CO2 separation membrane, CO2 separation element, and method for manufacturing a CO2 separation membrane

Abstract

This invention provides a technology for forming a more uniform film thickness in CO2 separation membranes. [Solution] The hydrophobic nonwoven fabric substrate 100 is permeable to gases and repels water-soluble CO2 separation solution. The CO2 separation gel layer 104 is provided on the hydrophobic nonwoven fabric substrate 100 and is formed by the drying of the CO2 separation solution. The hydrophobic nonwoven fabric substrate 100 has a modified portion 101 on the surface that comes into contact with the CO2 separation gel layer 104. The wettability of the modified portion 101 to the CO2 separation solution is greater than the wettability of the hydrophobic nonwoven fabric substrate 100 excluding the modified portion 101 to the CO2 separation solution.

Description

[Technical Field]

[0001] This disclosure relates to a CO2 separation membrane for separating CO2 from air, a CO2 separation element, and a method for manufacturing a CO2 separation membrane. [Background technology]

[0002] A CO2 separation element is constructed by coating a CO2 separation material onto a substrate. A porous substrate with CO2 permeability is used as the substrate (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 11-509251 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When forming a CO2 separation element, from the viewpoint of CO2 separation efficiency, it is preferable that the CO2 separation material be coated onto a porous substrate to achieve a more uniform film thickness. In other words, in order to improve CO2 separation efficiency, there is a need for technological development to form a more uniform film thickness.

[0005] This disclosure was made to solve the above-mentioned problems and aims to provide a technology for forming a more uniform film thickness in a CO2 separation membrane. [Means for solving the problem]

[0006] To solve the above problems, a CO2 separation membrane according to one embodiment of the present invention comprises a hydrophobic nonwoven fabric substrate that is permeable to gases and repels a water-soluble CO2 separation solution, and a CO2 separation gel layer provided on the hydrophobic nonwoven fabric substrate and formed by the drying of the CO2 separation solution. The hydrophobic nonwoven fabric substrate has a modified portion on the surface that contacts the CO2 separation gel layer. The wettability of the modified portion to the CO2 separation solution is greater than the wettability of the hydrophobic nonwoven fabric substrate excluding the modified portion to the CO2 separation solution.

[0007] Another aspect of the present invention is a method for manufacturing a CO2 separation membrane. This method comprises a surface treatment step of forming a modified portion on one surface of a hydrophobic nonwoven fabric substrate having gas permeability and CO2 separation solution penetration suppression by a wettability improvement treatment; a coating step of applying a CO2 separation solution to the modified portion; and a drying step of drying the applied CO2 separation solution to form a CO2 separation gel layer, which is a gel of the CO2 separation solution. The wettability of the modified portion to the CO2 separation solution is greater than the wettability of the hydrophobic nonwoven fabric substrate excluding the modified portion to the CO2 separation solution. [Effects of the Invention]

[0008] According to this disclosure, a more uniform film thickness can be formed in a CO2 separation membrane. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing an example of the installation of the CO2 separation system according to this embodiment. [Figure 2] Figures 2(a) and 2(b) show an overview of the CO2 separation element shown in Figure 1. [Figure 3] Figure 3 is a perspective view showing the stacked structure used as the CO2 separation element in Figure 1. [Figure 4] Figure 4 is a schematic cross-sectional view showing the structure of the CO2 separation membrane shown in Figures 2(a)-(b). [Figure 5] Figure 5 is a flowchart showing the manufacturing procedure for a CO2 separation membrane. [Figure 6]This table shows the evaluation results of the film-forming properties and film performance (CO2 permeance, CO2 / N2 selectivity) of the CO2 separation solutions in Examples 1-3 and Comparative Examples 1-4. [Modes for carrying out the invention]

[0010] Before describing this embodiment, let's outline it briefly. When a hydrophilic nonwoven fabric substrate is used as the substrate for forming a CO2 separation membrane, the CO2 separation material applied to the hydrophilic nonwoven fabric substrate penetrates into the interior of the hydrophilic nonwoven fabric substrate. In other words, almost no CO2 separation material remains on the coated surface of the hydrophilic nonwoven fabric substrate, making it difficult to form a CO2 separation membrane. Examples of hydrophilic nonwoven fabric substrates include polyester (PET: Polyethylene Terephthalate) or nylon. On the other hand, when using a hydrophobic nonwoven fabric as a substrate for forming a CO2 separation membrane, the hydrophobic nonwoven fabric repels the coated CO2 separation material, making it difficult to form a CO2 separation membrane with a uniform film thickness. Examples of hydrophobic nonwoven fabrics include polyethylene (PE) or polypropylene (PP).

[0011] Therefore, in this embodiment, a modified portion is provided on one surface of the hydrophobic nonwoven fabric substrate to improve its wettability with respect to the CO2 separation material. With this configuration, the CO2 separation solution penetrates only to the surface (modified portion) of the hydrophobic nonwoven fabric substrate, and penetration is suppressed in areas other than the modified portion. As a result, the hydrophobic nonwoven fabric substrate does not repel the CO2 separation solution, and the penetration of the CO2 separation solution into the interior of the nonwoven fabric is suppressed, making it possible to form a CO2 separation film on the surface of the hydrophobic nonwoven fabric substrate.

[0012] Hereinafter, embodiments will be described with reference to the drawings. Note that the following embodiments are an example of embodying the present disclosure and do not limit the technical scope of the present disclosure. Also, each figure described in the embodiments is a schematic figure, and the ratio of the size and thickness of each component in each figure does not necessarily reflect the actual dimensional ratio.

[0013] Embodiments of the present disclosure will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an installation example of the CO2 separation system 1. The CO2 separation system 1 is installed indoors in a building 2 such as a house. The CO2 separation system 1 is a device that removes a target gas (for example, CO2, etc.) from the air in the target indoor space. The CO2 separation system 1 includes a housing 10, a CO2 separation element 20, an indoor fan 31, an indoor filter 37, an outdoor fan 41, an outdoor filter 47, a first temperature control unit 4a, a second temperature control unit 4b, a control unit 5, an outdoor temperature detection unit 7, and an indoor temperature detection unit 8, which are collectively referred to as the temperature control unit 4.

