Rubber composition based on a highly saturated diene elastomer and a reinforcing resin

Abstract

The invention relates to a rubber composition exhibiting an improved trade-off between stiffness and hysteresis and to a tire comprising this composition. The composition is based on at least one elastomer matrix comprising more than 50 phr of at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing between 50 mol% and 95 mol% of the monomer units of the copolymer; a reinforcing filler; a vulcanisation system; from 1 to 30 phr of epoxy resin and between 1 and 15 phr of an amine hardener comprising at least two primary amine functions located on at least one six-atom aromatic ring, the at least one six-atom aromatic ring comprising at least one primary amine function and at least two identical or different radicals Ri chosen from the group consisting of C1-C6 linear or branched alkyl radicals, halogens, ethers, tertiary amines, thioethers, ketones, esters and amides, substituted by C1-C6 linear or branched alkyl radicals, such that the at least one six-atom aromatic ring does not comprise any hydrogen atoms in the ortho position with respect to the primary amine functions, the amine hardener comprising at least a second primary amine function located on the at least one six-atom aromatic ring or on an optional second six-atom aromatic ring of the amine hardener.

Description

[0001] RUBBER COMPOSITION BASED ON HIGHLY SATURATED DIENE ELASTOMER AND A REINFORCING RESIN

[0002] The present invention relates to rubber compositions intended in particular for the manufacture of tires or semi-finished products for tires.

[0003] Tire layers such as the tread or inner layers must meet a large number of technical requirements, often contradictory, including low rolling resistance, high wear resistance, good road behavior, as well as a good level of material cohesion.

[0004] In order to ensure good rigidity, particularly representative of road behavior, it is known to use rubber compositions with high levels of reinforcing fillers. However, as is known, increasing the filler level can penalize the hysteresis properties and therefore the rolling resistance of the tires.

[0005] High rigidity can also be achieved by incorporating certain reinforcing resins as disclosed in application WO 02 / 10269 which proposes rubber compositions having high rigidity during low deformations of the tire. Resistance to low deformations is one of the properties that a tire must have to respond to the stresses to which it is subjected.

[0006] Furthermore, it remains interesting that the solutions proposed to solve this problem do not penalize the other properties of the rubber composition, in particular hysteresis. Indeed, the use of a hysteretic composition in a tire can manifest itself by an increase in the internal temperature of the tire, which can lead to a decrease in the endurance of the tire. In view of the above, there is a permanent objective to provide rubber compositions that have an improved compromise between stiffness strength and hysteresis. Of course, it remains advantageous that the improvement of this compromise does not come at the expense of other properties of the composition, in particular, mechanical properties, such as elongation at break and breaking stress (or tensile strength), which are particularly important properties in many internal layers of tires.

[0007] Thus, there is a need to find ways to improve the endurance of tires comprising high-rigidity compositions without penalizing hysteresis, or even improving it, and without penalizing the mechanical properties of the composition. Continuing its research, the Applicant unexpectedly discovered that the combined use of highly saturated diene elastomer and a curing system based on epoxy resin and a particular amine hardener makes it possible to further improve the aforementioned performance compromise.

[0008] Thus, the invention relates to a rubber composition based on at least:

[0009] - an elastomer matrix comprising more than 50 pce of 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,

[0010] - a reinforcing charge,

[0011] - a vulcanization system,

[0012] - from 1 to 30 pce of epoxy resin,

[0013] - between 1 and 15 pce of an amine hardener comprising at least two primary amine functions, located on at least one aromatic cycle with six atoms, said at least one aromatic cycle with six atoms comprising:

[0014] ° at least one primary amine function, and

[0015] ° at least two radicals Ri, identical or different, chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, ethers, tertiary amines, thioethers, ketones, esters and amides, substituted by linear or branched C1-C6 alkyl radicals, such that the at least one aromatic ring with six atoms does not comprise a hydrogen atom located in the ortho position relative to the primary amine functions, said amine hardener comprising at least one second primary amine function located on said at least one aromatic ring with six atoms or on a possible second aromatic ring with six atoms of said amine hardener.

[0016] It also relates to a tire comprising a composition according to the invention.

[0017] I- DEFINITIONS

[0018] 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 manufacture of the composition; the composition can thus be in a totally or partially crosslinked state or in a non-crosslinked state. The term "elastomer matrix" means all the elastomers in the composition, including the copolymer defined below.

[0019] 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.

[0020] 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.

[0021] In this document, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0022] 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.

[0023] 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.

[0024] 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).

[0025] II- DESCRIPTION OF THE INVENTION

[0026] II- 1 Elastomer matrix

[0027] According to the invention, the elastomer matrix comprises more than 50 pce of at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer represent between 50% and 95% by mole of the monomer units of the copolymer (hereinafter referred to as "the copolymer").

[0028] The term "copolymer containing ethylene units and 1,3-diene units" means any copolymer comprising, within its structure, at least ethylene units and 1,3-diene units. The copolymer may thus comprise monomer units other than the ethylene units and the 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, the alpha-olefin units may be chosen from the group consisting of propylene, butene, pentene, hexene or mixtures thereof.

[0029] As is well known, the expression "ethylene unit" refers to the -(CH2-CH2)- motif resulting from the insertion of ethylene into the elastomer chain.

[0030] As is known, the expression "1,3-diene unit" refers to the 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.

[0031] Preferably, the 1,3-diene units are chosen 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. More preferably, the 1,3-diene units are for more than 50%, by mole, or even preferably exclusively, 1,3-butadiene units.

[0032] 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.

[0033] 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).

[0034] 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.

[0035] -CH2-CH(CH=CH2)- (II)

[0036] 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).

[0037] 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.

[0038] 0 < o+p < 25 (eq. 1)

[0039] 0 < o+p < 20 (eq. 2)

[0040] According to the invention, the copolymer, preferably the copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene), is a random copolymer.

[0041] 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.

[0042] The Mn of the copolymer is determined in a known manner, by size exclusion chromatography (SEC) as described in point IV-1 below.

[0043] 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 Al, WO 2018020122 Al and WO 2018020123 Al.

