WO2025204611A1 - Co2 separation membrane, co2 separation element, and method for producing co2 separation membrane - Google Patents

Abstract

A nonwoven fabric base material 100 is gas permeable. A protective film 102 is provided on the nonwoven fabric base material 100, and includes first pores that are gas permeable and suppress the penetration of a CO₂ separation solution. A CO₂ separation gel layer 104 is provided on the protective film 102, and is formed by drying the CO₂ separation solution. A porous cover material 106 is provided on the CO₂ separation gel layer 104, and is gas permeable and suppresses the passage of the CO₂ separation gel layer. The pore diameter of second pores is larger than the pore diameter of the first pores.

Description

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

The present disclosure relates to a _CO2 separation membrane that separates _CO2 from air, a _CO2 separation element, and a method for manufacturing a _CO2 separation membrane.

A _CO2 separation element is constructed by applying a _CO2 separation material to a substrate, which is a porous substrate that is permeable to _CO2 (see, for example, Patent Document 1).

Special Publication No. 11-509251

When a _CO2 separation material is applied to a nonwoven fabric used as a porous substrate, the _CO2 separation material penetrates into the nonwoven fabric, making it impossible to form a layer with a uniform thickness, and the desired _CO2 permeability and selectivity cannot be obtained.

The present disclosure has been made to solve the above-mentioned problems, and aims to provide a technology for suppressing the permeation of _CO2 separation materials and forming a separation membrane layer with a uniform thickness in a _CO2 separation membrane using a nonwoven fabric substrate.

To solve the above problems, a _CO2 separation membrane according to one embodiment of the present disclosure comprises a gas-permeable nonwoven fabric substrate, a protective membrane provided on the nonwoven fabric substrate and including first pores that are gas-permeable and inhibit permeation of a _CO2 separation solution, a _CO2 separation gel layer provided on the protective membrane and formed by drying the _CO2 separation solution, and a porous cover material provided on the _CO2 separation gel layer and including second pores that are gas-permeable and inhibit permeation of the _CO2 separation gel layer, the pore diameter of the second pores being larger than the pore diameter of the first pores.

Another aspect of the present disclosure is a method for producing a _CO2 separation membrane, comprising: a step of placing a protective membrane on at least one surface of a gas-permeable nonwoven fabric substrate, the protective membrane including first pores that are gas permeable and inhibit permeation of a _CO2 separation solution; a step of applying a _CO2 separation solution onto the protective membrane; a step of drying the applied _CO2 separation solution to form a gel body of the _CO2 separation solution; and a step of adhering a porous cover material onto the gel body, the second pores being gas permeable and inhibiting passage of the gel body, the second pores having a pore diameter larger than the first pores.

According to the present disclosure, in a CO ₂ separation membrane using a nonwoven fabric substrate, it is possible to suppress the permeation of CO ₂ separation materials and form a separation membrane layer with a uniform thickness.

FIG. 1 is a schematic diagram showing an example of installation of a CO ₂ separation system according to this embodiment. 2(a)-(b) are diagrams showing an outline of the _CO2 separation element of FIG. FIG. 3 is a perspective view showing a laminated structure used as the CO ₂ separation element of FIG. FIG. 4 is a cross-sectional view showing a schematic structure of the CO ₂ separation membrane of FIG. 2(a)-(b). FIG. 5 is a flowchart showing the procedure for manufacturing a _CO2 separation membrane. 1 is a table showing the evaluation results of CO ₂ separation material retention and membrane performance (CO ₂ permeance, CO ₂ /N ₂ selectivity) in Examples 1 to 3 and Comparative Examples 1 to 3. 7(a)-(b) are cross-sectional views showing the structure of another _CO2 separation membrane.

The following describes embodiments with reference to the drawings. Note that the following embodiments are examples that embody the present disclosure and do not limit the technical scope of the present disclosure. Furthermore, the figures described in the embodiments are schematic diagrams, and the ratios of the sizes and thicknesses of the components in each figure do not necessarily reflect the actual dimensional ratios.

An embodiment of the present disclosure will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an installation example of a _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 (e.g., _CO2 ) from the air in a target indoor space. The _CO2 separation system 1 includes a housing 10, _{a CO2} separation element 20, an indoor air fan 31, an indoor air filter 37, an outdoor air fan 41, an outdoor air filter 47, a first temperature adjustment unit 4a, a second temperature adjustment unit 4b (collectively referred to as a temperature adjustment unit 4), a control unit 5, an outdoor air temperature detection unit 7, and an indoor air temperature detection unit 8.

The housing 10 is the outer frame of the _CO2 separation system 1. An inside air inlet 33, an air supply inlet 35, an outside air inlet 43, and an exhaust inlet 45 are arranged on the outer periphery of the housing 10. The inside air inlet 33 is an intake port that draws air 39a into the _CO2 separation system 1. The inside air inlet 33 is connected to an indoor air inlet 51 provided in the building 2 by an inside air introduction duct 52. The indoor air inlet 51 is an opening provided in a target space of the building 2 and introduces air 39a (inside air) from the target space into the _CO2 separation system 1 as RA. The inside air introduction duct 52 is a duct that introduces inside air into the housing 10. One end of the inside air introduction duct 52 is connected to the indoor air inlet 51, and RA from indoors flows into the inside air introduction duct 52. The other end of the inside air introduction duct 52 is connected to the inside air inlet 33 and circulates RA within the housing 10. That is, air from the target space indoors is introduced as inside air into the inside air introduction duct 52 and circulates therethrough.

