WO2017175598A1

WO2017175598A1 - Gas separation membrane, gas separation module, gas separation device, and gas separation method

Info

Publication number: WO2017175598A1
Application number: PCT/JP2017/011915
Authority: WO
Inventors: 敦靖野崎; 基原田
Original assignee: 富士フイルム株式会社
Priority date: 2016-04-05
Filing date: 2017-03-24
Publication date: 2017-10-12
Also published as: JPWO2017175598A1

Abstract

Provided are: a gas separation membrane that can realize gas permeability and gas separation selectivity at a desirably high level, and further exhibit the above mentioned excellent separation performances (gas permeability and separation selectivity) sustainably even in the presence of plasticized impurities; and a gas separation module, a gas separation device, and a gas separation method using the gas separation membrane. The gas separation membrane has a gas separation layer containing a specific polyimide compound.

Description

Gas separation membrane, gas separation module, gas separation device, and gas separation method

The present invention relates to a gas separation membrane, a gas separation module, a gas separation device, and a gas separation method.

A material composed of a polymer compound has gas permeability specific to each material. Based on the property, a desired gas component can be selectively permeated and separated by a membrane composed of a specific polymer compound. As an industrial utilization mode of this gas separation membrane, it is related to the problem of global warming, and it is separated and recovered from a large-scale carbon dioxide generation source in a thermal power plant and / or a cement plant, a steelworks blast furnace, etc. Is being considered. And this membrane separation technique attracts attention as a means for solving environmental problems that can be achieved with relatively small energy. On the other hand, natural gas and biogas (gas generated by fermentation and anaerobic digestion of biological waste, organic fertilizer, biodegradable substances, sewage, garbage, energy crops, etc.) are mainly mixed gases containing methane and carbon dioxide. A membrane separation method has been studied as a means for removing impurities such as carbon dioxide.

In the purification of natural gas using a membrane separation method, excellent gas permeability and gas separation selectivity are required in order to separate gas more efficiently. Further, in an actual plant, the membrane is plasticized due to the influence of impurity components (for example, benzene, toluene, xylene) present in natural gas, and this causes a problem of reduction in gas separation selectivity. Therefore, the gas separation membrane is also required to have plastic resistance capable of continuously expressing desired gas separation selectivity even in the presence of the impurity component. In order to realize these, various membrane materials have been studied, and as part of this, gas separation membranes using polyimide compounds have been studied. For example, Patent Document 1 describes that a crosslinked polyimide compound obtained by crosslinking a polyimide compound via an ester linking group is used as a gas separation layer of a gas separation membrane.

In order to obtain a practical gas separation membrane, the gas separation layer must be made thin to ensure sufficient gas permeability, and a higher degree of gas separation selectivity must be realized. As a method for thinning the gas separation layer, there is a method in which a polymer compound such as a polyimide compound is made into an asymmetric membrane by a phase separation method, and a portion contributing to separation is made into a thin layer called a dense layer or a skin layer. In this asymmetric membrane, a portion other than the dense layer is allowed to function as a support layer that bears the mechanical strength of the membrane.
In addition to the asymmetric membrane, the gas separation layer responsible for the gas separation function and the support layer responsible for the mechanical strength are made of different materials, and the gas separation layer having gas separation ability is thinly formed on the gas permeable support layer. The form of the composite film formed in the above is also known.

JP2013-169485A

In general, gas permeability and gas separation selectivity are in a so-called trade-off relationship. Therefore, by adjusting the copolymerization component of the polyimide compound used in the gas separation layer, it is possible to improve either the gas permeability or the gas separation selectivity of the gas separation layer, but these characteristics are desired high It is difficult to achieve both levels.
In addition, polyimide compounds are generally poor in plastic resistance, and gas separation performance tends to deteriorate in the presence of plasticizing impurity components (such as toluene). In particular, when a polyimide compound having a high gas permeability is used for the gas separation layer, the gas separation layer is more easily affected and the swelling of the gas separation layer is promoted. Therefore, it has been difficult to achieve both gas permeability and plastic resistance at a desired high level in a gas separation layer using a polyimide compound.

In the present invention, gas permeability and gas separation selectivity can be realized at a desired high level, and the above-described excellent separation performance (gas permeability and separation selectivity) is maintained even in the presence of plasticizing impurities. The present invention relates to a gas separation membrane that can be expressed dynamically. The present invention also relates to a gas separation module, a gas separation apparatus, and a gas separation method using the gas separation membrane.

As a result of intensive studies, the present inventors have introduced a sulfonamide group into the main chain structure of a polyimide compound, and when such a polyimide compound is used in a gas separation layer of a gas separation membrane, gas permeability and plasticization are achieved. We have found that the coexistence of tolerance can be achieved by overcoming the traditional trade-off relationship. Furthermore, it has been found that this gas separation membrane exhibits excellent gas separation selectivity even under high pressure conditions. The present invention has been further studied and completed based on these findings.

The present invention includes the following embodiments.
[1]
A gas separation membrane having a gas separation layer containing a polyimide compound, wherein the polyimide compound is a structural unit represented by formula (1), a structural unit represented by formula (2), and formula (3). A gas separation membrane comprising at least one selected from the structural units represented.

In the formula (1), R represents a tetravalent group represented by any of the following formulas (I-1) to (I-28).

Here, X ¹ to X ³ each independently represents a single bond or a divalent linking group, L represents —CH═CH— or —CH ₂ —, and R ¹ and R ² each independently represents a hydrogen atom or a substituent. * Indicates a binding site with the carbonyl group in formula (1).

In formula (2) and formula (3), Z ¹ to Z ⁴ each independently represents a divalent linking group, Q ¹ and Q ² each independently represents a divalent group containing a sulfonamide group, Y ¹ represents a hydrogen atom, an alkyl group, an aryl group, or any group of formulas (4) to (6), X ¹⁺ represents an organic or inorganic cation, and n is an integer of 0 or more.

In the formulas (4) to (6), R ³ to R ⁶ each independently represents an alkyl group or an aryl group. * 1 is a binding site with a nitrogen atom.
[2]
The gas separation membrane according to [1], wherein Z ¹ to Z ⁴ are each independently a divalent group containing an arylene group and / or an alkylene group.
[3]
The gas separation membrane according to [1], wherein Z ¹ to Z ⁴ are each independently any one of the following formulas A-1 to A-11.

In the formula, W ¹ to W ⁵⁰ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, a sulfonamide group, or a carboxy group, and Z ¹¹ represents —CR ⁸ ₂ —, —O—, —NR ⁸ -, - S- or a single bond, ^{L 1} and ^{L 2} ^-CR each independently 9 -, - O -, - NR 9 -, - S- or a single bond. R ⁸ and R ⁹ each independently represents an alkyl group or an aryl group.
[4]
A gas separation membrane having a gas separation layer containing a polyimide compound, wherein the polyimide compound is represented by the structural unit represented by the formula (1), the structural unit represented by the formula (8), and the formula (9). A gas separation membrane comprising at least one selected from the structural units represented.

In formula (8) and formula (9), Z ⁵ to Z ¹⁰ each independently represent a divalent linking group, and Y ² and Y ³ each independently represent a hydrogen atom, an alkyl group, an aryl group, or formula (4) Represents any group of formula (6), and X ²⁺ and X ³⁺ each independently represent an organic or inorganic cation.

In the formulas (4) to (6), R ³ to R ⁶ each independently represents an alkyl group or an aryl group. * 1 is a binding site with a nitrogen atom.
[5]
The gas separation membrane according to [4], wherein Z ⁵ to Z ¹⁰ are each independently a divalent group containing an arylene group and / or an alkylene group.
[6]
The gas separation membrane according to [4], wherein Z ⁵ to Z ¹⁰ are each independently any one of the following formulas A-1 to A-11.

In the formula, W ¹ to W ⁵⁰ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, a sulfonamide group, or a carboxy group, and Z ¹¹ represents —CR ⁸ ₂ —, —O—, —NR ⁸ -, - S- or a single bond, ^{L 1} and ^{L 2} ^-CR each independently 9 -, - O -, - NR 9 -, - S- or a single bond. R ⁸ and R ⁹ each independently represents an alkyl group or an aryl group.
[7]
[1] to [6], further comprising a gas permeable support layer, wherein the gas separation layer is a gas separation composite membrane provided on the upper side of the gas permeable support layer. Gas separation membrane.
[8]
The gas-permeable support layer includes a porous layer and a nonwoven fabric layer,
The gas separation membrane according to any one of [1] to [7], wherein the gas separation layer, the porous layer, and the nonwoven fabric layer are provided in this order.
[9]
The gas separation membrane according to any one of [1] to [8], which is used for selectively permeating carbon dioxide from a gas containing carbon dioxide and methane.
[10]
[1] A gas separation module comprising the gas separation membrane according to any one of [1] to [8].
[11]
A gas separation device comprising the gas separation module according to [10].
[12]
A gas separation method for selectively permeating carbon dioxide from a gas containing carbon dioxide and methane, using the gas separation membrane according to any one of [1] to [9].