[0044] The copolymer may consist of a mixture of copolymers containing ethylene units and 1,3-diene units which differ from each other in their microstructures and / or in their macrostructures.

[0045] According to the invention, the elastomer matrix may comprise at least one other diene elastomer, which is not the copolymer as defined above, but this is not necessary. Thus, preferably, the content of the at least one copolymer is within a range from 60 to 100 phr, preferably from 80 to 100 phr. 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 elastomer matrix.

[0046] By "diene" elastomer (or indistinctly rubber), whether natural or synthetic, is meant 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.

[0047] When the elastomer 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, 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).

[0048] II-2 Reinforcing charge

[0049] The 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, in particular and more preferably between 20 and 150 nm.

[0050] 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 mass, preferably more than 80% by mass, of carbon black. More preferably, the reinforcing filler consists exclusively of carbon black, i.e. the carbon black represents 100% by mass of the reinforcing filler.

[0051] The blacks that can be used in the context of the present invention can be any black conventionally used in tires or their treads (so-called tire-grade blacks). Among the latter, mention will be made more particularly of reinforcing carbon blacks of the 100, 200, 300 series, or blacks of the 500, 600 or 700 series (ASTM grades), such as for example blacks NI 15, 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 support for certain 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 WO 97 / 36724 or WO 99 / 16600).

[0052] Among the above-mentioned carbon blacks, those having a BET specific surface area in the range of 100 to 160 m 2 / g, preferably 124 to 150 m 2 / g, are particularly preferred.

[0053] The BET specific surface area of ​​carbon blacks is measured according to standard D6556-2016 [multipoint method (at least 5 points) - gas: nitrogen - relative pressure range P / P0: 0.1 to 0.3],

[0054] 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, 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.

[0055] To couple the silica 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.

[0056] Preferably, when used, 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.

[0057] When a silica-elastomer coupling agent is used, the coupling agent content can easily be adjusted by a person skilled in the art. Typically, the coupling agent content is from 0.5% to 15% by weight relative to the amount of silica.

[0058] The level of reinforcing filler can easily be adjusted by a person skilled in the art depending on the use of the rubber composition. Advantageously, the level of reinforcing filler, in the composition according to the invention, is within a range from 10 to less than 100 phr, preferably from 15 to 90 phr. Preferably, the level of carbon black, in the composition according to the invention, is within a range from 10 to less than 100 phr, preferably from 15 to 90 phr, and the composition does not comprise any filler other than carbon black or comprises less than 10 phr, preferably less than 5 phr, more preferably the composition does not comprise any filler other than carbon black.

[0059] II-3 Vulcanization system

[0060] The vulcanization system is by definition sulfur-based. It may comprise molecular sulfur and / or at least one sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally, also preferably, various known vulcanization activators may be used such as zinc oxide, stearic acid or equivalent compound such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or known vulcanization retarders.

[0061] Sulphur is used at a preferential rate of between 0.5 and 12 pce, in particular between 1 and 10 pce. The vulcanisation accelerator is used at a preferential rate of between 0.5 and 10 pce, more preferably between 0.5 and 5.0 pce.

[0062] Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may 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, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0063] II-4 Epoxy resin

[0064] The composition according to the invention comprises between 1 and 30 pce of epoxy resin. Epoxy resins are reinforcing resins (or hardening resins) known to those skilled in the art for stiffening rubber compositions.

[0065] The epoxy resins usable in the present invention include all polyepoxide compounds. For example, the epoxy resin may be chosen from aromatic epoxy resins, alicyclic epoxides and aliphatic epoxides. For example, the aromatic epoxy resin may be an amine-aromatic epoxy resin. These resins are preferably novolac epoxy resins, that is to say epoxy resins obtained by acid catalysis, as opposed to resol resins, obtained by basic catalysis.

[0066] Particularly preferred among the aromatic epoxy compounds are epoxy resins selected from the group consisting of 2,2 bis[4-(glycidyloxy) phenyl] propane, polyfo-cresylglycidyl ether)-co-formaldehyde], polyfphenylglycidyl ether)-co-formaldehyde], poly[(phenylglycidyl ether)-co(hydroxybenzaldehyde glycidyl ether)] and mixtures of these compounds.

[0067] More preferably, the epoxy resin is selected from the group consisting of polyfo-cresylglycidyl ether)-co-formaldehyde], polyfo-phenylglycidyl ether)-co-formaldehyde], aromatic amine epoxy resins and mixtures of these compounds.

[0068] Examples of commercially available epoxy resins that can be used in the context of the present invention include, for example, the epoxy resin “DEN 439” from the company Uniqema, the epoxy resin “Tris(4-hydroxyphenyl)methane triglycidyl ether” from the company Sigma-Aldrich, and the epoxy cresol novolac resin araldite ECN 1299 from the company Huntsman.

[0069] The amount of epoxy resin is between 1 and 30 phr. Given the amine hardener used in the context of the present invention, below the minimum resin level indicated, the intended technical effect is insufficient, while above the maximum indicated, there is a risk of excessively high rigidity increase and excessive penalization of hysteresis and Mooney plasticity. For all these reasons, the epoxy resin level is between 5 and 25 phr. More preferably, the epoxy resin level in the composition according to the invention is between 10 and 20 phr.

[0070] II-5 Amino hardener

[0071] The epoxy resin of the composition of the invention is associated with a particular amine hardener which allows the crosslinking of the resin.

[0072] According to the invention, the amine hardener comprises at least two primary amine functions located on at least (i.e. one or more) one six-atom aromatic ring, said at least one six-atom aromatic ring comprising:

[0073] ° at least one primary amine function, and

[0074] ° at least two radicals Ri, identical or different, chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, and ethers, tertiary amines, thioethers, ketones, esters and amides, substituted by linear or branched C1-C6 alkyl radicals, such that the at least one aromatic ring with six atoms does not comprise a hydrogen atom located in the ortho position relative to the primary amine functions, said amine hardener comprising at least one second primary amine function located on said at least one aromatic ring with six atoms or on a possible second aromatic ring with six atoms of said amine hardener.

[0075] In other words, the amine hardener comprises one or more six-atom aromatic rings and at least two primary amine functions located on one or more of these six-atom aromatic rings.

