EP2471138A1 - Proton-conducting membranes for a fuel cell, and method for preparing such membranes - Google Patents

Proton-conducting membranes for a fuel cell, and method for preparing such membranes

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Publication number
EP2471138A1
EP2471138A1 EP10745649A EP10745649A EP2471138A1 EP 2471138 A1 EP2471138 A1 EP 2471138A1 EP 10745649 A EP10745649 A EP 10745649A EP 10745649 A EP10745649 A EP 10745649A EP 2471138 A1 EP2471138 A1 EP 2471138A1
Authority
EP
European Patent Office
Prior art keywords
membrane
matrix
irradiation
grafts
zones
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10745649A
Other languages
German (de)
French (fr)
Inventor
Thomas Xavier Alain Berthelot
Marie-Claude Laurence Clochard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Commissariat a lEnergie Atomique CEA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Publication of EP2471138A1 publication Critical patent/EP2471138A1/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0093—Chemical modification
    • B01D67/00931—Chemical modification by introduction of specific groups after membrane formation, e.g. by grafting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0093—Chemical modification
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/0032—Organic membrane manufacture by inducing porosity into non porous precursor membranes by elimination of segments of the precursor, e.g. nucleation-track membranes, lithography or laser methods
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • B01D71/78—Graft polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/20—Manufacture of shaped structures of ion-exchange resins
    • C08J5/22—Films, membranes or diaphragms
    • C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
    • C08J5/2218—Synthetic macromolecular compounds
    • C08J5/2231—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds
    • C08J5/2243—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds obtained by introduction of active groups capable of ion-exchange into compounds of the type C08J5/2231
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/20—Manufacture of shaped structures of ion-exchange resins
    • C08J5/22—Films, membranes or diaphragms
    • C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
    • C08J5/2218—Synthetic macromolecular compounds
    • C08J5/2231—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds
    • C08J5/2243—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds obtained by introduction of active groups capable of ion-exchange into compounds of the type C08J5/2231
    • C08J5/225—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds obtained by introduction of active groups capable of ion-exchange into compounds of the type C08J5/2231 containing fluorine
    • 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
    • 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
    • H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
    • H01M8/1072—Polymeric electrolyte materials characterised by the manufacturing processes by chemical reactions, e.g. insitu polymerisation or insitu crosslinking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/28—Pore treatments
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/34—Use of radiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/38—Graft polymerization
    • B01D2323/385—Graft polymerization involving radiation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2327/00—Characterised by the use of 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; Derivatives of such polymers
    • C08J2327/02—Characterised by the use of 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; Derivatives of such polymers not modified by chemical after-treatment
    • C08J2327/12—Characterised by the use of 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; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
    • C08J2327/16—Homopolymers or copolymers of vinylidene fluoride
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2351/00—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the invention relates to fuel cell proton conducting membranes, methods of making such membranes and fuel cell devices comprising such membranes.
  • the field of application of the invention is therefore that of fuel cells, and more particularly of fuel cells, comprising as electrolyte, a proton-conducting membrane, such as PEMFC ("Proton Exchange Membrane") fuel cells.
  • PEMFC Proton Exchange Membrane
  • Fuel Cell for Proton Exchange Membrane Fuel Cell Fuel Cell for Proton Exchange Membrane Fuel Cell).
  • a fuel cell generally comprises a stack of elementary cells in which an electrochemical reaction takes place between two reactants which are introduced continuously.
  • Fuel such as hydrogen, for cells operating with hydrogen / oxygen mixtures, or methanol for batteries operating with methanol / oxygen mixtures, is brought into contact with the anode, whereas the oxidant, generally oxygen, is brought into contact with the cathode.
  • the anode and the cathode are separated by an electrolyte of the type ionic conductive membrane.
  • the electrochemical reaction whose energy is converted into electrical energy, splits into two half-reactions:
  • the electrochemical reaction takes place at an electrode-membrane-electrode assembly.
  • the electrode-membrane-electrode assembly is a very thin assembly with a thickness of the order of a millimeter and each electrode is fed with the gases, for example using a fluted plate.
  • the ionic conducting membrane is generally an organic membrane containing ionic groups which, in the presence of water, allow the conduction of the protons produced at the anode by oxidation of hydrogen.
  • This membrane is generally between 50 and 150 microns and results from a compromise between the mechanical strength and the ohmic drop.
  • This membrane also allows the separation of gases.
  • the chemical and electrochemical resistance of these membranes allows, in general, battery operation over periods of over 1000 hours.
  • the polymer constituting the membrane must therefore fulfill a number of conditions relating to its mechanical, physicochemical and electrical properties which are, inter alia, those defined below.
  • the polymer must first be able to give thin films, 50 to 150 micrometers, dense, without defects.
  • the mechanical properties, elastic modulus, tensile strength, ductility, must make it compatible with assembly operations including, for example, clamping between metal frames.
  • the properties must be preserved by changing from dry to wet.
  • the polymer must have good thermal stability to hydrolysis and have good resistance to reduction and oxidation. This thermomechanical stability is appreciated in terms of variation of ionic resistance, and in terms of variation of the mechanical properties.
  • the polymer must finally have a high ionic conductivity, this conductivity being provided by acidic groups, such as carboxylic acid, phosphoric acid or sulfonic acid groups connected to the polymer chain.
  • acidic groups such as carboxylic acid, phosphoric acid or sulfonic acid groups connected to the polymer chain.
  • the membranes prepared with these products are inexpensive but do not have sufficient hydrogen stability at 50-60 ° C. for long-term applications.
  • polymers consisting of a perfluorinated linear main chain and a side chain carrying a sulfonic acid group.
  • the membranes currently used and in particular the membranes of the NAFION® type have a limit to the order of use of the temperature level of 90 0 C, an aging phenomenon after 3000-4000 hours of use, conductivity of the order of 60 mS. cm "1 and a high cost of $ 250/300.
  • a relatively low humidity level for example, less than 25% at the cathode and 50% at the anode
  • the invention relates to a proton exchange membrane consisting of a polymeric matrix comprising, in its thickness, substantially cylindrical zones passing through the latter, said zones comprising polymeric grafts chosen from polymeric grafts comprising a main chain, of which at least a portion of the carbon atoms is bonded to both -COOR and -SO3R or -PO3R2, where R is hydrogen, halogen, alkyl, or cationic counterion .
  • the membranes of the invention have the following advantageous characteristics: a significant ion exchange capacity, especially greater than 2.5 meq.g -1 , and this under relative humidity conditions of less than 20%;
  • Polymeric matrix is understood to mean the base portion of the membrane in which the substantially cylindrical zones comprising the grafts are formed, this matrix giving the shape to the membrane.
  • substantially cylindrical zones areas of generally cylindrical shape delimiting volumes of the matrix in which the aforementioned grafts are grafted, these zones passing through the thickness of said matrix, namely that they join two opposite faces of this matrix, which makes it possible to generate a conductive path through the thickness of the matrix.
  • graft is meant a polymer chain covalently bonded to the polymer constituting the matrix in the aforementioned areas.
  • the base polymer matrix may be a matrix made of a polymer chosen from polyurethanes, polyolefins, polycarbonates and polyethylene terephthalates, these polymers being advantageously fluorinated or even perfluorinated.
  • the polymeric matrix may be chosen from fluorinated polymer matrices such as polyvinylidene fluoride, copolymers of tetrafluoroethylene and tetrafluoropropylene (known by the abbreviation FEP), copolymers of ethylene and tetrafluoroethylene (known under the name of abbreviation ETFE), copolymers of hexafluoropropene and of vinylidene fluoride (known by the abbreviation HFP-co-VDF), of vinylidene fluoride and of trifluoroethylene (known under the abbreviation VDF-co-TrFE), of fluoride vinylidene, trifluoroethylene and monochlorotrifluoroethylene (known by the abbreviation VDF-co-TrFE-co-chloroTrFE).
  • fluorinated polymer matrices such as polyvinylidene fluoride, copolymers of tetrafluoroethylene and
  • Polymeric matrices based on fluoropolymers are advantageous in that they are resistant to corrosion, have good mechanical properties and low gas permeation. They are therefore particularly suitable for constituting fuel cell membranes.
  • a particularly advantageous matrix of this type is a polyvinylidene fluoride matrix.
  • Polyvinylidene fluoride is chemically inert (particularly resistant to corrosion), has good mechanical properties, has a glass transition temperature, which varies from -42 ° C. to -38 ° C., a melting temperature of 170 ° C. and a density of 1.75 g / cm 3 . It also has low gas permeation, which makes it particularly useful as a basis for building fuel cell membranes operating with hydrogen as fuel.
  • This polymer is easily extruded and can be in particular in two crystalline forms, depending on the orientation of the crystallites: the ⁇ phase and the ⁇ phase, the ⁇ phase being characterized in particular by piezoelectric properties.
  • the substantially cylindrical zones connect two opposite faces of the matrix and can pass through the thickness thereof, at variable or identical angles, for example in a perpendicular manner and be parallel to each other. They may have a diameter ranging from 50 to 100 microns, in which case they may be called microzones. They can also have a diameter ranging from 10 to 100 nm, in which case they can be described as nanozones. These zones may also be hollow, in which case the grafts will be linked to the wall of said zones.
