Separation membrane and method for producing same

Abstract

The present invention provides a separation membrane comprising an intermediate layer that is suitable for improving the permeation rate for acid gas while suppressing deterioration of the separation performance for acid gas. A separation membrane 10 according to the present invention comprises: a separation function layer 1; a porous support body 3 that supports the separation function layer 1; and an intermediate layer 2 that is disposed between the separation function layer 1 and the porous support body 3 and formed from an emulsion resin composition containing emulsion particles. The thickness of the intermediate layer 2 is 500 nm or less. In the emulsion resin composition, the mode diameter of the emulsion particles is 2,000 nm or greater.

Description

Separation membrane and method for producing the same

[0001] The present invention relates to a separation membrane and a method for producing the same.

[0002] Membrane separation has been developed as a method for separating acidic gases such as carbon dioxide from mixed gases. Compared to absorption methods, which separate acidic gases contained in mixed gases by absorbing them into an absorbent, membrane separation methods can efficiently separate acidic gases while reducing operating costs.

[0003] Separation membranes used in membrane separation methods include composite membranes in which a separation functional layer is formed on a porous support. In the field of separation membranes, an intermediate layer is sometimes disposed between the separation functional layer and the porous support in order to reduce the thickness of the separation functional layer (e.g., Patent Documents 1 and 2).

[0004] Japanese Patent No. 6186286 Japanese Patent Application Laid-Open No. 2019-209274

[0005] It is expected that if the intermediate layer in a separation membrane can be formed thinly, the permeation rate of acidic gases passing through the separation membrane will increase. However, when an attempt is made to form a thin intermediate layer, defects tend to occur in the intermediate layer, which in turn tends to reduce the separation performance of the separation membrane against acidic gases.

[0006] Therefore, an object of the present invention is to provide a separation membrane having an intermediate layer suitable for improving the permeation rate of acidic gases while suppressing a decrease in separation performance for acidic gases.

[0007] The present inventors have newly discovered that when an attempt is made to prepare a thin intermediate layer using an emulsion resin composition in which the emulsion particles have a large mode diameter, the emulsion particles tend to be crushed in the thickness direction of the intermediate layer and elongated in the plane direction of the intermediate layer. Based on this finding, the present inventors have further investigated and discovered that by appropriately adjusting the mode diameter of the emulsion particles, it is possible to form a thin intermediate layer while suppressing the occurrence of defects, thereby completing the present invention.

[0008] The present invention provides a separation membrane comprising: a separation functional layer; a porous support supporting the separation functional layer; and an intermediate layer disposed between the separation functional layer and the porous support and formed from an emulsion resin composition containing emulsion particles, wherein the thickness of the intermediate layer is 500 nm or less, and in the emulsion resin composition, the mode diameter of the emulsion particles is 2000 nm or more.

[0009] The present invention further provides a method for producing a separation membrane comprising a separation functional layer, a porous support supporting the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support, the method comprising: applying an emulsion resin composition containing emulsion particles onto the porous support to form a coating film; and drying the coating film to form the intermediate layer having a thickness of 500 nm or less, wherein the emulsion particles in the emulsion resin composition have a mode diameter of 2000 nm or more.

[0010] Furthermore, the present invention provides a laminate comprising a separation functional layer, a porous support supporting the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support, wherein when carbon dioxide at a pressure of 0.1 MPa is supplied to a space adjacent to one surface of a laminate constituted only by the porous support and the intermediate layer, the permeation rate T of carbon dioxide that permeates the laminate is CO2 is 4500 GPU or more, and the separation coefficient α of carbon dioxide relative to nitrogen of the laminate CO2 / N2 The separation membrane has a separation factor α of 1.4 or more. CO2 / N2 is the permeation rate T of nitrogen that permeates the laminate when nitrogen is supplied to the space at a pressure of 0.1 MPa. N2 The permeation rate T CO2 (GPU) ratio T CO2 / T N2 means.

[0011] According to the present invention, it is possible to provide a separation membrane having an intermediate layer suitable for improving the permeation rate of acidic gases while suppressing a decrease in separation performance for acidic gases.

[0012] It is a cross-sectional view showing a separation membrane according to one embodiment of the present invention, a schematic cross-sectional view of a membrane separation device provided with the separation membrane of the present invention, and a perspective view showing a modified example of a membrane separation device provided with the separation membrane of the present invention.

[0013] A separation membrane according to a first aspect of the present invention comprises a separation functional layer, a porous support supporting the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support and formed from an emulsion resin composition containing emulsion particles, wherein the thickness of the intermediate layer is 500 nm or less, and the emulsion particles in the emulsion resin composition have a mode diameter of 2000 nm or more.

[0014] In a second aspect of the present invention, for example, in the separation membrane according to the first aspect, the ratio of the mode diameter (nm) to the thickness (nm) of the intermediate layer is 10 or more.

[0015] In a third aspect of the present invention, for example, in the separation membrane according to the first or second aspect, the porous support has a surface facing the intermediate layer and including a plurality of openings, and the mode diameter is larger than the maximum diameter of the plurality of openings.

[0016] In a fourth aspect of the present invention, for example, in the separation membrane according to any one of the first to third aspects, the emulsion particles contain a silicone-based polymer.

[0017] In a fifth aspect of the present invention, for example, in the separation membrane according to any one of the first to fourth aspects, the content of the emulsion particles in the emulsion resin composition is 20 wt % or less.

[0018] In a sixth aspect of the present invention, for example, in the separation membrane according to any one of the first to fifth aspects, the emulsion resin composition contains water as a dispersion medium.

[0019] In a seventh aspect of the present invention, for example, in the separation membrane according to any one of the first to sixth aspects, the emulsion resin composition contains a surfactant.

[0020] In an eighth aspect of the present invention, for example, in the separation membrane according to any one of the first to seventh aspects, the emulsion resin composition has a surface tension of 40 mN / m or less.

[0021] In a ninth aspect of the present invention, for example, the separation membrane according to any one of the first to eighth aspects is used to separate an acidic gas from a mixed gas containing the acidic gas.

[0022] A tenth aspect of the present invention provides a method for manufacturing a separation membrane comprising a separation functional layer, a porous support supporting the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support, the method comprising: applying an emulsion resin composition containing emulsion particles onto the porous support to form a coating film; and drying the coating film to form the intermediate layer having a thickness of 500 nm or less, wherein the emulsion particles in the emulsion resin composition have a mode diameter of 2000 nm or more.

[0023] A separation membrane according to an eleventh aspect of the present invention comprises a separation functional layer, a porous support supporting the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support, wherein when carbon dioxide at a pressure of 0.1 MPa is supplied to a space adjacent to one surface of a laminate constituted only by the porous support and the intermediate layer, the carbon dioxide permeates the laminate at a permeation rate T CO2 is 4500 GPU or more, and the separation coefficient α of carbon dioxide relative to nitrogen of the laminate CO2 / N2 is 1.4 or more. CO2 / N2 is the permeation rate T of nitrogen that permeates the laminate when nitrogen is supplied to the space at a pressure of 0.1 MPa. N2 The permeation rate T CO2 (GPU) ratio T CO2 / T N2 means.

[0024] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0025] <Embodiment of Separation Membrane> As shown in Figure 1, a separation membrane 10 of this embodiment includes a separation function layer 1, an intermediate layer 2, and a porous support 3. The intermediate layer 2 is disposed between the separation function layer 1 and the porous support 3, and is in direct contact with both the separation function layer 1 and the porous support 3. The intermediate layer 2 is formed from an emulsion resin composition containing emulsion particles. In this specification, the emulsion resin composition refers to a resin composition containing a dispersion medium and emulsion particles dispersed in the dispersion medium. The emulsion particles refer to particles containing a polymer emulsified in the dispersion medium.

[0026] In this embodiment, the thickness of the intermediate layer 2 is 500 nm or less. This intermediate layer 2 is suitable for improving the permeation rate of acidic gases through the separation membrane 10. The thickness of the intermediate layer 2 is preferably 450 nm or less, and may be 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less, 200 nm or less, or even 150 nm or less. The lower limit of the thickness of the intermediate layer 2 is, for example, 50 nm or more, and may be 100 nm or more.

[0027] The thickness of the intermediate layer 2 can be determined by the following method. First, elemental analysis is performed on the intermediate layer 2 to determine the weight m (g / m) of a specific element per unit area of ​​the main surface of the intermediate layer 2. 2 ) is identified. For example, an X-ray fluorescence (XRF) analysis can be used as the elemental analysis. Next, from the weight m, the weight M (g / m) of the material of the intermediate layer 2 per unit area of ​​the main surface of the intermediate layer 2 is determined. 2 From the weight M, the density (g / m 3 ) and convert the unit to calculate the thickness of the intermediate layer 2. The density (true density) of the material of the intermediate layer 2 can be determined, for example, in accordance with the balance method defined in Japanese Industrial Standards (JIS) K0061:2001.

