RUBBER COMPOSITION WITH IMPROVED RESISTANCE TO AGGRESSIVE EFFECTS

Description

[0001] The present invention relates to rubber compositions having improved resistance to mechanical attack. It is particularly relevant to rubber articles such as pneumatic tires, non-pneumatic tires, tracks, conveyor belts or any other rubber article whose aforementioned performance would be advantageous.

[0002] In particular, the rubber compositions of the invention are very interesting when used in pneumatic tire treads for civil engineering vehicles. Indeed, these tires must have technical characteristics that are very different from those intended for vehicles traveling exclusively on the road (i.e., bituminous ground), because the nature of the off-road ground on which they mainly operate is very different, and in particular much more aggressive, due to its stony nature. Furthermore, unlike tires for passenger vehicles, for example, tires for large civil engineering machines must be able to withstand loads that can be extremely heavy. Consequently, the known solutions for tires traveling on bituminous ground are not directly applicable to off-road tires such as tires for civil engineering vehicles.

[0003] During rolling, a tread is subjected to mechanical stresses and aggressions resulting from direct contact with the ground. In the case of a tire mounted on a vehicle carrying heavy loads, the mechanical stresses and aggressions suffered by the tire are amplified by the effect of the weight it supports. Tires for mining vehicles in particular are subjected to high stresses, both locally: rolling on the macro-indenters represented by the stones that make up the tracks (crushed rock), and globally: significant torque transfer because the slopes of the tracks for entering or exiting the "pits", or open-cast mines, are of the order of 10%, and high stresses on the tires when the vehicles turn around for loading and unloading maneuvers.

[0004] This means that the crack initiations that occur in the tread of the tire under the effect of these stresses and these attacks tend to propagate further on the surface or inside the tread, which can cause localized or generalized tearing of the tread. These stresses can therefore lead to damage to the tread and therefore reduce the service life of the tread, and therefore of the tire.

[0005] This is particularly true for tires fitted to civil engineering vehicles which generally operate in mines or quarries. This is also true for rubber tracks or tires of any type of vehicle likely to carry heavy loads and move on stony ground, such as agricultural vehicles, construction vehicles, etc. The problem of resistance to mechanical aggression also concerns conveyor belts (or belt conveyors) which can receive large quantities of earth, ore, pebbles, rocks.

[0006] It is therefore important to have a rubber composition that is resistant to mechanical attack. To solve this problem, it is known to those skilled in the art that, for example, natural rubber can achieve high crack propagation resistance properties.

[0007] Manufacturers are therefore always looking for solutions to improve the resistance of rubber compositions to mechanical aggression. Preferably, these solutions should have little or no impact on the limiting properties (stress and elongation at break) in order to be able to absorb shocks or obstacles without breaking.

[0008] Continuing its research, the Applicant unexpectedly discovered that the combined use of a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing more than 50% by mole of the monomer units of the copolymer, of a specific 1,3-dipolar compound combined with a significant volume fraction of filler makes it possible to improve the resistance to mechanical attack, in compositions comprising mainly carbon black as a reinforcing filler.

[0009] Thus, the subject of the invention is a rubber composition based on at least: an elastomer matrix comprising more than 50 pce of a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing more than 50 mol% of the monomer units of the copolymer, a 1,3-dipolar compound corresponding to formula (I) Q-Sp-B (I) in which: ∘ Q comprises a dipole containing at least and preferably one nitrogen atom, ∘ Sp, preferably divalent, is an atom or a group of atoms linking Q to B, ∘ B comprises an imidazole ring corresponding to the following formula (II): in which: 3 of the 4 symbols Z, Y, R and R', identical or different, each represent an atom or a group of atoms, Z and Y being able to form together with the carbon atoms to which they are attached a cycle, and the fourth symbol Z, Y, R or R' denotes a direct attachment to Sp, a reinforcing filler comprising carbon black, the carbon black representing more than 50% by weight of the reinforcing filler, the volume fraction of filler in the rubber composition being greater than 18%, a crosslinking system.

[0010] The present invention also relates to rubber articles comprising a composition according to the invention, in particular a pneumatic or non-pneumatic tire tread. I- DEFINITIONS

[0011] 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.

[0012] 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 by mass of elastomer.

[0013] In this document, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0014] 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.

[0015] When a "majority" compound is referred to, within the meaning of the present invention, this compound is the majority among the compounds of the same type in the composition, that is to say that it is the one which represents the largest quantity by mass among the compounds of the same type. Thus, for example, a majority elastomer is the elastomer representing the largest mass relative to the total mass of the elastomers in the composition. In the same way, a so-called majority filler is the one representing the largest mass among the fillers in the composition. For example, in a system comprising a single elastomer, this is the majority within the meaning of the present invention; and in a system comprising two elastomers, the majority elastomer represents more than half of the mass of the elastomers. On the contrary, a "minority" compound is a compound which does not represent the largest mass fraction among the compounds of the same type.Preferably by majority, we mean present at more than 50%, preferably more than 60%, 70%, 80%, 90%, and more preferably the “majority” compound represents 100%.

[0016] In the present application, the term "all the monomer units of the copolymer" or "all the monomer units of the copolymer" means all the repeating units constituting the copolymer which result from the insertion of the monomers into the elastomer chain by polymerization. Unless otherwise indicated, the contents of a monomer unit or repeating unit in the copolymer containing ethylene units and 1,3-diene units are given as a molar percentage calculated on the basis of all the monomer units of the copolymer.

[0017] 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.

[0018] All glass transition temperature “Tg” values described herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to ASTM D3418 (1999). II- DESCRIPTION OF THE INVENTION II-1 Elastomeric matrix

[0019] The composition of the tire according to the invention has the essential characteristic of comprising an elastomer matrix comprising more than 50 pce of a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing more than 50% by mole of the monomer units of the copolymer.

[0020] In this document, the “copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing more than 50% by mole of the monomer units of the copolymer” may be designated by “the copolymer” or by “the copolymer containing ethylene units and 1,3-diene units” for the sake of simplification of drafting.

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

[0022] By "copolymer containing ethylene units and 1,3-diene units" is meant any copolymer comprising, within its structure, at least ethylene units and 1,3-diene units. The copolymer may thus comprise monomer units other than 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 from 3 to 6 carbon atoms. For example, the alpha-olefin units may be chosen from the group consisting of propylene, butene, pentene, hexene or mixtures thereof.

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

[0024] 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 isoprene. The 1,3-diene units are those, for example, of a 1,3-diene or a mixture of 1,3-dienes, the 1,3-diene(s) having from 4 to 12 carbon atoms, such as, in particular, 1,3-butadiene and isoprene. Preferably, the 1,3-diene is 1,3-butadiene.

[0025] Advantageously, the ethylene units in the copolymer represent between 50% and 95%, preferably between 55% and 90%, by mole of the monomer units of the copolymer.

[0026] Advantageously, the copolymer containing ethylene units and 1,3-diene units is a copolymer of ethylene and 1,3-diene, i.e. the copolymer does not contain units other than ethylene and 1,3-diene.

