rubber composition

Abstract

The present invention relates to a rubber composition containing a reinforcing filler, a crosslinking system, and more than 50 phr up to 100 phr of an elastomer which is an ethylene copolymer with a 1,3-diene CH2=CR-CH=CH2 (the symbol R represents a hydrocarbon chain having 3 to 20 carbon atoms), which rubber composition achieves a good compromise between the properties of stiffness and hysteresis.

Description

[Technical Field]

[0001] The present invention relates to diene rubber compositions intended for use in tires, containing primarily as elastomers copolymers of ethylene and 1,3-diene. [Background technology]

[0002] Diene rubber compositions commonly used in tires are rubber compositions reinforced with highly unsaturated diene elastomers such as polybutadiene, polyisoprene, and copolymers of butadiene and styrene. In particular, WO 2014114607 proposes the use of copolymers of ethylene and 1,3-butadiene in rubber compositions for tires. These copolymers are synthesized by copolymerization of ethylene and 1,3-butadiene in the presence of a catalyst system containing a rare earth metallocene. Reinforced rubber compositions of ethylene / 1,3-butadiene copolymers are specifically described to improve the trade-off between tire performance characteristics of wear resistance and rolling resistance. These diene rubber compositions, when crosslinked, exhibit much higher stiffness than conventional diene rubber compositions, and as a result may prove unsuitable for certain applications. Therefore, there is a need to significantly reduce the cure stiffness of such compositions containing ethylene-based diene rubbers. It is known to reduce the cure stiffness of diene rubber compositions by decreasing the crosslink density of the rubber composition, which unfortunately also increases the hysteresis of the rubber composition. The applicant has discovered reinforced rubber compositions based on copolymers of ethylene and 1,3-diene which do not have the above drawbacks, since they have an improved compromise between the properties of stiffness and hysteresis. Summary of the Invention

[0003] The present invention therefore provides a first object of a reinforcing filler, a crosslinking system and a composition of more than 50 phr to 100 phr of a polymer of ethylene and the formula (I) CH2=CR-CH=CH2(I) (The symbol R represents a hydrocarbon chain having 3 to 20 carbon atoms.) and a 1,3-diene copolymer of the above. Another subject of the present invention is a tire comprising a tread, preferably comprising in the tread the rubber composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0004] 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), while any interval of values ​​indicated by the expression "from 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 total of elastomers, if several elastomers are present). The expression "based on" used to define the 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 mole 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. This applies in particular to elastomers, plasticizers, fillers, etc. As defined above and useful for the purposes of the present invention, the 1,3-dienes of formula (I) are substituted 1,3-dienes, which may result in 1,2-configured units represented by formula (1) below, 3,4-configured units represented by formula (2) below, and 1,4-configured units whose trans form is represented by formula (3) below.

[0005] [ka]

[0006] As is also well known, an ethylene unit is a unit of the -(CH2-CH2)- moiety. The copolymers useful for the purposes of the present invention are copolymers of ethylene and 1,3-diene, meaning that the monomer units of the copolymer are units resulting from the polymerization of ethylene and 1,3-diene. The copolymers therefore comprise ethylene units and 1,3-diene units. According to any one embodiment of the present invention, the 1,3-diene may be the only compound, i.e., the only 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. The copolymers useful for the purposes of the present invention are advantageously statistical copolymers according to any one of the embodiments of the present invention. Preferably, the copolymer contains ethylene units that account for between 50 and 95 mol% of the monomer units of the copolymer, i.e., between 50 and 95 mol% of the ethylene and 1,3-diene units. Highly preferentially, the copolymer contains ethylene units that account for at least 60 mol% of the ethylene and 1,3-diene units. Even more preferentially, the copolymer contains ethylene units that account for at least 70 mol% of the ethylene and 1,3-diene units. Preferably, the copolymer contains ethylene units that account for at most 90 mol% of the ethylene and 1,3-diene units. According to one particular embodiment of the invention, the copolymer contains ethylene units accounting for up to 85 mol % of ethylene and 1,3-diene units. According to one preferred embodiment of the invention, in the copolymer of the invention, ethylene units represent from 60 mol % to 90 mol % of the ethylene and 1,3-diene units, advantageously from 70 mol % to 90 mol % of the ethylene and 1,3-diene units. According to another particular embodiment of the invention, in the copolymer of the invention, the ethylene units represent from 60 mol % to 85 mol % of the ethylene and 1,3-diene units, advantageously from 70 mol % to 85 mol % of the ethylene and 1,3-diene units.

[0007] In the formula (I) of the 1,3-dienes, the hydrocarbon chain represented by the symbol R is an unsaturated chain of 3 to 20 carbon atoms. Preferably, the symbol R represents a hydrocarbon chain having 6 to 16 carbon atoms. The hydrocarbon chain represented by the symbol R may be saturated or unsaturated. Preferably, the symbol R represents an aliphatic chain, in which case the hydrocarbon chain represented by the symbol R in the formula (I) of the 1,3-diene 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. Even better, the symbol R represents an unsaturated branched acyclic hydrocarbon chain. The hydrocarbon chain represented by the symbol R is advantageously an unsaturated branched acyclic chain 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 one preferred 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.

