WO2022185891A1

WO2022185891A1 - Separation membrane

Info

Publication number: WO2022185891A1
Application number: PCT/JP2022/005717
Authority: WO
Inventors: 永恵清水; 賢輔谷; 太幹岩崎
Original assignee: 日東電工株式会社
Priority date: 2021-03-02
Filing date: 2022-02-14
Publication date: 2022-09-09

Abstract

The present invention provides a separation membrane which is suitable for improving the permeation rate of an acidic gas. A separation membrane 10 according to the present invention contains an ionic liquid. The molecular weight of the ionic liquid is 220 or more. The anion contained in the ionic liquid has a cyano group. The viscosity of the ionic liquid at 25°C is, for example, 50 mPa·s or less.

Description

separation membrane

The present invention relates to separation membranes.

A membrane separation method has been developed as a method for separating acidic gases from mixed gases containing acidic gases such as carbon dioxide. The membrane separation method can efficiently separate the acid gas while suppressing the operating cost, compared to the absorption method in which the acid gas contained in the mixed gas is absorbed by an absorbent and separated.

Separation membranes used in the membrane separation method include composite membranes in which a separation functional layer is formed on a porous support. For example, Patent Literature 1 discloses a composite membrane having a structure containing an ionic liquid as a separation functional layer.

Japanese Patent Application Laid-Open No. 2020-37688

　Conventional separation membranes are required to further improve the permeation rate of acidic gases.

Therefore, an object of the present invention is to provide a separation membrane suitable for improving the permeation rate of acidic gases.

As a result of intensive studies, the present inventors have newly found that the molecular weight of the ionic liquid and the type of functional group contained in the ionic liquid, particularly the anionic functional group, affect the permeation rate of acidic gases in the separation membrane. Found it. Based on this knowledge, the present inventors further studied and found that the permeation rate of acidic gases can be improved by appropriately setting the molecular weight of the ionic liquid and the functional group of the anion, and completed the present invention. came to.

The present invention
A separation membrane containing an ionic liquid,
The ionic liquid has a molecular weight of 220 or more,
A separation membrane is provided in which the anion contained in the ionic liquid has a cyano group.

According to the present invention, a separation membrane suitable for improving the permeation rate of acidic gases can be provided.

1 is a cross-sectional view of a separation membrane according to one embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of a membrane separation device equipped with the separation membrane of the present invention; FIG. FIG. 3 is a perspective view schematically showing a modification of the membrane separation device provided with the separation membrane of the present invention.

Although the details of the present invention will be described below, the following description is not intended to limit the present invention to specific embodiments.

<Embodiment of Separation Membrane>
As shown in FIG. 1, the separation membrane 10 of this embodiment includes a separation functional layer 1 containing an ionic liquid L, and further includes an intermediate layer 2 and a porous support 3, for example. A porous support 3 supports the separation functional layer 1 . The intermediate layer 2 is arranged between the separation functional layer 1 and the porous support 3 and is in direct contact with the separation functional layer 1 and the porous support 3 respectively.

(separation functional layer)
The separation functional layer 1 is a layer that preferentially permeates the acid gas contained in the mixed gas. The separation functional layer 1 contains the ionic liquid L as described above. An ionic liquid is a salt (ionic compound) that is liquid at 25°C. The molecular weight of the ionic liquid L is 220 or more, preferably 225 or more. The upper limit of the molecular weight of the ionic liquid L is not particularly limited, and is 250, for example.

The ionic liquid L contains cations and anions. The anion contained in the ionic liquid L has a cyano group. The number of cyano groups contained in the anion is not particularly limited, and is, for example, 1-4, preferably 3-4. The anion having a cyano group is not particularly limited, and includes, for example, at least one selected from the group consisting of tetracyanoborate and tricyanometanide. The molecular weight of the anion is not particularly limited as long as the molecular weight of the ionic liquid L is 220 or more. The upper limit of the molecular weight of the anion is not particularly limited, and may be 200, 150, or 130, for example.

The cations contained in the ionic liquid L are not particularly limited as long as the ionic liquid L has a molecular weight of 220 or more, and include imidazolium ions, pyridinium ions, ammonium ions, phosphonium ions, and the like. The ionic liquid L preferably contains imidazolium ions as cations. The above ions exemplified as cations include, for example, substituents having 1 or more carbon atoms.

Examples of substituents having 1 or more carbon atoms include alkyl groups having 1 to 20 carbon atoms, cycloalkyl groups having 3 to 14 carbon atoms, aryl groups having 6 to 20 carbon atoms, and the like. , a cyano group, an amino group, an ether group, or the like (for example, a hydroxyalkyl group having 1 to 20 carbon atoms, etc.). Ether groups include, for example, polyalkylene glycol groups such as polyethylene glycol.

Examples of alkyl groups having 1 to 20 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n- nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n- nonadecyl group, n-eicosadecyl group, i-propyl group, sec-butyl group, i-butyl group, 1-methylbutyl group, 1-ethylpropyl group, 2-methylbutyl group, i-pentyl group, neopentyl group, 1,2 -dimethylpropyl group, 1,1-dimethylpropyl group, t-pentyl group, 2-ethylhexyl group, 1,5-dimethylhexyl group and the like.

The above alkyl group may be substituted with a cycloalkyl group. The number of carbon atoms in the alkyl group substituted by the cycloalkyl group is, for example, 1 or more and 20 or less. Alkyl groups substituted with cycloalkyl groups include cyclopropylmethyl groups, cyclobutylmethyl groups, cyclohexylmethyl groups, cyclohexylpropyl groups, and the like.

Cycloalkyl groups having 3 to 14 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecyl, norbornyl, bornyl, and adamantyl groups. . The cycloalkyl group may have 3 or more and 8 or less carbon atoms.

Examples of the aryl group having 6 to 20 carbon atoms include a phenyl group, toluyl group, xylyl group, mesityl group, anisyl group, naphthyl group, and benzyl group.

In the present embodiment, the ionic liquid L preferably contains an imidazolium ion represented by the following formula (1) as a cation.

In formula (1), R ¹ to R ⁵ are each independently a hydrogen atom or the above-described substituent having 1 or more carbon atoms. R ¹ is preferably a substituent having 1 or more carbon atoms, more preferably an alkyl group having 1 to 20 carbon atoms, still more preferably an alkyl group having 2 to 10 carbon atoms, particularly preferably ethyl or n-butyl group. R ³ is preferably a substituent having 1 or more carbon atoms, more preferably an alkyl group having 1 to 20 carbon atoms, still more preferably an alkyl group having 1 to 10 carbon atoms, particularly preferably methyl is the base. Each of R ² , R ⁴ and R ⁵ is preferably a hydrogen atom.

The molecular weight of the cation is not particularly limited as long as the molecular weight of the ionic liquid L is 220 or more, for example 100 or more, and may be 130 or more. The upper limit of the molecular weight of the cation is not particularly limited, and may be 200 or 150, for example.

The ionic liquid L is 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][B(CN) ₄ ]) (molecular weight 226) and 1-butyl-3-methylimidazolium tricyanometanide ([BMIM ][C(CN) ₃ ]) (molecular weight: 229). ) ₄ ]. [BMIM][C(CN) ₃ ] has a higher viscosity and is easier to handle than [EMIM][B(CN) ₄ ]. [C(CN) ₃ ] may be included.