The air inlet 35 is an outlet through which air 39b is discharged from the _CO2 separation system 1. The air inlet 35 is connected in communication with an indoor air outlet 53 provided in the building 2 via an indoor air outlet duct 54. The indoor air outlet 53 is an opening provided in the building 2 that supplies air 39b, whose _CO2 concentration has been reduced by the _CO2 separation element 20, to the target space as SA. The indoor air outlet duct 54 is a duct that supplies indoor air from the housing 10 to the target space. One end of the indoor air outlet duct 54 is connected to the air inlet 35, and the air 39b, whose _CO2 concentration has been reduced by the _CO2 separation element 20, flows into the duct. The other end of the indoor air outlet duct 54 is connected to the indoor air outlet 53, and supplies the air 39b in the duct to the target space as SA. In other words, the indoor air outlet duct 54 returns the air 39b to the target space.

The outside air port 43 is an intake port that draws air 49a into the _CO2 separation system 1. The outside air port 43 is connected in communication with an outdoor intake port 55 provided in the building 2 by an outside air introduction duct 56. The outdoor intake port 55 is an opening provided in the building 2 that introduces outdoor air 49a (outside air) as OA into the _CO2 separation system 1. The outside air introduction duct 56 is a duct that introduces outside air into the housing 10. One end of the outside air introduction duct 56 is connected to the outdoor intake port 55, and OA from 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 circulates the OA inside the housing 10. In other words, outdoor air is introduced into the outside air introduction duct 56 as outside air and circulates therethrough.

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 via an outdoor air outlet duct 58. The outdoor outlet 57 is an opening provided in the building 2 that discharges air 49b, whose _CO2 concentration has been increased by the _CO2 separation element 20, to the outdoors as EA. The outdoor air outlet duct 58 is a duct that supplies outdoor air from the housing 10 to the outdoors. One end of the outdoor air outlet duct 58 is connected to the exhaust port 45, and the air 49b, whose _CO2 concentration has been increased by the _CO2 separation element 20, flows into the duct. The other end of the outdoor air outlet 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 outlet duct 58 releases the air 49b to the outdoors.

Hereinafter, air 39a and air 39b may be collectively referred to as "inside air," and air 49a and air 49b may be collectively referred to as "outside air." Furthermore, inside air intake duct 52 and inside air outlet duct 54 may be collectively referred to as the "inside air duct," and outside air intake duct 56 and outside air outlet duct 58 may be collectively referred to as the "outside air duct."

Here, the diameter of each duct will be described. In this embodiment, the duct diameters of the outside air inlet duct 56 and the outside air outlet duct 58, through which outside air is ventilated, are smaller than the duct diameters of the inside air inlet duct 52 and the inside air outlet duct 54, through which inside air is ventilated. This is because the flow rate of outside air circulating within the _CO2 separation system 1 is made smaller than the flow rate of inside air. This makes it possible to suppress pressure loss on the outside air side. Furthermore, although heat exchange generally occurs due to the temperature difference between the outside air and the inside air, suppressing the flow rate of outside air makes it possible to suppress heat loss due to heat exchange.

A _CO2 separation element 20, an inside air fan 31 (circulation fan), an inside air filter 37, an outside air fan 41, and an outside air filter 47 are attached inside the housing 10. The _CO2 separation element 20 separates _CO2 from the inside air that has circulated through the inside air introduction duct 52, and introduces the _CO2 into the outside air that has circulated through the outside air introduction duct 56. This can also be said to be a member that selectively transmits _CO2 from the inside air to the outside air. Details of _{the CO2} separation element 20 will be described later.

The internal air fan 31 is a blower that draws in internal air from the target space through the internal air port 33 and discharges it into the target space through the air intake port 35. By driving the internal air fan 31, the internal air drawn in from the target space through the internal air port 33 passes through the internal air filter 37, the _CO2 separation element 20, and the internal air fan 31, and is then discharged into the target space through the air intake port 9. It is preferable that the air volume delivered by the internal air fan 31 be greater than the air volume delivered by the external air fan 41. The internal air filter 37 is a filter that removes dirt, dust, etc. from the internal air that has flowed 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.

The outdoor air fan 41 is a blower that draws in outdoor air from the outdoors through the outdoor air port 43 and discharges it outdoors through the exhaust port 45. When the outdoor air fan 41 is driven, outdoor air is drawn in from the outdoors through the outdoor air port 43, passes through the outdoor air filter 47, the _CO2 separation element 20, and the outdoor air fan 41, and is discharged outdoors through the exhaust port 45. The volume of air discharged by the outdoor air fan 41 is preferably smaller than the volume of air discharged by the indoor air fan 31. The outdoor air fan 41 is, for example, provided downstream of the outdoor air filter 47 and upstream of the _CO2 separation element 20. This arrangement allows the outdoor air to be heated by the heat generated by the operation of the outdoor air fan 41. Therefore, when the outdoor air is colder than the indoor air, heat loss due to heat exchange between the outdoor air and the indoor air is reduced. The outdoor air fan 41 may also be provided downstream of the _CO2 separation element 20. The outside air filter 47 is a filter that removes dirt, dust, and the like from the outside air that has flowed into the housing 10 and supplies the purified air to the CO ₂ separation element 20 , and is, for example, a HEPA filter.

