymer to radiation for less than 3 seconds.

16. A membrane comprising a cured polymer according to any one of claims 1 to 10.

17. A composite membrane comprising a porous support and a non-porous membrane according to claim 16 in contact with the porous support.

18. A gas separation cartridge comprising a membrane according to claim 16 or 17.

19. A gas separation cartridge according to claim 18 wherein the cartridge is in spiral-wound, plate-and-frame or envelope form.

20. 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 according to claim 18 or 19.

21 . Use of a membrane according to claim 16 or 17 for the separation a mixture comprising polar gas or vapour and non-polar gas or vapour.