Electrolyte membrane, electrolyte membrane with catalyst layer, membrane electrode assembly, polymer electrolyte fuel cell, and polymer electrolyte water electrolysis device

Abstract

To improve the mechanical strength of hydrocarbon-based electrolyte membranes. [Solution] An electrolyte membrane 10A comprising a porous membrane 1 and a hydrocarbon-based electrolyte polymer filled in the pores 2 of the porous membrane 1, wherein the porous membrane 1 is formed of a material containing a hydrocarbon-based resin, and the differential permeate flow rate distribution of the porous membrane 1 measured by the bubble point method has a peak in the pore diameter range of 0.01 to 1 μm.

Description

[Technical Field]

[0001] This disclosure relates to an electrolyte membrane, an electrolyte membrane with a catalyst layer, a membrane electrode assembly, a polymer electrolyte fuel cell, and a polymer electrolyte water electrolysis device. [Background technology]

[0002] In recent years, fuel cells have gained attention as a highly energy-efficient new energy technology, driven by environmental concerns. Among these, polymer electrolyte fuel cells (polymer electrolytes), which use polymer materials as electrolytes, are particularly noteworthy because they have a high maximum current density and operate at low temperatures, making them suitable for powering vehicles and other mobile devices, as well as for small-capacity power sources for portable electronic devices. Furthermore, from a carbon-neutral perspective, the utilization of polymer electrolyte hydrogen energy, an application of fuel cell technology, is also attracting attention.

[0003] As electrolyte membranes used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers, electrolyte membranes using fluorine-based electrolyte polymers (fluorine-based electrolyte membranes) are known (see, for example, Patent Document 1). Although fluorine-based electrolyte membranes are widely used in electrolyte applications due to their high proton conductivity, they have the problems of being expensive and having a large environmental impact.

[0004] For these reasons, the development of electrolyte membranes using hydrocarbon-based electrolyte polymers (hydrocarbon-based electrolyte membranes) is also progressing. For example, Patent Document 2 discloses an invention relating to a hydrocarbon-based electrolyte membrane consisting of a block copolymer containing one or more segments (A1) containing ionic groups and one or more segments (A2) that do not contain ionic groups. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-204119 [Patent Document 2] International Publication No. 2013-031675 [Overview of the project] [Problems that the invention aims to solve]

[0006] Hydrocarbon-based electrolyte membranes require higher mechanical strength to prevent rupture during transportation and use.

[0007] Therefore, one aspect of this disclosure aims to improve the mechanical strength of hydrocarbon-based electrolyte membranes. [Means for solving the problem]

[0008] This disclosure provides, in several respects, the following [1] to

[12] .

[0009] [1] The material comprises a porous membrane and a hydrocarbon-based electrolyte polymer filled in the pores of the porous membrane. The porous membrane is formed from a material containing a hydrocarbon resin. An electrolyte membrane in which the differential permeate flow rate distribution of the porous membrane, measured by the bubble point method, has a peak in the pore size range of 0.01 to 1 μm.

[0010] [2] The electrolyte membrane according to [1], wherein the differential permeation flow rate distribution of the porous membrane has a peak in the pore diameter range of 10 to 1000 μm.

[0011] [3] The electrolyte membrane according to [1] or [2], wherein the porosity of the porous membrane is 30 to 95 volume%.

[0012] [4] The electrolyte membrane according to any one of [1] to [3], wherein the hydrocarbon resin is a polyolefin resin.

[0013] [5] An electrolyte membrane according to any one of [1] to [4], having a layer containing the hydrocarbon-based electrolyte polymer on one or both sides of the porous membrane.

[0014] [6] The electrolyte membrane according to any one of [1] to [5], wherein the ratio of the thickness of the porous membrane to the thickness of the electrolyte membrane is 0.1 to 1.

[0015] [7] The hydrocarbon electrolyte polymer comprises hydrophilic constituent units having ion exchange groups and hydrophobic constituent units not having ion exchange groups. The electrolyte membrane according to any one of [1] to [6], wherein the ion exchange group comprises at least one selected from the group consisting of a sulfone group, an alkylsulfone group, and a sulfonimide group.

[0016] [8] The electrolyte membrane according to any one of [1] to [7], wherein the hydrocarbon-based electrolyte polymer comprises a polymer having a structure represented by the following formula (1). [ka] [In formula (1), A 1 This represents the constituent unit shown in formula (a1) below, A 2 This represents the constituent unit expressed by the following formula (a2): L 1 and L 2 Each of these independently represents a single bond, -O-, -S-, or -SO2-. n represents an integer between 10 and 100. * indicates a bond. Multiple A 1 They are identical to each other, Multiple A 2 They are identical to each other, Multiple L 1 They may be the same or different from each other. Multiple L 2 They may be the same or different from each other. [ka] [In formula (a1), IExG represents an ion exchange group, L 3 represents a single bond, -O-, -S-, -SO2- or -CO-, x represents an integer from 2 to 10, * represents a bond. The plurality of IExG may be the same or different from each other, The plurality of L 3 may be the same or different from each other.] [Chemical formula] [In formula (a2), Ar represents an arylene group having no ion exchange group, L 4 represents a single bond, -O-, -S-, -SO2- or -CO-, y represents an integer from 3 to 20, * represents a bond. The plurality of Ar may be the same or different from each other, [[ID=3-7]] The plurality of L 4 may be the same or different from each other.]

[0017] [9] [1] to [8] described in any one of the electrolyte membranes, and a catalyst layer disposed on one or both surfaces of the electrolyte membrane, an electrolyte membrane with a catalyst layer.

[0018]

[10] [1] to [8] described in any one of the electrolyte membranes, and an electrode layer disposed on one or both surfaces of the electrolyte membrane, a membrane electrode assembly.

[0019]

[11]

[10] A solid polymer fuel cell comprising the membrane electrode assembly described in.

[0020]

[12]

[10] A solid polymer water electrolysis device comprising the membrane electrode assembly described in. [Advantages of the Invention]

[0021] According to this disclosure, the mechanical strength of hydrocarbon-based electrolyte membranes can be improved. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 is a schematic cross-sectional view of an electrolyte membrane according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic plan view showing an example of a porous membrane. [Figure 3] Figure 3 is a schematic cross-sectional view of an electrolyte membrane according to another embodiment of the present disclosure. [Figure 4] Figure 4 is a planar SEM image of porous membrane A used in the example. [Figure 5] Figure 5 is a planar SEM image of porous membrane B used in the example. [Figure 6] Figure 6 is a planar SEM image of nonwoven fabric A used in the comparative example. [Figure 7] Figure 7 is a graph showing the differential permeation flow rate distribution of porous membrane A used in the example. [Figure 8] Figure 8 is a graph showing the differential permeation flow rate distribution of porous membrane B used in the example. [Figure 9] Figure 9 is a graph showing the differential permeation flow rate distribution of nonwoven fabric A used in the comparative example. [Modes for carrying out the invention]

[0023] The following describes exemplary embodiments of this disclosure. However, this disclosure is not limited to the embodiments described below. In this specification, numerical ranges indicated using "~" indicate a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. Also, unless otherwise explicitly stated, the units of the numbers before and after "~" are the same. Furthermore, each configuration and parameter disclosed in this specification can be combined in any way, and the upper and lower limits described individually can be combined in any way.

[0024] <Electrolyte membrane> Figure 1 is a schematic cross-sectional view of an electrolyte membrane according to one embodiment. The electrolyte membrane 10A in Figure 1 includes a porous membrane 1 and a filler 3 containing a hydrocarbon-based electrolyte polymer, which is filled into the pores 2 of the porous membrane 1. In the electrolyte membrane 10A, the porous membrane 1 is exposed on the surface of the electrolyte membrane 10A. Since the electrolyte membrane 10A contains a hydrocarbon-based electrolyte polymer as an electrolyte, it is a hydrocarbon-based electrolyte membrane. In this specification, "hydrocarbon-based electrolyte polymer" means an electrolyte polymer that is substantially free of fluorine atoms (i.e., the fluorine content in the electrolyte polymer is 5% by mass or less).

[0025] (porous membrane) The porous membrane 1 contributes to improving the mechanical strength of the electrolyte membrane 10A as a reinforcing material. The porous membrane 1 is, for example, in the form of a film and is formed from a material containing a hydrocarbon resin. The hydrocarbon resin is a resin consisting of hydrocarbon compounds that do not contain fluorine atoms in their molecules. Because the porous membrane is formed from a material containing a hydrocarbon resin, the hydrocarbon electrolyte polymer is more easily filled into the pores of the porous membrane, improving the mechanical strength and proton conductivity of the electrolyte membrane.

[0026] As the hydrocarbon resin, for example, at least one selected from the group consisting of polyolefin resins, polyester resins, polyphenylene sulfide resins, polyetherimide resins, polyimide resins, polyurethane resins, and polyethersulfone resins can be used. These resins provide sufficient stability in acidic environments in fuel cells and water electrolyzers. As the polyolefin resin, for example, at least one selected from the group consisting of polyethylene resins and polypropylene resins can be used. As the polyester resin, for example, at least one selected from the group consisting of polyethylene terephthalate resins and polybutylene terephthalate resins can be used.

[0027] From the viewpoint of reducing manufacturing costs and environmental impact, it is preferable to use polyolefin resins, and more preferable to use at least one resin selected from the group consisting of polyethylene and polypropylene. In other words, the porous membrane 1 is preferably a polyolefin resin film (a film mainly composed of polyolefin resin), and more preferably a polyethylene film (a film mainly composed of polyethylene) or a polypropylene film (a film mainly composed of polypropylene). Although polyolefin resins tend to have inferior mechanical strength, according to this disclosure, the mechanical strength can be improved, so even when using polyolefin resins, it is easy to obtain an electrolyte membrane with sufficient mechanical strength. Among polyolefin resins, polyethylene is most likely to provide excellent mechanical strength. In this specification, the main component means the component with the highest content among the contained components. The content of the main component is, for example, 60% by mass or more, and may be 80% by mass or more or 90% by mass or more.