[0008] Preferably, the copolymer of ethylene and 1,3-diene has a glass transition temperature of less than -35°C, preferably between -90°C and -35°C. According to a first variant of the invention, the copolymer contains 1,3-diene units in 1,2 or 3,4 configuration, accounting for more than 50 mol % of the 1,3-diene units. In other words, the copolymer contains more than 50 mol % of the 1,3-diene units in 1,2 or 3,4 configuration. In this variant, the remainder to 100 mol % of the 1,3-diene units in the copolymer is formed entirely or partially by 1,3-diene units in 1,4 configuration. According to this first variant, preferentially, the majority of the 1,3-diene units in 1,4 configuration are in the trans-1,4 configuration, and even more preferentially, all of the 1,3-diene units in 1,4 configuration are in the trans-1,4 configuration. According to a second variant of the invention, the 1,3-diene units in the copolymer contain more than 50% in the 1,4 configuration. In other words, the 1,3-diene units in the 1,4 configuration account for more than 50 mol% of the 1,3-diene units. In this variant, the remainder to 100 mol% of the 1,3-diene units in the copolymer is formed entirely or partially by 1,3-diene units in the 1,2 or 3,4 configuration. Preferably, the 1,3-diene units in the 1,4 configuration account for more than 70 mol% of the 1,3-diene units. Advantageously, the majority of the 1,3-diene units in the 1,4 configuration are in the trans-1,4 configuration, meaning that the 1,3-diene units in the trans-1,4 configuration account for more than 50 mol% of the 1,3-diene units in the 1,4 configuration.

[0009] The copolymers can be prepared by a process comprising the copolymerization of ethylene and a 1,3-diene in the presence of a catalyst system based on at least a metallocene of formula (II) below and an organomagnesium compound of formula (III) below: Cp 1 and Cp 2 may be the same or different and are cyclopentadienyl groups of 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 is a group that bridges the 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 2may be the same or different and represent a carbon group.

[0010] [ka]

[0011] Substituted fluorenyl groups include those substituted with alkyl groups having 1 to 6 carbon atoms or aryl groups having 6 to 12 carbon atoms. The choice of group is also guided by the availability of the corresponding substituted fluorene molecule, since substituted fluorenes are commercially available or easily synthesized. As substituted fluorenyl groups, mention may more particularly be made of 2,7-di(tert-butyl)fluorenyl and 3,6-di(tert-butyl)fluorenyl groups, where the 2-, 3-, 6- and 7-positions refer to the carbon atom positions of the ring shown in the diagram below, respectively, and the 9-position corresponds to the carbon atom to which the bridge P is attached.

[0012] [ka]

[0013] The catalyst system can be conventionally prepared by a process similar to that described in patent applications WO 2007054224 or WO 2007054223. For example, an organomagnesium compound and a 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. After its synthesis, the catalyst system is generally used in this form in the synthesis process for the copolymers of the present invention. 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 preformed monomer selected from a conjugated diene, ethylene, or a mixture of ethylene and a conjugated diene, in which case the catalyst system is based on at least a metallocene, an organomagnesium compound, and the preformed monomer. For example, the organomagnesium compound and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20°C to 80°C for 10 to 20 minutes to obtain a first reaction product, and then a preformed monomer selected from a conjugated diene, ethylene, or a mixture of ethylene and a conjugated diene is reacted with the first reaction product at a temperature ranging from 40°C to 90°C for 1 to 12 hours. The conjugated diene as preformed monomer is preferably a 1,3-diene, such as 1,3-butadiene, isoprene or a 1,3-diene of formula (I), in particular myrcene or β-farnesene. The catalyst system thus obtained can be used immediately in the process of the present invention or stored under an inert atmosphere until use in the process of the present invention.

[0014] The metallocenes used to prepare the catalyst system can be in the form of crystalline or amorphous powders, or in the form of single crystals. They can also be provided in the form of monomers or dimers, which depend on the method of preparation of the metallocene, as described, for example, in patent applications WO 2007054224 or WO 2007054223. Metallocenes can be prepared by processes similar to those described in patent applications WO 2007054224 or WO 2007054223, in particular by reacting a 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 such as 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, such as 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 an inert atmosphere. Typically, these reactions are carried out under anhydrous nitrogen or argon atmosphere, starting with anhydrous solvents and compounds.

[0015] The organomagnesium compounds used to meet the requirements of the present invention have the formula MgR 1 R 2 wherein R 1 and R 2 may be 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 one embodiment of the invention, the molar ratio of the organomagnesium compound to the metal Nd constituting the metallocene is preferably in the range from 1 to 100, and more preferentially greater than or equal to 1 and less than 10. In order to obtain copolymers with a high molar mass, a range of values ​​from 1 to less than 10 is particularly preferred.

[0016] When the copolymer useful for the purposes of the present invention is a copolymer having a microstructure defined according to the first variant of the invention, it is preferably a copolymer containing a metallocene of formula (II) where Cp 1 and Cp 2 may be the same or different, and are a substituted fluorenyl group and a group of formula C 13 For this variant, the metallocenes are prepared according to the process described in the present application using metallocenes of the formula: 13H8) are particularly suitable: [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}2]; [Me2SiFlu2Nd(μ-BH4)2Li(THF)]; [Me2SiFlu2Nd(μ-BH4)(THF)]; [{Me2SiFlu2Nd(μ-BH4)(THF)}2]; [Me2SiFlu2Nd(μ-BH4)]. When the copolymer useful for the purposes of the present invention is a copolymer having a microstructure defined according to the second variant of the invention, it is a copolymer containing a metallocene of formula (II) where Cp 1 represents a cyclopentadienyl group Cp of formula C5H4, and Cp 2 is the formula C 13 It is prepared according to the process described in this application using H8 (representing the fluorenyl group Flu).

