Separation function layer, separation membrane, and method of manufacturing separation function layer

Abstract

To provide a separation function layer that improves a deterioration in separation performance in long-time use.SOLUTION: A separation function layer 1 of the present invention includes polyimide, and a filler that is coupled to the polyimide via a covalent bond. The polyimide includes a constitutional unit A1 derived from tetracarboxylic dianhydrides a1 having a 6-membered ring acid anhydride structure, and a constitutional unit B derived from an amine compound. A separation membrane 10 of the present invention comprises the separation function layer 1, and a porous support 3 that supports the separation function layer 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a separation functional layer, a separation membrane, and a method for producing a separation functional layer. [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] Conventional separation membranes have room for improvement in terms of changes in separation performance over time. Therefore, the present invention provides a separation functional layer that reduces the deterioration of separation performance over long periods of use. [Means for solving the problem]

[0006] The present invention provides Polyimide and a filler bonded to the polyimide via a covalent bond; Including, The polyimide provides a separation functional layer containing a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered ring acid anhydride structure, and a structural unit B derived from an amine compound.

[0007] Furthermore, the present invention provides The separation functional layer, a porous support supporting the separation functional layer; A separation membrane comprising:

[0008] Furthermore, the present invention provides reacting the polyimide and the filler to form a covalent bond; preparing a separation functional layer including the polyimide and the filler bonded via the covalent bond; Including, The polyimide contains a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered ring acid anhydride structure, and a structural unit B derived from an amine compound, and the method for producing a separation functional layer is provided. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a separation functional layer in which the deterioration of separation performance when used for a long period of time is reduced. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view of 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 3] 1 is a schematic cross-sectional view 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

[0011] The separation functional layer according to the first aspect of the present invention is Polyimide and a filler bonded to the polyimide via a covalent bond; Including, The polyimide contains a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered ring acid anhydride structure, and a structural unit B derived from an amine compound.

[0012] In the second aspect of the present invention, for example, in the separation functional layer according to the first aspect, the amine compound has two or more amino groups.

[0013] In a third aspect of the present invention, for example, in the separation functional layer according to the first or second aspect, the filler has an amino group as a reactive site that forms a covalent bond with the polyimide.

[0014] In a fourth aspect of the present invention, for example, in the separation functional layer according to any one of the first to third aspects, the structural unit B includes a structural unit B1 derived from an amine compound b1 having a reactive site that forms a covalent bond with the filler.

[0015] In a fifth aspect of the present invention, for example, in the separation functional layer according to the fourth aspect, the ratio of the amount of substance of the structural unit B1 to the amount of substance of all the structural units B in the polyimide is less than 20 mol %.

[0016] In a sixth aspect of the present invention, for example, in the separation functional layer according to the fourth or fifth aspect, the amine compound b1 has a functional group capable of undergoing a condensation reaction with an amino group.

[0017] In the seventh aspect of the present invention, for example, in the separation functional layer according to any one of the fourth to sixth aspects, the structural unit B further includes a structural unit B2 derived from an amine compound b2 different from the amine compound b1.

[0018] In the eighth aspect of the present invention, for example, in the separation functional layer according to the seventh aspect, the structural unit B2 is represented by the following formula (C1), (C2), (C3), or (C4). [ka] In the formula (C1), R 1c ~R 4c are each independently a hydrogen atom or an optional substituent, In the formula (C2), R 5c ~R 8c are each independently a hydrogen atom or an optional substituent, In the formula (C3), R 9c ~R 16c are each independently a hydrogen atom or an arbitrary substituent, and X 3 is a single bond or any linking group, In the formula (C4), R 17c ~R 22c are each independently a hydrogen atom or an optional substituent, In the formulae (C1) to (C4), the optional substituent is a substituent other than the group containing the reactive site that forms a covalent bond with the filler.

[0019] In a ninth aspect of the present invention, for example, in the separation functional layer according to any one of the first to eighth aspects, the 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.

[0020] In a tenth aspect of the present invention, for example, the separation functional layer according to any one of the first to ninth aspects has a thickness of 1 μm or less.

[0021] The separation membrane according to the eleventh aspect of the present invention is A separation functional layer according to any one of the first to tenth aspects; a porous support supporting the separation functional layer; Equipped with.

[0022] A method for producing a separation functional layer according to a twelfth aspect of the present invention includes the steps of: reacting the polyimide and the filler to form a covalent bond; preparing a separation functional layer including the polyimide and the filler bonded via the covalent bond; Including, The polyimide contains a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered ring acid anhydride structure, and a structural unit B derived from an amine compound.

[0023] In a thirteenth aspect of the present invention, for example, in the production method according to the twelfth aspect, the reaction is carried out by heat treatment, The heat treatment temperature is 150°C or higher and 250°C or lower.

[0024] In a fourteenth aspect of the present invention, for example, in the manufacturing method according to the thirteenth aspect, the treatment time of the heat treatment is not less than 1 hour and not more than 10 hours.

[0025] 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.

[0026] <Embodiments of Separation Functional Layer> FIG. 1 is a cross-sectional view of a separation functional layer 1 according to this embodiment. The separation functional layer 1 in FIG. 1 can function as a self-supporting membrane (single-layer membrane). The separation functional layer 1 preferably allows acidic gases contained in a gas mixture to pass preferentially through. 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).

[0027] The separation functional layer 1 includes polyimide P and a filler. The polyimide P and the filler are bonded via a covalent bond. The covalent bond between the polyimide P and the filler reduces physical aging of the polyimide P. This reduces the deterioration of separation performance of the separation functional layer 1 according to this embodiment when used for a long period of time.

[0028] The polyimide P contains a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered ring acid anhydride structure S, and a structural unit B derived from an amine compound.

[0029] The structural unit A1 derived from the tetracarboxylic dianhydride a1 is a structural unit suitable for improving the permeability coefficient and permeation rate of acidic gases that permeate the separation functional layer 1. The tetracarboxylic dianhydride a1 has 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]

[0030] 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, 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 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.