In the present specification, the numerical value range represented by “to” means that the numerical values described before and after the numerical value range are included as a lower limit value and an upper limit value.
In the present specification, when there are a plurality of substituents, linking groups, and the like (hereinafter referred to as substituents) indicated by specific symbols, or when a plurality of substituents are specified simultaneously or alternatively, It means that a substituent etc. may mutually be same or different. The same applies to the definition of the number of substituents and the like. Further, when there are repetitions of a plurality of partial structures represented by the same indication in the formula, each partial structure or constituent unit (repeating unit) may be the same or different.

In this specification, about the display of a compound thru | or group, it uses for the meaning containing those salts and those ions other than a compound thru | or group itself. In addition, it means that a part of the structure is changed as long as the desired effect is achieved.
In the present specification, a substituent that does not clearly indicate substitution or non-substitution (the same applies to a linking group) means that the group may have an arbitrary substituent as long as a desired effect is achieved. . This is also the same for compounds that do not specify substitution or non-substitution.
In the present specification, the substituent group Z is a preferred range unless otherwise specified.

The gas separation membrane, gas separation module, and gas separation apparatus of the present invention can realize both gas permeability and plasticization resistance at a high level, not on a trade-off line, even when used under high pressure conditions. High-speed, high-selectivity gas separation with excellent plasticization resistance is possible.
According to the gas separation method of the present invention, gas can be separated with excellent gas permeability and excellent gas separation selectivity even under high pressure conditions, and high speed and high selectivity gas separation is possible. And excellent plasticization resistance.

It is sectional drawing which shows typically one Embodiment of the gas separation composite membrane of this invention. It is sectional drawing which shows typically another embodiment of the gas separation composite membrane of this invention.

Hereinafter, preferred embodiments of the present invention will be described.
The gas separation membrane of the present invention contains a specific polyimide compound in the gas separation layer.

[Polyimide compound]
In one embodiment, the polyimide compound includes at least one selected from the structural unit represented by the following formula (1), the structural unit represented by the formula (2), and the structural unit represented by the formula (3). .

In the formula (1), R represents a tetravalent group represented by any of the following formulas (I-1) to (I-28). Here, X ¹ to X ³ each independently represents a single bond or a divalent linking group, L represents —CH═CH— or —CH ₂ —, and R ¹ and R ² each independently represents a hydrogen atom or a substituent. * Indicates a binding site with the carbonyl group in formula (1).
R is preferably a group represented by the formula (I-1), (I-2) or (I-4), more preferably a group represented by (I-1) or (I-4). A group represented by (I-1) is particularly preferable.

In formulas (I-1), (I-9) and (I-18), X ¹ to X ³ each independently represents a single bond or a divalent linking group. As the divalent linking group, —C (R ^x ) ₂ — (R ^x represents a hydrogen atom or a substituent. When R ^x is a substituent, they may be linked to each other to form a ring), —O—, —SO ₂ —, —C (═O) —, —S—, —NR ^Y — (R ^Y represents a hydrogen atom, an alkyl group (preferably a methyl group or an ethyl group) or an aryl group (preferably a phenyl group). _{_{group)), - C 6 H 4}} - ( phenylene group), or a combination thereof, more preferably a single bond or -C ^(R _{x) 2} - are more preferable. When R ^x represents a substituent, specific examples thereof include a group selected from the substituent group Z described below, and among them, an alkyl group (preferable range is synonymous with the alkyl group shown in the substituent group Z described later). And an alkyl group having a halogen atom as a substituent is more preferable, and trifluoromethyl is particularly preferable. In the formula (I-18), X ³ is linked to one of the two left carbon atoms and is linked to one of the two right carbon atoms.

In the formulas (I-4), (I-15), (I-17), (I-20), (I-21) and (I-23), L represents —CH═CH— or —CH ₂ —. Indicates.

In formula (I-7), R ¹ and R ² each independently represents a hydrogen atom or a substituent. Examples of the substituent include a group selected from the substituent group Z described later. R ¹ and R ² may be bonded to each other to form a ring.
R ¹ and R ² are preferably each independently a hydrogen atom or an alkyl group, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom.

A substituent may be further added to the carbon atom shown in the formulas (I-1) to (I-28). Specific examples of the substituent include groups selected from the substituent group Z described later, and among them, an alkyl group or an aryl group is preferable.

In formula (2) and formula (3), Z ¹ to Z ⁴ each independently represent a divalent linking group, such as an arylene group (preferably a 1-5 cyclic arylene group, more preferably a phenylene group, A naphthylene group), an alkylene group (preferably a methylene group), an alkyleneoxy group (preferably an ethyleneoxy group, a propyleneoxy group) or two or more groups selected from these groups are linked by a single bond or a divalent group. (Preferably a group formed by connecting two or more arylene groups and / or alkylene groups with a single bond or a divalent group). Two or more groups selected from an arylene group, an alkylene group, and an alkyleneoxy group connected by the above divalent group are connected to each other by the substituents of these groups to form a ring together with the above divalent group. It may be formed. Examples of the divalent group include an alkylene group (preferably a methylene group), a cycloalkylene group (preferably a cyclohexylene group), and an alkyleneoxy group (preferably an ethyleneoxy group and a propyleneoxy group). Z ¹ to Z ⁴ are each independently preferably a divalent group containing an arylene group and / or an alkylene group, and more preferably any one of the following formulas A-1 to A-11.

W ¹ to W ⁵⁰ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, a sulfonamide group or a carboxy group, preferably an alkyl group or a carboxy group. Specific examples of the halogen atom, alkyl group, alkoxy group and sulfonamide group that can be taken by W ¹ to W ⁵⁰ include those exemplified in Substituent Group Z below.

Z ¹¹ represents —CR ⁸ ₂ —, —O—, —NR ⁸ —, —S— or a single bond, preferably —CR ⁸ ₂ —, —O—.

L ¹ and L ² each independently represent —CR ⁹ —, —O—, —NR ⁹ —, —S— or a single bond, preferably —CR ⁹ —, —O—.

R ⁸ and R ⁹ each independently represents an alkyl group or an aryl group. Alkyl groups that can be employed as R ⁸ and R ⁹ may be independently linear or branched, and may have a cyclic structure. The alkyl groups that can be taken as R ⁸ and R ⁹ each independently preferably have 1 to 20 carbon atoms, more preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 6, and more preferably 1 to 4 Particularly preferred. Preferred examples of this alkyl group include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, s-butyl, isobutyl, cyclobutyl, n-hexyl and cyclohexyl. preferable. A halogen-substituted alkyl group is preferred. Preferable specific examples of the halogen-substituted alkyl group include, for example, trifluoromethyl.

Q ¹ and Q ² each independently represent a divalent group containing a sulfonamide group, and examples thereof include a divalent group formed by combining a sulfonamide group with a group selected from an arylene group and a methylene group. . In the present specification, the sulfonamide group means a divalent group represented by —S (═O) (═O) NR ^Q — or —S (═O) (═O) N ⁺ —, and R ^Q represents a hydrogen atom or a substituent. In this divalent group, the connecting structure of the sulfonamide group and a group selected from an arylene group and a methylene group is preferably a single bond.

Y ¹ represents a hydrogen atom, an alkyl group, an aryl group, or any group of formulas (4) to (6).

R ³ to R ⁶ each independently represents an alkyl group or an aryl group.
* 1 is a binding site with a nitrogen atom.

Examples of the alkyl group or aryl group that Y ¹ and R ³ to R ⁶ can take include the above alkyl group or aryl group.

<Group represented by any one of formulas (4) to (6)>
When the polyimide compound includes a structural unit represented by the formula (2), it is preferable that Y ¹ includes a group represented by any ^one of the formulas (4) to (6). The groups represented by the formulas (4) to (6) are produced by a polymer reaction between a monovalent acid anhydride or monovalent acid halide compound and a sulfonamide group incorporated in the main chain of the polyimide compound. Can be formed. A monovalent acid anhydride and a monovalent acid halide compound can react with the sulfonamide group in the polyimide compound to form at least one of formula (4), formula (5) and formula (6). A monovalent compound is meant, and preferred examples include carboxylic acid anhydrides, sulfonic acid anhydrides, carboxylic acid chlorides, sulfonic acid chlorides, phosphoric acid chlorides and the like. Examples of the halide in the monovalent acid halide compound include chloride and bromide.
Specific examples of the monovalent acid anhydride and monovalent acid halide compound that can be used in the present invention are listed below, but the present invention is not limited thereto.

X ¹⁺ represents an organic or inorganic cation, and examples thereof include an ammonium cation and a sodium cation.
n is an integer of 0 or more, preferably 1 to 3.

In another embodiment, the polyimide compound comprises at least one selected from the structural unit represented by the formula (1), the structural unit represented by the formula (8), and the structural unit represented by the formula (9). It is preferable to include.

In formula (8) and formula (9), Z ⁵ to Z ¹⁰ each independently represent a divalent linking group, and examples thereof include an arylene group and an alkylene group (including a halogenated alkylene group). Z ⁵ to Z ¹⁰ are preferably each independently a divalent group containing an arylene group and / or an alkylene group, and more preferably any one of formulas A-1 to A-11.

