RUBBER COMPOSITION BASED ON HIGHLY SATURATED DIENEIC ELASTOMER

Abstract

The present invention relates to a rubber composition exhibiting improved stiffness and hysteresis, and to a tire comprising this composition. The rubber composition is based on at least one elastomeric matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing between 50% and 95% by mole of the monomer units of the copolymer; a reinforcing filler; a crosslinking system; and a processing agent comprising a saturated or unsaturated amide.

Description

Title of the invention: RUBBER COMPOSITION BASED ON HIGHLY SATURATED DIENIC ELASTOMER

[0001] The present invention relates to rubber compositions intended in particular for the manufacture of tires or semi-finished products for tires.

[0002] A tire must comply in a known manner with a large number of technical requirements, often contradictory, including low rolling resistance, high wear resistance, and high grip on both dry and wet roads.

[0003] Among these properties, rolling resistance and wear resistance prove to be the most important from an environmental point of view because they respectively reduce fuel consumption and extend the life of tires.

[0004] The diene rubber compositions traditionally used in tires are rubber compositions reinforced with highly unsaturated diene elastomers such as polybutadienes, polyisoprenes, and butadiene-styrene copolymers. It has been proposed, notably in document WO 2014 / 114607 A1, to use ethylene-1,3-butadiene (EBR) copolymers in tire rubber compositions. Rubber compositions reinforced with ethylene-1,3-butadiene copolymer are described, in particular, to improve the performance trade-off of a tire, namely wear resistance and rolling resistance. These diene rubber compositions, once crosslinked, exhibit significantly higher stiffness than the diene rubber compositions traditionally used and may therefore sometimes prove unsuitable for certain applications.

[0005] There is therefore a need to reduce the cured stiffness of such rubber compositions comprising an ethylene-based diene rubber. To achieve this, it is known to reduce the crosslinking density of the rubber composition. However, this solution is accompanied by an increase in the hysteresis of the rubber composition, which is detrimental to rolling resistance. Document WO 2021 / 053296 A1 addressed the aforementioned need by providing rubber compositions comprising a copolymer of ethylene and a 1,3-diene of the formula CH=CR-CH=CH, the symbol R representing a hydrocarbon chain having 3 to 20 carbon atoms.

[0006] However, it remains interesting to find solutions to reduce the rigidity of compositions which include copolymers of ethylene and 1,3-diene, while reducing hysteresis, i.e. improving the rolling resistance of a tire comprising these compositions.

[0007] Continuing its research, the Applicant unexpectedly discovered that the use of particular processing agents, classically used to improve the raw rheological properties of rubber compositions, in rubber compositions comprising a highly saturated diene elastomer, makes it possible to reduce both stiffness and hysteresis.

[0008] Thus, the invention relates to a rubber composition based on at least: - an elastomeric matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing between 50% and 95% by mole of the monomer units of the copolymer, - a reinforcing filler, - a crosslinking system, and - an implementing agent comprising an amide of formula (I), O N R3 r2 (I) in which, Ri and R2, whether identical or different, represent a hydrogen atom, an alkyl group in Ci-C4, R3 represents a saturated or unsaturated C5-C26 hydrocarbon group.

[0009] It also relates to a tire comprising a composition according to the invention. I- DEFINITIONS

[0010] The expression "composition based on" means a composition comprising the mixture and / or the in situ reaction product of the different constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacturing the composition; the composition can thus be in a totally or partially crosslinked state or in a non-crosslinked state.

[0011] By "elastomer matrix", we mean all the elastomers in the composition, including the copolymer defined below.

[0012] Unless otherwise indicated, the rates of units resulting from the insertion of a monomer into a copolymer are expressed as a molar percentage relative to the total monomer units of the copolymer.

[0013] The expression "part by weight per hundred parts by weight of elastomer" (or pce) is to be understood in the context of the present invention as the part, by mass per hundred parts of elastomer present in the rubber composition considered.

[0014] In the present, 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 domain of values ​​from greater than a to less than b (i.e., excluding the bounds a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from a to b (i.e., including the strict bounds a and b). In the present case, 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] The compounds mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already in use, that is to say, they may be partially or totally derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes, in particular, polymers, plasticizers, fillers, etc.

[0017] Unless otherwise indicated, all glass transition temperature values ​​“Tg” 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 Elastomer Matrix

[0018] According to the invention, the elastomeric matrix comprises at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing between 50% and 95% by mole of the monomer units of the copolymer (hereinafter referred to as "the copolymer").

[0019] By “copolymer containing ethylene units and 1,3-diene units” is meant any copolymer comprising, within its structure, at least ethylene units and 1,3-diene units. The copolymer may thus comprise monomer units other than ethylene units and 1,3-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, alpha-olefin units may be chosen from the group consisting of propylene, butene, pentene, hexene or mixtures thereof.