  • the matrix may comprise from 5.10 4 to 5.10 10 , preferably from 10 5 to 5.10 9 zones per cm 2 .
  • the polymeric grafts comprise a main chain, of which at least a portion of the carbon atoms is bonded to both a -COOR group and a -SO3R or -PO3R2 group, which means, in other words In other words, some of the carbon atoms of the main chain are doubly substituted, one substituent being a -COOR group while the other substituent is -SO3R or -PO3R2. This does not exclude the fact that carbon atoms adjacent to those bearing the -COOR group may also include -SO 3 R or -PO 3 R 2 groups.
  • Such grafts may include a sequence of the following type:
  • the groups X representing -COOR, while the groups Y represent a group -SO3R or -PO 3 R 2 .
  • Such grafts may result from the polymerization of acrylic monomers having at least one -CO2R group, such as acrylic acid, the resulting polymers having undergone a sulfonation or phosphanation step to introduce the -SO3R or -PO3R2 groups on at least one part of the atoms bearing -CO2R groups, R being as defined above.
  • the radical R in the groups -COOR, -SO3R or -PO3R2 may be a hydrogen atom, an atom halogen (for example, F or Cl) or an alkyl group, a cationic counterion, such as a cation derived from an alkali metal (such as Na + ).
  • Particular membranes according to the invention are membranes comprising a polymeric matrix in the form of a polyvinylidene fluoride film having cylindrical zones connecting two opposite faces of the matrix, said zones comprising grafts consisting of a main chain resulting from the polymerization of acrylic acid, at least a portion of the carbon atoms carrying the -COOH group derived from acrylic acid also carrying a -SO3R or -PO3R2 group, R having the same meaning as that given above .
  • other parts of the membrane may be coated with grafts as defined above, by overflow of the grafts included in said zones.
  • the invention also relates to a process for preparing a membrane as defined above.
  • the preparation method of the invention may comprise the following steps:
  • the polymeric matrix is of the same nature as that mentioned above and can be, in particular, a polyvinylidene fluoride matrix.
  • the irradiation step of a polymeric matrix may consist in subjecting said matrix to heavy ion bombardment.
  • heavy ions are ions, whose mass is greater than that of carbon. Generally, these are ions selected from krypton, lead, xenon.
  • this step may consist in bombarding the polymer matrix with a heavy ion beam, such as a 4.5 MeV / mau Pb ion beam or a 10 MeV Kr ion beam. / fc.
  • a heavy ion beam such as a 4.5 MeV / mau Pb ion beam or a 10 MeV Kr ion beam. / fc.
  • the heavy energy vector ion passes through the matrix, its speed decreases.
  • the ion gives up its energy, creating damaged areas, whose shape is approximately cylindrical.
  • These areas are called latent traces and include two regions: the heart and the halo of the trace.
  • the core of the trace is a totally degraded zone, namely an area where there is rupture of the constituent bonds of the material generating free radicals.
  • This core is also the region where the heavy ion transmits a considerable amount of energy to the electrons of the material. Then, from this heart, there is emission of secondary electrons, which will cause defects far from the heart, thus generating a halo.
  • the irradiation angle may be variable and may be set so as to create traces arranged according to a predetermined pattern, for example traces passing perpendicularly through the thickness of the matrix. It is understood that the heavy ion beam will be determined so as to generate substantially cylindrical areas.
  • the irradiation step can also be carried out by UV irradiation (in other words, irradiation using ultraviolet radiation) or electron irradiation, provided, however, that a mask delimiting the zones is preferably used. substantially cylindrical to be created by irradiation.
  • the irradiation step may be advantageously carried out by UV irradiation, which results in an in-depth modification of the polymeric matrix.
  • the method of the invention may comprise, after the irradiation step, a step of revealing the latent traces created by the irradiation step
  • the chemical revelation may consist in bringing the matrix into contact with a reagent able to hydrolyze the latent traces, so as to form hollow channels instead of these.
  • the latent traces generated have short chains of polymers formed by splitting existing chains during the passage of the ion in the material during the irradiation.
  • the rate of hydrolysis during the revelation is greater than that of the non-irradiated parts.
  • the reagents capable of revealing the latent traces are a function of the material constituting the matrix.
  • the latent traces can in particular be treated with a strongly basic and oxidizing solution, such as a KOH ION solution in the presence of KMnO 4 at 0.25% by weight at a temperature of 65 ° C.
  • a strongly basic and oxidizing solution such as a KOH ION solution in the presence of KMnO 4 at 0.25% by weight at a temperature of 65 ° C.
  • the polymeric matrix is, for example, constituted polyvinylidene fluoride (PVDF), poly (VDF-co-HFP) (vinylidene fluoride-co-hexafluoropropene), poly (VDF-co-TrFE) (vinylidene fluoride-co-trifluoroethylene), poly (VDF-co- co-TrFE-co-ChloroTrFE) (vinylidene fluoride-co-trifluoroethylene-co-monochlorotrifluoroethylene) and other perfluorinated polymers.
  • PVDF
  • a treatment with a basic solution may be sufficient for example for polymers such as polyethylene terephthalate (PET) and polycarbonate (PC).
  • PET polyethylene terephthalate
  • PC polycarbonate
  • the treatment leads to the formation of hollow cylindrical pores whose diameter is adjustable as a function of the attack time with the basic and oxidizing solution.
  • heavy ion irradiation will be carried out so that the membrane has a number of traces per cm 2 between 10 6 and 10 11 . Typically it will be from 5.10 7 to 5.10 10 , more especially to 10 10 . In any case it should be verified that the mechanical properties of the membrane are not significantly reduced by the amount of traces.
  • the method of the invention then comprises a grafting step of contacting the irradiated matrix and optionally revealed with an ethylenic monomer.
  • the grafting step of the ethylenic monomer is likely to take place in three phases:
  • reaction phase of the ethylenic monomer at the aforementioned zones this initiation phase being materialized by an opening of the double bond by reaction with a radical center of the matrix, the radical center thus "moving" from the matrix towards a carbon atom derived from said ethylenic monomer;
  • the free radicals present within the aforementioned zones cause the propagation of the polymerization reaction of the ethylenic monomer contacted with the matrix.
  • the radical reaction is thus, in this case, a radical polymerization reaction of the ethylenic monomer brought into contact, from the irradiated matrix.
  • the membranes obtained will thus comprise a polymer matrix grafted with polymers comprising repeating units resulting from the polymerization of the ethylenic monomer brought into contact with the irradiated matrix.
  • the process of the invention finally comprises a sulfonation or phosphanation step.
  • the sulphonation step consists of introducing a sulphonic group -SO3R into a molecule by carbon-sulfur direct bond, the sulphonation possibly taking place by a direct sulphonation reaction (addition reaction), a substitution reaction of an atom of halogen or a diazo group by a sulfonic group, an oxidation reaction of a sulfide group.
  • This sulfonation step in the context of the invention, may consist in treating the grafted matrix with a solution of chlorosulfonic acid.
  • the phosphanation step consists of introducing a phosphonic group -PO3R2 into a molecule, by direct carbon-phosphorus bond.
  • a step can be carried out by a Michaelis-Arbuzov or Michaelis-Becker reaction on a molecule carrying a halogen atom, thus leading to the formation of phosphonic acid ester, followed by a possible hydrolysis to allow the formation of phosphonic acid ester. obtaining the corresponding phosphonic acid.
  • a step can be carried out by a Friedel-Craft reaction followed by a possible hydrolysis leading to the corresponding phosphonic acid.
  • the invention relates to a fuel cell device comprising at least one membrane as defined above.
  • the membrane is placed between two electrodes, for example carbon fabric, possibly platinum, and impregnated for example with polymer, according to the invention. The whole is pressed by heating.
  • electrodes for example carbon fabric, possibly platinum, and impregnated for example with polymer, according to the invention. The whole is pressed by heating.
  • This assembly is then inserted between two plates (for example, in graphite, called bipolar plates, which ensure the distribution of the gases and the electrical conductivity).
  • PVDF polyvinylidene fluoride
  • the design of this membrane comprises three steps:
  • a PVDF ⁇ membrane in the form of a 9 ⁇ m thick film (from Solvay-Belgium) was extracted in a Sohxlet apparatus in toluene for 24 hours. Subsequently, the membrane was dried under vacuum at 60 ° C. for 12 hours. The membrane was then subjected to heavy ion irradiation 7 gKr 31+ (10 MeV amu- 1 , the electronic halting power of Kr being 40 MeV.cm 2 .mg -1 ) at a fluence of 10. ions / cm 2 under a helium atmosphere. The irradiation angle is set so as to generate essentially cylindrical areas crossing the thickness of the film perpendicularly. b) Radiografting of the membrane irradiated with poly (acrylic acid) grafts
  • the irradiated membrane prepared according to the above protocol is immersed in an acrylic acid / water solution (60/40) and 0.1% by weight of Mohr salt in a radiografting tube.
  • the tube is sparged with nitrogen for 15 minutes.
