RUBBER COMPOSITION BASED ON A COPOLYMER CONTAINING ETHYLENE AND DIENE UNITS AND POLYETHYLENE

Description

[0001] The present invention relates to rubber compositions intended in particular for the manufacture of tires, in particular rubber compositions constituting an internal layer of a tire, in particular the underlayer of the tire tread.

[0002] Reducing greenhouse gas emissions from transportation is one of the major challenges facing tire manufacturers. Tires represent a significant source of progress through lower rolling resistance, which has a direct impact on vehicle fuel consumption.

[0003] It is possible to define three types of zones within the tire: The radially outer zone in contact with the ambient air, this zone being essentially made up of the tread and the outer sidewall of the tire. An outer sidewall is an elastomeric layer arranged outside the carcass reinforcement relative to the internal cavity of the tire, between the crown and the bead so as to totally or partially cover the area of ​​the carcass reinforcement extending from the crown to the bead. The radially inner zone in contact with the inflation gas, this zone generally being made up of the layer impervious to inflation gases, sometimes called the inner sealing layer or inner rubber (“inner liner” in English). The internal zone of the tire, that is to say the one between the outer and inner zones. This zone includes layers or plies which are called herein internal layers of the tire.These are, for example, carcass plies, tread underlays, tire belt plies or any other layer that is not in contact with the ambient air or the tire inflation gas.

[0004] The rubber compositions constituting the internal layers of the tire, in particular the tread sub-layer and / or the internal layers of the bead area, must have sufficient rigidity, whether to improve road behavior in the case of the tread sub-layer, or to absorb the tensions of the carcass reinforcement and transmit the forces undergone by the tire from the sidewall to the rim, in the case of the bead.

[0005] To obtain rubber compositions with high rigidity, it has been proposed to introduce large quantities of reinforcing fillers into these rubber compositions. However, this solution penalizes hysteresis, negatively impacting rolling resistance.

[0006] Another solution to increase the rigidity of a rubber compound is to use reinforcing resins such as phenolic resins. However, this solution also leads to an increase in hysteresis, but also generally a degradation of the limiting properties. In addition, the use of such resins can be a disadvantage from a hygiene and environmental point of view because some resins release formaldehyde during tire manufacturing.

[0007] Reducing hysteresis by lowering or even eliminating the reinforcing filler content of rubber compositions, while maintaining high rigidity, and without using reinforcing resins, therefore remains a real technical difficulty for tire manufacturers.

[0008] Continuing its research, the applicant found, surprisingly, that the use of a specific polyolefin in a rubber composition made it possible to replace all or part of the reinforcing filler and to obtain a significant reduction in hysteresis while preserving, or even improving, the rigidity of said rubber composition, in particular at low deformation, and this while also preserving, or even improving, the limiting properties of the rubber composition, in particular the elongation at break and the breaking stress.

[0009] Thus, an object of the invention is a rubber composition based on: of an elastomer matrix containing more than 50 pce of at least one copolymer containing ethylene units and diene units, from 0 to 50 pce of reinforcing filler, at least 3 pce of a polyethylene and a crosslinking system.

[0010] Another subject of the invention is a tire comprising a composition according to the invention. I- DEFINITIONS

[0011] The expression "based on" used to define the constituents of a catalytic system or a composition means the mixture of these constituents, or the product of the reaction of some or all of these constituents with each other, at least partially, during the various phases of manufacturing the catalytic system or the composition. In the case of a composition, it can thus be in a totally or partially crosslinked state or in a non-crosslinked state.

[0012] By “elastomer matrix” is meant all the elastomers in the composition, including the copolymer defined below.

[0013] By the expression "part by weight per hundred parts by weight of elastomer" (or pce), it is meant, within the meaning of the present invention, the part, by mass per hundred parts of elastomer present in the rubber composition considered.

[0014] In this document, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0015] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the range of values ​​from more than a to less than b (i.e., excluding the limits a and b), while any interval of values ​​designated by the expression "from a to b" means the range of values ​​from a to b (i.e., including the strict limits a and b). In this document, when an interval of values ​​is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also and preferably designated.

[0016] When a "majority" compound is referred to, within the meaning of the present invention, this compound is the majority among the compounds of the same type in the composition, i.e. it is the one that represents the largest quantity by mass among the compounds of the same type. Thus, for example, a majority elastomer is the elastomer representing the largest mass relative to the total mass of the elastomers in the composition. In the same way, a so-called majority filler is the one representing the largest mass among the fillers in the composition. For example, in a system comprising a single elastomer, this is the majority within the meaning of the present invention; and in a system comprising two elastomers, the majority elastomer represents more than half of the mass of the elastomers. On the contrary, a "minority" compound is a compound that does not represent the largest mass fraction among the compounds of the same type.Preferably by majority, we mean present at more than 50%, preferably more than 60%, 70%, 80%, 90%, and more preferably the “majority” compound represents 100%.

[0017] In the present application, the term "all the monomer units of the copolymer" or "all the monomer units of the copolymer" means all the repeating units constituting the copolymer which result from the insertion of the monomers into the copolymer chain by polymerization. Unless otherwise indicated, the contents of a monomer unit or repeating unit in the copolymer of ethylene and 1,3-diene are given as a molar percentage calculated on the basis of all the monomer units of the copolymer.

[0018] The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already in use, i.e. they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes, in particular, polymers, plasticizers, fillers, etc.

