Separation membrane

Abstract

The present invention provides a novel separation membrane suitable for improving the permeation rate of a permeating fluid. A separation membrane 10A according to the present invention comprises a separation function layer 1 containing a polymer P and a porous support 3 supporting the separation function layer 1. The separation function layer 1 further contains an organic compound C which is different from the polymer P and which is solid at 25°C. The organic compound C content in the separation function layer 1 is 20 wt% or more, for example.

Description

Separation membrane

[0001] The present invention relates to a separation membrane.

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

[0003] Examples of separation membranes used in membrane separation methods include composite membranes in which a separation functional layer is formed on a porous support. Examples of materials for the separation functional layer include polymers such as polyimide (see, for example, Patent Document 1).

[0004] JP 2014-184424 A

[0005] Conventional separation membranes have room for improvement in the permeation rate of a permeating fluid through the separation membrane. Therefore, the present invention provides a novel separation membrane suitable for improving the permeation rate of a permeating fluid.

[0006] The present invention provides a separation membrane comprising: a separation functional layer containing a polymer; and a porous support supporting the separation functional layer, wherein the separation functional layer further contains an organic compound that is different from the polymer and is solid at 25°C.

[0007] According to the present invention, a new separation membrane suitable for improving the permeation rate of a permeating fluid can be provided.

[0008] Fig. 1 is a cross-sectional view schematically showing a separation membrane according to one embodiment of the present invention; Fig. 2 is a cross-sectional view schematically showing a separation membrane according to a modified example of the present invention; Fig. 3 is a schematic cross-sectional view of a membrane separation device provided with the separation membrane of the present invention; Fig. 4 is a perspective view schematically showing a modified example of a membrane separation device provided with the separation membrane of the present invention.

[0009] A separation membrane according to a first aspect of the present invention comprises a separation functional layer containing a polymer; and a porous support supporting the separation functional layer, wherein the separation functional layer further contains an organic compound that is different from the polymer and is solid at 25°C.

[0010] In a second aspect of the present invention, for example, in the separation membrane according to the first aspect, the content of the organic compound in the separation functional layer is 20 wt % or more.

[0011] In a third aspect of the present invention, for example, in the separation membrane according to the first or second aspect, the organic compound has a molecular weight of 500 or less.

[0012] In a fourth aspect of the present invention, for example, in the separation membrane according to any one of the first to third aspects, the organic compound has a ring structure.

[0013] In a fifth aspect of the present invention, for example, in the separation membrane according to any one of the first to fourth aspects, the organic compound has a polar group.

[0014] In a sixth aspect of the present invention, for example, in the separation membrane according to the fifth aspect, the polar group includes at least one selected from the group consisting of a carboxyl group, a hydroxyl group, an ester group, an ether group, a halogen group, a nitro group, an amino group, and a nitrile group.

[0015] In a seventh aspect of the present invention, for example, in the separation membrane according to any one of the first to sixth aspects, the organic compound is selected from the group consisting of coumarin-3-carboxylic acid, salicylic acid, 3-fluorobenzoic acid, phthalonitrile, 2,3-pyridinedicarboxylic acid, 4-nitrotoluene, isophthalic acid, 4-chlorobenzonitrile, chromone-2-carboxylic acid, 1-nitronaphthalene, 3-chlorobenzoic acid, 1-naphthylamine, acetylsalicylic acid, fluorobenzene, coumarin, 4-dimethylaminobenzoic acid, benzoic acid, chromone, phenoxazine, m-trifluoromethylbenzoic acid, 2-chlorophenol, 1,3-dichlorobenzene, quinazoline, 2-fluorobenzyl alcohol, o-tolunitrile, quinoline, benzoic acid, benzoyl benzoate ... The compound contains at least one selected from the group consisting of phosphorus, 1-naphthalenecarboxylic acid, 2-naphthalenecarboxylic acid, 3-fluorophenylacetic acid, 3-chlorobenzyl alcohol, phthalazine, 3,5-dinitroaniline, 2-fluorobenzoic acid, p-anisic acid, 2-methoxybenzyl alcohol, 3-(3-fluorophenyl)propionic acid, 3-methoxybenzonitrile, benzimidazole, 3-chlorophenylacetic acid, 2,6-pyridinedicarboxylic acid, 1-naphthol, cis-1,2-cyclohexanedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, caffeine, 4-hydroxymethylbenzoic acid, and 6-hydroxy-2-naphthonitrile.

[0016] In an eighth aspect of the present invention, for example, in the separation membrane according to any one of the first to seventh aspects, the polymer has a functional group containing an oxygen atom.

[0017] In a ninth aspect of the present invention, for example, in the separation membrane according to the eighth aspect, the functional group includes at least one selected from the group consisting of an ether group, an amide group, and an ester group.

[0018] In a tenth aspect of the present invention, for example, in the separation membrane according to any one of the first to ninth aspects, the polymer includes at least one selected from the group consisting of polyether block amide, polyvinyl ester, and polyether.

[0019] In an eleventh aspect of the present invention, for example, in the separation membrane according to any one of the first to tenth aspects, the thickness of the separation functional layer is 2 μm or less.

[0020] In a twelfth aspect of the present invention, for example, the separation membrane according to any one of the first to eleventh aspects further comprises an intermediate layer disposed between the separation functional layer and the porous support.

[0021] In a thirteenth aspect of the present invention, for example, the separation membrane according to any one of the first to twelfth aspects is used to separate an acidic gas from a mixed gas containing the acidic gas.

[0022] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0023] 1 , a separation membrane 10A of this embodiment includes a separation functional layer 1 containing a polymer P and a porous support 3 that supports the separation functional layer 1. The separation functional layer 1 further includes an organic compound C that is different from the polymer P and is solid at 25°C (specifically, at 25°C under atmospheric pressure (101.325 kPa)). In some cases, the separation membrane 10A may not include the porous support 3 and may be a free-standing membrane (single-layer membrane) that includes only the separation functional layer 1.

[0024] The separation membrane 10A preferably allows acidic gases contained in the mixed gas to pass preferentially through. According to the studies of the present inventors, the separation functional layer 1 containing the organic compound C tends to improve the permeation rate of the permeating fluid (especially acidic gases) passing through the separation membrane 10A.

[0025] The separation membrane 10A may further include an intermediate layer 2 disposed between the separation function layer 1 and the porous support 3. The intermediate layer 2 is preferably in direct contact with both the separation function layer 1 and the porous support 3.

[0026] (Separation functional layer) The separation functional layer 1 is preferably a layer that preferentially allows the acidic gas contained in the mixed gas to pass through, and is typically a dense layer (non-porous layer) in which no pores can be observed when observed at a magnification of 5000 times using a scanning electron microscope (SEM).

