WO2015193311A1

WO2015193311A1 - Method for preparation of a rubber composition comprising an epoxide elastomer cross-linked by a polycarboxylic acid

Info

Publication number: WO2015193311A1
Application number: PCT/EP2015/063471
Authority: WO
Inventors: Benoit SCHNELL; Etienne Fleury
Original assignee: Compagnie Generale Des Etablissements Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2014-06-18
Filing date: 2015-06-16
Publication date: 2015-12-23
Also published as: FR3022547A1; EP3157972A1; FR3022547B1

Abstract

The present invention relates to a process for preparation of a rubber composition made from at least one majority elastomer comprising epoxide functional groups, a reinforcing filler and a cross-linking system of said elastomer comprising a polycarboxylic acid and an imidazole, characterized in that the composition is prepared via a thermal mechanical mixing phase in the course of which all of the ingredients other than the cross-linking system are introduced together with, optionally, a part of the cross-linking system or all of the cross-linking system, at low temperature, i.e. at a maximum temperature of between 90°C and 10°C, the temperature at which the mixing is stopped.

Description

PROCESS FOR PREPARING A RUBBER COMPOSITION COMPRISING AN EPOXY ELASTOMER RETICULATED BY A POLYACID

The present invention relates to the process for the preparation of rubber compositions, in particular rubber compositions based on elastomers comprising epoxide functions.

It has been known, and has been customary for many years, to use in rubber tires rubber compositions whose elastomeric matrix is crosslinked with sulfur, this crosslinking is then called vulcanization. The conventional vulcanization system combines molecular sulfur and at least one vulcanization accelerator. However, it is known that such a system penalizes the implementation of the composition before cooking by the roasting phenomenon. It is recalled that the so-called "roasting" phenomenon leads rapidly, during the preparation of the rubber compositions, to premature vulcanizations ("scorching"), to very high viscosities in the green state, and ultimately to rubber compositions almost impossible to work and to implement industrially.

[003] As a result, the vulcanization systems have been improved over the years in combination with the methods of preparing the rubber compositions in order to overcome the disadvantages mentioned above. Thus, the compositions are often complex and include in addition to molecular sulfur, or a molecular sulfur donor, vulcanization accelerators, activators, and possibly vulcanization retarders. At present, it would be interesting for the manufacturers to find crosslinking systems as efficient as vulcanization, while simplifying the compositions and their preparation.

[004] Continuing their research, the applicants have previously found that specific tire compositions, crosslinked with a polycarboxylic acid could be simplified compared to conventional compositions, and that these compositions could have improved properties.

[005] At present, the Applicants have found that these compositions crosslinked with a poly-acid can be prepared according to a specific process, which makes it possible to improve the breaking properties of the compositions.

Accordingly, a first object of the invention relates to a process for preparing a rubber composition based on at least one major elastomer comprising epoxide functions, a reinforcing filler, and a crosslinking system of said elastomer comprising a polycarboxylic acid of general formula (I)

in which A represents a covalent bond or a hydrocarbon group comprising at least 1 carbon atom, optionally substituted and optionally interrupted by one or more heteroatoms,

and an imidazole of general formula

in which,

Ri represents a hydrocarbon group or a hydrogen atom,

R ₂ represents a hydrocarbon group,

R ₃ and R ₄ represent, independently of one another, a hydrogen atom or a hydrocarbon group,

or R ₃ and R ₄ together with the carbon atoms of the imidazole ring to which they are attached form a ring;

process in which the composition is prepared via a thermomechanical mixing phase during which are introduced all the ingredients other than the crosslinking system, optionally a part of the crosslinking system or the entire crosslinking system, at low temperature, it is that is to say up to a maximum temperature of between 90 ° C. and 110 ° C., at which temperature the mixing is stopped.

[007] Preferably, the subject of the invention is a process as defined above in which the temperature at which the kneading is stopped is in a range from 90 ° C. to 109 ° C., preferably 95 ° C. at 107 ° C, more preferably 95 ° C to 105 ° C.

Preferably, said method does not include any thermomechanical mixing step at a temperature above 110 ° C.

[008] Preferably, the invention relates to a process as defined above in which the composition prepared is such that the majority diene elastomer comprising epoxide functional groups represents from 30 to 100 phr, preferably from 50 to 100 phr, cutting with 0 to 70 phr, preferably from 0 to 50 phr, of one or more non-epoxy minority elastomers. Preferably, the composition prepared is such that the majority diene elastomer comprising epoxide functional groups, represents all 100 phr of elastomer. [009] Preferably also, the invention relates to a process as defined above in which the composition prepared is such that the majority elastomer comprising epoxide functions has a molar epoxidation rate in a range from 0, 1% to 80%, preferably in a range of 0.1% to 50%, more preferably in a range of 0.3% to 50%.

Preferably, the invention relates to a process as defined above in which the composition prepared is such that the majority elastomer comprising epoxide functional groups is chosen from the group consisting of epoxide diene elastomers, epoxidized olefinic elastomers and mixtures of these. According to a first preferred embodiment, the majority elastomer comprising epoxide functional groups is an epoxide diene elastomer, and preferably an epoxide diene elastomer chosen from the group consisting of epoxidized natural rubbers, epoxidized synthetic polyisoprenes and epoxidized polybutadienes. epoxidized butadiene-styrene copolymers and mixtures thereof. According to another embodiment, also preferred, the majority elastomer comprising epoxide functions is an olefinic elastomer comprising epoxide functions and preferably comprising between 50 and 95%, more preferably between 65 and 85% of olefin (molar percentages) . According to this last embodiment, the olefinic elastomer comprising epoxide functional groups is preferably an epoxidized ethylenic elastomer.

Also preferably, the invention relates to a process as defined above in which the composition prepared is such that A represents a covalent bond or a divalent hydrocarbon group comprising from 1 to 1800 carbon atoms, preferably from 2 to 300 carbon atoms, more preferably 2 to 100 carbon atoms, more preferably 2 to 65 carbon atoms. Preferably, A is a divalent group of aliphatic or aromatic type or a group comprising at least one aliphatic part and an aromatic part. More preferably, A is a divalent group of aliphatic type, or a group comprising at least one aliphatic part and an aromatic part, and even more preferably, A is a divalent group of saturated or unsaturated aliphatic type; very preferably A is an alkylene group. Preferably, A is interrupted by at least one heteroatom selected from oxygen, nitrogen and sulfur, preferably oxygen. Also preferably, A is substituted by at least one radical chosen from alkyl, cycloalkylalkyl, aryl, aralkyl, hydroxyl, alkoxy, amino and carbonyl radicals. Preferentially A is substituted with one or more carboxylic acid functions and / or with one or more hydrocarbon radicals chosen from alkyl, cycloalkyl, cycloalkylalkyl, aryl and aralkyl radicals, themselves substituted with one or more carboxylic acid functions. Alternatively and preferentially also, A does not contain any other carboxylic acid function. Preferably, the level of poly-acid is in a range from 0.2 to 100 phr, preferably from 0.2 to 50 phr.

