Separation functional layer and separation membrane

Abstract

Provided is a novel separation functional layer suitable for separating an acidic gas from a mixed gas containing the acidic gas. This separation function layer (1) contains an ionic liquid (L), a hydrophilic polymer (A) that forms a crystal structure in the ionic liquid (L), and a polymer (B) that is different from the polymer (A). This separation membrane (10) is provided with a separation function layer (1) and a porous support (3) that supports the separation function layer (1).

Description

Technical Field

[0001] The present invention relates to a separation functional layer and a separation membrane. Background Art

[0002] Membrane separation has been developed as a method for separating acid gases from mixed gases containing acid gases such as carbon dioxide. Compared to absorption methods, which separate acid gases contained in mixed gases by absorbing them into an absorbent, membrane separation can efficiently separate acid gases while reducing operating costs.

[0003] Examples of separation membranes used in membrane separation methods include composite membranes having a separation functional layer formed on a porous support. For example, Patent Document 1 discloses a composite membrane having a structure containing an ionic liquid as the separation functional layer. In Patent Document 1, the separation functional layer comprises an ionic liquid, a polymer network structure, and an inorganic particle network structure formed of inorganic particles.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-37688 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] There is a need for a new separation functional layer suitable for separating acid gases from mixed gases containing the acid gases.

[0009] Means for solving problems

[0010] The present invention provides a separation functional layer comprising:

[0011] Ionic liquids;

[0012] A hydrophilic polymer A that forms a crystal structure in the ionic liquid; and

[0013] A polymer B different from the polymer A.

[0014] Furthermore, the present invention provides a separation membrane comprising:

[0015] Separating functional layers; and

[0016] A porous support body supports the separation functional layer.

[0017] Furthermore, the present invention provides a separation membrane comprising:

[0018] Separating functional layers; and

[0019] a porous support supporting the separation functional layer,

[0020] The separation functional layer comprises an ionic liquid and a hydrophilic polymer A forming a crystal structure in the ionic liquid.

[0021] Effects of the Invention

[0022] According to the present invention, a new separation functional layer suitable for separating acid gas from a mixed gas containing the acid gas can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] [ Figure 1 ] is a cross-sectional view schematically showing a separation functional layer according to one embodiment of the present invention.

[0024] [ Figure 2 ] is a cross-sectional view schematically showing a separation membrane according to one embodiment of the present invention.

[0025] [ Figure 3 ] is a schematic cross-sectional view of a membrane separation device equipped with the separation membrane of the present invention.

[0026] [ Figure 4 ] is a three-dimensional view schematically showing a modified example of a membrane separation device having the separation membrane of the present invention.

[0027] [ Figure 5 ] is a graph showing the relationship between the content rate of the ionic liquid and the leakage rate of the ionic liquid for the separation functional layers of Examples C1 to C12;

[0028] [ Figure 6 ] is a graph showing the relationship between the content of the ionic liquid and the fracture energy of the separation functional layer for the separation functional layers of Examples C1 to C12.

[0029] [ Figure 7 ] is a graph showing the relationship between the content of the ionic liquid and the fracture stress of the separation functional layer in Examples C1 to C12. DETAILED DESCRIPTION

[0030] The separation functional layer according to the first embodiment of the present invention includes:

[0031] Ionic liquids;

[0032] A hydrophilic polymer A that forms a crystal structure in the above-mentioned ionic liquid; and

[0033] A polymer B different from the above polymer A.

[0034] In the second aspect of the present invention, for example, in the separation functional layer of the first aspect, the ionic liquid has hydrophilicity or amphiphilicity.

[0035] In the third aspect of the present invention, for example, in the separation functional layer of the first or second aspect, the ionic liquid includes at least one selected from the group consisting of 1-ethyl-3-methylimidazolium dicyanamide and 1-ethyl-3-methylimidazolium tricyanomethane.

[0036] In a fourth aspect of the present invention, for example, in the separation functional layer according to any one of the first to third aspects, the polymer A has a hydroxyl group.

[0037] In the fifth aspect of the present invention, for example, in the separation functional layer of the fourth aspect, the polymer A is bonded to the polymer B via a hydrogen bond derived from the hydroxyl group.

[0038] In a sixth aspect of the present invention, for example, in the separation functional layer according to any one of the first to fifth aspects, the polymer A contains polyvinyl alcohol.

[0039] In a seventh aspect of the present invention, for example, in the separation functional layer according to any one of the first to sixth aspects, the polymer B has at least one selected from the group consisting of an amide group and an imide group.

[0040] In an eighth aspect of the present invention, for example, in the separation functional layer according to any one of the first to seventh aspects, the polymer B is linear.

[0041] In a ninth aspect of the present invention, for example, in the separation functional layer according to any one of the first to eighth aspects, the polymer B comprises polyvinyl pyrrolidone.

[0042] In the tenth aspect of the present invention, for example, the content of the ionic liquid in the separation functional layer of any one of the first to ninth aspects is 60 wt% (weight %) or more.

[0043] In the eleventh aspect of the present invention, for example, the thickness of the separation functional layer according to any one of the first to tenth aspects is 100 μm or less.

[0044] In the twelfth aspect of the present invention, for example, the separation functional layer according to any one of the first to eleventh aspects has a breaking strength of 100 kPa or more.

[0045] In the thirteenth aspect of the present invention, for example, in the separation functional layer of any one of the first to twelfth aspects, when a mixed gas of carbon dioxide and hydrogen is supplied to a space adjacent to one surface of the separation functional layer and a space adjacent to the other surface of the separation functional layer is depressurized, the permeability coefficient of carbon dioxide permeating the separation functional layer is 100 barrers or more.

[0046] In which, the concentration of the above-mentioned carbon dioxide in the above-mentioned mixed gas is 50 vol% under standard conditions, the temperature of the above-mentioned mixed gas supplied to the space adjacent to the above-mentioned surface on one side is 30°C and the pressure is 0.1 MPa, and the space adjacent to the above-mentioned surface on the other side is depressurized in such a manner that the pressure in the space is reduced by 0.1 MPa relative to the atmospheric pressure in the measurement environment.

[0047] In a fourteenth aspect of the present invention, for example, the separation functional layer according to any one of the first to thirteenth aspects is used to separate the acid gas from a mixed gas containing the acid gas.

[0048] A separation membrane according to a fifteenth aspect of the present invention comprises:

[0049] The separation functional layer according to any one of the first to fourteenth aspects; and

[0050] A porous support that supports the separation functional layer.

[0051] The separation membrane according to the sixteenth aspect of the present invention comprises:

[0052] Separating functional layers; and

[0053] a porous support supporting the separation functional layer,

[0054] The separation functional layer comprises an ionic liquid and a hydrophilic polymer A that forms a crystal structure in the ionic liquid.

[0055] Hereinafter, the present invention will be described in detail, but the following description is not intended to limit the present invention to specific embodiments.

[0056] <Embodiment of Separation Functional Layer>

[0057] Figure 1 This is a cross-sectional view schematically illustrating the separation functional layer 1 of this embodiment. The separation functional layer 1 includes an ionic liquid L, a hydrophilic polymer A that forms a crystal structure in the ionic liquid L, and a polymer B different from polymer A. In the separation functional layer 1, the ionic liquid L is present in the space between polymers A and B, for example, and fills this space. The separation functional layer 1 is typically an ion gel membrane containing the ionic liquid L. In this specification, an ionic liquid refers to a salt (ionic compound) that is liquid at 25°C.

[0058] Figure 1 The separation functional layer 1 can function as a self-supporting membrane (single-layer membrane). The separation functional layer 1 can preferentially permeate the acidic gas contained in the mixed gas.

[0059] (ionic liquid)

[0060] The ionic liquid L contained in the separation functional layer 1 contains, for example, at least one ion selected from the group consisting of imidazolium ions, pyridinium ions, ammonium ions, and phosphonium ions, preferably imidazolium ions. These ions contain, for example, a substituent having 1 or more carbon atoms.

[0061] Examples of the substituent having 1 or more carbon atoms include alkyl groups having 1 to 20 carbon atoms, cycloalkyl groups having 3 to 14 carbon atoms, and aryl groups having 6 to 20 carbon atoms. These may be further substituted with a hydroxyl group, a cyano group, an amino group, or a monovalent ether group (e.g., a hydroxyalkyl group having 1 to 20 carbon atoms). Examples of the ether group include polyalkylene glycol groups such as polyethylene glycol.

[0062] Examples of the alkyl group having 1 to 20 carbon atoms include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, isopropyl, sec-butyl, isobutyl, 1-methylbutyl, 1-ethylpropyl, 2-methylbutyl, isopentyl, neopentyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, tert-pentyl, 2-ethylhexyl, and 1,5-dimethylhexyl. These groups may be further substituted with a hydroxyl group, a cyano group, an amino group, a monovalent ether group, or the like.

[0063] The above-mentioned alkyl groups may be substituted with cycloalkyl groups. The number of carbon atoms of the alkyl group substituted with cycloalkyl groups is, for example, 1 or more and 20 or less. Examples of the alkyl group substituted with cycloalkyl groups include cyclopropylmethyl, cyclobutylmethyl, cyclohexylmethyl, and cyclohexylpropyl groups, which may be further substituted with hydroxyl groups, cyano groups, amino groups, monovalent ether groups, and the like.

[0064] Examples of the cycloalkyl group having 3 to 14 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecyl, norbornyl, bornyl, and adamantyl groups, which may be further substituted with hydroxyl, cyano, amino, monovalent ether groups, and the like.

[0065] Examples of the aryl group having 6 to 20 carbon atoms include phenyl, tolyl, xylyl, mesityl, methoxyphenyl, naphthyl, and benzyl groups, which may be further substituted with hydroxyl, cyano, amino, or monovalent ether groups.

[0066] In the present embodiment, the ionic liquid L preferably contains an imidazolium ion represented by the following formula (1).

[0067] [Chemical Formula 1]

[0068]

[0069] In formula (1), R 1 ~R 5 Each independently represents a hydrogen atom or the above-mentioned substituent having 1 or more carbon atoms. 1 It is preferably a substituent having 1 or more carbon atoms, more preferably an alkyl group having 1 or more and 20 or less carbon atoms, further preferably an alkyl group having 2 or more and 10 or less carbon atoms, and particularly preferably an ethyl group or an n-butyl group. 3 It is preferably a substituent having 1 or more carbon atoms, more preferably an alkyl group having 1 or more and 20 or less carbon atoms, further preferably an alkyl group having 1 or more and 10 or less carbon atoms, and particularly preferably a methyl group. 2 、R 4 and R 5 Each is preferably a hydrogen atom.

