Crosslinkable fluoropolymer compositions for sealing fuel cells

Abstract

The present invention relates to fuel cells incorporating sealing means, particularly for sealing bipolar plates to membranes in PEM fuel cell stacks, with the resulting fuel cell stacks exhibiting superior leak resistance and reduced ion leaching into water.

Description

[Technical Field]

[0001] This application claims priority to European Patent Application No. 22184140.6, filed July 11, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to fuel cells incorporating sealing means, particularly for sealing bipolar plates to membranes in PEM fuel cell stacks, with the resulting fuel cell stacks exhibiting superior leak resistance and reduced ion leaching into water. [Background technology]

[0003] Fuel cell assemblies using proton exchange membranes are well known. Such assemblies typically include a stack of fuel cell modules, each having an anode and a cathode separated by a catalytic proton exchange membrane (PEM), with the modules in the stack electrically connected in series to provide the desired voltage output. Gaseous fuel, in the form of hydrogen or a hydrogen-containing mixture such as a "reformed" hydrocarbon, flows adjacent to a first side of the membrane, and oxygen, typically in the form of air, flows adjacent to the opposite side of the membrane. Hydrogen is catalytically oxidized at the anode-membrane interface, producing the resulting protons, H + moves through the membrane to the cathode-membrane interface where it reacts with anionic oxygen, O -2 Protons combine with the cathode to form water. Protons move only in those regions of the fuel cell where the anode and cathode are directly opposite each other across the membrane. Electrons flow from the anode through an external circuit to the cathode, performing electrical work on a load in the circuit.

[0004] A fuel cell assembly typically includes multiple fuel cell modules connected in series to form a fuel cell stack. For manufacturing convenience and to provide a more robust assembly, as is well known in the art, the anode for one cell and the cathode for an adjacent cell are typically formed as rigid plates and then bonded back-to-back to form a "bipolar plate." Thus, a fuel cell assembly typically consists of a stack of alternating bipolar plates and proton exchange membranes.

[0005] The bipolar plates must perform several functions: distribute fuel and oxidant within the cell, facilitate water management within the cell, carry electrical current from the cell, and facilitate thermal management.

[0006] At the periphery of the assembly, the plates and membranes are sealed together to contain reactant gases and / or coolant within the assembly. Thus, an important aspect of forming a stacked fuel cell assembly is preventing leakage between the membranes and the plates.

[0007] One prior art approach has been to use liquid injection molding techniques to mold liquid silicone rubber (LSR) gaskets directly onto the bipolar plates, which has proven difficult due to the complex shapes of the seal and plate geometries, as well as the very brittle nature of some of the composite materials typically used in forming the bipolar plates.

[0008] Chinese Patent No. 113346102 discloses the use of fluororubber as a sealant for proton exchange membrane fuel cells. Compared with general rubber, fluororubber has several excellent properties, including high temperature resistance, corrosion resistance, swelling resistance, aging resistance, compression set resistance, mechanical properties, high vacuum resistance, flame retardancy, and cold resistance.

[0009] U.S. Patent No. 9,105,884 further discloses the use of fluoroelastomers as fuel cell sealing means, and that such materials can also be applied in admixture with a curing agent. When heated to a predetermined temperature, or upon reaction with atmospheric moisture or exposure to ultraviolet (UV) radiation, the material can be cured in situ to form a resilient gasket that adheres to component surfaces. The gasket so formed can fill gaps between mating surfaces of various components for peripheral sealing.

[0010] Economical and reliable sealing of fuel cell components is a primary objective of the present invention. Summary of the Invention

[0011] The present invention provides a water-based fluoroelastomer crosslinkable composition for fuel cell seals that can be applied in latex form between fuel cell components, such as between bipolar plates and proton exchange membranes, using traditional coating application techniques to simplify the overall application process.

[0012] The resulting fuel cell stack exhibits excellent leak resistance and reduced ion leaching into the water, thus preventing degradation of the fuel cell efficiency.

[0013] Therefore, a first object of the present invention is a method for sealing a plurality of fuel cell components, the method comprising the following steps: - step a): depositing an aqueous crosslinkable composition [composition (C)] onto at least one surface of at least one of the plurality of fuel cell components; - step b): curing the composition (C) so that a seal is formed Includes; wherein the composition (C) is - an aqueous latex comprising particles of at least one vinylidene fluoride (VDF)-based fluoropolymer [polymer (A)] comprising repeating units derived from vinylidene fluoride (VDF) and optionally at least one further comonomer different from VDF; - at least one basic compound [base (B)]; - Formula (P-1)~(P-12): [ka] [In formula: - each J and J', equal to or different from each other, is independently at each occurrence CR* or N, where R* is H or C1-C 12 is a hydrocarbon group; - E is N or formula CR ° H is the basis of; - Z is a divalent hydrocarbon group containing 1 to 12 carbon atoms; - W is a bond or a bridging group selected from the group consisting of divalent hydrocarbon groups containing 1 to 12 carbon atoms (preferably divalent aliphatic groups containing 1 to 6 carbon atoms) and divalent fluorocarbon groups containing 1 to 12 carbon atoms (preferably divalent perfluoroaliphatic groups containing 1 to 6 carbon atoms); - Symbols in formulas (P-11) and (P-12): [ka] denotes an aromatic mononuclear or polynuclear ring fused to a pyridinium-type aromatic ring, which may contain one or more further nitrogen atoms, optionally quaternary nitrogen atoms, in the ring; - Equal to or different from each other, R 1 H , R 2 H , R 3 H , R 4 H , R 5 H , R 6 H , R 7 H, R 8 H , R 9 H , R 10 H , R 11 H , R 12 H , R 13 H , R 14 H , R 15 H , R 16 H , R 17 H , R 18 H , R 19 H , R 20 H , R 21 H , R 22 H , R 23 H , R 24 H , R 25 H , R 26 H , R 27 H , R 28 H , R 29 H , R 30 H , R 31 H , R 32 H , R 33 H , R 34 H , R 35 H , R 36 H and R° H Each of the following is independently at each occurrence -H or a group of the formula: [ka] (wherein R a and R b are independently H or a hydrocarbon C1-C6 group. is a group [group (alpha-H)]; Y, which may be equal to or different from each other, is independently oxygen or C1-C 12 a hydrocarbon group, which may be an aliphatic or aromatic group, which may contain one or more heteroatoms selected from N, O, S and halogens; -A (m-) is an anion having a valence of m; however, (i) When the salt (P) is of the formula (P-1), R 1 H , R 2 H , and R° H at least two of are groups (alpha-H); (ii) When the salt (P) is of the formula (P-2), R 3 H and R 4 H is the group (alpha-H); (iii) When the salt (P) is of the formula (P-3), R 5 H , R 6 H , R 7 H , and R 8 H at least two of are groups (alpha-H); (iv) When the salt (P) is of the formula (P-4), R 9 H , R 10 H , R 11 H , R 12 H , and R° H at least two of are groups (alpha-H); (v) When the salt (P) is of the formula (P-5), R 13 H , R 14 H and R° H at least two of are groups (alpha-H); (vi) When the salt (P) is of the formula (P-6), R15 H , R 16 H , R 17 H , and R° H at least two of are groups (alpha-H); (vii) When the salt (P) is of the formula (P-7), R 18 H , R 19 H , R 20 H , R 21 H , and R° H at least two of are groups (alpha-H); (viii) When the salt (P) is of the formula (P-8), R 22 H , R 23 H , R 24 H , and R° H at least two of are groups (alpha-H); (ix) When the salt (P) is of the formula (P-9), R 25 H , R 26 H , R 27 H , and R 28 H at least two of are groups (alpha-H); (x) When the salt (P) is of the formula (P-10), R 29 H , R 30 H , R 31 H , R 32 H , and R 28 H at least two of are groups (alpha-H); (xi) When the salt (P) is of the formula (P-11), R 33 H , R 34 H , and R 28 H at least two of are groups (alpha-H); (xii) When the salt (P) is of the formula (P-12), R 35 H , R 36 H and R° H at least two of which are groups (alpha-H) [Provided that] At least one pyridinium salt [salt (P)] according to any of the following: The method includes:

[0014] In another object, the present invention provides a seal for a fuel cell component, the seal being obtainable by curing a composition (C) as defined above.

