JP2016169450A - Electric conductive fiber sheet, gas diffusion electrode, membrane-electrode conjugate, solid polymer fuel cell and manufacturing method of electric conductive fiber sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric conductive fiber sheet with low electric resistance and a manufacturing method thereof, and a gas diffusion electrode, a membrane-electrode conjugate or a solid polymer fuel cell using the electric conductive fiber sheet.SOLUTION: An electric conductive fiber sheet contains electric conductive fiber containing first conductive particles, and in addition, second conductive particles outside of the electric conductive fiber. The electric conductive fiber sheet can be manufactured by feeding the second conductive particles before or after accumulation of the electric conductive fiber spun from spinning solution containing the first conductive particles. A gas diffusion electrode, a membrane-electrode conjugate or a solid polymer fuel cell use the electric conductive fiber sheet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive fiber sheet, a gas diffusion electrode, a membrane-electrode assembly, a polymer electrolyte fuel cell, and a method for producing a conductive fiber sheet.

  Conventionally, the conductive fiber sheet is used as a base material for a gas diffusion electrode for a fuel cell, as an electrode for an electric double layer capacitor, or as an electrode for a lithium ion secondary battery by utilizing its conductivity and porosity. The use of is being considered.

  For example, as a gas diffusion electrode in a polymer electrolyte fuel cell, in addition to conductivity, moisture retention to keep the polymer membrane moist under low humidification conditions, and water accumulates under high humidification conditions. Drainage is required to prevent this from happening. Therefore, conventionally, a fluororesin can be obtained by impregnating a conductive porous substrate such as carbon paper with a fluorine resin such as polytetrafluoroethylene or by applying a paste in which carbon powder and a fluorine resin are mixed. The area where the carbon powder and fluororesin exist, or the area where the carbon powder and fluororesin exist are used as a moisture management layer that provides the gas supply action to the catalyst layer, the moisturizing action, and the drainage action of the generated water. It was used as a gas diffusion layer for diffusing gas. However, such a gas diffusion electrode uses carbon paper or the like as a conductive porous base material, and the carbon fiber constituting the carbon paper has high rigidity, so it penetrates the catalyst layer, and the solid polymer membrane Could be damaged.

  The applicant of the present application also stated that “carbon black and a polytetrafluoroethylene resin or a polyvinylidene fluoride resin are applied to a base for a gas diffusion electrode comprising a glass nonwoven fabric in which a binder containing an acrylic resin and / or a vinyl acetate resin is adhered to glass fibers. (Patent Document 1), which is similar to the conventional gas diffusion electrode using carbon paper, the glass fiber has high rigidity. In some cases, the polymer film penetrates and damages the solid polymer film.

  Therefore, the applicant of the present application has proposed “a base material for a gas diffusion electrode comprising a non-woven fabric containing conductive fibers containing conductive particles at least inside an organic resin” (Patent Document 2). This base material for a gas diffusion electrode is flexible because it contains conductive fibers containing an organic resin, and the conductive fibers did not damage the solid polymer film and cause a short circuit. However, this base material for gas diffusion electrodes has a high electric resistance and is difficult to exhibit sufficient power generation performance.

  In this way, if the electrical resistance is high, not only the base material for the gas diffusion electrode but also the performance of the electrical double layer capacitor electrode, lithium ion secondary battery electrode, and other applications that require electrical conductivity. It was difficult to demonstrate.

JP 2008-204945 A WO2014 / 010715 pamphlet

  The present invention has been made under such circumstances, and a conductive fiber sheet having a low electrical resistance, a method for producing the same, and a gas diffusion electrode, a membrane-electrode assembly or a solid using the conductive fiber sheet. An object is to provide a polymer fuel cell.

  The invention according to claim 1 of the present invention is such that “in addition to the conductive fiber containing the first conductive particles, the conductive fiber contains the second conductive particles outside the conductive fiber. Sheet. "

  The invention according to claim 2 of the present invention is “the conductive fiber sheet according to claim 1, wherein the conductive fiber sheet has a region where the conductive fibers and the second conductive particles are mixed”.

  The invention according to claim 3 of the present invention is as follows: "The conductive fiber sheet according to claim 1 or 2, wherein the second conductive particles are bonded to the conductive fibers through a resin." . "

  The invention according to claim 4 of the present invention is as follows. "The conductive film according to any one of claims 1 to 3, wherein a film containing the second conductive particles is not formed between the conductive fibers." Fiber sheet. "

  The invention concerning Claim 5 of this invention is "the conductive fiber sheet as described in any one of Claims 1-4 characterized by not having the area | region which does not contain a conductive fiber."

  The invention according to claim 6 of the present invention is "the conductive fiber sheet according to any one of claims 1 to 5, wherein the conductive fiber is a continuous fiber."

  The invention according to claim 7 of the present invention is “a conductive fiber sheet, wherein the conductive fiber sheet according to any one of claims 1 to 6 is used as a base material for a gas diffusion electrode”. Is.

  The invention according to claim 8 of the present invention is “a gas diffusion electrode characterized in that a catalyst is supported on the conductive fiber sheet according to any one of claims 1 to 6”. .

  The invention according to claim 9 of the present invention is “a membrane-electrode assembly comprising the gas diffusion electrode according to claim 8”.

  The invention according to claim 10 of the present invention is “a polymer electrolyte fuel cell comprising the gas diffusion electrode according to claim 8”.

  The invention according to claim 11 of the present invention is characterized in that the second conductive particles are supplied before or after collecting the conductive fibers spun from the spinning solution containing the first conductive particles. The manufacturing method of the conductive fiber sheet of Claim 1. ".

  The invention according to claim 12 of the present invention is the conductive fiber sheet according to claim 11, wherein the second conductive particles are supplied by spraying a dispersion liquid containing the second conductive particles. Manufacturing method. "

  The invention according to claim 13 of the present invention is "the method for producing a conductive fiber sheet according to claim 12, wherein the dispersion liquid is fragmented and sprayed into droplets having a charge". .

  The invention according to claim 14 of the present invention is as described in any one of claims 11 to 13, wherein the spinning fiber containing the first conductive particles is spun into conductive fibers by an electrostatic spinning method. The manufacturing method of the conductive fiber sheet as described in an item | term.

  The invention according to claim 15 of the present invention is characterized in that "spinning of conductive fibers from a spinning solution containing first conductive particles and supply of second conductive particles are performed simultaneously." It is a manufacturing method of the conductive fiber sheet as described in any one of 11-14. "

  In the invention according to claim 1 of the present invention, in addition to the conductive fibers, the second conductive particles are included outside the conductive fibers. Therefore, the fiber sheet having excellent conductivity, that is, the conductivity having low electrical resistance. It is a fiber sheet.

  Since the invention concerning Claim 2 of this invention has the area | region where a conductive fiber and 2nd electroconductive particle are mixed, it is a conductive fiber sheet with low electrical resistance. In particular, when there is no region composed only of the second conductive particles, it is preferable because the second conductive particles do not easily fall off.

