Triblock polymer having a central block that is a statistical copolymer of a branched diene and ethylene and two terminal blocks, respectively polystyrene and polyvinylpyridine.

Abstract

The invention relates to a triblock polymer of formula ABC in which the symbol A represents a polystyrene block, the symbol B represents a random copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' represents a hydrocarbon chain having 3 to 20 carbon atoms, and the symbol C represents a polyvinylpyridine block, the styrene units of block A being present in the triblock polymer in a molar content of less than 15% of the repeating units constituting the triblock polymer, the vinylpyridine units of block C being present in the triblock polymer in a molar content of less than 5% of the repeating units constituting the triblock polymer, the triblock polymer having a Mooney viscosity ML(1+4) at 100°C greater than 30. The invention also relates to its synthesis process and a rubber composition containing it and intended for use in particular in a tire.

Description

Title of the invention: Triblock polymer having a central block statistical copolymer of a branched diene and ethylene and two terminal blocks, respectively polystyrene and polyvinylpyridine.

[0001] The field of the present invention is that of copolymers containing units of a branched 1,3-diene and ethylene units.

[0002] The Applicant has described statistical copolymers of ethylene and a branched 1,3-diene such as myrcene or [3-farnesene] in patent applications WO 2019180356 Al and WO 2020074804 Al, as well as copolymers of ethylene and 1,3-butadiene for example in patent application WO 2014114607 AL. The former, which differ from the latter by the branched structure of the 1,3-diene, may prove more suitable in certain applications because of their lower stiffness.

[0003] These copolymers, both the first and second types, are prepared by polymerizing a mixture of ethylene and a 1,3-diene, the 1,3-diene being a branched 1,3-diene for the first type and 1,3-butadiene for the second. Once synthesized, the copolymers undergo a series of operations after which they are generally baled. Among these operations are the finishing steps of spinning and drying the copolymers. Spinning, which aims to remove most of the water from the copolymers, is generally carried out in an extrusion machine called an "expeller"; drying, which allows the copolymers to be recovered with an even lower moisture content and in accordance with specifications, takes place in another extrusion machine called an "expeller".

[0004] The Applicant observed that carrying out these finishing steps was more challenging for the first copolymers than for the second, and could result in decreased productivity in the finishing steps. The Applicant attributes the difficulties encountered in the finishing steps of the first copolymers to the excessively low Mooney viscosity values ​​of the first copolymers. Therefore, there is a need to increase the Mooney viscosity of the first copolymers.

[0005] One of the methods known to those skilled in the art for increasing their Mooney viscosity is to increase their number-average molar mass by decreasing the ratio between the number of moles of organomagnesium compound and the number of moles of neodymocene used in the polymerization reaction. Even if the reactor is cleaned, placed under an inert atmosphere, and the solvents and monomers are purified before being brought into contact with the catalytic system, impurities such as water and carbon dioxide may still be present. Carbon and oxygen can be present in the polymerization reactor containing the polymerization solvent and monomers. These impurities can react with the organomagnesium compound upon its introduction into the polymerization reactor, thereby altering the Mg / Nd molar ratio, the ratio between the number of moles of organomagnesium compound and the number of moles of Nd. For a given neodymium content, the variation in the Mg / Nd molar ratio with the impurity content is greater when this molar ratio is low, which can lead to less precise control of the process in achieving the target Mn of the polymer to be synthesized. Consequently, there is a need to find an alternative solution to increase the Mooney viscosity of the copolymers.

[0006] The inventors discovered that replacing a statistical copolymer of ethylene and a branched 1,3-diene with a triblock polymer having the statistical copolymer as its central block and two terminal blocks, one a polystyrene, the other a polyvinylpyridine in given molar proportions, makes it possible to solve the problem mentioned.

[0007] The inventors also discovered that replacing a statistical copolymer of ethylene and a branched 1,3-diene with a triblock polymer according to the invention in a rubber composition comprising a reinforcing filler and a crosslinking system leads to a very significant increase in the high-temperature hysteresis, 100°C, of ​​the rubber composition. Substituting elastomers in the rubber composition is beneficial for improving the dry grip of a tire comprising the rubber composition in its tread.

[0008] Thus, a first object of the invention is a triblock polymer of formula ABC in which the symbol A represents a polystyrene block, the symbol B represents a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, and the symbol C represents a polyvinylpyridine block, the styrene units of block A being present in the triblock polymer in a molar content of less than 15% of the repeating motifs constituting the triblock polymer, the vinylpyridine units of block C being present in the triblock polymer in a molar content of less than 5% of the repeating motifs constituting the triblock polymer, the triblock polymer having a Mooney viscosity ML(l+4) at 100°C greater than 30.

[0009] A second object of the invention is a rubber composition comprising a triblock polymer according to the invention, a reinforcing filler and a crosslinking system.

[0010] A third object of the invention is a tire which includes a tread, which tire includes a rubber composition according to the invention, preferably in its tread.

[0011] Another object of the invention is a process for synthesizing a triblock polymer of formula ABC according to the invention, A representing a polystyrene block, B representing a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, C representing a polyvinylpyridine block, which process comprises, in the presence of a catalytic system based at least on a metallocene of formula (I) and an organomagnesium compound of formula (II), the statistical copolymerization of a monomer mixture of ethylene and the branched 1,3-diene, followed by the homopolymerization of a vinylpyridine, P(CpîCp2) Nd(BH4{uyjliy(THfy (I) R-Mg-A (II) Cp1 and Cp2, whether identical or different, being chosen from the group consisting of cyclopentadienyl groups and fluorenyl groups, the groups being substituted or not, Partiting a group bridging the two groups Cp1 and Cp2 and representing a ZR*R2 group, Z representing a silicon or carbon atom, R1 and R2, identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl, y, an integer, being equal to or greater than 0, x, an integer or not, being equal to or greater than 0, R comprising a benzene ring of which two carbon atoms are substituted, one of the two is substituted by a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in ortho position with respect to each of said two carbon atoms, the symbol A in formula (II) representing the polystyrene block constituting the triblock polymer according to the invention, in other words a polystyrene chain identical to the polystyrene block, block A, of formula ABC. Description of the implementation methods

[0012] Any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​greater than "a" and less than "b" (i.e., excluding bounds a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from "a" to "b" (i.e. including the strict bounds a and b).

[0013] The compounds mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already used, that is to say, they may be partially or totally derived from a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0014] The polymer according to the invention is a triblock polymer whose essential characteristic is having a Mooney viscosity ML(1+4) at 100°C greater than 30. Below a Mooney viscosity value of 30 or less, the finishing steps become difficult, as mentioned previously. Preferably, the triblock polymer has a Mooney viscosity ML(1+4) at 100°C greater than or equal to 40. A viscosity value ML(1+4) at 100°C greater than 40 further facilitates the finishing steps. The viscosity ML(1+4) at 100°C of the triblock polymer is advantageously less than 70. If the viscosity ML(1+4) at 100°C is greater than or equal to 70, the polymer may overheat during the finishing steps, and this overheating may result in partial degradation of the polymer.

[0015] The block represented by the symbol B in formula ABC and hereafter referred to as "block B" constitutes the central block of the triblock polymer. Block B is a statistical copolymer of ethylene and a branched 1,3-diene, meaning that the monomer units constituting block B are statistically distributed within block B. The two other blocks represented by A and C, hereafter referred to as block A and block C, constitute the terminal blocks of the triblock polymer. Block A and block C are homopolymers, respectively a polystyrene and a polyvinylpyridine.

[0016] In a known manner, an ethylene unit is understood to be a unit whose motif is -(CH2 -CH2)-. The ethylene units of block B, referred to as the central block, preferably represent more than 50% by mole of the repeating motifs constituting block B. In the present application, the proportion of ethylene units in block B, namely the number of moles of ethylene units in block B, is expressed as a mole percentage relative to the number of repeating motifs constituting block B. More preferably, the ethylene units of block B represent more than 60% by mole of the repeating motifs constituting block B. More preferably, the ethylene units of block B represent at least 70% by mole of the repeating motifs constituting block B.

[0017] According to a particular embodiment of the invention, the ethylene units in block B represent less than 90% by mole of the units that constitute block B, in which case the central block contains less than 90% by mole of ethylene units.

[0018] According to another particular embodiment of the invention, the ethylene units in the central block represent at most 85% by mole of the units that constitute the central block, in which case the central block contains at most 85% by mole of ethylene units.

