Gas Separation Membranes

Abstract

To provide a gas separation membrane or the like enabling such a highly efficient gas separation that organic substance-enriched gas can be stably taken out from mixed vapor containing water vapor and vapor of the organic substance even during long-time operation.SOLUTION: The gas separation membrane according to the present invention has an asymmetric structure constituted of a skin layer having a gas separation function and a porous layer supporting the skin layer, wherein a water vapor permeation speed (P'H2O) measured using mixed vapor of ethanol and water vapor is 100×10-5 cm3(STP) / (cm2.sec.cmHg) or more, a permeation speed ratio (P'H2O / P'EtOH) of the water vapor and the ethanol is 100 or more, a tensile elongation at break measured in a state of a hollow fiber membrane is 50% or higher, and a tensile elongation at break of the hollow fiber membrane processed for 8.5 hours by 60 mass% of ethanol water solutions at 150°C is 40% or higher of a tensile elongation at break of the hollow fiber membrane not yet processed.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a gas separation membrane and a method for producing the same, as well as a method for separating water vapor using the gas separation membrane and a method for producing a gas enriched with organic vapor. [Background technology]

[0002] Gas separation membranes are used in various gas separation processes. Many of these are gas separation membranes formed from glassy polymers with high selective gas permeability. In general, gas separation membranes formed from glassy polymers have a high selective gas permeability (degree of separation), but a disadvantage in that they have a low gas permeability coefficient (permeation rate). For this reason, many gas separation membranes formed from glassy polymers have an asymmetric structure consisting of a relatively thin dense separation layer (generally sometimes called a "skin layer") and a relatively thick porous layer that supports the separation layer, that is, a structure in which the separation layer that generates gas permeation resistance is made thin to prevent the gas permeation rate from becoming too small.

[0003] The gas separation membrane is preferably used as a hollow fiber gas separation membrane module. A hollow fiber gas separation membrane module is usually constructed by housing a hollow fiber membrane bundle consisting of a large number of hollow fiber membranes in a container having at least an inlet for mixed gas, an outlet for permeated gas, and an outlet for non-permeated gas. In the hollow fiber gas separation membrane module, the mixed gas is supplied to a space in contact with the inside or outside of the hollow fiber membrane. The mixed gas contains a component with high permeability in the gas separation membrane constituting the hollow fiber gas separation membrane module (hereinafter also referred to as "high permeability component") and a component with lower permeability than that (hereinafter also referred to as "low permeability component"). While the mixed gas flows in contact with the hollow fiber membrane, the highly permeable component in the mixed gas selectively permeates the membrane, and the permeated gas enriched with the highly permeable component is recovered from the outlet for the permeated gas. On the other hand, the concentration of the highly permeable component is reduced, and the non-permeated gas enriched with the low permeable component is recovered from the outlet for the non-permeated gas. In this way, gas separation is performed.

[0004] A method is known in which a gas separation process using a hollow fiber membrane is used to contact a mixed vapor mainly containing organic vapor and water vapor, and the water vapor, which is a highly permeable component, is selectively permeated and separated to obtain a gas enriched with organic matter. H2O / P' EtOH ) of 100 or more is known (Patent Document 1).

[0005] Regarding hollow fiber gas separation membranes, a technique is known that uses a specific manufacturing method to improve the water vapor transmission rate in a mixed gas of water vapor and nitrogen gas and also improve the mechanical strength compared to conventional techniques (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2-222717 [Patent Document 2] JP 2018-171570 A Summary of the Invention [Problem to be solved by the invention]

[0007] The conventional gas separation membrane described in Patent Document 1 has a high ratio of water vapor to alcohol permeation rates and high alcohol resistance, but its water vapor permeation rate is insufficient and there is room for improvement in terms of mechanical strength. Patent Document 2 describes an improvement in the water vapor transmission rate and mechanical strength of a gas separation membrane. However, no consideration has been given to achieving both high separation performance in a mixed vapor containing water vapor and alcohol, high water vapor transmission rate, mechanical strength, and alcohol resistance, or to achieving both high separation performance in a mixed vapor containing water vapor and nitrogen, high water vapor transmission rate, and mechanical strength. [Means for solving the problem]

[0008] The present invention has an asymmetric structure composed of a skin layer as a separating layer and a porous layer as a supporting layer, Water vapor transmission rate (P') measured using a mixture of ethanol and water vapor H2O ) is 100 x 10 -5 cm 3 (STP) / (cm 2 sec cmHg) or more, Permeation rate ratio of water vapor to ethanol (P' H2O / P' EtOH ) is 100 or more, The tensile elongation at break of the hollow fiber membrane is 50% or more, The present invention provides a gas separation membrane in which the tensile breaking elongation of the hollow fiber membrane after treatment with a 60% by mass aqueous ethanol solution at 150° C. for 8.5 hours is 40% or more of the level before the treatment.

[0009] The present invention also provides a method for separating water vapor from a mixed gas containing water vapor, using the gas separation membrane.

[0010] The present invention also provides a method for producing an organic-enriched gas from a mixed vapor containing water vapor and vapor of an organic substance, using the gas separation membrane.

[0011] The present invention also relates to a gas separator having an asymmetric structure composed of a skin layer having a gas separation function and a porous layer supporting the skin layer, Water vapor transmission rate (P') measured using a mixture of water vapor and nitrogen gas H2O ') is 100 x 10 -5 cm 3 (STP) / (cm 2 sec cmHg) or more, Water vapor to nitrogen transmission rate ratio (P' H2O ' / P' N2 ) is 300 or more, The tensile elongation at break measured in the hollow fiber membrane state is 50% or more, The present invention provides a gas separation membrane in which the tensile breaking elongation of the hollow fiber membrane after treatment with a 60% by mass aqueous ethanol solution at 150° C. for 8.5 hours is 40% or more of the level before the treatment.

[0012] The present invention also provides a method for separating water vapor from a mixed gas containing water vapor, using the gas separation membrane.

[0013] The present invention further provides a method for dehumidifying or humidifying air containing water vapor by using the gas separation membrane.

