WO2024014285A1 - Separation membrane and method for manufacturing same - Google Patents

Separation membrane and method for manufacturing same Download PDF

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Publication number
WO2024014285A1
WO2024014285A1 PCT/JP2023/023867 JP2023023867W WO2024014285A1 WO 2024014285 A1 WO2024014285 A1 WO 2024014285A1 JP 2023023867 W JP2023023867 W JP 2023023867W WO 2024014285 A1 WO2024014285 A1 WO 2024014285A1
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Prior art keywords
separation
separation membrane
functional layer
porous support
carbon dioxide
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PCT/JP2023/023867
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French (fr)
Japanese (ja)
Inventor
俊亮 佐山
和也 吉村
伶哉 日野
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日東電工株式会社
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Publication of WO2024014285A1 publication Critical patent/WO2024014285A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/10—Supported membranes; Membrane supports
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/58—Other polymers having nitrogen in the main chain, with or without oxygen or carbon only
    • B01D71/62—Polycondensates having nitrogen-containing heterocyclic rings in the main chain
    • B01D71/64—Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out

Definitions

  • the present invention relates to a separation membrane and a method for manufacturing the same.
  • Membrane separation methods have been developed as a method for separating acidic gases from mixed gases containing acidic gases such as carbon dioxide. Membrane separation methods can efficiently separate acidic gases while reducing operating costs, compared to absorption methods in which acidic gases contained in a gas mixture are absorbed by an absorbent and separated.
  • separation membranes used in membrane separation methods include composite membranes in which a separation functional layer is formed on a porous support.
  • the material for the separation functional layer include resins such as polyimide resin and polyether block amide resin.
  • Patent Document 1 discloses a separation membrane containing a polyimide resin.
  • the present invention a separation functional layer; a porous support directly in contact with the separation functional layer; Equipped with Each of the separation functional layer and the porous support contains polyimide,
  • the polyimide provides a separation membrane containing a structural unit derived from a tetracarboxylic dianhydride having a six-membered acid anhydride structure.
  • a new separation membrane suitable for separating acidic gas from a mixed gas containing acidic gas can be provided.
  • FIG. 1 is a cross-sectional view schematically showing a separation membrane according to an embodiment of the present invention.
  • FIG. 3 is a diagram for explaining a method for manufacturing a separation membrane.
  • FIG. 3 is a diagram for explaining a method for manufacturing a separation membrane.
  • 1 is a schematic cross-sectional view of a membrane separation device equipped with a separation membrane of the present invention.
  • FIG. 3 is a perspective view schematically showing a modified example of a membrane separation device equipped with the separation membrane of the present invention.
  • 1 is a scanning electron microscope (SEM) image of a cross section of the separation membrane of Example 1.
  • 3 is a SEM image of a cross section of the separation membrane of Example 2.
  • 3 is a SEM image of a cross section of the separation membrane of Example 3.
  • 3 is a SEM image of a cross section of the separation membrane of Example 4.
  • 3 is a SEM image of a cross section of the separation membrane of Example 5.
  • 3 is a SEM image of a cross section of the separation membrane of Example 6.
  • 3 is a SEM image of a cross section of the separation membrane of Example 7.
  • the separation membrane according to the first aspect of the present invention is a separation functional layer; a porous support directly in contact with the separation functional layer; Equipped with Each of the separation functional layer and the porous support contains polyimide,
  • the polyimide includes a structural unit derived from a tetracarboxylic dianhydride having a six-membered acid anhydride structure.
  • the porous support has continuous pores.
  • the separation functional layer and the porous support are integrated.
  • the material of the separation functional layer is the same as the material of the porous support.
  • the total thickness of the separation functional layer and the thickness of the porous support is 10 ⁇ m or more. It is.
  • the structural unit is represented by the following formula (A1).
  • R 1a to R 4a each independently represent a hydrogen atom or an arbitrary substituent.
  • a mixed gas consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane.
  • the permeation rate of carbon dioxide passing through the separation membrane is 100 GPU or more.
  • the concentration of carbon dioxide in the mixed gas is 50 vol% in a standard state, and the mixed gas supplied to the space adjacent to the one surface has a temperature of 30°C and a pressure of 0. 1 MPa, and the space adjacent to the other surface is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
  • a mixed gas consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane.
  • the separation coefficient ⁇ of carbon dioxide with respect to nitrogen is 20 or more.
  • the concentration of carbon dioxide in the mixed gas is 50 vol% in a standard state, and the mixed gas supplied to the space adjacent to the one surface has a temperature of 30°C and a pressure of 0. 1 MPa, and the space adjacent to the other surface is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
  • the method for manufacturing a separation membrane according to the ninth aspect of the present invention includes: Forming a coating film using a coating solution containing polyimide, a solvent, and a porosity agent; removing the porosity agent from the coating film; including.
  • the polyimide includes a structural unit derived from a tetracarboxylic dianhydride having a six-membered acid anhydride structure.
  • the boiling point of the porosity-forming agent is 50° C. or more higher than the boiling point of the solvent.
  • the porosity-forming agent includes at least one selected from the group consisting of an ether compound and a phosphoric acid compound. .
  • the solvent contains at least one selected from the group consisting of an amide compound and a lactone compound.
  • the coating film may be dried and/or the coating film may be washed with a cleaning liquid.
  • the porosity agent is removed from the coating film.
  • the separation membrane according to the fifteenth aspect of the present invention is A separation membrane comprising a separation functional layer and a porous support directly in contact with the separation functional layer,
  • the material of the separation functional layer is the same as the material of the porous support,
  • the total value of the thickness of the separation functional layer and the thickness of the porous support is 10 ⁇ m or more,
  • the concentration of carbon dioxide in the mixed gas is 50 vol% in a standard state
  • the mixed gas supplied to the space adjacent to the one surface has a temperature of 30°C and a pressure of 0. 1 MPa, and the space adjacent to the other surface is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
  • the separation membrane 10 of the present embodiment includes a separation functional layer 1 and a porous support 2, and is composed of only the separation functional layer 1 and the porous support 2, for example.
  • the porous support 2 is in direct contact with the separation functional layer 1 and supports the separation functional layer 1. It is preferable that the separation functional layer 1 and the porous support 2 are integrated. As used herein, "integrated" means that the members cannot be separated from each other non-destructively.
  • the separation functional layer 1 and the porous support 2 each contain polyimide.
  • the polyimide contained in the separation functional layer 1 is typically the same as the polyimide contained in the porous support 2.
  • the material of the separation functional layer 1 is preferably the same as the material of the porous support 2.
  • the separation membrane 10 may be made of only polyimide, or may be made of a single material.
  • the polyimide is typically a polyimide P containing a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered acid anhydride structure S.
  • Polyimide P further includes a structural unit B derived from a diamine. Note that, depending on the case, each of the separation functional layer 1 and the porous support 2 may contain a polyimide other than polyimide P.
  • the structural unit A1 is a structural unit suitable for improving the permeation rate of acidic gas passing through the separation membrane 10.
  • Tetracarboxylic dianhydride a1 has, for example, one or more, preferably two, acid anhydride structures S.
  • the 6-membered acid anhydride structure S is typically a glutaric anhydride structure represented by the following formula (1).
  • the tetracarboxylic dianhydride a1 may have a condensed ring, and the condensed ring may include an acid anhydride structure S.
  • the condensed ring may include an aromatic ring together with the acid anhydride structure S.
  • the aromatic ring contained in the condensed ring may be composed only of carbon atoms, or may be a heteroaromatic ring containing heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms.
  • the aromatic ring may be polycyclic or monocyclic. The number of carbon atoms in the aromatic ring is not particularly limited, and is, for example, 4 to 14.
  • aromatic ring examples include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a furan ring, a pyrrole ring, a pyridine ring, and a thiophene ring.
  • the fused ring may or may not have a substituent.
  • Substituents on the condensed ring are not particularly limited, and include halogen groups, hydrocarbon groups, and the like.
  • the halogen group include a fluoro group, a chloro group, a bromo group, and an iodo group.
  • the number of carbon atoms in the hydrocarbon group is not particularly limited, and is, for example, 1 to 15.
  • the hydrocarbon group is, for example, an alkyl group such as a methyl group, an ethyl group, or a propyl group.
  • the hydrocarbon group may be a halogenated hydrocarbon group in which a hydrogen atom is substituted with a halogen group.
  • Tetracarboxylic dianhydride a1 is represented by the following formula (a1), for example.
  • R 1a to R 4a are each independently a hydrogen atom or an arbitrary substituent.
  • the optional substituents are not particularly limited, and include halogen groups, hydrocarbon groups, and the like. Examples of the halogen group and hydrocarbon group include those mentioned above.
  • the structural unit A1 derived from the tetracarboxylic dianhydride a1 is represented by the following formula (A1), for example.
  • the structural unit A1 represented by the formula (A1) is derived from the tetracarboxylic dianhydride a1 represented by the above formula (a1).
  • the nitrogen atom contained in the imide group originates from the diamine reacted with the tetracarboxylic dianhydride a1.
  • R 1a to R 4a are the same as in formula (a1) and independently represent a hydrogen atom or an arbitrary substituent.
  • a specific example of the structural unit A1 represented by the formula (A1) is the following formula (A1-1).
  • the ratio p1 of the amount of the above structural unit A1 to the amount of all the structural units A derived from tetracarboxylic dianhydride is, for example, 50 mol% or more, 70 mol% or more, 90 mol% or more , 95 mol% or more, or even 99 mol% or more.
  • Polyimide P may contain only the above structural unit A1 as the structural unit A derived from tetracarboxylic dianhydride. However, in addition to the structural unit A1, the polyimide P may further contain a structural unit A2 derived from a tetracarboxylic dianhydride a2 having a five-membered acid anhydride structure.
  • the tetracarboxylic dianhydride a2 is not particularly limited, and examples thereof include pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, and the like.
  • polyimide P further includes structural unit B derived from diamine.
  • Diamines are compounds with two primary amino groups.
  • the diamine may or may not contain a functional group other than the primary amino group. Examples of other functional groups include carboxyl groups, hydroxyl groups, thiol groups, and sulfonyl groups.
  • the diamine may have at least one functional group f selected from the group consisting of a carboxyl group, a hydroxyl group, and a thiol group.
  • the diamine may further have an aromatic ring.
  • the aromatic ring include those mentioned above for the tetracarboxylic dianhydride a1.
  • the substituent on the aromatic ring includes, for example, a primary amino group.
  • the aromatic ring may have a substituent other than the substituent containing the primary amino group, or may have no other substituent.
  • Other substituents are not particularly limited, and include groups containing the above functional group f, halogen groups, hydrocarbon groups, and the like.
  • the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
  • other substituents may include a photopolymerizable functional group (for example, a vinyl group).
  • the diamine is represented by, for example, the following formula (b1), formula (b2), formula (b3), formula (b4), or formula (b5).
  • R 1b to R 30b are each independently a hydrogen atom or an arbitrary substituent.
  • the optional substituent include a group containing a functional group f, a halogen group, and a hydrocarbon group.
  • the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
  • X 1 and X 2 are a single bond or an arbitrary linking group.
  • the optional linking group is, for example, a divalent hydrocarbon group.
  • the divalent hydrocarbon group include alkylene groups such as methylene group, ethylene group, propane-1,3-diyl group, and propane-2,2-diyl group.
  • the divalent hydrocarbon group may be a halogenated hydrocarbon group in which a hydrogen atom is substituted with a halogen group.
  • the divalent hydrocarbon group may further have an aromatic ring. Examples of the aromatic ring include those mentioned above for the tetracarboxylic dianhydride a1.
  • the divalent hydrocarbon group may be a fluorenediyl group.
  • X 1 and X 2 may contain a functional group such as an ether group or an ester group together with or in place of the divalent hydrocarbon group.
  • the structural unit B derived from diamine may have at least one functional group F selected from the group consisting of carboxyl groups, hydroxyl groups, thiol groups, and metal salts thereof.
  • the metal contained in the metal salt as the functional group F is not particularly limited, and includes, for example, Li, Na, K, Be, Mg, Ca, Ba, Sc, Y, Ti, Zr, V, Cr, Mo, and Mn. , Fe, Co, Ni, Cu, Ag, Zn, B, Al, Ga, In, Pb, etc.
  • the metal salt as functional group F the metal is specifically present as a cation.
  • the valence of this metal cation is, for example, 1 or more, preferably 2 or more, and more preferably 3 or more.
  • the structural unit B contains a metal salt as the functional group F
  • a plurality of polyimides P can be coordinated to the metal cation contained in the metal salt via a functional group such as a carboxyl group.
  • the plurality of polyimides P are crosslinked with each other via the metal cations. Formation of such a crosslinked structure suppresses physical aging of the polyimide P, which tends to suppress deterioration of the separation performance of the separation functional layer 1 over time.
  • the polyimide P contains a metal salt as the functional group F
  • the separation performance of the separation functional layer 1 also tends to improve.
  • the metal salt as the functional group F is, for example, a functional group f contained in a polyimide P obtained from a monomer group containing tetracarboxylic dianhydride a1 and a diamine, by exchanging a dissociative proton with a metal cation.
  • a functional group f contained in a polyimide P obtained from a monomer group containing tetracarboxylic dianhydride a1 and a diamine by exchanging a dissociative proton with a metal cation.
  • the structural unit B derived from diamine is represented by, for example, the following formula (B1), formula (B2), formula (B3), formula (B4), or formula (B5).
  • the structural units B represented by formulas (B1) to (B5) are derived from diamines represented by formulas (b1) to (b5) above, respectively.
  • R 1b to R 4b are each independently a hydrogen atom or an arbitrary substituent.
  • the arbitrary substituent is, for example, a group containing the above-mentioned functional group F, a halogen group, a hydrocarbon group, or the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
  • R 5b to R 8b are each independently a hydrogen atom or an arbitrary substituent.
  • arbitrary substituents include, for example, a group containing a functional group F, a halogen group, a hydrocarbon group, and the like.
  • the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
  • a specific example of the structural unit B represented by formula (B2) is the following formula (B2-1).
  • R 9b to R 16b are each independently a hydrogen atom or an arbitrary substituent, and X 1 is a single bond or an arbitrary linking group.
  • arbitrary substituents include, for example, a group containing a functional group F, a halogen group, a hydrocarbon group, and the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
  • the arbitrary linking group is, for example, a divalent hydrocarbon group.
  • the divalent hydrocarbon group include those mentioned above.
  • X 1 may contain a functional group such as an ether group or an ester group together with or in place of the divalent hydrocarbon group.
  • R 17b to R 24b are each independently a hydrogen atom or an arbitrary substituent, and X 2 is a single bond or an arbitrary linking group.
  • arbitrary substituents include, for example, a group containing a functional group F, a halogen group, a hydrocarbon group, and the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
  • the arbitrary linking group is, for example, a divalent hydrocarbon group.
  • the divalent hydrocarbon group include those mentioned above.
  • X 2 may contain a functional group such as an ether group or an ester group together with or in place of the divalent hydrocarbon group.
  • R 25b to R 30b are each independently a hydrogen atom or an arbitrary substituent.
  • the arbitrary substituent is, for example, a group containing a functional group F, a halogen group, a hydrocarbon group, or the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
  • the structural unit B represented by formula (B5) is suitable for improving the rigidity of the polyimide P. Polyimide P, which has excellent rigidity, tends to suppress plasticization of the separation membrane 10 even when the pressure of the gas mixture to be separated is high.
  • structural unit B represented by the formula (B5) include the following formulas (B5-1) to (B5-2).
  • polyimide P structural units A derived from tetracarboxylic dianhydride and structural units B derived from diamine are arranged alternately.
  • examples of combinations of adjacent structural units A and B include the following formulas (A1-B1) and (A1-B5).
  • R 1a to R 4a , R 1b to R 4b , and R 25b to R 30b are the same as those described above for formula (A1), formula (B1), and formula (B5). .
  • the weight average molecular weight (Mw) of the polyimide P is, for example, 30,000 or more, preferably 50,000 or more, and more preferably 75,000 or more, from the viewpoint of the mechanical strength of the separation membrane 10.
  • the upper limit of the weight average molecular weight of polyimide P is not particularly limited, and is, for example, 1 million.
  • the weight average molecular weight of polyimide P can be determined by measuring the molecular weight distribution of polyimide P using, for example, a gel permeation chromatograph (GPC) equipped with a differential refractive index detector (RID), and from the obtained chromatogram (chart). It can be calculated using a standard polystyrene calibration curve.
  • GPC gel permeation chromatograph
  • RID differential refractive index detector
  • Polyimide P can be produced, for example, by the following method. First, diamine is dissolved in a solvent to obtain a solution.
  • the solvent include polar organic solvents such as N-methyl-2-pyrrolidone and 1,3-dioxolane.
  • the tetracarboxylic dianhydride group containing the above-mentioned tetracarboxylic dianhydride a1 is gradually added to the obtained solution.
  • the monomer group containing the tetracarboxylic dianhydride a1 and the diamine react to form a polyamic acid.
  • the addition of the tetracarboxylic dianhydride group is carried out, for example, under stirring conditions in a heating environment of 140° C. or higher for 3 to 20 hours.
  • polyimide P can be obtained by imidizing the polyamic acid.
  • the imidization method include a chemical imidization method and a thermal imidization method.
  • the chemical imidization method is a method of imidizing polyamic acid using a dehydration condensation agent, for example, under room temperature conditions.
  • Examples of the dehydration condensation agent include acetic anhydride, pyridine, and triethylamine.
  • the thermal imidization method is a method of imidizing polyamic acid by heat treatment. The temperature of the heat treatment is, for example, 180° C. or higher.
  • the separation functional layer 1 is, for example, a layer that can preferentially transmit acidic gas contained in a mixed gas, and is typically observed at a magnification of 5000 times using a scanning electron microscope (SEM). It is a dense layer (non-porous layer) in which no pores can be seen.
  • SEM scanning electron microscope
  • the content of polyimide in the separation functional layer 1 is, for example, 50 wt% or more, and may be 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or even 95 wt% or more.
  • the separation functional layer 1 may be substantially composed only of polyimide.
  • the thickness of the separation functional layer 1 is, for example, 50 ⁇ m or less, and may be 25 ⁇ m or less, 15 ⁇ m or less, 10 ⁇ m or less, 8 ⁇ m or less, 5 ⁇ m or less, 3 ⁇ m or less, or even 1 ⁇ m or less.
  • the lower limit of the thickness of the separation functional layer 1 may be 0.05 ⁇ m or 0.1 ⁇ m.
  • the thickness of the separation functional layer 1 can be determined by the following method. First, a cross section of the separation membrane 10 is observed using a scanning electron microscope. Using the obtained electron microscope image, the distance between a pair of mutually opposing principal surfaces of the separation functional layer 1 is measured at a plurality of arbitrary points (at least four points). The average value of the obtained values can be regarded as the thickness of the separation functional layer 1.
  • the porous support 2 is in direct contact with the separation functional layer 1 and supports the separation functional layer 1.
  • the porous support 2 has a porous structure. From the viewpoint of improving the permeability coefficient and permeation rate of acidic gases passing through the separation membrane 10, it is preferable that the porous support 2 has continuous pores that are continuously formed in a three-dimensional shape. However, the porous support 2 may have independent pores, or may have both continuous pores and independent pores. The porous support 2 may have through holes passing through the porous support 2.