[0019] According to the invention, "a branched 1,3-diene" means one or more branched 1,3-dienes. Suitable branched 1,3-dienes include, for example, myrcene, [3-farnesene, or a mixture thereof. The branched 1,3-diene is preferably myrcene, [3-famesene, or a mixture of myrcene and [3-farnesene]. Preferably, the expression "a branched 1,3-diene" refers to a single compound, that is, a single branched 1,3-diene. The branched 1,3-diene is more preferably myrcene.

[0020] Since the branched 1,3-diene useful for the purposes of the invention is a substituted 1,3-diene, the 1,3-diene can give rise to monomeric units of configuration 1,2 represented by formula (1), of configuration 3,4 represented by formula (2), and of configuration 1,4 whose trans form is represented below by formula (3). Preferably, the units of branched 1,3-diene in configuration 1,2 and the units of 1,3-diene in configuration 3,4 represent more than 50% by mole of the 1,3-diene units. When block B contains units of branched 1,3-diene that are more than 50% by mole of the units of configuration 1,2 or 3,4, the remainder to 100% of the units of branched 1,3-diene is preferably units of configuration 1,4-trans. W (2) (3)

[0021] According to the invention, block B is a statistical copolymer of ethylene and branched 1,3-diene, in which case the monomer units of block B are those resulting from the copolymerization of the only two monomers, namely ethylene and branched 1,3-diene, and are statistically distributed in block B.

[0022] The central block has a glass transition temperature (Tg) preferably between -90°C and -40°C, more preferably between -70°C and -50°C. The glass transition temperature of the central block can be adjusted, for example, by the chemical structure of the branched 1,3-diene, with the respective proportions of ethylene units and branched 1,3-diene units in block B.

[0023] Block B has a number-average molar mass, Mn, preferably greater than 100,000 g / mol. Block B has a number-average molar mass preferably less than 200,000 g / mol. Advantageously, block B has a number-average molar mass ranging from over 100,000 g / mol to under 200,000 g / mol. The block represented by the symbol A in formula ABC, and hereafter referred to as block A, has the essential characteristic of being a polystyrene. Preferably, block A represents linear polystyrene. Preferably, block A is atactic polystyrene. The A-block styrene units are present in the triblock polymer at a molar content of less than 15% of the repeating units constituting the triblock polymer. With a molar content of A-block styrene units below 15%, the triblock polymer exhibits elastomeric properties. Above 15%, the polymer begins to lose its elastomeric properties, and the finishing steps become problematic. The A-block styrene units are present in the triblock polymer at a molar content preferably greater than 2% of the repeating units constituting the triblock polymer. Preferably, block A has a number-average molar mass greater than 3,000 g / mol and less than or equal to 30,000 g / mol.

[0024] The block represented by the symbol C in the ABC formula and hereinafter referred to as block C has the essential characteristic of being a polyvinylpyridine. The vinylpyridine units of block C are present in the triblock polymer at a molar content of less than 5% of the repeating units constituting the triblock polymer. Vinylpyridine unit contents of block C greater than or equal to 5% lead to an increase in the rigidity of the triblock polymer, and the finishing steps become more difficult. The vinylpyridine units of block C are present in the triblock polymer at a molar content preferably greater than 0.1% of the repeating units constituting the triblock polymer. The vinylpyridine may be 4-vinylpyridine, 2-vinylpyridine, or a mixture thereof. Preferably, block C has a number-average molar mass of less than 10,000 g / mol.More preferably, block C has a number-average molar mass greater than 100 g / mol and less than 10,000 g / mol.

[0025] The triblock polymer according to the invention can be prepared according to a process, which includes the statistical copolymerization of a monomer mixture of ethylene and branched 1,3-diene in the presence of a catalytic system, followed by the subsequent polymerization of vinylpyridine.

[0026] The catalytic system (or catalytic composition) used in the statistical copolymerization of the monomer mixture and in the homopolymerization of vinylpyridine is based on at least one metallocene of formula (I) and one organomagnesium compound of formula (II) P^'Cp^p2) Nd(BH4hi+y> Liy (THF)x (!) R-Mg-A (II) Cp1 and Cp2, whether identical or different, being chosen from the group consisting of cyclopentadienyl groups and fluorenyl groups, the groups being substituted or not, Partiting a group bridging the two groups Cp1 and Cp2 and representing a ZR*R2 group, where Z represents a silicon or carbon atom, R1 and R2, identical or different, each represent an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl group, y, an integer, being equal to or greater than 0, x, an integer or not, being equal to or greater than 0 R comprising a benzene nucleus of which two carbon atoms are substituted, one of the two is substituted by a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in ortho position with respect to each of said two carbon atoms. The symbol A in formula (II) represents the polystyrene block constituting the triblock polymer according to the invention, in other words a polystyrene chain identical to the polystyrene block, block A, of formula ABC.

[0027] In formula (I), the neodymium atom is bonded to a ligand molecule consisting of two groups, Cp1 and Cp2, linked together by the P-bridge. Preferably, the symbol P, designated as the bridge, has the formula ZR*R2, where Z represents a silicon atom, and R1 and R2, which may be identical or different, represent an alkyl group comprising from 1 to 20 carbon atoms. More preferably, the P-bridge has the formula SiR*R2, where R1 and R2 are identical and as defined above. Even more preferably, P has the formula SiMe2.

[0028] Examples of substituted cyclopentadienyl and fluorenyl groups include those substituted by alkyl groups having 1 to 6 carbon atoms, or by aryl groups having 6 to 12 carbon atoms, or by trialkylsilyl groups such as SiMe3. The choice among alkyl, aryl, and trialkylsilyl groups is also guided by the accessibility of the corresponding molecules, namely the substituted cyclopentadienes and fluorenes, because the latter are commercially available or easily synthesized.

[0029] Examples of substituted cyclopentadienyl groups include those substituted at position 2 (or 5) as well as at position 3 (or 4), particularly those substituted at position 2, more specifically the tetramethylcyclopentadienyl group. In the present application, in the case of the cyclopentadienyl group, position 2 (or 5) refers to the position of the carbon atom adjacent to the carbon atom to which the P-bridge is attached, as shown in the diagram below. P

[0030] Examples of substituted fluorenyl groups include those substituted at positions 2,7, 3, or 6, particularly the 2,7-ditertiobutyl-fluorenyl and 3,6-ditertiobutyl-fluorenyl groups. Positions 2, 3, 6, and 7 respectively designate the positions of the carbon atoms in the rings as shown in the diagram below, with position 9 corresponding to the carbon atom to which the P-bridge is attached.

[0031] Preferably, Cp1 and Cp2 are identical and are chosen from the group consisting of substituted fluorenyl groups and the fluorenyl group. Advantageously, in formula (I), Cp1 and Cp2 each represent a substituted fluorenyl group or a fluorenyl group, preferably a fluorenyl group. The fluorenyl group has the formula C[3H8]. Preferably, the metallocene has the formula (la), (Ib), (le), (Id), or (le), in which the symbol Flu represents the fluorenyl group of formula C[3H8]. [{Me2SÎFlu2Nd(p-BH4)2U(THF)h] (la) [Me2SiFlu2Nd(p-BHi)2Li(THF)] (Ib) [Me2SiF!u2Nd(p-BH4)(THF)] (the) [{Me2SiFlu2Nd(|i-BH4){THF)}2] (Id) [Me2SiFlu2Nd(p-BH4)] (the)

[0032] The metallocene used to prepare the catalytic system may be in the form of crystalline or non-crystalline powder, or in the form of single crystals. The metallocene may be in monomeric or dimeric form, these forms depending on the method of preparation of the metallocene, as described, for example in patent application WO 2007054224. Metallocene can be prepared conventionally by a process analogous to that described in patent application WO 2007054224, in particular by reacting the salt of an alkali metal of the ligand with a rare-earth borohydride under inert and anhydrous conditions in a suitable solvent, such as an ether, like diethyl ether or tetrahydrofuran, or any other solvent known to those skilled in the art. After the reaction, the metallocene is separated from the reaction byproducts by techniques known to those skilled in the art, such as filtration or precipitation in a second solvent. The metallocene is then dried and isolated in solid form.

[0033] As with any synthesis carried out in the presence of an organometallic compound, the synthesis of metallocene takes place under anhydrous conditions in an inert atmosphere. Typically, the reactions are conducted using solvents and anhydrous compounds under anhydrous nitrogen or argon.