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

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

[0029] When the copolymer of ethylene and a 1,3-diene comprises units of formula (III) or units of formula (IV) or units of formula (III) and units of formula (IV), the molar percentages of the units of formula (III) and units of formula (IV) in the copolymer, respectively o and p, preferably satisfy the following equation (eq. 1), more preferably equation (eq. 2), o and p being calculated on the basis of all the monomer units of the copolymer. 0 < o + p ≤ 25 0 < o + p < 20

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

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

[0032] The Mn of the copolymer is determined in a known manner, by size exclusion chromatography (SEC) as described below: The SEC (Size Exclusion Chromatography) technique allows the separation of macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, the largest being eluted first. Without being an absolute method, SEC makes it possible to understand the molar mass distribution of a polymer. From commercial standard products, the different number-average (Mn) and weight-average (Mw) molar masses can be determined and the polydispersity index (Ip = Mw / Mn) calculated via a so-called MOORE calibration. There is no particular treatment of the polymer sample before analysis. It is simply solubilized in the elution solvent at a concentration of approximately 1 gL -1< .Then the solution is filtered through a 0.45µm porosity filter before injection. The equipment used is a "WATERS Acquity" or "WATERS Alliance" chromatographic chain. The elution solvent is tetrahydrofuran with a BHT (butylated hydroxytoluene) antioxidant of 250 ppm, the flow rate is 1 mL.min -1< , the column temperature is 35° C and the analysis time is 40 min. The columns used are a set of three Agilent columns with the trade name "InfinityLab PolyPore". The injected volume of the sample solution is 100 µL. The detector is a differential refractometer "Acquity refractometer" or "WATERS 2410" and the chromatographic data processing software is the "WATERS EMPOWER" system. The calculated average molar masses are relative to a calibration curve produced from standard polystyrenes.

[0033] The copolymer can be obtained according to different synthesis methods known to those skilled in the art, in particular depending on the targeted microstructure of the copolymer. Generally, it can be prepared by copolymerization of at least one 1,3-diene, 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 statistical, can also be prepared by a process using a preformed type catalytic system such as those described in documents WO 2017093654 A1, WO 2018020122 A1 and WO 2018020123 A1.

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

[0035] Advantageously, the rate of the copolymer containing ethylene units and 1,3-diene units in the composition is within a range from 60 to 100 pce, preferably from 80 to 100 pce.

[0036] The elastomer matrix may advantageously comprise only, as elastomer, the copolymer containing ethylene units and 1,3-diene units.

[0037] Alternatively, the elastomer matrix may further comprise a diene elastomer different from the copolymer containing ethylene units and 1,3-diene units (also referred to herein as "the other elastomer"). The other elastomer, when present, is in the minority, i.e. it represents less than 50%, 40%, 30%, 20%, or even less than 10% by weight of the elastomer matrix. For example, the level of the other elastomer in the composition may be within a range from 0 to 40 phr, preferably from 0 to 20 phr.

[0038] The other elastomer of the elastomer matrix of the tire according to the invention is preferably chosen from the group of highly unsaturated diene elastomers such as polybutadienes (abbreviated as "BR"), synthetic polyisoprenes (IR), natural rubber (NR), butadiene copolymers, isoprene copolymers and blends of these elastomers. The term "highly unsaturated diene elastomer" generally means a diene elastomer derived at least in part from conjugated diene monomers, having a content of units or patterns of diene origin (conjugated dienes) which is greater than 50% (mol %). II-2 1,3-Dipolar Compound

[0039] The rubber composition according to the invention comprises a 1,3-dipolar compound. The term 1,3-dipolar compound is understood according to the definition given by IUPAC.

[0040] The 1,3-dipolar compound has the formula (I): Q-Sp-B (I) in which: Q comprises a dipole containing at least and preferably one nitrogen atom, Sp, preferably divalent, is an atom or group of atoms linking Q to B, B comprises an imidazole ring corresponding to formula (II): in which: ∘ 3 of the 4 symbols Z, Y, R and R', identical or different, each represent an atom or a group of atoms, Z and Y being able to form together with the carbon atoms to which they are attached a cycle (of course when neither Z nor Y designates the 4th symbol), ∘and the only fourth symbol designates a direct attachment to Sp.

[0041] According to a first variant of the invention, R designates a direct connection to Sp, in which case R is the 4th symbol.

[0042] According to this variant, R' may be a hydrogen atom or a carbon group which may contain at least one heteroatom.

[0043] According to a preferred embodiment of this variant, R' represents a carbon group containing from 1 to 20 carbon atoms, preferably an aliphatic group, more preferably an alkyl group which preferably contains from 1 to 12 carbon atoms.

[0044] According to a second variant of the invention, R' designates a direct connection to Sp, in which case R' is the 4th symbol.

[0045] Depending on the first or second variant, Z and Y can each be a hydrogen atom.

[0046] According to the first variant or the second variant, Z and Y may together with the carbon atoms to which they are attached form a ring. The ring formed by Z, Y and the atoms to which Z and Y are attached may or may not be substituted and may contain at least one heteroatom. Z and Y may together with the two carbon atoms to which they are attached form an aromatic ring. In this case, the imidazole ring may be a substituted or unsubstituted benzimidazole.

[0047] According to a third variant of the invention, of course when Y and Z do not form together with the carbon atoms to which they are attached a cycle, Y or Z designates a direct attachment to Sp, in which case Y or Z is the 4th symbol.

[0048] According to the second or third variant of the invention, R advantageously represents a hydrogen atom or a carbon group which may contain at least one heteroatom. In this case, R may be a group of 1 to 20 carbon atoms, preferably an aliphatic group, more preferably an alkyl group preferably containing from 1 to 12 carbon atoms, even more preferably a methyl.

[0049] Advantageously, Sp is divalent.

[0050] Sp can be a group containing up to 20 carbon atoms, which group may contain at least one heteroatom. Sp can be an aliphatic or aromatic group.

[0051] When Sp is an aliphatic group, Sp preferably contains from 1 to 20 carbon atoms, more preferably from 1 to 12 carbon atoms, even more preferably from 1 to 6 carbon atoms, most preferably from 1 to 3 carbon atoms. When Sp is an aromatic group, Sp preferably contains from 6 to 20 carbon atoms, more preferably from 6 to 12 carbon atoms.

[0052] Advantageously, Sp is a divalent group chosen from alkylene groups containing from 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms, more preferably from 1 to 6 carbon atoms, even more preferably from 1 to 3 carbon atoms. More preferably, Sp O is a divalent group containing from 1 to 3 carbon atoms, preferably the methylene group.

[0053] As a divalent group Sp can also be suitable an arylene group containing preferably from 6 to 20 carbon atoms, more preferably from 6 to 12 carbon atoms.

[0054] Particularly suitable 1,3-dipolar compounds are compounds selected from the group consisting of nitrile oxides, nitrile imines and nitrones, in which case Q contains a -C≡N→O, -C≡N→N- or -C=N(→O)- unit.