[0020] In a known manner, the expression "ethylene unit" refers to the -(CH2-CH2)- motif resulting from the insertion of ethylene into the elastomer chain.

[0021] In a known manner, the expression "1,3-diene unit" refers to units resulting from the insertion of 1,3-diene by a 1,4 addition, a 1,2 addition or a 3,4 addition in the case of a substituted diene such as isoprene for example.

[0022] Preferably, the 1,3-diene units are selected from the group consisting of butadiene units, isoprene units, and mixtures of these 1,3-diene units. In particular, the 1,3-diene units of the copolymer may be 1,3-diene units having 4 to 12 carbon atoms, for example, 1,3-butadiene, 2-methyl-1,3-butadiene (or isoprene) units. Even more preferably, the 1,3-diene units are, for more than 50% by mole, or preferably exclusively, 1,3-butadiene units.

[0023] In the copolymer, the ethylene units represent 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.

[0024] Advantageously, the copolymer is a copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene), that is to say, according to the invention, a copolymer consisting exclusively of ethylene units and 1,3-diene units (preferably 1,3-butadiene).

[0025] When the copolymer is a copolymer of ethylene and a 1,3-diene, it advantageously contains units of formula (II) and / or (III). The presence of a saturated 6-member cyclic motif, 1,2-cyclohexanediyl, of formula (II) as a monomer unit in the copolymer can result from a series of very specific insertions of ethylene and 1,3-butadiene into the polymer chain during its growth. CH - CH -CH2-CH(CH=CH2)- (III)

[0026] For example, the copolymer of ethylene and a 1,3-diene may be devoid of formula units (II). In this case, it preferably contains formula units (III).

[0027] When the copolymer of ethylene and a 1,3-diene comprises units of formula (II) or units of formula (III) or units of formula (II) and units of formula (III), the molar percentages of the units of formula (II) and the units of formula (III) in the copolymer, respectively o and p, preferably satisfy the following equation (eq. 1), and 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 (eq. 1) 0 < o+p < 20 (eq. 2)

[0028] According to the invention, the copolymer, preferably the copolymer of ethylene and a 1,3-diene (preferably of 1,3-butadiene), is a statistical copolymer.

[0029] Advantageously, the number-average mass (Mn) of the copolymer, preferably of the copolymer of ethylene and a 1,3-diene (preferably of 1,3-butadiene) is in the range of 100,000 to 300,000 g / mol, preferably of 150,000 to 250,000 g / mol.

[0030] The Mn of the copolymer is determined in a known manner, by size exclusion chromatography (SEC) as described in point IV-1 below.

[0031] The copolymer can be obtained by various synthetic methods known to those skilled in the art, particularly depending on the desired microstructure of the copolymer. Generally, it can be prepared by copolymerization of at least one diene, preferably a 1,3-diene, preferably 1,3-butadiene, and ethylene, using known synthetic methods, particularly in the presence of a catalytic system comprising a metallocene complex. Examples include catalytic systems based on metallocene complexes, which are described in documents EP 1 092 731, WO 2004035639, WO 2007054223, and WO 2007054224 on behalf of the Applicant. The copolymer, including when statistical, can also be prepared by a process using a preformed catalytic system such as those described in documents WO 2017093654 Al, WO 2018020122 Al and WO 2018020123 AL

[0032] The copolymer may consist of a mixture of copolymers containing ethylene units and 1,3-diene units which differ from each other by their microstructures and / or by their macrostructures.

[0033] According to the invention, the elastomeric matrix may comprise at least one other diene elastomer, which is not the copolymer as defined above, but this is not necessary. Preferably, the proportion of the at least one copolymer is in the range of more than 50 to 100 parts per cent, preferably 60 to 100 parts per cent, and preferably 80 to 100 parts per cent. Advantageously, the at least one copolymer containing ethylene units and 1,3-diene units is the only elastomer in the composition, i.e., it represents 100% by mass of the elastomeric matrix.

[0034] By "diene" elastomer (or indistinctly rubber), whether natural or synthetic, is to be understood in a known manner as an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not). This definition includes the copolymer containing ethylene units and 1,3-diene units.

[0035] When the elastomeric matrix comprises at least one other diene elastomer, which is not the copolymer containing ethylene units and 1,3-diene units, the at least one other elastomer may be, for example, selected from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. Butadiene copolymers are particularly selected from the group consisting of butadiene-styrene copolymers (SBR). II-2 Reinforcing Load

[0036] The rubber composition according to the invention advantageously comprises a reinforcing filler, known for its ability to reinforce a rubber composition usable for the manufacture of tires. Such a reinforcing filler typically consists of particles whose average size (by mass) is less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, and in particular and more preferably between 20 and 150 nm.

