Use of a polymer as an adhesion primer between a fluoropolymer and a substrate, and methods for producing coatings, coated substrates, and devices comprising same

Abstract

The invention relates to a use of a polymer PA as an adhesion primer between a coating comprising at least one fluoropolymer and a substrate, wherein the polymer PA comprises a repeat unit derived from methyl methacrylate, and at least one graftable functional group arranged at at least one end of its polymer chain, and wherein the at least one graftable functional group is capable of being grafted to the substrate. The invention also relates to a method for treating a substrate, to a method for producing a coating based on one or more fluoropolymers on a treated substrate, to a treated substrate, to a treated substrate coated with a coating based on one or more fluorinated polymers, and to a device comprising the same.

Description

[0001] Description

[0002] Title: USE OF A POLYMER AS AN ADHESION PRIMER BETWEEN A FLUOROPOLYMER AND A SUBSTRATE, METHODS FOR PRODUCING COATINGS, COATED SUBSTRATES AND DEVICES COMPRISING THEM

[0003] Technical field

[0004] The invention relates to the field of adhesion of a fluoropolymer to a surface, in particular to a metal surface.

[0005] More particularly, the invention relates to the use of a PA polymer on the surface of a substrate as an adhesion primer between a fluoropolymer coating and a substrate.

[0006] The invention also relates to a method of treating a substrate, intended to increase its adhesion properties with a fluoropolymer.

[0007] The invention also relates to a method of manufacturing a coating based on fluorinated polymer(s) on a treated substrate.

[0008] The invention also relates to composites, in particular those capable of being obtained by the two aforementioned processes.

[0009] The invention finally relates to a device comprising a composite formed by stacking a substrate, an adhesion primer grafted to the substrate and a fluoropolymer.

[0010] Prior art

[0011] Fluoropolymers, for example those based on vinylidene fluoride CF2=CH2 (VDF) such as PVDF (polyvinylidene fluoride) are known to offer excellent mechanical stability properties, very high chemical inertness, as well as good resistance to aging. These qualities are exploited for very varied application areas. In particular, certain fluorinated polymers, such as vinylidene fluoride (VDF) based polymers, such as P(VDF-TrFE), P(VDF-TrFE-CTFE), P(VDF-TrFE-CFE) are used for their electroactive properties, particularly in electronic devices.

[0012] However, due to their high chemical inertness, fluoropolymers suffer from an adhesion problem on substrates, particularly on metallic substrates, which can be particularly problematic for certain applications. However, if the fluoropolymer is detached or delaminated from the surface of the substrate with which it is in direct contact, it can no longer fulfill its initial function (transformation of a physical quantity for a transducer, binder for an electrode, protective coating, thermal insulation, etc.). For example, a transducer formed by an electroactive fluoropolymer placed between two electrodes will no longer function or will function poorly if the fluoropolymer is detached or delaminated, even partially, from its electrodes. It is recalled that a polymer is said to be electroactive if it exhibits a response (deformation, temperature variation, etc.)) when an electric field is applied and / or if a stress (mechanical, thermal, etc.) induces an electrical response within the material.

[0013] A solution to overcome the problem of adhesion between a substrate and a fluoropolymer is generally to interpose a layer of primer between the substrate and the fluoropolymer to improve adhesion. For example, it is known from the prior art to use the primer DOWSIL™ Primer C, marketed by the Dow Chemical Company. As demonstrated in the examples, this adhesion primer proves to have limited performance with at least some fluoropolymers.

[0014] There is currently a need to provide new adhesion primers that can substantially increase the adhesion of a fluoropolymer to a substrate.

[0015] Objectives of the invention

[0016] An objective of the invention is to provide an adhesion primer for improving the adhesion of a fluoropolymer to a substrate.

[0017] According to certain embodiments, the application of the adhesion primer must modify as little as possible the useful properties of said fluoropolymer. According to certain embodiments where the fluoropolymer has electroactive properties, an objective of the invention is to essentially retain its electroactive properties.

[0018] Another objective of the invention is to provide a method for treating a substrate, intended to increase its adhesion properties with regard to fluorinated polymer(s). According to certain embodiments, an objective of the invention is to provide such a method which is easy and / or rapid and / or inexpensive to implement.

[0019] Another objective of the invention is also to provide a method for manufacturing a coating of a fluoropolymer on a substrate covered with an adhesion primer which is easy and / or quick and / or inexpensive to implement.

[0020] According to certain embodiments, the aforementioned methods must be able to be implemented under mild conditions.

[0021] According to certain embodiments, the aforementioned manufacturing methods are efficient, and can in particular be implemented sufficiently quickly. Another objective of the invention is to provide a composite comprising an adhesion primer adhering well to a substrate and intended to adhere well to a fluoropolymer.

[0022] Another objective of the invention is to provide a composite comprising a coating of a fluoropolymer adhering well to a substrate covered with an adhesion primer and / or a device incorporating this composite.

[0023] Summary of the invention

[0024] The invention relates, according to a first aspect, to the use of a PA polymer as an adhesion primer between a coating comprising at least one fluorinated polymer and a substrate, said PA polymer comprising a repeating unit derived from methyl methacrylate, and at least one graftable functional group arranged at at least one end of its polymer chain, said at least one graftable functional group being capable of being grafted to the substrate.

[0025] The inventors of the present invention have noticed that such a PA polymer, used as an adhesion primer, makes it possible to improve the adhesion of the fluoropolymer to a substrate in an interesting way. Without being bound by theory, it seems that this remarkable improvement in adhesion is due to the double condition fulfilled by the PA primer: a good affinity for the fluoropolymer, and at least one graftable functional group placed at one end of the polymer chain, making it possible to graft this end to the substrate, in particular by heat treatment.

[0026] According to certain embodiments, said at least one graftable functional group arranged at at least one end of the polymer chain of said PA polymer is chosen from the groups: nitroxy, carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0027] According to certain embodiments, said PA polymer comprises at one end of its chain at least one graftable functional group being a nitroxy.

[0028] According to certain embodiments, said PA polymer comprises at one end of its chain at least one graftable functional group chosen from the groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0029] According to certain embodiments, said PA polymer comprises at one end of its chain at least one graftable functional group being a nitroxy, and at another end of its chain at least one graftable functional group chosen from the groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid. According to certain embodiments, said at least one graftable functional group disposed at one end of the chain of said PA polymer is a hydroxyl function.

[0030] According to certain embodiments, said at least one graftable functional group arranged at one end of the chain of said PA polymer is a carboxyl function.

[0031] According to certain embodiments, the units derived from the methyl methacrylate of said PA polymer represent at least 40% by weight, preferably at least 50% by weight, and extremely preferably at least 70% by weight, relative to the total weight of the repeating units of said polymer.

[0032] According to certain embodiments, the units derived from the methyl methacrylate of the PA polymer represent at least 90% by weight, relative to the total weight of the repeating units of said polymer.

[0033] According to certain embodiments, said PA polymer is capable of being obtained by a nitroxide-controlled radical polymerization using an alkoxyamine. The alkoxyamine may in particular have the chemical formula: [Chem 1] in which:

[0034] - Ri is a cyclic or non-cyclic hydrocarbon group with or without heteroatom which may contain at least one metallic species;

[0035] - R2 is a cyclic or non-cyclic hydrocarbon group with or without heteroatom which may contain at least one metallic species;

[0036] - Ri and R2 may or may not be part of the same cyclic structure;

[0037] - Z is a monovalent hydrocarbon group, cyclic or not, with or without heteroatom.

[0038] According to certain embodiments, the group Z of the alkoxyamine of formula I is a group carrying one or more graftable functional groups, each graftable functional group being chosen from the groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0039] According to certain embodiments, the alkoxyamine of the nitroxide-controlled radical polymerization is chosen from:

[0040] - a compound of formula:

[0041] [Chem 2]

[0042] (H), and

[0043] - an adduct formed by the reaction of an equivalent of the compound of formula (II) with an acrylic, methacrylic, or vinylaromatic monomer carrying said at least one graftable functional group.

[0044] According to certain embodiments, said PA polymer is a linear polymer. According to certain embodiments, said PA polymer is a gradient or statistical type polymer. Advantageously, it does not comprise a repeating unit comprising a graftable functional group.

[0045] According to certain embodiments, said PA polymer is essentially constituted, or constituted, of repeating units derived from methyl methacrylate and styrene, the mass proportion of repeating units derived from styrene representing from 0.5% to 15%, and preferably from 1.0% to 10%, relative to the total mass of repeating units derived from methyl methacrylate and styrene.

[0046] According to certain embodiments, said PA polymer is an AB-type or ABA-type block polymer, in which the block(s) A comprise, independently of one another, at least one repeating unit comprising said at least one graftable functional group, and the block B comprises a repeating unit derived from methyl methacrylate. Advantageously, the block B of said PA polymer does not comprise a repeating unit comprising a graftable functional group.

[0047] According to certain embodiments, said PA polymer has a number-average molar mass of 1,000 g / mol to 100,000 g / mol, and preferably of 2,000 g / mol to 50,000 g / mol.

[0048] According to certain embodiments, said at least one fluoropolymer comprises at least 40 mol% of repeating unit derived from vinylidene fluoride, relative to the total sum of moles of repeating units constituting said polymer, and optionally at least one repeating unit derived from a monomer X, other than vinylidene fluoride, having the formula CXiX2=CX3X4, in which each group Xi, X2, X3 and X4 is independently chosen from H, Cl, F, Br, I and C1-C3 alkyl groups which are optionally partially or totally halogenated.

[0049] According to some embodiments, said at least one fluoropolymer is a PVDF. According to some embodiments, said at least one fluoropolymer is a P(VDF-TrFE), a P(VDF-TrFE-CTFE), a P(VDF-TrFE-CFE), or a mixture thereof.

[0050] According to certain embodiments, said at least one fluoropolymer is a P(VDF-TFE), a P(VDF-HFP), or a mixture thereof.

[0051] According to certain embodiments, said at least one fluoropolymer has a weight average molar mass greater than or equal to 100,000 g / mol, and more preferably greater than or equal to 200,000 g / mol.

