Separation membrane

Abstract

Provided is a novel separation membrane suitable for a membrane separation device (particularly a spiral membrane element). This separation membrane (10) is provided with a separation functional layer (1), a porous support (3) that supports the separation functional layer (1), and an intermediate layer (2) that is arranged between the separation functional layer (1) and the porous support (3). The porous support (3) has a surface (S1) facing the intermediate layer (2). The load area ratio Smr (c1) of the surface S1 as determined by the following test is less than 80%. And a test: performing three-dimensional analysis on the surface S1 of the porous support body 3 to obtain a load curve specified in JIS B0681-2: 2018. In the load curve, a height (c1) at which the difference from the height (c0) when the load area ratio is 0% coincides with the thickness of the intermediate layer (2) is determined. A load area ratio corresponding to the height c1 is read and determined as a load area ratio Smr (c1).

Description

TECHNICAL FIELD

[0001] The present application relates to a separation membrane. BACKGROUND

[0002] As a method for separating an acid gas such as carbon dioxide from a mixed gas containing the acid gas, a membrane separation method has been developed. The membrane separation method can suppress the operating cost and efficiently separate the acid gas as compared with an absorption method in which the acid gas contained in the mixed gas is absorbed to an absorbent to thereby be separated.

[0003] As a separation membrane used in the membrane separation method, a composite membrane obtained by forming a separation functional layer on a porous support can be cited. As the porous support, a laminate obtained by laminating a microporous layer on a surface of a nonwoven fabric is generally used (for example, Patent Literature 1).

[0004] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: Japanese Patent No. 6186286 SUMMARY

[0005] PROBLEMS TO BE SOLVED BY THE INVENTION A new type of separation membrane suitable for a membrane separation device, particularly a spiral type membrane element is required.

[0006] MEANS FOR SOLVING THE PROBLEMS The present application provides a separation membrane comprising: a separation functional layer, a porous support that supports the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support, the porous support has a surface S1 opposite to the intermediate layer, a load area ratio Smr(c1) of the surface S1 obtained by the following test is less than 80%.

[0007] Test: A three-dimensional analysis is performed on the surface S1 of the porous support to obtain a load curve prescribed in Japanese Industrial Standards (JIS) B0681-2:2018. In the load curve, a height c1 coinciding with the thickness of the intermediate layer and the difference from a height c0 at a load area ratio of 0% is determined. A load area ratio corresponding to the height c1 is read to be determined as the load area ratio Smr(c1).

[0008] Further, the present application provides a separation membrane comprising: a separation functional layer, a porous support that supports the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support, The separation membrane has a thickness of 130 μm or less. The separation coefficient α of the separation membrane when the separation membrane is contacted with nitrogen having a pressure of 2.0 MPa for 5 minutes is maintained at 70% or more.

[0009] The separation coefficient α is a ratio of a permeation rate T of carbon dioxide permeated through the separation membrane when carbon dioxide having a pressure of 0.6 MPa is supplied to a space adjacent to one surface of the separation membrane CO2 to a permeation rate T of nitrogen permeated through the separation membrane when nitrogen having a pressure of 0.6 MPa is supplied to the space N2 CO2 N2 .

[0010] Effects of the Invention According to the present application, a novel separation membrane suitable for a membrane separation device, particularly a spiral-type membrane element, can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0011] [ Figure 1 ] is a cross-sectional view schematically showing a separation membrane according to an embodiment of the present application.

[0012] [ Figure 2 ] is a graph for explaining a method for determining a load area ratio Smr(c1).

[0013] [ Figure 3 ] is a schematic cross-sectional view of a membrane separation device provided with a separation membrane according to the present application.

[0014] [ Figure 4 ] is a perspective view schematically showing a modification of a membrane separation device provided with a separation membrane according to the present application. DETAILED DESCRIPTION

[0015] A separation membrane according to a first embodiment of the present application includes: a separation functional layer, a porous support supporting the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support, the porous support has a surface S1 opposite to the intermediate layer, a load area ratio Smr(c1) of the surface S1 obtained by the following test is less than 80%.

[0016] ​​Test: A three-dimensional analysis was performed on the aforementioned surface S1 of the aforementioned porous support, and a load curve prescribed in Japanese Industrial Standards (JIS) B0681-2:2018 was obtained. In the aforementioned load curve, a height c1 coinciding with the thickness of the aforementioned intermediate layer and the difference from a height c0 at the time when the load area ratio was 0% was determined. A load area ratio corresponding to the aforementioned height c1 was read, and was determined as the aforementioned load area ratio Smr(c1).

[0017] In the second aspect of the present application, for example, the separation membrane according to the first aspect has a load area ratio Smr(c1) of 0.04% or more.

[0018] In the third aspect of the present application, for example, the separation membrane according to the first or second aspect has a thickness of 130 μm or less.

[0019] The fourth aspect of the present application relates to a separation membrane comprising: a separation function layer, a porous support that supports the aforementioned separation function layer, and an intermediate layer disposed between the aforementioned separation function layer and the aforementioned porous support, the aforementioned separation membrane has a thickness of 130 μm or less, a retention rate of a separation coefficient α of the aforementioned separation membrane when the aforementioned separation membrane is contacted with nitrogen having a pressure of 2.0 MPa for 5 minutes is 70% or more.

[0020] wherein the aforementioned separation coefficient α is a ratio T CO2 (GPU) of a permeation speed T N2 (GPU) of carbon dioxide permeated through the aforementioned separation membrane when carbon dioxide having a pressure of 0.6 MPa is supplied to a space adjacent to one face of the aforementioned separation membrane, to a permeation speed T CO2 (GPU) of nitrogen permeated through the aforementioned separation membrane when nitrogen having a pressure of 0.6 MPa is supplied to the aforementioned space. N2 .

[0021] In the fifth aspect of the present application, for example, the separation membrane according to any one of the first to fourth aspects has a porous support that is a fiber structure.

[0022] In the sixth aspect of the present application, for example, the separation membrane according to any one of the first to fifth aspects has a porous support having a thickness of 125 μm or less.

[0023] In the seventh aspect of the present application, for example, the separation membrane according to any one of the first to sixth aspects has a porous support having an ISO air permeability of 10.0 x 10 4 μm / (Pa s) or more.

[0024] In the eighth aspect of the present invention, for example, in the separation membrane involved in any of the first to seventh aspects, the aforementioned separation functional layer comprises polyimide.

[0025] In a ninth aspect of the present invention, for example, in the separation membrane involved in the eighth aspect, the aforementioned polyimide comprises structural units from tetracarboxylic acid dianhydrides having an anhydride structure with a 6-membered ring.

[0026] In the tenth aspect of the present invention, for example, in the separation membrane involved in the ninth aspect, the aforementioned structural unit is represented by the following formula (A1).

[0027] [Chemical Formula 1] In the aforementioned formula (A1), R 1a ~R 4a Each can be a hydrogen atom or an optional substituent, independent of the others.

[0028] In the eleventh aspect of the present invention, for example, in the separation membrane involved in any of the first to tenth aspects, the thickness of the aforementioned separation functional layer is 5.0 μm or less.

[0029] In the 12th aspect of the present invention, for example, in the separation membrane involved in any of the 1st to 11th aspects, the aforementioned intermediate layer is formed of an adhesive composition.

[0030] In a 13th aspect of the present invention, for example, in the separation membrane involved in the 12th aspect, the aforementioned adhesive composition comprises an organosilicon polymer.

[0031] In the 14th aspect of the present invention, for example, in the separation membrane involved in any of the 1st to 13th aspects, the thickness of the aforementioned intermediate layer is 5.0 μm or less.

[0032] In the 15th aspect of the present invention, for example, in the separation membrane involved in any of the 1st to 14th aspects, the peel strength between the aforementioned intermediate layer and the aforementioned porous support is 0.25 N / 25 mm or more.

[0033] The present invention will now be described in detail, but this description is not intended to limit the invention to specific embodiments.

[0034] <Implementation Methods of Separation Membranes> like Figure 1 As shown, the separation membrane 10 of this embodiment includes a separation functional layer 1, a porous support 3 supporting the separation functional layer 1, and an intermediate layer 2 disposed between the separation functional layer 1 and the porous support 3. The intermediate layer 2 preferably has direct contact with both the separation functional layer 1 and the porous support 3.

[0035] The porous support 3 has surfaces S1 and S2 that face each other. The surface S1 faces the intermediate layer 2, and in detail, is in direct contact with the intermediate layer 2. In the present embodiment, the load area ratio Smr(c1) of the surface S1 obtained by the following test is less than 80%.

[0036] Test: The surface S1 of the porous support 3 is subjected to three-dimensional analysis, and a load curve prescribed in JIS B0681-2:2018 is obtained. In the load curve, a height c1 that coincides with the thickness of the intermediate layer 2 from the height c0 at the time when the load area ratio is 0% is determined. The load area ratio corresponding to the height c1 is read, and is determined as the load area ratio Smr(c1).

[0037] In detail, the measurement of the load area ratio Smr(c1) can be performed using the following method. First, the porous support 3 taken out from the separation membrane 10, or the porous support 3 before being used for the production of the separation membrane 10 is prepared. The porous support 3 is cut into a size of 1 cm in length x 1 cm in width, and is used as a test piece. The surface S1 of the test piece is observed using a laser microscope. The observation based on the laser microscope can be performed under the following conditions.

[0038] • Observation conditions Wavelength of light source: 546 nm Resolution: 0.1 μm Observation range: 600 μm x 600 μm Next, using the obtained observation image, three-dimensional analysis is performed. The three-dimensional analysis can be performed using LMeye7 as a software, and further using FinePeak as an analysis algorithm. The load curve prescribed in JIS B0681-2:2018 can be obtained by the three-dimensional analysis. Figure 2 ). The load curve refers to a curve that shows the relationship between the height c and the load area ratio Smr in a coordinate system in which the height c (μm) of the surface S1 (in detail, the unevenness present on the surface S1) is taken as the longitudinal axis, and the proportion (load area ratio Smr (%)) of the area of the porous support 3 present in the region of a specific height c or more is taken as the lateral axis.

[0039] Next, as shown in Figure 2 , the height c0 at the time when the load area ratio Smr is 0% (i.e., the position of the outermost surface of the surface S1) is determined, and further, the height c1 that coincides with the thickness of the intermediate layer 2 from the height c0 is determined. That is, Figure 2 In this case, the difference |c0-c1| between the height c0 and the height c1 is the same as the thickness of the intermediate layer 2. The load area ratio corresponding to the height c1 can be read, and is determined as the load area ratio Smr(c1).

[0040] The load area ratio Smr(c1) can be used as an index relating to the pores (openings) present on the surface S1 of the porous support 3. In detail, the lower the load area ratio Smr(c1), the more pores of a larger pore diameter are present on the surface S1 of the porous support 3. As one example, in the case where the porous support 3 does not have a microporous layer and is composed only of a fibrous structure, there is a tendency for the load area ratio Smr(c1) to be less than 80%, particularly 50% or less.

[0041] The load area ratio Smr(c1) of the surface S1 in the porous support 3 is less than 80% as described above, and can also be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5.0% or less, 3.0% or less, 1.0% or less, 0.5% or less, and furthermore, 0.1% or less. The lower limit of the load area ratio Smr(c1) is, for example, 0.01% or more, and can also be 0.04% or more. In particular, in the case where the load area ratio Smr(c1) is 0.04% or more, the peeling strength of the porous support 3 from the intermediate layer 2 is sufficiently large, and it is easy to produce the separation membrane 10 using the transfer method described later.

