Composite membrane, membrane-electrode assembly, solid polymer-type fuel cell, solid polymer-type electrolysis device, and electrochemical hydrogen compression device

Abstract

This composite membrane comprises: a porous substrate which includes a polyolefin microporous membrane; a silica material which has a base containing silicon dioxide and has a sulfonic acid group on at least the surface of the base; and an ion exchange resin, wherein the composite membrane has a Gurley value of at least 1,000 sec / 100 mL.

Description

Composite membranes, membrane-electrode assemblies, polymer electrolyte fuel cells, polymer electrolyte electrolysis devices, and electrochemical hydrogen compression devices

[0001] The present disclosure relates to a composite membrane, a membrane-electrode assembly, a polymer electrolyte fuel cell, a polymer electrolyte electrolysis device, and an electrochemical hydrogen compression device.

[0002] In recent years, there has been an increasing need for improved performance of electrolyte membranes, particularly solid polymer electrolyte membranes. For example, a system that generates hydrogen by electrolyzing water using renewable energy such as solar or wind power, compresses the generated hydrogen to store it at high density, and supplies the hydrogen to a fuel cell where and when electricity is needed to generate electricity has attracted attention as an extremely clean energy system that does not generate carbon dioxide. Here, a water electrolysis method is known for electrolyzing water, in which an anode and a cathode are separated by an electrolyte membrane, and protons generated at the anode are transferred to the cathode through the electrolyte membrane and combined with electrons at the cathode to obtain hydrogen. The reaction formula at each electrode is as follows: Anode: H ２ O → 1 / 2O ２ +2H ＋ +2e － ・Cathode: 2H ＋ +2e － →H ２ On the other hand, in a fuel cell, protons produced by a hydrogen oxidation reaction at the negative electrode (anode) travel through the electrolyte membrane to the positive electrode (cathode), where they undergo an oxygen reduction reaction to generate water, generating electricity. The reaction formula at each electrode is as follows: Negative electrode: H ２ →2H ＋ +2e － ・Positive electrode: 1 / 2O ２ +2H ＋ +2e － →H ２ O

[0003] As is clear from the above operating principles, improving the proton conductivity of the electrolyte membrane is a common challenge in both water electrolysis and fuel cells. Possible methods for improving the proton conductivity of the electrolyte membrane include reducing the membrane thickness and reducing the dry mass per equivalent of ion exchange groups (equivalent weight: EW) of the electrolyte polymer. However, there is a natural limit to how thin the electrolyte membrane can be made, given the strength required as a separator between electrodes. Furthermore, reducing the EW can also reduce the proportion of the backbone portion of the electrolyte polymer, making it difficult to maintain a solid membrane.

[0004] In order to ensure the strength of the electrolyte membrane, there is an example in which a polymer electrolyte for a fuel cell is incorporated into the internal space (voids) of a porous polymer membrane, thereby achieving improved mechanical strength that would not be possible with the electrolyte itself (Patent Document 1). Also, a porous substrate suitable for retaining a polymer electrolyte in a porous polyethylene membrane has been proposed (Patent Document 2). Furthermore, there is a prior art in which the network structure of a porous thin film of ultra-high molecular weight polyolefin incorporates and contains an ion exchange resin, thereby providing a thin film electrolyte with excellent mechanical strength (Patent Document 3). Another prior art in which an ion conductor is incorporated and contained in a porous solid polymer membrane by utilizing capillary condensation is also provided (Patent Document 4).

[0005] Patent Document 1: JP 2005-166557 A Patent Document 2: JP 2011-241361 A Patent Document 3: JP 64-22932 A Patent Document 4: JP 1-158051 A

[0006] Although the above-mentioned methods have been investigated to improve the proton conductivity of electrolyte membranes, further improvement in the proton conductivity of electrolyte membranes is desired. Meanwhile, when an electrolyte membrane is installed in a device such as a fuel cell, the dimensional stability of the electrolyte membrane is also an important characteristic. Thus, the development of an electrolyte membrane that exhibits excellent proton conductivity and dimensional stability is desired. The present disclosure has been made in view of the above-mentioned conventional circumstances, and aims to provide a composite membrane that has excellent proton conductivity and dimensional stability, as well as a membrane-electrode assembly, a solid polymer fuel cell, a solid polymer electrolysis device, and an electrochemical hydrogen compression device that use this composite membrane.

[0007] Specific means for achieving the above object are as follows. <1> A composite membrane comprising a porous substrate including a polyolefin microporous membrane; a silica material having a substrate containing silicon dioxide and having sulfonic acid groups on at least the surface of the substrate; and an ion exchange resin, the composite membrane having a Gurley value of 1,000 seconds / 100 mL or more. <2> The composite membrane according to <1>, wherein the porosity of the porous substrate is 50% to 90%. <3> The composite membrane according to <1> or <2>, wherein at least a portion of the pores of the porous substrate are filled with the silica material and the ion exchange resin. <4> The composite membrane according to any one of <1> to <3>, comprising the porous substrate and an ion-conducting layer provided on at least one surface of the porous substrate, the ion-conducting layer containing the silica material and the ion exchange resin. <5> The composite membrane according to any one of <1> to <4>, wherein the ratio (A / B) of the average thickness A of the porous substrate to the average thickness B of the composite membrane is 0.10 to 1.0. <6> The composite membrane according to any one of <1> to <5>, wherein the ratio (C / D) of the basis weight C of the porous substrate to the basis weight D of the composite membrane is 0.03 to 0.5. <7> The composite membrane according to any one of <1> to <6>, wherein the ratio of the sulfur atom concentration to the sum of the silicon atom concentration and the sulfur atom concentration of the silica material, as determined by X-ray fluorescence spectroscopy (XRF), is 0.01% to 90%. <8> The composite membrane according to any one of <1> to <7>, wherein the substrate is in a particulate form. <9> The composite membrane according to any one of <1> to <8>, wherein the substrate is silica particles, and the number-average particle diameter of the primary particles of the silica particles is 1 nm to 500 nm. <10> A membrane-electrode assembly comprising the composite membrane according to any one of <1> to <9>, a cathode laminated on one surface of the composite membrane, and an anode laminated on the other surface of the composite membrane. <11> A polymer electrolyte fuel cell having the membrane-electrode assembly according to <10> and separators arranged on both sides of the membrane-electrode assembly. <12> A polymer electrolyte electrolysis device having the membrane-electrode assembly according to <10> and separators arranged on both sides of the membrane-electrode assembly. <13> An electrochemical hydrogen compression device having the composite membrane according to any one of <1> to <9>.

[0008] According to the present disclosure, it is possible to provide a composite membrane having excellent proton conductivity and dimensional stability, as well as a membrane-electrode assembly, a solid polymer fuel cell, a solid polymer electrolysis device, and an electrochemical hydrogen compression device that use this composite membrane.

[0009] 1A and 1B show cross-sectional views of one embodiment of a composite membrane of the present disclosure and another embodiment of a composite membrane of the present disclosure.

[0010] The present disclosure will be described in detail below. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure.

[0011] In the present disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved. In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, particles corresponding to each component may contain multiple types of particles. When multiple types of particles corresponding to each component are present in a composition, the particle size of each component refers to the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.In this disclosure, the term "layer" or "film" includes not only cases where the layer or film is formed over the entire area when the area where the layer or film is present is observed, but also cases where the layer or film is formed only in a part of the area.In this disclosure, the term "laminated" refers to stacking layers, and two or more layers may be bonded or detachable.In this disclosure, with respect to a porous substrate, "longitudinal direction" refers to the longitudinal direction of a porous substrate (polyolefin microporous membrane) produced in a long shape, and "width direction" refers to the direction perpendicular to the longitudinal direction of the porous substrate (polyolefin microporous membrane).

[0012] <Composite Membrane> The composite membrane of the present disclosure comprises a porous substrate containing a polyolefin microporous membrane, a substrate containing silicon dioxide, a silica material having sulfonic acid groups on at least the surface of the substrate, and an ion exchange resin, and has a Gurley value of 1,000 seconds / 100 mL or more. The composite membrane of the present disclosure has the above-described configuration, resulting in excellent proton conductivity and dimensional stability. The reason why the composite membrane of the present disclosure exhibits such effects is unclear, but the inventors speculate as follows. However, the following speculation is not intended to limit the composite membrane of the present disclosure, but is provided as an example. Porous substrates containing a polyolefin microporous membrane exhibit high mechanical strength. Therefore, it is speculated that the composite membrane of the present disclosure can be provided with excellent dimensional stability by including a porous substrate containing a polyolefin microporous membrane. Furthermore, the silica material has sulfonic acid groups on at least the surface of the silicon dioxide substrate, thereby exhibiting proton conductivity. Furthermore, the composite membrane of the present disclosure contains an ion exchange resin in addition to the silica material. Here, the ion exchange resin contains sulfonic acid groups, carboxyl groups, quaternary ammonium groups, or primary, secondary, or tertiary amino groups as ion exchange groups. In particular, sulfonic acid groups are preferred ion exchange groups contained in the ion exchange resin constituting the solid polymer electrolyte membrane. Silica materials have sulfonic acid groups on at least the surface of the silicon dioxide-containing substrate, and therefore have high affinity with ion exchange groups (especially sulfonic acid groups). By dispersing the silica material in the ion exchange resin, the ion exchange groups contained in the ion exchange resin and the sulfonic acid groups contained in the silica material interact in the composite membrane, facilitating the efficient establishment of proton conduction paths in the composite membrane. Therefore, it is believed that the composite membrane of the present disclosure exhibits excellent proton conductivity.

[0013] The porous substrate, silica material, and ion exchange resin that constitute the composite membrane of the present disclosure, as well as other elements that are used as needed, will be described below.

[0014] (Porous substrate) The composite membrane of the present disclosure contains a porous substrate comprising a polyolefin microporous membrane from the viewpoints of chemical stability, mechanical strength, and hydrophobicity. The porous substrate may be made of a polyolefin microporous membrane. In the present disclosure, a microporous membrane comprising a polyolefin is referred to as a "polyolefin microporous membrane." In the present disclosure, a microporous membrane refers to a membrane having a large number of micropores therein and a structure in which the micropores are connected, allowing gas or liquid to pass from one surface to the other surface.

[0015] The microporous polyolefin membrane preferably has a three-dimensional network structure made of polyolefin fibrils.

[0016] Examples of polyolefins contained in the polyolefin microporous membrane include polyethylene, polypropylene, polybutylene, polymethylpentene, copolymers of polypropylene and polyethylene, etc. Among these, polyethylene is preferred, and high-density polyethylene, and mixtures of high-density polyethylene and ultra-high molecular weight polyethylene are also preferred.

