Rubber composition based on copolymer containing ethylene units and diene units and polyethylene

Abstract

The present invention relates to a rubber composition that exhibits high stiffness and at the same time has improved limit properties without the use of large amounts of reinforcing fillers or reinforcing resins. [Solution] The composition is based on at least one elastomeric matrix containing more than 50 phr of at least one copolymer containing ethylene units and diene units, 0 to 50 phr of a reinforcing filler, at least 3 phr of polyethylene, and a crosslinking system.

Description

[Technical field]

[0001] The present invention relates to a rubber composition intended in particular for the manufacture of tires, and in particular to a rubber composition constituting the inner layer of a tire, and in particular the underlayer of the tread of the tire. [Background technology]

[0002] Reducing greenhouse gas emissions in the transportation sector is one of the major challenges facing tire manufacturers. Great strides have been made through tires by lowering rolling resistance, as it has a direct impact on a vehicle's fuel consumption. Within a tire, three types of regions can be defined: - the radially outer area in contact with the surrounding air, which area essentially consists of the tire tread and the outer sidewall of the tire. The outer sidewall is an elastomeric layer located outside the carcass reinforcement with respect to the internal cavity of the tire between the crown and the bead, so as to completely or partially cover the area of ​​the carcass reinforcement extending from the crown to the bead. - the radially inner area in contact with the inflation gas, which generally consists of a layer that is gas-tight to the inflation gas, and is sometimes known as the inner gas-tight layer or innerliner. the interior region of the tire, i.e. the region between the outer and inner regions, including layers or plies referred to herein as the inner layers of the tire, such as the carcass ply, the tread underlayer, the tire belt ply or any other layer that is not in contact with the surrounding air or with the inflation gases of the tire;

[0003] The rubber compositions constituting the inner layers of a tire, particularly the underlayer of the tread and / or the inner layers of the bead area, must have sufficient stiffness, whether for improving roadholding in the case of the underlayer of the tread, or for the beads, to absorb stresses from the carcass reinforcement and transmit the forces experienced by the tire from the sidewall to the rim. In order to obtain rubber compositions with high stiffness, it has been proposed to introduce large amounts of reinforcing fillers into these rubber compositions, however this solution is detrimental to the hysteresis and adversely affects the rolling resistance. Another solution to increase the stiffness of rubber compositions consists in using reinforcing resins such as phenolic resins. However, this solution also involves an increase in hysteresis, but generally also a decrease in limit properties. Moreover, the use of said resins can be disadvantageous from a hygiene and environmental point of view, since certain resins emit formaldehyde during tire manufacture. Thus, reducing hysteresis by reducing or even eliminating the reinforcing filler content of the rubber composition while retaining high stiffness and without the use of reinforcing resins remains a technically very challenging challenge for tire manufacturers. In the course of its research, the applicant has surprisingly found that the use of special polyolefins in rubber compositions allows the total or partial replacement of reinforcing fillers and preserves or even improves the stiffness, especially at low strain, of said rubber compositions, and while doing so, simultaneously preserves or even improves the limiting properties of the rubber compositions, especially the elongation at break and the stress at break. Summary of the Invention

[0004] Thus, one subject of the present invention is an elastomeric matrix containing more than 50 phr of at least one copolymer containing ethylene units and diene units; -0~50 phr of reinforcing filler, - at least 3 phr of polyethylene, -Cross-linked systems The rubber composition is based on Another subject of the invention is a tire comprising the composition of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] I-definition The expression "based on" used to define the components of a catalyst system or composition is understood to mean a mixture of these components or, at least in part, the reaction products of some or all of these components with one another during the various stages of production of the catalyst system or composition. Thus, in the case of a composition, the reaction products may be totally or partially crosslinked or non-crosslinked. "Elastomeric matrix" is understood to mean all of the elastomers of the composition, including the copolymers defined below. Within the meaning of the present invention, the expression "parts by weight per 100 parts by weight of elastomer" (or phr) should be understood to mean the ratio by weight per 100 parts by weight of elastomer present in the rubber composition under consideration. In this text, all indicated percentages (%) are percentages by weight (%), unless expressly indicated otherwise. Furthermore, any interval of values ​​expressed by the expression "between a and b" denotes a range of values ​​extending from above a to below b (i.e. the limits a and b are excluded), whereas any interval of values ​​expressed 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). In this document, when an interval of values ​​is expressed by the expression "from a to b", it also and preferentially means the interval expressed by the expression "between a and b".

[0006] When referring to a "major" compound, this is understood to mean, for the purposes of the present invention, that this compound is predominant among the compounds of the same type in the composition, i.e., the compound that occupies the largest amount by mass among the compounds of the same type. Thus, for example, the main elastomer is the elastomer that occupies the largest amount by mass with respect to the total mass of elastomers in the composition. Similarly, a "major" filler is the filler that occupies the largest amount by mass among the fillers of the composition. By way of example, in a system that contains only one elastomer, this elastomer is predominant for the purposes of the present invention, and in a system that contains two elastomers, the main elastomer occupies more than half the mass of the elastomer. In contrast, a "minor" compound is a compound that does not occupy the largest mass fraction among the compounds of the same type. Preferably, the term "major" is understood to mean that it is present in an amount of more than 50%, preferably more than 60%, more than 70%, more than 80%, more than 90%, and even more preferentially the "major" compound occupies 100%. In this patent application, the expressions "all of the monomer units of the copolymer" or "total amount of monomer units of the copolymer" mean all the constituent repeat units of the copolymer resulting from the insertion of the monomers into the copolymer chain by polymerization. Unless otherwise indicated, the content of monomer units or repeat units in copolymers of ethylene and 1,3-diene is given in molar percentages calculated based on all the monomer units of the copolymer. The compounds referred to in this description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or may be obtained from renewable starting materials derived from biomass. Likewise, the compounds referred to may originate from the reuse of used materials, i.e. they may partially or totally result from a recycling process or may be obtained from starting materials which are themselves the result of a recycling process. Polymers, plasticizers, fillers, etc. are of particular interest. Unless otherwise indicated, all glass transition temperature "Tg" values ​​given herein are measured by DSC (Differential Scanning Calorimetry) in known manner according to ASTM standard D3418 (1999).