[0042] (Separation function layer) The separation function layer 1 preferably allows the acidic gas contained in the mixed gas to permeate preferentially, and is typically a dense layer (non-porous layer) in which no pores can be confirmed when observed using a scanning electron microscope (SEM) at a magnification of 5000 times.

[0043] Typically, the separation function layer 1 contains a resin. As the resin contained in the separation function layer 1, for example, polyether block amide resin, polyamide resin, polyether resin, polyimide resin, cellulose acetate resin, silicone resin, and fluororesin can be given.

[0044] The separation function layer 1 preferably contains a polyimide, and particularly preferably contains a polyimide P containing a structural unit A1 derived from a tetracarboxylic dianhydride a1 having an acid anhydride structure S having a 6-membered ring. The polyimide P preferably further contains a structural unit B1 derived from a diamine b1. It is preferable that at least one of the structural unit A1 and the structural unit B1 has at least one functional group f selected from the group consisting of a carboxyl group, a hydroxyl group, a thiol group, and metal salts thereof, and it is preferable that the functional group f is a metal salt (particularly a metal salt of a carboxyl group). In particular, in the polyimide P, it is preferable that the structural unit B1 has the functional group f. The structural unit A1 can have or can not have the functional group f.

[0045] The structural unit A1 derived from the tetracarboxylic dianhydride a1 is a structural unit suitable for increasing the permeation coefficient and the permeation rate of the acid gas permeating through the separation function layer 1. The tetracarboxylic dianhydride a1 preferably has one or more (preferably two) anhydride structures S. Typically, the anhydride structure S of the six-membered ring is a glutaric anhydride structure represented by the following formula (1).

[0046] [Chemical Formula 2] The tetracarboxylic dianhydride a1 can also have at least one functional group g selected from the group consisting of a carboxyl group, a hydroxyl group, and a thiol group, and can not have the functional group g. Note that in the present specification, the functional group g is the same as the functional group f except that the metal salt is not included in the selection.

[0047] The tetracarboxylic dianhydride a1 can have a fused ring, and the fused ring can include the anhydride structure S. The fused ring can also include an aromatic ring together with the anhydride structure S. The aromatic ring included in the fused ring can be composed of only carbon atoms, or can be a heteroaromatic ring including a heteroatom such as an oxygen atom, a nitrogen atom, or a sulfur atom. The aromatic ring can be polycyclic, or monocyclic. The number of carbon atoms of the aromatic ring is not particularly limited, and is, for example, 4 to 14. As specific examples of the aromatic ring, a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a furan ring, a pyrrole ring, a pyridine ring, and a thiophene ring can be given.

[0048] The fused ring can have a substituent, or can not have a substituent. As the substituent of the fused ring, a halogen group, a hydrocarbon group, or the like can be given. As the halogen group, a fluorine group, a chlorine group, a bromine group, an iodine group, or the like can be given. The number of carbon atoms of the hydrocarbon group is not particularly limited, and is, for example, 1 to 15. The hydrocarbon group is, for example, an alkyl group such as a methyl group, an ethyl group, or a propyl group. The hydrocarbon group can also be a halogenated hydrocarbon group obtained by substituting a hydrogen atom with a halogen group. When the fused ring has a plurality of substituents, the plurality of substituents can be the same as or different from each other.

[0049] The tetracarboxylic dianhydride a1 is preferably represented by the following formula (a1).

[0050] [Chemical Formula 3] In formula (a1), R 1a ~R 4a are each independently a hydrogen atom or an optional substituent. As the optional substituent, a halogen group, a hydrocarbon group, or the like can be given. As the halogen group and the hydrocarbon group, the above-described groups can be given.

[0051] In the polyimide P, the structural unit A1 derived from the tetracarboxylic dianhydride a1 is preferably represented by the following formula (A1). The structural unit A1 represented by the formula (A1) is derived from the tetracarboxylic dianhydride a1 represented by the above formula (a1). Note that, in the formula (A1), the nitrogen atom included in the imide group is derived from the diamine which has reacted with the tetracarboxylic dianhydride a1.

[0052] [Chemical Formula 4] In the formula (A1), R 1a ~R 4a The same as the formula (a1), each independently is a hydrogen atom or an optional substituent. As a specific example of the structural unit A1 represented by the formula (A1), the following formula (A1-1) can be given.

[0053] [Chemical Formula 5] In the polyimide P, the ratio p1 of the amount of substance of the above structural unit A1 with respect to the amount of substance of the total structural unit A derived from the tetracarboxylic dianhydride is, for example, 50 mol% or more, and can be 70 mol% or more, 90 mol% or more, 95 mol% or more, and further, 99 mol% or more. The polyimide P can contain only the above structural unit A1 as the structural unit A derived from the tetracarboxylic dianhydride. Among them, the polyimide P can contain, in addition to the structural unit A1, a structural unit A2 derived from a tetracarboxylic dianhydride a2 having a 5-membered ring anhydride structure. As the tetracarboxylic dianhydride a2, there is no particular limitation, and for example, phthalic anhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, and the like can be given.

[0054] The structural unit B1 derived from the diamine b1, particularly the structural unit B1 having the functional group f is a structural unit suitable for improving the selectivity of the acidic gas permeating the separation functional layer 1. The diamine b1 is preferably a compound having 2 primary amino groups and further having at least one functional group g selected from the group consisting of a carboxyl group, a hydroxyl group, and a thiol group. The number of the functional group g in the diamine b1 is not particularly limited, and is, for example, 5 or less, preferably 2 or less, and particularly preferably 1. The smaller the number of the functional group g in the diamine b1, the more the solubility of the polyimide P is improved, and there is a tendency that the desired manufacturing method of the separation membrane 10 is easily applied.

[0055] The functional group g has a dissociative proton and can form a salt with a counter cation. In particular, from the viewpoint of easily forming a salt, the diamine b1 preferably has a carboxyl group as the functional group g. Note that the diamine b1 preferably does not have a group having a dissociative proton other than the functional group g, such as a sulfonic acid group. As one example, in the case where the diamine b1 does not contain a sulfonic acid group, the solubility of the polyimide P can be easily and appropriately adjusted.

[0056] The diamine b1 can further have an aromatic ring. As the aromatic ring, the aromatic rings described above with respect to the tetracarboxylic dianhydride a1 can be given. In the diamine b1, the substituents of the aromatic ring preferably include the functional group g and the primary amino group. The aromatic ring can have other substituents in addition to the substituents including the functional group g and the substituents including the primary amino group, or can not have other substituents. As the other substituents, there is no particular limitation, and a halogen group, a hydrocarbon group, or the like can be given. As the halogen group and the hydrocarbon group, the halogen groups and the hydrocarbon groups described above with respect to the tetracarboxylic dianhydride a1 can be given. Note that in the diamine b1, the other substituents can include a photopolymerizable functional group (for example, a vinyl group).

[0057] The diamine b1 is preferably represented by the following formula (b1), formula (b2), or formula (b3).

[0058] [Chemical Formula 6] In formula (b1), R 1b ~R 4b are each independently a hydrogen atom or an optional substituent. Among them, at least one selected from the group consisting of a halogen group, a hydrocarbon group, and the like is preferably a group including the functional group g, and more preferably the functional group g itself. As the halogen group and the hydrocarbon group, the halogen groups and the hydrocarbon groups described above with respect to the tetracarboxylic dianhydride a1 can be given. 1b ~R 4b is a group including the functional group g, and more preferably the functional group g itself. As the optional substituent other than the group including the functional group g, there is no particular limitation, and a halogen group, a hydrocarbon group, or the like can be given. As the halogen group and the hydrocarbon group, the halogen groups and the hydrocarbon groups described above with respect to the tetracarboxylic dianhydride a1 can be given.

[0059] In formula (b2), R 5b ~R 12b are each independently a hydrogen atom or an optional substituent, X 1 is a single bond or an optional linking group. Among them, at least one selected from the group consisting of a halogen group, a hydrocarbon group, and the like is preferably a group including the functional group g, and more preferably the functional group g itself. As the halogen group and the hydrocarbon group, the halogen groups and the hydrocarbon groups described above with respect to the tetracarboxylic dianhydride a1 can be given. 5b ~R 12b is a group including the functional group g, and more preferably the functional group g itself. As the optional substituent other than the group including the functional group g, there is no particular limitation, and a halogen group, a hydrocarbon group, or the like can be given. As the halogen group and the hydrocarbon group, the halogen groups and the hydrocarbon groups described above with respect to the tetracarboxylic dianhydride a1 can be given.

[0060] X1 The optional linking group is, for example, a divalent hydrocarbon group. As the divalent hydrocarbon group, for example, there can be mentioned methylene, ethylene, propane-1, 3-diyl, propane-2, 2-diyl, and the like alkylenes. The divalent hydrocarbon group can also be a halogenated hydrocarbon group obtained by substituting a hydrogen atom with a halogen group. X 1 An ether group, an ester group, and the like functional groups can also be included together with or instead of the divalent hydrocarbon group.

[0061] In formula (b3), R 13b R 20b are each independently a hydrogen atom or an optional substituent, X 2 is a single bond or an optional linking group. Among them, at least one selected from the group consisting of R 13b R 20b is a group including a functional group g, and preferably the functional group g itself. As the optional substituent other than the group including the functional group g, there is no particular limitation, and there can be mentioned a halogen group, a hydrocarbon group, and the like. As the halogen group and the hydrocarbon group, there can be mentioned the halogen group and the hydrocarbon group described above with respect to the tetracarboxylic dianhydride a1.

[0062] X in formula (b3) is a single bond or an optional linking group. Among them, at least one selected from the group consisting of R 2 The optional linking group is, for example, a divalent hydrocarbon group. As the divalent hydrocarbon group, there can be mentioned the divalent hydrocarbon group described above with respect to X 1 in formula (b3). X 2 An ether group, an ester group, and the like functional groups can also be included together with or instead of the divalent hydrocarbon group.

[0063] As described above, in the polyimide P, the structural unit B1 from the diamine b1 preferably has the functional group f. In particular, in the structural unit B1, as the functional group f, a metal salt of a carboxyl group, a metal salt of a hydroxyl group, or a metal salt of a thiol group is preferred, and a metal salt of a carboxyl group is particularly preferred.

[0064] With respect to the metal included in the metal salt as the functional group f, there is no particular limitation, and there can be mentioned, for example, Li, Na, K, Be, Mg, Ca, Ba, Sc, Y, Ti, Zr, V, Cr, Mo, Mn, Fe, Co, Ni, Cu, Ag, Zn, B, Al, Ga, In, Pb, and the like, and Mg, Fe, Al, and Ga are preferred, and Al is particularly preferred. That is, the metal salt as the functional group f is preferably an aluminum salt. Note that the metal included in the metal salt can also be Na, Ca, and the like.

[0065] In the metal salt as the functional group f, in detail, the metal exists as a cation. The valence of the metal (metal cation) included in the metal salt is, for example, 1 or more, preferably 2 or more, and more preferably 3 or more. As one example, the valence of the metal is 2 or 3.

[0066] When structural unit B1 contains a metal salt as a functional group f, multiple polyimides P can be coordinated with the metal cation contained in the metal salt via functional groups such as carboxyl groups. Thus, the multiple polyimides P are cross-linked with each other via the metal cation. By forming such a cross-linked structure, the physical aging of the polyimide P can be suppressed, thereby inhibiting the tendency of the separation performance of the separation functional layer 1 to decrease over time. When the polyimide P contains a metal salt as a functional group f, there is also a tendency to improve the separation performance of the separation functional layer 1. As described later, the metal salt as functional group f can be formed by exchanging the dissociable protons with the metal cations in a polyimide containing a tetracarboxylic dianhydride a1 and a diamine b1.