[0014] The present invention also provides a method for producing each of the gas separation membranes, comprising the steps of: The present invention provides a method for producing a gas separation membrane, which includes a step of performing a dry-wet phase inversion process using a polyimide solution containing a polyimide and a solvent containing a phenolic solvent and an aliphatic alcohol. Effect of the Invention

[0015] The gas separation membrane of the present invention is an asymmetric membrane that has both a high water vapor transmission rate and high water vapor / alcohol separation performance, and has excellent mechanical strength and alcohol resistance. Therefore, by using the gas separation membrane of the present invention, a highly efficient hollow fiber gas separation membrane module can be obtained that can stably extract organic-enriched gas from a mixed vapor containing water vapor and organic vapor even during long-term operation. The gas separation membrane of the present invention has a high water vapor transmission rate and high water vapor / nitrogen separation performance, and can be suitably used for dehumidifying or humidifying air that contains water vapor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will now be described based on its preferred embodiments. In the gas separation membrane of the present invention, the skin layer refers to a layer thinner than the porous layer, which is mainly responsible for the gas separation performance. The skin layer is a very dense layer compared to the porous layer, and is usually very thin, preferably having a thickness of 0.001 to 5 μm. In the gas separation membrane of the present invention, the porous layer refers to a relatively thick porous layer that supports the skin layer, and preferably has a thickness of 10 to 2000 μm. Since the gas separation membrane has the advantages of a large effective surface area and high pressure resistance, it is preferable to form a hollow fiber membrane, and it is more preferable to use a hollow fiber membrane with an inner diameter of about 10 to 3000 μm and an outer diameter of about 30 to 7000 μm. The diameter of the pores in the porous layer is not particularly limited, but is generally about 0.01 to 100 μm. The thickness of the skin layer and the porous layer, the inner diameter and outer diameter of the hollow fiber membrane, and the diameter of the pores can be measured using an optical microscope or an electron microscope. The skin layer and the porous layer are usually made of the same type of resin. The gas separation membrane of the present invention may have other layers made of the same material as the skin layer and porous layer or made of different materials, as long as the gas separation performance and support performance of the skin layer and porous layer are not impaired.

[0017] The gas separation membrane of the present invention has a high water vapor transmission rate. Specifically, the gas separation membrane has a water vapor transmission rate (P' H2O ) is 100 x 10 -5 cm 3 (STP) / (cm 2 ·sec·cmHg) or more, and 150×10 -5 cm 3 (STP) / (cm 2 ·sec·cmHg) or more, and 200×10 -5 cm 3 (STP) / (cm 2 The water vapor transmission rate is not particularly limited, but from the viewpoint of ease of manufacturing the gas separation membrane, it is preferable that the water vapor transmission rate is 10000×10 -5 cm 3 (STP) / (cm 2 sec cmHg) or less, and 5000×10 -5 cm 3 (STP) / (cm2 sec cmHg) or less, and 1000×10 -5 cm 3 (STP) / (cm 2 sec cmHg) or less, and more preferably 500×10 -5 cm 3 (STP) / (cm 2 It is particularly preferable that the temperature is equal to or lower than 0.1 sq. m / s. sec cmHg. In this specification, "STP" stands for 0°C, 1 atm, and is an abbreviation for "Standard Temperature and Pressure." In the present invention, the method for measuring the water vapor transmission rate is determined depending on the object to be separated. When evaluating the performance of separating water vapor and ethanol vapor, the water vapor transmission rate is measured using a mixed vapor of water vapor and ethanol vapor (P' H2O On the other hand, when evaluating the separation performance between water vapor and nitrogen, the measurement is performed using a mixture of water vapor and nitrogen gas (P' H2O ').

[0018] The gas separation membrane of the present invention has the above-mentioned high water vapor permeation rate, and also has a high permeation rate ratio (separation degree) between water vapor and ethanol vapor. This makes it possible to separate water vapor and ethanol with high efficiency using the gas separation membrane of the present invention. The gas separation membrane of the present invention has a high permeation rate ratio between water vapor and ethanol (P' H2O / P' EtOH ) is preferably 100 or more, more preferably 150 or more, even more preferably 200 or more, and most preferably 250 or more. The upper limit of the permeation rate ratio is not particularly limited, but from the standpoint of ease of production of the gas separation membrane, it is preferably 100,000 or less, more preferably 10,000 or less, more preferably 1,000 or less, and more preferably 500 or less.

[0019] In the present invention, the permeation rate of ethanol vapor may be any rate that satisfies the above-mentioned water vapor velocity and the permeation rate ratio between water vapor and ethanol vapor.

[0020] In this specification, the water vapor transmission rate, the transmission rate ratio between water vapor and ethanol vapor, and the ethanol transmission rate are all measured at 100° C. using a mixed vapor of water vapor and ethanol vapor, and can be measured by the method described in the Examples below. A gas separation membrane having the above water vapor transmission rate, the transmission rate ratio between water vapor and ethanol vapor, and the ethanol transmission rate within the above ranges can be obtained by adjusting the composition of the polyimide resin in a suitable gas separation membrane manufacturing method described below.

[0021] The gas separation membrane of the present invention is also excellent in the separation performance of water vapor and nitrogen. Specifically, the gas separation membrane of the present invention has a ratio of the permeation rates of water vapor and nitrogen (P' H2O ' / P' N2 ) is preferably 300 or more, more preferably 500 or more, even more preferably 1000 or more, and most preferably 2000 or more. The upper limit of the permeation rate ratio is not particularly limited, but from the viewpoint of ease of production of the gas separation membrane, it is preferably 10000 or less, and more preferably 5000 or less.

[0022] Gas separation membranes have a water vapor transmission rate (P' H2O ') is 100 x 10 -5 cm 3 (STP) / (cm 2 ·sec·cmHg) or more, and 150×10 -5 cm 3 (STP) / (cm 2 ·sec·cmHg) or more, and 200×10 -5 cm 3 (STP) / (cm 2 It is more preferable that the water vapor transmission rate (P' H2O Although there is no particular limitation on the molecular weight, it is preferable that the molecular weight is 1000×10 -5 cm 3 (STP) / (cm 2 sec cmHg) or less, and 500×10 -5 cm 3(STP) / (cm 2 It is more preferable that the blood pressure be less than 1.5 sec cmHg.

[0023] In this specification, the water vapor transmission rate (P') is measured using a mixed gas of water vapor and nitrogen. H2O '), the ratio of water vapor to nitrogen permeation rates (P' H2O ' / P' N2 ) and the nitrogen permeation rate are all at 35° C. and can be measured by the method described in the Examples below. A gas separation membrane having the above-mentioned water vapor permeation rate, water vapor / nitrogen permeation rate ratio, and nitrogen permeation rate within the above-mentioned ranges can be obtained by adjusting the composition of the polyimide resin in a suitable gas separation membrane manufacturing method described below.

