Rubber composition based on highly saturated diene elastomer and reinforcing resin

Abstract

The present invention relates to a rubber composition having an improved stiffness-hysteresis trade-off, and a tire comprising the same. The invention relates to a composition based on at least one elastomeric matrix comprising greater than 50 phr of at least one copolymer containing ethylene units and 1, 3-diene units, the ethylene units in the copolymer making up between 50 mol% and 95 mol% of the copolymer monomer units; a reinforcing filler; a vulcanization system; 1 phr to 30 phr of an epoxy resin and between 1 phr and 15 phr of an amine hardener comprising at least two primary amine functional groups on at least one six-membered aromatic ring comprising: at least one primary amine functional group, and at least two groups Ri, which may be the same or different, and an amine hardener selected from the group consisting of linear or branched C1-C6 alkyl groups, halogens, ethers substituted with linear or branched C1-C6 alkyl groups, tertiary amines, thioethers, ketones, esters and amides such that at least one six-membered aromatic ring does not contain any hydrogen atom located ortho to the primary amine function, said amine hardener comprising at least one second primary amine function, the second primary amine functional group is located on the at least one six-membered aromatic ring or a possible second six-membered aromatic ring of the amine hardener.

Description

Technical Field

[0001] The present invention relates to a rubber composition intended in particular for use in the manufacture of tires or semi-finished tire products. Background Art

[0002] Tire layers (such as the tread or inner layer) must meet many, often conflicting, technical requirements, including low rolling resistance, high wear resistance, good road properties and a good level of material cohesion.

[0003] In order to ensure good stiffness, which in particular reflects road performance, it is known to use rubber compositions with a high content of reinforcing fillers. However, it is known that increasing the filler content reduces the hysteresis properties of the tire and thus reduces rolling resistance.

[0004] High stiffness can also be achieved by introducing certain reinforcing resins, as disclosed in patent application WO 02 / 10269, which proposes a rubber composition with high stiffness at low tire strains. Resistance to small strains is one of the properties that a tire must have in order to respond to the stresses to which it is subjected.

[0005] In addition, the solution provided to solve this problem is also advantageously not to compromise other properties of the rubber composition, in particular hysteresis. This is because the use of hysteresis compositions in tires becomes apparent due to the increase in tire internal temperature, which can lead to a reduction in the durability of the tire. In view of the above, a continuing goal is to provide a rubber composition with an improved compromise between stiffness and hysteresis. Needless to say, it is advantageous that this compromised improvement should not be achieved at the expense of other properties of the composition, in particular mechanical properties, such as elongation at break and stress at break (or tensile strength), which are particularly important properties in many tire inner layers.

[0006] Therefore, there is a need to find ways to improve the durability of tires comprising high stiffness compositions without compromising the hysteresis, or even improving it, and without compromising the mechanical properties of the composition.

[0007] The Applicant continued his research and unexpectedly discovered that the use of highly saturated diene elastomers in combination with a curing system based on epoxy resins and specific amine hardeners makes it possible to further improve the aforementioned property compromise. Summary of the Invention

[0008] The subject of the present invention is therefore a rubber composition based on at least:

[0009] an elastomeric matrix comprising greater than 50 phr of at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units of said copolymer representing between 50 and 95 mol% of the monomer units of said copolymer;

[0010] - reinforcing fillers,

[0011] - Vulcanization system,

[0012] - 1 to 30 phr of epoxy resin;

[0013] - between 1 and 15 phr of an aminic hardener comprising at least two primary amine functions located on at least one six-membered aromatic ring comprising:

[0014] o at least one primary amine functional group; and

[0015] o at least two groups Ri, which may be the same or different, selected from linear or branched C1-C6 alkyl, halogen, ether substituted by linear or branched C1-C6 alkyl, tertiary amine, thioether, ketone, ester and amide,

[0016] such that at least one six-membered aromatic ring does not contain a hydrogen atom ortho to the primary amine functional group,

[0017] The amine hardener comprises at least one second primary amine functional group, which is located on the at least one six-membered aromatic ring or on a possible second six-membered aromatic ring of the amine hardener.

[0018] The present invention also provides a tyre comprising the composition according to the invention.

[0019] I-Definition

[0020] The expression "composition based on" is understood to mean that the composition comprises a mixture and / or in situ reaction products of the various components used, some of which are capable of reacting and / or intended to react with one another (at least partially) during the various stages of the manufacture of the composition; the composition may thus be in a completely or partially crosslinked state or in a non-crosslinked state.

[0021] The term "elastomeric matrix" refers to all elastomers in the composition, including copolymers as defined below.

[0022] Unless otherwise stated, the content of the units resulting from the insertion of a monomer into a copolymer is expressed as a molar percentage relative to all monomer units of the copolymer.

[0023] For the purposes of the present invention, the expression “parts by weight per 100 parts by weight of elastomer” (or phr) is understood to mean parts by mass per 100 parts of elastomer present in the rubber composition under consideration.

[0024] Herein, unless otherwise expressly stated, all percentages (%) shown are percentages (%) by mass.

[0025] In addition, any numerical interval represented by the expression "between a and b" represents a numerical range extending from greater than a to less than b (i.e., excluding the end values ​​a and b), while any numerical interval represented by the expression "a to b" means a numerical range extending from a to b (i.e., including the strict end values ​​a and b). Herein, when a numerical interval is represented by the expression "a to b", it is also preferably intended to represent the interval represented by the expression "between a and b".

[0026] The compounds mentioned in this specification may be of fossil origin or bio-based. In the latter case, they may be obtained partly or entirely from biomass or from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also be derived from the recycling of used materials, i.e., they may be produced partly or entirely from a recycling process or from raw materials themselves produced by a recycling process. This particularly relates to polymers, plasticizers, fillers, etc.

[0027] Unless otherwise stated, all glass transition temperature "Tg" values ​​stated herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to standard ASTM D3418 (1999).

[0028] II-Description of the Invention

[0029] II-1 Elastomer Matrix

[0030] According to the invention, the elastomeric matrix comprises more than 50 phr of at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units representing between 50 and 95 mol% of the monomer units of the copolymer (hereinafter referred to as "copolymer").

[0031] The term "copolymer containing ethylene units and 1,3-diene units" refers to any copolymer comprising at least ethylene units and 1,3-diene units within its structure. Thus, the copolymer may contain monomer units other than ethylene units and 1,3-diene units. For example, the copolymer may also contain α-olefin units, particularly α-olefin units containing 3 to 18 carbon atoms, advantageously 3 to 6 carbon atoms. For example, the α-olefin units may be selected from propylene, butene, pentene, hexene, or mixtures thereof.

[0032] In a known manner, the expression "ethylene unit" means a -(CH2-CH2)- unit resulting from the insertion of ethylene into the elastomer chain.

[0033] In a known manner, the expression “1,3-diene unit” means a unit which, in the case of substituted dienes, for example isoprene, results from the insertion of a 1,3-diene via 1,4 addition, 1,2 addition or 3,4 addition.

[0034] Preferably, the 1,3-diene units are selected from butadiene units, isoprene units, and mixtures of these 1,3-diene units. Specifically, the 1,3-diene units of the copolymer may be 1,3-diene units containing 4 to 12 carbon atoms, such as 1,3-butadiene or 2-methyl-1,3-butadiene (or isoprene) units. More preferably, the 1,3-diene units comprise greater than 50 mol%, and even more preferably, are exclusively 1,3-butadiene units.

[0035] In the copolymer, ethylene units account for between 50 mol% and 95 mol% of the monomer units in the copolymer. Advantageously, ethylene units in the copolymer account for between 55 mol% and 90 mol%, preferably 60 mol% to 90 mol%, preferably 70 mol% to 85 mol%.

[0036] 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, the copolymer consists exclusively of ethylene units and 1,3-diene (preferably 1,3-butadiene) units.

