JP2018018684A - Membrane-conductive porous sheet assembly and solid polymer electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane-conductive porous sheet assembly excellent in the effect of suppressing a dimensional change when being used, and a fuel cell excellent in power generation performance.SOLUTION: The present invention provides: [1] a membrane-conductive porous sheet assembly which includes a catalyst layer between a membrane and a conductive porous sheet, the conductive porous sheet containing conductive fibers containing conductive particles, and the membrane having a minimum 90° peel strength between the conductive porous sheet and the catalyst layer of 0.06 N/cm or more after having been repeatedly swelled and contacted; and [2] a solid polymer electrolyte fuel cell including the membrane-conductive porous sheet assembly of [1], as a membrane-electrode assembly.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a membrane-conductive porous sheet assembly and a polymer electrolyte fuel cell.

  Regarding energy used in various forms, exploring alternative fuels and conserving resources are important issues due to concerns over the depletion of petroleum resources. In the midst of this, active development has continued for fuel cells that convert various fuels into chemical energy and extract them as electric power. Among fuel cells, polymer electrolyte fuel cells are being actively developed because they can output in a low temperature region and can efficiently extract power while being relatively small.

  FIG. 1 is a schematic cross-sectional view showing the basic structure of a solid polymer fuel cell. In the figure, the same hatching is attached | subjected to the structural component which has the substantially the same structure or function as a material. The polymer electrolyte fuel cell has a membrane-electrode assembly (MEA) comprising a fuel electrode (gas diffusion electrode) 17a, a solid polymer electrolyte membrane 19 and an air electrode (gas diffusion electrode) 17c, as shown in FIG. It has a structure in which a plurality of cell units sandwiched between a pair of bipolar plates 11a and 11c are stacked. The fuel electrode 17a includes a catalyst layer 15a that decomposes into protons and electrons, and a gas diffusion layer 13a that supplies fuel gas to the catalyst layer 15a, and moisture management is provided between the catalyst layer 15a and the gas diffusion layer 13a. On the other hand, the air electrode 17c is composed of a catalyst layer 15c for reacting protons, electrons and oxygen-containing gas, and a gas diffusion layer 13c for supplying oxygen-containing gas to the catalyst layer 15c. A moisture management layer 14c is formed between the layer 15c and the gas diffusion layer 13c.

  Since the bipolar plate 11a has a groove capable of supplying a fuel gas, when the fuel gas is supplied through the groove of the bipolar plate 11a, the fuel gas diffuses through the gas diffusion layer 13a and permeates the moisture management layer 14a to pass through the catalyst layer 15a. To be supplied. The supplied fuel gas is decomposed into protons and electrons, and the protons move through the solid polymer electrolyte membrane 19 and reach the catalyst layer 15c. On the other hand, the electrons pass through an external circuit (not shown) and move to the air electrode 17c. On the other hand, since the bipolar plate 11c has a groove capable of supplying an oxygen-containing gas, when the oxygen-containing gas is supplied through the groove of the bipolar plate 11c, the oxygen-containing gas diffuses through the gas diffusion layer 13c and permeates the moisture management layer 14c. And supplied to the catalyst layer 15c. The supplied oxygen-containing gas reacts with protons that have moved through the solid polymer electrolyte membrane 19 and electrons that have moved through the external circuit to produce water. The generated water is discharged out of the fuel cell through the moisture management layer 14c. In the fuel electrode, water that has been reversely diffused from the air electrode passes through the moisture management layer 14a and is discharged out of the fuel cell.

  The functions necessary for the gas diffusion layer 13a and the moisture management layer 14a or the gas diffusion layer 13c and the moisture management layer 14c include moisture retention for keeping the solid polymer electrolyte membrane 19 moist under low humidification conditions, Under high humidification conditions, water accumulates in the fuel cell, and there is drainage to prevent flooding. Such gas diffusion layer 13a and moisture management layer 14a, or gas diffusion layer 13c and moisture management layer 14c are conventionally impregnated with a fluororesin such as polytetrafluoroethylene in a conductive porous sheet such as carbon paper, or By applying a paste in which carbon powder and fluororesin are mixed, the moisture management layers 14a and 14c in which the fluororesin is present or the carbon powder and fluororesin are present are formed, and regions where these are not present are formed. The gas diffusion layers 13a and 13c were used. However, in the moisture management layers 14a and 14c formed in this way, the fluororesin, or the carbon powder and the fluororesin soak into the conductive porous sheet more than necessary, and in the surface direction (direction perpendicular to the thickness). The drainage property and gas diffusibility of the product were likely to deteriorate. For example, in a situation where a large amount of water is generated, drainage and gas diffusibility are inferior, and this has been a factor in reducing the performance of fuel cells.

  For this reason, the applicant of the present application stated that “it is a self-supporting moisture management sheet that is disposed adjacent to the catalyst layer of the polymer electrolyte fuel cell, and the moisture management sheet is electrically conductive at least inside the hydrophobic organic resin. Moisture management sheet comprising a non-woven fabric containing conductive fibers containing particles "(Patent Document 1)," Non-woven fabric containing conductive fibers containing conductive particles at least inside an organic resin. " Proposed gas diffusion electrode substrate "(Patent Document 2). In Patent Document 1, which uses this moisture management sheet, a moisture management sheet is laminated on a solid polymer electrolyte membrane having a catalyst layer, a gas diffusion sheet is further laminated on the moisture management sheet, and bonded by hot pressing, -Disclosing producing an electrode assembly, and in the case of Patent Document 2 using a gas diffusion electrode using a base material for gas diffusion electrode, laminating a gas diffusion electrode on a solid polymer electrolyte membrane having a catalyst layer, It discloses that a membrane-electrode assembly is produced by bonding by hot pressing. However, when the membrane-electrode assembly is used, the bonding state cannot be sufficiently maintained, and the moisture management sheet or the gas diffusion electrode may be peeled off at a part of the membrane-electrode assembly. And the shrinkage could not be suppressed sufficiently. If the swelling and shrinkage of the solid polymer electrolyte membrane cannot be sufficiently suppressed in this way, the catalyst layer is ruptured by the stress caused by the deformation of the solid polymer electrolyte membrane, or the catalyst layer is easily peeled off from the solid polymer electrolyte membrane. As a result, an increase in material transport resistance and an increase in interface resistance between electrons and heat are caused, leading to a decrease in power generation performance.

In order to suppress such swelling and shrinkage of the solid polymer electrolyte membrane, the applicant of the present application further stated, “A gas diffusion electrode substrate including a nonwoven fabric containing conductive fibers containing conductive particles at least inside an organic resin. A gas diffusion electrode base material, characterized in that the material has a specific apparent Young's modulus of 40 [MPa / (g / cm ³ )] or more ”(Patent Document 3). ) Was proposed. In the case of Patent Document 3 in which a gas diffusion electrode using this base material for gas diffusion electrode is used, a solid polymer film is sandwiched between the catalyst support surfaces of the pair of gas diffusion electrodes and bonded by hot pressing. However, the effect of suppressing the swelling and shrinkage of the solid polymer electrolyte membrane is insufficient, and as a result, the power generation performance may be lowered.

  The above is the case of the polymer electrolyte fuel cell. In addition to the polymer electrolyte fuel cell, there is an air cell having a solid electrolyte membrane between the positive electrode and the negative electrode, and a diaphragm between the positive electrode and the negative electrode. Similarly, in the case of a redox flow battery or the like, the effect of suppressing the dimensional change of the solid electrolyte membrane or the diaphragm at the time of power generation or charge / discharge is insufficient, and the performance may be deteriorated.