Preferably, the invention relates to a process as defined above in which the composition prepared is such that,

R 1 represents a hydrogen atom or an alkyl group having from 1 to 20 carbon atoms, cycloalkyl having from 5 to 24 carbon atoms, aryl having from 6 to 30 carbon atoms or aralkyl having from 7 to 25 carbon atoms ; group which may optionally be interrupted by one or more heteroatoms and / or substituted,

- R ₂ represents an alkyl group having 1 to 20 carbon atoms, cycloalkyl having 5 to 24 carbon atoms, aryl having 6 to 30 carbon atoms or aralkyl having 7 to 25 carbon atoms; groups which may be interrupted by one or more heteroatoms and / or substituted,

R 3 and R ₄ independently represent identical or different groups selected from hydrogen or alkyl groups having 1 to 20 carbon atoms, cycloalkyls having 5 to 24 carbon atoms, aryl having 6 to 30 carbon atoms or aralkyl having from 7 to 25 carbon atoms; groups which may optionally be interrupted by heteroatoms and / or substituted, or R ₃ and R ₄ form together with the carbon atoms of the imidazole ring to which they are attached, a ring selected from aromatic, heteroaromatic or aliphatic rings, comprising 5 to 12 carbon atoms, preferably 5 or 6 carbon atoms.

More preferably, the invention relates to a process as defined above in which the composition prepared is such that R 1 represents a group chosen from alkyl groups having from 2 to 12 carbon atoms, or aralkyls having from 7 to 13 carbon atoms; groups that can be substituted. Preferentially, R 1 represents an aralkyl group having 7 to 13 carbon atoms which is optionally substituted and R ₂ represents an alkyl group having from 1 to 12 carbon atoms. Preferably, R 1 represents an aralkyl group having from 7 to 9 optionally substituted carbon atoms and R ₂ represents an alkyl group having from 1 to 4 carbon atoms. More preferably, R ₃ and R ₄ independently represent identical or different groups chosen from hydrogen or alkyl groups having 1 to 12 carbon atoms, cycloalkyls having 5 to 8 carbon atoms, aryls having 6 to 24 carbon atoms or aralkyls having 7 to 13 carbon atoms; groups which may optionally be substituted, or R ₃ and R ₄ form, with the carbon atoms of the imidazole ring to which they are attached, a phenyl, cyclohexene or cyclopentene ring.

Preferably, the invention relates to a process as defined above in which the composition prepared is such that the level of imidazole is in a range from 0.01 to 4 molar equivalents, and preferably from 0.01 to 3 molar equivalents, relative to the carboxylic acid functions present on the polycarboxylic acid of general formula (I).

Also preferably, the invention relates to a process as defined above wherein the composition prepared is such that the reinforcing filler comprises carbon black, silica or a mixture of carbon black and silica. Preferably, the level of reinforcing filler is in a range from 5 to 200 phr.

Preferably, the invention relates to a process as defined above in which all the ingredients of the composition including the ingredients of the crosslinking system are introduced during the thermomechanical mixing phase.

Alternatively and preferably also, the invention relates to a process as defined above in which the ingredients of the crosslinking system are not all introduced during the thermomechanical mixing phase, and wherein the method comprises a subsequent kneading phase in which the crosslinking system is completed or incorporated, and kneaded to a temperature below 110 ° C.

The invention also relates to a composition obtained by the process as defined above; a tire comprising such a composition and in particular a tire comprising such a composition in the tread.

I. Tests

The rubber compositions are characterized after cooking, as indicated below.

Traction tests

These tensile tests make it possible to determine the elastic stress and the properties at break. Unless otherwise indicated, they are carried out in accordance with the French standard NF T 46-002 of September 1988. Traction data processing also makes it possible to draw the modulus curve as a function of elongation. The module used here is the nominal secant modulus (or apparent) measured in first elongation, calculated by reducing to the initial section of the specimen. The measures of tensile strength to determine breaking stresses (in MPa) and elongations at break (in%) are carried out at a given temperature (usually 23 ° C or 40 ° C +/- 2 ° C), and under normal conditions hygrometry (50 +/- 5% relative humidity). These values can be converted to base 100 for easy comparison of results.

II. Compositions prepared by the process of the invention

The method according to the invention applies to a rubber composition based on at least one major elastomer comprising epoxide functions, at least one reinforcing filler, and a crosslinking system of said polymer comprising a polycarboxylic acid. of general formula (I) and an imidazole of general formula (II).

By the term "composition based" is meant a composition comprising the mixture and / or the reaction product of the various constituents used, some of these basic constituents being capable of or intended to react between they, at least in part, during the various phases of manufacture of the composition, in particular during its crosslinking or vulcanization.

By the term "molar equivalent", well known to those skilled in the art, is meant the quotient between the number of moles of the compound concerned and the number of moles of the reference compound. Thus, 2 equivalents of a compound B relative to a compound A represent 2 moles of the compound B when 1 mole of the compound A is used.

When reference is made to a "majority" compound, in the sense of the present invention, it is understood that this compound is predominant among the compounds of the same type in the composition, that is to say that it is the one which represents the largest quantity in mass among the compounds of the same type. Thus, for example, a majority polymer is the polymer representing the largest mass relative to the total mass of the polymers in the composition. In the same way, a so-called majority charge is that representing the largest mass among the charges of the composition. For example, in a system comprising a single polymer, it is the majority within the meaning of the present invention; and in a system comprising two polymers, the majority polymer accounts for more than half of the mass of the polymers.

On the contrary, a "minor" compound is a compound which does not represent the largest mass fraction among the compounds of the same type.

In the present description, unless otherwise expressly indicated, all the percentages (%) indicated are percentages (%) by weight. On the other hand, any range of values designated by the expression "between a and b" represents the range of values from more than a to less than b (i.e. terminals a and b excluded) while all Range of values referred to as "from a to b" means the range of values from a to b (i.e. including the strict limits a and b).

11.1. Elastomer Comprising Epoxide Functions (or Epoxidized Elastomer)

By elastomer or rubber (the two terms being in a known manner synonymous and interchangeable) comprising epoxide functions means any type of elastomer in the sense known to those skilled in the art, whether it is a homopolymer or block copolymer, random or otherwise, having elastomeric properties, functionalized epoxide (or epoxidized), that is to say carrying epoxide functional groups.

The epoxidized epoxidation rate (mol%) of the epoxidized elastomers may vary to a large extent according to the particular embodiments of the invention, preferably in a range from 0.1% to 80%, preferably in a range of from 0.1% to 50%, more preferably in a range of 0.3% to 50%. When the epoxidation rate is less than 0.1%, the intended technical effect may be insufficient while beyond 80%, the intrinsic properties of the polymer are degraded. For all these reasons, the degree of functionalization, in particular of epoxidation, is more preferably within a range of 0.3% to 30%, more preferably within a range of 0.3% to 20%.

The epoxidized elastomers are, in known manner, solid at room temperature (20 ° C); solid means any substance which does not have the capacity to take up, at the latest after 24 hours, under the sole effect of gravity and at ambient temperature (20 ° C.), the shape of the container which contains it .