[0015] In another object, the present invention provides a fuel cell assembly comprising a seal as defined above disposed between fuel cell components, and a fuel cell stack comprising a plurality of said fuel cell assemblies.

[0016] The fuel cell components are advantageously selected from bipolar plates and proton exchange membranes.

[0017] The seals of the present invention comprise a thin layer of cross-linkable fluoroelastomer disposed between fuel cell components, such as between the bipolar plates and the membrane. The resulting fuel cell stack exhibits excellent leak resistance and reduced ion leaching into water.

[0018] Some of the compositions (C) used in the method of the present invention are novel and represent further aspects of the present invention.

[0019] Therefore, in another object, the present invention provides an aqueous crosslinkable composition [composition (C1)], comprising: - an aqueous latex comprising particles of at least one vinylidene fluoride (VDF)-based fluoropolymer [polymer (A)] comprising repeating units derived from vinylidene fluoride (VDF) and optionally at least one further comonomer different from VDF; - expression R bm -NR H 2 (In the formula, R H Each of C1 to C 12 is a hydrocarbon group; -R bm is a monovalent hydrocarbon non-aromatic radical having 1 to 30 carbon atoms and at least one non-aromatic amine [base (B1)]; - at least one pyridinium salt [salt (P)] according to any of the formulae (P-1) to (P-12) as defined above; The composition (C1) is obtained by mixing the above. DETAILED DESCRIPTION OF THE INVENTION

[0020] The term "fuel cell component" is intended herein to mean each single cell component, such as a bipolar plate, an electrode, a membrane, or an entire proton exchange membrane.

[0021] The aqueous composition (C) of the present invention is obtained by mixing the latex of the polymer (A) with the salt (P) and the base (B), as detailed above.

[0022] The expression "latex" is used herein in accordance with its general meaning in the art, i.e., to denote a stable dispersion of particles of polymer (A) in an aqueous medium. A latex can therefore be distinguished, inter alia, from an aqueous slurry that can be prepared by dispersing a polymer in powder form in an aqueous medium and / or from a solution in a solvent that can swell or dissolve polymer (A).

[0023] The term "aqueous medium" is used herein in accordance with its ordinary meaning, i.e., is intended to denote a liquid phase consisting primarily of water, it being understood that small amounts, e.g., 1% by weight or less, of one or more organic solvents may be present without similarly affecting the aqueous nature of the medium.

[0024] Polymer (A) comprises repeat units derived from vinylidene fluoride (VDF) and optionally at least one further comonomer different from VDF.

[0025] More specifically, according to a particular embodiment, polymer (A) is: - repeating units derived from vinylidene fluoride (VDF) in an amount ranging from 60 to 100 mol%, preferably from 65 to 100 mol%, more preferably from 75 to 100 mol%, - optionally repeat units derived from at least one further comonomer different from VDF [comonomer (C)] in an amount ranging from 0 to 40 mol %, preferably from 0 to 35 mol %, more preferably from 0 to 25 mol %. Includes.

[0026] Comonomer (C) can be either a hydrogen-containing comonomer [comonomer (H)] or a fluorinated comonomer [comonomer (F)].

[0027] The term "hydrogen-containing comonomer [comonomer (H)]" is intended herein to mean an ethylenically unsaturated comonomer that does not contain a fluorine atom.

[0028] Non-limiting examples of suitable hydrogen-containing comonomers (H) include, among others, ethylene, propylene, vinyl monomers such as vinyl acetate, acrylic monomers, and styrene monomers such as styrene and p-methylstyrene.

[0029] The term "fluorinated comonomer [comonomer (F)]" is intended herein to mean an ethylenically unsaturated comonomer containing at least one fluorine atom.

[0030] The comonomer (C) is preferably a fluorinated comonomer [comonomer (F)].

[0031] Non-limiting examples of suitable fluorinated comonomers (F) include, inter alia: (a) C2-C8 perfluoroolefins such as tetrafluoroethylene (TFE) and hexafluoropropylene (HFP); (b) C2-C8 hydrogen-containing fluoroolefins such as vinyl fluoride, 1,2-difluoroethylene, trifluoroethylene, pentafluoropropylene, and hexafluoroisobutylene; (c)Formula CH2=CH-R f0 (In the formula, R f0 is a C1-C6 perfluoroalkyl group); (d) chloro- and / or bromo- and / or iodo-C2-C6 fluoroolefins such as chlorotrifluoroethylene (CTFE); (e) Formula CF2=CFOR f1 (In the formula, R f1 is a C1-C6 fluoro- or perfluoroalkyl group, for example, -CF3, -C2F5, -C3F7), (per)fluoroalkyl vinyl ethers; (f) Formula CF2 = CFOX0 (wherein X0 is a C1-C 12 Oxyalkyl group or C1-C 12 (per)fluoro-oxyalkyl vinyl ethers of (per)fluorooxyalkyl groups, such as perfluoro-2-propoxy-propyl groups; (g)Formula CF2=CFOCF2OR f2 (In the formula, R f2 is a C1-C6 fluoro- or perfluoroalkyl group, for example -CF3, -C2F5, -C3F7 or a C1-C6 (per)fluorooxyalkyl group having one or more ether groups, for example -C2F5-O-CF3), fluoroalkyl-methoxy-vinyl ethers; (h) Formula: [ka] (wherein R f3 , R f4 , R f5 and R f6each independently represents a C1-C6 fluoro- or per(halo)fluoroalkyl group containing a fluorine atom and optionally one or more oxygen atoms, e.g., -CF3, -C2F5, -C3F7, -OCF3, -OCF2CF2OCF3) Fluorodioxole Examples include:

[0032] The most preferred fluorinated comonomers (F) are tetrafluoroethylene (TFE), trifluoroethylene (TrFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), perfluoromethyl vinyl ether (PMVE), perfluoropropyl vinyl ether (PPVE) and vinyl fluoride, of which HFP is most preferred.

[0033] According to a particular embodiment, the polymer (A) comprises repeat units derived from vinylidene fluoride (VDF) and from at least one hydrophilic (meth)acrylic monomer (MA), optionally in combination with one or more fluorinated comonomers (F).

[0034] The term "at least one hydrophilic (meth)acrylic monomer (MA)" is understood to mean that the polymer (A) may comprise repeat units derived from one or more hydrophilic (meth)acrylic monomers (MA) as described above. In the remainder of the text, the expressions "hydrophilic (meth)acrylic monomer (MA)" and "monomer (MA)" are understood for the purposes of the present invention both in the plural and in the singular, i.e., they are understood to mean one or more both hydrophilic (meth)acrylic monomers (MA).

[0035] According to a particular embodiment, the polymer (A) consists essentially of repeat units deriving from VDF and from the monomer (MA).

[0036] According to another embodiment, polymer (A) consists essentially of repeat units deriving from VDF, from HFP and from monomer (MA).

[0037] The polymer (A) may further contain other moieties such as defects, end groups, etc., which do not affect or impair its physicochemical properties.

[0038] The hydrophilic (meth)acrylic monomer (MA) preferably has the formula: [ka] (In the formula, R1, R2, and R3, which may be the same or different, are each independently a hydrogen atom or a C1-C3 hydrocarbon group; R OH is a hydroxyl group or a C1-C5 hydrocarbon moiety containing at least one hydroxyl group; more preferably, each of R1, R2, and R3 is hydrogen, and R OH has the same meaning as detailed above, preferably R OH is OH) Follow.

[0039] Non-limiting examples of hydrophilic (meth)acrylic monomers (MA) are acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethylhexyl (meth)acrylate, among others.

[0040] The monomer (MA) is more preferably - Formula: [ka] Hydroxyethyl acrylate (HEA) - Formula: [ka] 2-hydroxypropyl acrylate (HPA) - Formula: [ka] of acrylic acid (AA), and - A mixture of these is selected among.