[0076] As is well known to those skilled in the art, the term “primary amine function” means an amine function in which the nitrogen atom is linked to two hydrogen atoms.

[0077] Preferably, the amine hardener comprises from 1 to 3, more preferably 1 or 2 six-atom aromatic rings.

[0078] Preferably, the amine hardener comprises from 2 to 4, more preferably 2 primary amine functions located on at least one six-atom aromatic ring of the amine hardener.

[0079] Among the halogens that may constitute the radicals Ri, mention may be made of fluorine, chlorine, bromine or iodine atoms. Preferably, the halogens are chosen from the group consisting of chlorine and bromine atoms, more preferably the halogens are chlorine atoms.

[0080] According to a first embodiment of the present invention, the amine hardener may comprise a six-atom aromatic ring comprising:

[0081] ° at least two primary amine functions, and

[0082] ° at least two radicals Ri, identical or different, chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, and ethers, tertiary amines, thioethers, ketones, esters and amides, substituted by linear or branched C1-C6 alkyl radicals, so that said cycle does not comprise a hydrogen atom located in the ortho position relative to the primary amine functions. According to a second embodiment of the present invention, the amine hardener may also comprise at least two aromatic cycles with six atoms, identical or different, said cycles each comprising:

[0083] ° at least one primary amine function, and

[0084] ° at least two radicals Ri, identical or different, chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, and ethers, tertiary amines, thioethers, ketones, esters and amides, substituted by linear or branched C1-C6 alkyl radicals, such that said cycles do not include a hydrogen atom located in the ortho position relative to the primary amine functions.

[0085] According to another embodiment, the amine hardener may also comprise several six-atom aromatic rings and at least two primary amine functions located only on one of the aromatic rings.

[0086] When the amine hardener comprises several (i.e. at least two) six-atom aromatic rings, these rings may be identical or different. They may, for example, differ from each other by the nature of the atoms constituting said rings and / or by the number of primary amine functions located on said rings and / or by the nature and / or number of radicals Ri arranged on said rings and / or by the position of the primary amine functions and radicals Ri on said rings. Preferably, when the amine hardener comprises several six-atom aromatic rings, these rings are identical.

[0087] As indicated above, the amine hardener comprises at least two radicals R 1 , identical or different, selected from the group consisting of linear or branched C 1 -C 6 alkyl radicals, halogens, and ethers, tertiary amines, thioethers, ketones, esters and amides, substituted by linear or branched C 1 -C 6 alkyl radicals. In the expression "ethers, tertiary amines, thioethers, ketones, esters and amides, substituted by linear or branched C 1 -C 6 alkyl radicals", a person skilled in the art understands that the terms "substituted by linear or branched C 1 -C 6 alkyl radicals" refer to each of the ethers, tertiary amines, thioethers, ketones, esters and amides.

[0088] Whatever the embodiment of the present invention, the amine hardener preferably comprises at least two radicals Ri, identical or different, chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, and ethers, tertiary amines, thioethers, substituted by linear or branched C1-C6 alkyl radicals. More preferably, the amine hardener comprises at least two radicals Ri, identical or different, chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, and thioethers substituted by linear or branched C1-C6 alkyl radicals.

[0089] Regardless of the embodiment of the present invention, the radicals Ri, which may be identical or different, are preferably chosen from the group consisting of linear or branched C 1 -C 6 alkyl radicals. In other words, all the radicals Ri of the amine hardener may be linear or branched C 1 -C 6 alkyl radicals, the linear or branched C 1 -C 6 alkyl radicals being preferably chosen from the group consisting of methyl, ethyl and propyl radicals.

[0090] Regardless of the embodiment of the present invention, the at least one six-atom aromatic ring of the amine hardener may comprise at least two radicals Ri, identical or different, chosen from the group consisting of halogens, and ethers, tertiary amines and thioethers, substituted by linear or branched C1-C6 alkyl radicals, and at least one radical Ri chosen from the group consisting of linear or branched C1-C6 alkyl radicals.

[0091] Regardless of the embodiment of the present invention, whether it is the radicals R 1 , or the radicals of ethers, tertiary amines, thioethers, ketones, esters or amides, the linear or branched C 1 -C 6 alkyl radicals may be chosen from the group consisting of methyl, ethyl, propyl, isopropyl, isobutyl and butyl radicals. Preferably, the linear or branched C 1 -C 6 alkyl radicals are chosen from the group consisting of methyl, ethyl and propyl radicals. More preferably, the linear or branched C 1 -C 6 alkyl radicals are chosen from the group consisting of methyl and ethyl radicals.

[0092] Regardless of the embodiment of the present invention, the atoms of the aromatic rings of the amine hardener may be carbon atoms, and optionally comprise nitrogen atoms. Preferably, all the atoms of the aromatic rings of the amine hardener are carbon atoms. In other words, the six-atom aromatic rings of the amine hardener are preferably six-carbon aromatic rings.

[0093] In formulas (III) to (VII) presented below, it is recalled that the radicals Ri may be identical or different. According to the first embodiment of the present invention, the amine hardener may correspond to formula (III): according to this embodiment, the amine hardener corresponds to formula

[0094] According to the second embodiment of the present invention, the amine hardener may in which n represents an integer ranging from 0 to 4, preferably from 1 to 3,

[0095] Ri and R2, identical or different, are chosen from the group consisting of a hydrogen atom and a methyl, ethyl, isobutyl or benzyl group, preferably Ri and R2 both represent a hydrogen atom.

[0096] Preferably, according to this embodiment, the amine hardener corresponds to formula (VI): in which n represents 1 or 2, preferably 1,

[0097] Ri and R2, identical or different, are chosen from the group consisting of a hydrogen atom, a methyl, ethyl, isobutyl or benzyl group, preferably Ri and R2 both represent a hydrogen atom.