[0017] An example of an embodiment of the polyolefin microporous membrane is a polyethylene microporous membrane containing only polyethylene as polyolefin.

[0018] An example of an embodiment of the polyolefin microporous film is a microporous film containing polypropylene, which has heat resistance such that it does not easily rupture when exposed to high temperatures.

[0019] An example of an embodiment of the microporous polyolefin membrane is a microporous polyolefin membrane containing at least a mixture of polyethylene and polypropylene.

[0020] An example of an embodiment of the microporous polyolefin membrane is a polyolefin microporous membrane having a laminate structure of two or more layers, at least one layer containing polyethylene and at least one layer containing polypropylene.

[0021] The weight average molecular weight (Mw) of the polyolefin contained in the polyolefin microporous membrane is preferably 500,000 to 5,000,000. When the Mw of the polyolefin is 500,000 or more, the microporous membrane can be imparted with sufficient mechanical properties. When the Mw of the polyolefin is 5,000,000 or less, the microporous membrane can be easily formed.

[0022] The weight average molecular weight (Mw) of the polyethylene contained in the polyolefin microporous membrane is preferably 800,000 or more, more preferably 1,000,000 or more, and even more preferably 1,100,000 or more, from the viewpoint of densifying the porous structure of the microporous membrane. The weight average molecular weight (Mw) of the polyethylene contained in the polyolefin microporous membrane is preferably 4,900,000 or less, more preferably 4,800,000 or less, and even more preferably 4,700,000 or less, from the viewpoint of increasing the porosity of the microporous membrane. When the polyolefin microporous membrane contains two or more types of polyethylene, the weight average molecular weight (Mw) of the mixture of two or more types of polyethylene is preferably within the above range.

[0023] The weight-average molecular weights of the polyolefin and polyethylene constituting the polyolefin microporous membrane can be obtained by dissolving the polyolefin microporous membrane in o-dichlorobenzene under heating and measuring the molecular weight by gel permeation chromatography (system: Alliance GPC 2000 manufactured by Waters Corporation, columns: GMH6-HT and GMH6-HTL) at a column temperature of 135°C and a flow rate of 1.0 mL / min. Monodisperse polystyrene (manufactured by Tosoh Corporation) is used to calibrate the molecular weight.

[0024] An example of an embodiment of the polyolefin microporous membrane is a microporous membrane containing a polyolefin composition (which in the present disclosure refers to a polyolefin mixture containing two or more polyolefins, and when the polyolefin contained is only polyethylene, it is referred to as a polyethylene composition.) The polyolefin composition forms a network structure as it fibrillates during stretching, and has the effect of increasing the porosity of the polyolefin microporous membrane.

[0025] The polyolefin composition has a weight average molecular weight of 9 × 10 ５A polyolefin composition containing 5% by mass to 90% by mass of the above ultra-high molecular weight polyethylene relative to the total amount of polyolefins is preferred, a polyolefin composition containing 10% by mass to 88% by mass is more preferred, and a polyolefin composition containing 15% by mass to 85% by mass is even more preferred.

[0026] The polyolefin composition has a weight average molecular weight of 9×10 ５ and an ultra-high molecular weight polyethylene having a weight average molecular weight of 2×10 ５ ~8 x 10 ５ and the density is 920 kg / m ３ ~960 kg / m ３ and a high-density polyethylene in a mass ratio of 5:95 to 95:5 (more preferably 10:90 to 90:10, and even more preferably 15:85 to 85:15).

[0027] An example of an embodiment of the polyolefin microporous membrane is a polyolefin microporous membrane that has been hydrophilization-treated. Examples of the hydrophilization-treated polyolefin microporous membrane include a polyolefin microporous membrane whose surface is coated with a hydrophilic compound (e.g., ethylene-vinyl alcohol copolymer), a polyolefin microporous membrane whose surface is polymerized with a monomer having a hydrophilic group, and a polyolefin microporous membrane that has been subjected to plasma treatment or corona treatment.

[0028] The proportion of the porous substrate in the composite membrane of the present disclosure is preferably 5.0% by mass or more, more preferably 5.5% by mass or more, and even more preferably 6.0% by mass or more, from the viewpoint of dimensional stability. The proportion of the porous substrate in the composite membrane of the present disclosure is preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 16% by mass or less, from the viewpoint of proton conductivity. The proportion of the porous substrate in the composite membrane of the present disclosure is preferably 5.0% by mass to 20% by mass, more preferably 5.5% by mass to 18% by mass, and even more preferably 6.0% by mass to 16% by mass.

[0029] (Method for producing polyolefin microporous membrane) The method for producing the polyolefin microporous membrane in the present disclosure is not particularly limited, and is preferably, for example, a method comprising the following steps (1) to (5). The polyolefin used as the raw material is as described above.

[0030] (1) Preparation of Polyolefin Solution A polyolefin solution is prepared by dissolving a polyolefin in a solvent. Examples of solvents include paraffin, liquid paraffin, paraffin oil, mineral oil, castor oil, tetralin, ethylene glycol, glycerin, decalin, toluene, xylene, diethyltriamine, ethyldiamine, dimethyl sulfoxide, and hexane. In this case, the solvents may be used alone or in combination of two or more. Among the solvents, examples of volatile solvents include solvents with a boiling point of less than 300°C under atmospheric pressure, such as decalin, toluene, xylene, diethyltriamine, ethyldiamine, dimethyl sulfoxide, hexane, tetralin, ethylene glycol, and glycerin. Examples of non-volatile solvents include solvents with a boiling point of 300°C or higher under atmospheric pressure, such as paraffin, liquid paraffin, paraffin oil, mineral oil, and castor oil. Examples of mixed solvents include a combination of decalin and liquid paraffin. Using liquid paraffin as the solvent tends to reduce the average pore size of the polyolefin microporous membrane. When decalin is used alone as a solvent, the average pore size of the polyolefin microporous membrane tends to be larger than when liquid paraffin is used in combination, although this is not limited to this, as the average pore size can also be controlled by other process parameters.

[0031] The polyolefin concentration of the polyolefin solution is preferably 1% by mass to 45% by mass, more preferably 10% by mass to 40% by mass. When the polyolefin concentration is 1% by mass or more, the gel composition obtained by cooling gelation can be maintained without being highly swollen by the solvent, making it less likely to deform and easier to handle. On the other hand, when the polyolefin concentration is 45% by mass or less, the pressure during extrusion can be suppressed, making it possible to maintain the discharge rate and resulting in excellent productivity.

[0032] (2) Extrusion of Polyolefin Solution The prepared polyolefin solution is kneaded in a single-screw extruder or twin-screw extruder and extruded through a T-die, cross-hanger die, or I-die at a temperature above the melting point and below 70°C above the melting point. In this case, a twin-screw extruder is preferably used. The polyolefin solution extruded from the die is then passed through a chill roll or cooling bath to form a gel composition. In this case, it is preferable to rapidly cool the polyolefin solution to below the gelation temperature to gel it.

[0033] (3) Solvent removal treatment Next, the solvent is removed from the gel composition. If a volatile solvent is used in preparing the polyolefin solution, the solvent can be removed from the gel composition by evaporation by heating or the like, which also serves as a preheating step. If a non-volatile solvent is used in preparing the polyolefin solution, the solvent can be removed by squeezing it out under pressure, for example. It is not necessary to completely remove the solvent.

[0034] (4) Stretching of Gel Composition Following the solvent removal treatment, the gel composition is stretched. A relaxation treatment may be performed before the stretching treatment. The stretching treatment involves heating the gel composition and stretching it uniaxially or biaxially at a predetermined magnification using a conventional tenter method, roll method, rolling method, or a combination of these methods. Biaxial stretching may be performed simultaneously or sequentially. Multi-stage longitudinal stretching or three- or four-stage stretching may also be used. The stretching temperature is preferably 80°C or higher and lower than the melting point of the polyolefin used in production, more preferably 90°C to 130°C. If the heating temperature is lower than the melting point, the gel composition is less likely to dissolve, allowing for smooth stretching. Furthermore, if the heating temperature is 80°C or higher, the gel composition is sufficiently softened, allowing for high-magnification stretching without film rupture during stretching. The stretching magnification varies depending on the thickness of the raw film, but it is preferable to stretch it uniaxially at least 2x, preferably 4x to 20x. After stretching, heat setting is carried out as necessary to provide thermal dimensional stability.

[0035] (5) Extraction and Removal of Solvent The stretched gel composition is immersed in an extraction solvent to extract the solvent, particularly the nonvolatile solvent. Examples of extraction solvents that can be used include easily volatile solvents such as hydrocarbons such as pentane, hexane, heptane, cyclohexane, decalin, and tetralin; chlorinated hydrocarbons such as methylene chloride, carbon tetrachloride, and methylene chloride; fluorinated hydrocarbons such as trifluoroethane; and ethers such as diethyl ether and dioxane. These solvents can be appropriately selected depending on the solvent, particularly the nonvolatile solvent, used in preparing the polyolefin solution, and can be used alone or in combination. Solvent extraction removes the solvent in the polyolefin microporous membrane to less than 1% by mass.

[0036] (Physical properties of porous substrate) From the viewpoint of increasing the strength of the porous substrate, the average film thickness of the porous substrate is preferably 0.01 μm or more, more preferably 3 μm or more, even more preferably 3.5 μm or more, particularly preferably 4 μm or more, and especially particularly preferably 5 μm or more. From the viewpoint of maintaining ion conductivity, the average film thickness of the porous substrate is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, particularly preferably 100 μm or less, and especially particularly preferably 50 μm or less. The average film thickness of the porous substrate is preferably 0.01 μm to 300 μm, more preferably 3 μm to 250 μm, even more preferably 3.5 μm to 200 μm, particularly preferably 4 μm to 100 μm, and especially particularly preferably 5 to 50 μm. The average film thickness of the porous substrate is measured at 20 points using a contact film thickness meter and averaged.

[0037] From the viewpoint of the filling rate of the silica material and the ion exchange resin, the porosity of the porous substrate is preferably 50% or more, more preferably 51% or more, even more preferably 52% or more, and particularly preferably 53% or more. From the viewpoint of the mechanical strength of the membrane, the porosity of the porous substrate is preferably 90% or less, more preferably 88% or less, even more preferably 85% or less, and particularly preferably 84% or less. The porosity of the porous substrate is preferably 50% to 90%, more preferably 51% to 88%, even more preferably 52% to 85%, and particularly preferably 53% to 84%.