[0070] In the ionic liquid L, the above-mentioned ions may form salts with counter anions. Examples of the counter anions include alkyl sulfate, toluenesulfonate, methanesulfonate, trifluoromethanesulfonate, toluenesulfonate, acetate, bis(fluorosulfonyl)imide, bis(trifluoromethanesulfonyl)imide, thiocyanate, dicyanamide, tricyanomethane anion (tricyanomethanide), tetracyanoborate, hexafluorophosphate, tetrafluoroborate, and halide ions, with dicyanamide, tetrafluoroborate, and tricyanomethane anion being preferred.

[0071] Specific examples of the ionic liquid L include 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, and 1-butyl-3-methylimidazolium tetrachloroferrate. Salt, 1-butyl-3-methylimidazolium iodide, 1-butyl-2,3-dimethylimidazolium chloride, 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium trifluoro(trifluoromethyl)borate, 1-butyl-3-methylimidazolium tribromide, 1,3-bis(mesityl) Imidazolium chloride, 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride, 1,3-diisopropylimidazolium tetrafluoroborate, 1,3-di-tert-butylimidazolium tetrafluoroborate, 1,3-dicyclohexylimidazolium tetrafluoroborate, 1,3-dicyclohexylimidazolium chloride, 1,2-dimethyl-3-propylimidazolium iodide, 1-hexyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium bromide, 1-methyl

[0014] Examples of the present invention include 1-methyl-3-propylimidazolium iodide, 1-methyl-3-n-octylimidazolium bromide, 1-methyl-3-n-octylimidazolium chloride, 1-methyl-3-n-octylimidazolium hexafluorophosphate, 1-methyl-3-[6-(methylsulfinyl)hexyl]imidazolium p-toluenesulfonate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tricyanomethane, 1-ethyl-3-methylimidazolium tetracyanoborate, and 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0072] The ionic liquid L contained in the separation functional layer 1 is preferably hydrophilic or amphiphilic. Combining the hydrophilic or amphiphilic ionic liquid L with the hydrophilic polymer A tends to improve the mechanical strength of the separation functional layer 1.

[0073] In this specification, the phrase "the ionic liquid is hydrophilic" means that the ionic liquid dissolved in water in the following Test 1, and that the ionic liquid did not dissolve in isopropyl alcohol (IPA) in the following Test 2, and phase separation was confirmed. The phrase "the ionic liquid is amphiphilic" means that the ionic liquid dissolved in water in the following Test 1, and that the ionic liquid dissolved in IPA in the following Test 2.

[0074] Test 1: At room temperature (25°C), add 0.5g of ionic liquid to a container such as a microtube. Add 0.5g of water (ion-exchanged water) to the container. Seal the container and shake it approximately 10 times. Let the container stand for 1 minute, and visually inspect to confirm dissolution of the ionic liquid in the water.

[0075] Test 2: At room temperature, add 0.5g of the ionic liquid to a container such as a microtube. Add 0.5g of IPA to the container. Seal the container and shake it manually approximately 10 times. Let the container stand for 1 minute, and visually inspect to confirm that the ionic liquid has dissolved in the IPA.

[0076] In this specification, in Test 1, when the ionic liquid does not dissolve in water and phase separation is confirmed, it is determined that the ionic liquid has hydrophobicity.

[0077] Examples of the hydrophilic or amphiphilic ionic liquid L include 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) and 1-ethyl-3-methylimidazolium tricyanomethane ([EMIM][TCM]). The ionic liquid L preferably contains at least one selected from the group consisting of [EMIM][DCA] and [EMIM][TCM], and more preferably contains [EMIM][DCA]. [EMIM][DCA] is suitable for improving the permeability of acidic gases through the separation functional layer 1.

[0078] From the perspective of gas separation performance, the content of ionic liquid L in the separation functional layer 1 is, for example, 5 wt% or greater, but may also be 30 wt% or greater, 50 wt% or greater, 60 wt% or greater, 70 wt% or greater, or even 80 wt% or greater. The separation functional layer 1 tends to have higher separation performance as the content of ionic liquid L increases. The upper limit of the content of ionic liquid L is not particularly limited, but may be, for example, 95 wt% or less, or 90 wt% or less. A content of ionic liquid L of 95 wt% or less tends to facilitate the self-sustaining performance of the separation functional layer 1.

[0079] In the separation functional layer 1 , the weight ratio of the ionic liquid L to the polymers (polymers A and B) is not particularly limited, and is, for example, 50 / 50 to 90 / 10.

[0080] (Polymer A)

[0081] As described above, polymer A forms a crystalline structure in the ionic liquid L. In other words, polymer A crystallizes in the ionic liquid L. In the ionic liquid L, polymer A may be crystallized as a whole, but preferably polymer A is partially crystallized. As an example, in the ionic liquid L, a portion of polymer A may be crystallized, and the other portion of polymer A may be swollen by the ionic liquid L. The so-called "polymer A forms a crystalline structure in the ionic liquid L" means that when an X-ray diffraction (XRD) measurement is performed on a sample containing polymer A and ionic liquid L at room temperature (25°C), a peak originating from the crystal structure of polymer A can be confirmed. The sample used in the XRD measurement is prepared as follows: 1.3 g of polymer A is dissolved in a mixed liquid containing 5 g of ionic liquid L and 10.24 g of water, and the resulting solution is dried at 30°C for 24 hours, and then further dried at 70°C for 24 hours. The drying of the solution can be carried out, for example, using a small dish made of polytetrafluoroethylene (PTFE).

[0082] The crystallization of polymer A is caused, for example, by physical crosslinking of multiple polymer A molecules in ionic liquid L. Physical crosslinking refers to the aggregation of multiple polymer molecules through interactions such as intermolecular forces. It can be said that polymer A has physical crosslinking points in ionic liquid L. It should be noted that polymer A does not have, for example, a chemical crosslinking structure. Chemical crosslinking refers to the bonding of multiple polymer molecules to each other via covalent bonds.

[0083] Furthermore, in this embodiment, polymer A is hydrophilic. In this specification, "a polymer is hydrophilic" means that the distance Ra between the Hansen solubility parameter of the polymer and the Hansen solubility parameter of H2O is less than 19 MPa. 1 / 2 .

[0084] The Hansen solubility parameter is a parameter derived from the Hildebrand solubility parameter, which is divided into three components: the dispersion term δD, the polarization term δP, and the hydrogen bonding term δH. Details of the Hansen solubility parameter are disclosed in "Hansen Solubility Parameters; A Users Handbook (CRC Press, 2007)." The Hansen solubility parameter can be calculated using well-known software such as HSPiP.

[0085] The distance Ra between the Hansen solubility parameter of the polymer and the Hansen solubility parameter of H2O can be calculated by the following formula (i). In formula (i), δD1, δP1 and δH1 are the dispersion terms of the polymer (MPa) 1 / 2 ), polarization term (MPa 1 / 2 ) and hydrogen bonding terms (MPa 1 / 2). δD2, δP2 and δH2 are the dispersion terms of H2O (18.1MPa 1 / 2 ), polarization term (17.1MPa 1 / 2 ) and hydrogen bonding terms (16.9MPa 1 / 2 ).

[0086] Ra={4×(δD1-δD2) 2 +(δP1-δP2) 2 +(δH1-δH2) 2} 1 / 2 (i)

[0087] The distance Ra1 between the Hansen solubility parameter of polymer A and the Hansen solubility parameter of H2O is preferably 18 MPa 1 / 2 Below, can also be 17MPa 1 / 2 Below, 16MPa 1 / 2 Below, 15MPa 1 / 2 Below, 14MPa 1 / 2 Below, 13MPa 1 / 2 Below, 12MPa 1 / 2 Below, 11MPa 1 / 2 Below, 10MPa 1 / 2 Below, and further can be 9MPa 1 / 2 The lower limit of the distance Ra1 is not particularly limited, but is, for example, 3 MPa. 1 / 2 Above, 5MPa is also possible 1 / 2 above.

[0088] Polymer A can be a homopolymer or a copolymer. As copolymers, random copolymers, block copolymers, alternating copolymers, graft copolymers, etc. can be mentioned. Polymer A preferably does not have a branched structure and is linear. However, polymer A may also have a branched structure. It should be noted that, in this specification, the so-called "polymer is linear" refers to that the structural units contained in the polymer are not branched but arranged in a straight line.

[0089] Polymer A preferably has a polar group such as a hydroxyl group. As an example, polymer A has hydrophilicity due to the polar group. In the separation functional layer 1, polymer A preferably has a hydroxyl group and is bonded to polymer B via a hydrogen bond derived from the hydroxyl group. In this case, the separation functional layer 1 tends to have high mechanical strength.

[0090] Polymer A preferably comprises polyvinyl alcohol (PVA). PVA can form a crystal structure in an ionic liquid L such as [EMIM][DCA], [EMIM][TCM]. Furthermore, the distance Ra between the Hansen solubility parameter of PVA and the Hansen solubility parameter of H2O is 8.1 MPa. 1 / 2 It can be said that PVA is hydrophilic.

[0091] The saponification degree of PVA as polymer A is preferably 70 mol% or more, and may be 75 mol% or more, 80 mol% or more, or even 85 mol% or more. The saponification degree of PVA may be 90 mol% or more depending on the circumstances. The upper limit of the saponification degree of PVA is not particularly limited, and may be, for example, 99 mol% or less, 95 mol% or less, or 85 mol% or less depending on the circumstances. When PVA with a low saponification degree is used as polymer A, there is a tendency for leakage of the ionic liquid L in the separation functional layer 1 to be further suppressed. The saponification degree of PVA can be measured in accordance with the provisions of Japanese Industrial Standard (JIS) K6726:1994.

[0092] The weight average molecular weight of polymer A is preferably more than 10,000, or more than 30,000, or more than 50,000. The weight average molecular weight of polymer A may be more than 130,000 depending on the circumstances. The higher the weight average molecular weight of polymer A, the more the mechanical strength of the separation functional layer 1 tends to be improved. The upper limit of the weight average molecular weight of polymer A is not particularly limited, and may be, for example, less than 300,000, or less than 200,000. About the weight average molecular weight of polymer A, for example, the molecular weight distribution of polymer A can be determined by a gel permeation chromatograph (GPC) having a differential refractive index detector (RID), and the obtained chromatogram (chart) is calculated using a calibration curve based on standard polystyrene.

[0093] The content of polymer A in the separation functional layer 1 is not particularly limited, and may be, for example, 1 wt% or greater, 5 wt% or greater, 10 wt% or greater, 15 wt% or greater, or even 20 wt% or greater. A higher content of polymer A tends to increase the strength of the separation functional layer 1. The upper limit of the content of polymer A is not particularly limited, and may be, for example, 30 wt% or less, and may be 20 wt% or less depending on circumstances.

[0094] (Polymer B)

[0095] As described above, polymer B is different from polymer A. Specifically, polymer A and polymer B have different compositions. For example, polymer B does not form a crystal structure in ionic liquid L. In other words, polymer B has higher solubility in ionic liquid L than polymer A.