[0034] The organomagnesium compound of formula (II) is used in the catalytic system as a co-catalyst. Preferably, the two substituents of said two carbon atoms with respect to which the magnesium atom is in the ortho position are identical. More preferably, they are methyl or ethyl. Advantageously, they are methyl.

[0035] Preferably, the organomagnesium compound of formula (II) corresponds to formula (11-1) in which A represents the polystyrene block, Ri and R5, identical or different, represent a methyl or an ethyl group, and R2, R3, and R4, identical or different, represent a hydrogen atom or an alkyl group. Preferably, Ri and R5 represent a methyl group. Preferably, R2 and R4 represent a hydrogen atom.

[0036] According to a preferred variant, Rb, R3, and R5 are identical. According to a more preferred variant, R2 and R4 represent a hydrogen atom, and Rh, R3, and R5 are identical. In a further preferred variant, R2 and R4 represent a hydrogen atom, and RB, R3, and R5 represent a methyl group.

[0037] The organomagnesium compound of formula (II) can be prepared by a process comprising the reaction of a living anionic polystyrene ALi with a halide of an organomagnesium compound of formula R-Mg-X, R being defined as in formula (II), A representing the polystyrene block, X being a halogen atom, preferably a A chlorine or bromine atom, more preferably a bromine atom, with the well-known symbol Li representing the lithium atom. Anionic polystyrene is commonly understood to be polystyrene prepared by anionic polymerization. Living polystyrene is also commonly understood to be polystyrene whose polymer chains possess a reactive center for polymerization, typically a carbon-lithium bond, particularly at the ends of the polymer chains.

[0038] Living anionic polystyrene is obtained conventionally by anionic polymerization of styrene in a solvent, referred to as the polymerization solvent. The polymerization solvent can be any hydrocarbon solvent known to be used in the polymerization of styrene. The polymerization solvent is preferably a hydrocarbon solvent, more preferably cyclohexane, methylcyclohexane, or toluene.

[0039] The ratio between the amount of solvent and the amount of styrene required for the formation of living anionic polystyrene is chosen by those skilled in the art according to the desired viscosity of the living polystyrene polymer solution. This viscosity depends not only on the concentration of the polymer solution, but also on many other factors such as the length of the polymer chains, the intermolecular interactions between the living polystyrene chains, the complexing power of the solvent, and the temperature of the polymer solution. Therefore, those skilled in the art adjust the amount of solvent on a case-by-case basis.

[0040] To initiate the polymerization of styrene, compounds well known to those skilled in the art can be used as initiators for the anionic polymerization of styrene. The initiator is, for example, a compound that has a carbon-lithium bond. Examples of initiators include organolithium compounds such as n-butyllithium, sec-butyllithium, and tert-butyllithium. The initiator is used at a rate chosen according to the desired chain length of the living polystyrene.

[0041] The polymerization temperature for forming living polystyrene can vary widely. Traditionally, it varies in a range from -20 to 100°C, preferably from 20 to 70°C.

[0042] To prepare the organomagnesium compound of formula (II), the reaction of anionic living polystyrene with the halide of an organomagnesium compound can be carried out by adding a solution of the anionic living polystyrene to a solution of the halide of an organomagnesium compound R-Mg-X, but it is preferably carried out by adding a solution of the halide of an organomagnesium compound R-Mg-X to a solution of the anionic living polystyrene. The solution of the anionic living polystyrene is generally a solution in a hydrocarbon solvent, preferably the polymerization solvent used for the synthesis of the anionic living polystyrene. The halide solution The solution of an organomagnesium compound R-Mg-X is generally a solution in an ether, preferably diethyl ether or dibutyl ether. The concentration of the living anionic polystyrene is preferably 0.01 to 1 mol of lithium equivalent (eq) / L, more preferably 0.05 to 0.2 mol of lithium equivalent / L, that of the solution of the organomagnesium compound R-Mg-X is preferably 1 to 5 mol / L, more preferably 2 to 3 mol / L.

[0043] The reaction between living anionic polystyrene and the halide of an organomagnesium compound R-Mg-X is typically carried out at a temperature ranging from 0°C to 60°C. Contact is preferably made at a temperature between 0°C and 23°C.

[0044] As with any synthesis carried out in the presence of organometallic compounds, the contacting and reaction take place under anhydrous conditions in an inert atmosphere. Typically, solvents and solutions are used under anhydrous nitrogen or argon. The various steps of the process are generally carried out under stirring.

[0045] Once the organomagnesium of formula (II) has been formed, the solution of the organomagnesium of formula (II) is typically stored before its use as a co-catalyst of the catalytic system in hermetically sealed containers, for example capped bottles, at a temperature between -25°C and 23°C, under an inert and anhydrous atmosphere.

[0046] The catalytic system can be prepared conventionally by a process analogous to that described in patent application WO 2007054224 or WO 2007054223. For example, the co-catalyst and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20 to 80°C for a time of 5 to 60 minutes. The amounts of co-catalyst and metallocene reacted are such that the ratio of the number of moles of Mg in the co-catalyst to the number of moles of rare-earth metal in the metallocene is preferably from 1 to 100, and more preferably from 1 to less than 10. The range of values ​​from 1 to less than 10 is particularly favorable for obtaining polymers with high molar masses. The catalytic system is usually prepared in a hydrocarbon solvent, aliphatic such as methylcyclohexane or aromatic such as toluene.Generally, after its synthesis, the catalytic system is used as is in the polymer synthesis process according to the invention.

[0047] The catalytic system is generally in the form of a solution in a hydrocarbon solvent. The hydrocarbon solvent can be aliphatic, such as methylcyclohexane, or aromatic, such as toluene. The hydrocarbon solvent is preferably aliphatic, and more preferably methylcyclohexane. Generally, the catalytic system is stored as a solution in the hydrocarbon solvent before being used in polymerization. This can then be referred to as A catalytic solution comprising the catalytic system and the hydrocarbon solvent. The concentration of the catalytic solution is typically defined by the metallocene content in the solution. The metallocene concentration preferably ranges from 0.0001 to 0.2 mol / L, and more preferably from 0.001 to 0.03 mol / L.

[0048] As with any synthesis carried out in the presence of an organometallic compound, the synthesis of the catalytic system takes place under anhydrous conditions in an inert atmosphere. Typically, the reactions are conducted using solvents and anhydrous compounds in anhydrous nitrogen or argon.

[0049] The catalytic system is used for the two polymerization steps: the statistical copolymerization of the monomer mixture and the subsequent homopolymerization of vinylpyridine. The two polymerization steps, that of the monomer mixture and that of vinylpyridine, are preferably carried out in solution, either continuously or batchwise, in a suitably stirred reactor. The polymerization solvent can be a hydrocarbon, aromatic, or aliphatic solvent. Examples of polymerization solvents include toluene and methylcyclohexane.

[0050] The catalytic system is generally introduced into the reactor containing the polymerization solvent and the monomer mixture containing ethylene and branched 1,3-diene. To achieve the desired macrostructure of the core block, those skilled in the art adjust the polymerization conditions, in particular the molar ratio of the organomagnesium compound to the Nd metal constituting the metallocene. The molar ratio can reach a value of 100, although a molar ratio below 10 is more favorable for obtaining polymers with high molar masses.

[0051] The preparation of the central block, block B, is carried out by the statistical copolymerization of the monomer mixture of ethylene and branched 1,3-diene. Preferably, a continuous addition of ethylene and branched 1,3-diene is made in the polymerization reactor, in which case the polymerization reactor is a fed reactor. This embodiment is particularly suitable for the statistical incorporation of ethylene and branched 1,3-diene.

[0052] The polymerization temperature generally varies in the range of 30 to 160°C, preferably from 30 to 120°C. During the preparation of block B, the temperature of the reaction medium is advantageously kept constant during copolymerization, and the total pressure in the reactor is also advantageously kept constant. The preparation of block B is completed by stopping the supply of monomers, in particular by dropping the reactor pressure, preferably to about 0.1 bar.

[0053] The preparation of the polyvinylpyridine block, block C, by the subsequent polymerization of vinylpyridine is carried out by adding vinylpyridine to the reactor. The vinylpyridine can be added to the reactor pure or diluted in a hydrocarbon solvent, preferably aliphatic such as methylcyclohexane. The vinylpyridine, pure or diluted, is introduced into the degassed reaction medium. The amount of vinylpyridine introduced into the reaction medium to be polymerized to form block C is adjusted by those skilled in the art according to the desired percentage of vinylpyridine in block form in the triblock polymer. It can vary, in particular, from 0.01 to 25 g per 100 g of block B formed, more particularly from 2 g to 25 g per 100 g of block B formed. The homopolymerization of the vinylpyridine is preferably carried out at the same temperature as the synthesis of block B.According to any one embodiment of the invention, the polymerization temperature for the synthesis of block C generally varies in the range of 30 to 160°C, preferably from 30 to 120°C. The synthesis of block C can typically be monitored by chromatographic analysis to track the consumption of vinylpyridine. The synthesis of block C is complete when block C reaches the desired number-average molar mass or when the conversion of the vinylpyridine polymerization reaction reaches the desired conversion, for example, 100%.