[0032] The tetracarboxylic dianhydride a1 is preferably represented by the following formula (a1). [ka]

[0033] 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.

[0034] 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 an amine compound that has reacted with the tetracarboxylic dianhydride a1. [ka]

[0035] 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]

[0036] 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.

[0037] As described above, polyimide P includes a structural unit B derived from an amine compound. An amine compound typically has two or more amino groups. Such an amine compound is typically a diamine. Therefore, polyimide P includes a structural unit B derived from a diamine. A diamine is a compound having two primary amino groups. The diamine may or may not include functional groups other than the primary amino groups.

[0038] The structural unit B derived from an amine compound preferably includes a structural unit B1 derived from an amine compound b1 having a reactive site that forms a covalent bond with the filler. The amine compound b1 is typically a diamine. The amine compound b1 may have, as the reactive site, a functional group capable of condensing with a functional group possessed by the filler, or may have at least one functional group f selected from the group consisting of a carboxyl group, an isocyanate group, a hydroxyl group, a thiol group, and a sulfonic acid group. The amine compound b1 preferably has a functional group capable of condensation with an amino group. That is, the functional group f is preferably a functional group capable of condensation with an amino group. Therefore, the functional group f is preferably at least one selected from the group consisting of a carboxyl group and an isocyanate group, and more preferably a carboxyl group. As a result, when the filler described below has an amino group as a reactive site that forms a covalent bond with the polyimide P, the polyimide P and the filler are bonded via an amide bond. When the filler has a hydroxy group, the functional group f may be at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, and an isocyanate group.When the filler has at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, and an isocyanate group, the functional group f may be at least one selected from the group consisting of a hydroxy group and a thiol group.

[0039] The number of functional groups f in the amine compound b1 is not particularly limited and may be, for example, 1 or more, or may be 2 or more. The upper limit of the number of functional groups f is, for example, 5 or less.

[0040] The amine compound b1 may further have an aromatic ring. Examples of the aromatic ring include those described above for the tetracarboxylic dianhydride a1. In the amine compound b1, the substituent on the aromatic ring preferably includes a functional group f or a primary amino group. The aromatic ring may have a substituent other than the substituent including the functional group f and the substituent including the primary amino group, or may have no other substituent. The other substituent is not particularly limited, and examples include a halogen group and a hydrocarbon group. Examples of the halogen group and the hydrocarbon group include those described above for the tetracarboxylic dianhydride a1. In the amine compound b1, the other substituent may include a photopolymerizable functional group (e.g., a vinyl group).

[0041] The amine compound b1 is represented by, for example, the following formula (b1), formula (b2), or formula (b3). [ka]

[0042] In formula (b1), R 1b ~R 4b are each independently a hydrogen atom or an arbitrary substituent, provided that R 1b ~R 4b At least one selected from the group consisting of is a group containing functional group f, preferably functional group f itself. Functional group f is preferably a carboxyl group or an isocyanate group, more preferably a carboxyl group. The optional substituent other than the group containing functional group f is not particularly limited, and examples thereof include halogen groups and hydrocarbon groups. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0043] In formula (b2), R 5b ~R 12b are each independently a hydrogen atom or an arbitrary substituent, and X 1 is a single bond or any linking group, provided that R 5b ~R 12bAt least one selected from the group consisting of is a group containing functional group f, preferably functional group f itself. Functional group f is preferably a carboxyl group or an isocyanate group, more preferably a carboxyl group. The optional substituents other than the group containing functional group f are not particularly limited, and examples thereof include halogen groups and hydrocarbon groups. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1. X 1 In the formula (I), the optional 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. 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.

[0044] In formula (b3), R 13b ~R 20b are each independently a hydrogen atom or an arbitrary substituent, and X 2 is a single bond or any linking group, provided that R 13b ~R 20b At least one selected from the group consisting of is a group containing functional group f, preferably functional group f itself. Functional group f is preferably a carboxyl group or an isocyanate group, more preferably a carboxyl group. The optional substituents other than the group containing functional group f are not particularly limited, and examples thereof include halogen groups and hydrocarbon groups. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1. X 2 In the formula (I), the optional linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include X 1 The above-mentioned items are included in 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.

[0045] The structural unit B1 derived from the amine compound b1 is represented, for example, by the following formula (B1), formula (B2), or formula (B3). The structural units B1 represented by formulas (B1) to (B3) are derived from the amine compound b1 represented by the above formulas (b1) to (b3), respectively. Formulas (B1) to (B3) represent the structural unit B1 before a covalent bond with a filler is formed. The same applies to specific examples of formulas (B1) to (B3) described below. [ka]

[0046] In formula (B1), R 1b ~R 4b are each independently a hydrogen atom or an arbitrary substituent, provided that R 1b ~R 4b At least one selected from the group consisting of is a group containing functional group f, and is preferably functional group f itself. The optional substituent other than the group containing functional group f is not particularly limited, and examples thereof include halogen groups and hydrocarbon groups. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0047] Specific examples of the structural unit B1 represented by formula (B1) include the following formulae (B1-1) to (B1-3). [ka]

[0048] In formula (B2), R 5b ~R 12b are each independently a hydrogen atom or an arbitrary substituent, and X 1 is a single bond or any linking group, provided that R 5b ~R 12bAt least one selected from the group consisting of is a group containing functional group f, and is preferably functional group f itself. The optional substituent other than the group containing functional group f is not particularly limited, and examples thereof include halogen groups and hydrocarbon groups. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0049] X in formula (B2) 1 In the formula (I), the optional linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include those described 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.

[0050] Specific examples of the structural unit B1 represented by formula (B2) include the following formulae (B2-1) to (B2-6). [ka]

[0051] In formula (B3), R 13b ~R 20b are each independently a hydrogen atom or an arbitrary substituent, and X 2 is a single bond or any linking group, provided that R 13b ~R 20b At least one selected from the group consisting of is a group containing functional group f, and is preferably functional group f itself. The optional substituent other than the group containing functional group f is not particularly limited, and examples thereof include halogen groups and hydrocarbon groups. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0052] X in formula (B3) 2 In the formula (I), the optional linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include those described 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.

