WO2015182676A1 - 高酸素透過性アイオノマー - Google Patents
高酸素透過性アイオノマー Download PDFInfo
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- WO2015182676A1 WO2015182676A1 PCT/JP2015/065304 JP2015065304W WO2015182676A1 WO 2015182676 A1 WO2015182676 A1 WO 2015182676A1 JP 2015065304 W JP2015065304 W JP 2015065304W WO 2015182676 A1 WO2015182676 A1 WO 2015182676A1
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D127/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers
- C09D127/02—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
- C09D127/12—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C09D127/18—Homopolymers or copolymers of tetrafluoroethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F214/18—Monomers containing fluorine
- C08F214/26—Tetrafluoroethene
- C08F214/262—Tetrafluoroethene with fluorinated vinyl ethers
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F214/18—Monomers containing fluorine
- C08F214/26—Tetrafluoroethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F14/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F14/02—Monomers containing chlorine
- C08F14/04—Monomers containing two carbon atoms
- C08F14/12—1,2- Dichloroethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F8/00—Chemical modification by after-treatment
- C08F8/12—Hydrolysis
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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
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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
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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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- 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
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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
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1039—Polymeric electrolyte materials halogenated, e.g. sulfonated polyvinylidene fluorides
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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
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1067—Polymeric electrolyte materials characterised by their physical properties, e.g. porosity, ionic conductivity or thickness
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
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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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- 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 highly oxygen permeable ionomer, an emulsion and an ionomer solution containing the ionomer, an electrode catalyst layer, a membrane electrode assembly, and a fuel cell.
- the membrane electrode assembly (MEA) constituting the polymer electrolyte fuel cell is provided with an electrode catalyst layer formed of a catalyst such as platinum and an ionomer. Since catalysts such as platinum are expensive, reduction of the amount of use thereof is required. However, when the amount of use of the catalyst is reduced, the performance of the battery tends to deteriorate. In order to avoid this disadvantage, attempts have been made to improve the oxygen permeability of the ionomer forming the electrode catalyst layer and to distribute oxygen throughout the electrode.
- Patent Document 1 discloses a hydrophilic structure having a hydrophobic asymmetric ring structure and a proton conductive group bonded to the asymmetric ring structure as a polymer electrolyte having high oxygen permeability and suitable as a cathode side catalyst layer ionomer. And a polymer electrolyte used as a cathode side catalyst layer ionomer is described.
- Patent Document 2 discloses that a cathode catalyst layer is a solid polymer as a membrane electrode assembly for a polymer electrolyte fuel cell capable of obtaining high power generation characteristics under high temperature and low or no humidifying operation conditions.
- the electrolyte polymer the ion exchange capacity is 0.9 to 2.5 meq / g dry resin, and the oxygen permeability coefficient measured by the high vacuum method at a temperature of 100 ° C. is 1 ⁇ 10 ⁇ 12 [cm 3 ( Normal) ⁇ cm / cm 2 ⁇ s ⁇ Pa] and a polymer (H) having an oxygen / nitrogen separation factor of 2.5 or more at 100 ° C.
- a membrane electrode assembly is described.
- the polymer (H) has a cyclic structure and a repeating unit (A) having no ion exchange group or a precursor group thereof, and / or a cyclic structure and an ion exchange group or a precursor group thereof.
- A no ion exchange group or a precursor group thereof
- B a repeating unit having a total proportion of the repeating unit (A) and the repeating unit (B) of all repeating units in the polymer (H) is 20 mol% or more. is there.
- Patent Document 3 as a solid polymer electrolyte material excellent in ion conductivity, water repellency and gas permeability, a repeating unit based on a fluorine-containing monomer that gives a polymer having an aliphatic ring structure in the main chain by radical polymerization;
- Patent Document 4 discloses a porous gas diffusion electrode including a catalyst layer containing a catalyst and a fluorine-containing ion exchange resin as a gas diffusion electrode having excellent electrode characteristics for an oxygen reduction reaction. Further includes a polymer compound having an oxygen permeability coefficient of 5 ⁇ 10 ⁇ 11 [cm 3 (Normal) ⁇ cm / cm 2 ⁇ s ⁇ Pa] or more and substantially not having an ion exchange group.
- a gas diffusion electrode is described which is characterized in that The polymer compound is a polymer including a repeating unit based on a perfluorocarbon having an aliphatic ring structure.
- Patent Document 5 includes polymerized units of monomer A and monomer B as ion conductive compositions useful for fuel cells, electrolytic cells, ion exchange membranes, sensors, electrochemical capacitors, and improved electrodes.
- An ion conductive composition is described that is formed from an ionomer that is SO 2 X.
- a gas diffusion electrode containing a catalyst and an ion exchange resin is used as a fuel electrode and an air electrode.
- the fuel electrode is provided on one side of the membrane-shaped solid polymer electrolyte, and the air electrode is provided on the other side.
- the ion exchange resin contained in the air electrode is an ion exchange comprising a copolymer including the following polymerization unit A, the following polymerization unit B, and the following polymerization unit C.
- a solid polymer electrolyte fuel cell characterized by being a resin is described.
- Polymerized unit A polymerized unit based on tetrafluoroethylene
- polymerized unit B polymerized unit based on perfluorovinyl ether having a sulfonic acid group
- polymerized unit C based on perfluorovinyl ether having no ion-exchange group or precursor group thereof Polymerized unit.
- the ionomers disclosed in Patent Documents 1 to 6 exhibit high oxygen permeability under both low and high humidification conditions close to the actual operating environment of a fuel cell, and in particular, fuel for automobiles. There is room for improvement with respect to the development of durability against frequent voltage fluctuations during power generation (hereinafter also referred to as “power generation durability”) required for batteries.
- power generation durability durability against frequent voltage fluctuations during power generation
- the present invention provides an ionomer having high oxygen permeability (particularly, high oxygen permeability is exhibited under both low and high humidification conditions) and high power generation durability. The purpose is to provide.
- the present inventors have a very limited equivalent weight and glass transition temperature, and a polymer having a repeating unit of fluorovinyl ether having no proton exchange group
- the present inventors have found that the oxygen permeability, power generation performance, and power generation durability are dramatically improved at the same time, and the present invention has been completed.
- the present invention is a highly oxygen permeable ionomer having a repeating unit A and a repeating unit B, an equivalent weight of 250 to 930, and a glass transition temperature of 100 to 130 ° C.
- Rf 11 represents a fluorinated hydrocarbon group having no proton exchange group having 1 or more carbon atoms. When the number of carbon atoms is 2 or more, oxygen atoms may be inserted between carbon-carbon atoms.
- Rp is a monovalent group having a proton exchange group.
- the repeating unit A has the general formula (3):
- Y 41 represents F or a perfluoroalkyl group having 1 to 3 carbon atoms.
- K 4 represents 0 or 1
- n 4 represents an integer of 1 to 8
- n 4 Y 41 s may be the same.
- M 4 represents an integer of 1 to 6, and is preferably at least one selected from the group consisting of repeating units represented by:
- the repeating unit B has the general formula (5):
- Y 51 represents F, Cl or a perfluoroalkyl group having 1 to 3 carbon atoms
- k 5 represents an integer of 0 to 2
- n 5 represents an integer of 0 to 8
- n 5 Y 51 may be the same or different
- Y 52 represents F or Cl
- m 5 represents an integer of 2 to 6.
- m 5 Y 52 may be the same or different
- Z 5 represents H, an alkali metal, an alkaline earth metal, or NR 51 R 52 R 53 R 54.
- R 51 , R 52 , R 53 and R 54 each independently represent an alkyl group having 1 to 3 carbon atoms or H. It is preferable that it is a repeating unit represented by.
- the repeating unit B has the general formula (6):
- Z 5 represents H, an alkali metal, an alkaline earth metal, or NR 51 R 52 R 53 R 54.
- R 51 , R 52 , R 53, and R 54 each independently represent 1 to 3 carbon atoms. It is preferably a repeating unit represented by the following formula:
- the high oxygen-permeable ionomer further has a repeating unit C, and the repeating unit C has the general formula (7):
- Rf 71 represents F, Cl or a linear or branched fluoroalkyl group having 1 to 9 carbon atoms
- Y 81 represents H or F
- Y 82 represents F or a linear or branched fluoroalkyl group having 1 to 9 carbon atoms
- Y 83 represents H, F, Cl or 1 to 9 carbon atoms. It is preferably at least one selected from the group consisting of repeating units represented by a linear or branched fluoroalkyl group.
- the repeating unit A is preferably 5 to 71 mol% with respect to all repeating units.
- the highly oxygen permeable ionomer of the present invention has high oxygen permeability regardless of the presence or absence of a cyclic structure in the main chain. Therefore, it can be manufactured at low cost, and a high-performance battery can be realized by using it for an electrode catalyst layer of a fuel cell. It is also possible to reduce the amount of catalyst used in the electrode catalyst layer.
- the membrane electrode assembly and fuel cell of the present invention are excellent in power generation performance and power generation durability.
- the high oxygen permeability ionomer has a glass transition temperature (Tg) of 100 to 130 ° C.
- Tg glass transition temperature
- the high oxygen-permeable ionomer preferably has a Tg of 105 ° C. or higher, more preferably 110 ° C. or higher, preferably 125 ° C. or lower, and more preferably 120 ° C. or lower.
- Tg melting of the ionomer can be suppressed at the expected operating temperature of the fuel cell in the future, and power generation durability can be improved.
- the temperature is below the upper limit of the preferable temperature, it is presumed that high oxygen permeability can be maintained without impairing the mobility of the ionomer.
- the glass transition temperature (Tg) can be measured using, for example, a dynamic viscoelasticity measuring apparatus DVA-225.
- the high oxygen permeability ionomer has an equivalent weight EW (dry mass in grams of perfluorocarbon sulfonic acid resin per equivalent of proton exchange group) of 250 to 930.
- EW dry mass in grams of perfluorocarbon sulfonic acid resin per equivalent of proton exchange group
- the upper limit of EW is preferably 910, and more preferably 890.
- the lower limit of EW is preferably 400, more preferably 450, and even more preferably 500.
- the equivalent weight EW is measured by the following method.
- a polymer electrolyte membrane in which the counter ion of the ion exchange group is in a proton state, approximately 2 to 20 cm 2 is immersed in 30 mL of a saturated NaCl aqueous solution at 25 ° C. and left for 30 minutes with stirring.
- the protons in the saturated NaCl aqueous solution are neutralized and titrated with 0.01N sodium hydroxide aqueous solution using phenolphthalein as an indicator.
- the polymer electrolyte membrane obtained after neutralization, in which the counter ion of the ion exchange group is in the state of sodium ions is rinsed with pure water, further vacuum dried and weighed.
- the high oxygen permeability ionomer has a repeating unit A and a repeating unit B.
- the repeating unit A has the general formula (1):
- Rf 11 represents a fluorinated hydrocarbon group having no proton exchange group having 1 or more carbon atoms. When the number of carbon atoms is 2 or more, oxygen atoms may be inserted between carbon-carbon atoms. It is a repeating unit represented by.
- the repeating unit A represents —SO 3 Z 2 (Z 2 represents H, an alkali metal, an alkaline earth metal, or NR 21 R 22 R 23 R 24.
- R 21 , R 22 , R 23, and R 24 each represents Independently a group having 1 to 3 carbon atoms or a group represented by —COOZ 2 (Z 2 is H, an alkali metal, an alkaline earth metal, or NR 21 R 22 R 23 R 24 .
- R 21 , R 22 , R 23 and R 24 each independently represents an alkyl group having 1 to 3 carbon atoms or H.
- the fluorinated hydrocarbon group is preferably an alkyl group having 2 or more carbon atoms in which an oxygen atom may be inserted between carbon-carbon atoms.
- the alkyl group preferably has 2 to 8 carbon atoms.
- the repeating unit A has the general formula (3):
- Y 41 represents F or a perfluoroalkyl group having 1 to 3 carbon atoms.