[0014] The housing 10 is the outer frame of the CO2 separation system 1. An indoor air inlet 33, an air supply port 35, an outdoor air inlet 43, and an exhaust port 45 are arranged on the outer periphery of the housing 10. The indoor air inlet 33 is a suction port that sucks air 39a into the CO2 separation system 1. The indoor air inlet 33 is communicatively connected to an indoor suction port 51 provided in the building 2 and an indoor air introduction duct 52. The indoor suction port 51 is an opening provided in the target space of the building 2 and is an opening for introducing the air 39a (indoor air) in the target space into the CO2 separation system 1 as RA. The indoor air introduction duct 52 is a duct for introducing indoor air into the housing 10. One end of the indoor air introduction duct 52 is connected to the indoor suction port 51, and RA from indoors flows into the indoor air introduction duct 52. The other end of the indoor air introduction duct 52 is connected to the indoor air inlet 33, and RA is circulated into the housing 10. That is, the air in the target space indoors is introduced and circulated as indoor air in the indoor air introduction duct 52.

[0015] The air supply port 35 is an outlet for discharging the air 39b from the CO2 separation system 1. The air supply port 35 is communicatively connected to the indoor outlet 53 provided in the building 2 and the indoor air discharge duct 54. The indoor outlet 53 is an opening provided in the building 2 and is an opening for supplying the air 39b with a reduced CO2 concentration by the CO2 separation element 20 as SA to the target space. The indoor air discharge duct 54 is a duct for supplying the indoor air from the housing 10 to the target space. One end of the indoor air discharge duct 54 is connected to the air supply port 35, and the air 39b with a reduced CO2 concentration by the CO2 separation element 20 flows into the duct. The other end of the indoor air discharge duct 54 is connected to the indoor outlet 53, and the air 39b in the duct is supplied as SA to the target space. That is, the indoor air discharge duct 54 refluxes the air 39b to the target space.

[0016] The outside air port 43 is a suction port for sucking the air 49a into the CO2 separation system 1. The outside air port 43 is communicatively connected to the outdoor suction port 55 provided in the building 2 and the outside air introduction duct 56. The outdoor suction port 55 is an opening provided in the building 2 and is an opening for introducing the outdoor air 49a (outside air) as OA into the CO2 separation system 1. The outside air introduction duct 56 is a duct for introducing the outside air into the housing 10. One end of the outside air introduction duct 56 is connected to the outdoor suction port 55, and the OA from the outside flows into the outside air introduction duct 56. The other end of the outside air introduction duct 56 is connected to the outside air port 43, and the OA is circulated into the housing 10. That is, the outside air is introduced and circulated as the outside air into the outside air introduction duct 56.

[0017] The exhaust port 45 is an outlet that discharges air 49b from the CO2 separation system 1 to the outdoors. The exhaust port 45 is connected to an outdoor outlet 57 provided in the building 2 by an outdoor air discharge duct 58. The outdoor outlet 57 is an opening provided in the building 2 that discharges air 49b, whose CO2 concentration has increased due to the CO2 separation element 20, to the outdoors as EA. The outdoor air discharge duct 58 is a duct that supplies outside air from the housing 10 to the outdoors. One end of the outdoor air discharge duct 58 is connected to the exhaust port 45, and air 49b, whose CO2 concentration has increased due to the CO2 separation element 20, flows into the duct. The other end of the outdoor air discharge duct 58 is connected to the outdoor outlet 57, and the air 49b in the duct is discharged to the outdoors as EA. In other words, the outdoor air discharge duct 58 releases air 49b to the outdoors.

[0018] Hereafter, air 39a and air 39b may be collectively referred to as "internal air," and air 49a and air 49b may be collectively referred to as "external air." Additionally, the internal air intake duct 52 and the internal air discharge duct 54 may be grouped together as an "internal air passage," and the external air intake duct 56 and the external air discharge duct 58 may be grouped together as an "external air passage."

[0019] Here, we will describe the diameter of each duct. In this embodiment, the diameters of the outside air intake duct 56 and the outside air outlet duct 58, through which outside air flows, are smaller than the diameters of the inside air intake duct 52 and the inside air outlet duct 54, through which inside air flows. This is to make the flow rate of outside air circulating within the CO2 separation system 1 smaller than the flow rate of inside air. This makes it possible to suppress pressure loss on the outside air side. In addition, heat exchange generally occurs due to the temperature difference between outside air and inside air, but since the flow rate of outside air is suppressed, heat loss due to heat exchange can be suppressed.

[0020] The enclosure 10 is equipped with a CO2 separation element 20, an internal fan 31 (circulation fan), an internal filter 37, an external fan 41, and an external filter 47. The CO2 separation element 20 separates CO2 from the internal air that has flowed through the internal air intake duct 52 and introduces the CO2 into the external air that has flowed through the external air intake duct 56. This can also be described as a component that selectively permeates CO2 from the internal air to the external air. Details of the CO2 separation element 20 will be described later.

[0021] The internal fan 31 is a blower that draws in internal air from the target space through the internal air port 33 and discharges it back into the target space through the air supply port 35. By driving the internal fan 31, the internal air drawn in from the target space through the internal air port 33 passes through the internal filter 37, the CO2 separation element 20, and the internal fan 31, and is discharged back into the target space through the air supply port 9. It is preferable that the airflow rate delivered by the internal fan 31 is greater than the airflow rate delivered by the external fan 41. The internal filter 37 is a filter that removes dirt and dust from the internal air flowing into the housing 10 and supplies the purified air to the CO2 separation element 20, and is, for example, a HEPA (High Efficiency Particulate Air) filter.

[0022] The outdoor fan 41 is a fan that draws in outside air from outdoors through the outdoor air inlet 43 and discharges it outdoors through the exhaust port 45. When the outdoor fan 41 is driven, the outside air drawn in from outdoors through the outdoor air inlet 43 passes through the outdoor air filter 47, the CO2 separation element 20, and the outdoor fan 41, and is discharged outdoors through the exhaust port 45. It is preferable that the airflow rate delivered by the outdoor fan 41 is smaller than the airflow rate delivered by the indoor fan 31. The outdoor fan 41 is installed, for example, downstream of the outdoor air filter 47 and upstream of the CO2 separation element 20. With this arrangement, the heat generated by the operation of the outdoor fan 41 can warm the outside air, and when the outside air is colder than the indoor air, the heat loss due to heat exchange between the outside air and the indoor air is reduced. The outdoor fan 41 may also be installed downstream of the CO2 separation element 20. The outside air filter 47 is a filter that removes dust and dirt from the outside air that flows into the housing 10 and supplies the purified air to the CO2 separation element 20, and is, for example, a HEPA filter.