[0055] When Q comprises a -C≡N→O motif, Q preferably comprises, more preferably represents, the motif corresponding to formula (V): in which four of the five symbols X 1 to X 5 , which may be identical or different, are each an atom or group of atoms and the fifth symbol denotes a direct attachment to Sp, where X 1 and X 5 are both different from H. The four of the five symbols X 1 to X 5 may be aliphatic or aromatic groups. Aliphatic groups may contain from 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms, more preferably from 1 to 6 carbon atoms, even more preferably from 1 to 3 carbon atoms. Aromatic groups may contain from 6 to 20 carbon atoms, preferably from 6 to 12 carbon atoms.

[0056] X 1 , X 3 and X 5 are each preferably an alkyl group of 1 to 6 carbon atoms, more preferably of 1 to 3 carbon atoms, even more preferably a methyl or ethyl group.

[0057] Advantageously, X 1 , X 3 and X 5 are identical. In addition, X 1 , X 3 and X 5 are each preferably an alkyl group of 1 to 6 carbon atoms, more preferably of 1 to 3 carbon atoms, even more preferably a methyl or ethyl group.

[0058] Particularly advantageously, the 1,3-dipolar compound is the compound 2,4,6-trimethyl-3-((2-methyl-1 H -imidazol-1-yl)methyl)benzonitrile oxide having the formula (Va) or the compound 2,4,6-triethyl-3-((2-methyl-1 H -imidazol-1-yl)methyl)benzonitrile oxide corresponding to the formula (Vb):

[0059] When Q includes a -C=N(→O)- motif, Q may include the motif corresponding to formula (VI) or (VII): in which: Y 1 is an aliphatic group, preferably an alkyl group preferably containing 1 to 12 carbon atoms, or an aromatic group containing 6 to 20 carbon atoms, preferably an alkylaryl group, more preferably a phenyl or tolyl group, and Y 2 , comprising a direct attachment to Sp, is an aliphatic group, preferably an alkylene group preferably containing 1 to 12 carbon atoms, or an aromatic group preferably containing 6 to 20 carbon atoms and comprising on its benzene ring the direct attachment to Sp.

[0060] In this case, the direct attachment of the benzene ring of Y 2 to Sp amounts to saying that Sp is a substituent of the benzene ring of Y 2 .

[0061] When Q comprises a -C=N(→O)- motif, the 1,3-dipolar compound may be the compound of formula (VIa), (VIb), (VIIa) or (VIIb):

[0062] 1,3-Dipolar compounds of formula (I) can be readily synthesized by following a synthetic method described in paragraph IV-2 below.

[0063] The quantity of the 1,3-dipolar compound introduced into the rubber composition is expressed in molar equivalent of imidazole ring. For example, if the 1,3-dipolar compound contains a single imidazole ring of formula (II) as defined above, one mole of 1,3-dipolar compound corresponds to one mole of imidazole ring. If the 1,3-dipolar compound contains two imidazole rings of formula (II) as defined above, one mole of 1,3-dipolar compound corresponds to two moles of imidazole ring. In the latter case, the use of the 1,3-dipolar compound according to one molar equivalent of imidazole ring corresponds to half a mole of 1,3-dipolar compound.

[0064] According to the invention, the amount of the 1,3-dipolar compound in the composition may be between 0 and 50, preferably between 0.01 and 15, molar equivalents per 100 moles of monomer units constituting the copolymer. For example, it may be between 4 and 15 molar equivalents, for example between 5 and 15 molar equivalents. However, preferably, the amount of 1,3-dipolar compound in the composition is preferably between 0 and 3 molar equivalents, more preferably between 0 and 2 molar equivalents, even more preferably between 0 and 1 molar equivalent, or even more preferably between 0 and 0.7 molar equivalents of imidazole ring per 100 moles of monomer units constituting the copolymer. These preferential ranges make it possible to more precisely optimize the compromise between the cured rigidity and the hysteresis of the rubber composition according to its application, particularly in a tire.More preferably, the amount of 1,3-dipolar compound in the composition is preferably between 0.03 and 3 molar equivalents, preferably between 0.05 and 2 molar equivalents, even more preferably between 0.07 and 1 molar equivalent, or even more preferably between 0.08 and 0.7 molar equivalents, of imidazole ring per 100 moles of monomer units constituting the copolymer. II-3 Charge

[0065] The composition according to the invention also has the essential characteristic of being based on a reinforcing filler comprising carbon black, the carbon black representing more than 50% by weight of the reinforcing filler, the volume fraction of filler in the rubber composition being greater than 18%.

[0066] The volume fraction of filler in a rubber composition is defined as the ratio of the volume of the filler to the volume of all the constituents of the composition, it being understood that the volume of all the constituents is calculated by adding the volume of each of the constituents of the composition.

[0067] The blacks that can be used in the context of the present invention can be any black conventionally used in pneumatic or non-pneumatic tires or their treads (so-called pneumatic 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 N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772). These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a 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). Mixtures of several carbon blacks can also be used in the prescribed rates.

[0068] Advantageously, the filler comprises more than 50% by weight, preferably more than 80% by weight, of carbon black. More preferably, the filler consists exclusively of carbon black, i.e. the carbon black represents 100% by weight of the filler.

[0069] Advantageously, the filler comprises more than 50% by weight, preferably more than 80% by weight, of at least one carbon black having a BET specific surface area in a range from 60 to 160 m 2 < / g, preferably from 70 to 130 m 2 < / g, preferably from 100 to 120 m 2 < / g. The BET specific surface area of the carbon blacks is measured according to the ASTM D6556-10 standard [multipoint method (at least 5 points) - gas: nitrogen - relative pressure range P / P0: 0.1 to 0.3].

[0070] Advantageously, the charge rate in the composition according to the invention is within a range from 47 to 120 phr, preferably from 49 to 110 phr, preferably from 50 to 105 phr, preferably from 55 to 85 phr.

[0071] Advantageously, the volume fraction of filler in the rubber composition is greater than 19%, preferably within a range from 20% to 26%, preferably from 21% to 24%.

[0072] Furthermore, the level of carbon black (whether there is one or more) in the composition according to the invention is advantageously within a range from 47 to 80 phr, preferably from 49 to 80 phr, preferably from 49 to 75 phr, preferably from 49 to 70 phr or from 50 to 75 phr, preferably from 55 to 75 phr.

[0073] Advantageously, the volume fraction of carbon black, preferably carbon black having a BET specific surface area in a range from 60 to 160 m 2 < / g, preferably from 70 to 130 m 2 < / g, in the rubber composition, is greater than 18%, preferably greater than 19%, preferably in a range from 20% to 26%, preferably from 21% to 24%.

[0074] The composition according to the invention may comprise fillers other than carbon black but this is not obligatory or preferable. This may in particular be an inorganic filler such as silica. II-4 Crosslinking system

[0075] The crosslinking system may be any type of system known to those skilled in the art in the field of tire rubber compositions. It may in particular be based on sulfur, and / or peroxide and / or bismaleimides.

