Composition based on at least one fluoropolymer and at least one hydrophilic polymer for a separator coating

Abstract

The present invention relates to a composition comprising a polymer P1 comprising monomer units derived from vinylidene fluoride and optionally a comonomer M1 compatible with vinylidene fluoride and a polymer P2 comprising monomer units derived from a monomer M2 of formula R1R2C=C(R3)C(O)R, in which the substituents R1, R2 and R3 are independently selected from the group consisting of H and a C1-C5 alkyl; R is selected from the group consisting of –NHC(CH3)2CH2C(O)CH3 or –OR', where R' is selected from the group consisting of H and a C1-C18 alkyl optionally substituted by one or more –OH groups or a five- or six-membered heterocycle comprising at least one nitrogen atom in its cyclic chain, characterised in that the crystallisation temperature of the composition is Tc < -3.7496x + 130, where x is the content, by weight, of the comonomer M1 relative to the total weight of the polymer P1.

Description

[0001] Title: Composition based on at least one fluorinated era and at least one coating of

[0002] Technical field

[0003] The present invention relates generally to the field of electrical energy storage in rechargeable secondary batteries of the Li-ion type. More specifically, the invention relates to a composition suitable for use as a coating for a separator.

[0004] Technological background of the invention

[0005] Lithium-ion batteries also include a separator positioned between the cathode and the anode. The separators must have low thickness, sufficient mechanical and temperature resistance, good electrochemical resistance to the voltages to which they are exposed, optimal affinity for the electrolyte and, more generally, excellent ionic conductivity. Polyvinylidene fluoride (PVDF) and its derivatives are of interest as a polyolefin separator coating, for their electrochemical stability and for their high dielectric constant which promotes the dissociation of ions and therefore conductivity. Separators based on PVDF copolymers on which side chains including hydrophilic units are grafted are known from US 2015 / 0155539.

[0006] There is still a need to develop new coatings for separators that are easy to apply and offer a good compromise between dry adhesion, wet adhesion, ionic conductivity and thermal stability.

[0007] The invention therefore aims to remedy at least one of the drawbacks of the prior art.

[0008] Summary of the invention

[0009] According to a first aspect, the present invention provides a composition comprising a polymer PI comprising monomeric units derived from vinylidene fluoride and optionally from a comonomer M1 compatible with vinylidene fluoride and a polymer P2 comprising monomeric units derived from a monomer M2 of formula R 1 R 2 C=C(R 3 )C(O)R in which the substituents R 1 , R 2 and R 3are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of H and C1-C5 alkyl optionally substituted by one or more -OH group(s) or a five- or six-membered heterocycle comprising at least one nitrogen atom in its ring chain, characterized in that the crystallization temperature of said composition is Te < -3.7496x + 130 with x being the mass content of comonomer Ml based on the total weight of said polymer PI. The crystallization temperature is determined according to ASTM D3418.

[0010] The present invention provides a composition having a good compromise between different properties such as adhesion, conductivity and thermal stability when used in the implementation of separator compositions. In particular, obtaining a composition whose crystallization temperature complies with the above equation makes it possible to achieve the desired properties. In certain cases, said composition may not have a crystallization temperature measurable by DSC according to the ASTM D3418 standard; these compositions are included in the compositions according to the present invention since the crystallization temperature is considered to be zero. This type of composition can be obtained with a high mass content of comonomer Ml in said polymer PI, for example greater than 20% by weight based on the total weight of said polymer PI.

[0011] According to a preferred embodiment, the mass ratio Pl / P2 varies from 95 / 5 to 5 / 95, advantageously from 95 / 5 to 25 / 75, preferably from 95 / 5 to 40 / 60, in particular from 95 / 5 to 50 / 50.

[0012] According to a preferred embodiment, said polymer PI is selected from the group consisting of vinylidene fluoride homopolymers and copolymers based on vinylidene fluoride and at least one comonomer M1 compatible with vinylidene fluoride.

[0013] According to a preferred embodiment, said at least one comonomer M1 compatible with vinylidene fluoride is selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trifluoropropenes, tetrafluoropropenes, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropenes, perfluoroalkylvinylethers, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, chlorotrifluoropropene and ethylene or a mixture thereof.

[0014] According to a preferred embodiment, said PI polymer comprises monomeric units carrying at least one of the following functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, or phosphonic groups; preferably monomeric units carrying at least one of the following functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, hydroxyl, carbonyl and mercapto.

[0015] According to a preferred embodiment, said polymer P2 contains monomeric units derived from a monomer selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid, methyl acrylic acid, methyl methacrylate, ethyl methacrylate, methacrylate propyl, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate,lauryl methacrylate, n-octyl methacrylate, ureido methacrylate and mixtures thereof. According to a preferred embodiment, the crystallization temperature of said composition is Te < - 3.7496x + 128 with x being the mass content of comonomer Ml based on the total weight of said polymer PI.,

[0016] According to a preferred embodiment, said composition is in the form of a latex.

