Crosslinked polymer, separation functional layer, and separation membrane

Abstract

To provide a novel polymer suitable for use in a separation functional layer.SOLUTION: In a crosslinked polymer of the present invention, a polymer containing carbon atoms is crosslinked via a hydrocarbon group, and the hydrocarbon group is bonded to the carbon atoms. A separation functional layer 1 of the present invention contains the crosslinked polymer. The separation membrane 10 of the present invention comprises the separation functional layer 1, and a porous support 3 that supports the separation functional layer 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a crosslinked polymer, a separation functional layer, and a separation membrane. [Background technology]

[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] Separation membranes used in membrane separation methods include composite membranes in which a separation functional layer is formed on a porous support. Materials for the separation functional layer include resins such as polyimide resins and polyether block amide resins. For example, Patent Document 1 discloses a separation membrane containing a polyimide resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-184424 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need for new polymers suitable for the separation functional layer. [Means for solving the problem]

[0006] The present invention provides Polymers containing carbon atoms are crosslinked via hydrocarbon groups, The hydrocarbon groups are bonded to the carbon atoms to provide a crosslinked polymer.

[0007] The present invention further provides a method for producing the above crosslinked polymer, comprising the steps of: reacting carbon atoms of the polymer with a crosslinker; A method for producing a crosslinked polymer is provided, wherein the crosslinking agent comprises a diether compound.

[0008] The present invention further provides a separation functional layer comprising the above crosslinked polymer.

[0009] Furthermore, the present invention provides a film-forming device comprising the above-mentioned separation functional layer and a porous support supporting the separation functional layer; A separation membrane comprising: [Effects of the Invention]

[0010] According to the present invention, a new polymer suitable for a separation functional layer can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a cross-sectional view schematically showing a separation functional layer according to one embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically showing a separation membrane according to one embodiment of the present invention. [Figure 3A] 1 is a schematic cross-sectional view of a membrane separation device equipped with a separation membrane of the present invention. [Figure 3B] FIG. 2 is a schematic cross-sectional view of another example of a membrane separation device equipped with a separation membrane of the present invention. [Figure 4] FIG. 10 is a perspective view schematically showing a modified example of a membrane separation device provided with a separation membrane of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The crosslinked polymer according to the first aspect of the present invention is Polymers containing carbon atoms are crosslinked via hydrocarbon groups, The hydrocarbon group is bonded to the carbon atom.

[0013] In a second aspect of the present invention, for example, in the crosslinked polymer according to the first aspect, the hydrocarbon group is an alkylene group.

[0014] In a third aspect of the present invention, for example, in the crosslinked polymer according to the second aspect, the alkylene group has 1 to 5 carbon atoms.

[0015] In a fourth aspect of the present invention, for example, in the crosslinked polymer according to any one of the first to third aspects, the polymer comprises an aromatic ring, The aromatic ring contains the carbon atom.

[0016] In a fifth aspect of the present invention, for example, in the crosslinked polymer according to the fourth aspect, the polymer comprises an electron donating group, The electron donating group is attached to the aromatic ring.

[0017] In a sixth aspect of the present invention, for example, in the crosslinked polymer according to any one of the first to fifth aspects, the polymer is a polyimide.

[0018] In a seventh aspect of the present invention, for example, in the crosslinked polymer according to the sixth aspect, the polyimide contains a structural unit A1 derived from a tetracarboxylic dianhydride having a six-membered ring acid anhydride structure, and a structural unit B derived from a diamine.

[0019] In the eighth aspect of the present invention, for example, in the crosslinked polymer according to the seventh aspect, the structural unit B has the carbon atom.

[0020] In a ninth aspect of the present invention, for example, in the crosslinked polymer according to the seventh or eighth aspect, the structural unit A1 is represented by the following formula (A1). [ka] In the formula (A1), R 1a ~R 4a are each independently a hydrogen atom or an optional substituent.

[0021] The separation functional layer according to the tenth aspect of the present invention comprises: The crosslinked polymer according to any one of the first to ninth aspects is included.

[0022] In an eleventh aspect of the present invention, for example, the separation functional layer according to the tenth aspect is used to separate an acidic gas from a mixed gas containing the acidic gas.

[0023] A separation membrane according to a twelfth aspect of the present invention comprises: A separation functional layer according to the tenth or eleventh aspect; a porous support supporting the separation functional layer; Equipped with.

[0024] A manufacturing method according to a thirteenth aspect of the present invention comprises the steps of: A method for producing a crosslinked polymer according to any one of the first to ninth aspects, reacting the carbon atoms of the polymer with a crosslinker; The crosslinking agent includes a diether compound.

[0025] In a fourteenth aspect of the present invention, for example, in the method for producing a crosslinked polymer according to the thirteenth aspect, the reaction is carried out in the presence of a catalyst.

[0026] 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.

[0027] <Embodiments of Crosslinked Polymers> In the crosslinked polymer of this embodiment, a polymer G containing carbon atoms is crosslinked via a hydrocarbon group, and the hydrocarbon group is bonded to the carbon atom. There is no linking group or functional group between the hydrocarbon group and the carbon atom, and they are directly bonded. In this specification, "a polymer containing carbon atoms is crosslinked via a hydrocarbon group" means that polymer G (more specifically, multiple molecules of polymer G) react with a crosslinking agent to form a crosslinked structure consisting of a hydrocarbon group. Therefore, in the crosslinked polymer of this embodiment, for example, two molecules of polymer G, polymer G1 and polymer G2, are crosslinked via a hydrocarbon group by bonding carbon atom g1 in polymer G1 and carbon atom g2 in polymer G2 to one hydrocarbon group.

[0028] The hydrocarbon group may be a divalent hydrocarbon group, and is preferably an alkylene group.

[0029] The number of carbon atoms in the alkylene group is preferably 1 to 10, more preferably 1 to 7, still more preferably 1 to 5, and particularly preferably 1 to 3. The alkylene group may be linear or branched. Examples of the alkylene group include methylene, 1-methylmethylene, 1,1-dimethylmethylene, ethylene, 1-methylethylene, 1-ethylethylene, 1,1-dimethylethylene, 1,2-dimethylethylene, 1-ethyl-2-methylethylene, trimethylene, 1-methyltrimethylene, 2-methyltrimethylene, 1,1-dimethyltrimethylene, 1,2-dimethyltrimethylene, 2,2-dimethyltrimethylene, 1-ethyltrimethylene, 2-ethyltrimethylene, tetramethylene, 1-methyltetramethylene, 2-methyltetramethylene, and pentamethylene, preferably methylene, ethylene, or trimethylene, and more preferably methylene. The carbon atom g1 may be bonded to one end of the main chain of the alkylene group, and the carbon atom g2 may be bonded to the other end of the main chain of the alkylene group. For example, the alkylene group may be linear, with the carbon atom g1 bonded to one end of the alkylene group and the carbon atom g2 bonded to the other end of the alkylene group.

[0030] Polymer G may contain an aromatic ring, and the aromatic ring may contain the carbon atoms (specifically, carbon atoms g1 and g2). That is, polymer G may be crosslinked by bonding a carbon atom constituting the aromatic ring contained in polymer G to the hydrocarbon group. The aromatic ring may be composed only of carbon atoms and hydrogen atoms, or may be a heteroaromatic ring containing a heteroatom such as an oxygen atom, a nitrogen atom, or a sulfur atom. 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 the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a fluorene ring, a furan ring, a pyrrole ring, a pyridine ring, and a thiophene ring.