Y ² and Y ³ each independently represent a hydrogen atom, an alkyl group, an aryl group or any one of the above formulas (4) to (6), and examples thereof include a hydrogen atom and an acetyl group.

X ²⁺ and X ³⁺ each independently represents an organic or inorganic cation, and examples thereof include an ammonium cation and a sodium cation.

When the structural unit of the polyimide compound has a sulfonamide group in the main chain of the polyimide compound, compared to the case where it is introduced into the side chain, the interaction between the polymers is improved, and the gas permeability and plasticization resistance are improved. Conceivable. When such a polyimide compound is used for a gas separation layer, it is possible to achieve both excellent gas permeability and plasticization resistance at a high level.
Further, by changing the aromatic units of Z ¹ to Z ¹⁰ , it is possible to satisfactorily adjust the balance of permeability, selectivity, and plasticization resistance.

The polyimide compound may have only one type of structural unit, but preferably has two or more types of structural units.
Moreover, it is preferable that the structural unit in a polyimide compound is a structural unit derived from the exemplary compound obtained by making the following diamine compound and a bifunctional acid anhydride and / or a bifunctional sulfonic acid halide compound react.
For example, a reaction scheme is shown below for one polyamide compound. This is an example in which a diamine compound, a bifunctional acid anhydride, and a bifunctional sulfonic acid halide compound are reacted one by one.

Examples of a diamine compound, a bifunctional acid anhydride, and a bifunctional sulfonic acid halide compound that are suitably obtained for synthesizing a polyimide compound are shown below.

The polyimide compound may be generated, for example, by a sequential polymerization reaction between a compound having two or more acid anhydride groups and a compound having two or more amino groups. Alternatively, it may be produced by a sequential polymerization reaction of a compound having two or more acid anhydride groups, a compound having two or more acid halide groups, and a compound having two or more amino groups.
The polyimide compound is a sequential polymerization reaction between a compound having two or more acid anhydride groups and a compound having at least one sulfonamide group in the main chain and having two or more amino groups (an acid anhydride compound and And a sequential polymerization reaction with a diamine compound containing at least one sulfonamide group).

The polyimide compound is preferably a linear polymer compound.
Moreover, it is preferable that a polyimide compound has a carboxy group, it is more preferable to have a carboxy group couple | bonded with the aromatic ring, and it is still more preferable to have at least the following structural unit.
It is preferable that 5 to 30 mol of the structural unit represented by the following formula (10) is contained with respect to 100 mol of the structural unit represented by the above formula (1).

Preferred specific examples of the polyimide compound are shown in the following table. Exemplified compounds PI-1 to PI-28 mean polymer compounds obtained by reacting the diamine compounds described above with compounds having two or more anhydride groups in the proportions (molar ratio) described in the table. To do.
Moreover, the weight average molecular weight (Mw) of a polymer is the value measured by GPC (gel filtration chromatography) method.
The polyimide compound used in the present invention is not limited to the specific examples described in the following table.

The polyimide compound may optionally contain other components as long as the effects of the present invention are not impaired.
Hereinafter, the monovalent basic compound will be described.

<Monovalent basic compound>
The polyimide compound preferably contains a monovalent basic compound.
The monovalent basic compound means a monovalent basic compound capable of forming a salt structure with the sulfonamide group in the polyimide compound, and preferable examples include alkali metal hydroxides, oxides or carbonic acid. Hydrogen salts, alkoxides (ROM), phenoxides (ArONa), etc., ammonia (gas or aqueous solution), amines other than diarylamines and triarylamines (diarylamines and triarylamines are almost neutral, And a heterocyclic salt such as pyridine, quinoline and piperidine, a hydrazine derivative, an amidine derivative, and a tetraalkylammonium hydroxide.
In the present specification, “forms a salt structure” means that a compound or group defined therein forms a salt as it is, and a part of the compound or salt is combined to form a salt. . For example, the anion of a specific compound may dissociate and only the cation moiety may form a salt with a sulfonamide group. Further, the “salt structure” may be dissociated in the gas separation layer.
Among the above monovalent basic compounds, alkali metal hydroxides, oxides or bicarbonates, alkoxides (ROM), phenoxides (ArONa), ammonia (gas or aqueous solution), and salts of nitrogen-containing compounds are preferred. Can be mentioned.
Specific examples of the monovalent basic compound are listed below, but the present invention is not limited thereto.

Specific examples of suitable polyimide compounds having a salt structure formed of a polyimide compound and a monovalent basic compound in the molecule are shown below. In addition, the polyimide compound used for this invention is not limited to these specific examples.

Specific examples of suitable polyimide compounds formed from a polyimide compound and an acid anhydride or acid halide compound are shown below. In addition, the polyimide compound used for this invention is not limited to these specific examples.

Substituent group Z:
An alkyl group (preferably an alkyl group having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 10 carbon atoms, such as methyl, ethyl, iso-propyl, tert-butyl, n-octyl) , N-decyl, n-hexadecyl, etc.), a cycloalkyl group (preferably a cycloalkyl group having 3 to 30 carbon atoms, more preferably 3 to 20 carbon atoms, particularly preferably 3 to 10 carbon atoms). For example, cyclopropyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (preferably an alkenyl group having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, and particularly preferably 2 to 10 carbon atoms. Vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), alkynyl groups (preferably having 2 to 0, more preferably an alkynyl group having 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, such as propargyl, 3-pentynyl, etc.), an aryl group (preferably having 6 to 30 carbon atoms, more An aryl group having 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms is preferable, and examples thereof include phenyl, p-methylphenyl, naphthyl, anthranyl, and the like, amino groups (amino groups, alkylamino groups, An arylamino group and a heterocyclic amino group, preferably an amino group having 0 to 30 carbon atoms, more preferably 0 to 20 carbon atoms, and particularly preferably 0 to 10 carbon atoms, such as amino, methylamino, dimethylamino; , Diethylamino, dibenzylamino, diphenylamino, ditolylamino, etc.), alkoxy group Preferably an alkoxy group having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms, and examples thereof include methoxy, ethoxy, butoxy, 2-ethylhexyloxy and the like. An aryloxy group (preferably an aryloxy group having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenyloxy, 1-naphthyloxy, 2-naphthyloxy, etc. A heterocyclic oxy group (preferably a heterocyclic oxy group having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as pyridyloxy, pyrazyloxy, Pyrimidyloxy, quinolyloxy, etc.),

An acyl group (preferably an acyl group having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as acetyl, benzoyl, formyl, pivaloyl, etc.), alkoxy A carbonyl group (preferably an alkoxycarbonyl group having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, etc.), aryloxy A carbonyl group (preferably an aryloxycarbonyl group having 7 to 30 carbon atoms, more preferably 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonyl), an acyloxy group ( Preferably 2-30 carbon atoms, more preferably 2-20 carbon atoms, especially Preferably, it is an acyloxy group having 2 to 10 carbon atoms, such as acetoxy, benzoyloxy, etc.), an acylamino group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably carbon atoms). An acylamino group of 2 to 10, for example, acetylamino, benzoylamino and the like),

An alkoxycarbonylamino group (preferably an alkoxycarbonylamino group having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonylamino), aryl Oxycarbonylamino group (preferably an aryloxycarbonylamino group having 7 to 30 carbon atoms, more preferably 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms, and examples thereof include phenyloxycarbonylamino group) A sulfonylamino group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfonylamino, benzenesulfonylamino, etc.), a sulfamoyl group (Preferably 0-30 carbon atoms, more preferred 0 to 20 carbon atoms, particularly preferably a sulfamoyl group having 0 to 12 carbon atoms, such as sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, and the like phenylsulfamoyl.),

An alkylthio group (preferably an alkylthio group having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylthio and ethylthio), an arylthio group (preferably An arylthio group having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenylthio, and a heterocyclic thio group (preferably having 1 to 30 carbon atoms). More preferably a heterocyclic thio group having 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio and the like. ),

A sulfonyl group (preferably a sulfonyl group having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as mesyl, tosyl, etc.), a sulfinyl group (preferably A sulfinyl group having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfinyl, benzenesulfinyl, etc.), ureido group (preferably having 1 carbon atom) -30, more preferably a ureido group having 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as ureido, methylureido, phenylureido, etc.), a phosphoramide group (preferably having a carbon number) A phosphoric acid amide group having 1 to 30, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, For example, diethyl phosphoric acid amide, phenylphosphoric acid amide, etc.), hydroxy group, mercapto group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, more preferably fluorine atom). ),

A cyano group, a carboxy group, an oxo group, a nitro group, a hydroxamic acid group, a sulfino group, a hydrazino group, an imino group, a heterocyclic group (preferably a 3- to 7-membered heterocyclic group, neither an aromatic heterocyclic ring nor aromatic The heteroatom may be a heterocycle, and examples of the heteroatom constituting the heterocycle include a nitrogen atom, an oxygen atom and a sulfur atom, preferably 0 to 30 carbon atoms, more preferably a heterocycle having 1 to 12 carbon atoms. Specific examples include imidazolyl, pyridyl, quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, carbazolyl, azepinyl, and the like, and a silyl group (preferably having a carbon number). A silyl group having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, and particularly preferably 3 to 24 carbon atoms. Examples thereof include trimethylsilyl and triphenylsilyl), silyloxy groups (preferably silyloxy groups having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, and particularly preferably 3 to 24 carbon atoms. , Triphenylsilyloxy, etc.).
These substituents may be further substituted with any one or more substituents selected from the above substituent group Z.
When there are a plurality of substituents in one structural site, these substituents are connected to each other to form a ring, or condensed with a part or all of the structural site to form an aromatic ring or an unsaturated heterocycle. A ring may be formed.

