Support for electrolyte membranes, and composite membranes in which an electrolyte membrane is supported by an electrolyte membrane support.

Abstract

The present invention provides a support for an electrolyte membrane that enables the creation of a composite membrane containing a large amount of proton-conducting components (such as electrolyte resins), and a composite membrane in which an electrolyte membrane is supported by the support. [Solution] The electrolyte membrane support comprises a sheet-like fiber aggregate, in which electrolyte resin particles are present in the voids of the fiber aggregate. The composite membrane is supported by the support.

Description

[Technical Field]

[0001] The present invention relates to a support for an electrolyte membrane, and a composite membrane in which an electrolyte membrane is supported by the electrolyte membrane support. [Background technology]

[0002] There are plans to thin down the electrolyte membranes responsible for proton conduction, which are used in fuel cells and hydrogen generators that produce hydrogen by electrolyzing water. To improve the durability of the thin membranes, there are plans to support the electrolyte membranes with a support for electrolyte membranes that has a sheet-like fiber aggregate such as nonwoven fabric, and use them as composite membranes.

[0003] Therefore, as will be described later, the applicant focused on Patent Document 1, listed below, as a sheet-like fiber aggregate to be provided in an electrolyte membrane support used for this purpose. Patent Document 1 discloses an ultrafine fiber nonwoven fabric having binder particles in its voids. It should be noted that Patent Document 1 only discloses that the ultrafine fiber nonwoven fabric can be used as a filter as a specific application, and that the type of resin constituting the binder particles is not particularly limited. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-285793 [Overview of the project] [Problems that the invention aims to solve]

[0005] The applicant attempted to prepare a composite film in which an electrolyte membrane is supported by an electrolyte membrane support by coating a sheet-like fiber aggregate, such as that disclosed in Patent Document 1, with a resin capable of forming an electrolyte membrane (hereinafter sometimes referred to as an electrolyte resin). However, the prepared composite film contains binder particles that are not intended to be directly involved in proton conductivity. As a result, it was not possible to increase the amount of proton-conducting components (including the electrolyte resin) present in the voids of the sheet-like fiber aggregate.

[0006] Furthermore, the applicant attempted to prepare a composite membrane in which an electrolyte membrane is supported by an electrolyte membrane support by coating a sheet-like fiber aggregate, which does not contain binder particles in its voids, with a proton-conducting electrolyte resin. However, because binder particles are not present in the voids of the fiber aggregate, the spaces between the constituent fibers tend to become narrow. As a result, the amount of proton-conducting components (including the electrolyte resin) present in the voids of the sheet-like fiber aggregate decreased. Consequently, it was not possible to increase the amount of proton-conducting components (including the electrolyte resin) present in the composite membrane.

[0007] As described above, using a composite membrane with a small amount of proton-conducting components present in the voids of a sheet-like fiber aggregate could potentially reduce the power generation performance of fuel cells and the hydrogen generation performance of hydrogen generators. Therefore, there was a need for a support for electrolyte membranes that could realize a composite membrane with a high proportion of proton-conducting components present in the voids of a sheet-like fiber aggregate.

[0008] The present invention is "(Claim 1) A support for an electrolyte membrane, comprising a sheet-like fiber aggregate, wherein electrolyte resin particles are present in the voids of the fiber aggregate. (Claim 2) The electrolyte membrane support according to claim 1, wherein the constituent resin of the fibers constituting the sheet-like fiber aggregate is an electrolyte resin. (Claim 3) A composite membrane comprising an electrolyte membrane supported by an electrolyte membrane support according to claim 1 or 2. [Effects of the Invention]

[0009] The sheet-like fiber aggregate of the electrolyte membrane support according to the present invention is characterized by the presence of proton-conducting electrolyte resin particles in its voids. Therefore, in a composite membrane prepared using this electrolyte membrane support, the electrolyte resin particles contained in the composite membrane can also directly contribute to proton conductivity. Furthermore, the presence of electrolyte resin particles in the voids of the sheet-like fiber aggregate prevents the spaces between the constituent fibers of the fiber aggregate from becoming too narrow. As a result, the amount of proton-conducting components (including electrolyte resin) present in the voids of the sheet-like fiber aggregate can be increased. Based on the above, this is a support for electrolyte membranes that can realize a composite membrane with a large amount of proton-conducting components present in the voids of a sheet-like fiber aggregate.