JP 2012-199225 A International Publication WO / 2014/010715 International Publication WO / 2014/185491

  The present invention has been made under such circumstances, and an object thereof is to provide a membrane-conductive porous sheet assembly excellent in the effect of suppressing the dimensional change of the membrane during use, and a fuel cell excellent in power generation performance. .

The present invention
[1] A membrane-conductive porous sheet assembly in which a catalyst layer is present between a membrane and a conductive porous sheet, wherein the conductive porous sheet contains conductive fibers containing conductive particles, A membrane-conductive porous sheet assembly, wherein the minimum 90 ° peel strength between the conductive porous sheet and the catalyst layer after swelling and shrinking is 0.06 N / cm or more,
[2] A polymer electrolyte fuel cell comprising the membrane-conductive porous sheet assembly according to claim 1 as a membrane-electrode assembly,
About.

  The membrane-conductive porous sheet assembly of [1] has a minimum 90 ° peel strength between the conductive porous sheet and the catalyst layer of 0.06 N / cm or more after the membrane has repeatedly swollen and contracted. The conductive porous sheet and the catalyst layer are well bonded. Therefore, the swelling and shrinkage of the film can be sufficiently suppressed during use. That is, the dimensional change of the film can be suppressed. As described above, since the stress due to the deformation of the film can be reduced, the catalyst layer can be prevented from being broken or peeled off from the film, so that a battery with excellent power generation performance can be manufactured. In addition, since an electroconductive fiber contains electroconductive particle, it is excellent in electroconductivity. In addition, if the conductive porous sheet is not filled with fluorine-based resin and / or carbon, the conductive porous sheet is inherently in a porous state, so that liquid permeability and gas diffusibility are also obtained in the surface direction. Are better.

  Since the polymer electrolyte fuel cell of [2] includes the membrane-conductive porous sheet assembly as a membrane-electrode assembly, it has excellent power generation performance.

Cross-sectional schematic diagram of the relevant part showing the basic structure of a polymer electrolyte fuel cell Front view of membrane-conductive porous sheet assembly showing a method for preparing a test piece when measuring the minimum 90 ° peel strength between the conductive porous sheet and the catalyst layer after the membrane repeats swelling and shrinking Figure

  The membrane-conductive porous sheet assembly of the present invention has a minimum 90 ° peel strength between the conductive porous sheet and the catalyst layer of 0.06 N / cm or more, and the conductive porous sheet and the catalyst layer adhere well. Yes. Therefore, dimensional change due to swelling and shrinkage of the membrane during use can be suppressed, and stress due to the deformation can be reduced, so that a battery with excellent power generation performance can be prevented by preventing breakage of the catalyst layer and peeling from the membrane It can be produced.

(Conductive porous sheet)
The conductive porous sheet constituting the membrane-conductive porous sheet assembly of the present invention contains conductive fibers containing conductive particles. The conductive fiber may be composed of an inorganic component, may be composed of an organic component, or may be composed of both an inorganic component and an organic component. Since the contained conductive porous sheet has flexibility, the gap between the conductive porous sheet and the adjacent member (for example, a catalyst layer, a gas diffusion layer, a bipolar plate, etc.) can be reduced, and the interface between electrons and heat can be reduced. This is preferable because the resistance can be reduced and, as a result, a battery having excellent power generation performance can be easily manufactured.

  Further, the organic component that can constitute the conductive fiber may be a hydrophobic organic resin or a hydrophilic organic resin, and is not particularly limited. The former hydrophobic organic resin is excellent in drainage because it is excellent in hydrophobicity even if a hydrophobic resin such as a fluororesin is not applied to the conductive porous sheet. For example, when a membrane-conductive porous sheet assembly is used as a membrane-electrode assembly of a polymer electrolyte fuel cell or a solid electrolyte membrane-electrode assembly of an air cell, the ability to discharge droplets generated when the battery is used Can be improved. On the other hand, when the membrane is a hydrophilic organic resin, when the membrane is an electrolyte membrane exhibiting good proton conductivity in a water-containing state, the membrane can be kept in a wet state, and an air battery or redox using an aqueous electrolyte can be used. In the case of a flow battery or the like, the electrolytic solution can be diffused throughout the conductive porous sheet, that is, the entire electrode. The organic resin does not contain diamond, graphite, or amorphous carbon.

  The “hydrophobic organic resin” is an organic resin having a contact angle with water of 90 ° or more. For example, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF) , Polyvinyl fluoride (PVF), perfluoroalkoxy fluororesin (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer (ETFE), ethylene / chlorotrifluoro Fluorine resins such as ethylene copolymer (ECTFE), vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer, and copolymers of various monomers constituting the resin; polyethylene (PE), polypropylene (PP ) And other polyolefin resins; polyethylene terf Rate (PET), polyester-based resins such as polyethylene naphthalate (PEN); and the like. These hydrophobic organic resins can be used alone or in combination of two or more. Among these, fluororesins are preferred because of their high heat resistance, chemical resistance, and hydrophobicity.

  On the other hand, the “hydrophilic organic resin” is an organic resin having a contact angle with water of less than 90 °, and examples thereof include cellulose such as rayon; polyacrylonitrile, acrylic oxide, polyacrylic acid, polymethacrylic acid, and the like. Acrylic resins; polyamide resins such as nylon 6 and nylon 66; polyvinyl alcohol resins; hydrophilic polyurethanes; polyvinyl pyrrolidone; thermosetting resins such as phenol resins, urea resins, melamine resins, unsaturated polyester resins, and epoxy resins; Examples thereof include resins having a hydrophilic group such as an amide group, a carboxyl group, a hydroxyl group, an amino group, and a sulfonic acid group. Moreover, these hydrophilic organic resins can also be used independently, and 2 or more types may be mixed or compounded. The conductive fiber of the present invention may be in a state where one or more types of hydrophobic organic resins and / or one or more types of hydrophilic organic resins are mixed or combined. Among these hydrophilic organic resins, it is preferable to include a thermosetting resin that can be a conductive fiber having high rigidity and can easily suppress swelling and shrinkage of the film by bonding with the catalyst layer. Among thermosetting resins, a phenol resin or an epoxy resin is preferable because it is excellent in heat resistance, acid resistance, and rigidity.

The conductive fiber constituting the conductive porous sheet of the present invention contains conductive particles so that the electron mobility is excellent. These conductive particles are particles having an electric resistivity of 10 ⁵ Ω · cm or less, and preferably 10 ³ Ω · cm or less so as to be excellent in conductivity, being 10 ¹ Ω · cm or less. Is more preferable. Such conductive particles are not particularly limited, and examples thereof include carbon black, carbon nanotubes, carbon nanofibers, metal particles, and metal oxide particles. Among these, carbon black is preferable in terms of chemical resistance, conductivity, and dispersibility. The particle size of the conductive particles is not particularly limited, but the average primary particle size is preferably 5 nm to 200 nm, and more preferably 10 nm to 100 nm. The average primary particle diameter of the conductive particles is preferably smaller than the fiber diameter of the conductive fibers so that the conductive particles are less likely to drop off and form a fiber form. In addition, carbon nanofibers such as vapor grown carbon fibers are preferable because they are in the form of fibers, so that the rigidity of the conductive fibers can be increased and swelling and shrinkage of the film can be easily suppressed.