[0067] The structural unit B1 derived from diamine b1 is preferably represented by the following formula (B1), formula (B2), or formula (B3). The structural unit B1 represented by formula (B1) is derived from the diamine b1 represented by formula (b1) above. The structural unit B1 represented by formula (B2) is derived from the diamine b1 represented by formula (b2) above. The structural unit B1 represented by formula (B3) is derived from the diamine b1 represented by formula (b3) above.

[0068] [Chemical Formula 7] In equation (B1), R 1b ~R 4b Each can be a hydrogen atom or an optional substituent, independently of the others. The substituent is chosen from R. 1b ~R 4b At least one of the constituent groups is a group containing functional group f, preferably functional group f itself. There are no particular limitations on the optional substituents other than the group containing functional group f, and examples include halogen groups, hydrocarbon groups, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0069] As a specific example of the structural unit B1 represented by formula (B1), formulas (B1-1) to (B1-6) can be given below. It should be noted that in formulas (B1-2), (B1-4) and (B1-6), M is an optional metal cation, preferably Mg ion, Fe ion, Al ion or Ga ion, and particularly preferably Al ion. M can also be Na ion or Ca ion.

[0070] [Chemical Formula 8] In equation (B2), R 5b ~R 12b Each of the following can be a hydrogen atom or an optional substituent: X 1It can be a single bond or an optional linking group. Wherein, it is selected from R. 5b ~R 12b At least one of the constituent groups is a group containing functional group f, preferably functional group f itself. There are no particular limitations on the optional substituents other than the group containing functional group f, and examples include halogen groups, hydrocarbon groups, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0071] X in equation (B2) 1 In this context, the optional linking group is, for example, a divalent hydrocarbon group. Examples of divalent hydrocarbon groups include those described above. X 1 It can also contain functional groups such as ether groups and ester groups together or in place of divalent hydrocarbon groups.

[0072] As a specific example of structural unit B1 represented by formula (B2), the following formulas (B2-1) to (B2-12) can be cited. It should be noted that in these formulas, M is an optional metal cation, preferably Mg ion, Fe ion, Al ion or Ga ion, and particularly preferably Al ion. M can also be Na ion or Ca ion.

[0073] [Chemical Formula 9] In formula (B3), R 13b ~R 20b Each of the following can be a hydrogen atom or an optional substituent: X 2 It can be a single bond or an optional linking group. Wherein, it is selected from R. 13b ~R 20b At least one of the constituent groups is a group containing functional group f, preferably functional group f itself. There are no particular limitations on the optional substituents other than the group containing functional group f, and examples include halogen groups, hydrocarbon groups, etc. Examples of halogen groups and hydrocarbon groups include those described above for tetracarboxylic dianhydride a1.

[0074] X in equation (B3) 2 In this context, the optional linking group is, for example, a divalent hydrocarbon group. Examples of divalent hydrocarbon groups include those described above. X 2 It can also contain functional groups such as ether groups and ester groups together or in place of divalent hydrocarbon groups.

[0075] As a specific example of structural unit B1 represented by formula (B3), the following formulas (B3-1) to (B3-6) can be cited. It should be noted that in these formulas, M is an optional metal cation, preferably Mg ion, Fe ion, Al ion or Ga ion, and particularly preferably Al ion. M can also be Na ion or Ca ion.

[0076] [Chemical Formula 10] The ratio p2 of the amount of substance of the structural unit B1, particularly the structural unit B1 having the functional group f, to the amount of substance of the total structural unit B from the diamine in the polyimide P is, for example, 1 mol% or more, preferably 3 mol% or more. The upper limit of the ratio p2 is not particularly limited, and is, for example, 60 mol%, and can also be 50 mol%, 40 mol%, 30 mol%, and further can also be 25 mol%. In the case where the ratio p2 is low, the solubility of the polyimide P can be improved, and there is a tendency that the desired manufacturing method in which the separation function layer 1 is easily applied is obtained. Further, in this case, there is also a tendency that the strength of the separation function layer 1 is increased. The ratio p2 is preferably 3 to 25 mol%. In the case where the ratio p2 is in this range, there is a tendency that the separation performance of the separation function layer 1 is good.

[0077] The polyimide P can further include a structural unit B2 from a diamine b2 having a sulfonyl group (-SO2-). The structural unit B2 is a structural unit suitable for increasing the permeation coefficient, the permeation speed of the acid gas permeating the separation function layer 1. The diamine b2 is a compound having a sulfonyl group, and having 2 primary amino groups. The number of the sulfonyl groups in the diamine b2 is not particularly limited, and is, for example, 5 or less, and is preferably 1. The diamine b2 preferably does not include the above-described functional group g or the like having a dissociative proton.

[0078] The diamine b2 preferably includes a ring structure having a sulfonyl group. Typically, the ring structure having a sulfonyl group is a thiophene 1,1-dioxide ring, or a tetrahydrothiophene 1,1-dioxide ring.

[0079] The diamine b2 can have a fused ring, and the fused ring can include a ring structure having a sulfonyl group. The fused ring can also include an aromatic ring together with the ring structure having a sulfonyl group. As the aromatic ring, the aromatic ring described above with respect to the tetracarboxylic dianhydride a1 can be cited.

[0080] In the diamine b2, the substituent of the fused ring preferably includes a primary amino group. The fused ring can have other substituents in addition to the substituent including a primary amino group, and can also not have other substituents. As the other substituents, there is no particular limitation, and a halogen group, a hydrocarbon group, or the like can be cited. As the halogen group and the hydrocarbon group, the halogen group and the hydrocarbon group described above with respect to the tetracarboxylic dianhydride a1 can be cited.

[0081] The diamine b2 is preferably represented by the following formula (c1).

[0082] [Chemical Formula 11] In formula (c1), R 1c ~R6c each independently is a hydrogen atom or an optional substituent. In formula (c1), the optional substituent is, for example, a substituent other than a group containing the above-mentioned functional group g, and specifically a halogen group, a hydrocarbon group, or the like. As the halogen group and the hydrocarbon group, the halogen group and the hydrocarbon group described above with respect to the tetracarboxylic dianhydride al can be mentioned.

[0083] In the polyimide P, the structural unit B2 from the diamine b2 is preferably represented by the following formula (C1). The structural unit B2 represented by formula (C1) is derived from the above-mentioned diamine b2 represented by formula (c1).

[0084] [Chemical Formula 12] In formula (C1), R 1c ~R 6c each independently is a hydrogen atom or an optional substituent. In formula (C1), the optional substituent is, for example, a substituent other than a group containing the above-mentioned functional group f, and specifically a halogen group, a hydrocarbon group, or the like. As the halogen group and the hydrocarbon group, the halogen group and the hydrocarbon group described above with respect to the tetracarboxylic dianhydride al can be mentioned. The structural unit B2 represented by formula (C1) is suitable for improving the rigidity of the polyimide P. According to the polyimide P excellent in rigidity, there is a tendency that the separation function layer 1 is less likely to be plasticized even in a case where the pressure of the mixed gas to be separated is high.

[0085] As the specific examples of the structural unit B2 represented by formula (C1), the following formulae (C1-1) to (C1-2) can be mentioned.

[0086] [Chemical Formula 13] In the polyimide P, the ratio p3 of the amount of substance of the above-mentioned structural unit B2 to the amount of substance of the total structural unit B from the diamine is not particularly limited, and is, for example, 5 mol% or more, and can be 10 mol% or more, 20 mol% or more, 30 mol% or more, and further can be 40 mol% or more. The upper limit of the ratio p3 is not particularly limited, and is, for example, 95 mol%, and can be 90 mol%, 80 mol%, 70 mol%, 60 mol%, and further can be 50 mol%.

[0087] The polyimide P can further contain a structural unit B3 from another diamine b3 other than the diamines bl and b2. The diamine b3 is a compound having 2 primary amino groups without the above-mentioned functional group g, a sulfonyl group. The diamine b3 preferably does not contain a group having a dissociable proton.

[0088] The diamine b3 can also have an aromatic ring. As the aromatic ring, the aromatic rings described above for the tetracarboxylic dianhydride a1 can be given. Among the diamine b3, the substituents of the aromatic ring preferably include a primary amino group. The aromatic ring can have other substituents in addition to the substituents including the primary amino group, or can have no other substituents. As the other substituents, there is no particular limitation, and a halogen group, a hydrocarbon group, or the like can be given. As the halogen group and the hydrocarbon group, the halogen groups and the hydrocarbon groups described above for the tetracarboxylic dianhydride a1 can be given.

[0089] The diamine b3 is preferably represented by the following formula (d1), formula (d2), or formula (d3).

[0090] [Chemical Formula 14] In formula (d1), R 1d ~R 4d are each independently a hydrogen atom or an optional substituent. In formula (d1), the optional substituent is, for example, a substituent other than a group including the functional group g described above and a group including a sulfonyl group, and is specifically a halogen group, a hydrocarbon group, or the like. As the halogen group and the hydrocarbon group, the halogen groups and the hydrocarbon groups described above for the tetracarboxylic dianhydride a1 can be given.

[0091] In formula (d2), R 5d ~R 8d are each independently a hydrogen atom or an optional substituent. In formula (d2), the optional substituent is, for example, a substituent other than a group including the functional group g described above and a group including a sulfonyl group, and is specifically a halogen group, a hydrocarbon group, or the like. As the halogen group and the hydrocarbon group, the halogen groups and the hydrocarbon groups described above for the tetracarboxylic dianhydride a1 can be given.

[0092] In formula (d3), R 9d ~R 16d are each independently a hydrogen atom or an optional substituent, and X 3 is a single bond or an optional linking group. In formula (d3), the optional substituent is, for example, a substituent other than a group including the functional group g described above and a group including a sulfonyl group, and is specifically a halogen group, a hydrocarbon group, or the like. As the halogen group and the hydrocarbon group, the halogen groups and the hydrocarbon groups described above for the tetracarboxylic dianhydride a1 can be given.

[0093] In formula (d3), X 3 is an optional linking group, for example, a divalent hydrocarbon group. As the divalent hydrocarbon group, the divalent hydrocarbon groups described above can be given. In formula (d3), X 3 The divalent hydrocarbon group can also have an aromatic ring. As the aromatic ring, the aromatic rings described above for the tetracarboxylic dianhydride a1 can be given. In formula (d3), X 3 The divalent hydrocarbon group in formula (d3) can also be a fluorene diyl group. In formula (d3), X 3An ether group, an ester group, or the like can also be included in place of or in addition to the divalent hydrocarbon group.

[0094] The structural unit B3 from the diamine b3 is preferably represented by the following formula (D1), formula (D2), or formula (D3). The structural unit B3 represented by formula (D1) is from the diamine b3 represented by formula (d1) described above. The structural unit B3 represented by formula (D2) is from the diamine b3 represented by formula (d2) described above. The structural unit B3 represented by formula (D3) is from the diamine b3 represented by formula (d3) described above.

[0095] [Chemical Formula 15] In formula (D1), R 1d ~R 4d are each independently a hydrogen atom or an optional substituent. In formula (D1), the optional substituent is, for example, a substituent other than a group including the functional group f described above, and is specifically a halogen group, a hydrocarbon group, or the like. As the halogen group and the hydrocarbon group, the halogen group and the hydrocarbon group described above with respect to the tetracarboxylic dianhydride a1 can be given. As a specific example of the structural unit B3 represented by formula (D1), the following formula (D1-1) can be given.

