Rubber composition based on highly saturated diene elastomers

Abstract

The present invention relates to a rubber composition based on at least one elastomeric matrix, a specific 1,3-dipolar compound, a filler and a crosslinking system. The elastomeric matrix comprises a copolymer containing ethylene units and 1,3-diene units in an amount greater than 50 phr, and the ethylene units in the copolymer account for more than 50 mol% of the monomer units of the copolymer. The filler mainly comprises silica, and the crosslinking system comprises at least one free radical polymerization initiator and a crosslinking aid selected from (meth)acrylate compounds, maleimide compounds, allyl compounds, vinyl compounds and mixtures thereof.

Description

Field of the Invention

[0001] The field of the invention is that of diene rubber compositions reinforced with inorganic fillers (such as silica) and which can be used in particular for the manufacture of tires for vehicles. The invention more particularly relates to the tread of pneumatic or non-pneumatic tires having an improved compromise between rolling resistance / wear. Background of the Invention

[0002] Due to the fact that the need for fuel economy and environmental protection has become a priority, it is desirable to produce mixtures having good abrasion resistance properties while having as low a hysteresis as possible, so as to be able to process them in the form of rubber compositions (compositions for pneumatic or non-pneumatic tires (such as treads)) which can be used for manufacturing the various semi-finished products involved.

[0003] In order to reduce the rolling resistance, it is known to use diene rubber compositions reinforced with inorganic fillers (such as silica). Diene rubber compositions reinforced with inorganic fillers generally contain a silane as a coupling agent, such as a polysulfide or a capped mercapto-silane (which is a silane with a protected thiol functional group). The silane is capable of creating an interaction between the diene elastomer and the inorganic filler and promotes the dispersion of the inorganic filler in the rubber composition.

[0004] Furthermore, in order to obtain the best reinforcing properties conferred by the fillers in the rubber composition and thus obtain high abrasion resistance, it is known that it is generally desirable for the filler to be present in the elastomeric matrix in a final form which is as finely divided and as uniformly distributed as possible. In fact, this condition can only be achieved if the filler on the one hand exhibits an excellent ability to be introduced into the matrix and to be de-aggregated during the mixing with the elastomer and on the other hand exhibits an excellent ability to be uniformly dispersed in this matrix. It is well known that carbon black has this ability. On the other hand, this is generally not the case for inorganic fillers (especially silica). This is because, for reasons of mutual affinity, these inorganic filler particles tend to agglomerate together in the elastomeric matrix. The negative consequences of these interactions are that the dispersion and reinforcing properties of the filler are limited to levels which are substantially lower than those which could theoretically be achieved (if all the (inorganic filler / elastomer) bonds which can be generated during the compounding operation were actually obtained). These interactions also tend to increase the consistency of the rubber composition in the uncured state and thus make it more difficult to process than in the presence of carbon black.

[0005] Thus, it remains difficult to develop compositions filled with silica as a filler and having excellent rolling resistance and good abrasion resistance.

[0006] This performance trade-off can be improved by using a novel rubber composition reinforced with inorganic fillers (especially specific silica of the highly dispersible type) in the tread of a tire. From the perspective of reinforcement, the inorganic filler is capable of competing with conventional tire-grade carbon black while providing these compositions with low hysteresis (which is equivalent to low rolling resistance of a tire incorporating the composition). The use of treads filled with such highly dispersible silica (referred to as "HD" or "HDS" for "highly dispersible" or "highly dispersible silica") has been widely described. The highly dispersible silica can be used in low rolling resistance tires (sometimes referred to as "green tires"), which is related to the energy savings provided to the user ("green tire concept"). Particular reference is made to patent applications EP 501227, EP 692492, EP 692493, EP 735088, EP 767206, EP786493, EP 881252, WO 99 / 02590, WO 99 / 02601, WO 99 / 02602, WO 99 / 06480, WO 00 / 05300, WO 000 / 05301. These prior art documents teach the use of HD silica with a BET specific surface area between 100 m 2 / g and 250 m 2 / g. In practice, one type of HD silica with a high specific surface area listed in the field of "green tires" is particularly the Zeosil 1165MP silica sold by Solvay (BET surface area equal to approximately 160 m 2 / g). Using this Zeosil 1165MP silica enables a good trade-off in terms of tire performance (especially satisfactory abrasion resistance and rolling resistance).

[0007] However, there is still a need to further improve the performance trade-off between abrasion resistance and rolling resistance. Summary of the Invention

[0008] In the course of continued research, the applicant unexpectedly found that the combined use of a highly saturated diene elastomer, a specific 1,3-dipolar compound, and a specific free radical crosslinking system in a silica-filled composition can further improve the above-mentioned performance trade-off.

[0009] Accordingly, a subject of the present invention is a rubber composition based at least on:

[0010] - an elastomeric matrix comprising more than 50 phr of a copolymer comprising ethylene units and 1,3-diene units, wherein the ethylene units in the copolymer account for more than 50 mol% of the monomer units of the copolymer,

[0011] - A 1,3-dipole compound, said 1,3-dipole compound corresponding to formula (I):

[0012]

[0013] wherein:

[0014] οQ represents an arylene ring, said arylene ring being optionally substituted by one or more identical or different, preferably saturated, linear or branched aliphatic hydrocarbon chains, said aliphatic hydrocarbon chains being optionally substituted or interrupted by one or more heteroatoms,

[0015] οE represents a divalent hydrocarbon group optionally containing one or more heteroatoms,

[0016] - A filler, said filler mainly comprising silica, and

[0017] - A crosslinking system, said crosslinking system comprising at least one free radical polymerization initiator and a crosslinking aid, said crosslinking aid being selected from (meth)acrylate compounds, maleimide compounds, allyl compounds, vinyl compounds and mixtures thereof.

[0018] Another subject of the present invention is a rubber article comprising the composition according to the present invention, in particular a tread of a pneumatic tire or a non-pneumatic tire. Detailed Description

[0019] I - Definitions

[0020] The expression "the composition is based on" should be understood to mean that the composition comprises a mixture of the various components used and / or an in-situ reaction product, some of these components being capable of and / or intended to react with each other at least partially during the various manufacturing stages of the composition; thus, the composition can be in a fully crosslinked or partially crosslinked state or in a non-crosslinked state.

[0021] For the purposes of the present invention, the expression "parts by weight per hundred parts by weight of elastomer" (or phr) should be understood to mean parts by mass per hundred parts by mass of elastomer.

[0022] In the present application, unless otherwise expressly stated, all percentages (%) shown are percentages by weight (%).

[0023] Furthermore, 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 limits a and b), while any numerical interval represented by the expression "from a to b" means a numerical range extending from a to b (i.e., including the strict limits a and b). In the present application, when a numerical interval is represented by the expression "from a to b", the interval represented by the expression "between a and b" is also preferably represented.

[0024] When referring to the "main" compound, for the purposes of the present invention, it is understood to mean that among the compounds of the same type in the composition, this compound is the main one, i.e., the compound that accounts for the largest mass among the compounds of the same type. Thus, for example, the main elastomer is the elastomer that accounts for the largest mass relative to the total mass of the elastomers in the composition. In the same way, the "main" filler is the filler that accounts for the largest weight among the fillers in the composition. For example, in a system containing only one elastomer, for the purposes of the present invention, the elastomer is the main one, and in a system containing two elastomers, the main elastomer accounts for more than half of the weight of the elastomers. On the contrary, a "minor" compound is a compound that does not account for the largest mass fraction among the compounds of the same type. Preferably, the term "main" is understood to mean present in an amount greater than 50%, preferably greater than 60%, 70%, 80%, 90%, and more preferably, the "main" compound accounts for 100%.

[0025] In the present application, the expression "all monomer units of the copolymer" or "total amount of monomer units of the copolymer" means all the constituent repeating units of the copolymer produced by inserting monomers into the elastomer chain by polymerization. Unless otherwise stated, the content of monomer units or repeating units in a copolymer containing ethylene units and 1,3-diene units is given as a mole percentage calculated based on all the monomer units of the copolymer.

[0026] The carbon-containing compounds mentioned in the specification can be compounds of fossil origin or bio-based origin. In the case where the compound is of biological origin, it can be partially or completely derived from biomass or obtained from renewable starting materials derived from biomass. Particular reference is made to polymers, plasticizers, fillers, etc.

[0027] According to standard ASTM D3418 (1999), the values of all glass transition temperatures "Tg" described in the present application are measured by DSC (differential scanning calorimetry) in a known manner.

[0028] II - DETAILED DESCRIPTION OF THE INVENTION

[0029] II-1 Elastomeric matrix

[0030] The basic feature of the composition of the tire according to the present invention is that it comprises an elastomeric matrix containing more than 50 phr of a copolymer containing ethylene units and 1,3-diene units, and the ethylene units in the copolymer account for more than 50 mol% of the monomer units of the copolymer.

[0031] In the present application, for the sake of simplicity, "a copolymer comprising ethylene units and 1,3-diene units, wherein the ethylene units in the copolymer account for more than 50 mol% of the monomer units of the copolymer" can be represented by "copolymer" or "a copolymer comprising ethylene units and 1,3-diene units".

[0032] The term "elastomeric matrix" is intended to mean all the elastomers of the composition.

[0033] The expression "a copolymer comprising ethylene units and 1,3-diene units" is understood to mean any copolymer that contains 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, especially α-olefin units having 3 to 18 carbon atoms, advantageously having 3 to 6 carbon atoms. For example, the α-olefin units may be selected from propylene, butene, pentene, hexene or mixtures thereof.

[0034] In a known manner, the expression "ethylene unit" represents a -(CH 2 -CH 2 )- unit obtained by inserting ethylene into the elastomeric chain.

[0035] In a known manner, the expression "1,3-diene unit" represents a unit obtained by inserting 1,3-diene by 1,4-addition, 1,2-addition or 3,4-addition (in the case of isoprene). The 1,3-diene unit is, for example, 1,3-diene or a mixture of 1,3-dienes, 1,3-dienes having 4 to 12 carbon atoms, such as very especially 1,3-butadiene and isoprene. Preferably, the 1,3-diene is 1,3-butadiene.

[0036] Advantageously, the ethylene units in the copolymer are between 50 mol% and 95 mol% of the monomer units of the copolymer, preferably between 55 mol% and 90 mol%.

[0037] Advantageously, the copolymer comprising ethylene units and 1,3-diene units is a copolymer of ethylene and 1,3-diene, i.e., the copolymer does not contain any units other than ethylene and 1,3-diene.