  • the content of polyimide in the porous support 2 is, for example, 50 wt% or more, and may be 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or even 95 wt% or more.
  • the porous support 2 may be substantially composed only of polyimide.
  • the polyimide content in the porous support 2 may be the same as the polyimide content in the separation functional layer 1.
  • the thickness of the porous support 2 is, for example, 10 ⁇ m or more, and may be 20 ⁇ m or more, 30 ⁇ m or more, 40 ⁇ m or more, or even 50 ⁇ m or more.
  • the upper limit of the thickness of the porous support 2 may be 300 ⁇ m or 100 ⁇ m.
  • the thickness of the porous support 2 can be determined by the method described above for the separation functional layer 1.
  • the total value V of the thickness of the separation functional layer 1 and the thickness of the porous support 2 is, for example, 10 ⁇ m or more, 20 ⁇ m or more, 30 ⁇ m or more, It may be 40 ⁇ m or more, 50 ⁇ m or more, or even 60 ⁇ m or more.
  • the upper limit of the total value V may be 300 ⁇ m or 100 ⁇ m.
  • the method for manufacturing the separation membrane 10 includes, for example, forming a coating film 6 using a coating liquid L containing polyimide, a solvent, and a porosity-forming agent, and forming a porous film from the coating film 6. and removing the agent.
  • the coating liquid L can be prepared, for example, by mixing polyimide, a solvent, and a porosity-forming agent.
  • the polyimide is typically the above-mentioned polyimide P containing a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered acid anhydride structure S.
  • polyimide P is more easily dissolved in a solvent than other polyimides, and is therefore suitable for the manufacturing method of this embodiment.
  • the content of polyimide in the coating liquid L can be adjusted as appropriate depending on the solubility of the polyimide, and is, for example, 1 wt% to 30 wt%.
  • the solvent is typically a good solvent that can dissolve the polyimide.
  • the solvent preferably contains at least one selected from the group consisting of an amide compound and a lactone compound, and more preferably an amide compound.
  • the amide compound include N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and N,N-dimethylacetamide (DMAc).
  • the lactone compound include ⁇ -butyrolactone.
  • the boiling point of the solvent is not particularly limited, and is, for example, 100°C to 250°C.
  • the content of the solvent in the coating liquid L is, for example, 30 wt% to 95 wt%.
  • the porosity agent is typically a poor solvent that hardly dissolves polyimide P.
  • the pore forming agent preferably contains at least one selected from the group consisting of an ether compound and a phosphoric acid compound, and more preferably contains an ether compound.
  • ether compounds include diethylene glycol, diethylene glycol monomethyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol, tetraethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol butyl methyl ether, and tripropylene.
  • glycol compounds such as glycol dimethyl ether, diethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol dibutyl ether, triethylene glycol butyl methyl ether, polyethylene glycol dimethyl ether, polyethylene glycol monomethyl ether, and polyethylene glycol.
  • Examples of the phosphoric acid compound include phosphoric ester compounds such as trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, and triethyl phosphate.
  • the boiling point of the porosity-forming agent is preferably higher than the boiling point of the solvent.
  • the boiling point of the pore-forming agent may be, for example, 50°C or more higher than the boiling point of the solvent, 80°C or more, or even 100°C or more higher.
  • the boiling point of the pore-forming agent is, for example, 200°C to 350°C.
  • the content of the porosity agent in the coating liquid L is, for example, 10 wt% to 50 wt%.
  • the content of the porosity-forming agent is preferably higher than the content of polyimide.
  • the coating film 6 can be formed, for example, by applying the coating liquid L onto the base material 5 (FIG. 2A).
  • Substrate 5 is typically a release liner.
  • the release liner include a film containing resin; paper; and a sheet containing a metal material such as aluminum or stainless steel. Sheets containing metallic materials tend to have high heat resistance.
  • the release liner is preferably a film containing resin from the viewpoint of excellent surface smoothness.
  • the polymers contained in the resin include polyolefins such as polyethylene, polypropylene, polybutene, polybutadiene, and polymethylpentene; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyvinyl chloride, vinyl chloride copolymers ; polyurethane; ethylene-vinyl acetate copolymer, etc., and polyester, particularly polyethylene terephthalate, is preferred.
  • polyolefins such as polyethylene, polypropylene, polybutene, polybutadiene, and polymethylpentene
  • polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate
  • polyvinyl chloride, vinyl chloride copolymers polyurethane
  • ethylene-vinyl acetate copolymer etc.
  • polyester particularly polyethylene terephthalate
  • the surface of the release liner may be subjected to release treatment.
  • the release treatment can be performed, for example, by applying a release treatment agent to the surface of the release liner.
  • the release agent include a silicone release agent, a long-chain alkyl release agent, a fluorine release agent, and a molybdenum sulfide release agent.
  • the release agent may be used alone or in combination of two or more.
  • the release liner is preferably a release-treated polyethylene terephthalate (PET) film.
  • the thickness of the base material 5 is not particularly limited, and is, for example, 5 to 100 ⁇ m, preferably 10 to 50 ⁇ m.
  • the method of applying the coating liquid L to the substrate 5 is not particularly limited, and for example, a spin coating method, a dip coating method, etc. can be used.
  • the coating liquid L may be applied to the base material 5 using an applicator, a wire bar, or the like.
  • pores are formed due to the porosity-forming agent, and a dense layer (skin layer) is formed near the surface of the coating film 6 that is exposed to the outside.
  • a porous support 2 having pores caused by the porosity-forming agent and a separation functional layer 1 corresponding to a skin layer are formed (FIG. 2B).
  • the porosity agent is removed from the coating film 6 so that the separation functional layer 1 and the porous support 2 are formed from the coating film 6.
  • the porosity agent can be removed from the coating film 6 by, for example, drying the coating film 6 and/or washing the coating film 6 with a cleaning liquid.
  • drying the coating film 6 the drying temperature is, for example, 50° C. to 300° C., and the drying time is, for example, 1 to 20 hours.
  • the coating film 6 may be dried in a reduced pressure atmosphere or a vacuum atmosphere.
  • the coating film 6 When cleaning the coating film 6 with a cleaning liquid, it is preferable to use a cleaning liquid that has high compatibility with the porosity-forming agent.
  • a cleaning liquid for example, water or alcohol such as methanol can be used.
  • the coating film 6 may be cleaned by immersing the coating film 6 in a cleaning liquid.
  • the solvent when removing the porosity agent from the coating film 6, the solvent is also removed from the coating film 6.
  • the solvent before removing the porosity agent from the coating film 6, the solvent may be removed from the coating film 6 in advance.
  • the solvent can be removed from the coating film 6 in advance by pre-drying the coating film 6.
  • the pre-drying conditions are, for example, a temperature of 50° C. to 150° C. and a time of 10 minutes to 5 hours.
  • the base material 5 is removed from the laminate of the separation functional layer 1 and the porous support 2. Thereby, the separation membrane 10 can be obtained.
  • Conventional methods for producing separation membranes include a direct method in which a coating solution containing a material for the separation functional layer is applied onto a porous support and the resulting coating film is dried to form a separation functional layer; Examples include a transfer method in which a separation functional layer formed on a base material is transferred to a porous support.
  • the separation functional layer 1 and the porous support 2 are manufactured by removing the porosity agent and the solvent from the coating film 6. That is, in the manufacturing method of this embodiment, the porous support 2 does not come into contact with the solvent originating from the coating film 6 after the porous support 2 is formed. Therefore, the separation membrane 10 produced by the production method of this embodiment tends to have higher separation performance than a separation membrane produced by a direct method.
  • the transfer method for example, when a thin separation functional layer with a thickness of about 1 ⁇ m or less is transferred to a porous support, defects are likely to occur in the separation functional layer. Furthermore, since the surface of the separation functional layer is in contact with the base material before transfer, impurities derived from the base material may adhere to the surface of the separation functional layer, which may reduce the separation performance. In contrast, in the manufacturing method of this embodiment, since there is no transfer operation, defects are less likely to occur in the separation functional layer 1. In addition, in the manufacturing method of the present embodiment, the separation functional layer 1 is usually formed near the surface of the coating film 6 on the opposite side to the surface of the coating film 6 that is in contact with the base material 5. Also, impurities derived from the base material 5 tend to be less likely to adhere.
  • Japanese Patent No. 4947989 discloses a method in which a porous film containing a polyimide precursor (polyamic acid) is produced and then polyimide is formed from the precursor by a thermal imidization method.
  • the porous film tends to shrink and deform due to the heat treatment of the thermal imidization method.
  • the coating liquid L containing polyimide since the coating liquid L containing polyimide is used, there is no need to perform thermal imidization on the coating film 6, etc., and the separation film of the desired shape and thickness is formed. 10 can be easily produced.
  • the separation membrane 10 is typically a flat membrane.
  • the separation membrane 10 may have a shape other than a flat membrane, for example, may be a hollow fiber membrane.
  • the separation membrane 10 of this embodiment tends to have high separation performance against acidic gases due to the separation functional layer 1 and the porous support 2.
  • the separation performance of the separation membrane 10 against acidic gas tends to improve.
  • the permeation rate T of carbon dioxide passing through the separation membrane 10 is, for example, 100 GPU or more, and may be 200 GPU or more, 300 GPU or more, 400 GPU or more, 500 GPU or more, or even 1000 GPU or more.
  • the upper limit of the transmission rate T is not particularly limited, and is, for example, 5000 GPU.
  • GPU means 10 ⁇ 6 ⁇ cm 3 (STP)/(sec ⁇ cm 2 ⁇ cmHg).
  • cm 3 (STP) means the volume of carbon dioxide at 1 atmosphere and 0°C.
  • the permeation rate T can be calculated by the following method. First, a mixed gas consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane 10 (for example, the main surface 11 on the separation functional layer side of the separation membrane 10), and the other surface of the separation membrane 10 is supplied with a gas mixture consisting of carbon dioxide and nitrogen. (For example, the space adjacent to the main surface 12 of the separation membrane 10 on the porous support side) is depressurized. Thereby, a permeated fluid that has passed through the separation membrane 10 is obtained. The weight of the permeate fluid and the volume proportions of carbon dioxide and nitrogen in the permeate fluid are determined. The transmission rate T can be calculated from the measurement results.
  • the concentration of carbon dioxide in the mixed gas is 50 vol% under standard conditions (0° C., 101 kPa).
  • the mixed gas supplied to the space adjacent to one surface of the separation membrane 10 has a temperature of 30° C. and a pressure of 0.1 MPa.
  • the space adjacent to the other surface of the separation membrane 10 is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
  • the separation coefficient ⁇ of carbon dioxide to nitrogen of the separation membrane 10 is not particularly limited, and may be, for example, 20 or more, 25 or more, 30 or more, or even 35 or more. .
  • the upper limit of the separation coefficient ⁇ is not particularly limited, and is, for example, 50.
  • the material of the separation functional layer is the same as the material of the porous support, and the total thickness of the separation functional layer and the porous support is 10 ⁇ m or more.
  • a separation membrane having a permeation rate T of 100 GPU or more and a separation coefficient ⁇ of 20 or more has not been known so far.
  • a separation membrane 10 comprising a separation functional layer 1 and a porous support 2 in direct contact with the separation functional layer 1,
  • the material of the separation functional layer 1 is the same as the material of the porous support 2,
  • the total value of the thickness of the separation functional layer 1 and the thickness of the porous support 2 is 10 ⁇ m or more,
  • the permeability coefficient C1 of carbon dioxide in consideration of the thickness of the separation functional layer 1 is, for example, 100 Barrer or more, 500 Barrer or more, 1000 Barrer or more, 1500 Barrer or more, 2000 Barrer or more, and even It may be 2500 Barrer or more.
  • the upper limit of the transmission coefficient C1 is not particularly limited, and is, for example, 5000 Barrer.
  • Barrer means 10 ⁇ 10 ⁇ cm 3 (STP) ⁇ cm/(sec ⁇ cm 2 ⁇ cmHg).
  • the transmission coefficient C1 (Barrer) is a value obtained by multiplying the transmission rate T (GPU) by the thickness ( ⁇ m) of the separation functional layer 1.
  • the above permeability coefficient C1 is approximately the same as the permeability coefficient C2 of carbon dioxide in the self-supporting membrane (single-layer membrane) of the separation functional layer 1.
  • the permeability coefficient C2 can be measured by the same method as the permeability coefficient C1, except that a self-supporting membrane of the separation functional layer 1 is used instead of the separation membrane 10.
  • the self-supporting membrane of the separation functional layer 1 can be produced, for example, by a method similar to the method for producing the separation membrane 10 described above, except that no porosity agent is used.
  • the rate of change R of the transmission coefficient calculated by the following formula (I) is, for example, -90% to 90%, preferably -50% to 50%, and -30% to 30%. Good too.
  • the rate of change R may be 0% or less.
  • the rate of change R tends to be adjusted to -50% or more.
  • the rate of change R tends to be less than -50%. Note that if the rate of change R exceeds 0% and the value of the above-mentioned separation coefficient ⁇ is very small, there is a possibility that a defect exists in the separation functional layer 1 included in the separation membrane 10.
  • Rate of change R 100 x (transmission coefficient C1 - transmission coefficient C2) / transmission coefficient C2 (I)
  • Applications of the separation membrane 10 of this embodiment include applications for separating acidic gas from a mixed gas containing acidic gas.
  • the mixed acidic gas include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, and nitrogen oxides (NOx), with carbon dioxide being preferred.
  • the mixed gas contains gases other than acidic gas.
  • gases include, for example, nonpolar gases such as hydrogen and nitrogen, and inert gases such as helium, with nitrogen being preferred.
  • the separation membrane 10 of this embodiment is suitable for use in separating carbon dioxide from a mixed gas containing carbon dioxide and nitrogen.
  • the use of the separation membrane 10 is not limited to the use of separating acidic gas from the above-mentioned mixed gas.
  • the membrane separation apparatus 100 of this embodiment includes a separation membrane 10 and a tank 20.
  • the tank 20 includes a first chamber 21 and a second chamber 22.
  • Separation membrane 10 is arranged inside tank 20. Inside the tank 20, the separation membrane 10 separates a first chamber 21 and a second chamber 22.
  • the separation membrane 10 extends from one of the pair of wall surfaces of the tank 20 to the other.
  • the first chamber 21 has an inlet 21a and an outlet 21b.
  • the second chamber 22 has an outlet 22a.
  • Each of the inlet 21a, the outlet 21b, and the outlet 22a is an opening formed in the wall surface of the tank 20, for example.
  • Membrane separation using the membrane separation device 100 is performed, for example, by the following method.
  • a mixed gas 30 containing an acidic gas is supplied to the first chamber 21 through the inlet 21a.
  • the concentration of acidic gas in the mixed gas 30 is not particularly limited, and in a standard state is, for example, 0.01 vol% (100 ppm) or more, preferably 1 vol% or more, more preferably 10 vol% or more, and even more preferably is 30 vol% or more, particularly preferably 50 vol% or more.
  • the upper limit of the concentration of acidic gas in the mixed gas 30 is not particularly limited, and is, for example, 90 vol% in a standard state.
  • the pressure inside the first chamber 21 may be increased by supplying the mixed gas 30.
  • the membrane separator 100 may further include a pump (not shown) for pressurizing the mixed gas 30.
  • the pressure of the mixed gas 30 supplied to the first chamber 21 is, for example, 0.1 MPa or more, preferably 0.3 MPa or more.
  • the pressure inside the second chamber 22 may be reduced while the mixed gas 30 is supplied to the first chamber 21.
  • the membrane separator 100 may further include a pump (not shown) for reducing the pressure inside the second chamber 22.
  • the pressure in the second chamber 22 may be reduced so that the space within the second chamber 22 is, for example, 10 kPa or more, preferably 50 kPa or more, more preferably 100 kPa or more smaller than the atmospheric pressure in the measurement environment.
  • the permeate fluid 35 By supplying the mixed gas 30 into the first chamber 21, it is possible to obtain a permeate fluid 35 having a higher content of acidic gas than the mixed gas 30 on the other side of the separation membrane 10. That is, the permeate fluid 35 is supplied to the second chamber 22 .
  • the permeate fluid 35 contains, for example, acidic gas as a main component. However, the permeate fluid 35 may contain a small amount of gas other than acidic gas. Permeate fluid 35 is discharged to the outside of tank 20 through outlet 22a.
  • the concentration of acidic gas in the mixed gas 30 gradually decreases from the inlet 21a of the first chamber 21 toward the outlet 21b.
  • the mixed gas 30 (non-permeable fluid 36) treated in the first chamber 21 is discharged to the outside of the tank 20 through the outlet 21b.
  • the membrane separation apparatus 100 of this embodiment is suitable for a flow type (continuous type) membrane separation method.
  • the membrane separation apparatus 100 of this embodiment may be used in a batch-type membrane separation method.
  • the membrane separation device 100 may be a spiral membrane element, a hollow fiber membrane element, or the like.
  • Figure 4 shows a spiral-shaped membrane element.
  • the membrane separation device 110 in FIG. 4 includes a central tube 41 and a stacked body 42.
  • the laminate 42 includes the separation membrane 10.
  • the central tube 41 has a cylindrical shape. A plurality of holes are formed on the surface of the center tube 41 to allow the permeate fluid 35 to flow into the center tube 41 .
  • Examples of materials for the center tube 41 include resins such as acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polyphenylene ether resin (PPE resin), and polysulfone resin (PSF resin); metals such as stainless steel and titanium. It will be done.
  • the inner diameter of the central tube 41 is, for example, in the range of 20 to 100 mm.
  • the laminate 42 further includes a supply side channel material 43 and a permeate side channel material 44.
  • the laminate 42 is wound around the central tube 41.
  • the membrane separation device 110 may further include an exterior material (not shown).
  • a resin net made of polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.
  • Membrane separation using the membrane separation device 110 is performed, for example, by the following method.
  • the permeated fluid 35 that has passed through the separation membrane 10 of the laminate 42 moves into the center tube 41 .
  • the permeate fluid 35 is discharged to the outside through the central pipe 41.
  • the mixed gas 30 (non-permeable fluid 36) processed by the membrane separator 110 is discharged to the outside from the other end of the wound stack 42. Thereby, the acidic gas can be separated from the mixed gas 30.
  • Example 1 Polyimide was synthesized using an automatic polymerization device (manufactured by METTLER TOLEDO, EasyMax402).
  • a separable flask (volume 400 mL) attached to the apparatus was equipped with a Dimroth, stirring rod, internal thermometer, nitrogen inlet tube, and flat stopper.
  • a coolant set at 10°C was circulated through the Dimroth chiller.
  • N 2 gas was passed through the flask at a flow rate of 100 mL/min.
  • the stirring speed was set at 300 rpm.
  • naphthalene-1,4,5,8-tetracarboxylic dianhydride NTDA
  • 9.11 g (75 mmol) of benzoic acid were further added as tetracarboxylic dianhydride.
  • the jacket temperature of the apparatus was raised to 180°C and stirred for 8 hours. At this time, the internal temperature of the flask was 172 to 175°C. After stirring, the internal temperature of the flask was cooled to 25° C. and left overnight.