[0017] Those skilled in the art will also choose polymerization conditions and concentrations of each reactant (component of the catalyst system, monomer) depending on the equipment (apparatus, reactor) used to carry out the polymerization and various chemical reactions. As known to those skilled in the art, copolymerization, as well as 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. The polymerization is preferably carried out in solution, either continuously or batchwise. The polymerization solvent may be an aromatic or aliphatic hydrocarbon solvent. Examples of polymerization solvents include toluene and methylcyclohexane. Monomers may be introduced into a reactor containing the polymerization solvent and the catalyst system, or conversely, the catalyst system may be introduced into a 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 ranges from 30°C to 150°C, preferentially from 30 to 120°C. Preferably, the copolymerization is carried out at a constant ethylene pressure.

[0018] 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 copolymers. The polymerization can be stopped by cooling the polymerization medium. The polymer can be recovered according to conventional techniques known to those skilled in the art, such as by precipitation, evaporation of the solvent under reduced pressure, or steam stripping.

[0019] The rubber composition of the present invention comprises from more than 50 phr to 100 phr of a copolymer of ethylene and a 1,3-diene of formula (I) as defined in any one of the above embodiments, including variants thereof. It is understood that the copolymer may consist of a mixture of copolymers differing from one another in their microstructure or their macrostructure. When the content of the copolymer of ethylene and a 1,3-diene of formula (I) is greater than 50 phr but less than 100 phr, the remainder to 100 phr can be provided by another elastomer, in particular another diene elastomer known to those skilled in the art. This other diene elastomer may be an elastomer commonly used in rubber compositions for tires, such as polybutadiene, polyisoprene, 1,3-butadiene copolymers, and isoprene copolymers. According to a preferred embodiment, the rubber composition comprises 100 phr of the copolymer of ethylene and a 1,3-diene of formula (I).

[0020] Another essential feature of the rubber composition of the present invention is that it contains a reinforcing filler. The rubber composition may contain any type of "reinforcing" filler known for its ability to reinforce rubber compositions usable in the manufacture of tires, such as organic fillers such as carbon black, or reinforcing inorganic fillers such as silica, combined in a known manner with a coupling agent, or a mixture of these two types of fillers. The reinforcing filler typically consists of nanoparticles whose (weight) average size is less than micrometers, generally less than 500 nm, most often between 20 and 200 nm, and particularly preferably between 20 and 150 nm. The content of the reinforcing filler is adjusted by those skilled in the art depending on the intended use of the rubber composition. According to one embodiment of the present invention, the content of the reinforcing filler in the rubber composition is 30 phr or more and 150 phr or less, preferably 35 phr or more and 100 phr or less. These ranges of the reinforcing filler defined in this embodiment make it possible to provide the rubber composition with an improved compromise between the reinforcement and stiffness properties of the rubber composition depending on the intended use of the rubber composition for tires, particularly treads.

[0021] The reinforcing filler may be silica, carbon black or a mixture of carbon black and silica. Preferably, silica represents more than 50% by weight of the reinforcing filler. Even more preferentially, silica represents more than 85% by weight of the reinforcing filler. The silica used may be any reinforcing silica known to those skilled in the art, in particular 450 ml 2 / g or less, preferably 30 to 400m 2 / g, especially 60-300m 2 The term "precipitated silica" may be any precipitated or fumed silica exhibiting a BET specific surface area and a CTAB specific surface area in the range of 1 / g / g. In the present disclosure, the BET specific surface area is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, page 309, February 1938), more specifically according to a method derived from standard NF ISO 5794-1, Appendix E, June 2010 [multipoint (5-point) volumetric method - gas: nitrogen - degassing under vacuum: 160°C for 1 hour - relative pressure p / po range: 0.05 to 0.17]. CTAB specific surface area values ​​were determined according to standard NF ISO 5794-1, Appendix G of June 2010. The process is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "external" surface of the reinforcing filler.

[0022] Any type of precipitated silica can be used, in particular highly dispersible precipitated silicas (called "HDS" or "highly dispersible silicas" for "highly dispersible"). These precipitated silicas, which may or may not be highly dispersible, are well known to those skilled in the art. Mention may be made, for example, of the silicas described in applications WO 03 / 016215-A1 and WO 03 / 016387-A1. Among commercially available HDS silicas, in particular Ultrasil® 5000GR and Ultrasil® 7000GR silicas from Evonik or Zeosil® 1085GR, Zeosil® 1115 MP, Zeosil® 1165MP, Zeosil® Premium 200MP and Zeosil® HRS 1200 MP silicas from Solvay may be used. As non-HDS silicas, the following commercially available silicas may be used: Ultrasil® VN2GR and Ultrasil® VN3GR silicas from Evonik, Zeosil® 175GR silica from Solvay or Hi-Sil EZ120G(-D), Hi-Sil EZ160G(-D), Hi-Sil EZ200G(-D), Hi-Sil 243LD, Hi-Sil 210 and Hi-Sil HDP 320G silicas from PPG. The silica may be a mixture of different silicas, in which case the proportion of silica in the reinforcing filler relates to all silicas.