[0052] The invention relates, according to a second aspect, to a method for treating a substrate, intended to increase its adhesion properties with a fluoropolymer, said method comprising: i) depositing on the substrate a composition comprising at least one PA polymer, said at least one PA polymer being said polymer capable of being grafted to a substrate according to the invention; ii) where appropriate, removing the solvent possibly present in the composition deposited in step i); iii) grafting at least a portion of said at least one PA polymer to the surface of the substrate; iv) recovering the substrate coated with a layer of said at least one PA polymer grafted onto the substrate.

[0053] According to certain embodiments, said composition comprising said at least one PA polymer comprises a solvent or a mixture of miscible solvents, in which said at least one PA polymer is in solution. Said composition comprising said at least one PA polymer may in particular be essentially constituted, or constituted, of said at least one PA polymer and said solvent or mixture of miscible solvents.

[0054] According to certain embodiments, the grafting of said at least one PA polymer to the surface of the substrate is carried out by at least one heating step at a temperature ranging from 50°C to 220°C, and preferably at a temperature ranging from 80°C to 200°C.

[0055] According to certain embodiments, the grafting of said at least one PA polymer to the surface of the substrate is carried out by at least one heating step at a temperature less than or equal to 200°C, preferably at a temperature less than or equal to 160°C, and more preferably at a temperature less than or equal to 120°C.

[0056] According to certain embodiments, said at least one heating step lasts 30 minutes or less, preferably 20 minutes or less, preferably 15 minutes or less, preferably 10 minutes or less, and extremely preferably 5 minutes or less.

[0057] According to certain embodiments, the thickness of the layer of PA polymer grafted onto the substrate is less than or equal to 500 nm, preferably less than or equal to 250 nm, more preferably less than or equal to 100 nm, and more preferably less than or equal to 50 nm. According to certain embodiments, the recovery of the substrate coated with a layer of said at least one PA polymer grafted onto the substrate comprises a step of washing using at least one solvent for said at least one PA polymer, following the grafting of said at least one portion of said at least one PA polymer to the surface of the substrate, in order to remove the fraction of said at least one PA polymer that has not been grafted.

[0058] In some embodiments, the substrate is a surface of glass, silicon, quartz, polymer material, metal, nitride, or a mixed surface composed of several of these materials.

[0059] The invention relates, according to a third aspect, to a method for manufacturing a coating based on fluoropolymer(s) on a treated substrate comprising: i) a method for treating a substrate according to the invention to form a substrate coated with a layer of PA polymer grafted onto the substrate; ii) a deposition of a composition comprising at least one fluoropolymer on said layer of grafted PA polymer obtained in the preceding step; iii) where appropriate, a removal of the solubilization solvent of said at least one fluoropolymer possibly present in said composition comprising said at least one fluoropolymer; and iv) a recovery of the treated substrate coated with said at least one fluoropolymer.

[0060] According to certain embodiments, said at least one fluoropolymer is a fluoropolymer according to the invention.

[0061] According to certain embodiments, said composition comprising said at least one fluoropolymer comprises a solvent or a mixture of miscible solvents, in which said at least one fluoropolymer is in solution.

[0062] According to certain embodiments, said composition comprising said at least one fluoropolymer is essentially constituted, or constituted, of said at least one fluoropolymer and said solvent or mixture of miscible solvents.

[0063] According to certain embodiments of the methods according to the second aspect or according to the third aspect, said composition comprising said at least one PA polymer and / or said composition comprising said at least one fluoropolymer comprise, independently of one another, a solvent or a mixture of miscible solvents chosen from: dimethylformamide; N-methyl-2-pyrrolidone; dimethylacetamide; dimethylsulfoxide; γ-butyrolactone; ketones, in particular acetone, methyl ethyl ketone (or butan-2-one), methyl isobutyl ketone, cyclopentanone, cyclohexanone, diisobutyl ketone; furans, in particular tetrahydrofuran; esters, including methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, and ethyl acetoacetate;carbonates, in particular dimethylcarbonate and propylene carbonate; and phosphates, in particular trimethylphosphate, triethylphosphate, and mixtures thereof. According to certain embodiments, said composition comprising said at least one PA polymer and said composition comprising said at least one fluoropolymer both comprise the same solvent or the same mixture of solvents.;

[0064] The invention relates, according to a fourth aspect, to a composite C1 comprising a coating R1 based on at least one PA polymer grafted to a substrate, said at least one PA polymer being said at least one PA polymer according to the invention.

[0065] According to certain embodiments, the composite C1 can be obtained by a method according to the invention.

[0066] The invention relates according to a fifth aspect to a composite C2 comprising a coating R2 comprising, being essentially constituted, or being constituted of at least one fluoropolymer, said coating R2 adhering to a composite C1 according to the invention, in which said coating R1 adheres to said coating R2. According to certain embodiments, the composite C2 is capable of being obtained by a method according to the invention.

[0067] The invention relates, according to a sixth aspect, to a device comprising a composite C2 according to the invention.

[0068] According to certain embodiments, said coating R2 is an electroactive coating, or an insulating and / or protective coating, or an electrode binder. According to certain embodiments, the device is an optoelectronic device, a transistor, in particular a field effect transistor, a chip, a battery, a photovoltaic cell, a light-emitting diode, in particular an organic light-emitting diode, a sensor, an actuator, a transformer, a haptic device, a microelectromechanical system, or a detector.

[0069] Brief of the fi

[0070] [Fig 1] schematically represents the 180° peel test carried out to evaluate the adhesion of a fluoropolymer-based film on a substrate partially covered with adhesion primer. detailed description of the invention

[0071] Fluoropolymer (PF)

[0072] The PF polymer is a fluoropolymer, that is to say it comprises repeating units (or units, or structural units, or motifs) which are derived from (that is to say which are obtained by polymerization of) fluorinated monomers. The PF polymer may in particular be a polymer comprising a vinylidene fluoride (VDF) repeating unit.

[0073] The PF polymer may in particular be a polymer based on the repeating unit derived from VDF, i.e. comprising at least 50% by mole of repeating unit derived from VDF, relative to the total sum of moles of repeating units constituting the PF polymer.

[0074] In some embodiments, the PF polymer is a PVDF homopolymer, i.e., is made up of the repeating unit derived from VDF.

[0075] In certain embodiments, the PF polymer is a copolymer (in the broad sense), that is to say it comprises units derived from at least one other monomer X than VDF.

[0076] A single monomer X can be used, or several different monomers X, depending on the case.

[0077] In some embodiments, monomer X may be of formula CXiX2=CX3X4, wherein each group Xi, X2, X3 and X4 is independently selected from H, Cl, F, Br, I and C1-C3 (preferably C1-C2) alkyl groups, which are optionally partially or fully halogenated - wherein monomer X is different from VDF (i.e., if X1 and X2 are H, at least one of X3 and X4 is not F; and if X1 and X2 are F, at least one of X3 and X4 is not H).

[0078] In some embodiments, each group X1, X2, X3 and X4 independently represents an H, F, Cl, I or Br atom, or a methyl group optionally comprising one or more substituents selected from F, Cl, I and Br.

[0079] In some embodiments, each group X1, X2, X3 and X4 independently represents an H, F, Cl, I or Br atom.

[0080] In some embodiments, only one of X1, X2, X3 and X4 represents a Cl or I or Br atom, and the others of the groups X1, X2, X3 and X4 independently represent: an H or F atom or a C1-C3 alkyl group optionally comprising one or more fluorine substituents; preferably, an H or F atom or a C1-C2 alkyl group optionally comprising one or more fluorine substituents; and more preferably, an H or F atom or a methyl group optionally comprising one or more fluorine substituents.

[0081] Examples of monomers X are: vinyl fluoride (VF), trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropene (HFP), trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene (in cis or preferably trans form), 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 or PPVE and perfluoromethylvinylether or PMVE).

[0082] In some embodiments, the monomer X comprises 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 (CFE) isomer is preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene (in cis or trans form, preferably trans) or 2-chloro-3,3,3-trifluoropropene.

[0083] In certain preferred embodiments, the PF polymer comprises units derived from VDF and HFP, or is a P(VDF-HFP) polymer consisting of units derived from VDF and HFP. Such a PF polymer is particularly useful for the manufacture of planarization or passivation layers of electronic devices.

[0084] The molar proportion of repeating units derived from HFP is preferably from 2 to 50%, in particular from 5 to 40%, in moles relative to the total number of moles of repeating units derived from VDF and HFP.

[0085] The P(VDF-HFP) copolymer may in particular be as described in documents WO 01 / 32726 and US 6,586,547 to which express reference is made.

[0086] In certain preferred embodiments, the PF polymer comprises units derived from VDF and TFE, or is a P(VDF-TFE) polymer consisting of units derived from VDF and TFE. This polymer is generally used for its piezoelectric properties.

[0087] The molar proportion of repeating units derived from TFE is preferably from 8% to 30%, preferably from 15% to 28%, more preferably from 18% to 25%, and extremely preferably from 20% to 22%, relative to the total number of moles of the units derived from VDF and TFE.

[0088] In some embodiments, the PF polymer comprises units derived from VDF and: CFE, or CTFE, or TrFE.

[0089] In certain preferred embodiments, the PF polymer comprises units derived from VDF and TrFE. Such a PF polymer is generally useful for the fabrication of electroactive layers.

[0090] According to certain advantageous embodiments, the PF polymer may in particular be a P(VDF-TrFE) polymer, i.e. consisting of units derived from VDF and TrFE. These polymers are generally used for their piezoelectric, pyroelectric and ferroelectric properties, for example in sensors, energy harvesting devices, actuators, loudspeakers or ferroelectric memories.