[0038] The porosity of the porous substrate is determined by the basis weight (Ws: g / m２ ), the true density of the polyolefin (ds: g / cm ３ ) and the film thickness (t: μm) of the porous substrate, the true density of the polyolefin is calculated using the following formula. When the porous substrate contains two or more types of polyolefin, the true density of the polyolefin means the true density of the mixture of two or more types of polyolefin. ε (%) = {1 - Ws / (ds t)} × 100

[0039] From the viewpoint of mechanical strength, the Gurley value of the porous substrate is preferably 0.1 seconds / 100 mL or more, more preferably 0.2 seconds / 100 mL or more, even more preferably 0.5 seconds / 100 mL or more, and particularly preferably 1 second / 100 mL or more. From the viewpoint of maintaining ionic conductivity, the Gurley value of the porous substrate is preferably 500 seconds / 100 mL or less, more preferably 450 seconds / 100 mL or less, even more preferably 400 seconds / 100 mL or less, and particularly preferably 300 seconds / 100 mL or less. The Gurley value of the porous substrate is preferably 0.1 seconds / 100 mL to 500 seconds / 100 mL, more preferably 0.2 seconds / 100 mL to 450 seconds / 100 mL, even more preferably 0.5 seconds / 100 mL to 400 seconds / 100 mL, and particularly preferably 1 second / 100 mL to 300 seconds / 100 mL. The Gurley value of the porous substrate is a value measured in accordance with JIS P8117:2009.

[0040] From the viewpoint of mechanical strength, the breaking strength of the porous substrate is preferably 50 MPa to 400 MPa, and more preferably 80 MPa to 300 MPa.

[0041] The breaking strength is measured using a tensile tester in accordance with JIS L1015:2010. The chuck distance is 100 mm and the tensile speed is 50 mm / min. The tensile tester may be an EZ-LX manufactured by Shimadzu Corporation or an equivalent device.

[0042] From the viewpoint of the filling ability of the silica material and the ion exchange resin, the average pore diameter of the porous substrate is preferably 0.001 μm or more, more preferably 0.005 μm or more, even more preferably 0.01 μm or more, and particularly preferably 0.02 μm or more. From the viewpoint of mechanical strength, the average pore diameter of the porous substrate is preferably 100 μm or less, more preferably 3.0 μm or less, even more preferably 2.0 μm or less, and particularly preferably 1.0 μm or less. The average pore diameter of the porous substrate is preferably 0.001 μm to 100 μm, more preferably 0.005 μm to 3.0 μm, even more preferably 0.01 μm to 2.0 μm, and particularly preferably 0.02 μm to 1.0 μm. The average pore diameter of the porous substrate can be measured using a perm porometer in accordance with ASTM E1294-89. A fluorine-based inert liquid is used as the immersion liquid.

[0043] The basis weight of the porous substrate is set to 0.5 g / m from the viewpoint of mechanical strength. ２ More than 0.7 g / m ２ More preferably, 1.0 g / m or more ２ More preferably, 1.5 g / m or more ２ The weight per unit area of ​​the porous substrate is particularly preferably 50.0 g / m from the viewpoint of improving proton conductivity. ２ Preferably, 45.0 g / m or less ２ More preferably, 40.0 g / m or less ２ More preferably, 20.0 g / m or less ２ The following is particularly preferred: The basis weight of the porous substrate is 0.5 g / m ２ ~50.0g / m ２ is preferred, and 0.7 g / m ２ ~45.0g / m ２ More preferably, 1.0 g / m ２ ~40.0g / m ２ More preferably, 1.5 g / m ２ ~20.0g / m ２ The following is particularly preferred: The basis weight of the porous substrate can be determined by measuring the weight of a sample of a certain size and dividing the weight by the area.

[0044] (Silica Material) In order to impart proton conductivity to the composite membrane of the present disclosure, the composite membrane has a substrate containing silicon dioxide and contains a silica material having sulfonic acid groups on at least the surface of the substrate. The sulfonic acid groups may be chemically bonded to the surface of the substrate.

[0045] The silica material used in the present disclosure will be described in detail below.

[0046] - Substrate - The silica material has a substrate containing silicon dioxide. The shape of the substrate is not particularly limited, and examples thereof include particulate, fibrous, plate-like, and thin-film-like substrates. From the viewpoint of the ability of the silica material to fill the pores of the porous substrate, the substrate is preferably in the form of particles.

[0047] Examples of particulate substrates containing silicon dioxide include silica particles. The silica particles may be crystalline or amorphous. The silica particles may be particles produced using a silicon compound such as water glass or alkoxysilane as a raw material, or may be particles obtained by pulverizing quartz. Specific examples of silica particles include silica particles produced by a sol-gel method, colloidal silica particles, fumed silica particles obtained by a gas phase method, and fused silica particles.

[0048] The number average particle diameter of the primary particles of the silica particles is preferably 1 nm to 500 nm, more preferably 5 nm to 300 nm, even more preferably 8 nm to 200 nm, and particularly preferably 10 nm to 100 nm. The number average particle diameter of the primary particles of the silica particles refers to a value calculated as the arithmetic mean of the circle-equivalent diameters of 50 silica particles obtained by observation with a scanning electron microscope. The primary particles of the silica particles may aggregate to form secondary particles. The volume average particle diameter of the secondary particles of the silica particles is preferably 500 nm to 500 μm, more preferably 1 μm to 300 μm, and even more preferably 10 μm to 150 μm. The volume average particle diameter of the secondary particles of the silica particles is a value measured using a laser diffraction particle size distribution analyzer, for example, a Mastersizer 2000 manufactured by Sysmex Corporation. Specifically, the volume average particle diameter is defined as the median particle diameter (D50) in the volume particle size distribution of a dispersion obtained by mixing and dispersing silica particles, water (dispersion medium), and a nonionic surfactant (Igepal CA630; dispersant).

[0049] Examples of fibrous substrates containing silicon dioxide include glass fibers such as long glass fibers (glass fiber) and short glass fibers (glass wool), and silica nanofibers. Glass fibers are preferably made of alkali-free glass (E-glass). The diameter of the glass fiber is not particularly limited, but is preferably 1 μm to 100 μm, more preferably 5 μm to 50 μm. The fiber length of the long glass fiber is not particularly limited. The fiber length of the short glass fiber is preferably 0.1 mm to 30 mm, more preferably 0.2 mm to 20 mm. The diameter of the glass fiber refers to the number-average fiber diameter, which indicates the average diameter of the glass fibers. The number-average fiber diameter refers to the arithmetic average when 50 glass fibers are randomly selected and the fiber diameter is measured using an optical microscope. The fiber length of the short glass fiber is a value obtained by visually measuring the length of 100 randomly selected fibers to the nearest 0.1 mm and then arithmetic mean.

[0050] Examples of thin-film substrates containing silicon dioxide include scaly glass particles. The volume average particle diameter of the scaly glass particles is preferably 0.1 μm to 200 μm, more preferably 0.2 μm to 150 μm, and even more preferably 0.2 μm to 100 μm. The volume average particle diameter of the scaly glass particles can be measured in the same manner as the volume average particle diameter of silica particles. The average thickness of the scaly glass particles is preferably 1 μm to 20 μm, more preferably 1.5 μm to 15 μm, and even more preferably 2 μm to 10 μm. The average thickness of the scaly glass particles refers to the arithmetic mean of the thicknesses of 50 randomly selected glass particles from 100 randomly selected glass particles measured with an optical microscope. The ratio of the volume average particle diameter to the average thickness of the scaly glass particles (aspect ratio: volume average particle diameter / average thickness) is preferably 1.2 to 2000, more preferably 1.5 to 1500, and even more preferably 2 to 1000. The aspect ratio of the scaly glass particles can be calculated as the ratio of the volume average particle diameter to the average thickness of the scaly glass particles determined by the above-mentioned method.

[0051] In addition to the above-mentioned thin film-like substrate, a plate-like substrate containing silicon dioxide may also be used. Examples of the plate-like substrate include a glass plate. From the viewpoint of processability, the substrate is preferably silica particles or glass fiber, and more preferably silica particles.

[0052] -Sulfonic Acid Group- In a silica material, sulfonic acid groups are present on at least the surface of the substrate. The sulfonic acid groups may be chemically bonded to the surface of the substrate. The presence of sulfonic acid groups on at least the surface of the substrate can be confirmed, for example, by the following method. X-ray photoelectron spectroscopy (XPS), X-ray fluorescence analysis (XRF), or the like is used to confirm whether sulfur atoms are present in the silica material and to quantify the amount of sulfur atoms present. Scanning electron microscope-energy dispersive X-ray spectrometry (SEM-EDX) is used to confirm whether sulfur atoms are present on the surface of the silica material. Furthermore, 0.1 g of the silica material is dispersed in 1.9 g of deionized water, and the pH of the dispersion (5 mass% dispersion) is measured at 25° C. If sulfur atoms are present on the surface of the silica material and the pH of the dispersion is 3 or less, it can be determined that sulfonic acid groups are present at least on the surface of the substrate.

[0053] In one embodiment, the ratio of sulfur atoms to silicon atoms (S / Si) contained in the silica material is preferably 0.001 to 0.25, more preferably 0.0015 to 0.2, and even more preferably 0.002 to 0.15. In another embodiment, the ratio of sulfur atoms to silicon atoms (S / Si) contained in the silica material is preferably 0.001 to 0.72, more preferably 0.0015 to 0.67, and even more preferably 0.002 to 0.62. The amounts of sulfur atoms and silicon atoms contained in the silica material used to calculate the ratio of sulfur atoms to silicon atoms (S / Si) are the atomic abundances determined by XPS measurement.

[0054] In one embodiment, the concentration of sulfur atoms contained in the silica material is preferably 50 mg / kg to 250 g / kg, more preferably 150 mg / kg to 200 g / kg, and even more preferably 300 mg / kg to 150 g / kg. In another embodiment, the concentration of sulfur atoms contained in the silica material is preferably 50 mg / kg to 50 g / kg, more preferably 150 mg / kg to 30 g / kg, and even more preferably 300 mg / kg to 20 g / kg. The concentration of sulfur atoms contained in the silica material refers to the atomic abundance determined by XRF measurement.

[0055] The degree of sulfonation of the silica material (degree of sulfonation based on XRF) is preferably 0.01% to 90%, more preferably 0.03% to 80%, and even more preferably 0.06% to 60%. The degree of sulfonation based on XRF is calculated as the ratio of the concentration of sulfur atoms to the sum of the concentrations of silicon atoms and sulfur atoms determined by XRF measurement.