[0019] Unless otherwise stated, all glass transition temperature “Tg” values ​​described herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to ASTM D3418 (1999). II- DESCRIPTION OF THE INVENTION II-1 Elastomeric matrix

[0020] According to the invention, the elastomer matrix comprises more than 50 pce of at least one copolymer containing ethylene units and diene units (hereinafter referred to as “the copolymer”).

[0021] By “elastomer matrix” we mean all the elastomers in the composition.

[0022] The term "copolymer containing ethylene units and diene units" means any copolymer comprising, within its structure, at least ethylene units and diene units. The copolymer may thus comprise monomer units other than the ethylene units and the diene units. For example, the copolymer may also comprise alpha-olefin units, in particular alpha-olefin units having from 3 to 18 carbon atoms, advantageously having 3 to 6 carbon atoms. For example, the alpha-olefin units may be chosen from the group consisting of propylene, butene, pentene, hexene or mixtures thereof.

[0023] As is well known, the expression "ethylene unit" refers to the -(CH 2 -CH 2 )- motif resulting from the insertion of ethylene into the elastomer chain.

[0024] "Diene unit" means a monomer unit resulting from the insertion of a monomer unit resulting from the polymerization of a conjugated diene monomer or a non-conjugated diene monomer, the diene unit comprising a carbon-carbon double bond. Preferably, the diene units are chosen 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 4 to 12 carbon atoms, for example 1,3-butadiene units, 2-methyl-1,3-butadiene units. More preferably, the diene units are predominantly, or even preferentially exclusively, 1,3-butadiene units.

[0025] In the copolymer, the ethylene units advantageously represent between 50% and 95% by mole of the monomer units of the copolymer, that is to say between 50% and 95% by mole of the monomer units of the copolymer. Advantageously, the ethylene units in the copolymer represent between 55% and 90%, preferably from 60% to 90%, preferably from 70% to 85%, by mole of the monomer units of the copolymer.

[0026] Advantageously, the copolymer (i.e., as a reminder, the 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, a copolymer consisting exclusively of ethylene units and 1,3-diene units (preferably 1,3-butadiene).

[0027] When the copolymer is a copolymer of ethylene and a 1,3-diene, it advantageously contains units of formula (I) and / or (II). The presence of a saturated 6-membered cyclic unit, 1,2-cyclohexanediyl, of formula (I) as a monomeric unit in the copolymer may result from a series of very specific insertions of ethylene and 1,3-butadiene into the polymer chain during its growth. -CH 2 -CH(CH=CH 2 )- (II)

[0028] For example, the copolymer of ethylene and a 1,3-diene may be devoid of units of formula (I). In this case, it preferably contains units of formula (II).

[0029] When the copolymer of ethylene and a 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 of the units of formula (I) and the units of formula (II) in the copolymer, respectively o and p, preferably satisfy the following equation (eq. 1), more preferably equation (eq. 2), o and p being calculated on the basis of all the monomer units of the copolymer. 0 < o + p ≤ 25 0 < o + p < 20

[0030] According to the invention, the copolymer, preferably the copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene), is a random copolymer.

[0031] Advantageously, the number average mass (Mn) of the copolymer, preferably of the copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene) is within a range from 100,000 to 300,000 g / mol, preferably from 150,000 to 250,000 g / mol.

[0032] The Mn of the copolymer is determined in a known manner, by size exclusion chromatography (SEC) as described in point IV-1.2 below.

[0033] The copolymer can be obtained according to different synthesis methods known to those skilled in the art, in particular depending on the targeted microstructure of the copolymer. Generally, it can be prepared by copolymerization of at least one diene, preferably a 1,3-diene, more preferably 1,3-butadiene, and ethylene and according to known synthesis methods, in particular in the presence of a catalytic system comprising a metallocene complex. Mention may be made, in this respect, of catalytic systems based on metallocene complexes, which catalytic systems are described in documents EP 1 092 731, WO 2004035639, WO 2007054223 and WO 2007054224 in the name of the Applicant. The copolymer, including when it is random, can also be prepared by a process using a preformed type catalytic system such as those described in documents WO 2017093654 A1, WO 2018020122 A1 and WO 2018020123 A1.

[0034] The copolymer may consist of a mixture of copolymers containing ethylene units and diene units which differ from each other by their microstructures and / or by their macrostructures.

[0035] According to the invention, the elastomer matrix may comprise at least one other elastomer, which is not a copolymer containing ethylene units and diene units, but this is not necessary or preferred. Thus, preferably, the content of the at least one copolymer containing ethylene units and diene units is within a range from 50 to 100 phr, preferably from 60 to 100 phr, more preferably from 80 to 100 phr. Advantageously, the at least one copolymer containing ethylene units and diene units is the only elastomer in the composition, i.e. it represents 100% by mass of the elastomer matrix.

[0036] When the elastomer matrix comprises at least one other elastomer, which is not a copolymer containing ethylene units and diene units, the at least one other elastomer may be a diene elastomer, for example chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. The butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR). II-2 Polyethylene

[0037] The rubber composition according to the invention also has the essential characteristic of comprising at least 3 pce of polyethylene.

[0038] Surprisingly, the Applicant has found that it is possible to replace all or part of the reinforcing fillers conventionally used in rubber compositions, particularly intended for the manufacture of tires, with polyethylene and to obtain rubber compositions which have significantly improved mechanical properties.

[0039] Polyethylene (also called “PE”) is a semi-crystalline polyolefin belonging to the family of thermoplastic polymers.

