WO2015193315A1

WO2015193315A1 - Rubber composition comprising an epoxide elastomer cross-linked by a polycarboxylic acid

Info

Publication number: WO2015193315A1
Application number: PCT/EP2015/063476
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: CN106459371A; FR3022550A1; FR3022550B1; CN106459371B

Abstract

The invention relates to a rubber composition based on at least a majority elastomer comprising epoxide functions, a reinforcing filler, and a system for cross-liking the elastomer, comprising an imidazole and a polycarboxylic acid of general formula (I), in which A represents a hydrocarbon divalent group comprising a majority of type (Ia) and/or (Ib) type radicals.

Description

- -

RUBBER COMPOSITION COMPRISING AN EPOXY ELASTOMER RETICULATED BY A CARBOXYLIC ACIDIC ACID

The present invention relates to 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 the use of a specific poly-acid makes it possible to improve the breaking properties of the compositions.

Accordingly, a first object of the invention relates to 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 divalent hydrocarbon group predominantly composed of radicals of the type (la)

wherein

Ra and Rb represent, independently of one another, a divalent hydrocarbon group,

p and q independently represent an integer greater than or equal to 2, it being understood that the Ra units may be identical or different in the radical (la), and that the Rb units may be identical or different in the radical (Ib);

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,

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.

[007] Preferably, the subject of the invention is a composition as defined above in which 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 preferably from 0 to 50 phr, of one or more non-epoxy minority elastomers. Preferably, the majority diene elastomer comprising epoxide functional groups, represents all 100 phr of elastomer. Preferably, the majority elastomer comprising epoxide functions has a molar epoxidation level in a range of from 0.1% to 80%, preferably in a range of 0.1% to 50%, more preferably in a range from 0.3% to 50%. More preferably, the elastomer The majority comprising epoxide functions is selected from the group consisting of epoxidized diene elastomers, epoxidized olefinic elastomers and mixtures thereof. 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 functional groups is an olefinic elastomer comprising epoxide functions, preferably comprising epoxide functional groups comprising between 50 and 95%, more preferably between 65 and 85% olefin. (molar percentages). Preferably, the olefinic elastomer comprising epoxide functional groups is an epoxidized ethylenic elastomer.

[008] Preferably, the subject of the invention is a composition as defined above in which A represents a divalent hydrocarbon group comprising from 4 to 1800 carbon atoms, preferably from 6 to 300 carbon atoms, more preferably from 8 to 100 carbon atoms, more preferably 8 to 65 carbon atoms.

[009] Preferably also, the subject of the invention is a composition as defined above in which A is a group such that the polycarboxylic acid compound of general formula (I) can be represented by the general formula (IA )

wherein Ra and p are as defined above, and wherein B1 and B2 are independently of each other, divalent hydrocarbon radicals which are the same or different, optionally substituted or interrupted by one or more heteroatoms selected from oxygen, nitrogen and sulfur. Preferably, B1 and B2 represent, independently of each other, divalent hydrocarbon radicals which are identical or different and are chosen from the group consisting of alkylenes comprising 1 to 6 carbon atoms and cycloalkylenes containing from 5 to 7 carbon atoms, arylenes comprising from 6 to 12 carbon atoms or aralkylenes comprising from 7 to 13 carbon atoms, these radicals optionally comprising radicals of the -C (= O) - and / or -O- type.

Alternatively and preferably also, the subject of the invention is a composition as defined above in which A is a group such as the poly-acid compound. carboxylic acid of the general formula (I) may be represented by the general formula (IB) or

wherein Ra, Rb, p and q are as defined above, and wherein B3, B4 and B5 are independently of each other, divalent hydrocarbon radicals which are the same or different, optionally substituted or interrupted by one or more selected heteroatoms among oxygen, nitrogen and sulfur. Preferably, B3, B4 and B5 represent, independently of one another, divalent hydrocarbon radicals which are identical or different and are chosen from the group consisting of alkylenes comprising from 1 to 6 carbon atoms, cycloalkylenes having from 5 to 7 carbon atoms, and arylenes comprising from 6 to 12 carbon atoms or aralkylenes comprising from 7 to 13 carbon atoms, these radicals optionally comprising radicals of the -C (= O) - and / or -O- type.

