Gas separation membrane and method for producing gas separation membrane

Abstract

Provided are: a gas separation membrane which has excellent gas permeability for carbon dioxide and good adhesion; and a method for producing the gas separation membrane. The gas separation membrane is characterized in that carbon dioxide is selectively permeated and separated from a mixed gas containing carbon dioxide, and the gas separation membrane is provided with: a sheet-shaped porous body having a first main surface and a second main surface which are in a front-back relationship with each other, and pores connecting the first main surface and the second main surface; and a separation layer that is provided on the first main surface and is made of a polymer material, a part of the separation layer enters the inside of the pores further than the first main surface, and the ratio B / A is 30% or more, where A is the average thickness of the separation layer and B is the depth of entry of the separation layer into the porous body.

Description

Technical Field

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

[0002] To achieve carbon neutrality, technologies are being studied to absorb and directly recover atmospheric carbon dioxide. Known technologies include chemical absorption / adsorption, which involves absorbing and adsorbing carbon dioxide using an absorbing liquid or adsorbent material, and membrane separation, which involves separating carbon dioxide using a gas separation membrane.

[0003] Patent Document 1 discloses a gas separation body capable of separating only specific gas components from a multi-component gas mixture. The gas separation body comprises a porous substrate and a metal with gas separation capabilities. The metal with gas separation capabilities fills and seals the interiors of small pores formed on the surface of the porous substrate. This allows the body to separate only specific gas components from a multi-component gas mixture that passes through the pores.

[0004] Furthermore, Patent Document 1 discloses a technique for forming a metal coating inside the pores of a porous substrate by plating.

[0005] However, the separation layer using metal has insufficient carbon dioxide gas permeability. On the other hand, when a non-metallic material such as an organic material is used in the separation layer, there is a possibility that the adhesion between the separation layer and the porous substrate cannot be sufficiently improved.

[0006] Therefore, it has become a challenge to realize a gas separation membrane having excellent carbon dioxide gas permeability and good adhesion of the separation layer.

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 10-113545 Summary of the Invention

[0008] The gas separation membrane involved in the application example of the present invention selectively allows carbon dioxide to pass through and separate from a mixed gas containing carbon dioxide, and comprises: a porous body, which has a first main surface and a second main surface in a front-back relationship with each other, and pores connecting the first main surface and the second main surface, and is in the form of a thin sheet; a separation layer, which is arranged on the first main surface and is composed of a polymer material, and a portion of the separation layer penetrates deeper into the interior of the pores than the first main surface, and when the average thickness of the separation layer is set to A and the penetration depth of the separation layer into the porous body is set to B, the ratio B / A is greater than 30%.

[0009] The manufacturing method of the gas separation membrane involved in the application example of the present invention is a method for manufacturing the gas separation membrane involved in the application example of the present invention, and comprises: a process of supplying liquid raw material to the first main surface of the porous body to form a coating; a process of hardening or solidifying the coating and forming the separation layer by performing a treatment of applying energy from the side of the coating opposite to the porous body; and a process of removing the unhardened or solidified portion of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a cross-sectional view schematically showing a gas separation membrane according to an embodiment.

[0011] Figure 2 It is a process diagram showing the structure of the method for producing a gas separation membrane according to the embodiment.

[0012] Figure 3 For use in Figure 2 sectional views illustrating a method for producing a gas separation membrane.

[0013] Figure 4 For use in Figure 2 sectional views illustrating a method for producing a gas separation membrane.

[0014] Figure 5 For use in Figure 2 sectional views illustrating a method for producing a gas separation membrane.

[0015] Figure 6 For use in Figure 2 sectional views illustrating a method for producing a gas separation membrane.

[0016] Figure 7 For use in Figure 2 sectional views illustrating a method for producing a gas separation membrane. DETAILED DESCRIPTION

[0017] Hereinafter, the gas separation membrane and the method for producing the gas separation membrane of the present invention will be described in detail based on the embodiments shown in the drawings.

[0018] 1. Structure of gas separation membrane

[0019] First, the structure of the gas separation membrane according to the embodiment will be described.

[0020] Figure 1 1 is a cross-sectional view schematically showing a gas separation membrane 1 according to an embodiment. Figure 1 The upper side of the gas separation membrane 1 shown is referred to as the “upstream side” or simply “upper”, and the lower side is referred to as the “downstream side” or simply “lower”.

[0021] Figure 1 The gas separation membrane 1 shown has a function of selectively allowing carbon dioxide to permeate through a mixed gas containing carbon dioxide and non-target components. Figure 1 The gas separation membrane 1 shown is a composite membrane comprising a porous body 2 and a separation layer 3. Non-target components refer to gas components other than carbon dioxide contained in a mixed gas. Examples of non-target components include nitrogen and methane, with nitrogen being particularly contemplated. Therefore, examples of the mixed gas described above include a mixture of carbon dioxide and nitrogen.

[0022] Figure 1 The porous body 2 shown is a porous membrane having a first main surface 21 and a second main surface 22, which are front and back, and pores 23. This porous body 2 has good gas permeability and mechanical properties, and supports the separation layer 3. This improves the mechanical properties of the gas separation membrane 1 as a whole without compromising the good gas selectivity of the separation layer 3.