[0031] The polymer G may further contain an electron-donating group. Typically, the electron-donating group is bonded to the aromatic ring. When the polymer G contains an electron-donating group bonded to the aromatic ring, the crosslinking reaction of the polymer G can proceed more easily in the production of a crosslinked polymer. This can increase the degree of crosslinking of the crosslinked polymer. The electron-donating group is, for example, a group having a substituent constant σ in the Hammett equation. p The electron-donating group refers to a substituent whose value is negative. Examples of the electron-donating group include alkyl groups and alkoxy groups. Examples of the alkyl group include methyl groups, ethyl groups, and propyl groups. Examples of the alkoxy group include methoxy groups, ethoxy groups, and propoxy groups.

[0032] The polymer G is typically a polyimide. That is, the crosslinked polymer is typically a crosslinked polyimide. The polyimide is preferably a polyimide P containing a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered ring acid anhydride structure S. The polyimide P preferably further contains a structural unit B derived from a diamine.

[0033] The structural unit A1 derived from the tetracarboxylic dianhydride a1 is a structural unit suitable for improving the permeability coefficient and permeation rate of an acidic gas that permeates a separation functional layer using, for example, polyimide P. The tetracarboxylic dianhydride a1 has, for example, one or more, preferably two, acid anhydride structures S. The six-membered ring acid anhydride structure S is typically a glutaric anhydride structure represented by the following formula (1). [ka]

[0034] The tetracarboxylic dianhydride a1 may have a fused ring, and the fused ring may contain an acid anhydride structure S. The fused ring may contain an aromatic ring together with the acid anhydride structure S. The aromatic ring contained in the fused ring may be composed only of carbon atoms and hydrogen atoms, or may be a heteroaromatic ring containing a heteroatom such as an oxygen atom, a nitrogen atom, or a sulfur atom. 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 the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a fluorene ring, a furan ring, a pyrrole ring, a pyridine ring, and a thiophene ring.

[0035] The fused ring may or may not have a substituent. The substituent of the fused ring is not particularly limited, and examples thereof include a halogen group and a hydrocarbon group. Examples of the halogen group include a fluoro group, a chloro group, a bromo group, and an iodo group. The number of carbon atoms in the hydrocarbon group is not particularly limited, and is, for example, 1 to 15. Examples of the hydrocarbon group include an alkyl group such as a methyl group, an ethyl group, and a propyl group. The hydrocarbon group may be a halogenated hydrocarbon group in which a hydrogen atom is substituted with a halogen group. When the fused ring has multiple substituents, the multiple substituents may be the same or different.

[0036] The tetracarboxylic dianhydride a1 is preferably represented by the following formula (a1). [ka]

[0037] In formula (a1), R 1a ~R 4a are each independently a hydrogen atom or an arbitrary substituent. The arbitrary substituent is not particularly limited, and examples thereof include a halogen group and a hydrocarbon group. Examples of the halogen group and the hydrocarbon group include those described above.

[0038] In the polyimide P, the structural unit A1 derived from the tetracarboxylic dianhydride a1 is preferably represented by the following formula (A1): The structural unit A1 represented by formula (A1) is derived from the tetracarboxylic dianhydride a1 represented by the above formula (a1). In formula (A1), the nitrogen atom contained in the imide group is derived from the diamine that has reacted with the tetracarboxylic dianhydride a1. [ka]

[0039] In formula (A1), R 1a ~R 4a are the same as in formula (a1) and are each independently a hydrogen atom or an arbitrary substituent. Specific examples of the structural unit A1 represented by formula (A1) include the following formula (A1-1). [ka]

[0040] In polyimide P, the ratio p1 of the amount of the structural unit A1 to the amount of all structural units A derived from tetracarboxylic dianhydride is, for example, 50 mol% or more, and may be 70 mol% or more, 90 mol% or more, 95 mol% or more, or even 99 mol% or more. Polyimide P may contain only the structural unit A1 as the structural unit A derived from tetracarboxylic dianhydride. However, polyimide P may further contain, in addition to structural unit A1, a structural unit A2 derived from tetracarboxylic dianhydride a2 having a five-membered ring acid anhydride structure. The tetracarboxylic dianhydride a2 is not particularly limited, and examples thereof include pyromellitic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride.

[0041] As described above, it is preferable that the polyimide P further contains a structural unit B derived from a diamine. A diamine is a compound having two primary amino groups. The diamine may or may not contain functional groups other than the primary amino groups. Examples of such functional groups include a carboxyl group, a hydroxyl group, a thiol group, and a sulfonyl group. The diamine may have at least one functional group f selected from the group consisting of a carboxyl group, a hydroxyl group, and a thiol group.

[0042] The diamine preferably has an aromatic ring. That is, the structural unit B preferably has an aromatic ring. The crosslinked polyimide may be one in which the carbon atoms constituting the aromatic ring contained in the structural unit B are bonded to a hydrocarbon group (e.g., an alkylene group), thereby crosslinking the polyimide P via the hydrocarbon group. The structural unit B may have an electron-donating group, and the electron-donating group may be bonded to the aromatic ring. Examples of the electron-donating group include those described above. The polyimide P may contain multiple different structural units B derived from a diamine. For example, the structural unit B may contain a structural unit having an electron-donating group and a structural unit not having an electron-donating group. The structural unit not having an electron-donating group may contain a functional group f.

[0043] Examples of the aromatic ring include those described above for the tetracarboxylic dianhydride a1. In the diamine, the substituent on the aromatic ring contains, for example, a primary amino group. The aromatic ring may have a substituent other than the substituent containing the primary amino group, or may have no other substituent. The other substituent is not particularly limited, and examples include a group containing the functional group f, a halogen group, and an electron-donating group. Examples of the halogen group include those described above for the tetracarboxylic dianhydride a1. Examples of the electron-donating group include those described above. In the diamine, the other substituent may contain a photopolymerizable functional group (for example, a vinyl group).

[0044] The diamine is represented by, for example, the following formula (b1), formula (b2), formula (b3), formula (b4) or formula (b5). [ka]

[0045] In formulas (b1) to (b5), R 1b ~R 30b are each independently a hydrogen atom or an arbitrary substituent. The arbitrary substituent is, for example, a group containing the functional group f, a halogen group, an electron-donating group, etc. Examples of the halogen group and the electron-donating group include those described above.

[0046] In formula (b3), R 10b and R 13b may be bonded to each other to form a ring, and R 12b and R 15b may be bonded to each other to form a ring. 17b and R 21b may be bonded to each other to form a ring, and R 20b and R 22b may be bonded to each other to form a ring.

[0047] In formulas (b3) and (b4), X 1 and X 2 is a single bond or an arbitrary linking group. The arbitrary linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include alkylene groups such as methylene, ethylene, propane-1,3-diyl, and propane-2,2-diyl. The divalent hydrocarbon group may be a halogenated hydrocarbon group in which a hydrogen atom is substituted with a halogen group. The divalent hydrocarbon group may further have an aromatic ring. Examples of the aromatic ring include those described above for tetracarboxylic dianhydride a1. The divalent hydrocarbon group may be a fluorenediyl group. X 1 and X 2 may contain a functional group such as an ether group or an ester group in addition to or instead of the divalent hydrocarbon group.

[0048] The structural unit B derived from a diamine is represented, for example, by the following formula (B1), (B2), (B3), (B4) or (B5): The structural units B represented by formulas (B1) to (B5) are derived from the diamines represented by the above formulas (b1) to (b5), respectively. [ka]

[0049] In formula (B1), R 1b ~R 4b are each independently a hydrogen atom or an arbitrary substituent. In formula (B1), the arbitrary substituent is, for example, a group containing the functional group f, a halogen group, an electron-donating group, etc. Examples of the halogen group and the electron-donating group include those described above.