[0053] Specific examples of the structural unit B1 represented by formula (B3) include the following formulae (B3-1) to (B3-3). [ka]

[0054] The polyimide P may contain, as the structural unit B, a structural unit B1 represented by formula (B2).

[0055] In the polyimide P, the ratio p1 of the amount of constituent unit B1 derived from the amine compound b1 to the amount of all constituent units B derived from the amine compound is preferably less than 20 mol%, more preferably 15 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. This configuration can reduce physical aging of the polyimide P. This reduces the degradation of separation performance of the separation functional layer 1 of this embodiment over extended use. Furthermore, the separation functional layer 1 of this embodiment can improve the initial permeability coefficient and permeation rate of acidic gases. The ratio p1 is preferably greater than 0 mol%, more preferably 0.1 mol% or more, and even more preferably 0.5 mol% or more. This configuration can further improve the permeability coefficient and permeation rate of acidic gases passing through the separation functional layer 1. However, the constituent unit B does not necessarily have to contain the constituent unit B1 derived from the amine compound b1. That is, the ratio p1 may be 0 mol% or more.

[0056] In the polyimide P, the structural unit B preferably further includes a structural unit B2 derived from an amine compound b2 different from the amine compound b1. The amine compound b2 typically does not have a reactive site that forms a covalent bond with the filler in the separation functional layer 1. The structural unit B preferably includes structural units B1 and B2. However, the structural unit B may consist only of the structural unit B1.

[0057] The amine compound b2 is typically a diamine. The amine compound b2 may further have an aromatic ring. Examples of the aromatic ring include those described above for the tetracarboxylic dianhydride a1. In the amine compound b2, 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 not have any other substituent. The other substituent is not particularly limited, and examples include a halogen group and a hydrocarbon group. Examples of the halogen group and the hydrocarbon group include those described above for the tetracarboxylic dianhydride a1. In the diamine, the other substituent may contain a photopolymerizable functional group (for example, a vinyl group).

[0058] The amine compound b2 is represented by, for example, the following formula (c1), (c2), (c3), or (c4). [ka]

[0059] In formulas (c1) to (c4), R 1c ~R 22c are each independently a hydrogen atom or an arbitrary substituent. The arbitrary substituent is a substituent other than a group containing a reactive site that forms a covalent bond with the filler, and is typically a substituent other than a group containing the functional group f described above. Specific examples of the optional substituent include a halogen group and a hydrocarbon group. Examples of the halogen group and the hydrocarbon group include those described above for the tetracarboxylic dianhydride a1.

[0060] In formula (c3), X 3is 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 3 may contain a functional group such as an ether group or an ester group in addition to or instead of the divalent hydrocarbon group.

[0061] The structural unit B2 derived from the amine compound b2 is represented, for example, by the following formula (C1), (C2), (C3), or (C4): The structural units B represented by formulas (C1) to (C4) are derived from the amine compound b2 represented by the above formulas (c1) to (c4), respectively. [ka]

[0062] In formula (C1), R 1c ~R 4c are each independently a hydrogen atom or an arbitrary substituent. In formula (C1), the arbitrary substituent is a substituent other than a group containing a reactive site that forms a covalent bond with a filler, and is typically a substituent other than a group containing the above-mentioned functional group f. In detail, the arbitrary substituent is a halogen group, a hydrocarbon group, etc. Examples of the halogen group and the hydrocarbon group include those described above for the tetracarboxylic dianhydride a1. Specific examples of the structural unit B2 represented by formula (C1) include the following formula (C1-1). [ka]

[0063] In formula (C2), R 5c ~R 8care each independently a hydrogen atom or an arbitrary substituent. In formula (C2), the arbitrary substituent is a substituent other than a group containing a reactive site that forms a covalent bond with the filler, and is typically a substituent other than a group containing the functional group f. More specifically, the arbitrary substituent is a halogen group, a hydrocarbon group, or the like. Examples of the halogen group and the hydrocarbon group include those described above for the tetracarboxylic dianhydride a1. Specific examples of the structural unit B2 represented by formula (C2) include the following formula (C2-1). [ka]

[0064] In formula (C3), R 9c ~R 16c are each independently a hydrogen atom or an arbitrary substituent, and X 3 is a single bond or an arbitrary linking group. In formula (C3), the optional substituent is a substituent other than a group containing a reactive site that forms a covalent bond with the filler, and is typically a substituent other than a group containing the above-mentioned functional group f. In detail, the optional substituent is a halogen group, a hydrocarbon group, etc. Examples of the halogen group and the hydrocarbon group include those described above for the tetracarboxylic dianhydride a1.

[0065] X in formula (C3) 3 In the formula (I), the optional linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include those described above. X 3 may contain a functional group such as an ether group or an ester group in addition to or instead of the divalent hydrocarbon group.

[0066] Specific examples of the structural unit B2 represented by formula (C3) include the following formulae (C3-1) to (C3-3). [ka]

[0067] In formula (C4), R 17c ~R 22care each independently a hydrogen atom or an arbitrary substituent. In formula (C4), the arbitrary substituent is a substituent other than a group containing a reactive site that forms a covalent bond with the filler, and is typically a substituent other than a group containing the functional group f. In detail, the arbitrary substituent is a halogen group, a hydrocarbon group, etc. Examples of the halogen group and the hydrocarbon group include those described above for the tetracarboxylic dianhydride a1. The structural unit B2 represented by formula (C4) is suitable for improving the rigidity of the polyimide P. A polyimide P with excellent rigidity tends to be able to suppress plasticization of the separation functional layer 1 even when the pressure of the mixed gas to be separated is high.

[0068] Specific examples of the structural unit B2 represented by formula (C4) include the following formulae (C4-1) and (C4-2). [ka]

[0069] The polyimide P may contain, as the structural unit B, a structural unit B2 represented by formula (C4), or may contain a structural unit B2 represented by formula (C1) and a structural unit B2 represented by formula (C4).