Preferably, Ra and Rb represent, independently of one another, a divalent group chosen from the group consisting of alkylene groups having from 1 to 20 carbon atoms, cycloalkylene having from 5 to 24 carbon atoms, arylene having from 6 to 30 carbon atoms or aralkylene having from 7 to 25 carbon atoms; group which may optionally be interrupted by one or more heteroatoms and / or substituted. More preferably, Ra and Rb represent, independently of one another, a divalent group chosen from the group consisting of alkylene groups having from 1 to 12 carbon atoms, or aralkylene having from 7 to 13 carbon atoms; grouping which may possibly be substituted. Even more preferably, Ra and Rb represent, independently of one another, an alkylene group having from 1 to 12 carbon atoms, and very preferably Ra and Rb represent, independently of one another, an alkylene group having from 4 to to 8 carbon atoms.

Preferably, the subject of the invention is a composition as defined above in which Ra and / or Rb are substituted by at least one radical chosen from alkyl, cycloalkylalkyl, aryl, aralkyl, hydroxyl and alkoxy radicals. amino and carbonyl. Preferably, Ra and / or Rb are substituted by one or more 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 preferably also, Ra and / or Rb do not have other carboxylic acid functional groups.

[0013] Preferably also, the subject of the invention is a composition as defined above in which p and q represent, independently of one another, an integer comprised in a range from 2 to 100, preferably 4 to at 50, better, from 6 to 30.

Preferably, the subject of the invention is a composition as defined above in which 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 composition as defined above in which,

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 chosen from hydrogen or alkyl groups having 1 to 20 carbon atoms, cycloalkyls having 5 to 24 carbon atoms, aryls having 6 to 30 carbon atoms; or aralkyls having 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 composition as defined above wherein 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. Preferably, Ri 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 from 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 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 composition as defined above in which the level of imidazole is in a range from 0.01 to 4 molar equivalents, and preferably from 0.01 to 3 equivalents. molar, with respect to the carboxylic acid functions present on the polycarboxylic acid of general formula (I).

Preferably, the invention relates to a composition as defined above in which the reinforcing filler comprises carbon black, silica or a mixture of carbon black and silica. Preferably, the total level of reinforcing filler is between 5 and 200 phr. Preferably, the reinforcing filler comprises silica as a majority.

Preferably, the invention relates to a composition as defined above wherein the composition further comprises a silica covering agent. Preferably, the silica covering agent is chosen from the group consisting of hydroxylated or hydrolysable silanes, polyols, polyethers, amines, hydroxylated or hydrolysable polysiloxanes, guanidine derivatives, alkali metal or alkaline hydroxides. -terreux and mixtures of such compounds.

The invention also relates to a tire comprising a composition as defined above, preferably as a tread composition.

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. A treatment of the recordings of - - traction also makes it possible to draw the modulus curve according to the 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. We measure in second elongation (Le., After an accommodation cycle at the extension rate provided for the measurement itself) the nominal secant modulus (or apparent stress, in MPa) at 10% or 50% elongation ( respectively noted MSA10 or MSA50). The tensile measurements for determining the breaking stresses (in MPa) and the elongations at break (in%) and the secant accommodated modules are carried out at a given temperature (usually 23 ° C or 40 ° C +/- 2 ° C ), and under normal humidity conditions (50 +/- 5% relative humidity). These values can be converted to base 100 for easy comparison of results.

II. Composition of the invention

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

By the expression composition "based on" 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, the meaning of the present invention is understood to mean 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 any range of values designated by the term "from a to b" means the range 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 otherwise specified in the present application, according to ASTM D3418 of 1999.

The epoxidized elastomer may be selected 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 epoxy 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 epoxidized functional groups.

A first characteristic of epoxy diene elastomers, is therefore to be diene elastomers. These diene elastomers, which by definition are non-thermoplastic 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 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 level 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 (NR), 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 blocks, statistics, 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.

Polybutadienes and, in particular, those having a content in units -1, 2 of between 4% and 80% or those having a content of cis-1,4 are preferably suitable. above 80%, polyisoprenes, butadiene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and more particularly between 20% and 40%, a content of bonds -1. , 2 of the butadiene part of between 4% and 65%, a content of trans-1,4 bonds of 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 particularly 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 epoxidized diene elastomer useful for the needs 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" - -

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 epoxidized functions. In this case, they can be obtained either by postpolymerization modification (see for example J. Appl 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, 37, 2822). For example, US201 10098404 discloses emulsion copolymerization of 1,3-butadiene, styrene and glycidyl methacrylate.