  • polyimide, N,N-dimethylformamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent, and polyethylene glycol monomethyl ether 400 (manufactured by NOF Corporation) as a porosity agent were added in the weight ratios shown in Table 1. Added to a cup with a lid. Next, the obtained mixture was stirred for 25 minutes at 2000 rpm using a stirring device (Awatori Rentaro manufactured by Thinky), and further defoamed for 5 minutes at 2200 rpm. As a result, a coating liquid in which the polyimide was uniformly dissolved in the solvent was obtained.
  • a coating liquid was applied onto a base material (75SG2 manufactured by Panac) to form a coating film with a thickness of 300 ⁇ m.
  • the coating film was dried at 60° C. for 30 minutes using an oven. The coated film was once taken out of the oven and further dried at 130° C. for 30 minutes.
  • the coating film was peeled off from the base material and immersed in methanol for 30 minutes. As a result, the porosity-forming agent was removed from the coating film, and a separation functional layer and a porous support were formed.
  • the separation membrane of Example 1 was obtained by vacuum drying at 60° C. for 1 hour and further drying at 300° C. for 30 minutes.
  • the thicknesses of the separation functional layer and porous support were determined by the method described above.
  • a gas permeation test was conducted on the separation membrane produced in the example by the following method. First, a separation membrane was set in a metal cell and sealed with an O-ring to prevent leakage. Next, the mixed gas was injected into the metal cell so that the mixed gas came into contact with the main surface of the separation membrane on the separation functional layer side.
  • the gas mixture consisted essentially of carbon dioxide and nitrogen. The concentration of carbon dioxide in the gas mixture was 50 vol% under standard conditions.
  • the mixed gas injected into the metal cell had a temperature of 30° C. and a pressure of 0.1 MPa. Next, the pressure in the space (permeation side space) in the metal cell adjacent to the main surface of the separation membrane on the porous support side was reduced using a vacuum pump.
  • the pressure in the permeation side space was reduced so that the pressure in the space was 0.1 MPa lower than the atmospheric pressure in the measurement environment.
  • a permeate fluid was obtained from the main surface of the separation membrane on the porous support side. Based on the composition of the obtained permeate fluid, the weight of the permeate fluid, etc., the permeation rate T of carbon dioxide, the separation coefficient ⁇ of carbon dioxide with respect to nitrogen ⁇ (CO 2 /N 2 ), and the permeation coefficient C1 of carbon dioxide were calculated. .
  • the permeability coefficient C2 of carbon dioxide in the separation functional layer was determined.
  • the transmission coefficient C2 was 1743 Barrer.
  • the rate of change R of the transmission coefficient was calculated using the above formula (I).
  • the separation membrane of the example has high values for both the carbon dioxide permeation rate T and the carbon dioxide separation coefficient ⁇ , and is suitable for separating acidic gas from a mixed gas containing acidic gas. I can say that there is. From the results of Examples 1 to 7, it can be seen that when the porous support has continuous pores, the rate of change R of the permeability coefficient tends to be a relatively high value.
  • the separation membrane of this embodiment is suitable for separating acidic gas from a mixed gas containing acidic gas.
  • the separation membrane of this embodiment is suitable for separating carbon dioxide from off-gas of chemical plants or thermal power generation.

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Abstract

The present invention provides a new separation membrane that is suitable for separating an acidic gas from a gas mixture containing the acidic gas. A separation membrane 10 according to the present invention is provided with a separation function layer 1 and a porous support 2 that is in direct contact with the separation function layer 1. The separation function layer 1 and the porous support 2 each contain a polyimide. The polyimide includes a structural unit A1 derived from a tetracarboxylic dianhydride a1 that has an acid anhydride structure S having a six-membered ring. For example, the porous support 2 has continuous holes.

Description

分離膜、及びその製造方法Separation membrane and its manufacturing method
　本発明は、分離膜、及びその製造方法に関する。 The present invention relates to a separation membrane and a method for manufacturing the same.
　二酸化炭素などの酸性ガスを含む混合気体から酸性ガスを分離する方法として、膜分離法が開発されている。膜分離法は、混合気体に含まれる酸性ガスを吸収剤に吸収させて分離する吸収法と比べて、運転コストを抑えながら酸性ガスを効率的に分離することができる。 Membrane separation methods have been developed as a method for separating acidic gases from mixed gases containing acidic gases such as carbon dioxide. Membrane separation methods can efficiently separate acidic gases while reducing operating costs, compared to absorption methods in which acidic gases contained in a gas mixture are absorbed by an absorbent and separated.
　膜分離法に用いられる分離膜としては、分離機能層を多孔性支持体の上に形成した複合膜が挙げられる。分離機能層の材料としては、例えば、ポリイミド樹脂、ポリエーテルブロックアミド樹脂などの樹脂が挙げられる。例えば、特許文献１には、ポリイミド樹脂を含む分離膜が開示されている。 Examples of separation membranes used in membrane separation methods include composite membranes in which a separation functional layer is formed on a porous support. Examples of the material for the separation functional layer include resins such as polyimide resin and polyether block amide resin. For example, Patent Document 1 discloses a separation membrane containing a polyimide resin.
特開２０１４－１８４４２４号公報Japanese Patent Application Publication No. 2014-184424
　酸性ガスを含む混合気体から酸性ガスを分離することに適した新たな分離膜が求められている。 There is a need for a new separation membrane suitable for separating acidic gas from a gas mixture containing acidic gas.
　本発明は、
　分離機能層と、
　前記分離機能層に直接接する多孔性支持体と、
を備え、
　前記分離機能層及び前記多孔性支持体のそれぞれがポリイミドを含み、
　前記ポリイミドは、６員環の酸無水物構造を有するテトラカルボン酸二無水物に由来する構成単位を含む、分離膜を提供する。 The present invention
a separation functional layer;
a porous support directly in contact with the separation functional layer;
Equipped with
Each of the separation functional layer and the porous support contains polyimide,
The polyimide provides a separation membrane containing a structural unit derived from a tetracarboxylic dianhydride having a six-membered acid anhydride structure.
　本発明によれば、酸性ガスを含む混合気体から酸性ガスを分離することに適した新たな分離膜を提供できる。 According to the present invention, a new separation membrane suitable for separating acidic gas from a mixed gas containing acidic gas can be provided.
本発明の一実施形態にかかる分離膜を模式的に示す断面図である。1 is a cross-sectional view schematically showing a separation membrane according to an embodiment of the present invention. 分離膜の製造方法を説明するための図である。FIG. 3 is a diagram for explaining a method for manufacturing a separation membrane. 分離膜の製造方法を説明するための図である。FIG. 3 is a diagram for explaining a method for manufacturing a separation membrane. 本発明の分離膜を備えた膜分離装置の概略断面図である。1 is a schematic cross-sectional view of a membrane separation device equipped with a separation membrane of the present invention. 本発明の分離膜を備えた膜分離装置の変形例を模式的に示す斜視図である。FIG. 3 is a perspective view schematically showing a modified example of a membrane separation device equipped with the separation membrane of the present invention. 実施例１の分離膜の断面の走査型電子顕微鏡（ＳＥＭ）画像である。1 is a scanning electron microscope (SEM) image of a cross section of the separation membrane of Example 1. 実施例２の分離膜の断面のＳＥＭ画像である。3 is a SEM image of a cross section of the separation membrane of Example 2. 実施例３の分離膜の断面のＳＥＭ画像である。3 is a SEM image of a cross section of the separation membrane of Example 3. 実施例４の分離膜の断面のＳＥＭ画像である。3 is a SEM image of a cross section of the separation membrane of Example 4. 実施例５の分離膜の断面のＳＥＭ画像である。3 is a SEM image of a cross section of the separation membrane of Example 5. 実施例６の分離膜の断面のＳＥＭ画像である。3 is a SEM image of a cross section of the separation membrane of Example 6. 実施例７の分離膜の断面のＳＥＭ画像である。3 is a SEM image of a cross section of the separation membrane of Example 7.
　本発明の第１態様にかかる分離膜は、
　分離機能層と、
　前記分離機能層に直接接する多孔性支持体と、
を備え、
　前記分離機能層及び前記多孔性支持体のそれぞれがポリイミドを含み、
　前記ポリイミドは、６員環の酸無水物構造を有するテトラカルボン酸二無水物に由来する構成単位を含む。 The separation membrane according to the first aspect of the present invention is
a separation functional layer;
a porous support directly in contact with the separation functional layer;
Equipped with
Each of the separation functional layer and the porous support contains polyimide,
The polyimide includes a structural unit derived from a tetracarboxylic dianhydride having a six-membered acid anhydride structure.
　本発明の第２態様において、例えば、第１態様にかかる分離膜では、前記多孔性支持体が連続孔を有する。 In the second aspect of the present invention, for example, in the separation membrane according to the first aspect, the porous support has continuous pores.
　本発明の第３態様において、例えば、第１又は第２態様にかかる分離膜では、前記分離機能層と前記多孔性支持体とが一体化している。 In the third aspect of the present invention, for example, in the separation membrane according to the first or second aspect, the separation functional layer and the porous support are integrated.
　本発明の第４態様において、例えば、第１～第３態様のいずれか１つにかかる分離膜では、前記分離機能層の材料は、前記多孔性支持体の材料と同じである。 In the fourth aspect of the present invention, for example, in the separation membrane according to any one of the first to third aspects, the material of the separation functional layer is the same as the material of the porous support.
　本発明の第５態様において、例えば、第１～第４態様のいずれか１つにかかる分離膜では、前記分離機能層の厚さ、及び前記多孔性支持体の厚さの合計値が１０μｍ以上である。 In the fifth aspect of the present invention, for example, in the separation membrane according to any one of the first to fourth aspects, the total thickness of the separation functional layer and the thickness of the porous support is 10 μm or more. It is.
　本発明の第６態様において、例えば、第１～第５態様のいずれか１つにかかる分離膜では、前記構成単位は、下記式（Ａ１）で表される。
Figure JPOXMLDOC01-appb-C000002
 　前記式（Ａ１）において、Ｒ1a～Ｒ4aは、互いに独立して、水素原子又は任意の置換基である。 In the sixth aspect of the present invention, for example, in the separation membrane according to any one of the first to fifth aspects, the structural unit is represented by the following formula (A1).
Figure JPOXMLDOC01-appb-C000002
 In the formula (A1), R 1a to R 4a each independently represent a hydrogen atom or an arbitrary substituent.
　本発明の第７態様において、例えば、第１～第６態様のいずれか１つにかかる分離膜では、前記分離膜の一方の面に隣接する空間に、二酸化炭素及び窒素からなる混合気体を供給するとともに、前記分離膜の他方の面に隣接する空間を減圧した場合に、前記分離膜を透過する二酸化炭素の透過速度が１００ＧＰＵ以上である。
　ここで、前記混合気体における前記二酸化炭素の濃度は、標準状態で５０ｖｏｌ％であり、前記一方の面に隣接する空間に供給される前記混合気体は、温度が３０℃であり、圧力が０．１ＭＰａであり、前記他方の面に隣接する空間は、当該空間内の圧力が測定環境における大気圧に対して０．１ＭＰａ小さくなるように減圧されている。 In a seventh aspect of the present invention, for example, in the separation membrane according to any one of the first to sixth aspects, a mixed gas consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane. At the same time, when the space adjacent to the other surface of the separation membrane is depressurized, the permeation rate of carbon dioxide passing through the separation membrane is 100 GPU or more.
Here, the concentration of carbon dioxide in the mixed gas is 50 vol% in a standard state, and the mixed gas supplied to the space adjacent to the one surface has a temperature of 30°C and a pressure of 0. 1 MPa, and the space adjacent to the other surface is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
　本発明の第８態様において、例えば、第１～第７態様のいずれか１つにかかる分離膜では、前記分離膜の一方の面に隣接する空間に、二酸化炭素及び窒素からなる混合気体を供給するとともに、前記分離膜の他方の面に隣接する空間を減圧した場合に、窒素に対する二酸化炭素の分離係数αが２０以上である。
　ここで、前記混合気体における前記二酸化炭素の濃度は、標準状態で５０ｖｏｌ％であり、前記一方の面に隣接する空間に供給される前記混合気体は、温度が３０℃であり、圧力が０．１ＭＰａであり、前記他方の面に隣接する空間は、当該空間内の圧力が測定環境における大気圧に対して０．１ＭＰａ小さくなるように減圧されている。 In the eighth aspect of the present invention, for example, in the separation membrane according to any one of the first to seventh aspects, a mixed gas consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane. At the same time, when the space adjacent to the other surface of the separation membrane is depressurized, the separation coefficient α of carbon dioxide with respect to nitrogen is 20 or more.
Here, the concentration of carbon dioxide in the mixed gas is 50 vol% in a standard state, and the mixed gas supplied to the space adjacent to the one surface has a temperature of 30°C and a pressure of 0. 1 MPa, and the space adjacent to the other surface is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
　本発明の第９態様にかかる分離膜の製造方法は、
　ポリイミド、溶剤、及び多孔化剤を含む塗布液を用いて塗布膜を形成することと、
　前記塗布膜から前記多孔化剤を除去することと、
を含む。 The method for manufacturing a separation membrane according to the ninth aspect of the present invention includes:
Forming a coating film using a coating solution containing polyimide, a solvent, and a porosity agent;
removing the porosity agent from the coating film;
including.
　本発明の第１０態様において、例えば、第９態様にかかる製造方法では、前記ポリイミドは、６員環の酸無水物構造を有するテトラカルボン酸二無水物に由来する構成単位を含む。 In the tenth aspect of the present invention, for example, in the manufacturing method according to the ninth aspect, the polyimide includes a structural unit derived from a tetracarboxylic dianhydride having a six-membered acid anhydride structure.
　本発明の第１１態様において、例えば、第９又は第１０態様にかかる製造方法では、前記多孔化剤の沸点は、前記溶剤の沸点より５０℃以上高い。 In the eleventh aspect of the present invention, for example, in the manufacturing method according to the ninth or tenth aspect, the boiling point of the porosity-forming agent is 50° C. or more higher than the boiling point of the solvent.
　本発明の第１２態様において、例えば、第９～第１１態様のいずれか１つにかかる製造方法では、前記多孔化剤は、エーテル化合物及びリン酸化合物からなる群より選ばれる少なくとも１つを含む。 In the twelfth aspect of the present invention, for example, in the manufacturing method according to any one of the ninth to eleventh aspects, the porosity-forming agent includes at least one selected from the group consisting of an ether compound and a phosphoric acid compound. .
　本発明の第１３態様において、例えば、第９～第１２態様のいずれか１つにかかる製造方法では、前記溶剤は、アミド化合物及びラクトン化合物からなる群より選ばれる少なくとも１つを含む。 In the thirteenth aspect of the present invention, for example, in the production method according to any one of the ninth to twelfth aspects, the solvent contains at least one selected from the group consisting of an amide compound and a lactone compound.
　本発明の第１４態様において、例えば、第９～第１３態様のいずれか１つにかかる製造方法では、前記塗布膜を乾燥させる、及び／又は、前記塗布膜を洗浄液で洗浄することによって、前記塗布膜から前記多孔化剤を除去する。 In a fourteenth aspect of the present invention, for example, in the manufacturing method according to any one of the ninth to thirteenth aspects, the coating film may be dried and/or the coating film may be washed with a cleaning liquid. The porosity agent is removed from the coating film.
　本発明の第１５態様にかかる分離膜は、
　分離機能層と、前記分離機能層に直接接する多孔性支持体とを備えた分離膜であって、
　前記分離機能層の材料は、前記多孔性支持体の材料と同じであり、
　前記分離機能層の厚さ、及び前記多孔性支持体の厚さの合計値が１０μｍ以上であり、
　前記分離膜の一方の面に隣接する空間に、二酸化炭素及び窒素からなる混合気体を供給するとともに、前記分離膜の他方の面に隣接する空間を減圧した場合に、前記分離膜を透過する二酸化炭素の透過速度が１００ＧＰＵ以上であり、かつ、窒素に対する二酸化炭素の分離係数αが２０以上である。
　ここで、前記混合気体における前記二酸化炭素の濃度は、標準状態で５０ｖｏｌ％であり、前記一方の面に隣接する空間に供給される前記混合気体は、温度が３０℃であり、圧力が０．１ＭＰａであり、前記他方の面に隣接する空間は、当該空間内の圧力が測定環境における大気圧に対して０．１ＭＰａ小さくなるように減圧されている。 The separation membrane according to the fifteenth aspect of the present invention is
A separation membrane comprising a separation functional layer and a porous support directly in contact with the separation functional layer,
The material of the separation functional layer is the same as the material of the porous support,
The total value of the thickness of the separation functional layer and the thickness of the porous support is 10 μm or more,
When a gas mixture consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane and the pressure is reduced in a space adjacent to the other surface of the separation membrane, the amount of carbon dioxide that permeates through the separation membrane The carbon permeation rate is 100 GPU or more, and the separation coefficient α of carbon dioxide with respect to nitrogen is 20 or more.
Here, the concentration of carbon dioxide in the mixed gas is 50 vol% in a standard state, and the mixed gas supplied to the space adjacent to the one surface has a temperature of 30°C and a pressure of 0. 1 MPa, and the space adjacent to the other surface is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
　以下、本発明の詳細を説明するが、以下の説明は、本発明を特定の実施形態に制限する趣旨ではない。 The details of the present invention will be described below, but the following description is not intended to limit the present invention to specific embodiments.
＜分離膜の実施形態＞
　図１に示すように、本実施形態の分離膜１０は、分離機能層１及び多孔性支持体２を備えており、例えば、分離機能層１及び多孔性支持体２のみから構成されている。多孔性支持体２は、分離機能層１に直接接しており、分離機能層１を支持している。分離機能層１と多孔性支持体２とは一体化していることが好ましい。本明細書において、「一体化」とは、部材同士を非破壊で互いに分離できないことを意味する。 <Embodiment of separation membrane>
As shown in FIG. 1, the separation membrane 10 of the present embodiment includes a separation functional layer 1 and a porous support 2, and is composed of only the separation functional layer 1 and the porous support 2, for example. The porous support 2 is in direct contact with the separation functional layer 1 and supports the separation functional layer 1. It is preferable that the separation functional layer 1 and the porous support 2 are integrated. As used herein, "integrated" means that the members cannot be separated from each other non-destructively.
　分離機能層１及び多孔性支持体２のそれぞれはポリイミドを含む。分離機能層１に含まれるポリイミドは、典型的には、多孔性支持体２に含まれるポリイミドと同じである。特に、分離機能層１の材料は、多孔性支持体２の材料と同じであることが好ましい。一例として、分離膜１０は、ポリイミドのみから構成されていてもよく、単一の材料で構成されていてもよい。 The separation functional layer 1 and the porous support 2 each contain polyimide. The polyimide contained in the separation functional layer 1 is typically the same as the polyimide contained in the porous support 2. In particular, the material of the separation functional layer 1 is preferably the same as the material of the porous support 2. As an example, the separation membrane 10 may be made of only polyimide, or may be made of a single material.
