Terpolymer of ethylene and 1,3-diene

Abstract

The present invention relates to terpolymers of ethylene, a first 1,3-diene having 4 to 6 carbon atoms, and a second 1,3-diene of the formula CH2=CR-CH=CH2, said terpolymers containing more than 50 mole percent ethylene units and at least 1 mole percent units of the second 1,3-diene, where the symbol R represents a hydrocarbon chain having 3 to 20 carbon atoms. The polymers offer an improved compromise between ethylene content, stiffness, and crystallinity of polymers for use in tires.

Description

[Technical field]

[0001] The field of the invention is that of copolymers of conjugated dienes and ethylene which are rich in ethylene units and can be used as elastomers in rubber compositions for tires. [Background technology]

[0002] The diene elastomers most widely used in tire manufacturing are polybutadiene, polyisoprene, especially natural rubber, and copolymers of 1,3-butadiene and styrene. What these elastomers have in common is the high molar ratio of diene units in the elastomer, generally much higher than 50%, which can make them sensitive to oxidation, especially under the action of ozone. The applicant company, on the contrary, has described elastomers that are relatively depleted in diene units, in particular with a view to reducing their sensitivity to oxidation phenomena. These elastomers are described, for example, in document WO 2007054223. They are copolymers of 1,3-butadiene and ethylene containing more than 50 mol % of ethylene units. These elastomers are described as ethylene-rich diene elastomers.

[0003] Ethylene-rich copolymers of 1,3-butadiene and ethylene are crystalline and experience an increase in their crystallinity with ethylene content. The presence of crystalline portions in the copolymer can be problematic when the copolymer is used in a rubber composition. When the copolymer is brought to a temperature equal to or exceeding the melting point of the crystalline portion, the composition containing the copolymer also experiences a decrease in its stiffness, since melting of the crystalline portion of the copolymer leads to a decrease in its stiffness. This dependency of stiffness as a function of temperature can therefore lead to fluctuations in the properties of the rubber composition, making the copolymer unsuitable for certain applications that require better temperature stability of properties. It would be advantageous to have available diene polymers rich in ethylene units whose crystallinity is reduced, or even eliminated in practice. In document WO 2007054224, the applicant company described ethylene-rich diene copolymers that exhibit reduced crystallinity. These copolymers are copolymers of 1,3-butadiene and ethylene that further contain saturated 6-membered cyclic hydrocarbon motifs. Nevertheless, these copolymers introduced into a rubber composition can give the rubber composition an excessively high stiffness. The high stiffness of the rubber composition is due to the equally high stiffness of the elastomer. The high stiffness of the rubber composition can also be problematic as it renders the rubber composition unsuitable for certain applications. In attempting to achieve its objective of synthesizing ethylene-rich diene elastomers, the Applicant Company has discovered new polymers that make it possible to solve the above-mentioned problems by exhibiting an improved compromise between ethylene content, stiffness and crystallinity, in particular for use in tires. Summary of the Invention

[0004] Thus, a first subject of the present invention is a compound comprising ethylene, a first 1,3-diene having 4 to 6 carbon atoms and a compound of formula (I) CH2=CR-CH=CH2(I) (The symbol R represents a hydrocarbon chain having 3 to 20 carbon atoms.) with a second 1,3-diene, preferably an elastomer, which terpolymer contains more than 50 mol % of ethylene units and at least 1 mol % of units of the second 1,3-diene. A second subject of the invention is the process for the preparation of the terpolymers of the invention. The present invention also relates to a rubber composition comprising the terpolymer of the present invention, a reinforcing filler and a crosslinking system, wherein the terpolymer is an elastomer. The present invention also relates to a tire comprising the rubber composition of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] Detailed Description Any interval of values ​​indicated by the expression "between a and b" denotes a range of values ​​greater than "a" and less than "b" (i.e. excluding the limits a and b), whereas any interval of values ​​indicated by the expression "a to b" means a range of values ​​extending from "a" to "b" (i.e. including the precise limits a and b). The abbreviation "phr" means parts by weight per 100 parts by weight of elastomer (or of the sum of the elastomers, if several elastomers are present). The expression "based on" used to define components of a catalyst system or composition is intended to mean a mixture of these components or the product of the reaction of some or all of these components with one another. Unless otherwise indicated, the content of units resulting from the incorporation of a monomer into a copolymer is expressed as a molar percentage relative to all of the monomer units of the copolymer. The compounds referred to in this description may be of fossil origin or bio-based. If bio-based, they may be partially or completely derived from biomass or may be obtained from renewable starting materials derived from biomass. Elastomers, plasticizers, fillers, etc. are of particular relevance.

[0006] The essential feature of the first 1,3-diene is that it contains 4 to 6 carbon atoms. The first 1,3-diene is either a single compound, i.e. a single 1,3-diene having 4 to 6 carbon atoms, or a mixture of different 1,3-dienes having 4 to 6 carbon atoms. As 1,3-dienes having 4 to 6 carbon atoms, mention may be made in particular of 1,3-butadiene and isoprene. The first 1,3-diene is preferentially 1,3-butadiene. The essential feature of the second 1,3-diene is that it corresponds to the following formula (I) in which the symbol R represents a hydrocarbon chain having from 3 to 20 carbon atoms: CH2=CR-CH=CH2(I) The second 1,3-diene is either a single compound, i.e. a single 1,3-diene of formula (I), or a mixture of 1,3-dienes of formula (I), i.e. a mixture of 1,3-dienes in which the groups represented by the symbol R are different from one another. Preferably, the symbol R represents a hydrocarbon chain having 6 to 16 carbon atoms. The hydrocarbon chain represented by the symbol R may be a saturated or unsaturated chain. Preferably, the symbol R represents an aliphatic chain, in which case the hydrocarbon chain represented by the symbol R in formula (I) of the 1,3-dienes is an aliphatic hydrocarbon chain. It may be a straight or branched chain, in which case the symbol R represents a straight or branched chain. Preferably, the hydrocarbon chain is acyclic, in which case the symbol R represents an acyclic chain. Better still, the symbol R represents an unsaturated branched cyclic hydrocarbon chain. The hydrocarbon chain represented by the symbol R is an unsaturated branched acyclic chain advantageously containing 3 to 20 carbon atoms, in particular 6 to 16 carbon atoms. Very advantageously, the 1,3-diene is myrcene or β-farnesene. According to a preferential embodiment of the invention, the 1,3-diene is myrcene. According to another preferred embodiment of the invention, the 1,3-diene is β-farnesene.

