Separation functional layer, separation membrane, and method for manufacturing the separation functional layer

Abstract

This invention provides a novel separation layer suitable for separating acidic gases from a gas mixture containing acidic gases. [Solution] The separation functional layer 1 of the present invention contains a crosslinked polyimide. The crosslinked polyimide is obtained by crosslinking polyimide P via covalent bonds. The polyimide P contains a constituent unit A1 derived from a tetracarboxylic dianhydride having a 6-membered ring acid anhydride structure. The separation membrane 10 of the present invention comprises a separation functional layer 1 and a porous support 3 that supports the separation functional layer 1.

Description

[Technical Field]

[0001] The present invention relates to a separation functional layer, a separation membrane, and a method for manufacturing a separation functional layer. [Background technology]

[0002] Membrane separation is a method developed to separate acidic gases, such as carbon dioxide, from gas mixtures containing them. Compared to absorption methods, which separate acidic gases by having an absorbent absorb them, membrane separation can efficiently separate acidic gases while keeping operating costs down.

[0003] Examples of separation membranes used in membrane separation methods include composite membranes in which a separation functional layer is formed on a porous support. Examples of materials for the separation functional layer include resins such as polyimide resin and polyether block amide resin. For example, Patent Document 1 discloses a separation membrane containing polyimide resin. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-184424 [Overview of the project] [Problems that the invention aims to solve]

[0005] There is a need for a new separation layer suitable for separating acidic gases from a gas mixture containing acidic gases. [Means for solving the problem]

[0006] The present invention A separation functional layer containing crosslinked polyimide, The aforementioned crosslinked polyimide is a polyimide that has been crosslinked via covalent bonds. The polyimide provides a separation functional layer containing a constituent unit A1 derived from a tetracarboxylic dianhydride having a six-membered ring acid anhydride structure.

[0007] Furthermore, the present invention, The above separation functional layer, A porous support that supports the separation functional layer, A separation membrane is provided that has the following features.

[0008] Furthermore, the present invention, A method for manufacturing the above-mentioned separation functional layer, The aforementioned manufacturing method is The process involves applying the coating solution containing the polyimide onto a substrate to form a coating film, The coating film is dried to form the crosslinked polyimide from the polyimide, The present invention provides a method for manufacturing a separation functional layer, including [a specific component]. [Effects of the Invention]

[0009] According to the present invention, a novel separation functional layer suitable for separating acidic gases from a gas mixture containing acidic gases can be provided. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing a separation functional layer according to one embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view showing a separation membrane according to one embodiment of the present invention. [Figure 3] This is a schematic cross-sectional view of a membrane separation apparatus equipped with the separation membrane of the present invention. [Figure 4] This is a schematic perspective view showing a modified example of a membrane separation apparatus equipped with the separation membrane of the present invention. [Modes for carrying out the invention]

[0011] The separation functional layer according to the first aspect of the present invention is A separation functional layer containing crosslinked polyimide, The aforementioned crosslinked polyimide is a polyimide that has been crosslinked via covalent bonds. The polyimide contains a constituent unit A1 derived from a tetracarboxylic dianhydride having a six-membered ring acid anhydride structure.

[0012] In a second embodiment of the present invention, for example, in the separation functional layer according to the first embodiment, the polyimide further comprises a constituent unit B1 derived from a diamine, and at least one of the constituent units A1 and B1 has at least one functional group f selected from the group consisting of a sulfonic acid group, a carboxyl group, a hydroxyl group and a thiol group.

[0013] In a third aspect of the present invention, for example, in the separation functional layer according to the second aspect, the crosslinked polyimide is formed by the reaction of the functional group f with a crosslinking agent.

[0014] In a fourth aspect of the present invention, for example, in the separation functional layer according to the third aspect, the crosslinking agent includes at least one selected from the group consisting of epoxy crosslinking agents and amine crosslinking agents.

[0015] In a fifth aspect of the present invention, for example, in the separation functional layer according to the third aspect, the crosslinking agent functions as a condensing agent that promotes the condensation reaction of the functional group f.

[0016] In a sixth embodiment of the present invention, for example, in the separation functional layer according to any one of the second to fifth embodiments, the constituent unit B1 has the functional group f.

[0017] In a seventh embodiment of the present invention, for example, in the separation functional layer according to the sixth embodiment, in the polyimide, the ratio of the amount of substance of the constituent unit B1 having the functional group f to the amount of substance of all constituent units B derived from the diamine is 1 to 60 mol%.

[0018] In the eighth embodiment of the present invention, for example, in the separation functional layer according to the sixth or seventh embodiment, the constituent unit B1 is represented by the following formula (B1). [Chemical formula] In the above formula (B1), Ar 1 and Ar 2 are, independently of each other, aromatic groups, and Ar 3 is an aromatic group containing the functional group f.

[0019] In the ninth aspect of the present invention, for example, in the separation functional layer according to any one of the sixth to eighth aspects, the structural unit B1 is represented by the following formula (B2). [Chemical formula] In the above formula (B2), R 1b ~R 16b are, independently of each other, a hydrogen atom or an arbitrary substituent. However, at least one selected from the group consisting of R 9b ~R 16b is a group containing the functional group f.

[0020] In the tenth aspect of the present invention, for example, in the separation functional layer according to the ninth aspect, in the above formula (B2), at least one selected from the group consisting of R 9b ~R 12b is a group containing the functional group f, and at least one selected from the group consisting of R 13b ~R 16b is a group containing the functional group f.

[0021] In the eleventh aspect of the present invention, for example, in the separation functional layer according to any one of the first to tenth aspects, the structural unit A1 is represented by the following formula (A1). [Chemical formula] In the above formula (A1), R 1a ~R 4a are, independently of each other, a hydrogen atom or an arbitrary substituent.

[0022] In the twelfth embodiment of the present invention, for example, the separation functional layer according to any one of the first to eleventh embodiments has a gel fraction of 70% or more.

[0023] In a thirteenth aspect of the present invention, for example, a separation functional layer according to any one of the first to twelfth aspects is used to separate an acidic gas from a gas mixture containing an acidic gas.

[0024] A separation membrane according to a 14th aspect of the present invention is A separation function layer according to any one of the 1st to 13th embodiments, A porous support that supports the separation functional layer, It is equipped with.

[0025] A manufacturing method according to a 15th aspect of the present invention is: A method for manufacturing a separation functional layer according to any one of the first to thirteen embodiments, The aforementioned manufacturing method is The process involves applying the coating solution containing the polyimide onto a substrate to form a coating film, The coating film is dried to form the crosslinked polyimide from the polyimide, Includes.

[0026] The details of the present invention will be described below, but the following description is not intended to limit the present invention to any particular embodiment.

[0027] <Embodiment of the separation function layer> Figure 1 is a cross-sectional view of the separation functional layer 1 of this embodiment. The separation functional layer 1 in Figure 1 can function as a self-supporting membrane (single-layer membrane). The separation functional layer 1 preferably allows acidic gases contained in the gas mixture to permeate preferentially. Typically, the separation functional layer 1 is a dense layer (non-porous layer) in which no pores can be observed when viewed with a scanning electron microscope (SEM) at a magnification of 5000x.

[0028] The separation functional layer 1 contains a crosslinked polyimide. In this embodiment, the crosslinked polyimide is a polyimide P that has been crosslinked via covalent bonds. In this specification, "polyimide P is crosslinked via covalent bonds" means that a crosslinked structure is formed when polyimide P (more specifically, multiple polyimide P molecules) react with a crosslinking agent to form covalent bonds. Preferably, the crosslinked polyimide does not have metal ions or ionic bonds formed by the coordination of polyimide P to metal ions.

[0029] Polyimide P preferably contains a constituent unit A1 derived from a tetracarboxylic dianhydride a1 having a 6-membered ring acid anhydride structure S, and further contains a constituent unit B1 derived from a diamine b1. Preferably, at least one of constituent units A1 and B1 has at least one functional group f selected from the group consisting of a sulfonic acid group, a carboxyl group, a hydroxyl group, and a thiol group, and preferably the functional group f is a sulfonic acid group. In particular, in polyimide P, it is preferable that constituent unit B1 has functional group f. Constituent unit A1 may or may not have functional group f.

[0030] The constituent unit A1 derived from tetracarboxylic dianhydride a1 is a constituent unit suitable for improving the permeation rate of acidic gases permeating the separation functional layer 1. Tetracarboxylic dianhydride a1 preferably has one or more, preferably two, acid anhydride structures S. The 6-membered ring acid anhydride structure S is typically a glutaric acid anhydride structure represented by the following formula (1). [ka]

[0031] Tetracarboxylic acid dianhydride a1 may have the above-mentioned functional group f together with the acid anhydride structure S, or it may not have the functional group f. Tetracarboxylic acid dianhydride a1 may have a fused ring, and the fused ring may contain the 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 consist only of carbon atoms, or it may be a heteroaromatic ring containing heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms. The aromatic ring may be polycyclic or monocyclic. The number of carbon atoms in the aromatic ring is not particularly limited, for example, 4 to 14. Specific examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, phenanthrene rings, fluorene rings, furan rings, pyrrole rings, pyridine rings, and thiophene rings.

[0032] The fused ring may or may not have substituents. Substituents of the fused ring are not particularly limited and include halogen groups and hydrocarbon groups. Examples of halogen groups include fluoro groups, chloro groups, bromo groups, and iodo groups. The number of carbon atoms in the hydrocarbon group is not particularly limited and is, for example, 1 to 15. Examples of hydrocarbon groups are alkyl groups such as methyl groups, ethyl groups, and propyl groups. The hydrocarbon group may also be a halogenated hydrocarbon group in which a hydrogen atom is substituted with a halogen group. When the fused ring has multiple substituents, the substituents may or may not be the same.