　ポリイミドは、典型的には、６員環の酸無水物構造Ｓを有するテトラカルボン酸二無水物ａ１に由来する構成単位Ａ１を含むポリイミドＰである。ポリイミドＰは、ジアミンに由来する構成単位Ｂをさらに含む。なお、場合によっては、分離機能層１及び多孔性支持体２のそれぞれは、ポリイミドＰ以外の他のポリイミドを含んでいてもよい。 The polyimide is typically a polyimide P containing a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered acid anhydride structure S. Polyimide P further includes a structural unit B derived from a diamine. Note that, depending on the case, each of the separation functional layer 1 and the porous support 2 may contain a polyimide other than polyimide P.
　ポリイミドＰにおいて、構成単位Ａ１は、分離膜１０を透過する酸性ガスの透過速度を向上させることに適した構成単位である。テトラカルボン酸二無水物ａ１は、例えば、１つ以上、好ましくは２つ、の酸無水物構造Ｓを有する。６員環の酸無水物構造Ｓは、典型的には、下記式（１）で表されるグルタル酸無水物構造である。
Figure JPOXMLDOC01-appb-C000003
 In polyimide P, the structural unit A1 is a structural unit suitable for improving the permeation rate of acidic gas passing through the separation membrane 10. Tetracarboxylic dianhydride a1 has, for example, one or more, preferably two, acid anhydride structures S. The 6-membered acid anhydride structure S is typically a glutaric anhydride structure represented by the following formula (1).
Figure JPOXMLDOC01-appb-C000003
　テトラカルボン酸二無水物ａ１は、縮合環を有していてもよく、当該縮合環が酸無水物構造Ｓを含んでいてもよい。縮合環は、酸無水物構造Ｓとともに、芳香環を含んでいてもよい。縮合環に含まれる芳香環は、炭素原子のみから構成されていてもよく、酸素原子、窒素原子、硫黄原子などのヘテロ原子を含む複素芳香環であってもよい。芳香環は、多環式であってもよく、単環式であってもよい。芳香環の炭素数は、特に限定されず、例えば４～１４である。芳香環の具体例としては、ベンゼン環、ナフタレン環、アントラセン環、フェナントレン環、フラン環、ピロール環、ピリジン環及びチオフェン環が挙げられる。 The tetracarboxylic dianhydride a1 may have a condensed ring, and the condensed ring may include an acid anhydride structure S. The condensed ring may include an aromatic ring together with the acid anhydride structure S. The aromatic ring contained in the condensed ring may be composed only of carbon atoms, or may be a heteroaromatic ring containing heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms. The aromatic ring may be polycyclic or monocyclic. The number of carbon atoms in the aromatic ring is not particularly limited, and is, for example, 4 to 14. Specific examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a furan ring, a pyrrole ring, a pyridine ring, and a thiophene ring.
　縮合環は、置換基を有していてもよく、置換基を有していなくてもよい。縮合環の置換基としては、特に限定されず、ハロゲン基、炭化水素基などが挙げられる。ハロゲン基としては、フルオロ基、クロロ基、ブロモ基、ヨード基などが挙げられる。炭化水素基の炭素数は、特に限定されず、例えば１～１５である。炭化水素基は、例えば、メチル基、エチル基、プロピル基などのアルキル基である。炭化水素基は、水素原子がハロゲン基で置換されたハロゲン化炭化水素基であってもよい。縮合環が複数の置換基を有するとき、複数の置換基は、互いに同じであってもよく、異なっていてもよい。 The fused ring may or may not have a substituent. Substituents on the condensed ring are not particularly limited, and include halogen groups, hydrocarbon groups, and the like. Examples of the halogen group include a fluoro group, a chloro group, a bromo group, and an iodo group. The number of carbon atoms in the hydrocarbon group is not particularly limited, and is, for example, 1 to 15. The hydrocarbon group is, for example, an alkyl group such as a methyl group, an ethyl group, or a propyl group. The hydrocarbon group may be a halogenated hydrocarbon group in which a hydrogen atom is substituted with a halogen group. When the condensed ring has a plurality of substituents, the plurality of substituents may be the same or different.
　テトラカルボン酸二無水物ａ１は、例えば、下記式（ａ１）で表される。
Figure JPOXMLDOC01-appb-C000004
 Tetracarboxylic dianhydride a1 is represented by the following formula (a1), for example.
Figure JPOXMLDOC01-appb-C000004
　式（ａ１）において、Ｒ1a～Ｒ4aは、互いに独立して、水素原子又は任意の置換基である。任意の置換基としては、特に限定されず、ハロゲン基、炭化水素基などが挙げられる。ハロゲン基及び炭化水素基としては、上述したものが挙げられる。 In formula (a1), R 1a to R 4a are each independently a hydrogen atom or an arbitrary substituent. The optional substituents are not particularly limited, and include halogen groups, hydrocarbon groups, and the like. Examples of the halogen group and hydrocarbon group include those mentioned above.
　ポリイミドＰにおいて、テトラカルボン酸二無水物ａ１に由来する構成単位Ａ１は、例えば、下記式（Ａ１）で表される。式（Ａ１）で表される構成単位Ａ１は、上記の式（ａ１）で表されるテトラカルボン酸二無水物ａ１に由来している。なお、式（Ａ１）において、イミド基に含まれる窒素原子は、テトラカルボン酸二無水物ａ１と反応したジアミンに由来する。
Figure JPOXMLDOC01-appb-C000005
 In polyimide P, the structural unit A1 derived from the tetracarboxylic dianhydride a1 is represented by the following formula (A1), for example. The structural unit A1 represented by the formula (A1) is derived from the tetracarboxylic dianhydride a1 represented by the above formula (a1). In addition, in formula (A1), the nitrogen atom contained in the imide group originates from the diamine reacted with the tetracarboxylic dianhydride a1.
Figure JPOXMLDOC01-appb-C000005
　式（Ａ１）において、Ｒ1a～Ｒ4aは、式（ａ１）と同じであり、互いに独立して、水素原子又は任意の置換基である。式（Ａ１）で表される構成単位Ａ１の具体例としては、下記式（Ａ１－１）が挙げられる。
Figure JPOXMLDOC01-appb-C000006
 In formula (A1), R 1a to R 4a are the same as in formula (a1) and independently represent a hydrogen atom or an arbitrary substituent. A specific example of the structural unit A1 represented by the formula (A1) is the following formula (A1-1).
Figure JPOXMLDOC01-appb-C000006
　ポリイミドＰにおいて、テトラカルボン酸二無水物に由来する全ての構成単位Ａの物質量に対する、上記の構成単位Ａ１の物質量の比率ｐ１は、例えば５０ｍｏｌ％以上であり、７０ｍｏｌ％以上、９０ｍｏｌ％以上、９５ｍｏｌ％以上、さらには９９ｍｏｌ％以上であってもよい。ポリイミドＰは、テトラカルボン酸二無水物に由来する構成単位Ａとして、上記の構成単位Ａ１のみを含んでいてもよい。ただし、ポリイミドＰは、構成単位Ａ１以外に、５員環の酸無水物構造を有するテトラカルボン酸二無水物ａ２に由来する構成単位Ａ２をさらに含んでいてもよい。テトラカルボン酸二無水物ａ２としては、特に限定されず、例えば、ピロメリット酸二無水和物、４，４’－（ヘキサフルオロイソプロピリデン）ジフタル酸無水物などが挙げられる。 In polyimide P, the ratio p1 of the amount of the above structural unit A1 to the amount of all the structural units A derived from tetracarboxylic dianhydride is, for example, 50 mol% or more, 70 mol% or more, 90 mol% or more , 95 mol% or more, or even 99 mol% or more. Polyimide P may contain only the above structural unit A1 as the structural unit A derived from tetracarboxylic dianhydride. However, in addition to the structural unit A1, the polyimide P may further contain a structural unit A2 derived from a tetracarboxylic dianhydride a2 having a five-membered acid anhydride structure. The tetracarboxylic dianhydride a2 is not particularly limited, and examples thereof include pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, and the like.
　上述のとおり、ポリイミドＰは、ジアミンに由来する構成単位Ｂをさらに含む。ジアミンは、２つの１級アミノ基を有する化合物である。ジアミンは、１級アミノ基以外の他の官能基を含んでいてもよく、含まなくてもよい。他の官能基としては、カルボキシル基、ヒドロキシル基、チオール基、スルホニル基などが挙げられる。ジアミンは、カルボキシル基、ヒドロキシル基及びチオール基からなる群より選ばれる少なくとも１つの官能基ｆを有していてもよい。 As described above, polyimide P further includes structural unit B derived from diamine. Diamines are compounds with two primary amino groups. The diamine may or may not contain a functional group other than the primary amino group. Examples of other functional groups include carboxyl groups, hydroxyl groups, thiol groups, and sulfonyl groups. The diamine may have at least one functional group f selected from the group consisting of a carboxyl group, a hydroxyl group, and a thiol group.
　ジアミンは、芳香環をさらに有していてもよい。芳香環としては、テトラカルボン酸二無水物ａ１について上述したものが挙げられる。ジアミンにおいて、芳香環の置換基が、例えば、１級アミノ基を含んでいる。芳香環は、１級アミノ基を含む置換基以外の他の置換基を有していてもよく、他の置換基を有していなくてもよい。他の置換基としては、特に限定されず、上記の官能基ｆを含む基、ハロゲン基、炭化水素基などが挙げられる。ハロゲン基及び炭化水素基としては、テトラカルボン酸二無水物ａ１について上述したものが挙げられる。なお、ジアミンにおいて、他の置換基は、光重合性の官能基（例えば、ビニル基）を含んでいてもよい。 The diamine may further have an aromatic ring. Examples of the aromatic ring include those mentioned above for the tetracarboxylic dianhydride a1. In the diamine, the substituent on the aromatic ring includes, for example, a primary amino group. The aromatic ring may have a substituent other than the substituent containing the primary amino group, or may have no other substituent. Other substituents are not particularly limited, and include groups containing the above functional group f, halogen groups, hydrocarbon groups, and the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1. Note that in the diamine, other substituents may include a photopolymerizable functional group (for example, a vinyl group).
　ジアミンは、例えば、下記式（ｂ１）、式（ｂ２）、式（ｂ３）、式（ｂ４）又は式（ｂ５）で表される。
Figure JPOXMLDOC01-appb-C000007
 The diamine is represented by, for example, the following formula (b1), formula (b2), formula (b3), formula (b4), or formula (b5).
Figure JPOXMLDOC01-appb-C000007
　式（ｂ１）～（ｂ５）において、Ｒ1b～Ｒ30bは、互いに独立して、水素原子又は任意の置換基である。任意の置換基は、例えば、官能基ｆを含む基、ハロゲン基、炭化水素基などである。ハロゲン基及び炭化水素基としては、テトラカルボン酸二無水物ａ１について上述したものが挙げられる。 In formulas (b1) to (b5), R 1b to R 30b are each independently a hydrogen atom or an arbitrary substituent. Examples of the optional substituent include a group containing a functional group f, a halogen group, and a hydrocarbon group. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
　式（ｂ３）及び（ｂ４）において、Ｘ1及びＸ2は、単結合又は任意の連結基である。任意の連結基は、例えば、２価の炭化水素基である。２価の炭化水素基としては、例えば、メチレン基、エチレン基、プロパン－１，３－ジイル基、プロパン－２，２－ジイル基などのアルキレン基が挙げられる。２価の炭化水素基は、水素原子がハロゲン基で置換されたハロゲン化炭化水素基であってもよい。２価の炭化水素基は、芳香環をさらに有していてもよい。芳香環としては、テトラカルボン酸二無水物ａ１について上述したものが挙げられる。２価の炭化水素基は、フルオレンジイル基であってもよい。Ｘ1及びＸ2は、２価の炭化水素基とともに、又は２価の炭化水素基に代えて、エーテル基やエステル基などの官能基を含んでいてもよい。 In formulas (b3) and (b4), X 1 and X 2 are a single bond or an arbitrary linking group. The optional linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include alkylene groups such as methylene group, ethylene group, propane-1,3-diyl group, and propane-2,2-diyl group. The divalent hydrocarbon group may be a halogenated hydrocarbon group in which a hydrogen atom is substituted with a halogen group. The divalent hydrocarbon group may further have an aromatic ring. Examples of the aromatic ring include those mentioned above for the tetracarboxylic dianhydride a1. The divalent hydrocarbon group may be a fluorenediyl group. X 1 and X 2 may contain a functional group such as an ether group or an ester group together with or in place of the divalent hydrocarbon group.
　ジアミンに由来する構成単位Ｂは、カルボキシル基、ヒドロキシル基、チオール基及びこれらの金属塩からなる群より選ばれる少なくとも１つの官能基Ｆを有していてもよい。官能基Ｆとしての金属塩に含まれる金属としては、特に限定されず、例えば、Ｌｉ、Ｎａ、Ｋ、Ｂｅ、Ｍｇ、Ｃａ、Ｂａ、Ｓｃ、Ｙ、Ｔｉ、Ｚｒ、Ｖ、Ｃｒ、Ｍｏ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｂ、Ａｌ、Ｇａ、Ｉｎ、Ｐｂなどが挙げられる。官能基Ｆとしての金属塩において、金属は、詳細には、カチオンとして存在する。この金属カチオンの価数は、例えば１以上であり、好ましくは２以上であり、より好ましくは３以上である。 The structural unit B derived from diamine may have at least one functional group F selected from the group consisting of carboxyl groups, hydroxyl groups, thiol groups, and metal salts thereof. The metal contained in the metal salt as the functional group F is not particularly limited, and includes, for example, Li, Na, K, Be, Mg, Ca, Ba, Sc, Y, Ti, Zr, V, Cr, Mo, and Mn. , Fe, Co, Ni, Cu, Ag, Zn, B, Al, Ga, In, Pb, etc. In the metal salt as functional group F, the metal is specifically present as a cation. The valence of this metal cation is, for example, 1 or more, preferably 2 or more, and more preferably 3 or more.
　構成単位Ｂが官能基Ｆとして金属塩を含む場合、複数のポリイミドＰが、カルボキシル基などの官能基を介して、金属塩に含まれる金属カチオンに配位することができる。これにより、複数のポリイミドＰが、金属カチオンを介して互いに架橋する。このような架橋構造が形成されることによって、ポリイミドＰの物理エージング（physical aging）が抑制され、これにより、分離機能層１の分離性能が経時的に低下することを抑制できる傾向がある。ポリイミドＰが官能基Ｆとして金属塩を含む場合、分離機能層１の分離性能が向上する傾向もある。官能基Ｆとしての金属塩は、例えば、テトラカルボン酸二無水物ａ１とジアミンとを含むモノマー群から得られたポリイミドＰに含まれる官能基ｆについて、解離性のプロトンを金属カチオンと交換させることによって形成することができる。 When the structural unit B contains a metal salt as the functional group F, a plurality of polyimides P can be coordinated to the metal cation contained in the metal salt via a functional group such as a carboxyl group. As a result, the plurality of polyimides P are crosslinked with each other via the metal cations. Formation of such a crosslinked structure suppresses physical aging of the polyimide P, which tends to suppress deterioration of the separation performance of the separation functional layer 1 over time. When the polyimide P contains a metal salt as the functional group F, the separation performance of the separation functional layer 1 also tends to improve. The metal salt as the functional group F is, for example, a functional group f contained in a polyimide P obtained from a monomer group containing tetracarboxylic dianhydride a1 and a diamine, by exchanging a dissociative proton with a metal cation. can be formed by
　ジアミンに由来する構成単位Ｂは、例えば、下記式（Ｂ１）、式（Ｂ２）、式（Ｂ３）、式（Ｂ４）又は式（Ｂ５）で表される。式（Ｂ１）～式（Ｂ５）で表される構成単位Ｂは、それぞれ、上記の式（ｂ１）～式（ｂ５）で表されるジアミンに由来している。 The structural unit B derived from diamine is represented by, for example, the following formula (B1), formula (B2), formula (B3), formula (B4), or formula (B5). The structural units B represented by formulas (B1) to (B5) are derived from diamines represented by formulas (b1) to (b5) above, respectively.
Figure JPOXMLDOC01-appb-C000008
Figure JPOXMLDOC01-appb-C000008
　式（Ｂ１）において、Ｒ1b～Ｒ4bは、互いに独立して、水素原子又は任意の置換基である。式（Ｂ１）において、任意の置換基は、例えば、上記の官能基Ｆを含む基、ハロゲン基、炭化水素基などである。ハロゲン基及び炭化水素基としては、テトラカルボン酸二無水物ａ１について上述したものが挙げられる。 In formula (B1), R 1b to R 4b are each independently a hydrogen atom or an arbitrary substituent. In formula (B1), the arbitrary substituent is, for example, a group containing the above-mentioned functional group F, a halogen group, a hydrocarbon group, or the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
　式（Ｂ１）で表される構成単位Ｂの具体例としては、下記式（Ｂ１－１）～（Ｂ１－７）が挙げられる。なお、これらの式において、Ｍは、任意の金属カチオンである。
Figure JPOXMLDOC01-appb-C000009
 Specific examples of the structural unit B represented by formula (B1) include the following formulas (B1-1) to (B1-7). Note that in these formulas, M is any metal cation.
Figure JPOXMLDOC01-appb-C000009
　式（Ｂ２）において、Ｒ5b～Ｒ8bは、互いに独立して、水素原子又は任意の置換基である。式（Ｂ２）において、任意の置換基は、例えば、官能基Ｆを含む基、ハロゲン基、炭化水素基などである。ハロゲン基及び炭化水素基としては、テトラカルボン酸二無水物ａ１について上述したものが挙げられる。式（Ｂ２）で表される構成単位Ｂの具体例としては、下記式（Ｂ２－１）が挙げられる。
Figure JPOXMLDOC01-appb-C000010
 In formula (B2), R 5b to R 8b are each independently a hydrogen atom or an arbitrary substituent. In formula (B2), arbitrary substituents include, for example, a group containing a functional group F, a halogen group, a hydrocarbon group, and the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1. A specific example of the structural unit B represented by formula (B2) is the following formula (B2-1).
Figure JPOXMLDOC01-appb-C000010
　式（Ｂ３）において、Ｒ9b～Ｒ16bは、互いに独立して、水素原子又は任意の置換基であり、Ｘ1は、単結合又は任意の連結基である。式（Ｂ３）において、任意の置換基は、例えば、官能基Ｆを含む基、ハロゲン基、炭化水素基などである。ハロゲン基及び炭化水素基としては、テトラカルボン酸二無水物ａ１について上述したものが挙げられる。 In formula (B3), R 9b to R 16b are each independently a hydrogen atom or an arbitrary substituent, and X 1 is a single bond or an arbitrary linking group. In formula (B3), arbitrary substituents include, for example, a group containing a functional group F, a halogen group, a hydrocarbon group, and the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
　式（Ｂ３）のＸ1において、任意の連結基は、例えば、２価の炭化水素基である。２価の炭化水素基としては、上述したものが挙げられる。Ｘ1は、２価の炭化水素基とともに、又は２価の炭化水素基に代えて、エーテル基やエステル基などの官能基を含んでいてもよい。 In X 1 of formula (B3), the arbitrary linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include those mentioned above. X 1 may contain a functional group such as an ether group or an ester group together with or in place of the divalent hydrocarbon group.
　式（Ｂ３）で表される構成単位Ｂの具体例としては、下記式（Ｂ３－１）～（Ｂ３－１５）が挙げられる。なお、これらの式において、Ｍは、任意の金属カチオンである。
Figure JPOXMLDOC01-appb-C000011
 Specific examples of the structural unit B represented by the formula (B3) include the following formulas (B3-1) to (B3-15). Note that in these formulas, M is any metal cation.