[0027] As described above, the separation functional layer 1 contains a polymer P and an organic compound C. The polymer P is typically an organic polymer. The polymer P preferably has a functional group F containing an oxygen atom. The functional group F preferably contains at least one selected from the group consisting of an ether group, an amide group, an ester group, a hydroxyl group, and a carboxyl group, more preferably contains at least one selected from the group consisting of an ether group, an amide group, and an ester group, and even more preferably contains at least one selected from the group consisting of an ether group and an amide group. The functional group F may be contained in the main chain of the polymer P or in a side chain of the polymer P.

[0028] The polymer P preferably contains at least one selected from the group consisting of polyether block amide, polyvinyl ester, and polyether, and particularly preferably contains polyether block amide.

[0029] The polyether block amide is a block copolymer containing a polyether block PE and a polyamide block PA. The polyether block amide is represented, for example, by the following formula (1):

[0030] In formula (1), R 1 is a divalent hydrocarbon group having 1 to 15 carbon atoms. 1 In the formula, the divalent hydrocarbon group may have 1 to 10 carbon atoms, or may have 1 to 5 carbon atoms. 1 In the formula (R), the divalent hydrocarbon group is preferably a linear or branched alkylene group. 1 Specific examples of R include an ethylene group and a butane-1,4-diyl group. 2 is a divalent hydrocarbon group having 1 to 20 carbon atoms. 2 In the formula, the divalent hydrocarbon group may have 3 to 18 carbon atoms, or may have 3 to 15 carbon atoms. 2 In the formula (R), the divalent hydrocarbon group is preferably a linear or branched alkylene group. 2 Specific examples include a pentane-1,5-diyl group and an undecane-1,11-diyl group.

[0031] In formula (1), the ratio of x to y (x:y) is, for example, 1:9 to 9:1, preferably 5:5 to 9:1, and more preferably 6:4 to 8:2. n is an integer of 1 or more.

[0032] A specific example of the polyether block amide is PEBAX (registered trademark) MH1657 manufactured by Arkema.

[0033] An example of the polyvinyl ester is polyvinyl acetate (PVAc).

[0034] Examples of polyethers include polyalkylene glycols such as polyethylene glycol (PEG), polypropylene glycol, and polytetramethylene glycol.

[0035] The distance Ra between the Hansen solubility parameter of polymer P and that of H2O is 19 MPa. 1 / 2 The Hansen solubility parameter is a solubility parameter introduced by Hildebrand divided into three components: a dispersion term δD, a polarization term δP, and a 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 known software such as HSPiP.

[0036] The distance Ra between the Hansen solubility parameter of polymer P and the Hansen solubility parameter of HO can be calculated from the following formula (i): In formula (i), δD1, δP1, and δH1 are the dispersion terms (MPa) of polymer P, respectively. 1 / 2 ), polarization term (MPa 1 / 2 ) and the hydrogen bond term (MPa 1 / 2 ) δD2, δP2 and δH2 are the dispersion terms of H2O (18.1 MPa), respectively. 1 / 2 ), polarization term (17.1 MPa 1 / 2 ) and hydrogen bond term (16.9 MPa 1 / 2) Ra = {4 × (δD1 - δD2) 2 + (δP1 - δP2) 2 + (δ H1 - δ H2) 2} 1 / 2 (i)

[0037] The distance Ra between the Hansen solubility parameter of the polymer P and the Hansen solubility parameter of HO is preferably 18 MPa. 1 / 2 is less than 17 MPa 1 / 2 Below, 16MPa 1 / 2 Below, further 15 MPa 1 / 2 The lower limit of the distance Ra may be, for example, 5 MPa. 1 / 2 or more, 8 MPa 1 / 2 or more, even 10 MPa 1 / 2 For example, the distance Ra between the Hansen solubility parameter of PEBAX MH1657 and the Hansen solubility parameter of HO is 12.4 MPa. 1 / 2 is.

[0038] The content of polymer P in the separation functional layer 1 is, for example, 95 wt% or less, and may be 90 wt% or less, 80 wt% or less, 70 wt% or less, 60 wt% or less, 50 wt% or less, 40 wt% or less, or even 30 wt% or less. The lower limit of the content of polymer P is, for example, 10 wt% or more, and may even be 20 wt% or more.

[0039] As described above, organic compound C is solid at 25°C. Solid organic compound C is less likely to leak out of the separation functional layer 1 than a liquid compound. Therefore, in the separation membrane 10A, the content of organic compound C in the separation functional layer 1 tends not to decrease over time during use. However, in some cases, organic compound C may be liquid at 25°C (specifically, at atmospheric pressure (101.325 kPa) at 25°C).

[0040] As described above, the organic compound C is a compound different from the polymer P and is typically a low molecular weight compound. The molecular weight of the organic compound C is, for example, 500 or less, and may be 400 or less, 300 or less, or even 200 or less. The lower limit of the molecular weight of the organic compound C is, for example, 50 or more, 100 or more, or even 150 or more. The molecular weight of the organic compound C may exceed 500 in some cases.

[0041] In another aspect, the present invention provides a separation membrane 10A comprising a separation functional layer 1 containing a polymer P and a porous support 3 supporting the separation functional layer 1, wherein the separation functional layer 1 further contains an organic compound C that is different from the polymer P and has a molecular weight of 500 or less.

[0042] It is preferable that the organic compound C does not contain an ionic bond and does not form a salt, in other words, it is preferable that all chemical bonds contained in the organic compound C are covalent bonds.

[0043] It is preferable that organic compound C does not dissolve in water when the following test 1 is performed. Test 1: 0.5 g of organic compound C is added to a container such as a microtube at 25°C, and 0.5 g of water (ion-exchanged water) is further added to the container. Next, the container is sealed and then shaken by hand about 10 times. The container is left to stand for 1 minute, and it is visually confirmed whether organic compound C has dissolved in water inside the container.

[0044] Furthermore, it is preferable that the organic compound C dissolves in isopropyl alcohol (IPA) when the following test 2 is performed. Organic compound C with high solubility in IPA is easily dissolved in the coating liquid used to prepare the separation functional layer 1, making it easy to apply a desirable manufacturing method for the separation functional layer 1. Test 2: 0.5 g of organic compound C is added to a container such as a microtube at 25°C, and 0.5 g of isopropyl alcohol is further added to the container. Next, the container is sealed and then shaken by hand approximately 10 times. The container is left to stand for 1 minute, and it is visually confirmed whether the organic compound C has dissolved in the isopropyl alcohol inside the container.

[0045] The organic compound C may have a ring structure or a polar group. It is preferable that the organic compound C has both a ring structure and a polar group. In the organic compound C, the polar group may be directly bonded to the ring structure. In the organic compound C, the polar group may be contained within the ring structure. In this specification, the polar group means a group containing a heteroatom such as an oxygen atom, a nitrogen atom, a sulfur atom, or a halogen atom. Organic compounds C having a ring structure tend to be able to suppress the permeation of gases other than acidic gases through the separation functional layer 1. Organic compounds C having a polar group tend to further promote the permeation of acidic gases through the separation functional layer 1.