[0023] All carbon blacks are suitable, especially those commonly used in tires or their treads. Among these, particular mention should be made of the 100, 200 and 300 series reinforcing carbon blacks, or the 500, 600 or 700 series blacks (ASTM D-1765-2017 grades), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683 and N772 blacks. These carbon blacks can be used in the isolated form as they are commercially available, or in any other form, for example, as a carrier for some of the rubber additives used. The carbon black may be a mixture of different carbon blacks, in which case the carbon black content refers to all the carbon blacks. Preferably, carbon black is used in a content of 20 phr or less, more preferentially 10 phr or less (for example, the carbon black content may be in the range of 0.5 to 20 phr, in particular 1 to 10 phr). Advantageously, the carbon black content in the rubber composition is 5 phr or less. Within the indicated interval, the coloring properties (black colorant) and UV stabilization properties of carbon black are advantageous, without adversely affecting the typical performance qualities contributed by silica.

[0024] To bond a reinforcing inorganic filler, in this case silica, to an elastomer, at least difunctional coupling agents (bonding agents) intended to ensure a sufficient bond of chemical and / or physical properties between the inorganic filler (the surface of its particles) and the elastomer can be used in a known manner, in which case the rubber composition comprises a coupling agent for bonding the silica to the elastomer. In particular, organosilanes or polyorganosilanes that are at least difunctional are used. The term "difunctional" is intended to mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the elastomer. In particular, silane polysulfides, which are called "symmetrical" or "asymmetrical", depending on their specific structure, are used, as described in, for example, applications WO03 / 002648-A1 (or US2005 / 016651-A1) and WO03 / 002649-A1 (or US2005 / 016650-A1).Without limiting the following definition, silane polysulfides corresponding to the following formula (IV) are particularly suitable:

[0025] [ka]

[0026] -x is an integer of 2 to 8 (preferably 2 to 5); The symbols A may be the same or different and are divalent hydrocarbon radicals (preferably C-C 18 Alkylene group or C6-C 12 Arylene groups, more particularly C1-C 10 alkylene, especially C1-C4 alkylene, especially propylene); the symbols Z may be identical or different and are of the following three formulae:

[0027] [ka]

[0028] is equivalent to During the ceremony: -R a The groups may be substituted or unsubstituted, may be the same or different, and may be C-C 18 Alkyl groups, C5-C 18 Cycloalkyl group or C6-C 18 represents an aryl group (preferably a C1-C6 alkyl group, cyclohexyl or phenyl, in particular a C1-C4 alkyl group, more in particular methyl and / or ethyl), -R b The groups may be substituted or unsubstituted, may be the same or different, and may be C-C 18 Alkoxy group or C5-C 18 a cycloalkoxyl group (preferably a group selected from C1-C8 alkoxyl and C5-C8 cycloalkoxyl, more preferentially a group selected from C1-C4 alkoxyl, in particular methoxyl and ethoxyl), or a hydroxyl group, or two R b Group is C3-C 18 represents a group that becomes a dialkoxyl group. In the case of mixtures of alkoxysilane polysulfides corresponding to formula (V) above, in particular the usual commercial mixtures, the average value of the "x" index is preferably a fraction in the range ranging from 2 to 5, and more preferentially close to 4.

[0029] Examples of silane polysulfides include bis((C1-C4)alkoxy(C1-C4)alkylsilyl(C1-C4)alkyl) polysulfides (especially disulfides, trisulfides or tetrasulfides), such as bis(3-trimethoxysilylpropyl) or bis(3-triethoxysilylpropyl) polysulfides. Among these compounds, bis(3-triethoxysilylpropyl)tetrasulfide (abbreviated as TESPT) of the formula [(C2H5O)3Si(CH2)3S2]2, sold under the name Si69 by Evonik, or bis(triethoxysilylpropyl)disulfide (abbreviated as TESPD) of the formula [(C2H5O)3Si(CH2)3S]2, sold under the name Si75 by Evonik, are particularly suitable. Preferred examples include bis(mono(C1-C4)alkoxyldi(C1-C4)alkylsilylpropyl)polysulfides (especially disulfides, trisulfides or tetrasulfides), more particularly bis(monoethoxydimethylsilylpropyl)tetrasulfide, such as those described in the above-mentioned patent application WO 02 / 083782-A1 (or US Pat. No. 7,217,751-B2). Of course, mixtures of the above coupling agents may also be utilized. The content of coupling agent in the composition of the present invention is advantageously 25 phr or less, and it is generally understood that it is desirable to use it in as small an amount as possible. Typically, the content of coupling agent accounts for 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler. The content is preferably in the range of 0.5 to 20 phr, and more preferably in the range of 3 to 15 phr. This content can be easily adjusted by those skilled in the art depending on the content of reinforcing inorganic filler used in the composition of the present invention.

[0030] The crosslinking system useful for the purposes of the present invention is preferentially a vulcanization system, i.e., based on sulfur and a primary vulcanization accelerator. The sulfur is typically provided in the form of molecular sulfur or a sulfur donor, preferably in molecular form. Molecular sulfur is also referred to as molecular sulfur. The term "sulfur donor" refers to any compound that releases sulfur atoms, optionally compounded in the form of polysulfide chains, capable of inserting into polysulfide chains formed during the vulcanization and crosslinking of elastomer chains. Various known secondary vulcanization accelerators or vulcanization activators, such as zinc oxide, stearic acid, guanidine derivatives (especially diphenylguanidine), etc., are added to the vulcanization system incorporated during the first non-productive stage and / or the productive stage. The sulfur content is preferably between 0.5 and 3.0 phr, and the content of the primary accelerator is preferably between 0.5 and 5.0 phr. These preferential contents may be applied to any one embodiment of the present invention. As vulcanization accelerator (primary or secondary) any compound capable of acting as an accelerator of the vulcanization of diene elastomers in the presence of sulfur may be used, in particular accelerators of the thiazole type and also their derivatives, accelerators of the sulfenamide type for primary accelerators, or accelerators of the thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type for secondary accelerators.