[0010] Another electrolyte membrane support according to the present invention, comprising a sheet-like fiber aggregate, is characterized in that the constituent resin of the fibers constituting the sheet-like fiber aggregate is an electrolyte resin. Therefore, in a composite membrane prepared using this electrolyte membrane support, the constituent fibers of the sheet-like fiber aggregate can also directly contribute to proton conductivity. Based on the above, this is a support for electrolyte membranes that enables the creation of composite membranes with a higher proportion of proton-conducting components.

[0011] Furthermore, since the electrolyte membrane is supported by the electrolyte membrane support according to the present invention, it is a composite membrane with excellent proton conductivity. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a photograph, instead of a drawing, showing a scanning electron microscope (SEM) image of a cross-section of a polybenzimidazole nanofiber nonwoven fabric (Comparative Example 1). [Figure 2]Figure 2 is a photograph substituting for a drawing, showing a cross-sectional SEM image of a polybenzimidazole nanofiber nonwoven fabric (Example 1) in which electrolyte resin particles are present in the voids thereof.

Mode for Carrying Out the Invention

[0013] (Support for Electrolyte Membrane of the Present Invention) The support for the electrolyte membrane of the present invention (hereinafter sometimes simply referred to as "support") includes a sheet-like fiber aggregate and electrolyte resin particles present in the voids of the fiber aggregate. The sheet-like fiber aggregate (hereinafter sometimes simply referred to as "fiber aggregate") that can be used in the present invention can be, for example, a nonwoven fabric, a fiber web, a woven fabric, a knitted fabric, or the like. Among these, since it is flexible and has excellent handleability, it is excellent in the production efficiency of a composite membrane used in a fuel cell, so it is preferable to adopt a nonwoven fabric as the sheet-like fiber aggregate.

[0014] The fiber material used to form the fiber aggregate (preferably a nonwoven fabric) can be appropriately adjusted to realize a composite membrane rich in proton conductivity and is not particularly limited. The constituent fibers of the fiber assembly can be composed of the following organic resins. For example, polybenzimidazole resin (hereinafter sometimes simply referred to as "PBI"), polyolefin resin (such as polyethylene, polypropylene, polymethylpentene, polyolefin resin with a structure in which a part of hydrocarbons is substituted with a halogen such as a cyano group, fluorine or chlorine), styrene resin, polyether resin (such as polyethylene glycol, polypropylene glycol, polyether ether ketone, polyacetal, modified polyphenylene ether, aromatic polyether ketone, etc.), phenolic resin, melamine resin, urea resin, epoxy resin, polyester resin (such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, polylactic acid, wholly aromatic polyester resin, unsaturated polyester resin, etc.), polyimide resin, polyamideimide resin, polyamide resin (such as aromatic polyamide resin such as aramid resin, aromatic polyetheramide resin, nylon resin, etc.), urethane resin, fluorine resin (such as polytetrafluoroethylene, polyvinylidene fluoride, perfluorosulfonic acid resin, Nafion (registered trademark), etc.), polysaccharides (such as starch, cellulose resin, pullulan, alginic acid, hyaluronic acid, etc.), proteins (such as gelatin, collagen, etc.), vinyl alcohol resin (such as polyvinyl alcohol, polyvinyl acetate, etc.), polycaprolactone, polyglycolic acid, polyvinylpyrrolidone, acrylic resin (such as polyacrylonitrile resin copolymerized with acrylic ester or methacrylic ester, modacrylic resin copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride, etc.), and other known resins can be mentioned.

[0015] In particular, since it serves as a support for electrolyte membranes that is excellent in mechanical properties, chemical durability, and heat resistance, it is preferable to use PBI, polyethersulfone, polyimide, polyamideimide, polyetherimide, polyetheretherketone, polyphenylene ether, or fluororesin (polyvinylidene fluoride resin, polytetrafluoroethylene) as the organic resin. In particular, it is preferable to use PBI as the organic resin so that the fiber aggregate can also contribute to proton conductivity.