[0046] In a preferred embodiment, the ring structure includes an aromatic ring. The ring structure may be composed only of an aromatic ring. The aromatic ring may be composed only of carbon atoms, or may be a heteroaromatic ring containing a heteroatom. The aromatic ring may be polycyclic or monocyclic. The number of carbon atoms in the aromatic ring is not particularly limited and is, for example, 4 to 14. Specific examples of ring structures including an aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a furan ring, a coumarin ring, a chromone ring, a pyrrole ring, a pyridine ring, a purine ring, a thiophene ring, a phenoxazine ring, a quinazoline ring, a quinoline ring, a phthalazine ring, and a benzimidazole ring.

[0047] In another preferred embodiment, the ring structure does not contain an aromatic ring. This ring structure may be composed only of carbon atoms, or may be a heterocyclic ring containing a heteroatom. The ring structure may be polycyclic or monocyclic. The number of carbon atoms in the ring structure is not particularly limited, and is, for example, 4 to 14. Specific examples of ring structures not containing an aromatic ring include a cyclopropane ring, a cyclobutane ring, and a cyclohexane ring.

[0048] Examples of polar groups include groups containing oxygen atoms, groups containing halogen atoms, and groups containing nitrogen atoms. Specific examples of groups containing oxygen atoms include carboxyl groups, hydroxyl groups, ester groups, and ether groups. Specific examples of groups containing halogen atoms include halogen groups such as fluoro groups and chloro groups. Specific examples of groups containing nitrogen atoms include nitro groups, amino groups, and nitrile groups. The polar group preferably contains at least one selected from the group consisting of carboxyl groups, hydroxyl groups, ester groups, ether groups, halogen groups, nitro groups, amino groups, and nitrile groups, and more preferably contains a carboxyl group.

[0049] Organic compound C is coumarin-3-carboxylic acid, salicylic acid, 3-fluorobenzoic acid, phthalonitrile, 2,3-pyridinedicarboxylic acid, 4-nitrotoluene, isophthalic acid, 4-chlorobenzonitrile, chromone-2-carboxylic acid, 1-nitronaphthalene, 3-chlorobenzoic acid, 1-naphthylamine, acetylsalicylic acid, fluorobenzene, coumarin, 4-dimethylaminobenzoic acid, benzoic acid, chromone, phenoxazine, m-trifluoromethylbenzoic acid, 2-chlorophenol, 1,3-dichlorobenzene, quinazoline, 2-fluorobenzyl alcohol, o-tolunitrile, quinoline, 1-naphthalenecarboxylic acid, 2 ...

[0039] Preferably, the organic solvent contains at least one selected from the group consisting of carboxylic acid, 3-fluorophenylacetic acid, 3-chlorobenzyl alcohol, phthalazine, 3,5-dinitroaniline, 2-fluorobenzoic acid, p-anisic acid, 2-methoxybenzyl alcohol, 3-(3-fluorophenyl)propionic acid, 3-methoxybenzonitrile, benzimidazole, 3-chlorophenylacetic acid, 2,6-pyridinedicarboxylic acid, 1-naphthol, cis-1,2-cyclohexanedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, caffeine, 4-hydroxymethylbenzoic acid, and 6-hydroxy-2-naphthonitrile.In particular, the organic compound C is selected from the group consisting of coumarin-3-carboxylic acid, salicylic acid, 3-fluorobenzoic acid, phthalonitrile, 2,3-pyridinedicarboxylic acid, 4-nitrotoluene, 4-chlorobenzonitrile, chromone-2-carboxylic acid, 1-nitronaphthalene, 3-chlorobenzoic acid, 1-naphthylamine, acetylsalicylic acid, fluorobenzene, coumarin, 4-dimethylaminobenzoic acid, chromone, phenoxazine, m-trifluoromethylbenzoic acid, 2-chlorophenol, 1,3-dichlorobenzene, quinazoline, 2-fluorobenzyl alcohol, o-tolunitrile, quinoline, 1-naphthalenecarboxylic acid, 2-naphthalenecarboxylic acid, It is preferable that the solvent contains at least one selected from the group consisting of 3-fluorophenylacetic acid, 3-chlorobenzyl alcohol, phthalazine, 3,5-dinitroaniline, 2-fluorobenzoic acid, p-anisic acid, 2-methoxybenzyl alcohol, 3-(3-fluorophenyl)propionic acid, 3-methoxybenzonitrile, benzimidazole, 3-chlorophenylacetic acid, 2,6-pyridinedicarboxylic acid, 1-naphthol, cis-1,2-cyclohexanedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, caffeine, 4-hydroxymethylbenzoic acid, and 6-hydroxy-2-naphthonitrile.

[0050] In another aspect, the present invention provides a separation functional layer 1 including a polymer P and an organic compound C, wherein the organic compound C is selected from the group consisting of coumarin-3-carboxylic acid, salicylic acid, 3-fluorobenzoic acid, phthalonitrile, 2,3-pyridinedicarboxylic acid, 4-nitrotoluene, 4-chlorobenzonitrile, chromone-2-carboxylic acid, 1-nitronaphthalene, 3-chlorobenzoic acid, 1-naphthylamine, acetylsalicylic acid, fluorobenzene, coumarin, 4-dimethylaminobenzoic acid, chromone, phenoxazine, m-trifluoromethylbenzoic acid, 2-chlorophenol, 1,3-dichlorobenzene, quinazoline, 2-fluorobenzyl alcohol, o-tolunitrile, quinoline, 1-naphthalenecarboxylic acid, 2-naphthalenecarboxylic acid, 3-fluoro ...phthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, 1-naphthalenecarboxylic acid, The present invention provides a separation membrane (10A) containing at least one selected from the group consisting of 2-fluorophenylacetic acid, 3-chlorobenzyl alcohol, phthalazine, 3,5-dinitroaniline, 2-fluorobenzoic acid, p-anisic acid, 2-methoxybenzyl alcohol, 3-(3-fluorophenyl)propionic acid, 3-methoxybenzonitrile, benzimidazole, 3-chlorophenylacetic acid, 2,6-pyridinedicarboxylic acid, 1-naphthol, cis-1,2-cyclohexanedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, caffeine, 4-hydroxymethylbenzoic acid, and 6-hydroxy-2-naphthonitrile.