[0007] II - Description of the Invention II-1 Elastomer matrix According to the invention, the elastomeric matrix comprises more than 50 phr of at least one copolymer containing ethylene units and diene units (hereinafter referred to as "copolymer"). The term "elastomeric matrix" is understood to mean all the elastomers of the composition. The term "copolymer containing ethylene and diene units" is understood to mean any copolymer that contains at least ethylene and diene units in its structure. Thus, the copolymer may contain monomer units other than ethylene and diene units. For example, the copolymer may contain alpha-olefin units, in particular alpha-olefin units having 3 to 18 carbon atoms, advantageously 3 to 6 carbon atoms. For example, the alpha-olefin units may be selected from the group consisting of propylene, butene, pentene, hexene or mixtures thereof. In a known manner, the expression "ethylene unit" refers to a -(CH2-CH2)- subunit resulting from the insertion of ethylene into the elastomeric chain. The term "diene unit" is understood to mean a monomer unit resulting from the insertion of a monomer subunit resulting from the polymerization of a conjugated or non-conjugated diene monomer, the diene unit comprising a carbon-carbon double bond. Preferably, the diene unit is selected from the group consisting of butadiene units, isoprene units and mixtures of these diene units. In particular, the diene units of the copolymer may be 1,3-diene units having from 4 to 12 carbon atoms, such as 1,3-butadiene or 2-methyl-1,3-butadiene units. More preferably, the diene units are mainly, or preferentially even exclusively, 1,3-butadiene units. In the copolymer, the ethylene units advantageously represent between 50 and 95 mol% of the monomer units of the copolymer, i.e. between 50 and 95 mol% of the monomer units of the copolymer. Advantageously, the ethylene units in the copolymer represent between 55 and 90 mol%, preferably between 60 and 90 mol%, preferably between 70 and 85 mol% of the monomer units of the copolymer.

[0008] Advantageously, the copolymer (i.e., for the record, at least one copolymer containing ethylene units and diene units) is a copolymer of ethylene and 1,3-diene (preferably 1,3-butadiene), i.e., according to the invention, the copolymer consists exclusively of ethylene and 1,3-diene (preferably 1,3-butadiene) units. When the copolymer is a copolymer of ethylene and a 1,3-diene, said copolymer advantageously contains units of formula (I) and / or (II): The presence of the saturated 6-membered cyclic unit of formula (I), 1,2-cyclohexanediyl, as a monomer unit in the copolymer can be attributed to a very specific sequence of insertions of ethylene and 1,3-butadiene into the polymer chain during its growth. [ka]

[0009] For example, a copolymer of ethylene and a 1,3-diene may not have units of formula (I), in which case the copolymer preferably contains units of formula (II). When the copolymer of ethylene and 1,3-diene comprises units of formula (I) or units of formula (II) or units of formula (I) and units of formula (II), the molar percentages o and p, respectively, of the units of formula (I) and units of formula (II) in the copolymer preferably satisfy the following equation (eq. 1) and more preferentially the following equation (eq. 2), where o and p are calculated based on all the monomer units of the copolymer. 0 <o+p≦25 (eq. 1) 0 <o+p<20 (eq. 2)

[0010] According to the invention, the copolymer, preferably a copolymer of ethylene and a 1,3-diene, preferably 1,3-butadiene, is a random copolymer. Advantageously, the number average mass (Mn) of the copolymer, preferably of ethylene and of a 1,3-diene, preferably of 1,3-butadiene, is in the range ranging from 100,000 to 300,000 g / mol, preferably from 150,000 to 250,000 g / mol. The Mn of the copolymer is determined in known manner by size exclusion chromatography (SEC) as described below in point IV-1.2. The copolymers can be obtained according to various synthesis methods known to those skilled in the art, in particular depending on the targeted microstructure of the copolymer. In general, the copolymers can be prepared by copolymerization of at least a diene, preferably a 1,3-diene, more preferably 1,3-butadiene, with ethylene, in accordance with known synthesis methods, in particular in the presence of a catalyst system comprising a metallocene complex. In this respect, mention can be made of catalyst systems based on metallocene complexes, which are described in documents EP 1 092 731, WO 2004035639, WO 2007054223 and WO 2007054224 in the name of the applicant. The copolymers, including when they are random, can also be prepared via a process using a preformed type catalyst system, such as those described in documents WO 2017093654 A1, WO 2018020122 A1 and WO 2018020123 A1. The copolymer may consist of a mixture of copolymers containing ethylene units and diene units, differing from one another by reason of their microstructure and / or their macrostructure.

[0011] According to the invention, the elastomeric matrix can contain at least one other elastomer that is not a copolymer containing ethylene units and diene units, but this is neither essential nor preferred. Preferentially, therefore, the content of at least one copolymer containing ethylene units and diene units is in a range ranging from 50 to 100 phr, preferably from 60 to 100 phr, and even more preferably from 80 to 100 phr. Advantageously, the at least one copolymer containing ethylene units and diene units is the only elastomer of the composition, i.e. it represents 100% by weight of the elastomeric matrix. When the elastomeric matrix comprises at least one other elastomer which is not a copolymer containing ethylene and diene units, this at least one other elastomer may be, for example, a diene elastomer selected from the group consisting of polybutadienes (BRs), natural rubbers (NR), synthetic isoprenes (IRs), butadiene copolymers, isoprene copolymers and mixtures of these elastomers. The butadiene copolymers are in particular selected from the group consisting of butadiene / styrene copolymers (SBRs).

[0012] II-2 Polyethylene The rubber composition of the present invention also has the essential feature of containing at least 3 phr of polyethylene. Surprisingly, the Applicant has found that it is possible to replace all or part of the reinforcing fillers normally used in rubber compositions intended in particular for the manufacture of tires with polyethylene and to obtain rubber compositions which exhibit significantly improved mechanical properties. Polyethylene (also called "PE") is a semi-crystalline polyolefin that belongs to the family of thermoplastic polymers. In the context of the present invention, the term "polyethylene" refers to an ethylene homopolymer, i.e. a polymer obtained from ethylene as the only monomer. However, the presence of propylene, 1-butene, 1-hexene or 1-octene monomers in this polymer is excluded. However, if these monomers are present, they are present as impurities and in small amounts, preferably less than 5% by weight relative to the total weight of polyethylene and impurities. Copolymers of ethylene and propylene (also called EP, EPM or EPR for "ethylene propylene rubber") do not fall within the above definition of polyethylene.