[0028] For example, when the material of the intermediate layer 2 is polydimethylsiloxane (PDMS), the thickness of the intermediate layer 2 can be determined by the following method. First, the weight m of silicon (Si) per unit area of ​​the main surface of the intermediate layer 2 is determined by elemental analysis. Si (g / m 2) to determine the weight m Si Based on the atomic weight of silicon (28.09) and the molecular weight per one PDMS structural unit (composition formula: C2H6OSi) (74.15), the weight M of PDMS per unit area of ​​the main surface of the intermediate layer 2 was calculated by the following formula: PDMS (g / m 2 ) is calculated. PDMS (g / m 2 )=weight m Si (g / m 2 ) x 74.15 / 28.09

[0029] Next, the weight M of PDMS per unit area of ​​the main surface of the intermediate layer 2 PDMS (g / m 2 ), and the density of PDMS (980000 g / m 3 ) the thickness of the intermediate layer 2 can be calculated by the following formula: Thickness of the intermediate layer 2 (μm) = Weight M PDMS (g / m 2 ) / 980000(g / m 3 ) x 10 6

[0030] Furthermore, in this embodiment, the emulsion resin composition has a mode diameter of the emulsion particles of 2000 nm or more. When an intermediate layer 2 is produced from this emulsion resin composition, the emulsion particles tend to be crushed in the thickness direction of the intermediate layer 2 and elongated in the plane direction of the intermediate layer 2. Stretching the emulsion particles in the plane direction inhibits the emulsion particles from penetrating into the porous support 3, and also reduces the occurrence of unevenness in the thickness of the intermediate layer 2. As a result, in this embodiment, defects such as pinholes and chips tend to be less likely to occur in the intermediate layer 2. With an intermediate layer 2 in which the occurrence of defects is suppressed, adjusting its thickness to 500 nm or less tends to improve the permeation rate of acidic gases while suppressing a decrease in the separation performance of the separation membrane 10 for acidic gases.

[0031] In the emulsion resin composition, the mode diameter of the emulsion particles is preferably 3,000 nm or more, and may be 4,000 nm or more, 5,000 nm or more, 8,000 nm or more, 10,000 nm or more, 13,000 nm or more, 15,000 nm or more, 18,000 nm or more, or even 20,000 nm or more. The upper limit of the mode diameter is not particularly limited as long as the thickness of the intermediate layer 2 can be adjusted to 500 nm or less, and may be, for example, 100,000 nm or less, or 50,000 nm or less.

[0032] According to the studies of the present inventors, when the emulsion particles contain a silicone-based polymer, the emulsion particles tend to be crushed in the thickness direction of the intermediate layer 2 when the intermediate layer 2 is prepared from the emulsion resin composition. Therefore, when the emulsion particles contain a silicone-based polymer, the mode diameter of the emulsion particles does not necessarily need to be 2000 nm or more and may be less than 2000 nm. In this case, the mode diameter of the emulsion particles in the emulsion resin composition may be, for example, 200 nm or more, 250 nm or more, 300 nm or more, 500 nm or more, 800 nm or more, 1000 nm or more, 1200 nm or more, 1500 nm or more, or even 1800 nm or more.

[0033] In another aspect, the present invention provides a separation membrane (10) comprising: a separation functional layer (1); a porous support (3) supporting the separation functional layer (1); and an intermediate layer (2) disposed between the separation functional layer (1) and the porous support (3) and formed from an emulsion resin composition containing emulsion particles, wherein the thickness of the intermediate layer (2) is 500 nm or less, and in the emulsion resin composition, the emulsion particles contain a silicone-based polymer and have a mode diameter of 200 nm or more.

[0034] The mode diameter of emulsion particles in an emulsion resin composition can be determined by the following method. First, the particle size distribution of the emulsion resin composition is measured using a particle size distribution analyzer based on the laser diffraction / scattering method. Specifically, the particle size distribution can be measured using a laser diffraction / scattering particle size analyzer (e.g., the MT3300EXII manufactured by Microtrac) in accordance with the provisions of ISO 13320:2009 "Particle Size Analysis - Laser Diffraction Method." When the emulsion resin composition contains particles other than emulsion particles, it is preferable to separately prepare an emulsion resin composition before adding the other particles, or an emulsion resin composition from which the other particles have been removed, and measure the particle size distribution. The particle diameter with the highest frequency of occurrence (mode) in the obtained particle size distribution can be determined as the mode diameter. It is preferable that the particle size distribution exhibits a single unimodal peak, with the apex of the peak corresponding to the mode. However, the particle size distribution may also exhibit multiple peaks or multimodal peaks.

[0035] In this embodiment, the ratio R1 of the mode diameter (nm) of the emulsion particles in the emulsion resin composition to the thickness (nm) of the intermediate layer 2 is preferably 10 or more, and may be 30 or more, 50 or more, 80 or more, 100 or more, 130 or more, or even 150 or more. The upper limit of the ratio R1 is, for example, 500 or less, 300 or less, or even 200 or less.

[0036] (Separation Functional Layer) The separation functional layer 1 is, for example, a layer that allows preferential permeation of acidic gases contained in a mixed gas. In a preferred embodiment, the separation functional layer 1 contains a resin. Examples of resins contained in the separation functional layer 1 include (meth)acrylic resins, polyether block amide resins, polyamide resins, polyether resins, polyimide resins, cellulose acetate resins, silicone resins, and fluororesins. The separation functional layer 1 preferably contains a polyether block amide resin. In this embodiment, the separation functional layer 1 preferably consists essentially of a resin. In this specification, "consisting essentially of" means excluding other components that alter the essential characteristics of the referenced material, and means, for example, that 95 wt% or more, or even 99 wt% or more of the material is composed of the material. However, the separation functional layer 1 may further contain additives such as a leveling agent in addition to the resin.

[0037] In another preferred embodiment, the separation functional layer 1 contains an ionic liquid. Ionic liquids are salts (ionic compounds) that are liquid at 25°C. The separation functional layer 1 has, for example, a double-network gel containing an ionic liquid. The double-network gel is a gel having two types of network structures that are independent of each other. The double-network gel includes, for example, a first network structure mainly composed of organic materials, a second network structure mainly composed of inorganic materials, and an ionic liquid. In this specification, "mainly composed" means that 50 wt% or more, or even 70 wt% or more, of the material in question is composed.

[0038] The organic material for forming the first network structure includes a polymer such as polyacrylamide (particularly, polydialkylacrylamide such as polydimethylacrylamide). The polymer contained in the organic material has structural units derived from an acrylamide derivative and may further include a crosslinked structure. A polymer including a crosslinked structure can be produced by a known method. For example, first, a prepolymer having a structural unit with an N-hydroxysuccinimide ester group is prepared. The structural unit with an N-hydroxysuccinimide ester group is derived from, for example, N-acryloxysuccinimide. Next, a polymer including a crosslinked structure can be obtained by reacting the prepolymer with an amine-based crosslinking agent. The amine-based crosslinking agent is a compound having two or more primary amino groups, such as ethylene glycol bis(3-aminopropyl) ether.

[0039] The second network structure may include a network of a plurality of particles. The network of a plurality of particles may be formed, for example, by a plurality of particles bonded to each other by hydrogen bonds. The particles included in the second network structure may include an inorganic material or an organic material. Examples of inorganic materials included in the particles include silica, titania, and alumina. In one example, the particles included in the second network structure are silica particles.

[0040] In this embodiment, examples of the ionic liquid include an ionic liquid having imidazolium, pyridinium, ammonium, or phosphonium and a substituent having one or more carbon atoms.

[0041] In the ionic liquid having an imidazolium and a substituent having one or more carbon atoms, examples of the substituent having one or more carbon atoms include an alkyl group having from 1 to 20 carbon atoms, a cycloalkyl group having from 3 to 14 carbon atoms, and an aryl group having from 6 to 20 carbon atoms, which may be further substituted with a hydroxy group, a cyano group, an amino group, a monovalent ether group, or the like (for example, a hydroxyalkyl group having from 1 to 20 carbon atoms).

[0042] Examples of the alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, an n-eicosadecyl group, an Examples of the alkyl group include an alkyl group, an i-propyl group, a sec-butyl group, an i-butyl group, a 1-methylbutyl group, a 1-ethylpropyl group, a 2-methylbutyl group, an i-pentyl group, a neopentyl group, a 1,2-dimethylpropyl group, a 1,1-dimethylpropyl group, a t-pentyl group, a 2-ethylhexyl group, and a 1,5-dimethylhexyl group, which may be further substituted with a hydroxy group, a cyano group, an amino group, a monovalent ether group, or the like.

[0043] The alkyl group may be substituted with a cycloalkyl group. The number of carbon atoms in the alkyl group substituted with a cycloalkyl group is, for example, 1 or more and 20 or less. Examples of the alkyl group substituted with a cycloalkyl group include a cyclopropylmethyl group, a cyclobutylmethyl group, a cyclohexylmethyl group, and a cyclohexylpropyl group, which may be further substituted with a hydroxy group, a cyano group, an amino group, a monovalent ether group, or the like.

[0044] Examples of the cycloalkyl group having from 3 to 14 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclododecyl group, a norbornyl group, a bornyl group, and an adamantyl group, which may be further substituted with a hydroxy group, a cyano group, an amino group, a monovalent ether group, or the like.