[0033] The tetracarboxylic dianhydride a1 is preferably represented by the following formula (a1). [ka]

[0034] In equation (a1), R 1a ~R 4a These are, independently of each other, a hydrogen atom or any substituent. The substituents are not particularly limited and include halogen groups, hydrocarbon groups, etc. Examples of halogen groups and hydrocarbon groups are those mentioned above.

[0035] In polyimide P, the constituent unit A1 derived from tetracarboxylic dianhydride a1 is preferably represented by the following formula (A1). The constituent 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 formed by the reaction with tetracarboxylic dianhydride a1. [ka]

[0036] In equation (A1), R 1a ~R 4a These are the same as in formula (a1), and are independently hydrogen atoms or any substituent. A specific example of the constituent unit A1 represented by formula (A1) is shown in formula (A1-1) below. [ka]

[0037] In polyimide P, the ratio p1 of the amount of substance of the above-mentioned constituent unit A1 to the amount of substance of all constituent 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 above-mentioned constituent unit A1 as the constituent unit A derived from tetracarboxylic dianhydride. However, polyimide P may further contain constituent unit A2 derived from tetracarboxylic dianhydride a2 having a five-membered ring acid anhydride structure, in addition to constituent unit A1. The tetracarboxylic dianhydride a2 is not particularly limited, and examples include pyromellitic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride.

[0038] The constituent unit B1 derived from diamine b1, particularly the constituent unit B1 having a functional group f, is a constituent unit suitable for improving the selectivity of acidic gases permeating the separation functional layer 1. Diamine b1 is preferably a compound having two primary amino groups and further having the above-mentioned functional group f. The number of functional groups f in diamine b1 is not particularly limited and may be, for example, 1 or more, or 2 or more. The upper limit of the number of functional groups f is, for example, 5 or less.

[0039] Diamine b1 may further have an aromatic ring. Examples of aromatic rings include those described above for tetracarboxylic dianhydride a1. In diamine b1, it is preferable that the substituents of the aromatic ring include a functional group f or a primary amino group. The aromatic ring may have substituents other than those containing functional group f and substituents containing a primary amino group, or it may not have any other substituents. Other substituents are not particularly limited and include halogen groups and hydrocarbon groups. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1. In addition, in diamine b1, the other substituents may include photopolymerizable functional groups (e.g., vinyl groups).

[0040] Diamine b1 is preferably represented by the following formula (b1). [ka]

[0041] In equation (b1), Ar 1 and Ar 2 These are aromatic groups, independently of each other. In this specification, an aromatic group means a group containing an aromatic ring. 1 and Ar 2 The aromatic rings included in are those described above for tetracarboxylic dianhydride a1, and are preferably benzene rings. The nitrogen atom of the amino group in formula (b1) is Ar 1 Aromatic rings contained in, or Ar 2 It is preferable that it is directly bonded to the aromatic ring contained in. 1 and Ar2 It is preferable that the above-mentioned functional group f is not included.

[0042] In equation (b1), Ar 3 Ar is an aromatic group containing the functional group f. 3 The aromatic rings included in are those described above for tetracarboxylic dianhydride a1, and preferably a fluorene ring. The functional group f is Ar 3 It is preferable that it is directly bonded to the aromatic ring contained in. Note that formula (b1) is Ar 1 and Ar 2 Each of them is Ar 3 This indicates that it is directly bonded to the aromatic ring contained in Ar. 3 Among the atoms (specifically carbon atoms) that make up the aromatic ring contained in, Ar 1 The atom to which it is bonded is argon. 2 It is preferable that the atoms bonded to each other are the same, but they may be different.

[0043] The diamine b1 is preferably represented by the following formula (b2). Formula (b2) is an example of the above formula (b1). [ka]

[0044] In equation (b2), R 1b ~R 16b R is a hydrogen atom or any substituent, independently of each other. 9b ~R 16b At least one selected from the group consisting of is a group containing a functional group f, preferably the functional group f itself. Any substituent other than the group containing the functional group f is not particularly limited and includes halogen groups, hydrocarbon groups, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0045] In equation (b2), R 9b ~R 12b At least one selected from the group consisting of is a group containing a functional group f, and R13b ~R 16b Preferably, at least one selected from the group consisting of is a group containing a functional group f. In a particularly preferred form, R 9b ~R 12b One of them is a group containing a functional group f, and R 13b ~R 16b One of these is a group containing the functional group f. 1b ~R 8b It is preferable that it does not contain the functional group f.

[0046] The constituent unit B1 derived from diamine b1 is preferably represented by the following formula (B1). The constituent unit B1 represented by formula (B1) is derived from the diamine b1 represented by the above formula (b1). [ka]

[0047] In equation (B1), Ar 1 and Ar 2 This is the same as formula (b1), and they are aromatic groups independently of each other. 3 This is the same as formula (b1) and is an aromatic group containing the functional group f.

[0048] The constituent unit B1 is preferably represented by the following formula (B2). Formula (B2) is an example of the above formula (B1) and is derived from the diamine b1 represented by the above formula (b2). [ka]

[0049] In equation (B2), R 1b ~R 16b R is a hydrogen atom or any substituent, independently of each other. 9b ~R 16bAt least one selected from the group consisting of is a group containing a functional group f, preferably the functional group f itself. Any substituent other than the group containing the functional group f is not particularly limited and includes halogen groups, hydrocarbon groups, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0050] In equation (B2), R 9b ~R 12b At least one selected from the group consisting of is a group containing a functional group f, and R 13b ~R 16b Preferably, at least one selected from the group consisting of is a group containing a functional group f. In a particularly preferred form, R 9b ~R 12b One of them is a group containing a functional group f, and R 13b ~R 16b One of these is a group containing the functional group f. 1b ~R 8b It is preferable that it does not contain the functional group f.

[0051] In formula (B2), the fluorene ring tends to be positioned in a twisted orientation relative to the two benzene rings due to steric hindrance. For example, in formula (B2), the fluorene ring extends from the front to the back of the page. Thus, in formula (B2), it is preferable that the direction in which the fluorene ring extends and the direction in which the main chain of polyimide P extends are different, and that these directions are orthogonal. In a crosslinked polyimide formed from polyimide P containing such a structural unit B1, an appropriate gap is formed within the molecule, and it tends not to inhibit the permeation of acidic gases.

[0052] Specific examples of the constituent unit B1 represented by equation (B2) include the following equations (B2-1) to (B2-2). [ka]

[0053] Note that diamine b1 and constituent unit B1 are not limited to those described above. For example, diamine b1 may be represented by the following formulas (c1), (c2), or (c3). [ka]

[0054] In equation (c1), R 1c ~R 4c R is a hydrogen atom or any substituent, independently of each other. 1c ~R 4c At least one selected from the group consisting of is a group containing a functional group f, preferably the functional group f itself. Any substituent other than the group containing the functional group f is not particularly limited and includes halogen groups, hydrocarbon groups, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0055] In equation (c2), R 5c ~R 12c Each is independently a hydrogen atom or any substituent, and X 1 R is a single bond or any linking group. 5c ~R 12c At least one selected from the group consisting of is a group containing a functional group f, preferably the functional group f itself. Any substituent other than the group containing the functional group f is not particularly limited and includes halogen groups, hydrocarbon groups, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0056] X in equation (c2) 1 In this, any linking group is, for example, a divalent hydrocarbon group. Examples of divalent hydrocarbon groups include alkylene groups such as methylene, ethylene, propane-1,3-diyl, and propane-2,2-diyl. The divalent hydrocarbon group may also be a halogenated hydrocarbon group in which a hydrogen atom is substituted with a halogen group. 1It may contain a divalent hydrocarbon group, or, in place of the divalent hydrocarbon group, a functional group such as an ether group or an ester group.

[0057] In equation (c3), R 13c ~R 20c Each is independently a hydrogen atom or any substituent, and X 2 R is a single bond or any linking group. 13c ~R 20c At least one selected from the group consisting of is a group containing a functional group f, preferably the functional group f itself. Any substituent other than the group containing the functional group f is not particularly limited and includes halogen groups, hydrocarbon groups, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0058] X in equation (c3) 2 In this, any linking group is, for example, a divalent hydrocarbon group. Examples of divalent hydrocarbon groups include X 1 The above points can be cited regarding X. 2 It may contain a divalent hydrocarbon group, or, in place of the divalent hydrocarbon group, a functional group such as an ether group or an ester group.

[0059] In formulas (c1) to (c3), the functional group f does not have to be a sulfonic acid group. In formulas (c1) to (c3), the functional group f may be at least one selected from the group consisting of a carboxyl group, a hydroxyl group, and a thiol group, and may be a carboxyl group.

[0060] The constituent unit B1 derived from diamine b1 may be represented by the following formulas (C1), (C2), or (C3). The constituent unit B1 represented by formula (C1) is derived from the diamine b1 represented by formula (C1) above. The constituent unit B1 represented by formula (C2) is derived from the diamine b1 represented by formula (C2) above. The constituent unit B1 represented by formula (C3) is derived from the diamine b1 represented by formula (C3) above. [ka]

[0061] In formula (C1), R 1c ~R 4c are, independently of each other, a hydrogen atom or an arbitrary substituent. However, at least one selected from the group consisting of R 1c ~R 4c is a group containing a functional group f, preferably the functional group f itself. The arbitrary substituent other than the group containing the functional group f is not particularly limited, and examples thereof include a halogen group and a hydrocarbon group. Examples of the halogen group and the hydrocarbon group are the same as those described above for the tetracarboxylic dianhydride a1.

[0062] Specific examples of the structural unit B1 represented by formula (C1) include the following formulas (C1-1) to (C1-3).