- K 4 represents 0 or 1
- n 4 represents an integer of 1 to 8
- n 4 Y 41 s may be the same.
- M 4 represents an integer of 1 to 6, and is preferably at least one selected from the group consisting of repeating units represented by:
- the repeating unit A represented by the general formula (3) includes —CF 2 —CF (—O—CF 2 CF 2 CF 3 ) —, —CF 2 —CF (—O—CF 2 CF 2 CF 2 CF 3 ) — And —CF 2 —CF (—O—CF 2 CF 3 ) — are preferred, —CF 2 —CF (—O—CF 2 CF 2 CF 3 ) — Is more preferable.
- k 4 is preferably 0.
- Y 41 is preferably F or a trifluoromethyl group.
- n 4 is preferably 1 or 2.
- m 4 is preferably an integer of 1 to 3.
- the repeating unit A is preferably —CF 2 —CF (—O—CF 2 CF 2 CF 3 ) — among those described above.
- the preferred molecular weight of the repeating unit A is 180 to 1000.
- a more preferred lower limit is 190, and a more preferred lower limit is 210.
- a more preferred upper limit is 900, and a more preferred upper limit is 700.
- the oxygen permeability tends to be higher and the EW tends to be smaller.
- the high oxygen-permeable ionomer further has a repeating unit B.
- the repeating unit B has the general formula (2):
- Rp is a monovalent group having a proton exchange group
- —SO 3 Z 2 Z 2 represents H, an alkali metal, an alkaline earth metal, or NR 21 R 22 R 23 R 24.
- R 21 , R 22 , R 23, and R 24 Are each independently an alkyl group having 1 to 3 carbon atoms or a group represented by H).
- the repeating unit B has the general formula (5):
- Y 51 represents F, Cl or a perfluoroalkyl group having 1 to 3 carbon atoms
- k 5 represents an integer of 0 to 2
- n 5 represents an integer of 0 to 8
- n 5 Y 51 may be the same or different
- Y 52 represents F or Cl
- m 5 represents an integer of 2 to 6.
- m 5 Y 52 may be the same or different
- Z 5 represents H, an alkali metal, an alkaline earth metal, or NR 51 R 52 R 53 R 54.
- R 51 , R 52 , R 53 and R 54 each independently represent an alkyl group having 1 to 3 carbon atoms or H. It is preferable that it is a repeating unit represented by.
- Y 51 is preferably F or a trifluoromethyl group.
- k 5 is preferably 0.
- n 5 is preferably 0 or 1, and n 5 is particularly preferably 0 in terms of excellent proton conductivity.
- Y 51 is preferably CF 3 .
- Y 52 is preferably F.
- m 5 is preferably 2.
- Z 5 is preferably H, Na, K or NH 4 .
- the repeating unit B has the general formula (6):
- Z 5 represents H, an alkali metal, an alkaline earth metal, or NR 51 R 52 R 53 R 54.
- R 51 , R 52 , R 53, and R 54 each independently represent 1 to 3 carbon atoms. It is more preferably a repeating unit represented by the following: Z 5 is preferably H, Na, K or NH 4 .
- the high oxygen permeability ionomer preferably further has a repeating unit C.
- the repeating unit C has the general formula (7):
- Rf 71 represents F, Cl or a linear or branched fluoroalkyl group having 1 to 9 carbon atoms
- Y 81 represents H or F
- Y 82 represents F or a linear or branched fluoroalkyl group having 1 to 9 carbon atoms
- Y 83 represents H, F, Cl or 1 to 9 carbon atoms. It is preferably at least one selected from the group consisting of repeating units represented by a linear or branched fluoroalkyl group.
- Rf 71 is preferably F. Both Y 81 and Y 83 are preferably H. Y 82 is preferably a linear fluoroalkyl group represented by C 4 F 9 or C 6 F 13 .
- the repeating unit C -CF 2 -CF 2 -, - CF 2 -CFCF 3 -, - CF 2 -CFCl -, - CH 2 -CFH -, - CH 2 -CF 2 -, - CF 2 -CFH- And at least one selected from the group consisting of —CH 2 —C (CF 3 ) 2 — and —CH 2 —CH (CF 2 ) 4 F— is preferred, —CF 2 —CF 2 —, —CH 2 — CF 2 -, - CF 2 -CFCl -, - CH 2 -CFH- and -CF 2 -CFCF 3 - at least one member selected from the group consisting of more preferably, -CF 2 -CF 2 -, - CF 2 More preferable is at least one selected from the group consisting of —CFCl— and —CF 2 —CFCF 3 —, and at least one selected from the group consisting of —CF
- an ionomer having the repeating unit A exhibits high oxygen permeability and exhibits good power generation characteristics when used as a cathode of a fuel cell.
- the repeating unit A is considered to play an important role in forming an oxygen diffusion path.
- the higher the ratio of the repeating unit A the higher the oxygen permeability. I found it. This tendency becomes more prominent as the gas supplied to the fuel cell has a relatively low humidity.
- the repeating unit A is preferably 5 to 71 mol%, more preferably 5.5 mol% or more, still more preferably 6.0 mol% or more, more preferably 25 mol% based on all repeating units. % Or less, more preferably 21 mol% or less.
- the repeating unit B is preferably 13 to 45 mol%, more preferably 14 mol% or more, still more preferably 16 mol% or more, and 42 mol% or less with respect to all repeating units. More preferably, it is still more preferably 40 mol% or less.
- the molar ratio (A / B) of the repeating unit A to the repeating unit B is preferably 0.1 to 5.0, more preferably 0.15 or more, and 0 .2 or more is more preferable, 3.0 or less is more preferable, and 2.5 or less is more preferable. When the molar ratio is within this range, sufficient proton conductivity and oxygen permeability can be realized.
- the repeating unit C is preferably 16 to 82 mol% with respect to all repeating units.
- the repeating unit C is more preferably 50 mol% or more with respect to all repeating units, still more preferably 52 mol% or more with respect to all repeating units, particularly preferably 54 mol% or more, More preferably, it is 80 mol% or less, and still more preferably 78 mol% or less.
- the content (mol%) of the repeating units A to C in the high oxygen permeable ionomer can be measured by melt NMR. Appears in the spectrum of the melt 19 F-NMR, SO 2 F from the peak in the vicinity of 45 ppm, and -CF 3 groups near -80ppm and -OCF 2 - peak derived from a group, -CF near -120 ppm 2 - group and The content (mol%) can be calculated by calculating using the intensity ratio of the peak derived from the —OCF (CF 3 ) — group.
- the high oxygen permeability ionomer has a molar ratio (A / B) of the repeating unit A to the repeating unit B of 0.1 to 5.0 and an equivalent weight (EW) of 250 to 930. preferable. More preferably, the molar ratio (A / B) between the repeating unit A and the repeating unit B is 0.15 to 3.0, and the equivalent weight (EW) is 400 to 900, and more preferably the repeating unit A The molar ratio (A / B) between the unit A and the repeating unit B is 0.2 to 2.5, and the equivalent weight (EW) is 450 to 890.
- the high oxygen permeability ionomer preferably has a number average molecular weight of 1 to 2,000,000 because the processability, electrical conductivity, and mechanical strength are all excellent.
- the number average molecular weight is more preferably 3 to 1,000,000.
- the number average molecular weight is a value measured by a GPC (gel permeation chromatograph) method.
- the number average molecular weight can be calculated based on standard polystyrene by the following method.
- TOSOH HLC-8020 is used, and the column is three polystyrene gel MIX columns (Tosoh GMH series, 30 cm size), 40 ° C., NMP (containing 5 mmol / L LiBr) solvent, flow rate 0.7 mL / min. Can do.
- the sample concentration can be 0.1 wt% and the implantation amount can be 500 ⁇ L.
- the number average molecular weight is more preferably about 100,000 to 800,000 in terms of polystyrene, still more preferably about 130,000 to 700,000, and particularly preferably about 160,000 to 600,000.
- the high oxygen-permeable ionomer is more excellent in workability, electrical conductivity, and mechanical strength, and therefore preferably has a melt flow rate (MFR) of 0.1 to 1000, preferably 0.5 or more. More preferably, it is more preferably 1.0 or more, more preferably 200 or less, and still more preferably 100 or less.
- MFR melt flow rate
- the MFR can be measured using a MELT INDEXER TYPE C-5059D (trade name, manufactured by Toyo Seiki Co., Ltd.) under the conditions of 270 ° C. and a load of 2.16 kg in accordance with ASTM standard D1238.
- the high oxygen permeability ionomer of the present invention preferably has an oxygen permeability coefficient (cc ⁇ cm / (cm 2 ⁇ sec ⁇ cmHg)) of 3.0 ⁇ 10 ⁇ 9 or more, and 5.0 ⁇ 10 ⁇ 9 or more. More preferably, it is 6.0 ⁇ 10 ⁇ 9 or more, even more preferably 8.0 ⁇ 10 ⁇ 9 or more, and further preferably 1.0 ⁇ 10 ⁇ 8 or more. Particularly preferred.
- the oxygen transmission coefficient can be measured according to JIS K7126-2 and ISO 15105-2.
- As the oxygen permeability coefficient the larger one of the value measured at 80 ° C. and 30% RH and the value measured at 80 ° C. and 90% RH is adopted.
- the highly oxygen permeable ionomer of the present invention preferably does not contain a cyclic structure in the main chain.
- Examples of the cyclic structure in the main chain include the following structures.
- R 71 is an alkylene group having 1 or more carbon atoms.
- the alkylene group may be a fluoroalkylene group. When it is an alkylene group of 2 or more, it may be linear or branched, and the upper limit of the carbon number is about 20.
- R 72 is —CF 2 — or —CFR 73 — ( R 73 is an alkyl group having 1 to 3 carbon atoms or a fluoroalkyl group.)
- the cyclic structure is usually a 5-membered or 6-membered ring.
- R 81 is an alkylene group having 1 or more carbon atoms.
- the alkylene group may be a fluoroalkylene group.
- the upper limit of the number of carbon atoms is about 20.
- the cyclic structure is usually a 5-membered ring or a 6-membered ring.
- the ionomer can be prepared by a conventionally known method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. Among them, emulsion polymerization or solution polymerization is preferably used.
- emulsion polymerization the high oxygen permeable ionomer is obtained in the form of an emulsion in which the high oxygen permeable ionomer particles are dispersed in water.
- a fluoromonomer constituting the repeating unit A, a fluoromonomer constituting the repeating unit B, a method for continuously supplying the fluoromonomer constituting the repeating unit C into the pressure vessel, Or the method of supplying by dividing is preferable.
- the fluoromonomer constituting the repeating unit C is a gas monomer
- the pressure decreases when the monomer is consumed with the polymerization reaction. Therefore, it is preferable to supply the gas monomer so as to maintain the pressure.
- the fluoromonomer constituting the repeating unit A and the fluoromonomer constituting the repeating unit B are liquid, they can be supplied according to the consumption of the fluoromonomer constituting the repeating unit C so as to have a desired polymer composition.
- a method for supplying the liquid monomer a method of press-fitting using a pump, a method of press-fitting and pressurizing the monomer container, and the like can be appropriately selected.
- a method in which the fluoromonomer constituting the repeating unit A and the fluoromonomer constituting the repeating unit B are mixed in advance with a desired composition is preferable in terms of easy operation.
- the ionomer also includes a precursor polymer obtained by radical polymerization of a fluoromonomer constituting the repeating unit A, a precursor monomer of the fluoromonomer constituting the repeating unit B, and a fluoromonomer constituting the repeating unit C in an aqueous medium.
- a production method comprising: a polymerization step for obtaining an emulsion; and a hydrolysis step for converting the precursor polymer into a high oxygen permeable ionomer by adding an alkali to the emulsion to obtain an emulsion containing the high oxygen permeable ionomer. Can be manufactured.
- the high oxygen permeable ionomer is obtained in the form of an emulsion in which the high oxygen permeable ionomer particles are dispersed in water.