[0023] Separation layer 3 is composed of a polymer material that is denser (lower in porosity) than porous body 2. This separation layer 3 seals the upper ends of pores 23. Furthermore, separation layer 3 achieves a good gas selectivity by selectively allowing carbon dioxide in the mixed gas supplied upstream to the downstream side of gas separation membrane 1 to permeate. As a result, gas separation membrane 1 is able to separate carbon dioxide from the mixed gas.

[0024] The gas separation membrane 1 of this embodiment has the function of selectively allowing carbon dioxide to pass through. This characteristic is quantitatively expressed by the gas selectivity. Specifically, when the non-target component is nitrogen, the gas permeability of nitrogen through the gas separation membrane 1 is R N2 , the carbon dioxide gas permeability of the gas separation membrane 1 is defined as R CO2 At this time, the gas selectivity R of the gas separation membrane 1 is CO2 / R N2 It is preferably 10 or more, more preferably 20 or more and 50 or less. CO2 / R N2 When the concentration is within the above range, the gas separation membrane 1 can efficiently separate and recover carbon dioxide from the mixed gas.

[0025] Furthermore, when the gas selectivity is below the lower limit, the recovered carbon dioxide will contain a high concentration of non-target components, such as nitrogen. Consequently, if the recovered carbon dioxide is stored or used, this may result in reduced economic efficiency and processing performance. On the other hand, the gas selectivity can be higher than the upper limit, but in this case, it may be difficult to fully increase the carbon dioxide gas permeability of the gas separation membrane 1, and achieving such a gas selectivity may increase the difficulty and cost of manufacturing the gas separation membrane 1.

[0026] In addition, the nitrogen gas permeability R of the gas separation membrane 1 is N2 and the carbon dioxide gas permeability R of the gas separation membrane 1 CO2 The measurements were performed according to the gas permeability test method (Part 1: Differential Pressure Method) specified in JIS K 7126-1:2006. A gas permeability measuring device was used for the measurements. Examples of gas permeability measuring devices include the GTR-11A / 31A manufactured by GTR-TEC 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 allows the gas permeability of nitrogen and carbon dioxide to be measured.

[0027] In the gas separation membrane 1 according to this embodiment, the carbon dioxide gas permeability R CO2 It is preferably 15 GPU or more, more preferably 100 GPU or more and 20,000 GPU or less, and even more preferably 200 GPU or more and 15,000 GPU or less. Thus, it is possible to realize a gas separation membrane 1 that can reduce the input amount of energy required for separation, specifically, can reduce the pressure difference between the upstream side and the downstream side of the gas separation membrane 1. In addition, when the gas permeability R CO2 If the carbon dioxide gas permeability R is lower than the lower limit, the separation of carbon dioxide requires more energy, which may lead to reduced economic performance. CO2 If the value exceeds the upper limit, it may be difficult to maintain a balance with the above-mentioned gas selection ratio. -10 mol·m -2 ·s -1 ·Pa -1 .

[0028] Furthermore, the separation layer 3 is preferably in close contact with the porous body 2. "In close contact" in this specification means that the interface between the separation layer 3 and the porous body 2 is airtight. This airtightness allows the separation layer 3 to isolate the pores 23 of the porous body 2 from one another. In other words, since there is no gap between the separation layer 3 and the porous body 2, communication between the pores 23 through the gap can be suppressed.

[0029] 1.1.Porous body

[0030] The porous body 2 is a thin, porous sheet having pores 23 and exhibiting excellent gas permeability. Furthermore, the porous body 2 has higher rigidity than the separation layer 3 and is responsible for ensuring the mechanical properties of the gas separation membrane 1, such as self-support and durability. Furthermore, if the separation layer 3 has sufficient mechanical properties, the porous body 2 may be omitted.

[0031] Examples of the structural material of the porous body 2 include polymer materials, ceramic materials, and metal materials. Furthermore, the structural material of the porous body 2 may be a composite material of these materials and other materials.

[0032] Examples of the polymer material 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 ether, polysulfone, polyethersulfone, polyimide, polyaramid, and nylon.

[0033] Examples of ceramic materials include alumina, cordierite, mullite, silicon carbide, and zirconia, and examples of metal materials include stainless steel.

[0034] Among them, a filter with a continuous cell structure is preferably used for the porous body 2. A filter with a continuous cell structure, also known as an absolute type filter, has continuous and independent pores 23 extending from the first main surface 21 to the second main surface 22. Therefore, when forming the separation layer 3, it is easy to fill the pores 23 with liquid raw material, resulting in reliable formation of the separation layer 3 for each pore 23. This allows for a gas separation membrane 1 with excellent gas permeability without compromising the gas selectivity of the separation layer 3.

[0035] Filters composed of an aggregate of fibers are also called nominal filters. In such filters, pores 23 may be discontinuous or inadvertently connected. Consequently, when forming separation layer 3, it becomes difficult to fill pores 23 with liquid raw material, potentially causing defects in separation layer 3.

[0036] The shape of the porous body 2 is Figure 1 In addition to the flat plate shape shown, it may also be in a spiral shape, a tubular shape, a hollow filament shape, or the like.

[0037] 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. Thus, the porous body 2 has the necessary and sufficient rigidity to support the separation layer 3. Furthermore, 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, resulting in a decrease in the processing performance of the gas separation membrane 1 or a decrease in the adhesion of the separation layer 3.