[0028] The material containing the hydrocarbon resin may consist solely of the hydrocarbon resin, but may also contain other components as long as they do not impair the effects of the present disclosure. Other components may include, for example, at least one selected from the group consisting of water-retaining inorganic substances and radical scavenging agents. Specifically, for example, at least one selected from the group consisting of silica, cerium oxide, and manganese oxide may be used. The total content of other components may be 0 to 10% by mass, based on the total mass of the material.

[0029] The porous membrane 1 has finer pores compared to membranes formed from fibers such as nonwoven fabrics. Specifically, the differential permeate flow rate distribution of the porous membrane 1, measured by the bubble point method, has a peak (hereinafter also referred to as the "first peak") in the pore diameter range of 0.01 to 1 μm.

[0030] The bubble point method is a method specified in ASTM F316-86 and JIS K 3832. It involves impregnating a porous material with a liquid and gradually increasing the pressure of the supplied air. The pore diameter is calculated by measuring the pressure at which the liquid is forced out of the pores (bubble point) and the flow rate of gas permeating through the membrane at each pressure (gas permeation flow rate). In the bubble point method, the gas permeation flow rate at each measurement point (each pore diameter) is determined by calculating the difference in cumulative permeation flow rate between individual measurement points from the cumulative data of gas permeation flow rate corresponding to the applied pressure of the supplied gas (cumulative permeation flow rate). The differential permeation flow rate distribution shows the relationship between the ratio of the gas permeation flow rate at each measurement point (hereinafter referred to as "differential permeation flow rate") to the cumulative permeation flow rate and the pore diameter (distribution of differential permeation flow rate with respect to pore diameter). In the differential permeation flow rate distribution, peaks appear in the range of pore diameters where there are more pores. In this specification, for example, within a pore diameter range of one to two orders of magnitude, such as 0.01 to 1 μm, the point where the differential permeation flow rate is maximum is considered a peak in the differential permeation flow rate distribution, and the position of the peak's apex (peak top) is considered the peak's position. The differential permeation flow rate distribution can be measured, for example, under the following conditions. [conditions] A Φ25mm sample piece is immersed in a wetting solution (Galpore (surface tension 16.3 dyne / cm)), placed in the sample chamber, and measurement begins. During the measurement, the supply air pressure is controlled, and the cumulative gas permeation flow rate with respect to the applied pressure is measured. Then, the following relationship is expressed: The relationship D = 0.415 × γ ÷ P (D: pore size, γ: surface tension of the reagent, P: pressure) Using this method, the pore diameter D is calculated from the applied pressure and the surface tension of the reagent. Additionally, the difference in cumulative permeation flow rate between measurement points (differential permeation flow rate) is calculated from the measured gas permeation flow rate (cumulative permeation flow rate) at each measurement point. The differential permeation flow rate distribution is determined by plotting the obtained differential permeation flow rates against the pore diameter corresponding to the pressure at each measurement point.

[0031] By having a first peak in the differential permeation flow rate distribution of the porous membrane within the above-mentioned pore diameter range, it is possible to improve the packing efficiency of the hydrocarbon-based electrolyte polymer while suppressing a decrease in the strength of the porous membrane, thereby improving the mechanical strength and proton conductivity of the electrolyte membrane. This effect may be particularly pronounced when a polyolefin-based resin is used as the material for the porous membrane. From the viewpoint of easily obtaining a similar effect, the pore diameter range in which the first peak is located may be 0.01 to 0.5 μm or 0.01 to 0.1 μm.

[0032] The porous membrane 1 may have two or more pores of different size ranges. That is, the porous membrane 1 may have a multi-pore structure. Figure 2 is a plan view showing an example of a porous membrane having a multi-pore structure. The porous membrane (multi-pore membrane) 11 in Figure 2 has pores 2a (hereinafter also referred to as "small-diameter pores 2a") with a pore diameter of 0.01 to 1 μm and pores 2b (hereinafter also referred to as "large-diameter pores 2b") with a pore diameter of 10 to 1000 μm. The large-diameter pores 2b in Figure 2 are through-holes with a circular opening shape and are arranged in a staggered pattern. However, the shape and arrangement of the large-diameter pores 2b are not particularly limited.

[0033] The differential permeate flow rate distribution of the multi-component porous membrane 11 has the first peak (a peak located in the pore diameter range of 0.01 to 1 μm) and a peak located in the pore diameter range of 10 to 1000 μm (hereinafter also referred to as the "second peak"). By using a multi-component porous membrane 11 having such a differential permeate flow rate distribution as the porous membrane 1, not only is it easier to improve mechanical strength, but it is also easier to obtain better proton conductivity. From the viewpoint of easily obtaining similar effects, the pore diameter range where the second peak is located may be 20 to 500 μm or 50 to 200 μm.

[0034] The differential permeation flow rate distribution with respect to the pore size of the multi-component porous membrane 11 may have other peaks besides the first and second peaks described above, but from the viewpoint of making it easier to obtain better proton conductivity, the second peak may be the largest peak in the differential permeation flow rate distribution. Here, the largest peak refers to the peak with the largest peak value (i.e., the value of the differential permeation flow rate at the peak's apex). Furthermore, from the viewpoint of making it easier to improve mechanical strength, the first peak may be the second largest peak after the second peak.

[0035] The porosity of the porous membrane 1 may be 30 vol% or more, 40 vol% or more, 50 vol% or more, or 70 vol% or more, from the viewpoint of obtaining better proton conductivity. The porosity of the porous membrane 1 may be 95 vol% or less, 90 vol% or less, 85 vol% or less, or 80 vol% or less, from the viewpoint of improving mechanical strength. From the above viewpoint, the porosity of the porous membrane 1 may be 30-95 vol%, 40-90 vol%, 50-85 vol%, 70-85 vol%, or 70-80 vol%. The above porosity can be determined, for example, from the pore volume calculated by the mercury intrusion method using a POREMASTER GT (manufactured by Quantachrome Instruments).

[0036] The thickness of the porous membrane 1 may be set according to the size of the applicable device (e.g., polymer electrolyte fuel cell and polymer electrolyte water electrolysis device), and may be, for example, greater than 0 μm, 0.5 μm or more, or 1 μm or more, and may be 200 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, or 15 μm or less. The thickness of the porous membrane 1 may be greater than 0 μm and 200 μm or less, greater than 0 μm and 100 μm or less, 0.5 to 50 μm, 1 to 25 μm, or 1 to 15 μm. The thicker the porous membrane, the easier it is to obtain higher mechanical strength, and the thinner the porous membrane, the easier it is to obtain better proton conductivity. Note that the thickness of the porous membrane described above is the average thickness measured at any five locations in the cross-section of the porous membrane.

[0037] The porous membrane 1 can be obtained by conventionally known methods. Specifically, for example, a method can be used in which pores are formed in a film made of a material containing the hydrocarbon resin described above by chemical etching, laser processing, etc. In this method, for example, a multi-component porous membrane 11 having a multi-component porous structure can be obtained by using a porous membrane having a single-component pore structure instead of a film made of a material containing a hydrocarbon resin. Alternatively, for example, when forming a film with a material containing a hydrocarbon resin, a template (particles, etc.) can be added, and after film formation, the template can be removed by performing a process such as stretching. In this method, for example, a multi-component porous membrane 11 can be obtained by using templates of different sizes. The method for forming the film may be a known method, for example, a solution casting method, a dispersion casting method, a melt press method, or a melt extrusion method. As the porous membrane 1, commercially available products such as the ultra-high molecular weight polyethylene porous sheet NR2451 manufactured by Flon Chemical Co., Ltd., the polyolefin flat membrane "Hypore" manufactured by Asahi Kasei Corporation, and the polyethylene microporous membrane "Polam" manufactured by Tokuyama Corporation can also be used.

[0038] (filling material) The filler 3 includes a hydrocarbon electrolyte polymer. The hydrocarbon electrolyte polymer includes, for example, hydrophilic constituent units having ion exchange groups and hydrophobic constituent units not having ion exchange groups.

[0039] Ion exchange groups, also known as ionic groups, have the property of being able to exchange ions with other ions by releasing ions (e.g., cations). Examples of ion exchange groups include sulfone groups, alkyl sulfone groups, perfluoroalkyl sulfone groups, sulfonimide groups, phosphonic acid groups, phosphate groups, and carboxyl groups. Note that some of these ion exchange groups also exist as salts. For example, the sulfone group is -SO3M 1 / q(M represents H or a metal (for example, at least one selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, Al, Fe, Pt, Rh, Ru, Ir, and Pd), and q represents the valence of M (for example, an integer from 1 to 4)). The metal represented by M exists as an ion (cation), and -SO3 - It forms salt.

[0040] The alkyl sulfone group is, for example, -R 1 SO3M 1 / q It is represented as R 1 R is an alkanediyl group, and its carbon number is preferably 1 to 12. 1 Specific examples include a methylene group, a butane-1,4-diyl group, or a hexane-1,6-diyl group. M and q are the same as above.

[0041] The sulfonimide group is, for example, -SO2NM 1 / q SO2R 2 It is represented as R 2 R is an alkyl group, and its number of carbon atoms is preferably 1 to 6. 2 Specific examples include methyl, ethyl, or propyl groups. M and q are the same as above.

[0042] From the viewpoint of obtaining better proton conductivity, hydrocarbon electrolyte polymers preferably contain at least one group selected from the group consisting of sulfone groups, alkyl sulfone groups, and sulfonimide groups as ion exchange groups, and more preferably contain sulfone groups. From a similar viewpoint, it is even more preferable that the majority of the multiple ion exchange groups present in the hydrocarbon electrolyte polymer are of the above-mentioned preferred form, and it is particularly preferable that all of the multiple ion exchange groups present in the hydrocarbon electrolyte polymer are of the above-mentioned preferred form.

