Separation membrane

Abstract

The present invention relates to a separation membrane comprising a laminate of at least a porous substrate and a resin layer. The resin layer contains at least a hydrophilic resin, a hydrophobic resin, and a crosslinked component resin. The rate of reduction of the hydrophilic resin content before and after wet heat treatment at 120°C for 24 hours is 0.1-10%. The present invention addresses the problem of providing a separation membrane having high moist heat resistance.

Description

Separation membrane

[0001] The present invention relates to a separation membrane, and more particularly to a gas separation membrane suitable for use as a humidifying membrane in a solid polymer electrolyte fuel cell.

[0002] Fuel cells are a mechanism for electrically extracting energy generated when hydrogen and oxygen react to produce water. Because they are highly energy efficient and produce only water as an exhaust, they are expected to become widespread as a clean energy source. A solid polymer electrolyte fuel cell, which uses a solid polymer membrane as an electrolyte, is composed of a solid polymer electrolyte membrane and electrodes arranged on both sides of the membrane. In solid polymer electrolyte fuel cells, the solid polymer electrolyte membrane is, for example, an ion-exchange membrane with proton exchange groups. This membrane functions as an ion-conductive electrolyte by performing proton exchange in a saturated water-saturated state. Therefore, solid polymer electrolyte fuel cells generally include a battery system that performs the cell reaction and a humidification system that humidifies the raw gas supplied to the battery system. The humidification system may be connected to the fuel cell as a separate humidifier, or it may be integrated into the battery system.

[0003] Separation membranes are used in a wide variety of applications, including water treatment, blood purification, and gas separation, and are therefore used in a wide range of environments. In particular, gas separation membranes that selectively separate water vapor are expected to be used in harsh environments with high temperatures and humidity, such as in humidification modules for solid polymer electrolyte fuel cells (hereinafter sometimes referred to as fuel cell humidification modules).

[0004] Humidification systems for solid polymer electrolyte fuel cells typically include a feed gas flow path through which a feed gas is introduced, an exhaust gas flow path through which exhaust gas from the cell system is introduced, and a water vapor permeable membrane separating these flow paths. The water vapor contained in the exhaust gas is selectively permeated through the gas separation membrane, which selectively separates water vapor, and introduced from the exhaust gas flow path into the feed gas flow path. The water vapor is then brought into contact with the feed gas in the feed gas flow path, thereby humidifying the feed gas. Therefore, gas permeable membranes used in fuel cell humidification systems are required to have gas barrier properties and high water vapor permeability. Conventional gas permeable membranes include those in which a perfluorosulfonic acid-based ion exchange resin is formed on the surface of a porous polymer substrate (see Patent Document 1), those in which a polymer substrate is impregnated with a moisture-permeable organic component (see Patent Document 2), and those in which a resin liquid containing an organic component is applied to a polymer substrate (see Patent Document 3).

[0005] JP 2002-117878 A JP 2007-203280 A Japanese Patent No. 7294130 A

[0006] As mentioned above, separation membranes are expected to be used in a variety of environments, making durability important. Humidifying membranes for fuel cell vehicle humidifiers, in particular, are expected to be used in high-temperature, high-humidity environments of 100°C and 80% RH or higher. Furthermore, fuel cell vehicles are also expected to require improved (increased) fuel cell output and a more compact fuel cell system overall. In solid polymer electrolyte fuel cells, high temperatures and humidity in the cell system facilitate proton exchange in the solid polymer electrolyte membrane and reduce the electrical resistance of the polymer electrolyte membrane and electrodes, thereby improving fuel cell output. Therefore, gas separation membranes contained in fuel cell humidification systems are required to have water vapor permeability per membrane area and moisture and heat resistance that can withstand operation in high-temperature, high-humidity environments. The gas separation membrane disclosed in Patent Document 1 uses fluorine-based resin materials as its constituent components, which poses challenges in terms of moisture and heat resistance. The gas separation membrane disclosed in Patent Document 2 can ensure moisture and heat resistance by selecting the right combination of materials, but it is difficult to increase the water vapor permeability per membrane area. Furthermore, the heat exchange sheet disclosed in Patent Document 3 uses a vinylpyrrolidone-based material as a constituent component, and therefore can ensure water vapor permeability in a room temperature environment. However, in the high-temperature and high-humidity environment described above, the leaching of the hydrophilic resin cannot be completely suppressed, and therefore there is a problem with humidity and heat resistance.

[0007] Therefore, an object of the present invention is to provide a separation membrane that not only has water vapor permeability and gas barrier properties but also has excellent resistance to moisture and heat by suppressing the elution of a hydrophilic resin.

[0008] In order to solve these problems, the present invention has the following features. That is, (1) A separation membrane comprising a laminate of at least a porous substrate and a resin layer, the resin layer containing at least a hydrophilic resin, a hydrophobic resin, and a cross-linking component resin, wherein the rate of decrease in the content of the hydrophilic resin before and after wet heat treatment at 120°C for 24 hours is 0.1% to 10%. (2) The separation membrane according to (1), in which the amount of water adsorbed by the laminate after wet heat treatment at 120°C for 24 hours is 0.1 g / cm3 to 1.3 g / cm3 per unit volume of the resin layer. (3) A separation membrane in which the cross-linking conversion rate of the hydrophilic resin is 3% to 30%. (4) The separation membrane according to any of (1) to (3), in which the cross-linking component resin is an acrylic resin. (5) The separation membrane according to (4), wherein the content of the acrylic resin is 2% by mass or more and 13% by mass or less relative to the mass of the entire resin layer, and the acrylic resin has a crosslinked structure, and the crosslinked structure of the acrylic resin includes a structure represented by the following chemical formula (I) or (II):

[0009]

[0010] (R １ and R ２ is an alkyl chain of any length, X １ ~X ６ indicates any element or molecular structure.)

[0011]

[0012] (R １ ~R ４ is an alkyl chain of any length, X １ ~X ８represents any element or molecular structure.) (6) The separation membrane according to any one of (1) to (5), wherein the hydrophilic resin is polyvinylpyrrolidone and / or vinylpyrrolidone copolymer. (7) The separation membrane according to any one of (1) to (6), wherein the hydrophobic resin is a urethane resin. (8) The separation membrane according to any one of (1) to (7), wherein the thickness of the resin layer is 10 nm or more and 1000 nm or less. (9) The separation membrane according to any one of (1) to (7), wherein the water contact angle of the resin layer is 67° or more and 83° or less. (10) The separation membrane according to any one of (1) to (7), wherein the absolute value of the heat shrinkage rate in the in-plane direction at 100°C for 30 minutes is 4% or less. (11) The separation membrane according to any one of (1) to (7), wherein the absolute value of the heat shrinkage rate in the in-plane direction at 100°C for 30 minutes is 2.5% or less. (12) The separation membrane according to any one of (1) to (7), wherein the absolute value of the linear swelling rate in the in-plane direction when the separation membrane is immersed in water at 20°C for 2 hours is 4% or less. (13) The separation membrane according to any one of (1) to (7), wherein the absolute value of the linear swelling rate in the in-plane direction when the separation membrane is immersed in water at 20°C for 2 hours is 2.5% or less. (14) The separation membrane according to any one of (1) to (7), wherein the content of the polyvinylpyrrolidone and / or vinylpyrrolidone copolymer is 50% by mass or more and 95% by mass or less with respect to the entire resin layer. (15) The separation membrane according to any one of (1) to (7), wherein the basis weight of the resin layer is 0.1 g / m ２ Above, 3.0g / m ２(16) The separation membrane according to any one of (1) to (7), wherein the ratio of the basis weight of the resin layer to the basis weight of the porous substrate (basis weight of resin layer / basis weight of porous substrate) is 0.01 or more and 0.18 or less. (17) A method for producing the separation membrane according to any one of (1) to (16), comprising the steps of applying a coating composition containing polyvinylpyrrolidone and / or a vinylpyrrolidone copolymer, a urethane resin, and an acrylate having two or more carbon-carbon double bonds to the porous substrate to form a coating film, and then irradiating the coating film with ultraviolet light. (18) A gas separation membrane using the separation membrane according to any one of (1) to (16). (19) A fuel cell humidifying membrane using the gas separation membrane according to (18). (20) A fuel cell humidifying module using the fuel cell humidifying membrane according to (19). (21) A fuel cell system using the fuel cell humidifying module according to (20). (22) Two-wheeled and four-wheeled automobiles, ships, aircraft, and moving objects using the fuel cell system according to (21).

[0013] The separation membrane of the present invention can exhibit high water vapor permeability and gas barrier properties. It also has excellent moisture and heat resistance due to a mechanism that suppresses elution of the hydrophilic resin in high-temperature, high-humidity environments. Furthermore, it has excellent shape stability, which can increase the productivity of the separation membrane and fuel cell humidification modules that use this separation membrane.

[0014] Fig. 1 is a conceptual diagram of a test piece for measuring the thermal shrinkage rate and linear swelling rate of the gas separation membrane of the present invention. Fig. 2 is a schematic diagram of an air conditioner. Fig. 3 is a block diagram related to the power supply of a fuel cell vehicle. Fig. 4 is a schematic diagram of a cross section of an embodiment of the gas separation membrane of the present invention. Fig. 5 is a conceptual diagram of a method for evaluating the water vapor transmission rate of the gas separation membrane of the present invention. Fig. 6 is a conceptual diagram of a method for evaluating the air transmission rate of the gas separation membrane of the present invention.

[0015] The following describes the embodiments of the invention. [Separation membrane] The separation membrane of the present invention comprises a laminate of at least a porous substrate and a resin layer, and the resin layer contains at least a hydrophilic resin, a hydrophobic resin, and a cross-linking component resin. In this laminate, the pores in the porous substrate are blocked by the resin layer, so the separation membrane has excellent gas barrier properties. Therefore, in a gas separation device using this separation membrane, the raw gas and the exhaust gas are reliably separated. Gas barrier properties refer to the barrier properties of gases excluding water vapor, and a low air permeation rate is considered to have excellent gas barrier properties.

[0016] The separation membrane of the present invention is suitable for use in separating water or hydrophilic gas molecules such as water vapor and ammonia. In particular, the separation membrane of the present invention is suitable for use in separating water vapor because it contains a hydrophilic resin. The separation of water vapor and air will be described below.

[0017] The resin layer in the separation membrane of the present invention contains a hydrophilic resin, which ensures the migration of water vapor from one side of the resin layer to the other side, thereby improving the water vapor permeability of the separation membrane. Furthermore, the resin layer contains a hydrophobic resin and a crosslinking component resin in addition to the hydrophilic resin, which allows the resin layer to have high moisture and heat resistance, resulting in excellent moisture and heat resistance of the separation membrane.

