Gas separation membrane and method for manufacturing gas separation membrane

Abstract

To provide a gas separation membrane excellent in gas permeability of carbon dioxide and in adhesion of a separation membrane and its manufacturing method.SOLUTION: The gas separation membrane, which separates carbon dioxide by selective permeation from a mixture gas containing carbon dioxide, comprises: a porous body having a first main face and a second main face having front and rear relation with each other and pores which combine the first main face with the second main face, to shape a sheet-like form; and a separation layer provided on the first main face and constituted of a high polymer material. The gas separation membrane is characterized in that a part of the separation layer penetrates into the pores rather than the first main face, and in that a ratio B / A is 30% or more when an average thickness of the separation layer is A, and a penetration depth of the separation layer into the porous body is B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] To achieve carbon neutrality, technologies are being considered to capture and directly capture carbon dioxide from the atmosphere. Known technologies include chemical absorption and adsorption, which involves absorbing and adsorbing carbon dioxide into an absorbent or adsorbent, and membrane separation, which separates carbon dioxide using a gas separation membrane.

[0003] Patent Document 1 discloses a gas separator having a gas separation ability that allows only specific gas components to permeate from a multi-component mixed gas. This gas separator has a porous substrate and a metal having gas separation ability. The metal having gas separation ability fills and blocks the inside of small pores open on the surface of the porous substrate. This allows only specific gas components to be separated from the multi-component mixed gas that passes through the small pores.

[0004] Furthermore, Patent Document 1 discloses that a metal coating is formed inside the small pores of a porous substrate by plating. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-113545 Summary of the Invention [Problem to be solved by the invention]

[0006] However, separation layers using metals do not have sufficient gas permeability to carbon dioxide, and there is a concern that if a non-metallic material such as an organic material is used for the separation layer, the adhesion between the separation layer and the porous substrate may not be sufficiently enhanced.

[0007] Therefore, the realization of a gas separation membrane that has excellent carbon dioxide gas permeability and good adhesion of the separation layer has become an issue. [Means for solving the problem]

[0008] The gas separation membrane according to the application example of the present invention is A gas separation membrane that selectively permeates and separates carbon dioxide from a mixed gas containing carbon dioxide, a sheet-like porous body having a first main surface and a second main surface that are opposite each other, and pores connecting the first main surface and the second main surface; a separation layer provided on the first main surface and made of a polymer material; Equipped with a portion of the separation layer extends deeper into the pores than the first main surface; When the average thickness of the separation layer is A and the penetration depth of the separation layer into the porous body is B, the ratio B / A is 30% or more.

[0009] A method for producing a gas separation membrane according to an application example of the present invention includes: A method for producing a gas separation membrane according to an application example of the present invention, comprising: supplying a liquid raw material to the first main surface of the porous body to form a coating film; a step of applying energy to the coating film from the opposite side of the porous body to harden or solidify the coating film, thereby forming the separation layer; removing any uncured or unhardened portions of the coating; It has. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view schematically showing a gas separation membrane according to an embodiment. [Figure 2] 1 is a process diagram showing the configuration of a method for producing a gas separation membrane according to an embodiment. [Figure 3] 3 is a cross-sectional view illustrating a method for manufacturing the gas separation membrane shown in FIG. 2. FIG. [Figure 4] 3 is a cross-sectional view illustrating a method for manufacturing the gas separation membrane shown in FIG. 2. FIG. [Figure 5] 3 is a cross-sectional view illustrating a method for manufacturing the gas separation membrane shown in FIG. 2. FIG. [Figure 6] 3 is a cross-sectional view illustrating a method for manufacturing the gas separation membrane shown in FIG. 2. FIG. [Figure 7] 3 is a cross-sectional view illustrating a method for manufacturing the gas separation membrane shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas separation membrane and a method for producing a gas separation membrane according to the present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0012] 1. Gas separation membrane structure First, the configuration of the gas separation membrane according to the embodiment will be described.

[0013] Fig. 1 is a cross-sectional view schematically showing a gas separation membrane 1 according to an embodiment. In the following description, the upper side of the gas separation membrane 1 shown in Fig. 1 will be referred to as the "upstream side" or simply "top", and the lower side will be referred to as the "downstream side" or simply "bottom".

[0014] The gas separation membrane 1 shown in FIG. 1 has the function of selectively allowing carbon dioxide to permeate from a mixed gas containing carbon dioxide and a non-target component. The gas separation membrane 1 shown in FIG. 1 is a composite membrane having a porous body 2 and a separation layer 3. The non-target component refers to a gas component other than carbon dioxide that is contained in the mixed gas. Examples of the non-target component include nitrogen and methane, with nitrogen being particularly presumed. Therefore, the mixed gas mentioned above includes a mixed gas of carbon dioxide and nitrogen.

[0015] The porous body 2 shown in Figure 1 is a porous membrane having a first main surface 21 and a second main surface 22, which are opposite surfaces, and pores 23. Such porous body 2 has good gas permeability and good mechanical properties, and supports the separation layer 3. This makes it possible to improve the mechanical properties of the entire gas separation membrane 1 without impairing the good gas selectivity of the separation layer 3.

[0016] The separation layer 3 is made of a polymer material that is denser (has a lower porosity) than the porous body 2. Such a separation layer 3 closes the upper ends of the pores 23. The separation layer 3 selectively allows carbon dioxide in the mixed gas supplied to the upstream side of the gas separation membrane 1 to permeate to the downstream side, thereby achieving a good gas selectivity ratio. This enables the gas separation membrane 1 to separate carbon dioxide from the mixed gas.

