Gas separation membrane and manufacturing method therefor

Abstract

This gas separation membrane comprises a polymer having an alkylene oxide unit, wherein: the alkylene oxide unit includes a branched alkylene oxide unit having at least 3 carbon atoms; and the content ratio of the branched alkylene oxide unit having at least 3 carbon atoms in said gas separation membrane is at least 20 mol% in 100 mol% of the alkylene oxide unit in said gas separation membrane.

Description

Gas separation membrane and method for manufacturing the same

[0001] The present invention relates to a gas separation membrane and a method for producing the same.

[0002] Towards achieving net-zero carbon emissions by 2050, the development of methods for selectively separating and recovering carbon dioxide from gas mixtures is attracting attention. Known methods for selectively separating and recovering carbon dioxide from gas mixtures include, for example, chemical absorption and membrane separation. Among these, membrane separation, which requires less energy to selectively separate carbon dioxide, is attracting particular attention. This membrane separation method uses a gas separation membrane and utilizes a pressure difference to separate and recover carbon dioxide from a gas mixture.

[0003] The performance of the gas separation membrane used in membrane separation methods greatly affects the carbon dioxide separation efficiency.

[0004] Conventionally, gas separation membranes used in membrane separation methods include, for example, gas separation membranes made of polymers of unsaturated carboxylic acid esters having two double bonds or their prepolymers (see, for example, Patent Document 1), and weight-average molecular weight 10 obtained by polymerizing oxirane compounds. ４ ~10 ７ Gas separation membranes made of polyether polymers (see, for example, Patent Document 2) are being considered.

[0005] Japanese Patent Publication No. 08-24603 Japanese Patent Publication No. 2003-205224

[0006] However, the gas separation membrane described in Patent Document 1 had the problem of having a low carbon dioxide permeability coefficient. Furthermore, the gas separation membrane described in Patent Document 2 did not necessarily have low hygroscopicity, and had the problem of its membrane performance deteriorating easily when in contact with moisture.

[0007] This invention has been made in view of the above circumstances, and aims to provide a gas separation membrane with a high carbon dioxide permeability coefficient and low hygroscopicity, and a method for manufacturing the same.

[0008] The present inventors conducted diligent studies to solve the above problems and, as a result, found that the above problems can be solved when a gas separation membrane containing a polymer having alkylene oxide units contains branched alkylene oxide units with 3 or more carbon atoms in a predetermined proportion, thus completing the present invention. Although the detailed mechanism by which the permeability coefficient of carbon dioxide increases when the gas separation membrane contains a predetermined polymer is unknown, it is presumed that packing of the polymer is suppressed due to steric hindrance by alkyl groups (e.g., methyl groups) as branches in the branched alkylene oxide units contained in the polymer, thereby improving the amorphousness of the polymer. Furthermore, although the detailed mechanism by which the hygroscopicity decreases when the gas separation membrane contains a predetermined polymer is unknown, it is presumed that the hydrophobicity of the polymer is improved due to the presence of alkyl groups (e.g., methyl groups) as branches in the branched alkylene oxide units contained in the polymer.

[0009] The present invention is as follows: [1] A gas separation membrane comprising a polymer having alkylene oxide units, wherein the alkylene oxide units comprise branched alkylene oxide units having 3 or more carbon atoms, and the content ratio of the branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane is 20 mol% or more out of 100 mol% of the alkylene oxide units in the gas separation membrane. [2] The gas separation membrane according to [1] above, wherein the content ratio of the branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane is 80 mol% or more out of 100 mol% of the alkylene oxide units in the gas separation membrane. [3] The gas separation membrane according to [1] or [2] above, wherein the branched alkylene oxide units having 3 or more carbon atoms are propylene oxide units. [4] The gas separation membrane according to any one of [1] to [3] above, wherein the polymer has structural units derived from a monomer having a polyoxyalkylene chain and a (meth)acryloyl group. [5] The gas separation membrane according to any one of [1] to [4] above, wherein the content of the polymer is 50 to 100% by mass of 100% by mass of the gas separation membrane. [6] The gas separation membrane according to any one of [1] to [5] above, wherein when the gas separation membrane is left standing for 24 hours in an atmosphere of relative humidity of 82 to 83%, the amount of moisture absorbed by the gas separation membrane is 10% by mass or less. [7] The gas separation membrane according to any one of [1] to [6] above, wherein the enthalpy of fusion of the gas separation membrane is 80 J / g or less. [8] A method for producing a gas separation membrane, comprising preparing a gas separation membrane composition containing a monofunctional monomer having alkylene oxide units in the molecule and one (meth)acryloyl group in one molecule, and curing the prepared gas separation membrane composition to produce a gas separation membrane containing a polymer having the alkylene oxide units, wherein the alkylene oxide units include branched alkylene oxide units having 3 or more carbon atoms, and the content ratio of the branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane composition is 20 mol% or more out of 100 mol% of the alkylene oxide units in the gas separation membrane composition.

[0010] According to the present invention, a gas separation membrane with a high carbon dioxide permeability coefficient and low hygroscopicity, and a method for producing the same can be provided.

[0011] The present invention will now be described in detail. In this specification, preferred provisions can be adopted at will, and combinations of preferred provisions can be said to be more preferred. In this specification, the notation "XX to YY" means "XX or more and YY or less". In this specification, the lower and upper limits of preferred numerical ranges (for example, ranges of content, etc.) that are described in steps can be combined independently. For example, from the notation "preferably 10 to 90, more preferably 30 to 60", the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to get "10 to 60". Also, in numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with the values ​​shown in the examples. In this specification, "polymer having structural units derived from monomer X" means "polymer obtained by polymerizing monomer X as a raw material monomer (raw material oligomer)". In this specification, "alkylene oxide unit" means a structural unit derived from alkylene oxide that is present in the polymer or the raw material monomer (raw material oligomer) of the polymer. In this specification, “branched alkylene oxide” means an alkylene oxide having one or more alkyl groups as branches. In this specification, “(meth)acrylate” means encompassing both acrylate and methacrylate. “Acrylate” is a compound having one or more acryloyl groups in one molecule. “Methacrylate” is a compound having one or more methacryloyl groups in one molecule. In this specification, “(meth)acryloyl group” is used to mean encompassing both acryloyl group and methacryloyl group, and “(meth)acryloyloxy group” means encompassing both acryloyloxy group and methacryloyloxy group. In this disclosure and in this specification, “(meth)acrylic acid” means encompassing both acrylic acid and methacrylic acid, and “(meth)acrylamide” means encompassing both acrylamide and methacrylamide. In this specification, “number of functional groups” means the number of (meth)acryloyl groups and (meth)acryloyloxy groups in one molecule, unless otherwise specified.In this specification, "average number of functional groups" means the average number of (meth)acryloyl groups and (meth)acryloyloxy groups per molecule, where one unit is the number-average molecular weight obtained based on the chemical formula, unless otherwise specified. In this specification, "index" in the reaction between an isocyanate group-containing compound and a hydroxyl group-containing compound means the value obtained by dividing the number of moles of isocyanate groups in the isocyanate group-containing compound by the number of moles of hydroxyl groups in the hydroxyl group-containing compound and multiplying by 100. In this specification, the hydroxyl value of a hydroxyl group-containing compound is obtained by measurement in accordance with JIS K1557:2007. In this specification, "average number of hydroxyl groups" refers to the average number of active hydrogens per molecule, where one unit is the number-average molecular weight obtained based on the chemical formula of the initiator. In this specification, "light irradiation intensity" means the value (peak intensity) obtained by irradiating the light-receiving part with ultraviolet light for 10 seconds using an ultraviolet irradiometer (UIT-250, manufactured by Ushio Inc.). In this specification, "relative humidity" means the ratio of the amount of water vapor in the atmosphere to the amount of water vapor in the saturated water vapor at 1 atmosphere and 40°C.

[0012] [Gas Separation Membrane] The gas separation membrane of this embodiment (hereinafter sometimes simply referred to as "this embodiment") contains a polymer having alkylene oxide units (hereinafter sometimes simply referred to as "polymer"). The alkylene oxide units include branched alkylene oxide units having 3 or more carbon atoms. The content ratio of branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane is 20 mol% or more out of 100 mol% of alkylene oxide units in the gas separation membrane. With this configuration, a gas separation membrane with a high carbon dioxide permeability coefficient and low hygroscopicity can be obtained. That is, the gas separation membrane of this embodiment is not particularly limited as long as it contains at least the predetermined polymer, and may or may not contain other additives as needed.

[0013] As the content ratio of a branched alkylene oxide unit having 3 or more carbon atoms in the gas separation membrane, there is no particular limitation as long as it is 20 mol% or more in 100 mol% of the alkylene oxide units in the gas separation membrane. However, from the viewpoint of improving the permeability of carbon dioxide in the gas separation membrane, in 100 mol% of the alkylene oxide units in the gas separation membrane, it is preferably 40 mol% or more, more preferably 60 mol% or more, and particularly preferably 80 to 100 mol%. The content ratio of the branched alkylene oxide unit having 3 or more carbon atoms in the gas separation membrane can be determined by the measurement method described in the examples. In the examples of this specification, the content ratio of the branched alkylene oxide unit having 3 or more carbon atoms in the gas separation membrane is calculated based on the charging ratio when manufacturing the gas separation membrane. However, when the charging ratio when manufacturing the gas separation membrane is unknown, １ It can be calculated from the integration ratio of the H-NMR spectrum.

[0014] There is no particular limitation on the branched alkylene oxide unit having 3 or more carbon atoms in the gas separation membrane. For example, propylene oxide unit (-O-CH(CH ３ )-CH ２ -), 1,2-butylene oxide unit (-O-CH(CH ２ CH ３ )-CH ２ -), 2,3-epoxybutane unit (-O-CH(CH ３ )-CH(CH ３ )-), isobutylene oxide unit (-O-C(CH ３ ) ２ -CH ２ -), 1-hexene oxide unit (-O-CH(CH ２ CH ２ CH ２ CH ３ )-CH ２ -), 1-octene oxide unit (-O-CH(CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ )-CH ２Examples include (-O-CH(CH)). These may be used individually or in combination of two or more. Among these, propylene oxide units (-O-CH(CH)) are used, from the viewpoint of increasing the proportion of ether oxygen per unit weight and improving the permeability of the gas separation membrane to carbon dioxide. ３ ) - CH ２ -) is preferable.