[0051] The content of organic compound C in the separation functional layer 1 is, for example, 5 wt% or more, and may be 10 wt% or more, 20 wt% or more, 30 wt% or more, 40 wt% or more, 50 wt% or more, 60 wt% or more, or even 70 wt% or more. The higher the content of organic compound C, the higher the permeation rate of the permeating fluid passing through the separation membrane 10A tends to be. However, if the content of organic compound C exceeds 10 wt% (particularly 12 wt%), the strength of the separation functional layer 1 may be reduced. In this embodiment, since the porous support 3 supports the separation functional layer 1, even if the strength of the separation functional layer 1 itself is reduced, the separation membrane 10A as a whole tends to have sufficient strength for practical use. The upper limit of the content of organic compound C may be, for example, 90 wt% or less, or even 80 wt% or less.

[0052] In the separation functional layer 1, the total content of the polymer P and the organic compound C is, for example, 80 wt % or more, and may be 90 wt % or more, 95 wt % or more, or even 99 wt % or more. The separation functional layer 1 may be substantially composed of only the polymer P and the organic compound C. However, the separation functional layer 1 may contain components other than the polymer P and the organic compound C.

[0053] The thickness of the separation functional layer 1 is, for example, 50 μm or less, and may be 25 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, or even 2 μm or less. The thickness of the separation functional layer 1 may be 0.05 μm or more, or may be 0.1 μm or more.

[0054] (Intermediate Layer) The intermediate layer 2 is preferably formed from an emulsion resin composition. The emulsion resin composition refers to a liquid containing a dispersion medium and a polymer emulsified in the dispersion medium. The emulsion resin composition preferably contains water as the dispersion medium. That is, the emulsion resin composition is preferably an oil-in-water (O / W) emulsion. The emulsion resin composition may contain an organic solvent as the dispersion medium instead of or in addition to water.

[0055] The emulsion resin composition preferably contains a silicone-based polymer. The silicone-based polymer has, for example, a structural unit A represented by the following formula (2).

[0056] In formula (2), R 3 and R 4 are each independently a hydrogen atom or a hydrocarbon group. The hydrocarbon group may be linear or branched. The number of carbon atoms in the hydrocarbon group is not particularly limited and is, for example, 1 to 5, preferably 1 to 4, and more preferably 1 to 3. The hydrocarbon group is preferably a linear or branched alkyl group. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. The hydrocarbon group may also be an unsaturated hydrocarbon group such as a vinyl group. R3 and R 4 is preferably a hydrogen atom, a methyl group, an ethyl group or a vinyl group.

[0057] The number of structural units A contained in the silicone polymer is not particularly limited, and is, for example, 100 to 100,000, preferably 200 to 90,000, and more preferably 500 to 80,000.

[0058] The silicone-based polymer contains, for example, structural unit A as a main component, and preferably consists essentially of structural unit A. In this specification, "main component" refers to the structural unit that is contained in the largest amount by weight of all the structural units that make up the silicone-based polymer. However, the silicone-based polymer may further contain structural units other than structural unit A.

[0059] A specific example of the silicone polymer is dimethylpolysiloxane. The silicone polymer may be a cyclic siloxane represented by the following formula (3):

[0060] In formula (3), R 3 and R 4 is the same as in formula (2). n is not particularly limited and is, for example, 100 to 100,000, preferably 200 to 90,000, and more preferably 500 to 80,000.

[0061] The weight average molecular weight of the silicone polymer is not particularly limited, and may be, for example, 1×10 4 ~1 x 10 6 is.

[0062] In the emulsion resin composition, the silicone-based polymer is dispersed, for example, in the form of particles. The average particle size of the silicone-based polymer is not particularly limited and is, for example, 10 to 1,000 nm, preferably 50 to 800 nm. In this specification, the average particle size refers to the median size determined from the particle size distribution measured using a particle size distribution analyzer based on a laser diffraction / scattering method. In particular, the average particle size of the silicone-based polymer can be measured using a laser diffraction / scattering particle size distribution analyzer (e.g., LS 13 320 manufactured by Beckman Coulter) in accordance with the provisions of ISO 13320:2009 "Particle size analysis - laser diffraction method -".

[0063] The method for producing the emulsion resin composition containing a silicone polymer is not particularly limited, and known methods such as those disclosed in JP-A-2004-339283 can be used as appropriate.

[0064] The emulsion resin composition may further contain a surfactant for dispersing the silicone polymer. Examples of surfactants include anionic surfactants such as alkyl sulfates, alkylbenzene sulfonates, and alkyl phosphates; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, and polyoxyethylene fatty acid esters; cationic surfactants such as quaternary ammonium salts and alkylamine acetates; and amphoteric surfactants such as alkyl betaines and alkyl imidazolines. In particular, from the viewpoint of dispersion stability of the silicone polymer, it is preferable to use nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers. Specific examples of these nonionic surfactants include polyoxyethylene octyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, and polyoxyethylene styrenated phenyl ether. The surfactants can be used alone or in combination of two or more.

[0065] The emulsion resin composition may contain a hydrophilic polymer instead of or in addition to the silicone-based polymer. In this specification, "hydrophilic polymer" refers to a polymer having a contact angle with water of 100° or less, preferably 90° or less, and more preferably 85.2° or less. The contact angle with water can be evaluated by the sessile drop method specified in Japanese Industrial Standards (JIS) R3257:1999 using a sheet composed of the polymer to be evaluated. The lower limit of the contact angle with water of the hydrophilic polymer is not particularly limited, but may be, for example, 30°, 50°, or 74.0°.

[0066] The hydrophilic polymer includes, for example, at least one selected from the group consisting of urethane-based polymers, (meth)acrylic-based polymers, (meth)acrylic urethane-based polymers, ester-based polymers, and vinyl ester-based polymers, and preferably includes a urethane-based polymer.

[0067] Examples of urethane-based polymers include polyurethanes obtained by reacting polyols with polyisocyanates, and modified products thereof. The urethane-based polymer may be a urethane prepolymer having an isocyanate group or a blocked isocyanate group at its terminal.

[0068] Examples of polyols include polyether polyols such as polyethylene glycol, polypropylene glycol, and polyoxytetramethylene ether glycol obtained by ring-opening polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, etc.; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, octanediol, 1,4-butynediol, dipropylene glycol, bisphenol A, and bisphenol A with propylene oxide. Examples of suitable low molecular weight glycols include saturated or unsaturated low molecular weight glycols such as bisphenol A ethylene oxide adducts, hydrogenated bisphenol A, and the like; polyester polyols obtained by dehydration condensation of such low molecular weight glycols with dibasic acids such as adipic acid, maleic acid, fumaric acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, and suberic acid, or the corresponding acid anhydrides; polyester polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone and β-methyl-δ-valerolactone; and polymeric polyols commonly used in the production of polyurethanes, such as polycarbonate polyols and polybutadiene glycols. Instead of the low molecular weight glycols, various polyols such as glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, pentaerythritol, and sorbitol can also be used. From the viewpoint of dispersibility in the emulsion resin composition, the polyol is preferably one having a hydrophilic portion such as an ethylene oxide adduct.