[0091] The molar proportion of repeating units derived from TrFE is preferably from 15% to 50%, preferably from 17% to 35%, and more preferably from 18% to 32.5%, relative to the total number of moles of units derived from VDF and TrFE. Such polymers are ferroelectrics. The term "ferroelectric" is understood to mean an electroactive polymer characterized by a hysteresis cycle of the electric displacement-applied electric field curve. Its coercive field at 25°C is typically lower in absolute value than 60 V / pm and higher than 40 V / pm. Its remanent polarization at 25°C is quite high, and can typically reach a value higher than 50 mC / m 2 The Curie temperature corresponds to a ferroelectric -> paraelectric (FE -> PE) crystal structure transition, called the Curie transition.

[0092] The molar proportion of repeating units derived from TrFE may in particular be from 15% to 18%, or from 18% to 22.5%, or from 22.5% to 27.5%. According to particular embodiments, the molar proportion of repeating units derived from TrFE is from 18.0% to 22.5%, relative to the total number of moles of the units derived from VDF and TrFE.

[0093] The molar proportion of repeat units derived from TrFE can also be from 27.5% to 32.5%, or from 32.5% to 37.5%, or from 37.5% to 42.5%, or from 42.5% to 47.5%, or from 47.5% to 50%, relative to the total number of moles of the motifs derived from VDF and TrFE.

[0094] According to certain advantageous embodiments, the polymer PF may comprise units derived from VDF, TrFE and another monomer X as defined above, different from VDF and TrFE, or else be a polymer P(VDF-TrFE-X) consisting of units derived from VDF, TrFE and another monomer X as defined above, different from VDF and TrFE. In this case, preferably, the other monomer X is chosen from TFE, HFP, trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene (in cis or preferably trans form), bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene.

[0095] CTFE or CFE are particularly preferred. Indeed, P(VDF-TrFE-CTFE) and P(VDF-TrFE-CFE) terpolymers are known to have a high dielectric constant (“high-k”) as well as for their electrostrictive and electrocaloric properties and are used for example as “High-k” dielectric in organic thin film transistors (OTFT), actuators and electrocaloric devices.

[0096] The molar proportion of units derived from TrFE is preferably from 10% to 60%, more preferably from 15% to 55% and more preferably from 20% to 50%, relative to the total number of moles of units derived from VDF and TrFE. The molar proportion of units derived from another monomer X, in addition to VDF and TrFE (the monomer X being in particular CTFE or CFE), relative to the number of moles of units constituting the polymer PF, is preferably from 0.05% to 15%, and more preferably from 2% to 12%. According to certain embodiments, X is CTFE or CFE, the molar proportion of X relative to the number of moles of units constituting the polymer PF, being from 4% to 10%. P(VDF-TrFE-CFE) and P(VDF-TrFE-CTFE) having the above-mentioned proportions of TrFE and CFE or CTFE are relaxor ferroelectrics.The term "relaxing ferroelectric" refers to an electroactive polymer characterized by a relaxor-ferroelectric (RFE) paraelectric (PE) crystalline transition over a wide temperature range. At this transition, a broad peak in dielectric permittivity is observed, the temperature of this maximum depending on the frequency of the applied electric field: the lower the frequency of the electric field, the more the dielectric permittivity maximum is shifted towards low temperatures. At the (RFE)->(PE) transition temperatures or slightly higher, the application of an electric field makes it possible to generate and align the nanopolar regions, inducing an entropy variation, and thus a significant electrocaloric effect over a wide temperature range.Relaxant ferroelectric polymers are characterized at 25°C, and at a frequency of about 1 Hz by a hysteresis cycle of the "electric displacement" curve as a function of the "applied electric field" much finer than the hysteresis cycle of a ferroelectric polymer. They typically have a coercive field less than or equal in absolute value to 45 V / pm and a remanent polarization less than or equal to 40 mC / m. 2 In the embodiments where X is CTFE or CFE, the molar proportion of units derived from CTFE or CFE may in particular be from 0.05% to 0.5%, or from 0.5% to 2%, or from 2% to 3%, or from 3% to 4%, or from 10% to 12%, or from 12% to 15%, relative to the number of moles of the units constituting the PF polymer.

[0097] The molar composition of units in fluoropolymers can be determined by various means such as infrared spectroscopy or RAMAN spectroscopy. Classical methods of elemental analysis in carbon, fluorine and chlorine or bromine or iodine, such as X-ray fluorescence spectroscopy, allow the mass composition of polymers to be calculated unambiguously, from which the molar composition is deduced.

[0098] Multi-nucleus NMR techniques, including proton (1 H) and fluorine (19 F), can also be used by analyzing a solution of the polymer in a suitable deuterated solvent. The NMR spectrum is recorded on an FT-NMR spectrometer equipped with a multi-nuclear probe. The specific signals given by the different monomers are then identified in the spectra produced according to one or the other nucleus. Thus, for example, the unit derived from TrFE gives a specific signal in proton NMR characteristic of the CFH group (at approximately 5 - 7 ppm, when the solvent is pyridine for example). The same is true for the CH2 groups of VDF (massive between 2 - 4 ppm, when the solvent is pyridine for example). The relative integration of the two signals gives the relative abundance of the two monomers, i.e. the VDF / TrFE molar ratio. Similarly, the CF3 group, for example, gives characteristic and well-isolated signals in fluorine NMR.The combination of the relative integrations of the different signals obtained in proton NMR and fluorine NMR leads to a system of equations whose resolution leads to obtaining the molar concentrations of the units resulting from the different monomers.

[0099] Finally, it is possible to combine elemental analysis, for example for heteroatoms such as chlorine, bromine or iodine, and NMR analysis. Thus, the content of CTFE-derived units in a P(VDF-TrFE-CTFE) terpolymer, for example, can be determined by measuring the chlorine content by elemental analysis.

[0100] The person skilled in the art thus has a range of methods or combinations of methods enabling him to determine unambiguously and with the necessary precision the composition of fluorinated polymers.

[0101] The PF polymer is preferably random. The PF polymer is preferably linear.

[0102] PF polymer can be produced using any known process, such as emulsion polymerization, suspension polymerization and solution polymerization.

[0103] When the fluoropolymer comprises units derived from VDF and / or TrFE as well as another monomer X as described above, it is preferable to use the method described in document WO 2010 / 116105. This method makes it possible to obtain polymers of high molecular weight and suitable structuring.

[0104] In brief, the preferred method includes the following steps:

[0105] - loading an initial mixture containing only VDF and / or TrFE (without the other monomer X) into a stirred autoclave containing water;

[0106] - heating the autoclave to a predetermined temperature, close to the polymerization temperature;

[0107] - injecting a radical polymerization initiator mixed with water into the autoclave, in order to reach a pressure in the autoclave which is preferably at least 80 bars, so as to form a suspension of the VDF and / or TrFE monomers in water;

[0108] - the injection of a second mixture of VDF and / or TrFE and X into the autoclave;

[0109] - as soon as the polymerization reaction starts, the continuous injection of said second mixture into the autoclave reactor, in order to maintain the pressure at an essentially constant level, preferably at least 80 bars.

[0110] The radical polymerization initiator may be, in particular, an organic peroxide of the peroxydicarbonate type. It is generally used in an amount of 0.1 to 10 g per kilogram of the total monomer loading. Preferably, the amount used is 0.5 to 5 g / kg.

[0111] The initial mixture advantageously comprises only VDF and / or TrFE in a proportion equal to that of the desired final polymer.

[0112] The second mixture advantageously has a composition which is adjusted so that the total composition of monomers introduced into the autoclave, including the initial mixture and the second mixture, is equal to or approximately equal to the composition of the desired final polymer.

[0113] The weight ratio between the second mixture and the initial mixture is preferably from 0.5 to 2, more preferably from 0.8 to 1.6.

[0114] Implementing this process with an initial mixture and a second mixture makes the process independent of the reaction start-up phase, which is often unpredictable. The polymers thus obtained are in the form of a powder, without a crust or skin.

[0115] The pressure in the autoclave reactor is preferably 80 to 110 bars, and the temperature is maintained at a level preferably of 40°C to 60°C.

[0116] The second mixture can be injected continuously into the autoclave. It can be compressed before being injected into the autoclave, for example by using one or two successive compressors, generally at a pressure higher than the pressure in the autoclave.

[0117] After synthesis, the polymer can be washed and dried.

[0118] The weight average molar mass Mw of the PF polymer is preferably at least 100,000 g. mol' 1 , preferably at least 200,000 g. mol' 1 and more preferably at least 300,000 g. mol' 1 or at least 400,000 g. mol' 1. It can be adjusted by changing some process parameters, such as the temperature in the reactor, or by adding a transfer agent. The molecular weight distribution can be estimated by SEC (size exclusion chromatography) with dimethylformamide (DMF) as eluent, with a set of 3 columns of increasing porosity. The stationary phase is a styrene-DVB gel. The detection method is based on a measurement of the refractive index, and the calibration is carried out with polystyrene standards. The sample is dissolved at 0.5 g / L in DMF and filtered through a 0.45 µm nylon filter.

[0119] Composition based on fluorinated polymer(s)

[0120] The composition comprises at least one, i.e. one or more, fluoropolymer PF.

[0121] The determinants "a" and "the" have been used before "fluoropolymer PF". They mean by default, and unless otherwise stated, "at least one" and "said at least one" fluoropolymer PF. They include, according to particular embodiments, cases where the composition comprises only one type of fluoropolymer. The PF polymer can be dissolved in a solvent or a mixture of solvents. By "solution", we mean a homogeneous dispersion of the constituents in the solvent, at the molecular level. The term solution is used here in contrast to a suspension of polymer particles in a liquid vehicle, and in contrast to a polymer emulsion or latex.

[0122] Preferably, the solvent is chosen from: dimethylformamide; N-methyl-2-pyrrolidone; dimethylacetamide; dimethylsulfoxide; γ-butyrolactone; ketones, in particular acetone, methyl ethyl ketone (or butan-2-one), methyl isobutyl ketone, cyclopentanone, cyclohexanone, diisobutyl ketone; furans, in particular tetrahydrofuran; esters, in particular methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, and ethyl acetoacetate; carbonates, in particular dimethylcarbonate and propylene carbonate; and phosphates, in particular trimethylphosphate and triethylphosphate. Mixtures of these compounds can also be used.