- Y 91 represents F, Cl or a perfluoroalkyl group having 1 to 3 carbon atoms
- k 9 represents an integer of 0 to 2
- n 9 represents an integer of 0 to 8
- n 9 Y 91 may be the same or different Y 92 represents F or Cl
- m 9 represents an integer of 2 to 6.
- m 9 Y 92 may be the same or different Y 93 is It is preferably a fluoromonomer represented by a halogen atom.
- Y 91 is preferably F or a trifluoromethyl group.
- k 9 is preferably 0.
- n 9 is preferably 0 or 1, and particularly preferably 0.
- Y 92 is preferably F.
- m 9 is preferably an integer of 2 to 4, particularly preferably 2.
- Y 93 is preferably F.
- the precursor monomer is Formula (10): CF 2 ⁇ CF—O—CF 2 CF 2 —SO 2 Y 93 (Wherein Y 93 represents a halogen atom), and is preferably a fluoromonomer. Y 93 is preferably F.
- alkali examples include aqueous solutions of NaOH, KOH and the like.
- the aqueous medium is not particularly limited as long as it is liquid and contains water. By being an aqueous medium, it is excellent in environmental load and cost. Also, the dispersion stability is improved.
- the content of water in the aqueous medium is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, and 90% by mass or more. Particularly preferred. Most preferably, the aqueous medium consists essentially of water.
- the aqueous medium may contain, together with water, a fluorine-free organic solvent such as alcohol, ether or ketone, a fluorine-containing organic solvent having a boiling point of 40 ° C. or lower, and the like.
- a fluorine-free organic solvent such as alcohol, ether or ketone
- a fluorine-containing organic solvent having a boiling point of 40 ° C. or lower, and the like.
- the radical polymerization may be performed in the presence of a surfactant.
- a surfactant a known fluorine-containing anionic surfactant is preferable.
- the radical polymerization is preferably performed by adding a polymerization initiator.
- the polymerization initiator is not particularly limited as long as it can generate radicals at the polymerization temperature, and known oil-soluble and / or water-soluble polymerization initiators can be used. A redox initiator may also be used.
- the concentration of the polymerization initiator is appropriately determined depending on the molecular weight and reaction rate of the target fluorine-containing copolymer.
- polymerization initiator examples include persulfates such as ammonium persulfate and potassium persulfate, and organic peroxides such as disuccinic acid peroxide, diglutaric acid peroxide, and tert-butyl hydroperoxide.
- persulfates such as ammonium persulfate and potassium persulfate
- organic peroxides such as disuccinic acid peroxide, diglutaric acid peroxide, and tert-butyl hydroperoxide.
- a combination of a persulfate or an organic peroxide and a reducing agent such as sodium sulfite, a bisulfite such as sodium hydrogen sulfite, a bromate, diimine, or oxalic acid.
- the radical polymerization can be performed under a pressure of 0.05 to 5.0 MPa. A preferable pressure range is 0.1 to 1.5 MPa.
- the radical polymerization can be performed at a temperature of 5 to 100 ° C. A preferred temperature range is 10-90 ° C.
- a known stabilizer, chain transfer agent, or the like may be added depending on the purpose.
- the present invention is also an emulsion characterized by comprising the above-mentioned highly oxygen permeable ionomer and water and / or an organic solvent.
- the emulsion can be suitably used as a raw material for forming an electrode catalyst layer of a fuel cell.
- the emulsion is preferably an emulsion for forming an electrode catalyst layer of a fuel cell.
- the content of the high oxygen-permeable ionomer in the emulsion is preferably 2 to 50% by mass, more preferably 5% by mass or more, further preferably 10% by mass or more, and 40% by mass. More preferably, it is more preferably 30% by mass or less, and particularly preferably 25% by mass or less.
- the present invention is also an ionomer solution characterized by containing the above-mentioned highly oxygen permeable ionomer and water and / or an organic solvent.
- the ionomer solution can be suitably used as a raw material for forming an electrode catalyst layer of a fuel cell.
- the ionomer solution is preferably an ionomer solution for forming an electrode catalyst layer of a fuel cell.
- the content of the high oxygen-permeable ionomer in the ionomer solution is preferably 2 to 50% by mass, more preferably 5% by mass or more, still more preferably 10% by mass or more, and 40% by mass. % Or less, more preferably 30% by mass or less, and particularly preferably 25% by mass or less.
- organic solvent examples include protic organic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, butanol, and glycerin, and non-protons such as N, N-dimethylformamide, N, N-dimethylacetamide, and N-methylpyrrolidone.
- protic organic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, butanol, and glycerin
- non-protons such as N, N-dimethylformamide, N, N-dimethylacetamide, and N-methylpyrrolidone.
- An organic solvent can be used alone or in combination of two or more.
- the ionomer solution may contain an organic additive.
- the ionomer solution may contain an inorganic additive.
- organic additive for example, a compound in which an atom is easily extracted by a radical, for example, hydrogen bonded to a tertiary carbon, a carbon-halogen bond, or the like is included.
- aromatic compounds partially substituted with the above functional groups such as polyaniline, polybenzimidazole, polybenzoxazole, polybenzothiazole, polybenzooxadiazole, phenylated polyquinoxaline, phenylated polyquinoline, etc. And unsaturated heterocyclic compounds.
- a thioether compound is also mentioned.
- dialkylthioethers such as dimethylthioether, diethylthioether, dipropylthioether, methylethylthioether, methylbutylthioether; cyclic thioethers such as tetrahydrothiophene, tetrahydroapiran; methylphenyl sulfide, ethylphenyl sulfide, diphenyl sulfide, dibenzyl And aromatic thioethers such as sulfide.
- a metal oxide is mentioned, for example.
- metal oxides may be used alone or as a mixture, for example, tin-added indium oxide (ITO), antimony-added tin oxide (ATO), aluminum zinc oxide (ZnO.Al 2 O 3 ), etc. Can be mentioned.
- ITO tin-added indium oxide
- ATO antimony-added tin oxide
- ZnO.Al 2 O 3 aluminum zinc oxide
- the mass ratio of the organic solvent to water is preferably 10/90 to 90/10, more preferably 30/70 or more, and 70/30 or less. It is more preferable.
- the high oxygen permeability ionomer can be suitably used as a raw material for forming a catalyst paste.
- the catalyst paste preferably contains the high oxygen permeable ionomer, water and / or an organic solvent, and a catalyst.
- the catalyst paste can be suitably used as a raw material for forming an electrode catalyst layer of a fuel cell.
- the catalyst paste is preferably a catalyst paste for forming an electrode catalyst layer of a fuel cell.
- the catalyst is not particularly limited as long as it has activity in the electrode catalyst layer, and is appropriately selected according to the purpose of use of the fuel cell in which the electrode catalyst layer is used.
- the catalyst is preferably a catalytic metal.
- the catalyst is preferably a metal that promotes a hydrogen oxidation reaction and an oxygen reduction reaction, such as platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, More preferably, it is at least one metal selected from the group consisting of vanadium and alloys thereof. Of these, platinum is preferable.
- the particle diameter of the catalytic metal is not limited, but is preferably 10 to 1000 angstroms, more preferably 10 to 500 angstroms, and most preferably 15 to 100 angstroms.
- the content of the high oxygen permeable ionomer in the catalyst paste is preferably 5 to 30% by mass, more preferably 8% by mass or more, with respect to the catalyst paste. Is more preferably 20% by mass or less, and further preferably 15% by mass or less.
- the content of the catalyst in the catalyst paste is preferably 50 to 200% by mass, more preferably 80% by mass or more, and 100% by mass or more with respect to the high oxygen permeable ionomer. Is more preferably 150% by mass or less, and further preferably 130% by mass or less.
- the catalyst paste preferably further contains a conductive agent.
- the catalyst and the conductive agent are composite particles (for example, Pt-supported carbon) made of a conductive agent carrying the catalyst particles.
- the high oxygen permeable ionomer also functions as a binder.
- the conductive agent is not limited as long as it is conductive particles (conductive particles).
- conductive particles conductive particles
- carbon black such as furnace black, channel black, and acetylene black, activated carbon, graphite, and various metals (excluding catalytic metals).
- It is preferably at least one type of conductive particles selected from the group consisting of:
- the particle size of these conductive agents is preferably 10 angstroms to 10 ⁇ m, more preferably 50 angstroms to 1 ⁇ m, and most preferably 100 to 5000 angstroms.
- the composite particles are preferably 1 to 99% by mass, more preferably 10 to 90% by mass, and most preferably 30 to 70% by mass of the catalyst particles with respect to the conductive particles.
- Pt catalyst-carrying carbons such as TEC10E40E, TEC10E50E, and TEC10E50HT manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. are preferable examples.
- the content of the composite particles is preferably 1.0 to 3.0% by mass, more preferably 1.4 to 2.9% by mass, and still more preferably 1.% by mass with respect to the high oxygen-permeable ionomer. It is 7 to 2.9% by mass, particularly preferably 1.7 to 2.3% by mass.
- the catalyst paste may further contain a water repellent.
- the catalyst paste may further contain polytetrafluoroethylene (hereinafter referred to as PTFE) in order to improve water repellency.
- PTFE polytetrafluoroethylene
- the shape of PTFE is not particularly limited, but may be any shape as long as it is regular, preferably in the form of particles or fibers, and these may be used alone or in combination. .
- the content of PTFE is preferably 0.01 to 30.0% by mass, more preferably 1.0 to 25.0% by mass, and still more preferably 2.10% by mass with respect to the high oxygen-permeable ionomer. It is 0 to 20.0% by mass, particularly preferably 5.0 to 10.0% by mass.
- the catalyst paste may further contain a metal oxide for improving hydrophilicity.
- a metal oxide for improving hydrophilicity Is not particularly restricted but includes metal oxides, Al 2 O 3, B 2 O 3, MgO, SiO 2, SnO 2, TiO 2, V 2 O 5, WO 3, Y 2 O 3, ZrO 2, Zr It is preferably at least one metal oxide selected from the group consisting of 2 O 3 and ZrSiO 4 .
- at least one metal oxide selected from the group consisting of Al 2 O 3 , SiO 2 , TiO 2 and ZrO 2 is preferable, and SiO 2 is particularly preferable.
- the metal oxide may be in the form of particles or fibers, but it is particularly desirable that the metal oxide be amorphous.
- amorphous as used herein means that no particulate or fibrous metal oxide is observed even when observed with an optical microscope or an electron microscope.
- SEM scanning electron microscope
- TEM transmission electron microscope
- the content of the metal oxide is preferably 0.01 to 100% by mass, more preferably 0.01 to 45% by mass, and still more preferably 0.01 to 100% by mass with respect to the high oxygen permeable ionomer. It is 25% by mass, particularly preferably 0.5 to 6.0% by mass.
- the present invention is also an electrode catalyst layer using the high oxygen-permeable ionomer.
- the electrode catalyst layer is preferably made of the catalyst paste.
- the electrode catalyst layer can be manufactured at low cost and has high oxygen permeability.
- the electrode catalyst layer can be suitably used for a fuel cell.
- the electrode catalyst layer includes the high oxygen permeable ionomer and the catalyst.
- the amount of the high oxygen permeable ionomer supported on the electrode area is preferably 0.001 to 10 mg / cm 2 , more preferably 0.01 to 5 mg / cm 2 , and still more preferably 0.1 to 1 mg. / Cm 2 .
- the electrode catalyst layer of the present invention is preferably composed of a high oxygen permeable ionomer, a catalyst and a conductive agent.
- the electrode catalyst layer is composed of a high oxygen-permeable ionomer and catalyst particles and composite particles (for example, Pt-supported carbon) made of a conductive agent supporting the catalyst particles. is there.
- the high oxygen permeable ionomer also functions as a binder.
- the conductive agent is not limited as long as it is conductive particles (conductive particles).
- conductive particles conductive particles
- carbon black such as furnace black, channel black, and acetylene black, activated carbon, graphite, and various metals (excluding catalytic metals). It is preferable that it is at least 1 type of electroconductive particle selected from the group which consists of.