[0040] In the context of the present invention, the term "polyethylene" designates ethylene homopolymers, i.e. polymers obtained from ethylene as the sole monomer. However, it is not excluded that monomers of propylene, butene-1, hexene-1 or octene-1 are present in this polymer. However, if these monomers are present, they are present as impurities and in small proportions, preferably less than 5% by weight relative to the total weight of the polyethylene and the impurities. Copolymers of ethylene and propylene (also called EP, EPM or EPR for "ethylene propylene rubber") do not fall within the scope of the definition of polyethylene mentioned above.

[0041] 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" means a polyethylene that has not undergone a crosslinking reaction. It is therefore not a crosslinked polyethylene also called PER (or "PEX" in English for "PE crosslinked"). PER crosslinked polyethylenes are obtained by polymerization of ethylene monomer followed by a crosslinking reaction which may be crosslinking using a peroxide (PEX-A process), crosslinking by irradiation (PEX-C process), crosslinking by silane and a crosslinking catalyst (PEX-B process). Of course, the non-crosslinked polyethylene may undergo a crosslinking step after its incorporation into a rubber composition in accordance with the invention, for example during the curing of a tire comprising a rubber composition in accordance with the invention.

[0042] Preferably, the polyethylene is chosen from the group consisting of high density polyethylenes (“PE-HD” or also “HDPE” for “high density polyethylene”), low density polyethylenes (“PE-BD” or also “LDPE” for “low density polyethylene”), linear low density polyethylenes (“PE-BDL” or also “LLDPE” for “linear low density polyethylene”), medium density polyethylenes (“PE-MD” or “MDPE” for “medium density polyethylene”), very high molecular weight polyethylenes (“PE-UHMW”), very low density polyethylenes (“PE-VLD”) and mixtures of these polyethylenes. High density polyethylenes are particularly preferred.

[0043] Preferably, the polyethylene, in particular high density polyethylene, has a density in a range from 940 to 970 kg / m 3< , more preferably in a range from 940 to 965 kg / m 3< , even more preferably in a range from 950 to 970 kg / m 3< . The density is measured at 23°C according to the ISO 1183-2019 standard.

[0044] Preferably, the polyethylene, in particular high density polyethylene, has a melt flow rate at 190°C under 5 kg in a range from 2 to 25 g / 10 min, preferably in a range from 2.5 to 22 g / 10 min, more preferably still in a range from 10 to 25 g / 10 min. The melt flow rate (MFR 190°C / 5 Kg) (“MFR” for “Mass Flow Rate” is measured according to the ISO 1133-1-2012 standard at 190°C through a standardized die under the action of a piston weighted with a mass of 5 Kg).

[0045] The polyethylene that can be used in the context of the invention may be a functionalized or non-functionalized polyethylene.

[0046] By "non-functionalized polyethylene" is meant a polyethylene which has not been modified after its polymerization by grafting of a functional group comprising at least one heteroatom chosen from Si, N, S, O and Cl. In other words, non-functionalized polyethylene consists essentially of a mixture of carbon and hydrogen atoms and does not comprise heteroatoms chosen from the group consisting of Si, N, S, O and Cl. If these heteroatoms are present in the polyethylene, they are present as an impurity.

[0047] Even more preferably, the polyethylene is a non-functionalized and preferably non-crosslinked polyethylene, in particular of high density, has a density measured at 23°C according to the ISO 1183-2019 standard in a range from 940 to 970 kg / m 3< and a melt flow index (190°C / 5 kg) measured according to the ISO 1133-1-2012 standard in a range from 2 to 25 g / 10 min. Even more preferably, the non-functionalized and preferably non-crosslinked polyethylene, in particular of high density, has a density measured at 23°C according to the ISO 1183-2019 standard in a range from 950 to 970 kg / m 3< and a melt flow index (190°C / 5 kg) in a range from 10 to 25 g / 10 min.

[0048] Usable non-functionalized polyethylene can be obtained by conventional processes such as polymerization in the presence of metallocene catalysts. After polymerization, the polyethylene is granulated without any crosslinking reaction. Non-functionalized polyethylenes are commercially available from suppliers such as Dow Global Technologies, BASF, Silon, ENI, etc.

[0049] The polyethylene that can be used in the context of the invention may also be a functionalized polyethylene. For the purposes of the present invention, the term "functionalized polyethylene" means a polyethylene that has undergone a modification reaction, after its polymerization, so as to comprise at least one functional group comprising at least one heteroatom chosen from the group consisting of Si, N, O, S and Cl. Particularly suitable functional groups are those comprising at least one function such as: silanol, an alkoxysilane, a chlorine atom. The modification or functionalization of a polyethylene may be carried out by any known means, in particular by grafting a functional group comprising at least one heteroatom. At the end of this reaction, the functionalized polyethylene does not undergo a crosslinking reaction.Functionalized polyethylenes may be commercially available from suppliers such as Dow Global Technologies, BASF, Silon, ENI.

[0050] Preferably, 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 “alkoxysilane polyethylene”; these three expressions being equivalent and interchangeable.

[0051] Alkoxysilane functionalized polyethylene is obtained by grafting a silane compound of formula (I) onto polyethylene CH 2 =CR-(COO) x (C n H 2n )ySiR' 3 (I) in which: R is a hydrogen atom or a methyl group; x, y is an integer 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', identical or different, is a chemical group selected from the group consisting of alkoxy groups having from 1 to 12 carbon atoms (for example methoxy, ethoxy, butoxy), aryloxy groups having from 6 to 12 carbon atoms (for example phenoxy), aliphatic acyloxy groups having from 1 to 12 carbon atoms (for example formyloxy, acetyloxy, propanoyloxy) substituted or unsubstituted amine groups (for example alkylamino).