[0037] When the copolymer is a copolymer of ethylene and a 1,3-diene, the copolymer advantageously comprises units of formula (I) and / or (II). The saturated six-membered ring unit of formula (I), i.e., 1,2-cyclohexanediyl, present as a monomer unit in the copolymer can be generated by a series of very specific insertions of ethylene and 1,3-butadiene into the polymer chain during the growth of the polymer chain.

[0038]

[0039] -CH2-CH(CH=CH2)-(II)

[0040] For example, a copolymer of ethylene and 1,3-diene may contain no units of formula (I). In this case, it preferably comprises units of formula (II).

[0041] When the copolymer of ethylene and 1,3-diene comprises units of formula (I), or units of formula (II), or units of formula (I) and units of formula (II), the molar percentages o and p of the units of formula (I) and the units of formula (II) in the copolymer, respectively, preferably satisfy the following formula 1, more preferably the following formula 2, wherein o and p are calculated based on all monomer units of the copolymer:

[0042] 0 < o+p ≤ 25 (Equation 1)

[0043] 0 < o+p < 20 (Equation 2)

[0044] According to the present invention, the copolymer, preferably a copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene), is a random copolymer.

[0045] Advantageously, the number average mass (Mn) of the copolymer, preferably of ethylene and a 1,3-diene, preferably 1,3-butadiene, is in the range of 100,000 to 300,000 g / mol, preferably 150,000 to 250,000 g / mol.

[0046] The Mn of the copolymers is determined in a known manner by size exclusion chromatography (SEC), as described below in point IV-1.

[0047] Copolymers can be obtained according to various synthesis methods known to those skilled in the art, in particular according to the target microstructure of the copolymer. Generally, they can be prepared by copolymerizing at least a diene (preferably 1,3-diene, more preferably 1,3-butadiene) with ethylene according to known synthesis methods, in particular in the presence of a catalyst system comprising a metallocene complex. In this regard, metallocene-based catalyst systems can be mentioned, which are described in EP1 092 731, WO 2004 / 035639, WO 2007 / 054223, and WO 2007 / 054224 under the name of the present applicant. Copolymers (including those that are random) can also be prepared by using a preformed catalyst system (e.g., those described in WO 2017 / 093654 A1, WO 2018 / 020122 A1, and WO 2018 / 020123 A1).

[0048] The copolymer may consist of a mixture of copolymers containing ethylene units and 1,3-diene units, these copolymers differing from one another by their microstructure and / or their macrostructure.

[0049] According to the invention, the elastomeric matrix may contain at least one other diene elastomer than the aforementioned copolymer, but this is not essential. Thus, preferably, the content of the at least one copolymer is within the range of 60 to 100 phr, preferably 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, that is, it represents 100% by weight of the elastomeric matrix.

[0050] The term "diene" elastomer (or, without distinction, rubber), whether natural or synthetic, is understood in a known manner to mean an elastomer composed at least in part (i.e., a homopolymer or copolymer) of diene monomer units (monomers bearing two conjugated or non-conjugated carbon-carbon double bonds). This definition includes copolymers containing ethylene units and 1,3-diene units.

[0051] When the elastomeric matrix comprises at least one other diene elastomer that is not a copolymer containing ethylene units and 1,3-diene units, the at least one other elastomer may be chosen, for example, from polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers. The butadiene copolymers are particularly chosen from styrene / butadiene copolymers (SBR).

[0052] II-2 Reinforcement Filler

[0053] The composition according to the invention advantageously comprises a reinforcing filler known to be capable of reinforcing rubber compositions that can be used to manufacture tires. This reinforcing filler generally consists of particles having an average size (by mass) less than a micrometer, generally less than 500 nanometers, most often between 20 and 200 nanometers, and in particular and more preferably between 20 and 150 nanometers.

[0054] The reinforcing filler may comprise carbon black, silica or a mixture thereof. Advantageously, the reinforcing filler of the composition according to the present invention comprises greater than 50% by mass, preferably greater than 80% by mass, of carbon black. More preferably, the reinforcing filler consists solely of carbon black, that is, carbon black accounts for 100% by mass of the reinforcing filler.

[0055] The carbon black that can be used in the context of the present invention can be any carbon black conventionally used in tires or their treads ("tire-grade" carbon black). Among the latter, more particular mention will be made of the reinforcing carbon blacks of the 100, 200 and 300 series, or the carbon blacks of the 500, 600 or 700 series (ASTM grades), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683 and N772 carbon blacks. These carbon blacks can be used in commercially available isolated form or in any other form, for example as carriers for some rubber engineering additives used. The carbon black can, for example, have been introduced into diene elastomers, in particular isoprene elastomers, in the form of a masterbatch (see, for example, patent applications WO 97 / 36724 and WO 99 / 16600).

[0056] Among the above carbon blacks, those with a BET specific surface area of ​​100 m2 / g to 160 m2 / g, preferably 124 m2 / g, are particularly preferred. 2 / g to 150m 2 / g range of carbon black.

[0057] The BET specific surface area of ​​carbon black is measured according to standard D6556-2016 [multi-point (minimum 5 points) method - gas: nitrogen - relative pressure p / p0 range: 0.1 to 0.3].

[0058] Any type of precipitated silica, in particular highly dispersible precipitated silica (referred to as "HDS"), can be suitable as the silica. These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. For example, the silicas described in patent applications WO 03 / 016215-A1 and WO 03 / 016387-A1 may be mentioned. Among the commercially available HDS silicas, in particular those available from Evonik can be used. 5000GR and 7000GR silica or obtained from Solvay 1085GR, 1115MP, 1165MP, Premium 200MP and HRS1200MP silica. As non-HDS silica, the following commercial silicas can be used: VN2GR and

[0059] VN3GR silica, obtained from Solvay 175GR silica or Hi-Sil EZ120G(-D), Hi-Sil EZ160G(-D), Hi-Sil EZ200G(-D), Hi-Sil 243LD, Hi-Sil 210 and Hi-Sil HDP 320G silicas available from PPG Company.

[0060] In order to couple the silica to the diene elastomer, it is possible to use, in a known manner, at least bifunctional coupling agents (or binders) intended to provide a satisfactory chemical and / or physical bond between the inorganic filler (the surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. The term "bifunctional" means that the compound has 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 containing a silicon atom, the first functional group being capable of interacting with the hydroxyl groups of the inorganic filler, and a second functional group containing a sulfur atom, the second functional group being capable of interacting with the diene elastomer.

[0061] Preferably, when used, the organosilane is chosen from organosilane polysulfides (which may be symmetrical or asymmetrical), such as bis(3-triethoxysilylpropyl)tetrasulfide with the abbreviation TESPT, sold under the name Si69 by the company Evonik, or bis(triethoxysilylpropyl)disulfide with the abbreviation TESPD, sold under the name Si75 by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes such as S-[3-(triethoxysilyl)propyl]thiooctanoate sold under the name NXT Silane by the company Momentive. More preferably, the organosilane is an organosilane polysulfide.

[0062] When using an agent for coupling silica to an elastomer, the content of the coupling agent can be easily adjusted by a person skilled in the art. Typically, the content of the coupling agent is 0.5% to 15% by weight based on the amount of silica.

[0063] A person skilled in the art can easily adjust the content of reinforcing filler according to the use of the rubber composition. Advantageously, the content of reinforcing filler in the composition according to the invention is in the range of 10 phr to less than 100 phr, preferably 15 phr to 90 phr.

[0064] Preferably, the content of carbon black in the composition according to the present invention is in the range of 10 phr to less than 100 phr, preferably 15 phr to 90 phr, and the composition does not contain any filler other than carbon black, or contains less than 10 phr, preferably less than 5 phr, of any filler other than carbon black; more preferably, the composition does not contain any filler other than carbon black.