  • Mohr salt has been used to limit the homopolymerization of acrylic acid.
  • the tube is then sealed and placed in a bath at 60 ° C. for 1 hour.
  • the membrane obtained was then extracted from the solution and then washed with water and extracted with boiling water using a Sohxlet apparatus for 24 hours. It was then dried for 12 hours under high vacuum.
  • the radiografting rate was calculated by the following ratio: where W f and W 1 represent the weight of the membrane respectively after and before grafting of the acrylic acid monomer. The degree of grafting has been estimated at 50% by mass.
  • the membrane was analyzed by Fourier transform infrared spectrometry in ATR mode. The specific vibration band of poly (acrylic acid) at 1703 cm -1 was observed The membrane is hereafter called PVDF-g-PAA membrane. c) Suifonation of the grafted membrane
  • the PVDF-g-PAA membrane was immersed in a solution of 100% chlorosulfonic acid at room temperature for 6 hours. The membrane is then rinsed twice with dichloromethane
  • the membrane obtained was dried under vacuum at 50 ° C. for 12 hours.
  • the membrane was analyzed by Fourier transform infrared spectrometry in ATR mode.
  • the membrane obtained is called by the membrane more PVDF-g-PAA SO 3 H.
  • the PVDF-g-PAA-SO 3 H membrane was dipped in 1M NaCl solution for 24 hours at room temperature. The solution was titrated with 0.01 M sodium hydroxide solution using phenolphthalein as a color indicator. The IEC is then determined by the following formula:
  • IEC (in meq. G "1 ) (VN OH ) / m with V representing the volume of NaOH at equivalence, N 0 H the normality of the sodium hydroxide solution and m the total mass of the membrane.
  • the IEC for the PVDF-g-PAA-SO 3 H membrane was evaluated at 3 meq.g ⁇ e) Determination of the water recovery (RH) of the PVDF-g-PAA-SO 3 H membrane
  • the PVDF-g-PAA-SO 3 H membrane was placed under high vacuum for 24 hours and then its mass was determined. Subsequently, the membrane was dipped in a deionized water solution for 24 hours. The membrane was subsequently buffered with absorbent paper and weighed.
  • the water recovery (RH) is calculated according to the following formula:
  • RH (mass%) [(HIf-In 1 ) / md * 100 with m f representing the mass of the membrane after hydration and In 1 the mass of the dry membrane.
  • the water recovery of the PVDF-g-PS-SO 3 H membrane was evaluated at 14% by mass.

Abstract

The invention relates to a proton-exchange membrane consisting of a polymer matrix including, in the body thereof, substantially cylindrical areas passing through the latter, said areas including polymer grafts selected from among polymer grafts including a main chain, at least a portion of the carbon atoms of which are bonded both to a -COOR group and to a -SO3R or -PO3R2 group, R being a hydrogen atom, a halogen atom, an alkyl group or a cationic counter-ion.

Description

MEMBRANES CONDUCTRICES DE PROTONS POUR PILE A COMBUSTIBLE ET PROCEDE DE PREPARATION DESDITES PROTON CONDUCTIVE MEMBRANES FOR FUEL CELL AND PROCESS FOR PREPARING SAME
MEMBRANES DESCRIPTION MEMBRANES DESCRIPTION
DOMAINE TECHNIQUE TECHNICAL AREA
L' invention a trait à des membranes conductrices de protons de pile à combustible, à des procédés d'élaboration de ces membranes ainsi qu'à des dispositifs de pile à combustible comprenant ce type de membranes .  The invention relates to fuel cell proton conducting membranes, methods of making such membranes and fuel cell devices comprising such membranes.
Le domaine d'application de l'invention est donc celui des piles à combustible, et plus particulièrement des piles à combustible, comprenant en tant qu' électrolyte, une membrane conductrice de protons, tels que les piles à combustible PEMFC (« Proton Exchange Membrane Fuel CeIl » pour Pile à combustible à membrane échangeuse de protons) .  The field of application of the invention is therefore that of fuel cells, and more particularly of fuel cells, comprising as electrolyte, a proton-conducting membrane, such as PEMFC ("Proton Exchange Membrane") fuel cells. Fuel Cell for Proton Exchange Membrane Fuel Cell).
ÉTAT DE LA TECHNIQUE ANTÉRIEURE STATE OF THE PRIOR ART
Une pile à combustible comporte, généralement, un empilement de cellules élémentaires, au sein desquelles a lieu une réaction électrochimique entre deux réactifs qui sont introduits de manière continue. Le combustible, tel que l'hydrogène, pour les piles fonctionnant avec des mélanges hydrogène/oxygène, ou le méthanol pour des piles fonctionnant avec des mélanges méthanol/oxygène, est amené au contact de l'anode, alors que le comburant, généralement l'oxygène, est amené au contact de la cathode. L'anode et la cathode sont séparées par un électrolyte du type membrane conductrice ionique. La réaction électrochimique, dont l'énergie est convertie en énergie électrique, se scinde en deux demi-réactions : A fuel cell generally comprises a stack of elementary cells in which an electrochemical reaction takes place between two reactants which are introduced continuously. Fuel, such as hydrogen, for cells operating with hydrogen / oxygen mixtures, or methanol for batteries operating with methanol / oxygen mixtures, is brought into contact with the anode, whereas the oxidant, generally oxygen, is brought into contact with the cathode. The anode and the cathode are separated by an electrolyte of the type ionic conductive membrane. The electrochemical reaction, whose energy is converted into electrical energy, splits into two half-reactions:
- une oxydation du combustible, se déroulant à l'interface anode/électrolyte produisant, dans le cas des piles à hydrogène des protons H+, qui vont traverser l' électrolyte en direction de la cathode, et des électrons, qui rejoignent le circuit extérieur, afin de concourir à la production d'énergie électrique ;  an oxidation of the fuel, taking place at the anode / electrolyte interface producing, in the case of hydrogen cells, H + protons, which will cross the electrolyte in the direction of the cathode, and electrons, which join the external circuit, to contribute to the production of electrical energy;
- une réduction du comburant, se déroulant à l'interface électrolyte/cathode, avec production d'eau, dans le cas des piles à hydrogène.  a reduction of the oxidant, taking place at the electrolyte / cathode interface, with production of water, in the case of hydrogen cells.
La réaction électrochimique a lieu au niveau d'un assemblage électrode-membrane-électrode.  The electrochemical reaction takes place at an electrode-membrane-electrode assembly.
L' assemblage électrode-membrane-électrode est un assemblage très mince d'une épaisseur de l'ordre du millimètre et chaque électrode est alimentée par les gaz, par exemple à l'aide d'une plaque cannelée.  The electrode-membrane-electrode assembly is a very thin assembly with a thickness of the order of a millimeter and each electrode is fed with the gases, for example using a fluted plate.
La membrane conductrice ionique est généralement une membrane organique contenant des groupes ioniques qui, en présence d'eau, permettent la conduction des protons produits à l'anode par oxydation de l'hydrogène.  The ionic conducting membrane is generally an organic membrane containing ionic groups which, in the presence of water, allow the conduction of the protons produced at the anode by oxidation of hydrogen.
L'épaisseur de cette membrane est comprise en général entre 50 et 150 μm et résulte d'un compromis entre la tenue mécanique et la chute ohmique. Cette membrane permet également la séparation des gaz. La résistance chimique et électrochimique de ces membranes permet, en général, un fonctionnement en pile sur des durées supérieures à 1 000 heures. Le polymère constituant la membrane doit donc remplir un certain nombre de conditions relatives à ses propriétés mécaniques, physico-chimiques et électriques qui sont, entre autres, celles définies ci-après. The thickness of this membrane is generally between 50 and 150 microns and results from a compromise between the mechanical strength and the ohmic drop. This membrane also allows the separation of gases. The chemical and electrochemical resistance of these membranes allows, in general, battery operation over periods of over 1000 hours. The polymer constituting the membrane must therefore fulfill a number of conditions relating to its mechanical, physicochemical and electrical properties which are, inter alia, those defined below.
Le polymère doit tout d' abord pouvoir donner des films minces, de 50 à 150 micromètres, denses, sans défauts. Les propriétés mécaniques, module élastique, contrainte à la rupture, ductilité, doivent le rendre compatible avec les opérations d'assemblage comprenant, par exemple, un serrage entre des cadres métalliques .  The polymer must first be able to give thin films, 50 to 150 micrometers, dense, without defects. The mechanical properties, elastic modulus, tensile strength, ductility, must make it compatible with assembly operations including, for example, clamping between metal frames.
Les propriétés doivent être préservées en passant de l'état sec à l'état humide.  The properties must be preserved by changing from dry to wet.
Le polymère doit avoir une bonne stabilité thermique à l'hydrolyse et présenter une bonne résistance à la réduction et à l'oxydation. Cette stabilité thermomécanique s'apprécie en terme de variation de résistance ionique, et en terme de variation des propriétés mécaniques.  The polymer must have good thermal stability to hydrolysis and have good resistance to reduction and oxidation. This thermomechanical stability is appreciated in terms of variation of ionic resistance, and in terms of variation of the mechanical properties.