The level (mol%) of epoxidation of the epoxide 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 level of O is between 50 and 95%, preferentially between 65 and 85% This olefinic elastomer is therefore a copolymer also comprising 5 to 50 mol% of non-olefinic units, that is to say other than 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 units, noted A 'are present in the carbon chain such that the molar level 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 epoxidized 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 described above 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 epoxidized olefinic elastomers may be chosen from non-olefinic monomers which do not lead 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 1.100.

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 The carriers of epoxide groups have been described, for example, in the documents EP 0247580 or US Pat. No. 5,557,080. Also, Arkema proposes commercially epoxidized polyethylenes under the trade names Lotader AX8840 and Lotader AX8900.

The compositions of the invention may contain a single epoxidized elastomer or a mixture of several epoxidized elastomers (which will then be noted in the singular 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 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 from 70 to 100 phr, of epoxidized elastomer predominant 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.

II.2. Reinforcing charge

Any type of reinforcing filler known for its ability to reinforce a rubber composition that can be used for manufacturing 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 for 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 N1 15, N 134, N234, N326, N330, N339, N347 or N375, will also be mentioned. , depending on the intended applications, blacks of higher series (for example 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 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, for example, of the silicas Ultrasil 7000 and Ultrasil 7005 from the company Degussa, the silicas Zeosil 1 165MP, 1 135MP and 1 1 15MP from the company Rhodia, the silica Hi -Sil EZ150G from the PPG company, the Zeopol 8715, 8745 and 8755 silicas of the Huber Company, the high surface area silicas as described in the application 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 between 5 and 200 phr, more preferably between 10 and 150 phr, the optimum being in a known manner. different according to - - the specific applications targeted: the level of reinforcement expected on a bicycle tire, for example, is of course less than that required on a tire capable of driving at high speed in a sustained manner, for example a motorcycle tire, a tire for a vehicle for tourism or for commercial vehicles such as heavy goods vehicles.

According to a preferred embodiment of the invention, silica is the majority reinforcing filler. Preferably, a reinforcing filler comprising between 5 and 150 phr, more preferably between 10 and 120 phr of inorganic filler, particularly of silica, is used; 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 compositions 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 12 phr.

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 hardening the composition of the invention. This crosslinking system comprises a (that is to say at least one) specific polycarboxylic acid of general formula (I) and one (that is to say at least one) imidazole of general formula (II) . - - ll.3.a. Poly-

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

in which A represents a divalent hydrocarbon group predominantly composed of radicals of the type (Ia) and / or (Ib),

in which Ra and Rb independently of one another represent a divalent hydrocarbon group, p and q independently represent an integer greater than or equal to 2, it being understood that the Ra units may be identical or different in the radical (la), and that the Rb units may be the same or different in the radical (Ib).

Preferably in the poly-acid of general formula (I), A represents a covalent bond or a divalent hydrocarbon group comprising from 4 to 1800 carbon atoms, preferably from 6 to 300 carbon atoms, more preferably from 8 to 100 carbon atoms, and very preferably 8 to 65 carbon atoms. Above 1800 carbon atoms, the poly-acid is a less effective crosslinking agent.

Preferably in the poly-acid of general formula (I), A is a group such that the polycarboxylic acid compound of general formula (I) can be represented by the general formula (IA)

in which Ra and p are as defined above, and wherein B1 and B2 represent, independently of one another, divalent hydrocarbon radicals which are identical or different, optionally substituted or interrupted by one or more heteroatoms chosen from oxygen, nitrogen and sulfur. - -

Preferably, B1 and B2 represent, independently of one another, divalent hydrocarbon radicals which are identical or different and are chosen from the group consisting of alkylenes comprising from 1 to 6 carbon atoms, cycloalkylenes having from 5 to 7 carbon atoms. carbon atoms, arylenes comprising from 6 to 12 carbon atoms or aralkylenes comprising from 7 to 13 carbon atoms, optionally comprising radicals of the -C (= O) - and / or -O- type.