[0038] The average thickness of the porous body 2 is an average value of thicknesses in the stacking direction measured at ten locations of the porous body 2. The thickness of the porous body 2 is measured using, for example, a thickness gauge.

[0039] The porous body 2 has pores 23, and its average inner diameter is referred to as the "average pore diameter". The average pore diameter of the porous body 2 is preferably greater than or equal to 0.01 μm and less than or equal to 1000 μm, more preferably greater than or equal to 0.1 μm and less than or equal to 500 μm, further preferably greater than or equal to 0.5 μm and less than or equal to 300 μm, and particularly preferably greater than or equal to 1 μm and less than or equal to 100 μm. In this way, it is possible to suppress the separation layer 3 from escaping to the downstream side of the porous body 2 while fully ensuring the gas permeability of carbon dioxide in the porous body 2. In addition, when the average pore diameter of the porous body 2 is lower than the lower limit value, the gas permeability of carbon dioxide in the porous body 2 may be reduced. On the other hand, when the average pore diameter of the porous body 2 is higher than the upper limit value, the separation layer 3 may be escaping to the downstream side of the porous body 2.

[0040] The average pore diameter of the porous body 2 is measured using a through-pore diameter evaluation device after removing the separation layer 3 from the gas separation membrane 1 and taking out the porous body 2. Examples of the through-pore diameter evaluation device include a Palm Porometer manufactured by PMI.

[0041] The porosity of the porous body 2 is preferably 20% to 90%, more preferably 30% to 80%. This allows the porous body 2 to have both good gas permeability and sufficient rigidity.

[0042] The porosity of the porous body 2 was measured using the above-mentioned through-pore diameter evaluation apparatus after removing the separation layer 3 from the gas separation membrane 1 .

[0043] 1.2. Separation layer

[0044] The separation layer 3 is provided on the first main surface 21 of the porous body 2 and is composed of a polymer material. The separation layer 3 is a substantially dense membrane and has a good affinity for carbon dioxide molecules. Due to this affinity, the separation layer 3 selectively allows carbon dioxide to permeate.

[0045] 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, a gas separation membrane 1 can be achieved that reduces the energy required for carbon dioxide separation, specifically, reduces the pressure difference between the upstream and downstream sides of the gas separation membrane 1. However, if the average thickness of the separation layer 3 is below the lower limit, the probability of defects in the separation layer 3 may increase, or the separation layer 3 may become more susceptible to damage. On the other hand, if the average thickness of the separation layer 3 is above the upper limit, the carbon dioxide gas permeability of the separation layer 3 may decrease, resulting in an increase in the energy required for separation or a decrease in the flexibility of the separation layer 3.

[0046] Furthermore, the average thickness of the separation layer 3 is preferably 0.0050% to 1.0% of the average thickness of the porous body 2, more preferably 0.010% to 0.50%, and even more preferably 0.030% to 0.30%. This optimizes the thickness ratio of the two layers, thereby achieving a good balance between the mechanical properties, gas selectivity, and gas permeability of the gas separation membrane 1.

[0047] The average thickness of the separation layer 3 is obtained as the average value of thicknesses at 10 locations when observing the cross section of the gas separation membrane 1 under magnification. For example, a scanning electron microscope or a transmission electron microscope is used for magnification observation.

[0048] As described above, the thin separation layer 3 made of a polymer material has good gas permeability but tends to have low adhesion to the porous body 2. If the separation layer 3 has low adhesion, it may peel from the porous body 2.

[0049] In contrast, in the gas separation membrane 1 according to this embodiment, a portion of the separation layer 3 penetrates further into the pores 23 than the first main surface 21. Furthermore, when the average thickness of the separation layer 3 is represented by A and the penetration depth of the separation layer 3 into the porous body 2 is represented by B, in the gas separation membrane 1, the ratio B / A is 30% or greater.

[0050] This structure ensures the adhesion of the separation layer 3 even when a membrane made of a polymer material is used as the separation layer 3 and the average thickness A is thin. This provides a gas separation membrane 1 having excellent carbon dioxide gas permeability and good adhesion of the separation layer 3.

[0051] Furthermore, 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.

[0052] In addition, the average thickness A of the separation layer 3 and the penetration depth B of the separation layer 3 into the porous body 2 were measured as follows.

[0053] First, cut the gas separation membrane 1 in the thickness direction and magnify the cross section for observation. At this time, set the magnification so that the thickness of the separation layer 3 as a whole can be captured in one image. Next, take a picture of the magnified image, and in the resulting image, determine the contour lines of the upper surface and the lower surface of the separation layer 3. Furthermore, draw two parallel straight lines L31 and L32 that approximate the two contour lines, and set the distance between the straight lines L31 and L32 as the average thickness A. Figure 1 , an example of straight lines L31 and L32 is shown.

[0054] In addition, the contour line of the upper surface of the porous body 2 is determined in the image. Then, a straight line L21 is drawn that approximates the contour line. In addition, the straight line L21 is also parallel to the two parallel straight lines L31 and L32. And, the distance between the straight line L21 and the straight line L32 is set as the penetration depth B. Figure 1 , an example of the straight line L21 is shown.