[0038] When the copolymer is a copolymer of ethylene and 1,3-diene, the copolymer advantageously contains units of formula (II) and / or formula (III). The presence of the saturated six-membered cyclic unit (1,2-cyclohexanediyl) of formula (II) 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.

[0039]

[0040] -CH 2 -CH(CH=CH 2 )- (III)

[0041] For example, the copolymer of ethylene and a 1,3-diene may not contain units of formula (II). In this case, it preferably contains units of formula (III).

[0042] When the copolymer of ethylene and a 1,3-diene contains units of formula (II) or units of formula (III) or units of formula (II) and units of formula (III), the mole percentages (o and p respectively) of the units of formula (II) and the units of formula (III) in the copolymer preferably satisfy the following equation (Equation 1), more preferably satisfy Equation (Equation 2), and o and p are calculated based on all the monomer units of the copolymer.

[0043] 0 < o + p ≤ 25 (Equation 1)

[0044] 0 < o + p < 20 (Equation 2)

[0045] 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.

[0046] Advantageously, the number-average mass (Mn) of the copolymer (preferably a copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene)) is in the range of 100,000 g / mol to 300,000 g / mol, preferably 150,000 g / mol to 250,000 g / mol.

[0047] In a known manner, the Mn of the copolymer is determined by size-exclusion chromatography (SEC) described below.

[0048] The SEC (size-exclusion chromatography) technique can separate macromolecules in a solution according to the size of the macromolecules by a column filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, and the macromolecules with the largest volume are eluted first. SEC gives an image of the polymer molar mass distribution, but it is not an absolute method. The respective number-average molar mass (Mn) and weight-average molar mass (Mw) can be determined from commercially available standard samples, and the polydispersity index (PI = Mw / Mn) can be calculated by "molar" calibration. No special treatment is carried out on the polymer sample before analysis. The polymer sample is at about 1 g·l -1The concentration is simply dissolved in the elution solvent. Then, before injection, the solution is filtered through a filter with a porosity of 0.45 μm. The device used is a Waters Acquity or Waters Alliance chromatographic line. The elution solvent is tetrahydrofuran containing 250 ppm of BHT (butylated hydroxytoluene) antioxidant, and the flow rate is 1 ml / min -1 , the column temperature is 35 °C, and the analysis time is 40 min. The column used is a set of three Agilent columns commercially named InfinityLab PolyPore. The volume of the injected sample solution is 100 μl. The detector is an Acquity or Waters 2410 differential refractometer, and the software used for processing chromatographic data is the Waters Empower system. The calculated average molar mass is relative to the calibration curve generated by polystyrene standards

[0049] The copolymer can be obtained according to various synthesis methods known to those skilled in the art, particularly depending on the target microstructure of the copolymer. Generally, it can be prepared by copolymerization of at least one 1,3-diene (preferably 1,3-butadiene) and ethylene in the presence of a catalytic system containing a metallocene complex according to a known synthesis method. In this regard, reference may be made to the metallocene complex-based catalytic systems described in the documents EP 1092731, WO 2004035639, WO 2007054223, and WO 2007054224 in the name of the applicant. The copolymer can also be prepared by using a preformed type of catalytic system (such as the catalytic systems described in the documents WO2017093654 A1, WO 2018020122 A1, and WO 2018020123 A1) (including when it is a random copolymer)

[0050] The copolymer can consist of a mixture of copolymers containing ethylene units and diene units with different microstructures and / or macrostructures from each other

[0051] Advantageously, the content of the copolymer containing ethylene units and 1,3-diene units in the composition is in the range of 60 phr to 100 phr, preferably 80 phr to 100 phr

[0052] The elastomeric matrix can advantageously contain only the copolymer containing ethylene units and 1,3-diene units as the elastomer

[0053] Alternatively, the elastomeric matrix may also contain a diene elastomer other than the copolymer comprising ethylene units and 1,3-diene units (also referred to herein as "other elastomer"). When other elastomers are present, they are in a minor proportion, i.e., they account for less than 50 wt%, 40 wt%, 30 wt%, 20 wt% or even less than 10 wt% of the elastomeric matrix. For example, the content of other elastomers in the composition may range from 0 phr to 40 phr, preferably from 0 phr to 20 phr.

[0054] The other elastomers of the elastomeric matrix of the tire according to the invention are preferably selected from highly unsaturated diene elastomers such as polybutadiene (abbreviated as "BR"), synthetic polyisoprene (IR), natural rubber (NR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers. "Highly unsaturated diene elastomer" is generally understood to mean a diene elastomer which is at least partly made from conjugated diene monomers and has a diene source (conjugated diene) unit content of more than 50% (mol%).

[0055] II-2 1,3-dipolar compound

[0056] 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.

[0057] The 1,3-dipolar compound corresponds to formula (I):

[0058]

[0059] wherein:

[0060] οQ represents an arylene diyl ring which is optionally substituted by one or more identical or different, preferably saturated, linear or branched aliphatic hydrocarbon chains which are optionally substituted or interrupted by one or more heteroatoms,

[0061] οE represents a divalent hydrocarbon group which optionally contains one or more heteroatoms.

[0062] For the purposes of the present invention, "arylene diyl ring" is understood to mean a monocyclic or polycyclic aromatic hydrocarbon group derived from an aromatic hydrocarbon (from which two hydrogen atoms have been removed). Thus, the arylene diyl ring is a divalent group.

[0063] For the purposes of the present invention, "monocyclic or polycyclic aromatic hydrocarbon group" is understood to mean one or more aromatic rings whose backbone consists of carbon atoms. In other words, there are no heteroatoms in the backbone of the ring. The arylene diyl ring may be monocyclic (i.e., consisting of a single ring) or polycyclic (i.e., consisting of a plurality of fused aromatic hydrocarbon rings); then such fused rings together have at least two consecutive carbon atoms. These rings may be fused unilaterally or cross-fused unilaterally.

[0064] Preferably, the arylene ring contains 6 to 14 carbon atoms.

[0065] The arylene ring may be unsubstituted, partially substituted or fully substituted. The arylene ring is partially substituted when one or two or more hydrogen atoms (but not all atoms) are replaced by one or two or more preferably saturated, linear or branched aliphatic hydrocarbon chains, which aliphatic hydrocarbon chains are optionally substituted by one or more heteroatoms. The chain is also referred to as a substituent. If all hydrogen atoms are replaced by the chain, the arylene ring is fully substituted. The substituents of the arylene ring may be the same or different from each other.

[0066] Preferably, when the arylene ring is substituted by one or more identical or different, preferably saturated, linear or branched aliphatic hydrocarbon chains, the aliphatic hydrocarbon chains are optionally substituted or interrupted by one or more heteroatoms, and this or these chains may be inert with respect to the N-substituted imidazolidinone functional group and the oxynitrile.

[0067] For the purposes of the present invention, a "hydrocarbon chain that is inert with respect to the N-substituted imidazolidinone functional group and the oxynitrile" is understood to mean a hydrocarbon chain that does not react with either the N-substituted imidazolidinone functional group or the oxynitrile. Thus, the hydrocarbon chain that is inert with respect to the N-substituted imidazolidinone functional group and the oxynitrile is preferably an aliphatic hydrocarbon chain that does not have an alkenyl or alkynyl functional group capable of reacting with the functional group or the group, i.e., a saturated, linear or branched aliphatic hydrocarbon chain that is optionally substituted or interrupted by one or more heteroatoms and preferably contains 1 to 24 carbon atoms.

[0068] Preferably, the group Q is C 6 -C 14 an arylene ring, the C 6 -C 14 The arylene ring is optionally substituted by one or more identical or different, preferably saturated, linear or branched aliphatic hydrocarbon chains, which aliphatic hydrocarbon chains are optionally substituted or interrupted by one or more heteroatoms. More preferably, the group Q is C 6 -C 14 an arylene ring, the C 6 -C 14 The arylene ring is optionally substituted by one or more identical or different, saturated, linear or branched C 1 -C 24 hydrocarbon chains, the C 1 -C 24 The hydrocarbon chains are optionally substituted or interrupted by one or more nitrogen heteroatoms, sulfur heteroatoms or oxygen heteroatoms. Even more preferably, the group Q is C 6 -C 14 an arylene ring, the C6 -C 14 The arylene ring is optionally substituted by one or more identical or different substituents selected from C 1 -C 12 (more preferably C 1 -C 6 , still more preferably C 1 -C 4 ) alkyl, OR’ group, -NHR’ group, and -SR’ group, where R’ is C 1 -C 12 , more preferably C 1 -C 6 , still more preferably C 1 -C 4 alkyl group.

[0069] Preferably, the compounds of formula (I) are selected from the compounds of formula (Ia) and (Ib):

[0070]

[0071] Wherein:

[0072] - The four groups selected from X 1 to X 5 of formula (Ia) and the six groups selected from X 1 to X 7 of formula (Ib) may be the same or different and represent a hydrogen atom, a halogen atom, or preferably a saturated, linear or branched aliphatic hydrocarbon chain, which is optionally substituted or interrupted by one or more heteroatoms,

[0073] - One group selected from X 1 to X 5 of formula (Ia) and one group selected from X 1 to X 7 of formula (Ib) represent a covalent bond of group E capable of attaching to a group of the following formula (IV):

[0074]

[0075] Preferably, in the compounds of formula (Ia) and (Ib), the four groups of formula (Ia) selected from X 1 to X 5 except for the covalent bond of group E capable of attaching to the group of formula (IV) and the six groups of formula (Ib) selected from X 1 to X 7 except for the covalent bond of group E capable of attaching to the group of formula (IV) may be the same or different and represent a hydrogen atom or a saturated, linear or branched C 1 -C 24Aliphatic hydrocarbon chain, said C 1 -C 24 The aliphatic hydrocarbon chain is optionally substituted or interrupted by one or more heteroatoms.

[0076] Even more preferably, in the compounds of formula (Ia) and (Ib), the four groups of formula (Ia) selected from X 1 to X 5 other than the covalent bond of group E representing the group capable of attaching to the group of formula (IV) and the six groups of formula (Ib) selected from X 1 to X 7 other than the covalent bond of group E representing the group capable of attaching to the group of formula (IV) may be the same or different and are selected from a hydrogen atom, C 1 -C 12 (more preferably C 1 -C 6 , even more preferably C 1 -C 4 ) alkyl, -OR' group, -NHR' group and -SR' group, wherein R' is C 1 -C 12 , more preferably C 1 -C 6 , even more preferably C 1 -C 4 alkyl.