[0037] The reinforcing filler may comprise carbon black, silica, or a mixture thereof. Advantageously, the reinforcing filler of the composition according to the invention comprises more than 50% by weight, preferably more than 80% by weight, of silica, relative to the total weight of the reinforcing filler.

[0038] Any type of precipitated silica may be suitable, 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, one can notably use the “Ulsil ® 5000GR”, “Ulsil ® 7000GR” silicas from the company Evonik, the “Zeosil ® 1085GR”, “Zeosil® 1115 MP”, “Zeosil® 1165MP”, “Zeosil® Premium 200MP”, “Zeosil® HRS 1200 MP” silicas from the Solvay Company.As non-HDS silica, the following commercial silicas may be used: “Ultrasil® VN2GR”, “Ultrasil® VN3GR” silicas from Evonik, “Zeosil® 175GR” silica from Solvay, “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” silicas from PPG.

[0039] To couple the silica to the diene elastomer, a coupling agent (or bonding agent) that is at least bifunctional is used in a well-known manner to ensure sufficient chemical and / or physical connection between the inorganic filler (surface of its particles) and the diene elastomer. In particular, the following are used: organosilanes or polyorganosiloxanes that are at least bifunctional. "Bifunctional" means a compound possessing 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 might comprise a first functional group consisting of a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic filler, and a second functional group consisting of a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

[0040] Preferably, the organosilanes are chosen from the group consisting of polysulfide organosilanes (symmetric or asymmetric) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated TESPT and marketed under the name "Si69" by Evonik, or bis-(triethoxysilylpropyl) disulfide, abbreviated TESPD and marketed under the name "Si75" by Evonik, polyorganosiloxanes, mercaptosilanes, and blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl octanethioate) marketed by Momentive under the name "NXT Silane". More preferably, the organosilane is a polysulfide organosilane.

[0041] The coupling agent content can easily be adjusted by a person skilled in the art. Typically and preferably, the coupling agent content represents 0.5% to 15% by weight relative to the amount of silica.

[0042] The reinforcing filler content can easily be adjusted by a person skilled in the art according to the use of the rubber composition. Advantageously, the reinforcing filler content in the composition according to the invention is in the range of 20 to less than 200 parts per annum, preferably from 25 to 150 parts per annum, preferably from 30 to 100 parts per annum.

[0043] Preferably, the composition according to the invention comprises from 20 to less than 200 pc, preferably from 25 to 150 pc, preferably from 30 to 100 pc of silica, and from 0.5 to 10 pc, preferably less than 1 to 5 pc of carbon black.

[0044] The blacks usable within the scope of the present invention can be any black conventionally used in tires or their treads (so-called tire-grade blacks). Among the latter, special mention should be made of reinforcing carbon blacks of the 100, 200, and 300 series, or blacks of the 500, 600, or 700 series (ASTM grades), such as NI 15, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772 blacks. These carbon blacks can be used in isolation, as commercially available, or in any other form, for example, as a carrier for some of the rubber additives used. The 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 WO 97 / 36724 or WO 99 / 16600). II-3 Implementing Agent

[0045] "Processing aids" are known to improve the raw rheological properties, in particular the Mooney index, and therefore to improve the processability, of a rubber composition comprising a reinforcing filler. These compounds are also called "processing aids" in English.

[0046] Surprisingly, the Applicant has found that the use of certain specific processing agents, in the presence of a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing between 50% and 95% by mole of the monomer units of the copolymer in a rubber composition, makes it possible to improve the hysteresis of the composition while decreasing its rigidity.

[0047] Thus, the rubber composition of the invention has as its essential characteristic comprising an amide of formula (I), O N R3 r2 (I) in which, Ri and R2, whether identical or different, represent a hydrogen atom, an alkyl group in Ci-C4, R3 represents a saturated or unsaturated C5-C26 hydrocarbon group.

[0048] As an example of an implementing agent that can be used in the context of the present invention and is available commercially, one can cite for example the "DEUREX A 26 P"; the "DEUREX A 28 P" of the company DEUREX.

[0049] Preferably, in the amide of formula (I), Ri and R2 represent a hydrogen atom.

[0050] Preferably also, in the amide of formula (I), R3 represents a hydrocarbon group in Ci0-C26, preferably in saturated or unsaturated Ci7-C26.

[0051] The implementing agent may, for example, be selected from the group consisting of erucamide, behenamide, ceroamide, lignoceramide, oleamide, stearamide and mixtures thereof. Advantageously, the implementing agent is selected from the group consisting of erucamide, oleamide, stearamide and mixtures thereof.

[0052] Preferably, in the rubber composition, the rate of the implementing agent is in the range of 1 to 15 parts per annum, preferably from 3 to 10 parts per annum. II-4 Crosslinking System

[0053] The crosslinking system can be any type of system known to those skilled in the art in the field of tire rubber compositions. In particular, it can be based on sulfur, and / or peroxide, and / or bismaleimides.