  Such conductive particles may be present in any manner in the conductive fiber, but are preferably present in the fiber. This is because if the conductive particles are present only on the outer surface of the conductive fiber, the fiber internal component becomes a resistance component and tends to be inferior in conductivity. From the viewpoint of conductivity, it is preferable that at least a part of the conductive particles exposed on the surface of the conductive fiber and the conductive particles embedded in the conductive fiber are included. In addition, it is preferable that an electroconductive fiber does not have a branched structure so that the dispersion | variation in a fiber diameter is comparatively small and the smoothness of the surface of an electroconductive porous sheet is excellent. The conductive fiber containing such conductive particles can be obtained, for example, by spinning a spinning solution containing a resin and conductive particles.

  The conductive fiber of the present invention is a fiber containing conductive particles, and the content of the conductive particles is not particularly limited, but the mass ratio between the conductive particles and the resin so as to be excellent in conductivity. Is preferably 10 to 90:90 to 10, more preferably 20 to 80:80 to 20, and still more preferably 30 to 70:70 to 30. This is because when the conductive particles are less than 10 mass%, the conductivity tends to be insufficient, and when the conductive particles exceed 90 mass%, the fiber shape retention tends to be lowered.

  The average fiber diameter of the conductive fibers constituting the conductive porous sheet of the present invention is not particularly limited, but is preferably 10 nm to 10 μm, more preferably 50 nm to 7 μm, and 100 nm to 5 μm. Is more preferable. When the average fiber diameter is larger than 10 μm, there are few contact points between the conductive fibers, and the conductivity tends to be insufficient. On the other hand, when the average fiber diameter is smaller than 10 nm, it is difficult to contain the conductive particles inside the fiber. Because there is. In addition, it is preferable that the average fiber diameter of a conductive fiber is 5 times or more of the primary particle diameter of an electroconductive particle so that an electroconductive particle cannot drop out easily.

  In the present invention, “average fiber diameter” means an arithmetic average value of fiber diameters at 40 points, and “fiber diameter” is a value measured based on a micrograph, and the conductive particles exposed from the fiber surface. When it is composed of only fibers, it means the diameter including the conductive particles exposed from the fiber surface, and the conductive particles do not contain the conductive fibers exposed from the fiber surface, or the conductive particles are Even if the conductive fiber contains conductive fibers exposed from the fiber surface, the conductive particles are exposed from the fiber surface when the conductive particles include conductive fibers having portions not exposed from the fiber surface. Means the diameter at the missing part.

  The conductive fiber of the present invention is preferably a continuous fiber so as to have excellent electron mobility. Such a conductive continuous fiber can be produced, for example, by an electrostatic spinning method or a spunbond method. In particular, a conductive continuous fiber formed by an electrostatic spinning method is suitable because it has excellent electron mobility. It is. “Continuous fiber” in the present invention, when taking a photograph of a conductive porous sheet using an electron microscope at a magnification at which one side of the photographed image is about 60 times the average fiber diameter of the conductive fiber, It means that the number of ends of the conductive fiber per one electron micrograph is 0.3 or less. In other words, the total number of ends of conductive fibers in 20 electron micrographs is divided by the number of photographs (20), which means that the number of ends of conductive fibers per electron micrograph is 0.3 or less. To do. In addition, the photography is performed in the location which is continuously different in the center part which does not include the cutting part of the conductive porous sheet. For example, when confirming whether a conductive fiber having an average fiber diameter of 1 μm is a continuous fiber, photography using an electron microscope is performed at different locations in the central portion not including the cut portion of the conductive porous sheet. , The number of ends of the conductive fiber per one electron micrograph is calculated, and if it is 0.3 or less, it is considered as a continuous fiber. be able to.

  The conductive porous sheet of the present invention contains the conductive fibers as described above, but the fluorine inherently possessed by the conductive porous sheet is used to improve the liquid permeability and gas diffusibility. It is preferable that nothing is filled, such as a system resin and / or conductive particles (for example, carbon particles). That is, it is preferable to be composed only of fibers such as conductive fibers, and it is more preferable to be composed only of conductive fibers.

  Although the form of the electroconductive porous sheet of this invention is not specifically limited, For example, it can be a nonwoven fabric, a textile fabric, and a knitted fabric. Among these, the nonwoven fabric is preferable because the pore diameters are relatively uniform and the liquid permeability and gas diffusibility can be excellent.

  When the conductive porous sheet of the present invention is in the form of a nonwoven fabric, the conductive fibers may be bonded together by an adhesive, but are bonded by a resin constituting the conductive fibers so as to be excellent in conductivity. Is preferred. Examples of the suitable resin bond include entanglement between conductive fibers, plasticization bond with a solvent, fusion by heat, or bond by curing.

  The content ratio of the conductive fibers in the conductive porous sheet of the present invention is preferably 10 mass% or more, more preferably 50 mass% or more, and more preferably 70 mass% or more so that the mobility of electrons is excellent. Is more preferably 90% by mass or more, particularly preferably composed of only conductive fibers (100% by mass). As fibers other than conductive fibers, hydrophobic organic resin fibers such as fluorine fibers, polyolefin fibers and polyester fibers, hydrophilic organic fibers such as cellulose, polyamide fibers, acrylic fibers, polyvinyl alcohol fibers and hydrophilic polyurethane fibers. Resin fibers or thermosetting resin fibers such as phenol fibers can be included.

Conductive porous sheet of the present invention may be contain fibers other than the conductive fibers, as high conductivity, it is preferable electric resistance of 300mΩ · cm ² or less, 150mΩ · cm ² More preferably, it is more preferably 50 mΩ · cm ² or less. The “electric resistance” of the present invention is a method in which a conductive porous sheet (25 cm ² ) cut into 5 cm square is sandwiched between metal plates plated with gold from both sides, and a current of 1 A is applied under a pressure of 2 MPa in the stacking direction of the metal plates. The voltage (V) is measured with (I) applied. Then, resistance was calculated (R = V / I), further, a value obtained by multiplying the area of the conductive porous sheet (25 cm ^2).

  In order to make the conductive porous sheet excellent in conductivity, the conductive particles preferably occupy 10 to 90 mass% of the conductive porous sheet, more preferably 20 to 80 mass%, more preferably 30 to 30%. More preferably, it occupies 70 mass%.

The basis weight of the conductive porous sheet of the present invention is not particularly limited, but is preferably 0.1 to 100 g / m ² from the viewpoint of handleability and productivity, and is 0.1 to 50 g / m ² . Is more preferable. The thickness is not particularly limited, but is preferably 1 to 500 μm, more preferably 1 to 250 μm, and further preferably 3 to 100 μm. The thinner the conductive porous sheet is, the lower the resistance is, and the volume occupied by the membrane-conductive porous sheet assembly can be reduced. This “weight per unit” is a value obtained by cutting a conductive porous sheet into 10 cm square and preparing a sample, and converting the mass of the sample to a mass of 1 m ² , and “thickness” is a thickness gauge ( ) Made by Mitutoyo: code No. 547-321: measuring force 1.5N or less).

The conductive porous sheet of the present invention preferably has a porosity of 60% or more so as to be excellent in liquid permeability and gas diffusibility even in the plane direction by utilizing the inherent porosity. It is more preferable to have a porosity, and it is even more preferable to have a porosity of 80% or more. The upper limit of the porosity is not particularly limited, but is preferably 99% or less, more preferably 95% or less, and still more preferably 90% or less from the viewpoint of form stability. This “porosity P (unit:%)” is a value obtained from the following equation.
P = 100- (Fr1 + Fr2 + .. + Frn)
Here, Frn indicates the filling rate (unit:%) of component n constituting the conductive porous sheet, and is a value obtained from the following formula.
Frn = [M × Prn / (T × SGn)] × 100
Here, M is the basis weight of the conductive porous sheet (unit: g / cm ² ), T is the thickness of the conductive porous sheet (unit: cm), and Prn is the component n in the conductive porous sheet (for example, resin, conductive SGn means the specific gravity (unit: g / cm ³ ) of component n, respectively.