Here, an overview of _CO2 separation by the _CO2 separation element 20 will be described. FIGS. 2(a)-(b) show an overview of the _CO2 separation element 20. FIG. 2(a) is a cross-sectional view showing a simplified configuration of the _CO2 separation element 20. A target gas passage 16 through which internal air (target gas) flows from left to right and a sweep gas passage 17 through which external air (sweep gas) flows from left to right are arranged vertically stacked. A _CO2 separation membrane 22 is disposed between the target gas passage 16 and the sweep gas passage 17. The target gas introduced into the target gas passage 16 contains a mixture of _CO2 18 and _N2 19. While actual air also contains _O2 and _other gases, these are omitted here for clarity. When the gas to be treated flows along the _CO2 separation membrane 22 in the gas to be treated air passage 16, the _CO2 separation membrane 22 selectively allows _CO2 18 in the gas to be treated to permeate and discharges the _CO2 18 into the sweep gas in the sweep gas air passage 17. As a result, the concentration of _CO2 18 in the gas to be treated decreases and the concentration of _CO2 18 in the sweep gas increases.

2(b) shows the configuration of a _CO2 separation element 20 for more efficiently separating _CO2 18 than that shown in Fig. 2(a). The _CO2 separation element 20 includes first to third treatment gas passages 16a to 16c collectively referred to as treatment gas passages 16, first _{to third sweep gas passages 17a to 17c collectively referred to as sweep gas passages 17, and first to fifth CO2 separation membranes 22a to 22e collectively referred to as CO2 separation membranes} 22. The number of treatment gas passages 16 and sweep gas passages 17 is not limited to three. Arranged in this order from top to bottom are a first sweep gas duct 17a, a first treatment target gas duct 16a, a second sweep gas duct 17b, a second treatment target gas duct 16b, a third sweep gas duct 17c, and a third treatment target gas duct 16c. A first _CO2 separation membrane 22a is arranged between the first sweep gas duct 17a and the first treatment target gas duct 16a, a second _CO2 separation membrane 22b is arranged between the first treatment target gas duct 16a and the second sweep gas duct 17b, and a third CO2 _separation membrane 22c is arranged between the second sweep gas duct 17b and the second treatment target gas duct 16b. A fourth _CO2 separation membrane 22d is disposed between the second treatment target gas passage 16b and the third sweep gas passage 17c, and a fifth _CO2 separation membrane 22e is disposed between the third sweep gas passage 17c and the third treatment target gas passage 16c. As in Figure 2(a), CO2 ₁₈ in the treatment target gas flowing through the treatment target gas passage 16 is selectively permeated by the _CO2 separation membrane 22 and discharged into the sweep gas in the sweep gas passage 17.

FIG. 3 is a perspective view showing a laminated structure 6 used as a _CO2 separation element 20. Hereinafter, the laminated structure 6 will be described as having a vertical stacking direction, but this does not necessarily indicate the direction in actual use. The laminated structure 6 is a structure in which rectangular frames 14 and rectangular _CO2 separation element pieces 21 formed of _CO2 separation membranes 22 are alternately stacked in the vertical direction, and the target gas air passages 16 and the sweep gas air passages 17 intersecting the target gas air passages 16 are alternately formed layer by layer. More specifically, the laminated structure 6 is formed by repeatedly stacking the _CO2 separation element pieces 21 and the frames 14 while fitting the _CO2 separation element pieces 21 into the frames 14 at the ends from both the top and bottom. When fitting _{the CO2} separation element pieces 21 into the frames 14 from both the top and bottom, the frames 14 are stacked orthogonally so that each layer is staggered. 2(b), target gas passages 16 through which the target gas flows and sweep gas passages 17 through which the sweep gas flows are alternately formed. By circulating the target gas taken in from the target space through the target gas passages 16 and circulating the sweep gas through the sweep gas passages 17, the target gas and the sweep gas flow alternately and perpendicularly through the respective passages. In this way, the stacked structure 6 allows the target gas and the sweep gas to flow alternately and perpendicularly in the stacking direction of the _CO2 separation element pieces 21. This allows the _CO2 separation element 20 to selectively permeate _CO2 from the target gas side to the sweep gas side through the _CO2 separation membrane 22 of the _CO2 separation element piece 21.

The _CO2 separation element piece 21 is a sheet-like member composed of a _CO2 separation membrane 22 for transmitting _CO2 from the target gas to the sweep gas when the target gas and the sweep gas flow across the _CO2 separation element piece 21. Since the _CO2 separation element piece 21 is fitted and bent by the frame 14, it is preferable to use a member having the flexibility and strength to withstand this. The _CO2 separation membrane 22 uses the _CO2 partial pressure difference as the driving force for _CO2 permeation, allowing CO2 to permeate from high- _CO2 concentration gas to low _{- CO2} concentration gas, so the _CO2 concentration relationship between the target gas and the sweep gas is target gas > sweep gas. Return to Figure 1.

The first temperature adjustment unit 4a adjusts the temperature of the outside air by heating or cooling the outside air flowing into the _CO2 separation element 20. The first temperature adjustment unit 4a is also referred to as an outside air temperature adjustment unit. The first temperature adjustment unit 4a is, for example, a heater/Peltier element attached to the outside air inlet duct 56. The first temperature adjustment unit 4a may also be an outside air fan 41 provided between the _CO2 separation element 20 and the outside air duct. In this case, the outside air is heated using the exhaust heat of the outside air fan 41, thereby making effective use of the exhaust heat of the outside air fan 41. The second temperature adjustment unit 4b adjusts the temperature of the inside air by heating or cooling the inside air flowing into the _CO2 separation element 20. The second temperature adjustment unit 4b is also referred to as an inside air temperature adjustment unit. The second temperature adjustment unit 4b is, for example, a heater/Peltier element attached to the inside air inlet duct 52.

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. Known technology can be used to detect the temperature, so a detailed description will be omitted here. Information relating to the outside air temperature detected by the outside air temperature detection unit 7 is sent 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 relating to the inside air temperature detected by the inside air temperature detection unit 8 is sent to the control unit 5.