Preferably in the poly-acid of general formula (I), A is a group such that the polycarboxylic acid compound of general formula (I) can be represented by the general formula (IB) or (IC)

wherein Ra, Rb, p and q are as defined above, and wherein B3, B4 and B5 are independently of each other, divalent hydrocarbon radicals which are the same or different, optionally substituted or interrupted by one or more heteroatoms selected from 1 oxygen, nitrogen and sulfur.

Preferably, B3, B4 and B5 represent, independently of one another, divalent hydrocarbon radicals which are identical or different and are chosen from the group consisting of alkylenes comprising 1 to 6 carbon atoms, and cycloalkylenes having from 5 to 7 atoms. carbon, arylenes comprising from 6 to 12 carbon atoms or aralkylenes comprising from 7 to 13 carbon atoms, these radicals optionally comprising radicals of the -C (= O) - and / or -O- type.

Preferably in the above formulas, Ra and Rb represent, independently of one another, a divalent group chosen from the group consisting of alkylene groups having from 1 to 20 carbon atoms, cycloalkylene having from 5 to 24 carbon atoms, arylene having 6 to 30 carbon atoms or aralkylene having 7 to 25 carbon atoms; group which may optionally be interrupted by one or more heteroatoms and / or substituted. - -

More preferably, Ra and Rb represent, independently of one another, a divalent group chosen from the group consisting of alkylene groups having from 1 to 12 carbon atoms, or aralkylene having from 7 to 13 carbon atoms; grouping which may possibly be substituted. Preferably, Ra and Rb represent, independently of one another, an alkylene group having from 1 to 12 carbon atoms, and in particular an alkylene group having from 4 to 8 carbon atoms.

Preferably, Ra and / or Rb are substituted with at least one radical chosen from alkyl, cycloalkylalkyl, aryl, aralkyl, hydroxyl, alkoxy, amino and carbonyl radicals.

Also preferably, Ra and / or Rb are 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 several carboxylic acid functions.

In a preferred embodiment, Ra and / or Rb do not include other carboxylic acid function.

Preferably, p and q represent, independently of each other, an integer comprised in a range from 2 to 100, preferably from 4 to 50, more preferably from 6 to 30.

For the proper functioning of the invention, it is preferable that the level of poly-acid is in a range from 0.2 to 100 phr, preferably from 0.2 to 50 phr, more preferably from 0 to 50 phr. , 4 to 27 phr, and more preferably still from 0.9 to 25 phr. Below 0.2 phr of poly-acid, the effect of the crosslinking is insensitive while beyond 100 phr of poly-acid, the poly-acid, crosslinking agent, becomes predominant by weight relative to the elastomeric matrix.

For example, as poly-acids useful for the purposes of the invention, mention may be made of polyesters described in the following documents: JP05062890, CN1247198, J. Polym. Sci. Part A 1993, 31, 1825 or J. Mat. Sci. Technol. 1994, 10 (5), 351.

Il.3.b. imidazole

The imidazole useful for the crosslinking system according to the invention is an imidazole of 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 together with the carbon atoms of the imidazole ring to which they are attached, form a ring.

Preferably, the imidazole of general formula (I I) 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 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.

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 from 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 ₄ 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

Obviously, and according to 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. - -

11.4. Various additives

The rubber compositions of the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended for the production of treads, for example pigments, protective agents such as waxes anti-ozone, anti-ozonants chemicals, antioxidants, 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 (in particular silica) or, more generally, processing aid agents that can be used in a known manner, by improving the dispersion of the filler in the rubber matrix and lowering the viscosity of the compositions, to improve their ability to implement in the green state.

If it is present, the silica covering agent is preferably selected from the group consisting of hydroxylated or hydrolyzable silanes, polyols, polyethers, amines, hydroxylated or hydrolyzable polysiloxanes, guanidine derivatives. alkali or alkaline earth metal hydroxides and mixtures of such compounds; more preferably, in the group consisting of amines, guanidine derivatives, hydroxides of alkali or alkaline earth metals and mixtures of such compounds; preferably, in the group consisting of primary amines, guanidine derivatives, alkali metal or alkaline earth metal hydroxides and mixtures of such compounds; and most preferably, the silica capping agent is diphenylguanidine or octadecylamine.

If present, the silica covering agent is present at a level within a range from 0.5 to 30 phr, preferably from 1 to 15 phr.