[0045] Examples of the aryl group having 6 to 20 carbon atoms include a phenyl group, a toluyl group, a xylyl group, a mesityl group, an anisyl group, a naphthyl group, and a benzyl group, which may be further substituted with a hydroxy group, a cyano group, an amino group, a monovalent ether group, or the like.

[0046] The imidazolium and the compound having a substituent having one or more carbon atoms may further have a substituent such as an alkyl group, and may form a salt with a counter anion. Examples of the counter anion include alkyl sulfate, tosylate, methanesulfonate, acetate, bis(fluorosulfonyl)imide, bis(trifluoromethanesulfonyl)imide, thiocyanate, dicyanamide, tricyanomethanide, tetracyanoborate, hexafluorophosphate, tetrafluoroborate, and halide. From the viewpoint of gas separation performance, bis(fluorosulfonyl)imide, bis(trifluoromethanesulfonyl)imide, dicyanamide, tricyanomethanide, and tetracyanoborate are preferred.

[0047] Specific examples of the ionic liquid having an imidazolium and a substituent having one or more carbon atoms include 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium tetrachloroferrate, 1-butyl-3-methylimidazolium iodide, 1-butyl-2,3-dimethylimidazolium chloride, 1-butyl-2,3-dimethylimidazolium hexafluorophosphate ...bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium tetrachloroferrate, 1-butyl-3-methylimidazolium iodide, 1-butyl-2,3-dimethylimidazolium chloride, 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium butyl-2,3-dimethylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium trifluoro(trifluoromethyl)borate, 1-butyl-3-methylimidazolium tribromide, 1,3-dimesitylimidazolium chloride, 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride, 1,3-diisopropylimidazolium tetrafluoroborate, 1,3-di-tert-butylimidazolium tetrafluoroborate, 1,3-dicyclohexylimidazolium tetrafluoroborate, 1,3-dicyclohexylimidazolium chloride, 1,2-dimethyl-3-propylimidazolium iodide, 1-hexyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium bromide, 1-methyl-3-propylimidazolium iodide, 1-methyl-3-n-octylimidazolium bromide, 1-methyl-3-n-octylimidazolium Examples of suitable imidazolium compounds include 1-methyl-3-n-octylimidazolium hexafluorophosphate, 1-methyl-3-[6-(methylsulfinyl)hexyl]imidazolium p-toluenesulfonate, 1-ethyl-3-methylimidazolium tricyanomethanide, 1-ethyl-3-methylimidazolium tetracyanoborate, and 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0048] Among these, from the viewpoint of gas separation performance, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ([EMI][FSI]), 1-ethyl-3-methylimidazolium dicyanamide ([EMI][DCA]), 1-ethyl-3-methylimidazolium tricyanomethanide ([EMI][TCM]), 1-ethyl-3-methylimidazolium tetracyanoborate ([EMI][TCB]), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][TF2N]), and 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C2OHim][TF2N]) are particularly preferred.

[0049] The method for producing the double network gel is not particularly limited, and for example, the method disclosed in E. Kamio et al., Adv. Mater, 29, 1704118 (2017) can be used.

[0050] The ionic liquid content in the double network gel is, for example, 50 wt% or more, preferably 60 wt% or more, more preferably 70 wt% or more, and even more preferably 80 wt% or more. The higher the ionic liquid content, the more the separation functional layer 1 can preferentially transmit acidic gases contained in the mixed gas. The upper limit of the ionic liquid content is not particularly limited and is, for example, 95 wt%.

[0051] The content of the first network structure in the double-network gel, which is primarily made of organic material, is, for example, 1 wt% or more, preferably 5 wt% or more, and more preferably 10 wt% or more. The upper limit of the content of the first network structure is, for example, 15 wt%. From the viewpoint of improving the strength of the double-network gel, the content of the second network structure in the double-network gel, which is primarily made of inorganic material, is, for example, 1 wt% or more. The upper limit of the content of the second network structure is, for example, 5 wt%. The ratio of the total weight of the first network structure and the second network structure to the weight of the double-network gel is, for example, 2 wt% or more, preferably 5 wt% or more, and more preferably 10 wt% or more. This ratio is preferably 20 wt% or less. In this embodiment, the separation functional layer 1 preferably consists essentially of a double-network gel.

[0052] The thickness of the separation functional layer 1 is, for example, 50 μm or less, preferably 25 μm or less, and more preferably 15 μm or less. In some cases, 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. The thickness of the separation functional layer 1 may be 0.05 μm or more, or 0.1 μm or more.

[0053] (Intermediate Layer) As described above, in this embodiment, the intermediate layer 2 is formed from an emulsion resin composition containing emulsion particles. The emulsion particles typically contain a polymer emulsified in a dispersion medium, and preferably consist solely of the polymer. Examples of the polymer contained in the emulsion particles include a silicone-based polymer and a hydrophilic polymer. The emulsion particles preferably contain a silicone-based polymer. The emulsion resin composition may contain only one type of emulsion particle, or two or more types of emulsion particles.

[0054] The silicone polymer has, for example, a structural unit A represented by the following formula (1).

[0055] In formula (1), R 1 and R 2 are each independently a hydrogen atom or a hydrocarbon group. The hydrocarbon group may be linear or branched. The number of carbon atoms in the hydrocarbon group is not particularly limited and is, for example, 1 to 5, preferably 1 to 4, and more preferably 1 to 3. The hydrocarbon group is preferably a linear or branched alkyl group. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. The hydrocarbon group may also be an unsaturated hydrocarbon group such as a vinyl group. R 1 and R 2 is preferably a hydrogen atom, a methyl group, an ethyl group or a vinyl group.

[0056] The number of structural units A contained in the silicone polymer is not particularly limited, and is, for example, 100 to 100,000, preferably 200 to 90,000, and more preferably 500 to 80,000.

[0057] The silicone-based polymer contains, for example, structural unit A as a main component, and preferably consists essentially of structural unit A. In this specification, "main component" refers to the structural unit that is contained in the largest amount by weight of all the structural units that make up the silicone-based polymer. However, the silicone-based polymer may further contain structural units other than structural unit A.

[0058] A specific example of the silicone polymer is dimethylpolysiloxane. The silicone polymer may be a cyclic siloxane represented by the following formula (2):

[0059] In formula (2), R 1 and R 2 is the same as in formula (1). n is not particularly limited and is, for example, 100 to 100,000, preferably 200 to 90,000, and more preferably 500 to 80,000.

[0060] The weight average molecular weight of the silicone polymer is not particularly limited, and may be, for example, 1×10 4 ~1 x 10 6 is.

[0061] As used herein, the term "hydrophilic polymer" refers to a polymer having a contact angle with water of 100° or less, preferably 90° or less, and more preferably 85.2° or less. The contact angle with water can be evaluated by the sessile drop method defined in Japanese Industrial Standards (JIS) R3257:1999 using a sheet made of the polymer to be evaluated. The lower limit of the contact angle with water of the hydrophilic polymer is not particularly limited, but may be, for example, 30°, 50°, or 74.0°.

[0062] Examples of hydrophilic polymers include urethane-based polymers, (meth)acrylic-based polymers, (meth)acrylic urethane-based polymers, ester-based polymers, and vinyl ester-based polymers.

[0063] Examples of urethane-based polymers include polyurethanes obtained by reacting polyols with polyisocyanates, and modified products thereof. The urethane-based polymer may be a urethane prepolymer having an isocyanate group or a blocked isocyanate group at its terminal.

[0064] Examples of polyols include polyether polyols such as polyethylene glycol, polypropylene glycol, and polyoxytetramethylene ether glycol obtained by ring-opening polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, etc.; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, octanediol, 1,4-butynediol, dipropylene glycol, bisphenol A, and bisphenol A with propylene oxide. Examples of suitable low molecular weight glycols include saturated or unsaturated low molecular weight glycols such as bisphenol A ethylene oxide adducts, hydrogenated bisphenol A, and the like; polyester polyols obtained by dehydration condensation of such low molecular weight glycols with dibasic acids such as adipic acid, maleic acid, fumaric acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, and suberic acid, or the corresponding acid anhydrides; polyester polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone and β-methyl-δ-valerolactone; and polymeric polyols commonly used in the production of polyurethanes, such as polycarbonate polyols and polybutadiene glycols. Instead of the low molecular weight glycols, various polyols such as glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, pentaerythritol, and sorbitol can also be used. From the viewpoint of dispersibility in the emulsion resin composition, the polyol is preferably one having a hydrophilic portion such as an ethylene oxide adduct.

[0065] The polyisocyanate may be an aromatic, aliphatic, or alicyclic diisocyanate, such as 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, or methylene diisocyanate. cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and dimer diisocyanate in which the carboxyl group of a dimer acid is converted into an isocyanate group.

[0066] Examples of blocking agents for isocyanate groups include bisulfites and sulfonic acid group-containing phenols, alcohols, lactams, oximes, and active methylene compounds.