The control unit 5 receives the outdoor air temperature detected by the outdoor air temperature detection unit 7 and the indoor air temperature detected by the indoor air temperature detection unit 8. The control unit 5 controls the temperature adjustment unit 4 based on the outdoor air temperature and the indoor air temperature. Specifically, the control unit 5 controls the first temperature adjustment unit 4a so that the temperature difference between the temperature of the indoor air introduced into the _CO2 separation element 20 and the temperature of the outdoor 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 outdoor air. This reduces heat loss due to heat exchange in the _CO2 separation element 20. For example, when the outdoor air temperature is 5°C and the indoor air temperature is 25°C, if the temperature is not controlled, the air supplied to the target space by the indoor air fan 31 will drop to about 15°C through heat exchange, requiring extra air conditioning energy to maintain the indoor air at 25°C. On the other hand, if the temperature is controlled to keep the outdoor air at 25°C, no heat exchange occurs, and therefore no extra air conditioning energy is required. Furthermore, when the temperature control is performed using the exhaust heat of the outside air fan 41, the energy required for the temperature control is also zero. The control unit 5 may control the second temperature adjustment unit 4b.

The subject of the device, system, or method disclosed herein comprises a computer. When this computer executes a program, the functions of the subject of the device, system, or method disclosed herein are realized. The computer's main hardware configuration is a processor that operates according to the program. The processor may be of any type, as long as it can realize the functions by executing the program. The processor is composed of one or more electronic circuits, including semiconductor integrated circuits (ICs) or LSIs (Large Scale Integration). Multiple electronic circuits may be integrated into a single chip, or may be provided on multiple chips. Multiple chips may be consolidated into a single device, or may be provided on multiple devices. The program is recorded on a non-transitory recording medium such as a computer-readable ROM, optical disc, or hard disk drive. The program may be pre-stored on the recording medium, or may be supplied to the recording medium via a wide area network, including the Internet.

(CO ₂ separation membrane 22)
The _CO2 separation membrane 22 will be described in more detail below. Figure 4 is a cross-sectional view schematically illustrating the structure of the _CO2 separation membrane 22. The _CO2 separation membrane 22 includes a nonwoven fabric substrate 100, a protective film 102 provided on the nonwoven fabric substrate 100, a _CO2 separation gel layer 104 provided on the protective film 102, and a porous cover material 106 provided on the _CO2 separation gel layer 104. The present inventors have focused on the viscosity of the _CO2 separation gel material when applied and after drying for the protective film 102 and porous cover material 106 provided on the nonwoven fabric substrate 100 used in the _CO2 separation membrane 22, and have found that by designing and selecting the pore diameter and thickness of the protective film 102 and porous cover material 106 according to the viscosity based on the following logic, a _CO2 separation membrane 22 with a uniform thickness can be formed, and desired _CO2 permeability and _CO2 / _N2 selectivity can be obtained.

The Lucas-Washburn equation (1) is commonly used to describe the penetration of liquids.
Here, l represents the penetration depth, r represents the capillary radius, γ represents the surface tension of the liquid, θ represents the contact angle, η represents the viscosity, and t represents the time.

In this embodiment, formula (1) is transformed into formula (2), and it is determined that an appropriate substrate capable of supporting the coating liquid, i.e., the _CO2 separation solution or gel to be applied, satisfies formula (2).
Here, l represents the thickness (m) of the substrate, r represents the pore radius (m) of the substrate, γ represents the surface tension (N/m) of the coating liquid or gel, θ represents the contact angle (rad) between the coating liquid or gel and the substrate, η represents the viscosity (mPa s) of the coating liquid or gel, and t represents the time (s) until the liquid loses its fluidity. In this embodiment, the time t is set to 30 seconds, which is the time it is generally considered that the applied liquid loses its fluidity.

The nonwoven fabric substrate 100 is gas permeable. It is also preferable that the nonwoven fabric substrate 100 has sufficient mechanical strength. Examples of fiber materials that can be used include polyester (PET: Polyethylene Terephthalate), polyethylene (PE: Polyethylene), polypropylene (PP: Polypropylene), polyphenylene sulfide (PPS: Polyphenylenesulfide), vinylon, rayon, nylon, and fluorine-based fibers.

The protective film 102 includes pores (hereinafter also referred to as "first pores") that are gas permeable and inhibit the penetration of the _CO2 separation solution. The protective film 102 includes a polymer having a porous structure. The porous cover material 106 includes pores (hereinafter also referred to as "second pores") that are gas permeable and inhibit the passage of the _CO2 separation gel layer 104. The porous cover material 106 includes a nonwoven fabric. In other words, the protective film 102 and the porous cover material 106 have in common the fact that they are both gas permeable. Here, the protective film 102 and the porous cover material 106 use substrates with pore sizes and thicknesses that satisfy formula (2). Here, the pore sizes and thicknesses of the first pores and the second pores required differ depending on the viscosity of the _CO2 separation solution when applied or the _CO2 separation gel after drying.

The surface tension is determined by the composition of the _CO2 separation material, while the contact angle is determined by both the material of the substrate and the composition of the _CO2 separation material. In the case of a _CO2 separation material composition using water as the solvent, the contact angle is larger when the substrate is hydrophobic than when it is hydrophilic, which can suppress the penetration of the coating liquid or gel into the substrate. For example, when a coating liquid with a viscosity η = 20,000 mPa·s and a surface tension γ = 0.072 N/m is applied to a polyester protective film, the contact angle θ = 81°, and if the pore radius is 0.5 μm, the substrate thickness l must be greater than 65 μm. When the same coating liquid is applied to a polyacrylonitrile protective film, the contact angle θ = 21°, and if the pore radius is 0.5 μm, the substrate thickness l must be greater than 159 μm, indicating that a thicker film is required. Similarly, when using a protective film of the same thickness, the upper limit of the pore radius of a hydrophilic film is smaller than that of a hydrophobic film. Porous cover materials also show a similar tendency depending on the material.