[0096] [Chemical Formula 16] In formula (D2), R 5d ~R 8d are each independently a hydrogen atom or an optional substituent. In formula (D2), the optional substituent is, for example, a substituent other than a group including the functional group f described above, and is specifically a halogen group, a hydrocarbon group, or the like. As the halogen group and the hydrocarbon group, the halogen group and the hydrocarbon group described above with respect to the tetracarboxylic dianhydride a1 can be given. As a specific example of the structural unit B3 represented by formula (D2), the following formula (D2-1) can be given.

[0097] [Chemical Formula 17] In formula (D3), R 9d ~R 16d are each independently a hydrogen atom or an optional substituent, and X 3 is a single bond or an optional linking group. In formula (D3), the optional substituent is, for example, a substituent other than a group including the functional group f described above, and is specifically a halogen group, a hydrocarbon group, or the like. As the halogen group and the hydrocarbon group, the halogen group and the hydrocarbon group described above with respect to the tetracarboxylic dianhydride a1 can be given. In formula (D3), X 3 is a single bond or an optional linking group. In formula (D3), the optional substituent is, for example, a substituent other than a group including the functional group f described above, and is specifically a halogen group, a hydrocarbon group, or the like. As the halogen group and the hydrocarbon group, the halogen group and the hydrocarbon group described above with respect to the tetracarboxylic dianhydride a1 can be given. In formula (D3), X 3An ether group, an ester group, or the like can also be included in place of or in addition to the divalent hydrocarbon group. Specific examples of the structural unit B3 represented by formula (D3) include the following formulae (D3-1) to (D3-3).

[0098] [Chemical Formula 18] The ratio p4 of the amount of substance of the above-described structural unit B3 in the polyimide P with respect to the amount of substance of the total structural unit B from diamines is not particularly limited and is, for example, 5 mol% or more, and can be 10 mol% or more, 20 mol% or more, 30 mol% or more, and further can be 40 mol% or more. The upper limit of the ratio p4 is not particularly limited and is, for example, 95 mol%, and can be 90 mol%, 80 mol%, 70 mol%, 60 mol%, and further can be 50 mol%.

[0099] In the polyimide P, the structural unit A from tetracarboxylic dianhydride and the structural unit B from diamine are arranged alternately. In the polyimide P, as a combination of adjacent structural units A and B, for example, formulae (A1-B1), (A1-B2), (A1-C1), (A1-D1), and the like can be given. Note that in these formulae, R 1a ~R 4a , R 1b ~R 12b , R 1c ~R 6c , and R 1d ~R 4d are the same as the groups described above with respect to formula (A1), formula (B1), formula (B2), formula (C1), and formula (D1).

[0100] [Chemical Formula 19] The weight average molecular weight (Mw) of the polyimide P is, for example, 30,000 or more, preferably 50,000 or more, and more preferably 75,000 or more, from the viewpoint of the mechanical strength of the separation function layer 1. The upper limit of the weight average molecular weight of the polyimide P is not particularly limited and is, for example, 1 million. The weight average molecular weight of the polyimide P can be determined by measuring the molecular weight distribution of the polyimide P using a gel permeation chromatograph (GPC) equipped with a differential refractive index detector (RID), and calculating from the obtained chromatogram using a standard curve obtained from standard polystyrene.

[0101] The content of the polyimide P in the separation function layer 1 is, for example, 50% by weight or more, and can be 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, and further can be 95% by weight or more. The separation function layer 1 can be composed substantially only of the polyimide P.

[0102] The separation function layer 1 can further contain other components in addition to the polyimide P. As the other components, fillers and the like can be given. As the fillers, for example, the fillers exemplified for the intermediate layer 2 described later can be given. In the separation function layer 1, the fillers are preferably dispersed in a matrix containing the polyimide P. The fillers can be spaced apart from each other in the matrix, or can be partially aggregated.

[0103] The thickness of the separation function layer 1 is, for example, 10 μm or less, and can be 8.0 μm or less, 5.0 μm or less, 4.0 μm or less, 3.0 μm or less, and further can be 2.0 μm or less. The thickness of the separation function layer 1 can be 0.05 μm or more, and can be 0.1 μm or more.

[0104] (Intermediate Layer) The intermediate layer 2 is preferably formed of an adhesive composition, particularly an adhesive composition containing an organosilicon-based polymer. The so-called organosilicon-based polymer refers to a polymer having a structural unit containing a siloxane bond. In this specification, the adhesive composition containing the organosilicon-based polymer is sometimes referred to as an "organosilicon-based adhesive".

[0105] As the organosilicon-based adhesive, a peroxide crosslinking type organosilicon-based adhesive, an addition reaction type organosilicon-based adhesive, a living energy ray curable organosilicon-based adhesive, and the like can be given. The peroxide crosslinking type organosilicon-based adhesive contains an organic peroxide (for example, benzoyl peroxide and the like). Crosslinking by radicals is generated by the organic peroxide. As the addition reaction type organosilicon-based adhesive, a hydrosilylation type organosilicon-based adhesive and the like can be given. The hydrosilylation type organosilicon-based adhesive contains a siloxane crosslinking agent containing an SiH group, and a platinum-based catalyst. Crosslinking is generated by a hydrosilylation reaction using the platinum-based catalyst. The living energy ray curable organosilicon-based adhesive is subjected to a crosslinking reaction by light such as ultraviolet rays, electron beams, and the like. In particular, the addition reaction type organosilicon-based adhesive, for example, the hydrosilylation type organosilicon-based adhesive is preferable in terms of not easily leaving residues in the intermediate layer 2, in terms of being able to react at low temperature, and in terms of the reaction speed.

[0106] The organosilicon-based adhesive preferably contains an organosilicon resin component and a silicone rubber component as the organosilicon-based polymer in terms of easy control of adhesiveness, peelability, and aggregability.

[0107] The silicone resin component is not particularly limited, and is preferably a branched-chain polyorganosiloxane containing a hydroxyl group bonded to a silicon atom in the molecule, and more preferably a polyorganosiloxane having at least one unit selected from the group consisting of an M unit (R3SiO 1 / 2 ), a Q unit (SiO2), a T unit (RSiO 3 / 2 ), and a D unit (R2SiO). In the above units, R is independently a monovalent hydrocarbon group or a hydroxyl group. As the monovalent hydrocarbon group, an alkyl group (e.g., methyl, ethyl, propyl, etc.), an alkenyl group (e.g., vinyl, etc.), and an aryl group (e.g., phenyl, etc.) can be mentioned. In particular, the silicone resin component is preferably an MQ resin composed of an M unit (R3SiO 1 / 2 ) and a Q unit (SiO2). The silicone resin component can be used alone or in combination of two or more.

[0108] The silicone rubber component is not particularly limited, and is preferably a straight-chain polyorganosiloxane represented by the following formula (2).

[0109] [Chemical Formula 20] In formula (2), R is independently a methyl group, a phenyl group, or an alkenyl group. n is 100 to 10,000. The silicone rubber component can be used alone or in combination of two or more.

[0110] In the peroxide crosslinking type silicone-based adhesive, the above silicone rubber component preferably contains a methyl group. In the peroxide crosslinking type silicone-based adhesive, the methyl group of the silicone rubber component can be crosslinked by a radical reaction. In the hydrosilylation type silicone-based adhesive, the above silicone rubber component preferably contains an alkenyl group, particularly a vinyl group. In the hydrosilylation type silicone-based adhesive, the alkenyl group of the silicone rubber component can be crosslinked by a hydrosilylation reaction.

[0111] The adhesive composition (silicone-based adhesive) can contain an additive other than the silicone resin component and the silicone rubber component. As the additive, for example, a material for allowing a crosslinking reaction to proceed (an organic peroxide, a siloxane crosslinking agent containing an SiH group, a platinum-based catalyst, etc.), an adhesion improver (e.g., X-92-185 manufactured by Shin-Etsu Chemical Co., Ltd.), a silane coupling agent, a filler, a plasticizer, an anti-aging agent, an antistatic agent, a colorant (a pigment, a dye), a filler described later, etc. can be mentioned. The additive can be used alone or in combination of two or more.

[0112] The adhesive composition (silicone-based adhesive) can further contain an organic solvent (e.g., toluene, xylene, etc.).

[0113] As specific examples of the adhesive composition (silicone-based adhesive), "KR-3700", "KR-3701", "KR-3704", and the like manufactured by Shin-Etsu Chemical Co., Ltd. can be given. These commercial products are provided as a product in a form in which both a silicone rubber component and a silicone resin component are contained. The silicone-based adhesive can also contain a mixture of these commercial products.

[0114] As described above, the intermediate layer 2 is preferably formed of an adhesive composition, particularly an adhesive composition containing a silicone-based polymer (silicone-based adhesive). The intermediate layer 2 formed of the silicone-based adhesive preferably contains a crosslinked product of the silicone-based polymer. The content ratio of the crosslinked product of the silicone-based polymer in the intermediate layer 2 is not particularly limited, and is, for example, 60% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more. The intermediate layer 2 can also be substantially composed of the crosslinked product of the silicone-based polymer.

[0115] The intermediate layer 2 can further contain the above-described additive, particularly a filler. The intermediate layer 2 containing the filler is suitable for increasing the permeation speed of the acid gas in the separation membrane 10. The filler can contain an inorganic material, or can contain an organic material. As the inorganic material contained in the filler, zeolite, silica, titanium oxide, alumina, and the like can be given. As the organic material, a (meth)acrylic polymer and the like can be given. In the present specification, the "(meth)acrylic polymer" refers to an acrylic polymer and / or a methacrylic polymer.

[0116] The filler can contain a metal-organic framework (MOF). The metal-organic framework is also referred to as a porous coordination polymer (PCP). The metal-organic framework preferably contains a metal ion and an organic ligand. As the metal ion, a Cu ion, a Zn ion, and the like can be given. The organic ligand preferably contains an aromatic ring. As the aromatic ring contained in the organic ligand, a benzene ring, an imidazole ring, and the like can be given. As the organic ligand, trimesic acid, 2-methylimidazole, and the like can be given. As specific examples of the metal-organic framework, HKUST-1, ZIF-8, and the like can be given.

[0117] Typically, the shape of the filler is particulate. In the present specification, the particulate includes a spherical shape, an ellipsoidal shape, a flaky shape, a fibrous shape, and the like.

[0118] The average particle diameter of the filler is not particularly limited, and is, for example, 5 μm or less, and can also be 1 μm or less, 800 nm or less, 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, and further, 100 nm or less. The lower limit of the average particle diameter of the filler is, for example, 1 nm. The average particle diameter of the filler can be determined using the following method. First, the cross section of the intermediate layer 2 is observed using a transmission electron microscope. In the obtained electron microscope image, the area of a specific filler is calculated by image processing. The diameter of a circle having the same area as the calculated area is regarded as the particle diameter (the diameter of the particle) of the specific filler. The particle diameters of an arbitrary number (at least 50) of fillers are calculated, and the average of the calculated values is regarded as the average particle diameter of the filler.

[0119] From the viewpoint of suppressing the increase in the storage elastic modulus of the intermediate layer 2, the content of the filler in the intermediate layer 2 is, for example, 40 wt% or less, and can also be 30 wt% or less, 20 wt% or less, and further, 10 wt% or less. The lower limit of the content of the filler in the intermediate layer 2 is not particularly limited, and is, for example, 1 wt% from the viewpoint of improving the permeation speed of the acid gas.