[0067] To improve dispersibility in the emulsion resin composition, a hydrophilic group such as a carboxylate may be introduced into the urethane polymer.

[0068] The (meth)acrylic polymer has, for example, a structural unit derived from alkyl(meth)acrylate as a main component. In this specification, "(meth)acrylate" means acrylate and / or methacrylate.

[0069] The alkyl group contained in the alkyl (meth)acrylate is not particularly limited, and may be, for example, a linear, branched, or cyclic alkyl group having 2 to 14 carbon atoms.

[0070] Examples of alkyl (meth)acrylates include alkyl acrylates having an alkyl group containing 2 to 14 carbon atoms, preferably alkyl acrylates having an alkyl group containing 4 to 9 carbon atoms. Examples of alkyl acrylates include n-butyl acrylate, isobutyl acrylate, s-butyl acrylate, isoamyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, nonyl acrylate, and isononyl acrylate.

[0071] The alkyl (meth)acrylate may be, for example, an alkyl methacrylate ester having an alkyl group having 2 to 14 carbon atoms, preferably an alkyl methacrylate ester having an alkyl group having 2 to 10 carbon atoms. Examples of alkyl methacrylate esters include ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, bornyl methacrylate, and isobornyl methacrylate.

[0072] The alkyl (meth)acrylate may be one of the above-mentioned alkyl (meth)acrylates or a combination of two or more of them. The content of the alkyl (meth)acrylate-derived structural unit in the (meth)acrylic polymer is not particularly limited, and is, for example, 70 to 100 wt %, preferably 85 to 99 wt %, and more preferably 87 to 99 wt %.

[0073] The (meth)acrylic polymer may further contain a structural unit derived from a copolymerizable monomer copolymerizable with alkyl (meth)acrylate. Examples of copolymerizable monomers include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; alkyl (meth)acrylates having an alkyl group having 1 or 15 or more carbon atoms; (meth)acrylic acid aryl esters such as phenyl (meth)acrylate; vinyl esters such as vinyl acetate and vinyl propionate; styrene-based monomers such as styrene; epoxy group-containing monomers such as glycidyl (meth)acrylate and methylglycidyl (meth)acrylate; hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (meth)acrylamide, and N-methylolpropane (meth)acryl nitrogen atom-containing monomers such as amides, (meth)acryloylmorpholine, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; functional monomers such as 2-methacryloyloxyethyl isocyanate; olefin-based monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; vinyl ether-based monomers such as vinyl ether; halogen atom-containing monomers such as vinyl chloride; vinyl group-containing heterocyclic compounds such as N-vinylpyrrolidone, N-(1-methylvinyl)pyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, and N-vinylmorpholine; N-vinylcarboxylic acid amides;Maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide; N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide succinimide monomers such as N-(meth)acryloyl-8-oxyoctamethylene succinimide; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; phosphoric acid group-containing monomers; polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methacrylic acid glycol-based acrylic ester monomers such as methoxyethylene glycol and methoxypolypropylene glycol (meth)acrylate; acrylic ester monomers containing a heterocycle or a halogen atom such as tetrahydrofurfuryl (meth)acrylate and fluorine (meth)acrylate; (mono- or poly)alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetraethylene glycol di(meth)acrylate, and propylene glycol di(meth)acrylate; esters of (meth)acrylic acid and polyhydric alcohols such as neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; polyfunctional vinyl compounds such as divinylbenzene;Examples of the compound include compounds having a reactive unsaturated double bond, such as allyl (meth)acrylate and vinyl (meth)acrylate;

[0074] Examples of (meth)acrylic urethane-based polymers include reaction products of (meth)acrylic polyols and polyisocyanates. Examples of (meth)acrylic polyols include (meth)acrylic polymers containing structural units derived from hydroxyl group-containing (meth)acrylates. Examples of hydroxyl group-containing (meth)acrylates include those described above for (meth)acrylic polymers. Examples of polyisocyanates include those described above for urethane-based polymers. The polyisocyanates may be urethane prepolymers having isocyanate groups.

[0075] Examples of the ester polymer include those obtained by polycondensation of dicarboxylic acids and diols. Examples of dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, 2-methylterephthalic acid, 5-sulfoisophthalic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalene. Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as dicarboxylic acid; alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanoic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, and fumaric acid; and derivatives thereof (for example, lower alkyl esters of dicarboxylic acids). These can be used alone or in combination of two or more.

[0076] Examples of diols include aliphatic diols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, and polyoxytetramethylene glycol; alicyclic diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, and 1,4-cyclohexanedimethylol; and aromatic diols such as xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone. These may be used alone or in combination of two or more.

[0077] Vinyl ester polymers have, for example, structural units derived from vinyl esters. Examples of vinyl esters include vinyl acetate and vinyl propionate. Vinyl ester polymers may further have structural units derived from olefins such as ethylene and propylene. A specific example of a vinyl ester polymer is an ethylene-vinyl acetate copolymer.

[0078] The weight average molecular weight of the hydrophilic polymer is not particularly limited, and may be, for example, 1×10 4 ~1 x 10 7 is.

[0079] The emulsion particle content in the emulsion resin composition is, for example, 20 wt % or less, and may be 15 wt % or less, 10 wt % or less, 8 wt % or less, or even 5 wt % or less. The lower the emulsion particle content, the easier it is to adjust the thickness of the intermediate layer 2 to a smaller value. The lower limit of the emulsion particle content is not particularly limited, and is, for example, 1 wt % or more.

[0080] The emulsion resin composition preferably further contains a surfactant. Examples of the surfactant include a surfactant for dispersing emulsion particles (e.g., an emulsifier) ​​and other surfactants (e.g., a surface conditioner) other than the surfactant. Examples of the surfactant for dispersing emulsion particles include anionic surfactants such as alkyl sulfates, alkylbenzene sulfonates, and alkyl phosphates; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, and polyoxyethylene fatty acid esters; cationic surfactants such as quaternary ammonium salts and alkylamine acetates; and amphoteric surfactants such as alkyl betaines and alkyl imidazolines. In particular, from the viewpoint of dispersion stability of the emulsion particles, it is preferable to use nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers. Specific examples of these nonionic surfactants include polyoxyethylene octyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, and polyoxyethylene styrenated phenyl ether.

[0081] Other surfactants include, for example, silicone surfactants. Silicon surfactants include, for example, modified polysiloxanes having hydrophilic groups. Examples of hydrophilic groups include hydroxyl groups, carboxylic acid groups, sulfonic acid groups, (meth)acrylic groups, ester groups, and ether groups. Specific examples of the modifying groups of modified polysiloxanes include -(CH2CHO) n -R (n is an integer of 5 to 30, R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), -(CHCHOHCH) n—H (n is an integer of 5 to 30). Specific examples of modified polysiloxanes include polyether-modified polydimethylsiloxanes. Commercially available silicone surfactants include the "BYK" series manufactured by BYK Japan, the "Toray Silicone" series manufactured by Dow Corning Toray, the "TSF" series manufactured by Momentive Performance Materials, and the "KP" and "KF" series manufactured by Shin-Etsu Silicones. An example of the "BYK" series manufactured by BYK Japan is BYK-349. BYK-349 tends to suppress a decrease in the permeation rate of acidic gases passing through the intermediate layer 2. BYK-349 has high dispersibility in water and is suitable for emulsion resin compositions containing water as a dispersion medium.

[0082] In addition to the surfactants mentioned above, other surfactants include nonionic surfactants such as the "Noigen LF-X" series manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and surfactants such as the "Olfine" series and "Silface" series manufactured by Nissin Chemical Industry Co., Ltd. An example of the "Noigen LF-X" series is Noigen LF-40X.

[0083] The additional surfactant can improve the wettability of the emulsion resin composition to, for example, a metal roll of a coater such as a gravure coater, depending on the type of surfactant. Therefore, when the emulsion resin composition contains the additional surfactant, the emulsion resin composition tends to be uniformly applied using a coater equipped with a metal roll. Uniform application of the emulsion resin composition tends to reduce variations in the thickness of the intermediate layer 2 formed from the emulsion resin composition.

[0084] The content of the surfactant in the emulsion resin composition is not particularly limited and is, for example, 0.01 wt % to 10 wt %. When the emulsion resin composition contains a surfactant, the weight ratio of the surfactant to the weight of all solids in the emulsion resin composition is not particularly limited and is, for example, 15 wt % or less, or may be 5 wt % or less, or may be 1 wt % or less. If the weight ratio of the surfactant is 15 wt % or less, for example, when the emulsion resin composition is applied onto a porous support 3, the emulsion resin composition can be sufficiently prevented from penetrating into the porous support 3.

[0085] The emulsion resin composition typically contains a dispersion medium. The emulsion resin composition preferably contains water as the dispersion medium. That is, the emulsion resin composition is preferably an oil-in-water (O / W) emulsion. The emulsion resin composition may contain an organic solvent as the dispersion medium instead of water or in addition to water. Examples of the organic solvent contained in the emulsion resin composition include 2-ethylhexanol, butyl cellosolve, dipropylene glycol, ethylene glycol, propylene glycol, normal propyl alcohol, and isopropanol. From the viewpoint of dispersibility of the polymer in the emulsion resin composition, ethylene glycol and propylene glycol are preferred.