  The surface of the conductive fiber constituting the conductive porous sheet of the present invention may be covered with a fluororesin. Thus, when it coat | covers with a fluorine-type resin, it is excellent in hydrophobicity and is excellent in drainage. For example, when a membrane-conductive porous sheet assembly is used as a membrane-electrode assembly of a polymer electrolyte fuel cell or a solid electrolyte membrane-electrode assembly of an air cell, the ability to discharge droplets generated when the battery is used Is excellent.

  Examples of the fluororesin include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), perfluoroalkoxy fluororesin (PFA), tetrafluoroethylene. Ethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride / tetrafluoroethylene / hexafluoro Examples thereof include a propylene copolymer and a copolymer of various monomers constituting the resin.

  Moreover, the electroconductive porous sheet can contain carbon in the space | gap of an electroconductive porous sheet so that it may be excellent in electroconductivity. Examples of the carbon include carbon black, carbon nanotube, and carbon nanofiber.

  The conductive porous sheet of the present invention can be produced by a conventional method. For example, the conductive fibers constituting the conductive porous sheet in the form of a suitable non-woven fabric can be obtained by spinning using a spinning solution in which a resin and conductive particles are mixed. A fiber web can be formed by collecting and accumulating. When the fiber web is moderately intertwined, it can be used as a conductive porous sheet if it has a certain level of strength, and in order to impart or improve the strength, plasticization with a solvent, fusion by heat, adhesive The conductive porous sheet can also be formed by bonding by adhesion, curing of the resin, or the like.

  In addition, it is preferable that the conductive fiber which comprises the fiber web formed by collecting and accumulating the conductive fiber directly is a continuous fiber. It is because it is excellent in terms of conductivity and strength by being a continuous fiber.

  Further, it is preferable that the conductive fiber is spun by using a spinning solution containing a thermosetting resin (particularly a phenol resin or an epoxy resin) so that the conductive fiber has high rigidity. Furthermore, when the conductive fiber contains a thermosetting resin, it is preferable to increase the rigidity of the conductive fiber by curing with heat. As will be described later, when the conductive porous sheet and the catalyst layer are bonded by the thermosetting resin constituting the conductive fiber, the thermosetting resin is in a semi-cured state, and a so-called B-stage state. It is preferable to perform heat treatment under the following conditions. In this case, it is preferable to perform heat treatment so that the resin layer is completely cured after being adhered to the catalyst layer. Conditions for curing the thermosetting resin or conditions for semi-curing differ depending on the type of the thermosetting resin, and thus are appropriately set according to the type of the thermosetting resin.

  As a method for forming a fiber web, for example, an electrostatic spinning method, a spun bond method, a melt blow method, or a spinning solution discharged from a liquid discharging unit as disclosed in JP 2009-287138 A is used. On the other hand, a method of discharging the gas in parallel and applying a shearing force to the spinning solution in a straight line to form a fiber can be exemplified. Among these, according to the electrostatic spinning method or the method disclosed in Japanese Patent Application Laid-Open No. 2009-287138, conductive fibers having a small fiber diameter can be spun, so that the conductive porous sheet is thin and has low resistance. In addition, a membrane-conductive porous sheet assembly having a small volume can be produced. In particular, the electrospinning method is preferable because continuous conductive fibers can be spun, the end portions of the fibers are small, and the membrane is hardly damaged. In addition, when using a spinning solution in which conductive particles are mixed in a solution in which a resin is dissolved in a solvent, as in the electrostatic spinning method or the method disclosed in JP2009-287138A, the solvent is volatilized during spinning. If a spinning solvent is removed by solvent replacement after forming a fiber web using a material that is difficult to form, conductive fibers tend to be in a plasticized state, and as a result, a conductive porous sheet having excellent conductivity is produced. It is also preferable because the conductive fibers are in close contact with each other and the contact resistance is lowered.

  Also, after winding the spun conductive fiber as a continuous fiber, the conductive fiber is cut into a desired fiber length to make a short fiber, and then a fiber web is formed by a known dry method or wet method, and plasticized with a solvent. Bonding by heat fusion, adhesive bonding, resin curing, etc. can be used to form a conductive porous sheet.

  When the resin constituting the conductive fiber is an acrylic oxide, a spinning solution in which an acrylic resin and conductive particles are mixed is spun to form a conductive fiber, and the fiber web containing the conductive fiber is directly formed. After forming indirectly or indirectly, by heating at a temperature of 200 to 300 ° C. in the air, the conductivity of the conductive porous sheet can be further increased by using the acrylic resin as acrylic oxide. Alternatively, after the conductive fiber spun using a spinning solution in which acrylic resin and conductive particles are mixed is heated in air at a temperature of 200 to 300 ° C., the acrylic resin is converted to acrylic oxide, It is also possible to form a nonwoven fabric using conductive fibers made of conductive particles.

  Furthermore, when the conductive fiber surface is coated with a fluorine-based resin so that the conductive porous sheet can easily extrude liquid water, a solution or paste containing the fluorine-based resin is applied, spread, or impregnated on the conductive porous sheet. After applying by a method such as carrying out, it is dried and fired. Similarly, when carbon is contained in the voids of the conductive porous sheet, similarly, a solution or paste containing carbon and a fluororesin is applied to the conductive porous sheet by a method such as application, dispersion, or impregnation, and then drying and Bake.

(film)
The membrane constituting the membrane-conductive porous sheet assembly of the present invention varies depending on the application of the membrane-conductive porous sheet assembly, but can be a conventionally known one. For example, when a membrane-conductive porous sheet assembly is used as a membrane-electrode assembly of a polymer electrolyte fuel cell, a perfluorocarbon sulfonic acid resin membrane, a sulfonated aromatic hydrocarbon resin membrane, an alkyl sulfone It can be an electrolyte membrane such as a fluorinated aromatic hydrocarbon resin membrane or an inorganic-organic composite resin membrane.

  Further, when the membrane-conductive porous sheet assembly is used as a solid electrolyte membrane-electrode assembly for an air battery, the membrane may be an ion conductive solid electrolyte suitable for the negative electrode material, and is not particularly limited. For example, it can be composed of an inorganic solid electrolyte, a polymer electrolyte, or a gel electrolyte.

  Further, when the membrane-conductive porous sheet assembly is used as a diaphragm-electrode assembly of a redox flow battery, the membrane has excellent separability between ions of the positive electrode active material and ions of the negative electrode active material, and allows proton transmission. Any material can be used as long as it has excellent properties, and is not particularly limited. For example, it can be composed of an ion exchange membrane such as a cation exchange membrane or an anion exchange membrane.

  In addition, any film | membrane may be reinforced with reinforcement materials, such as a nonwoven fabric.

(Catalyst layer)
Although the catalyst layer of the membrane-conductive porous sheet assembly of the present invention varies depending on the use of the membrane-conductive porous sheet assembly, it can be a conventionally known one.