[0077] Advantageously, in formula (Ia), X 2 represents the covalent bond of group E representing the group capable of attaching to the group of formula (IV) as defined above, and X 1 , X 3 , X 4 and X 5 may be the same or different and represent a hydrogen atom or preferably a saturated, linear or branched C 1 -C 24 aliphatic hydrocarbon chain, said C 1 -C 24 aliphatic hydrocarbon chain is optionally substituted or interrupted by one or more heteroatoms. More preferably, X 2 represents the covalent bond of group E representing the group capable of attaching to the group of formula (IV) as defined above, and X 1 , X 3 , X 4 and X 5 may be the same or different and are selected from a hydrogen atom, C 1 -C 12 (more preferably C 1 -C 6 , even more preferably C 1 -C 4 ) alkyl, -OR' group, -NHR' group and -SR' group, wherein R' is C 1-C 12 , more preferably C 1 -C 6 , even more preferably C 1 -C 4 alkyl group.

[0078] Even more preferably, in this embodiment, X 2 represents a covalent bond of group E capable of attaching to the group of formula (IV) as defined above, X 4 represents a hydrogen atom, X 1 , X 3 and X 5 represent preferably saturated, linear or branched C 1 -C 24 aliphatic hydrocarbon chains, said C 1 -C 24 aliphatic hydrocarbon chains are optionally substituted or interrupted by one or more heteroatoms. Even more preferably, X 2 represents a covalent bond of group E capable of attaching to the group of formula (IV) as defined above, X 4 represents a hydrogen atom, X 1 , X 3 and X 5 are the same or different and are selected from C 1 -C 12 (more preferably C 1 -C 6 , even more preferably C 1 -C 4 ) alkyl groups, -OR' groups, -NHR' groups and -SR' groups, where R' is C 1 -C 12 , more preferably C 1 -C 6 , even more preferably C 1 -C 4 alkyl group.

[0079] Advantageously, in formula (Ib), X 1 represents a covalent bond of group E capable of attaching to the group of formula (IV) as defined above, X 2 to X 7 may be the same or different and represent a hydrogen atom or preferably saturated, linear or branched C 1 -C 24 aliphatic hydrocarbon chains, said C 1 -C 24 aliphatic hydrocarbon chains are optionally substituted or interrupted by one or more heteroatoms. More preferably, X 1 represents a covalent bond of group E capable of attaching to the group of formula (IV) as defined above, X 2 to X 7 may be the same or different and are selected from a hydrogen atom, C1 -C 12 (more preferably -C 1 -C 6 , even more preferably -C 1 -C 4 ) alkyl, -OR' group, -NHR' group, and -SR' group, where R' is -C 1 -C 12 , more preferably -C 1 -C 6 , even more preferably -C 1 -C 4 alkyl. Even more preferably, in this embodiment, X 1 represents a covalent bond of group E capable of attaching to the group of formula (IV) as defined above, X 2 to X 7 are the same and represent a hydrogen atom.

[0080] In the compounds of formulas (I), (Ia), and (Ib), group E is a divalent hydrocarbon group optionally containing one or more heteroatoms. For the purposes of the present invention, "divalent hydrocarbon group" is understood to mean a spacer group (or linking group) that forms a bridge between group Q and the N-substituted imidazolidinone group, and the spacer group is saturated or unsaturated (preferably saturated), linear or branched -C 1 -C 24 hydrocarbon chain, and the -C 1 -C 24 hydrocarbon chain may optionally contain one or more heteroatoms, such as N, O, and S. The hydrocarbon chain may optionally be substituted, provided that the substituents do not react with the nitrile oxide and N-substituted imidazolidinone groups as defined above.

[0081] Preferably, in the compounds of formulas (I), (Ia), and (Ib), group E is a preferably saturated, linear or branched -C 1 -C 24 , more preferably -C 1 -C 10 , even more preferably -C 1 -C 6 hydrocarbon chain, and the hydrocarbon chain is optionally interrupted by one or more nitrogen atoms, sulfur atoms, or oxygen atoms.

[0082] Preferably, in the compounds of formulas (I), (Ia), and (Ib), group E is selected from -R-, -NH-R-, -O-R-, and -S-R-, where R is a linear or branched -C 1 -C 24 , preferably -C 1 -C 10 , more preferably -C 1 -C 6 alkylene.

[0083] Still more preferably, in the compounds of formula (I), (Ia) and (Ib), the group E is selected from -R- and -OR-, where R is a linear or branched C 1 -C 24 , preferably C 1 -C 10 , more preferably C 1 -C 6 alkylene.

[0084] Still more preferably, in the compounds of formula (I), (Ia) and (Ib), the group E is selected from -CH 2 -, -CH 2 -CH 2 -, -CH 2 -CH 2 -CH 2 -, -CH 2 -CH 2 -CH 2 -CH 2 -, -O-CH 2 -, -O-CH 2 -CH 2 -, -O-CH 2 -CH 2 -CH 2 - and -O-CH 2 -CH 2 -CH 2 -CH 2 -.

[0085] Advantageously, the 1,3-dipolar compound is selected from the compounds of formula (V) to (X) below and their meso forms:

[0086]

[0087]

[0088] Advantageously, the 1,3-dipolar compound is selected from the compounds of formula (V), (IX) and (X) and their meso forms.

[0089] The amount of the 1,3-dipolar compound introduced into the rubber composition is expressed as the molar equivalent of the imidazole ring. For example, if the 1,3-dipolar compound contains only one imidazole ring of formula (II) defined above, one mole of the imidazole ring corresponds to one mole of the 1,3-dipolar compound. If the 1,3-dipolar compound contains two imidazole rings of formula (II) defined above, two moles of the imidazole ring correspond to one mole of the 1,3-dipolar compound. In the latter case, the 1,3-dipolar compound used according to one molar equivalent of the imidazole ring corresponds to half a mole of the 1,3-dipolar compound.

[0090] According to the present invention, the amount of 1,3-dipolar compound in the composition can be between 0 and 50 molar equivalents, preferably between 0.01 and 15 molar equivalents per 100 molar monomer units constituting the copolymer. For example, it can be between 4 and 15 molar equivalents, such as 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, still more preferably between 0 and 1 molar equivalent, and actually even more preferably between 0 and 0.7 molar equivalent of imidazole ring per 100 molar monomer units constituting the copolymer. These preferred ranges can more finely optimize the trade-off between the stiffness and hysteresis of the rubber composition in the cured state according to the application of the composition (especially its application in tires). More preferably, the amount of 1,3-dipolar compound in the composition is preferably between 0.1 and 3 molar equivalents, more preferably between 0.1 and 2 molar equivalents, still more preferably between 0.1 and 1 molar equivalent, and actually even more preferably between 0.1 and 0.7 molar equivalent of imidazole ring per 100 molar monomer units constituting the copolymer.

[0091] The compound of formula (I) (especially the compounds of formula (Ia), (Ib) and (V) to (X)) can be obtained by a synthesis method comprising the following consecutive steps:

[0092] (b1) Reaction of a compound of formula (XIII) with a compound of formula (XIV) in the presence of at least one polar solvent S1 and at least one base at a temperature T1 of 70 °C to 150 °C to form a compound of formula (XV):

[0093]

[0094] wherein Q is as defined above and Y represents a nucleophilic group,

[0095]

[0096] wherein E is as defined above and Z represents an electrofugal group;

[0097]

[0098] (b2) Reaction of the compound of formula (XV) with an aqueous solution of hydroxylamine at a temperature T2 of 30 °C to 70 °C to obtain an oxime compound of formula (XVI):

[0099]

[0100] (c) Step of recovering the oxime compound of formula (XVI);

[0101] (d) A step of oxidizing the oxime compound of formula (XVI) using an oxidizing agent in the presence of at least one organic solvent S2, wherein the content of the oxidizing agent is at least 6 molar equivalents relative to the molar amount of the oxime compound of formula (XVI).

[0102] For the purposes of the present application, a "polar solvent" is understood to mean a solvent having a dielectric constant greater than 2.2.

[0103] For the purposes of the present application, a "leaving group" is understood to mean a leaving group that takes away its bonding electron pair.

[0104] For the purposes of the present application, a "nucleophilic group" is understood to mean a compound containing at least one atom with a free electron pair or containing an atom with a negative charge.

[0105] As described above, the method for synthesizing the compound of formula (I) particularly includes consecutive steps (b1) and (b2).

[0106] The two steps (b1) and (b2) can be separated by a step of separating and purifying the compound of formula (XV).

[0107] Alternatively, the two steps (b1) and (b2) can be carried out according to the one-pot synthesis method, that is, steps (b1) and (b2) are "one-pot" (two-step one-pot synthesis method), that is, the intermediate compound of formula (XV) is not separated.

[0108] The method includes step (b1) of reacting the compound of formula (XIII) having group Y as described above with the compound of formula (XIV) having group Z as described above.

[0109] Preferably, group Y is selected from a hydroxyl group, a thiol group, a primary amine or a secondary amine functional group.

[0110] Group Z can be selected from chlorine, bromine, iodine, a mesylate group, a tosylate group, an acetate group and a trifluoromethanesulfonate group.

[0111] Step (b1) of the method is carried out at a temperature T1 of 70 °C to 150 °C in the presence of at least one polar solvent S1 and at least one base.

[0112] The polar solvent S1 can be a water-miscible polar solvent, preferably a protic solvent.

[0113] Examples of the solvent S1 that can be used in the method are dimethylformamide (DMF), dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone (DMI), 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU), isopropanol, acetonitrile, ethanol, n-butanol and n-propanol.

[0114] Preferably, the protonic solvent is an alcohol solvent.

[0115] Advantageously, relative to the weight of the solvent, the compound of formula (XIII) is present in an amount of 5% to 40% by weight, preferably 10% to 30% by weight.

[0116] The base may be selected from alkali metal alkoxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydroxides, alkaline earth metal hydroxides and mixtures thereof.

[0117] Advantageously, there may be added:

[0118] - one or more catalysts selected from catalysts of the silver(I) salt type, phase transfer catalysts of the quaternary ammonium type and mixtures thereof;

[0119] - one or more ionic liquids.

[0120] Preferably, the base is selected from sodium methoxide, potassium carbonate and sodium hydroxide, more preferably potassium carbonate.

[0121] According to a particular embodiment of the method, relative to the molar amount of the compound of formula (XIII), the molar amount of the base is from 1.5 to 8 molar equivalents, preferably from 2 to 6 molar equivalents.

[0122] As described above, step (b1) of the method is carried out at a temperature T1 of from 70 °C to 150 °C.

[0123] Preferably, the temperature T1 is a temperature in the range from 70 °C to 120 °C, more preferably from 80 °C to 110 °C.