[0017] According to another aspect, the present invention provides a separator for an electrochemical device selected from the group: Li-ion, capacitor, electric double layer capacitor, and membrane electrode assembly (MEA) for fuel cell, said separator comprising a porous support and said composition according to the present invention.

[0018] According to a preferred embodiment, said composition has a mass ratio P1 / P2 varying from 95 / 5 to 5 / 95.

[0019] According to another aspect, the present invention provides a Li-ion secondary battery comprising an anode, a cathode and a separator, wherein said separator is according to the present invention.

[0020] Detailed description of the invention

[0021] According to a first aspect of the present invention, a composition comprising a polymer PI and a polymer P2 is provided. Said polymer PI is a fluoropolymer, i.e. comprising monomeric units containing at least one fluorine atom. Said polymer P2 is a polymer comprising monomeric units containing at least one hydrophilic group. Said polymers PI and P2 may be in a crosslinked or non-crosslinked form and may be linear or branched.

[0022] According to a preferred embodiment, the composition comprising said polymers PI and P2 and having a crystallization temperature as defined in the present invention makes it possible to achieve good compromises in the targeted properties depending on the applications in which the composition is used. Thus, when the composition is used in a separator, it allows a good compromise between dry adhesion and solvent resistance as demonstrated in the present application.

[0023] Advantageously, the properties referred to above are obtained when said composition has a crystallization temperature of said composition is Te < -3.7496x + 128 with x being the mass content of comonomer Ml based on the total weight of said polymer PI. Preferably, said composition has a crystallization temperature of said composition is Te < -3.7496x + 126 with x being the mass content of comonomer Ml based on the total weight of said polymer PI. More preferably, said composition has a crystallization temperature of said composition is Te < -3.7496x + 124 with x being the mass content of comonomer Ml based on the total weight of said polymer PI. In particular, said composition has a crystallization temperature of said composition is Te < -3.7496x + 122 with x being the mass content of comonomer Ml based on the total weight of said polymer PI.More particularly, said composition has a crystallization temperature of said composition is Te < -3.7496x + 120 with x being the mass content of comonomer Ml based on the total weight of said polymer PI. Preferably, said composition has a crystallization temperature of said composition is Te < -3.7496x + 118 with x being the mass content of comonomer Ml based on the total weight of said polymer PI. Advantageously, said composition has a crystallization temperature of said composition is Te < -3.7496x + 116 with x being the mass content of comonomer Ml based on the total weight of said polymer PI. Preferably, said composition has a crystallization temperature of said composition is Te < -3.7496x + 115 with x being the mass content of comonomer Ml based on the total weight of said polymer PI.

[0024] Preferably, in the composition, the mass ratio between the polymer PI and the polymer P2 varies from 95 / 5 to 5 / 95, advantageously from 95 / 5 to 25 / 75, preferably from 95 / 5 to 40 / 60, more preferably from 95 / 5 to 50 / 50, in particular from 95 / 5 to 60 / 40, preferably from 90 / 10 to 65 / 35.

[0025] The contents indicated are expressed by weight, unless otherwise indicated. For all ranges indicated, the limits are included, unless otherwise indicated. i) PI Polymer

[0026] Preferably, said PI polymer is based on a vinylidene fluoride monomer (CF2=CH2 or VDF), i.e. it comprises monomeric units derived from vinylidene fluoride. Said PI polymer may also be designated by the abbreviation PVDF.

[0027] According to one embodiment, the polymer PI is a homopolymer of vinylidene fluoride. In this case, x is equal to 0 and the crystallization temperature of said composition is less than 130°C.

[0028] According to another embodiment, the polymer PI is a copolymer of vinylidene fluoride with at least one comonomer Ml compatible with vinylidene fluoride. The comonomers Ml compatible with vinylidene fluoride can be halogenated (fluorinated, chlorinated or brominated) or non-halogenated.Examples of suitable fluorinated comonomers Ml are: vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2, 3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropenes and in particular 1,1,3,3,3-pentafluoropropene or 1, 2, 3,3,3-pentafluoropropene, perfluoroalkylvinylethers and in particular those of general formula Rf-O-CF-CF2, Rf being an alkyl group, preferably C1 to C4 (preferred examples being perfluoropropylvinylether and perfluoromethylvinylether).

[0029] The fluorinated comonomer may contain a chlorine or bromine atom. It may in particular be chosen from bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene. Chlorofluoroethylene may denote either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene isomer is preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

[0030] The VDF copolymer may also comprise non-halogenated monomers such as ethylene, and / or acrylic or methacrylic comonomers. The polymer PI preferably contains at least 50 mol% vinylidene fluoride, advantageously at least 60 mol% vinylidene fluoride, preferably at least 70 mol% vinylidene fluoride. The comonomer M1 may be present in a content of 1 to 50%, advantageously 2 to 30% by weight relative to the weight of said polymer PI.