[0016] Furthermore, the organic resins mentioned above may also contain acidic functional groups such as sulfonic acid groups, phosphonic acid groups, and carboxylic acid groups in their side chains. For example, electrolyte resins such as acid-doped basic resins (e.g., acid-doped PBI), fluorine-based resins such as Nafion, sulfonated polyethersulfones, sulfonated polyimides, sulfonated polyetherimides, sulfonated polyetheretherketones, and sulfonated polyphenylene ethers can be used. In particular, it is most preferable to use acid-doped PBI in order to prepare a composite film with higher proton conductivity. The acid used to acid-dope PBI is not particularly limited as long as it is an acid that can interact with the imidazole group using acid-base interaction, but for example, phytic acid, phosphoric acid, sulfonic acid, carboxylic acid, etc. can be used. Alternatively, basic functional groups such as amino groups, imidazole groups, and pyridine groups, and their salts such as ammonium salts, imidazolium salts, and pyridinium salts may be included.

[0017] These organic resins may consist of either linear or branched polymers, and the resins may be block copolymers or random copolymers. Furthermore, the three-dimensional structure and crystalline properties of the resins may vary.

[0018] The method for producing the fiber aggregate can be appropriately selected, but for example, it can be carried out by subjecting the known organic resin described above to electrospinning. Known manufacturing apparatus capable of carrying out electrospinning and manufacturing methods using the same are disclosed, for example, in Japanese Patent Publication No. 2003-73964, Japanese Patent Publication No. 2004-238749, and Japanese Patent Publication No. 2005-194675. In order to enable stable electrospinning, the inner diameter of the nozzle used for spinning is preferably 0.2 to 1 mm.

[0019] In the present invention, the average fiber diameter of the fibers constituting the fiber aggregate is usually 10 nm to 5 μm, preferably 50 nm to 2 μm, and more preferably 100 nm to 1 μm. In this invention, "average fiber diameter" refers to the arithmetic mean of the individual fiber diameters of 50 fibers, and "fiber diameter" refers to the diameter of a circle in a direction perpendicular to the long axis of the fiber, measured from an electron microscope image of the fiber taken at 1000 to 10000x magnification. If the cross-section of the fiber is not circular but has an irregular shape, the cross-sectional area of ​​the irregular shape is measured, and the diameter of the circle having that cross-sectional area is considered to be the fiber diameter.

[0020] The thin fiber diameter of the constituent fibers makes it easier to thin the composite film, improving proton conductivity in the thickness direction. Furthermore, the large specific surface area of ​​the constituent fibers is preferable when the fiber aggregate consists of fibers made of organic resin doped with many acids, as it allows for the preparation of a composite film with even greater proton conductivity.

[0021] The porosity of the fiber aggregate is preferably 50% or more, more preferably 70% or more, and even more preferably 85% or more. A higher porosity allows for a larger amount of electrolyte resin (for example, a fluoropolymer such as Nafion®) to be filled in, which is preferable as it allows for the preparation of a composite film with high proton conductivity. On the other hand, if the porosity is made too high, the surface of the fiber aggregate (especially nonwoven fabrics) tends to become fuzzy, making it difficult to handle. Therefore, the upper limit for the porosity is 99%.

[0022] The porosity (P, unit: %) is the filling ratio Fr of N components n (unit: %) that make up the fiber assembly, and is calculated by the formula (1). N is an integer of 2 or more, and n is an integer from 1 to N.

[0023]

Equation

[0024]

Equation

[0025] The basis weight and thickness of the fiber assembly can be adjusted as appropriate. The basis weight can be 0.1 to 20 g / m 2 , can be 0.5 to 15 g / m 2 , and can be 1 to 10 g / m 2 . And its thickness is preferably 100 μm or less, preferably 75 μm or less, and preferably 50 μm or less. On the other hand, it is practical for the thickness to be 1 μm or more. In the present invention, the basis weight refers to the mass converted per 1 m 2 on the main surface of the measurement object, and the thickness refers to the value measured using a thickness gauge (manufactured by Mitutoyo Corporation, code No.: 547-401, measuring force: 3.5 N or less).