[0024] In the present invention, the mechanical strength of a gas separation membrane is represented by the breaking stress or breaking elongation in a tensile test when the membrane is a hollow fiber. Hereinafter, the breaking stress is referred to as the tensile breaking stress, and the breaking elongation is referred to as the tensile breaking elongation. These are values ​​measured at a temperature of 23°C using a tensile tester with a sample effective length of 20 mm and a tensile speed of 10 mm / min. The tensile breaking stress is the value obtained by dividing the breaking load at the tensile breaking of the hollow fiber membrane by the membrane cross-sectional area of ​​the hollow fiber [unit: MPa], and the tensile breaking elongation is the value of 100×(L-L0) / L0 [unit: %], where L0 is the original length of the hollow fiber and L is the length at the tensile breaking.

[0025] From the viewpoint of excellent mechanical strength and stable gas separation, the gas separation membrane of the present invention has a tensile breaking elongation measured in the state of a hollow fiber membrane of 50% or more, preferably 70% or more, and more preferably 90% or more. The upper limit of the tensile breaking elongation of the gas separation membrane is not limited, but is usually 1000% or less, and from the viewpoint of ease of production, etc., it is more preferably 500% or less, more preferably 300% or less, and more preferably 200% or less.

[0026] From the viewpoint of excellent mechanical strength and stable gas separation, the gas separation membrane preferably has a tensile breaking stress measured in the state of a hollow fiber membrane of 55 MPa or more, more preferably 58 MPa or more, and particularly preferably 61 MPa or more. The upper limit of the tensile breaking stress of the gas separation membrane is not limited, but is usually 1000 MPa or less, and from the viewpoint of ease of production, etc., it is more preferably 500 MPa or less, more preferably 200 MPa or less, and more preferably 100 MPa or less.

[0027] When the gas separation membrane is a hollow fiber membrane, the tensile breaking stress or tensile breaking elongation within the above range is particularly useful because the membrane has excellent pressure resistance and durability when assembled into a module. The hollow fiber membrane in the separation membrane module is continuously or intermittently subjected to deformation stress due to the flow rate, flow velocity, pressure, temperature, and fluctuations thereof of the gas flowing inside and outside the hollow fiber and discharged, but the hollow fiber membrane formed of the gas separation membrane of the present invention is unlikely to break or break because it has a tensile breaking elongation of 50% or more, preferably a tensile breaking elongation of 50% or more and a tensile breaking stress of 55 MPa or more.

[0028] In order to obtain a gas separation membrane having the above-mentioned tensile stress at break and tensile elongation at break, a suitable method for producing a gas separation membrane, which will be described later, may be employed.

[0029] Furthermore, the gas separation membrane of the present invention has excellent alcohol resistance. Specifically, the tensile breaking elongation of the hollow fiber membrane after 8.5 hours of treatment with a 60% by mass aqueous ethanol solution at 150°C is preferably 40% or more, more preferably 50% or more, and particularly preferably 60% or more, of the membrane before treatment. Such a gas separation membrane of the present invention is unlikely to deteriorate due to hydrolysis caused by contact with alcohol at high temperatures, and can stably maintain gas separation performance for water vapor and alcohol vapor even when subjected to long-term gas separation. In terms of ease of production of the gas separation membrane, it is preferable that the tensile breaking elongation of the hollow fiber membrane after 8.5 hours of treatment with a 60% by mass aqueous ethanol solution at 150°C is 99.9% or less of the membrane before treatment. The alcohol resistance can be measured by the following method. A hollow fiber gas separation membrane is immersed in a 60% by mass aqueous ethanol solution in a sealed container and heated at 150°C for 8.5 hours. The heated gas separation membrane is dried at 100°C, and the tensile elongation at break E1 is measured by the above method. The tensile elongation at break E0 of another hollow fiber gas separation membrane in the same hollow fiber membrane bundle is measured in a state where it has not been treated with the heated aqueous alcohol solution, and the value of E1 / E0 x 100 (%) is taken as the alcohol resistance. In order to set the alcohol resistance of the gas separation membrane of the present invention within the above range, a preferred composition described below may be used as the resin composition constituting the gas separation membrane.

[0030] The material constituting the gas separation membrane of the present invention is not particularly limited, and examples thereof include polyimide, polyamide, polysulfone, polyethersulfone, polyamideimide, polyetherimide, polycarbonate, etc. Among these, the gas separation membrane is preferably made of polyimide in terms of durability, heat resistance, separation properties, etc.

[0031] As a preferred embodiment of the polyimide constituting the gas separation membrane of the present invention, an aromatic polyimide represented by a repeating unit of the following general formula (1) will be described, but the present invention is not limited thereto.

[0032] [ka] [In formula (1), B is a tetravalent unit derived from the tetracarboxylic acid component, and A is a divalent unit derived from the diamine component.]

[0033] The tetracarboxylic acid component constituting unit B preferably contains 3,3',4,4'-biphenyltetracarboxylic acids in terms of processability, water resistance, and alcohol resistance. Examples of 3,3',4,4'-biphenyltetracarboxylic acids include 3,3',4,4'-biphenyltetracarboxylic acid, its acid dianhydride, and its acid ester. In terms of easily obtaining the desired water vapor permeability and water vapor / ethanol permeation rate ratio, as well as ethanol resistance and mechanical properties, the proportion of 3,3',4,4'-biphenyltetracarboxylic acids in the tetracarboxylic acid component constituting unit B is particularly preferably 90 mol% or more, even more preferably 95 mol% or more, and most preferably 99 mol% or more.

[0034] Examples of the tetracarboxylic acids constituting the unit B other than 3,3',4,4'-biphenyltetracarboxylic acids include pyromellitic acid, benzophenonetetracarboxylic acid, diphenyl ether tetracarboxylic acid, 2,2-bis[4-dicarboxyphenoxy)phenyl]propane, and acid dianhydrides and acid esters thereof.

[0035] In terms of water resistance and alcohol resistance, the diamine component constituting unit A preferably contains diaminodiphenyl ethers and / or bis(aminophenoxy)benzenes. Examples of diaminodiphenyl ethers include compounds constituting units represented by the following formula (A1), and specific examples thereof include 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, and 3,3'-diaminodiphenyl ether.