[0031] According to one embodiment, the PI polymer is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)), having a weight percentage of hexafluoropropylene monomer units of 2 to 30%, advantageously 2 to 25%, preferably 2 to 20%, preferably 4 to 15% by weight relative to the weight of said PI polymer. According to another embodiment, the PI polymer is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)), having a weight percentage of hexafluoropropylene monomer units of 20 to 30%, advantageously 20 to 25% by weight relative to the weight of said PI polymer.

[0032] According to one embodiment, the PI polymer is a copolymer of vinylidene fluoride and tetrafluoroethylene (TFE).

[0033] According to one embodiment, the PI polymer is a copolymer of vinylidene fluoride and chlorotrifluoroethylene (CTFE).

[0034] According to one embodiment, the polymer PI is a VDF-TFE-HFP terpolymer. According to one embodiment, the polymer PI is a VDF-TrFE-TFE terpolymer (TrFE being trifluoroethylene). In these terpolymers, the mass content of VDF is at least 10%, the comonomers being present in variable proportions.

[0035] According to one embodiment, the PI polymer comprises monomeric units carrying at least one of the following functional groups: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic. The function is introduced by a chemical reaction which may be grafting, or a copolymerization of the vinylidene fluoride (VDF) monomer with a monomer carrying at least one of said functional groups and a vinyl function capable of copolymerizing with the VDF monomer, according to techniques well known to those skilled in the art, or by adsorption of a polymer carrying the functionality in the PI polymer.Thus, preferably, said monomeric units are derived from a polymer comprising them and having a molar mass of less than 100,000 g / mol, preferably less than 50,000 g / mol, in particular less than 20,000 g / mol. The latter can be grafted onto or adsorbed by said PI polymer.

[0036] According to one embodiment, the functional group carries a carboxylic acid function which is a (meth)acrylic acid type group chosen from acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate and hydroxyethylhexyl(meth)acrylate. Thus, said PI polymer may comprise monomeric units derived from a monomer selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and hydroxyethylhexyl methacrylate. According to one embodiment, the units carrying the carboxylic acid function further comprise a heteroatom chosen from oxygen, sulfur, nitrogen and phosphorus.

[0037] According to one embodiment, the functionality is introduced via the transfer agent used during the synthesis process. Preferably, the transfer agent is a polymer with a molar mass of less than or equal to 20,000 g / mol and carrying functional groups chosen from the groups: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic; preferably carboxylic acid, carboxylic acid anhydride, carboxylic acid esters. An example of a transfer agent of this type is acrylic acid oligomers. The transfer agent can be grafted onto or adsorbed by the PI polymer.

[0038] Said PI polymer may comprise terminal groups consisting of said transfer agent. In particular, the transfer agent is a polymer with a molar mass less than or equal to 20,000 g / mol and bearing functional groups selected from the group consisting of carboxylic acid or carboxylic acid ester. The molar mass of the transfer agent may be determined by GPC analysis carried out on a Waters 2695e equipment coupled to a Wyatt Wyatt NEON refractometer equipped with two PL Gel mixed C columns and a guard column (7.8 mm ID x 30 cm, 5 μm) under the following conditions: Temperature: 35°C; flow rate: 1.0 mL / min; injection volume: 100 pL; concentration 1 mg / mL in THF (HPLC grade); calibration using 12 samples of poly(methylmethacrylate) from 535 to 2,210,000 g / mol.

[0039] The content of functional groups in said PI polymer is at least 0.01 mol%, preferably at least 0.1 mol%, and at most 15 mol%, preferably at most 10 mol%.

[0040] The PI polymer preferably has a high molecular weight. By high molecular weight, as used herein, is meant a PI polymer having a melt viscosity greater than 100 Pa.s, preferably greater than 500 Pa.s, more preferably greater than 1000 Pa.s, according to ASTM method D-3835 measured at 232°C and 100 sec-1.

[0041] According to one embodiment, the PI polymer carrying functional groups can crosslink either by self-condensation of its functional groups or by reaction with a catalyst and / or a crosslinking agent, such as melamine resins, epoxy resins and the like, as well as known low molecular weight crosslinking agents such as di- or higher polyisocyanates, polyaziridines, polycarbodiimides, polyoxazolines, dialdehydes such as glyoxal, acetoacetates, malonates, acetals, di- and trifunctional thiols and acrylates, cycloaliphatic epoxy molecules, organosilanes such as epoxysilanes and amino silanes, carbamates, diamines and triamines, inorganic chelating agents such as certain zinc and zirconium salts, titaniums, glycourils and other aminoplasts.In some cases, functional groups from other polymerization ingredients, such as surfactants, initiators, seed particles, may be involved in the crosslinking reaction. When two or more functional groups are involved in the crosslinking process, the complementary reactive group pairs are, for example, hydroxyl-isocyanate, acid-epoxy, amine-epoxy, hydroxyl-melamine, acetoacetate-acid. Acrylate and / or methacrylate monomers not containing functional groups capable of entering into crosslinking reactions after polymerization should preferably represent 70% or more by weight of the total monomer mixture, and more preferably should be greater than 90% by weight.According to one embodiment, the PI polymer comprises a crosslinking agent selected from the group consisting of isocyanates, diamines, adipic acid, dihydrazides and combinations thereof.