The Tg of the elastomers described below is measured in a known manner by DSC (Differential Scanning Calorimetry), for example and unless different indications specified in the present application, according to ASTM D3418 of 1999.

The epoxidized elastomer may be chosen from the group consisting of epoxidized diene elastomers, epoxidized olefinic elastomers and mixtures thereof. Preferably, the epoxidized elastomer is chosen from epoxidized olefinic elastomers and mixtures thereof. According to another preferred variant of the invention, the epoxidized elastomer is chosen from epoxide diene elastomers and mixtures thereof.

By elastomer of the epoxide diene type, it is recalled that must be understood an elastomer which is derived at least in part (ie a homopolymer or a copolymer) of monomers dienes (monomers bearing two carbon-carbon double bonds, conjugated or not ), this polymer being functionalized, that is to say that it carries epoxide functional groups. A first characteristic of epoxy diene elastomers, is therefore to be diene elastomers. These diene elastomers, which are non-thermoplastic by definition in the present application, having a Tg in the vast majority of cases which is negative (that is to say less than 0 ° C.), can be classified in a known manner into two categories. : those said to be "essentially unsaturated" and those termed "essentially saturated". Butyl rubbers, such as, for example, copolymers of dienes and alpha-olefins of the EPDM type, fall into the category of essentially saturated diene elastomers, with a level of units of diene origin which is low or very low, always less than 15. % (mole%). By contrast, essentially unsaturated diene elastomer is understood to mean a diene elastomer derived at least in part from conjugated diene monomers having a proportion of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%). . In the category of "essentially unsaturated" diene elastomers, the term "highly unsaturated" diene elastomer is particularly understood to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.

It is preferred to use at least one diene elastomer of the highly unsaturated type, in particular a diene elastomer chosen from the group consisting of natural rubber (N), synthetic polyisoprenes (IR), polybutadienes (BR), copolymers butadiene, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR), isoprene-copolymers of butadiene-styrene (SBIR) and mixtures of such copolymers.

The diene elastomers above may be for example block, statistical, sequenced, microsequenced, and be prepared in dispersion or in solution; they may be coupled and / or starred or functionalized with a coupling agent and / or starring or functionalization.

Preferably polybutadienes and in particular those having a content of units -1, 2 between 4% and 80% or those having a content of cis-1, 4 greater than 80%, polyisoprenes, copolymers of butadiene-styrene and in particular those having a styrene content of between 5% and 50% by weight and more particularly between 20% and 40%, a 1,2-butadiene content of the butadiene part of between 4% and 65%. %, a content of trans-1,4 bonds between 20% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 90% by weight and a glass transition temperature of 40 ° C to - 80 ° C, isoprene-styrene copolymers and especially those having a styrene content of between 5% and 50% by weight and a Tg between -25 ° C and -50 ° C.

In the case of butadiene-styrene-isoprene copolymers are especially suitable those having a styrene content of between 5% and 50% by weight and more particularly between 10% and 40%, an isoprene content of between 15% and 60% by weight and more particularly between 20% and 50%, a butadiene content of between 5% and 50% by weight and more particularly between 20% and 40%, a content in units -1, 2 of the part butadiene content between 4% and 85%, a content in trans-1,4 units of the butadiene part of between 6% and 80%, a content in units -1, 2 plus -3,4 of the isoprenic part of between 5% and % and 70% and a content of trans-1,4 units of the isoprenic portion of between 10% and 50%, and more generally any butadiene-styrene-isoprene copolymer having a Tg between -20 ° C and -70 ° C .

A second essential characteristic of the epoxide diene elastomer useful for the purposes of the invention is that it is functionalized, bearing epoxide functional groups.

The epoxide functions present in the diene elastomer are obtained by copolymerization or post-polymerization modification, and will either be carried directly by the skeleton of the chain, or carried by a side group according to the method of production, for example by epoxidation or any other modification of the diene functions present in the elastomeric chain after copolymerization.

The epoxy diene elastomers may, for example, be obtained in a known manner by epoxidation of the equivalent epoxidized diene elastomer, for example by chlorohydrin or bromohydrin-based processes or processes based on hydrogen peroxides, alkyl hydroperoxides or peracids (such as peracetic acid or performic acid), see in particular Kautsch. Gummi Kunstst. 2004, 57 (3), 82. The epoxide functions are then in the polymer chain. Mention may in particular be made of epoxidized natural rubbers (abbreviated to "ENR"); such ENR are for example sold under the names "ENR-25" and "ENR-50" (epoxidation rate of 25% and 50% respectively) by the company Guthrie Polymer. The epoxidized BRs are also well known, sold for example by the company Sartomer under the name "Poly Bd" (for example "Poly Bd 605E"). Epoxidized SBRs can be prepared by epoxidation techniques well known to those skilled in the art.

Such epoxide diene elastomers and processes for obtaining them are well known to those skilled in the art and commercially available. Diene elastomers bearing epoxide groups have been described for example in US 2003/120007 or EP 0763564, US 6903165 or EP 1403287. Preferably, the epoxidized diene elastomer is chosen from the group consisting of epoxidized natural rubbers (NR) (abbreviated "ENR"), epoxidized synthetic polyisoprenes (IR) and epoxidized polybutadienes (BR), preferably having cis-1,4 bond ratio greater than 90%, epoxidized butadiene-styrene copolymers (SBR) and mixtures of these elastomers.

The epoxy diene elastomers may also have pendant epoxide functional groups. In this case, they can be obtained either by postpolymerization modification (see, for example, J. Appt Polym Sci 1999, 73, 1733); or by radical copolymerization of the diene monomers with monomers carrying epoxide functional groups, in particular methacrylic acid esters comprising epoxide functional groups, such as, for example, glycidyl methacrylate (this radical polymerization, especially in bulk, in solution or in dispersed medium - In particular dispersion, emulsion or suspension - is well known to those skilled in the field of polymer synthesis, for example the following reference: Macromolecules 1998, 31, 2822). For example, US20110098404 describes the emulsion copolymerization of 1,3-butadiene, styrene and glycidyl methacrylate.

The level (mol%) of epoxidation of the epoxidized diene elastomers previously described may vary to a large extent according to the particular embodiments of the invention, preferably in a range from 0.1% to 80%, preferentially in a range of 0.1% to 50%, more preferably in a range of 0.3% to 50%. When the epoxidation rate is less than 0.1%, the intended technical effect may be insufficient while beyond 80%, the intrinsic properties of the polymer are degraded. For all these reasons, the rate of functionalization, especially epoxidation, is more preferably in a range of 0.3% to 30%.

By elastomer epoxidized olefinic type, it is recalled that must be understood an epoxidized functionalized elastomer, that is to say, it carries epoxidized functional groups, and whose elastomeric chain is a carbon chain comprising predominantly Olefin monomer units denoted O (molar level greater than 50%). More specifically, the molar ratio of O is between 50 and 95%, preferably between 65 and 85%. This olefinic elastomer is therefore a copolymer also comprising 5 to 50 mol% of nonolefinic units, that is to say different from O). These non-olefinic units consist in part or in their entirety of units bearing the epoxidized functional groups, noted R, necessary for the needs of the invention. In the case where the non-olefinic units are not entirely R units, other reasons, noted A 'are present in the carbon chain in such a way that the molar ratio of R + A 'is strictly less than 50%.