According to studies by the present inventors, there is a tendency that the lower the viscosity of the ionic liquid L, the higher the permeation rate of the acidic gas through the separation membrane 10 . The viscosity of the ionic liquid L at 25° C. is, for example, 50 mPa·s or less, preferably 30 mPa·s or less, and more preferably 20 mPa·s or less. The lower limit of the viscosity of the ionic liquid at 25°C is not particularly limited, and is, for example, 1 mPa·s. The viscosity of the ionic liquid can be measured under the following conditions using a commercially available viscosity/viscoelasticity measuring device (for example, Rheostress RS600 manufactured by Thermo HAAKE).
Cone: C60/Ti
Measurement temperature: 25°C (room temperature)
Shear rate γ (dγ/dt): 1 [1/s]
Rotation speed: 30 [s]

It is preferable that the ionic liquid L itself has a high permeation rate of acidic gas when formed into a film. As an example, the permeation rate T0 of carbon dioxide permeating the membrane (liquid membrane) of the ionic liquid L is, for example, 600 GPU or more, preferably 650 GPU or more, more preferably 700 GPU or more, and still more preferably 750 GPU or more. be. The upper limit of the transmission speed T0 is not particularly limited, and is, for example, 1500 GPU. However, 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 T0 can be measured by the method described in Examples.

From the viewpoint of gas separation performance, the content of the ionic liquid L in the separation functional layer 1 is, for example, 5 wt% or more, preferably 30 wt% or more, more preferably 50 wt% or more, and still more preferably 60 wt% or more. , particularly preferably 70 wt % or more, and particularly preferably 80 wt % or more. The higher the content of the ionic liquid L, the higher the separation performance of the separation membrane 10 tends to be. The upper limit of the content of the ionic liquid L is not particularly limited, and is, for example, 95 wt%, and may be 90 wt%. When the content of the ionic liquid L is 95 wt % or less, there is a tendency that the self-sustainability of the separation membrane 10 can be easily ensured.

[Double network gel]
The separation functional layer 1 has a double network gel containing the ionic liquid L, for example. A double network gel is a gel comprising two types of networks independent of each other, eg interpenetrating networks. In this embodiment, the double network gel includes, for example, a first network structure mainly composed of an inorganic material and a second network structure mainly composed of an organic material. As used herein, "mainly composed of" means that 50 wt% or more, further 70 wt% or more, particularly 90 wt% or more, especially 99 wt% or more is composed of the material.

[First network structure]
The inorganic material contained in the first network structure includes, for example, inorganic particles, inorganic polymers, etc., and preferably contains inorganic particles. The first network structure is composed of, for example, a network of inorganic particles. A network of inorganic particles is formed, for example, by bonding a plurality of inorganic particles to each other via hydrogen bonding or the like.

The inorganic particles are not particularly limited as long as they can form a network by aggregation or the like, and examples thereof include particles of inorganic oxides such as silica, titania, zirconia, alumina, copper oxide, layered silicate, and zeolite. be done. From the viewpoint of cohesion, the inorganic particles preferably contain silica particles. As silica particles, fumed silica (for example, Aerosil 200, etc.), colloidal silica, and the like are preferable. The inorganic particles can be used singly or in combination of two or more. The inorganic particles may be subjected to various surface treatments such as dimethylsilyl treatment and trimethylsilyl treatment.

The specific surface area of the inorganic particles measured by the BET (Brunauer-Emmett-Teller) method is preferably 20 m ² /g or more, more preferably 50 m ² /g or more, from the viewpoint of the reinforcing effect. This specific surface area is preferably 300 m ² /g or less, more preferably 200 m ² /g or less, from the viewpoint of the coating properties of the dispersion for producing the first network structure.

From the viewpoint of the reinforcing effect, the primary particle diameter of the inorganic particles is preferably 1 nm or more, more preferably 5 nm or more. The primary particle size of the inorganic particles is preferably 100 nm or less, more preferably 50 nm or less, from the viewpoint of the stability of the dispersion for producing the first network structure. The primary particle size of the inorganic particles means the diameter of a circle having the same area as that of the primary particles of the inorganic particles calculated from an electron microscope image obtained by observation with a transmission electron microscope.

Inorganic polymers are formed, for example, by polymerization of inorganic monomers. The inorganic monomer is not particularly limited, and examples thereof include mineral salts of metals such as Si, Ti, Zr, Al, Sn, Fe, Co, Ni, Cu, Zn, Pb, Ag, In, Sb, Pt, and Au. , organic acid salts, alkoxides, complexes (chelates) and the like, among which compounds containing Si (silicon-containing compounds) are preferred. These inorganic monomers form inorganic substances (metal oxides, hydroxides, carbides, metals, etc.) by, for example, hydrolysis or thermal decomposition, and then initiate polymerization. The inorganic monomer may be a partial hydrolyzate of the compounds mentioned above.

Silicon-containing compounds can form inorganic polymers, for example, by dehydration condensation polymerization. The silicon-containing compound may be gaseous, liquid, or solid under normal temperature and normal pressure. The silicon-containing compound is not particularly limited as long as it can form an inorganic polymer, and examples thereof include silicon oxide and silicate. The silicon-containing compound may be a compound represented by the following formula (2).
Si(R6) ⁴ _-x (OR7) _x ( ² )

In formula (2), x is an integer of 1-4. R ⁶ and R ⁷ are each independently a linear or branched alkyl group. In R ⁶ and R ⁷ , the number of carbon atoms in the alkyl group is, for example, 1-6, preferably 1-4, more preferably 1-2. Examples of linear alkyl groups include methyl, ethyl, propyl, butyl, pentyl, and hexyl groups. Examples of branched alkyl groups include isopropyl and isobutyl groups.

Specific examples of the compound represented by formula (2) include tetramethoxyorthosilicate, tetraethoxyorthosilicate (tetraethylorthosilicate), methyltriethoxyorthosilicate, methyltrimethoxyorthosilicate, octyltriethoxyorthosilicate, dimethyldi Ethoxyorthosilicate and the like can be mentioned, and one or more of these can be used in combination. In particular, tetraethoxyorthosilicate (TEOS) is preferable from the viewpoint of three-dimensional cross-linking by condensation polymerization and expression of high cross-linking density.

The content of the first network structure in the separation functional layer 1 is not particularly limited, and is, for example, 1 to 5 wt%.

A method for producing the first network structure is not particularly limited, and a known method can be used. The first network structure containing inorganic particles can be produced, for example, by the following method. First, the ionic liquid L and inorganic particles are mixed. The resulting mixed solution may optionally contain a dispersion medium such as alcohol such as ethanol, propanol, butanol, or water. This mixture is treated at a predetermined temperature (eg, 5 to 50° C., preferably 15 to 30° C.) for a predetermined time (eg, less than 5 minutes, preferably less than 1 minute). Thereby, a network of inorganic particles is formed in the presence of the ionic liquid L, and a first network structure can be obtained.

A first network structure containing an inorganic polymer formed from an inorganic monomer, particularly a silicon-containing compound, can be produced, for example, by the following method. First, the ionic liquid L and an inorganic monomer are mixed. The obtained mixed solution may contain a catalyst (for example, a dehydration condensation catalyst) for chemically bonding inorganic monomers together, a cross-linking aid, a dispersion medium, and the like, if necessary. Catalysts include acid catalysts such as HCl. Examples of the dispersion medium include those described above.

In the mixed liquid, the ratio of the mass of the catalyst to the mass of the inorganic monomer is not particularly limited, and is, for example, 0.01 to 20 wt%, preferably 0.05 to 10 wt%, more preferably 0.1 to 5 wt%. The ratio of the mass of the cross-linking aid to the mass of the inorganic monomer is not particularly limited, and is, for example, 0.01 to 20 wt%, preferably 0.05 to 15 wt%, more preferably 0.1 to 10 wt%.

Next, the mixture is treated at a predetermined temperature (eg, 5 to 100°C, preferably 15 to 60°C) for a predetermined time (eg, less than 5 minutes, preferably less than 1 minute). Thereby, an inorganic polymer is formed from the inorganic monomer in the presence of the ionic liquid L, and the first network structure can be obtained.