[0050] Specific examples of the structural unit B represented by formula (B1) include the following formulae (B1-1) to (B1-6). [ka]

[0051] In formula (B2), R 5b ~R 8b are each independently a hydrogen atom or an arbitrary substituent. In formula (B2), the arbitrary substituent is, for example, a group containing functional group f, a halogen group, an electron-donating group, etc. Examples of the halogen group and the electron-donating group include those described above. Specific examples of the structural unit B represented by formula (B2) include the following formulae (B2-1) to (B2-2). [ka]

[0052] In formula (B3), R 9b ~R 16b are each independently a hydrogen atom or an arbitrary substituent, and X 1is a single bond or an arbitrary linking group. In formula (B3), the arbitrary substituent is, for example, a group containing the functional group f, a halogen group, an electron-donating group, etc. Examples of the halogen group and the electron-donating group include those described above. In formula (B3), R 10b and R 13b may be bonded to each other to form a ring, and R 12b and R 15b may be bonded to each other to form a ring.

[0053] X in formula (B3) 1 In the formula (I), the optional linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include those mentioned above. X 1 may contain a functional group such as an ether group or an ester group in addition to or instead of the divalent hydrocarbon group.

[0054] Specific examples of the structural unit B represented by formula (B3) include the following formulae (B3-1) to (B3-18). [ka] [ka]

[0055] In formula (B4), R 17b ~R 24b are each independently a hydrogen atom or an arbitrary substituent, and X 2 is a single bond or an arbitrary linking group. In formula (B4), the arbitrary substituent is, for example, a group containing the functional group f, a halogen group, an electron-donating group, etc. Examples of the halogen group and the electron-donating group include those described above. In formula (B4), R 17b and R 21b may be bonded to each other to form a ring, and R 20b and R 22b may be bonded to each other to form a ring.

[0056] X in formula (B4) 2In the formula (I), the optional linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include those mentioned above. X 2 may contain a functional group such as an ether group or an ester group in addition to or instead of the divalent hydrocarbon group.

[0057] Specific examples of the structural unit B represented by formula (B4) include the following formulae (B4-1) to (B4-5). [ka]

[0058] In formula (B5), R 25b ~R 30b are each independently a hydrogen atom or an arbitrary substituent. In formula (B5), the arbitrary substituent is, for example, a group containing functional group f, a halogen group, an electron-donating group, etc. Examples of the halogen group and the electron-donating group include those described above. The structural unit B represented by formula (B5) is suitable for improving the rigidity of polyimide P. Polyimide P with excellent rigidity tends to be able to suppress plasticization of the separation functional layer using polyimide P (and its crosslinked polyimide) even when the pressure of the mixed gas to be separated is high.

[0059] Specific examples of the structural unit B represented by formula (B5) include the following formulae (B5-1) and (B5-2). [ka]

[0060] In polyimide P, structural units A derived from tetracarboxylic dianhydride and structural units B derived from diamine are arranged alternately. Examples of combinations of adjacent structural units A and B in polyimide P include the following formulae (A1-B3) and (A1-B5). In these formulae, R 1a ~R 4a , R 9b ~R 16b , and R 25b~R 30b is the same as that described above for formula (A1), formula (B3), and formula (B5). Polyimide P may include a structure represented by the following formula (A1-B3) and a structure represented by the following formula (A1-B5). [ka]

[0061] The weight-average molecular weight (Mw) of polyimide P is, for example, 30,000 or more, preferably 50,000 or more, and more preferably 75,000 or more, from the viewpoint of the mechanical strength of the separation functional layer when used in the separation functional layer. The upper limit of the weight-average molecular weight of polyimide P is not particularly limited, and is, for example, 300,000. The weight-average molecular weight of polyimide P can be calculated, for example, by measuring the molecular weight distribution of polyimide P using a gel permeation chromatograph (GPC) equipped with a refractive index detector (RID) and using a calibration curve based on standard polystyrene from the obtained chromatogram (chart).

[0062] The gel fraction of the crosslinked polymer according to this embodiment may be, for example, 50.0% or more, 70.0% or more, 75.0% or more, 80.0% or more, 85.0% or more, or even 90.0%. The upper limit of the gel fraction of the crosslinked polymer is, for example, 100.0% or less.

[0063] (Method of manufacturing crosslinked polymer) The method for producing a crosslinked polymer according to this embodiment includes reacting carbon atoms of a polymer G with a crosslinking agent. The crosslinking agent includes a diether compound. As described above, the polymer G is preferably a polyimide P.

[0064] Polyimide P can be prepared, for example, by the following method: First, a diamine is dissolved in a solvent to obtain a solution. Examples of the solvent include N-methyl-2-pyrrolidone, nitrobenzene, benzonitrile, α-chloronaphthalene, phenol, m-cresol, and p-chlorophenol.

[0065] Next, tetracarboxylic dianhydrides including the tetracarboxylic dianhydride a1 are gradually added to the resulting solution. This causes a reaction between the tetracarboxylic dianhydride a1 and the diamine-containing monomers to form polyamic acid. The addition of the tetracarboxylic dianhydrides is carried out, for example, under stirring conditions for 3 to 20 hours in a heated environment at 140°C or higher. Polyimide P can be obtained by imidizing the polyamic acid. Examples of imidization methods include chemical imidization and thermal imidization. Chemical imidization is a method in which polyamic acid is imidized, for example, at room temperature using a dehydration condensation agent. Examples of dehydration condensation agents include acetic anhydride, pyridine, and triethylamine. Thermal imidization is a method in which polyamic acid is imidized by heat treatment. The heat treatment temperature is, for example, 180°C or higher. The polyamic acid formation reaction and the imidization of polyamic acid may proceed in parallel. The polyimide P formation reaction (imidization) may be carried out in the presence of a catalyst that promotes polyimide formation. Such catalysts include, for example, aromatic carboxylic acids such as benzoic acid and p-hydroxybenzoic acid, and aromatic amines such as isoquinoline.

[0066] The crosslinking agent includes a diether compound. In the production method according to this embodiment, the diether compound is a compound represented by the formula: R 2 OR 1 -OR 3 and R 1 , R 2 and R 3 are each independently any hydrocarbon group, the carbon atoms of the polymer G (polyimide P) are reacted with a crosslinking agent to form a crosslinked polymer G (polyimide P) molecule. 1 At this time, R 1 is bonded to a carbon atom of the polymer G (polyimide P). In this way, a crosslinked polymer (crosslinked polyimide) can be obtained. Preferably, R 1 is a divalent hydrocarbon group, and R 2 and R 3 are each independently a monovalent hydrocarbon group.

[0067] Examples of diether compounds include dimethoxymethane, methoxyethoxymethane, diethoxymethane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-methoxy-2-ethoxyethane, 1,2-diisopropoxyethane, 1,3-dimethoxypropane, 1,3-diethoxypropane, and 1,3-diisopropoxypropane, and preferably dimethoxymethane.

[0068] The reaction between the carbon atoms of the polymer G and the crosslinker is typically carried out in the presence of a catalyst. The catalyst is preferably a Lewis acid catalyst. Examples of Lewis acid catalysts include iron(III) chloride, iron(III) bromide, and aluminum chloride.

[0069] <Embodiments of Separation Functional Layer> FIG. 1 is a cross-sectional view schematically showing a separation functional layer 1 of this embodiment. The separation functional layer 1 of FIG. 1 can function as a free-standing membrane (single-layer membrane). The separation functional layer 1 preferably allows acidic gases contained in a mixed gas to pass preferentially through it. The separation functional layer 1 is typically a dense layer (non-porous layer) in which no pores are visible when observed at a magnification of 5000 times using a scanning electron microscope (SEM).