[0086] The content of the dispersion medium in the emulsion resin composition is not particularly limited, and may be, for example, 50 wt % or more, 80 wt % or more, or even 90 wt % or more. The upper limit of the content of the dispersion medium is, for example, 99 wt % or less, or may be 95 wt % or less.

[0087] The emulsion resin composition may further contain other additives in addition to the emulsion particles, surfactant, and dispersion medium, such as particles other than the emulsion particles (filler), a crosslinking agent, etc.

[0088] When the intermediate layer 2 is formed from an emulsion resin composition containing other particles, the permeation rate of the acidic gas passing through the intermediate layer 2 tends to be further improved. The other particles are not particularly limited as long as they do not contain a polymer emulsified in a dispersion medium. The other particles may contain an inorganic material or an organic material. Examples of inorganic materials include zeolite and silica. The other particles preferably have hydrophilicity and high dispersibility in water.

[0089] The average particle diameter of the other particles is preferably smaller than the thickness of the intermediate layer 2 formed from the emulsion resin composition. The average particle diameter of the other particles is, for example, 150 nm or less, and may be 100 nm or less, or 50 nm or less. The lower limit of the average particle diameter of the other particles is not particularly limited, and is, for example, 1 nm or more. In this specification, the average particle diameter refers to the median diameter determined from the particle size distribution measured with a particle size distribution measuring device based on a laser diffraction / scattering method.

[0090] The other particles may have pores. The average pore size of the other particles is not particularly limited and is, for example, 0.1 nm to 5 nm. The density of the other particles is not particularly limited and is, for example, 0.5 to 5 g / cm. 3 is.

[0091] Specific examples of other particles include the "Zeoal" series manufactured by Nakamura Choukou Co., Ltd. and the "AEROSIL" series manufactured by Nippon Aerosil Co., Ltd. Examples of the "Zeoal" series manufactured by Nakamura Choukou Co., Ltd. include Zeoal 4A 50nm and Zeoal ZSM-5. These fillers contain zeolite. Examples of the "AEROSIL" series manufactured by Nippon Aerosil Co., Ltd. include AEROSILOX 50. This filler contains silica. Zeoal 4A 50nm and AEROSILOX 50 tend to be more hydrophilic and more dispersible in water than Zeoal ZSM-5.

[0092] The crosslinking agent is used, for example, to crosslink the polymer contained in the emulsion particles. The crosslinking agent may also be a water-insoluble crosslinking agent for crosslinking a polymer containing a carboxyl group. The water-insoluble crosslinking agent is, for example, a water-insoluble compound having two or more (e.g., 2 to 6, preferably 3 to 5) functional groups reactive with a carboxyl group. In this specification, water-insoluble means that the weight of the compound soluble in 100 parts by weight of water at 25°C is 5 parts by weight or less, preferably 3 parts by mass or less, and more preferably 2 parts by mass or less. The weight of the water-soluble compound can be measured by the following method. First, equal weights of water (25°C) and the compound are mixed and stirred using a mixer at 300 rpm for 10 minutes. The resulting mixture is separated into an aqueous phase and an oil phase by centrifugation. Next, the aqueous phase is removed and dried at 120°C for 1 hour. The weight of the non-volatile components in the aqueous phase (the weight of the compound soluble in 100 parts by weight of water) is calculated from the loss on drying.

[0093] The functional group capable of reacting with a carboxyl group is not particularly limited, and examples thereof include an epoxy group, an isocyanate group, a carbodiimide group, and the like. From the viewpoint of reactivity, an epoxy group is preferred. In particular, a glycidylamino group is preferred from the viewpoint of low contamination, since it has high reactivity and therefore is less likely to leave unreacted material in the crosslinking reaction. That is, as the non-water-soluble crosslinking agent, an epoxy-based crosslinking agent having an epoxy group is preferred, and a crosslinking agent having a glycidylamino group (a glycidylamino-based crosslinking agent) is particularly preferred.

[0094] Examples of water-insoluble crosslinking agents include glycidylamino-based crosslinking agents such as 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (e.g., trade name "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc.) and 1,3-bis(N,N-diglycidylaminomethyl)benzene (e.g., trade name "TETRAD-X" manufactured by Mitsubishi Gas Chemical Company, Inc.); and other epoxy-based crosslinking agents such as Tris(2,3-epoxypropyl)isocyanurate (e.g., trade name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.).

[0095] The content of other additives in the emulsion resin composition is not particularly limited and is, for example, 0.01 wt % to 10 wt %. The emulsion resin composition may not contain other additives.

[0096] The solid content concentration in the emulsion resin composition is not particularly limited, and is, for example, 1 to 40 wt %.

[0097] The emulsion resin composition can be prepared, for example, by the following method. First, a dispersion (emulsion) containing emulsion particles is prepared. This dispersion may be a polymerization liquid obtained by synthesizing a polymer by emulsion polymerization, or may be a dispersion obtained by dispersing a polymer synthesized by a method other than emulsion polymerization in a dispersion medium. Next, an emulsion resin composition can be prepared by adding additives to this dispersion and mixing it, as necessary. A slurry containing additives (e.g., other particles) and a dispersion medium (e.g., water) may be added to the dispersion. Note that when the emulsion particles contain a silicone-based polymer, the emulsion resin composition can be prepared using the method disclosed in JP 2004-339283 A, etc.

[0098] In this embodiment, the surface tension of the emulsion resin composition is preferably 40 mN / m or less. In this case, the emulsion resin composition tends to be easily applied to the porous support 3. The surface tension of the emulsion resin composition may be 35 mN / m or less. The lower limit of the surface tension is not particularly limited, and may be, for example, 10 mN / m or more, 20 mN / m or more, or even 30 mN / m or more. The surface tension of the emulsion resin composition can be measured by the du Nouy method (ring method).

[0099] As described below, the intermediate layer 2 can be produced, for example, by removing the dispersion medium from the emulsion resin composition. Therefore, the intermediate layer 2 contains a component derived from the emulsion resin composition. As an example, the intermediate layer 2 contains a polymer derived from the emulsion particles. This polymer may be a crosslinked polymer in which the polymer contained in the emulsion particles is crosslinked with a crosslinking agent, or may be the polymer contained in the emulsion particles itself.

[0100] The content of the polymer (particularly the silicone-based polymer) in the intermediate layer 2 is not particularly limited and is, for example, 10 wt % or more, preferably 30 wt % or more, more preferably 50 wt % or more, even more preferably 70 wt % or more, particularly preferably 80 wt % or more, may be 90 wt % or more, may be 95 wt % or more, or may be 99 wt % or more. The intermediate layer 2 may be composed essentially of polymer only. The higher the polymer content in the intermediate layer 2, the higher the permeation rate of the permeating fluid through the separation membrane 10 tends to be.

[0101] The intermediate layer 2 may further contain other components in addition to the polymer. Examples of other components include a surfactant derived from the emulsion resin composition and particles other than emulsion particles. For example, when the intermediate layer 2 contains other particles, the particles are embedded in a matrix containing the polymer, and preferably dispersed in the matrix. In the intermediate layer 2, the other particles may be partially aggregated.

[0102] The surfactant content in the intermediate layer 2 is not particularly limited and may be, for example, 15 wt % or less, 5 wt % or less, or even 1 wt % or less. The lower limit of the surfactant content is not particularly limited and may be, for example, 0.01 wt % or more. The other particle content in the intermediate layer 2 is not particularly limited and may be, for example, 30 wt % or less, 15 wt % or less, 5 wt % or less, or even 1 wt % or less. The lower limit of the other particle content is not particularly limited and may be, for example, 0.01 wt % or more. The intermediate layer 2 may not contain surfactants or other particles.

[0103] The intermediate layer 2 has a surface 2A facing the separation functional layer 1. The surface 2A is typically in direct contact with the separation functional layer 1. The surface 2A of the intermediate layer 2 preferably has a relatively small contact angle with water. The surface 2A of the intermediate layer 2 having a small contact angle with water is suitable for improving adhesion to the separation functional layer 1. The contact angle with water of the surface 2A of the intermediate layer 2 is, for example, 120° or less, and preferably 110° or less. The lower limit of this contact angle is not particularly limited and is, for example, 70°. The contact angle can be evaluated by the sessile drop method specified in JIS R3257:1999.

[0104] The surface 2A of the intermediate layer 2 may be subjected to an adhesion-facilitating treatment. Examples of the adhesion-facilitating treatment include surface treatments such as application of a primer, corona discharge treatment, and plasma treatment.

[0105] (Porous Support) The porous support 3 supports the separation function layer 1 via the intermediate layer 2. Examples of the porous support 3 include nonwoven fabrics; porous polytetrafluoroethylene; aromatic polyamide fibers; porous metals; sintered metals; porous ceramics; porous polyesters; porous nylons; activated carbon fibers; latex; silicone; silicone rubber; permeable (porous) polymers containing at least one selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polycarbonate, polysulfone, polyether ether ketone, polyacrylonitrile, polyimide, and polyphenylene oxide; metal foams having open or closed cells; polymer foams having open or closed cells; silica; porous glass; mesh screens, etc. The porous support 3 may be a combination of two or more of these. It is preferable that the porous support 3 contains polysulfone.