[0026] The electrolyte resin used to constitute the electrolyte resin particles according to the present invention is not particularly limited as long as it is a proton-conducting organic resin, but for example, PBI, acid-doped basic resins (e.g., acid-doped PBI), fluorine-based resins such as Nafion, sulfonated polyethersulfone resins, sulfonated polyethersulfone, sulfonated polyimide, sulfonated polyetherimide, sulfonated polyetheretherketone, sulfonated polyphenylene ether, etc. can be used. In particular, it is preferable to use PBI as the organic resin because it is excellent in mechanical properties and chemical durability as well as heat resistance, making it a support for electrolyte membranes. Furthermore, since a composite film with higher proton conductivity can be prepared, it is preferable that the electrolyte resin particles are composed solely of electrolyte resin.

[0027] The average particle size of the electrolyte resin particles is adjusted as appropriate, but can be between 10 nm and 10 μm, between 100 nm and 5 μm, or between 500 nm and 3 μm. "Average particle size" refers to the arithmetic mean of the particle diameters of 50 particles to be measured, while "particle diameter" refers to the maximum diameter of the particle measured based on an electron microscope image of the particle. If the particle is not circular, the "particle diameter" is defined as the area of ​​the particle as seen in the electron microscope image obtained by imaging, and the diameter of a circle with the same area. The shape of the electrolyte resin particles is not particularly limited. Examples include spherical (approximately spherical and perfectly spherical), fibrous, needle-shaped (e.g., tetrapod-shaped), plate-shaped, polyhedral, feather-shaped, and amorphous shapes. Furthermore, the electrolyte resin particles may be hollow or solid.

[0028] (Method for manufacturing an electrolyte membrane support according to the present invention) The following example illustrates a method for fabricating electrolyte membrane supports. For example, by collecting a group of fibers spun using electrospinning onto a suitable substrate, and simultaneously using the electrostatic spraying method described later, electrolyte resin particles contained in the dispersion subjected to the electrostatic spraying method are discharged onto the fiber group collected on the substrate, thereby causing the electrolyte resin particles to be present in the voids of the fiber web composed of these fibers. At this time, the electrolyte resin particles initially contained in the dispersion are heated during the electrostatic spraying process or in the subsequent heating process, causing the particles to bond together and form electrolyte resin particles with a larger average particle size.

[0029] Alternatively, the electrolyte resin contained in the solution subjected to the electrostatic spraying method described later is atomized using the electrostatic spraying method described later, and the atomized solution is discharged towards the group of fibers collected on the substrate, thereby causing the electrolyte resin particles to be present in the voids of the fiber web composed of these fibers.

[0030] In addition to the electrostatic spraying method described above, fiber webs containing electrolyte resin particles in the voids may also be prepared by methods such as ejecting particles using compressed gas, or spraying a dispersion containing particles using compressed gas or ultrasound.

[0031] The fiber web containing electrolyte resin particles in the resulting voids can be removed from the substrate to obtain a sheet-like fiber assembly. Alternatively, by performing appropriate heat treatment (e.g., high-temperature heat drying, heat pressing, etc.) on the fiber web, a sheet-like fiber assembly with improved mechanical durability can be obtained. The sheet-like fiber assembly thus obtained can be used as a support for an electrolyte membrane on its own. Alternatively, other fabrics (nonwoven, woven, or knitted), films, or foams can be laminated onto the fiber assembly to use it as a support for an electrolyte membrane.

[0032] In the electrolyte membrane support according to the present invention, the constituent fibers of the fiber aggregate may be bonded together by electrolyte resin particles. In that case, the electrolyte membrane support has improved mechanical strength, which is preferable.

[0033] The ratio of constituent fibers to electrolyte resin particles in the fiber aggregate constituting the electrolyte membrane support is adjusted as appropriate to realize a composite membrane with high proton conductivity. For example, the ratio of the mass of the constituent fibers to the mass of the electrolyte resin particles can be 10:90 to 90:10, 20:80 to 80:20, 30:70 to 70:30, or 40:60 to 60:40. The ratio of constituent fibers to electrolyte resin particles in the fiber aggregate constituting the electrolyte membrane support can be calculated by checking the manufacturing process and determining the mass of the constituent fibers and electrolyte resin particles used in the manufacturing of the fiber aggregate constituting the electrolyte membrane support.