[0070] The separation functional layer 1 contains the above-mentioned crosslinked polymer, which is preferably a crosslinked polyimide.

[0071] The content of the crosslinked polymer in the separation functional layer 1 is, for example, 50 wt% or more, and may be 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or even 95 wt% or more, or 100 wt% or less. The separation functional layer 1 may be composed essentially of crosslinked polymers. However, the separation functional layer 1 may contain an uncrosslinked polymer G (e.g., an uncrosslinked polyimide P) in addition to the crosslinked polymer.

[0072] The separation functional layer 1 may further contain other components besides the crosslinked polymer. Examples of such other components include nanoparticles. Examples of nanoparticles include those exemplified for the intermediate layer 2 described below. In the separation functional layer 1, the nanoparticles are dispersed in a matrix containing, for example, a crosslinked polymer. The nanoparticles may be spaced apart within the matrix or may be partially aggregated. The separation functional layer 1 may contain particles other than nanoparticles. Such particles may contain inorganic materials or organic materials. Examples of inorganic materials contained in the particles include silica, titania, alumina, and zeolite. Examples of organic materials include resin materials such as polytetrafluoroethylene.

[0073] The thickness of the separation functional layer 1 is, for example, 500 μm or less, and may be 300 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, 20 μm or less, or even 10 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. The thickness of the separation functional layer 1 can be measured, for example, by observing a cross section of the separation functional layer 1 with a scanning electron microscope.

[0074] (Method of manufacturing the separation functional layer) In this embodiment, the method for producing the separation functional layer 1 includes reacting carbon atoms of the polymer G with a crosslinking agent to obtain a crosslinked polymer, and producing a separation functional layer containing the crosslinked polymer. The method for producing the separation functional layer 1 preferably includes applying a coating liquid L1 containing polyimide P to a substrate to form a coating film, drying the coating film to obtain a polyimide P film, and immersing the film in a liquid L2 containing a crosslinking agent to react the carbon atoms of the polyimide P with the crosslinking agent. After the reaction, the film is washed and dried to obtain the separation functional layer 1 containing the crosslinked polyimide.

[0075] The content of polyimide P in the coating liquid L1 can be adjusted appropriately depending on the solubility of polyimide P, and is, for example, 1 wt % to 30 wt %.

[0076] The coating liquid L1 preferably further contains a solvent. The solvent is typically a good solvent capable of dissolving the polyimide P. Examples of the solvent include amide compounds, lactone compounds, 1,3-dioxolane, nitrobenzene, benzonitrile, α-chloronaphthalene, phenol, m-cresol, and p-chlorophenol. The solvent preferably contains at least one selected from the group consisting of amide compounds and lactone compounds, and more preferably contains an amide compound. Examples of the amide compound include N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and N,N-dimethylacetamide (DMAc). Examples of the lactone compound include γ-butyrolactone.

[0077] The content of the solvent in the coating liquid L1 is not particularly limited, and is, for example, 30 wt % to 99 wt %.

[0078] The coating liquid L1 may further contain a surfactant (leveling agent) to improve coating properties. However, according to the investigations of the present inventors, when the coating liquid L1 contains a surfactant, the separation performance of the produced separation functional layer 1 tends to decrease. Therefore, it is preferable that the coating liquid L1 does not contain a surfactant.

[0079] The substrate to which the coating liquid L1 containing polyimide P is applied is typically a release liner or glass. Examples of the substrate include soda glass; a film containing a resin; paper; and a sheet containing a metal material such as aluminum or stainless steel. Sheets containing metal materials tend to have high heat resistance. In terms of excellent surface smoothness, the substrate is preferably a film containing a resin or a laminate of such a film and soda glass. In the substrate, examples of the polymer 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, vinyl chloride copolymers; polyurethanes; ethylene-vinyl acetate copolymers; and polyimides, with polyimides being preferred.

[0080] The surface of the substrate may be subjected to a release treatment. The release treatment can be carried out by applying a release treatment agent to the surface of the substrate. Examples of the release treatment agent include silicone-based release treatment agents, long-chain alkyl-based release treatment agents, fluorine-based release treatment agents, and molybdenum sulfide-based release treatment agents. The release treatment agents may be used alone or in combination of two or more. The substrate may be a polyimide film that has been subjected to a release treatment.

[0081] The thickness of the substrate is not particularly limited and is, for example, 5 μm to 100 μm, and preferably 10 μm to 50 μm.

[0082] Before applying the coating liquid L1, the substrate may be subjected to a surface modification treatment. If the substrate has been subjected to a release treatment, the surface modification treatment may be performed on the surface of the substrate that has been subjected to the release treatment. Examples of the surface modification treatment include corona treatment, plasma treatment, excimer treatment, and flame treatment, and corona treatment is preferred.

[0083] Surface modification treatment can be carried out by irradiating the surface of the substrate with active energy rays. Specific examples of active energy rays include electron beams, ion beams, plasma beams, and ultraviolet rays. When corona treatment is performed as the surface modification treatment, the discharge rate is, for example, 0.1 kW·min / m 2 The upper limit of the discharge amount is not particularly limited, and may be, for example, 10 kW min / m 2 is.

[0084] The method for applying the coating liquid L1 to the substrate is not particularly limited, and for example, spin coating, dip coating, slot die coating, etc. may be used. The coating liquid L1 may be applied to the substrate using an applicator, a wire bar, etc. The coating liquid L1 may be applied to the surface of a substrate that has been subjected to a release treatment or a surface modification treatment.

[0085] A coating film is formed by applying the coating liquid L1 to a substrate. The thickness of the coating film can be adjusted appropriately depending on the desired thickness of the separation functional layer 1, and is, for example, 1 μm to 100 μm.

[0086] The drying conditions for the coating film are not particularly limited, and for example, the drying temperature is 50°C to 200°C and the drying time is 1 minute to 10 hours. The coating film can be dried using a heater or the like. As an example, the coating film may be dried by passing it through a heating unit equipped with a heater. The coating film may be dried by passing it through multiple heating units. The set temperatures of the multiple heating units may be the same or different.

[0087] In the method for producing the separation functional layer 1 of this embodiment, it is preferable to further include removing the substrate from the laminate after drying the coating film on the substrate to obtain a laminate of the polyimide P film and the substrate, and before immersing the film in a liquid L2 containing a crosslinking agent. By removing the substrate, a free-standing film of the polyimide P film can be obtained, and the free-standing film can be immersed in the liquid L2 containing a crosslinking agent.

[0088] Crosslinking agents include those described above in the embodiments of the method for making the crosslinked polymer.

[0089] The liquid L2 containing the crosslinking agent preferably further contains a catalyst and a solvent, such as 1,2-dichloroethane and acetonitrile. The catalyst may be any of those described above in the embodiment of the method for producing a crosslinked polymer.

[0090] The content of the crosslinking agent in the liquid L2 is, for example, 0.1 w / v % to 20 w / v % relative to the volume of the solvent.

[0091] The content of the catalyst in the liquid L2 is not particularly limited, and is, for example, 0.1 w / v % to 20 w / v % relative to the volume of the solvent.

[0092] The conditions for immersing the polyimide P film in the liquid L2, that is, the conditions for the above reaction, are, for example, a temperature of 20° C. to 80° C. and a time of 0.2 to 10 hours.

[0093] After removing the membrane after the reaction from the liquid L2, it is preferable to wash the membrane, and then dry the membrane to obtain the separation functional layer 1 that functions as a self-supporting membrane.

[0094] The drying conditions are not particularly limited, and for example, the drying temperature is 50° C. to 200° C. and the drying time is 1 minute to 10 hours. The film after the reaction can be dried, for example, by the same means as for drying the coated film described above.