[0076] Preferably, the crosslinking system is sulfur-based, in which case it is referred to as a vulcanization system. The sulfur can be provided in any form, in particular in the form of molecular sulfur and / or sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally, also preferably, various known vulcanization activators can 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 even known vulcanization retarders.

[0077] Sulfur is used at a preferential rate of between 0.3 and 12 pce, in particular between 0.5 and 5.0 pce. The vulcanization accelerator is used at a preferential rate of between 0.5 and 10 pce, more preferably between 0.5 and 5.0 pce.

[0078] 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. II-5 Possible additives

[0079] The rubber compositions may optionally also comprise all or part of the usual additives usually used in elastomer compositions for tires, such as for example plasticizers (such as plasticizing oils and / or plasticizing resins), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents, reinforcing resins (as described for example in application WO 02 / 10269).

[0080] Advantageously, the composition according to the invention does not comprise any hydrocarbon plasticizing resin or comprises less than 10 phr, preferably less than 5 phr. More preferably, the composition according to the invention does not comprise any hydrocarbon plasticizing resin. The composition according to the invention also advantageously does not comprise any plasticizing oil that is liquid at 20°C or comprises less than 15 phr, preferably less than 10 phr, preferably less than 5 phr. More preferably, the composition according to the invention does not comprise any plasticizing oil that is liquid at 20°C. II-6 Preparation of rubber compositions

[0081] The compositions in accordance with the invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first phase of working or thermomechanical mixing (so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents are introduced into a suitable mixer such as a conventional internal mixer (for example of the 'Banbury' type), in particular the elastomeric matrix, the reinforcing filler, any other various additives, with the exception of the crosslinking system. The incorporation of the possible filler into the elastomer can be carried out in one or more stages by thermomechanical mixing.In the case where the filler is already incorporated in whole or in part into the elastomer in the form of a masterbatch as described for example in applications WO 97 / 36724 or WO 99 / 16600, it is the masterbatch which is directly mixed and where appropriate the other elastomers or fillers present in the composition which are not in the form of a masterbatch are incorporated, as well as any other various additives other than the crosslinking system. The non-productive phase can be carried out at high temperature, up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C, for a duration generally of between 2 and 10 minutes.a second phase of mechanical work (so-called "productive" phase), which is carried out in an external mixer such as a cylinder mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 120°C, for example between 40°C and 100°C. The crosslinking system is then incorporated, and everything is then mixed for a few minutes, for example between 5 and 15 min.

[0082] Such phases have been described for example in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.

[0083] The final composition thus obtained is then calendered, for example, in the form of a sheet or plate, in particular for characterization in the laboratory, or extruded (or co-extruded with another rubber composition) in the form of a semi-finished (or profiled) rubber product usable, for example, as a tire tread. These products can then be used for the manufacture of tires, according to techniques known to those skilled in the art.

[0084] 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.

[0085] Also described herein is a process for preparing the rubber composition according to the invention comprising the following steps: adding during a first so-called non-productive step to the copolymer the 1,3-dipolar compound, the filler, by thermomechanically mixing until reaching a maximum temperature between 130 and 200°C, cooling the whole to a temperature below 100°C, then incorporating the crosslinking system, mixing the whole until a maximum temperature below 120°C.

[0086] The amount of 1,3-dipolar compound added is preferably between 0 and 3 molar equivalents, more preferably between 0 and 2 molar equivalents, even more preferably between 0 and 1 molar equivalent, or even more preferably between 0 and 0.7 molar equivalents of imidazole ring per 100 moles of monomer units constituting the copolymer. For each of these preferential ranges, the lower limit is preferably at least 0.1 molar equivalent of 1,3-dipolar compound.

[0087] Advantageously, the 1,3-dipolar compound is mixed with the copolymer before the introduction of the other constituents of the rubber composition, in particular before the addition of the filler. The contact time between the copolymer and the 1,3-dipolar compound which are mixed, preferably thermomechanically kneaded, is adjusted according to the mixing conditions, in particular thermomechanical kneading, in particular according to the temperature. The higher the temperature, the shorter this contact time. Typically it is 1 to 5 minutes for a temperature of 100 to 130°C.

[0088] Preferably, at least one antioxidant is added to the copolymer before its introduction into a mixer, in particular at the end of the synthesis of the copolymer as is done conventionally.

[0089] After incorporating all the ingredients of the rubber composition, the final composition thus obtained is then calendered, for example in the form of a sheet or plate, in particular for characterization in the laboratory, or extruded, to form for example a rubber profile used as a rubber component for the manufacture of the tire. II -7 Rubber articles

[0090] The present invention also relates to a rubber article comprising at least one composition according to the invention.

[0091] In view of the improved performance compromise within the scope of the present invention, the rubber article is advantageously selected from the group consisting of pneumatic tires, non-pneumatic tires, tracks and conveyor belts. Preferably, the rubber article is a pneumatic or non-pneumatic tire.

[0092] More particularly, the invention also relates to a pneumatic or non-pneumatic tire provided with a tread comprising a composition according to the invention.

[0093] A tread has a tread surface provided with a sculpture formed by a plurality of grooves delimiting raised elements (blocks, ribs) so as to generate edges of material as well as hollows. These grooves represent a volume of hollows which, relative to the total volume of the tread (including both the volume of raised elements and that of all the grooves) is expressed by a percentage designated herein by "volume hollow rate". A volume hollow rate equal to zero indicates a tread without grooves or hollows.

[0094] The present invention is particularly well suited to the treads of tires intended to equip civil engineering, agricultural and heavy goods vehicles, more particularly civil engineering vehicles whose tires are subjected to very specific constraints, in particular the stony ground on which they roll. Thus, advantageously, the pneumatic or non-pneumatic tire provided with a tread comprising a composition according to the invention is a tire for a civil engineering, agricultural or heavy goods vehicle, preferably for civil engineering. These tires are provided with treads which have, compared to the thicknesses of the treads of tires for light vehicles, in particular for passenger vehicles or vans, large thicknesses of rubber material.Typically the wearing part of the tread of a heavy goods vehicle tire has a thickness of at least 15 mm, that of a civil engineering vehicle at least 30 mm, or even up to 120 mm. Thus, the tread of the tire according to the invention advantageously has one or more grooves whose average depth ranges from 15 to 120 mm, preferably 65 to 120 mm.

[0095] The tires according to the invention may have a diameter ranging from 20 to 63 inches, preferably from 35 to 63 inches.

[0096] Furthermore, the average volumetric hollow rate over the entire tread of the pneumatic or non-pneumatic tire according to the invention may be within a range from 5 to 40%, preferably from 5 to 25%.

[0097] The invention also relates to a rubber track comprising at least one rubber element comprising a composition according to the invention, the at least one rubber element preferably being an endless rubber belt or a plurality of rubber pads, as well as a rubber conveyor belt comprising a composition according to the invention.