[0007] The terpolymer of the present invention is a terpolymer of ethylene, a first 1,3-diene, and a second 1,3-diene, meaning that the monomer units of the terpolymer are units resulting from the polymerization of ethylene, the first 1,3-diene, and the second 1,3-diene. Thus, the copolymer comprises units of ethylene, units of the first 1,3-diene, and units of the second 1,3-diene. Since the second 1,3-diene is a substituted 1,3-diene, its polymerization can produce units having a 1,2 configuration represented by the following formula (1), units having a 3,4 configuration represented by the following formula (2), and units having a 1,4 configuration whose trans form is represented by the following formula (3).

[0008] [ka]

[0009] As is well known, the first 1,3-dienes can give rise to units of 1,2 or 3,4 configuration as well as units of 1,4 configuration, as is the case, for example, with isoprene. As is also well known, the ethylene unit is a unit of the -(CH2-CH2)- motif. The terpolymer of the invention is advantageously a statistical terpolymer according to any one of the embodiments of the invention. Very advantageously, the terpolymer is an atactic polymer according to any one of the embodiments of the invention. According to the invention, the terpolymer contains more than 50 mol% of ethylene units. Preferably, the terpolymer contains more than 60 mol% of ethylene units. Even more preferentially, the terpolymer contains at least 70 mol% of ethylene units. The terpolymer preferentially contains at most 90 mol % of ethylene units, and more preferentially at most 85 mol % of ethylene units.

[0010] According to the invention, the terpolymer contains at least 1 mol% of units of a second 1,3-diene. Preferably, the terpolymer contains at most 20 mol% of units of a second 1,3-diene. Even more preferentially, the terpolymer contains at most 10 mol% of units of a second 1,3-diene. According to one embodiment of the present invention, the terpolymer contains more than 60% to 90% by mole of ethylene units and 1% to 20% by mole, preferentially 1% to 10% by mole of units of a second 1,3-diene. According to this embodiment of the present invention, the terpolymer preferentially contains less than 30% by mole of units of a first 1,3-diene, or preferentially contains less than 20% by mole of units of a first 1,3-diene. According to another embodiment of the invention, the terpolymer contains 70% to 90% by mole of ethylene units and 1% to 20% by mole, preferentially 1% to 10% by mole of units of a second 1,3-diene. According to this embodiment of the invention, the terpolymer contains preferentially less than 20% by mole of units of a first 1,3-diene. According to yet another embodiment of the invention, the terpolymer contains more than 60% to 85% by mole of ethylene units and 1% to 20% by mole, preferentially 1% to 10% by mole of units of a second 1,3-diene. According to this embodiment of the invention, the terpolymer preferentially contains less than 30% by mole of units of a first 1,3-diene, or preferentially contains less than 20% by mole of units of a first 1,3-diene.

[0011] According to yet another embodiment of the invention, the terpolymer contains 70% to 85% by mole of ethylene units and 1% to 20% by mole, preferentially 1% to 10% by mole of units of a second 1,3-diene. According to this embodiment of the invention, the terpolymer preferentially contains less than 20% by mole of units of a first 1,3-diene. According to any one of the embodiments of the invention, the terpolymer preferentially contains less than 80 mol % of ethylene units, and more preferentially at most 75 mol % of ethylene units. According to a particular embodiment of the invention, especially when the first 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes, one of which is 1,3-butadiene, the terpolymer further contains units of the 1,2-cyclohexanediyl motif. The presence of these cyclic structures in the terpolymer is due to a very specific insertion of ethylene and 1,3-butadiene during polymerization. The content of units of the 1,2-cyclohexanediyl motif in the terpolymer varies depending on the respective contents of ethylene and 1,3-butadiene in the terpolymer. The terpolymer preferably contains less than 15 mol% of units of the 1,2-cyclohexanediyl motif.

[0012] Preferably, the terpolymers of the invention have a glass transition temperature below -35°C, preferentially between -70°C and -35°C. The terpolymers can be prepared by a process, which is another subject of the present invention, comprising the polymerization of a mixture of ethylene, a first 1,3-diene and a second 1,3-diene in the presence of a catalytic system based on at least a metallocene of formula (II) below and an organomagnesium compound of formula (III) below:

[0013] [ka]

[0014] Cp 1 and Cp 2are identical or different and are a cyclopentadienyl group of the formula C5H4, 13 H8 is selected from the group consisting of unsubstituted fluorenyl groups and substituted fluorenyl groups; P is two Cp 1 and Cp 2 ZR 3 R 4 group, Z represents silicon or carbon atom, R 3 and R 4 are the same or different and each represents an alkyl group containing 1 to 20 carbon atoms, preferably methyl, y is an integer greater than or equal to 0; x, which may or may not be an integer, is greater than or equal to 0; L represents an alkali metal selected from the group consisting of lithium, sodium and potassium; N represents a molecule of an ether, preferably diethyl ether or tetrahydrofuran, R 1 and R 2 are the same or different and represent carbon groups. Substituted fluorenyl groups can include those substituted with an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. The choice of group is also guided by the availability of the corresponding molecule, which is a substituted fluorene, since substituted fluorenes are commercially available or can be easily synthesized. As substituted fluorenyl groups, mention may more particularly be made of the 2,7-di(tert-butyl)fluorenyl and 3,6-di(tert-butyl)fluorenyl groups, where the 2-, 3-, 6- and 7-positions respectively refer to the positions of the carbon atoms of the ring shown in the scheme below, and the 9-position corresponds to the carbon atom to which the bridge P is attached.

[0015] [ka]

[0016] The catalyst system can be prepared conventionally by a process similar to that described in patent application WO 2007054224 or WO 2007054223. For example, the organomagnesium compound and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature ranging from 20° C. to 80° C., for a time period between 5 and 60 minutes. The catalyst system is generally prepared in an aliphatic hydrocarbon solvent, such as methylcyclohexane, or an aromatic hydrocarbon solvent, such as toluene. The catalyst system is generally used in this form in the synthesis process of the polymer of the invention after its synthesis. Alternatively, the catalyst system can be prepared by a process similar to that described in patent application WO 2017093654 A1 or patent application WO 2018020122 A1. According to this alternative, the catalyst system further contains a preformation monomer selected from a conjugated diene, ethylene or a mixture of ethylene and conjugated diene, in which case the catalyst system is based on at least a metallocene, an organomagnesium compound and a preformation monomer. For example, the organomagnesium compound and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature between 20°C and 80°C for 10 to 20 minutes to obtain a first reaction product, and then a preformation monomer selected from a conjugated diene, ethylene or a mixture of ethylene and conjugated diene is reacted with this first reaction product at a temperature in the range of 40°C to 90°C for 1 hour to 12 hours. The catalyst system thus obtained can be used immediately in the process of the invention or stored under an inert atmosphere until it is used in the process of the invention.