[0052] In particular, the preferred compounds of formula (I) may be those for which: - R is a hydrogen atom or a methyl group; - x, y is an integer equal to 0 or 1 with the condition that when x=1 then y=1 - n is an integer ranging from 1 to 12; preferably from 1 to 4; - each R', identical or different, is an alkoxy group having from 1 to 12 carbon atoms, preferably methoxy, ethoxy, butoxy.

[0053] The grafting of the compound of formula (I) onto polyethylene can be carried out by a radical reaction in the presence of peroxides. The grafting reaction can be carried out in an extruder. At the extruder outlet, a silane-grafted and non-crosslinked polyethylene is obtained. An example of a grafting process is described in paragraphs

[0042] to

[0048] of document EP2407496A1. Silane-grafted polyethylenes are commercially available from suppliers such as Dow Global Technologies, BASF, Silon, ENI, etc.

[0054] Preferably, the functionalized and preferably non-crosslinked polyethylene, in particular alkoxysilane functionalized polyethylene, may be chosen from the group consisting of high density polyethylenes, low density polyethylenes, linear low density polyethylenes, medium density polyethylenes, very high molecular weight polyethylenes, very low density polyethylenes and mixtures of these polyethylenes. Even more preferably, the functionalized and non-crosslinked polyethylene, in particular alkoxysilane functionalized and non-crosslinked polyethylene, is a high density polyethylene.

[0055] Preferably, the functionalized and preferably non-crosslinked polyethylene, in particular alkoxysilane functionalized polyethylene, has a density in a range from 940 to 970 kg / m 3< , more preferably in a range from 940 to 965 kg / m 3< . The density is measured at 23°C according to the ISO 1183-2019 standard.

[0056] Preferably, the functionalized and preferably non-crosslinked polyethylene, in particular the alkoxysilane functionalized and non-crosslinked polyethylene, has a melt flow rate at 190°C under 5 kg in a range from 2 to 25 g / 10 min, preferably in a range from 2.5 to 22 g / 10 min. The melt flow rate (MFR 190°C / 5 Kg) (“MFR” for “Mass Flow Rate” is measured according to the ISO 1133-1-2012 standard at 190°C through a standardized die under the action of a piston weighted with a mass of 5 Kg).

[0057] Even more preferably, the functionalized and preferably non-crosslinked polyethylene, in particular the alkoxysilane functionalized polyethylene, has a density measured at 23°C according to the ISO 1183-2019 standard in a range from 940 to 970 kg / m 3< and a melt flow index (MFR 190°C / 5 Kg) measured according to the ISO 1133-1-2012 standard in a range from 2 to 25 g / 10 min. Even more preferably, its density measured at 23°C according to the ISO 1183-2019 standard is in a range from 940 to 960 kg / m 3< and having a melt flow index (190°C / 5 Kg) in a range from 2 to 10 g / 10 min.

[0058] Preferably, the level of polyethylene in the rubber composition, whether functionalized, in particular alkoxysilane, or non-functionalized, is within a range from 3 pce to 75 pce, preferably from 4 to 60 pce, more preferably from 5 to 50 pce. II-3 Reinforcing charge

[0059] The rubber composition in accordance with the invention has the other essential characteristic of comprising from 0 to 50 pce of reinforcing filler. In other words, the composition may not comprise a reinforcing filler, or if it does, at a rate which is less than 50 pce.

[0060] Advantageously, the level of reinforcing filler in the composition according to the invention is within a range from 0 to 40 phr, preferably from 0 to 35 phr, preferably from 0 to 20 phr. For example, the level of reinforcing filler in the composition according to the invention may be within a range from 2 to 40 phr, for example from 5 to 35 phr, for example from 5 to 20 phr.

[0061] The reinforcing filler may be any type of so-called reinforcing filler, known for its ability to reinforce a rubber composition that can be used in particular for the manufacture of tires, for example an organic filler such as carbon black, an inorganic filler such as silica or a mixture of these two types of fillers. Such a reinforcing filler typically consists of nanoparticles whose average size (by mass) is less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, in particular and more preferably between 20 and 150 nm. Advantageously, the reinforcing filler is chosen from carbon blacks, silicas and their mixtures.

[0062] Suitable carbon blacks are all carbon blacks, including those conventionally used in tires or their treads. Among the latter, we will particularly mention the reinforcing carbon blacks of the 100, 200, 300 series, or the blacks of the 500, 600 or 700 series (ASTM D-1765-2017 grades), such as for example blacks N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772). These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a carrier for some of the rubber additives used. Carbon blacks could, for example, already be incorporated into the diene elastomer, in particular isoprene, in the form of a masterbatch (see, for example, applications WO97 / 36724-A2 or WO99 / 16600-A1).

[0063] Advantageously, if a reinforcing filler is present in the composition, it comprises mainly, preferably exclusively, carbon black.

[0064] When a reinforcing inorganic filler is used, it may in particular be mineral fillers of the siliceous type, preferably silica (SiO 2 ) or of the aluminous type, in particular alumina (Al 2 O 3 ). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET specific surface area and a CTAB specific surface area both less than 450 m 2 < / g, preferably within a range from 30 to 400 m 2 < / g, in particular from 60 to 300 m 2 < / g.

[0065] By "reinforcing inorganic filler" is meant here any inorganic or mineral filler, whatever its color and origin (natural or synthetic), also called "white" filler, "clear" filler or even "non-black" filler as opposed to carbon black, capable of reinforcing on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires. As is known, certain reinforcing inorganic fillers may be characterized in particular by the presence of hydroxyl groups (-OH) on their surface.