  In the invention according to claim 3 of the present invention, since the second conductive particles are bonded via the resin, the conductive fibers are flexible, and as a result, the conductive fiber sheet is flexible. Therefore, there is a low risk that the conductive fiber sheet damages the adjacent material. For example, even if a conductive fiber sheet is used as a base material for a gas diffusion electrode, the solid polymer film is hardly damaged.

  In the invention according to claim 4 of the present invention, since the film containing the second conductive particles is not formed between the conductive fibers, the voids of the conductive fiber sheet can be effectively used. That is, when a film containing the second conductive particles is formed, there is a tendency that the voids of the conductive fiber sheet in the vicinity of the film cannot be effectively used. The space | gap of a fiber sheet can be utilized effectively.

  The invention according to claim 5 of the present invention does not have a region that does not include conductive fibers, that is, consists of only a mixed region of conductive fibers and second conductive particles, or in addition to the mixed region, conductive Since there is a region consisting only of fibers and no region consisting only of the second conductive particles, there is an effect that the second conductive particles are unlikely to fall off.

  The invention according to claim 6 of the present invention is excellent in conductivity in the length direction of the conductive fiber because the conductive fiber is a continuous fiber. That is, the conductivity in the surface direction of the conductive fiber sheet is particularly excellent.

  In the invention according to claim 7 of the present invention, since the conductive fiber sheet is used as a base material for a gas diffusion electrode, it is possible to produce a solid polymer fuel cell having low electric resistance and exhibiting sufficient power generation performance.

  The invention according to claim 8 of the present invention is a gas diffusion electrode capable of producing a polymer electrolyte fuel cell having a low electric resistance and sufficient power generation performance since a catalyst is supported on the conductive fiber sheet. is there.

  Since the invention according to claim 9 of the present invention is provided with the gas diffusion electrode, it is possible to manufacture a polymer electrolyte fuel cell having low electric resistance and capable of exhibiting sufficient power generation performance.

  The invention according to claim 10 of the present invention is a solid polymer fuel cell having the gas diffusion electrode and having low electric resistance and exhibiting sufficient power generation performance.

  According to the eleventh aspect of the present invention, since the second conductive particles are supplied before or after the spun conductive fibers are accumulated, the second conductive particles are contained outside the conductive fibers. A conductive fiber sheet can be manufactured.

  In the invention according to claim 12 of the present invention, since the second conductive particles are supplied by spraying the dispersion liquid containing the second conductive particles, the coating containing the second conductive particles between the conductive fibers. Easy to produce no conductive fiber sheet.

  In the invention according to claim 13 of the present invention, the dispersion liquid is fragmented and sprayed into charged droplets, and the droplets are electrically repelled and fragmented. 2 It is easy to produce a conductive fiber sheet without a film containing conductive particles. In addition, since the droplet has a charge, the droplet can be reliably bonded to the conductive fiber by setting the charge opposite to that of the conductive fiber.

  In the invention according to claim 14 of the present invention, since conductive fibers are spun by the electrostatic spinning method, it is possible to spin thin, uniform conductive fibers and continuous fibers. Therefore, it is possible to produce a conductive fiber sheet that is excellent in conductivity, has a large surface area, and can effectively use the conductive fiber surface.

  According to the fifteenth aspect of the present invention, the conductive fiber sheet has a region in which the conductive fibers and the second conductive particles are mixed in order to simultaneously spin the conductive fibers and supply the second conductive particles. Can be manufactured. In addition, since the area | region which consists only of 2nd electroconductive particle will not be formed unless spinning of electroconductive fiber and supply of 2nd electroconductive particle are performed simultaneously and only 2nd electroconductive particle is not supplied, 2nd A conductive fiber sheet in which conductive particles are less likely to fall off can be manufactured.

Electron micrograph on the conductive fiber sheet surface in Example 1 Electron micrograph on the conductive fiber sheet surface in Example 2 Electron micrograph on the conductive fiber sheet surface in Example 3 Electron micrograph on conductive fiber sheet surface in Example 5 Electron micrograph on the surface of the conductive fiber sheet in Comparative Example 1

  Since the conductive fiber sheet of the present invention contains the second conductive particles outside the conductive fibers in addition to the conductive fibers containing the first conductive particles, the conductive fiber sheet is excellent in conductivity. is there. That is, it is a conductive fiber sheet with low electrical resistance. In the present invention, the conductive particles constituting the conductive fibers are expressed as “first conductive particles”, and the conductive particles contained outside the conductive fibers are expressed as “second conductive particles”. Thus, the conductive particles are distinguished.

  The first conductive particles constituting the conductive fiber of the present invention are not particularly limited, and examples thereof include carbon-based particles such as carbon black, carbon nanotubes, and carbon nanofibers, metal particles, and metal oxide particles. be able to. Among these, carbon-based particles are preferable from the viewpoint of chemical resistance, conductivity and dispersibility, and carbon black is particularly preferable.

  Although the shape of the first conductive particles of the present invention is not particularly limited, for example, spherical (substantially spherical or true spherical), fibrous, needle-like (for example, tetrapot-like), flat plate shape, polyhedral shape, It can be a feather or an irregular shape. The first conductive particles may be hollow or solid.

  The particle size of the first 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. In addition, the conductive fiber may contain two or more types of first conductive particles that differ in terms of the material and / or average primary particle size. In the present invention, the “average primary particle size” basically represents the number average particle size of particles obtained from a particle size distribution meter by a dynamic light scattering method. For example, an aggregate or structure such as carbon black is used. When it is difficult to measure by the above-mentioned dynamic light scattering method, such as particles that have formed a state called, take an electron micrograph of the particle, the arithmetic average of the diameter of 50 particles in the electron micrograph The value is the average primary particle size. In this case, when the particle shape is non-circular on the photograph, the diameter of a circle having the same area as the particle area on the photograph is regarded as the particle diameter.

  The conductive fiber of the present invention contains the first conductive particles as described above, but the first conductive particles are preferably bonded to each other through a resin. This is because the conductive fibers are excellent in flexibility by being bonded through the resin as described above, and the first conductive particles are not easily dropped off.

  The resin that can form such conductive fibers may be any resin that can adhere the first conductive particles to each other, and may be a hydrophobic organic resin, a hydrophilic organic resin, or a resin of these resins. It may be a mixed resin or a composite resin, and is not particularly limited. When the conductive fiber sheet of the present invention is used as a base material for a gas diffusion electrode, the hydrophobic organic resin exhibits excellent water permeability without being impregnated with a hydrophobic resin such as a fluorine resin. It is suitable because of its excellent drainage and gas diffusibility. In addition, since a hydrophilic organic resin can retain moisture, a solid polymer fuel cell that can keep the solid polymer membrane moist even under low humidity and can exhibit sufficient power generation performance. This is preferable because it can be manufactured. In particular, the inclusion of only a hydrophobic organic resin is preferable because it exhibits excellent drainage and gas diffusibility.