[Second network structure]
The organic material contained in the second network structure includes, for example, a prepolymer crosslinked product (a polymer having a crosslinked structure, specifically a chemically crosslinked structure). The second network structure may consist essentially of crosslinked prepolymers. The weight average molecular weight (Mw) of this crosslinked product is, for example, 5,000 or more, preferably 10,000 or more, more preferably 20,000 or more, and even more preferably 40,000 or more. The upper limit of the weight average molecular weight of the crosslinked product is not particularly limited, and is, for example, 5 million, preferably 2 million, more preferably 1.5 million. When the weight average molecular weight of the crosslinked product is 40000 or more, the mechanical strength of the separation functional layer 1 tends to be improved. The weight average molecular weight of the crosslinked product is obtained by measuring the molecular weight distribution of the crosslinked product by, for example, a gel permeation chromatograph (GPC) equipped with a differential refractive index detector (RID). From the obtained chromatogram (chart), It can be calculated using a standard polystyrene calibration curve.

[Prepolymer]
A prepolymer has a polymer chain containing constituent units derived from monomers. This polymer chain is formed, for example, by radical polymerization of a monomer. In the prepolymer crosslinked product, a plurality of polymer chains are crosslinked by crosslinked chains. The polymer chain and the crosslinked chain are preferably linked by at least one bond selected from the group consisting of hydrazone bond, amide bond, imide bond, urethane bond, ether bond and ester bond.

The prepolymer may be a homopolymer, copolymer, or mixture thereof. Copolymers include random copolymers, block copolymers, alternating copolymers, graft copolymers, and the like. As an example, the prepolymer may contain a (meth)acrylic polymer having a structural unit derived from a (meth)acrylate monomer as a main component. As used herein, "(meth)acrylate" means acrylate and/or methacrylate. The term "main component" means a structural unit that is contained in the largest amount on a weight basis among all the structural units that constitute the prepolymer.

The prepolymer is preferably a polymer having cross-linking points capable of reacting with the cross-linking agent described below. Cross-linking points are located at either the terminal, main chain or side chain of the prepolymer. The cross-linking point is preferably located on the side chain of the prepolymer from the viewpoint of obtaining a highly three-dimensionally cross-linked product.

The prepolymer preferably has a functional group, especially a polar group, that functions as a cross-linking point. A polar group means an atomic group containing atoms other than carbon and hydrogen, and typically means an atomic group containing at least one selected from the group consisting of N atoms and O atoms. By having a polar group in the prepolymer, a highly three-dimensionally crosslinked product can be easily obtained. A crosslinked product of a prepolymer having a polar group also tends to be able to stably retain an ionic liquid.

Polar groups include, for example, amino groups, amide groups, imide groups, morpholino groups, carboxyl groups, ester groups, hydroxyl groups, and ether groups. The amino group includes not only a primary amino group but also a secondary amino group and a tertiary amino group substituted with an alkyl group or the like. The amide group includes a (meth)acrylamide group, an acetamide group, a pyrrolidone group and the like. The ether group includes polyalkyl ether groups such as polyethylene glycol group and polypropylene glycol group; epoxy group; vinyloxy group and the like.

The prepolymer preferably contains structural units derived from polar group-containing monomers, particularly polar group-containing (meth)acrylate monomers. The polar group-containing monomer preferably contains, for example, at least one selected from the group consisting of amide group-containing monomers, imide group-containing monomers, amino group-containing monomers, epoxy group-containing monomers and vinyloxy group-containing monomers. More preferably, it contains at least one selected from the group consisting of monomers, imide group-containing monomers and vinyloxy group-containing monomers.

Examples of amide group-containing monomers include acrylamide, methacrylamide, N-vinylpyrrolidone, N,N-diallylacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N- diethylacrylamide, N,N-diethylmethacrylamide, N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, diacetoneacrylamide and the like.

Examples of imide group-containing monomers include N-(meth)acryloyloxysuccinimide, N-(meth)acryloyloxymethylenesuccinimide, and N-(meth)acryloyloxyethylenesuccinimide.

Examples of amino group-containing monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, 3-ethyloxetan-3-yl (meth)acrylate, and allyl glycidyl ether.

Examples of vinyloxy group-containing monomers include 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, 2-vinyloxyethyl (meth)acrylate, and 4-vinyloxypropyl (meth)acrylate.

The polar group-containing monomers may be used singly or in combination of two or more. For example, a prepolymer may be formed by copolymerizing methylacrylamide or dimethylacrylamide with N,N'-methylenebisacrylamide, diacetoneacrylamide (DAAm), N-acryloyloxysuccinimide (NSA), or the like. As an example, the prepolymer may contain structural units derived from dimethylacrylamide and structural units derived from N-acryloyloxysuccinimide.

The prepolymer may contain a structural unit that functions as a cross-linking agent, such as a structural unit derived from a polyfunctional (meth)acrylate. A prepolymer having this constitutional unit can be self-crosslinked. A polyfunctional (meth)acrylate means a monomer having two or more (meth)acryloyl groups in one molecule. Polyfunctional (meth)acrylates include, for example, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth) Acrylate, dipentaerythritol hexaacrylate and the like.

From the viewpoint of the mechanical strength of the separation functional layer 1, the weight average molecular weight (Mw) of the prepolymer is preferably 2500 or more, more preferably 5000 or more, and even more preferably 10000 or more. The upper limit of the weight average molecular weight of the prepolymer is not particularly limited, and is, for example, 2,500,000, preferably 1,000,000, more preferably 750,000. The weight average molecular weight of the prepolymer can be determined by the method described above for crosslinked products.

A prepolymer is obtained, for example, by polymerizing a monomer having a functional group that functions as a cross-linking point in the presence of a polymerization initiator. From the viewpoint of improving the flexibility and stretchability of the separation functional layer 1, the polymerization of the monomer is preferably radical polymerization. Radical polymerization may be thermal polymerization or photopolymerization (for example, polymerization by ultraviolet irradiation).

As the polymerization initiator, an azo polymerization initiator, a peroxide initiator, a redox initiator obtained by combining a peroxide and a reducing agent, a substituted ethane initiator, or the like can be used. When performing photopolymerization, various photopolymerization initiators can be used. In photopolymerization, a photosensitizer such as 2-oxoglutarate may be used.

Azo polymerization initiators include 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis-2-methylbutyronitrile, dimethyl-2,2′-azobis(2-methylbutyronitrile), pionate), 4,4′-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′-azobis[2-(5- methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutyramidine) dihydro chloride and the like.

Persulfates such as potassium persulfate and ammonium persulfate; dibenzoyl peroxide, t-butyl permaleate, t-butyl hydroperoxide, di-t-butyl peroxide, t- Butyl peroxybenzoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, hydrogen peroxide etc.

Examples of redox initiators include a combination of peroxide and ascorbic acid (such as a combination of aqueous hydrogen peroxide and ascorbic acid), a combination of peroxide and iron (II) salt (a combination of aqueous hydrogen peroxide and iron ( II) combinations with salts, etc.), combinations of persulfates and sodium hydrogen sulfite, and the like.

Examples of substituted ethane-based initiators include phenyl-substituted ethane.

Photopolymerization initiators include acetophenone, ketal, benzophenone, benzoin, benzoyl, xanthone, active halogen compounds (triazine, halomethyloxadiazole, coumarin), acridine, biimidazole, An oxime ester system and the like can be mentioned.

Acetophenone-based photopolymerization initiators include, for example, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, p-dimethylaminoacetophenone, 4 '-isopropyl-2-hydroxy-2-methyl-propiophenone, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 2- tolyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone and the like.

Examples of ketal-based photopolymerization initiators include benzyl dimethyl ketal and benzyl-β-methoxyethyl acetal.

Examples of benzophenone-based photopolymerization initiators include benzophenone, 4,4'-(bisdimethylamino)benzophenone, 4,4'-(bisdiethylamino)benzophenone, and 4,4'-dichlorobenzophenone.

Benzoin-based or benzoyl-based photopolymerization initiators include, for example, benzoin isopropyl ether, benzoin isobutyl ether, benzoin methyl ether, and methyl o-benzoyl benzoate.

Examples of xanthone-based photopolymerization initiators include diethylthioxanthone, diisopropylthioxanthone, monoisopropylthioxanthone, and chlorothioxanthone.