[0095] The manufacturing method of this embodiment may further include subjecting the obtained separation functional layer 1 to a heat treatment (annealing treatment). This step tends to improve the separation performance of the separation functional layer 1 and also suppress deterioration of the separation performance of the separation functional layer 1 over time. This step also makes it possible to obtain a separation functional layer 1 that contains almost no residual solvent by sufficiently volatilizing the solvent. The annealing treatment may be performed before or after removing the substrate from the laminate of the separation functional layer 1 and the substrate.

[0096] The temperature of the heat treatment may be, for example, higher than 200°C, 230°C or higher, or even 250°C or higher. The upper limit of the heat treatment temperature is not particularly limited and may be, for example, 350°C or lower, or 300°C or lower. The heat treatment time is, for example, 1 minute or longer, or may be 10 minutes or longer, or 30 minutes or longer. The upper limit of the heat treatment time is not particularly limited and may be, for example, 24 hours or shorter.

[0097] The manufacturing method of this embodiment is not limited to the above. Instead of the coating liquid L1 containing polyimide P, a coating liquid containing polyamic acid, a precursor of polyimide P, may be used. This coating liquid may be applied to a substrate, and the polyamic acid may be imidized to form polyimide P, thereby producing a polyimide P film. Alternatively, the substrate may be immersed in liquid L2 without removing it from the laminate of the polyimide P film and substrate to carry out a crosslinking reaction, followed by washing and drying to form a separation functional layer 1 on the substrate. In this case, it is preferable to further include removing the substrate from the laminate of the separation functional layer 1 and substrate. By removing the substrate, a separation functional layer 1 that functions as a free-standing membrane can be obtained.

[0098] (Characteristics of the separation functional layer) As described above, it is preferable that the separation functional layer 1 preferentially permeates the acidic gas contained in the mixed gas. As an example, when a mixed gas consisting of carbon dioxide and methane is supplied to a space adjacent to one surface of the separation functional layer 1, the permeation rate T of carbon dioxide permeating the separation functional layer 1 is CO2 is, for example, 70 GPU or more, and may be 80 GPU or more, 90 GPU or more, 100 GPU or more, 150 GPU or more, or even 200 GPU or more. CO2 The upper limit is not particularly limited, and is, for example, 1000 GPUs. -6 ·cm 3 (STP) / (sec cm 2 ·cmHg).

[0099] As an example, the permeability coefficient C of carbon dioxide passing through the separation functional layer 1 when a mixed gas consisting of carbon dioxide and methane is supplied to a space adjacent to one surface of the separation functional layer 1 is taken into consideration. CO2 is, for example, 300 Barrer or more, and may be 500 Barrer or more, 550 Barrer or more, 600 Barrer or more, 700 Barrer or more, or even 1000 Barrer or more. CO2 The upper limit of the value is not particularly limited, and is, for example, 5000 Barrer. -10 ·cm 3 (STP)·cm / (sec·cm 2 cm 3 (STP) means the volume of carbon dioxide at 1 atmosphere and 0°C. CO2 [Barrer] is the permeation rate T CO2 This is the value obtained by multiplying [GPU] by the thickness (μm) of the separation functional layer 1.

[0100] As described above, the separation functional layer 1 of this embodiment contains the above-mentioned crosslinked polymer crosslinked via a hydrocarbon group. This allows the separation functional layer 1 of this embodiment to improve the permeation rate and permeation coefficient of acidic gases. Furthermore, in the separation functional layer 1 of this embodiment, crosslinking suppresses physical aging of the crosslinked polyimide, which can suppress deterioration of the separation performance of the separation functional layer 1 over time.

[0101] Permeability coefficient C CO2 and permeation rate T CO2 can be determined by the following method. First, a mixed gas consisting of carbon dioxide and methane is supplied to the space adjacent to one surface of the separation functional layer 1, and argon gas is injected as a sweep gas into the space adjacent to the other surface of the separation functional layer 1. This results in a permeated fluid that has permeated the separation functional layer 1. The weight of the permeated fluid, as well as the volume ratio of carbon dioxide and the volume ratio of methane in the permeated fluid, are measured. From the measurement results, the permeation coefficient C CO2 and permeation rate T CO2In the above operation, the concentration of carbon dioxide in the mixed gas is 50 vol% under standard conditions (0°C, 101 kPa). The mixed gas supplied to the space adjacent to one surface of the separation functional layer 1 has a temperature of 30°C and a pressure of 0.1 MPa.

[0102] The above transmission coefficient C CO2 and permeation rate T CO2 Under the measurement conditions, the separation coefficient α of the separation functional layer 1 for carbon dioxide relative to methane is not particularly limited, and may be, for example, 15 or more, or 20 or more. The upper limit of the separation coefficient α is not particularly limited, and may be, for example, 100 or 60. The separation coefficient α can be calculated from the following formula. In the following formula, the permeation rate T CH4 is the transmission coefficient C CO2 and permeation rate T CO2 This is the permeation rate of methane that permeates through the separating functional layer 1 under the measurement conditions. Separation coefficient α = permeation rate T CO2 / transmission rate T CH4

[0103] (Use of separation functional layer) The separation functional layer 1 of this embodiment can be used to separate acidic gases from a gas mixture containing acidic gases. Examples of acidic gases in the gas mixture include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, and nitrogen oxides (NOx), with carbon dioxide being preferred. The gas mixture also contains other gases besides the acidic gas. Examples of other gases include nonpolar gases such as hydrogen, nitrogen, and methane, and inert gases such as helium, with nitrogen and methane being preferred. The separation functional layer 1 of this embodiment is particularly suitable for separating carbon dioxide from a gas mixture containing carbon dioxide and methane. However, the use of the separation functional layer 1 is not limited to separating acidic gases from the above-mentioned gas mixture.

[0104] <Embodiments of separation membrane> As shown in Fig. 2, the separation membrane 10 of this embodiment includes the above-mentioned separation functional layer 1, and further includes a porous support 3. As shown in Fig. 2, the separation membrane 10 preferably further includes an intermediate layer 2 disposed between the separation functional layer 1 and the porous support 3. The porous support 3 supports the separation functional layer 1. The intermediate layer 2 is in direct contact with both the separation functional layer 1 and the porous support 3. However, in some cases, the separation membrane 10 may not include the intermediate layer 2, and the porous support 3 may be in direct contact with the separation functional layer 1 and support the separation functional layer 1.

[0105] (middle class) The intermediate layer 2 preferably contains a resin, and more preferably further contains nanoparticles dispersed in the resin (matrix). The nanoparticles may be separated from one another within the matrix, or may be partially aggregated. However, the intermediate layer 2 may not contain nanoparticles, and may be essentially composed of a resin.

[0106] The material of the matrix is ​​not particularly limited, and examples thereof 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, polyolefin resins such as polymethylpentene, polyurethane resins, etc. The matrix preferably contains a silicone resin and a polyurethane resin.

[0107] The nanoparticles may contain an inorganic material or an organic material. Examples of inorganic materials contained in the nanoparticles include silica, titania, and alumina. The nanoparticles preferably contain silica.