[0066] Any type of precipitated silica may be used, in particular highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. Examples include the silicas described in applications WO03 / 016215-A1 and WO03 / 016387-A1. Among the commercial HDS silicas, we can notably use the silicas “Ultrasil ®< 5000GR”, “Ultrasil ®< 7000GR” from the company Evonik, the silicas “Zeosil ®< 1085GR”, “Zeosil ®< 1115 MP”, “Zeosil ®< 1165MP”, “Zeosil ®< Premium 200MP”, “Zeosil ®< HRS 1200 MP” from the company Solvay.As non-HDS silica, the following commercial silicas can be used: silicas “Ultrasil ®< VN2GR”, “Ultrasil ®< VN3GR” from Evonik, silica “Zeosil ®< 175GR” from Solvay, silicas “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

[0067] The reinforcing inorganic filler may be a mixture of different reinforcing inorganic fillers, in which case the proportions of reinforcing inorganic filler in the reinforcing filler relate to all of the reinforcing inorganic fillers.

[0068] To couple the reinforcing inorganic filler to the diene elastomer, it is possible to use, in a well-known manner, an at least bifunctional coupling agent (or bonding agent) intended to ensure a sufficient connection, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. By "bifunctional", we 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, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic filler and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

[0069] Preferably, the organosilanes are chosen from the group consisting of polysulfurized organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, marketed under the name “Si69” by the company Evonik or bis-(triethoxysilylpropyl) disulfide, abbreviated to TESPD, marketed under the name “Si75” by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate marketed by the company Momentive under the name “NXT Silane”. More preferably, the organosilane is a polysulfurized organosilane.

[0070] Of course, mixtures of the coupling agents described above could also be used.

[0071] When a reinforcing inorganic filler is used, the content of coupling agent in the composition of the invention can easily be adjusted by a person skilled in the art. Typically, the level of coupling agent represents from 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler. II-4 Crosslinking system

[0072] The crosslinking system may be any type of system known to those skilled in the art in the field of tire rubber compositions. It may in particular be based on sulfur and / or peroxide and / or bismaleimides.

[0073] Preferably, the crosslinking system comprises, preferably consists of, a peroxide, preferably an organic peroxide.

[0074] The term "organic peroxide" refers to an organic compound, i.e. one containing carbon, with an -OO- group (two oxygen atoms linked by a single covalent bond). During the crosslinking process, the organic peroxide decomposes at its unstable OO bond into free radicals. These free radicals allow the creation of crosslinking bonds.

[0075] The organic peroxide is preferably selected from the group comprising or consisting of dialkyl peroxides, monoperoxycarbonates, diacyl peroxides, peroxyketals or peroxyesters.

[0076] Preferably, the dialkyl peroxides are 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)hexyne-3, 2,5-dimethyl-2,5-di(t-amylperoxy)hexyne-3, α,α'-di-[(t-butyl-peroxy)isopropyl]benzene, α,α'-di-[(t-amyl-peroxy)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.

[0077] Some monoperoxycarbonates such as OO-tert-butyl-O-(2-ethylhexyl) monoperoxycarbonate, OO-tert-butyl-O-isopropyl monoperoxycarbonate and OO-tert-amyl-O-2-ethyl hexyl monoperoxycarbonate, may also be used.

[0078] Among the diacyl peroxides, the preferred peroxide is benzoyl peroxide.

[0079] 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 trimer cyclic peroxide), 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 peroxyesters are selected from the group consisting of tert-butylperoxybenzoate, tert-butylperoxy-2-ethylhexanoate and tert-butylperoxy-3,5,5-trimethylhexanoate.

[0080] 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, ditertbutyl peroxide, tertbutylcumyl peroxide, 2,5-bis(tertbutylperoxy)-2,5-dimethylhexane, n-butyl-4,4'-di(tert-butylperoxy) valerate, OO-(t-butyl)-O-(2-ethylhexyl) monoperoxycarbonate, tert-butyl peroxyisopropylcarbonate, tert-butyl peroxybenzoate, tert-butyl peroxy-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-butyl peroxyisopropylcarbonate, tert-butyl peroxybenzoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof.

[0081] The level of peroxide, preferably organic peroxide, in the composition is advantageously within a range from 0.1 to 10 phr, preferably from 0.5 to 5 phr, more preferably from 1 to 4 phr. As an example of peroxide that can be used in the context of the present invention and is commercially available, mention may be made of "Dicup" from the company Hercules Powder Co., "Perkadox Y12" from the company Noury ​​van der Lande, "Peroximon F40" from the company Montecatini Edison SpA, "Trigonox" from the company Noury ​​van der Lande, "Varox" from the company RTVanderbilt Co., or even "Luperko" from the company Wallace & Tiernan, Inc.

[0082] Furthermore, the composition according to the invention is advantageously free of 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 and preferably less than 0.1 phr. The sulfur may be molecular sulfur or come from a sulfur-donating agent, such as alkyl phenol disulfides (APDS). II-5 Possible additives

[0083] The rubber compositions according to the invention may optionally also comprise all or part of the usual additives usually used in elastomer compositions for tires, such as for example plasticizers (such as plasticizing oils and / or plasticizing resins), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents, reinforcing resins (as described for example in application WO 02 / 10269).