[0120] The intermediate layer 2 formed from the adhesive composition has a tendency to have a low storage elastic modulus. As one example, the storage elastic modulus of the intermediate layer 2 at 25°C is, for example, 1.0 x 10 5 Pa or less, preferably 0.95 x 10 5 Pa or less, and can also be 0.90 x 10 5 Pa or less, and can also be 0.85 x 10 5 Pa or less. There is a tendency that the lower the storage elastic modulus of the intermediate layer 2, the greater the adhesive strength of the intermediate layer 2 to the porous support 3. The storage elastic modulus of the intermediate layer 2 at 25°C is preferably 0.1 x 10 5 Pa or more.

[0121] The storage elastic modulus of the intermediate layer 2 at 25°C can be determined using the following method. First, a sample for measurement is prepared from the material that constitutes the intermediate layer 2. The sample for measurement is in the shape of a disc. The diameter of the bottom surface of the sample for measurement is 8 mm, and the thickness is 2 mm. The sample for measurement can also be a sample obtained by punching a laminate in which a plurality of intermediate layers 2 are stacked into a disc shape. Next, dynamic viscoelasticity measurement is performed on the sample for measurement. In the dynamic viscoelasticity measurement, an "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific, Inc. can be used. From the results of the dynamic viscoelasticity measurement, the storage elastic modulus of the intermediate layer 2 at 25°C can be determined. Note that the conditions for the dynamic viscoelasticity measurement are as described below.

[0122] • Measurement conditions Frequency: 1 Hz Deformation mode: Torsion Measurement temperature: -70°C to 150°C Temperature increase rate: 5°C / min The thickness of the intermediate layer 2 is, for example, 10 μm or less, and can be 8.0 μm or less, 5.0 μm or less, 4.0 μm or less, 3.0 μm or less, and further, 2.0 μm or less. The thickness of the intermediate layer 2 can be 0.05 μm or more, and can be 0.1 μm or more, and further, 0.5 μm or more.

[0123] (Porous support) In the present embodiment, the porous support 3 preferably has only a main body portion and does not have a microporous layer made of a polymer or the like. The porous support 3 can be composed of only a single material. The porous support 3 is preferably a fibrous structure such as a fabric, a nonwoven fabric, a net, a mesh, or the like, and is typically a nonwoven fabric. As the fiber included in the fibrous structure, for example, natural fibers such as wood pulp, cotton, hemp (e.g., manila hemp), and the like; and chemical fibers (synthetic fibers) such as polyester fibers, polyphenylene sulfide (PPS) fibers, rayon, vinylon, acetate fibers, polyvinyl alcohol (PVA) fibers, polyamide fibers, polyolefin fibers, polyurethane fibers, and the like can be given. As the porous support 3, a nonwoven fabric composed of polyester fibers such as polyethylene terephthalate (PET) fibers, and a nonwoven fabric composed of PPS fibers are preferable. In the present embodiment, the intermediate layer 2 preferably directly contacts the fibrous structure (in detail, a nonwoven fabric).

[0124] Viewed from another aspect, the present application provides a separation membrane 10 that includes: a separation function layer 1, a porous support 3 that supports the separation function layer 1, and An intermediate layer 2 is disposed between the separation functional layer 1 and the porous support 3 and is in direct contact with the porous support 3; The porous support 3 is a fiber structure.

[0125] As described above, in this embodiment, the porous support 3 does not have, for example, a microporous layer, and tends to have a small thickness. The thickness of the porous support 3 is, for example, 200 μm or less, but may also be 150 μm or less, 125 μm or less, 110 μm or less, 100 μm or less, 80 μm or less, and further may be 60 μm or less. The lower limit of the thickness of the porous support 3 is, for example, 10 μm or more, but may also be 30 μm or more, and further may be 50 μm or more.

[0126] In this embodiment, regarding the porous support 3, since the surface area ratio Smr(c1) of the surface S1 is low, it tends to have high air permeability when used alone. As an example, the ISO air permeability of the porous support 3 is, for example, 5.0 × 10⁻⁶. 4 μm / (Pa·s) or higher, or 10.0×10 4 μm / (Pa·s) or higher, 20.0×10 4 μm / (Pa·s) or higher, 30.0×10 4 μm / (Pa·s) or higher, 40.0×10 4 μm / (Pa·s) or higher, 50.0×10 4 μm / (Pa·s) or higher, 70.0×10 4 μm / (Pa·s) or higher, and thus can be 100.0 × 10 4 μm / (Pa·s) or higher. The upper limit of the ISO permeability of the porous support 3 is not particularly limited, for example, it is 1000.0 × 10⁻⁶. 4 The ISO permeability of the porous support 3 can be determined according to the Oken-type tester method specified in JIS P8117:2009.

[0127] In this embodiment, the intermediate layer 2 and the porous support 3 are preferably bonded with sufficient strength. As an example, the peel strength between the intermediate layer 2 and the porous support 3 is, for example, 0.25 N / 25 mm or more, and may also be 0.50 N / 25 mm or more, 0.75 N / 25 mm or more, 1.00 N / 25 mm or more, 1.25 N / 25 mm or more, 1.50 N / 25 mm or more, 1.75 N / 25 mm or more, and may even be 2.00 N / 25 mm or more. There is no particular upper limit to this peel strength; for example, it may be 10.0 N / 25 mm or less.

[0128] The peeling strength of the intermediate layer 2 from the porous support 3 can be measured by the following method. First, the intermediate layer 2 is formed on an evaluation sheet (DIAFOIL T100-50, manufactured by Mitsubishi Rayon Co., Ltd., thickness: 50 μm). The intermediate layer 2 can be formed by the method described later. Next, the entire surface of the intermediate layer 2 is laminated to the porous support 3, and a 2-kg roller is passed over the laminate once to press them together. Thus, a laminate having the evaluation sheet, the intermediate layer 2, and the porous support 3 in this order is formed. The laminate is cut into a test piece having a width of 25 mm and a length of 100 mm. Next, the entire surface of the porous support 3 provided on the test piece is laminated to a polyethylene terephthalate film by means of a double-sided adhesive tape (No. 500, manufactured by Nitto Electric Industrial Co., Ltd.), and a 2-kg roller is passed over the laminate once to press them together. Next, using a commercially available tensile testing machine, the porous support 3 is peeled from the intermediate layer 2 together with the film under conditions of a peeling angle of 180° and a peeling speed of 100 mm / min. The peeling force at this time can be regarded as the peeling strength of the intermediate layer 2 from the porous support 3. Note that the measurement is performed in an atmosphere at 23°C.

[0129] (Method for producing separation membrane) The separation membrane 10 of the present embodiment can be produced by the following method. First, a coating solution containing a material of the separation function layer 1 is applied to a substrate, and dried, thereby forming the separation function layer 1.

[0130] In one preferred mode, the coating solution contains a polyimide Q having at least one functional group g selected from the group consisting of a carboxyl group, a hydroxyl group, and a thiol group, and a compound M having a metal. In this mode, the polyimide Q is a precursor of the polyimide P, and the polyimide P can be formed from the polyimide Q by exchanging a proton dissociable from the functional group g with a metal cation. As described later, according to this coating solution, the polyimide P having a metal salt as the functional group f can be formed.

[0131] The polyimide Q can be produced by the following method. First, a diamine group containing the above-described diamine b1 is dissolved in a solvent to obtain a solution. As the solvent, for example, a polar organic solvent such as N-methyl-2-pyrrolidone, 1,3-dioxolane, or the like can be used.

[0132] Next, a tetracarboxylic dianhydride group containing the above-described tetracarboxylic dianhydride a1 is slowly added to the obtained solution. Thus, the monomer group containing the tetracarboxylic dianhydride a1 and the diamine b1 is reacted to form a polyamic acid. The addition of the tetracarboxylic dianhydride group is preferably performed under heating at 140°C or higher for 3 to 20 hours under stirring.

[0133] Next, the polyamic acid is imidized to obtain polyimide Q. Examples of imidization methods include chemical imidization and thermal imidization. Chemical imidization involves imidizing the polyamic acid using a dehydrating condensing agent at, for example, room temperature. Examples of dehydrating condensing agents include acetic anhydride, pyridine, and triethylamine. Thermal imidization involves imidizing the polyamic acid by heat treatment. The heat treatment temperature is, for example, 180°C or higher.

[0134] The content of polyimide Q in the coating solution can be appropriately adjusted according to the solubility of polyimide Q, for example, from 1 wt% to 30 wt%. The weight ratio of polyimide Q to the total weight of polyimide Q and solvent in the coating solution is, for example, from 1 wt% to 30 wt%.

[0135] Examples of metals present in compound M include those described above concerning metals contained in metal salts as functional group f. In compound M, the metal preferably exists as a cation. Examples of compounds M include, for instance, metal complexes having a metal and ligands coordinated to that metal, and inorganic salts containing a metal. Compound M preferably contains a metal complex.

[0136] In metal complexes, the ligands are preferably volatile. As an example, the boiling point of the ligand can be between 20°C and 260°C at atmospheric pressure (101.325 kPa). Volatile ligands readily evaporate during the drying of the coating film (described later) and are unlikely to remain in the separation functional layer 1. It should be noted that the ligands may also be non-volatile. In this case, a washing operation can be performed after the formation of the separation functional layer 1, thereby easily removing the ligands from the separation functional layer 1.

[0137] In metal complexes, the ligand is typically an organic ligand having functional groups for coordination with a metal. The number of carbon atoms in the organic ligand is not particularly limited, and is, for example, 1 to 10. Examples of functional groups included in the organic ligand include, for example, carbonyl groups such as ketone groups. The number of functional groups included in the organic ligand is, for example, 1 or more, and may also be 2 or more. Specific examples of organic ligands include acetylacetone (acac). Specific examples of metal complexes include Al(acac)3, Fe(acac)2, Ga(acac)3, Mg(acac)2, etc.

[0138] As the inorganic salt, there can be mentioned chloride, nitrate, sulfate, etc., and specifically, there can be mentioned LiCl, NaCl, KCl, AgNO3, MgCl2, CaCl2, BaCl2, NiCl2, ZnCl2, CuCl2, Pb(NO3)2, Al(NO3)3, Fe2(SO4)3, Ga(NO3)3, Fe(NO3)2, Mg(NO3)2, etc.

[0139] The ratio of the weight of the compound M to the weight of the polyimide Q in the coating liquid can be appropriately adjusted depending on the composition of the polyimide Q, etc., and is, for example, 1 to 20% by weight, and can also be 1 to 10% by weight. The ratio of the amount of substance of the compound M to the amount of substance of the functional group g contained in the polyimide Q in the coating liquid is not particularly limited, and is, for example, 2.0 or more.

[0140] In the case where the coating liquid contains the metal complex as the compound M, the coating liquid can further contain a ligand. The ratio of the weight of the ligand to the weight of the polyimide Q in the coating liquid can be appropriately adjusted depending on the content of the polyimide Q, the metal complex, etc., and is, for example, 1 to 20% by weight, and can also be 1 to 10% by weight.

[0141] The coating liquid preferably further contains a solvent. Typically, the solvent is a good solvent capable of dissolving the polyimide Q. The solvent preferably contains at least one selected from the group consisting of an amide compound and a lactone compound, and more preferably contains an amide compound. As the amide compound, there can be mentioned, for example, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), etc. As the lactone compound, there can be mentioned, for example, γ-butyrolactone, etc.

[0142] The content of the solvent in the coating liquid is, for example, 30% by weight to 95% by weight. The ratio of the weight of the solvent to the total weight of the polyimide Q and the solvent in the coating liquid is, for example, 30% by weight to 95% by weight.