Chemical formula

[0063] In formula (C2), R 5c ~R 12c are, independently of each other, a hydrogen atom or an arbitrary substituent, and X 1 is a single bond or an arbitrary linking group. However, at least one selected from the group consisting of R 5c ~R 12c is a group containing a functional group f, preferably the functional group f itself. The arbitrary substituent other than the group containing the functional group f is not particularly limited, and examples thereof include a halogen group and a hydrocarbon group. Examples of the halogen group and the hydrocarbon group are the same as those described above for the tetracarboxylic dianhydride a1.

[0064] In X 1 of formula (C2), the arbitrary linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group are the same as those described above. X 1 may contain a functional group such as an ether group or an ester group together with the divalent hydrocarbon group or in place of the divalent hydrocarbon group.

[0065] Specific examples of the structural unit B1 represented by the formula (C2) include the following formulas (C2-1) to (C2-6).

Chemical formula

[0066] In the formula (C3), R 13c ~R 20c are, independently of each other, a hydrogen atom or an arbitrary substituent, and X 2 is a single bond or an arbitrary linking group. However, at least one selected from the group consisting of R 13c ~R 20c is a group containing the functional group f, preferably the functional group f itself. The arbitrary substituent other than the group containing the functional group f is not particularly limited, and examples thereof include a halogen group and a hydrocarbon group. Examples of the halogen group and the hydrocarbon group are the same as those described above for the tetracarboxylic dianhydride a1.

[0067] In X 2 of the formula (C3), the arbitrary linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group are the same as those described above. X 2 may contain a functional group such as an ether group or an ester group together with the divalent hydrocarbon group or in place of the divalent hydrocarbon group.

[0068] Specific examples of the structural unit B1 represented by the formula (C3) include the following formulas (C3-1) to (C3-3).

Chemical formula

[0069] In polyimide P, the ratio p2 of the amount of substance of constituent unit B1 having a functional group f, particularly constituent unit B1 represented by formula (B2), to the amount of substance of all constituent units B derived from diamine, is, for example, 1 mol% or more, and preferably 3 mol% or more. The upper limit of the ratio p2 is not particularly limited and may be, for example, 60 mol%, 50 mol%, 40 mol%, 30 mol%, or even 25 mol%. When the ratio p2 is low, the solubility of polyimide P is improved, and it tends to be easier to apply a desirable manufacturing method for the separation functional layer 1. Furthermore, in this case, the strength of the separation functional layer 1 also tends to improve. The ratio p2 is preferably 1 to 60 mol%. When the ratio p2 is within this range, the separation performance of the separation functional layer 1 tends to be good.

[0070] Polyimide P may further contain structural unit B2 derived from diamine b2 having a sulfonyl group (-SO2-). Structural unit B2 is suitable for improving the permeation rate of acidic gases permeating through the separation functional layer 1. Diamine b2 is a compound having two primary amino groups along with a sulfonyl group. The number of sulfonyl groups in diamine b2 is not particularly limited, for example, 5 or less, and preferably 1. It is preferable that diamine b2 does not contain groups having dissociable protons, such as the functional group f described above.

[0071] Diamine b2 preferably contains a ring structure having a sulfonyl group. The ring structure having a sulfonyl group is typically a thiophene 1,1-dioxide ring or a tetrahydrothiophene 1,1-dioxide ring.

[0072] Diamine b2 may have a fused ring, and the fused ring may contain a ring structure having a sulfonyl group. The fused ring may contain an aromatic ring along with the ring structure having a sulfonyl group. Examples of aromatic rings include those described above for tetracarboxylic dianhydride a1.

[0073] In diamine b2, it is preferable that the substituent of the condensed ring contains a primary amino group. The condensed ring may have substituents other than the substituent containing the primary amino group, or it may not have any substituents. Other substituents are not particularly limited and include halogen groups and hydrocarbon groups. Examples of halogen groups and hydrocarbon groups are those described above for tetracarboxylic dianhydride a1.

[0074] Diamine b2 is preferably represented by the following formula (d1). [ka]

[0075] In equation (d1), R 1d ~R 6d These are, independently of each other, a hydrogen atom or any substituent. In formula (d1), any substituent is, for example, a substituent other than the group containing the functional group f described above, and more specifically, a halogen group, a hydrocarbon group, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0076] In polyimide P, the constituent unit B2 derived from diamine b2 is preferably represented by the following formula (D1). The constituent unit B2 represented by formula (D1) is derived from the diamine b2 represented by the above formula (d1). [ka]

[0077] In equation (D1), R 1d ~R 6dThese are, independently of each other, a hydrogen atom or any substituent. In formula (D1), any substituent is, for example, a substituent other than the group containing the functional group f described above, and more specifically, a halogen group, a hydrocarbon group, etc. Examples of halogen groups and hydrocarbon groups are those described above for tetracarboxylic dianhydride a1. The constituent unit B2 represented by formula (D1) is suitable for improving the rigidity of polyimide P. With polyimide P having excellent rigidity, it is possible to suppress plasticization of the separation functional layer 1 even when the pressure of the mixed gas to be separated is high.

[0078] Specific examples of the constituent unit B2 represented by equation (D1) include the following equations (D1-1) to (D1-2). [ka]

[0079] In polyimide P, the ratio p3 of the amount of substance of the above-mentioned constituent unit B2 to the amount of substance of all constituent unit B derived from the diamine is not particularly limited and may be, for example, 5 mol% or more, 10 mol% or more, 20 mol% or more, or even 30 mol% or more. The upper limit of the ratio p3 is not particularly limited and may be, for example, 95 mol%, 90 mol%, 80 mol%, 70 mol%, 60 mol%, or even 50 mol%.

[0080] Polyimide P may further contain constituent unit B3 derived from other diamines b3 other than diamines b1 and b2. Diamine b3 is a compound that does not have the above-mentioned functional group f or sulfonyl group, but has two primary amino groups. Preferably, diamine b3 does not contain a group having a dissociable proton.

[0081] Diamine b3 may further have an aromatic ring. Examples of aromatic rings include those described above for tetracarboxylic dianhydride a1. In diamine b3, it is preferable that the substituent of the aromatic ring contains a primary amino group. The aromatic ring may have substituents other than those containing a primary amino group, or it may not have any substituents at all. Examples of other substituents are not particularly limited and include halogen groups and hydrocarbon groups. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0082] Diamine b3 is preferably represented by the following formulas (e1), (e2), or (e3). [ka]

[0083] In equation (e1), R 1e ~R 4e These are, independently of each other, a hydrogen atom or any substituent. In formula (e1), any substituent is, for example, a substituent other than the group containing the functional group f and the group containing the sulfonyl group, and more specifically, a halogen group, a hydrocarbon group, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0084] In equation (e2), R 5e ~R 8e These are, independently of each other, a hydrogen atom or any substituent. In formula (e2), any substituent is, for example, a substituent other than the group containing the functional group f and the group containing the sulfonyl group, and more specifically, a halogen group, a hydrocarbon group, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0085] In equation (e3), R 9e ~R 16e Each is independently a hydrogen atom or any substituent, and X 3is a single bond or any linking group. In formula (e3), any substituent is, for example, a substituent other than the group containing the functional group f and the group containing the sulfonyl group, and more specifically, a halogen group, a hydrocarbon group, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0086] X in equation (e3) 3 In this, any linking group is, for example, a divalent hydrocarbon group. Examples of divalent hydrocarbon groups include those mentioned above. 3 In this, the divalent hydrocarbon group may further have an aromatic ring. Examples of aromatic rings include those described above for tetracarboxylic dianhydride a1. 3 The divalent hydrocarbon group in may be a full orangeyl group. 3 It may contain a divalent hydrocarbon group, or, in place of the divalent hydrocarbon group, a functional group such as an ether group or an ester group.

[0087] The constituent unit B3 derived from diamine b3 is preferably represented by the following formulas (E1), (E2), or (E3). The constituent unit B3 represented by formula (E1) is derived from the diamine b3 represented by the above formula (e1). The constituent unit B3 represented by formula (E2) is derived from the diamine b3 represented by the above formula (e2). The constituent unit B3 represented by formula (E3) is derived from the diamine b3 represented by the above formula (e3). [ka]

[0088] In equation (E1), R 1e ~R 4eThese are, independently of each other, a hydrogen atom or any substituent. In formula (E1), any substituent is, for example, a substituent other than the group containing the functional group f described above, and more specifically, a halogen group, a hydrocarbon group, etc. Examples of halogen groups and hydrocarbon groups are those described above for tetracarboxylic dianhydride a1. A specific example of the constituent unit B3 represented by formula (E1) is shown in formula (E1-1) below. [ka]

[0089] In equation (E2), R 5e ~R 8e These are, independently of each other, a hydrogen atom or any substituent. In formula (E2), any substituent is, for example, a substituent other than the group containing the functional group f described above, and more specifically, a halogen group, a hydrocarbon group, etc. Examples of halogen groups and hydrocarbon groups are those described above for tetracarboxylic dianhydride a1. A specific example of the constituent unit B3 represented by formula (E2) is shown in formula (E2-1) below. [ka]

[0090] In equation (E3), R 9e ~R 16e Each is independently a hydrogen atom or any substituent, and X 3 X is a single bond or any linking group. In formula (E3), any substituent is, for example, a substituent other than the group containing the functional group f described above, and in detail, a halogen group, a hydrocarbon group, etc. Examples of halogen groups and hydrocarbon groups are those described above for tetracarboxylic dianhydride a1. X in formula (E3) 3 In this, any linking group is, for example, a divalent hydrocarbon group. Examples of divalent hydrocarbon groups include those mentioned above. 3This may include a divalent hydrocarbon group, or, in place of the divalent hydrocarbon group, a functional group such as an ether group or an ester group. Specific examples of the constituent unit B3 represented by formula (E3) are shown in the following formulas (E3-1) to (E3-3). [ka]

[0091] In polyimide P, the ratio p4 of the amount of substance of the above-mentioned constituent unit B3 to the amount of substance of all constituent units B derived from the diamine is not particularly limited and may be, for example, 5 mol% or more, 10 mol% or more, 20 mol% or more, or even 30 mol% or more. The upper limit of the ratio p4 is not particularly limited and may be, for example, 95 mol%, 90 mol%, 80 mol%, 70 mol%, 60 mol%, or even 50 mol%.