[0043] The hydrocarbon electrolyte polymer may be, for example, a polymer having a structure represented by the following formula (1) (hereinafter also referred to as "polymer (P)").

[0044] [ka]

[0045] In formula (1), A 1 This is a constituent unit represented by the following formula (a1) (hereinafter referred to as "constituent unit A 1 It is also called ". ) indicates A 2 This is a constituent unit represented by the following formula (a2) (hereinafter referred to as "constituent unit A 2 It is also called ". ) indicates L 1 and L 2 Each of these independently represents a single bond, -O-, -S-, or -SO2-, n is an integer between 10 and 100, and * represents a bond. Multiple A 1 These are identical to each other, and multiple A 2 These are identical to each other, and multiple L 1 These may be the same or different from each other, and there may be multiple L 2 They may be the same or different from one another.

[0046] [ka]

[0047] In formula (a1), IExG represents an ion exchange group, L 3 represents a single bond, -O-, -S-, -SO2-, or -CO-, x represents an integer from 2 to 10, and * represents a bond. Multiple IExGs may be identical or different from each other, and multiple L 3 They may be the same or different from one another.

[0048] [ka]

[0049] In formula (a2), Ar represents an arylene group that does not have an ion exchange group, and L 4represents a single bond, -O-, -S-, -SO2-, or -CO-, y represents an integer from 3 to 20, and * represents a bond. Multiple Ars may be the same or different from each other, and multiple L 4 They may be the same or different from one another.

[0050] Polymer (P) possesses excellent proton conductivity. Therefore, by using polymer (P), the proton conductivity of the electrolyte membrane can be improved. The reason why polymer (P) has excellent proton conductivity is not clear, but it is thought to be due to multiple hydrophilic constituent units A that are identical to each other. 1 (Hydrophilic part) and multiple identical hydrophobic constituent units A 2 Because the hydrophobic regions are precisely arranged, the ion exchange groups are lined up at equal intervals, and it is presumed that these ion exchange groups self-assemble in a higher-order structure, inducing a microphase separation structure, thereby forming good proton conduction paths within the polymer (P). 1 The presence of three or more ion exchange groups densely packed together is also presumed to contribute to improved phase separation and proton conductivity. These effects are particularly pronounced in high-humidity environments (for example, under humidity levels of 80% RH or higher).

[0051] Polymer (P) can also improve the gas barrier properties of the electrolyte membrane. The reason for this is presumed to be as follows: Since polymer (P) is composed of arylene groups containing benzene rings in its main chain, the solubility of hydrogen and oxygen is low, and segment movement is restricted, suppressing gas diffusion in the membrane, thus improving the gas barrier properties of the electrolyte membrane.

[0052] As shown in formula (1), polymer (P) is composed of constituent unit A 1 and constituent unit A 2 The linking group (L 1 or L 2The structure has a continuous repeating structure (the structure in [ ] in formula (1)) via ). The number of repeats (n) of the structure is 10 to 100, and may be 15 or more or 20 or more, and may be 80 or less or 50 or less. When the number of repeats (n) is 15 or more, it tends to have excellent gas barrier properties, and when the number of repeats (n) is 50 or less, it tends to have excellent solubility in solvents and permeability to porous membranes. The number of repeats (n) of the structure is preferably 15 to 80, and more preferably 20 to 50.

[0053] [Constituent Unit A] 1 ] Constituent unit A 1 This is an aromatic ring having an ion exchange group (IExG) linked to a linking group (L 3 It has a continuous structure via ). Details of the ion exchange group are as described above.

[0054] Constituent unit A 1 From the viewpoint of obtaining better proton conductivity, the linking group (L 3 It is preferable that the constituent unit A contains at least one group selected from the group consisting of -SO2- and -CO-, and more preferably contains -SO2-. From a similar viewpoint, constituent unit A 1 Multiple linking groups (L) present inside 3 It is even more preferable that the majority of these are of the above-described preferred embodiment.

[0055] Constituent unit A 1 The linking group inside (L 3 From the viewpoint of achieving both superior proton conductivity and chemical durability, the bond is preferably a single bond or -SO2-.

[0056] Linking group (L 3 The bonding position of the constituent unit A is not particularly limited, but it is preferably located at the ortho or meta position relative to the ion exchange group, and more preferably at the ortho position. 1 It is preferable that it contains a 1,4-phenylene group having an ion exchange group.

[0057] Constituent unit A1 In equation (a1), the number of repeating structures (x) in the brackets [ ] is preferably 2 to 8, and more preferably 3 to 5, from the viewpoint of obtaining better proton conductivity and excellent resistance to hot water.

[0058] Constituent unit A 1 From the viewpoint of obtaining superior proton conductivity, it is preferable that the structure includes at least one structure selected from the group consisting of the structure represented by the following formula (a1-1) (hereinafter referred to as "structure (a1-1)") and the structure represented by the following formula (a1-2) (hereinafter referred to as "structure (a1-2)").

[0059] [ka]

[0060] [ka]

[0061] In equations (a1-1) and (a1-2), IExG and * have the same meaning as described above. Multiple IExGs may be the same or different from one another. x in equation (a1-1) 1 x represents an integer between 2 and 10, and x in equation (a1-2) 2 This represents an integer between 2 and 5. However, the constituent unit A 1 If it includes both structure (a1-1) and structure (a1-2), then x 1 and 2x 2 The sum is between 2 and 10. 1 The value is preferably 2 to 5, and more preferably 2 to 3. 2 The number is preferably 2 to 3, and more preferably 2.

[0062] Constituent unit A 1 It may consist only of structure (a1-1), or it may include structure (a1-1) and structures other than structure (a1-1). In the latter case, structure (a1-1) and structures other than structure (a1-1) are linking groups (L 3They may be connected by ). Similarly, constituent unit A 1 It may consist only of structure (a1-2), or it may include structure (a1-2) and structures other than structure (a1-2). In the latter case, structure (a1-2) and structures other than structure (a1-2) are linking groups (L 3 They may be connected by ).

[0063] Constituent unit A 1 This can be a constituent unit represented by any of the following formulas (A1-1) to (A1-4).

[0064] [ka]

[0065] IExG and * in equations (A1-1) to (A1-4), and L in equations (A1-3) to (A1-4). 3 This is synonymous with the above. Multiple IExG may be the same as or different from each other, and multiple L 3 They may be the same or different from one another.

[0066] Polymer (P) constituent unit A 1 From the viewpoint of obtaining better proton conductivity and excellent chemical durability, it is preferable that the constituent unit is one of those represented by formulas (A1-1) to (A1-4), and more preferably that it is the constituent unit represented by formula (A1-2).

[0067] [Constituent Unit A] 2 ] Constituent unit A 2 In this case, the arylene group (Ar) which does not have an ion exchange group is linked to the L group. 4 It has a continuous structure via ).

[0068] The arylene group is a divalent aromatic hydrocarbon group, having a structure in which two hydrogen atoms have been removed from an aromatic hydrocarbon. The number of aromatic rings in the arylene group is preferably 1 to 4, more preferably 1 to 2, and even more preferably 1, from the viewpoint of solubility in solvents and permeability to porous membranes. The arylene group may have substituents other than ion exchange groups, but it is preferable that it has no substituents.

[0069] The arylene group may be at least one selected from the group consisting of phenylene, naphthylene, fluorene, anthracylene, phenanthrylene, triphenylene, pyrenylene, and tetrasenylene groups.

[0070] Constituent unit A 2 From the viewpoint of solubility in the solvent and permeability to porous membranes, the arylene group preferably contains at least one selected from the group consisting of phenylene group, naphthylene group, and fluorene group, more preferably contains a phenylene group, and even more preferably contains a 1,4-phenylene group. From a similar viewpoint, constituent unit A 2 It is even more preferable that the majority of the multiple arylene groups present in the constituent unit A are of the above preferred embodiment. 2 It is particularly preferable that all of the multiple arylene groups present are, independently, phenylene groups, naphthylene groups, or fluorene groups.

[0071] Constituent unit A 2 From the viewpoint of having excellent solubility in solvents and permeability into porous membranes, and further improving the mechanical strength of the electrolyte membrane, the linking group (L 4 It is preferable that the constituent unit A contains at least one group selected from the group consisting of -SO2-, -CO-, and a single bond, and more preferably contains -SO2- or -CO-. From a similar viewpoint, constituent unit A 2 Multiple linking groups (L) present inside 4 It is even more preferable that the majority of ) are of the above preferred embodiment, and constituent unit A 2 Multiple linking groups (L) present inside 4All of the above may be in the preferred form described above.

[0072] Constituent unit A 2 The linking group inside (L 4 From the viewpoint of obtaining better proton conductivity and better mechanical strength, the bond is preferably a single bond, -O-, or -SO2-.

[0073] Constituent unit A 2 In formula (a2), the number of repeats (y) of the structure in brackets [ ] is preferably 4 to 12, and more preferably 5 to 10, from the viewpoint of obtaining better proton conductivity and excellent resistance to hot water.

[0074] Constituent unit A 2 In equation (a2), the number of repeating structures (y) in the brackets [ ] is preferably 2 to 7 more than the number of repeating structures (x) in equation (a1) (x + (2 to 7)), from the viewpoint of achieving both superior proton conductivity and resistance to hot water.

[0075] Constituent unit A 2 From the viewpoint of having excellent solubility in the solvent and permeability to the porous membrane, and further improving the mechanical strength of the electrolyte membrane, it is preferable that the material includes at least one structure selected from the group consisting of the structure represented by the following formula (a2-1) and the structure represented by the following formula (a2-2).

[0076] [ka]

[0077] [ka]

[0078] In equations (a2-1) and (a2-2), Ar and * have the same meanings as described above. Multiple Ars may be the same or different from one another.

[0079] Constituent unit A 2Specific examples thereof include a structural unit represented by the following formula (A2).

