WO2017082276A1 - Conductive porous sheet, polymer electrolyte fuel cell, and conductive porous sheet production method - Google Patents

Conductive porous sheet, polymer electrolyte fuel cell, and conductive porous sheet production method Download PDF

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Publication number
WO2017082276A1
WO2017082276A1 PCT/JP2016/083179 JP2016083179W WO2017082276A1 WO 2017082276 A1 WO2017082276 A1 WO 2017082276A1 JP 2016083179 W JP2016083179 W JP 2016083179W WO 2017082276 A1 WO2017082276 A1 WO 2017082276A1
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Prior art keywords
porous sheet
conductive porous
fiber
organic material
carbon
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PCT/JP2016/083179
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French (fr)
Japanese (ja)
Inventor
達規 伊藤
佳織 針谷
隆 多羅尾
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日本バイリーン株式会社
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Priority to JP2017550347A priority Critical patent/JP6691924B2/en
Publication of WO2017082276A1 publication Critical patent/WO2017082276A1/en

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    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
    • D04H3/002—Inorganic yarns or filaments
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
    • D04H3/08—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating
    • D04H3/12—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating with filaments or yarns secured together by chemical or thermo-activatable bonding agents, e.g. adhesives, applied or incorporated in liquid or solid form
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/04—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of carbon-silicon compounds, carbon or silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
    • H01B5/02—Single bars, rods, wires, or strips
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/40—Fibres
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/96—Carbon-based electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a conductive porous sheet, a polymer electrolyte fuel cell, and a method for producing a conductive porous sheet.
  • a conductive porous 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.
  • a fiber web in which carbon fibers and a papermaking binder are mixed is made, and the fiber web is impregnated with a thermosetting resin such as a phenol resin and cured, and then the temperature is 1000 ° C. or more.
  • a thermosetting resin such as a phenol resin
  • a carbon fiber sheet produced by firing at a temperature is known. This carbon fiber sheet was excellent in electrical conductivity, but had a small surface area because the fibers were bonded using a thermosetting resin such as a phenol resin.
  • a conductive porous body that can solve such problems, the applicant of the present application states that “a conductive material in which fibrous materials having a first conductive material and a second conductive material that connects between the first conductive materials are gathered.
  • This conductive porous body had a large specific surface area, but was inferior in flexibility, such as being broken by a slight bending, and inferior in handling properties.
  • the present invention has been made under such circumstances, and an object thereof is to provide a conductive porous sheet having excellent mechanical properties and conductivity, and a method for producing the same, since it has excellent flexibility and excellent handling properties. To do. Another object of the present invention is to provide a polymer electrolyte fuel cell using the conductive porous sheet.
  • a conductive porous sheet mainly composed of carbon fibers, in which carbon fibers are joined at intersections, and the conductive porous sheet does not break in a three-point bending test [2] The conductive porous sheet according to [1], wherein the carbon fiber is curved, [3] The conductive porous sheet according to [1] or [2], wherein the breaking strength is 0.30 MPa or more, [4] The conductive porous sheet according to any one of [1] to [3], which is used as a substrate for an electrode, [5] A polymer electrolyte fuel cell comprising the conductive porous sheet according to any one of [1] to [4] as a base for a gas diffusion electrode, [6] A step of forming a precursor fiber including a first carbonizable organic material and a second carbonizable organic material made of an organic material different from the first carbonizable organic material, and an intersection of the precursor fibers can be first carbonized.
  • the conductive porous sheet of [1] of the present invention is excellent in handling properties because it has flexibility that does not break even in a three-point bending test. Moreover, since it joins at the intersection of carbon fibers, not only is mechanical strength excellent, but it is excellent also in electroconductivity.
  • the conductive porous sheet of [2] of the present invention is excellent in flexibility because the carbon fiber is curved, and when the conductive porous sheet is bent, the curved portion of the carbon fiber is stretched, Since the intersection where the carbon fibers are joined together is not easily broken simply by stretching the curved portion of the carbon fiber, it is difficult to break when bent.
  • the conductive porous sheet of [3] of the present invention has excellent mechanical strength with a breaking strength of 0.30 MPa or more.
  • the conductive porous sheet of [4] of the present invention is excellent in flexibility, mechanical strength, and conductivity, it can exhibit excellent electrode performance when used as a substrate for electrodes.
  • the polymer electrolyte fuel cell of [5] of the present invention includes the conductive porous sheet as a base material for a gas diffusion electrode.
  • the conductive porous sheet is excellent in electrical conductivity and mechanical strength, and also has excellent flexibility that does not break even when bent, and is difficult to break even when stretched by swelling and shrinking of the solid polymer film. The power generation performance can be demonstrated stably.
  • Electron micrograph on the main surface of the conductive porous sheet of Example 1 (2000 times) Electron micrograph on the main surface of the conductive porous sheet of Example 2 (2000 times) Electron micrograph on the main surface of the conductive porous sheet of Example 3 (2000 times) Electron micrograph on the main surface of the conductive porous sheet of Example 4 (2000 times) Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 1 (2000 times) Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 2 (2000 times) Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 3 (2000 times) Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 4 (2000 times) Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 5 (2000 times) Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 6 (2000 times) Electron micrograph showing the state of joining at the intersection of carbon fibers (50,000 times) Electron
  • the conductive porous sheet of the present invention is mainly composed of carbon fibers and joined at the intersections of the carbon fibers, it has excellent mechanical strength and conductivity. Moreover, since it has the softness
  • the carbon fiber used in the present invention can be, for example, a PAN-based carbon fiber.
  • the carbon fiber can contain a conductive material. It is preferable to include a conductive material in this manner because it is more excellent in conductivity and mechanical strength.
  • Such conductive materials include, for example, fullerene, carbon nanotube, carbon nanohorn, graphite, graphene, vapor grown carbon fiber, carbon black, metal (for example, gold, platinum, titanium, nickel, aluminum, silver, zinc, iron , Copper, manganese, cobalt, stainless steel, etc.), one type selected from the group of metal oxides of the metal, or two or more types.
  • carbon nanotubes are preferable because they are excellent in electrical conductivity, are easily oriented in the length direction in carbon fibers, and can increase electrical conductivity and mechanical strength. Further, when carbonizing, there is a difference between the shrinkage rate in the portion where the carbon nanotubes are present and the shrinkage rate in the portion where the carbon nanotubes are not present, and the curved carbon fibers tend to be curved. When bent, the curved portion is easy to stretch and is excellent in flexibility, so that it preferably contains carbon nanotubes.
  • a suitable carbon nanotube may be a single-walled carbon nanotube, a multi-walled carbon nanotube, or a coiled one.
  • the size of the suitable conductive material is not particularly limited, but when the conductive material is in the form of particles, the average particle size is preferably 5 nm to 50 ⁇ m so that carbon fibers can be easily formed.
  • the thickness is more preferably 20 nm to 25 ⁇ m, and further preferably 30 nm to 10 ⁇ m.
  • each said lower limit and each upper limit can be arbitrarily combined as desired.
  • This “average particle size” basically represents the number average particle size of the particles obtained from a particle size distribution meter by the dynamic light scattering method. For example, a state called an aggregate or structure such as carbon black was formed.
  • the fiber diameter is preferably 10 nm to 5000 nm, more preferably 10 nm to 1000 nm, still more preferably 10 nm to 500 nm, and more preferably 10 nm to 250 nm. More preferably.
  • each said lower limit and each upper limit can be arbitrarily combined as desired.
  • the fiber length is preferably a fiber length having an aspect ratio of 1000 or less, and more preferably a fiber length of 500 or less so that the fiber length can be easily dispersed in the carbon fiber.
  • the amount of the conductive material is not particularly limited, but the carbon fiber has 1 mass in order to be excellent in conductivity, mechanical strength and flexibility.
  • % Is preferably contained, more preferably 5 mass% or more, and even more preferably 10 mass% or more.
  • flexibility tends to be low, it is preferably contained at 80 mass% or less, more preferably at 50 mass% or less, and even more preferably at 40 mass% or less.
  • each said lower limit and each upper limit can be arbitrarily combined as desired.
  • the carbon fiber of the present invention is preferably curved regardless of whether or not it contains a conductive material.
  • the carbon fiber is curved, even if the carbon fibers are joined at the intersection, when the conductive porous sheet is bent, the curved portion of the carbon fiber is stretched, and the flexibility is excellent. This is because the intersection where the carbon fibers are joined to each other is not easily broken simply by stretching the curved portion of the carbon fiber, so that it is difficult to break when bent.
  • the carbon fiber of the present invention is free of voids inside the fiber, it is suitable because it is excellent in mechanical strength and conductivity. “There is no void inside the fiber” means that the entire cross section of the carbon fiber having a continuous contour and a clear cross sectional shape is accommodated in the cut surface in the thickness direction of the conductive porous sheet. The observation of the carbon fibers in the visual field is carried out at 10 locations, which means that the number of carbon fibers in which no voids are observed is 70% or more.
  • the carbon fiber contains the conductive material as described above, and when the conductive porous sheet is cut in the thickness direction, the gap that is clearly formed by dropping the conductive material is the gap. Not included.
  • the carbon fiber contains a conductive material containing voids.
  • the carbon fiber composed mainly of the conductive porous sheet is “no void inside the fiber”, that is, the carbon fiber joined at the intersection is preferably “no void inside the fiber”, Since carbon fibers that are not bonded have little influence on the mechanical strength and the like of the conductive porous sheet, there may or may not be voids inside the fibers.
  • the average fiber diameter of the carbon fiber of the present invention is not particularly limited, but is preferably 50 ⁇ m or less, more preferably 30 ⁇ m or less, and even more preferably 20 ⁇ m or less. If the average fiber diameter exceeds 50 ⁇ m, the number of contact points between the carbon fibers in the conductive porous sheet is small, and the mechanical strength and conductivity of the conductive porous sheet tend to be inferior.
  • the lower limit of the average fiber diameter of the carbon fiber is not particularly limited, but it is realistic that it is 0.1 ⁇ m or more. The lower limit and each upper limit can be arbitrarily combined as desired.
  • the “average fiber diameter” in the present invention means an arithmetic average value of fiber diameters at 40 points of the carbon fiber, and the “fiber diameter” is a width orthogonal to the length direction when the carbon fiber is observed with a micrograph. is there.
  • the carbon fiber is continuous so as to be excellent in conductivity.
  • a continuous carbon fiber is obtained by, for example, spinning a continuous precursor fiber by a spinning solution containing a carbonizable organic material by an electrostatic spinning method or a spunbond method, and then carbonizing the carbonizable organic material. Can be manufactured.
  • the conductive porous sheet of the present invention is mainly composed of carbon fibers, but can be composed of two or more types of carbon fibers.
  • presence or absence of conductive material difference in conductive material (type, shape, size, length, etc.), difference in content of conductive material, presence or absence of voids inside carbon fiber, average fiber diameter, fiber length, etc.
  • It can be composed of two or more types of carbon fibers that differ in at least one point.
  • the conductive porous sheet of the present invention is mainly composed of the above-described carbon fiber, it has excellent conductivity.
  • the “main body” in the present invention means that the carbon fiber occupies 50 mass% or more of the conductive porous sheet. The higher the ratio of the carbon fiber, the better the conductivity. It preferably occupies 70 mass% or more of the porous sheet, more preferably occupies 90 mass% or more, and most preferably consists of 100 mass% carbon fiber.
  • examples of materials that can form conductive porous sheets include fullerenes, carbon nanotubes, carbon nanohorns, graphite, graphene, vapor-grown carbon fibers, carbon black, fine particles such as metals and metal oxides; rayon , Recycled fibers such as polynosic and cupra, semi-synthetic fibers such as acetate fibers, nylon fibers, vinylon fibers, fluorine fibers, polyvinyl chloride fibers, polyester fibers, acrylic fibers, polyethylene fibers, polyolefin fibers or polyurethane fibers, Glass fibers, inorganic fibers such as ceramic fibers, plant fibers such as cotton and hemp, animal fibers such as wool and silk; activated carbon powder (for example, steam activated carbon, alkali-treated activated carbon, acid-treated activated carbon, etc.), inorganic particles (for example, , Manganese dioxide
  • Non-conductive materials such as iron oxide, copper oxide, nickel oxide, cobalt oxide, zinc oxide, titanium-containing
  • the conductive porous sheet of the present invention is excellent in mechanical strength and conductivity because carbon fibers are joined at an intersection.
  • the carbon fibers are bonded to each other with a carbide of an organic material so that the carbon fibers are excellent in adhesion and the conductivity is excellent.
  • an organic fiber containing two or more types of carbonizable organic materials and bonding the organic fibers with one or more types of carbonizable organic materials, followed by carbonization the carbon fibers are bonded at the intersection. It can be a perforated sheet.
  • FIG. 11 is an electron micrograph (50000 times) on the main surface of the conductive porous sheet, but it is confirmed that carbon fibers are bonded to each other because a water-like film can be observed at the intersection of carbon fibers. it can.
  • FIG. 12 is an electron micrograph (50000 times) on the main surface of the conductive porous sheet, but the carbon fibers are not joined to each other because a water-fouling film cannot be observed at the intersection of the carbon fibers. Can be confirmed.
  • the conductive porous sheet of the present invention is mainly composed of carbon fibers, it may have a single-layer structure or a multilayer structure of two or more layers, and the content ratio of carbon fibers gradually increases. It may change.
  • a multilayer structure having two or more layers made of carbon fibers having different fiber diameters may be used.
  • the carbon fiber abundance ratio may be different on the main surface of the conductive porous sheet.
  • the main surface of the conductive porous sheet it has a region mainly composed of carbon fibers having a small fiber diameter and a region mainly composed of carbon fibers having a large fiber diameter, and either region is dotted, linear, and / Or can have a curved shape (such as a circle).
  • the abundance ratio of the carbon fibers may gradually change on the main surface of the conductive porous sheet.
  • the form of the conductive porous sheet of the present invention is not particularly limited, and may be, for example, a nonwoven fabric form in which fibers are randomly oriented, or a woven or knitted form in which fibers are regularly oriented.
  • the non-woven fabric is suitable because it has many intersections between carbon fibers, is excellent in electrical conductivity, has fine voids, and has a high porosity, and preferably comprises only a non-woven fabric.
  • the conductive porous sheet of the present invention is mainly composed of the above-described carbon fiber, but has flexibility that does not break in the three-point bending test and has excellent handling properties.
  • the “three-point bending test” in the present invention is performed by the following procedure using a load-displacement measuring unit (manufactured by Imada Co., Ltd., FSA-1KE-5N + GA-10N). (1) The conductive porous sheet is cut and five test pieces (flow direction test pieces) of 50 mm (flow direction at the time of manufacturing the conductive porous sheet) ⁇ 10 mm [width direction (direction perpendicular to the flow direction)] are obtained.
  • test pieces width direction test pieces
  • 50 mm [width direction] ⁇ 10 mm flow direction during production of the conductive porous sheet
  • the fulcrum is arranged so that the distance between the metal rod-shaped fulcrums having a rounded end of 2 ⁇ 0.2 mm is 16 mm.
  • a test piece is arranged so as to straddle between fulcrums.
  • a bar-shaped metal pressure wedge having a roundness with a tip of 5 ⁇ 0.1 mm is set at a speed of 1 mm / min.
  • the test piece is pushed from above the test piece to the fulcrum until the distance between the initial position of the upper surface or the lower surface of the test piece and the broken position becomes 4 mm.
  • the indentation length and the stress are measured sequentially, and when the stress drops abruptly, the indentation length at this time is defined as the bending deflection (mm).
  • mm bending deflection
  • the bending deflection amount is measured for each of the five flow direction test pieces and the five width direction test pieces, and among the five flow direction test pieces, the bending deflection amount indicating the maximum value and the minimum value are indicated. Three of the three flow direction test pieces excluding the bending deflection, and three of the five width direction test pieces, excluding the bending deflection showing the maximum value and the bending deflection showing the minimum value. The arithmetic average value of three test pieces in the width direction is calculated. As a result, a value larger than the arithmetic average value of the bending deflection is adopted as the “bending deflection”. (6) When the amount of bending deflection is more than 4 mm, it is determined that the conductive porous sheet of the test piece is “not broken”.
  • the basis weight of the conductive porous sheet of the present invention is not particularly limited, but the basis weight is preferably 0.5 to 500 g / m 2 so as to be excellent in mechanical strength and conductivity. / M 2 is more preferred, 5 to 300 g / m 2 is still more preferred, and 5 to 200 g / m 2 is even more preferred.
  • the thickness is not particularly limited, but is preferably 1 to 2000 ⁇ m, more preferably 3 to 1000 ⁇ m, still more preferably 5 to 500 ⁇ m, and further preferably 10 to 300 ⁇ m. In addition, each lower limit and each upper limit in the said fabric weight and thickness can be combined arbitrarily as desired.
  • the “weight per unit” in the present invention is a value obtained by measuring the mass of a sample obtained by cutting a conductive porous sheet into a 10 cm square and converting it to a mass of 1 m 2
  • “thickness” is a thickness gauge. This is a value measured using Mitutoyo Corporation (code No. 547-401: measuring force 3.5 N or less).
  • Conductive porous sheet of the invention are excellent in electrical conductivity, the degree is preferably an electric resistance of 20 m [Omega ⁇ cm 2 or less, more preferably at 15m ⁇ ⁇ cm 2 or less, 10 m [Omega ⁇ cm 2 less more preferably in the range, further preferably at 8m ⁇ ⁇ cm 2 or less, and even more preferably 6m ⁇ ⁇ cm 2 or less.
  • the conductive porous sheet of the present invention has excellent mechanical strength, but the degree of breakage is preferably 0.30 MPa or more, more preferably 0.40 MPa or more, and 0.50 MPa. More preferably, it is more preferably 0.60 MPa or more.
  • This breaking strength is a quotient obtained by dividing the breaking load by the cross-sectional area of the conductive porous sheet.
  • the breaking load is a value measured under the following conditions.
  • the cross-sectional area is the width of the conductive porous sheet (test piece) at the time of measurement. And the value obtained from the product of thickness.
  • the breaking load is measured for 10 flow direction test pieces and 10 width direction test pieces, and the arithmetic average value of 20 test pieces is taken as the breaking load.
  • Test piece 50 test pieces (flow direction test piece) of 50 mm (flow direction during manufacture of the test piece) ⁇ 5 mm [width direction (direction orthogonal to the flow direction)], 50 mm [width direction] ⁇ 5 mm (test piece) 10 test pieces (width direction test piece) in the manufacturing direction)
  • Product name Small tensile tester (model: TSM-41-cre, manufactured by Search Inc.) Spacing between chucks: 20 mm
  • Tensile speed 20 mm / min.
  • the conductive porous sheet of the present invention is mainly composed of carbon fibers, but the specific apparent Young's modulus is preferably 100 [MPa / (g / cm 3 )] or more.
  • the high specific Young's modulus means that the rigidity is high, and because it is a highly conductive conductive porous sheet, it has excellent dimensional stability, is easy to handle by itself, and is wound into a roll shape. There is an advantage that it can be stored and transported. For example, when such a conductive porous sheet having a high apparent Young's modulus is used as a base material for an electrode of a polymer electrolyte fuel cell, swelling and shrinkage of the polymer electrolyte membrane can be suppressed. Cracks due to swelling and shrinkage of the molecular film can be prevented.
  • this specific apparent Young's modulus is a value obtained by dividing the apparent Young's modulus, which is an index of rigidity of the conductive porous sheet, by the apparent density of the conductive porous sheet. .
  • the apparent Young's modulus is the same, when the apparent density is high and low, the lower apparent density is the same apparent Young's modulus even though the amount of carbon fiber is small.
  • the rigidity of each carbon fiber is so high that it is expressed by the specific apparent Young's modulus, which is the apparent Young's modulus of the conductive porous sheet divided by the apparent density. ing. The higher the specific Young's modulus is, the higher the rigidity of each carbon fiber is.
  • each said lower limit and upper limit can be arbitrarily combined as desired.
  • This “specific apparent Young's modulus” is a value obtained by the following procedure.
  • the apparent density (g / cm 3 ) is calculated by dividing the basis weight (g / cm 2 ) of the conductive porous sheet to be evaluated by the thickness (cm).
  • 10 directional test specimens obtained by cutting the conductive porous sheet into a rectangular shape of 50 mm in the flow direction during the production of the conductive porous sheet and 5 mm in the width direction (direction perpendicular to the flow direction); And 10 horizontal direction test pieces cut into a rectangular shape of 50 mm in the width direction and 5 mm in the flow direction are respectively collected.
  • the apparent Young's modulus is obtained by dividing the tensile stress by the strain at the maximum point (dimensionalless) [elongation length of test piece (mm) ⁇ initial test piece length (mm)].
  • the arithmetic average value of the apparent Young's modulus of the 20 test pieces is calculated and set as the “average apparent Young's modulus”.
  • the “average apparent Young's modulus” is calculated by dividing the average apparent Young's modulus by the apparent density.
  • the conductive porous sheet of the present invention when used as a base material for a gas diffusion electrode of a polymer electrolyte fuel cell and a gas diffusion layer is formed, when the surface smoothness is low, the conductive porous sheet and The conductive porous sheet may pierce other materials that abut (in the case of polymer electrolyte fuel cells, the solid polymer membrane), possibly damaging other materials, and other materials (solid polymer membranes)
  • a gap is formed between the solid polymer membrane and / or the separator and the conductive porous sheet, resulting in poor adhesion and sufficient performance (in the case of a polymer electrolyte fuel cell). , Power generation performance) tends to be difficult to demonstrate.
  • the surface of the conductive porous sheet is smooth so that other materials are not easily damaged and sufficient performance is easily exhibited.
  • the “average arithmetic average surface roughness” on the main surface of the conductive porous sheet is preferably 0.01 ⁇ m to 20 ⁇ m, more preferably 0.1 ⁇ m to 10 ⁇ m, and more preferably 0.1 ⁇ m to 5 ⁇ m. It is more preferable that the thickness is 0.1 to 4 ⁇ m.
  • each said lower limit and each upper limit can be arbitrarily combined as desired.
  • This “average arithmetic average surface roughness” is a laser microscope (OLS4100, manufactured by Olympus) that can prepare a sample by cutting a conductive porous sheet into 5 cm square and measure roughness (three-dimensional) parameters in accordance with ISO25178. Is used to mean the value obtained by further averaging the values of each arithmetic average surface roughness (Sa) after measuring the arithmetic average surface roughness (Sa) for each of five evaluation regions (260 ⁇ m ⁇ 260 ⁇ m) in the sample. To do.
  • OLS4100 laser microscope
  • the conductive porous sheet of the present invention preferably has a porosity of 50% or more so that the voids can be effectively utilized.
  • a porous porous conductive sheet is used as, for example, an electrode substrate of a polymer electrolyte fuel cell, a fuel cell having excellent drainage and gas diffusibility and high power generation performance can be produced.
  • the shape stability of the conductive porous sheet tends to be extremely lowered, and therefore it is preferably 99% or less.
  • each said lower limit and upper limit can be arbitrarily combined as desired.
  • the porosity P (unit:%) is a value obtained from the following formula.
  • P 100- (Fr1 + Fr2 + .. + Frn)
  • 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
  • M is the mass per unit (unit: g / cm 2 ) of the conductive porous sheet
  • T is the thickness (cm) of the conductive porous sheet
  • Prn is the component n (for example, carbon fiber) in the conductive porous sheet.
  • SGn means the specific gravity (unit: g / cm 3 ) of component n.
  • the conductive porous sheet of the present invention is not only excellent in mechanical strength and conductivity, but is flexible and excellent in handling properties, and therefore can be suitably used as an electrode substrate.
  • an electrode substrate For example, when used as an electrode of a lithium ion secondary battery or an electric double layer capacitor, a secondary battery or capacitor having a large capacity can be produced.
  • a base material for a gas diffusion electrode of a polymer electrolyte fuel cell a polymer electrolyte fuel cell capable of exhibiting excellent power generation performance can be produced.
  • the conductive porous sheet of the present invention when the conductive porous sheet of the present invention is provided as the base material for the gas diffusion electrode of the solid polymer fuel cell, the conductive porous sheet of the present invention is porous. If nothing is filled, the drainage property in the thickness direction and the surface direction of the gas diffusion electrode substrate (conductive porous sheet) is excellent, and the diffusibility of the supplied gas is excellent.
  • fluororesin examples include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), perfluoroalkoxy fluororesin (PFA), tetrafluoroethylene.
  • PTFE polytetrafluoroethylene
  • PCTFE polychlorotrifluoroethylene
  • PVDF polyvinylidene fluoride
  • PVDF polyvinyl fluoride
  • PVF polyvinyl fluoride
  • PFA perfluoroalkoxy fluororesin
  • Ethylene / hexafluoropropylene copolymer FEP
  • Ethylene / hexafluoropropylene copolymer ETFE
  • ETFE ethylene / tetrafluoroethylene copolymer
  • ECTFE ethylene / chlorotrifluoroethylene copolymer
  • vinylidene fluoride / tetrafluoroethylene / hexafluoro Examples thereof include a propylene copolymer and a copolymer of various monomers constituting the resin.
  • examples of carbon include carbon fiber, fullerene, carbon nanotube, carbon nanohorn, graphite, graphene, vapor growth carbon fiber, and carbon black.
  • the polymer electrolyte fuel cell of the present invention can be exactly the same as a conventional polymer electrolyte fuel cell except that the above-mentioned conductive porous sheet is provided as a base material for a gas diffusion electrode. That is, a cell in which a bonded body of a gas diffusion electrode having a catalyst supported on the surface of a gas diffusion electrode substrate (conductive porous sheet) as described above and a solid polymer film is sandwiched between a pair of bipolar plates. It has a structure in which a plurality of units are stacked.
  • Such a conductive porous sheet of the present invention includes, for example, a step of forming a precursor fiber including a first carbonizable organic material and a second carbonizable organic material made of an organic material different from the first carbonizable organic material.
  • a conductive porous sheet that does not break in the three-point bending test can be manufactured by the process of carbonizing the carbon fiber while it is bonded at the intersection to form a curved carbon fiber. According to this manufacturing method, after joining the intersections of the precursor fibers, carbonized while being joined at the intersections to form a curved carbon fiber, the conductivity, excellent in flexibility, mechanical strength, and conductivity A perforated sheet can be produced.
  • first, a first carbonizable organic material and a second carbonizable organic material made of an organic material different from the first carbonizable organic material are prepared.
  • the first carbonizable organic material and the second carbonizable organic material are not particularly limited.
  • thermosetting resins such as resins, thermosetting polyimide resins, thermosetting polyimide resins, thermosetting polyamide resins; polystyrene resins, polyester resins, polyolefin resins, polyimide resins, polyamide resins, polyamideimide resins, polyvinyl acetate resins, Thermoplastic resins such as vinyl chloride resin, fluororesin, polyacrylonitrile resin, acrylic resin, polyether resin, polyvinyl alcohol, polyvinyl pyrrolidone, pitch, polyamino acid resin, polybenzimidazole resin; cellulose (polysaccharide), tar; Mention may be made of a copolymer of a monomer of the resin component (e.g., acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylon
  • thermosetting resin is included as the first carbonizable organic material or the second carbonizable organic material.
  • the thermosetting resin is included, as described later, the intersection of the precursor fibers containing the first carbonizable organic material and the second carbonizable organic material is joined by the thermosetting resin, and at the time of carbonization, This is because it is easy to maintain the joined state.
  • a phenol resin and / or an epoxy resin are suitable because they are excellent in conductivity after carbonization in addition to the above-described action.
  • a carbonizable organic material having a carbonization process or a carbonization rate different from that of the thermosetting resin is preferable to use.
  • the first or second carbonizable organic material having a different carbonization process not only the spinnability is improved, but also the chemical change mechanism (optimum temperature, time, decomposition, etc.) in the carbonization process is different. This is because differences in shrinkage rate, fluidity, and the like cause bending during carbonization to easily form a curved carbon fiber.
  • thermosetting resin such as a phenol resin and / or an epoxy resin
  • polyacrylonitrile resin As the first carbonizable organic material or the second carbonizable organic material, a thermosetting resin such as a phenol resin and / or an epoxy resin, and as the second carbonizable organic material or the first carbonizable organic material, a polyacrylonitrile resin.
  • a thermoplastic resin such as pitch
  • polyacrylonitrile resin is suitable as the first carbonizable organic material or the second carbonizable organic material because it has a high carbonization rate and easily forms carbon fibers having no voids inside the fibers.
  • the conductive material can be a conductive material as described above, and is preferably a carbon nanotube.
  • the conductive material when carbonizing, there is a difference between the shrinkage rate in the portion where the carbon nanotubes are present and the shrinkage rate in the portion where the carbon nanotubes are not present, which tends to be a curved carbon fiber. Even if it is bent, the curved portion is easy to stretch, so it has excellent flexibility.
  • silicone such as polydimethylsiloxane and metal alkoxide (methoxide such as silicon, aluminum, titanium, zirconium, boron, tin, and zinc) are used.
  • metal alkoxide methoxide such as silicon, aluminum, titanium, zirconium, boron, tin, and zinc
  • ethoxide, a propoxide, a butoxide, etc. can be used in combination with a polymer obtained by polymerizing a known inorganic compound.
  • a spinning solution containing the first carbonizable organic material and the second carbonizable organic material as described above is prepared to form the precursor fiber.
  • a spinning solution including a conductive material is prepared.
  • a spinning solution containing silicone and an inorganic polymer is prepared.
  • the solvent constituting the spinning solution is not particularly limited as long as the first carbonizable organic material and the second carbonizable organic material can be dissolved.
  • Examples thereof include carbon, methylene chloride, chloroform, trichloroethane, ethylene carbonate, diethyl carbonate, propylene carbonate, water, and the like.
  • These solvents can be a single solvent or a mixed solvent.
  • a poor solvent can be added as long as there is no problem in spinnability
  • the solid content concentration in the spinning solution is not particularly limited, but is preferably 1 to 50 mass%, more preferably 5 to 30 mass%. This is because when the content is less than 1 mass%, the productivity is extremely lowered, and when the content exceeds 50 mass%, the spinning tends to become unstable.
  • each said lower limit and each upper limit can be arbitrarily combined as desired.
  • the solid content mass ratio of the 1st carbonizable organic material and the 2nd carbonizable organic material in a spinning liquid changes with combinations of the 1st carbonizable organic material and the 2nd carbonizable organic material, it does not specifically limit
  • the first carbonizable organic material is made of an organic material having a high carbonization rate such as polyacrylonitrile resin and the second carbonizable organic material is made of a thermosetting resin such as an epoxy resin
  • the first carbonizable organic material and the first carbonizable organic material are superior in electrical conductivity due to the first carbonizable organic material, and excellent in mechanical strength, electrical conductivity, and flexibility due to bending by the second carbonizable organic material.
  • the solid content ratio with the carbonizable organic material is preferably 40 to 90:60 to 10, more preferably 50 to 80:50 to 20, and 50 to 70:50 to 30. And even more preferred.
  • each said lower limit and each upper limit can be arbitrarily combined as desired.
  • the first carbonizable organic material and the second carbonizable organic material are selected so as to have excellent conductivity. It is preferable to include a conductive material having a mass of 1 to 90, and more preferable to include a conductive material having a mass of 5 to 50 with respect to a total mass of 100 solids of the carbonizable organic material. More preferably, a conductive material having a mass of ⁇ 40 is included. In addition, each said lower limit and each upper limit can be arbitrarily combined as desired.
  • a spinning fiber containing the first carbonizable organic material and the second carbonizable organic material as described above is spun to form a precursor fiber.
  • a method of forming this precursor fiber for example, a dry spinning method, an electrostatic spinning method, and a gas parallel to a spinning solution discharged from a liquid discharging unit as disclosed in JP-A-2009-287138 is used. And a method of producing a fiber by applying a shearing force in a straight line to the spinning solution.
  • the electrospinning method or the spinning method disclosed in Japanese Patent Application Laid-Open No. 2009-287138 is preferable because a precursor fiber having a small average fiber diameter of 3 ⁇ m or less can be easily spun.
  • the dry spinning method or the electrostatic spinning method is preferable because continuous precursor fibers can be spun.
  • the electrospinning method is suitable because a precursor fiber having a continuous fiber length can be spun in addition to a small fiber diameter.
  • seat shape can be formed by collecting the precursor fiber spun by the above methods directly with a collection body.
  • the “precursor fiber” in the present invention means a fiber in a state where neither the first carbonizable organic material nor the second carbonizable organic material is carbonized, and the first carbonizable organic material and the second carbonized carbon. Since all of the possible organic materials are carbonized to form carbon fiber, it is expressed as a precursor fiber in the sense of a fiber that is a source of carbon fiber.
  • a sheet in which precursor fibers are gathered is formed.
  • the sheet in which the precursor fibers are gathered can be formed, for example, by collecting the spun precursor fibers directly by a collecting body, or winding the spun precursor fibers as continuous fibers and then cutting them to a desired fiber length. After forming into short fibers, it can be formed by a dry method such as a card method, an air array method, or a wet method, and can be formed by weaving or knitting by a conventional method using continuous precursor fibers. You can also.
  • the method of collecting the spun precursor fiber directly with a collector is preferable because it can be a precursor fiber having a continuous fiber length and is excellent in productivity.
  • thermosetting resin is included as the first carbonizable organic material or the second carbonizable organic material
  • thermosetting resin is In order to cure, the thermosetting resin can be bonded by performing a heat treatment at a temperature at which the thermosetting resin is thermally cured. Since the heat curing conditions such as the heat treatment temperature and time vary depending on the thermosetting resin, they are appropriately adjusted according to the thermosetting resin.
  • a solvent capable of dissolving the first carbonizable organic material or the second carbonizable organic material was applied to the sheet in which the precursor fibers were assembled, and the first carbonizable organic material or the second carbonizable organic material was dissolved. Later, bonding can be performed by drying and removing the solvent. Since the plasticizing joining conditions such as the type of solvent, the solvent application amount, the solvent temperature, the drying temperature, and the drying time vary depending on the first carbonizable organic material or the second carbonizable organic material, It adjusts suitably according to the organic material which can be carbonized.
  • the precursor fiber sheet mainly composed of the precursor fibers can be formed by the above-described method.
  • the precursor fibers include materials other than the precursor fibers
  • the precursor fibers are aggregated when the precursor fibers are spun.
  • the material other than the precursor fiber can be applied when forming the sheet or after forming the sheet in which the precursor fibers are aggregated.
  • a precursor fiber sheet in which carbon nanotubes are mixed can be formed by spraying carbon nanotubes on the flow of spun precursor fibers.
  • the precursor fiber constituting the precursor fiber sheet is carbonized while being joined at the intersection, and a conductive porous sheet that is not broken by a three-point bending test is manufactured as a curved carbon fiber.
  • the conductive porous sheet having excellent flexibility, mechanical strength, and conductivity Can be manufactured. That is, the precursor fiber contains the first carbonizable organic material and the second carbonizable organic material, and has different shrinkage rates when carbonized, and thus becomes a curved carbon fiber.
  • This carbonization is not particularly limited as long as the first carbonizable organic material and the second carbonizable organic resin can be carbonized.
  • the maximum temperature is 800 to 3000 ° C. in an inert gas atmosphere such as nitrogen, helium, and argon. It can be performed by heating.
  • the rate of temperature rise is preferably 5 to 100,000 ° C./min, and more preferably 5 to 1000 ° C./min.
  • the holding time at the maximum temperature is preferably within 3 hours, more preferably 1 to 120 minutes. In each of these parameters, the lower limit and the upper limit can be arbitrarily combined as desired.
  • the polyacrylonitrile resin is included as the first carbonizable organic material or the second carbonizable organic material constituting the precursor fiber.
  • an infusibilization step may be performed before the carbonization treatment. This infusibilization can be performed by heating at a temperature of 200 to 300 ° C. for 10 to 120 minutes in an oxidizing atmosphere. The infusible heating can be carried out twice or more under different conditions of temperature or time.
  • the conductive porous sheet of the present invention preferably has a large porosity of 50% or more.
  • the conductive porous sheet having such a high porosity is a carbon fiber having an average fiber diameter of 0.1 ⁇ m to 50 ⁇ m.
  • the porosity is easily satisfied.
  • Precursor fibers which are the basis of carbon fibers having such an average fiber diameter are easy to produce by, for example, the electrostatic spinning method or the spinning method disclosed in JP-A-2009-287138.
  • the binder fills the gaps between the precursor fibers or covers the periphery of the intersections of the precursor fibers more than necessary, and the porosity tends to be low. Therefore, when the first carbonizable organic material or the second carbonizable organic material constituting the precursor fiber is bonded without using a binder, the porosity is easily satisfied.
  • the conductive porous sheet of the present invention can impart or improve physical properties suitable for each application by various post-processing.
  • a conductive porous sheet of the present invention is used as a base material for a gas diffusion electrode of a polymer electrolyte fuel cell, in order to increase the water repellency of the conductive porous sheet and to enhance drainage and gas diffusion properties, A conductive porous sheet is immersed in a fluorine-based dispersion such as a tetrafluoroethylene dispersion to give a fluorine-based resin, and then sintered at a temperature of 300 to 350 ° C.
  • carbon fibers without voids inside are easy to manufacture by using an organic material having a high carbonization rate for both the first carbonizable organic material and the second carbonizable organic material. That is, since there are few organic materials which lose
  • the first carbonizable organic material or the second carbonizable organic material having a high carbonization rate include polyacrylonitrile, epoxy resin, and phenol resin.
  • a rigid conductive porous sheet having a specific apparent Young's modulus of 100 MPa / (g / cm 3 ) or more is easy to manufacture by forming carbon fibers from a rigid material. That is, the first carbonizable organic material and / or the second carbonizable organic material can be easily manufactured by using a thermosetting resin, particularly an epoxy resin or a phenol resin.
  • the average arithmetic average surface roughness on the main surface is 0.01 ⁇ m to 20 ⁇ m (preferably 0.1 ⁇ m to 10 ⁇ m, more preferably 0.1 ⁇ m to 5 ⁇ m, and more preferably 0.1 to 4 ⁇ m.
  • the conductive porous sheet is, for example, a carbon fiber having an average fiber diameter of 20 ⁇ m or less, a non-woven fabric in the form of the conductive porous sheet, and / or a static porous sheet. It is easy to produce by directly producing by an electrospinning method and a method as disclosed in JP-A-2009-287138.
  • each said minimum and each upper limit in the said average arithmetic average surface roughness can be arbitrarily combined as desired.
  • EP a second carbonizable organic material
  • a dispersion was prepared by mixing with the solution.
  • EP carbonizable organic material
  • a second spinning solution having a solid content mass ratio of CNT: PAN: EP of 10:60:30 and a solid content concentration of 25 mass% was prepared.
  • CNT carbon nanotubes synthesized by CVD (trade name: VGCF-H (manufactured by Showa Denko KK), fiber diameter: 150 nm, aspect ratio: 40, multi-walled carbon nanotubes] are used as the conductive material.
  • DMF was further added to dilute to obtain a dispersion solution in which the carbon nanotubes were dispersed.
  • a sixth spinning solution having a solid content of 20 mass% at 30:30 was prepared.
  • CNT carbon nanotubes synthesized by CVD (trade name: VGCF-H (manufactured by Showa Denko KK), fiber diameter: 150 nm, aspect ratio: 40, multi-walled carbon nanotubes] are used as the conductive material.
  • DMF was further added to dilute to obtain a dispersion solution in which the carbon nanotubes were dispersed.
  • a seventh spinning solution having a solid content concentration of 25 mass% was prepared at 60:30.
  • Example 1 The first spinning solution is formed by spinning the precursor continuous fiber under the following conditions by the electrostatic spinning method, and is directly accumulated on the stainless drum as the counter electrode, and is composed of only the precursor continuous fiber, and the intersection of the fibers is joined. A non-woven fabric precursor fiber assembly sheet was formed.
  • Electrode Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 5 g / hour Distance between nozzle tip and stainless steel drum: 10 cm Applied voltage: 10 kV Temperature / humidity: 25 ° C / 30% RH
  • the precursor fiber assembly sheet was heat-treated for 1 hour with a hot air dryer at a temperature of 150 ° C. to cure the epoxy resin, thereby obtaining a precursor fiber sheet in which the intersections of the fibers were joined.
  • the precursor fiber sheet is oxidized in air at a temperature of 220 ° C. for 30 minutes and at a temperature of 260 ° C. for 1 hour to infusibilize the PAN constituting the precursor continuous fiber, so that the infusible precursor fiber A sheet was used.
  • the infusibilized precursor fiber sheet is subjected to carbonization firing treatment (temperature increase rate: 10 ° C./min) at a temperature of 1300 ° C. for 1 hour in a nitrogen gas atmosphere using a vacuum substitution type electric furnace to obtain a precursor continuous fiber.
  • PAN and EP constituting carbon are made into carbon continuous fibers, and are composed of continuous carbon fibers, and have a non-woven structure and are bonded to each other at the intersection of continuous carbon fibers (unit weight: 6.5 g / m 2 , thickness: 65 ⁇ m, fiber diameter: 1.1 ⁇ m, porosity: 91%).
  • the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image
  • Example 2 A conductive perforated sheet composed of continuous carbon fibers and having a non-woven structure and joined at the intersection of continuous carbon fibers (except for the use of the second spinning liquid as the spinning liquid).
  • the basis weight was 10 g / m 2 , the thickness was 84 ⁇ m, the fiber diameter was 0.7 ⁇ m, and the porosity was 94%.
  • the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image
  • Example 3 Similar to Example 2, except that the PAN constituting the precursor continuous fiber was not infusible without performing the oxidation treatment, the carbon continuous fibers having a single-layer structure having only a non-woven fabric structure.
  • a conductive porous sheet (weight per unit area: 10 g / m 2 , thickness: 84 ⁇ m, fiber diameter: 0.7 ⁇ m, porosity: 94%) was produced.
  • the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image
  • the carbon continuous fiber was in the state where the inside of the fiber had no voids, and the mass ratio of CNT in the carbon continuous fiber was 12 mass%.
  • Example 4 A conductive perforated sheet composed of continuous carbon fibers and having a non-woven structure joined at the intersection of continuous carbon fibers (except for the use of the third spinning liquid as the spinning liquid)
  • the basis weight was 5.6 g / m 2 , the thickness was 34 ⁇ m, the fiber diameter was 0.8 ⁇ m, and the porosity was 91%.
  • the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image
  • Example 1 In the same manner as in Example 1 except that the fourth spinning solution is used as the spinning solution and spinning is performed under the following electrostatic spinning conditions, the nonwoven fabric is formed of only PAN precursor continuous fibers and the intersections of the fibers are not joined. A precursor fiber assembly sheet was formed.
  • Electrode Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 1 g / hour Distance between nozzle tip and stainless steel drum: 8 cm Applied voltage: 10 kV Temperature / humidity: 25 ° C / 30% RH
  • the precursor fiber assembly sheet is subjected to an oxidation treatment in air at a temperature of 220 ° C. for 30 minutes and at a temperature of 260 ° C. for 1 hour to infusibilize the PAN constituting the precursor continuous fiber, and then a vacuum replacement type Using an electric furnace, carbonization firing treatment (temperature increase rate: 10 ° C./min) for 1 hour at a temperature of 1300 ° C.
  • PAN constituting the precursor continuous fiber is carbonized to be a carbon continuous fiber
  • Conductive porous sheet consisting of continuous carbon fibers only and having a non-woven structure, in which intersections of continuous carbon fibers are not joined (weight: 5 g / m 2 , thickness: 20 ⁇ m, fiber diameter: 0.3 ⁇ m, Porosity: 86%) was produced.
  • the carbon continuous fiber was linear.
  • the carbon continuous fiber was in a state of being fully filled without voids inside the fiber.
  • Comparative Example 2 Before carrying out the oxidation treatment, the precursor fiber assembly sheet is immersed in a mixed solution of DMF / water adjusted to a concentration of 7 mass%, squeezed between a pair of rolls, and then placed in an oven set at a temperature of 80 ° C. for 10 minutes. Subsequently, only the carbon continuous fiber was obtained in the same manner as in Comparative Example 1 except that the mixed solvent was removed by heat treatment in an oven set at a temperature of 160 ° C., and the intersection of the PAN precursor continuous fibers was adhered.
  • a conductive porous sheet having a single-layer structure having a nonwoven fabric structure and joined at the intersections of carbon continuous fibers (weight: 5 g / m 2 , thickness: 18 ⁇ m, fiber diameter: 0.3 ⁇ m, porosity: 85%) was made.
  • carbon continuous fiber was linear.
  • the carbon continuous fiber was in a state of being fully filled without voids inside the fiber.
  • Example 3 A single-layered carbon continuous fiber having a non-woven structure consisting of carbon continuous fibers in the same manner as in Example 1, except that the fifth spinning liquid was used as the spinning liquid and spinning was performed under the following electrostatic spinning conditions.
  • the electroconductive porous sheet (weight per unit: 8 g / m 2 , thickness: 62 ⁇ m, fiber diameter: 0.6 ⁇ m, porosity: 93%) in which the crossing points are not joined was prepared.
  • the carbon continuous fiber was in a state of being fully filled without voids inside the fiber.
  • Electrode Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 1 g / hour Distance between nozzle tip and stainless steel drum: 8 cm Applied voltage: 10 kV Temperature / humidity: 25 ° C / 40% RH
  • Comparative Example 4 Similar to Comparative Example 3, except that no oxidation treatment was performed and the PAN constituting the precursor continuous fiber was not infusible, the carbon continuous fibers having a single-layer structure having only a non-woven fabric structure.
  • the electroconductive porous sheet (weight per unit: 8 g / m 2 , thickness: 62 ⁇ m, fiber diameter: 0.6 ⁇ m, porosity: 93%) in which the crossing points are not joined was prepared.
  • the carbon continuous fiber was linear as shown in FIG.
  • the sixth spinning solution is obtained by spinning the precursor continuous fiber by the electrospinning method under the following conditions, and directly accumulating on the stainless drum as the counter electrode, and only the precursor continuous fiber is joined. A non-woven fabric precursor fiber assembly sheet was formed.
  • Electrode Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 4 g / hour Distance between nozzle tip and stainless steel drum: 14 cm Applied voltage: 10 kV Temperature / humidity: 25 ° C / 30% RH
  • the precursor fiber assembly sheet was heat-treated with a hot air dryer at a temperature of 150 ° C. for 1 hour to cure the epoxy resin and obtain a precursor fiber sheet in which the intersections of the fibers were joined.
  • carbonization baking treatment temperature increase rate: 10 ° C./min
  • a conductive porous sheet having a single layer structure joined at the intersection of carbon continuous fibrous materials (weight per unit: 20 g / m 2 , thickness: 40 ⁇ m, average fiber diameter: 1.3 ⁇ m, porosity: 73%) is produced. did.
  • CNT orientated in the length direction of the continuous carbon fiber was disperse
  • CNTs are composed of carbon continuous fibers in a porous and continuous state in which the CNTs are partially connected by EP carbide and THV carbide, and the intersections of the carbon continuous fibers are between EP carbide and THV. It was in a bonded state with carbides.
  • the seventh spinning solution is obtained by spinning the precursor continuous fiber under the following conditions by the electrospinning method, and is directly accumulated on the stainless drum as the counter electrode, and is composed only of the precursor continuous fiber. A non-woven fabric precursor fiber assembly sheet was formed.
  • Electrode Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 4 g / hour Distance between nozzle tip and stainless steel drum: 14 cm Applied voltage: 17 kV Temperature / humidity: 25 ° C / 35% RH
  • the precursor fiber assembly sheet was heat-treated with a hot air dryer at a temperature of 150 ° C. for 1 hour to cure the epoxy resin and obtain a precursor fiber sheet in which the intersections of the fibers were joined.
  • the precursor fiber sheet is subjected to an oxidation treatment in air at a temperature of 220 ° C. for 30 minutes and at a temperature of 260 ° C. for 1 hour, so that the PAN constituting the precursor continuous fiber is infusible and a part of EP is obtained.
  • a fluidized infusible precursor fiber sheet was obtained.
  • the infusibilized precursor fiber sheet is subjected to carbonization baking treatment (temperature increase rate: 10 ° C./min) for 1 hour at a temperature of 800 ° C. in a nitrogen atmosphere using a tubular furnace, thereby forming a precursor continuous fiber PAN.
  • carbonization baking treatment temperature increase rate: 10 ° C./min
  • bonded to each other at the intersection of carbon continuous fibrous materials having a non-woven structure 5 g / m 2 , thickness: 15 ⁇ m, average fiber diameter: 0.8 ⁇ m, porosity: 82%).
  • the conductive porous sheets of Comparative Examples 3 to 4 had relatively high electrical resistance and low mechanical strength. This was considered because the intersection of carbon fibers was not joined.
  • the conductive porous sheet of the present invention is excellent in flexibility, and excellent in mechanical strength and conductivity, despite being composed of rigid carbon fibers. It was a thing. The excellent flexibility is because the carbon fibers are curved between the intersections where the carbon fibers are joined, so that the stress for bending can be dispersed, and the mechanical strength and conductivity are excellent. It was thought that this was because the intersections of the carbon fibers were joined.
  • the conductive porous sheet of the present invention is excellent in mechanical strength, conductivity, and flexibility, and can be suitably used as an electrode substrate.
  • it is useful as an electrode of a lithium ion secondary battery or an electric double layer capacitor, and as a base material for a gas diffusion electrode of a polymer electrolyte fuel cell.

Abstract

The purpose of the present invention is to provide a conductive porous sheet that has excellent handleability as a result of having excellent flexibility and that also has excellent mechanical strength and conductivity. The purpose of the present invention is also to provide a production method for the conductive porous sheet. The purpose of the present invention is also to provide a polymer electrolyte fuel cell that uses the conductive porous sheet. This conductive porous sheet mainly comprises carbon fibers that are joined at the intersections. The conductive porous sheet does not break in a three-point bending test. The solid polymer fuel cell is provided with the conductive porous sheet as a gas diffusion electrode substrate. The conductive porous sheet can be produced as curved carbon fibers by joining the intersections of precursor fibers, which include a first carbonizable organic material and a second carbonizable organic material that is different from the first carbonizable organic material, using the first carbonizable organic material or the second carbonizable organic material, and then carbonizing the resulting product.

Description

導電性多孔シート、固体高分子形燃料電池、及び導電性多孔シートの製造方法Conductive porous sheet, polymer electrolyte fuel cell, and method for producing conductive porous sheet
　この発明は、導電性多孔シート、固体高分子形燃料電池、及び導電性多孔シートの製造方法に関する。 The present invention relates to a conductive porous sheet, a polymer electrolyte fuel cell, and a method for producing a conductive porous sheet.
　従来から導電性多孔シートはその導電性と多孔性を利用して、燃料電池用のガス拡散電極用基材として、また、電気二重層キャパシタの電極として、或いは、リチウムイオン二次電池の電極としての使用が検討されている。 Conventionally, a conductive porous 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.
　このような導電性多孔シートとして、炭素繊維と抄造用バインダとを混合した繊維ウエブを抄造し、前記繊維ウエブにフェノール樹脂等の熱硬化性樹脂を含浸し、硬化させた後に、１０００℃以上の温度で焼成することにより製造した、炭素繊維シートが知られている。この炭素繊維シートは導電性の優れるものであったが、繊維間をフェノール樹脂等の熱硬化性樹脂を用いて接着しているため、表面積の小さいものであった。 As such a conductive porous sheet, a fiber web in which carbon fibers and a papermaking binder are mixed is made, and the fiber web is impregnated with a thermosetting resin such as a phenol resin and cured, and then the temperature is 1000 ° C. or more. A carbon fiber sheet produced by firing at a temperature is known. This carbon fiber sheet was excellent in electrical conductivity, but had a small surface area because the fibers were bonded using a thermosetting resin such as a phenol resin.
　このような問題点を解決できる導電性多孔体として、本願出願人は、「第１導電性材料と第１導電性材料間を繋ぐ第２導電性材料とを有する繊維状物が集合した導電性多孔体であり、前記導電性多孔体は比表面積が１００ｍ２／ｇ以上、かつ２ＭＰａ加圧後における厚さの維持率が６０％以上であることを特徴とする、導電性多孔体」（特許文献１）を提案した。この導電性多孔体は比表面積の広いものであったが、少しの曲げで破断するなど柔軟性に劣り、ハンドリング性に劣るものであった。 As a conductive porous body that can solve such problems, the applicant of the present application states that “a conductive material in which fibrous materials having a first conductive material and a second conductive material that connects between the first conductive materials are gathered. A conductive porous body characterized in that the conductive porous body has a specific surface area of 100 m 2 / g or more and a thickness maintenance ratio of 60% or more after pressing at 2 MPa ”(patent Reference 1) was proposed. This conductive porous body had a large specific surface area, but was inferior in flexibility, such as being broken by a slight bending, and inferior in handling properties.
　このようなハンドリング性を改善した炭素繊維不織布として、「電界紡糸可能な高分子物質と、この高分子物質とは異なる有機化合物と、遷移金属とを含む組成物を電界紡糸して得られた不織布を炭素化してなることを特徴とするフレキシブル炭素繊維不織布。」（特許文献２）が提案されている。この炭素繊維不織布は確かにフレキシブルであったが、機械的強度が劣り、しかも導電性に劣るものであった。 As such a carbon fiber nonwoven fabric with improved handling properties, “a nonwoven fabric obtained by electrospinning a composition containing a polymer substance capable of electrospinning, an organic compound different from this polymer substance, and a transition metal” A flexible carbon fiber non-woven fabric characterized by carbonizing a carbon fiber "(Patent Document 2) has been proposed. This carbon fiber nonwoven fabric was indeed flexible, but it had poor mechanical strength and poor conductivity.
国際公開第２０１５／１４６９８４号International Publication No. 2015/146984 国際公開第２０１１／０７０８９３号International Publication No. 2011/070893
　本発明はこのような状況下においてなされたものであり、柔軟性に優れるためハンドリング性に優れるとともに、機械的強度及び導電性の優れる導電性多孔シート、及びその製造方法を提供することを目的とする。また、この導電性多孔シートを用いた固体高分子形燃料電池を提供することも目的とする。 The present invention has been made under such circumstances, and an object thereof is to provide a conductive porous sheet having excellent mechanical properties and conductivity, and a method for producing the same, since it has excellent flexibility and excellent handling properties. To do. Another object of the present invention is to provide a polymer electrolyte fuel cell using the conductive porous sheet.
　本発明は、
［１］炭素繊維を主体とし、炭素繊維同士が交差点で接合した導電性多孔シートであり、前記導電性多孔シートが三点曲げ試験において破断しないことを特徴とする、導電性多孔シート、
［２］炭素繊維が湾曲していることを特徴とする、［１］の導電性多孔シート、
［３］破断強度が０．３０ＭＰａ以上であることを特徴とする、［１］又は［２］の導電性多孔シート、
［４］電極用基材として用いる、［１］～［３］のいずれかの導電性多孔シート、
［５］［１］～［４］のいずれかの導電性多孔シートを、ガス拡散電極用基材として備えていることを特徴とする、固体高分子形燃料電池、
［６］第１炭化可能有機材料と、第１炭化可能有機材料とは異なる有機材料からなる第２炭化可能有機材料とを含む前駆繊維を形成する工程、前記前駆繊維の交差点を第１炭化可能有機材料又は第２炭化可能有機材料で接合して、前駆繊維を主体とする前駆繊維シートを形成する工程、前記前駆繊維シートを構成する前駆繊維を、その交差点で接合した状態のまま炭化して、湾曲した炭素繊維とする工程、を備えている、三点曲げ試験で破断しない導電性多孔シートの製造方法
に関する。 The present invention
[1] A conductive porous sheet mainly composed of carbon fibers, in which carbon fibers are joined at intersections, and the conductive porous sheet does not break in a three-point bending test,
[2] The conductive porous sheet according to [1], wherein the carbon fiber is curved,
[3] The conductive porous sheet according to [1] or [2], wherein the breaking strength is 0.30 MPa or more,
[4] The conductive porous sheet according to any one of [1] to [3], which is used as a substrate for an electrode,
[5] A polymer electrolyte fuel cell comprising the conductive porous sheet according to any one of [1] to [4] as a base for a gas diffusion electrode,
[6] A step of forming a precursor fiber including a first carbonizable organic material and a second carbonizable organic material made of an organic material different from the first carbonizable organic material, and an intersection of the precursor fibers can be first carbonized. Joining with an organic material or a second carbonizable organic material to form a precursor fiber sheet mainly composed of precursor fibers, carbonizing the precursor fibers constituting the precursor fiber sheet while being joined at the intersection It is related with the manufacturing method of the electroconductive porous sheet which is equipped with the process made into curved carbon fiber, and does not fracture | rupture in a three-point bending test.
　本発明の［１］の導電性多孔シートは、三点曲げ試験においても破断しない柔軟性を有するため、ハンドリング性に優れている。また、炭素繊維同士の交差点で接合しているため、機械的強度が優れているばかりでなく、導電性にも優れている。 The conductive porous sheet of [1] of the present invention is excellent in handling properties because it has flexibility that does not break even in a three-point bending test. Moreover, since it joins at the intersection of carbon fibers, not only is mechanical strength excellent, but it is excellent also in electroconductivity.
　本発明の［２］の導電性多孔シートは、炭素繊維が湾曲しているため、導電性多孔シートを曲げた場合に、炭素繊維の湾曲部が引き伸ばされるため柔軟性に優れており、また、炭素繊維の湾曲部が引き伸ばされるだけで炭素繊維同士が接合した交差点が破壊されにくいため、曲げた際に破断しにくいものである。 The conductive porous sheet of [2] of the present invention is excellent in flexibility because the carbon fiber is curved, and when the conductive porous sheet is bent, the curved portion of the carbon fiber is stretched, Since the intersection where the carbon fibers are joined together is not easily broken simply by stretching the curved portion of the carbon fiber, it is difficult to break when bent.
　本発明の［３］の導電性多孔シートは、破断強度が０．３０ＭＰａ以上の機械的強度の優れるものである。 The conductive porous sheet of [3] of the present invention has excellent mechanical strength with a breaking strength of 0.30 MPa or more.
　本発明の［４］の導電性多孔シートは、柔軟性、機械的強度及び導電性に優れているため、電極用基材として用いると、優れた電極性能を発揮できる。 Since the conductive porous sheet of [4] of the present invention is excellent in flexibility, mechanical strength, and conductivity, it can exhibit excellent electrode performance when used as a substrate for electrodes.
　本発明の［５］の固体高分子形燃料電池は、前記導電性多孔シートをガス拡散電極用基材として備えている。前記導電性多孔シートは導電性、機械的強度に優れ、更に、曲げても破断しにくい柔軟性に優れたものであり、固体高分子膜の膨潤と収縮によって引き伸ばされたとしても破損しにくいため、安定して発電性能を発揮できる。 [5] The polymer electrolyte fuel cell of [5] of the present invention includes the conductive porous sheet as a base material for a gas diffusion electrode. The conductive porous sheet is excellent in electrical conductivity and mechanical strength, and also has excellent flexibility that does not break even when bent, and is difficult to break even when stretched by swelling and shrinking of the solid polymer film. The power generation performance can be demonstrated stably.
　本発明の［６］の導電性多孔シートの製造方法は、前駆繊維同士の交差点を接合した後に、その交差点で接合した状態のまま炭化して、湾曲した炭素繊維としているため、柔軟性、機械的強度、及び導電性の優れる導電性多孔シートを製造することができる。 In the method for producing a conductive porous sheet of [6] of the present invention, after joining the intersections of the precursor fibers, carbonized while being joined at the intersections to form a curved carbon fiber, flexibility, machine It is possible to produce a conductive porous sheet having excellent mechanical strength and conductivity.
実施例１の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Example 1 (2000 times) 実施例２の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Example 2 (2000 times) 実施例３の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Example 3 (2000 times) 実施例４の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Example 4 (2000 times) 比較例１の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 1 (2000 times) 比較例２の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 2 (2000 times) 比較例３の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 3 (2000 times) 比較例４の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 4 (2000 times) 比較例５の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 5 (2000 times) 比較例６の導電性多孔シートの主面における電子顕微鏡写真（２０００倍）Electron micrograph on the main surface of the conductive porous sheet of Comparative Example 6 (2000 times) 炭素繊維の交差点で接合した状態を示す電子顕微鏡写真（５００００倍）Electron micrograph showing the state of joining at the intersection of carbon fibers (50,000 times) 炭素繊維の交差点が接合していない状態を示す電子顕微鏡写真（５００００倍）Electron micrograph showing the state where the intersection of carbon fibers is not joined (50,000 times)
　本発明の導電性多孔シートは炭素繊維を主体とし、炭素繊維同士の交差点で接合しているため、機械的強度が優れているとともに、導電性に優れている。また、三点曲げ試験において破断しない柔軟性を有するため、ハンドリング性に優れている。 Since the conductive porous sheet of the present invention is mainly composed of carbon fibers and joined at the intersections of the carbon fibers, it has excellent mechanical strength and conductivity. Moreover, since it has the softness | flexibility which does not fracture in a three-point bending test, it is excellent in handling property.
　本発明で用いる炭素繊維は、例えば、ＰＡＮ系炭素繊維であることができる。また、炭素繊維は導電性材料を含んでいることができる。このように導電性材料を含んでいると、より導電性、機械的強度が優れているため好適である。このような導電性材料は、例えば、フラーレン、カーボンナノチューブ、カーボンナノホーン、グラファイト、グラフェン、気相成長カーボンファイバー、カーボンブラック、金属（例えば、金、白金、チタン、ニッケル、アルミ、銀、亜鉛、鉄、銅、マンガン、コバルト、ステンレスなど）、前記金属の金属酸化物の群の中から選ばれる１種類、又は２種類以上から構成することができる。これらの中でも、カーボンナノチューブは導電性に優れ、しかも炭素繊維中において長さ方向に配向しやすく、導電性、機械的強度を高めることができるため好適である。更に、炭化する際における、カーボンナノチューブの存在する部分における収縮率と、カーボンナノチューブの存在しない部分における収縮率との間に差が生じ、湾曲した炭素繊維となりやすく、このような湾曲した炭素繊維は曲げた場合に湾曲した部分が伸びやすく、柔軟性に優れていることからも、カーボンナノチューブを含んでいるのが好ましい。なお、好適であるカーボンナノチューブは、単層カーボンナノチューブであっても、多層カーボンナノチューブであっても、コイル状となったものであっても良い。 The carbon fiber used in the present invention can be, for example, a PAN-based carbon fiber. The carbon fiber can contain a conductive material. It is preferable to include a conductive material in this manner because it is more excellent in conductivity and mechanical strength. Such conductive materials include, for example, fullerene, carbon nanotube, carbon nanohorn, graphite, graphene, vapor grown carbon fiber, carbon black, metal (for example, gold, platinum, titanium, nickel, aluminum, silver, zinc, iron , Copper, manganese, cobalt, stainless steel, etc.), one type selected from the group of metal oxides of the metal, or two or more types. Among these, carbon nanotubes are preferable because they are excellent in electrical conductivity, are easily oriented in the length direction in carbon fibers, and can increase electrical conductivity and mechanical strength. Further, when carbonizing, there is a difference between the shrinkage rate in the portion where the carbon nanotubes are present and the shrinkage rate in the portion where the carbon nanotubes are not present, and the curved carbon fibers tend to be curved. When bent, the curved portion is easy to stretch and is excellent in flexibility, so that it preferably contains carbon nanotubes. A suitable carbon nanotube may be a single-walled carbon nanotube, a multi-walled carbon nanotube, or a coiled one.
　この好適である導電性材料の大きさは特に限定するものではないが、導電性材料が粒子形状の場合、炭素繊維を形成しやすいように、平均粒径は５ｎｍ～５０μｍであるのが好ましく、２０ｎｍ～２５μｍであるのがより好ましく、３０ｎｍ～１０μｍであるのが更に好ましい。なお、前記の各下限と各上限は、所望により、任意に組み合わせることができる。この「平均粒径」は、基本的に、動的光散乱法による粒度分布計から求めた粒子の数平均粒子径を表すが、例えば、カーボンブラックなどのアグリゲートもしくはストラクチャーと呼ばれる状態を形成した粒子などの、上記動的光散乱法による測定が難しい場合には、粒子の電子顕微鏡写真を撮影し、電子顕微鏡写真に写っている５０個の粒子の直径の算術平均値を平均粒径とする。この場合、粒子の形状が写真上、非円形である場合には、写真上における、粒子の面積と同じ面積を有する円の直径を、粒子の直径とみなす。 The size of the suitable conductive material is not particularly limited, but when the conductive material is in the form of particles, the average particle size is preferably 5 nm to 50 μm so that carbon fibers can be easily formed. The thickness is more preferably 20 nm to 25 μm, and further preferably 30 nm to 10 μm. In addition, each said lower limit and each upper limit can be arbitrarily combined as desired. This “average particle size” basically represents the number average particle size of the particles obtained from a particle size distribution meter by the dynamic light scattering method. For example, a state called an aggregate or structure such as carbon black was formed. When measurement by the dynamic light scattering method is difficult, such as particles, take an electron micrograph of the particles and use the arithmetic average value of the diameters of 50 particles in the electron micrograph as the average 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.
　また、導電性材料が繊維形状をしている場合、繊維径は１０ｎｍ～５０００ｎｍであるのが好ましく、１０ｎｍ～１０００ｎｍであるのがより好ましく、１０ｎｍ～５００ｎｍであるのが更に好ましく、１０ｎｍ～２５０ｎｍであるのが更に好ましい。なお、前記の各下限と各上限は、所望により、任意に組み合わせることができる。なお、繊維長は炭素繊維中で分散しやすいように、アスペクト比が１０００以下となる繊維長であるのが好ましく、５００以下となる繊維長であるのがより好ましい。 When the conductive material has a fiber shape, the fiber diameter is preferably 10 nm to 5000 nm, more preferably 10 nm to 1000 nm, still more preferably 10 nm to 500 nm, and more preferably 10 nm to 250 nm. More preferably. In addition, each said lower limit and each upper limit can be arbitrarily combined as desired. The fiber length is preferably a fiber length having an aspect ratio of 1000 or less, and more preferably a fiber length of 500 or less so that the fiber length can be easily dispersed in the carbon fiber.
　このように炭素繊維が導電性材料を含んでいる場合、導電性材料の量は特に限定するものではないが、導電性、機械的強度及び柔軟性に優れているように、炭素繊維中、１ｍａｓｓ％以上含まれているのが好ましく、５ｍａｓｓ％以上含まれているのがより好ましく、１０ｍａｓｓ％以上含まれているのが更に好ましい。一方で、柔軟性が低くなる傾向があるため、８０ｍａｓｓ％以下含まれているのが好ましく、５０ｍａｓｓ％以下含まれているのがより好ましく、４０ｍａｓｓ％以下含まれているのが更に好ましい。なお、前記の各下限と各上限は、所望により、任意に組み合わせることができる。 When the carbon fiber contains a conductive material as described above, the amount of the conductive material is not particularly limited, but the carbon fiber has 1 mass in order to be excellent in conductivity, mechanical strength and flexibility. % Is preferably contained, more preferably 5 mass% or more, and even more preferably 10 mass% or more. On the other hand, since flexibility tends to be low, it is preferably contained at 80 mass% or less, more preferably at 50 mass% or less, and even more preferably at 40 mass% or less. In addition, each said lower limit and each upper limit can be arbitrarily combined as desired.