The lower the viscosity η of the _CO2 separation solution to be applied, the thicker the protective film must be, or the smaller the pore size, or both. For example, if a coating solution with a viscosity η = 300,000 mPa·s and a surface tension γ = 0.072 N/m is applied to a polyacrylonitrile protective film, the substrate thickness l must be greater than 41 μm if the contact angle θ = 21° and the pore radius is 0.5 μm. On the other hand, if a coating solution with a lower viscosity η = 20,000 mPa·s and a surface tension γ = 0.072 N/m is applied to a polyacrylonitrile protective film, the substrate thickness l must be greater than 159 μm if the contact angle θ = 21° and the pore radius is 0.5 μm, indicating that a thicker film is required. Similarly, when a protective film of the same thickness is used, the upper limit of the pore radius of the film is smaller when a coating liquid with a low viscosity is used than when a coating liquid with a high viscosity is used. The same tendency is observed for porous cover materials depending on the viscosity of the gel.

The protective film 102 can be made of resin materials such as PET, PE, PP, PPS, polyacrylonitrile (PAN), polyethersulfone, etc. Note that melt-blown nonwoven fabrics or nonwoven fabrics made of nanofibers, which have finer fiber diameters than typical nonwoven fabrics, have small pore radii and are denser, so can be used as a protective film if formula (2) is satisfied. The nonwoven fabric used as the protective film 102 can be made of, for example, PET, PE, PP, cellulose, etc.

The porous cover material 106 can be made of nonwoven fabrics such as PET, PE, PP, PPS, vinylon, rayon, nylon, and fluorine-based fibers, or resin materials such as PET, PE, PP, PPS, PAN, polyethersulfone, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polyimide. In general, nonwoven fabrics are more breathable than resin materials and therefore less likely to resist gas permeation, while resin materials are easier to control the pore size than nonwoven fabrics, making it possible to suppress gel penetration.

By drying and gelling the applied _CO2 separation solution, the viscosity in the gel state increases significantly compared to the solution state. Therefore, the porous cover material 106 has less stringent restrictions on pore size and film thickness than the protective film 102, allowing for the use of a more breathable material. In other words, the pore size of the second pores is made larger than the pore size of the first pores. This allows for a _CO2 separation membrane with a protected gel surface to be used in a _CO2 separation element while suppressing a decrease in _CO2 separation membrane performance.

The _CO2 separation gel layer 104 is formed by drying the _CO2 separation solution and contains a _CO2 carrier within a gel film of a hydrophilic polymer containing water. 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.

Examples of _CO2 carriers that can be used include alkali metal carbonates, alkali metal bicarbonates, alkali metal hydroxides, and amino acids. When an amino acid ( _RNH2 ) is dissolved in water, the amino group (NH2) is protonated and dissociates to form _NH3 ⁺ _. However, as shown in Chemical Formula 1 below, carbon dioxide does not react with the protonated amino group ( _NH3 ⁺ ), but rather with the free amino group ( _NH2 ). Therefore, when using an amino acid as a _CO2 carrier, it is necessary to add a deprotonating agent to the solution containing the amino acid to convert _NH3 ⁺ to _NH2 . The deprotonating agent may be one that is sufficiently basic to remove a proton from the protonated _NH3 ⁺ and convert it _to NH2; hydroxides or carbonates of alkali metal elements are suitable.
(Chem.1)
CO ₂ +RNH ₂ +H ₂ O → HCO ₃ ^- +RNH ₃ ⁺

(Manufacturing method)
A method for manufacturing a _CO2 separation membrane 22 according to this embodiment will be described with reference to FIG. 5. FIG. 5 is a flowchart showing the manufacturing procedure for the _CO2 separation membrane 22. First, a coating solution is prepared as an aqueous solution containing a hydrophilic polymer and a _CO2 carrier (S10). More specifically, the _CO2 carrier is added to water and stirred until dissolved. The resulting solution is further supplemented with a hydrophilic polymer and stirred at room temperature for, for example, three days or more to obtain a coating solution. When an amino acid is used as the _CO2 carrier, a deprotonating agent is added in the same manner as the amino acid.

Furthermore, a protective film 102 is placed on at least one surface of the nonwoven fabric substrate 100 (S12). Step 12 may be performed before step 10. Next, the coating liquid ( _CO2 separation solution) obtained in step 10 is applied with an applicator to the surface of the layered porous membrane on which the protective film 102 is bonded to the nonwoven fabric substrate 100, facing the protective film 102, and spread evenly (S14). The coating thickness in the sample of the example described below is 500 μm. Here, although the coating liquid may penetrate into the pores in the protective film 102, by selecting a protective film 102 that satisfies formula (2), not all of the coating liquid passes through, and the coating liquid is carried in the pores of the protective film 102, on the surface, or both.

After coating, the nonwoven fabric substrate 100 with the protective film 102 is dried, for example, at 60°C for about 30 minutes to gel the coating solution and produce a _CO2 separation gel layer 104 (S16). In other words, the applied _CO2 separation solution is dried to form a gel body of the _CO2 separation solution.