[0042] In some embodiments, the PVDF homopolymer and VDF copolymers are composed of bio-based VDF. The term "bio-based" means "derived from biomass". This improves the ecological footprint of the separator. The bio-based VDF may be characterized by a renewable carbon content, i.e., carbon of natural origin and originating from a biomaterial or biomass, of at least 1 atomic % as determined by the 14C content according to standard NF EN 16640. The term "renewable carbon" indicates that the carbon is of natural origin and originates from a biomaterial (or biomass), as indicated below.According to certain embodiments, the bio-carbon content of the VDF may be greater than 5%, preferably greater than 10%, preferably greater than 25%, preferably greater than or equal to 33%, preferably greater than 50%, preferably greater than or equal to 66%, preferably greater than 75%, preferably greater than 90%, preferably greater than 95%, preferably greater than 98%, preferably greater than 99%, advantageously equal to 100%.

[0043] The homopolymeric PI polymers and VDF copolymers used in the invention can be obtained by known polymerization methods such as emulsion or suspension polymerization.

[0044] According to one embodiment, they are prepared by an emulsion polymerization process in the absence of fluorinated surfactant.

[0045] The polymerization of vinylidene fluoride preferably results in a latex generally having a solids content of 10 to 60% by weight, preferably 10 to 50%, and having a weight average particle size of less than 1 micrometer, preferably less than 1000 nm, preferably less than 800 nm, and more preferably less than 600 nm. The weight average particle size is generally at least 20 nm, preferably at least 50 nm, and advantageously the average size is in the range of 100 to 400 nm. The polymer particles may form agglomerates having a weight average size of 1 to 30 micrometers, and preferably 2 to 20 micrometers. The agglomerates may break into discrete particles during formulation and application to a substrate. ii) Polymer P2

[0046] As mentioned above, said polymer P2 comprises monomeric units derived from a monomer M2 of formula R 1 R2 C=C(R 3 )C(O)R in which the substituents R 1 , R 2 and R 3are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of H and C1-C5 alkyl optionally substituted with one or more -OH groups or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its ring chain. Said heterocycle may be saturated or unsaturated or aromatic. Said heterocycle may be monocyclic or bicyclic. Said heterocycle may be a pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, oxindole, isatin, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone ring. Said heterocycle may be substituted by one or more C1-C5 alkyl groups.As mentioned above, the Ci-Cis alkyl is optionally substituted by said heterocycle. The latter may be linked to the alkyl chain by the nitrogen atom or any other atoms forming the heterocycle. Preferably the heterocycle is 2-pyrrolidone, delta-lactam, succinimide, 2-imidazolidinone, 4-imidazolidinone.

[0047] Preferably, said polymer P2 comprises monomeric units derived from a monomer M2 of alkyl (meth)acrylate of formula R 1 R 2 C=C(R 3 )C(O)R in which the substituents R 1 , R 2 and R 3are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of C1-C1s alkyl optionally substituted by one or more -OH groups or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its ring chain. Said polymer P2 comprises monomeric units derived from an alkyl (meth)acrylate monomer M2 of formula R 1 R 2 C=C(R 3 )C(O)R in which the substituents R 1 , R 2 and R 3are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is -OR' with R' selected from the group consisting of H and C1-C5 alkyl optionally substituted with one or more -OH groups. Preferably, the heterocycle is as defined above, in particular the heterocycle is 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone. The term "alkyl (meth)acrylate" encompasses alkyl acrylates and alkyl methacrylates.

[0048] According to a preferred embodiment, the substituent R' is selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, n-dodecyl, amyl, isoamyl, hexyl, 2-ethylhexyl, lauryl, n-octyl, hydroxybutyl, hydroxypropyl, hydroxyethyl, ureido-substituted ethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl.

[0049] In particular, said polymer P2 comprises monomeric units derived from a monomer M2 of alkyl (meth)acrylate of formula R 1 R 2 C=C(R 3 )C(O)R in which the substituents R 1 and R 2 are H; R 3 is H or CH3; R is -OR' with R' selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, hydroxyethyl, hydroxy propyl, hydroxy butyl, 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone.