[0017] The gas separation membrane 1 according to this embodiment has the function of selectively permeating carbon dioxide, and this characteristic is quantitatively expressed by the gas selectivity ratio. Specifically, when the non-target component is nitrogen, the nitrogen gas permeability of the gas separation membrane 1 is expressed as R N2 The carbon dioxide gas permeability of the gas separation membrane 1 is R CO2 In this case, the gas selectivity R of the gas separation membrane 1 is CO2 / R N2 is preferably 10 or more, and more preferably 20 or more and 50 or less. CO2 / R N2 When is within the above range, the gas separation membrane 1 can efficiently separate and recover carbon dioxide in the mixed gas.

[0018] If the gas selectivity ratio is below the lower limit, the recovered carbon dioxide will contain a large amount of non-target components such as nitrogen. This may result in reduced economic efficiency and ease of handling when storing or utilizing the recovered carbon dioxide. On the other hand, if the gas selectivity ratio exceeds the upper limit, it may be difficult to sufficiently increase the carbon dioxide gas permeability of the gas separation membrane 1, and the manufacturing difficulty and cost of the gas separation membrane 1 that achieves such a gas selectivity ratio may increase.

[0019] The nitrogen gas permeability R of the gas separation membrane 1 N2 and the carbon dioxide gas permeability R of the gas separation membrane 1 CO2 are measured in accordance with the gas permeability test method (Part 1: differential pressure method) specified in JIS K 7126-1:2006. A gas permeability measuring device is used for the measurement. Examples of gas permeability measuring devices include the GTR-11A / 31A manufactured by GTR Tech Co., Ltd. In this device, the gas that has permeated the gas separation membrane 1 is introduced into a gas chromatograph, and the gas permeability of each component is measured. This makes it possible to measure the gas permeability of nitrogen and carbon dioxide.

[0020] In addition, in the gas separation membrane 1 according to this embodiment, the gas permeability R CO2 However, the gas permeability R of carbon dioxide is preferably 15 GPU or more, more preferably 100 GPU to 20,000 GPU, and even more preferably 200 GPU to 15,000 GPU. This reduces the amount of energy input required for separation, specifically, it is possible to realize a gas separation membrane 1 that can reduce the pressure difference between the upstream and downstream sides of the gas separation membrane 1. CO2 If the gas permeability R of carbon dioxide is less than the lower limit, a large amount of energy is required to separate the carbon dioxide, which may result in a decrease in economic efficiency. CO2 If exceeds the upper limit, it may be difficult to maintain a balance with the gas selectivity ratio. -10 mol m -2 ·s -1 Pa -1 is.

[0021] Furthermore, the separation layer 3 is preferably in close contact with the porous body 2. In this specification, "close contact" means that there is airtightness at the adhesive interface between the separation layer 3 and the porous body 2. Due to this airtightness, the separation layer 3 isolates the pores 23 of the porous body 2 from each other. In other words, because there are no gaps between the separation layer 3 and the porous body 2, communication between the pores 23 via the gaps can be suppressed.

[0022] 1.1.Porous materials The porous body 2 is a porous sheet having pores 23 and has good gas permeability. The porous body 2 has higher rigidity than the separation layer 3 and is responsible for ensuring the mechanical properties such as the self-supporting ability and durability of the entire gas separation membrane 1. If the separation layer 3 has sufficient mechanical properties, the porous body 2 may be omitted.

[0023] Examples of the constituent material of the porous body 2 include polymeric materials, ceramic materials, and metal materials. The constituent material of the porous body 2 may also be a composite material of these materials and other materials.

[0024] Examples of polymeric materials include polyolefin resins such as polyethylene and polypropylene, fluorine-containing resins such as polytetrafluoroethylene, polyvinyl fluoride and polyvinylidene fluoride, polystyrene, cellulose, cellulose acetate, polyurethane, polyacrylonitrile, polyphenylene oxide, polysulfone, polyethersulfone, polyimide, polyaramid, nylon, and the like.

[0025] Examples of ceramic materials include alumina, cordierite, mullite, silicon carbide, zirconia, etc. Examples of metal materials include stainless steel, etc.

[0026] Of these, a filter with an open-cell structure is preferably used for the porous body 2. A filter with an open-cell structure is also called an absolute-type filter, and has pores 23 that are continuous from the first main surface 21 to the second main surface 22 and are independent of each other. This makes it easy to fill the pores 23 with liquid raw material when forming the separation layer 3, and as a result, separation layer 3 can be reliably formed for each pore 23. This makes it possible to achieve a gas separation membrane 1 with excellent gas permeability without compromising the high gas selectivity of the separation layer 3.

[0027] A filter made of an aggregate of fibers is also called a nominal-type filter. In this filter, the pores 23 may be discontinuous or may be unintentionally connected to each other. This makes it difficult to fill the pores 23 with the liquid raw material when forming the separation layer 3, which may result in defects in the separation layer 3.

[0028] The shape of the porous body 2 may be a flat plate as shown in FIG. 1, or may be a spiral, tubular, hollow fiber, or other shape.