[0054] Preferably, the crosslinking system is sulfur-based; this is then referred to as a vulcanization system. Advantageously, the vulcanization system comprises molecular sulfur and / or at least one sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally and also preferably, various known vulcanization activators such as zinc oxide, stearic acid, or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders may be used.

[0055] Sulfur is used at a preferential rate of between 0.5 and 12 parts per annum, in particular between 1 and 10 parts per annum. The vulcanization accelerator is used at a preferential rate of between 0.5 and 10 parts per annum, more preferably between 0.5 and 5.0 parts per annum.

[0056] Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-ter-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-ter-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0057] Particularly advantageously, the crosslinking system comprises sulfur and a vulcanization accelerator, and the mass ratio of the sulfur content to the vulcanization accelerator content is in the range of 0.2 to 1.5, preferably 0.3 to 1, and even more preferably 0.4 to 0.9. II-5 Plasticizing System

[0058] Although not necessary for the implementation of the present invention, the plasticizing system of the rubber composition according to the invention may comprise a plasticizing resin having a glass transition temperature above 20°C, referred to as "high Tg", (also referred to as "plasticizing resin" in the present for the sake of simplicity of drafting).

[0059] The term "resin" is reserved in this application, by definition known to those skilled in the art, for a compound which is solid at room temperature (23°C), as opposed to a liquid plasticizing compound such as an oil.

[0060] Plasticizing resins are polymers well known to those skilled in the art, essentially carbon- and hydrogen-based but potentially containing other types of atoms, and are particularly useful as plasticizing or tackifying agents in polymer matrices. They are generally miscible (i.e., compatible) at the ratios used with the polymer compositions for which they are intended, so as to act as true diluents. They have been described, for example, in the book entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander, and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9), Chapter 5 of which is devoted to their applications, particularly in pneumatic rubber (5.5. "Rubber Tires and Mechanical Goods"). They can be aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, of the aliphatic / aromatic type, i.e. based on aliphatic and / or aromatic monomers.They can be natural or synthetic, petroleum-based or not (if so, also known as petroleum resins). Their Tg is preferably above 20°C (most often between 30°C and 95°C).

[0061] As is known, these plasticizing resins can also be described as thermoplastic resins in that they soften upon heating and can thus be molded. They can also be defined by a softening point or temperature. The softening temperature of a plasticizing resin is generally about 50 to 60°C higher than its Tg value. The softening point is measured according to ISO 4625 (Ring and Bail method). The macrostructure (Mw, Mn, and Ip) is determined by size exclusion chromatography (SEC) as described below.

[0062] As a reminder, SEC analysis, for example, consists of separating macromolecules in solution according to their size using columns filled with a porous gel; the molecules are separated according to their hydrodynamic volume, with the largest being eluted first. The sample to be analyzed is simply pre-solubilized in a suitable solvent, tetrahydrofuran at a concentration of 1 g / liter. The solution is then filtered through a 0.45 µm porosity filter before being injected into the apparatus. The apparatus used is, for example, a "Waters Alliance" chromatographic system under the following conditions: - elution solvent is tetrahydrofuran, - temperature 35°C; - concentration 1 g / litre; - flow rate: 1 ml / min; - injected volume: 100 cu in; - Moore calibration with polystyrene standards; - set of 3 "Waters" columns in series ("Styragel HR4E", "Styragel HR1" and "Styragel HR 0.5"); - detection by differential refractometer (for example "WATERS 2410") which can be equipped with operating software (for example "Waters Millennium").

[0063] A Moore calibration is performed using a series of commercial polystyrene standards with a low Ip value (less than 1.2) and known molar masses, covering the range of masses to be analyzed. The mass average molar mass (Mw), the number average molar mass (Mn), and the polymolecularity index (Ip = Mw / Mn) are deduced from the recorded data (mass distribution curve of the molar masses).

[0064] All molar mass values ​​indicated in this application are therefore relative to calibration curves made with polystyrene standards.

[0065] The plasticizing resin may have at least one, preferably two or three, more preferably all of the following characteristics: - a Tg greater than 25°C (in particular between 30°C and 100°C), more preferably greater than 30°C (in particular between 30°C and 95°C); - a softening point above 50°C (in particular between 50°C and 150°C); - an average number molar mass (Mn) between 300 and 2000 g / mol, preferably between 400 and 1500 g / mol; - a polymolecularity index (Ip) less than 3, preferably 2 (reminder: Ip = Mw / Mn with Mw average molar mass by weight).