[0036] [ka]

[0037] Examples of bis(aminophenoxy)benzenes include compounds that constitute a unit represented by the following formula (A2). Specific examples include 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, and 1,3-bis(3-aminophenoxy)benzene.

[0038] [ka]

[0039] In terms of easily obtaining the desired water vapor permeability and permeation rate ratio between water vapor and ethanol vapor or nitrogen, as well as alcohol resistance and mechanical properties, it is particularly preferable that the diamine component constituting unit A is made up of diaminodiphenyl ethers and / or bis(aminophenoxy)benzenes in a proportion of 90 mol % or more, even more preferably 95 mol % or more, and most preferably 99 mol % or more.

[0040] In terms of easily obtaining the desired water vapor permeability, water vapor to ethanol permeation rate ratio, alcohol resistance, and mechanical properties, it is preferable that the diamine component constituting the unit A contains diaminodiphenyl ethers and bis(aminophenoxy)benzenes. When the diamine component contains diaminodiphenyl ethers and bis(aminophenoxy)benzenes, the molar ratio of the diaminodiphenyl ethers to the bis(aminophenoxy)benzenes (the former:the latter) is preferably 5:95 to 95:5, more preferably 10:90 to 90:10, and most preferably 20:80 to 80:20.

[0041] In terms of easily obtaining the desired water vapor permeability and water vapor to ethanol permeation rate ratio, as well as alcohol resistance and mechanical properties, the diaminodiphenyl ether is preferably 4,4'-diaminodiphenyl ether.

[0042] Furthermore, in order to easily obtain the desired water vapor permeability and water vapor to ethanol permeation rate ratio, as well as alcohol resistance and mechanical properties, it is preferable that the bis(aminophenoxy)benzene is 1,4-bis(4-aminophenoxy)benzene.

[0043] The polyimide constituting the gas separation membrane of the present invention is preferably mainly composed of a constitutional unit represented by the following formula (II) and a constitutional unit represented by the following formula (III), in particular, in that the desired water vapor permeability and water vapor to ethanol permeation rate ratio, as well as ethanol resistance and mechanical properties can be easily obtained. The proportion of the constitutional unit represented by formula (II) or formula (III) among all the constitutional units of the polyimide constituting the gas separation membrane of the present invention is preferably 90 mol % or more, more preferably 95 mol % or more, and most preferably 99 mol % or more. In the polyimide constituting the gas separation membrane of the present invention, the preferable ratio (molar ratio) of the constitutional unit represented by formula (II) to the constitutional unit represented by formula (III) can be the same as the preferable ratio of the diaminodiphenyl ethers and bis(aminophenoxy)benzenes described above.

[0044] [ka] [ka]

[0045] Examples of the diamine component constituting the unit A other than diaminodiphenyl ethers and bis(aminophenoxy)benzenes include 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 2,2-bis(4-aminophenyl)propane, 2-(4-aminophenyl)-2-(3-aminophenyl)propane, 2,2-(4-(4-aminophenoxy)phenyl]propane, O-tolidine, o-, m- or p-phenylenediamine, 3,5-diaminobenzoic acid, 2,6-diaminopyridine, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, and bis[4-(4-aminophenoxy)phenyl]sulfone.

[0046] <Suitable method for producing gas separation membrane> A preferred embodiment of the method for producing a gas separation membrane of the present invention is a method for producing a gas separation membrane by a dry-wet phase inversion method using a polymer solution containing a polymer and a mixed solvent of a halogenated phenol and an aliphatic alcohol. A more preferred embodiment is a method for forming a gas separation membrane by a dry-wet phase inversion method using a polymer solution containing a polyimide, parachlorophenol, and glycerin. The method will be described in detail below.

[0047] As one embodiment of the method for preparing the polymer solution used in the present invention, a method for preparing a polyimide solution will be described. The preparation of the polyimide solution is preferably carried out by a two-stage method in which a tetracarboxylic acid component and a diamine component are added to an organic polar solvent in a predetermined composition ratio, and a polyamic acid is generated by polymerization reaction at a low temperature of about room temperature, followed by heating for thermal imidization or adding pyridine or the like for chemical imidization, or a one-stage method in which a tetracarboxylic acid component and a diamine component are added to an organic polar solvent in a predetermined composition ratio, and a polymerization-imidization reaction is carried out at a high temperature of about 100 to 250°C, preferably about 130 to 200°C. When the imidization reaction is carried out by heating, it is preferable to carry out the reaction while removing the water or alcohol that is eliminated. The amount of the tetracarboxylic acid component and the diamine component to be used relative to the organic polar solvent is preferably such that the solid concentration of the polyimide in the solvent is about 5 to 50% by mass, more preferably 5 to 40% by mass.

[0048] Suitable examples of organic polar solvents include phenolic solvents such as phenol, cresol, and xylenol, catechols such as catechol and resorcin having two hydroxyl groups directly on the benzene ring, halogenated phenols such as 3-chlorophenol, 4-chlorophenol (same as parachlorophenol described below), 3-bromophenol, 4-bromophenol, and 2-chloro-5-hydroxytoluene, and amide solvents such as N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, and N,N-diethylacetamide, and mixtures thereof. Among these, amide solvents and phenolic solvents are preferred, phenolic solvents are more preferred, halogenated phenols are even more preferred, and 4-chlorophenol is particularly preferred.

[0049] The polyimide solution obtained by polymerization and imidization can be directly used for spinning as described below. Alternatively, for example, the obtained polyimide solution is poured into a solvent in which polyimide is insoluble to precipitate the polyimide, isolated, and then re-dissolved in an organic polar solvent to a predetermined concentration to prepare an aromatic polyimide solution, which can be used for spinning.

[0050] The asymmetric gas separation membrane of the present invention can be suitably obtained by a wet-dry phase inversion method using a polymer solution. The wet-dry phase inversion method is a known method in which a polymer solution is brought into contact with a coagulation liquid to cause phase inversion to form a membrane. The wet-dry phase inversion method is a phase inversion method in which the solvent on the surface of a polymer solution in a membrane shape is evaporated to form a thin dense layer, and then the membrane is immersed in a coagulation liquid (a solvent that is compatible with the solvent of the polymer solution and is insoluble in the polymer), and the phase separation phenomenon that occurs at that time is utilized to form micropores to form a porous layer, and this method was proposed by Loeb et al. (for example, U.S. Patent No. 3,133,132).