[0050] Thus the alkyl (meth)acrylate may be methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid, methyl acrylic acid, methyl methacrylate, ureido methacrylate and mixtures thereof. Among these, alkyl acrylates with an alkyl group having 1 to 8 carbon atoms are preferred, and alkyl acrylates with an alkyl group having 1 to 5 carbon atoms are more preferable. These compounds can be used alone or as a mixture of two or more.Thus, said polymer P2 may be a homopolymer of a monomer M2 as defined above or a copolymer resulting from a mixture of one or more monomers M2 as defined above.

[0051] The term "acrylate" herein includes both acrylates and methacrylates.

[0052] The optional ethylenically unsaturated compound copolymerizable with alkyl acrylate and alkyl methacrylate includes:

[0053] - (A) an alkenyl compound containing a functional group, and

[0054] - (B) an alkenyl compound without a functional group.

[0055] The alkenyl compound (A) containing a functional group includes, for example, α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, crotonic acid, itaconic acid and the like; vinyl ester compounds such as vinyl acetate, vinyl neodecanoate and the like; amide compounds such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethacrylamide, diacetone acrylamide and the like; acrylic acid esters such as 2-hydroxyethyl acrylate, N-dialkylaminoethyl acrylate, glycidyl acrylate, n-dodecyl acrylate, fluoroalkyl acrylate and the like;methacrylic acid esters such as dialkylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate, n-octyl methacrylate, t-butyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate and the like; maleic anhydride, and alkenyl glycidyl ether compounds such as allyl glycidyl ether and the like. Of these, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, N-methylolacrylamide, N-methylolmethacrylamide, diacetone acrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and allyl glycidyl ether are preferred. These compounds can be used alone or in mixtures of two or more.;

[0056] The functional group-free alkenyl compound (B) includes, for example, conjugated dienes such as 1,3-butadiene, isoprene and the like; divinyl hydrocarbon compounds such as divinyl benzene and the like; and alkenyl cyanides such as acrylonitrile, methacrylonitrile and the like. Among these, preferred are 1,3-butadiene, and acrylonitrile. These compounds may be used alone or as a mixture of two or more.

[0057] It is preferable that the functional alkenyl compound (A) is used in an amount of less than 50% by weight relative to the weight of the monomer mixture and that the functional group-free alkenyl compound (B) is used in an amount of less than 30% by weight relative to the weight of the monomer mixture.

[0058] Method of preparing the composition

[0059] Said composition according to the present invention can be prepared by a process comprising the steps of: a) Providing a reactor containing said polymer PI comprising monomeric units derived from vinylidene fluoride, b) Adding at least one monomer M2 of formula R 1 R 2 C=C(R 3 )C(O)R as defined in the present application in said reactor and contacting said polymer PI with said at least one monomer M2 for at least 5 minutes; c) Carrying out the polymerization of said at least one monomer M2 to form said composition.

[0060] Said PI polymer is preferably in the form of a latex.

[0061] During step b), at least one monomer M2 of formula R 1 R 2 C=C(R 3)C(O)R as defined in the present application is added to said reactor. During step b), preferably all of the monomers constituting the polymer P2 are added, if the latter contains different monomeric units of formula R 1 R 2 C=C(R 3)C(O)R. The addition of all of said at least one monomer M2 constituting the polymer P2 in step b) makes it possible to improve the intimacy of the mixture between the polymer PI and all of the monomeric units constituting the polymer P2. Preferably, said at least one monomer M2 is selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxybutyl acrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid, methyl acrylic acid, methyl methacrylate, ureido methacrylate and combinations thereof.Step b) may optionally also comprise the addition of an alkenyl compound (A) and / or (B) as described above in relation to the polymer P2.

[0062] During step b), the polymer PI and said at least one monomer M2 are brought into contact for a sufficiently long time to allow said monomer M2 to impregnate the particles of the polymer PI before carrying out the polymerization thereof. This contact time is at least 5 minutes, preferably 10 minutes, in particular at least 15 minutes, more particularly at least 20 minutes. Preferably, the monomer M2 is added before the initiator. This makes it possible to obtain the preferred compositions of the present invention.

[0063] Said method also comprises a step c) during which said at least one monomer M2 is polymerized. Step c) is preferably carried out in the presence of water. Step c) of polymerization of said at least one monomer M2 is carried out in the presence of an initiator.Said initiator may be a persulfate initiator such as sodium persulfate, potassium persulfate, barium persulfate, or ammonium persulfate; alkali metal bisulfites; peroxides such as benzoyl peroxide, or dicumyl peroxide; hydroperoxides such as methyl hydroperoxide or tert-butyl hydroperoxide; acyloins such as benzoin; peracetates such as methyl peracetate, tert-butyl peracetate; perbenzoates such as tert-butyl perbenzoate; peroxalates such as dimethyl peroxalate or di(tert-butyl) peroxalate; azo compounds such as azo-bisisobutyronitrile or dimethyl azo-bis-isobutyrate. The initiator is preferably added in a content of 0.005 to 1% by weight based on the weight of said at least one monomer M2 and optionally of said alkenyl compounds (A) and (B) if present.