[0023] Here, we will explain the overview of CO2 separation by the CO2 separation element 20. Figures 2(a) and 2(b) show an overview of the CO2 separation element 20. Figure 2(a) is a cross-sectional view showing a simplified configuration of the CO2 separation element 20. As shown in Figure 2, the CO2 separation element 20 is formed by stacking a gas passage 16 through which internal air (gas to be treated) flows from left to right, and a sweep gas passage 17 through which external air (sweep gas) flows from left to right, in the vertical direction. A CO2 separation membrane 22 is placed between the gas passage 16 and the sweep gas passage 17. The gas to be treated introduced into the gas passage 16 contains a mixture of CO218 and N219. Actual air also contains O2, etc., but these are omitted here for clarity of explanation. As the gas to be treated flows through the gas to be treated airflow passage 16 along the CO2 separation membrane 22, the CO2 separation membrane 22 selectively permeates the CO218 in the gas to be treated and discharges it into the sweep gas in the sweep gas airflow passage 17. As a result, the concentration of CO218 in the gas to be treated decreases, while the concentration of CO218 in the sweep gas increases.

[0024] Figure 2(b) shows the configuration of the CO2 separation element 20 for more efficient CO218 separation than Figure 2(a). The CO2 separation element 20 includes the first to third target gas airflow passages 16a to 16c, collectively referred to as the target gas airflow passage 16; the first to third sweep gas airflow passages 17a to 17c, collectively referred to as the sweep gas airflow passage 17; and the first to fifth CO2 separation membranes 22a to 22e, collectively referred to as the CO2 separation membrane 22. The number of target gas airflow passages 16 and sweep gas airflow passages 17 is not limited to "3". From top to bottom, the first sweep gas airflow passage 17a, the first target gas airflow passage 16a, the second sweep gas airflow passage 17b, the second target gas airflow passage 16b, the third sweep gas airflow passage 17c, and the third target gas airflow passage 16c are arranged in that order. Furthermore, a first CO2 separation membrane 22a is positioned between the first sweep gas airflow 17a and the first gas to be treated airflow 16a, a second CO2 separation membrane 22b is positioned between the first gas to be treated airflow 16a and the second sweep gas airflow 17b, and a third CO2 separation membrane 22c is positioned between the second sweep gas airflow 17b and the second gas to be treated airflow 16b. A fourth CO2 separation membrane 22d is positioned between the second gas to be treated airflow 16b and the third sweep gas airflow 17c, and a fifth CO2 separation membrane 22e is positioned between the third sweep gas airflow 17c and the third gas to be treated airflow 16c. Similar to Figure 2(a), CO218 of the gas to be treated flowing through the gas to be treated airflow 16 is selectively permeated through the CO2 separation membrane 22 and discharged into the sweep gas in the sweep gas airflow 17.

[0025] Figure 3 is a perspective view showing a laminated structure 6 used as a CO2 separation element 20. In the following description, the stacking direction of the laminated structure 6 will be described as the vertical up-and-down direction, but this does not necessarily represent the direction in actual use. The laminated structure 6 is a structure in which rectangular frames 14 and rectangular CO2 separation element pieces 21 made of CO2 separation membranes 22 are alternately stacked in the vertical direction, and the treated gas airflow passage 16 and the sweep gas airflow passage 17 that intersects the treated gas airflow passage 16 are alternately configured one layer at a time. More specifically, the laminated structure 6 is constructed by repeatedly stacking the CO2 separation element pieces 21 and frames 14 while fitting the CO2 separation element pieces 21 to the ends of the frames 14 from both the upper and lower surfaces. When fitting the CO2 separation element pieces 21 to the frames 14 from both the upper and lower surfaces, the frames 14 are stacked orthogonally so that they are staggered one layer at a time. With this configuration, as shown in Figure 2(b), alternating treated gas air passages 16 through which the treated gas passes and sweep gas air passages 17 through which the sweep gas passes are formed. By allowing the treated gas taken in from the target space to flow through the treated gas air passage 16 and the sweep gas to flow through the sweep gas air passage 17, the treated gas and sweep gas flow alternately orthogonally through each air passage. In this way, the laminated structure 6 allows the treated gas and sweep gas to flow alternately orthogonally in the stacking direction of the CO2 separation element piece 21. As a result, the CO2 separation element 20 can selectively permeate CO2 from the treated gas side to the sweep gas side through the CO2 separation membrane 22 of the CO2 separation element piece 21.

[0026] The CO2 separation element piece 21 is a sheet-like member composed of a CO2 separation membrane 22 that allows CO2 to permeate from the gas to be treated to the sweep gas when the gas to be treated and the sweep gas flow with the CO2 separation element piece 21 in between. Since the CO2 separation element piece 21 is fitted and bent by the frame 14, it is preferable to use a material that has sufficient elasticity and strength to withstand this bending. The CO2 separation membrane 22 uses the difference in CO2 partial pressure as the driving force for CO2 permeation, allowing CO2 to permeate from high-concentration CO2 gas to low-concentration CO2 gas. Therefore, the relationship between the CO2 concentrations in the gas to be treated and the sweep gas is that the gas to be treated > the sweep gas. Return to Figure 1.

[0027] The first temperature control unit 4a is a device that adjusts the temperature of the outside air by heating or cooling the outside air flowing into the CO2 separation element 20. The first temperature control unit 4a is also called the outside air temperature control unit. The first temperature control unit 4a is, for example, a heater or Peltier element attached to the outside air intake duct 56. Alternatively, the first temperature control unit 4a may be an outside air fan 41 installed between the CO2 separation element 20 and the outside air passage. In this case, the outside air is heated using the exhaust heat from the outside air fan 41, so the exhaust heat from the outside air fan 41 is effectively utilized. The second temperature control unit 4b is a device that adjusts the temperature of the inside air by heating or cooling the inside air flowing into the CO2 separation element 20. The second temperature control unit 4b is also called the inside air temperature control unit. The second temperature control unit 4b is, for example, a heater or Peltier element attached to the inside air intake duct 52.

[0028] The outside air temperature detection unit 7 is attached to the outside air intake duct 56 and detects the temperature of the outside air flowing through the outside air intake duct 56. Since known techniques can be used for temperature detection, a detailed explanation is omitted here. Information regarding the outside air temperature detected by the outside air temperature detection unit 7 is transmitted to the control unit 5. The inside air temperature detection unit 8 detects the temperature of the inside air flowing through the inside air intake duct 52. Information regarding the inside air temperature detected by the inside air temperature detection unit 8 is transmitted to the control unit 5.