[0065] II-3 Vulcanization system

[0066] According to definition, the vulcanization system is sulfur-based. It may contain molecular sulfur and / or at least one sulfur-donating agent. Preferably, at least one vulcanization accelerator is also present, and optionally, various known vulcanization activators such as zinc oxide, stearic acid or equivalent compounds (e.g. stearates), transition metal salts, guanidine derivatives (particularly diphenylguanidine), or known vulcanization retarders may also be used.

[0067] Sulfur is preferably used in an amount between 0.5 and 12 phr, in particular between 1 and 10 phr. The amount of vulcanization accelerator used is preferably between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr.

[0068] As accelerators, any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used, in particular thiazole-type accelerators and their derivatives, or accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type. As examples of such accelerators, mention may be made of the following compounds: 2-mercaptobenzothiazolyl disulfide (abbreviated to MBTS), N-cyclohexyl-2-benzothiazolesulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolesulfenamide (DCBS), N-(tert-butyl)-2-benzothiazolesulfenamide (TBBS), N-(tert-butyl)-2-benzothiazolesulfenimide (TBSI), tetrabenzylthiuram disulfide (TBZTD), zinc dibenzyldithiocarbamate (ZBEC) and mixtures of these compounds.

[0069] II-4 Epoxy Resin

[0070] The composition according to the invention comprises between 1 and 30 phr of epoxy resin.Epoxy resins are reinforcing resins (or curing resins) known to those skilled in the art for stiffening rubber compositions.

[0071] Epoxy resins useful in the present invention include all polyepoxide compounds. For example, the epoxy resin may be selected from aromatic epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. For example, the aromatic epoxy resin may be an aromatic amine epoxy resin. These resins are preferably novolac epoxy resins, i.e., epoxy resins obtained by acid catalysis, rather than resol resins obtained by base catalysis.

[0072] Specifically, among the aromatic epoxide compounds, preferred are epoxy resins selected from the group consisting of 2,2-bis[4-(glycidyloxy)phenyl]propane, poly[(o-cresyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-(hydroxybenzaldehyde glycidyl ether)], and mixtures thereof.

[0073] More preferably, the epoxy resin is selected from poly[(o-cresyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-formaldehyde], aromatic amine epoxy resins and mixtures of these compounds.

[0074] As examples of commercially available epoxy resins that can be used in the context of the present invention, mention may be made of the epoxy resin DEN 439 from Uniqema, the epoxy resin tris(4-hydroxyphenyl)methane triglycidyl ether from Sigma-Aldrich or the epoxy cresol novolac resin Araldite ECN 1299 from Huntsman.

[0075] The amount of epoxy resin ranges from 1 to 30 phr. Given the aminic hardeners used in the context of the present invention, below the indicated minimum epoxy resin content, the desired technical effect is insufficient; while above the indicated maximum content, there is a risk of excessive increase in stiffness and excessive impairment of hysteresis and Mooney plasticity. For all these reasons, the epoxy resin content ranges from 5 to 25 phr. More preferably, the epoxy resin content in the composition according to the invention is between 10 and 20 phr.

[0076] II-5 Amine Hardener

[0077] The epoxy resin in the composition of the present invention is combined with a specific amine hardener to crosslink the resin.

[0078] According to the present invention, the amine hardener comprises at least two primary amine functional groups located on at least one (i.e. one or more) six-membered aromatic ring, wherein the at least one six-membered aromatic ring comprises:

[0079] o at least one primary amine functional group; and

[0080] o at least two groups Ri, which may be the same or different, selected from linear or branched C1-C6 alkyl, halogen, ether substituted by linear or branched C1-C6 alkyl, tertiary amine, thioether, ketone, ester and amide,

[0081] such that at least one six-membered aromatic ring does not contain a hydrogen atom ortho to the primary amine functional group,

[0082] The amine hardener comprises at least one second primary amine functional group, which is located on the at least one six-membered aromatic ring or on a possible second six-membered aromatic ring of the amine hardener.

[0083] In other words, the amine hardener comprises one or more six-membered aromatic rings and at least two primary amine functional groups, wherein the primary amine functional groups are located on only one of these six-membered aromatic rings or are distributed over several of them.

[0084] In a manner known to the person skilled in the art, the term "primary amine function" refers to an amine function in which a nitrogen atom is bonded to two hydrogen atoms.

[0085] The amine hardener preferably contains 1 to 3, more preferably 1 or 2, six-membered aromatic rings.

[0086] The amine hardener preferably comprises 2 to 4, more preferably 2, primary amine functional groups, and the primary amine functional groups are located on at least one six-membered aromatic ring of the amine hardener.

[0087] Among the halogens that can constitute the group Ri, mention may be made of fluorine, chlorine, bromine or iodine atoms. Preferably, the halogen is chosen from chlorine and bromine atoms; more preferably, the halogen is a chlorine atom.

[0088] According to a first embodiment of the present invention, the amine hardener may comprise a six-membered aromatic ring comprising:

[0089] o at least two primary amine functional groups, and

[0090] o at least two groups Ri, which may be the same or different, selected from linear or branched C1-C6 alkyl, halogen, ether substituted by linear or branched C1-C6 alkyl, tertiary amine, thioether, ketone, ester and amide,

[0091] Such that the ring contains no hydrogen atom ortho to the primary amine functionality.

[0092] According to a second embodiment of the present invention, the amine hardener may further comprise at least two identical or different six-membered aromatic rings, each of which comprises:

[0093] o at least one primary amine functional group; and

[0094] o at least two groups Ri, which may be the same or different, selected from linear or branched C1-C6 alkyl, halogen, ether substituted by linear or branched C1-C6 alkyl, tertiary amine, thioether, ketone, ester and amide,

[0095] Such that the ring contains no hydrogen atom ortho to the primary amine functionality.

[0096] According to another embodiment, the amine hardener may further include several six-membered aromatic rings and at least two primary amine functional groups located on only one of the aromatic rings.

[0097] When the amine hardener comprises several (i.e. at least two) six-membered aromatic rings, these rings may be identical or different. For example, they may differ in the nature of the atoms constituting the rings and / or the number of primary amine functional groups located on the rings and / or the nature and / or number of groups Ri located on the rings and / or the positions of the primary amine functional groups and groups Ri on the rings. Preferably, when the amine hardener comprises several six-membered aromatic rings, these rings are identical.

[0098] As described above, the amine hardener comprises at least two groups R, which may be the same or different and are selected from a linear or branched C1-C6 alkyl group, a halogen, an ether substituted with a linear or branched C1-C6 alkyl group, a tertiary amine, a thioether, a ketone, an ester, and an amide. In the expression "ether, tertiary amine, thioether, ketone, ester, and amide substituted with a linear or branched C1-C6 alkyl group," it is clearly understood by those skilled in the art that the term "substituted with a linear or branched C1-C6 alkyl group" refers to each of the ether, tertiary amine, thioether, ketone, ester, and amide.

[0099] Regardless of the embodiment of the present invention, the aminic hardener preferably comprises at least two groups Ri, which may be the same or different, selected from linear or branched C1-C6 alkyl, halogen, ether substituted by linear or branched C1-C6 alkyl, tertiary amine and thioether. Again preferably, the aminic hardener comprises at least two groups Ri, which may be the same or different, selected from linear or branched C1-C6 alkyl, halogen and thioether substituted by linear or branched C1-C6 alkyl.

[0100] Regardless of the embodiment of the present invention, the groups R may be the same or different and are preferably selected from linear or branched C1-C6 alkyl groups. In other words, all groups R of the amine hardener may be linear or branched C1-C6 alkyl groups, and the linear or branched C1-C6 alkyl groups are preferably selected from methyl, ethyl and propyl groups.