[0013] Preferably, the polyethylene that can be used in the context of the present invention is a non-crosslinked polyethylene. For the purposes of the present invention, the term "non-crosslinked polyethylene" is understood to mean a polyethylene that has not undergone a crosslinking reaction. It is therefore not a crosslinked polyethylene, also called PEX (instead of "crosslinked PE"). Crosslinked polyethylene PEX is obtained after polymerization of ethylene monomers by a crosslinking reaction that can be crosslinking with peroxides (PEX-A process), crosslinking by irradiation (PEX-C process), crosslinking by silanes and a crosslinking catalyst (PEX-B process). Naturally, non-crosslinked polyethylene can undergo a crosslinking step after its incorporation into the rubber composition of the present invention, for example during the curing of a tire that comprises the rubber composition of the present invention. Preferentially, the polyethylene is selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), ultra high molecular weight polyethylene (UHMWPE), very low density polyethylene (VLDPE) and mixtures of these polyethylenes. High density polyethylene is particularly preferred. Preferentially, polyethylene, especially high density polyethylene, is used, with a molecular weight of 940 to 970 kg / m 3 in the range of 940 to 965 kg / m 3 in the range up to 950-970 kg / m 3The density is measured at 23°C according to ISO standard 1183-2019. Preferentially, the polyethylene, in particular the high density polyethylene, has a melt flow rate in the range ranging from 2 to 25 g / 10 min, preferably ranging from 2.5 to 22 g / 10 min, and more preferentially ranging from 10 to 25 g / 10 min, at 190° C. under 5 kg. The melt flow rate (MFR 190° C. / 5 kg) ("MFR" instead of "Mass Flow Rate") is measured according to ISO standard 1133-1-2012 at 190° C. through a standardized die under the action of a piston weighted with a mass of 5 kg. The polyethylene that can be used in the context of the present invention can be functionalized or non-functionalized polyethylene.

[0014] The term "non-functionalized polyethylene" is understood to mean a polyethylene that has not been modified, after its polymerization, by grafting a functional group containing at least one heteroatom selected from Si, N, S, O and Cl. In other words, a non-functionalized polyethylene essentially consists of a mixture of carbon and hydrogen atoms and does not contain heteroatoms selected from the group consisting of Si, N, S, O and Cl. If these heteroatoms are present in the polyethylene, they are present as impurities. Even more preferentially, the polyethylene is a non-functionalized and preferably non-crosslinked polyethylene, in particular a non-functionalized and preferably non-crosslinked high density polyethylene, having a viscosity of 940 to 970 kg / m, measured according to ISO standard 1183-2019 at 23°C. 3 and a melt flow rate (190°C / 5kg) in the range of 2 to 25 g / 10 min, measured according to ISO standard 1133-1-2012. More preferably, the non-functionalized and preferably non-crosslinked polyethylene, in particular the non-functionalized and preferably non-crosslinked high density polyethylene, has a melt flow rate (190°C / 5kg) in the range of 950 to 970 kg / m, measured according to ISO standard 1183-2019 at 23°C. 3 and a melt flow rate (190°C / 5kg) ranging from 10 to 25 g / 10 min.

[0015] Usable non-functionalized polyethylene can be obtained by known conventional processes, for example, in particular by polymerization in the presence of metallocene catalysts. At the end of the polymerization, the polyethylene is pelletized without any crosslinking reaction. Non-functionalized polyethylene is commercially available from suppliers such as, for example, Dow Global Technologies, BASF, Silon, ENI, etc. The polyethylene that can be used in the context of the present invention can also be a functionalized polyethylene. For the purposes of the present invention, the term "functionalized polyethylene" is understood to mean a polyethylene that has undergone a modification reaction after its polymerization so as to include at least one functional group containing at least one heteroatom selected from the group consisting of Si, N, O, S and Cl. Particularly suitable functional groups are those that contain at least one function such as, for example, silanol, alkoxysilane, chlorine atom. The modification or functionalization of the polyethylene can be achieved by any known means, in particular by grafting a functional group containing at least one heteroatom. At the end of this reaction, the functionalized polyethylene does not undergo a crosslinking reaction. The functionalized polyethylene can be commercially available from suppliers such as, for example, Dow Global Technologies, BASF, Silon, ENI, etc.

[0016] Preferentially, the functionalized and preferably non-crosslinked polyethylene comprises at least one alkoxysilane functional group. In the remainder of the description, this polyethylene will be designated by the expression "alkoxysilane-functionalized polyethylene" or by the expression "silane-grafted polyethylene" or by the expression "alkoxysilane polyethylene", these three expressions being equivalent and interchangeable. The alkoxysilane-functionalized polyethylene is obtained by grafting a silane compound of formula (I) below onto polyethylene. CH2=CR-(COO) x (C n H 2n )ySiR'3(I) During the ceremony: -R is a hydrogen atom or a methyl group; - x, y are integers equal to 0 or 1, provided that when x=1, then y=; -n is an integer ranging from 1 to 12, preferably from 1 to 4; - each R' may be the same or different and is a chemical group selected from the group consisting of an alkoxy group having 1 to 12 carbon atoms (e.g., methoxy, ethoxy, butoxy), an aryloxy group having 6 to 12 carbon atoms (e.g., phenoxy), an aliphatic acyloxy group having 1 to 12 carbon atoms (e.g., formyloxy, acetyloxy, propanoyloxy), a substituted or unsubstituted amino group (e.g., alkylamino).

[0017] In particular, preferred compounds of formula (I) are -R is a hydrogen atom or a methyl group; - x, y are integers equal to 0 or 1, with the proviso that when x=1, then y=1; - n is an integer ranging from 1 to 12, preferably from 1 to 4; - each R', which may be the same or different, is an alkoxy group having 1 to 12 carbon atoms, preferably methoxy, ethoxy, butoxy; It may be a compound. The compound of formula (I) can be grafted onto polyethylene by radical reaction in the presence of peroxide. The grafting reaction can be carried out in an extruder. At the exit of the extruder, silane-grafted and non-crosslinked polyethylene is obtained. An example of the grafting process is described in document EP2407496A1, paragraphs

[0042] to

[0048] . Silane-grafted polyethylene is commercially available from suppliers such as Dow Global Technologies, BASF, Silon, ENI, etc.