[0084] The composition does not require the use of reinforcing resins (or hardening resins) known to those skilled in the art for stiffening rubber compositions, in particular by increasing their Young's Modulus or the dynamic shear complex G*. Particularly advantageously, the composition according to the invention does not comprise reinforcing resin or comprises less than 1 phr, preferably less than 0.5 phr. Examples of such reinforcing resins can be found in chapter II.3 of application WO20198679A1. II-6 Preparation of rubber compositions

[0085] The compositions in accordance with the invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first phase of working or thermomechanical mixing (so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents are introduced into a suitable mixer such as a conventional internal mixer (for example of the 'Banbury' type), in particular the elastomeric matrix, the reinforcing filler, any other various additives, with the exception of the crosslinking system. The incorporation of the possible filler into the elastomer can be carried out in one or more stages by thermomechanical mixing.In the case where the filler is already incorporated in whole or in part into the elastomer in the form of a masterbatch as described for example in applications WO 97 / 36724 or WO 99 / 16600, it is the masterbatch which is directly mixed and where appropriate the other elastomers or fillers present in the composition which are not in the form of a masterbatch are incorporated, as well as any other various additives other than the crosslinking system. The non-productive phase can be carried out at high temperature, up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C, for a duration generally of between 2 and 10 minutes.a second phase of mechanical work (so-called "productive" phase), which is carried out in an external mixer such as a roller mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 120°C, for example between 40°C and 100°C. The crosslinking system is then incorporated, and everything is then mixed for a few minutes, for example between 5 and 15 min.

[0086] Such phases have been described for example in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.

[0087] The final composition thus obtained is then calendered, for example, in the form of a sheet or plate, in particular for characterization in the laboratory, or extruded (or co-extruded with another rubber composition) in the form of a semi-finished (or profiled) rubber usable, for example, as a tire sidewall. These products can then be used for the manufacture of tires, according to techniques known to those skilled in the art.

[0088] The composition can be either in the raw state (before crosslinking or vulcanization), or in the cooked state (after crosslinking or vulcanization), can be a semi-finished product which can be used in a tire.

[0089] Crosslinking (or curing), where appropriate vulcanization, is carried out in a known manner at a temperature generally between 130°C and 200°C, for a sufficient time which may vary for example between 5 and 90 min depending in particular on the curing temperature, the crosslinking system adopted and the crosslinking kinetics of the composition considered. II-7 Pneumatics

[0090] The present invention also relates to a tire comprising a rubber composition according to the invention.

[0091] The composition defined in the present description is particularly well suited to the internal layers of tires. Thus, preferably, the composition according to the invention is present at least in at least one internal layer of the tire.

[0092] Advantageously, the inner layer of the tire is chosen from the group consisting of carcass plies, crown plies, bead fillers, crown feet, decoupling layers, edge rubbers, filler rubbers, tread sub-layer and combinations of these inner layers, preferably the tread sub-layer. In this document, the term "edge rubber" means a layer positioned in the tire directly in contact with the end of a reinforcing ply, the end of a reinforcing element or another edge rubber.

[0093] The tire according to the invention may be intended to equip motor vehicles of the passenger car, SUV ("Sport Utility Vehicles"), or two-wheeled vehicles (particularly motorcycles), or airplanes, or even industrial vehicles chosen from vans, "Heavy Goods Vehicles" - i.e. metro, bus, road transport vehicles (trucks, tractors, trailers), off-road vehicles such as agricultural or civil engineering vehicles -, and others. IV- EXAMPLES IV-1 Measurements and tests used IV-1.1 Determination of the microstructure of elastomers:

[0094] The microstructure of ethylene and butadiene copolymers is determined by 1H NMR analysis, supplemented by 13C NMR analysis when the resolution of 1H NMR spectra does not allow the attribution and quantification of all species. Measurements are carried out using a BRUKER 500MHz NMR spectrometer at frequencies of 500.43 MHz for proton observation and 125.83MHz for carbon observation. For non-soluble elastomers with the ability to swell in a solvent, a 4mm z-grad HRMAS probe is used to observe the proton and carbon in proton-decoupled mode. Spectra are acquired at rotation speeds of 4000Hz to 5000Hz. For measurements on soluble elastomers, a liquid NMR probe is used to observe the proton and carbon in proton-decoupled mode.The preparation of insoluble samples is done in rotors filled with the analyzed material and a deuterated solvent allowing swelling, generally deuterated chloroform (CDCl3). The solvent used must always be deuterated and its chemical nature can be adapted by the skilled person. The quantities of material used are adjusted to obtain spectra with sufficient sensitivity and resolution. Soluble samples are dissolved in a deuterated solvent (approximately 25mg of elastomer in 1mL), generally deuterated chloroform (CDCl3). The solvent or solvent blend used must always be deuterated and its chemical nature can be adapted by the skilled person. In both cases (soluble sample or swollen sample). For proton NMR, a single 30° pulse sequence is used. The spectral window is adjusted to observe all the resonance lines belonging to the analyzed molecules.The number of accumulations is adjusted to obtain a sufficient signal-to-noise ratio for the quantification of each pattern. The recycling time between each pulse is adapted to obtain a quantitative measurement. For carbon NMR, a single 30° pulse sequence is used with proton decoupling only during acquisition to avoid "Nuclear Overhauser" (NOE) effects and remain quantitative. The spectral window is adjusted to observe all the resonance lines belonging to the analyzed molecules. The number of accumulations is adjusted to obtain a sufficient signal-to-noise ratio for the quantification of each pattern. The recycling time between each pulse is adapted to obtain a quantitative measurement. NMR measurements are carried out at 25°C. IV-1.2 Determination of the macrostructure of polymers by size exclusion chromatography (SEC) : a) Principle of measurement:

[0095] Size exclusion chromatography (SEC) separates macromolecules in solution according to their size using columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, with the largest being eluted first. Combined with 3 detectors (3D), a refractometer, a viscometer, and a 90° light scattering detector, SEC can be used to assess the absolute molar mass distribution of a polymer. The various number-average (Mn) and weight-average (Mw) absolute molar masses and the dispersity (D = Mw / Mn) can also be calculated. b) Preparation of the polymer:

[0096] Each sample is solubilized in tetrahydrofuran at a concentration of approximately 1 g / L. The solution is then filtered through a 0.45µm porosity filter before injection. c) 3D SEC analysis:

[0097] To determine the number-average molar mass (Mn), and where appropriate the weight-average molar mass (Mw) and the polydispersity index (Ip) of polymers, the method below is used.