[0034] The porosity of the electrolyte membrane support is preferably 50% or more, more preferably 70% or more, and even more preferably 85% or more. A higher porosity allows for a larger amount of electrolyte resin (e.g., fluororesin such as Nafion®) to be filled in, which is preferable as it allows for the preparation of a composite membrane with high proton conductivity. On the other hand, if the porosity is too high, the surface of the fiber aggregate (especially the nonwoven fabric) tends to become fuzzy, making it difficult to handle, so the upper limit of the porosity is 99%. The porosity (P, unit: %) can be determined in the same way as the method for calculating the porosity of the fiber aggregate described above, by substituting "fiber aggregate" with "electrolyte membrane support".

[0035] Furthermore, the basis weight and thickness of the electrolyte membrane support can be adjusted as needed. The basis weight ranges from 0.3 to 30 g / m². 2 It can be 1-20g / m 2 It can be 3-10g / m 2 It can be such that the thickness is preferably 100 μm or less, preferably 75 μm or less, and preferably 50 μm or less. On the other hand, a thickness of 1 μm or more is practical.

[0036] In addition, in the electrolyte membrane support of the present invention, the constituent fibers of the fiber aggregate may be made of the same electrolyte resin that constitutes the electrolyte resin particles. For example, in Example 5 described later, an electrolyte membrane support comprising a fiber aggregate and electrolyte resin particles made of the same type of resin (PBI) is obtained using a spinning solution containing PBI and an electrostatic spray solution containing PBI. By using an electrolyte membrane support made of the same type of resin in this way, an electrolyte membrane support can be obtained in which the interfacial resistance between the electrolyte resin particles and the constituent fibers of the fiber aggregate is reduced. As a result, a composite membrane with higher proton conductivity can be realized, which is preferable.

[0037] (The composite film of the present invention) The composite film of the present invention can be manufactured, for example, by applying an electrolyte resin to a support for the electrolyte film of the present invention obtained as described above.

[0038] The electrolyte resin included in the composite membrane of the present invention can be appropriately selected and used as long as it has proton conductivity. In addition to the electrolyte resins mentioned above, for example, perfluorosulfonic acid polymers such as Aquivion®, sulfonated polyarylene ethers, sulfonated polyethersulfones, sulfonated polyimides, sulfonated polybenzimidazoles, sulfonated polyphenylenes, sulfonated polyphenylene oxides, sulfonated polyphenylene sulfides, sulfonated polystyrenes or copolymers thereof, or polyvinyl sulfonic acid or copolymers thereof can be used.

[0039] In the composite membrane of the present invention, when the electrolyte resin particles constituting the electrolyte membrane support and the electrolyte resin constituting the electrolyte membrane are of the same type, a composite membrane can be obtained in which the interfacial resistance between the electrolyte membrane support and the electrolyte membrane is reduced. As a result, a composite membrane with higher proton conductivity can be realized, which is preferable.

[0040] The thinner the composite film of the present invention, the better its proton conductivity and therefore the more desirable it is. For this reason, the thickness is preferably 50 μm or less, more preferably 45 μm or less, even more preferably 40 μm or less, even more preferably 35 μm or less, and even more preferably 30 μm or less. Since the composite film of the present invention is supported by an electrolyte membrane support, even a thin film with a thickness of 30 μm or less has excellent mechanical strength and ease of handling. On the other hand, the lower limit of the thickness is preferably 1 μm or more in order to have excellent mechanical strength and ease of handling.

[0041] The mass of the electrolyte membrane in relation to the mass of the composite membrane of the present invention is preferably 50 to 99% by mass, more preferably 60 to 95% by mass, and even more preferably 72 to 90% by mass. Furthermore, the higher the percentage of electrolyte resin (excluding fiber aggregates) in the electrolyte membrane support portion of the composite membrane, the more proton-conducting components can be present in the composite membrane, indicating that the electrolyte membrane support is capable of achieving this. Therefore, the percentage is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. The upper limit is less than 100%.