[0056] In some embodiments, the proportion of the silica material in the composite membrane of the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more, from the viewpoint of ionic conductivity. In some embodiments, the proportion of the silica material in the composite membrane of the present disclosure is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of dimensional stability. In some embodiments, the proportion of the silica material in the composite membrane of the present disclosure is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 15% by mass, and even more preferably 0.8% by mass to 10% by mass. In other embodiments, the proportion of the silica material in the composite membrane of the present disclosure is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, and even more preferably 0.8% by mass or more, from the viewpoint of ionic conductivity. In other embodiments, the proportion of the silica material in the composite membrane of the present disclosure is preferably 45% by mass or less, more preferably 35% by mass or less, and even more preferably 25% by mass or less, from the viewpoint of dimensional stability. In another embodiment, the proportion of the silica material in the composite membrane of the present disclosure is preferably 0.5% by mass to 45% by mass, more preferably 0.7% by mass to 35% by mass, and even more preferably 0.8% by mass to 25% by mass.

[0057] -Method for producing silica material- A silica material has sulfonic acid groups on at least the surface of a substrate. The method for providing sulfonic acid groups on at least the surface of a substrate is not particularly limited. For example, the silica material used in the present disclosure can be produced by contacting the above-described substrate with a sulfonating agent. The method for contacting the substrate with the sulfonating agent is not particularly limited, and examples include a method of immersing the substrate in the sulfonating agent and a method of spraying the sulfonating agent onto the substrate. The temperature of the sulfonating agent when contacting the substrate with the sulfonating agent is preferably 10°C to 90°C, more preferably 15°C to 80°C, and even more preferably 20°C to 70°C. The immersion time when immersing the substrate in the sulfonating agent is preferably 5 to 120 minutes, more preferably 10 to 100 minutes, and even more preferably 15 to 60 minutes. When the substrate is immersed in the sulfonating agent, the ratio of the substrate to the sulfonating agent is preferably 1,000 to 50,000 parts by mass, more preferably 2,000 to 30,000 parts by mass, and even more preferably 3,000 to 20,000 parts by mass, per 100 parts by mass of the substrate. A stirring treatment may be performed when the substrate is immersed in the sulfonating agent. The stirring method is not particularly limited, and examples include stirring using a stirring blade or a stirring device with a planetary rotation mechanism. Using a stirring device with a planetary rotation mechanism can efficiently remove air bubbles. After contacting the substrate with the sulfonating agent, the substrate may be washed with ion-exchanged water, deionized water, or the like and filtered, and, if necessary, further washed with an organic solvent such as acetone and filtered. The substrate may then be dried to obtain a silica material.

[0058] Examples of sulfonating agents include fuming sulfuric acid, concentrated sulfuric acid, dilute sulfuric acid, sulfuric anhydride, etc., and fuming sulfuric acid or concentrated sulfuric acid is preferred, with fuming sulfuric acid being more preferred. The concentration of sulfur trioxide in fuming sulfuric acid is preferably 10% by mass to 80% by mass, more preferably 15% by mass to 75% by mass, and even more preferably 20% by mass to 70% by mass.

[0059] (Ion Exchange Resin) The composite membrane of the present disclosure contains an ion exchange resin to impart proton conductivity to the composite membrane. The ion exchange group contained in the ion exchange resin is not particularly limited, and examples thereof include sulfonic acid groups, carboxy groups, quaternary ammonium groups, and primary, secondary, or tertiary amino groups. Among these, sulfonic acid groups are preferred because of their excellent proton conductivity.

[0060] The type of ion exchange resin contained in the composite membrane of the present disclosure is not particularly limited, and examples of the ion exchange resin include aromatic ion exchange resins and fluorine-based ion exchange resins.

[0061] Examples of aromatic ion exchange resins include sulfonated aromatic polymers such as polyphenylene, polyphenylene sulfide, polyphenylene oxide, diphenyl paraphenylene oxide, polysulfone, polyether sulfone, polyether ketone, polyether ether ketone, polyether ketone ketone, polyether nitrile, polyamide, polybenzazole, and polyimide. More specifically, sulfonated polyphenylene containing a structural unit represented by general formula (I), sulfonated polyphenylene sulfide containing a structural unit represented by general formula (II), sulfonated polyphenylene oxide containing a structural unit represented by general formula (III), sulfonated polydiphenyl paraphenylene oxide containing a structural unit represented by general formula (IV), sulfonated polysulfone containing a structural unit represented by general formula (V), sulfonated polyether sulfone containing a structural unit represented by general formula (VI), and sulfonated polyether sulfone containing a structural unit represented by general formula (VII). Examples of suitable ion exchange resins include sulfonated polyether ketones containing structural units represented by general formula (VIII), sulfonated polyether ether ketones containing structural units represented by general formula (VIII), sulfonated polyether ketone ketones containing structural units represented by general formula (IX), sulfonated polyether nitriles containing structural units represented by general formula (X), sulfonated polyamides containing structural units represented by general formula (XI), sulfonated polybenzazoles containing structural units represented by general formula (XII), and sulfonated polyimides containing structural units represented by general formula (XIII). Among these, sulfonated polyether sulfones containing structural units represented by general formula (VI), sulfonated polyphenylene sulfides containing structural units represented by general formula (II), and sulfonated polysulfones containing structural units represented by general formula (V) are preferred, and sulfonated polyether sulfones containing structural units represented by general formula (VI) are more preferred. In the present disclosure, two or more types of ion exchange resins may be used in combination. When two or more types of ion exchange resins are used in combination, for example, a sulfonated polyethersulfone containing a structural unit represented by general formula (VI) may be used in combination with a sulfonated resin other than polyethersulfone.In the general formulae (I) to (XIII), n represents an integer of 1 or 2 or more.

[0062]

[0063]

[0064] The sulfonation rate of the aromatic ion exchange resin is preferably 5 mol % to 90 mol %, more preferably 8 mol % to 80 mol %, and even more preferably 10 mol % to 70 mol %. In the present disclosure, the sulfonation rate of the aromatic ion exchange resin refers to the proportion of structural units substituted with sulfonic acid groups to all structural units contained in the aromatic ion exchange resin.

[0065] Examples of fluorine-based ion exchange resins include perfluorosulfonic acid electrolyte polymers such as Nafion (registered trademark), Aciplex (registered trademark), Flemion (registered trademark), Aquivion, and Goreselect.

[0066] The EW of the ion exchange resin is preferably 200 or more, more preferably 250 or more, even more preferably 300 or more, and particularly preferably 350 or more. The EW is preferably 2600 or less, more preferably 2300 or less, even more preferably 2000 or less, and particularly preferably 1700 or less. An EW of 2600 or less further improves the ionic conductivity of the composite membrane. An EW of 200 or more further improves the dimensional stability of the composite membrane. The EW of the ion exchange resin is preferably 200 to 2600.

[0067] The EW of an acid-type ion exchange resin is measured by the following method. Approximately 0.02 g to 0.10 g of ion exchange resin is immersed in 50 mL of 25°C saturated aqueous NaCl solution (0.26 g / mL), left to stand for 10 minutes with stirring, and then neutralization titration is performed using 0.01 N aqueous sodium hydroxide solution (special grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with phenolphthalein (special grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as an indicator. The Na-type ion exchange membrane obtained after neutralization is rinsed with pure water, vacuum dried, and weighed. The equivalent weight EW (g / eq) is calculated using the following formula, where M (mmol) is the equivalent of sodium hydroxide required for neutralization and W (mg) is the mass of the Na-type ion exchange membrane: EW = (W / M) - 22

[0068] In some embodiments, the proportion of ion exchange resin in the composite membrane of the present disclosure is preferably 70.0% by mass or more, more preferably 75.0% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of ionic conductivity. In some embodiments, the proportion of ion exchange resin in the composite membrane of the present disclosure is preferably 98.0% by mass or less, more preferably 95.0% by mass or less, and even more preferably 93.0% by mass or less, from the viewpoint of dimensional stability. In some embodiments, the proportion of ion exchange resin in the composite membrane of the present disclosure is preferably 70.0% by mass to 98.0% by mass, more preferably 75.0% by mass to 95.0% by mass, and even more preferably 80.0% by mass to 93.0% by mass. In other embodiments, the proportion of ion exchange resin in the composite membrane of the present disclosure is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, from the viewpoint of ionic conductivity. In another aspect, from the viewpoint of dimensional stability, the proportion of the ion exchange resin in the composite membrane of the present disclosure is preferably 95% by mass or less, more preferably 94% by mass or less, and even more preferably 93% by mass or less. In another aspect, the proportion of the ion exchange resin in the composite membrane of the present disclosure is preferably 50% by mass to 95% by mass, more preferably 60% by mass to 94% by mass, and even more preferably 70% by mass to 93% by mass.

[0069] When a composite membrane is prepared using an ion exchange resin containing fluorine atoms in its molecular structure, hydrofluoric acid may be generated by decomposition of the ion exchange resin when the composite membrane operates as a solid polymer electrolyte membrane, etc. Therefore, the ion exchange resin is preferably an ion exchange resin that does not contain fluorine atoms in its molecular structure or has a fluorine atom content of 50 mass% or less in its molecular structure.

[0070] The composite membrane of the present disclosure may use, in combination with the ion exchange resin, other resins that exhibit low or no ion exchange capacity (hereinafter, sometimes referred to as non-ion exchange resins). In the present disclosure, a non-ion exchange resin refers to one having an EW of 10,000 or more. Specific examples of non-ion exchange resins include resins containing structural units represented by the above-mentioned general formulas (I) to (XIII).