[0055] For magnified observation, for example, a scanning electron microscope or a transmission electron microscope is used.

[0056] If the ratio B / A is below the lower limit, the penetration depth B is insufficient, and the adhesion of the separation layer 3 is reduced. In this case, delamination of the separation layer 3 may occur, reducing the durability of the gas separation membrane 1. On the other hand, the ratio B / A may be higher than the upper limit, but the excessive penetration depth B may cause the thickness of the separation layer 3 covering the first main surface 21 of the porous body 2 to become too thin. In this case, the adhesion of the separation layer 3 may be reduced.

[0057] The constituent material of the separation layer 3 is a polymer material. Examples of polymer 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 ether, polysulfone, polyethersulfone, polyimide, polyaramid, organopolysiloxane, polyethylene terephthalate (PET), polyacetal (POM), and polylactic acid (PLA). Furthermore, the constituent material of the separation layer 3 can be a composite material of one or more of these polymer materials. Furthermore, the polymer material can also be a thermoplastic resin, a thermosetting resin, or a light-hardening resin.

[0058] Among them, organopolysiloxane is preferably used as the structural material of the separation layer 3. One molecule of organopolysiloxane contains at least R 1 SiO 3 / 2 Units represented by R 2 R 3 SiO 2 / 2 Units represented by R (D units) and 4 R 5 R 6 SiO 1 / 2 In addition, in each unit, R 1 ~R 6 The organopolysiloxane is composed of a combination of these T units, D units, and M units.

[0059] As the specific example of organopolysiloxane, 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, vinyl-terminated diphenylsiloxane / dimethylsiloxane copolymer, vinyl-terminated polydimethylsiloxane, amino-terminated polydimethylsiloxane, phenyl-terminated polydimethylsiloxane, hydrogen-terminated polydimethylsiloxane, dimethylsiloxane-methylhydrogensiloxane copolymer, etc. can be listed. Vinyl-terminated expressions such as expression that at least one end of the main chain contained in the organopolysiloxane is substituted by a substituent such as vinyl. In addition, these also include the form of forming a crosslinked reaction product. Furthermore, the structural material of the separation layer 3 may be one of these substances or a composite of two or more thereof, or may be a composite material having organopolysiloxane as a main component and other resin components in combination according to a mass ratio.

[0060] In addition, organopolysiloxane has a good affinity for carbon dioxide. Therefore, the separation layer 3 containing organopolysiloxane exhibits a high gas selectivity with respect to carbon dioxide.

[0061] Furthermore, as needed, any functional group may be introduced using a coupling agent or the like on the upstream side of the separation layer 3. By appropriately selecting the functional group, the affinity for carbon dioxide can be further increased.

[0062] 2. Method for manufacturing gas separation membrane

[0063] Next, the method for manufacturing the gas separation membrane according to the embodiment will be described. Figure 1 The method using the gas separation membrane 1 shown will be described as an example.

[0064] Figure 2 It is a process diagram showing the configuration of a method for producing a gas separation membrane according to an embodiment. Figures 3 to 7 For use in Figure 2 sectional views illustrating a method for producing a gas separation membrane.

[0065] Figure 2 The method for producing a gas separation membrane shown includes a coating film forming step S102 , an energy applying step S104 , and an unnecessary portion removing step S106 .

[0066] 2.1. Coating film formation process

[0067] In the coating film forming step S102, as Figure 3 As shown, 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 penetrates into the pores 23. 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.

[0068] The raw material liquid 40 is appropriately set according to the structural material of the separation layer 3 to be produced.

[0069] For example, when the separation layer 3 contains a thermosetting resin, the raw material solution 40 contains an uncured or semi-cured thermosetting resin, a curing agent, a polymerization initiator, and the like.

[0070] When the separation layer 3 includes a photocurable resin, the raw material solution 40 includes an uncured or semi-cured photocurable resin, a curing agent, a photopolymerization initiator, and the like.

[0071] Furthermore, the raw material solution 40 may contain any monomer component that can be polymerized by plasma, electron beam, or the like.

[0072] Examples of a method for supplying the raw material liquid 40 include a dipping method, a dripping method, an inkjet method, a dispensing method, a spray method, a screen printing method, a coater coating method, and a spin coating method.

[0073] Furthermore, the porous body 2 may be pretreated before supplying the raw material liquid 40. Examples of the pretreatment include plasma treatment, ultraviolet irradiation treatment, and ozone treatment.

[0074] After supplying the raw material liquid 40, the supplied raw material liquid 40 may be left to stand as needed. The standing time is not particularly limited, but is preferably 24 hours or less, more preferably 1 hour or more and 20 hours or less.

[0075] The supplied raw material liquid 40 penetrates into the pores 23 by capillary action.

[0076] When the suction lift height is used to represent the extent to which the raw material liquid 40 penetrates through capillary action, the greater the surface tension of the raw material liquid 40, the higher the suction lift height. The greater the density of the raw material liquid 40 and the inner radius of the pore 23, the lower the suction lift height. For example, when the raw material liquid 40 is silicone oil and the inner radius of the pore 23 is 1 mm, a suction lift height of approximately 4.5 mm can be ensured. Therefore, when a porous body 2 having a thickness below this suction lift height is used, the raw material liquid 40 can be efficiently immersed in the pores 23 and can be maintained in this state. As a result, the first main surface 21 of the porous body 2 and the interior of the pores 23 can be covered by the raw material liquid 40, ultimately forming a separation layer 3 with high coverage and few defects.