[0080] [Chemical formula]

[0081] Ar and L in formula (A2) 4 and * have the same meanings as described above, Q represents a group having a structure represented by formula (a2-1) or formula (a2-2), and y 1 and y 2 each independently represent an integer of 2 to 4. y 1 and y 2 are preferably 2 to 3. A plurality of Ars may be the same as or different from each other, and a plurality of Ls 4 may be the same as or different from each other.

[0082] [Linking group] From the viewpoint of obtaining more excellent proton conductivity and more excellent mechanical strength, the polymer (P) has a linking group (L 1 or L 2 ) between the structural unit A 1 and the structural unit A 2 preferably contains at least one group selected from the group consisting of a single bond, -O-, and -S-, and more preferably contains -O-. From the same viewpoint, among the linking groups (L 1 and L 2 ) between the structural unit A 1 and the structural unit A 2 ) present in plurality in the polymer (P), it is more preferable that the majority are those in the above preferred mode, and it is particularly preferable that all of the linking groups (L 1 and L 2 ) between the structural unit A 1 and the structural unit A 2 ) present in plurality in the polymer (P) are those in the above preferred mode.

[0083] The linking group (L 1 and L 2 ) between the structural unit A 1 and the structural unit A 2From the viewpoint of obtaining better proton conductivity and better mechanical strength, each of the bonds is preferably a single bond, -O-, or -S-, and more preferably -O-.

[0084] The polymer (P) may consist of a structure represented by formula (1) and terminal structures bonded to the structure. The polymer (P) may be, for example, a compound represented by any of the following formulas (1-1) to (1-3).

[0085] [ka]

[0086] A in equations (1-1) to (1-3) 1 , A 2 , L 1 , L 2 And n are the same as above. However, in equations (1-1) and (1-2), Z 2 L that binds 2 This is a single bond. 1 and Z 2 Each of these independently represents a hydroxyl group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group. Examples of halogen atoms include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Examples of alkylborane groups include diethylborane, diciamilborane, dicyclohexylborane, and 9-borabicyclo[3.3.1]nonane. Examples of boronic acid ester groups include pinacol boronic acid ester, 1,3-propanediol boronic acid ester, biscyclohexyldiol boronic acid ester, neopentyl glycol boronic acid ester, and catechol boronic acid ester.

[0087] Polymer (P) may contain multiple polymer units (hereinafter also referred to as "polymer unit A") that have the structure represented by formula (1). For example, polymer (P) may contain three or more polymer units A and three or more crosslinking groups that bond to polymer units A. Polymer (P) having such crosslinking groups (hereinafter also referred to as "crosslinked polymer (P')") has excellent swelling resistance.

[0088] Polymer unit A is formed, for example, from any of the compounds represented by formulas (1-1) to (1-3) above, with terminal group Z 1 and Z 2 It has a structure that excludes the following. Of the two terminal groups of polymer unit A, the terminal group that bonds to the crosslinking group is A 1 It is fine if A 2 It may also be the case that the terminal group that bonds to the crosslinking group is L 2 In the case of a single bond represented by (i.e., Z in equations (1-1) and (1-2)), 2 L that binds 2 (In this case) the terminal group that bonds to the crosslinking group is A 2 It is assumed that the two end groups of polymer unit A may each be bonded to different crosslinking groups. Of the two end groups of polymer unit A, the end group opposite to the end group bonded to the crosslinking group is the end group Z mentioned above. 1 and Z 2 It may be bonded to either one of the two. Multiple polymer units A bonded to a single crosslinking group may be identical or different from one another.

[0089] The crosslinking group may be a group derived from a known crosslinkable compound. From the viewpoint of chemical stability, the crosslinking group preferably has one or more aromatic rings. In this case, it is preferable that the polymer unit A is bonded to the aromatic ring of the crosslinking group. Polymer unit A may be directly bonded to the aromatic ring, or it may be bonded to the aromatic ring via -O-, -S-, or -SO2-. The number of aromatic rings that the crosslinking group has is preferably one or two.

[0090] The crosslinking group may be, for example, a group represented by the following formula (c).

[0091] [ka]

[0092] In formula (c), E represents a hydroxyl group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group, and L 5 L represents a single bond, -O-, -S-, -SO2-, or -CO-. 6 represents a single bond, -O-, -S-, or -SO2-, * represents a bond that connects to polymer unit A, p, q, r, and s are integers from 0 to 5, and z is 0 or 1. However, p+q is 3 or greater, p+r is from 0 to 5, q+s is from 0 to 5, and if z is 0, then r and p are 0. If there are multiple E's, they may be the same or different from each other. 5 If there are multiple L 5 They may be the same or different from each other. Multiple L 6 They may be the same or different from one another.

[0093] The group represented by formula (c) may be, for example, a group represented by any of the following formulas (c1) to (c5). The signs in formulas (c1) to (c5) are the same as those above. Some or all of the E in the groups represented by formulas (c1) to (c5) may be replaced with hydrogen atoms.

[0094] [ka]

[0095] The number of crosslinking groups in the crosslinked polymer (P') may be one or more. The multiple crosslinking groups may be the same or different from each other.

[0096] The crosslinked polymer (P') may contain crosslinking groups that bond to two polymer units A. Such crosslinking groups may have the same structure as the crosslinking groups that bond to three or more polymer units A, except that the number of bonds that bond to polymer units A is different.

[0097] From the viewpoint of obtaining better proton conductivity, the proportion of the structure represented by formula (1) in the entire polymer (P) is preferably 80% by mass or more. From a similar viewpoint, the proportion of the structure represented by formula (1) in the entire polymer (P) may be 85% by mass or more, or 90% by mass or more. The proportion of the structure represented by formula (1) in the entire polymer (P) may be less than 100% by mass. The proportion of the structure represented by formula (1) in the entire polymer (P) may be 80% by mass or more and less than 100% by mass, or 85% by mass or more and less than 100% by mass.

[0098] Polymer (P) can be obtained, for example, by reacting (polymerizing) a compound represented by the following formula (b1) (hereinafter also referred to as "compound (b1)") with a compound represented by the following formula (b2) (hereinafter also referred to as "compound (b2)"). That is, polymer (P) can be a polymer of compound (b1) and compound (b2).

[0099] [ka]

[0100] In formula (b1), A 1 This is synonymous with the above, and X 1b and X 2b Each of these independently represents a halogen atom. Examples of halogen atoms include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0101] [ka]

[0102] In formula (b2), A 2 This is synonymous with the above, Z 1b and Z 2bEach of these independently represents a hydroxyl group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group. Examples of halogen atoms, alkylborane groups, and boronic acid ester groups are given above, Z 1 and Z 2 These are the same examples as halogen atoms, alkylborane groups, and boronic acid ester groups represented by .

[0103] In the above method, constituent unit A 1 and constituent unit A 2 A structure in which these are arranged alternately (a repeating structure) can be formed throughout the entire polymer. Therefore, according to the above method, the number of repeats n in formula (1) can be easily set to 10 or more.

[0104] According to the above method, L in equation (1) 1 and L 2 A polymer (P) is obtained in which the bonds are -O-, -S-, or single bonds. Specifically, Z 1b and Z 2b If at least one of them is a hydroxyl group, then L in formula (1) 1 and L 2 A polymer (P) is obtained in which at least one of the elements is -O-, Z 1b and Z 2b If at least one of them is a thiol group, then L in formula (1) 1 and L 2 A polymer (P) is obtained in which at least one of the elements is -S-, Z 1b and Z 2b If at least one of them is a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group, then L in formula (1) 1 and L 2 A polymer (P) is obtained in which at least one of the bonds is a single bond.

[0105] As for compound (b1), X 1b and / or X 2b Multiple types of compounds with different properties can be used. Similarly, as compound (b2), Z 1b and / or Z 2bMultiple types of compounds with different properties can be used.

[0106] Compound (b1) and compound (b2) can be reacted (polymerized) by, for example, an aromatic nucleophilic substitution reaction in a solvent in the presence of a base.

[0107] The solvent used in the reaction is preferably one that is a good solvent for compound (b1), compound (b2), and polymer (P), and that allows for the high molecular weight of polymer (P) during polymerization. For example, at least one selected from the group consisting of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea is preferably used.

[0108] A base is used to enhance the nucleophilicity of compound (b2). The base is not particularly limited as long as it can deprotonate compound (b2). For example, alkali metal hydroxides and carbonates, alkaline earth metal hydroxides and carbonates, and organic bases such as amines can be used. The alkali metal may be lithium, sodium, potassium, rubidium, or cesium. The alkaline earth metal may be magnesium, calcium, strontium, or barium.

[0109] The reaction temperature may be in the range of 25°C to 350°C. From the viewpoint of excellent reaction rate, the reaction temperature is preferably 60°C or higher, and more preferably 100°C or higher. From the viewpoint of suppressing polymer decomposition, the reaction temperature is preferably 300°C or lower, and more preferably 250°C or lower. The reaction temperature may also be in the range of 60°C to 300°C or 100°C to 250°C.

[0110] Compound (b1) and compound (b2) can also be reacted (polymerized) by a cross-coupling reaction in a solvent in the presence of a catalyst. Examples of solvents that can be used in the reaction are the same as examples of solvents that can be used in the aromatic nucleophilic substitution reaction described above.

[0111] There are no particular restrictions on the catalyst as long as it can carry out the cross-coupling reaction, and conventionally known catalysts can be used. For coupling reactions between halogens, for example, copper catalysts, nickel catalysts, or palladium catalysts can be used. For coupling reactions between halogens and boronic acid groups, alkylborane groups, or boronic acid ester groups, for example, conventionally known catalysts used in the Suzuki-Miyaura coupling reaction (palladium catalysts or nickel catalysts) can be used.

[0112] The copper catalyst may be, for example, copper(I) 2-thiophenecarboxylate or tetrakis(acetonitrile)copper(I) hexafluorophosphate.