[0017] The metallocenes used to prepare the catalytic system can be in the form of crystalline or amorphous powders or in the form of single crystals. The metallocenes can also be provided in the form of monomers or dimers, which form depends on the method of preparation of the metallocenes, for example as described in patent applications WO 2007054224 or WO 2007054223. The metallocenes can be prepared in a process similar to that described in patent applications WO 2007054224 or WO 2007054223, in particular by reaction of the alkali metal salt of the ligand with a rare earth metal borohydride under inert and anhydrous conditions in a suitable solvent, for example an ether, for example 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 by-products by techniques known to those skilled in the art, for example filtration or precipitation from a second solvent. Finally, the metallocene is dried and isolated in solid form. As with any synthesis carried out in the presence of an organometallic compound, the synthesis of metallocenes and the synthesis of the catalyst system are carried out under anhydrous conditions and in an inert atmosphere. Typically, these reactions are carried out under anhydrous nitrogen or argon starting with anhydrous solvents and compounds.

[0018] The organomagnesium compound used in accordance with the present invention has the formula MgR 1 R 2 wherein R 1 and R 2 are the same or different and represent a carbon group. A carbon group is understood to mean a group containing one or more carbon atoms. Preferably, R 1 and R 2 Contains 2 to 10 carbon atoms. More preferentially, R 1 and R 2 Each represents an alkyl. The organomagnesium compound is preferably a dialkylmagnesium compound, more preferably butylethylmagnesium or butyloctylmagnesium, and even more preferably butyloctylmagnesium. According to any one of the embodiments of the invention, the molar ratio of the organomagnesium compound to the metal Nd constituting the metallocene is preferably in the range ranging from 1 to 100, more preferentially greater than or equal to 1 and less than 10. To obtain polymers with high molar mass, a range of values ​​ranging from 1 to less than 10 is particularly preferred.

[0019] When the terpolymer is a polymer containing units of the 1,2-cyclohexanediyl motif, it can be prepared according to the process described in this patent application by the reaction of formula (II), where Cp 1 and Cp 2 are the same or different, and are a substituted fluorenyl group and a group of formula C 13 For this alternative, the metallocene is selected from the group consisting of unsubstituted fluorenyl groups of formula C 13 Particularly suitable are metallocenes of the formula: [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}2]; [Me2SiFlu2Nd(μ-BH4)2Li(THF)]; [Me2SiFlu2Nd(μ-BH4)(THF)]; [{Me2SiFlu2Nd(μ-BH4)(THF)}2]; [Me2SiFlu2Nd(μ-BH4)]. The skilled artisan will also choose the polymerization conditions and the concentrations of each reactant (component of the catalyst system, monomers) depending on the equipment (apparatus, reactor) used to carry out the polymerization and the various chemical reactions. As known to the skilled artisan, the polymerization, as well as the handling of the monomers, catalyst system and polymerization solvent, are carried out under anhydrous conditions and in an inert atmosphere. The polymerization solvent is typically an aliphatic or aromatic hydrocarbon solvent.

[0020] The polymerization is preferably carried out in solution, continuously or batchwise. The polymerization solvent can be an aromatic or aliphatic hydrocarbon solvent. Examples of polymerization solvents include toluene and methylcyclohexane. The monomers can be introduced into the reactor containing the polymerization solvent and the catalyst system, or conversely, the catalyst system can be introduced into the reactor containing the polymerization solvent and the monomers. The copolymerization is typically carried out under anhydrous conditions and in the absence of oxygen, optionally in the presence of an inert gas. The polymerization temperature generally varies within a range ranging from 30°C to 150°C, preferentially from 30 to 120°C. Preferably, the copolymerization is carried out at constant ethylene pressure. During the polymerization of ethylene and 1,3-diene in a polymerization reactor, ethylene and 1,3-diene may be added continuously to the polymerization reactor, in which case the polymerization reactor is a fed reactor. This embodiment is very particularly suitable for the synthesis of statistical terpolymers.

[0021] The polymerization can be stopped by cooling the polymerization medium or by the addition of an alcohol. The polymer can be recovered according to conventional techniques known to those skilled in the art, for example, by precipitation, evaporation of the solvent under reduced pressure, or steam stripping. Alternatively, instead of the alcohol, a functionalizing agent can be added, in which case a polymer having functional groups such as amine, silanol or alkoxysilane functional groups is recovered. According to a particular embodiment of the invention, the terpolymer has amine, alkoxysilane or silanol functional groups. According to a first alternative in which the functional groups carried by the polymer are amine functions, the functionalizing agent is preferably a compound of formula (IV) below: Si(Fc 1 ) 3-g (Rc 2 ) g (Rca) (IV) Symbol Fc 1 are the same or different and represent an alkoxy group, Symbol Rc 2 are the same or different and represent a hydrogen atom or a hydrocarbon chain, The symbol Rca represents a hydrocarbon chain substituted with an amine functional group; g is an integer ranging from 0 to 1.

[0022] In formula (IV), the symbol Fc 1 The alkoxy group represented by the formula (I) is preferably methoxy or ethoxy. In formula (IV), the amine function indicated by the symbol Rca, i.e. the amine function of the functionalizing agent, is a protected primary amine function, a protected secondary amine function or a tertiary amine function. As protecting groups for primary and secondary amine functions, mention may be made of silyl groups, such as trimethylsilyl and tert-butyldimethylsilyl groups. Preferably, the amine function of the functionalizing agent is a tertiary amine function. Advantageously, the amine function of the functionalizing agent is a protected primary amine function, a protected secondary amine function or a tertiary amine function of the formula (-N(R B )2(in the formula, each R B is a tertiary amine of alkyl, preferentially methyl or ethyl. Functionalizing agents for preparing polymers with amine functions according to the first alternative include the compounds (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)methyldiethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldiethoxysilane, (N,N-dimethylaminopropyl)trimethoxysilane, (N,N-dimethylaminopropyl)triethoxysilane, (N-(3-trimethoxysilyl)propyl)-N-(trimethylsilyl)silaneamine and and (N-(3-triethoxysilyl)propyl)-N-(trimethylsilyl)silaneamine, preferably (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldimethoxysilane, (N,N-dimethylaminopropyl)trimethoxysilane and (N-(3-trimethoxysilyl)propyl)-N-(trimethylsilyl)silaneamine, more preferably (N,N-dimethylaminopropyl)trimethoxysilane and (N-(3-trimethoxysilyl)propyl)-N-(trimethylsilyl)silaneamine.