[0054] The synthesis of block C can be stopped by cooling the polymerization medium or by adding an alcohol, preferably an alcohol containing 1 to 3 carbon atoms, for example ethanol. The triblock polymer can be recovered using conventional techniques known to those skilled in the art, such as precipitation, evaporation of the solvent under reduced pressure, or steam stripping.

[0055] Alternatively, the triblock polymer can be prepared by another process which differs from that described in that the co-catalyst is not the organomagnesium of formula (II), but the living anionic polystyrene ALi and the molar ratio between the number of moles of living polymer and the number of moles of Nd atoms in the metallocene varies in a range from 0.8 to 1.2.

[0056] The triblock polymer is typically an elastomer and can be used in a rubber composition, another object of the invention.

[0057] The rubber composition may include any type of so-called reinforcing filler, known for its ability to strengthen a rubber composition usable for the manufacture of tires, for example an organic filler such as carbon black, a reinforcing inorganic filler such as silica combined with a known coupling agent, or a mixture of these two types of filler. Such a reinforcing filler typically consists of nanoparticles whose average size (by mass) is less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, in particular and more preferably between 20 and 150 nm. The reinforcing filler ratio is adjusted by a person skilled in the art according to the use of the rubber composition.

[0058] The crosslinking system may be based on sulfur, sulfur donors, peroxides, bismaleimides, or mixtures thereof. The crosslinking system is preferably a vulcanization system, that is, a system based on sulfur (or a sulfur-donating agent) and a primary vulcanization accelerator. Various known secondary accelerators or vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine), or known vulcanization retardants, may be added to this basic vulcanization system.

[0059] The rubber composition may also contain other additives known to be used in tire rubber compositions, such as plasticizers, anti-ozonants, antioxidants.

[0060] The rubber composition according to the invention is typically manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first thermomechanical working or mixing phase (so-called "non-productive" phase) at high temperature of the ingredients of the rubber composition with the exception of the crosslinking system, up to a maximum temperature between 130°C and 200°C, followed by a second mechanical working phase (so-called "productive" phase) down to a lower temperature, typically below 110°C, for example between 40°C and 100°C, a finishing phase during which the crosslinking system is incorporated.

[0061] After the incorporation of all the ingredients of the rubber composition, the final composition thus obtained can be calendered, for example in the form of a sheet or plate, in particular for characterization in the laboratory, or extruded, for example to form a rubber profile used as a rubber component or semi-finished product, in particular for the manufacture of a tire.

[0062] Thus, according to a particular embodiment of the invention, the rubber composition according to the invention, which can be either in the raw state (before crosslinking or vulcanization) or in the cured state (after crosslinking or vulcanization), is in a tire, for example in a tire tread.

[0063] Crosslinking (or curing), where applicable vulcanization, is carried out in a known manner at a temperature generally between 130°C and 200°C, for a sufficient time which can vary for example between 5 and 120 min depending in particular on the curing temperature, the crosslinking system adopted and the crosslinking kinetics of the composition considered.

[0064] The rubber composition according to the invention, which can be either in the raw state (before crosslinking or vulcanization) or in the cooked state (after crosslinking or vulcanization), can be used in a semi-finished article for pneumatics.

[0065] The tire, another object of the invention, which includes a tread, comprises the rubber composition according to the invention defined under any one of the embodiments of the invention, preferably in its tread.

[0066] In the present invention, the term "pneumatic" (in English, "tire") refers to a pneumatic or non-pneumatic tire. A pneumatic tire typically comprises two beads for contact with a rim, a crown consisting of at least one crown reinforcement and a tread, and two sidewalls. The tire is reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic tire, on the other hand, typically comprises a base, designed, for example, for mounting on a rigid rim, a crown reinforcement connecting to a tread, and a deformable structure, such as spokes, ribs, or dimples, this structure being arranged between the base and the crown. Such non-pneumatic tires do not necessarily include a sidewall. Non-pneumatic tires are described, for example, in documents WO 03 / 018332 and FR2898077.According to any one of the embodiments of the invention, the tire according to the invention is preferably a pneumatic tire.

[0067] In summary, the invention is preferably implemented according to any one of the following embodiments 1 to 25:

[0068] Mode 1: Triblock polymer of formula ABC in which the symbol A represents a polystyrene block, the symbol B represents a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, and the symbol C represents a polyvinylpyridine block, the styrene units of block A being present in the triblock polymer in a molar content of less than 15% of the repeating motifs constituting the triblock polymer, the vinylpyridine units of block C being present in the triblock polymer in a molar content of less than 5% of the repeating motifs constituting the triblock polymer, the triblock polymer having a Mooney viscosity ML(l+4) at 100°C greater than 30.

[0069] Mode 2: Triblock polymer according to mode 1 in which the ethylene units of block B represent more than 50% by mole of the repeating motifs constituting block B.

[0070] Mode 3: Triblock polymer according to any one of modes 1 to 2 in which the ethylene units of block B represent more than 60% by mole of the repeating motifs constituting block B.

[0071] Mode 4: Triblock polymer according to any one of modes 1 to 3 in which the ethylene units of block B represent at least 70% by mole of the repeating motifs constituting block B.

[0072] Mode 5: Triblock polymer according to any one of modes 1 to 4 in which the ethylene units of block B represent at most 85% by mole of the repeating motifs constituting block B.

[0073] Mode 6: Triblock polymer according to any one of modes 1 to 5 in which vinylpyridine is 4-vinylpyridine, 2-vinylpyridine or a mixture thereof.

[0074] Mode 7: Triblock polymer according to any one of modes 1 to 6 in which block B has a glass transition temperature between -90°C and -40°C.

[0075] Mode 8: Triblock polymer according to any one of modes 1 to 7 in which block B has a glass transition temperature between -70°C and -50°C.

[0076] Mode 9: Triblock polymer according to any one of modes 1 to 8 in which the branched 1,3-diene is myrcene or [3-farnesene or a mixture of myrcene and [3-farnesene.

[0077] Mode 10: Triblock polymer according to any one of modes 1 to 8 in which the branched 1,3-diene is myrcene.

[0078] Mode 11: Triblock polymer according to any one of modes 1 to 10 in which block A has a number-average molar mass greater than 3,000 g / mol and less than or equal to 30,000 g / mol.

[0079] Mode 12: Triblock polymer according to any one of modes 1 to 11 in which block C has a number-average molar mass of less than 10,000 g / mol.

[0080] Mode 13: Triblock polymer according to any one of modes 1 to 12 in which block B has a number-average molar mass greater than 100,000 g / mol.

[0081] Mode 14: Triblock polymer according to mode 13 in which block B has a number-average molar mass of less than 200,000 g / mol.

[0082] Mode 15: Triblock polymer according to any one of modes 1 to 14, which triblock polymer has a Mooney viscosity ML (1+4) at 100°C greater than or equal to 40.

[0083] Mode 16: Triblock polymer according to any one of modes 1 to 15, which triblock polymer has a Mooney viscosity ML (1+4) at 100°C of less than 70.

[0084] Mode 17: Triblock polymer according to any one of modes 1 to 16, in which the styrene units of block A are present in a molar content greater than 2% of the repeating motifs constituting the triblock polymer.

[0085] Mode 18: Triblock polymer according to any one of modes 1 to 17, in which the vinylpyridine units of block C are present in a molar content greater than 0.1% of the repeating motifs constituting the triblock polymer.

[0086] Mode 19: Rubber composition comprising a triblock polymer according to any one of modes 1 to 18, a reinforcing filler and a crosslinking system.

[0087] Mode 20: Tire which includes a tread, which tire includes a rubber composition defined in mode 19, preferably in its tread.