  The “hydrophobic organic resin” is an organic resin having a contact angle with water of 90 ° or more. For example, a fluororesin [for example, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), Polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), perfluoroalkoxy fluororesin (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer (ETFE) , Ethylene / chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (THV), and copolymers of various monomers constituting the resin], polyolefin resins [ For example, polyethylene (PE), polypropylene (PP), Copolymer of various monomers constituting the resin], polyester resin [for example, polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) ), Polybutylene naphthalate (PBN)] and the like. In addition, these hydrophobic organic resins can be used alone or in combination of two or more. Among these, fluororesins are particularly preferable because they are excellent in 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 °. For example, cellulose [for example, rayon], polyamide-based resin [for example, nylon 6, nylon 66], acrylic Resin [for example, polyacrylic acid, polymethacrylic acid], resin having a hydrophilic group (amide group, carboxyl group, hydroxyl group, amino group, sulfonic acid group, etc.) [for example, hydrophilic polyurethane, polyvinylpyrrolidone], polyacrylonitrile, Examples thereof include acrylic oxide, polyvinyl alcohol resin, and polyethylene glycol resin. Moreover, these hydrophilic organic resins can also be used independently and can also be used in mixture of 2 or more types or in combination. Among these, polyacrylonitrile is preferable because of its excellent heat resistance. Polyacrylonitrile is less likely to collapse due to swelling of the solid polymer film, and can maintain the voids of the conductive fiber sheet. Therefore, it is suitable when the conductive fiber sheet of the present invention is used as a base material for a gas diffusion electrode. It is.

  In addition, when using the electroconductive fiber sheet of this invention for the use which requires rigidity, the thermosetting resin may be sufficient as the said hydrophobic organic resin and / or hydrophilic organic resin. Further, in addition to the thermosetting resin, a curing accelerator may be included. For example, when the conductive fiber sheet of the present invention is used as a base material for a gas diffusion electrode, the conductive fiber sheet has a certain degree of rigidity, thereby suppressing the swelling and shrinkage of the solid polymer film, thereby Since the film can be prevented from cracking and the gas diffusion electrode is not easily crushed by swelling of the solid polymer film, the voids can be maintained and the gas diffusibility can be maintained.

  The “thermosetting resin” is not particularly limited, and examples thereof include a phenol resin, an epoxy resin, a thermosetting polyimide resin, a melamine resin, an unsaturated polyester resin, and a diallyl phthalate resin. Among these, a phenol resin and an epoxy resin are preferable because they are excellent in heat resistance and acid resistance and can increase the rigidity of the conductive fiber by heat treatment. When the conductive fiber contains a thermosetting resin, it may be composed of one kind of thermosetting resin, or two or more kinds of thermosetting resins may be mixed or combined. One or more types of thermosetting resins and one or more types of thermoplastic hydrophobic organic resins or thermoplastic hydrophilic organic resins may be mixed or combined.

  As described above, when the conductive fiber of the present invention contains a resin in addition to the first conductive particles, the mass ratio of the first conductive particles to the resin is not particularly limited. In order to be excellent in flexibility, it is preferably 10 to 90:90 to 10, more preferably 20 to 80:80 to 20, still more preferably 30 to 70:70 to 30, More preferably, it is 40-70: 60-30. If the first conductive particles are less than 10 mass%, the conductivity tends to be insufficient, whereas if the first conductive particles is more than 90 mass%, sufficient flexibility tends not to be obtained. Because.

  When the conductive fiber of the present invention contains a resin in addition to the first conductive particles, the positional relationship between the first conductive particles and the resin is as long as the resin adheres the first conductive particles. There is no particular limitation. However, if the first conductive particles are present only on the outer surface of the conductive fiber, the resin component inside the conductive fiber becomes a resistance component and tends to be inferior in conductivity. The first conductive particles are preferably present. Moreover, it is preferable that the 1st electroconductive particle is exposed to the outer surface of an electroconductive fiber so that the electroconductivity between electroconductive fibers is excellent. As described above, the conductive fibers in which the first conductive particles are present on the inner and outer surfaces of the conductive fibers and the first conductive particles are exposed on the outer surfaces include, for example, a resin and the first conductive particles. It can be produced by spinning a spinning solution.

  The average fiber diameter of the conductive fiber of the present invention is not particularly limited, but is preferably 10 nm to 10 μm. When the average fiber diameter is larger than 10 μm, the number of contact points between the conductive fibers is small and the conductivity tends to be insufficient. On the other hand, when the average fiber diameter is smaller than 10 nm, the handling property of the conductive fiber sheet tends to be inferior. Because. In addition, it is preferable that the average fiber diameter of a conductive fiber is 5 times or more of the average primary particle diameter of a 1st electroconductive particle so that a 1st electroconductive particle cannot drop out easily.

  The “average fiber diameter” in the present invention means an arithmetic average value of fiber diameters at 40 conductive fibers, and the “fiber diameter” means the length of the conductive fiber measured based on a micrograph. The length in the direction orthogonal to the direction. In addition, when the first conductive particles are exposed on the entire outer surface of the conductive fiber, the thickness including the first conductive particles is the fiber diameter, and the conductive fiber includes a resin, When the first conductive particles are exposed only on a part of the outer surface of the conductive fiber, the diameter of the portion where the first conductive particles are not exposed is defined as the fiber diameter.

  The conductive fiber of the present invention is preferably a continuous fiber so as to be excellent in conductivity. In addition, when using the electroconductive fiber sheet of this invention as a base material for gas diffusion electrodes, there exists an effect that there is substantially no fiber edge part of electroconductive fiber and a solid polymer film is not damaged. Such continuous conductive fibers can be produced, for example, by an electrostatic spinning method or a spunbond method. Note that “continuous fiber” means that the end of the conductive fiber cannot be confirmed when a 5,000-fold electron micrograph of the conductive fiber sheet is taken.

  The conductive fiber sheet of the present invention is a fiber sheet excellent in conductivity because it contains the second conductive particles outside the conductive fiber in addition to the conductive fiber as described above. In other words, the presence of the second conductive particles outside the conductive fiber increases the chances of contact between the second conductive particles and the first conductive particles and / or other second conductive particles. Since many paths are formed, the conductive fiber sheet has a low electrical resistance. Note that “externally” means that the second conductive particles do not constitute conductive fibers and exist as a material different from the conductive fibers.

  As this 2nd electroconductive particle, the electroconductive particle similar to the 1st electroconductive particle which comprises electroconductive fiber can be used. That is, the second conductive particles can be, for example, carbon-based particles such as carbon black, carbon nanotubes, and carbon nanofibers, metal particles, metal oxide particles, and the like. Among these, carbon-based particles are preferable from the viewpoint of chemical resistance, conductivity and dispersibility, and carbon black is particularly preferable. The shape can be, for example, spherical (substantially spherical or true spherical), fibrous, needle-like (for example, tetrapot-like), flat plate shape, polyhedral shape, feather shape, irregular shape, and hollow. Can also be solid. The average primary particle size of the second conductive particles is preferably 5 nm to 200 nm, and more preferably 10 nm to 100 nm. In addition, you may contain 2 or more types of 2nd electroconductive particle which differs in the point of a raw material and / or an average primary particle size. The second conductive particles may be the same as the first conductive particles, or may be different in terms of the material and / or the average primary particle size.