[0077] Furthermore, in the aforementioned filter with an interconnected cell structure, the pores 23 have few mid-stream branches and a relatively stable inner radius. Therefore, it is believed that capillary action facilitates the infiltration of the raw material liquid 40. Therefore, by using a filter with an interconnected cell structure as the porous body 2, the raw material liquid 40 can be efficiently and reliably infiltrated into the pores 23.

[0078] Furthermore, in order to cover the first principal surface 21 and the interior of the pores 23 with the raw material liquid 40, the first principal surface 21 of the porous body 2 may also be required to have high smoothness. Therefore, when the surface roughness of the first principal surface 21 of the porous body 2 is measured using a measuring device, the maximum height roughness is preferably 200 nm or less, and more preferably 100 nm or less. Within this range, the probability of the first principal surface 21 being covered by the raw material liquid 40 is increased.

[0079] In addition, since the pores 23 are open on the first main surface 21, their influence is reflected in the surface roughness measurement result. In view of this, the lower limit value of the maximum height roughness is preferably 2 nm or more, and more preferably 10 nm or more.

[0080] Regarding the surface roughness measuring device, a laser microscope equipped with a white interferometer is used. Among such laser microscopes, for example, the VK-X3000 manufactured by KEYENCE Co., Ltd. can be cited. In addition, when measuring the maximum height roughness of the first main surface 21, first, the shape of the first main surface 21 is scanned at a magnification of 50 times. Thus, the concave and convex shape of the first main surface 21 is obtained. Next, the highest point and the lowest point are determined within the range excluding the pores 23 in the image. Next, the height difference between these two points is calculated and set as the maximum height roughness. That is, based on the measurement results of the concave and convex shape on the first main surface 21, the maximum height difference is obtained in the part excluding the pores 23, and it is set as the maximum height roughness of the first main surface 21.

[0081] After the raw material liquid 40 is impregnated into the pores 23, the supplied raw material liquid 40 is dried as needed. Figure 4 As shown in FIG. 4 , a coating film 42 is obtained on the first main surface 21. Figure 4 As shown, a portion of the coating 42 also penetrates into the pores 23. Drying can be natural drying, forced drying, or a combination of both. Natural drying is, for example, a method of leaving the coating at room temperature for at least one hour. Forced drying includes, for example, heating at a temperature of 50°C to 250°C for at least 10 minutes, leaving the coating under reduced pressure, or blowing gas.

[0082] 2.2. Energy application process

[0083] like Figure 5 As shown, in the energy application step S104, a process of applying energy E from the upper side of the coating film 42 (the side opposite to the porous body 2) is performed. The process of applying energy E can be any process that can harden or solidify the coating film 42 by the applied energy E. For example, the process of irradiating energy rays such as infrared rays, visible light, and ultraviolet rays, the process of irradiating plasma, the process of irradiating electron beams, etc. can be cited. By these processes, the coating film 42 is hardened or solidified, and a Figure 6 The separation layer 3 is shown. In the following description, "hardening or curing" is omitted and referred to as "hardening".

[0084] According to such a treatment, the solidification of the raw material liquid 40 is accompanied by a volume reduction, so that the separation layer 3 is formed so as to embrace the porous body 2. This can improve the adhesion of the separation layer 3.

[0085] Furthermore, the above-described treatment easily smoothes the upper surface of the raw material liquid 40, making it less susceptible to intrusion into the pores 23. Consequently, the average thickness A exhibits minimal variation, and even when the average thickness A is reduced, the formation of pinholes and the like can be suppressed. Consequently, a gas separation membrane 1 having excellent gas permeability and good adhesion of the separation layer 3 can be efficiently manufactured.

[0086] In the above-mentioned treatment, the entire coating film 42 may be hardened, but in this embodiment, Figure 6 As shown, only a portion of the thickness of the coating film 42 is hardened. In the above-described process, since energy E is applied from the upper side of the coating film 42, the hardening of the coating film 42 progresses from the upper surface of the coating film 42 toward the lower side. Therefore, before the entire coating film 42 is hardened, it is possible to stop applying energy E and harden only the upper portion of the coating film 42. This makes it easy to control the penetration depth B of the formed separation layer 3.

[0087] In addition, the process of applying energy E is optimized according to the structure of the raw material liquid 40 .

[0088] For example, when the raw material liquid 40 contains an uncured or semi-cured thermosetting resin, the above-mentioned treatment is preferably a treatment in which energy rays are irradiated onto the coating film 42, and more preferably a treatment in which infrared rays are irradiated as the energy rays. This allows the coating film 42 to be heated in a non-contact manner, thereby allowing the coating film 42 to be cured without being damaged. As a result, a high-quality separation layer 3 with few defects can be formed.

[0089] Examples of the infrared irradiation device include an infrared flash lamp, a halogen lamp, and a light-emitting diode. In this case, the wavelength of the irradiated energy beam is not particularly limited, but is greater than 780 nm and less than 1 mm.