[0113] The nickel catalyst may be, for example, bis(1,5-cyclooctadiene)nickel(0), dibromobis(triphenylphosphine)nickel(II), or [1,1'-bis(diphenylphosphino)ferrocene]dichloronickel(II).

[0114] The palladium catalyst may be, for example, tetrakis(triphenylphosphine)palladium(0), palladium(II) acetate, bis(triphenylphosphine)palladium(II) dichloride, or [1,1'-bis(diphenylphosphine)ferrocene]dichloropalladium(II).

[0115] The reaction temperature may be in the range of 0°C to 350°C. From the viewpoint of excellent reaction rate, the reaction temperature is preferably 30°C or higher, and more preferably 60°C or higher. From the viewpoint of suppressing polymer decomposition, the reaction temperature is preferably 300°C or lower, and more preferably 250°C or lower. The reaction temperature may also be in the range of 30°C to 300°C or 60°C to 250°C.

[0116] In the aromatic nucleophilic substitution and cross-coupling reactions described above, it is preferable to remove water from the reaction system in order to increase the molecular weight of the polymer (P). The method of dehydration is not particularly limited, but for example, a method of azeotropic dehydration by coexisting an azeotropic solvent in the reaction system, a method of continuously removing it from the reaction system by heating above the boiling point of water, or a method of coexisting a water-absorbing agent such as a molecular sieve can be used. The azeotropic solvent is not particularly limited as long as it can remove water, and for example, at least one selected from the group consisting of benzene, toluene, cyclohexane, and xylene may be used.

[0117] The above aromatic nucleophilic substitution and cross-coupling reactions are preferably carried out under an inert atmosphere (for example, under a nitrogen or argon atmosphere). After the polymerization reaction is complete, the polymer can be recovered from the reaction solution and purified to obtain the desired polymer. Methods for recovering the polymer from the reaction solution include, for example, adding the reaction solution to a solvent in which the polymer has low solubility and precipitating the polymer as a solid for recovery, or removing the solvent from the reaction solution by evaporation and recovering the polymer as a solid. Methods for purifying the polymer include, for example, washing in a solvent in which the polymer has low solubility and the by-product inorganic salts and residual monomer-derived compounds have high solubility, or washing using a Soxhlet extractor. The methods for recovering and purifying the polymer are not limited to these methods.

[0118] Polymer (P) can also be obtained by oxidizing a polymer having the structure represented by formula (1) (for example, a polymer of compound (b1) and compound (b2)). More specifically, polymer (P) is obtained from among polymers having the structure represented by formula (1), L 1 , L 2 , L 3 or L 4 It may be an oxide of a polymer containing a -S- (sulfide group) (hereinafter referred to as "sulfide-containing polymer"). From the viewpoint of excellent chemical durability, the sulfide-containing polymer is a polymer having the structure represented by formula (1), L 1 , L2 , L 3 and L 4 However, it is preferable that each polymer independently consists of a single bond, -S-, or -SO2-.

[0119] The method for oxidizing the sulfide-containing polymer is not particularly limited and may be any known method for oxidizing the sulfide group (-S-) to obtain a sulfonyl group (-SO2-). One such method is to immerse the sulfide-containing polymer in a mixture containing acetic acid, sulfuric acid, and hydrogen peroxide. The concentration of acetic acid in the mixture may be, for example, 50 to 90% by mass. The concentration of sulfuric acid in the mixture may be, for example, 5 to 25% by mass. The concentration of hydrogen peroxide in the mixture may be, for example, 1 to 15% by mass. The immersion time may be, for example, 1 to 100 hours. In the above method, heating may be performed after immersion. The heating temperature may be, for example, 30 to 120°C, and the heating time may be, for example, 0.1 to 24 hours.

[0120] The polymer (P) obtained by the above method is a polymer having the structure represented by formula (1), and L 1 , L 2 , L 3 or L 4 The polymer contains -SO2- (sulfonyl group). The polymer may be a complete oxide in which all of the sulfide groups in the sulfide-containing polymer are oxidized to sulfonyl groups, or a partial oxide in which some of the sulfide groups in the sulfide-containing polymer are oxidized to sulfonyl groups. The degree of oxidation can be adjusted, for example, by impregnation time, heating temperature, and heating time.

[0121] Polymer (P) can also be obtained by reacting (polymerizing) a polymer of compound (b1) and compound (b2) or an oxide thereof with a compound having three or more groups that react with the polymer or oxide to form a crosslink (hereinafter also referred to as "crosslinkable compound (d)"). In other words, polymer (P) can be a reaction product of a polymer of compound (b1) and compound (b2) or an oxide thereof with a crosslinkable compound (d).

[0122] The above method can yield a crosslinked polymer (for example, the crosslinked polymer (P') described above) in which a polymer of compound (b1) and compound (b2) or its oxide is used as the polymer unit. According to the above method, a crosslinked structure can be formed while maintaining a precisely arranged structure, and both excellent proton conductivity and excellent swelling resistance can be achieved.

[0123] The crosslinkable compound (d) may be a known crosslinkable compound, for example, a low molecular weight compound with a molecular weight of 1000 or less. The group that reacts with the polymer or its oxide to form a crosslink is, for example, a hydroxyl group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group.

[0124] From the viewpoint of chemical stability, the crosslinkable compound (d) preferably has one or more aromatic rings. In this case, the group that reacts with the polymer or its oxide to form a crosslink is preferably directly bonded to the aromatic ring. The number of aromatic rings in the crosslinkable compound (d) is preferably one or two.

[0125] The crosslinkable compound (d) may be, for example, a compound represented by the following formula (d).

[0126] [ka]

[0127] In formula (d), E, ​​L 5 And z are as defined above, and t and u are integers from 0 to 5, respectively. However, t+u is 3 or greater, and if z is 0, then t is 0. Multiple E's may be the same or different from each other. Of the multiple E's, 3 or more E's are terminal groups (X) of the polymer or its oxide. 1b , X 2b , Z 1b or Z 2b It reacts with ) to form crosslinks.

[0128] Polymers of compound (b1) and compound (b2) and their oxides, as well as crosslinkable compound (d), may be used individually or in combination of multiple types.

[0129] The reaction between a polymer of compound (b1) and compound (b2) or its oxide and a crosslinkable compound (d) can be carried out in the same manner as the reaction between compound (b1) and compound (b2).

[0130] A method for obtaining polymer (P) may include a step of protonating ion exchange groups that form a salt with metal ions. This step may involve immersing the polymer obtained by the method described above (for example, a polymer of compound (b1) and compound (b2) or its oxide, or a reaction product of the polymer or oxide and a crosslinkable compound (d)) in an acid (for example, hydrochloric acid) to protonate the ion exchange groups (for example, sulfone groups). By washing and drying the compound (for example, powder) after immersion, the metal ions of the polymer before immersion are replaced with protons, and a polymer (P) with protonated ion exchange groups is obtained.

[0131] From the viewpoint of superior proton conductivity and mechanical strength, hydrocarbon electrolyte polymers are preferably free of fluorine atoms (fluorine content is below the detection limit).

[0132] The number-average molecular weight of the hydrocarbon electrolyte polymer may be 20,000 or more, 25,000 or more, or 30,000 or more from the viewpoint of superior proton conductivity and improved mechanical strength of the electrolyte membrane, and may be 300,000 or less, 200,000 or less, or 150,000 or less from the viewpoint of superior solubility in the solvent and permeability to the porous membrane. From these viewpoints, the number-average molecular weight of the hydrocarbon electrolyte polymer may be 20,000 to 300,000, 25,000 to 200,000, or 30,000 to 150,000.

[0133] The weight-average molecular weight of the hydrocarbon electrolyte polymer may be 40,000 or more, 50,000 or more, or 60,000 or more from the viewpoint of superior proton conductivity and improved mechanical strength of the electrolyte membrane, and may be 500,000 or less, 300,000 or less, or 200,000 or less from the viewpoint of superior solubility in the solvent and permeability to porous membranes. From these viewpoints, the weight-average molecular weight of the hydrocarbon electrolyte polymer may be 40,000 to 500,000, 50,000 to 300,000, or 60,000 to 200,000.

[0134] The number-average molecular weight and weight-average molecular weight of hydrocarbon electrolyte polymers are measured by gel permeation chromatography (GPC) and are expressed as standard polyethylene glycol / oxide (PEG / PEO) equivalent values.

[0135] From the viewpoint of obtaining better proton conductivity, the content (filling amount) of hydrocarbon-based electrolyte polymer in the electrolyte membrane 10A may be 50 parts by mass or more, 90 parts by mass or more, or 350 parts by mass or more, per 100 parts by mass of porous membrane. From the viewpoint of further improving mechanical strength, the content (filling amount) of hydrocarbon-based electrolyte polymer may be 3000 parts by mass or less, 2000 parts by mass or less, 1000 parts by mass or less, or 600 parts by mass or less, per 100 parts by mass of porous membrane. From the above viewpoint, the content (filling amount) of hydrocarbon-based electrolyte polymer may be 50 to 3000 parts by mass, 90 to 2000 parts by mass, 350 to 1000 parts by mass, or 350 to 600 parts by mass, per 100 parts by mass of porous membrane.

[0136] The filler 3 may contain other components besides hydrocarbon electrolyte polymers, to the extent that they do not impair the effects of the present disclosure. These other components may include, for example, at least one selected from the group consisting of water-retaining inorganic substances and radical scavengers. Specifically, for example, at least one selected from the group consisting of silica, cerium oxide, and manganese oxide may be used. The total content of these other components may be 0 to 10% by mass, 0 to 6% by mass, or 0 to 3% by mass, based on the total solid content of the filler.