  The mass ratio of the conductive fibers and the second conductive particles is not particularly limited, but is preferably 1 to 99:99 to 1, more preferably 10 to 90:90 to 10. 30 to 85:70 to 15 is more preferable, and 50 to 80:50 to 20 is more preferable. When the mass ratio of the second conductive particles exceeds 99 mass%, the area of only the second conductive particles is formed, and the second conductive particles tend to fall off, and the handleability of the conductive fiber sheet tends to deteriorate. This is because if the mass ratio of the second conductive particles is less than 1 mass%, the electrical resistance increases and the conductivity tends to be insufficient.

  The second conductive particles may be present in any way, but preferably exist so as to have a region where the conductive fibers and the second conductive particles are mixed. This is because when the conductive fibers and the second conductive particles are mixed, the conductivity between the conductive fibers can be increased, and the conductive fiber sheet can have a low electric resistance. In addition, since the second conductive particles are present between the conductive fibers, the voids of the conductive fiber sheet are secured, and the voids of the conductive fiber sheet can be effectively used. In particular, when the conductive fiber and the second conductive particles are mixed only and there is no region including only the second conductive particles, it is preferable because the second conductive particles are difficult to drop off.

  Or it is preferable that the 2nd electroconductive particle exists so that it may not have the area | region which does not contain electroconductive fiber. In other words, if there is only a mixed region of conductive fibers and second conductive particles, or if there is a region consisting only of conductive fibers in addition to the mixed region, there is a region consisting only of the second conductive particles. This is because the second conductive particles are less likely to fall off.

  The mixed region may exist in any way, but generally the conductive fibers are oriented in the surface direction of the conductive fiber sheet, and the conductivity in the thickness direction of the conductive fiber sheet is low. Since it tends to be insufficient, the mixed region exists in the thickness direction of the conductive fiber sheet, and it is preferable that the conductivity in the thickness direction is excellent. However, it may exist in the surface direction. In both the surface direction and the thickness direction, if the conductive fiber and the second conductive particles are mixed only, the conductivity in either the surface direction or the thickness direction is excellent. Therefore, it is particularly suitable.

  However, if the region contains 1% or more in the plane direction and / or the thickness direction, the second conductive particles are present, so that the conductivity is excellent. Thus, when it is an area where only a part is mixed, any area may be mixed. For example, in a case where only a part in the thickness direction is mixed, a region including one surface of the conductive fiber sheet may be mixed, or there is a mixed region between both surfaces. May be.

  Thus, when the mixed region exists only in a part of the conductive fiber sheet, the remaining region is a region made of only the conductive fiber, a region made of only the second conductive particles, the conductive fiber and the first one. It can be a region composed of fibers or particles other than the two conductive particles, or a region composed of fibers or particles other than the second conductive particles and the conductive fibers.

  In addition, when it has the area | region where a conductive fiber sheet is mixed partially, the number does not need to be one place and may be two or more places. In the case of having two or more mixed regions, the mixed mass ratio and mixed state of the conductive fibers and the second conductive particles may be the same or different.

  In addition, when the mixed region exists only in a part in the surface direction of the conductive fiber sheet, the mixed region may be regularly present in a staggered pattern, a lattice intersection, or randomly. May be. However, it is preferable that there is a region where regularly mixed regions exist because of excellent conductivity uniformity.

  Furthermore, it is preferable that a film containing the second conductive particles is not formed between the conductive fibers. This is because if the coating film containing the second conductive particles is not formed between the conductive fibers, the voids of the conductive fiber sheet can be used effectively. That is, when a film containing the second conductive particles is formed between the conductive fibers, there is a tendency that the voids of the conductive fiber sheet in the vicinity of the film cannot be effectively used, but the second conductive particles are included. This is because if the film is not formed, the voids of the conductive fiber sheet can be used effectively. Thus, as the state of “not forming a film containing second conductive particles”, for example, the second conductive particles are in the state of individual primary particles, the state of secondary particles in which the primary particles are aggregated, It is in a state of being bonded or adhered to the conductive fibers without filling between adjacent conductive fibers in terms of dots, lines or surfaces. In addition, the 2nd electroconductive particle may be in the state which adhere | attached or adhered to the surface of electroconductive fiber, and may be in the state which was sunk into the inside of electroconductive fiber, and was adhered or adhered.

  In addition, it is preferable that the second conductive particles are bonded via a resin so that the second conductive particles do not easily fall off and the conductive fibers are flexible, and as a result, the conductive fiber sheet is flexible. Thus, when a conductive fiber sheet is flexible, there exists an effect that it is hard to produce a restriction | limiting in the use use of a conductive fiber sheet. For example, even when a conductive fiber sheet is used as a base material for a gas diffusion electrode, there is an effect that the solid polymer film is hardly damaged.

  The resin for adhering the second conductive particles to the conductive fibers may be a resin involved in adhesion between the first conductive particles (hereinafter, sometimes referred to as “first organic resin”). However, it may be a resin different from the resin involved in the adhesion between the first conductive particles (hereinafter sometimes referred to as “second organic resin”), but the adhesion between the first conductive particles. It is preferable that the resin is involved in the above because it is difficult to lower the conductivity. Even when the second conductive particles are bonded to the conductive fibers through the resin, the second conductive particles are bonded without forming a film between the conductive fibers. preferable.

  When the second conductive particles are bonded with the second organic resin, the second organic resin is the same hydrophobic organic resin as the first organic resin, a hydrophilic organic resin, a thermosetting hydrophobic organic resin, And / or a thermosetting hydrophilic organic resin.

  The conductive fiber sheet of the present invention contains the second conductive particles in addition to the conductive fibers, but the total amount of the conductive fibers and the second conductive particles in the conductive fiber sheet is excellent in conductivity. As described above, it is preferably 10% by mass or more of the entire conductive fiber sheet, more preferably 50% by mass or more, further preferably 70% by mass or more, and further preferably 90% by mass or more. Most preferably, it is composed only of conductive fibers and second conductive particles.

  In addition, as a material other than the conductive fiber and the second conductive particle constituting the conductive fiber sheet of the present invention, an organic resin fiber containing one kind or two or more kinds of the first organic resin can be included. In addition to the conductive particles, for example, inorganic particles (for example, manganese dioxide, iron oxide, copper oxide, nickel oxide, cobalt oxide, zinc oxide, titanium-containing oxide, zeolite, catalyst-supporting ceramics, silica, etc.), ions Non-conductive materials such as exchange resin powders and plant seeds can be included.

  The conductive fibers constituting the conductive fiber sheet of the present invention may be bonded together in any way. For example, they may be bonded by entanglement, bonding by plasticizing the first organic resin with a solvent, bonding by fusing the first organic resin by heat, or a combination thereof.