When a compound or a substituent includes an alkyl group, an alkenyl group, etc., these may be linear or branched, and may be substituted or unsubstituted. When an aryl group, a heterocyclic group, or the like is included, they may be monocyclic or condensed, and may be substituted or unsubstituted.
In the present specification, what is simply described as a substituent refers to this substituent group Z unless otherwise specified. Further, when only the name of each group is described (for example, when only “alkyl group” is described), preferred ranges and specific examples of the corresponding group of this substituent group Z are applied. .

The molecular weight of the polyimide compound is preferably 10,000 to 1,000,000 as a weight average molecular weight, more preferably 15,000 to 500,000, and still more preferably 20,000 to 200,000. Even more preferably, it is 50,000 to 150,000.

In the present specification, unless otherwise specified, the molecular weight and the dispersity are values measured using a GPC (gel filtration chromatography) method, and the molecular weight is a weight average molecular weight in terms of polystyrene. The gel packed in the column used in the GPC method is preferably a gel having an aromatic compound as a structural unit, for example, a gel made of a styrene-divinylbenzene copolymer. Two to six columns are preferably connected and used. Examples of the solvent used include ether solvents such as tetrahydrofuran and amide solvents such as N-methylpyrrolidinone. The measurement is preferably performed at a solvent flow rate in the range of 0.1 to 2 mL / min, and most preferably in the range of 0.5 to 1.5 mL / min. By performing the measurement within this range, the apparatus is not loaded and the measurement can be performed more efficiently. The measurement temperature is preferably 10 to 50 ° C, most preferably 20 to 40 ° C. Note that the column and carrier to be used can be appropriately selected according to the physical properties of the polymer compound that is symmetrical to the measurement.

[Synthesis of polyimide compounds]
The polyimide compound can be synthesized by condensation polymerization of a bifunctional acid anhydride (tetracarboxylic dianhydride) having a specific structure and a diamine having a specific structure. As a method for this, a general book (for example, Ikuo Imai, edited by Rikio Yokota, “Latest Polyimide: Fundamentals and Applications”, NTS Corporation, August 25, 2010, p. 3-49). , Etc.) can be carried out with appropriate reference to the methods described in the above.

The polyimide compound can be obtained by mixing each of the above raw materials in a solvent and performing condensation polymerization by a conventional method as described above.
Examples of the solvent include, but are not limited to, ester organic solvents such as methyl acetate, ethyl acetate, and butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol, cyclopentanone, and cyclohexanone. Aliphatic ketone-based organic solvents, ether-based organic solvents such as ethylene glycol dimethyl ether, dibutyl ether, tetrahydrofuran, methylcyclopentyl ether, and dioxane, N-methylpyrrolidone, 2-pyrrolidone, dimethylformamide, dimethylimidazolidinone, and dimethylacetamide Examples thereof include sulfur-containing organic solvents such as amide organic solvents, dimethyl sulfoxide, and sulfolane. These organic solvents are appropriately selected as long as it is possible to dissolve tetracarboxylic dianhydride as a reaction substrate, diamine compound, polyamic acid as a reaction intermediate, and polyimide compound as a final product. Is. Preferably, ester type (preferably butyl acetate), aliphatic ketone type (preferably methyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol, cyclopentanone, cyclohexanone), ether type (diethylene glycol monomethyl ether, methyl cyclopentyl ether), amide Solvents based on systems (preferably N-methylpyrrolidone) and sulfur-based systems (dimethyl sulfoxide, sulfolane) are preferred. Moreover, these can be used combining 1 type (s) or 2 or more types of solvent.

The polymerization reaction temperature is not particularly limited, and a temperature that can be usually employed in the synthesis of a polyimide compound can be employed. Specifically, it is preferably −50 to 250 ° C., more preferably −25 to 225 ° C., still more preferably 0 ° C. to 200 ° C., and particularly preferably 20 ° C. to 190 ° C.

The polyimide compound is obtained by imidizing the polyamic acid produced by the above polymerization reaction by dehydrating and ring-closing reaction in the molecule. As a method for dehydrating and ring-closing, a general book (for example, Ikuo Imai, edited by Rikio Yokota, “Latest Polyimide: Fundamentals and Applications”), NTS Corporation, August 25, 2010, p. 3 to 49, etc.) can be referred to. For example, it is heated to 120 ° C. to 200 ° C. to react while removing by-produced water out of the system, pyridine, triethylamine, DBU (1,8-diazabicyclo [5.4.0] undeca In the presence of a basic catalyst such as -7-ene), a technique such as so-called chemical imidization using a dehydration condensing agent such as acetic anhydride, dicyclohexylcarbodiimide, or triphenyl phosphite is preferably used.

The total concentration of tetracarboxylic dianhydride and diamine compound in the polymerization reaction solution of the polyimide compound is not particularly limited, but is preferably 5 to 70% by mass, more preferably 5 to 50% by mass, and 5 to 30%. More preferred is mass%.

Preferred examples of the polyimide compound represented by the formula (1) are as follows.

<N-substituted product>

[Gas separation membrane]
[Gas separation composite membrane]
In the gas separation composite membrane which is a preferred embodiment of the gas separation membrane of the present invention, a gas separation layer containing a specific polyimide compound is formed on the upper side of the gas permeable support layer. This composite membrane is preferably produced by applying the coating liquid (dope) containing the polyimide compound on at least the surface of the porous support to form the gas separation layer. In this specification, the application includes an aspect in which a coating solution is attached to the surface by dipping.
FIG. 1 is a longitudinal sectional view schematically showing a gas separation composite membrane 10 which is a preferred embodiment of the present invention. 1 is a gas separation layer, 2 is a support layer which consists of a porous layer. FIG. 2 is a cross-sectional view schematically showing a gas separation composite membrane 20 which is another preferred embodiment of the present invention. In this embodiment, a nonwoven fabric layer 3 is added as a support layer in addition to the gas separation layer 1 and the porous layer 2. In this embodiment, the gas permeable support layer includes a porous layer 2 on the gas separation layer 1 side and a nonwoven fabric layer 3 on the opposite side, and the gas separation layer 1 is located above the gas permeable support layer. Is provided. That is, in the gas separation composite membrane 20, the gas separation layer 1, the porous layer 2, and the nonwoven fabric layer 3 are provided in this order.
1 and 2 show an embodiment in which carbon dioxide is selectively permeated from a mixed gas containing carbon dioxide and methane to make the permeated gas rich in carbon dioxide.

In the present specification, “upper support layer” means that another layer may be interposed between the support layer and the gas separation layer. As for the upper and lower expressions, unless otherwise specified, the side to which the gas to be separated is supplied is “upper”, and the side from which the separated gas is discharged is “lower”.

The gas separation composite membrane may be formed or disposed on the surface or the inner surface of a porous support (support layer), and can be formed on at least the surface to easily form a composite membrane. . By forming a gas separation layer on at least the surface of the porous support, a composite membrane having the advantages of having both high separation selectivity, high gas permeability, and mechanical strength can be obtained. The thickness of the separation layer is preferably a thin film as much as possible under the condition of imparting high gas permeability while maintaining mechanical strength and separation selectivity.

In the gas separation composite membrane, the thickness of the gas separation layer is not particularly limited. The thickness of the gas separation layer is preferably from 0.01 to 5.0 μm, and more preferably from 0.05 to 2.0 μm.

The porous support (porous layer) preferably applied to the support layer is not particularly limited as long as it has the purpose of meeting mechanical strength and imparting high gas permeability. It may be a material. An organic polymer porous film is preferable, and the thickness thereof is 1 to 3,000 μm, preferably 5 to 500 μm, and more preferably 5 to 150 μm. The pore structure of this porous membrane usually has an average pore diameter of 10 μm or less, preferably 0.5 μm or less, more preferably 0.2 μm or less. The porosity is preferably 20 to 90%, more preferably 30 to 80%.
Here, that the support layer has “gas permeability” means that carbon dioxide is supplied to the support layer (a film composed of only the support layer) at a temperature of 40 ° C. with a total pressure of 5 MPa on the gas supply side. This means that the permeation rate of carbon dioxide is 1 × 10 ⁻⁵ cm ³ (STP) / cm ² · sec · cmHg (10 GPU) or more. Further, the gas permeability of the support layer is such that when carbon dioxide is supplied at a temperature of 40 ° C. and the total pressure on the gas supply side is 5 MPa, the carbon dioxide permeation rate is 3 × 10 ⁻⁵ cm ³ (STP) / It is preferably cm ² · sec · cmHg (30 GPU) or more, more preferably 100 GPU or more, and further preferably 200 GPU or more.
Examples of the material for the porous membrane include conventionally known polymers such as polyolefin resins such as polyethylene and polypropylene, fluorine-containing resins such as polytetrafluoroethylene, polyvinyl fluoride, and polyvinylidene fluoride, polystyrene, and cellulose acetate. And various resins such as polyurethane, polyacrylonitrile, polyphenylene oxide, polysulfone, polyethersulfone, polyimide, and polyaramid. The shape of the porous membrane can be any shape such as a flat plate shape, a spiral shape, a tubular shape, and a hollow fiber shape.