Preferably, the compositions of the invention are devoid 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 of the invention. Preferably, the compositions 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 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 compositions of the invention

The rubber compositions can 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. temperature, up to a maximum temperature of between 90 ° C. and 190 ° C., preferably from 100 ° C. to 135 ° C., optionally followed by a second mechanical working phase (so-called "productive" phase) up to a greater low temperature, typically below 1 10 ° C, for example between 40 ° C and 100 ° C, finishing phase during which may be incorporated the crosslinking system.

The compositions are thus 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 than the poly-acid and imidazole, optionally poly-acid and imidazole, up to a maximum temperature of between 90 ° C. and 190 ° C., preferably in the range of from 100 ° C. to 135 ° C., at which temperature the mixing is carried out stopped.

Preferably, the method for preparing the compositions of the invention does not include any thermomechanical mixing step at a temperature greater than 135 ° C.

According to a first preferred embodiment, the poly-acid and imidazole are added to the composition during the first phase of work previously described; in this case the process for preparing the compositions of the invention may be a single-stage mixing process.

Preferably, according to this first embodiment, the ingredients are introduced in the following order: epoxidized elastomer, 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 first mixing phase, or if neither of them are added during this step, they are at a later stage. - -

Thus, according to the second embodiment, the preparation comprises a subsequent mechanical working phase (so-called "productive" phase), during which the crosslinking system is completed (if only the poly-acid or imidazole has 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 to a lower temperature, that is to say less than 1 10 ° C, preferably between 40 ° C and 100 ° C, the temperature at which the kneading is stopped.

It is understood that the second embodiment includes three variants in the moment of addition of the ingredients of the crosslinking system: the case where the poly-acid is introduced during the first phase of work and the imidazole is introduced during the subsequent work phase, 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.

II.6. Use in pneumatic

The rubber composition obtained may for example be used in different parts of said tire, in particular in the crown, the zone of the bead, the zone of the sidewall and the tread (especially in the underlayer of the tread ).

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, in rubber composition (or "elastomer", both being considered as synonyms), of any shape and thickness, in particular sheet, strip, or other element of any straight section, for example rectangular or triangular.

Firstly, 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, Le., The portion intended to come into contact with the tread, road during taxiing, and secondly the belt reinforcing said vertex. The thickness of this elastomeric layer is preferably within a range from 0.5 to 10 mm, especially in a range from 1 to 5 mm.

According to another preferred embodiment of the invention, the rubber composition of the invention may be used to form an elastomeric layer, disposed in the region of the region of the bead of the tire, radially between the carcass ply, the bead and the overturning of the carcass ply.

[00119] Also, the composition 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 of the invention to form an elastomeric layer disposed in the area of the sidewall of the tire.

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

The tires in which the composition of the invention is usable, are particularly intended for passenger vehicles such as two-wheeled vehicles (motorcycle, bicycle), industrial vehicles chosen from vans, "heavy-weight" - ie, metro , buses, road transport vehicles (trucks, tractors, trailers), off-the-road vehicles, agricultural or civil engineering machinery, aircraft, other transport or handling vehicles. 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

III.1. Preparation of specific diacids of the invention

Polyester A: The Capa® 2100 (polycaprolactone terminated diol molecular weight ~ 1000 g / mol, supplied by Perstorp, 30 g) is introduced into a monocolon of 500 ml with 150 ml of chloroform. After azeotropic distillation, the succinic anhydride (Sigma Aldrich, 6.6 g) and the DMAP (dimethylaminopyridine, Sigma Aldrich, 0.27 g) are added to the reaction medium. The reaction is carried out for 4 hours at 40 ° C according to the reaction scheme below. The product of synthesis is finally recovered after three aqueous extractions (chloroform / water), drying on anhydrous sodium sulphate and evaporation of the solvents under vacuum. Polyester A is obtained with a yield of 89%. - -

Polyester B: The Capa® 2100 (polycaprolactone terminated diol molecular weight ~ 1000 g / mol, supplied by Perstorp, 30 g) is introduced into a 500 mL monocolon with 150 mL of chloroform. After azeotropic distillation, phthalic anhydride (Sigma Aldrich, 9.1 g) and DMAP (dimethylaminopyridine, Sigma Aldrich, 0.25 g) are added to the reaction medium. The reaction is carried out for 4 hours at 60 ° C. according to the reaction scheme below. The product of synthesis is finally recovered after three aqueous extractions (chloroform / water), drying on anhydrous sodium sulphate and evaporation of the solvents under vacuum. Polyester B is obtained with a yield of 75%.