[0029] The average thickness of the porous body 2 is not particularly limited, but is preferably 1 μm or more and 3000 μm or less, more preferably 5 μm or more and 500 μm or less, and even more preferably 10 μm or more and 150 μm or less. This provides the porous body 2 with the necessary and sufficient rigidity to support the separation layer 3. If the average thickness of the porous body 2 is below the lower limit, the rigidity may be insufficient. On the other hand, if the average thickness of the porous body 2 is above the upper limit, the rigidity of the porous body 2 may be too high, which may reduce the handleability of the gas separation membrane 1 or reduce the adhesion of the separation layer 3.

[0030] The average thickness of the porous body 2 is the average value of thicknesses measured in the stacking direction at 10 points on the porous body 2. The thickness of the porous body 2 can be measured using, for example, a thickness gauge.

[0031] The porous body 2 has pores 23, the average inner diameter of which is referred to as the "average pore diameter." The average pore diameter of the porous body 2 is preferably 0.01 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 500 μm or less, even more preferably 0.5 μm or more and 300 μm or less, and particularly preferably 1 μm or more and 100 μm or less. This makes it possible to sufficiently ensure the carbon dioxide gas permeability of the porous body 2 while preventing the separation layer 3 from leaking to the downstream side of the porous body 2. If the average pore diameter of the porous body 2 is below the lower limit, the carbon dioxide gas permeability of the porous body 2 may decrease. On the other hand, if the average pore diameter of the porous body 2 exceeds the upper limit, the separation layer 3 may leak to the downstream side of the porous body 2.

[0032] The average pore diameter of the porous body 2 is measured with a through-pore diameter evaluation device after removing the separation layer 3 from the gas separation membrane 1 to extract the porous body 2 alone. An example of the through-pore diameter evaluation device is a Perm Porometer manufactured by PMI.

[0033] The porosity of the porous body 2 is preferably 20% or more and 90% or less, and more preferably 30% or more and 80% or less, so that the porous body 2 can have both good gas permeability and sufficient rigidity.

[0034] The porosity of the porous body 2 is measured after the separation layer 3 is removed from the gas separation membrane 1 using the through-pore diameter evaluation device described above.

[0035] 1.2. Separation layer The separation layer 3 is provided on the first main surface 21 of the porous body 2 and is made of a polymer material. The separation layer 3 is essentially a dense membrane and has good affinity with carbon dioxide molecules. Due to this affinity, the separation layer 3 selectively allows carbon dioxide to permeate.

[0036] The average thickness of the separation layer 3 is not particularly limited, but is preferably 10 nm to 1000 nm, more preferably 10 nm to 800 nm, even more preferably 30 nm to 500 nm, and particularly preferably 50 nm to 200 nm. This provides the separation layer 3 with sufficient gas permeability. As a result, the amount of energy input required for carbon dioxide separation can be reduced; specifically, a gas separation membrane 1 can be realized that can reduce the pressure difference between the upstream and downstream sides of the gas separation membrane 1. Note that if the average thickness of the separation layer 3 is below the lower limit, the separation layer 3 may be more likely to have defects or be more susceptible to breakage. On the other hand, if the average thickness of the separation layer 3 exceeds the upper limit, the carbon dioxide gas permeability of the separation layer 3 may decrease, increasing the amount of energy input required for separation, or the separation layer 3 may be less flexible.

[0037] The average thickness of the separation layer 3 is preferably 0.0050% to 1.0%, more preferably 0.010% to 0.50%, and even more preferably 0.030% to 0.30% of the average thickness of the porous body 2. This optimizes the thickness ratio of the two layers, allowing the gas separation membrane 1 to have a good balance of mechanical properties, gas selectivity, and gas permeability.

[0038] The average thickness of the separation layer 3 is determined, for example, by observing the cross section of the gas separation membrane 1 at a magnification and averaging the thicknesses at 10 points. For example, a scanning electron microscope or a transmission electron microscope is used for the magnification observation.

[0039] As described above, the separation layer 3 made of a polymer material and having a thin film thickness has good gas permeability, but tends to have poor adhesion to the porous body 2. If the adhesion of the separation layer 3 is poor, there is a risk that it will peel off from the porous body 2.

[0040] In contrast, in the gas separation membrane 1 according to this embodiment, part of the separation layer 3 penetrates deeper into the pores 23 than the first main surface 21. When the average thickness of the separation layer 3 is A and the penetration depth of the separation layer 3 into the porous body 2 is B, in the gas separation membrane 1, the ratio B / A is 30% or more.

[0041] With this configuration, even when a membrane made of a polymer material is used as the separation layer 3 and the average thickness A is reduced, it is possible to ensure the adhesion of the separation layer 3. This makes it possible to realize a gas separation membrane 1 that has excellent carbon dioxide gas permeability and good adhesion of the separation layer 3.

[0042] The ratio B / A is preferably 30% or more and 90% or less, more preferably 40% or more and 80% or less, and even more preferably 50% or more and 70% or less.

[0043] The average thickness A of the separation layer 3 and the penetration depth B of the separation layer 3 into the porous body 2 are each measured as follows.

[0044] First, the gas separation membrane 1 is cut in the thickness direction, and the cross section is observed under magnification. The magnification is set so that the entire thickness of the separation layer 3 can be captured in a single image. Next, an enlarged image is captured, and the contour lines of the upper and lower surfaces of the separation layer 3 are identified in the resulting image. Two parallel straight lines L31 and L32 are then drawn to approximate the two contour lines, and the distance between the lines L31 and L32 is defined as the average thickness A. Figure 1 shows an example of the lines L31 and L32.

