P(VDF-trfe-VC) polymer and method for obtaining same

Abstract

The invention relates to a method for manufacturing a P(VDF-TrFE-VC) polymer and to the polymers obtained.

Description

[0001] Description

[0002] Title: P(VDF-TrFE-VC) polymer and production process

[0003] technical field

[0004] The invention relates to the field of polymers comprising repeating units resulting from the polymerization of vinylidene fluoride, VDF, and trifluoroethylene, TrFE. The invention relates in particular to terpolymers of P(VDF-TrFE-VC), where VC stands for vinyl chloride, as well as their production process.

[0005] Previous art

[0006] VDF- and TrFE-based polymers are known as ferroelectric materials. They can be used in a variety of applications, including transducers, actuators, and sensors. It is also known that using a third monomer with a bulky substituent can disrupt the crystallization of VDF- and TrFE-based ferroelectric polymers, thereby modifying their ferroelectric properties. Specifically, P(VDF-TrFE-CTFE) and P(VDF-TrFE-CFE) are known to exhibit ferroelectric-relaxer properties. These polymers are characterized by a ferroelectric-relaxer (RFE) to 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 lower temperatures. They are also characterized by a narrowed hysteresis loop in the "electric displacement" curve as a function of the "applied electric field".

[0007] To the inventors' knowledge, three prior art documents address the manufacture of P(VDF-TrFE-VC) exclusively by bulk polymerization at room temperature, by adding all the monomers to the initial mixture. The first document is US20088119. It discloses such polymers in Examples 41-44, with the following respective molar chemical compositions: [VDF; TrFE; VC] = [55.1; 33.1; 11.8], [VDF; TrFE; VC] = [58.3; 34.7; 7.0], [VDF; TrFE; VC] = [66.7; 30.5; 2.8], and [VDF; TrFE; VC] = [53.8; 38.8; 7.4].

[0008] The second document is: Chung, TC, & Petchsuk, A. (2002). Synthesis and properties of ferroelectric fluoroterpolymers with Curie transition at ambient temperature. Macromolecules, 35(20), 7678-7684. This document discloses a P(VDF-TrFE-VC), C-1, with a molar chemical composition [VDF; TrFE; VC] = [55.1; 33.1; 11.8] and a P(VDF-TrFE-VC), C-2, with a molar chemical composition [VDF; TrFE; VC] = [58.3; 34.7; 7.0]. The thermal properties of these polymers have been reported. In particular, it can be observed that the P(VDF-TrFE-VC) “C-2” according to Chung et al. has a melting point about 5°C higher and a Curie temperature about 5°C lower compared to P(VDF-TrFE-CTFE) “A-2” obtained by the same manufacturing process and having a similar chemical composition in VDF, TrFE and termonomer.The document indicates that the terpolymers were prepared using a bulk polymerization process at room temperature with an oxygen-activated organoborane initiator. The precise manufacturing conditions of the P(VDF-TrFE-VC) terpolymer were not specified, making it impossible to replicate the experiment. The molecular weights obtained appear quite low, as the polymers produced have a molecular weight > 20,000, a value considered high.

[0009] The third document is: Chung, TC, & Petchsuk, A. (2003, August). Ferroelectric fluoro-terpolymers with high dielectric constant and large electromechanical response at ambient temperature. In Smart Structures and Materials 2003: Active Materials: Behavior and Mechanics (Vol. 5053, pp. 41-50). SPIE. The document indicates that the terpolymers were prepared by a bulk polymerization process at ambient temperature using an oxidation-activated trialkylborane initiator. The precise manufacturing conditions of the P(VDF-TrFE-VC) terpolymer were not specified, making it impossible to replicate the experiment. The molecular weights obtained appear quite low, as the polymers produced have a molecular weight > 20,000, and this limit is characterized as a high molecular weight.Polymers 111-1 to III-3 are P(VDF-TrFE-VC) with respective molar chemical compositions [VDF ; TrFE ; VC] = [58.3 ;34.7 ;7.0], [VDF ; TrFE ; VC] = [62.3 ;28.4 ;9.3] and [VDF ; TrFE ; VC] = [55.1 ;33.1 ;11.0].

[0010] There is currently a need to supply new polymers including VDF and TrFE, such as P(VDF-TrFE-VC), which may exhibit interesting electroactive properties.

[0011] Objective of the invention

[0012] One objective of the invention is, according to certain embodiments at least, to propose a manufacturing process for P(VDF-TrFE-VC), which can be implemented on an industrial scale.

[0013] One objective of the invention is, according to at least some embodiments, to provide a process for manufacturing a P(VDF-TrFE-VC) having a weight average molar mass Mw well above 20,000 g / mol.

[0014] One objective of the invention is, according to certain embodiments at least, to provide a method for manufacturing a P(VDF-TrFE-VC) in a repeatable manner.

[0015] One objective of the invention is, according to at least some embodiments, to provide a process for manufacturing a P(VDF-TrFE-VC) having a sufficiently homogeneous chemical composition.

[0016] One objective of the invention is, according to at least some embodiments, to propose a process for manufacturing a P(VDF-TrFE-VC) that can be implemented in a limited time.

[0017] An objective of the invention is to provide a P(VDF-TrFE-VC), in particular capable of being obtained according to a process of the invention, possessing advantageous electroactive properties.