[0137] Preferably, the filler 3 completely fills the pores 2 of the porous membrane 1, but it is not necessary for some of the pores 2 of the porous membrane 1 to be filled with the filler 3. The proportion of voids (porosity) originating from the porous membrane 1 in the electrolyte membrane 10A can be calculated by performing a cross-sectional observation of the electrolyte membrane and binarizing the void and non-void areas by image analysis. From the viewpoint of obtaining higher mechanical strength and better proton conductivity, the proportion of voids (porosity) originating from the porous membrane 1 in the electrolyte membrane 10A may be 0 to 0.1 volume%, and may also be 0 to 0.01 volume%, or 0 to 0.001 volume%,.

[0138] (Method for manufacturing electrolyte membranes) The electrolyte membrane 10A is obtained by filling a porous membrane 1 with a filler containing a hydrocarbon-based electrolyte polymer. One method for filling the porous membrane 1 with the filler 3 is to impregnate the porous membrane 1 with a solution containing the filler 3, and then dry the solution.

[0139] A method for manufacturing the electrolyte membrane 10A may include, for example, a step of applying a solution containing the filler 3 onto a substrate to form a coating film (a), a step of placing the porous membrane 1 on the coating film and impregnating the porous membrane 1 with the solution (b), and a step of drying the solution (c). In this method, from the viewpoint of more thoroughly impregnating the porous membrane 1 with the solution, a step of applying the solution containing the filler to the surface of the porous membrane 1 opposite to the substrate (b-2) may be performed after step (b). The substrate may be peeled off and removed after step (c). If the ion exchange groups of the hydrocarbon electrolyte polymer contain metal ions, a step of substituting the metal ions with protons (d) may be performed after step (c).

[0140] For example, a glass substrate can be used as the substrate. The solvent used in the solution is not particularly limited as long as it is a solvent capable of dissolving hydrocarbon electrolyte polymers, and for example, at least one selected from the group consisting of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea can be used.

[0141] There are no particular restrictions on the method of applying the solution. Examples of application methods include the applicator method, bar coating method, spin coating method, spray coating method, dip coating method, nozzle coating method, gravure coating method, reverse roll coating method, die coating method, air doctor coating method, blade coating method, rod coating method, curtain coating method, knife coating method, transfer roll coating method, squeeze coating method, impregnation coating method, kiss coating method, calender coating method, or extrusion coating method.

[0142] The drying method is not particularly limited, as long as it can sufficiently remove the solvent from the solution. In the case of heat drying, the drying temperature may be, for example, 20 to 150°C, and the drying time may be, for example, 0.2 to 24 hours.

[0143] Step (d) may be, for example, a step of immersing the film obtained in step (c) in an acid (e.g., hydrochloric acid). By washing and drying the film after immersion, an electrolyte film is obtained in which the metal ions of the hydrocarbon electrolyte polymer are replaced with protons.

[0144] As described above, the electrolyte membrane 10A has a structure in which the porous membrane 1 and the hydrocarbon electrolyte polymer are combined, resulting in improved mechanical strength and making it less likely to break during transportation or use. Therefore, the electrolyte membrane 10A can increase the durability of polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. In addition to polymer electrolyte fuel cells and polymer electrolyte water electrolyzers, the electrolyte membrane 10A can also be used in redox flow batteries, electrochemical hydrogen pumps, chlor-alkali electrolyzers, solid acid catalysts, membrane-type humidity control devices, gas separation membranes, and the like.

[0145] The electrolyte membrane of this disclosure has been described above using electrolyte membrane 10A as an example, but the electrolyte membrane of this disclosure is not limited to the above.

[0146] In another embodiment, the electrolyte membrane may have layers other than the porous membrane and the layer containing the hydrocarbon electrolyte polymer filling the pores of the porous membrane (hereinafter also referred to as the "composite layer"). For example, the electrolyte membrane may further have a layer containing the hydrocarbon electrolyte polymer (hereinafter also referred to as the "electrolyte polymer layer") in addition to the composite layer. Having the electrolyte polymer layer on one or both sides of the porous membrane makes it easier to obtain better proton conductivity. In particular, forming the outermost surface of the electrolyte membrane with the electrolyte polymer layer improves the adhesion of the electrolyte membrane to the catalyst layer and improves proton conductivity. An electrolyte membrane having an electrolyte polymer layer will be described in more detail below with reference to Figure 3.

[0147] Figure 3 is a schematic cross-sectional view showing an electrolyte membrane of another embodiment. The electrolyte membrane 10B in Figure 3 has a composite layer 4 and layers containing hydrocarbon-based electrolyte polymers (a first electrolyte polymer layer 5 and a second electrolyte polymer layer 6). In the electrolyte membrane 10B, the porous membrane 1 is not exposed on the surface of the electrolyte membrane 10B, and the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 are provided on the surface of the composite layer 4.

[0148] The composite layer 4 is a layer comprising a porous membrane 1 and a filler 3 containing a hydrocarbon-based electrolyte polymer, which fills the pores 2 of the porous membrane 1. The composite layer 4 may be the electrolyte membrane 10A described above. That is, the porous membrane 1 and filler 3 in the composite layer 4 may be the same as the porous membrane 1 and filler 3 in the electrolyte membrane 10A.

[0149] The details of the hydrocarbon-based electrolyte polymers contained in the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 are the same as the details of the hydrocarbon-based electrolyte polymers contained in the electrolyte membrane 10A. The hydrocarbon-based electrolyte polymers contained in the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be the same as or different from the hydrocarbon-based electrolyte polymers contained in the composite layer 4.

[0150] The first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be formed from a filler 3 that fills the composite layer 4. That is, the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may consist only of hydrocarbon-based electrolyte polymers, and may also contain other components that can be included in the filler 3, to the extent that they do not impair the effects of the present disclosure.

[0151] The compositions of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be the same or different from each other.

[0152] The thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be greater than 0 μm, 0.5 μm or more, 1 μm or more, or 5 μm or more, and may be 100 μm or less, 50 μm or less, 25 μm or less, or 15 μm or less, respectively. The thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be greater than 0 μm and 100 μm or less, and may be 0.5 to 50 μm, 1 to 25 μm, 5 to 25 μm, or 5 to 15 μm, respectively. Furthermore, the total thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be greater than 0 μm and 200 μm or less, and may be 1 to 50 μm or 2 to 30 μm. The thinner the electrolyte polymer layer, the easier it is to obtain better proton conductivity, and the thicker the electrolyte polymer layer, the easier it is to obtain the effect of improving mechanical strength due to the composite layer. Note that the thickness of the electrolyte polymer layer described above is the average thickness measured at any five locations in the cross-section of the electrolyte polymer layer.

[0153] The thicknesses of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 are preferably thinner than the thickness of the composite layer 4, from the viewpoint of easily obtaining the effect of improving mechanical strength by the composite layer.

[0154] The electrolyte polymer layers 5 and 6 in the electrolyte membrane 10B can be easily formed by adjusting the amount of solution used in the method for manufacturing the electrolyte membrane 10A described above.

[0155] In the electrolyte membrane 10B, electrolyte polymer layers are provided on both sides of the composite layer 4, but an electrolyte membrane having an electrolyte polymer layer may have the electrolyte polymer layer on only one side of the composite layer. That is, the electrolyte membrane may have only one of the first electrolyte polymer layer and the second electrolyte polymer layer. The details (thickness, etc.) of these layers are as described above. The range of hydrocarbon-based electrolyte polymer content when the electrolyte membrane has an electrolyte polymer layer is the same as the range of hydrocarbon-based electrolyte polymer content in the electrolyte membrane 10A described above.

[0156] The ratio (D2 / D1) of the thickness of the porous membrane to the thickness of the electrolyte membrane D1 may be 0.1 to 1. A ratio (D2 / D1) of 0.1 or higher tends to improve mechanical strength. From a similar viewpoint, the above ratio (D2 / D1) may be 0.3 or higher or 0.5 or higher. From the viewpoint of adhesion of the electrolyte membrane to the catalyst layer, the ratio (D2 / D1) may be 0.95 or lower or 0.9 or lower. From the above viewpoint, the above ratio (D2 / D1) may be 0.3 to 0.95 or 0.5 to 0.9. Note that the thickness D2 of the porous membrane may be rephrased as the thickness of the composite layer.

[0157] When the electrolyte membrane has an electrolyte polymer layer, the ratio (D2 / D3) of the thickness D2 of the porous membrane to the total thickness D3 of the electrolyte polymer layer in the electrolyte membrane may be 0.1 to 30. If the ratio (D2 / D3) is 0.1 or greater, the mechanical strength tends to improve, and if it is 30 or less, the adhesion of the electrolyte membrane to the catalyst layer tends to improve. From a similar viewpoint, the above ratio (D2 / D3) may be 0.4 or greater or 1 or greater, 19 or less or 9 or less, or 0.4 to 19 or 1 to 9. Here, the total thickness D3 of the electrolyte polymer layer means the thickness of one electrolyte polymer layer if the electrolyte polymer layer is present on only one side of the composite layer, and the sum of the thicknesses of the two electrolyte polymer layers if the electrolyte polymer layer is present on both sides of the composite layer. Note that the thickness D2 of the porous membrane may be rephrased as the thickness of the composite layer.

[0158] If the electrolyte membrane has layers other than the composite layer, the thickness of the electrolyte membrane may be 5 to 300 μm, 10 to 200 μm, or 20 to 100 μm. The above-mentioned thickness of the electrolyte membrane is the average thickness measured at any five locations in the cross-section of the electrolyte membrane.

[0159] In another embodiment, the electrolyte membrane may have a plurality of the above-mentioned composite layers. The electrolyte membrane may have a structure in which, for example, two composite layers are laminated via the above-mentioned electrolyte polymer layer.

[0160] <Electrolyte membrane with catalyst layer> An electrolyte membrane with a catalyst layer according to one embodiment comprises the electrolyte membrane of the above embodiment and a catalyst layer disposed on one or both sides of the electrolyte membrane.