[0029] The control unit 5 receives the outside air temperature detected by the outside air temperature detection unit 7 and the inside air temperature detected by the inside air temperature detection unit 8. Based on the outside air temperature and the inside air temperature, the control unit 5 controls the temperature control unit 4. Specifically, the control unit 5 controls the first temperature control unit 4a so that the temperature difference between the temperature of the inside air introduced into the CO2 separation element 20 and the temperature of the outside air introduced into the CO2 separation element 20 is smaller than the temperature difference between the temperature of the air in the target space and the temperature of the outside air. This reduces the heat loss due to heat exchange in the CO2 separation element 20. For example, when the outside air is 5°C and the inside air is 25°C, if the temperature is not controlled, the air supplied to the target space by the inside air fan 31 will drop to about 15°C due to heat exchange, so extra air conditioning energy will be required to maintain the inside air at 25°C. On the other hand, if the temperature is controlled to set the outside air to 25°C, no heat exchange occurs, so the extra air conditioning energy is zero. Furthermore, if temperature control is performed using the exhaust heat from the outside air fan 41, the energy required for temperature control becomes zero. The second temperature control unit 4b may also be controlled by the control unit 5.

[0030] The subject of the apparatus, system, or method in this disclosure comprises a computer. The functions of the subject of the apparatus, system, or method in this disclosure are realized by the computer executing a program. The computer comprises a processor as its main hardware component, which operates according to the program. The processor is of any type as long as it can realize its functions by executing the program. The processor consists of one or more electronic circuits, including semiconductor integrated circuits (ICs) or LSIs (Large Scale Integrations). Multiple electronic circuits may be integrated on one chip or provided on multiple chips. Multiple chips may be aggregated in one device or provided on multiple devices. The program is recorded on a non-temporary recording medium such as a ROM, optical disc, or hard disk drive that is readable by the computer. The program may be pre-stored on the recording medium or supplied to the recording medium via a wide-area communication network, including the Internet.

[0031] (CO2 separation membrane 22) The CO2 separation membrane 22 will be described in more detail below. Figure 4 is a schematic cross-sectional view showing the structure of the CO2 separation membrane 22. The CO2 separation membrane 22 comprises a hydrophobic nonwoven fabric substrate 100, a CO2 separation gel layer 104, and a porous cover material 106.

[0032] The hydrophobic nonwoven fabric substrate 100 is a structure that is permeable to gases and repels CO2 separation solution. Here, "repelling" refers to the state in which defects (pores) occur in the CO2 separation gel layer 104 when a CO2 separation gel layer 104 of the thickness (e.g., 3 μm to 100 μm) necessary to obtain the desired CO2 separation performance (selectivity ratio, permeance, etc.) is formed. Furthermore, "repelling" indicates that the contact angle of the hydrophobic nonwoven fabric substrate 100 is 90° or greater. The contact angle is one of the indicators in wettability evaluation, and is the angle formed between a dropped liquid droplet and a solid surface. The larger the contact angle of the solid, the lower the wettability and the easier it is to repel liquid. On the other hand, the smaller the contact angle of the solid, the higher the wettability and the less likely it is to repel liquid. Even when applying a CO2 separation solution to a hydrophobic nonwoven fabric substrate 100, it may be possible to prevent the occurrence of defects by increasing the film thickness of the CO2 separation gel layer 104, but this is not practical because it reduces the CO2 separation performance.

[0033] The hydrophobic nonwoven fabric base material 100 is composed of porous materials such as polyethylene (PE), polypropylene (PP), polyphenylene sulfide (PPS), or fluorine-based fibers.

[0034] In this embodiment, as an example, the porosity of the hydrophobic nonwoven fabric substrate 100 is set to 67%. Preferably, the porosity of the hydrophobic nonwoven fabric substrate 100 is in the range of 40% to 90%. In other words, it is desirable that the porosity of the hydrophobic nonwoven fabric substrate 100 is in a range that can suppress the permeation of the CO2 separation solution while ensuring as much air permeability as possible.

[0035] The porosity of the hydrophobic nonwoven fabric substrate 100 affects the surface area of ​​the CO2 separation gel layer 104 in contact with CO2 in the air. The higher the porosity, the larger the surface area of ​​the CO2 separation gel layer 104 in contact with CO2 in the air, which promotes the dissolution or desorption reaction of CO2 and improves CO2 separation performance. For example, if the porosity is less than 40%, the CO2 permeance (permeability, one of the performance indicators of permeability) [mol / (m³] 2 The pressure (·s·kPa) becomes less than half of what it is when the porosity is 40% or higher. On the other hand, if the porosity is greater than 90%, for example, the retention of the CO2 separation gel layer deteriorates, and defects occur in the CO2 separation gel layer 104.

[0036] Furthermore, the average pore size of the hydrophobic nonwoven fabric substrate 100 in this embodiment is, for example, 30 μm. The average pore size of the hydrophobic nonwoven fabric substrate 100 is, for example, in the range of 20 μm to 100 μm.

[0037] As described above, the hydrophobic nonwoven fabric substrate 100 repels the CO2 separation solution. In other words, the hydrophobic nonwoven fabric substrate 100 does not have wettability to the CO2 separation solution, and even if the CO2 separation solution is applied to, for example, PE, it is difficult to form a CO2 separation gel layer 104 with the desired CO2 separation performance.

[0038] Therefore, the hydrophobic nonwoven fabric base material 100 is provided with a modified portion 101 on one side to which the CO2 separation solution is applied, which improves the wettability to the CO2 separation solution.

[0039] The modified portion 101 is a part of the hydrophobic nonwoven fabric substrate 100 whose wettability to the CO2 separation solution has been improved. The modified portion 101 is provided on the surface of the hydrophobic nonwoven fabric substrate 100 that is in contact with the CO2 separation gel layer 104. The modified portion 101 is formed by, for example, irradiating the surface of the hydrophobic nonwoven fabric substrate 100 to which the CO2 separation solution is applied with plasma. In other words, the modified portion 101 is formed integrally with the hydrophobic nonwoven fabric substrate 100. With this configuration, compared to the case where the hydrophobic nonwoven fabric substrate 100 (excluding the modified portion 101), which suppresses the penetration of the CO2 separation solution, and the modified portion 101, which allows the CO2 separation solution to penetrate, are formed from different materials, delamination between the different materials does not occur, thus improving the strength of the CO2 separation membrane 22.