[0015] When a gas separation membrane is left standing for 24 hours in an atmosphere of relative humidity 82-83%, there are no particular restrictions on the amount of moisture absorbed by the gas separation membrane, but it is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less. Within this range, even if the gas separation membrane comes into contact with moisture, swelling of the gas separation membrane is less likely to occur, and the formation of a water film on the contact surface and the elution of membrane components are less likely to occur, so the membrane performance is less likely to deteriorate easily. The amount of moisture absorbed by the gas separation membrane can be determined by the measurement method described in the examples.

[0016] There are no particular restrictions on the enthalpy of fusion of the gas separation membrane, but from the viewpoint of increasing the amorphous nature of the gas separation membrane and improving the permeability of carbon dioxide, it is preferably 80 J / g or less, more preferably 70 J / g or less, and particularly preferably 60 J / g or less. The enthalpy of fusion of the gas separation membrane can be determined by the measurement method described in the examples.

[0017] There are no particular restrictions on the thickness of the gas separation membrane, but it is preferably 0.1 to 100.0 μm, more preferably 0.1 to 50.0 μm, and most preferably 0.1 to 25.0 μm. If the thickness is above the lower limit of the above range, the mechanical strength and carbon dioxide separation selectivity tend to improve, and if it is below the upper limit of the above range, the gas permeability tends to improve. The thickness of the gas separation membrane can be determined by the measurement method described in the examples.

[0018] <Polymer> The polymer contained in the gas separation membrane of this embodiment has alkylene oxide units. The alkylene oxide units in the polymer include branched alkylene oxide units having 3 or more carbon atoms. The polymer preferably has structural units derived from monomers containing alkylene oxide units, for example, and structural units derived from monomers having a polyoxyalkylene chain and a (meth)acryloyl group. The polymer may have alkylene oxide units in the main chain, or in the side chains, or in both the main chain and the side chains. There are no particular restrictions on the content of branched alkylene oxide units having 3 or more carbon atoms in the polymer, but from the viewpoint of improving the carbon dioxide permeability of the gas separation membrane, it is preferably 40 mol% or more, more preferably 60 mol% or more, even more preferably 80 mol% or more, and particularly preferably 85 to 100 mol% of the alkylene oxide units in the polymer out of 100 mol%. The content of branched alkylene oxide units having 3 or more carbon atoms in the polymer can be determined by the same method as the method for determining the content of branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane, i.e., by the measurement method described in the examples. In the examples of this specification, the content of branched alkylene oxide units having 3 or more carbon atoms in the polymer is calculated using the charge ratio when manufacturing the gas separation membrane, but if the charge ratio when manufacturing the gas separation membrane is unknown, １It can be calculated from the integration ratio of the H-NMR spectrum. Furthermore, the content of branched alkylene oxide units having 3 or more carbon atoms in a polymer polymerized using two or more monomers as raw material monomers (for example, polymer (1) polymerized using monofunctional monomer (A) and monofunctional monomer (B), described later, as raw material monomers) can be calculated from the total mole percent of alkylene oxide units in the two or more monomers and the total mole percent of branched alkylene oxide units having 3 or more carbon atoms in the two or more monomers. In addition, if the gas separation membrane contains two or more polymers, the content of branched alkylene oxide units having 3 or more carbon atoms in the polymer can be calculated from the total mole percent of alkylene oxide units in the two or more polymers and the total mole percent of branched alkylene oxide units having 3 or more carbon atoms in the two or more polymers.

[0019] There are no particular restrictions on branched alkylene oxide units with three or more carbon atoms; for example, propylene oxide units (-O-CH(CH) ３ ) - CH ２ -), 1,2-butylene oxide unit (-O-CH(CH ２ CH ３ ) - CH ２ -), 2,3-epoxybutane units (-O-CH(CH ３ )-CH(CH ３ )-), isobutylene oxide unit (-O-C(CH ３ ) ２ -CH ２ -), 1-hexene oxide unit (-O-CH(CH ２ CH ２ CH ２ CH ３ ) - CH ２ -), 1-octenoxide unit (-O-CH(CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ) - CH ２Examples include (-O-CH(CH)). These may be used individually or in combination of two or more. Among these, propylene oxide units (-O-CH(CH)) are used, from the viewpoint of increasing the proportion of ether oxygen per unit weight and improving the permeability of the gas separation membrane to carbon dioxide. ３ ) - CH ２ -) is preferable.

[0020] There are no particular restrictions on the number-average molecular weight of the polymer, but it is preferably 10,000 to 1,000,000, more preferably 30,000 to 1,000,000, and most preferably 50,000 to 1,000,000. If it is above the lower limit of the above range, it is easier to obtain a membrane with sufficient mechanical strength as a gas separation membrane, and if it is below the upper limit of the above range, it is easier to process during molding. The number-average molecular weight of the polymer is the polystyrene-equivalent molecular weight determined by measuring it by gel permeation chromatography (GPC) based on a calibration curve created using a standard polystyrene sample.

[0021] There are no particular restrictions on the polymer content, but it is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and most preferably 70 to 100% by mass, of 100% by mass of the gas separation membrane. If the polymer content is above the lower limit of the above range, it is easier to obtain a membrane with high mechanical strength. １ It is determined by H-NMR.

[0022] There are no particular restrictions on the content of structural units derived from alkylene oxide unit-containing monomers (hereinafter sometimes simply referred to as "monomer (1)"), but it is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and particularly preferably 90 to 100% by mass, out of 100% by mass of all structural units in the polymer. If it is above the lower limit of the above range, gas permeability will be good, and if it is below the upper limit of the above range, it will be easier to manufacture. The content of structural units derived from alkylene oxide unit-containing monomers is １ It is determined by H-NMR.

[0023] There are no particular restrictions on monomer (1), but from the viewpoint of ease of manufacture, monomers having a polyoxyalkylene chain as an alkylene oxide unit and a (meth)acryloyl group are preferred. The content of branched alkylene oxide units having 3 or more carbon atoms in the polyoxyalkylene chain is adjusted in consideration of the content of branched alkylene oxide units having 3 or more carbon atoms in a polymer having structural units derived from the target monomer (1) (hereinafter sometimes simply referred to as "polymer (1)"). Therefore, when polymerizing two or more monomers (1) as raw material monomers to produce the target polymer (1), it is not necessary for any of the monomers (1) to have branched alkylene oxide units having 3 or more carbon atoms.

[0024] The raw material monomer for polymer (1) is not particularly limited as long as it contains monomer (1), and may or may not contain other monomers other than monomer (1), i.e., monomers that do not have alkylene oxide units. There are no particular limitations on the other monomers, but from the viewpoint of improving the film-forming properties and mechanical strength of the gas separation membrane, monomers that have a (meth)acryloyl group but do not have structural units derived from alkylene oxide (hereinafter sometimes simply referred to as "monomer (C)") are preferred.

[0025] There are no particular restrictions on the monomer (1) content, but from the viewpoint of improving the carbon dioxide permeability of the gas separation membrane, it is preferably 70 to 100 mol%, more preferably 80 to 100 mol%, and most preferably 90 to 100 mol%, of the monomer used as a raw material monomer for polymer (1) in 100 mol%.

[0026] When monomer (C) is included in the raw material monomer of polymer (1), there are no particular restrictions on the content of monomer (C). However, from the viewpoint of improving the film-forming properties and mechanical strength of the gas separation membrane, it is preferably 30 mol% or less, more preferably 20 mol% or less, and particularly preferably 10 mol% or less, of 100 mol% of the monomer used as the raw material monomer of polymer (1).

[0027] The monomer having a polyoxyalkylene chain and a (meth)acryloyl group is not particularly limited. It may be a monofunctional monomer having one (meth)acryloyl group in one monomer molecule (hereinafter also simply referred to as a monofunctional monomer), or a polyfunctional monomer having two or more (meth)acryloyl groups in one monomer molecule (hereinafter also simply referred to as a polyfunctional monomer). These may be used individually or in combination of two or more. Among these, monofunctional monomers are preferred.

[0028] There are no particular restrictions on the molar ratio (monofunctional monomer:polyfunctional monomer) of monofunctional monomer to polyfunctional monomer in monomer (1), but it is preferably 1:99 to 100:0, more preferably 10:90 to 100:0, and particularly preferably 20:80 to 100:0. If the molar ratio of monofunctional monomer is above the lower limit of the above range, the gas permeability of the gas separation membrane is improved, and if the molar ratio of monofunctional monomer is below the upper limit of the above range, the crack resistance of the gas separation membrane tends to be higher.

[0029] There are no particular limitations on the monofunctional monomer having a polyoxyalkylene chain and a (meth)acryloyl group. Examples include (i) a monomer having a polyoxyalkylene chain, a group having a urethane bond derived from an isocyanate group-containing compound, and a (meth)acryloyloxy group, wherein the monomer has one (meth)acryloyloxy group per molecule (hereinafter sometimes simply referred to as "monofunctional monomer (A)"), and (ii) a monomer having a polyoxyalkylene chain and a (meth)acryloyloxy group without a urethane bond derived from an isocyanate group-containing compound, wherein the monomer has one (meth)acryloyloxy group per molecule (hereinafter sometimes simply referred to as "monofunctional monomer (B)"). These may be used individually or in combination of two or more.

[0030] There are no particular restrictions on the content of monofunctional monomer (A), but from the viewpoint of ensuring excellent polymerizability, it is preferably 30 to 100 mol%, more preferably 40 to 100 mol%, and most preferably 50 to 100 mol%, of monomer (1) 100 mol%.

[0031] There are no particular restrictions on the content of monofunctional monomer (B), but from the viewpoint of improving the flexibility of the gas separation membrane, it is preferably 0 to 70 mol%, more preferably 0 to 60 mol%, and particularly preferably 0 to 50 mol% of monomer (1) in 100 mol%.

[0032] There are no particular restrictions on the total content of monofunctional monomer (A) and monofunctional monomer (B), but from the viewpoint of improving the carbon dioxide permeability of the gas separation membrane, it is preferably 80 to 100 mol%, more preferably 90 to 100 mol%, and particularly preferably 100 mol%, of monomer (1) 100 mol%.