The monomers O may come from any olefin known to those skilled in the art, such as, for example, ethylene, propylene, butylene, isobutylene, these monomers being optionally substituted by linear alkyl groups or branched.

Preferably O is an ethylene unit [-CH2-CH2-], and in this preferred case, the epoxidized olefinic elastomer is an epoxidized ethylenic elastomer, which makes it possible to further improve the compromise between the stiffness performance and the hysteresis in tire compositions.

An essential characteristic of the epoxidized olefinic elastomer useful for the needs of the invention is that it is functionalized, bearing epoxidized functional groups.

The epoxidized function can be carried directly by the carbon skeleton, and is then mainly obtained by epoxidation of carbon-carbon double bonds initially present after copolymerization. This epoxidation of unsaturated polymers is well known to those skilled in the art, and can be carried out, for example, by chlorohydrin or bromohydrin-based processes, direct oxidation processes or hydrogen peroxide-based processes. alkyl hydroperoxides or peracids (such as peracetic acid or performic acid).

The epoxide function may also be pendent and is then either already present in a monomer involved in the copolymerization with the olefin (this monomer may be, for example, glycidyl methacrylate, allyl glycidyl ether or vinyl glycidyl ether), or obtained by the post-copolymer modification of a pendant function.

The rate (mol%) of unit R of the epoxidized olefinic elastomers previously described may vary to a large extent according to the particular embodiments of the invention, preferably in a range from 0.1% to 50%, preferentially in a range of 0.3% to 50%, more preferably in a range of 0.3% to 30%, more preferably in a range of 0.3 to 20%. When the level of R units is less than 0.1%, the intended technical effect may be insufficient while beyond 50%, the elastomer would no longer be predominantly olefinic.

When the non-olefinic units are not entirely constituted by epoxy functional groups R, other non olefinic units A 'are present in the chain, so that the total molar level represented by the monomers O, R and A 'are equal to 100%. The non-olefinic monomers useful in the preparation of the epoxidized olefinic elastomers may be chosen from nonolefinic monomers not not leading to unsaturations and monomers which once polymerized lead to unsaturations carried by the elastomeric chain (other than diene monomers).

The non-olefinic monomers that do not lead to unsaturations are essentially vinyl and acrylic / methacrylic monomers. For example, such monomers may be chosen from styrene, vinyl acetate, vinyl alcohol, acrylonitrile, methyl acrylate and methyl methacrylate, these monomers being optionally substituted with alkyl, aryl or other functionalized groups.

For example also, the non-dienic monomers useful for the preparation of olefinic type elastomers bearing copolymerization unsaturations are all those known to those skilled in the art to form unsaturated elastomers, such as, for example, methacrylate. of dicyclopentadienyloxyethyl.

The epoxidized olefinic elastomers have a Tg in the vast majority of cases which is negative (that is to say less than 0 ° C).

The epoxidized olefinic elastomers have a number-average molar mass (Mn) of at least 10,000 g / mol, preferably at least 15,000 g / mol and at most 1,500,000 g / mol. The polydispersity index Ip, equal to Mw / Mn (Mw being the weight average molar mass), is between 1.05 and 11.00.

Preferably, and in summary, the olefinic elastomer comprising epoxide functional groups is therefore a copolymer having at least 50% (in moles) of monomeric olefin units, and with a number of different monomeric units greater than or equal to 2, preferably from 2 to 5, and more preferably from 2 or 3. This copolymer may be obtained by copolymerization or by post-polymerization modification of an elastomer. The epoxide functional groups present in the olefinic copolymer, obtained by copolymerization or by post-polymerization modification, will either be carried directly by the skeleton of the chain or carried by a lateral group according to the method of production, for example by epoxidation or any other modification of the diene functions present in the elastomeric chain after copolymerization.

Epoxidized olefinic elastomers and processes for obtaining them are well known to those skilled in the art and commercially available. Olefinic elastomers bearing epoxide groups have been described, for example, in EP 0247580 or US Pat. No. 5,557,080. Arkema also commercially offers epoxidized polyethylenes under the trade names Lotader AX8840 and Lotader AX8900. The compositions prepared by the process of the invention may contain a single epoxidized elastomer or a mixture of several epoxidized elastomers (which will then be singularly noted as being "the epoxidized elastomer" to represent the sum of the epoxidized elastomers of the composition).

The epoxidized elastomer is predominant in the rubber composition of the process of the invention, that is to say that it is either the only elastomer or is the one which represents the largest mass, among the elastomers of the composition.

According to a preferred embodiment of the invention, the rubber composition comprises, for example, from 30 to 100 phr, in particular from 50 to 100 phr, preferably 70 to 100 phr, of predominantly epoxidized elastomer in blending with 0 to 70 phr, in particular from 0 to 50 phr and preferably 0 to 30 phr, of one or more other elastomers, minority, non-epoxidized.

According to another preferred embodiment of the invention, the composition comprises for all 100 pce elastomer, one or more epoxidized elastomers.

11.2. Reinforcing charge

Any type of reinforcing filler known for its ability to reinforce a rubber composition that can be used for the manufacture of tires, for example an organic filler such as carbon black, a reinforcing inorganic filler such as silica, may be used. or a blend of these two types of filler, including a carbon black and silica blend.

As carbon blacks are suitable all carbon blacks, including the black type HAF, ISAF, SAF conventionally used in tires (so-called pneumatic grade black). Among these, the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), for example the N115, N134, N234, N326, N330, N339, N347 or N375 blacks, or even targeted applications, blacks of higher series (eg N660, N683, N772). The carbon blacks could for example already be incorporated into an isoprene elastomer in the form of a masterbatch (see for example WO 97/36724 or WO 99/16600).

As examples of organic fillers other than carbon blacks, mention may be made of the functionalized polyvinyl organic fillers as described in applications WO-A-2006/069792, WO-A-2006/069793, WO-A-1, 2008/003434 and WO-A-2008/003435. By "reinforcing inorganic filler" must be understood in the present application, by definition, any inorganic or mineral filler (whatever its color and its natural or synthetic origin), also called "white" charge, charge " clear "or" non-black filler "charge as opposed to carbon black, capable of reinforcing on its own, with no other means than an intermediate coupling agent, a rubber composition for the manufacture of pneumatic, in other words able to replace, in its reinforcing function, a conventional carbon black pneumatic grade; such a filler is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface.

The physical state in which the reinforcing inorganic filler is present is indifferent, whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the term "reinforcing inorganic filler" also refers to mixtures of different reinforcing inorganic fillers, in particular highly dispersible siliceous and / or aluminous fillers as described below.