[0066] The above-mentioned preferred high Tg plasticizing resins are well known to those skilled in the art and are commercially available, for example sold with regard to: - polylimonene resins: by the company DRT under the name "Dercolyte L120" (Mn=625 g / mol; Mw=1010 g / mol; Ip=l.6; Tg=72°C) or by the company ARIZONA under the name "Sylvagum TR7125C" (Mn=630 g / mol; Mw=950 g / mol; Ip=l.5; Tg=70°C); - C5 / vinylaromatic copolymer resins, in particular C5 / styrene or C5 / C9: by Neville Chemical Company under the names "Super Nevtac 78", "Super Nevtac 85" or "Super Nevtac 99", by Goodyear Chemicals under the name "Wingtack Extra", by Kolon under the names "Hikorez T1095" and "Hikorez Tl 100", by Exxon under the names "Escorez 2101" and "Escorez 1273"; - limonene / styrene copolymer resins: by DRT under the name "Dercolyte TS 105" of the DRT company, by ARIZONA Chemical Company under the names "ZT115LT" and "ZT5100".

[0067] The plasticizing resin having a glass transition temperature above 20°C may be selected from the group comprising or consisting of cyclopentadiene homopolymer or copolymer resins (abbreviated CPD), dicyclopentadiene homopolymer or copolymer resins (abbreviated DCPD), terpene homopolymer or copolymer resins, C5-cut homopolymer or copolymer resins, C9-cut homopolymer or copolymer resins, alpha-methyl-styrene homopolymer or copolymer resins and their mixtures.Preferably, the plasticizing resin is chosen from the group comprising or consisting of (D)CPD / vinylaromatic copolymer resins, (D)CPD / terpene copolymer resins, terpene phenol copolymer resins, (D)CPD / C5 cut copolymer resins, (D)CPD / C9 cut copolymer resins, terpene / vinylaromatic copolymer resins, terpene / phenol copolymer resins, C5 cut / vinylaromatic copolymer resins, and mixtures thereof.

[0068] The term "terpene" here includes in a known way the alpha-pinene, beta-pinene and limonene monomers; preferably a limonene monomer is used, a compound which is known to exist in the form of three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or dipentene, racemic of the dextrorotatory and levorotatory enantiomers. Suitable examples of vinylaromatic monomers include styrene, alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyl-toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, and any vinylaromatic monomer derived from a C9 cut (or more generally from a C8 to C1 cut).

[0069] In particular, we can mention the plasticizing resins chosen from the group consisting of homopolymer (D)CPD resins, (D)CPD / styrene copolymer resins, polylimonene resins, limonene / styrene copolymer resins, limonene / D(CPD) copolymer resins, C5 / styrene copolymer resins, C5 / C9 copolymer resins, and mixtures of these resins.

[0070] All the above-mentioned plasticizing resins are well known to those skilled in the art and are commercially available, for example, sold by DRT under the name "Dercolyte" for polylimonene resins, by Neville Chemical Company under the name "Super Nevtac", by Kolon under the name "Hikorez", or by Exxon Mobil under the name "Escorez" for C5 / styrene or C5-cut resins. / C9 cut, or by the company Struktol under the name "40 MS" or "40 NS" (mixtures of aromatic and / or aliphatic resins).

[0071] The proportion of plasticizing resin having a glass transition temperature above 20°C in the composition according to the invention can be in a range from 10 to 120, preferably from 20 to 110 pc, preferably from 30 to 80 pc, preferably from 40 to 75 pc.

[0072] Although not necessary for the implementation of the present invention, the plasticizing system of the rubber composition according to the invention may include a liquid plasticizer at 23°C, referred to as a "low Tg" plasticizer, that is to say, one which by definition has a Tg below -20°C, preferably below -40°C. According to the invention, the composition may optionally include from 0 to 60 parts per cent of a liquid plasticizer at 23°C.

[0073] When a liquid plasticizer at 23°C is used, its level in the composition according to the invention can be in a range from 1 to 120 parts per annum, preferably from 2 to 80 parts per annum, preferably still from 3 to 40 parts per annum.

[0074] Any liquid plasticizer at 23°C (or extending oil), whether aromatic or non-aromatic, known for its plasticizing properties with respect to diene elastomers, is usable. At room temperature (23°C), these plasticizers or oils, with varying degrees of viscosity, are liquids (that is to say, substances that eventually take the shape of their container), unlike plasticizing resins, which are solid at room temperature.

[0075] Particularly suitable are liquid plasticizers at 23°C selected from the group comprising or consisting of liquid diene polymers, polyolefinic oils, naphthenic oils, paraffinic oils, DAE oils, MES (Medium Extracted Solvates) oils, TDAE (Treated Distillate Aromatic Extracts) oils, RAE (Residual Aromatic Extract oils), TRAE (Treated Residual Aromatic Extract) oils and SRAE (Safety Residual Aromatic Extract oils), mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these liquid plasticizers at 23°C.

[0076] Preferably, the liquid plasticizer at 23 °C is chosen from the group comprising or consisting of MES oils, TDAE oils, naphthenic oils, vegetable oils and mixtures of these liquid plasticizers at 23 °C.