[0098] The number-average molar mass (Mn), weight-average molar mass (Mw) and polydispersity index of the polymer (hereinafter referred to as sample) are determined absolutely by triple detection size exclusion chromatography (SEC). Triple detection size exclusion chromatography has the advantage of measuring average molar masses directly without calibration.

[0099] 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 chromatography equipment. To apply this method, it must be ensured 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 dn / dc value.

[0100] To determine the average molar masses, the previously prepared and filtered 1g / l solution is used and injected into the chromatographic system. The equipment used is a "WATERS alliance" chromatographic chain. The elution solvent is tetrahydrofuran containing 250 ppm of BHT (2,6-diter-butyl 4-hydroxy toluene), the flow rate is 1 mL.min -1< , the system temperature 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 injected volume of the sample solution is 100 µL. The detection system is composed of a Wyatt differential viscometer with the trade name “VISCOSTAR II”, a Wyatt differential refractometer with the trade name “OPTILAB T-REX” with a wavelength of 658 nm, 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 masses and the polydispersity index, the value of the refractive index increment dn / dc of the sample solution obtained above is integrated. The software for processing the chromatographic data is the “ASTRA de Wyatt” system. IV-1.3 Determination of crystallinity

[0101] Crystallinity is measured by measuring the enthalpy of fusion observed in the case of ethylene and 1,3-diene copolymers. This endothermic phenomenon is observed during the analysis of the thermogram of the DSC (Differential Scanning Calorimetry) measurement. The measurement is carried out by back and forth scanning from -150°C to 200°C under an inert atmosphere (helium) with a ramp of 20°C / min.

[0102] The signal corresponding to the endothermic phenomenon (melting) is integrated and the crystallinity rate is the ratio between the measured enthalpy and that of perfectly crystalline polyethylene (290J / g). IV-1.4 Dynamic properties (after curing): Tensile test

[0103] These tensile tests are used to determine yield stresses and breaking properties. Unless otherwise stated, they are carried out in accordance with the NF ISO 37 standard of February 2018. Processing of the tensile recordings also allows the modulus curve to be plotted as a function of elongation. The modulus used here is the true secant modulus measured at first elongation, calculated by referring to the true section of the specimen at any time during the test. The nominal secant moduli (or apparent stresses, in MPa) at 10%, with an elongation noted MSV10, are measured at first elongation.

[0104] The elongation at break (AR%) and breaking stress (CR) tests are based on the NF ISO 37 standard of December 2005 on a type H2 dumbbell specimen and are measured at a tensile speed of 500 mm / min. The elongation at break is expressed as a % elongation. The breaking stress is expressed in MPa.

[0105] All these traction measurements are carried out under normal temperature (23±2°C) and hygrometry (50±5% relative humidity) conditions, according to the French standard NF T 40-101 (December 1979).

[0106] The dynamic properties G*(10%) are measured on a viscoanalyzer (Metravib VA4000), according to the ASTM D 5992-96 standard. The response of a crosslinked composition sample (cylindrical specimen 4 mm thick and 400 mm 2< in cross-section) is recorded, subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under the defined temperature conditions, for example at 60°C according to the ASTM D 1349-14 standard. A strain amplitude sweep is carried out from 0.1 to 50% (forward cycle), then from 50% to 1% (return cycle). The results used are the complex dynamic shear modulus G*. For the return cycle, the complex dynamic shear modulus G* at 10% strain, at 60°C, is indicated.

[0107] For ease of reading, the results are given as a base of 100 (percentage), with the value 100 being assigned to the control. A result greater than 100 indicates an improvement in the property concerned. IV-2 Synthesis of the copolymer

[0108] In polymer synthesis, all reagents are obtained commercially except for metallocenes. BOMAG butyloctylmagnesium (20% in heptane, C = 0.88 mol.L -1< ) ​​is obtained from Chemtura and is stored in a Schlenk tube under an inert atmosphere. Ethylene, N35 grade, is obtained from Air Liquide and is used without prior purification.

[0109] The copolymer of ethylene and 1,3-butadiene: elastomer E1 (in accordance with the invention) is synthesized according to the procedure described below.

[0110] In a reactor containing methylcyclohexane at 80°C, as well as ethylene (Et) and butadiene (Bd) in the proportions indicated in Table 1, butyloctylmagnesium (BOMAG) is added to neutralize the impurities in the reactor, then the catalytic system (see Table 1). At this point, the reaction temperature is regulated at 80°C and the polymerization reaction starts. The polymerization reaction proceeds at a constant pressure of 8 bar. The reactor is supplied throughout the polymerization with ethylene and butadiene (Bd) in the proportions defined in Table 1. The polymerization reaction is stopped by cooling, degassing the reactor and adding ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in a vacuum oven to constant mass. The catalytic system is a preformed catalytic system.It is prepared in methylcyclohexane from a metallocene, [Me 2 SiFlu 2 Nd(µ-BH 4 ) 2 Li(THF)], a co-catalyst, butyloctylmagnesium (BOMAG), and a preformation monomer, 1,3-butadiene, in the contents indicated in Table 1. It is prepared according to a preparation method in accordance with paragraph II.1 of patent application WO 2017 / 093654 A1.