[0042] The composite membrane of the present invention may contain, for example, inorganic particles in the electrolyte membrane constituting the composite membrane. The inclusion of these inorganic particles has the following effects: (1) improved mechanical properties of the composite membrane, (2) improved durability of the composite membrane, and (3) enhanced ionic conductivity of the composite membrane. Examples of such inorganic particles include cerium salt particles, ceria particles, silica particles, titania particles, zirconia particles, yttria-stabilized zirconia particles, and alumina particles.

[0043] The average particle diameter of the inorganic particles is preferably 1 nm to 1 μm, more preferably 500 nm or less, and even more preferably 100 nm or less. Furthermore, the mass of the inorganic particles as a percentage of the mass of the composite film is preferably 1 to 40% by mass, more preferably 3 to 30% by mass, and even more preferably 5 to 20% by mass. [Examples]

[0044] The present invention will be specifically described below with reference to examples, but these examples are not intended to limit the scope of the present invention.

[0045] Manufacturing Example 1: Preparation of PBI Nanofiber Nonwoven Fabric (Comparative Example 1) Specific gravity 1.3g / cm 3 PBI was dissolved in dimethylacetamide (DMAc) to prepare a spinning solution with a polymer concentration of 20 wt%. Under the following spinning conditions, a group of PBI fibers spun by electrospinning was collected on a substrate to create a PBI web. The prepared PBI web was peeled from the substrate and heat-treated at 180°C for 30 minutes to obtain a PBI nonwoven fabric. The PBI nonwoven fabric obtained in this way was used as a support for the electrolyte membrane.

[0046] <Spinning conditions> Spinning solution discharge rate: 1 mL / hr, minimum distance between nozzle tip and substrate: 6 cm, temperature: 25°C, humidity: 30% relative humidity (RH), nozzle inner diameter: 0.33 mm, voltage: 15 kV, substrate: aluminum foil.

[0047] (Comparative Example 2) A PBI nonwoven fabric was obtained in the same manner as in Comparative Example 1, except that the basis weight was changed. The PBI nonwoven fabric obtained in this way was used as a support for the electrolyte membrane.

[0048] (Example 1) As described in Comparative Example 1, a group of PBI fibers spun using electrospinning was collected on a substrate. Simultaneously, a dispersion of Nafion particles with a polymer concentration of 20 wt% (DE2021; Fujifilm Wako Pure Chemical Industries) was electrostatically sprayed from a nozzle under the following conditions (the same conditions were used for Examples 2-4 described later). This caused the Nafion particles, which are electrolyte resin particles contained in the dispersion, to be ejected onto the substrate. In this way, a PBI web was created in which Nafion particles with a larger average particle size were present due to the bonding of each particle within the voids. The prepared PBI web was peeled from the substrate and heat-treated at 180°C for 30 minutes to obtain a PBI nonwoven fabric in which Nafion particles with an increased average particle size were present in the voids. The PBI nonwoven fabric obtained in this way was used as a support for the electrolyte membrane.

[0049] <Conditions for electrostatic spraying> Discharge rate: 0.5 mL / hr, minimum distance between nozzle tip and substrate: 10 cm, temperature: 25°C, humidity: 30% RH, nozzle inner diameter: 0.33 mm, voltage: 20 kV, substrate: aluminum foil.

[0050] (Example 2) As described in Comparative Example 2, a group of PBI fibers spun using electrospinning was collected on a substrate. Simultaneously, a dispersion of Nafion particles with a polymer concentration of 20 wt% (DE2021; Fujifilm Wako Pure Chemical Industries) was electrostatically sprayed from a nozzle under the conditions described in Example 1. This caused the Nafion particles, which are electrolyte resin particles contained in the dispersion, to be ejected onto the substrate. In this way, a PBI web was prepared in which Nafion particles with a larger average particle size were present due to the bonding of each particle within the voids. The prepared PBI web was peeled from the substrate and heat-treated at 180°C for 30 minutes to obtain a PBI nonwoven fabric in which Nafion particles with an increased average particle size were present in the voids. The PBI nonwoven fabric obtained in this way was used as a support for the electrolyte membrane.