[0018] Preferentially, the functionalized and preferably non-crosslinked polyethylene, in particular the alkoxysilane-functionalized polyethylene, may be selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, medium density polyethylene, ultra-high molecular weight polyethylene, very low density polyethylene, and mixtures of these polyethylenes. Even more preferentially, the functionalized and non-crosslinked polyethylene, in particular the alkoxysilane-functionalized and non-crosslinked polyethylene, is a high density polyethylene. Preferentially, the functionalized and preferably non-crosslinked polyethylene, in particular the alkoxysilane-functionalized polyethylene, has a crosslinking capacity of 940 to 970 kg / m 3 in the range of 940 to 965 kg / m 3 The density is measured according to ISO standard 1183-2019 at 23 ° C. Preferentially, the functionalized and preferably non-crosslinked polyethylene, in particular the alkoxysilane-functionalized and non-crosslinked polyethylene, has a melt flow rate in the range ranging from 2 to 25 g / 10 min, preferably ranging from 2.5 to 22 g / 10 min, at 190 ° C under 5 kg. The melt flow rate (MFR 190 ° C / 5 kg) ("MFR" instead of "Mass Flow Rate") is measured according to ISO standard 1133-1-2012 at 190 ° C through a standardized die under the action of a piston weighted with a mass of 5 kg. Even more preferentially, the functionalized and preferably non-crosslinked polyethylene, in particular the alkoxysilane-functionalized polyethylene, has a crosslinking coefficient of 940 to 970 kg / m, measured according to ISO standard 1183-2019 at 23°C. 3 and a melt flow rate (MFR 190°C / 5kg) ranging from 2 to 25 g / 10 min, measured according to ISO standard 1133-1-2012. More preferably, its density, measured according to ISO standard 1183-2019 at 23°C, is between 940 and 960 kg / m 3 and it has a melt flow rate (190° C. / 5 kg) ranging from 2 to 10 g / 10 min. Preferentially, the content of polyethylene in the rubber composition, whether it is functionalized, in particular alkoxysilane-functionalized, or non-functionalized, is in the range ranging from 3 phr to 75 phr, preferably from 4 to 60 phr, and more preferably from 5 to 50 phr.

[0019] II-3 Reinforcing filler The rubber composition of the present invention has a further essential feature of containing 0 to 50 phr of a reinforcing filler, in other words, the composition may not contain a reinforcing filler, or, if the composition contains a reinforcing filler, it contains the reinforcing filler in an amount less than 50 phr. Advantageously, the content of reinforcing fillers in the composition of the invention is in the range ranging from 0 to 40 phr, preferably from 0 to 35 phr, preferably from 0 to 20 phr. For example, the content of reinforcing fillers in the composition of the invention may be in the range ranging from 2 to 40 phr, such as from 5 to 35 phr, for example from 5 to 20 phr. The reinforcing filler may be any type of "reinforcing" filler known for its ability to reinforce rubber compositions that can be used in particular to manufacture tires, for example organic fillers such as carbon black, inorganic fillers such as silica, or a mixture of these two types of fillers. The reinforcing filler typically consists of nanoparticles, the average size (by mass) of which is less than 1 μm, generally less than 500 nm, usually between 20 and 200 nm, in particular and more preferentially between 20 and 150 nm. Advantageously, the reinforcing filler is chosen from carbon black, silica, and mixtures thereof. Suitable carbon blacks include all carbon blacks, in particular those conventionally used in tires or tire treads. Among the latter blacks, more particular mention will be made of the reinforcing carbon blacks of the 100, 200 and 300 series, or the blacks of the 500, 600 or 700 series (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, as commercially available, in isolated form or in any other form, for example as support for some of the rubber additives used. Carbon blacks can also be, for example, already incorporated in diene elastomers, in particular isoprene elastomers, in the form of masterbatches (see, for example, patent applications WO97 / 36724-A2 and WO99 / 16600-A1). Advantageously, when a reinforcing filler is present in the composition, it comprises primarily, preferably exclusively, carbon black.

[0020] When a reinforcing inorganic filler is used, it may in particular be a mineral filler of siliceous type, preferentially silica (SiO2), or a mineral filler of aluminous type, in particular alumina (Al2O3). The silica used may be any reinforcing silica known to the person skilled in the art, in particular one having a BET specific surface area and also a CTAB specific surface area both of 450 m 2 / g, preferably 30 to 400m 2 / g, especially 60-300m 2 The silica may be any precipitated or fumed silica in the range spanning 0.1 to 1.0 μm / g. The term "reinforcing inorganic filler" should be understood in this specification to mean any inorganic or mineral filler, whatever its color and its origin (natural or synthetic), also known as "white fillers", "clear fillers" or "non-black fillers", in contrast to carbon black, capable of reinforcing, by itself alone, without any other means than intermediate coupling agents, the rubber compositions intended for the manufacture of tires. There are also reinforcing inorganic fillers which can be characterized in a known manner, in particular by the presence of hydroxyl (-OH) groups on their surface.

[0021] Any type of precipitated silica can be used, in particular highly dispersed precipitated silica (called "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, either highly dispersible or not, are well known to the person skilled in the art. For example, mention may be made of the silicas described in patent applications WO03 / 016215-A1 and WO03 / 016387-A1. Among the commercially available HDS silicas, in particular the Ultrasil® 5000GR and Ultrasil® 7000GR silicas from Evonik or the Zeosil® 1085GR, Zeosil® 1115MP, 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 utilized: 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 reinforcing inorganic filler may be a mixture of different reinforcing inorganic fillers, in which case the proportion of the reinforcing inorganic fillers in the reinforcing filler relates to all the reinforcing inorganic fillers.

[0022] To link the reinforcing inorganic filler to the diene elastomer, it is possible to use, in a known manner, at least difunctional coupling agents (or bonding agents) intended to provide a satisfactory bond, chemical and / or physical properties between the inorganic filler (the surface of its particles) and the diene elastomer. In particular, it is possible to use organosilanes or polyorganosilanes that are at least difunctional. The term "difunctional" is understood 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 diene elastomer. For example, the difunctional compound may comprise a first functional group comprising a silicon atom, said first functional group capable of interacting with the hydroxyl groups of the inorganic filler, and a second functional group comprising a sulfur atom, said second functional group capable of interacting with the diene elastomer. Preferentially, the organosilane is selected from the group consisting of organosilane polysulfides (symmetrical or asymmetrical), such as bis(3-triethoxysilylpropyl)tetrasulfide (abbreviated as TESPT) sold under the name Si69 by Evonik, or bis(triethoxysilylpropyl)disulfide (abbreviated as TESPD) sold under the name Si75 by Evonik, polyorganosilanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl)octanethioate sold under the name NXT silane by Momentive. Even more preferentially, the organosilane is an organosilane polysulfide. Of course, mixtures of the above coupling agents may also be utilized. When using a reinforcing inorganic filler, a person skilled in the art can easily adjust the content of the coupling agent in the composition of the present invention. Typically, the content of the coupling agent corresponds to 0.5% by weight to 15% by weight based on the amount of the reinforcing inorganic filler.