III.2. Compositions according to the invention

The compositions according to the invention (C2 and C3) and the control composition (C1) were 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 Rhodia;

(3) Poly (acrylonitrile-co-butadiene), terminated dicarboxy, CAS 68891 -46-3, from Aldrich, M = 3800 g / mol

(4) Diacid-terminated polyester A, M = 1300 g / mol;

(5) Diacid-terminated polyester B, M = 1200 g / mol;

(6) 1-Benzyl-2-methylimidazole, CAS = 13750-62-4 from Sigma-Aldrich;

(7) Diphenylguanidine "Perkacit DPG" from the company Flexsys.

The properties of compositions C1 to C3 were measured as indicated above and the results are shown in Table 2 below.

Table 2

In the compositions of the invention there is a very clear improvement in the breaking properties of the compositions, compared to the same composition prepared with a poly-acid which does not meet the criteria of the invention. Furthermore, in the compositions, it may be noted that the replacement of the conventional vulcanization system by a poly-acid and imidazole crosslinking system, as prescribed for the invention makes it possible to overcome the known disadvantages of sulfur systems.

Claims

claims

1. 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),

wherein

p and q independently represent an integer greater than or equal to 2,

it being understood that the Ra units may be identical or different in the radical (la), and that the Rb units may be identical or different in the radical (Ib);

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,

R ₃ and R ₄ represent, independently of one another, a hydrogen atom 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.

2. Composition according to claim 1, in which 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.

3. Composition according to any one of the preceding claims, in which the majority diene elastomer comprising epoxide functional groups represents all of the 100 phr of elastomer.

4. Composition according to any one of the preceding claims, in which the majority elastomer comprising epoxide functional groups has a molar epoxidation level 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%.

5. Composition according to any one of the preceding claims wherein the majority elastomer comprising epoxide functional groups is selected from the group consisting of epoxidized diene elastomers, epoxidized olefinic elastomers and mixtures thereof.

6. Composition according to any one of the preceding claims wherein the majority elastomer comprising epoxide functional groups is an epoxide diene elastomer.

7. Composition according to any one of the preceding claims, in which 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, copolymers of butadiene-styrene epoxides and mixtures thereof.

8. Composition according to any one of claims 1 to 5 wherein the major elastomer comprising epoxide functions is an olefinic elastomer comprising epoxide functions.

9. The composition of claim 8 wherein the olefinic elastomer comprising epoxide functions comprises between 50 and 95%, more preferably between 65 and 85% olefin (molar percentages).

10. Composition according to any one of claims 8 or 9 wherein the olefinic elastomer comprising epoxide functional groups is an epoxidized ethylenic elastomer.

1 1. Composition according to any one of the preceding claims, in which A represents a divalent hydrocarbon group comprising from 4 to 1800 carbon atoms, preferably from 6 to 300 carbon atoms.

12. Composition according to any one of the preceding claims, in which A represents a divalent hydrocarbon group containing from 8 to 100 carbon atoms, preferably from 8 to 65 carbon atoms.

13. Composition according to any one of the preceding claims wherein A is a group such that the polycarboxylic acid compound of general formula (I) can be represented by the general formula (IA)

wherein Ra and p are as defined in claim 1, and wherein B1 and B2 are independently of each other, divalent hydrocarbon radicals which are the same or different, optionally substituted or interrupted by one or more heteroatoms selected from 1 oxygen, nitrogen and sulfur.

14. Composition according to claim 13 wherein B1 and B2 represent, independently of each other, divalent hydrocarbon radicals which are identical or different and are chosen from the group consisting of alkylenes comprising from 1 to 6 carbon atoms, the cycloalkylenes having from 1 to 6 carbon atoms. 5 to 7 carbon atoms, the arylenes comprising 6 to 12 carbon atoms or the aralkylenes comprising 7 to 13 carbon atoms, these radicals optionally comprising radicals of the -C (= O) - and / or -O- type; .