- the particle size of these conductive agents is preferably 10 angstroms to 10 ⁇ m, more preferably 50 angstroms to 1 ⁇ m, and most preferably 100 to 5000 angstroms.
- the composite particles are preferably 1 to 99% by mass, more preferably 10 to 90% by mass, and most preferably 30 to 70% by mass of the catalyst particles with respect to the conductive particles.
- Pt catalyst supporting carbon such as TEC10E40E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. can be mentioned as a suitable example.
- the content of the composite particles is preferably 20 to 95% by mass, more preferably 40 to 90% by mass, still more preferably 50 to 85% by mass, and particularly preferably 60% by mass with respect to the total mass of the electrode catalyst layer. ⁇ 80% by mass.
- the supported amount of the catalyst metal relative to the electrode area is preferably 0.001 to 10 mg / cm 2 , more preferably 0 in the state where the electrode catalyst layer is formed. 0.01 to 5 mg / cm 2 , more preferably 0.1 to 1 mg / cm 2 .
- the thickness of the electrode catalyst layer is preferably 0.01 to 200 ⁇ m, more preferably 0.1 to 100 ⁇ m, and most preferably 1 to 50 ⁇ m.
- the electrode catalyst layer may contain a water repellent as necessary.
- the electrode catalyst layer may further contain polytetrafluoroethylene (hereinafter referred to as PTFE) in order to improve water repellency.
- PTFE polytetrafluoroethylene
- the shape of PTFE is not particularly limited, but may be any shape as long as it is regular, preferably in the form of particles or fibers, and these may be used alone or in combination.
- the PTFE content is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass, and most preferably the total mass of the electrode catalyst layer. 0.1 to 5% by mass.
- the electrode catalyst layer may further contain a metal oxide for improving hydrophilicity.
- the metal oxide is not particularly limited, but Al 2 O 3 , B 2 O 3 , MgO, SiO 2 , SnO 2 , TiO 2 , V 2 O 5 , WO 3 , Y 2 O 3 , ZrO 2 It is preferably at least one metal oxide selected from the group consisting of Zr 2 O 3 and ZrSiO 4 . Among these, at least one metal oxide selected from the group consisting of Al 2 O 3 , SiO 2 , TiO 2 and ZrO 2 is preferable, and SiO 2 is particularly preferable.
- the form of the metal oxide may be in the form of particles or fibers, but it is particularly desirable that the form be amorphous.
- amorphous as used herein means that no particulate or fibrous metal oxide is observed even when observed with an optical microscope or an electron microscope.
- SEM scanning electron microscope
- TEM transmission electron microscope
- the content of the metal oxide is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass, and most preferably 0.1 to 5% by mass with respect to the total mass of the electrode catalyst layer. It is.
- the porosity of the electrode catalyst layer is not particularly limited, but is preferably 10 to 90% by volume, more preferably 20 to 80% by volume, and most preferably 30 to 60% by volume.
- the electrode catalyst layer is A polymerization step for obtaining an emulsion containing a highly oxygen-permeable ionomer by radical polymerization of a fluoromonomer constituting the repeating unit A, a fluoromonomer constituting the repeating unit B, and a fluoromonomer constituting the repeating unit C in an aqueous medium; A step of dispersing a catalyst in the emulsion to prepare a catalyst paste; Applying the catalyst paste to a substrate; Drying the catalyst paste applied to the substrate to obtain an electrode catalyst layer; It can manufacture suitably by the manufacturing method containing.
- the electrode catalyst layer also has A polymerization step of obtaining an emulsion containing a precursor polymer by radical polymerization of a fluoromonomer constituting the repeating unit A, a precursor monomer of the fluoromonomer constituting the repeating unit B, and a fluoromonomer constituting the repeating unit C in an aqueous medium; , A hydrolysis step of converting the precursor polymer to a high oxygen permeable ionomer by adding an alkali to the emulsion to obtain an emulsion containing the high oxygen permeable ionomer; A step of dispersing a catalyst in the emulsion to prepare a catalyst paste; Applying the catalyst paste to a substrate; Drying the catalyst paste applied to the substrate to obtain an electrode catalyst layer; It can manufacture suitably by the manufacturing method containing.
- the electrode catalyst layer also has A polymerization step for obtaining an emulsion containing a highly oxygen-permeable ionomer by radical polymerization of a fluoromonomer constituting the repeating unit A, a fluoromonomer constituting the repeating unit B, and a fluoromonomer constituting the repeating unit C in an aqueous medium; Adding an organic solvent to the emulsion to obtain an ionomer solution in which a high oxygen-permeable ionomer is dissolved; A step of preparing a catalyst paste by dispersing a catalyst in the ionomer solution; Applying the catalyst paste to a substrate; Drying the catalyst paste applied to the substrate to obtain an electrode catalyst layer; It can manufacture suitably by the manufacturing method containing.
- the electrode catalyst layer also has A polymerization step of obtaining an emulsion containing a precursor polymer by radical polymerization of a fluoromonomer constituting the repeating unit A, a precursor monomer of the fluoromonomer constituting the repeating unit B, and a fluoromonomer constituting the repeating unit C in an aqueous medium; , A hydrolysis step of converting the precursor polymer to a high oxygen permeable ionomer by adding an alkali to the emulsion to obtain an emulsion containing the high oxygen permeable ionomer; Adding an organic solvent to the emulsion to obtain an ionomer solution in which a high oxygen-permeable ionomer is dissolved; A step of preparing a catalyst paste by dispersing a catalyst in the ionomer solution; Applying the catalyst paste to a substrate; Drying the catalyst paste applied to the substrate to obtain an electrode catalyst layer; It can manufacture suitably by the manufacturing method containing.
- Y 91 represents F, Cl or a perfluoroalkyl group having 1 to 3 carbon atoms
- k 9 represents an integer of 0 to 2
- n 9 represents an integer of 0 to 8
- n 9 Y 91 may be the same or different Y 92 represents F or Cl
- m 9 represents an integer of 2 to 6.
- m 9 Y 92 may be the same or different Y 93 is It is preferably a fluoromonomer represented by a halogen atom.
- Y 91 is preferably F or a trifluoromethyl group.
- k 9 is preferably 0.
- n 9 is preferably 0 or 1, and particularly preferably 0.
- Y 92 is preferably F.
- m 9 is preferably an integer of 2 to 4, particularly preferably 2.
- Y 93 is preferably F.
- the precursor monomer is Formula (10): CF 2 ⁇ CF—O—CF 2 CF 2 —SO 2 Y 93 (Wherein Y 93 represents a halogen atom), and is preferably a fluoromonomer. Y 93 is preferably F.
- alkali examples include aqueous solutions of NaOH, KOH and the like.
- the aqueous medium is not particularly limited as long as it is liquid and contains water. By being an aqueous medium, it is excellent in environmental load and cost. Also, the dispersion stability is improved.
- the content of water in the aqueous medium is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, and 90% by mass or more. Particularly preferred. Most preferably, the aqueous medium consists essentially of water.
- the aqueous medium may contain, together with water, a fluorine-free organic solvent such as alcohol, ether or ketone, a fluorine-containing organic solvent having a boiling point of 40 ° C. or lower, and the like.
- a fluorine-free organic solvent such as alcohol, ether or ketone
- a fluorine-containing organic solvent having a boiling point of 40 ° C. or lower, and the like.
- the radical polymerization may be performed in the presence of a surfactant.
- a surfactant a known fluorine-containing anionic surfactant is preferable.
- the radical polymerization is preferably performed by adding a polymerization initiator.
- the polymerization initiator is not particularly limited as long as it can generate radicals at the polymerization temperature, and known oil-soluble and / or water-soluble polymerization initiators can be used. A redox initiator may also be used.
- the concentration of the polymerization initiator is appropriately determined depending on the molecular weight and reaction rate of the target fluorine-containing copolymer.
- polymerization initiator examples include persulfates such as ammonium persulfate and potassium persulfate, and organic peroxides such as disuccinic acid peroxide, diglutaric acid peroxide, and tert-butyl hydroperoxide.
- persulfates such as ammonium persulfate and potassium persulfate
- organic peroxides such as disuccinic acid peroxide, diglutaric acid peroxide, and tert-butyl hydroperoxide.
- a combination of a persulfate or an organic peroxide and a reducing agent such as sodium sulfite, a bisulfite such as sodium hydrogen sulfite, a bromate, diimine, or oxalic acid.
- the radical polymerization can be performed under a pressure of 0.05 to 5.0 MPa. A preferable pressure range is 1.5 to 3.0 MPa.
- the radical polymerization can be performed at a temperature of 10 to 100 ° C. A preferred temperature range is 50-90 ° C.
- a known stabilizer, chain transfer agent, or the like may be added depending on the purpose.
- organic solvent examples include protic organic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, butanol, and glycerin, and non-protons such as N, N-dimethylformamide, N, N-dimethylacetamide, and N-methylpyrrolidone.
- protic organic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, butanol, and glycerin
- non-protons such as N, N-dimethylformamide, N, N-dimethylacetamide, and N-methylpyrrolidone.
- An organic solvent can be used alone or in combination of two or more.
- the dissolution method is not particularly limited. For example, first, for example, a mixed solvent of water and a protic organic solvent is added to the emulsion under such a condition that the total solid concentration is 1 to 50% by mass. Next, the composition is placed in an autoclave having a glass inner cylinder as necessary, and the air inside is replaced with an inert gas such as nitrogen. Heat and stir for 12 hr. Thereby, an ionomer solution is obtained.
- the step of obtaining an ionomer solution is preferably a step of adding an organic solvent to the obtained emulsion and then heating to obtain an ionomer solution in which the high oxygen-permeable ionomer is dissolved.
- the higher the total solid content concentration the better from the viewpoint of yield. However, if the concentration is increased, undissolved substances may be formed, so 1 to 50% by mass is preferable, more preferably 3 to 40% by mass, and still more preferably 5%. ⁇ 30% by mass.
- the composition ratio of water and the protic organic solvent in the resulting ionomer solution depends on the dissolution method, dissolution conditions, type of polymer electrolyte, total solid content concentration, dissolution temperature, stirring speed, etc. Although it can be appropriately selected, 10 to 1000 parts by mass of the protic organic solvent is preferable with respect to 100 parts by mass of water, and particularly preferably 10 to 500 parts by mass of the organic solvent with respect to 100 parts by mass of water.
- the ionomer solution includes an emulsion (a liquid particle in which liquid particles are dispersed as colloidal particles or coarser particles to form a milk), and a suspension (solid particles in a liquid are colloidal particles or Such as those dispersed as particles that can be seen with a microscope), colloidal liquid (macromolecules dispersed), micellar liquid (a lyophilic colloidal dispersion system made up of many small molecules associated by intermolecular forces), etc. 1 type (s) or 2 or more types may be contained.
- emulsion a liquid particle in which liquid particles are dispersed as colloidal particles or coarser particles to form a milk
- a suspension solid particles in a liquid are colloidal particles or Such as those dispersed as particles that can be seen with a microscope
- colloidal liquid macromolecules dispersed
- micellar liquid a lyophilic colloidal dispersion system made up of many small molecules associated by intermolecular forces
- the ionomer solution can be concentrated.
- the concentration method is not particularly limited. For example, there are a method of heating and evaporating the solvent, a method of concentrating under reduced pressure, and the like.
- the solid fraction of the resulting coating solution is preferably 0.5 to 50% by mass in consideration of handleability and productivity.
- the ionomer solution is more preferably filtered from the viewpoint of removing coarse particle components.
- the filtration method is not particularly limited, and a general method conventionally performed can be applied. For example, a method of pressure filtration using a filter obtained by processing a filter medium having a normally used rated filtration accuracy is typically mentioned.
- the filter it is preferable to use a filter medium whose 90% collection particle size is 10 to 100 times the average particle size of the particles.