[0106] The porous support 3 has a surface 3A facing the intermediate layer 2 and including a plurality of openings (more specifically, pores). The surface 3A is typically in direct contact with the intermediate layer 2. The maximum diameter L1 of the plurality of openings on the surface 3A is, for example, 500 nm or less, and may be 300 nm or less, 100 nm or less, 80 nm or less, or even 50 nm or less. The lower limit of the maximum diameter L1 of the plurality of openings is, for example, 10 nm or more, and may be 20 nm or more.

[0107] The maximum diameter L1 of the multiple openings can be measured by the following method. First, the surface 3A of the porous support 3 is observed at multiple arbitrary locations (at least three locations) using a scanning electron microscope (SEM). Observation using the SEM is performed, for example, at a magnification of 100,000 to 200,000. The observation range using the SEM can be set appropriately depending on the magnification. For example, at a magnification of 200,000, it is preferable to observe a range of approximately 0.6 μm in length and approximately 0.5 μm in width. From the obtained SEM image, the area (opening area) of each opening is calculated by image processing. For each opening, the diameter of a circle having the same area as the calculated area is considered to be the diameter of the opening. Of the identified diameters, the largest diameter is identified as the maximum diameter L1.

[0108] The mode diameter of the emulsion particles in the emulsion resin composition is preferably larger than the maximum diameter L1. In this case, when the intermediate layer 2 is produced from the emulsion resin composition, the emulsion particles are further prevented from penetrating into the porous support 3. The ratio R2 of the mode diameter (nm) of the emulsion particles to the maximum diameter L1 (nm) is preferably 100 or more, and may be 300 or more, 500 or more, or even 600 or more. The upper limit of the ratio R2 is not particularly limited and may be, for example, 2000 or less.

[0109] The surface 3A of the porous support 3 preferably has a relatively large contact angle with water. The surface 3A of the porous support 3 having a large contact angle with water is suitable for preventing an emulsion resin composition containing water as a dispersion medium from penetrating into the porous support 3 when the emulsion resin composition is applied. The contact angle of the surface 3A of the porous support 3 with water is, for example, 60° or more, and preferably 70° or more. The upper limit of this contact angle is not particularly limited and is, for example, 120°. The contact angle can be evaluated by the sessile drop method specified in JIS R3257:1999.

[0110] The thickness of the porous support 3 is not particularly limited and is, for example, 10 μm or more, preferably 20 μm or more, and 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, and more preferably 150 μm or less.

[0111] (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, and may also be a hollow fiber membrane.

[0112] (Method for producing separation membrane) A method for producing the separation membrane 10 of the present embodiment includes, for example, applying the emulsion resin composition described above onto a porous support 3 to form a coating film, and drying the coating film to form an intermediate layer 2 having a thickness of 500 nm or less.

[0113] Specifically, the separation membrane 10 can be produced by the following method. First, an emulsion resin composition is prepared by the method described above. The emulsion resin composition is applied to the surface 3A of the porous support 3 to form a coating film. The method for applying the emulsion resin composition is not particularly limited, and for example, spin coating, dip coating, slot die coating, gravure coating, comma coating, spray coating, etc. can be used. The emulsion resin composition may also be applied using an applicator, a wire bar, a non-wire bar, etc. The thickness of the coating film is not particularly limited, and is, for example, 1 μm to 10 μm.

[0114] Next, the coating film is dried to form an intermediate layer 2. The method for drying the coating film is not particularly limited as long as an intermediate layer 2 having a thickness of 500 nm or less can be formed. The coating film can be dried, for example, under heating conditions. When the coating film is dried under heating conditions, the emulsion particles are crushed in the thickness direction of the coating film and tend to be stretched in the plane direction of the coating film. In other words, when the coating film is dried under heating conditions, an intermediate layer 2 having a thickness of 500 nm or less tends to be formed. The heating temperature of the coating film is, for example, 50°C or higher, and may be 80°C or higher, or even 100°C or higher. The upper limit of the heating temperature of the coating film is not particularly limited, and may be, for example, 200°C or lower, or 150°C or lower. The heating time of the coating film is, for example, 0.5 minutes or longer, and may be 5 minutes or longer.

[0115] Next, if necessary, an adhesion-facilitating treatment is applied to the surface 2A of the intermediate layer 2. Examples of the adhesion-facilitating treatment include surface treatments such as application of a primer, corona discharge treatment, and plasma treatment.

[0116] Next, a coating liquid containing the material for the separation functional layer 1 is prepared. The coating liquid containing the material for the separation functional layer 1 is applied onto the surface 2A of the intermediate layer 2 to obtain a coating film. The separation functional layer 1 can be formed by drying this coating film. The coating method and drying conditions for the coating liquid can be the same as those described above for the intermediate layer 2. The method for applying the coating liquid containing the material for the separation functional layer 1 is not particularly limited, and for example, spin coating, dip coating, slot die coating, gravure coating, comma coating, spray coating, etc. can be used. The coating liquid containing the material for the separation functional layer 1 may also be applied using an applicator, a wire bar, a non-wire bar, etc. By forming the separation functional layer 1 on the intermediate layer 2, a separation membrane 10 is obtained.

[0117] In the manufacturing method of this embodiment, the intermediate layer 2 is produced using an emulsion resin composition in which the mode diameter of the emulsion particles is 2000 nm or more, which tends to suppress the occurrence of defects in the intermediate layer 2. Therefore, it is easy to uniformly apply a coating liquid containing the material of the separation functional layer 1 to the surface 2A of this intermediate layer 2. The separation membrane 10 formed by this method tends to have good separation performance for acidic gases.

[0118] (Characteristics of Separation Membrane) The separation membrane 10 of this embodiment can, for example, preferentially permeate acidic gases contained in a mixed gas. As an example, when carbon dioxide is supplied at a pressure of 0.1 MPa to a space adjacent to one side of the separation membrane 10, the permeation rate T1 of carbon dioxide permeating the separation membrane 10 is CO2 is, for example, 10 GPU or more, 50 GPU or more, 100 GPU or more, 500 GPU or more, 800 GPU or more, 1000 GPU or more, 1300 GPU or more, or even 1500 GPU or more. CO2 The upper limit is not particularly limited, and is, for example, 5000 GPUs or less. -6 ·cm 3 (STP) / (sec cm 2 cm 3 (STP) means the volume of a gas at 1 atmosphere and 0°C.

[0119] Transmission rate T1 CO2 can be calculated by the following method. First, carbon dioxide is supplied at a pressure of 0.1 MPa and a temperature of 25°C 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 separation functional layer side). As a result, a permeated fluid (carbon dioxide) that has permeated the separation membrane 10 is obtained from the other main surface of the separation membrane 10 (for example, the main surface 12 of the separation membrane 10 on the porous support side). The flow rate of this permeated fluid is measured with a mass flow meter, and from the obtained results, the permeation rate T1 of carbon dioxide is calculated. CO2 Depending on the flow rate of the permeating fluid, a soap film flow meter may be used instead of the mass flow meter.

[0120] Separation coefficient α1 of carbon dioxide relative to nitrogen of separation membrane 10 CO2 / N2 is not particularly limited, and may be, for example, 20 or more, 30 or more, 35 or more, or even 37 or more. CO2 / N2 The upper limit of is not particularly limited, and is, for example, 100 or less.

[0121] Separation factor α1 CO2 / N2 is the permeation rate T1 of nitrogen permeating through the separation membrane 10 when nitrogen is supplied at a pressure of 0.1 MPa to a space adjacent to one side of the separation membrane 10.N2 (GPU) The permeation rate T1 of carbon dioxide permeating through the separation membrane 10 when carbon dioxide at a pressure of 0.1 MPa is supplied to the space CO2 (GPU) ratio T1 CO2 / T1 N2 Nitrogen permeation rate T1 N2 is the permeation rate T1 of carbon dioxide, except that nitrogen at a pressure of 0.1 MPa and a temperature of 25°C is used instead of carbon dioxide. CO2 can be measured by the method described above.

[0122] In this embodiment, the permeation rate T2 of carbon dioxide permeating the laminate of the porous support 3 and the intermediate layer 2 is CO2 and the separation factor α2 of carbon dioxide to nitrogen CO2 / N2 In another aspect, the present invention provides a laminate comprising a separation functional layer 1, a porous support 3 supporting the separation functional layer 1, and an intermediate layer 2 disposed between the separation functional layer 1 and the porous support 3, wherein when carbon dioxide at a pressure of 0.1 MPa is supplied to a space adjacent to one side of the laminate constituted only by the porous support 3 and the intermediate layer 2, the permeation rate T2 of carbon dioxide permeating the laminate tends to be high. CO2 is 4500 GPU or more, and the separation coefficient α2 of the carbon dioxide relative to nitrogen of the laminate CO2 / N2 The separation membrane 10 has a separation coefficient α2 of 1.4 or more. CO2 / N2 is the permeation rate T2 of nitrogen that permeates the laminate when nitrogen is supplied to the space at a pressure of 0.1 MPa. N2 (GPU) Transmission rate T2 CO2 (GPU) ratio T2 CO2 / T2 N2 means.