[0088] Mode 21: A process for synthesizing a triblock polymer of formula ABC defined in any one of modes 1 to 18, A representing a polystyrene block, B representing a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, C representing a polyvinylpyridine block, which process comprises, in the presence of a catalytic system based on at least one metallocene of formula (I) and an organomagnesium compound of formula (II), the statistical copolymerization of a monomer mixture of ethylene and the branched 1,3-diene, followed by the homopolymerization of a vinylpyridine, PjCp^p2) (THF)x (I) R-Mg-A (II) Cp1 and Cp2, whether identical or different, being chosen from the group consisting of cyclopentadienyl groups and fluorenyl groups, the groups being substituted or not, Partiting a group bridging the two groups Cp1 and Cp2 and representing a ZR*R2 group, Z representing a silicon or carbon atom, R1 and R2, identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl, y, an integer, being equal to or greater than 0, x, an integer or not, being equal to or greater than 0, R comprising a benzene ring of which two carbon atoms are substituted, one of the two is substituted by a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in ortho position with respect to each of said two carbon atoms, the symbol A in formula (II) representing the polystyrene block constituting the triblock polymer.

[0089] Mode 22: A process according to mode 21 in which the organomagnesium compound of formula (II) corresponds to formula (II-1) in which A represents the polystyrene block, Ri and R5, identical or different, represent a methyl or an ethyl, and R2, R3 and R4, identical or different, represent a hydrogen atom or an alkyl.

[0090] Mode 23: Method according to mode 22 in which Ri and R5 represent a methyl.

[0091] Mode 24: A method according to mode 22 or 23 in which R2 and R4 represent a hydrogen atom.

[0092] Mode 25: Method according to any one of modes 22 to 24 in which RB R3 and R5 are identical.

[0093] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of several examples of embodiments of the invention, given by way of illustration and not limitation. Examples

[0094] The designation EMR is used to designate a statistical copolymer of ethylene and myrcene; the designation VP is used to designate a homopolymer of 4-vinylpyridine; the designation PS is used to designate a homopolymer of styrene; the designation Mes is used to designate the mesityl group.

[0095] All reagents are commercially obtained except for the metallocene of formula [{Me2SiFlu2Nd(p-BH4)2Li(THF)}2] which is prepared according to the procedure described in document WO 2007054224. Styrene (Sigmal-Aldrich) is dried for 24 hours on CaH2 and then distilled under vacuum. The ethylene, of N35 grade, comes from the company Air Liquide and is used without prior purification. The myrcene, with a purity of 92.5% by weight, comes from the company DRT and is purified on an alumina column. 2-mesitylmagnesium bromide, at 1 mol / L in THF, comes from Sigma-Aldrich (2-mesitylmagnesium bromide). n-Butyl lithium (1.6 M in hexane, Sigma-Aldrich) is used as received. Also from Sigma-Aldrich are 4-vinylpyridine and sec-BuLi at 1.4 M in cyclohexane. 4-Vinylpyridine is purified according to the following procedure: 100 mL of 4-vinylpyridine (Sigma-Aldrich, 95% purity, containing 100 ppm hydroquinone) are placed in a Steinie bottle containing 30 g of alumina. The bottle is then capped and shaken for 30 minutes at room temperature (23°C) protected from light. BOMAG butyl methylmagnesium (20% by mass in heptane, C = 0.88 mol L *) comes from Lanxess and is stored in a metal cylinder under an inert atmosphere. The purified polymerization solvents (toluene, methylcyclohexane, cyclohexane) are purified through three alumina columns. The methylcyclohexane solvent from BioSolve is dried and purified on alumina columns in a solvent fountain from mBraun and used in an inert atmosphere. All reactions are carried out in an inert atmosphere (argon) in Steinie bottles and sealed, inert reactors.

[0096] Mooney viscosity measurement: To measure Mooney viscosity, an oscillating consistometer as described in ASTM D1646-2007 (Reapproved 2012) is used. The Mooney viscosity measurement is performed according to the following principle: the elastomer is molded in a cylindrical chamber heated to 100°C under pressure. After a one-minute preheating period, the rotor rotates within the specimen at 2 revolutions per minute, and the torque required to maintain this rotation is measured after 4 minutes of 8 rotations. Mooney viscosity (ML 1+4) is expressed in Mooney units (MU, with 1 MU = 0.83 Newton-meters). Nuclear magnetic resonance (NMR):

[0097] Nuclear magnetic resonance (NMR): Spectra were acquired on a Brüker Avance III 500 MHz spectrometer equipped with a 5 mm BBIz-grad "broadband" cryo-probe. Samples were solubilized in CDC13 chloroform. Calibration was performed on the protonated impurity of deuterated chloroform at 7.26 ppm by ¹H NMR. The quantitative ¹H NMR experiment used a single 30° pulse sequence and a 5-second repetition delay between each acquisition.

[0098] Nuclear magnetic resonance (NMR) (block polymer synthesis): Block polymers are solubilized in CDC13 chloroform. Calibration is performed on the protonated impurity of deuterated chloroform at 7.26 ppm by ¹H NMR. The quantitative ¹H NMR experiment uses a single 30° pulse sequence and a 5-second repetition delay between each acquisition. 64 to 256 accumulations are performed. Two-dimensional ¹H / ¹³C experiments are used to determine the unit structure of the polymers. The ¹H-¹³C HMBC (heteronuclear multiple bond correlation) experiment detects long-range correlations by J-coupling between protons and carbon-13 nuclei. The ¹H NMR spectra and the edited ¹H / ¹³C IJ HSQC 2D NMR correlation spectrum allow for the determination of the block polymer microstructure and the proportion of each block in the sample.

[0099] Determination of the percentage of block polymer by DOSY: The DOS Y experiment, an NMR method, allows for the analysis of complex mixtures and the detection of trace elements. The aim of this experiment is to demonstrate that the block polymer constitutes the majority of the sample and that the presence of homopolymer is very low. DOS Y NMR analysis allows the separation of species present, particularly polymer matrices, by analyzing their diffusion coefficient in solution. The principle of the technique is as follows: The DOS Y experiment consists of recording proton spectra by varying the applied gradient strength (G) and thus the diffusion strength. A linear increase in the gradient intensity will lead to an exponential decrease in the NMR signal intensity. The DOSY experiment will produce a two-dimensional map. The second dimension F2 of the DOSY corresponds, after processing by the Fourier transform, to the dimension 1H. The first dimension Fl corresponds to the decay of the NMR signal as a function of the applied gradient force. After processing the dimension F2, the diffusion coefficient is extracted from equation (1), and a DOSY map is obtained. I=I0.exp(-Dy2 G2 ô2 (A-ô / 3)) (1) If the two matrices have the same diffusion coefficient, this means that the two matrices have the same hydrodynamic radius and are therefore grafted. Conversely, if the two matrices have different diffusion coefficients, this means that they are free from each other. The equation that describes the diffusion coefficient is as follows: The experiment was conducted on samples of poly(styrene-b-poly(ethylene-co-myrcene) and poly(styrene-b-poly(ethylene-co-myrcene)-b-4-vinylpyridine) synthesized according to the process according to the invention. Recording two 1D 1H NMR spectra with a scattering filter, one with a magnetic field gradient set at 90% of the maximum power of the gradient amplifier and the other at 1% of this value, allows, by comparison with the 1H NMR spectrum, observation of the signal loss due to spatial scattering of molecules and magnetization relaxation. The signal loss due to scattering is then attributed to "small molecules" not bound to the polymer matrix (reagents, antioxidants, solvents, etc.).

[0100] High-temperature size exclusion chromatography (SEC-3D): The number-average molar mass (Mn), the weight-average molar mass (Mw), and the polydispersity index of the prepared polymers (hereinafter referred to as the sample) are Determined absolutely by triple-detection size exclusion chromatography (SEC-3D). Triple-detection size exclusion chromatography has the advantage of directly measuring mean molar masses without calibration. SEC / 3D analyses are performed on a WATERS system equipped with three mixed-BLS columns and Wyatt refractometric, differential viscometric, and light scattering detectors. Samples are prepared at a concentration of 5 g L⁻¹ in tetrahydrofuran, and analyses are carried out at 35°C at a flow rate of 1 mL min⁻¹. The mobile phase flow rate is µL / min. Data are acquired and processed using ASTRA software, and the dn / dc of ethylene-based copolymers is assumed to be 0.1000 by default.

[0101] Differential scanning calorimetry (DSC): The glass transition temperature (Tg) of the polymers is determined by differential scanning calorimetry (DSC). DSC analyses are performed on a DSC 3+ instrument (Mettler Toledo) with sealed aluminum crucibles (40 qL) and under a nitrogen flow (20 mL min⁻¹). Thermograms of homopolymers, diblock polymers, and triblock polymers are obtained according to the following program repeated three times: ramp from +180 °C to -80 °C at 10 °C min⁻¹, 5-min isotherm at -80 °C, ramp from -80 °C to +180 °C at 10 °C min⁻¹, 5-min isotherm at +180 °C.