[0051] (Example 3) A PBI nonwoven fabric was obtained in the same manner as in Example 2, except that the Nafion dispersion was changed to a dispersion of another Nafion particle with a polymer concentration of 20 wt% (DE2020; Fujifilm Wako Pure Chemical Industries), in which Nafion particles with a larger average particle size due to the bonding of each particle within the voids were obtained. The PBI nonwoven fabric obtained in this way was used as a support for the electrolyte membrane.

[0052] (Example 4) A PBI nonwoven fabric containing S-PES particles in its voids was obtained using the same method as in Example 2, except that the dispersion of Nafion particles used in Example 2 was replaced with a 20 wt% polymer concentration sulfonated polyethersulfone (S-PES) solution (solvent: DMAc). The PBI nonwoven fabric obtained in this way was used as a support for the electrolyte membrane.

[0053] (Example 5) Specific gravity 1.3g / cm 3 PBI was dissolved in dimethylacetamide (DMAc) to prepare a spinning solution with a polymer concentration of 18 wt%. PBI fibers spun using electrospinning under the following spinning conditions were collected on a substrate.

[0054] <Spinning conditions> Spinning solution discharge rate: 0.5 mL / hr, minimum distance between nozzle tip and substrate: 6 cm, temperature: 25°C, humidity: 30% relative humidity (RH), nozzle inner diameter: 0.33 mm, voltage: 13 kV, substrate: aluminum foil.

[0055] Simultaneously, a 14 wt% polymer PBI solution (solvent: DMAc) was electrostatically sprayed from a nozzle under the following conditions. This created a PBI web in which PBI particles were present in the voids. The prepared PBI web was peeled from the substrate and heat-treated at 180°C for 30 minutes to obtain a PBI nonwoven fabric in which PBI particles were present in the voids.

[0056] <Conditions for electrostatic spraying> Discharge rate: 0.5 mL / hr, minimum distance between nozzle tip and substrate: 6 cm, temperature: 25°C, humidity: 30% RH, nozzle inner diameter: 0.33 mm, voltage: 11 kV, substrate: aluminum foil.

[0057] In all of the nonwoven fabrics prepared in Examples 1 to 5 as described above, the PBI fibers, which are the constituent fibers of the nonwoven fabric, were bonded together by electrolyte resin particles.

[0058] (Evaluation of physical properties) Table 1 shows the measurement results of each physical property of the electrolyte membrane supports prepared in the comparative example and the example.

[0059] [Table 1]

[0060] Manufacturing Example 2: Fabrication of Composite Films (Comparative Example 3) Nafion dispersion (DE2021; Fujifilm Wako Pure Chemical Industries) was applied to a polyethylene terephthalate (PET) film using a coating device (slit thickness: 100 μm). The electrolyte membrane support prepared in Comparative Example 1 was placed on the coated area, and then Nafion dispersion was applied to its exposed main surface using a coating device (slit thickness: 150 μm). The mixture was then treated in an oven set to 80°C for 1 hour, followed by treatment at 140°C for 10 minutes. This process allowed the Nafion particles to bond together, forming an electrolyte membrane, which was then supported by the electrolyte membrane support to create a composite membrane. In Comparative Example 3, the composite membrane had Nafion completely filled into the voids of the fiber aggregate in the electrolyte membrane support that constituted the composite membrane.

[0061] (Comparative Example 4, Examples 6-9) Instead of the electrolyte membrane support prepared in Comparative Example 1, • Support for electrolyte membrane prepared in Comparative Example 2 (Comparative Example 4), • Support for electrolyte membrane prepared in Example 1 (Example 6), • Support for electrolyte membrane prepared in Example 2 (Example 7), • Support for electrolyte membrane prepared in Example 3 (Example 8), • Support for electrolyte membrane prepared in Example 4 (Example 9), A composite membrane was prepared in the same manner as in Comparative Example 3, except that the Nafion particles were bonded together to form a Nafion electrolyte membrane, which was then supported by an electrolyte membrane support. In Comparative Example 4, the composite membrane was such that Nafion was completely filled into the voids of the fiber aggregate in the electrolyte membrane support that constituted the composite membrane. Furthermore, in all of the composite membranes of Examples 6 to 9, Nafion and electrolyte resin particles were filled without any gaps in the voids of the fiber aggregates provided in the electrolyte membrane support that constitutes the composite membrane.