The conductive fiber sheet of the present invention preferably has a porosity of 20% or more, more preferably a porosity of 30% or more so that the voids of the conductive fiber sheet can be used effectively. More preferably, it has a porosity of 50% or more. The upper limit of the porosity is not particularly limited, but is preferably 99% or less from the viewpoint of form stability. The porosity P (unit:%) is a value obtained from the following formula.
P = 100- (Fr1 + Fr2 + .. + Frn)
Here, Frn shows the filling rate (unit:%) of the component n which comprises an electroconductive fiber sheet, and says the value obtained from the following formula | equation.
Frn = [M × Prn / (T × SGn)] × 100
Here, M is the basis weight of the conductive fiber sheet (unit: g / cm ² ), T is the thickness (cm) of the conductive fiber sheet, and Prn is the component n in the conductive fiber sheet (for example, the first conductive particles). , First organic resin, second conductive particles, and the like), SGn means specific gravity (unit: g / cm ³ ) of component n.

The basis weight of the conductive fiber sheet of the present invention is not particularly limited, but it has a certain amount of conductive fiber, is excellent in conductivity, and is 0.1 to 200 g from the viewpoint of handleability and productivity. / ^m is preferably from ^2, more preferably from 0.3～100G / ^{m 2,} and even more preferably 0.5 to 50 g / ^{m 2.} Also, the thickness is not particularly limited, but is preferably 1 to 1000 μm, more preferably 5 to 500 μm, still more preferably 10 to 400 μm, and further preferably 10 to 300 μm. .

“Weight” in the present invention refers to a value obtained by measuring the mass of a 10 cm square conductive fiber sheet and converting it to a mass of 1 m ^2. “Thickness” is a thickness gauge (manufactured by Mitutoyo Corporation: cord) No. 547-401: Measurement force 3.5N or less).

  Since the conductive fiber sheet of the present invention has a low electrical resistance, it can be suitably used for applications that require electrical conductivity. For example, it can be suitably used as a gas diffusion electrode substrate for a fuel cell, as an electrode for an electric double layer capacitor, or as an electrode for a lithium ion secondary battery.

  In particular, when the conductive fiber sheet of the present invention is used as a base material for a gas diffusion electrode, it is possible to produce a polymer electrolyte fuel cell having a low electric resistance and exhibiting sufficient power generation performance. In addition, since the conductive fiber sheet is porous, the gas diffusion electrode base material (conductive fiber sheet) is not filled in the space of the gas diffusion electrode base material (conductive fiber sheet). In addition to being excellent in drainage in the thickness direction and surface direction, it is excellent in diffusibility of the supplied gas.

  In addition, the fluorine resin and / or carbon may be included in the gaps of the gas diffusion electrode substrate (conductive fiber sheet). Since the former fluorine-based resin is contained, liquid water is easily pushed out, so that drainage is excellent. Moreover, electroconductivity can further be improved by containing the latter carbon.

  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.

  Examples of carbon include carbon black, carbon nanotube, and carbon nanofiber.

  The gas diffusion electrode of the present invention can produce a polymer electrolyte fuel cell having a low electrical resistance and sufficient power generation performance because a catalyst is supported on the conductive fiber sheet. In the gas diffusion electrode of the present invention, the catalyst is supported on the surface of the conductive fiber and / or the second conductive particles, and not only the electron conduction by the contact between the catalysts but also the conductive fiber and / or the second conductive property. Since the electron conduction path is also formed by particles, there are few catalysts isolated from the electron conduction path. As a result, the catalyst can be used efficiently and the amount of catalyst can be reduced.

  The gas diffusion electrode of the present invention has the same structure as a conventional gas diffusion electrode except that the conductive fiber sheet as described above is used as a base for a gas diffusion electrode. For example, the catalyst may be platinum, platinum alloy, palladium, palladium alloy, titanium, manganese, magnesium, lanthanum, vanadium, zirconium, iridium, rhodium, ruthenium, gold, nickel-lanthanum alloy, titanium-iron alloy, or the like. It is possible to carry one or more kinds of catalysts selected from these.

  In addition to the catalyst, it is preferable to include an electron conductor and a proton conductor. As the electron conductor, conductive particles similar to the first conductive particles such as carbon black are suitable. It may be carried on an electron conductor (conductive particles). Moreover, an ion exchange resin is suitable as the proton conductor.

  Such a gas diffusion electrode can be manufactured by the following method, for example. First, a catalyst (for example, carbon powder carrying a catalyst such as platinum) is added and mixed in a single or mixed solvent composed of ethyl alcohol, propyl alcohol, butyl alcohol, ethylene glycol dimethyl ether, etc., and this is mixed with an ion exchange resin. The solution is added and mixed uniformly by ultrasonic dispersion or the like to obtain a catalyst dispersion suspension. Then, the catalyst dispersion suspension can be coated or dispersed on the conductive fiber sheet as described above, and dried to produce a gas diffusion electrode.

  Since the membrane-electrode assembly of the present invention includes the gas diffusion electrode as described above, a polymer electrolyte fuel cell having a low electric resistance and exhibiting sufficient power generation performance can be produced.

  The membrane-electrode assembly of the present invention can be exactly the same as the conventional membrane-electrode assembly except that it includes the gas diffusion electrode as described above. For example, as the solid polymer film, a perfluorocarbon sulfonic acid resin film, a sulfonated aromatic hydrocarbon resin film, an alkylsulfonated aromatic hydrocarbon resin film, or the like can be used.

  Such a membrane-electrode assembly can be manufactured, for example, by sandwiching a solid polymer membrane between the catalyst support surfaces of a pair of gas diffusion electrodes and hot pressing. Further, after applying the catalyst dispersion suspension as described above to a support to form a catalyst layer, this catalyst layer is transferred to a solid polymer film, and then the conductive fiber sheet as described above is applied to the catalyst layer. Can be manufactured also by a method of laminating so as to abut and hot pressing.

  Since the polymer electrolyte fuel cell of the present invention includes the gas diffusion electrode, the polymer electrolyte fuel cell has a low electric resistance and can exhibit sufficient power generation performance.

  The fuel cell of the present invention can be exactly the same as a conventional fuel cell except that it includes the gas diffusion electrode as described above. For example, it has a structure in which a plurality of cell units sandwiching a membrane-electrode assembly as described above between a pair of bipolar plates are stacked. For example, a plurality of cell units can be stacked and fixed.

  The bipolar plate is not particularly limited as long as the bipolar plate has high conductivity, does not transmit gas, and has a flow path capable of supplying gas to the gas diffusion electrode. A carbon-resin composite material, a metal material, or the like can be used.

  The conductive fiber sheet of the present invention can be produced, for example, by supplying the second conductive particles before or after collecting the conductive fibers spun from the spinning solution containing the first conductive particles. it can.

  More specifically, first, a spinning solution containing the first conductive particles is prepared. As described above, the first conductive particles are preferably carbon black. As described above, since the first conductive particles constituting the conductive fiber are preferably bonded to each other via the first organic resin, the spinning solution contains the first organic resin as described above. It is preferable. When the first conductive particles are bonded to each other through the first organic resin, the amount of the first conductive particles is preferably 10 to 90 mass% of the solid content of the entire spinning solution, and is preferably 20 to 80 mass%. It is more preferable that it is 30-70 mass%, and it is still more preferable that it is 40-70 mass%.

  When the spinning solution contains the first organic resin, the spinning solution may be one in which the first organic resin is dissolved in the solvent and the first conductive particles are dispersed, or the first organic resin is contained in the solvent. The first conductive particles may be dispersed, or the first organic resin may be melted and the first conductive particles may be dispersed in the melt of the first organic resin. May be. When the first organic resin is dissolved in the solvent, the solvent is not particularly limited as long as it can dissolve the first organic resin.

  When the first organic resin is dissolved in the solvent, the solid content concentration in the spinning solution is not particularly limited, but is preferably 1 to 50 mass%, and more preferably 5 to 30 mass%. This is because if it is less than 1 mass%, the spinnability is extremely lowered, and if it exceeds 50 mass%, the spinning tends to become unstable.

  On the other hand, 2nd electroconductive particle is prepared. As described above, the second conductive particles are preferably carbon black. In addition, since the dispersion liquid containing the second conductive particles is sprayed to supply the second conductive particles, it is easy to produce a conductive fiber sheet without a film containing the second conductive particles between the conductive fibers. It is preferable to prepare a dispersion of two conductive particles.

  As will be described later, it is preferable that the dispersion liquid is fragmented and sprayed into charged droplets. However, a dispersion liquid in which only the second conductive particles are dispersed is difficult to fragment into charged droplets. Since there is a tendency, it is preferable to prepare a dispersion liquid containing the second organic resin in addition to the second conductive particles so that the liquid droplets are easily fragmented. When preparing such a dispersion containing the second organic resin, the amount of the second conductive particles is not particularly limited as long as the dispersion can be fragmented into charged droplets. In order not to impair the conductivity of the particles, the amount of the second conductive particles is preferably adjusted to be 30 to 99 mass% of the total solid content of the second conductive particles and the second organic resin, and preferably 60 to 99 mass%. It is more preferable to prepare so that it may become, and it is still more preferable to prepare so that it may become 90-99 mass%. Thus, in the dispersion containing the second organic resin, the amount of the second organic resin that is a resistance component is small (in some cases, the second organic resin may not be included), and the second conductive particles and Since the conductivity with the first conductive particles and / or the other second conductive particles is hardly hindered, it is easy to produce a fiber sheet excellent in conductivity, that is, a conductive fiber sheet with low electrical resistance.

  Thus, when preparing the dispersion liquid containing the second organic resin, the solvent in the dispersion liquid may be any solvent that can dissolve the second organic resin or that can disperse the second organic resin. There is no particular limitation. In addition, when a dispersion liquid contains 2nd organic resin, the dispersion liquid may disperse | distribute 2nd electroconductive particle in the melt of 2nd organic resin.

  Next, the spinning solution is spun to form conductive fibers, and the second conductive particles are collected with respect to the conductive fibers before being collected on a collector such as a conveyor, or after collecting the conductive fibers with the collector. The dispersion containing the second conductive particles is preferably sprayed to form a conductive fiber integrated sheet containing the second conductive particles outside the conductive fibers in addition to the conductive fibers. If the conductive fiber integrated sheet has strength, the conductive fiber integrated sheet can be used as the conductive fiber sheet as it is, and the first organic resin and / or the second organic resin can be used to impart or improve the strength. Can be made into a conductive fiber sheet by bonding the conductive fibers together by plasticizing with a solvent, fusing with the first organic resin and / or the second organic resin, adhesion with an adhesive, or the like.

  The spinning method of the conductive fiber is not particularly limited. For example, for the spinning solution discharged from the liquid discharging unit as disclosed in, for example, the electrostatic spinning method, Japanese Patent Application Laid-Open No. 2009-287138. Examples thereof include a method in which gas is discharged in parallel and a fiber is formed by applying a shearing force to the spinning solution in a straight line, a spunbond method, a melt blow method, and the like. Among these spinning methods, the electrostatic spinning method or the spunbond method is preferable because continuous fibers can be spun. In addition, according to the electrostatic spinning method, the method disclosed in JP2009-287138A, or the melt blow method, a thin conductive fiber having an average fiber diameter of 3 μm or less can be spun and a conductive fiber sheet having a large surface area can be produced. it can. In particular, according to the electrospinning method, a conductive fiber that is thin, has a uniform fiber diameter, can be spun, has excellent conductivity, has a large surface area, and can effectively use the surface of the conductive fiber. This is preferable because a sheet can be produced.

  In addition, when the spinning solution is a solution in which the first organic resin is dissolved or dispersed in the solvent and the first conductive particles are dispersed, the conductive fiber accumulation is performed using a solvent that does not easily volatilize during spinning. When the solvent of the spinning solution is removed by solvent substitution after the sheet is formed, the conductive fibers tend to be in a plasticized state, and as a result, it is easy to produce a conductive fiber sheet having high conductivity and low electrical resistance. .

  Further, the method for supplying the second conductive particles to the conductive fibers is not particularly limited. For example, a method of ejecting the second conductive particles by the action of a compressed gas, a dispersion liquid containing the second conductive particles And a method in which the dispersion liquid containing the second conductive particles is fragmented and sprayed into charged droplets by the action of static electricity. Among these supply methods, when the second conductive particles are supplied by spraying the dispersion liquid containing the second conductive particles, the conductivity without the film containing the second conductive particles between the conductive fibers is provided. The fiber sheet is preferable because it is easy to manufacture. In particular, the method of fragmenting and spraying the dispersion liquid containing the second conductive particles into charged droplets by the action of static electricity makes it difficult to form a film containing the second conductive particles between the conductive fibers. It is preferable because the two conductive particles are in a primary particle state or a secondary particle state and easily adhere or adhere to the conductive fibers in a point manner. That is, since the droplets are repelled electrically and fragmented, it is difficult to form a film including the second conductive particles between the conductive fibers. In addition, since the droplet has a charge, the droplet can be reliably bonded to the conductive fiber by setting the charge opposite to that of the conductive fiber. Also from this point, it is preferable to spin the conductive fiber by an electrostatic spinning method.

  In this manufacturing method, when the spinning of the conductive fibers and the supply of the second conductive particles are performed simultaneously, a conductive fiber sheet having a region where the conductive fibers and the second conductive particles are mixed can be manufactured. In addition, since the area | region which consists only of 2nd electroconductive particle will not be formed unless spinning of electroconductive fiber and supply of 2nd electroconductive particle are performed simultaneously and only 2nd electroconductive particle is not supplied, 2nd A conductive fiber sheet in which conductive particles are less likely to fall off can be manufactured.

  In addition, before conducting the spinning of the conductive fiber and supplying the second conductive particles at the same time, it is possible to supply only the second conductive particles and form a region composed of only the second conductive particles. After spinning the fiber and supplying the second conductive particles at the same time, it is possible to supply only the second conductive particles to form a region composed only of the second conductive particles.

  However, before conducting the spinning of the conductive fibers and supplying the second conductive particles at the same time, it is possible to spin only the conductive fibers to form a region made of only the conductive fibers, and to spin the conductive fibers. After supplying the second conductive particles at the same time, when only the conductive fibers are spun to form a region made of only the conductive fibers, there is no region containing no conductive fibers, that is, the second conductive particles. Since the electroconductive fiber sheet which does not have the area | region which consists only of can be manufactured, the electroconductive fiber sheet which a 2nd electroconductive particle cannot fall easily can be manufactured.

  The conductive fiber sheet having a region where the conductive fibers and the second conductive particles are mixed by supplying the second conductive particles to the conductive fibers before or after collecting the conductive fibers. Can be manufactured, but the supply position is not particularly limited. However, when spraying the dispersion liquid containing the second conductive particles, the dispersion liquid may be sprayed on the collection position of the conductive fibers so that the conductive fibers are easily adhered or adhered to the electrostatic fibers. preferable.

  In addition, when the dispersion liquid containing the second conductive particles contains the second organic resin, the second organic resin acts as a resistance component in terms of conductivity, so that the heat treatment is performed after forming the conductive fiber integrated sheet. It is preferable to thermally decompose the second organic resin to increase the conductivity. When the conductive fibers contain the first organic resin, only the second organic resin is thermally decomposed so as not to impair the adhesion between the first conductive particles by the first organic resin. preferable. Since such heat treatment conditions differ depending on the second organic resin (and the first organic resin when the first organic resin is included), the conditions are appropriately set by confirming by experiments.

  Furthermore, when the first organic resin and / or the second organic resin is a polyacrylonitrile (PAN) and / or a polyacrylonitrile (PAN) copolymer, the temperature is increased in air after forming the conductive fiber integrated sheet. By heating at 200 to 300 ° C., the conductivity of the conductive fiber sheet can be further increased by using polyacrylonitrile (PAN) and / or polyacrylonitrile (PAN) copolymer as an acrylic oxide.

  The above is the basic manufacturing method of the conductive fiber sheet of the present invention, but after collecting the conductive fibers so that the adhesion between the conductive fibers can be improved and the conductivity can be further improved. , Before supplying the second conductive particles, after collecting the conductive fibers, after supplying the second conductive particles, and in some cases after thermally decomposing the second organic resin It is also possible to apply pressure. In addition, this pressurization force should just be a pressurization force which does not destroy the space | gap of a conductive fiber and a conductive fiber integration sheet, and is not specifically limited.

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

(Preparation of spinning solution)
Vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (= first organic resin) was added to N, N-dimethylformamide (DMF) and dissolved using a rocking mill to obtain a solution having a concentration of 10 mass%. .

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

(Preparation of spray dispersion)
Water dispersion of Ketjen Black (= second conductive particles, primary particle size 40 nm) [manufactured by Lion Corporation, Lion Paste W-311N, solid content: 16.5 mass%] and polyethylene glycol (= second organic Resin, Wako Pure Chemical Industries, Ltd., molecular weight: 500,000) and pure water were mixed to prepare a spray dispersion having a ketjen black concentration of 12 mass% and a polyethylene glycol concentration of 0.7 mass%.

Example 1
The spinning solution is subjected to electrostatic spinning under the conditions shown below, and conductive continuous fibers containing acetylene black in its entirety including the inside (the acetylene blacks are passed through a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer). And the acetylene black is also exposed on the outer surface), and is directly accumulated on the stainless drum as the counter electrode, and at the same time, the dispersion for spraying is charged with the liquid by the action of static electricity under the following conditions. It is fragmented into droplets and sprayed from the upper part of the stainless drum toward the conductive continuous fiber accumulation position. In both the surface direction and the thickness direction, the conductive continuous fibers are intertwined with each other and conductive. Vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer or polyethylene Only Ketjen black via alkylene glycol to prepare a conductive fiber sheet comprising only mixing region adhered. In the conductive fiber sheet, the mass ratio of the continuous conductive fiber to the ketjen black was 70:30. As shown in the electron micrograph in FIG. 1, the surface of the conductive fiber sheet was in a state where the ketjen black was in contact with the surface of the conductive fiber in a point-contact manner without forming a film. The physical properties of the conductive fiber sheet are as shown in Table 1.

<Electrostatic spinning conditions>
Electrode: Metal nozzle (inner diameter 0.41 mm) and stainless steel drum discharge rate: 2.8 g / hour Distance between nozzle tip and stainless steel drum: 10 cm
Applied voltage: 12 kV
Temperature / humidity: 25 ° C / 35% RH

<Electrostatic spray conditions>
Electrode: Metal nozzle (inner diameter: 0.41 mm) and stainless steel drum discharge rate: 1.2 g / hour Distance between nozzle tip and stainless steel drum: 10 cm
Applied voltage: 15 kV
Temperature / humidity: 25 ° C / 35% RH

(Example 2)
Conductive continuous fibers in both the surface direction and the thickness direction were the same as in Example 1 except that the discharge amount under the electrostatic spraying condition was changed from 1.2 g / hour to 2.4 / hour. Conductives consisting only of a mixed region in which only ketjen black adheres to the outside of the conductive continuous fiber via vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer or polyethylene glycol. Fiber sheet was manufactured. In the conductive fiber sheet, the mass ratio of the conductive continuous fiber to the ketjen black was 55:45. As shown in the electron micrograph of FIG. 2, the surface of the conductive fiber sheet was in a state where the ketjen black was in contact with the surface of the conductive fiber in a point-contact manner without forming a film. The physical properties of the conductive fiber sheet are as shown in Table 1.

(Example 3)
Conductive continuous fiber containing acetylene black in its entirety, including the inside (the acetylene blacks are copolymerized with vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, by electrospinning the spinning solution under the same conditions as in Example 1. The acetylene black was exposed on the outer surface and the acetylene black was exposed on the outer surface, and was directly accumulated on a stainless drum as a counter electrode to obtain a continuous fiber accumulation sheet.

  Thereafter, the spinning of the conductive continuous fibers was stopped, and the dispersion for spraying was fragmented into charged droplets by the action of static electricity under the same conditions as in Example 1, and the conductive continuous fibers accumulated from the upper part of the stainless drum. Sprayed toward the sheet, and in the thickness direction, polyethylene is formed on one surface of a region consisting essentially of conductive continuous fibers in which conductive continuous fibers are entangled with each other, and a region consisting only of these conductive continuous fibers. A conductive fiber sheet having a region consisting only of ketjen black adhered via glycol was produced. In the conductive fiber sheet, the mass ratio of the continuous conductive fiber to the ketjen black was 70:30. The region side surface of the conductive fiber sheet made only of ketjen black is shown in FIG. 3 as an electron micrograph (the left side is a photo of the region side surface made of only conductive continuous fibers, and the right side is the region side made only of ketjen black. As shown in the surface photograph, the ketjen black was in an aggregated state. The physical properties of the conductive fiber sheet are as shown in Table 1. It should be noted that the ketjen black on the surface of the region side made of only ketjen black was in a state of being easily dropped off.