[0096] The polymer B is preferably hydrophilic. However, the polymer B may not be hydrophilic. The distance Ra2 between the Hansen solubility parameter of the polymer B and the Hansen solubility parameter of H2O is, for example, 30 MPa. 1 / 2 Below, preferably less than 19MPa 1 / 2 The lower limit of the distance Ra2 is not particularly limited, for example, 3 MPa 1 / 2 Above, 5MPa is also possible 1 / 2 above.

[0097] When polymer A has a hydroxyl group, polymer B preferably has a functional group that can form a hydrogen bond with the hydroxyl group. As such a functional group, amide groups, imide groups, etc. can be enumerated. Polymer B preferably has at least one selected from the group consisting of amide groups and imide groups, more preferably has amide groups. As an example, polymer B can have a ring structure (lactam structure) comprising an amide group.

[0098] In a preferred embodiment of the present invention, polymer B does not have a chemically cross-linked structure. The polymer B may be a homopolymer or a copolymer. Examples of the copolymer include the copolymers described above for polymer A. The polymer B preferably does not have a branched structure and is linear. Examples of the polymer B that does not have a chemically cross-linked structure include polyvinyl pyrrolidone (PVP).

[0099] In another preferred embodiment of the present invention, polymer B has a chemically crosslinked structure. In other words, polymer B is a crosslinked prepolymer. The embodiment in which polymer B is a crosslinked prepolymer is described in detail below.

[0100] [Prepolymer]

[0101] The prepolymer used to form polymer B has a polymer chain comprising structural units derived from monomers. The polymer chain is formed, for example, by free radical polymerization of the monomers. In the crosslinked prepolymer, multiple polymer chains are crosslinked via crosslinking chains. The polymer chains and crosslinking chains are preferably bonded via at least one bond selected from the group consisting of a hydrazone bond, an amide bond, an imide bond, a urethane bond, an ether bond, and an ester bond.

[0102] The prepolymer can be a homopolymer, a copolymer, or a mixture thereof. As a copolymer, the copolymer described above for polymer A can be cited. As an example, the prepolymer can include a (meth)acrylic acid polymer. A (meth)acrylic acid polymer is a polymer having a structural unit U derived from a monomer b containing a (meth)acryloyl group and / or a (meth)acrylamide group. A (meth)acrylic acid polymer, for example, has a structural unit U derived from monomer b as a main component, or can be substantially composed only of structural unit U. Wherein, the (meth)acrylic acid polymer can also include other structural units other than structural unit U. It should be noted that, in this specification, "(meth)acrylic acid / acyl-" refers to acrylic acid / acyl- and / or methacrylic acid / acyl-. Generally, when the prepolymer includes a (meth)acrylic acid polymer, its cross-linked product can also be said to be a (meth)acrylic acid polymer. That is, polymer B can also be a (meth)acrylic acid polymer.

[0103] The prepolymer is preferably a polymer having crosslinking points capable of reacting with a crosslinking agent described below. The crosslinking points are located at any one of the ends, main chains, and side chains of the prepolymer. From the perspective of obtaining a highly three-dimensionally crosslinked product, the crosslinking points are preferably located at the side chains of the prepolymer.

[0104] The prepolymer preferably has functional groups, particularly polar groups, that function as crosslinking points. A polar group refers to an atomic group containing atoms other than carbon and hydrogen, typically an atomic group containing at least one member selected from the group consisting of nitrogen and oxygen atoms. The presence of polar groups in the prepolymer facilitates the formation of a highly three-dimensionally crosslinked product. Crosslinked prepolymers containing polar groups also tend to stably retain ionic liquids.

[0105] Examples of polar groups include amino groups, amide groups, imide groups, morpholino groups, carboxyl groups, ester groups, hydroxyl groups, and ether groups. Amino groups include not only primary amino groups but also secondary and tertiary amino groups substituted with alkyl groups. Examples of amide groups include (meth)acrylamide groups, acetamide groups, and pyrrolidone groups. Examples of ether groups include polyalkyl ether groups such as polyethylene glycol groups and polypropylene glycol groups; epoxy groups; and vinyloxy groups.

[0106] The prepolymer preferably contains a structural unit derived from a polar group-containing monomer. The polar group-containing monomer preferably contains at least one selected from the group consisting of an amide group-containing monomer, an imide group-containing monomer, an amino group-containing monomer, an epoxy group-containing monomer, an vinyloxy group-containing monomer, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer, and more preferably contains at least one selected from the group consisting of an amide group-containing monomer, an imide group-containing monomer, an vinyloxy group-containing monomer, and a carboxyl group-containing monomer.

[0107] Examples of the amide group-containing monomer include acrylamide, methacrylamide, N-vinyl pyrrolidone, N,N-diallylacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, and diacetoneacrylamide.

[0108] Examples of the imide group-containing monomer include N-(meth)acryloyloxysuccinimide, N-(meth)acryloyloxymethylenesuccinimide, and N-(meth)acryloyloxyethylenesuccinimide.

[0109] Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0110] Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3-ethyloxetan-3-yl (meth)acrylate, and allyl glycidyl ether.

[0111] Examples of the vinyloxy group-containing monomer include 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, 2-vinyloxyethyl (meth)acrylate, and 4-vinyloxypropyl (meth)acrylate.

[0112] Examples of the carboxyl group-containing monomer include (meth)acrylic acid and the like.

[0113] Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth)acrylate and the like.

[0114] Polar group-containing monomers can be used alone or as a mixture of two or more. For example, N,N'-methylenebisacrylamide, diacetone acrylamide (DAAm), N-acryloyloxysuccinimide (NSA), etc. can be copolymerized with N-methylacrylamide or N,N-dimethylacrylamide (DMAAm) to form a prepolymer. As an example, the prepolymer can contain structural units derived from N,N-dimethylacrylamide and structural units derived from N-acryloyloxysuccinimide, or can be a copolymer of N,N-dimethylacrylamide and N-acryloyloxysuccinimide.

[0115] The prepolymer may contain structural units derived from monomers other than the polar group-containing monomer. Examples of such other monomers include alkyl (meth)acrylates such as methyl (meth)acrylate and n-butyl (meth)acrylate. As one example, the prepolymer may contain structural units derived from n-butyl (meth)acrylate and structural units derived from (meth)acrylic acid, or may be a copolymer of n-butyl (meth)acrylate and (meth)acrylic acid.

[0116] For example, polymer B includes at least one structure selected from the group consisting of a structure derived from a copolymer of N,N-dimethylacrylamide and N-acryloyloxysuccinimide and a structure derived from a copolymer of n-butyl (meth)acrylate and (meth)acrylic acid, and preferably includes a structure derived from a copolymer of N,N-dimethylacrylamide and N-acryloyloxysuccinimide.

[0117] The prepolymer may contain a structural unit that functions as a crosslinking agent, for example, a structural unit derived from a multifunctional (meth)acrylate. A prepolymer having such a structural unit can undergo self-crosslinking. A multifunctional (meth)acrylate refers to a monomer having two or more (meth)acryloyl groups in one molecule. Examples of multifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexaacrylate.

[0118] From the perspective of the mechanical strength of the separation functional layer 1, the weight average molecular weight (Mw) of the prepolymer is preferably 2,500 or greater, more preferably 5,000 or greater, and even more preferably 10,000 or greater. The upper limit of the weight average molecular weight of the prepolymer is not particularly limited, but is, for example, 2.5 million, preferably 1 million, and more preferably 750,000. The weight average molecular weight of the prepolymer can be determined using the method described above for the cross-linked product.

[0119] The prepolymer is obtained, for example, by polymerizing a monomer having a functional group that functions as a crosslinking point in the presence of a polymerization initiator. From the perspective of improving the flexibility and stretchability of the separation functional layer 1, the polymerization of the monomer is preferably free radical polymerization. Free radical polymerization may be thermal polymerization or photopolymerization (e.g., polymerization performed by ultraviolet irradiation).

[0120] As polymerization initiators, azo polymerization initiators, peroxide initiators, redox initiators based on a combination of a peroxide and a reducing agent, substituted ethane initiators, etc. can be used. When photopolymerization is performed, various photopolymerization initiators can be used. In photopolymerization, photosensitizers such as 2-oxoglutaric acid can be used.

[0121] Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, dimethyl-2,2'-azobis(2-methylpropionate), 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride.

[0122] Examples of the peroxide-based initiator include persulfates such as potassium persulfate and ammonium persulfate; dibenzoyl peroxide, t-butyl peroxymaleate, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, and hydrogen peroxide.

[0123] Examples of the redox initiator include combinations of peroxides and ascorbic acid (such as combinations of aqueous hydrogen peroxide and ascorbic acid), combinations of peroxides and iron (II) salts (such as combinations of aqueous hydrogen peroxide and iron (II) salts), and combinations of persulfates and sodium bisulfite.

[0124] Examples of the substituted ethane initiator include phenyl-substituted ethane.

[0125] Examples of the photopolymerization initiator include acetophenone-based, ketal-based, benzophenone-based, benzoin-based, benzoyl-based, xanthone-based, active halogen compounds (triazine-based, halomethyloxadiazole-based, coumarin-based), acridine-based, biimidazole-based, and oxime ester-based.

[0126] Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, p-dimethylaminoacetophenone, 4'-isopropyl-2-hydroxy-2-methyl-propiophenone, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 2-tolyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone.

[0127] Examples of the ketal-based photopolymerization initiator include benzyl dimethyl ketal and benzyl-β-methoxyethyl acetal.

[0128] Examples of the benzophenone-based photopolymerization initiator include benzophenone, 4,4′-(bisdimethylamino)benzophenone, 4,4′-(bisdiethylamino)benzophenone, and 4,4′-dichlorobenzophenone.

[0129] Examples of the benzoin-based or benzoyl-based photopolymerization initiator include benzoin isopropyl ether, benzoin isobutyl ether, benzoin methyl ether, and methyl o-benzoylbenzoate.

[0130] Examples of the xanthone-based photopolymerization initiator include diethylthioxanthone, diisopropylthioxanthone, monoisopropylthioxanthone, and chlorothioxanthone.

[0131] Examples of the triazine-based photopolymerization initiator include 2,4-bis(trichloromethyl)-6-p-methoxyphenyl-s-triazine, 2,4-bis(trichloromethyl)-6-p-methoxyphenyl-s-triazine, 2,4-bis(trichloromethyl)-6-p-methoxyphenyl-s-triazine, 2,4-bis(trichloromethyl)-6-(1-p-dimethylaminophenyl)-1,3-butadienyl-s-triazine, 2,4-bis(trichloromethyl)-6-biphenyl-s-triazine, 2,4-bis(trichloromethyl)-6-(p-methylbiphenyl)-s-triazine, and p-hydroxyethoxyphenyl-2,6- Bis(trichloromethyl)-s-triazine, methoxyphenylvinyl-2,6-bis(trichloromethyl)-s-triazine, 3,4-dimethoxyphenylvinyl-2,6-bis(trichloromethyl)-s-triazine, 4-benzoxol-2,6-bis(trichloromethyl)-s-triazine, 4-(o-bromo-p-N,N-(diethoxycarbonylamino)-phenyl)-2,6-bis(chloromethyl)-s-triazine, 4-(p-N,N-diethoxycarbonylamino)-phenyl)-2,6-bis(chloromethyl)-s-triazine, etc.