  For example, when the membrane-conductive porous sheet assembly is used as a membrane-electrode assembly of a polymer electrolyte fuel cell, it can be a layer containing a catalyst and an ion exchange resin. The catalyst is not particularly limited. For example, platinum, platinum alloy [ruthenium, rhodium, palladium, osmium, iridium, gold, silver, chromium, iron, titanium, manganese, cobalt, nickel, molybdenum, tungsten, An alloy of one or more metals selected from aluminum, silicon, zinc, and tin and platinum], or platinum or a platinum alloy may be a catalyst supported on carbon such as activated carbon or carbon black. In addition, a catalyst can contain 1 type, or 2 or more types. The catalyst of the cathode side catalyst layer and the catalyst of the anode side catalyst layer may be the same or different. On the other hand, the ion exchange resin can be the same as the electrolyte membrane described above. That is, it can be a perfluorocarbon sulfonic acid resin, a sulfonated aromatic hydrocarbon resin, an alkylsulfonated aromatic hydrocarbon resin, an inorganic-organic composite resin, or the like. In particular, the same electrolyte membrane is preferable because the affinity between the catalyst layer and the electrolyte membrane is excellent. The ion exchange resin of the cathode side catalyst layer and the ion exchange resin of the anode side catalyst layer may be the same or different. Moreover, the ion exchange resin of any catalyst layer may be comprised from 1 type, or may be comprised from 2 or more types.

  When the membrane-conductive porous sheet assembly is used as a solid electrolyte membrane-electrode assembly for an air battery, the catalyst layer is a layer containing a catalyst and a water repellent / binder such as a fluororesin. Can do. The catalyst is not particularly limited as long as it is a particle that causes an oxygen reduction reaction at the positive electrode and has catalytic activity, and is not particularly limited, but for the above-mentioned polymer electrolyte fuel cell. In addition to the catalyst, manganese dioxide, activated carbon, perovskite complex oxide, metal-containing pigment, and the like can be used.

  Furthermore, when the membrane-conductive porous sheet assembly is used as a membrane-electrode assembly of a redox flow battery, the catalyst layer can be a layer containing a catalyst and an ion exchange resin. Although it does not specifically limit as this catalyst, For example, it can be metal oxides, such as a tin oxide and a bismuth oxide, a graphene oxide, a carbon nanotube, a metal carrying | support carbon material.

  In any catalyst layer, an electron conductor can be included in addition to the catalyst. The electron conductor is preferably conductive particles similar to the conductive particles contained in conductive fibers such as carbon black.

(Membrane-conductive porous sheet assembly)
The membrane-conductive porous sheet assembly of the present invention has a conductive porous sheet, a membrane, and a catalyst layer as described above, a catalyst layer is present between the membrane and the conductive porous sheet, and the membrane is The minimum 90 ° peel strength between the conductive porous sheet and the catalyst layer after repeated swelling and shrinkage is 0.06 N / cm or more, and the conductive porous sheet and the catalyst layer are well bonded. Therefore, even when the membrane-conductive porous sheet assembly is used, swelling and shrinkage of the membrane can be sufficiently suppressed, and stress due to the deformation can be reduced, so that the catalyst layer can be broken or peeled off from the membrane. Can be prevented. The larger the minimum 90 ° peel strength is, the better the action is. Therefore, the minimum 90 ° peel strength is more preferably 0.08 N / cm or more, and more preferably 0.10 N / cm or more. More preferably, it is 12 N / cm or more. As the minimum 90 ° peel strength increases, the swelling and shrinkage of the film can be suppressed, so there is no particular upper limit.

This “minimum 90 ° peel strength between the conductive porous sheet and the catalyst layer after the membrane repeats swelling and shrinking” is a value obtained by the following procedure.
(1) A 50 mm square membrane-conductive porous sheet assembly is immersed in hot water maintained at a temperature of 80 ° C. for 1 hour in a water bath.
(2) After lightly wiping off moisture, it is placed in a dryer set at a temperature of 60 ° C. and dried for 1 hour.
(3) By repeating the operations (1) to (2) three times, the membrane is repeatedly swollen and contracted.
(4) Cut the membrane-conductive porous sheet assembly into 1 cm wide strips as shown in FIG. 2 to prepare five test pieces.
(5) A peel test attachment [manufactured by Imada Co., Ltd.] in which one side of a double-sided tape is attached to one conductive porous sheet surface of a test piece, and the other side of the double-sided tape is incorporated in a vertical electric measurement stand. Secure to the test bench.
(6) Part of the conductive porous sheet / catalyst layer / membrane / catalyst layer of the test piece is peeled off with tweezers to form a grip portion, and fixed to a digital force gauge (manufactured by Imada Co., Ltd.) with a clip.
(7) The conductive porous sheet / catalyst layer / membrane / catalyst layer of the test piece was measured at a speed of 60 mm / min. Then, the load (N) at a displacement of 10 to 30 mm in a stable adhesive state is measured.
(8) The 90 ° peel strength is calculated by dividing the load by the width of the test piece (1 cm).
(9) The 90 ° peel strength is measured for five test pieces, and the 90 ° peel strength having the weakest strength is defined as the minimum 90 ° peel strength (unit: N / cm).

  The membrane-conductive porous sheet assembly of the present invention can be produced, for example, by forming a catalyst layer on both surfaces of the membrane, then laminating the conductive porous sheet on each catalyst layer, and heating and pressing.

  Hereinafter, a membrane-electrode assembly of a polymer electrolyte fuel cell will be described as an example. In a single solvent or mixed solvent composed of ethyl alcohol, propyl alcohol, butyl alcohol, ethylene glycol dimethyl ether, etc., a catalyst and an ion exchange resin After uniformly mixing with an ultrasonic disperser, etc., a catalyst paste is prepared, and this catalyst paste is coated or spread on both sides of the membrane to form a catalyst layer, and then a conductive porous sheet is laminated on each catalyst layer. Then, by heating and pressurizing, the conductive fiber constituent resin can be flowed or melted and solidified or cured to be adhered to the catalyst layer.

  When the conductive particles of the conductive fiber of the present invention are exposed from the fiber surface, the exposed area of the resin on the fiber surface is small, but the resin flows or melts by heating and solidifies or cures, thereby The minimum 90 ° peel strength can be obtained by bonding. In addition, by containing conductive particles, the fiber shape can be maintained even when the resin flows or melts by heating, and the porosity of the conductive porous sheet can be maintained. Excellent gas diffusivity.

  In addition, the heating and pressing at the time of manufacturing the membrane-conductive porous sheet assembly can be performed by, for example, a hot press machine, and the heating temperature can be the minimum 90 ° peel strength. Although not particularly limited, the lower limit is the temperature at which the resin begins to flow by heating, the temperature at which other materials (catalyst layer constituent materials, membranes, etc.) are not deteriorated, and the coating is not formed by liquefaction of the resin. It is desirable that the upper limit is in the range. For example, when a cresol novolac epoxy resin is a main ingredient and a novolac type phenol resin is a curing agent, the heating temperature is preferably 100 ° C to 200 ° C, more preferably 130 ° C to 180 ° C, and more preferably 150 to 160 ° C. More preferably, the temperature is set to ° C.

  The pressure at the time of heating and pressurization is not particularly limited as long as it is a pressure that can achieve the minimum 90 ° peel strength, but it is preferably 0.1 MPa or more, and preferably 1 MPa or more. More preferably, it is 1.2 MPa or more. On the other hand, when the pressure is too strong, voids in the conductive porous sheet are reduced, and liquid permeability and / or gas diffusibility tends to deteriorate. Therefore, the pressure is preferably 20 MPa or less, and is 10 MPa or less. More preferably, it is 5 MPa or less.