[0124] As described above, step (b1) of the method is followed by step (b2) of adding an aqueous hydroxylamine solution to the reaction medium comprising the compound of formula (XV) at a temperature T2 of from 30 °C to 70 °C.

[0125] Preferably, the addition of the aqueous hydroxylamine solution is carried out when the conversion of the compound of formula (XIII) is at least 70% by weight.

[0126] Advantageously, the temperature T2 varies from 40 °C to 60 °C.

[0127] As previously mentioned, the method further comprises a step (c) of recovering the oxime compound of formula (XVI).

[0128] Preferably, the oxime compound of formula (XVI) is recovered by precipitation with water, optionally followed by washing with water.

[0129] The method further comprises step (d) of oxidizing an oxime compound of formula (XVI) to produce a compound of formula (I) (particularly a preferred compound) in the presence of at least one organic solvent S2 using an oxidizing agent; the amount of the oxidizing agent is at least 6 molar equivalents, preferably 6.5 to 15 molar equivalents, relative to the molar amount of the oxime compound of formula (XVI).

[0130] These amounts of the oxidizing agent can be added in one portion or in batches in step (d), preferably added in two portions in step (d).

[0131] Preferably, the oxidizing agent is selected from sodium hypochlorite, N-bromosuccinimide in the presence of a base, and N-chlorosuccinimide in the presence of a base; preferably, the oxidizing agent is sodium hypochlorite.

[0132] Preferably, the organic solvent S2 is an organic solvent selected from chlorinated solvents and solvents of the ester, ether, and alcohol types, more preferably selected from dichloromethane, ethyl acetate, butyl acetate, diethyl ether, isopropanol, and ethanol, and still more preferably selected from ethyl acetate and butyl acetate.

[0133] Preferably, relative to the total weight of the combination comprising the oxime compound of formula (XVI), the organic solvent S2, and the oxidizing agent, the oxime compound of formula (XVI) accounts for 1% to 30% by weight, preferably 1% to 20% by weight. Preferably, after step (d), the method comprises step (e) of recovering the compound of formula (I).

[0134] Before step (b1), the method may comprise step (a2) of preparing a compound of formula (XIV) by reacting a compound of the following formula (XVII) with a reagent capable of forming a nucleofugic group Z:

[0135]

[0136] wherein E is as defined above.

[0137] Preferably, the reagent capable of forming a nucleofugic group Z is thionyl chloride.

[0138] Preferably, step (a2) is carried out in the absence or presence of at least one solvent S 4 (preferably a chlorinated solvent, more preferably dichloromethane).

[0139] Advantageously, step (a3) of recovering the compound of formula (X) is carried out immediately after step (a2), preferably by purification using toluene, more preferably by crystallization of the compound of formula (X) from toluene.

[0140] Other methods for obtaining 1,3-dipolar compounds corresponding to formula (I) are known to those skilled in the art, in particular from the document WO2012 / 07441.

[0141] II-3 Filler

[0142] A further essential feature of the composition according to the invention lies in its being based on a filler which mainly comprises silica.

[0143] The silica used in the composition according to the invention can be any silica known to those skilled in the art, in particular any precipitated silica or pyrogenic silica having a BET specific surface area and a CTAB specific surface area both less than 450 m 2 / g, preferably from 30 m 2 / g to 400 m 2 / g, and in particular any precipitated silica or pyrogenic silica having a BET specific surface area in the range from 60 m 2 / g to 300 m 2 / g. The silica advantageously has a BET specific surface area in the range from 125 m 2 / g to 200 m 2 / g and / or a CTAB specific surface area in the range from 140 m 2 / g to 170 m 2 / g.

[0144] The BET specific surface area of the silica is determined by gas adsorption using the Brunauer - Emmett - Teller method described in "The Journal of the American Chemical Society" (Volume 60, page 309, February 1938), more specifically according to the method adapted from Standard NF ISO 5794 - 1, Appendix E of June 2010 [multi - point (5 points) volume method - gas: nitrogen - vacuum degassing: 1 hour at 160 °C - relative pressure p / p 0 range: 0.05 to 0.17].

[0145] The CTAB specific surface area value of the silica is determined according to Standard NF ISO 5794 - 1, Appendix G of June 2010. This method is based on the adsorption of CTAB (N - hexadecyl - N,N,N - trimethylammonium bromide) on the "outer" surface of the filler.

[0146] Any type of precipitated silica can be used, especially highly dispersible precipitated silica (for "highly dispersible" or "highly dispersible silica", referred to as "HDS"). These precipitated silicas (whether or not they are highly dispersible precipitated silicas) are well known to those skilled in the art. These precipitated silicas include, for example, the silicas described in applications WO03 / 016215 - A1 and WO03 / 016387 - A1. Among the commercially available HDS silicas, those from Evonik's 5000GR and 7000GR silica, or those from Solvay's 1085GR, 1115MP, 1165MP, Premium 200MP and HRS 1200MP silica can be particularly used. As non - HDS silicas, the following commercially available silicas can be used: VN2GR and VN3GR silica from Evonik, 175GR silica from Solvay, or Hi - Sil EZ120G(-D), Hi - Sil EZ160G(-D), Hi - Sil EZ200G(-D), Hi - Sil 243LD, Hi - Sil 210, and Hi - Sil HDP 320G silica from PPG. VN3GR silica, from Solvay's 175GR silica, or from PPG's Hi - Sil EZ120G(-D), Hi - Sil EZ160G(-D), Hi - Sil EZ200G(-D), Hi - Sil 243LD, Hi - Sil 210, and Hi - Sil HDP 320G silica.

[0147] Advantageously, the filler contains more than 70% by weight, preferably more than 80% by weight of silica.

[0148] Preferably, the content of silica is in the range of 5 phr to 60 phr, preferably 10 phr to 55 phr, more preferably 15 phr to 50 phr.

[0149] In order to couple the silica to the copolymer, at least a bifunctional coupling agent (or binder) (hereinafter simply referred to as "coupling agent") designed to provide satisfactory chemical and / or physical properties between the silica (on the surface of its particles) and the copolymer can be used in a known manner. Particularly, at least bifunctional organosilanes or polyorganosiloxanes are used. The term "bifunctional" is understood to mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the copolymer. For example, such a bifunctional compound can contain a first functional group containing a silicon atom and a second functional group containing a sulfur atom, the first functional group being capable of interacting with the hydroxyl groups of the inorganic filler, and the second functional group being capable of interacting with the copolymer.

[0150] Examples of coupling agents can be found by the person skilled in the art in the following documents: WO 02 / 083782, WO 02 / 30939, WO 02 / 31041, WO 2007 / 061550, WO 2006 / 125532, WO 2006 / 125533, WO 2006 / 125534, US 6849754, WO 99 / 09036, WO 2006 / 023815, WO 2007 / 098080, WO 2010 / 072685 and WO 2008 / 055986.

[0151] The use of a coupling agent is not mandatory, but is preferred. If a coupling agent is used, the content of the coupling agent in the composition according to the invention is advantageously between 0.5% by weight and 15% by weight relative to the weight of the silica. The person skilled in the art can easily adjust the amount of the coupling agent according to the content of the reinforcing inorganic filler used in the composition according to the invention.

[0152] Advantageously, the coupling agent is an organosilane selected from organosilane polysulfides, polyorganosiloxanes, mercapto silanes, acrylosilanes and méthacrylosilanes.

[0153] The composition according to the invention may comprise fillers other than silica, but this is not mandatory. These fillers may in particular be organic fillers, such as carbon black.

[0154] The carbon black that can be used in the context of the present invention can be any carbon black conventionally used in pneumatic or non-pneumatic tires or their treads ("tire grade" carbon black). Among the tire grade carbon blacks, the reinforcing carbon blacks of the 100, 200 and 300 series, or the carbon blacks of the 500, 600 or 700 series (ASTM grades) will be mentioned more particularly, such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683 and N772 carbon blacks. These carbon blacks can be used in a commercially available individual state, or in any other form (such as as a carrier for some of the rubber additives used). The carbon black can for example already have been introduced into a copolymer (in particular an isoprene copolymer) in the form of a masterbatch (see for example applications WO 97 / 36724 and WO 99 / 16600). Mixtures of several carbon blacks can also be used in a defined amount.

[0155] Advantageously, carbon black is used in an amount of less than or equal to 20 phr, more preferably less than or equal to 10 phr (for example, the carbon black content can range from 0.5 phr to 20 phr, especially from 1 phr to 10 phr). Within this range, the coloring properties (black colorant) and UV stabilizing properties of carbon black are benefited without adversely affecting the typical performance quality provided by the reinforcing inorganic filler.

[0156] Preferably, the filler comprises silica between 80 wt% and 99 wt% and carbon black between 1 wt% and 20 wt%.

[0157] II-4 Crosslinking system

[0158] The composition according to the invention further comprises a crosslinking system comprising at least one free radical polymerization initiator and a crosslinking aid selected from (meth)acrylate compounds, maleimide compounds, allyl compounds, vinyl compounds and mixtures thereof.

[0159] Free radical polymerization initiator

[0160] The free radical polymerization initiator is a source of free radicals required for the polymerization of the composition according to the invention. These compounds are well known to those skilled in the art and are described, for example, in particular in the documents WO 2002 / 22688 A1 and FR 2899808A1 and in the document by Denisov et al. (Handbook of Free Radical Initiators, John Wiley & Sons, 2003).

[0161] Preferably, according to the invention, at least the free radical polymerization initiator is selected from peroxides, azo compounds, redox (oxidation / reduction) systems and mixtures thereof, preferably from peroxides, azo compounds and mixtures thereof. More preferably, at least the free radical polymerization initiator is a peroxide or a mixture of peroxides. It can be any peroxide known to those skilled in the art. Among the peroxides known to those skilled in the art, organic peroxides are preferably used in the context of the present invention.

[0162] The term "organic peroxide" is understood to mean an organic compound (i.e., a carbon-containing compound) containing an -O-O- group (two oxygen atoms linked by a covalent single bond). During the crosslinking process, the organic peroxide decomposes at its unstable O-O bond, thereby generating free radicals. These free radicals are capable of generating crosslinking bonds.

[0163] The organic peroxides are preferably selected from the group consisting of or consisting of the following compounds: dialkyl peroxides, monoperoxycarbonates, diacyl peroxides, peroxyketals and peroxyesters.

[0164] Preferably, the dialkyl peroxide is selected from or consists of the group of compounds including the following: dicumyl peroxide, di(tert-butyl) peroxide, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-amylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne, 2,5-dimethyl-2,5-di(tert-amylperoxy)hex-3-yne, α,α'-di[(tert-butylperoxy)isopropyl]benzene, α,α'-di[(tert-amylperoxy)isopropyl]benzene, di(tert-amyl) peroxide, 1,3,5-tri[(tert-butylperoxy)isopropyl]benzene, 1,3-dimethyl-3-(tert-butylperoxy)butanol, and 1,3-dimethyl-3-(tert-amylperoxy)butanol.