Triazine-based photopolymerization initiators include, for example, 2,4-bis(trichloromethyl)-6-p-methoxyphenyl-s-triazine, 2,4-bis(trichloromethyl)-6-p-methoxystyryl-s -triazine, 2,4-bis(trichloromethyl)-6-(1-p-dimethylaminophenyl)-1,3-butadienyl-s-triazine, 2,4-bis(trichloromethyl)-6-biphenyl-s -triazine, 2,4-bis(trichloromethyl)-6-(p-methylbiphenyl)-s-triazine, p-hydroxyethoxystyryl-2,6-di(trichloromethyl)-s-triazine, methoxystyryl-2 ,6-di(trichloromethyl)-s-triazine, 3,4-dimethoxystyryl-2,6-di(trichloromethyl)-s-triazine, 4-benzoxolane-2,6-di(trichloromethyl)- s-triazine, 4-(o-bromo-pN,N-(diethoxycarbonylamino)-phenyl)-2,6-di(chloromethyl)-s-triazine, 4-(pN,N- diethoxycarbonylamino)-phenyl)-2,6-di(chloromethyl)-s-triazine and the like.

Examples of halomethyloxadiazole-based photopolymerization initiators include 2-trichloromethyl-5-styryl-1,3,4-oxodiazole, 2-trichloromethyl-5-(cyanostyryl)-1,3, 4-oxodiazole, 2-trichloromethyl-5-(naphth-1-yl)-1,3,4-oxodiazole, 2-trichloromethyl-5-(4-styryl)styryl-1,3,4 - oxodiazole and the like.

Coumarin-based photopolymerization initiators include, for example, 3-methyl-5-amino-((s-triazin-2-yl)amino)-3-phenylcoumarin, 3-chloro-5-diethylamino-((s-triazine -2-yl)amino)-3-phenylcoumarin, 3-butyl-5-dimethylamino-((s-triazin-2-yl)amino)-3-phenylcoumarin and the like.

Examples of acridine-based photopolymerization initiators include 9-phenylacridine and 1,7-bis(9-acridinyl)heptane.

Biimidazole-based photopolymerization initiators include, for example, 2-(o-chlorophenyl)-4,5-diphenylimidazolyl dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazolyl dimer, 2 lophine dimers such as -(2,4-dimethoxyphenyl)-4,5-diphenylimidazolyl dimer; 2-mercaptobenzimidazole; 2,2'-dibenzothiazolyl disulfide and the like.

Examples of oxime ester photopolymerization initiators include 1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyloxime)], ethanone, 1-[9-ethyl-6-( 2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime) and the like.

The polymerization initiator can be used alone or in combination of two or more. The polymerization initiator is preferably 2,2'-azobisisobutyronitrile. The amount of the polymerization initiator to be blended is not particularly limited, and is, for example, 0.1 parts by mass or more, preferably 0.3 parts by mass or more, relative to 100 parts by mass of the monomer. The amount of the polymerization initiator compounded is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, relative to 100 parts by mass of the monomer.

The prepolymer synthesis may be performed in the presence of a solvent. As the solvent, organic solvents are preferable, and examples include ketone organic solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ester organic solvents such as methyl acetate, ethyl acetate and butyl acetate; dimethylformamide, dimethyl sulfoxide, N-methyl- Polar solvents such as 2-pyrrolidone; alcohol-based organic solvents such as methyl alcohol, ethyl alcohol and isopropyl alcohol; aromatic hydrocarbon-based organic solvents such as toluene and xylene; aliphatic hydrocarbons such as n-hexane, cyclohexane and methylcyclohexane System/alicyclic hydrocarbon-based organic solvents; cellosolve-based organic solvents such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; ether-based organic solvents such as tetrahydrofuran and dioxane; carbitols such as n-butyl carbitol and iso-amyl carbitol and organic solvents. An organic solvent can be used 1 type or in combination of 2 or more types.

The method for synthesizing the prepolymer is not particularly limited, and solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, atom transfer radical polymerization (ATRP: Atom Transfer Radical Polymerization), reversible addition-fragmentation chain transfer polymerization (Raft: Reversible Known methods such as Addition Fragmentation chain Transfer) can be used, but solution polymerization is preferred from the viewpoint of workability. As an example, the prepolymer may be synthesized by photopolymerization in the presence of a solvent or by solventless photopolymerization, particularly UV polymerization.

Examples of ATRP initiators include tert-butyl 2-bromoisobutyrate, methyl 2-bromoisobutyrate, 2-bromoisobutyryl bromide, ethyl 2-bromoisobutyrate, 2-hydroxyethyl 2-bromoisobutyrate, ethylenebis(2- bromoisobutyrate), 1-tris(hydroxymethyl)ethane, and pentaerythritol tetrakis(2-bromoisobutyrate).

ATRP catalyst ligands include, for example, 2,2′-bipyridyl, 4,4′-dimethyl-2,2′-dipyridyl, 4,4′-di-tert-butyl-2,2′-dipyridyl, 4,4'-dinonyl-2,2'-dipyridyl, N-butyl-2-pyridylmethanimine, N-octyl-2-pyridylmethanimine, N-dodecyl-N-(2-pyridylmethylene)amine, N- octadecyl-N-(2-pyridylmethylene)amine, N,N,N',N'',N''-pentamethyldiethylenetriamine and the like.

Examples of metal salts for ATRP catalysts include copper (I) chloride, copper (II) chloride, copper (I) bromide, copper (II) bromide, titanium (II) chloride, titanium (III) chloride, titanium chloride (IV), titanium (IV) bromide, iron (II) chloride, and the like.

RAFT agents include, for example, cyanomethyl-dodecyltrithiocarbonate, 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid, 2-cyano-2-propyldodecyltrithiocarbonate and the like.

When the prepolymer is synthesized by thermal polymerization, the polymerization temperature is, for example, 25-80°C, preferably 30-70°C, more preferably 40-60°C. When the prepolymer is synthesized by photopolymerization, the polymerization temperature is preferably 10 to 60.degree. C., more preferably 20 to 50.degree. C., still more preferably 20 to 40.degree.

When the prepolymer is synthesized by thermal polymerization, the polymerization time is, for example, 1 to 100 hours, preferably 20 to 80 hours, more preferably 30 to 70 hours, still more preferably 40 to 60 hours. When the prepolymer is synthesized by photopolymerization, the polymerization time is, for example, 0.1 to 100 hours, preferably 1 to 70 hours, more preferably 5 to 40 hours, still more preferably 10 to 30 hours.

When synthesizing a prepolymer by photopolymerization, the wavelength of the ultraviolet light to be used is not particularly limited as long as the monomer can be radically polymerized. More preferably 300 to 400 nm. Although the intensity of the ultraviolet rays is not particularly limited, it is, for example, 1 to 3000 mJ/(cm ² ·s), preferably 10 to 2000 mJ/(cm ² ·s), considering the polymerization time and safety.

[Crosslinking agent]
A crosslinked product of a prepolymer can be formed, for example, by reacting the prepolymer with a crosslinking agent. However, when the prepolymer contains a structural unit that functions as a cross-linking agent, the cross-linked product of the prepolymer can be formed by reaction between the prepolymers. The cross-linking agent can be appropriately selected according to the composition of the prepolymer. Examples of cross-linking agents include polyfunctional (meth)acrylates, hydrazide-based cross-linking agents, amine-based cross-linking agents, isocyanate-based cross-linking agents, epoxy-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, metal chelate-based cross-linking agents, Examples include metal salt-based cross-linking agents, peroxide-based cross-linking agents, oxazoline-based cross-linking agents, urea-based cross-linking agents, carbodiimide-based cross-linking agents, and coupling agent-based cross-linking agents (for example, silane coupling agents). A cross-linking agent can be used 1 type or in combination of 2 or more types.

Examples of polyfunctional (meth)acrylates include those mentioned above for prepolymers.