[0143] Note that the coating liquid is not limited to the coating liquid of the above composition. In another preferred mode, the coating liquid contains the polyimide P instead of the polyimide Q and the compound M described above. In this mode, the polyimide P preferably has at least one functional group f selected from the group consisting of a carboxyl group, a hydroxyl group, a thiol group, and metal salts thereof.

[0144] Typically, the base material is a release liner. As the base material, for example, a film containing a resin; paper; a sheet containing a metal material such as aluminum, stainless steel, or the like can be given. The sheet containing a metal material tends to have high heat resistance. From the viewpoint of excellent surface smoothness, the base material is preferably a film containing a resin. Among the base materials, as the polymer contained in the resin, polyethylene, polypropylene, polybutylene, polybutadiene, polymethylpentene, and the like polyolefins; polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and the like polyesters; polyvinyl chloride, a chlorovinyl copolymer; polyurethane; ethylene-vinyl acetate copolymer; polyimide, and the like can be given, and polyimide is preferable.

[0145] The surface of the base material can be subjected to a release treatment. The release treatment can be performed by imparting a release treatment agent to the surface of the base material. As the release treatment agent, a silicone-based release treatment agent, a long-chain alkyl-based release treatment agent, a fluorine release treatment agent, a molybdenum sulfide-based release treatment agent, and the like can be given. The release treatment agent can be used alone or in combination with two or more. The base material is preferably a film made of polyimide subjected to a release treatment.

[0146] The thickness of the base material is not particularly limited, and is, for example, 5 to 100 μm, and preferably 10 to 50 μm.

[0147] Note that, before the coating liquid is coated, the base material can be subjected to a surface modification treatment. In the case where the base material is subjected to a release treatment, the surface modification treatment can also be performed on the surface of the base material subjected to the release treatment. As the surface modification treatment, a corona treatment, a plasma treatment, an excimer treatment, a flame treatment, and the like can be given, and a corona treatment is preferable.

[0148] The surface modification treatment can be performed by irradiating active energy rays to the surface of the base material. Specific examples of the active energy rays are electron rays, ion rays, plasma rays, ultraviolet rays, and the like. In the case where a corona treatment is performed as the surface modification treatment, the discharge amount is, for example, 0.1 kW·min / m 2 The upper limit of the discharge amount is not particularly limited, and is, for example, 10 kW·min / m 2 .

[0149] The method of coating the coating liquid to the base material is not particularly limited, and, for example, a spin coating method, a dip coating method, a slot die coating method, and the like can be used. The coating liquid can also be coated to the base material using an applicator, a wire bar, or the like. The coating liquid can also be coated to the surface of the base material subjected to a release treatment, a surface modification treatment, or the like.

[0150] The coating film can be formed by coating the coating liquid to the base material. The thickness of the coating film can be appropriately adjusted depending on the thickness of the separation function layer 1 targeted, and is, for example, 1 μm to 100 μm.

[0151] In the present embodiment, the separation function layer 1 can be obtained by drying the coating film. The drying conditions of the coating film are not particularly limited, and for example, the drying temperature is from 50°C to 200°C, and the drying time is from 1 minute to 10 hours. The drying of the coating film can be performed using a heater or the like. As one example, the coating film can be passed through a heating section provided with a heater to thereby perform the drying. The drying of the coating film can also be performed by passing the coating film through a plurality of heating sections. The set temperatures of the plurality of heating sections can be the same as or different from each other.

[0152] In the case where the coating liquid contains the polyimide Q having the functional group g and the compound M having a metal, when the coating film is dried, the dissociative proton included in the functional group g of the polyimide Q exchanges with the metal (metal cation) of the compound M. In particular, in the case where the compound M is a metal complex and the ligand included in the metal complex is volatile, since the ligand volatilizes at the time of drying, there is a tendency to promote the exchange of the dissociative proton of the functional group g with the metal of the compound M. By the exchange of the dissociative proton of the functional group g with the metal of the compound M, a metal salt of the functional group g is formed, and a polyimide P is formed from the polyimide Q. In the separation function layer 1 obtained by this method, the plurality of molecules of the polyimide P are generally crosslinked to each other via the metal cation. Due to this crosslinked structure, there is a tendency that the separation function layer 1 has high solvent resistance.

[0153] Note that the exchange of the dissociative proton included in the functional group g of the polyimide Q with the metal of the compound M can also be performed after the formation of the separation function layer 1. For example, a coating liquid containing the above-described polyimide Q and a solvent is applied to a substrate, and is dried to thereby form the separation function layer 1. The separation function layer 1 can be immersed in a solution containing the above-described compound M to thereby exchange the dissociative proton of the functional group g with the metal of the compound M. The solution containing the compound M is preferably an aqueous solution containing the above-described inorganic salt. The concentration of the inorganic salt in the aqueous solution is not particularly limited, and is, for example, from 0.01 to 1 mol / L. The conditions of the operation of immersing the separation function layer 1 in the solution containing the compound M are not particularly limited, and can be performed at room temperature for 1 to 48 hours. The separation function layer 1 after the immersion in the above-described solution can also be further subjected to a water-based washing treatment and a drying treatment. The drying treatment can be performed at a temperature of 150°C or lower for 1 to 24 hours.

[0154] The method of forming the separation function layer 1 is not limited to the above-described method. The separation function layer 1 can also be formed by applying a coating liquid containing the above-described polyimide P and a solvent to a substrate and performing drying. In addition, the separation function layer 1 can also be produced by applying a coating liquid containing a precursor of the polyimide P, that is, a polyamic acid, to a substrate, and forming the polyimide P by imidizing the polyamic acid.

[0155] For the produced separation functional layer 1, further heat treatment (annealing treatment) can be performed. By this treatment, the separation performance of the separation functional layer 1 is improved, and the tendency of the separation performance of the separation functional layer 1 to decrease over time is also suppressed. By this treatment, the separation functional layer 1 which is almost free from residual solvent can also be obtained by sufficiently volatilizing the solvent.

[0156] The temperature of the heat treatment is, for example, higher than 200°C, and can be 230°C or higher, and further can be 250°C or higher. The upper limit of the temperature of the heat treatment is not particularly limited, and is, for example, 350°C or lower, and can be 300°C or lower. The time of the heat treatment is, for example, 1 minute or more, and can be 10 minutes or more, and can be 30 minutes or more. The upper limit of the time of the heat treatment is not particularly limited, and is, for example, 24 hours or less.

[0157] Next, a coating liquid containing the material of the intermediate layer 2 is applied to the separation functional layer 1, and further dried, thereby forming the intermediate layer 2. Typically, the coating liquid containing the material of the intermediate layer 2 is the above-described adhesive composition. As the application method of the coating liquid, the above-described methods described above for the separation functional layer 1 can be cited. By applying the coating liquid to the separation functional layer 1, a coating film is formed. By drying the coating film, the intermediate layer 2 is formed. The drying of the coating film can be performed under a heating condition. As one example, in the case where the coating liquid is an addition reaction type silicone-based adhesive, the coating film can be heated at 100 to 130°C to dry it. It is preferable that the cross-linking reaction of the silicone-based polymer is performed at the same time as the drying of the coating film by using the above-described heating condition, thereby forming a cross-linked product of the silicone-based polymer. The heating time of the coating film is, for example, 1 minute or more, and can be 5 minutes or more. By drying the coating film, a laminate having a substrate, a separation functional layer 1, and an intermediate layer 2 in this order can be obtained. In this laminate, the intermediate layer 2 is exposed to the outside of the laminate.

[0158] Next, the intermediate layer 2 of the above-described laminate is attached to the porous support 3. The method of attaching the intermediate layer 2 to the porous support 3 is not particularly limited, and known methods can be used. For example, the intermediate layer 2 and the porous support 3 can be laminated, and a roller can be reciprocated to press them, thereby attaching the intermediate layer 2 to the porous support 3. By removing the substrate from the obtained laminate, a separation membrane 10 can be obtained.

[0159] In the past, a separation membrane has been produced by forming an intermediate layer by applying a coating solution containing a material for the intermediate layer to a porous support, and further forming a separation functional layer on the intermediate layer (for example, Patent Document 1). In this method, in order to suppress the penetration of the coating solution into the inside of the porous support, the pore diameter of the pores on the surface of the porous support on the intermediate layer side must be small. Therefore, in this method, a porous support obtained by laminating a microporous layer on the surface of a nonwoven fabric is generally used. However, in this porous support, the thickness is large by the amount of the microporous layer provided.

[0160] According to the research by the present inventors, if a transfer method of transferring the separation functional layer and the intermediate layer to a porous support is employed, it is not necessary to adjust the pore diameter of the pores on the surface of the porous support on the intermediate layer side to be small, and it is not necessary to use a porous support having a microporous layer. In the present embodiment, by using a porous support 3 not having a microporous layer, it is possible to adjust the thickness (total film thickness) of the separation membrane 10 to be small. If a separation membrane 10 having a small thickness is employed, it is possible to easily increase the membrane area of the separation membrane 10 that can be mounted in a membrane separation device (particularly, a spiral-type membrane element). Thus, it can be said that the separation membrane 10 of the present embodiment is suitable for a membrane separation device (particularly, a spiral-type membrane element). In addition, by using a porous support 3 not having a microporous layer, there is also a tendency that the separation membrane 10 can be produced at a low cost.

[0161] (Shape of separation membrane) In the present embodiment, typically, the separation membrane 10 is a flat membrane. However, the separation membrane 10 can also be in a shape other than a flat membrane, and can also be a hollow fiber membrane.

[0162] In the present embodiment, there is a tendency that the thickness of the porous support 3 is small, and the thickness of the separation membrane 10 is also small. The thickness of the separation membrane 10 is, for example, 135 μm or less, and can also be 130 μm or less, 120 μm or less, 110 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, and further, 70 μm or less. The lower limit of the thickness of the separation membrane 10 is, for example, 20 μm or more, and can also be 30 μm or more, 40 μm or more, and further, 50 μm or more.

[0163] (Properties of separation membrane) The separation membrane 10 has a tendency that the pressure resistance is high due to the presence of the porous support 3. As one example, the maintenance rate of the separation coefficient a of the separation membrane 10 when the separation membrane 10 is contacted with nitrogen having a pressure of 2.0 MPa for 5 minutes is 70% or more. Here, the separation coefficient a refers to the permeation speed T of carbon dioxide permeated through the separation membrane 10 when carbon dioxide having a pressure of 0.6 MPa is supplied to the space adjacent to one face of the separation membrane 10. CO2(GPU) relative to the permeation rate T of nitrogen through the separation membrane 10 when nitrogen at a pressure of 0.6 MPa is supplied to the space N2 (GPU) ratio T CO2 / T N2 .

[0164] According to the present inventors, a separation membrane having a thickness of 130 μm or less and a retention rate of the separation factor α of 70% or more has not been known.

[0165] Viewed from another aspect, the present application provides a separation membrane 10 having: a separation function layer 1, a porous support 3 that supports the separation function layer 1, and an intermediate layer 2 disposed between the separation function layer 1 and the porous support 3, the thickness of the separation membrane 10 is 130 μm or less, the retention rate of the separation factor α of the separation membrane 10 when the separation membrane 10 is contacted with nitrogen at a pressure of 2.0 MPa for 5 minutes is 70% or more.