[0123] In some embodiments, the solvent may be N-methyl-2-pyrrolidone.

[0124] In some embodiments, the solvent may be selected from the list consisting of: dimethylformamide, N-methyl-2-pyrrolidone, dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, diisobutyl ketone, tetrahydrofuran, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, ethyl acetoacetate, dimethyl carbonate, propylene carbonate, trimethylphosphate, triethylphosphate. Mixtures of these compounds may also be used.

[0125] The composition, in solution form, preferably comprises from 0.1 to 60% by weight, preferably from 0.5 to 30% by weight, more preferably from 1 to 20% by weight, and extremely preferably from 3 to 15% by weight of non-volatile dry matter.

[0126] The composition may optionally comprise one or more additives, in particular chosen from surface tension modifying agents, rheology modifying agents, ageing resistance modifying agents, pigments or dyes, fillers (including nanofillers). The additive(s) generally represent less than 10%, preferably less than 5%, and even more preferably less than 1% by weight relative to the weight of PF polymer.

[0127] In some embodiments, the composition consists essentially of, or consists of, at least one fluoropolymer. The composition may optionally include one or more additives. In some embodiments, the composition consists essentially of, or consists of, at least one fluoropolymer and one or more miscible solvents. The composition may optionally include one or more additives.

[0128] Adhesion Primer Polymer (PA)

[0129] PA polymer is a polymer suitable for improving the adhesion of fluoropolymer to a substrate by being used as an adhesion primer between the fluoropolymer and the substrate. This polymer includes units derived from the polymerization of methyl methacrylate (MMA) in order to allow good affinity between the PF fluoropolymer chains and the polymer chains of the PA primer.

[0130] Indeed, poly(methyl methacrylate) is known to have good affinity with fluorinated polymers, particularly with poly(vinylidene fluoride) with which it is even miscible in all proportions (Flory-Huggins parameter X between PVDF and PMMA negative).

[0131] Advantageously, the Flory-Huggins parameter x between the fluoropolymer PF, in particular PVDF, and the primer PA is less than or equal to 0.5 and preferably less than or equal to 0. In the case where the polymer PA is a block polymer, it is one of the blocks, and according to certain embodiments all the blocks, which has / have a Flory-Huggins parameter x with the fluoropolymer PF, in particular PVDF, strictly less than 0.5, and preferably strictly less than 0.

[0132] The proportion of units derived from methyl methacrylate is generally at least 40% by weight, relative to the total weight of the PA primer.

[0133] According to advantageous embodiments, the proportion of units derived from methyl methacrylate may be at least 50%, and preferably at least 70%, by weight relative to the total weight of PA polymer. The proportion of units derived from methyl methacrylate may in particular be at least 55%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90% by weight, relative to the total weight of PA polymer.

[0134] According to particular embodiments, the proportion of units derived from methyl methacrylate may be at least 90% by weight, relative to the total weight of PA polymer. The proportion of units derived from methyl methacrylate may in particular be at least 91%, or at least 92%, or at least 93%, or at least 94%, or at least 95% by weight, relative to the total weight of PA polymer.

[0135] The PA primer comprises at least one functional group intended to improve adhesion with a substrate, in particular by grafting to the surface of this substrate, referred to in the invention as a graftable functional group. Said at least one graftable functional group is arranged at at least one end of the polymer chain of the PA primer.

[0136] Grafting consists of the formation of a strong interaction between the substrate and the PA primer, in particular by the formation of covalent bonds.

[0137] The PA primer is preferably a linear polymer and has two ends.

[0138] The PA primer can be either a statistical or gradient copolymer, or a block copolymer. The term "statistical copolymer" means a copolymer resulting from the polymerization of at least two monomers in which the distribution of the monomer units along the chain follows a statistical law, for example of the Bernoullian type (Markov zero order) or Markovian of the first or second order. The term "gradient copolymer" means a copolymer resulting from the polymerization of at least two monomers generally obtained by living or pseudo-living polymerization, such as the NMP polymerization presented below. Thanks to these polymerization modes, the polymer chains grow simultaneously and therefore incorporate the same ratios of comonomers at all times. The distribution of the comonomers in the polymer chains therefore depends on the evolution, during the synthesis, of the relative concentrations of the comonomers.

[0139] The term "block copolymer" means a copolymer resulting from the polymerization of at least two monomers, comprising one or more uninterrupted sequences of each of the distinct polymer species, the polymer sequences being chemically different from one or more of the other(s) and being linked together by a chemical bond (covalent, ionic, hydrogen bond, or coordination).

[0140] In some embodiments, "group disposed at one end of the polymer chain" may mean that a group is located at the end of the polymer chain.

[0141] The graftable functional group may be arranged at one end, or at two ends, or at several ends, or at all ends of the polymer chain. In the preferred case where the polymer is linear, the graftable functional group may be arranged at one end or at both ends of the polymer chain.

[0142] Preferably, the polymer chain does not comprise any graftable functional group(s) apart from said at least one graftable functional group arranged at one of the ends, or at two of the ends, or at several of the ends, or at all of the ends of the polymer chain. In the preferred case where the polymer is linear, said at least one graftable functional group may be arranged at only one end of the polymer chain, the polymer chain not comprising any other graftable functional group apart from said at least one graftable functional group arranged at only one end of the polymer chain. In the preferred case where the polymer is linear, said at least one graftable functional group may be arranged at both ends of the polymer chain, the polymer chain not comprising any other graftable functional group apart from said at least one graftable functional group at both ends of the polymer chain.

[0143] Said at least one graftable functional group arranged at said at least one end of the polymer chain of the PA primer can be introduced by a polymerization initiator (as exemplified in the present application) and / or by a chain limiting agent or by a capping agent.

[0144] A set of graftable functional groups arranged at said at least one end of the polymer chain of the PA primer can be introduced using a repeating unit having said at least one graftable functional group in a small block “A” in the case of a block polymer. The block polymer can in particular be of type AB or ABA, the block “A” comprising a repeating unit comprising at least one graftable functional group and the block “B” having a good affinity for the fluoropolymer PF.

[0145] The at least one graftable functional group arranged at at least one end of the polymer chain of the PA primer can advantageously be chosen from: nitroxy, carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0146] According to certain embodiments, the at least one graftable functional group disposed at one end of the polymer chain of the PA primer may be a nitroxy.

[0147] According to certain embodiments, the at least one graftable functional group disposed at one end of the polymer chain of the PA primer may be chosen from: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0148] According to preferred embodiments, the at least one graftable functional group arranged at one end of the polymer chain of the PA primer can be chosen from: hydroxyl, carboxyl, and phosphonic acid.

[0149] According to particular embodiments, the at least one graftable functional group arranged at one end of the polymer chain of the PA primer is chosen from: hydroxyl and carboxyl.

[0150] According to certain embodiments, the PA primer comprises at one end of its chain at least one graftable functional group, in particular a single graftable functional group, being a hydroxyl.

[0151] According to certain embodiments, the PA primer comprises at one end of its chain at least one graftable functional group, in particular a single graftable functional group, being a carboxyl.

[0152] According to certain embodiments, the PA primer comprises at the same end of its chain a graftable functional group being a hydroxyl and a graftable functional group being a carboxyl. According to certain embodiments, the PA primer comprises at one of the ends of its chain a nitroxy and does not comprise any other graftable functional group.

[0153] According to certain embodiments, the PA primer comprises at one end of its chain a nitroxy and comprises at another end of its chain at least one graftable functional group chosen from: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0154] According to certain embodiments, the PA primer comprises at one end of its chain a nitroxy and comprises at another end of its chain at least one graftable functional group chosen from: hydroxyl, carboxyl, and phosphonic acid.

[0155] According to certain embodiments, the PA primer comprises at one end of its chain a nitroxy and comprises at another end of its chain at least one graftable functional group chosen from: hydroxyl and carboxyl.

[0156] According to certain embodiments, the PA primer comprises at one end of its chain a nitroxy and comprises at another end of its chain a single graftable functional group, being a hydroxyl.

[0157] According to certain embodiments, the PA primer comprises at one end of its chain a nitroxy and comprises at another end of its chain a single graftable functional group, being a carboxyl.

[0158] According to certain embodiments, the PA primer comprises at one end of its chain a nitroxy and comprises at another end of its chain a graftable functional group being a hydroxyl and a graftable functional group being a carboxyl.

[0159] According to certain embodiments, the PA primer may comprise at least one other repeating unit different from that resulting from the polymerization of methyl methacrylate.

[0160] According to certain embodiments, the PA primer may in particular comprise at least one repeating unit comprising said at least one graftable functional group. These embodiments relate in particular to cases where the PA polymer is a block polymer, in particular an AB or ABA type block polymer, where the block(s) A each comprise, independently of one another, said at least one repeating unit comprising said at least one graftable functional group and the block “B” has a good affinity for the fluoropolymer PF. Advantageously, said at least one repeating unit comprising at least one graftable functional group does not comprise a crosslinkable function. In particular, it does not comprise a group of oxirane, aziridine or thiirane type, or a carbon-carbon double bond, or a carbon-carbon triple bond.In these embodiments, block B advantageously has a Flory-Huggins parameter x with the fluorinated polymer PF less than or equal to 0.5 and preferably less than or equal to 0. Block B preferably comprises at least 70% by mass of repeating unit derived from methyl methacrylate relative to the total mass of block B. The proportion of units derived from methyl methacrylate in block B may in particular be at least 55%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90% by weight, relative to the total weight of block B. According to particular embodiments, the proportion of units derived from methyl methacrylate in block B may be at least 91%, or at least 92%, or at least 93%, or at least 94%, or at least 95% by weight, relative to the total weight of block B. Block B preferably does not comprise a repeating unit comprising a graftable functional group.