[0070] In the polyimide P, the ratio p2 of the amount of constituent units B2 derived from the amine compound b2 to the amount of all constituent units B derived from the amine compound is preferably more than 80 mol%, more preferably 85 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more. The ratio p2 is, for example, 100 mol% or less, preferably less than 100 mol%, more preferably 99.9 mol% or less, and even more preferably 99.5 mol% or less.

[0071] In polyimide P, structural units A derived from tetracarboxylic dianhydride and structural units B derived from amine compounds are arranged alternately. Examples of combinations of adjacent structural units A and B in polyimide P include the following formulae (A1-B2), (A1-C1), and (A1-C4). In these formulae, R 1a ~R 4a , R 5b ~R 12b , R 1c ~R 4c , and R 17c ~R 22c is the same as described above for formula (A1), formula (B2), formula (C1), and formula (C4). [ka]

[0072] The weight-average molecular weight (Mw) of the 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 1. The upper limit of the weight-average molecular weight of the polyimide P is not particularly limited and is, for example, 1,000,000. The weight-average molecular weight of the polyimide P can be calculated, for example, by measuring the molecular weight distribution of the 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).

[0073] The content of polyimide P in the separation functional layer 1 may be, for example, 50 wt% or more, 60 wt% or more, 70 wt% or more, or even 75 wt% or more, or may be 95 wt% or less, 90 wt% or less, 85 wt% or less, or even 80 wt% or less.

[0074] The separation functional layer 1 contains fillers bonded to polyimide P via covalent bonds. The fillers are dispersed in a matrix containing polyimide P. The fillers may be separated from one another within the matrix, or may be partially aggregated.

[0075] The covalent bond between the polyimide P and the filler is formed by a reaction between the polyimide P and the filler during the manufacturing process of the separation functional layer 1. The reaction is, for example, a dehydration condensation reaction. The reaction can occur between the structural unit A derived from a tetracarboxylic dianhydride and the filler, and between the structural unit B derived from an amine compound and the filler, particularly between the structural unit B1 derived from an amine compound b1 and the filler. The covalent bond preferably includes a covalent bond bonding the structural unit B and the filler, and more preferably includes a covalent bond bonding the functional group f contained in the structural unit B1 and the filler. This configuration can further reduce the deterioration of separation performance of the separation functional layer 1 during long-term use. The covalent bond may include a covalent bond formed between an atom constituting the structural unit A and the filler, and a covalent bond formed between the functional group f contained in the structural unit B1 and the filler. The covalent bond can be, for example, an amide bond, an ether bond, an ester bond, or a disulfide bond, and is preferably an amide bond.

[0076] The filler may have at least one functional group X selected from the group consisting of an amino group, a carboxyl group, a sulfonic acid group, an isocyanate group, a hydroxyl group, and a thiol group as a reactive site that forms a covalent bond with the polyimide P. The functional group X preferably has an amino group, and more preferably a primary amino group. The functional group X is a functional group capable of forming a covalent bond with the polyimide P, such as a functional group capable of condensing with a functional group possessed by the polyimide P. For example, when the filler has an amino group and the polyimide P (typically, the structural unit B1 of the polyimide P) has a carboxyl group, the filler bonds to the polyimide P via an amide bond. Unreacted amino groups possessed by the filler may remain in the separation functional layer 1. Furthermore, when the structural unit B1 of the polyimide P has a hydroxyl group, the functional group X may be at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, and an isocyanate group. When the structural unit B1 of the polyimide P has at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, and an isocyanate group, the functional group X may be at least one selected from the group consisting of a hydroxy group and a thiol group.

[0077] The filler may include, for example, a metal-organic framework (MOF), or may include an inorganic material.

[0078] MOFs contain metal ions and organic ligands.

[0079] The metal ions include, for example, ions of transition metals or rare earth elements, preferably tetravalent metal ions, more preferably at least one ion selected from the group consisting of Zr, Ti, and Ce, and even more preferably Zr ions.

[0080] In addition to the functional group for coordinating to the metal ion, the organic ligand contains a functional group X. The functional group X is as described above.

[0081] The functional group for coordinating with a metal ion is not particularly limited and may be, for example, a carboxyl group. The organic ligand may contain two carboxyl groups as functional groups for coordinating with a metal ion. That is, the organic ligand may contain a dicarboxylic acid derivative containing the functional group X, or may contain a terephthalic acid derivative containing the functional group X.

[0082] The organic ligand is, in particular, a hydrocarbon compound containing a functional group X and a functional group for coordinating to a metal ion, and is preferably a dicarboxylic acid derivative containing the functional group X. The number of carbon atoms in the organic ligand is not particularly limited and is, for example, 3 to 25, and preferably 3 to 10. The organic ligand may contain an aromatic ring. In the organic ligand, the aromatic ring is preferably composed of carbon atoms. However, the aromatic ring 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, but is preferably monocyclic. The aromatic ring is, for example, a benzene ring.

[0083] The organic ligand is preferably a terephthalic acid derivative containing a functional group X. Such an organic ligand is represented, for example, by the following formula (1): In formula (1), X is a functional group X. [ka]

[0084] A specific example of the first organic ligand is 2-aminoterephthalic acid.

[0085] The MOF may be, for example, a UiO-type MOF. The MOF is represented, for example, by the following formula (2): This shows a simplified UiO-66 derivative composed of organic ligands and zirconium ions. [ka]

[0086] Examples of inorganic materials contained in the filler include zeolite, silica, titania, and alumina. The filler is preferably an inorganic material surface-modified with a modifying group, more preferably silica surface-modified with a modifying group. The modifying group is capable of forming a covalent bond with polyimide P, such as the functional group X described above.

[0087] The shape of the filler is not particularly limited, and may be, for example, particulate. In this specification, "particulate" includes spherical, ellipsoidal, scaly, fibrous, and the like. The average particle size of the filler is not particularly limited, and may be, for example, 10 μm or less, 1 μm or less, 500 nm or less, 300 nm or less, or even 100 nm or less. The lower limit of the average particle size of the filler is not particularly limited, and may be, for example, 1 nm.