[0018] Summary of the invention

[0019] The invention relates to a process for manufacturing a P(VDF-TrFE-VC) polymer by polymerization of vinylidene fluoride, VDF, trifluoroethylene, TrFE, and vinyl chloride, VC, said process comprising: - injecting into a reactor an initial composition Ci essentially consisting of, or consisting of, VDF, TrFE, and optionally VC, to form a mixture of monomers Mi, where Yi represents the molar proportion, expressed as a percentage, of VC monomer relative to the total number of moles of VDF, TrFE, and VC monomers in the composition Ci,

[0020] - the initiation of polymerization of the Mi monomer mixture; and,

[0021] - the continuation of polymerization at a substantially constant pressure in the reactor, by injection into the reactor of VDF, TrFE and VC monomers of composition C2, and optionally by injection of an inert fluid, where Y2 represents the molar proportion, expressed as a percentage, of VC monomer relative to the total number of moles of VDF, TrFE and VC monomers in composition C2, Y2 being strictly greater than Y1.

[0022] According to some embodiments, P(VDF-TrFE-VC) has a targeted composition C P in the repeating units resulting from the polymerization of VDF, TrFE and VC, where Y P represents the target molar proportion, expressed as a percentage, in units resulting from the polymerization of VC relative to the total number of moles in units resulting from the polymerization of VDF, TrFE and VC in composition C P said process being characterized in that the ratio Y1 to Y Pis greater than or equal to 0 and strictly less than 1, and the ratio Y2 to Y P is greater than or equal to 1.

[0023] According to some embodiments, the ratio Y1 to Yp is greater than or equal to 0.05.

[0024] According to some embodiments, the ratio Y1 to Yp is less than or equal to 0.85.

[0025] Depending on some embodiments, Yp is worth from 0.1% to 20.0%.

[0026] According to some embodiments, it being understood that Xp represents the target molar proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in composition Cp, Xp is from 30.0% to 100%, preferably from 45.0% to 90.0%, and more preferably from 50.0% to 80.0%.

[0027] According to certain embodiments, it being understood that X1 represents the molar proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition C1, that X2 represents the molar proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition C2, that the parameter AX1 is calculated as follows: [Math 1] AX2 is calculated as follows:

[0028] AX1 satisfies the following inequality: -10.0 < AX1 < 10.0; and / or

[0029] AX2 satisfies the following inequality: -10.0 < AX2 < 10.0.

[0030] According to some embodiments, the polymerization carried out is a suspension polymerization or an emulsion polymerization, and preferably is a suspension polymerization.

[0031] According to some embodiments, the polymerization carried out is a suspension polymerization, with an aqueous solution or water being used as the suspension liquid.

[0032] According to some embodiments, the continuation of polymerization is carried out without injection of inert fluid in order to maintain a substantially constant pressure in the reactor.

[0033] According to certain embodiments, the total polymerization time is strictly less than 48 hours, preferably strictly less than 24 hours, and preferably less than or equal to 12 hours. The invention also relates to a polymer P(VDF-TrFE-VC), having a chemical composition C in repeating units resulting from the polymerization of VDF, TrFE, and VC, where X represents the mole proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in composition C, and where Y represents the mole proportion, expressed as a percentage, in units resulting from the polymerization of VC relative to the total number of moles in units resulting from the polymerization of VDF, TrFE, and VC in composition C, characterized in that the parameter X satisfies the inequality: 30 < X ​​< 100, and the parameter Y satisfies the inequality: 0.1 < Y ​​< 20.0.

[0034] According to some embodiments, Y > 0.5.

[0035] According to some embodiments, Y < 15.0.

[0036] According to particular embodiments, Y satisfies the following inequality: 3.0 < Y < 6.0.

[0037] According to some embodiments, the polymer has a weight average molar mass Mw greater than or equal to 50,000 g / mol, preferably greater than or equal to 100,000 g / mol, and more preferably greater than or equal to 200,000 g / mol.

[0038] According to certain embodiments, the polymer can be obtained by a process according to the invention.

[0039] Detailed description of the invention

[0040] Figure 1 illustrates the shape of a hysteresis loop for a polymer according to the invention. The x-axis represents the applied electric field. The y-axis represents the polarization of the polymer.

[0041] Process

[0042] The invention relates to a process for manufacturing a P(VDF-TrFE-VC) polymer by polymerization of vinylidene fluoride, VDF, trifluoroethylene, TrFE, and vinyl chloride, VC. The process comprises injecting into a reactor an initial composition Ci essentially consisting of, or consisting of, VDF, TrFE, and optionally VC, to form a mixture of monomers Mi, then initiating the polymerization of the monomer mixture Mi, and finally continuing the polymerization at a substantially constant pressure in the reactor, by injecting into the reactor VDF, TrFE and VC monomers of composition C2 and optionally by injecting an inert fluid.

[0043] Let Y1 be the molar proportion, expressed as a percentage, of VC monomer relative to the total number of moles of VDF, TrFE and VC monomers in composition Ci. Let Y2 be the molar proportion, expressed as a percentage, of VC monomer relative to the total number of moles of VDF, TrFE and VC monomers in composition C2.

[0044] The inventors realized that introducing VC into a mixture of VDF and TrFE, particularly in mixture M1, significantly slowed the polymerization rate. Therefore, they proposed adding the monomers in two stages, using an initial composition Ci forming an initial mixture M1 and a secondary composition C2, which helps to maintain a substantially constant polymerization pressure. They selected the value of Y2 to be strictly greater than that of Y1. In this way, polymerization can be carried out in a shorter time than in embodiments where the entire quantity of the three monomers is introduced at the beginning of polymerization.

[0045] In some embodiments, the polymerization process can be carried out over a total duration of less than 48 hours. Preferably, the polymerization process can be carried out over a total duration of less than 24 hours. Even more preferably, the polymerization process can be carried out over a total duration of 12 hours or less.