[0092] In polyimide P, constituent units A derived from tetracarboxylic dianhydride and constituent units B derived from diamine are arranged alternately. Examples of adjacent constituent unit combinations of A and B in polyimide P include the following formulas: (A1-B2), (A1-C2), (A1-D1), (A1-E1), etc. Note that in these formulas, R 1a ~R 4a , R 1b ~R 16b , R 5c ~R 12c , R 1d ~R 6d and R 1e ~R 4e The same applies to equations (A1), (B2), (C2), (D1), and (E1) as described above. [ka]

[0093] 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 1. The upper limit of the weight-average molecular weight of polyimide P is not particularly limited, and is, for example, 1 million. The weight-average molecular weight of polyimide P can be calculated by measuring the molecular weight distribution of polyimide P using a gel permeation chromatograph (GPC) equipped with a differential refractive index detector (RID), and then using a calibration curve with standard polystyrene from the obtained chromatogram (chart).

[0094] In this embodiment, it is preferable that the crosslinked polyimide is formed by the reaction of a functional group f in polyimide P with a crosslinking agent. In this case, the structure and performance of the crosslinked polyimide can be easily adjusted depending on the type of crosslinking agent.

[0095] For example, a functional group f reacts with a functional group H contained in the crosslinking agent to form a covalent bond between the functional group f and the crosslinking agent. In multiple polyimide P molecules, a crosslinked structure is formed by the reaction of the functional group f with the functional group H of the crosslinking agent. In this case, the crosslinked polyimide usually has a crosslinked structure in which multiple polyimide P molecules are indirectly linked to each other via the crosslinking agent. However, the crosslinking agent may also be a condensing agent that forms a crosslinked structure by promoting a condensation reaction between the functional groups f in multiple polyimide P molecules. In this specification, such a condensing agent is also classified as a crosslinking agent that reacts with a functional group f. When a condensing agent is used, the crosslinked polyimide usually has a crosslinked structure in which multiple polyimide P molecules are directly linked to each other.

[0096] Examples of crosslinking agents containing the functional group H include epoxy crosslinking agents, amine crosslinking agents, and isocyanate crosslinking agents. Preferably, the crosslinking agent contains at least one selected from the group consisting of epoxy crosslinking agents and amine crosslinking agents.

[0097] Epoxy crosslinking agents are compounds (epoxy compounds) that contain an epoxy group as a functional group H. The number of epoxy groups in an epoxy compound is typically two or more, but may be three to five. Epoxy compounds may be used individually or in combination of two or more.

[0098] Specific examples of epoxy compounds include, for example, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether.

[0099] Commercially available epoxy crosslinking agents include "TETRAD-C" and "TETRAD-X" from Mitsubishi Gas Chemical Company, "Epiclon CR-5L" from DIC Corporation, "Denacol EX-512" from Nagase ChemteX Corporation, and "TEPIC-G" from Nissan Chemical Industries, Ltd.

[0100] Amine-based crosslinking agents are compounds (amine compounds) that contain an amino group as a functional group H. The number of amino groups in an amine compound is typically two or more, but may be three or more. Amine compounds may be used individually or in combination of two or more.

[0101] Specific examples of amine compounds include aziridine and polyethyleneimine.

[0102] Isocyanate crosslinking agents are compounds containing an isocyanate group as a functional group H (isocyanate compounds). The number of isocyanate groups in an isocyanate compound is typically two or more, but may be three to five. Isocyanate compounds may be used individually or in combination of two or more.

[0103] Examples of isocyanate compounds include aliphatic isocyanate compounds, alicyclic isocyanate compounds, and aromatic isocyanate compounds.

[0104] Examples of aliphatic isocyanate compounds include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; and 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0105] Examples of alicyclic isocyanate compounds include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0106] Aromatic isocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3, Examples include 3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropanediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0107] Examples of isocyanate-based crosslinking agents include polymers (dimers, trimers, pentamers, etc.) of the above-mentioned isocyanate compounds, adducts obtained by adding them to polyhydric alcohols such as trimethylolpropane, urea-modified compounds, biuret-modified compounds, allophanate-modified compounds, isocyanurate-modified compounds, carbodiimide-modified compounds, urethane prepolymers obtained by adding them to polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc.

[0108] Examples of commercially available isocyanate-based crosslinking agents include "Duranate TPA-100" from Asahi Kasei Chemicals, and "Coronate L," "Coronate HL," "Coronate HK," "Coronate HX," and "Coronate 2096" from Tosoh Corporation.

[0109] Examples of crosslinking agents that function as condensing agents include Eaton's reagent (a mixture of P2O5 and methanesulfonic acid) and acidic compounds such as polyphosphate. In particular, Eaton's reagent is suitable for sufficiently advancing the crosslinking reaction of polyimide P and increasing the gel fraction of the separation functional layer 1.

[0110] The crosslinked polyimide content 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. The separation functional layer 1 may be composed substantially of only crosslinked polyimide. However, the separation functional layer 1 may also contain uncrosslinked polyimide P in addition to crosslinked polyimide.

[0111] The separation functional layer 1 may further contain other components besides crosslinked polyimide. Examples of other components include nanoparticles. Examples of nanoparticles include those exemplified for the intermediate layer 2 described later. In the separation functional layer 1, it is preferable that the nanoparticles are dispersed in a matrix containing crosslinked polyimide. The nanoparticles may be spaced apart from each other within the matrix, or they may be partially aggregated.

[0112] 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, 5.0 μm or less, and even 2.0 μm or less. The thickness of the separation functional layer 1 may be 0.05 μm or more, and may be 0.1 μm or more. According to the inventors' studies, when a conventional separation functional layer with a thickness of about 5.0 μm or less is used, the separation functional layer deteriorates when used for a long period of time, and the separation performance (especially the permeation rate of acidic gases) tends to decrease. However, in the separation functional layer 1 of this embodiment, even when the thickness is small, the decrease in separation performance when used for a long period of time tends to be suppressed due to the inclusion of cross-linked polyimide.

[0113] The gel fraction of the separation functional layer 1 is not particularly limited and may be, for example, 60% or more, 70% or more, 80% or more, 85% or more, or even 90% or more. The higher the gel fraction of the separation functional layer 1, the more likely it is that the deterioration of separation performance when the separation functional layer 1 is used for a long period of time can be suppressed. The upper limit of the gel fraction of the separation functional layer 1 is, for example, 99% or less.

[0114] The gel fraction of the separation functional layer 1 can be evaluated by the following method. First, prepare the separation functional layer 1 in a dry state. In this specification, "dry state" means that the liquid content, such as water, in the separation functional layer 1 is 0.5 wt% or less.

[0115] Next, the separation functional layer 1 is cut into a 2cm x 2cm piece to form a test specimen, and its weight A (g) is measured. This test specimen is immersed in N-methyl-2-pyrrolidone (NMP) in the sample bottle and left at room temperature (25°C) for one week. Next, the weight C (g) of the filter paper is measured, and the contents of the sample bottle are filtered through the filter paper. During filtration, the filter paper is washed with NMP. The filter paper and the insoluble matter attached to the filter paper are collected and washed with methanol to remove the NMP. Next, it is dried at 130°C for one hour, and the weight D (g) after drying is measured. The weight B (g) of the insoluble matter (B=DC) is obtained by subtracting weight C from weight D. Based on weights A and B, the gel fraction (%) of the separation functional layer 1 can be calculated using the following formula. Gel fraction (%) = 100 × B / A

[0116] (Method for manufacturing the separation function layer) In this embodiment, the method for producing the separation functional layer 1 preferably includes applying a coating solution containing polyimide P onto a substrate to form a coating film, and drying the coating film to form a crosslinked polyimide from the polyimide P.

[0117] Polyimide P can be prepared by the following method. First, the diamine group including the above-mentioned diamine b1 is dissolved in a solvent to obtain a solution. Examples of solvents include polar organic solvents such as N-methyl-2-pyrrolidone.

[0118] Next, the group of tetracarboxylic dianhydrides, including tetracarboxylic dianhydride a1, is gradually added to the obtained solution. This causes the monomer group, which includes tetracarboxylic dianhydride a1, to react with the group of diamine b1, forming a polyamic acid. The addition of the tetracarboxylic dianhydride group is preferably carried out under stirring conditions for 3 to 20 hours in a heated environment of 140°C or higher.

[0119] Next, 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 of imidizing the polyamic acid using a dehydrating condensation agent, for example, under room temperature conditions. Examples of dehydrating condensation agents include acetic anhydride, pyridine, and triethylamine. Thermal imidization is a method of imidizing the polyamic acid by heat treatment. The temperature of the heat treatment is not particularly limited, but is, for example, 180°C or higher.

[0120] The polyimide P content in the coating solution can be adjusted as appropriate according to the solubility of polyimide P, for example, from 1 wt% to 30 wt%.

[0121] The coating solution preferably further contains a solvent. The solvent is typically a good solvent capable of dissolving polyimide P. 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 amide compounds include N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and N,N-dimethylacetamide (DMAc). Examples of lactone compounds include γ-butyrolactone.

[0122] The solvent content in the coating solution is not particularly limited, and is, for example, 30 wt% to 99 wt%.