[0041] More preferably, the monomer (MA) is AA and / or HEA, even more preferably AA.

[0042] The amount of (MA) monomer repeat units in polymer (A) can be determined by any suitable method, including, inter alia, acid-base titration, suitable for determining the acrylic acid content, NMR methods, suitable for quantifying (MA) monomers containing aliphatic hydrogen in the side chain (e.g., HPA, HEA), and weight balance based on the total (MA) monomer feed and unreacted residual (MA) monomer during the preparation of polymer (A).

[0043] According to these embodiments, polymer (A) preferably comprises at least 0.1 mol %, more preferably at least 0.2 mol % of repeat units derived from said hydrophilic (meth)acrylic monomer (MA), and / or polymer (A) preferably comprises at most 10 mol %, more preferably at most 7.5 mol %, even more preferably at most 5 mol %, and most preferably at most 3 mol % of repeat units derived from said hydrophilic (meth)acrylic monomer (MA).

[0044] According to these embodiments, the polymer (A) is cured in accordance with ASTM D3835 for 100 seconds. -1 The polymer (A) generally has a melt viscosity (MV) of at least 15 kpoise when measured at a shear rate of 100 kpoise or less and at a temperature of 230° C. The MV of the polymer (A) is not particularly limited, but it is generally understood that an MV of 100 kpoise or less, preferably less than 80 kpoise, will be suitable to ensure optimum properties in coating applications.

[0045] According to a particular embodiment, said polymer (A) comprising repeat units derived from vinylidene fluoride (VDF) and optionally at least one further comonomer different from VDF is a fluoroelastomer [fluoroelastomer (A)].

[0046] For the purposes of the present invention, the term "fluoroelastomer" [fluoroelastomer (A)] is intended to indicate a fluoropolymer resin that serves as a base component for obtaining a true elastomer, said fluoropolymer resin comprising more than 10% by weight, preferably more than 30% by weight, of repeating units derived from VDF and at least one ethylenically unsaturated monomer containing at least one fluorine atom (hereinafter referred to as (per)fluorinated monomer), and optionally at least one ethylenically unsaturated monomer not containing a fluorine atom (hereinafter referred to as hydrogen-containing monomer). True elastomers are defined by the ASTM Special Technical Bulletin No. 184 standard as materials that can be stretched at room temperature to twice their inherent length and, after being held under tension for 5 minutes, immediately return to within 10% of their original length as soon as they are released.

[0047] The fluoroelastomer (A) is generally an amorphous product or a polymer having a low degree of crystallinity (less than 20% by volume of crystalline phase) and a glass transition temperature (T g In most cases, the fluoroelastomer (A) advantageously has a T of less than 10°C, preferably less than 5°C, more preferably less than 0°C, and even more preferably less than -5°C. g It has.

[0048] The fluoroelastomer (A) typically contains at least 15 mol %, preferably at least 20 mol %, more preferably at least 35 mol % of repeat units derived from VDF, based on the total repeat units of the fluoroelastomer.

[0049] The fluoroelastomer (A) typically comprises at most 85 mol %, preferably at most 80 mol %, more preferably at most 78 mol % of repeat units derived from VDF, based on the total repeat units of the fluoroelastomer.

[0050] Non-limiting examples of suitable (per)fluorinated monomers from which the repeating units contained in the fluoroelastomer (A) are derived, among others: (a) C2-C8 perfluoroolefins, such as tetrafluoroethylene (TFE) and hexafluoropropylene (HFP); (b) Vinyl fluoride (VF), trifluoroethylene (TrFE), formula CH2=CH-R f (In the formula, R f hydrogen-containing C2-C8 olefins different from VDF, such as perfluoroalkylethylenes in which (C1-C6 perfluoroalkyl group) (c) C2-C8 chloro- and / or bromo- and / or iodo-fluoroolefins such as chlorotrifluoroethylene (CTFE); (d) Formula CF2=CFOR f (In the formula, R f is a C1-C6 (per)fluoroalkyl group, such as CF3, C2F5, C3F7), (per)fluoroalkyl vinyl ether (PAVE); (e) Formula CF2 = CFOX (wherein X is a C1-C 12 (per)fluoro-oxy-alkyl vinyl ethers ((per)fluoro)-oxyalkyl, for example, perfluoro-2-propoxypropyl group); (f) Formula: [ka] (wherein R f3 , R f4 , R f5 , R f6 are independently selected among C1-C6 (per)fluoroalkyl groups, optionally containing a fluorine atom and one or more oxygen atoms, such as, in particular, -CF3, -C2F5, -C3F7, -OCF3, -OCF2CF2OCF3) (Per)fluorodioxole; preferably perfluorodioxole; (g) Formula: CFX2=CX2OCF2OR''f [In the formula, R'' f is selected from linear or branched C1-C6 (per)fluoroalkyl; C5-C6 cyclic (per)fluoroalkyl; and linear or branched C2-C6 (per)fluorooxyalkyl containing 1-3 catenary oxygen atoms, where X2=F, H; preferably, X2 is F and R'' f is -CF2CF3(MOVE1), -CF2CF2OCF3(MOVE2); or -CF3(MOVE3)] and (per)fluoro-methoxy-vinyl ether (hereinafter referred to as MOVE) having the formula:

[0051] Generally, it is preferred that the fluoroelastomer (A) contains repeating units derived from HFP in addition to repeating units derived from VDF.

[0052] In this case, the fluoroelastomer (A) typically contains at least 10 mol %, preferably at least 12 mol %, more preferably at least 15 mol % of repeat units derived from HFP, based on the total repeat units of the fluoroelastomer.

[0053] Furthermore, the fluoroelastomer (A) typically contains at most 45 mol %, preferably at most 40 mol %, more preferably at most 35 mol % of repeat units derived from HFP, based on the total repeat units of the fluoroelastomer.

[0054] Fluoroelastomers (A) suitable for the compositions of the present invention may contain, in addition to repeating units derived from VDF and HFP, the following: - General formula: [ka] wherein R1, R2, R3, R4, R5 and R6, which are equal to or different from each other, are H, halogen, or an optionally halogenated group of C1 to C5, optionally containing one or more oxygen groups; Z is a linear or branched C1 to C5 alkyl group optionally containing an oxygen atom. 18 an optionally halogenated alkylene or cycloalkylene group, or a (per)fluoropolyoxyalkylene group repeating units derived from at least one bis-olefin [bis-olefin (OF)] having the formula: - repeat units derived from at least one (per)fluorinated monomer other than VDF and HFP; and - repeating units derived from at least one hydrogen-containing monomer may include one or more of:

[0055] Examples of hydrogen-containing monomers are non-fluorinated alpha-olefins, including ethylene, propylene, 1-butene, diene monomers, styrene monomers, among others, with alpha-olefins typically being used. C2-C8 non-fluorinated alpha-olefins (O1), more specifically ethylene and propylene, may be selected to achieve improved base resistance.

[0056] The bis-olefins (OF) are preferably represented by the formulae (OF-1), (OF-2) and (OF-3): (OF-1) [ka] (wherein j is an integer of 2 to 10, preferably 4 to 8, and R1, R2, R3, and R4 are equal to or different from each other and each is H, F, or C 1~5 alkyl or (per)fluoroalkyl groups; (OF-2) [ka] wherein each A, equal to or different from each other and at each occurrence, is independently selected from F, Cl, and H; and each B, equal to or different from each other and at each occurrence, is independently selected from F, Cl, H, and OR. B (where R B is a branched or straight-chain alkyl group which may be partially, substantially, or fully fluorinated or chlorinated; E is an optionally fluorinated divalent group having 2 to 10 carbon atoms, which may have inserted ether linkages; preferably, E is -(CF2) where m is an integer from 3 to 5. m - group; a preferred bis-olefin of the (OF-2) type is F2C=CF-O-(CF2)5-O-CF=CF2) (OF-3) [ka] wherein E, A and B have the same meaning as defined above; R5, R6, R7 are equal to or different from each other; and R6, R7 are H, F or C. 1~5 alkyl or (per)fluoroalkyl group) and n is selected from the group consisting of:

[0057] The most preferred fluoroelastomer (A) has the following composition (in mole % based on the total moles of fluoroelastomer units): (i) Vinylidene fluoride (VDF) 45-85%; hexafluoropropene (HFP) 15-45%; tetrafluoroethylene (TFE) 0-30%; (ii) Vinylidene fluoride (VDF) 20-30%; hexafluoropropene (HFP) 18-27%; C2-C8 non-fluorinated olefins (O1) 5-30%; perfluoroalkyl vinyl ethers (PAVE) 0-35%; bis-olefins (OF) 0-5%; (iii) Vinylidene fluoride (VDF) 60-75%; hexafluoropropene (HFP) 10-25%; tetrafluoroethylene (TFE) 0-20%; perfluoroalkyl vinyl ether (PAVE) 1-15% It has the following characteristics.