[0046] We note C P The target composition consists of repeating units resulting from the polymerization of VDF, TrFE, and VC in the polymer P(VDF-TrFE-CTFE). In particular, X is denoted P the target molar proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in composition C P X Pgenerally corresponds to approximately the amount of VDF consumed in the reactor, divided by the sum of the amounts of VDF and TrFE consumed totally in the reactor, for polymerization.

[0047] We denote Y P the target molar proportion, expressed as a percentage, in units resulting from the polymerization of VC relative to the total number of moles in units resulting from the polymerization of VDF, TrFE, and VC in the Cp composition. Y P generally corresponds to approximately the amount of VC consumed totally in the reactor, divided by the sum of the amounts of VDF, TrFE and VC consumed totally in the reactor for polymerization.

[0048] According to advantageous embodiments, the Yi-to-Y ratio P , which can be denoted Yi / Y P , is greater than or equal to 0 and strictly less than 1, and the ratio Y2 to Y P , which can be noted as Y2 / Y P , is greater than or equal to 1.

[0049] The method according to the invention is generally implemented for Y P ranging from 0.1% to 20.0%.

[0050] According to certain preferred embodiments, Y P is greater than or equal to 0.5%. Y P may in particular be greater than or equal to 1.0%, or greater than or equal to 1.5%.

[0051] According to certain preferred embodiments, Y P is less than or equal to 15.0%. Y P may in particular be less than or equal to 12.5%, or less than or equal to 10.0%.

[0052] According to certain preferred embodiments, Y P can have a value ranging from 0.5% to 15%, in particular ranging from 1.0% to 12.5%, and more specifically ranging from 1.5% to 10.0%.

[0053] According to specific embodiments, Y P is worth from 1.5% to 3.0%, or from 3.0% to 6.0%, or from 6.0% to 7.5%, or from 7.5% to 10.0%.

[0054] According to some preferred embodiments, the Yi / Y ratioP is strictly greater than 0, and advantageously greater than or equal to 0.05. This notably allows for mitigating inhomogeneities in the chemical composition of the polymer compared to a process where the ratio Yi / Y P is strictly less than 0.05, in particular in the case where Yi is equal to 0. For the purposes of the present invention, "homogeneity of chemical composition" means that the different polymer chains have essentially the same proportion of VDF, TrFE and VC.

[0055] According to some preferred embodiments, the Yi / Y ratio P is less than or equal to 0.85. This notably allows for limiting the total polymerization time compared to a process where the Yi / Y ratio P is strictly greater than 0.85, particularly in the case where the Yi / Y ratio P is equal to 1. According to some embodiments, the ratio Yi / Y Pis preferably less than or equal to 0.80, preferably less than or equal to 0.75, preferably less than or equal to 0.70, preferably less than or equal to 0.65, preferably less than or equal to 0.60, preferably less than or equal to 0.55, and preferably less than or equal to 0.50.

[0056] According to some embodiments, the Yi / Y ratio P value is from 0.05 to 0.5.

[0057] The Yi / Y ratio P may in particular be less than or equal to 0.45, or be less than or equal to 0.40, or be less than or equal to 0.35, or be less than or equal to 0.30, or be less than or equal to 0.25.

[0058] The parameter AY2 is defined as follows:

[0059] [Math 3]

[0060] The parameter AY2 is positive, zero, or negative.

[0061] The parameter AY2 is advantageously positive or zero.

[0062] In embodiments where Yp < 6.0, the parameter AY2 is advantageously positive or zero.

[0063] In embodiments where Yp > 6.0, and especially in embodiments where Yp > 7.5, AY2 can be negative.

[0064] According to preferred embodiments, AY2 is less than or equal to 10.0. AY2 is advantageously less than or equal to 7.5, and even more advantageously less than or equal to 5.0. According to some embodiments, AY2 may be less than or equal to 4.0, or less than or equal to 3.0, or less than or equal to 2.5, or less than or equal to 2.0, or less than or equal to 1.5, or less than or equal to 1.0.

[0065] The method according to the invention is generally implemented for X P ranging from 30.0% to 100%.

[0066] According to some embodiments, X Pmay in particular be less than or equal to 100%, or be less than or equal to 95.0%, or be less than or equal to 90.0%, or be less than or equal to 85.0%, or be less than or equal to 80.0%, or be less than or equal to 75.0%.

[0067] According to some embodiments, X P may in particular be greater than or equal to 35.0%, or greater than or equal to 45.0%, or greater than or equal to 50.0%, or greater than or equal to 55.0%, or greater than or equal to 60.0%.

[0068] According to preferred embodiments, X P ranges from 45.0% to 90.0%. According to more preferred embodiments, X P ranges from 50.0% to 80.0%.

[0069] Let X1 be the molar proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition Ci. Let X2 be the molar proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition C2.

[0070] The AX1 parameter is defined as follows:

[0071] [Math 4]

[0072] The AX2 parameter is defined as follows:

[0073] [Math 5]

[0074] The process according to the invention is generally implemented for AX1 ranging from -10.0 to 10.0. It is advantageously implemented for AX1 ranging from -5.0 to 5.0. The process according to the invention is generally implemented for AX2 ranging from -10.0 to 10.0. It is advantageously implemented for AX2 ranging from -5.0 to 5.0. The polymerization involved can be bulk polymerization, suspension polymerization, or emulsion polymerization. In order to implement the process on an industrial scale and / or with high molecular weights, the polymerization is preferably suspension polymerization or emulsion polymerization.

[0075] The process according to the present invention can in particular be implemented by suspension polymerization, as detailed below.

[0076] In these embodiments, the monomers of the mixture Mi are suspended in a liquid, called the suspension liquid. The suspension liquid is advantageously water or an aqueous solution.