As reinforcing inorganic fillers are particularly suitable mineral fillers of the siliceous type, in particular of silica (SiO ₂ ), or of the aluminous type, in particular of alumina (Al ₂ O 3). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface and a CTAB specific surface both less than 450 m ² / g, preferably from 30 to 400 m ² / g. As highly dispersible precipitated silicas (referred to as "HDS"), mention may be made of, for example, the Ultrasil 7000 and Ultrasil 7005 silicas from Degussa, the Zeosil 1 165MP, 1135MP and 1 115MP silicas from Rhodia, Hi-Sil silica. EZ150G from PPG, the Zeopol 8715, 8745 and 8755 silicas from Huber, the high surface area silicas as described in WO 03/16837.

The reinforcing inorganic filler used, in particular if it is silica, preferably has a BET surface area of between 45 and 400 m ² / g, more preferably between 60 and 300 m ² / g.

Preferably, the total reinforcing filler content (carbon black and / or reinforcing inorganic filler such as silica) is in a range from 5 to 200 phr, more preferably from 10 to 150 phr, the optimum. being in a known manner different according to the particular applications concerned: the level of reinforcement expected on a bicycle tire, for example, is of course less than that required on a tire capable of running at high speed in a sustained manner, for example a motorcycle tire, a tire for passenger vehicles or commercial vehicles such as heavy goods vehicles. According to a preferred embodiment of the invention, there is used a reinforcing filler comprising from 5 to 150 phr, more preferably from 10 to 120 phr of inorganic filler, particularly silica, the majority; and optionally carbon black; the carbon black, when present, is preferably used at a level of less than 20 phr, more preferably less than 10 phr, for example between 0.1 and 10 phr, better still from 0.1 to 5 phr. This preferred embodiment is also particularly preferred when the majority elastomer of the composition is an epoxidized isoprene rubber, more particularly epoxidized natural rubber.

To couple the reinforcing inorganic filler to the elastomer, it is possible to use, in known manner, at least one bifunctional coupling agent (or bonding agent) intended to ensure a sufficient chemical and / or physical connection between the inorganic filler (surface of its particles) and the diene elastomer, in particular organosilanes or bifunctional polyorganosiloxanes.

In the rubber compositions prepared by the process of the invention, the content of coupling agent is preferably in a range from 0 to 20 phr, more preferably from 0 to 16 phr and even more preferably from 0 to 20 phr. 12 pce.

Those skilled in the art will understand that as an equivalent load of the reinforcing inorganic filler described in this paragraph, could be used a reinforcing filler of another nature, particularly organic, since this reinforcing filler would be covered an inorganic layer such as silica, or would comprise on its surface functional sites, especially hydroxyl, requiring the use of a coupling agent to establish the bond between the filler and the elastomer.

11 - 3 - Crosslinking system of the epoxidized polymer

The epoxidized polymer and the reinforcing filler described above is associated with a crosslinking system, capable of crosslinking or curing the composition prepared by the method of the invention. This crosslinking system comprises a (that is to say at least one) polycarboxylic acid of general formula (I) and one (that is to say at least one) imidazole of general formula (II).

II .3. at. Poly-

The poly-acid useful for the purposes of the invention is a polycarboxylic acid of general formula (I)

wherein A represents a covalent bond or a hydrocarbon group having at least 1 carbon atoms, optionally substituted and optionally interrupted by one or more heteroatoms.

Preferably in the poly-acid of general formula (I), A represents a covalent bond or a divalent hydrocarbon group comprising from 1 to 1800 carbon atoms, preferentially from 2 to 300 carbon atoms, more preferably from 2 to 300 carbon atoms. 100 carbon atoms, and very preferably from 2 to 65 carbon atoms. Above 1800 carbon atoms, the poly-acid is a less effective crosslinking agent. Thus, A preferably represents a divalent hydrocarbon group comprising from 3 to 65 carbon atoms, preferentially from 5 to 65 carbon atoms, more preferably from 8 to 65 carbon atoms, and even more preferably from 10 to 65 carbon atoms.

Preferably in the poly-acid of general formula (I), A may be a divalent group of aliphatic or aromatic type or a group comprising at least one aliphatic part and an aromatic part. Preferably, A may be a divalent group of the aliphatic type, or a group comprising at least one aliphatic part and an aromatic part. Alternatively, and preferably also, A may be a divalent group of saturated or unsaturated aliphatic type, for example an alkylene group.

The group A of the poly-acid of general formula (I) may be interrupted by at least one heteroatom selected from oxygen, nitrogen and sulfur, preferably oxygen.

Also, the group A of the poly-acid of general formula (I) may be substituted by at least one radical chosen from alkyl, cycloalkylalkyl, aryl, aralkyl, hydroxyl, alkoxy, amino and carbonyl radicals.

The poly-acid of general formula (I) can comprise more than two carboxylic acid functions, in this case the group A is substituted with one or more carboxylic acid functions and / or with one or more hydrocarbon radicals selected from the group consisting of alkyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl radicals, themselves substituted by one or more carboxylic acid functions.

In a preferred embodiment, the radical A has no other carboxylic acid function, the poly-acid is a diacid. The level of poly-acid is preferably in a range from 0.2 to 100 phr, preferably from 0.2 to 50 phr, more preferably from 0.4 to 27 phr, and more preferably from 0 to 25 phr. , 9 to 25 phr. Below 0.2 phr of poly-acid, the effect of the crosslinking is not sensitive whereas beyond 100 phr of poly-acid, the poly-acid, crosslinking agent, becomes predominant by weight relative to the polymeric matrix.

The poly-acids useful for the purposes of the invention are either commercially available or easily prepared by those skilled in the art according to well-known techniques such as the chemical routes described for example in the US document. 7534917 as well as in references cited in this document, or biological routes, such as fermentation described in US3843466.

For example, as polyacids available commercially and useful for the purposes of the invention, mention may be made of: oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, terephthalic acid or polyacids such as trimesic acid or 3,4-bis (carboxymethyl) cyclopentanecarboxylic acid. Among the diacids of higher mass, mention may be made of polybutadiene, terminated dicarboxy (Aldrich, CAS 68891 -79-2), poly (acrylonitrile-co-butadiene), terminated dicarboxy (Aldrich, CAS 68891 -46-3), poly (ethylene oxide), 4-arm, terminated carboxylic acid (Aldrich), poly (ethylene glycol) bis (carboxymethyl) ether (Aldrich, CAS 39927-08-7), polybutadiene, terminated dicarboxy (Sartomer, Krasol LBM32 ") or also commercial polyesters such as those mentioned in the following documents: JP05062890, CN1247198 or J. Polym. Sci. Part A 1993, 31, 1825.

Il.3.b. imidazole

The imidazole useful for the crosslinking system according to the invention is an imidazole of general formula (II)

in which,

i represents a hydrocarbon group or a hydrogen atom,

R ₂ represents a hydrocarbon group,

R 3 and R ₄ represent, independently of one another, a hydrogen atom or a hydrocarbon group, or R ₃ and R ₄ together with the carbon atoms of the imidazole ring to which they are attached, form a ring.