[0161] The catalyst layer is, for example, a layer composed of an anode catalyst or a cathode catalyst, such as in a polymer electrolyte fuel cell or polymer electrolyte water electrolysis device. Hereinafter, a layer composed of an anode catalyst will be referred to as the anode catalyst layer, and a layer composed of a cathode catalyst will be referred to as the cathode catalyst layer.

[0162] The composition of the catalyst layer is not particularly limited and can be a conventionally known configuration for catalyst layers (anode catalyst layer, cathode catalyst layer) in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. The catalyst layer may be formed of a conductive composition containing, for example, an anode catalyst or cathode catalyst and a conductive material. The catalyst layer may also contain an ionomer.

[0163] As an anode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting the oxidation reaction of a fuel such as hydrogen can be used. As an anode catalyst in a polymer electrolyte water electrolysis device, a metal catalyst capable of promoting the oxygen evolution reaction can be used. For example, at least one selected from the group consisting of platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, and vanadium, as well as two or more alloys thereof, can be used.

[0164] As a cathode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting the reduction reaction of oxygen can be used, and as a cathode catalyst in a polymer electrolyte water electrolysis device, a metal catalyst capable of promoting the hydrogen evolution reaction can be used. For example, at least one selected from the group consisting of platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, and vanadium, as well as two or more alloys thereof, can be used.

[0165] As the conductive material, at least one selected from the group consisting of furnace black, Ketjen black, channel black, acetylene black, activated carbon, and graphite can be used.

[0166] Conventional known materials can be used as the ionomer; for example, an ionomer containing a perfluoro electrolyte can be used. Alternatively, the above polymer (P) can be used as the ionomer. It is preferable to use a material with high oxygen permeability as the ionomer. There are no particular restrictions on the amount of ionomer added to the catalyst layer, but it is preferable to adjust the amount within a range where oxygen diffusion is not easily inhibited.

[0167] The catalyst layer may further contain additives such as water repellents like fluorinated carbon, binders such as fluororesins and hydrocarbon resins having sulfone groups.

[0168] A laminate comprising an electrolyte membrane with an anode catalyst layer and a cathode catalyst layer on both sides (for example, a laminate with a layer configuration of "anode catalyst layer / electrolyte membrane / cathode catalyst layer") is also called a CCM (Catalyst Coated Membrane) and is suitably used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers.

[0169] <Membrane electrode assembly> One embodiment of the membrane electrode assembly comprises the electrolyte membrane of the above embodiment and an electrode layer disposed on one or both sides of the electrolyte membrane.

[0170] The electrode layer comprises, for example, the catalyst layer (anode catalyst layer or cathode catalyst layer) in the electrolyte membrane with catalyst layer of the above embodiment. Hereinafter, the electrode layer comprising the anode catalyst layer will be referred to as the anode layer, and the electrode layer comprising the cathode catalyst layer will be referred to as the cathode layer.

[0171] The configuration of the electrode layer is not particularly limited and may be a configuration conventionally known as the electrode layer (anode layer, cathode layer) of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis device. The electrode layer may consist, for example, of the catalyst layer (anode catalyst layer or cathode catalyst layer) and a gas diffusion substrate. If the catalyst layer itself has gas diffusivity, the electrode layer may consist only of the catalyst layer. As the gas diffusion substrate, for example, a porous membrane can be used. As the gas diffusion substrate, in addition to gas diffusivity, materials that have water repellency and conductivity (for example, carbon fiber substrates such as carbon nonwoven fabric or carbon paper, or titanium fiber sintered bodies) can also be used.

[0172] A laminate comprising an electrolyte membrane with an anode layer and a cathode layer as electrode layers on both sides (for example, a laminate with a layer configuration of "gas diffusion substrate / anode catalyst layer / electrolyte membrane / cathode catalyst layer / gas diffusion substrate") is also called an MEA (Membrane Electrode Assembly) and is suitably used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers.

[0173] <Polymer electrolyte fuel cell> A polymer electrolyte fuel cell according to one embodiment comprises the membrane electrode assembly of the above embodiment.

[0174] The configuration of a polymer electrolyte fuel cell is not particularly limited and may be a conventionally known configuration, except that it uses the membrane electrode assembly of the above embodiment. A polymer electrolyte fuel cell may, for example, comprise two or more membrane electrode assemblies. Two or more membrane electrode assemblies may be stacked (laminated) with a separator in between. A separator conventionally known for polymer electrolyte fuel cells can be used as the separator.

[0175] <Solid polymer water electrolysis device> One embodiment of a solid polymer water electrolysis apparatus includes the membrane electrode assembly of the above embodiment.

[0176] The configuration of the polymer electrolyte water electrolysis apparatus is not particularly limited, and can be a conventionally known configuration except for the use of the membrane electrode assembly of the above embodiment. The polymer electrolyte water electrolysis apparatus may, for example, further include a power supply element outside the membrane electrode assembly. It may also include two or more membrane electrode assemblies. [Examples]

[0177] The contents of this disclosure will be described in more detail below using examples and comparative examples, but this disclosure is not limited to the following examples.

[0178] <Synthesis of hydrocarbon electrolyte polymers> (Synthesis of hydrophilic monomer (M1)) A 10 L flask equipped with a dropping funnel, reflux condenser, and mechanical stirrer was purged with nitrogen, and 101 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl and 4 L of anhydrous tetrahydrofuran were added, and stirring was started. The mixture was cooled to -70°C in a methanol-dry ice bath, and 320 mL of 2.6 mol / L n-butyllithium-hexane solution was added dropwise. The mixture was stirred for 1 hour while remaining cooled in the bath. 40 mL of sulfur dioxide gas was introduced into the flask with nitrogen gas. The mixture was stirred for 30 minutes while remaining cooled in the bath. After that, the bath was removed and the temperature was raised to 0°C. The precipitated solid was filtered off by suction filtration and washed with 200 mL of tetrahydrofuran. The recovered solid was dissolved in 2 L of pure water, 260 mL of 35% hydrogen peroxide solution was added, and the mixture was stirred for 18 hours. The solid was removed by suction filtration, and 600 g of sodium chloride was added to the recovered filtrate. The precipitated white solid was collected by suction filtration and purified by recrystallization with water / isopropyl alcohol. The obtained solid was dried under reduced pressure to obtain a hydrophilic monomer represented by the following formula (M1). The yield was 65%.

[0179] [ka]

[0180] (Synthesis of hydrophobic monomer (M2)) Into a 200 mL flask equipped with a stirrer, a Dean-Stark tube, a reflux condenser, and a calcium chloride tube, 4.0 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl, 14.8 g of [1,1'-biphenyl]-4,4'-diol, and 13.2 g of potassium carbonate were charged, and 50 mL of N,N-dimethylacetamide (DMAc) and 50 mL of toluene were added. The temperature was raised to 160 °C in an oil bath while stirring, and heating and stirring were continued for 4 hours. Toluene was extracted from the Dean-Stark tube, and the temperature was raised to 180 °C in an oil bath. After the temperature was raised, heating and stirring were continued for 8 hours. After the reaction solution was allowed to cool to room temperature, the reaction solution was poured into 200 mL of 10% hydrochloric acid, and the precipitated white solid was filtered off. The solid obtained by filtration was washed with 300 mL of ethanol and dried. The dried solid was purified by recrystallization from a mixed solution of N-methyl-pyrrolidone (NMP) / ethanol. The obtained solid was dried under reduced pressure to obtain a hydrophobic monomer (M2) represented by the following formula (M2). The yield was 50%.

[0181] [Chemical formula]

[0182] (Synthesis of Polymer (P1)) In a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 1.181 g of the hydrophilic monomer (M1), 0.983 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, and 0.507 g of potassium carbonate were added, and the flask was purged with nitrogen. Then, 10 mL of dimethyl sulfoxide (DMSO) and 10 mL of cyclohexane were added. The resulting mixture was heated to 130 °C and dehydrated under reflux for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was carried out at 130 °C for 150 hours. After allowing the reaction mixture to cool to room temperature, it was reprecipitated and purified with 300 mL of isopropyl alcohol (IPA), and the solid was recovered by suction filtration. The recovered solid was washed with water, immersed in 6 mol / L hydrochloric acid for 1 hour, and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain polymer (P1) having the structure represented by the following formula (P1). The yield was 97%. Note that n in equation (P1) was calculated from the number-average molecular weight, which will be discussed later.

[0183] [ka] [In equation (P1), n ​​represents a positive number (approximately 20).]

[0184] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of polymer (P1) were measured under the following conditions. The Mn of polymer (P1) was 30,000, and the Mw was 61,000. [Measurement conditions] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were measured by GPC. Polymer (P1) was dissolved at a concentration of 1 mg / mL in an eluent (N,N-dimethylformamide solvent containing 10 mmol / L lithium bromide) to prepare the sample solution. A Tosoh HLC-8320GPC was used as the apparatus. Two Tosoh TSKgel SuperAWM-H columns (6.0 mm inner diameter, 15 cm length) were used. A differential refractometer detector was used. The flow rate was 0.6 mL / min and the temperature was 40°C. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined by converting them to standard polyethylene glycol / oxide (PEG / PEO).

[0185] <Preparation of porous membrane and nonwoven fabric> A polyethylene microporous membrane (6 μm thick) with a single-pore structure was prepared as porous membrane A, and a polypropylene nonwoven fabric (25 μm thick) was prepared as nonwoven fabric A. Furthermore, porous membrane B was obtained by forming through-holes with an aperture diameter of 50 to 300 μm in porous membrane A using a laser. Planar SEM images of porous membrane A, porous membrane B, and nonwoven fabric A, taken using a scanning electron microscope (SEM), are shown in Figures 4 to 6, respectively. The magnification of the planar SEM image of porous membrane A (Figure 4) is 10,000x, the magnification of the planar SEM image of porous membrane B (Figure 5) is 100x, and the magnification of the planar SEM image of nonwoven fabric A (Figure 6) is 50x.