[0123] The coating solution preferably further contains a crosslinking agent. Examples of crosslinking agents include those mentioned above. In the coating solution, the ratio of the weight of the crosslinking agent to the weight of the polyimide P can be appropriately adjusted according to the composition of the polyimide P, and may be, for example, 0.01 wt% or more, 0.1 wt% or more, or even 0.5 wt% or more. The upper limit of this ratio is not particularly limited and may be, for example, 20 wt% or less, 10 wt% or less, or even 5 wt% or less. In the coating solution, the ratio of the amount of substance of the crosslinking agent to the amount of substance of the functional group f contained in the polyimide P is not particularly limited and may be, for example, 2.0 or more.

[0124] The substrate to which the coating solution containing polyimide P is applied is typically a release liner. Examples of substrates include resin-containing films; paper; and sheets containing metal materials such as aluminum or stainless steel. Sheets containing metal materials tend to have high heat resistance. The substrate is preferably a resin-containing film because of its excellent surface smoothness. Examples of polymers contained in the resin of the substrate 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.

[0125] The surface of the substrate may be treated with a release agent. The release agent can be applied to the surface of the substrate by applying a release agent. Examples of release agents include silicone-based release agents, long-chain alkyl-based release agents, fluorine-based release agents, and molybdenum sulfide-based release agents. The release agents may be used alone or in combination of two or more. The substrate is preferably a polyimide film that has been treated with a release agent.

[0126] The thickness of the substrate is not particularly limited, and is, for example, 5 to 100 μm, preferably 10 to 50 μm.

[0127] Furthermore, a surface modification treatment may be performed on the substrate before applying the coating solution. If the substrate has been subjected to a stripping treatment, the surface modification treatment may be performed on the surface of the substrate that has been stripped. Examples of surface modification treatments include corona treatment, plasma treatment, excimer treatment, and flame treatment, with corona treatment being preferred.

[0128] Surface modification can be performed 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 used as a surface modification treatment, the discharge rate is, for example, 0.1 kW·min / m 2 That concludes the explanation. The upper limit of the discharge rate is not particularly limited; for example, 10 kW·min / m 2 That is the case.

[0129] The method of applying the coating solution to the substrate is not particularly limited, and methods such as spin coating, dip coating, and slot die coating can be used. The coating solution may also be applied to the substrate using an applicator or wire bar. The coating solution may be applied to the surface of a substrate that has undergone stripping treatment or surface modification treatment.

[0130] A coating film is formed by applying the coating solution to the substrate. The thickness of the coating film can be appropriately adjusted according to the desired thickness of the separation functional layer 1, for example, from 1 μm to 100 μm.

[0131] In this embodiment, as described above, the separation functional layer 1 is obtained by drying the coating film and forming a crosslinked polyimide from the polyimide P. 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 section equipped with a heater. The coating film may also be dried by passing it through multiple heating sections. The set temperatures of the multiple heating sections may be the same or different from each other.

[0132] When the coating solution contains a crosslinking agent, the functional group f of polyimide P tends to react with the crosslinking agent when the coating film is dried. This forms a crosslinked structure, resulting in a crosslinked polyimide.

[0133] The crosslinked polyimide may be formed after the coating film has been dried to form a dry film. For example, a coating solution containing the polyimide P and solvent described above may be applied to a substrate and dried to form a dry film. This dry film may then be immersed in a solution containing a crosslinking agent, and further heat treatment may be performed as needed to form the crosslinked polyimide. The conditions for the heat treatment are not particularly limited; for example, the heating temperature may be 50°C to 100°C and the heating time may be 1 minute to 10 hours. This method is suitable for embodiments in which a condensing agent such as Eaton's reagent is used as the crosslinking agent.

[0134] The film, after being immersed in the above solution, may be further subjected to washing with water and drying.

[0135] The manufacturing method of this embodiment may also include further heat treatment (annealing) of the obtained separation functional layer 1. This step tends to improve the separation performance of the separation functional layer 1 and also suppress the deterioration of its separation performance over time. This step also makes it possible to obtain a separation functional layer 1 that contains almost no residual solvent by allowing the solvent to evaporate sufficiently. The annealing treatment may be performed before removing the substrate from the laminate of the separation functional layer 1 and the substrate, or after removing the substrate.

[0136] The heat treatment temperature may be higher than, for example, 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 may be, for example, 1 minute or more, 10 minutes or more, or 30 minutes or more. The upper limit of the heat treatment time is not particularly limited and may be, for example, 24 hours or lower.

[0137] 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 self-supporting membrane can be obtained.

[0138] The manufacturing method of this embodiment is not limited to those described above. Instead of a coating solution containing polyimide P, a coating solution containing polyamic acid, which is a precursor of polyimide P, may be used. The separation functional layer 1 may be prepared by applying this coating solution onto a substrate, imidizing the polyamic acid to form polyimide P, and then forming a crosslinked polyimide from the polyimide P.

[0139] (Characteristics of the isolation layer) As described above, it is preferable that the separation function layer 1 preferentially permeates acidic gases contained in the mixed gas. As an example, when a mixed gas consisting of carbon dioxide and nitrogen is supplied to the space adjacent to one side of the separation function layer 1 using the separation function layer 1 in its initial state, the permeation rate T1 of carbon dioxide permeating through the separation function layer 1 is, for example, 30 GPU or more, and may be 50 GPU or more, 60 GPU or more, 70 GPU or more, 80 GPU or more, or even 90 GPU or more. The upper limit of the permeation rate T1 is not particularly limited, for example, 300 GPU. Note that GPU is 10 -6 ·cm 3 (STP) / (sec·cm 2 This means cmHg. 3 (STP) refers to the volume of carbon dioxide at 1 atmosphere and 0°C.

[0140] The permeation rate T1 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 side of the separation functional layer 1, and the space adjacent to the other side of the separation functional layer 1 is depressurized. This yields a permeate fluid that has permeated through the separation functional layer 1. The weight of the permeate fluid, as well as the volume ratio of carbon dioxide and nitrogen in the permeate fluid, are measured. The permeation rate T1 can be calculated from the measurement results. In 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 side 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 side of the separation functional layer 1 is depressurized so that the pressure inside the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.

[0141] Under the above measurement conditions for the permeation rate T1, the separation coefficient α of carbon dioxide relative to nitrogen in the separation functional layer 1 is, for example, 20 or more, and may be 30 or more, 35 or more, 38 or more, or even 40 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. However, in the following formula, X A and X B These are the volume ratios of carbon dioxide and nitrogen in the gas mixture, respectively. A and Y B These are the volume ratios of carbon dioxide and nitrogen in the permeate fluid that has passed through the separation functional layer 1, respectively. Separation coefficient α = (Y A / Y B ) / (X A / X B )

[0142] As described above, the separation functional layer 1 of this embodiment contains crosslinked polyimide. In this separation functional layer 1, physical aging of the crosslinked polyimide is suppressed, which tends to prevent the separation performance of the separation functional layer 1 from deteriorating over time. In particular, the separation functional layer 1 of this embodiment tends to suppress the deterioration of separation performance (especially the permeation rate of acidic gases) when used for a long period of time.

[0143] 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 heat-treated at 85°C for 500 hours (durability test). After the durability test, the carbon dioxide permeation rate T2 is measured for the separation functional layer 1 using the same method as for the permeation rate T1. The deterioration of the separation performance can be evaluated based on the ratio of the permeation rate T2 to the permeation rate T1, T2 / T1 (maintenance rate of the permeation rate).

[0144] In the separation function layer 1, the above ratio T2 / T1 may be, for example, 70% or more, and may also be 75% or more, 80% or more, 85% or more, or even 90% or more. The upper limit of the ratio T2 / T1 is, for example, 110%.

[0145] The transmission speed T2 after the durability test is, for example, 30 GPU or more, and may be 50 GPU or more, 60 GPU or more, 70 GPU or more, or even 75 GPU or more. The upper limit of the transmission speed T2 is not particularly limited, and is, for example, 300 GPU.

[0146] Furthermore, the separation coefficient α of carbon dioxide relative to nitrogen in the separation functional layer 1 after the durability test may be, for example, 20 or more, 25 or more, or even 30 or more. The upper limit of the separation coefficient α after the durability test is not particularly limited and may be, for example, 100 or 60. The separation coefficient α after the durability test can be determined by the same method as described above, except that the separation functional layer 1 after the durability test is used.

[0147] (Applications of the isolation layer) One application of the separation function layer 1 of this embodiment is the separation of 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 other gases besides acidic gases. 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. In particular, the separation function layer 1 of this embodiment is suitable for separating carbon dioxide from a gas mixture containing carbon dioxide and nitrogen. However, the application of the separation function layer 1 is not limited to the separation of acidic gases from the gas mixture described above.

[0148] <Embodiment of a separation membrane> As shown in Figure 2, the separation membrane 10 of this embodiment preferably comprises the separation functional layer 1 described above, and further comprises an intermediate layer 2 and a porous support 3. The porous support 3 supports the separation functional layer 1. The intermediate layer 2 is disposed between the separation functional layer 1 and the porous support 3 and is in direct contact with both the separation functional layer 1 and the porous support 3.

[0149] (Middle class) The intermediate layer 2 preferably contains a resin, and more preferably contains nanoparticles dispersed in the resin (matrix). The nanoparticles may be spaced apart from each other within the matrix, or they may be partially aggregated. However, the intermediate layer 2 may not contain nanoparticles and may be substantially composed of resin.

[0150] The matrix material is not particularly limited and includes, for example, silicone resins such as polydimethylsiloxane; fluororesins such as polytetrafluoroethylene; epoxy resins such as polyethylene oxide; polyimide resins; polysulfone resins; polyacetylene resins such as polytrimethylsilylpropine and polydiphenylacetylene; polyolefin resins such as polymethylpentene; and polyurethane resins. The matrix preferably contains silicone resin and polyurethane resin.

[0151] Nanoparticles may contain inorganic materials or organic materials. Examples of inorganic materials that can be included in nanoparticles include silica, titania, and alumina. It is preferable that the nanoparticles contain silica.