[0108] The nanoparticles may have a surface modified with a modifying group containing a carbon atom. Nanoparticles having a surface modified with this modifying group have excellent dispersibility in a matrix. The nanoparticles are preferably silica nanoparticles which may have a surface modified with a modifying group. The modifying group preferably further contains a silicon atom. In the nanoparticles, the surface modified with the modifying group is preferably represented by the following formulas (I) to (III). [ka]

[0109] R in formulas (I) to (III) 1 ~R 6 are each independently a hydrocarbon group which may have a substituent. The number of carbon atoms in the hydrocarbon group is not particularly limited as long as it is 1 or more. The number of carbon atoms in the hydrocarbon group may be, for example, 25 or less, 20 or less, 10 or less, or 5 or less. In some cases, the number of carbon atoms in the hydrocarbon group may be more 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. Examples of the substituent on the hydrocarbon group include an amino group and an acyloxy group. Examples of the acyloxy group include a (meth)acryloyloxy group.

[0110] In another preferred embodiment, R 1 ~R 6 The hydrocarbon group, which may have the 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 improving the permeability coefficient of acidic gases in separation membrane 10. [ka]

[0111] In formula (IV), R 7 is an alkylene group having 1 to 5 carbon atoms which may have a substituent. The alkylene group may be linear or branched. Examples of the alkylene group include a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, and a pentane-1,5-diyl group, and preferably a propane-1,3-diyl group. Examples of the substituent of the alkylene group include an amide group and an amino alkylene group.

[0112] In formula (IV), R 8 R is an alkyl group or aryl group having 1 to 20 carbon atoms, which may have a substituent. The alkyl group may be linear or branched. Examples of the substituents on the alkyl group and aryl group include an amino group and a carboxyl group. 8 is, for example, a 3,5-diaminophenyl group.

[0113] In the nanoparticles, the surface modified with the modifying group is preferably represented by the following formula (V). [ka]

[0114] The modifying group is not limited to the structures shown in formulas (I) to (III). The modifying group may be any of R 1 ~R 6 Instead of the above, the modifying group may contain a polymer chain having a polyamide structure or a polydimethylsiloxane structure. In the modifying group, the polymer chain is preferably directly bonded to the silicon atom. The shape of the polymer chain may be, for example, linear, dendrimer, or hyperbranched.

[0115] The method for modifying the surface of nanoparticles with a modifying group is not particularly limited. As an example, the surface of nanoparticles can be modified by reacting hydroxy groups present on the surface of nanoparticles with a known silane coupling agent. When the modifying group contains a polyamide structure, the surface of nanoparticles can be modified by the method disclosed in JP 2010-222228 A.

[0116] The average particle size of the nanoparticles is not particularly limited as long as it is on the nanometer order (<1000 nm), and is, for example, 100 nm or less, preferably 50 nm or less, and more preferably 20 nm or less. The lower limit of the average particle size of the nanoparticles is, for example, 1 nm. The average particle size of the nanoparticles can be determined by the following method. First, the cross section of the intermediate layer 2 is observed with a transmission electron microscope. In the obtained electron microscope image, the area of ​​a specific nanoparticle is calculated by image processing. The diameter of a circle having the same area as the calculated area is regarded as the particle size of that specific nanoparticle (particle diameter). The particle sizes of an arbitrary number (at least 50) of nanoparticles are calculated, and the average of the calculated values ​​is regarded as the average particle size of the nanoparticles. The shape of the nanoparticles is not particularly limited, and may be spherical, ellipsoidal, scaly, or fibrous.

[0117] The nanoparticle content in the intermediate layer 2 is, for example, 5 wt% or more, preferably 10 wt% or more, and more preferably 15 wt% or more. There is no particular upper limit to the nanoparticle content in the intermediate layer 2, and it is, for example, 30 wt%.

[0118] 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 preferably a layer having a thickness of less than 50 μm.

[0119] (porous support) 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, permeable (porous) polymers containing at least one selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyether ether ketone, polyacrylonitrile, polyimide, and polyphenylene oxide, open-cell or closed-cell metal foams, open-cell or closed-cell polymer foams, silica, porous glass, and mesh screens. The porous support 3 may also be a combination of two or more of these materials. For example, the porous support 3 may be a laminate of a nonwoven fabric and a porous polysulfone layer.

[0120] Alternatively, the porous support 3 may contain the crosslinked polymer described above. In this case, the crosslinked polymer contained in the porous support 3 is typically the same as the crosslinked polymer contained in the separation function layer 1, and is preferably a crosslinked polyimide. In particular, the material of the porous support 3 is preferably the same as the material of the separation function layer 1. As an example, the separation membrane 10 may be composed only of a crosslinked polymer (typically a crosslinked polyimide), or may be composed of a single material. In such a case, it is preferable that the separation membrane 10 does not include the intermediate layer 2, the porous support 3 is in direct contact with the separation function layer 1, and the separation function layer 1 and the porous support 3 are integrated. In this specification, "integrated" means that the components cannot be separated from each other without destruction.

[0121] The content of the crosslinked polymer in the porous support 3 is, for example, 50 wt% or more, and may be 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or even 95 wt% or more. The porous support 3 may be composed essentially of crosslinked polymers only. However, the porous support 3 may contain uncrosslinked polymers G (e.g., uncrosslinked polyimide P) in addition to the crosslinked polymers. The content of the crosslinked polymer in the porous support 3 may be the same as the content of the crosslinked polymer in the separation functional layer 1.

[0122] The porous support 3 has an average pore size of, for example, 0.01 μm 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.

[0123] (Method of manufacturing separation membrane) The separation membrane 10 can be produced by the following method. First, a laminate of a porous support 3 and an intermediate layer 2 is prepared. This laminate can be produced by the following method. First, a coating liquid 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 for example, spin coating or 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 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-promoting treatment if necessary. Examples of adhesion-promoting treatments include surface treatments such as application of a primer, corona discharge treatment, and plasma treatment.

[0124] Next, a separation functional layer 1 is formed on the intermediate layer 2 in the laminate of the porous support 3 and the intermediate layer 2. This allows a separation membrane 10 to be obtained. As an example, first, a separation functional layer 1 formed on a substrate is prepared by the method described above, then a coating liquid containing the material for the intermediate layer 2 is applied onto the separation functional layer 1 and dried to form the intermediate layer 2, and the laminate of the intermediate layer 2 and the separation functional layer 1 is transferred to the porous support 3, thereby producing the separation membrane 10.

[0125] The method for producing the separation membrane 10 is not limited to the above method, and for example, a laminate of the porous support 3 and the intermediate layer 2 may be used as a substrate, and the manufacturing method described above for the separation functional layer 1 may be carried out. In this way, the separation membrane 10 is obtained.

[0126] (Separation membrane shape) In this embodiment, the separation membrane 10 is typically a flat membrane. However, the separation membrane 10 may have a shape other than a flat membrane, for example, a hollow fiber membrane. The separation membrane 10 may have a configuration as shown in FIG. 2, or may include a separation function layer 1 and a porous support 3 but may not include an intermediate layer 2. In this case, as described above, the separation function layer 1 and the porous support 3 may be integrated.

[0127] <Embodiment of Membrane Separation Device> 3A is a schematic cross-sectional view showing an example of a membrane separation device of this embodiment. As shown in FIG. 3A, the membrane separation device 100 of this embodiment includes a separation membrane 10 and a tank 20. In the membrane separation device 100, it is also possible to use a separation functional layer 1 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 and the second chamber 22. The separation membrane 10 extends from one to the other of a pair of wall surfaces of the tank 20.

[0128] 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 preferably openings formed in the wall surface of the tank 20.

[0129] 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.

[0130] 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, and preferably 0.3 MPa or more.

[0131] The pressure inside the second chamber 22 may be reduced while the gas mixture 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, for example, by 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.

[0132] By supplying the gas mixture 30 into the first chamber 21, a permeated fluid 35 having a higher acid gas content than the gas mixture 30 can be obtained on the other side of the separation membrane 10. That is, the permeated fluid 35 is supplied to the second chamber 22. The permeated fluid 35 preferably contains an acid gas as a main component. However, the permeated fluid 35 may contain small amounts of gases other than the acid gas. The permeated fluid 35 is discharged to the outside of the tank 20 through the outlet 22a.