[0045] Furthermore, the contour line of the upper surface of the porous body 2 is identified within the image. Then, a straight line L21 that approximates this contour line is drawn. This straight line L21 is also parallel to the two parallel lines L31 and L32. The distance between the lines L21 and L32 is defined as the penetration depth B. An example of the straight line L21 is shown in FIG. 1. For magnified observation, for example, a scanning electron microscope or a transmission electron microscope is used.

[0046] If the ratio B / A is below the lower limit, the penetration depth B will be insufficient, resulting in a decrease in the adhesion of the separation layer 3. In this case, peeling of the separation layer 3 will occur, and the durability of the gas separation membrane 1 will decrease. On the other hand, the ratio B / A may exceed the upper limit, but the penetration depth B will be excessive, which may result in the thickness of the portion of the separation layer 3 covering the first main surface 21 of the porous body 2 becoming too thin. In this case, the adhesion of the separation layer 3 may decrease.

[0047] The constituent material of the separation layer 3 is a polymeric material. Examples of polymeric materials include polyolefin resins such as polyethylene and polypropylene, fluorine-containing resins such as polytetrafluoroethylene, polyvinyl fluoride, and polyvinylidene fluoride, polystyrene, cellulose, cellulose acetate, polyurethane, polyacrylonitrile, polyphenylene oxide, polysulfone, polyethersulfone, polyimide, polyaramid, organopolysiloxane, polyethylene terephthalate (PET), polyacetal (POM), and polylactic acid (PLA). The constituent material of the separation layer 3 may be one or a composite material of two or more of these polymeric materials. The polymeric material may be a thermoplastic resin, a thermosetting resin, or a photocurable resin.

[0048] Among these, organopolysiloxane is preferably used as the constituent material of the separation layer 3. One molecule of organopolysiloxane has the basic constituent units R 1 SiO 3 / 2 Units expressed as T units, R 2 R 3 SiO 2 / 2 Units expressed by (D units) and R 4 R 5 R 6 SiO 1 / 2 It contains at least the unit (M unit) represented by the following formula: 1 ~R 6 is an aliphatic hydrocarbon or a hydrogen atom. Organopolysiloxane is composed of a combination of these T units, D units, and M units.

[0049] Specific examples of organopolysiloxanes include polydimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, polysulfone / polyhydroxystyrene / polydimethylsiloxane copolymer, dimethylsiloxane / methylvinylsiloxane copolymer, dimethylsiloxane / diphenylsiloxane / methylvinylsiloxane copolymer, methyl-3,3,3-trifluoropropylsiloxane / methylvinylsiloxane copolymer, dimethylsiloxane / methylphenylsiloxane / methylvinylsiloxane copolymer, diphenylsiloxane / dimethylsiloxane copolymer with vinyl terminals, polydimethylsiloxane with vinyl terminals, polydimethylsiloxane with amino terminals, polydimethylsiloxane with phenyl terminals, polydimethylsiloxane with H terminals, and dimethylsiloxane-methylhydrosiloxane copolymer. The term "vinyl terminal" indicates that at least one end of the main chain contained in the organopolysiloxane is substituted with a substituent such as a vinyl group. These also include forms in which a crosslinked product is formed. The constituent material of the separation layer 3 may be a composite of one or more of these, or a composite material in which, by mass ratio, organopolysiloxane is the main component and other resin components are used in combination.

[0050] Organopolysiloxane has a good affinity for carbon dioxide, so the separation layer 3 containing organopolysiloxane exhibits a high gas selectivity ratio for carbon dioxide.

[0051] If necessary, any functional group may be introduced to the upstream surface of the separation layer 3 using a coupling agent or the like. By appropriately selecting the functional group, the affinity for carbon dioxide can be further increased.

[0052] 2. Gas separation membrane manufacturing method Next, a method for producing a gas separation membrane according to an embodiment will be described. Note that the following description will be given taking as an example a method for producing the gas separation membrane 1 shown in FIG.

[0053] 2 is a process diagram showing the configuration of a method for producing a gas separation membrane according to an embodiment, and FIGS. 3 to 7 are cross-sectional views illustrating the method for producing the gas separation membrane shown in FIG.

[0054] The method for producing a gas separation membrane shown in FIG. 2 includes a coating film forming step S102, an energy applying step S104, and an unnecessary portion removing step S106.

[0055] 2.1.Coating film formation process 3, in the coating film forming step S102, a raw material liquid 40 (liquid raw material) is supplied to the first main surface 21 of the porous body 2. The raw material liquid 40 covers the first main surface 21 and also penetrates into the pores 23. In order to promote the penetration of the raw material liquid 40, the upper part of the porous body 2 may be pressurized, the lower part of the porous body 2 may be depressurized, or the porous body 2 may be heated.

[0056] The raw material liquid 40 is appropriately selected depending on the constituent material of the separation layer 3 to be manufactured. For example, when the separation layer 3 contains a thermosetting resin, the raw material liquid 40 contains an uncured or semi-cured thermosetting resin, a curing agent, a polymerization initiator, and the like.

[0057] Furthermore, when the separation layer 3 contains a photocurable resin, the raw material liquid 40 contains an uncured or semi-cured photocurable resin, a curing agent, a photopolymerization initiator, and the like.

[0058] In addition, the raw material liquid 40 may contain any monomer component that can be polymerized by plasma, electron beams, or the like.