[0071] When the composite membrane of the present disclosure uses an ion exchange resin and a non-ion exchange resin in combination, the content ratio of the ion exchange resin to the non-ion exchange resin is not particularly limited. For example, the content ratio of the ion exchange resin to the non-ion exchange resin may be adjusted so that the EW of the mixture of the ion exchange resin and the non-ion exchange resin is the desired value. In the present disclosure, "using an ion exchange resin and a non-ion exchange resin in combination" means that the ion exchange resin and the non-ion exchange resin are in a mutually compatible state. The non-ion exchange resin does not include the polyolefin constituting the porous substrate. The EW of the mixture of the ion exchange resin and the non-ion exchange resin is preferably 200 or more, more preferably 250 or more, even more preferably 300 or more, and particularly preferably 350 or more. Furthermore, the EW is preferably 2600 or less, more preferably 2300 or less, even more preferably 2000 or less, and particularly preferably 1700 or less. An EW of 2600 or less further improves the ionic conductivity of the composite membrane. Furthermore, an EW of 200 or more further improves the dimensional stability of the composite membrane. The EW of the mixture of ion exchange resin and non-ion exchange resin is preferably 200 to 2600. In one embodiment, the mass-based content of the ion exchange resin in the mixture of ion exchange resin and non-ion exchange resin is preferably 1 mass% to 95 mass%, more preferably 5 mass% to 90 mass%, and even more preferably 10 mass% to 80 mass%. In another embodiment, the sulfonation ratio of the mixture of ion exchange resin and non-ion exchange resin is preferably 5 mol% to 90 mol%, more preferably 8 mol% to 80 mol%, and even more preferably 10 mol% to 70 mol%. In the present disclosure, the sulfonation ratio of the mixture of ion exchange resin and non-ion exchange resin when both the ion exchange resin and the non-ion exchange resin are aromatic refers to the proportion of structural units substituted with sulfonic acid groups among all structural units contained in the ion exchange resin and the non-ion exchange resin.When both the ion exchange resin and the non-ion exchange resin are aromatic, the sulfonation ratio of the ion exchange resin (or the mixture of the ion exchange resin and the non-ion exchange resin when the ion exchange resin and the non-ion exchange resin are used in combination) is the value determined from the ratio of unit structures having sulfonic acid groups to unit structures not having sulfonic acid groups, as measured by proton NMR. Furthermore, when the types and molecular weights (e.g., weight average molecular weights) of the structural units constituting the ion exchange resin and the non-ion exchange resin in the mixture, as well as the sulfonation ratio of the ion exchange resin, are known, the sulfonation ratio of the mixture is determined by calculation based on these values.

[0072] Note that the durability of ion exchange resins may decrease as the sulfonation rate increases. Therefore, when an ion exchange resin with a relatively low sulfonation rate is used, it is not necessary to use it in combination with a non-ion exchange resin. Furthermore, when an ion exchange resin with a relatively low sulfonation rate is used in combination with a non-ion exchange resin, the mass-based content of the ion exchange resin in the mixture of the ion exchange resin and the non-ion exchange resin may be relatively high. On the other hand, when an ion exchange resin with a relatively high sulfonation rate is used, it is preferable to use the ion exchange resin in combination with a non-ion exchange resin. For example, when a sulfonated polyethersulfone having a sulfonation rate of 1 mol % to 20 mol % (preferably 3 mol % to 18 mol %, more preferably 5 mol % to 15 mol %) is used as the ion exchange resin, the sulfonated polyethersulfone may be used alone as the ion exchange resin. On the other hand, when a sulfonated polyethersulfone having a sulfonation rate of more than 20 mol% and not more than 60 mol% (preferably 25 mol% to 50 mol%, more preferably 30 mol% to 45 mol%) is used as the ion exchange resin, the sulfonated polyethersulfone may be used in combination with a non-ion exchange resin as the ion exchange resin from the viewpoint of durability of the composite membrane. In this case, the mass content of the ion exchange resin in the mixture of the ion exchange resin and the non-ion exchange resin is preferably 10 mass% to 95 mass%, more preferably 20 mass% to 90 mass%, and even more preferably 25 mass% to 85 mass%.

[0073] The weight average molecular weight (Mw) of the ion exchange resin is preferably 30,000 to 1,000,000, more preferably 35,000 to 800,000, and even more preferably 40,000 to 500,000, from the viewpoint of the durability and mechanical properties of the composite membrane. The weight average molecular weight of the non-ion exchange resin is preferably 30,000 to 1,000,000, more preferably 50,000 to 800,000, and even more preferably 80,000 to 500,000, from the viewpoint of the durability of the composite membrane. The weight average molecular weight of the mixture of ion exchange resin and non-ion exchange resin is preferably 50,000 to 800,000, more preferably 80,000 to 650,000, and even more preferably 100,000 to 500,000, from the viewpoint of the durability of the composite membrane. In the present disclosure, the weight average molecular weight of the resin refers to a value measured by gel permeation chromatography (GPC).

[0074] In the composite membrane of the present disclosure, the content of the silica material relative to the total of the silica material and the ion exchange resin (when a non-ion exchange resin is used in combination, the total amount of the ion exchange resin and the non-ion exchange resin) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 0.7% by mass or more, from the viewpoint of improving membrane formability. In the composite membrane of the present disclosure, the content of the silica material relative to the total of the silica material and the ion exchange resin is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less, from the viewpoint of improving membrane formability. In the composite membrane of the present disclosure, the content of the silica material relative to the total of the silica material and the ion exchange resin is preferably 0.01% by mass to 90% by mass, more preferably 0.1% by mass to 80% by mass, even more preferably 0.5% by mass to 60% by mass, and particularly preferably 0.7% by mass to 50% by mass.

[0075] (Characteristics of Composite Membrane) From the viewpoint of gas barrier properties, the Gurley value of the composite membrane is 1,000 seconds / 100 mL or more, preferably 2,000 seconds / 100 mL or more, and more preferably 10,000 seconds / 100 mL or more. The Gurley value of the porous substrate is a value measured in accordance with JIS P8117:2009.

[0076] From the viewpoint of increasing the strength of the composite membrane, the average thickness of the composite membrane is preferably 3 μm or more, more preferably 4 μm or more, even more preferably 5 μm or more, particularly preferably 10 μm or more, and especially particularly preferably 15 μm or more. From the viewpoint of maintaining proton conductivity, the average thickness of the composite membrane is preferably 400 μm or less, more preferably 350 μm or less, even more preferably 300 μm or less, particularly preferably 150 μm or less, and especially particularly preferably 100 μm or less. The average thickness of the composite membrane is preferably 3 μm to 400 μm, more preferably 4 μm to 350 μm, even more preferably 5 μm to 300 μm, particularly preferably 10 μm to 150 μm, and especially particularly preferably 15 μm to 100 μm. The average thickness of the composite membrane is determined by measuring at 20 points with a contact-type thickness meter and averaging the measurements.

[0077] From the viewpoint of dimensional stability, the ratio (A / B) of the average membrane thickness A of the porous substrate to the average membrane thickness B of the composite membrane is preferably 0.10 or more, more preferably 0.12 or more, even more preferably 0.13 or more, and particularly preferably 0.14 or more. From the viewpoint of proton conductivity, the ratio (A / B) is preferably 1.0 or less, more preferably 0.80 or less, even more preferably 0.70 or less, and particularly preferably 0.60 or less. The ratio (A / B) is preferably 0.10 to 1.0, more preferably 0.12 to 0.80, even more preferably 0.13 to 0.70, and particularly preferably 0.14 to 0.60.

[0078] The basis weight of the composite membrane is 1 g / m from the viewpoint of handling. ２ More than 2 g / m is preferable. ２ More preferably, 5 g / m or more ２ More preferably, 7 g / m ２ The weight of the composite membrane is particularly preferably 100 g / m from the viewpoint of dimensional stability. ２ Preferably, 70 g / m or less ２ More preferably, 50 g / m or less ２ More preferably, 45 g / m or less ２ The following is particularly preferred: The basis weight of the composite membrane is 1 g / m ２ ~100g / m ２ is preferred, and 2 g / m ２ ~70g / m ２More preferably, 5 g / m ２ ~50g / m ２ More preferably, 7 g / m ２ ~45g / m ２ The weight per unit area of ​​the composite membrane is determined by measuring the weight of a sample of a certain size and dividing the weight by the area.

[0079] From the viewpoint of dimensional stability, the ratio (C / D) of the basis weight C of the porous substrate to the basis weight D of the composite membrane is preferably 0.03 or more, more preferably 0.04 or more, even more preferably 0.05 or more, and particularly preferably 0.055 or more. From the viewpoint of proton conductivity, the ratio (C / D) is preferably 0.5 or less, more preferably 0.4 or less, even more preferably 0.3 or less, and particularly preferably 0.2 or less. The ratio (C / D) is preferably 0.03 to 0.5, more preferably 0.04 to 0.4, even more preferably 0.05 to 0.3, and particularly preferably 0.055 to 0.2.

[0080] (Structure of Composite Membrane) The composite membrane of the present disclosure is not particularly limited in structure as long as it contains the above-mentioned porous substrate, silica material, and ion exchange resin. In order to ensure ionic conductivity between one side and the other side of the composite membrane, it is preferable that at least a portion of the pores of the porous substrate are filled with the silica material and the ion exchange resin, and it is more preferable that the entire pores of the porous substrate are filled with the silica material and the ion exchange resin.

[0081] The composite membrane of the present disclosure may have a structure including a porous substrate and an ion-conducting layer containing a silica material and an ion-exchange resin provided on at least one side of the porous substrate. The structure of the composite membrane of the present disclosure will be described below with reference to the drawings. The following drawings are schematic cross-sectional views primarily for illustrating the stacking order of layers, and the structure of each layer is omitted or simplified. The sizes of components in each drawing are conceptual, and the relative size relationships between components are not limited thereto. Components having substantially the same function are assigned the same reference numerals throughout the drawings, and redundant descriptions may be omitted. Figure 1 shows a cross-sectional view of one embodiment of the composite membrane of the present disclosure. The composite membrane 40 shown in Figure 1 includes a porous substrate 20 and ion-conducting layers 30 provided on both sides of the porous substrate 20. At least a portion of the pores of the porous substrate 20 are filled with a silica material and an ion-exchange resin. It is more preferable that the entire pores of the porous substrate are filled with a silica material and an ion-exchange resin. Figure 2 shows a cross-sectional view of another embodiment of the composite membrane of the present disclosure. The composite membrane 40 shown in Figure 2 includes a porous substrate 20 and an ion conduction layer 30 provided on one surface of the porous substrate 20. At least a portion of the pores of the porous substrate 20 are filled with a silica material and an ion exchange resin. It is more preferable that the entire pores of the porous substrate are filled with the silica material and the ion exchange resin. Details of the porous substrate 20 and the silica material and ion exchange resin that make up the ion conduction layer 30 are as described above.