[0152] Nanoparticles may have a surface modified with a modifying group containing carbon atoms. Nanoparticles having a surface modified with such a modifying group exhibit excellent dispersibility in the matrix. Preferably, the nanoparticles are silica nanoparticles that may have a surface modified with a modifying group. Preferably, the modifying group further contains silicon atoms. In nanoparticles, the surface modified with the modifying group is preferably represented by the following formulas (I) to (III). [ka]

[0153] R in equations (I) to (III) 1 ~R 6 These are hydrocarbon groups that may have substituents independently of each other. 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 greater than 25. The hydrocarbon group may be a linear or branched chain hydrocarbon group, or an alicyclic or aromatic cyclic hydrocarbon group. In a preferred embodiment, the hydrocarbon group is a linear or branched alkyl group having 1 to 8 carbon atoms. The hydrocarbon group is, for example, a methyl group or an octyl group, and is preferably a methyl group. Examples of substituents on the hydrocarbon group include an amino group and an acyloxy group. An example of an acyloxy group is a (meth)acryloyloxy group.

[0154] In another preferred form, R in equations (I) to (III) 1 ~R 6The hydrocarbon group which may have the substituents mentioned above is represented by the following formula (IV). Nanoparticles having a surface modified with a modifying group containing the hydrocarbon group represented by formula (IV) are suitable for improving the permeation rate of acidic gas in the separation membrane 10. [ka]

[0155] In equation (IV), R 7 This is an alkylene group having 1 to 5 carbon atoms, which may have substituents. The alkylene group may be linear or branched. Examples of alkylene groups include methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl, and pentane-1,5-diyl, with propane-1,3-diyl being preferred. Examples of substituents on the alkylene group include amide groups and aminoalkylene groups.

[0156] In equation (IV), R 8 R is an alkyl or aryl group having 1 to 20 carbon atoms, which may have substituents. The alkyl group may be linear or branched. Examples of substituents on alkyl and aryl groups include amino groups and carboxyl groups. 8 For example, this is a 3,5-diaminophenyl group.

[0157] In nanoparticles, the surface modified by the modifying group is preferably represented by the following formula (V). [ka]

[0158] The modifying group is not limited to the structures shown in formulas (I) to (III). The modifying group is R in formulas (I) to (III). 1 ~R 6Alternatively, the polymer chain may contain a polyamide structure or a polydimethylsiloxane structure. Preferably, in the modifying group, this polymer chain is directly bonded to a silicon atom. Examples of the polymer chain's shape include linear, dendrimeric, and hyperbranched structures.

[0159] The method for modifying the surface of nanoparticles with a modifying group is not particularly limited. For example, the surface of nanoparticles can be modified by reacting hydroxyl groups present on the surface of nanoparticles with a known silane coupling agent. If the modifying group includes a polyamide structure, the surface of nanoparticles can be modified by the method disclosed in Japanese Patent Application Publication No. 2010-222228.

[0160] The average particle size of the nanoparticles is not particularly limited as long as it is on the order of nanometers (<1000 nm), 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 considered to be the particle size (diameter of the particle) of that specific nanoparticle. The particle size of any number of nanoparticles (at least 50) is calculated, and the average of the calculated values ​​is considered to be the average particle size of the nanoparticles. The shape of the nanoparticles is not particularly limited and may be spherical, ellipsoidal, flaky, or fibrous.

[0161] 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. The upper limit of the nanoparticle content in the intermediate layer 2 is not particularly limited, but is, for example, 30 wt%.

[0162] 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. It is preferable that the intermediate layer 2 is a layer having a thickness of less than 50 μm.

[0163] (porous support) The porous support 3 supports the separation functional layer 1 via the intermediate layer 2. Examples of the porous support 3 include nonwoven fabric; porous polytetrafluoroethylene; aromatic polyamide fiber; porous metal; sintered metal; porous ceramic; porous polyester; porous nylon; activated carbon fiber; latex; silicone; silicone rubber; permeable (porous) polymer containing at least one selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyetheretherketone, polyacrylonitrile, polyimide, and polyphenylene oxide; metal foam having open or closed cells; polymer foam having open or closed cells; silica; porous glass; mesh screen, etc. The porous support 3 may be a combination of two or more of these. As an example, the porous support 3 may be a laminate of a nonwoven fabric and a polysulfone porous layer.

[0164] The porous support 3 has an average pore diameter of, for example, 0.01 to 0.4 μm. The thickness of the porous support 3 is not particularly limited, but is, for example, 10 μm or 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.

[0165] (Method for manufacturing separation membranes) The separation film 10 can be manufactured by the following method. First, a laminate of a porous support 3 and an intermediate layer 2 is prepared. This laminate can be manufactured by the following method. First, a coating solution containing the material for the intermediate layer 2 is prepared. Next, the coating solution containing the material for the intermediate layer 2 is applied to the porous support 3 to form a coating film. The method of applying the coating solution is not particularly limited, and for example, a spin coating method or a dip coating method can be used. The coating solution may also be applied using a wire bar or the like. Next, the coating film is dried to form the intermediate layer 2. Drying of the coating film can be carried out 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 treated with an easy-adhesion treatment as needed. Examples of easy-adhesion treatments include surface treatments such as application of a primer, corona discharge treatment, and plasma treatment.

[0166] 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 for the creation of a 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 above-described manufacturing method for the separation functional layer 1.

[0167] The method for producing the separation membrane 10 is not limited to the method described above, and the separation membrane 10 may also be produced by the following method. First, a separation functional layer 1 is prepared on a substrate such as a peelable liner by the method described above. Next, an intermediate layer 2 is formed by coating a coating solution containing the material for the intermediate layer 2 onto the separation functional layer 1 and drying it. The laminate of the intermediate layer 2 and the separation functional layer 1 is transferred to a porous support 3. This gives rise to the separation membrane 10.

[0168] (Shape of the separation membrane) 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, and may be a hollow fiber membrane. For example, the separation membrane 10 as a hollow fiber membrane may have a separation functional layer 1 and a porous support 3, but may not have an intermediate layer 2.

[0169] <Embodiment of Membrane Separation Device> As shown in FIG. 3, the membrane separation device 100 of the present embodiment includes a separation membrane 10 and a tank 20. In the membrane separation device 100, instead of the separation membrane 10, the separation functional layer 1 can also be used alone. 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 of the pair of wall surfaces of the tank 20 to the other.

[0170] The first chamber 21 has an inlet 21a and an outlet 21b. The second chamber 22 has an outlet 22a. Each of the inlet 21a, the outlet 21b, and the outlet 22a is preferably an opening formed in the wall surface of the tank 20.

[0171] The membrane separation using the membrane separation device 100 is performed by the following method. First, a mixed gas 30 containing an acidic gas is supplied to the first chamber 21 through the inlet 21a. The concentration of the acidic gas in the mixed gas 30 is not particularly limited. Under standard conditions, for example, it is 0.01 vol% (100 ppm) or more, preferably 1 vol% or more, more preferably 10 vol% or more, still more preferably 30 vol% or more, and particularly preferably 50 vol% or more. The upper limit value of the concentration of the acidic gas in the mixed gas 30 is not particularly limited. Under standard conditions, for example, it is 90 vol%.

[0172] The pressure inside the first chamber 21 may be increased by the supply of the mixed gas 30. The membrane separation device 100 may further include a pump (not shown) for increasing the pressure of the mixed gas 30. The pressure of the mixed gas 30 supplied to the first chamber 21 is, for example, 0.1 MPa or more, preferably 0.3 MPa or more.

[0173] The second chamber 22 may be depressurized while the mixed gas 30 is supplied to the first chamber 21. The membrane separation device 100 may further include a pump (not shown) for depressurizing the second chamber 22. The second chamber 22 may be depressurized such that the space inside the second chamber 22 is, for example, 10 kPa or more, preferably 50 kPa or more, and more preferably 100 kPa or more, than the atmospheric pressure in the measurement environment.

[0174] By supplying the mixed gas 30 into the first chamber 21, a permeate fluid 35 with a higher acidic gas content than the mixed gas 30 can be obtained on the other side of the separation membrane 10. That is, the permeate fluid 35 is supplied to the second chamber 22. Preferably, the permeate fluid 35 contains acidic gas as its main component. However, the permeate fluid 35 may also contain small amounts of other gases besides acidic gas. The permeate fluid 35 is discharged to the outside of the tank 20 through the outlet 22a.

[0175] The concentration of acidic gas in the gas mixture 30 gradually decreases from the inlet 21a to the outlet 21b of the first chamber 21. The gas mixture 30 (impermeable fluid 36) treated in the first chamber 21 is discharged to the outside of the tank 20 through the outlet 21b.

[0176] The membrane separation apparatus 100 of this embodiment is suitable for a continuous flow membrane separation method. However, the membrane separation apparatus 100 of this embodiment may also be used for a batch membrane separation method.

[0177] <Modified example of a membrane separation device> The membrane separation device 100 may be a spiral-type membrane element, a hollow fiber membrane element, or the like. Figure 4 shows a spiral-type membrane element. The membrane separation device 110 in Figure 4 comprises a central tube 41 and a laminate 42. The laminate 42 contains the separation membrane 10. The laminate 42 may also contain a separation functional layer 1 by itself instead of the separation membrane 10.

[0178] The central tube 41 has a cylindrical shape. Multiple holes are formed on the surface of the central tube 41 to allow the permeable 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.

[0179] The laminate 42 further includes a supply-side channel material 43 and a permeate-side channel material 44 in addition to the separation membrane 10. The laminate 42 is wound around the central tube 41. The membrane separation device 110 may further include an outer casing material (not shown).

[0180] For the supply-side channel material 43 and the permeate-side channel material 44, for example, a resin net made of polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.