[0059] Examples of methods for supplying the raw material liquid 40 include a dipping method, a dropping method, an inkjet method, a dispenser method, a spray method, a screen printing method, a coater application method, and a spin coating method.

[0060] Note that the porous body 2 may be subjected to pretreatment before supplying the raw material liquid 40. Examples of pretreatment include plasma treatment, ultraviolet irradiation treatment, and ozone treatment.

[0061] After supplying the raw material liquid 40, the supplied raw material liquid 40 may be allowed to stand, if necessary. The time for standing is not particularly limited, but is preferably 24 hours or less, and more preferably 1 hour or more and 20 hours or less.

[0062] The supplied raw material liquid 40 penetrates into the pores 23 due to capillary action. When the degree to which the raw material liquid 40 penetrates due to capillary action is expressed as a wicking height, the wicking height increases as the surface tension of the raw material liquid 40 increases, and decreases as the density of the raw material liquid 40 and the inner radius of the pores 23 increase. For example, if the raw material liquid 40 is silicone oil and the inner radius of the pores 23 is 1 mm, a wicking height of approximately 4.5 mm can be ensured. Therefore, when a porous body 2 having a thickness equal to or less than this wicking height is used, the raw material liquid 40 can efficiently penetrate the pores 23 and be maintained in that state. This allows the raw material liquid 40 to cover the first main surface 21 and the inside of the pores 23 of the porous body 2, ultimately forming a separation layer 3 with a high coverage and few defects.

[0063] In the open-cell filter described above, the pores 23 have few branches and a relatively stable inner radius. This is thought to make it easier for the raw material liquid 40 to penetrate through them by capillary action. Therefore, by using a filter with an open-cell structure as the porous body 2, the raw material liquid 40 can be efficiently and reliably penetrated into the pores 23.

[0064] Furthermore, in order to cover the first main surface 21 and the inside of the pores 23 with the raw material liquid 40, the first main surface 21 of the porous body 2 is also required to have high smoothness. When the surface roughness of the first main surface 21 of the porous body 2 is measured with a measuring device, the maximum height roughness is preferably 200 nm or less, and more preferably 100 nm or less. If it is within this range, the probability that the first main surface 21 can be covered with the raw material liquid 40 increases.

[0065] In addition, since the first main surface 21 has open pores 23, the influence of these pores is reflected in the measurement results of the surface roughness. In light of this, the lower limit of the maximum height roughness is preferably 2 nm or more, and more preferably 10 nm or more.

[0066] A laser microscope equipped with a white light interferometer is used as a surface roughness measuring device. An example of such a laser microscope is the VK-X3000 manufactured by Keyence Corporation. When measuring the maximum height roughness of the first main surface 21, the shape of the first main surface 21 is first scanned at a magnification of 50x. This allows the uneven shape of the first main surface 21 to be obtained. Next, the highest and lowest points are identified within the image, excluding the pores 23. The height difference between these two points is then calculated and used as the maximum height roughness. In other words, the maximum height difference is determined within the area excluding the pores 23 from the measurement results of the uneven shape of the first main surface 21, and this is used as the maximum height roughness of the first main surface 21.

[0067] After the raw material liquid 40 has penetrated into the pores 23, the supplied raw material liquid 40 is dried as necessary. This results in a coating film 42 provided on the first main surface 21, as shown in FIG. 4. Note that a portion of the coating film 42 also penetrates into the pores 23, as shown in FIG. 4. The drying may be natural drying, forced drying, or a combination of both. Natural drying is, for example, a method of leaving the film at room temperature for at least one hour. Forced drying is, for example, a method of heating the film at a temperature of 50°C to 250°C for at least 10 minutes, a method of placing the film under reduced pressure, or a method of blowing gas.

[0068] 2.2. Energy application process In the energy application step S104, as shown in FIG. 5, a process is performed in which energy E is applied from the upper side of the coating film 42 (the side opposite the porous body 2). The process of applying energy E may be any process that can harden or solidify the coating film 42 by the applied energy E, and examples thereof include a process of irradiating with energy rays such as infrared light, visible light, or ultraviolet light, a process of irradiating with plasma, and a process of irradiating with an electron beam. These processes harden or solidify the coating film 42, forming the separation layer 3 shown in FIG. 6. In the following description, "hardening" will be used to abbreviate "hardening or solidifying."

[0069] According to such a treatment, the volume of the raw material liquid 40 is reduced when it is cured, so that the separation layer 3 is formed so as to embrace the porous body 2. This makes it possible to improve the adhesion of the separation layer 3.

[0070] Furthermore, the above-described treatment tends to make the upper surface of the raw material liquid 40 smooth, making it less susceptible to infiltration into the pores 23. This reduces variation in the average thickness A, and even if the average thickness A is reduced, the occurrence of pinholes and the like can be suppressed. As a result, a gas separation membrane 1 with good gas permeability and good adhesion of the separation layer 3 can be efficiently produced.

[0071] In the above process, the entire coating film 42 may be cured, but in this embodiment, as shown in Figure 6, only a portion of the thickness of the coating film 42 is cured. In the above process, energy E is applied from above the coating film 42, so that curing of the coating film 42 progresses downward from the upper surface of the coating film 42. Therefore, by stopping the application of energy E before the entire coating film 42 has cured, it is possible to cure only the upper part of the coating film 42. This makes it possible to easily control the penetration depth B of the separation layer 3 that is formed.