[0051] The polymer contained in the polymer solution preferably contains a polyimide. Examples of the polyimide include the preferred polyimides listed above. Therefore, it is preferable to include a polyimide represented by the above general formula (1), in which 90 mol % or more of the tetracarboxylic acid component is 3,3',4,4'-biphenyltetracarboxylic acids, and the diamine component contains aminodiphenyl ethers and / or bis(aminophenoxy)benzenes, and 90 mol % or more of the diamine component is diaminodiphenyl ethers and / or bis(aminophenoxy)benzenes. In particular, it is preferable to include a polyimide that is 3,3',4,4'-biphenyltetracarboxylic acids, the diamine component contains aminodiphenyl ethers and bis(aminophenoxy)benzenes, and 90 mol % or more of the diamine component is diaminodiphenyl ethers and bis(aminophenoxy)benzenes, in terms of reliably obtaining the gas separation membrane of the present invention. A more preferable composition of the polyimide is as described above. The polymer solution preferably contains 50% by mass or more of polyimide based on the total amount of polymer, further preferably 70% by mass or more, and may contain 100% by mass.

[0052] In the present invention, the solvent of the polymer solution used in the dry-wet phase inversion method preferably contains a solvent capable of dissolving the polymer and an aliphatic alcohol. By containing an aliphatic alcohol in the polymer solution, a gas separation membrane having sufficiently high mechanical strength when made into a hollow fiber membrane can be obtained.

[0053] The solvent capable of dissolving the polymer is preferably an organic polar solvent, and may be the organic polar solvent used when synthesizing the polymer by polymerizing the monomer. In one embodiment of the present invention, when the polymer is a polyimide, the organic polar solvent may be any solvent capable of dissolving the polyimide, and examples of the organic polar solvent include the organic polar solvent used in the preparation of the polyimide solution described above.

[0054] The aliphatic alcohol contained as a solvent in the polymer solution preferably has a boiling point of 60° C. or higher, more preferably 70° C. or higher, more preferably 120° C. or higher, even more preferably 150° C. or higher, and particularly preferably 200° C. or higher. The aliphatic alcohol may be a monohydric aliphatic alcohol or a dihydric or higher aliphatic polyhydric alcohol, but is preferably an aliphatic polyhydric alcohol, and more preferably a trihydric or higher polyhydric alcohol.

[0055] The monohydric aliphatic alcohol as a solvent for the polymer solution is preferably acyclic, may be linear or branched, and has, for example, 1 to 7 carbon atoms. The monohydric aliphatic alcohol is not particularly limited, but examples thereof include propanols such as methanol, ethanol, 1-propanol, and isopropanol, butanols such as 1-butanol, 2-butanol, and isobutanol, pentanols such as amyl alcohol, isoamyl alcohol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, and neopentyl alcohol, hexanols such as 1-hexanol, 2-hexanol, and 3-hexanol, and heptanols such as 1-heptanol, 2-heptanol, 3-heptanol, and 4-heptanol. Among these, ethanol is preferred.

[0056] The aliphatic polyhydric alcohol used as a solvent for the polymer solution is preferably acyclic and may be linear or branched, and has, for example, preferably 2 to 10 carbon atoms, more preferably 3 to 8. The aliphatic polyhydric alcohol refers to a dihydric or higher alcohol, and is preferably a trihydric or higher alcohol. Examples of the aliphatic polyhydric alcohol include, but are not limited to, dihydric aliphatic alcohol solvents such as ethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,2-, 1,3- or 2,3-butanediol, 2-methyl-1,4-butanediol, neopentyl glycol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, 2-methyl-1,7-heptanediol, 3-methyl-1,7-heptanediol, and 4-methyl-1,7-heptanediol; and trihydric or higher alcohol solvents such as glycerin and diglycerin. Among these, when glycerin is used, a uniform porous layer is easily formed, and a hollow fiber membrane having excellent mechanical strength can be obtained.

[0057] The aliphatic alcohols may be used alone or in combination of two or more kinds.

[0058] The content of the aliphatic alcohol in the polymer solution is preferably 5 to 30% by mass, more preferably 5 to 20% by mass, based on the total mass of the polymer solution. When the content of the aliphatic alcohol is within this range, the mechanical properties of the resulting hollow fiber are excellent. When the polymer solution is used in the spinning process described below, the solid content concentration of the polymer solution is preferably 5 to 50% by mass in terms of membrane formation, more preferably 5 to 40% by mass, and particularly preferably 10 to 30% by mass. The solution viscosity of the polymer solution is preferably 50 to 30,000 poise at the discharge temperature in the spinning process, and particularly preferably 100 to 20,000 poise, since a stable shape such as a hollow fiber shape can be obtained after discharge.

[0059] The aliphatic alcohol may be mixed into a solution in which the polymer is dissolved, or an isolated polymer, an organic polar solvent, and an aliphatic alcohol may be mixed at the same time. When mixing, the mixture may be heated so that the polymer dissolves in the organic polar solvent.

[0060] As one embodiment of the present invention, a method for producing a hollow fiber membrane by a dry-wet phase inversion method using a polymer solution will be described below.

[0061] First, in the spinning step (spinning dope discharge step), the spinning nozzle used for discharging the spinning dope may be any nozzle capable of extruding the spinning dope into a hollow fiber, and a tube-in-orifice type nozzle is suitable. Usually, the temperature range of the polymer solution (preferably a polyimide solution) during extrusion depends on the polymer contained in the dope, the type of solvent, the viscosity, etc., and is preferably about 20°C to 150°C, more preferably 30°C to 120°C. In addition, spinning is performed while supplying gas or liquid to the inside of the hollow fiber extruded from the nozzle.

[0062] In the coagulation process that follows the spinning process, the hollow filament discharged from the nozzle is once extruded into the air or an inert gas atmosphere such as nitrogen, and then introduced into a coagulation bath and immersed in the coagulation liquid. The coagulation liquid is preferably one that does not substantially dissolve the polymer component and is compatible with the solvent of the polymer component. Although not particularly limited, water, lower alcohols such as methanol, ethanol, and propyl alcohol, ketones having lower alkyl groups such as acetone, diethyl ketone, and methyl ethyl ketone, or mixtures thereof are preferably used. In addition, when the polymer solution is a polyimide solution and the solvent of the polyimide solution is an amide-based solvent, an aqueous solution of the amide-based solvent is also preferable.