Figure JPOXMLDOC01-appb-C000011
　式（Ｂ４）において、Ｒ17b～Ｒ24bは、互いに独立して、水素原子又は任意の置換基であり、Ｘ2は、単結合又は任意の連結基である。式（Ｂ４）において、任意の置換基は、例えば、官能基Ｆを含む基、ハロゲン基、炭化水素基などである。ハロゲン基及び炭化水素基としては、テトラカルボン酸二無水物ａ１について上述したものが挙げられる。 In formula (B4), R 17b to R 24b are each independently a hydrogen atom or an arbitrary substituent, and X 2 is a single bond or an arbitrary linking group. In formula (B4), arbitrary substituents include, for example, a group containing a functional group F, a halogen group, a hydrocarbon group, and the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1.
　式（Ｂ４）のＸ2において、任意の連結基は、例えば、２価の炭化水素基である。２価の炭化水素基としては、上述したものが挙げられる。Ｘ2は、２価の炭化水素基とともに、又は２価の炭化水素基に代えて、エーテル基やエステル基などの官能基を含んでいてもよい。 In X 2 of formula (B4), the arbitrary linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include those mentioned above. X 2 may contain a functional group such as an ether group or an ester group together with or in place of the divalent hydrocarbon group.
　式（Ｂ４）で表される構成単位Ｂの具体例としては、下記式（Ｂ４－１）～（Ｂ４－６）が挙げられる。なお、これらの式において、Ｍは、任意の金属カチオンである。
Figure JPOXMLDOC01-appb-C000012
 Specific examples of the structural unit B represented by formula (B4) include the following formulas (B4-1) to (B4-6). Note that in these formulas, M is any metal cation.
Figure JPOXMLDOC01-appb-C000012
　式（Ｂ５）において、Ｒ25b～Ｒ30bは、互いに独立して、水素原子又は任意の置換基である。式（Ｂ５）において、任意の置換基は、例えば、官能基Ｆを含む基、ハロゲン基、炭化水素基などである。ハロゲン基及び炭化水素基としては、テトラカルボン酸二無水物ａ１について上述したものが挙げられる。式（Ｂ５）で表される構成単位Ｂは、ポリイミドＰの剛直性を向上させることに適している。剛直性に優れたポリイミドＰによれば、分離対象の混合気体の圧力が高い場合であっても、分離膜１０が可塑化することを抑制できる傾向がある。 In formula (B5), R 25b to R 30b are each independently a hydrogen atom or an arbitrary substituent. In formula (B5), the arbitrary substituent is, for example, a group containing a functional group F, a halogen group, a hydrocarbon group, or the like. Examples of the halogen group and hydrocarbon group include those mentioned above for the tetracarboxylic dianhydride a1. The structural unit B represented by formula (B5) is suitable for improving the rigidity of the polyimide P. Polyimide P, which has excellent rigidity, tends to suppress plasticization of the separation membrane 10 even when the pressure of the gas mixture to be separated is high.
　式（Ｂ５）で表される構成単位Ｂの具体例としては、下記式（Ｂ５－１）～（Ｂ５－２）が挙げられる。
Figure JPOXMLDOC01-appb-C000013
 Specific examples of the structural unit B represented by the formula (B5) include the following formulas (B5-1) to (B5-2).
Figure JPOXMLDOC01-appb-C000013
　ポリイミドＰでは、テトラカルボン酸二無水物に由来する構成単位Ａと、ジアミンに由来する構成単位Ｂとが交互に並んでいる。ポリイミドＰにおいて、隣接する構成単位Ａ及びＢの組み合わせとしては、例えば、下記式（Ａ１－Ｂ１）、式（Ａ１－Ｂ５）などが挙げられる。なお、これらの式において、Ｒ1a～Ｒ4a、Ｒ1b～Ｒ4b、及びＲ25b～Ｒ30bは、式（Ａ１）、式（Ｂ１）及び式（Ｂ５）について、上述したものと同じである。
Figure JPOXMLDOC01-appb-C000014
 In polyimide P, structural units A derived from tetracarboxylic dianhydride and structural units B derived from diamine are arranged alternately. In polyimide P, examples of combinations of adjacent structural units A and B include the following formulas (A1-B1) and (A1-B5). In addition, in these formulas, R 1a to R 4a , R 1b to R 4b , and R 25b to R 30b are the same as those described above for formula (A1), formula (B1), and formula (B5). .
Figure JPOXMLDOC01-appb-C000014
　ポリイミドＰの重量平均分子量（Ｍｗ）は、分離膜１０の機械的強度の観点から、例えば３００００以上であり、好ましくは５００００以上であり、より好ましくは７５０００以上である。ポリイミドＰの重量平均分子量の上限値は、特に限定されず、例えば１００万である。ポリイミドＰの重量平均分子量は、例えば、示差屈折率検出器（ＲＩＤ）を備えたゲルパーミエーションクロマトグラフ（ＧＰＣ）によって、ポリイミドＰの分子量分布を測定し、得られたクロマトグラム（チャート）から、標準ポリスチレンによる検量線を用いて算出することができる。 The weight average molecular weight (Mw) of the polyimide P is, for example, 30,000 or more, preferably 50,000 or more, and more preferably 75,000 or more, from the viewpoint of the mechanical strength of the separation membrane 10. The upper limit of the weight average molecular weight of polyimide P is not particularly limited, and is, for example, 1 million. The weight average molecular weight of polyimide P can be determined by measuring the molecular weight distribution of polyimide P using, for example, a gel permeation chromatograph (GPC) equipped with a differential refractive index detector (RID), and from the obtained chromatogram (chart). It can be calculated using a standard polystyrene calibration curve.
　ポリイミドＰは、例えば、次の方法によって作製できる。まず、ジアミンを溶媒に溶解させ、溶液を得る。溶媒としては、例えば、Ｎ－メチル－２－ピロリドン、１，３－ジオキソランなどの極性有機溶媒が挙げられる。 Polyimide P can be produced, for example, by the following method. First, diamine is dissolved in a solvent to obtain a solution. Examples of the solvent include polar organic solvents such as N-methyl-2-pyrrolidone and 1,3-dioxolane.
　次に、得られた溶液に、上記のテトラカルボン酸二無水物ａ１を含むテトラカルボン酸二無水物群を徐々に添加する。これにより、テトラカルボン酸二無水物ａ１とジアミンを含むモノマー群が反応し、ポリアミド酸が形成される。テトラカルボン酸二無水物群の添加は、例えば、１４０℃以上の加熱環境下で３～２０時間、撹拌条件下で行われる。 Next, the tetracarboxylic dianhydride group containing the above-mentioned tetracarboxylic dianhydride a1 is gradually added to the obtained solution. As a result, the monomer group containing the tetracarboxylic dianhydride a1 and the diamine react to form a polyamic acid. The addition of the tetracarboxylic dianhydride group is carried out, for example, under stirring conditions in a heating environment of 140° C. or higher for 3 to 20 hours.
　次に、ポリアミド酸をイミド化することによって、ポリイミドＰを得ることができる。イミド化の方法としては、例えば、化学イミド化法及び熱イミド化法が挙げられる。化学イミド化法は、脱水縮合剤を用いて、例えば室温条件下でポリアミド酸をイミド化する方法である。脱水縮合剤としては、例えば、無水酢酸、ピリジン及びトリエチルアミンが挙げられる。熱イミド化法は、加熱処理によって、ポリアミド酸をイミド化する方法である。加熱処理の温度は、例えば、１８０℃以上である。 Next, polyimide P can be obtained by imidizing the polyamic acid. Examples of the imidization method include a chemical imidization method and a thermal imidization method. The chemical imidization method is a method of imidizing polyamic acid using a dehydration condensation agent, for example, under room temperature conditions. Examples of the dehydration condensation agent include acetic anhydride, pyridine, and triethylamine. The thermal imidization method is a method of imidizing polyamic acid by heat treatment. The temperature of the heat treatment is, for example, 180° C. or higher.
（分離機能層）
　分離機能層１は、例えば、混合気体に含まれる酸性ガスを優先的に透過させることができる層であり、典型的には、走査型電子顕微鏡（ＳＥＭ）を用いて、拡大倍率５０００倍で観察したときに、孔が確認できない緻密層（無孔層）である。 (separation functional layer)
The separation functional layer 1 is, for example, a layer that can preferentially transmit acidic gas contained in a mixed gas, and is typically observed at a magnification of 5000 times using a scanning electron microscope (SEM). It is a dense layer (non-porous layer) in which no pores can be seen.
　分離機能層１におけるポリイミドの含有率は、例えば５０ｗｔ％以上であり、６０ｗｔ％以上、７０ｗｔ％以上、８０ｗｔ％以上、９０ｗｔ％以上、さらには９５ｗｔ％以上であってもよい。分離機能層１は、実質的にポリイミドのみから構成されていてもよい。 The content of polyimide in the separation functional layer 1 is, for example, 50 wt% or more, and may be 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or even 95 wt% or more. The separation functional layer 1 may be substantially composed only of polyimide.
　分離機能層１の厚さは、例えば５０μｍ以下であり、２５μｍ以下、１５μｍ以下、１０μｍ以下、８μｍ以下、５μｍ以下、３μｍ以下、さらには１μｍ以下であってもよい。分離機能層１の厚さの下限値は、０．０５μｍであってもよく、０．１μｍであってもよい。分離機能層１の厚さは、次の方法によって特定できる。まず、分離膜１０の断面を走査型電子顕微鏡で観察する。得られた電子顕微鏡像を用いて、分離機能層１の互いに向かい合う１対の主面の間の距離を任意の複数の点（少なくとも４点）において測定する。得られた値の平均値を分離機能層１の厚さとみなすことができる。 The thickness of the separation functional layer 1 is, for example, 50 μm or less, and may be 25 μm or less, 15 μm or less, 10 μm or less, 8 μm or less, 5 μm or less, 3 μm or less, or even 1 μm or less. The lower limit of the thickness of the separation functional layer 1 may be 0.05 μm or 0.1 μm. The thickness of the separation functional layer 1 can be determined by the following method. First, a cross section of the separation membrane 10 is observed using a scanning electron microscope. Using the obtained electron microscope image, the distance between a pair of mutually opposing principal surfaces of the separation functional layer 1 is measured at a plurality of arbitrary points (at least four points). The average value of the obtained values can be regarded as the thickness of the separation functional layer 1.
（多孔性支持体）
　上述のとおり、多孔性支持体２は、分離機能層１に直接接しており、分離機能層１を支持している。多孔性支持体２は、多孔質構造を有する。分離膜１０を透過する酸性ガスの透過係数や透過速度を向上させる観点から、多孔性支持体２は、三次元状に連続して形成されている連続孔を有することが好ましい。ただし、多孔性支持体２は、独立孔を有していてもよく、連続孔及び独立孔の両方を有していてもよい。多孔性支持体２は、多孔性支持体２を貫通する貫通孔を有していてもよい。 (Porous support)
As described above, the porous support 2 is in direct contact with the separation functional layer 1 and supports the separation functional layer 1. The porous support 2 has a porous structure. From the viewpoint of improving the permeability coefficient and permeation rate of acidic gases passing through the separation membrane 10, it is preferable that the porous support 2 has continuous pores that are continuously formed in a three-dimensional shape. However, the porous support 2 may have independent pores, or may have both continuous pores and independent pores. The porous support 2 may have through holes passing through the porous support 2.
　多孔性支持体２におけるポリイミドの含有率は、例えば５０ｗｔ％以上であり、６０ｗｔ％以上、７０ｗｔ％以上、８０ｗｔ％以上、９０ｗｔ％以上、さらには９５ｗｔ％以上であってもよい。多孔性支持体２は、実質的にポリイミドのみから構成されていてもよい。多孔性支持体２におけるポリイミドの含有率は、分離機能層１におけるポリイミドの含有率と同じであってもよい。 The content of polyimide in the porous support 2 is, for example, 50 wt% or more, and may be 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or even 95 wt% or more. The porous support 2 may be substantially composed only of polyimide. The polyimide content in the porous support 2 may be the same as the polyimide content in the separation functional layer 1.
　多孔性支持体２の厚さは、例えば１０μｍ以上であり、２０μｍ以上、３０μｍ以上、４０μｍ以上、さらには５０μｍ以上であってもよい。多孔性支持体２の厚さの上限値は、３００μｍであってもよく、１００μｍであってもよい。多孔性支持体２の厚さは、分離機能層１について上述した方法によって特定することができる。 The thickness of the porous support 2 is, for example, 10 μm or more, and may be 20 μm or more, 30 μm or more, 40 μm or more, or even 50 μm or more. The upper limit of the thickness of the porous support 2 may be 300 μm or 100 μm. The thickness of the porous support 2 can be determined by the method described above for the separation functional layer 1.
　なお、分離機能層１の厚さ、及び多孔性支持体２の厚さの合計値Ｖ（典型的には、分離膜１０の厚さ）は、例えば１０μｍ以上であり、２０μｍ以上、３０μｍ以上、４０μｍ以上、５０μｍ以上、さらには６０μｍ以上であってもよい。合計値Ｖの上限値は、３００μｍであってもよく、１００μｍであってもよい。 The total value V of the thickness of the separation functional layer 1 and the thickness of the porous support 2 (typically, the thickness of the separation membrane 10) is, for example, 10 μm or more, 20 μm or more, 30 μm or more, It may be 40 μm or more, 50 μm or more, or even 60 μm or more. The upper limit of the total value V may be 300 μm or 100 μm.
（分離膜の製造方法）
　図２Ａ及び２Ｂに示すように、分離膜１０の製造方法は、例えば、ポリイミド、溶剤、及び多孔化剤を含む塗布液Ｌを用いて塗布膜６を形成することと、塗布膜６から多孔化剤を除去することと、を含む。 (Separation membrane manufacturing method)
As shown in FIGS. 2A and 2B, the method for manufacturing the separation membrane 10 includes, for example, forming a coating film 6 using a coating liquid L containing polyimide, a solvent, and a porosity-forming agent, and forming a porous film from the coating film 6. and removing the agent.
　塗布液Ｌは、例えば、ポリイミド、溶剤、及び多孔化剤を混合することによって作製できる。ポリイミドは、典型的には、６員環の酸無水物構造Ｓを有するテトラカルボン酸二無水物ａ１に由来する構成単位Ａ１を含む上述のポリイミドＰである。特に、ポリイミドＰは、他のポリイミドと比べて溶剤に溶解しやすく、本実施形態の製造方法に適している。ただし、本実施形態の製造方法では、ポリイミドＰ以外の他のポリイミドを用いることも可能である。塗布液Ｌにおけるポリイミドの含有率は、ポリイミドの溶解性に応じて適宜調整でき、例えば１ｗｔ％～３０ｗｔ％である。 The coating liquid L can be prepared, for example, by mixing polyimide, a solvent, and a porosity-forming agent. The polyimide is typically the above-mentioned polyimide P containing a structural unit A1 derived from a tetracarboxylic dianhydride a1 having a six-membered acid anhydride structure S. In particular, polyimide P is more easily dissolved in a solvent than other polyimides, and is therefore suitable for the manufacturing method of this embodiment. However, in the manufacturing method of this embodiment, it is also possible to use polyimides other than polyimide P. The content of polyimide in the coating liquid L can be adjusted as appropriate depending on the solubility of the polyimide, and is, for example, 1 wt% to 30 wt%.
　溶剤は、典型的には、ポリイミドを溶解させることができる良溶媒である。溶剤は、アミド化合物及びラクトン化合物からなる群より選ばれる少なくとも１つを含むことが好ましく、アミド化合物を含むことがより好ましい。アミド化合物としては、例えば、Ｎ，Ｎ－ジメチルホルムアミド（ＤＭＦ）、Ｎ－メチル－２－ピロリドン（ＮＭＰ）、Ｎ，Ｎ－ジメチルアセトアミド（ＤＭＡｃ）などが挙げられる。ラクトン化合物としては、例えば、γ-ブチロラクトンなどが挙げられる。 The solvent is typically a good solvent that can dissolve the polyimide. The solvent preferably contains at least one selected from the group consisting of an amide compound and a lactone compound, and more preferably an amide compound. Examples of the amide compound include N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and N,N-dimethylacetamide (DMAc). Examples of the lactone compound include γ-butyrolactone.
　溶剤の沸点は、特に限定されず、例えば１００℃～２５０℃である。塗布液Ｌにおける溶剤の含有率は、例えば３０ｗｔ％～９５ｗｔ％である。 The boiling point of the solvent is not particularly limited, and is, for example, 100°C to 250°C. The content of the solvent in the coating liquid L is, for example, 30 wt% to 95 wt%.
　多孔化剤は、典型的には、ポリイミドＰをほとんど溶解させない貧溶媒である。多孔化剤は、エーテル化合物及びリン酸化合物からなる群より選ばれる少なくとも１つを含むことが好ましく、エーテル化合物を含むことがより好ましい。エーテル化合物としては、例えば、ジエチレングリコール、ジエチレングリコールモノメチルエーテル、トリエチレングリコール、トリエチレングリコールモノメチルエーテル、トリエチレングリコールジメチルエーテル、テトラエチレングリコール、テトラエチレングリコールモノメチルエーテル、テトラエチレングリコールジメチルエーテル、ジエチレングリコールブチルメチルエーテル、トリプロピレングリコールジメチルエーテル、ジエチレングリコールモノブチルエーテル、エチレングリコールモノフェニルエーテル、ジエチレングリコールジブチルエーテル、トリエチレングリコールブチルメチルエーテル、ポリエチレングリコールジメチルエーテル、ポリエチレングリコールモノメチルエーテル、ポリエチレングリコールなどのグリコール化合物が挙げられる。 The porosity agent is typically a poor solvent that hardly dissolves polyimide P. The pore forming agent preferably contains at least one selected from the group consisting of an ether compound and a phosphoric acid compound, and more preferably contains an ether compound. Examples of ether compounds include diethylene glycol, diethylene glycol monomethyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol, tetraethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol butyl methyl ether, and tripropylene. Examples include glycol compounds such as glycol dimethyl ether, diethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol dibutyl ether, triethylene glycol butyl methyl ether, polyethylene glycol dimethyl ether, polyethylene glycol monomethyl ether, and polyethylene glycol.
　リン酸化合物としては、例えば、リン酸トリメチル、リン酸エチルジメチル、リン酸ジエチルメチル、リン酸トリエチルなどのリン酸エステル化合物が挙げられる。 Examples of the phosphoric acid compound include phosphoric ester compounds such as trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, and triethyl phosphate.
　多孔性支持体２を容易に作製する観点から、多孔化剤の沸点は、溶剤の沸点よりも高いことが好ましい。多孔化剤の沸点は、例えば、溶剤の沸点よりも５０℃以上高くてもよく、８０℃以上、さらには１００℃以上高くてもよい。多孔化剤の沸点は、例えば、２００℃～３５０℃である。塗布液Ｌにおける多孔化剤の含有率は、例えば１０ｗｔ％～５０ｗｔ％である。多孔化剤の含有率は、ポリイミドの含有率よりも高いことが好ましい。 From the viewpoint of easily producing the porous support 2, the boiling point of the porosity-forming agent is preferably higher than the boiling point of the solvent. The boiling point of the pore-forming agent may be, for example, 50°C or more higher than the boiling point of the solvent, 80°C or more, or even 100°C or more higher. The boiling point of the pore-forming agent is, for example, 200°C to 350°C. The content of the porosity agent in the coating liquid L is, for example, 10 wt% to 50 wt%. The content of the porosity-forming agent is preferably higher than the content of polyimide.