[0077] The reaction can be initiated by adding a radical polymerization initiator, which may be an organic peroxide such as a peroxydicarbonate. It is generally used in an amount of 0.1 to 10 g per kilogram of the total monomer charge. Preferably, the amount used is 0.5 to 5 g / kg. The amount used may be 0.5 to 1.5 g / kg, or 1.5 to 3 g / kg, or 3.0 to 5 g / kg. Generally, the initiation of the reaction itself is carried out by the combined action of adding the polymerization initiator and a temperature increase, which is accompanied by a pressure increase. The initiator may be added to the reactor after or before the monomer composition Ci has been injected into the reactor. In some embodiments, the initiator is added to the reactor after the monomer composition Ci has been injected into the reactor.According to some embodiments, the initiator is added to the reactor after a temperature rise in the reactor to a predetermined temperature, in particular to a predetermined temperature close to the temperature at which polymerization is initiated.

[0078] Furthermore, it can be advantageous to add a suspending agent to the reaction medium to facilitate the suspension of the monomers in the suspension liquid. A cellulose derivative, particularly a cellulose ether such as methylcellulose, ethylhydroxyethylcellulose, or hydroxypropylmethylcellulose, can be used in an amount of 0.1 to 5 g per kilogram of the total weight of the monomers in mixture Mi. Preferably, the amount used is 0.25 to 3.5 g / kg. The amount used can be 0.25 to 1.0 g / kg, 1.0 to 3.0 g / kg, or 3.0 to 3.5 g / kg. The suspending agent can be added to the reactor after or before the monomer composition Ci has been injected into the reactor. According to advantageous embodiments, the suspending agent is added to the reactor after the composition Ci of VDF, TrFE and optionally VC monomers has been injected into the reactor.

[0079] Finally, a chain length regulating agent can, according to certain embodiments, be added to the reaction medium. Ethyl acetate, diethyl carbonate, or an alcohol such as isopropanol can be used, in an amount of 1 to 100 g per kilogram of the total monomer loading. Preferably, the amount used is 2 to 40 g / kg. The chain length regulating agent can be added to the reactor after or before the monomer composition Ci has been injected into the reactor. It can be added all at once or in fractions over several injections.

[0080] The reaction medium is preferably stirred to suspend the monomers in the suspension liquid and / or during the polymerization reaction.

[0081] Preferably, polymerization is essentially carried out under temperature and pressure conditions for which the monomers in the reactor are in a supercritical state.

[0082] Polymerization can be carried out at a target polymerization pressure, specifically a target polymerization continuation pressure, of 50 to 130 bar, and preferably at a pressure of 70 to 110 bar. The initiation and subsequent continuation of polymerization result in a pressure drop in the reactor due to the consumption of some of the monomers. This pressure drop is compensated for by injecting VDF, TrFE, and VC monomers of composition C2 into the reactor, and optionally by injecting an inert fluid, in order to maintain a substantially constant pressure. "Substantially constant" is defined as a pressure that can vary by ±30%, preferably ±20%, and preferably ±15%. In some embodiments, the pressure can vary by ±10% or ±5%.

[0083] In some less preferred embodiments, the pressure drop during polymerization is partially compensated by the injection of an inert fluid. This inert fluid is advantageously a suspension fluid of the same or different nature as the suspension fluid used to suspend the VDF, TrFE, and VC monomers of mixture Mi in the reactor. In some embodiments, the suspension fluid injected to maintain a substantially constant pressure during polymerization is of the same nature as the suspension fluid used to suspend the VDF, TrFE, and VC monomers of mixture Mi in the reactor.

[0084] According to some preferred embodiments, the pressure decrease during polymerization is compensated by injecting only VDF, TrFE and VC monomers of composition C2 into the reactor. In other words, preferably, the pressure is maintained substantially constant during polymerization without additional injection of inert fluid.

[0085] Polymerization can be carried out primarily at a reaction medium temperature higher than the critical temperature of the monomer mixture in the reactor. This temperature is generally less than or equal to 90°C. In some embodiments, this temperature is less than or equal to 80°C, or less than or equal to 75°C, or less than or equal to 70°C. This temperature is generally greater than or equal to 35°C. In some embodiments, this temperature is greater than or equal to 40°C, or greater than or equal to 45°C. To control the reaction medium temperature, the reactor is equipped with temperature control means (for example, with a double jacket through which a heat transfer fluid circulates). In some preferred embodiments, the temperature is maintained substantially constant during the continuation of polymerization at substantially constant pressure.By substantially constant we mean a temperature that can vary by plus or minus 30%, preferably by plus or minus 20%, preferably still by plus or minus 15%, and even more preferably by plus or minus 10% around a target polymerization temperature, in particular around a target polymerization continuation temperature.

[0086] The polymerization continuation step at substantially constant pressure ends when the injection of C2 composition monomers ceases. In one scenario, this cessation can occur either when the reactor has reached its full capacity, with the polymer and water occupying the entire reactor volume. In another scenario, this cessation can be implemented because a predetermined quantity of C2 composition monomers has been added during the polymerization continuation step at substantially constant pressure. In this case, it is advantageous to abruptly stop the polymerization reaction by adding a termination agent and / or by rapidly cooling the reaction medium in order to avoid introducing chemical inhomogeneity into the P(VDF-TrFE-VC).

[0087] The reactor can then be drained. The collected product can be filtered, washed, and dried in a manner known per se.

[0088] Let Q1 be the total mass of VDF, TrFE, and VC initially injected to form mixture Mi. Let Q2 be the total mass of VDF, TrFE, and VC, of ​​composition C2, injected during the continuation of the polymerization. The process according to the invention is generally implemented such that the ratio Q2 / Q1 is greater than or equal to 0.25. The ratio Q2 / Q1 is preferably greater than or equal to 0.30, preferably greater than or equal to 0.35, preferably greater than or equal to 0.40, preferably greater than or equal to 0.50, preferably greater than or equal to 0.60, preferably greater than or equal to 0.70, and even more preferably greater than or equal to 0.75.