[0123] Transmission rate T2 CO2 is a permeation rate T1 except that a laminate composed of only the porous support 3 and the intermediate layer 2 is used instead of the separation membrane 10. CO2 can be measured by the method described above. Similarly, the permeation rate T2 N2 is a permeation rate T1 except that a laminate composed of only the porous support 3 and the intermediate layer 2 is used instead of the separation membrane 10. N2The above laminate can be produced by forming the intermediate layer 2 on the porous support 3.

[0124] Transmission rate T2 CO2 As described above, the permeation rate T2 is preferably 4500 GPU or more, and may be 4800 GPU or more, 5000 GPU or more, 6000 GPU or more, 7000 GPU or more, 8000 GPU or more, or even 9000 GPU or more. CO2 The upper limit is not particularly limited, and may be, for example, 20,000 GPU or less, or 15,000 GPU or less.

[0125] Separation factor α2 CO2 / N2 As described above, the separation factor α2 is preferably 1.4 or more, and may be 1.8 or more, 2.0 or more, 3.0 or more, 3.5 or more, 4.0 or more, 5.0 or more, 6.0 or more, or even 8.0 or more. CO2 / N2 can also be used as an indicator of the presence or absence of defects in the intermediate layer 2. For example, when the intermediate layer 2 contains a silicone-based polymer, the separation factor α2 CO2 / N2 If the separation factor α2 is 1.4 or more, it can be determined that the occurrence of defects in the intermediate layer 2 is sufficiently suppressed. CO2 / N2 The upper limit is not particularly limited, and may be, for example, 20 or less, or 10 or less.

[0126] (Applications of Separation Membrane) Applications of the separation membrane 10 of this embodiment include applications for separating acidic gases from a gas mixture containing acidic gases. Examples of acidic gases in the gas mixture include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, and nitrogen oxides (NOx), with carbon dioxide being preferred. The gas mixture contains other gases in addition to the acidic gas. Examples of other gases include non-polar 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 applications for separating carbon dioxide from a gas mixture containing carbon dioxide and nitrogen. However, the application of the separation membrane 10 is not limited to applications for separating acidic gases from the above-mentioned gas mixture.

[0127] <Embodiment of Membrane Separation Apparatus> As shown in Fig. 2, a 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. The separation membrane 10 is disposed inside the tank 20. Inside the tank 20, the separation membrane 10 separates the first chamber 21 from the second chamber 22. The separation membrane 10 extends from one to the other of a pair of wall surfaces of the tank 20.

[0128] The first chamber 21 has an inlet 21 a and an outlet 21 b. The second chamber 22 has an outlet 22 a. The inlet 21 a, the outlet 21 b, and the outlet 22 a are, for example, openings formed in the wall surface of the tank 20.

[0129] Membrane separation using the membrane separation device 100 is performed, for example, by the following method. First, a gas mixture 30 containing an acidic gas is supplied to the first chamber 21 through the inlet 21a. The concentration of the acidic gas in the gas mixture 30 is not particularly limited, and is, for example, 0.01 vol% (100 ppm) or more under standard conditions, preferably 1 vol% or more, more preferably 10 vol% or more, even more preferably 30 vol% or more, and particularly preferably 50 vol% or more. The upper limit of the concentration of the acidic gas in the gas mixture 30 is not particularly limited, and is, for example, 90 vol% under standard conditions.

[0130] The pressure inside the first chamber 21 may be increased by the supply of the mixed gas 30. The membrane separation apparatus 100 may further include a pump (not shown) for increasing the pressure of 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.

[0131] The second chamber 22 may be depressurized while the gas mixture 30 is supplied to the first chamber 21. The membrane separation apparatus 100 may further include a pump (not shown) for depressurizing the second chamber 22. The second chamber 22 may be depressurized so that the space within the second chamber 22 is reduced in pressure by, for example, 10 kPa or more, preferably 50 kPa or more, and more preferably 100 kPa or more relative to the atmospheric pressure in the measurement environment.

[0132] By supplying the gas mixture 30 into the first chamber 21, a permeated fluid 35 having a higher acid gas content than the gas mixture 30 can be obtained on the other side of the separation membrane 10. That is, the permeated fluid 35 is supplied to the second chamber 22. The permeated fluid 35 contains, for example, an acid gas as a main component. However, the permeated fluid 35 may also contain small amounts of gases other than the acid gas. The permeated fluid 35 is discharged to the outside of the tank 20 through the outlet 22a.

[0133] The concentration of the acid gas in the mixed gas 30 gradually decreases from the inlet 21a to the outlet 21b of the first chamber 21. The mixed gas 30 (non-permeated fluid 36) treated in the first chamber 21 is discharged to the outside of the tank 20 through the outlet 21b.

[0134] The membrane separation apparatus 100 of this embodiment is suitable for a continuous membrane separation method, but may also be used for a batch-type membrane separation method.

[0135] <Modifications of Membrane Separation Device> The membrane separation device 100 may be a spiral membrane element, a hollow fiber membrane element, or the like. Fig. 3 shows a spiral membrane element. The membrane separation device 110 of Fig. 3 includes a central tube 41 and a stack 42. The stack 42 includes the separation membrane 10.

[0136] 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 interior of 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. The inner diameter of the central tube 41 is, for example, in the range of 20 to 100 mm.

[0137] The laminate 42 further includes a feed-side channel material 43 and a permeate-side channel material 44 in addition to the separation membrane 10. The laminate 42 is wound around a central tube 41. The membrane separation device 110 may further include an exterior material (not shown).

[0138] The feed-side channel material 43 and the permeate-side channel material 44 may be, for example, a resin net made of polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE).

[0139] Membrane separation using the membrane separation device 110 is performed, for example, by the following method. First, the gas mixture 30 is supplied to one end of the wound stack 42. The permeated fluid 35 that has permeated the separation membrane 10 of the stack 42 moves into the interior of the central tube 41. The permeated fluid 35 is discharged to the outside through the central tube 41. The gas mixture 30 (non-permeated fluid 36) that has been treated in the membrane separation device 110 is discharged to the outside from the other end of the wound stack 42. This allows acidic gases to be separated from the gas mixture 30.

[0140] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0141] Example 1 First, an emulsion resin composition was prepared by mixing an aqueous emulsion containing emulsion particles composed of a silicone polymer (KM-9749 manufactured by Shin-Etsu Chemical Co., Ltd.), a surface conditioner (Noigen LF-40X manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and ion-exchanged water for dilution. In the emulsion resin composition, the content of the silicone polymer was 10.0 wt %, and the content of the surface conditioner was 0.1 wt %.

[0142] Next, a porous support was prepared, in which a microporous layer of polysulfone was formed on a polyester nonwoven fabric. The prepared emulsion resin composition was applied to the microporous layer of the porous support using an applicator, yielding a coating film (thickness: 5 μm). The resulting coating film was dried at 130°C for 1 minute to form an intermediate layer. This resulted in a laminate consisting only of the porous support and the intermediate layer.

[0143] Next, a coating solution was prepared by mixing the acrylic polymer, BYK-378 (manufactured by BYK-Chemie) as a surface conditioner, and a mixed solvent for dilution (70 wt% isopropanol, 30 wt% ion-exchanged water). In the coating solution, the content of the acrylic polymer was 1.0 wt%, and the content of the surface conditioner was 0.1 wt%.

[0144] The coating solution was applied to the intermediate layer using an applicator to obtain a coating film (thickness: 35 μm). The coating film was dried at 70° C. for 1 minute to form a separation functional layer. This resulted in the separation membrane of Example 1, which was composed of a porous support, an intermediate layer, and a separation functional layer.

[0145] (Examples 2 to 4 and Comparative Examples 1 to 3) Separation membranes of Examples 2 to 4 and Comparative Examples 1 to 3 were obtained by the same method as Example 1, except that the components and their contents in the emulsion resin composition were changed as shown in Table 1. In Comparative Example 3, an emulsion resin composition was prepared by combining two types of aqueous emulsions. This emulsion resin composition contained emulsion particles composed of a silicone-based polymer and emulsion particles composed of a urethane-based polymer.

[0146] <Emulsion Resin Composition> [Mode Diameter of Emulsion Particles] The particle size distribution of the emulsion resin compositions prepared in the Examples and Comparative Examples was measured using a particle size distribution analyzer (MT3300EXII manufactured by Microtrac) based on a laser diffraction / scattering method. The particle diameter appearing most frequently (mode) in the obtained particle size distribution was identified as the mode diameter of the emulsion particles. The results are shown in Table 1. In the emulsion resin compositions of Examples 1 to 4 and Comparative Examples 1 and 2, one unimodal peak appeared in the particle size distribution. In the emulsion resin composition of Comparative Example 3, two unimodal peaks appeared.