[0058] Regardless of the type of polymer (A), the particles of polymer (A) generally have an average primary particle size of less than 1 μm. For the purposes of the present invention, the term "primary particles" is intended to mean primary particles of polymer (A) that result directly from aqueous emulsion polymerization, without isolating the polymer from the latex (i.e., particle-stabilized emulsion). Primary particles of polymer (A) are therefore intended to be distinguishable from agglomerates (i.e., collections of primary particles) that may be obtained by recovery and conditioning steps in the production of such polymers, such as concentration and / or coagulation of the aqueous latex of polymer (A) to obtain the respective powder, followed by drying and homogenization.

[0059] Preferably, the particles of polymer (A) in dispersion (D) have an average primary particle size, measured according to ISO 13321, of more than 20 nm, more preferably more than 30 nm, even more preferably more than 50 nm, and / or not more than 600 nm, more preferably less than 400 nm, even more preferably less than 350 nm.

[0060] Preferred salts (P) of formula (P-1) are represented by the formulae (P-1-a) to (P-1-e): [ka] (In the formula: -R a and R b has the meaning as defined above, preferably R a and R b is H; - Y has the meaning as defined above, preferably Y is methyl; - Equal to or different from each other, R p and R q Each of these is H or C1 to C 12 is a hydrocarbon group; - A and m have the meanings as defined above. It is in accordance with the following.

[0061] More preferably, the salt (P) of formula (P-1) is represented by the formulas (P-1-g) to (P-1-p): [ka] wherein A and m have the meanings as detailed above. The present invention has one of the following characteristics.

[0062] A preferred salt (P) of formula (P-2) is represented by formula (P-2-a): [ka] (In the formula: -R a and R b has the meaning as defined above, preferably R a and R b is H; - Y has the meaning as defined above, preferably Y is methyl; - Equal to or different from each other, R p and R q Each of these is H or C1 to C 12 is a hydrocarbon group; - A and m have the meanings as defined above. It is in accordance with the following.

[0063] More preferably, the salt (P) of formula (P-2) is a salt of formula (P-2-b): [ka] wherein A and m have the meanings as detailed above. It has the following characteristics.

[0064] A preferred salt (P) of formula (P-3) is represented by formula (P-3-a): [ka] (In the formula: -R a and R bhas the meaning as defined above, preferably R a and R b is H; - Y has the meaning as defined above, preferably Y is methyl; - A and m have the meanings as defined above. It is in accordance with the following.

[0065] More preferably, the salt (P) of formula (P-3) is a salt of formula (P-3-b): [ka] wherein A and m have the meanings as detailed above. It has the following characteristics.

[0066] A preferred salt (P) of formula (P-4) is represented by formula (P-4-a): [ka] (In the formula: -R a and R b has the meaning as defined above, preferably R a and R b is H; w is an integer from 1 to 12, preferably from 1 to 6, and most preferably equal to 3; - A and m have the meanings as defined above. It is in accordance with the following.

[0067] More preferably, the salt (P) of formula (P-4) is of formula (P-4-b) or (P-4-c): [ka] wherein A and m have the meanings as detailed above and w=3. It has the following characteristics.

[0068] A preferred salt (P) of formula (P-5) is represented by formula (P-5-a): [ka] (In the formula: -R a and R b has the meaning as defined above, preferably R a and R b is H; - Y has the meaning as defined above, preferably Y is methyl; - A and m have the meanings as defined above. It is in accordance with the following.

[0069] More preferably, the salt (P) of formula (P-5) is of formula (P-5-b) or (P-5-c): [ka] wherein A and m have the meanings as detailed above. It has the following characteristics.

[0070] A preferred salt (P) of formula (P-11) is represented by formula (P-11-a): [ka] (In the formula: -R a and R b has the meaning as defined above, preferably R a and R b is H; - Y has the meaning as defined above, preferably Y is methyl; - A and m have the meanings as defined above. It is in accordance with the following.

[0071] More preferably, the salt (P) of formula (P-11) is a salt of formula (P-11-b): [ka] wherein A and m have the meanings as detailed above. It has the following characteristics.

[0072] A preferred salt (P) of formula (P-12) is represented by formula (P-12-a): [ka] (In the formula: -R a and R b has the meaning as defined above, preferably R a and R b is H; - Y has the meaning as defined above, preferably Y is methyl; - A and m have the meanings as defined above. It is in accordance with the following.

[0073] More preferably, the salt (P) of formula (P-12) is a salt of formula (P-12-b): [ka] wherein A and m have the meanings as detailed above. It has the following characteristics.

[0074] The choice of the anion A in formulae (P-1) to (P-12) is not particularly critical, and it is nevertheless understood that anions selected from the group consisting of arylsulfonates, in particular (fluoro)alkylsulfonates having a C1-C6 (fluoro)alkyl chain, such as tosylate (p-toluenesulfonate), fluorine-free alkylsulfonates, for example mesylate (methanesulfonate), and fluorine-containing (especially perfluorinated) alkylsulfonates, for example triflate (trifluoromethanesulfonate); halides (iodide, bromide, chloride) are particularly preferred from a synthetic point of view due to their ready availability.

[0075] The applicant has surprisingly found that a salt (P) of any of formulas (P-1) to (P-12) containing a ring-quaternized pyridinium-type nitrogen and having at least two groups in the ortho or para position relative to the ring-quaternized pyridinium-type nitrogen containing the reactive hydrogen atom is an effective crosslinking agent for crosslinking VDF polymers when combined with a basic compound in an aqueous medium.

[0076] Without being bound by this theory, the Applicant believes that said ortho- or para-groups containing at least one hydrogen atom in alpha position relative to the aromatic ring have acidic properties such that, in the presence of a base (B), they give rise to the corresponding carbanions; the carbanions so formed have sufficient reactive / nucleophilic properties to ensure the activation and grafting of VDF polymer chains so as to generate a three-dimensional crosslinked network in the coated film and layers obtained therefrom.

[0077] Collectively, exemplary compounds that have been found to be particularly useful in the compositions of the present invention are those listed below having formulae (Ex-1) through (Ex-9): [ka]

[0078] The compositions of the invention generally contain salt (P) in an amount of at least 0.1, preferably at least 0.5, more preferably at least 1 part by weight per 100 parts by weight of polymer (A) (phr).

[0079] The composition of the invention generally comprises salt (P) in an amount of at most 30, preferably at most 20, more preferably at most 15 parts by weight per 100 parts by weight of polymer (A).

[0080] The base (B) suitable for use in the composition (C) of the present invention is not particularly limited, and one or more organic bases (B) can be used.