[0033] There are no particular restrictions on the molar ratio of monofunctional monomer (A) to monofunctional monomer (B) in monomer (1), but it is preferably 30:70 to 100:0, more preferably 40:60 to 100:0, and particularly preferably 50:50 to 100:0. If the molar ratio of monofunctional monomers is above the lower limit of the above range, the polymerization reaction of the polymer proceeds more easily, and if the molar ratio of monofunctional monomer (A) is below the upper limit of the above range, it becomes easier to achieve both flexibility and strength in the gas separation membrane.

[0034] (Monofunctional monomer (A)) Monofunctional monomer (A) is a monomer having a polyoxyalkylene chain, a group having a urethane bond derived from an isocyanate group-containing compound, and a (meth)acryloyloxy group, wherein the monomer has one (meth)acryloyloxy group in one molecule. Monofunctional monomer (A) has the effect of giving gas separation membranes gas permeability and gas separation selectivity.

[0035] There are no particular restrictions on the urethane bond content in one molecule of monofunctional monomer (A), but it is preferably 0.17 to 59.00% by mass, more preferably 0.30 to 11.80% by mass, and particularly preferably 0.33 to 2.36% by mass, per 100% by mass of monofunctional monomer (A). If it is above the lower limit of the above range, the flexibility of the gas separation membrane tends to improve, and if it is below the upper limit of the above range, the polymerization reaction of the polymer proceeds more easily. The urethane bond content in one molecule of monofunctional monomer (A) can be calculated by assuming that the total amount of isocyanate groups in the isocyanate group-containing compound used in the production of monofunctional monomer (A) forms urethane bonds, and using the following formula: (Number of moles of isocyanate groups in the isocyanate group-containing compound × Molecular weight of urethane bond (59) / Mass of monofunctional monomer (A)) × 100 (%)

[0036] There are no particular restrictions on the number-average molecular weight of the monofunctional monomer (A), but it is preferably 200 to 35,000, more preferably 1,000 to 20,000, and most preferably 5,000 to 18,000. If it is above the lower limit of the above range, it becomes easier to form films, and if it is below the upper limit of the above range, it becomes easier to polymerize. The number-average molecular weight of the monofunctional monomer (A) can be determined by the measurement method described in the examples.

[0037] In the manufacturing process of monofunctional monomer (A), by-products containing polyoxyalkylene chains other than monofunctional monomer (A) may be produced. Examples of by-products containing polyoxyalkylene chains include compounds having two (meth)acryloyloxy groups, compounds without (meth)acryloyloxy groups, and compounds without urethane bonds. There are no particular restrictions on the purity of monofunctional monomer (A) in the product, but from the viewpoint of fully exhibiting the function of monofunctional monomer (A), it is preferably 80% by mass or more, more preferably 85 to 100% by mass, of 100% by mass of monofunctional monomer (A). The purity of monofunctional monomer (A) can be calculated by measuring the hydroxyl value of the polyoxyalkylene chain before and after the addition of (meth)acryloyloxy groups and determining the percentage of remaining hydroxyl groups.

[0038] When the product can be considered as a monofunctional monomer (A), the average number of functional groups obtained from the number-average molecular weight and the number of functional groups of the product can be considered as the average number of functional groups of the monofunctional monomer (A). In this case, there are no particular restrictions on the average number of functional groups in the product, but from the viewpoint of fully exhibiting the function of the monofunctional monomer (A), it is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. The average number of functional groups can be adjusted to this range by adjusting the amount of impurities contained in the raw materials for the production of the monofunctional monomer (A) or by adjusting the index described later. Furthermore, in this specification, the average number of functional groups can be calculated using the average number of functional groups of the raw materials and the index.

[0039] There are no particular restrictions on the monofunctional monomer (A), and examples include the reaction product (1), reaction product (2), reaction product (3), etc., as shown below. These may be used individually or in combination of two or more. Among these, it is preferable to include one or more selected from the group consisting of reaction product (1) and reaction product (2), with reaction product (1) being preferred, from the viewpoint of having a low by-product content and excellent curing efficiency when manufacturing gas separation membranes.

[0040] There are no particular restrictions on the total content of reaction product (1) and reaction product (2), but from the viewpoint of having a low by-product content and excellent curing efficiency when manufacturing gas separation membranes, it is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 100% by mass, of 100% by mass of monofunctional monomer (A). When monofunctional monomer (A) contains reaction product (1) and reaction product (2), there are no particular restrictions on their mass ratio, but from the viewpoint of ease of manufacture, it is preferable that reaction product (1):reaction product (2) = 1:0 to 1:1.

[0041] Reaction product (1) is an equimolar reaction product of a polyoxyalkylene monool and a compound having an isocyanate group and a (meth)acryloyloxy group. Reaction product (2) is an equimolar reaction product of a polyoxyalkylene monool, a diisocyanate, and a compound having a group that reacts with an isocyanate group and a (meth)acryloyloxy group. Reaction product (3) is an equimolar reaction product of a polyoxyalkylene polyol and a compound having an isocyanate group and a (meth)acryloyloxy group.

[0042] There are no particular restrictions on the compounds having an isocyanate group and a (meth)acryloyloxy group that are the raw materials for reaction product (1) and reaction product (3). However, from the viewpoint of availability, compounds having one isocyanate group and a (meth)acryloyloxy group are preferred, (meth)acrylates having an isocyanate group bonded to an aliphatic hydrocarbon group and an alicyclic hydrocarbon group are more preferred, and isocyanate alkyl (meth)acrylates are particularly preferred. Furthermore, there are no particular restrictions on the number of carbon atoms in the alkyl group excluding the isocyanate alkyl group of the isocyanate alkyl (meth)acrylate, but from the viewpoint of availability, it is preferably 8 or less, more preferably 4 or less. There are no particular restrictions on the compounds having an isocyanate group and a (meth)acryloyloxy group. Examples include 2-isocyanate ethyl (meth)acrylate and isocyanate methyl methacrylate. There are no particular restrictions on commercially available products. Examples include Karenz-AOI and Karenz-MOI (both manufactured by Resonac Co., Ltd.).

[0043] There are no particular restrictions on the diisocyanate used as the raw material for reaction product (2). Examples include non-yellowing modified aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and various modified forms of these diisocyanates (modified forms having two isocyanate groups). These may be used individually or in combination of two or more. Among these, aliphatic diisocyanates and alicyclic diisocyanates are preferred from the viewpoint of excellent light resistance, weather resistance, heat resistance, and the ability to maintain transparency. There are no particular restrictions on the non-yellowing modified aromatic diisocyanates. Examples include xylylene diisocyanate and tetramethylxylylene diisocyanate. There are no particular restrictions on the aliphatic diisocyanates. Examples include 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate. There are no particular restrictions on the alicyclic diisocyanates, and examples include isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,5-norbornane diisocyanate, and 2,6-norbornane diisocyanate.

[0044] There are no particular restrictions on the group that reacts with the isocyanate group in the compound having a group that reacts with the isocyanate group and a (meth)acryloyloxy group, which are the raw materials for reaction product (2). Examples include hydroxyl groups and amino groups having a nitrogen atom to which a hydrogen atom is bonded. There are no particular restrictions on the number of hydroxyl groups and the number of hydrogen atoms bonded to the nitrogen atom in the group that reacts with the isocyanate group, but from the viewpoint of uniformly adding the (meth)acryloyloxy group, it is preferably one. There are no particular restrictions on the group that reacts with the isocyanate group, but from the viewpoint of improving durability such as suppressing yellowing after film formation of the gas separation membrane, a hydroxyl group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group is preferred. There are no particular restrictions on the compound having a group that reacts with the isocyanate group and a (meth)acryloyloxy group, but from the viewpoint of availability, hydroxyalkyl (meth)acrylate and hydroxycycloalkyl (meth)acrylate are preferred, and hydroxyalkyl (meth)acrylate with 8 or fewer carbon atoms in the hydroxyalkyl group is more preferred. There are no particular limitations on specific examples of compounds having a group that reacts with an isocyanate group and a (meth)acryloyloxy group. Examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. There are no particular limitations on commercially available products. Examples include Light Ester HO-250 (N), Light Ester HOP (N), Light Ester HOA (N), Light Ester HOP-A (N), Light Ester HOB (N) (all are product names of Kyoei Chemical Co., Ltd.), and 4-HBA (product name of Osaka Organic Chemical Industry Co., Ltd.).

[0045] There are no particular restrictions on the average number of hydroxyl groups per molecule of polyoxyalkylene monool, which is the raw material for reaction product (1) and reaction product (2), but it is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. If it is above the lower limit of the above range, the unreacted components decrease and the strength of the gas separation membrane tends to improve, and if it is below the upper limit of the above range, a bifunctional crosslinking component is suitable and it is easier to achieve both the mechanical strength of the gas separation membrane and the gas permeability. There are no particular restrictions on the hydroxyl value of polyoxyalkylene monool, but from the viewpoint of setting a suitable range for the content of urethane bonds in one molecule of monofunctional monomer (A), it is preferably 1.5 to 740.0 mg KOH / g, more preferably 1.6 to 290.0 mg KOH / g, even more preferably 2.5 to 70.0 mg KOH / g, and particularly preferably 3.0 to 12.0 mg KOH / g.