[0069] The polyisocyanate may be an aromatic, aliphatic, or alicyclic diisocyanate, such as 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, or methylene diisocyanate. cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and dimer diisocyanate in which the carboxyl group of a dimer acid is converted into an isocyanate group.

[0070] Examples of blocking agents for isocyanate groups include bisulfites and sulfonic acid group-containing phenols, alcohols, lactams, oximes, and active methylene compounds.

[0071] To improve dispersibility in the emulsion resin composition, a hydrophilic group such as a carboxylate may be introduced into the urethane polymer.

[0072] The weight average molecular weight of the hydrophilic polymer is not particularly limited, and may be, for example, 1×10 4 ~1 x 10 7 is.

[0073] In the emulsion resin composition, the hydrophilic polymer is dispersed, for example, in the form of particles. The average particle size of the hydrophilic polymer is not particularly limited and is, for example, 10 to 1,000 nm, and preferably 50 to 800 nm. The average particle size of the hydrophilic polymer can be measured by the method described above for the silicone-based polymer.

[0074] The emulsion resin composition containing the hydrophilic polymer can be prepared, for example, by emulsion polymerizing the monomer components for forming the hydrophilic polymer in the presence of an emulsifier (surfactant).

[0075] The emulsion resin composition may further contain a surfactant for dispersing the hydrophilic polymer, such as those described above for the silicone polymer.

[0076] The emulsion resin composition may further contain another surfactant different from the surfactant for dispersing the silicone polymer or hydrophilic polymer described above. The other surfactant can improve the wettability of the emulsion resin composition to, for example, a metal roll of a coater such as a gravure coater, depending on the type of surfactant. Therefore, when the emulsion resin composition contains another surfactant, the emulsion resin composition tends to be uniformly applied using a coater equipped with a metal roll. Uniform application of the emulsion resin composition tends to reduce variations in the thickness of the intermediate layer 2 formed from the emulsion resin composition.

[0077] The emulsion resin composition may further contain a crosslinking agent and a filler. When the intermediate layer 2 is formed from an emulsion resin composition containing a filler, the permeation rate of the fluid passing through the intermediate layer 2 tends to increase. The filler may contain an inorganic material or an organic material. Examples of inorganic materials contained in the filler include zeolite and silica. It is preferable that the filler be hydrophilic and have high dispersibility in water.

[0078] The solids concentration in the emulsion resin composition is not particularly limited and is, for example, 10 to 60 wt %. When the emulsion resin composition contains a surfactant, the weight ratio of the surfactant to the weight of all solids in the emulsion resin composition is not particularly limited and is, for example, 15 wt % or less, or may be 5 wt % or less, or may be 1 wt % or less. If the weight ratio of the surfactant is 15 wt % or less, for example, when the emulsion resin composition is applied onto a porous support 3, the emulsion resin composition can be sufficiently prevented from penetrating into the porous support 3.

[0079] The intermediate layer 2 can be prepared, for example, by removing the dispersion medium from the emulsion resin composition. Therefore, the intermediate layer 2 contains components derived from the emulsion resin composition. As an example, the intermediate layer 2 contains at least one selected from the group consisting of a silicone-based polymer and a hydrophilic polymer, and preferably contains both a silicone-based polymer and a hydrophilic polymer. The silicone-based polymer contained in the intermediate layer 2 may be a crosslinked product of the silicone-based polymer contained in the emulsion resin composition. Similarly, the hydrophilic polymer contained in the intermediate layer 2 may be a crosslinked product of the hydrophilic polymer contained in the emulsion resin composition.

[0080] The content of the silicone-based polymer in the intermediate layer 2 is not particularly limited and is, for example, 10 wt % or more, preferably 30 wt % or more, more preferably 50 wt % or more, even more preferably 70 wt % or more, particularly preferably 80 wt % or more, and may be 90 wt % or more, 95 wt % or more, or even 99 wt % or more. The intermediate layer 2 may be substantially composed of a silicone-based polymer. The higher the content of the silicone-based polymer in the intermediate layer 2, the higher the permeation rate of the permeating fluid from the separation membrane 10A tends to be. However, the content of the silicone-based polymer in the intermediate layer 2 may be less than 10 wt % or 5 wt % or less. The intermediate layer 2 may be substantially free of a silicone-based polymer.

[0081] The content of the hydrophilic polymer in the intermediate layer 2 is not particularly limited and may be, for example, 1 wt % or more, preferably 5 wt % or more, and more preferably 10 wt % or more. The higher the content of the hydrophilic polymer in the intermediate layer 2, the more likely it is that the adhesion between the separation functional layer 1 and the intermediate layer 2 will improve. In some cases, the intermediate layer 2 may be substantially composed of a hydrophilic polymer. The upper limit of the content of the hydrophilic polymer in the intermediate layer 2 is not particularly limited and may be, for example, 90 wt %, preferably 70 wt %, more preferably 50 wt %, even more preferably 30 wt %, and particularly preferably 20 wt %. In some cases, the intermediate layer 2 may be substantially free of a hydrophilic polymer. The content of the hydrophilic polymer in the intermediate layer 2 is preferably 10 wt % to 20 wt %.

[0082] The intermediate layer 2 may further contain other components in addition to the silicone-based polymer and the hydrophilic polymer. Examples of other components include a surfactant and a filler derived from the emulsion resin composition. That is, the intermediate layer 2 may contain a surfactant and a filler. For example, when the intermediate layer 2 contains a filler, the filler is embedded in a matrix containing the silicone-based polymer or the hydrophilic polymer, and is preferably dispersed in the matrix. In the intermediate layer 2, the filler may be partially aggregated.

[0083] The surfactant content in the intermediate layer 2 is not particularly limited and may be, for example, 15 wt % or less, 5 wt % or less, or 1 wt % or less. The lower limit of the surfactant content is not particularly limited and may be, for example, 0.1 wt %. The filler content in the intermediate layer 2 is not particularly limited and may be, for example, 60 wt % or less, 40 wt % or less, 20 wt % or less, or 10 wt % or less. The lower limit of the filler content is not particularly limited and may be, for example, 1 wt %.

[0084] The intermediate layer 2 is not limited to one formed from an emulsion resin composition, and may be one formed from a pressure-sensitive adhesive composition other than an emulsion resin composition. Examples of pressure-sensitive adhesive compositions include silicone-based pressure-sensitive adhesives containing a silicone-based polymer and (meth)acrylic pressure-sensitive adhesives containing a (meth)acrylic polymer. The intermediate layer 2 formed from these pressure-sensitive adhesives may have holes.