Example 4
The spinning solution was subjected to electrostatic spinning under the same conditions as in Example 1, and the conductive continuous fiber containing acetylene black in its entirety including the inside (the acetylene blacks were vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer) And the acetylene black is also exposed on the outer surface), and is directly accumulated on the stainless steel drum as the counter electrode. At the same time, the spray dispersion is charged by the action of static electricity under the conditions shown below. The liquid droplets were fragmented and sprayed from the upper part of the stainless drum toward the conductive continuous fiber accumulation position to form a conductive fiber integrated sheet in which conductive continuous fibers and ketjen black were mixed.

  Thereafter, the spinning of the conductive continuous fibers is stopped, and only spraying of the spray dispersion liquid is continued. In the thickness direction, the conductive continuous fibers are substantially entangled with each other, and the conductive continuous fibers are externally connected. In addition, a mixed region where only ketjen black is bonded via vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer or polyethylene glycol, and a ketjen bonded to one surface of this mixed region via polyethylene glycol A conductive fiber sheet having a region consisting only of black was produced. In the mixed region, the mass ratio of the conductive continuous fiber and the ketjen black was 70:30, and the mass ratio of the mixed region and the region consisting only of the ketjen black was 70:30. The surface of the region made of only the ketjen black of this conductive fiber sheet was in a state in which the ketjen black similar to FIG. 3 was aggregated. The physical properties of this conductive fiber sheet were as shown in Table 1. It should be noted that the ketjen black on the surface of the region side made of only ketjen black was in a state of being easily dropped off.

(Example 5)
The spinning solution was subjected to electrostatic spinning under the same conditions as in Example 1, and the conductive continuous fiber containing acetylene black in its entirety including the inside (the acetylene blacks were vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer) And the acetylene black is also exposed on the outer surface, and is directly accumulated on the stainless steel drum as the counter electrode. At the same time, the dispersion liquid for spraying is dropped by the action of compressed air under the conditions shown below. And is sprayed from the upper part of the stainless drum toward the collection position of the conductive continuous fibers, and the conductive continuous fibers are intertwined with each other in both the surface direction and the thickness direction. A vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer or polyethylene group is placed outside the continuous fiber. Only Ketjen black via call to prepare a conductive fiber sheet comprising only mixing region adhered. The mass ratio of the conductive continuous fiber to the ketjen black in the conductive fiber sheet was 84:16. As shown in the electron micrograph in FIG. 4, the surface of the conductive fiber sheet was in a state where the ketjen black was adhered in a state where a film was partially formed between the conductive fibers. The physical properties of the conductive fiber sheet are as shown in Table 1.

(Condition for spraying with compressed air)
Nozzle: Metal nozzle (inner diameter: 0.2 mm)
Discharge amount: 1.4 g / hour Compressed air pressure: 147 kPa

(Comparative Example 1)
The conductive fiber sheet which consists only of the area | region where electroconductive continuous fiber intertwined also in any direction of a surface direction and thickness direction like Example 1 except not having sprayed the dispersion liquid for spraying. Manufactured. The surface of this conductive fiber sheet was in a state as shown in the electron micrograph of FIG. The physical properties of the conductive fiber sheet are as shown in Table 1.

(Measurement of electrical resistance)
A conductive fiber sheet (25 cm ² ) cut into 5 cm square is sandwiched between carbon plates from both sides, and a voltage (V) is applied while applying a current (I) of 1 A under a pressure of 2 MPa in the laminating direction of the carbon plates. Was measured. Subsequently, the resistance (R = V / I) was calculated, and the electric resistance was calculated by multiplying the area (25 cm ² ) of the conductive fiber sheet.

From Table 1 and FIGS.
(1) From the comparison between Example 1 and Comparative Example 1, by including the second conductive particles, the conductivity is more excellent and the electrical resistance is lowered.
(2) From the comparison between Example 1 and Example 2, when the second conductive particles are increased, the conductivity is more excellent and the electrical resistance is decreased.
(3) From the comparison between Example 1 and Example 3, the one having the region where the conductive fibers and the second conductive particles are mixed is more excellent in electrical conductivity and lower in electrical resistance.
(4) From the comparison between Example 1 and Example 5, the state in which the second conductive particles are in point contact with the surface of the conductive fibers when the dispersion liquid is fragmented and sprayed into charged droplets. Or since it can be in the state which has not formed the membrane | film | coat containing 2nd electroconductive particle, the electroconductive fiber sheet which can utilize a space | gap effectively can be manufactured.
(5) From Example 4, the conductive fiber sheet having a region containing only the second conductive particles and a region where the conductive fibers and the second conductive particles are mixed is also obtained from the conductive fibers and the second conductive particles. Like the conductive fiber sheet (Example 1) which consists only of the area | region where is mixed, it must be excellent in electroconductivity.

  Since the conductive fiber sheet of the present invention has a low electrical resistance, it can be suitably used for applications that require electrical conductivity. For example, it can be suitably used as a gas diffusion electrode substrate for a fuel cell, as an electrode for an electric double layer capacitor, or as an electrode for a lithium ion secondary battery.

Claims (15)

In addition to the conductive fiber containing 1st electroconductive particle, the 2nd electroconductive particle is contained outside the electroconductive fiber, The electroconductive fiber sheet characterized by the above-mentioned. The conductive fiber sheet according to claim 1, wherein the conductive fiber sheet has a region in which conductive fibers and second conductive particles are mixed. The conductive fiber sheet according to claim 1 or 2, wherein the second conductive particles are bonded to the conductive fibers via a resin. The conductive fiber sheet according to any one of claims 1 to 3, wherein a film containing the second conductive particles is not formed between the conductive fibers. The conductive fiber sheet according to any one of claims 1 to 4, wherein the conductive fiber sheet does not have a region not including conductive fibers. The conductive fiber sheet according to any one of claims 1 to 5, wherein the conductive fiber is a continuous fiber. A conductive fiber sheet using the conductive fiber sheet according to any one of claims 1 to 6 as a base material for a gas diffusion electrode. A gas diffusion electrode, wherein a catalyst is supported on the conductive fiber sheet according to any one of claims 1 to 6. A membrane-electrode assembly comprising the gas diffusion electrode according to claim 8. A solid polymer fuel cell comprising the gas diffusion electrode according to claim 8. The conductive fiber sheet according to claim 1, wherein the second conductive particles are supplied before or after the conductive fibers spun from the spinning solution containing the first conductive particles are accumulated. Method. The method for producing a conductive fiber sheet according to claim 11, wherein the second conductive particles are supplied by spraying a dispersion liquid containing the second conductive particles. The method for producing a conductive fiber sheet according to claim 12, wherein the dispersion liquid is fragmented and sprayed into charged droplets. The method for producing a conductive fiber sheet according to any one of claims 11 to 13, wherein a conductive fiber is spun from the spinning liquid containing the first conductive particles by an electrostatic spinning method. The electroconductivity according to any one of claims 11 to 14, wherein the spinning of the conductive fibers from the spinning solution containing the first conductive particles and the supply of the second conductive particles are performed simultaneously. For producing a conductive fiber sheet.

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