[0161] In these embodiments, the A block(s) represent in total less than 50% by weight of the total weight of the PA block polymer. The A block(s) may represent less than 40% by weight, or less than 30% by weight, or less than 25% by weight, or less than 20% by weight, or less than 15% by weight, or less than 10% by weight, of the total weight of the PA block polymer. According to certain embodiments, said at least one repeating unit comprising said at least one graftable functional group may represent less than 20% by weight, or less than 15% by weight, or less than 10% by weight, or less than 5% by weight, of the total weight of the PA block polymer.

[0162] Advantageously, the block(s) A have, independently of one another, less affinity with the fluoropolymer PF than the block B. The proportion of units derived from methyl methacrylate in each block A may represent less than 25%, or less than 20%, or less than 15%, or less than 10%, or less than 5% by weight relative to the total weight of said block A. The block(s) A may, independently of one another, not contain any repeating unit derived from methyl methacrylate. According to certain embodiments, the block(s) A have, independently of one another, a Flory-Huggins parameter x with the fluoropolymer PF strictly greater than 0.5.

[0163] According to certain embodiments, a repeating unit comprising said at least one graftable functional group may in particular be chosen from acrylic, methacrylic, non-(meth)acrylic vinyl monomers. It may in particular be chosen from: acrylic acid or its salts, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate, silylated acrylates, phosphorus-containing acrylates such as alkylene glycol phosphate acrylates, methacrylic acid or its salts, hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate, silylated methacrylates such as 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropylmethyl dimethoxysilane, methacryloxymethyl trimethoxysilane, 3-methacryloxypropyl tris(2-methoxyethoxy) silane, phosphorus-containing methacrylates such as alkylene glycol phosphate methacrylates,non-meth(acrylic) silylated vinyl monomers, such as vinyl trimethoxysilane, vinyl diimethoxymethylsilane, vinyl triethoxysilane, vinyl tripropoxysilane, vinyl triisopropoxysilane, vinyl tris(methoxyethoxy)silane, vinyl tributoxysilane, vinyl triacetoxysilane, vinyl trichlorosilane, vinyl methyldichlorosilane, vinyltris(2-methoxyethoxy)silane, and silylated styrenic monomers.,

[0164] According to certain embodiments, a repeating unit comprising said at least one graftable functional group may in particular be chosen from acrylic acid or its salts, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate, methacrylic acid or its salts, and hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate.

[0165] When the PA primer is a statistical or gradient polymer, said at least one other repeating unit different from that derived from methyl methacrylate preferably does not comprise a graftable functional group.

[0166] According to certain embodiments, said at least one repeating unit other than that derived from methyl methacrylate does not comprise a graftable functional group.

[0167] Such a repeating unit may in particular be chosen from vinylaromatic monomers such as styrene or substituted styrenes, in particular alpha-methylstyrene, tert-butylstyrene, ortho-, meta-, or para-methylstyrene, ortho-, meta- or para-ethylstyrene, o-methyl-p-isopropylstyrene, alkyl, cycloalkyl or aryl acrylates such as methyl, ethyl, propyl, butyl, ethylhexyl or phenyl acrylate, etheralkyl acrylates such as 2-methoxyethyl acrylate, alkoxy- or aryloxy-polyalkylene glycol acrylates such as methoxypolyethylene glycol acrylates, ethoxypolyethylene glycol acrylates, methoxypolypropylene glycol, methoxy-polyethylene glycol-polypropylene glycol acrylates, fluorinated acrylates, isobornyl acrylate, 4-tert-butyl cyclohexyl acrylate, alkyl, cycloalkyl, alkenyl or aryl methacrylates such as methyl, ethyl, propyl, butyl methacrylate,lauryl, cyclohexyl, allyl, phenyl or naphthyl, etheralkyl methacrylates such as 2-ethoxyethyl methacrylate, alkoxy- or aryloxy-polyalkylene glycol methacrylates such as methoxypolyethylene glycol methacrylates, ethoxypolyethylene glycol methacrylates, methoxypolypropylene glycol methacrylates, methoxy-polyethylene glycol-polypropylene glycol methacrylates, and fluorinated methacrylates such as 2,2,2-trifluoroethyl methacrylate.,

[0168] Advantageously, said at least one repeating unit other than that derived from methyl methacrylate not comprising a graftable functional group also does not comprise a crosslinkable function. In particular, it does not comprise a group of oxirane, aziridine or thiirane type, or a carbon-carbon double bond, or a carbon-carbon triple bond. For example, said at least one repeating unit other than that derived from methyl methacrylate not comprising a functional group is advantageously not a unit derived from glycidyl methacrylate.

[0169] According to certain embodiments, said at least one other repeating unit than that derived from methyl methacrylate not comprising a graftable functional group represents less than 50%, or less than 40%, or less than 30%, or less than 25%, or less than 20%, or less than 15%, by weight relative to the total weight of PA polymer.

[0170] According to certain embodiments, the PA primer is a polymer, essentially consisting of, or consisting of, a repeating unit derived from methyl methacrylate, optionally of at least one repeating unit different from methyl methacrylate and not comprising a graftable functional group, and also optionally of at least one repeating unit different from methyl methacrylate comprising a graftable functional group.

[0171] According to particular embodiments, the PA primer is a block polymer, in particular of the ABA or AB type, in which:

[0172] - the block(s) A each comprise, independently of one another, said at least one repeat unit comprising said at least one graftable functional group;

[0173] - the proportion of units derived from methyl methacrylate in each block A represents less than 25%, or less than 20%, or less than 15%, or less than 10%, or less than 5% by weight relative to the total weight of said block A;

[0174] - block B does not include any repeating unit comprising a graftable functional group;

[0175] - the proportion of units derived from methyl methacrylate in block B represents at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90% by weight, relative to the total weight in block B; and,

[0176] - the A block(s) represent in total less than 50% by weight of the total weight of the PA block polymer.

[0177] According to particular embodiments, the PA primer is a statistical or gradient polymer, essentially consisting of, or consisting of, a repeating unit derived from methyl methacrylate and at least one different repeating unit of methyl methacrylate and not comprising a graftable functional group.

[0178] The PA primer may for example be a random or gradient polymer, consisting of repeating units derived from methyl methacrylate and styrene, the mass proportion of repeating units derived from styrene representing from 0.5% to 15%, and preferably from 1.0% to 10%, relative to the total mass of repeating units derived from methyl methacrylate and styrene. Advantageously, the PA primer has a number-average molar mass of 1000 g / mol to 100,000 g / mol, and preferably from 2000 g / mol to 50,000 g / mol. The molecular weight distribution can be estimated by SEC with polystyrene standards.

[0179] The PA primer can be implemented by any polymerization technique known to those skilled in the art. It is generally manufactured by radical polymerization and preferably by controlled radical polymerization. Among the controlled radical polymerization techniques, we can cite: NMP ("Nitroxide Mediated Polymerization"), RAFT ("Reversible Addition and Fragmentation Transfer"), ATRP ("Atom Transfer Radical Polymerization"), INIFERTER ("Initiator-Transfer-Termination"), and RITP ("Reverse Iodine Transfer Polymerization").

[0180] According to advantageous embodiments, the PA primer can be manufactured by NMP, i.e. by nitroxide-controlled radical polymerization, using an alkoxyamine carrying at least one graftable functional group. This synthesis technique is well known to those skilled in the art and is for example described in EP1468029 and EP1526138. Block polymers comprising MMA as a repeating unit are commercially available under the name Nanostrength® (Arkema).

[0181] Alkoxyamine

[0182] Alkoxyamines have the chemical formula: [Chem 3] in which:

[0183] - Ri is a cyclic or non-cyclic hydrocarbon group with or without heteroatom which may contain at least one metallic species;

[0184] - R2 is a cyclic or non-cyclic hydrocarbon group with or without heteroatom which may contain at least one metallic species;

[0185] - Ri and R2 may or may not be part of the same cyclic structure;

[0186] - Z is a monovalent hydrocarbon group, cyclic or not, with or without heteroatom.

[0187] According to advantageous embodiments, Z comprises a graftable functional group. Preferably, the alkoxyamines are those whose nitroxide (also called controlling fragment) is chosen from the following:

[0188] - nitroxides of formula: (with R=H, alkyl fragment, SO2-Ph, SCteMe, Na, K),

[0189] (with R=H, Me),

[0190]

[0191]

[0192]

[0193]

[0194] - (2,2,6,6-tetramethylpiperidin-1-yl)oxy or (2,2,6,6-tetramethylpiperidin-1 - yl)oxyl,

[0195] - N-tert-butyl-1-phenyl-2-methylpropyl nitroxide, - N-(2-hydroxymethylpropyl)-1-phenyl-2-methylpropyl nitroxide,

[0196] - N-tert-butyl-1-dibenzylphosphono-2,2-dimethyl-propyl nitroxide

[0197] -N-tert-butyl-1-di(2,2,2-trifluoroethyl)phosphono-2,2-dimethylpropyl-nitroxide,

[0198] - N-tertiobutyl [(1-diethylphosphono)-2-methylpropyl] nitroxide,

[0199] - N-(1-methylethyl)-1-cyclohexyl-1-(diethylphosphono)nitroxide,

[0200] - N-(1-phenylbenzyl)-[(1-diethylphosphono)-1-methylethyl]nitroxide,

[0201] - N-phenyl-1-diethylphosphono-2,2-dimethylpropylnitroxide,

[0202] - N-phenyl-1-diethylphosphono-1-methylethylnitroxide,

[0203] - N-(1-phenyl2-methylpropyl)-1-diethylphosphonomethylethylnitroxide,

[0204] - and N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide.

[0205] The latter nitroxide is the preferred nitroxide for the polymerization of acrylic or methacrylic repeating unit(s). A commercially available alkoxyamine comprising this nitroxide is N-(2-methylpropyl)-N-(1 - diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxyprop-2-yl)hydroxylamine having the following structural formula (II):

[0206] [Chem 4]

[0207] This compound is marketed by the company ARKEMA under the name Blocbuilder®.