- the filter medium may be filter paper or a filter medium such as a sintered metal filter. Particularly in the case of filter paper, the 90% collection particle size is preferably 10 to 50 times the average particle size of the particles.
- the 90% collection particle size is preferably 50 to 100 times the average particle size of the particles. Setting the 90% collection particle size to be 10 times or more of the average particle size prevents the pressure necessary for liquid feeding from becoming too high, or the filter is blocked in a short period of time. Can be suppressed. On the other hand, setting it to 100 times or less of the average particle diameter is preferable from the viewpoint of satisfactorily removing particle agglomerates and resin undissolved materials that cause foreign matters in the film.
- the manufacturing method includes a step of dispersing the catalyst in the obtained emulsion or ionomer solution to prepare a catalyst paste, a step of applying the catalyst paste to the base material, and drying the catalyst paste applied to the base material to form an electrode. Obtaining a catalyst layer.
- the step of preparing the catalyst paste by dispersing the catalyst in the obtained emulsion or ionomer solution is a catalyst in which composite particles comprising catalyst particles and a conductive agent carrying the catalyst particles are dispersed in the obtained emulsion or ionomer solution. It is preferable to prepare a paste.
- the manufacturing method may further include a step of immersing in an inorganic acid such as hydrochloric acid after the electrode catalyst layer is formed.
- the acid treatment temperature is preferably 5 to 90 ° C., more preferably 10 to 70 ° C., and most preferably 20 to 50 ° C.
- the present invention is also a membrane electrode assembly (hereinafter also referred to as “MEA”) characterized by comprising the above electrode catalyst layer. Since the membrane electrode assembly of the present invention includes the electrode catalyst layer, it has excellent battery characteristics and mechanical strength, and is excellent in stability.
- the membrane electrode assembly can be suitably used for a fuel cell.
- MEA membrane electrode assembly
- the electrode catalyst layer as an anode includes a catalyst that easily oxidizes fuel (for example, hydrogen) to easily generate protons, and the electrode catalyst layer as a cathode reacts protons and electrons with an oxidizing agent (for example, oxygen or air). And a catalyst that produces water.
- fuel for example, hydrogen
- oxidizing agent for example, oxygen or air
- the catalyst metal described above can be suitably used as the catalyst.
- gas diffusion layer commercially available carbon cloth or carbon paper can be used.
- Typical examples of the former include carbon cloth E-tek and B-1 manufactured by DE NORA NORTH AMERICA, USA.
- Typical examples of the latter include CARBEL (registered trademark, Japan Gore-Tex Co., Ltd.), manufactured by Toray Industries, Inc. Examples thereof include TGP-H and carbon paper 2050 manufactured by SPECTRACORP.
- a structure in which the electrode catalyst layer and the gas diffusion layer are integrated is called a “gas diffusion electrode”.
- MEA can also be obtained by bonding the gas diffusion electrode to the electrolyte membrane.
- a typical example of a commercially available gas diffusion electrode is a gas diffusion electrode ELAT (registered trademark) (using carbon cloth as a gas diffusion layer) manufactured by DE NORA NORTH AMERICA.
- the MEA can be produced, for example, by sandwiching an electrolyte membrane between electrode catalyst layers and joining them by hot pressing. More specifically, a paste obtained by dispersing a commercially available platinum-supported carbon (for example, TEC10E40E manufactured by Tanaka Kikinzoku Co., Ltd.) as a catalyst in the above-described high oxygen-permeable ionomer dispersed or dissolved in a mixed solution of alcohol and water. Shape. A certain amount of this is applied to one side of each of the two PTFE sheets and dried to form an electrode catalyst layer. Next, the application surfaces of the PTFE sheets face each other, and an electrolyte membrane is sandwiched between them.
- TEC10E40E manufactured by Tanaka Kikinzoku Co., Ltd.
- the MEA After transferring and joining by hot pressing at 100 to 200 ° C., the MEA can be obtained by removing the PTFE sheet.
- a person skilled in the art knows how to make MEAs. The method for producing the MEA is described, for example, in JOURNAL OF APPLIED ELECTROCHEMISTRY, 22 (1992) p. 1-7.
- the MEA (including an MEA having a structure in which a pair of gas diffusion electrodes are opposed to each other) is further combined with constituent components used in general fuel cells such as a bipolar plate and a backing plate to constitute a fuel cell.
- the present invention also provides a fuel cell comprising the membrane electrode assembly.
- the fuel cell is preferably a solid polymer fuel cell.
- the fuel cell of the present invention is not particularly limited as long as it has the above-mentioned membrane electrode assembly, and may usually contain components such as gas constituting the fuel cell. Since the fuel cell of the present invention includes the membrane electrode assembly having the electrode catalyst layer, the fuel cell is excellent in battery characteristics and mechanical strength, and is excellent in stability.
- the bipolar plate means a composite material of graphite and resin having a groove for flowing a gas such as fuel or oxidant on its surface, or a metal plate.
- the bipolar plate has a function of a flow path for supplying fuel and oxidant to the vicinity of the electrode catalyst.
- a fuel cell is manufactured by inserting and stacking a plurality of MEAs between such bipolar plates.
- MFR melt flow rate
- the glass transition point (Tg) of the film sample was measured using a dynamic viscoelasticity measuring apparatus DVA-225.
- the sample size was a grip length of 20 mm and a width of 5 mm, and the temperature profile was raised from room temperature to 300 ° C. at a rate of 5 ° C./min.
- the measured ⁇ dispersion temperature was defined as the glass transition temperature (Tg).
- the gas permeability coefficient of oxygen of the membrane sample was measured using a flow type gas permeability measuring device GTR-30XFAFC manufactured by GTR Tech Co., Ltd.
- the supply gas flow rates were TEST gas (oxygen) 30 cc / min and carrier gas (He) 100 kPa.
- the heating and humidifying conditions of the gas were 80 ° C. 30% RH and 80 ° C. 90% RH.
- Oxygen gas that has permeated the membrane sample from the TEST gas side to the FLOW side is introduced into a gas chromatograph G2700TF manufactured by Yanaco Analytical Co., Ltd., and the gas permeation amount is quantified.
- Permeation amount is X (cc)
- membrane sample thickness is T (cm)
- transmission area is A (cm 2 )
- measuring tube passage time is D (sec)
- Electrocatalyst ink was obtained by stirring for 10 minutes at 3000 rpm.
- an automatic screen printer product name: LS-150, manufactured by Neurong Seimitsu Kogyo Co., Ltd.
- the electrocatalyst ink was applied to both sides of the polymer electrolyte membrane, and the platinum amount was 0.2 mg on the anode side / ME 2 and cathode side 0.3 mg / cm 2 were applied, and dried and solidified at 140 ° C. for 5 minutes to obtain MEA.
- a 6-liter SUS-316 pressure vessel equipped with a stirring blade and temperature control jacket was charged with 2940 g of reverse osmosis membrane water, 60 g of C 7 F 15 COONH 4 , and 230 g of mixed monomer, and the system was replaced with nitrogen. A post-vacuum was applied, and then TFE was introduced until the internal pressure reached 0.10 MPaG. While stirring at 400 rpm, the temperature was adjusted so that the internal temperature was 20 ° C. Polymerization was initiated by injecting 6 g of (NH 4 ) 2 S 2 O 8 dissolved in 20 g of water, and injecting 0.6 g of Na 2 SO 3 dissolved in 20 g of water.
- polymerization was continued by adding TFE so that the internal pressure was maintained at 0.10 MPaG. 1.1 times the amount of mixed monomer was continuously added to the consumption of TFE. Further, those obtained by dissolving Na 2 SO 3 0.6 g of water 20g, was injected every hour. Six hours after the start of the polymerization, when 400 g of TFE was additionally introduced, the TFE was released, and the polymerization was stopped to obtain 4262 g of a polymerization solution (precursor emulsion). The solid content concentration of the obtained precursor emulsion was 19.5 mass%. In the obtained polymerization solution, 2.5 kg of water was added to 2 kg, and nitric acid was added to cause coagulation.
- the obtained precursor polymer was contacted in an aqueous solution in which potassium hydroxide (15% by mass) and methyl alcohol (50% by mass) were dissolved at 80 ° C. for 20 hours for hydrolysis treatment. Then, it was immersed in 60 degreeC water for 5 hours. Next, the treatment of immersing in a 2N hydrochloric acid aqueous solution at 60 ° C. for 1 hour was repeated 5 times by renewing the hydrochloric acid aqueous solution every time and then protonated, then washed with ion-exchanged water and dried to obtain a fluorinated polymer electrolyte.
- the obtained fluoropolymer electrolyte solution having a solid content concentration of 5% by mass was concentrated under reduced pressure at 80 ° C. to prepare a high oxygen-permeable ionomer solution having a solid content concentration of 20% by mass.
- Example 1 A high oxygen permeable ionomer emulsion solution was prepared as follows. 2 kg of the polymerization liquid (precursor emulsion) obtained in Example 1 was diluted twice with pure water, stirred in a 10 L three-necked flask, the temperature was set to 80 ° C., and 10% by mass of water. While the aqueous sodium oxide solution was added dropwise, the pH was maintained at 10 or more, and —SO 2 F contained in the fluoropolymer was hydrolyzed. After about 3 hours, no decrease in pH was observed, but hydrolysis was continued for another 2 hours and stopped.
- Example 1 dilute sulfuric acid was added to adjust the pH to 8, and ultrafiltration was performed using an ultrafiltration device manufactured by Millipore.
- An ultrafiltration membrane having a molecular weight cut off of 10,000 (Pelicon 2 Filter manufactured by Millipore) was sandwiched between stainless steel holders manufactured by Millipore, and an ultrafiltration unit was provided.
- the precursor emulsion obtained in Example 1 was hydrolyzed as described in Synthesis Example 1, and then placed in a 10 L beaker, and the ultrafiltration was performed using a liquid feed pump (Easy-load MasterFlex 1 / P manufactured by Millipore). Supplied to the unit.
- the filtrate containing impurities was discharged out of the system, and the treatment liquid was returned to the beaker.
- Ultrafiltration is performed while adding an amount of purified water corresponding to the removed filtrate as appropriate to a beaker, and when the electrical conductivity of the filtrate reaches 10 ⁇ S ⁇ cm ⁇ 1 , the addition of pure water is stopped, When 1 L was reached, ultrafiltration was stopped to obtain an aqueous dispersion A.
- a Twin Cond B-173 electrical conductivity meter manufactured by HORIBA, Ltd. was used for the measurement of electrical conductivity. The ultrafiltration treatment time was 5 hours.
- the solid content concentration of the obtained precursor emulsion was 23.0% by mass.
- 100 g of water was added to 100 g, and nitric acid was added to cause coagulation. After filtering the coagulated polymer, water redispersion and filtration were repeated three times, followed by drying in a hot air dryer at 90 ° C. for 24 hours and then at 120 ° C. for 5 hours to obtain 22.0 g of polymer (precursor polymer). Obtained.
- the obtained polymer had an MFR of 28 g / 10 min.
- the monomer composition was calculated from the measurement result of melt NMR.
- the obtained polymer was hydrolyzed, protonated, dissolved and concentrated in the same manner as in Example 1 to obtain a highly oxygen permeable ionomer solution having a solid content of 20% by mass.
- TFE was introduced until the internal pressure reached 0.70 MPaG. While stirring at 500 rpm, the temperature was adjusted so that the internal temperature was 47 ° C. Polymerization was initiated by press-fitting 6 g of (NH 4 ) 2 S 2 O 8 dissolved in 20 g of water. Thereafter, TFE was added to maintain the internal pressure at 0.7 MPaG and polymerization was continued. CF 2 ⁇ CF—O— (CF 2 ) 2 —SO 2 F, which is 0.7 times the amount of TFE consumption, was continuously added. Five hours after the start of the polymerization, when 800 g of TFE was additionally introduced, the TFE was released and the polymerization was stopped to obtain 4701 g of a polymerization solution (precursor emulsion).
- the solid content concentration of the obtained precursor emulsion was 27.6% by mass.