[0101] Regardless of the embodiment of the present invention, at least one six-membered aromatic ring of the amine hardener may comprise at least two groups Ri, which may be the same or different, chosen from halogen, ether substituted by a linear or branched C1-C6 alkyl group, a tertiary amine and a thioether; and at least one group Ri, Ri chosen from a linear or branched C1-C6 alkyl group.

[0102] Regardless of the embodiment of the present invention, whether it is an R group or an ether, tertiary amine, thioether, ketone, ester or amide group, the linear or branched C1-C6 alkyl group can be selected from methyl, ethyl, propyl, isopropyl, isobutyl and butyl. Preferably, the linear or branched C1-C6 alkyl group is selected from methyl, ethyl and propyl. More preferably, the linear or branched C1-C6 alkyl group is selected from methyl and ethyl.

[0103] Regardless of the embodiment of the present invention, the atoms in the aromatic ring of the amine hardener can be carbon atoms, and can optionally contain nitrogen atoms. Preferably, all atoms in the aromatic ring of the amine hardener are carbon atoms. In other words, the six-membered aromatic ring of the amine hardener preferably contains six carbon atoms.

[0104] In the formulae (III) to (VII) presented below, it should be recalled that the radicals Ri can be identical or different.

[0105] According to a first embodiment of the present invention, the amine hardener may correspond to formula (III):

[0106]

[0107] Preferably, according to this embodiment, the amine hardener corresponds to formula (IV):

[0108]

[0109] According to a second embodiment of the present invention, the amine hardener may also correspond to formula (V):

[0110]

[0111] in:

[0112] n represents an integer of 0 to 4, preferably an integer of 1 to 3,

[0113] R1 and R2 may be the same or different and are selected from hydrogen atoms and methyl, ethyl, isobutyl or benzyl groups; preferably, R1 and R2 both represent hydrogen atoms.

[0114] Preferably, according to this embodiment, the amine hardener corresponds to formula (VI):

[0115]

[0116] in:

[0117] n represents 1 or 2, preferably 1;

[0118] R1 and R2 may be the same or different and are selected from hydrogen atoms and methyl, ethyl, isobutyl or benzyl groups; preferably, R1 and R2 both represent hydrogen atoms.

[0119] Again preferably, according to this embodiment, the amine hardener corresponds to formula (VII):

[0120]

[0121] Very preferably, according to the invention, the amine hardener is selected from the compounds of the following formulae (VIII) to (XIII) and mixtures of these compounds:

[0122]

[0123] As examples of commercially available amine hardeners that can be used in the context of the present invention, mention may be made of Ethacure 100 or Ethacure 300 from the company Albemarle and Lonzacure DETDA, Lonzacure MDEA or Lonzacure MCDEA from the company Lonza.

[0124] The amount of aminic hardener is between 1 and 15 phr. Below the indicated minimum values, the desired technical effect has proven to be insufficient, while above the indicated maximum values, there is a risk of adversely affecting the processing of the composition in its raw state. Advantageously, the content of aminic hardener is in the range of 5 to 10 phr, preferably 2 to 8 phr.

[0125] II-6 Possible additives

[0126] The rubber composition according to the present invention may also optionally contain all or part of the common additives commonly used in elastomer compositions for tires, such as plasticizers (e.g., plasticizing oils and / or plasticizing resins), reinforcing or non-reinforcing fillers other than those mentioned above, pigments, protective agents (e.g., anti-ozonant waxes), chemical antiozonants, antioxidants, and anti-fatigue agents.

[0127] Advantageously, the composition according to the invention comprises a condensation accelerator, which is particularly advantageous for shortening the curing time of the composition.

[0128] Therefore, the composition of the invention advantageously comprises an imidazole of general formula (XIV):

[0129]

[0130] in:

[0131] -R a represents a hydrogen atom or a hydrocarbon radical optionally interrupted and / or substituted by one or more heteroatoms;

[0132] -R b represents a hydrocarbon group;

[0133] -R c and R d independently of one another represent a hydrogen atom or a hydrocarbon radical which is optionally interrupted and / or substituted by one or more heteroatoms;

[0134] - or R c and R d Together with the carbon atoms of the imidazole ring to which they are attached, they form a ring which is optionally interrupted and / or substituted by one or more heteroatoms.

[0135] The expression "optionally interrupted and / or substituted by one or more heteroatoms" means that the group Ra 、R c and R d When they represent a hydrocarbyl group, they may independently be interrupted by heteroatoms (i.e., in other words, heteroatoms are inserted into the hydrocarbyl chain) and / or substituted by functional groups, preferably selected from nitrogen, oxygen and sulfur. The term "functional group" refers to a group containing heteroatoms, preferably selected from amino, alkylamine, alkoxy and hydroxy, preferably selected from hydroxy and amino.

[0136] The term "amino" refers to a group having the formula -NH2. The term "hydroxy" refers to a group having the formula -OH.

[0137] Preferably, the imidazole of general formula (XIV) has the following group:

[0138] -R a is chosen from a hydrogen atom, an alkyl group containing 1 to 20 carbon atoms, a cycloalkyl group containing 5 to 24 carbon atoms, an aryl group containing 6 to 30 carbon atoms and an aralkyl group containing 7 to 25 carbon atoms, these groups being optionally substituted;

[0139] -R b is chosen from an alkyl group containing 1 to 20 carbon atoms, a cycloalkyl group containing 5 to 24 carbon atoms, an aryl group containing 6 to 30 carbon atoms, and an aralkyl group containing 7 to 25 carbon atoms;

[0140] -R c and R d R is independently selected from a hydrogen atom or an alkyl group containing 1 to 20 carbon atoms, a cycloalkyl group containing 5 to 24 carbon atoms, an aryl group containing 6 to 30 carbon atoms or an aralkyl group containing 7 to 25 carbon atoms, which groups are optionally substituted; or c and R d Together with the carbon atoms of the imidazole ring to which they are attached, they form a ring selected from an aromatic, heteroaromatic or aliphatic ring and containing 5 to 12 carbon atoms, preferably 5 or 6 carbon atoms.

[0141] Preferably, R a is selected from alkyl groups containing 2 to 12 carbon atoms and aralkyl groups containing 7 to 13 carbon atoms, which are optionally substituted. More preferably, R a is selected from aralkyl groups containing 7 to 13 carbon atoms, which are optionally substituted; R b is selected from an alkyl group containing 1 to 12 carbon atoms. Even more preferably, R a is selected from aralkyl groups containing 7 to 11 carbon atoms, which are optionally substituted; R b is selected from alkyl groups containing 1 to 4 carbon atoms.

[0142] Preferably, R c and Rd is independently selected from hydrogen and an alkyl group containing 1 to 12 carbon atoms, a cycloalkyl group containing 5 to 8 carbon atoms, an aryl group containing 6 to 24 carbon atoms and an aralkyl group containing 7 to 13 carbon atoms. Alternatively and also preferably, R c and R d Together with the carbon atom of the imidazole ring to which they are attached, they form a phenyl, cyclohexene or cyclopentene ring.

[0143] Very preferably, R c and R d represents a hydrogen atom, R a and R b The selection is as described above.

[0144] In a preferred embodiment, R a is a decalinyl group containing 11 to 13 carbon atoms, optionally substituted with at least one hydroxyl group, R b is an alkyl group containing 1 to 4 carbon atoms, R c and R d are independently selected from hydrogen atoms and alkyl groups containing 1 to 12 carbon atoms. The term "decalinyl" refers to a group of formula (XV) wherein n represents an integer between 1 and 3:

[0145]

[0146] Preferably, R a is a decalinyl group containing 11 to 13 carbon atoms and substituted with at least one hydroxyl group, R b is an alkyl group containing 1 to 3 carbon atoms, R c and R d is a hydrogen atom. Very preferably, R a is 2-naphthol-1-methyl, R b is methyl, R c and R d is a hydrogen atom, then compound (XIV) corresponds to formula (XVI):

[0147]

[0148] The rubber composition according to the invention preferably contains from 0.1 to 5 phr of imidazole of general formula (XIV). Below this minimum content, the technical effect is not significant, while above these contents, the imidazole of general formula (XIV) may compete with the amine hardener and modify the network obtained during the crosslinking process. Preferably, the composition contains from 0.1 to 3 phr, preferably from 0.2 to 3 phr, more preferably from 0.2 to 2 phr of imidazole of general formula (XIV).