[0088] The average particle size of the filler can be determined, for example, by the following method. First, a cross section of the separation functional layer 1 is observed using a transmission electron microscope. In the obtained electron microscope image, the area of ​​a specific filler is calculated by image processing. The diameter of a circle having the same area as the calculated area is regarded as the particle size (particle diameter) of that specific filler. The particle sizes of an arbitrary number of fillers (at least 50) are calculated, and the average of the calculated values ​​is regarded as the average particle size of the filler.

[0089] The separation functional layer 1 may further contain other components in addition to the polyimide P and the filler.

[0090] 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, 15 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, or even 1 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. According to the inventors' studies, when a conventional separation functional layer having a thickness of about 5.0 μm or less is used, the separation functional layer tends to deteriorate and its separation performance (particularly, the permeation rate of acidic gases) tends to decrease over long-term use. However, in the separation functional layer 1 of this embodiment, even when the thickness is small, the separation functional layer contains a filler bonded to the polyimide P via a covalent bond, which tends to suppress the deterioration of separation performance over long-term use.

[0091] (Method of manufacturing the separation functional layer) The method for producing a separation functional layer according to this embodiment includes reacting a polyimide and a filler to form a covalent bond, and producing a separation functional layer including the polyimide and filler bonded via the covalent bond. The polyimide is polyimide P including a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered ring acid anhydride structure S, and a structural unit B derived from an amine compound. The production method according to this embodiment allows production of a separation functional layer 1. The explanations of polyimide P, structural unit A1, and structural unit B of polyimide P described above for separation functional layer 1 apply to the polyimide P in the production method according to this embodiment.

[0092] The polyimide P can be prepared, for example, by the following method: First, the amine compound (diamine) is dissolved in a solvent to obtain a solution. Examples of the solvent include polar organic solvents such as N-methyl-2-pyrrolidone and 1,3-dioxolane.

[0093] Next, tetracarboxylic dianhydrides including the tetracarboxylic dianhydride a1 are gradually added to the resulting solution. This causes the tetracarboxylic dianhydride a1 to react with 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.

[0094] Next, polyamic acid is imidized to obtain polyimide P. 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.

[0095] The reaction between the polyimide P and the filler is typically carried out by heat treatment. The heat treatment conditions are not limited as long as a covalent bond between the polyimide P and the filler is formed. For example, the heat treatment temperature may be 150°C to 250°C, or 180°C to 220°C. The heat treatment time may be 1 hour to 10 hours, or 4 hours to 8 hours.

[0096] In a preferred embodiment, a coating liquid L containing polyimide P and a filler is heat-treated to form a covalent bond between the polyimide P and the filler. The coating liquid L is typically a dispersion in which the filler is dispersed in a polyimide P solution. In this embodiment, the heat-treated coating liquid L, i.e., the coating liquid L containing the polyimide P and the filler bonded via a covalent bond, may be applied to a substrate to form a coating film, and the coating film may be dried to produce the separation functional layer 1. As described above, by forming a covalent bond in solution to crosslink the polyimide P and the filler, the reaction efficiency between the polyimide P and the filler is improved, the reaction time is shortened, and the concentration of polyimide P in the coating liquid L can be reduced.

[0097] The viscosity of the coating liquid L after the heat treatment is preferably 30 Pa s or less. According to the above configuration, it is possible to easily form a coating film and control the film thickness. The lower limit of the viscosity of the coating liquid L after the heat treatment is not particularly limited, but is, for example, 0.001 Pa s or more.

[0098] In another preferred embodiment, a coating liquid L containing polyimide P and a filler is applied onto a substrate to form a coating film, and the coating film is then heat-treated to form a covalent bond between the polyimide P and the filler. In this embodiment, the coating film may be dried after formation and during the heat treatment to form the covalent bond. In this manner, the separation functional layer 1 can be produced.

[0099] The content of polyimide P in the coating liquid L can be adjusted appropriately depending on the solubility of polyimide P, and is, for example, 1 wt % to 30 wt %.

[0100] The coating liquid L may further contain a highly polar organic solvent such as N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), 1,3-dioxolane, etc. Such organic solvents are suitable for dissolving the polyimide P.

[0101] The substrate to which the coating liquid L is applied is typically a release liner. Alternatively, the substrate may be a glass plate. Examples of the substrate include a film containing a resin; paper; a sheet containing a metal material such as aluminum or stainless steel; and a glass plate. Sheets containing metal materials tend to have high heat resistance. The substrate is preferably a film containing a resin because of its excellent surface smoothness. 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.

[0102] 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.

[0103] The thickness of the substrate is not particularly limited and is, for example, 5 to 100 μm, and preferably 10 to 50 μm.

[0104] The substrate may be subjected to a surface modification treatment before being coated with the coating liquid L. When 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.

[0105] 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.

[0106] The method for applying the coating liquid L to the substrate is not particularly limited, and for example, spin coating, dip coating, slot die coating, etc. may be used. The coating liquid L may be applied to the substrate using an applicator, a wire bar, etc. The coating liquid L may be applied to the surface of a substrate that has been subjected to a release treatment or a surface modification treatment.

[0107] A coating film is formed by applying the coating liquid L 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.

[0108] The drying conditions for the coated film are a drying temperature of, for example, 50°C to 140°C, preferably 60°C to 130°C, and a drying time of, for example, 1 minute to 5 hours, preferably 1 hour to 3 hours. The coated film can be dried using, for example, a heater. As an example, the coated film may be dried by passing it through a heating unit equipped with a heater. The coated 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.

[0109] 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 to prevent the separation performance of the separation functional layer 1 from deteriorating 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.

[0110] The temperature of the heat treatment may be, for example, 130°C or higher, 150°C or higher, 200°C or higher, or even 250°C or higher. The upper limit of the temperature of the heat treatment is not particularly limited and may be, for example, 350°C or lower, or 300°C or lower. The time of the heat treatment may be, for example, 1 minute or longer, 10 minutes or longer, or 30 minutes or longer. The upper limit of the time of the heat treatment may be, for example, 24 hours or shorter, 5 hours or shorter, or even 1 hour or shorter.