[0046] There are no particular restrictions on the polyoxyalkylene monool, and examples include compounds obtained by ring-opening addition polymerization of an alkylene oxide to an initiator having an active hydrogen-containing group and having one or more active hydrogens, wherein the initiator residue has a polyoxyalkylene chain and hydroxyl groups corresponding to the number of active hydrogens in the initiator. There are no particular restrictions on the alkylene oxide that can be used as a raw material for polyoxyalkylene monool, and examples include ethylene oxide and branched alkylene oxides having three or more carbon atoms. These may be used individually or in combination of two or more. There are no particular restrictions on exemplary and preferred compounds of branched alkylene oxides having three or more carbon atoms that can be used as a raw material for polyoxyalkylene monool, and examples include propylene oxide, 1,2-butylene oxide, 2,3-epoxybutane, isobutylene oxide, 1-hexene oxide, and 1-octenoxide. These may be used individually or in combination of two or more. Among these, propylene oxide is preferred from the viewpoint that it ultimately plays a part in the branched alkylene oxides with 3 or more carbon atoms in the polymer contained in the gas separation membrane. There are no particular restrictions on the active hydrogen-containing group of the initiator, and examples include hydroxyl groups, carboxyl groups, and amino groups having one hydrogen atom bonded to a nitrogen atom. These may be used individually or in combination of two or more. Among these, hydroxyl groups and carboxyl groups are preferred from the viewpoint of controlling the reaction of the polymer. There are no particular restrictions on the hydroxyl group, but alcoholic hydroxyl groups are preferred from the viewpoint of ease of polymerization. There are no particular restrictions on the initiator having one active hydrogen atom, and examples include monohydric alcohols, monohydric phenols, monohydric carboxylic acids, and amine compounds having one hydrogen atom bonded to a nitrogen atom. These may be used individually or in combination of two or more. Among these, monohydric alcohols and monohydric carboxylic acids are preferred from the viewpoint of polarity when used as a gas separation membrane, and monohydric aliphatic alcohols and monohydric aliphatic carboxylic acids are more preferred. Furthermore, a polyoxyalkylene monool with a lower molecular weight than the target polyoxyalkylene monool can be used as an initiator.There are no particular restrictions on the number of carbon atoms in the monohydric aliphatic alcohol, but from the viewpoint of the flexibility of the gas separation membrane, it is preferably 1 to 20, more preferably 2 to 8. There are no particular restrictions on the number of carbon atoms in the monohydric aliphatic carboxylic acid, but from the viewpoint of the strength of the gas separation membrane, including the carbon atoms of the carboxyl group, it is preferably 2 to 20, more preferably 2 to 8.

[0047] There are no particular restrictions on the polyoxyalkylene chains in the polyoxyalkylene monool, but from the viewpoint of improving flexibility, it is preferable that they consist only of propylene oxide units, or a combination of propylene oxide units and other alkylene oxide units, more preferably that they consist only of propylene oxide units, or a combination of propylene oxide units and ethylene oxide units, and particularly preferably that they consist only of propylene oxide units. There are no particular restrictions on the content of propylene oxide units, but from the viewpoint of achieving both water resistance and flexibility, it is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, of the alkylene oxide units in 100% by mass of the polyoxyalkylene monool.

[0048] There are no particular restrictions on the method for producing low-hydroxyl value (i.e., high-molecular-weight) polyoxyalkylene monools. For example, low-hydroxyl value (i.e., high-molecular-weight) polyoxyalkylene monools can be produced by ring-opening addition polymerization of a branched alkylene oxide (especially propylene oxide) having 3 or more carbon atoms as an initiator in the presence of a complex metal cyanide catalyst. High-hydroxyl value polyoxyalkylene monools can be produced using an alkaline catalyst such as KOH.

[0049] In the production of polyoxyalkylene monools, the initiator and alkylene oxide introduced into the reaction system are usually low in moisture, having had water removed by methods such as degassing under reduced pressure. Generally, the moisture content of the initiator in the production of polyoxyalkylene monools is preferably low, preferably 500 ppm by mass or less, and more preferably 300 ppm by mass or less. When the moisture content is within this range, the amount of polyoxyalkylenediol produced from water is suppressed, which in turn suppresses the amount of by-products resulting from the polyoxyalkylenediol, making it easier to adjust the upper limit of the average number of hydroxyl groups in the resulting polyoxyalkylene monool to 1.2 or less. Furthermore, the moisture content of the polyoxyalkylene monools used as raw materials for reaction product (1) and reaction product (2) is preferably low, preferably 300 ppm by mass or less, more preferably 250 ppm by mass or less, and particularly preferably 50 to 200 ppm by mass relative to the polyoxyalkylene monool. When the moisture content is within the above range, the formation of by-products, which are reaction products of moisture and isocyanate group-containing compounds, is reduced, improving the stability of reaction product (1) and reaction product (2). Furthermore, it is easier to suppress changes in the appearance of the curable composition containing reaction product (1) and reaction product (2) over time, and the elastic modulus of the cured product tends to be good.

[0050] There are no particular restrictions on the polyoxyalkylene polyol used as the raw material for reaction product (3), but from the viewpoint of achieving both flexibility and strength of the gas separation membrane, it is preferably polyoxyalkylenediol. There are no particular restrictions on the average number of hydroxyl groups in one molecule of the polyoxyalkylene polyol, but from the viewpoint of increasing the mechanical strength of the gas separation membrane, it is preferably 1.6 to 2.0, more preferably 1.8 to 1.96. In other words, it is preferable that the polyoxyalkylene polyol used as the raw material for reaction product (3) is polyoxyalkylenediol. There are no particular restrictions on the content of branched alkylene oxide units having 3 or more carbon atoms in the polyoxyalkylene polyol, but from the viewpoint of suppressing crystallization of the gas separation membrane, it is preferably 80 to 100% by mass of alkylene oxide units per 100% by mass. The content of branched alkylene oxide units having 3 or more carbon atoms can be measured by the same method as for polymers. There are no particular restrictions on the branched alkylene oxide units having 3 or more carbon atoms in polyoxyalkylene polyols; for example, propylene oxide units (-O-CH(CH) ３ ) - CH ２ -), 1,2-butylene oxide unit (-O-CH(CH ２ CH ３ ) - CH ２ -), 2,3-epoxybutane units (-O-CH(CH ３ )-CH(CH ３ )-), isobutylene oxide unit (-O-C(CH ３ ) ２ -CH ２ -), 1-hexene oxide unit (-O-CH(CH ２ CH ２ CH ２ CH ３ ) - CH ２ -), 1-octenoxide unit (-O-CH(CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ) - CH ２Examples include (-O-CH(CH)). These may be used individually or in combination of two or more. Among these, propylene oxide units (-O-CH(CH)) are particularly noteworthy from the viewpoint of increasing the proportion of ether oxygen per unit weight. ３ ) - CH ２ -) is preferred. There are no particular restrictions on the hydroxyl value of the polyoxyalkylene polyol, but from the viewpoint of providing a suitable range for the content of urethane bonds in one molecule of monofunctional monomer (A), it is preferably 3.0 to 1810.0 mg KOH / g, and more preferably 5.5 to 131.0 mg KOH / g.

[0051] There are no particular restrictions on the method for producing polyoxyalkylene polyols. For example, polyoxyalkylene polyols can be produced by ring-opening addition polymerization of an alkylene oxide to an initiator having an active hydrogen-containing group and having two or more active hydrogens. The polyoxyalkylene polyol produced by the above method has hydroxyl groups corresponding to the number of active hydrogens in the initiator residue, the polyoxyalkylene chain, and the initiator. There are no particular restrictions on the initiator having two or more active hydrogens, but from the viewpoint of improving the strength of the gas separation membrane, compounds having two or more hydroxyl groups are preferred. There are no particular restrictions on the alkylene oxide used as a raw material for polyoxyalkylene polyols. Examples include ethylene oxide and branched alkylene oxides having three or more carbon atoms. These may be used individually or in combination of two or more. There are no particular restrictions on the branched alkylene oxides having 3 or more carbon atoms that can be used as raw materials for polyoxyalkylene polyols. Examples include propylene oxide, 1,2-butylene oxide, 2,3-epoxybutane, isobutylene oxide, 1-hexene oxide, and 1-octenoxide. These may be used individually or in combination of two or more. Among these, propylene oxide is preferred from the viewpoint that it ultimately contributes to a portion of the branched alkylene oxides having 3 or more carbon atoms in the polymer contained in the gas separation membrane. There are no particular restrictions on the active hydrogen-containing group of the initiator. Examples include hydroxyl groups, carboxyl groups, and amino groups having hydrogen atoms bonded to a nitrogen atom. Among these, hydroxyl groups are preferred from the viewpoint of the durability of the gas separation membrane, and alcoholic hydroxyl groups are more preferred. There are no particular restrictions on initiators having 2 or more active hydrogen atoms. Examples include polyhydric alcohols, polyhydric phenols, polyhydric carboxylic acids, and amine compounds having 2 or more hydrogen atoms bonded to a nitrogen atom. Among these, divalent aliphatic alcohols are preferred from the viewpoint of balancing reactivity during polymerization with the durability of the gas separation membrane, and divalent aliphatic alcohols having 2 to 8 carbon atoms are more preferred. In addition, a polyoxyalkylene polyol with a lower molecular weight than the target polyoxyalkylene polyol can be used as an initiator.There are no particular restrictions on the initiator, and examples include ethylene glycol; polypropylene glycol such as propylene glycol and dipropylene glycol; 1,4-butanediol; and the like.

[0052] -Reaction Product (1)- Reaction product (1) is an equimolar reaction product of polyoxyalkylene monool and a compound having an isocyanate group and a (meth)acryloyloxy group. As the compound having an isocyanate group and a (meth)acryloyloxy group, isocyanate alkyl (meth)acrylate is preferred.

[0053] Since polyoxyalkylene monool and isocyanate alkyl (meth)acrylate each have one group capable of urethane formation in one molecule, it is easy to control the number of urethane bonds in one molecule of the reaction product (1). When the number of urethane bonds in one molecule of the reaction product (1) is small, the viscosity of the gas separation membrane composition tends to be low. Also, since both polyoxyalkylene monool and isocyanate alkyl (meth)acrylate are compounds that have one reactive group, by-products are less likely to be produced, and it is easy to obtain a highly pure reaction product (1) after removing unreacted material. If unreacted material remains, it is preferable from the viewpoint of the stability of the reaction product that the unreacted material is polyoxyalkylene monool. From the viewpoint of obtaining a reaction product with little unreacted material, it is preferable to react the two at an index of 90 to 100, and more preferably at an index of 100. There is no particular limit to the average number of functional groups of the reaction product (1), but it is preferable to have 0.9 to 1.1. If the value is above the lower limit of the above range, it becomes easier to suppress the bleed-out of unreacted substances after the formation of the gas separation membrane, and if it is below the upper limit of the above range, the gas separation membrane is more likely to exhibit flexibility.