[0098] The invention relates to the previously described rubber articles both in the raw state (i.e., before curing) and in the cured state (i.e., after crosslinking or vulcanization). III- PREFERRED EMBODIMENTS

[0099] In view of the foregoing, preferred embodiments of the invention are described below: 1.Rubber composition based on at least: an elastomer matrix comprising more than 50 pce of a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing more than 50% by mole of the monomer units of the copolymer, a 1,3-dipolar compound corresponding to formula (I) Q-Sp-B (I) in which: ∘ Q comprises a dipole containing at least and preferably one nitrogen atom, ∘ Sp, preferably divalent, is an atom or a group of atoms linking Q to B, ∘ B comprises an imidazole ring corresponding to the following formula (II): in which: 3 of the 4 symbols Z, Y, R and R', identical or different, each represent an atom or a group of atoms, Z and Y being able to form together with the carbon atoms to which they are attached a cycle, and the fourth symbol Z, Y, R or R' denotes a direct attachment to Sp, a reinforcing filler comprising carbon black, the carbon black representing more than 50% by weight of the reinforcing filler, the volume fraction of filler in the rubber composition being greater than 18%, a crosslinking system. 2. Composition according to embodiment 1, in which the ethylene units in the copolymer represent between 50% and 95%, preferably between 55% and 90%, by mole of the monomer units of the copolymer. 3. A 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. 4.A composition according to any one of the preceding embodiments, wherein the 1,3-diene is 1,3-butadiene. 5. Composition according to any one of the preceding embodiments, in which the copolymer contains units of formula (III) or units of formula (IV) or units of formula (III) and of formula (IV): -CH2-CH(CH=CH2)- (IV) 6. Composition according to embodiment 5, in which the molar percentages of the units of formula (III) and of the units of formula (IV) 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 0 < o + p ≤ 25 0 < o + p < 20 7. Composition according to any one of the preceding embodiments, in which the copolymer containing ethylene units and 1,3-diene units is a random copolymer. 8.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. 9. Composition according to any one of the preceding embodiments, in which R' denotes a direct attachment to Sp. 10. A composition according to any one of the preceding embodiments, wherein Z and Y are each a hydrogen atom. 11. Composition according to any one of embodiments 1 to 9, in which Z and Y together with the carbon atoms to which they are attached form a cycle, preferably aromatic. 12. Composition according to any one of the preceding embodiments, in which R represents a hydrogen atom or a carbon group which may contain at least one heteroatom and preferably containing from 1 to 20 carbon atoms. 13.Composition according to any one of the preceding embodiments, in which R is an aliphatic group, preferably an alkyl group which preferably contains from 1 to 12 carbon atoms. 14. Composition according to any one of the preceding embodiments, in which R is methyl. 15. A composition according to any preceding embodiment, wherein Sp is a group containing up to 20 carbon atoms and which may contain at least one heteroatom. 16. Composition according to any one of the preceding embodiments, in which Sp is an aliphatic group preferably containing from 1 to 20 carbon atoms, more preferably from 1 to 12 carbon atoms, even more preferably from 1 to 6 carbon atoms, or an aromatic group preferably containing from 6 to 20 carbon atoms, more preferably from 6 to 12 carbon atoms. 17.Composition according to any one of the preceding embodiments, in which Sp is an alkylene group containing from 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms, more preferably from 1 to 6 carbon atoms, even more preferably from 1 to 3 carbon atoms, or an arylene group preferably containing from 6 to 20 carbon atoms, more preferably from 6 to 12 carbon atoms. 18. A composition according to any one of the preceding embodiments, wherein the 1,3-dipolar compound is selected from the group consisting of nitrile oxides, nitrile imines and nitrones. 19. Composition according to any one of the preceding embodiments, in which Q contains a -C=N → O unit. 20. Composition according to any one of the preceding embodiments, in which Q comprises, preferably represents the unit corresponding to formula (V): in which: four of the five symbols X 1 to X 5, identical or different, are each an atom or a group of atoms, preferably an aliphatic group or an aromatic group, and the fifth symbol designates a direct attachment to Sp, knowing that X 1 and X 5 are not hydrogen atoms. 21. Composition according to embodiment 20, in which X 1 , X 3 and X 5 are identical. 22. Composition according to embodiment 20 or 21 in which X 1 , X 3 and X 5 are each an alkyl group of 1 to 6 carbon atoms, preferably of 1 to 3 carbon atoms. 23. A composition according to any one of embodiments 20 to 22, wherein X 1 , X 3 and X 5 are each methyl or ethyl, preferably methyl. 24.A composition according to any one of the preceding embodiments, wherein the 1,3-dipolar compound is 2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide or 2,4,6-triethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide, preferably 2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide. 25. Composition according to any one of the preceding embodiments, in which the level of the 1,3-dipolar compound is between 0 and 50, preferably between 0.01 and 15, molar equivalents, for example between 4 and 15 molar equivalents, per 100 moles of monomer units constituting the copolymer. 26.Composition according to any one of embodiments 1 to 24, in which the level of the 1,3-dipolar compound is between 0.1 and 3 molar equivalents, preferably between 0.1 and 2 molar equivalents, even more preferably between 0.1 and 1 molar equivalent, or even more preferably between 0.1 and 0.7 molar equivalents, of imidazole ring per 100 moles of monomer units constituting the copolymer. 27. Composition according to any one of the preceding embodiments, in which the filler comprises more than 70% by weight, preferably more than 80% by weight of carbon black. 28. Composition according to any one of the preceding embodiments, in which the filler comprises 100% by weight of carbon black. 29.Composition according to any one of the preceding embodiments, in which the charge rate is within a range from 47 to 120 pce, preferably from 49 to 110 pce, preferably from 50 to 105 pce, preferably from 55 to 85. 30. Composition according to any one of the preceding embodiments, in which the volume fraction of filler in the rubber composition is greater than 19%, preferably within a range from 20% to 26%, preferably from 21% to 24%. 31. Composition according to any one of the preceding embodiments, in which the carbon black content is within a range from 47 to 80 pce, preferably from 49 to 80 pce, preferably from 49 to 75 pce, preferably from 49 to 70 pce, or from 50 to 75 pce, preferably from 55 to 75 pce. 32.Composition according to any one of the preceding embodiments, in which the volume fraction of carbon black in the rubber composition is greater than 18%, preferably greater than 19%, preferably within a range from 20% to 26%, preferably from 21% to 24%. 33. Composition according to any one of the preceding embodiments, which composition does not comprise hydrocarbon plasticizing resin or comprises less than 10 pce, preferably less than 5 pce. 34. Composition according to any one of the preceding embodiments, the composition does not comprise liquid plasticizing oil at 20°C or comprises less than 15 pce, preferably less than 10 pce, preferably less than 5 pce. 35. Composition according to any one of the preceding embodiments, in which the crosslinking system is a vulcanization system based on molecular sulfur and / or sulfur donor agent. 36.Rubber article comprising a composition as defined in any one of embodiments 1 to 35. 37. A rubber article according to embodiment 36, said article being selected from the group consisting of pneumatic tires, non-pneumatic tires, tracks and conveyor belts. 38. Pneumatic or non-pneumatic tire provided with a tread comprising a composition as defined in any one of embodiments 1 to 35. 39. Bandage according to embodiment 38, being a bandage for a civil engineering, agricultural or heavy goods vehicle, preferably for civil engineering. 40. Tire according to embodiment 38 or 39, in which the composition is present in at least 50%, preferably at least 70%, of the volume of the tread. 41.Tire according to any one of embodiments 38 to 40, the tread of which has one or more grooves whose average depth is in a range from 30 to 120 mm, preferably from 45 to 75 mm. 42. Tire according to any one of embodiments 38 to 41 having an average volumetric hollow rate over the entire tread within a range from 5 to 40%, preferably from 5 to 25%. 43. A tire according to any one of embodiments 38 to 42, having a diameter in a range from 20 to 63 inches, preferably from 35 to 63 inches. 44. Track comprising at least one rubber element comprising a composition as defined in any one of embodiments 1 to 35. 45. A track according to embodiment 44, wherein the at least one rubber element is an endless rubber belt or a plurality of rubber pads. 46.Rubber conveyor belt comprising a composition as defined in any one of embodiments 1 to 35. IV- EXAMPLES IV-1 Measurements and tests used Determination of molar masses: Analysis by Size Exclusion Chromatography of copolymers