[0081] Among the organic bases (B), in particular: (j) General formula (B1m) or (B1d): R bm -[C(O)] t -NR H 2(B1m) R H 2N-[C(O)] t’ -R dm -[C(O)] t” -NR H 2(B1d) (In the formula: - each of t, t' and t'', which are equal to or different from one another and for each occurrence, is zero or one; -R H each independently represents H or C1-C 12 is a hydrocarbon group; -R bm is a monovalent hydrocarbon non-aromatic group having 1 to 30 carbon atoms; -R bm is a divalent hydrocarbon non-aromatic group having 1 to 30 carbon atoms non-aromatic amines or amides according to (jj) General formula (B2m) or (B2d): [ka] (In the formula: Cy represents a divalent aliphatic group containing at least 4 carbon atoms, optionally containing one or more ethylenically unsaturated double bonds, and optionally containing one or more catenary nitrogen atoms, which together with the nitrogen atoms bound to it form a ring; - Cy' represents a trivalent aliphatic group containing at least 5 carbon atoms, optionally containing one or more ethylenically unsaturated double bonds, and optionally containing one or more catenary nitrogen atoms, which together with the nitrogen atoms bound to it form a ring. Alicyclic secondary or tertiary amines according to (jjj) General formula (B3): Ar b -{[C(O)] t -NRH 2} w (B3) (In the formula: - equal or different from each other and for each occurrence, t is zero or 1; - w is an integer from 1 to 4; -R H each independently represents H or C1-C 12 is a hydrocarbon group; - Ar b is a mononuclear or polynuclear aromatic group optionally containing one or more catenary heteroatoms selected from the group consisting of S and O) Aromatic amines or amides according to (jv) heteroaromatic amines containing at least one nitrogen atom contained in a heteroaromatic ring, in particular pyridine derivatives; (v) Formula (B4) or (B5): [ka] (In the formula: - Equal to or different from each other, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 each independently represents H or C1-C 12 (It is a hydrocarbon group) Guanidine derivatives of and the corresponding salts of said guanidines (B4) and (B5), in particular the corresponding N-quaternized hydrohalide salts (preferably the hydrochlorides); (vj) metal alkoxylates, preferably alkoxylates of aliphatic alcohols Examples include:

[0082] Among the bases of formula (B1m) and (B1d), -R bm is a monovalent aliphatic linear group having 6 to 30 carbon atoms, optionally containing one or more ethylenically unsaturated double bonds; -R dm is a divalent aliphatic linear group having 6 to 30 carbon atoms, optionally containing one or more ethylenically unsaturated double bonds; The above are particularly preferred.

[0083] Among the above non-aromatic amines or amides, in particular: - Formula CH3(CH2) 17 -NH2 octadecylamine; - Formula H2N-C(O)-(CH2) 11 -CH=CH-(CH2)7CH3 erucamide; - oleamide of formula H2N-C(O)-(CH2)7-CH=CH-(CH2)7CH3; - hexamethylenediamine of the formula H2N-(CH2)6-NH2; - N,N-dimethyloctylamine; - N,N-dimethyldodecylamine; - Trioctylamine; - Trimethylamine; - Trihexylamine Examples include:

[0084] Among the above alicyclic secondary or tertiary amines, those of the formula: [ka] Examples of suitable cyclopentadiene compounds include 1,8-diazabicycloundec-7-ene (DBU) of the formula:

[0085] Exemplary embodiments of said guanidine derivatives of formula (B-4) are, inter alia, guanidine hydrochloride and di-o-tolylguanidine.

[0086] Exemplary embodiments of said metal alkoxylates are potassium tert-butylate, sodium ethylate and sodium methylate, among others.

[0087] Exemplary embodiments of said heteroaromatic amines are, among others, trimethylpyridine isomers.

[0088] In one preferred embodiment of the present invention, the base (B) is of the formula R bm -NR H 2 (In the formula, R H Each of C1 to C 12 is a hydrocarbon group; -R bm is a monovalent hydrocarbon non-aromatic radical having 1 to 30 carbon atoms It is a non-aromatic amine.

[0089] In a more preferred embodiment of the present invention, the base (B) is trihexylamine.

[0090] The amount of base (B) will be adjusted by those skilled in the art, taking into consideration the type and basicity of the base (B) used.

[0091] Nevertheless, it is understood that composition (C) generally comprises at least 0.1 parts by weight, preferably at least 0.2 parts by weight, more preferably at least 0.25 parts by weight of said base (B) (as detailed above) per 100 parts by weight of polymer (A).

[0092] Furthermore, composition (C) generally comprises at most 30 parts by weight, preferably at most 25 parts by weight, more preferably at least 20 parts by weight of said base (B) per 100 parts by weight of polymer (A).

[0093] The base (B) and the salt (P) may be added during the preparation of the composition (C) in a preliminary step to generate the corresponding carbanion of the salt (P).

[0094] As stated above, composition (C) is an aqueous composition, ie it is a composition comprising a liquid medium containing water as the main component.

[0095] Although small amounts of organic solvents may be present, it is generally understood that the liquid medium of composition (C) consists essentially of water, and that the solvent is preferably present in limited amounts, for example less than 1% by weight, relative to the total weight of composition (C), so as not to adversely alter the aqueous nature of the composition and all its advantageous environmental aspects.

[0096] The present invention further relates to a method for making a composition (C) as detailed above, said method comprising mixing an aqueous latex of a polymer (A), a base (B) and a salt (P) as detailed above.

[0097] In general, the process according to the invention comprises a first step of mixing the base (B) and the salt (P) to obtain a premix, and a second step of mixing said premix with an aqueous latex of the polymer (A).

[0098] Generally, in the first step, the base (B) and the salt (P) are mixed in a liquid medium, more particularly in an aqueous medium, i.e., a liquid medium consisting essentially of water. Small amounts of one or more organic solvents may be tolerated in the aqueous medium in which the base (B) and the salt (P) are mixed, provided that their amount does not exceed 1% by weight, based on the aqueous medium. Examples of organic solvents that may be present as solubilizing agents for the salt (P) are, inter alia, tetrahydrofuran (THF) and acetonitrile.

[0099] The base (B) and salt (P) are mixed in said aqueous medium in a first step, advantageously at a temperature of at least 10°C, preferably at least 15°C and generally at most 60°C, more preferably at most 50°C (it being understood that mixing at room temperature may be preferred and is generally effective overall).

[0100] Without being bound by this theory, the applicant believes that in this first step of forming a premix of base (B) and salt (P), a reactive hydrogen atom ortho or para to the ring-quaternized pyridinium-type nitrogen of salt (P) is removed to provide the corresponding carbanion, which is the actual effective crosslinker for polymer (A).

[0101] The mixing of the base (B) and the salt (P) in the aqueous medium can be carried out in a conventional mixing device, generally in a vessel equipped with a stirring means.

[0102] In the second step, the method includes mixing the premix with the aqueous latex of polymer (A). Generally, the premix is added stepwise to the aqueous latex of polymer (A); more specifically, the addition of the premix formed in the aqueous medium can be carried out dropwise.

[0103] The mixing of the aqueous latex of polymer (A) with salt (P) and base (B) or with a premix thereof is generally carried out in a mixing device, which generally operates at low shear rates in order to minimize coagulation phenomena induced by shear stresses.

[0104] Mixing is generally carried out at a temperature of from 10 to 45°C, preferably from 15 to 35°C (it being understood that mixing at room temperature may be preferred and is generally more effective overall).

[0105] In step a) of the method of the present invention, the aqueous crosslinkable sealing composition (C) can be applied onto at least one surface of at least one of the plurality of fuel cell components in latex form using traditional coating application techniques such as spray coating, dip coating, cast film, impregnation, screen printing, etc.

[0106] After application of composition (C) onto at least one surface of the fuel cell component, the composition layer is preferably dried before subjecting it to step b), which is preferably carried out at a temperature comprised between 30°C and 100°C, preferably between 40°C and 50°C.

[0107] In step b) of the method, curing of composition (C) can be obtained by thermally crosslinking the aqueous crosslinkable sealing composition (C) once it has been applied onto at least one surface of a fuel cell component, such as onto at least one surface of a proton exchange membrane or onto at least one surface of a bipolar plate, thus providing a fuel cell assembly with improved performance, particularly in terms of leakage resistance, and resulting in a reduced overall metal ion content that may be found to leach into water during operation of the fuel cell.

[0108] Thermal crosslinking can be carried out by heating composition (C) at a temperature that may vary from about 150°C to about 400°C, preferably below 300°C, more preferably below 200°C.