In the gas separation composite membrane, it is preferable that a support is formed in order to impart further mechanical strength to the lower portion of the support layer forming the gas separation membrane. Examples of such a support include woven fabrics, nonwoven fabrics, nets, and the like, but nonwoven fabrics are preferably used in terms of film forming properties and cost. As the nonwoven fabric, fibers made of polyester, polypropylene, polyacrylonitrile, polyethylene, polyamide or the like may be used alone or in combination. The nonwoven fabric can be produced, for example, by making a main fiber and a binder fiber uniformly dispersed in water using a circular net or a long net, and drying with a dryer. In addition, for the purpose of removing fluff or improving mechanical properties, it is also preferable to apply a heat treatment by sandwiching the nonwoven fabric between two rolls.

<Method for producing gas separation composite membrane>
The production method of the composite membrane is preferably a production method including forming a gas separation layer by applying a coating liquid containing the polyimide compound on a support. The content of the polyimide compound in the coating solution is not particularly limited, but is preferably 0.1 to 30% by mass, and more preferably 0.5 to 10% by mass. If the content of the polyimide compound is too low, when the gas separation layer is formed on the porous support, the coating liquid easily penetrates into the lower layer, which may cause defects in the surface layer that contributes to gas separation. Becomes higher. In addition, if the content of the polyimide compound is too high, when the gas separation layer is formed on the porous support, the coating solution may be filled in the pores at a high concentration, and the gas permeability may be lowered. is there. The gas separation membrane of the present invention can be appropriately produced by adjusting the molecular weight, structure, composition, and solution viscosity of the polymer in the separation layer.

The organic solvent used as a medium for the coating solution is not particularly limited, but is a hydrocarbon organic solvent such as n-hexane and n-heptane, or an ester organic such as methyl acetate, ethyl acetate, or butyl acetate. Solvent, lower alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol, aliphatics such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol, cyclopentanone, and cyclohexanone Ketone, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol methyl ether, di Lopylene glycol methyl ether, tripropylene glycol methyl ether, ethylene glycol phenyl ether, propylene glycol phenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, dibutyl ether, Examples include ether organic solvents such as tetrahydrofuran, methylcyclopentyl ether, and dioxane, N-methylpyrrolidone, 2-pyrrolidone, dimethylformamide, dimethylimidazolidinone, dimethylsulfoxide, and dimethylacetamide. These organic solvents are appropriately selected as long as they do not adversely affect the substrate, such as ester-based (preferably butyl acetate), alcohol-based (preferably methanol, ethanol, isopropanol). , Isobutanol), aliphatic ketones (preferably methyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol, cyclopentanone, cyclohexanone), ether type (ethylene glycol, diethylene glycol monomethyl ether, methyl cyclopentyl ether) are preferred, and more preferred are fats Group-based ketones, alcohols, and ethers. Moreover, these can be used 1 type or in combination of 2 or more types.

(Other layers between the support layer and the gas separation layer)
In the gas separation composite membrane, another layer may exist between the support layer and the gas separation layer. A preferred example of the other layer is a siloxane compound layer. By providing the siloxane compound layer, the unevenness on the outermost surface of the support can be smoothed, and the separation layer can be easily thinned. Examples of the siloxane compound that forms the siloxane compound layer include those in which the main chain is made of polysiloxane and compounds in which the main chain includes a siloxane structure and a non-siloxane structure.
In the present specification, the term “siloxane compound” means an organopolysiloxane compound unless otherwise specified.

-Siloxane compounds whose main chain consists of polysiloxane-
Examples of the siloxane compound having a main chain made of polysiloxane that can be used in the siloxane compound layer include one or more polyorganosiloxanes represented by the following formula (i) or (ii). Moreover, these polyorganosiloxanes may form a crosslinking reaction product. As the cross-linking reaction, for example, compounds represented by the following formula (i) is cross-linked by a polysiloxane compound having a group capable of linking by reacting with the reactive group X ^S of the formula (i) at both ends The compound of the form is mentioned.

In the formula (i), R ^S is a non-reactive group, and is an alkyl group (preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms) or an aryl group (preferably having 6 to 6 carbon atoms). 15, more preferably an aryl group having 6 to 12 carbon atoms, and still more preferably phenyl).
X ^S is a reactive group, and is selected from a hydrogen atom, a halogen atom, a vinyl group, a hydroxy group, and a substituted alkyl group (preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms). It is preferably a group.
Y ^S and Z ^S each independently have the same ^meaning as any of the above R ^S and X ^S.
m is an integer of 1 or more, preferably 1 to 100,000.
n is an integer of 0 or more, preferably 0 to 100,000.

Wherein ^{^{^{(ii), X S, Y}}} S, Z S, R S, m and n are ^X S of each formula ^{^{(i), Y S, Z}} S, R S, and m and n synonymous.

In the formulas (i) and (ii), when the non-reactive group R ^S is an alkyl group, examples of the alkyl group include methyl, ethyl, hexyl, octyl, decyl, and octadecyl. When the non-reactive group R is a fluoroalkyl group, examples of the fluoroalkyl group include —CH ₂ CH ₂ CF ₃ and —CH ₂ CH ₂ C ₆ F ₁₃ .

In the formulas (i) and (ii), when the reactive group ^XS is a substituted alkyl group, examples of the alkyl group include a hydroxyalkyl group having 1 to 18 carbon atoms and an aminoalkyl group having 1 to 18 carbon atoms. A carboxyalkyl group having 1 to 18 carbon atoms, a chloroalkyl group having 1 to 18 carbon atoms, a glycidoxyalkyl group having 1 to 18 carbon atoms, a glycidyl group, an epoxycyclohexylalkyl group having 7 to 16 carbon atoms, carbon Examples thereof include a (1-oxacyclobutan-3-yl) alkyl group, a methacryloxyalkyl group, and a mercaptoalkyl group having 4 to 18.
The number of carbon atoms of the alkyl group constituting the hydroxyalkyl group is preferably an integer of 1 to 10, for example, —CH ₂ CH ₂ CH ₂ OH.
The number of carbon atoms in the alkyl group constituting the aminoalkyl group is preferably an integer of 1 to 10, for example, —CH ₂ CH ₂ CH ₂ NH ₂ .
The number of carbon atoms of the alkyl group constituting the carboxyalkyl group is preferably an integer of 1 to 10, and examples thereof include —CH ₂ CH ₂ CH ₂ COOH.
The alkyl group constituting the chloroalkyl group preferably has an integer of 1 to 10, and a preferred example is —CH ₂ Cl.
A preferable carbon number of the alkyl group constituting the glycidoxyalkyl group is an integer of 1 to 10, and a preferred example is 3-glycidyloxypropyl.
The preferable number of carbon atoms of the epoxy cyclohexyl alkyl group having 7 to 16 carbon atoms is an integer of 8 to 12.
A preferable carbon number of the (1-oxacyclobutan-3-yl) alkyl group having 4 to 18 carbon atoms is an integer of 4 to 10.
A preferable carbon number of the alkyl group constituting the methacryloxyalkyl group is an integer of 1 to 10, and examples thereof include —CH ₂ CH ₂ CH ₂ —OOC—C (CH ₃ ) ═CH ₂ .
A preferable carbon number of the alkyl group constituting the mercaptoalkyl group is an integer of 1 to 10, and examples thereof include —CH ₂ CH ₂ CH ₂ SH.
m and n are preferably numbers that give a molecular weight of 5,000 to 1,000,000 of the compound.

In the formulas (i) and (ii), a reactive group-containing siloxane unit (wherein the number is a structural unit represented by n) and a siloxane unit having no reactive group (where the number is m) There is no particular limitation on the distribution of the structural units represented. That is, in formulas (i) and (ii), (Si (R ^S ) (R ^S ) —O) units and (Si (R ^S ) (X ^S ) —O) units may be randomly distributed. .

-Compounds containing siloxane and non-siloxane structures in the main chain-
Examples of the compound containing a siloxane structure and a non-siloxane structure in the main chain that can be used in the siloxane compound layer include compounds represented by the following formulas (iii) to (vi).

Wherein ^{(iii), R S,} m and n have the same meanings as ^R S, m and n, respectively formula (i). R ^L is —O— or —CH ₂ —, and R ^S1 is a hydrogen atom or methyl. Both ends of formula (iii) are preferably each independently an amino group, a hydroxyl group, a carboxy group, a trimethylsilyl group, an epoxy group, a vinyl group, a hydrogen atom, or a substituted alkyl group.