　塗布膜６は、例えば、塗布液Ｌを基材５の上に塗布することによって形成することができる（図２Ａ）。基材５は、典型的には、はく離ライナーである。はく離ライナーとしては、例えば、樹脂を含むフィルム；紙；アルミニウムやステンレス鋼などの金属材料を含むシートなどが挙げられる。金属材料を含むシートは、耐熱性が高い傾向がある。はく離ライナーは、表面平滑性に優れる点から、樹脂を含むフィルムであることが好ましい。はく離ライナーにおいて、樹脂に含まれるポリマーとしては、ポリエチレン、ポリプロピレン、ポリブテン、ポリブタジエン、ポリメチルペンテンなどのポリオレフィン；ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレートなどのポリエステル；ポリ塩化ビニル、塩化ビニル共重合体；ポリウレタン；エチレン－酢酸ビニル共重合体などが挙げられ、ポリエステル、特にポリエチレンテレフタレート、が好ましい。 The coating film 6 can be formed, for example, by applying the coating liquid L onto the base material 5 (FIG. 2A). Substrate 5 is typically a release liner. Examples of the release liner include a film containing resin; paper; and a sheet containing a metal material such as aluminum or stainless steel. Sheets containing metallic materials tend to have high heat resistance. The release liner is preferably a film containing resin from the viewpoint of excellent surface smoothness. In release liners, the polymers contained in the resin include polyolefins such as polyethylene, polypropylene, polybutene, polybutadiene, and polymethylpentene; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyvinyl chloride, vinyl chloride copolymers ; polyurethane; ethylene-vinyl acetate copolymer, etc., and polyester, particularly polyethylene terephthalate, is preferred.
　はく離ライナーの表面には、剥離処理が施されていてもよい。剥離処理は、例えば、はく離ライナーの表面に剥離処理剤を付与することによって行うことができる。剥離処理剤としては、シリコーン系剥離処理剤、長鎖アルキル系剥離処理剤、フッ素剥離処理剤、硫化モリブデン系剥離処理剤などが挙げられる。剥離処理剤は、単独又は２種以上組み合わせて用いられてもよい。はく離ライナーは、好ましくは、剥離処理が施されたポリエチレンテレフタレート（ＰＥＴ）製のフィルムである。 The surface of the release liner may be subjected to release treatment. The release treatment can be performed, for example, by applying a release treatment agent to the surface of the release liner. Examples of the release agent include a silicone release agent, a long-chain alkyl release agent, a fluorine release agent, and a molybdenum sulfide release agent. The release agent may be used alone or in combination of two or more. The release liner is preferably a release-treated polyethylene terephthalate (PET) film.
　基材５の厚さは、特に限定されず、例えば５～１００μｍであり、好ましくは１０～５０μｍである。 The thickness of the base material 5 is not particularly limited, and is, for example, 5 to 100 μm, preferably 10 to 50 μm.
　塗布液Ｌを基材５に塗布する方法は、特に限定されず、例えば、スピンコート法、ディップコート法などを利用できる。アプリケータやワイヤーバーなどを利用して塗布液Ｌを基材５に塗布してもよい。 The method of applying the coating liquid L to the substrate 5 is not particularly limited, and for example, a spin coating method, a dip coating method, etc. can be used. The coating liquid L may be applied to the base material 5 using an applicator, a wire bar, or the like.
　塗布膜６から多孔化剤を除去すると、多孔化剤に起因して孔が形成されるとともに、外部に露出している塗布膜６の表面付近では緻密な層（スキン層）が形成される。これにより、多孔化剤に起因する孔を有する多孔性支持体２と、スキン層に相当する分離機能層１とが形成される（図２Ｂ）。言い換えると、本実施形態の製造方法では、塗布膜６から分離機能層１及び多孔性支持体２が形成されるように、塗布膜６から多孔化剤が除去される。 When the pore-forming agent is removed from the coating film 6, pores are formed due to the porosity-forming agent, and a dense layer (skin layer) is formed near the surface of the coating film 6 that is exposed to the outside. As a result, a porous support 2 having pores caused by the porosity-forming agent and a separation functional layer 1 corresponding to a skin layer are formed (FIG. 2B). In other words, in the manufacturing method of this embodiment, the porosity agent is removed from the coating film 6 so that the separation functional layer 1 and the porous support 2 are formed from the coating film 6.
　本実施形態の製造方法では、例えば、塗布膜６を乾燥させる、及び／又は、塗布膜６を洗浄液で洗浄することによって、塗布膜６から多孔化剤を除去することができる。塗布膜６を乾燥させる場合、乾燥温度は、例えば５０℃～３００℃であり、乾燥時間は、例えば１～２０時間である。塗布膜６の乾燥は、減圧雰囲気又は真空雰囲気で行ってもよい。 In the manufacturing method of this embodiment, the porosity agent can be removed from the coating film 6 by, for example, drying the coating film 6 and/or washing the coating film 6 with a cleaning liquid. When drying the coating film 6, the drying temperature is, for example, 50° C. to 300° C., and the drying time is, for example, 1 to 20 hours. The coating film 6 may be dried in a reduced pressure atmosphere or a vacuum atmosphere.
　塗布膜６を洗浄液で洗浄する場合、洗浄液としては、多孔化剤との相溶性が高いものを用いることが好ましい。洗浄液としては、例えば、水や、メタノールなどのアルコールを用いることができる。一例として、塗布膜６を洗浄液に浸漬させることによって、塗布膜６を洗浄してもよい。 When cleaning the coating film 6 with a cleaning liquid, it is preferable to use a cleaning liquid that has high compatibility with the porosity-forming agent. As the cleaning liquid, for example, water or alcohol such as methanol can be used. As an example, the coating film 6 may be cleaned by immersing the coating film 6 in a cleaning liquid.
　なお、塗布膜６から多孔化剤を除去するときには、溶剤も塗布膜６から除去される。ただし、塗布膜６から多孔化剤を除去する前に、塗布膜６から溶剤を予め除去してもよい。一例として、溶剤の沸点が多孔化剤の沸点よりも低い場合には、塗布膜６を予備乾燥することによって、塗布膜６から溶剤を予め除去することができる。予備乾燥の条件は、例えば、温度が５０℃～１５０℃であり、時間が１０分間～５時間である。 Note that when removing the porosity agent from the coating film 6, the solvent is also removed from the coating film 6. However, before removing the porosity agent from the coating film 6, the solvent may be removed from the coating film 6 in advance. For example, if the boiling point of the solvent is lower than the boiling point of the porosity-forming agent, the solvent can be removed from the coating film 6 in advance by pre-drying the coating film 6. The pre-drying conditions are, for example, a temperature of 50° C. to 150° C. and a time of 10 minutes to 5 hours.
　次に、分離機能層１及び多孔性支持体２の積層体から基材５を取り除く。これにより、分離膜１０を得ることができる。 Next, the base material 5 is removed from the laminate of the separation functional layer 1 and the porous support 2. Thereby, the separation membrane 10 can be obtained.
　分離膜の従来の製造方法としては、多孔性支持体の上に、分離機能層の材料を含む塗布液を塗布し、得られた塗布膜を乾燥させて分離機能層を形成する直接法や、基材上に形成した分離機能層を多孔性支持体に転写する転写法などが挙げられる。 Conventional methods for producing separation membranes include a direct method in which a coating solution containing a material for the separation functional layer is applied onto a porous support and the resulting coating film is dried to form a separation functional layer; Examples include a transfer method in which a separation functional layer formed on a base material is transferred to a porous support.
　直接法では、塗布液の溶剤によっては、塗布液の塗布時に多孔性支持体の一部が溶剤に溶解することがある。このとき、多孔性支持体に含まれる孔の一部が消失し、作製した分離膜の分離性能が低下することがある。これに対して、本実施形態の製造方法では、塗布膜６から多孔化剤や溶剤を除去することによって、分離機能層１及び多孔性支持体２を作製する。すなわち、本実施形態の製造方法では、多孔性支持体２の形成後に、多孔性支持体２が塗布膜６に由来する溶剤と接触しない。そのため、本実施形態の製造方法で作製された分離膜１０は、直接法で作製された分離膜と比べて、分離性能が高い傾向がある。 In the direct method, depending on the solvent of the coating solution, a part of the porous support may be dissolved in the solvent during application of the coating solution. At this time, some of the pores contained in the porous support may disappear, and the separation performance of the prepared separation membrane may deteriorate. On the other hand, in the manufacturing method of this embodiment, the separation functional layer 1 and the porous support 2 are manufactured by removing the porosity agent and the solvent from the coating film 6. That is, in the manufacturing method of this embodiment, the porous support 2 does not come into contact with the solvent originating from the coating film 6 after the porous support 2 is formed. Therefore, the separation membrane 10 produced by the production method of this embodiment tends to have higher separation performance than a separation membrane produced by a direct method.
　転写法では、例えば、厚さが１μｍ程度以下の薄い分離機能層を多孔性支持体に転写するときに、分離機能層に欠陥が生じやすい。また、転写前には、分離機能層の表面が基材に接しているため、分離機能層の表面に基材由来の不純物が付着し、これにより、分離性能が低下することもある。これに対して、本実施形態の製造方法では、転写操作がないため、分離機能層１に欠陥が生じにくい。また、本実施形態の製造方法において、分離機能層１は、通常、基材５に接触している塗布膜６の表面とは反対側の表面付近に形成されるため、分離機能層の表面には、基材５由来の不純物が付着しにくい傾向もある。 In the transfer method, for example, when a thin separation functional layer with a thickness of about 1 μm or less is transferred to a porous support, defects are likely to occur in the separation functional layer. Furthermore, since the surface of the separation functional layer is in contact with the base material before transfer, impurities derived from the base material may adhere to the surface of the separation functional layer, which may reduce the separation performance. In contrast, in the manufacturing method of this embodiment, since there is no transfer operation, defects are less likely to occur in the separation functional layer 1. In addition, in the manufacturing method of the present embodiment, the separation functional layer 1 is usually formed near the surface of the coating film 6 on the opposite side to the surface of the coating film 6 that is in contact with the base material 5. Also, impurities derived from the base material 5 tend to be less likely to adhere.
　なお、特許第４９４７９８９号には、ポリイミドの前駆体（ポリアミド酸）を含む多孔質フィルムを作製してから、熱イミド化法によって前駆体からポリイミドを形成する方法が開示されている。しかし、この方法では、熱イミド化法の加熱処理によって、多孔質フィルムが収縮及び変形する傾向がある。これに対して、本実施形態の製造方法では、ポリイミドを含む塗布液Ｌを用いるため、塗布膜６などに対して熱イミド化法を行う必要がなく、目的とした形状及び厚さの分離膜１０を容易に作製できる。 Note that Japanese Patent No. 4947989 discloses a method in which a porous film containing a polyimide precursor (polyamic acid) is produced and then polyimide is formed from the precursor by a thermal imidization method. However, in this method, the porous film tends to shrink and deform due to the heat treatment of the thermal imidization method. On the other hand, in the manufacturing method of the present embodiment, since the coating liquid L containing polyimide is used, there is no need to perform thermal imidization on the coating film 6, etc., and the separation film of the desired shape and thickness is formed. 10 can be easily produced.
（分離膜の形状）
　本実施形態において、分離膜１０は、典型的には平膜である。ただし、分離膜１０は、平膜以外の形状であってもよく、例えば、中空糸膜であってもよい。 (Shape of separation membrane)
In this embodiment, the separation membrane 10 is typically a flat membrane. However, the separation membrane 10 may have a shape other than a flat membrane, for example, may be a hollow fiber membrane.
（分離膜の特性）
　本実施形態の分離膜１０は、分離機能層１及び多孔性支持体２に起因して、酸性ガスに対する分離性能が高い傾向がある。特に、分離機能層１及び多孔性支持体２のそれぞれが上述のポリイミドＰを含む場合、分離膜１０の酸性ガスに対する分離性能が向上する傾向がある。一例として、分離膜１０を透過する二酸化炭素の透過速度Ｔは、例えば１００ＧＰＵ以上であり、２００ＧＰＵ以上、３００ＧＰＵ以上、４００ＧＰＵ以上、５００ＧＰＵ以上、さらには１０００ＧＰＵ以上であってもよい。透過速度Ｔの上限値は、特に限定されず、例えば５０００ＧＰＵである。なお、ＧＰＵは、１０-6・cm3(STP)/(sec・cm2・cmHg)を意味する。cm3(STP)は、１気圧、０℃での二酸化炭素の体積を意味する。 (Characteristics of separation membrane)
The separation membrane 10 of this embodiment tends to have high separation performance against acidic gases due to the separation functional layer 1 and the porous support 2. In particular, when each of the separation functional layer 1 and the porous support 2 contains the above-mentioned polyimide P, the separation performance of the separation membrane 10 against acidic gas tends to improve. As an example, the permeation rate T of carbon dioxide passing through the separation membrane 10 is, for example, 100 GPU or more, and may be 200 GPU or more, 300 GPU or more, 400 GPU or more, 500 GPU or more, or even 1000 GPU or more. The upper limit of the transmission rate T is not particularly limited, and is, for example, 5000 GPU. Note that GPU means 10 −6 ·cm 3 (STP)/(sec·cm 2 ·cmHg). cm 3 (STP) means the volume of carbon dioxide at 1 atmosphere and 0°C.
　透過速度Ｔは、次の方法によって算出できる。まず、分離膜１０の一方の面（例えば分離膜１０の分離機能層側の主面１１）に隣接する空間に、二酸化炭素及び窒素からなる混合気体を供給するとともに、分離膜１０の他方の面（例えば分離膜１０の多孔性支持体側の主面１２）に隣接する空間を減圧する。これにより、分離膜１０を透過した透過流体が得られる。透過流体の重量、並びに、透過流体における二酸化炭素の体積比率及び窒素の体積比率を測定する。測定結果から透過速度Ｔを算出できる。上記の操作において、混合気体における二酸化炭素の濃度は、標準状態（０℃、１０１ｋＰａ）で５０ｖｏｌ％である。分離膜１０の一方の面に隣接する空間に供給される混合気体は、温度が３０℃であり、圧力が０．１ＭＰａである。分離膜１０の他方の面に隣接する空間は、空間内の圧力が測定環境における大気圧に対して０．１ＭＰａ小さくなるように減圧されている。 The permeation rate T can be calculated by the following method. First, a mixed gas consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane 10 (for example, the main surface 11 on the separation functional layer side of the separation membrane 10), and the other surface of the separation membrane 10 is supplied with a gas mixture consisting of carbon dioxide and nitrogen. (For example, the space adjacent to the main surface 12 of the separation membrane 10 on the porous support side) is depressurized. Thereby, a permeated fluid that has passed through the separation membrane 10 is obtained. The weight of the permeate fluid and the volume proportions of carbon dioxide and nitrogen in the permeate fluid are determined. The transmission rate T can be calculated from the measurement results. In the above operation, the concentration of carbon dioxide in the mixed gas is 50 vol% under standard conditions (0° C., 101 kPa). The mixed gas supplied to the space adjacent to one surface of the separation membrane 10 has a temperature of 30° C. and a pressure of 0.1 MPa. The space adjacent to the other surface of the separation membrane 10 is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
　上記の透過速度Ｔの測定条件において、分離膜１０の窒素に対する二酸化炭素の分離係数αは、特に限定されず、例えば２０以上であり、２５以上、３０以上、さらには３５以上であってもよい。分離係数αの上限値は、特に限定されず、例えば５０である。分離係数αは、以下の式から算出することができる。ただし、下記式において、ＸA及びＸBは、それぞれ、混合気体における二酸化炭素の体積比率及び窒素の体積比率である。ＹA及びＹBは、それぞれ、分離膜１０を透過した透過流体における二酸化炭素の体積比率及び窒素の体積比率である。
分離係数α＝（ＹA／ＹB）／（ＸA／ＸB） Under the above measurement conditions for the permeation rate T, the separation coefficient α of carbon dioxide to nitrogen of the separation membrane 10 is not particularly limited, and may be, for example, 20 or more, 25 or more, 30 or more, or even 35 or more. . The upper limit of the separation coefficient α is not particularly limited, and is, for example, 50. The separation coefficient α can be calculated from the following formula. However, in the following formula, X A and X B are the volume ratio of carbon dioxide and the volume ratio of nitrogen in the mixed gas, respectively. Y A and Y B are the volume ratio of carbon dioxide and the volume ratio of nitrogen in the permeate fluid that has passed through the separation membrane 10, respectively.
Separation coefficient α=(Y A /Y B )/(X A /X B )
　なお、本発明者が知る限り、分離機能層の材料が多孔性支持体の材料と同じであり、分離機能層の厚さ、及び多孔性支持体の厚さの合計値が１０μｍ以上である分離膜であって、透過速度Ｔが１００ＧＰＵ以上であり、かつ分離係数αが２０以上である分離膜は、これまで知られていない。 As far as the present inventor knows, the material of the separation functional layer is the same as the material of the porous support, and the total thickness of the separation functional layer and the porous support is 10 μm or more. A separation membrane having a permeation rate T of 100 GPU or more and a separation coefficient α of 20 or more has not been known so far.
　すなわち、本発明は、その別の側面から、
　分離機能層１と、分離機能層１に直接接する多孔性支持体２とを備えた分離膜１０であって、
　分離機能層１の材料は、多孔性支持体２の材料と同じであり、
　分離機能層１の厚さ、及び多孔性支持体２の厚さの合計値が１０μｍ以上であり、
　分離膜１０の一方の面に隣接する空間に、二酸化炭素及び窒素からなる混合気体を供給するとともに、分離膜１０の他方の面に隣接する空間を減圧した場合に、分離膜１０を透過する二酸化炭素の透過速度Ｔが１００ＧＰＵ以上であり、かつ、窒素に対する二酸化炭素の分離係数αが２０以上である、分離膜１０を提供する。 That is, from another aspect of the present invention,
A separation membrane 10 comprising a separation functional layer 1 and a porous support 2 in direct contact with the separation functional layer 1,
The material of the separation functional layer 1 is the same as the material of the porous support 2,
The total value of the thickness of the separation functional layer 1 and the thickness of the porous support 2 is 10 μm or more,
When a mixed gas of carbon dioxide and nitrogen is supplied to the space adjacent to one surface of the separation membrane 10 and the pressure is reduced in the space adjacent to the other surface of the separation membrane 10, the amount of carbon dioxide that permeates through the separation membrane 10 A separation membrane 10 having a carbon permeation rate T of 100 GPU or more and a separation coefficient α of carbon dioxide relative to nitrogen of 20 or more is provided.