[0040] The wettability of the modified portion 101 to the CO2 separation solution is greater than the wettability of the hydrophobic nonwoven fabric substrate 100 before the modified portion 101 is formed. Specifically, the contact angle of the modified portion 101 is about 5° to 20° smaller than the contact angle of the hydrophobic nonwoven fabric substrate 100 before the modified portion 101 is formed. In other words, the contact angle of the modified portion 101 is about 5° to 20° smaller than the contact angle of one surface of the hydrophobic nonwoven fabric substrate 100 excluding the modified portion 101. As mentioned above, the contact angle of the hydrophobic nonwoven fabric substrate 100 before the modified portion 101 is formed, or the contact angle of one surface of the hydrophobic nonwoven fabric substrate 100 excluding the modified portion 101, is 90° or more. To put it another way, the contact angle of one surface of the hydrophobic nonwoven fabric substrate 100 changes due to surface treatment by plasma or the like.

[0041] If the change in contact angle is less than 5°, sufficient wettability cannot be ensured, and the coating liquid is repelled. On the other hand, if the change in contact angle is greater than 20°, the wettability improves excessively, and the CO2 separation solution penetrates into the interior of the hydrophobic nonwoven fabric substrate 100.

[0042] The CO2 separation gel layer 104 is formed by drying the CO2 separation solution and contains CO2 carriers within a water-containing hydrophilic polymer gel membrane. Examples of hydrophilic polymers that can be used include polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyvinyl alcohol-polyacrylate copolymer (PVA / PAA salt copolymer), chitosan, polyvinylamine, polyallylamine, and polyvinylpyrrolidone.

[0043] As CO2 carriers, for example, alkali metal carbonates, alkali metal bicarbonates, alkali metal hydroxides, or amino acids can be used. When an amino acid (RNH2) dissolves in water, the amino group (NH2) is protonated to NH3. + It dissociates as shown in (Chemical Formula 1) below, but carbon dioxide is a protonated amino group (NH3 + It does not react with ) but reacts with free amino groups (NH2). (chemical 1) CO2 + RNH2 + H2O → HCO3 - +RNH3 + Therefore, when using amino acids as CO2 carriers, a deprotonating agent is added to the solution in which the amino acids are dissolved, and NH3 + It is necessary to convert it to NH2. The deprotonating agent is protonated NH3. + Any substance that is strong enough to remove a proton and convert it to NH2 is acceptable, and hydroxides or carbonates of alkali metal elements can be suitably used.

[0044] The CO2 separation solution is applied such that the thickness of the CO2 separation gel layer 104 is greater than the surface roughness of the hydrophobic nonwoven fabric substrate 100. In other words, the thickness of the CO2 separation gel layer 104 is such that no part of the hydrophobic nonwoven fabric substrate 100 is exposed from the surface of the CO2 separation gel layer 104. For example, if the height of the highest surface irregularity of the hydrophobic nonwoven fabric substrate 100 is 5 μm, the thickness of the CO2 separation gel layer 104 will be at least 5 μm.

[0045] The porous cover material 106 has gas permeability and the ability to suppress the passage of the CO2 separation gel layer 104. As materials for the porous cover material 106, nonwoven fabrics such as PE, PP, polyester (PET: Polyethylene Terephthalate), polyphenylene sulfide (PPS: Polyphenylene Sulfide), vinylon, rayon, nylon, and fluorine-based fibers, and resin materials such as polyacrylonitrile (PAN: Polyacrylonitrile), polyethersulfone, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polyimide can be used. Generally, when using nonwoven fabrics, the permeability is higher than that of resin materials, thus reducing resistance to gas permeation. When using resin materials, the pore size is easier to control than with nonwoven fabrics, thus suppressing the penetration of the CO2 separation solution.

[0046] The porous cover material 106 has a porosity greater than or equal to that of the hydrophobic nonwoven fabric substrate 100. When the CO2 separation solution is dried and gelled after coating, the viscosity increases significantly in the gel state compared to the solution state. Therefore, the porous cover material 106 can be made with less restriction on the specifications for gel retention than the hydrophobic nonwoven fabric substrate 100 to which the CO2 separation solution is applied, and a more permeable material can be used. In other words, the porosity of the porous cover material 106 can be greater than or equal to that of the hydrophobic nonwoven fabric substrate 100. This allows the CO2 separation membrane 22, in which the surface of the CO2 separation gel layer is protected while suppressing a decrease in CO2 separation membrane performance, to be used in the CO2 separation element 20.

[0047] (Manufacturing method) The method for manufacturing the CO2 separation membrane 22 according to this embodiment will be described with reference to Figure 5. Figure 5 is a flowchart showing the manufacturing procedure for the CO2 separation membrane 22. First, a coating solution is prepared, which is an aqueous solution containing a hydrophilic polymer and a CO2 carrier (S10). More specifically, a CO2 carrier is added to water and stirred until dissolved, and then a hydrophilic polymer is added to the resulting solution and stirred for at least 3 days at room temperature to obtain a coating solution. When an amino acid is used as the CO2 carrier, a deprotonating agent is added in the same way as the amino acid.

[0048] Next, a surface treatment step is performed to form a modified area on one side of the hydrophobic nonwoven fabric substrate 100 by a wettability improvement treatment, thereby improving its wettability to the CO2 separation solution (S12). For example, plasma treatment, corona treatment, flame treatment, UV irradiation, UV ozone treatment, etc., can be used for the wettability improvement treatment. Step 12 may be performed before step 10. Next, a coating step is performed in which the coating liquid (CO2 separation solution) obtained in step 10 is applied with an applicator to the side of the hydrophobic nonwoven fabric substrate 100 that has undergone the wettability improvement treatment, and spread uniformly (S14). The coating thickness in the sample of the example described later is 500 μm.

[0049] Next, a drying step is performed (S16) in which the coated hydrophobic nonwoven fabric substrate 100 is dried at, for example, 60°C for about 30 minutes to gel the coating solution and generate a CO2 separation gel layer 104. In other words, the applied CO2 separation solution is dried to form a gel body of the CO2 separation solution. Next, the porous cover material 106 is adhered to the CO2 separation gel layer 104 obtained in step 16. As a result, a three-layer structure CO2 separation membrane 22 is fabricated, consisting of a hydrophobic nonwoven fabric substrate 100, a CO2 separation gel layer 104, and a porous cover material 106, as schematically shown in Figure 4 (S18).