[0063] The fibers obtained in the coagulation step are washed with a washing solvent such as ethanol as necessary, and then the coagulation liquid and / or washing solvent on the outside and inside of the hollow fibers are replaced using a replacement solvent, for example, an aliphatic hydrocarbon such as isopentane, n-hexane, isooctane, n-heptane, etc. The hollow fibers are then dried at 100 to 200°C to obtain the hollow fibers.

[0064] The asymmetric gas separation membrane, which is the hollow fiber membrane of the present invention, can be suitably used in a modularized form. The inner diameter of the hollow fiber membrane is preferably about 30 to 500 μm. A typical gas separation membrane module can be obtained by bundling about 100 to 1,000,000 hollow fiber membranes (preferably 100 to 200,000) of appropriate lengths, fixing both ends of the hollow fiber membrane bundle with a tube plate made of a thermosetting resin or the like so that at least one end of the hollow fiber is kept open, and storing and attaching the resulting hollow fiber membrane element consisting of the hollow fiber membrane bundle and the tube plate in a container equipped with at least a mixed gas inlet, a permeate gas outlet, and a non-permeate gas outlet so that the space leading to the inside of the hollow fiber membrane and the space leading to the outside of the hollow fiber membrane are separated. In a gas separation membrane module, a mixed gas is supplied from a mixed gas inlet to a space adjacent to the inside or outside of a hollow fiber membrane, and as the mixed gas flows adjacent to the hollow fiber membrane, specific components in the mixed gas selectively permeate the membrane, and the permeated gas is discharged from a permeated gas outlet, and the non-permeated gas that does not permeate the membrane is discharged from a non-permeated gas outlet, thereby performing gas separation.

[0065] The asymmetric gas separation membrane of the present invention can separate and recover various gas species with a high degree of separation (permeation rate ratio), but is particularly suitable for use in separating water vapor. When separating water vapor using the gas separation membrane of the present invention, for example, when performing dehumidification, a mixed gas containing water vapor is supplied to the space in contact with the inside or outside of the hollow fiber membrane in the gas separation membrane module, and the water vapor is selectively permeated to the permeation side of the membrane, and a dehumidified gas can be obtained very efficiently as a non-permeated gas. In addition, a carrier gas may be flowed in a countercurrent direction to the mixed gas supplied to the space on the permeation gas side, for example, to promote recovery of the permeation gas, and in this case, a non-permeation gas may be used as the carrier gas.

[0066] The gas separation membrane of the present invention has an extremely high water vapor permeation rate, so that dehumidification and / or humidification can be performed very efficiently and suitably. When dehumidification is performed, a mixed gas containing water vapor can be supplied to a space in contact with the inside or outside of a hollow fiber membrane in a gas separation membrane module equipped with the gas separation membrane of the present invention, whereby the water vapor is selectively permeated to the permeation side of the membrane, and a dehumidified gas can be obtained very efficiently as a non-permeation gas. In particular, it is preferable to supply a mixed gas containing water vapor to the inside of the hollow fiber membrane and introduce a dried carrier gas into the space outside the hollow fiber membrane so as to flow countercurrently to the mixed gas, since this allows for more efficient dehumidification. Furthermore, it is preferable to recycle a part of the dehumidified gas obtained on the non-permeation side of the gas separation membrane as the carrier gas, as a simple method for introducing the carrier gas. In the case of humidification, a mixed gas containing a larger amount of water vapor (high water vapor partial pressure) is supplied to the space in contact with the inside or outside of the hollow fiber membrane, and a gas containing a smaller amount of water vapor (low water vapor partial pressure) is supplied to the space on the opposite side of the hollow fiber membrane, so that the water vapor selectively permeates the membrane, and the gas containing a smaller amount of water vapor can be easily humidified. In particular, it is desirable to supply the mixed gas containing a larger amount of water vapor and the gas containing a smaller amount of water vapor in a countercurrent manner across the hollow fiber membrane, as this is highly efficient.

[0067] For example, the mixed gas to be subjected to water vapor separation by the gas separation membrane of the present invention is preferably a mixed vapor containing a mixture of organic vapor and water vapor. The organic concentration of the mixed vapor of the organic vapor and water vapor is not particularly limited, but the organic concentration is preferably 50 mass% or more, particularly about 60 to 95 mass%. The organic matter has a boiling point of 200°C or less, preferably a boiling point of 150°C or less, and particularly preferably is an organic matter that is liquid at room temperature (25°C). Examples of such organic substances include aliphatic alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, and ethylene glycol, alicyclic alcohols such as cyclohexanol, aromatic alcohols such as benzyl alcohol, organic carboxylic acids such as formic acid, acetic acid, propionic acid, and butyric acid, esters such as ethyl acetate and butyl acetate, ketones such as acetone and methyl ethyl ketone, cyclic ethers such as tetrahydrofuran and dioxane, and organic amines such as dibutylamine and aniline. The gas separation membrane and gas separation method of the present invention can be suitably used when dehydrating a mixed vapor, particularly a "mixed vapor consisting of water vapor and alcohol vapor" obtained by evaporating an aqueous alcohol solution such as methanol, ethanol, or isopropanol. By using the separation membrane of the present invention for separating water vapor from the mixed vapor (for example, dehumidifying), it is possible to perform stable and highly efficient gas separation even for a long time and / or at high temperatures, and obtain a gas enriched in organic vapor.

[0068] In addition, since the gas separation membrane of the present invention has excellent water vapor and nitrogen separation performance, it can be suitably used for dehumidifying and / or humidifying air, for example, in instrumentation equipment, dry air production for pneumatic brakes, and medical humidifiers. In addition, since the gas separation membrane of the present invention has excellent resistance to moist heat and high air dehumidification efficiency, it can suitably dehumidify and / or humidify the supply gas for fuel cells. A solid polymer fuel cell is generally constructed by stacking a power generation element in which both sides of a hydrogen ion conductive solid polymer electrolyte membrane are sandwiched between carbon electrodes carrying a platinum catalyst, a separator having a flow distribution function for supplying a fuel gas such as hydrogen or an oxidizing gas such as oxygen to each electrode and discharging exhaust gas from the electrode, and a current collector arranged on the outside of the separator. In this battery, when the solid polymer electrolyte membrane dries, the ion conductivity decreases and contact failure occurs between the solid polymer electrolyte membrane and the electrodes, resulting in a rapid decrease in output, so it is important to control the humidity of the solid polymer electrolyte membrane to be constant. For this reason, it is necessary to humidify the supply gas (fuel gas and / or oxidizing gas) (if there is too much moisture, dehumidification is performed instead of humidification). EXAMPLES

[0069] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0070] <Example 1> (Preparation of polyimide solution) (1) 28.8 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter also referred to as "s-BPDA"), 8.0 g of 4,4-diamino-diphenyl ether (hereinafter also referred to as "44DE"), and 17.5 g of 1,4-bis(4-aminophenoxy)benzene (hereinafter also referred to as "TPEQ") were polymerized in a separable flask together with 217 g of a solvent of parachlorophenol at a polymerization temperature of 190°C for 10 hours to obtain a polyimide solution with a polymer concentration of 19% by mass. (2) 32.5 g of glycerin was added to the polyimide solution obtained in (1) above, and the mixture was stirred at 190°C for 2 hours to obtain a polyimide solution having a solution viscosity of 2,500 poise at 100°C, a solids concentration of 17% by mass, and a glycerin concentration of 11% by mass.