[0087] Preferably, the imidazole of general formula (II) have groups such as:

R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, cycloalkyl having 5 to 24 carbon atoms, aryl having 6 to 30 carbon atoms or aralkyl having 7 to 25 carbon atoms; group which may optionally be interrupted by one or more heteroatoms and / or substituted,

R ₂ represents an alkyl group having 1 to 20 carbon atoms, cycloalkyl having 5 to 24 carbon atoms, aryl having 6 to 30 carbon atoms or aralkyl having 7 to 25 carbon atoms; groups which may be interrupted by one or more heteroatoms and / or substituted,

R ₃ and R ₄ independently represent identical or different groups chosen from hydrogen or alkyl groups having from 1 to 20 carbon atoms, cycloalkyls having from 5 to 24 carbon atoms, aryls having from 6 to 30 carbon atoms or aralkyls having 7 to 25 carbon atoms; groups which may optionally be interrupted by heteroatoms or substituted, or R 3 and R ₄ together with the carbon atoms of imidazole ring to which they are attached, a ring selected from aromatic, heteroaromatic or aliphatic hydrocarbons, comprising from 5 to 12 carbon atoms, preferably 5 or 6 carbon atoms.

Preferably, R 1 represents a group chosen from alkyl groups having from 2 to 12 carbon atoms, or aralkyls having from 7 to 13 carbon atoms; groups that can be substituted. More preferably, R 1 represents an aralkyl group having 7 to 13 carbon atoms which is optionally substituted and R ₂ represents an alkyl group having from 1 to 12 carbon atoms. Even more preferably, R 1 represents an aralkyl group having from 7 to 9 carbon atoms which is optionally substituted and R ₂ represents an alkyl group having from 1 to 4 carbon atoms.

Preferably, R 3 and R ₄ independently represent identical or different groups chosen from hydrogen or alkyl groups having 1 to 12 carbon atoms, cycloalkyls having from 5 to 8 carbon atoms, aryls having from 6 to 24 carbon atoms or aralkyls having 7 to 13 carbon atoms; groups that can be substituted. Alternatively and preferably also R ₃ and R represent, together with the carbon atoms of the imidazole ring to which they are attached, a phenyl, cyclohexene or cyclopentene ring.

For a good functioning of the invention, the imidazole content is preferably in a range from 0.01 to 4 molar equivalents, and preferably from 0.01 to 3 molar equivalents, relative to the acid functions. carboxylic compounds present on the polycarboxylic acid of general formula (I). Below 0.01 molar equivalents, no effect of the imidazole coagent is observed with respect to the situation where the poly-acid is used alone while above a value of 4 molar equivalents, no There is no additional benefit compared to lower rates. Thus, the level of imidazole is more preferably in a range from 0.01 to 2.5 molar equivalents, and preferably from 0.01 to 2 molar equivalents, and still more preferably from 0.01 to 1 molar equivalents. , 5 molar equivalents relative to the carboxylic acid functional groups present on the polycarboxylic acid of general formula (I).

The imidazoles useful for the purposes of the invention are either commercially available or easily prepared by those skilled in the art according to well-known techniques as described for example in JP201221 1 122, JP2007269658 or again in Science of Synthesis 2002, 12, 325-528.

For example, as commercially available imidazoles useful for the purposes of the invention, mention may be made of 1,2-dimethylimidazole, 1-decyl-2-methylimidazole, or 1-benzyl-2. -methylimidazole.

II.3.C. Poly-acid and imidazole

[0093] Clearly, and in accordance with the definition of the expression "based on" for the present invention, a composition based on the poly-acid of general formula (I) and on imidazole of general formula ( II) presented above could be a composition in which said poly-acid and said imidazole would have previously reacted together to form a salt between one or more acid functional groups of the poly-acid and respectively one or more imidazole nuclei.

II.4. Various additives

The rubber compositions prepared by the process of the invention may also comprise all or part of the usual additives normally used in elastomer compositions intended for the production of treads, such as, for example, pigments, protection such as anti-ozone waxes, chemical anti-ozonants, anti-oxidants, anti-fatigue agents, crosslinking agents other than those mentioned above, reinforcing resins or plasticizers. Preferably, this plasticizer is a solid hydrocarbon resin (or plasticizing resin), an extender oil (or plasticizing oil), or a mixture of both.

These compositions may also contain, in addition to the coupling agents, coupling activators, inorganic charge-covering agents or, more generally, processing aid agents that are capable of being used in a known manner, thanks to an improvement of the dispersion of the filler in the rubber matrix and a lowering of the viscosity of the compositions, to improve their ability to implement in the green state, these agents being, for example, hydrolysable silanes such as alkylalkoxysilanes, polyols, polyethers, primary, secondary or tertiary amines, hydroxylated or hydrolyzable polyorganosiloxanes.

Preferably, the compositions prepared by the process of the invention are free of crosslinking system other than that described above, and which comprises at least one poly-acid and at least one imidazole. In other words, the crosslinking system based on at least one poly-acid and at least one imidazole is preferably the only crosslinking system in the composition prepared by the method of the invention. Preferably, the compositions prepared by the process of the invention are devoid of a vulcanization system, or contain less than 1 phr, preferably less than 0.5 phr and more preferably less than 0.2 phr. Thus, the composition prepared by the process of the invention is preferably free of molecular sulfur or contains less than 1 phr, preferably less than 0.5 phr and more preferably less than 0.2 phr. Similarly, the composition is preferably devoid of any vulcanization accelerator, as known to those skilled in the art, or contains less than 1 phr, preferably less than 0.5 phr and more preferably less than 0.2 phr. pc.

II.5. Process for the preparation of the invention

In the usual manner, the rubber compositions may be manufactured in appropriate mixers, using two successive preparation phases well known to those skilled in the art: a first phase of work or thermomechanical mixing (so-called "non-productive phase"") at high temperature, up to a maximum temperature of between 130 ° C and 190 ° C, followed by a second mechanical working phase (so-called" productive "phase) to a lower temperature, typically less than 1 10 ° C, for example between 40 ° C and 100 ° C, finishing phase during which may be incorporated the crosslinking system. [0098] At present, the applicants have found that the first phase of work can be performed at a lower temperature than the temperatures usually used, which, with an appropriate introduction of the ingredients, has a beneficial effect on the breaking properties of the products. manufactured compositions.

Thus, according to the invention, the compositions are prepared by a process including a phase (or step) of work or thermomechanical mixing during which are introduced at least the epoxidized elastomer, the reinforcing filler, optional additives other that the poly-acid and imidazole, optionally the poly-acid and imidazole, at low temperature, that is to say up to a maximum temperature of between 90 ° C. and 110 ° C., preferentially included in a range from 90 ° C to 109 ° C, preferably from 95 ° C to 107 ° C, more preferably from 95 ° C to 105 ° C, at which temperature the mixing is stopped.

Preferably, the method of the invention does not comprise any thermomechanical mixing phase at a temperature greater than 110 ° C., more preferably no thermomechanical mixing phase at a temperature above 109 ° C., more preferably still no phase. thermomechanical mixing at a temperature above 107 ° C and very preferably no thermomechanical mixing phase at a temperature above 105 ° C.