[0085] The thickness of the intermediate layer 2 is not particularly limited and is, for example, less than 50 μm, preferably 40 μm or less, more preferably 30 μm or less, even more preferably 10 μm or less, and particularly preferably 5 μm or less. The smaller the thickness of the intermediate layer 2, the more likely it is to suppress a decrease in the permeation rate of the permeating fluid through the separation membrane 10A. The lower limit of the thickness of the intermediate layer 2 is not particularly limited and is, for example, 0.1 μm.

[0086] (Porous Support) The porous support 3 is a member that supports the separation function layer 1 via the intermediate layer 2. Examples of the porous support 3 include nonwoven fabrics, porous polytetrafluoroethylene, aromatic polyamide fibers, porous metals, sintered metals, porous ceramics, porous polyesters, porous nylons, activated carbon fibers, latex, silicone, silicone rubber, polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polycarbonate, polysulfone, polyether ether ketone, polyacrylonitrile, polyimide, and polyphenylene oxide. Permeable (porous) polymers containing at least one selected from the group consisting of metal foams having open or closed cells, polymer foams having open or closed cells, silica, porous glass, and mesh screens. The porous support 3 may be a combination of two or more of these.

[0087] The porous support 3 has an average pore size of, for example, 0.01 to 0.4 μm. The thickness of the porous support 3 is not particularly limited and is, for example, 10 μm or more, preferably 20 μm or more, and more preferably 50 μm or more. 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.

[0088] (Shape of Separation Membrane) In this embodiment, the separation membrane 10A is typically a flat membrane. However, the separation membrane 10A may have a shape other than a flat membrane, and may also be a hollow fiber membrane.

[0089] (Method for manufacturing separation membrane) The separation membrane 10A can be manufactured, for example, by the following method. First, a polymer P is mixed with a solvent such as water or an organic solvent to prepare a mixed solution. A lower alcohol such as isopropyl alcohol (IPA) can be used as the organic solvent. The mixed solution may be subjected to a reflux treatment. An organic compound C is added to this mixed solution, and a solvent is further added as necessary to prepare a coating solution.

[0090] Next, the coating liquid is applied to a substrate to obtain a coating film. The method for applying the coating liquid is not particularly limited, and for example, spin coating can be used. The thickness of the separation functional layer 1 formed from the coating film can be adjusted by adjusting the rotation speed of the spin coater, the solid content concentration of the coating liquid, etc.

[0091] The substrate to which the coating liquid is applied is typically a laminate of a porous support 3 and an intermediate layer 2. This laminate can be produced, for example, by the following method. First, a coating liquid (e.g., the emulsion resin composition described above) containing the material for the intermediate layer 2 is prepared. Next, the coating liquid containing the material for the intermediate layer 2 is applied onto the porous support 3 to form a coating film. The method for applying the coating liquid is not particularly limited, and methods such as spin coating and dip coating can be used. The coating liquid may also be applied using a wire bar or the like. Next, the coating film is dried to form the intermediate layer 2. The coating film can be dried, for example, under heating conditions. The heating temperature of the coating film is, for example, 50°C or higher. The heating time of the coating film is, for example, 1 minute or more, and may be 5 minutes or more. Furthermore, the surface of the intermediate layer 2 may be subjected to an adhesion-enhancing treatment, if necessary. Examples of adhesion-enhancing treatments include surface treatments such as application of a primer, corona discharge treatment, and plasma treatment.

[0092] When the substrate is a laminate of the porous support 3 and the intermediate layer 2, the separation functional layer 1 is formed by drying the coating film formed on the substrate, and the separation membrane 10A is obtained. The drying conditions for the coating film can be the same as those described above for the intermediate layer 2.

[0093] The substrate is not limited to a laminate of the porous support 3 and the intermediate layer 2, and may also be a release liner. When the substrate is a release liner, the separation membrane 10A can be produced by the following method. First, a coating film formed on the substrate is dried to form the separation functional layer 1. Next, a coating liquid containing the material for the intermediate layer 2 (for example, the above-mentioned pressure-sensitive adhesive composition) is applied onto 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 the porous support 3. In this way, the separation membrane 10A is obtained.

[0094] (Characteristics of Separation Membrane) In the separation membrane 10A, the permeation rate of the permeating fluid tends to be improved by the separation functional layer 1 containing the organic compound C. As an example, the permeation rate T of carbon dioxide permeating through the separation membrane 10A is, for example, 5 GPU or more, and may be 10 GPU or more, 20 GPU or more, 50 GPU or more, 100 GPU or more, 120 GPU or more, 150 GPU or more, 200 GPU or more, 250 GPU or more, 300 GPU or more, 350 GPU or more, 400 GPU or more, or even 450 GPU or more. The upper limit of the permeation rate T is not particularly limited, and may be, for example, 3000 GPU or less, or 1000 GPU or less. Note that the GPU is 10 -6 ·cm 3 (STP) / (sec cm 2 cm 3 (STP) means the volume of a gas at 1 atmosphere and 0°C.

[0095] The permeation rate T can be calculated by the following method. First, a test gas consisting of carbon dioxide is supplied to a space adjacent to one side of the separation membrane 10A (for example, the main surface 11 on the separation function layer side of the separation membrane 10A). This test gas has a temperature of 25°C and a pressure of 0.6 MPa. As a result, a permeated fluid that has permeated the separation membrane 10A is obtained in a space adjacent to the other side of the separation membrane 10A (for example, the main surface 12 on the porous support side of the separation membrane 10A). The weight of the permeated fluid is measured, and the permeation rate T can be calculated from the measurement results.

[0096] The ratio T / T of the permeation rate T (GPU) of carbon dioxide permeating through the separation membrane 10A to the permeation rate T (GPU) of carbon dioxide permeating through a measurement separation membrane having the same configuration as the separation membrane 10A except that the separation functional layer 1 does not contain the organic compound C is, for example, 105% or more, and may be 120% or more, 150% or more, 200% or more, 250% or more, 300% or more, 350% or more, or even 400% or more. The upper limit of the ratio T / T is not particularly limited and may be, for example, 1000% or less. The permeation rate T can be measured by the method described above for the permeation rate T.

[0097] The separation factor α of the separation membrane 10A for carbon dioxide relative to nitrogen is not particularly limited and may be, for example, 5 or more, 10 or more, 20 or more, 30 or more, 40 or more, 50 or more, or even 60 or more. The upper limit of the separation factor α is not particularly limited and may be, for example, 100 or less. The separation factor α can be determined by the following method. First, the permeation rate of nitrogen permeating through the separation membrane 10A is measured by the method described above for the permeation rate T, except that a test gas consisting of nitrogen is used. The ratio of the carbon dioxide permeation rate T (GPU) to the nitrogen permeation rate (GPU) is determined as the separation factor α.

[0098] The ratio α / α of the separation factor α of the separation membrane 10A for carbon dioxide relative to nitrogen to the separation factor α of the separation membrane for measurement is, for example, 40% or more, and may be 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or even 100% or more. The upper limit of the ratio α / α is not particularly limited and may be, for example, 150% or less. The separation factor α can be measured by the method described above for the separation factor α.