Le polymère doit enfin posséder une forte conductivité ionique, cette conductivité étant apportée par des groupements acides, tels que des groupements acide carboxylique, acide phosphorique ou acide sulfonique reliés à la chaîne du polymère.  The polymer must finally have a high ionic conductivity, this conductivity being provided by acidic groups, such as carboxylic acid, phosphoric acid or sulfonic acid groups connected to the polymer chain.
Depuis plusieurs décennies, il a été proposé différents types de polymères conducteurs protoniques utilisables pour constituer des membranes de pile à combustible. On a tout d'abord mis en oeuvre des résines de type phénolique sulfonées préparées par sulfonation de produits polycondensés, tels que les polymères phénol-formaldéhyde . For several decades, it has been proposed various types of proton conductive polymers used to form fuel cell membranes. Sulfonated phenolic resins prepared by sulfonation of polycondensed products, such as phenol-formaldehyde polymers, were first used.
Les membranes préparées avec ces produits sont peu coûteuses, mais n'ont pas une stabilité à l'hydrogène suffisante à 50-600C pour des applications de longue durée. The membranes prepared with these products are inexpensive but do not have sufficient hydrogen stability at 50-60 ° C. for long-term applications.
Actuellement, des performances acceptables sont obtenues à partir de polymères constituées d'une chaîne principale linéaire perfluorée et d'une chaîne latérale portant un groupement acide sulfonique.  Currently, acceptable performance is obtained from polymers consisting of a perfluorinated linear main chain and a side chain carrying a sulfonic acid group.
Parmi ces polymères les plus connus, et qui sont disponibles dans le commerce, on peut citer les polymères déposés sous les marques NAFION® de la société Dupont de Nemours.  Among these known polymers, which are commercially available, mention may be made of the polymers deposited under the NAFION® brands of the Dupont de Nemours Company.
Toutefois, les membranes utilisées actuellement et notamment les membranes du type NAFION® présentent une limite au niveau de la température d'utilisation de l'ordre de 900C, un phénomène de vieillissement au bout de 3000-4000 heures d'utilisation, une conductivité de l'ordre de 60 mS . cm"1 et un coût élevé de 250/300 $. However, the membranes currently used and in particular the membranes of the NAFION® type have a limit to the order of use of the temperature level of 90 0 C, an aging phenomenon after 3000-4000 hours of use, conductivity of the order of 60 mS. cm "1 and a high cost of $ 250/300.
Les inventeurs se sont ainsi fixé comme objectif de proposer de nouvelles membranes aptes à surmonter tout ou partie des inconvénients des membranes de l'art antérieur et, en particulier, présentant les avantages suivants :  The inventors have thus set themselves the objective of proposing new membranes capable of overcoming all or part of the disadvantages of the membranes of the prior art and, in particular, having the following advantages:
- être une barrière efficace aux gaz O2/H2 aux pressions de fonctionnement des piles à combustibles (par exemple sous 4 bars de pression) ; - avoir une conductivité protonique importante avec un minimum de quantité d'eau (par exemple, sous 20% d'humidité) ; - be an effective barrier to O2 / H2 gas at operating pressures of fuel cells (for example under 4 bar pressure); have a high proton conductivity with a minimum amount of water (for example, under 20% humidity);
- une bonne stabilité thermique à des températures de fonctionnement élevées (par exemple o U L-) ;  good thermal stability at high operating temperatures (for example o U L-);
- un taux d'humidité relativement faible (par exemple, inférieur à 25% à la cathode et 50% à l'anode) ;  a relatively low humidity level (for example, less than 25% at the cathode and 50% at the anode);
- un temps de vie long ;  - a long life time;
- être bon marché.  - be cheap.
EXPOSÉ DE L'INVENTION STATEMENT OF THE INVENTION
Ainsi, l'invention a trait à une membrane échangeuse de protons consistant en une matrice polymérique comprenant, dans son épaisseur, des zones sensiblement cylindriques traversant cette dernière, lesdites zones comprenant des greffons polymériques choisis parmi les greffons polymériques comprenant une chaîne principale, dont au moins une partie des atomes de carbone est liée à la fois à un groupe -COOR et à un groupe -SO3R ou -PO3R2, R représentant un atome d'hydrogène, un atome d'halogène, un groupe alkyle ou un contre-ion cationique.  Thus, the invention relates to a proton exchange membrane consisting of a polymeric matrix comprising, in its thickness, substantially cylindrical zones passing through the latter, said zones comprising polymeric grafts chosen from polymeric grafts comprising a main chain, of which at least a portion of the carbon atoms is bonded to both -COOR and -SO3R or -PO3R2, where R is hydrogen, halogen, alkyl, or cationic counterion .
De par l'association d'une architecture particulière (en l'occurrence, une membrane présentant des zones sensiblement cylindriques reliant deux faces opposées de la matrice) avec une constitution polymérique particulière, les membranes de l'invention présentent les caractéristiques avantageuses suivantes : - une capacité d'échange ionique importante, notamment supérieure à 2,5 méq.g'1, et ce dans des conditions d'humidité relative inférieure à 20% ; By the combination of a particular architecture (in this case a membrane having substantially cylindrical zones connecting two opposite faces of the matrix) with a particular polymeric constitution, the membranes of the invention have the following advantageous characteristics: a significant ion exchange capacity, especially greater than 2.5 meq.g -1 , and this under relative humidity conditions of less than 20%;
- une reprise d'eau (« water uptake ») moindre que les membranes de l'art antérieur, telles que les membranes en Nafion, dans les mêmes conditions, occasionnant ainsi un gonflement moindre de la membrane et ainsi des meilleures propriétés mécaniques ;  a water uptake less than the membranes of the prior art, such as Nafion membranes, under the same conditions, thus causing less swelling of the membrane and thus better mechanical properties;
- une capacité à assurer une conduction protonique à des températures de travail supérieures à 800C, par exemple 1200C ; - an ability to ensure proton conduction in working temperatures above 80 0 C, e.g., 120 0 C;
- une résistance à des pressions de 10 bars ;  a resistance at pressures of 10 bar;
- une inertie vis-à-vis des phénomènes de corrosion .  - Inertia vis-à-vis the phenomena of corrosion.
Avant d'entrer plus en détail dans la description de l'invention, nous proposons les définitions suivantes.  Before going into more detail in the description of the invention, we propose the following definitions.
Par matrice polymérique, on entend la partie de base de la membrane dans laquelle sont réalisées les zones sensiblement cylindriques comprenant les greffons, cette matrice donnant la forme à la membrane.  Polymeric matrix is understood to mean the base portion of the membrane in which the substantially cylindrical zones comprising the grafts are formed, this matrix giving the shape to the membrane.
Par zones sensiblement cylindriques, on entend des zones de forme globalement cylindrique délimitant des volumes de la matrice dans lesquels sont greffés les greffons susmentionnés, ces zones traversant l'épaisseur de ladite matrice, à savoir qu'elles rejoignent deux faces opposées de cette matrice, ce qui permet d'engendrer un chemin conducteur de part en part de l'épaisseur de la matrice. By substantially cylindrical zones is meant areas of generally cylindrical shape delimiting volumes of the matrix in which the aforementioned grafts are grafted, these zones passing through the thickness of said matrix, namely that they join two opposite faces of this matrix, which makes it possible to generate a conductive path through the thickness of the matrix.
Par greffon, on entend une chaîne polymérique liée de façon covalente au polymère constitutif de la matrice dans les zones susmentionnées .  By graft is meant a polymer chain covalently bonded to the polymer constituting the matrix in the aforementioned areas.
La matrice polymérique de base peut être une matrice en un polymère choisi parmi les polyuréthanes, les polyoléfines, les polycarbonates, les polyéthylènetéréphtalates, ces polymères étant avantageusement fluorés voire perfluorés.  The base polymer matrix may be a matrix made of a polymer chosen from polyurethanes, polyolefins, polycarbonates and polyethylene terephthalates, these polymers being advantageously fluorinated or even perfluorinated.
De préférence, la matrice polymérique peut être choisie parmi les matrices en polymère fluoré tels que le polyfluorure de vinylidène, les copolymères de tétrafluoroéthylène et de tétrafluoropropylène (connus sous l'abréviation FEP), les copolymères d'éthylène et de tétrafluoroéthylène (connus sous l'abréviation ETFE), les copolymères d' hexafluoropropène et de fluorure de vinylidène (connus sous l'abréviation HFP- co-VDF), de fluorure de vinylidène et de trifluoroéthylène (connus sous l'abréviation VDF-co- TrFE) , de fluorure de vinylidène, de trifluoroéthylène et de monochlorotrifluoroéthylène (connu sous l'abréviation VDF-co-TrFE-co-chloroTrFE) .  Preferably, the polymeric matrix may be chosen from fluorinated polymer matrices such as polyvinylidene fluoride, copolymers of tetrafluoroethylene and tetrafluoropropylene (known by the abbreviation FEP), copolymers of ethylene and tetrafluoroethylene (known under the name of abbreviation ETFE), copolymers of hexafluoropropene and of vinylidene fluoride (known by the abbreviation HFP-co-VDF), of vinylidene fluoride and of trifluoroethylene (known under the abbreviation VDF-co-TrFE), of fluoride vinylidene, trifluoroethylene and monochlorotrifluoroethylene (known by the abbreviation VDF-co-TrFE-co-chloroTrFE).