- 250 g of water was added to 200 g, and nitric acid was added to cause coagulation.
- examples of WO 2005/028522 The fluorination treatment was performed based on the description in 1 to obtain 55.0 g of a polymer (precursor polymer).
- the obtained polymer had an MFR of 3.0 g / 10 min.
- the monomer composition was calculated from the measurement result of melt NMR.
- the obtained polymer was hydrolyzed, protonated, dissolved and concentrated in the same manner as in Example 1 to obtain an ionomer solution having a solid content of 20% by mass.
- a 6-liter SUS-316 pressure vessel equipped with a stirring blade and temperature control jacket was charged with 2940 g of reverse osmosis membrane water, 60 g of C 7 F 15 COONH 4 , and 200 g of a mixed monomer, and the system was replaced with nitrogen. A post-vacuum was applied, and then TFE was introduced until the internal pressure reached 0.26 MPaG. While stirring at 500 rpm, the temperature was adjusted so that the internal temperature became 30 ° C. Polymerization was initiated by injecting 6 g of (NH 4 ) 2 S 2 O 8 dissolved in 20 g of water, and injecting 0.6 g of Na 2 SO 3 dissolved in 20 g of water.
- polymerization was continued by adding TFE so that the internal pressure was maintained at 0.10 MPaG.
- An equal amount of mixed monomer was continuously added to the consumption of TFE.
- those obtained by dissolving Na 2 SO 3 0.6 g of water 20g was injected every hour.
- the TFE was released and the polymerization was stopped to obtain 4061 g of a polymerization solution (precursor emulsion).
- the solid content concentration of the obtained precursor emulsion was 11.4% by mass.
- 2.5 kg of water was added to 2 kg, and nitric acid was added to cause coagulation.
- the obtained polymer had an MFR of 61 g / 10 min.
- the monomer composition was calculated from the measurement result of melt NMR.
- the obtained polymer was hydrolyzed, protonated, dissolved and concentrated in the same manner as in Example 1 to obtain an ionomer solution having a solid content of 20% by mass.
- a 6-liter SUS-316 pressure vessel equipped with a stirring blade and temperature control jacket was charged with 2940 g of reverse osmosis membrane water, 60 g of C 7 F 15 COONH 4 , and 200 g of a mixed monomer, and the system was replaced with nitrogen. A post-vacuum was applied, and then TFE was introduced until the internal pressure reached 0.10 MPaG. While stirring at 500 rpm, the temperature was adjusted so that the internal temperature became 15 ° C. Polymerization was initiated by injecting 6 g of (NH 4 ) 2 S 2 O 8 dissolved in 20 g of water, and injecting 0.6 g of Na 2 SO 3 dissolved in 20 g of water.
- polymerization was continued by adding TFE so that the internal pressure was maintained at 0.10 MPaG. 2.2 amount of mixed monomer was continuously added to the consumption of TFE. Further, those obtained by dissolving Na 2 SO 3 0.6 g of water 20g, was injected every hour. 5 hours after the start of the polymerization, when 200 g of TFE was additionally introduced, the TFE was released to stop the polymerization, and 4103 g of a polymerization solution (precursor emulsion) was obtained. The solid content concentration of the obtained precursor emulsion was 14.0% by mass. Of the obtained polymerization solution, 250 g of water was added to 200 g, and nitric acid was added to cause coagulation.
- Example 3 A precursor polymer was obtained in the same manner as in Example 1 except that the composition of the mixed monomer was C3VE 500 g and N0SF 500 g, and 1.7 times the amount of the mixed monomer was continuously added to the amount of TFE consumed. The obtained precursor polymer was hydrolyzed, protonated, dissolved, and concentrated in the same manner as in Example 1 to obtain a highly oxygen permeable ionomer solution having a solid content of 20% by mass.
- Example 4 A precursor polymer was obtained in the same manner as in Example 1 except that the internal temperature was 15 ° C. The obtained precursor polymer was hydrolyzed, protonated, dissolved, and concentrated in the same manner as in Example 1 to obtain a highly oxygen permeable ionomer solution having a solid content of 20% by mass.
- Example 5 A precursor polymer was obtained in the same manner as in Comparative Example 3 except that the composition of the mixed monomer was C3VE268 g and N0SF732 g. The obtained precursor polymer was hydrolyzed, protonated, dissolved, and concentrated in the same manner as in Example 1 to obtain a highly oxygen permeable ionomer solution having a solid content of 20% by mass.
- CF 2 CF-O- (CF 2 CF (CF 3) -O) 2 - (CF 2) was charged C3VE16.45g instead of 3 F [n2VE] 38.45G, the internal pressure and 0.07MPaG, internal temperature
- a precursor polymer was obtained in the same manner as in Example 2 except that the temperature was 10 ° C.
- the obtained precursor polymer was hydrolyzed, protonated, dissolved, and concentrated in the same manner as in Example 1 to obtain a highly oxygen permeable ionomer solution having a solid content of 20% by mass.
- Example 7 The same procedure as in Example 1 was performed except that the amount of platinum in the cathode catalyst layer was 0.1 mg / cm 2 in the MEA production.
- Comparative Example 4 A precursor polymer was obtained in the same manner as in Comparative Example 2 except that the internal pressure was set to 0.13 MPaG, the internal temperature was set to 18 ° C., and 1.2 times the amount of the mixed monomer was continuously added to the TFE consumption. . The obtained precursor polymer was hydrolyzed, protonated, dissolved and concentrated in the same manner as in Example 1 to obtain an ionomer solution having a solid content of 20% by mass.
- Example 5 A precursor polymer was obtained in the same manner as in Example 2 except that the internal pressure was 0.20 MPaG and the internal temperature was 30 ° C. The obtained precursor polymer was hydrolyzed, protonated, dissolved and concentrated in the same manner as in Example 1 to obtain an ionomer solution having a solid content of 20% by mass.
- Example 6 A precursor polymer was obtained in the same manner as in Example 3 except that the composition of the mixed monomer was C3VE 400 g, N0SF 600 g, and the internal pressure was 0.07 MPaG. The obtained precursor polymer was hydrolyzed, protonated, dissolved and concentrated in the same manner as in Example 1 to obtain an ionomer solution having a solid content of 20% by mass.
- CF 2 CF—O—CF 2 CF (CF 3 ) —O—CF 2 CF 2 —SO 2 F