[0089] Polymer

[0090] The invention also relates to a polymer P(VDF-TrFE-VC). X denotes the mole proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in the polymer. Y denotes the mole proportion, expressed as a percentage, in units resulting from the polymerization of VC relative to the total number of moles in units resulting from the polymerization of VDF, TrFE, and VC in the polymer.

[0091] The value of the parameter X can be determined by proton NMR. The polymer is dissolved in a suitable deuterated solvent and the NMR spectrum is recorded on an FT-NMR spectrometer equipped with a multi-nuclear probe.

[0092] The quantity of VC can be determined by measuring the mass content of chlorine by elemental analysis and / or by implementing an NMR.

[0093] According to the invention, the parameter Y can be from 0.1% to 20.0%.

[0094] According to some preferred embodiments, Y is greater than or equal to 0.5%. In particular, Y may be greater than or equal to 1.0%, or greater than or equal to 1.5%.

[0095] According to some preferred embodiments, Y is less than or equal to 15.0%. In particular, Y may be less than or equal to 12.5%, or less than or equal to 10.0%.

[0096] According to some preferred embodiments, Y can have a value ranging from 0.5% to 15%, in particular from 1.0% to 12.5%, and more particularly from 1.5% to 10.0%.

[0097] Depending on specific embodiments, Y is worth from 1.0% to 1.5%, or from 1.5% to 3.0%, or from 3.0% to 6.0%, or from 6.0% to 7.5%, or from 7.5% to 10.0%, or from 10.0% to 12.5%.

[0098] According to the invention, X can be worth from 30.0% to 100%.

[0099] According to some embodiments, X may in particular be less than or equal to 100%, or less than or equal to 95.0%, or less than or equal to 90.0%, or less than or equal to 85.0%, or less than or equal to 80.0%, or less than or equal to 75.0%.

[0100] According to some embodiments, X may in particular be greater than or equal to 35.0%, or greater than or equal to 45.0%, or greater than or equal to 50.0%, or greater than or equal to 55.0%, or greater than or equal to 60.0%.

[0101] Depending on preferred embodiments, X ranges from 45.0% to 90.0%. Depending on more preferred embodiments, X ranges from 50.0% to 80.0%.

[0102] The P(VDF-TrFE-VC) of the invention essentially consists of, or is composed of, repeating units resulting from the polymerization of VDF, TrFE, and VC. In some embodiments, it may include at least one additional repeating unit resulting from the polymerization of a monomer other than VDF, TrFE, and VC. This optional additional repeating unit is preferably in a minor proportion, that is, it may represent less than 25%, less than 10%, less than 5%, less than 2%, or less than 1% molar relative to the number of moles of repeating units resulting from VC in the polymer. In other embodiments, the P(VDF-TrFE-VC) of the invention consists of repeating units resulting from the polymerization of VDF, TrFE, and VC.

[0103] The P(VDF-TrFE-VC) according to the invention is capable of being obtained according to a process of the invention.

[0104] Emulsion polymerization or suspension polymerization, and in particular suspension polymerization, allows the production of P(VDF-TrFE-VC) of any molar mass. The P(VDF-TrFE-VC) according to the invention, obtainable by a process of the invention, generally have a weight-average molar mass Mw greater than or equal to 50,000 g / mol and less than or equal to 5,000,000 g / mol. The weight-average molar mass can be adjusted by modifying certain process parameters, such as the temperature in the reactor, or by adding a chain-regulating agent. The molecular weight distribution can be estimated by SEC (size-exclusion chromatography) with dimethylformamide (DMF) as the eluent, using a set of three 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 calibration is performed using polystyrene standards. The sample is dissolved at 0.5 g / L in DMF and filtered through a 0.45 µm nylon filter. According to certain preferred embodiments, the weight-average molar mass Mw of the polymer is at least 100,000 g / mol, and preferably at least 200,000 g / mol.

[0105] Composition

[0106] The polymer according to the invention can be formulated within a composition. The composition comprises a single polymer or, alternatively, a mixture of polymers according to the invention. In some embodiments, the composition may comprise at least one polymer according to the invention and at least one liquid vehicle for said polymer. This composition, commonly referred to as "ink," can be prepared by dissolving or suspending the polymer(s) according to the invention in the liquid vehicle. Preferably, the liquid vehicle is a solvent.Advantageously, this solvent is a polar aprotic solvent, in particular one that may be selected from: dimethylformamide; dimethylacetamide; dimethyl sulfoxide; ketones, in particular acetone, methylethyl ketone, methylisobutyl ketone, and cyclopentanone; furans, in particular tetrahydrofuran; esters, in particular methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and propylene glycol methyl ether; carbonates, in particular dimethyl carbonate; phosphates, in particular triethyl phosphate, or mixtures thereof. The total mass concentration of polymers in the liquid vehicle may be, in particular, from 0.1 to 30%, preferably from 0.5 to 20%.

[0107] According to certain embodiments, the composition may include one or more other polymers than those of the invention, in particular possessing polar or reactive functions enabling the adhesion of the composition to a given substrate to be improved.

[0108] The composition may optionally include one or more additives, in particular chosen from surface tension modifying agents, rheology modifying agents, heat capacity modifying agents, resistance to aging modifying agents, adhesion modifying agents, pigments or dyes, flame retardants or crosslinking aid additives.