[0064] Optionally, step c) is carried out in the presence of a chain transfer agent. The chain transfer agent may be an oxygenated compound such as an alcohol, carbonate, ketone, ester, ether; a halocarbon or hydrohalocarbon compound such as chlorocarbons, hydrochlorocarbons, chlorofluorocarbons, hydrochlorofluorocarbons; ethane or propane. Alternatively, the chain transfer agent may be a polymer with a molar mass less than or equal to 20,000 g / mol and carrying functional groups chosen from the groups: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic. An example of such a transfer agent is acrylic acid oligomers.Preferably, if present, the chain transfer agent is added in a content of 0.05 to 5% by weight based on the weight of said at least one monomer M2 and optionally of said alkenyl compounds (A) and (B) if present.

[0065] Other compounds may also be used in the implementation of said composition according to the present method as mentioned in the protocol described in WO 2007 / 018783.

[0066] Step c) can be carried out at a temperature of 20°C to 160°C. Step c) can be carried out at a pressure of 280 to 20000 kPa.

[0067] Preferably, steps b) and c) are carried out with stirring.

[0068] Said composition is preferably obtained in the form of a latex, that is to say in the form of a dispersion in an aqueous medium.

[0069] Thus, said composition is an aqueous dispersion obtained by emulsion polymerization of 5 to 100, preferably 5-95 parts by weight of a mixture of monomers having at least one monomer M2 selected from the group consisting of alkyl acrylates whose alkyl groups have 1-18 carbon atoms and alkyl methacrylates whose alkyl groups have 1-18 carbon atoms and optionally an ethylenically unsaturated compound copolymerizable with the alkyl acrylates and the alkyl methacrylates, in an aqueous medium in the presence of 100 parts by weight of particles of a polymer PI as defined above. The particles of the polymer PI serve as a seed for the polymerization of the monomers M2. The particles of the polymer PI can be added in any state to the polymerization system, as long as they are dispersed in an aqueous medium in the form of particles.Since the PI polymer is generally produced as an aqueous dispersion, it is convenient for the as-produced aqueous dispersion to be used as seed particles.

[0070] The product of the polymerization is a latex that can be used in this form, generally after filtration of the solid by-products of the polymerization process. For use in latex form, the latex can be stabilized by the addition of a surfactant, which can be the same as or different from the surfactant present during the polymerization (if any). This subsequently added surfactant can, for example, be an ionic or non-ionic surfactant. The particles of the polymer PI used as seed can have a homogeneous or heterogeneous character or gradient between the core and the surface of the particles, in terms of composition (content of comonomer HFP, for example) and / or molecular weight. In said composition, the polymer chains PI and P2 are entangled to form an interpenetrating polymer network (IPN) as defined by Kl U PAC; which is different from a preformed polymer blend.Preferably, the polymer chains PI and P2 are entangled to form a sequential interpenetrating polymer network as defined by IUPAC.

[0071] Said composition according to the present invention can be used as one of the materials used for the preparation of a separator in an electrochemical device. In this application, the mass ratio P1 / P2 preferably varies from 95 / 5 to 5 / 95, in particular from 95 / 5 to 40 / 60, preferably from 90 / 10 to 50 / 50. Preferably, the polymer PI is a copolymer of vinylidene fluoride and at least one comonomer compatible therewith as described above.In particular, the PI polymer may be a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)), having a weight percentage of hexafluoropropylene monomer units of 2 to 30%, advantageously of 2 to 25%, preferably of 2 to 20% by weight relative to the weight of the PI polymer; or a copolymer of vinylidene fluoride and tetrafluoroethylene (TFE); or a copolymer of vinylidene fluoride and chlorotrifluoroethylene (CTFE); or a terpolymer of VDF-TFE-HFP as described above. Furthermore, said PI polymer may comprise monomeric units selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and hydroxyethylhexyl methacrylate.