Les matrices polymériques à base de polymères fluorés sont avantageuses, en ce sens qu'elles sont résistantes à la corrosion, présentent de bonnes propriétés mécaniques et une faible perméation aux gaz. Elles sont donc particulièrement adaptées pour constituer des membranes de piles à combustible. Une matrice de ce type particulièrement avantageuse est une matrice en polyfluorure de vinylidène. Le polyfluorure de vinylidène est inerte chimiquement (résistant notamment à la corrosion) , présente de bonnes propriétés mécaniques, a une température de transition vitreuse, qui varie de -420C à -38°C, une température de fusion de 1700C et une densité de 1,75 g/cm3. Il présente également une faible perméation aux gaz, ce qui le rend particulièrement intéressant comme base pour constituer des membranes de pile à combustible fonctionnant avec de l'hydrogène comme combustible. Ce polymère s'extrude aisément et peut se présenter notamment sous deux formes cristallines, selon l'orientation des cristallites : la phase α et la phase β, la phase β se caractérisant notamment par des propriétés piézoélectriques. Polymeric matrices based on fluoropolymers are advantageous in that they are resistant to corrosion, have good mechanical properties and low gas permeation. They are therefore particularly suitable for constituting fuel cell membranes. A particularly advantageous matrix of this type is a polyvinylidene fluoride matrix. Polyvinylidene fluoride is chemically inert (particularly resistant to corrosion), has good mechanical properties, has a glass transition temperature, which varies from -42 ° C. to -38 ° C., a melting temperature of 170 ° C. and a density of 1.75 g / cm 3 . It also has low gas permeation, which makes it particularly useful as a basis for building fuel cell membranes operating with hydrogen as fuel. This polymer is easily extruded and can be in particular in two crystalline forms, depending on the orientation of the crystallites: the α phase and the β phase, the β phase being characterized in particular by piezoelectric properties.
Les zones sensiblement cylindriques relient deux faces opposées de la matrice et peuvent traverser l'épaisseur de celle-ci, selon des angles variables ou identiques, par exemple de façon perpendiculaire et être parallèles entre elles. Elles peuvent présenter un diamètre allant de 50 à 100 μm, auquel cas on pourra les qualifier de microzones. Elles peuvent présenter également un diamètre allant de 10 à 100 nm, auquel cas on peut les qualifier de nanozones. Ces zones peuvent être également creuses, auquel cas les greffons seront liés sur la paroi desdites zones.  The substantially cylindrical zones connect two opposite faces of the matrix and can pass through the thickness thereof, at variable or identical angles, for example in a perpendicular manner and be parallel to each other. They may have a diameter ranging from 50 to 100 microns, in which case they may be called microzones. They can also have a diameter ranging from 10 to 100 nm, in which case they can be described as nanozones. These zones may also be hollow, in which case the grafts will be linked to the wall of said zones.
Classiquement, la matrice peut comprendre de 5.104 à 5.1010, de préférence, de 105 à 5.109 zones par cm2. Selon l'invention, les greffons polymériques comprennent une chaîne principale, dont au moins une partie des atomes de carbone est liée à la fois à un groupe -COOR et à un groupe -SO3R ou -PO3R2, ce qui signifie, en d'autres termes, que certains des atomes de carbone de la chaîne principale sont doublement substitués, un des substituants étant un groupe -COOR tandis que l'autre substituant est un groupe -SO3R ou -PO3R2. Ceci n'exclut pas le fait que les atomes de carbone adjacents à ceux porteurs du groupe -COOR puissent comprendre également des groupes -SO3R ou -PO3R2. Conventionally, the matrix may comprise from 5.10 4 to 5.10 10 , preferably from 10 5 to 5.10 9 zones per cm 2 . According to the invention, the polymeric grafts comprise a main chain, of which at least a portion of the carbon atoms is bonded to both a -COOR group and a -SO3R or -PO3R2 group, which means, in other words In other words, some of the carbon atoms of the main chain are doubly substituted, one substituent being a -COOR group while the other substituent is -SO3R or -PO3R2. This does not exclude the fact that carbon atoms adjacent to those bearing the -COOR group may also include -SO 3 R or -PO 3 R 2 groups.
Ainsi, de tels greffons peuvent comprendre un enchaînement du type suivant :  Thus, such grafts may include a sequence of the following type:
les groupes X représentant -COOR, tandis que les groupes Y représentent un groupe -SO3R ou -PO3R2. the groups X representing -COOR, while the groups Y represent a group -SO3R or -PO 3 R 2 .
De tels greffons peuvent résulter de la polymérisation de monomères acryliques comportant au moins un groupe -CO2R, tels que l'acide acrylique, les polymères résultants ayant subi une étape de sulfonation ou phosphanation pour introduire les groupes -SO3R ou -PO3R2 sur au moins une partie des atomes porteurs des groupes -CO2R, R étant tel que défini ci-dessus.  Such grafts may result from the polymerization of acrylic monomers having at least one -CO2R group, such as acrylic acid, the resulting polymers having undergone a sulfonation or phosphanation step to introduce the -SO3R or -PO3R2 groups on at least one part of the atoms bearing -CO2R groups, R being as defined above.
Le radical R dans les groupes -COOR, -SO3R ou -PO3R2 peut être un atome d'hydrogène, un atome d'halogène (par exemple, F ou Cl) ou un groupe alkyle, un contre-ion cationique, tel qu'un cation issu d'un métal alcalin (comme Na+) . The radical R in the groups -COOR, -SO3R or -PO3R2 may be a hydrogen atom, an atom halogen (for example, F or Cl) or an alkyl group, a cationic counterion, such as a cation derived from an alkali metal (such as Na + ).
Des membranes particulières conformes à l'invention sont des membranes comprenant une matrice polymérique sous forme d'un film en polyfluorure de vinylidène présentant des zones cylindriques reliant deux faces opposées de la matrice, lesdites zones comprenant des greffons consistant en une chaîne principale résultant de la polymérisation de l'acide acrylique, au moins une partie des atomes de carbone porteurs du groupe -COOH issu de l'acide acrylique étant porteur également d'un groupe -SO3R ou -PO3R2, R ayant la même signification que celle donnée ci-dessus.  Particular membranes according to the invention are membranes comprising a polymeric matrix in the form of a polyvinylidene fluoride film having cylindrical zones connecting two opposite faces of the matrix, said zones comprising grafts consisting of a main chain resulting from the polymerization of acrylic acid, at least a portion of the carbon atoms carrying the -COOH group derived from acrylic acid also carrying a -SO3R or -PO3R2 group, R having the same meaning as that given above .
Hormis les zones susmentionnées, d'autres parties de la membrane peuvent être revêtues par des greffons tels que définis ci-dessus, par débordement des greffons compris dans lesdites zones.  Apart from the aforementioned zones, other parts of the membrane may be coated with grafts as defined above, by overflow of the grafts included in said zones.
L' invention a également trait à un procédé de préparation d'une membrane telle que définie ci- dessus .  The invention also relates to a process for preparing a membrane as defined above.
Le procédé de préparation de l'invention peut comprendre les étapes suivantes :  The preparation method of the invention may comprise the following steps:
- une étape d'irradiation d'une matrice polymérique, de sorte à former des zones irradiées de forme sensiblement cylidrique traversant l'épaisseur de la matrice ;  a step of irradiating a polymeric matrix, so as to form irradiated zones of substantially cylindrical shape passing through the thickness of the matrix;
- éventuellement une étape de révélation des traces latentes créées par l'étape d'irradiation ;  optionally a step of revealing the latent traces created by the irradiation step;
- une étape de greffage des zones irradiées par réaction radicalaire avec un monomère éthylénique, moyennant quoi l'on obtient la chaîne principale des greffons ; a grafting step of the irradiated zones by radical reaction with an ethylenic monomer, whereby we obtain the main chain of grafts;
- une étape de sulfonation ou de phosphonation desdites chaînes principales.  a step of sulphonating or phosphonating said main chains.
La matrice polymérique est de même nature que celle mentionnée ci-dessus et peut être, en particulier, une matrice en polyfluorure de vinylidène.  The polymeric matrix is of the same nature as that mentioned above and can be, in particular, a polyvinylidene fluoride matrix.
L'étape d'irradiation d'une matrice polymérique peut consister à soumettre ladite matrice à un bombardement par des ions lourds.  The irradiation step of a polymeric matrix may consist in subjecting said matrix to heavy ion bombardment.
On précise que par ions lourds, on entend des ions, dont la masse est supérieure à celle du carbone. Généralement, il s'agit d'ions choisis parmi le krypton, le plomb, le xénon.  It is specified that heavy ions are ions, whose mass is greater than that of carbon. Generally, these are ions selected from krypton, lead, xenon.