[0100] a) For copolymers soluble at room temperature in tetrahydrofuran (THF), the molar masses were determined by size exclusion chromatography in THF. The samples were injected using a "Waters 717" injector and a "Waters 515 HPLC" pump at a flow rate of 1 ml.min -1< into a series of "Polymer Laboratories" columns. This series of columns, placed in a thermostatically controlled chamber at 45°C, is composed of: 1 PL Gel 5 µm precolumn, 2 PL Gel 5 µm Mixte C columns, 1 PL Gel 5 µm-500 Å column.

[0101] Detection was performed using a Waters 410 refractometer. Molar masses were determined by universal calibration using polystyrene standards certified by Polymer Laboratories and dual detection with refractometer and viscometer coupling.

[0102] Although not an absolute method, SEC allows us to understand the distribution of molecular masses of a polymer. From commercial standard products of the polystyrene type, the different average masses in number (Mn) and in weight (Mw) can be determined and the polymolecularity index calculated (Ip = Mw / Mn).

[0103] b) For the copolymers insoluble at room temperature in tetrahydrofuran, the molar masses were determined in 1,2,4-trichlorobenzene. They were first dissolved hot (4 h at 150°C), then injected at 150°C with a flow rate of 1 ml.min -1< into a "Waters Alliance GPCV 2000" chromatograph equipped with three "Styragel" columns (2 "HT6E" columns and 1 "HT2" column). Detection was carried out using a "Waters" refractometer. The molar masses were determined by relative calibration using polystyrene standards certified by "Polymer Laboratories". Determination of mole fractions

[0104] Reference is made to the article “Investigation of ethylene / butadiene copolymers microstructure by 1H and 13C NMR, Llauro MF, Monnet C., Barbotin F., Monteil V., Spitz R., Boisson C., Macromolecules 2001, 34, 6304-6311”, for a detailed description of the H NMR and 13< C NMR techniques which were specifically used in the present application to determine the molar fractions of the ethylene units, conjugated diene units and any units trans -1,2 cyclohexane. NMR analysis

[0105] The structural analysis as well as the determination of the molar purities of the synthetic molecules are carried out by NMR analysis. The spectra are acquired on a BRUKER Avance 3400 MHz spectrometer equipped with a BBFO-zgrad 5 mm broadband probe. The quantitative 1< H NMR experiment uses a single 30° pulse sequence and a repetition delay of 3 seconds between each of the 64 acquisitions. The samples are solubilized in deuterated dimethyl sulfoxide (DMSO). This solvent is also used for the Iock signal. Calibration is carried out on the proton signal of deuterated DMSO at 2.44 ppm compared to a TMS reference at 0 ppm. The 1< H NMR spectrum coupled with the 2D HSQC 1< H / 13< C and HMBC 1< H / 13< C experiments allows the structural determination of the molecules (see attribution tables). Molar quantifications are carried out from the quantitative 1D 1< H NMR spectrum. Mooney ML 1 + 4

[0106] The Mooney plasticity measurement is carried out according to the following principle and in accordance with ASTM D-1646. The generally raw polymer is molded in a cylindrical chamber heated to a given temperature, usually 100°C. After one minute of preheating, an L-type rotor rotates within the specimen at 2 revolutions per minute and the torque needed to maintain this movement is measured after 4 minutes of rotation. The Mooney plasticity (ML 1+4) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Newton.meters). Caterpillar test

[0107] This test is representative of resistance to aggression. It consists of rolling a metal track mounted on a pneumatic tire mounted on a wheel and vehicle, and inflated, on which are fixed rubber pads of a given composition, on a track filled with stones for a certain time. At the end of the rolling, the pads are removed and the number of cuts visible to the naked eye on the surface is counted. The lower the number, the better the resistance performance to aggression.

[0108] To carry out this test, pads of different compositions were manufactured (see Table 1 below) according to the process described in point IV-4 below. To obtain a pad, the non-crosslinked composition obtained in point IV-4 was calendered to a thickness of 5.5 mm, plates were cut (2 of 260x120 mm, 2 of 250x100 mm and 2 of 235x90 mm) and then stacked in a pyramidal shape. This block of 6 plates was then inserted into a pyramidal mold with a rectangular base of 260x120 mm and a flat top of 235x90 mm in surface area, and baked at a temperature of 120°C for 300 minutes at a pressure of 180 bars, thus allowing the crosslinking of the composition.

[0109] The pads were then mounted on two Caterpillar X-TRACK10 metal tracks, which were themselves mounted on two MICHELIN XMINE D2 12.00R24 tires from the rear axle of a SCANIA R410 truck. The tires were re-cut to support the tracks. The tires were inflated to a pressure of 7 bars and carried a load of 4,250 kg per tire.

[0110] The truck drove on a flat track covered with 30 / 60 porphyry pebbles obtained from SONVOLES Murcia, Spain, for 5 hours at a speed of 5 km / h. The pebble density on the track was approximately 1000 to 1500 pebbles per square meter.

[0111] At the end of the test, the cuts visible on the surface of the pads were counted. The result was averaged based on 6 pads. The results of performance against aggression are expressed as a percentage base 100 compared to the control composition T1. A result greater than 100 indicates an improvement in resistance to aggression. Tensile test (after baking)

[0112] The elongation at break (AR%) and breaking stress (CR) tests are based on the NF ISO 37 standard of December 2005 on a type H2 dumbbell specimen and are measured at a tensile speed of 500 mm / min. The elongation at break is expressed as a % elongation. The breaking stress is expressed in MPa. These values are expressed on a base of 100 compared to the control composition T1. A value greater than 100 indicates an improvement in the mechanical properties of the composition considered compared to the control composition.