[0149] Imidazoles that can be used in the context of the present invention are commercially available or can be easily prepared by a person skilled in the art using known techniques, such as those described in documents JP2012211122, JP2007269658 or Science of Synthesis 2002, 12, 325-528.

[0150] For example, as commercially available imidazoles that can be used for the purposes of the present 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, which is commercially available under the name Aradur 3123 from the company Huntsman.

[0151] II-7 Preparation of rubber composition

[0152] The composition according to the invention can be manufactured in a suitable mixer using two consecutive preparation stages known to those skilled in the art:

[0153] The first stage is a thermomechanical processing or kneading phase (referred to as the "non-preparative" phase), which can be carried out in a single thermomechanical step. During this phase, all the necessary components, in particular the elastomer matrix, reinforcing fillers, epoxy resin, and various other optional additives, with the exception of the vulcanization system, the aminic hardener, and any optional condensation accelerator, are introduced into a suitable mixer, such as a standard internal mixer (e.g., Banbury type). The optional filler can be introduced into the elastomer simultaneously with the thermomechanical kneading, either in one portion or in several portions. In the case where the filler has already been fully or partially incorporated into the elastomer in the form of a masterbatch (as described, for example, in patent applications WO 97 / 36724 or WO 99 / 16600), the masterbatch is kneaded directly and, where appropriate, the other elastomers or fillers present in the composition in non-masterbatch form, as well as any other optional additives, with the exception of the vulcanization system, are introduced. The non-preparative phase can be carried out at elevated temperatures, up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C, for a period of time generally between 2 and 10 minutes.

[0154] The second stage is a mechanical processing (called the "preparation" stage), which can be carried out in an open mixer (for example an open mill) after cooling the mixture obtained during the first non-preparation stage down to a relatively low temperature, typically below 120° C., for example between 40° C. and 100° C. The vulcanization system is then introduced and the combined mixture is then mixed for a few minutes (for example between 5 and 15 minutes).

[0155] Such stages are described, for example, in patent applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO 00 / 05300 or WO 00 / 05301.

[0156] The final composition thus obtained is then calendered, for example, into the form of a sheet or slab, in particular for laboratory characterization, or extruded (or co-extruded with another rubber composition) into the form of a rubber semi-product (or molded part) that can be used, for example, as an inner layer of a tire. These products can then be used to manufacture tires according to techniques known to those skilled in the art.

[0157] The composition may be in the raw state (before crosslinking or vulcanization) or in the cured state (after crosslinking or vulcanization), or may be a semi-finished product capable of being used in a tire.

[0158] The composition can be crosslinked in a manner known to those skilled in the art, for example at a temperature between 130° C. and 200° C. under pressure.

[0159] II-8 Rubber products

[0160] 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.

[0161] More specifically, the present 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 all or part of the inner layer of the tire. The inner layer is preferably selected from the group consisting of carcass plies, crown plies, bead fillers, crown pads, decoupling layers, edge rubbers, filling rubbers, tread sublayers, and combinations thereof. More preferably, the inner layer is selected from the group consisting of bead fillers, crown pads, tread sublayers, and combinations thereof. More preferably, the inner layer is selected from the group consisting of bead fillers, crown pads, and combinations thereof.

[0162] The tyre according to the invention may be intended to equip any type of vehicle, in particular a motor vehicle, without any particular limitation.

[0163] III - Preferred Embodiments

[0164] In view of the above, the preferred embodiments of the present invention are as follows:

[0165] 1. A rubber composition based on at least:

[0166] an elastomeric matrix comprising greater than 50 phr of at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units of said copolymer representing between 50% and 95% by mole of the monomer units of said copolymer,

[0167] - reinforcing fillers,

[0168] - Vulcanization system,

[0169] - 1 to 30 phr of epoxy resin;

[0170] - between 1 and 15 phr of an aminic hardener comprising at least two primary amine functions located on at least one six-membered aromatic ring comprising:

[0171] o at least one primary amine functional group; and

[0172] o at least two groups Ri, which may be the same or different, selected from linear or branched C1-C6 alkyl, halogen, ether substituted by linear or branched C1-C6 alkyl, tertiary amine, thioether, ketone, ester and amide,

[0173] such that at least one six-membered aromatic ring does not contain a hydrogen atom ortho to the primary amine functional group,

[0174] The amine hardener comprises at least one second primary amine functional group, which is located on the at least one six-membered aromatic ring or on a possible second six-membered aromatic ring of the amine hardener.

[0175] 2. The rubber composition according to embodiment 1, wherein the ethylene units in the copolymer account for between 55 mol% and 90 mol% of the monomer units of the copolymer.

[0176] 3. The 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.

[0177] 4. The rubber composition of any one of the preceding embodiments, wherein the 1,3-diene is 1,3-butadiene.

[0178] 5. The rubber composition according to any one of the preceding embodiments, wherein the copolymer comprises units of formula (I) or units of formula (II), or units of formula (I) and formula (II):

[0179]

[0180] -CH2-CH(CH=CH2)-(II)

[0181] 6. The rubber composition according to embodiment 5, wherein the molar percentages o and p of the units of formula (I) and (II) in the copolymer respectively satisfy the following formula 1, preferably the following formula 2, wherein o and p are calculated based on all monomer units of the copolymer:

[0182] 0 < o+p ≤ 25 (Equation 1)

[0183] 0 < o+p < 20 (Equation 2)

[0184] 7. The rubber composition according to any one of the preceding embodiments, wherein the copolymer containing ethylene units and 1,3-diene units is a random copolymer.

[0185] 8. The rubber composition according to any one of the preceding embodiments, wherein the content of the copolymer containing ethylene units and 1,3-diene units is in the range of 60 to 100 phr, preferably 80 to 100 phr.

[0186] 9. The rubber composition according to any one of the preceding embodiments, wherein the epoxy resin is selected from aromatic epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins.

[0187] 10. The rubber composition according to any one of embodiments 1 to 8, wherein the epoxy resin is selected from 2,2-bis[4-(glycidyloxy)phenyl]propane, poly[(o-cresyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-(hydroxybenzaldehyde glycidyl ether)], and mixtures of these compounds.

[0188] 11. The rubber composition according to any one of the preceding embodiments, wherein the content of epoxy resin is between 5 and 25 phr, preferably between 10 and 20 phr.

[0189] 12. The rubber composition according to any one of the preceding embodiments, wherein the groups Ri may be the same or different and are selected from linear or branched C1-C6 alkyl, halogen, ether substituted with linear or branched C1-C6 alkyl, tertiary amine and thioether.

[0190] 13. The rubber composition according to any one of the preceding embodiments, wherein the groups Ri may be the same or different and are selected from linear or branched C1-C6 alkyl groups.

[0191] 14. The rubber composition according to any one of embodiments 1 to 12, wherein at least one six-membered aromatic ring of the aminic hardener comprises at least two groups Ri, which may be the same or different, selected from halogen, ether substituted with a linear or branched C1-C6 alkyl group, a tertiary amine, and a thioether; and at least one group Ri is selected from a linear or branched C1-C6 alkyl group.