Next, a porous cover material 106 is adhered to the _CO2 separation gel layer 104 side of the protective membrane 102 of the nonwoven fabric substrate 100 with the protective membrane 102 obtained in step 16. As a result, a CO2 separation membrane 22 having a four-layer structure including the nonwoven fabric substrate 100/protective membrane 102/ _CO2 separation gel layer 104/ _porous cover material 106 is produced (S18), as schematically shown in Figure 4.

(Experimental Method)
The experimental method for evaluating the membrane performance of each sample in the examples and comparative examples described below will be described. A _CO2 separation membrane 22 is fixed between the raw gas supply side chamber and the permeation side chamber of a gas permeation cell (membrane area: 9.62 ^cm2 ) using two rubber gaskets as sealants. At a temperature of 27°C and atmospheric pressure, a raw gas mixture of _N2 gas and 400 ppm _CO2 is humidified by bubbling through deionized water to a relative humidity of 70%. This raw gas is supplied to the supply side chamber at a flow rate of 2000 cc/min, and a sweep gas (He gas) is supplied to the permeation side chamber at a flow rate of 10 cc/min.

The composition of the gas recovered from the permeation side chamber is quantified using a gas chromatograph, and the _CO2 and _N2 permeance (= permeability, one of the performance indicators of permeability) [mol/( ^m2 ·s·kPa)] is calculated from the gas chromatograph quantification results and the flow rate of He in the sweep gas, and the _CO2 / _N2 selectivity is calculated from the ratio. Note that the higher the _CO2 permeance and _CO2 / _N2 selectivity of the _CO2 separation membrane used in this method, the higher its performance is considered to be. To perform _CO2 separation indoors under room temperature conditions, for example, at a temperature of 10 to 40°C, it is preferable that the _CO2 permeance be 2 x ^10-5 mol/( ^m2 ·s·kPa) or more and the _CO2 / _N2 selectivity be 5,000 or more.

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 at least three days to obtain a _CO2 separation solution (e.g., viscosity 22,620 mPa s) (S10 in FIG. 5). The _CO2 separation solution obtained in step 10 is applied to a thickness of 500 μm using an applicator onto the surface of a layered porous membrane consisting of a PET nonwoven fabric (e.g., 120 μm thick, 130 μm pore size) as the nonwoven fabric substrate 100 and a polyethylene (PE) porous membrane (e.g., 30 μm thick, 3 μm pore size) as the protective membrane 102, facing the PE porous membrane (S14 in FIG. 5).

The coated layered porous membrane is dried at 60°C for approximately 30 minutes to gel the _CO2 separation solution and produce a CO2 _gel layer (S16 in Figure 5). A PET nonwoven fabric (e.g., 100 μm thick, 20 μm pore size) is attached to the _CO2 separation gel layer 104 side of the layered porous membrane surface obtained in step 16 as a porous cover material 106. As a result, a membrane with a four-layer structure of PET nonwoven fabric/PE porous membrane/gel layer/PET nonwoven fabric is produced (S18 in Figure 5), as shown schematically in Figure 1.

Example 2
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 at least three days to obtain a _CO2 separation solution (e.g., viscosity 22,620 mPa s) (S10 in FIG. 5). The _CO2 separation solution obtained in step 10 is applied to a thickness of 500 μm using an applicator onto the surface of a layered porous membrane consisting of a PET nonwoven fabric (e.g., film thickness 160 μm, pore size 100 μm) as the nonwoven fabric substrate 100 and a polyacrylonitrile (PAN) porous membrane (e.g., film thickness 40 μm, pore size 50 nm) as the protective membrane 102, facing the PAN porous membrane (S14 in FIG. 5).

The coated layered porous membrane is dried at 60°C for approximately 30 minutes to gel the _CO2 separation solution and produce a gel layer (S16 in Figure 5). A PET nonwoven fabric (e.g., 100 μm thick, 20 μm pore size) is attached to the gel layer side of the layered porous membrane surface obtained in step 16 as a porous cover material 106. As a result, a membrane with a four-layer structure of PET nonwoven fabric/PAN porous membrane/gel layer/PET nonwoven fabric is produced (S18 in Figure 5), as shown schematically in Figure 1.

Example 3
2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate are added to 43.3 g of water and stirred at room temperature for at least three days to obtain a _CO2 separation solution (e.g., viscosity 320,000 mPa s) (S10 in FIG. 5). The _CO2 separation solution obtained in step 10 is applied to a thickness of 250 μm using an applicator onto the surface of a layered porous membrane consisting of a PET nonwoven fabric (e.g., film thickness 70 μm, pore size 110 μm) as the nonwoven fabric substrate 100 and a polyacrylonitrile (PAN) porous membrane (e.g., film thickness 20 μm, pore size 50 nm) as the protective membrane 102, facing the PAN porous membrane (S14 in FIG. 5).

The coated layered porous membrane is dried at 60°C for about 30 minutes to gel the _CO2 separation solution and produce a gel layer (S16 in Figure 5). A PET nonwoven fabric (e.g., 100 μm thick, 20 μm pore size) is attached to the gel layer side of the layered porous membrane surface obtained in step 16 as a porous cover material 106. As a result, a membrane with a four-layer structure of PET nonwoven fabric/PAN porous membrane/gel layer/PET nonwoven fabric is produced (S18 in Figure 5), as shown schematically in Figure 1.