Plus particulièrement, cette étape peut consister à bombarder la matrice polymérique avec un faisceau d'ions lourds, tel qu'un faisceau d'ions Pb d'intensité 4,5 MeV/mau ou un faisceau d'ions Kr d'intensité 10 MeV/mau.  More particularly, this step may consist in bombarding the polymer matrix with a heavy ion beam, such as a 4.5 MeV / mau Pb ion beam or a 10 MeV Kr ion beam. / fc.
D'un point de vue mécanistique, lorsque l'ion lourd vecteur d'énergie traverse la matrice, sa vitesse diminue. L'ion cède son énergie, en créant des zones endommagées, dont la forme est approximativement cylindrique. Ces zones sont appelées traces latentes et comprennent deux régions : le cœur et le halo de la trace. Le cœur de la trace est une zone totalement dégradée, à savoir une zone où il y a rupture des liaisons constitutives du matériau générant des radicaux libres. Ce cœur est également la région où l'ion lourd transmet une quantité considérable d'énergie aux électrons du matériau. Puis, à partir de ce cœur, il y a émission d'électrons secondaires, qui vont provoquer des défauts loin du cœur, générant ainsi un halo. From a mechanistic point of view, when the heavy energy vector ion passes through the matrix, its speed decreases. The ion gives up its energy, creating damaged areas, whose shape is approximately cylindrical. These areas are called latent traces and include two regions: the heart and the halo of the trace. The core of the trace is a totally degraded zone, namely an area where there is rupture of the constituent bonds of the material generating free radicals. This core is also the region where the heavy ion transmits a considerable amount of energy to the electrons of the material. Then, from this heart, there is emission of secondary electrons, which will cause defects far from the heart, thus generating a halo.
Dans le cas de l'irradiation par ions lourds, le dépôt d'énergie se répartit radialement par rapport à la trajectoire rectiligne de l'ion traversant et crée des zones d' endommagement localisées autour du passage des ions. Ce type d'irradiation est donc inhomogène dans le volume du matériau laissant des parties non irradiées. L'angle d'irradiation peut être variable et peut être fixé de sorte à créer des traces disposées selon un schéma prédéterminé, par exemple des traces traversant l'épaisseur de la matrice de façon perpendiculaire. Il s'entend que le faisceau d'ions lourds sera déterminé de sorte à générer des zones sensiblement cylindriques.  In the case of heavy ion irradiation, energy deposition is distributed radially with respect to the straight path of the through ion and creates localized areas of damage around the ion path. This type of irradiation is therefore inhomogeneous in the volume of the material leaving unirradiated parts. The irradiation angle may be variable and may be set so as to create traces arranged according to a predetermined pattern, for example traces passing perpendicularly through the thickness of the matrix. It is understood that the heavy ion beam will be determined so as to generate substantially cylindrical areas.
L'étape d'irradiation peut être également réalisée par irradiation UV (soit en d'autres termes, irradiation au moyen d'un rayonnement ultraviolet) ou irradiation aux électrons, sous réserve toutefois d'utiliser, de préférence, un masque délimitant les zones sensiblement cylindriques à créer par 1' irradiation .  The irradiation step can also be carried out by UV irradiation (in other words, irradiation using ultraviolet radiation) or electron irradiation, provided, however, that a mask delimiting the zones is preferably used. substantially cylindrical to be created by irradiation.
En particulier, l'étape d'irradiation peut se faire avantageusement, par irradiation UV, ce qui entraîne une modification en profondeur de la matrice polymérique .  In particular, the irradiation step may be advantageously carried out by UV irradiation, which results in an in-depth modification of the polymeric matrix.
Le procédé de l'invention peut comprendre, après l'étape d'irradiation, une étape de révélation des traces latentes créées par l'étape d'irradiation La révélation chimique peut consister à mettre en contact la matrice avec un réactif apte à hydrolyser les traces latentes, de façon à former des canaux creux à la place de celles-ci. The method of the invention may comprise, after the irradiation step, a step of revealing the latent traces created by the irradiation step The chemical revelation may consist in bringing the matrix into contact with a reagent able to hydrolyze the latent traces, so as to form hollow channels instead of these.
Selon ce mode de réalisation particulier, suite à l'irradiation de la matrice polymérique par des ions lourds, les traces latentes générées présentent des chaînes courtes de polymères formées par scission des chaînes existantes lors du passage de l'ion dans la matière durant l'irradiation. Dans ces traces latentes, la vitesse d'hydrolyse lors de la révélation est plus importante que celle des parties non irradiées. Ainsi, il est possible de procéder à une révélation sélective. Les réactifs susceptibles d'assurer la révélation des traces latentes sont fonction du matériau constitutif de la matrice.  According to this particular embodiment, following the irradiation of the polymer matrix with heavy ions, the latent traces generated have short chains of polymers formed by splitting existing chains during the passage of the ion in the material during the irradiation. In these latent traces, the rate of hydrolysis during the revelation is greater than that of the non-irradiated parts. Thus, it is possible to carry out a selective revelation. The reagents capable of revealing the latent traces are a function of the material constituting the matrix.
Ainsi, les traces latentes peuvent notamment être traitées par une solution fortement basique et oxydante, comme une solution KOH ION en présence de KMnO4 à 0,25% en poids à une température de 65°C, lorsque la matrice polymérique est par exemple constituée de polyfluorure de vinylidène (PVDF), de poly (VDF-co-HFP) (fluorure de vinylidène-co- hexafluoropropène) , de poly (VDF-co-TrFE) (fluorure de vinylidène-co-trifluoroéthylène) , poly (VDF-co-TrFE-co- ChloroTrFE) (fluorure de vinylidène-co- trifluoroéthylène-co- monochlorotrifluoroéthylène) et autres polymères perfluorés. Un traitement avec une solution basique, éventuellement couplée avec une sensibilisation des traces par UV, peut suffire par exemple pour des polymères comme du polyéthylene téréphthalate (PET) et du polycarbonate (PC) . Le traitement conduit à la formation de pores cylindriques creux dont le diamètre est modulable en fonction du temps d'attaque avec la solution basique et oxydante. Généralement l'irradiation par ions lourds sera effectuée de telle sorte que la membrane comporte un nombre de traces par cm2 compris entre 106 et 1011. Typiquement il sera compris entre 5.107 et 5.1010, plus spécialement vers 1010. En tout état de cause il convient de vérifier que les propriétés mécaniques de la membrane ne sont pas amoindries de façon significative par la quantité de traces. Thus, the latent traces can in particular be treated with a strongly basic and oxidizing solution, such as a KOH ION solution in the presence of KMnO 4 at 0.25% by weight at a temperature of 65 ° C., when the polymeric matrix is, for example, constituted polyvinylidene fluoride (PVDF), poly (VDF-co-HFP) (vinylidene fluoride-co-hexafluoropropene), poly (VDF-co-TrFE) (vinylidene fluoride-co-trifluoroethylene), poly (VDF-co- co-TrFE-co-ChloroTrFE) (vinylidene fluoride-co-trifluoroethylene-co-monochlorotrifluoroethylene) and other perfluorinated polymers. A treatment with a basic solution, possibly coupled with a trace sensitization by UV, may be sufficient for example for polymers such as polyethylene terephthalate (PET) and polycarbonate (PC). The treatment leads to the formation of hollow cylindrical pores whose diameter is adjustable as a function of the attack time with the basic and oxidizing solution. Generally heavy ion irradiation will be carried out so that the membrane has a number of traces per cm 2 between 10 6 and 10 11 . Typically it will be from 5.10 7 to 5.10 10 , more especially to 10 10 . In any case it should be verified that the mechanical properties of the membrane are not significantly reduced by the amount of traces.
Le procédé de l'invention comprend ensuite une étape de greffage consistant à mettre en contact la matrice irradiée et éventuellement révélée avec un monomère éthylénique.  The method of the invention then comprises a grafting step of contacting the irradiated matrix and optionally revealed with an ethylenic monomer.
Sans être lié par la théorie, l'étape de greffage du monomère éthylénique est susceptible de se dérouler en trois phases :  Without being bound by theory, the grafting step of the ethylenic monomer is likely to take place in three phases:
- une phase de réaction du monomère éthylénique au niveau des zones susmentionnées, cette phase d' initiation se matérialisant par une ouverture de la double liaison par réaction avec un centre radicalaire de la matrice, le centre radicalaire se « déplaçant » ainsi de la matrice vers un atome de carbone issu dudit monomère éthylénique ;  a reaction phase of the ethylenic monomer at the aforementioned zones, this initiation phase being materialized by an opening of the double bond by reaction with a radical center of the matrix, the radical center thus "moving" from the matrix towards a carbon atom derived from said ethylenic monomer;
- une phase de polymérisation du monomère éthylénique à partir du centre radicalaire créé sur le premier monomère greffé ; - une phase de terminaison par recombinaison radicalaire ou transfert suivant l'environnement du milieu réactionnel. a polymerization phase of the ethylenic monomer from the radical center created on the first grafted monomer; a phase of termination by radical recombination or transfer according to the environment of the reaction medium.