[0050] (Experimental method) The experimental method for evaluating the membrane performance of each sample in the examples and comparative examples described later will be explained. The CO2 separation membrane 22 was placed in a gas permeation cell (membrane area: 9.62 cm²). 2Between the raw material gas supply side chamber and the permeation side chamber of [[ID=]], two rubber gaskets are used as sealing materials for fixing. At a temperature of 27 °C and under atmospheric pressure, the raw material gas in which 400 ppm of CO2 is mixed with N2 gas is humidified by bubbling through deionized water to a relative humidity of 70%. This raw material gas is supplied to the supply side chamber at a flow rate of 2000 cc / min. Also, the sweep gas (He gas) is humidified by bubbling through deionized water to a relative humidity of 70%. This sweep gas is supplied to the permeation side chamber at a flow rate of 70 cc / min.

[0051] The composition of the gas recovered from the permeation side chamber is quantified by gas chromatography, and the permeance of CO2 and N2 (= permeability, one of the performance indicators of permeability) [mol / (m 2 ·s·kPa)] is calculated from the quantification result of the gas chromatography and the flow rate of He in the sweep gas, and the CO2 / N2 selectivity is calculated from the ratio. Note that the CO2 separation membrane used in this method is judged to be of higher performance the higher the CO2 permeance and the CO2 / N2 selectivity are. Under room temperature conditions, for example, at a temperature of 10 to 40 °C, for indoor CO2 separation, for example, the CO2 permeance is 2×10 -5 mol / (m 2 ·s·kPa) or more, and the CO2 / N2 selectivity is preferably 5,000 or more.

[0052] (Example 1) 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate are added to 86.6 g of water and stirred at room temperature for 3 days or more to obtain a CO2 separation solution (coating solution) (S10 in FIG. 5). Also, on one surface of a PP nonwoven fabric (for example, manufactured by Tapirus, P020FW-00X, surface roughness 3.8 μm, contact angle 128°, porosity 67%) as the hydrophobic nonwoven fabric substrate 100, surface treatment is performed by plasma treatment (for example, manufactured by Asumi Giken, plasma surface modification cleaning device, PS150, supply voltage 20V, treatment time 10 sec) to form a modified part (contact angle 122°) (S12 in FIG. 5). The CO2 separation solution obtained in step 10 is applied to the surface of the modified part formed in step 12 with an applicator to a thickness of 500 μm (S14 in FIG. 5).

[0053] The hydrophobic nonwoven fabric after coating is dried at 60°C for approximately 30 minutes to gel the CO2 separation solution and generate a CO2 gel layer (S16 in Figure 5). A PP nonwoven fabric (e.g., Tapirus, P010SW-00X, 85% porosity) is bonded to the surface of the CO2 separation gel layer 104 obtained in step 16 as a porous cover material 106. As a result, a three-layer film structure of PP nonwoven fabric / gel layer / PP nonwoven fabric is produced, as schematically shown in Figure 4 (S18 in Figure 5).

[0054] (Example 2) 86.6 g of water is mixed with 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate, and the mixture is stirred at room temperature for at least 3 days to obtain a CO2 separation solution (coating solution) (S10 in Figure 5). Furthermore, one side of a hydrophobic nonwoven fabric substrate 100, a PP nonwoven fabric (e.g., Tapirus, P010SW-00X, surface roughness 10.3 μm, contact angle 136°, porosity 85%), is surface-treated by plasma treatment (e.g., Asumi Giken, plasma surface modification and cleaning device, PS150, supply voltage 20V, treatment time 10 sec) to form a modified area (contact angle 129°) (S12 in Figure 5). The CO2 separation solution obtained in step 10 is applied to the surface of the modified area formed in step 12 to a thickness of 500 μm using an applicator (S14 in Figure 5).

[0055] The hydrophobic nonwoven fabric after coating is dried at 60°C for approximately 30 minutes to gel the CO2 separation solution and generate a CO2 gel layer (S16 in Figure 5). A PP nonwoven fabric (e.g., Tapirus, P010SW-00X, 85% porosity) is bonded to the surface of the CO2 separation gel layer 104 obtained in step 16 as a porous cover material 106. As a result, a three-layer film structure of PP nonwoven fabric / gel layer / PP nonwoven fabric is produced, as schematically shown in Figure 4 (S18 in Figure 5).

[0056] (Example 3) 86.6 g of water is mixed with 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate, and the mixture is stirred at room temperature for at least 3 days to obtain a CO2 separation solution (coating solution) (S10 in Figure 5). A hydrophobic nonwoven fabric substrate 100 is prepared using a PP nonwoven fabric (e.g., Tapirus, P020SW-00X, surface roughness 12.0 μm, contact angle 138°, porosity 84%). One side of this nonwoven fabric is surface-treated with plasma (e.g., Asumi Giken, plasma surface modification and cleaning device, PS150, supply voltage 100V, processing time 30 sec) to form a modified area (contact angle 123°) (S12 in Figure 5). The CO2 separation solution obtained in step 10 is then applied to the surface of the modified area formed in step 12 to a thickness of 500 μm using an applicator (S14 in Figure 5).

[0057] The hydrophobic nonwoven fabric after coating is dried at 60°C for approximately 30 minutes to gel the CO2 separation solution and generate a CO2 gel layer (S16 in Figure 5). A PP nonwoven fabric (e.g., Tapirus, P010SW-00X, 85% porosity) is bonded to the surface of the CO2 separation gel layer 104 obtained in step 16 as a porous cover material 106. As a result, a three-layer film structure of PP nonwoven fabric / gel layer / PP nonwoven fabric is produced, as schematically shown in Figure 4 (S18 in Figure 5).

[0058] (Comparative Example 1) Add 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate to 86.6 g of water and stir at room temperature for at least 3 days to obtain a CO2 separation solution (coating solution) (S10 in Figure 5). The CO2 separation solution obtained in step 10 is applied to one side of a PET nonwoven fabric (for example, PY120-31 manufactured by Awa Paper Co., Ltd., surface roughness 4.7 μm, contact angle 81°, porosity 41%) to a thickness of 500 μm using an applicator (S14 in Figure 5). Note that although S14 in Figure 5 is described as "coating to the modified area," in this comparative example no modified area is formed, so strictly speaking, the CO2 separation solution is applied to the nonwoven fabric substrate where no modified area has been formed. The coated nonwoven fabric is dried at 60°C for about 30 minutes to gel the CO2 separation solution (S16 in Figure 5).