[0208] Derivatives of the abovementioned alkoxyamines, in particular derivatives of the alkoxyamine of formula (I), can be obtained by the reaction of an equivalent of alkoxyamine with an acrylic, methacrylic, or vinylaromatic monomer carrying said at least one graftable functional group. These monomers may in particular be chosen from: silylated styrenes, acrylic acid and its salts, hydroxyalkyl acrylates, in particular C2-C10 hydroxyalkyl acrylates and for example 2-hydroxyethyl acrylate, phosphorus-containing acrylates such as alkylene glycol phosphate acrylates, silylated acrylates, methacrylic acid and its salts, hydroxyalkyl methacrylates, in particular C2-C10 hydroxyalkyl methacrylates and for example 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, and methacrylates such as 3-methacryloylpropyltrimethylsilane.

[0209] Composition based on Polymer(s) Adhesion Primer (PA)

[0210] The composition comprises at least one, i.e., one or more, PA primers. For the sake of brevity and clarity, in the remainder of the section devoted to the composition, the determinants "a" and "the" have been used before "PA primer". They mean by default, and unless otherwise stated, "at least one" and "said at least one" PA primer. They include, according to particular embodiments, cases where the composition comprises only one type of PA primer.

[0211] The PA polymer can be dissolved in a solvent or a mixture of solvents. By "solution" is meant a homogeneous dispersion of the constituents in the solvent, at the molecular level. The term solution is used here in contrast to a suspension of polymer particles in a liquid vehicle, and in contrast to a polymer emulsion or latex.

[0212] Preferably, the solvent is chosen from: dimethylformamide; N-methyl-2-pyrrolidone; dimethylacetamide; dimethylsulfoxide; γ-butyrolactone; ketones, in particular acetone, methyl ethyl ketone (or butan-2-one), methyl isobutyl ketone, cyclopentanone, cyclohexanone, diisobutyl ketone; furans, in particular tetrahydrofuran; esters, in particular methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, and ethyl acetoacetate; carbonates, in particular dimethylcarbonate and propylene carbonate; and phosphates, in particular trimethylphosphate and triethylphosphate. Mixtures of these compounds can also be used.

[0213] In some embodiments, the solvent may be N-methyl-2-pyrrolidone.

[0214] In some embodiments, the solvent may be selected from the list consisting of: dimethylformamide, N-methyl-2-pyrrolidone, dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, diisobutyl ketone, tetrahydrofuran, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, ethyl acetoacetate, dimethyl carbonate, propylene carbonate, trimethylphosphate, triethylphosphate. Mixtures of these compounds may also be used.

[0215] The composition, in solution form, preferably comprises from 0.05 to 30% by weight, preferably from 0.1 to 20% by weight, more preferably from 0.25 to 10% by weight, and extremely preferably from 0.5% to less than 5% by weight of non-volatile solids.

[0216] The composition may optionally comprise one or more additives, in particular chosen from surface tension modifying agents, rheology modifying agents, aging resistance modifying agents, pigments or dyes, fillers (including nanofillers). The other additive(s) generally represent less than 10%, preferably less than 5%, and even more preferably less than 1% by weight relative to the weight of PA polymer. According to certain embodiments, the composition is essentially constituted, or constituted, of at least one PA primer. The composition may optionally comprise one or more additives.

[0217] According to certain embodiments, the composition is essentially composed of, or consisting of, at least one PA polymer and one or more miscible solvents. The composition may optionally comprise one or more additives other than the PA primer.

[0218] According to certain embodiments, the composition based on PA primer(s), respectively the composition based on fluoropolymer(s), are solutions in which the PA primer(s), respectively the fluoropolymer(s) are dispersed in the same solvent or the same mixture of solvents.

[0219] Method of treating a substrate

[0220] The substrate on which the composition based on primary PA adhesion polymer(s) can be deposited may be an electrical conductor, an electrical insulator or a semiconductor. The substrate may in particular be a surface of glass, or silicon, or quartz, or polymer material (in particular polyethylene terephthalate, polyethylene naphthalate, PEDOT-PSS), or metal, or a mixed surface composed of several different materials.

[0221] According to certain preferred variants, the substrate is or comprises a metallic surface M, comprising gold, silver, chromium, aluminum, copper, lithium, zinc, nickel, cobalt, manganese, and their alloys. According to certain preferred variants, the substrate is or comprises an oxidized surface, with functions of the -M-OH type, M representing a metallic atom which may in particular be gold, silver, chromium, aluminum, copper, lithium, zinc, nickel, cobalt, manganese, and their alloys.

[0222] According to certain preferred variants, the substrate is or comprises a surface comprising silanol -SiOH functions, and in particular a glass or silicon surface.

[0223] The application of the composition to form a primer layer may include spreading by discrete or continuous means. The deposition may be carried out in particular by spin-coating, by spray coating, by bar coating, by slotted head coating, by dip coating, by roll-to-roll printing, by screen printing, by flexographic printing, by lithographic printing or by inkjet printing, by electrospinning, or by extrusion.

[0224] According to advantageous embodiments, the deposition of a composition in the form of a solution can be carried out by coating, in particular with a bar or a film puller ("bar coating"), or by screen printing. When the composition is applied in the form of a solution, the solvent must be evaporated after deposition. The evaporation can be carried out at room temperature (23°C) and / or by heating to a temperature preferably ranging from 50 to 150°C, a temperature range which has the advantage of allowing the grafting of at least a portion of PA primer onto the substrate at the same time as causing the evaporation of the solvent. The layer can be subjected to ventilation to facilitate evaporation. The evaporation time can be, for example, from 1 minute to 1 hour, preferably from 2 minutes to 45 minutes, and more preferably from 3 minutes to 30 minutes.The duration of evaporation may be, in particular, 30 minutes or less, or 20 minutes or less, or 15 minutes or less, or 10 minutes or less, or 5 minutes or less.

[0225] One or more annealing steps may be carried out after the formation of the dry layer comprising said at least one PA primer. The annealing makes it possible in particular to obtain the grafting, and where appropriate the increase in grafting, of at least a fraction of PA primer onto the substrate. The annealing step(s) may in particular be carried out, independently of one another, at a temperature of 50°C to 220°C, and preferably ranging from 80°C to 220°C. The temperature of each annealing may in particular be from 50°C to 65°C, or from 65°C to 70°C, or from 70°C to 75°C, or from 75°C to 80°C, or from 80°C to 85°C, or from 85°C to 90°C, or from 90°C to 95°C, or from 95°C to 100°C, or from 100°C to 105°C, or from 105°C to 110°C, or from 110°C to 115°C, or from 115°C to 120°C, or from 120°C to 130°C, or from 130°C to 140°C, or from 140°C to 150°C, or from 150°C to 160°C, or from 160°C to 170°C, or from 170°C to 180°C, or from 180°C to 190°C, or from 190°C to 200°C, or from 200°C to 220°C.The duration of each annealing may be, for example, from 30 seconds to 1 hour, preferably from 1 minute to 30 minutes, and more preferably from 2 minutes to 20 minutes, it being understood that, generally speaking, the higher the temperature of an annealing, the shorter the duration of this annealing may be. The duration of each annealing may be 20 minutes or less, or 15 minutes or less, or 10 minutes or less, or 5 minutes or less. The duration of each annealing may be 1 minute or more, 2 minutes or more, or 3 minutes or more.

[0226] The annealing may in particular be carried out in a single step by subjecting the primer layer to a temperature of 50 to 220°C, preferably 80°C to 200°C. The duration of this single annealing may be, for example, 1 minute to 1 hour, and preferably 2 minutes to 30 minutes. The duration of this single annealing may be 30 minutes or less, or 20 minutes or less, or 10 minutes or less, or 5 minutes or less. The duration of this single annealing may be 1 minute or more, 2 minutes or more, or 3 minutes or more.

[0227] In some embodiments, particularly in embodiments where the primer is applied as a solution and the solvent is evaporated at a temperature below 50°C, a single anneal may be performed at a temperature of 160°C or less for a period of 30 minutes or less, or for a period of 20 minutes or less, or for a period of 10 minutes or less, or for a period of 5 minutes or less.

[0228] In some embodiments, particularly in embodiments where the primer is applied as a solution and the solvent is evaporated at a temperature below 50°C, a single anneal may be performed at a temperature of 120°C or less for a period of 30 minutes or less, or for a period of 20 minutes or less, or for a period of 10 minutes or less, or for a period of 5 minutes or less.

[0229] According to certain embodiments, in particular in the embodiments where the primer is applied in the form of a solution and the solvent is evaporated at a temperature ranging from 50°C to 150°C, i.e. allowing the grafting to be initiated, a single annealing can be carried out at a temperature strictly higher than the evaporation temperature for a duration of 10 minutes or less, or for a duration of 5 minutes or less.

[0230] For example, in some embodiments, particularly in embodiments where the primer is applied as a solution and the solvent is evaporated at a temperature ranging from 70°C to 120°C, a single anneal may be performed at a temperature of greater than 120°C for a period of 10 minutes or less, or for a period of 5 minutes or less.

[0231] Thus, the grafting of the primer to the substrate can be carried out in one or more steps, by heating during the evaporation of the solvent (in the case where the composition is applied in the form of a solution) and / or during at least one annealing step. The grafting can in particular be carried out by one or more heating steps at a temperature of 50 to 220°C, preferably 80°C to 200°C. For each heater, the temperature ranges can be chosen from the following ranges: 50°C to 65°C, or from 65°C to 70°C, or from 70°C to 75°C, or from 75°C to 80°C, or from 80°C to 85°C, or from 85°C to 90°C, or from 90°C to 95°C, or from 95°C to 100°C, or from 100°C to 105°C, or from 105°C to 110°C, or from 110°C to 115°C, or from 115°C to 120°C, or from 120°C to 130°C, or from 130°C to 140°C, or from 140°C to 150°C, or from 150°C to 160°C, or from 160°C to 170°C, or from 170°C to 180°C, or from 180°C to 190°C, or from 190°C to 200°C, or from 200°C to 220°C.

[0232] According to certain embodiments, the grafting can be carried out in one or more steps, by heating to a temperature less than or equal to 200°C, and preferably less than or equal to 160°C, and preferably still less than or equal to 120°C.