Examples of hydrazide cross-linking agents include isophthalic acid dihydrazide, terephthalic acid dihydrazide, phthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, naphthalene acid dihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutamic acid dihydrazide, and adipine. acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, brassylic acid dihydrazide, dodecanedioic acid dihydrazide, acetonedicarboxylic acid dihydrazide, fumaric acid dihydrazide, maleic acid dihydrazide, itaconic acid dihydrazide, trimellitic acid dihydrazide, Polyvalent hydrazides such as 1,3,5-benzenetricarboxylic acid dihydrazide, aconitic acid dihydrazide, and pyromellitic acid dihydrazide can be mentioned, and adipic acid dihydrazide is preferred.

Examples of amine cross-linking agents include hexamethylenediamine, 1,12-dodecanediamine, hexamethylenediamine carbamate, N,N-dicinnamylidene-1,6-hexanediamine, tetramethylenepentamine, and hexamethylenediamine cinnamaldehyde adducts. aliphatic polyvalent amines such as; 4,4-(p-phenylenediisopropylidene)dianiline, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4-diaminobenzanilide, 4,4-bis(4-aminophenoxy ) Aromatic polyamines such as biphenyl, m-xylylenediamine, p-xylylenediamine, 1,3,5-benzenetriamine; Examples include diamines having polyether in the chain, and 1,12-dodecanediamine and diethylene glycol bis-3-aminopropyl ether are preferred.

Examples of isocyanate-based cross-linking agents include 1,6-hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, and the like. Alicyclic polyisocyanates such as isophorone diisocyanate, cyclohexyl diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate; 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenyl Propane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate , naphthylene-1,5-diisocyanate, 3,3′-dimethoxydiphenyl-4,4′-diisocyanate, xylylene-1,4-diisocyanate and xylylene-1,3-diisocyanate.

Examples of isocyanate-based cross-linking agents include dimers and trimers of the exemplified isocyanate compounds, reaction products or polymers (e.g., dimers and trimers of diphenylmethane diisocyanate, reaction products of trimethylolpropane and tolylene diisocyanate products, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate) and the like can also be used. As the isocyanate-based cross-linking agent, a reaction product of trimethylolpropane and tolylene diisocyanate is preferred.

Examples of epoxy-based cross-linking agents include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1, 6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, penta erythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipate diglycidyl ester, o-phthalate diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, Resorcinol diglycidyl ether, bisphenol S diglycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)benzene, 1,3-bis(N,N-diglycidylaminomethyl)toluene, 1,3,5 - 2 or more or 3 or more epoxies in one molecule such as triglycidyl isocyanuric acid, N,N,N',N'-tetraglycidyl-m-xylylenediamine, glycerin triglycidyl ether, trimethylolpropane glycidyl ether Epoxy compounds having groups are mentioned, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane is preferred.

The content of the second network structure in the separation functional layer 1 is not particularly limited, and is, for example, 1 to 15 wt%.

The method for producing the second network structure is not particularly limited, and includes, for example, the following method. First, the ionic liquid L and the prepolymer are mixed. The obtained mixed solution may contain the above-mentioned cross-linking agent, monomer, dispersion medium, etc., if necessary. Monomers include, for example, the polar group-containing monomers described above for the prepolymer. Dispersion media include those described above for the first network structure.

The amount of the cross-linking agent used in the mixed solution is, for example, 0.02 to 8 parts by mass, preferably 0.08 to 5 parts by mass, based on 100 parts by mass of the prepolymer and the monomer in total.

Next, the mixture is treated at a predetermined temperature (eg, 5 to 100°C, preferably 15 to 60°C) for a predetermined time (eg, less than 5 minutes, preferably less than 1 minute). Thereby, a crosslinked product of the prepolymer is formed in the presence of the ionic liquid L, and a second network structure can be obtained.

The example of the organic material contained in the second network structure is not limited to the crosslinked prepolymer. For example, instead of the prepolymer, a monomer may be mixed with the ionic liquid L and polymerized to form the second network structure composed of a polymer of the monomer. Monomers include, for example, those described above for the prepolymer. Polymerization of the monomers can be carried out, for example, by solvent-free photopolymerization, in particular UV polymerization.

The production of the second network structure may be performed before the production of the first network structure, may be carried out after the production of the first network structure, or may be carried out simultaneously with the production of the first network structure. As an example, an ionic liquid L, a material for producing a first network structure (inorganic particles, inorganic monomers, etc.), and a material for producing a second network structure (prepolymer, etc.) are mixed to obtain Both the first network structure and the second network structure may be produced by subjecting the mixture to a predetermined treatment. In this case, the solid content concentration of the mixed liquid is, for example, 0.5 wt % or more, preferably 1.0 wt % or more, and more preferably 2.0 wt % or more, from the viewpoint of coatability. The solid content concentration of the mixed liquid is, for example, 50 wt % or less, preferably 40 wt % or less, and more preferably 30 wt % or less, from the viewpoint of producing a thin separation function layer 1 .

[Physical properties of separation functional layer]
The thickness of the separation functional layer 1 is, for example, 50 μm or less, preferably 25 μm or less, more preferably 15 μm or less. The thickness of the separation functional layer 1 may be 10 μm or less, 5.0 μm or less, or 2.0 μm or less depending on the case. The thickness of the separation functional layer 1 may be 0.05 μm or more, or may be 0.1 μm or more.

(middle layer)
The intermediate layer 2 contains, for example, a resin and further contains nanoparticles dispersed in the resin (matrix). The nanoparticles may be spaced apart from each other within the matrix or may be partially aggregated. However, the intermediate layer 2 may not contain nanoparticles, and may be substantially composed of resin.

The material of the matrix is not particularly limited, and examples thereof include silicone resins such as polydimethylsiloxane; fluorine resins such as polytetrafluoroethylene; epoxy resins such as polyethylene oxide; polyimide resins; polyacetylene resins such as; and polyolefin resins such as polymethylpentene. The matrix preferably contains a silicone resin.

The nanoparticles may contain inorganic materials or organic materials. Inorganic materials included in nanoparticles include, for example, silica, titania, and alumina. The nanoparticles preferably contain silica.

The nanoparticles may have surfaces modified with modifying groups containing carbon atoms. Nanoparticles having surfaces modified with this modifying group are excellent in dispersibility in a matrix. The nanoparticles are for example silica nanoparticles which may have their surfaces modified by modifying groups. The modifying group further comprises, for example, a silicon atom. In nanoparticles, the surfaces modified with modifying groups are represented by the following formulas (I) to (III), for example.

R ⁸ to R ¹³ in formulas (I) to (III) are each independently a hydrocarbon group which may have a substituent. The number of carbon atoms in the hydrocarbon group is not particularly limited as long as it is 1 or more. The number of carbon atoms in the hydrocarbon group may be, for example, 25 or less, 20 or less, 10 or less, or 5 or less. In some cases, the hydrocarbon group may have more than 25 carbon atoms. The hydrocarbon group may be a linear or branched chain hydrocarbon group, or an alicyclic or aromatic cyclic hydrocarbon group. In one preferred form, the hydrocarbon group is a linear or branched alkyl group having 1 to 8 carbon atoms. A hydrocarbon group is, for example, a methyl group or an octyl group, preferably a methyl group. Substituents of hydrocarbon groups include, for example, amino groups and acyloxy groups. Examples of acyloxy groups include (meth)acryloyloxy groups.

In another preferred form, the hydrocarbon group optionally having substituents described above for R ⁸ to R ¹³ in formulas (I) to (III) is represented by formula (IV) below. A nanoparticle having a surface modified with a modifying group containing a hydrocarbon group represented by formula (IV) is suitable for improving the acidic gas permeation rate in the separation membrane 10 .