[0023] II-4 Crosslinked system The crosslinking system may be any type of system known to those skilled in the art of rubber compositions for tires. It may in particular be based on sulfur and / or peroxides and / or bismaleimides. Preferentially, the crosslinking system comprises, preferably consists of, a peroxide, preferably an organic peroxide. The term "organic peroxide" is understood to mean an organic compound, i.e. a carbon-containing compound containing an -OO- group (two oxygen atoms linked by a single covalent bond). During the crosslinking process, the organic peroxide decomposes at its labile OO bond to give free radicals. These free radicals allow the creation of crosslinks. The organic peroxide is preferably selected from the group comprising or consisting of dialkyl peroxides, monoperoxycarbonates, diacyl peroxides, peroxyketals and peroxyesters. Preferably, the dialkyl peroxide is selected from the group comprising or consisting of dicumyl peroxide, di(t-butyl)peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-amylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hex-3-yne, 2,5-dimethyl-2,5-di(t-amylperoxy)hex-3-yne, α,α'-di[(t-butylperoxy)isopropyl]benzene, α,α'-di[(t-amylperoxy)isopropyl]benzene, di(t-amyl)peroxide, 1,3,5-tri[(t-butylperoxy)isopropyl]benzene, 1,3-dimethyl-3-(t-butylperoxy)butanol, and 1,3-dimethyl-3-(t-amylperoxy)butanol.

[0024] Certain monoperoxycarbonates may also be used, such as OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate, OO-tert-butyl O-isopropyl monoperoxycarbonate, and OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate. Among the diacyl peroxides, the preferred peroxide is benzoyl peroxide. Among the peroxyketals, preferred peroxides are selected from the group comprising or consisting of 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl 4,4-di(t-butylperoxy)valerate, ethyl 3,3-di(t-butylperoxy)butyrate, 2,2-di(t-amylperoxy)propane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (or methyl ethyl ketone peroxide cyclic trimer), 3,3,5,7,7-pentamethyl-1,2,4-trioxepane, n-butyl 4,4-bis(t-amylperoxy)valerate, ethyl 3,3-di(t-amylperoxy)butyrate, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)cyclohexane, and mixtures thereof. Preferably, the peroxyester is selected from the group consisting of tert-butylperoxybenzoate, tert-butylperoxy-2-ethylhexanoate, and tert-butylperoxy-3,5,5-trimethylhexanoate.

[0025] In summary, the organic peroxide is particularly preferably selected from the group consisting of dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl)peroxide, tert-butylcumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, n-butyl 4,4-di(tert-butylperoxy)valerate, OO-(t-butyl)O-(2-ethylhexyl)monoperoxycarbonate, tert-butylperoxyisopropyl carbonate, tert-butylperoxybenzoate, tert-butylperoxy-3,5,5-trimethylhexanoate, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene, and mixtures thereof. More preferably, the organic peroxide is selected from the group consisting of dicumyl peroxide, n-butyl 4,4-di(tert-butylperoxy)valerate, OO-(t-butyl)O-(2-ethylhexyl)monoperoxycarbonate, tert-butylperoxyisopropyl carbonate, tert-butylperoxybenzoate, tert-butylperoxy-3,5,5-trimethylhexanoate, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene, and mixtures thereof.

[0026] The content of peroxide, preferably organic peroxide, in the composition is advantageously in the range ranging from 0.1 to 10 phr, preferably from 0.5 to 5 phr and even better from 1 to 4 phr. As examples of commercially available peroxides that can be used in the context of the present invention, mention may be made of Dicup from Hercules Powder Co., Perkadox Y12 from Noury ​​van der Lande, Peroximon F40 from Montecatini Edison SpA, Trigonox from Noury ​​van der Lande, Varox from RT Vanderbilt Co. or Luperko from Wallace & Tiernan Inc. Furthermore, the composition of the present invention advantageously does not contain sulfur as a vulcanizing agent or contains less than 0.9 phr, preferably less than 0.5 phr, preferably less than 0.3 phr, preferably less than 0.2 phr, preferably less than 0.1 phr of sulfur, which may be molecular sulfur or a sulfur donor, such as alkylphenol disulfide (APDS).

[0027] II-5 Possible Additives The rubber composition of the present invention may optionally contain all or some of the useful additives conventionally used in elastomeric tire compositions, such as plasticizers (e.g. plasticizing oils and / or plasticizing resins), pigments, protective agents such as antiozonant waxes, chemical antiozonants, antioxidants, antifatigue agents, reinforcing resins (e.g. those described in application WO 02 / 10269). The composition does not require the use of reinforcing resins (or curing resins) known to those skilled in the art to harden rubber compositions, in particular by increasing their Young's modulus or also their complex dynamic shear modulus G*. Particularly advantageously, the composition of the present invention does not contain reinforcing resins or contains less than 1 phr, preferably less than 0.5 phr, of reinforcing resins. Examples of said reinforcing resins can be found in chapter II.3 of patent application WO20198679A1.

[0028] II-6 Preparation of Rubber Composition The compositions of the invention can be prepared in a suitable mixer using two successive preparation steps well known to those skilled in the art: - a first thermomechanical processing or kneading stage ("non-productive" stage), which can be carried out in a single thermomechanical step, during which all the necessary components other than the crosslinking system, in particular the elastomer matrix, the reinforcing fillers and the various other optional additives, are introduced into a suitable mixer, such as a standard internal mixer (for example of the Banbury type). The incorporation of the optional fillers into the elastomer can be carried out in one or several batches while being thermomechanically kneaded. For example, when the elastomer is already fully or partially incorporated with fillers in the form of a masterbatch, as described in patent applications WO 97 / 36724 and WO 99 / 16600, it is the masterbatch that is kneaded directly, and, if appropriate, also with other elastomers or fillers present in the composition but not in the form of a masterbatch, and with the various other optional additives other than the crosslinking system. The non-productive stage can be carried out at elevated temperatures up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C, for a time generally between 2 and 10 minutes; - a second machining step ("productive" step), which is carried out in an external mixer, such as an open mill, after cooling the mixture obtained during the first non-productive step to a lower temperature, typically below 120°C, for example between 40°C and 100°C. The crosslinking system is then incorporated, and the combined mixture is mixed for a period of several minutes, for example between 5 and 15 minutes. Said steps are described, for example, in patent applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO 00 / 05300 and WO 00 / 05301.