[0102] Dynamic properties: Dynamic properties are measured according to ASTM D 5992-96 and ASTM D 1349-99. The tan(φ) values, denoted "tan(φ) 0 °C" and "tan(φ) 100 °C", are taken from a temperature sweep at 0.7 MPa at 0 °C and 100 °C, respectively. They indicate wet surface grip performance and dry surface grip performance, respectively: the higher the tan(φ) value, the better the corresponding grip performance. Polymer synthesis:

[0103] Example 1: Synthesis of an unfunctionalized EMR polymer (block B): In an 80 L reactor, 53 L of methylcyclohexane and 450 mL of a BOMAG solution in methylcyclohexane at a concentration of 0.0134 mol / L are added. The temperature in the reactor is raised to 80°C and the myrcene and ethylene monomers are injected at a controlled flow rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor.

[0104] The catalytic system (6.3 mmol of Ndcat, i.e., 4 g of Ndcat) is injected into the reactor at a concentration of 0.0062 mol / L in methylcyclohexane to initiate the polymerization reaction of ethylene and myrcene. The temperature The polymerization process is regulated at a temperature of 80°C, and the pressure in the reactor increases to 8 bar. The pressure in the reactor is maintained constant at 8 bar by feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97.

[0105] The conversion of the polymerization reaction is measured by dry extract, and when a mass of 5.3 kg of polymer is reached after 70 min of polymerization, the injection of monomers into the reactor is stopped. The weighed mass of copolymer, 5.3 kg after 70 min, allows the determination of the average catalytic activity of the catalytic system, expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol.h), of 726 kg / mol.h.

[0106] 550 mL of 1 mol / L ethanol are injected to stop the polymerization. 226 mL An antioxidant, Irganox 1520L at 218 g / L, is injected into the reactor. The reactor contents are transferred to another reactor, called the "stripping reactor," to remove the solvent by steam distillation while maintaining a temperature of 100°C. The copolymer is recovered and then dried for 48 hours in an oven at 60°C under vacuum and nitrogen purging.

[0107] The molar contents of ethylene and myrcene in block B are respectively 74% and 26%, percentages calculated with respect to the number of constituent motifs of block B.

[0108] The microstructure and macrostructure characteristics of the polymer are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of ethylene and myrcene units.

[0109] Example 2: synthesis of an EMR-Z?-VP diblock polymer (diblock of formula BC) Step 1816: Synthesis of the first block (block B): In an 80 L reactor, 53 L of methylcyclohexane and 450 mL of a BOMAG solution in methylcyclohexane at a concentration of 0.0134 mol / L are added. The temperature in the reactor is raised to 80°C and the myrcene and ethylene monomers are injected at a controlled rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor. The catalytic system (6.3 mmol of Nd, equivalent to 4 g of Nd) at a concentration of 0.0062 mol / L in methylcyclohexane is injected into the reactor to initiate the polymerization reaction of ethylene and myrcene. The polymerization temperature is regulated at 80°C, and the pressure in the reactor is increased to 8 bar. The pressure is maintained constant at 8 bar by continuously feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97. The conversion of the polymerization reaction is measured by dry extract, and when a mass of 5.9 kg of polymer is reached after 65 min of polymerization, the injection of monomers into the reactor is stopped. The molar contents of ethylene and myrcene in block B are 74% and 26%, respectively, percentages calculated relative to the number of constituent units of block B. The catalytic system is a preformed catalytic system. It is prepared in methylcyclohexane from the metallocene, [Me2Si(Flu)2Nd(q-BH4)2Li(THF)], the co-catalyst, butylloctylmagnesium (BOMAG), and a preforming monomer, 1,3-butadiene. It is prepared according to a preparation method conforming to paragraph II.1 of patent application WO 2017093654 A1: In a reactor containing 100 mL of the hydrocarbon solvent methylcyclohexane (MCH), the co-catalyst butylctylmagnesium (BOMAG) is added with a molar ratio of Mg / Nd = 2.2, followed by butadiene with a molar ratio of butadiene / Nd = 90. The metallocene [Me2Si(Flu)2Nd(q-BH4)2Li(THF)] is then added to the reaction medium (0.71 mmol). The preformation takes place at a temperature of 80°C for 5 h. The resulting catalytic solution is stored at -5°C before use.

[0110] 2 — step: synthesis of the second block (block C): 268 mL of a pure 4-vinylpyridine solution (5% mass of the target EMR copolymer mass) are then transferred under overpressure into the reactor. The temperature in the reactor is maintained at 80°C throughout the 4-vinylpyridine polymerization reaction (30 min). Then, 550 mL of 1 mol / L ethanol in methylcyclohexane is injected to stop the polymerization reaction. 226 mL of the antioxidant Irganox 1520L at 218 g / L in methylcyclohexane is injected into the reactor. The reactor contents are transferred to a separate reactor, called a "stripping reactor," to remove the solvent by steam stripping while maintaining a temperature of 100°C. The polymer is recovered and then dried for 48 hours in an oven at 60°C under vacuum and nitrogen purging. The weighed mass of polymer, 5.9 Kg, allows us to determine the average catalytic activity of the catalytic system expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol.h) during the first step (65 min), i.e. 924 Kg / mol.h. The micro- and macro-structural characteristics of the dibloc polymer are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of ethylene, myrcene, and 4-vinylpyridine units.

[0111] Example 3: Synthesis of a PS-e-EMR diblock polymer (diblock of formula AB) 1 — step: synthesis of the first block (block A) and transmetallation reaction In an 80 L reactor containing 11.5 L of cyclohexane and heated to 40°C, 1.2 L of 10.6 mol of styrene is introduced. Polymerization of the styrene is initiated by a 0.5 L solution of 55 mmol sec-butyllithium at a concentration of 0.11 mol / L in methylcyclohexane. The conversion of styrene is monitored by dry extract analysis, and 100% conversion is achieved after 37 min, yielding 1.1 kg of polystyrene. Once the living polystyrene (LPSI) is formed, a transmetallation reaction is carried out to form the PSMgMes species. For this purpose, 2-mesitylmagnesium bromide in toluene solution at a concentration of 0.1 mol / L (1 eq / L, 550 mL) is then injected into the 80 L reactor at a temperature of 40°C. The temperature in the reactor is maintained at 40°C for 10 min. Next, 39.1 L of cyclohexane is introduced into the polymerization reactor and the polymer solution is heated to 80°C in the reactor.

[0112] 2 — step: synthesis of the second block (block B): During the temperature rise of the polymer solution (up to 80°C), the myrcene and ethylene monomers are injected at a controlled rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor. The metallocene {Me2Si(Ci3H8)2Nd(BH4)2.Li(THF)}2(Nd cat) (6.3 mmol of Nd, or 4 g of Nd) is injected into the reactor in a solution of 500 mL of cyclohexane. The polymerization temperature is regulated at 80°C, and the pressure in the reactor is increased to 8 bar. The pressure in the reactor is maintained constant at 8 bar by feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97. The conversion of the polymerization reaction is measured by dry extract, and when the mass of 4.2 Kg corresponding to the formation of the second block is reached after 52 min of polymerization of ethylene and myrcene, the injection of monomers into the reactor is stopped. The mass weighed corresponding to the formation of the second block, 4.2 kg, allows us to determine the average catalytic activity of the catalytic system, expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol.h), as 794 kg / mol.h. The molar contents of ethylene and myrcene in block B are 74% and 26% respectively, percentages calculated in relation to the number of constituent units of block B. 550 mL of 1 mol / L ethanol are injected to stop the polymerization reaction. 226 mL of an antioxidant, Irganox 1520L at 218 g / L, are injected into the reactor. The contents of the reactor are then transferred to another reactor called the "stripping reactor." "to remove the solvent by steam distillation while maintaining a temperature of 100°C. The polymer is recovered and then dried on an extrusion line. The weighed mass of the resulting PS-e-EMR diblock is 5.3 kg." The micro- and macro-structural characteristics of the diblock are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of styrene, ethylene, and myrcene units.