[0023] According to a second alternative, in which the functional groups carried by the polymer are silanol or alkoxysilane functional groups, the functionalizing agent is preferably a compound of formula (V) below: Si(Fc 1 ) 4-g (Rc 2 ) g (V) Symbol Fc 1 are the same or different and represent an alkoxy group or a halogen atom. Symbol Rc 2 are the same or different and are hydrogen atoms, hydrocarbon chains or chemical functional groups Fc 2 represents a hydrocarbon chain substituted with g is an integer ranging from 0 to 2. In formula (V), the symbol Fc 1 When Fc represents an alkoxy group, the alkoxy group is preferably methoxy or ethoxy. 1 When represents a halogen atom, the halogen atom is preferably chlorine. In formula (V), the symbol Rc 2 Among the hydrocarbon chains of the formula: embedded image, mention may be made of alkyl, preferably alkyl having up to 6 carbon atoms, and more preferentially methyl or ethyl, and better still methyl.

[0024] In formula (V), the symbol Rc 2 The chemical functional group Fc 2 Among the hydrocarbon chains substituted with , mention may be made of alkanediyl chains, preferably containing up to 6 carbon atoms, and more preferentially the 1,3-propanediyl group, which is a substituent, i.e. the chemical functional group Fc 2 In other words, one valence of the alkanediyl chain has a functional group Fc 2 and the other valence is used for the silicon of the methoxysilane functional group. In formula (V), the term "chemical functional group" means a group that is different from a saturated hydrocarbon group and can participate in a chemical reaction. 2Those skilled in the art will appreciate that the chemical functional group Fc in formula (V) is a group that is chemically inert to the chemical entities present in the polymerization medium. 2 may be in protected form, such as in the case of a primary amine, secondary amine or thiol functional group. 2 Examples of functional groups include ether, thiol ether, protected primary amine, protected secondary amine, tertiary amine, protected thiol or silyl functional groups. 2 is a protected primary amine functional group, a protected secondary amine functional group, a tertiary amine functional group, or a protected thiol functional group. Protecting groups for primary amine, secondary amine, and thiol functional groups can include silyl groups, such as trimethylsilyl and tert-butyldimethylsilyl groups.

[0025] According to the second alternative, functionalizing agents for the preparation of polymers with silanol or alkoxysilane functional groups include the compounds dimethoxydimethylsilane, diethoxydimethylsilane, dimethoxydiethylsilane, diethoxydiethylsilane, (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)methyldiethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldiethoxysilane, 3-methoxy 3,8,8,9,9-pentamethyl-2-oxa-7-thia-3,8-disiladecane, trimethoxymethylsilane, triethoxymethylsilane, trimethoxyethylsilane, triethoxyethylsilane, (N,N-dimethylaminopropyl)trimethoxysilane, (N,N-dimethylaminopropyl)triethoxysilane, (N-(3-trimethoxysilyl)propyl)-N-(trimethylsilyl)silaneamine, (N-(3-triethoxysilyl)propyl)-N-(trimethylsilyl)silaneamine and 3,3-dimethoxy -8,8,9,9-tetramethyl-2-oxa-7-thia-3,8-disiladecane, preferably dimethoxydimethylsilane, dimethoxydiethylsilane, (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldimethoxysilane, 3-methoxy-3,8,8,9,9-pentamethyl-2-oxa-7-thia-3,8-disiladecane, trimethoxymethylsilane, trimethoxyethylsilane, (N,N-dimethylaminopropyl)trimethoxysilane, (N-(3-trimethoxysilane), Mention may be made, more preferentially, of trimethoxymethylsilane, trimethoxyethylsilane, (N,N-dimethylaminopropyl)trimethoxysilane, (N-(3-trimethoxysilyl)propyl)-N-(trimethylsilyl)silaneamine and 3,3-dimethoxy-8,8,9,9-tetramethyl-2-oxa-7-thia-3,8-disiladecane.

[0026] Whether the first or second alternative is used, the functionalizing agent is typically added to the polymerization medium. It is typically added to the polymerization medium at a conversion of monomers selected by the skilled artisan depending on the desired macrostructure of the copolymer. Since the polymerization stage is generally carried out under ethylene pressure, degassing of the polymerization reactor may be carried out prior to the addition of the functionalizing agent. The functionalizing agent is added under inert and anhydrous conditions to the polymerization medium maintained at the polymerization temperature. Typically, 0.25 to 10 moles of functionalizing agent per mole of catalyst are utilized, preferably 2 to 4 moles of functionalizing agent per mole of catalyst. The functionalizing agent is contacted with the polymerization medium for a time sufficient to allow the polymerization reaction. This contact time is judiciously selected by the skilled artisan as a function of the concentration of the reaction medium and the temperature of the reaction medium. Typically, the functionalization reaction is carried out with stirring at a temperature ranging from 17°C to 80°C for a period of 0.01 to 24 hours.

[0027] When the functionalizing agent carries a protected functional group as described above, the polymer functionalization step can be followed by a hydrolysis reaction to form a copolymer with a deprotected functional group, such as a primary amine, secondary amine or thiol functional group. When the functionalization reaction results in the formation of a polymer bearing alkoxysilane functional groups, the reaction for functionalization of the polymer may be followed by a hydrolysis reaction. The hydrolysis of the polymer bearing alkoxysilane functional groups leads to the preparation of a polymer that also bears silanol functional groups.

[0028] The terpolymer of the present invention, as described according to any one of the embodiments of the present invention, including their preferred alternatives, exhibits both a lower stiffness and a comparable, indeed even lower, crystallinity than copolymers of ethylene and 1,3-butadiene, despite the same ethylene content. The replacement of a copolymer of ethylene and 1,3-butadiene with the terpolymer of the present invention in a rubber composition can give the rubber composition a lower stiffness, despite the same ethylene content. The terpolymer of the present invention is advantageously an elastomer. It is particularly intended for use in rubber compositions, in particular for tires.