[0113] All these traction measurements are carried out under normal temperature (23±2°C) and hygrometry (50±5% relative humidity) conditions, according to the French standard NF T 40-101 (December 1979). IV-2 Synthesis of the 1,3-dipolar compound 2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide

[0114] This compound can be prepared according to the following reaction scheme: IV.2-1-Synthesis of 2-(chloromethyl)-1,3,5-trimethylbenzene:

[0115] This compound can be obtained according to a procedure described in the article Zenkevich, IG; Makarov, AA; Russian Journal of General Chemistry; vol. 77; nb. 4; (2007); p. 611 - 619 (Zhurnal Obshchei Khimii; vol. 77; nb. 4; (2007); p. 653 - 662)

[0116] A mixture of mesitylene (100.0 g, 0.832 mol), para-formaldehyde (26.2 g, 0.874 mol) and hydrochloric acid (240 ml, 37%, 2.906 mol) in acetic acid (240 ml) is stirred and heated very slowly (1.5 hours) to 37°C. After returning to room temperature, the mixture is diluted with water (1.01) with CH 2 Cl 2 (200 ml), the product is extracted with CH 2 Cl 2 (4 times per 50 ml). The organic phases are combined, then washed with water (5 times per 100 ml) and evaporated to 11-12 mbar (bath temperature = 42°C). A colorless oil (133.52 g, yield 95%) is obtained. After 15-18 hours at +4°C, the oil crystallized. The crystals were filtered, washed with petroleum ether cooled to -18°C (40 ml), then dried for 3 to 5 hours under atmospheric pressure at room temperature. A white solid (95.9 g, yield 68%) with a melting point of 39°C was obtained. The molar purity was greater than 96% (1H NMR). IV.2-2-Synthesis of 3-(chloromethyl)-2,4,6-trimethylbenzaldehyde:

[0117] This compound can be obtained according to a procedure described in the article Yakubov, AP; Tsyganov, DV; Belen'kii, LI; Krayushkin, MM; Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation); vol. 40; nb. 7.2; (1991); p. 1427 - 1432 (Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya; nb. 7; (1991); p. 1609 - 1615)

[0118] To a solution of TiCl 4 (90.0 g, 0.474 mol) in dichloromethane (200 ml) at 17°C is added under argon for 10-12 minutes a solution of 2-(chloromethyl)-1,3,5-trimethylbenzene (20.0 g, 0.118 mol) and dichloromethylmethyl ether (27.26 g, 0.237 mol) in dichloromethane (200 ml). After stirring for 15-20 minutes at 17-20 °C, water (1000 ml) and ice (500 g) are added to the reaction medium. After stirring for 10-15 minutes, the organic phase is separated. The aqueous phase is extracted with CH 2 Cl 2 (3 times per 75 ml). The combined organic phases are washed with water (4 times per 100 ml) and evaporated under reduced pressure to yield a solid (bath temperature = 28°C). The target product (22.74 g) is obtained with a yield of 97%. Its melting point is 58°C. The molar purity estimated by 1< H NMR is 95% mol. IV.2-3-Synthesis of 2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl) benzaldehyde:

[0119]

[0120] A mixture of 3-(chloromethyl)-2,4,6-trimethylbenzaldehyde (10.0 g, 0.051 mol) and imidazole (10.44 g, 0.127 mol) in DMF (10 ml) was stirred at 80°C for one hour.

[0121] After returning to 40-50°C, the mixture is diluted with water (200ml), and stirred for 10 minutes. The precipitate obtained is filtered and washed on the filter with water (4 times per 25ml) then dried at room temperature. A white solid (7.92g, yield 64%) with a melting point of 161°C is obtained. The molar purity is 91% (1<H NMR). IV.2-4-Synthesis of 2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzaldehyde oxime:

[0122]

[0123] To a solution of 2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl) benzaldehyde (20.3 g, 0.084 mol) in EtOH (110 ml) at 40°C, an aqueous solution of hydroxylamine (809 g, 0.134 mol, 50% in water, Aldrich) in EtOH (10 ml) is added. The reaction mixture is stirred for 2.5 hours at a temperature of 50 to 55°C. After returning to 23°C, the precipitate obtained is filtered and washed twice on the filter with an EtOH / H 2 O mixture (10 ml / 15 ml) and dried for 15 to 20 hours under atmospheric pressure at room temperature. A white solid (19.57 g, yield 91%) with a melting point of 247°C is obtained. The molar purity is greater than 87% (1< H NMR). IV.2-5-Synthesis of 2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide:

[0124]

[0125] To a mixture of 2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzaldehyde oxime (8.80 g, 0.034 mol) in CH 2 Cl 2 (280 ml) at 6°C is added dropwise an aqueous solution of NaOCl (4% active chlorine, Aldrich, 49 ml) over 5 minutes. The temperature of the reaction medium is maintained between 6 and 8°C. The reaction medium is then stirred for 2 hours at 8°C to 21°C. The organic phase is separated. The organic phase is washed with water (3 times per 50 ml). After concentration under reduced pressure (bath temperature = 22-23°C, 220 mbar), petroleum ether (10 ml) is added, the solvent is evaporated to 8-10 ml, and the solution is kept at -18°C for 10-15 hours to obtain a precipitate. The precipitate is filtered and washed on the filter with the mixture of CH 2 Cl 2 / petroleum ether (2 ml / 6 ml) then with petroleum ether (2 times 10 ml) and finally dried for 10-15 hours under atmospheric pressure at room temperature.A white solid (5.31 g, yield 61%) with a melting point of 139 °C is obtained.

[0126] The molar purity is greater than 95% mol (1< H NMR). IV-3 Preparation of compositions

[0127] In the following examples, the rubber compositions were produced as described in point II-6 above. In particular, the manufacture of these compositions is carried out as follows: the elastomer, where appropriate the 1,3-dipolar compound which is kneaded alone with the elastomer for approximately 1 minute at 120°C, is introduced into an internal mixer (final filling rate: approximately 70% by volume), the initial tank temperature of which is approximately 80°C, followed by the filler and the various other ingredients, with the exception of the vulcanization system. Thermomechanical work (non-productive phase) is then carried out in one step, lasting approximately 3 to 6 minutes, until a maximum "drop" temperature of 160°C is reached.The mixture thus obtained is recovered, cooled and then the vulcanization system is incorporated into a mixer (homo-finisher) at 23°C, mixing everything (productive phase) for an appropriate time (for example between 5 and 12 min).

[0128] The compositions thus obtained are then calendered, either in the form of plates (with a thickness ranging from 2 to 3 mm) or thin sheets of rubber, for the measurement of their physical or mechanical properties, or in the form of profiles directly usable, after cutting and / or assembly to the desired dimensions, for example as semi-finished products for tires, in particular for treads as semi-finished products for rubber tracks.