  In the above method, the catalyst layer is formed by coating or spraying the catalyst paste on both sides of the film. Instead, the catalyst paste is coated or sprayed on a transfer substrate such as a polytetrafluoroethylene substrate. After forming the catalyst layer, the catalyst layer can be transferred by hot pressing on both sides of the membrane.

  Moreover, in the said method, although the electroconductive porous sheet is laminated | stacked on each catalyst layer, by laminating | stacking the electroconductive fiber which spun directly on the catalyst layer, it forms and laminates simultaneously with an electroconductive porous sheet. You can also

  As another method for producing a membrane-conductive porous sheet assembly, two sets of laminated sheets are prepared by laminating a conductive porous sheet and a catalyst layer and bonding the conductive fibers constituting the conductive porous sheet to the catalyst layer. After that, these laminated sheets can be produced by laminating such that the catalyst layers are in contact with both surfaces of the membrane and bonding them with the conductive fiber constituting resin constituting the conductive porous sheet.

  The catalyst layer can be formed by coating or spreading the above-mentioned catalyst paste on a conductive porous sheet, or the catalyst layer can be formed by coating or spreading the catalyst paste on a transfer substrate such as a polytetrafluoroethylene substrate. Then, it can be transferred to a conductive porous sheet. Furthermore, the conductive porous sheet is directly accumulated on the catalyst layer formed by coating or spraying the catalyst paste on the transfer base material such as a polytetrafluoroethylene base material, thereby simultaneously laminating the conductive porous sheet. You can also Moreover, adhesion | attachment with the film | membrane of a lamination sheet can be implemented by heat pressurization (for example, hot press). The heating and pressurization may be any conditions as long as the minimum 90 ° peel strength can be obtained, and is not particularly limited. However, when hot pressing is performed, the conditions may be the same as those in the above-described method. it can.

  As another method for producing a membrane-conductive porous sheet assembly, the conductive porous sheet and the catalyst layer can be bonded via an uncured thermosetting resin. For example, after forming a catalyst layer on both sides of the film, the uncured thermosetting resin and the conductive porous sheet are laminated on each catalyst layer in this order, heated and pressurized, and then uncured thermosetting resin. Can be produced by bonding the conductive porous sheet and the catalyst layer. In addition, it is preferable to contain the above-mentioned electroconductive particle to the same extent so that the thermosetting resin of a non-hardened state may be excellent in electroconductivity.

  This uncured thermosetting resin can be composed of the same thermosetting resin as the thermosetting resin that constitutes the conductive fiber, but it is conductive so that it has excellent adhesion to the conductive porous sheet. When the conductive fiber constituting the porous fiber sheet contains a thermosetting resin, the uncured thermosetting resin is preferably the same type as the thermosetting resin constituting the conductive fiber, and the same It is more preferable that

  The uncured thermosetting resin may be in any state and may be a liquid or a solid such as particles or fibers. Among these, it is preferable that the uncured thermosetting resin is a fiber because it is difficult to block the voids of the conductive porous sheet and is excellent in gas diffusibility. In particular, when the thermosetting fibers are in a web state bonded by entanglement, semi-curing, etc., it is preferable because it can be bonded to the catalyst layer and the dimensional stability of the membrane-conductive porous sheet assembly is more excellent. is there. Such a suitable uncured thermosetting resin fiber is, for example, an electrospinning method or a spinning solution discharged from a liquid discharging unit as disclosed in JP 2009-287138 A. On the other hand, it is possible to fabricate by spinning the gas in parallel and applying a shearing force to the spinning solution in the form of a single linear fiber, and if the spun uncured thermosetting resin fibers are accumulated, the web state It can be. In addition, the spun uncured thermosetting resin fiber can be directly laminated on the catalyst layer or the conductive porous sheet to obtain a web state.

  The method for forming the catalyst layer on the film may be a method of coating or spreading the catalyst paste, or a method for transferring the catalyst layer in the same manner as described above. Further, the curing condition of the uncured thermosetting resin is not particularly limited as long as the minimum 90 ° peel strength can be obtained. The conditions can be the same as in the case of.

  Furthermore, as another method for producing a membrane-conductive porous sheet assembly, two sets of laminated sheets obtained by laminating an uncured thermosetting resin and a catalyst layer in this order on a conductive porous sheet were prepared, and then these laminated sheets were used. Can be manufactured by adhering by curing the uncured thermosetting resin by laminating the catalyst layer so that the catalyst layer is in contact with both surfaces of the film and applying heat and pressure. The formation of the catalyst layer, the formation of the uncured thermosetting resin, heating and pressurization, and the like can be performed under the same conditions as in the above-described method. Moreover, it is preferable to contain the above-mentioned electroconductive particle to the same extent so that the uncured thermosetting resin may be excellent in electroconductivity.

  In any case, one conductive porous sheet and the other conductive porous sheet may be the same, and regarding the conductive particles, the type, particle size, presence state, content; For fibers, average fiber diameter, fiber length, constituent resin, presence / absence of coating with fluororesin; for conductive porous sheet, morphology, bonding state, conductive fiber content, electrical resistance, conductive particle occupancy, The conductive porous sheet may be different in terms of basis weight, thickness, porosity, manufacturing method, presence or absence of filling with fluororesin and / or conductive particles, and the like.

  The manufacturing method described above is a manufacturing method in the case where a conductive porous sheet is used for both electrodes such as a membrane-electrode assembly of a solid polymer fuel cell. In the case where only the catalyst layer is present, a membrane-conductive porous sheet can be similarly produced except that the membrane and / or the catalyst layer may be different.

(Solid polymer fuel cell)
Since the polymer electrolyte fuel cell of the present invention (hereinafter sometimes simply referred to as “fuel cell”) includes the membrane-conductive porous sheet assembly of the present invention as a membrane-electrode assembly, Since the catalyst layer is hardly broken or peeled off even in a hot water environment during power generation, the power generation performance is excellent. In particular, when the conductive fiber contains an organic resin, the conductive porous sheet has flexibility, so the gap between the conductive porous sheet and the adjacent member (for example, gas diffusion layer, bipolar plate) should be reduced. Since the interface resistance between electrons and heat is small, the power generation performance is excellent.

  The fuel cell of the present invention can be exactly the same as a conventional fuel cell except that the membrane-conductive porous sheet assembly of the present invention as described above is provided as a membrane-electrode assembly. For example, it has a structure in which a plurality of cell units in which a membrane-conductive porous sheet assembly as described above is sandwiched between a pair of bipolar plates are stacked. Such a fuel cell can be manufactured, for example, by stacking a plurality of cell units and fixing them.

  The bipolar plate is not particularly limited as long as it has a flow path that is highly conductive, does not transmit gas, and can supply gas to the conductive porous sheet. For example, carbon or metal Or a porous material such as a mesh or a foam.

  In the fuel cell of the present invention, a conductive porous sheet (hereinafter referred to as “gas diffusion porous sheet”) that can act as a gas diffusion layer between the membrane-conductive porous sheet assembly and the bipolar plate. It is also possible to make a cell unit. When the gas diffusion porous sheet is thus interposed, the conductive porous sheet constituting the membrane-conductive porous sheet assembly can act as a moisture management layer in the conventional gas diffusion layer. However, it does not penetrate into the gas diffusion porous sheet that acts as a gas diffusion layer, and does not hinder the drainage and gas diffusion properties of the gas diffusion porous sheet, so that the drainage and gas diffusion properties inherent to the gas diffusion porous sheet can be exhibited. The fuel cell is excellent in drainage and gas diffusibility.