[0109] The composition may optionally include fillers, including nanofillers, such as barium strontium titanate (BST) nanowires.

[0110] Movie

[0111] The polymer according to the invention possesses, in at least some embodiments, sufficient mechanical properties to allow it to be formed into a film. The film can be prepared using the polymer according to the invention or a composition comprising it, for example by applying an ink to a substrate or by extrusion or hot melt compression.

[0112] The substrate can be of any nature and in particular consist of one or more layers of glass or metal(s) or organic (in particular polymeric).

[0113] The film may optionally be stretched if necessary. Stretching (when performed) is preferably carried out at a rate of at least 10% to 700%. Specifically, the film may have a stretch rate of at least 150%, 200%, 250%, 300%, 350%, or 400%. The stretch rate is the ratio of the film's surface area after stretching to its surface area before stretching.

[0114] The films can also, after optionally being stretched, be annealed, that is to say, heated to a temperature below Tfm, preferably below T pm , and preferably lower than Tim, for several hours, then cooled. The annealing temperature is generally from 70°C to 140°C, and can, according to some embodiments, be from 90°C to 120°C.

[0115] Stretching and annealing usually allow for an increase in crystallinity as well as dielectric strength.

[0116] The invention makes it possible to obtain films of desired thickness. Specifically, the film can have a thickness ranging from 1 micrometer to 100 micrometers. Among these thicknesses, the thinnest may be preferred to avoid generating excessively high voltages. Thus, films with a thickness of 1 to 50 micrometers, and even 1 to 10 micrometers, are particularly desirable.

[0117] Electrodes can be deposited on the film, notably by metallization or by deposition of conductive material (silver, copper, conductive polymer, silver nanowires, carbon black, NTC, etc...).

[0118] According to some embodiments, the film prepared from the polymer according to the invention can be a layer of a multilayer device.

[0119] Applications

[0120] Due to its electroactive properties, in particular ferroelectric or ferroelectric relaxer, the polymer according to the invention can be used in actuators, and in particular for haptics, microfluidics, or in loudspeakers.

[0121] Furthermore, due to a high dielectric constant, the polymer according to the invention can also be used in an energy storage system, in particular a capacitor, an organic transistor, or an electrostatic clutch.

[0122] Examples of a P(VDF-TrFE-VC) according to the invention

[0123] A first monomer mixture Mi, consisting of 436 g of VDF, 239 g of TrFE, and 4.3 g of VC, i.e., with a composition [Xi;Yi] = [70.0 mol%; 0.7 mol%], was introduced at room temperature into a stirred reactor containing 2.0 kg of demineralized water. Methylhydroxypropyl cellulose was then used to facilitate the suspension of the monomer mixture Mi in the water.

[0124] The monomer suspension was then heated to 65°C. Once this temperature was reached, 5.1 g of polymerization initiator (dipropyl peroxydicarbonate) was introduced into the reactor. The pressure in the reactor reached 90 bar before polymerization began. Polymerization initiation can be detected by a decrease in reactor pressure due to monomer consumption. From the moment polymerization began, a C2 composition of VDF, TrFE, VC with [X2; Y2] = [68.1 mol%; 7.0 mol%] was continuously injected to maintain a pressure of approximately 90 bar in the reactor.

[0125] The reaction was stopped by cooling the reactor after the introduction of 265 g of the secondary mixture. The polymerization reaction lasted 7.0 hours. The polymer produced was washed with demineralized water. The polymer obtained is a P(VDF-TrFE-VC) with a molar composition [X;Y] of [65.9 mol%; 4.7 mol%] and a weight-average molar mass Mw greater than 200,000 g / mol.

[0126] Example 2 (invention)

[0127] Example 2 was carried out under the same conditions as Example 1, but with the proportions [Xi;Yi] and [X2;Y2] modified. In this example, the first monomer mixture Mi of VDF, TrFE, VC has the composition [X1;Yi] = [67.5 mol%; 1.1 mol%] and the composition C2 of VDF, TrFE, VC has the composition [X2;Y2] = [67.5 mol%; 7.3 mol%]. The polymerization reaction lasted 7.0 hours. The resulting polymer is a P(VDF-TrFE-VC) with a molar composition [X;Y] of [65.0 mol%; 9.1 mol%] and a weight-average molar mass Mw greater than 200,000 g / mol.

[0128] Example 3 (invention)

[0129] Example 3 was carried out under the same conditions as Example 1, but with the proportions [X1;Yi] and [X2;Y2] modified. In this example, the first monomer mixture M1 of VDF, TrFE, VC has the composition [X1;Yi] = [70.0 mol%; 2.5 mol%] and the composition C2 of VDF, TrFE, VC has the composition [X2;Y2] = [68.1 mol%; 9 mol%]. The polymerization reaction lasted 7.0 hours. The resulting polymer is a P(VDF-TrFE-VC) with a molar composition [X;Y] of [68.0 mol%; 11.9 mol%] and a weight-average molar mass Mw greater than 200,000 g / mol.

[0130] Comparative example 1a: Synthesis of a P(VDF-TrFE-CTFE), using the same type of polymerization, and with the same average molar chemical composition of VDF, TrFE and termonomer

[0131] A first monomer mixture consisting of 378 g of VDF and 234 g of TrFE (VDF molar ratio to the total number of moles of VDF and TrFE equal to 65.5 mol%) was introduced at room temperature into a stirred reactor containing 2.5 kg of demineralized water. Methylhydroxypropyl cellulose was then used to facilitate the suspension of the first monomer mixture in the water. The monomer suspension was then heated to 50°C. Once this temperature was reached, 4.2 g of a polymerization initiator (dipropyl peroxydicarbonate) was added to the reactor. The pressure in the reactor reached 90 bar before polymerization began. The initiation of polymerization can be detected by a decrease in pressure in the reactor due to monomer consumption.From the start of polymerization, a mixture of VDF, TrFE and CTFE with a molar composition of [VDF / (VDF+TrFE) ; CTFE / (VDF+TrFE+CTFE) ] = [65.5%mol ; 9.0%mol] was continuously injected so as to maintain a pressure in the reactor essentially equal to 90 bars.