[0233] The grafting may last in total from 1 minute to 2 hours, and preferably less than 1 hour, preferably even less than 45 minutes, preferably even less than 30 minutes, and more preferably less than 15 minutes. The grafting may in particular last 15 minutes or less, 10 minutes or less, or 5 minutes or less.

[0234] According to certain embodiments, the grafting can be carried out by one or more heating steps at a temperature less than or equal to 200°C, and preferably less than or equal to 160°C, and even more preferably less than or equal to 120°C, for a total duration of 45 minutes or less, preferably 30 minutes or less, preferably 20 minutes or less, preferably 15 minutes or less, and even more preferably 10 minutes or less, and more preferably 5 minutes or less.

[0235] According to particular embodiments, the grafting can be carried out by one or more heating steps at a temperature less than or equal to 160°C for a total duration less than or equal to 15 minutes.

[0236] According to particular embodiments, the grafting can be carried out by a single heating step at a temperature less than or equal to 160°C for a duration less than or equal to 15 minutes.

[0237] According to particular embodiments, the grafting can be carried out by one or more heating steps at a temperature less than or equal to 120°C for a total duration less than or equal to 10 minutes.

[0238] According to particular embodiments, the grafting can be carried out by a single heating step at a temperature less than or equal to 120°C for a duration less than or equal to 10 minutes.

[0239] Once at least one fraction of PA primer has been grafted to the surface of the substrate, washing using at least one solvent for said at least one PA polymer can be carried out in order to remove the fraction of said at least one PA polymer which has not been grafted.

[0240] The primer layer grafted to the surface of the substrate is generally very thin. It may have a thickness less than or equal to 500 nm, preferably less than or equal to 250 nm, preferably still less than or equal to 100 nm, and more preferably less than or equal to 50 nm. It may in particular have a thickness less than or equal to 40 nm, or less than or equal to 30 nm, or less than or equal to 20 nm, or less than or equal to 15 nm.

[0241] The composite formed by stacking the substrate and the thin layer of grafted primer constitutes a treated substrate capable of exhibiting good adhesion properties with a fluoropolymer.

[0242] Method of manufacturing a coating of fluoropolymer(s) on a treated substrate

[0243] The application of the composition based on fluoropolymer(s) to form a coating on the substrate treated with the primer layer may comprise spreading by discrete or continuous means. The deposition may be carried out in particular by spin-coating, by spray coating, by coating in particular with a bar or film puller, by coating with a slotted head, by immersion, by dip coating, by roll-to-roll printing, by screen printing, by flexographic printing, by lithographic printing or by inkjet printing, by electrospinning, or by extrusion.

[0244] According to particular embodiments, the deposition of a composition not comprising a solvent can be carried out by extrusion.

[0245] According to particular embodiments, the deposition of a composition in the form of a solution can be carried out by coating, in particular with a bar or a film puller ("bar coating") or by screen printing.

[0246] When the composition is applied in solution form, the solvent must be evaporated after deposition. Evaporation may be carried out at room temperature (23°C) and / or by heating to a temperature preferably ranging from 50 to 150°C. The layer may be subjected to ventilation to facilitate evaporation. The evaporation time may be, for example, from 1 minute to 24 hours, preferably from 2 minutes to 5 hours, and more preferably from 3 minutes to 2 hours. The evaporation time may in particular be less than 1 hour. The evaporation time may in particular be 30 minutes or less, or 20 minutes or less, or 15 minutes or less, or 10 minutes or less.

[0247] The dry coating of fluorinated polymer(s) formed may have a thickness of 1 μm to a thickness of the order of a millimeter. Such thicknesses may be obtained by deposition of a single layer according to one of the aforementioned methods or by deposition of successive layers produced by iteration of at least one of the aforementioned methods.

[0248] According to certain embodiments, the coating has a thickness of 1 μm to 100 μm. The coating may in particular have a thickness of 1 μm to 10 μm, or of 10 μm to 50 μm, or of 50 μm to 100 μm. The coating may in particular be in the form of a film of substantially constant thickness.

[0249] According to certain embodiments, the coating has a thickness of 100 μm to 1000 μm. The coating may in particular have a thickness of 100 μm to 250 μm, or of 250 μm to 500 μm, or of 500 μm to 1000 μm. The coating may in particular have a substantially constant thickness.

[0250] According to certain embodiments, the coating has a thickness strictly greater than 1000 μm, for example 1 to 2 mm.

[0251] According to certain embodiments, the grafted primer layer has a thickness generally not exceeding 20%, preferably not exceeding 10%, preferably not exceeding 5%, and more preferably not exceeding 1% of the thickness of the coating of fluoropolymer(s).

[0252] One or more annealing steps may be carried out after the formation of the coating to increase the crystallization of the fluoropolymer in a manner known per se. Each annealing step may be carried out at a temperature ranging from 50°C to 150°C, and preferably from 70°C to 140°C. The composite formed by the stacking of the substrate, the layer of PA primer(s) grafted to the substrate and the coating of PF fluorinated polymer(s) generally exhibits very good adhesion to the substrate / grafted PA primer(s) interface and to the grafted PA primer(s) / PF fluorinated polymer(s) interface, so that in the examples presented below, the ruptures observed during the application of shear force to the interface of the grafted PA primer / PF fluorinated polymer, only cohesive type ruptures of the PF fluorinated polymer could be observed.

[0253] In embodiments where the fluoropolymer is a ferroelectric polymer, for example P(VDF-TrFE), the composite formed by the stack of the substrate, the PA primer layer grafted to the substrate and the PF fluoropolymer coating, can then be polarized according to methods known per se: by contact polarization by applying a direct or alternating voltage or by contactless polarization using the Corona effect.

[0254] Device

[0255] The invention also relates to a device comprising such a composite. The coating of fluorinated polymer(s) may be electroactive, be an insulating and / or protective coating, or even be an electrode binder.

[0256] The device may in particular be an optoelectronic device, a transistor, in particular a field effect transistor, a chip, a battery, a photovoltaic cell, a light-emitting diode, in particular an organic light-emitting diode, a sensor, an actuator, a transformer, a haptic device, a microelectromechanical system and a detector.

[0257] Use

[0258] The invention relates to the use of PA polymer(s) as adhesion primer(s) between a composition based on fluorinated polymer(s) and a substrate to improve the adhesion of the fluorinated polymer(s) to the substrate.

[0259] The examples below show in particular that the use of a very thin layer of PA primer can significantly increase the adhesion of a fluoropolymer to any type of substrate, and in particular substrates which are generally known to have very low adhesion for fluoropolymers such as aluminium.

[0260] The use of the PA primer can make it possible to obtain an adhesion between a coating based on fluoropolymer(s), in particular a P(VDF-TrFE) and its treated substrate, in particular aluminum, greater than or equal to 1.0 N Z25 mm, or greater than or equal to 1.5 N / 25 mm, or greater than or equal to 2 N / 25 mm, or greater than or equal to 3 N / 25 mm, or greater than or equal to 4 N / 25 mm, or greater than or equal to 5 N / 25 mm, or greater than or equal to 6 N / 25 mm, or greater than or equal to 7 N / 25 mm, or greater than or equal to 8 N / 25 mm, or greater than or equal to 9 N / 25 mm, as measured according to a peel test at

[0261] 180° performed at a speed of 0.5 mm / s on a 25 mm wide strip of coating.

[0262] Examples

[0263] Example 1 - Raw materials

[0264] Synthesis of primaries P1 and P2 (gradient) - primaries according to the invention

[0265] This synthesis was implemented by nitroxide-controlled polymerization.

[0266] A hydroxy-functionalized alkoxyamine was prepared from the alkoxyamine BlocBuilder®MA, marketed by Arkema. This alkoxyamine has the chemical formula:

[0267] [Chem 5]

[0268] In a 1 L nitrogen-purged flask, 226.17 g of BlocBuilder®MA (1 equivalent), 68.9 g of 2-hydroxyethyl acrylate (1 equivalent), and 548 g of isopropanol were introduced. The reaction mixture was heated at reflux (80 °C) for 4 h and then the isopropanol was evaporated under vacuum. 297 g of hydroxyl-functionalized alkoxyamine were obtained in the form of a very viscous yellow oil.

[0269] Toluene, styrene (S) and methyl methacrylate (MMA) monomers, and hydroxyl-functionalized alkoxyamine were introduced into a stainless steel reactor equipped with a mechanical stirrer and a double jacket. The amount of hydroxyl-functionalized alkoxyamine and the mass of monomers introduced made it possible to control the molecular weight of the polymer in a manner known per se.

[0270] The mass ratio between the styrene (S) and methyl methacrylate (MMA) monomers was: 5 / 95 respectively. The mass loading of toluene was set at 30% relative to the reaction medium. The reaction mixture was stirred and degassed by bubbling nitrogen at room temperature for 30 minutes. The temperature of the reaction medium was then brought to 115°C. Time t=0 was started at room temperature (23°C). The temperature was maintained at 115°C throughout the polymerization. Samples were taken at regular intervals to determine the polymerization kinetics by gravimetry (dry extract measurement). The polymerization reaction was carried out up to a conversion rate of approximately 70, then the reaction medium was cooled to 60°C and the solvent and residual monomers were evaporated under vacuum.After evaporation, methyl ethyl ketone (MEK) was added to the reaction medium in such a quantity that a copolymer solution of the order of 25% by mass was produced. This copolymer solution was then introduced dropwise into a beaker containing a non-solvent (heptane), so as to precipitate the copolymer. The mass ratio between solvent and non-solvent (methyl ethyl ketone / heptane) was of the order of 1 / 10. The precipitated copolymer was recovered in the form of a white powder after filtration and drying.

[0271] Synthesis of the P3 primer (block) - primer according to the invention

[0272] A nitroxide-controlled polymerization reaction was carried out analogously to Example 1. BlocBuilder®MA alkoxyamine (non-functionalized) was used for the polymerization. Methyl methacrylate (MMA) monomer and the monomer mixture of 2-hydroxyethyl methacrylate (HEMA) and n-butyl acrylate (ABu) were added sequentially to obtain a block copolymer P(MMA-b-ABu / HEMA) (polymer P3).