According to a first preferred embodiment, the poly-acid and imidazole are added to the composition during the previously described working phase, which is essential to the process according to the invention; in this case, the process of the invention may preferably be a one-step mixing process.

Preferably, according to this first embodiment, the ingredients are introduced in the following order: the epoxidized elastomer, the reinforcing filler, optional additives other than poly-acid and imidazole, poly-acid and imidazole.

According to a second embodiment, also preferred, if only the poly-acid or imidazole is added to the composition during the essential step of the process of the invention, or if neither of them are added. during this step, they are at a later stage.

Thus, the method of the invention, according to the second embodiment comprises a subsequent mechanical working phase (so-called "productive" phase), during which the crosslinking system is completed (if only the poly-acid or imidazole was added during the first phase of work) or incorporated (if none of the poly-acid or imidazole was added during the first phase of work) and kneaded, up to one more low temperature, ie less than 110 ° C, preferably between 40 ° C and 100 ° C, the temperature at which the mixing is stopped.

It will be understood that the second preferred embodiment of the invention includes three variants in the moment of adding the ingredients of the crosslinking system: the case where the poly-acid is introduced during the essential working phase of the invention. the invention, or first phase of work and the imidazole is introduced during the subsequent phase of work, called productive; the case where imidazole is introduced during the first phase of work and the poly-acid is introduced during the subsequent work phase; and finally the case where the poly-acid and imidazole are introduced during the so-called productive work phase.

The composition thus obtained can then be calendered, for example in the form of a sheet, a plate especially for a characterization in the laboratory, or extruded, for example to form a rubber profile, such as for example a tread, which can be used for the manufacture of a tire.

11.6. Use in pneumatic

The rubber composition obtained by the process according to the invention may for example be used in different parts of said tire, in particular in the crown, the bead zone, the flank zone and the tread (especially in the sub-section). tread layer).

According to a preferred embodiment of the invention, the rubber composition described above can be used in the tire as an elastomeric layer in at least a portion of the tire.

By elastomeric "layer" is meant any three-dimensional element, made of rubber composition (or "elastomer", both of which are considered to be synonymous), of any shape and thickness, in particular sheet, strip, or other element of any straight section, for example rectangular or triangular.

First of all, the elastomer layer may be used as a tread sub-layer disposed in the crown of the tire, on the one hand between the tread, ie, the portion intended to come into contact with the road. during driving, and secondly the belt reinforcing said vertex. The thickness of this elastomeric layer is preferably in a range from 0.5 to 10 mm, especially in a range of 1 to 5 mm.

According to another preferred embodiment of the invention, the rubber composition prepared by the process of the invention can be used to form a elastomeric layer, disposed in the region of the region of the bead of the tire, radially between the carcass ply, the bead wire and the overturning of the carcass ply.

[00112] Also, the composition prepared by the method of the invention can be used in the crown plies (tire belt) or in the zone between the ends of the crown plies and the carcass ply.

Another preferred embodiment may be the use of the composition prepared by the process of the invention to form an elastomeric layer disposed in the area of the tire sidewall.

Alternatively, the composition prepared by the process of the invention may advantageously be used in the tread of the tire.

The tires in which the process of the invention is usable, or in which the use of compositions prepared according to the invention is possible, are especially intended for passenger vehicles as for two-wheeled vehicles (motorcycle, bicycle). , industrial vehicles selected from light trucks, "heavy goods vehicles" - the., metro, bus, road transport machinery (trucks, tractors, trailers), off-the-road vehicles, agricultural or civil engineering machinery, airplanes, other vehicles transportation or handling. The invention as well as its advantages will be readily understood in the light of the description and the following exemplary embodiments.

III. EXAMPLES OF CARRYING OUT THE INVENTION

111.1. Preparation of the control composition C1

It is introduced into an internal mixer (final filling ratio: about 70% by volume), the initial vessel temperature of which is about 100 ° C., the epoxidized elastomer and then the reinforcing filler with the poly-acid, imidazole and other additives. The total duration of the thermomechanical work is about 4 minutes, until reaching a maximum temperature of "fall" of 150 ° C.

The mixture thus obtained is recovered, cooled and the compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties. either extruded in the form of a profile.

111.2. Preparation of a composition C2, example according to the process of the invention

It is introduced into an internal mixer (final filling ratio: approximately 70% by volume), the initial vessel temperature of which is approximately 70 ° C., successively the epoxidized elastomer and then the reinforcing filler, followed by the other additives and the poly-acid and finally the imidazole. The total duration of the thermomechanical work is about 4 minutes, until reaching a maximum temperature of "fall" of 100 ° C.

The mixture thus obtained is recovered, cooled then the compositions thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties. either extruded in the form of a profile.

The compositions prepared as indicated above are presented in Table 1 below.

Table 1

(1) PEEPOX epoxy polyethylene "Lotader AX8900", the Arkema company comprising 8% glycidyl methacrylate, 24% methyl acrylate and 68% ethylene;

(2) 160 MP silica, "Zeosil 1 165MP" from the company hodia;

(3) Poly (acrylonitrile-co-butadiene), terminated dicarboxy, CAS 68891-46-3, from Aldrich

(4) 1-Benzyl-2-methylimidazole, CAS = 13750-62-4 from Sigma-Aldrich.

The properties of compositions C1 and C2 were measured as indicated above and the results are shown in Table 2 below.

Table 2

In the compositions prepared according to the process of the invention, a marked improvement in the breaking properties of the compositions is noted, in comparison with the same composition prepared in the usual manner for the rubber compositions. Moreover, in the compositions, it can be noted that the replacement of the Conventional vulcanization by a polyacid and imidazole crosslinking system, as prescribed for the invention makes it possible to overcome the known disadvantages of sulfur systems.

Claims

claims

A process for the preparation of a rubber composition based on at least one major elastomer comprising epoxide functions, a reinforcing filler, and a system for crosslinking said elastomer comprising a polycarboxylic acid of general formula (I)

and an imidazole of the general formula (II)

in which,

Ri represents a hydrocarbon group or a hydrogen atom,

R ₂ represents a hydrocarbon group,

or R 3 and R ₄ taken together with the carbon atoms of imidazole ring to which they are attached, a ring;

characterized in that the composition is prepared via a thermomechanical mixing phase during which all the ingredients other than the crosslinking system, optionally part of the crosslinking system or the entire crosslinking system, are introduced at low temperature, that is to say up to a maximum temperature of between 90 ° C. and 110 ° C., at which temperature the mixing is stopped.

2. Process according to claim 1, in which the temperature at which the kneading is stopped is in a range from 90 ° C to 109 ° C, preferably from 95 ° C to 107 ° C, more preferably from 95 ° C to 105 ° C.

3. Method according to any one of the preceding claims characterized in that said method comprises no thermomechanical mixing phase at a temperature above 110 ° C.

4. Process according to any one of the preceding claims, in which the composition prepared is such that the majority diene elastomer comprising epoxide functional groups represents from 30 to 100 phr, preferably from 50 to 100 phr, in a blend with 0 to 70 phr, preferably from 0 to 50 phr, of one or more non-epoxy minority elastomers.