[0059] (Comparative Example 2) 86.6 g of water is mixed with 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate, and the mixture is stirred at room temperature for at least 3 days to obtain a CO2 separation solution (coating solution) (S10 in Figure 5). The CO2 separation solution obtained in step 10 is applied to one side of a PP nonwoven fabric (for example, Tapirus, P020FW-00X, surface roughness 3.8 μm, contact angle 128°, porosity 67%) to a thickness of 500 μm using an applicator (S14 in Figure 5). Note that although S14 in Figure 5 is described as "coating to the modified area," in this comparative example no modified area is formed, so strictly speaking, the CO2 separation solution is applied to the nonwoven fabric substrate without a modified area. The coated nonwoven fabric is dried at 60°C for about 30 minutes to gel the CO2 separation solution (S16 in Figure 5).

[0060] (Comparative Example 3) 86.6 g of water is mixed with 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate, and the mixture is stirred at room temperature for at least 3 days to obtain a CO2 separation solution (coating solution) (S10 in Figure 5). Furthermore, one side of a hydrophobic nonwoven fabric substrate 100, a PP nonwoven fabric (e.g., Tapirus, P020FW-00X, surface roughness 3.8 μm, contact angle 128°, porosity 67%), is surface-treated by plasma treatment (e.g., Asumi Giken, plasma surface modification and cleaning device, PS150, supply voltage 100V, treatment time 60 sec) to form a modified area (contact angle 106°) (S12 in Figure 5). The CO2 separation solution obtained in step 10 is applied to the surface of the modified area formed in step 12 to a thickness of 500 μm using an applicator (S14 in Figure 5). The nonwoven fabric after coating is dried at 60°C for approximately 30 minutes to gel the CO2 separation solution (S16 in Figure 5).

[0061] (Comparative Example 4) 86.6 g of water is mixed with 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate, and the mixture is stirred at room temperature for at least 3 days to obtain a CO2 separation solution (coating solution) (S10 in Figure 5). Additionally, one side of a hydrophobic nonwoven fabric substrate 100 (e.g., Tapirus, P010SW-00X, surface roughness 10.3 μm, contact angle 136°, porosity 85%) is surface-treated by plasma treatment (e.g., Asumi Giken, plasma surface modification and cleaning device, PS150, supply voltage 20V, treatment time 5 sec) to form a modified area (contact angle 132°) (S12 in Figure 5). The CO2 separation solution obtained in step 10 is applied to the surface of the modified area formed in step 12 to a thickness of 500 μm using an applicator (S14 in Figure 5). The nonwoven fabric after coating is dried at 60°C for approximately 30 minutes to gel the CO2 separation solution (S16 in Figure 5).

[0062] (Performance evaluation results) Figure 6 is a table showing the evaluation results of film formation and film performance (CO2 permeance, CO2 / N2 selectivity) of the CO2 separation solutions in Examples 1-3 and Comparative Examples 1-4. In Example 1, the modification treatment resulted in a contact angle of 122° in the modified area, which was 6° smaller than the contact angle of 128° in the hydrophobic nonwoven fabric substrate excluding the modified area. As a result, wettability was improved and a uniform film was formed. Consequently, the CO2 permeance was 1.2 × 10⁻⁶. -4 mol / (m 2 The CO2 / N2 selectivity was 27,000 (·s·kPa). In Example 2, the modification treatment resulted in a contact angle of 129° in the modified area, which was 7° smaller than the contact angle of 136° in the hydrophobic nonwoven fabric substrate excluding the modified area. As a result, wettability was improved and the film was formed uniformly. Consequently, the CO2 permeance was 1.1 × 10⁻⁶. -4 mol / (m 2 The CO2 / N2 selectivity was 24,000 (·s·kPa). In Example 3, the modification treatment resulted in a contact angle of 123° in the modified area, which was 15° smaller than the contact angle of 138° in the hydrophobic nonwoven fabric substrate excluding the modified area. As a result, wettability was improved and the film was formed uniformly. Consequently, the CO2 permeance was 1.2 × 10⁻⁶. -4 mol / (m 2The CO2 permeance and CO2 / N2 selectivity were 28,000 (·s·kPa). Examples 1 to 3 achieved very high CO2 permeance and CO2 / N2 selectivity. This is because modifying the surface of the hydrophobic nonwoven fabric substrate improved film-forming properties, allowing for the formation of a uniform film without defects.

[0063] On the other hand, in Comparative Example 1, the nonwoven fabric substrate used was PET, which originally has a low contact angle of 81°. In Comparative Example 3, due to excessive modification treatment, the contact angle of the modified portion became 106°, which was 22° smaller than the contact angle of the hydrophobic nonwoven fabric substrate excluding the modified portion (128°). As a result, the CO2 separation solution penetrated, and the film was not formed uniformly. Consequently, no CO2 separation film was formed on the surface, and therefore, CO2 permeability and selectivity could not be measured. Furthermore, in Comparative Example 2, the contact angle of the nonwoven fabric substrate used was 128°, and no modified section was provided to improve wettability. Similarly, in Comparative Example 4, the modification treatment was insufficient, resulting in a contact angle of 132° for the modified section. This was only 4° smaller than the 136° contact angle of the hydrophobic nonwoven fabric substrate excluding the modified section. As a result, the CO2 separation solution being applied was repelled, and the film was not formed uniformly. Consequently, defects (pores) were formed in some areas, making it impossible to measure CO2 permeability and selectivity.

[0064] According to this embodiment, the hydrophobic nonwoven fabric substrate 100 is provided with a modified portion 101 on the surface that contacts the CO2 separation gel layer 104. Since the wettability of the modified portion 101 to the CO2 separation solution is greater than the wettability of the hydrophobic nonwoven fabric substrate 100 excluding the modified portion 101, a more uniform film thickness can be formed in the CO2 separation membrane 22. Furthermore, since the contact angle of the modified portion 101 is 5° to 20° smaller than the contact angle of the hydrophobic nonwoven fabric substrate 100 excluding the modified portion 101, a more uniform film thickness can be formed in the CO2 separation membrane 22. In addition, since the hydrophobic nonwoven fabric substrate 100 contains at least one of polypropylene and polyethylene, it can repel water-soluble CO2 separation solutions. Furthermore, since the porosity of the porous cover material 106 is greater than or equal to the porosity of the hydrophobic nonwoven fabric substrate 100, the CO2 separation performance can be improved. Furthermore, since the thickness of the CO2 separation gel layer 104 is greater than the surface roughness of the hydrophobic nonwoven fabric substrate 100, it is possible to prevent a portion of the hydrophobic nonwoven fabric substrate 100 from being exposed.