[0132] Examples of the halomethyloxadiazole-based photopolymerization initiator include 2-trichloromethyl-5-phenylvinyl-1,3,4-oxadiazole, 2-trichloromethyl-5-(cyanostyryl)-1,3,4-oxadiazole, 2-trichloromethyl-5-(naphthalen-1-yl)-1,3,4-oxadiazole, and 2-trichloromethyl-5-(4-phenylvinyl)phenylvinyl-1,3,4-oxadiazole.

[0133] Examples of the coumarin-based photopolymerization initiator include 3-methyl-5-amino-((s-triazin-2-yl)amino)-3-phenylcoumarin, 3-chloro-5-diethylamino-((s-triazin-2-yl)amino)-3-phenylcoumarin, and 3-butyl-5-dimethylamino-((s-triazin-2-yl)amino)-3-phenylcoumarin.

[0134] Examples of the acridine-based photopolymerization initiator include 9-phenylacridine and 1,7-bis(9-acridinyl)heptane.

[0135] Examples of the biimidazole photopolymerization initiator include lophine dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazolyl dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazolyl dimer, and 2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazolyl dimer; 2-mercaptobenzimidazole; and 2,2'-dibenzothiazole disulfide.

[0136] Examples of the oxime ester photopolymerization initiator include 1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyl oxime)], and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(O-acetyl oxime).

[0137] The polymerization initiator can be used alone or in combination of two or more. The polymerization initiator is preferably 2,2'-azobisisobutyronitrile. The amount of the polymerization initiator is not particularly limited, but is, for example, 0.1 parts by mass or more, preferably 0.3 parts by mass or more, relative to 100 parts by mass of the monomer. The amount of the polymerization initiator is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, relative to 100 parts by mass of the monomer.

[0138] The synthesis of the prepolymer can also be carried out in the presence of a solvent. The solvent is preferably an organic solvent, for example, ketone organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester organic solvents such as methyl acetate, ethyl acetate, and butyl acetate; polar solvents such as dimethylformamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone; alcohol organic solvents such as methanol, ethanol, and isopropanol; aromatic hydrocarbon organic solvents such as toluene and xylene; aliphatic / alicyclic hydrocarbon organic solvents such as n-hexane, cyclohexane, and methylcyclohexane; cellosolve organic solvents such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; ether organic solvents such as tetrahydrofuran and dioxane; and carbitol organic solvents such as n-butyl carbitol and isoamyl carbitol. The organic solvent can be used alone or in combination of two or more.

[0139] The method for synthesizing the prepolymer is not particularly limited, and known methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, atom transfer radical polymerization (ATRP), and reversible addition fragmentation chain transfer polymerization (RAFT) can be used. From the perspective of operability, solution polymerization is preferred. For example, the prepolymer can be synthesized by photopolymerization in the presence of a solvent or by photopolymerization, particularly UV polymerization, in the absence of a solvent.

[0140] Examples of the ATRP initiator include halogenated alkyl compounds such as tert-butyl 2-bromoisobutyrate, methyl 2-bromoisobutyrate, 2-bromoisobutyryl bromide, ethyl 2-bromoisobutyrate, 2-hydroxyethyl 2-bromoisobutyrate, ethylenebis(2-bromoisobutyrate), 1-tris(hydroxymethyl)ethane, and pentaerythritol tetrakis(2-bromoisobutyrate).

[0141] Examples of the ATRP catalyst ligand include 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 4,4'-di-tert-butyl-2,2'-bipyridine, 4,4'-dinonyl-2,2'-bipyridine, N-butyl-2-pyridylmethanimine, N-octyl-2-pyridylmethanimine, N-dodecyl-N-(2-pyridylmethylene)amine, N-octadecyl-N-(2-pyridylmethylene)amine, and N,N,N',N",N"-pentamethyldiethylenetriamine.

[0142] Examples of the metal salt for ATRP catalysts include copper (I) chloride, copper (II) chloride, copper (I) bromide, copper (II) bromide, titanium (II) chloride, titanium (III) chloride, titanium (IV) chloride, titanium (IV) bromide, and iron (II) chloride.

[0143] Examples of the RAFT agent include cyanomethyl-dodecyl trithiocarbonate, 2-(dodecylthiothiocarbonylthio)-2-methylpropionic acid, and 2-cyano-2-propyldodecyl trithiocarbonate.

[0144] When the prepolymer is synthesized by thermal polymerization, the polymerization temperature is, for example, 25 to 80° C., preferably 30 to 70° C., more preferably 40 to 60° C. When the prepolymer is synthesized by photopolymerization, the polymerization temperature is preferably 10 to 60° C., more preferably 20 to 50° C., further preferably 20 to 40° C.

[0145] When the prepolymer is synthesized by thermal polymerization, the polymerization time is, for example, 1 to 100 hours, preferably 20 to 80 hours, more preferably 30 to 70 hours, and even more preferably 40 to 60 hours. When the prepolymer is synthesized by photopolymerization, the polymerization time is, for example, 0.1 to 100 hours, preferably 1 to 70 hours, more preferably 5 to 40 hours, and even more preferably 10 to 30 hours.

[0146] When synthesizing a prepolymer by photopolymerization, the wavelength of the ultraviolet light used is not particularly limited as long as it can cause free radical polymerization of the monomer. For example, it can be selected from the wavelength range of 200 to 550 nm, preferably 250 to 500 nm, and more preferably 300 to 400 nm. The intensity of the ultraviolet light is not particularly limited. Considering the polymerization time and safety, it is, for example, 1 to 3000 mJ / (cm 2 ·s), preferably 10 to 2000 mJ / (cm 2 ·s).

[0147] [Crosslinking agent]

[0148] Polymer B can be formed by the reaction of a prepolymer and a cross-linking agent, for example. Wherein, in the case where the prepolymer includes a structural unit that functions as a cross-linking agent, polymer B can be formed by the reaction of prepolymers with each other. The cross-linking agent can be appropriately selected according to the composition of the prepolymer. As a cross-linking agent, for example, polyfunctional (meth) acrylate, hydrazide cross-linking agent, amine cross-linking agent, isocyanate cross-linking agent, epoxy cross-linking agent, aziridine cross-linking agent, melamine cross-linking agent, metal chelate cross-linking agent, metal salt cross-linking agent, peroxide cross-linking agent, oxazoline cross-linking agent, urea cross-linking agent, carbodiimide cross-linking agent, coupling agent cross-linking agent (such as silane coupling agent) etc. can be cited. The cross-linking agent can be used as one or in combination of two or more. Polymer B is preferably a cross-linked product based on at least one cross-linking agent selected from the group consisting of an amine cross-linking agent and an epoxy cross-linking agent, more preferably a cross-linked product based on an amine cross-linking agent, more preferably a reactant of a prepolymer and an amine cross-linking agent in detail.

[0149] Examples of the polyfunctional (meth)acrylate include the polyfunctional (meth)acrylates described above for the prepolymer.

[0150] Examples of the hydrazide crosslinking agent include polyhydrazides such as isophthalic acid dihydrazide, terephthalic acid dihydrazide, phthalic acid dihydrazide, 2,6-naphthalene dicarboxylic acid dihydrazide, naphthoic acid dihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutamic acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, tridecanedioic acid dihydrazide, dodecanedioic acid dihydrazide, acetone dicarboxylic acid dihydrazide, fumaric acid dihydrazide, maleic acid dihydrazide, itaconic acid dihydrazide, trimellitic acid dihydrazide, 1,3,5-benzenetricarboxylic acid dihydrazide, aconitic acid dihydrazide, and pyromellitic acid dihydrazide. Adipic acid dihydrazide is preferred.

[0151] Examples of the amine crosslinking agent include aliphatic polyamines such as hexamethylenediamine, 1,12-dodecanediamine, hexamethylenediamine carbamate, N,N-dicinnamylene-1,6-hexanediamine, tetramethylenepentamine, and hexamethylenediamine cinnamaldehyde adducts; 4,4-methylenedianiline, m-phenylenediamine, 4,4-diaminodiphenyl ether, 3,4-diaminodiphenyl ether, 4,4-(m-phenylenediisopropylidene)diphenylamine, 4,4-(p-phenylenediisopropylidene)diphenylamine, and the like. Aromatic polyamines such as phenylenediisopropylidene)diphenylamine, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4-diaminobenzanilide, 4,4-bis(4-aminophenoxy)biphenyl, m-phenylenediamine, p-phenylenediamine, and 1,3,5-phenyltriamine; diamines having a polyether in the main chain such as polyethylene glycol diamine, polypropylene glycol diamine, and diethylene glycol bis(3-aminopropyl) ether, preferably diethylene glycol bis(3-aminopropyl) ether.

[0152] Examples of the isocyanate crosslinking agent include aliphatic polyisocyanates such as 1,6-hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate, cyclohexyl diisocyanate, hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate; 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-toluene diisocyanate, 2,6'-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-toluene diisocyanate, 2,6'-toluene diisocyanate, 4,4'-toluene ... - Aromatic polyisocyanates such as diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0153] As the isocyanate crosslinking agent, dimers, trimers, reaction products or polymers of the exemplified isocyanate compounds (for example, dimers and trimers of diphenylmethane diisocyanate, reaction products of trimethylolpropane and toluene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate) etc. can also be used. As the isocyanate crosslinking agent, the reaction product of trimethylolpropane and toluene diisocyanate is preferred.

[0154] Examples of the epoxy crosslinking agent include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidyl aniline, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, Epoxy compounds having two or more or three or more epoxy groups in one molecule, such as diglycidyl phthalate, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol S diglycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)benzene, 1,3-bis(N,N-diglycidylaminomethyl)toluene, 1,3,5-triglycidyl isocyanurate, N,N,N',N'-tetraglycidyl-m-xylenediamine, glycerol triglycidyl ether, and trimethylolpropane glycidyl ether, are preferred, with 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane being preferred.

[0155] It should be noted that polymer B may also be a (meth)acrylic acid-based polymer without a crosslinked structure. For example, polymer B may contain structural units derived from an alkyl (meth)acrylate such as methyl (meth)acrylate or n-butyl (meth)acrylate as a main component, or may be substantially composed solely of such structural units. Polymer B may also have the composition and structure described above for the prepolymer.