[0090] Furthermore, when the raw material liquid 40 contains an uncured or semi-cured optically curable resin, the aforementioned treatment is preferably a treatment in which energy rays are irradiated onto the coating film 42, and more preferably a treatment in which visible light or ultraviolet rays are irradiated as the energy rays. This allows the coating film 42 to be cured in a non-contact manner. As a result, a high-quality separation layer 3 with few defects can be formed.

[0091] Examples of the irradiation device for visible light or ultraviolet light include xenon lamps, excimer lamps, cold cathode ultraviolet lamps, femtosecond lasers, light emitting diodes, etc. Furthermore, the wavelength of the energy ray irradiated in this case is not particularly limited, but the wavelength is 380 nm to 780 nm for visible light and 10 nm to less than 380 nm for ultraviolet light.

[0092] Moreover, when the raw material liquid 40 contains a monomer component, the above-mentioned treatment is preferably set as a treatment of irradiating the coating film 42 with plasma or electron beam. Thus, the monomer component is polymerized by the action of the plasma or electron beam, so that the coating film 42 can be hardened in a non-contact manner. As a result, a separation layer 3 with few defects and high quality can be formed. In addition, the monomer component may contain oligomers and prepolymers in addition to monomers. In addition, the plasma can be either vacuum plasma or atmospheric pressure plasma.

[0093] Silicone oil is preferably used in the raw material liquid 40. Silicone oil is stable and easy to handle, and due to its low surface tension, it has excellent permeability and defoaming properties into the porous body 2. Therefore, the raw material liquid 40 containing silicone oil is particularly useful for forming the separation layer 3.

[0094] 2.3. Do not perform partial removal process

[0095] In the unnecessary portion removal step S106, the uncured or unhardened portion (unnecessary portion) of the coating film 42 is removed. This allows efficient formation of the separation layer 3 in which the ratio B / A is controlled to a predetermined value. Figure 7 As shown, the gas separation membrane 1 according to the embodiment can be produced efficiently.

[0096] In order to remove the unnecessary portion, a cleaning process using a cleaning liquid, an ashing process, etc. are used. Among them, the unnecessary portion can be easily removed by the cleaning process.

[0097] In the cleaning solution, it is preferred to use a solvent that can dissolve the unwanted portion. As specific examples, n-hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone etc. can be enumerated. In addition, in the cleaning solution, in addition to these solvents, any additives can also be added.

[0098] The contact time of the unnecessary portion with the cleaning solution is not particularly limited, but is preferably 5 minutes to 120 minutes, more preferably 10 minutes to 60 minutes. This allows the unnecessary portion to be removed while suppressing degradation of the formed separation layer 3.

[0099] Furthermore, if necessary, the unnecessary portion may be subjected to vibration treatment while being in contact with the cleaning liquid, or the cleaning liquid may be subjected to ultrasonic irradiation treatment or stirring treatment.

[0100] 3. Effects of the above implementation methods

[0101] The gas separation membrane 1 according to the above embodiment is a gas separation membrane that selectively allows carbon dioxide to permeate and separate from a mixed gas containing carbon dioxide, and includes a porous body 2 and a separation layer 3. The porous body 2 has a first main surface 21 and a second main surface 22, which are front and back, and pores 23 connecting the first main surface 21 and the second main surface 22, and is in the form of a thin sheet. The separation layer 3 is provided on the first main surface 21 and is composed of a polymer material. In addition, in the gas separation membrane 1 according to the above embodiment, a portion of the separation layer 3 penetrates deeper into the pores 23 than the first main surface 21. Moreover, when the average thickness of the separation layer 3 is represented by A and the penetration depth of the separation layer 3 into the porous body 2 is represented by B, in the gas separation membrane 1 according to the above embodiment, the ratio B / A is 30% or more.

[0102] With such a structure, it is possible to obtain a gas separation membrane 1 having excellent carbon dioxide gas permeability and good adhesion of the separation layer 3 to the porous body 2 .

[0103] Furthermore, in the gas separation membrane 1 according to the above embodiment, the porous body 2 is a filter having an interconnected cell structure.

[0104] With this structure, when forming the separation layer 3, the liquid raw material can be easily filled into the pores 23, resulting in that the separation layer 3 can be reliably formed for each pore 23. This allows for a gas separation membrane 1 having excellent gas permeability without compromising the high gas selectivity of the separation layer 3.

[0105] In the gas separation membrane 1 according to the above embodiment, the average thickness of the porous body 2 is 1 μm to 3000 μm, and the average pore diameter of the porous body 2 is 0.01 μm to 1000 μm.

[0106] With this structure, the porous body 2 has the rigidity necessary and sufficient to support the separation layer 3. Furthermore, the separation layer 3 can be prevented from escaping to the downstream side of the porous body 2 while ensuring a sufficient carbon dioxide gas permeability of the porous body 2.

[0107] Furthermore, in the gas separation membrane 1 according to the above embodiment, the average thickness of the separation layer 3 is 10 nm to 1000 nm, and the surface roughness of the separation layer 3 is 200 nm or less.

[0108] This structure allows the separation layer 3 to have sufficient gas permeability. Consequently, it is possible to achieve a gas separation membrane 1 that reduces the amount of energy required for carbon dioxide separation, specifically, that reduces the pressure difference between the upstream and downstream sides of the gas separation membrane 1. Furthermore, when a liquid raw material is used to form the separation layer 3, the probability of the raw material liquid 40 covering the first main surface 21 increases. This results in a gas separation membrane 1 having a separation layer 3 with a high coverage rate.