[0111] The manufacturing method of this embodiment preferably further includes removing the substrate from the laminate of the separation functional layer 1 and the substrate. By removing the substrate, a separation functional layer 1 that functions as a free-standing membrane can be obtained.

[0112] (Characteristics of the separation functional layer) As described above, it is preferable that the separation functional layer 1 preferentially transmits acidic gases contained in the mixed gas. As an example, when a mixed gas consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one side of the separation functional layer 1 using the separation functional layer 1 in an initial state, the permeability coefficient C1 of carbon dioxide that permeates the separation functional layer 1 taking into consideration the thickness of the separation functional layer 1 is, for example, 100 Barrer or more, 500 Barrer or more, 550 Barrer or more, or even 700 Barrer or more. The upper limit of the permeability coefficient C1 is not particularly limited and is, for example, 5000 Barrer. However, the Barrer is not limited to 10 -10 ·cm 3 (STP)·cm / (sec·cm 2 ·cmHg).

[0113] The permeability coefficient C1 can be determined by the following method. First, a mixed gas consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation functional layer 1, and the space adjacent to the other surface of the separation functional layer 1 is depressurized. This results in a permeated fluid that has permeated through 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 nitrogen in the permeated fluid, are measured. The permeability coefficient C1 can be calculated from the measurement results. In the above operation, the carbon dioxide concentration 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. The space adjacent to the other surface of the separation functional layer 1 is depressurized so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.

[0114] Under the above conditions for measuring the permeability coefficient C1, the separation coefficient α1 of carbon dioxide relative to nitrogen of the separation functional layer 1 is not particularly limited, and may be, for example, 20 or more, 25 or more, or even 30 or more. The upper limit of the separation coefficient α1 is not particularly limited, and may be, for example, 100 or 60. The separation coefficient α1 can be calculated from the following formula. In the following formula, X A and X Bare the volume fractions of carbon dioxide and nitrogen in the gas mixture, respectively. Y A and Y B are the volume ratio of carbon dioxide and the volume ratio of nitrogen in the permeated fluid that has permeated the separating functional layer 1, respectively. Separation factor α1=(Y A / Y B ) / (X A / X B )

[0115] As described above, the separation functional layer 1 of this embodiment contains polyimide P and a filler bonded to the polyimide P via a covalent bond. In this separation functional layer 1, physical aging of the polyimide is suppressed, which can prevent the separation performance of the separation functional layer 1 from decreasing over time. In particular, the separation functional layer 1 of this embodiment prevents the decrease in separation performance (particularly the permeation rate of acidic gases) when used for a long period of time.

[0116] The deterioration of the separation performance of the separation functional layer 1 due to long-term use can be evaluated by the following method. First, the separation functional layer 1 is stored in an environment of 85°C for two weeks (336 hours) (durability test). After the durability test, the carbon dioxide permeability coefficient C2 of the separation functional layer 1 is measured using the same method as for the permeability coefficient C1. The deterioration of separation performance can be evaluated based on the ratio C2 / C1 of the permeability coefficient C2 to the permeability coefficient C1 (permeability coefficient maintenance rate).

[0117] In the separation functional layer 1, the transmission coefficient maintenance rate is, for example, 60% or more, and may be 68% or more, 75% or more, 80% or more, 85% or more, or even 90% or more. The upper limit of the transmission coefficient maintenance rate is, for example, 110%.

[0118] The permeability coefficient C2 after the durability test is, for example, 100 Barrer or more, and may be 300 Barrer or more, 400 Barrer or more, 450 Barrer or more, or even 500 Barrer or more. The upper limit of the permeability coefficient C2 is not particularly limited, and is, for example, 5000 Barrer.

[0119] The separation factor α2 of carbon dioxide relative to nitrogen of the separation functional layer 1 after the durability test is, for example, 20 or more, and may be 30 or more, or even 35 or more. The upper limit of the separation factor α2 after the durability test is not particularly limited and may be, for example, 100 or 60. The separation factor α2 after the durability test can be determined by the same method as the separation factor α1 described above, except that the separation functional layer 1 after the durability test is used.

[0120] In the separation functional layer 1, the ratio α2 / α1 of the separation coefficient α2 to the separation coefficient α1 (separation coefficient maintenance rate) is, for example, 80% or more, 90% or more, or even 100% or more. The upper limit of the transmission coefficient maintenance rate is, for example, 200%.

[0121] (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 contains gases other than 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 nitrogen. However, the use of the separation functional layer 1 is not limited to separating acidic gases from the above-mentioned gas mixture.

[0122] <Embodiments of separation membrane> As shown in Fig. 2, the separation membrane 10 of this embodiment includes the above-described 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.

[0123] (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.

[0124] 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.

[0125] 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.

[0126] 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]

[0127] R in formulas (I) to (III) 1 ~R 6are 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.

[0128] 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]

[0129] 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.

[0130] In formula (IV), R 8R 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.

[0131] In the nanoparticles, the surface modified with the modifying group is preferably represented by the following formula (V). [ka]

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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%.

[0136] 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.

[0137] (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.

[0138] 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.

[0139] (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.

[0140] Next, the 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 for the production of the separation membrane 10. As an example, the separation membrane 10 can be produced by using the laminate of the porous support 3 and the intermediate layer 2 as a substrate and carrying out the production method described above for the separation functional layer 1.

[0141] The method for producing the separation membrane 10 is not limited to the above method, and the separation membrane 10 may also be produced by the following method. First, a separation functional layer 1 formed on a substrate is prepared by the above method. Next, 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. 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 10 is obtained.

[0142] (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. As an example, the separation membrane 10 as a hollow fiber membrane may include a separation function layer 1 and a porous support 3, but may not include an intermediate layer 2.

[0143] <Embodiment of Membrane Separation Device> As shown in FIG. 3, 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] <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.

[0152] 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.

[0153] 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).

[0154] 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).