[0054] -Reaction Product (2)- Reaction product (2) is an equimolar reaction product of polyoxyalkylene monool, diisocyanate, and a compound having a group that reacts with the isocyanate group and a (meth)acryloyloxy group. Aliphatic diisocyanates and alicyclic diisocyanates are preferred as the diisocyanate. There are no particular restrictions on the compound having a group that reacts with the isocyanate group and a (meth)acryloyloxy group, but from the viewpoint of improving the curing rate of reaction product (2), hydroxyalkyl (meth)acrylates and hydroxycycloalkyl (meth)acrylates are preferred, and hydroxyalkyl (meth)acrylates with 8 or fewer carbon atoms in the hydroxyalkyl group are more preferred. There are no particular limitations on the reaction product (2), and examples include (a) a reaction product obtained by reacting a polyoxyalkylene monool with a diisocyanate at an index of 200, and then reacting the resulting reaction product (a reaction product having an isocyanate group) with a hydroxyalkyl (meth)acrylate at an index of 100; and (b) a reaction product obtained by simultaneously reacting a polyoxyalkylene monool with an equimolar amount of hydroxyalkyl (meth)acrylate relative to the polyoxyalkylene monool and a diisocyanate in an amount with an index of 100 relative to the sum of the polyoxyalkylene monool and the hydroxyalkyl (meth)acrylate. These may be used individually or in combination of two or more. Among these, the reaction product of (a) is preferred from the viewpoint of producing fewer by-products. When producing the reaction product of (a), the amount of hydroxyalkyl (meth)acrylate used may be in excess, and the excess hydroxyalkyl (meth)acrylate can be used as a raw material for polymer (1) together with the reaction product of (a) as at least part of monomer (C). The average number of functional groups of the reaction product (2) is not particularly limited, but is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. If it is above the lower limit of the above range, it becomes easier to suppress the bleed-out of unreacted substances after the formation of the gas separation membrane, and if it is below the upper limit of the above range, the gas separation membrane is more likely to exhibit flexibility.

[0055] -Reaction Product (3)- Reaction product (3) is an equimolar reaction product of a polyoxyalkylene polyol and a compound having an isocyanate group and a (meth)acryloyloxy group. Polyoxyalkylenediol is preferred as the polyoxyalkylene polyol. Isocyanate alkyl (meth)acrylate is preferred as the compound having an isocyanate group and a (meth)acryloyloxy group. Reaction product (3) is a reaction product having hydroxyl groups, and the number of hydroxyl groups is not limited to one. Therefore, as long as the compound having an isocyanate group and a (meth)acryloyloxy group is a compound having one isocyanate group and is an equimolar reaction product, the starting material polyoxyalkylene polyol may be a compound having two or more hydroxyl groups. There are no particular restrictions on the average number of functional groups of reaction product (3), but it is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. If the value is above the lower limit of the above range, it becomes easier to increase the mechanical strength of the gas separation membrane, and if it is below the upper limit of the above range, it becomes easier to achieve a balance between the mechanical strength and gas permeability of the gas separation membrane.

[0056] (Monofunctional monomer (B)) Monofunctional monomer (B) is a monomer that does not have a urethane bond derived from an isocyanate group-containing compound, and has a polyoxyalkylene chain and a (meth)acryloyloxy group, and has one (meth)acryloyloxy group in one molecule. Monofunctional monomer (B) has the effect of giving gas separation membranes gas permeability and gas separation selectivity.

[0057] There are no particular restrictions on the number-average molecular weight of the monofunctional monomer (B), but it is preferably 100 to 35,000, more preferably 1,000 to 20,000, and most preferably 5,000 to 18,000. If it is above the lower limit of the above range, film formation becomes easier, and if it is below the upper limit of the above range, polymerization becomes easier. The number-average molecular weight of the monofunctional monomer (B) can be determined by the measurement method described in the examples.

[0058] In the manufacturing process of monofunctional monomer (B), by-products containing polyoxyalkylene chains other than monofunctional monomer (B) may be produced. Examples of by-products containing polyoxyalkylene chains include compounds having two (meth)acryloyloxy groups and compounds without (meth)acryloyloxy groups. There are no particular restrictions on the purity of monofunctional monomer (B) in the product, but from the viewpoint of fully exhibiting the function of monofunctional monomer (B), it is preferably 80% by mass or more, and more preferably 85 to 100% by mass, of 100% by mass of monofunctional monomer (B). The purity of monofunctional monomer (B) can be determined by the same method as for determining the purity of monofunctional monomer (A).

[0059] If the product can be considered as a monofunctional monomer (B), the average number of functional groups obtained from the number-average molecular weight and the number of functional groups of the product can be considered as the average number of functional groups of the monofunctional monomer (B). In this case, there are no particular restrictions on the average number of functional groups in the product, but from the viewpoint of fully exhibiting the function of the monofunctional monomer (B), it is preferably 0.8 to 1.2, and more preferably 0.9 to 1.1. The average number of functional groups can be adjusted to this range by adjusting the amount of impurities contained in the raw material for the production of the monofunctional monomer (B).

[0060] There are no particular restrictions on the monofunctional monomer (B), and examples include equimolar reaction products of polyoxyalkylene monool and (meth)acrylic acid having a functional group that reacts with the hydroxyl group of the polyoxyalkylene monool. For the physical properties, manufacturing method, and raw materials used in the manufacturing of the polyoxyalkylene monool used as the monofunctional monomer (B), refer to the description of polyoxyalkylene monool as a raw material for reaction product (1) and reaction product (2). There are no particular restrictions on the equimolar reaction product of polyoxyalkylene monool and (meth)acrylic acid having a functional group that reacts with the hydroxyl group of the polyoxyalkylene monool, and examples include polyethylene glycol monomethyl ether (meth)acrylate, polypropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, and polypropylene glycol monomethyl ether (meth)acrylate. These may be used individually or in combination of two or more.

[0061] (Monomer (C)) Monomer (C) is a monomer that has a (meth)acryloyl group but does not have an alkylene oxide unit. Monomer (C) may be a monofunctional monomer or a polyfunctional monomer. These may be used alone or in combination of two or more. Among these, monofunctional monomers are preferred. Monomer (C) has the effect of increasing the strength of the gas separation membrane.

[0062] There are no particular restrictions on the number-average molecular weight of monomer (C), but it is preferably 70 to 35,000, more preferably 1,000 to 20,000, and most preferably 5,000 to 18,000. If it is above the lower limit of the above range, film formation becomes easier, and if it is below the upper limit of the above range, polymerization becomes easier. The number-average molecular weight of monomer (C) can be determined by the measurement method described in the examples. The average number of functional groups of monomer (C) is preferably 0.8 to 1.2, more preferably 0.9 to 1.1, from the viewpoint of fully exhibiting its function.

[0063] There are no particular restrictions on the monomer (C), and examples include hydroxyalkyl (meth)acrylates such as 4-hydroxybutyl (meth)acrylate and 6-hydroxyhexyl (meth)acrylate; dihydroxyalkyl (meth)acrylate; alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, lauryl (meth)acrylate, isostearyl (meth)acrylate, and isodecyl (meth)acrylate; and (meth)acrylamides such as 4-(meth)acryloylmorpholine, N,N-dimethyl (meth)acrylamide, and N,N-diethyl (meth)acrylamide. These may be used individually or in combination of two or more.

[0064] <Other Additives> The gas separation membrane may further contain other additives as needed. There are no particular restrictions on the other additives, and examples include tackifiers, plasticizers, amine compounds, silica, etc. These may be used individually or in combination of two or more.

[0065] (Tackifier) ​​A tackifier is used to improve the adhesion of a gas separation membrane. There are no particular restrictions on the tackifier, and examples include rosin esters, terpene phenols, hydrogenated terpene phenols, etc. These may be used individually or in combination of two or more.

[0066] (Plasticizer) Plasticizers are used to improve the flexibility of the gas separation membrane. There are no particular restrictions on the plasticizer, and examples include adipic acid esters and phthalic acid esters. These may be used individually or in combination of two or more.

[0067] (Amine Compounds) Amine compounds are used to improve the permeability of gas separation membranes to carbon dioxide. There are no particular limitations on the amine compounds, and examples include alkanolamines such as monoethanolamine and diethanolamine; aliphatic amines such as diamylamine, diallylamine, and dibutylamine; polyamidoamine dendrimers; and so on. These may be used individually or in combination of two or more.

[0068] (Silica) Silica is used to improve the strength of gas separation membranes. There are no particular restrictions on the type of silica, and examples include spherical silica, flake silica, porous silica, hollow silica, etc. These may be used individually or in combination of two or more types.

[0069] If the gas separation membrane contains other additives (tackifiers, plasticizers, amine compounds, silica, etc.), there are no particular restrictions on the amount of other additives, but it is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, and particularly preferably 0 to 30% by mass, of 100% by mass of the gas separation membrane. If it is above the lower limit of the above range, the gas separation membrane becomes easier to mold by plasticization, and if it is below the upper limit of the above range, the content of components that contribute to gas separation capacity increases, and the gas separation performance of the gas separation membrane tends to improve.

[0070] [Method for Manufacturing a Gas Separation Membrane] The method for manufacturing a gas separation membrane according to this embodiment involves preparing a gas separation membrane composition containing a monofunctional monomer having alkylene oxide units in the molecule and one (meth)acryloyl group in one molecule, and curing the prepared gas separation membrane composition to produce a gas separation membrane containing a polymer having alkylene oxide units, wherein the alkylene oxide units include branched alkylene oxide units having 3 or more carbon atoms, and the content ratio of branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane composition is 20 mol% or more out of 100 mol% of alkylene oxide units in the gas separation membrane composition. By this manufacturing method, a gas separation membrane with a high carbon dioxide permeability coefficient and low hygroscopicity can be obtained. The monofunctional monomer having alkylene oxide units in the molecule is, for example, monofunctional monomer (A) and monofunctional monomer (B).

[0071] <Preparation of Gas Separation Membrane Composition> The gas separation membrane composition prepared by the gas separation membrane production method of this embodiment contains a monofunctional monomer having an alkylene oxide unit in its molecule (monofunctional monomer (A) or monofunctional monomer (B)) as an essential component. That is, the gas separation membrane composition is not particularly limited as long as it contains at least a monofunctional monomer having an alkylene oxide unit in its molecule (monofunctional monomer (A) or monofunctional monomer (B)), and may or may not contain monomer (C), other additives (tackifiers, plasticizers, amine compounds, silica, etc.), solvents, photopolymerization initiators, and other components as needed. The gas separation membrane production method of this embodiment is a production method for producing a gas separation membrane containing polymer (1). There are no particular restrictions on the content of branched alkylene oxide units having 3 or more carbon atoms in polymer (1), but from the viewpoint of improving the carbon dioxide permeability of the gas separation membrane, it is preferably 40 mol% or more, more preferably 60 mol% or more, even more preferably 80 mol% or more, and particularly preferably 85 to 100 mol% of the alkylene oxide units in polymer (1) per 100 mol%.