Example 4
2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate are added to 43.3 g of water and stirred at room temperature for at least three days to obtain a _CO2 separation solution (e.g., viscosity 320,000 mPa s) (S10 in FIG. 5). The _CO2 separation solution obtained in step 10 is applied to a thickness of 500 μm using an applicator onto the surface of the upper PET nonwoven fabric of a layered nonwoven fabric consisting of a melt-blown PET nonwoven fabric (e.g., 50 μm thick, 2 μm pore size) as the protective film 102 and a PET nonwoven fabric (e.g., 70 μm thick, 80 μm pore size) as the nonwoven fabric substrate 100, each adhered to the top and bottom surfaces of the melt-blown PET nonwoven fabric (S14 in FIG. 5). At this time, the applied PET nonwoven fabric does not prevent the _CO2 separation solution from penetrating, so the _CO2 separation solution penetrates into the PET nonwoven fabric up to the interface with the melt-blown PET nonwoven fabric, and penetration is suppressed on the surface of the melt-blown PET nonwoven fabric.

The coated layered nonwoven fabric is dried at 60°C for approximately 30 minutes to gel the _CO2 separation solution and produce a gel layer (S16 in Figure 5). A PET nonwoven fabric (e.g., 100 μm thick, 20 μm pore size) is attached to the gel layer side of the layered nonwoven fabric surface obtained in step 16 as a porous cover material 106. As a result, as shown schematically in Figure 7(a) below, a four-layer membrane is produced: PET nonwoven fabric (nonwoven fabric substrate 100), melt-blown PET nonwoven fabric (gel-impregnated nonwoven fabric 112), gel layer partially impregnated in the PET nonwoven fabric (gel layer 110 partially impregnated in the nonwoven fabric), and PET nonwoven fabric (porous cover material 106) (S18 in Figure 5).

(Comparative 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 at least 3 days to obtain a _CO2 separation solution (e.g., viscosity 22,620 mPa s) (Step 1). The _CO2 separation solution obtained in Step 1 is applied to one side of a PET nonwoven fabric (e.g., 100 μm thick, 50 μm pore size) as a nonwoven fabric substrate using an applicator to a thickness of 500 μm (Step 2). The applied layered porous membrane is dried at 60 ° C for about 30 minutes, and the _CO2 separation solution is gelled to form a gel layer (Step 3).

(Performance evaluation results)
6 is a table showing the evaluation results of _CO2 separation material retention and membrane performance ( _CO2 permeance, _CO2 / _N2 selectivity) in Examples 1 to 3 and Comparative Examples 1 to 3. In Example 1, the _CO2 permeance was 9.0 x ^10-5 mol/( ^m2 ·s·kPa), and the _CO2 / _N2 selectivity was 17,000. In Example 2, the _CO2 permeance was 1.0 x ^10-4 mol/( ^m2 ·s·kPa), and the _CO2 / _N2 selectivity was 19,500. In Example 3, the _CO2 permeance was 1.0 x ^10-4 mol/( ^m2 ·s·kPa), and the _CO2 / _N2 selectivity was 21,000. In Example 4, the _CO2 permeance was 9.3 x ^10-5 mol/( ^m2 ·s·kPa) and the _CO2 / _N2 selectivity was 16,000. In Examples 1 to 4, extremely high _CO2 permeance and _CO2 / _N2 selectivity were achieved. This is because the use of an appropriate substrate that satisfies formula (2) enabled the formation of a uniform membrane without defects.

On the other hand, in Comparative Example 1, the CO ₂ /N ₂ selectivity was 250, which was significantly lower than in Examples 1 to 4. This is because the protective substrate did not satisfy formula (2) for the applied CO ₂ separation solution, so the membrane was not formed uniformly and the raw material gas passed directly through defective parts of the membrane.

Although the _CO2 separation membrane 22 has been described so far as a four-layer structure including a nonwoven fabric substrate 100, a protective membrane 102, a _CO2 separation gel layer 104, and a porous cover material 106, this structure is not necessarily limited to this. Figures 7(a) and 7(b) are cross-sectional views schematically illustrating the structure of another _CO2 separation membrane 22. For example, nonwoven fabrics may be placed on both the top and bottom surfaces of the protective membrane 102. In this case, a _CO2 separation solution is applied to one of the nonwoven fabrics. Since the applied nonwoven fabric does not prevent the _CO2 separation solution from penetrating, the _CO2 separation solution impregnates the nonwoven fabric up to the interface with the protective membrane 102, suppressing penetration on the surface of the protective membrane 102. When a porous cover material 106 is adhered to the gel layer side of the nonwoven fabric surface, a four-layer structure is obtained, including a nonwoven fabric substrate 100, a protective membrane 102, a gel layer 110 partially impregnated in the nonwoven fabric, and a porous cover material 106, as shown schematically in Figure 7(a).

If the coated nonwoven fabric is sufficiently thicker than the film thickness of the _CO2 separation solution after penetration, the gel layer after drying will not be exposed to the surface, and the porous cover material 106 is not necessary. As shown schematically in Figure 7(b), a three-layer structure will be formed, including the nonwoven fabric substrate 100, the protective film 102, and the nonwoven fabric 120 fully impregnated with gel. In this case, in order to maintain the gel layer after drying, the nonwoven fabric 120 fully impregnated with gel must satisfy formula (2).

Furthermore, if the protective film 102 is made of a material with a finer fiber diameter than typical nonwoven fabrics, such as a melt-blown nonwoven fabric or a nonwoven fabric made of nanofibers, and has a small, dense pore radius, the nonwoven fabric below the protective film 102 is not necessarily required, and a three-layer structure consisting of a nonwoven fabric protective film/gel layer/porous cover material may also be used.