[0072] The process of applying the energy E is optimized depending on the composition of the raw material liquid 40. For example, when the raw material liquid 40 contains an uncured or semi-cured thermosetting resin, the above treatment is preferably a treatment of irradiating the coating film 42 with energy rays, more preferably a treatment of irradiating the coating film 42 with infrared rays as the energy rays. This allows the coating film 42 to be heated without contact, and therefore the coating film 42 can be cured without being damaged, etc. As a result, a high-quality separation layer 3 with few defects can be formed.

[0073] Examples of infrared ray irradiators include infrared flash lamps, halogen lamps, light-emitting diodes, etc. The wavelength of the energy rays irradiated in this case is not particularly limited, but is preferably more than 780 nm and 1 mm or less.

[0074] Furthermore, when the raw material liquid 40 contains an uncured or semi-cured photocurable resin, the above treatment is preferably a treatment of irradiating the coating film 42 with energy rays, more preferably a treatment of irradiating the coating film 42 with visible light or ultraviolet light as the energy rays. This allows the coating film 42 to be cured without contact. As a result, a high-quality separation layer 3 with few defects can be formed.

[0075] Examples of visible light or ultraviolet light irradiation devices include xenon lamps, excimer lamps, cold cathode ultraviolet lamps, femtosecond lasers, light-emitting diodes, etc. The wavelength of the energy beam irradiated in this case is not particularly limited, but visible light is 380 nm or more and 780 nm or less, and ultraviolet light is 10 nm or more and less than 380 nm.

[0076] Furthermore, when the raw material liquid 40 contains a monomer component, the above treatment is preferably a treatment of irradiating the coating film 42 with plasma or electron beams. This polymerizes the monomer component due to the action of the plasma or electron beam, allowing the coating film 42 to harden without contact. As a result, a high-quality separation layer 3 with few defects can be formed. Note that the monomer component may contain an oligomer or prepolymer in addition to a monomer. The plasma may be vacuum plasma or atmospheric pressure plasma.

[0077] Silicone oil is preferably used for the raw material liquid 40. Silicone oil is stable and easy to handle, and has low surface tension, which gives it excellent permeability and defoaming properties for the porous body 2. For this reason, the raw material liquid 40 containing silicone oil is particularly useful for forming the separation layer 3.

[0078] 2.3.Unnecessary part removal process In the unnecessary portion removal step S106, uncured or unsolidified portions (unnecessary portions) of the coating film 42 are removed. This makes it possible to efficiently form a separation layer 3 in which the ratio B / A is controlled to a predetermined value. As a result, the gas separation membrane 1 according to the embodiment can be efficiently manufactured, as shown in FIG.

[0079] The unnecessary portions can be removed by a cleaning process using a cleaning liquid, an ashing process, etc. Among these, the unnecessary portions can be easily removed by the cleaning process.

[0080] The cleaning liquid preferably uses a solvent capable of dissolving the unnecessary parts. Specific examples include normal hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. In addition to these solvents, the cleaning liquid may contain any additives.

[0081] The contact time between the unnecessary parts and the cleaning solution is not particularly limited, but is preferably 5 to 120 minutes, more preferably 10 to 60 minutes, which allows the unnecessary parts to be removed and prevents deterioration of the formed separation layer 3.

[0082] Furthermore, if necessary, vibration may be applied to the unwanted parts while they are in contact with the cleaning liquid, or ultrasonic irradiation or agitation may be performed on the cleaning liquid.

[0083] 3. Effects of the above embodiment The gas separation membrane 1 according to the embodiment is a gas separation membrane that selectively permeates and separates carbon dioxide from a mixed gas containing carbon dioxide, and includes a porous body 2 and a separation layer 3. The porous body 2 is sheet-shaped and has a first main surface 21 and a second main surface 22 that are opposite each other, and pores 23 connecting the first main surface 21 and the second main surface 22. The separation layer 3 is provided on the first main surface 21 and is made of a polymer material. In the gas separation membrane 1 according to the embodiment, a portion of the separation layer 3 extends deeper into the pores 23 than the first main surface 21. Furthermore, when the average thickness of the separation layer 3 is A and the penetration depth of the separation layer 3 into the porous body 2 is B, the ratio B / A in the gas separation membrane 1 according to the embodiment is 30% or more.

[0084] With this configuration, a gas separation membrane 1 having excellent gas permeability to carbon dioxide and excellent adhesion of the separation layer 3 to the porous body 2 can be obtained.

[0085] In the gas separation membrane 1 according to the embodiment, the porous body 2 is a filter with an open-cell structure.

[0086] With this configuration, when forming separation layer 3, the liquid raw material can be easily filled into pores 23, and as a result, separation layer 3 can be reliably formed for each pore 23. This makes it possible to realize a gas separation membrane 1 with excellent gas permeability without impairing the high gas selectivity of separation layer 3.

[0087] In the gas separation membrane 1 according to the embodiment, the porous body 2 has an average thickness of 1 μm or more and 3000 μm or less, and an average pore diameter of 0.01 μm or more and 1000 μm or less.

[0088] With this configuration, the porous body 2 has the necessary and sufficient rigidity to support the separation layer 3. In addition, the gas permeability of the porous body 2 to carbon dioxide can be sufficiently ensured, while preventing the separation layer 3 from escaping to the downstream side of the porous body 2.