  Examples of the gas diffusion porous sheet include carbon paper, carbon nonwoven fabric, and glass fiber nonwoven fabric filled with a conductive agent and a fluorine resin; acid-resistant organic fibers (for example, polytetrafluoroethylene fibers, Organic fiber made of polyvinylidene fluoride fiber, polyparaphenylene terephthalamide fiber, polyolefin fiber, polyphenylene sulfide fiber, polyester fiber typified by polyethylene terephthalate fiber or polytrimethylene terephthalate fiber, or two or more kinds thereof. Nonwoven fabric filled with a conductive agent and a fluororesin; porous bodies or meshes of acid-resistant metals (for example, stainless steel, titanium, etc.) can be mentioned.

(application)
The membrane-conductive porous sheet assembly of the present invention sufficiently suppresses swelling and shrinkage of the membrane, is excellent in dimensional stability, and can reduce stress due to its deformation. It can be suitably used for a battery that requires a film having excellent dimensional stability. For example, it can be used as a solid electrolyte membrane-electrode assembly of an air battery or a diaphragm-electrode assembly of a redox flow battery.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

(Production of electrolyte membrane with catalyst layer)
0.8 g of platinum-supported carbon particles (manufactured by Tanaka Kikinzoku Co., Ltd., TEC10V40E) is added to 10.4 g of ethylene glycol dimethyl ether and dispersed by ultrasonic treatment, and then 5 mass% Nafion (registered resin solution), which is an ion exchange resin solution. (Trademark) solution (manufactured by Sigma-Aldrich, USA) (4.0 g) was added, dispersed by ultrasonic treatment, and further stirred with a stirrer to prepare a catalyst paste.

Next, this catalyst paste was applied to a support [Naflon (registered trademark), polytetrafluoroethylene tape, manufactured by Nichias Co., Ltd., thickness: 0.1 mm] cut to a square of 50 mm, and heated at 60 ° C. with a hot air dryer. The catalyst layer having a platinum loading of 0.5 mg / cm ² was formed by drying at 0 ° C.

  On the other hand, Nafion (registered trademark) NRE212CS (manufactured by DuPont, USA, melting point: 200 ° C. or higher) was prepared as an electrolyte membrane. After transferring the catalyst layer on both surfaces of the electrolyte membrane, the catalyst layer was joined by hot pressing under conditions of a temperature of 140 ° C., a pressure of 2.5 MPa, and a time of 10 minutes, and an electrolyte membrane with a catalyst layer (catalyst layer: 50 mm square) was attached. Produced.

<Example 1>
A vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer was added to N, N-dimethylformamide (DMF) and dissolved using a rocking mill to obtain a solution having a concentration of 10 mass%.

  Next, acetylene black (Denka black granular product, manufactured by Denki Kagaku Kogyo Co., Ltd., average primary particle size: 35 nm) was mixed with the solution as conductive particles, and stirred.

  Further, a thermosetting resin composed of a cresol novolac epoxy resin as a main component and a novolac type phenol resin as a curing agent is added to the solution, and acetylene black, a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer, and an epoxy resin are added. A spinning solution having a solid mass ratio of 50:40:10 and a solid content concentration of 12 mass% was prepared.

Thereafter, the spinning solution was spun by an electrostatic spinning method, and then directly accumulated, and conductive continuous fibers containing acetylene black (average fiber diameter: 400 nm, acetylene black partially exposed from the fiber surface and embedded inside) The conductive porous nonwoven fabric (weight per unit area: 14 g / m ² , thickness: 50 μm, electrical resistance: 6 mΩ · cm ²⁾ , voids containing only acetylene black, having no branched structure, and having an epoxy resin in an uncured state Rate: 84%, nothing is filled). The electrospinning conditions were as follows.

<Electrostatic spinning conditions>
Electrode: Metal nozzle (inner diameter 0.33 mm) and stainless steel drum Discharge amount: 2 g / hour Distance between nozzle tip and stainless steel drum: 10 cm
Applied voltage: 12 kV
Temperature / humidity: 25 ° C / 35% RH

  Next, the conductive porous nonwoven fabric is cut into 50 mm squares and laminated on both surfaces of the catalyst layer-attached electrolyte membrane so as to completely overlap the catalyst layer-attached electrolyte membrane, and then the temperature is 150 ° C. and the pressure is 1.5 MPa. The epoxy resin constituting the conductive continuous fiber was cured by hot pressing under the condition of 4 minutes, thereby producing an electrolyte membrane-conductive porous sheet assembly.

<Example 2>
In the same manner as in <Example 1>, after forming a conductive porous nonwoven fabric by an electrostatic spinning method, a heat-treated porous nonwoven fabric (weight per unit area: 150 ° C., heat treatment for 30 minutes and cured epoxy resin) 14 g / m ² , thickness: 50 μm, electric resistance: 6 mΩ · cm ² , porosity: 84%, nothing is filled).

Next, after winding the cured conductive porous nonwoven fabric on a stainless steel drum, the spinning solution prepared in the same manner as in Example 1 was spun by the electrospinning method under the same conditions as in Example 1 and directly applied to the cured conductive material. Conductive continuous fiber containing acetylene black accumulated on a porous nonwoven fabric (average fiber diameter: 400 nm, including acetylene black partially exposed from the fiber surface and acetylene black buried inside, having no branched structure) Only intertwined, uncured conductive porous nonwoven fabric layer with epoxy resin not cured (weight per unit: 2 g / m ² , thickness: 6 μm, porosity: 84%, nothing is filled) and cured conductivity A laminated conductive porous nonwoven fabric composed of two layers of porous nonwoven fabric layer was prepared.

  Next, after the laminated conductive porous nonwoven fabric is cut into 50 mm square and laminated on both surfaces of the electrolyte membrane with catalyst layer so that the uncured conductive porous nonwoven fabric layer surface completely overlaps with the catalyst layer of the electrolyte membrane with catalyst layer The epoxy resin constituting the conductive continuous fiber constituting the uncured conductive porous nonwoven fabric is cured by hot pressing under the conditions of a temperature of 150 ° C., a pressure of 1.5 MPa, and a time of 4 minutes. A porous porous sheet assembly was produced.

<Comparative Example 1>
A carbon non-woven fabric having a microporous layer made of a fluororesin and carbon particles on one side (made by Freudenberg, product name H15C5, basis weight: 94 g / m ² , thickness: 170 μm, average fiber diameter of carbon fibers: 10 μm, electrical resistance : 8 mΩ · cm ² ).

  Further, a 5 mass% Nafion (registered trademark) solution (manufactured by Sigma Aldrich, USA) and acetylene black [Denka Black (registered trademark) granular product, manufactured by Denki Kagaku Kogyo Co., Ltd., average primary particle size: 35 nm] The adhesive solution was prepared by mixing such that the ratio was [Nafion (solid content)]: [acetylene black] = 4: 5.

And the said adhesive solution was apply | coated to the microporous layer surface of the said carbon nonwoven fabric so that it might become ² mg / cm <2> (solid content), and it dried, and produced the carbon nonwoven fabric with an adhesive layer.

  Next, the carbon non-woven fabric with an adhesive layer is cut into 50 mm square and laminated on both surfaces of the electrolyte membrane with a catalyst layer so that the adhesive layer completely overlaps with the catalyst layer of the electrolyte membrane with the catalyst layer. By hot pressing under conditions of a pressure of 1.5 MPa and a time of 4 minutes, an adhesive membrane-conductive porous sheet assembly was produced by adhering with a Nafion resin constituting the adhesive layer. The electrolyte membrane with a catalyst layer peeled off and could not be handled.