According to this embodiment, the _CO2 separation gel layer 104 formed by drying the _CO2 separation solution is disposed between the protective membrane 102, which has permeation suppression properties of the _CO2 separation solution, and the porous cover material 106, which has permeation suppression properties of the _CO2 separation gel layer 104. This allows for the formation of a layer with a uniform thickness. Furthermore, since the _CO2 separation gel layer 104 is formed with a uniform thickness, desired _CO2 permeability and selectivity can be obtained. Furthermore, since the CO2 separation gel layer 104 formed by drying the _CO2 separation solution is disposed between the protective membrane 102, which has permeation suppression properties of the _CO2 separation solution, and the porous cover material 106, which has permeation suppression properties of the _CO2 separation gel layer 104, permeation of the _CO2 separation material is suppressed in a _CO2 separation membrane using a _nonwoven fabric substrate, allowing for the formation of a separation membrane layer with a uniform thickness. Furthermore, since the porous cover material 106 includes a nonwoven fabric, the manufacturing cost of the _CO2 separation membrane 22 can be reduced.

An outline of one aspect of the present disclosure is as follows.
(Item 1)
a gas-permeable nonwoven substrate (100);
a protective film (102) provided on the nonwoven fabric substrate (100) and including first pores that are gas permeable and inhibit the permeation of a _CO2 separation solution;
a _CO2 separation gel layer (104) provided on the protective film (102) and formed by drying the _CO2 separation solution;
a porous cover material (106) provided on the _CO2 separation gel layer (104) and including second pores that are permeable to gas and inhibit passage of the _CO2 separation gel layer (104);
A CO ₂ separation membrane (22) in which the pore diameter of the second pores is larger than the pore diameter of the first pores.

(Item 2)
2. The _CO2 separation membrane (22) according to claim 1, wherein the protective membrane (102) comprises a polymer having a porous structure.

(Item 3)
3. The _CO2 separation membrane (22) according to claim 1 or 2, wherein the porous covering material (106) comprises a nonwoven fabric.

(Item 4)
A _CO2 separation element (20) formed by stacking the _CO2 separation membrane (22) according to any one of items 1 to 3.

(Item 5)
a placing step of placing a protective film (102) having first pores that are gas permeable and have permeation suppression properties for a _CO2 separation solution on at least one surface of a gas-permeable nonwoven fabric substrate (100);
a coating step of coating the _CO2 separation solution on the protective film (102);
a drying step of drying the applied _CO2 separation solution to form a gel body of the _CO2 separation solution;
a cover material bonding step of bonding a porous cover material (106) on the gel body, the second pores having gas permeability and inhibiting passage of the gel body, and having a pore diameter larger than that of the first pores;
A method for producing a CO ₂ separation membrane (22) comprising:

The present disclosure has been described above based on an embodiment. This embodiment is merely an example, and those skilled in the art will understand that various modifications are possible to the combination of each component or each treatment process, and that such modifications are also within the scope of the present disclosure.

According to this disclosure, in a CO2 separation membrane using a nonwoven fabric substrate, it is possible to suppress the permeation of CO2 separation materials and form a separation membrane layer with a uniform thickness.

REFERENCE SIGNS LIST 1 _CO2 separation system, 2 building, 4 temperature control unit, 5 control unit, 6 laminated structure, 7 outdoor air temperature detection unit, 8 indoor air temperature detection unit, 10 housing, 14 frame, 16 treatment target gas air duct, 17 sweep gas air duct, 18 _CO2 , 19 _N2 , 20 _CO2 separation element, 21 _CO2 separation element piece, 22 _CO2 separation membrane, 31 indoor air fan, 33 indoor air outlet, 35 air supply port, 37 indoor air filter, 41 outdoor air fan, 43 outdoor air outlet, 45 exhaust port, 47 outdoor air filter, 51 indoor intake port, 52 indoor air introduction duct, 53 indoor outlet, 54 indoor air outlet duct, 55 outdoor intake port, 56 Outside air intake duct, 57 outdoor air outlet, 58 outside air outlet duct, 100 nonwoven fabric substrate, 102 protective film, ₁₀₄ CO2 separation gel layer, 106 porous cover material, 110 gel layer partially impregnated into nonwoven fabric, 112 gel-impregnated nonwoven fabric, 120 nonwoven fabric completely impregnated with gel, 122 gel layer impregnated into nonwoven fabric.

Claims (5)

a gas-permeable nonwoven fabric substrate;
a protective film provided on the nonwoven fabric substrate, the protective film including first pores that are gas permeable and inhibit the permeation of a _CO2 separation solution;
a _CO2 separation gel layer provided on the protective film and formed by drying the _CO2 separation solution;
a porous cover material provided on the _CO2 separation gel layer and including second pores that are permeable to gas and inhibit passage of the _CO2 separation gel layer;
A CO ₂ separation membrane, wherein the pore diameter of the second pore is larger than the pore diameter of the first pore. The _CO2 separation membrane according to claim 1 , wherein the protective membrane comprises a polymer having a porous structure. The _CO2 separation membrane according to claim 1 or 2, wherein the porous cover material comprises a nonwoven fabric. A _CO2 separation element formed by stacking the _CO2 separation membrane according to any one of claims 1 to 3. a placing step of placing a protective film having first pores that is gas permeable and has a property of suppressing permeation of a _CO2 separation solution on at least one surface of a gas-permeable nonwoven fabric substrate;
a coating step of coating the CO ₂ separation solution on the protective film;
a drying step of drying the applied _CO2 separation solution to form a gel body of the _CO2 separation solution;
a cover material bonding step of bonding a porous cover material on the gel body, the second pores having gas permeability and inhibiting passage of the gel body, the second pores having a pore diameter larger than that of the first pores;
A method for producing a CO ₂ separation membrane comprising: