WO2014014055A1 - 多孔質電極基材、その製造方法、膜-電極接合体、及び固体高分子型燃料電池 - Google Patents
多孔質電極基材、その製造方法、膜-電極接合体、及び固体高分子型燃料電池 Download PDFInfo
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- 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
- H01M4/8663—Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
- H01M4/8668—Binders
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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
- D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
- D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
- D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
- D04H1/4209—Inorganic fibres
- D04H1/4242—Carbon fibres
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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
- D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
- D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
- D04H1/58—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives
- D04H1/60—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives the bonding agent being applied in dry state, e.g. thermo-activatable agents in solid or molten state, and heat being applied subsequently
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- 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
- H01M4/8605—Porous electrodes
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- 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
- H01M4/8825—Methods for deposition of the catalytic active composition
- H01M4/8846—Impregnation
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- 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
- H01M4/8875—Methods for shaping the electrode into free-standing bodies, like sheets, films or grids, e.g. moulding, hot-pressing, casting without support, extrusion without support
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- 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
- H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
- H01M4/8882—Heat treatment, e.g. drying, baking
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- 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
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
- H01M8/0234—Carbonaceous material
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- 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
- H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
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- 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
- H01M2008/1095—Fuel cells with polymeric electrolytes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0082—Organic polymers
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- 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
- H01M4/8803—Supports for the deposition of the catalytic active composition
- H01M4/8807—Gas diffusion layers
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- 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
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- 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 porous electrode base material that can be used in a fuel cell and the like, a method for producing the same, a membrane-electrode assembly including the porous electrode base material, and a polymer electrolyte fuel cell.
- porous electrode base material in which oxidized short fibers are made and then fired at a high temperature to carbonize the oxidized short fibers (Patent Document). 3).
- a mat comprising a plurality of carbon fibers for use in a gas diffusion electrode substrate; and a plurality of acrylic pulp fibers incorporated into the carbon fiber mat, the acrylic pulp fibers comprising a carbon fiber mat
- a gas diffusion layer for a fuel cell that is cured and carbonized after being incorporated into a gas
- a gas diffusion electrode substrate comprising a non-graphitized carbon fiber nonwoven network and a mixture of graphite particles and a hydrophobic polymer disposed in the nonwoven network, the graphite particles
- a porous electrode substrate having a longest dimension of at least 90% of less than 100 ⁇ m has been proposed (see Patent Document 6).
- porous electrode base material porous carbon electrode base material
- Patent Document 1 has sufficient gas permeability and conductivity, the manufacturing process is complicated, so the manufacturing cost is low. Tended to be higher.
- the porous electrode substrate disclosed in Patent Document 2 has excellent properties in terms of mechanical strength, surface smoothness, and gas permeability, and conductivity can be improved by adding carbon powder. Although it is high, the manufacturing process is complicated and the manufacturing cost tends to increase.
- the carbon fiber sheet (porous electrode base material) disclosed in Patent Document 3 can be reduced in cost, but according to the production method described in the same document, the shrinkage during firing may be large and obtained. In some cases, the thickness unevenness of the porous electrode substrate and the sheet waviness were large. When shrinkage or thickness unevenness occurs in the porous electrode base material, the performance is not uniform depending on the location of the base material, and the quality deteriorates. Further, when the swell of the porous electrode base material becomes large, the contact with other members in the fuel cell becomes insufficient, and there arises a problem that the performance and durability of the fuel cell are lowered.
- the porous electrode base material disclosed in Patent Document 4 can be reduced in cost, but the acrylic pulp used may have a low carbonization rate at the time of carbonization, in order to improve handling properties Required to add more acrylic pulp.
- the porous electrode substrate disclosed in Patent Document 5 has no carbonization step in the production process and can greatly reduce the cost.
- the fibril is composed of a water repellent material and a conductive material that bind carbon short fibers. In some cases, the conductivity of the split fiber having a portion is not sufficient, and the conductivity of the porous electrode substrate is low.
- the porous electrode substrate disclosed in Patent Document 6 is formed from short carbon fibers, carbon powder, and a fluororesin, and can reduce the cost because the carbonization step of firing at a high temperature can be omitted in the manufacturing process.
- there is no component that binds short carbon fibers and it is necessary to increase the amount of carbon powder and fluorine-based resin in order to increase sheet strength and electrical conductivity in the thickness direction, making it difficult to achieve both electrical conductivity and gas diffusibility. There was a problem that there was.
- the present invention overcomes the above problems, and provides a porous electrode substrate having a high sheet strength, a sufficient gas permeability and conductivity, and a low production cost, and a method for producing the same. Objective. Another object of the present invention is to provide a membrane-electrode assembly and a polymer electrolyte fuel cell using the porous electrode substrate.
- step (1) further includes a step (5) of heat and pressure molding in which the precursor sheet is heated below 200 ° C. and pressurized at a pressure of 20 kPa to 10 MPa.
- step (4) and the step (2) further includes a step (5) of heat and pressure molding in which the precursor sheet is heated below 200 ° C. and pressurized at a pressure of 20 kPa to 10 MPa.
- the step (6) further comprising a step (6) of drying the precursor sheet at a temperature of 70 ° C. or higher and lower than 150 ° C. between the step (2) and the step (3).
- the production method according to any one of [1] to [4].
- the fiber (b) is a fibrillar oxidation precursor fiber (b2) having a core part and a fibril part branched from the core part.
- the manufacturing method in any one.
- the difference between the maximum value and the minimum value of the height from the flat plate is 2 mm or less when the porous electrode substrate is placed on the flat plate so that the length is 250 mm and the width is 250 mm.
- the porous electrode substrate according to any one of [13] to [15].
- Gas permeability per unit thickness is 750 ml / hr / cm 2 / mmAq ⁇ mm or more, 2000 ml / hr / cm 2 / mmAq ⁇ mm or less, and penetration resistance per unit thickness is 0.18 m ⁇ ⁇ cm 2 / Mm or less, and the ratio of gas air permeability to penetration resistance is 260 ml / hr / cm 2 / mmAq / (m ⁇ ⁇ cm 2 ) or more. Electrode material.
- porous electrode base material is a three-dimensional entangled structure having a structure in which the oxidized fibers (B) are three-dimensionally entangled with each other.
- a membrane-electrode assembly comprising the porous electrode substrate according to any one of [12] to [18].
- a polymer electrolyte fuel cell comprising the membrane-electrode assembly according to [19].
- the aspect of the present invention has the following other aspects.
- the manufacturing method of the porous electrode base material which has the process (3) heat-processed at the temperature below degrees C.
- the fiber (b) containing a granular material having a softening point of 250 ° C. or more and less than 400 ° C. and having a melting point of 400 ° C. or more is made of a polymer having a softening point of 250 ° C. or more and less than 400 ° C. and having a melting point of 400 ° C. or more.
- the fiber (b) containing a granular material having a softening point of 250 ° C. or more and less than 400 ° C. and having a melting point of 400 ° C. or more is made of a polymer having a softening point of 250 ° C. or more and less than 400 ° C. and having a melting point of 400 ° C. or more.
- Oxidized fiber precursor short fiber (b1) containing a particulate material and / or a fibrillated oxidized precursor fiber containing a granular material having a softening point of 250 ° C. or higher and lower than 400 ° C. and a melting point of 400 ° C. or higher The production method according to any one of the above, which is b2).
- It consists of fluorocarbon resin containing short-melting-point carbon short fibers (A), oxidized fibers (B) containing a granular material having a melting point of 400 ° C. or higher, and carbon powder (C2), and is porous having a length of 250 mm and a width of 250 mm on a flat plate
- a porous electrode substrate in which the difference between the maximum value and the minimum value of the height from the flat plate of the porous electrode substrate when the electrode substrate is allowed to stand is 2 mm or less.
- the aspect of the present invention has the following other aspects.
- the short carbon fibers (A) are joined together via the oxidized fiber (B) containing the carbon powder (C1), and the short carbon fibers (A) are further bonded to the carbon powder (C2). ) Containing a porous electrode base material bonded with a fluororesin.
- the carbon short fibers (A) are joined to each other via the carbon powder (C1), and the carbon short fibers (A) and the oxidized fiber (B) containing the carbon powder (C1) are combined with carbon powder (C2). ) Containing a porous electrode base material bonded with a fluororesin.
- the short carbon fibers (A) are joined to each other via the oxidized fibers (B) containing the carbon powder (C1), and the short carbon fibers (A) are joined to each other by a fluorine resin containing the carbon powder (C2).
- a porous electrode substrate having high sheet strength, sufficient gas permeability and conductivity, and low manufacturing cost can be obtained.
- a porous electrode substrate having the above-described advantages can be produced at a low cost.
- fiber (b) containing a granular material having a melting point of 400 ° C. or higher and containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. “containing a granular material having a melting point of 400 ° C. or higher” Fiber (b) "or” fiber (b) ".
- oxidized fiber (B) containing a granular material having a melting point of 400 ° C. or higher may be referred to as “oxidized fiber (B)”.
- the porous electrode substrate according to the present embodiment is made of a short carbon fiber (A), an oxidized fiber (B) containing a granular material having a melting point of 400 ° or more, and a fluororesin containing carbon powder (C2). In general, it is composed.
- the fiber (b) is composed of a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. and a granular material having a melting point of 400 ° C. or higher.
- the “oxidized fiber (B) precursor fiber containing” it has the following structure mainly through each step in the production method described later.
- the porous electrode substrate according to the present embodiment can have the following (I) to (III) and a combination thereof. It should be noted that structures other than the following (I) to (III) can be taken.
- the carbon short fibers (A) are bonded to each other via oxidized fibers (B) containing granular materials having a melting point of 400 ° C. or higher, and the carbon short fibers (A) are further bonded to the fluororesin.
- the short carbon fibers (A) are bonded to each other via oxidized fibers (B) containing granular materials having a melting point of 400 ° C. or higher, and the oxidized fibers (B) are made of the fluororesin.
- the carbon short fibers (A) are bonded to each other via oxidized fibers (B) containing granular materials having a melting point of 400 ° C. or higher. Further, the carbon short fibers (A) and the oxidized fibers ( B) and a portion formed by bonding with each other by the fluororesin.
- the porous electrode substrate of this embodiment may form a three-dimensional entangled structure.
- the porous electrode base material is a three-dimensional entangled structure, which includes short carbon fibers (A) constituting the structure and a granular material having a melting point of 400 ° C. or higher by an entanglement process described later.
- Oxidized fibers (B) that are entangled with each other and joined together, so that the short carbon fibers (A) and the oxidized fibers (B) containing particulate matter having a melting point of 400 ° C. or higher are three-dimensional of the porous electrode substrate.
- the porous electrode substrate is a sheet or plate
- the longitudinal direction of the oxidized fiber (B) extends not only in the plane direction but also in the thickness direction. Means an (orientated) structure.
- the shape of the porous electrode substrate can be selected as necessary from known shapes in the field of fuel cells, and can be, for example, a sheet shape or a spiral shape.
- the porous electrode substrate of this embodiment has extremely small undulations.
- the term “swell” is small, for example, when the sheet is formed into a sheet shape, the plane direction is flat and there are few irregularities (a wrinkle or a curve in the thickness direction of the sheet). More specifically, when the sheet-like porous electrode substrate having a length of 250 mm and a width of 250 mm is left on the flat plate, the difference between the maximum value and the minimum value of the height of the porous electrode substrate from the flat plate is 2 mm. Or less, preferably 1 mm or less. As will be described later, this small swell can be heat-treated at 250 to 400 ° C.
- the porous electrode substrate of the present embodiment has an advantage that the contact with other members is sufficient in the fuel cell due to the small undulation, and the performance and durability of the fuel cell are improved.
- the basis weight of the sheet-like porous electrode substrate is preferably 15 g / m 2 or more and 100 g / m 2 or less.
- the basis weight is the weight per unit area.
- gas permeability and handling properties are improved.
- the porosity of the sheet-like porous electrode substrate is preferably 50% or more and 90% or less.
- the porosity is calculated by, for example, a porosimeter or a density meter. In this range, gas permeability and conductivity are good.
- the thickness of the sheet-like porous electrode substrate is preferably 50 ⁇ m or more and 300 ⁇ m or less. In this range, the gas permeability and handling properties are good.
- the porosity of the porous electrode substrate means that the surface and the inside are porous and have a high porosity as described above.
- the gas air permeability of the porous electrode substrate 100ml / hr / cm 2 / mmAq or more is preferably not more than 30000ml / hr / cm 2 / mmAq . In this range, good gas diffusibility can be expressed inside the fuel cell using the porous electrode substrate.
- the electrical resistance (penetration direction resistance) of the thickness direction of a porous electrode base material is 50 m (ohm) * cm ⁇ 2 > or less.
- the electrical resistance (through-direction resistance) is measured, for example, when measuring a sheet-like porous electrode base material, with pressure applied so that the porous electrode base material is in close contact with the electrode plate with the porous electrode base material sandwiched between the electrode plates.
- the gas air permeability of the porous electrode base material and the gas air permeability per unit thickness of the porous electrode base material are calculated from the gas air permeability and thickness.
- a measuring method based on ISO-5636-5 can be mentioned.
- this measurement method there is a means for measuring the time taken for 200 mL of air to permeate using a Gurley densometer and calculating the gas air permeability (ml / hr / cm 2 / mmAq). is there.
- the gas air permeability per unit thickness of the porous electrode substrate is preferably 750 ml / hr / cm 2 / mmAq ⁇ mm or more and 2000 ml / hr / cm 2 / mmAq ⁇ mm or less. In this range, good gas diffusibility can be expressed inside the fuel cell using the porous electrode substrate.
- the penetration direction resistance per unit thickness of the porous electrode substrate is preferably 0.18 m ⁇ ⁇ cm 2 / mm or less. In this range, good conductivity can be expressed inside the fuel cell using the porous electrode substrate.
- the ratio between the gas permeability and the penetration resistance is preferably 260 ml / hr / cm 2 / mmAq / (m ⁇ ⁇ cm 2 ) or more. In this range, it is possible to achieve both gas diffusivity and conductivity of a fuel cell using a porous electrode substrate. Furthermore, all of the above-mentioned advantages can be obtained by satisfying all three preferable ranges of the gas permeability per unit thickness, the penetration resistance per unit thickness, and the ratio of the gas permeability and penetration resistance. Therefore, it is more preferable.
- porous electrode substrate of the present embodiment include the following (i) to (v).
- a porous electrode substrate having a difference between a maximum value and a minimum value from a flat plate of 2 mm or less when allowed to stand on top.
- Gas permeability per unit thickness is 750 ml / hr / cm 2 / mmAq ⁇ mm or more, 2000 ml / hr / cm 2 / mmAq ⁇ mm or less, and penetration resistance per unit thickness is 0.18 m ⁇ ⁇ cm 2
- the manufacturing method of the porous electrode base material which concerns on this embodiment does not include the carbonization process of 1000 degreeC or more, manufacturing cost is low.
- the porous electrode base material according to the present embodiment can be manufactured without a carbonization step of 1000 ° C. or higher, and thus becomes a porous electrode base material with low manufacturing cost.
- the porous electrode base material of this embodiment does not contain a carbide of resin that bonds (bonds) the short carbon fibers (A). Therefore, the porous electrode substrate of the present invention is a fluororesin containing carbon fiber (A) and oxidized fiber (B) containing carbonaceous particles (C2) and a granular material having a flexible melting point of 400 ° C. or higher.
- the flexibility is large and the deformation amount inside the fuel cell is reduced. Can be bigger.
- the short carbon fiber (A) dispersed in the precursor sheet becomes one of the fibers constituting the porous electrode substrate.
- the short carbon fibers (A) include those obtained by cutting carbon fibers such as polyacrylonitrile-based carbon fibers (hereinafter referred to as “PAN-based carbon fibers”), pitch-based carbon fibers, and rayon-based carbon fibers into a predetermined fiber length. Is mentioned.
- the short carbon fiber (A) is preferably a PAN-based carbon fiber. By using a PAN-based carbon fiber for the short carbon fiber (A), the mechanical strength of the porous electrode substrate can be obtained.
- the average fiber length of the short carbon fibers (A) is preferably 2 mm or more and 12 mm or less from the viewpoint of dispersibility. Furthermore, the average fiber diameter of the short carbon fibers (A) is more preferably 3 ⁇ m or more and 9 ⁇ m or less. Within this range, the dispersibility of the short carbon fibers is further improved, and the production cost is also improved. The average fiber diameter of the short carbon fibers (A) is more preferably 4 ⁇ m or more and 8 ⁇ m or less. In this range, the smoothness of the porous electrode substrate is good. In addition, the average fiber diameter of a carbon short fiber (A) can be measured with an optical microscope or an electron microscope.
- the short carbon fiber (A) that is one fiber constituting the porous electrode base material is dispersed in the porous electrode base material.
- “dispersed in the porous electrode substrate” means that the direction of the short carbon fibers (A) (long direction) is substantially parallel to the surface of the sheet-like porous electrode substrate. Or it may exist in the thickness direction of the porous electrode substrate. Further, the orientation direction of the short carbon fibers (A) substantially parallel to the surface of the sheet-like porous electrode substrate may be substantially random, and the orientation in a specific direction is high. May be.
- the short carbon fibers (A) are present in the porous electrode substrate while maintaining a substantially straight shape (for example, the fiber shape is a straight line). Further, in the porous electrode substrate, the short carbon fibers (A) are not directly chemically bonded or joined together, but are joined by oxidized fibers (B) containing granular materials having a melting point of 400 ° C. or higher. Yes.
- the content of the short carbon fiber (A) in the porous electrode substrate is 40% by mass or more based on the total of the short carbon fiber (A) and the oxidized fiber (B) containing a granular material having a melting point of 400 ° C. or higher. 90 mass% or less is preferable.
- the content of the short carbon fiber (A) is sufficient to maintain the mechanical strength of the porous electrode base material and to provide sufficient penetration direction resistance. 50 mass% or more and 90 mass% or less are more preferable with respect to the total mass of the oxidation fiber (B) containing a granular material whose melting
- the oxidized fiber (B) containing a particulate material having a melting point of 400 ° C. or higher is a fiber that joins the carbon short fibers (A) to each other in the porous electrode substrate.
- Oxidized fibers (B) are present in a bent or curved state at the joint where the carbon short fibers (A) are joined in the porous electrode substrate.
- the oxidized fiber means that the fiber is oxidized by heating and pressurizing, causing the polymer used to react with oxygen.
- the oxidized fibers (B) preferably form a network structure that is entangled with each other not only in the planar direction of the porous electrode substrate but also in the thickness direction. In this structure, the handling property and conductivity of the porous electrode substrate are good.
- the content of the oxidized fiber (B) containing the particulate material having a melting point of 400 ° C. or higher in the porous electrode substrate is 10% by mass or more based on the total mass of the short carbon fiber (A) and the oxidized fiber (B). 60 mass% or less is preferable.
- the content of the oxidized fiber (B) is more preferably 10% by mass or more and 50% by mass or less with respect to the total of the short carbon fiber (A) and the oxidized fiber (B). In this range, the mechanical strength of the porous electrode substrate can be kept sufficient, and a sufficient penetration direction resistance can be obtained.
- Oxidized fiber (B) containing a granular material having a melting point of 400 ° C. or higher is oxidized (oxidation treatment) by a heat treatment in step (3) to be described later on (b) containing a granular material having a melting point of 400 ° C. or higher. Is obtained. Therefore, the oxidized fiber (B) is an oxidized fiber derived from the fiber (b).
- the oxidized fiber (B) contains a particulate material having a melting point of 400 ° C. or higher. As will be described later, the presence of the particulate material makes the conductivity and productivity of the porous electrode substrate good.
- the content of the particulate material having a melting point of 400 ° C. or higher in the oxidized fiber (B) is preferably 10% by mass or more and 90% by mass or less with respect to the entire mass including the polymer of the oxidized fiber (B).
- the fiber (b) will be described later.
- a granular material having a melting point of 400 ° C. or higher that can be used in this embodiment will also be described later.
- the oxidized fiber (B) containing a granular material having a melting point of 400 ° C. or higher is a fiber obtained by oxidizing a fiber (b) containing a granular material having a melting point of 400 ° C. or higher, which will be described later, and used for the fiber (b).
- the polymer (polymer) which can be oxidized is contained. Examples of such a polymer include an oxidative polymer such as an acrylic polymer, a cellulose polymer, and a phenol polymer.
- a precursor sheet in which short carbon fibers (A) and fibers (b) containing a granular material having a melting point of 400 ° C. or higher are dispersed in the plane direction ( According to 1)>, a precursor sheet can be produced.
- This precursor sheet is a sheet that becomes a precursor of the porous electrode substrate.
- the precursor sheet obtained in step (1) described later is a precursor sheet in which short carbon fibers (A) and fibers (b) containing a granular material having a melting point of 400 ° C. or higher are dispersed.
- the precursor sheet comprises short carbon fibers (A) and fibers (b) containing particulate matter having a melting point of 400 ° C. or higher.
- seat of this invention does not contain sheet-like binders, such as polyvinyl alcohol (PVA) and polyvinyl acetate, from a viewpoint of reduction of manufacturing cost and expression of electroconductivity.
- the fiber (b) contains a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. substantially consisting of this polymer (mainly composed of this polymer excluding impurities. Or a mixture containing this polymer is adjusted to a softening point of 250 ° C. or higher and lower than 400 ° C.
- the short carbon fiber (A) is subjected to a heat treatment at a temperature of 250 ° C. or higher and lower than 400 ° C.
- the fiber shape can be maintained when bonding the electrodes, thereby suppressing the undulation of the porous electrode substrate.
- the softening point of the polymer contained in the fiber (b) is less than 250 ° C.
- the fiber form cannot be maintained in the heat treatment step at a temperature of 250 ° C. or more and less than 400 ° C. in the presence of oxygen, and the fiber shrinks. And a large undulation occurs in the porous electrode substrate.
- the softening point of the polymer contained in the fiber (b) is 400 ° C. or higher
- the short carbon fiber (A) can be bonded in the step of heat treatment at a temperature of 250 ° C. or higher and lower than 400 ° C. in the presence of oxygen. Therefore, the resistance of the porous electrode base material increases and the mechanical strength decreases.
- the dispersion state of the particulate material having a melting point of 400 ° C. or higher in the fiber is not particularly limited, and it may be uniformly dispersed in the fiber or may be localized in the core portion or the fiber surface portion.
- the porous electrode substrate of the present embodiment is manufactured by a manufacturing method described later.
- the precursor sheet is heat-treated at a temperature of 250 to 400 ° C. in the presence of oxygen as described later. It is manufactured by doing. Therefore, in order that the porous electrode substrate after the heat treatment step maintains the shape of the sheet and does not generate swell, the fiber constituting the fiber (b) which is a constituent component of the precursor sheet has a softening point. It is essential to contain a polymer having a temperature of 250 ° C. or higher and lower than 400 ° C. (consisting essentially of this polymer).
- an oxidized fiber precursor fiber containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. which will be described later, and a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C.
- an oxidized fiber precursor fiber containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. is preferable.
- the fiber containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. does not contain a granular material having a melting point of 400 ° C. or higher. Large deformation occurs due to heat treatment at temperature. If the fiber that is a constituent component of the precursor sheet is greatly deformed, a problem of waviness of the porous electrode substrate may occur when the porous electrode substrate is manufactured. Therefore, in the present invention, the fiber (b) is largely deformed as described above by incorporating a granular material having a melting point of 400 ° C. or higher into a fiber containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. Shrinkage can be prevented, and as a result, the occurrence of waviness of the porous electrode substrate can be suppressed.
- an oxidized fiber precursor containing a polymer having a softening point described later of 250 ° C. or higher and lower than 400 ° C. and containing a granular material having a melting point of 400 ° C. or higher.
- oxidized fiber precursor short fiber (b1) containing a polymer having a softening point of 250 ° C. or more and less than 400 ° C. and a melting point of 400 ° C. or more is referred to as “melting point of 400 ° C. or more”.
- oxidized fiber precursor short fiber (b1) or “oxidized fiber precursor short fiber (b1)” containing particulate matter.
- a fibrillated oxidized fiber precursor fiber (b2) containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. and a melting point of 400 ° C. or higher” is referred to as “melting point of 400 ° C. or higher.
- the fiber (b) containing a granular material having a melting point of 400 ° C. or higher uses only one of the above-described constituent materials and physical properties as the fiber (b) containing a granular material having a melting point of 400 ° C. or higher. May be.
- a plurality of different fibers may be used in combination. For example, even in fibers using the same material as the constituent material of the particulate material and the polymer, the mass ratio of the polymer to the particulate material is different, and the freeness evaluation value (measured by the freeness evaluation described later) is different.
- a plurality of materials having different fiber diameters may be used in combination. Furthermore, you may use together these fiber from which the kind of polymer or the constituent material (carbon powder seed
- the fiber (b) containing a granular material having a melting point of 400 ° C. or higher can be configured to contain a granular material having a melting point of 400 ° C. or higher and a polymer (polymer).
- the content of the particulate matter having a melting point of 400 ° C. or more in the fiber (b) containing the particulate matter having a melting point of 400 ° C. or more is 10% by mass or more and 90% by mass or less with respect to the mass of the entire fiber (b). Preferably there is. In this range, sufficient fiber strength of the fiber (b) and conductivity after heat treatment can be obtained. Further, the upper limit of the content of the particulate material having a melting point of 400 ° C.
- the polymer used for the fiber (b) containing the granular material having a melting point of 400 ° C. or higher is a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C.
- a heat treatment step (step (2 described later)
- the residual mass in)) is preferably 60% by mass or more. In this mass range, the mechanical strength of the porous electrode substrate can be kept sufficient, and the environmental load can be reduced.
- the residual mass in the heat treatment step (step (3) described later) is preferably 80% by mass or more. In this case, the maximum residual mass of the polymer after heat treatment is considered to be 100% by mass, so the range of the residual mass of the polymer is preferably 60 to 100% by mass, and particularly preferably 80 to 100% by mass.
- polymers examples include acrylonitrile polymers (acrylonitrile polymers), cellulose polymers, phenol polymers, and tetrafluoroethylene polymers. From the viewpoint of reducing production costs, acrylonitrile polymers (acrylonitrile polymers) can be used. Coalesced), cellulosic polymers and phenolic polymers. These polymers may be used alone or as a mixture comprising a plurality of polymer species. When used as a mixture, when one or more types of polymers have a residual mass of 60% by mass or more in the heat treatment step (step (3) described later), the other polymer to be mixed is a heat treatment step (step (3) described later). ) May be 60% by mass or less.
- polymers when used as a mixture, when one or more types of polymers are polymers having a softening point of 250 ° C. or higher and lower than 400 ° C., other polymers to be mixed may not be polymers having a softening point of 250 ° C. or higher and lower than 400 ° C. good.
- a polymer is not particularly limited, and a methacrylic acid polymer, an acrylic acid polymer, a vinyl polymer, a cellulose polymer, a styrene polymer, and the like can be used.
- the carbon short fibers (A) can be bonded to each other from spinnability and low temperature to high temperature, and the residual amount in the heat treatment step In view of the large size, the entanglement with the short carbon fibers (A), and the sheet strength, it is preferable to use an acrylonitrile-based polymer.
- the acrylonitrile-based polymer may be an acrylonitrile-based polymer (homopolymer) obtained by homopolymerizing acrylonitrile, or an acrylonitrile-based polymer (copolymer) obtained by copolymerizing acrylonitrile and other monomers.
- the acrylonitrile-based polymer preferably contains 50% by mass or more, more preferably 80% by mass or more, based on the total mass of the acrylonitrile-based polymer. With this range, the fiber (b) can be spun. Also, mechanical strength can be obtained after heat treatment of the porous electrode substrate. That is, the content of acrylonitrile units is preferably 50 to 100% by mass, and more preferably 80 to 100% by mass.
- the monomer copolymerized with acrylonitrile is not particularly limited as long as it is an unsaturated monomer constituting a general acrylic fiber.
- Methacrylic acid esters acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, N-methylol acrylamide, diacetone acrylamide, styrene, vinyl toluene, vinyl acetate, vinyl chloride, vinylidene chloride, vinylidene bromide, vinyl fluoride, And vinylidene fluoride.
- the residual mass of the acrylonitrile-based polymer is preferably 60 to 100% by mass in the heat treatment step (step (2) described later).
- the weight average molecular weight of the acrylonitrile polymer is not particularly limited, but is preferably 50,000 to 1,000,000.
- the weight average molecular weight of the acrylonitrile-based polymer is 50,000 or more, the spinnability is improved and the yarn quality of the fiber tends to be improved. Further, when the weight average molecular weight of the acrylonitrile-based polymer is 1,000,000 or less, the polymer concentration that gives the optimum viscosity of the spinning dope increases, and the productivity tends to improve.
- fusing point is 400 degreeC or more is not specifically limited,
- the fibrillated oxidized fiber precursor fiber (b2) containing a granular material having a melting point of 400 ° C. or higher can be used as the fiber (b) containing a granular material having a melting point of 400 ° C. or higher.
- Fibrous fibers such as fibrillar carbon precursor fibers (b2) containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C.
- the acrylonitrile-based polymer can be one or both of an acrylonitrile homopolymer and an acrylonitrile copolymer of acrylonitrile and the other monomers described above.
- the fiber (b) is "an oxidized fiber precursor fiber containing a polymer having a softening point of 250 ° C or higher and lower than 400 ° C and a melting point of 400 ° C or higher"
- the fiber (b) is of the type Depending on the mixing ratio of the granular material and the polymer, and further the mixing ratio of the short carbon fibers (A), the mass of the first fiber (b) and the melting point of 400 ° C. in the finally obtained porous electrode substrate
- the ratio (ratio) of the mass remaining as the oxidized fiber (B) containing the above granular material is different.
- the short carbon fiber (A) and the fiber (b) containing the granular material having a melting point of 400 ° C. or higher are based on the total of the short carbon fiber (A) and the fiber (b) containing the granular material having a melting point of 400 ° C. or higher. 10 mass% or more and 90 mass% or less is preferable.
- the content rate of the fiber (b) containing the granular material having a melting point of 400 ° C. or higher in the precursor sheet is the short carbon fiber (A) and the fiber (b) containing the granular material having a melting point of 400 ° C. or higher in the precursor sheet. 10 mass% or more and 60 mass% or less are more preferable with respect to the total mass of. In this range, the mechanical strength of the porous electrode substrate can be kept sufficient, and the penetration resistance can be made sufficient.
- the fiber containing the polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. is shrunk in the heat treatment at a temperature of 250 to 400 ° C. in the step (2) of the production method described later,
- the granular material In order to suppress the occurrence of undulation of the porous electrode substrate, it is contained in a fiber containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. That is, the granular material must be able to maintain its shape by heat treatment in step (2) described later.
- the melting point of the particulate material needs to exceed the softening point of the polymer. Specifically, it is necessary to be 400 ° C. or higher, preferably 500 ° C. or higher which is 100 ° C. higher than the softening point. The higher the melting point of the granular material, the better, but it is usually 4000 ° C. or lower. That is, as an example of the particulate material, particles having a melting point of 400 to 4000 ° C., preferably 500 to 4000 ° C., more preferably 3000 to 4000 ° C. can be used. For example, the carbon black used in this embodiment has a melting point of about 3550 ° C.
- Examples of the particulate material having a melting point of 400 ° C. or higher include carbon powder (C1), silica, titania, and the like, and carbon powder (C1) is preferable from the viewpoint of expressing the conductivity of the porous electrode substrate.
- Carbon powder (C1) is a powder mainly composed of carbon. Although it does not specifically limit as carbon powder (C1), Carbon black, graphite powder, carbon fiber milled fiber, activated carbon, nanocarbon, etc. can be used. Carbon black or a mixture of carbon black and graphite powder is preferably used in terms of conductivity and cost.
- the carbon powder (C1) contains at least carbon black.
- Carbon black generally exists as a structure (ageromate) in which primary particles having an average particle diameter of several tens of nanometers are fused together to form a structure, and the structures are bonded by van der Waalska.
- Carbon black has a remarkably larger number of particles per unit mass than graphite powder, and at a certain critical concentration or higher, agelatomate forms a three-dimensional network to form a macroscopic conductive path. Therefore, the use of carbon black for the carbon powder (C1) further improves the conductivity of the porous electrode substrate.
- the ratio of carbon black contained in the carbon powder is more preferably in the range of 70 to 100% by mass, and particularly preferably in the range of 80 to 90% by mass with respect to the entire carbon powder.
- graphite powder as carbon powder. Since the graphite powder has a highly crystalline graphite structure, it exhibits high conductivity.
- the average particle diameter of primary particles of graphite powder is generally several micrometers to several hundred micrometers.
- the ratio of the graphite powder contained in the carbon powder is preferably in the range of 10 to 20% by mass with respect to the mass of the entire carbon powder.
- carbon black for example black, channel black, acetylene black, lamp black, thermal black, ketjen black, etc. can be used, but acetylene black or ketjen black excellent in electrical conductivity and dispersibility is more preferable, From the viewpoint of conductivity, ketjen black is particularly preferable.
- graphite powder pyrolytic graphite, spherical graphite, flake graphite, massive graphite, earthy graphite, artificial graphite, expanded graphite, and the like can be used, and pyrolytic graphite or spherical graphite having excellent conductivity is preferable.
- the primary particles of the oxidized fiber (B) containing a granular material having a melting point of 400 ° C. or higher and the granular material having a melting point of 400 ° C. or higher in the fiber (b) containing a granular material having a melting point of 400 ° C. or higher are uniform in primary particles. Even if it is dispersed in the primary particles, the primary particles may be aggregated. In addition, the primary particles and aggregates of the particulate material may be uniformly dispersed or localized in the oxidized fiber (B) and the fiber (b).
- the core is localized in the center of the fiber (for example, the core is localized near the central axis in the radial cross section of the substantially cylindrical fiber).
- the one having a shell structure or the one having a core-shell structure localized in the fiber surface layer portion can be used. From the viewpoint of improving the electrical conductivity and mechanical strength of the porous electrode substrate, it is preferable to form a core-shell structure in which carbon powder (C1) is localized in the fiber surface layer.
- the content of the particulate material having a melting point of 400 ° C. or higher in the fiber (b) containing the granular material having a melting point of 400 ° C. or higher is preferably 10% by mass or more and 90% by mass or less. This range provides sufficient fiber strength for the fiber (b). Further, the upper limit of the average content of the granular material having a melting point of 400 ° C. or higher is desirably high within a range where spinning is possible, but 70% by mass or less is particularly preferable from the viewpoint of spinning stability at the fiber production stage. When carbon powder (C1) is used as a granular material having a melting point of 400 ° C.
- the average content of carbon powder (C1) in this fiber (b) is from the viewpoint of sufficient fiber strength and electrical conductivity. It is preferable that it is 10 mass% or more and 90 mass% or less with respect to the whole mass of the fiber (b) including a polymer etc.
- the content of the granular material having a melting point of 400 ° C. or higher in the localized portion is the fiber (b) from the viewpoint of conductivity. It is preferable that it is 60 to 90 mass% with respect to the whole mass. Further, the content of the particulate material is particularly preferably 70% by mass or more and 90% by mass or less with respect to the entire mass of the fiber (b).
- the oxidized fiber precursor short fiber (b1) containing a granular material having a melting point of 400 ° C. or higher can be produced using the above-mentioned acrylonitrile polymer (acrylonitrile polymer), cellulose polymer, or phenol polymer as a raw material.
- acrylonitrile polymer acrylonitrile polymer
- cellulose polymer cellulose polymer
- phenol polymer a raw material for oxidized fiber precursor fibers.
- a general spinning method using a granular material having a melting point of 400 ° C. or higher and a polymer that can be used as a raw material for oxidized fiber precursor fibers.
- a spinning stock solution in which an acrylonitrile-based polymer and a granular material having a melting point of 400 ° C. or higher are dissolved in a solvent or dispersed in a dispersion medium a dry method or a wet method is used.
- a long fiber can be produced by spinning using a known spinning
- the oxidized fiber precursor short fiber (b1) can be obtained by cutting a long-fiber oxidized fiber precursor fiber containing a granular material having a melting point of 400 ° C. or higher into an appropriate length.
- the average fiber length of the oxidized fiber precursor short fiber (b1) containing a granular material having a melting point of 400 ° C. or higher is preferably 2 mm or more and 20 mm or less from the viewpoint of dispersibility.
- the average fiber length can be measured by measuring the fiber length of a plurality of fibers (for example, 20 to 100 fibers, 50 in this embodiment) with an optical microscope and an electron microscope, and obtaining the average. it can.
- the cross-sectional shape of the oxidized fiber precursor short fiber (b1) containing a granular material having a melting point of 400 ° C. or higher is not particularly limited, and one having a high roundness or one having an irregular cross-sectional shape may be used.
- the average diameter of the oxidized fiber precursor short fiber (b1) containing a granular material having a melting point of 400 ° C. or higher is 20 ⁇ m or less. In this range, the mechanical strength of the porous electrode substrate can be kept sufficient.
- the average fiber diameter (diameter) of the fiber is measured by measuring the fiber length of a plurality of fibers (50 in this embodiment) in the same manner as described above using an optical microscope and an electron microscope, and calculating the average. Can do.
- An example of the oxidized fiber precursor fiber (b1) includes an oxidized fiber precursor fiber (b) containing the above-described carbon powder (C1).
- the fibrillated oxidized fiber precursor fiber (b2) containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. and containing a granular material having a melting point of 400 ° C. or higher for example, the following can be used.
- Oxidized fiber precursor fiber (b2-1) containing a polymer having a softening point of 250 ° C. or more and less than 400 ° C., having a structure in which many fibrils are branched, and having a melting point of 400 ° C. or more” Sometimes referred to as “oxidized fiber precursor fiber (b2-1)”.
- the oxidized fiber precursor fiber (b2-1) is 0.05 ⁇ m in diameter from a fibrous trunk (core body) having a diameter (average fiber diameter measured by the above-described method) of 3 ⁇ m or more and 100 ⁇ m or less.
- a large number of fibrils of 5 ⁇ m or less for example, 0.1 to 3 ⁇ m
- branched for example, 10 to 100 fibrils per core.
- the fibrillated oxidized fiber precursor fiber (b2) containing a granular material having a melting point of 400 ° C. or higher, the carbon fiber (A) and the granular material having a melting point of 400 ° C. or higher are contained in the precursor sheet.
- the fibrillated oxidized fiber precursor fibers (b2) to be entangled well, and it becomes easy to obtain a precursor sheet having excellent handling properties and mechanical strength.
- the freeness of the fibrillated oxidized fiber precursor fiber (b2) containing a particulate material having a melting point of 400 ° C. or higher is not particularly limited, but generally the freeness is not limited.
- the mechanical strength of the precursor sheet is improved, but the gas permeability of the porous electrode substrate tends to decrease.
- the fibrillated oxidized fiber precursor fiber (b2) containing a granular material having a melting point of 400 ° C. or higher has the above-described constituent materials and physical characteristics as oxidized fiber precursor fibers (b2-1) or (b2-2). Only one type may be used. Further, a plurality of these oxidized fiber precursor fibers (b2-1) or (b2-2) may be used in combination. For example, even in fibers using the same material as the constituent material of the particulate material and the polymer, the mass ratio of the polymer to the particulate material is different, and the freeness evaluation value (measured by the freeness evaluation described later) is different. A plurality of materials having different fiber diameters may be used in combination.
- the method for producing the oxidized fiber precursor fiber (b2-1) having a granular material having a melting point of 400 ° C. or higher is also not particularly limited, but is produced using a jet coagulation method with easy control of the freeness described later. It is preferable to do.
- the oxidized fiber precursor fiber (b2-1) can be produced by the following method using the apparatus shown in FIG.
- a spinning stock solution in which a raw material (for example, acrylonitrile polymer and carbon black) of the oxidized fiber precursor fiber (b2-1) is dissolved in a solvent or dispersed in a dispersion medium is discharged into a mixing cell through a spinning discharge port, Fibrous carbon precursor fiber raw material containing water vapor injected into the mixing cell at an angle of 0 ° or more and less than 90 ° with respect to the discharge line direction of the spinning dope, and containing a granular material having a melting point of 400 ° C. or more in the mixing cell Solidify under shear flow rate.
- a raw material for example, acrylonitrile polymer and carbon black
- a fibrillated carbon precursor fiber containing carbon powder is obtained by discharging the formed solidified body together with the solvent or dispersion medium and water vapor from the mixing cell into the solidified liquid.
- the coagulation liquid water or a mixed liquid of water and the above-mentioned solvent or dispersion medium can be used.
- the particulate material having a melting point of 400 ° C. or higher may be dispersed substantially uniformly or locally in the acrylonitrile-based polymer.
- the oxidized fiber precursor fiber (b2-1) thus obtained has a fibril part in which fibers having a small fiber diameter gathered and a trunk having a large fiber diameter (stem part, core part) solidified without much contact with water vapor.
- the fibril part of the oxidized fiber precursor fiber (b2-1) includes the entanglement between the oxidized fiber precursor fiber (b2-1) and the short carbon fiber (A), and the fibril part of the oxidized fiber precursor fiber (b2-1).
- the entanglement with each other is good, and the trunk of the oxidized fiber precursor fiber (b2-1) can exhibit strength as a binder.
- the fiber diameter of the fibril part is preferably 2 ⁇ m or less in order to improve the entanglement with the short carbon fibers to be mixed.
- the fiber diameter of the fibril part is preferably 0.05 to 2 ⁇ m.
- the trunk (core portion) preferably has a diameter (value measured in the same manner as the average fiber diameter of the fibers) of 100 ⁇ m or less.
- a diameter value measured in the same manner as the average fiber diameter of the fibers
- the diameter of a core part is 10 micrometers or more from a viewpoint of expressing intensity
- the oxidized fiber precursor fiber (b2-1) preferably has a plurality of fibril parts with respect to one core part, and it is considered that the more fibril parts with respect to one core part, the more preferable. There are many fibril parts present per core part (as a guide, there are 10 to 100 fibril parts per core part), and the function that the oxidized fiber precursor fiber (b2-1) is entangled with the short carbon fiber. Get higher.
- the thickness of the core is constant or changes steplessly. Thereby, it can prevent easily that the level
- the oxidized fiber precursor fiber (b2-1) is produced by the above method, it is often difficult to keep the thickness of the core portion constant because water vapor randomly scatters. May change in thickness. However, a gradual change in the thickness of the core tends to be seen when the water vapor to be sprayed cools into droplets, increasing the water vapor ejection pressure and increasing the temperature, etc. By the method, it is possible to easily prevent the thickness of the core portion from changing stepwise.
- a method for producing an oxidized fiber precursor fiber (b2-2) containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. and containing a granular material having a melting point of 400 ° C. or higher fibrillated by beating is not particularly limited.
- a fibrillated easily split fiber sea-island composite fiber cut to a fiber length described later is beaten with a refiner or a pulper to be fibrillated.
- Long-fiber easily splittable sea-island composite fibers are composed of two or more types of constituent compounds or polymers with different physical properties such as fiber length and fiber diameter that are incompatible with each other and are incompatible. ) Can be used.
- the polymer described above is preferably used as one of the polymers used for the easily split sea-island composite fiber.
- the other polymer includes the acrylonitrile-based polymer and It is desired that a spinning stock solution that dissolves in a common solvent and dissolves both polymers stably exists. That is, the other polymer is incompatible with the acrylonitrile polymer when dissolved in the same solvent as the acrylonitrile polymer and has a miscibility enough to form a sea-island structure during spinning. Is desired.
- Examples of other polymers that satisfy these demands include polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl pyrrolidone, cellulose acetate, acrylic resin, methacrylic resin, and phenol resin. Among these, cellulose acetate, an acrylic resin, and a methacrylic resin are preferable from the viewpoint of the above-described balance of demand.
- the other polymer may be one type or two or more types. When one kind of polymer and another polymer are mixed, the mixing ratio of the first polymer is preferably 40 to 90% by mass, and more preferably 50 to 80% by mass with respect to the total mass of the two types.
- the splittable sea-island composite fiber used for the oxidized fiber precursor fiber (b2-2) can be produced by a normal wet spinning method.
- an acrylonitrile-based polymer for example, first, an acrylonitrile-based polymer and another polymer are dissolved in a solvent to prepare a spinning dope.
- a spinning stock solution obtained by dissolving an acrylonitrile-based polymer in a solvent and a spinning stock solution obtained by dissolving another polymer in a solvent may be mixed with a static mixer or the like to obtain a spinning stock solution.
- dimethylamide, dimethylformamide, dimethyl sulfoxide and the like can be used as the solvent.
- An easily split fiber sea-island composite fiber can be obtained by supplying these spinning stock solutions to a spinning machine, spinning from a nozzle, and performing wet heat drawing, washing, drying and dry heat drawing.
- the particulate material having a melting point of 400 ° C. or higher may be dispersed only in the acrylonitrile polymer or other polymer or in both polymers.
- the dispersed state may be dispersed substantially uniformly or may be localized in either polymer or both polymers.
- the cross-sectional shape in the fiber radial direction of the splittable sea-island composite fiber is not particularly limited.
- the fineness of the easily split sea-island composite fiber is preferably 1 dtex or more and 10 dtex or less. With this value, the dispersibility of the easily split sea-island composite fiber is increased, and breakage due to shrinkage during carbonization is suppressed.
- the average fiber length measured by measuring the fiber length of 50 fibers of easily splittable sea-island composite fibers using an optical microscope and an electron microscope and determining the average is 1 mm from the viewpoint of dispersibility after beating.
- the thickness is preferably 20 mm or less.
- the easily splittable sea-island composite fiber it is preferable to use a fiber that has been subjected to an operation of breaking the fiber by applying mechanical external force, that is, beating.
- the easily splittable sea-island composite fiber is beaten by peeling of the phase separation interface by beating, and at least a part thereof is split and fibrillated.
- the beating method is not particularly limited, and for example, fibrillation can be performed by a refiner, a pulper, a beater, or a jet of pressurized water (water jet punching).
- the fibrillation state changes depending on the beating method and beating time.
- the freeness evaluation ISO-5267-2 (Canadian Standard free methods)
- the freeness of the oxidized fiber precursor fiber (b2-2) is not particularly limited, but in this production method, for example, it becomes a value of about 10 to 650 ml.
- a refiner is used as a beating method, and 10 minutes is used as a beating time.
- Carbon powder (C2) is a powder containing carbon as a main constituent material. Although it does not specifically limit as carbon powder (C2), Carbon black, graphite powder, carbon fiber milled fiber, activated carbon, nanocarbon, etc. can be used. Carbon black or a mixture of carbon black and graphite powder is preferably used in terms of conductivity and cost.
- the carbon powder (C2) preferably contains at least carbon black.
- Carbon black generally exists as a structure (ageromate) in which primary particles having an average particle diameter of several tens of nanometers are fused together to form a structure, and the structures are bonded by van der Waalska.
- Carbon black has a remarkably larger number of particles per unit mass than graphite powder, and at a certain critical concentration or higher, agelatomate forms a three-dimensional network to form a macroscopic conductive path. Therefore, the use of carbon black for the carbon powder (C1) further improves the conductivity of the porous electrode substrate.
- the proportion of carbon black contained in the carbon powder is more preferably in the range of 70 to 90% by mass, and particularly preferably in the range of 80 to 90% by mass with respect to the total mass of the carbon powder.
- the carbon powder contains other than carbon black. This is because a dispersion containing only carbon black as carbon powder tends to increase in viscosity. As carbon powder other than carbon black, for example, graphite powder is desirable. By adding graphite powder, the viscosity of the dispersion can be lowered while maintaining the concentration of carbon powder.
- graphite powder Since graphite powder has a highly crystalline graphite structure, it exhibits high conductivity.
- the average particle diameter of primary particles of graphite powder is generally several micrometers to several hundred micrometers.
- the ratio of the graphite powder contained in the carbon powder is preferably in the range of 10 to 20% by mass with respect to the total mass of the carbon powder.
- carbon black there can be used fourness black, channel black, acetylene black, lamp black, thermal black, ketjen black, etc., but acetylene black or ketjen black, which is excellent in electrical conductivity, is more preferable and conductive. From the viewpoint, ketjen black is particularly preferable.
- the graphite powder pyrolytic graphite, spherical graphite, flake graphite, massive graphite, earthy graphite, artificial graphite, expanded graphite, and the like can be used, and pyrolytic graphite or spherical graphite having excellent conductivity is preferable.
- the granular material having a melting point of 400 ° C. or higher and the carbon powder (C2) may be the same or different carbon materials.
- the content of the carbon powder (C2) in the porous electrode substrate is 10 to 10 when the total of the short carbon fibers (A) and the oxidized fibers (B) containing the particulate matter having a melting point of 400 ° C. or more is 100 parts by mass. 100 parts by mass is preferable, and 10 to 50 parts by mass is more preferable. By selecting this range, the porous electrode substrate conductivity is improved and the strength of the porous electrode substrate can be secured.
- a fluorine-based resin refers to a resin obtained by polymerizing a compound containing fluorine.
- the fluororesin is not particularly limited, but includes tetrafluoroethylene (TFE), hexafluoropropylene (HFP), vinylidene fluoride (VDF), chlorotrifluoroethylene (CTFE), vinyl fluoride, perfluoroalkyl vinyl ether, Homopolymers or copolymers of fluorine-based monomers such as perfluoro (allyl vinyl ether), perfluoro (butenyl vinyl ether) (PBVE), perfluoro (2,2-dimethyl-1,3-dioxole) (PDD) Can be used.
- ETFE ethylene-tetrafluoroethylene copolymer
- ECTFE ethylene-chlorotrifluoroethylene copolymer
- EFE ethylene-tetrafluoroethylene copolymer
- ECTFE ethylene-chlorotrifluoroethylene copolymer
- fluorinated resins are preferably in the form of being dissolved in a solvent or being dispersed in a dispersion medium such as water or alcohol in a granular form.
- a dispersion medium such as water or alcohol in a granular form.
- the binder performance at the time of joining electrically oxidized and the short fiber (A) and the oxidation fiber (B) containing carbon powder (C1) can be expressed.
- Commercially available products in the form of solutions, dispersions, or granules include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl.
- PTFE polytetrafluoroethylene
- FEP tetrafluoroethylene-hexafluoropropylene copolymer
- PVDF polyvinylidene fluoride
- These fluorine resins have water repellency.
- the content of the fluororesin in the porous electrode substrate is 10 to 100 when the total of the short carbon fibers (A) and the oxidized fibers (B) containing granular materials having a melting point of 400 ° C. or more is 100 parts by mass. Mass parts are preferred, and 10 to 40 parts by mass are more preferred. By selecting this range, the porous electrode substrate conductivity is improved and the strength of the porous electrode substrate can be secured.
- This fluorine-based resin preferably has a residual mass of 80% by mass or more in a heat treatment step (step (3) described later). By this range, the mechanical strength of the porous electrode substrate is kept sufficient, and the environmental load is low. More preferably, it is 95% or more.
- the mass ratio of the carbon powder (C2) to the fluororesin after the heat treatment step (step (3) to be described later) is from 2: 8 to 8: 2 from the viewpoints of conductivity and binder performance.
- the carbon powder and the fluororesin are used in the step (2) described later, it is preferable to use a mixture obtained by mixing into a slurry dispersion.
- a slurry dispersion When these are in the form of a slurry, the impregnation property when impregnating the precursor sheet comprising the carbon short fiber (A) and the fiber (b) containing a granular material having a melting point of 400 ° C. or higher is enhanced.
- a dispersion solvent it is preferable to use water, alcohol, or a mixture thereof from the viewpoint of handleability and production cost.
- the concentration of the carbon powder (C2) in the dispersion is preferably 4% by mass or more with respect to the total mass of the dispersion.
- the concentration of the carbon powder (C2) is preferably 8% by mass or less.
- the dispersion liquid has a low viscosity and a high impregnation property, and the impregnation operation is facilitated.
- the concentration of the carbon powder (C2) is more preferably 6 to 8% by mass with respect to the total mass of the dispersion.
- the concentration of the fluororesin in the dispersion is preferably 2% by mass or more with respect to the total mass of the dispersion for imparting water repellency (water repellency) to the porous electrode substrate, so that the conductivity is not hindered. 6 mass% or less is preferable with respect to the total mass of the dispersion, and 3 to 6 mass% is more preferable.
- a dispersant such as a surfactant can be used in order to disperse the carbon powder (C2) and the fluororesin.
- a dispersing agent Aromatic sulfonates, such as polyethers, such as polyoxyethylene alkylphenyl ether, and a naphthalene sulfonate can be used.
- the carbon powder (C2) and the carbon powder (C2) in the fluororesin may have primary particles evenly dispersed or primary particles may be aggregated, but from the viewpoint of conductivity, the primary particles are aggregated. Is more preferable. Furthermore, it is preferable that the aggregate is localized in the carbon powder (C2) and the fluororesin.
- a material that disappears in the heat treatment step may be mixed and used.
- these materials nylon fibers, olefin fibers, methacrylic acid resin particles and the like can be used.
- the manufacturing method of the porous electrode base material of this embodiment should just have the following process (1), the process (2), and the process (3) at least.
- Step (1) carbon short fiber (A) and fiber (b) containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. and containing a granular material having a melting point of 400 ° C. or higher, and a plane direction of the sheet Step (1) for producing a precursor sheet dispersed with respect to
- Step (2) Step (2) of impregnating the precursor sheet with carbon powder (C2) and a fluororesin.
- Step (3) Step (3) of heat-treating the precursor sheet at a temperature of 250 ° C. or higher and lower than 400 ° C. in the presence of oxygen after step (2).
- it can have the process (4) which forms a three-dimensional entanglement structure between a process (1) and a process (2) by entanglement-processing a precursor sheet
- the manufacturing method of this embodiment does not have a carbonization process at 1000 degreeC or more from a viewpoint of manufacturing cost.
- a method for producing a porous electrode base material includes impregnating carbon powder (C2) and a fluororesin into a precursor sheet in which short carbon fibers (A) and fibers (b) are dispersed in a plane direction, and oxygen
- a porous electrode substrate is obtained by heat treatment at 250 ° C. to 400 ° C. in the presence (more specifically, in the air). That is, the fiber (b) dispersed in the precursor sheet is oxidized by heat treatment to obtain an oxidized fiber (B) containing a particulate material having a melting point of 400 ° C. or higher.
- the short carbon fibers (A) and the fibers (b) can be dispersed in the plane direction, and further can be dispersed three-dimensionally by an entanglement process or the like. Furthermore, it is possible to subject the precursor sheet to heat and pressure molding as necessary before the heat treatment.
- the short carbon fibers (A) are not bonded to each other by heat treatment, but when the precursor sheet is heat-treated at a temperature of 250 ° C. or higher and lower than 400 ° C. in the presence of oxygen as described later (step (3)).
- a part of the fibers (b) in the precursor sheet dissolve and play the role of an adhesive component.
- the fiber (b) is “an oxidized fiber precursor fiber containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. and a melting point of 400 ° C. or higher”
- the carbon short fiber (A) They form a partial structure joined together via an oxidized fiber (B) containing a granular material having a melting point of 400 ° C. or higher.
- step (3) when the fluororesin in the precursor sheet is heat-treated at a temperature of 250 ° C. or higher and lower than 400 ° C., it acts as a binder.
- a partial structure in which the fibers (A) are joined together by a fluororesin containing carbon powder (C2) is formed.
- the “short carbon fiber (A)” and the “oxidized fiber (B) containing a granular material having a melting point of 400 ° C. or more” are joined by dissolving the fiber (b) itself in the step (3). Is also bonded with a fluororesin containing carbon powder (C2).
- the part where “carbon short fiber (A)” and “oxidized fiber (B) containing granular material having a melting point of 400 ° C. or higher” are also joined by “fluorine resin containing carbon powder (C2)”. As a result, the resistance of the portion decreases and the strength also increases.
- step (2) when “fluorine resin containing carbon powder (C2)” is interposed between “carbon short fiber (A)” and “fiber (b)”, “carbon short fiber (A ) "And” Oxidized fiber (B) containing a granular material having a melting point of 400 ° C or higher "can also form a partial structure joined by" fluorine resin containing carbon powder (C2) ".
- Oxidized fibers (B) containing a granular material having a melting point of 400 ° C. or higher are in contact with each other, in the step (3), “containing a granular material having a melting point of 400 ° C. or higher”.
- Oxidized fibers (B) "have a partial structure joined together. There may be a case where the joining portion is further joined by “a fluororesin containing carbon powder (C2)”.
- fluorine resin containing carbon powder (C2) when “fluorine resin containing carbon powder (C2)” is interposed between “oxidized fibers (B) containing a granular material having a melting point of 400 ° C. or higher” in step (2), Can also form a partial structure in which the oxidized fibers (B) containing a particulate substance of 400 ° C. or higher are joined to each other by “fluorine resin containing carbon powder (C2)”.
- the porous electrode substrate of the present embodiment can have the structure as described in (I) to (III) above. As described above, structures other than the above (I) to (III) can be taken.
- Step (1) Short carbon fibers (A) and fibers (b) containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. and a granular material having a melting point of 400 ° C. or higher were dispersed in the plane direction.
- Step (1) for producing precursor sheet> First, the process which manufactures the precursor sheet
- “carbon short fiber (A)” in a liquid medium to be described later and a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. and a melting point of 400 ° C. or higher are included.
- the fiber (b) containing the carbon fiber (b) "is dispersed in one plane and dried to make paper, the carbon short fiber (A) in the air, the carbon short fiber (A), and the softening Paper making method such as a dry method in which a fiber (b) containing a polymer having a point of 250 ° C. or higher and lower than 400 ° C. and containing a granular material having a melting point of 400 ° C. or higher is dispersed and piled up on one plane.
- a wet method from the viewpoint of high uniformity of the sheet.
- fiber (b) containing a polymer having a softening point of 250 ° C. or higher and lower than 400 ° C. and containing a granular material having a melting point of 400 ° C. or higher is used.
- the short carbon fiber (A) is opened (helps a single fiber after separating and converging from a plurality of fibers), and further opening the single fiber. Prevents reconvergence.
- the fiber (b) is preferably made by wet paper making using a fibrillated oxidized fiber precursor fiber (b2) containing a particulate material having a melting point of 400 ° C. or higher.
- the sheet strength is improved by the intertwining of the short carbon fibers (A) and the fibers (b) containing the particulate material having a melting point of 400 ° C. or higher. Furthermore, it can be manufactured without using a sheet-like binder such as polyvinyl alcohol or polyvinyl acetate that substantially melts or dissolves during the production of the precursor sheet to bind the short carbon fibers (A). Moreover, it is also preferable to use the entanglement process process (4) mentioned later. Through this step, the sheet strength is improved by entanglement of the short carbon fiber (A) and the fiber (b) containing a granular material having a melting point of 400 ° C. or higher, and substantially melts during the production of the precursor sheet. Or it can manufacture, without using sheet-like binders, such as a polyvinyl alcohol fiber which melt
- wet papermaking can be performed using a sheet binder.
- the sheet-formed binder has a role as a glue that binds each component in a precursor sheet containing carbon short fibers (A) and fibers (b) containing a granular material having a melting point of 400 ° C. or higher.
- the sheet binder polyvinyl alcohol (PVA), polyvinyl acetate, or the like can be used.
- PVA polyvinyl alcohol
- polyvinyl alcohol is preferable because it has excellent binding power in the paper making process and the short carbon fibers (A) are less dropped.
- the binder as described above is used from the viewpoint of giving priority to the reduction of manufacturing cost and the expression of conductivity. Absent.
- liquid medium in which the short carbon fiber (A) and the fiber (b) containing a granular material having a melting point of 400 ° C. or higher are dispersed include fibers containing a granular material having a melting point of 400 ° C. or higher, such as water and alcohol.
- examples thereof include a medium in which (b) does not dissolve. Among these, it is preferable to use water from a viewpoint of productivity.
- Examples of the method of mixing the short carbon fiber (A) and the fiber (b) containing a granular material having a melting point of 400 ° C. or higher include a method of stirring and dispersing in water and a method of directly mixing these, but it is uniformly dispersed. From the viewpoint of achieving this, a method of diffusing and dispersing in water is preferable. It is possible to improve the strength of the precursor sheet by mixing the short carbon fiber (A) and the fiber (b) containing a granular material having a melting point of 400 ° C. or more, and making paper to produce the precursor sheet. it can. Moreover, it can prevent that the carbon short fiber (A) peels from a precursor sheet
- the wet-made sheet can be made into a precursor sheet by drying using a roll drying or floating drying method.
- These precursor sheets can be produced by either a continuous method or a batch method, but are preferably produced by a continuous method from the viewpoint of productivity and mechanical strength of the precursor sheet.
- the basis weight of the precursor sheet is preferably 10 g / m 2 or more and 200 g / m 2 or less. By this range, the handling properties of the precursor sheet and the gas permeability, conductivity and handling properties when used as a porous electrode substrate can be improved. Moreover, it is preferable that the thickness of a precursor sheet
- a step of impregnating the precursor sheet with carbon powder (C2) and a fluororesin is performed.
- the impregnation referred to in the present embodiment is a step of impregnating the carbon powder (C2) and the fluororesin into the precursor sheet, that is, carbon powder (C2) and fluorine in the gap between the fibers constituting the precursor sheet. This means a process of adding a resin.
- the method for impregnating the precursor sheet with the carbon powder (C2) and the fluororesin is not particularly limited as long as the carbon powder (C2) and the fluororesin can be applied to the precursor sheet.
- a carbon powder (C2) and a fluororesin are uniformly impregnated and coated from the surface of the precursor sheet using a coater, and a carbon powder ( A method of uniformly impregnating and coating C2) and a fluorine-based resin, a dip-nip method using a squeezing device, and the like can be used.
- the number of impregnations of the precursor sheet with the carbon powder (C2) and the fluororesin is not particularly limited, but it is preferable to reduce the number of impregnations from the viewpoint of reducing the manufacturing cost.
- impregnation is performed multiple times, even if the impregnated carbon powder (C2) and the fluorine resin slurry are the same, slurry having different slurry concentration, carbon powder and fluorine resin type, and mixing ratio are used. May be.
- the impregnation amount of the carbon powder and the fluororesin in the thickness direction of the precursor sheet may be uniform or may have a concentration gradient.
- the impregnation time is not particularly limited, but can be, for example, 1 second to 10 minutes.
- Step (3) Step (3) of heat-treating the precursor sheet at a temperature of 150 ° C. or higher and lower than 400 ° C. in the presence of oxygen after step (2)>
- a step of heat-treating the precursor sheet impregnated with the carbon powder (C2) and the fluororesin at a temperature of 150 ° C. or higher and lower than 400 ° C. in the presence of oxygen is performed.
- the short carbon fiber (A) is favorably fused with the fiber (b) containing a particulate material having a melting point of 400 ° C.
- the temperature of the heat treatment is preferably 200 ° C. or more in order to soften and melt the fluororesin, and preferably less than 400 ° C. in order to suppress thermal decomposition of the fluororesin. That is, the temperature of the heat treatment is preferably 200 to 400 ° C., and more preferably 300 to 370 ° C. for achieving both sufficient softening and melting and suppression of thermal decomposition.
- an atmosphere having an oxygen concentration of 5 to 80% is preferable. In terms of cost, the atmosphere can be preferably used.
- the heat treatment method is not particularly limited, and a heat treatment method using a high-temperature atmosphere furnace or a far-infrared heating furnace, a direct heat treatment method using a hot plate, a hot roll, or the like can be applied.
- the heat treatment time can be, for example, 1 minute to 2 hours.
- a process of forming a three-dimensional entangled structure by entanglement of the precursor sheet is performed.
- the short carbon fibers (A) in the precursor sheet and the fibers (b) containing a granular material having a melting point of 400 ° C. or higher are also entangled in the thickness direction of the precursor sheet.
- Interlacing is a process of crossing and entanglement.
- Three-dimensional entanglement structure means that fibers whose mutual positional relationship is located not only in the plane direction of the sheet but also in the thickness direction intersect with each other. It is a matching structure.
- the entanglement process may be a method by which a three-dimensional entangled structure is formed, and can be performed by a known method. For example, a method of entanglement with each other by applying an external force to the entanglement process can be taken.
- a mechanical entanglement method such as a needle punching method, a high pressure liquid injection method such as a water jet punching method, a high pressure gas injection method such as a steam jet punching method, or a combination thereof can be used.
- the entanglement process is preferably a high-pressure liquid injection method. According to this method, breakage of the short carbon fibers (A) in the entanglement process can be easily suppressed, and appropriate entanglement can be easily obtained. This method will be described in detail below.
- the precursor sheet is placed on a support member having a smooth surface, and the liquid to be jetted (liquid columnar flow, liquid sector flow, liquid slit flow, etc.) is applied to the carbon in the precursor sheet.
- This is a treatment method in which the short fiber (A) and the fiber (b) containing a granular material having a melting point of 400 ° C. or more are entangled.
- the support member having a substantially smooth surface used in the high-pressure liquid jet treatment method the pattern of the support member is not formed on the resulting entangled structure, and the jetted liquid is quickly removed. It can be selected and used as needed from those to be used.
- the precursor sheet is manufactured on a support member having a substantially smooth surface, and then the high-pressure liquid injection treatment can be continuously performed because the precursor sheet is entangled.
- the liquid used for the high-pressure liquid jet treatment may be anything other than a solvent that dissolves the fibers constituting the precursor sheet, but it is usually preferable to use water or warm water.
- the hole diameter of each injection nozzle in the high-pressure liquid injection nozzle is preferably 0.01 mm or more and 1.0 mm or less, more preferably 0.05 mm or more and 0.3 mm or less from the viewpoint of obtaining a sufficient confounding effect. preferable.
- the distance between the nozzle injection hole and the laminate is preferably 0.5 cm or more and 5 cm or less.
- the pressure of the liquid is preferably 0.5 MPa or more, and more preferably 1.0 MPa or more.
- the confounding process may be performed in a single row or in a plurality of rows. When performing in a plurality of rows, it is effective to increase the pressure of the high-pressure liquid ejection processing in the second and subsequent rows rather than the first row.
- the entanglement process by high-pressure liquid injection of the precursor sheet may be repeated a plurality of times. That is, after performing the precursor sheet high-pressure liquid injection treatment, the precursor sheet may be further laminated, and the high-pressure liquid injection treatment may be performed. An injection process may be performed. These operations may be repeated.
- the high-pressure liquid jet nozzle having one or a plurality of rows of nozzle holes can be vibrated in the width direction of the sheet.
- the confounding structure precursor is controlled by controlling the frequency and the phase difference of the high-pressure liquid jet nozzles that vibrate in the sheet width direction. Periodic patterns appearing on the sheet can be easily suppressed.
- the carbon short fiber (A) and the fiber (b) containing a granular material having a melting point of 400 ° C. or higher by the entanglement process are the thickness direction of the precursor sheet.
- the structure is also oriented.
- a step of heating and pressing the precursor sheet is performed. This step is preferably performed before the step (2) of impregnating the carbon powder (C2) and the fluororesin. This is because the short carbon fiber (A) is joined with the fiber (b) containing a granular material having a melting point of 400 ° C. or more, and thickness unevenness of the porous electrode substrate is reduced.
- Any technique can be applied to the heat and pressure molding as long as the technique can uniformly heat and mold the precursor sheet. For example, a method of hot pressing by applying smooth rigid plates to both surfaces of the precursor sheet, a method of using a roll press device, and a continuous belt press device can be mentioned.
- a continuously manufactured precursor sheet is heat-press molded
- a method using a roll press device or a continuous belt press device is preferable. Thereby, the carbonization process can be performed continuously.
- the heating temperature in the heat and pressure molding is preferably less than 200 ° C., more preferably 120 to 190 ° C. By this range, the surface of the precursor sheet can be effectively smoothed.
- the molding pressure is not particularly limited as long as it is higher than 2 kPa. However, when the content ratio of the fiber (b) containing the particulate material having a melting point of 400 ° C. or higher in the precursor sheet is large, it is easy even if the molding pressure is low.
- the surface of the precursor sheet can be smoothed.
- the molding pressure is preferably 20 kPa or more and 10 MPa or less.
- the time for heat and pressure molding can be, for example, 1 second to 10 minutes.
- the rigid plate or belt contains a granular material having a melting point of 400 ° C. or higher (b) It is preferable to apply a release agent such as silicon or fluorine in advance so as not to adhere, or to put a release paper treated with a release agent between the precursor sheet and the rigid plate or belt.
- a release agent such as silicon or fluorine
- the drying treatment is preferably performed at a temperature of 70 ° C. or higher and lower than 150 ° C. With this range, the dispersion solvent can be removed from the precursor sheet impregnated with the carbon powder (C2) and the fluororesin.
- the time for the drying treatment can be appropriately selected according to the dry state, and can be, for example, 1 minute to 1 hour.
- the drying method is not particularly limited, and heat treatment using a high-temperature atmosphere furnace or far-infrared heating furnace, direct heat treatment using a hot plate, a hot roll, or the like can be applied.
- a drying treatment using a high-temperature atmosphere furnace is preferable in that adhesion of the carbon powder and the fluororesin to the heating source can be suppressed.
- the dispersed short carbon fibers (A) are joined together by the oxidized fiber (B) containing the carbon powder (C1), and further, the short carbon fiber (A) and the melting point are 400.
- Oxidized fiber (B) containing granular material (carbon black) at or above ° C is joined by carbon powder (C2) and fluororesin, so that the carbonization step at 1000 ° C or above may be omitted. This is possible and the manufacturing cost can be reduced.
- the porous electrode substrate according to the present embodiment can be used as, for example, a porous electrode substrate for a polymer electrolyte fuel cell used for a polymer electrolyte fuel cell.
- the short carbon fibers (A) in the porous electrode base material are networked oxidation containing a granular material having a melting point of 400 ° C. or more. Bonded by the fiber (B), the short carbon fibers (A) are bonded by a fluorine-based resin containing carbon powder (C2), and the “carbon short fibers (A)” and “particulate matter having a melting point of 400 ° C.
- the joint portion with the “network-like oxidized fiber (B) to be contained” is further joined with “a fluororesin containing carbon powder (C2)”.
- the porous electrode substrate of the present embodiment can be used for a membrane-electrode assembly.
- a membrane-electrode assembly using a porous electrode substrate as an electrode for a cathode (anode) and an anode (cathode), respectively, can be constructed.
- a laminated body in which a catalyst layer is formed on both surfaces of the membrane is formed, and this laminated body is sandwiched between two porous electrode base materials, and each of the two porous electrode base materials is used as a cathode and It can be formed as an anode.
- the laminate is appropriately selected.
- a laminate in which a catalyst layer mainly composed of a platinum catalyst is formed on both surfaces of an electrolyte membrane made of a fluororesin that has proton conductivity can be used.
- an electrolyte membrane a polymer electrolyte membrane such as perfluorosulfonic acid can be used.
- a catalyst-supporting carbon in which Pt (platinum), Ru (ruthenium) or the like is supported on carbon can be used.
- the membrane-electrode assembly using the porous electrode substrate of the present embodiment can be used for production of a solid polymer fuel cell.
- the structure of the solid polymer fuel cell is appropriate as long as fuel (for example, hydrogen gas, oxygen gas, or a mixed gas containing them) is supplied to the membrane-electrode assembly and electricity can be taken out from the cathode and anode.
- the membrane-electrode assembly is sandwiched between partition members (carbon separators) containing carbon as a main constituent material to form a single cell solid polymer fuel cell.
- a structure serving as a gas flow path is provided on the surface of the partition member, and in this embodiment, the surface of the partition member has a bellows shape, so that the gas can easily flow.
- the partition member can take a straight or zigzag structure.
- the gas permeability of the porous electrode base material was measured as follows. In accordance with ISO-5636-5, the time taken for 200 mL of air to permeate was measured using a Gurley densometer, and the gas permeability (ml / hr / cm 2 / mmAq) was calculated.
- the thickness of the porous electrode substrate is randomly determined for a porous electrode substrate having a substantially uniform thickness using a thickness measuring device dial thickness gauge (trade name: 7321, manufactured by Mitutoyo Corporation). The thickness of the selected part was measured. The size of the probe was 10 mm in diameter, and the measurement pressure was 1.5 kPa.
- oxidized fiber (B) containing granular material having melting point of 400 ° C. or higher The content of oxidized fiber (B) containing granular material having melting point of 400 ° C. or higher is granular with melting point of 400 ° C. or higher. It calculated from the following formula from the basis weight of the porous electrode substrate produced without impregnating the substance and the fluororesin and the basis weight of the carbon short fiber (A) used. Content rate (%) of oxidized fiber (B) containing particulate matter having melting point of 400 ° C.
- Available Carbon powder (C1) 83 g of carbon black (Mitsubishi Chemical Corporation, product name: # 3230B, melting point: 3550 ° C. or higher) is mixed and dissolved in 800 g of dimethylacetamide with a three-one motor, and acrylic polymer spinning containing carbon powder Stock solutions were prepared.
- the obtained mixed solution (spinning stock solution) was extruded under nitrogen pressure of 0.1 MPa, and this spinning stock solution was discharged from a 12000 hole nozzle into a dimethylformamide aqueous solution having a concentration of 30% by mass and a temperature of 35 ° C. through a gear pump.
- the obtained coagulated fiber was washed and desolvated while being stretched 6 times in boiling water, and then the fiber length was cut to 3 mm to obtain carbon powder (C1) having an average fiber diameter of 10 ⁇ m containing an acrylonitrile polymer.
- the oxidized fiber precursor short fiber (b1) contained was obtained.
- the obtained mixed liquid is extruded under nitrogen pressure of 0.1 MPa, and a fixed amount is supplied to the nozzle channel 1 shown in FIG. 1 using a gear pump, and at the same time, water vapor is supplied from the inlet 3 to the water vapor channel 4. did.
- the amount of steam supplied was determined by regulating the supply pressure with a pressure reducing valve.
- Y-shaped solution discharge port 2 cylindrical mixing cell 5 having a diameter of 2 mm and a length of 10 mm
- water vapor channel 4 is slit-shaped and the opening is adjusted to 390 ⁇ m, and the center line A and slit of the solution channel
- the angle C formed with the center line B is 60 degrees.
- the supply amount of the mixed solution was 36 ml / min, the supply pressure of water vapor was 350 kPa, and the mixture cell was ejected from the mixing cell outlet 6 into water at a temperature of 30 ° C.
- the acrylonitrile polymer floating in the coagulation bath is collected, washed with water at room temperature overnight, and dehydrated to obtain a polymer (acrylonitrile polymer) having a softening point of 250 ° C or higher and lower than 400 ° C.
- An oxidized fiber precursor fiber (b2-1) containing a granular material (carbon black) having a melting point of 400 ° C. or higher and having a structure in which a large number of fibrils are branched is obtained.
- the obtained oxidized fiber precursor fiber (b2-1) was measured by ISO-5267-2 pulp drainage test method (1) Canadian standard type, and the freeness was 175 ml.
- the total draw ratio is increased to 3.0 times by the wet spinning method in which the spinning solution is discharged and solidified from the nozzle base into a coagulation bath (adjusted so that dimethylacetamide is 30% by mass and water is 70% by mass). It was spun so that it might become.
- the obtained mixed solution was extruded under nitrogen pressure of 0.1 MPa, and this spinning solution was discharged from a 12000 hole nozzle into a dimethylformamide aqueous solution (concentration 30 mass%, temperature 35 ° C.) through a gear pump. Wet spinning.
- the obtained coagulated fiber was washed and desolvated while being stretched 3 times in boiling water, then the fiber length was cut to 3 mm, and a disk refiner (manufactured by Kumagai Riki Kogyo Co., Ltd., trade name: KRK high concentration disk refiner, Oxidized fiber precursor fiber (b2-2) containing carbon powder (C1) fibrillated by beating was obtained by beating using a disc clearance of 0.3 mm and a rotational speed of 5000 rpm.
- a disk refiner manufactured by Kumagai Riki Kogyo Co., Ltd., trade name: KRK high concentration disk refiner
- Oxidized fiber precursor fiber (b2-2) containing carbon powder (C1) fibrillated by beating was obtained by beating using a disc clearance of 0.3 mm and a rotational speed of 5000 rpm.
- Example 1 As the carbon short fiber (A), a PAN-based carbon fiber having an average fiber diameter of 7 ⁇ m and an average fiber length of 3 mm was prepared. Further, an oxidized fiber precursor fiber (b2) containing carbon powder (C1) fibrillated by beating obtained in Production Example 2 as an oxidized fiber precursor fiber (b) containing a particulate material having a melting point of 400 ° C. or higher. -1) was prepared.
- the short carbon fiber (A) is dispersed in water so that the fiber concentration becomes 1% (10 g / L), and is disaggregated through a disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.). ).
- the oxidized fiber precursor fiber (b2-1) is dispersed in water so that the fiber concentration becomes 1% (10 g / L), and is disaggregated through a disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.). A slurry fiber (Sb) was obtained.
- the short carbon fibers (A) and the oxidized fiber precursor fibers (b2-1) containing carbon powder (C1) having a structure in which a large number of fibrils are branched have a mass ratio of 50:50 and are contained in the slurry.
- the disaggregation slurry fiber (SA), the disaggregation slurry fiber (Sb), and the dilution water were weighed so that the solid concentration was 1.5 g / L, and prepared in a slurry supply tank. Further, polyacrylamide was added to prepare a papermaking slurry having a viscosity of 22 mPa ⁇ s.
- a net drive unit and a sheet-like material conveying device consisting of a net that continuously rotates by connecting a flat woven mesh made of plastic net with a width of 60cm x length of 585cm in a belt shape, slurry supply
- a papermaking slurry supply apparatus having a part width of 48 cm and a supply slurry amount of 30 L / min, and a processing apparatus comprising a vacuum dehydration apparatus disposed under the net were used.
- the papermaking slurry was supplied onto the plain weave mesh by a metering pump.
- the papermaking slurry was supplied after being widened to a predetermined size through a flow box for rectification into a uniform flow. Thereafter, it passed through the part to be naturally dehydrated and dehydrated with a vacuum dehydrator to obtain a precursor sheet (before entanglement treatment).
- a high-pressure liquid jet processing apparatus provided with the following three water jet nozzles (nozzles 1 to 3) was disposed downstream of the continuous precursor sheet manufacturing apparatus.
- Nozzle 1 hole diameter ⁇ (diameter) 0.15 mm ⁇ 501 holes, pitch in the width direction hole 1 mm (1001 holes / width 1 m), one row arrangement, nozzle effective width 500 mm.
- Nozzle 2 hole diameter ⁇ 0.15 mm ⁇ 501 holes, pitch in the width direction hole 1 mm (1001 holes / width 1 m), one row arrangement, nozzle effective width 500 mm.
- Nozzle 3 hole diameter ⁇ 0.15 mm ⁇ 1002 holes, width-direction hole pitch 1.5 mm, three rows, row pitch 5 mm, nozzle effective width 500 mm.
- the pressurized water jet pressure is 1 MPa (nozzle 1)
- the pressure is 1 MPa (nozzle 2)
- the pressure is 1 MPa (nozzle 3)
- the precursor sheet is passed through the nozzle 1, nozzle 2, and nozzle 3 in this order and entangled.
- a entangled precursor sheet was obtained.
- This entangled precursor sheet (before drying) was dried at 150 ° C. for 3 minutes with a pin tenter tester (trade name: PT-2A-400, manufactured by Sakurai Dyeing Machine Co., Ltd.), with a basis weight of 40 g / m 2.
- a precursor sheet (hereinafter, also simply referred to as a precursor sheet) was obtained.
- the dispersion state of the short carbon fiber (A) and the oxidized fiber precursor fiber (b2-1) in the precursor sheet was good when observed under a microscope. Moreover, the entanglement of both fibers was also good and the handling property was good.
- Ketjen Black manufactured by Lion Corporation
- carbon powder (C2) and polytetrafluoroethylene particle dispersion trade name: PTFE Dispersion 31-JR, Mitsui-Dupont Fluoro Chemical Co., Ltd.
- fluororesin And polyoxyethylene octyl phenyl ether was prepared as a dispersant.
- the mixture of carbon powder (C2) and fluororesin was adjusted as follows and impregnated.
- porous electrode substrate was obtained by heat treatment in a batch atmosphere furnace in the atmosphere at 360 ° C. for 1 hour.
- the obtained porous electrode substrate had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by the oxidized fibers (B) containing the carbon powder (C1), and the melting point of the short carbon fibers (A) is 400.
- Oxidized fiber (B) containing granular material (carbon black) at a temperature of 0 ° C. or higher was bonded with carbon powder (C2) and a fluororesin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- the composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 2 A porous electrode substrate (Example 2) was obtained in the same manner as in Example 1 except that the mass ratio of the short carbon fibers (A) to the oxidized fiber precursor fibers (b2-1) was 60:40. It was.
- the obtained porous electrode substrate (Example 2) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing a granular material (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 3 A porous electrode substrate (Example 3) was obtained in the same manner as in Example 1 except that the mass ratio of the short carbon fiber (A) and the oxidized fiber precursor fiber (b2-1) was 70:30. It was.
- the obtained porous electrode substrate (Example 3) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing particulate matter (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 4 A porous electrode substrate (Example 4) was obtained in the same manner as in Example 1 except that the mass ratio of the short carbon fibers (A) to the oxidized fiber precursor fibers (b2-1) was 85:15. It was.
- the obtained porous electrode substrate (Example 4) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing particulate matter (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 5 As in Example 4, except that the oxidized fiber precursor fiber (b2-2) obtained in Production Example 3 was used as the fiber (b) containing a granular material (carbon black) having a melting point of 400 ° C. or higher. Thus, a porous electrode substrate (Example 5) was obtained.
- the obtained porous electrode substrate (Example 5) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing a granular material (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 6 As in Example 4, except that the oxidized fiber precursor short fiber (b1) obtained in Production Example 1 was used as the fiber (b) containing a granular material (carbon black) having a melting point of 400 ° C. or higher. A porous electrode substrate (Example 6) was obtained.
- the obtained porous electrode substrate (Example 6) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing particulate matter (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 7 The oxidized fiber precursor short fiber (b1) obtained in Production Example 1 and the oxidized fiber precursor obtained in Production Example 2 as fibers (b) containing a particulate material (carbon black) having a melting point of 400 ° C. or higher.
- a porous electrode substrate (Example 7) was obtained in the same manner as in Example 4 except that the fiber (b2-1) was used and the mass ratio was 70:15:15. .
- the obtained porous electrode substrate (Example 7) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing granular materials (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 8 The carbon powder (C2), the fluororesin, and the dispersant were mixed in such a manner that the carbon powder (C2) and the fluororesin had a mass ratio of 4.0 mass%, 4.0 mass%, and 4.5 mass%, respectively.
- a porous electrode substrate (Example 8) was obtained in the same manner as in Example 4 except that the dispersion was prepared.
- the obtained porous electrode substrate (Example 8) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing particulate matter (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 9 As the carbon powder (C2), ketjen black (manufactured by Lion Corporation) and pyrolytic graphite (trade name: PC-H, manufactured by Ito Graphite Industries Co., Ltd.) were used, and the ratio (mass ratio) was 90:10.
- a porous electrode substrate (Example 9) was obtained in the same manner as in Example 4 except that.
- the obtained porous electrode substrate (Example 9) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing particulate matter (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 10 A porous electrode substrate (Example 10) was obtained in the same manner as in Example 1 except that the entanglement process by the high-pressure liquid injection process was not performed.
- the obtained porous electrode substrate had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing granular materials (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 11 A porous electrode substrate (Example 11) was obtained in the same manner as in Example 1 except that the pressure heating molding treatment was not performed.
- the obtained porous electrode substrate (Example 11) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing particulate matter (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 12 Porous electrode substrate (Example 12) in the same manner as in Example 1 except that the precursor sheet was impregnated with a mixture of carbon powder (C2) and fluororesin, and then the drying treatment was not performed. Got.
- the obtained porous electrode substrate (Example 12) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing granular material (carbon black) whose melting
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B) containing particulate matter (carbon black) having a melting point of 400 ° C. or higher. Furthermore, the carbon short fiber (A) and the oxidized fiber (B) containing a granular material (carbon black) having a melting point of 400 ° C. or more were bonded with the carbon powder (C2) and the fluorine resin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Table 1 The composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 13 (1) Production of membrane-electrode assembly (MEA) Two sets of porous electrode substrates obtained in Example 4 were prepared as cathode electrode and anode electrode porous electrodes. Further, a catalyst layer (catalyst layer area: 25 cm 2 , Pt) composed of catalyst-supported carbon (catalyst: Pt, catalyst support amount: 50 mass%) on both surfaces of a perfluorosulfonic acid polymer electrolyte membrane (film thickness: 30 ⁇ m). The laminated body which formed the adhesion amount: 0.3 mg / cm ⁇ 2 >) was made easy. The laminate was sandwiched between cathode and anode porous carbon electrode substrates, and joined to obtain an MEA.
- the fuel cell characteristics were evaluated by measuring the current density-voltage characteristics of this single cell. Hydrogen gas was used as the fuel gas, and air was used as the oxidizing gas.
- the single cell temperature was 80 ° C.
- the fuel gas utilization rate was 60%
- the oxidizing gas utilization rate was 40%.
- the humidification of the fuel gas and the oxidizing gas was performed by passing the fuel gas and the oxidizing gas through an 80 ° C. bubbler, respectively.
- the current density was 0.8 A / cm 2
- the cell voltage of the fuel battery cell was 0.584 V
- the internal resistance of the cell was 4.8 m ⁇ , which showed good characteristics.
- An acrylonitrile polymer spinning stock solution containing no carbon powder (C1) is prepared by using 150 g and 850 g of acrylonitrile polymer and dimethylacetamide, respectively, without using a granular material having a melting point of 400 ° C. or higher.
- An oxidized fiber precursor fiber having a melting point of 400 ° C. or higher and having a structure in which a large number of fibrils are branched is obtained in the same manner as in Production Example 2 except that is used.
- a porous electrode substrate (Comparative Example 1) was used in the same manner as in Example 1 except that an oxidized fiber precursor fiber having a structure in which a large number of fibrils were branched and having a melting point of 400 ° C. or higher was not used.
- the obtained porous electrode substrate (Comparative Example 1) had good gas permeability and thickness, but had in-plane shrinkage during heat treatment, and the sheet waviness was 3 mm. It became high compared with. Further, the penetration direction resistance was higher than that in Example 1. Further, the content of oxidized fiber (B ′) containing no particulate matter having a melting point of 400 ° C. or higher was 49% by mass.
- the dispersed short carbon fibers (A) are joined together by oxidized fibers (B ′) containing no particulate matter having a melting point of 400 ° C. or higher, and further carbon.
- the short fiber (A) and the oxidized fiber (B ′) containing no particulate matter having a melting point of 400 ° C. or higher were joined by the carbon powder (C2) and the fluororesin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- the composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 2 A porous electrode substrate (Comparative Example 2) was obtained in the same manner as in Example 1 except that the heat treatment was performed without impregnating the dispersion liquid of the carbon powder (C2) and the fluororesin.
- the obtained porous electrode substrate (Comparative Example 2) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 1 mm or less, and the gas permeability and thickness were good respectively.
- the penetration direction resistance was higher than that in Example 1.
- the content rate of the oxidized fiber (B) containing a granular material having a melting point of 400 ° C. or higher was 49% by mass.
- the dispersed short carbon fibers (A) were joined together by oxidized fibers (B) containing granular materials having a melting point of 400 ° C. or higher. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- the composition and evaluation results of the porous electrode substrate are shown in Table 1.
- Example 3 A polyvinylidene fluoride fiber having a structure in which a large number of fibrils were branched was obtained in the same manner as in Production Example 2 except that polyvinylidene fluoride (manufactured by ATOFINA, trade name: KYNAR9000) was used instead of the acrylonitrile polymer. Furthermore, a porous electrode base material (Comparative Example 3) was obtained in the same manner as in Example 1 except that polyvinylidene fluoride fibers containing a granular material at 400 ° C. or higher having a structure in which many fibrils were branched.
- polyvinylidene fluoride fibers containing a granular material at 400 ° C. or higher having a structure in which many fibrils were branched.
- the obtained porous electrode substrate (Comparative Example 3) has a large amount of deformation of the polyvinylidene fluoride fiber during heat treatment, cannot suppress the thickness and undulation, and the undulation of the sheet is 10 mm or more. In comparison, it was very high and it was difficult to incorporate it into a fuel cell, and it could not be used as a porous electrode substrate for a fuel cell.
- Example 14 A porous electrode substrate (Example 14) was obtained in the same manner as in Example 10 except that the pressure heating molding treatment was not performed.
- the obtained porous electrode substrate (Example 14) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 2 mm or less, and the gas permeability, thickness, and penetration direction resistance were good. . Moreover, the content rate of the oxidation fiber (B) containing carbon powder (C1) became 49 mass%.
- the dispersed short carbon fibers (A) are joined together by the oxidized fibers (B) containing the carbon powder (C1), and the short carbon fibers (A) ) And oxidized fiber (B) containing carbon powder (C1) were bonded by carbon powder (C2) and fluororesin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Example 15 A porous electrode substrate (Example 15) was obtained in the same manner as in Example 14 except that the step of drying treatment was not performed.
- the obtained porous electrode substrate (Example 15) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 2 mm or less, and the gas permeability, thickness and penetration direction resistance were good. It was. Moreover, the content rate of the oxidation fiber (B) containing carbon powder (C1) became 49 mass%.
- the dispersed short carbon fibers (A) are joined together by the oxidized fibers (B) containing the carbon powder (C1), and the short carbon fibers (A) ) And oxidized fiber (B) containing carbon powder (C1) were bonded by carbon powder (C2) and fluororesin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
- Example 4 A porous electrode substrate (Comparative Example 4) was obtained in the same manner as in Example 1 except that the carbon powder (C2) was not used and only the fluororesin dispersion was impregnated.
- the obtained porous electrode substrate (Comparative Example 4) had no in-plane shrinkage during heat treatment, the sheet waviness was as small as 2 mm or less, and the gas permeability and thickness were good respectively.
- the penetration direction resistance was higher than that in Example 1.
- the content rate of the oxidized fiber (B) containing a granular material having a melting point of 400 ° C. or higher was 49% by mass.
- the dispersed short carbon fibers (A) are joined together by the oxidized fibers (B) containing the carbon powder (C1), and the short carbon fibers (A) ) And an oxidized fiber (B) containing carbon powder (C1) were bonded to each other by a fluororesin. Even when a compressive load having a surface pressure of 1.5 MPa was applied to the porous electrode substrate, the sheet form could be maintained.
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Abstract
Description
本実施形態に係る多孔質電極基材は、炭素短繊維(A)と、融点が400°以上の粒状物質を含有する酸化繊維(B)と、炭素粉(C2)を含有するフッ素系樹脂を備えて概略構成される。本実施形態に係る多孔質電極基材は、例えば、繊維(b)は軟化点が250℃以上400℃未満のポリマー及び融点が400℃以上の粒状物質からなる「融点が400℃以上の粒状物質を含有する酸化繊維(B)の前駆体繊維」である場合には、主に後述する製造方法における各工程を介して、以下の様な構造を有している。以下の接合されてなるとは、異なる化合物が分子結合(結合)以外の分子間力等の作用で密着していることを指す。本実施形態に係る多孔質電極基材は、以下の(I)~(III)及びこれらを組み合わせた構造を取りえる。なお、下記する(I)~(III)以外の構造も取りうる。
<炭素短繊維(A)>
前駆体シートに分散させた炭素短繊維(A)は、多孔質電極基材を構成する繊維の1つとなる。炭素短繊維(A)としては、例えば、ポリアクリロニトリル系炭素繊維(以下「PAN系炭素繊維」と称する)、ピッチ系炭素繊維、レーヨン系炭素繊維等の炭素繊維を所定の繊維長に切断したものが挙げられる。炭素短繊維(A)は、PAN系炭素繊維が好ましい。炭素短繊維(A)にPAN系炭素繊維を用いることで、多孔質電極基材の機械的強度が得られる。
融点が400℃以上の粒状物質を含有する酸化繊維(B)は、多孔質電極基材中で炭素短繊維(A)同士を接合する繊維である。酸化繊維(B)は、多孔質電極基材では炭素短繊維(A)を接合する部位である接合部において屈曲状または湾曲状になっている状態で存在している。酸化繊維とは、繊維が加熱及び加圧によって、用いるポリマーが酸素と結合する反応を起こし、酸化していることを意味する。融点が400℃以上の粒状物質を含有する酸化繊維(B)は、それぞれがほぼ直線状のみからなる繊維構造を形成していても、直線状の繊維が相互に交差した状態で結合し網目状となった網目構造を形成していても良い。酸化繊維(B)は、多孔質電極基材の平面方向だけでなく、厚み方向にも互いに絡まり合った網目構造を形成していることが好ましい。この構造において、多孔質電極基材のハンドリング性や導電性が良好となる。
本実施形態では、後述するように、<炭素短繊維(A)と、融点が400℃以上の粒状物質を含有する繊維(b)とを平面方向に分散させた前駆体シートを製造する工程(1)>によって、前駆体シートを製造することができる。この前駆体シートは、多孔質電極基材の前駆体となるシートである。後述する工程(1)で得られる前駆体シートは、炭素短繊維(A)と、融点が400℃以上の粒状物質を含有する繊維(b)とが分散した前駆体シートである。前駆体シートは、炭素短繊維(A)と、融点が400℃以上の粒状物質を含有する繊維(b)とを含んでなる。なお、本発明の前駆体シートは、製造コストの低減および導電性の発現の観点から、ポリビニルアルコール(PVA)、ポリ酢酸ビニル等のシート化バインダーを含まないものが好ましい。
当該繊維(b)は、軟化点250℃以上400℃未満のポリマーを含有することを必須とする。繊維(b)が軟化点250℃以上400℃未満のポリマーを含有するとは、実質的にこのポリマーからなる(不純物を除き主にこのポリマーから構成される、以下、単に「このポリマーからなる」ともいう)、又はこのポリマーを含む混合物が軟化点250℃以上400℃未満に調整されている、等の概念を含む。繊維(b)が含んでなるポリマーが、軟化点が250℃以上400℃未満であることより、後述する酸素存在下、250℃以上400℃未満の温度で熱処理する工程において炭素短繊維(A)を接合する際に繊維形状を保持することができ、これにより多孔質電極基材のうねりを抑制することができる。繊維(b)が含有するポリマーの軟化点が250℃未満であると、酸素存在下、250℃以上400℃未満の温度で熱処理する工程において、繊維形態を保持することができず、繊維の収縮が起こり、多孔質電極基材に大きなうねりが発生する。また繊維(b)が含有するポリマーの軟化点が400℃以上であると、酸素存在下、250℃以上400℃未満の温度で熱処理する工程において、炭素短繊維(A)を接合することができず、多孔質電極基材の抵抗が増大すること、機械的強度が低下する。
融点が400℃以上の粒状物質は、後述する製造方法の工程(2)における250~400℃未満の温度で熱処理において、軟化点が250℃以上400℃未満のポリマーを含有する繊維が収縮し、多孔質電極基材のうねりを発生させるのを抑制するために、軟化点が250℃以上400℃未満のポリマーを含有する繊維中に含有させている。即ち、粒状物質は後述する工程(2)における熱処理で、形状を保つことができるものでなくてはならない。従って、粒状物質の融点は前記したポリマーの軟化点を超えている必要がある。具体的には、400℃以上である必要があり、好ましくは前記軟化点より100℃以上高い500℃以上である。粒状物質の融点は高ければ高い方がよいが、通常は4000℃以下である。すなわち、粒状物質の例としては融点が400~4000℃、好ましくは500~4000℃、さらに好ましくは3000~4000℃といった粒子を用いることができる。例えば本実施形態で用いるカーボンブラックは融点が約3550℃である。
軟化点が250℃以上400℃未満のポリマーを含有し、融点が400℃以上の粒状物質を含有するフィブリル状酸化繊維前駆体繊維(b2)として、例えば以下のものを用いることができる。
軟化点が250℃以上400℃未満のポリマーを含有し、直径100μm以下の繊維状の幹(芯部)より、直径が数μm以下(例えば0.1~3μm)のフィブリルが多数分岐した構造を有し、融点が400℃以上の粒状物質を含有する酸化繊維前駆体繊維(b2-1)の製造方法も特に限定されないが、後述する濾水度のコントロールが容易な噴射凝固法を用いて製造することが好ましい。噴射凝固法による酸化繊維前駆体繊維(b2-1)の製造は、例えば図1に示す装置を用いて以下の方法で製造できる。酸化繊維前駆体繊維(b2-1)の原料(例えばアクリロニトリル系重合体およびカーボンブラック)を溶媒に溶解もしくは分散媒に分散させた紡糸原液を紡糸吐出口に通して混合セル内に吐出すると同時に、水蒸気を紡糸原液の吐出線方向に対して0度以上、90度未満の角度で混合セル内に噴出し、混合セル内で融点が400℃以上の粒状物質を含有するフィブリル状炭素前駆体繊維原料を剪断流速の下で凝固させる。形成された凝固体を前記溶媒もしくは分散媒と水蒸気と共に混合セルから凝固液中に排出することで炭素粉を含有するフィブリル状炭素前駆体繊維が得られる。凝固液としては水または、水と前記溶媒もしくは分散媒との混合液を用いることができる。このとき、融点が400℃以上の粒状物質はアクリロニトリル系重合体中で、ほぼ均一に分散しても、局在していても良い。
軟化点が250℃以上400℃未満のポリマーを含有し、叩解によってフィブリル化した融点が400℃以上の粒状物質を含有する酸化繊維前駆体繊維(b2-2)の製造方法も特に限定されないが、後述するように、フィブリル化が容易な、長繊維状の易割繊性海島複合繊維を後述する繊維長にカットしたものを、リファイナーやパルパーなどによって叩解しフィブリル化したものを用いる。長繊維状の易割繊性海島複合繊維は、共通の溶剤に溶解し、かつ非相溶性である2種類以上の、構成化合物又は繊維長や繊維径等の物理的性質が異なるポリマー(異種ポリマー)を用いて製造することができる。
炭素粉(C1)とは、炭素を主な構成素材とする粉である。炭素粉(C2)としては、特に限定されないが、カーボンブラック、黒鉛粉、炭素繊維ミルドファイバー、活性炭、ナノカーボンなどを用いることができる。導電性の発現の点とコストの点で、カーボンブラック、またはカーボンブラックと黒鉛粉の混合物を用いることが好ましい。
フッ素系樹脂(フッ素樹脂、フッ素化樹脂)は、フッ素を含む化合物を重合して得られる樹脂を指す。フッ素系樹脂としては、特に限定されないが、テトラフルオロエチレン(TFE)、ヘキサフルオロプロピレン(HFP)、フッ化ビニリデン(VDF)、クロロトリフルオロエチレン(CTFE)、フッ化ビニル、パーフルオロアルキルビエルエーテル、パーフルオロ(アリルビニルエーテル)、パーフルオロ(ブテニルビニルエーテル)(PBVE)、パーフルオロ(2,2-ジメチル-1,3-ジオキソール)(PDD)等のフッ素系モノマーの単独重合物または共重合物を用いることができる。また、これらとエチレンに代表されるオレフィン類との共重合物であるエチレンーテトラフルオロエチレン共重合体(ETFE)、エチレンークロロトリフルオロエチレン共重合体(ECTFE)等も用いることができる。
熱処理工程(後述する工程(3))後の炭素粉(C2)とフッ素系樹脂の質量比は、導電性の発現とバインダー性能の発現の点から、2:8~8:2であることが好ましく、4:6~7:3であることがより好ましい。
本実施形態の多孔質電極基材の製造方法は、少なくとも以下の工程(1)と工程(2)、工程(3)を有していればよい。
多孔質電極基材の製造方法は、炭素短繊維(A)と、繊維(b)とを平面方向に分散させた前駆体シートに、炭素粉(C2)とフッ素系樹脂とを含浸させ、酸素存在下(より具体的には大気中)で250℃~400℃で熱処理することにより多孔質電極基材を得るものである。即ち、前駆体シート中に分散させた繊維(b)を熱処理により酸化処理し、融点が400℃以上の粒状物質を含有する酸化繊維(B)を得る。なお、前駆体シートにおいて、炭素短繊維(A)、および繊維(b)は、平面方向に分散することができ、さらに交絡処理などにより3次元に分散することができる。さらに、熱処理の前に必要に応じてこの前駆体シートに対して、加熱加圧成型の処理をすることもできる。
まず、炭素短繊維(A)と繊維(b)とを、平面方向に分散させた前駆体シートを製造する工程を行う。平面方向に分散させるとは、一定の面(平面)に対して略均一に配置させることで、これにより炭素短繊維(A)と繊維(b)がシート状を形成する。前駆体シートの製造方法としては、後述する液体の媒体中に「炭素短繊維(A)」と、「軟化点が250℃以上400℃未満のポリマーを含有し、融点が400℃以上の粒状物質を含有する繊維(b)」とを一平面に対して分散させた後に乾燥させて抄造する湿式法、空気中に炭素短繊維(A)と、「炭素短繊維(A)」と、「軟化点が250℃以上400℃未満のポリマーを含有し、融点が400℃以上の粒状物質を含有する繊維(b)」とを一平面に対して分散させて降り積もらせる乾式法、などの抄紙方法を適用できる。しかし、シートの均一性が高いという観点から、湿式法を用いることが好ましい。
次いで、前駆体シートに炭素粉(C2)とフッ素系樹脂とを含浸させる工程を行う。本実施形態でいう含浸とは前駆体シート中に炭素粉(C2)とフッ素系樹脂とをしみこませる工程、即ち、前駆体シートを構成する繊維と繊維の隙間に、炭素粉(C2)とフッ素系樹脂とを入れる工程を意味する。前駆体シートに炭素粉(C2)とフッ素系樹脂とを含浸する方法としては、前駆体シートに炭素粉(C2)とフッ素系樹脂とを付与することができる方法であれば特に限定されない。具体的には、例えばコーターを用いて前駆体シート表面から炭素粉(C2)とフッ素系樹脂とを均一に含浸およびコートする方法、スプレー装置および滴下装置を用いて前駆体シート表面から炭素粉(C2)とフッ素系樹脂とを均一に含浸およびコートする方法、絞り装置を用いたdip-nip方法などを用いることができる。
次いで、炭素粉(C2)とフッ素系樹脂とを含浸した前駆体シートを、酸素存在下、150℃以上400℃未満の温度で熱処理する工程を行う。この操作により、融点が400℃以上の粒状物質を含有する繊維(b)による炭素短繊維(A)の融着を良好に行い、かつ、バインダー成分のフッ素系樹脂を焼結し、炭素短繊維(A)と融点が400℃以上の粒状物質を含有する繊維(b)との接合を良好に行うことができる。熱処理の温度は、フッ素系樹脂を軟化溶融させるために200℃以上が好ましく、フッ素系樹脂の熱分解を抑制するために400℃未満が好ましい。すなわち、熱処理の温度は200~400℃が好ましく、十分な軟化溶融と熱分解の抑制を両立する理由から、300~370℃がさらに好ましい。
次いで、前駆体シートを交絡処理して3次元交絡構造を形成する工程を行う。この工程は、前駆体シート中の炭素短繊維(A)と融点が400℃以上の粒状物質を含有する繊維(b)とを前駆体シートの厚み方向にも交絡させる。交絡とは、交差させ絡まらせる処理であり、三次元交絡構造とは、繊維の相互の位置関係がシートの平面方向だけでなく厚み方向にも位置しているような繊維が、互いに交差し絡みあっている構造である。交絡処理は、3次元交絡構造が形成される方法であればよく、公知の方法で実施できる。例えば、交絡処理には外力を加えることで互いに絡み合わせる方法をとることができる。この方法には、ニードルパンチング法などの機械交絡法、ウォータージェットパンチング法などの高圧液体噴射法、スチームジェットパンチング法などの高圧気体噴射法、或いはこれらの組み合わせによる方法を用いることができる。交絡処理は、高圧液体噴射法が好ましい。この方法によれば、交絡工程での炭素短繊維(A)の破断を容易に抑制でき、かつ適度な交絡性が容易に得られる。以下に、この方法について詳しく説明する。
高圧液体噴射処理法は、表面が平滑な支持部材上に前駆体シートを載せ、噴射される液体(液体柱状流、液体扇形流又は液体スリット流等)を当てることによって、前駆体シート中の炭素短繊維(A)と融点が400℃以上の粒状物質を含有する繊維(b)とを交絡させる処理方法である。ここで、この高圧液体噴射処理法に用いる実質的に表面が平滑な支持部材としては、支持部材の模様が、得られる交絡構造体に形成されることなく、かつ噴射された液体が速やかに除かれるようなものから必要に応じて選択して用いることができる。その具体例としては30~200メッシュの金網又はプラスチックネット或いはロール等を挙げることができる。実質的に表面平滑な支持部材上で前駆体シートを製造した後、高圧液体噴射処理することが、交絡構造前駆体シートを連続的に製造でき、生産性の観点から好ましい。
次いで、前駆体シートを加熱加圧成型する工程を行う。この工程は、炭素粉(C2)とフッ素系樹脂とを含浸させる工程(2)の前に行うことが好ましい。炭素短繊維(A)を融点が400℃以上の粒状物質を含有する繊維(b)で接合させ、かつ多孔質電極基材の厚みムラを低減させるためである。加熱加圧成型は、前駆体シートを均等に加熱加圧成型できる技術であれば、いかなる技術も適用できる。例えば、前駆体シートの両面に平滑な剛板を当てて熱プレスする方法、ロールプレス装置、連続ベルトプレス装置を用いる方法が挙げられる。
次いで、前駆体シートを乾燥処理する工程を行う。乾燥処理は70℃以上150℃未満の温度で行うことが好ましい。この範囲により、炭素粉(C2)とフッ素系樹脂とを含浸した前駆体シートから分散溶媒を除去することができる。乾燥処理の時間は乾燥状態に応じて適宜選択できるが、例えば1分間~1時間とすることができる。
本実施形態の多孔質電極基材は、膜-電極接合体に用いることができる。多孔質電極基材を電極としてそれぞれ陰極(アノード)及び陽極(カソード)に用いた膜-電極接合体を構成することができる。具体例としては、膜の両面に触媒層が形成された積層体を形成し、この積層体を2枚の多孔質電極基材で挟み込んで、2枚の多孔質電極基材のそれぞれを陰極及び陽極として形成することができる。積層体は適宜選ばれるが、例としてはプロトン伝導性をしますフッ素樹脂からなる電解質膜の両面に白金触媒を主成分とする触媒層を形成したものが利用できる。電解質膜の例としてはパーフルオロスルホン酸系などの高分子電解質膜が使用できる。触媒層としてはカーボンに、Pt(白金)、Ru(ルテニウム)などを担持させた触媒担持カーボン等が使用できる。
本実施形態の多孔質電極基材を用いた前記膜-電極接合体は、固体高分子燃料電池の製造に用いることができる。固体高分子燃料電池の構造は前記膜-電極接合体に燃料(例えば水素ガス、酸素ガス、又はこれらを含有する混合ガス)を供給し陰極及び陽極から電気を取り出せる構造であれば適宜である。本実施形態では、炭素を主な構成素材とする隔壁部材(カーボンセパレータ)によって前記膜-電極接合体を挟み、単セルの固体高分子燃料電池としている。隔壁部材の表面にはガスの流路となる構造が設けられ、本実施形態では隔壁部材の表面が蛇腹状となっていることでガスが流れやすくなっている。隔壁部材はその他にストレート状、ジグザグ状といった構造をとることができる。
多孔質電極基材のガス透気度の測定は以下のように行った。ISO-5636-5に準拠し、ガーレーデンソメーターを使用して200mLの空気が透過するのにかかった時間を測定し、ガス透気度(ml/hr/cm2/mmAq)を算出した。
多孔質電極基材の厚みは、厚み測定装置ダイヤルシックネスゲージ((株)ミツトヨ製、商品名:7321)を使用して、厚みのほぼ均一な多孔質電極基材について無作為に選択した一部分の厚みを測定した。測定子の大きさは直径10mmで、測定圧力は1.5kPaとした。
多孔質電極基材の厚さ方向の電気抵抗(貫通方向抵抗)の測定は以下のように行った。金メッキした銅板に多孔質電極基材を挟み、銅板の上下から1MPaで加圧し、10mA/cm2の電流密度で電流を流したときの抵抗値を測定し、次式より求めた。
貫通方向抵抗(mΩ・cm2)=測定抵抗値(mΩ)×試料面積(cm2)
融点が400℃以上の粒状物質を含有する酸化繊維(B)の含有率は、融点が400℃以上の粒状物質とフッ素系樹脂とを含浸させずに作製した多孔質電極基材の目付と、使用した炭素短繊維(A)目付から、次式より算出した。
融点が400℃以上の粒状物質を含有する酸化繊維(B)の含有率(%)=[多孔質電極基材目付(g/m2)-炭素短繊維(A)目付(g/m2)]÷多孔質電極基材目付(g/m2)×100。
多孔質電極基材のうねりの指標として、平板上に縦250mm横250mmの多孔質電極基材を静置した際の、多孔質電極基材の平板からの高さの最大値と最小値の差を算出した。
水系懸濁重合法により合成したアクリロニトリル/酢酸ビニル=93/7(質量比)の組成を有する質量平均分子量140000のアクリル系ポリマー(軟化点:320℃以上)117gと融点が400℃以上の粒状物質であり炭素粉(C1)としてカーボンブラック(三菱化学株式会社製、製品名:♯3230B、融点:3550℃以上)83gをジメチルアセトアミド800gにスリーワンモーターにて混合溶解させ、炭素粉を含むアクリル系ポリマー紡糸原液を調製した。
次いで、得られた紡糸原液を80℃に昇温し、その温度に保ったまま、ギヤポンプを用いて紡糸ノズルへ定量供給した。そして、紡糸原液をノズルの口金より凝固浴(ジメチルアセトアミドが30質量%で、水が70質量%となるように調整)に吐出し凝固させる湿式紡糸方法より、総延伸倍率が3.0倍になるように紡糸した。
炭素短繊維(A)として、平均繊維径が7μm、平均繊維長が3mmのPAN系炭素繊維を用意した。また、融点が400℃以上の粒状物質を含有する酸化繊維前駆体繊維(b)として、製造例2で得られた叩解によってフィブリル化した炭素粉(C1)を含有する酸化繊維前駆体繊維(b2-1)を用意した。
ノズル2:孔径φ0.15mm×501孔、幅方向孔間ピッチ1mm(1001孔/幅1m)、1列配置、ノズル有効幅500mm。
ノズル3:孔径φ0.15mm×1002孔、幅方向孔間ピッチ1.5mm、3列配置、列間ピッチ5mm、ノズル有効幅500mm。
炭素短繊維(A)と酸化繊維前駆体繊維(b2-1)との質量比を60:40としたこと以外は実施例1と同様にして、多孔質電極基材(実施例2)を得た。
炭素短繊維(A)と酸化繊維前駆体繊維(b2-1)との質量比を70:30としたこと以外は実施例1と同様にして、多孔質電極基材(実施例3)を得た。
炭素短繊維(A)と酸化繊維前駆体繊維(b2-1)との質量比を85:15としたこと以外は実施例1と同様にして、多孔質電極基材(実施例4)を得た。
融点が400℃以上の粒状物質(カーボンブラック)を含有する繊維(b)として、製造例3で得られた酸化繊維前駆体繊維(b2-2)を用いたこと以外は実施例4と同様にして、多孔質電極基材(実施例5)を得た。
融点が400℃以上の粒状物質(カーボンブラック)を含有する繊維(b)として、製造例1で得られた酸化繊維前駆体短繊維(b1)を用いたこと以外は実施例4と同様にして、多孔質電極基材(実施例6)を得た。
融点が400℃以上の粒状物質(カーボンブラック)を含有する繊維(b)として、製造例1で得られた酸化繊維前駆体短繊維(b1)と、製造例2で得られた酸化繊維前駆体繊維(b2-1)とを用い、それぞれの質量比を70:15:15としたものを用いたこと以外は実施例4と同様にして、多孔質電極基材(実施例7)を得た。
炭素粉(C2)、フッ素系樹脂および分散剤が、それぞれ4.0質量%、4.0質量%および4.5質量%となるように、炭素粉(C2)とフッ素系樹脂との混合物の分散液を調製したこと以外は実施例4と同様にして、多孔質電極基材(実施例8)を得た。
炭素粉(C2)としてケッチェンブラック(ライオン(株)製)と熱分解黒鉛(商品名:PC-H、伊藤黒鉛工業(株)製)、を用い、その比率(質量比)を90:10としたこと以外は実施例4と同様にして、多孔質電極基材(実施例9)を得た。
高圧液体噴射処理による交絡処理を実施しなかったこと以外は実施例1と同様にして、多孔質電極基材(実施例10)を得た。
加圧加熱成型処理を実施しなかったこと以外は実施例1と同様にして、多孔質電極基材(実施例11)を得た。
炭素粉(C2)とフッ素系樹脂との混合物を前駆体シートに含浸させた後、乾燥処理を実施しなかったこと以外は実施例1と同様にして、多孔質電極基材(実施例12)を得た。
(1)膜-電極接合体(MEA)の製造
実施例4で得られた多孔質電極基材2組を、カソード用およびアノード用の多孔質電極基材として用意した。また、パーフルオロスルホン酸系の高分子電解質膜(膜厚:30μm)の両面に触媒担持カーボン(触媒:Pt、触媒担持量:50質量%)からなる触媒層(触媒層面積:25cm2、Pt付着量:0.3mg/cm2)を形成した積層体を容易した。この積層体を、カソード用およびアノード用の多孔質炭素電極基材で挟持し、これらを接合して、MEAを得た。
得られたMEAを、蛇腹状のガス流路を有する2枚のカーボンセパレーターによって挟み、固体高分子型燃料電池(単セル)を形成した。
融点が400℃以上の粒状物質を用いず、アクリロニトリル系重合体及びジメチルアセトアミドの配合量をそれぞれ150g、及び850gとして炭素粉(C1)を含まないアクリロニトリル系重合体紡糸原液を調製し、この紡糸原液を用いた以外は製造例2と同様にしてフィブリルが多数分岐した構造を有する融点が400℃以上の粒状物質を含まない酸化繊維前駆体繊維を得た。さらにこのフィブリルが多数分岐した構造を有する融点が400℃以上の粒状物質を含まない酸化繊維前駆体繊維を用いたこと以外は実施例1と同様にして、多孔質電極基材(比較例1)を得た。
炭素粉(C2)とフッ素系樹脂との混合物の分散液を含浸させずに、熱処理したこと以外は実施例1と同様にして、多孔質電極基材(比較例2)を得た。
アクリロニトリル系重合体に変えてポリフッ化ビニリデン(ATOFINA社製、商品名:KYNAR9000)を用いた以外は製造例2と同様にしてフィブリルが多数分岐した構造を有するポリフッ化ビニリデン繊維を得た。さらにこのフィブリルが多数分岐した構造を有する400℃以上の粒状物質を含むポリフッ化ビニリデン繊維を用いたこと以外は実施例1と同様にして、多孔質電極基材(比較例3)を得た。
加圧加熱成型処理を実施しないこと以外は実施例10と同様にして、多孔質電極基材(実施例14)を得た。
乾燥処理する工程を実施しないこと以外は実施例14と同様にして、多孔質電極基材(実施例15)を得た。
炭素粉(C2)を用いず、フッ素系樹脂の分散液のみを含浸すること以外は実施例1と同様にして、多孔質電極基材(比較例4)を得た。
2 分割繊維製造用紡糸原液の吐出口
3 水蒸気の流入口
4 スリット状水蒸気流路
5 混合セル部
6 混合セル部の出口
A 分割繊維製造用紡糸原液の吐出線
B 水蒸気の噴射線
C AとBのなす角
Claims (20)
- 炭素短繊維(A)と、軟化点が250℃以上400℃未満のポリマー及び融点が400℃以上の粒状物質を含有する繊維(b)とを、平面方向に分散させて前駆体シートとする工程(1)と、
前記前駆体シートに粉状の炭素を含有する炭素粉(C2)とフッ素元素及び樹脂成分を含有するフッ素系樹脂とを含浸させる工程(2)と、
前記含浸させた前駆体シートを酸素存在下、250℃以上400℃未満の温度で熱処理する工程(3)と
を含むことを特徴とする多孔質電極基材の製造方法。 - 前記工程(1)と前記工程(2)との間に、前記前駆体シートの前記繊維に外力を加えることで前記繊維が互いに絡み合わさった3次元交絡構造を形成させる交絡処理を行う工程(4)を更に含むことを特徴とする請求項1に記載の製造方法。
- 前記工程(1)と工程(2)との間に、前記前駆体シートを200℃未満で加熱し20kPa~10MPaの圧力で加圧する加熱加圧成型の工程(5)を更に含むことを特徴とする請求項1に記載の製造方法。
- 前記工程(4)と前記工程(2)との間に、前記前駆体シートを200℃未満で加熱し20kPa~10MPaの圧力で加圧する加熱加圧成型の工程(5)を更に含むことを特徴とする請求項2に記載の製造方法。
- 前記工程(2)と前記工程(3)との間に、前記前駆体シートを70℃以上150℃未満の温度で乾燥処理する工程(6)を更に含むことを特徴とする請求項1から4のいずれか1項に記載の製造方法。
- 前記繊維(b)が、前記熱処理により酸化される酸化繊維前駆体繊維(b1)であることを特徴とする請求項1から5のいずれか1項に記載の製造方法。
- 前記繊維(b)が、芯部及び前記芯部より繊維が分岐したフィブリル部を有するフィブリル状酸化前駆体繊維(b2)であることを特徴とする請求項1から6のいずれか1項に記載の製造方法。
- 前記粒状物質が、炭素を含有する炭素粉(C1)であることを特徴とする請求項1から7のいずれか1項に記載の多孔質電極基材の製造方法。
- 前記炭素粉(C1)が、カーボンブラックであることを特徴とする請求項8に記載の多孔質電極基材の製造方法。
- 前記炭素粉(C2)が、カーボンブラック又は黒鉛粉を含有することを特徴とする請求項1から9のいずれか1項に記載の製造方法。
- 1000℃以上で炭素化する工程を含まないことを特徴とする請求項1から10のいずれか1項に記載の多孔質電極基材の製造方法。
- 請求項1から11のいずれか1項に記載の製造方法で製造された多孔質電極基材。
- 炭素短繊維(A)と、軟化点が250℃以上400℃未満のポリマー及び融点が400℃以上の粒状物質を含有する酸化繊維(B)と、粉状の炭素を含有する炭素粉(C2)とフッ素元素及び樹脂成分を含有するフッ素系樹脂とを備え、
前記炭素短繊維(A)が前記酸化繊維(B)を介して相互に接合されてなる部位を有することを特徴とする多孔質電極基材。 - 前記炭素短繊維(A)が前記フッ素系樹脂を介して相互に接合されてなる部位をさらに有することを特徴とする請求項13に記載の多孔質電極基材。
- 前記炭素短繊維(A)と前記酸化繊維(B)とが前記フッ素系樹脂により相互に接合されてなる部位をさらに有することを特徴とする請求項13又は14に記載の多孔質電極基材。
- 前記多孔質電極基材を縦250mm横250mmとなるよう平板上に静置した際に平板からの高さの最大値と最小値の差が2mm以下であることを特徴とする請求項13から15のいずれか1項に記載の多孔質電極基材。
- 単位厚みあたりのガス透気度が750ml/hr/cm2/mmAq・mm以上、2000ml/hr/cm2/mmAq以下、単位厚みあたりの貫通方向抵抗が0.18mΩ・cm2/mm以下、かつ、ガス透気度と貫通方向抵抗の比は260ml/hr/cm2/mmAq/mΩ・cm2以上であることを特徴とする請求項12~16のいずれか1項に記載の多孔質電極基材。
- 前記多孔質電極基材が前記酸化繊維(B)が互いに立体的に絡み合った構造を備えた3次元交絡構造体であることを特徴とする請求項13~17のいずれか1項に記載の多孔質電極基材。
- 請求項12~18のいずれか1項に記載の多孔質電極基材を備えてなることを特徴とする膜-電極接合体。
- 請求項19に記載の膜-電極接合体を備えてなることを特徴とする固体高分子型燃料電池。
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JP2018028151A (ja) * | 2016-08-15 | 2018-02-22 | 三菱製紙株式会社 | 炭素短繊維不織布の製造方法 |
JP2021143454A (ja) * | 2017-06-06 | 2021-09-24 | 日本バイリーン株式会社 | 炭素繊維シ−ト、ガス拡散電極、膜−電極接合体、固体高分子形燃料電池、及び炭素繊維シートの製造方法 |
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JP2018028151A (ja) * | 2016-08-15 | 2018-02-22 | 三菱製紙株式会社 | 炭素短繊維不織布の製造方法 |
JP2021143454A (ja) * | 2017-06-06 | 2021-09-24 | 日本バイリーン株式会社 | 炭素繊維シ−ト、ガス拡散電極、膜−電極接合体、固体高分子形燃料電池、及び炭素繊維シートの製造方法 |
JP7145274B2 (ja) | 2017-06-06 | 2022-09-30 | 日本バイリーン株式会社 | 炭素繊維シ-ト、ガス拡散電極、膜-電極接合体、固体高分子形燃料電池、及び炭素繊維シートの製造方法 |
JP7394923B2 (ja) | 2017-06-06 | 2023-12-08 | 日本バイリーン株式会社 | 炭素繊維シ-ト、ガス拡散電極、膜-電極接合体、固体高分子形燃料電池、及び炭素繊維シートの製造方法 |
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JP5664791B2 (ja) | 2015-02-04 |
EP2876714A1 (en) | 2015-05-27 |
EP2876714A4 (en) | 2015-07-15 |
JPWO2014014055A1 (ja) | 2016-07-07 |
US20150155568A1 (en) | 2015-06-04 |
CN104471765B (zh) | 2017-03-08 |
CN104471765A (zh) | 2015-03-25 |
KR20150033659A (ko) | 2015-04-01 |
KR101654488B1 (ko) | 2016-09-05 |
EP2876714B1 (en) | 2017-08-30 |
CA2878948C (en) | 2017-10-24 |
CA2878948A1 (en) | 2014-01-23 |
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