[0031] Crosslinking (or curing), and if necessary vulcanization, is generally carried out at temperatures between 130°C and 200°C for a sufficient time, for example between 5 and 90 minutes, which may vary depending, inter alia, on the cure temperature, the crosslinking system chosen and the crosslinking kinetics of the composition under consideration. The rubber composition of the invention may contain all or some of the usual additives commonly used in elastomeric compositions intended for the manufacture of tires, in particular pigments, protective agents such as antiozonant waxes, chemical antiozonants, antioxidants and plasticizers. According to one particular embodiment of the present invention, the rubber composition also contains a plasticizer. The content of plasticizer in the rubber composition can vary widely, depending in particular on the content of reinforcing fillers in the rubber composition and on the nature of the plasticizer used. Preferably, it is greater than 10 phr and less than or equal to 100 phr, preferably greater than or equal to 30 phr and less than or equal to 90 phr.

[0032] According to a particularly preferred embodiment of the present invention, the rubber composition contains a hydrocarbon resin as a plasticizer. This embodiment is particularly preferred for use in tread rubber compositions. Hydrocarbon resins, also known as hydrocarbon plasticizing resins, are polymers well known to those skilled in the art that are essentially based on carbon and hydrogen but may contain other types of atoms, such as oxygen, and can be used in polymer matrices, particularly as plasticizers or tackifiers. They are essentially at least partially miscible (i.e., compatible) with the polymer compositions for which they are intended, so that, at the dosages used, they act as true diluents. They are described, for example, in the book by R. Mildenberg, M. Zander, and G. Collin entitled "Hydrocarbon Resins" (New York, VCH, 1997, ISBN 3-527-28617-9), whose Chapter 5 deals specifically with their application in the field of tire rubber (5.5. "Rubber Tires and Mechanical Goods"). In a known manner, these hydrocarbon resins are sometimes described as thermoplastic resins, meaning that they soften and are moldable when heated. The softening point of the hydrocarbon resin is measured according to ISO standard 4625 (the "ring and ball" method). Tg is measured according to ASTM standard D3418 (1999). The macrostructure (Mw, Mn, and PI) of the hydrocarbon resin is determined by size exclusion chromatography (SEC); solvent: tetrahydrofuran; temperature: 35°C; concentration: 1 g / L; flow rate: 1 ml / min; solution filtered through a filter with a porosity of 0.45 μm before injection; Moore calibration with polystyrene standards; a set of three Waters columns in series (Styragel HR4E, HR1, and HR0.5); detection by a differential refractometer (Waters 2410) and its associated operating software (Waters Empower).

[0033] The hydrocarbon resins may be of the aliphatic or aromatic or aliphatic / aromatic type, i.e., based on aliphatic and / or aromatic monomers. They may be natural or synthetic, and may or may not be petroleum-based (in which case they are also known as petroleum resins). Preferably, the hydrocarbon plasticized resins have a glass transition temperature above 20°C. Advantageously, the hydrocarbon plasticized resin has at least one of the following characteristics, and more preferentially all of them: Tg above -30°C; - number average molecular weight (Mn) between 300 g / mol and 2000 g / mol, more preferentially between 400 g / mol and 1500 g / mol; A polydispersity index (PI) of less than −3, and more preferentially less than 2 (as a reminder: PI=Mw / Mn, where Mw is the weight average molecular weight).

[0034] Preferably, the hydrocarbon plasticized resin is selected from the group consisting of cyclopentadiene homopolymer resins, cyclopentadiene copolymer resins, dicyclopentadiene homopolymer resins, dicyclopentadiene copolymer resins, terpene homopolymer resins, terpene copolymer resins, C5 cut homopolymer resins, C5 cut copolymer resins, C9 cut homopolymer resins, C9 cut copolymer resins, hydrogenated cyclopentadiene homopolymer resins and hydrogenated cyclopentadiene copolymer resins. More preferentially, the hydrocarbon plasticized resin is a hydrogenated or non-hydrogenated C9 cut copolymer resin or a dicyclopentadiene copolymer resin. By way of example, mention may be made in particular of a C9 cut copolymer resin and a hydrogenated dicyclopentadiene copolymer resin.

[0035] As plasticizers useful for the purposes of the present invention, mention may also be made of hydrocarbon liquid plasticizers known for softening rubber compositions by diluting the elastomers and reinforcing fillers of the rubber composition. Their Tg is typically below -20°C, preferentially below -40°C. Any hydrocarbon extender oil or any hydrocarbon liquid plasticizer known for its plasticizing properties for diene elastomers can be used. These plasticizers or these oils, which are more or less viscous at ambient temperature (23°C), are liquids (i.e., substances capable of ultimately taking the shape of their container), in contrast to hydrocarbon plasticizing resins, which are essentially solid at ambient temperature. Hydrocarbon liquid plasticizers may include liquid diene polymers, polyolefin oils, naphthenic oils, paraffinic oils, DAE oils, MES (Medium Extracted Solvate) oils, TDAE (Treated Distillate Aromatic Extract) oils, RAE (Residual Aromatic Extract) oils, TRAE (Treated Residual Aromatic Extract) oils and SRAE (Safety Residual Aromatic Extract) oils, mineral oils, and mixtures of these compounds. Preferably, the hydrocarbon liquid plasticizer is selected from the group consisting of liquid diene polymers, aliphatic polyolefin oils, paraffin oils, MES oils, TDAE oils, TRAE oils, SRAE oils, mineral oils and mixtures thereof.More preferentially, the hydrocarbon liquid plasticizer is a liquid diene polymer, aliphatic polyolefin oils, paraffin oils, MES oils or mixtures thereof.