[0029] Another subject of the present invention is a rubber composition characterized in that it comprises the elastomer of the present invention, a reinforcing filler and a crosslinking system. The rubber composition may contain any type of "reinforcing" filler known for its ability to reinforce rubber compositions that can be used to manufacture tires, such as organic fillers such as carbon black, reinforcing inorganic fillers such as silica, in combination with coupling agents in a known manner, or a mixture of these two types of fillers. The reinforcing fillers typically consist of nanoparticles whose (weight) average size is less than micrometers, generally less than 500 nm, most often between 20 nm and 200 nm, and particularly more preferentially between 20 nm and 150 nm. The content of reinforcing fillers is adjusted by the skilled person depending on the application of the rubber composition. The crosslinking system may be based on sulfur, sulfur donors, peroxides, bismaleimides or mixtures thereof. The crosslinking system is preferentially a vulcanization system, i.e. a system based on sulfur (or a sulfur donor) and a primary vulcanization accelerator. In addition to this basic vulcanization system, there may be various known secondary vulcanization accelerators or vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (especially diphenylguanidine), or known vulcanization retarders. The rubber composition may further contain other additives known for use in tire compositions, such as plasticizers, antiozonants or antioxidants.

[0030] The rubber compositions of the present invention are typically produced in a suitable mixer using two successive preparation stages well known to those skilled in the art: a first thermomechanical processing or kneading stage ("non-production" stage) at high temperature up to a maximum temperature between 130°C and 200°C, then a second mechanical processing stage ("production" stage) reduced to a lower temperature, typically below 110°C, for example between 40°C and 100°C, during the final stage of which the crosslinking system is incorporated. The rubber composition of the present invention may be in an uncured state (before crosslinking or vulcanization) or in a cured state (after crosslinking or vulcanization) and can be used in semi-finished products for tires. Another subject of the invention is a tyre, which comprises the rubber composition of the invention as defined in any one of its embodiments.

[0031] In summary, the present invention is advantageously carried out according to any one of the following embodiments 1 to 35. Embodiment 1: A method for producing a 1,3-diene having ethylene, a first 1,3-diene having 4 to 6 carbon atoms, and a 1,3-diene having the formula (I) CH2=CR-CH=CH2(I) (The symbol R represents a hydrocarbon chain having 3 to 20 carbon atoms.) with a second 1,3-diene, wherein the terpolymer contains more than 50 mol % ethylene units and at least 1 mol % units of the second 1,3-diene. Embodiment 2: The terpolymer of embodiment 1, wherein the terpolymer contains greater than 60 mole % ethylene units. Embodiment 3: The terpolymer of embodiment 1 or 2, wherein the terpolymer contains at least 70 mol % ethylene units. Embodiment 4: The terpolymer of any one of embodiments 1 to 3, wherein the terpolymer contains up to 90 mol % ethylene units. Embodiment 5: The terpolymer of any one of embodiments 1 to 4, wherein the terpolymer contains up to 85 mol % ethylene units. Embodiment 6: The terpolymer of any one of embodiments 1-5, wherein the terpolymer contains up to 20 mol % of units of a second 1,3-diene. Embodiment 7: The terpolymer of any one of embodiments 1-6, wherein the terpolymer contains up to 10 mol % of units of a second 1,3-diene.

[0032] Embodiment 8: A terpolymer according to embodiment 1, in which the terpolymer contains more than 60 mol% to 90 mol% of ethylene units and 1 mol% to 20 mol%, preferentially 1 mol% to 10 mol% of units of a second 1,3-diene. Embodiment 9: A terpolymer according to embodiment 1, wherein the terpolymer contains from 70 mol % to 90 mol % of ethylene units and from 1 mol % to 20 mol %, preferentially from 1 mol % to 10 mol % of units of a second 1,3-diene. Embodiment 10: A terpolymer according to embodiment 1, in which the terpolymer contains from more than 60 mol% to 85 mol% of ethylene units and from 1 mol% to 20 mol%, preferentially from 1 mol% to 10 mol% of units of a second 1,3-diene. Embodiment 11: A terpolymer according to embodiment 1, wherein the terpolymer contains from 70 mol % to 85 mol % of ethylene units and from 1 mol % to 20 mol %, preferentially from 1 mol % to 10 mol % of units of a second 1,3-diene. Embodiment 12: The terpolymer of any one of embodiments 8 to 10, wherein the terpolymer contains less than 30 mol % of units of the first 1,3-diene. Embodiment 13: The terpolymer of any one of embodiments 8 to 11, wherein the terpolymer contains less than 20 mol % of units of the first 1,3-diene. Embodiment 14: The terpolymer of any one of embodiments 8 to 13, wherein the first 1,3-diene is 1,3-butadiene, isoprene, or a mixture of 1,3-dienes, one of which is 1,3-butadiene. Embodiment 15: The terpolymer of any one of embodiments 8 to 14, wherein the first 1,3-diene is 1,3-butadiene.

[0033] Embodiment 16: A terpolymer according to embodiment 14 or 15, wherein the terpolymer further contains units of a 1,2-cyclohexanediyl motif. Embodiment 17: The terpolymer of embodiment 16, wherein the terpolymer contains less than 15 mol % of units of the 1,2-cyclohexanediyl motif. Embodiment 18: A terpolymer according to any one of embodiments 1 to 17, wherein the symbol R represents a hydrocarbon chain having from 6 to 16 carbon atoms. Embodiment 19: A terpolymer according to any one of embodiments 1 to 18, wherein the symbol R represents a saturated or unsaturated chain. Embodiment 20: A terpolymer according to any one of embodiments 1 to 19, wherein the symbol R represents an aliphatic chain. Embodiment 21: A terpolymer according to any one of embodiments 1 to 20, wherein the symbol R represents an acyclic chain. Embodiment 22: A terpolymer according to any one of embodiments 1 to 21, wherein the symbol R represents a linear or branched chain.

[0034] Embodiment 23: The terpolymer of any one of embodiments 1 to 22, wherein the terpolymer has a glass transition temperature of less than -35°C. Embodiment 24: The terpolymer of any one of embodiments 1 to 23, wherein the terpolymer has a glass transition temperature between -70°C and -35°C. Embodiment 25: The terpolymer of any one of embodiments 1 to 24, wherein the second 1,3-diene is myrcene. Embodiment 26: The terpolymer of any one of embodiments 1 to 24, wherein the second 1,3-diene is β-farnesene. Embodiment 27: The terpolymer of any one of embodiments 1 to 26, wherein the terpolymer is a statistical terpolymer. Embodiment 28: The terpolymer of any one of embodiments 1 to 27, wherein the terpolymer has an amine, alkoxysilane, or silanol functional group. Embodiment 29: The terpolymer of any one of embodiments 1 to 28, wherein the terpolymer contains less than 80 mol % ethylene units. Embodiment 30: The terpolymer of any one of embodiments 1 to 29, wherein the terpolymer contains up to 75 mol % ethylene units.