[0165] Some monoperoxycarbonates can also be used, such as O-(2-ethylhexyl) monoperoxycarbonate OO-tert-butyl ester, O-isopropyl monoperoxycarbonate OO-tert-butyl ester, and O-(2-ethylhexyl) monoperoxycarbonate OO-tert-amyl ester.

[0166] Among the diacyl peroxides, the preferred peroxide is benzoyl peroxide.

[0167] Among the peroxyketals, the preferred peroxides are selected from or consist of the group of compounds including the following: 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl 4,4-di(tert-butylperoxy)valerate, ethyl 3,3-di(tert-butylperoxy)butyrate, 2,2-di(tert-amylperoxy)propane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (or methyl ethyl ketone peroxide cyclic trimer), 3,3,5,7,7-pentamethyl-1,2,4-trioxepane, n-butyl 4,4-bis(tert-amylperoxy)valerate, ethyl 3,3-di(tert-amylperoxy)butyrate, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-amylperoxy)cyclohexane, and mixtures thereof. Preferably, the peroxy esters are selected from tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, and tert-butyl peroxy-3,5,5-trimethylhexanoate.

[0168] In general, the organic peroxides are particularly preferably selected from dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl) peroxide, tert-butyl cumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, n-butyl 4,4'-bis(tert-butylperoxy)valerate, O-(2-ethylhexyl) monoperoxycarbonate OO-(tert-butyl) ester, tert-butyl isopropylcarbonate peroxide, tert-butyl benzoate peroxide, tert-butyl 3,5,5-trimethylhexanoate peroxide, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof. More preferably, the organic peroxides are selected from dicumyl peroxide, n-butyl 4,4'-bis(tert-butylperoxy)valerate, O-(2-ethylhexyl) monoperoxycarbonate OO-(tert-butyl) ester, tert-butyl isopropylcarbonate peroxide, tert-butyl benzoate peroxide, tert-butyl 3,5,5-trimethylhexanoate peroxide, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof.

[0169] As examples of commercially available peroxides that can be used in the context of the present invention, mention may be made of Dicup from Hercules Powder Co., Perkadox Y12 from Noury van der Lande, Peroximon F40 from Montecatini Edison S.p.A., Trigonox from Noury van der Lande, Varox from R.T. Vanderbilt Co. or Luperko from Wallace & Tiernan Inc.

[0170] The term "azo compound" is understood to mean a compound whose molecular structure contains at least one -N=N- bond (two nitrogen atoms linked by a covalent double bond).

[0171] Preferably, the azo compound is selected from 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 4,4'-azobis(4-cyanopentanoic acid), 1,1'-azobis(cyclohexanecarbonitrile), 2-(tert-butylazo)-2-cyanopropane, 2,2'-azobis[2-methyl-N-(1,1)-bis(hydroxymethyl)-2-hydroxyethyl]propionamide, 2,2'-azobis(2-methyl-N-hydroxyethyl)propionamide, 2,2'-azobis(N,N'-dimethyleneisobutyramide) dichloride, 2,2'-azobis(2-amidinopropane) dichloride, 2,2'-azobis(N,N'-dimethyleneisobutyramide), 2,2'-azobis(2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide), 2,2'-azobis(2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(isobutyramide) dihydrate, and mixtures thereof.

[0172] As an example of a commercially available azo compound that can be used in the context of the present invention, 2,2'-azobis(isobutyronitrile) from Sigma-Aldrich may be mentioned.

[0173] The term "redox system" is understood to mean a combination of compounds that cause an oxidation-reduction reaction resulting in the generation of free radicals.

[0174] For example, it can be a combination of a peroxide and a tertiary amine (e.g., benzoyl peroxide plus dimethylaniline), or a combination of a hydroperoxide and a transition metal (e.g., cumene hydroperoxide plus cobalt naphthenate mixture).

[0175] Advantageously, the content of the free radical initiator (preferably an organic peroxide) in the composition according to the present invention is in the range of 0.1 phr to 10 phr, preferably 0.1 phr to 3 phr, more preferably 0.2 phr to 2.5 phr.

[0176] Relative to the weight of the crosslinking aid, the content of the free radical polymerization initiator in the composition is preferably in the range of 1 wt% to 10 wt%, preferably between 1.25 wt% and 8 wt%, preferably between 2 wt% and 5 wt%, preferably between 3 wt% and 4 wt%.

[0177] Crosslinking aid

[0178] According to the present invention, the crosslinking aid is selected from (meth)acrylate compounds, maleimide compounds, allyl compounds, vinyl compounds, and mixtures thereof.

[0179] Preferably, the crosslinking aid comprises a (meth)acrylate compound in the form of a metal salt or an ester or a polymer form.

[0180] More preferably, the crosslinking aid comprises an acrylate derivative of formula (XI):

[0181] [X] p A(XI)

[0182] wherein:

[0183] -[X] p corresponds to a group of formula (XII):

[0184]

[0185] wherein:

[0186] οR 1 、R 2 and R 3 independently represent a hydrogen atom or a C 1 -C 8 hydrocarbyl group, said C 1 -C 8 hydrocarbyl group being selected from alkylaryl, aryl, arylalkyl and linear, branched or cyclic alkyl, and optionally interrupted by one or more heteroatoms, R 2 and R 3 being able to jointly form a non-aromatic ring,

[0187] ο(*) represents the attachment point of the group of formula (XII) to A,

[0188] -A represents an atom selected from alkaline earth metals or transition metals, a carbon atom or a C 1 -C 30 hydrocarbyl group, said C 1 -C 30 hydrocarbyl group being optionally interrupted and / or substituted by one or more heteroatoms,

[0189] -A contains p free valences, the value of p being from 2 to 6,

[0190] -It should be understood that the 2 to 6 X groups are the same or different.

[0191] According to the present invention, the bond between X and A can be an ionic bond or a covalent bond. It is clearly understood by those skilled in the art that when A represents an atom selected from alkaline earth metals and transition metals (in particular Zn or Mg), the bond between X and A is an ionic bond. Furthermore, it is clearly understood by those skilled in the art that when A represents a carbon atom or a C 1 -C 30 hydrocarbyl group, the bond between X and A is a covalent bond.

[0192] Cyclic alkyl is understood to mean an alkyl containing one or more rings.

[0193] A hydrocarbyl group or chain interrupted by one or more heteroatoms is understood to mean a group or chain containing one or more heteroatoms, each heteroatom being between two carbon atoms of the group or the chain, or between a carbon atom of the group or the chain and another heteroatom of the group or the chain, or between two other heteroatoms of the group or the chain.

[0194] A hydrocarbyl group or chain substituted by one or more heteroatoms is understood to mean a group or chain containing one or more heteroatoms, each heteroatom being covalently bonded to the hydrocarbyl group or chain without interrupting the hydrocarbyl group or chain.

[0195] The heteroatoms of A can be selected from oxygen atoms, sulfur atoms, nitrogen atoms, silicon atoms, phosphorus atoms and combinations thereof. Preferably, the heteroatoms of A are selected from oxygen atoms and sulfur atoms. More preferably, the heteroatom of A is an oxygen atom.

[0196] In other words, A advantageously represents a linear, branched or cyclic C 4 -C 30 hydrocarbyl group, wherein the C 4 -C 30 hydrocarbyl group is interrupted and / or substituted by one or more heteroatoms selected from oxygen atoms, sulfur atoms, nitrogen atoms, silicon atoms or phosphorus atoms and combinations thereof, preferably selected from oxygen atoms and sulfur atoms. More preferably, A advantageously represents a linear, branched or cyclic (preferably linear or branched) C 4 -C 30 hydrocarbyl group, wherein the C 4 -C 30 hydrocarbyl group is interrupted and / or substituted by one or more oxygen atoms and / or sulfur atoms, preferably interrupted and / or substituted by one or more oxygen atoms.

[0197] Preferably, A represents a linear, branched or cyclic (preferably linear or branched) C 4 -C 30 hydrocarbyl group, wherein the C 4 -C 30 hydrocarbyl group is interrupted by one or more oxygen atoms and / or sulfur atoms, preferably interrupted by one or more oxygen atoms. More preferably, A represents a linear or branched C 4 -C 30 alkyl group interrupted by one or more oxygen atoms.

[0198] When A represents a C 4 -C 30 hydrocarbyl group, it can be, for example, C 5 -C 20 , preferably C 6 -C 16 hydrocarbyl group.

[0199] When A comprises a cyclic hydrocarbon group, it may be a non-aromatic cyclic hydrocarbon group or an aromatic cyclic hydrocarbon group.

[0200] R 1 , R 2 , R 3 The heteroatoms of the A group may independently be oxygen, sulfur, nitrogen, phosphorus or silicon atoms, preferably oxygen or nitrogen atoms.

[0201] Regardless of the nature of the A group, R 1 , R 2 and R 3 can independently represent a hydrogen atom, a methyl group or an ethyl group; preferably, R 1 , R 2 and R 3 Each independently represents a hydrogen atom or a methyl group.

[0202] Advantageously, R 1 Can represent methyl, R 2 and R 3 may each represent a hydrogen atom. 1 , R 2 and R 3 may each represent a hydrogen atom.

[0203] The valence number p depends on the nature of the group A. According to the invention, p may be 2, 3, 4, 5 or 6. Preferably, p is 2, 3 or 4, preferably 2 or 3, preferably 2.

[0204] Advantageously, regardless of R 1 , R 2 and R 3 How the group:

[0205] -A represents an atom selected from alkaline earth metals or transition metals, a carbon atom or C 1 -C 13 , preferably C 1 -C 8 The hydrocarbon group,

[0206] -A contains p free valences, the value of p is 2 to 4,

[0207] It is to be understood that the X groups of the 2 to 4 acrylate derivatives of formula (VIII) are identical or different, preferably identical.

[0208] According to the invention, when A represents an atom selected from alkaline earth metals or transition metals, it may, for example, be an atom selected from Zn and Mg.

[0209] When A means C 1 -C 13 , preferably C 1 -C8 When it is a hydrocarbyl group, it can be, for example, C 1 -C 7 , preferably C 1 -C 6 hydrocarbyl group.

[0210] Preferably, A represents a C 1 -C 13 hydrocarbyl group, and the C 1 -C 13 hydrocarbyl group is selected from the following groups:

[0211]

[0212] wherein m is an integer from 1 to 13, and (*) represents the attachment point of A to the group of formula (IX).