[0166] In detail, the retention rate of the separation factor α can be determined using the following method. First, a test piece is produced by laminating the separation membrane 10 in an initial state to a permeation spacer (#1000 manufactured by KB SEIREN). In the test piece, the permeation spacer is positioned on the porous support 3 side of the separation membrane 10. The test piece is set in a cell and sealed with an O-ring in a manner that does not leak. Next, nitrogen is injected into the cell in a manner that the nitrogen contacts one main surface (the main surface 11 on the separation function layer side) of the separation membrane 10. The temperature of the nitrogen is 30°C and the pressure is 0.6 MPa. As a result, a permeation fluid (nitrogen) that has permeated the separation membrane 10 can be obtained from the other main surface (the main surface 12 on the porous support side) of the separation membrane 10. The flow rate of the permeation fluid is measured using a mass flow meter, and the permeation rate T N2 (GPU) of nitrogen in the initial state is determined from the obtained results.

[0167] Next, carbon dioxide is injected into the cell in a manner that the carbon dioxide contacts the above-mentioned main surface 11. The temperature of the carbon dioxide is 30°C and the pressure is 0.6 MPa. As a result, a permeation fluid (carbon dioxide) that has permeated the separation membrane 10 can be obtained from the above-mentioned main surface 12. The flow rate of the permeation fluid is measured using a mass flow meter, and the permeation rate T CO2 (GPU) of carbon dioxide in the initial state is determined from the obtained results. CO2 (GPU) relative to the permeation rate T N2 (GPU) ratio T CO2 / T N2 Separation coefficient a1 in the initial state.

[0168] Next, a pressurization test was performed on the separation membrane 10. Specifically, nitrogen was injected into the metal tank so as to contact the main surface 11 with the nitrogen. In the pressurization test, the temperature of the nitrogen was 30°C, and the pressure was 2.0 MPa. The separation membrane 10 was contacted with the nitrogen at a pressure of 2.0 MPa for 5 minutes by the pressurization test. The permeation rate T N2 (GPU) and the permeation rate T CO2 (GPU) were determined by the same method as described above. The ratio T CO2 (GPU) of the permeation rate T N2 (GPU) after the pressurization test to the permeation rate T CO2 / T N2 Separation coefficient a2 after the pressurization test.

[0169] Next, the ratio a2 / a1 of the separation coefficient a2 after the pressurization test to the separation coefficient a1 in the initial state was calculated. The calculated value obtained can be regarded as the maintenance rate of the separation coefficient a.

[0170] The maintenance rate of the separation coefficient a is preferably 80% or more, and can be 85% or more, 90% or more, 95% or more, and further can be 98% or more. The upper limit of the maintenance rate of the separation coefficient a is, for example, 120% or less, and can be 115% or less, 110% or less, and further can be 100% or less.

[0171] Note that the permeation rate T CO2 For example, 10 GPU or more, 20 GPU or more, 30 GPU or more, 40 GPU or more, 50 GPU or more, 60 GPU or more, and further 70 GPU or more. The higher the upper limit of the permeation rate T CO2 in the initial state is, the more preferable it is, and thus is not particularly limited, and can be set to, for example, 2000 GPU or less. In addition, the permeation rate T N2 For example, 50 GPU or less, and can be less than 10 GPU. GPU means 10 -6 cmHg. 3 (STP) / (sec cm 2 cmHg). cmHg means 1 cm of mercury. 3 (STP) means the volume of carbon dioxide at 1 atm and 0°C.

[0172] The separation coefficient a1 in the initial state (ratio T CO2 / T N2For example, it can be 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, and further, 18 or more. The upper limit of the separation factor a1 is, for example, 100 or less, and can be 50 or less.

[0173] The permeation rate T of carbon dioxide after the pressure test CO2 For example, it can be 10 GPU or more, 20 GPU or more, 30 GPU or more, 40 GPU or more, 50 GPU or more, 60 GPU or more, and further, 70 GPU or more. The higher the upper limit of the permeation rate T after the pressure test CO2 , the more preferable it is, and thus is not particularly limited, and can be set to 2000 GPU or less, for example. In addition, the permeation rate T of nitrogen after the pressure test N2 For example, it can be 50 GPU or less, and can be less than 10 GPU.

[0174] The separation factor a2 after the pressure test CO2 (T N2 / T MD ) is, for example, 10 or more, 12 or more, 14 or more, 15 or more, 17 or more, and further, 20 or more. The upper limit of the separation factor a2 is, for example, 100 or less, and can be 50 or less.

[0175] The separation membrane 10 has a tendency to have a large tensile strength due to the presence of the porous support 3. The separation membrane 10 having a large tensile strength has a tendency to have a high maintenance rate of the separation factor a. As one example, the tensile strength Y MD of the separation membrane 10 in the MD direction (the traveling direction in the manufacturing process of the porous support 3) is, for example, 5.0 N / 50 mm or more, 10 N / 50 mm or more, 20 N / 50 mm or more, 30 N / 50 mm or more, 50 N / 50 mm or more, 80 N / 50 mm or more, 100 N / 50 mm or more, and further, 150 N / 50 mm or more. The upper limit of the tensile strength Y MD is, for example, 500 N / 50 mm or less.

[0176] In addition, the tensile strength Y CD of the separation membrane 10 in the CD direction (the direction orthogonal to the MD direction) is, for example, 5.0 N / 50 mm or more, 10 N / 50 mm or more, 20 N / 50 mm or more, and further, 50 N / 50 mm or more. The upper limit of the tensile strength Y CD is, for example, 500 N / 50 mm or less.

[0177] The tensile strength Y MDThe following method can be used for the measurement. First, for the separation membrane 10, cut out as a test piece in such a manner that the length in the MD direction becomes 70 mm and the length in the CD direction becomes 70 mm. Set the test piece on a tensile tester in such a manner that 2 chucks are arranged in the MD direction of the test piece. The maximum stress at the time of a tensile test under conditions in which the distance between the chucks is 50 mm and the tensile speed is 100 mm / min can be regarded as the tensile strength Y MD . For the tensile strength Y CD , in addition to setting the test piece on a tensile tester in such a manner that 2 chucks are arranged in the CD direction of the test piece, the measurement can be performed by the same method as the tensile strength Y MD .

[0178] (Use of Separation Membrane) As the use of the separation membrane 10 of the present embodiment, a use for separating an acid gas from a mixed gas containing the acid gas can be given. As the acid gas of the mixed gas, carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxide (SOx), hydrogen cyanide, nitrogen oxide (NOx), and the like can be given, and carbon dioxide is preferred. The mixed gas contains other gas than the acid gas. As the other gas, for example, nonpolar gas such as hydrogen, nitrogen, and methane, and nonreactive gas such as helium can be given, and nitrogen, methane, and the like are preferred. The separation membrane 10 of the present embodiment is particularly suitable for a use for separating carbon dioxide from a mixed gas containing carbon dioxide and nitrogen. However, the use of the separation membrane 10 is not limited to the use for separating the acid gas from the above-described mixed gas.

[0179] <Embodiment of Membrane Separation Device> As shown in Figure 3 , the membrane separation device 100 of the present embodiment is provided with the separation membrane 10 and the tank 20. The tank 20 is provided with the 1st chamber 21 and the 2nd chamber 22. The separation membrane 10 is disposed inside the tank 20. Inside the tank 20, the separation membrane 10 separates the 1st chamber 21 and the 2nd chamber 22. The separation membrane 10 extends from one of a pair of wall surfaces of the tank 20 to the other.

[0180] The 1st chamber 21 has an inlet 21a and an outlet 21b. The 2nd chamber 22 has an outlet 22a. Each of the inlet 21a, the outlet 21b, and the outlet 22a is preferably an opening formed in a wall surface of the tank 20.

[0181] The membrane separation using the membrane separation apparatus 100 is performed by the following method. First, the mixed gas 30 containing the acid gas is supplied to the first chamber 21 via the inlet 21a. The concentration of the acid gas in the mixed gas 30 is not particularly limited, and is, for example, 0.01 vol% (100 ppm) or more, preferably 1 vol% or more, more preferably 10 vol% or more, further preferably 30 vol% or more, and particularly preferably 50 vol% or more, under a standard state. The upper limit of the concentration of the acid gas in the mixed gas 30 is not particularly limited, and is, for example, 90 vol% under a standard state.

[0182] The pressure in the first chamber 21 can also be increased by the supply of the mixed gas 30. The membrane separation apparatus 100 can further include a pump (not shown) for increasing the pressure of the mixed gas 30. The pressure of the mixed gas 30 supplied into the first chamber 21 is, for example, 0.1 MPa or more, and preferably 0.3 MPa or more.

[0183] The pressure in the second chamber 22 can also be decreased while the mixed gas 30 is supplied into the first chamber 21. The membrane separation apparatus 100 can further include a pump (not shown) for decreasing the pressure in the second chamber 22. The second chamber 22 can be depressurized so that the space in the second chamber 22 is less than the atmospheric pressure in the measurement environment by, for example, 10 kPa or more, preferably 50 kPa or more, and more preferably 100 kPa or more.

[0184] By supplying the mixed gas 30 into the first chamber 21, the permeated fluid 35 having a higher content of the acid gas than the mixed gas 30 can be obtained on the other face side of the separation membrane 10. That is, the permeated fluid 35 is supplied to the second chamber 22. The permeated fluid 35 preferably contains the acid gas as a main component. The permeated fluid 35 can also contain a small amount of other gas than the acid gas. The permeated fluid 35 is discharged to the outside of the tank 20 via the outlet 22a.

[0185] The concentration of the acid gas in the mixed gas 30 gradually decreases from the inlet 21a toward the outlet 21b of the first chamber 21. The mixed gas 30 (non-permeated fluid 36) treated in the first chamber 21 is discharged to the outside of the tank 20 via the outlet 21b.

[0186] The membrane separation apparatus 100 of the present embodiment is suitable for a flow-through (continuous) membrane separation method. However, the membrane separation apparatus 100 of the present embodiment can also be used for a batch membrane separation method.

[0187] <Modification of Membrane Separation Apparatus> The membrane separation apparatus 100 can be a spiral-type membrane element, a hollow fiber membrane element, or the like. Figure 4 A spiral-type membrane element is shown. Figure 4The membrane separation device 110 has a center pipe 41 and a laminate 42. The laminate 42 includes the separation membrane 10.

[0188] The center pipe 41 has a cylindrical shape. A plurality of holes for flowing the permeated fluid 35 into the inside of the center pipe 41 are formed on the surface of the center pipe 41. As a material of the center pipe 41, for example, a resin such as acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polyphenylene ether resin (PPE resin), polysulfone resin (PSF resin), and a metal such as stainless steel, titanium, and the like can be given. The inner diameter of the center pipe 41 is in the range of, for example, 20 to 100 mm.

[0189] The laminate 42 includes, in addition to the separation membrane 10, a supply-side flow path member 43 and a permeated-side flow path member 44. The laminate 42 is wound around the center pipe 41. The membrane separation device 110 can further have an outer packaging member (not shown).

[0190] As the supply-side flow path member 43 and the permeated-side flow path member 44, for example, a resin mesh formed of polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.

[0191] Membrane separation using the membrane separation device 110 is performed by the following method. First, the mixed gas 30 is supplied to one end of the wound laminate 42. The permeated fluid 35 that has permeated the separation membrane 10 of the laminate 42 moves to the inside of the center pipe 41. The permeated fluid 35 is discharged to the outside via the center pipe 41. The mixed gas 30 (non-permeated fluid 36) treated with the membrane separation device 110 is discharged to the outside from the other end of the wound laminate 42. Thus, it is possible to separate the acid gas from the mixed gas 30.

[0192] Example Hereinafter, the present application will be described in more detail by examples and comparative examples, but the present application is not limited thereto.