[0018] Here, the mechanism by which the resin layer contains a hydrophilic resin, a hydrophobic resin, and a crosslinking component resin, and thereby has excellent moist heat resistance, is considered to be as follows. That is, since the hydrophobic resin is water-insoluble, the outflow of the hydrophobic resin itself from the resin layer is suppressed. Then, in the resin layer, the hydrophobic resin with the above-described properties is localized on the surface of the resin layer to form a water-insoluble coating, thereby suppressing the outflow of the hydrophilic resin from the resin layer, and the crosslinked structure of the crosslinking component resin formed on the surface or inside of the resin layer also suppresses the outflow of the hydrophilic resin from the resin layer, resulting in excellent moist heat resistance of the separation membrane.

[0019] Furthermore, because the effect of suppressing the outflow of the hydrophilic resin from the resin layer can be more significantly obtained, the content ratio of the hydrophilic resin to the hydrophobic resin in the resin layer (hydrophilic resin content (mass%) / hydrophobic resin content (mass%)) is preferably 9.0 or less. It is more preferably 7.0 or less, even more preferably 6.0 or less, and particularly preferably 5.0 or less. On the other hand, from the viewpoint of improving the water vapor transmission rate of the separation membrane, the content ratio of the hydrophilic resin to the hydrophobic resin (hydrophilic resin content (mass%) / hydrophobic resin content (mass%)) is preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. Note that the contents of the hydrophilic resin and the hydrophobic resin both refer to the contents of the entire resin layer. Separation membranes are required to have high water vapor permeability and gas barrier properties, and the greater the difference between the amount of water vapor permeating per unit area and unit time, i.e., the water vapor transmission rate, and the amount of air permeating per unit area and unit time, i.e., the air transmission rate, the better the separation membrane can be said to be. Therefore, the water vapor transmission rate of the separation membrane is 0.003 g / min / cm ２ More than 0.006 g / min / cm ２ More preferably, the air permeation rate is 10 NmL / min / cm. ２ Preferably, less than 1 NmL / min / cm ２ The following is more preferable: Furthermore, the unit of water vapor transmission rate is NmL / min / cm ２ When converted into a water vapor transmission rate, it is more preferable that the water vapor transmission rate is 10 times or more the transmission rate of air.

[0020] The thickness of the separation membrane is preferably thin from the viewpoint of pressure loss when made into a fuel cell humidifying element. On the other hand, if the thickness is excessively thin, the strength of the fuel cell humidifying element and handling during fabrication of the fuel cell humidifying element may deteriorate. For these reasons, the thickness of the separation membrane is preferably 5 μm or more, more preferably 9 μm or more. Furthermore, the thickness of the separation membrane is preferably 30 μm or less, more preferably 15 μm or less.

[0021] The basis weight of the separation membrane is 3 g / m ２ More than 5 g / m ２More preferably, the basis weight of the separation membrane is 15 g / m ２ Preferably, 10 g / m or less ２ The following is more preferable. By setting the basis weight of the separation membrane to be equal to or less than the above-mentioned upper limit, the thickness of the separation membrane can be reduced, and humidity exchange efficiency can be improved. Furthermore, by setting the basis weight of the separation membrane to be equal to or more than the above-mentioned lower limit, the separation membrane can maintain strength sufficient to withstand the heat and tension that occurs during lamination processing with the flow path material in the process of molding the separation membrane into a fuel cell humidifying element.

[0022] The absolute value of the heat shrinkage rate in the in-plane direction of the separation membrane (the direction horizontal to the film surface) at 100°C for 30 minutes is preferably 4% or less, more preferably 2.5% or less. Here, the linear swelling rate in the in-plane direction is a value calculated based on the formula: [Heat shrinkage rate in the in-plane direction (%)] = {([In-plane length after heating] - [In-plane length before heating]) ÷ [In-plane length before heating]} × 100. By keeping the heat shrinkage rate in the in-plane direction within the above range, it is possible to suppress changes in tension when the separation membrane is fixed in a high-temperature environment, and to suppress damage and deterioration of the separation membrane due to environmental changes.

[0023] The thermal shrinkage can be measured by the following method. First, five 120 mm square test pieces are prepared, and marks are made on the test pieces in the longitudinal direction (or machine direction) and transverse direction of the sheet as shown in Figure 1. Next, as shown in Figure 1, the distance between the gauge lines (L ０ and T ０ ) is marked and measured with a scale ruler capable of measuring to a minimum of 0.5 mm. Next, the test piece is placed horizontally in a thermostatic chamber adjusted to 100°C for 30 minutes, removed, and then returned to the same standard state as before the test, and the distances between the gauge lines in the longitudinal and transverse directions (L and T) are measured again. The same measurement is performed on all five test pieces, and the average values ​​are calculated as the thermal shrinkage in the L and T directions. In the present invention, an absolute value of the in-plane thermal shrinkage at 100°C for 30 minutes of 4% or less means that the absolute values ​​of the thermal shrinkage in both the L and T directions are 4% or less.

[0024] The absolute value of the linear swelling ratio in the in-plane direction (horizontal to the film surface) of the separation membrane is preferably 4% or less, more preferably 2.5% or less. Here, the linear swelling ratio in the thickness direction or in-plane direction is a value calculated based on the formula: [Linear swelling ratio in the thickness direction or in-plane direction (%)] = {([Thickness in the thickness direction or in-plane direction after swelling] - [Thickness in the thickness direction or in-plane direction before swelling]) ÷ [Thickness in the thickness direction or in-plane direction before swelling]} × 100. By keeping the linear swelling ratio in the in-plane direction within the above range, it is possible to suppress changes in tension when the separation membrane is fixed in a high-humidity environment, and to suppress destruction and deterioration of the separation membrane due to environmental changes.

[0025] The linear swelling ratio can be measured by the following method. First, five 120 mm square test pieces are prepared, and marks are made on the test pieces in the longitudinal direction (or machine direction) and transverse direction of the sheet as shown in Figure 1. Next, as shown in Figure 1, the distance between the gauge lines (L ０ and T ０ ) and measure it with a scale ruler that can measure down to 0.5 mm. Next, the test piece is left to stand in a water bath adjusted to 25°C for 2 hours, and after taking it out, water droplets adhering to the surface of the test piece are removed with gauze or the like, and after returning it to the same standard condition as before the test, the distances between the gauge lines in the longitudinal and transverse directions (L and T) are measured again. The same measurement is performed on all five test pieces, and the average values ​​are calculated as the linear swelling ratios in the L direction and T direction. In the present invention, the absolute value of the thermal shrinkage ratio at 100°C for 30 minutes in the plane of the linear swelling ratio being 4% or less means that the absolute values ​​of the thermal shrinkage ratios in both the L direction and the T direction are 4% or less.

[0026] The reduction rate of the hydrophilic resin content of the separation membrane before and after the moist heat treatment is preferably 0.1% by mass or more and 10% by mass or less. By setting it to 0.1% by mass or more and 10% by mass or less, it is possible to prevent a decrease in water vapor permeability over time when the separation membrane of the present invention is used, particularly in a high-temperature and high-humidity environment, and to obtain a separation membrane having moist heat resistance. Here, the reduction rate of the hydrophilic resin content before and after the moist heat treatment can be calculated by the formula: ([1660 cm of the resin layer before the moist heat treatment] －１ Peak intensity at 1660 cm of the resin layer after wet heat treatment －１Peak intensity at 1660 cm of the resin layer before the wet heat treatment －１ When the rate of decrease in the hydrophilic resin content before and after the moist heat treatment is within the above range, the separation membrane can maintain its water vapor permeability over a long period of time in a high humidity environment.

[0027] In this specification, when polyvinylpyrrolidone and polyvinylpyrrolidone copolymers are used as the hydrophilic resin, the peak intensity to be extracted is 1660 cm －１ However, it is necessary to check the peak intensity at the wave number or wavelength corresponding to the functional group that exhibits the hydrophilicity of the hydrophilic resin used.

[0028] The peak intensity can be measured by the following method. A test piece of the separation membrane is prepared, and the resin surface is subjected to Fourier transform infrared spectroscopy using the total reflection measurement method. The measurement mode is selected as the ATR method (total reflection method), and after background correction, the measurement is performed. The peak intensity of 1660 cm in the resin layer of the gas separation membrane is measured. －１ The measurement conditions are resolution 4 and number of accumulations 32. －１ The intensity of the CH absorption peak derived from the ethylene group in the vicinity (A ＣＨ ) and 1660 cm －１ The intensity of the C═O absorption peak derived from polyvinylpyrrolidone in the vicinity (A ＣＯ In this case, in order to adjust the degree of adhesion of the test piece, －１ Nearby peaks and 1365 cm －１ Measurements are taken while changing the degree of contact so that the peaks in the vicinity are constant.

[0029] Next, the test piece of the separation membrane was subjected to wet heat treatment in an autoclave at 120°C for 24 hours, dried in a room temperature environment for 12 hours or more, and then measured for the 1660 cm －１ The peak intensity is calculated at

[0030] The amount of moisture adsorbed by the separation membrane before and after the moist heat treatment was 0.1 g / cm 3 1.3g / cm or more 3 Preferably, 0.4 g / cm or less 31.3g / cm or more 3 The following is more preferable. Here, the amount of moisture adsorption before and after the moist heat treatment is a value calculated based on the formula: ([weight of separation membrane before moist heat treatment] - [weight of separation membrane after moist heat treatment]) / [weight of separation membrane before moist heat treatment] / [volume of resin layer] x 100. When the amount of moisture adsorption before and after the moist heat treatment is equal to or less than the above upper limit, it is possible to prevent a decrease in water vapor permeability due to moisture remaining inside the separation membrane as adsorbed water in a high humidity environment. Furthermore, when the amount of moisture adsorption is equal to or greater than the above lower limit, moisture absorption from the atmosphere is promoted, improving water vapor permeability.

[0031] The weight of the separation membrane after the moist heat treatment can be measured by the following method: A test piece of the separation membrane is prepared, subjected to moist heat treatment in an autoclave at 120°C for 24 hours, and then dried in a room temperature environment for 12 hours or more, after which the weight is measured.

[0032] In order to obtain the separation membrane characteristics described above, when the resin layer of the separation membrane contains polyvinylpyrrolidone and / or polyvinylpyrrolidone copolymer, urethane resin, or acrylic resin, the UV irradiation dose to the separation membrane in the separation membrane production process is 500 mJ / cm ２ More than 5600mJ / cm ２ By setting the amount of UV irradiation on the separation membrane within the above range, each resin contained in the resin layer is appropriately crosslinked, and high water vapor permeability and moist heat resistance are obtained.

[0033] [Porous substrate] The porous substrate used in the present invention has air permeability and water vapor permeability, and has a large number of fine through-holes.Porous substrates made of polymer resins are preferably used because they have little strength loss in high humidity environments and are easy to form thin films.The polymer resin constituting the porous substrate may be any of polyolefin resins, polycarbonates, polyamides, polyimides, polyamideimides, aromatic polyamides, fluorine-based resins, etc., but polyolefin resins are preferred from the viewpoints of production cost and availability. Examples of monomer components constituting the polyolefin resin include ethylene, propylene, 1-butene, 1-pentene, 3-methylpentene-1, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 5-ethyl-1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, and 5-methyl-2-norbornene. Examples include, but are not limited to, homopolymers of these monomers, copolymers of at least two monomers selected from the group consisting of these monomers, and blends of these homopolymers and copolymers. In addition to the above monomer components, for example, vinyl alcohol, maleic anhydride, etc. may also be copolymerized. In particular, in the case of a porous substrate, from the viewpoints of adjusting the porosity and pore size, film-forming properties, and reducing production costs, it is more preferable that the monomer component constituting the above-mentioned resin is one or more selected from the group consisting of ethylene and propylene.

[0034] The basis weight of the porous substrate is preferably 15 g / m ２ or less, more preferably 10 g / m ２ More preferably, 7 g / m or less ２ or less, while preferably 1 g / m ２ More preferably, 3 g / m ２ More preferably, 5 g / m ２That's all. By setting the basis weight of the porous substrate to the above-mentioned upper limit or less, the thickness of the porous substrate can be reduced, and the humidity exchange efficiency of a separation membrane using the porous substrate can be improved. Furthermore, by setting the basis weight of the porous substrate to the above-mentioned lower limit or more, the porous substrate can maintain strength that can withstand the heat and tension that occurs during the coating process of the coating liquid and during lamination processing with a flow path material in the process of molding the separation membrane into a fuel cell humidifying element.

[0035] The thickness of the porous substrate is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less, and is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. By setting the thickness of the porous substrate to the above-mentioned upper limit value or less, the heat and humidity exchange efficiency of the separation membrane can be improved. Furthermore, by setting the thickness of the porous substrate to the above-mentioned lower limit value or more, it is possible to maintain strength that can withstand the heat and tension during coating of the coating liquid on the first surface of the porous substrate and lamination processing with the flow path material in the process of molding the separation membrane using the porous substrate into a fuel cell humidifying element.

[0036] The density of the porous substrate is preferably 0.2 g / cm ３ More preferably, 0.3 g / cm ３ More preferably, 0.4 g / cm ３ On the other hand, it is preferably 8.0 g / cm ３ or less, more preferably 7.0 g / cm ３ More preferably 6.0 g / cm or less ３ The density of the porous substrate significantly affects the water vapor transmission rate of the separation membrane, and by setting the density to the above-mentioned upper limit or less, the water vapor transmission rate of the separation membrane increases. On the other hand, by setting the density to the above-mentioned lower limit or more, the wettability of the coating liquid to the porous substrate is improved. This makes it possible to apply a thin coating of the coating liquid to the first surface of the porous substrate.

[0037] The porosity of the porous substrate is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more. The porosity of the porous substrate is thought to be correlated with the water vapor transmission rate, and the higher the porosity, the higher the water vapor transmission rate of the porous substrate and the higher the water vapor transmission rate of the separation membrane using it.

[0038] The pore diameter of the porous substrate is preferably 20 nm or more, more preferably 30 nm or more, and even more preferably 40 nm or more. On the other hand, it is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less. The pore diameter of the porous substrate is thought to be correlated with the water vapor transmission rate of the porous substrate, and by setting the pore diameter to the above-mentioned lower limit value or more, the water vapor transmission rate of the porous substrate is improved, and the water vapor transmission rate of the separation membrane is also improved. On the other hand, by setting the pore diameter to the above-mentioned upper limit value or less, the wettability of the coating liquid to the porous substrate is increased. This makes it possible to apply a thin coating of the coating liquid to the first surface of the porous substrate.

[0039] As a method for forming a membrane from a porous substrate, a known wet method or a known dry method can be adopted.

[0040] The resin constituting the porous substrate may contain various additives such as antioxidants, heat stabilizers, light stabilizers, neutralizers, antistatic agents, lubricants consisting of organic particles, as well as antiblocking agents, fillers, and incompatible polymers, as long as the effects of the present invention are not impaired. In particular, it is preferable to add an antioxidant to suppress oxidative deterioration of polypropylene and the like due to thermal history. Furthermore, if necessary, surface modification such as corona treatment, plasma treatment, surfactant impregnation, and hydrophilization treatment such as surface grafting may be performed.

[0041] [Resin Layer] The resin layer of the present invention contains at least a hydrophilic resin, a hydrophobic resin, and a crosslinking component resin. The content of the hydrophilic resin in the resin layer of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on the entire resin layer. It is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less. When the content of the hydrophilic resin is at least the above lower limit, the separation membrane has an excellent water vapor transmission rate. When the content of the hydrophilic resin is at most the above upper limit, the separation membrane has excellent moist heat resistance.

[0042] The water contact angle of the resin layer of the present invention is preferably 67° to 90°, more preferably 67° to 83°. When the water contact angle is equal to or greater than the above lower limit, the water vapor permeability of the separation membrane is excellent. When the water contact angle is equal to or less than the above upper limit, elution of the hydrophilic resin contained in the resin layer is suppressed, and the separation membrane has excellent moist heat resistance.

[0043] (1) Hydrophilic Resin The hydrophilic resin contained in the resin layer of the present invention has hygroscopic properties, and a separation membrane laminated with a resin layer containing a hydrophilic resin can achieve high water vapor permeability. The hydrophilic resin used in the present invention is not particularly limited as long as it has at least one selected from the group consisting of a carboxyl group, a carbonyl group, a sulfonic acid group, an amino group, a hydroxyl group, an oxyethylene group, and a quaternary ammonium group at its terminal or side chain. However, from the viewpoint of excellent hygroscopic properties, a hydrophilic resin having a carbonyl group at its terminal or side chain is preferred. Specific examples include urethane, polyvinyl alcohol, polyvinylpyrrolidone, polyvinylamine, polyvinyl methoxyacetal, polyethylene glycol, polyoxyethylene, polyoxyalkylene alkyl ether, sodium polyacrylate, sodium polyacrylsulfonate, cellulose acetate, and carboxymethyl cellulose. These resins can be used alone or in combination of two or more thereof. In particular, the hydrophilic resin preferably contains polyvinylpyrrolidone and / or a vinylpyrrolidone copolymer, because of its excellent moisture absorption and solubility in solvents, which can favorably wet the porous film with a coating liquid, provide excellent membrane-forming properties, and ensure excellent long-term durability when used as a separation membrane. By including polyvinylpyrrolidone and / or a vinylpyrrolidone copolymer, the resin layer can be made highly hygroscopic, and a separation membrane laminated with the resin layer can be made to have a high water vapor transmission rate. The moisture absorption of polyvinylpyrrolidone or the like is preferably such that the moisture absorption rate at 23°C and 75% RH is 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 48% by mass or less, and particularly preferably 25% by mass or more and 45% by mass or less. When the moisture absorption rate is above the lower limit, the resin layer can be made highly hygroscopic, and the separation membrane can be made to have a high water vapor transmission rate. When the moisture absorption rate is below the upper limit, swelling due to moisture absorption of the resin layer can be suppressed, and the separation membrane can be made to have high moist heat resistance.

[0044] In the present invention, polyvinylpyrrolidone refers to a polymer in which only N-vinylpyrrolidone is polymerized, and vinylpyrrolidone copolymer refers to a polymer in which N-vinylpyrrolidone is the main monomer and vinyl acetate, vinyl caprolactam, or the like is copolymerized as a comonomer. The type and content ratio (comonomer / main monomer) of the comonomer in the vinylpyrrolidone copolymer are not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected depending on the solubility in the solvent used and the physical properties of the coating liquid. The molecular weight of polyvinylpyrrolidone or vinylpyrrolidone copolymer is not particularly limited, but since this facilitates achieving a viscosity that allows the formation of a coating film of uniform thickness when applied to the porous substrate as a coating liquid, the weight-average molecular weight of polyvinylpyrrolidone or vinylpyrrolidone copolymer is preferably 1,000 to 600,000, more preferably 60,000 to 500,000, and particularly preferably 150,000 to 400,000. Examples of the polyvinylpyrrolidone include the "Luvitec K" (registered trademark) series manufactured by BASF. Examples of vinylpyrrolidone copolymers include the "Luvitec VA" (registered trademark) series and the "Luvicap" (registered trademark) series.

[0045] Furthermore, it is preferable that at least a portion of the polyvinylpyrrolidone, etc., contained in the resin layer is crosslinked. Crosslinking further inhibits dissolution of the polyvinylpyrrolidone, etc., into condensed water when the fuel cell humidifying element is used in an environment where condensation or ice forms on the surface of the separation membrane. Therefore, the content of the polyvinylpyrrolidone, etc., contained in the resin layer of the separation membrane of the fuel cell humidifying element after use in such an environment is hardly reduced compared to the content of the polyvinylpyrrolidone, etc., contained in the resin layer of the separation membrane of the fuel cell humidifying element before use. As a result, the resin layer of the separation membrane after use contains almost the same amount of polyvinylpyrrolidone, etc., which enhances the water vapor transmission rate of the separation membrane, as before use. Therefore, the water vapor transmission rate of the separation membrane after use is hardly reduced compared to the water vapor transmission rate of the separation membrane before use, and the moisture and heat resistance of the separation membrane is further improved. The mechanism by which the crosslinked structure further prevents polyvinylpyrrolidone and the like from dissolving in condensed water is believed to be that the crosslinking increases the apparent molecular weight of the polyvinylpyrrolidone and the like, which makes it possible for the urethane resin to more significantly prevent the polyvinylpyrrolidone and the like from leaking out of the resin layer, and that the crosslinking reduces the number of carbonyl groups that improve the water solubility of polyvinylpyrrolidone and the like.

[0046] Furthermore, even if at least a portion of the polyvinylpyrrolidone, etc., contained in the resin layer is crosslinked, the separation membrane will have excellent shape stability. The mechanism by which this effect is achieved is believed to be that the resin layer of the separation membrane of the present invention contains a urethane resin in addition to polyvinylpyrrolidone, etc., and this urethane resin is highly flexible, so that the flexible urethane resin alleviates the shrinkage stress generated in the resin layer due to crosslinking of polyvinylpyrrolidone, etc. The following is also believed to contribute to the improvement of the shape stability of the separation membrane. That is, when the resin layer contains a urethane resin in addition to polyvinylpyrrolidone, etc., penetration of the resin layer-forming coating film into the pores present in the porous substrate is suppressed. As a result, compared to when a resin layer is formed using a resin layer-forming coating film containing polyvinylpyrrolidone, etc. but not a urethane resin, a resin layer that more reliably blocks the pores present in the porous substrate can be formed with a smaller amount of resin layer-forming coating film per unit area of ​​the separation membrane. Therefore, the smaller the amount of coating film for forming the resin layer per unit area of ​​the separation membrane, the smaller the ratio of the basis weight of the resin layer to the basis weight of the porous substrate (basis weight of resin layer / basis weight of porous substrate). Therefore, the effect of stress that attempts to change the shape of the separation membrane of the resin layer containing polyvinylpyrrolidone or the like having a crosslinked structure on the ability of the porous substrate to stabilize the shape of the separation membrane is reduced, and as a result, it is believed that the shape stability of the separation membrane is excellent.

[0047] Furthermore, due to the property of urethane resins that they can easily form strong thin films, even if the coating film for forming the resin layer provided on the surface of the porous substrate is thin, a strong resin layer can be formed that more reliably blocks the pores present in the porous substrate.

[0048] That is, due to the above circumstances, when at least a portion of the polyvinylpyrrolidone or the like contained in the resin layer is crosslinked, the separation membrane has very good resistance to moist heat.

[0049] (2) Hydrophobic Resin The hydrophobic resin contained in the resin layer of the present invention serves to limit the elution of the hydrophilic resin in a high-temperature, high-humidity environment. The hydrophobic resin may be, for example, polyethylene, polypropylene, polystyrene, or a urethane resin. However, from the viewpoint of toughness and flexibility, the resin layer of the separation membrane of the present invention preferably contains a urethane resin. Urethane resins are insoluble in water and can provide higher moist heat resistance than resin layers composed solely of water-soluble resins such as polyvinylpyrrolidone. Furthermore, because urethane resins have tough and flexible physical properties, resin layers containing urethane resins are strong even when thin and provide excellent pore-blocking properties for the porous substrate. Furthermore, even when the separation membrane is bent or stretched, cracks and peeling are less likely to occur. Furthermore, although the pores in the porous substrate tend to deform due to bending or stretching of the separation membrane, a resin layer containing a highly flexible urethane resin can more reliably block even deformed pores. Furthermore, by more reliably blocking the pores with the resin layer, the separation membrane can stably exhibit high gas barrier properties. As described above, when the resin layer of the separation membrane of the present invention contains a hydrophobic resin, the resin layer contributes to realizing high gas barrier properties of the separation membrane. ２ It is preferable that the basis weight of the hydrophobic resin in the resin layer is 0.04 g / m or more, because this leads to more excellent gas barrier properties of the separation membrane and, when the polyvinylpyrrolidone or the like contained in the resin layer has a crosslinked structure, leads to more excellent shape stability of the separation membrane. ２ More preferably, it is 0.08 g / m or more. ２ On the other hand, the basis weight of the hydrophobic resin in the resin layer is preferably 0.6 g / m or more. ２ For the same reasons as above, the basis weight of the hydrophobic resin in the resin layer is preferably 0.20 g / m or less, because this results in an excellent water vapor transmission rate of the separation membrane. ２ More preferably, it is 0.16 g / m or less. ２ It is even more preferable that:

[0050] The hydrophobic resin preferably has a hydrophilic group such as a hydroxyl group or a carbonyl group. The hydrophobic resin has a hydrophilic group, which improves its affinity with the polyvinylpyrrolidone, etc., and facilitates the formation of a resin layer with a uniform thickness when mixed with polyvinylpyrrolidone, etc. Furthermore, the hydrophobic resin has a hydrophilic group, which facilitates dispersion of the hydrophobic resin in an aqueous solvent, so that water can sometimes be used as a solvent for the coating liquid for forming the resin layer.

[0051] The urethane resin used in the present invention may be a polyurethane resin having a weight-average molecular weight of 10,000 or more. When the resin layer contains a polyurethane resin, it is preferable that the polyurethane resin is dispersed in water or an organic solvent and supplied in the form of a dispersion to the coating liquid for forming the resin layer. When a polyurethane resin dispersion is used, it is advantageous in that a resin layer of uniform thickness can be formed under low-temperature heat treatment conditions. Since the porous substrate used in the present invention may have low heat resistance, the glass transition temperature of the polyurethane resin is preferably 80 ° C or less, particularly preferably 60 ° C or less. When the glass transition temperature is within the above-mentioned preferred range, the thermal impact on the porous substrate can be reduced during the drying process when forming the resin layer, which is preferable.

[0052] Examples of polyurethane resins that can be used include the "ADEKA BONTITOR" (registered trademark) series manufactured by ADEKA Corporation, the "OLESTAR" (registered trademark) series manufactured by Mitsui Chemicals, Inc., the "BONDIC" (registered trademark) series and "HYDRAN" (registered trademark) series manufactured by DIC Corporation, the "IMPLANIL" (registered trademark) series manufactured by Covestro Deutschland AG, the "SOFRANATE" (registered trademark) series manufactured by Sekisui Soflanwiz Co., Ltd., the "POISE" (registered trademark) series manufactured by Kao Corporation, the "SANPRENE" (registered trademark) series manufactured by Sanyo Chemical Industries, Ltd., the "EIZELAX" (registered trademark) series manufactured by Hodogaya Chemical Co., Ltd., the "SUPERFLEX" (registered trademark) series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., the "NEOREZ" (registered trademark) series manufactured by Covestro (Netherlands) B.V., and the "SANCURE" (registered trademark) series manufactured by Lubrizol Advanced Materials.

[0053] (3) Crosslinking Component Resin The crosslinking component resin contained in the resin layer of the present invention is not particularly limited as long as it is polyethylene, epoxy resin, acrylic resin, or the like. However, as shown in the examples, when polyvinylpyrrolidone is used as the hydrophilic resin and crosslinking is performed by UV irradiation, a UV-curable resin is used, and an acrylic resin that crosslinks by radicals is preferred. Acrylic resins have excellent durability against water and heat, and thus the inclusion of an acrylic resin improves the overall durability of the resin layer against water and heat, i.e., its humid heat durability. Furthermore, the acrylic resin preferably contains an acrylic resin formed by crosslinking an acrylate having two or more carbon-carbon double bonds. Furthermore, the acrylic resin preferably has a crosslinked structure, and the crosslinked structure preferably includes a structure represented by the following chemical formula (I) or (II). These acrylic resins have a three-dimensional crosslinked structure, thereby improving the humid heat durability of the resin layer. Furthermore, an acrylic resin having a crosslinked structure including a structure represented by chemical formula (III) or (IV), formed by crosslinking an acrylate having three or more carbon-carbon double bonds, is more preferred because it increases the crosslink density of the acrylic resin and further improves the humid heat durability of the resin layer. Particularly preferred from the viewpoint of achieving the highest crosslink density is an acrylic resin having a crosslinked structure including a structure represented by chemical formula (V), which is formed by crosslinking acrylates having six carbon-carbon double bonds.

[0054]

[0055] (R １ ~R ２ is an alkyl chain of any length, X １ ~X ６ indicates any element or molecular structure.)

[0056]

[0057] (R １ ~R ４ is an alkyl chain of any length, X １ ~X ８ indicates any element or molecular structure.)

[0058]

[0059] (R１ ~R ３ is an alkyl chain of any length, X １ ~X ７ indicates any element or molecular structure.)

[0060]

[0061] (R １ ~R ５ is an alkyl chain of any length, X １ ~X ９ indicates any element or molecular structure.)

[0062]

[0063] (R １ ~R ８ is an alkyl chain of any length, X １ ~X １２ represents any element or molecular structure.) X in chemical formulas (I) to (V) １ ~X １２ The element or molecular structure of R is arbitrary and is not particularly limited, but examples of the element include a hydrogen atom, and examples of the molecular structure include a vinyl group, a vinylene group, or a molecular structure having a carbon-carbon double bond and an ester bond. １ ~R ８ The length of the alkyl chain is preferably an alkyl chain having a carbon number of 1 to 30. By having an alkyl chain in this range, the ratio of carbon-carbon double bonds to the molecular weight of the acrylic resin becomes high, and a high crosslink density can be obtained relative to the content of acrylic resin in the resin layer.

[0064] Examples of acrylates having two or more carbon-carbon double bonds include triethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, etc. Among these, pentaerythritol tetraacrylate, which has four carbon-carbon double bonds, and dipentaerythritol hexaacrylate, which has six carbon-carbon double bonds, are preferred because they have many carbon-carbon double bonds, can increase crosslink density, and can provide a highly durable resin layer.

[0065] The content of the acrylic resin is preferably 2% by mass or more and 13% by mass or less relative to the weight of the entire resin layer. The higher the content of the acrylic resin, the greater the effect of improving durability, so the content is preferably 2% by mass or more. On the other hand, if the content of the acrylic resin is high, the content of polyvinylpyrrolidone and the like and urethane resin in the resin layer will relatively decrease, resulting in a decrease in moisture permeability and gas barrier properties. Therefore, the content of the acrylic resin is preferably 13% by mass or less.

[0066] (4) Additives The resin layer of the present invention may contain additives as needed, such as inorganic or organic particles, flame retardants, mildew inhibitors, preservatives, flame retardants, dyes, pigments, etc.

[0067] The addition of inorganic or organic particles can sometimes adjust the smoothness of the separation membrane surface to a preferred state. Furthermore, the use of inorganic or organic particles whose surfaces have been subjected to a hydrophilic treatment tends to increase the moisture absorption of the resin layer.

[0068] By adding an antifungal agent or antiseptic, it may be possible to inhibit the generation of mold or unpleasant odors when the separation membrane of the present invention is used in a high-humidity environment or in a wet state due to condensation.

[0069] By adding a flame retardant, the flame retardancy of the separation membrane of the present invention can be improved.

[0070] By adding dyes or pigments, the separation membrane can be colored to any desired color tone. Furthermore, since the resin layer is colored, it can be easily observed visually, which may facilitate defect inspection and quality control during the separation membrane production process.

[0071] (5) Basis Weight of Resin Layer If the basis weight of the resin layer is too low, the pores present in the porous substrate may not be sufficiently blocked, which may impair the gas barrier properties of the separation membrane. On the other hand, if it is too high, the water vapor transmission rate of the separation membrane may be impaired. Furthermore, when the resin layer absorbs and releases moisture, or when polyvinylpyrrolidone or the like contained in the resin layer has a crosslinked structure, the shrinkage of the resin layer may become large, which may cause deformation of the separation membrane. From the above points, the basis weight of the resin layer is 0.1 g / m ２ It is preferable that the content is 0.2 g / m or more.２ More preferably, it is 0.4 g / m or more. ２ On the other hand, the basis weight of the resin layer is 3.0 g / m or more. ２ Preferably, the content is 1.0 g / m or less. ２ More preferably, it is 0.8 g / m or less. ２ It is particularly preferable that the resin layer has a basis weight within the above-mentioned preferred range, the separation membrane of the present invention can achieve high gas barrier properties and good shape stability. (6) Thickness of Resin Layer If the resin layer is too thin, the hydrophilic resin contained in the resin layer cannot fully exhibit its properties, which may impair the water vapor permeability of the separation membrane. In addition, the properties of the hydrophobic resin may not be exhibited, which may impair the moist heat resistance. On the other hand, if the resin layer is too thick, it may hinder the movement of moisture absorbed into the functional layer, which may impair the water vapor permeability of the separation membrane. From the above points, the thickness of the resin layer is preferably 10 nm or more and 1000 nm or less. If the thickness of the resin layer is within the above-mentioned range, the separation membrane of the present invention can achieve high water vapor permeability and moist heat resistance.