In the formula (iv), m and n are synonymous with m and n in the formula (i), respectively.

In the formula (v), m and n have the same meanings as m and n in the formula (i), respectively.

In the formula (vi), m and n are synonymous with m and n in the formula (i), respectively. It is preferable that both ends of the formula (vi) are independently bonded with an amino group, a hydroxyl group, a carboxy group, a trimethylsilyl group, an epoxy group, a vinyl group, a hydrogen atom, or a substituted alkyl group.

In the formula (vii), m and n are synonymous with m and n in the formula (i), respectively. It is preferable that both ends of the formula (vii) are independently bonded with an amino group, a hydroxyl group, a carboxy group, a trimethylsilyl group, an epoxy, a vinyl group, a hydrogen atom, or a substituted alkyl group.

In the formulas (iii) to (vii), the siloxane structural unit and the non-siloxane structural unit may be randomly distributed.

The compound containing a siloxane structure and a non-siloxane structure in the main chain preferably contains 50 mol% or more of siloxane structural units, more preferably 70 mol% or more, based on the total number of moles of all repeating structural units. .

The weight average molecular weight of the siloxane compound used in the siloxane compound layer is preferably 5,000 to 1,000,000 from the viewpoint of achieving both a thin film and durability. The method for measuring the weight average molecular weight is as described above.

Furthermore, the preferable example of the siloxane compound which comprises a siloxane compound layer is enumerated below.
Polydimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, polysulfone / polyhydroxystyrene / polydimethylsiloxane copolymer, dimethylsiloxane / methylvinylsiloxane copolymer, dimethylsiloxane / diphenylsiloxane / methylvinylsiloxane copolymer, methyl -3,3,3-trifluoropropylsiloxane / methylvinylsiloxane copolymer, dimethylsiloxane / methylphenylsiloxane / methylvinylsiloxane copolymer, diphenylsiloxane / dimethylsiloxane copolymer terminal vinyl, polydimethylsiloxane terminal vinyl, One or more selected from polydimethylsiloxane terminal H and dimethylsiloxane / methylhydrosiloxane copolymer. In addition, the form which forms the crosslinking reaction material is also contained in these compounds.

In the gas separation composite membrane, the thickness of the siloxane compound layer is preferably 0.01 to 5 μm and more preferably 0.05 to 1 μm from the viewpoint of smoothness and gas permeability.
Further, the gas permeability at 40 ° C. and 4 MPa of the siloxane compound layer is preferably 100 GPU or more, more preferably 300 GPU or more, and further preferably 1,000 GPU or more in terms of carbon dioxide transmission rate.

[Gas separation asymmetric membrane]
The gas separation membrane may be an asymmetric membrane. The asymmetric membrane can be formed by a phase change method using a solution containing a polyimide compound. The phase inversion method is a known method for forming a film while bringing a polymer solution into contact with a coagulation liquid to cause phase conversion. In the present invention, a so-called dry / wet method is suitably used. The dry and wet method evaporates the solution on the surface of the polymer solution in the form of a film to form a thin dense layer, and then immerses it in a coagulation liquid (solvent that is compatible with the solvent of the polymer solution and the polymer is insoluble), This is a method of forming a porous layer by forming micropores using the phase separation phenomenon that occurs at that time, and proposed by Rob Thrillerjan et al. (For example, US Pat. No. 3,133,132) It is.

In the gas separation asymmetric membrane, the thickness of the surface layer contributing to gas separation called a dense layer or skin layer is not particularly limited. The thickness of the surface layer is preferably 0.01 to 5.0 μm and more preferably 0.05 to 1.0 μm from the viewpoint of imparting practical gas permeability. On the other hand, the porous layer below the dense layer lowers the gas permeability resistance and at the same time plays a role of imparting mechanical strength, and its thickness is particularly limited as long as it is self-supporting as an asymmetric membrane. It is not limited. This thickness is preferably 5 to 500 μm, more preferably 5 to 200 μm, and even more preferably 5 to 100 μm.

The gas separation asymmetric membrane may be a flat membrane or a hollow fiber membrane. The asymmetric hollow fiber membrane can be produced by a dry and wet spinning method. The dry-wet spinning method is a method for producing an asymmetric hollow fiber membrane by applying a dry-wet method to a polymer solution that is discharged from a spinning nozzle and has a hollow fiber-like target shape. More specifically, the polymer solution is discharged from a nozzle into a hollow fiber-shaped target shape, and after passing through an air or nitrogen gas atmosphere immediately after discharge, the polymer is not substantially dissolved and is compatible with the solvent of the polymer solution. In this method, an asymmetric structure is formed by immersing in a coagulating liquid containing, then dried, and further heat-treated as necessary to produce a separation membrane.

The solution viscosity of the solution containing the polyimide compound discharged from the nozzle is 2 to 17,000 Pa · s, preferably 10 to 1,500 Pa · s, particularly preferably 20 to 1,000 Pa · s at the discharge temperature (for example, 10 ° C.). It is preferable that a shape after discharge such as a hollow fiber shape can be stably obtained. For immersion in the coagulation liquid, the film is immersed in the primary coagulation liquid and solidified to such an extent that the shape of the hollow fiber or the like can be maintained. It is preferable to solidify. It is efficient to dry the coagulated film after replacing the coagulating liquid with a solvent such as hydrocarbon. The heat treatment for drying is preferably performed at a temperature lower than the softening point or secondary transition point of the used polyimide compound.

In the gas separation membrane, a siloxane compound layer may be provided as a protective layer on the gas separation layer.

[Uses and characteristics of gas separation membranes]
Gas separation membranes (composite membranes and asymmetric membranes) can be suitably used in gas separation recovery methods and gas separation purification methods. For example, hydrogen, helium, carbon monoxide, carbon dioxide, hydrogen sulfide, oxygen, nitrogen, ammonia, sulfur oxides, nitrogen oxides, methane, hydrocarbons such as ethane, unsaturated hydrocarbons such as propylene, tetrafluoroethane Thus, a gas separation membrane capable of efficiently separating a specific gas from a gas mixture containing a gas such as a perfluoro compound can be obtained. In particular, a gas separation membrane that selectively separates carbon dioxide from a gas mixture containing carbon dioxide / hydrocarbon (methane) is preferable.

In particular, when the gas to be separated is a mixed gas containing carbon dioxide and methane, the permeation rate of carbon dioxide in the mixed gas at 40 ° C. and 5 MPa is preferably more than 20 GPU, more than 30 GPU. Is more preferably 35 to 500 GPU, still more preferably 50 to 500 GPU, and particularly preferably 80 to 500 GPU. The permeation rate ratio of carbon dioxide to methane (R _CO2 / R _CH4 ) is preferably 10 or more, more preferably 15 or more, further preferably 20 or more, and more preferably 30 or more. Further preferred. R _CO2 represents the permeation rate of carbon dioxide, and R _CH4 represents the permeation rate of methane.
1 GPU is 1 × 10 ⁻⁶ cm ³ (STP) / cm ² · sec · cmHg.

[Other ingredients]
Various polymer compounds can be added to the gas separation layer of the gas separation membrane in order to adjust the membrane properties. High molecular compounds include acrylic polymers, polyurethane resins, polyamide resins, polyester resins, epoxy resins, phenol resins, polycarbonate resins, polyvinyl butyral resins, polyvinyl formal resins, shellac, vinyl resins, acrylic resins, rubber resins. Waxes and other natural resins can be used. Two or more of these may be used in combination.
In addition, a nonionic surfactant, a cationic surfactant, and / or an organic fluoro compound can be added to adjust liquid properties.

Specific examples of the surfactant include alkylbenzene sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfonate of higher fatty acid ester, sulfate ester of higher alcohol ether, sulfonate of higher alcohol ether, higher alkyl Anionic surfactants such as alkyl carboxylates of sulfonamides and alkyl phosphates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, ethylene oxide adducts of acetylene glycol And nonionic surfactants such as ethylene oxide adduct of glycerin and polyoxyethylene sorbitan fatty acid ester. In addition, amphoteric surfactants such as alkyl betaines and amide betaines, silicon surfactants, and fluorosurfactants are also included. Including these, the surfactant can be appropriately selected from conventionally known surfactants and derivatives thereof.

The gas separation layer of the gas separation membrane may contain a polymer dispersant. Specific examples of the polymer dispersant include polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyethylene glycol, polypropylene glycol, and polyacrylamide. Among them, polyvinyl pyrrolidone is preferably used.

The conditions for forming the gas separation membrane are not particularly limited, but the temperature is preferably −30 to 100 ° C., more preferably −10 to 80 ° C., and particularly preferably 5 to 50 ° C.

When forming the film, a gas such as air or oxygen may coexist, but an inert gas atmosphere is desirable.
In the gas separation membrane, the content of the polyimide compound in the gas separation layer is not particularly limited as long as desired gas separation performance can be obtained. From the viewpoint of further improving the gas separation performance, the content of the polyimide compound in the gas separation layer is preferably 20% by mass or more, more preferably 40% by mass or more, and 60% by mass or more. Is more preferable, and 70% by mass or more is particularly preferable. The content of the polyimide compound in the gas separation layer may be 100% by mass, but is usually 99% by mass or less.