[0098] More preferably, according to this embodiment, the amine hardener corresponds to formula (VII):

[0099] Very preferably, according to the invention, the amine hardener is chosen from the group consisting of the compounds of formulas (VIII) to (XIII) below and the mixtures of these compounds:

[0100] Examples of commercially available amine hardeners that can be used in the context of the present invention include, for example, “Ethacure 100” or “Ethacure 300 from Albemarle, “Lonzacure DETDA”, “Lonzacure MDEA” or “Lonzacure MCDEA” from Lonza. The amount of amine hardener is between 1 and 15 phr. Below the minimum indicated, the intended technical effect has proven insufficient, whereas above the maximum indicated, there is a risk of penalizing the implementation of the compositions in the raw state. Advantageously, the level of amine hardener is within a range of 5 to 10 phr, preferably 2 to 8 phr.

[0101] II-6 Possible additives

[0102] 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), reinforcing or non-reinforcing fillers other than those mentioned above, pigments, protective agents such as antiozone waxes, chemical antiozonants, antioxidants, anti-fatigue agents.

[0103] Advantageously, the composition according to the invention comprises a condensation accelerator, which is particularly advantageous for reducing the cooking time of the composition.

[0104] Thus, the composition according to the invention advantageously comprises an imidazole of general formula (XIV): in which,

[0105] - Ra represents a hydrogen atom or a hydrocarbon group, optionally interrupted by one or more heteroatoms and / or substituted,

[0106] - Rb represents a hydrocarbon group,

[0107] - Rc and Ra represent, independently of each other, a hydrogen atom or a hydrocarbon group, optionally interrupted by one or more heteroatoms and / or substituted,

[0108] - or Rc and Ra form together with the carbon atoms of the imidazole ring to which they are attached, a ring optionally interrupted by one or more heteroatoms and / or substituted. By the expression "optionally interrupted by one or more heteroatoms and / or substituted", it is meant that the groups Ra, Rc and Ra may, independently and when they represent a hydrocarbon group, be interrupted by a heteroatom (i.e. in other words that a heteroatom is intercalated in the hydrocarbon chain), preferentially chosen from nitrogen, oxygen and sulfur, and / or substituted by a functional group. By functional group, is meant a group comprising a heteroatom, preferentially chosen from amino, alkylamine, alkoxyl and hydroxyl groups, preferentially chosen from hydroxyl and amino groups.

[0109] An amino group means a group of the formula -NH2. A hydroxyl group means a group of the formula -OH.

[0110] Preferably, the imidazole of general formula (XIV) has groups such as:

[0111] - Ra is selected from the group consisting of a hydrogen atom, alkyl groups having from 1 to 20 carbon atoms, cycloalkyl groups having from 5 to 24 carbon atoms, aryl groups having from 6 to 30 carbon atoms, aralkyl groups having from 7 to 25 carbon atoms, optionally substituted,

[0112] - Rb is selected from the group consisting of alkyl groups having from 1 to 20 carbon atoms, cycloalkyl groups having from 5 to 24 carbon atoms, aryl groups having from 6 to 30 carbon atoms or aralkyl groups having from 7 to 25 carbon atoms,

[0113] - Rc and Ra are independently selected from the group consisting of a hydrogen atom, alkyl groups having from 1 to 20 carbon atoms, cycloalkyl groups having from 5 to 24 carbon atoms, aryl groups having from 6 to 30 carbon atoms or aralkyl groups having from 7 to 25 carbon atoms; optionally substituted, or Rc and Ra form together with the carbon atoms of the imidazole ring to which they are attached, a ring selected from aromatic, heteroaromatic or aliphatic rings, comprising from 5 to 12 carbon atoms, preferably 5 or 6 carbon atoms.

[0114] Preferably, Ra is chosen from the group consisting of alkyl groups having from 2 to 12 carbon atoms and aralkyl groups having from 7 to 13 carbon atoms, optionally substituted. More preferably, Ra is chosen from the group consisting of aralkyl groups having from 7 to 13 carbon atoms, optionally substituted and Rb is chosen from the group consisting of alkyl groups having from 1 to 12 carbon atoms. Even more preferably, Ra is chosen from the group consisting of aralkyl groups having from 7 to 11 carbon atoms, optionally substituted and Rb is chosen from the group consisting of alkyl groups having from 1 to 4 carbon atoms. Preferably, Rc and Ra are independently selected from the group consisting of hydrogen, alkyl groups having 1 to 12 carbon atoms, cycloalkyl groups having 5 to 8 carbon atoms, aryl groups having 6 to 24 carbon atoms, and aralkyl groups having 7 to 13 carbon atoms.Alternatively and also preferentially, Rc and Ra form with the carbon atoms of the imidazole ring to which they are attached, a phenyl, cyclohexene, or cyclopentene ring.

[0115] Very preferably, Rc and Ra represent the hydrogen atom, Ra and Rb being chosen as described previously.

[0116] In a preferred arrangement, Ra is a naphthylalkyl group comprising from 11 to 13 carbon atoms, optionally substituted by at least one hydroxyl group, Rb is an alkyl group having from 1 to 4 carbon atoms, Rc and Ra are independently selected from the group consisting of a hydrogen atom and alkyl groups having from 1 to 12 carbon atoms. By naphthylalkyl group is meant a group of general formula (XV), where n represents an integer between 1 and 3:

[0117] Preferably, Ra is a naphthylalkyl group comprising from 11 to 13 carbon atoms substituted by at least one hydroxyl group, Rb is an alkyl group having from 1 to 3 carbon atoms, Rc and Ra are a hydrogen atom. Very preferably, Ra is a 2-naphthol-1-methyl group, Rb is a methyl group, Rc and Ra are the hydrogen atom, the compound (XIV) then corresponding to the formula (XVI):

[0118] The rubber composition according to the invention preferably comprises from 0.1 to 5 pce of imidazole of general formula (XIV). Below this minimum content, the technical effect is not significant, whereas above these contents the imidazole of general formula (XIV) could compete with the amine hardener and modify the network obtained during crosslinking. Preferably, the composition comprises from 0.1 to 3 pce, preferably from 0.2 to 3 pce, preferably from 0.2 to 2 pce of imidazole of general formula (XIV).

[0119] The imidazoles that can be used in the context of the invention are either commercially available or easily prepared by those skilled in the art according to well-known techniques such as described for example in documents JP2012211122, JP2007269658 or in Science of Synthesis 2002, 72, 325-528.