[0082] (Method for Producing Composite Membrane) The composite membrane of the present disclosure may be produced by any method. For example, the composite membrane of the present disclosure may be produced by applying a liquid composition containing an ion exchange resin, a silica material, and a solvent to a porous substrate, or by contacting a porous substrate with a coating film formed from the liquid composition. The solvent contained in the liquid composition may be any solvent capable of dissolving or dispersing the ion exchange resin. Examples of the solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, and tert-butanol; diol solvents such as ethylene glycol, 1,2-propylene glycol, and 1,3-propylene glycol; aprotic solvents such as dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone; fluorine-containing alcohols; and fluorine-containing ethers. The liquid composition may contain additives such as dispersants (e.g., surfactants), wetting agents, antifoaming agents, and pH adjusters, as needed. A coating film formed from the liquid composition can be obtained, for example, by applying the liquid composition to a substrate. Examples of substrates include plastic films such as Teflon (registered trademark), polyester, polyimide, and polycarbonate; metal films such as aluminum, copper, iron, and stainless steel; and glass. Examples of methods for applying the liquid composition include batch methods such as the doctor knife method, bar coater method, spin coater method, and screen printing; and continuous methods such as the post-metering method and the pre-metering method. The post-metering method is a method in which an excess coating liquid is applied and then removed to achieve a predetermined film thickness. The pre-metering method is a method in which only the amount of coating liquid necessary to achieve a predetermined film thickness is applied. Examples of post-metering methods include an air doctor coater method, a blade coater method, a rod coater method, a knife coater method, a squeeze coater method, an impregnation coater method, and a comma coater method, while examples of pre-metering methods include a die coater method, a reverse roll coater method, a transfer roll coater method, a gravure coater method, a kiss roll coater method, a cast coater method, a spray coater method, a curtain coater method, a calendar coater method, and an extrusion coater method. A drying treatment may be performed to remove the solvent from the applied liquid composition. Drying is performed, for example, in a high-temperature environment. The drying temperature is preferably 40°C to 100°C.There is no particular limitation on the drying time, and the drying may be continued until the composite membrane becomes self-supporting.

[0083] The composite membrane of the present disclosure may be produced, for example, as follows: A liquid composition is applied to a substrate such as glass to form a coating film, and then a porous substrate is laminated on this coating film, allowed to stand for a while, and then dried to obtain a laminate having an ion-conducting layer on one side of the porous substrate. Next, a liquid composition is applied to the other side of the porous substrate to form a coating film, and then allowed to stand for a while, and then dried to obtain a laminate having ion-conducting layers on both sides of the porous substrate. Next, the laminate is washed with purified water such as ion-exchanged water or distilled water and dried to obtain a composite membrane. Alternatively, the composite membrane of the present disclosure may be produced, for example, as follows: A liquid composition is applied to a substrate such as glass to form a coating film, and then a porous substrate is laminated on this coating film, and then allowed to stand for a while, and then dried to obtain a laminate having an ion-conducting layer on one side of the porous substrate. Next, the laminate is washed with purified water such as ion-exchanged water or distilled water and dried to obtain a composite membrane. Drying conditions, coating conditions, washing conditions, etc. are appropriately set in consideration of the shape, film thickness, etc. of the composite membrane.

[0084] <Membrane-electrode assembly> The membrane-electrode assembly of the present disclosure includes the composite membrane of the present disclosure, a cathode laminated on one surface of the composite membrane, and an anode laminated on the other surface of the composite membrane. The membrane-electrode assembly of the present disclosure may have a configuration other than the composite membrane, the anode, and the cathode. For example, a gas diffusion layer may be disposed on the surface of the cathode opposite the composite membrane and on the surface of the anode opposite the composite membrane. The membrane-electrode assembly of the present disclosure is suitable for use in a polymer electrolyte fuel cell or a polymer electrolyte electrolysis device.

[0085] Examples of methods for producing a membrane electrode assembly include (1) a method in which a coating liquid containing an ion exchange resin, a catalyst metal, and a solvent is prepared, the coating liquid is directly applied to a composite membrane, the solvent in the coating liquid is dried to remove the coating liquid to form a catalyst layer, and the resulting mixture is sandwiched between gas diffusion layers on both sides, (2) a method in which the coating liquid is applied to a substrate that will serve as a gas diffusion layer, the substrate is dried to form a catalyst layer, and the resulting catalyst layer is then bonded to the composite membrane by a method such as hot pressing, and (3) a method in which the coating liquid is applied to a film (substrate) that is sufficiently stable against the solvent in the coating liquid, the substrate is dried to form a catalyst layer, the catalyst layer is hot pressed onto the composite membrane, the substrate film is peeled off, and the resulting mixture is sandwiched between gas diffusion layers. The ion exchange resin contained in the coating liquid may be the same as the ion exchange resin that constitutes the composite membrane.

[0086] When the membrane-electrode assembly of the present disclosure is used in a polymer electrolyte fuel cell, the gas diffusion layer is responsible for supplying fuel such as hydrogen or air to the electrode, collecting electrons generated by chemical reactions at the electrode, and keeping the composite membrane moist. Conventionally known materials with excellent gas permeability, acid resistance, electrical conductivity, and mechanical strength, such as carbon paper or carbon cloth, can be used as the gas diffusion layer. It is also preferable to provide a microporous layer on the electrode-side gas diffusion layer surface to promote water drainage and moisture retention in the gas diffusion layer. When the membrane-electrode assembly of the present disclosure is used in a polymer electrolyte electrolysis device, conventionally known materials composed of carbon materials such as carbon paper or carbon cloth, or metal materials such as stainless steel (e.g., Fe—Cr alloys, Fe—Ni—Cr alloys), aluminum, zinc, nickel, or titanium can be used as the gas diffusion layer.

[0087] When the membrane-electrode assembly of the present disclosure is used in a polymer electrolyte fuel cell, the catalyst contained in the catalyst layer may be the same or different between the anode side (hydrogen electrode) and the cathode side (air electrode), but a metal catalyst made of platinum or a platinum alloy supported on carbon is preferred. The carbon support is preferably a carbon support having a specific surface area of ​​50 m, because the metal catalyst is supported on the carbon support with good dispersibility and has excellent long-term stable electrode reaction activity. ２ / g to 2000m ２ / g is preferable. The metal catalyst is preferably a platinum catalyst because it is highly active in the hydrogen oxidation reaction at the anode and the oxygen reduction reaction at the cathode in a polymer electrolyte fuel cell. A platinum alloy is also preferable because it may further enhance the stability and activity of the electrode catalyst. The platinum alloy is preferably an alloy of platinum and one or more metals selected from the group consisting of platinum group metals other than platinum (ruthenium, rhodium, palladium, osmium, and iridium), gold, silver, chromium, iron, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, and tin. The platinum alloy may contain an intermetallic compound of platinum and a metal that can be alloyed with platinum. When a gas containing carbon monoxide is supplied to the anode, using an alloy containing platinum and ruthenium is preferable because it stabilizes the activity of the catalyst. When the membrane-electrode assembly of the present disclosure is used in a solid polymer electrolysis device, a metal catalyst made of platinum or a platinum alloy supported on carbon is preferably used on the cathode side (hydrogen electrode), while iridium, platinum, or the like can be used as a catalyst on the anode side (air electrode).

[0088] <Solid Polymer Electrolyte Fuel Cells, Solid Polymer Electrolysis Devices, and Electrochemical Hydrogen Compression Devices> The composite membrane of the present disclosure can be used in solid polymer fuel cells, solid polymer electrolysis devices, electrochemical hydrogen compression devices, and the like. Solid polymer electrolysis devices can produce hydrogen and other gases by electrolyzing water or organic solvents. The solid polymer fuel cells and solid polymer electrolysis devices of the present disclosure include a membrane-electrode assembly of the present disclosure and separators disposed on both sides of the membrane-electrode assembly. A single cell is formed by disposing a separator on the outer side of the membrane-electrode assembly of the present disclosure. Such a single cell may be used alone, or multiple single cells may be stacked with a cooling plate or the like interposed therebetween to form a solid polymer fuel cell or solid polymer electrolysis device. The separator serves to block fuel and air between solid polymer fuel cell stacks or solid polymer electrolysis device stacks and to provide a fuel flow path. Conventionally known carbon materials or metal materials such as stainless steel may be used. The electrochemical hydrogen compression device of the present disclosure also includes the composite membrane of the present disclosure. The electrochemical hydrogen compression device of the present disclosure may include, for example, the composite membrane of the present disclosure, a cathode provided on one side of the composite membrane, an anode provided on the other side of the composite membrane, an anode supply channel for supplying a hydrogen-containing gas to the anode, a cathode discharge channel for extracting purified hydrogen gas generated from the cathode, and a power source for applying a voltage to the anode and the cathode.

[0089] The composite membrane of the present disclosure will be described in more detail below with reference to examples. The materials, amounts used, ratios, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the composite membrane of the present disclosure should not be construed as being limited by the specific examples shown below.

[0090] (Preparation of porous substrate A) 60 parts by mass of ultra-high molecular weight polyethylene having a weight average molecular weight (Mw) of 4.6 million and 100 parts by mass of polyethylene terephthalate having a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m ３A polyethylene composition was prepared by mixing 40 parts by mass of a high-density polyethylene having a polyethylene composition of 100% by mass with 100% by mass of a polyethylene terephthalate (PE) copolymer. Next, a polyethylene solution was prepared by mixing the polyethylene composition with decalin as a solvent so that the concentration of the polyethylene composition was 25% by mass. The polyethylene solution was extruded into a sheet form through a die at 166°C, and the extrudate was then cooled in a water bath at 20°C to obtain a first gel-like sheet. The first gel-like sheet was pre-dried at 30°C for 7 minutes, then stretched 1.2 times in the longitudinal direction, and then dried at 60°C for 5 minutes to obtain a second gel-like sheet. The residual amount of solvent in the second gel-like sheet was adjusted to less than 1% by mass. Next, as a second stretching step, the second gel-like sheet was stretched 3.5 times in the longitudinal direction at 90°C, and then stretched 9.0 times in the transverse direction at 125°C. Immediately after the second stretching step, a heat treatment (heat setting) was performed at 128°C. The heat-set sheet was continuously immersed in a methylene chloride bath divided into three tanks for a total of 2.5 minutes, while the solvent in the sheet was extracted. In addition, when the side where immersion starts is the first tank and the side where immersion ends is the third tank, the purity of the cleaning solvent is (low) first tank < second tank < third tank (high). After carrying out the sheet from the methylene chloride bath, the sheet was dried on a heated roll at 40 ° C to remove methylene chloride. Thereafter, the sheet was annealed in a heated atmosphere at 110 ° C. Through the above processes, a porous substrate A made of a polyolefin porous membrane was obtained. The physical properties of the obtained porous substrate A are shown in Table 1. The measurement method for each physical property will be described later.