[Separation method of gas mixture]
The gas separation method of the present invention is a method for separating a specific gas from a mixed gas of two or more components using the gas separation membrane of the present invention. The gas separation method includes selectively permeating carbon dioxide from a mixed gas containing carbon dioxide and methane. The pressure during gas separation is preferably 0.5 to 10 MPa, more preferably 1 to 10 MPa, and further preferably 2 to 7 MPa. The gas separation temperature is preferably −30 to 90 ° C., more preferably 15 to 70 ° C. In the mixed gas containing carbon dioxide and methane gas, the mixing ratio of carbon dioxide and methane gas is not particularly limited, but is preferably carbon dioxide: methane gas = 1: 99 to 99: 1 (volume ratio). More preferably, methane gas = 5: 95 to 90:10.

[Gas separation module or gas separation device]
A gas separation module can be prepared using the gas separation membrane of the present invention. Examples of the module include a spiral type, a hollow fiber type, a pleat type, a tubular type, and a plate and frame type.
In addition, a gas separation apparatus having means for separating and recovering or purifying gas can be obtained by using the gas separation composite membrane or the gas separation module of the present invention. The gas separation composite membrane of the present invention may be applied to, for example, a membrane used in combination with an absorbing solution and / or a gas separation / recovery device as an absorption hybrid method as described in JP-A-2007-297605.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In this example, “parts” and “%” mean “parts by mass” and “mass%” unless otherwise specified.

(Synthesis example)
<Synthesis of sulfonamide-containing diamine (SA-1)>
In a three-necked flask equipped with a condenser and a stirrer, 51.9 g of 1,4-phenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 250 g of acetonitrile were weighed and stirred while cooling to 0 to 5 ° C. Next, after dissolving 28.1 g of 4,4′-biphenyldisulfonyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) in 300 g of tetrahydrofuran, the solution was transferred to a dropping funnel and placed in the above-mentioned three-necked flask for 1 hour. Added dropwise and then stirred for 1 hour. The reaction solution was returned to room temperature, stirred for 2 hours, and then dissolved by adding 328 g of a 1M aqueous sodium hydroxide solution and 500 g of pure water. The reaction solution was transferred to a separatory funnel and separated and washed three times with 500 mL of ethyl acetate, and the aqueous phase was recovered. In a 5 L beaker, 17.5 g of ammonium chloride (manufactured by Kanto Chemical Co., Inc.) was weighed and dissolved in 2 L of pure water. While stirring at room temperature, the recovered aqueous phase was dropped into a 5 L beaker, and the precipitated crystals were collected by filtration. The crystals were reslurry washed with 1 L of pure water, and the crystals were collected by filtration. Then, the crystals were reslurry washed with 500 mL of chloroform, and then the crystals were collected by filtration and then vacuum-dried at 40 ° C. for 24 hours to obtain the target product (SA-1) 20 .5 g was obtained. The desired product was confirmed from the NMR spectrum.
SA-2 to SA-18 were synthesized in the same manner as described above except that the raw materials were appropriately changed.

<Synthesis of sulfonamide-containing diamine (SA-6)>
In a three-necked flask equipped with a condenser and a stirrer, 500.0 g of chlorosulfonic acid was weighed, and then 130.96 g of diphenylsulfone (manufactured by Aldrich) was added at room temperature, followed by stirring at room temperature for 1 hour. . The reaction solution was heated to 80 ° C. and stirred for 8 hours. The reaction solution was cooled to room temperature with stirring, crystallized in 2 L of ice-cold water, stirred for 30 minutes, and then collected by filtration and dissolved in 6 L of ethyl acetate. This ethyl acetate solution was transferred to a separating funnel, and separated and washed twice with pure water, and then separated and washed with saturated saline. The organic phase was transferred to an Erlenmeyer flask, 30 g of magnesium sulfate was added and stirred, and the solid matter was removed by filtration. Then, the ethyl acetate was distilled off using an evaporator, followed by vacuum drying at 40 ° C. for 24 hours. 145 g of precursor (S-6) (disulfonic acid chloride) was obtained. The precursor (S-6) was confirmed from the NMR spectrum. The precursor S-6 was analyzed by ¹ NMR. The results are shown below.
¹ NMR data (heavy D tetrahydrofuran, 400 MHz, internal standard: tetramethylsilane)
δ (ppm) = 8.00-8.04 (t, 2H), 8.43-8.48 (d, 2H), 8.56-8.59 (d, 2H), 8.76 (s, 2H)

In a three-necked flask equipped with a condenser and a stirrer, 43.26 g of 1,4-phenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 200 g of acetonitrile were weighed and stirred while cooling to 0 to 5 ° C. After dissolving 20.76 g of the precursor (S-6) obtained above in 200 g of tetrahydrofuran, it was transferred to a dropping funnel, dropped into the stirring three-necked flask over 1 hour, and then stirred for 1 hour. . The reaction solution was returned to room temperature and stirred for 2 hours, and then 205 g of 1M sodium hydroxide aqueous solution and 300 g of pure water were added and dissolved. The reaction solution was transferred to a separatory funnel and separated and washed three times with 500 mL of ethyl acetate, and the aqueous phase was recovered. In a 3 L beaker, 12.04 g of ammonium chloride (manufactured by Kanto Chemical Co., Inc.) was weighed and dissolved in 1 L of pure water. While stirring at room temperature, the recovered aqueous phase was dropped into a 3 L beaker, and the precipitated crystals were collected by filtration. The crystals were reslurry washed with 1 L of pure water, and the crystals were collected by filtration. Then, the crystals were reslurry washed with 500 mL of methanol, and then the crystals were collected by filtration and then vacuum-dried at 40 ° C. for 24 hours to obtain the target product (SA-6) 26 0.1 g was obtained. The desired product was confirmed from the NMR spectrum.
The target product (SA-6) was analyzed by ¹ NMR. The results are shown below.
¹ NMR data (heavy DMSO, 400 MHz, internal standard: tetramethylsilane)
δ (ppm) = 5.04 (s, 4H), 6.32-6.34 (d, 4H), 6.56-6.59 (d, 4H), 7.82-7.86 (t, 2H), 7.89-7.91 (d, 2H), 7.98-8.00 (d, 2H), 8.15 (s, 2H), 9.69 (s, 2H)

<Synthesis of polyimide compound (PI-1)>
In a three-necked flask equipped with a condenser and a stirrer, 12.37 g of SA-1 and 93.8 g of N-methyl-2-pyrrolidone obtained by the same method as the above synthesis method were weighed and cooled on ice. While stirring, a uniform solution was obtained. 11.11 g of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to this homogeneous solution, stirred at 0-10 ° C. for 1 hour, and then reacted at room temperature for 6 hours. I let you. Next, 29.3 g of N-methyl-2-pyrrolidone, 7.91 g of pyridine, and 6.38 g of acetic anhydride were added in this order, and reacted at 80 ° C. for 3 hours. The reaction solution was added to 0.4 L of methanol to precipitate polyimide. This was collected by filtration, washed and dried to obtain 19.2 g of a polyimide compound (PI-1) having a weight average molecular weight of 115,000. It was confirmed from the NMR spectrum, IR spectrum, and GPC (polystyrene conversion) that it was the target product.
PI-2 to PI-28 were synthesized in the same manner as described above except that the raw materials were appropriately changed.

<Synthesis Example of Polyimide Compound (PIC-3)>
In a three-necked flask equipped with a condenser and a stirrer, 3.00 g of polyimide compound PI-1 obtained by the above synthesis method and 27.0 g of N-methyl-2-pyrrolidone were weighed and stirred at room temperature. A homogeneous solution was obtained. 3.00 g of pyridine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1.96 g of acetic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, stirred at room temperature for 1 hour, and reacted at 80 ° C. for 3 hours. Next, 10 g of N-methyl-2-pyrrolidone, 20 g of acetone and 5.00 g of acetic acid were added in this order and dissolved. The reaction solution was added to 0.2 L of methanol to precipitate a polyimide compound. This was collected by filtration, washed and dried to obtain 2.8 g of a polyimide compound (PIC-3) having a weight average molecular weight of 125,000. It was confirmed from the NMR spectrum, IR spectrum, and GPC (polystyrene conversion) that it was the target product.
PIC-1 to PIC-2 and PIC-4 to PIC-11 can be synthesized in the same manner as described above except that the raw materials are appropriately changed.

In the examples, “weight average molecular weight” was calculated by a standard polystyrene conversion method using gel permeation chromatography (GPC). However, a GPC column packed with polystyrene cross-linked gel (TSKgel SuperAWM-H; manufactured by Tosoh Corporation) and N-methylpyrrolidone (phosphoric acid and lithium bromide 0.01 mol / L each) were used as a GPC solvent.