[0109] In another object, the present invention provides a seal for a fuel cell component, the seal being obtainable by curing a composition (C) as defined above.

[0110] The seal of the present invention comprises a thin layer of a crosslinkable fluoroelastomer disposed between fuel cell components, such as between a bipolar plate and a proton exchange membrane. When the seal of the present invention is used in a fuel cell stack, the amount of ions is reduced due to the specific components of the composition (C) used; furthermore, the excellent leakage resistance of the seal of the present invention prevents ion leaching and maintains the efficiency of the fuel cell.

[0111] Some of the compositions (C) used in the method of the present invention are novel and represent further aspects of the present invention.

[0112] Therefore, in another aspect, the present invention provides an aqueous composition [composition (C1)], comprising: - an aqueous latex comprising particles of at least one vinylidene fluoride (VDF)-based fluoropolymer [polymer (A)] comprising repeating units derived from vinylidene fluoride (VDF) and optionally at least one further comonomer different from VDF; - expression R bm -NR H 2 (In the formula, R H Each of C1 to C 12 is a hydrocarbon group; -R bm is a monovalent hydrocarbon non-aromatic radical having 1 to 30 carbon atoms at least one non-aromatic amine [base (B1)]; at least one pyridinium salt [salt (P)] according to any of the formulae (P-1) to (P-12), as detailed above; The composition (C1) is obtained by mixing the above.

[0113] In a more preferred embodiment of the present invention, the base (B) in composition (C1) is trihexylamine.

[0114] To the extent that the disclosure of any patents, patent applications, and publications incorporated herein by reference contradicts the statements of this application to the extent that a term may be unclear, the statements of this application shall control.

[0115] The present invention will now be described with reference to the following examples, the purposes of which are merely illustrative and are not intended to limit the scope of the invention.

[0116] Experimental section raw materials Tecnoflon® TN latex, commercially available from Solvay Specialty Polymers; solids content equal to 65-68% by weight. [Example]

[0117] Preparation Example 1 - Formula: [ka] 1,2,4,6-tetramethyl-pyridinium p-toluenesulfonate

[0118] A three-necked round-bottom flask equipped with a thermometer, condenser, and stirrer was charged with CHCl (85 ml) and methyl p-toluenesulfonate (25.50 g). 2,4,6-trimethylpyridine (16.59 g) was then added dropwise at room temperature. The reaction was stirred at 50°C and completed after 22 hours. The liquid phase was removed by evaporation under vacuum to give a white powder, which was dispersed in diethyl ether (50 ml) with stirring. The liquid phase was filtered off, and 39.13 g of pure product was recovered as a white powder in 93% yield (mp 161°C; 1% weight loss: 266°C). 1 H NMR (solvent DO, TMS reference): +7.70 ppm (d; 2H; ortho-H; p-toluenesulfonate); +7.55 ppm (s; 2H; meta-H; 1,2,4,6-tetramethylpyridinium); +7.39 ppm (d; 2 H; meta-H; p-toluenesulfonate; +4.0 (s; 3H; NCH3; 1,2,4,6-tetramethyl-pyridinium); +2.74 (s; 6H; ortho-CH3; 1,2,4,6-tetramethyl-pyridinium); 2.53 (s; 3H; para-CH3; 1,2,4,6-tetramethyl-pyridinium); +2.44 ppm (s; 3H; para-CH3; p-toluenesulfonate).

[0119] Preparation Example 2: Preparation of pyridinium salt and trihexylamine solution To a solution of 1,2,4,6-tetramethyl-pyridinium p-toluenesulfonate (13.7 g; 0.05 mol) in water (90 ml) was added trihexylamine (24 g, 0.1 mol) in water (17.5 ml). The mixture (Preparation A) was stirred at room temperature for 2.5 hours.

[0120] Preparation Example 3: Preparation of Pyridinium Salts and Sodium Hydroxide (Comparative) To a solution of 1,2,4,6-tetramethyl-pyridinium p-toluenesulfonate (13.7 g; 0.05 mol) in water (90 ml) was added sodium hydroxide (4.2 g, 0.1 mol) in water (17.5 ml). The mixture (Preparation B) was stirred at room temperature for 2.5 hours.

[0121] Example 1: Preparation of Composition CA 9.2 g of Preparation A was added dropwise to 140 g of TN latex. The system was left stirring at room temperature for 60 minutes. The resulting aqueous dispersion was then cast onto a chromated aluminum Q-panel test substrate. The coated panel was dried at 40°C for 1 hour and then baked in an air oven at 190°C for 60 minutes.

[0122] Example 2 - Comparative: Preparation of Composition CB 9.7 g of Preparation B was added dropwise to 140 g of TN latex. The system was left stirring for 60 minutes (18-22°C). The resulting aqueous dispersion was then cast onto a chromated aluminum Q-panel test substrate. The coated panel was dried at 40°C for 1 hour and then baked in an air oven at 190°C for 60 minutes.

[0123] Immersion Test The coated panels (from both CA and CB compositions) were placed in a jar filled with deionized water according to ASTM D1193 Type I. The conductivity of the solution was measured. The jar was then placed in an oven at 80°C for 15 days. The final conductivity of the aqueous solution was then measured to check the amount of ionic species leached into the water.

[0124] The leachate was then injected into the fuel cell and the variation in current was measured before and after leachate injection: a lower Delta I means a smaller impact of the leachate on membrane efficiency and power generation.

[0125] The results are summarized in Table 1.

[0126] Determination of metal ion content The amount of metals in compositions CA and CB was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0127] Compositions CA and CB were preheated to remove water; the residue was then calcined (at 550° C., either with a Bunsen flame or a semi-assisted muffle), and the residue was then dissolved in acid (H 2 SO 4 ).

[0128] The acid solution thus obtained was injected into an inductively coupled plasma (ICP) source.

[0129] The excited atoms emit radiation of typical and defined wavelengths that produce an emission spectrum, the intensity of which is proportional to the concentration of free atoms in the source.

[0130] The concentration of each element was obtained by comparison with a calibration curve.

[0131] The results are reported in Table 1.

[0132] [Table 1]

[0133] As shown in Table 1, the water conductivity after the immersion test was lower when the composition containing trihexylamine was used instead of the one with the inorganic base.

[0134] In addition, the fluctuation in current when the leachate was injected into the fuel cell was also much smaller for the composition containing trihexylamine, thus meeting the high purity requirements necessary for fuel cell applications.

[0135] Furthermore, the results demonstrate that the aqueous crosslinkable compositions according to the invention have a lower metal ion content compared to compositions containing inorganic bases, thanks to the presence of certain non-aromatic amines; this makes the compositions of the invention particularly suitable for use in preparing seals for fuel cells.

[0136] In view of the above, it has been found that the compositions of the present invention are suitable for easy application onto fuel cell components to provide fluoroelastomer latex compositions crosslinked with pyridinium salts and specific organic bases that enable efficient sealing and minimize degradation of fuel cell efficiency due to ionic leaching.