[0132] The reaction was stopped by cooling the reactor after the introduction of 650 g of the secondary mixture. The polymer produced was washed with demineralized water.

[0133] The polymer obtained is a P(VDF-TrFE-CTFE) with a molar chemical composition [VDF / (VDF+TrFE) ; CTFE / (VDF+TrFE+CTFE) ] = [66.0 %mol ; 4.5 %mol], the unit contents resulting from the polymerization of VDF, TrFE and CTFE being determined by NMR.

[0134] Comparative example 1b: Synthesis of a P(VDF-TrFE) according to the prior art with the same average molar chemical composition VDF / (VDF / TrFE)

[0135] A first monomer mixture consisting of 378 g of VDF and 234 g of TrFE (molar ratio of VDF to the total number of moles of VDF and TrFE equal to 65.0 mol%) was introduced at room temperature into a stirred reactor containing 2.6 kg of demineralized water. Methylhydroxypropyl cellulose was then used to facilitate the suspension of the monomer mixture Mi in the water.

[0136] The monomer suspension was then heated to 52°C. Once this temperature was reached, 1.8 g of polymerization initiator (dipropyl peroxydicarbonate) was introduced into the reactor. The pressure in the reactor reached 90 bar before polymerization began. Polymerization initiation can be detected by a decrease in reactor pressure due to monomer consumption. From the moment polymerization began, demineralized water was continuously injected to maintain a pressure of approximately 90 bar in the reactor. The reaction was stopped by cooling the reactor after the introduction of 380 kg of water. The resulting polymer was washed with demineralized water.

[0137] The polymer obtained is a P(VDF-TrFE) having a molar chemical composition in VDF units relative to VDF and TrFE units equal to 65.3%mol, as determined by NMR.

[0138] Characterizations

[0139] Differential scanning calorimetry (DSC) analyses were performed on a Mettler Toledo apparatus equipped with an internal cooler and operating under a nitrogen (N2) flow on the example and comparative polymers.

[0140] The thermal measurement procedure consists of two successive thermal cycles, each cycle consisting of:

[0141] - an isothermal period of 5 min at -50°C;

[0142] - a temperature increase at 10°C / min up to 250°C;

[0143] - an isothermal period of 5 minutes at 250°C;

[0144] - a temperature cooling at 10°C / min down to -50°C, marking the end of a cycle.

[0145] The table below shows the peak values ​​of the Curie temperature (Tcurie(°C), solid-solid transition) and the melting temperature (Tf (°C), solid-solid transition), measured in second heating for the different polymers.

[0146] [Table 1]

[0147] The P(VDF-TrFE-VC) polymer according to the invention therefore has thermal properties almost identical to those of a P(VDF-TrFE-CTFE) having a comparable molar chemical composition in VDF, TrFE, and termonomer. This differs from the findings of the second prior art document, CHUNG et al. (2002), cited above. Indeed, that document shows a P(VDF-TrFE-VC) having a melting point approximately 5°C higher and a Curie temperature approximately 5°C lower compared to the P(VDF-TrFE-CTFE) having a similar chemical composition in VDF, TrFE, and termonomer, and obtained by the same bulk polymerization process at room temperature by adding all the monomers initially.

[0148] Table 2 below compares the thermal characterizations of Examples 2 and 3 according to the invention with respect to Test III-2 of the third prior art document CHUNG & AL. (2003) and Test C-1 of the second prior art document CHUNG & AL. (2002).

[0149] [Table 2] In view of the thermal characterizations presented in Table 2 comparing two polymers manufactured according to a process of the invention and two prior art polymers having chemical compositions similar to those of the polymers according to the invention, it is noteworthy that the polymers according to the invention are different from those of the prior art.

[0150] To evaluate the electroactive properties of polymers, polymer films were prepared from a 14 wt% solution in methyl ethyl ketone filtered to 0.2 µm. The solution was coated onto a glass plate and allowed to dry for 12 hours. The films were then detached from the surface and placed in a vacuum oven at 80°C for 4 hours to evaporate the solvent. The films were subsequently placed in an oven for 1 hour at 15°C below the polymer's melting point, as measured by differential scanning calorimetry.

[0151] Polarization hysteresis was measured on the films by recording several polarization hysteresis cycles at 25°C with an alternating electric field (sinusoidal signal with a period of 18 s) of maximum amplitude equal to 150 V / pm.

[0152] Coercive field values ​​(E c , V.prrr 1 ), maximum polarization (Pmax, mC.m' 2) and remanent polarization (Pr, mC.nr 2 ) polarization hysteresis was identified on hysteresis loops of the type shown in Figure 1, and was compiled in the table below.

[0153] [Table 3]

[0154] The P(VDF-TrFE-VC) polymer according to the invention therefore has electroactive properties resembling in some aspects P(VDF-TrFE-CTFE) having a comparable molar chemical composition in VDF, TrFE and termonomer, and in other aspects P(VDF-TrFE) having a comparable chemical composition in VDF / (VDF+TrFE).

[0155] More specifically, like P(VDF-TrFE-CTFE), P(VDF-TrFE-VC) according to the invention has a thinned hysteresis cycle, characterized by lower Prêt Ec values ​​compared to P(VDF-TrFE), indicating a tendency towards ferroelectric-relaxer properties.