In formula (IV), R ¹⁴ is an optionally substituted alkylene group having 1 to 5 carbon atoms. The alkylene group may be linear or branched. Examples of the alkylene group include methylene group, ethylene group, propane-1,3-diyl group, butane-1,4-diyl group and pentane-1,5-diyl group, preferably propane-1,3 - is a diyl group. Examples of substituents for the alkylene group include an amido group and an aminoalkylene group.

In formula (IV), R ¹⁵ is an optionally substituted C 1-20 alkyl group or aryl group. Alkyl groups may be linear or branched. Alkyl groups and aryl groups include, for example, those described above for ionic liquids. Substituents for the alkyl group and aryl group include an amino group and a carboxyl group. R ¹⁵ is, for example, a 3,5-diaminophenyl group.

In nanoparticles, the surface modified with a modifying group is preferably represented by the following formula (V).

Modifying groups are not limited to the structures shown in formulas (I)-(III). The modifying group may contain a polymer chain having a polyamide structure or a polydimethylsiloxane structure in place of R ⁸ -R ¹³ in formulas (I) - (III). In modifying groups, for example, the polymer chain is directly attached to a silicon atom. The shape of the polymer chain includes, for example, linear, dendrimer, and hyperbranched.

The method of modifying the surface of nanoparticles with modifying groups is not particularly limited. For example, the surface of nanoparticles can be modified by reacting hydroxyl groups present on the surface of the nanoparticles with a known silane coupling agent. When the modifying group contains a polyamide structure, the surface of the nanoparticles can be modified, for example, by the method disclosed in JP-A-2010-222228.

The average particle size of the nanoparticles is not particularly limited as long as it is on the order of nanometers (<1000 nm), and is, for example, 100 nm or less, preferably 50 nm or less, and more preferably 20 nm or less. The lower limit of the average particle size of nanoparticles is, for example, 1 nm. The average particle size of nanoparticles can be specified, for example, by the following method. First, a cross section of the intermediate layer 2 is observed with a transmission electron microscope. In the obtained electron microscope image, the area of specific nanoparticles is calculated by image processing. The diameter of a circle having the same area as the calculated area is taken as the particle size (particle diameter) of that particular nanoparticle. The particle size of an arbitrary number (at least 50) of nanoparticles is calculated, and the average value of the calculated values is regarded as the average particle size of the nanoparticles. The shape of the nanoparticles is not particularly limited, and may be spherical, ellipsoidal, scaly, or fibrous.

The content of nanoparticles in the intermediate layer 2 is, for example, 5 wt% or more, preferably 10 wt% or more, and more preferably 15 wt% or more. The upper limit of the content of nanoparticles in the intermediate layer 2 is not particularly limited, and is, for example, 30 wt %.

The thickness of the intermediate layer 2 is not particularly limited, and is, for example, less than 50 μm, preferably 40 μm or less, more preferably 30 μm or less. The lower limit of the thickness of the intermediate layer 2 is not particularly limited, and is, for example, 1 μm. The intermediate layer 2 is, for example, a layer having a thickness of less than 50 μm.

(Porous support)
The porous support 3 supports the separation functional layer 1 with the intermediate layer 2 interposed therebetween. Porous support 3 includes, for example, nonwoven fabric; porous polytetrafluoroethylene; aromatic polyamide fiber; porous metal; sintered metal; porous ceramic; silicone; silicone rubber; permeation containing at least one selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyetheretherketone, polyacrylonitrile, polyimide and polyphenylene oxide open-celled or closed-celled metal foams; open-celled or closed-celled polymeric foams; silica; porous glass; The porous support 3 may be a combination of two or more of these.

The porous support 3 has an average pore size of, for example, 0.01-0.4 μm. The thickness of the porous support 3 is not particularly limited, and is, for example, 10 μm or more, preferably 20 μm or more, more preferably 50 μm or more. The thickness of the porous support 3 is, for example, 300 μm or less, preferably 200 μm or less, more preferably 150 μm or less.

(Separation membrane manufacturing method)
Separation membrane 10 can be produced, for example, by the following method. First, the ionic liquid L, a material (inorganic particles, inorganic monomers, etc.) for producing the first network structure, and a material (prepolymer, etc.) for producing the second network structure are mixed to obtain a mixed solution. .

Next, this mixed solution is applied to a base material to obtain a coating film. A method for applying the mixed liquid is not particularly limited, and for example, a spin coating method can be used. The thickness of the separation functional layer 1 formed from the coating film can be adjusted by adjusting the rotational speed of the spin coater, the solid content concentration in the coating liquid, and the like. The mixture may be applied to the substrate using an applicator, wire bar, or the like.

The substrate to which the coating liquid is applied is typically a laminate of the porous support 3 and the intermediate layer 2. This laminate can be produced, for example, by the following method. First, a coating liquid containing a material for the intermediate layer 2 is prepared. Next, a coating liquid containing the material of the intermediate layer 2 is applied onto the porous support 3 to form a coating film. A method for applying the coating liquid is not particularly limited, and for example, a spin coating method, a dip coating method, or the like can be used. The coating liquid may be applied using a wire bar or the like. Next, the coating film is dried to form the intermediate layer 2 . The coating film can be dried, for example, under heating conditions. The heating temperature of the coating film is, for example, 50° C. or higher. The heating time of the coating film is, for example, 1 minute or longer, and may be 5 minutes or longer. Further, the surface of the intermediate layer 2 may be subjected to an adhesion-facilitating treatment as necessary. The adhesion-facilitating treatment includes surface treatment such as application of a primer, corona discharge treatment, and plasma treatment.

Next, a predetermined treatment is performed on the coating film formed on the base material to produce a first network structure and a second network structure. Thereby, a double network gel containing the ionic liquid L is formed, and the separation functional layer 1 can be obtained. When the substrate is a laminate of the porous support 3 and the intermediate layer 2, the separation membrane 10 is obtained by forming the separation functional layer 1 on the substrate.

The base material is not limited to the laminate of the porous support 3 and the intermediate layer 2, and may be a transfer film. When the substrate is a transfer film, the separation membrane 10 can be produced by the following method. First, a coating film formed on a substrate is subjected to a predetermined treatment to produce the separation functional layer 1 . Next, the intermediate layer 2 is formed by applying a coating liquid containing the material of the intermediate layer 2 onto the separation function layer 1 and drying it. A laminate of the intermediate layer 2 and the separation functional layer 1 is transferred to the porous support 3 . Thereby, the separation membrane 10 is obtained.

(Characteristics of separation membrane)
In the separation membrane 10 of this embodiment, the separation functional layer 1 contains the ionic liquid L described above. According to studies by the present inventors, the ionic liquid L tends to improve the permeation rate of the acidic gas in the separation membrane 10 . If the permeation rate of the acidic gas in the separation membrane 10 is improved, for example, the membrane area required for separating the mixed gas can be reduced.

As an example, the permeation rate T of carbon dioxide permeating through the separation membrane 10 is, for example, 480 GPU or higher, preferably 500 GPU or higher, more preferably 530 GPU or higher, and still more preferably 550 GPU or higher. The upper limit of the transmission speed T is not particularly limited, and is, for example, 1000 GPU. However, 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 speed T can be calculated by the following method. First, a mixed gas containing carbon dioxide and nitrogen is supplied to a space adjacent to one surface of the separation membrane 10 (for example, the main surface 11 of the separation membrane 10 on the side of the separation functional layer), and the other surface of the separation membrane 10 is supplied. A space adjacent to (for example, the main surface 12 of the separation membrane 10 on the porous support side) is decompressed. As a result, a permeated fluid that has passed through the separation membrane 10 is obtained. The weight of the permeate and the volume fraction of carbon dioxide and nitrogen in the permeate are measured. The permeation rate T can be calculated from the measurement results. In the above operation, the concentration of carbon dioxide in the gas mixture is 50 vol% under standard conditions (0°C, 101 kPa). The mixed gas supplied to the space adjacent to one side 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 decompressed so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.