[0192] 15. The rubber composition according to any one of the preceding embodiments, wherein the linear or branched C1-C6 alkyl group is selected from methyl, ethyl, propyl, isopropyl, isobutyl and butyl, preferably from methyl and ethyl.

[0193] 16. The rubber composition according to any one of the preceding embodiments, wherein the at least one six-membered aromatic ring is an aromatic ring containing six carbon atoms.

[0194] 17. The rubber composition according to any one of the preceding embodiments, wherein the amine hardener corresponds to formula (III):

[0195]

[0196] 18. The rubber composition according to any one of the preceding embodiments, wherein the amine hardener corresponds to formula (IV):

[0197]

[0198] 19. The rubber composition of any one of embodiments 1 to 16, wherein the amine hardener corresponds to formula (V):

[0199]

[0200] in:

[0201] n represents an integer of 0 to 4, preferably an integer of 1 to 3,

[0202] R1 and R2 may be the same or different and are selected from hydrogen atoms and methyl, ethyl, isobutyl or benzyl groups; preferably, R1 and R2 both represent hydrogen atoms.

[0203] 20. The rubber composition of any one of embodiments 1 to 16 or 19, wherein the amine hardener corresponds to formula (VI):

[0204]

[0205] in:

[0206] n represents 1 or 2, preferably 1;

[0207] R1 and R2 may be the same or different and are selected from hydrogen atoms and methyl, ethyl, isobutyl or benzyl groups; preferably, R1 and R2 both represent hydrogen atoms.

[0208] 21. The rubber composition of any one of embodiments 1 to 16, wherein the amine hardener corresponds to formula (VII):

[0209]

[0210] 22. The rubber composition according to any one of embodiments 1 to 16, wherein the amine hardener is selected from the compounds of the following formulae (VIII) to (XIII) and mixtures of these compounds:

[0211]

[0212] 23. The rubber composition according to any one of the preceding embodiments, wherein the content of the amine hardener is in the range of 5 to 10 phr, preferably 2 to 8 phr.

[0213] 24. The rubber composition according to any one of the preceding embodiments, further comprising an imidazole of formula (XIV):

[0214]

[0215] in:

[0216] °R a represents a hydrogen atom or a hydrocarbon radical which is optionally interrupted and / or substituted by one or more heteroatoms,

[0217] °R b represents a hydrocarbon group,

[0218] °R c and R d independently of one another represent a hydrogen atom or a hydrocarbon radical which is optionally interrupted and / or substituted by one or more heteroatoms,

[0219] ° or R c and R d Together with the carbon atoms of the imidazole ring to which they are attached, they form a ring which is optionally interrupted and / or substituted by one or more heteroatoms.

[0220] 25. The rubber composition according to embodiment 24, wherein, in the imidazole of formula (XIV):

[0221] -R a is chosen from a hydrogen atom, an alkyl group containing 1 to 20 carbon atoms, a cycloalkyl group containing 5 to 24 carbon atoms, an aryl group containing 6 to 30 carbon atoms and an aralkyl group containing 7 to 25 carbon atoms, which are optionally substituted;

[0222] -R b is chosen from an alkyl group containing 1 to 20 carbon atoms, a cycloalkyl group containing 5 to 24 carbon atoms, an aryl group containing 6 to 30 carbon atoms, and an aralkyl group containing 7 to 25 carbon atoms;

[0223] -R c and R d R is independently selected from a hydrogen atom or an alkyl group containing 1 to 20 carbon atoms, a cycloalkyl group containing 5 to 24 carbon atoms, an aryl group containing 6 to 30 carbon atoms or an aralkyl group containing 7 to 25 carbon atoms, which groups are optionally substituted; or c and R d Together with the carbon atoms of the imidazole ring to which they are attached, they form a ring selected from an aromatic, heteroaromatic or aliphatic ring and containing 5 to 12 carbon atoms, preferably 5 or 6 carbon atoms.

[0224] 26. The rubber composition according to any one of embodiments 24 and 25, wherein in the imidazole of formula (XIV), R a is selected from alkyl groups containing 2 to 12 carbon atoms and aralkyl groups containing 7 to 13 carbon atoms, which are optionally substituted.

[0225] 27. The rubber composition according to any one of embodiments 24 to 26, wherein in the imidazole of formula (XIV), R a is selected from aralkyl groups containing 7 to 13 carbon atoms, which are optionally substituted, R b is selected from alkyl groups containing 1 to 12 carbon atoms.

[0226] 28. The rubber composition according to any one of embodiments 24 to 27, wherein, in the imidazole of formula (XIV), R a is selected from aralkyl groups containing 7 to 11 carbon atoms, which are optionally substituted, R b is selected from alkyl groups containing 1 to 4 carbon atoms.

[0227] 29. The rubber composition according to any one of embodiments 24 to 28, wherein in the imidazole of formula (XIV), R c and R d R is independently selected from a hydrogen atom and an alkyl group containing 1 to 12 carbon atoms, a cycloalkyl group containing 5 to 8 carbon atoms, an aryl group containing 6 to 24 carbon atoms, and an aralkyl group containing 7 to 13 carbon atoms. c and R d Very preferred is a hydrogen atom.

[0228] 30. The rubber composition according to any one of embodiments 24 to 28, wherein, in the imidazole of formula (XIV), Rc and R d Together with the carbon atom of the imidazole ring to which they are attached, they form a phenyl, cyclohexene or cyclopentene ring.

[0229] 31. The rubber composition according to embodiment 24, wherein in the imidazole of formula (XIV), R a is a decalinyl group containing 11 to 13 carbon atoms, which is optionally substituted with at least one hydroxyl group, R b is an alkyl group containing 1 to 4 carbon atoms, R c and R d are independently selected from a hydrogen atom and an alkyl group containing 1 to 12 carbon atoms.

[0230] 32. The rubber composition according to embodiment 31, wherein R a is a decalinyl group containing 11 to 13 carbon atoms and substituted with at least one hydroxyl group, R b is an alkyl group containing 1 to 3 carbon atoms, R c and R d is a hydrogen atom, and preferably, R a is 2-naphtholmethyl, R b is methyl, R c and R d is a hydrogen atom, compound (XIV) corresponds to formula (XVI):

[0231]

[0232] 33. The rubber composition according to any one of embodiments 24 to 32, wherein the content of imidazole of formula (XIV) ranges from 0.1 phr to 5 phr, preferably from 0.1 phr to 3 phr.

[0233] 34. The rubber composition of any one of the preceding embodiments, wherein the reinforcing filler comprises carbon black, silica, or a mixture thereof.

[0234] 35. The rubber composition according to any one of the preceding embodiments, wherein the reinforcing filler comprises more than 50% by weight, preferably more than 80% by weight, of carbon black.

[0235] 36. The rubber composition according to any one of embodiments 34 and 35, wherein the BET specific surface area of ​​the carbon black is 100 m 2 / g to 160m 2 / g, preferably 124m 2 / g to 150m 2 / g range.

[0236] 37. The rubber composition according to any one of the preceding embodiments, wherein the content of reinforcing filler is in the range from 10 phr to less than 100 phr, preferably from 15 phr to 90 phr.

[0237] 38. A rubber article comprising a composition as defined in any one of embodiments 1 to 37.

[0238] 39. A tyre comprising a composition as defined in any one of embodiments 1 to 37.

[0239] 40. The tire according to embodiment 39, wherein the composition as defined in any one of embodiments 1 to 37 is present in at least one inner layer, preferably selected from the group consisting of carcass plies, crown plies, bead fillers, crown pads, decoupling layers, edge rubbers, filling rubbers, tread underlayers, and combinations of these inner layers. DETAILED DESCRIPTION

[0240] IV-Examples

[0241] IV-1 Measurements and Tests Used

[0242] Mechanical properties

[0243] These tensile tests allow the determination of elastic stress and fracture properties. Processing the tensile record also allows the plotting of the modulus as a function of elongation. The modulus used here is the nominal (or apparent) secant modulus measured during the first elongation, calculated by returning to the original cross-section of the test specimen. The stress at break (BS, in MPa) and the elongation at break (EB, 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.