- Polymerization was carried out by adding 10 g of a solution in which 5 wt% of nC 3 F 7 COO—) 2 was dissolved. While feeding TFE intermittently from the outside of the polymerization tank, the TFE pressure was decreased from the initial 0.645 MPa-G to 0.643 MPa-G at the end, and polymerization was performed for 30 minutes.
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Abstract
Description
重合単位A:テトラフルオロエチレンに基づく重合単位、重合単位B:スルホン酸基を有するパーフルオロビニルエーテルに基づく重合単位、重合単位C:イオン交換基又はその前駆体の基を有しないパーフルオロビニルエーテルに基づく重合単位。
本発明は、上記現状に鑑み、酸素透過性が高く(特に、低加湿と高加湿のいずれの条件でも高酸素透過性を発現する)、かつ高い発電耐久性をも発現することができるアイオノマーを提供することを目的とする。
繰り返し単位A:一般式(1):
繰り返し単位B:一般式(2):
からなる群より選択される少なくとも1種であることが好ましい。
本発明の膜電極接合体及び燃料電池は、発電性能と発電耐久性に優れる。
理由は定かではないが、Tgが上記の好ましい温度の下限以上であると、今後見込まれる燃料電池の運転温度において、アイオノマーの溶融が抑えられ、発電耐久性を向上でき、一方、Tgが上記の好ましい温度の上限以下であると、アイオノマーの運動性を損なうことがなく高酸素透過性を保持できると推察される。
EW=(W/M)-22
本発明の高酸素透過性アイオノマーにおいて、繰り返し単位Aは、酸素の拡散経路を形成する上で重要な役割を果たすと考えられ、繰り返し単位Aの比率を高めるほど、酸素透過性が向上することを見出した。この傾向は、燃料電池に供給されるガスが、相対的に低湿度であるほど顕著である。
一方、アイオノマーとしての機能を発現するためには、繰り返し単位Bが有するプロトン交換基が適切な量で存在することも重要である。そのためには、モノマーBの共重合比率を適切な数値に管理することが好ましく、結果としてモノマーAの共重合比率の上限が設定される。
溶融19F-NMRのスペクトルに現れる、45ppm付近のSO2F由来のピーク、及び-80ppm付近の-CF3基及び-OCF2-基に由来するピーク、-120ppm付近の-CF2-基及び-OCF(CF3)-基に由来するピークの強度の比率を用いて計算することによって含有量(モル%)を算出できる。
TOSOH社製 HLC-8020を用い、カラムはポリスチレンゲル製MIXカラム(東ソーGMHシリーズ、30cmサイズ)を3本、40℃、NMP(5mmol/L LiBr含有)溶剤、流速0.7mL/分で行うことができる。サンプル濃度は、0.1重量%で打ち込み量は500μLで行うことができる。数平均分子量がポリスチレン換算値で10万~80万程度のものが更に好ましく、13万~70万程度のものが更により好ましく、16万~60万程度のものが特に好ましい。
乳化重合により、上記高酸素透過性アイオノマー粒子が水に分散したエマルションの形態で、上記高酸素透過性アイオノマーが得られる。
ポリマーの組成を正確に制御するためには、圧力容器内に繰り返し単位Aを構成するフルオロモノマー、繰り返し単位Bを構成するフルオロモノマー、繰り返し単位Cを構成するフルオロモノマーを連続的に供給する方法、又は分割して供給する方法が好ましい。
繰り返し単位Cを構成するフルオロモノマーが気体モノマーの場合、重合反応に伴ってモノマーが消費されると、圧力が低下するので、圧力を維持するよう気体モノマーを供給することが好ましい。
繰り返し単位Aを構成するフルオロモノマー、繰り返し単位Bを構成するフルオロモノマーは液体であるので、望むポリマー組成になるように、繰り返し単位Cを構成するフルオロモノマーの消費量に応じて供給することができる。液体モノマーの供給方法は、ポンプを用いて圧入する方法や、モノマー容器を加圧して圧入する方法などを適宜選択することができる。また、繰り返し単位Aを構成するフルオロモノマーと繰り返し単位Bを構成するフルオロモノマーを所望の組成で予め混合しておく方法は、操作が簡便になる点で好ましい。
一般式(9):CF2=CF(CF2)k9-O-(CF2CFY91-O)n9-(CFY92)m9-SO2Y93
(式中、Y91は、F、Cl又は炭素数1~3のパーフルオロアルキル基を表す。k9は0~2の整数、n9は0~8の整数を表し、n9個のY91は、同一でも異なっていてもよい。Y92はF又はClを表す。m9は2~6の整数を表す。m9個のY92は、同一でも異なっていてもよい。Y93はハロゲン原子を表す。)で表されるフルオロモノマーであることが好ましい。
一般式(10):CF2=CF-O-CF2CF2-SO2Y93
(式中、Y93はハロゲン原子を表す。)で表されるフルオロモノマーであることが好ましい。Y93はFであることが好ましい。
また、チオエーテル化合物も挙げられる。例えば、ジメチルチオエーテル、ジエチルチオエーテル、ジプロピルチオエーテル、メチルエチルチオエーテル、メチルブチルチオエーテルのようなジアルキルチオエーテル;テトラヒドロチオフェン、テトラヒドロアピランのような環状チオエーテル;メチルフェニルスルフィド、エチルフェニルスルフィド、ジフェニルスルフィド、ジベンジルスルフィドのような芳香族チオエーテル等が挙げられる。
繰り返し単位Aを構成するフルオロモノマー、繰り返し単位Bを構成するフルオロモノマー及び繰り返し単位Cを構成するフルオロモノマーを水性媒体中でラジカル重合して高酸素透過性アイオノマーを含むエマルションを得る重合工程と、
上記エマルションに触媒を分散させて触媒ペーストを調製する工程と、
上記触媒ペーストを基材に塗布する工程と、
基材に塗布した触媒ペーストを乾燥させて電極触媒層を得る工程と、
を含む製造方法により好適に製造することができる。
繰り返し単位Aを構成するフルオロモノマー、繰り返し単位Bを構成するフルオロモノマーの前駆体モノマー及び繰り返し単位Cを構成するフルオロモノマーを水性媒体中でラジカル重合して前駆体ポリマーを含むエマルションを得る重合工程と、
前記エマルションにアルカリを添加することによって、前駆体ポリマーを高酸素透過性アイオノマーに変換して、高酸素透過性アイオノマーを含むエマルションを得る加水分解工程と、
上記エマルションに触媒を分散させて触媒ペーストを調製する工程と、
上記触媒ペーストを基材に塗布する工程と、
基材に塗布した触媒ペーストを乾燥させて電極触媒層を得る工程と、
を含む製造方法により好適に製造することができる。
繰り返し単位Aを構成するフルオロモノマー、繰り返し単位Bを構成するフルオロモノマー及び繰り返し単位Cを構成するフルオロモノマーを水性媒体中でラジカル重合して高酸素透過性アイオノマーを含むエマルションを得る重合工程と、
上記エマルションに有機溶媒を添加して高酸素透過性アイオノマーが溶解したアイオノマー溶液を得る工程と、
上記アイオノマー溶液に触媒を分散させて触媒ペーストを調製する工程と、
上記触媒ペーストを基材に塗布する工程と、
基材に塗布した触媒ペーストを乾燥させて電極触媒層を得る工程と、
を含む製造方法により好適に製造することができる。
繰り返し単位Aを構成するフルオロモノマー、繰り返し単位Bを構成するフルオロモノマーの前駆体モノマー及び繰り返し単位Cを構成するフルオロモノマーを水性媒体中でラジカル重合して前駆体ポリマーを含むエマルションを得る重合工程と、
前記エマルションにアルカリを添加することによって、前駆体ポリマーを高酸素透過性アイオノマーに変換して、高酸素透過性アイオノマーを含むエマルションを得る加水分解工程と、
上記エマルションに有機溶媒を添加して高酸素透過性アイオノマーが溶解したアイオノマー溶液を得る工程と、
上記アイオノマー溶液に触媒を分散させて触媒ペーストを調製する工程と、
上記触媒ペーストを基材に塗布する工程と、
基材に塗布した触媒ペーストを乾燥させて電極触媒層を得る工程と、
を含む製造方法により好適に製造することができる。
一般式(9):CF2=CF(CF2)k9-O-(CF2CFY91-O)n9-(CFY92)m9-SO2Y93
(式中、Y91は、F、Cl又は炭素数1~3のパーフルオロアルキル基を表す。k9は0~2の整数、n9は0~8の整数を表し、n9個のY91は、同一でも異なっていてもよい。Y92はF又はClを表す。m9は2~6の整数を表す。m9個のY92は、同一でも異なっていてもよい。Y93はハロゲン原子を表す。)で表されるフルオロモノマーであることが好ましい。
一般式(10):CF2=CF-O-CF2CF2-SO2Y93
(式中、Y93はハロゲン原子を表す。)で表されるフルオロモノマーであることが好ましい。Y93はFであることが好ましい。
イオン交換基の対イオンがプロトンの状態となっている高分子電解質膜、およそ2~20cm2を、25℃、飽和NaCl水溶液30mLに浸漬し、攪拌しながら30分間放置した。次いで、飽和NaCl水溶液中のプロトンを、フェノールフタレインを指示薬として0.01N水酸化ナトリウム水溶液を用いて中和滴定した。中和後に得られた、イオン交換基の対イオンがナトリウムイオンの状態となっている高分子電解質膜を、純水ですすぎ、さらに真空乾燥して秤量した。中和に要した水酸化ナトリウムの物質量をM(mmol)、イオン交換基の対イオンがナトリウムイオンの高分子電解質膜の重量をW(mg)とし、下記式により当量重量EW(g/eq)を求めた。
EW=(W/M)-22
前駆体ポリマーのMFRは、ASTM規格D1238に従って、270℃、荷重2.16kgの条件下で、MELT INDEXER TYPE C-5059D(商品名、東洋精機社製)を用いて測定した。MFRの単位として、押し出された前駆体の質量を10分間当たりのグラム数で表した。
動的粘弾性測定装置DVA-225を用いて、膜サンプルのガラス転移点(Tg)を測定した。サンプルサイズは、つかみ長20mm、幅5mmで、温度プロファイルは室温から300℃まで5℃/minで昇温した。測定されたα分散温度をガラス転移温度(Tg)とした。
GTRテック(株)製フロー式ガス透過率測定装置GTR-30XFAFCを用いて膜サンプルの酸素のガス透過係数を測定した。供給ガス流量は、TESTガス(酸素)30cc/min、キャリアーガス(He)100kPaとした。ガスの加温加湿条件は、80℃30%RHと80℃90%RHを採用した。
TESTガス側からFLOW側に膜サンプルを透過してきた酸素ガスをヤナコ分析工業(株)製ガスクロマトグラフG2700TFに導入して、ガス透過量を定量化する。
透過量をX(cc)、補正係数をk(=1.0)、膜サンプルの膜厚をT(cm)、透過面積をA(cm2)、計量管通過時間をD(sec)、酸素分圧をp(cmHg)とした時のガス透過係数P(cc・cm/(cm2・sec・cmHg))は下記式から計算される。
P=(X×k×T/(A×D×p))
高温低加湿条件下におけるMEAの性能を評価するため、以下のような手順で発電試験を実施した。
(1)電極触媒インクの調製
固形分濃度20質量%のアイオノマー溶液、電極触媒(TEC10E40E、田中貴金属工業(株)製、白金担持量36.7wt%)を白金/パーフルオロスルホン酸ポリマーが1/1.15(重量)となるように配合し、次いで、固形分(電極触媒とパーフルオロスルホン酸ポリマーの和)が11wt%となるようにエタノールを加え、ホモジナイザー(アズワン社製)により回転数が3000rpmで10分間、撹拌することで電極触媒インクを得た。
(2)MEAの作製
自動スクリーン印刷機(製品名:LS-150、ニューロング精密工業株式会社製)を用い、高分子電解質膜の両面に前記電極触媒インクを、白金量がアノード側0.2mg/cm2、カソード側0.3mg/cm2となるように塗布し、140℃、5分の条件で乾燥・固化させることでMEAを得た。
(3)燃料電池単セルの作製
前記MEAの両極にガス拡散層(製品名:GDL35BC、MFCテクノロジー社製)を重ね、次いでガスケット、バイポーラプレート、バッキングプレートを重ねることで燃料電池単セルを得た。
(4)発電試験
前記燃料電池単セルを評価装置(東陽テクニカ社製燃料電池評価システム890CL)にセットして、発電試験を実施した。
発電の試験条件はセル温度80℃、アノードの加湿ボトル60℃、カソードを無加湿に設定し、アノード側に水素ガス、カソード側に空気ガスを、それぞれ0.3A/cm2でのガス利用率が75%、55%の条件で供給した。また、アノード側とカソード側の両方を無加圧(大気圧)とした。
本条件で、電流密度が0.5A/cm2での電圧値(IV)を測定した。
(5)負荷変動試験
前記燃料電池単セルを評価装置(東陽テクニカ社製燃料電池評価システム890CL)にセットして、負荷変動試験を実施した。
負荷変動の試験条件は、セル温度80℃、アノードの加湿ボトル70℃、カソードの加湿ボトル70℃に設定し、アノード側に水素ガス、カソード側に空気ガスを流し、0.8Vを15秒と0.5Vを15秒の電圧サイクルで、0.8Vでのガス流量がアノード/カソード=39/171mL/min、0.5Vでのガス流量がアノード/カソード=156/685mL/minとなるように供給した。また、アノード側とカソード側の両方を無加圧(大気圧)とした。
本条件で、試験前と6万サイクル後の0.3A/cm2での電圧値の差を測定した。
本試験を行うことで、電極バインダーの発電耐久性を評価することができる。
CF2=CF-O-(CF2)2CF3〔C3VE〕、CF2=CF-O-(CF2)2-SO3H〔N0SF〕及びCF2=CF2〔TFE〕に由来する繰り返し単位を、それぞれ12.5モル%、17.3モル%、70.2モル%含み、EWが876の高酸素透過性アイオノマーを以下のように作製した。
予め、CF2=CF-O-(CF2)2CF3 370gとCF2=CF-O-(CF2)2-SO2F 630gを混合した混合モノマーを準備した。
攪拌翼と温調用ジャケットを備えた内容積6リットルのSUS-316製耐圧容器に、逆浸透膜水2940g、C7F15COONH4 60g、及び混合モノマー230gを仕込み、系内を窒素で置換した後真空とし、その後TFEを内圧が0.10MPaGになるまで導入した。400rpmで攪拌しながら、内温が20℃になるように温調を行った。(NH4)2S2O8 6gを20gの水に溶解させたものを圧入し、さらにNa2SO3 0.6gを20gの水に溶解させたものを圧入して重合を開始した。その後、内圧が0.10MPaGを維持するようにTFEを追加して重合を継続した。TFEの消費量に対して1.1倍量の混合モノマーを連続的に追加した。また、Na2SO3 0.6gを20gの水に溶解させたものを、1時間おきに圧入した。
重合開始から6時間後、追加でTFEを400g導入した時点でTFEを放圧し、重合を停止し、4262gの重合液(前駆体エマルション)を得た。得られた前駆体エマルションの固形分濃度は19.5質量%であった。