[0071] (Method for producing asymmetric hollow fiber membrane) The polyimide solution obtained in (2) above was filtered through a 400-mesh wire net, then discharged from a hollow fiber spinning nozzle (circular opening outer diameter 1000 μm, circular opening slit width 200 μm, core opening outer diameter 600 μm). The discharged hollow fiber-shaped body was passed through a nitrogen atmosphere, and then immersed in a coagulation liquid consisting of a 75% by mass ethanol aqueous solution at 0 ° C to form a wet fiber. This was immersed in ethanol at 50 ° C for 2 hours to complete the solvent removal treatment, and further immersed and washed in isooctane at 70 ° C for 3 hours to replace the solvent, then dried at 100 ° C for 30 minutes, and then heat-treated at 220 ° C for 30 minutes. All of the obtained hollow fiber membranes had an outer diameter of 380 μm and an inner diameter of 270 μm.

[0072] The gas permeability, mechanical properties, and alcohol resistance of the obtained hollow fiber membrane were measured by the following methods. The results are shown in Table 1.

[0073] (Method for measuring water vapor permeability and ethanol permeability of hollow fiber membrane using a mixed vapor of ethanol and water vapor) The device is made of eight hollow fiber membranes, a stainless steel pipe, and an epoxy resin adhesive, and has an effective length of 70 mm and an effective surface area of ​​8 cm. 2 An element for evaluating the permeability of the above was prepared and attached to a stainless steel container to form a pencil module. A 60% by mass aqueous ethanol solution was vaporized in an evaporator under atmospheric pressure to produce a "mixed vapor containing ethanol vapor and water vapor," and the mixed vapor was heated to 100°C by a heater and supplied to the pencil module (100°C) and brought into contact with the surface of the supply side (outside of the hollow fiber membrane) of the hollow fiber membrane. The permeation side (inside of the hollow fiber membrane) of the hollow fiber membrane was maintained at a reduced pressure of 4 mmHg to separate the mixed vapor into gas. In gas separation, the "permeation gas with a high concentration of water vapor" obtained from the permeation gas outlet of the gas separation vessel was condensed in a dry ice-ethanol trap to collect the condensate. Among the components of the condensate collected in the trap, the ethanol concentration was analyzed by gas chromatography analysis, and the moisture content was determined by subtracting the ethanol content from the total amount. The "mixed vapor containing ethanol vapor and water vapor" before passing through was also condensed in a dry ice-ethanol trap to collect the condensate, and the ethanol concentration was analyzed by gas chromatography analysis, and the moisture content was determined by subtracting the ethanol content from the total amount. From the obtained concentrations of each component, the effective surface area of ​​the membrane, and the supply pressure, the permeation rate of water vapor and the permeation rate of ethanol were calculated, and the selective permeability of water vapor relative to ethanol (gas separation performance) was calculated from these values.

[0074] (Method for measuring water vapor permeability of hollow fiber membrane using a mixture of nitrogen and water vapor) Approximately eight hollow fiber membranes, a stainless steel pipe, and epoxy resin adhesive are used to create a membrane with an effective length of 80 mm and an effective surface area of ​​10 cm. 2 An element for evaluating the permeability of the pencil module was prepared and attached to a stainless steel container to form a pencil module. Nitrogen gas containing saturated water vapor at 15°C was blown into the hollow fiber of this pencil module at 5kgf(G) / cm. 2 A constant amount was supplied at a pressure of 1000 psi, and the dry gas obtained from the outlet side of the membrane was used as the product gas. The permeation side of the membrane was at atmospheric pressure, and in order to obtain a sufficient partial pressure difference in water vapor between the supply side and non-permeation side of the membrane, 20% of the product gas, which had a low water vapor concentration, was further supplied to the permeation side. The dew points of the supply gas and product gas were detected with a mirror-type dew point meter, and the water vapor partial pressure was calculated. The water vapor transmission rate of the membrane (P') was calculated from the measured amount of water vapor (water vapor partial pressure), the supply gas amount, and the effective membrane area. H2O' ) was calculated. These measurements were carried out at 35°C.

[0075] (Method for measuring nitrogen gas permeability of hollow fiber membrane) The membrane is made of eight hollow fiber membranes, a stainless steel pipe, and an epoxy resin adhesive, and has an effective length of 80 mm and an effective surface area of ​​10 cm. 2An element for evaluating the permeability of 5kgf(G) / cm was created and attached to a stainless steel container to form a pencil module. 2 The permeation flow rate was measured by supplying nitrogen pure gas of 1000 ml. The permeation rate of nitrogen gas was calculated from the measured amount of permeated nitrogen gas, the supply pressure, and the effective membrane area. These measurements were performed at 35°C.

[0076] (Measurement of tensile breaking stress and tensile breaking elongation of hollow fiber membrane) Using a tensile tester, measurements were performed at a temperature of 23° C., an effective length of 20 mm, and a tensile speed of 10 mm / min. Measurements were performed on five samples, and the average value was calculated.

[0077] (Alcohol resistance) A hollow fiber gas separation membrane was immersed in a 60% by mass aqueous ethanol solution in a sealed container and heated at 150°C for 8.5 hours. After immersion, the gas separation membrane was dried at 100°C, and the tensile elongation at break E1 was measured using the method described above. For another hollow fiber gas separation membrane produced using the same method and conditions, the tensile elongation at break E0 was measured without treatment with the heated aqueous alcohol solution, and the value E1 / E0 x 100 (%) was taken as the alcohol resistance. Measurements were performed on five samples, and the average value was calculated.