[0072] The content of branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane composition is not particularly limited as long as it is 20 mol% or more of the total 100 mol% of alkylene oxide units related to monomers contained in the gas separation membrane composition. However, from the viewpoint of improving the carbon dioxide permeability of the gas separation membrane, it is preferably 40 mol% or more, more preferably 60 mol% or more, and particularly preferably 80 to 100 mol%. The content of branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane composition can be determined by the same method as the method for determining the content of branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane, i.e., by the measurement method described in the examples. In the examples of this specification, the content of branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane composition is calculated by the charge ratio when manufacturing the gas separation membrane. However, if the charge ratio when manufacturing the gas separation membrane is unknown, １ It can be calculated from the integral ratio of the H-NMR spectrum.

[0073] There are no particular restrictions on the total content of monofunctional monomer (A) and monofunctional monomer (B) in the gas separation membrane composition, but it is preferably 20 to 99% by mass, more preferably 30 to 90% by mass, and particularly preferably 40 to 80% by mass, of 100% by mass of the gas separation membrane composition. If it is above the lower limit of the above range, it contributes to increasing the thickness of the gas separation membrane and the mechanical strength of the gas separation membrane tends to increase, and if it is below the upper limit of the above range, uniform mixing of the gas separation membrane composition becomes easier and viscosity decreases, making it easier to obtain a gas separation membrane of uniform thickness.

[0074] There are no particular restrictions on the content of monofunctional monomer (A) in the gas separation membrane composition, but it is preferably 10 to 100% by mass, more preferably 20 to 100% by mass, and most preferably 30 to 100% by mass, based on 100% by mass of the gas separation membrane composition. If the content is above the lower limit of the above range, the membrane strength of the gas separation membrane tends to be high, and if it is below the upper limit of the above range, the flexibility of the gas separation membrane tends to be high.

[0075] There are no particular restrictions on the content of monofunctional monomer (B) in the gas separation membrane composition, but it is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, and most preferably 0 to 30% by mass, based on 100% by mass of the gas separation membrane composition. If the content is above the lower limit of the above range, the flexibility of the gas separation membrane tends to increase, and if it is below the upper limit of the above range, the membrane strength of the gas separation membrane tends to increase.

[0076] When the gas separation membrane composition contains monomer (C), there are no particular restrictions on the monomer (C) content, but it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, and most preferably 0 to 10% by mass, of 100% by mass of the gas separation membrane composition. If it is above the lower limit of the above range, it becomes easier to adjust the mechanical strength of the gas separation membrane, and if it is below the upper limit of the above range, the content of components that contribute to the gas separation ability of the gas separation membrane increases, making it easier to improve the gas separation performance.

[0077] If the gas separation membrane composition contains other additives (tackifiers, plasticizers, amine compounds, silica, etc.), there are no particular restrictions on the total content of the other additives, but it is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, and particularly preferably 0 to 30% by mass, of 100% by mass of the gas separation membrane composition. If it is above the lower limit of the above range, the gas separation membrane becomes easier to mold by plasticization, and if it is below the upper limit of the above range, the content of components that contribute to the gas separation ability of the gas separation membrane increases, making it easier to improve the gas separation performance.

[0078] (Solvent) The gas separation membrane composition may further contain a solvent as needed. There are no particular restrictions on the solvent, and examples include 2-butanone, methanol, ethanol, water, acetone, etc. These may be used individually or in combination of two or more. Among these, 2-butanone, methanol, and water are preferred from the viewpoint of the solubility of the raw materials of the gas separation membrane composition and the volatility of the solvent, with 2-butanone being more preferred.

[0079] When the gas separation membrane composition contains a solvent, there are no particular restrictions on the solvent content, but it is preferably 1 to 80% by mass, more preferably 10 to 70% by mass, and most preferably 15 to 60% by mass, based on 100% by mass of the gas separation membrane composition. If the solvent content is above the lower limit of the above range, uniform mixing of the gas separation membrane composition becomes easier, the viscosity decreases, and it becomes easier to obtain a gas separation membrane of uniform thickness. If the solvent content is below the upper limit of the above range, it contributes to increasing the thickness of the gas separation membrane and makes it easier to increase the mechanical strength of the gas separation membrane.

[0080] (Photopolymerization Initiator) The gas separation membrane composition may further contain a photopolymerization initiator as needed. There are no particular restrictions on the photopolymerization initiator, and examples include benzoin ketals such as 2,2-dimethoxy-1,2-diphenylethane-1-one; hydroxyketones such as 1-hydroxycyclohexylphenyl ketone and 2-hydroxy-2-methyl-1-phenylpropane-1-one; 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, and 1,2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane Amino ketones such as -1-one; oxime esters such as 1-[(4-phenylthio)phenyl]-1,2-octadione-2-(benzoyl)oxime; phosphine oxides such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide; benzophenone, N,N'-tetramethyl Examples include benzophenones such as til-4,4'-diaminobenzophenone, N,N'-tetraethyl-4,4'-diaminobenzophenone, and 4-methoxy-4'-dimethylaminobenzophenone; quinones such as 2-ethylanthraquinone, phenanthrenequinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-phenylanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, and 1,4-naphthoquinone; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, and benzoin phenyl ether; benzoins such as benzoin, methylbenzoin, and ethylbenzoin; benzyl such as benzyldimethylketal; acridines such as 9-phenylacridine and 1,7-bis(9,9'-acridinylheptane); N-phenylglycine; coumarin; and the like. These may be used individually or in combination of two or more types.Among these, 1-hydroxycyclohexylphenyl ketone and 2-hydroxy-2-methyl-1-phenylpropan-1-one are preferred from the viewpoint of absorption wavelength, and 1-hydroxycyclohexylphenyl ketone is more preferred.

[0081] There are no particular restrictions on commercially available photopolymerization initiators, and examples include Omnirad 184 (product name manufactured by iGM RESINS B.V.), Omnirad 369 (product name manufactured by iGM RESINS B.V.), and Omnirad 907 (product name manufactured by iGM RESINS B.V.). These may be used individually or in combination of two or more. Among these, Omnirad 184 (product name manufactured by iGM RESINS B.V.) and Omnirad 369 (product name manufactured by iGM RESINS B.V.) are preferred from the viewpoint of absorption wavelength, and Omnirad 184 (product name manufactured by iGM RESINS B.V.) is more preferred.

[0082] When the gas separation membrane composition contains a photopolymerization initiator, there are no particular restrictions on the amount of the photopolymerization initiator, but it is preferably 0.001 to 10.000% by mass, more preferably 0.001 to 5.000% by mass, and particularly preferably 0.001 to 1.000% by mass, based on 100% by mass of the gas separation membrane composition. If the amount is above the lower limit of the above range, the polymerization rate tends to be fast, and if it is below the upper limit of the above range, the molecular weight of the gas separation membrane tends to be large.

[0083] (Other Components) The gas separation membrane composition may further contain other components as needed. There are no particular restrictions on the other components, and examples include polymerization inhibitors, photocuring accelerators, ultraviolet absorbers, light stabilizers, antioxidants, etc. These may be used individually or in combination of two or more.

[0084] Polymerization inhibitors are used to improve the storage stability of a gas separation membrane composition and to facilitate the adjustment of the molecular weight of the cured polymer by adding a smaller amount of the polymerization inhibitor than the photopolymerization initiator to the gas separation membrane composition. There are no particular restrictions on the polymerization inhibitor, and examples include hydroquinone-based polymerization inhibitors such as 2,5-di-tert-butylhydroquinone; catechol-based polymerization inhibitors such as p-tert-butylcatechol; anthraquinone-based polymerization inhibitors; phenothiazine-based polymerization inhibitors; hydroxytoluene-based polymerization inhibitors; and the like. These may be used individually or in combination of two or more.

[0085] Photocuring accelerators are used to suppress poor curing of gas separation membrane compositions due to factors such as oxygen inhibition. Examples of photocuring accelerators include tertiary amines such as dialkylaminobenzoic acid esters; phosphines such as triphenylphosphine, tributylphosphine, tri(p-methylphenyl)phosphine, and tri(nonylphenyl)phosphine; diprenyl glycerin ether; isoprenyl methacrylate; and the like. These may be used individually or in combination of two or more.

[0086] Ultraviolet absorbers are used to prevent ultraviolet degradation of gas separation membrane compositions and improve their weather resistance. There are no particular limitations on the ultraviolet absorbers, and examples include benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and benzoate-based ultraviolet absorbers. There are no particular limitations on benzotriazole-based ultraviolet absorbers, but for example, those described in paragraph

[0076] of International Publication No. 2014 / 017328 can be used. These may be used individually or in combination of two or more.

[0087] Light stabilizers are used to prevent photodegradation of gas separation membrane compositions and improve their weather resistance. There are no particular limitations on the light stabilizers, and examples include hindered amine-based light stabilizers. There are no particular limitations on the hindered amine-based light stabilizers, and for example, those described in paragraph

[0077] of International Publication No. 2014 / 017328 can be used. These may be used individually or in combination of two or more.

[0088] Antioxidants are used to prevent oxidation of the gas separation membrane composition and improve its weather resistance and heat resistance. There are no particular limitations on the antioxidant; examples include phenolic and phosphorus-based antioxidants. There are no particular limitations on the phenolic antioxidant; for example, those described in paragraph

[0078] of International Publication No. 2014 / 017328 can be used. There are no particular limitations on the phosphorus-based antioxidant; for example, those described in paragraph

[0078] of International Publication No. 2014 / 017328 can be used. These may be used individually or in combination of two or more.

[0089] If the gas separation membrane composition contains other components, there are no particular restrictions on the total content of the other components, but it is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, and most preferably 0 to 30% by mass, of 100% by mass of the gas separation membrane composition. If it is above the lower limit of the above range, the weather resistance and oxidation resistance of the gas separation membrane tend to be high, and if it is below the upper limit of the above range, the mechanical strength of the gas separation membrane tend to be high.