[0072] Said composition is preferably used in the separator coating. In addition to said composition, the separator coating may contain inorganic particles that serve to form micropores in the coating (the interstices between inorganic particles). The addition of inorganic particles may also contribute to heat resistance or improve wettability. In one embodiment, said coating comprises from 50 to 99 percent by weight of inorganic particles, based on the weight of the coating. These inorganic particles must be electrochemically stable (not subject to oxidation and / or reduction in the range of voltages used). In addition, powdered inorganic materials preferably have high ionic conductivity. Materials with a low density are preferred over materials with a higher density, since the weight of the produced battery can be reduced.The dielectric constant is preferably equal to or greater than 5. According to one embodiment, said inorganic particles are chosen from the group consisting of: BaTiO3, Pb(Zr,Ti)O3, Pb 1-x LaxZryO3 (0 <x<l, 0<y<l), PBMg3Nb2 / 3)3,PbTiO3, hafnie (HfO (HfO2), SrTiO 3, SnO2, CeO2, MgO, NiO, CaO, ZnO, Y2O3, bohémite (y-AIO(OH)), AI2O3, TiO2, SiC, ZrO2, silicate de bore, BaSO4, nano-argiles, ou leurs mélanges. Dans ce cas, le rapport des solides du polymère PI et P2 aux particules inorganiques est de 0,5 à 40 parties en poids de solides du polymère PI et P2 pour 60 à 99,5 parties en poids de particules inorganiques. Avantageusement, le rapport des solides du polymère PI et P2 aux particules inorganiques est de 0,5 à 35 pour 65 à 99,5 parties en poids de particules inorganiques. De préférence, le rapport des solides du polymère PI et P2 aux particules inorganiques est de 0,5 à 30 pour 70 à 99,5 parties en poids de particules inorganiques.The separator coating may optionally comprise from 0 to 15% by weight based on the polymer, and preferably 0.1 to 10% by weight of additives, selected from thickeners, pH adjusting agents, anti-settling agents, surfactants, wetting agents, fillers, anti-foaming agents and fugitive or non-fugitive adhesion promoters. The fillers mentioned herein in the additives are different from the inorganic particles mentioned above.

[0073] Said separator according to the present invention comprises a coating, as described above, optionally arranged on one or both faces of a porous support. In this case, the coating is used to coat the support of a separator, on at least one face, in the form of a monolayer or multilayers. There is no particular limitation in the choice of the support which is coated with the coating of the invention, as long as it is a porous substrate having pores. Said support may comprise a single layer or several distinct layers. When it comprises several layers, the coating as described in the present invention is arranged on the external face of the support, that is to say on the face which will first be in contact with the electrolytic composition used in the battery. Advantageously, the application of the coating to the support is done by aqueous means or by solvent means.The porous substrate may take the form of a membrane or a fibrous fabric. When the porous substrate is fibrous, it may be a nonwoven web forming a porous web, such as a web obtained by direct spinning or melt-blowing (of the "spunbond" or "melt-blown" type) or electro-spinning. Examples of porous substrates useful in the invention as a support include, but are not limited to: polyolefins, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene or mixtures thereof. However, other heat-resistant engineering plastics may be used without particular limitation. Nonwoven materials made of natural and synthetic materials may also be used as the substrate of the separator.The porous substrate generally has a thickness of 1 to 50 µm, and are typically membranes obtained by extrusion and stretching (wet or dry processes) or cast nonwovens. The porous substrate preferably has a porosity of between 5% and 95%. The average pore size (diameter) is preferably between 0.001 and 50 µm, more preferably between 0.01 and 10 µm.

[0074] According to an alternative embodiment, said separator does not comprise a porous support. In this case, said separator consists of the coating as described above and comprising said composition; this is deposited directly on the cathode or on the anode of the electrochemical device. The absence of a porous support makes it possible to limit the production costs of the electrochemical device and the dimensions thereof. In this case, said coating replaces the porous support. In this embodiment, said polymer resin preferably has a porosity of 5 to 95%. The average pore size of said polymer resin is preferably between 0.001 and 50 μm, more preferably between 0.01 and 10 μm.

[0075] According to another alternative embodiment, said separator does not comprise a porous support and said separator is in the form of a gel. Said separator is as described in the present application. Said separator is formed into a gel by usual techniques such as solvent casting or extrusion. The separator coating of the invention has an excellent compromise of properties for the application of separator coating: good adhesion in dry and wet state, good resistance to electrolyte solvent(s) characterized by good retained integrity and moderate swelling.

[0076] Example

[0077] The crystallization temperature is measured by DSC during cooling, following the following program:

[0078] - Heating from 10°C to 200°C at 10°C / min

[0079] - Keep for 1 minute at 200°C

[0080] - Cooling from 200°C to -80°C at 5°C / min.

[0081] Preparation of a composition according to the invention (Example 1)

[0082] The polymer PI used in Example 1 is a P(VDF-HFP) copolymer latex. It is used as a seed to synthesize the composition according to the present application by an emulsion polymerization process following the protocol described in WO 2007 / 018783 in the presence of a chain transfer agent of the acrylic acid oligomer type with a molar mass of less than 20,000 g / mol. In Example 1, the monomer M2 used to prepare the polymer P2 is a mixture of methyl (meth)acrylate, ethyl acrylate and methacrylic acid in a mass proportion of 58 / 40 / 2. The monomers M2 are brought into contact with the polymer PI for a period of 25 minutes before carrying out the polymerization of the monomers M2.

[0083] Preparation of a latex blend (Example 2 - Comparative composition): Polymer PI and polymer P2 are prepared independently of each other by an emulsion polymerization process. In this example, polymer P2 is prepared in the absence of a seed of polymer PI. The two polymers in latex form are then blended in a ratio of 70 / 30. The composition of polymers PI and P2 is the same as that of polymers PI and P2 in Example 1.