[0036] The rubber composition before crosslinking may be prepared in a suitable mixer using two successive preparation stages according to general procedures well known to those skilled in the art: a first thermomechanical processing or kneading stage (sometimes called the "non-productive" stage) at elevated temperatures up to a maximum temperature of between 110°C and 190°C, preferably between 130°C and 180°C, followed by a second mechanical processing stage (sometimes called the "productive" stage) at lower temperatures, typically below 110°C, for example between 40°C and 100°C, during which sulfur or sulfur donors and vulcanization accelerators are incorporated during the final stage. By way of example, the first (non-productive) stage is carried out in a single thermomechanical step, during which all necessary ingredients except the crosslinking system, optional additional processing aids and various other additives are introduced into a suitable mixer, for example a standard internal mixer. The total duration of the kneading in this non-productive stage is preferably between 1 and 15 minutes. After cooling of the mixture thus obtained during the first non-productive stage, the crosslinking system is then incorporated at low temperature, usually in an external mixer such as an open mill; then everything is mixed for a few minutes, for example between 2 and 15 minutes (productive stage). The rubber composition can be calendered or extruded in the form of sheets or slabs, especially for laboratory characterization, or in the form of rubber semi-finished products (or profiled elements) that can be used for tires. The composition can be in the uncured state (before crosslinking or vulcanization) or in the cured state (after crosslinking or vulcanization), and can be a semi-finished product that can be used for tires. Another object of the present invention is a tire comprising a tread, which preferably comprises in the tread the rubber composition of the present invention.

[0037] In summary, the present invention is advantageously carried out according to any one of the following embodiments 1 to 24. Embodiment 1: A reinforcing filler, a crosslinking system, and a copolymer of ethylene and a copolymer of formula (I) CH2=CR-CH=CH2(I) (The symbol R represents a hydrocarbon chain having 3 to 20 carbon atoms.) A rubber composition comprising an elastomer which is a copolymer of a 1,3-diene and a methyl methyl acrylate. Embodiment 2: The rubber composition of embodiment 1, wherein the copolymer contains between 50 and 95 mole percent of ethylene units and 1,3-diene units. Embodiment 3: The rubber composition according to any one of embodiments 1 and 2, wherein the copolymer contains ethylene units accounting for at least 60 mol %, preferably at least 70 mol %, of the ethylene and 1,3-diene units. Embodiment 4: The rubber composition of any one of embodiments 1 to 3, wherein the copolymer contains up to 90 mol % of ethylene units and 1,3-diene units. Embodiment 5: The rubber composition of any one of embodiments 1 to 4, wherein the copolymer contains up to 85 mol % of ethylene units and 1,3-diene units.

[0038] Embodiment 6: The rubber composition of any one of embodiments 1 to 5, wherein the symbol R represents a hydrocarbon chain having 6 to 16 carbon atoms. Embodiment 7: The rubber composition of any one of embodiments 1 to 6, wherein the symbol R represents an acyclic chain. Embodiment 8: The rubber composition according to any one of embodiments 1 to 7, wherein the symbol R represents a straight chain or a branched chain. Embodiment 9: The rubber composition of any one of embodiments 1 to 8, wherein the symbol R represents an aliphatic chain. Embodiment 10: The rubber composition of any one of embodiments 1 to 9, wherein the copolymer has a glass transition temperature of less than -35°C, preferably between -90°C and -35°C. Embodiment 11: The rubber composition of any one of embodiments 1 to 10, wherein the copolymer contains 1,3-diene units in a 1,2 or 3,4 configuration, accounting for more than 50 mole percent of the 1,3-diene units. Embodiment 12: The rubber composition of any one of embodiments 1 to 11, wherein the 1,3-diene is myrcene or β-farnesene. Embodiment 13: The rubber composition of any one of embodiments 1 to 12, wherein the copolymer is a statistical copolymer. Embodiment 14: The rubber composition of any one of embodiments 1 to 13, wherein the composition comprises 100 phr of the copolymer of ethylene and of the 1,3-diene of formula (I).

[0039] Embodiment 15: The rubber composition of any one of embodiments 1 to 14, wherein the reinforcing filler is silica, carbon black, or a mixture of carbon black and silica. Embodiment 16: The rubber composition according to any one of embodiments 1 to 15, wherein the reinforcing filler content is equal to or greater than 30 phr and equal to or less than 150 phr. Embodiment 17: The rubber composition according to any one of embodiments 1 to 16, wherein the reinforcing filler content is equal to or greater than 35 phr and equal to or less than 100 phr. Embodiment 18: The rubber composition of any one of embodiments 1 to 17, wherein the reinforcing filler comprises silica comprising more than 50% by weight of the reinforcing filler. Embodiment 19: The rubber composition of any one of embodiments 1 to 18, wherein the composition comprises a plasticizer. Embodiment 20: The rubber composition according to any one of embodiments 1 to 19, wherein the plasticizer content is greater than 10 phr and less than or equal to 100 phr. Embodiment 21: The rubber composition according to any one of embodiments 1 to 20, wherein the plasticizer content is equal to or greater than 30 phr and equal to or less than 90 phr. Embodiment 22: The rubber composition of any one of embodiments 1 to 21, wherein the composition comprises a hydrocarbon resin as a plasticizer. Embodiment 23: A tire comprising a tread, wherein the tire comprises the rubber composition of any one of embodiments 1 to 22. Embodiment 24: The tire of embodiment 23, wherein the rubber composition is in the tread. These and other features of the invention will be better understood on reading the following description of some exemplary embodiments of the invention, given by way of illustration and not of limitation. [Example]