[0156] Moreover, like P(VDF-TrFE), P(VDF-TrFE-VC) has a high Pmax value, indicating greater polarization of the dipoles than for P(VDF- TrFE-CTFE) in a given field.

[0157] Dielectric permittivity measurements were performed at a low field (1V) on unpolarized films using a Novocontrol instrument, marketed by Novocontrol Technologies, equipped with the Alpha-A analyzer and a Peltier-based Heat / Cool System PHECOS chamber for temperature control. Measurements were taken at 1 kHz at various temperatures between -20°C and 110°C.

[0158] The table below compiles the maximum relative permittivity measurements (£max, unitless), and the temperature at which these permittivities were measured (T, °C).

[0159] [Table 4]

[0160] The P(VDF-TrFE-VC) polymer according to the invention has a higher maximum dielectric permittivity compared to P(VDF-TrFE-CTFE) having a comparable molar chemical composition of VDF, TrFE, and termonomer, as well as compared to P(VDF-TrFE) having a comparable chemical composition of VDF / (VDF+TrFE). Furthermore, like P(VDF-TrFE-CTFE), P(VDF-TrFE-VC) exhibits a maximum permittivity at a relatively low temperature, which is lower than the temperature at which the maximum dielectric permittivity of P(VDF-TrFE) has a comparable chemical composition of VDF / (VDF+TrFE) is reached. This allows the terpolymers according to the invention to be used for their high dielectric permittivity at temperatures close to room temperature.

Claims

Demands 1. A process for manufacturing a P(VDF-TrFE-VC) polymer by polymerizing vinylidene fluoride, VDF, trifluoroethylene, TrFE, and vinyl chloride, VC, said process comprising: - the injection into a reactor of an initial composition Ci essentially consisting of, or consisting of, VDF, TrFE, and optionally VC, to form a mixture of monomers Mi, where Yi represents the molar proportion, expressed as a percentage, of VC monomer relative to the total number of moles of VDF, TrFE, and VC monomers in the composition Ci, the initiation of the polymerization of the Mi monomer mixture; and, - the continuation of polymerization at a substantially constant pressure in the reactor, by injection into the reactor of VDF, TrFE and VC monomers of composition C2, and optionally by injection of an inert fluid, where Y2 represents the molar proportion, expressed as a percentage, of VC monomer relative to the total number of moles of VDF, TrFE and VC monomers in composition C2, Y2 being strictly greater than Y1.

2. A process according to claim 1 wherein the P(VDF-TrFE-VC) has a composition specified in C P in the repeating units resulting from the polymerization of VDF, TrFE and VC, where Y P represents the target molar proportion, expressed as a percentage, in units resulting from the polymerization of VC relative to the total number of moles in units resulting from the polymerization of VDF, TrFE and VC in composition C P said process being characterized in that the ratio Y1 to Y Pis greater than or equal to 0 and strictly less than 1, and the ratio Y2 to Y P is greater than or equal to 1.

3. A method according to claim 2, characterized in that the ratio Y1 to Y P is greater than or equal to 0.

05.

4. A method according to any one of claims 2 and 3, characterized in that the ratio Yi to Y P is less than or equal to 0.

85.

5. A method according to any one of claims 2 to 4, characterized in that Y P ranges from 0.1% to 20.0%.

6. A method according to any one of claims 2 to 5, wherein X P represents the target molar proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in composition C P characterized in that X Pis worth from 30.0% to 100%, preferably from 45.0% to 90.0%, and even more preferably from 50.0% to 80.0%.

7. Method according to claim 6, where Xi represents the molar proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition Ci, where X2 represents the molar proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition C2, the parameter AX1 is calculated as follows: [Math 6] The AX2 parameter is calculated as follows: [Math 7] said process being characterized in that: AX1 satisfies the following inequality: -10.0 < AX1 < 10.0; and / or AX2 satisfies the following inequality: -10.0 < AX2 < 10.

0.

8. A method according to any one of claims 1 to 7, wherein the polymerization carried out is a suspension polymerization or a Emulsion polymerization, and preferably suspension polymerization.

9. A process according to claim 8, wherein the polymerization carried out is a suspension polymerization, an aqueous solution or water being used as the suspension liquid.

10. A process according to any one of claims 1 to 9, wherein the continuation of polymerization is carried out without injection of inert fluid in order to maintain a substantially constant pressure in the reactor.

11. A process according to any one of claims 1 to 10, characterized in that the total polymerization time is strictly less than 48 hours, preferably strictly less than 24 hours, and preferably less than or equal to 12 hours.

12. Polymer P(VDF-TrFE-VC) capable of being obtained by the process according to any one of claims 1 to 11, having a chemical composition C in repeating units resulting from the polymerization of VDF, TrFE and VC, where X represents the mole proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in composition C and, where Y represents the mole proportion, expressed as a percentage, in units resulting from the polymerization of VC relative to the total number of moles in units resulting from the polymerization of VDF, TrFE and VC in composition C, characterized in that the parameter X satisfies the inequality: 30 < X ​​< 100, and the parameter Y satisfies the inequality 0.1 < Y ​​< 20.

0.

13. Polymer according to claim 12, characterized in that: Y > 0.

5.

14. Polymer according to any one of claims 12 and 13, characterized in that: Y < 15.

0.

15. Polymer according to any one of claims 12 to 14, characterized in that Y satisfies the following inequality: 3.0 < Y < 6.

0.

16. Polymer according to any one of claims 12 to 15, having a weight average molar mass Mw greater than or equal to 50,000 g / mol, preferably greater than or equal to 100,000 g / mol, and more preferably greater than or equal to 200,000 g / mol.

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