[0029] The final composition thus obtained can then be calendered, for example in the form of sheets or slabs, in particular for laboratory characterization, or extruded (or coextruded with other rubber compositions) in the form of rubber semi-finished products (or profiled elements) that can be used, for example, as tire sidewalls. These products can then be used for tire manufacture, according to techniques known to those skilled in the art. The composition may be in either the raw state (before crosslinking or vulcanization) or in the cured state (after crosslinking or vulcanization) and may be a semi-finished product that can be used in a tire. Crosslinking (or curing) or, where appropriate, vulcanization is carried out in known manner, at temperatures generally between 130°C and 200°C, for a sufficient time which may range, for example, between 5 and 90 minutes, depending in particular on the curing temperature, the crosslinking system employed and the crosslinking kinetics of the composition under consideration.

[0030] II-7 Tires A subject of the invention is also a tire comprising the rubber composition of the invention. The composition defined in this description is particularly well suited for the inner layer of a tire. Preferably, therefore, the composition of the invention is present at least in at least one inner layer of a tire. Advantageously, the inner layer of the tire is selected from the group consisting of carcass ply, crown ply, bead wire filling, crown foot, decoupling layer, edge rubber, filler rubber, tread underlayer and combinations of these inner layers, preferably the tread underlayer. In this text, the term "edge rubber" is understood to mean a layer that is placed in the tire in direct contact with the end of a reinforcing ply, the end of a reinforcing element or another edge rubber. The tyre of the invention may be intended to be fitted on a passenger car type motor vehicle, an SUV (sport utility vehicle), or a two-wheeled vehicle (in particular a motorcycle), or an aircraft, or an industrial vehicle chosen from vans, heavy duty vehicles, i.e. subways, buses, heavy road transport vehicles (lorries, tractors, trailers) or off-road vehicles, such as heavy agricultural vehicles or civil engineering installations.

[0031] III - Preferred Embodiments In view of the above, preferred embodiments of the present invention are described below. 1. A rubber composition based on an elastomeric matrix containing more than 50 phr of at least one copolymer containing ethylene units and diene units, 0 to 50 phr of a reinforcing filler, at least 3 phr of a polyethylene, and a crosslinking system. 2. The rubber composition according to embodiment 1, wherein the copolymer containing ethylene units and diene units is a copolymer of ethylene and a 1,3-diene. 3. The rubber composition according to embodiment 2, wherein the 1,3-diene is 1,3-butadiene.

[0032] 4. A rubber composition according to any one of embodiments 2 and 3, wherein the copolymer contains units of formula (I) below or units of formula (II) below, or units of formula (I) and units of formula (II). [ka]

[0033] 5. The rubber composition according to embodiment 4, wherein the molar percentages o and p of units of formula (I) and units of formula (II) in the copolymer, respectively, satisfy the following equation (eq. 1) and preferentially the following equation (eq. 2), where O and p are calculated based on all monomer units of the copolymer: 0 <o+p≦25 (eq. 1) 0 <o+p<20 (eq. 2) 6. The rubber composition according to any one of the preceding embodiments, wherein the ethylene units in the copolymer account for between 50 mol % and 95 mol %, preferably between 55 mol % and 90 mol %, of the monomer units of the copolymer. 7. The rubber composition according to any one of embodiments 1 to 6, wherein the copolymer is a random copolymer. 8. The rubber composition according to any one of the preceding embodiments, wherein the copolymer has a number average mass Mn ranging from 100,000 to 300,000 g / mol, preferably from 150,000 to 250,000 g / mol. 9. The rubber composition according to any one of the preceding embodiments, wherein the content of copolymer containing ethylene units and diene units is in the range extending from 60 to 100 phr, preferably from 80 to 100 phr.

[0034] 10. The rubber composition according to any one of embodiments 1 to 9, wherein the polyethylene is a non-crosslinked polyethylene. 11. The rubber composition according to any one of embodiments 1 to 10, wherein the polyethylene is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, medium density polyethylene, ultra-high molecular weight polyethylene, very low density polyethylene, and mixtures of these polyethylenes. 12. The rubber composition according to any one of embodiments 1 to 11, wherein the polyethylene is a non-crosslinked high density polyethylene (HDPE). 13. Polyethylene: 940-970kg / m 3 in the range of 940 to 965 kg / m 3 13. The rubber composition according to any one of embodiments 1 to 12, having a density in the range ranging from 0.1 to 0.5. 14. The rubber composition according to any one of embodiments 1 to 13, wherein the polyethylene has a melt flow rate in the range of 2 to 25 g / 10 min, preferably 2.5 to 22 g / 10 min, at 190° C. under 5 kg. 15. The rubber composition according to any one of embodiments 1 to 14, wherein the polyethylene is functionalized. 16. The rubber composition of embodiment 15, wherein the functionalized polyethylene comprises at least one alkoxysilane functional group. 17. The rubber composition according to any one of the preceding embodiments, wherein the polyethylene content is in the range extending from 3 to 75 phr, preferably from 4 to 60 phr. 18. The rubber composition according to any one of the preceding embodiments, wherein the reinforcing filler content is in the range extending from 0 to 40 phr, preferably from 0 to 35 phr. 19. The rubber composition according to any one of the preceding embodiments, wherein the reinforcing filler is selected from carbon black, silica, and mixtures thereof. 20. The rubber composition of any one of embodiments 1-19, wherein the reinforcing filler comprises primarily, and preferably exclusively, carbon black.