[0129] Curing is carried out at 150°C. The applied curing time, t' c (90), is the time required for the composition torque to reach 90% of the composition's maximum torque. The composition torques are measured at 150°C with an oscillating chamber rheometer, according to DIN 53529 - Part 3 (June 1983). t' c (90), is determined according to NF T 43-015 for each of the compositions. From one composition to another, it varies approximately from 20 to 40 minutes. IV-4 Rubber composition tests

[0130] The examples presented below aim to compare the performance compromise between rigidity, elongation at break and resistance to mechanical attack of three compositions in accordance with the present invention (C1 and C2) with five control compositions (T0 to T4).

[0131] Table 1 presents the tested compositions (in pce), as well as the results obtained.

[0132] The control composition T0 corresponds to a composition conventionally used in treads of civil engineering tires. Compositions T1, T3 and T4 differed respectively from compositions T2, C1 and C2 in that they do not comprise a 1,3-dipolar compound in accordance with the invention. The carbon black content between compositions T1 and T2, T3 and C1, and T4 and C2 were respectively adjusted to remain at a constant filler volume fraction. [Table 1] Components T0 T1 T2 T3 C1 T4 C2 Natural rubber 100 - - - - - - EBR(1) - 100 100 100 100 100 100 1,3-Dipolar compound(2) - - 2.1 - 2.1 - 2.1 N234(3) 40 40 41 52 53 65 67 Silica(4) 15 - - - - - - %vol charge 20% 16% 16% 20% 20% 24% 24% Anti-ozone wax(5) 1 1 1 1 1 1 1 Antioxidant(6) 1.5 2 2 2 2 2 2 Stearic acid 1 1.5 1.5 1.5 1.5 1.5 1.5 ZnO(7) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Sulfur 1.7 0.6 0.6 0.6 0.6 0.6 0.6 Accelerator (8) 1.2 1.3 1.3 1.3 1.3 1.3 1.3 Properties Caterpillar punch 100 101 99 120 129 189 223 (1) EBR: Elastomer with 74 mol% ethylene unit, 7.5 mol% 1,2-cyclohexanediyl unit, 11.5 mol% 1,2-unit, 7 mol% 1,4-unit; Mooney at 100°C: 68; Mn: 148,110 g / mol prepared according to a process for the polymerization of ethylene and butadiene in accordance with Example 4-2 of patent EP 1 954 705 B1 (2) 1,3-dipolar compound whose synthesis is described above in paragraph IV.2 (2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide) (3) Carbon black grade N234 according to ASTM D-1765 standard (4) Silica “Zeosil 1165MP” from Solvay (5) Anti-ozone wax “VARAZON 4959” from Sasol Wax (6) N-1,3-dimethylbutyl-N-phenylparaphenylenediamine “Santoflex 6-PPD” from Flexsys (7) Industrial grade zinc oxide from Umicore (8) N-cyclohexyl-2-benzothiazyl sulfenamide "Santocure CBS" from Flexsys

[0133] The results presented in Table 1 above show that the specific combination of a 1,3-dipolar compound in accordance with the invention with a high filler volume fraction in a composition based on a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing more than 50 mol% of the monomer units of the copolymer makes it possible to improve the resistance to mechanical attack.

[0134] The compositions in accordance with the invention are useful for numerous applications in the field of pneumatic or non-pneumatic tires, in particular in treads for which high resistance to mechanical attack is desired.

Claims

1. Rubber composition based on at least: - an elastomer matrix comprising more than 50 phr of a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing more than 50 mol% of the monomer units of the copolymer, - a 1,3-dipolar compound corresponding to the formula (I)         Q-Sp-B     (I) in which: ∘ Q comprises a dipole containing at least and preferably one nitrogen atom, ∘ Sp, which is preferably divalent, is an atom or a group of atoms connecting Q to B, ∘ B comprises an imidazole ring corresponding to the following formula (II) in which: • three of the four symbols Z, Y, R and R', which are identical or different, each represent an atom or a group of atoms, it being possible for Z and Y to form, together with the carbon atoms to which they are attached, a ring, • and the fourth symbol Z, Y, R or R' denotes a direct attachment to Sp, - a reinforcing filler comprising carbon black, the carbon black representing more than 50% by weight of the reinforcing filler, the fraction by volume of filler in the rubber composition being greater than 18%, - a crosslinking system.

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

3. Composition according to either one of the preceding claims, wherein the 1,3-diene is 1,3-butadiene.

4. Composition according to any one of the preceding claims, wherein R' denotes a direct attachment to Sp, Z and Y are each a hydrogen atom and R represents a hydrogen atom or a carbon-based group which can contain at least one heteroatom and preferably containing from 1 to 20 carbon atoms.

5. Composition according to any one of the preceding claims, wherein Sp is a group containing up to 20 carbon atoms and which can contain at least one heteroatom.

6. Composition according to any one of the preceding claims, wherein the 1,3-dipolar compound is selected from the group consisting of nitrile oxides, nitrilimines and nitrones.

7. Composition according to any one of the preceding claims, wherein Q comprises, preferably represents, the unit corresponding to the formula (V): in which: four of the five symbols X1 to X5, which are identical or different, are each an atom or a group of atoms, preferentially an aliphatic group or an aromatic group, and the fifth symbol denotes a direct attachment to Sp, it being known that X1 and X5 are not hydrogen atoms.

8. Composition according to any one of the preceding claims, wherein the 1,3-dipolar compound is 2,4,6-trimethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide or 2,4,6-triethyl-3-((2-methyl-1H-imidazol-1-yl)methyl)benzonitrile oxide, preferably 2,4,6-trimethyl-3-((2-methyl-lH-imidazol-1-yl)methyl)benzonitrile oxide.

9. Composition according to any one of the preceding claims, wherein the content of the 1,3-dipolar compound is of between 0.03 and 3 molar equivalents, preferentially between 0.05 and 2 molar equivalents, more preferentially still between 0.07 and 1 molar equivalent, of imidazole ring per 100 mol of monomer units constituting the copolymer.

10. Composition according to any one of the preceding claims, wherein the filler comprises 100% by weight of carbon black.

11. Composition according to any one of the preceding claims, wherein the content of filler is within a range extending from 47 to 120 phr, preferably from 49 to 110 phr, preferably from 50 to 105 phr, more preferably from 55 to 85 phr.

12. Composition according to any one of the preceding claims, wherein the fraction by volume of filler in the rubber composition is greater than 19%, preferably within a range extending from 20% to 26%, preferably from 21% to 24%.

13. Composition according to any one of the preceding claims, wherein the content of carbon black is within a range extending from 47 to 80 phr, preferably from 49 to 80 phr, preferably from 49 to 75 phr, preferably from 49 to 70 phr.

14. Composition according to any one of the preceding claims, wherein the fraction by volume of carbon black in the rubber composition is greater than 18%, preferably greater than 19%, preferably within a range extending from 20% to 26%, preferably from 21% to 24%.

15. Rubber article comprising a composition as defined in any one of Claims 1 to 14, said article preferably being selected from the group consisting of pneumatic tyres, non-pneumatic tyres, caterpillar tracks and conveyor belts.