[0213] Advantageously, the C 1 -C 13 hydrocarbyl group is a *-(CH 2 ) m -* group, wherein m is an integer from 1 to 13, preferably from 1 to 8, more preferably from 1 to 6, and (*) represents the attachment point of A to the group of formula (IX).

[0214] Thus, according to the present invention, the acrylate derivatives of formula (VIII) can be selected from zinc dimethacrylate (ZDMA), magnesium dimethacrylate (MgDMA), zinc diacrylate (ZDA), magnesium diacrylate (MgDA), trimethylolpropane trimethacrylate (TMPTMA), trimethylolpropane triacrylate (TMPTA), 1,6 - hexanediol diacrylate (HDDA) and mixtures thereof.

[0215] Examples of commercially available ones are diacrylate derivatives, such as zinc diacrylate (ZDA) Dymalink 633 from Cray Valley, zinc dimethacrylate (ZDMA) Dymalink 634 from Cray Valley, trimethylolpropane trimethacrylate (TMPTMA) SR351 from Sartomer or 1,6 - hexanediol diacrylate (HDDA) from Sigma - Aldrich.

[0216] Advantageously, the content of the cross - linking aid (preferably the total content of the cross - linking aid) in the composition according to the present invention is in the range of 1 phr to 20 phr, preferably 2 phr to 10 phr, more preferably between 2 phr and 5 phr.

[0217] Advantageously, the amount of free radical polymerization initiator in the composition is in the range of 1% to 10% by weight, preferably between 1.25% and 8% by weight, preferably between 2% and 5% by weight, preferably between 3% and 4% by weight, relative to the weight of the crosslinking aid in the composition.

[0218] Also advantageously, the ratio of the content of silica to the content of crosslinking aid is in the range of 2 to 9, preferably 3 to 7.

[0219] Sulfur

[0220] Furthermore, the composition according to the invention advantageously does not contain sulfur as a vulcanizing agent, or contains less than 0.5 phr, preferably less than 0.3 phr, preferably less than 0.2 phr, preferably less than 0.1 phr of sulfur as a vulcanizing agent. The sulfur can be elemental sulfur or can be derived from a sulfur donor, such as alkylphenol disulfide (APDS).

[0221] II-5 Possible additives

[0222] The rubber composition may also optionally contain all or some of the common additives typically used in elastomeric compositions for tires, such as plasticizers (such as plasticizing oils and / or plasticizing resins), pigments, protective agents (such as anti-ozone waxes, chemical anti-ozone agents, antioxidants), anti-fatigue agents, reinforcing resins (such as the reinforcing resins described in application WO02 / 10269).

[0223] II-6 Preparation of the rubber composition

[0224] The composition according to the invention can be manufactured in two successive preparation stages known to those skilled in the art in a suitable mixer:

[0225] - The first stage of thermomechanical working or kneading ("non-production stage") can be carried out in a single thermomechanical step in which all the necessary components (in particular the elastomeric matrix, fillers, crosslinking aids and optionally other various additives other than the free radical polymerization initiator) are introduced into a suitable mixer (such as a standard closed mixer (such as a 'Banbury' type)). The optional fillers can be introduced into the elastomer by thermomechanical kneading either in one go or in batches. In the case where the fillers have been added in whole or in part to the elastomer in the form of a masterbatch (such as described in applications WO 97 / 36724 and WO 99 / 16600), the masterbatch kneaded directly, other elastomers or fillers present in the composition not in the form of a masterbatch (if appropriate) and optionally other various additives are added in addition to the crosslinking system. The non-production stage can be carried out at a high temperature, the maximum temperature being between 110 °C and 200 °C, preferably between 130 °C and 185 °C, and the duration generally being between 2 minutes and 10 minutes;

[0226] - After cooling the mixture obtained during the first non-production stage to a lower temperature (usually below 120 °C, for example between 40 °C and 100 °C), a second stage ("production" stage) of mechanical working is carried out in an open mixer (for example, a mill). Then a free-radical polymerization initiator is introduced and the combined mixture is kneaded for a few minutes, for example between 5 minutes and 15 minutes.

[0227] These stages have been described, for example, in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO 00 / 05300 or WO 00 / 05301.

[0228] The final composition thus obtained is then calendered (especially for laboratory characterization) in the form of sheets or plates, for example, or extruded (or co-extruded with another rubber composition) in the form of a rubber semi-finished product (or molding element) that can be used, for example, for a tire tread. These products can then be used to manufacture tires according to techniques known to those skilled in the art.

[0229] Crosslinking of the composition can be carried out under pressure, for example, at a temperature between 130 °C and 200 °C, in a manner known to those skilled in the art.

[0230] This application also describes a method for preparing a rubber composition according to the invention further comprising a crosslinking system, the method comprising the following steps:

[0231] - During the first "non-production" stage, a 1,3-dipolar compound, a filler and a crosslinking aid are added to the copolymer by thermomechanical kneading until a maximum temperature between 130 °C and 200 °C is reached,

[0232] - Cooling the combined mixture to a temperature below 100 °C,

[0233] - Subsequently introducing a free-radical polymerization initiator,

[0234] - Kneading the combined mixture to a maximum temperature below 120 °C.

[0235] The amount of 1,3-dipolar compound added is preferably between 0 molar equivalents and 3 molar equivalents, more preferably between 0 molar equivalents and 2 molar equivalents, still more preferably between 0 molar equivalents and 1 molar equivalent, and in fact even still more preferably between 0 molar equivalents and 0.7 molar equivalents of imidazole ring / 100 moles of monomer units constituting the copolymer. For each of these preferred ranges, the lower limit is preferably at least 0.1 molar equivalent of 1,3-dipolar compound.

[0236] Advantageously, the 1,3-dipolar compound is mixed with the copolymer before introducing the other components of the rubber composition, in particular before adding the filler. The contact time between the intimately mixed (in particular thermomechanically kneaded) copolymer and the 1,3-dipolar compound is adjusted according to the mixing (in particular thermomechanical kneading) conditions, in particular according to the temperature. The higher the temperature, the shorter the contact time. Generally, at a temperature of 100°C to 130°C, it is 1 to 5 minutes.

[0237] Preferably, at least one antioxidant is preferably incorporated into the copolymer before introducing it into the mixer, in particular at the end of the synthesis of the copolymer, as is conventionally done.

[0238] After introducing all the components of the rubber composition, the resulting final composition is then calendered (especially for laboratory characterization) or extruded, for example in the form of sheets or slabs, so as to form a rubber molding element, for example intended to be used as a rubber component for manufacturing tires.

[0239] II-7 Rubber article

[0240] Another subject of the present invention is a rubber article comprising at least one composition according to the present invention.

[0241] In view of the improved performance compromise within the context of the present invention, the rubber article is advantageously selected from pneumatic tires, non-pneumatic tires, tracks and conveyor belts. Preferably, the rubber article is a pneumatic tire or a non-pneumatic tire.

[0242] More particularly, another subject of the present invention is a pneumatic tire or a non-pneumatic tire provided with a tread comprising at least one composition according to the present invention.

[0243] Another subject of the present invention is a rubber track and a rubber conveyor belt comprising a composition according to the present invention, said rubber track comprising at least one rubber element, said at least one rubber element comprising at least one composition according to the present invention, said at least one rubber element being preferably an endless rubber belt or a plurality of rubber pads.

[0244] The present invention relates to the above-mentioned rubber articles in the unvulcanized state (i.e. before curing) and in the cured state (i.e. after crosslinking or vulcanization).

[0245] III - Preferred embodiments

[0246] According to the above description, the preferred embodiments of the present invention are described as follows:

[0247] 1. A rubber composition, said rubber composition being at least based on:

[0248] - An elastomeric matrix comprising a copolymer containing ethylene units and 1,3-diene units in an amount greater than 50 phr, wherein the ethylene units in the copolymer account for more than 50 mol% of the monomer units of the copolymer,

[0249] - A 1,3-dipolar compound corresponding to formula (I):

[0250]

[0251] wherein:

[0252] οQ represents an arylene ring which is optionally substituted by one or more identical or different, preferably saturated, linear or branched aliphatic hydrocarbon chains, which aliphatic hydrocarbon chains are optionally substituted or interrupted by one or more heteroatoms,

[0253] οE represents a divalent hydrocarbon group optionally containing one or more heteroatoms,

[0254] - A filler mainly comprising silica, and

[0255] - A crosslinking system comprising at least one free radical polymerization initiator and a crosslinking aid selected from (meth)acrylate compounds, maleimide compounds, allyl compounds, vinyl compounds and mixtures thereof.

[0256] 2. The composition according to embodiment 1, wherein the ethylene units in the copolymer are between 50 mol% and 95 mol%, preferably between 55 mol% and 90 mol%, of the monomer units of the copolymer.

[0257] 3. The composition according to any one of the foregoing embodiments, wherein the copolymer containing ethylene units and 1,3-diene units is a copolymer of ethylene and 1,3-diene.

[0258] 4. The composition according to any one of the foregoing embodiments, wherein the 1,3-diene is 1,3-butadiene.

[0259] 5. The composition according to any one of the foregoing embodiments, wherein the copolymer comprises units of formula (II) or units of formula (III) or units of formula (II) and units of formula (III):

[0260]

[0261] -CH 2 -CH(CH=CH 2 )- (III)

[0262] 6. A composition according to any one of the foregoing embodiments, wherein the mole percentages (o and p, respectively) of the units of formula (II) and the units of formula (III) in the copolymer satisfy the following equation (Equation 1), preferably satisfy Equation (Equation 2), and o and p are calculated based on all monomer units of the copolymer.

[0263] 0 < o + p ≤ 25 (Equation 1)

[0264] 0 < o + p < 20 (Equation 2)

[0265] 7. A composition according to any one of the foregoing embodiments, wherein the copolymer comprising ethylene units and 1,3-diene units is a random copolymer.

[0266] 8. A composition according to any one of the foregoing embodiments, wherein the content of the copolymer comprising ethylene units and 1,3-diene units is in the range of 60 phr to 100 phr, preferably 80 phr to 100 phr.

[0267] 9. A composition according to any one of the foregoing embodiments, wherein the compound of formula (I) is selected from the compounds of formula (Ia) and (Ib):

[0268]

[0269]

[0270] Wherein:

[0271] - The four groups of formula (Ia) selected from X 1 to X 5 and the six groups of formula (Ib) selected from X 1 to X 7 may be the same or different and represent a hydrogen atom, a halogen atom, or preferably a saturated, linear or branched aliphatic hydrocarbon chain, which aliphatic hydrocarbon chain is optionally substituted or interrupted by one or more heteroatoms.