[0040] II.1 Tests and measurements: II.1-1 Determination of the microstructure of elastomers: Spectroscopic characterization and determination of the microstructure of copolymers of ethylene and 1,3-myrcene is performed by nuclear magnetic resonance (NMR) spectroscopy. Spectrometer: A Bruker Avance III HD 400 MHz spectrometer equipped with a Bruker cryo-BBFO z-grad 5 mm probe is used for these measurements. Experiment: Using high frequency pulses at an inclination angle of 30° 1 H experiments were recorded with 128 replicates and a 5-second recycle delay. 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. Sample preparation: Dissolve 25 mg of sample in 1 ml of deuterated chloroform (CDCl3). Sample calibration: 1 H and 13 The chemical shift axis of C is δ relative to the protonated impurity (CHCl3) of the solvent. 1H = 7.2 ppm and δ 13C Calibrate at =77 ppm.

[0041] Spectral assignments for copolymers of ethylene and 1,3-myrcene (see Chem 1): In the representation Chem 1, the symbols R1 and R2 represent the attachment points of the units to the polymer chain. In the representation Chem 1, signals of the insertion types of 1,3-dienes A, B and C were observed in the various 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 moieties A, B and C are presented in Table 1. Moieties A, B and C correspond to units of 3,4 configuration, 1,2 configuration and trans-1,4 configuration, respectively. 1D using Topspin software 1 Quantification was performed from the integration of the 1 H NMR spectra. The integrated signals of the quantification of the different parts are as follows: Ethylene: The signal at 1.2 ppm corresponds to 4 protons. Total myrcene: signal number 1 (1.59 ppm) corresponds to 6 protons. Form A: Signal number 7 (4.67 ppm) corresponds to two protons. Type B: Signal number 8' (5.54 ppm) corresponds to one proton. Quantification of the microstructure is performed in mole percentage (mol%) as follows: Mole% of parts = parts of 1 H integral * 100 / Σ(each part 1 H integral).

[0042] [Table 1]

[0043] 1D using Topspin software 1 Quantification was performed from the integration of the 1 H NMR spectra. The integrated signals for quantification of the various parts are as follows: Ethylene: The signal at 1.2 ppm corresponds to 4 protons. Total myrcene: signal number 1 (1.59 ppm) corresponds to 6 protons. Form A: Signal number 7 (4.67 ppm) corresponds to two protons. Type B: Signal number 8' (5.54 ppm) corresponds to one proton. Quantification of the microstructure is performed in mole percentage (mol%) as follows: Mole% of parts = parts of 1H integral * 100 / Σ(each part 1 H integral).

[0044] [ka]

[0045] II.1-2 Determination of the glass transition temperature of polymers: The glass transition temperature is measured using a differential calorimeter (differential scanning calorimeter) according to ASTM standard D3418 (1999). II.1-3 Stiffness and hysteresis of rubber compositions: The dynamic properties are measured in a viscosity analyzer (Metravib VA4000) according to standard D5992-96. Samples of the vulcanized compositions (4 mm thick and 400 mm long) are subjected to a simple alternating sinusoidal shear stress during a temperature sweep from a minimum temperature below the Tg of the elastomer of the composition to a maximum temperature above 100°C, with a forced stress of 0.7 MPa and a frequency of 10 Hz. 2 The response of a cylindrical specimen with a cross-sectional area of ​​1000 mm is recorded. The results are the complex dynamic shear modulus (G * ) and loss factor tanδ; G * is recorded at a temperature of 60°C, and the loss factor tan δ is recorded at 20°C and 40°C. Stiffness and hysteresis results are expressed on a base 100 basis relative to the control recorded as a reference. Values ​​below 100 indicate values ​​lower than the control.

[0046] II.2. Polymer Synthesis: In the synthesis of the copolymers of the present invention, the 1,3-diene used is myrcene, ie a 1,3-diene of formula (I) in which R is a hydrocarbon group having 6 carbon atoms. In myrcene, R corresponds to the formula CH2-CH2-CH=CMe2. All reagents are obtained commercially, except for the metallocene [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}], which is prepared according to the procedure described in patent application WO 2007054224. 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. Mooney viscosity is measured using a vibrating consistometer as described in ASTM standard D1646 (1999). The measurement is carried out according to the following principle: the sample to be analyzed in the uncured state (i.e., before curing) is cast (molded) in a cylindrical chamber heated to a given temperature (100°C). After 1 minute of preheating, a rotor rotates inside the specimen at 2 revolutions per minute, and the operating torque required to maintain this movement is measured after 4 minutes of rotation. Mooney viscosity (ML) is expressed in "Mooney units" (MU, 1 MU = 0.83 Newton-meters).

