WO2014095588A1

WO2014095588A1 - Tyre comprising a rubber composition comprising an epoxy resin and a polyacid

Info

Publication number: WO2014095588A1
Application number: PCT/EP2013/076427
Authority: WO
Inventors: Catherine MOUGIN; Anne-Frédérique SALIT
Original assignee: Compagnie Generale Des Etablissements Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2012-12-17
Filing date: 2013-12-12
Publication date: 2014-06-26
Also published as: CN104884521B; FR2999582A1; FR2999582B1; CN104884521A

Abstract

The present invention relates to a tyre comprising a rubber composition based on at least one diene elastomer, a reinforcing filler, a crosslinking system, an epoxy resin, at a content included in a range of from 1 to 20 phr, a polycarboxylic acid of general formula (I) in which A is a covalent bond or a hydrocarbon-based group comprising at least one carbon atom, which is optionally substituted and optionally interrupted with one or more heteroatoms, and an imidazole of general formula (II) in which R₁ is a hydrocarbon-based group or a hydrogen atom, R₂ is a hydrocarbon-based group, R₃ and R₄ are, independently of one another, a hydrogen atom or a hydrocarbon-based group, or else R₃ and R₄ together form, with the carbon atoms of the imidazole ring to which they are attached, a ring.

Description

PNEUMATIC COMPRISING A RUBBER COMPOSITION

COMPRISING AN EPOXY RESIN AND A POLYACID

The present invention relates to tires provided with rubber compositions, in particular rubber compositions having a high rigidity.

It is known to use in certain tire parts, rubber compositions having high rigidity at low tire deformations (see WO 02/10269). Resistance to small deformations is one of the properties that must present a tire to respond to the stresses to which it is subjected.

This stiffening can be obtained by increasing the rate of reinforcing filler or by incorporating certain reinforcing resins into the rubber compositions constituting the parts of the tire.

However, in a known manner, increasing the stiffness of a rubber composition by increasing the loading rate can penalize the hysteresis properties and therefore the rolling resistance of the tires. However, we always try to lower the rolling resistance of tires to reduce fuel consumption for economic and environmental purposes.

[005] Conventionally, this increase in stiffness is obtained by incorporating reinforcing resins based on an acceptor / methylene donor system. The terms "methylene acceptor" and "methylene donor" are well known to those skilled in the art and widely used to designate compounds capable of reacting together to generate by condensation a three-dimensional reinforcing resin which is superimposed, interpenetrated with the reinforcing filler / elastomer network on the one hand, with the elastomer / sulfur network on the other hand (if the crosslinking agent is sulfur). The methylene acceptor previously described is associated with a hardening agent capable of crosslinking or hardening, also commonly called "methylene donor". The crosslinking of the resin is then caused during the firing of the rubber matrix, by formation of methylenic bridges (-CH ₂ -) between the carbons at the ortho and / or para positions of the phenolic rings of the resin and the methylene donor. and thus creating a three-dimensional resin network.

The methylene donors conventionally used in tire rubber compositions are hexamethylenetetramine (abbreviated to HMT), or hexamethoxymethylmelamine (abbreviated to HMMM or H3M), or hexaethoxymethylmelamine. [007] However, it is desirable to find alternatives to conventional reinforcing resins.

[008] Previously, the Applicants have discovered during their research that the usual reinforcing resins can advantageously be replaced by an epoxy resin with a diamine as a hardener. The use of this couple of epoxy resin and diamine reagents makes it possible to obtain rubber compositions having a higher rigidity at low deformation compared to conventional rubber compositions, without appreciably degrading the hysteresis, as described in document FR. 2951 182.

[009] Continuing their research, the Applicants have now found that the diamine hardener of the epoxy resin can advantageously be replaced by a poly-carboxylic acid hardener that is to say comprising several carboxylic acid functions, in the presence of a imidazole. Indeed, the compositions provided with an epoxy resin reinforcing resin and a poly-carboxylic acid hardener surprisingly have improved processability properties and stiffness similar or better than those comprising compositions comprising prior art.

Accordingly, a first object of the invention relates to a tire comprising a rubber composition based on at least one diene elastomer, a reinforcing filler, a crosslinking system, an epoxy resin, at a rate included in a range from 1 to 20 phr, a polycarboxylic acid of general formula (I)

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

and an imidazole of the general formula (II)

in which, R 1 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.

Preferably, the invention also relates to a tire as defined above in which 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 preferentially, A represents a divalent hydrocarbon group comprising from 2 to 100 carbon atoms, preferably from 2 to 50 carbon atoms. Even more preferably, A represents a divalent hydrocarbon group comprising from 3 to 50 carbon atoms. Even more preferably, A represents a divalent hydrocarbon group having from 4 to 30 carbon atoms, preferably from 10 to 40 carbon atoms.

More preferably, the invention also relates to a tire as defined above wherein A is a divalent group of aliphatic or aromatic type or a group comprising at least one aliphatic portion and an aromatic portion. Preferably, A is a divalent group of the aliphatic type, or a group comprising at least one aliphatic part and an aromatic part. More preferably, A is a divalent group of saturated or unsaturated aliphatic type. Even more preferably, A is an alkylene group. Also preferably, A is interrupted by at least one heteroatom selected from oxygen, nitrogen and sulfur, preferably oxygen. Preferably, A is substituted with at least one radical chosen from alkyl, cycloalkylalkyl, aryl, aralkyl, hydroxyl, alkoxy, amino and carbonyl radicals. More 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 by one or more carboxylic acid functions. Alternatively and preferably also, A does not contain any other carboxylic acid function.