[0133] The concentration of acid 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.

[0134] The membrane separation apparatus 100 of this embodiment is suitable for a flow-through (continuous) membrane separation method, but may also be used for a batch-type membrane separation method.

[0135] In some cases, the second chamber 22 may further have an inlet. FIG. 3B is a schematic cross-sectional view showing another example of the membrane separation device of this embodiment. In the membrane separation device 110 shown in FIG. 3B, the separation membrane 10 is disposed inside the tank 20 and separates the first chamber 21 and the second chamber 22. In the membrane separation device 110, it is also possible to use a separation functional layer 1 alone instead of the separation membrane 10. The first chamber 21 has an inlet 21a and an outlet 21b. The second chamber 22 has an inlet 22b and an outlet 22a. It is preferable that the inlet 21a, the outlet 21b, the inlet 22b, and the outlet 22a are each an opening formed in the wall surface of the tank 20. In FIG. 4, the inlet 21a and the outlet 22a are formed on the same wall surface, and the outlet 21b and the inlet 22b are formed on the same wall surface, but the configuration of the membrane separation device 110 is not limited to this. For example, the inlet 21a and the inlet 22b may be formed on the same wall surface, and the outlet 21b and the outlet 22a may be formed on the same wall surface. The inside of the second chamber 22 may be at atmospheric pressure, or a sweep gas may be supplied thereto.

[0136] Membrane separation using the membrane separation device 110 is performed, for example, by a sweep method. Specifically, while the mixed gas 30 is supplied to the first chamber 21, a sweep gas is supplied to the second chamber 22. This results in a permeated fluid 35 that has permeated the separation membrane 10. The permeated fluid 35 is discharged to the outside of the tank 20 through the outlet 22a.

[0137] <Modification 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 laminate 42. The laminate 42 includes a separation membrane 10. The laminate 42 may include a separation functional layer 1 alone, instead of the separation membrane 10.

[0138] 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.

[0139] In addition to the separation membrane 10, 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).

[0140] 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).

[0141] Membrane separation using the membrane separation device 110 is performed in the following manner. First, the mixed gas 30 is supplied to one end of the wound stack 42. The permeated fluid 35 that has permeated the separation membrane 10 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 mixed gas 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 acid gases to be separated from the mixed gas 30. [Example]

[0142] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0143] [Fabrication of separation functional layer] Example 1 First, polyimide P1 was synthesized using an automated polymerization apparatus (Mettler-Toledo, EasyMax 402). The attached separable flask (400 mL capacity) was equipped with a Dimroth tube, a stirrer, an internal thermometer, a nitrogen inlet tube, and a flat stopper. A Dimroth chiller was used to circulate the coolant, set at 10 °C. N2 gas was passed through the flask at a flow rate of 100 mL / min. The stirring speed was set at 300 rpm. Next, 42.9 g of 1-methyl-2-pyrrolidone (superhydrous) (NMP) was added as the solvent, and 3.38 g (9 mmol) of 9,9-bis(3-methyl-4-aminophenyl)fluorene (BMAPF) and 2.46 g (9 mmol) of 3,7-diamino-2,8-dimethyldibenzothiophene sulfone (DDBT) were added as the diamine. The mixture was stirred at room temperature to dissolve the diamine in the solvent. To the resulting solution, 4.81 g (18 mmol) of naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTDA) as a tetracarboxylic dianhydride and 4.38 g (36 mmol) of benzoic acid were further added. The jacket temperature of the apparatus was raised to 180°C, and the mixture was stirred for 8 hours. After stirring, the internal temperature of the flask was cooled to 25°C and allowed to stand overnight.

[0144] Next, 4.63 g (36 mmol) of isoquinoline was added, and the jacket temperature was raised again to 180 °C and stirred for 8 hours. After leaving the reaction solution overnight, 160.8 g of NMP was added to dilute the reaction solution. Next, using a dropping funnel, 241 mL of methanol was added dropwise to the reaction solution over approximately 30 minutes to perform reprecipitation purification. The precipitated polyimide was filtered and washed twice with 80 mL of methanol. After washing, the filtered polyimide was dried in a hot air circulation dryer at 60 °C for 15 hours and then further dried in a vacuum dryer at 100 °C for 8 hours. This yielded 10 g of polyimide P1.

[0145] Next, the prepared polyimide P1 was dissolved in NMP to prepare a coating solution. Next, a substrate was prepared by attaching a release liner (Fujiko, PI-50-SCA0) that had been corona-treated (0.5 kW, 3 m / min) to soda glass. The coating solution was placed on the release liner, and a coating film was formed using an applicator. The coating film was dried at 130°C for 1 hour to obtain a polyimide P1 film.

[0146] A liquid containing 5 w / v% dimethoxymethane as a crosslinking agent, 3 w / v% iron (III) chloride as a catalyst, and 1,2-dichloroethane as a solvent was prepared. Next, the polyimide P1 film peeled from the release liner was immersed in the liquid. The weight of the film relative to the liquid was adjusted to 0.5 w / v%. Immersion at 50°C for 1 hour allowed the polyimide P1 to react with dimethoxymethane, forming a crosslinked polyimide film. After removing the film from the liquid, it was washed by immersing it in methanol for 1 hour three times. After washing, the film was vacuum dried at 120°C for 10 hours to obtain the separation functional layer (freestanding film) of Example 1.

[0147] Example 2 Polyimide P2 was obtained in the same manner as polyimide P1, except that the amount of 9,9-bis(3-methyl-4-aminophenyl)fluorene (BMAPF) added was changed to 4.52 g (12 mmol) and the amount of 3,7-diamino-2,8-dimethyldibenzothiophenesulfone (DDBT) added was changed to 1.65 g (6 mmol).

[0148] A separation functional layer (freestanding film) of Example 2 was obtained in the same manner as in Example 1, except that polyimide P2 was used.

[0149] Example 3 Polyimide P3 was obtained in the same manner as polyimide P1, except that the amount of 9,9-bis(3-methyl-4-aminophenyl)fluorene (BMAPF) added was changed to 5.06 g (13.5 mmol) and the amount of 3,7-diamino-2,8-dimethyldibenzothiophenesulfone (DDBT) added was changed to 1.23 g (4.5 mmol).

[0150] A separation functional layer (freestanding film) of Example 3 was obtained in the same manner as in Example 1, except that polyimide P3 was used.

[0151] Example 4 A separation functional layer (freestanding membrane) of Example 4 was obtained in the same manner as in Example 2, except that the solvent in the liquid in which the polyimide P2 membrane was immersed was changed to acetonitrile.

[0152] Example 5 A separation functional layer (freestanding membrane) of Example 5 was obtained in the same manner as in Example 4, except that the crosslinking agent was changed to 1,2-dimethoxyethane.

[0153] Example 6 A separation functional layer (freestanding membrane) of Example 6 was obtained in the same manner as in Example 4, except that the crosslinking agent was changed to 1,3-dimethoxypropane.

[0154] Example 7 Polyimide P2 was obtained in the same manner as in Example 2.

[0155] Next, silica filler (AEROSIL RX200, Nippon Aerosil Co., Ltd.) and NMP were mixed and dispersed for 10 minutes using an ultrasonic homogenizer. The dispersion and polyimide P2 were added to a 50 mL screw tube to obtain a mixed solution. At this time, the silica filler was adjusted to 10 wt % relative to the polyimide P2. In this way, a coating solution was prepared.