[0090] <Curing of Gas Separation Membrane Composition> In the method for producing a gas separation membrane of this embodiment, the desired gas separation membrane can be obtained by curing the gas separation membrane composition, that is, by polymerizing the various monomers contained in the gas separation membrane composition.

[0091] There are no particular restrictions on the curing method, but curing by light irradiation is preferred from the viewpoint of curing speed. The solvent in the gas separation membrane composition may or may not be removed before curing by light irradiation. From the viewpoint of increasing the molecular weight of the polymer in the gas separation membrane, it is preferable to remove the solvent before curing by light irradiation.

[0092] There are no particular restrictions on the wavelength range of the irradiation light, but it is preferably 300 to 450 nm, more preferably 320 to 400 nm, and most preferably 340 to 380 nm. If the wavelength is above the lower limit of the above range, the decomposition of the polymer is more easily suppressed, and if it is below the upper limit of the above range, the curing reaction proceeds more easily. There are no particular restrictions on the intensity of the light irradiation, but it is preferably 10 to 1,000 mW / cm². ２ More preferably 30 to 500 mW / cm² ２ Particularly preferred is 50 to 300 mW / cm² ２ The above range is greater than or equal to the lower limit, which makes it easier to shorten the polymerization time, and greater than or equal to the upper limit, which makes polymerization proceed more easily. There are no particular restrictions on the irradiation time of light, but it is preferably 1 to 500 seconds, more preferably 5 to 300 seconds, and most preferably 10 to 150 seconds. The above range is greater than or equal to the lower limit, which makes it easier to obtain a sufficient degree of film hardening, and greater than or equal to the upper limit, which makes it easier to reduce the heat generated by the sample due to ultraviolet irradiation.

[0093] There are no particular restrictions on the method for removing the solvent before curing by light irradiation, but from the viewpoint of ease of manufacture, heat drying is preferred. There are no particular restrictions on the heating temperature for heat drying, but it is preferably 30 to 200°C, more preferably 30 to 150°C, and most preferably 30 to 120°C. If the temperature is above the lower limit of the above range, it becomes easier to sufficiently remove the solvent, and if it is below the upper limit of the above range, it becomes easier to obtain a uniform film. There are no particular restrictions on the heating time for heat drying, but it is preferably 1 to 60 minutes, more preferably 3 to 60 minutes, and most preferably 5 to 60 minutes. If the heating time is above the lower limit of the above range, it becomes easier to sufficiently remove the solvent, and if it is below the upper limit of the above range, deterioration of the gas separation membrane composition due to heat becomes less likely.

[0094] The gas separation membrane of this embodiment is suitable as a gas separation membrane for separating carbon dioxide gas from a mixture of carbon dioxide-containing gases (for example, a mixture of carbon dioxide gas and nitrogen gas, a mixture of carbon dioxide gas and air, a mixture of carbon dioxide gas and hydrogen gas, or a mixture of these gases with a high water content).

[0095] The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples, and various modifications are possible without departing from the spirit of the invention. Examples 1 to 3 and 5 are examples, and Example 4 is a comparative example.

[0096] [Measurement of physical properties of various monomers] The following measurements were performed on the various monomers used.

[0097] <Measurement of Number-Average Molecular Weight (Mn)> The number-average molecular weight of various monomers was determined as polystyrene-equivalent molecular weight by GPC (Gel Permeation Chromatography) under the following conditions: • Analytical instrument: Tosoh Corporation, HLC-8320GPC • Column: Resona Corporation, GF-1G 7B + GF-7M HQ + GF-7M HQ • Column size: GF-1G 7B: 7.5 mmφ × 5 cm, GF-7M HQ: 7.5 mmφ × 30 cm, total 65 cm • Column temperature: 40°C • Flow rate: 0.6 ml / min • Injection volume: 50 μl • Eluent: N,N-dimethylformamide • Detector: Differential refractometer (RI) • Standard sample: Polystyrene

[0098] [Manufacturing of Gas Separation Membranes] Using the monofunctional monomers shown below, gas separation membranes 1 to 5 were manufactured as shown in Examples 1 to 5.

[0099] <Monofunctional Monomers> ・Monofunctional Monomer 1: Monofunctional monomer (A), compound represented by the following structural formula (1) (n=213), branched alkylene oxide with 3 or more carbon atoms: propylene oxide, content of branched alkylene oxide units with 3 or more carbon atoms: 100 mol% out of 100 mol% of alkylene oxide units, number average molecular weight: 12,600 ・Monofunctional Monomer 2: Monofunctional monomer (B), compound represented by the following structural formula (2) (n=23), branched alkylene oxide with 3 or more carbon atoms: none, content of branched alkylene oxide units with 3 or more carbon atoms: 0 mol% out of 100 mol% of alkylene oxide units, number average molecular weight: 1,100, product name: m-PEG-acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) • Monofunctional monomer 3; Monofunctional monomer (B), compound represented by the following structural formula (2) (n=344), branched alkylene oxide with 3 or more carbon atoms: none, percentage of branched alkylene oxide units with 3 or more carbon atoms: 0 mol% out of 100 mol% of alkylene oxide units, number average molecular weight: 15,200, purity: 90% by mass, trade name: m-PEG-acrylate (manufactured by BroadPharm)

[0100] ... (1) (In structural formula (1), Bu is an n-butyl group (-CH ２ CH ２ CH ２ CH ３ ) represents. )

[0101] ... (2)

[0102] (Example 1) In a glass vial containing a magnetic stirrer, 79.8 parts by mass of monofunctional monomer 1, 0.2 parts by mass of 1-hydroxycyclohexylphenyl ketone (photopolymerization initiator: Omnirad 184, manufactured by iGM RESINS B.V.), and 20.0 parts by mass of 2-butanone were charged. This was mixed at 40°C for 10 minutes, filtered through a PTFE syringe filter (pore size 1 μm), and spin-coated onto the surface of an SO sheet (manufactured by I-Cello Co., Ltd.) using a spin-coating machine (MS-A-150, manufactured by Mikasa Corporation; spin-coating conditions: rotated at 500 rpm for 3 seconds, then at 3000 rpm for 20 seconds). After spin-coating, the solvent was removed by heating at 120°C for 5 minutes, and then irradiated with light in a nitrogen atmosphere (wavelength of irradiation light: 365 nm, irradiation intensity: 100 mW / cm²). ２ (Light irradiation time: 100 seconds). After light irradiation, a hydrophilic PTFE membrane (pore size 0.1 μm, H010A025A, manufactured by Toyo Roshi Co., Ltd.) was attached to the UV irradiation surface, the PET layer of the SO sheet was peeled off and the PVA layer was dissolved with ultrapure water, and the membrane was dried under reduced pressure (-0.1 MPaG) at room temperature to obtain gas separation membrane 1.

[0103] (Examples 2-3) Gas separation membranes 2-3 were obtained in the same manner as in Example 1, except that monofunctional monomer 1 and monofunctional monomer 2 were used in the blending ratio (molar ratio) shown in Table 1 instead of monofunctional monomer 1.

[0104] (Example 4) In Example 1, monofunctional monomer 2 (79.4 parts by mass) was used instead of monofunctional monomer 1 (79.8 parts by mass). Also in Example 1, methanol (19.8 parts by mass) was used instead of 2-butanone (20.0 parts by mass). Also in Example 1, 0.8 parts by mass of 1-hydroxycyclohexylphenyl ketone (photopolymerization initiator: Omnirad 184, manufactured by iGM RESINS B.V.) was used instead of 0.2 parts by mass. Also in Example 1, a silicon substrate (50 mm square) hydrophobized by coating and heat treatment with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) was used instead of SO sheet (manufactured by Aicello Co., Ltd.). Furthermore, in Example 1, the spin coating conditions were changed from rotating at 500 rpm for 3 seconds followed by 3000 rpm for 20 seconds to rotating at 500 rpm for 3 seconds followed by 1000 rpm for 20 seconds. Also, the solvent removal conditions were changed from heating at 120°C for 5 minutes to heating at 30°C for 15 minutes. Except for the above, the gas separation membrane 4 was obtained in the same manner as in Example 1.

[0105] (Example 5) In Example 4, monofunctional monomer 2 (79.4 parts by mass) was replaced with monofunctional monomer 1 and monofunctional monomer 3 (total parts by mass of monofunctional monomer 1 and monofunctional monomer 3: 39.8 parts by mass) in the blending ratio (molar ratio) shown in Table 1. Also, in Example 4, the amount of methanol charged was replaced with 59.8 parts by mass instead of 19.8 parts by mass. Also, in Example 4, the amount of 1-hydroxycyclohexylphenyl ketone (photopolymerization initiator: Omnirad 184, manufactured by iGM RESINS B.V.) charged was replaced with 0.4 parts by mass instead of 0.8 parts by mass. Also, the solvent removal conditions were changed from heating at 300°C for 15 minutes to heating at 70°C for 5 minutes. Except for the above, a gas separation membrane 5 was obtained in the same manner as in Example 4.

[0106] [Physical Property Measurement of Gas Separation Membranes 1-5] The following measurements were performed on gas separation membranes 1-5. The measurement results are shown in Table 1.

[0107] <Measurement of the content ratio of branched alkylene oxide units having 3 or more carbon atoms> The content ratio of branched alkylene oxide units having 3 or more carbon atoms contained in the alkylene oxide units of each gas separation membrane produced was determined from the charging ratio of the monomers (monofunctional monomer (A) and monofunctional monomer (B)) in the gas separation membrane composition. Also, the content ratio of branched alkylene oxide units having 3 or more carbon atoms contained in the alkylene oxide units of the polymer was determined by the same method as described above. Further, the content ratio of branched alkylene oxide units having 3 or more carbon atoms contained in the alkylene oxide units of the gas separation membrane composition was determined by the same method as described above.

[0108] <Measurement of the thickness of the gas separation membrane> The thickness of each gas separation membrane produced was determined by the following method. For the one with hydrophilized PTFE membranes attached to both sides of the gas separation membrane, the thickness was measured using a micrometer (OMV-25MX, manufactured by Mitutoyo Corporation), and the thickness of the gas separation membrane was calculated by subtracting the thickness of each of the two PTFE membranes.