[0084] Comparative composition of example 3

[0085] Example 3 is carried out from a composition consisting of the polymer PI in latex form of Example 1.

[0086] Preparation of coating compositions:

[0087] At room temperature: 10g of alumina (Sumitomo Chemical AES-11) are added to 20g of an aqueous solution of CMC (Nippon paper FT-3) at 0.5% by weight, then dispersed in a mixer (Filmix Model 40-L) for 30sec at 30m / s. To this dispersion is added the latex (or both latexes in the case of mixtures of PVDF latex and acrylic latex according to the ratio indicated in the table) so as to incorporate 4g of the corresponding polymer(s) (quantity of latex adjusted according to the solids content of each latex in the range 30-45%) and demineralized water to make up to a total of 50g of preparation. The mixture is then homogenized with a vertical stirrer (IKA, Euro-ST) for 10min at 600rpm. To 48g of this mixture, 0.24g of wetting agent (BYK349) is added, intended to facilitate the spreading of the formulation on the separator, by mixing under the same conditions as for the latex.

[0088] Application of coating compositions:

[0089] The coating composition is applied at room temperature ~22°C using a hand applicator (bar coater Hohsen Corp., wet deposit thickness ~23Hm, hand application speed about 100mm / sec) on a sample of Celgard 2400 separator (single-layer PP, thickness 25um, width 89mm, length about 30cm), then dried on a plate at 65°C for 10min. The dry deposit has a thickness measured at 5-6Hm depending on the samples (micrometer Mitsutoyo Digimatic Indicator IDH053D). The resulting separator has a width of 89mm and a length of 30cm.

[0090] The results are presented in Table 1 below.

[0091] [Table 1]

[0092] The separator coating according to the invention presents an excellent compromise of properties for the intended application: good dry adhesion and good resistance to electrolyte solvent(s) characterized by good retained integrity. On the other hand, the comparative examples with a crystallization temperature higher than the value defined by the equation -3.7496x + 130 show at least one very unfavorable property.

Claims

Claims 1. Composition comprising a polymer PI comprising monomeric units derived from vinylidene fluoride and optionally from a comonomer M1 compatible with vinylidene fluoride and a polymer P2 comprising monomeric units derived from a monomer M2 of formula R 1 R 2 C=C(R 3 )C(O)R in which the substituents R 1 , R 2 and R 3are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of -NHC(CH3)2CH2C(O)CH3 or -OR' with R' selected from the group consisting of H and C1-C5 alkyl optionally substituted by one or more -OH group(s) or a five- or six-membered heterocycle comprising at least one nitrogen atom in its ring chain, characterized in that the crystallization temperature of said composition is Te < -3.7496x + 130 with x being the mass content of comonomer Ml based on the total weight of said polymer PI.

2. Composition according to claim 1 characterized in that the mass ratio Pl / P2 varies from 95 / 5 to 5 / 95, advantageously from 95 / 5 to 25 / 75, preferably from 95 / 5 to 40 / 60, in particular from 95 / 5 to 50 / 50.

3. Composition according to any one of the preceding claims, characterized in that said polymer PI is selected from the group consisting of vinylidene fluoride homopolymers and copolymers based on vinylidene fluoride and at least one comonomer Ml compatible with vinylidene fluoride.

4. Composition according to the preceding claim, characterized in that said at least one comonomer M1 compatible with vinylidene fluoride is selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trifluoropropenes, tetrafluoropropenes, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropenes, perfluoroalkylvinylethers, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, chlorotrifluoropropene and ethylene or a mixture thereof.

5. Composition according to any one of the preceding claims, characterized in that said polymer PI comprises monomeric units carrying at least one of the following functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, or phosphonic groups; preferably monomeric units carrying at least one of the following functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, hydroxyl, carbonyl and mercapto.

6. Composition according to any one of the preceding claims, characterized in that said polymer P2 contains monomeric units derived from a monomer M2 selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid, methyl acrylic acid, methyl methacrylate, methacrylate ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate,hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, ureido methacrylate and mixtures thereof., 7. Composition according to any one of the preceding claims, characterized in that the crystallization temperature of said composition is Te < -3.7496x + 128 with x being the mass content of comonomer Ml based on the total weight of said polymer PI.

8. Composition according to any one of the preceding claims, characterized in that it is in the form of a latex.

9. Separator for electrochemical device selected from the group: Li-ion, capacitor, electric double layer capacitor, and membrane electrode assembly (MEA) for fuel cell, said separator comprising a porous support and said composition according to any one of the preceding claims 1 to 8.

10. Separator according to the preceding claim, characterized in that said composition has a mass ratio P1 / P2 varying from 95 / 5 to 5 / 95.

11. A Li-ion secondary battery comprising an anode, a cathode and a separator, wherein said separator is according to claim 9 or claim 10.

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