[0072] (7) Method for forming a resin layer and method for manufacturing a gas separation membrane A resin layer-forming coating liquid containing the above-mentioned urethane resin, acrylic resin, polyvinylpyrrolidone, etc., and, if necessary, additives and solvents, can be applied to a substrate, and the solvent can be dried as needed to form a resin layer on the substrate. Alternatively, a resin layer-forming coating liquid containing polyvinylpyrrolidone, etc., a coating liquid containing a urethane resin, and a coating liquid containing an acrylic resin can be prepared, and the resin films formed by each coating liquid can be individually formed and laminated to form a resin layer. Alternatively, a coating liquid containing at least one of urethane resin, acrylic resin, polyvinylpyrrolidone, etc., and a coating liquid containing other components can be prepared, and the resin films formed by each coating liquid can be individually formed and laminated to form a resin layer. In these cases, it is possible to arbitrarily select which of the resin film containing polyvinylpyrrolidone, the resin film containing urethane resin, and the resin film containing acrylic resin is first formed on the porous substrate.

[0073] In the present invention, from the viewpoint of being able to form a uniform resin layer and simplifying the coating process, it is preferable to form the resin layer using a coating liquid containing polyvinylpyrrolidone or the like, a urethane resin, and an acrylic resin.

[0074] It is also preferable to use an aqueous solvent as the solvent for the coating liquid, because the use of an aqueous solvent for the coating liquid not only makes it possible to prevent the solvent from rapidly evaporating during the drying step and form a resin layer with a uniform thickness, but also has an advantage in terms of environmental impact.

[0075] Examples of the aqueous solvent include water-soluble solvents selected from the group consisting of water, alcohols such as ethanol, isopropyl alcohol, and butanol, ketones such as acetone and methyl ethyl ketone, and glycols such as ethylene glycol, diethylene glycol, and propylene glycol.

[0076] The coating liquid can be applied to the porous substrate by known wet coating methods, such as spray coating, dip coating, spin coating, knife coating, kiss coating, gravure coating, slot die coating, roll coating, bar coating, screen printing, inkjet printing, pad printing, and other types of printing. The coating may be performed in multiple steps, or two different coating methods may be combined. Preferred coating methods are gravure coating, bar coating, and slot die coating, which are wet coating methods.

[0077] After the coating process, the solvent is removed from the coated coating liquid in the drying process. As a method for removing the solvent, convection hot air drying in which hot air is applied to the porous substrate, radiant heat drying in which the substrate absorbs infrared radiation from an infrared drying device and converts it into heat to heat and dry, and conduction heat drying in which the substrate is heated and dried by heat conduction from a wall surface heated by a heat medium can be applied. Among them, convection hot air drying is preferred because it has a high drying rate. The drying temperature needs to be processed at or below the melting point of the resin used in the porous substrate, more preferably 80 ° C or less, even more preferably 60 ° C or less. By setting the drying temperature in the above range, the thermal shrinkage rate of the porous substrate is preferably 5% or less.

[0078] The following steps can also be exemplified as a method for producing a separation membrane. An acrylate having two or more carbon-carbon double bonds is further mixed with the coating liquid for forming the resin layer, which contains the aforementioned polyvinylpyrrolidone or the like and a urethane resin, to obtain a coating liquid composition containing polyvinylpyrrolidone or the like, a urethane resin, and an acrylate having two or more carbon-carbon double bonds. Next, this coating liquid composition is applied to a porous substrate to form a coating film. Then, if necessary, the porous substrate after the coating film formation is heated to dry the solvent, and then 500 mJ / m is applied to this coating film. ２ The acrylic resin or the like is crosslinked by irradiating the resin with ultraviolet light of the above formula (1) or (2). By employing a separation membrane manufacturing method including such steps, a crosslinked acrylic resin structure as shown in the above-described chemical formula (1) or (2) can be formed in the resin layer. Furthermore, when the acrylate crosslinks, in addition to crosslinking between acrylates, crosslinking structures between the acrylate and polyvinylpyrrolidone and between the acrylate and urethane resin are also formed. Furthermore, when the components contained in the resin layer are polyvinylpyrrolidone or the like, a urethane resin, and an acrylic resin, by setting the amount of ultraviolet light irradiation to the above-described values, it is possible to further improve the durability of the resin layer while suppressing membrane degradation due to ultraviolet light.

[0079] (8) Crosslinking As described above, the acrylic resin contained in the resin layer formed on the substrate has a crosslinked structure. In addition, it is preferable that the urethane resin and / or polyvinylpyrrolidone contained in the resin layer formed on the substrate have a crosslinked structure.

[0080] Polyvinylpyrrolidone and the like undergo cure shrinkage during crosslinking, which may impair the shape stability of the separation membrane. The larger the basis weight of the resin layer, the greater the stress of cure shrinkage. On the other hand, the larger the basis weight of the porous substrate, the more it can withstand the stress of cure shrinkage. That is, in order to maintain the shape stability of the separation membrane, it is preferable that the basis weight of the resin layer is small and the basis weight of the porous substrate is large. Specifically, the ratio of the basis weight of the resin layer to the basis weight of the porous substrate (basis weight of resin layer / basis weight of porous substrate) is preferably 0.18 or less, more preferably 0.10 or less. When it is in the above preferred range, the shape stability of the separation membrane becomes better when polyvinylpyrrolidone and the like are crosslinked, which is preferable. On the other hand, the lower limit of this basis weight ratio is not particularly limited, but is preferably 0.01 or more because it can achieve excellent gas barrier properties. Furthermore, the lower limit of the basis weight of the resin layer is 0.1 g / m, regardless of the basis weight of the porous substrate. ２ More than 0.2 g / m is preferable. ２ When the content is in the above-mentioned preferred range, the gas barrier properties of the separation membrane can be made even better.

[0081] The crosslinking method is not particularly limited, but a method of modifying the composition of the coating film by irradiation with active energy rays such as ultraviolet light is preferably used because it causes little temperature rise and little damage to the porous substrate. The ultraviolet light treatment may be performed once or repeatedly performed two or more times. When performing the ultraviolet light treatment, the oxygen concentration may be reduced to suppress reaction inhibition by oxygen. When performing the treatment with a reduced oxygen concentration, the oxygen gas is preferably 1.0% by volume or less, and more preferably 0.5% by volume or less, when the total volume of the gas in the system is 100% by volume. The relative humidity may be any value. Furthermore, in the ultraviolet light treatment, it is more preferable to reduce the oxygen concentration using nitrogen gas.

[0082] As the ultraviolet light source, known sources such as a high-pressure mercury lamp, a metal halide lamp, a microwave electrodeless lamp, a low-pressure mercury lamp, and a xenon lamp can be used.

[0083] The cumulative amount of ultraviolet light irradiation is 50 to 3,000 mJ / cm when the components contained in the resin layer are polyvinylpyrrolidone, urethane resin, and acrylic resin. ２ is preferably 100 to 1,000 mJ / cm ２ More preferably, 500 to 700 mJ / cm ２ It is particularly preferable that the integrated light amount is 50 mJ / cm ２ If the integrated light amount is 3,000 mJ / cm or more, the elution of the hydrophilic resin is suppressed by crosslinking of the components contained in the resin layer, and the resin layer has a high resistance to moisture and heat, and a decrease in humidifying performance due to adsorption of moisture inside the film is suppressed, which is preferable. ２ If the content is less than this, damage to the substrate is reduced, and a decrease in humidifying performance due to an excessively high crosslink conversion rate of the components contained in the resin layer can be suppressed, which is preferable.

[0084] (9) Crosslinking Conversion Ratio The crosslinking conversion ratio in the present invention indicates the proportion of crosslinked structures among crosslinkable structures such as polyvinylpyrrolidone.

[0085] The crosslinking conversion rate was measured by Fourier transform infrared spectroscopy, and the peak of the double bond site of polyvinylpyrrolidone, etc. (1660 cm ―１ around 3,500-3,600 cm ―１ ) and the decrease in the peaks of double bonds, hydroxyl groups or carboxyl groups in 1H-NMR before and after crosslinking.

[0086] The crosslinking conversion rate of the separation membrane can be measured from the peak intensity of the uncrosslinked resin layer and the resin layer after crosslinking by Fourier transform infrared spectroscopy.

[0087] Alternatively, the crosslinking conversion rate can be determined by the following procedure.

[0088] First, pyrolysis gas chromatography (pyrolysis GC-MS) is used to identify the components contained in the resin layer, and the content of the components contained in the resin layer is then determined. Next, the resin layer of the separation membrane is peeled off to obtain only the resin layer of the separation membrane. The obtained resin layer is dissolved in a quantity of ethanol or methyl acetate to obtain solution A. Next, polyvinylpyrrolidone, etc. is dissolved in solution B so that the mass concentration of polyvinylpyrrolidone, etc. is the same as that of solution A to obtain solution B. Fourier transform infrared spectroscopy is performed on the two solutions, and the crosslinking conversion rate is determined from the ratio of peak intensities.

[0089] The crosslinking conversion rate is preferably 0.2% or more and 50% or less, more preferably 3% or more and 30% or less, and even more preferably 10% or more and 20% or less. By setting the ratio at or above the lower limit, detachment of polyvinylpyrrolidone and the like from the resin layer in a high-temperature, high-humidity environment is suppressed, resulting in excellent shape stability. Furthermore, by setting the ratio at or below the upper limit, the presence of uncrosslinked polyvinylpyrrolidone and the like can be suppressed from decreasing the water vapor transmission rate. [Possible Applications of Separation Membranes] The separation membrane of the present invention is suitable for use as a fuel cell humidifying membrane, and the humidifying membrane is suitable for use in a fuel cell humidifying module, and the fuel cell humidifying module is suitable for use in a fuel cell system. The membrane can also be used in exhaust gas separation and recovery devices, deodorizing devices, humidity control devices, air conditioners such as dehumidifiers, humidifiers, and dehumidifiers, total heat exchangers, inkjet devices, composting devices, and the like.

[0090] (1) Humidity Control Device Next, a humidity control device containing the separation membrane of the present invention will be described. This humidity control device is a device that exchanges water vapor between two fluids via the separation membrane of the present invention. For example, this humidity control device is a device that supplies air containing water or water vapor to one side of the separation membrane and supplies dry air to the other side through the separation membrane, causing the water vapor to permeate the separation membrane and humidify the dry air. Alternatively, this humidity control device is a device that supplies dry air or a hygroscopic liquid such as a lithium chloride aqueous solution to one side of the separation membrane and supplies air containing water vapor to the other side through the separation membrane, causing the water vapor to permeate the separation membrane and dehumidify the air containing water vapor.