[0047] 2.1-Ethylene and 1,3-butadiene copolymer: Elastomer E1 At 80°C, butyloctylmagnesium (BOMAG) is added to a reactor containing methylcyclohexane, ethylene (Et), and butadiene (Bd) in the ratios shown in Table 2 below to neutralize impurities in the reactor, and then the catalyst system is added (see Table 2). At this time, the reaction is controlled at 80°C, and the polymerization reaction begins. The polymerization reaction is carried out at a constant pressure of 8 bar. Ethylene and butadiene are fed to the reactor in the ratios shown in Table 2 throughout the polymerization. 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 to a constant weight in an oven under vacuum. The Mooney viscosity of E1 is 85. The catalyst system is a preformed catalyst system prepared in methylcyclohexane from the metallocene [MeSi(Flu)Nd(μ-BH)Li(THF)], the cocatalyst butyloctylmagnesium (BOMAG), and the preformed monomer 1,3-butadiene in the amounts shown in Table 2. The catalyst system is prepared according to the preparation method described in paragraph II.1 of patent application WO 2017093654 A1.

[0048] 2.2-Ethylene and myrcene copolymer: Elastomer E2 Synthesize the polymer according to the following procedure: At 80°C, butyloctylmagnesium (BOMAG) is added to a reactor containing methylcyclohexane, ethylene, and myrcene (My) in the ratios shown in Table 2 to neutralize impurities in the reactor, and then the catalyst system is added (see Table 2). At this time, the polymerization reaction begins by controlling the reaction temperature at 80°C. The polymerization reaction is carried out at a constant pressure of 8 bar. Ethylene and myrcene are fed to the reactor in the ratios shown in Table 2 throughout the polymerization. The polymerization reaction is terminated by cooling, degassing the reactor, and adding ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying to a constant weight in an oven under vacuum. The Mooney viscosity of E2 is 17. The catalyst system is a preformed catalyst system prepared in methylcyclohexane from the metallocene [MeSi(Flu)Nd(μ-BH)Li(THF)], the cocatalyst butyloctylmagnesium (BOMAG), and the preformed monomer 1,3-butadiene in the amounts shown in Table 2. The catalyst system is prepared according to the preparation method described in paragraph II.1 of patent application WO 2017093654 A1. The polymer microstructure and polymer properties are shown in Tables 3 and 4 below.

[0049] 2.3 Preparation of rubber composition: The rubber compositions, the formulations of which are shown in Table 5 below, expressed in phr (parts by weight per 100 parts of elastomer), were prepared according to the following procedure: the copolymer, the reinforcing filler, and the various other components, excluding the vulcanization system, were continuously introduced into an internal mixer (final filling level: about 70% by volume), the initial container temperature being about 80°C. Then, a thermomechanical process (non-productive phase) was carried out in one step, lasting a total of about 5 minutes, until a maximum "dropping" temperature of 150°C was reached. After the mixture thus obtained was collected and cooled, the sulfur and accelerators were incorporated into the mixer (homofinisher) at 40°C, and everything was mixed for about 10 minutes (productive phase). The compositions thus obtained were subsequently calendered in the form of rubber slabs (2-3 mm thick) or thin sheets for the measurement of their physical and mechanical properties. Composition C1 containing elastomer E1, a copolymer of ethylene and 1,3-butadiene, is not a composition of the invention. Composition C2 containing elastomer E2, a copolymer of ethylene and myrcene, is a composition of the invention.

[0050] 2.4 Results: The results are shown in Table 6 below. Composition C2 has a lower stiffness than composition C1, without the hysteresis properties being affected. This result is obtained due to the comparable diene unit content (14% for elastomer E1 and 13% for elastomer E2) and the much higher ethylene unit content in E2 than in E1 (87% vs. 78%). Despite the much higher ethylene content, rubber composition C2 of the present invention shows an improved compromise between stiffness and hysteresis properties.

[0051] [Table 2]

[0052] [Table 3]

[0053] [Table 4]

[0054] [Table 5] (1) N234 (2) Zeosil 1165 MP, from Solvay-Rhodia, in the form of micropearls (3) MES / HPD (Catenex SNR, from Shell) (4) Escorez 5600 C9 / dicyclopentadiene hydrocarbon resin from Exxon (Tg=55°C) (5) N-(1,3-dimethylbutyl)-N-phenyl-para-phenyldiamine (Santoflex 6-PPD, from Flexsys) (6) TESPT (Si69, from Evonik) (7) Pristerene 4931 Stearin, from Uniqema (8) Diphenylguanidine (9) Zinc Oxide, Industrial Grade, from Umicore (10) N-cyclohexyl-2-benzothiazole sulfenamide (Santocure CBS, from Flexsys)

[0055] [Table 6]

Claims

1. Reinforcing fillers, crosslinked systems, and ethylene in an amount of more than 50 phr to 100 phr; A rubber composition comprising an elastomer which is a copolymer with a 1,3-diene, the 1,3-diene being myrcene or β-farnesene.

2. 2. The rubber composition of claim 1, wherein the copolymer contains between 50 and 95 mole percent ethylene units, based on 100 mole percent of the total of ethylene units and 1,3-diene units.

3. 3. The rubber composition according to claim 1, wherein the copolymer contains ethylene units in an amount of at least 60 mol % relative to 100 mol % in total of ethylene units and 1,3-diene units.

4. 4. The rubber composition according to claim 1, wherein the copolymer contains ethylene units in an amount of up to 90 mol % relative to 100 mol % in total of ethylene units and 1,3-diene units.

5. The rubber composition according to any one of claims 1 to 4, wherein the copolymer has a glass transition temperature of less than -35°C.

6. 6. The rubber composition according to claim 1, wherein the reinforcing filler is silica, carbon black, or a mixture of carbon black and silica.

7. The rubber composition according to any one of claims 1 to 6, wherein the composition comprises a plasticizer.

8. A tire comprising a tread, said tire comprising the rubber composition according to any one of claims 1 to 7.

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