[0120] For example, as commercially available imidazoles useful for the purposes of the invention, mention may be made of 1,2-dimethylimidazole, 1-decyl-2-methylimidazole, 1-benzyl-2-methylimidazole or 1-((2-Methyl-1H-Imidazol-1-yl)Methyl)Naphthalen-2-ol commercially available under the name "Aradur 3123" from the company Huntsman.

[0121] II-7 Preparation of rubber compositions

[0122] 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:

[0123] - a first working phase 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, the epoxy resin, any other various additives, with the exception of the vulcanization system, the amine hardener and any condensation accelerator. 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 kneaded 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 vulcanization 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.

[0124] - a second phase of mechanical work (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 vulcanization system is then incorporated, and everything is then mixed for a few minutes, for example between 5 and 15 min.

[0125] Such phases have been described for example in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.

[0126] 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 else extruded (or co-extruded with another rubber composition) in the form of a semi-finished (or profiled) rubber usable, for example, as an internal layer of a tire. These products can then be used for the manufacture of tires, according to techniques known to those skilled in the art.

[0127] 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.

[0128] 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.

[0129] II-8 Rubber article

[0130] 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.

[0131] More particularly, the invention also relates to a pneumatic or non-pneumatic tire provided with at least one inner layer comprising a composition according to the invention. The composition according to the invention may constitute part or all of the inner layer of the tire. The inner layer is preferably 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. More preferably, the inner layer is chosen from the group consisting of bead fillers, crown feet, tread sub-layer and combinations of these inner layers. More preferably, the inner layer is chosen from the group consisting of bead fillers, crown feet and the combination of these inner layers.

[0132] The tire according to the invention can be intended to equip any type of vehicle, in particular motor vehicles, without any particular limitation.

[0133] III- PREFERRED EMBODIMENTS

[0134] In view of the foregoing, preferred embodiments of the invention are described below:

[0135] 1. Rubber composition based on at least:

[0136] - an elastomer matrix comprising more than 50 pce of 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,

[0137] - a reinforcing charge,

[0138] - a vulcanization system,

[0139] - from 1 to 30 pce of epoxy resin,

[0140] - between 1 and 15 pce of an amine hardener comprising at least two primary amine functions, located on at least one aromatic cycle with six atoms, said at least one aromatic cycle with six atoms comprising:

[0141] ° at least one primary amine function, and

[0142] ° at least two radicals Ri, identical or different, chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, ethers, tertiary amines, thioethers, ketones, esters and amides, substituted by linear or branched C1-C6 alkyl radicals, such that the at least one aromatic ring with six atoms does not comprise a hydrogen atom located in the ortho position relative to the primary amine functions, said amine hardener comprising at least one second primary amine function located on said at least one aromatic ring with six atoms or on a possible second aromatic ring with six atoms of said amine hardener.

[0143] 2. Rubber composition according to embodiment 1, in which the ethylene units in the copolymer represent between 55% and 90% by mole of the monomer units of the copolymer.

[0144] 3. A rubber composition according to any one of the preceding embodiments, wherein the copolymer containing ethylene units and 1,3-diene units is a copolymer of ethylene and 1,3-diene.

[0145] 4. A rubber composition according to any one of the preceding embodiments, wherein the 1,3-diene is 1,3-butadiene.

[0146] 5. Rubber composition according to any one of the preceding embodiments, in which the copolymer contains units of formula (I) or units of formula (II) or units of formula (I) and of formula (II):

[0147] -CH2-CH(CH=CH2)- (II)

[0148] 6. Rubber composition according to any one of embodiment 5, wherein the molar percentages of the units of formula (1) and the units of formula (2) in the copolymer, respectively o and p, satisfy the following equation (eq. 1), preferentially to equation (eq. 2), o and p being calculated on the basis of all the monomer units of the copolymer.

[0149] 0 < o+p < 25 (eq. 1)

[0150] 0 < o+p < 20 (eq. 2)

[0151] 7. A rubber composition according to any preceding embodiment, wherein the copolymer containing ethylene units and 1,3-diene units is a random copolymer.

[0152] 8. Rubber composition according to any one of the preceding embodiments, in which the content of the copolymer containing ethylene units and 1,3-diene units is within a range from 60 to 100 pce, preferably from 80 to 100 pce.

[0153] 9. Rubber composition according to any one of the preceding embodiments, in which the epoxy resin is chosen from aromatic epoxy resins, alicyclic epoxies and aliphatic epoxies.

[0154] 10. A rubber composition according to any one of embodiments 1 to 8, wherein the epoxy resin is selected from the group consisting of 2,2 bis[4-(glycidyloxy)phenyl]propane, polyfo-cresylglycidyl ether)-co-formaldehyde], polyfphenylglycidyl ether)-co-formaldehyde], poly[(phenylglycidyl ether)-co(hydroxybenzaldehyde glycidyl ether)] and mixtures of these compounds.

[0155] 11. Rubber composition according to any one of the preceding embodiments, in which the epoxy resin content is between 5 and 25 pce, preferably between 10 and 20 pce.

[0156] 12. Rubber composition according to any one of the preceding embodiments, in which the radicals Ri, identical or different, are chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, ethers, tertiary amines and thioethers, substituted by linear or branched C1-C6 alkyl radicals.

[0157] 13. Rubber composition according to any one of the preceding embodiments, in which the radicals Ri, identical or different, are chosen from the group consisting of linear or branched C1-C6 alkyl radicals.

[0158] 14. Rubber composition according to any one of embodiments 1 to 12, in which the at least one six-atom aromatic ring of the amine hardener comprises at least two radicals Ri, identical or different, chosen from the group consisting of halogens, and ethers, tertiary amines and thioethers, substituted by linear or branched C1-C6 alkyl radicals, and at least one radical Ri chosen from the group consisting of linear or branched C1-C6 alkyl radicals.

[0159] 15. Rubber composition according to any one of the preceding embodiments, in which the linear or branched C 1 -C 6 alkyl radicals are chosen from the group consisting of methyl, ethyl, propyl, isopropyl, isobutyl and butyl radicals, preferably from the group consisting of methyl and ethyl radicals.