[0193] (Example 1) [Synthesis of polyimide] First, synthesis of the polyimide was performed using an automatic polymerization device (EasyMax402, manufactured by METTLER TOLEDO). A detachable flask (400 mL) attached to the device was equipped with a Dimroth condenser, a stirring rod, an internal thermometer, a nitrogen inlet tube, and a flat plug. A coolant set to 10°C was circulated in the cooler of the Dimroth condenser. N2 gas was circulated at a flow rate of 100 mL / min in the flask. The stirring speed was set to 300 rpm. Next, 1-methyl-2-pyrrolidinone (super dehydrated) 96.1 g as a solvent, 2,4,6-trimethyl-1,3-phenylenediamine (TrMPD) 2.62 g (17.5 mmol) as a diamine, 3,7-diamino-2,8-dimethyl-dibenzothiophene sulfone (DDBT) 4.80 g (17.5 mmol), and 5,5'-methylenebis(2-aminobenzoic acid) (MBAA) 2.11 g (0.5 mmol) were added to the flask. They were stirred at room temperature, whereby the diamine was dissolved in the solvent. Further, naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTDA) 9.53 g (35.5 mmol) as a tetracarboxylic dianhydride and benzoic acid 8.54 g (70 mmol) were added to the obtained solution. The jacket temperature of the device was warmed to 180°C, and stirring was performed for 8 hours. At this time, the internal temperature of the flask was 172 to 175°C. After the stirring, the internal temperature of the flask was cooled to 25°C, and left to stand overnight.

[0194] Next, isoquinoline 9.04 g (70 mmol) was added, and the jacket temperature was again warmed to 180°C, and stirring was performed for 8 hours. After the reaction solution was left to stand overnight, 1-methyl-2-pyrrolidinone 226 g was added, whereby the reaction solution was diluted. Next, methanol 650 mL was added dropwise to the reaction solution over about 30 minutes using a dropping funnel, and reprecipitation purification was performed. The precipitated polyimide was separated by filtration, and the polyimide was washed with methanol 300 mL twice. After the washing, the polyimide separated by filtration 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. Thus, the polyimide was obtained in a yield of 17.1 g.

[0195] [Manufacture of separation function layer] Next, the polyimide was added to a 50 mL screw tube, further N-methyl-2-pyrrolidone (NMP) as a solvent and acetylacetone as a ligand were added, to obtain a mixed solution. For the mixed solution, a 5-minute stirring operation and a 5-minute defoaming operation were repeatedly performed 2 times. Next, NMP and Al(acac)3 as a metal complex were added to another screw tube, further ultrasonic treatment using an ultrasonic washer was performed, to thereby obtain an Al(acac)3 solution. The Al(acac)3 solution was further mixed with the above mixed solution, a 5-minute stirring operation and a 5-minute defoaming operation were repeatedly performed 2 times, to thereby prepare a coating solution containing the polyimide. Note that the stirring operation and the defoaming operation were performed using an Awatori Rentaro manufactured by Thinky Co. The content rate of the polyimide in the coating solution was 8 wt%.

[0196] Next, the above coating solution was applied to the polyimide film (Fujico Co., Ltd., SCA0) subjected to the release treatment, to thereby produce a coating film (30 μm in thickness). The coating film was dried at 130°C for 10 minutes, to thereby obtain a separation functional layer having a thickness of 2 μm. Note that by drying the coating film, protons of dissociation of the functional group g (carboxyl group) contained in the polyimide were exchanged with Al of the metal complex. Thus, an Al salt of the functional group g was formed.

[0197] Next, the silicone-based adhesive (Shin-Etsu Silicone Co., Ltd., KR-3701) was diluted with toluene, to thereby prepare a coating solution having a solid content concentration of 6 wt%. The coating solution was applied to the separation functional layer, to thereby produce a coating film (100 μm in thickness). The coating film was dried at 130°C for 3 minutes, to thereby form an intermediate layer having a thickness of 3 μm. Thus, a laminate having the polyimide film, the separation functional layer, and the intermediate layer in this order was obtained.

[0198] Next, the intermediate layer of the above laminate was laminated to the porous support, and they were pressure-bonded under conditions of 0.3 MPa and 1 m / min. As the porous support, a nonwoven fabric made of PET (Apolo Co., Ltd., N401) was used. Next, a double-sided tape was attached to the surface of the polyimide film, and fixed to a support table. Further, a tape was attached to the surface of the porous support, and the laminate of the separation functional layer, the intermediate layer, and the porous support was peeled from the polyimide film while holding the tape. Thus, the separation membrane of Example 1 was obtained.

[0199] (Examples 2 to 5) The separation membranes of Examples 2 to 5 were obtained by the same method as in Example 1, except that the kind of the porous support and the thickness of each layer were changed as shown in Table 1.

[0200] (Example 6) First, using the same method as in Example 1, a separation functional layer with a thickness of 4 μm was fabricated on the polyimide film. This separation functional layer was then peeled off from the polyimide film, thereby obtaining the separation membrane of Example 6, which consists only of the separation functional layer.

[0201] [Physical Properties of Porous Supports] (ISO breathability) For the porous support used in the fabrication of the separation membrane, the ISO permeability was determined according to the Wangyan test machine method specified in JIS P8117:2009. The ISO permeability was determined using a digital Wangyan permeability tester EGO1 (manufactured by Asahi Seiko Corporation) under the conditions of a test pressure of 0.05 MPa and a test time of 60 seconds.

[0202] (Area ratio Smr(c1)) For the porous support used in the fabrication of the separation membrane, the surface of the intermediate layer was observed using a laser microscope using the method described above, and a three-dimensional analysis was performed to generate a load curve. The laser microscope used was the Lasertec OPTELICS hybrid laser microscope, and the objective lens was the M-PLANAPO 50X from Mitutoyo. Using the obtained load curve, the height c1, which corresponds to the difference between the height c0 at 0% load area ratio and the thickness of the intermediate layer, was determined, and the load area ratio Smr(c1) corresponding to height c1 was also determined.

[0203] [Peel strength] A layer with the same composition and thickness as the intermediate layer of the separation membrane is made on the evaluation sheet, and the peel strength between the intermediate layer and the porous support is measured by the method described above.

[0204] [Physical properties of separation membranes] (Tensile strength) For the prepared separation membrane, the tensile strength Y in the MD direction was determined using the method described above. MD Tensile strength Y in the CD direction CD As a tensile testing machine, the Autograph AGX-V manufactured by Shimadzu Corporation was used.

[0205] (Maintenance rate of separation coefficient α) For the prepared separation membrane, the nitrogen permeation rate T in the initial state was determined using the method described above. N2 (GPU) and carbon dioxide permeation rate T CO2 (GPU), determine their ratio T CO2 / T N2The initial separation coefficient α1 is used. Further, a pressure test is conducted using the method described above, and the nitrogen permeation rate T after the pressure test is measured. N2 (GPU) and carbon dioxide permeation rate T CO2 (GPU), determine their ratio T CO2 / T N2 The separation coefficient α2 after the pressure test is used as the ratio of the separation coefficient α2 after the pressure test to the separation coefficient α1 in the initial state, α2 / α1. The calculated value is regarded as the maintenance rate of the separation coefficient α.

[0206] [Table 1] [Table 2] The abbreviations in Table 1 are as follows.

[0207] N401: Nonwoven fabric made of PET (manufactured by Awa Paper Co., Ltd., N401) S54: Nonwoven fabric made of PET (manufactured by Hokuetsu Corporation, S54) N301: Nonwoven fabric made of PET (manufactured by Awa Paper Co., Ltd., N301) PS0100S-Fine: Nonwoven fabric made of PPS (manufactured by Hirose Paper Co., Ltd., PS0100S-Fine) As can be seen from Tables 1 and 2, in Examples 1 to 5, where the load area ratio Smr(c1) of the surface opposite the intermediate layer of the porous support is less than 80%, the thickness of the separation membrane can be adjusted to be relatively small. Based on the separation membranes of Examples 1 to 5, the membrane area of ​​the separation membrane that can be mounted in a membrane separation device (especially a spiral membrane element) can be easily increased, and therefore it can be said that it is suitable for membrane separation devices.

[0208] Furthermore, compared with the separation membrane of Example 6 which lacks a porous support, the separation membranes of Examples 1-5 exhibit a high retention rate of the separation coefficient α and good pressure resistance.

[0209] It should be noted that the initial carbon dioxide permeation rate T of the separation membranes in Examples 1-5 CO2 The values ​​are 10 GPUs or more, and the separation coefficient α1 is 10 or more, both of which are sufficient for practical use.

[0210] Industrial availability The separation membrane of this embodiment is suitable for separating acidic gases from a gas mixture containing acidic gases. The separation membrane of this embodiment is particularly suitable for separating carbon dioxide from exhaust gases from chemical plant equipment or thermal power generation facilities.

Claims

1. A separation membrane comprising: a separation functional layer, a porous support body that supports the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support body, the porous support body having a surface S1 opposite the intermediate layer, a load area ratio Smr(c1) of the surface S1 obtained by the following test is less than 80%, Test: a three-dimensional analysis is performed on the surface S1 of the porous support body to obtain a load curve prescribed in Japanese Industrial Standards (JIS) B0681-2:2018; in the load curve, a height c1 that coincides with the thickness of the intermediate layer and the difference from a height c0 at a load area ratio of 0% is determined; and a load area ratio corresponding to the height c1 is read to be determined as the load area ratio Smr(c1). The load area ratio Smr(c1) is 0.04% or more.

3. The separation membrane according to claim 1, having a thickness of 130 μm or less.

4. A separation membrane comprising: a separation functional layer, a porous support body that supports the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support body, the separation membrane having a thickness of 130 μm or less, a retention rate of a separation factor α of the separation membrane when the separation membrane is contacted with nitrogen at a pressure of 2.0 MPa for 5 minutes is 70% or more, and the porous support body is a fibrous structure. The thickness of the porous support body is 125 μm or less. The separation functional layer contains a polyimide. The polyimide contains a structural unit derived from a tetracarboxylic dianhydride having an anhydride structure of a 6-membered ring.

2. The separation membrane of claim 1, wherein, The structural unit is represented by the following formula (A1), [Chemical Formula 1] The thickness of the separation functional layer is 5.0 μm or less. The intermediate layer is formed of an adhesive composition. The adhesive composition contains a silicone-based polymer. The thickness of the intermediate layer is 5.0 μm or less. The peeling strength of the intermediate layer from the porous support body is 0.25 N / 25 mm or more. ​ wherein The separation coefficient a is a ratio of a permeation rate T of carbon dioxide permeated through the separation membrane when carbon dioxide is supplied to a space adjacent to one face of the separation membrane at a pressure of 0.6 MPa CO2 to a permeation rate T of nitrogen permeated through the separation membrane when nitrogen is supplied to the space at a pressure of 0.6 MPa N2 (GPU) CO2 (GPU) N2 .

5. The separation membrane as claimed in claim 1 or 4, wherein, ​ 6. The separation membrane of claim 1 or 4, wherein, ​ 7. The separation membrane as claimed in claim 1 or 4, wherein, The ISO air permeability of the porous support is 10.0 x 10 4 μm / (Pa s) or more.

8. The separation membrane of claim 1 or 4, wherein, ​ 9. The separation membrane of claim 8, wherein, ​ 10. The separation membrane of claim 9, wherein, ​ ​ In the formula (A1), R 1a 4a each independently is a hydrogen atom or an optional substituent.​ 11. The separation membrane of claim 1 or 4, wherein, ​ 12. The separation membrane of claim 1 or 4, wherein, ​ 13. The separation membrane of claim 12, wherein, ​ 14. The separation membrane of claim 1 or 4, wherein, ​ 15. The separation membrane of claim 1 or 4, wherein, ​

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