　本発明の炭素繊維は導電性材料を含んでいるか、含んでいないかに関わらず、湾曲しているのが好ましい。炭素繊維が湾曲していると、炭素繊維同士が交差点で接合していたとしても、導電性多孔シートを曲げた場合に、炭素繊維の湾曲部が引き伸ばされるため柔軟性に優れており、また、炭素繊維の湾曲部が引き伸ばされるだけで炭素繊維同士が接合した交差点が破壊されにくいため、曲げた際に破断しにくいためである。 The carbon fiber of the present invention is preferably curved regardless of whether or not it contains a conductive material. When the carbon fiber is curved, even if the carbon fibers are joined at the intersection, when the conductive porous sheet is bent, the curved portion of the carbon fiber is stretched, and the flexibility is excellent. This is because the intersection where the carbon fibers are joined to each other is not easily broken simply by stretching the curved portion of the carbon fiber, so that it is difficult to break when bent.
　本発明の炭素繊維は繊維内部に空隙のない状態にあると、機械的強度及び導電性に優れているため好適である。この「繊維内部に空隙がない」とは、導電性多孔シートの厚さ方向における切断面において、輪郭が連続しており、横断面形状が明確な炭素繊維の横断面全体が１～３本納まる視野での炭素繊維の観察を１０箇所で実施し、空隙が観察されない炭素繊維の本数が７０％以上であることを意味する。なお、炭素繊維が前述のような導電性材料を含んでおり、導電性多孔シートを厚さ方向に切断した時に、導電性材料が脱落して形成されたことが明らかな空隙は、上記空隙に含まない。また、導電性材料自体が多孔で空隙を含んでいたとしても、導電性材料は不連続で、炭素繊維の機械的強度等へ与える影響が小さいため、炭素繊維が空隙を含む導電性材料を含んでいても、繊維内部に空隙がないとみなす。なお、炭素繊維は導電性多孔シートを主体として構成する炭素繊維が「繊維内部に空隙がない」のが好ましく、つまり、交差点で接合した炭素繊維が「繊維内部に空隙がない」のが好ましく、接合していない炭素繊維は、導電性多孔シートの機械的強度等へ与える影響が小さいため、繊維内部に空隙があっても、なくても良い。 When the carbon fiber of the present invention is free of voids inside the fiber, it is suitable because it is excellent in mechanical strength and conductivity. “There is no void inside the fiber” means that the entire cross section of the carbon fiber having a continuous contour and a clear cross sectional shape is accommodated in the cut surface in the thickness direction of the conductive porous sheet. The observation of the carbon fibers in the visual field is carried out at 10 locations, which means that the number of carbon fibers in which no voids are observed is 70% or more. In addition, the carbon fiber contains the conductive material as described above, and when the conductive porous sheet is cut in the thickness direction, the gap that is clearly formed by dropping the conductive material is the gap. Not included. Even if the conductive material itself is porous and contains voids, the conductive material is discontinuous and has little influence on the mechanical strength of the carbon fiber, so the carbon fiber contains a conductive material containing voids. However, it is considered that there are no voids inside the fiber. In addition, it is preferable that the carbon fiber composed mainly of the conductive porous sheet is “no void inside the fiber”, that is, the carbon fiber joined at the intersection is preferably “no void inside the fiber”, Since carbon fibers that are not bonded have little influence on the mechanical strength and the like of the conductive porous sheet, there may or may not be voids inside the fibers.
　本発明の炭素繊維の平均繊維径は特に限定するものではないが、５０μｍ以下であるのが好ましく、３０μｍ以下であるのがより好ましく、２０μｍ以下であるのが更に好ましい。平均繊維径が５０μｍを上回ると、導電性多孔シートにおける炭素繊維同士の接触点数が少なく、導電性多孔シートの機械的強度、導電性に劣る傾向があるためである。なお、炭素繊維の平均繊維径の下限は特に限定するものではないが、０．１μｍ以上であるのが現実的である。なお、前記の下限と各上限は、所望により、任意に組み合わせることができる。 The average fiber diameter of the carbon fiber of the present invention is not particularly limited, but is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. If the average fiber diameter exceeds 50 μm, the number of contact points between the carbon fibers in the conductive porous sheet is small, and the mechanical strength and conductivity of the conductive porous sheet tend to be inferior. The lower limit of the average fiber diameter of the carbon fiber is not particularly limited, but it is realistic that it is 0.1 μm or more. The lower limit and each upper limit can be arbitrarily combined as desired.
　本発明における「平均繊維径」は、炭素繊維の４０点における繊維径の算術平均値を意味し、「繊維径」は、炭素繊維を顕微鏡写真で観察した際の長さ方向に直交する幅である。 The “average fiber diameter” in the present invention means an arithmetic average value of fiber diameters at 40 points of the carbon fiber, and the “fiber diameter” is a width orthogonal to the length direction when the carbon fiber is observed with a micrograph. is there.
　なお、炭素繊維は導電性に優れているように、連続しているのが好ましい。このような連続した炭素繊維は、例えば、炭化可能な有機材料を含む紡糸液を用いて、静電紡糸法又はスパンボンド法により連続した前駆繊維を紡糸した後に、前記炭化可能な有機材料を炭化して製造することができる。 In addition, it is preferable that the carbon fiber is continuous so as to be excellent in conductivity. Such a continuous carbon fiber is obtained by, for example, spinning a continuous precursor fiber by a spinning solution containing a carbonizable organic material by an electrostatic spinning method or a spunbond method, and then carbonizing the carbonizable organic material. Can be manufactured.
　本発明の導電性多孔シートは炭素繊維を主体としているが、２種類以上の炭素繊維から構成することができる。例えば、導電性材料の有無、導電性材料の相違（種類、形状、大きさ、長さなど）、導電性材料の含有量の相違、炭素繊維内部の空隙の有無、平均繊維径、繊維長など、少なくとも１点で相違する２種類以上の炭素繊維から構成することができる。 The conductive porous sheet of the present invention is mainly composed of carbon fibers, but can be composed of two or more types of carbon fibers. For example, presence or absence of conductive material, difference in conductive material (type, shape, size, length, etc.), difference in content of conductive material, presence or absence of voids inside carbon fiber, average fiber diameter, fiber length, etc. , It can be composed of two or more types of carbon fibers that differ in at least one point.
　本発明の導電性多孔シートは上述のような炭素繊維を主体としているため、導電性に優れている。本発明における「主体」とは、導電性多孔シートの５０ｍａｓｓ％以上を炭素繊維が占めることを意味するが、炭素繊維の占める割合が高い程、導電性に優れているため、炭素繊維は導電性多孔シートの７０ｍａｓｓ％以上を占めているのが好ましく、９０ｍａｓｓ％以上を占めているのがより好ましく、１００ｍａｓｓ％炭素繊維からなるのが最も好ましい。 Since the conductive porous sheet of the present invention is mainly composed of the above-described carbon fiber, it has excellent conductivity. The “main body” in the present invention means that the carbon fiber occupies 50 mass% or more of the conductive porous sheet. The higher the ratio of the carbon fiber, the better the conductivity. It preferably occupies 70 mass% or more of the porous sheet, more preferably occupies 90 mass% or more, and most preferably consists of 100 mass% carbon fiber.
　なお、炭素繊維以外に導電性多孔シートを構成できる材料としては、例えば、フラーレン、カーボンナノチューブ、カーボンナノホーン、グラファイト、グラフェン、気相成長カーボンファイバー、カーボンブラック、金属や金属酸化物などの微粒子；レーヨン、ポリノジック、キュプラなどの再生繊維、アセテート繊維などの半合成繊維、ナイロン繊維、ビニロン繊維、フッ素繊維、ポリ塩化ビニル繊維、ポリエステル繊維、アクリル繊維、ポリエチレン繊維、ポリオレフィン繊維又はポリウレタン繊維などの合成繊維、ガラス繊維、セラミック繊維などの無機繊維、綿、麻などの植物繊維、羊毛、絹などの動物繊維；活性炭粉体（例えば、水蒸気賦活炭、アルカリ処理活性炭、酸処理活性炭など）、無機粒子（例えば、二酸化マンガン、酸化鉄、酸化銅、酸化ニッケル、酸化コバルト、酸化亜鉛、チタン含有酸化物、ゼオライト、触媒担持セラミックス、シリカなど）、イオン交換樹脂粉体、植物の種子などの非導電性材料；を挙げることができる。 In addition to carbon fibers, examples of materials that can form conductive porous sheets include fullerenes, carbon nanotubes, carbon nanohorns, graphite, graphene, vapor-grown carbon fibers, carbon black, fine particles such as metals and metal oxides; rayon , Recycled fibers such as polynosic and cupra, semi-synthetic fibers such as acetate fibers, nylon fibers, vinylon fibers, fluorine fibers, polyvinyl chloride fibers, polyester fibers, acrylic fibers, polyethylene fibers, polyolefin fibers or polyurethane fibers, Glass fibers, inorganic fibers such as ceramic fibers, plant fibers such as cotton and hemp, animal fibers such as wool and silk; activated carbon powder (for example, steam activated carbon, alkali-treated activated carbon, acid-treated activated carbon, etc.), inorganic particles (for example, , Manganese dioxide Non-conductive materials such as iron oxide, copper oxide, nickel oxide, cobalt oxide, zinc oxide, titanium-containing oxide, zeolite, catalyst-supporting ceramics, silica, etc.), ion-exchange resin powder, plant seeds; it can.
　本発明の導電性多孔シートは炭素繊維同士が交差点で接合しているため、機械的強度、導電性に優れている。なお、炭素繊維同士の接合は炭素繊維同士の密着性に優れ、導電性に優れているように、有機材料の炭化物によって接合しているのが好ましい。例えば、炭化可能な有機材料を２種類以上含む有機繊維を用い、この有機繊維同士を１種類以上の炭化可能な有機材料によって接合した後に炭化させることによって、炭素繊維同士が交差点で接合した導電性多孔シートとすることができる。 The conductive porous sheet of the present invention is excellent in mechanical strength and conductivity because carbon fibers are joined at an intersection. In addition, it is preferable that the carbon fibers are bonded to each other with a carbide of an organic material so that the carbon fibers are excellent in adhesion and the conductivity is excellent. For example, by using an organic fiber containing two or more types of carbonizable organic materials and bonding the organic fibers with one or more types of carbonizable organic materials, followed by carbonization, the carbon fibers are bonded at the intersection. It can be a perforated sheet.
　このような炭素繊維同士が交差点で接合した状態は、電子顕微鏡写真で確認することができる。例えば、図１１は導電性多孔シートの主面における電子顕微鏡写真（５００００倍）であるが、炭素繊維同士の交差点に水掻き状の膜を観察できることから、炭素繊維同士が接合していることを確認できる。一方で、図１２は導電性多孔シートの主面における電子顕微鏡写真（５００００倍）であるが、炭素繊維同士の交差点に水掻き状の膜を観察できないことから、炭素繊維同士が接合していないことを確認できる。 Such a state in which the carbon fibers are joined at the intersection can be confirmed by an electron micrograph. For example, FIG. 11 is an electron micrograph (50000 times) on the main surface of the conductive porous sheet, but it is confirmed that carbon fibers are bonded to each other because a water-like film can be observed at the intersection of carbon fibers. it can. On the other hand, FIG. 12 is an electron micrograph (50000 times) on the main surface of the conductive porous sheet, but the carbon fibers are not joined to each other because a water-fouling film cannot be observed at the intersection of the carbon fibers. Can be confirmed.
　本発明の導電性多孔シートは炭素繊維を主体としている限り、一層構造を有するものであっても、二層以上の多層構造を有するものであっても良いし、炭素繊維の含有比率が徐々に変化していても良い。例えば、繊維径の異なる炭素繊維からなる層を二層以上有する多層構造であっても良い。 As long as the conductive porous sheet of the present invention is mainly composed of carbon fibers, it may have a single-layer structure or a multilayer structure of two or more layers, and the content ratio of carbon fibers gradually increases. It may change. For example, a multilayer structure having two or more layers made of carbon fibers having different fiber diameters may be used.
　また、導電性多孔シートの主面において、炭素繊維の存在比率が異なっていても良い。例えば、導電性多孔シートの主面において、繊維径の細い炭素繊維を主体とする領域と繊維径の太い炭素繊維を主体とする領域とを有し、いずれかの領域が点状、直線状及び／又は曲線状（円状など）に有することができる。更に、導電性多孔シートの主面において、炭素繊維の存在比率が徐々に変化していても良い。 Further, the carbon fiber abundance ratio may be different on the main surface of the conductive porous sheet. For example, on the main surface of the conductive porous sheet, it has a region mainly composed of carbon fibers having a small fiber diameter and a region mainly composed of carbon fibers having a large fiber diameter, and either region is dotted, linear, and / Or can have a curved shape (such as a circle). Furthermore, the abundance ratio of the carbon fibers may gradually change on the main surface of the conductive porous sheet.
　本発明の導電性多孔シートの形態は特に限定するものではないが、例えば、繊維がランダムに配向した不織布形態、繊維が規則正しく配向した織物又は編物形態であることができる。特に、不織布形態であると、炭素繊維同士の交差点が多く、導電性に優れ、また空隙が微細で、高空隙率であるため好適であり、不織布形態のみからなるのが好ましい。 The form of the conductive porous sheet of the present invention is not particularly limited, and may be, for example, a nonwoven fabric form in which fibers are randomly oriented, or a woven or knitted form in which fibers are regularly oriented. In particular, the non-woven fabric is suitable because it has many intersections between carbon fibers, is excellent in electrical conductivity, has fine voids, and has a high porosity, and preferably comprises only a non-woven fabric.
　本発明の導電性多孔シートは上述のような炭素繊維を主体としているが、三点曲げ試験において破断しない柔軟性を有する、ハンドリング性に優れるものである。本発明における「三点曲げ試験」は、荷重－変位測定ユニット（株式会社イマダ製、ＦＳＡ－１ＫＥ－５Ｎ＋ＧＡ－１０Ｎ）を用い、次の手順により行なう。
（１）導電性多孔シートを裁断し、５０ｍｍ（導電性多孔シートの製造時の流れ方向）×１０ｍｍ［幅方向（流れ方向と直交する方向）］の試験片（流れ方向試験片）を５枚と、５０ｍｍ［幅方向］×１０ｍｍ（導電性多孔シートの製造時の流れ方向）の試験片（幅方向試験片）を５枚採取する。
（２）先端が２±０．２ｍｍの丸みを有する金属製棒状支点の間の距離が１６ｍｍとなるように、支点を配置する。
（３）支点間を跨ぐように、試験片を配置する。
（４）試験片の支点間の中央部（一方の支点から８ｍｍの地点）に対して、先端が５±０．１ｍｍの丸みを有する棒状の金属製加圧くさびを、速度１ｍｍ／ｍｉｎ．で、試験片の上方から前記支点間へ、試験片の上面又は下面の初期位置と折れた位置との距離が４ｍｍとなるまで押し込む。この時、押し込み長さと応力とを逐次測定し、応力が急激に降下した場合、この時の押し込み長さを曲げたわみ量（ｍｍ）とする。なお、４ｍｍとなるまで押し込んでも、応力が急激に降下しなかった場合、曲げたわみ量は４ｍｍ超と判断する。（５）前記曲げたわみ量の測定を、流れ方向試験片５枚と幅方向試験片５枚のそれぞれについて行い、流れ方向試験片５枚のうち、最大値を示す曲げたわみ量と最小値を示す曲げたわみ量を除いた３枚の流れ方向試験片３枚の算術平均値と、幅方向試験片５枚のうち、最大値を示す曲げたわみ量と最小値を示す曲げたわみ量を除いた３枚の幅方向試験片３枚の算術平均値をそれぞれ算出する。その結果、曲げたわみ量の算術平均値のより大きい値を「曲げたわみ量」として採用する。
（６）前記曲げたわみ量が４ｍｍ超である場合、その試験片の導電性多孔シートを「破断しない」と判断する。 The conductive porous sheet of the present invention is mainly composed of the above-described carbon fiber, but has flexibility that does not break in the three-point bending test and has excellent handling properties. The “three-point bending test” in the present invention is performed by the following procedure using a load-displacement measuring unit (manufactured by Imada Co., Ltd., FSA-1KE-5N + GA-10N).
(1) The conductive porous sheet is cut and five test pieces (flow direction test pieces) of 50 mm (flow direction at the time of manufacturing the conductive porous sheet) × 10 mm [width direction (direction perpendicular to the flow direction)] are obtained. Then, five test pieces (width direction test pieces) of 50 mm [width direction] × 10 mm (flow direction during production of the conductive porous sheet) are collected.
(2) The fulcrum is arranged so that the distance between the metal rod-shaped fulcrums having a rounded end of 2 ± 0.2 mm is 16 mm.
(3) A test piece is arranged so as to straddle between fulcrums.
(4) A bar-shaped metal pressure wedge having a roundness with a tip of 5 ± 0.1 mm is set at a speed of 1 mm / min. Then, the test piece is pushed from above the test piece to the fulcrum until the distance between the initial position of the upper surface or the lower surface of the test piece and the broken position becomes 4 mm. At this time, the indentation length and the stress are measured sequentially, and when the stress drops abruptly, the indentation length at this time is defined as the bending deflection (mm). In addition, even if it pushes in until it becomes 4 mm, when stress does not fall rapidly, it is judged that the amount of bending deflection exceeds 4 mm. (5) The bending deflection amount is measured for each of the five flow direction test pieces and the five width direction test pieces, and among the five flow direction test pieces, the bending deflection amount indicating the maximum value and the minimum value are indicated. Three of the three flow direction test pieces excluding the bending deflection, and three of the five width direction test pieces, excluding the bending deflection showing the maximum value and the bending deflection showing the minimum value. The arithmetic average value of three test pieces in the width direction is calculated. As a result, a value larger than the arithmetic average value of the bending deflection is adopted as the “bending deflection”.
(6) When the amount of bending deflection is more than 4 mm, it is determined that the conductive porous sheet of the test piece is “not broken”.
　本発明の導電性多孔シートの目付は特に限定するものではないが、機械的強度、導電性に優れているように、目付は０．５～５００ｇ／ｍ２であるのが好ましく、１～４００ｇ／ｍ２であるのがより好ましく、５～３００ｇ／ｍ２であるのが更に好ましく、５～２００ｇ／ｍ２であるのが更に好ましい。また、厚さも特に限定するものではないが、１～２０００μｍであるのが好ましく、３～１０００μｍであるのがより好ましく、５～５００μｍであるのが更に好ましく、１０～３００μｍが更に好ましい。なお、前記目付と厚さにおける、各下限と各上限は、所望により、任意に組み合わせることができる。本発明における「目付」は、導電性多孔シートを１０ｃｍ角に切断して得た試料の質量を測定し、１ｍ２の大きさの質量に換算した値をいい、「厚さ」は、シックネスゲージ（（株）ミツトヨ製：コードＮｏ．５４７－４０１：測定力３．５Ｎ以下）を用いて測定した値をいう。 The basis weight of the conductive porous sheet of the present invention is not particularly limited, but the basis weight is preferably 0.5 to 500 g / m 2 so as to be excellent in mechanical strength and conductivity. / M 2 is more preferred, 5 to 300 g / m 2 is still more preferred, and 5 to 200 g / m 2 is even more preferred. The thickness is not particularly limited, but is preferably 1 to 2000 μm, more preferably 3 to 1000 μm, still more preferably 5 to 500 μm, and further preferably 10 to 300 μm. In addition, each lower limit and each upper limit in the said fabric weight and thickness can be combined arbitrarily as desired. The “weight per unit” in the present invention is a value obtained by measuring the mass of a sample obtained by cutting a conductive porous sheet into a 10 cm square and converting it to a mass of 1 m 2 , and “thickness” is a thickness gauge. This is a value measured using Mitutoyo Corporation (code No. 547-401: measuring force 3.5 N or less).
　本発明の導電性多孔シートは導電性に優れるものであるが、その程度は電気抵抗が２０ｍΩ・ｃｍ２以下であるのが好ましく、１５ｍΩ・ｃｍ２以下であるのがより好ましく、１０ｍΩ・ｃｍ２以下であるのが更に好ましく、８ｍΩ・ｃｍ２以下であるのが更に好ましく、６ｍΩ・ｃｍ２以下であるのが更に好ましい。この「電気抵抗」は、５ｃｍ角に切断した導電性多孔シート（２５ｃｍ２）を、両面側から金メッキを施した金属プレートで挟み、金属プレートの積層方向に、２ＭＰａで加圧下、１Ａの電流（Ｉ）を印加した状態で、電圧（Ｖ）を計測する。続いて、抵抗（Ｒ＝Ｖ／Ｉ）を算出し、更に、導電性多孔シートの面積（２５ｃｍ２）を乗じることによって得られる値である。 Conductive porous sheet of the invention are excellent in electrical conductivity, the degree is preferably an electric resistance of 20 m [Omega · cm 2 or less, more preferably at 15mΩ · cm 2 or less, 10 m [Omega · cm 2 less more preferably in the range, further preferably at 8mΩ · cm 2 or less, and even more preferably 6mΩ · cm 2 or less. This “electric resistance” is obtained by sandwiching a conductive porous sheet (25 cm 2 ) cut into 5 cm square with a metal plate plated with gold from both sides and applying a current of 1 A under a pressure of 2 MPa in the metal plate lamination direction. 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).