[0181] Membrane separation using the membrane separation device 110 is performed by the following method. First, a mixed gas 30 is supplied to one end of the wound laminate 42. The permeate fluid 35 that has permeated through the separation membrane 10 of the laminate 42 moves into the center tube 41. The permeate fluid 35 is discharged to the outside through the center tube 41. The mixed gas 30 (impermeable fluid 36) processed by the membrane separation device 110 is discharged to the outside from the other end of the wound laminate 42. This makes it possible to separate acidic gas from the mixed gas 30. [Examples]

[0182] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0183] (Example 1) [Synthesis of sulfonated diamines] 9,9-bis(4-aminophenyl)fluorene-2,7-disulfonic acid (BAPFDS) was synthesized by the following method. First, under an N2 atmosphere, 25.0 g (71.75 mmol) of 9,9-bis(4-aminophenyl)fluorene (BAPF) was added to a 500 mL three-necked flask equipped with a stirrer, and the mixture was cooled to 0°C in an ice bath. Next, under an N2 atmosphere, 100 mL of concentrated sulfuric acid was added while cooling in an ice bath, and the mixture was stirred at a stirring speed of 100 rpm for 30 minutes.

[0184] Next, the flask was removed from the ice bath and slowly heated to 55°C to completely dissolve the BAPF in concentrated sulfuric acid. Then, it was heated to 100°C and reacted for 5 hours. After the reaction mixture cooled to room temperature, it was transferred to 1000g of ice water, where a large amount of white, cotton-like solid precipitated. The precipitate was washed several times by stirring in ice water.

[0185] Next, 100 g of a 5 wt% NaOH solution was added dropwise to completely dissolve the precipitate in the solution. This solution was filtered by suction and the filtrate was collected. Dilute hydrochloric acid solution (38% concentrated hydrochloric acid / ion-exchanged water = 20 / 80 vol%) was added dropwise to the collected filtrate until the pH was approximately 3. This caused a white, cotton-like solid to precipitate again. The precipitate was washed with ion-exchanged water until it became neutral, and dried at 150°C for 10 hours to obtain BAPFDS.

[0186] [Synthesis of polyimide P1] Next, polyimide P1 was synthesized using a separable flask (2000 mL capacity) and an oil bath. The separable flask was fitted with a Liebig condenser, stirring rod, internal thermometer, nitrogen inlet tube, and flat stopper. Cooling liquid set to 10°C was circulated through the Liebig condenser chiller. N2 gas was circulated into the flask at a flow rate of 100 mL / min. The stirring speed was set to 300 rpm. Next, 610 g of 1-methyl-2-pyrrolidone (super-anhydrous) was added to the flask as a solvent, and the following diamines were added: 9.859 g (0.066 mol) of 2,4,6-trimethyl-1,3-phenylenediamine (TrMPD), 18.003 g (0.066 mol) of 3,7-diamino-2,8-dimethyldibenzothiophenesulfone (DDBT), 28.606 g (0.056 mol) of 9,9-bis(4-aminophenyl)fluorene-2,7-disulfonic acid (BAPFDS), and 11.384 g (0.112 mol) of triethylamine. These were stirred at room temperature to dissolve the diamines in the solvent. To the obtained solution, 51.036 g (0.190 mol) of naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTDA) and 45.794 g (0.375 mol) of benzoic acid were further added. The oil bath temperature was raised to 180°C and the mixture was stirred for 8 hours. At this time, the internal temperature of the flask was 172-175°C. After stirring, the internal temperature of the flask was cooled to 25°C and left to stand overnight.

[0187] Next, 48.433 g (0.375 mol) of isoquinoline was added, and the oil bath temperature was raised again to 180°C and stirred for 8 hours. After letting the reaction mixture stand overnight, the reaction mixture was diluted by adding 1500 g of 1-methyl-2-pyrrolidone. Next, using a dropping funnel, 5000 mL of methanol was added dropwise to the reaction mixture over approximately 30 minutes for reprecipitation purification. The precipitated polyimide was filtered off, and the polyimide was washed twice with 500 mL of methanol. After washing, the filtered polyimide was dried in a hot air circulating dryer at 60°C for 15 hours, and then dried in a vacuum dryer at 100°C for 8 hours. This yielded polyimide in which the sulfonic acid groups were modified with triethylamine.

[0188] Next, the obtained polyimide was added to 1000 g of a dilute hydrochloric acid solution (38% concentrated hydrochloric acid / ion-exchanged water = 20 / 80 vol%), and stirred at 100 rpm for 48 hours to remove the modification of the above triethylamine. Thereafter, the polyimide was filtered off, and the operation of washing with ion-exchanged water was repeated a plurality of times. Next, it was dried in a hot air circulation dryer at 60 ° C for 15 hours, and further dried in a vacuum dryer at 100 ° C for 8 hours. As a result, 71.6 g of polyimide P1 was obtained. Polyimide P1 had a sulfonic acid group as the functional group f.

[0189] [Production of separation functional layer] The above polyimide P1 was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a coating solution with a solid content concentration of 4 wt%. This coating solution was applied onto a polyimide film subjected to a peeling treatment to obtain a coating film. The thickness of the coating film was adjusted to be 3 μm after drying. This coating film was heat-dried at 130 ° C for 30 minutes, and further heat-treated at 300 ° C for 10 minutes under a nitrogen atmosphere to obtain the separation functional layer (self-supporting film) of Example 1. This self-supporting film was peeled off from the polyimide film and used. In Example 1, no crosslinked polyimide was formed from polyimide P1.

[0190] (Examples 2 to 3) When producing the separation functional layer, an epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, TETRAD-C (1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane)) was added to the coating solution, and as shown in Table 1, except that the ratio of the weight of the epoxy-based crosslinking agent to the weight of polyimide P1 was adjusted, the separation functional layers (self-supporting films) of Examples 2 to 3 were obtained by the same method as in Example 1. In Examples 2 to 3, during the drying of the coating film, the functional group f (sulfonic acid group) contained in polyimide P1 reacted with the epoxy-based crosslinking agent, and a crosslinked polyimide was formed from polyimide P1. This crosslinked polyimide had a structure in which polyimide P1 was crosslinked via a covalent bond.

[0191] (Examples 4 to 5) The separation functional layers (self-supporting films) of Examples 4 and 5 were obtained by the same method as in Example 1, except that an amine-based crosslinking agent (Epomin (polyethyleneimine), weight-average molecular weight 600, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the coating solution when preparing the separation functional layer, and the ratio of the weight of the amine-based crosslinking agent to the weight of polyimide P1 was adjusted as shown in Table 1. In Examples 4 and 5, during the drying of the coated film, the functional group f (sulfonic acid group) contained in polyimide P1 reacted with the amine-based crosslinking agent to form a crosslinked polyimide from polyimide P1. This crosslinked polyimide had a structure in which polyimide P1 was crosslinked via covalent bonds.

[0192] (Example 6) First, a separation functional layer (dried film) was prepared using the same method as in Example 1. This film was peeled from the polyimide film and immersed in Eaton's reagent in a glass container. In this state, heating at 80°C for 2 hours caused a condensation reaction of the functional group f (sulfonic acid group) contained in polyimide P1 to proceed, forming a crosslinked polyimide. This crosslinked polyimide had a structure in which polyimide P1 was crosslinked via covalent bonds. This film was removed from the container, washed by immersion in deionized water for 4 hours, and this process was repeated three times, followed by a drying treatment to obtain the separation functional layer (self-supporting film) of Example 6.

[0193] (Example 7) First, polyimide P2 was prepared using the same method as in Example 1, except that the type and ratio of diamines were changed as shown in Table 1, and the treatment with dilute hydrochloric acid solution was omitted. Polyimide P2 had a carboxyl group as the functional group f.

[0194] Next, polyimide P2 was added to a 10L pail, and then N-methyl-2-pyrrolidone (NMP) as a solvent and acetylacetone as a ligand were added to obtain a mixture. This mixture was stirred for 1 hour at a rotation speed of 700-1400 rpm using a propeller-type stirring blade. Next, NMP and Al(acac)3 as a metal complex were added to another screw-cap tube, and then ultrasonic treatment was performed using an ultrasonic cleaner to obtain an Al(acac)3 solution. The Al(acac)3 solution and the above mixture were further mixed, and the coating solution was prepared by stirring for 1 hour at a rotation speed of 700-1400 rpm using a propeller-type stirring blade.

[0195] In the coating solution, the ratio of the weight of polyimide P2 to the total weight of polyimide P2 and NMP was 8 wt%, and the ratio of the weight of NMP to the total weight was 92 wt%. In the coating solution, the ratio of the weight of Al(acac)3 to the weight of polyimide P2, and the ratio of the weight of acetylacetone to the weight of polyimide P2, were both 6 wt%.

[0196] Next, a peel-treated polyethylene terephthalate (PET) film (Mitsubishi Chemical Corporation, MRF75T302) was prepared as the substrate. A discharge rate of 0.25 kW·min / m was applied to the peel-treated surface of this substrate. 2 Corona treatment was performed under the specified conditions. Next, the above coating solution was applied to the substrate to form a coating film. The coating solution was applied using a slot die.

[0197] Next, the coated film was dried by transporting it at a speed of 1 m / min and passing it through three heating sections. Specifically, the coated film passed through the first heating section, the second heating section, and the third heating section in that order. The set temperature of the first heating section was 100°C, the set temperature of the second heating section was 130°C, and the set temperature of the third heating section was 130°C. The time it took for the coated film to pass through the first to third heating sections (drying time) was 6 minutes. By drying the coated film, a separation functional layer was obtained. Furthermore, as the coated film dried, the dissociable protons of the functional group f (carboxyl group) contained in polyimide P2 were exchanged with Al of the metal complex. As a result, a crosslinked polyimide was formed in which polyimide P2 was crosslinked via ionic bonds.