[0035] 21. The rubber composition according to any one of the preceding embodiments, wherein the crosslinking system is based on sulfur and / or peroxide and / or bismaleimide. 22. The crosslinking system is preferably selected from the group consisting of dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl)peroxide, tert-butylcumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, n-butyl 4,4-di(tert-butylperoxy)valerate, OO-(t-butyl)O-(2-ethylhexyl)monoperoxycarbonate, tert-butylperoxyisopropyl carbonate, tert-butylperoxybenzoate, tert-butylperoxy-3,5,5-trimethylhexanoate, 1,3(4)-bis(t 22. The rubber composition according to any one of the preceding embodiments, comprising at least one organic peroxide selected from the group consisting of dicumyl peroxide, n-butyl 4,4-di(tert-butylperoxy)valerate, OO-(t-butyl)O-(2-ethylhexyl)monoperoxycarbonate, tert-butylperoxyisopropylcarbonate, tert-butylperoxybenzoate, tert-butylperoxy-3,5,5-trimethylhexanoate, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene, and mixtures thereof. 23. The rubber composition according to any one of embodiments 1 to 22, wherein the peroxide content is in the range ranging from 0.1 to 10 phr, preferably from 0.5 to 5 phr, and more preferably from 1 to 4 phr. 24. The rubber composition according to any one of the preceding embodiments, wherein the composition does not contain sulfur as a vulcanizing agent or contains less than 0.9 phr, preferably less than 0.5 phr, preferably less than 0.3 phr, preferably less than 0.2 phr, preferably less than 0.1 phr of sulfur. 25. The rubber composition according to any one of the preceding embodiments, wherein the composition does not contain a reinforcing resin or contains less than 1 phr, preferably less than 0.5 phr, of a reinforcing resin. 26. A tire comprising the rubber composition according to any one of embodiments 1 to 25, wherein the rubber composition is preferably present in at least one interior layer of the tire. 27. The tire of embodiment 26, wherein at least one inner layer of the tire is selected from the group consisting of carcass ply, crown ply, bead wire filling, crown foot, decoupling layer, edge rubber, filler rubber, tread underlayer, and combinations of these inner layers, preferably a tread underlayer. EXAMPLES

[0036] IV - Example IV-1 Measurements and tests used IV-1.1 Determination of the microstructure of elastomers: The microstructure of the ethylene-butadiene copolymer is 1 As determined by H NMR analysis, 1 When the resolution of a H NMR spectrum does not allow the assignment and quantification of all species 13The measurements are supported by C NMR analysis. Measurements are performed on a Bruker 500 MHz NMR spectrometer at frequencies of 500.43 MHz for proton observations and 125.83 MHz for carbon observations. For insoluble elastomers capable of swelling in the solvent, a 4 mm z-grad HRMAS probe is used in proton decoupling mode for proton and carbon observations. Spectra are acquired at a spinning speed of 4000 Hz to 5000 Hz. For measurements on soluble elastomers, a liquid NMR probe is used in proton decoupling mode for proton and carbon observations. The preparation of the insoluble samples is performed in a rotor filled with the material to be analyzed and a deuterated solvent that allows swelling, typically deuterated chloroform (CDCl3). The solvent used must always be deuterated, and the skilled person can adapt its chemistry. The amount of material used is adjusted to obtain spectra of sufficient sensitivity and resolution. Soluble samples are dissolved in a deuterated solvent (approximately 25 mg of elastomer in 1 ml), typically deuterated chloroform (CDCl3). The solvent or solvent blend used must always be deuterated, and the skilled person can adapt its chemistry. In both cases (soluble or swollen samples), a 30° single pulse sequence is used for proton NMR. A spectral window is set to observe all resonance lines belonging to the analyzed molecule. The number of accumulations is adjusted to obtain a signal-to-noise ratio sufficient for the quantification of each unit. A recycle delay is adapted between each pulse to obtain a quantitative measurement. For carbon NMR, a 30° single pulse sequence with proton decoupling is used only during the acquisition to avoid the nuclear Overhauser effect (NOE) and to maintain quantitation. A spectral window is set to observe all resonance lines belonging to the analyzed molecule. The number of accumulations is adjusted to obtain a signal-to-noise ratio sufficient for the quantification of each unit. A recycle delay is adapted between each pulse to obtain a quantitative measurement. The NMR measurements are performed at 25°C.

[0037] IV-1.2 Determination of polymer macrostructure by size exclusion chromatography (SEC): a) Measurement principle: Size Exclusion Chromatography, or SEC, allows the separation of macromolecules in a solution according to their size by passing them through a column packed with a porous gel. The macromolecules are separated according to their hydrodynamic volume, with the bulkiest being eluted first. Combining three detectors (3D), namely refractometer, viscometer and 90° light scattering detector, SEC allows the distribution of the absolute molar mass of a polymer to be known. 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 about 1 g / l. This solution is then filtered through a filter with a porosity of 0.45 μm before injection. c) 3D SEC analysis: To determine the number-average molar mass (Mn) of a polymer, and optionally 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 (hereinafter samples) are determined in an absolute manner by triple detection size exclusion chromatography (SEC), which has the advantage that the average molar mass is measured directly without calibration. The refractive index increment dn / dc value of the sample solution is measured online using the peak area detected by the refractometer (RI) of the liquid chromatograph. To apply this method, it must be verified that 100% of the sample mass is injected and eluted through the column. The RI peak area depends on the sample concentration, 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 to inject 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), with a flow rate of 1 ml min 1 . -1The 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 injected is 100 μl. The detection system consists of a Wyatt differential viscometer with the trade name Viscostar II, a Wyatt differential refractometer with a wavelength of 658 nm with the trade name Optilab T-Rex, and a Wyatt multi-angle static light scattering detector with a wavelength of 658 nm and the trade name Dawn Heleos 8+. 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 chromatographic data processing is the Astra system from Wyatt.

[0038] IV-1.3 Determination of crystallinity The degree of crystallinity is measured by measuring the enthalpy of fusion observed for copolymers of ethylene and 1,3-diene. This endothermic phenomenon is observed during the analysis of DSC (differential scanning calorimetry) thermograms. The measurement is performed by scanning back and forth from -150°C to 200°C with a gradient of 20°C / min under an inert (helium) atmosphere. The signal corresponding to the endothermic (melting) event is integrated and the crystallinity is the ratio of the measured enthalpy to that of perfectly crystalline polyethylene (290 J / g). % Crystallinity = (Measured enthalpy (J / g)) / (Theoretical enthalpy for 100% crystalline polyethylene (J / g)).