[0035] Embodiment 31: A rubber composition comprising at least one terpolymer according to any one of embodiments 1 to 30, a reinforcing filler and a crosslinking system, wherein the terpolymer is an elastomer.

[0041] Embodiment 32: The rubber composition of embodiment 31, wherein the reinforcing filler comprises carbon black or silica. Embodiment 33: The rubber composition according to embodiment 31 or 32, wherein the crosslinking system is a vulcanization system. Embodiment 34: A tire comprising the rubber composition according to any one of embodiments 31 to 33. Embodiment 35: A process for preparing a terpolymer according to any one of embodiments 1 to 30, comprising at least a metallocene of formula (II) and an organomagnesium compound

[0036] [ka]

[0037] (Cp 1 and Cp 2 are identical or different and are a cyclopentadienyl group of the formula C5H4, 13 H8 is selected from the group consisting of unsubstituted fluorenyl groups and substituted fluorenyl groups; P is two Cp 1 and Cp 2 ZR 3 R 4 group, Z represents silicon or carbon atom, R 3 and R 4 are the same or different and each represents an alkyl group containing 1 to 20 carbon atoms, preferably methyl, y is an integer greater than or equal to 0; x, which may or may not be an integer, is greater than or equal to 0; L represents an alkali metal selected from the group consisting of lithium, sodium and potassium; N represents a molecule of an ether, preferably diethyl ether or tetrahydrofuran, R 1 and R 2 are the same or different and represent carbon groups. 1. A process comprising the polymerization of a mixture of ethylene, a first 1,3-diene, and a second 1,3-diene in the presence of a catalyst system based on These and other features of the invention will be better understood on reading the following description of some implementations of the invention, given by way of illustration and not of limitation. EXAMPLES

[0038] 1) Determination of polymer macrostructure by size exclusion chromatography (SEC): a) Measurement principle Size Exclusion Chromatography, or SEC, allows the separation of macromolecules according to their size through a column packed with a porous gel. Macromolecules are separated according to their thermodynamic volume, with the bulkiest being eluted first. Combining three detectors (3D), namely refractometer, viscometer and 90° light scattering detector, SEC allows the understanding of the absolute molar mass distribution of polymers. The various number-average (Mn) and weight-average (Mw) absolute molar masses as well as the dispersity (D=Mw / Mn) can also be calculated. b) Preparation of the polymer: Each sample is dissolved in tetrahydrofuran at a concentration of approximately 1 g / l, and the solution is then filtered through a filter with a porosity of 0.45 μm before injection.

[0039] c) 3D SEC analysis: To determine the number-average molar mass (Mn) of the polymers, and, where appropriate, the weight-average molar mass (Mw) and the polydispersity index (PI), the following method is used. The number-average molar mass (Mn), weight-average molar mass (Mw) and polydispersity index of the polymers (hereafter samples) are determined in an absolute manner by triple detection size exclusion chromatography (SEC), which offers the advantage of measuring the average molar mass directly without calibration. The value of the refractive index increment dn / dc of the sample solution is measured in-line using the peak area detected by the refractometer (RI) of the liquid chromatography instrument. To apply this method, it must be verified that 100% of the sample mass is injected and eluted through the column. The area of ​​the RI peak depends on the concentration of the sample, the RI detector constant and the value of dn / dc. To determine the average molar mass, a previously prepared and filtered solution of 1 g / l is used and injected into the chromatographic system. The equipment used is a Waters Alliance chromatographic line. The elution solvent is tetrahydrofuran containing 250 ppm BHT (2,6-di(tert-butyl)-4-hydroxytoluene) and the flow rate is 1 ml min -1 The temperature of the system is 35° C. and the analysis time is 60 min. The columns used are a set of three Agilent columns with the trade name PL Gel Mixed B LS. The volume of the sample solution is 100 μl. The detection system consists of a Wyatt differential viscometer with the trade name Viscostar II, a Wyatt differential refractometer with the trade name Optilab T-Rex at a wavelength of 658 nm and a Wyatt multi-angle static light scattering detector with the trade name Dawn Heleos 8+ at a wavelength of 658 nm. For the calculation of the number average molar mass and the polydispersity index, the values ​​of the refractive index increment dn / dc of the sample solution obtained above are integrated. The software for processing the chromatographic data is the Astra system from Wyatt.

[0040] 2) Determination of polymer microstructure: a) Determination of the microstructure of ethylene-butadiene-mil center polymers: Spectral characterization and measurement of the microstructure of ethylene-butadiene-myrcene copolymers is performed by nuclear magnetic resonance (NMR) spectroscopy. For these measurements, a Bruker Avance III HD 400 MHz spectrometer equipped with a Bruker cryo-BBFO z-grad 5 mm probe is used. Radio frequency pulses are used with a tilt angle of 30°. 1 H experiments were recorded with 128 repetitions and a 5 second recycle delay. HSQC (Heteronuclear Single Quantum Coherence) and HMBC (Heteronuclear Multiple-Bond Correlation) 1 H- 13C NMR correlation experiments are recorded with 128 repeats and 128 increments. The experiments are carried out at 25° C. 25 mg of sample is dissolved in 1 ml of deuterated ortho-dichlorobenzene (ODCB). 1 H and 13 The chemical shift axis of C is δ 1H = 7.2 ppm (for the most heavily shielded signal) and δ 13C = 127 ppm (for the least shielded signal). Possible monomer units in the terpolymer are -CH2-CH(CH=CH2)-, -CH2-CH=CH-CH2-, -CH2-CH2-, 1,2-cyclohexanediyl motif and the following structures, where R1 and R2 represent the polymer chain:

[0041] [ka]

[0042] The 1,2-cyclohexanediyl motif has the following structure:

[0043] [ka]

[0044] Signals of myrcene intercalation type A were observed in the different spectra recorded. According to S. Georges et al. (S. Georges, M. Bria, P. Zinck and M. Visseaux., Polymer, 55 (2014), 3869-3878), the signal of -CH=group number 8'' characteristic of type C is identical to the signal of -CH=group number 3. 1 H and 13 C chemical shifts are shown. The chemical shifts of the signals characteristic of the polymers are shown in Table 1 below (for ethylene-butadiene-mil center polymers other than those of 1,3-butadiene units). 1 H and 13C signal assignments are shown in the table.