　また、本発明の導電性多孔シートは機械的強度の優れるものであるが、その程度は破断強度が０．３０ＭＰａ以上であるのが好ましく、０．４０ＭＰａ以上であるのがより好ましく、０．５０ＭＰａ以上であるのが更に好ましく、０．６０ＭＰａ以上であるのが更に好ましい。この破断強度は破断荷重を導電性多孔シートの断面積で除した商であり、破断荷重は次の条件で測定した値であり、断面積は測定時の導電性多孔シート（試験片）の幅と厚さの積から得られる値である。なお、流れ方向試験片１０枚と幅方向試験片１０枚について破断荷重の測定を行ない、２０枚の試験片の算術平均値を破断荷重とする。 In addition, the conductive porous sheet of the present invention has excellent mechanical strength, but the degree of breakage is preferably 0.30 MPa or more, more preferably 0.40 MPa or more, and 0.50 MPa. More preferably, it is more preferably 0.60 MPa or more. This breaking strength is a quotient obtained by dividing the breaking load by the cross-sectional area of the conductive porous sheet. The breaking load is a value measured under the following conditions. The cross-sectional area is the width of the conductive porous sheet (test piece) at the time of measurement. And the value obtained from the product of thickness. The breaking load is measured for 10 flow direction test pieces and 10 width direction test pieces, and the arithmetic average value of 20 test pieces is taken as the breaking load.
　試験片：５０ｍｍ（試験片の製造時の流れ方向）×５ｍｍ［幅方向（流れ方向と直交する方向）］の試験片（流れ方向試験片）１０枚、５０ｍｍ［幅方向］×５ｍｍ（試験片の製造時の流れ方向）の試験片（幅方向試験片）１０枚
　製品名：小型引張試験機（型式：ＴＳＭ－４１－ｃｒｅ、サーチ株式会社製）
　チャック間間隔：２０ｍｍ
　引張速度：２０ｍｍ／ｍｉｎ． Test piece: 50 test pieces (flow direction test piece) of 50 mm (flow direction during manufacture of the test piece) × 5 mm [width direction (direction orthogonal to the flow direction)], 50 mm [width direction] × 5 mm (test piece) 10 test pieces (width direction test piece) in the manufacturing direction) Product name: Small tensile tester (model: TSM-41-cre, manufactured by Search Inc.)
Spacing between chucks: 20 mm
Tensile speed: 20 mm / min.
　本発明の導電性多孔シートは炭素繊維を主体としているが、比見掛ヤング率が１００［ＭＰａ／（ｇ／ｃｍ３）］以上であるのが好ましい。この比見掛ヤング率が高いということは剛性が高いことを意味し、剛性の高い導電性多孔シートであることによって、寸法安定性に優れており、また、単独で取扱いやすく、ロール形状に巻き取って保管又は輸送できるという利点がある。例えば、このような比見掛ヤング率の高い導電性多孔シートを固体高分子形燃料電池の電極用基材として使用すると、固体高分子膜の膨潤及び収縮を抑制することができるため、固体高分子膜の膨潤及び収縮による亀裂を防止することができる。 The conductive porous sheet of the present invention is mainly composed of carbon fibers, but the specific apparent Young's modulus is preferably 100 [MPa / (g / cm 3 )] or more. The high specific Young's modulus means that the rigidity is high, and because it is a highly conductive conductive porous sheet, it has excellent dimensional stability, is easy to handle by itself, and is wound into a roll shape. There is an advantage that it can be stored and transported. For example, when such a conductive porous sheet having a high apparent Young's modulus is used as a base material for an electrode of a polymer electrolyte fuel cell, swelling and shrinkage of the polymer electrolyte membrane can be suppressed. Cracks due to swelling and shrinkage of the molecular film can be prevented.
　この比見掛ヤング率は後述の測定方法から理解できるように、導電性多孔シートの剛性の指標である見掛ヤング率を、導電性多孔シートの見掛密度で除して得られる値である。つまり、同じ見掛ヤング率であっても、見掛密度が高い場合と低い場合とでは、見掛密度が低い方が炭素繊維の量が少ないにも関わらず、同じ見掛ヤング率であるということは、それだけ１本１本の炭素繊維の剛性が高いことを意味しているため、導電性多孔シートの見掛ヤング率を見掛密度で除した値である比見掛ヤング率で表現している。この比見掛ヤング率が高い程、個々の炭素繊維の剛性が高いため、２００［ＭＰａ／（ｇ／ｃｍ３）］以上であるのがより好ましく、３００［ＭＰａ／（ｇ／ｃｍ３）］以上であるのが更に好ましく、４００［ＭＰａ／（ｇ／ｃｍ３）］以上であるのが更に好ましく、５００［ＭＰａ／（ｇ／ｃｍ３）］以上であるのが更に好ましく、５５０［ＭＰａ／（ｇ／ｃｍ３）］以上であるのが更に好ましく、６００［ＭＰａ／（ｇ／ｃｍ３）］以上であるのが更に好ましい。一方で、比見掛ヤング率が高すぎると、炭素繊維の剛性が高すぎて、固体高分子膜を損傷するなど、悪影響を及ぼす場合があるため、２０００［ＭＰａ／（ｇ／ｃｍ３）］以下であるのが好ましい。なお、前記の各下限と上限は、所望により、任意に組み合わせることができる。 As can be understood from the measurement method described later, this specific apparent Young's modulus is a value obtained by dividing the apparent Young's modulus, which is an index of rigidity of the conductive porous sheet, by the apparent density of the conductive porous sheet. . In other words, even when the apparent Young's modulus is the same, when the apparent density is high and low, the lower apparent density is the same apparent Young's modulus even though the amount of carbon fiber is small. This means that the rigidity of each carbon fiber is so high that it is expressed by the specific apparent Young's modulus, which is the apparent Young's modulus of the conductive porous sheet divided by the apparent density. ing. The higher the specific Young's modulus is, the higher the rigidity of each carbon fiber is. Therefore, it is more preferably 200 [MPa / (g / cm 3 )] or more, and 300 [MPa / (g / cm 3 )]. More preferably, it is more preferably 400 [MPa / (g / cm 3 )] or more, still more preferably 500 [MPa / (g / cm 3 )] or more, and 550 [MPa / (G / cm 3 )] or more is more preferable, and 600 [MPa / (g / cm 3 )] or more is more preferable. On the other hand, if the specific apparent Young's modulus is too high, the rigidity of the carbon fiber is too high, and the solid polymer film may be adversely affected. Therefore, 2000 [MPa / (g / cm 3 )] It is preferable that: In addition, each said lower limit and upper limit can be arbitrarily combined as desired.
　この「比見掛ヤング率」は、次の手順により得られる値である。
（１）評価対象の導電性多孔シートの目付（ｇ／ｃｍ２）を厚さ（ｃｍ）で除して、見掛密度（ｇ／ｃｍ３）を算出する。
（２）導電性多孔シートを、導電性多孔シートの製造時の流れ方向に５０ｍｍで、幅方向（流れ方向と直交する方向）］に５ｍｍの長方形状に裁断したたて方向試験片１０枚、及び幅方向に５０ｍｍで、流れ方向に５ｍｍの長方形状に裁断したよこ方向試験片１０枚を、それぞれ採取する。
（３）前記各試験片の引張りせん断試験を、小型引張試験機（サーチ社製、ＴＳＭ－４１－ｃｒｅ）を用い、チャック間距離２０ｍｍ、引張り速度２０ｍｍ／ｍｉｎ．の条件で実施し、各々荷重－伸び曲線を描く。
（４）前記各々の荷重－伸び曲線における原点近くで伸長変化に対する荷重変化の最大点（接線角の最大点）における荷重（Ｎ）を、引張りせん断試験をする前の試験片の断面積［厚さ（Ｔ）×５］（単位：ｍｍ２）で除して、引張り応力（ＭＰａ）を算出する。
（５）前記引張り応力を、最大点におけるひずみ（無次元）［試験片の伸び長さ（ｍｍ）÷初期試験片長さ（ｍｍ）］で除することで、見掛けヤング率を各々求める。
（６）２０枚の試験片の見掛けヤング率の算術平均値を算出し、「平均見掛けヤング率」とする。
（７）前記平均見掛けヤング率を前記見掛密度で除して、「比見掛ヤング率」を算出する。 This “specific apparent Young's modulus” is a value obtained by the following procedure.
(1) The apparent density (g / cm 3 ) is calculated by dividing the basis weight (g / cm 2 ) of the conductive porous sheet to be evaluated by the thickness (cm).
(2) 10 directional test specimens obtained by cutting the conductive porous sheet into a rectangular shape of 50 mm in the flow direction during the production of the conductive porous sheet and 5 mm in the width direction (direction perpendicular to the flow direction); And 10 horizontal direction test pieces cut into a rectangular shape of 50 mm in the width direction and 5 mm in the flow direction are respectively collected.
(3) The tensile shear test of each test piece was performed using a small tensile tester (manufactured by Search, TSM-41-cre), a chuck-to-chuck distance of 20 mm, and a pulling speed of 20 mm / min. The test is carried out under the conditions described above, and each load-elongation curve is drawn.
(4) The load (N) at the maximum load change point (maximum point of tangential angle) with respect to the extension change near the origin in each load-elongation curve is the cross-sectional area [thickness of the test piece before the tensile shear test] (T) × 5] (unit: mm 2 ) to calculate the tensile stress (MPa).
(5) The apparent Young's modulus is obtained by dividing the tensile stress by the strain at the maximum point (dimensionalless) [elongation length of test piece (mm) ÷ initial test piece length (mm)].
(6) The arithmetic average value of the apparent Young's modulus of the 20 test pieces is calculated and set as the “average apparent Young's modulus”.
(7) The “average apparent Young's modulus” is calculated by dividing the average apparent Young's modulus by the apparent density.
　また、本発明の導電性多孔シートを固体高分子形燃料電池のガス拡散電極用基材として使用し、ガス拡散層を形成した場合のように、表面平滑性が低いと、導電性多孔シートと当接する他の材料（固体高分子形燃料電池の場合には、固体高分子膜）に導電性多孔シートが突き刺さり、他の材料を損傷させる可能性があり、また、他の材料（固体高分子形燃料電池の場合には、固体高分子膜及び／又はセパレータ）と導電性多孔シートとの間に隙間が生じて密着性が悪くなり、十分な性能（固体高分子形燃料電池の場合には、発電性能）を発揮しにくい傾向がある。そのため、他の材料を損傷しにくいように、また、十分な性能を発揮しやすいように、導電性多孔シートの表面は平滑であるのが好ましい。具体的には、導電性多孔シートの主面における「平均算術平均表面粗さ」は０．０１μｍ～２０μｍであるのが好ましく、０．１μｍ～１０μｍであるのがより好ましく、０．１μｍ～５μｍであるのが更に好ましく、０．１～４μｍであるのが更に好ましい。なお、前記の各下限と各上限は、所望により、任意に組み合わせることができる。この「平均算術平均表面粗さ」は、導電性多孔シートを５ｃｍ角に裁断して試料を用意し、ＩＳＯ２５１７８に準拠した粗さ（３次元）パラメーターを測定可能なレーザー顕微鏡（オリンパス製、ＯＬＳ４１００）を用いて、試料における５箇所の評価領域（２６０μｍ×２６０μｍ）について、それぞれ算術平均表面粗さ（Ｓａ）を測定した後、各算術平均表面粗さ（Ｓａ）の値を更に平均した値を意味する。 In addition, when the conductive porous sheet of the present invention is used as a base material for a gas diffusion electrode of a polymer electrolyte fuel cell and a gas diffusion layer is formed, when the surface smoothness is low, the conductive porous sheet and The conductive porous sheet may pierce other materials that abut (in the case of polymer electrolyte fuel cells, the solid polymer membrane), possibly damaging other materials, and other materials (solid polymer membranes) In the case of a fuel cell, a gap is formed between the solid polymer membrane and / or the separator and the conductive porous sheet, resulting in poor adhesion and sufficient performance (in the case of a polymer electrolyte fuel cell). , Power generation performance) tends to be difficult to demonstrate. Therefore, it is preferable that the surface of the conductive porous sheet is smooth so that other materials are not easily damaged and sufficient performance is easily exhibited. Specifically, the “average arithmetic average surface roughness” on the main surface of the conductive porous sheet is preferably 0.01 μm to 20 μm, more preferably 0.1 μm to 10 μm, and more preferably 0.1 μm to 5 μm. It is more preferable that the thickness is 0.1 to 4 μm. In addition, each said lower limit and each upper limit can be arbitrarily combined as desired. This “average arithmetic average surface roughness” is a laser microscope (OLS4100, manufactured by Olympus) that can prepare a sample by cutting a conductive porous sheet into 5 cm square and measure roughness (three-dimensional) parameters in accordance with ISO25178. Is used to mean the value obtained by further averaging the values of each arithmetic average surface roughness (Sa) after measuring the arithmetic average surface roughness (Sa) for each of five evaluation regions (260 μm × 260 μm) in the sample. To do.
　更に、本発明の導電性多孔シートは空隙を有効に活用できるように、空隙率が５０％以上であるのが好ましい。このような空隙率の導電性多孔シートを、例えば、固体高分子形燃料電池の電極基材として使用すると、排水性およびガス拡散性に優れ、発電性能の高い燃料電池を作製することができる。空隙率が高い方が、空隙がより多く、空隙をより有効に活用できるため、空隙率は６０％以上であるのがより好ましく、７０％以上であるのが更に好ましく、８０％以上であるのが更に好ましく、９０％以上であるのが更に好ましい。一方で、９９％を超えると、導電性多孔シートの形態安定性が極端に低下する傾向があるため、９９％以下であるのが好ましい。なお、前記の各下限と上限は、所望により、任意に組み合わせることができる。 Furthermore, the conductive porous sheet of the present invention preferably has a porosity of 50% or more so that the voids can be effectively utilized. When such a porous porous conductive sheet is used as, for example, an electrode substrate of a polymer electrolyte fuel cell, a fuel cell having excellent drainage and gas diffusibility and high power generation performance can be produced. The higher the void ratio, the more voids and the more effective utilization of the voids. Therefore, the void ratio is more preferably 60% or more, further preferably 70% or more, and 80% or more. Is more preferably 90% or more. On the other hand, if it exceeds 99%, the shape stability of the conductive porous sheet tends to be extremely lowered, and therefore it is preferably 99% or less. In addition, each said lower limit and upper limit can be arbitrarily combined as desired.
　この空隙率Ｐ（単位：％）は、次の式から得られる値をいう。
　Ｐ＝１００－（Ｆｒ１＋Ｆｒ２＋・・＋Ｆｒｎ）
　ここで、Ｆｒｎは導電性多孔シートを構成する成分ｎの充填率（単位：％）を示し、次の式から得られる値をいう。
　Ｆｒｎ＝［Ｍ×Ｐｒｎ／（Ｔ×ＳＧｎ）］×１００
　ここで、Ｍは導電性多孔シートの単位あたりの質量（単位：ｇ／ｃｍ２）、Ｔは導電性多孔シートの厚さ（ｃｍ）、Ｐｒｎは導電性多孔シートにおける成分ｎ（例えば、炭素繊維）の存在質量比率、ＳＧｎは成分ｎの比重（単位：ｇ／ｃｍ３）をそれぞれ意味する。 The porosity P (unit:%) is a value obtained from the following formula.
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 mass per unit (unit: g / cm 2 ) of the conductive porous sheet, T is the thickness (cm) of the conductive porous sheet, and Prn is the component n (for example, carbon fiber) in the conductive porous sheet. ) Existing mass ratio, SGn means the specific gravity (unit: g / cm 3 ) of component n.
　本発明の導電性多孔シートは機械的強度、導電性に優れているばかりでなく、柔軟でハンドリング性に優れるものであるため、電極用基材として好適に用いることができる。例えば、リチウムイオン二次電池又は電気二重層キャパシタの電極として用いた場合、容量の大きい二次電池又はキャパシタを作製できる。また、固体高分子形燃料電池のガス拡散電極用基材として用いた場合、優れた発電性能を発揮できる固体高分子形燃料電池を作製できる。 The conductive porous sheet of the present invention is not only excellent in mechanical strength and conductivity, but is flexible and excellent in handling properties, and therefore can be suitably used as an electrode substrate. For example, when used as an electrode of a lithium ion secondary battery or an electric double layer capacitor, a secondary battery or capacitor having a large capacity can be produced. Further, when used as a base material for a gas diffusion electrode of a polymer electrolyte fuel cell, a polymer electrolyte fuel cell capable of exhibiting excellent power generation performance can be produced.
　このように固体高分子形燃料電池のガス拡散電極用基材として、本発明の導電性多孔シートを備えている場合、本発明の導電性多孔シートは多孔性であるため、炭素繊維間の空隙に何も充填されていなければ、ガス拡散電極用基材（導電性多孔シート）の厚さ方向及び面方向への排水性に優れているとともに、供給したガスの拡散性に優れている。 As described above, when the conductive porous sheet of the present invention is provided as the base material for the gas diffusion electrode of the solid polymer fuel cell, the conductive porous sheet of the present invention is porous. If nothing is filled, the drainage property in the thickness direction and the surface direction of the gas diffusion electrode substrate (conductive porous sheet) is excellent, and the diffusibility of the supplied gas is excellent.
　なお、ガス拡散電極用基材（導電性多孔シート）の炭素繊維間の空隙に、フッ素系樹脂及び／又はカーボンを含んでいると、前者のフッ素系樹脂を含有していることによって、液水が押し出されやすいため、排水性に優れ、後者のカーボンを含有していることによって、導電性に優れている。 In addition, when the fluorine resin and / or carbon is contained in the space | gap between the carbon fibers of the base material for gas diffusion electrodes (conductive porous sheet), liquid water is contained by including the former fluorine resin. Since it is easy to be extruded, it is excellent in drainage, and by containing the latter carbon, it is excellent in electroconductivity.
　このフッ素系樹脂としては、例えば、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリクロロトリフルオロエチレン（ＰＣＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリフッ化ビニル（ＰＶＦ）、ペルフルオロアルコキシフッ素樹脂（ＰＦＡ）、四フッ化エチレン・六フッ化プロピレン共重合体（ＦＥＰ）、エチレン・四フッ化エチレン共重合体（ＥＴＦＥ）、エチレン・クロロトリフルオロエチレン共重合体（ＥＣＴＦＥ）、フッ化ビニリデン・テトラフルオロエチレン・ヘキサフルオロプロピレン共重合体、及び前記樹脂を構成する各種モノマーの共重合体、などを挙げることができる。 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.
　また、カーボンとしては、例えば、炭素繊維、フラーレン、カーボンナノチューブ、カーボンナノホーン、グラファイト、グラフェン、気相成長カーボンファイバー、カーボンブラックなどを挙げることができる。 Further, examples of carbon include carbon fiber, fullerene, carbon nanotube, carbon nanohorn, graphite, graphene, vapor growth carbon fiber, and carbon black.
　本発明の固体高分子形燃料電池は、前述の導電性多孔シートをガス拡散電極用基材として備えていること以外は、従来の固体高分子形燃料電池と全く同様であることができる。つまり、上述のようなガス拡散電極用基材（導電性多孔シート）の表面に触媒が担持されたガス拡散電極と、固体高分子膜との接合体を、１対のバイポーラプレートで挟んだセル単位を複数積層した構造からなる。 The polymer electrolyte fuel cell of the present invention can be exactly the same as a conventional polymer electrolyte fuel cell except that the above-mentioned conductive porous sheet is provided as a base material for a gas diffusion electrode. That is, a cell in which a bonded body of a gas diffusion electrode having a catalyst supported on the surface of a gas diffusion electrode substrate (conductive porous sheet) as described above and a solid polymer film is sandwiched between a pair of bipolar plates. It has a structure in which a plurality of units are stacked.
　このような本発明の導電性多孔シートは、例えば、第１炭化可能有機材料と、第１炭化可能有機材料とは異なる有機材料からなる第２炭化可能有機材料とを含む前駆繊維を形成する工程、前記前駆繊維の交差点を第１炭化可能有機材料又は第２炭化可能有機材料で接合して、前駆繊維を主体とする前駆繊維シートを形成する工程、前記前駆繊維シートを構成する前駆繊維を、その交差点で接合した状態のまま炭化して、湾曲した炭素繊維とする工程、により、三点曲げ試験で破断しない導電性多孔シートを製造することができる。この製造方法によると、前駆繊維同士の交差点を接合した後に、その交差点で接合した状態のまま炭化して、湾曲した炭素繊維としているため、柔軟性、機械的強度、及び導電性の優れる導電性多孔シートを製造することができる。 Such a conductive porous sheet of the present invention includes, for example, a step of forming a precursor fiber including a first carbonizable organic material and a second carbonizable organic material made of an organic material different from the first carbonizable organic material. A step of joining the intersections of the precursor fibers with the first carbonizable organic material or the second carbonizable organic material to form a precursor fiber sheet mainly composed of the precursor fibers, the precursor fibers constituting the precursor fiber sheet, A conductive porous sheet that does not break in the three-point bending test can be manufactured by the process of carbonizing the carbon fiber while it is bonded at the intersection to form a curved carbon fiber. According to this manufacturing method, after joining the intersections of the precursor fibers, carbonized while being joined at the intersections to form a curved carbon fiber, the conductivity, excellent in flexibility, mechanical strength, and conductivity A perforated sheet can be produced.
　より具体的には、まず、第１炭化可能有機材料と、第１炭化可能有機材料とは異なる有機材料からなる第２炭化可能有機材料とを用意する。この第１炭化可能有機材料、第２炭化可能有機材料としては特に限定するものではないが、例えば、フェノール樹脂、尿素樹脂、メラミン樹脂、不飽和ポリエステル樹脂、エポキシ樹脂、キシレン樹脂、ウレタン樹脂、シリコーン樹脂、熱硬化性ポリイミド樹脂、熱硬化性ポリイミド樹脂、熱硬化性ポリアミド樹脂などの熱硬化性樹脂；ポリスチレン樹脂、ポリエステル樹脂、ポリオレフィン樹脂、ポリイミド樹脂、ポリアミド樹脂、ポリアミドイミド樹脂、ポリ酢酸ビニル樹脂、塩化ビニル樹脂、フッ素樹脂、ポリアクリロニトリル樹脂、アクリル樹脂、ポリエーテル系樹脂、ポリビニルアルコール、ポリビニルピロリドン、ピッチ、ポリアミノ酸樹脂、ポリベンゾイミダゾール樹脂などの熱可塑性樹脂；セルロース（多糖類）、タール；又はこれら樹脂のモノマーを成分とする共重合体（例えば、アクリロニトリル・ブタジエン・スチレン共重合体、アクリロニトリル・スチレン共重合体など）などを挙げることができる。 More specifically, first, a first carbonizable organic material and a second carbonizable organic material made of an organic material different from the first carbonizable organic material are prepared. The first carbonizable organic material and the second carbonizable organic material are not particularly limited. For example, phenol resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, xylene resin, urethane resin, silicone Thermosetting resins such as resins, thermosetting polyimide resins, thermosetting polyimide resins, thermosetting polyamide resins; polystyrene resins, polyester resins, polyolefin resins, polyimide resins, polyamide resins, polyamideimide resins, polyvinyl acetate resins, Thermoplastic resins such as vinyl chloride resin, fluororesin, polyacrylonitrile resin, acrylic resin, polyether resin, polyvinyl alcohol, polyvinyl pyrrolidone, pitch, polyamino acid resin, polybenzimidazole resin; cellulose (polysaccharide), tar; Mention may be made of a copolymer of a monomer of the resin component (e.g., acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer).