<Comparative example 2>
A vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (melting point: 146 ° C.) was added to N, N-dimethylformamide (DMF) and dissolved using a rocking mill to obtain a solution having a concentration of 10 mass%.

  Next, acetylene black (Denka Black granular product, manufactured by Denki Kagaku Kogyo Co., Ltd., average primary particle size: 35 nm) was mixed as the conductive particles in the solution, stirred, and further diluted by adding DMF to acetylene. Black was dispersed to prepare a spinning solution having a solid mass ratio of acetylene black and vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer of 40:60 and a solid content concentration of 11 mass%.

Then, using this spinning solution, in the same manner as in <Example 1>, conductive continuous fibers containing acetylene black (average fiber diameter: 420 nm, acetylene black partially exposed from the fiber surface and acetylene embedded inside) Conductive porous nonwoven fabric intertwined only with black (not having a branched structure) (weight per unit: 11 g / m ² , thickness: 50 μm, electrical resistance: 10 mΩ · cm ² , porosity: 88%, filled with anything The electrolyte membrane-conductive porous sheet assembly was manufactured.

<Comparative Example 3>
A conductive porous nonwoven fabric was produced in the same manner as in <Comparative Example 2>.

  Next, the conductive porous nonwoven fabric was cut into 50 mm square, and laminated on both surfaces of the catalyst layer-attached electrolyte membrane so that the conductive porous nonwoven fabric completely overlapped with the catalyst layer-attached electrolyte membrane, the temperature was 100 ° C., An electrolyte membrane-conductive porous sheet assembly was manufactured by hot pressing under conditions of a pressure of 1.5 MPa and a time of 4 minutes.

<Comparative Example 4>
A spinning solution was prepared in the same manner as in Example 1, and a conductive porous nonwoven fabric was prepared by an electrostatic spinning method, followed by heat treatment for 30 minutes with a hot air dryer set at a temperature of 150 ° C., and thermosetting. A cured conductive porous non-woven fabric (weight per unit: 14 g / m ² , thickness: 50 μm, electrical resistance: 6 mΩ · cm ² , porosity: 84%, nothing is filled) cured with epoxy resin, which is a conductive resin did.

  Next, after cutting the cured conductive porous nonwoven fabric into 50 mm square and laminating on both sides of the catalyst layer-attached electrolyte membrane so that the cured conductive porous nonwoven fabric completely overlaps the catalyst layer of the catalyst layer-attached electrolyte membrane, An electrolyte membrane-conductive porous sheet assembly was produced by hot pressing under conditions of a temperature of 150 ° C., a pressure of 1.5 MPa, and a time of 4 minutes.

<Measurement of minimum 90 ° peel strength>
Minimum 90 ° peel strength between conductive porous sheet and catalyst layer in electrolyte membrane-conductive porous sheet assembly of Examples 1-2 and Comparative Examples 1-4 after the electrolyte membrane repeated swelling and shrinking Was measured by the method described above. The results are shown in Table 1.

<Measurement of swelling ratio of electrolyte membrane and evaluation of adhesion>
The 50 mm square electrolyte membrane-conductive porous sheet assembly of Examples 1 and 2 and Comparative Examples 1 to 4, and the 50 mm square electrolyte membrane with a catalyst layer as a reference example were each maintained at a temperature of 80 ° C. in a water bath. It was immersed in hot water for 1 hour. After immersion, the length of the four sides of the conductive porous sheet (50 mm square) was measured with a ruler. When part or all of the conductive porous sheet and the electrolyte membrane with a catalyst layer is peeled off (Comparative Examples 2 to 4, Reference Example), the length of the four sides of the catalyst layer (50 mm square) is determined by a ruler. Measured at.

And after calculating the average dimension (= Dm, unit: mm) per side from the following formula 1, the swelling ratio (= Sr, unit:%) of the electrolyte membrane was calculated from the following formula 2. The results are shown in Table 1.
Dm = (a + b + c + d) / 4 Formula 1
Sr = (Dm / 50) × 100 (2)
Here, ad means the length (unit: mm) of each side of the four sides of the conductive porous sheet or the catalyst layer after immersion in hot water.

Moreover, the adhesion state of the electroconductive porous sheet and the electrolyte membrane with a catalyst layer after immersion in hot water was visually observed and evaluated according to the following criteria. The results are shown in Table 1.
○: No separation was observed between the conductive porous sheet and the electrolyte membrane with a catalyst layer. Δ: Partial separation was observed between the conductive porous sheet and the electrolyte membrane with a catalyst layer. The sheet and the electrolyte membrane with the catalyst layer were completely peeled off

  From Table 1, after immersion in hot water, in the electrolyte membrane-conductive porous sheet assembly of Comparative Examples 2 and 4, peeling from the catalyst layer was observed at a part (four sides) of the conductive porous sheet, and the swelling rate Was 105.8% or more, whereas in the electrolyte membrane-conductive porous sheet assembly of Examples 1 and 2, peeling of the conductive porous sheet was not observed, and the swelling rate was 103.4% or less. Thus, it was found that the electrolyte membrane-conductive porous sheet assembly of the present invention was excellent in the effect of suppressing the dimensional change of the membrane. In addition, a correlation was found between the adhesion state and the minimum 90 ° peel strength, and when the minimum 90 ° peel strength was 0.06 N / cm or more, it was found that the effect of suppressing the dimensional change of the film was excellent. It was.

  These results indicate that the electrolyte membrane-conductive porous sheet assembly of Examples 1 and 2 flows and hardens the uncured epoxy resin constituting the conductive continuous fiber by heat during hot pressing. It was estimated that the adhesion with the catalyst layer was strengthened.

  In addition, since Example 1 and Example 2 showed the same minimum 90 ° peel strength, heat in an uncured state in such an amount as to come into surface contact with the contact surface of the conductive porous sheet with the catalyst layer. If it was provided with curable resin, it was estimated that it was excellent in adhesiveness with the catalyst layer, and the dimensional change of the film could be suppressed.

  Since the membrane-conductive porous sheet assembly of the present invention is excellent in the effect of suppressing the dimensional change of the membrane, it is suitable as a battery material using a membrane that easily causes a dimensional change. In particular, it can be suitably used as a membrane-electrode assembly of a polymer electrolyte fuel cell.

11a (Fuel electrode side) Bipolar plate 11c (Air electrode side) Bipolar plate 13a (Fuel electrode side) Gas diffusion layer 13c (Air electrode side) Gas diffusion layer 14a (Fuel electrode side) Moisture management layer 14c (Air electrode side) Moisture Management layer 15a (Fuel electrode side) Catalyst layer 15c (Air electrode side) Catalyst layer 17a Fuel electrode 17c Air electrode 19 Solid polymer electrolyte membrane

Claims (2)

A membrane-conductive porous sheet assembly in which a catalyst layer is present between the membrane and the conductive porous sheet, wherein the conductive porous sheet contains conductive fibers containing conductive particles, and the membrane swells and contracts The membrane-conductive porous sheet assembly is characterized in that the minimum 90 ° peel strength between the conductive porous sheet and the catalyst layer after repeating the above is 0.06 N / cm or more. A polymer electrolyte fuel cell comprising the membrane-conductive porous sheet assembly according to claim 1 as a membrane-electrode assembly.

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