En d'autres termes, les radicaux libres présents au sein des zones susmentionnées engendrent la propagation de la réaction de polymérisation du monomère éthylénique mis en contact avec la matrice. La réaction radicalaire est ainsi, dans ce cas de figure, une réaction de polymérisation radicalaire du monomère éthylénique mis en contact, à partir de la matrice irradiée .  In other words, the free radicals present within the aforementioned zones cause the propagation of the polymerization reaction of the ethylenic monomer contacted with the matrix. The radical reaction is thus, in this case, a radical polymerization reaction of the ethylenic monomer brought into contact, from the irradiated matrix.
A l'issue de la phase de polymérisation, les membranes obtenues comprendront ainsi une matrice polymérique greffée par des polymères comprenant des unités répétitives issues de la polymérisation du monomère éthylénique mis en contact avec la matrice irradiée .  At the end of the polymerization phase, the membranes obtained will thus comprise a polymer matrix grafted with polymers comprising repeating units resulting from the polymerization of the ethylenic monomer brought into contact with the irradiated matrix.
Si l'on représente le monomère éthylénique par la formule =-R, le schéma réactionnel peut être le suivant : If the ethylenic monomer is represented by the formula = -R, the reaction scheme can be as follows:
Matrice MatriceMatrix Matrix
MatriceMatrix
Après l'étape de greffage, le procédé de l'invention comprend enfin une étape de sulfonation ou de phosphanation .  After the grafting step, the process of the invention finally comprises a sulfonation or phosphanation step.
L'étape de sulfonation consiste à introduire un groupe sulfonique -SO3R dans une molécule par liaison directe carbone-soufre, la sulfonation pouvant intervenir par une réaction de sulfonation directe (réaction d'addition), une réaction de substitution d'un atome d'halogène ou d'un groupe diazoïque par un groupe sulfonique, une réaction d'oxydation d'un groupe sulfure.  The sulphonation step consists of introducing a sulphonic group -SO3R into a molecule by carbon-sulfur direct bond, the sulphonation possibly taking place by a direct sulphonation reaction (addition reaction), a substitution reaction of an atom of halogen or a diazo group by a sulfonic group, an oxidation reaction of a sulfide group.
Cette étape de sulfonation, dans le cadre de l'invention, peut consister à traiter la matrice greffée avec une solution d'acide chlorosulfonique .  This sulfonation step, in the context of the invention, may consist in treating the grafted matrix with a solution of chlorosulfonic acid.
L'étape de phosphanation consiste à introduire un groupement phosphonique -PO3R2 dans une molécule, par liaison directe carbone-phosphore. Une telle étape peut être réalisée par une réaction de Michaelis-Arbuzov ou Michaelis-Becker sur une molécule porteur d'un atome halogène, conduisant ainsi à la formation d'ester d'acide phosphonique, suivie d'une éventuelle hydrolyse pour permettre l'obtention de l'acide phosphonique correspondant. Pour des molécules comportant des groupes aryles, une telle étape peut être réalisée par une réaction de Friedel-Craft suivie d'une éventuelle hydrolyse conduisant à l'acide phosphonique correspondant. The phosphanation step consists of introducing a phosphonic group -PO3R2 into a molecule, by direct carbon-phosphorus bond. Such a step can be carried out by a Michaelis-Arbuzov or Michaelis-Becker reaction on a molecule carrying a halogen atom, thus leading to the formation of phosphonic acid ester, followed by a possible hydrolysis to allow the formation of phosphonic acid ester. obtaining the corresponding phosphonic acid. For molecules containing aryl groups, such a step can be carried out by a Friedel-Craft reaction followed by a possible hydrolysis leading to the corresponding phosphonic acid.
Enfin, l'invention a trait à un dispositif de pile à combustible comprenant au moins une membrane telle que définie ci-dessus.  Finally, the invention relates to a fuel cell device comprising at least one membrane as defined above.
Pour préparer un tel dispositif, la membrane est placée entre deux électrodes, par exemple, en tissu de carbone, éventuellement platiné, et imprégnées par exemple par du polymère, selon l'invention. L'ensemble est pressé par chauffage.  To prepare such a device, the membrane is placed between two electrodes, for example carbon fabric, possibly platinum, and impregnated for example with polymer, according to the invention. The whole is pressed by heating.
Cet ensemble est ensuite inséré entre deux plaques (par exemple, en graphite, appelées plaques bipolaires, qui assurent la distribution des gaz et la conductivité électrique) .  This assembly is then inserted between two plates (for example, in graphite, called bipolar plates, which ensure the distribution of the gases and the electrical conductivity).
L'invention va maintenant être décrite, en référence aux exemples suivants, donnés à titre indicatif et non limitatif.  The invention will now be described, with reference to the following examples, given for information only and not limiting.
BRÈVE DESCRIPTION DES DESSINS BRIEF DESCRIPTION OF THE DRAWINGS
La figure unique illustre, de façon schématique, les différentes étapes du procédé mises en œuvre dans le cadre des exemples 1 et 2. EXPOSE DETAILLE D'UN MODE DE REALISATION PARTICULIER The single figure illustrates, schematically, the different steps of the method implemented in the context of Examples 1 and 2. DETAILED DESCRIPTION OF A PARTICULAR EMBODIMENT
EXEMPLE 1 EXAMPLE 1
Cet exemple illustre la préparation d'une membrane en polyfluorure de vinylidène (PVDF) comprenant des zones essentiellement cylindriques traversant l'épaisseur de la membrane de façon perpendiculaire, ces zones étant greffées par des greffons comportant du poly (acide acrylique) sulfoné.  This example illustrates the preparation of a polyvinylidene fluoride (PVDF) membrane comprising substantially cylindrical zones traversing the thickness of the membrane perpendicularly, these areas being grafted with grafts comprising sulfonated poly (acrylic acid).
La conception de cette membrane comprend trois étapes :  The design of this membrane comprises three steps:
- une étape d'irradiation d'une membrane de base en PVDF par des ions lourds ;  a step of irradiating a PVDF base membrane with heavy ions;
- une étape de radiogreffâge au sein des zones générées par l'irradiation par des greffons poly (acide acrylique) ; et  a radiografting step within the zones generated by the irradiation with poly (acrylic acid) grafts; and
- une étape de sulfonation desdits greffons . a) Irradiation aux ions lourds de la membrane de base en PVDF  a step of sulphonating said grafts. a) Heavy ion irradiation of the PVDF base membrane
Une membrane de PVDF β se présentant sous forme d'un film d'épaisseur 9 μm (provenant de Solvay- Belgique) a été extraite dans un appareil dit de Sohxlet dans du toluène pendant 24 heures. Par la suite, la membrane a été séchée sous vide à 600C pendant 12 heures. La membrane a été ensuite soumise à une irradiation aux ions lourds 7gKr31+ (10 MeV. amu"1, le pouvoir d' arrêt électronique du Kr étant de 40 MeV. cm2.mg"1) à une fluence de 1010 ions/cm2 sous une atmosphère d'hélium. L'angle d'irradiation est fixé de sorte à générer des zones essentiellement cylindriques traversant l'épaisseur du film de façon perpendiculaire . b) Radiogreffâge de la membrane irradiée par des greffons poly (acide acrylique) A PVDF β membrane in the form of a 9 μm thick film (from Solvay-Belgium) was extracted in a Sohxlet apparatus in toluene for 24 hours. Subsequently, the membrane was dried under vacuum at 60 ° C. for 12 hours. The membrane was then subjected to heavy ion irradiation 7 gKr 31+ (10 MeV amu- 1 , the electronic halting power of Kr being 40 MeV.cm 2 .mg -1 ) at a fluence of 10. ions / cm 2 under a helium atmosphere. The irradiation angle is set so as to generate essentially cylindrical areas crossing the thickness of the film perpendicularly. b) Radiografting of the membrane irradiated with poly (acrylic acid) grafts
La membrane irradiée préparée selon le protocole ci-dessus est plongée dans une solution acide acrylique/eau (60/40) et 0,1% en masse de sel de Mohr dans un tube de radiogreffâge . Le tube est soumis à un barbotage à l'azote pendant 15 minutes. Le sel de Mohr a été employé pour limiter l' homopolymérisation de l'acide acrylique. Le tube est ensuite scellé puis placé dans un bain à 600C pendant 1 heure. La membrane obtenue a alors été extraite de la solution puis nettoyée à l'eau et extraite à l'eau bouillante à l'aide d'un appareil de Sohxlet pendant 24 heures. Elle a ensuite été séchée pendant 12 heures sous vide poussé . The irradiated membrane prepared according to the above protocol is immersed in an acrylic acid / water solution (60/40) and 0.1% by weight of Mohr salt in a radiografting tube. The tube is sparged with nitrogen for 15 minutes. Mohr salt has been used to limit the homopolymerization of acrylic acid. The tube is then sealed and placed in a bath at 60 ° C. for 1 hour. The membrane obtained was then extracted from the solution and then washed with water and extracted with boiling water using a Sohxlet apparatus for 24 hours. It was then dried for 12 hours under high vacuum.