[0091] (2) Air Conditioner Next, an air conditioner containing the separation membrane of the present invention will be described. This air conditioner is, for example, a device for controlling humidity in ordinary homes, buildings, offices, factories, etc., such as a humidifier, dehumidifier, dehumidifier, or air conditioner. The humidity of the taken-in outside air is adjusted by a membrane module in which the separation membrane of the present invention is laminated. An example of a schematic diagram of an air conditioner is shown in Figure 2. When outside air is taken into the air conditioner 20, it passes through an air filter 21, a cooling coil 22, a heating coil 23, a membrane module 24, and a blower 25 in this order, and is then supplied into the room. The cooling coil 22 or the heating coil 23 operates depending on whether the room is to be humidified or dehumidified.

[0092] (3) Fuel Cell Humidifying Module Next, an example of a method for manufacturing a fuel cell humidifying module will be described. The separation membrane of the present invention is used as a fuel cell humidifying membrane by laminating a sheet-like member (a flow path material for the feed gas) with a flow path for controlling the feed gas on one side of the fuel cell humidifying membrane, and a sheet-like member (a flow path material for the exhaust gas) with a flow path for controlling the flow of the exhaust gas on the other side. The flow path material for the feed gas and the flow path material for the exhaust gas are typically formed on the front and back of a single sheet-like member to increase the density of the laminate. A fuel cell humidifying module is formed by laminating multiple layers of these fuel cell humidifying membranes and flow path materials. Furthermore, a reinforcing material may be sandwiched between the flow path material and the fuel cell humidifying membrane to prevent the fuel cell element sheet from sagging into the flow path material due to gas pressure. The reinforcing material preferably has a larger average pore size than the porous substrate and high tensile and compressive strengths, such as a nonwoven fabric, mesh, or porous substrate. Using these materials prevents the fuel cell humidifying membrane from sagging into the flow path without impairing moisture permeability.

[0093] (4) Fuel Cell System Next, a fuel cell system including a fuel cell humidifying module using the separation membrane of the present invention will be described. This fuel cell system is applicable to, for example, fuel cell vehicles and household fuel cells.

[0094] The fuel cell system includes at least the above-mentioned fuel cell humidifying module 31 and a fuel cell 32. An example of this fuel cell system is not particularly limited, but includes a system in which air and / or hydrogen humidified by the fuel cell humidifying module is supplied to the fuel cell while power is supplied to the fuel cell.

[0095] (5) Mobile Vehicles Next, we will explain mobile vehicles incorporating a fuel cell system. These mobile vehicles are driven by energy obtained using the fuel cell system. In the case of a fuel cell vehicle, for example, as shown in FIG. 3, the obtained power is supplied to a motor 34 and a battery 35 via a power control unit 33. Furthermore, in the case of vehicles that require a large amount of energy for driving, such as large vehicles, ships, and aircraft, the required specifications can be adjusted by freely changing the number of fuel cell humidifying modules installed.

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The measurement methods used in these examples are shown below.

[0097] <Measurement Method> (1) Basis Weight of Separation Membrane Five 100 mm square separation membrane test pieces were prepared and left to stand for 24 hours in an atmosphere at a temperature of 20°C and a humidity of 65% RH. After that, the mass (g) of each of the five test pieces was measured, and the average value was calculated as 1 m ２ Mass per unit (g / m ２ ) and the basis weight of the separation membrane (g / m ２ )

[0098] (2) Basis weight of porous substrate Five test pieces (1) were immersed in 200 ml of solvent (ethyl acetate) filled in a 300 ml container for 2 minutes, and the front and back surfaces of the five test pieces were wiped five times. Next, the five test pieces were again immersed in 200 ml of solvent (ethyl acetate) filled in a 300 ml container for 2 minutes. Subsequently, the five test pieces were left standing for 24 hours in an atmosphere at a temperature of 20 ° C. and a humidity of 65% RH to obtain a test piece of a porous substrate in which the resin layer was removed from the separation membrane. Thereafter, the mass (g) of each of the five test pieces was measured, and the average value was calculated as 1 m ２ Mass per unit (g / m ２) and the basis weight of the porous substrate (g / m ２ )

[0099] (3) Basis Weight of Resin Layer Next, the basis weight of the resin layer (g / m) was calculated from the basis weight of the separation membrane and the basis weight of the porous substrate obtained in (1) and (2) using the following formula: ２ The weight per unit area of ​​the resin layer (g / m ２ ) = basis weight of separation membrane (g / m ２ ) - basis weight of porous substrate (g / m ２ ).

[0100] (4) Identification and Content of Components Contained in Resin Layer A 5 g test piece of the separation membrane was measured by pyrolysis gas chromatography (pyrolysis GC-MS) to identify the components contained in the resin layer, and further, the content of the components contained in the resin layer was determined.

[0101] (5) Basis weight of urethane resin Based on the content of each component constituting the resin layer determined in (4), the ratio of the content of urethane resin contained in the resin layer to the content of all components constituting the resin layer (content of urethane resin / content of all components constituting the resin layer) was calculated, and the basis weight of the resin layer determined in (3) was multiplied by this ratio to obtain the basis weight of the urethane resin.

[0102] (6) Thickness of Separation Membrane Three 200 mm square test pieces were taken from different positions on the sample (separation membrane), and left to stand for 24 hours in an atmosphere at a temperature of 20°C and a humidity of 65% RH. Thereafter, the thickness (μm) of each of the three test pieces was measured at five points, namely, the center and four corners, using a measuring instrument (Model ID-112, manufactured by Mitutoyo Corporation), and the average value of 15 measured values ​​was used as the thickness.

[0103] (7) Water Vapor Transmission Rate of Separation Membrane (Before Wet Heat Treatment) The water vapor transmission rate was evaluated using a water vapor transmission rate evaluation device 100 as shown in FIG. 4, which sandwiches a separation membrane and a reinforcing material from the resin layer side of the separation membrane. In FIG. 4, 101 is an evaluation cell, 102 is a separation membrane, 103 is a reinforcing material, 104 is a humidity-conditioned air inlet, 105 is a humidity-conditioned air outlet, 106 is a dry air inlet, 107 is a dry air outlet, 108 is an air flow meter, 109 is a humidifier, and 110 is a temperature and humidity measurement point. In 100, humidity-conditioned air from 104 and dry air from 106 are introduced into 101, and water vapor that permeates 102 flows out from 107. By measuring the relative humidity and pressure at 110, the amount of water vapor transmission per hour flowing out from 107 is calculated. The reinforcing material was a mesh material made of polyphenylene sulfide with an opening ratio of 60% and a thickness of 200 μm.

[0104] Dry air at a temperature of 60°C and a pressure of 100 kPaG was passed through the porous substrate side of the separation membrane, and humidified air at a temperature of 100°C, 40% RH, and a pressure of 50 kPaG, which had been humidified by a humidifier, was passed through the resin layer side of the separation membrane in a counterflow manner, with each pass passing through one pass. The amount of water vapor permeation per hour was measured, and the water vapor permeation rate (g / min / cm) per unit membrane area and unit time was calculated. ２ ) and calculated the converted values.

[0105] (8) Air permeation rate of separation membrane (before moist heat treatment) The air permeation rate (gas barrier property) was evaluated using an air permeation rate evaluation device 111 as shown in Figure 5. In Figure 5, 112 denotes an air inlet, 113 denotes an air outlet, 114 denotes an air flow meter, 115 denotes a pressure gauge, and 116 denotes a sealing plug. Air flowing in from 112 permeates through 102 and flows out from 113 because 116 is sealed. Therefore, the amount of air permeating at 114 and the differential pressure before and after 102 at 115 are measured, and the unit pressure and the amount of air permeating per unit time are calculated.

[0106] First, the air of temperature 25 ° C and relative humidity 10% is made to flow from the surface of porous substrate side to the surface of resin layer side at a pressure of 50 kPa, and the air permeation amount on the resin side is measured, and the numerical value converted into the air permeation amount per unit membrane area and unit time is calculated.At this time, when the air permeation amount from the surface of porous substrate side of membrane to the surface of resin layer side is small, there is a possibility that accurate air permeation amount cannot be measured, so the pressure to be applied is increased to 120 kPa, and the air permeation amount is measured, and correction is carried out as necessary.

[0107] (9) Moist Heat Resistance of Separation Membrane A 100 mm square separation membrane was subjected to moist heat treatment in an autoclave at 100°C for 10 hours, and then dried at room temperature for at least 12 hours. The water vapor transmission rate and air transmission rate were then measured using the methods described in (7) and (8). The rate of change was calculated from the measured water vapor transmission rates before and after the accelerated test using the following formula: Rate of change (%) = {(Measured value after accelerated test - Measured value before accelerated test) / Measured value before accelerated test} × 100. Note that if the durability of the separation membrane is low, some of the polyvinylpyrrolidone and other components contained in the resin layer will leak out or be denatured after moist heat treatment, reducing the hygroscopicity of the resin layer. This will decrease the water vapor transmission rate of the humidified membrane, resulting in a negative rate of change. Furthermore, if much of the resin layer in the separation membrane leaks out due to moist heat treatment, more moisture will permeate, increasing the water vapor transmission rate of the humidified membrane and resulting in a positive rate of change. Therefore, it can be said that the smaller the absolute value of the rate of change in water vapor transmission rate, the more durable the separation membrane.

[0108] The air permeability rate after wet heat treatment was 10 NmL / min / cm ２ A humidifying membrane with a pressure exceeding 1 / MPa was judged to have air leakage, and it can be said that the more leakage-free the humidifying membrane, the more excellent its durability.

[0109] (10) Crosslinking Conversion Rate The crosslinking conversion rate was calculated by the following procedure.

[0110] First, five test pieces of the separation membrane were prepared, and the resin surface was subjected to Fourier transform infrared spectroscopy measurement using the total reflection measurement method. The measurement mode was selected as the ATR method (total reflection method), and after background correction, the measurement was performed. －１ The measurement conditions were a resolution of 4 and an accumulation of 32 times.－１ The intensity of the CH absorption peak derived from the ethylene group in the vicinity (A ＣＨ ) and 1660 cm －１ The intensity of the C═O absorption peak derived from polyvinylpyrrolidone in the vicinity (A ＣＯ In this case, in order to adjust the degree of adhesion of the test piece, －１ Nearby peaks and 1365 cm －１ Measurements were carried out while changing the degree of contact so that the peaks around the respective points remained constant.

[0111] Next, based on the content of each component constituting the resin layer determined in (4), the ratio of the content of each component constituting the resin layer to the content of all components constituting the resin layer (for example, in the case of polyvinylpyrrolidone, the content of polyvinylpyrrolidone / the content of all components constituting the resin layer) was calculated. Next, the thickness of the test piece resin layer was measured from SEM image observation. A resin layer composed of the same content ratio as the separation membrane test piece was applied to a porous substrate from which the resin layer was removed in the same manner as in (2) at an easy-to-measure magnification using SEM image observation, and the thickness was measured using the same method to make the resin layer thickness uniform. Fourier transform infrared spectroscopy measurement of the total reflection measurement method was performed in the same manner, and the thickness of the resin layer before crosslinking (A ＣＨ ) and (A ＣＯ ) was sought.