[0186] <Measurement of differential permeation flow rate> The differential permeation flow rate distribution was measured for porous membrane A, porous membrane B, and nonwoven fabric A using the bubble point method with a porometer "POROLUX Revo (manufactured by APTCO, Belgium)" under the following conditions. Figure 7 shows the differential permeation flow rate distribution for porous membrane A, Figure 8 shows the differential permeation flow rate distribution for porous membrane B, and Figure 9 shows the differential permeation flow rate distribution for nonwoven fabric A. [conditions] A Φ25mm sample piece was immersed in a wetting solution (Galpore (surface tension 16.3 dyne / cm)), placed in the sample chamber, and measurements were started. During the measurement, the supply air pressure was controlled, and the cumulative gas permeation flow rate with respect to the applied pressure was measured. Then, the following relationship was obtained: The relationship D = 0.415 × γ ÷ P (D: pore size, γ: surface tension of the reagent, P: pressure) Using this method, the pore diameter D was calculated from the applied pressure and the surface tension of the reagent. Additionally, the difference in cumulative permeation flow rate between measurement points (differential permeation flow rate) was calculated from the measured gas permeation flow rate (cumulative permeation flow rate) at each measurement point. The differential permeation flow rate distribution was determined by plotting the obtained differential permeation flow rates against the pore diameter corresponding to the pressure at each measurement point.

[0187] As shown in Figures 7 and 8, the differential permeation flow rate distributions of porous membrane A and porous membrane B showed a first peak with its peak top at a pore diameter of 0.02 μm. In addition, the differential permeation flow rate distribution of porous membrane B showed a second peak with its peak top at a pore diameter of 77 μm. On the other hand, in the differential permeation flow rate distribution of nonwoven fabric A, no peaks were observed in the pore diameter range of 0.01 to 1 μm, and a second peak with its peak top at a pore diameter of 81 μm was observed.

[0188] <Measurement of porosity> Using a POREMASTER GT (Quantachrome Instruments) instrument, the porosity of porous membrane A, porous membrane B, and nonwoven fabric A was determined by calculating the pore volume using the mercury intrusion method. The porosity of porous membrane A was 40 vol%, the porosity of porous membrane B was 50 vol%, and the porosity of nonwoven fabric A was 80 vol%.

[0189] <Example 1> Polymer (P1) was dissolved in DMSO to obtain a solution containing 15% by mass of polymer (P1). The obtained solution was applied to a glass substrate using an applicator, and then porous membrane A was placed on the resulting coating. Next, the polymer solution was applied to the side of porous membrane A opposite to the glass substrate side using an applicator. After that, the electrolyte membrane of Example 1 was obtained by drying at 60°C for 20 hours. The electrolyte membrane had a composite layer containing porous membrane A and polymer (P1) filling the pores of porous membrane A, as well as an electrolyte polymer layer containing polymer (P1) on both sides of the composite layer. The thickness of the composite layer was 6 μm, and the thickness of the electrolyte membrane (sum of the thickness of the composite layer and the electrolyte polymer layer) was 11 μm. The polymer (P1) content was 270 parts by mass per 100 parts by mass of porous membrane A. In this example, the thickness of the electrolyte membrane was measured using a film thickness gauge (PG-02, manufactured by TECLOCK CORPORATION).

[0190] <Example 2> An electrolyte membrane of Example 2 was obtained in the same manner as in Example 1, except that porous membrane B was used instead of porous membrane A. The electrolyte membrane had a composite layer containing porous membrane B and polymer (P1) filling the pores of porous membrane B, as well as an electrolyte polymer layer containing polymer (P1) on both sides of the composite layer. The thickness of the composite layer was 6 μm, and the thickness of the electrolyte membrane (sum of the thickness of the composite layer and the electrolyte polymer layer) was 19 μm. The polymer (P1) content was 340 parts by mass per 100 parts by mass of porous membrane B.

[0191] <Comparative Example 1> The electrolyte membrane of Comparative Example 1 was obtained in the same manner as in Example 1, except that nonwoven fabric A was used instead of porous membrane A. The electrolyte membrane had a composite layer containing nonwoven fabric A and polymer (P1) filling the pores of nonwoven fabric A, as well as an electrolyte polymer layer containing polymer (P1) on both sides of the composite layer. The thickness of the composite layer was 25 μm, and the thickness of the electrolyte membrane (sum of the thickness of the composite layer and the electrolyte polymer layer) was 30 μm. The polymer (P1) content was 1000 parts by mass per 100 parts by mass of nonwoven fabric A.

[0192] <Comparative Example 2> Polymer (P1) was dissolved in DMSO to obtain a solution containing 15% by mass of polymer (P1). The obtained solution was cast onto a glass substrate and dried at 60°C for 20 hours to obtain an electrolyte film with a thickness of 63 μm.

[0193] <Rating> (Proton conductivity evaluation) The proton conductivity of the obtained electrolyte membrane was measured using the method described below. The results are shown in Table 1. [Evaluation Method] A gas diffusion substrate coated with a catalyst ink containing Pt-supported carbon powder (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E) and an ionomer (manufactured by Chemours, DE521) was used to fabricate a membrane electrode assembly (MEA) sandwiching an electrolyte membrane, which was then incorporated into a battery cell with a predetermined fastening torque. With the cell temperature at 80 °C and the supply gas at 100% RH, hydrogen was supplied to the anode and nitrogen was supplied to the cathode at 200 Ncc / min each, and the membrane resistance was measured by the AC impedance method. The proton conductivity was calculated by multiplying the membrane resistance of the obtained electrolyte membrane by the electrode area and dividing by the membrane thickness, and then calculating the reciprocal.

[0194] (Mechanical Strength Evaluation) The tensile breaking strength of the obtained electrolyte membrane was measured by the following method using a precision universal testing machine (AG-X manufactured by Shimadzu Corporation) equipped with a thermo-hygrostat chamber. The results are shown in Table 1. [Evaluation Method] The electrolyte membrane fabricated in a dumbbell shape (JIS K 6251 type) was placed on the chuck inside the thermo-hygrostat chamber of the precision universal testing machine. After holding at a temperature of 80 °C and a relative humidity of 60 °C for 3 hours, the electrolyte membrane was pulled at a test speed of 10 mm / min, and the load with respect to the strain was measured. The tensile stress was calculated by dividing the obtained load by the cross-sectional area of the electrolyte membrane, and the tensile stress at the time when the electrolyte membrane broke was defined as the tensile breaking stress.

[0195]

Table 1

Explanation of Symbols

[0196] 1… porous membrane, 2… pores, 2a… small-diameter pores, 2b… large-diameter pores, 3… filler containing a hydrocarbon-based electrolyte polymer, 4… composite layer, 5… first electrolyte polymer layer, 6… second electrolyte polymer layer, 10A, 10B… electrolyte membranes.

Claims

1. The material comprises a porous membrane and a hydrocarbon-based electrolyte polymer filled in the pores of the porous membrane. The porous membrane is formed from a material containing a hydrocarbon resin. An electrolyte membrane in which the differential permeation flow rate distribution of the porous membrane, measured by the bubble point method, has a peak in the pore diameter range of 0.01 to 1 μm.

2. The electrolyte membrane according to claim 1, wherein the differential permeation flow rate distribution of the porous membrane has a peak in the pore diameter range of 10 to 1000 μm.

3. The electrolyte membrane according to claim 1, wherein the porosity of the porous membrane is 30 to 95 volume%.

4. The electrolyte membrane according to claim 1, wherein the hydrocarbon resin is a polyolefin resin.

5. The electrolyte membrane according to claim 1, wherein the porous membrane has a layer containing the hydrocarbon-based electrolyte polymer on one or both sides of the porous membrane.

6. The electrolyte membrane according to claim 1, wherein the ratio of the thickness of the porous membrane to the thickness of the electrolyte membrane is 0.1 to 1.

7. The hydrocarbon electrolyte polymer comprises hydrophilic constituent units having ion exchange groups and hydrophobic constituent units not having ion exchange groups. The electrolyte membrane according to claim 1, wherein the ion exchange group comprises at least one selected from the group consisting of a sulfone group, an alkylsulfone group, and a sulfonimide group.

8. The electrolyte membrane according to claim 1, wherein the hydrocarbon-based electrolyte polymer includes a polymer having a structure represented by the following formula (1). 【Chemistry 1】 [In formula (1), A １ This represents a constituent unit expressed by the following formula (a1): A ２ This represents the constituent unit shown in the following formula (a2): L １ and L ２ These are, independently, a single bond, -O-, -S-, or -SO-. ２ - indicates, n represents an integer between 10 and 100. * indicates a coupling. Multiple A １ They are identical to each other, Multiple A ２ They are identical to each other, Multiple L １ They may be the same or different from each other. A plurality of Ls ２ may be the same as or different from each other. 【Chemistry 2】 [In formula (a1), IExG indicates an ion exchange group. L ３ These are single bonds, -O-, -S-, -SO ２ Show - or -CO-, x represents an integer between 2 and 10. * indicates a coupling. Multiple IExGs may be identical or different from one another. Multiple L ３ These may be identical or different from one another. 【Transformation 3】 [In formula (a2), Ar represents an arylene group that does not have an ion exchange group. L ４ These are single bonds, -O-, -S-, -SO ２ Show - or -CO-, y represents an integer between 3 and 20. * indicates a coupling. Multiple Ars may be identical or different from one another. Multiple L ４ These may be identical or different from one another.

9. An electrolyte membrane with a catalyst layer, comprising an electrolyte membrane according to any one of claims 1 to 8, and a catalyst layer disposed on one or both sides of the electrolyte membrane.

10. A membrane electrode assembly comprising an electrolyte membrane according to any one of claims 1 to 8, and an electrode layer disposed on one or both sides of the electrolyte membrane.

11. A polymer electrolyte fuel cell comprising the membrane electrode assembly described in claim 10.

12. A solid polymer water electrolysis apparatus comprising the membrane electrode assembly described in claim 10.

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