Claims

1. 1. A method of sealing a plurality of fuel cell components, the method comprising the steps of: step a): depositing an aqueous crosslinkable composition [composition (C)] onto at least one surface of at least one of said plurality of fuel cell components; step b): curing said composition (C) so as to form a seal; Including; The composition (C) an aqueous latex comprising particles of at least one vinylidene fluoride (VDF)-based fluoropolymer [polymer (A)] comprising repeating units derived from vinylidene fluoride (VDF) and optionally at least one further comonomer different from VDF; at least one basic compound [base (B)]; - Formulas (P-1) to (P-12): 【Chemical 1】 [In the formula: each of J and J', equal to or different from each other, independently at each occurrence, is C-R* or N, where R* is H or C １ ~C １２ is a hydrocarbon group; E is N or of the formula C-R° Ｈ is a group of Z is a divalent hydrocarbon group containing 1 to 12 carbon atoms; W is a bond or a bridging group selected from the group consisting of divalent hydrocarbon groups containing 1 to 12 carbon atoms (preferably divalent aliphatic groups containing 1 to 6 carbon atoms) and divalent fluorocarbon groups containing 1 to 12 carbon atoms (preferably divalent perfluoroaliphatic groups containing 1 to 6 carbon atoms); Symbols in formulas (P-11) and (P-12): 【Chemistry 2】 denotes an aromatic mononuclear or polynuclear ring fused to a pyridinium-type aromatic ring, which may contain one or more further nitrogen atoms, optionally quaternary nitrogen atoms, in the ring; - equal to or different from each other, １ Ｈ , R ２ Ｈ , R ３ Ｈ , R ４ Ｈ , R ５ Ｈ , R ６ Ｈ , R ７ Ｈ , R ８ Ｈ , R ９ Ｈ , R １０ Ｈ , R １１ Ｈ , R １２ Ｈ , R １３ Ｈ , R １４ Ｈ , R １５ Ｈ , R １６ Ｈ , R １７ Ｈ , R １８ Ｈ , R １９ Ｈ , R ２０ Ｈ , R ２１ Ｈ , R ２２ Ｈ , R ２３ Ｈ , R ２４ Ｈ , R ２５ Ｈ , R ２６ Ｈ , R ２７ Ｈ , R ２８ Ｈ , R ２９ Ｈ , R ３０ Ｈ , R ３１ Ｈ , R ３２ Ｈ , R ３３ Ｈ , R ３４ Ｈ , R ３５ Ｈ , R ３６ Ｈ and R° Ｈ Each of the following is independently at each occurrence -H or a group of the formula: 【Chemistry 3】 (wherein R ａ , and R ｂ are independently H or a hydrocarbon C １ ~C ６ (based on a group [group (alpha-H)] of the formula: Y, which are equal to or different from each other, are independently oxygen or C １ ~C １２ hydrocarbon groups, which may in particular be aliphatic or aromatic groups, which may contain one or more heteroatoms selected from N, O, S and halogens; - A （ｍ－） is an anion having a valence m; however, (i) When the salt (P) is of the formula (P-1), R １ Ｈ , R ２ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (ii) When the salt (P) is of the formula (P-2), R ３ Ｈ and R ４ Ｈ is the group (alpha-H); (iii) When the salt (P) is of the formula (P-3), R ５ Ｈ , R ６ Ｈ , R ７ Ｈ , and R ８ Ｈ at least two of are groups (alpha-H); (iv) When the salt (P) is of the formula (P-4), R ９ Ｈ , R １０ Ｈ , R １１ Ｈ , R １２ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (v) When the salt (P) is of the formula (P-5), R １３ Ｈ , R １４ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (vi) When the salt (P) is of the formula (P-6), R １５ Ｈ , R １６ Ｈ , R １７ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (vii) When the salt (P) is of the formula (P-7), R １８ Ｈ , R １９ Ｈ , R ２０ Ｈ , R ２１ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (viii) When the salt (P) is of the formula (P-8), R ２２ Ｈ , R ２３ Ｈ , R ２４ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (ix) When the salt (P) is of the formula (P-9), R ２５ Ｈ , R ２６ Ｈ , R ２７ Ｈ , and R ２８ Ｈ at least two of are groups (alpha-H); (x) When the salt (P) is of the formula (P-10), R ２９ Ｈ , R ３０ Ｈ , R ３１ Ｈ , R ３２ Ｈ , and R ２８ Ｈ at least two of are groups (alpha-H); (xi) When the salt (P) is of the formula (P-11), R ３３ Ｈ , R ３４ Ｈ , and R ２８ Ｈ at least two of are groups (alpha-H); (xii) When the salt (P) is of the formula (P-12), R ３５ Ｈ , R ３６ Ｈ and R° Ｈ provided that at least two of are groups (alpha-H). at least one pyridinium salt [salt (P)] according to any of the following: A method comprising:

2. The polymer (A) is - repeat units derived from vinylidene fluoride (VDF) in an amount ranging from 60 to 100 mol %, preferably from 65 to 100 mol %, more preferably from 75 to 100 mol %, optionally repeat units derived from at least one further comonomer [comonomer (C)] different from VDF in an amount ranging from 0 to 40 mol %, preferably from 0 to 35 mol %, more preferably from 0 to 25 mol %. The method of claim 1 , comprising:

3. The comonomer (C) is preferably a hydrogen-containing comonomer [comonomer (H)] which is an ethylenically unsaturated comonomer containing no fluorine atoms, selected from the group consisting of ethylene, propylene, vinyl monomers such as vinyl acetate, acrylic monomers, and styrene monomers such as styrene and p-methylstyrene; or, preferably: (a) C such as tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) ２ ~C ８ perfluoroolefin; (b) C fluorides such as vinyl fluoride, 1,2-difluoroethylene, trifluoroethylene, pentafluoropropylene, and hexafluoroisobutylene ２ ~C ８ hydrogen-containing fluoroolefins; (c) Formula CH ２ =CH-R ｆ０ (In the formula, R ｆ０ is C １ ~C ６ perfluoroalkyl ethylenes, each of which is a perfluoroalkyl group; (d) chloro-, and / or bromo-, and / or iodo-C, such as chlorotrifluoroethylene (CTFE) ２ ~C ６ Fluoroolefins; (e) Formula CF ２ =CFOR ｆ１ (In the formula, R ｆ１ is C １ ~C ６ Fluoro- or perfluoroalkyl groups, such as —CF ３ , -C ２ F ５ , -C ３ F ７ (per)fluoroalkyl vinyl ethers of the formula (I) (f) Formula CF ２ =CFOX ０ (In the formula, X ０ is a C having one or more ether groups １ ~C １２ Oxyalkyl group or C １ ~C １２ (per)fluoro-oxyalkyl vinyl ethers of (per)fluorooxyalkyl groups, for example perfluoro-2-propoxy-propyl groups; (g) Formula CF ２ = CFOCF ２ OR ｆ２ (In the formula, R ｆ２ is C １ ~C ６ Fluoro- or perfluoroalkyl groups, such as —CF ３ , -C ２ F ５ , -C ３ F ７ or C having one or more ether groups １ ~C ６ (Per)fluorooxyalkyl groups, such as -C ２ F ５ -O-CF ３ fluoroalkyl-methoxy-vinyl ethers of the formula (h) Formula: 【Chemistry 4】 (wherein R ｆ３ , R ｆ４ , R ｆ５ and R ｆ６ each independently containing a fluorine atom and optionally one or more oxygen atoms; １ ~C ６ Fluoro- or per(halo)fluoroalkyl groups, such as —CF ３ , -C ２ F ５ , -C ３ F ７ , -OCF ３ , -OCF ２ CF ２ OCF ３ is) Fluorodioxole 3. The method according to claim 1 or claim 2, wherein the comonomer (F) is a fluorinated comonomer which is an ethylenically unsaturated comonomer containing at least one fluorine atom selected from the group consisting of:

4. The polymer (A) comprises repeat units derived from vinylidene fluoride (VDF) and at least one hydrophilic (meth)acrylic monomer (MA), optionally in combination with one or more fluorinated comonomers (F), said hydrophilic (meth)acrylic monomer (MA) having the formula: 【Chemistry 5】 (wherein R1, R2, and R3, which are equal to or different from each other, are independently a hydrogen atom or C １ ~C ３ is a hydrocarbon group, R ＯＨ is a hydroxyl group or a C containing at least one hydroxyl group １ ~C ５ is a hydrocarbon moiety; more preferably, each of R, R, and R is hydrogen, and R ＯＨ has the same meaning as detailed above, preferably R ＯＨ The method of claim 3 according to

5. Polymer (A) has the following composition (in mole % relative to the total moles of fluoroelastomer units): (i) vinylidene fluoride (VDF) 45-85%; hexafluoropropene (HFP) 15-45%; tetrafluoroethylene (TFE) 0-30%; (ii) vinylidene fluoride (VDF) 20-30%; hexafluoropropene (HFP) 18-27%; C ２ ~C ８ Non-fluorinated olefin (O1) 5-30%; perfluoroalkyl vinyl ether (PAVE) 0-35%; bis-olefin (OF) 0-5%; (iii) vinylidene fluoride (VDF) 60-75%; hexafluoropropene (HFP) 10-25%; tetrafluoroethylene (TFE) 0-20%; perfluoroalkyl vinyl ether (PAVE) 1-15% The method according to any one of claims 1 to 4, wherein the fluoroelastomer (A) is selected from the group consisting of fluoroelastomers having the formula:

6. The salt (P) of formula (P-1) is represented by the formulas (P-1-g) to (P-1-p): 【Chemistry 6】 (In the formula, A （ｍ－） is an anion having a valence of m The method according to any one of claims 1 to 5, wherein the method comprises any one of the following:

7. 7. The method according to any one of claims 1 to 6, wherein composition (C) comprises salt (P) in an amount of at least 0.1, preferably at least 0.5, more preferably at least 1 part by weight per 100 parts by weight of polymer (A) (phr) and / or in an amount of at most 20, preferably at most 15, more preferably at most 10 parts by weight per 100 parts by weight of polymer (A).