　これらの中でも、第１炭化可能有機材料又は第２炭化可能有機材料として、熱硬化性樹脂を含んでいるのが好ましい。熱硬化性樹脂を含んでいると、後述のように、第１炭化可能有機材料と第２炭化可能有機材料とを含む前駆繊維同士の交差点を熱硬化性樹脂によって接合し、炭化の際に、その接合状態を維持しやすいためである。特に、フェノール樹脂及び／又はエポキシ樹脂は前記作用に加えて、炭化後の導電性にも優れているため好適である。 Among these, it is preferable that a thermosetting resin is included as the first carbonizable organic material or the second carbonizable organic material. When the thermosetting resin is included, as described later, the intersection of the precursor fibers containing the first carbonizable organic material and the second carbonizable organic material is joined by the thermosetting resin, and at the time of carbonization, This is because it is easy to maintain the joined state. In particular, a phenol resin and / or an epoxy resin are suitable because they are excellent in conductivity after carbonization in addition to the above-described action.
　また、第１炭化可能有機材料又は第２炭化可能有機材料として、熱硬化性樹脂とは炭化過程又は炭化率の異なる炭化可能有機材料を使用するのが好ましい。つまり、炭化過程が異なる第１又は第２炭化可能有機材料を含んでいることによって、紡糸性が改善されるだけでなく、炭化過程における化学変化機構（最適温度、時間、分解等）が異なり、収縮率や流動性等の差が生じることによって、炭化時に湾曲し、湾曲した炭素繊維を形成しやすいためである。例えば、第１炭化可能有機材料又は第２炭化可能有機材料として、フェノール樹脂及び／又はエポキシ樹脂などの熱硬化性樹脂と、第２炭化可能有機材料又は第１炭化可能有機材料として、ポリアクリロニトリル樹脂、ピッチなどの熱可塑性樹脂とを使用すると、炭化時における収縮率が異なることから、湾曲した炭素繊維を形成することができる。特に、ポリアクリロニトリル樹脂は炭化率が高く、繊維内部に空隙がない炭素繊維を形成しやすいことから、第１炭化可能有機材料又は第２炭化可能有機材料として好適である。 Further, it is preferable to use a carbonizable organic material having a carbonization process or a carbonization rate different from that of the thermosetting resin as the first carbonizable organic material or the second carbonizable organic material. In other words, by including the first or second carbonizable organic material having a different carbonization process, not only the spinnability is improved, but also the chemical change mechanism (optimum temperature, time, decomposition, etc.) in the carbonization process is different. This is because differences in shrinkage rate, fluidity, and the like cause bending during carbonization to easily form a curved carbon fiber. For example, as the first carbonizable organic material or the second carbonizable organic material, a thermosetting resin such as a phenol resin and / or an epoxy resin, and as the second carbonizable organic material or the first carbonizable organic material, a polyacrylonitrile resin. When a thermoplastic resin such as pitch is used, since the shrinkage rate during carbonization is different, curved carbon fibers can be formed. In particular, polyacrylonitrile resin is suitable as the first carbonizable organic material or the second carbonizable organic material because it has a high carbonization rate and easily forms carbon fibers having no voids inside the fibers.
　なお、炭素繊維の導電性、機械的強度に優れているように、また、湾曲した炭素繊維を形成しやすいように、導電性材料を用意するのが好ましい。この導電性材料としては前述のような導電性材料であることができ、カーボンナノチューブであるのが好ましい。つまり、炭化する際における、カーボンナノチューブの存在する部分における収縮率と、カーボンナノチューブの存在しない部分における収縮率との間に差が生じ、湾曲した炭素繊維となりやすく、このような湾曲した炭素繊維は曲げても湾曲した部分が伸びやすいため、柔軟性に優れている。 In addition, it is preferable to prepare a conductive material so that the carbon fiber is excellent in conductivity and mechanical strength, and so that a curved carbon fiber is easily formed. The conductive material can be a conductive material as described above, and is preferably a carbon nanotube. In other words, when carbonizing, there is a difference between the shrinkage rate in the portion where the carbon nanotubes are present and the shrinkage rate in the portion where the carbon nanotubes are not present, which tends to be a curved carbon fiber. Even if it is bent, the curved portion is easy to stretch, so it has excellent flexibility.
　また、前述のような第１炭化可能有機材料又は第２炭化可能有機材料に加えて、ポリジメチルシロキサンなどのシリコーンや、金属アルコキシド（ケイ素、アルミニウム、チタン、ジルコニウム、ホウ素、スズ、亜鉛などのメトキシド、エトキシド、プロポキシド、ブトキシドなど）が重合した無機ポリマーなど、公知の無機系化合物が重合してなるポリマーを併用することもできる。 In addition to the first carbonizable organic material or the second carbonizable organic material as described above, silicone such as polydimethylsiloxane and metal alkoxide (methoxide such as silicon, aluminum, titanium, zirconium, boron, tin, and zinc) are used. , An ethoxide, a propoxide, a butoxide, etc.) can be used in combination with a polymer obtained by polymerizing a known inorganic compound.
　前述のような材料を準備した後、前駆繊維を形成するために、前述のような第１炭化可能有機材料及び第２炭化可能有機材料を含む紡糸液を調製する。好ましくは、導電性材料も含む紡糸液を調製する。場合によっては、シリコーンや無機ポリマーも含む紡糸液を調製する。 After preparing the materials as described above, a spinning solution containing the first carbonizable organic material and the second carbonizable organic material as described above is prepared to form the precursor fiber. Preferably, a spinning solution including a conductive material is prepared. In some cases, a spinning solution containing silicone and an inorganic polymer is prepared.
　紡糸液を構成する溶媒は、第１炭化可能有機材料及び第２炭化可能有機材料が溶解可能な溶媒であれば良く、特に限定するものではないが、例えば、アセトン、メタノール、エタノール、プロパノール、イソプロパノール、テトラヒドロフラン、ジメチルスルホキシド、１，４－ジオキサン、ピリジン、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ，Ｎ－ジメチルアセトアミド、Ｎ－メチル－２－ピロリドン、アセトニトリル、ギ酸、トルエン、ベンゼン、シクロヘキサン、シクロヘキサノン、四塩化炭素、塩化メチレン、クロロホルム、トリクロロエタン、エチレンカーボネート、ジエチルカーボネート、プロピレンカーボネート、水等を挙げることができ、これらの溶媒の単独溶媒、又は混合溶媒であることができる。なお、紡糸性に問題がない範囲で、貧溶媒を添加することもできる。 The solvent constituting the spinning solution is not particularly limited as long as the first carbonizable organic material and the second carbonizable organic material can be dissolved. For example, acetone, methanol, ethanol, propanol, isopropanol , Tetrahydrofuran, dimethyl sulfoxide, 1,4-dioxane, pyridine, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, acetonitrile, formic acid, toluene, benzene, cyclohexane, cyclohexanone, tetrachloride Examples thereof include carbon, methylene chloride, chloroform, trichloroethane, ethylene carbonate, diethyl carbonate, propylene carbonate, water, and the like. These solvents can be a single solvent or a mixed solvent. In addition, a poor solvent can be added as long as there is no problem in spinnability.
　なお、紡糸液における固形分濃度は特に限定するものではないが、１～５０ｍａｓｓ％であるのが好ましく、５～３０ｍａｓｓ％であるのがより好ましい。１ｍａｓｓ％を下回ると、生産性が極端に低下し、５０ｍａｓｓ％を上回ると、紡糸が不安定になる傾向があるためである。なお、前記の各下限と各上限は、所望により、任意に組み合わせることができる。 The solid content concentration in the spinning solution is not particularly limited, but is preferably 1 to 50 mass%, more preferably 5 to 30 mass%. This is because when the content is less than 1 mass%, the productivity is extremely lowered, and when the content exceeds 50 mass%, the spinning tends to become unstable. In addition, each said lower limit and each upper limit can be arbitrarily combined as desired.
　また、紡糸液における第１炭化可能有機材料と第２炭化可能有機材料との固形分質量比は、第１炭化可能有機材料と第２炭化可能有機材料の組合せによって異なるため、特に限定するものではないが、例えば、第１炭化可能有機材料がポリアクリロニトリル樹脂のような炭化率の高い有機材料からなり、第２炭化可能有機材料がエポキシ樹脂のような熱硬化性樹脂からなる場合には、第１炭化可能有機材料による導電性に優れ、しかも第２炭化可能有機材料による接合による機械的強度、導電性、及び湾曲することによる柔軟性に優れているように、第１炭化可能有機材料と第２炭化可能有機材料との固形分比は４０～９０：６０～１０であるのが好ましく、５０～８０：５０～２０であるのがより好ましく、５０～７０：５０～３０であるのが更に好ましい。なお、前記の各下限と各上限は、所望により、任意に組み合わせることができる。 Moreover, since the solid content mass ratio of the 1st carbonizable organic material and the 2nd carbonizable organic material in a spinning liquid changes with combinations of the 1st carbonizable organic material and the 2nd carbonizable organic material, it does not specifically limit However, for example, when the first carbonizable organic material is made of an organic material having a high carbonization rate such as polyacrylonitrile resin and the second carbonizable organic material is made of a thermosetting resin such as an epoxy resin, The first carbonizable organic material and the first carbonizable organic material are superior in electrical conductivity due to the first carbonizable organic material, and excellent in mechanical strength, electrical conductivity, and flexibility due to bending by the second carbonizable organic material. The solid content ratio with the carbonizable organic material is preferably 40 to 90:60 to 10, more preferably 50 to 80:50 to 20, and 50 to 70:50 to 30. And even more preferred. In addition, each said lower limit and each upper limit can be arbitrarily combined as desired.
　なお、第１炭化可能有機材料と第２炭化可能有機材料に加えて、好適である導電性材料を含んでいる場合には、導電性に優れているように、第１炭化可能有機材料と第２炭化可能有機材料の固形分の総質量１００に対して、１～９０の質量の導電性材料を含ませるのが好ましく、５～５０の質量の導電性材料を含ませるのがより好ましく、１０～４０の質量の導電性材料を含ませるのが更に好ましい。なお、前記の各下限と各上限は、所望により、任意に組み合わせることができる。 In addition to the first carbonizable organic material and the second carbonizable organic material, in the case where a suitable conductive material is included, the first carbonizable organic material and the second carbonized organic material are selected so as to have excellent conductivity. It is preferable to include a conductive material having a mass of 1 to 90, and more preferable to include a conductive material having a mass of 5 to 50 with respect to a total mass of 100 solids of the carbonizable organic material. More preferably, a conductive material having a mass of ˜40 is included. In addition, each said lower limit and each upper limit can be arbitrarily combined as desired.
　次いで、上述のような第１炭化可能有機材料と第２炭化可能有機材料とを含む紡糸液を紡糸して前駆繊維を形成する。この前駆繊維を形成する方法として、例えば、乾式紡糸法、静電紡糸法、特開２００９－２８７１３８号公報に開示されているような、液吐出部から吐出された紡糸液に対してガスを平行に吐出し、紡糸液に対して、１本の直線状に剪断力を作用させて繊維化する方法、を挙げることができる。これらの中でも、静電紡糸法、又は特開２００９－２８７１３８号公報に開示された紡糸方法によれば、平均繊維径が３μｍ以下の繊維径の小さい前駆繊維を紡糸しやすいため好適である。また、乾式紡糸法又は静電紡糸法によれば、連続した前駆繊維を紡糸できるため好適である。特に、静電紡糸法によれば、繊維径が小さいことに加えて、連続した繊維長を有する前駆繊維を紡糸できるため好適である。なお、前述のような方法により紡糸した前駆繊維を直接、捕集体で捕集することによって、シート状に集積した前駆繊維を形成することができる。 Next, a spinning fiber containing the first carbonizable organic material and the second carbonizable organic material as described above is spun to form a precursor fiber. As a method of forming this precursor fiber, for example, a dry spinning method, an electrostatic spinning method, and a gas parallel to a spinning solution discharged from a liquid discharging unit as disclosed in JP-A-2009-287138 is used. And a method of producing a fiber by applying a shearing force in a straight line to the spinning solution. Among these, the electrospinning method or the spinning method disclosed in Japanese Patent Application Laid-Open No. 2009-287138 is preferable because a precursor fiber having a small average fiber diameter of 3 μm or less can be easily spun. Further, the dry spinning method or the electrostatic spinning method is preferable because continuous precursor fibers can be spun. In particular, the electrospinning method is suitable because a precursor fiber having a continuous fiber length can be spun in addition to a small fiber diameter. In addition, the precursor fiber accumulated by the sheet | seat shape can be formed by collecting the precursor fiber spun by the above methods directly with a collection body.
　なお、本発明における「前駆繊維」とは、第１炭化可能有機材料、第２炭化可能有機材料のいずれもが炭化していない状態の繊維を意味し、第１炭化可能有機材料、第２炭化可能有機材料のいずれもが炭化して炭素繊維を構成するため、炭素繊維の素となる繊維という意味で、前駆繊維と表現している。 The “precursor fiber” in the present invention means a fiber in a state where neither the first carbonizable organic material nor the second carbonizable organic material is carbonized, and the first carbonizable organic material and the second carbonized carbon. Since all of the possible organic materials are carbonized to form carbon fiber, it is expressed as a precursor fiber in the sense of a fiber that is a source of carbon fiber.
　このように前駆繊維を形成した後に、前駆繊維の交差点を第１炭化可能有機材料又は第２炭化可能有機材料で接合して、前駆繊維を主体とする前駆繊維シートを形成する。そのため、まず、前駆繊維が集合したシートを形成する。この前駆繊維が集合したシートは、例えば、紡糸した前駆繊維を直接、捕集体で捕集することによって形成することができるし、紡糸した前駆繊維を連続繊維として巻き取り、次いで所望繊維長に切断して短繊維とした後、カード法、エアレイ法などの乾式法、又は湿式法により形成することができるし、連続した前駆繊維を用いて、常法により織ったり、編んだりして形成することもできる。これらの中でも、紡糸した前駆繊維を直接、捕集体で捕集する方法は、連続した繊維長を有する前駆繊維であることができ、生産性にも優れているため好適である。 After forming the precursor fibers in this manner, the intersection of the precursor fibers is joined with the first carbonizable organic material or the second carbonizable organic material to form a precursor fiber sheet mainly composed of the precursor fibers. Therefore, first, a sheet in which precursor fibers are gathered is formed. The sheet in which the precursor fibers are gathered can be formed, for example, by collecting the spun precursor fibers directly by a collecting body, or winding the spun precursor fibers as continuous fibers and then cutting them to a desired fiber length. After forming into short fibers, it can be formed by a dry method such as a card method, an air array method, or a wet method, and can be formed by weaving or knitting by a conventional method using continuous precursor fibers. You can also. Among these, the method of collecting the spun precursor fiber directly with a collector is preferable because it can be a precursor fiber having a continuous fiber length and is excellent in productivity.
　このような前駆繊維が集合したシートを構成する前駆繊維同士の交差点を、第１炭化可能有機材料又は第２炭化可能有機材料で接合する。この接合方法は特に限定するものではないが、例えば、前述のように、第１炭化可能有機材料又は第２炭化可能有機材料として、熱硬化性樹脂を含んでいる場合は、熱硬化性樹脂が硬化するように、熱硬化性樹脂が熱硬化する温度で熱処理を実施して接合することができる。この熱処理温度、時間等の熱硬化条件は、熱硬化性樹脂によって異なるため、熱硬化性樹脂に応じて、適宜調整する。また、第１炭化可能有機材料又は第２炭化可能有機材料を溶解させることのできる溶媒を前駆繊維が集合したシートに付与し、第１炭化可能有機材料又は第２炭化可能有機材料を溶解させた後に、前記溶媒を乾燥除去することによって接合することができる。この溶媒の種類、溶媒付与量、溶媒温度、乾燥温度、乾燥時間等の可塑化接合条件は、第１炭化可能有機材料又は第２炭化可能有機材料によって異なるため、第１炭化可能有機材料又は第２炭化可能有機材料に応じて、適宜調整する。 The intersection of the precursor fibers constituting the sheet in which such precursor fibers are assembled is joined with the first carbonizable organic material or the second carbonizable organic material. Although this joining method is not particularly limited, for example, as described above, when the thermosetting resin is included as the first carbonizable organic material or the second carbonizable organic material, the thermosetting resin is In order to cure, the thermosetting resin can be bonded by performing a heat treatment at a temperature at which the thermosetting resin is thermally cured. Since the heat curing conditions such as the heat treatment temperature and time vary depending on the thermosetting resin, they are appropriately adjusted according to the thermosetting resin. Further, a solvent capable of dissolving the first carbonizable organic material or the second carbonizable organic material was applied to the sheet in which the precursor fibers were assembled, and the first carbonizable organic material or the second carbonizable organic material was dissolved. Later, bonding can be performed by drying and removing the solvent. Since the plasticizing joining conditions such as the type of solvent, the solvent application amount, the solvent temperature, the drying temperature, and the drying time vary depending on the first carbonizable organic material or the second carbonizable organic material, It adjusts suitably according to the organic material which can be carbonized.
　なお、前駆繊維同士の交差点の接合を、バインダにより実施することも考えられるが、バインダを使用した場合、バインダが前駆繊維によって形成される空隙を埋めたり、バインダが前駆繊維同士の交差点周辺を必要以上に覆ってしまい、結果として得られる導電性多孔シートの空隙を十分に利用できなくなる場合があるため、前駆繊維を構成する第１炭化可能有機材料又は第２炭化可能有機材料によって接合するのが好ましい。例えば、導電性多孔シートをガス拡散電極用基材として使用する場合、ガス又は液水の透過性が低下する傾向がある。 In addition, it is conceivable to join the intersections of the precursor fibers with a binder, but when a binder is used, the binder fills the gap formed by the precursor fibers, or the binder needs around the intersection of the precursor fibers Since it may cover the above and the space | gap of the electroconductive porous sheet obtained as a result may become unable to fully utilize, joining by the 1st carbonizable organic material or the 2nd carbonizable organic material which comprises a precursor fiber may be carried out. preferable. For example, when a conductive porous sheet is used as a base material for a gas diffusion electrode, the permeability of gas or liquid water tends to decrease.
　なお、前駆繊維を主体とする前駆繊維シートは、上述のような方法により形成することができるが、前駆繊維以外の材料を含む場合には、前駆繊維を紡糸する際、前駆繊維の集合したシートを形成する際、或いは前駆繊維の集合したシートを形成した後に、前駆繊維以外の材料を付与することができる。例えば、カーボンナノチューブを、紡糸した前駆繊維の流れに対して噴霧することにより、カーボンナノチューブの混在する前駆繊維シートを形成することができる。 The precursor fiber sheet mainly composed of the precursor fibers can be formed by the above-described method. However, when the precursor fibers include materials other than the precursor fibers, the precursor fibers are aggregated when the precursor fibers are spun. The material other than the precursor fiber can be applied when forming the sheet or after forming the sheet in which the precursor fibers are aggregated. For example, a precursor fiber sheet in which carbon nanotubes are mixed can be formed by spraying carbon nanotubes on the flow of spun precursor fibers.
　そして、前駆繊維シートを構成する前駆繊維を、その交差点で接合した状態のまま炭化して、湾曲した炭素繊維として、三点曲げ試験で破断しない導電性多孔シートを製造する。本発明においては、前駆繊維の交差点を接合した後に、その交差点で接合した状態のまま炭化して、湾曲した炭素繊維としているため、柔軟性、機械的強度、及び導電性の優れる導電性多孔シートを製造することができる。つまり、前駆繊維は第１炭化可能有機材料と第２炭化可能有機材料を含んでおり、炭化する際の収縮率が異なるため、湾曲した炭素繊維となる。 Then, the precursor fiber constituting the precursor fiber sheet is carbonized while being joined at the intersection, and a conductive porous sheet that is not broken by a three-point bending test is manufactured as a curved carbon fiber. In the present invention, after joining the intersections of the precursor fibers, carbonized while being joined at the intersections to form a curved carbon fiber, the conductive porous sheet having excellent flexibility, mechanical strength, and conductivity Can be manufactured. That is, the precursor fiber contains the first carbonizable organic material and the second carbonizable organic material, and has different shrinkage rates when carbonized, and thus becomes a curved carbon fiber.
　この炭化は第１炭化可能有機材料及び第２炭化可能有機樹脂を炭化できれば良く、特に限定するものではないが、例えば、窒素、ヘリウム、アルゴン等の不活性気体雰囲気中、最高温度８００～３０００℃で加熱して行うことができる。なお、昇温速度は５～１０００００℃／分であるのが好ましく、５～１０００℃／分であるのがより好ましい。また、最高温度での保持時間は、３時間以内であるのが好ましく、１～１２０分間であるのがより好ましい。なお、これらの各パラメータにおいて、前記の各下限と各上限は、所望により、任意に組み合わせることができる。 This carbonization is not particularly limited as long as the first carbonizable organic material and the second carbonizable organic resin can be carbonized. For example, the maximum temperature is 800 to 3000 ° C. in an inert gas atmosphere such as nitrogen, helium, and argon. It can be performed by heating. The rate of temperature rise is preferably 5 to 100,000 ° C./min, and more preferably 5 to 1000 ° C./min. The holding time at the maximum temperature is preferably within 3 hours, more preferably 1 to 120 minutes. In each of these parameters, the lower limit and the upper limit can be arbitrarily combined as desired.
　以上のような方法により、本発明の導電性多孔シートを製造することができるが、前駆繊維を構成する第１炭化可能有機材料又は第２炭化可能有機材料として、ポリアクリロニトリル樹脂を含んでいる場合には、炭化処理後も繊維形状を維持できるように、炭化処理の前に不融化工程を実施してもよい。この不融化は、酸化雰囲気中、温度２００～３００℃で１０～１２０分間加熱して実施できる。なお、不融化の加熱は２回以上、温度又は時間の異なる条件で実施することができる。 When the conductive porous sheet of the present invention can be produced by the method as described above, the polyacrylonitrile resin is included as the first carbonizable organic material or the second carbonizable organic material constituting the precursor fiber. In order to maintain the fiber shape even after the carbonization treatment, an infusibilization step may be performed before the carbonization treatment. This infusibilization can be performed by heating at a temperature of 200 to 300 ° C. for 10 to 120 minutes in an oxidizing atmosphere. The infusible heating can be carried out twice or more under different conditions of temperature or time.