[0272] - One group of formula (Ia) selected from X 1 to X 5 and one group of formula (Ib) selected from X 1 to X 7 represents a covalent bond of a group E capable of attaching to the following formula (IV):

[0273]

[0274] 10. A composition according to any one of the foregoing embodiments, wherein the group E is preferably a saturated, linear or branched C 1 - C 24 , preferably C1 -C 10 , more preferably C 1 -C 6 hydrocarbon chain, said hydrocarbon chain being optionally interrupted by one or more nitrogen atoms, sulfur atoms or oxygen atoms.

[0275] 11. The composition according to any one of the foregoing embodiments, wherein the 1,3-dipolar compound is selected from compounds of the following formulas (V) to (X) and their meso forms:

[0276]

[0277]

[0278] 12. The composition according to embodiment 11, wherein the 1,3-dipolar compound is selected from compounds of formulas (V), (IX) and (X) and their meso forms.

[0279] 13. The composition according to any one of the foregoing embodiments, wherein the content of the 1,3-dipolar compound is between 0 molar equivalents and 50 molar equivalents, preferably between 0.01 molar equivalents and 15 molar equivalents, for example between 4 molar equivalents and 15 molar equivalents per 100 molar monomer units constituting the copolymer.

[0280] 14. The composition according to any one of embodiments 1 to 12, wherein the content of the 1,3-dipolar compound is between 0.1 molar equivalent and 3 molar equivalents, preferably between 0.1 molar equivalent and 2 molar equivalents, even more preferably between 0.1 molar equivalent and 1 molar equivalent, and in fact even more preferably between 0.1 molar equivalent and 0.7 molar equivalents of imidazole ring per 100 molar monomer units constituting the diene elastomer.

[0281] 15. The composition according to any one of the foregoing embodiments, wherein the filler comprises more than 70% by weight, preferably more than 80% by weight of silica.

[0282] 16. The composition according to any one of the foregoing embodiments, wherein the filler comprises silica between 80% and 99% by weight and carbon black between 1% and 20% by weight.

[0283] 17. The composition according to any one of the foregoing embodiments, wherein the content of silica is in the range of 5 phr to 60 phr, preferably 10 phr to 55 phr, more preferably 15 phr to 50 phr.

[0284] 18. The composition according to any one of the foregoing embodiments, the composition further comprises a reagent for coupling silica to the copolymer, the coupling agent is preferably an organosilane, and the organosilane is selected from organosilane polysulfides, polyorganosiloxanes, mercapto silanes, acryloxy silanes and methacryloxy silanes.

[0285] 19. The composition according to any one of the foregoing embodiments, wherein the free radical polymerization initiator is selected from peroxides, azo compounds, redox (oxidation / reduction) systems and mixtures thereof.

[0286] 20. The composition according to any one of the foregoing embodiments, wherein the free radical polymerization initiator is an organic peroxide, and the organic peroxide is selected from dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl) peroxide, tert-butyl cumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, n-butyl 4,4'-bis(tert-butylperoxy)valerate, O-(2-ethylhexyl) monoperoxycarbonate OO-(tert-butyl) ester, tert-butyl isopropyl carbonate peroxide, tert-butyl benzoate peroxide, tert-butyl 3,5,5-trimethylhexanoate peroxide, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof, preferably selected from dicumyl peroxide, n-butyl 4,4'-bis(tert-butylperoxy)valerate, O-(2-ethylhexyl) monoperoxycarbonate OO-(tert-butyl) ester, tert-butyl isopropyl carbonate peroxide, tert-butyl benzoate peroxide, tert-butyl 3,5,5-trimethylhexanoate peroxide, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof.

[0287] 21. The composition according to any one of the foregoing embodiments, wherein the content of the free radical polymerization initiator is in the range of 0.1 phr to 3 phr, preferably 0.2 phr to 2.5 phr.

[0288] 22. The composition according to any one of the foregoing embodiments, wherein, relative to the weight of the crosslinking aid, the content of the free radical polymerization initiator is in the range of 1 wt% to 10 wt%, preferably between 1.25 wt% and 8 wt%, preferably between 2 wt% and 5 wt%, preferably between 3 wt% and 4 wt%.

[0289] 23. The composition according to any one of the foregoing embodiments, wherein the crosslinking aid comprises an acrylate derivative of formula (XI):

[0290] [X] p A(XI)

[0291] Wherein:

[0292] ο[X]p Group corresponding to formula (XII):

[0293]

[0294] wherein:

[0295] ·R 1 、R 2 and R 3 independently represent a hydrogen atom or a C 1 -C 8 hydrocarbyl group, and the C 1 -C 8 hydrocarbyl group is selected from alkylaryl, aryl, arylalkyl, and linear, branched or cyclic alkyl groups, and is optionally interrupted by one or more heteroatoms, R 2 and R 3 can together form a non-aromatic ring,

[0296] ·(*) represents the attachment point of the group of formula (XII) to A,

[0297] οA represents an atom selected from alkaline earth metals or transition metals, a carbon atom or a C 1 -C 30 hydrocarbyl group, and the C 1 -C 30 hydrocarbyl group is optionally interrupted and / or substituted by one or more heteroatoms,

[0298] οA contains p free valences, and the value of p is from 2 to 6,

[0299] It should be understood that the 2 to 6 X groups are the same or different.

[0300] 24. The composition according to embodiment 23, wherein in the acrylate derivative of formula (XI):

[0301] οA represents an atom selected from alkaline earth metals or transition metals, a carbon atom or a C 1 -C 13 hydrocarbyl group,

[0302] οA contains p free valences, and the value of p is from 2 to 4,

[0303] It should be understood that the 2 to 4 X groups are the same or different.

[0304] 25. The composition according to embodiment 23 or 24, wherein R 1 、R 2 and R 3 independently of one another represent a hydrogen atom, a methyl or an ethyl group.

[0305] 26. The composition according to any one of embodiments 23 to 25, wherein R1 represents methyl, R 2 and R 3 each represents a hydrogen atom.

[0306] 27. The composition according to any one of embodiments 23 to 25, wherein R 1 , R 2 and R 3 each represents a hydrogen atom.

[0307] 28. The composition according to any one of embodiments 23 to 27, wherein p is 2 or 3, preferably 2.

[0308] 29. The composition according to any one of embodiments 23 to 27, wherein A represents an atom selected from Zn and Mg.

[0309] 30. The composition according to any one of embodiments 23 to 27, wherein A represents C 1 -C 13 hydrocarbyl, and the C 1 -C 13 hydrocarbyl is selected from the following groups:

[0310]

[0311] wherein m is an integer from 1 to 13, and (*) represents the attachment point of A to the group of formula (XII).

[0312] 31. The composition according to any one of the foregoing embodiments, wherein the content of the crosslinking aid is in the range of 1 phr to 20 phr, preferably 2 phr to 10 phr, and more preferably between 2 phr and 5 phr.

[0313] 32. The composition according to any one of the foregoing embodiments, wherein the ratio of the content of silica to the content of the crosslinking aid is in the range of 2 to 9, preferably 3 to 7.

[0314] 33. The composition according to any one of the foregoing embodiments, wherein the composition does not contain molecular sulfur or sulfur donors as vulcanizing agents, or contains less than 0.5 phr, preferably less than 0.3 phr, and more preferably less than 0.1 phr of molecular sulfur or sulfur donors as vulcanizing agents.

[0315] 34. A rubber product comprising the composition defined in any one of embodiments 1 to 33.

[0316] 35. The rubber product according to embodiment 34, wherein the product is selected from pneumatic tires, non-pneumatic tires, rubber tracks, and conveyor belts.

[0317] 36. An inflated or non-inflated tire, said inflated or non-inflated tire comprising the composition defined in any one of embodiments 1 to 33.

[0318] 37. The inflated or non-inflated tire according to embodiment 36, wherein the composition defined in any one of embodiments 1 to 33 is present in the tread.

[0319] IV - Examples

[0320] IV-1 Measurements and tests used

[0321] Determination of molar mass: Size exclusion chromatography analysis of the copolymer

[0322] a) For copolymers soluble in tetrahydrofuran (THF) at room temperature, the molar mass was determined by size exclusion chromatography in THF. Samples were injected into a series of Polymer Laboratories columns at a flow rate of 1 ml.min -1 using a Waters 717 syringe and a Waters 515 HPLC pump. The series of columns placed in a chamber maintained at a constant temperature of 45 °C consisted of:

[0323] - 1 PL Gel 5 μm pre-column,

[0324] - 2 PL Gel 5 μm Mixed C columns,

[0325] - 1 PL Gel column.

[0326] Detection was carried out using a Waters 410 refractometer. The molar mass was determined by universal calibration using polystyrene standard samples certified by Polymer Laboratories and double detection using a refractometer connected to a viscometer.

[0327] SEC enables an understanding of the molecular mass distribution of polymers, but it is not an absolute method. Based on standard commercial polystyrene types, various number-average masses (Mn) and weight-average masses (Mw) can be determined, and the polydispersity index (PI = Mw / Mn) can be calculated.

[0328] b) For copolymers insoluble in tetrahydrofuran at ambient temperature, the molar mass was determined in 1,2,4-trichlorobenzene. First, the copolymer was dissolved under thermal conditions (4 hours at 150 °C), and then at 150 °C at a flow rate of 1 ml.min -1The flow rate is used to inject it into a Waters Alliance GPCV 2000 chromatograph equipped with three Styragel columns (2 HT6E columns and 1 HT2 column). Detection is carried out using a Waters refractometer. The molar mass is determined by relative calibration using polystyrene standards certified by Polymer Laboratories.

[0329] Determination of molar fraction

[0330] For the 1 H NMR and 13 C NMR techniques specifically used in this application for determining the molar fractions of ethylene units, conjugated diene units, and any trans-1,2-cyclohexane units, refer to the article "Investigation of ethylene / butadiene copolymers microstructure by 1 H and 13 C NMR, Llauro M.F., Monnet C., Barbotin F., Monteil V., Spitz R., Boisson C., Macromolecules 2001, 34, 6304-6311".

[0331] NMR analysis

[0332] The structural analysis of the synthesized molecules and the determination of molar purity are carried out by NMR analysis. Spectra are acquired on a Bruker Avance 3400 MHz spectrometer equipped with a 5 mm BBFOZ-class "broadband" probe. Quantitative 1 H NMR experiments use a simple 30° pulse sequence and a repetition time of 3 seconds between each of the 64 acquisitions. The sample is dissolved in deuterated dimethyl sulfoxide (DMSO). This solvent is also used to lock the signal. Calibration is carried out on the proton signal of deuterated DMSO at 2.44 ppm relative to the TMS reference at 0 ppm. 1 H NMR spectra together with 2D 1 H / 13 C HSQC and 1 H / 13 C HMBC experiments can determine the molecular structure (refer to the assignment table). Molar quantification is carried out by quantitative 1D 1 H NMR spectra.