8. The base (B) is represented by the formula R ｂｍ -NR Ｈ ２ (In the formula, R Ｈ Each of the groups independently represents C １ ~C １２ is a hydrocarbon group; -R ｂｍ is a monovalent hydrocarbon non-aromatic radical having 1 to 30 carbon atoms.

8. The method according to claim 1, wherein the non-aromatic amine is selected from the group consisting of:

9. 9. The method according to claim 1, wherein in step a), the composition (C) is applied onto at least one surface of at least one of the plurality of fuel cell components in latex form using traditional coating application techniques such as spray coating, dip coating, cast film, impregnation, screen printing, etc.

10. 10. The method according to any one of claims 1 to 9, wherein in step b) of the method, curing of composition (C) is obtained by thermal crosslinking it by heating said composition (C) at a temperature ranging from about 150°C to about 400°C, preferably below 300°C, more preferably below 200°C.

11. The method according to any one of claims 1 to 10, wherein the plurality of fuel cell components comprises bipolar plates and proton exchange membranes.

12. A seal for a fuel cell component, said seal being obtainable by curing a composition (C), said crude product (C) comprising: an aqueous latex comprising particles of at least one vinylidene fluoride (VDF)-based fluoropolymer [polymer (A)] comprising repeating units derived from vinylidene fluoride (VDF) and optionally at least one further comonomer different from VDF; at least one basic compound [base (B)]; - Formulas (P-1) to (P-12): 【Chemistry 7】 [In the formula: each of J and J', equal to or different from each other, independently at each occurrence, is C-R* or N, where R* is H or C １ ~C １２ is a hydrocarbon group; E is N or of the formula C-R° Ｈ is a group of Z is a divalent hydrocarbon group containing 1 to 12 carbon atoms; W is a bond or a bridging group selected from the group consisting of divalent hydrocarbon groups containing 1 to 12 carbon atoms (preferably divalent aliphatic groups containing 1 to 6 carbon atoms) and divalent fluorocarbon groups containing 1 to 12 carbon atoms (preferably divalent perfluoroaliphatic groups containing 1 to 6 carbon atoms); Symbols in formulas (P-11) and (P-12): 【Chemistry 8】 denotes an aromatic mononuclear or polynuclear ring fused to a pyridinium-type aromatic ring, which may contain one or more further nitrogen atoms, optionally quaternary nitrogen atoms, in the ring; - R equal to or different from each other １ Ｈ , R ２ Ｈ , R ３ Ｈ , R ４ Ｈ , R ５ Ｈ , R ６ Ｈ , R ７ Ｈ , R ８ Ｈ , R ９ Ｈ , R １０ Ｈ , R １１ Ｈ , R １２ Ｈ , R １３ Ｈ , R １４ Ｈ , R １５ Ｈ , R １６ Ｈ , R １７ Ｈ , R １８ Ｈ , R １９ Ｈ , R ２０ Ｈ , R ２１ Ｈ , R ２２ Ｈ , R ２３ Ｈ , R ２４ Ｈ , R ２５ Ｈ , R ２６ Ｈ , R ２７ Ｈ , R ２８ Ｈ、 R ２９ Ｈ , R ３０ Ｈ , R ３１ Ｈ , R ３２ Ｈ , R ３３ Ｈ , R ３４ Ｈ , R ３５ Ｈ , R ３６ Ｈ and R° Ｈ Each of the following is independently at each occurrence -H or a group of the formula: 【Chemistry 9】 (wherein R ａ , and R ｂ are independently H or a hydrocarbon C １ ~C ６ (based on a group [group (alpha-H)] of the formula: Y, which are equal to or different from each other, are independently oxygen or C １ ~C １２ hydrocarbon groups, which may in particular be aliphatic or aromatic groups, which may contain one or more heteroatoms selected from N, O, S and halogens; - A （ｍ－） is an anion having a valence m; however, (i) When the salt (P) is of the formula (P-1), R １ Ｈ , R ２ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (ii) When the salt (P) is of the formula (P-2), R ３ Ｈ and R ４ Ｈ is the group (alpha-H); (iii) When the salt (P) is of the formula (P-3), R ５ Ｈ , R ６ Ｈ , R ７ Ｈ , and R ８ Ｈ at least two of are groups (alpha-H); (iv) When the salt (P) is of the formula (P-4), R ９ Ｈ , R １０ Ｈ , R １１ Ｈ , R １２ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (v) When the salt (P) is of the formula (P-5), R １３ Ｈ , R １４ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (vi) When the salt (P) is of the formula (P-6), R １５ Ｈ , R １６ Ｈ , R １７ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (vii) When the salt (P) is of the formula (P-7), R １８ Ｈ , R １９ Ｈ , R ２０ Ｈ , R ２１ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (viii) When the salt (P) is of the formula (P-8), R ２２ Ｈ , R ２３ Ｈ , R ２４ Ｈ , and R° Ｈ at least two of are groups (alpha-H); (ix) When the salt (P) is of the formula (P-9), R ２５ Ｈ , R ２６ Ｈ , R ２７ Ｈ , and R ２８ Ｈ at least two of are groups (alpha-H); (x) When the salt (P) is of the formula (P-10), R ２９ Ｈ , R ３０ Ｈ , R ３１ Ｈ , R ３２ Ｈ , and R ２８ Ｈ at least two of are groups (alpha-H); (xi) When the salt (P) is of the formula (P-11), R ３３ Ｈ , R ３４ Ｈ , and R ２８ Ｈ at least two of are groups (alpha-H); (xii) When the salt (P) is of the formula (P-12), R ３５ Ｈ , R ３６ Ｈ and R° Ｈ provided that at least two of are groups (alpha-H). at least one pyridinium salt [salt (P)] according to any of the following: Including, seal.

13. The at least one basic compound [base (B)] in composition (C) is represented by the formula R ｂｍ -NR Ｈ ２ (In the formula, R Ｈ Each of the groups independently represents C １ ~C １２ is a hydrocarbon group; -R ｂｍ is a monovalent hydrocarbon non-aromatic radical having 1 to 30 carbon atoms.

12. The seal of claim 11, wherein the non-aromatic amine is selected from the group consisting of:

14. A fuel cell assembly comprising the seal of claim 12 or 13 disposed between fuel cell components.

15. A fuel cell stack comprising a plurality of fuel cell assemblies according to claim 14.

16. An aqueous crosslinkable composition [composition (C1)], an aqueous latex comprising particles of at least one vinylidene fluoride (VDF)-based fluoropolymer [polymer (A)] comprising repeating units derived from vinylidene fluoride (VDF) and optionally at least one further comonomer different from VDF; - expression R ｂｍ -NR Ｈ ２ (In the formula, R Ｈ Each of the groups independently represents C １ ~C １２ hydrocarbon group) at least one non-aromatic amine [base (B1)]; - Formulas (P-1) to (P-12): 【Chemistry 10】 at least one pyridinium salt [salt (P)] according to any of the following: An aqueous crosslinkable composition [composition (C1)] obtained by mixing the above.

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