[0198] Next, the substrate was removed from the laminate of the separation functional layer and the substrate. Furthermore, the separation functional layer was subjected to further heat treatment. The heat treatment was carried out at 300°C for 30 minutes. This yielded the separation functional layer (self-supporting film) of Example 7.

[0199] (Example 8) First, polyimide P3 was prepared using the same method as in Example 1, except that the type and ratio of diamines were changed as shown in Table 1. Polyimide P3 had a sulfonic acid group as the functional group f.

[0200] Next, a separation functional layer (dried film) was prepared using the same method as in Example 1, except that polyimide P3 was used. This film was peeled from the polyimide film, immersed in methanol for 24 hours, then removed and immersed in acetone for 15 hours. The immersed film was dried in a vacuum dryer at 120°C for 8 hours. The dried film was immersed in an aqueous solution of Al(NO3)3 with a concentration of 0.1 mol / L for 24 hours. During this time, the aqueous solution was replaced with fresh solution three times. Through this operation, the dissociable protons of the functional group f (sulfonic acid group) contained in polyimide P3 were exchanged with Al. As a result, a crosslinked polyimide was formed in which polyimide P3 was crosslinked via ionic bonds.

[0201] Next, the membrane was washed by immersing it in deionized water for 24 hours. During this procedure, the deionized water was replaced with fresh water three times. Then, the membrane was dried at 120°C for 8 hours. This yielded the separation functional layer (self-supporting membrane) of Example 8.

[0202] (Example 9) The separation functional layer (self-supporting membrane) of Example 9 was obtained by the same method as in Example 8, except that polyimide P4 was prepared by changing the ratio of diamines as shown in Table 1, and polyimide P4 was used instead of polyimide P3.

[0203] (Example 10) The separation functional layer (self-supporting membrane) of Example 10 was obtained by the same method as in Example 7, except that polyimide P1 prepared in Example 1 was used instead of polyimide P2, and the ratio of the weight of Al(acac)3 to the weight of polyimide P1 and the weight of acetylacetone to the weight of polyimide P1 in the coating solution were changed to 15 wt%.

[0204] (Example 11) The separation functional layer (self-supporting membrane) of Example 11 was obtained by the same method as in Example 7, except that polyimide P5 was prepared by changing the ratio of diamines as shown in Table 1, polyimide P5 was used instead of polyimide P2, and the ratio of the weight of Al(acac)3 to the weight of polyimide P5 and the weight of acetylacetone to the weight of polyimide P5 in the coating solution were changed to 25 wt%.

[0205] [Characterization of the separation layer] (Gas permeation test) The carbon dioxide permeation rate T1 and the carbon dioxide separation coefficient α (CO2 / N2) relative to nitrogen were measured for the fabricated separation functional layer using the following method. First, the separation functional layer was set in a metal cell and sealed with an O-ring to prevent leakage. Next, a gas mixture was injected into the metal cell so that it contacted one main surface of the separation functional layer. The gas mixture consisted substantially of carbon dioxide and nitrogen. The concentration of carbon dioxide in the gas mixture was 50 vol% under standard conditions. The gas mixture injected into the metal cell was at 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 reduced to 0.1 MPa less than the atmospheric pressure in the measurement environment. As a result, permeated fluid was obtained from the other main surface of the separation functional layer. Based on the composition and weight of the obtained permeated fluid, the permeation rate T1 and the separation coefficient α were calculated.

[0206] (Durability test) The fabricated separation functional layer was subjected to a durability test by heat treatment at 85°C for 500 hours. After the durability test, the carbon dioxide permeation rate T2 of the separation functional layer was measured using the same method as for permeation rate T1. From the obtained results, the ratio of permeation rate T2 to permeation rate T1, T2 / T1 (maintenance rate of permeation rate), was calculated.

[0207] [Mechanical strength] The fabricated separation functional layer was subjected to a bending test using the following method. First, the separation functional layer was cut into pieces measuring 50 mm in length and 50 mm in width to create test specimens. Next, these test specimens were wound onto a cylindrical roll with an outer diameter of 5 mm and left at room temperature for 24 hours. After the bending test, the separation functional layer was visually inspected for any breakage.

[0208] [Gel fraction] The gel fraction of the prepared separation functional layer was measured using the method described above.

[0209] [Table 1]

[0210] The abbreviations used in Table 1 are as follows: NTDA: Naphthalene-1,4,5,8-tetracarboxylic dianhydride (in formula (a1), R 1a ~R 4a (A compound in which hydrogen atoms are present) TrMPD: 2,4,6-trimethyl-1,3-phenylenediamine (in formula (e1), R 1e , R 2e and R 4e is a methyl group, R 3e (A compound in which hydrogen atoms are present) DDBT:3,7-diamino-2,8-dimethyldibenzothiophenesulfone (in formula (d1), R 2d and R 5d is a methyl group, R 1d , R 3d , R 4d and R 6d (A compound in which hydrogen atoms are present) MBAA: 5,5'-Methylenebis(2-aminobenzoic acid) (In formula (c2), R 5c and R 10c is a carboxyl group, R 6c ~R 9c , R 11c and R 12c X is a hydrogen atom, 1 (A compound in which the methylene group is) BAPFDS: 9,9-bis(4-aminophenyl)fluorene-2,7-disulfonic acid (in formula (b2), R 10b and R 15b is a sulfonic acid group, R 1b ~R 9b , R 11b ~R 14b and R 16b (A compound in which hydrogen atoms are present) TETRAD-C: Epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, TETRAD-C (1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane)) PEI: Amine-based crosslinking agent (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Epomin (polyethyleneimine), weight-average molecular weight 600)

[0211] As can be seen from Table 1, the separation functional layers of Examples 2 to 6, which contain crosslinked polyimides formed by covalent bonding of polyimides, showed a higher retention rate of permeation rate compared to the separation functional layer of Example 1, which does not contain crosslinked polyimides, and the separation functional layers of Examples 7 to 11, which contain crosslinked polyimides formed by ionic bonding of polyimides. From these results, it can be said that the separation functional layer of this embodiment is suitable for separating acidic gases from a gas mixture containing acidic gases.

[0212] The separation functional layers in Examples 2-6 tended to have a higher gel fraction compared to the separation functional layers in Examples 7-11. Furthermore, the separation functional layers in Examples 2-6 had an initial transmission velocity T1 of 50 GPU or higher and a separation coefficient α of 30 or higher, both of which were practically sufficient values. [Industrial applicability]

[0213] The separation layer and separation membrane of this embodiment are suitable for separating acidic gases from a gas mixture containing acidic gases. In particular, the separation layer and separation membrane of this embodiment are suitable for separating carbon dioxide from off-gas in chemical plants or thermal power plants. [Explanation of Symbols]

[0214] 1 Separation functional layer 2. Middle class 3 Porous support 10 Separation membrane 100,110 Membrane separation equipment

Claims

1. A separation functional layer containing crosslinked polyimide, The aforementioned crosslinked polyimide is a polyimide that has been crosslinked via covalent bonds. The polyimide is a separation functional layer comprising a constituent unit A1 derived from a tetracarboxylic dianhydride having a six-membered ring acid anhydride structure.

2. The polyimide further comprises a constituent unit B1 derived from a diamine, The separation functional layer according to claim 1, wherein at least one of the constituent units A1 and B1 has at least one functional group f selected from the group consisting of a sulfonic acid group, a carboxyl group, a hydroxyl group and a thiol group.

3. The separation functional layer according to claim 2, wherein the crosslinked polyimide is formed by a reaction between the functional group f and the crosslinking agent.

4. The separation functional layer according to claim 3, wherein the crosslinking agent comprises at least one selected from the group consisting of epoxy crosslinking agents and amine crosslinking agents.

5. The separation functional layer according to claim 3, wherein the crosslinking agent functions as a condensing agent that promotes the condensation reaction of the functional group f.

6. The separation functional layer according to claim 2, wherein the constituent unit B1 has the functional group f.

7. The separation functional layer according to claim 6, wherein the ratio of the amount of substance of the constituent unit B1 having the functional group f to the amount of substance of all constituent units B derived from the diamine is 1 to 60 mol%.

8. The aforementioned structural unit B1 is represented by the following formula (B1), and is the separation functional layer according to claim 6. 【Chemistry 1】 In the above formula (B1), Ar 1 and Ar 2 These are, independently of each other, aromatic groups, and Ar 3 This is an aromatic group containing the aforementioned functional group f.

9. The aforementioned structural unit B1 is represented by the following formula (B2), and is the separation functional layer according to claim 6. 【Chemistry 2】 In the above formula (B2), R 1b ~R 16b R is a hydrogen atom or any substituent, independently of each other. 9b ~R 16b At least one selected from the group consisting of the above is a group containing the functional group f.

10. In the formula (B2), R 9b ~R 12b At least one selected from the group consisting of is a group containing the functional group f, and R 13b ~R 16b The separation functional layer according to claim 9, wherein at least one selected from the group consisting of is a group containing the functional group f.

11. The aforementioned structural unit A1 is represented by the following formula (A1), and is the separation functional layer according to claim 1. 【Transformation 3】 In the above formula (A1), R 1a ~R 4a These are, independently of each other, a hydrogen atom or any substituent.

12. The separation functional layer according to claim 1, wherein the gel fraction is 70% or more.

13. A separation functional layer according to claim 1, used for separating an acidic gas from a gas mixture containing an acidic gas.

14. A separation functional layer according to any one of claims 1 to 13, A porous support that supports the separation functional layer, A separation membrane equipped with [a specific feature].

15. A method for manufacturing a separation functional layer according to any one of claims 1 to 13, The aforementioned manufacturing method is The process involves applying the coating solution containing the polyimide onto a substrate to form a coating film, The coating film is dried to form the crosslinked polyimide from the polyimide, A method for manufacturing a separation functional layer, including the following:

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