[0111] The microstructure of copolymer E1 and its properties are shown in Tables 2 and 3. For the microstructure, Table 2 shows the molar ratios of ethylene units (Eth), 1,3-butadiene units, 1,2-cyclohexanediyl units (cycle). [Table 1] Synthesis E1 Metallocene concentration (mmol / L) 0,07 Alkylating agent concentration (mmol / L) 0,33 Preformation monomer / Nd metal molar ratio 90 Diet composition (%mol Et / Bd) 80 / 20 [Table 2] Elastomer E1 Ethylene (mol%) 79 Butadiene 1.3 (mol%) 14 1,2-cyclohexanediyl (mol%) 7 [Table 3] Elastomer E1 Tg (°C) -41 Mn (g / mol) 130 700 IV-3 Preparation of compositions

[0112] In the following examples, the rubber compositions were produced as described in point II-6 above. In particular, the “non-productive” phase was carried out in a 0.4 liter mixer for 2 minutes, for an average paddle speed of 80 revolutions per minute until a maximum drop temperature of 130°C was reached. The “productive” phase was carried out in a cylinder tool at 23°C for 10 minutes.

[0113] The crosslinking of the composition was carried out in an MA plate type mold at a temperature of 170°C for 15 minutes, under pressure. IV-4 Rubber Tests

[0114] The examples presented below aim to compare the mechanical properties of 3 compositions in accordance with the invention (C1, C2, C3) with two control compositions (T1 and T2). Tables 4 and 5 present the compositions tested (in pce), as well as the results obtained. [Table 4] Components T1 C1 C2 C3 NR (1)< - - - - EBR (2)< 100 100 100 100 HDPE (3)< (%vol) - 13 (10) 28 (20) 55 (33) Peroxide (4)< 1 1 1 1 Properties MSV10 100 220 340 820 AR (%) 100 255 641 873 CR 100 161 467 1 050 (1) Natural rubber (2) Elastomer E1 prepared above: Elastomer with 79 mol% ethylene unit, 7 mol% 1,2-cyclohexanediyl unit, 8 mol% 1,2-unit, 6 mol% 1,4-unit (3) High density polyethylene “427985” from Sigma-Aldrich. Density = 0.952g / cm 3< measured according to ISO 1183-2019. Melt flow index (MFR) = 12g / 10 min measured at 190°C under the action of a piston weighted with a mass of 5kg in accordance with ISO 1133-1-2012 (4) Peroxide “Dicup” from Sigma-Aldrich [Table 5] Components T2 C3 NR (1)< 100 - EBR (2)< - 100 HDPE (3) < (%vol) 52 (33) 55 (33) Peroxide (4)< 1 1 Properties MSV10 100 121 G* à 10% 100 300 AR (%) 100 166 CR 100 121 (1) to (4): see Table 4

[0115] The inventors have demonstrated that the specific association of a copolymer containing ethylene units and diene units and a polyethylene, in accordance with the invention, makes it possible to significantly improve all of the measured mechanical properties, in particular the limit properties.

Claims

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

2. Rubber composition according to Claim 1, wherein the copolymer containing ethylene units and diene units is a copolymer of ethylene and of 1,3-diene.

3. Rubber composition according to Claim 2, wherein the 1,3-diene is 1,3-butadiene.

4. Rubber composition according to any one of the preceding claims, wherein the ethylene units in the copolymer represent between 50 mol% and 95 mol%, preferably between 55 mol% and 90 mol%, of the monomer units of the copolymer.

5. Rubber composition according to any one of the preceding claims, wherein the copolymer is a random copolymer.

6. Rubber composition according to any one of the preceding claims, wherein the polyethylene is a non-crosslinked polyethylene.

7. Rubber composition according to any one of the preceding claims, wherein the polyethylene is selected from the group consisting of high density polyethylenes, low density polyethylenes, linear low density polyethylenes, medium density polyethylenes, ultra high molecular weight polyethylenes, very low density polyethylenes, and mixtures of these polyethylenes, preferably the polyethylene is a high density non-crosslinked polyethylene.

8. Rubber composition according to any one of the preceding claims, wherein the polyethylene has a density within a range extending from 940 to 970 kg / m3, more preferentially within a range extending from 940 to 965 kg / m3.

9. Rubber composition according to any one of the preceding claims, wherein the polyethylene has a melt flow rate at 190°C under 5 kg within a range extending from 2 to 25 g / 10 min, preferably within a range extending from 2.5 to 22 g / 10 min.

10. Rubber composition according to any one of the preceding claims, wherein the polyethylene is functionalized.

11. Rubber composition according to Claim 10, wherein the functionalized polyethylene comprises at least one alkoxysilane functional group.

12. Rubber composition according to any one of the preceding claims, wherein the content of polyethylene is within a range extending from 3 to 75 phr, preferably from 4 to 60 phr.

13. Rubber composition according to any one of the preceding claims, wherein the content of reinforcing filler is within a range extending from 0 to 40 phr, preferably from 0 to 35 phr.

14. Rubber composition according to any one of the preceding claims, wherein the reinforcing filler is selected from carbon blacks, silicas, and mixtures thereof.

15. Tyre comprising a rubber composition defined in any one of Claims 1 to 14, preferably present in at least one internal layer of the tyre.