[0160] 16. A rubber composition according to any preceding embodiment, wherein the at least one six-atom aromatic ring is a six-carbon aromatic ring.

[0161] 17. Rubber composition according to any one of the preceding embodiments, in which the amine hardener corresponds to formula (III):

[0162] 18. Rubber composition according to any one of embodiments 1 to 16, in which the amine hardener corresponds to formula (IV):

[0163] 19. Rubber composition according to any one of embodiments 1 to 16, in which the amine hardener corresponds to formula (V): n represents an integer ranging from 0 to 4, preferably from 1 to 3,

[0164] Ri and R2, identical or different, are chosen from the group consisting of a hydrogen atom and a methyl, ethyl, isobutyl or benzyl group, preferably Ri and R2 both represent a hydrogen atom.

[0165] 20. Rubber composition according to any one of embodiments 1 to 16 or 19, in which the amine hardener corresponds to formula (VI): in which n represents 1 or 2, preferably 1,

[0166] Ri and R2, identical or different, are chosen from the group consisting of a hydrogen atom, a methyl, ethyl, isobutyl or benzyl group, preferably Ri and R2 both represent a hydrogen atom.

[0167] 21. Rubber composition according to any one of embodiments 1 to 16, in which the amine hardener corresponds to formula (VII):

[0168] 22. Rubber composition according to any one of embodiments 1 to 16, in which the amine hardener is chosen from the group consisting of the compounds of formulae (VIII) to (XIII) below and the mixtures of these compounds:

[0169] 23. Rubber composition according to any one of the preceding embodiments, in which the level of amine hardener is within a range from 5 to 10 pce, preferably from 2 to 8 pce.

[0170] 24. Rubber composition according to any one of the preceding embodiments, further comprising an imidazole of formula (XIV): in which,

[0171] ° Ra represents a hydrogen atom or a hydrocarbon group, optionally interrupted by one or more heteroatoms and / or substituted,

[0172] ° Rb represents a hydrocarbon group,

[0173] ° Rc and Rd represent, independently of each other, a hydrogen atom or a hydrocarbon group, optionally interrupted by one or more heteroatoms and / or substituted,

[0174] ° or Rc and Rd form together with the carbon atoms of the imidazole ring to which they are attached, a ring possibly interrupted by one or more heteroatoms and / or substituted.

[0175] 25. Rubber composition according to embodiment 24, in which, in the imidazole of formula (XIV):

[0176] - Ra is selected from the group consisting of a hydrogen atom, alkyl groups having from 1 to 20 carbon atoms, cycloalkyl groups having from 5 to 24 carbon atoms, aryl groups having from 6 to 30 carbon atoms, aralkyl groups having from 7 to 25 carbon atoms, optionally substituted,

[0177] - Rb is selected from the group consisting of alkyl groups having from 1 to 20 carbon atoms, cycloalkyl groups having from 5 to 24 carbon atoms, aryl groups having from 6 to 30 carbon atoms or aralkyl groups having from 7 to 25 carbon atoms,

[0178] - Rc and Ra are independently selected from the group consisting of a hydrogen atom, alkyl groups having from 1 to 20 carbon atoms, cycloalkyl groups having from 5 to 24 carbon atoms, aryl groups having from 6 to 30 carbon atoms or aralkyl groups having from 7 to 25 carbon atoms, optionally substituted, or Rc and Ra form together with the carbon atoms of the imidazole ring to which they are attached, a ring selected from aromatic, heteroaromatic or aliphatic rings, comprising from 5 to 12 carbon atoms, preferably 5 or 6 carbon atoms.

[0179] 26. Rubber composition according to any one of embodiments 24 to 25, in which, in the imidazole of formula (XIV), Ra is selected from the group consisting of alkyl groups having from 2 to 12 carbon atoms and aralkyl groups having from 7 to 13 carbon atoms, optionally substituted.

[0180] 27. A rubber composition according to any one of embodiments 24 to 26, wherein, in the imidazole of formula (XIV), Ra is selected from the group consisting of aralkyl groups having from 7 to 13 optionally substituted carbon atoms and Rb is selected from the group consisting of alkyl groups having from 1 to 12 carbon atoms.

[0181] 28. A rubber composition according to any one of embodiments 24 to 27, wherein, in the imidazole of formula (XIV), Ra is selected from the group consisting of aralkyl groups having from 7 to 11 optionally substituted carbon atoms and Rb is selected from the group consisting of alkyl groups having from 1 to 4 carbon atoms.

[0182] 29. A rubber composition according to any one of embodiments 24 to 28, wherein, in the imidazole of formula (XIV), Rc and Ra are independently selected from the group consisting of a hydrogen atom and alkyl groups having from 1 to 12 carbon atoms, cycloalkyl groups having from 5 to 8 carbon atoms, aryl groups having from 6 to 24 carbon atoms and aralkyl groups having from 7 to 13 carbon atoms, Rc and Ra being very preferably the hydrogen atom.

[0183] 30. Rubber composition according to any one of embodiments 24 to 28, in which, in the imidazole of formula (XIV), Rc and Ra form with the carbon atoms of the imidazole ring to which they are attached, a phenyl, cyclohexene, or cyclopentene ring.

[0184] 31. A rubber composition according to embodiment 24, wherein in the imidazole of formula (XIV), Ra is a naphthylalkyl group comprising from 11 to 13 carbon atoms, optionally substituted by at least one hydroxyl group, Rb is an alkyl group having from 1 to 4 carbon atoms, Rc and Ra are independently selected from the group consisting of a hydrogen atom and alkyl groups having from 1 to 12 carbon atoms.

[0185] 32. Rubber composition according to embodiment 31, in which Ra is a naphthylalkyl group comprising from 11 to 13 carbon atoms substituted by at least one hydroxyl group, Rb is an alkyl group having from 1 to 3 carbon atoms, Rc and Ra are a hydrogen atom, and in which preferably Ra is a 2-naphtholmethyl group, Rb is a methyl group, Rc and Ra are the hydrogen atom, the compound (XIV) then corresponding to the formula (XVI):

[0186] 33. Rubber composition according to any one of embodiments 24 to 32, in which the level of imidazole of formula (XIV) is within a range from 0.1 to 5 pce, preferably from 0.1 to 3 pce.