Le taux de radiogreffâge a été calculé par le rapport suivant : où Wf et W1 représentent le poids de la membrane respectivement après et avant greffage du monomère acide acrylique Le taux de greffage a été estimé à 50% en masse. La membrane a été analysée par spectrométrie infrarouge à transformée de Fourier en mode ATR. La bande de vibration spécifique du poly (acide acrylique) à 1703 cm"1 a été observée. La membrane est intitulée par la suite membrane PVDF-g-PAA. c) Suifonation de la membrane greffée The radiografting rate was calculated by the following ratio: where W f and W 1 represent the weight of the membrane respectively after and before grafting of the acrylic acid monomer. The degree of grafting has been estimated at 50% by mass. The membrane was analyzed by Fourier transform infrared spectrometry in ATR mode. The specific vibration band of poly (acrylic acid) at 1703 cm -1 was observed The membrane is hereafter called PVDF-g-PAA membrane. c) Suifonation of the grafted membrane
La membrane PVDF-g-PAA a été immergée dans une solution d'acide chlorosulfonique à 100% à température ambiante pendant 6 heures. La membrane est ensuite rincée deux fois avec du dichlorométhane The PVDF-g-PAA membrane was immersed in a solution of 100% chlorosulfonic acid at room temperature for 6 hours. The membrane is then rinsed twice with dichloromethane
(2*50 mL) , dans du tétrahydrofurane (2*50 mL) puis dans l'eau désionisée (2*50 mL) . Afin de réacidifier la membrane, elle est plongée dans une solution d'acide sulfurique IM à température ambiante pendant 3 heures. Après trois rinçages dans de l'eau désionisée(2 * 50 mL), in tetrahydrofuran (2 * 50 mL) and then in deionized water (2 * 50 mL). In order to reacidify the membrane, it is immersed in a solution of sulfuric acid IM at room temperature for 3 hours. After three rinses in deionized water
(3*100 mL) , la membrane obtenue a été séchée sous vide à 500C pendant 12 heures. La membrane a été analysée par spectrométrie infrarouge à transformée de Fourier en mode ATR. Les bandes de vibration spécifiques du groupe SO3 à 1029 cm"1 et du groupe -C=O du poly (acide acrylique) à 1703 cm"1 ont été observées. La membrane obtenue est intitulée par la suite membrane PVDF-g-PAA- SO3H. d) Détermination de la capacité d'échange ionique (CEI) de la membrane PVDF-g-PAA-SO3H (3 * 100 mL), the membrane obtained was dried under vacuum at 50 ° C. for 12 hours. The membrane was analyzed by Fourier transform infrared spectrometry in ATR mode. The specific vibration bands of the group SO 3 at 1029 cm -1 and the group -C = O of the poly (acrylic acid) at 1703 cm -1 have been observed. The membrane obtained is called by the membrane more PVDF-g-PAA SO 3 H. d) Determination of ion exchange capacity (IEC) of the membrane PVDF-g-PAA-SO 3 H
La membrane PVDF-g-PAA-SO3H a été plongée dans une solution de NaCl IM pendant 24 heures à température ambiante. La solution a été titrée avec une solution de soude à 0,01 M en utilisant la phénolphtaléine comme indicateur coloré. La CEI est alors déterminée par la formule suivante : The PVDF-g-PAA-SO 3 H membrane was dipped in 1M NaCl solution for 24 hours at room temperature. The solution was titrated with 0.01 M sodium hydroxide solution using phenolphthalein as a color indicator. The IEC is then determined by the following formula:
CEI (en méq. g"1) = (V.NOH) /m avec V représentant le volume de NaOH à l'équivalence, N0H la normalité de la solution de soude et m la masse totale de la membrane. La CEI de la membrane PVDF-g-PAA-SO3H a été évaluée à 3 méq.g λ e) Détermination de la reprise hydrique (RH) de la membrane PVDF-g-PAA-SO3H IEC (in meq. G "1 ) = (VN OH ) / m with V representing the volume of NaOH at equivalence, N 0 H the normality of the sodium hydroxide solution and m the total mass of the membrane. The IEC for the PVDF-g-PAA-SO 3 H membrane was evaluated at 3 meq.g λ e) Determination of the water recovery (RH) of the PVDF-g-PAA-SO 3 H membrane
La membrane PVDF-g-PAA-SO3H a été placée sous vide poussé pendant 24 heures puis sa masse a été déterminée. Par la suite, la membrane a été plongée dans une solution d'eau désionisée pendant 24 heures. La membrane a été par la suite tamponnée à l'aide d'un papier absorbant et pesée. La reprise hydrique (RH) est calculée selon la formule suivante : The PVDF-g-PAA-SO 3 H membrane was placed under high vacuum for 24 hours and then its mass was determined. Subsequently, the membrane was dipped in a deionized water solution for 24 hours. The membrane was subsequently buffered with absorbent paper and weighed. The water recovery (RH) is calculated according to the following formula:
RH (%masse) = [ (HIf-In1) /mj *100 avec mf représentant la masse de la membrane après hydratation et In1 la masse de la membrane sèche. RH (mass%) = [(HIf-In 1 ) / md * 100 with m f representing the mass of the membrane after hydration and In 1 the mass of the dry membrane.
La reprise hydrique de la membrane PVDF-g- PS-SO3H a été évaluée à 14% en masse. The water recovery of the PVDF-g-PS-SO 3 H membrane was evaluated at 14% by mass.

Claims

REVENDICATIONS
1. Membrane échangeuse de protons consistant en une matrice polymérique comprenant, dans son épaisseur, des zones sensiblement cylindriques traversant cette dernière, lesdites zones comprenant des greffons polymériques choisis parmi les greffons polymériques comprenant une chaîne principale, dont au moins une partie des atomes de carbone est liée à la fois à un groupe -COOR et à un groupe -SO3R ou -PO3R2, R représentant un atome d'hydrogène, un atome d'halogène, un groupe alkyle ou un contre-ion cationique.  A proton exchange membrane consisting of a polymeric matrix comprising, in its thickness, substantially cylindrical zones passing through the latter, said zones comprising polymeric grafts chosen from polymeric grafts comprising a main chain, at least a portion of which are carbon atoms. is bound to both a -COOR group and a -SO3R or -PO3R2 group, where R represents a hydrogen atom, a halogen atom, an alkyl group or a cationic counterion.
2. Membrane selon la revendication 1, dans laquelle la matrice polymérique est une matrice en polymère fluoré. The membrane of claim 1, wherein the polymeric matrix is a fluoropolymer matrix.
3. Membrane selon la revendication 1 ou 2 , dans laquelle la matrice polymérique est une matrice en polyfluorure de vinylidène. The membrane of claim 1 or 2, wherein the polymeric matrix is a polyvinylidene fluoride matrix.
4. Membrane selon l'une quelconque des revendications précédentes, dans laquelle les greffons résultent de la polymérisation de monomères acryliques comportant au moins un groupe -CO2R, les polymères résultants ayant subi une étape de sulfonation ou phosphanation pour introduire les groupes -SO3R ou -PO3R2 sur au moins une partie des atomes porteurs des groupes -CO2R, R étant tel que défini à la revendication 1. Membrane according to any one of the preceding claims, in which the grafts result from the polymerization of acrylic monomers comprising at least one -CO 2 R group, the resulting polymers having undergone a sulfonation or phosphanation step for introducing the -SO 3 R groups or - PO3R2 on at least a portion of the atoms bearing -CO2R groups, R being as defined in claim 1.
5. Procédé de préparation d'une membrane telle que définie selon l'une quelconque des revendications 1 à 4, comprenant les étapes suivantes : 5. Process for preparing a membrane as defined in any one of claims 1 to 4, comprising the following steps:
une étape d'irradiation d'une matrice polymérique, de sorte à former des zones irradiées de forme sensiblement cylindriques traversant l'épaisseur de la matrice ;  a step of irradiating a polymeric matrix, so as to form irradiated zones of substantially cylindrical shape passing through the thickness of the matrix;
éventuellement une étape de révélation des traces latentes créées par l'étape d'irradiation ;  optionally a step of revealing the latent traces created by the irradiation step;
- une étape de greffage des zones irradiées par réaction radicalaire avec un monomère éthylénique, moyennant quoi l'on obtient la chaîne principale des greffons ;  a step of grafting the irradiated zones by radical reaction with an ethylenic monomer, whereby the main chain of the grafts is obtained;
une étape de sulfonation ou de phosphonation desdites chaînes principales.  a step of sulfonation or phosphonation of said main chains.
6. Procédé de préparation selon la revendication 5, dans lequel l'étape d'irradiation est réalisée par bombardement aux ions lourds, par irradiation UV ou par irradiation aux électrons. 6. Preparation process according to claim 5, wherein the irradiation step is carried out by heavy ion bombardment, by UV irradiation or by electron irradiation.
7. Procédé de préparation selon la revendication 5 ou 6, dans lequel l'étape d'irradiation est réalisée par irradiation UV. 7. Preparation process according to claim 5 or 6, wherein the irradiation step is carried out by UV irradiation.
8. Dispositif de pile à combustible comprenant au moins une membrane telle que définie selon l'une quelconque des revendications 1 à 6. Fuel cell device comprising at least one membrane as defined in any one of claims 1 to 6.
EP10745649A 2009-08-27 2010-08-26 Proton-conducting membranes for a fuel cell, and method for preparing such membranes Withdrawn EP2471138A1 (en)

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