[0147] [Surface Tension] The surface tension of the emulsion resin compositions prepared in the Examples and Comparative Examples was measured by the du Nouy method (ring method). Specifically, a platinum ring with a diameter of 14 mm was first suspended above the emulsion resin composition. The ring was positioned so that the surface surrounded by the ring was parallel to the liquid surface of the emulsion resin composition. The ring was then submerged in the emulsion resin composition and pulled vertically upward at a speed of 0.7 mm / s, and then removed from the emulsion resin composition (pre-wetting treatment).

[0148] The ring was again submerged in the emulsion resin composition and pulled up vertically at a speed of 0.2 mm / s to remove it from the emulsion resin composition. At this time, a liquid film was formed between the ring and the liquid surface of the emulsion resin composition near the liquid surface of the emulsion resin composition. The force applied to the ring by the liquid film was measured, and the maximum value was determined as the surface tension. The surface tension was measured at 25°C using a surface tensiometer (DY-700, manufactured by Kyowa Interface Science Co., Ltd.).

[0149] The surface tension of each of the emulsion resin compositions prepared in the Examples and Comparative Examples was 31 to 34 mN / m.

[0150] <Intermediate layer> [Thickness] For the laminates composed only of the porous support and the intermediate layer prepared in the examples and comparative examples, the thickness of the intermediate layer was measured by the method described above. Specifically, the intermediate layer was subjected to elemental analysis by X-ray fluorescence (XRF) analysis using an X-ray fluorescence analyzer (manufactured by Rigaku Corporation, "ZSX Primus III+"), and the thickness of the intermediate layer was determined based on the obtained results. The results are shown in Table 1.

[0151] <Porous Support> [Maximum Diameter of Openings] The maximum diameter of the openings was measured for the porous supports used in the Examples and Comparative Examples. First, three locations on the surface of the porous support on the microporous layer side were observed using a scanning electron microscope (SEM). From the obtained SEM images, the area (opening area) of each opening was calculated by image processing. For each opening, the diameter of a circle having the same area as the calculated area was considered to be the diameter of the opening. Of the identified diameters, the largest diameter was identified as the maximum diameter. The results are shown in Table 1.

[0152] <Laminate> [Characteristics Evaluation] The characteristics of the laminates composed only of the porous support and intermediate layer produced in the Examples and Comparative Examples were evaluated by the following method. First, the laminate was set in a metal cell and sealed with an O-ring to prevent leakage. Next, carbon dioxide was injected into the metal cell at a pressure of 0.1 MPa and a temperature of 25°C so that the carbon dioxide contacted the main surface of the laminate on the intermediate layer side. As a result, a permeating fluid (carbon dioxide) was obtained from the main surface of the laminate on the porous support side. The flow rate of the permeating fluid was measured, and from the obtained results, the carbon dioxide permeation rate T2 CO2 (GPU) was measured.

[0153] Furthermore, the nitrogen permeation rate T2 N2 The nitrogen permeation rate T2 was measured. N2 is the permeation rate T2 of carbon dioxide, except that nitrogen at a pressure of 0.1 MPa and a temperature of 25 ° C. was used instead of carbon dioxide. CO2 was measured by the above-mentioned method. Based on the obtained results, the nitrogen permeation rate T2 N2 Carbon dioxide permeation rate T2 relative to (GPU) CO2 (GPU) ratio T2 CO2 / T2 N2 The calculated value is used as the separation coefficient α2 of carbon dioxide relative to nitrogen. CO2 / N2 It was considered that.

[0154] [Surface Observation] The surfaces of the intermediate layer side of the laminates composed only of the porous support and intermediate layer produced in the Examples and Comparative Examples were observed using an SEM. The SEM observation was performed at a magnification of 30,000 times. As a result, almost no defects in the intermediate layer were observed in the laminates of Examples 1 to 4. On the other hand, in Comparative Examples 1 to 3, it was confirmed that chipping occurred in part of the intermediate layer, and the surface of the porous support was exposed at that location.

[0155] <Separation membrane> [Characteristics evaluation] The separation membranes produced in the examples and comparative examples were measured for the carbon dioxide permeation rate T1 using the same method as for measuring the permeation rate of the laminate, except that the measurement object was changed to a separation membrane. CO2 (GPU) and nitrogen permeation rate T1 N2 Based on the results obtained, the nitrogen permeation rate T1 N2 Carbon dioxide permeation rate T1 relative to (GPU) CO2 (GPU) ratio T1 CO2 / T1 N2 The calculated value is used as the separation coefficient α1 of carbon dioxide relative to nitrogen. CO2 / N2 It was considered that.

[0156]

[0157] The abbreviations in Table 1 are as follows: KM-9749: Aqueous emulsion containing emulsion particles composed of a silicone-based polymer (KM-9749 manufactured by Shin-Etsu Chemical Co., Ltd.) KM-9772: Aqueous emulsion containing emulsion particles composed of a silicone-based polymer (KM-9772 manufactured by Shin-Etsu Chemical Co., Ltd.) Polon-MF-56-T: Aqueous emulsion containing emulsion particles composed of a silicone-based polymer (Polon-MF-56-T manufactured by Shin-Etsu Chemical Co., Ltd.) W-6010: Aqueous emulsion containing emulsion particles composed of a urethane-based polymer (Takelac W-6010 manufactured by Mitsui Chemicals)

[0158] As can be seen from Table 1, in the examples, compared to the comparative examples, the carbon dioxide permeation rate T2 CO2 , and the separation factor α2 of carbon dioxide relative to nitrogen CO2 / N2 In addition, the separation membranes of the examples also had higher carbon dioxide permeation rates T1 CO2 , and the separation factor α1 of carbon dioxide relative to nitrogen CO2 / N2 From these results, it can be said that the intermediate layers prepared in the examples are suitable for improving the permeation rate of acidic gases while suppressing a decrease in the separation performance of the separation membrane against acidic gases.

[0159] As described above, in Comparative Examples 1 to 3, SEM observation confirmed that a chip had occurred in a part of the intermediate layer, and the surface of the porous support was exposed at that location. In Comparative Examples 1 to 3, the separation factor α2 CO2 / N2 In addition, when a separation functional layer was formed on the laminates prepared in Comparative Examples 1 to 3, it was difficult to uniformly apply a coating solution containing the material for the separation functional layer to the surface of the intermediate layer, and this resulted in a low separation coefficient α1 of the separation membrane. CO2 / N2 It is estimated that the number of cases has also decreased.

[0160] The separation membrane of this embodiment is suitable for separating an acid gas from a gas mixture containing the acid gas, and in particular, for separating carbon dioxide from off-gas of a chemical plant or thermal power plant.

Claims

1. A separation membrane comprising: a separation functional layer; a porous support supporting the separation functional layer; and an intermediate layer disposed between the separation functional layer and the porous support and formed from an emulsion resin composition containing emulsion particles, wherein the thickness of the intermediate layer is 500 nm or less, and the emulsion particles in the emulsion resin composition have a mode diameter of 2000 nm or more.

2. The separation membrane according to claim 1, wherein the ratio of the mode diameter (nm) to the thickness (nm) of the intermediate layer is 10 or greater.

3. The separation membrane according to claim 1, wherein the porous support has a surface facing the intermediate layer and including a plurality of openings, and the mode diameter is larger than the maximum diameter of the plurality of openings.

4. The separation membrane of claim 1, wherein the emulsion particles comprise a silicone-based polymer.

5. The separation membrane according to claim 1, wherein the content of the emulsion particles in the emulsion resin composition is 20 wt % or less.

6. The separation membrane according to claim 1, wherein the emulsion resin composition contains water as a dispersion medium.

7. The separation membrane according to claim 1, wherein the emulsion resin composition contains a surfactant.

8. The separation membrane according to claim 1, wherein the emulsion resin composition has a surface tension of 40 mN / m or less.

9. The separation membrane according to claim 1, which is used to separate an acid gas from a gas mixture containing the acid gas.

10. A method for producing a separation membrane comprising a separation functional layer, a porous support supporting the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support, the method comprising: applying an emulsion resin composition containing emulsion particles onto the porous support to form a coating film; and drying the coating film to form the intermediate layer having a thickness of 500 nm or less, wherein the mode diameter of the emulsion particles in the emulsion resin composition is 2000 nm or more.

11. A laminate comprising a separation functional layer, a porous support supporting the separation functional layer, and an intermediate layer disposed between the separation functional layer and the porous support, wherein when carbon dioxide at a pressure of 0.1 MPa is supplied to a space adjacent to one surface of a laminate consisting only of the porous support and the intermediate layer, the permeation rate T of carbon dioxide passing through the laminate is CO2 is 4500 GPU or more, and the separation coefficient α of carbon dioxide relative to nitrogen of the laminate CO2 / N2 A separation membrane having a separation factor α of 1.4 or more. CO2 / N2 is the permeation rate T of nitrogen that permeates the laminate when nitrogen is supplied to the space at a pressure of 0.1 MPa. N2 The permeation rate T CO2 (GPU) ratio T CO2 / T N2 means.

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