[0155] 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]

[0156] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0157] [Fabrication of separation functional layer] Example 1 <Synthesis of polyimide P1> First, polyimide was synthesized using an automatic polymerization apparatus (Mettler-Toledo, EasyMax402). The separable flask (400 mL capacity) attached to the apparatus was equipped with a Dimroth tube, a stirring rod, an internal thermometer, a nitrogen inlet tube, and a flat stopper. A cooling liquid set to 10°C was circulated through the Dimroth chiller. N2 gas was circulated through the flask at a flow rate of 100 mL / min. The stirring speed was set to 300 rpm. A flask was charged with 143 g of 1-methyl-2-pyrrolidone (super-dehydrated) as a solvent, and 7.1359 g (47.5 mmol) of 2,4,6-trimethyl-1,3-phenylenediamine (TrMPD) as diamines, 13.0312 g (47.5 mmol) of 3,7-diamino-2,8-dimethyldibenzothiophene sulfone (DDBT), and 1.4314 g (5 mmol) of 5,5'-methylenebis(2-aminobenzoic acid) (MBAA) as diamines. The mixture was stirred at room temperature to dissolve the diamines in the solvent. To the resulting solution, 27.4694 g (102 mmol) of naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTDA) as a tetracarboxylic dianhydride and 23.9259 g (196 mmol) of benzoic acid were further added. The jacket temperature of the apparatus was raised to 180° C., and stirring was continued for 8 hours. At this time, the internal temperature of the flask was 172 to 175° C. After stirring, the internal temperature of the flask was cooled to 25° C., and the flask was allowed to stand overnight.

[0158] Next, 25.3044 g (196 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, 819 g of 1-methyl-2-pyrrolidone (NMP) was added to dilute the reaction solution. Next, using a dropping funnel, 1887 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 500 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 48 g of polyimide P1.

[0159] <Filler synthesis> First, 1.92 g of zirconium chloride (ZrCl4: manufactured by Nacalai Tesque) and 1.49 g of 2-aminoterephthalic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in 278.23 g of dehydrated N,N-dimethylformamide (DMF) (manufactured by Nacalai Tesque) and 58.03 g of acetic acid. Next, the solution was refluxed at 150°C for 22 hours to obtain a white powder. The resulting white powder was collected by centrifugation. This powder was washed three times with DMF and then washed three more times with acetone. After washing, the powder was dried at 60°C for 24 hours and then vacuum dried at 120°C for 8 hours. This resulted in a metal-organic framework (UiO-66(Zr)-NH2) as the filler of Example 1.

[0160] <Creating a separation functional layer> The polyimide P1 and filler were placed in a screw tube at a weight ratio of 80:20. NMP was added as a solvent to the screw tube to achieve a solids concentration of 10 wt%. Using a stirring device (Thinky Corporation's Awatori Rentaro), the mixture was stirred at 2000 rpm for 25 minutes, and then degassed at 2200 rpm for 5 minutes. Next, the mixture was refluxed at 180°C for 8 hours while stirring, thereby carrying out a thermal crosslinking treatment. This crosslinked the polyimide P1 and the filler. The mixture was then allowed to cool to room temperature while stirring. In this way, a coating liquid containing polyimide P1 and a filler that forms a covalent bond with polyimide P1 was prepared.

[0161] Next, the coating solution was cast onto a glass plate (manufactured by AS ONE Corporation, GB200, thickness 5 mm) using an applicator with a gap of 50 μm to form a coating film. The coating film was heated and dried in an oven at 130 ° C for 1 minute to form a coating film. Thereafter, it was further heated and dried in an oven at 150 ° C for 30 minutes to obtain the separation functional layer (freestanding film) of Example 1. This freestanding film was peeled off from the glass plate and used.

[0162] Example 2 The separation functional layer of Example 2 was produced in the same manner as in Example 1, except that the gap of the applicator was changed to 100 μm when forming the coating film.

[0163] Example 3 The separation functional layer of Example 3 was produced in the same manner as in Example 1, except that the filler was changed to silica particles surface-modified with amino groups (manufactured by EVONIK, AEROSIL (registered trademark) R504).

[0164] Example 4 <Synthesis of polyimide P2> Polyimide synthesis was performed 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 a coolant set at 10°C. N2 gas was circulated through the flask at a flow rate of 100 mL / min. The stirring speed was set at 300 rpm. The flask was charged with 157 g of 1-methyl-2-pyrrolidone (super-dehydrated) as the solvent and 7.5115 g (50 mmol) of TrMPD and 13.7170 g (50 mmol) of DDBT as the diamines. The mixture was stirred at room temperature to dissolve the diamines in the solvent. To the resulting solution, 27.4694 g (102 mmol) of NTDA as a tetracarboxylic dianhydride and 24.5358 g (201 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. At this time, the internal temperature of the flask was 172 to 175°C. After stirring, the internal temperature of the flask was cooled to 25°C, and the mixture was allowed to stand overnight.

[0165] Next, 25.9502 g (201 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, 779 g of NMP was added to dilute the reaction solution. Next, using a dropping funnel, 1000 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 500 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 45 g of polyimide P2.

[0166] <Preparation of separation functional layer> A separation functional layer of Example 4 was produced in the same manner as in Example 1, except that polyimide P1 was changed to polyimide P2.

[0167] (Comparative Example 1) Polyimide P1 was placed in a screw tube, and NMP was added as a solvent to achieve a solids concentration of 10 wt%. Using a stirring device (Thinky Corporation's Awatori Rentaro), the mixture was stirred at 2000 rpm for 25 minutes, and then degassed at 2200 rpm for 5 minutes to obtain a coating solution. A separation functional layer for Comparative Example 1 was produced in the same manner as in Example 1, except that the coating solution was cast onto a glass plate.

[0168] (Comparative Example 2) The separation functional layer of Comparative Example 2 was produced in the same manner as Comparative Example 1, except that the gap of the applicator was changed to 100 μm when forming the coating film.