[0273] Table 1 below summarizes the type of polymerization used, the mass composition in monomer units and the number-average molar mass for each primer obtained (SEC with polystyrene standards).

[0274] [Table 1] Solutions of the different primers (P1; P2; P3) were prepared at 1% by mass in methyl ethyl ketone (MEK).

[0275] Fluoropolymer PF-1

[0276] A P(VDF-TrFE) copolymer, consisting of repeating units derived from vinylidene fluoride (VDF) and trifluoroethylene (TrFE), having a VDF:TrFE molar ratio of 80.0:20.0 (Piezotech®FC20, marketed by Arkema), was used as the fluoropolymer. This polymer is referred to as “PF-1” in the following examples.

[0277] A solution of PF-1 was prepared at 10% by mass in methyl ethyl ketone (MEK).

[0278] Example 2 - Preparation of PF-1 test films on primed or unprimed aluminum substrate

[0279] The substrates used were 15 μm thick 1235 aluminum sheets. They were previously cleaned with a cloth soaked in ethanol.

[0280] The primers (P1; P2; P3) were grafted as follows. For each primer, the primer solution was dispensed by bar-coating to obtain a regular deposit homogeneously covering the area of ​​interest to be adhered (half of the aluminum substrate), then the film was left to dry for a few minutes at room temperature. The substrate was then placed in an oven at the chosen temperature (see Table 2 below) for 4 minutes, then it was allowed to return to room temperature quickly and placed in a bath of good primer solvent (MEK) for a few minutes in order to remove the excess of ungrafted primer on the surface of the substrate, and finally, the substrate thus functionalized on half of the surface was dried under a flow of compressed air. The thickness of the dry films of grafted primers thus obtained was approximately 7 nm.

[0281] A control test was also implemented, for which no primer was deposited or grafted onto the surface of the aluminum substrate.

[0282] The PF-1 solution was dispensed by bar-coating over the entire surface of the functionalized substrates (e.g. #1-#8) or non-functionalized (#0: control) in order to obtain a wet film with a theoretical thickness of 500 μm, then the film was left to dry at room temperature for about fifteen minutes. The film was then placed in an oven for 20 minutes at 140°C in order to increase the crystallinity of PF-1. Then the film was rapidly cooled to room temperature. The substrates thus prepared were cut into strips of 25 mm on each side to carry out an adhesion test.

[0283] Samples #1-#8 all include a portion where the PF-1 film is resting on the primed area and a portion where it is resting directly on the aluminum substrate.

[0284] The control sample (#0) corresponds to a PF-1 film resting on the entire aluminum substrate.

[0285] [Table 2]

[0286] Adhesion test using a tensile machine

[0287] The samples produced were tested on an Instron 5565 type tensile testing machine, equipped with a 100 N force sensor, via a 180° peel test carried out at a speed of 0.5 mm / s, according to the diagram described in Figure 1. With reference to this figure, the PF-1 film 3, deposited on the aluminum substrate 1 comprising a primer 2 grafted onto part of its surface (except the control which does not include a primer layer) undergoes a 180° peel test by applying a tensile force 4.

[0288] The results of these tests are shown in Table 3 below. The column titled “Tensile Force” represents the force applied during the peel test and is expressed in Newtons per 25 mm (N / 25 mm).

[0289] Two types of rupture could be observed: either an adhesive type rupture between two layers, or a cohesive type rupture of a material of a given layer. [Table 3]

[0290] It is notable that the primers P1, P2, and P3 allow very high adhesion forces to be achieved compared to that obtained for the control test. Furthermore, the type of rupture obtained for the tests from the substrates coated with one of the primers P1, P2, and P3 is cohesive unlike the type of rupture obtained for the control test. That is to say, the adhesion force between the substrate functionalized by the primer and the PF-1 copolymer film is greater than the cohesive force of the PF-1 copolymer itself: consequently the film breaks before it can be peeled from its functionalized substrate.

[0291] Example 3 - Comparison with tests carried out using substrates coated with DowsilTM Primer C

[0292] DOWSILTM Primer C is an adhesion promoter marketed by the Dow Chemical Company, specifically designed for polyvinylidene fluoride. According to its technical data sheet, it is a silane-based adhesion promoter.

[0293] The substrates used were 15 μm thick 1235 aluminum foils as in Example 2. They were previously cleaned with an ethanol-soaked cloth. The aluminum substrates were coated on one half of their surface with DOWSILTM Primer C in three different ways:

[0294] - process a): by applying the primer to the substrate and drying for 20 minutes at room temperature (23°C): this is the application process recommended on the product technical sheet at room temperature;

[0295] - process b): by applying the primer and drying for 1 hour at room temperature (23°C): this is the drying time recommended on the product's technical data sheet at a temperature of 5°C; - process c): by applying the primer to the substrate and drying for 20 minutes at room temperature (23°C) followed by annealing at 120°C for 4 minutes: the temperature and annealing time correspond to the grafting conditions used for P1, P2, and P3.

[0296] PF-1 test films on aluminum substrate partially coated with DOWSILTM Primer C were prepared as described above in Example 2. The samples were tested using a 180° peel test performed at a speed of 0.5 mm / s as in Example 2.

[0297] The results of these tests are presented in Table 4 below.

[0298] [Table 4]

[0299] The use of DOWSILTM Primer C certainly improves the adhesion between the PF-1 polymer and its substrate (tensile forces of the order of 8 to 22 times greater than for the control test without primer), but the rupture remains of the adhesive type. Furthermore, the adhesion obtained is much lower than that obtained using primers P1, P2, and P3.

Claims

Claims 1. Use of a PA polymer as an adhesion primer between a coating comprising at least one fluorinated polymer and a substrate, said PA polymer comprising a repeating unit derived from methyl methacrylate, and at least one graftable functional group arranged at at least one end of its polymer chain, said at least one graftable functional group being capable of being grafted to the substrate.

2. Use according to claim 1, in which said PA polymer comprises at one end of its chain at least one graftable functional group being a nitroxy.

3. Use according to any one of claims 1 and 2, in which said PA polymer comprises at one end of its chain at least one graftable functional group chosen from the groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

4. Use according to any one of claims 1 to 3, in which said at least one graftable functional group arranged at one end of the chain of said PA polymer is a hydroxyl function.

5. Use according to any one of claims 1 to 4, in which said at least one graftable functional group arranged at one end of the chain of said PA polymer is a carboxyl function.

6. Use according to any one of claims 1 to 5, in which the units derived from the methyl methacrylate of said PA polymer represent at least 40% by weight, preferably at least 50% by weight, and extremely preferably at least 70% by weight, relative to the total weight of the repeating units of said polymer.

7. Use according to any one of claims 1 to 6, in which said PA polymer is capable of being obtained by a nitroxide-controlled radical polymerization using an alkoxyamine.

8. Use according to claim 7, in which the alkoxyamine of the nitroxide-controlled radical polymerization is chosen from: a compound of formula: [Chem 7] (H), and - an adduct formed by the reaction of an equivalent of the compound of formula (II) with an acrylic, methacrylic, or vinylaromatic monomer carrying said at least one graftable functional group.

9. Use according to any one of claims 1 to 8, wherein said PA polymer is a gradient or statistical type polymer, and does not comprise a repeating unit comprising a graftable functional group.

10. Use according to claim 9, in which said PA polymer is essentially constituted, or constituted, of repeating units derived from methyl methacrylate and styrene, the mass proportion of repeating units derived from styrene representing from 0.5% to 15%, and preferably from 1.0% to 10%, relative to the total mass of repeating units derived from methyl methacrylate and styrene.

11. Use according to any one of claims 1 to 8, in which said PA polymer is a polymer with AB-type or ABA-type blocks, in which the block(s) A comprise, independently of one another, at least one repeating unit comprising said at least one graftable functional group, and the block B comprises a repeating unit derived from methyl methacrylate.

12. Use according to claim 11, in which block B of said PA polymer does not comprise a repeating unit comprising a graftable functional group.

13. Use according to any one of claims 1 to 12, in which said at least one fluoropolymer comprises at least 40 mol% of repeating unit derived from vinylidene fluoride, relative to the total sum of moles of repeating units constituting said polymer, and optionally at least one repeating unit derived from a monomer X, other than vinylidene fluoride, having the formula CXiX2=CX3X4, in which each group Xi, X2, X3 and X4 is chosen so as to independent from H, Cl, F, Br, I and C1-C3 alkyl groups which are optionally partially or fully halogenated.

14. Use according to any one of claims 1 to 13, wherein said at least one fluoropolymer is a P(VDF-TrFE), a P(VDF-TrFE-CTFE), a P(VDF-TrFE-CFE), or a mixture thereof.

15. A method of manufacturing a coating based on fluoropolymer(s) on a substrate comprising: i) depositing on the substrate a composition comprising at least one PA polymer, said at least one PA polymer being said polymer capable of being grafted to a substrate according to any one of claims 1 to 14; ii) where appropriate, removing the solvent possibly present in the composition deposited in step i); iii) grafting at least a portion of said at least one PA polymer to the surface of the substrate; iv) recovering the substrate coated with a layer of said at least one PA polymer grafted onto the substrate; v) depositing a composition comprising at least one fluoropolymer on said layer of grafted PA polymer obtained in the preceding step; vi) where appropriate, removing the solubilization solvent of said at least one fluoropolymer possibly present in said composition comprising said at least one fluoropolymer;and vii) recovery of the treated substrate coated with said at least one fluoropolymer.; 16. Composite C2 comprising a coating R2 comprising, being essentially constituted, or being constituted of at least one fluoropolymer, said coating R2 adhering to a composite C1, said composite C1 comprising a coating R1 based on at least one PA polymer grafted to a substrate, said at least one PA polymer being said at least one PA polymer according to any one of claims 1 to 14, wherein said coating R1 adheres to said coating R2.

17. Device comprising a composite C2 according to claim 16.

Images