　さらに、上記の透過速度Ｔの測定条件において、分離機能層１の厚さを考慮した二酸化炭素の透過係数Ｃ１は、例えば１００Ｂａｒｒｅｒ以上であり、５００Ｂａｒｒｅｒ以上、１０００Ｂａｒｒｅｒ以上、１５００Ｂａｒｒｅｒ以上、２０００Ｂａｒｒｅｒ以上、さらには２５００Ｂａｒｒｅｒ以上であってもよい。透過係数Ｃ１の上限値は、特に限定されず、例えば５０００Ｂａｒｒｅｒである。ただし、Ｂａｒｒｅｒは、１０-10・cm3(STP)・cm/(sec・cm2・cmHg)を意味する。透過係数Ｃ１（Ｂａｒｒｅｒ）は、透過速度Ｔ（ＧＰＵ）に分離機能層１の厚さ（μｍ）を乗じた値である。 Further, under the above measurement conditions of the permeation rate T, the permeability coefficient C1 of carbon dioxide in consideration of the thickness of the separation functional layer 1 is, for example, 100 Barrer or more, 500 Barrer or more, 1000 Barrer or more, 1500 Barrer or more, 2000 Barrer or more, and even It may be 2500 Barrer or more. The upper limit of the transmission coefficient C1 is not particularly limited, and is, for example, 5000 Barrer. However, Barrer means 10 −10 ·cm 3 (STP)·cm/(sec·cm 2 ·cmHg). The transmission coefficient C1 (Barrer) is a value obtained by multiplying the transmission rate T (GPU) by the thickness (μm) of the separation functional layer 1.
　上記の透過係数Ｃ１は、分離機能層１の自立膜（単層膜）における二酸化炭素の透過係数Ｃ２と同程度であることが好ましい。透過係数Ｃ２は、分離膜１０に代えて、分離機能層１の自立膜を用いることを除き、透過係数Ｃ１と同じ方法によって測定することができる。分離機能層１の自立膜は、例えば、多孔化剤を用いないことを除き、上述の分離膜１０の製造方法と同様の方法によって作製できる。 It is preferable that the above permeability coefficient C1 is approximately the same as the permeability coefficient C2 of carbon dioxide in the self-supporting membrane (single-layer membrane) of the separation functional layer 1. The permeability coefficient C2 can be measured by the same method as the permeability coefficient C1, except that a self-supporting membrane of the separation functional layer 1 is used instead of the separation membrane 10. The self-supporting membrane of the separation functional layer 1 can be produced, for example, by a method similar to the method for producing the separation membrane 10 described above, except that no porosity agent is used.
　一例として、下記式（Ｉ）で算出される透過係数の変化率Ｒは、例えば－９０％～９０％であり、好ましくは－５０％～５０％であり、－３０％～３０％であってもよい。変化率Ｒは、０％以下であってもよい。分離膜１０において、多孔性支持体２が連続孔を有している場合、変化率Ｒは、－５０％以上に調整される傾向がある。一方、多孔性支持体２が連続孔を有しておらず、独立孔を有する場合、変化率Ｒは、－５０％を下回る傾向がある。なお、変化率Ｒが０％を上回り、かつ、上述の分離係数αの値が非常に小さい場合には、分離膜１０に含まれる分離機能層１に欠陥が存在する可能性がある。
変化率Ｒ＝１００×（透過係数Ｃ１－透過係数Ｃ２）／透過係数Ｃ２　　　（Ｉ） As an example, the rate of change R of the transmission coefficient calculated by the following formula (I) is, for example, -90% to 90%, preferably -50% to 50%, and -30% to 30%. Good too. The rate of change R may be 0% or less. In the separation membrane 10, when the porous support 2 has continuous pores, the rate of change R tends to be adjusted to -50% or more. On the other hand, when the porous support 2 does not have continuous pores but has independent pores, the rate of change R tends to be less than -50%. Note that if the rate of change R exceeds 0% and the value of the above-mentioned separation coefficient α is very small, there is a possibility that a defect exists in the separation functional layer 1 included in the separation membrane 10.
Rate of change R = 100 x (transmission coefficient C1 - transmission coefficient C2) / transmission coefficient C2 (I)
（分離膜の用途）
　本実施形態の分離膜１０の用途としては、酸性ガスを含む混合気体から酸性ガスを分離する用途が挙げられる。混合気体の酸性ガスとしては、二酸化炭素、硫化水素、硫化カルボニル、硫黄酸化物（ＳＯｘ）、シアン化水素、窒素酸化物（ＮＯｘ）などが挙げられ、好ましくは二酸化炭素である。混合気体は、酸性ガス以外の他のガスを含んでいる。他のガスとしては、例えば、水素、窒素などの非極性ガス、及び、ヘリウムなどの不活性ガスが挙げられ、好ましくは窒素である。特に、本実施形態の分離膜１０は、二酸化炭素及び窒素を含む混合気体から二酸化炭素を分離する用途に適している。ただし、分離膜１０の用途は、上記の混合気体から酸性ガスを分離する用途に限定されない。 (Applications of separation membrane)
Applications of the separation membrane 10 of this embodiment include applications for separating acidic gas from a mixed gas containing acidic gas. Examples of the mixed acidic gas include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, and nitrogen oxides (NOx), with carbon dioxide being preferred. The mixed gas contains gases other than acidic gas. Other gases include, for example, nonpolar gases such as hydrogen and nitrogen, and inert gases such as helium, with nitrogen being preferred. In particular, the separation membrane 10 of this embodiment is suitable for use in separating carbon dioxide from a mixed gas containing carbon dioxide and nitrogen. However, the use of the separation membrane 10 is not limited to the use of separating acidic gas from the above-mentioned mixed gas.
＜膜分離装置の実施形態＞
　図３に示すとおり、本実施形態の膜分離装置１００は、分離膜１０及びタンク２０を備えている。タンク２０は、第１室２１及び第２室２２を備えている。分離膜１０は、タンク２０の内部に配置されている。タンク２０の内部において、分離膜１０は、第１室２１と第２室２２とを隔てている。分離膜１０は、タンク２０の１対の壁面の一方から他方まで延びている。 <Embodiment of membrane separation device>
As shown in FIG. 3, the membrane separation apparatus 100 of this embodiment includes a separation membrane 10 and a tank 20. The tank 20 includes a first chamber 21 and a second chamber 22. Separation membrane 10 is arranged inside tank 20. Inside the tank 20, the separation membrane 10 separates a first chamber 21 and a second chamber 22. The separation membrane 10 extends from one of the pair of wall surfaces of the tank 20 to the other.
　第１室２１は、入口２１ａ及び出口２１ｂを有する。第２室２２は、出口２２ａを有する。入口２１ａ、出口２１ｂ及び出口２２ａのそれぞれは、例えば、タンク２０の壁面に形成された開口である。 The first chamber 21 has an inlet 21a and an outlet 21b. The second chamber 22 has an outlet 22a. Each of the inlet 21a, the outlet 21b, and the outlet 22a is an opening formed in the wall surface of the tank 20, for example.
　膜分離装置１００を用いた膜分離は、例えば、次の方法によって行われる。まず、入口２１ａを通じて、酸性ガスを含む混合気体３０を第１室２１に供給する。混合気体３０における酸性ガスの濃度は、特に限定されず、標準状態で、例えば０．０１ｖｏｌ％（１００ｐｐｍ）以上であり、好ましくは１ｖｏｌ％以上であり、より好ましくは１０ｖｏｌ％以上であり、さらに好ましくは３０ｖｏｌ％以上であり、特に好ましくは５０ｖｏｌ％以上である。混合気体３０における酸性ガスの濃度の上限値は、特に限定されず、標準状態で、例えば９０ｖｏｌ％である。 Membrane separation using the membrane separation device 100 is performed, for example, by the following method. First, a mixed gas 30 containing an acidic gas is supplied to the first chamber 21 through the inlet 21a. The concentration of acidic gas in the mixed gas 30 is not particularly limited, and in a standard state is, for example, 0.01 vol% (100 ppm) or more, preferably 1 vol% or more, more preferably 10 vol% or more, and even more preferably is 30 vol% or more, particularly preferably 50 vol% or more. The upper limit of the concentration of acidic gas in the mixed gas 30 is not particularly limited, and is, for example, 90 vol% in a standard state.
　混合気体３０の供給によって、第１室２１内が昇圧されてもよい。膜分離装置１００は、混合気体３０を昇圧するためのポンプ（図示せず）をさらに備えていてもよい。第１室２１に供給される混合気体３０の圧力は、例えば０．１ＭＰａ以上、好ましくは０．３ＭＰａ以上である。 The pressure inside the first chamber 21 may be increased by supplying the mixed gas 30. The membrane separator 100 may further include a pump (not shown) for pressurizing the mixed gas 30. The pressure of the mixed gas 30 supplied to the first chamber 21 is, for example, 0.1 MPa or more, preferably 0.3 MPa or more.
　第１室２１に混合気体３０を供給した状態で、第２室２２内を減圧してもよい。膜分離装置１００は、第２室２２内を減圧するためのポンプ（図示せず）をさらに備えていてもよい。第２室２２は、第２室２２内の空間が測定環境における大気圧に対して、例えば１０ｋＰａ以上、好ましくは５０ｋＰａ以上、より好ましくは１００ｋＰａ以上小さくなるように減圧されてもよい。 The pressure inside the second chamber 22 may be reduced while the mixed gas 30 is supplied to the first chamber 21. The membrane separator 100 may further include a pump (not shown) for reducing the pressure inside the second chamber 22. The pressure in the second chamber 22 may be reduced so that the space within the second chamber 22 is, for example, 10 kPa or more, preferably 50 kPa or more, more preferably 100 kPa or more smaller than the atmospheric pressure in the measurement environment.
　第１室２１内に混合気体３０が供給されることによって、分離膜１０の他方の面側において混合気体３０よりも酸性ガスの含有率が高い透過流体３５を得ることができる。すなわち、透過流体３５が第２室２２に供給される。透過流体３５は、例えば、酸性ガスを主成分として含んでいる。ただし、透過流体３５は、酸性ガス以外の他のガスを少量含んでいてもよい。透過流体３５は、出口２２ａを通じて、タンク２０の外部に排出される。 By supplying the mixed gas 30 into the first chamber 21, it is possible to obtain a permeate fluid 35 having a higher content of acidic gas than the mixed gas 30 on the other side of the separation membrane 10. That is, the permeate fluid 35 is supplied to the second chamber 22 . The permeate fluid 35 contains, for example, acidic gas as a main component. However, the permeate fluid 35 may contain a small amount of gas other than acidic gas. Permeate fluid 35 is discharged to the outside of tank 20 through outlet 22a.
　混合気体３０における酸性ガスの濃度は、第１室２１の入口２１ａから出口２１ｂに向かって徐々に低下する。第１室２１で処理された混合気体３０（非透過流体３６）は、出口２１ｂを通じて、タンク２０の外部に排出される。 The concentration of acidic gas in the mixed gas 30 gradually decreases from the inlet 21a of the first chamber 21 toward the outlet 21b. The mixed gas 30 (non-permeable fluid 36) treated in the first chamber 21 is discharged to the outside of the tank 20 through the outlet 21b.
　本実施形態の膜分離装置１００は、流通式（連続式）の膜分離方法に適している。ただし、本実施形態の膜分離装置１００は、バッチ式の膜分離方法に用いられてもよい。 The membrane separation apparatus 100 of this embodiment is suitable for a flow type (continuous type) membrane separation method. However, the membrane separation apparatus 100 of this embodiment may be used in a batch-type membrane separation method.
＜膜分離装置の変形例＞
　膜分離装置１００は、スパイラル型の膜エレメント、中空糸膜エレメントなどであってもよい。図４は、スパイラル型の膜エレメントを示している。図４の膜分離装置１１０は、中心管４１及び積層体４２を備えている。積層体４２が分離膜１０を含んでいる。 <Modified example of membrane separation device>
The membrane separation device 100 may be a spiral membrane element, a hollow fiber membrane element, or the like. Figure 4 shows a spiral-shaped membrane element. The membrane separation device 110 in FIG. 4 includes a central tube 41 and a stacked body 42. The laminate 42 includes the separation membrane 10.
　中心管４１は、円筒形状を有している。中心管４１の表面には、中心管４１の内部に透過流体３５を流入させるための複数の孔が形成されている。中心管４１の材料としては、例えば、アクリロニトリル・ブタジエン・スチレン共重合樹脂（ＡＢＳ樹脂）、ポリフェニレンエーテル樹脂（ＰＰＥ樹脂）、ポリサルフォン樹脂（ＰＳＦ樹脂）などの樹脂；ステンレス鋼、チタンなどの金属が挙げられる。中心管４１の内径は、例えば２０～１００ｍｍの範囲にある。 The central tube 41 has a cylindrical shape. A plurality of holes are formed on the surface of the center tube 41 to allow the permeate fluid 35 to flow into the center tube 41 . Examples of materials for the center tube 41 include resins such as acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polyphenylene ether resin (PPE resin), and polysulfone resin (PSF resin); metals such as stainless steel and titanium. It will be done. The inner diameter of the central tube 41 is, for example, in the range of 20 to 100 mm.
　積層体４２は、分離膜１０の他に、供給側流路材４３及び透過側流路材４４をさらに含む。積層体４２は、中心管４１の周囲に巻回されている。膜分離装置１１０は、外装材（図示せず）をさらに備えていてもよい。 In addition to the separation membrane 10, the laminate 42 further includes a supply side channel material 43 and a permeate side channel material 44. The laminate 42 is wound around the central tube 41. The membrane separation device 110 may further include an exterior material (not shown).
　供給側流路材４３及び透過側流路材４４としては、例えばポリフェニレンサルファイド（ＰＰＳ）又はエチレン－クロロトリフルオロエチレン共重合体（ＥＣＴＦＥ）からなる樹脂製ネットを用いることができる。 As the supply side channel material 43 and the permeate side channel material 44, for example, a resin net made of polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.
　膜分離装置１１０を用いた膜分離は、例えば、次の方法によって行われる。まず、巻回された積層体４２の一端に混合気体３０を供給する。積層体４２の分離膜１０を透過した透過流体３５が中心管４１の内部に移動する。透過流体３５は、中心管４１を通じて外部に排出される。膜分離装置１１０で処理された混合気体３０（非透過流体３６）は、巻回された積層体４２の他端から外部に排出される。これにより、混合気体３０から酸性ガスを分離することができる。 Membrane separation using the membrane separation device 110 is performed, for example, by the following method. First, the mixed gas 30 is supplied to one end of the wound laminate 42 . The permeated fluid 35 that has passed through the separation membrane 10 of the laminate 42 moves into the center tube 41 . The permeate fluid 35 is discharged to the outside through the central pipe 41. The mixed gas 30 (non-permeable fluid 36) processed by the membrane separator 110 is discharged to the outside from the other end of the wound stack 42. Thereby, the acidic gas can be separated from the mixed gas 30.
　以下に、実施例及び比較例により本発明をさらに詳細に説明するが、本発明はこれに限定されるものではない。 The present invention will be explained in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
（実施例１）
　まず、自動重合装置（メトラー・トレド社製、EasyMax402）を用いて、ポリイミドの合成を行った。装置に付属しているセパラブルフラスコ（容量４００ｍＬ）には、ジムロート、撹拌棒、内部温度計、窒素導入管及び平栓を装着した。ジムロートのチラーには、１０℃に設定された冷却液を循環させた。フラスコ内には、１００ｍＬ／ｍｉｎの流量で、Ｎ2ガスを流通させた。撹拌速度は、３００ｒｐｍに設定した。次に、フラスコに、溶媒として１－メチル－２－ピロリドン（超脱水）１０１．５２ｇ、ジアミンとして２，４，６－トリメチル－１，３－フェニレンジアミン（ＴｒＭＰＤ）２．８０ｇ、及び３，７－ジアミノ－２，８－ジメチルジベンゾチオフェンスルホン（ＤＤＢＴ）５．１１４８ｇを加えた。これらを室温下で撹拌させることによってジアミンを溶媒に溶解させた。得られた溶液に、テトラカルボン酸二無水物としてナフタレン－１，４，５，８－テトラカルボン酸二無水物（ＮＴＤＡ）１０．０ｇと、安息香酸９．１１ｇ（７５ｍｍｏｌ）をさらに加えた。装置のジャケット温度を１８０℃に昇温し、８時間撹拌した。このとき、フラスコの内温は、１７２～１７５℃であった。撹拌後、フラスコの内温を２５℃まで冷却し、一晩静置させた。 (Example 1)
First, polyimide was synthesized using an automatic polymerization device (manufactured by METTLER TOLEDO, EasyMax402). A separable flask (volume 400 mL) attached to the apparatus was equipped with a Dimroth, stirring rod, internal thermometer, nitrogen inlet tube, and flat stopper. A coolant set at 10°C was circulated through the Dimroth chiller. N 2 gas was passed through the flask at a flow rate of 100 mL/min. The stirring speed was set at 300 rpm. Next, in a flask, 101.52 g of 1-methyl-2-pyrrolidone (super dehydrated) as a solvent, 2.80 g of 2,4,6-trimethyl-1,3-phenylenediamine (TrMPD) as a diamine, and 3,7 5.1148 g of -diamino-2,8-dimethyldibenzothiophenesulfone (DDBT) was added. The diamine was dissolved in the solvent by stirring these at room temperature. To the obtained solution, 10.0 g of naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTDA) and 9.11 g (75 mmol) of benzoic acid were further added as tetracarboxylic dianhydride. The jacket temperature of the apparatus was raised to 180°C and stirred for 8 hours. At this time, the internal temperature of the flask was 172 to 175°C. After stirring, the internal temperature of the flask was cooled to 25° C. and left overnight.
　次に、イソキノリン９．６３ｇ（７５ｍｍｏｌ）を加え、再びジャケット温度を１８０℃に昇温し、８時間撹拌した。反応液を一晩静置させた後、１－メチル－２－ピロリドン２３９ｇを加えることによって反応液を希釈した。次に、滴下ロートを用いて、メタノール６６１ｍＬを反応液に３０分程度かけて滴下し、再沈殿精製を行った。析出したポリイミドをろ別し、メタノール３００ｍＬを用いてポリイミドを洗浄する操作を２回行った。洗浄後、ろ別したポリイミドを６０℃の熱風循環乾燥機で１５時間乾燥させ、さらに、１００℃の真空乾燥機で８時間乾燥させた。これにより、収量１７ｇでポリイミド（ＰＩ－１）を得た。 Next, 9.63 g (75 mmol) of isoquinoline was added, the jacket temperature was raised to 180° C. again, and the mixture was stirred for 8 hours. After the reaction solution was allowed to stand overnight, the reaction solution was diluted by adding 239 g of 1-methyl-2-pyrrolidone. Next, using a dropping funnel, 661 mL of methanol was added dropwise to the reaction solution over about 30 minutes to perform reprecipitation purification. The precipitated polyimide was filtered out, and the polyimide was washed twice with 300 mL of methanol. After washing, the filtered polyimide was dried in a hot air circulation dryer at 60°C for 15 hours, and further dried in a vacuum dryer at 100°C for 8 hours. As a result, polyimide (PI-1) was obtained in a yield of 17 g.