[0078] <Examples 2 and 3> The glycerin concentration and solids concentration of the polyimide solution obtained in (2) of Example 1 (Preparation of polyimide solution) were adjusted to the values ​​shown in Table 1. Except for this, polyimide hollow fiber membranes were obtained in the same manner as in Example 1. The gas permeability and mechanical properties of each hollow fiber membrane were measured by the methods described above. The results are shown in Table 1. The circularity of the hollow fiber membrane obtained in Example 2 was measured by the following method and was 95%.

[0079] (Circularity) The hollow fiber membrane embedded in the epoxy resin was cut into thin films using a razor along the thickness direction of the hollow fiber membrane. The thin films obtained were observed under an optical microscope (50 or 100x magnification). The major and minor diameters of the outer diameter of 10 randomly selected hollow fibers were measured, and the major / minor ratio was averaged.

[0080] <Comparative Example 1> In (2) of Example 1 (Preparation of polyimide solution), glycerin was not added, and the solids concentration of the polyimide solution obtained in (2) was adjusted to the value shown in Table 1. Except for these points, polyimide hollow fiber membranes were obtained in the same manner as in Example 1. The gas permeability and mechanical properties of each hollow fiber membrane were measured by the methods described above. The results are shown in Table 1.

[0081] <Comparative Example 2> In (2) of Example 1 (Preparation of polyimide solution), the polyimide solution prepared in (1) above was replaced with the polyimide solution prepared in (1') below, and glycerin was not added. Except for these points, the procedure was the same as in Example 1 to obtain a polyimide hollow fiber membrane. The gas permeability and mechanical properties of the obtained hollow fiber membrane were measured by the methods described above. The results are shown in Table 1. 26.2 g of (1')s-BPDA, 26.4 g of 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (hereinafter also referred to as "6FDA"), and 30.0 g of 44DE were polymerized in a separable flask together with 406 g of parachlorophenol as a solvent at a polymerization temperature of 190°C for 10 hours to obtain polyimide solution A with a polymer concentration of 16 mass%. 23.2 g of s-BPDA and 16.0 g of 44DE were polymerized in a separable flask together with 191 g of a solvent, parachlorophenol, at a polymerization temperature of 190° C. for 10 hours to obtain a polyimide solution B having a polymer concentration of 16 mass %. Polyimide solution A and polyimide solution B were mixed and stirred at 190° C. for 2 hours to obtain a polyimide solution having a solution viscosity of 2300 poise at 100° C. and a solids concentration of 16 mass %.

[0082] [Table 1] [Industrial Applicability]

[0083] The gas separation membrane of the present invention has a water vapor transmission rate (P' H2O ) is 100 x 10 -5 cm 3 (STP) / (cm 2 ·sec·cmHg) or more, the ratio of water vapor to ethanol permeation rate (P' H2O / P' EtOH ) of 100 or more and high water vapor / ethanol separation performance, and furthermore, has excellent mechanical strength and high alcohol resistance. Therefore, by using the gas separation membrane of the present invention, it is possible to provide a compact hollow fiber gas separation membrane module that can separate water vapor from a mixed vapor containing water vapor and organic vapor and extract an organic-enriched gas stably and efficiently for a long period of time. Furthermore, the gas separation membrane of the present invention has excellent water vapor / nitrogen separation performance and is suitable for use in humidification and / or dehumidification.

Claims

1. The membrane has an asymmetric structure composed of a skin layer having a gas separation function and a porous layer supporting the skin layer, The water vapor transmission rate (P') measured using a mixture of ethanol and water vapor H2O ) is 100 x 10 -5 cm 3 (STP) / (cm 2 sec cmHg) or more, The ratio of the water vapor permeation rate to the ethanol permeation rate (P' H2O / P' EtOH ) is 100 or more, The tensile elongation at break measured in the hollow fiber membrane state is 50% or more, A gas separation membrane made of polyimide, in which the tensile breaking elongation of a hollow fiber membrane after treatment with a 60% by mass aqueous ethanol solution at 150° C. for 8.5 hours is 40% or more before the treatment, wherein the polyimide is represented by the following general formula (1): 【Chemistry 1】 [In formula (1), B is a tetravalent unit derived from a tetracarboxylic acid component, and A is a divalent unit derived from a diamine component], in which 90 mol % or more of the tetracarboxylic acid component is 3,3',4,4'-biphenyltetracarboxylic acids, and 90 mol % or more of the diamine component is diaminodiphenyl ethers and / or bis(aminophenoxy)benzenes.

2. 2. The gas separation membrane according to claim 1, wherein the diamine component contains diaminodiphenyl ethers and bis(aminophenoxy)benzenes in a molar ratio of the former:the latter of 5:95 to 95:

5.

3. 3. The gas separation membrane according to claim 1, which has a tensile breaking stress of 55 MPa or more measured in a hollow fiber membrane state.

4. The water vapor transmission rate (P') measured using a mixture of water vapor and nitrogen gas H2O ') is 100 x 1 0 -5 cm 3 (STP) / (cm 2 sec cmHg) or more, The ratio of water vapor and nitrogen transmission rates (P' H2O ' / P' N2 4. The gas separation membrane according to claim 1, wherein the molecular weight is 300 or more.

5. A method for producing a gas separation membrane according to any one of claims 1 to 4, The method includes the steps of performing a dry-wet phase inversion process using a polyimide solution containing a polyimide and a solvent containing a phenolic solvent and an aliphatic alcohol, The polyimide is represented by the following general formula (1): 【Chemistry 2】 [In formula (1), B is a tetravalent unit derived from a tetracarboxylic acid component, and A is a divalent unit derived from a diamine component.], 90 mol % or more of the tetracarboxylic acid component is 3,3',4,4'-biphenyltetracarboxylic acids, and the diamine component contains aminodiphenyl ethers and bis(aminophenoxy)benzenes, and 90 mol % or more of the diamine component is diaminodiphenyl ethers and bis(aminophenoxy)benzenes.

6. A method for separating water vapor from a mixed gas containing water vapor, using the gas separation membrane according to any one of claims 1 to 4.

7. A method for producing a gas enriched with organic vapor from a mixed vapor containing water vapor and organic vapor, using the gas separation membrane according to any one of claims 1 to 4.

8. A method for dehumidifying or humidifying air containing water vapor, using the gas separation membrane according to any one of claims 1 to 4.

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