15. Composition according to any one of claims 1 to 12 wherein A is a group such that the polycarboxylic acid compound of general formula (I) can be represented by the general formula (IB) or (IC)

wherein Ra, Rb, p and q are as defined in claim 1, and wherein B3, B4 and B5 are independently of each other, divalent hydrocarbon radicals which are the same or different, optionally substituted or interrupted by one or more heteroatoms selected from oxygen, nitrogen and sulfur.

The composition of claim 15 wherein B3, B4 and B5 are independently of each other, divalent hydrocarbon radicals, the same or different, selected from the group consisting of alkylenes having 1 to 6 carbon atoms, the cycloalkylenes having with 7 carbon atoms, the arylenes comprising from 6 to 12 carbon atoms or the aralkylenes comprising from 7 to 13 carbon atoms, optionally comprising radicals of the -C (= O) - and / or -O- type.

17. A composition according to any one of the preceding claims wherein Ra and Rb independently of one another represent a divalent group selected from the group consisting of alkylene groups having 1 to 20 carbon atoms, cycloalkylene having 24 carbon atoms, arylene having 6 to 30 carbon atoms or aralkylene having 7 to 25 carbon atoms; group which may optionally be interrupted by one or more heteroatoms and / or substituted.

18. A composition according to any one of the preceding claims wherein Ra and Rb independently of one another represent a divalent group selected from the group consisting of alkylene groups having 1 to 12 carbon atoms, or aralkylene having 7 to 13 carbon atoms; grouping which may possibly be substituted.

19. Composition according to any one of the preceding claims, in which Ra and Rb represent, independently of one another, an alkylene group having from 1 to 12 carbon atoms.

20. Composition according to any one of the preceding claims, in which Ra and Rb represent, independently of one another, an alkylene group having from 4 to 8 carbon atoms.

21. A composition according to any one of the preceding claims wherein Ra and / or Rb are substituted with at least one radical selected from alkyl, cycloalkylalkyl, aryl, aralkyl, hydroxyl, alkoxy, amino and carbonyl radicals.

22. Composition according to any one of the preceding claims, in which Ra and / or Rb are 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 by one or more carboxylic acid functions.

23. Composition according to any one of the preceding claims, in which Ra and / or Rb do not comprise any other carboxylic acid function.

24. Composition according to any one of the preceding claims, in which p and q represent, independently of one another, an integer comprised in a range from 2 to 100, preferably from 4 to 50, more preferably from 6 to 30.

25. Composition according to any one of the preceding claims, in which the poly-acid content is in a range from 0.2 to 100 phr, preferably from 0.2 to 50 phr.

26. Composition according to any one of the preceding claims wherein,

27. Composition according to any one of the preceding claims, in which R 1 represents a group chosen from alkyl groups having from 2 to 12 carbon atoms, or aralkyls having 7 to 13 carbon atoms; groups that can be substituted.

28. Composition according to any one of the preceding claims, in which 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.

29. Composition according to any one of the preceding claims, in which R 1 represents an optionally substituted aralkyl group having 7 to 9 carbon atoms and R ₂ represents an alkyl group having from 1 to 4 carbon atoms.

30. Composition according to any one of the preceding claims wherein 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 atoms. carbon, aryls having 6 to 24 carbon atoms or aralkyls having 7 to 13 carbon atoms; groups that can be substituted.

31. Composition according to any one of Claims 1 to 29, in which 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.

32. Composition according to any one of the preceding claims, in which the imidazole content is 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).

33. Composition according to any one of the preceding claims wherein the reinforcing filler comprises carbon black, silica or a mixture of carbon black and silica.

34. Composition according to any one of the preceding claims wherein the total content of reinforcing filler is between 5 and 200 phr.

35. Composition according to the preceding claim wherein the reinforcing filler comprises silica as a majority.

36. Composition according to any one of the preceding claims wherein the composition further comprises a silica-coating agent.

37. Composition according to the preceding claim wherein the silica covering agent is selected from the group consisting of hydroxylated or hydrolyzable silanes, polyols, polyethers, amines, hydroxylated polysiloxanes or hydrolyzable, guanidine derivatives, alkali or alkaline earth metal hydroxides and mixtures of such compounds.

38. A tire comprising a composition according to any one of claims 1 to 37.

39. A tire according to the preceding claim wherein said composition is that of the tread.