[0089] In the gas separation membrane 1 according to the embodiment, the average thickness of the separation layer 3 is 10 nm or more and 1000 nm or less, and the surface roughness of the separation layer 3 is 200 nm or less.

[0090] With this configuration, the separation layer 3 has sufficient gas permeability. As a result, it is possible to reduce the amount of energy input required to separate carbon dioxide, specifically, to realize a gas separation membrane 1 that can reduce the pressure difference between the upstream and downstream sides of the gas separation membrane 1. Furthermore, when the separation layer 3 is formed using a liquid raw material, there is a high probability that the first main surface 21 can be covered with the raw material liquid 40. This allows for the production of a gas separation membrane 1 having a separation layer 3 with a high coverage rate.

[0091] In the gas separation membrane 1 according to the embodiment, the polymer material contains organopolysiloxane.

[0092] With this configuration, a gas separation membrane 1 that exhibits a high gas selectivity ratio to carbon dioxide can be obtained.

[0093] Furthermore, the method for manufacturing a gas separation membrane according to the embodiment is a method for manufacturing a gas separation membrane 1 according to the embodiment, and includes a coating film formation step S102, an energy application step S104, and an unnecessary portion removal step S106. In the coating film formation step S102, a raw material liquid 40 (liquid raw material) is supplied to the first main surface 21 of the porous body 2 to form a coating film 42. In the energy application step S104, energy is applied to the coating film 42 from the side opposite the porous body 2, thereby hardening or solidifying the coating film 42 to form a separation layer 3. In the unnecessary portion removal step S106, portions of the coating film 42 that have not hardened or solidified (unnecessary portions) are removed.

[0094] According to this configuration, a gas separation membrane 1 having excellent gas permeability to carbon dioxide and excellent adhesion of the separation layer 3 to the porous body 2 can be produced efficiently.

[0095] In the method for producing a gas separation membrane according to the embodiment, the raw material liquid 40 (liquid raw material) contains an uncured or semi-cured thermosetting resin, and the energy application process is a process in which infrared rays are irradiated onto the coating film 42 to heat the coating film 42, thereby curing the thermosetting resin.

[0096] According to this configuration, the coating film 42 can be heated without contact, and can be cured without causing damage to the coating film 42. As a result, a high-quality separation layer 3 with few defects can be formed.

[0097] In the method for producing a gas separation membrane according to the embodiment, the liquid raw material 40 (liquid raw material) contains an uncured or semi-cured photocurable resin, and the energy application process is a process in which the coating film 42 is irradiated with visible light or ultraviolet light to cure the photocurable resin.

[0098] With this configuration, the coating film 42 can be cured without contact, and as a result, a high-quality separation layer 3 with few defects can be formed.

[0099] In the method for producing a gas separation membrane according to the embodiment, the raw material liquid 40 (liquid raw material) contains a monomer component, and the energy-imparting treatment is a treatment in which the coating film 42 is irradiated with plasma or an electron beam to polymerize the monomer component.

[0100] With this configuration, the coating film 42 can be cured without contact, and as a result, a high-quality separation layer 3 with few defects can be formed.

[0101] The gas separation membrane and the method for manufacturing the gas separation membrane according to the present invention have been described above based on the preferred embodiments, but the present invention is not limited to these.

[0102] For example, the gas separation membrane of the present invention may be one in which each part of the above embodiment is replaced with a component having a similar function, or one in which any component is added to the above embodiment.

[0103] Furthermore, the method for producing a gas separation membrane according to the present invention may be such that any step for any purpose is added to the above-described embodiment. [Example]

[0104] Next, specific examples of the present invention will be described. 4. Fabrication of Gas Separation Membranes Example 1 First, a porous body was prepared having the structure shown in Table 1. Details of the porous body will be described later.

[0105] Next, silicone oil was placed on the top surface of the porous body as a raw material liquid and spread with a squeegee. This confirmed that the silicone oil had permeated all the pores of the porous body. Shin-Etsu Chemical Co., Ltd.'s KF-96L-10CS silicone oil was used.

[0106] Next, the porous body permeated with silicone oil was left to stand in the air at room temperature for 14 hours while the outer periphery of the porous body was held.

[0107] Next, the porous body was placed in a vacuum plasma device and subjected to plasma treatment under the following conditions.

[0108] Plasma gas: Argon ·Distance between electrodes: 10cm Argon gas flow rate: 346sccm RF power: 600W

[0109] Next, the plasma-treated porous body was immersed in normal hexane and left to stand for 30 minutes, thereby removing uncured silicone oil. In this manner, the gas separation membrane of Example 1 was obtained.

[0110] 4.1. Examples 2 to 13 and Comparative Examples 1 to 4 A gas separation membrane was obtained in the same manner as in Example 1, except that the configuration of the gas separation membrane was changed as shown in Table 1 or Table 2.

[0111] 5. Evaluation of gas separation membranes The gas separation membranes of each example and each comparative example were evaluated as follows.

[0112] 5.1. Gas permeability and gas selectivity for carbon dioxide A test sample was prepared by cutting a circle with a diameter of 5 cm from each of the gas separation membranes of each example and comparative example. Next, a gas mixture of carbon dioxide and nitrogen in a volume ratio of 13:87 was supplied to the upstream side of the test sample using a gas permeability measuring device. The total pressure on the upstream side was adjusted to 5 MPa, the partial pressure of carbon dioxide to 0.65 MPa, the flow rate to 500 mL / min, and the temperature to 40°C. The gas components that permeated the test sample were then analyzed by gas chromatography.