[0062] (Evaluation of physical properties) Table 2 shows the measurement results of each physical property for the composite films of Comparative Examples 3-4 and Examples 6-9. The "Thickness of the electrolyte membrane support portion (μm)" and "Percentage of electrolyte resin excluding fiber aggregates contained in the electrolyte membrane support portion (%)" in the table were calculated using the following method.

[0063] (How to determine the thickness of the support portion for the electrolyte membrane) First, a cross-section is formed by cutting the composite film in the thickness direction using a cryo-ion milling device. Then, an electron microscope image of the cross-section is taken. Then, at five randomly selected locations on the main surface of the composite film as seen in the electron microscope image, the length of the electrolyte membrane support contained within the composite film, in a direction parallel to the thickness direction of the composite film, is measured. The average of the five lengths obtained from these measurements is then defined as the thickness (in μm) of the electrolyte membrane support portion in the composite film.

[0064] (Method for determining the percentage of electrolyte resin, excluding fiber aggregates, contained in the electrolyte membrane support portion) The answer is obtained by substituting each value into the following formula. Y = 100 × {1 - A / (B × C)} The algebra used in the calculation formula is as follows: Y: Percentage of electrolyte resin excluding fiber aggregates included in the electrolyte membrane support portion (unit: %) A: Basis weight (unit: g / m²) of the fiber aggregate contained in the electrolyte membrane support used to prepare the composite membrane. 2 ) B: Thickness of the support portion for the electrolyte membrane (unit: μm) C: Specific gravity of the resin that makes up the constituent fibers of the fiber aggregate (unit: g / cm³) 3 )

[0065] [Table 2]

[0066] The composite membrane prepared using the electrolyte membrane support prepared in Example 1 had a higher percentage of electrolyte resin, excluding the fiber aggregates contained in the electrolyte membrane support portion, compared to the composite membrane prepared using the electrolyte membrane support prepared in Comparative Example 1. Similarly, the composite membrane prepared using the electrolyte membrane support prepared in Example 2 had a higher percentage of electrolyte resin, excluding the fiber aggregates contained in the electrolyte membrane support portion, compared to the composite membrane prepared using the electrolyte membrane support prepared in Comparative Example 2. From the above, the electrolyte membrane support according to the present invention (specifically, the electrolyte membrane support prepared in Examples 1 to 5) can realize a composite membrane in which there is a large amount of proton-conducting component (including electrolyte resin) present in the voids of the sheet-like fiber aggregate.

[0067] Furthermore, the constituent fibers of the fiber aggregates in the electrolyte membrane supports prepared in Examples 1 to 5 are made of electrolyte resin. Therefore, the constituent fibers of the fiber aggregates in the electrolyte membrane supports can also directly contribute to proton conductivity. As a result, these electrolyte membrane supports enable the creation of composite membranes with a higher proportion of proton-conducting components.

[0068] Furthermore, the electrolyte membrane support prepared in Example 5 is composed of the same electrolyte resin for both the constituent fibers of the fiber aggregate and the electrolyte resin particles. Therefore, the electrolyte membrane support has reduced interfacial resistance between the electrolyte resin particles and the constituent fibers of the fiber aggregate. As a result, it is an electrolyte membrane support capable of realizing a composite membrane with higher proton conductivity. [Industrial applicability]

[0069] The electrolyte membrane support of the present invention can be used to support an electrolyte membrane and as a composite membrane. This composite membrane can then be used as an electrolyte membrane responsible for proton conduction in fuel cells, hydrogen generators that produce hydrogen by electrolyzing water, and the like.

Claims

1. A support for an electrolyte membrane, comprising a sheet-like fiber aggregate, wherein electrolyte resin particles are present in the voids of the fiber aggregate.

2. The electrolyte membrane support according to claim 1, wherein the constituent resin of the fibers constituting the sheet-like fiber aggregate is an electrolyte resin.

3. A composite membrane comprising an electrolyte membrane supported by an electrolyte membrane support according to claim 1 or 2.

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