[0045] [Table 1]

[0046] 1D using Topspin software 1 Quantification was performed from integration of 1 H NMR spectra. The integrated signals for quantification of the various motifs are as follows: Ethylene: all signals between 0.5 ppm and 3.0 ppm by subtraction of the aliphatic contributions of the other motifs of the terpolymer. This calculation corresponds to the four protons of the ethylene motif. Form A: signal number 7 (4.67 ppm) corresponds to two protons. The proportion of type C is not directly accessible, but can be calculated from signal number 3+8'' by subtracting the contribution of type A. PB1-4: The signal between 5.71 ppm and 5.32 ppm corresponds to two protons (by removing the contribution of PB1-2). PB1-2: The signals between 5.11 ppm and 4.92 ppm correspond to two protons. Cyclohexane ring: the signals between 1.80 and 1.70 ppm correspond to two protons. The microstructure is quantified in mole percentage (mol%) as follows: Mole% of motif = Mole% of motif 1 H integral*100 / Σ(for each motif 1 H integral).

[0047] b) Determination of the microstructure of ethylene-butadiene-farnese center polymers: Spectral characterization and measurement of the microstructure of ethylene-butadiene-farnesene copolymers are performed by nuclear magnetic resonance (NMR) spectroscopy. For these measurements, a Bruker Avance III HD 400 MHz spectrometer equipped with a Bruker cryo-BBFO z-grad 5 mm probe is used. Radio frequency pulses are used with a tilt angle of 30°. 1 H experiments were recorded with 128 repetitions and a 5 second wait time. HSQC (Heteronuclear Single Quantum Coherence) and HMBC (Heteronuclear Multiple-Bond Correlation) 1 H- 13 C NMR correlation experiments are recorded with 128 repeats and 128 increments. The experiments are carried out at 25° C. 25 mg of sample is dissolved in 1 ml of deuterated ortho-dichlorobenzene (ODCB). 1 H and 13 The chemical shift axis of C is δ 1H = 7.2 ppm (for the most heavily shielded signal) and δ 13C = 127 ppm (for the least shielded signal). Possible monomer units in the terpolymer are -CH2-CH(CH=CH2)-, -CH2-CH=CH-CH2-, -CH2-CH2-, 1,2-cyclohexanediyl motif and the following structures, where R1 and R2 represent the polymer chain:

[0048] [ka]

[0049] The signals of the farnesene intercalation type A were observed in the different spectra recorded. The signal of -CH= group no. 11'', characteristic of type C, is identical to the -CH= groups no. 3 and no. 7. 1 H and 13 C chemical shifts are shown. The chemical shifts of the signals characteristic of the polymers are shown in Table 2 (ethylene-butadiene-farnese center polymers other than those of 1,3-butadiene units). 1 H and 13 C signal assignments are shown in the table.

[0050] [Table 2]

[0051] 1D using Topspin software 1 Quantification was performed from integration of 1 H NMR spectra. The integrated signals for quantification of the various motifs are as follows: Farnesene motif type A: from signal number 14 CH2= for two protons, Farnesene motif type C: from signals no. 3, 11″ and no. 7 CH= for two protons (by subtracting the contribution of type A), Farnesene motif type B: Signal number 11'' specific to this type for one proton. PB1-4: The signal between 5.71 ppm and 5.32 ppm corresponds to two protons (by removing the contribution of PB1-2). PB1-2: The signals between 5.11 ppm and 4.92 ppm correspond to two protons. Cyclohexane ring: the signals between 1.80 and 1.70 ppm correspond to two protons. The ethylene motif was determined by integrating all of the aliphatic signals (approximately 0.5-3 ppm) and subtracting all other aliphatic motifs (PB1-4, PB1-2, EBR ring, farnesene types A and C). The microstructure is quantified in mole percentage (mol%) as follows: Mole% of motif = Mole% of motif 1 H integral*100 / Σ(for each motif 1 H integral).

[0052] 3) Determination of the glass transition temperature of a polymer: The glass transition temperature is measured according to ASTM standard D3418 (1999) using a differential calorimeter (differential scanning calorimeter). 4) Determination of the stiffness of the polymer (uncured state): The measurements are carried out in shear mode on an Anton Paar model MCR301 rheometer using cylindrical specimens of controlled geometry (thickness between 1.5 and 3 mm and diameter between 22 and 28 mm). The samples are subjected to a sinusoidal shear stress over a frequency range extending from 0.01 Hz to 100 Hz at a fixed temperature (corresponding to the end of the course of the glass transition of the elastomer over a temperature sweep at 10 Hz). The stiffness value chosen to be the stiffness of the rubbery plateau of the sample is the value of the shear modulus G' for the frequency at which the loss modulus G'' reaches its maximum, according to C. Liu, J. He, E. van Ruymbeke, R. Keunings and C. Bailly, Evaluation of different methods for the determination of the plateau modulus and the entanglement molecular weight, Polymer, 47 (2006), 4461-4479. 5) Determination of polymer crystallinity: The melting and crystallization temperatures and enthalpies of the polymers used are determined by differential scanning calorimetry (DSC) using ISO standard 11357-3:2011. The reference enthalpy for polyethylene is 277.1 J / g (based on Polymer Handbook, 4th Edition, J. Brandrup, EH Immergut and EA Grulke, 1999).

[0053] 6) Polymer synthesis: In the synthesis of the terpolymers of the present invention, the first 1,3-diene used is 1,3-butadiene and the second 1,3-diene is myrcene or β-farnesene. Myrcene is a 1,3-diene of formula (I) where R is a hydrocarbon radical of formula CH2-CH2-CH=CMe2 having 6 carbon atoms. All reactants are commercially obtained, except for the metallocenes [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}] and [Me2SiCpFluNd(μ-BH4)2Li(THF)], which are prepared according to the procedures described in patent applications WO 2007054224 and WO 2007054223. Butyloctylmagnesium BOMAG (20% in heptane, C = 0.88 mol l -1 ) originates from Chemtura and is stored under inert atmosphere in a Schlenk tube. N35 grade ethylene originates from Air Liquide and is used without prior purification. Myrcene (purity ≥ 95%) is obtained from Sigma-Aldrich.