[0113] Next, from the analysis results, the carbon dioxide gas permeability R of the gas separation membrane CO2 and nitrogen gas permeability R N2 and the gas selectivity ratio R of carbon dioxide to nitrogen CO2 / R N2 was calculated.

[0114] Next, the measured carbon dioxide gas permeability R CO2 The carbon dioxide gas permeability of the gas separation membrane was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1 or Table 2.

[0115] A: Carbon dioxide gas permeability R CO2 There are more than 200 GPUs B: Carbon dioxide gas permeability R CO2 is between 100 and 200 GPUs C: Carbon dioxide gas permeability R CO2 is between 15 and 100 GPUs D: Carbon dioxide gas permeability R CO2 has less than 15 GPUs

[0116] In addition, the calculated gas selectivity ratio of carbon dioxide R CO2 / RN2 The gas selectivity of the gas separation membranes for carbon dioxide was evaluated based on the following criteria. The evaluation results are shown in Table 1 or Table 2.

[0117] A: Gas selectivity R CO2 / R N2 is 20 or more B: Gas selectivity R CO2 / R N2 is greater than or equal to 10 and less than 20 C: Gas selectivity R CO2 / R N2 is greater than or equal to 5 and less than 10 D: Gas selectivity R CO2 / R N2 is less than 5

[0118] 5.2. Mechanical properties The gas separation membranes of each example and comparative example were folded into an accordion shape and then stretched. This procedure was repeated 10 times, and the gas separation membranes were then cut into circles with a diameter of 5 cm to prepare test specimens.

[0119] Next, the gas selectivity R of the test piece was measured using the same method as in 5.1. CO2 / R N2 The gas selectivity R before the bending operation was calculated. CO2 / R N2 and the gas selectivity R after the bending operation. CO2 / R N2 The difference between and is the gas selectivity R CO2 / R N2 This decrease in the gas selectivity R CO2 / R N2 The calculated degree of deterioration was used to evaluate the mechanical properties of the gas separation membranes relative to the evaluation criteria below. The evaluation results are shown in Tables 1 and 2.

[0120] A: The decrease in gas selectivity is small (less than 3) B: The gas selectivity ratio is moderately reduced (3 or more and less than 6) C: The gas selectivity ratio decreases significantly (6 or more but less than 9) D: The decrease in gas selectivity is particularly large (9 or more)

[0121] [Table 1]

[0122] [Table 2]

[0123] As is clear from Tables 1 and 2, the gas separation membranes of the examples were found to be excellent in gas permeability and gas selectivity for carbon dioxide.

[0124] Furthermore, it was found that the gas separation membranes of each Example had superior adhesion of the separation layer to the porous body compared to the gas separation membranes of each Comparative Example. [Explanation of symbols]

[0125] 1...gas separation membrane, 2...porous body, 3...separation layer, 21...first main surface, 22...second main surface, 23...pores, 40...raw material liquid, 42...coating film, A...average thickness, B...penetration depth, E...energy, L21...straight line, L31...straight line, L32...straight line, S102...coating film formation step, S104...energy application step, S106...unwanted portion removal step

Claims

1. A gas separation membrane that selectively permeates and separates carbon dioxide from a mixed gas containing carbon dioxide, a sheet-like porous body having a first main surface and a second main surface that are opposite each other, and pores connecting the first main surface and the second main surface; a separation layer provided on the first main surface and made of a polymer material; Equipped with a portion of the separation layer extends deeper into the pores than the first main surface; A gas separation membrane characterized in that, when the average thickness of the separation layer is A and the penetration depth of the separation layer into the porous body is B, the ratio B / A is 30% or more.

2. 2. The gas separation membrane according to claim 1, wherein the porous body is a filter having an open-cell structure.

3. The average thickness of the porous body is 1 μm or more and 3000 μm or less, 3. The gas separation membrane according to claim 1, wherein the average pore diameter of the porous body is 0.01 μm or more and 1000 μm or less.

4. the average thickness A of the separation layer is 10 nm or more and 1000 nm or less, 3. The gas separation membrane according to claim 1, wherein the surface roughness of the porous body is 200 nm or less.

5. 3. The gas separation membrane according to claim 1, wherein the polymer material comprises an organopolysiloxane.

6. 10. A method for producing the gas separation membrane of claim 1, comprising: a step of supplying a liquid raw material to the first main surface of the porous body to form a coating film; a step of applying energy to the coating film from the opposite side of the porous body to harden or solidify the coating film, thereby forming the separation layer; removing any uncured or unhardened portions of the coating; A method for producing a gas separation membrane, comprising:

7. the liquid raw material includes an uncured or semi-cured thermosetting resin; 7. The method for producing a gas separation membrane according to claim 6, wherein the energy application treatment is a treatment in which the coating film is irradiated with infrared rays to heat the coating film, thereby curing the thermosetting resin.

8. the liquid raw material contains an uncured or semi-cured photocurable resin, 7. The method for producing a gas separation membrane according to claim 6, wherein the energy application treatment is a treatment in which the photocurable resin is cured by irradiating the coating with visible light or ultraviolet light.

9. the liquid raw material contains a monomer component, 7. The method for producing a gas separation membrane according to claim 6, wherein the energy-imparting treatment is a treatment in which the coating film is irradiated with plasma or electron beams to polymerize the monomer component.

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