[0156] The weight average molecular weight of polymer B is, for example, 5,000 or more, preferably 10,000 or more, more preferably 20,000 or more, and further preferably 40,000 or more. The upper limit of the weight average molecular weight of polymer B is not particularly limited, and is, for example, 5,000,000, preferably 2,000,000, and more preferably 1,500,000. The weight average molecular weight of polymer B can be measured by the method described above for polymer A.

[0157] The content of polymer B in the separation functional layer 1 is not particularly limited, and may be, for example, 1 wt% or greater, 5 wt% or greater, 10 wt% or greater, or even 15 wt% or greater. A higher content of polymer B tends to improve the acid gas permeability of the separation functional layer 1. The upper limit of the polymer B content is not particularly limited, and may be, for example, 30 wt% or less, or 20 wt% or less. It should be noted that the separation functional layer 1 may not contain polymer B, depending on circumstances.

[0158] In the separation functional layer 1 , the weight ratio of polymer A to polymer B (A / B) is not particularly limited, and may be, for example, 20 / 80 to 80 / 20, 40 / 60 to 80 / 20, or 60 / 40 to 80 / 20.

[0159] (Other ingredients)

[0160] The separation functional layer 1 may further contain other components in addition to the ionic liquid L, the polymer A, and the polymer B. Examples of other components include surfactants and the like.

[0161] (Method for producing separation functional layer)

[0162] The method for producing the separation functional layer 1 includes, for example, at least one step selected from the group consisting of the following step (i) and step (ii).

[0163] Step (i): Drying the mixed liquid M1 containing the ionic liquid L, the polymer A, and the polymer B.

[0164] Step (ii): In a mixed solution M2 comprising the ionic liquid L, the polymer A, the prepolymer and the cross-linking agent, the prepolymer is reacted with the cross-linking agent to form the polymer B.

[0165] First, the production method including step (i) will be described. The production method including step (i) is suitable for producing the separation functional layer 1 including the polymer B having no chemically crosslinked structure.

[0166] The mixed liquid M1 further contains a solvent such as water. The concentration of the nonvolatile components (ionic liquid L, polymer A and polymer B) in the mixed liquid M1 is not particularly limited, and is, for example, 10 wt% to 90 wt%, or 20 wt% to 50 wt%.

[0167] In a preferred embodiment of the present invention, the separation functional layer 1 is produced by drying a coating film produced by applying the mixed solution M1 to a substrate. The substrate is typically a release liner. Examples of release liners include films containing resins, paper, and sheets containing metal materials such as aluminum and stainless steel. Sheets containing metal materials tend to have high heat resistance. From the perspective of excellent surface smoothness, the release liner is preferably a film containing resin. In the release liner, examples of polymers contained in the resin include polyolefins such as polyethylene, polypropylene, polybutene, polybutadiene, and polymethylpentene; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyvinyl chloride and vinyl chloride copolymers; polyurethanes; and ethylene-vinyl acetate copolymers. Polyesters are preferred, and polyethylene terephthalate is particularly preferred.

[0168] The surface of the release liner may be subjected to a release treatment. For example, the release treatment can be performed by applying a release agent to the surface of the release liner. Examples of release agents include silicone release agents, long-chain alkyl release agents, fluorine release agents, and molybdenum sulfide release agents. Release agents may be used alone or in combination of two or more. The release liner is preferably a polyethylene terephthalate (PET) film subjected to a release treatment.

[0169] The thickness of the release liner is not particularly limited, and is, for example, 5 to 100 μm, preferably 10 to 50 μm.

[0170] The method for applying the mixed liquid M1 to the substrate is not particularly limited, and for example, spin coating, dip coating, etc. can be used. The mixed liquid M1 can also be applied to the substrate using an applicator, a wire rod, etc. By applying the mixed liquid M1 to the substrate, a coating film is formed.

[0171] In another preferred embodiment of the present invention, the mixed liquid M1 is placed in a mold and then dried to produce the separation functional layer 1. The mold is typically a small dish made of PTFE.

[0172] The drying process of the mixed liquid M1 (specifically, the coating film produced by applying the mixed liquid M1 to a substrate, or the mixed liquid M1 disposed in a mold) can be performed, for example, by leaving the mixed liquid M1 at room temperature. However, the mixed liquid M1 can also be dried by heating the mixed liquid M1. The drying process time is, for example, 1 hour or more, or 5 hours or more. By peeling the separation functional layer 1 from the substrate or mold, the separation functional layer 1 that functions as a self-supporting film can be obtained.

[0173] Next, the production method including step (ii) will be described. According to the production method including step (ii), a separation functional layer 1 including the polymer B having a chemically crosslinked structure can be obtained.

[0174] The mixed liquid M2 has the same composition as the mixed liquid M1, except that it contains a prepolymer and a cross-linking agent instead of polymer B. For example, the separation functional layer 1 can be produced by applying the mixed liquid M2 to a substrate and then reacting the prepolymer and the cross-linking agent, or by placing the mixed liquid M2 in a mold and then reacting the prepolymer and the cross-linking agent. The substrate and mold described above can be used.

[0175] The reaction of the prepolymer and the cross-linking agent can be carried out, for example, by heat-treating the mixed liquid M2 (specifically, a coating film produced by applying the mixed liquid M2 to a substrate, or a mixed liquid M2 disposed in a mold). The temperature of the heat treatment is not particularly limited, and may be, for example, 30°C or higher, or 50°C to 110°C. The time of the heat treatment is, for example, 1 minute or more, or 5 minutes or more. By allowing the reaction of the prepolymer and the cross-linking agent to proceed, a polymer B having a cross-linked structure is formed. Thus, a separation functional layer 1 comprising the ionic liquid L, the polymer A, and the polymer B is formed.

[0176] (Physical properties of separation functional layer, etc.)

[0177] The thickness of the separation functional layer 1 is, for example, 500 μm or less, preferably 300 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, 15 μm or less, 10 μm or less, 5.0 μm or less, or 2.0 μm or less. The thickness of the separation functional layer 1 may be 0.05 μm or more, or 0.1 μm or more.

[0178] The separation functional layer 1 tends to have high mechanical strength due to polymer A. As an example, when the separation functional layer 1 is subjected to a tensile test, the breaking strength of the separation functional layer 1 is, for example, 100 kPa or more, preferably 300 kPa or more, 500 kPa or more, 1000 kPa or more, 1500 kPa or more, 2000 kPa or more, 2500 kPa or more, and more preferably 3000 kPa or more. The upper limit of the breaking strength of the separation functional layer 1 is not particularly limited, and is, for example, 10000 kPa or less. The tensile test of the separation functional layer 1 can be performed in accordance with the provisions of JIS K 7161-1:2014. In this specification, the breaking strength refers to the tensile failure stress σ specified in JIS K 7161-1:2014. b .

[0179] In the case of the separation functional layer 1, there is also a tendency to suppress the leakage of the ionic liquid L. As an example, when the separation functional layer 1 is subjected to a compression test, the ratio of the weight of the ionic liquid L leaked from the separation functional layer 1 to the weight of the ionic liquid L contained in the separation functional layer 1 (leakage rate) can be, for example, 5.0 wt% or less, 3.0 wt% or less, or even 2.0 wt% or less. During the compression test, the ionic liquid L may not substantially leak from the separation functional layer 1. Here, the compression test is performed by applying a compressive load of 1.16 MPa to the separation functional layer 1 for 2 minutes. At this time, the direction of applying the compressive load is aligned with the thickness direction of the separation functional layer 1. The compression test is performed at room temperature (25°C).

[0180] As described above, the separation functional layer 1 can allow the acidic gas contained in the mixed gas to pass through preferentially. As an example, the permeation rate T1 of carbon dioxide through the separation functional layer 1 can be, for example, 0.1 GPU or more, 0.3 GPU or more, 0.4 GPU or more, 0.5 GPU or more, 0.6 GPU or more, 0.7 GPU or more, 0.8 GPU or more, 0.9 GPU or more, and further can be 1.0 GPU or more. The upper limit of the permeation rate T1 is not particularly limited, for example, it can be 1000 GPU or less, or 10 GPU or less depending on the situation. It should be noted that GPU refers to 10 -6 cm 3 (STP) / (sec·cm 2 cmHg).

[0181] The permeability coefficient C1 of carbon dioxide to the separation functional layer 1 is, for example, 100 barrers or more, preferably 150 barrers or more, 170 barrers or more, 200 barrers or more, 230 barrers or more, 250 barrers or more, 270 barrers or more, and more preferably 300 barrers or more. The upper limit of the permeability coefficient C1 is not particularly limited, and is, for example, 1000 barrers. Barrer refers to 10 -10 cm 3 (STP)·cm / (sec·cm 2 cmHg). 3 (STP) refers to the volume of carbon dioxide at 1 atmosphere and 0° C. The permeability coefficient C1 (Barrer) is a value obtained by multiplying the permeation rate T1 (GPU) by the thickness (μm) of the separation functional layer 1 .

[0182] The permeation rate T1 and the permeation coefficient C1 can be calculated using the following method. First, a mixed gas obtained by carbon dioxide and hydrogen is supplied to the space adjacent to the surface on one side of the separation functional layer 1, and the space adjacent to the surface on the other side of the separation functional layer 1 is depressurized. In this way, a permeated fluid passing through the separation functional layer 1 is obtained. The weight of the permeated fluid, and the volume ratio of carbon dioxide and the volume ratio of hydrogen in the permeated fluid are measured. Based on the measurement results, the permeation rate T1 and the permeation coefficient C1 can be calculated. In the above operation, the concentration of carbon dioxide in the mixed gas is 50 vol% under standard conditions (0°C, 101 kPa). The temperature of the mixed gas supplied to the space adjacent to the surface on one side of the separation functional layer 1 is 30°C and the pressure is 0.1 MPa. The space adjacent to the surface on the other side of the separation functional layer 1 is depressurized in such a way that the pressure in the space is reduced by 0.1 MPa relative to the atmospheric pressure in the measurement environment.

[0183] Under the above-mentioned measurement conditions of the permeation rate T1 and the permeation coefficient C1, the separation coefficient α1 of carbon dioxide to hydrogen in the separation functional layer 1 is not particularly limited, and is, for example, 5 or more, preferably 6 or more, 7 or more, 8 or more, 9 or more, and more preferably 10 or more. The upper limit of the separation coefficient α1 is not particularly limited, and is, for example, 50 or less. The separation coefficient α1 can be calculated according to the following formula. In the following formula, X A and X B are the volume ratio of carbon dioxide and the volume ratio of hydrogen in the mixed gas respectively. A and Y B They are the volume ratio of carbon dioxide and the volume ratio of hydrogen in the permeated fluid that has permeated the separation functional layer 1 , respectively.