[0054] Example 1 not according to the invention: Synthesis of a copolymer of ethylene and 1,3-butadiene The polymer is synthesized according to the following procedure. In a 500 ml glass reactor containing 300 ml of toluene, the cocatalyst, butyloctylmagnesium (BOMAG), is added, followed by the metallocene [Me2SiCpFluNd(μ-BH4)2Li(THF)]. The alkylation time is 10 minutes and the reaction temperature is 20° C. The respective amounts of the components of the catalytic system appear in Table 3 below. Subsequently, the monomers are added according to their respective ratios shown in Table 3. Ethylene (Eth) and 1,3-butadiene (Bde) are in the form of a gas mixture. The polymerization is carried out at 80° C. and a constant ethylene pressure of 4 bar. The polymerization reaction is stopped by cooling, degassing the reactor and adding 10 ml of ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in an oven under vacuum to constant weight.

[0055] Example 2 not according to the invention: Synthesis of a copolymer of ethylene and 1,3-butadiene The polymer is synthesized according to the following procedure. In a 500 ml glass reactor containing 300 ml of methylcyclohexane, the cocatalyst, butyloctylmagnesium (BOMAG), is added, followed by the metallocene [Me2Si(Flu)2Nd(μ-BH4)2Li(THF)]. The alkylation time is 10 minutes and the reaction temperature is 20° C. The respective amounts of the components of the catalytic system appear in Table 3. Subsequently, the monomers are added according to the respective ratios shown in Table 3. Ethylene (Eth) and 1,3-butadiene (Bde) are in the form of a gas mixture. The polymerization is carried out at 80° C. and a constant ethylene pressure of 4 bar. The polymerization reaction is stopped by cooling, degassing the reactor and adding 10 ml of ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in an oven under vacuum to constant weight.

[0056] Example 3 not in accordance with the invention: Synthesis of a copolymer of ethylene and 1,3-butadiene The polymer is synthesized according to the following procedure. The cocatalyst, butyloctylmagnesium (BOMAG), is added to the reactor containing methylcyclohexane, followed by the metallocene [Me2Si(Flu)2Nd(μ-BH4)2Li(THF)]. The alkylation time is 10 minutes and the reaction temperature is 20° C. The amounts of each of the components of the catalyst system appear in Table 3. The monomers are then added continuously according to their respective ratios as shown in Table 3. The polymerization is carried out at 80° C. and a constant ethylene pressure of 4 bar. The polymerization reaction is stopped by cooling, degassing the reactor and adding ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in an oven under vacuum to constant weight.

[0057] Inventive Examples 4-10: Terpolymers of Ethylene, 1,3-Butadiene, and Myrcene or β-Farnesene The polymer is synthesized according to the following procedure. The cocatalyst, butyloctylmagnesium (BOMAG), is added to the reactor containing the hydrocarbon solvent: methylcyclohexane (MCH). The alkylation time is 10 min and the reaction temperature is 20°C. The polymerization is carried out in a 500 ml glass reactor containing 300 ml of the polymerization solvent methylcyclohexane, the catalyst system and the monomers, i.e. myrcene (Myr) or β-farnesene (Far), which are introduced into the reactor in liquid form and ethylene / 1,3-butadiene in gaseous form, at 80° C. and a constant pressure of 4 bar. The polymerization reaction is stopped by cooling and degassing the reactor. The copolymer is recovered by precipitation from methanol followed by drying or by direct drying. The amounts of each of the components of the catalyst system, the composition of the gaseous mixture of ethylene and 1,3-butadiene and the amount of myrcene or β-farnesene in the feed appear in Table 4 below.

[0058] 7) Results: The properties of the synthesized polymers appear in Tables 5 and 6 below. The elastomers of Examples 4-9, despite having comparable or even higher ethylene unit contents, have much lower crystallinity than the elastomer of Example 1. Even the elastomers of Examples 7 and 10, which have ethylene unit contents of over 80%, exhibit much lower crystallinity than the elastomer of Example 1, which has much fewer ethylene units. Comparison of Examples 4, 6 and 8 with Example 2 further shows that the incorporation of a second 1,3-diene unit in a polymer in a content according to the invention makes it possible to reduce the stiffness of the polymer while keeping the content of ethylene units comparable. A comparison of the elastomers of Examples 5 and 9 with the elastomer of Example 2 further shows that the incorporation of a second 1,3-diene unit at a content as low as 1% allows for a reduction in the stiffness of the elastomer, even though the elastomers of Examples 5 and 9 have the same high ethylene unit content as the elastomer of Example 2. The elastomers of Examples 5 and 9 also have a lower crystallinity than the elastomer of Example 3, which exhibits a similar ethylene unit content. The presence in the ethylene-rich diene copolymer of 1,3-diene units of formula (I) in a content according to the invention makes it possible to achieve an improved compromise between the content of ethylene units in the polymer and the crystallinity and stiffness of the polymer.

[0059] [Table 3]

[0060] [Table 4]

[0061] [Table 5]

[0062] [Table 6]

Claims

1. ethylene, a first 1,3-diene having from 4 to 6 carbon atoms, and a 1,3-diene represented by the following formula (I): CH 2 =CR-CH=CH 2 (I) (The symbol R represents a hydrocarbon chain having 3 to 20 carbon atoms.) and a second 1,3-diene, said terpolymer containing more than 50 mol % and up to 85 mol % of ethylene units, less than 30 mol % of units of the first 1,3-diene, and at least 1 mol % and up to 20 mol % of units of the second 1,3-diene.

2. 10. The terpolymer of claim 1, wherein the terpolymer contains greater than 60 mole percent ethylene units.

3. 3. The terpolymer of claim 1 or 2, wherein the first 1,3-diene is 1,3-butadiene or isoprene.

4. 3. The terpolymer of claim 1 or 2, wherein the terpolymer further contains units of a 1,2-cyclohexanediyl motif and the first 1,3-diene is 1,3-butadiene or a mixture of first 1,3-dienes, one of which is 1,3-butadiene.

5. 5. The terpolymer according to claim 1, wherein the symbol R represents a hydrocarbon chain having from 6 to 16 carbon atoms.

6. 6. The terpolymer of claim 1, wherein the second 1,3-diene is myrcene or β-farnesene.

7. The terpolymer of any one of claims 1 to 6, wherein the terpolymer is a statistical terpolymer.

8. The terpolymer of any one of claims 1 to 7, wherein the terpolymer has amine, alkoxysilane or silanol functional groups.

9. A rubber composition comprising at least one terpolymer according to any one of claims 1 to 8, a reinforcing filler and a crosslinking system, wherein said terpolymer is an elastomer.

10. A tire comprising the rubber composition of claim 9.

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