[0112] Using the obtained peak intensity, the crosslinking conversion rate (1660 cm of the resin layer) was calculated. －１ Peak intensity at 1660 cm in the resin layer before crosslinking －１ Peak intensity at 1660 cm in the resin layer before crosslinking －１ The contact angle was measured by the following procedure.

[0113] First, a 20 mm square test piece was prepared and set horizontally on the base of the contact angle meter. A drop of water was dropped onto the center of the test piece using a dropper, and the contact angle was measured. (12) Reduction Rate of Hydrophilic Resin Content The reduction rate of the hydrophilic resin content was calculated using the following procedure.

[0114] First, a test piece of the separation membrane was prepared, and the resin surface was subjected to Fourier transform infrared spectroscopy measurement using the total reflection measurement method. The measurement mode was selected as the ATR method (total reflection method), and the measurement was performed after background correction. －１ The measurement conditions were a resolution of 4 and an accumulation of 32 times. －１ The intensity of the CH absorption peak derived from the ethylene group in the vicinity (A ＣＨ ) and 1660 cm －１ The intensity of the C═O absorption peak derived from polyvinylpyrrolidone in the vicinity (A ＣＯ In this case, in order to adjust the degree of adhesion of the test piece, －１ Nearby peaks and 1365 cm －１ Measurements were carried out while changing the degree of contact so that the peaks around the respective points remained constant.

[0115] Next, the test piece of the separation membrane was subjected to wet heat treatment in an autoclave at 120°C for 24 hours, dried in a room temperature environment for 12 hours or more, and then measured for the 1660 cm －１ The peak intensity was determined.

[0116] Using the obtained peak intensity, the reduction rate of the hydrophilic resin content (1660 cm of the resin layer before the wet heat treatment) was calculated. －１ Peak intensity at 1660 cm of the resin layer after wet heat treatment －１ Peak intensity at 1660 cm of the resin layer before the wet heat treatment －１ The absorbance was calculated as the peak intensity at 100 times ...

[0117] First, a 50 mm square test piece was prepared, dried at 50° C. for 1 hour, and then its mass (g) was measured. Thereafter, it was subjected to wet heat treatment in an autoclave at 120° C. for 24 hours, dried at 50° C. for 3 hours, and then its mass (g) was measured.

[0118] Next, the thickness of the resin layer of the test piece was measured from the SEM image observation, and the volume of the resin layer was calculated by multiplying the obtained thickness by the area of ​​the test piece (here, 50 mm × 50 mm).

[0119] Using the obtained weight and volume, the amount of water adsorption due to the moist heat treatment was calculated as (weight of separation membrane before moist heat treatment - weight of separation membrane after moist heat treatment) / weight of separation membrane before moist heat treatment / volume of resin layer × 100.

[0120] (14) In-plane Heat Shrinkage Five 120 mm square test pieces were prepared, and the longitudinal (or machine) and transverse directions of the sheet were marked on the test pieces as shown in FIG. 1 . Next, as shown in FIG. 1 , marks were made in the center of the test pieces to measure the distance between the gauge lines (L0 and T0), and the distances were measured using a scale capable of measuring to a minimum of 0.5 mm. Next, the test pieces were placed horizontally in a thermostatic chamber adjusted to 100°C for 30 minutes, removed, and then returned to the same standard condition as before the test, and the distances between the gauge lines in the longitudinal and transverse directions (L and T) were measured again. The same measurement was performed on all five test pieces, and the average values ​​were calculated as the heat shrinkage in the L and T directions. Since the heat shrinkage generally differs between the L and T directions, the larger of the absolute values ​​of the heat shrinkage in the L and T directions was used as the heat shrinkage of the test piece.

[0121] (15) Linear swelling ratio in the in-plane direction Five 120 mm square test pieces marked in the same manner as in (14) were prepared and measured using a scale ruler capable of measuring down to 0.5 mm. Next, the test pieces were placed in a water bath adjusted to 25 ± 2 ° C for 2 hours, removed, and water droplets adhering to the surface of the test pieces were removed with gauze or the like. After returning to the same standard condition as before the test, the distances between the gauge lines in the longitudinal and transverse directions (L and T) were measured again. The same measurement was performed on all five test pieces, and the average values ​​were calculated as the linear swelling ratios in the L and T directions. Note that since the linear swelling ratio generally differs in the L and T directions, the larger of the absolute values ​​of the linear swelling ratios in the L and T directions was used as the thermal shrinkage ratio of the test piece.

[0122] (Example 1) As a porous substrate, a basis weight of 5.6 g / m ２ A polyethylene porous film having a thickness of 10 μm, a porosity of 43%, and a pore diameter of 33 nm was prepared. The physical properties were a water vapor transmission rate of 101 g / m ２ / hr, and the carbon dioxide interception rate was 2%.

[0123] Next, a coating composition for the resin layer was prepared by the following procedure.

[0124] As materials for the resin layer, polyvinylpyrrolidone ("Luvitec K85" (registered trademark) manufactured by BASF) and an aqueous dispersion of polyurethane resin ("Superflex 150" (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solids concentration: 30% by mass) were used, and as an acrylic resin raw material, an acrylate mainly composed of dipentaerythritol hexaacrylate ("Light Acrylate DPE-6A" (registered trademark) manufactured by Kyoeisha Chemical Co., Ltd.) was prepared. A mixed solution of ethanol and water was used as the solvent. The Luvitec K85, Superflex 150, Light Acrylate DPE-6A, ethanol, and water were mixed in a mass ratio of 3.0:2.7:0.2:67.1:27.0 and stirred until a uniform liquid was obtained to obtain a mixed solution with a solids content of 4% by mass. Furthermore, a UV initiator (Omnirad (registered trademark) 184 manufactured by IGM Resins) was added to the coating composition in an amount of 3 mass % relative to Luvitec K85 to prepare a coating composition for the resin layer.

[0125] Next, a resin layer was formed on the surface of the porous substrate by the following procedure, as shown in FIG.

[0126] The coating composition for the resin layer was applied to the surface of the porous substrate using a bar coater No. 4 so that the thickness of the resin layer after drying would be about 200 nm. After application, the coating was dried for 1 minute in a hot air oven set at 60 ° C. Next, the porous substrate with the resin layer applied was attached to a mount with tape, and a UV irradiation device ("ECS-301" manufactured by iGraphics Co., Ltd.) was used to irradiate the porous substrate with 500 mJ / cm under atmospheric pressure. ２ The resin layer was crosslinked by irradiating with UV at an irradiation dose of 1000 W. The above procedure resulted in a separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer. The structure of this separation membrane is shown in Table 1.

[0127] (Example 2) UV irradiation dose: 1000 mJ / cm ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0128] (Example 3) UV irradiation dose: 1500 mJ / cm ２A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0129] (Example 4) UV irradiation dose: 3000 mJ / cm ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0130] (Example 5) UV irradiation dose: 5600 mJ / cm ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained by the same procedure as in Example 1, except that the acrylic resin raw material was an acrylate containing tripentaerythritol acrylate as the main component and the UV irradiation dose was 200 mJ / cm. ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained by the same procedure as in Example 1, except that the UV irradiation dose was 9000 mJ / cm. The structure of this separation membrane is shown in Table 1. (Example 7) An acrylate containing triethylene glycol diacrylate as the main component ("Light Acrylate 3EG-A" (registered trademark) manufactured by Kyoeisha Chemical Co., Ltd.) was used as the acrylic resin raw material. ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above-mentioned procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0131] (Comparative Example 1) The size of the bar coater was changed to No. 3, and the coating composition was applied so that the thickness of the resin layer after drying would be 160 nm, and the UV irradiation dose was 200 mJ / cm ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above-mentioned procedure was repeated. The configuration of this gas separation membrane is shown in Table 1.

[0132] (Comparative Example 2) UV irradiation dose: 200 mJ / cm ２A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above-mentioned procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0133] (Comparative Example 3) The coating composition was prepared by mixing Luvitec K85, Superflex 150, Light Acrylate DPE-6A, ethanol, and water in a mass ratio of 3.0:2.0:0.4:67.6:27.0, and the UV irradiation dose was 200 mJ / cm ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 10% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above-mentioned procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0134] (Comparative Example 4) UV irradiation amount: 50 mJ / cm ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0135] (Comparative Example 5) An acrylate containing triethylene glycol diacrylate as a main component ("Light Acrylate 3EG-A" (registered trademark) manufactured by Kyoeisha Chemical Co., Ltd.) was used as the acrylic resin raw material, and the UV irradiation dose was 200 mJ / cm ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above-mentioned procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0136] (Comparative Example 6) As a porous substrate, a basis weight of 6.7 g / m ２ A polyethylene porous film having a thickness of 12 μm, a porosity of 43%, and a pore diameter of 33 nm was prepared. The physical properties were a water vapor transmission rate of 101 g / m ２ / hr, and the carbon dioxide interception rate was 2%.

[0137] The above content and UV irradiation dose of 200 mJ / cm ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above-mentioned procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0138] (Comparative Example 7) As a porous substrate, a basis weight of 6.1 g / m ２ A polyethylene porous film having a thickness of 10 μm, a porosity of 38%, and a pore diameter of 33 nm was prepared. The physical properties were a water vapor transmission rate of 90 g / m ２ / hr, and the carbon dioxide shielding rate was 2.5%. ２ A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that the above-mentioned procedure was repeated. The configuration of this separation membrane is shown in Table 1.

[0139] Comparative Example 8 A coating composition for a resin layer was prepared by the following procedure.

[0140] Luvitec K85, ethanol, and water were mixed in a mass ratio of 10.0:50.0:40.0, and stirred until a homogeneous liquid was obtained, to prepare a mixed solution with a solid content of 10 mass %.

[0141] Next, a resin layer was formed on the surface of the same porous substrate as in Example 1. A schematic diagram is shown in FIG.

[0142] The coating composition for the resin layer was applied to the surface of the porous substrate using a bar coater No. 6. After application, the coating was dried for 1 minute in a hot air oven set at 60°C. UV irradiation was not performed, and the resin layer was not crosslinked. By the above procedure, a separation membrane whose resin layer was 100% by mass of polyvinylpyrrolidone was obtained.

[0143] The structure of this separation membrane is shown in Table 1.

[0144] Comparative Example 9 A separation membrane containing 75% by mass of polyvinylpyrrolidone and 5% by mass of acrylic resin in the resin layer was obtained in the same manner as in Example 1, except that UV irradiation was not performed and the resin layer was not crosslinked. The configuration of this separation membrane is shown in Table 1.

[0145] The structure of this gas separation membrane is shown in Table 1.