[0333] Mooney ML 1+4

[0334] Mooney plasticity measurements are carried out according to the following principle and according to the standard ASTM D - 1646. The usually unprocessed polymer is molded in a cylindrical chamber heated to a given temperature (usually 100 °C). After preheating for one minute, an L - shaped rotor rotates at 2 revolutions per minute within the specimen, and the working torque for maintaining this movement is measured after 4 minutes of rotation. The Mooney plasticity (ML1 + 4) is expressed in "Mooney units" (MU, 1 MU = 0.83 Newton - meters).

[0335] Dynamic properties (after curing): Tensile test

[0336] These tensile tests can determine the elastic stress and fracture properties. Unless otherwise specified, these tests are carried out according to the French standard NF T 46 - 002 of September 1988. Processing the tensile records can also plot the curve of modulus versus elongation. The modulus used in this article is the nominal (or apparent) secant modulus measured in the first elongation and calculated by normalizing to the initial cross - section of the specimen. The nominal secant modulus (or apparent stress, in MPa) is measured at 100% and 300% elongation (denoted as MSA100 and MSA300 respectively) in the first elongation. The reinforcement index, which is the ratio of the MSA300 modulus to the MSA100 modulus, is expressed as a base 100 relative to the control composition T1. A value greater than 100 indicates an improvement in the reinforcement of the composition under consideration compared to the control composition.

[0337] The elongation at break (EB%) and breaking stress (BS) tests are based on the standard NF ISO 37 of December 2005 on H2 dumbbell - shaped specimens and are measured at a tensile speed of 500 mm / min. The elongation at break is expressed as a percentage of elongation. The breaking stress is expressed in MPa. These values are expressed as a base 100 relative to the control composition T1. A value greater than 100 indicates an improvement in the mechanical properties of the composition under consideration compared to the control composition.

[0338] All these tensile measurements are carried out under standard conditions of temperature (23 ± 2 °C) and humidity (50 ± 5% relative humidity) according to the French standard NF T 40 - 101 (December 1979).

[0339] The dynamic properties G* and tan(δ)max are measured on a viscosity analyzer (Metravib VA4000) according to the standard ASTM D 5992 - 96. According to the standard ASTM D 1349 - 99, a sample of the cross - linked composition (with a thickness of 4 mm and a cross - section of 400 mm 2Response of cylindrical specimens). Strain amplitude sweeps were performed from 0.15% to 50% (outward cycle) and then from 50% to 0.15% (return cycle). The results used were the non-linearity (NL or ΔG*) and the loss factor tan(δ). For the return cycle, the maximum value of the observed tan(δ) is shown and denoted as tan(δ)max. The non-linearity (NL or ΔG*) is the shear modulus difference between 0.15% and 50% strain, expressed in MPa. The non-linearity and tan(δ)max are expressed relative to a base of 100 for the control composition T1. Values less than 100 indicate an improvement in the hysteresis (and thus rolling resistance) of the composition under consideration compared to the control composition.

[0340] IV-2 Preparation of the composition

[0341] In the following examples, the rubber compositions were prepared as described in point II-6 above. In particular, these compositions were manufactured in the following manner: the elastomer, optionally a 1,3-dipolar compound (which was kneaded alone with the elastomer at 110 °C for about 2 minutes), then silica, a coupling agent, a crosslinking aid, and various other ingredients except peroxide were introduced into a closed mixer (final filling degree: about 70% by volume), the initial vessel temperature of which was about 110 °C. Then, thermomechanical processing (non-production stage) was carried out in one step, which lasted about 5 to 6 minutes until a maximum "discharge" temperature of 160 °C was reached. The mixture thus obtained was recovered and cooled, and then the peroxide was introduced into the mixer (homogenizing finisher) at 23 °C, and all substances were mixed (production stage) for an appropriate time (e.g., between 5 and 12 minutes).

[0342] Subsequently, the compositions thus obtained were calendered in the form of rubber sheets (thickness range from 2 mm to 3 mm) or rubber flake sheets (for measuring their physical or mechanical properties), or in the form of molding elements that could be directly used as, for example, tire semi-finished products (especially treads) after cutting and / or assembling into the desired dimensions.

[0343] Crosslinking was carried out at 150 °C. The crosslinking time t’ c (90) is the time required for the torque of the composition to reach 90% of the maximum torque of the composition. The torque of the composition was measured at 150 °C using an oscillating disk rheometer according to standard DIN 53529 - Part 3 (June 1983). For each composition, t’c(90) was determined according to standard NF T 43-015. It varied from about 20 minutes to 40 minutes from one composition to another.

[0344] IV-3 Testing of the rubber composition

[0345] The aim of the examples shown below is to compare the performance trade - offs between the reinforcement, breaking stress and rolling resistance of the composition (C1) according to the invention and three control compositions (T1 to T3).

[0346] Table 1 shows the compositions tested (in phr) and the results obtained.

[0347] The control compositions differ from the composition C1 according to the invention in that they do not contain the 1,3 - dipolar compound and / or cross - linking aid according to the invention.

[0348] [Table 1]

[0349] Components T1 T2 T3 C1 EBR(1) 100 100 100 100 1,3-dipolar compound(2) - 2.1 - 2.1 Silica(3) 30 30 30 30 Coupling agent(4) 3 3 3 3 Peroxide(5) 1.6 1.6 1.6 1.6 Crosslinking aid(6) - - 5 5 Properties MSA300 / MSA100 100 101 338 403 BS at 23 °C 100 110 176 163 NL at 60 °C 100 48 118 39

[0350] (1) Elastomer containing 79 mol% of ethylene units, 7 mol% of 1,2 - cyclohexanediyl units, 8 mol% of 1,2 units and 6 mol% of 1,4 units; Mooney at 100 °C: 60; Mn: 156600 g / mol

[0351] (2) 1,3 - dipolar compound, the synthesis of which is described in paragraph 1.1 on pages 15 to 23 of document WO 2012 / 07441

[0352] (3) Silica Zeosil 1165MP from Solvay

[0353] (4) Triethoxysilylpropyltetrasulfide (TESPT) liquid silane, Si69 from Evonik

[0354] (5) 1,1 - bis(tert - butylperoxy) - 3,5,5 - trimethylcyclohexane, Luperox 231 XL40 from Arkema

[0355] (6) Hexanediol diacrylate (HDDA), SR238 from Sartomer

[0356] The results shown in Table 1 above indicate that, compared with the control composition T1, in compositions based on highly saturated diene elastomers cross - linked with peroxides, the specific combination of the 1,3 - dipolar compound and cross - linking aid according to the invention can significantly improve the reinforcement and rolling resistance of the composition while exhibiting improved breaking stress.

[0357] The composition according to the invention can be used in many applications in the field of pneumatic or non - pneumatic tires, in particular for treads where a good trade - off between the properties of reinforcement, breaking stress and rolling resistance is desired.

Claims

1. A rubber composition, said rubber composition being based at least on: - An elastomeric matrix, said elastomeric matrix comprising a copolymer comprising ethylene units and 1,3-diene units in an amount greater than 50 phr, and the ethylene units in the copolymer accounting for more than 50 mol% of the monomer units of the copolymer, - A 1,3-dipolar compound, said 1,3-dipolar compound corresponding to formula (I): Wherein: ○ Q represents an aromatic diyl ring, said aromatic diyl ring being optionally substituted by one or more identical or different aliphatic hydrocarbon chains, said aliphatic hydrocarbon chains being optionally substituted or interrupted by one or more heteroatoms, ○ E represents a divalent hydrocarbon group optionally containing one or more heteroatoms, - A filler, said filler mainly comprising silica, and - A crosslinking system, said crosslinking system comprising at least one free radical polymerization initiator and a crosslinking aid, said crosslinking aid being selected from zinc dimethacrylate, magnesium dimethacrylate, zinc diacrylate, magnesium diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, and mixtures thereof, Wherein the content of the 1,3-dipolar compound is between 0 and 50 molar equivalents per 100 moles of the monomer units constituting the copolymer, the filler comprises more than 70 wt% of silica, and the content of the crosslinking aid is in the range of 1 phr to 20 phr.

2. The composition according to claim 1, wherein, In the compound of formula (I) selected from formula (Ia) and (Ib): wherein: - The group of formula (Ia) is selected from X 1 to X 5 among four groups, and the group of formula (Ib) is selected from X 1 to X 7 among six groups, which may be the same or different and represent a hydrogen atom, a halogen atom, or an aliphatic hydrocarbon chain, and the aliphatic hydrocarbon chain is optionally substituted or interrupted by one or more heteroatoms - The group of formula (Ia) is selected from X 1 to X 5 and the group of formula (Ib) is selected from X 1 to X 7 represents a covalent bond of group E that can be attached to a group of the following formula (IV):

3. The composition according to claim 1, wherein, Group E is C 1 -C 24 hydrocarbon chain, which hydrocarbon chain is optionally interrupted by one or more nitrogen atoms, sulfur atoms or oxygen atoms.

4. The composition according to claim 1, wherein, The 1,3-dipolar compound is selected from compounds of the following formulas (V) to (X) and their meso forms:

5. The composition according to claim 1, said composition further comprising a reagent for coupling silica to the copolymer.

6. The composition according to claim 1, wherein, The free radical polymerization initiator is selected from peroxides, azo compounds, redox systems, and mixtures thereof.

7. The composition according to claim 1, wherein, The free radical polymerization initiator is an organic peroxide, said organic peroxide being selected from dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl) peroxide, tert-butyl cumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, n-butyl 4,4'-bis(tert-butylperoxy)valerate, O-(2-ethylhexyl) monoperoxycarbonate OO-(tert-butyl) ester, tert-butyl isopropyl carbonate peroxide, tert-butyl benzoate peroxide, tert-butyl 3,5,5-trimethylhexanoate peroxide, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene, and mixtures thereof.

8. The composition according to claim 1, wherein, The content of the free radical polymerization initiator is in the range of 1 wt% to 10 wt% relative to the weight of the crosslinking aid.

9. A rubber article, said rubber article comprising at least one composition defined in any one of claims 1 to 8.

10. The rubber article according to claim 9, said article being selected from pneumatic tires, non-pneumatic tires, rubber tracks, and conveyor belts.

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