[0169] (Comparative Example 3) Polyimide P1 and the above metal organic framework (UiO-66(Zr)-NH2) as a filler were charged into a screw tube at a weight ratio of 80:20. NMP as a solvent was added to the screw tube so that the solid content concentration was 10 wt%. A coating solution was obtained by stirring at 2000 rpm for 25 minutes using a stirring device (Thinky Corporation's Awatori Rentaro) and then degassing at 2200 rpm for 5 minutes. The separation functional layer of Comparative Example 3 was produced in the same manner as in Example 1, except that the coating solution was cast onto a glass plate. That is, the separation functional layer of Comparative Example 3 was obtained in the same manner as in Example 1, except that the thermal crosslinking treatment of the coating solution was not performed.

[0170] Thickness The thickness of the separation functional layer in Examples 1 to 4 and Comparative Examples 1 to 3 was determined by the above-mentioned method.

[0171] [Characteristics evaluation of the separation functional layer] (Gas permeation test) For the separation functional layers of Examples 1 to 4 and Comparative Examples 1 to 3, the carbon dioxide permeability coefficient C1 and the carbon dioxide separation coefficient α1 relative to nitrogen were measured by the following method. First, the separation functional layer was placed 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 nitrogen. 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, the space within the metal cell adjacent to the other main surface of the separation functional layer was depressurized using a vacuum pump. At this time, the pressure in this space was depressurized so that the pressure within this space was 0.1 MPa lower than the atmospheric pressure in the measurement environment. As a result, a permeated fluid was obtained from the other main surface of the separation functional layer. The permeability coefficient C1 and separation coefficient α1 were calculated based on the composition, weight, etc. of the obtained permeated fluid.

[0172] (Durability test) The prepared separation functional layer was stored at 85°C for two weeks (336 hours) and subjected to a durability test. After the durability test, the separation functional layer was measured for the carbon dioxide permeability coefficient C2 and the carbon dioxide to nitrogen separation factor α2 using the same method as for the permeability coefficient C1 and separation factor α1. From the results obtained, the ratio C2 / C1 of the permeability coefficient C2 to the permeability coefficient C1 (permeability coefficient maintenance rate) and the ratio α2 / α1 of the separation factor α2 to the separation factor α1 (separation factor maintenance rate) were calculated.

[0173] [Table 1]

[0174] As can be seen from Table 1, the separation functional layers of Examples 1 to 4, which contain polyimide and a filler bonded to the polyimide via a covalent bond, had a higher permeability coefficient maintenance rate than the separation functional layers of Comparative Examples 1 and 2, which do not contain a filler, and the separation functional layer of Comparative Example 3, which does not have a covalent bond between the polyimide and the filler. From this result, it can be said that the separation functional layer of this embodiment reduces the decline in separation performance when used for a long period of time.

[0175] Unlike Comparative Examples 1 to 3, the separating functional layers of Examples 1 to 4 had an improved permeability coefficient maintenance rate, and the permeability coefficient C1 and separation coefficient α1 in the initial state were also sufficiently high. [Industrial Applicability]

[0176] The separation functional layer and separation membrane of this embodiment are suitable for separating acidic gases from a gas mixture containing acidic gases, and in particular, for separating carbon dioxide from off-gas from a chemical plant or thermal power plant. [Explanation of symbols]

[0177] 1 Separation functional layer 2. Middle class 3 Porous support 10 Separation membrane 100,110 Membrane separation equipment

Claims

1. Polyimide and a filler bonded to the polyimide via a covalent bond; Including, The polyimide comprises a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered ring acid anhydride structure, and a structural unit B derived from an amine compound.

2. The separation functional layer according to claim 1 , wherein the amine compound has two or more amino groups.

3. The separation functional layer according to claim 1 , wherein the filler has an amino group as a reactive site that forms a covalent bond with the polyimide.

4. The separation functional layer according to claim 1 , wherein the structural unit B comprises a structural unit B1 derived from an amine compound b1 having a reactive site that forms a covalent bond with the filler.

5. 5. The separation functional layer according to claim 4, wherein in the polyimide, the ratio of the amount of substance of the structural unit B1 to the amount of substance of all the structural units B is less than 20 mol%.

6. The separation functional layer according to claim 4 , wherein the amine compound b1 has a functional group capable of undergoing a condensation reaction with an amino group.

7. The separation functional layer according to claim 4 , wherein the structural unit B further comprises a structural unit B2 derived from an amine compound b2 different from the amine compound b1.

8. The separation functional layer according to claim 7 , wherein the structural unit B2 is represented by the following formula (C1), formula (C2), formula (C3), or formula (C4): 【Chemical 1】 In the formula (C1), R 1c ~R 4c are each independently a hydrogen atom or an optional substituent, In the formula (C2), R 5c ~R 8c are each independently a hydrogen atom or an optional substituent, In the formula (C3), R 9c ~R 16c are each independently a hydrogen atom or an arbitrary substituent, and X 3 is a single bond or any linking group, In the formula (C4), R 17c ~R 22c are each independently a hydrogen atom or an optional substituent, In the formulae (C1) to (C4), the optional substituent is a substituent other than the group containing the reactive site that forms a covalent bond with the filler.

9. The separation functional layer according to claim 1 , wherein the structural unit A1 is represented by the following formula (A1): 【Chemistry 2】 In the formula (A1), R 1a ~R 4a are each independently a hydrogen atom or an optional substituent.

10. The separation functional layer according to claim 1 , which has a thickness of 1 μm or less.

11. The separation functional layer according to any one of claims 1 to 10, a porous support supporting the separation functional layer; A separation membrane comprising:

12. reacting the polyimide and the filler to form a covalent bond; preparing a separation functional layer including the polyimide and the filler bonded via the covalent bond; Including, The polyimide contains a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered ring acid anhydride structure, and a structural unit B derived from an amine compound.

13. The reaction is carried out by heat treatment, The method for producing a separation functional layer according to claim 12, wherein the heat treatment temperature is 150°C or higher and 250°C or lower.

14. The method for producing a separation functional layer according to claim 13, wherein the heat treatment time is from 1 hour to 10 hours.

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