[0187] 34. A rubber composition according to any one of the preceding embodiments, wherein the reinforcing filler comprises carbon black, silica or a mixture thereof.

[0188] 35. Rubber composition according to any one of the preceding embodiments, in which the reinforcing filler comprises more than 50% by weight, preferably more than 80% by weight of carbon black.

[0189] 36. Rubber composition according to any one of embodiments 34 to 35, in which the carbon black has a BET specific surface area in a range from 100 to 160 m 2 / g, preferably 124 to 150 m 2 / g.

[0190] 37. Rubber composition according to any one of the preceding embodiments, in which the level of the reinforcing filler is within a range from 10 to less than 100 pce, preferably from 15 to 90 pce.

[0191] 38. Rubber article comprising a composition as defined in any one of embodiments 1 to 37.

[0192] 39. Tire comprising a composition as defined in any one of embodiments 1 to 37.

[0193] 40. Tire according to embodiment 39, in which the composition defined in any one of embodiments 1 to 37 is present in at least one internal layer, preferably 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 internal layers.

[0194] IV- EXAMPLES

[0195] IV- 1 Measurements and tests used

[0196] Mechanical properties

[0197] These tensile tests allow the determination of yield stresses and properties at break. Processing of the tensile records also allows the plotting of the modulus curve as a function of elongation. The modulus used here is the nominal (or apparent) secant modulus measured at first elongation, calculated by referring to the initial section of the specimen. The stresses at break (CR in MPa) and the elongations at break (AR in %) are measured at 23 °C ± 2 °C, according to standard NF T 46-002 of September 1988. The energy at break is equal to the product of the elongation at break and the stress at break.

[0198] The elongation at break results are expressed as a percentage based on 100 compared to the control composition T1 or T2 as appropriate. A result greater than 100 indicates an improvement in the mechanical properties of the composition considered.

[0199] The dynamic properties G* and tan(ô)max are measured on a viscoanalyzer (Metravib VA4000), according to ASTM D5992-96. The response of a sample of vulcanized composition (cylindrical specimen 2 mm thick and 79 mm 2 section), subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, at 60°C according to standard ASTM D 1349-09. A strain amplitude sweep is carried out from 0.01% to 50% (forward cycle), then from 50% to 0.01% (return cycle).

[0200] The results used are the complex dynamic shear modulus G* and the loss factor tan(ô)max. On the forward cycle, the value of G* at 5% deformation is recorded, as well as the loss factor, noted tan(ô)max.

[0201] The results of G* at 60°C at 5% strain on the forward cycle and of tan(ô)max at 60°C on the forward cycle are expressed in performance base 100, the value 100 being attributed to the control T1 or T2 as the case may be. A result greater than 100 indicates that the composition of the example considered is respectively more rigid and less hysteretic, reflecting respectively a better rigidity for the application considered and a lower hysteresis.

[0202] Determination of the microstructure of elastomers by nuclear magnetic resonance (NMR):

[0203] 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 but having 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 (CDCL). 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 25 mg of elastomer in 1 ml), generally deuterated chloroform (CDCL). 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.

[0204] Determination of the macrostructure of polymers by size exclusion chromatography (SEC):

[0205] 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: a solvent reservoir, a pumping system, an injector, a set of columns and detectors. The measurement chain is equipped with a Waters Alliance e2695 module and a Waters fRI410 refractometer.

[0206] The mobile phase is eluted with a flow rate of 1 mL / min. The polymer is solubilized in THF in the presence of 1% wt of diisopropylamine and 1% wt of triethylamine at a concentration of 1 g / L. A volume of 100 pL is injected through a set of 3 size exclusion chromatography columns of the A GILENT brand (MIXED B LS). The columns are thermostated in an oven at 35°C. The stationary phase of the columns is based on a polystyrene divinylbenzene gel with controlled porosity. The polymer chains are separated according to the hydrodynamic volume they occupy when they are solubilized in the solvent. The larger the volume they occupy, the less accessible the pores of the columns are and the shorter their elution time. Detection is ensured by a refractometer (RI) thermostated at 35°C. Each elution volume is associated with a mass via Moore calibration (certified standard passage: standard polystyrenes from Polymer Standard Service (Mainz).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) as well as the polydispersity (Ip = Mw / Mn).

[0207] Mooney ML 1+4

[0208] For polymers and rubber compounds, Mooney viscosities ML(l+4) at 100°C are measured using an oscillating consistometer according to ASTM D-1646 (1999). The Mooney plasticity measurement is carried out according to the following principle: the raw compound (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 / minute and the torque needed to maintain this movement after 4 minutes of rotation is measured. The Mooney plasticity ML(l+4) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Nm).

[0209] IV-2 Synthesis of copolymer El:

[0210] In polymer synthesis, all reagents are obtained commercially except for metallocenes. Butyloctylmagnesium BOMAG (20% in Theptane, C = 0.88 mol.L 1 ) comes from Chemtura and is stored in a Schlenk tube under an inert atmosphere. Ethylene, grade N35, comes from Air Liquide and is used without prior purification.

[0211] The copolymer of ethylene and 1,3-butadiene: elastomer E1 (in accordance with the invention) is synthesized according to the procedure described below.

[0212] 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, [Me2SiFlu2Nd(p-BH4)2Li(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 AL.

[0213] 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).

[0214] [Table 1]

[0215] [Table 2]

[0216] [Table 3] IV-3 Preparation of compositions

[0217] In the following examples, the rubber compositions were produced as described in point II-7 above. In particular, the “non-productive” phase was carried out in a 0.4 liter mixer for 3.5 minutes, for an average paddle speed of 50 revolutions per minute until a maximum drop temperature of 165°C was reached. The “productive” phase was carried out in a cylinder tool at 40°C for 5 minutes.

[0218] The crosslinking of the composition was carried out at a temperature between 130°C and 200°C, under pressure.