5. Process according to any one of the preceding claims, in which the composition prepared is such that the majority diene elastomer comprising epoxide functional groups represents all of the 100 phr of elastomer.

6. Process according to any one of the preceding claims, in which the composition prepared is such that the majority elastomer comprising epoxide functional groups has a molar epoxidation level ranging from 0.1% to 80%, preferentially in the range from 0.1% to 80%. a range of 0.1% to 50%, more preferably in a range of 0.3% to 50%.

7. Process according to any one of the preceding claims wherein the composition prepared is such that the majority elastomer comprising epoxide functional groups is selected from the group consisting of epoxide diene elastomers, epoxidized olefinic elastomers and mixtures thereof.

8. Process according to any one of the preceding claims, in which the composition prepared is such that the majority elastomer comprising epoxide functional groups is an epoxide diene elastomer.

9. Process according to the preceding claim wherein the composition prepared is such that the majority elastomer comprising epoxide functional groups is an epoxide diene elastomer chosen from the group consisting of epoxidized natural rubbers, epoxidized synthetic polyisoprenes, epoxidized polybutadienes, epoxidized butadiene-styrene copolymers and mixtures thereof.

10. Process according to any one of claims 1 to 7 wherein the composition prepared is such that the majority elastomer comprising epoxide functions is an olefinic elastomer comprising epoxide functions.

1. Method according to the preceding claim wherein the composition prepared is such that the olefinic elastomer comprising epoxide functions comprises between 50 and 95%, more preferably between 65 and 85% of olefin (molar percentages).

12. The process as claimed in claim 10, in which the composition prepared is such that the olefinic elastomer comprising epoxide functional groups is an epoxidized ethylenic elastomer.

13. Process according to any one of the preceding claims, in which the composition prepared is such that A represents a covalent bond or a divalent hydrocarbon group comprising from 1 to 1800 carbon atoms, preferably from 2 to 300 carbon atoms.

14. Process according to the preceding claim, in which the composition prepared is such that A represents a divalent hydrocarbon group comprising from 2 to 100 carbon atoms, preferably from 2 to 65 carbon atoms.

15. Process according to any one of the preceding claims, in which the composition prepared is such that A is a divalent group of aliphatic or aromatic type or a group comprising at least one aliphatic part and an aromatic part.

16. Process according to any one of the preceding claims, in which the composition prepared is such that A is a divalent group of aliphatic type, or a group comprising at least one aliphatic part and an aromatic part.

17. Process according to any one of the preceding claims wherein the composition prepared is such that A is a divalent group of saturated or unsaturated aliphatic type.

18. A process according to any one of the preceding claims wherein the composition prepared is such that A is an alkylene group.

19. Process according to any one of the preceding claims wherein the composition prepared is such that A is interrupted by at least one heteroatom selected from oxygen, nitrogen and sulfur, preferably oxygen.

20. The process as claimed in any one of the preceding claims, in which the composition prepared is such that A is substituted with at least one radical chosen from alkyl, cycloalkylalkyl, aryl, aralkyl, hydroxyl, alkoxy, amino and carbonyl radicals.

21. Process according to any one of the preceding claims, in which the composition prepared is such that A is substituted with one or more carboxylic acid functions and / or with one or more hydrocarbon radicals chosen from alkyl, cycloalkyl, cycloalkylalkyl and aryl radicals. aralkyl, themselves substituted by one or more carboxylic acid functions.

22. The process as claimed in any one of the preceding claims, in which the composition prepared is such that A does not contain any other carboxylic acid function.

23. Method according to any one of the preceding claims wherein the composition prepared is such that the level of poly-acid is in a range from 0.2 to 100 phr, preferably from 0.2 to 50 phr.

24. The process as claimed in any one of the preceding claims, in which the composition prepared is such that

i represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, cycloalkyl having 5 to 24 carbon atoms, aryl having 6 to 30 carbon atoms or aralkyl having 7 to 25 carbon atoms; group which may optionally be interrupted by one or more heteroatoms and / or substituted,

R ₃ and R ₄ independently represent identical or different groups chosen from hydrogen or alkyl groups having from 1 to 20 carbon atoms, cycloalkyls having from 5 to 24 carbon atoms, aryls having from 6 to 30 carbon atoms or aralkyls having 7 to 25 carbon atoms; groups which may optionally be interrupted by hetero atoms and / or substituted, or R 3 and R ₄ together with the carbon atoms of the imidazole ring to which they are attached, form a ring selected from aromatic, heteroaromatic or aliphatic rings, comprising from to 12 carbon atoms, preferably 5 or 6 carbon atoms.

25. The process as claimed in any one of the preceding claims, in which the composition prepared is such that R 1 represents a group chosen from alkyl groups having from 2 to 12 carbon atoms, or aralkyls having from 7 to 13 carbon atoms; groups that can be substituted.

26. A process according to any one of the preceding claims wherein the composition prepared is such that R 1 represents an aralkyl group having 7 to 13 carbon atoms optionally substituted and R ₂ represents an alkyl group having 1 to 12 carbon atoms.

27. Process according to any one of the preceding claims, in which the composition prepared is such that R 1 represents an aralkyl group having 7 to 9 carbon atoms which is optionally substituted and R ₂ represents an alkyl group having from 1 to 4 carbon atoms.

28. Process according to any one of the preceding claims, in which the composition prepared is such that R ₃ and R ₄ independently represent identical or different groups chosen from hydrogen or alkyl groups having from 1 to 12 carbon atoms, cycloalkyls. having 5 to 8 carbon atoms, aryls having 6 to 24 carbon atoms or aralkyls having 7 to 13 carbon atoms; groups that can be substituted.

29. Process according to any one of claims 1 to 27 wherein the composition prepared is such that R ₃ and R ₄ form, with the imidazole ring carbon atoms to which they are attached, a phenyl, cyclohexene or cyclopentene ring.

30. The method as claimed in any one of the preceding claims, in which the composition prepared is such that the level of imidazole is in a range from 0.01 to 4 molar equivalents, and preferably from 0.01 to 3 molar equivalents. , with respect to the carboxylic acid functions present on the polycarboxylic acid of general formula (I).

31. A process according to any one of the preceding claims wherein the composition prepared is such that the reinforcing filler comprises carbon black, silica or a mixture of carbon black and silica.

32. Process according to any one of the preceding claims, in which the composition prepared is such that the level of reinforcing filler is in a range from 5 to 200 phr.

33. Process according to any one of the preceding claims in which all the ingredients of the composition including the ingredients of the crosslinking system are introduced during the thermomechanical mixing phase.

34. Process according to any one of claims 1 to 32 in which the ingredients of the crosslinking system are not all introduced during the thermomechanical kneading phase, characterized in that the process comprises a subsequent kneading phase in which the Crosslinking system is completed or incorporated and kneaded to a temperature below 1 10 ° C.

35. Composition obtained by the process as defined in any one of Claims 1 to 34.

36. A tire comprising a composition according to claim 35.

37. A tire according to the preceding claim wherein the composition according to claim 35 is that of the tread.