Under the conditions for measuring the permeation rate T described above, the separation coefficient α of carbon dioxide with respect to nitrogen of the separation membrane 10 is not particularly limited, and is, for example, 20 or more, preferably 25 or more, and more preferably 30 or more. The upper limit of the separation factor α is not particularly limited, and is 100, for example. The separation factor 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, respectively, in the permeated fluid that has passed through the separation membrane 10 .
Separation factor α = (Y _A /Y _B )/(X _A /X _B )

Applications of the separation membrane 10 of the present embodiment include applications for separating acidic gases from mixed gases containing acidic gases. The acid gas of the mixed gas includes carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, nitrogen oxides (NOx), etc. Carbon dioxide is preferred. The mixed gas contains other gases than acid gas. Other gases include, for example, hydrogen, non-polar gases such as nitrogen, and inert gases such as helium, preferably nitrogen. In particular, the separation membrane 10 of this embodiment is suitable for separating carbon dioxide from a mixed gas containing carbon dioxide and nitrogen. However, the application of the separation membrane 10 is not limited to the application of separating acidic gas from the mixed gas.

<Embodiment of Membrane Separator>
As shown in FIG. 2 , the membrane separation device 100 of this embodiment includes a separation membrane 10 and a tank 20 . The tank 20 has 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 the first chamber 21 and the second chamber 22 . Separation membrane 10 extends from one of a pair of wall surfaces of tank 20 to the other.

The first chamber 21 has an entrance 21a and an exit 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. First, a mixed gas 30 containing acid gas is supplied to the first chamber 21 through the inlet 21a. The concentration of the acid gas in the mixed gas 30 is not particularly limited, and is, for example, 0.01 vol% (100 ppm) or more, preferably 1 vol% or more, more preferably 10 vol% or more, and even more preferably, under standard conditions. is 30 vol% or more, particularly preferably 50 vol% or more. The upper limit of the acid gas concentration in the mixed gas 30 is not particularly limited, and is, for example, 90 vol % under standard conditions.

By supplying the mixed gas 30, the inside of the first chamber 21 may be pressurized. The membrane separation device 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 higher, preferably 0.3 MPa or higher.

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

By supplying the mixed gas 30 into the first chamber 21 , a permeate fluid 35 having a higher acid gas content than the mixed gas 30 can be obtained on the other side of the separation membrane 10 . That is, the permeating fluid 35 is supplied to the second chamber 22 . The permeating fluid 35 contains, for example, acid gas as a main component. However, the permeating fluid 35 may contain a small amount of gas other than the acid gas. The permeated fluid 35 is discharged to the outside of the tank 20 through the outlet 22a.

The concentration of acid 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-permeating fluid 36) processed in the first chamber 21 is discharged to the outside of the tank 20 through the outlet 21b.

The membrane separation device 100 of this embodiment is suitable for a flow-type (continuous) membrane separation method. However, the membrane separation apparatus 100 of this embodiment may be used for a batch-type membrane separation method.

<Modification of Membrane Separator>
As shown in FIG. 3 , the membrane separation device 110 of this embodiment includes a central tube 41 and a laminate 42 . A laminate 42 includes the separation membrane 10 . The membrane separation device 110 is a spiral membrane element.

The central tube 41 has a cylindrical shape. A plurality of holes are formed on the surface of the central tube 41 to allow the permeating fluid 35 to flow into the central tube 41 . Examples of materials for the central tube 41 include resins such as acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polyphenylene ether resin (PPE resin), and polysulfone resin (PSF resin); and metals such as stainless steel and titanium. be done. The inner diameter of the central tube 41 is, for example, in the range of 20-100 mm.

The laminate 42 further includes, in addition to the separation membrane 10, a feed-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).

As the feed side channel material 43 and the permeation side channel material 44, for example, 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. First, the mixed gas 30 is supplied to one end of the wound laminate 42 . The permeated fluid 35 that permeates the separation membrane 10 of the laminate 42 moves inside the central tube 41 . The permeating fluid 35 is discharged outside through the central tube 41 . The mixed gas 30 (non-permeating fluid 36) processed by the membrane separation device 110 is discharged outside from the other end of the wound laminate 42. As shown in FIG. Thereby, the acid gas can be separated from the mixed gas 30 .

The present invention will be described in more detail below with examples and comparative examples, but the present invention is not limited to these.

(Comparative example 1)
[Synthesis of prepolymer]
First, a reflux tube was attached to a three-necked flask to assemble a synthesizing apparatus. A vacuum pump and an _N2 cylinder were connected to the three-way cock. A total of 5 sets of nitrogen replacement were performed, with one set of the operation of evacuating and supplying nitrogen once every 2 minutes. After purging with nitrogen, 1,4-dioxane was added into the three-necked flask using a glass syringe. A vial was then charged with N,N-dimethylacrylamide (DMAAm) (14.6 g, 147.28 mmol), N-acryloyloxysuccinimide (NSA) (1.32 g, 1.56 mmol) and 2,2'-azo. Bisisobutyronitrile (AIBN) (0.256 g, 1.56 mmol) was weighed out in this order and stirred for several minutes. The molar ratio of DMAAm and NSA (DMAAm/NSA) was 95/5. The resulting mixture was added into a three-necked flask using a syringe. The solution in the three-necked flask was stirred with a stirrer for about 10 minutes. Next, the reflux tube was connected to a cooling device, and polymerization was carried out for 24 hours under reflux using an oil bath set at 60°C.

The solution after polymerization was transferred to an eggplant flask and treated with an evaporator at 60°C for 30 minutes or longer to remove 1,4-dioxane from the solution. Next, THF was added to the eggplant flask to dissolve the white solid. Next, using a dropper, the resulting solution was dropped drop by drop into hexane cooled to -10°C while stirring to obtain a precipitate. A prepolymer (poly(DMAAm-co-NSA)) was obtained by treating the precipitate in a constant temperature bath at 30° C. under a vacuum atmosphere for 24 hours.

[Preparation of Separation Membrane]
First, a 6 wt % hexane solution of silicone resin (YSR3022 manufactured by Momentive Performance Materials) was applied onto the porous support. An ultrafiltration membrane (NTU-3175M manufactured by Nitto Denko Corporation) was used as the porous support. The hexane solution was applied using a spin coater under conditions of 500 rpm and 40 seconds. Next, the obtained coating film was dried at 90° C. for 15 minutes. Thus, a laminate of the porous support and the intermediate layer was obtained. The thickness of the intermediate layer was 2 μm.

Next, silica particles (Aerosil 200) for forming the first network structure, the above prepolymer, diethylene glycol (3-aminopropyl) ether as a cross-linking agent for the prepolymer, 1-ethyl-3- as an ionic liquid Methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]) and ethanol were mixed and stirred at room temperature for 1 minute. Thus, a mixed liquid (gel precursor solution) was obtained.

Next, the obtained gel precursor solution was applied onto the laminate of the porous support and the intermediate layer. The solution was applied using a spin coater under conditions of 2000 rpm and 40 seconds. The resulting coating film was dried in a dryer at 60° C. for 5 minutes. As a result, a first network structure composed of a network of silica particles and a second network structure composed of a crosslinked product of the prepolymer were formed to obtain a separation functional layer. The content of the ionic liquid in the separation functional layer was 80 wt%. The separation functional layer had a thickness of 2 μm. A separation membrane of Comparative Example 1 was obtained by forming a separation functional layer on the laminate of the porous support and the intermediate layer.

(Comparative Examples 2-3 and Examples 1-2)
Separation membranes of Comparative Examples 2 and 3 and Examples 1 and 2 were obtained in the same manner as in Comparative Example 1, except that the type of ionic liquid was changed as shown in Table 1.

(Comparative Example 4)
An attempt was made to produce a separation functional layer in the same manner as in Comparative Example 1, except that 1-butyl-3-methylimidazolium acetate ([BMIM][OAc]) was used as the ionic liquid. However, when [BMIM][OAc] is used, when the gel precursor solution is applied onto the laminate of the porous support and the intermediate layer, the ionic liquid leaks out from the resulting coating film. A separation functional layer could not be formed. It is speculated that the leakage of the ionic liquid from the coating film was caused by insufficient compatibility between the prepolymer and the ionic liquid.