[0099] (Applications of Separation Membrane) Applications of the separation membrane 10A of this embodiment include applications for separating acidic gases from mixed gases containing acidic gases. Examples of acidic gases in mixed gases include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, and nitrogen oxides (NOx), with carbon dioxide being preferred. The mixed gas contains other gases in addition to the acidic gas. Examples of other gases include non-polar gases such as hydrogen and nitrogen, and inert gases such as helium, with nitrogen being preferred. In particular, the separation membrane 10A of this embodiment is suitable for applications for separating carbon dioxide from mixed gases containing carbon dioxide and nitrogen. However, the application of the separation membrane 10A is not limited to applications for separating acidic gases from the above-mentioned mixed gases.

[0100] <Modified Example of Separation Membrane> In the separation membrane 10A, the intermediate layer 2 is not an essential component, and the separation membrane 10A does not necessarily have to have the intermediate layer 2. As shown in Fig. 2, a separation membrane 10B according to a modified example does not have the intermediate layer 2, and the separation functional layer 1 is in direct contact with the porous support 3. Except for this, the configuration of the separation membrane 10B is the same as the configuration of the separation membrane 10A. Therefore, elements common to the separation membrane 10A and the modified separation membrane 10B are denoted by the same reference numerals, and their description will be omitted.

[0101] In this embodiment, the separation membrane 10B is typically a flat membrane. However, the separation membrane 10B may have a shape other than a flat membrane, and may be a hollow fiber membrane.

[0102] The separation membrane 10B can be produced, for example, by the following method. First, the above-mentioned coating solution containing the polymer P and the organic compound C is prepared. This coating solution is applied to the porous support 3 to obtain a coating membrane. The coating membrane is dried to form the separation function layer 1, and the separation membrane 10B is obtained.

[0103] <Embodiment of Membrane Separation Apparatus> As shown in Fig. 3, the membrane separation apparatus 100 of this embodiment includes a separation membrane 10A and a tank 20. Note that the membrane separation apparatus 100 may include the separation membrane 10B described in Fig. 2 instead of the separation membrane 10A. The tank 20 includes a first chamber 21 and a second chamber 22. The separation membrane 10A is disposed inside the tank 20. Inside the tank 20, the separation membrane 10A separates the first chamber 21 from the second chamber 22. The separation membrane 10A extends from one to the other of a pair of wall surfaces of the tank 20.

[0104] The first chamber 21 has an inlet 21 a and an outlet 21 b. The second chamber 22 has an outlet 22 a. The inlet 21 a, the outlet 21 b, and the outlet 22 a are preferably openings formed in the wall surface of the tank 20.

[0105] Membrane separation using the membrane separation device 100 is performed by the following method. First, a gas mixture 30 containing an acidic gas is supplied to the first chamber 21 through the inlet 21a. The concentration of the acidic gas in the gas mixture 30 is not particularly limited, and is, for example, 0.01 vol% (100 ppm) or more under standard conditions, preferably 1 vol% or more, more preferably 10 vol% or more, even more preferably 30 vol% or more, and particularly preferably 50 vol% or more. The upper limit of the concentration of the acidic gas in the gas mixture 30 is not particularly limited, and is, for example, 90 vol% under standard conditions.

[0106] The pressure inside the first chamber 21 may be increased by the supply of the mixed gas 30. The membrane separation apparatus 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 more, preferably 0.3 MPa or more.

[0107] The second chamber 22 may be depressurized while the gas mixture 30 is supplied to the first chamber 21. The membrane separation apparatus 100 may further include a pump (not shown) for depressurizing the second chamber 22. The second chamber 22 may be depressurized so that the space within the second chamber 22 is reduced in pressure 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.

[0108] By supplying the gas mixture 30 into the first chamber 21, a permeated fluid 35 having a higher acidic gas content than the gas mixture 30 can be obtained on the other side of the separation membrane 10A. That is, the permeated fluid 35 is supplied to the second chamber 22. The permeated fluid 35 preferably contains an acidic gas as a main component. However, the permeated fluid 35 may also contain small amounts of gases other than the acidic gas. The permeated fluid 35 is discharged to the outside of the tank 20 through the outlet 22a.

[0109] The concentration of the acid gas in the mixed gas 30 gradually decreases from the inlet 21a to 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.

[0110] The membrane separation apparatus 100 of this embodiment is suitable for a continuous membrane separation method, but may also be used for a batch-type membrane separation method.

[0111] <Modifications of Membrane Separation Device> The membrane separation device 100 may be a spiral membrane element, a hollow fiber membrane element, or the like. Fig. 4 shows a spiral membrane element. The membrane separation device 110 of Fig. 4 includes a central tube 41 and a stack 42. The stack 42 includes a separation membrane 10A (or separation membrane 10B).

[0112] The central tube 41 has a cylindrical shape. A plurality of holes are formed on the surface of the central tube 41 to allow the permeating fluid 35 to flow into the interior of the central tube 41. Examples of materials for the central tube 41 include resins such as acrylonitrile-butadiene-styrene copolymer resin (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 central tube 41 is, for example, in the range of 20 to 100 mm.

[0113] In addition to the separation membrane 10A, the laminate 42 further includes a feed-side channel material 43 and a permeate-side channel material 44. The laminate 42 is wound around a central tube 41. The membrane separation device 110 may further include an exterior material (not shown).

[0114] The feed-side channel material 43 and the permeate-side channel material 44 may be, for example, a resin net made of polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE).

[0115] Membrane separation using the membrane separation device 110 is performed in the following manner. First, the gas mixture 30 is supplied to one end of the wound stack 42. The permeated fluid 35 that has permeated the separation membrane 10A of the stack 42 moves into the interior of the central tube 41. The permeated fluid 35 is discharged to the outside through the central tube 41. The gas mixture 30 (non-permeated fluid 36) that has been 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 gas mixture 30.

[0116] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0117] Example 1 First, an emulsion resin composition was prepared by mixing an aqueous emulsion containing a silicone polymer (POLON-MF-56 manufactured by Shin-Etsu Chemical Co., Ltd.), an aqueous emulsion containing a urethane polymer (Takelac W-6010 manufactured by Mitsui Chemicals, Inc.), and ion-exchanged water for dilution. Next, the prepared emulsion resin composition was applied to a porous support using an applicator (gap: 50 μm) to obtain a coating film. A polysulfone porous substrate manufactured by Nitto Denko Corporation was used as the porous support. The obtained coating film was dried at 130°C for 10 minutes to form an intermediate layer having a thickness of 1 μm.