[0091] (Preparation of porous substrate B) 12 parts by mass of ultra-high molecular weight polyethylene having a weight average molecular weight of 4.6 million and 12 parts by mass of polyethylene terephthalate having a weight average molecular weight of 560,000 and a density of 950 kg / m ３A polyethylene composition was used, which was a mixture of 3 parts by mass of a high-density polyethylene (HPE) and 72 parts by mass of liquid paraffin and 13 parts by mass of decalin (a pre-prepared solvent mixture) so that the polyethylene composition had a concentration of 15% by mass. A polyethylene solution was prepared by mixing the polyethylene solution with a pre-prepared solvent mixture of 72 parts by mass of liquid paraffin and 13 parts by mass of decalin. The polyethylene solution was extruded into a sheet form through a die at 160°C. The extrudate was then cooled to 25°C in a water bath, and a water flow was created on the surface of the water bath to prevent the mixed solvent released from the gelled sheet and floating on the water surface from re-adhering to the sheet, yielding a gel-like sheet. The gel-like sheet was dried at 55°C for 10 minutes and then at 95°C for 10 minutes to remove the decalin from the gel-like sheet. The gel-like sheet was then stretched in the longitudinal direction at 100°C at a stretching ratio of 5.5 times, and subsequently in the transverse direction at 110°C at a stretching ratio of 13 times, followed immediately by heat treatment (heat setting) at 135°C. Next, the gel-like sheet was continuously immersed in two separate methylene chloride baths for 30 seconds each, while extracting the liquid paraffin in the sheet. Note that the side where immersion begins is the first tank, and the side where immersion ends is the second tank, and the purity of the cleaning solvent is (low) first tank < (high) second tank. Thereafter, the methylene chloride was dried and removed at 45 ° C, and the porous substrate B made of a polyolefin porous membrane was obtained by annealing while being conveyed on a roller heated to 120 ° C. The physical properties of the obtained porous substrate B are shown in Table 1.

[0092] (Preparation of porous substrate C) 15 parts by mass of ultra-high molecular weight polyethylene having a weight average molecular weight (Mw) of 4.6 million and 15 parts by mass of polyethylene having a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m ３A polyethylene composition was prepared by mixing 85 parts by mass of a high-density polyethylene having a polyethylene composition of 100% by mass with 100% by mass of a polyethylene terephthalate (PE) copolymer. Next, a polyethylene solution was prepared by mixing the polyethylene composition with decalin as a solvent so that the concentration of the polyethylene composition was 30% by mass. The polyethylene solution was extruded into a sheet form through a die at a temperature of 158°C, and the extrudate was then cooled in a water bath at a water temperature of 20°C to obtain a first gel-like sheet. The first gel-like sheet was pre-dried at 60°C for 10 minutes, then subjected to a primary stretching in the longitudinal direction at 1.2 times its original length, and then subjected to main drying at 60°C for 5 minutes to obtain a second gel-like sheet. The residual amount of solvent in the second gel-like sheet was adjusted to less than 1% by mass. Next, as a secondary stretching, the second gel-like sheet was stretched in the longitudinal direction at a temperature of 90°C at a stretching ratio of 4.5 times, and subsequently stretched in the transverse direction at a temperature of 125°C at a stretching ratio of 10.0 times. Immediately after the secondary stretching, a heat treatment (heat setting) was performed at 134°C. The heat-set sheet was continuously immersed in a methylene chloride bath divided into three tanks for a total of 2.5 minutes, while the solvent in the sheet was extracted. In addition, when the side where immersion starts is the first tank and the side where immersion ends is the third tank, the purity of the cleaning solvent is (low) first tank < second tank < third tank (high). After carrying out the sheet from the methylene chloride bath, the sheet was dried on a heated roll at 40 ° C to remove methylene chloride. Thereafter, the sheet was annealed in a heated atmosphere at 80 ° C. A porous substrate C made of a polyolefin porous membrane was obtained through the above processes. The physical properties of the obtained porous substrate C are shown in Table 1.

[0093] -Weight-average molecular weight of polyethylene- The weight-average molecular weight of polyethylene was measured by gel permeation chromatography. Specifically, the polyethylene to be measured was heated and dissolved in o-dichlorobenzene, and measurement was carried out by gel permeation chromatography (system: Alliance GPC 2000 manufactured by Waters Corporation, columns: GMH6-HT and GMH6-HTL) under conditions of a column temperature of 135°C and a flow rate of 1.0 mL / min. Monodisperse polystyrene (manufactured by Tosoh Corporation) was used to calibrate the molecular weight.

[0094] (Characteristics of porous substrate) The characteristics of the porous substrate were measured by the following method. - Average film thickness A of porous substrate - The average film thickness A of the porous substrate was measured using a contact film thickness meter (manufactured by Mitutoyo Corporation, ABS Digimatic Indicator, Model ID: ID-S112X). Specifically, the film thickness of the porous substrate was measured at 20 points, and the arithmetic mean value was taken as the average film thickness A of the porous substrate. As the contact terminal, a cylindrical terminal with a bottom surface having a diameter of 6.5 mm was used.

[0095] -Weight C of Porous Substrate- A 10 cm x 10 cm sample was prepared by cutting the porous substrate. The weight C of the porous substrate was determined by multiplying the measured mass of the sample by 100.

[0096] -Porosity of Porous Substrate- The porosity (ε) of the porous substrate was calculated by the following formula: ε (%) = {1 - Ws / (ds·t)} × 100, where Ws is the basis weight (g / m) of the porous substrate. ２ ) ds: true density of polyolefin (g / cm ３ ) t: film thickness of porous substrate (μm) The basis weight of the porous substrate was determined by the method described above.

[0097] -Air permeability (Gurley value) of porous substrate- The Gurley value of the porous substrate was measured using a Gurley densometer manufactured by Toyo Seiki Seisaku-sho in accordance with JIS P8117: 2009. The measurement was performed by measuring the time it took for 200 ml of air to pass through a 28.6 mmφ sample, and then halving that time to convert it to a value per 100 ml.

[0098] - Average pore diameter of porous substrate - The average pore diameter of the porous substrate was determined by the half-dry method specified in ASTM E1294-89 using a PMI Perm Porometer (model: CFP-1200-AEXL) and PMI Galwick (surface tension 15.9 dyn / cm) as the immersion liquid. The measurement temperature was 25°C, and the measurement pressure was changed in the range of 0 kPa to 600 kPa.

[0099]

[0100] (Production of Silica Material) 10 parts by mass of silicon dioxide (Sigma-Aldrich, primary particle number average particle diameter: 10 nm to 20 nm, silica particles) was gradually added to 400 parts by mass of concentrated sulfuric acid (concentration: 99.9%) at 25°C, and the mixture was treated at 1500 rpm for 15 minutes using a SpeedMixer DAC400 manufactured by Hauschild, to obtain a dispersion of silica particles dispersed in concentrated sulfuric acid. The resulting dispersion was gradually added to 4000 parts by mass of deionized water, washed, and then filtered to recover the resulting silica particles as a residue. The recovered silica particles were further washed with 4000 parts by mass of deionized water and filtered to recover the residue. The resulting residue was washed with 200 parts by mass of acetone and filtered again. The residue was dried in a hot air dryer at 80°C to obtain 14.5 parts by mass of a particulate silica material. The degree of sulfonation of this silica material based on XRF was 0.3% as measured by the method described below.The pH of the dispersion of this silica material was 1.2 as measured by the method described below.

[0101] - pH Measurement - 0.1 g of silica material was dispersed in 1.9 g of deionized water to prepare a dispersion (5 mass % dispersion). The pH of the dispersion was measured at 25°C using a pH meter (PCE-PH18).

[0102] - Measurement of sulfonation degree - The silica material was weighed into a measurement container under a helium atmosphere and measured using an XRF measurement device (PANalytical AxiosMAX). The sulfur atom concentration and silicon atom concentration were determined from the obtained spectrum, and the ratio of the sulfur atom concentration to the total of the silicon atom concentration and sulfur atom concentration was taken as the sulfonation degree. In addition, SEM-EDX measurement confirmed that the silica material had sulfonic acid groups on its surface. - Measurement of number-average particle diameter of primary particles - The number-average particle diameter of primary particles of silica particles was calculated as the arithmetic average of the circle-equivalent diameters of 50 silica particles determined by observation with a scanning electron microscope.

[0103] (Preparation of Liquid Composition 1) The above-mentioned silica material was added to N,N-dimethylacetamide (DMAc) and dispersed in an ultrasonic bath until uniform, thereby obtaining a silica material dispersion. Subsequently, sulfonated polyethersulfone (s-PES, EW: 500 g / eq, weight-average molecular weight: 140,000, acts as an ion exchange resin) with a sulfonation rate of 34.1 mol% was added to the silica material dispersion while stirring, thereby obtaining Liquid Composition 1 with a solids concentration of 10% by mass and a silica material content of 1% by mass relative to the solids. The weight-average molecular weight of s-PES was determined according to the following method. Device name: High performance liquid chromatograph LC-20A series (Shimadzu Corporation) Column oven: CTO-20A Mobile phase: N-methyl-2-pyrrolidone Autosampler: SIL-20AHT LC workstation: LC solution Flow rate: 0.3 ml / min Differential refractometer detector: RID-10A Oven temperature: 60°C Molecular weight standard sample: Polystyrene

[0104] (Preparation of Liquid Composition 2) Liquid composition 2 was obtained in the same manner as in preparation of liquid composition 1, except that the solid concentration was 10% by mass and the content of silica material in the solids was 2% by mass.

[0105] (Preparation of Liquid Composition 3) Liquid composition 3 was obtained in the same manner as in preparation of liquid composition 1, except that the solid concentration was 10% by mass and the content of silica material in the solids was 5% by mass.

[0106] (Preparation of Liquid Composition 4) Liquid composition 4 was obtained in the same manner as in preparation of liquid composition 1, except that the solid concentration was 10% by mass and the content of silica material in the solids was 10% by mass.

[0107] (Preparation of Liquid Composition 5) N,N-dimethylacetamide (DMAc) was stirred while sulfonated polyethersulfone (s-PES, EW: 500 g / eq, weight average molecular weight: 140,000) having a sulfonation rate of 34.1 mol% was added to obtain Liquid Composition 5 having a solid concentration of 10 mass% and a silica material content of 0 mass% in the solid content.

[0108] [Example 1] Liquid composition 1 was cast onto a glass plate using a doctor knife (200 μm), and porous substrate A was laminated on the cast liquid composition 1 without wrinkles. After leaving it to stand for 10 minutes, it was dried for 30 minutes in a hot air dryer at 60°C. Liquid composition 1 was cast onto the dried laminate using a doctor knife (200 μm) and then left to stand for 10 minutes. After drying for 30 minutes in a hot air dryer at 60°C, it was washed with ion-exchanged water for 10 minutes. It was further fixed to a metal frame and dried for 10 minutes at 60°C to obtain composite membrane 1.