(Comparative Example 5)
A separation membrane of Comparative Example 5 was prepared in the same manner as in Comparative Example 1, except that a coating solution containing polyether block amide (Pebax manufactured by Arkema) was used instead of the gel precursor solution.

[Viscosity of ionic liquid]
The viscosities at 25° C. of the ionic liquids used in Comparative Examples 1-4 and Examples 1-2 were measured. The viscosity was measured using Rheostress RS600 manufactured by Thermo HAAKE under the conditions described above.

[Characteristic evaluation of liquid film]
For the ionic liquid membranes (liquid membranes) used in Comparative Examples 1-4 and Examples 1-2, the permeation rate T0 of carbon dioxide was measured by the following method. First, an ionic liquid was dropped onto a PTFE porous membrane A (Merck Co., Ltd. Omnipore membrane filter, pore size 0.45 μm, thickness 65 μm, PTFE) placed on a PET release liner, followed by vacuum drying at 40°C. Machine dried for 1 hour. As a result, the porous PTFE membrane A was impregnated with the ionic liquid, and the porous PTFE membrane A impregnated with the ionic liquid was obtained. The PTFE porous membrane A impregnated with the ionic liquid was regarded as the ionic liquid membrane. Next, a PET release liner was placed on top of the ionic liquid film and pressed together using a rubber roller. Thereby, the thickness of the film of the ionic liquid was adjusted to be uniform.

Next, a PTFE porous membrane B (Temish NTF1133 manufactured by Nitto Denko Corporation) was set in the metal cell. Furthermore, the ionic liquid membrane (the PTFE porous membrane A impregnated with the ionic liquid) was placed on the PTFE porous membrane B and sealed with an O-ring to prevent leakage. Next, the mixed gas was injected into the metal cell so that the main surface of the PTFE porous membrane A was in contact with the mixed gas. The gas mixture consisted essentially of carbon dioxide and nitrogen. The concentration of carbon dioxide in the mixed gas was 50 vol% under standard conditions. The temperature of the gas mixture injected into the metal cell was 30°C. The pressure of the mixed gas was 0.1 MPa. Into the metal cell, Ar was introduced as a sweep gas at a flow rate of 10 mL/min. As a result, a permeating fluid was obtained from the main surface of the PTFE porous membrane B. The permeation rate T0 of carbon dioxide was calculated based on the obtained composition of the permeated fluid, the weight of the permeated fluid, and the like.

[Characteristics evaluation of separation membrane]
Next, the separation coefficient α of carbon dioxide with respect to nitrogen (CO ₂ /N ₂ ) and the permeation rate T of carbon dioxide were measured for the separation membranes of Examples and Comparative Examples by the following methods. First, the 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 was in contact with the main surface of the separation membrane on the side of the separation functional layer. The gas mixture consisted essentially of carbon dioxide and nitrogen. The concentration of carbon dioxide in the mixed gas was 50 vol% under standard conditions. The gas mixture injected into the metal cell had a temperature of 30° C. and a pressure of 0.1 MPa. Next, the space in the metal cell adjacent to the main surface of the separation membrane on the porous support side was evacuated with a vacuum pump. At this time, the space was decompressed so that the pressure in the space was 0.1 MPa lower than the atmospheric pressure in the measurement environment. As a result, a permeated fluid was obtained from the main surface of the separation membrane on the porous support side. The separation factor α and the carbon dioxide permeation rate T were calculated based on the obtained composition of the permeated fluid, the weight of the permeated fluid, and the like.

[simulation]
Using the separation membranes of Examples and Comparative Examples, a simulation was performed when a membrane separation apparatus was operated. Specifically, the operating conditions of the membrane separation device, the type of separation membrane used in the membrane separation device, the composition of the mixed gas, the composition of the permeating fluid, etc. are determined in advance, and in this case, the mixed gas is used using the membrane separation device. We calculated the membrane area and energy consumption required to separate the Process modeling software Symmetry manufactured by Schlumberger was used for the calculation. In the simulation, it was assumed that 300 t/year of mixed gas consisting of carbon dioxide and nitrogen was treated using two membrane separators arranged in series. The concentration of carbon dioxide in the gas mixture was set at 10 wt% and the concentration of carbon dioxide in the permeate was set at 95 wt%. Carbon dioxide recovery was set at 95%.

Abbreviations in Table 1 are as follows.
[EMIM] [TFSI]: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [EMIM] [C(CN) ₃ ]: 1-ethyl-3-methylimidazolium tricyanometanide [EMIM] [B(CN) ₄ ]: 1-ethyl-3-methylimidazolium tetracyanoborate [BMIM] [C(CN) ₃ ]: 1-butyl-3-methylimidazolium tricyanometanide [EMIM] [BF ₄ ]: 1-ethyl-3-methylimidazolium tetrafluoroborate [BMIM] [OAc]: 1-butyl-3-methylimidazolium acetate

As can be seen from Table 1, the separation membranes of Examples containing an ionic liquid having a molecular weight of 220 or more and having a cyano group as an anion have a higher acid gas (carbon dioxide) permeation rate than the separation membranes of Comparative Examples. Improved. Furthermore, as can be seen from the simulation results, the separation membranes of Examples were also suitable for reducing the membrane area required to separate mixed gases.

The separation membrane of the present embodiment is suitable for separating acidic gases from mixed gases containing acidic gases. In particular, the separation membrane of this embodiment is suitable for separating carbon dioxide from off-gases of chemical plants or thermal power plants.

Claims

A separation membrane containing an ionic liquid,
The ionic liquid has a molecular weight of 220 or more,
A separation membrane, wherein the anion contained in the ionic liquid has a cyano group.
The separation membrane according to claim 1, wherein the ionic liquid has a viscosity of 50 mPa·s or less at 25°C.
The separation membrane according to claim 1 or 2, wherein the anion includes at least one selected from the group consisting of tetracyanoborate and tricyanometanide.
The separation membrane according to any one of claims 1 to 3, wherein the ionic liquid contains imidazolium ions.
Any one of claims 1 to 4, wherein the ionic liquid contains at least one selected from the group consisting of 1-ethyl-3-methylimidazolium tetracyanoborate and 1-butyl-3-methylimidazolium tricyanometanide. or the separation membrane according to item 1.
The separation membrane according to any one of claims 1 to 5, which has a double network gel containing the ionic liquid.
The separation membrane according to claim 6, wherein the double network gel further includes a first network structure mainly composed of an inorganic material and a second network structure mainly composed of an organic material.
The separation membrane according to claim 7, wherein the inorganic material contains inorganic particles.
The separation membrane according to claim 7 or 8, wherein the organic material includes a prepolymer crosslinked product.
The separation membrane according to claim 9, wherein the prepolymer contains a (meth)acrylic polymer.
The separation membrane according to any one of claims 1 to 10, comprising a separation functional layer containing the ionic liquid and a porous support supporting the separation functional layer.
The separation membrane according to claim 11, further comprising an intermediate layer arranged between the separation functional layer and the porous support.
The separation membrane according to claim 11 or 12, wherein the content of the ionic liquid in the separation functional layer is 80 wt% or more.
A gas mixture containing carbon dioxide and nitrogen is supplied to the space adjacent to one side of the separation membrane, and when the pressure in the space adjacent to the other side of the separation membrane is reduced, the carbon dioxide permeates the separation membrane. The separation membrane according to any one of claims 1 to 13, which has a carbon permeation rate of 480 GPU or more.
Here, the concentration of carbon dioxide in the mixed gas is 50 vol % in the 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 0.5. 1 MPa, and the space adjacent to the other surface is decompressed so that the pressure in the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment.
The separation membrane according to any one of claims 1 to 14, which is used for separating carbon dioxide from a mixed gas containing carbon dioxide and nitrogen.