　次に、ポリイミド、溶剤としてのＮ，Ｎ－ジメチルホルムアミド（富士フイルム和光純薬社製）、及び多孔化剤としてのポリエチレングリコールモノメチルエーテル４００（日油社製）を表１に示した重量比率で蓋つきカップに加えた。次に、得られた混合物について、撹拌装置（シンキー社製のあわとり練太郎）を用いて、２０００ｒｐｍで２５分間撹拌を行い、さらに、２２００ｒｐｍで５分間脱泡させた。これにより、ポリイミドが溶剤に均一に溶解した塗布液が得られた。 Next, polyimide, N,N-dimethylformamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent, and polyethylene glycol monomethyl ether 400 (manufactured by NOF Corporation) as a porosity agent were added in the weight ratios shown in Table 1. Added to a cup with a lid. Next, the obtained mixture was stirred for 25 minutes at 2000 rpm using a stirring device (Awatori Rentaro manufactured by Thinky), and further defoamed for 5 minutes at 2200 rpm. As a result, a coating liquid in which the polyimide was uniformly dissolved in the solvent was obtained.
　次に、基材（パナック社製の７５ＳＧ２）の上に、塗布液を塗布し、厚さ３００μｍの塗布膜を作製した。次に、オーブンを用いて、塗布膜を６０℃で３０分間乾燥させた。塗布膜をオーブンから一度取り出し、さらに１３０℃で３０分間乾燥させた。次に、塗布膜を基材から剥離してメタノールに３０分間浸漬させた。これにより、塗布膜から多孔化剤が除去され、分離機能層及び多孔性支持体が形成された。次に、６０℃で１時間真空乾燥させ、さらに３００℃で３０分間乾燥させることによって、実施例１の分離膜を得た。 Next, a coating liquid was applied onto a base material (75SG2 manufactured by Panac) to form a coating film with a thickness of 300 μm. Next, the coating film was dried at 60° C. for 30 minutes using an oven. The coated film was once taken out of the oven and further dried at 130° C. for 30 minutes. Next, the coating film was peeled off from the base material and immersed in methanol for 30 minutes. As a result, the porosity-forming agent was removed from the coating film, and a separation functional layer and a porous support were formed. Next, the separation membrane of Example 1 was obtained by vacuum drying at 60° C. for 1 hour and further drying at 300° C. for 30 minutes.
（実施例２～７）
　溶剤及び多孔化剤の種類、塗布液中の各成分の重量比率、並びに、塗布膜の厚さを表１に示すように変更したことを除き、実施例１と同じ方法によって、実施例２～７の分離膜を得た。 (Examples 2 to 7)
Examples 2~ A separation membrane of No. 7 was obtained.
（参考例１）
　まず、実施例１で作製したポリイミドと、Ｎ－メチル－２－ピロリドンとを１０：９０の重量比率で混合し、塗布液を作製した。この塗布液を基材（パナック社の７５ＳＧ２）の上に塗布し、厚さ５０μｍの塗布膜を作製した。塗布膜を乾燥させることによって、参考例１の分離機能層（自立膜）を得た。 (Reference example 1)
First, the polyimide prepared in Example 1 and N-methyl-2-pyrrolidone were mixed at a weight ratio of 10:90 to prepare a coating liquid. This coating liquid was applied onto a base material (75SG2 manufactured by Panac) to form a coating film with a thickness of 50 μm. By drying the coating film, a separation functional layer (self-supporting film) of Reference Example 1 was obtained.
［厚さ］
　実施例で作製した分離膜について、上述の方法によって、分離機能層及び多孔性支持体の厚さを特定した。 [thickness]
Regarding the separation membranes produced in Examples, the thicknesses of the separation functional layer and porous support were determined by the method described above.
［ガス透過試験］
　実施例で作製した分離膜について、以下の方法によって、ガス透過試験を行った。まず、分離膜を金属セル中にセットし、リークが発生しないようにＯリングでシールした。次に、分離膜の分離機能層側の主面に混合気体が接触するように、金属セル内に混合気体を注入した。混合気体は、実質的に二酸化炭素及び窒素からなっていた。混合気体における二酸化炭素の濃度は、標準状態で５０ｖｏｌ％であった。金属セル内に注入された混合気体は、温度が３０℃であり、圧力が０．１ＭＰａであった。次に、分離膜の多孔性支持体側の主面に隣接する金属セル内の空間（透過側空間）を真空ポンプで減圧した。このとき、透過側空間は、空間内の圧力が測定環境における大気圧に対して０．１ＭＰａ小さくなるように減圧されていた。これにより、分離膜の多孔性支持体側の主面から透過流体が得られた。得られた透過流体の組成、透過流体の重量などに基づいて、二酸化炭素の透過速度Ｔ、窒素に対する二酸化炭素の分離係数α（ＣＯ2／Ｎ2）、及び二酸化炭素の透過係数Ｃ１を算出した。 [Gas permeation test]
A gas permeation test was conducted on the separation membrane produced in the example by the following method. First, a separation membrane was set in a metal cell and sealed with an O-ring to prevent leakage. Next, the mixed gas was injected into the metal cell so that the mixed gas came into contact with the main surface of the separation membrane on the separation functional layer side. The gas mixture consisted essentially of carbon dioxide and nitrogen. The concentration of carbon dioxide in the gas mixture was 50 vol% under standard conditions. The mixed gas injected into the metal cell had a temperature of 30° C. and a pressure of 0.1 MPa. Next, the pressure in the space (permeation side space) in the metal cell adjacent to the main surface of the separation membrane on the porous support side was reduced using a vacuum pump. At this time, the pressure in the permeation side space was reduced so that the pressure in the space was 0.1 MPa lower than the atmospheric pressure in the measurement environment. As a result, a permeate fluid was obtained from the main surface of the separation membrane on the porous support side. Based on the composition of the obtained permeate fluid, the weight of the permeate fluid, etc., the permeation rate T of carbon dioxide, the separation coefficient α of carbon dioxide with respect to nitrogen α (CO 2 /N 2 ), and the permeation coefficient C1 of carbon dioxide were calculated. .
　さらに、分離膜に代えて、参考例１の分離機能層（自立膜）を用いて、上記のガス透過試験を行うことによって、分離機能層における二酸化炭素の透過係数Ｃ２を特定した。透過係数Ｃ２は、１７４３Ｂａｒｒｅｒであった。この透過係数Ｃ２と透過係数Ｃ１に基づいて、上記の式（Ｉ）によって、透過係数の変化率Ｒを算出した。 Furthermore, by performing the above gas permeation test using the separation functional layer (self-standing membrane) of Reference Example 1 instead of the separation membrane, the permeability coefficient C2 of carbon dioxide in the separation functional layer was determined. The transmission coefficient C2 was 1743 Barrer. Based on the transmission coefficient C2 and the transmission coefficient C1, the rate of change R of the transmission coefficient was calculated using the above formula (I).
［断面観察］
　実施例の分離膜について、その断面を走査型電子顕微鏡（ＳＥＭ）で観察した。結果を図５Ａ～５Ｇに示す。図５Ａ～５Ｆからわかるとおり、実施例１～６の分離膜において、多孔性支持体は、三次元状に連続して形成されている連続孔を有していた。一方、実施例７の分離膜では、多孔性支持体は、独立孔を有していた（図５Ｇ）。 [Cross-sectional observation]
The cross section of the separation membrane of the example was observed using a scanning electron microscope (SEM). The results are shown in Figures 5A-5G. As can be seen from FIGS. 5A to 5F, in the separation membranes of Examples 1 to 6, the porous support had continuous pores that were continuously formed in a three-dimensional shape. On the other hand, in the separation membrane of Example 7, the porous support had independent pores (FIG. 5G).
Figure JPOXMLDOC01-appb-T000015
Figure JPOXMLDOC01-appb-T000015
　なお、表１中の略称は以下のとおりである。
　ＤＭＦ：Ｎ，Ｎ－ジメチルホルムアミド（富士フイルム和光純薬社製、沸点１５３℃）
　ＤＭＡｃ：Ｎ，Ｎ－ジメチルアセトアミド（富士フイルム和光純薬社製、沸点１６５℃）
　ＮＭＰ：Ｎ－メチル－２－ピロリドン（富士フイルム和光純薬社製、沸点２０２℃）
　Ｍ４００：ポリエチレングリコールモノメチルエーテル４００（日油社製、沸点２９０℃～３１０℃）
　ＰＥＧ２００：ポリエチレングリコール２００（富士フイルム和光純薬社製、沸点２５０℃）
　ＴＥＰ：リン酸トリエチル（東京化成社製、沸点２１６℃）
　ブチルジグライム：ジエチレングリコールジブチルエーテル（東京化成社製、沸点２５５℃） In addition, the abbreviations in Table 1 are as follows.
DMF: N,N-dimethylformamide (manufactured by Fujifilm Wako Pure Chemical Industries, boiling point 153°C)
DMAc: N,N-dimethylacetamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., boiling point 165°C)
NMP: N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, boiling point 202°C)
M400: Polyethylene glycol monomethyl ether 400 (manufactured by NOF Corporation, boiling point 290°C to 310°C)
PEG200: Polyethylene glycol 200 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., boiling point 250°C)
TEP: Triethyl phosphate (manufactured by Tokyo Kasei Co., Ltd., boiling point 216°C)
Butyl diglyme: diethylene glycol dibutyl ether (manufactured by Tokyo Kasei Co., Ltd., boiling point 255°C)
　表１からわかるとおり、実施例の分離膜は、二酸化炭素の透過速度Ｔ及び二酸化炭素の分離係数αの両方が高い値であり、酸性ガスを含む混合気体から酸性ガスを分離することに適していると言える。実施例１～７の結果からは、多孔性支持体が連続孔を有する場合に、透過係数の変化率Ｒが比較的高い値となる傾向が読み取れる。 As can be seen from Table 1, the separation membrane of the example has high values for both the carbon dioxide permeation rate T and the carbon dioxide separation coefficient α, and is suitable for separating acidic gas from a mixed gas containing acidic gas. I can say that there is. From the results of Examples 1 to 7, it can be seen that when the porous support has continuous pores, the rate of change R of the permeability coefficient tends to be a relatively high value.
　本実施形態の分離膜は、酸性ガスを含む混合気体から酸性ガスを分離することに適している。特に、本実施形態の分離膜は、化学プラント又は火力発電のオフガスから二酸化炭素を分離することに適している。
  The separation membrane of this embodiment is suitable for separating acidic gas from a mixed gas containing acidic gas. In particular, the separation membrane of this embodiment is suitable for separating carbon dioxide from off-gas of chemical plants or thermal power generation.

Claims (15)

  1. 　分離機能層と、
    　前記分離機能層に直接接する多孔性支持体と、
    を備え、
    　前記分離機能層及び前記多孔性支持体のそれぞれがポリイミドを含み、
    　前記ポリイミドは、６員環の酸無水物構造を有するテトラカルボン酸二無水物に由来する構成単位を含む、分離膜。     a separation functional layer;
    a porous support directly in contact with the separation functional layer;
    Equipped with
    Each of the separation functional layer and the porous support contains polyimide,
    The polyimide is a separation membrane including a structural unit derived from a tetracarboxylic dianhydride having a six-membered acid anhydride structure.
  2. 　前記多孔性支持体が連続孔を有する、請求項１に記載の分離膜。 The separation membrane according to claim 1, wherein the porous support has continuous pores.
  3. 　前記分離機能層と前記多孔性支持体とが一体化している、請求項１に記載の分離膜。 The separation membrane according to claim 1, wherein the separation functional layer and the porous support are integrated.
  4. 　前記分離機能層の材料は、前記多孔性支持体の材料と同じである、請求項１に記載の分離膜。 The separation membrane according to claim 1, wherein the material of the separation functional layer is the same as the material of the porous support.
  5. 　前記分離機能層の厚さ、及び前記多孔性支持体の厚さの合計値が１０μｍ以上である、請求項１に記載の分離膜。 The separation membrane according to claim 1, wherein the total thickness of the separation functional layer and the porous support is 10 μm or more.
  6. 　前記構成単位は、下記式（Ａ１）で表される、請求項１に記載の分離膜。
    Figure JPOXMLDOC01-appb-C000001
     　前記式（Ａ１）において、Ｒ1a～Ｒ4aは、互いに独立して、水素原子又は任意の置換基である。     The separation membrane according to claim 1, wherein the structural unit is represented by the following formula (A1).
    Figure JPOXMLDOC01-appb-C000001
     In the formula (A1), R 1a to R 4a each independently represent a hydrogen atom or an arbitrary substituent.
  7. 　前記分離膜の一方の面に隣接する空間に、二酸化炭素及び窒素からなる混合気体を供給するとともに、前記分離膜の他方の面に隣接する空間を減圧した場合に、前記分離膜を透過する二酸化炭素の透過速度が１００ＧＰＵ以上である、請求項１に記載の分離膜。
    　ここで、前記混合気体における前記二酸化炭素の濃度は、標準状態で５０ｖｏｌ％であり、前記一方の面に隣接する空間に供給される前記混合気体は、温度が３０℃であり、圧力が０．１ＭＰａであり、前記他方の面に隣接する空間は、当該空間内の圧力が測定環境における大気圧に対して０．１ＭＰａ小さくなるように減圧されている。     When a gas mixture consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane and the pressure is reduced in a space adjacent to the other surface of the separation membrane, the amount of carbon dioxide that permeates through the separation membrane The separation membrane according to claim 1, having a carbon permeation rate of 100 GPU or more.
    Here, the concentration of carbon dioxide in the mixed gas is 50 vol% in a standard state, and the mixed gas supplied to the space adjacent to the one surface has a temperature of 30°C and a pressure of 0. 1 MPa, and the space adjacent to the other surface is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
  8. 　前記分離膜の一方の面に隣接する空間に、二酸化炭素及び窒素からなる混合気体を供給するとともに、前記分離膜の他方の面に隣接する空間を減圧した場合に、窒素に対する二酸化炭素の分離係数αが２０以上である、請求項１に記載の分離膜。
    　ここで、前記混合気体における前記二酸化炭素の濃度は、標準状態で５０ｖｏｌ％であり、前記一方の面に隣接する空間に供給される前記混合気体は、温度が３０℃であり、圧力が０．１ＭＰａであり、前記他方の面に隣接する空間は、当該空間内の圧力が測定環境における大気圧に対して０．１ＭＰａ小さくなるように減圧されている。     When a gas mixture consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane, and the space adjacent to the other surface of the separation membrane is depressurized, the separation coefficient of carbon dioxide to nitrogen is determined. The separation membrane according to claim 1, wherein α is 20 or more.
    Here, the concentration of carbon dioxide in the mixed gas is 50 vol% in a standard state, and the mixed gas supplied to the space adjacent to the one surface has a temperature of 30°C and a pressure of 0. 1 MPa, and the space adjacent to the other surface is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
  9. 　ポリイミド、溶剤、及び多孔化剤を含む塗布液を用いて塗布膜を形成することと、
    　前記塗布膜から前記多孔化剤を除去することと、
    を含む、分離膜の製造方法。     Forming a coating film using a coating solution containing polyimide, a solvent, and a porosity agent;
    removing the porosity agent from the coating film;
    A method for producing a separation membrane, including:
  10. 　前記ポリイミドは、６員環の酸無水物構造を有するテトラカルボン酸二無水物に由来する構成単位を含む、請求項９に記載の製造方法。 The manufacturing method according to claim 9, wherein the polyimide contains a structural unit derived from a tetracarboxylic dianhydride having a 6-membered acid anhydride structure.
  11. 　前記多孔化剤の沸点は、前記溶剤の沸点より５０℃以上高い、請求項９に記載の製造方法。 The manufacturing method according to claim 9, wherein the boiling point of the porosity-forming agent is 50°C or more higher than the boiling point of the solvent.
  12. 　前記多孔化剤は、エーテル化合物及びリン酸化合物からなる群より選ばれる少なくとも１つを含む、請求項９に記載の製造方法。 The manufacturing method according to claim 9, wherein the porosity-forming agent contains at least one selected from the group consisting of an ether compound and a phosphoric acid compound.
  13. 　前記溶剤は、アミド化合物及びラクトン化合物からなる群より選ばれる少なくとも１つを含む、請求項９に記載の製造方法。 The manufacturing method according to claim 9, wherein the solvent contains at least one selected from the group consisting of an amide compound and a lactone compound.
  14. 　前記塗布膜を乾燥させる、及び／又は、前記塗布膜を洗浄液で洗浄することによって、前記塗布膜から前記多孔化剤を除去する、請求項９に記載の製造方法。 The manufacturing method according to claim 9, wherein the porosity agent is removed from the coating film by drying the coating film and/or washing the coating film with a cleaning liquid.
  15. 　分離機能層と、前記分離機能層に直接接する多孔性支持体とを備えた分離膜であって、
    　前記分離機能層の材料は、前記多孔性支持体の材料と同じであり、
    　前記分離機能層の厚さ、及び前記多孔性支持体の厚さの合計値が１０μｍ以上であり、
    　前記分離膜の一方の面に隣接する空間に、二酸化炭素及び窒素からなる混合気体を供給するとともに、前記分離膜の他方の面に隣接する空間を減圧した場合に、前記分離膜を透過する二酸化炭素の透過速度が１００ＧＰＵ以上であり、かつ、窒素に対する二酸化炭素の分離係数αが２０以上である、分離膜。
    　ここで、前記混合気体における前記二酸化炭素の濃度は、標準状態で５０ｖｏｌ％であり、前記一方の面に隣接する空間に供給される前記混合気体は、温度が３０℃であり、圧力が０．１ＭＰａであり、前記他方の面に隣接する空間は、当該空間内の圧力が測定環境における大気圧に対して０．１ＭＰａ小さくなるように減圧されている。     A separation membrane comprising a separation functional layer and a porous support directly in contact with the separation functional layer,
    The material of the separation functional layer is the same as the material of the porous support,
    The total value of the thickness of the separation functional layer and the thickness of the porous support is 10 μm or more,
    When a gas mixture consisting of carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane and the pressure is reduced in a space adjacent to the other surface of the separation membrane, the amount of carbon dioxide that permeates through the separation membrane A separation membrane having a carbon permeation rate of 100 GPU or more and a separation coefficient α of carbon dioxide relative to nitrogen of 20 or more.
    Here, the concentration of carbon dioxide in the mixed gas is 50 vol% in a standard state, and the mixed gas supplied to the space adjacent to the one surface has a temperature of 30°C and a pressure of 0. 1 MPa, and the space adjacent to the other surface is reduced in pressure so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
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JP2003236352A (en) * 2002-02-15 2003-08-26 Ube Ind Ltd New separation membrane and method for manufacturing the same
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JP2014184424A (en) * 2012-09-25 2014-10-02 Ube Ind Ltd Asymmetric hollow fiber gas separation membrane and gas separation method
CN108043232A (en) * 2017-12-06 2018-05-18 上海交通大学 A kind of hexatomic ring polyimide copolymer seperation film and its preparation method and application
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Publication number Priority date Publication date Assignee Title
JP2002355938A (en) * 2001-05-30 2002-12-10 Tonen Chem Corp Composite film, its manufacturing method, and separator for battery using the same or filter
JP2003236352A (en) * 2002-02-15 2003-08-26 Ube Ind Ltd New separation membrane and method for manufacturing the same
JP2008086903A (en) * 2006-10-02 2008-04-17 Ube Ind Ltd ASYMMETRIC MEMBRANE FORMED BY Si ATOM CONTAINING POLYIMIDE, GAS SEPARATING MEMBRANE AND GAS SEPARATING METHOD
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