[0219] IV-4 Rubber composition tests

[0220] The examples presented below aim to compare the performance compromise between rigidity, hysteresis and mechanical properties (elongation at break and breaking stress) of a composition in accordance with the present invention (Cl) with three control compositions (Tl to T3).

[0221] Table 4 presents the tested compositions (in pce), as well as the results obtained.

[0222] Composition Cl differs from control composition Tl only by the nature of the butadiene-styrene copolymer. Control compositions T2 and T3 allow us to study the impact of the absence of the curing system based on epoxy resin and amine hardener.

[0223] The results of composition Cl are expressed as a percentage base 100 relative to the control composition Tl and the results of composition T3 are expressed as a percentage base 100 relative to the control composition T2.

[0224] [Table 4]

[0225] (1) Natural rubber

[0226] (2) Elastomer El obtained by the process described in point IV-2 above

[0227] (3) Carbon black grade NI 15 according to ASTM D-1765

[0228] (4) Epoxy thermosetting resin “Araldite ECN 1299 CH” from Huntsman

[0229] (5) Huntsman Company “Ethacure 300” amine hardener

[0230] (6) Nl,3-dimethylbutyl-N-phenylparaphenylenediamine “Santoflex 6-PPD” from Flexsys

[0231] (7) Stearic acid “Pristerene 4931” from Uniqema

[0232] (8) Industrial grade zinc oxide from Umicore

[0233] (9) Imidazole accelerator “Aradur 3123ES” from Huntsman

[0234] (10) N-cyclohexyl-2-benzothiazyl sulfenamide “Santocure CBS” from Flexsys

[0235] * not available

[0236] The results presented in Table 4 above show that the combination of a copolymer according to the invention and a curing system based on epoxy resin and an amine hardener according to the invention makes it possible to improve both the rigidity and the hysteresis of the composition without penalizing the mechanical properties, or even by improving them. The comparison of the control compositions T2 and T3 shows that this effect is not linked to the simple presence of the copolymer according to the invention. The compositions in accordance with the invention are particularly useful for applications requiring an excellent rigidity / hysteresis compromise, such as in tires, in particular in the internal layers of tires.

Claims

Claims 1. Rubber composition based on at least: - an elastomer matrix comprising more than 50 pce of 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 charge, - a vulcanization system, - from 1 to 30 pce of epoxy resin, - between 1 and 15 pce of an amine hardener comprising at least two primary amine functions, located on at least one six-atom aromatic ring, said at least one six-atom aromatic ring comprising: o at least one primary amine function, and o at least two identical or different Ri radicals, chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, ethers, tertiary amines, thioethers, ketones, esters and amides, substituted by linear or branched C1-C6 alkyl radicals, such that the at least one six-atom aromatic ring does not comprise a hydrogen atom located in the ortho position relative to the primary amine functions, said amine hardener comprising at least one second primary amine function located on said at least one six-atom aromatic ring or on a possible second six-atom aromatic ring of said amine hardener.

2. A 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, the 1,3-diene preferably being 1,3-butadiene.

3. A rubber composition according to any preceding claim, wherein the level of the copolymer containing ethylene units and 1,3- units diene is included in a range from 60 to 100 pce, preferably from 80 to 100 pce.

4. Rubber composition according to any one of the preceding claims, wherein the epoxy resin is selected from aromatic epoxy resins, alicyclic epoxy resins and aliphatic epoxy resins, preferably the epoxy resin is selected from the group consisting of 2,2 bis[4-(glycidyloxy) phenyl] propane, polyfo-cresylglycidyl ether)-co-formaldehyde], polyfphenylglycidyl ether)-co-formaldehyde], poly[(phenylglycidyl ether)-co(hydroxybenzaldehyde glycidyl ether)] and mixtures of these compounds.

5. Rubber composition according to any one of the preceding claims, in which the epoxy resin content is between 5 and 25 phr, preferably between 10 and 20 phr.

6. Rubber composition according to any one of the preceding claims, in which the radicals Ri, identical or different, are chosen from the group consisting of linear or branched C1-C6 alkyl radicals, halogens, ethers, tertiary amines and thioethers, substituted by linear or branched C1-C6 alkyl radicals, preferably the radicals Ri, identical or different, are chosen from the group consisting of linear or branched C1-C6 alkyl radicals.

7. A rubber composition according to any preceding claim, wherein the at least one six-membered aromatic ring is a six-membered aromatic ring.

8. A rubber composition according to any one of the preceding claims, wherein the amine hardener corresponds to any one of formulae (III) to (V) and (VII): - Ri and R2, identical or different, are chosen from the group consisting of a hydrogen atom and a methyl, ethyl, isobutyl or benzyl group, preferably Ri and R2 both represent a hydrogen atom.

9. Rubber composition according to any one of claims 1 to 7, in which the amine hardener is chosen from the group consisting of the compounds of formulas (VIII) to (XIII) below and mixtures of these compounds:

10. Rubber composition according to any one of the preceding claims, in which the level of amine hardener is within a range of 5 to 10 phr, preferably 2 to 8 phr.

11. A rubber composition according to any one of the preceding claims, further comprising an imidazole of formula (XIV): in which, o Ra represents a hydrogen atom or a hydrocarbon group, optionally interrupted by one or more heteroatoms and / or substituted, o Rb represents a hydrocarbon group, o Rc and Rd represent, independently of one another, a hydrogen atom or a hydrocarbon group, optionally interrupted by one or more heteroatoms and / or substituted, o or Rc and Rd form together with the carbon atoms of the imidazole ring to which they are attached, a ring optionally interrupted by one or more heteroatoms and / or substituted.

12. Rubber composition according to claim 11, in which the level of imidazole of formula (XIV) is within a range from 0.1 to 5 pce, preferably from 0.1 to 3 pce.

13. A rubber composition according to any preceding claim, wherein the reinforcing filler comprises more than 50% by weight, preferably more than 80% by weight of carbon black.

14. Rubber composition according to any one of the preceding claims, in which the level of the reinforcing filler is within a range from 10 to less than 100 phr, preferably from 15 to 90 phr.

15. A tire comprising a rubber composition as defined in any one of claims 1 to 14, wherein the composition is preferably present in at least one inner layer, preferably selected 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.

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