[0184] Separation coefficient α1=(Y A / Y B ) / (X A / X B )

[0185] (Purpose of separation functional layer)

[0186] As an application of the separation functional layer 1 of this embodiment, the application of separating acidic gas from a mixed gas containing acidic gas can be cited. Examples of acidic gases in the mixed gas include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, nitrogen oxides (NOx), etc., preferably carbon dioxide. The mixed gas may contain other gases besides acidic gases. Examples of other gases include non-polar gases such as hydrogen and nitrogen, and inert gases such as helium, preferably hydrogen. The separation functional layer 1 of this embodiment is particularly suitable for separating carbon dioxide from a mixed gas containing carbon dioxide and hydrogen. However, the application of the separation functional layer 1 is not limited to the application of separating acidic gases from the above-mentioned mixed gas.

[0187] <Embodiment of Separation Membrane>

[0188] like Figure 2 As shown, the separation membrane 10 of this embodiment includes the above-mentioned separation functional layer 1 and, for example, further includes a porous support 3. The porous support 3 supports the separation functional layer 1. The separation membrane 10 may further include an intermediate layer 2 disposed between the separation functional layer 1 and the porous support 3. The intermediate layer 2 is, for example, directly in contact with each of the separation functional layer 1 and the porous support 3.

[0189] It should be noted that the separation functional layer 1 included in the separation membrane 10 may not contain the polymer B depending on circumstances.

[0190] From another aspect, the present invention provides a separation membrane 10 comprising:

[0191] Separation functional layer 1; and

[0192] A porous support 3 supporting the separation functional layer 1,

[0193] The separation functional layer 1 includes an ionic liquid L and a hydrophilic polymer A forming a crystal structure in the ionic liquid L.

[0194] (Middle layer)

[0195] The intermediate layer 2 may contain, for example, a resin and nanoparticles dispersed in the resin (matrix). The nanoparticles may be separated from each other or partially aggregated within the matrix. However, the intermediate layer 2 may also contain no nanoparticles or may be substantially composed of the resin.

[0196] The material of the matrix is not particularly limited. Examples include silicone resins such as polydimethylsiloxane; fluororesins such as polytetrafluoroethylene; epoxy resins such as polyethylene oxide; polyimide resins; polysulfone resins; polyacetylene resins such as polytrimethylsilylpropyne and polydiphenylacetylene; and polyolefin resins such as polymethylpentene. The matrix preferably comprises a silicone resin.

[0197] Nanoparticles may contain inorganic materials or organic materials. Examples of inorganic materials contained in nanoparticles include silicon dioxide, titanium dioxide, and aluminum oxide. Preferably, the nanoparticles contain silicon dioxide.

[0198] Nanoparticles may also have surfaces modified with modifying groups comprising carbon atoms. Nanoparticles having surfaces modified with such modifying groups have excellent dispersibility in a matrix. Nanoparticles may, for example, be silica nanoparticles having surfaces modified with modifying groups. The modifying groups may also comprise silicon atoms. In nanoparticles, surfaces modified with modifying groups are represented, for example, by the following formulas (I) to (III).

[0199] [Chemical Formula 2]

[0200]

[0201] R in formula (I) to (III) 6 ~R 11Each is independently a hydrocarbon group that may have a substituent. The number of carbon atoms of the hydrocarbon group may be 1 or more and is not particularly limited. The number of carbon atoms of the hydrocarbon group may be, for example, 25 or less, 20 or less, 10 or less, or 5 or less. Depending on the circumstances, the number of carbon atoms of the hydrocarbon group may be greater than 25. The hydrocarbon group may be a linear or branched chain hydrocarbon group, or an alicyclic or aromatic cyclic hydrocarbon group. In a preferred embodiment, the hydrocarbon group is a linear or branched alkyl group having 1 to 8 carbon atoms. The hydrocarbon group is, for example, a methyl group or an octyl group, preferably a methyl group. As a substituent of the hydrocarbon group, for example, an amino group and an acyloxy group can be mentioned. As an acyloxy group, for example, a (meth)acryloyloxy group can be mentioned.

[0202] In another preferred embodiment, for R of formula (I) to (III) 6 ~R 11 The hydrocarbon group optionally having a substituent described above is represented by the following formula (IV): Nanoparticles having a surface modified with a modifying group containing a hydrocarbon group represented by formula (IV) are suitable for increasing the permeation rate of acidic gases in the separation membrane 10 .

[0203] [Chemical Formula 3]

[0204]

[0205] In formula (IV), R 12 An alkylene group having 1 to 5 carbon atoms and optionally having a substituent. The alkylene group may be linear or branched. Examples of the alkylene group include methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, and pentane-1,5-diyl, with propane-1,3-diyl being preferred. Substituents of the alkylene group include amide groups and aminoalkylene groups.

[0206] In formula (IV), R 13 is an alkyl group or aryl group having 1 to 20 carbon atoms and optionally having a substituent. The alkyl group may be linear or branched. Examples of the alkyl group and aryl group include the groups described above for the ionic liquid L. Examples of substituents for the alkyl group and aryl group include amino groups, carboxyl groups, and the like. R 13 For example, it is 3,5-diaminophenyl.

[0207] In the nanoparticles, the surface modified with the modifying group is preferably represented by the following formula (V).

[0208] [Chemical Formula 4]

[0209]

[0210] The modifying group is not limited to the structures shown in formulas (I) to (III). The modifying group may also include a polymer chain having a polyamide structure or a polydimethylsiloxane structure instead of R in formulas (I) to (III). 6 ~R 11 In the modification group, for example, the polymer chain is directly bonded to the silicon atom. Examples of the shape of the polymer chain include linear, dendritic, and hyperbranched.

[0211] The method utilizing the modifying group to modify the surface of the nanoparticle is not particularly limited. For example, the surface of the nanoparticle can be modified by reacting the hydroxyl groups present on the surface of the nanoparticle with a known silane coupling agent. When the modifying group comprises a polyamide structure, the surface of the nanoparticle can be modified by the method disclosed in Japanese Patent Application Laid-Open No. 2010-222228.

[0212] The average particle size of the nanoparticles is not particularly limited as long as it is nanoscale (<1000nm), for example, less than 100nm, preferably less than 50nm, and more preferably less than 20nm. The lower limit of the average particle size of the nanoparticles is, for example, 1nm. The average particle size of the nanoparticles can be determined, for example, by the following method. First, a cross section of the intermediate layer 2 is observed using a transmission electron microscope. In the obtained electron microscope image, the area of the specific nanoparticles is calculated by image processing. The diameter of a circle having the same area as the calculated area is regarded as the particle size (diameter of the particle) of the specific nanoparticles. The particle size of any number (at least 50) of nanoparticles is calculated separately, and the average value of the calculated values is regarded as the average particle size of the nanoparticles. The shape of the nanoparticles is not particularly limited, and can be spherical, ellipsoidal, scaly, or fibrous.

[0213] The content of the nanoparticles in the intermediate layer 2 is, for example, 5 wt% or more, preferably 10 wt% or more, and more preferably 15 wt% or more. The upper limit of the content of the nanoparticles in the intermediate layer 2 is not particularly limited, but is, for example, 30 wt%.

[0214] The thickness of the intermediate layer 2 is not particularly limited, and is, for example, less than 50 μm, preferably 40 μm or less, and more preferably 30 μm or less. The lower limit of the thickness of the intermediate layer 2 is not particularly limited, and is, for example, 1 μm. The intermediate layer 2 is, for example, a layer having a thickness of less than 50 μm.

[0215] (Porous support)

[0216] The porous support 3 supports the separation functional layer 1 via the intermediate layer 2. Examples of the porous support 3 include: nonwoven fabric; porous polytetrafluoroethylene; aromatic polyamide fiber; porous metal; sintered metal; porous ceramic; porous polyester; porous nylon; activated carbon fiber; latex; silicone; silicone rubber; a permeable (porous) polymer comprising at least one selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyetheretherketone, polyacrylonitrile, polyimide, and polyphenylene ether; metal foam having open or closed cells; polymer foam having open or closed cells; silica; porous glass; mesh; and the like. The porous support 3 may be a combination of two or more of the above.

[0217] The porous support 3 has an average pore diameter of, for example, 0.01 to 0.4 μm. The thickness of the porous support 3 is not particularly limited, but is, for example, 10 μm or greater, preferably 20 μm or greater, and more preferably 50 μm or greater. The thickness of the porous support 3 is, for example, 300 μm or less, preferably 200 μm or less, and more preferably 150 μm or less.

[0218] (Method for producing separation membrane)

[0219] The separation membrane 10 can be produced, for example, by the following method. First, a laminate of a porous support 3 and an intermediate layer 2 is prepared. The laminate can be produced, for example, by the following method. First, a coating liquid containing the material of the intermediate layer 2 is prepared. Then, the coating liquid containing the material of the intermediate layer 2 is coated on the porous support 3 to form a coating film. The coating method of the coating liquid is not particularly limited, and for example, spin coating, dip coating, etc. can be used. The coating liquid can also be applied using a wire rod, etc. Then, the coating film is dried to form the intermediate layer 2. The drying of the coating film can be carried out, for example, under heating conditions. The heating temperature of the coating film is, for example, above 50°C. The heating time of the coating film is, for example, above 1 minute, and can also be above 5 minutes. In addition, the surface of the intermediate layer 2 can be subjected to an easy-adhesion treatment as needed. Examples of easy-adhesion treatments include surface treatments such as primer coating, corona discharge treatment, and plasma treatment.

[0220] Next, a mixed solution M1 (or mixed solution M2) for forming the separation functional layer 1 is applied onto the intermediate layer 2 in the laminate of the porous support 3 and the intermediate layer 2. The resulting coated film is dried. Thus, the separation functional layer 1 can be formed on the intermediate layer 2, thereby obtaining a separation membrane 10. It should be noted that in this embodiment, the strength of the separation functional layer 1 is improved. Therefore, the separation functional layer 1 can also be formed on the intermediate layer 2 in a roll-to-roll manner.

[0221] It should be noted that the method for producing the separation membrane 10 is not limited to the method described above. For example, the separation membrane 10 can also be produced using the following method. First, a separation functional layer 1 formed on a substrate such as a release liner is prepared using the method described above. Next, a coating solution containing the material of the intermediate layer 2 is applied to the separation functional layer 1 and dried to form the intermediate layer 2. The laminate of the intermediate layer 2 and the separation functional layer 1 is transferred to a porous support 3. Thus, the separation membrane 10 is obtained.

[0222] (Shape of separation membrane)

[0223] In this embodiment, the separation membrane 10 is typically a flat membrane. However, the separation membrane 10 may also have a shape other than a flat membrane, for example, a hollow fiber membrane. As an example, the separation membrane 10 as a hollow fiber membrane may include the separation function layer 1 and the porous support 3 without the intermediate layer 2.