<Synthesis Example of Polyimide Compound (PIB-2)>
In a 200 ml three-necked flask, 95 g of N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.) was weighed, and then 5 g of polyimide compound PI-1 was added and dissolved while stirring. Next, 0.079 g of triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was weighed and added, and stirred at room temperature for 1 hour. The reaction solution was added to 0.5 L of methanol to precipitate a polyimide compound. This was collected by filtration, washed and dried to obtain 4.5 g of a polyimide compound (PIB-2) having a weight average molecular weight of 119,000. It was confirmed from the NMR spectrum, IR spectrum, and GPC (polystyrene conversion) that it was the target product.
PIB-1 and PIB-3 to PIB-6 can be synthesized in the same manner as described above except that the raw materials are appropriately changed.

[Example 1]
<Production of composite membrane>
The gas separation composite membrane shown in FIG. 2 was produced (the smooth layer is not shown in FIG. 2).
In a 30 ml brown vial, 1.4 g of polyimide compound (PI-2) and 8.6 g of methyl ethyl ketone were mixed and stirred for 30 minutes, and then 1-hydroxycyclohexyl phenyl ketone (manufactured by Aldrich, product number: 40,561). 28 mg of -2) was added, and the mixture was further stirred for 30 minutes to obtain a polymer solution. A polyacrylonitrile porous membrane (manufactured by GMT) is allowed to stand on a 10 cm square clean glass plate, and the above polymer solution is cast on the porous support membrane surface using an applicator to obtain a polyimide compound (PI-2). A gas separation layer containing was formed to obtain a composite membrane (Example 1). The thickness of the polyimide compound (PI-2) layer was about 1 μm, and the thickness of the polyacrylonitrile porous film including the nonwoven fabric was about 180 μm.
These polyacrylonitrile porous membranes had a molecular weight cut-off of 100,000 or less.

[Examples 2 to 8, Comparative Examples 1 and 2]
<Production of other composite films>
The polyimide compounds in Example 1 were changed as shown in Table 4, and composite films of Examples 2 to 8 were produced.
In addition, the polyimide compounds in Example 1 were changed as shown in Table 4, and composite films of Comparative Examples 1 and 2 were produced.
The comparative polyimide compounds used in Comparative Examples 1 and 2 are shown below.

<Evaluation of gas separation performance>
The gas separation performance of each obtained composite membrane was evaluated as follows. Use a mass flow controller to adjust the volume ratio of carbon dioxide (CO ₂ ) and methane (CH ₄ ) to 1: 1 using a SUS316 stainless steel cell (DENISSEN) with high pressure resistance, and mixed gas Was adjusted so that the total pressure on the gas supply side was 5 MPa (partial pressure of CO ₂ and CH ₄ : 2.5 MPa), and was supplied to each composite membrane. The permeability of each gas of CO ₂ and CH ₄ was measured by TCD detection type gas chromatography. The gas permeability of each composite membrane was compared by calculating the gas permeability (Permeance). The unit of gas permeability was expressed in GPU (GPU) units (1 GPU = 1 × 10 ⁻⁶ cm ³ (STP) / (s · cm ² · cmHg)).
Regarding the gas separation selectivity, a carbon dioxide / methane permeation ratio of 30 or more was evaluated as A, 20 or more and less than 30 as evaluation B, 10 or more and less than 20 as evaluation C, and 0 or more and less than 10 as evaluation D.
Regarding the gas permeability of carbon dioxide in the mixed gas, the gas permeability of 80 GPU or more was evaluated as A, the evaluation of 50 GPU or more and less than 80 GPU was evaluated B, the evaluation of 20 GPU or more and less than 50 GPU was evaluated C, and the evaluation of D was less than 20 GPU.

<Toluene resistance test>
A 1% by mass solution of the polyimide compound of each Example and Comparative Example was dried overnight to prepare a bulk sample of about 150 to 180 mg. Next, the mixture was aged at 90 ° C. for 1 week, and allowed to stand in a 25 ° C., 20% RH environment for more than half a day, and the mass was measured as the initial mass. Thereafter, these bulk samples were stored in a vapor atmosphere equilibrium toluene atmosphere container, and mass measurement was performed after 7 days. The change in mass (mass after 7 days / initial mass) was calculated and used as the toluene swelling rate.
Regarding toluene resistance, evaluation A was a toluene swelling ratio of less than 10%, evaluation B was 10% or more and less than 25%, evaluation C was 25% or more and less than 40%, and evaluation D was a toluene swelling ratio of 40% or more.

As shown in Table 4 above, the gas separation membrane using the polyimide compound of the comparative example was inferior in toluene resistance (plasticization resistance) (Comparative Examples 1 and 2).
On the other hand, the gas separation membrane of the present invention containing the polyimide compound of the example can realize gas permeability and gas separation selectivity at a desired high level, and is excellent in toluene resistance (plasticization resistance). (Examples 1 to 8).

From the above results, it was found that the gas separation membrane of the present invention can provide an excellent gas separation method, a gas separation module, and a gas separation apparatus equipped with this gas separation module.

DESCRIPTION OF SYMBOLS 1 Gas separation layer 2 Porous layer 3

Nonwoven fabric layer

10, 20 Gas separation composite membrane

Claims

A gas separation membrane having a gas separation layer containing a polyimide compound, wherein the polyimide compound is a structural unit represented by formula (1), a structural unit represented by formula (2), and formula (3). A gas separation membrane comprising at least one selected from the structural units represented.

In the formula (1), R represents a tetravalent group represented by any of the following formulas (I-1) to (I-28).

Here, X 1 to X 3 each independently represents a single bond or a divalent linking group, L represents —CH═CH— or —CH 2 —, and R 1 and R 2 each independently represents a hydrogen atom or a substituent. * Indicates a binding site with the carbonyl group in formula (1).

In formula (2) and formula (3), Z 1 to Z 4 each independently represents a divalent linking group, Q 1 and Q 2 each independently represents a divalent group containing a sulfonamide group, Y 1 represents a hydrogen atom, an alkyl group, an aryl group, or any group of formulas (4) to (6), X 1+ represents an organic or inorganic cation, and n is an integer of 0 or more.

In the formulas (4) to (6), R 3 to R 6 each independently represents an alkyl group or an aryl group. * 1 is a binding site with a nitrogen atom.
The gas separation membrane according to claim 1, wherein Z 1 to Z 4 are each independently a divalent group containing an arylene group and / or an alkylene group.
The gas separation membrane according to claim 1, wherein Z 1 to Z 4 are each independently any one of the following formulas A-1 to A-11.

In the formula, W 1 to W 50 each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, a sulfonamide group, or a carboxy group, and Z 11 represents —CR 8 2 —, —O—, —NR 8 -, - S- or a single bond, L 1 and L 2 -CR each independently 9 -, - O -, - NR 9 -, - S- or a single bond. R 8 and R 9 each independently represents an alkyl group or an aryl group.
A gas separation membrane having a gas separation layer containing a polyimide compound, wherein the polyimide compound is represented by the structural unit represented by the formula (1), the structural unit represented by the formula (8), and the formula (9). A gas separation membrane comprising at least one selected from the structural units represented.

In the formula (1), R represents a tetravalent group represented by any of the following formulas (I-1) to (I-28).

Here, X 1 to X 3 each independently represents a single bond or a divalent linking group, L represents —CH═CH— or —CH 2 —, and R 1 and R 2 each independently represents a hydrogen atom or a substituent. * Indicates a binding site with the carbonyl group in formula (1).

In formula (8) and formula (9), Z 5 to Z 10 each independently represent a divalent linking group, and Y 2 and Y 3 each independently represent a hydrogen atom, an alkyl group, an aryl group, or formula (4) Represents any group of formula (6), and X 2+ and X 3+ each independently represent an organic or inorganic cation.

In the formulas (4) to (6), R 3 to R 6 each independently represents an alkyl group or an aryl group. * 1 is a binding site with a nitrogen atom.
The gas separation membrane according to claim 4, wherein Z 5 to Z 10 are each independently a divalent group containing an arylene group and / or an alkylene group.
The gas separation membrane according to claim 4, wherein Z 5 to Z 10 are each independently any one of the following formulas A-1 to A-11.

In the formula, W 1 to W 50 each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, a sulfonamide group, or a carboxy group, and Z 11 represents —CR 8 2 —, —O—, —NR 8 -, - S- or a single bond, L 1 and L 2 -CR each independently 9 -, - O -, - NR 9 -, - S- or a single bond. R 8 and R 9 each independently represents an alkyl group or an aryl group.
The gas according to any one of claims 1 to 6, further comprising a gas permeable support layer, wherein the gas separation layer is a gas separation composite membrane provided on the upper side of the gas permeable support layer. Separation membrane.
The gas-permeable support layer includes a porous layer and a nonwoven fabric layer,
The gas separation membrane according to any one of claims 1 to 7, wherein the gas separation layer, the porous layer, and the nonwoven fabric layer are provided in this order.
The gas separation membrane according to any one of claims 1 to 8, which is used for selectively permeating carbon dioxide from a gas containing carbon dioxide and methane.
A gas separation module comprising the gas separation membrane according to any one of claims 1 to 8.
A gas separation apparatus comprising the gas separation module according to claim 10.
A gas separation method for selectively permeating carbon dioxide from a gas containing carbon dioxide and methane, using the gas separation membrane according to any one of claims 1 to 9.