[0118] Next, a polyether block amide (PEBAX MH1657 manufactured by Arkema) as polymer P was mixed with isopropyl alcohol (IPA) and water (weight ratio IPA / water = 70 / 30) as solvents to prepare a mixed solution with a solids concentration of 2 wt %. This mixed solution was added to a flask and refluxed at 80°C for 2 hours. Next, coumarin-3-carboxylic acid as organic compound C was added to the mixed solution, and further diluted with IPA and water (weight ratio IPA / water = 70 / 30) as solvents to prepare a coating solution.

[0119] Next, the prepared coating solution was applied onto the intermediate layer using an applicator (gap: 50 μm) to obtain a coating film. The obtained coating film was then dried in an oven at 60°C for 30 minutes to form a separation functional layer. This resulted in the separation membrane of Example 1. In Example 1, the thickness of the separation functional layer was approximately 1 μm. The content of organic compound C in the separation functional layer was 50 wt%.

[0120] Examples 2 to 47 Separation membranes of Examples 2 to 47 were obtained in the same manner as in Example 1, except that the type of organic compound C was changed as shown in Tables 1 and 2.

[0121] Comparative Example 1 A separation membrane of Comparative Example 1 was obtained in the same manner as in Example 1, except that organic compound C was not used.

[0122] Examples 48 to 53 Separation membranes of Examples 48 to 53 were obtained in the same manner as in Example 1, except that the type of polymer P and the type of organic compound C were changed as shown in Tables 3 and 4.

[0123] Comparative Examples 2 and 3 Separation membranes of Comparative Examples 2 and 3 were obtained in the same manner as in Example 1, except that the type of polymer P was changed as shown in Tables 3 and 4 and that organic compound C was not used.

[0124] [Evaluation of separation membrane characteristics] The carbon dioxide permeation rate T and the carbon dioxide relative to nitrogen separation factor α (CO2 / N2) of the prepared separation membrane were measured by the following method. First, the separation membrane was set in a metal cell and sealed with an O-ring to prevent leakage. Next, a test gas consisting of carbon dioxide was injected into the metal cell so that it contacted the main surface of the separation membrane on the separation function layer side. The test gas had a temperature of 25°C and a pressure of 0.6 MPa. As a result, a permeated fluid was obtained from the main surface of the separation membrane on the porous support side. The permeation rate T was calculated based on the weight of the obtained permeated fluid, etc.

[0125] Next, the permeation rate of nitrogen through the separation membrane was measured by the method described above for the permeation rate T, except that the test gas used was nitrogen. The ratio of the carbon dioxide permeation rate T (GPU) to the nitrogen permeation rate (GPU) was determined as the separation factor α.

[0126]

[0127]

[0128]

[0129]

[0130] The abbreviations in Tables 1 to 4 are as follows: PEBAX: polyether block amide (PEBAX MH1657 manufactured by Arkema) PVAc: polyvinyl acetate (PVAc manufactured by Sigma-Aldrich, weight-average molecular weight 100,000) PEG: polyethylene glycol (PEG manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., weight-average molecular weight 500,000)

[0131] The organic compound C used in Examples 1 to 47 was all solid at 25°C. As can be seen from Tables 1 and 2, the separation membranes of Examples 1 to 47, in which the separation functional layer contained solid organic compound C, had higher carbon dioxide permeation rates T than Comparative Example 1. Similarly, as can be seen from Table 3, the separation membranes of Examples 48 to 50, in which the separation functional layer contained solid organic compound C, had higher carbon dioxide permeation rates T than Comparative Example 2. As can be seen from Table 4, the separation membranes of Examples 51 to 53, in which the separation functional layer contained solid organic compound C, had higher carbon dioxide permeation rates T than Comparative Example 3. Thus, the separation membranes of the Examples had improved permeation rates of the permeating fluid.

[0132] The separation membrane of this embodiment is suitable for separating an acid gas from a gas mixture containing the acid gas, and in particular, for separating carbon dioxide from off-gas of a chemical plant or thermal power plant.

Claims

1. A separation membrane comprising: a separation functional layer containing a polymer; and a porous support supporting the separation functional layer, wherein the separation functional layer further contains an organic compound that is different from the polymer and is solid at 25°C.

2. The separation membrane according to claim 1, wherein the content of the organic compound in the separation functional layer is 20 wt % or more.

3. The separation membrane according to claim 1, wherein the organic compound has a molecular weight of 500 or less.

4. The separation membrane according to claim 1, wherein the organic compound has a ring structure.

5. The separation membrane according to claim 1, wherein the organic compound has a polar group.

6. The separation membrane according to claim 5, wherein the polar group includes at least one selected from the group consisting of a carboxyl group, a hydroxyl group, an ester group, an ether group, a halogen group, a nitro group, an amino group, and a nitrile group.

7. The organic compound is coumarin-3-carboxylic acid, salicylic acid, 3-fluorobenzoic acid, phthalonitrile, 2,3-pyridinedicarboxylic acid, 4-nitrotoluene, isophthalic acid, 4-chlorobenzonitrile, chromone-2-carboxylic acid, 1-nitronaphthalene, 3-chlorobenzoic acid, 1-naphthylamine, acetylsalicylic acid, fluorobenzene, coumarin, 4-dimethylaminobenzoic acid, benzoic acid, chromone, phenoxazine, m-trifluoromethylbenzoic acid, 2-chlorophenol, 1,3-dichlorobenzene, quinazoline, 2-fluorobenzyl alcohol, o-tolunitrile, quinoline, 1-naphthalenecarboxylic acid, 2-naphthalenecarboxamide, 2-naphthalenecarb ...

2. The separation membrane according to claim 1, comprising at least one selected from the group consisting of 2-fluorophenylacetic acid, 3-fluorophenylacetic acid, 3-chlorobenzyl alcohol, phthalazine, 3,5-dinitroaniline, 2-fluorobenzoic acid, p-anisic acid, 2-methoxybenzyl alcohol, 3-(3-fluorophenyl)propionic acid, 3-methoxybenzonitrile, benzimidazole, 3-chlorophenylacetic acid, 2,6-pyridinedicarboxylic acid, 1-naphthol, cis-1,2-cyclohexanedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, caffeine, 4-hydroxymethylbenzoic acid, and 6-hydroxy-2-naphthonitrile.

8. The separation membrane according to claim 1, wherein the polymer has a functional group containing an oxygen atom.

9. The separation membrane according to claim 8, wherein the functional group includes at least one selected from the group consisting of an ether group, an amide group, and an ester group.

10. The separation membrane according to claim 1, wherein the polymer comprises at least one selected from the group consisting of polyether block amides, polyvinyl esters, and polyethers.

11. The separation membrane according to claim 1, wherein the separation functional layer has a thickness of 2 μm or less.

12. The separation membrane according to claim 1, further comprising an intermediate layer disposed between the separation functional layer and the porous support.

13. The separation membrane according to claim 1, which is used to separate an acid gas from a gas mixture containing the acid gas.

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