[0109] Furthermore, in the gas separation membrane 1 according to the above embodiment, the polymer material includes organopolysiloxane.

[0110] With such a structure, it is possible to obtain a gas separation membrane 1 that exhibits a high gas selectivity for carbon dioxide.

[0111] The method for manufacturing a gas separation membrane according to the above-described embodiment is a method for manufacturing the gas separation membrane 1 according to the above-described embodiment, and includes a coating film forming step S102, an energy application step S104, and an unnecessary portion removal step S106. 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 to form a coating film 42. In the energy application step S104, energy is applied to the coating film 42 from the side opposite to the porous body 2, thereby hardening or solidifying the coating film 42 and forming the separation layer 3. In the unnecessary portion removal step S106, the unhardened or unsolidified portion (unnecessary portion) of the coating film 42 is removed.

[0112] According to such a structure, the gas separation membrane 1 having excellent carbon dioxide gas permeability and good adhesion of the separation layer 3 to the porous body 2 can be efficiently produced.

[0113] Furthermore, in the gas separation membrane manufacturing method according to the above-described embodiment, the raw material liquid 40 (liquid raw material) contains an uncured or semi-cured thermosetting resin. Furthermore, the energy application treatment is a treatment for curing the thermosetting resin by irradiating the coating film 42 with infrared rays to heat the coating film 42.

[0114] According to such a structure, the coating film 42 can be heated in a non-contact manner, and thus 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.

[0115] In the gas separation membrane manufacturing method according to the above embodiment, the raw material liquid 40 (liquid raw material) contains an uncured or semi-cured optically hardening resin. Furthermore, the energy application treatment involves irradiating the coating film 42 with visible light or ultraviolet light to cure the optically hardening resin.

[0116] According to such a structure, the coating film 42 can be cured in a non-contact manner. As a result, a high-quality separation layer 3 with few defects can be formed.

[0117] In the gas separation membrane manufacturing method according to the above embodiment, the raw material liquid 40 (liquid raw material) contains a monomer component, and the energy application treatment is a treatment for irradiating the coating film 42 with plasma or electron beams to polymerize the monomer component.

[0118] According to such a structure, the coating film 42 can be cured in a non-contact manner. As a result, a high-quality separation layer 3 with few defects can be formed.

[0119] As mentioned above, the gas separation membrane and the method for producing the gas separation membrane according to the present invention have been described based on preferred embodiments, but the present invention is not limited thereto.

[0120] For example, the gas separation membrane according to the present invention may have a structure in which each component of the above-described embodiment is replaced with a structure having the same function, or may have a structure in which arbitrary structures are added to the above-described embodiment.

[0121] Furthermore, the method for producing a gas separation membrane according to the present invention may include additional steps for any purpose in the above-mentioned embodiment.

[0122] Example

[0123] Next, specific examples of the present invention will be described.

[0124] 4. Fabrication of gas separation membranes

[0125] Example 1

[0126] First, a porous body having the structure shown in Table 1 was prepared. The details of the porous body will be described later.

[0127] Next, silicone oil, a raw material liquid, was placed on the upper surface of the porous body and spread with a spatula. This confirmed that the silicone oil had penetrated all the pores of the porous body. KF-96L-10CS, manufactured by Shin-Etsu Chemical Co., Ltd., was used as the silicone oil.

[0128] Next, the porous body was left standing at room temperature for 14 hours in the atmosphere while the outer periphery of the porous body was impregnated with silicone oil.

[0129] Next, the porous body was placed in a vacuum plasma device and subjected to plasma treatment. The plasma treatment conditions were as follows.

[0130] Plasma gas: Argon

[0131] Distance between electrodes: 10cm

[0132] Argon flow rate: 346 sccm

[0133] RF power: 600W

[0134] Next, the plasma-treated porous body was immersed in n-hexane and allowed to stand for 30 minutes to remove uncured silicone oil.

[0135] The gas separation membrane of Example 1 was obtained in the above manner.

[0136] 4.1. Examples 2 to 13 and Comparative Examples 1 to 4

[0137] A gas separation membrane was obtained in the same manner as in Example 1 except that the structure of the gas separation membrane was changed as shown in Table 1 or Table 2.

[0138] 5. Evaluation of gas separation membranes

[0139] The gas separation membranes of the Examples and Comparative Examples were evaluated as follows.

[0140] 5.1. Carbon dioxide gas permeability and gas selectivity

[0141] The gas separation membranes of each Example and Comparative Example were cut into circular shapes with a diameter of 5 cm to prepare test samples. Next, using a gas permeability measurement device, a mixed gas consisting of carbon dioxide and nitrogen at a volume ratio of 13:87 was supplied upstream of the test samples. The upstream total pressure was adjusted to 5 MPa, the carbon dioxide partial pressure to 0.65 MPa, the flow rate to 500 mL / min, and the temperature to 40°C. The gas components permeating the test samples were then analyzed by gas chromatography.

[0142] Next, the carbon dioxide gas permeability R of the gas separation membrane was calculated based on the analysis results. CO2 And the gas permeability R of nitrogen N2 , and calculate the gas selectivity ratio R of carbon dioxide to nitrogen CO2 / R N2 .