[0039] IV-1.4 Dynamic properties (after curing): Tensile test These tensile tests allow the measurement of elastic stress and breaking properties. Unless otherwise indicated, they are carried out in accordance with standard NF ISO 37 of February 2018. Processing of the tensile records also makes it possible to plot a curve of modulus as a function of elongation. The modulus used here is the true secant modulus measured at the first elongation and is calculated by normalizing to the true cross-sectional area of ​​the specimen at any moment of the test. The nominal secant modulus (or apparent stress (MPa)) at 10% elongation, designated MSV10, is measured at the first elongation. The elongation at break (EB%) and stress at break (BS) tests are determined according to standard NF ISO 37 of December 2005 for H2 dumbbell specimens at a tensile speed of 500 mm / min. The elongation at break is expressed as a percentage of elongation. The stress at break is expressed in MPa. All these tensile measurements are carried out under standard conditions of temperature (23±2° C.) and hygroscopicity (50±5% relative humidity), according to French standard NF T 40-101 (December 1979). The dynamic properties G*(10%) are measured according to ASTM standard D 5992-96 with a viscosity analyzer (Metravib VA4000). Samples of the crosslinked compositions (4 mm thick and 400 mm long) are subjected to a simple alternating sine shear stress according to ASTM standard D 1349-14 at a frequency of 10 Hz under specified temperature conditions, e.g. 60°C. 2 The response of a specimen (cylindrical specimen with cross section of 0.1 mm) is recorded. A strain amplification sweep is performed from 0.1% to 50% (outward cycle) and then from 50% to 1% (return cycle). The result utilized is the complex dynamic shear modulus G*. For the return cycle, the complex dynamic shear modulus G* at 10% strain and 60°C is shown. For better readability, we present the results as a base 100 (percentage) and assign a value of 100 to the control. A result greater than 100 indicates an improvement in the property of interest.

[0040] IV-2 Synthesis of copolymers For the synthesis of the polymer, all reactants except the metallocene are obtained commercially. Butyloctylmagnesium BOMAG (20% in heptane, C = 0.88 mol.l -1 ) is from Chemtura and stored in a Schlenk tube under inert atmosphere. N35 grade ethylene is obtained from Air Liquide and used without prior purification. The copolymer of ethylene and 1,3-butadiene, elastomer E1 (according to the invention), is synthesized according to the following procedure. At 80°C, butyloctylmagnesium (BOMAG) is added to a reactor containing methylcyclohexane, and also ethylene (Et) and butadiene (Bd) in the proportions shown in Table 1 to neutralize impurities in the reactor, and then the catalyst system is added (see Table 1). At this time, the polymerization reaction begins by controlling the reaction temperature at 80°C. The polymerization reaction occurs at a constant pressure of 8 bar. Ethylene and butadiene (Bd) are fed to the reactor in the proportions shown in Table 1 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 constant weight in an oven under vacuum. The catalyst system is a preformed catalyst system. It is prepared from the metallocene, [Me2SiFlu2Nd(μ-BH4)2Li(THF)] in the contents shown in Table 1 in methylcyclohexane, the cocatalyst, butyloctylmagnesium (BOMAG), and the preformed monomer, 1,3-butadiene. It is prepared according to the preparation method according to paragraph II.1 of patent application WO 2017 / 093654 A1. The microstructure of copolymer E1 and its properties are shown in Tables 2 and 3. With regard to the microstructure, Table 2 shows the molar content of ethylene (Eth) units, 1,3-butadiene units and 1,2-cyclohexanediyl (ring) units.

[0041] [Table 1]

[0042] [Table 2]

[0043] [Table 3]

[0044] IV-3 Preparation of Composition In the following examples, the rubber compositions were prepared as described in point II-6 above. In particular, the "non-productive" stage was carried out in a 0.4 liter mixer for 2 minutes, at an average blade speed of 80 revolutions per minute, until a maximum drop temperature of 130° C. was reached. The "productive" stage was carried out in an open mill at 23° C. for 10 minutes. Crosslinking of the composition was carried out under pressure at a temperature of 170° C. for 15 minutes in a mold of the MA plate type.

[0045] IV-4 Rubber Testing The purpose of the following examples is to compare the mechanical properties of three compositions according to the invention (C1, C2, C3) with two control compositions (T1 and T2). The compositions (phr) tested and the results obtained are presented in Tables 4 and 5.

[0046] [Table 4] (1) Natural rubber (2) Elastomer E1 prepared above: an elastomer containing 79 mol% ethylene units, 7 mol% 1,2-cyclohexanediyl units, 8 mol% 1,2 units and 6 mol% 1,4 units. ((3)) High density polyethylene “427985” from Sigma-Aldrich. Density measured according to ISO standard 1183-2019 = 0.952 g / cm 3 Melt flow rate (MFR) measured according to ISO standard 1133-1-2012 under the action of a piston weighted with a mass of 5 kg at 190 °C = 12 g / 10 min (4) “Dicup” peroxide from Sigma-Aldrich

[0047] [Table 5] (1)~(4): See Table 4

[0048] The inventors have demonstrated that the specific combination of the copolymers containing ethylene and diene units of the present invention with polyethylene allows a significant improvement in all measured mechanical properties, especially the limiting properties.

Claims

1. An elastomer matrix containing more than 50 phr of at least one copolymer containing ethylene units and diene units, 0 to 50 phr of a reinforcing filler, at least 3 phr of polyethylene, and a crosslinking system-based rubber composition.

2. The copolymer containing ethylene units and diene units is a copolymer of ethylene and 1,3-diene, The rubber composition according to Claim 1, wherein the ethylene units in the copolymer occupy a range between 50 mol% and 95 mol% of the monomer units of the copolymer.

3. The rubber composition according to Claim 1, wherein the polyethylene is uncrosslinked polyethylene.

4. The rubber composition according to Claim 1, wherein the polyethylene is selected from the group consisting of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, ultra-high molecular weight polyethylene, ultra-low density polyethylene, and mixtures of these polyethylenes.

5. The polyethylene has a density in the range of 940 to 970 kg / m 3 The rubber composition according to claim 1, which has a density within the range of.

6. The rubber composition according to Claim 1, wherein the polyethylene has a melt flow rate in the range of 2 to 25 g / 10 min at 190 °C under 5 kg.

7. The polyethylene is functionalized, The rubber composition according to Claim 1, wherein the functionalized polyethylene contains at least one alkoxysilane functional group.

8. The rubber composition according to Claim 1, wherein the content of the polyethylene ranges from 3 to 75 phr.

9. The content of the reinforcing filler ranges from 0 to 40 phr, and The rubber composition according to Claim 1, wherein the reinforcing filler is selected from carbon black, silica, and mixtures thereof.

10. A tire comprising the rubber composition according to any one of Claims 1 to 9.