[0065] An overview of one aspect of this disclosure is as follows: (Item 1) A hydrophobic nonwoven fabric base material (100) that is permeable to gases and repels water-soluble CO2 separation solutions, The device comprises a CO2 separation gel layer (104) provided on the hydrophobic nonwoven fabric substrate (100) and formed by drying the CO2 separation solution, The hydrophobic nonwoven fabric substrate (100) has a modified portion (101) on the surface that comes into contact with the CO2 separation gel layer (104), The wettability of the modified portion (101) to the CO2 separation solution is greater than the wettability of the hydrophobic nonwoven fabric substrate (100) excluding the modified portion (101) to the CO2 separation solution. CO2 separation membrane (22).

[0066] (Item 2) The CO2 separation membrane (22) according to item 1, wherein the contact angle of the modified portion (101) is 5° to 20° smaller than the contact angle of the hydrophobic nonwoven fabric substrate (100) excluding the modified portion (101).

[0067] (Item 3) The hydrophobic nonwoven fabric substrate (100) is a CO2 separation membrane (22) according to item 1, comprising at least one of polypropylene and polyethylene.

[0068] (Item 4) The CO2 separation gel layer (104) is further provided with a porous cover material (106) having gas permeability and the ability to suppress the passage of the CO2 separation gel layer (104), The porosity of the porous cover material (106) is greater than or equal to that of the hydrophobic nonwoven fabric substrate (100). CO2 separation membrane (22) as described in item 1.

[0069] (Item 5) The CO2 separation membrane (22) described in item 1, wherein the thickness of the CO2 separation gel layer (104) is greater than the surface roughness of the hydrophobic nonwoven fabric substrate (100).

[0070] (Item 6) A CO2 separation element (20) formed by stacking CO2 separation membranes (22) as described in item 1.

[0071] (Item 7) A surface treatment step in which a modified portion (101) is formed on one surface of a hydrophobic nonwoven fabric substrate (100) having gas permeability and CO2 separation solution penetration suppression by a wettability improvement treatment, A coating step of applying the CO2 separation solution to the modified section (101), A drying step in which the applied CO2 separation solution is dried to form a CO2 separation gel layer (104) which is a gel of the CO2 separation solution, Equipped with, A method for producing a CO2 separation membrane (22), wherein the wettability of the modified portion (101) to the CO2 separation solution is greater than the wettability of the hydrophobic nonwoven fabric substrate (100) excluding the modified portion (101) to the CO2 separation solution.

[0072] The present disclosure has been described above based on embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible for each component or combination of processing processes, and that such modifications are also within the scope of the present disclosure. [Explanation of Symbols]

[0073] 1 CO2 separation system, 2 Building, 4 Temperature control unit, 5 Control unit, 6 Laminated structure, 7 Outdoor temperature detection unit, 8 Indoor temperature detection unit, 10 Housing, 14 Frame, 16 Airflow path for gas to be processed, 17 Sweep gas airflow path, 18 CO2, 19 N2, 20 CO2 separation element, 21 CO2 separation element piece, 22 CO2 separation membrane, 31 Indoor fan, 33 Indoor vent, 35 Intake vent, 37 Indoor filter, 41 Outdoor fan, 43 Outdoor vent, 45 Exhaust vent, 47 Outdoor filter, 51 Indoor intake, 52 Indoor air intake duct, 53 Indoor outlet, 54 Indoor air outlet duct, 55 Outdoor intake, 56 Outdoor air intake duct, 57 Outdoor outlet 58 Outdoor air outlet duct, 100 Hydrophobic nonwoven fabric substrate, 101 Modified section, 104 CO2 separation gel layer, 106 Porous cover material.

Claims

1. It has gas permeability and is water-soluble CO ２ A hydrophobic nonwoven fabric substrate that repels the separation solution, Provided on the aforementioned hydrophobic nonwoven fabric substrate, CO ２ CO formed by drying of the separated solution ２ A separation gel layer is provided, The hydrophobic nonwoven fabric substrate is the CO ２ The surface in contact with the separation gel layer is equipped with a modified portion. The aforementioned CO ２ The wettability of the modified part to the separation solution is the CO ２ The wettability of the hydrophobic nonwoven fabric substrate excluding the modified portion to the separation solution is greater than that of the hydrophobic nonwoven fabric substrate excluding the modified portion. CO ２ Separation membrane.

2. The contact angle of the modified portion is 5° to 20° smaller than the contact angle of the hydrophobic nonwoven fabric substrate excluding the modified portion, as described in claim 1. ２ Separation membrane.

3. The hydrophobic nonwoven fabric substrate contains at least one of polypropylene and polyethylene, and is the CO separation membrane according to claim 1. ２ Separation membrane.

4. The aforementioned CO ２ Provided on top of the separation gel layer, the permeability of gas and the CO ２ The porous cover material further comprises a material having the property of inhibiting the passage of the separation gel layer. The porosity of the porous cover material is greater than or equal to the porosity of the hydrophobic nonwoven fabric substrate. CO as described in claim 1 ２ Separation membrane.

5. The aforementioned CO ２ The CO2 separation layer thickness is greater than the surface roughness of the hydrophobic nonwoven fabric substrate, as described in claim 1. ２ Separation membrane.

6. CO as described in claim 1 ２ CO formed by stacking separation membranes ２ Separation element.

7. Gas permeability and CO ２ A surface treatment step in which a modified portion is formed on one surface of a hydrophobic nonwoven fabric substrate having the property of suppressing the penetration of a separation solution by a wettability improvement treatment, The CO ２ A coating step in which the separation solution is applied, The CO applied ２ The separated solution is dried, and the CO ２ CO2 is a gel in the separation solution. ２ A drying step to form a separation gel layer, Equipped with, The aforementioned CO ２ The wettability of the modified part to the separation solution is the CO ２ The wettability of the hydrophobic nonwoven fabric substrate excluding the modified portion to the separation solution is greater than that of CO ２ A method for manufacturing separation membranes.

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