得られた重合液のうち、2kgに水2.5kgを追加し、硝酸を加えて凝析させた。凝析したポリマーを濾過した後、水の再分散と濾過を3回繰り返し、熱風乾燥器で90℃で24時間、引き続き120℃で5時間乾燥し、213gのポリマー(前駆体ポリマー)を得た。得られたポリマーのMFRは88g/10分であった。溶融NMRの測定結果から、モノマー組成を算出した。
得られた固形分濃度5質量%のフッ素系高分子電解質溶液を80℃にて減圧濃縮して、固形分濃度20質量%の高酸素透過性アイオノマー溶液を作製した。
高酸素透過性アイオノマーのエマルション溶液を以下のように作製した。
実施例1で得られた上記重合液(前駆体エマルション)のうち2kgを純水で2倍に希釈し、容積10Lの三口フラスコ中で攪拌し、温度を80℃にして、10質量%の水酸化ナトリウム水溶液を滴下しながらpHを10以上に保持して、含フッ素ポリマーが有する-SO2Fの加水分解を行った。約3時間後にpHの低下がみられなくなったが、加水分解を更に2時間継続し、停止した。
CF2=CF-O-(CF2CF(CF3)-O)2-(CF2)3F〔n2VE〕、CF2=CF-O-(CF2)2-SO3H及びCF2=CF2に由来する繰り返し単位を、それぞれ6.3モル%、36.5モル%、57.2モル%含み、EWが538の高酸素透過性アイオノマーを以下のように作製した。
攪拌翼と温調用ジャケットを備えた内容積0.5リットルのSUS-316製耐圧容器に、逆浸透膜水250g、C3F7-O-CF(CF3)CF2-O-CF(CF3)COONH4 25g、CF2=CF-O-(CF2CF(CF3)-O)2-(CF2)3F 38.45g、CF2=CF-O-(CF2)2-SO2F61.55gを仕込み、系内を窒素で置換した後真空とし、その後TFEを内圧が0.12MPaGになるまで導入した。550rpmで攪拌しながら、内温が15℃になるように温調を行った。(NH4)2S2O8 0.5gを5gの水に溶解させたものを圧入し、さらにNa2SO3 0.06gを7gの水に溶解させたものを圧入して重合を開始した。その後、内圧が0.12MPaGを維持するようにTFEを追加して重合を継続した。また、Na2SO3 0.06gを7gの水に溶解させたものを、1時間おきに圧入した。
重合開始から6時間後、追加でTFEを30g導入した時点でTFEを放圧し、重合を停止し、450gの重合液(前駆体エマルション)を得た。得られた前駆体エマルションの固形分濃度は23.0質量%であった。
得られた重合液のうち、100gに水100gを追加し、硝酸を加えて凝析させた。凝析したポリマーを濾過した後、水の再分散と濾過を3回繰り返し、熱風乾燥器で90℃で24時間、引き続き120℃で5時間乾燥し、22.0gのポリマー(前駆体ポリマー)を得た。得られたポリマーのMFRは28g/10分であった。溶融NMRの測定結果から、モノマー組成を算出した。
得られたポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%の高酸素透過性アイオノマー溶液を得た。
CF2=CF-O-(CF2)2-SO3H及びCF2=CF2に由来する繰り返し単位を、それぞれ18.5モル%、81.5モル%含み、EWが719の比較アイオノマーを以下のように作製した。
攪拌翼と温調用ジャケットを備えた内容積6リットルのSUS-316製耐圧容器に、逆浸透膜水2940g、C7F15COONH4 60g、CF2=CF-O-(CF2)2-SO2F 50gを仕込み、系内を窒素で置換した後真空とし、その後TFEを内圧が0.70MPaGになるまで導入した。500rpmで攪拌しながら、内温が47℃になるように温調を行った。(NH4)2S2O8 6gを20gの水に溶解させたものを圧入して重合を開始した。その後、内圧が0.7MPaGを維持するようにTFEを追加して重合を継続した。TFEの消費量に対して0.7倍量のCF2=CF-O-(CF2)2-SO2Fを連続的に追加した。
重合開始から5時間後、追加でTFEを800g導入した時点でTFEを放圧し、重合を停止し、4701gの重合液(前駆体エマルション)を得た。得られた前駆体エマルションの固形分濃度は27.6質量%であった。
得られた重合液のうち、200gに水250gを追加し、硝酸を加えて凝析させた。凝析したポリマーを濾過した後、水の再分散と濾過を3回繰り返し、熱風乾燥器で90℃で24時間、引き続き120℃で5時間乾燥し、更に国際公開第2005/028522号の実施例1の記載に基づいてフッ素化処理を施し、55.0gのポリマー(前駆体ポリマー)を得た。得られたポリマーのMFRは3.0g/10分であった。溶融NMRの測定結果から、モノマー組成を算出した。
得られたポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%のアイオノマー溶液を得た。
CF2=CF-O-(CF2)2CF3、CF2=CF-O-(CF2)2-SO3H及びCF2=CF2に由来する繰り返し単位を、それぞれ15.2モル%、7.6モル%、77.2モル%含み、EWが1826の高酸素透過性アイオノマーを以下のように作製した。
予め、CF2=CF-O-(CF2)2CF3 646gとCF2=CF-O-(CF2)2-SO2F 354gを混合した混合モノマーを準備した。
攪拌翼と温調用ジャケットを備えた内容積6リットルのSUS-316製耐圧容器に、逆浸透膜水2940g、C7F15COONH4 60g、及び混合モノマー200gを仕込み、系内を窒素で置換した後真空とし、その後TFEを内圧が0.26MPaGになるまで導入した。500rpmで攪拌しながら、内温が30℃になるように温調を行った。(NH4)2S2O8 6gを20gの水に溶解させたものを圧入し、さらにNa2SO3 0.6gを20gの水に溶解させたものを圧入して重合を開始した。その後、内圧が0.10MPaGを維持するようにTFEを追加して重合を継続した。TFEの消費量に対して等量の混合モノマーを連続的に追加した。また、Na2SO3 0.6gを20gの水に溶解させたものを、1時間おきに圧入した。
重合開始から6時間後、追加でTFEを400g導入した時点でTFEを放圧し、重合を停止し、4061gの重合液(前駆体エマルション)を得た。得られた前駆体エマルションの固形分濃度は11.4質量%であった。
得られた前駆体エマルションのうち、2kgに水2.5kgを追加し、硝酸を加えて凝析させた。凝析したポリマーを濾過した後、水の再分散と濾過を3回繰り返し、熱風乾燥器で90℃で24時間、引き続き120℃で5時間乾燥し、220gのポリマー(前駆体ポリマー)を得た。得られたポリマーのMFRは61g/10分であった。溶融NMRの測定結果から、モノマー組成を算出した。
得られたポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%のアイオノマー溶液を得た。
CF2=CF-O-(CF2)2CF3、CF2=CF-O-(CF2)2-SO3H及びCF2=CF2に由来する繰り返し単位を、それぞれ33.5モル%、12.5モル%、54.0モル%含み、EWが1423の高酸素透過性アイオノマーを以下のように作製した。
予め、CF2=CF-O-(CF2)2CF3 646gとCF2=CF-O-(CF2)2-SO2F 354gを混合した混合モノマーを準備した。
攪拌翼と温調用ジャケットを備えた内容積6リットルのSUS-316製耐圧容器に、逆浸透膜水2940g、C7F15COONH4 60g、及び混合モノマー200gを仕込み、系内を窒素で置換した後真空とし、その後TFEを内圧が0.10MPaGになるまで導入した。500rpmで攪拌しながら、内温が15℃になるように温調を行った。(NH4)2S2O8 6gを20gの水に溶解させたものを圧入し、さらにNa2SO3 0.6gを20gの水に溶解させたものを圧入して重合を開始した。その後、内圧が0.10MPaGを維持するようにTFEを追加して重合を継続した。TFEの消費量に対して2.2量の混合モノマーを連続的に追加した。また、Na2SO3 0.6gを20gの水に溶解させたものを、1時間おきに圧入した。
重合開始から5時間後、追加でTFEを200g導入した時点でTFEを放圧し、重合を停止し、4103gの重合液(前駆体エマルション)を得た。得られた前駆体エマルションの固形分濃度は14.0質量%であった。
得られた重合液のうち、200gに水250gを追加し、硝酸を加えて凝析させた。凝析したポリマーを濾過した後、水の再分散と濾過を3回繰り返し、熱風乾燥器で90℃で24時間、引き続き120℃で5時間乾燥し、27.2gのポリマー(前駆体ポリマー)を得た。得られたポリマーのMFRは16g/10分であった。溶融NMRの測定結果から、モノマー組成を算出した。
得られたポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%のアイオノマー溶液を得た。
混合モノマーの組成をC3VE500g、N0SF500gとし、TFEの消費量に対して1.7倍量の混合モノマーを連続的に追加した以外は実施例1と同様にして前駆体ポリマーを得た。
得られた前駆体ポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%の高酸素透過性アイオノマー溶液を得た。
内温を15℃とする以外は、実施例1と同様にして前駆体ポリマーを得た。
得られた前駆体ポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%の高酸素透過性アイオノマー溶液を得た。
混合モノマーの組成をC3VE268g、N0SF732gとした以外は比較例3と同様にして前駆体ポリマーを得た。
得られた前駆体ポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%の高酸素透過性アイオノマー溶液を得た。
CF2=CF-O-(CF2CF(CF3)-O)2-(CF2)3F〔n2VE〕38.45gの代わりにC3VE16.45gを仕込み、内圧を0.07MPaGとし、内温を10℃とする以外は、実施例2と同様にして前駆体ポリマーを得た。
得られた前駆体ポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%の高酸素透過性アイオノマー溶液を得た。
MEA作製においてカソード触媒層中の白金量を0.1mg/cm2とする以外は、実施例1と同様にした。
内圧を0.13MPaGとし、内温を18℃とし、TFEの消費量に対して1.2倍量の混合モノマーを連続的に追加した以外は比較例2と同様にして前駆体ポリマーを得た。
得られた前駆体ポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%のアイオノマー溶液を得た。
内圧を0.20MPaGとし、内温を30℃とする以外は、実施例2と同様にして前駆体ポリマーを得た。
得られた前駆体ポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%のアイオノマー溶液を得た。
混合モノマーの組成をC3VE400g、N0SF600gとし、内圧を0.07MPaGとした以外は実施例3と同様にして前駆体ポリマーを得た。
得られた前駆体ポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%のアイオノマー溶液を得た。
2リットルのステンレス製オートクレーブに、CF2=CF-O-CF2CF(CF3)-O-CF2CF2-SO2F〔N1SF〕:1.33kgとC3VE0.47kgを仕込んだ後、窒素でパージし、続いてテトラフルオロエチレン(TFE:CF2=CF2)でパージした。温度を25℃とし、TFEの圧力を0.645MPa-G(ゲージ圧力)とした後、CF2=CF-O-CF2CF(CF3)-O-CF2CF2-SO2Fに(n-C3F7COO-)2を5重量%溶解した溶液を10g添加して重合を実施した。重合槽の系外からTFEを断続的にフィードしつつ、TFE圧力を初期0.645MPa-Gから終了時0.643MPa-Gまで降下させて30分間重合した。重合槽の系内のTFEを窒素でパージし大気圧とした後、固形分比率8.4wt%のモノマーを分散媒とする前駆体ポリマー分散液を得た。この分散液にメタノールを3倍体積量添加しスラリーを沈降させた後に静置して上澄みを除去し、続いて、メタノール/CFC113=1/2(体積比)で洗浄と静置による上澄み除去を3回繰り返した後に、110℃で16時間減圧乾燥し、42gの粉体を得た。当該粉体(完全な固体となった前駆体ポリマー)の当量重量952であった。
得られた前駆体ポリマーを、実施例1と同様に加水分解、プロトン化、溶解、濃縮処理を施して、固形分濃度20質量%のアイオノマー溶液を得た。
実施例1~7及び比較例1~7で得られたアイオノマー溶液をキャスト製膜して、厚み50μmのフィルムを作製した。
また、比較例8として、市販のナフィオン溶液(Nafion 1021 SIGMA-ALDRICH社製)を用いて、実施例1と同様にして、厚み50μmのフィルムを作製した。
得られたフィルムの酸素透過係数を測定し、結果を表1に示した。
実施例の高酸素透過性アイオノマーは、比較例と比較して、酸素透過係数が改善されていることがわかる。
実施例及び比較例で得られたアイオノマー溶液を用い、前述のように、電流密度が0.5A/cm2での電圧値(IV)を測定した。
結果を表1に示した。
実施例の高酸素透過性アイオノマーは、比較例6以外の比較例と比較して、高い電圧値を示しており、発電性能に優れることがわかる。
実施例7より、触媒層中に使用する白金量を小さくしても高い発電性能を発現することがわかる。
尚、比較例6は、酸素透過性および発電性能は高いが、下記負荷変動試験による電圧差が0.05Vと大きく、同程度の発電性能を示す実施例2と比較しても2.5倍の電圧差を示す(即ち発電耐久性として2.5倍以上劣る)ため、発電性能と発電耐久性を両立し得るものではないことがわかる。
実施例及び比較例で得られたアイオノマー溶液を用い、前述のように、試験前と6万サイクル後の0.3A/cm2での電圧値の差を測定した。
結果を表1に示した。
実施例の高酸素透過性アイオノマーは、比較例と比較して、高い電圧値を示しており、発電耐久性に優れることがわかる。
以上より、実施例1~7は低加湿及び高加湿の両方の条件における高酸素透過性と、発電性能と、発電耐久性とを両立できることがわかる。
Claims (11)
- 繰り返し単位Aは、全繰り返し単位に対して5~71モル%である請求項1、2、3、4又は5記載の高酸素透過性アイオノマー。
- 請求項1、2、3、4、5又は6記載の高酸素透過性アイオノマーと水を含むエマルション。
- 請求項1、2、3、4、5又は6記載の高酸素透過性アイオノマーと水を含むアイオノマー溶液。
- 請求項1、2、3、4、5又は6記載の高酸素透過性アイオノマーを用いた電極触媒層。
- 請求項9記載の電極触媒層を備える膜電極接合体。
- 請求項10記載の膜電極接合体を備える燃料電池。
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