[0109] <Gas permeation test (CO ２ Permeability coefficient C ＣＯ２ and CO ２ / N ２ <Measurement of separation coefficient α)> Using each gas separation membrane produced, the carbon dioxide permeability coefficient (CO ２ Permeability coefficient C ＣＯ２ [Barrer]), and the carbon dioxide separation coefficient with respect to nitrogen (CO ２ / N ２ Separation coefficient α) was measured. Here, as the gas separation membrane for the gas permeation test, the one with hydrophilized PTFE membranes (pore diameter 0.1 μm) attached to both sides of the gas separation membrane was used. First, each gas separation membrane was placed in a metal cell (membrane area 9.6 cm ２It was set in ( ), and sealed with an O-ring so that no leakage occurred. Next, the mixed gas was injected into the metal cell so that the mixed gas contacted one main surface of the gas separation membrane. The mixed gas consisted of carbon dioxide (100 sccm) and nitrogen (100 sccm), the concentration of carbon dioxide was 50 vol% under standard conditions, the temperature of the mixed gas was 30 °C, and the pressure of the mixed gas was 0.1 MPaA (atmospheric pressure). Argon was injected at 40 sccm into the space in the metal cell adjacent to the other main surface of the gas separation membrane. Thereby, the permeated fluid was obtained from the other main surface of the gas separation membrane. The obtained permeated fluid was analyzed and quantified by a gas chromatograph (GC-8A, manufactured by Shimadzu Corporation) to measure the composition of the permeated fluid, and based on the following formula, the CO ２ Permeability coefficient C ＣＯ２ [Barrer], and CO ２ / N ２ Separation factor α was calculated. Note that Q ＣＯ２ is the permeation rate of carbon dioxide [mol / s], Q Ｎ２ is the permeation rate of nitrogen [mol / s], ΔP ＣＯ２ is the differential pressure of carbon dioxide [kPa] between one main surface of the gas separation membrane and the other main surface of the gas separation membrane, ΔP Ｎ２ is the differential pressure of nitrogen [kPa] between one main surface of the gas separation membrane and the other main surface of the gas separation membrane, t [μm] is the membrane thickness of the gas separation membrane, and A is the gas permeation area [m ２ . CO ２ Permeability coefficient C ＣＯ２ = Q ＣＯ２ × t / (3.35 × 10 ７ × ΔP ＣＯ２ × A) N ２ Permeability coefficient C Ｎ２ = Q Ｎ２ × t / (3.35 × 10 ７ × ΔP Ｎ２ × A) CO ２ / N ２ Separation factor α = C / C Ｎ２ CO ２ Permeability coefficient C ＣＯ２ [Barrer], and CO ２ / N ２ Separation factor α was evaluated according to the following evaluation criteria. 〔Evaluation criteria (CO ２ Permeability coefficient CＣＯ２ ) A: 500 or more B: 200 or more but less than 500 C: Less than 200 If the evaluation is A, CO ２ Transmittance coefficient C ＣＯ２ It can be said that is particularly excellent. Also, in the case of B, CO ２ Transmittance coefficient C ＣＯ２ It can be said that it is quite good. On the other hand, in the case of evaluation C, CO ２ Transmittance coefficient C ＣＯ２ It cannot be said to be excellent. [Evaluation Criteria (CO)] ２ / N ２ [Separation coefficient α)] A: 10 or more B: 5 or more but less than 10 C: Less than 5 If evaluation is A, CO ２ / N ２ The separation coefficient α is particularly excellent. Also, in the case of B, CO ２ / N ２ The separation coefficient α can be said to be sufficiently good. On the other hand, in the case of evaluation C, CO ２ / N ２ The separation coefficient α is not particularly good.

[0110] <Hygroscopicity Test> The hygroscopicity of each gas separation membrane manufactured was determined by the following method. Gas separation membrane samples 1 to 3 were prepared for the hygroscopicity test of gas separation membranes 1 to 3 (see preparation method below). For the hygroscopicity test of gas separation membranes 4 and 5, gas separation membranes 4 and 5 manufactured in Examples 4 and 5 were used as gas separation membrane samples 4 and 5, respectively. (Preparation of gas separation membrane samples 1 to 3) In Examples 1 to 3, 19.8 parts by mass of 2-butanone were used instead of 20.0 parts by mass. Also, in Examples 1 to 3, 0.8 parts by mass of 1-hydroxycyclohexylphenyl ketone (photopolymerization initiator: Omnirad 184, manufactured by iGM RESINS B.V.) were used instead of 0.2 parts by mass. Furthermore, in Examples 1 to 3, instead of SO sheets (manufactured by Aicello Co., Ltd.), a silicon substrate (50 mm square) hydrophobized by coating and heat-treating with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) was used. Except as above, gas separation membrane samples 1 to 3 were obtained in the same manner as in Examples 1 to 3. Next, each gas separation membrane sample was placed in a polystyrene case together with a container of saturated potassium chloride aqueous solution, sealed with silicone grease, and left to stand for 24 hours in an atmosphere of 40°C and relative humidity of 82-83%. Assuming that the mass of the hydrophobized silicon substrate remained constant before and after the moisture absorption test, the amount of moisture absorbed by the gas separation membrane was calculated using the following formula: Amount of moisture absorbed [mass %] = 100 × {(sample mass after 24 hours of humidification) - (sample mass before humidification)} / {(sample mass before humidification) - (mass of hydrophobized silicon substrate)} The amount of moisture absorbed was evaluated according to the following evaluation criteria. [Evaluation Criteria (Moisture Absorption)] A: Less than 5% by mass B: 5% by mass or more and less than 10% by mass C: 10% by mass or more If the evaluation is A, the moisture absorption can be said to be particularly low. Also, even if the evaluation is B, the moisture absorption can be said to be sufficiently low. On the other hand, if the evaluation is C, the moisture absorption cannot be said to be low.

[0111] <Measurement of Enthalpy of Melting> The enthalpy of melting of each gas separation membrane manufactured was determined by the following method. First, each gas separation membrane sample, manufactured using the same method as the hygroscopicity test, was peeled off from the hydrophobic silicon substrate using a spatula to prepare a sample for measurement. Next, measurements were taken using a differential scanning calorimeter (DSC) (Q-200, TA Corporation) in the range of -80°C to 200°C at a heating rate of 10°C / min, and the enthalpy of melting of the gas separation membrane was calculated from the integral value of the obtained endothermic peak.

[0112]

[0113] As can be seen from the measurement results shown in Table 1, gas separation membranes 1 to 3 (where the content of branched alkylene oxide units with 3 or more carbon atoms in the gas separation membrane is 20 mol% or more out of 100 mol% of alkylene oxide units in the gas separation membrane) were found to have a higher carbon dioxide permeability coefficient and lower hygroscopicity compared to gas separation membrane 4 (where the content of branched alkylene oxide units with 3 or more carbon atoms in the gas separation membrane is less than 20 mol% out of 100 mol% of alkylene oxide units in the gas separation membrane).

[0114] As can be seen from the measurement results shown in Table 1, gas separation membrane 5 (where the content of branched alkylene oxide units with 3 or more carbon atoms in the gas separation membrane is 20 mol% or more out of 100 mol% of alkylene oxide units in the gas separation membrane) was found to have lower hygroscopicity compared to gas separation membrane 4 (where the content of branched alkylene oxide units with 3 or more carbon atoms in the gas separation membrane is less than 20 mol% out of 100 mol% of alkylene oxide units in the gas separation membrane). Furthermore, from the measurement results shown in Table 1, it was found that the enthalpy of fusion of gas separation membrane 5 was lower than that of gas separation membrane 4. When a gas separation membrane has a lower enthalpy of fusion, it can be said that the gas separation membrane has a higher amorphousness. And if the amorphousness of the gas separation membrane is higher, it is presumed that the gas separation membrane has a higher carbon dioxide permeability. Therefore, it is presumed that gas separation membrane 5, like gas separation membranes 1 to 3, has a higher carbon dioxide permeability compared to gas separation membrane 4. Based on the measurement results of gas separation membrane 5, it can be said that even if the polymer is polymerized using different monomers as raw material monomers, as long as the content of branched alkylene oxide units with 3 or more carbon atoms in the gas separation membrane is 20 mol% or more out of 100 mol% of alkylene oxide units in the gas separation membrane, a gas separation membrane with a high carbon dioxide permeability coefficient and low hygroscopicity can be obtained.

Claims

1. A gas separation membrane comprising a polymer having alkylene oxide units, wherein the alkylene oxide units include branched alkylene oxide units having 3 or more carbon atoms, and the content ratio of the branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane is 20 mol% or more out of 100 mol% of the alkylene oxide units in the gas separation membrane.

2. The gas separation membrane according to claim 1, wherein the content of the branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane is 80 mol% or more out of 100 mol% of the alkylene oxide units in the gas separation membrane.

3. The gas separation membrane according to claim 1 or 2, wherein the branched alkylene oxide unit having 3 or more carbon atoms is a propylene oxide unit.

4. The gas separation membrane according to claim 1 or 2, wherein the polymer has structural units derived from monomers having a polyoxyalkylene chain and a (meth)acryloyl group.

5. The gas separation membrane according to claim 1 or 2, wherein the content of the polymer is 50 to 100% by mass of 100% by mass of the gas separation membrane.

6. The gas separation membrane according to claim 1 or 2, wherein when the gas separation membrane is left standing for 24 hours in an atmosphere of relative humidity 82-83%, the amount of moisture absorbed by the gas separation membrane is 10% by mass or less.

7. The gas separation membrane according to claim 1 or 2, wherein the enthalpy of fusion of the gas separation membrane is 80 J / g or less.

8. A method for producing a gas separation membrane, comprising preparing a gas separation membrane composition containing a monofunctional monomer having alkylene oxide units in the molecule and one (meth)acryloyl group in one molecule, and curing the prepared gas separation membrane composition to produce a gas separation membrane containing a polymer having the alkylene oxide units, wherein the alkylene oxide units include branched alkylene oxide units having 3 or more carbon atoms, and the content ratio of the branched alkylene oxide units having 3 or more carbon atoms in the gas separation membrane composition is 20 mol% or more out of 100 mol% of the alkylene oxide units in the gas separation membrane composition.

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