[0244] The elongation at break results are expressed as a percentage relative to the control composition T1 or T2, as the case may be, based on 100. A result greater than 100 indicates an improvement in the mechanical properties of the composition in question.

[0245] The dynamic properties G* and tan(δ)max were measured using a viscoanalyzer (Metravib VA4000) in accordance with ASTM D5992-96. The response of samples of the vulcanized composition (cylindrical test specimens with a thickness of 2 mm and a cross-section of 79 mm²) subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz and 60° C. in accordance with ASTM D 1349-09 was recorded. The strain amplitude was swept from 0.01% to 50% (outward cycle) and then from 50% to 0.01% (return cycle).

[0246] The results used are the complex dynamic shear modulus G* and the loss factor tan(δ)max. In the outward cycle, the G* value and the loss factor (expressed as tan(δ)max) at 5% strain are recorded.

[0247] The results for G* at 5% strain during the outward cycle and tan(δ)max at 60°C during the outward cycle are both expressed as properties based on a value of 100, with a value of 100 being assigned to the control composition T1 or T2 (as appropriate). Results greater than 100 indicate that the compositions of the examples considered have higher stiffness and lower hysteresis, respectively, which translates to better stiffness and lower hysteresis, respectively, for the applications considered.

[0248] Determination of the microstructure of elastomers by nuclear magnetic resonance (NMR):

[0249] The microstructure of ethylene-butadiene copolymer is 1 H NMR analysis was performed to determine when 1When the resolution of the H NMR spectrum is insufficient to attribute and quantify all species, 13C NMR analysis is supplemented. Measurements are performed using a Bruker 500MHz NMR spectrometer, with proton observations performed at a frequency of 500.43MHz and carbon observations performed at a frequency of 125.83MHz. For elastomers that are insoluble but swellable in solvent, an HRMAS 4mm z-grad probe is used, which can observe protons and carbon in proton decoupling mode. Spectra are acquired at a rotation speed of 4000Hz to 5000Hz. For measurements of soluble elastomers, a liquid NMR probe is used, which can observe protons and carbon in proton decoupling mode. Insoluble samples are prepared in a rotating cup containing the material to be analyzed and a deuterated solvent (usually deuterated chloroform CDCl3) that allows swelling. The solvent used must always be a deuterated solvent, and its chemical properties can be adjusted by those skilled in the art. The amount of material used is adjusted to obtain a spectrum with sufficient sensitivity and resolution. Soluble samples are dissolved in a deuterated solvent (approximately 25 mg of elastomer in 1 ml), typically deuterated chloroform (CDCl3). The solvent or solvent mixture used must always be a deuterated solvent, the chemical nature of which can be adjusted by a person skilled in the art. In both cases (soluble samples or swollen samples): For proton NMR, a 30° single pulse sequence is used. The spectral window is adjusted to observe all resonance lines belonging to the molecule being analyzed. The accumulation number is set so that a signal-to-noise ratio sufficient for quantification of each unit is obtained. A recycle delay between each pulse is suitable for achieving quantitative measurements. For carbon NMR, a 30° single pulse sequence is used, with proton decoupling only during acquisition to avoid the "nuclear Overhauser" effect (NOE) and maintain quantification. The spectral window is adjusted to observe all resonance lines belonging to the molecule being analyzed. The accumulation number is set so that a signal-to-noise ratio sufficient for quantification of each unit is obtained. A recycle delay between each pulse is suitable for achieving quantitative measurements. NMR measurements are performed at 25°C.

[0250] The macrostructure of the polymer was determined by size exclusion chromatography (SEC):

[0251] Size exclusion chromatography (SEC) fractionates polymer chains in a solvent based on their hydrodynamic volume. Like all chromatography systems, this technique relies on the elution of the solute (polymer) through a column containing a stationary phase. The system consists of the following sequence: solvent reservoir, pump system, injector, column set, and detector. The measurement system is equipped with a Waters Alliance e2695 module and a Waters fRI410 refractometer.

[0252] The mobile phase was eluted at a flow rate of 1 ml / min. The polymer was dissolved in THF at a concentration of 1 g / L in the presence of 1 wt% diisopropylamine and 1 wt% triethylamine. A 100 μL volume was injected through a set of three Agilent size exclusion chromatography columns (Mixed B LS). The columns were thermostatted at 35°C in an oven. The stationary phase of the columns was based on a polystyrene / divinylbenzene gel with controlled porosity. Polymer chains were separated based on the hydrodynamic volume they occupied when dissolved in the solvent. The greater the volume occupied by a polymer chain, the fewer column pores it could access, resulting in a shorter elution time. Detection was performed using a refractometer (RI) thermostatted at 35°C. Each elution volume was related to mass using a Moore calibration (calibration based on certified polystyrene standards obtained from Polymer Standard Service (Mainz)). Data acquisition and analysis were performed using Waters Empower software. The number-average molar mass (Mn), the weight-average molar mass (Mw) and the degree of dispersion (PI=Mw / Mn) can then be determined.

[0253] Mooney viscosity ML 1+4

[0254] For polymer and rubber composition, according to standard ASTM D-1646 (1999), use oscillation consistency meter to measure Mooney viscosity ML (1+4) at 100 ℃.Mooney plasticity measurement is carried out according to the following principle: the composition in the unprocessed state (before solidification) is molded in a cylindrical chamber heated to 100 ℃.After preheating for 1 minute, the rotor rotates with 2 rpm in the sample, and after rotating for 4 minutes, the working torque for maintaining this motion is measured.Mooney plasticity ML (1+4) is represented by "Mooney unit" (MU, 1MU=0.83Nm).

[0255] IV-2 Synthesis of copolymer E1:

[0256] In the polymer synthesis, all reagents except the metallocene were commercially available. Butyloctylmagnesium BOMAG (20% in heptane, C = 0.88 mol·l-1) was obtained from Chemtura and stored in a Schlenk tube under an inert atmosphere. N35 grade ethylene was obtained from Air Liquide and used without prior purification.

[0257] The copolymer of ethylene and 1,3-butadiene, ie, the elastomer E1 (according to the present invention), was synthesized according to the following procedure.

[0258] To a reactor containing methylcyclohexane, ethylene (Et), and butadiene (Bd) at 80°C, butyloctyl magnesium (BOMAG) was added in the proportions shown in Table 1 to neutralize impurities in the reactor. The catalyst system (see Table 1) was then added. The reaction temperature was then adjusted to 80°C, and the polymerization reaction began. The polymerization reaction was carried out at a constant pressure of 8 bar. Throughout the polymerization, ethylene and butadiene (Bd) were fed to the reactor in the proportions specified in Table 1. The polymerization reaction was terminated by cooling, degassing the reactor, and adding ethanol. An antioxidant was added to the polymer solution. The copolymer was recovered by drying in a vacuum oven to constant weight. This catalyst system was a preformed catalyst system. It was prepared in methylcyclohexane from the metallocene [Me2SiFlu2Nd(μ-BH4)2Li(THF)], the cocatalyst butyloctyl magnesium (BOMAG), and the preformed monomer 1,3-butadiene in the amounts shown in Table 1. It is prepared according to the preparation method of patent application WO 2017 / 093654A1, paragraph II.1.

[0259] The microstructure of copolymer E1 and its properties are shown in Tables 2 and 3. With respect to the microstructure, Table 2 shows the molar ratios of ethylene (Eth) units, 1,3-butadiene units, and 1,2-cyclohexanediyl (ring) units.