[0146] Comparative Example 10 A coating composition for a resin layer was prepared by the following procedure.

[0147] Superflex 150, ethanol, and water were mixed in a mass ratio of 13.3:30.0:56.7, and the mixture was stirred until it became a homogeneous liquid, to prepare a mixed solution with a solid content of 4 mass %.

[0148] A separation membrane having a resin layer of 100% by mass of urethane resin was obtained by the same procedure as in Comparative Example 1 except for the above.

[0149] The structure of this separation membrane is shown in Table 1.

[0150] The results of the evaluation of each separation membrane are shown in Table 2.

[0151] The separation membranes of Examples 1 to 5 and Comparative Examples 1 to 7 exhibit high water vapor transmission rates because they contain polyvinylpyrrolidone in the resin layer. Furthermore, because they contain urethane resin, they exhibit low air transmission rates and good gas barrier properties. Furthermore, these separation membranes have high resistance to moist heat.

[0152] The separation membrane of Comparative Example 10 did not have a sufficient water vapor transmission rate because it did not contain polyvinylpyrrolidone in the resin layer. These evaluation results show that it is difficult to achieve both gas barrier properties and water vapor permeability when the resin layer does not contain polyvinylpyrrolidone or the like.

[0153] The separation membrane of Comparative Example 1 has a ratio of water vapor permeation rate to air permeation rate of not more than 1. This is because the separation membrane of Example 1 has a small basis weight of the resin layer, and the resin layer is unable to sufficiently block the pores of the porous substrate, resulting in a weak gas barrier property.

[0154] The separation membrane of Comparative Example 3 has a higher acrylic resin content and a relatively lower urethane resin content than the separation membrane of Comparative Example 2. The separation membrane of Comparative Example 3 has a high air permeation rate, which indicates that the urethane resin contributes to improving gas barrier properties.

[0155] When the separation membranes of Comparative Examples 1 to 4 are compared with the separation membranes of Examples 1 to 5, the gas-separation membranes of Examples 1 to 5, which have a high crosslinking conversion rate of polyvinylpyrrolidone, show less change in water vapor transmission rate and air transmission rate after moist heat treatment than the separation membranes of Comparative Examples 1 to 4. This indicates that the increased crosslinking conversion rate between polyvinylpyrrolidone molecules suppresses the detachment of the resin layer due to moist heat treatment. Furthermore, when the separation membranes of Examples 1 to 4 are compared with the separation membrane of Example 5, the separation membranes of Examples 1 to 4, which have a low crosslinking conversion rate of polyvinylpyrrolidone, show a greater change in water vapor transmission rate before and after moist heat treatment than the separation membrane of Example 5. This indicates that when the crosslinking conversion rate between polyvinylpyrrolidone molecules is high, the content ratio of non-crosslinked polyvinylpyrrolidone decreases, and a sufficient water vapor transmission rate is not obtained.

[0156] Furthermore, the separation membranes of Examples 1 to 5 and Comparative Examples 1 to 4 contain an acrylic resin formed by crosslinking an acrylate having six carbon-carbon double bonds, while the separation membrane of Comparative Example 5 contains an acrylic resin formed by crosslinking an acrylate having two carbon-carbon double bonds. Comparing the separation membrane of Comparative Example 2 with the separation membrane of Comparative Example 5, it can be seen that the more acrylic resin formed by crosslinking an acrylate having more carbon-carbon double bonds, the smaller the change in gas permeation rate before and after moist heat treatment and the higher moist heat resistance can be obtained.

[0157] Furthermore, when the separation membranes of Examples 1 to 5 are compared with the separation membrane of Example 6, it is found that the separation membrane of Example 6, which has a low crosslinking conversion rate of the hydrophilic resin, adsorbs more water upon moist heat treatment and has a lower water vapor transmission rate than the separation membranes of Examples 1 to 5. This is thought to be because, in the separation membrane having an acrylic resin with an extremely high number of double bonds, crosslinking mainly occurs between the acrylic resins themselves, and crosslinking of the hydrophilic resin does not occur, so the hydrophilicity of the resin layer is maintained in a very high state, and water vapor taken into the resin layer is retained in the resin layer, inhibiting permeation.

[0158] Furthermore, when the separation membranes of Examples 1 to 5 are compared with the separation membrane of Example 7, it is found that the separation membrane of Example 7, which has a high crosslinking conversion rate of the hydrophilic resin, has a lower amount of water adsorption and a lower water vapor transmission rate than the separation membranes of Examples 1 to 5. This is thought to be because, in order to obtain the same level of moist heat resistance with a separation membrane having an acrylic resin with few double bonds as with a separation membrane having an acrylic resin with many double bonds, the UV irradiation dose was increased, causing the hydrophilic resin to crosslink extensively, losing its hydrophilicity and resulting in a decrease in the water vapor permeability of the separation membrane.

[0159] Furthermore, when the separation membrane of Comparative Example 2 is compared with the separation membrane of Comparative Example 6, the separation membrane of Comparative Example 2, which has a small basis weight of the porous substrate, exhibits a higher water vapor transmission rate than the separation membrane of Comparative Example 6. This indicates that when the basis weight of the porous substrate is large, a sufficient water vapor transmission rate cannot be obtained when permeating the porous substrate. Furthermore, when the separation membrane of Comparative Example 2 is compared with the separation membrane of Comparative Example 7, the separation membrane of Comparative Example 2, which has a high porosity of the porous substrate, exhibits a higher water vapor transmission rate than the separation membrane of Comparative Example 7. This indicates that when the porosity of the porous substrate is low, a sufficient water vapor transmission rate cannot be obtained when permeating the porous substrate.

[0160] Furthermore, when the separation membrane of Comparative Example 2 is compared with the separation membranes of Comparative Examples 8 and 9, the change in air permeation rate before and after the moist heat treatment is smaller for the separation membrane of Comparative Example 2 than for the separation membranes of Comparative Examples 8 and 9. This indicates that the separation membrane of Comparative Example 2 has a cross-linked resin layer, and the cross-linked structure prevents the resin layer from falling off even after the moist heat treatment and continues to close the pores of the porous substrate, thereby contributing to improved moist heat resistance.

[0161]

[0162]

[0163] 1. Separation membrane test piece 2. Marker 20. Air conditioner 21. Air filter 22. Cooling coil 23. Heating coil 24. Separation membrane module 25. Blower 26. Outside air 27. Intake air 31. Fuel cell humidification module 32. Fuel cell 33. Power control unit 34. Motor 35. Battery 100. Water vapor transmission rate evaluation device 101. Evaluation cell 102. Separation membrane 103. Reinforcement material 104. Humidity-conditioned air inlet 105. Humidity-conditioned air outlet 106. Dry air inlet 107. Dry air outlet 108. Air flow meter 109. Humidifier 110. Temperature and humidity measurement points 111. Air transmission rate evaluation device 112. Air inlet 113. Air outlet 114. Air flow meter 115. Pressure gauge 116. Sealing plug 201. Separation membrane 202. Resin layer 203. Porous substrate

Claims

1. A separation membrane comprising at least a laminate of a porous substrate and a resin layer, the resin layer containing at least a hydrophilic resin, a hydrophobic resin, and a crosslinking component resin, and a rate of decrease in the content of the hydrophilic resin before and after wet heat treatment at 120°C for 24 hours of time of 0.1% by mass or more and 10% by mass or less.

2. The amount of moisture adsorbed by subjecting the laminate to a wet heat treatment at 120°C for 24 hours is 0.1 g / cm per unit volume of the resin layer. 3 1.3g / cm or more 3 The separation membrane according to claim 1 , wherein:

3. A separation membrane in which the crosslinking conversion rate of the hydrophilic resin is 3% or more and 30% or less.

4. The separation membrane according to any one of claims 1 to 3, wherein the cross-linking component resin is an acrylic resin.

5. The separation membrane described in claim 4, wherein the content of the acrylic resin is 2 mass% or more and 13 mass% or less with respect to the total mass of the resin layer, the acrylic resin has a crosslinked structure, and the crosslinked structure of the acrylic resin includes a structure represented by the following chemical formula (I) or (II). (R １ and R ２ is an alkyl chain of any length, X １ ~X ６ indicates any element or molecular structure.) (R １ ~R ４ is an alkyl chain of any length, X １ ~X ８ indicates any element or molecular structure.) 6. The separation membrane according to any one of claims 1 to 5, wherein the hydrophilic resin is polyvinylpyrrolidone and / or a vinylpyrrolidone copolymer.

7. The separation membrane according to any one of claims 1 to 6, wherein the hydrophobic resin is a urethane resin.

8. The separation membrane according to any one of claims 1 to 7, wherein the resin layer has a thickness of 10 nm or more and 1,000 nm or less.

9. The separation membrane according to any one of claims 1 to 7, wherein the resin layer has a contact angle with water of 67° or more and 83° or less.

10. The separation membrane according to any one of claims 1 to 7, wherein the absolute value of the heat shrinkage rate in the in-plane direction of the separation membrane at 100°C for 30 minutes is 4% or less.

11. The separation membrane according to any one of claims 1 to 7, wherein the absolute value of the heat shrinkage rate in the in-plane direction of the separation membrane at 100°C for 30 minutes is 2.5% or less.

12. The separation membrane according to any one of claims 1 to 7, wherein the absolute value of the linear swelling rate in the in-plane direction of the separation membrane when immersed in water at 20°C for 2 hours is 4% or less.

13. The separation membrane according to any one of claims 1 to 7, wherein the absolute value of the linear swelling rate in the in-plane direction when the separation membrane is immersed in water at 20°C for 2 hours is 2.5% or less.

14. The separation membrane according to any one of claims 1 to 7, wherein the content of the polyvinylpyrrolidone and / or vinylpyrrolidone copolymer is 50% by mass or more and 95% by mass or less based on the entire resin layer.

15. The weight of the resin layer is 0.1 g / m ２ Above, 3.0g / m ２ The separation membrane according to any one of claims 1 to 7, wherein:

16. The separation membrane according to claim 15, wherein the ratio of the basis weight of the resin layer to the basis weight of the porous substrate (basis weight of resin layer / basis weight of porous substrate) is 0.01 or more and 0.18 or less.

17. A method for producing a separation membrane according to any one of claims 1 to 16, comprising the steps of applying a coating composition containing polyvinylpyrrolidone and / or a vinylpyrrolidone copolymer, a urethane resin, and an acrylate having two or more carbon-carbon double bonds onto the porous substrate to form a coating film, and then irradiating the coating film with ultraviolet light.

18. A gas separation membrane using the separation membrane according to any one of claims 1 to 16.

19. A fuel cell humidification membrane using the gas separation membrane according to claim 18.

20. A fuel cell humidifying module using the fuel cell humidifying membrane according to claim 19.

21. A fuel cell system using the fuel cell humidification module according to claim 20.

22. A two-wheeled or four-wheeled automobile, ship, aircraft or moving body using the fuel cell system according to claim 21.

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