[0224] (Characteristics of Separation Membrane)

[0225] The separation membrane 10 of this embodiment can preferentially permeate acidic gases contained in a mixed gas due to the separation functional layer 1. As an example, the permeation rate T2 of carbon dioxide permeating the separation membrane 10 is, for example, 50 GPU or higher, 80 GPU or higher, 100 GPU or higher, 120 GPU or higher, 150 GPU or higher, or even 180 GPU or higher. The upper limit of the permeation rate T2 is not particularly limited, but is, for example, 1000 GPU or lower.

[0226] The permeation rate T2 can be measured using the method described above for the permeation rate T1 and permeation coefficient C1 of the separation functional layer 1. At this time, a mixed gas composed of carbon dioxide and hydrogen is supplied, for example, to the space adjacent to the main surface 11 on the separation functional layer side of the separation membrane 10. Furthermore, the space adjacent to the main surface 12 on the porous support side of the separation membrane 10 is decompressed.

[0227] Under the measurement conditions of the permeation rate T2, the separation coefficient α2 of carbon dioxide for hydrogen in the separation membrane 10 is not particularly limited, and is, for example, 5 or greater, preferably 6 or greater, 7 or greater, 8 or greater, 9 or greater, and more preferably 10 or greater. The upper limit of the separation coefficient α2 is not particularly limited, and is, for example, 50 or less. The separation coefficient α2 can be calculated using the method described above for the separation coefficient α1.

[0228] <Embodiment of membrane separation device>

[0229] like Figure 3As shown, the membrane separation device 100 of this embodiment includes a separation membrane 10 and a tank 20. In the membrane separation device 100, the separation functional layer 1 may be used alone instead of the separation membrane 10. The tank 20 includes a first chamber 21 and a second chamber 22. The separation membrane 10 is disposed inside the tank 20. Inside the tank 20, the separation membrane 10 separates the first chamber 21 from the second chamber 22. The separation membrane 10 extends from one of a pair of walls of the tank 20 to the other.

[0230] The first chamber 21 has an inlet 21a and an outlet 21b. The second chamber 22 has an outlet 22a. The inlet 21a, the outlet 21b, and the outlet 22a are each an opening formed in the wall surface of the tank 20, for example.

[0231] Membrane separation using the membrane separation device 100 is performed, for example, by the following method. First, a mixed gas 30 containing an acidic gas is supplied to the first chamber 21 through the inlet 21a. The concentration of the acidic gas in the mixed gas 30 is not particularly limited, but under standard conditions, it is, for example, 0.01 vol% (100 ppm) or higher, preferably 1 vol% or higher, more preferably 10 vol% or higher, further preferably 30 vol% or higher, and particularly preferably 50 vol% or higher. The upper limit of the acidic gas concentration in the mixed gas 30 is not particularly limited, but under standard conditions, it is, for example, 90 vol%.

[0232] The pressure in the first chamber 21 may be increased by supplying the mixed gas 30. The membrane separation device 100 may further include a pump (not shown) for increasing the pressure of the mixed gas 30. The pressure of the mixed gas 30 supplied to the first chamber 21 is, for example, 0.1 MPa or higher, preferably 0.3 MPa or higher.

[0233] The pressure inside the second chamber 22 may be reduced while the mixed gas 30 is being supplied to the first chamber 21. The membrane separation device 100 may further include a pump (not shown) for reducing the pressure inside the second chamber 22. The pressure inside the second chamber 22 may be reduced by, for example, 10 kPa or more, preferably 50 kPa or more, and more preferably 100 kPa or more relative to the atmospheric pressure in the measurement environment.

[0234] By supplying the mixed gas 30 into the first chamber 21, a permeated fluid 35 having a higher acid gas content than the mixed gas 30 can be obtained on the other side of the separation membrane 10. Specifically, the permeated fluid 35 is supplied to the second chamber 22. The permeated fluid 35 contains, for example, acid gas as a main component. However, the permeated fluid 35 may also contain a small amount of other gases besides acid gas. The permeated fluid 35 is discharged to the outside of the tank 20 through the outlet 22a.

[0235] The concentration of acidic gas in the mixed gas 30 gradually decreases from the inlet 21a toward the outlet 21b of the first chamber 21. The mixed gas 30 (non-permeated fluid 36) treated in the first chamber 21 is discharged to the outside of the tank 20 through the outlet 21b.

[0236] The membrane separation apparatus 100 of this embodiment is suitable for a flow-through (continuous) membrane separation method. However, the membrane separation apparatus 100 of this embodiment can also be used for a batch-type membrane separation method.

[0237] <Modification of membrane separation device>

[0238] The membrane separation device 100 may be a spiral membrane element, a hollow fiber membrane element, or the like. Figure 4 A spiral-type membrane element is shown. Figure 4 The membrane separation device 110 includes a central tube 41 and a stack 42. The stack 42 includes a separation membrane 10. The stack 42 may include a separation functional layer 1 alone instead of the separation membrane 10.

[0239] The center tube 41 has a cylindrical shape. Multiple holes are formed on the surface of the center tube 41 to allow the permeating fluid 35 to flow into the center tube 41. Examples of materials for the center tube 41 include resins such as acrylonitrile-butadiene-styrene copolymer (ABS resin), polyphenylene ether resin (PPE resin), and polysulfone resin (PSF resin); and metals such as stainless steel and titanium. The inner diameter of the center tube 41 is, for example, in the range of 20 to 100 mm.

[0240] The stack 42 includes, in addition to the separation membrane 10, a feed-side flow path material 43 and a permeate-side flow path material 44. The stack 42 is wound around the central tube 41. The membrane separation device 110 may further include an outer packaging material (not shown).

[0241] As the feed-side flow path material 43 and the permeate-side flow path material 44, for example, a resin mesh made of polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.

[0242] In the membrane separation device 110, stress is applied to the separation membrane 10 in contact with the feed-side flow path material 43 and the permeate-side flow path material 44. As described above, the separation functional layer 1 of the separation membrane 10 tends to have high strength, and therefore the properties of the separation membrane 10 are rarely degraded by this stress. For example, the separation coefficient α2 of the separation membrane 10 tends to remain largely unchanged before and after the membrane separation device 110 is manufactured.

[0243] Membrane separation using the membrane separation device 110 is performed, for example, using the following method. First, a mixed gas 30 is supplied to one end of a wound stack 42. A permeated fluid 35, which has permeated the separation membranes 10 of the stack 42, moves into the interior of the central tube 41. The permeated fluid 35 passes through the central tube 41 and is discharged to the outside. The mixed gas 30 (non-permeated fluid 36) treated in the membrane separation device 110 is discharged to the outside from the other end of the wound stack 42. This allows acidic gases to be separated from the mixed gas 30.

[0244] Example

[0245] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0246] (Example A1)

[0247] First, 4 g of polyvinyl alcohol (PVA, manufactured by Sigma Aldrich, weight-average molecular weight 85,000-124,000, degree of saponification 87-89 mol%), polymer A, was added to 36 g of water and heated to 90°C. Stirring was performed until the PVA was completely dissolved, thereby preparing a PVA aqueous solution. Next, 1.6 g of polyvinyl pyrrolidone (PVP, manufactured by Sigma Aldrich, weight-average molecular weight 360,000), polymer B, was added to 38.4 g of water. Stirring was performed at 25°C until the PVP was completely dissolved, thereby preparing a PVP aqueous solution.

[0248] Next, 1.5 g of the PVA aqueous solution, 1.5 g of the PVP aqueous solution, and 0.63 g of 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) as ionic liquid L were mixed and stirred thoroughly until completely dissolved, thereby obtaining a mixed liquid.

[0249] The obtained mixed solution was then placed in a PTFE mold (small dish), dried in a 30°C thermostat for 48 hours, and further dried on a 70°C hot plate for 3 hours. Thus, the separation functional layer (self-supporting membrane) of Example A1 was obtained.

[0250] (Example A2-A3)

[0251] Except that the weight ratio of the ionic liquid L to the polymers A and B was changed as shown in Table 1, the separation functional layers (self-supporting membranes) of Examples A2 and A3 were obtained by the same method as Example A1.

[0252] (Example A4)

[0253] A separation functional layer (self-supporting membrane) of Example A4 was obtained by the same method as in Example A1 except that the polymer B was not used and the weight ratio of the ionic liquid L to the polymer A was 75 / 25.

[0254] (Example A5)

[0255] The same method as in Example A1 was used to prepare a separation functional layer (self-supporting membrane) except that polymer A was not used and the weight ratio of ionic liquid L to polymer B was set to 75 / 25. However, the mixed liquid did not solidify sufficiently and no separation functional layer could be obtained.

[0256] [Compression test]

[0257] Compression tests were performed on the separation functional layers of Examples A1 to A4 using the above method. The ratio of the weight of ionic liquid leaking from the separation functional layer during the compression test relative to the weight of ionic liquid L contained in the separation functional layer (leakage rate) was determined. The results are shown in Table 1.

[0258] [Tensile test]

[0259] The separation functional layers of Examples A1 to A4 were subjected to tensile tests using the above-described method to measure their breaking strength. The results are shown in Table 1.

[0260] [Gas permeation test]

[0261] For the separation functional layers of Examples A1 to A4, a differential pressure gas permeation tester (manufactured by GTR Tech, GTR-31AHND) was used to measure the permeation rate T1 of carbon dioxide, the permeation coefficient C1 of carbon dioxide, and the separation coefficient α1 (CO2 / H2) of carbon dioxide relative to hydrogen by the following method. First, a separation functional layer cut into about 3 cm square was placed in a metal chamber and sealed with an O-ring to prevent leakage. Next, a mixed gas was injected into the metal chamber in such a way that the mixed gas was in contact with the main surface of one side of the separation functional layer. The mixed gas was essentially composed of carbon dioxide and hydrogen. The concentration of carbon dioxide in the mixed gas was 50 vol% under standard conditions. The temperature of the mixed gas injected into the metal chamber was 30°C and the pressure was 0.1 MPa. Next, a vacuum pump was used to decompress the space in the metal chamber adjacent to the main surface of the other side of the separation functional layer. At this time, the pressure in the space was reduced by 0.1 MPa relative to the atmospheric pressure in the measurement environment. Thus, a permeated fluid was obtained from the main surface of the other side of the separation functional layer. The permeation rate T1, permeation coefficient C1, and separation coefficient α1 were calculated based on the composition and weight of the permeated fluid obtained. The results are shown in Table 1.

[0262] [Table 1]

[0263]

[0264] As can be seen from Table 1, the separation functional layers of Examples A1 to A3 comprising the polymer A and the polymer B have better carbon dioxide permeation performance than that of Example A4.

[0265] (Example B1)

[0266] First, prepare an ultrafiltration membrane (NTU-3175M, manufactured by Nitto Denko Corporation) as a porous support. Next, prepare a 6wt% decane solution of a silicone resin (YSR3022, manufactured by Momentive Performance Materials), and further add a catalyst (YC6831, manufactured by Momentive Performance Materials Corporation) of 1% of the solid content of the silicone resin and acetylacetone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a curing retarder of 3% of the solid content of the silicone resin. The obtained solution is applied to the porous support. The coating is carried out using a rod coater under the condition of a coating thickness of 68.6μm. Then, the obtained coating film is dried at 130°C for 5 minutes. Thus, a laminate of a porous support and an intermediate layer is obtained. The thickness of the intermediate layer is about 1μm. Furthermore, the laminate is subjected to a corona treatment with an output power of 0.1kW.

[0267] Next, a PVA aqueous solution and a PVP aqueous solution were prepared by the same method as in Example A1. Next, 1.5 g of the PVA aqueous solution, 1.5 g of the PVP aqueous solution, 0.63 g of 1-ethyl-3-methylimidazolium dicyanamide salt ([EMIM][DCA]) as the ionic liquid L, and 0.018 g of a surfactant (manufactured by AGC Seimi Chemical Co., Ltd., SURFLON S-243) were mixed and stirred thoroughly until completely dissolved. Thus, a mixed solution was obtained. The obtained mixed solution was applied to the above-mentioned laminate to obtain a coating film. The coating of the mixed solution was carried out using a spin coater at 1000 rpm. The coating film was placed at 25°C for more than 1 day to dry it, thereby producing a separation functional layer. Thus, the separation membrane (composite membrane) of Example B1 was obtained.

[0268] (Examples B2 to B5)

[0269] Except that the weight ratios of the ionic liquid L, polymers A, and B were changed as shown in Table 2, separation membranes (composite membranes) of Examples B2 to B5 were obtained by the same method as in Example B1.

[0270] (Example B6)

[0271] A separation membrane (composite membrane) of Example B6 was obtained by the same method as in Example B1 except that 1-ethyl-3-methylimidazolium tricyanomethane ([EMIM][TCM]) was used as the ionic liquid L.

[0272] (Example B7)

[0273] A separation membrane (composite membrane) of Example B7 was obtained by the same method as in Example B1 except that the polymer B was not used and the weight ratio of the ionic liquid L to the polymer A was 75 / 25.

[0274] (Example B8)

[0275] First, a reflux tube was installed on a three-necked flask to assemble the synthesis device. A vacuum pump and a N2 high-pressure gas cylinder were connected to the three-way stopcock. One set consisted of evacuating the flask and supplying nitrogen every 2 minutes, and a total of 5 nitrogen substitutions were performed. After nitrogen substitution, 1,4-dioxane was added to the three-necked flask using a glass syringe. Next, N,N-dimethylacrylamide (DMAAm) (14.6 g, 147.28 mmol), N-acryloyloxysuccinimide (NSA) (1.32 g, 7.80 mmol), and 2,2'-azobisisobutyronitrile (AIBN) (0.256 g, 1.56 mmol) were measured into a small vial in sequence and stirred for several minutes. The molar ratio of DMAAm to NSA (DMAAm / NSA) was 95 / 5. Using a syringe, the resulting mixture was added to the three-necked flask. The solution in the three-necked flask was stirred for about 10 minutes using a stirrer. Next, the reflux line was connected to a cooling device, and polymerization was carried out under reflux for 24 hours using an oil bath set at 60°C.

[0276] The post-polymerization solution was transferred to an eggplant-shaped flask and treated at 60°C for more than 30 minutes using an evaporator to remove 1,4-dioxane from the solution. THF was then added to the flask to dissolve the white solid. The resulting solution was then added dropwise to hexane cooled to -10°C using a dropper while stirring to obtain a precipitate. The precipitate was treated in a 30°C thermostat under a vacuum atmosphere for 24 hours to obtain a prepolymer (poly(DMAAm-co-NSA)).

[0277] Next, polyvinyl alcohol (PVA, manufactured by Sigma Aldrich, weight-average molecular weight 85,000-124,000, degree of saponification 87-89 mol%) as polymer A is added to water and the temperature is raised to 90°C. Stir until the PVA is completely dissolved to prepare a PVA aqueous solution. To this PVA aqueous solution, the above-mentioned prepolymer (poly(DMAAm-co-NSA)) is added and stirred for 1 hour. Furthermore, 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) as ionic liquid L is added and stirred for 30 minutes. Diethylene glycol bis(3-aminopropyl) ether as a cross-linking agent is added to the resulting mixed solution and stirred for 3 minutes. Thus, a mixed solution for forming a separation functional layer is prepared.

[0278] Next, the obtained mixed solution is applied to a laminate of a porous support and an intermediate layer to obtain a coating film. As the laminate of the porous support and the intermediate layer, the laminate described in Example B1 (a laminate subjected to corona treatment with an output power of 0.1 kW) is used. The coating of the mixed solution is carried out using a spin coater at 1000 rpm. Next, the coating film is placed at 25°C for more than 1 day to dry it. Thus, the reaction of the prepolymer and the cross-linking agent proceeds to form polymer B, thereby obtaining the separation membrane (composite membrane) of Example B8. It should be noted that in the separation membrane, the weight ratio of the ionic liquid L to the polymer (polymer A and B) is 75 / 25, and the weight ratio of polymer A to polymer B (A / B) is 71 / 29.

[0279] (Example B9)

[0280] A separation membrane (composite membrane) was prepared by the same method as in Example B1, except that polymer A was not used and the weight ratio of ionic liquid L to polymer B was set to 75 / 25. However, the mixed liquid did not solidify sufficiently and no separation functional layer was formed.

[0281] [Gas permeation test]

[0282] The carbon dioxide permeation rate T2 and the separation coefficient α2 (CO2 / H2) of carbon dioxide to hydrogen were measured for the separation membranes of Examples B1 to B8 by the methods described above for Examples A1 to A4. The results are shown in Table 2.

[0283] [Table 2]

[0284]

[0285] As apparent from Table 2, the separation membranes of Examples B1 to B8 including the separation functional layer containing at least the polymer A have good carbon dioxide permeation performance.

[0286] (Example C1)

[0287] As polymer A, polyvinyl alcohol a1 (PVA, manufactured by Tokyo Chemical Industry, degree of polymerization 2000, weight-average molecular weight 88000, degree of saponification 80 mol%) was used, and the weight ratio of ionic liquid L to polymer A was set to 40 / 60. Except for this, the separation functional layer (self-supporting membrane) of Example C1 was obtained by the same method as Example A4.

[0288] (Example C2)

[0289] A separation functional layer (self-supporting membrane) of Example C2 was obtained by the same method as Example C1 except that polyvinyl alcohol a2 (PVA, manufactured by Sigma Aldrich, weight average molecular weight 85,000-124,000, saponification degree 87-89 mol %) was used as polymer A.

[0290] (Example C3)

[0291] A separation functional layer (self-supporting membrane) of Example C3 was obtained by the same method as Example C1 except that polyvinyl alcohol a3 (PVA, manufactured by Sigma Aldrich, weight average molecular weight 85,000-124,000, saponification degree 99 mol %) was used as polymer A.

[0292] (Examples C4~C12)

[0293] Except for changing the type of polymer A and the weight ratio of ionic liquid L to polymer A as shown in Table 3, separation functional layers (self-supporting membranes) of Examples C4 to C12 were obtained by the same method as Example C1.

[0294] [Compression test]

[0295] Compression tests were performed on the separation functional layers of Examples C1 to C12 using the above method. The ratio of the weight of ionic liquid leaking from the separation functional layer during the compression test to the weight of ionic liquid L contained in the separation functional layer (leakage rate) was determined. The results are shown in Table 3.

[0296] [Tensile test]

[0297] The separation functional layers of Examples C1 to C12 were subjected to a tensile test using the above-described method to measure the breaking energy and breaking strength (breaking stress).

[0298] [Table 3]

[0299]

[0300] Figures 5-7 This is a graph showing the relationship between the content of ionic liquid and various properties for the separation functional layers of Examples C1 to C12. Figures 5-7 (in particular Figure 5 ) It can be seen that when PVA with a low saponification degree is used, there is a tendency for the leakage of ionic liquid to be further suppressed in the separation functional layer. It should be noted that these results also show that the saponification degree of PVA has no significant effect on the mechanical strength of the separation functional layer.

[0301] Industrial applicability

[0302] The separation functional layer and separation membrane of this embodiment are suitable for separating acid gases from mixed gases containing acid gases. In particular, the separation functional layer and separation membrane of this embodiment are suitable for separating carbon dioxide from exhaust gases from chemical plants or thermal power plants.

Claims

1. A separation functional layer comprising: Ionic liquids; A hydrophilic polymer A that forms a crystal structure in the ionic liquid; and A polymer B different from the polymer A.

2. The separation functional layer according to claim 1, wherein The ionic liquid has hydrophilicity or amphiphilicity.

3. The separation functional layer according to claim 1, wherein The ionic liquid includes at least one selected from the group consisting of 1-ethyl-3-methylimidazolium dicyanamide and 1-ethyl-3-methylimidazolium tricyanomethane.

4. The separation functional layer according to claim 1, wherein The polymer A has a hydroxyl group.

5. The separation functional layer according to claim 4, wherein The polymer A is bonded to the polymer B via a hydrogen bond derived from the hydroxyl group. The separation functional layer according to claim 1 , wherein: The polymer A comprises polyvinyl alcohol.

7. The separation functional layer according to claim 1, wherein The polymer B has at least one selected from the group consisting of an amide group and an imide group.

8. The separation functional layer according to claim 1, wherein The polymer B is linear.

9. The separation functional layer according to claim 1, wherein The polymer B comprises polyvinylpyrrolidone.

10. The separation functional layer according to claim 1, wherein The content of the ionic liquid is 60 wt% or more. The separation functional layer according to claim 1 , having a thickness of 100 μm or less. The separation functional layer according to claim 1 , having a breaking strength of 100 kPa or more.

13. The separation functional layer according to claim 1, wherein When a mixed gas of carbon dioxide and hydrogen is supplied to a space adjacent to one surface of the separation functional layer and the space adjacent to the other surface of the separation functional layer is depressurized, the permeability coefficient of carbon dioxide passing through the separation functional layer is 100 barrers or more. In which, the concentration of the carbon dioxide in the mixed gas is 50 vol% under standard conditions, the temperature of the mixed gas supplied to the space adjacent to the surface on one side is 30°C and the pressure is 0.1 MPa, and the space adjacent to the surface on the other side is depressurized in such a way that the pressure in the space is reduced by 0.1 MPa relative to the atmospheric pressure in the measurement environment. 14 . The separation functional layer according to claim 1 , which is used to separate acid gas from a mixed gas containing the acid gas.

15. A separation membrane comprising: The separation functional layer according to any one of claims 1 to 14; and A porous support body supports the separation functional layer.

16. A separation membrane comprising: Separating functional layers; and a porous support supporting the separation functional layer, in, The separation functional layer includes an ionic liquid and a hydrophilic polymer A that forms a crystal structure in the ionic liquid.

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