[0260] [Table 1]

[0261] synthesis E1 Metallocene concentration (mmol / l) 0.07 Alkylating agent concentration (mmol / l) 0.36 Preformed monomer / Nd metal molar ratio 90 Feed composition (mol% Et / Bd) 80 / 20

[0262] [Table 2]

[0263] Elastomer E1 Ethylene (mol%) 77 1,3-Butadiene (mol%) 15 1,2-Cyclohexanediyl (mol%) 8

[0264] [Table 3]

[0265] Elastomer E1 Tg(℃) -40 Mn (g / mol) 177 000 Mooney viscosity at 100°C (ML(1+4)) 80

[0266] IV-3 Preparation of Composition

[0267] In the following examples, the rubber compositions were prepared as described in point II-7 above. Specifically, the "non-preparation" phase was carried out in a 0.4-liter mixer (with an average blade speed of 50 rpm) for 3.5 minutes until a maximum drop temperature of 165°C was reached. The "preparation" phase was carried out in a cylindrical tool at 40°C for 5 minutes.

[0268] Crosslinking of the composition is carried out at a temperature between 130° C. and 200° C. and under pressure.

[0269] IV-4 Tests on Rubber Compositions

[0270] The purpose of the examples presented below is to compare the performance compromise between stiffness, hysteresis and mechanical properties (elongation at break and stress at break) of a composition according to the invention (C1) and three reference compositions (T1 to T3).

[0271] The compositions tested (in phr) are presented in Table 4, as well as the results obtained.

[0272] Composition C1 differs from control composition T1 only in the nature of the copolymer based on butadiene and styrene.Control compositions T2 and T3 make it possible to study the influence of a curing system that does not include an epoxy resin and an aminic hardener.

[0273] The results for composition C1 are expressed as a percentage relative to the control composition T1 (based on 100), while the results for composition T3 are expressed as a percentage relative to the control composition T2 (based on 100).

[0274] [Table 4]

[0275] Composition T1 C1 T2 T3 NR(1) 100 - 100 - Elastomer E1(2) - 100 - 100 N115(3) 60 60 60 60 Curing resin (4) 19.5 19.5 - - Hardener (5) 4.4 4.4 - - 6PPD(6) 2.0 2.0 2.0 2.0 Stearic acid (7) 1.0 1.0 1.0 1.0 ZnO(8) 2.7 2.7 2.7 2.7 sulfur 5.0 5.0 5.0 5.0 Accelerator (9) 2.0 2.0 - - CBS(10) 0.9 0.9 0.9 0.9 performance EB at 23°C 100 100 NA* NA* BS at 23°C 100 110 NA* NA* G*5% at 60℃ 100 145 100 152 tan(δ)max at 60℃ 100 113 100 83

[0276] (1) Natural rubber

[0277] (2) Elastomer E1 obtained according to the method described in point IV-2 above

[0278] (3) N115 grade carbon black according to ASTM D-1765

[0279] (4) Araldite ECN 1299CH thermosetting epoxy resin, available from Huntsman Co. (5) Ethacure 300 amine hardener, available from Huntsman Co.

[0280] (6) Santoflex 6-PPD, N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine, obtained from Flexsys

[0281] (7) Pristerene 4931 stearic acid, obtained from Uniqema

[0282] (8) Industrial grade zinc oxide, obtained from Umicore

[0283] (9) Aradur 3123ES imidazole-based accelerator, available from Huntsman

[0284] (10) Santocure CBS, N-cyclohexyl-2-benzothiazole sulfenamide, obtained from Flexsys

[0285] *Not obtained

[0286] The results shown in Table 4 above demonstrate that the combination of the copolymer according to the invention and the curing system according to the invention based on an epoxy resin and an amine hardener simultaneously improves the stiffness and hysteresis of the composition without compromising the mechanical properties, or even improves them. A comparison of the control compositions T2 and T3 shows that this effect is not solely due to the presence of the copolymer according to the invention. The composition according to the invention is particularly suitable for applications requiring an excellent compromise between stiffness and hysteresis, such as tires, and in particular the inner layers of tires.

Claims

1. A rubber composition based on at least: an elastomeric matrix comprising greater than 50 phr of at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units of said copolymer representing between 50% and 95% by mole of the monomer units of said copolymer, - reinforcing fillers, - Vulcanization system, - 1 to 30 phr of epoxy resin, - between 1 and 15 phr of an aminic hardener comprising at least two primary amine functions located on at least one six-membered aromatic ring comprising: o at least one primary amine functional group, and o at least two groups Ri, which may be the same or different, selected from linear or branched C1-C6 alkyl, halogen, ether substituted by linear or branched C1-C6 alkyl, tertiary amine, thioether, ketone, ester and amide, such that at least one six-membered aromatic ring does not contain a hydrogen atom ortho to the primary amine functional group, The amine hardener comprises at least one second primary amine functional group, which is located on the at least one six-membered aromatic ring or on a possible second six-membered aromatic ring of the amine hardener.

2. The 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, and the 1,3-diene is preferably 1,3-butadiene.

3. The rubber composition according to any one of the preceding claims, wherein The content of the copolymer containing ethylene units and 1,3-diene units ranges from 60 to 100 phr, preferably from 80 to 100 phr.

4. The 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: 2,2-bis[4-(glycidyloxy)phenyl]propane, poly[(o-tolyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-formaldehyde], poly[(phenyl glycidyl ether)-co-(hydroxybenzaldehyde glycidyl ether)] and mixtures of these compounds.

5. The rubber composition according to any one of the preceding claims, wherein The content of epoxy resin is between 5 and 25 phr, preferably between 10 and 20 phr.

6. The rubber composition according to any one of the preceding claims, wherein The groups Ri may be the same or different and are selected from linear or branched C1-C6 alkyl, halogen, ether substituted by linear or branched C1-C6 alkyl, tertiary amine and thioether; preferably, the groups Ri may be the same or different and are selected from linear or branched C1-C6 alkyl.

7. The rubber composition according to any one of the preceding claims, wherein The at least one six-membered aromatic ring is an aromatic ring containing six carbon atoms.

8. The rubber composition according to any one of the preceding claims, wherein The amine hardener corresponds to any one of formulas (III) to (V) and (VII): Wherein, in formula (V): -n represents an integer from 0 to 4, preferably an integer from 1 to 3, - R1 and R2 may be the same or different and are selected from hydrogen atoms and methyl, ethyl, isobutyl or benzyl groups; preferably, R1 and R2 both represent hydrogen atoms.

9. The rubber composition according to any one of claims 1 to 7, wherein The amine hardener is selected from the compounds of the following formulae (VIII) to (XIII) and mixtures of these compounds:

10. The rubber composition according to any one of the preceding claims, wherein The content of the amine hardener is in the range of 5 phr to 10 phr, preferably 2 phr to 8 phr.

11. The rubber composition according to any one of the preceding claims, further comprising an imidazole of formula (XIV): in: o R a represents a hydrogen atom or a hydrocarbon radical which is optionally interrupted and / or substituted by one or more heteroatoms, o R b represents a hydrocarbon group, o R c and R d independently of one another represent a hydrogen atom or a hydrocarbon radical which is optionally interrupted and / or substituted by one or more heteroatoms, - or R c and R d Together with the carbon atoms of the imidazole ring to which they are attached, they form a ring which is optionally interrupted and / or substituted by one or more heteroatoms.

12. The rubber composition according to claim 11, wherein The content of imidazole of formula (XIV) is in the range of 0.1 phr to 5 phr, preferably 0.1 phr to 3 phr.

13. The 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 carbon black.

14. The rubber composition according to any one of the preceding claims, wherein The content of the reinforcing filler is in the range of 10 phr to less than 100 phr, preferably 15 phr 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 carcass plies, cap plies, bead fillers, cap blocks, decoupling layers, edge rubbers, filling rubbers, undertreads and combinations of these inner layers.

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