[0113] Example 4: Synthesis of a triblock polymer PS-e-EMR-Z?-VP (triblock polymer of formula ABC) Step 1816: Synthesis of the first block (block A) and transmetallation reaction: In an 80 L reactor containing cyclohexane (11.5 L) and heated to 40°C, 1.2 L of styrene (10.6 mol) is introduced. The polymerization of styrene is initiated by a solution of sec-butyllithium (55 mmol, 0.5 L) at a concentration of 0.11 mol / L in methylcyclohexane. The conversion of styrene is monitored by dry extract, and 100% conversion is achieved after 35 min, yielding 1.1 kg of polystyrene. Once the living polystyrene (LPSI) is formed, a transmetallation reaction is carried out to form the PSMgMes species. For this purpose, 2-mesitylmagnesium bromide is injected in solution in toluene at a concentration of 0.5 mol / L (1 eq / Li, 122 mL) into the 80 L reactor at a temperature of 40°C. The temperature in the reactor is maintained at 40°C for 10 min. Next, 39.1 L of cyclohexane is introduced into the polymerization reactor and the polymer solution is heated to 80°C in the reactor.

[0114] 2 — step: synthesis of the second block (block B): During the temperature rise of the polymer solution (up to 80°C), the myrcene and ethylene monomers are injected at a controlled rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor. The metallocene {Me2Si(Ci3H8)2Nd(BH4)2.Li(THF)}2(Nd cat) (6.3 mmol of Nd, or 4 g of Nd) is injected into the reactor in a solution of 500 mL of cyclohexane. The polymerization temperature is regulated at 80°C, and the pressure in the reactor is increased to 8 bar. The pressure in the reactor is maintained constant at 8 bar by feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97. The conversion of the polymerization reaction is measured by dry extract, and when the mass of 4.2 Kg corresponding to the formation of the second block is reached after 47 min of polymerization of ethylene and myrcene, the injection of monomers into the reactor is stopped. The mass weighed corresponding to the formation of the second block, 4.2 kg, allows the determination of the average catalytic activity of the catalytic system, expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol.h), as 897 kg / mol.h. The molar contents of ethylene and myrcene in block B are 74% and 26% respectively, percentages calculated in relation to the number of constituent units of block B.

[0115] 3 — step: synthesis of the third block (block C): 268 mL of a pure 4-vinylpyridine solution (5% mass of the target PS-b-EMR block polymer mass, i.e. a target Mn of block C of 5500 g / mol) are then transferred by overpressure into the reactor. The temperature in the reactor is maintained at 80°C throughout the 4-vinylpyridine polymerization reaction (30 min). Then, 550 mL of 1 mol / L ethanol is injected to stop the polymerization reaction. 226 mL of the antioxidant Irganox 1520L at 218 g / L is injected into the reactor. The reactor contents are transferred to another reactor, called the "stripping reactor," to remove the solvent by steam distillation while maintaining a temperature of 100°C. The polymer is then recovered and dried on an extrusion line.

[0116] The weighed mass corresponding to the formation of the first two blocks is 5.3 kg. The micro-structural and macro-structural characteristics of the triblock are shown in Table 1. The rate of units is expressed as a molar percentage calculated relative to the total number of moles of styrene, ethylene and myrcene units.

[0117] Example 5: Synthesis of an EMR copolymer (block B) In an 80 L reactor, 53 L of methylcyclohexane and 450 mL of a BOMAG solution in methylcyclohexane at a concentration of 0.0357 mol / L are added. The temperature in the reactor is raised to 80°C and the myrcene and ethylene monomers are injected at a controlled rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor.

[0118] The catalytic system (7 mmol of Ndcat, i.e., 4 g of Ndcat) is injected into the reactor at a concentration of 0.0062 mol / L in methylcyclohexane to initiate the polymerization reaction of ethylene and myrcene. The polymerization temperature is regulated at 80°C, and the pressure in the reactor is increased to 8 bar. The pressure in the reactor is maintained constant at 8 bar by feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97.

[0119] The conversion of the polymerization reaction is measured by dry extract, and when the mass of 5.6 kg of polymer is reached after 63 min of polymerization, The injection of monomers into the reactor is stopped. The weighed mass of copolymer, 5.6 kg after 63 min, allows the determination of the average catalytic activity of the catalytic system expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol.h), of 762 kg / mol.h.

[0120] 550 mL of 1 mol / L ethanol are injected to stop the polymerization. 226 mL An antioxidant, Irganox 1520L at 218 g / L, is injected into the reactor. The reactor contents are transferred to another reactor, called the "stripping reactor," to remove the solvent by steam distillation while maintaining a temperature of 100°C. The copolymer is recovered and then dried for 48 hours in an oven at 60°C under vacuum and nitrogen purging.

[0121] The molar contents of ethylene and myrcene in block B are respectively 73% and 27%, percentages calculated with respect to the number of constituent motifs of block B.

[0122] The microstructure and macrostructure characteristics of the polymer are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of ethylene and myrcene units.

[0123] Example 6: Synthesis of a PS-e-EMR diblock polymer (diblock of formula AB) 1 — Step: Synthesis of the first block (block A) and transmetallation reaction. In an 80 L reactor containing cyclohexane (11.5 L) and heated to 40°C, 1.2 L of styrene (10.6 mol) is introduced. The polymerization of styrene is initiated by a solution of sec-butyllithium (55 mmol, 0.5 L) at a concentration of 0.11 mol / L in methylcyclohexane. The conversion of styrene is monitored by dry extract, and 100% conversion is achieved after 37 min, yielding 1.1 kg of polystyrene. Once the living polystyrene (PSLi) is formed, a transmetallation reaction is carried out to form the PSMgMes species. For this purpose, 2-mesitylmagnesium bromide in toluene solution at a concentration of 0.1 mol / L (1 eq / L, 550 mL) is then injected into the 80 L reactor at a temperature of 40°C. The temperature in the reactor is maintained at 40°C for 10 min. Next, 39.1 L of cyclohexane is introduced into the polymerization reactor and the polymer solution is heated to 80°C in the reactor.

[0124] 2 — step: synthesis of the second block (block B): During the temperature rise of the polymer solution (up to 80°C), the myrcene and ethylene monomers are injected at a controlled rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor. The metallocene {Me2Si(Ci3H8)2Nd(BH4)2.Li(THF)}2(Nd cat) (6.3 mmol of Nd, i.e., 4 g of Nd) is injected into the reactor in a solution in 500 mL of cyclohexane. The polymerization temperature is regulated at 80°C, and the pressure in the reactor increases to 8 bar. The pressure in the reactor is maintained constant at 8 bar by feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97. The conversion of the polymerization reaction is measured by dry extract, and when the mass of 4.2 Kg corresponding to the formation of the second block is reached after 52 min of polymerization of ethylene and myrcene, the injection of monomers into the reactor is stopped. The mass weighed corresponding to the formation of the second block, 4.2 kg, allows the average catalytic activity of the catalytic system, expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol.h), to be determined to be 959 kg / mol.h. The molar contents of ethylene and myrcene in block B are 74% and 26% respectively, percentages calculated in relation to the number of constituent units of block B. (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane (64 mmol, 4 eq / Mg) in methylcyclohexane solution at a concentration of 0.4 mol / L is then transferred under pressure into the reactor. The functionalization reaction is carried out at 80°C for 15 min, after which 550 mL of 1 mol / L ethanol is injected to stop the functionalization reaction. 226 mL of an antioxidant, Irganox 1520L at 218 g / L, is injected into the reactor. The contents of the reactor are transferred to another reactor, called the "stripping reactor," to remove the solvent by steam distillation while maintaining a temperature of 100°C. The copolymer is recovered and then dried for 48 hours in an oven at 60°C under vacuum and nitrogen purging. The weight of the resulting PS- / »-EMR diblock is 4.5 kg. The micro- and macro-structural characteristics of the diblock are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of styrene, ethylene, and myrcene units.

[0125] The microstructure and macrostructure characteristics of the diblock are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of styrene, ethylene and myrcene units.

[0126] The microstructure and macrostructure characteristics of the synthesized polymers are shown in Table 1 and Table 2. The rate of units is expressed as a molar percentage calculated relative to the total number of moles of styrene, ethylene, myrcene and 4-vinylpyridine units.