[0077] Advantageously, the composition according to the invention comprises both a plasticizing resin having a glass transition temperature above 20°C and a liquid plasticizer at 23°C as defined above at the aforementioned rates. II-6 Possible Additions

[0078] The rubber compositions according to the invention may optionally also include all or part of the usual additives commonly used in elastomer compositions for tires, such as, for example, fillers (reinforcing or non-reinforcing / other than those mentioned above), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants. II-7 Preparation of compositions

[0079] Rubber compositions according to the invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: - a first thermomechanical working or mixing phase (the so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents, including the elastomeric matrix, the reinforcing filler, the epoxy resin, and any other miscellaneous additives, are introduced into a suitable mixer such as a standard internal mixer (for example, a "Banbury" type mixer). These include the elastomer matrix, the reinforcing filler, the epoxy resin, and any other miscellaneous additives, with the exception of the crosslinking system, the amine hardener, and any condensation accelerator. The incorporation of the filler into the elastomer can be carried out in one or more stages by thermomechanical mixing.In cases 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, the masterbatch is directly mixed, and where applicable, other elastomers or fillers present in the composition that are not in masterbatch form, as well as any other miscellaneous additives other than the crosslinking system, are incorporated. The non-productive phase can be carried out at high temperature, up to a maximum temperature between 110°C and 200°C, preferably between 130°C and 185°C, for a duration generally between 2 and 10 minutes. - a second mechanical working phase (the so-called "productive" phase), which can be 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 the whole is then mixed for a few minutes, for example between 5 and 15 min.

[0080] Such phases have been described for example in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.

[0081] The final composition thus obtained is then calendered, for example in the form of a sheet or plate, particularly for characterization in the laboratory, or extruded (or co-extruded with another rubber composition) under the A semi-finished (or profiled) rubber product usable, for example, as an inner layer of a tire. These products can then be used for tire manufacturing, according to techniques known to those skilled in the art.

[0082] 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 that can be used in a tire.

[0083] The crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 130°C and 200°C, under pressure. II-8 Rubber Article

[0084] The present invention also relates to a rubber article comprising at least one composition according to the invention. Preferably, the rubber article is a tire.

[0085] In the present invention, the term "tire" refers to a pneumatic or non-pneumatic tire. A pneumatic tire typically comprises two beads for contact with a rim, a crown consisting of at least one crown reinforcement and a tread, and two sidewalls. The tire is reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic tire typically comprises a base, designed, for example, for mounting on a rigid rim, a crown reinforcement connecting to a tread, and a deformable structure, such as spokes, ribs, or dimples, this structure being arranged between the base and the crown. Such non-pneumatic tires do not necessarily include sidewalls. Non-pneumatic tires are described, for example, in documents WO 03 / 018332 and FR2898077.Advantageously, the tire according to the invention is preferably a pneumatic tire.

[0086] More particularly, the invention also relates to a tire comprising a composition according to the invention. The composition according to the invention is preferably present in the tread of the tire. It may constitute part or all of the tread of the tire.

[0087] The tire according to the invention can be intended to equip any type of vehicle, in particular motor vehicles, without any particular limitation. III- EXAMPLES III-1 Measurements and tests used Dynamic properties#(after cooking)

[0088] The dynamic properties are measured on a viscoanalyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a sample of A vulcanized composition (cylindrical specimen 4 mm thick and 400 mm² cross-section) is subjected to sinusoidal alternating simple shear loading at a frequency of 10 Hz during a temperature sweep under a fixed stress of 0.7 MPa. The complex dynamic shear modulus G* is recorded at 60°C. The same sample is also subjected, at a temperature of 40°C, to a strain amplitude sweep from 0.1% to 100% (forward cycle), then from 100% to 1% (reverse cycle). The nonlinearity (denoted NL or AG*) is the difference in shear modulus between 0.1% and 100% strain in MPa.

[0089] For readability, the results are shown on a scale of 100 (percentage), with 100 assigned to the control Tl. For G*, a result greater than 100 indicates a decrease in stiffness, which in this case represents an improvement in stiffness compared to the control composition. For non-linearity, a result greater than 100 indicates a decrease in hysteresis and therefore an improvement in the rolling resistance of the composition under consideration compared to the control composition.

[0090] Determination of the microstructure of elastomers by nuclear magnetic resonance (NMR):

[0091] Ethylene and 1,3-butadiene copolymers are characterized by ¹H,¹³C NMR spectroscopy. The NMR spectra are recorded on a Brüker Avance III 500 MHz spectrometer equipped with a 5 mm BBIz-grad "broadband" cryo-probe. The quantitative ¹H NMR experiment uses a single 30° pulse sequence and a 5-second repetition delay between each acquisition. 64 to 256 accumulations are performed. The quantitative ¹³C NMR experiment uses a single 30° pulse sequence with proton decoupling and a 10-second repetition delay between each acquisition. 1024 to 10240 accumulations are performed. The two-dimensional ¹H / ¹³C experiments are used to determine the polymer structure. The determination of the microstructure of copolymers is defined in the literature, according to the article by Llauro et al., Macromolecules 2001, 34, 6304-6311.