[0143] Next, the measured carbon dioxide gas permeability R CO2 The carbon dioxide gas permeability in the gas separation membrane was evaluated in accordance with the following evaluation criteria. The evaluation results are shown in Table 1 or Table 2.

[0144] A: Carbon dioxide gas permeability R CO2 More than 200 GPUs

[0145] B: Carbon dioxide gas permeability R CO2More than 100 GPUs and less than 200 GPUs

[0146] C: Carbon dioxide gas permeability R CO2 More than 15 GPUs and less than 100 GPUs

[0147] D: Carbon dioxide gas permeability R CO2 Less than 15 GPUs

[0148] In addition, the calculated gas selectivity ratio R of carbon dioxide is CO2 / R N2 The gas selectivity of carbon dioxide in the gas separation membrane was evaluated in accordance with the following evaluation criteria. The evaluation results are shown in Table 1 or Table 2.

[0149] A: Gas selection ratio R CO2 / R N2 More than 20

[0150] B: Gas selection ratio R CO2 / R N2 10 or more and less than 20

[0151] C: Gas selection ratio R CO2 / R N2 5 or more and less than 10

[0152] D: Gas selection ratio R CO2 / R N2 Less than 5

[0153] Mechanical properties

[0154] The gas separation membranes of each example and comparative example were folded into a corrugated shape and then unfolded. This operation was repeated 10 times, and then the gas separation membranes were cut into circular pieces with a diameter of 5 cm to prepare test pieces.

[0155] Next, the gas selectivity R was calculated for the test piece using the same method as in 5.1. CO2 / R N2 Then, the gas selection ratio R before the bending operation is performed CO2 / R N2 Compared with the gas selection ratio R after the bending operation CO2 / R N2 The difference between the two is the gas selectivity ratio R CO2 / R N2 The reduction is calculated based on the reduction in the gas selectivity R due to the bending operation. CO2 / R N2The calculated degree of deterioration is used as an indicator of the degree of deterioration. The mechanical properties of the gas separation membrane were relatively evaluated by comparing the calculated degree of deterioration with the following evaluation criteria. The evaluation results are shown in Table 1 or Table 2.

[0156] A: The reduction in gas selectivity is small (less than 3)

[0157] B: The gas selectivity ratio decreases moderately (3 or more and less than 6)

[0158] C: The gas selectivity ratio decreases significantly (6 or more and less than 9)

[0159] D: The gas selectivity ratio decreases significantly (above 9)

[0160] Table 1 Table @

[0161]

[0162] Table 2

[0163] Table 2

[0164]

[0165] As is clear from Tables 1 and 2, the gas separation membranes of the respective Examples are excellent in carbon dioxide gas permeability and gas selectivity.

[0166] Furthermore, it was found that the gas separation membranes of the examples had better adhesion of the separation layer to the porous body than the gas separation membranes of the comparative examples.

[0167] Explanation of symbols

[0168] 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; A…average thickness; B…penetration depth; E…energy; L21…straight line; L31…straight line; L32…straight line; S102…coating formation step; S104…energy application step; S106…unnecessary portion removal step.

Claims

1. A gas separation membrane, characterized in that: The gas separation membrane selectively allows carbon dioxide to permeate and separate from a mixed gas containing carbon dioxide, and comprises: A porous body having a first main surface and a second main surface in a front-to-back relationship and pores connecting the first main surface and the second main surface, and being in a sheet shape; a separation layer provided on the first main surface and made of a polymer material, A portion of the separation layer extends further into the pores than the first main surface, When the average thickness of the separation layer is represented by A and the penetration depth of the separation layer into the porous body is represented by B, the ratio B / A is 30% or more.

2. The gas separation membrane according to claim 1, wherein The porous body is a filter with a continuous bubble structure.

3. The gas separation membrane according to claim 1 or 2, wherein The average thickness of the porous body is 1 μm or more and 3000 μm or less, The porous body has an average pore diameter of 0.01 μm or more and 1000 μm or less.

4. The gas separation membrane according to claim 1 or 2, wherein The average thickness A of the separation layer is greater than or equal to 10 nm and less than or equal to 1000 nm, The surface roughness of the porous body is 200 nm or less.

5. The gas separation membrane according to claim 1 or 2, wherein The polymer material includes organopolysiloxane.

6. A method for manufacturing a gas separation membrane, characterized in that: The method for manufacturing the gas separation membrane is a method for manufacturing the gas separation membrane according to claim 1, and comprises: supplying a liquid raw material to the first main surface of the porous body to form a coating film; a step of hardening or solidifying the coating film and forming the separation layer by performing a treatment of applying energy from the side of the coating film opposite to the porous body; The process of removing the uncured or unhardened portion of the coating film.

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

8. The method for producing a gas separation membrane according to claim 6, wherein: The liquid raw material includes uncured or semi-cured optically hardening resin. The energy application treatment is a treatment for curing the photocurable resin by irradiating the coating film with visible light or ultraviolet light.

9. The method for producing a gas separation membrane according to claim 6, wherein: The liquid raw material contains a monomer component, The energy application treatment is a treatment for polymerizing the monomer component by irradiating the coating film with plasma or electron beam.

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