[0109] Example 2 Composite membrane 2 was obtained in the same manner as in Example 1, except that liquid composition 2 was used instead of liquid composition 1.

[0110] Example 3 Composite membrane 3 was obtained in the same manner as in Example 1, except that liquid composition 3 was used instead of liquid composition 1.

[0111] Example 4 Composite membrane 4 was obtained in the same manner as in Example 1, except that liquid composition 4 was used instead of liquid composition 1.

[0112] [Example 5] Liquid composition 3 was cast onto a glass plate using a doctor knife (100 μm), and porous substrate B was laminated on the cast liquid composition 3 without wrinkles. After leaving it to stand for 10 minutes, it was dried for 30 minutes in a hot air dryer at 60°C. Liquid composition 3 was cast onto the dried laminate using a doctor knife (100 μm) and then left to stand for 10 minutes. After drying for 30 minutes in a hot air dryer at 60°C, it was washed with ion-exchanged water for 10 minutes. It was further fixed to a metal frame and dried for 10 minutes at 60°C to obtain composite film 5.

[0113] Example 6 A composite membrane 6 was obtained in the same manner as in Example 5, except that liquid composition 4 was used instead of liquid composition 3.

[0114] Example 7 A composite membrane 7 was obtained in the same manner as in Example 3, except that the porous substrate C was used instead of the porous substrate A.

[0115] Reference Example 1 Liquid composition 1 was cast onto a glass plate using a doctor knife (200 μm), and the cast liquid composition 1 was left to stand for 10 minutes, and then dried in a hot air dryer at 60°C for 30 minutes. Liquid composition 1 was cast again onto the dried resin film using a doctor knife (200 μm), and then left to stand for 10 minutes. After drying for 30 minutes in a hot air dryer at 60°C, the film was washed with ion-exchanged water for 10 minutes. The film was then fixed to a metal frame and dried for 10 minutes at 60°C to obtain reference resin film 1.

[0116] Reference Example 2 A reference resin film 2 was obtained in the same manner as in Reference Example 1, except that Liquid Composition 3 was used instead of Liquid Composition 1.

[0117] [Reference Example 3] Liquid composition 3 was cast onto a glass plate using a doctor knife (200 μm) and dried for 30 minutes in a hot air dryer at 60°C. The resulting mixture was washed with ion-exchanged water for 10 minutes. It was then fixed to a metal frame and dried for 10 minutes at 60°C to obtain reference resin film 3.

[0118] Reference Example 4 A reference resin film 4 was obtained in the same manner as in Reference Example 1, except that Liquid Composition 4 was used instead of Liquid Composition 1.

[0119] Comparative Example 1 Liquid composition 5 was cast onto a glass plate using a doctor knife (200 μm), and porous substrate A was laminated on the cast liquid composition 5 without wrinkles. After leaving it to stand for 10 minutes, it was dried for 30 minutes in a hot air dryer at 60°C. Liquid composition 5 was cast onto the dried laminate using a doctor knife (200 μm) and then left to stand for 10 minutes. After drying for 30 minutes in a hot air dryer at 60°C, it was washed with ion-exchanged water for 10 minutes. It was further fixed to a metal frame and dried for 10 minutes at 60°C to obtain comparative composite membrane 1.

[0120] Comparative Example 2 Liquid composition 5 was cast onto a glass plate using a doctor knife (100 μm), and porous substrate B was laminated on the cast liquid composition 5 without wrinkles. After leaving it to stand for 10 minutes, it was dried for 10 minutes in a hot air dryer at 60°C. Liquid composition 5 was cast onto the dried laminate using a doctor knife (100 μm) and then left to stand for 10 minutes. After drying for 30 minutes in a hot air dryer at 60°C, it was washed with ion-exchanged water for 10 minutes. It was further fixed to a metal frame and dried for 10 minutes at 60°C to obtain comparative composite membrane 2.

[0121] [Comparative Example 3] Liquid composition 5 was cast onto a glass plate using a doctor knife (200 μm), and the cast liquid composition 5 was left to stand for 10 minutes and then dried in a hot air dryer at 60°C for 30 minutes. Liquid composition 5 was cast again onto the dried resin film using a doctor knife (200 μm) and then left to stand for 10 minutes. After drying for 30 minutes in a hot air dryer at 60°C, the film was washed with ion-exchanged water for 10 minutes. The film was then fixed to a metal frame and dried for 10 minutes at 60°C to obtain comparative resin film 3.

[0122] (Evaluation) The composite membranes and resin membranes obtained in the Examples, Reference Examples, and Comparative Examples as described above were evaluated by the following methods. The results obtained are shown in Table 2. - Basis weight D of composite membrane and basis weight of resin membrane - The basis weight D of the composite membrane and the basis weight of the resin membrane were determined in the same manner as the above-mentioned "Basis weight C of porous substrate". - Average film thickness B of composite membrane and average film thickness of resin membrane - The average film thickness B of the composite membrane and the average film thickness of the resin membrane were determined in the same manner as the above-mentioned "Average film thickness A of porous substrate".

[0123] - Amount of adhesion - The amount of adhesion of the silica material and the ion exchange resin to the porous substrate was calculated from the basis weight C of the porous substrate and the basis weight D of the composite membrane obtained as described above. ２ ) = basis weight D (g / m ２ ) - basis weight C (g / m ２ )

[0124] -Air permeability (Gurley value) of composite membrane and resin membrane- The Gurley values ​​of the composite membrane and resin membrane were determined in the same manner as in the above-mentioned "Air permeability (Gurley value) of porous substrate." In Table 2, "∞" means that the Gurley value is 10,000 seconds / 100 mL or more.

[0125] - Content of each component (mass %) - The percentage of s-PES, porous substrate, and silica material (sSiO ) in the entire composite membrane was calculated based on the amount of silica material and ion exchange resin attached to the porous substrate, the proportion of s-PES and silica material in the solid content contained in the liquid composition, and the basis weight of the composite membrane and porous substrate. ２ The content (mass%) of

[0126] - Proton Conductivity - The proton conductivity of the composite membrane and the resin membrane was measured by the following method. Using an electrochemical impedance measurement device (TSC Battery manufactured by RHD Instruments), impedance measurement was performed in the thickness direction of the composite membrane or the resin membrane in the frequency range of 50 Hz to 107 Hz, and the proton conductivity was measured and used as an index of proton conductivity. The composite membranes and the resin membranes used in the above measurements had been stored in deionized water and were heated to 80°C in a measurement cell before being subjected to the proton conductivity measurement.

[0127] - Area change rate - The composite film and resin film were dried in a dryer at 50°C until there was no change in weight. Thereafter, the lengths of the composite film and resin film in the longitudinal and width directions were measured (Condition 1). The linear distance connecting the centers of the opposing sides was taken as the length in the longitudinal direction and the length in the width direction. The composite film and resin film were kept in pure water for 64 hours, then subjected to hot water treatment at 80°C for 2 hours, and the lengths in the longitudinal and width directions were immediately measured (Condition 2). The dimensional change rate was calculated using the above measurement results, and the area was calculated by length in the longitudinal direction x length in the width direction, and the area change rate was calculated as follows: Area change rate A = [area (Condition 2) - area (Condition 1)] x 100 / area (Condition 2)

[0128] - Ratio (A / B) of average film thickness A of porous substrate to average film thickness B of composite membrane - From the average film thickness A of the porous substrate and the average film thickness B of the composite membrane determined as described above, the ratio (A / B) of the average film thickness A of the porous substrate to the average film thickness B of the composite membrane was calculated. - Ratio (C / D) of basis weight C of porous substrate to basis weight D of composite membrane - From the basis weight C of the porous substrate and the basis weight D of the composite membrane determined as described above, the ratio (C / D) of the basis weight C of the porous substrate to the basis weight D of the composite membrane was calculated.

[0129]

[0130] As is clear from the evaluation results in Table 2, the composite membranes of the Examples are superior in proton conductivity and dimensional stability compared to the composite membranes or resin membranes of the Comparative Examples. Furthermore, as shown in Table 2, the proton conductivity was measured for the composite membranes of Examples 1-7 and Comparative Examples 1-2, which indicates that a proton conduction path is established between one surface and the other surface of these composite membranes. This suggests that at least a portion of the pores of the porous substrate are filled with a silica material and an ion exchange resin, and that the composite membrane of the present invention is provided with an ion-conducting layer.

[0131] The disclosure of Japanese Patent Application No. 2023-158829, filed on September 22, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A composite membrane comprising: a porous substrate including a polyolefin microporous membrane; a silica material having a substrate including silicon dioxide and having sulfonic acid groups on at least the surface of the substrate; and an ion exchange resin, the composite membrane having a Gurley value of 1,000 seconds / 100 mL or more.

2. The composite membrane according to claim 1, wherein the porosity of said porous substrate is from 50% to 90%.

3. The composite membrane according to claim 1, wherein the pores of the porous substrate are at least partially filled with the silica material and the ion exchange resin.

4. The composite membrane according to claim 1, comprising: the porous substrate; and an ion-conducting layer, containing the silica material and the ion exchange resin, provided on at least one surface side of the porous substrate.

5. The composite membrane according to claim 1, wherein the ratio (A / B) of the average thickness A of the porous substrate to the average thickness B of the composite membrane is 0.10 to 1.

0.

6. The composite membrane according to claim 1, wherein the ratio (C / D) of the basis weight C of the porous substrate to the basis weight D of the composite membrane is 0.03 to 0.

5.

7. The composite membrane according to claim 1, wherein the ratio of the concentration of sulfur atoms to the total concentration of silicon atoms and sulfur atoms in the silica material, as determined by X-ray fluorescence spectroscopy (XRF), is 0.01% to 90%.

8. The composite membrane of claim 1, wherein said substrate is in particulate form.

9. The composite membrane according to claim 1, wherein the substrate is silica particles, and the number average particle size of the primary particles of the silica particles is 1 nm to 500 nm.

10. A membrane-electrode assembly comprising the composite membrane according to any one of claims 1 to 9, a cathode laminated on one surface of the composite membrane, and an anode laminated on the other surface of the composite membrane.

11. A solid polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 10 and separators disposed on both sides of the membrane-electrode assembly.

12. A solid polymer electrolytic device comprising the membrane-electrode assembly according to claim 10 and separators disposed on both sides of the membrane-electrode assembly.

13. An electrochemical hydrogen compression device having the composite membrane according to any one of claims 1 to 9.

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