[0092] The NMR measurements are carried out at 25°C. The copolymers are in solution in a deuterated solvent (approximately 25mg of elastomer in ImL), generally deuterated chloroform (CDC13).

[0093] Determination of the macrostructure of polymers by size exclusion chromatography (SEC):

[0094] Size exclusion chromatography (SEC) allows the fractionation of polymer chains in a solvent according to their hydrodynamic volume. Like any chromatographic system, the technique is based on the elution of a solute (the polymer) through a column containing a stationary phase. The system is composed, in this order, of: a solvent reservoir, a pumping system, a injector, a set of columns and detectors. The measurement chain is equipped with a Waters Alliance e2695 module and a Waters fRI410 refractometer.

[0095] The mobile phase is eluted at a flow rate of 1 mL / min. The polymer is solubilized in THF in the presence of 1 wt% diisopropylamine and 1 wt% triethylamine at a concentration of 1 g / L. A volume of 100 pL is injected through a set of three AGELENT (MIXED B LS) size-exclusion chromatography columns. The columns are oven-heated at 35°C. The stationary phase of the columns is based on a divinylbenzene polystyrene gel with controlled porosity. The polymer chains are separated according to the hydrodynamic volume they occupy when solubilized in the solvent. The larger the volume they occupy, the less accessible the column pores are to them, and the shorter their elution time. Detection is performed using a refractometer (RI) thermostated at 35°C.Each elution volume is associated with a mass via Moore calibration (certified standard: Polymer Standard Service (Mainz) standard polystyrenes). The WATERS: EMPOWER software is used for data acquisition and analysis. It is then possible to determine the number-average molar masses (Mn), the mass-average molar masses (Mw), and the polydispersity (Ip = Mw / Mn). Determination of Mooney viscosity ML 1+4

[0096] For polymers and rubber compositions, the Mooney viscosities ML(1 + 4) at 100°C are measured using an oscillating consistometer according to ASTM D-1646 (1999). The Mooney plasticity measurement is performed according to the following principle: the composition in its raw state (i.e., before curing) is molded in a cylindrical chamber heated to 100°C. After one minute of preheating, the rotor rotates within the specimen at 2 revolutions per minute, and the torque required to maintain this rotation after 4 minutes of rotation is measured. The Mooney plasticity ML(1 + 4) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Nm). III-2 Synthesis of the El copolymer

[0097] The El (EBR) elastomer is prepared in the presence of a catalytic system based on a metallocene [Me2Si(Flu)2Nd(q-BH4)2Li(THF)] and a co-catalyst, butylloctylmagnesium, according to the following procedure.

[0098] In a reactor containing methylcyclohexane, the co-catalyst (0.36 mmol / L) is added, followed by the metallocene (0.07 mmol / L). The alkylation time is 10 minutes, and the reaction temperature is 20°C. Subsequently, ethylene and 1,3-butadiene are added continuously in molar amounts of 80% and 20%, respectively, to the reactor. Polymerization is carried out at 80°C under a pressure of 8 bar. The polymerization reaction is stopped by cooling and degassing the reactor. Ethanol is added. An antioxidant is added to the polymer solution. The copolymer is recovered by vacuum oven drying to constant mass according to a method conforming to that described in application WO2020 / 212184A1. III-3 Preparation of compositions

[0099] In the following examples, the rubbery compositions were produced as described in section 11-7 above. In particular, the "non-productive" phase was carried out in a 0.4-liter mixer for 3.5 minutes, at an average paddle speed of 60 revolutions per minute, until a maximum drop temperature of 165°C was reached. The "productive" phase was carried out on a roller tool at 40°C for 5 minutes.

[0100] The crosslinking of the composition was carried out at a temperature of 160°C, under pressure. III-4 Tests of Rubber Compositions

[0101] The examples presented below are intended to compare the performance trade-off, stiffness and hysteresis of compositions according to the present invention (Cl to C3) with control compositions (Tl to T3).

[0102] Table 1 presents the compositions tested (in pieces), as well as the results obtained.

[0103] Compositions Cl, C2, C3, T2, and T3 differ from the control composition T1 solely by the presence of a specific implementing agent with a constant silica volume fraction in the composition and a constant coupling agent ratio relative to the amount of silica. The implementing agent used for compositions Cl, C2, and C3 conforms to the invention. The implementing agent used for compositions T2 and T3 does not conform to the invention.