[0127] Table 1: Example Example 1 Example 2 Example 3 Example 4 EMR Polymer EMR-6-VP PS-e-EMR PS-e-EMR-Z?- VP Ethylene (%mol) 73 72.8 66 64.6 Styrene (%mol) 0 0 12 10.8 Myrcene (%mol) 27 25.6 22 22.4 4-Vinylpyridine (%mol) 0 1.6 0 2.2 Mn block PS (g / mol) - - 30000 25600 Dispersion block PS - - 1.01 1.03 Mn polymer (g / mol) 145700 174300 134000 151300 Dispersion polymer 1.3 1.43 1.36 1.24 ML polymer 16 26 32 49 Tg (°C) polymer -60 -65 -62 -64

[0128] Table 2: Example Example 5 Example 6 Polymer EMR PS-6-EMR Ethylene (%mol) 73 66 Styrene (%mol) 0 10 Myrcene (%mol) 27 24 4-Vinylpyridine (%mol) 0 0 Mn block PS (g / mol) - 23700 Dispersance block PS - 1.37 Mn polymer (g / mol) 163000 128700 Dispersance polymer 1.7 1.37 ML polymer 28 37 Tg (°C) polymer -64°C

[0129] The EMR elastomer, a statistical copolymer of ethylene and branched 1,3-diene, of Example 1, which nevertheless has a number average molar, Mn, of the same order of magnitude as that of the elastomers of Examples 2 and 3, has a Mooney viscosity much lower than 30, which suggests difficulties in the finishing steps of the elastomer.

[0130] The results of Example 4 show that the addition of two terminal blocks, respectively a polystyrene and a polyvinylpyridine, to an EMR chain makes it possible to significantly increase the Mooney viscosity, from 16 to 49. This increase in the Mooney viscosity to values ​​greater than 30, which makes it possible to facilitate the finishing steps of the polymer, is obtained without the glass transition temperature and the dispersity of the elastomer being significantly modified. Preparation of rubber compounds:

[0131] The rubber compositions are prepared according to the following procedure: Rubber compositions whose formulation, expressed in parts per hundred parts of elastomer (pce), is shown in Table 2 and Table 3, were prepared in an internal mixer into which the copolymer, the reinforcing filler, and the various other ingredients, with the exception of the vulcanizing system, are successively introduced. A thermomechanical process (non-productive phase) is then carried out in one step, lasting approximately 5 minutes in total, until a maximum "drop" temperature of 150°C is reached. The mixture thus obtained is recovered, cooled, and then sulfur and the accelerator are incorporated in a mixer (homo-finisher) at 40°C, with the mixture being blended (productive phase) for about ten minutes.The compositions thus obtained are then calendered either in the form of plates (2 to 3 mm thick) or thin sheets of rubber for the measurement of their physical or mechanical properties after vulcanization at 150°C. The applied curing time, T(99), is the time required for the torque of the compositions of the invention to reach 99% of the maximum torque of these compositions, i.e. 20 minutes.

[0132] (1) Polymer of Example 5 (2) Polymer of example 6 (3) Polymer of example 4 (4) "Zeosil 1165 MP" from Solvay-Rhodia in the form of micropearls, CTAB 160 m2 / g, precipitated silica (5) ASTM N234 Grade Carbon Black (6) “Su-640” resin from Kolon Industries (Tg= 83°C, 100% aliphatic, Mn 398 g / mol). (7) Liquid silane triethoxysilylpropyltetrasulfide (TESPT) “Si69” from the Evonik company (8) N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine “Santaflex 6PPD” from the company Flexys (9) Diphenylguanidine “Perkacit DPG” from Flexsys (10) Stearic acid “Pristerene 4931” from Uniqema (11) Industrial grade zinc oxide from Umicore (12) N-cyclohexyl-2-benzothiazol-sulfenamide “Santicure CBS” from Flexsys

[0133] Only compositions C3 and C6, which contain a block polymer according to the invention, in this case P3, are compositions according to the invention. These are the ones that exhibit the highest hysteresis at high temperature (100°C).

[0134] Table 3: Ingredients Composition C 1 Composition C 2 Composition C 3 Pl(l) 100 P2 (2) 100 P3 (3) 100 Silica (4) 86 86 86 N234 (5) 3 3 3 Plasticizing resin ( 6) 30 30 30 Si69 (7) 6.88 6.88 6.88 6PPD (8) 3.8 3.8 3.8 DPG (9) 1.72 1.72 1.72 Stearic acid (10) 3 3 3 ZnO(ll) 0.9 0.9 0.9 Soluble sulfur 0.9 0.9 0.9 CBS (12) 2.3 2.3 2.3 Properties at firing temperature tan(δ) 100°C 0.14 0.284 0.389 tan(ô) 0°C 0.607 0.399 0.518

[0135] Table 4: Ingredients Composition C 4 Composition C 5 Composition C 6 Pl(l) 100 P2 (2) 100 P3 (3) 100 Silica (4) 69 69 69 N234 (5) 3 3 3 Si69 (7) 5.52 5.52 5.52 6PPD (8) 3.8 3.8 3.8 DPG (9) 1.38 1.38 1.38 Stearic acid (10) 3 3 3 ZnO(ll) 0.9 0.9 0.9 Soluble sulfur 0.9 0.9 0.9 CBS (12) 2.3 2.3 2.3 Properties at δ δ 100°C 0.129 0.267 0.382 tan(δ) 0°C 0.346 0.29 0.228

Claims

Demands

1. Triblock polymer of formula ABC in which the symbol A represents a polystyrene block, the symbol B represents a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, and the symbol C represents a polyvinylpyridine block, the styrene units of block A being present in the triblock polymer in a molar content of less than 15% of the repeating units constituting the triblock polymer, the vinylpyridine units of block C being present in the triblock polymer in a molar content of less than 5% of the repeating units constituting the triblock polymer, the triblock polymer having a Mooney viscosity ML(l+4) at 100°C greater than 30.

2. Triblock polymer according to claim 1 in which the ethylene units of block B represent more than 50% by mole of the repeating motifs constituting block B.

3. Triblock polymer according to any one of claims 1 to 2 wherein the ethylene units of block B represent more than 60% by mole of the repeating motifs constituting block B, preferably at least 70% by mole of the repeating motifs constituting block B.

4. Triblock polymer according to any one of claims 1 to 3 wherein the ethylene units of block B represent at most 85% by mole of the repeating motifs constituting block B.

5. Triblock polymer according to any one of claims 1 to 4 wherein vinylpyridine is 4-vinylpyridine, 2-vinylpyridine or a mixture thereof.

6. Triblock polymer according to any one of claims 1 to 5 wherein block B has a glass transition temperature between -90°C and -40°C, preferably between -70°C and -50°C.

7. Triblock polymer according to any one of claims 1 to 6 wherein the branched 1,3-diene is myrcene or [3-famesene or a mixture of myrcene and [3-farnesene, preferably myrcene.

8. Triblock polymer according to any one of claims 1 to 7 wherein block A has a number-average molar mass greater than 3,000 g / mol and less than or equal to 30,000 g / mol.

9. Triblock polymer according to any one of claims 1 to 8 wherein block C has a number-average molar mass of less than 10,000 g / mol.

10. Triblock polymer according to any one of claims 1 to 9 wherein block B has a number-average molar mass greater than 100,000 g / mol and preferably less than 200,000 g / mol.

11. Triblock polymer according to any one of claims 1 to 10, wherein triblock polymer has a Mooney viscosity ML (1+4) at 100°C greater than or equal to 40.

12. Rubber composition comprising a triblock polymer according to any one of claims 1 to 11, a reinforcing filler and a crosslinking system.

13. A tire comprising a tread, which tire comprises a rubber composition defined in claim 12, preferably in its tread.

14. A process for synthesizing a triblock polymer of formula ABC defined in any one of claims 1 to 11, A representing a polystyrene block, B representing a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, C representing a polyvinylpyridine block, which process comprises, in the presence of a catalytic system based on at least one metallocene of formula (I) and an organomagnesium compound of formula (II), the statistical copolymerization of a monomer mixture of ethylene and the branched 1,3-diene, followed by the homopolymerization of a vinylpyridine, P(Cp1Cp2)Liy (THF)* (!) R-Mg-A (II) Cp1 and Cp2, identical or different, being selected from the group consisting by cyclopentadienyl groups and fluorenyl groups, the groups being substituted or not, Pétant a group bridging the two groups Cp1 and Cp2 and representing a ZR*R2 group, Z representing a silicon or carbon atom, R1 and R2, identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl, y, an integer, being equal to or greater than 0, x, an integer or not, being equal to or greater than 0, R comprising a benzene ring of which two carbon atoms are substituted, one of the two is substituted by a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in ortho position with respect to each of said two carbon atoms, the symbol A in formula (II) representing the polystyrene block constituting the triblock polymer.