　なお、本発明の導電性多孔シートは空隙率が５０％以上と空隙が多いのが好ましいが、このような空隙率の高い導電性多孔シートは、平均繊維径が０．１μｍ～５０μｍの炭素繊維を主体としていると、前記空隙率を満たしやすい。このような平均繊維径の炭素繊維の素となる前駆繊維は、例えば、静電紡糸法又は特開２００９－２８７１３８号公報に開示されている紡糸方法により製造しやすい。また、前駆繊維同士の交差点を接合するためにバインダを使用すると、バインダが前駆繊維間の空隙を埋めたり、前駆繊維同士の交差点の周辺を必要以上に覆ってしまい、空隙率が低くなる傾向があるため、バインダを使用することなく、前駆繊維を構成する第１炭化可能有機材料又は第２炭化可能有機材料で接合させると、前記空隙率を満たしやすい。 The conductive porous sheet of the present invention preferably has a large porosity of 50% or more. However, the conductive porous sheet having such a high porosity is a carbon fiber having an average fiber diameter of 0.1 μm to 50 μm. When the main component is, the porosity is easily satisfied. Precursor fibers which are the basis of carbon fibers having such an average fiber diameter are easy to produce by, for example, the electrostatic spinning method or the spinning method disclosed in JP-A-2009-287138. Also, if a binder is used to join the intersections of the precursor fibers, the binder fills the gaps between the precursor fibers or covers the periphery of the intersections of the precursor fibers more than necessary, and the porosity tends to be low. Therefore, when the first carbonizable organic material or the second carbonizable organic material constituting the precursor fiber is bonded without using a binder, the porosity is easily satisfied.
　また、本発明の導電性多孔シートは、各種後加工により、各用途に適合する物性を付与又は向上させることができる。例えば、本発明の導電性多孔シートを固体高分子形燃料電池のガス拡散電極用基材として使用する場合、導電性多孔シートの撥水性を高め、排水性及びガス拡散性を高めるために、ポリテトラフルオロエチレンディスパージョンなどのフッ素系ディスパージョン中に、導電性多孔シートを浸漬して、フッ素系樹脂を付与した後、温度３００～３５０℃で焼結することができる。 Further, the conductive porous sheet of the present invention can impart or improve physical properties suitable for each application by various post-processing. For example, when the conductive porous sheet of the present invention is used as a base material for a gas diffusion electrode of a polymer electrolyte fuel cell, in order to increase the water repellency of the conductive porous sheet and to enhance drainage and gas diffusion properties, A conductive porous sheet is immersed in a fluorine-based dispersion such as a tetrafluoroethylene dispersion to give a fluorine-based resin, and then sintered at a temperature of 300 to 350 ° C.
　更に、内部に空隙のない炭素繊維は、第１炭化可能有機材料、第２炭化可能有機材料のいずれも炭化率の高い有機材料を使用することによって製造しやすい。つまり、炭化時に消失する有機材料が少ないため、内部に空隙のない炭素繊維を製造しやすい。この炭化率の高い第１炭化可能有機材料又は第２炭化可能有機材料として、例えば、ポリアクリロニトリル、エポキシ樹脂、フェノール樹脂などを挙げることができる。 Furthermore, carbon fibers without voids inside are easy to manufacture by using an organic material having a high carbonization rate for both the first carbonizable organic material and the second carbonizable organic material. That is, since there are few organic materials which lose | disappear at the time of carbonization, it is easy to manufacture carbon fiber without a space | gap inside. Examples of the first carbonizable organic material or the second carbonizable organic material having a high carbonization rate include polyacrylonitrile, epoxy resin, and phenol resin.
　更に、比見掛ヤング率が１００ＭＰａ／（ｇ／ｃｍ３）以上の剛性のある導電性多孔シートは、炭素繊維を剛性のある材料から形成することによって製造しやすい。つまり、第１炭化可能有機材料及び／又は第２炭化可能有機材料として、熱硬化性樹脂、特にはエポキシ樹脂、フェノール樹脂を使用することによって、製造しやすい。 Furthermore, a rigid conductive porous sheet having a specific apparent Young's modulus of 100 MPa / (g / cm 3 ) or more is easy to manufacture by forming carbon fibers from a rigid material. That is, the first carbonizable organic material and / or the second carbonizable organic material can be easily manufactured by using a thermosetting resin, particularly an epoxy resin or a phenol resin.
　更に、主面における平均算術平均表面粗さが０．０１μｍ～２０μｍ（０．１μｍ～１０μｍであるのが好ましく、０．１μｍ～５μｍであるのがより好ましく、０．１～４μｍであるのが更に好ましい）である導電性多孔シートは、例えば、平均繊維径が２０μｍ以下の炭素繊維を使用することにより、導電性多孔シートの形態を不織布とすることにより、及び／又は導電性多孔シートを静電紡糸法、特開２００９－２８７１３８号公報に開示されているような方法により直接製造することによって、製造しやすい。なお、前記平均算術平均表面粗さにおける、前記の各下限と各上限は、所望により、任意に組み合わせることができる。 Further, the average arithmetic average surface roughness on the main surface is 0.01 μm to 20 μm (preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 5 μm, and more preferably 0.1 to 4 μm. More preferably, the conductive porous sheet is, for example, a carbon fiber having an average fiber diameter of 20 μm or less, a non-woven fabric in the form of the conductive porous sheet, and / or a static porous sheet. It is easy to produce by directly producing by an electrospinning method and a method as disclosed in JP-A-2009-287138. In addition, each said minimum and each upper limit in the said average arithmetic average surface roughness can be arbitrarily combined as desired.
　以下に、本発明の実施例を記載するが、本発明は以下の実施例に限定されるものではない。 Examples of the present invention will be described below, but the present invention is not limited to the following examples.
　＜第１紡糸液の調製＞
　ポリアクリロニトリル（＝ＰＡＮ、第１炭化可能有機材料）をＮ，Ｎ－ジメチルホルムアミド（ＤＭＦ）に加え、ロッキングミルを用いて溶解させ、固形分濃度２０ｍａｓｓ％の溶液を得た。 <Preparation of the first spinning solution>
Polyacrylonitrile (= PAN, first carbonizable organic material) was added to N, N-dimethylformamide (DMF) and dissolved using a rocking mill to obtain a solution having a solid concentration of 20 mass%.
　次いで、前記溶液に、クレゾールノボラックエポキシ樹脂を主剤とし、ノボラック型フェノール樹脂を硬化剤とする第２炭化可能有機材料（＝ＥＰ）を加えて混合し、攪拌した後、さらにＤＭＦを加えて希釈して、ＰＡＮ：ＥＰの固形分質量比が７０：３０で、固形分濃度が２５ｍａｓｓ％の第１紡糸液を調製した。 Next, a second carbonizable organic material (= EP) containing a cresol novolac epoxy resin as a main component and a novolac type phenol resin as a curing agent is added to the solution, mixed, stirred, and further diluted with DMF. Thus, a first spinning solution having a solid content mass ratio of PAN: EP of 70:30 and a solid content concentration of 25 mass% was prepared.
　＜第２紡糸液の調製＞
　ポリアクリロニトリル（＝ＰＡＮ、第１炭化可能有機材料）をＮ，Ｎ－ジメチルホルムアミド（ＤＭＦ）に加え、ロッキングミルを用いて溶解させ、固形分濃度２０ｍａｓｓ％の溶液を得た。 <Preparation of the second spinning solution>
Polyacrylonitrile (= PAN, first carbonizable organic material) was added to N, N-dimethylformamide (DMF) and dissolved using a rocking mill to obtain a solution having a solid concentration of 20 mass%.
　次いで、導電性材料として、ＣＶＤ法で合成されたカーボンナノチューブ［＝ＣＮＴ、商品名：ＶＧＣＦ－Ｈ（昭和電工（株）製）、繊維径：１５０ｎｍ、アスペクト比：４０、多層カーボンナノチューブ］を前記溶液に混合して分散液を調製した。 Next, as a conductive material, carbon nanotubes synthesized by CVD (= CNT, trade name: VGCF-H (manufactured by Showa Denko KK), fiber diameter: 150 nm, aspect ratio: 40, multi-walled carbon nanotubes] A dispersion was prepared by mixing with the solution.
　そして、前記分散液にクレゾールノボラックエポキシ樹脂を主剤とし、ノボラック型フェノール樹脂を硬化剤とする第２炭化可能有機材料（＝ＥＰ）を加えて混合し、攪拌した後、さらにＤＭＦを加えて希釈して、ＣＮＴ：ＰＡＮ：ＥＰの固形分質量比が１０：６０：３０で、固形分濃度が２５ｍａｓｓ％の第２紡糸液を調製した。 Then, a second carbonizable organic material (= EP) containing a cresol novolac epoxy resin as a main component and a novolac type phenol resin as a curing agent is added to the dispersion, mixed, stirred, and further diluted with DMF. Thus, a second spinning solution having a solid content mass ratio of CNT: PAN: EP of 10:60:30 and a solid content concentration of 25 mass% was prepared.
　＜第３紡糸液の調製＞
　カーボンナノチューブ（ＣＮＴ）に替えて、カーボンブラック（＝ＣＢ、電気化学工業（株）製、商品名：デンカブラック粒状品、平均粒径：３５ｎｍ）を使用したこと以外は、第２紡糸液と同様に調製して、ＣＢ：ＰＡＮ：ＥＰの固形分質量比が１０：６０：３０で、固形分濃度が２０ｍａｓｓ％の第３紡糸液を調製した。 <Preparation of third spinning solution>
Similar to the second spinning solution except that carbon black (= CB, manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: Denka black granular product, average particle size: 35 nm) was used instead of carbon nanotube (CNT). A third spinning solution having a solid content mass ratio of CB: PAN: EP of 10:60:30 and a solid content concentration of 20 mass% was prepared.
　＜第４紡糸液の調製＞
　ポリアクリロニトリルをＮ，Ｎ－ジメチルホルムアミド（ＤＭＦ）に加え、ロッキングミルを用いて溶解させ、固形分濃度が１６ａｓｓ％の第４紡糸液を調製した。 <Preparation of the fourth spinning solution>
Polyacrylonitrile was added to N, N-dimethylformamide (DMF) and dissolved using a rocking mill to prepare a fourth spinning solution having a solid content concentration of 16 ass%.
　＜第５紡糸液の調製＞
　ポリアクリロニトリル（＝ＰＡＮ）、フェノール樹脂（＝ＰＨ、群栄化学工業製、ＰＳＫ－２３２０）、Ｔｉｔａｎｉｕｍ（ＩＶ）ｂｕｔｏｘｉｄｅ（＝ＴＩ、アルドリッチ社製）を、Ｎ，Ｎ－ジメチルホルムアミド（ＤＭＦ）に溶解させ、ＰＡＮ：ＰＨ：ＴＩの固形分質量比が４４：４４：１２で、固形分濃度が２５ｍａｓｓ％の第５紡糸液を調製した。 <Preparation of fifth spinning solution>
Polyacrylonitrile (= PAN), phenol resin (= PH, manufactured by Gunei Chemical Industry Co., Ltd., PSK-2320), Titanium (IV) butoxide (= TI, manufactured by Aldrich) are dissolved in N, N-dimethylformamide (DMF) A fifth spinning solution having a solid content mass ratio of PAN: PH: TI of 44:44:12 and a solid content concentration of 25 mass% was prepared.
　＜第６紡糸液の調製＞
　フッ化ビニリデン・テトラフルオロエチレン・ヘキサフルオロプロピレン共重合物（＝ＴＨＶ、第１炭化可能有機材料）をＮ，Ｎ－ジメチルホルムアミド（ＤＭＦ）に加え、ロッキングミルを用いて溶解させ、固形分濃度１０ｍａｓｓ％の溶液を得た。 <Preparation of the sixth spinning solution>
A vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (= THV, first carbonizable organic material) is added to N, N-dimethylformamide (DMF), dissolved using a rocking mill, and a solid content concentration of 10 mass. % Solution was obtained.
　次いで、導電性材料として、ＣＶＤ法で合成されたカーボンナノチューブ（ＣＮＴ）［商品名：ＶＧＣＦ－Ｈ（昭和電工（株）製）、繊維径：１５０ｎｍ、アスペクト比：４０、多層カーボンナノチューブ］を前記溶液に混合し、撹拌した後、更にＤＭＦを加えて希釈し、カーボンナノチューブを分散させた分散溶液を得た。 Next, carbon nanotubes (CNT) synthesized by CVD (trade name: VGCF-H (manufactured by Showa Denko KK), fiber diameter: 150 nm, aspect ratio: 40, multi-walled carbon nanotubes] are used as the conductive material. After mixing with the solution and stirring, DMF was further added to dilute to obtain a dispersion solution in which the carbon nanotubes were dispersed.
　そして、前記分散溶液に、クレゾールノボラックエポキシ樹脂を主剤とし、ノボラック型フェノール樹脂を硬化剤とする第２炭化可能有機材料（＝ＥＰ）を加え、ＣＮＴ：ＴＨＶ：ＥＰの固形分質量比が４０：３０：３０で、固形分濃度が２０ｍａｓｓ％の第６紡糸液を調製した。 Then, a second carbonizable organic material (= EP) containing a cresol novolac epoxy resin as a main component and a novolac type phenol resin as a curing agent is added to the dispersion solution, and the solid content mass ratio of CNT: THV: EP is 40: A sixth spinning solution having a solid content of 20 mass% at 30:30 was prepared.
　＜第７紡糸液の調製＞
　ポリアクリロニトリル（＝ＰＡＮ）をＮ，Ｎ－ジメチルホルムアミド（ＤＭＦ）に加え、ロッキングミルを用いて溶解させ、固形分濃度１８ｍａｓｓ％の溶液を得た。 <Preparation of the seventh spinning solution>
Polyacrylonitrile (= PAN) was added to N, N-dimethylformamide (DMF) and dissolved using a rocking mill to obtain a solution having a solid concentration of 18 mass%.
　次いで、導電性材料として、ＣＶＤ法で合成されたカーボンナノチューブ（ＣＮＴ）［商品名：ＶＧＣＦ－Ｈ（昭和電工（株）製）、繊維径：１５０ｎｍ、アスペクト比：４０、多層カーボンナノチューブ］を前記溶液に混合し、撹拌した後、更にＤＭＦを加えて希釈し、カーボンナノチューブを分散させた分散溶液を得た。 Next, carbon nanotubes (CNT) synthesized by CVD (trade name: VGCF-H (manufactured by Showa Denko KK), fiber diameter: 150 nm, aspect ratio: 40, multi-walled carbon nanotubes] are used as the conductive material. After mixing with the solution and stirring, DMF was further added to dilute to obtain a dispersion solution in which the carbon nanotubes were dispersed.
　そして、前記分散溶液に、ビスフェノールＡ型エポキシ樹脂を主剤とし、ノボラック型フェノール樹脂を硬化剤とする第２炭化可能有機材料（＝ＥＰ）を加え、ＣＮＴ：ＰＡＮ：ＥＰの固形分質量比が１０：６０：３０で、固形分濃度が２５ｍａｓｓ％の第７紡糸液を調製した。 Then, a second carbonizable organic material (= EP) containing bisphenol A type epoxy resin as a main component and novolac type phenol resin as a curing agent is added to the dispersion solution, and the solid content mass ratio of CNT: PAN: EP is 10 A seventh spinning solution having a solid content concentration of 25 mass% was prepared at 60:30.
　（実施例１）
　前記第１紡糸液を静電紡糸法により次の条件で前駆連続繊維を紡糸し、対向電極であるステンレスドラム上に、直接、集積させて、前駆連続繊維のみからなり、繊維同士の交差点が接合していない不織布形態の前駆繊維集合シートを形成した。 Example 1
The first spinning solution is formed by spinning the precursor continuous fiber under the following conditions by the electrostatic spinning method, and is directly accumulated on the stainless drum as the counter electrode, and is composed of only the precursor continuous fiber, and the intersection of the fibers is joined. A non-woven fabric precursor fiber assembly sheet was formed.
　（静電紡糸条件）
　電極：金属性ノズル（内径：０．３３ｍｍ）とステンレスドラム
　吐出量：５ｇ／時間
　ノズル先端とステンレスドラムとの距離：１０ｃｍ
　印加電圧：１０ｋＶ
　温度／湿度：２５℃／３０％ＲＨ (Electrostatic spinning conditions)
Electrode: Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 5 g / hour Distance between nozzle tip and stainless steel drum: 10 cm
Applied voltage: 10 kV
Temperature / humidity: 25 ° C / 30% RH
　次いで、前記前駆繊維集合シートを、温度１５０℃の熱風乾燥機で１時間熱処理してエポキシ樹脂を硬化させ、繊維同士の交差点を接合した前駆繊維シートを得た。 Next, the precursor fiber assembly sheet was heat-treated for 1 hour with a hot air dryer at a temperature of 150 ° C. to cure the epoxy resin, thereby obtaining a precursor fiber sheet in which the intersections of the fibers were joined.
　続いて、前記前駆繊維シートに対して、空気中、温度２２０℃で３０分、及び温度２６０℃で１時間の酸化処理を行い、前駆連続繊維を構成するＰＡＮを不融化し、不融化前駆繊維シートとした。 Subsequently, the precursor fiber sheet is oxidized in air at a temperature of 220 ° C. for 30 minutes and at a temperature of 260 ° C. for 1 hour to infusibilize the PAN constituting the precursor continuous fiber, so that the infusible precursor fiber A sheet was used.
　そして、不融化前駆繊維シートを、真空置換式電気炉を用い、窒素ガス雰囲気下、温度１３００℃で１時間の炭化焼成処理（昇温速度：１０℃／分）を実施して、前駆連続繊維を構成するＰＡＮおよびＥＰを炭化して炭素連続繊維とし、炭素連続繊維のみからなり、不織布構造を有する一層構造の、炭素連続繊維同士の交差点で接合した導電性多孔シート（目付：６．５ｇ／ｍ２、厚さ：６５μｍ、繊維径：１．１μｍ、空隙率：９１％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図１に示すように、炭素連続繊維は繊維同士の交差点間においても湾曲した状態にあった。なお、炭素連続繊維は繊維内部に空隙のない内部充実した状態にあった。 Then, the infusibilized precursor fiber sheet is subjected to carbonization firing treatment (temperature increase rate: 10 ° C./min) at a temperature of 1300 ° C. for 1 hour in a nitrogen gas atmosphere using a vacuum substitution type electric furnace to obtain a precursor continuous fiber. PAN and EP constituting carbon are made into carbon continuous fibers, and are composed of continuous carbon fibers, and have a non-woven structure and are bonded to each other at the intersection of continuous carbon fibers (unit weight: 6.5 g / m 2 , thickness: 65 μm, fiber diameter: 1.1 μm, porosity: 91%). When the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image | photographed and observed, as shown in FIG. 1, the carbon continuous fiber was in the curved state also between the intersections of fibers. In addition, the carbon continuous fiber was in a state of being fully filled without voids inside the fiber.
　（実施例２）
　紡糸液として第２紡糸液を用いたこと以外は実施例１と同様にして、炭素連続繊維のみからなり、不織布構造を有する一層構造の、炭素連続繊維同士の交差点で接合した導電性多孔シート（目付：１０ｇ／ｍ２、厚さ：８４μｍ、繊維径：０．７μｍ、空隙率：９４％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図２に示すように、炭素連続繊維は繊維同士の交差点間においても湾曲した状態にあった。なお、炭素連続繊維は繊維内部に空隙のない内部充実した状態にあり、また、炭素連続繊維におけるＣＮＴの質量比率は１２ｍａｓｓ％であった。 (Example 2)
A conductive perforated sheet composed of continuous carbon fibers and having a non-woven structure and joined at the intersection of continuous carbon fibers (except for the use of the second spinning liquid as the spinning liquid). The basis weight was 10 g / m 2 , the thickness was 84 μm, the fiber diameter was 0.7 μm, and the porosity was 94%. When the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image | photographed and observed, as shown in FIG. 2, the carbon continuous fiber was in the curved state also between the intersections of fibers. In addition, the carbon continuous fiber was in the state where the inside of the fiber had no voids, and the mass ratio of CNT in the carbon continuous fiber was 12 mass%.
　（実施例３）
　酸化処理を行わず、前駆連続繊維を構成するＰＡＮを不融化しなかったこと以外は、実施例２と同様にして、炭素連続繊維のみからなり、不織布構造を有する一層構造の、炭素連続繊維同士の交差点で接合した導電性多孔シート（目付：１０ｇ／ｍ２、厚さ：８４μｍ、繊維径：０．７μｍ、空隙率：９４％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図３に示すように、炭素連続繊維は繊維同士の交差点間においても湾曲した状態にあった。なお、炭素連続繊維は繊維内部に空隙のない内部充実した状態にあり、また、炭素連続繊維におけるＣＮＴの質量比率は１２ｍａｓｓ％であった。 (Example 3)
Similar to Example 2, except that the PAN constituting the precursor continuous fiber was not infusible without performing the oxidation treatment, the carbon continuous fibers having a single-layer structure having only a non-woven fabric structure. A conductive porous sheet (weight per unit area: 10 g / m 2 , thickness: 84 μm, fiber diameter: 0.7 μm, porosity: 94%) was produced. When the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image | photographed and observed, as shown in FIG. 3, the carbon continuous fiber was in the curved state also between the intersections of fibers. In addition, the carbon continuous fiber was in the state where the inside of the fiber had no voids, and the mass ratio of CNT in the carbon continuous fiber was 12 mass%.