[0104] [Tables 1] Compositions Tl Cl C2 C3 T2 T3 Elastomer El( 1) 100 100 100 100 100 100 Silica(2) 85.5 86.5 88.0 86.5 87.5 86.5 Volume fraction of (2) 18% 18% 18% 18% 18% 18% Coupling agent(3) 6.8 7.0 7.0 7.0 7.0 7.0 N234(4) 3.0 3.0 3.0 3.0 3.0 3.0 Plasticizing resin(5) 50 50 50 50 50 50 Liquid plasticizing agent(6) 22 22 22 22 22 22 Compound 1(7) - 5.0 - - - - Compound 2(8) - - 5.0 - - - Compound 3(9) - - - 5.0 - - Compound 4(10) - - - - 5.0 - Compound 5(11) - - - - - 5.0 6PPD(12) 2 2 2 2 2 2 Stearic acid(13) 2 2 2 2 2 2 ZnO(14) 1 1 1 1 1 1 Sulfur 1 1 1 1 1 1 Accelerator(15) 2 2 2 2 2 2 Properties AG* at 40°C (base 100) 100 147 136 130 90 97 G* at 60°C (base 100) 100 121 120 136 101 100

[0105] (1) Elastomer obtained by the process described in point III-2 above (2) Silica “Zeosil 1165MP” from the Solvay company (3) Liquid silane triethoxysilylpropyltetrasulfide (TESPT) “Si69” from the Evonik company (4) Cabot Company ASTM N234 Carbon Black (5) Polylimonene resin “Dercolite L120” from the company DRT (Tg = 72°C) (6) TDAE oil “Vivatec 500” from British Petroleum (7) Implementing agent: Erucamide “DEUREX A 26 P” from the company DEUREX (8) Implementing agent: Oleamide “DEUREX A 27 P” from the company DEUREX (9) Implementing agent: Stearamide “DEUREX A 28 P” from the company DEUREX (10) Implementing agent: Complex mixture of aromatic and aliphatic hydrocarbon resins “Struktol 40MS” from the Struktol company (mixture including in particular aliphatic and aromatic hydrocarbon resins) (11) Implementing agent: Ethylene-bis-stearamide “DEUREX X 20 A” from the company DEUREX (12) Nl,3-dimethylbutyl-N-phenylparaphenylenediamine “Santaflex 6-PPD” from Flexsys (13) Stearic acid “Pristerene 4931” from the company Uniqema (14) Industrial grade zinc oxide from Umicore (15) N-cyclohexyl-2-benzothiazyl sulfenamide “Santocure CBS” from Flexsys

[0106] The results presented in Table 1 above show that the combination of a copolymer according to the invention and a specific implementing agent according to the invention makes it possible to improve both the hysteresis, and therefore the rolling resistance, and the rigidity of the composition.

Claims

Demands

1. Rubber composition based on at least: - an elastomeric matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing between 50% and 95% by mole of the monomer units of the copolymer, - a reinforcing filler, - a crosslinking system, and - a processing agent comprising an amide of formula (I), O Ri\ JL N R3 r2 (I) in which Ri and R2, identical or different, represent a hydrogen atom, a Ci-C4 alkyl group, R3 represents a saturated or unsaturated C5-C26 hydrocarbon group.

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

3. Rubber composition according to any one of the preceding claims, wherein 1,3-diene is 1,3-butadiene.

4. Rubber composition according to any one of the preceding claims, wherein the proportion of at least one copolymer containing ethylene units and 1,3-diene units is in the range of 50 to 100 parts per cent, preferably 80 to 100 parts per cent.

5. Rubber composition according to any one of the preceding claims, wherein, in the amide of formula (I), Ri and R2 represent a hydrogen atom.

6. Rubber composition according to any one of the preceding claims, wherein, in the amide of formula (I), R3 represents a hydrocarbon group in Ci0-C26, preferably in saturated or unsaturated Ci7-C26.

7. Rubber composition according to any one of the preceding claims, wherein the implementing agent is selected from the group consisting of erucamide, behenamide, ceroamide, lignoceramide, oleamide, stearamide and mixtures thereof, preferably from the group consisting of erucamide, oleamide, stearamide and mixtures thereof.

8. Rubber composition according to any one of the preceding claims, wherein the rate of the implementing agent is in the range of 1 to 15 pc, preferably 3 to 10 pc.

9. Rubber composition according to any one of the preceding claims, wherein the reinforcing filler comprises more than 50% by weight, preferably more than 80% by weight of silica.

10. Rubber composition according to any one of the preceding claims, wherein the rate of the reinforcing filler is in the range of 20 to less than 200 pc, preferably from 30 to 100 pc.

11. Rubber composition according to any one of the preceding embodiments, wherein the crosslinking system is a vulcanizing system based on molecular sulfur and / or a sulfur-donating agent.

12. A tire comprising a composition as defined in any one of claims 1 to 11, the composition being preferably present in the tread of the tire.