[0156] Next, a substrate was prepared by attaching a release liner (Fujiko, PI-50-SCA0) that had been corona-treated (0.5 kW, 3 m / min) to soda glass. The coating solution was placed on the release liner, and a coating film was formed using an applicator. The coating film was dried at 130°C for 1 hour to obtain a film containing polyimide P2 and particles.

[0157] A separation functional layer (freestanding membrane) of Example 7 was obtained by carrying out the crosslinking reaction, washing and drying of the membrane in the same manner as in Example 1, except that the above membrane was used.

[0158] Example 8 A separation functional layer (freestanding membrane) of Example 8 was obtained in the same manner as in Example 7, except that PTFE powder (Seishin Enterprise Co., Ltd., TFW-3000FP) was used instead of the silica filler.

[0159] Example 9 A separation functional layer (freestanding membrane) of Example 9 was obtained in the same manner as in Example 7, except that zeolite nanoparticles (Nakamura Choukou Co., Ltd., Zeoal 4a 300 nm) were used instead of the silica filler.

[0160] (Comparative Example 1) Polyimide P1 was obtained in the same manner as in Example 1. The prepared polyimide P1 was dissolved in NMP to prepare a coating solution. Next, a substrate was prepared by attaching a release liner (manufactured by Fujiko, PI-50-SCA0) that had been corona-treated (0.5 kW, 3 m / min) to soda glass. The coating solution was placed on the release liner, and a coating film was formed using an applicator. The coating film was dried at 130°C for 1 hour to obtain a polyimide P1 film. The polyimide P1 film was peeled off from the release liner and washed by immersing it in methanol for 1 hour three times. After washing, the film was vacuum-dried at 120°C for 10 hours to obtain a separation functional layer (freestanding film) of Comparative Example 1. That is, Comparative Example 1 was prepared in the same manner as Example 1, except that immersion crosslinking of the polyimide P1 film was not performed.

[0161] (Comparative Example 2) Polyimide P2 was obtained in the same manner as in Example 2. A separation functional layer (freestanding membrane) of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that polyimide P2 was used. That is, Comparative Example 2 was produced in the same manner as in Example 2, except that immersion crosslinking of the membrane of polyimide P2 was not performed.

[0162] (Comparative Example 3) Polyimide P3 was obtained in the same manner as in Example 3. A separation functional layer (freestanding membrane) of Comparative Example 3 was obtained in the same manner as in Comparative Example 1, except that polyimide P3 was used. That is, Comparative Example 3 was produced in the same manner as in Example 3, except that immersion crosslinking of the polyimide P3 membrane was not performed.

[0163] [Gel fraction measurement] The gel fractions of the separation functional layers of Examples 1 to 6 and Comparative Examples 1 to 3 were measured using the following method. First, 20 mg of the separation functional layer (freestanding membrane) and an amount of NMP sufficient to fill the sample tube were placed in a 13.5 mL sample tube. The membrane was immersed in NMP and allowed to stand overnight at room temperature (25°C). After standing, the NMP in the sample tube was removed, and the membrane in the sample tube was washed with methanol. The washing was performed by adding methanol to the sample tube and stirring at room temperature for 1 hour, three times with the methanol replaced each time, followed by another replacement of the methanol and stirring at room temperature overnight. The methanol in the sample tube was removed, and the membrane was dried at 80°C under vacuum for 5 hours, after which it was weighed. The gel fraction was calculated using the following formula from the weight W1 (20 mg) of the membrane before immersion in NMP and the weight W2 of the membrane after immersion and washing. Gel fraction [%] = W2 / W1 × 100

[0164] [Characteristics evaluation of the separation functional layer] (Gas permeation test) The carbon dioxide permeation rate T for the separating functional layers of Examples 1 to 9 and Comparative Examples 1 to 3 was measured by the following method. CO2 , the transmission coefficient C CO2The separation coefficient α of carbon dioxide relative to methane was measured. First, the separation functional layer was set in a metal cell and sealed with an O-ring to prevent leakage. Next, a mixed gas was injected into the metal cell so that the mixed gas contacted one main surface of the separation functional layer. The mixed gas consisted essentially of carbon dioxide and methane. The carbon dioxide concentration in the mixed gas was 50 vol% under standard conditions. The mixed gas injected into the metal cell had a temperature of 30°C and a pressure of 0.1 MPa. Next, a sweep gas (argon gas) was injected into the metal cell adjacent to the other main surface of the separation functional layer. As a result, a permeated fluid was obtained from the other main surface of the separation functional layer. Based on the composition, weight, etc. of the obtained permeated fluid, the permeation rate T CO2 , the transmission coefficient C CO2 and the separation factor α was calculated.

[0165] [Table 1]

[0166] [Table 2]

[0167] The abbreviations in Tables 1 and 2 are as follows: BMAPF: 9,9-bis(3-methyl-4-aminophenyl)fluorene DDBT: 3,7-diamino-2,8-dimethyldibenzothiophene sulfone

[0168] As can be seen from Tables 1 and 2, the separation functional layers of Examples 1 to 9 had a higher permeation rate T CO2 and the permeability coefficient C CO2 showed high values ​​and were favorable.

[0169] From the above results, it can be said that the crosslinked polymer of this embodiment and the separation functional layer of this embodiment are suitable for separating acidic gases from a mixed gas containing acidic gases. [Industrial Applicability]

[0170] The crosslinked polymer, separation functional layer, and separation membrane of this embodiment are suitable for separating acidic gases from a gas mixture containing acidic gases. In particular, the crosslinked polymer, separation functional layer, and separation membrane of this embodiment are suitable for separating carbon dioxide from biogas. [Explanation of symbols]

[0171] 1 Separation functional layer 2. Middle class 3 Porous support 10 Separation membrane 100,110 Membrane separation equipment

Claims

1. Polymers containing carbon atoms are crosslinked via hydrocarbon groups, A crosslinked polymer, wherein said hydrocarbon groups are bonded to said carbon atoms.

2. The crosslinked polymer of claim 1 , wherein the hydrocarbon group is an alkylene group.

3. The crosslinked polymer according to claim 2, wherein the alkylene group has 1 to 5 carbon atoms.

4. the polymer contains an aromatic ring; The crosslinked polymer of claim 1 , wherein said aromatic ring comprises said carbon atom.

5. the polymer comprises an electron donating group; The crosslinked polymer of claim 4 , wherein the electron donating group is attached to the aromatic ring.

6. The crosslinked polymer of claim 1 , wherein the polymer is a polyimide.

7. The crosslinked polymer according to claim 6 , wherein the polyimide comprises a structural unit A1 derived from a tetracarboxylic dianhydride having a six-membered ring acid anhydride structure and a structural unit B derived from a diamine.

8. The crosslinked polymer of claim 7 , wherein said structural unit B has said carbon atom.

9. The crosslinked polymer according to claim 7 , wherein the structural unit A1 is represented by the following formula (A1): 【Chemical 1】 In the formula (A1), R 1a ~R 4a are each independently a hydrogen atom or an optional substituent.

10. A separation functional layer comprising the crosslinked polymer according to any one of claims 1 to 9.

11. The separation functional layer according to claim 10, which is used to separate an acidic gas from a gas mixture containing the acidic gas.

12. The separation functional layer according to claim 10; a porous support supporting the separation functional layer; A separation membrane comprising:

13. A method for producing the crosslinked polymer according to any one of claims 1 to 9, comprising: reacting the carbon atoms of the polymer with a crosslinker; The method for producing a crosslinked polymer, wherein the crosslinking agent comprises a diether compound.

14. The method for producing a crosslinked polymer according to claim 13, wherein the reaction is carried out in the presence of a catalyst.

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