　（実施例４）
　紡糸液として第３紡糸液を用いたこと以外は実施例１と同様にして、炭素連続繊維のみからなり、不織布構造を有する一層構造の、炭素連続繊維同士の交差点で接合した導電性多孔シート（目付：５．６ｇ／ｍ２、厚さ：３４μｍ、繊維径：０．８μｍ、空隙率：９１％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図４に示すように、炭素連続繊維は繊維同士の交差点間においても湾曲した状態にあった。なお、炭素連続繊維は繊維内部に空隙のない内部充実した状態にあり、また、炭素連続繊維におけるカーボンブラックの質量比率は１２ｍａｓｓ％であった。 Example 4
A conductive perforated sheet composed of continuous carbon fibers and having a non-woven structure joined at the intersection of continuous carbon fibers (except for the use of the third spinning liquid as the spinning liquid) The basis weight was 5.6 g / m 2 , the thickness was 34 μm, the fiber diameter was 0.8 μm, and the porosity was 91%. When the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image | photographed and observed, as shown in FIG. 4, the carbon continuous fiber was in the curved state also between the intersections of fibers. In addition, the carbon continuous fiber was in the state where the inside of the fiber was free from voids, and the mass ratio of carbon black in the carbon continuous fiber was 12 mass%.
　（比較例１）
　紡糸液として第４紡糸液を用い、次の静電紡糸条件で紡糸したこと以外は実施例１と同様にして、ＰＡＮ前駆連続繊維のみからなり、繊維同士の交差点が接合していない不織布形態の前駆繊維集合シートを形成した。 (Comparative Example 1)
In the same manner as in Example 1 except that the fourth spinning solution is used as the spinning solution and spinning is performed under the following electrostatic spinning conditions, the nonwoven fabric is formed of only PAN precursor continuous fibers and the intersections of the fibers are not joined. A precursor fiber assembly sheet was formed.
　（静電紡糸条件）
　電極：金属性ノズル（内径：０．３３ｍｍ）とステンレスドラム
　吐出量：１ｇ／時間
　ノズル先端とステンレスドラムとの距離：８ｃｍ
　印加電圧：１０ｋＶ
　温度／湿度：２５℃／３０％ＲＨ (Electrostatic spinning conditions)
Electrode: Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 1 g / hour Distance between nozzle tip and stainless steel drum: 8 cm
Applied voltage: 10 kV
Temperature / humidity: 25 ° C / 30% RH
　次いで、前記前駆繊維集合シートに対して、空気中、温度２２０℃で３０分、及び温度２６０℃で１時間の酸化処理を行い、前駆連続繊維を構成するＰＡＮを不融化した後、真空置換式電気炉を用い、窒素ガス雰囲気下、温度１３００℃で１時間の炭化焼成処理（昇温速度：１０℃／分）を実施し、前駆連続繊維を構成するＰＡＮを炭化して炭素連続繊維とし、炭素連続繊維のみからなり、不織布構造を有する一層構造の、炭素連続繊維同士の交差点が接合していない導電性多孔シート（目付：５ｇ／ｍ２、厚さ：２０μｍ、繊維径：０．３μｍ、空隙率：８６％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図５に示すように、炭素連続繊維は直線状であった。なお、炭素連続繊維は繊維内部に空隙のない内部充実した状態にあった。 Next, the precursor fiber assembly sheet is subjected to an oxidation treatment in air at a temperature of 220 ° C. for 30 minutes and at a temperature of 260 ° C. for 1 hour to infusibilize the PAN constituting the precursor continuous fiber, and then a vacuum replacement type Using an electric furnace, carbonization firing treatment (temperature increase rate: 10 ° C./min) for 1 hour at a temperature of 1300 ° C. in a nitrogen gas atmosphere, PAN constituting the precursor continuous fiber is carbonized to be a carbon continuous fiber, Conductive porous sheet consisting of continuous carbon fibers only and having a non-woven structure, in which intersections of continuous carbon fibers are not joined (weight: 5 g / m 2 , thickness: 20 μm, fiber diameter: 0.3 μm, Porosity: 86%) was produced. When the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image | photographed and observed, as shown in FIG. 5, the carbon continuous fiber was linear. In addition, the carbon continuous fiber was in a state of being fully filled without voids inside the fiber.
　（比較例２）
　酸化処理を実施する前に、濃度７ｍａｓｓ％に調整したＤＭＦ／水の混合溶液に、前駆繊維集合シートを浸漬し、一対のロール間で絞った後、温度８０℃に設定したオーブン中で１０分間、続いて温度１６０℃に設定したオーブンで加熱処理することによって混合溶媒を除去して、ＰＡＮ前駆連続繊維同士の交差点を接着させたこと以外は、比較例１と同様にして、炭素連続繊維のみからなり、不織布構造を有する一層構造の、炭素連続繊維同士の交差点が接合した導電性多孔シート（目付：５ｇ／ｍ２、厚さ：１８μｍ、繊維径：０．３μｍ、空隙率：８５％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図６に示すように、炭素連続繊維は直線状であった。なお、炭素連続繊維は繊維内部に空隙のない内部充実した状態にあった。 (Comparative Example 2)
Before carrying out the oxidation treatment, the precursor fiber assembly sheet is immersed in a mixed solution of DMF / water adjusted to a concentration of 7 mass%, squeezed between a pair of rolls, and then placed in an oven set at a temperature of 80 ° C. for 10 minutes. Subsequently, only the carbon continuous fiber was obtained in the same manner as in Comparative Example 1 except that the mixed solvent was removed by heat treatment in an oven set at a temperature of 160 ° C., and the intersection of the PAN precursor continuous fibers was adhered. A conductive porous sheet having a single-layer structure having a nonwoven fabric structure and joined at the intersections of carbon continuous fibers (weight: 5 g / m 2 , thickness: 18 μm, fiber diameter: 0.3 μm, porosity: 85%) Was made. When the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image | photographed and observed, as shown in FIG. 6, the carbon continuous fiber was linear. In addition, the carbon continuous fiber was in a state of being fully filled without voids inside the fiber.
　（比較例３）
　紡糸液として第５紡糸液を用い、次の静電紡糸条件で紡糸したこと以外は、実施例１と同様にして、炭素連続繊維のみからなり、不織布構造を有する一層構造の、炭素連続繊維同士の交差点が接合していない導電性多孔シート（目付：８ｇ／ｍ２、厚さ：６２μｍ、繊維径：０．６μｍ、空隙率：９３％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図７に示すように、炭素連続繊維は直線状であった。なお、炭素連続繊維は繊維内部に空隙のない内部充実した状態にあった。 (Comparative Example 3)
A single-layered carbon continuous fiber having a non-woven structure consisting of carbon continuous fibers in the same manner as in Example 1, except that the fifth spinning liquid was used as the spinning liquid and spinning was performed under the following electrostatic spinning conditions. The electroconductive porous sheet (weight per unit: 8 g / m 2 , thickness: 62 μm, fiber diameter: 0.6 μm, porosity: 93%) in which the crossing points are not joined was prepared. When the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image | photographed and observed, as shown in FIG. 7, the carbon continuous fiber was linear. In addition, the carbon continuous fiber was in a state of being fully filled without voids inside the fiber.
　（静電紡糸条件）
　電極：金属性ノズル（内径：０．３３ｍｍ）とステンレスドラム
　吐出量：１ｇ／時間
　ノズル先端とステンレスドラムとの距離：８ｃｍ
　印加電圧：１０ｋＶ
　温度／湿度：２５℃／４０％ＲＨ (Electrostatic spinning conditions)
Electrode: Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 1 g / hour Distance between nozzle tip and stainless steel drum: 8 cm
Applied voltage: 10 kV
Temperature / humidity: 25 ° C / 40% RH
　（比較例４）
　酸化処理を行わず、前駆連続繊維を構成するＰＡＮを不融化しなかったこと以外は、比較例３と同様にして、炭素連続繊維のみからなり、不織布構造を有する一層構造の、炭素連続繊維同士の交差点が接合していない導電性多孔シート（目付：８ｇ／ｍ２、厚さ：６２μｍ、繊維径：０．６μｍ、空隙率：９３％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図８に示すように、炭素連続繊維は直線状であった。なお、炭素連続繊維は繊維内部に空隙のない内部充実した状態にあった。 (Comparative Example 4)
Similar to Comparative Example 3, except that no oxidation treatment was performed and the PAN constituting the precursor continuous fiber was not infusible, the carbon continuous fibers having a single-layer structure having only a non-woven fabric structure. The electroconductive porous sheet (weight per unit: 8 g / m 2 , thickness: 62 μm, fiber diameter: 0.6 μm, porosity: 93%) in which the crossing points are not joined was prepared. When the electron micrograph (2000 times) in the main surface of this electroconductive porous sheet was image | photographed and observed, the carbon continuous fiber was linear as shown in FIG. In addition, the carbon continuous fiber was in a state of being fully filled without voids inside the fiber.
　（比較例５）
　前記第６紡糸液を静電紡糸法により次の条件で前駆連続繊維を紡糸し、対向電極であるステンレスドラム上に、直接、集積して、前駆連続繊維のみからなり、繊維同士の交差点が接合していない不織布形態の前駆繊維集合シートを形成した。 (Comparative Example 5)
The sixth spinning solution is obtained by spinning the precursor continuous fiber by the electrospinning method under the following conditions, and directly accumulating on the stainless drum as the counter electrode, and only the precursor continuous fiber is joined. A non-woven fabric precursor fiber assembly sheet was formed.
　（静電紡糸条件）
　電極：金属性ノズル（内径：０．３３ｍｍ）とステンレスドラム
　吐出量：４ｇ／時間
　ノズル先端とステンレスドラムとの距離：１４ｃｍ
　印加電圧：１０ｋＶ
　温度／湿度：２５℃／３０％ＲＨ (Electrostatic spinning conditions)
Electrode: Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 4 g / hour Distance between nozzle tip and stainless steel drum: 14 cm
Applied voltage: 10 kV
Temperature / humidity: 25 ° C / 30% RH
　次いで、前記前駆繊維集合シートを、温度１５０℃の熱風乾燥機で１時間熱処理して、エポキシ樹脂を硬化させ、繊維同士の交差点を接合した前駆繊維シートを得た。 Next, the precursor fiber assembly sheet was heat-treated with a hot air dryer at a temperature of 150 ° C. for 1 hour to cure the epoxy resin and obtain a precursor fiber sheet in which the intersections of the fibers were joined.
　そして、前記前駆繊維シートを、管状炉を用いる、アルゴンガス雰囲気下、温度８００℃で１時間の炭化焼成処理（昇温速度：１０℃／分）を実施し、前駆連続繊維を構成するＴＨＶおよびＥＰを炭化させるとともに、ＴＨＶの大部分を消失させて炭素連続繊維状物とし、炭素連続繊維状物（ＣＮＴ：ＥＰ炭化物とＴＨＶ炭化物の総量の質量比＝５２：４８）のみからなり、不織布構造を有する一層構造の、炭素連続繊維状物同士の交差点で接合した導電性多孔シート（目付：２０ｇ／ｍ２、厚さ：４０μｍ、平均繊維径：１．３μｍ、空隙率：７３％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図９に示すように、炭素連続繊維状物の長さ方向に配向したＣＮＴが全体に分散しており、これらＣＮＴ間がＥＰ炭化物とＴＨＶの炭化物で部分的に繋がって結合した、多孔性で連続した状態の炭素連続繊維状物からなり、炭素連続繊維状物同士の交差点がＥＰ炭化物及びＴＨＶの炭化物で結合した状態にあった。 Then, the precursor fiber sheet is subjected to carbonization baking treatment (temperature increase rate: 10 ° C./min) for 1 hour at a temperature of 800 ° C. in an argon gas atmosphere using a tubular furnace, and THV constituting the precursor continuous fiber and While carbonizing EP, most of THV is lost to form a carbon continuous fibrous material, which consists of carbon continuous fibrous material (CNT: mass ratio of total amount of EP carbide and THV carbide = 52: 48), and has a non-woven structure. A conductive porous sheet having a single layer structure joined at the intersection of carbon continuous fibrous materials (weight per unit: 20 g / m 2 , thickness: 40 μm, average fiber diameter: 1.3 μm, porosity: 73%) is produced. did. When the electron micrograph (2000 times) was image | photographed and observed in the main surface of this electroconductive porous sheet, as shown in FIG. 9, CNT orientated in the length direction of the continuous carbon fiber was disperse | distributed to the whole. These CNTs are composed of carbon continuous fibers in a porous and continuous state in which the CNTs are partially connected by EP carbide and THV carbide, and the intersections of the carbon continuous fibers are between EP carbide and THV. It was in a bonded state with carbides.
　（比較例６）
　前記第７紡糸液を静電紡糸法により次の条件で前駆連続繊維を紡糸し、対向電極であるステンレスドラム上に、直接、集積して、前駆連続繊維のみからなり、繊維同士の交差点が接合していない不織布形態の前駆繊維集合シートを形成した。 (Comparative Example 6)
The seventh spinning solution is obtained by spinning the precursor continuous fiber under the following conditions by the electrospinning method, and is directly accumulated on the stainless drum as the counter electrode, and is composed only of the precursor continuous fiber. A non-woven fabric precursor fiber assembly sheet was formed.
　（静電紡糸条件）
　電極：金属性ノズル（内径：０．３３ｍｍ）とステンレスドラム
　吐出量：４ｇ／時間
　ノズル先端とステンレスドラムとの距離：１４ｃｍ
　印加電圧：１７ｋＶ
　温度／湿度：２５℃／３５％ＲＨ (Electrostatic spinning conditions)
Electrode: Metal nozzle (inner diameter: 0.33 mm) and stainless steel drum Discharge amount: 4 g / hour Distance between nozzle tip and stainless steel drum: 14 cm
Applied voltage: 17 kV
Temperature / humidity: 25 ° C / 35% RH
　次いで、前記前駆繊維集合シートを、温度１５０℃の熱風乾燥機で１時間熱処理して、エポキシ樹脂を硬化させ、繊維同士の交差点を接合した前駆繊維シートを得た。 Next, the precursor fiber assembly sheet was heat-treated with a hot air dryer at a temperature of 150 ° C. for 1 hour to cure the epoxy resin and obtain a precursor fiber sheet in which the intersections of the fibers were joined.
　続いて、前記前駆繊維シートに対して、空気中、温度２２０℃で３０分、及び温度２６０℃で１時間の酸化処理を行い、前駆連続繊維を構成するＰＡＮを不融化およびＥＰの一部を流動させた不融化前駆繊維シートとした。 Subsequently, the precursor fiber sheet is subjected to an oxidation treatment in air at a temperature of 220 ° C. for 30 minutes and at a temperature of 260 ° C. for 1 hour, so that the PAN constituting the precursor continuous fiber is infusible and a part of EP is obtained. A fluidized infusible precursor fiber sheet was obtained.
　そして、前記不融化前駆繊維シートを、管状炉を用い、窒素雰囲気下、温度８００℃で１時間の炭化焼成処理（昇温速度：１０℃／分）を実施し、前駆連続繊維を構成するＰＡＮおよびＥＰを炭化させ、（ＣＮＴ：ＰＡＮ炭化物とＥＰ炭化物の総量の質量比＝１４：８６）不織布構造を有する一層構造の、炭素連続繊維状物同士の交差点で接合した導電性多孔シート（目付：５ｇ／ｍ２、厚さ：１５μｍ、平均繊維径：０．８μｍ、空隙率：８２％）を作製した。この導電性多孔シートの主面における電子顕微鏡写真（２０００倍）を撮影し、観察したところ、図１０に示すように、炭化の際に、樹脂の流動および炭化過程の違いから多孔化したＰＡＮ炭化物とＥＰ炭化物からなる炭素連続繊維状物が見られた。 Then, the infusibilized precursor fiber sheet is subjected to carbonization baking treatment (temperature increase rate: 10 ° C./min) for 1 hour at a temperature of 800 ° C. in a nitrogen atmosphere using a tubular furnace, thereby forming a precursor continuous fiber PAN. And conductive carbon sheet (weight per unit area: mass ratio of the total amount of CNT: PAN carbide and EP carbide = 14: 86) bonded to each other at the intersection of carbon continuous fibrous materials having a non-woven structure. 5 g / m 2 , thickness: 15 μm, average fiber diameter: 0.8 μm, porosity: 82%). An electron micrograph (2000 × magnification) on the main surface of this conductive porous sheet was taken and observed, and as shown in FIG. 10, the PAN carbide was made porous due to the difference in resin flow and carbonization process during carbonization. And carbon continuous fiber made of EP carbide.
　（導電性多孔シートの評価）
　実施例１～４及び比較例１～６の導電性多孔シートに関して、前述の方法により、三点曲げ試験（曲げたわみ量）、電気抵抗、破断強度、及び比見掛ヤング率の測定を行なった。この結果は表１に示す通りであった。 (Evaluation of conductive porous sheet)
With respect to the conductive porous sheets of Examples 1 to 4 and Comparative Examples 1 to 6, the three-point bending test (bending deflection amount), electrical resistance, breaking strength, and specific apparent Young's modulus were measured by the methods described above. . The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　比較例１～２の導電性多孔シートは加圧くさびを１．５ｍｍ押し込むと応力が急激に降下し、破断するものであった。これは炭素繊維が湾曲していないためであると考えられた。また、比較例１の導電性多孔シートは比較的電気抵抗の高いものであった。これは炭素繊維の交差点で接合していないためであると考えられた。 In the conductive porous sheets of Comparative Examples 1 and 2, when the pressure wedge was pushed 1.5 mm, the stress dropped sharply and broke. This was thought to be because the carbon fibers were not curved. Moreover, the conductive porous sheet of Comparative Example 1 had a relatively high electrical resistance. This was thought to be because the carbon fibers were not joined at the intersection.
　また、比較例３～４の導電性多孔シートは比較的電気抵抗が高く、機械的強度も低いものであった。これは、炭素繊維同士の交差点が接合していないためであると考えられた。 In addition, the conductive porous sheets of Comparative Examples 3 to 4 had relatively high electrical resistance and low mechanical strength. This was considered because the intersection of carbon fibers was not joined.
　更に、比較例５の導電性多孔シートは加圧くさびを３．０ｍｍ押し込むと応力が急激に降下し、破断するものであった。これは炭素繊維が多孔質であり、また、導電性材料の含有割合が高いためであると考えられた。 Furthermore, when the conductive wedge sheet of Comparative Example 5 was pressed with a pressure wedge of 3.0 mm, the stress dropped suddenly and broke. This was thought to be because the carbon fiber was porous and the content of the conductive material was high.
　比較例６の導電性多孔シートは繊維状物が多孔性のため、繊維が脆く、加圧くさびを２．６ｍｍ以上押し込むと応力が急激に低下し、破断するものであった。 In the conductive porous sheet of Comparative Example 6, since the fibrous material was porous, the fiber was fragile, and when the pressure wedge was pushed by 2.6 mm or more, the stress was drastically reduced and it was broken.
　これに対して、実施例１～４の結果から、本発明の導電性多孔シートは剛直な炭素繊維から構成されているにも関わらず、柔軟性に優れ、しかも機械的強度及び導電性の優れるものであった。柔軟性に優れているのは、炭素繊維同士が接合した交差点間において、炭素繊維が湾曲しているため曲げに対する応力を分散できるためであり、また、機械的強度及び導電性に優れているのは、炭素繊維同士の交差点が接合しているためであると考えられた。 On the other hand, from the results of Examples 1 to 4, the conductive porous sheet of the present invention is excellent in flexibility, and excellent in mechanical strength and conductivity, despite being composed of rigid carbon fibers. It was a thing. The excellent flexibility is because the carbon fibers are curved between the intersections where the carbon fibers are joined, so that the stress for bending can be dispersed, and the mechanical strength and conductivity are excellent. It was thought that this was because the intersections of the carbon fibers were joined.
　本発明の導電性多孔シートは機械的強度、導電性、及び柔軟性の優れるものであり、電極用基材として好適に用いることができる。例えば、リチウムイオン二次電池又は電気二重層キャパシタの電極として、また、固体高分子形燃料電池のガス拡散電極用基材として有用である。
　以上、本発明を特定の態様に沿って説明したが、当業者に自明の変法や改良は本発明の範囲に含まれる。 The conductive porous sheet of the present invention is excellent in mechanical strength, conductivity, and flexibility, and can be suitably used as an electrode substrate. For example, it is useful as an electrode of a lithium ion secondary battery or an electric double layer capacitor, and as a base material for a gas diffusion electrode of a polymer electrolyte fuel cell.
As mentioned above, although this invention was demonstrated along the specific aspect, the modification and improvement obvious to those skilled in the art are contained in the scope of the present invention.

Claims (6)

  1. 　炭素繊維を主体とし、炭素繊維同士が交差点で接合した導電性多孔シートであり、前記導電性多孔シートが三点曲げ試験において破断しないことを特徴とする、導電性多孔シート。 A conductive porous sheet comprising a conductive porous sheet mainly composed of carbon fibers and bonded to each other at intersections, and the conductive porous sheet does not break in a three-point bending test.
  2. 　炭素繊維が湾曲していることを特徴とする、請求項１記載の導電性多孔シート。 The conductive porous sheet according to claim 1, wherein the carbon fiber is curved.
  3. 　破断強度が０．３０ＭＰａ以上であることを特徴とする、請求項１又は２に記載の導電性多孔シート。 The conductive porous sheet according to claim 1, wherein the breaking strength is 0.30 MPa or more.
  4. 　電極用基材として用いる、請求項１～３のいずれか一項に記載の導電性多孔シート。 The conductive porous sheet according to any one of claims 1 to 3, which is used as an electrode substrate.
  5. 　請求項１～４のいずれか一項に記載の導電性多孔シートを、ガス拡散電極用基材として備えていることを特徴とする、固体高分子形燃料電池。 A solid polymer fuel cell comprising the conductive porous sheet according to any one of claims 1 to 4 as a base material for a gas diffusion electrode.
  6. 　第１炭化可能有機材料と、第１炭化可能有機材料とは異なる有機材料からなる第２炭化可能有機材料とを含む前駆繊維を形成する工程、
    前記前駆繊維の交差点を第１炭化可能有機材料又は第２炭化可能有機材料で接合して、前駆繊維を主体とする前駆繊維シートを形成する工程、
    前記前駆繊維シートを構成する前駆繊維を、その交差点で接合した状態のまま炭化して、湾曲した炭素繊維とする工程、
    を備えている、三点曲げ試験で破断しない導電性多孔シートの製造方法。     Forming a precursor fiber including a first carbonizable organic material and a second carbonizable organic material made of an organic material different from the first carbonizable organic material;
    Joining the intersections of the precursor fibers with a first carbonizable organic material or a second carbonizable organic material to form a precursor fiber sheet mainly composed of precursor fibers;
    A step of carbonizing the precursor fiber constituting the precursor fiber sheet in a state where the precursor fiber is bonded at the intersection, to obtain a curved carbon fiber;
    A method for producing a conductive porous sheet that does not break in a three-point bending test.
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