More preferably, the invention also relates to a tire as defined above in which the level of polycarboxylic acid is in a range from 0.2 to 4 molar equivalents, and preferably 0.3 at 3 molar equivalents, relative to the epoxide functions present on the epoxy resin. Preferably, the level of poly-carboxylic acid is in a range from 0.5 to 2 molar equivalents, and preferably from 0.5 to 1.5 molar equivalents, based on the epoxide functional groups present on the epoxy resin.

Preferably, the invention also relates to a tire 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 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 5 to 12 carbon atoms, preferably 5 or 6 carbon atoms.

Preferably, the invention also relates to a tire as defined above in which 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.

[0016] Preferably also, the invention also relates to a tire as defined above 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 atoms. of carbon.

Preferably, the invention also relates to a tire as defined above in which R 1 represents an aralkyl group having from 7 to 9 carbon atoms. optionally substituted carbon and R ₂ represents an alkyl group having 1 to 4 carbon atoms.

Also preferably, the invention also relates to a tire as defined above in which 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. 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.

Preferably, the invention also relates to a tire as defined above in which the level of imidazole is in a range from 0.01 to 2 molar equivalents, and preferably from 0.01 to 1, 2 molar equivalents, relative to the carboxylic acid functions present on the polycarboxylic acid of general formula (I). More preferably, the level of imidazole is in a range from 0.01 to 0.8 molar equivalents, and preferably from 0.01 to 0.5 molar equivalents, relative to the carboxylic acid functional groups present on the poly- carboxylic acid of general formula (I).

Preferably, the invention also relates to a tire as defined above in which the diene elastomer is chosen from the group consisting of natural rubber, synthetic polyisoprenes, polybutadienes, butadiene copolymers, copolymers of isoprene and mixtures of these elastomers.

Preferably, the invention also relates to a tire as defined above in which the epoxy resin content is in a range from 3 to 20 phr. More preferably, the level of epoxy resin is in a range from 5 to 18 phr.

[0022] Preferably, the invention also relates to a tire as defined above in which the reinforcing filler comprises carbon black, silica or a mixture of carbon black and silica. Preferably, the amount of reinforcing filler is between 20 and 200 phr.

The invention also relates to a process for preparing a rubber composition as defined above, comprising the following steps: incorporating into a diene elastomer, during a first step (called "nonproductive"), a reinforcing filler, thermomechanically kneading the whole until a maximum temperature of between 110 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

- Then incorporate, in a second step (called "productive"), a crosslinking system;

knead everything to a maximum temperature below 1 10 ° C;

process in which, between 1 and 20 phr of an epoxy resin, a polycarboxylic acid of general formula (I) as defined above, and an imidazole of general formula (II) as defined above are also added independently of one another and indifferently during the first step, and / or during the second step.

According to a first embodiment, the invention also relates to a method as defined above which comprises the following steps:

incorporating in a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, between 1 and 20 phr of an epoxy resin, a polycarboxylic acid of general formula (I) such that defined above, and an imidazole of general formula (II) as defined above by kneading thermomechanically all until a maximum temperature between 1 10 ° C and 190 ° C;

- cool all at a temperature below 100 ° C;

then incorporate, during a second step (called "productive"), a crosslinking system;

knead to a maximum temperature below 1 10 ° C.

According to a second embodiment, the invention also relates to a method as defined above which comprises the following steps:

incorporating into a diene elastomer, during a first step (called "nonproductive"), a reinforcing filler, thermomechanically kneading the whole until a maximum temperature of between 110 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

- Then incorporate, during a second step (called "productive"), a crosslinking system, between 1 and 20 phr of an epoxy resin, a poly-carboxylic acid of general formula (I) as defined above, and an imidazole of general formula (II) as defined above;

knead to a maximum temperature below 1 10 ° C.

According to a third embodiment, the invention also relates to a method as defined above which comprises the following steps:

to incorporate in a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, and between 1 and 20 phr of an epoxy resin, by thermomechanically kneading the whole until reaching a maximum temperature between 110 ° C and 190 ° C;

- cool all at a temperature below 100 ° C;

then, during a second stage (called "productive"), incorporate a crosslinking system, a polycarboxylic acid of general formula (I) as defined above, and an imidazole of general formula (II) such as as defined above;

knead to a maximum temperature below 1 10 ° C.

According to a fourth embodiment, the invention also relates to a method as defined above which comprises the following steps:

incorporating in a diene elastomer, during a first step (called "nonproductive"), a reinforcing filler, a polycarboxylic acid of general formula (I) as defined above, and an imidazole of general formula (II) as defined above by kneading thermomechanically all until a maximum temperature of between 110 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

then incorporate, during a second step (called "productive"), a crosslinking system, and between 1 and 20 phr of an epoxy resin;

- mix everything up to a maximum temperature below 1 10 ° C.

According to a fifth embodiment, the invention also relates to a method as defined above which comprises the following steps:

to incorporate in a diene elastomer, during a first step (called "nonproductive"), a reinforcing filler, between 1 and 20 phr of an epoxy resin and an imidazole of general formula (II) as defined hereinabove. above, kneading thermomechanically all until reaching a maximum temperature between 1 10 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

then incorporate, during a second step (called "productive"), a crosslinking system, and a polycarboxylic acid of general formula (I) as defined above;

knead to a maximum temperature below 1 10 ° C.

According to a sixth embodiment, the invention also relates to a method as defined above which comprises the following steps:

to incorporate in a diene elastomer, during a first step (so-called "non-productive"), a reinforcing filler, a polycarboxylic acid of general formula (I) as defined above, by thermomechanically kneading the whole until reaching a maximum temperature of between 110 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

then incorporate, during a second step (called "productive"), a crosslinking system, between 1 and 20 phr of an epoxy resin and an imidazole of general formula (II) as defined above;

knead to a maximum temperature below 1 10 ° C.

According to a seventh embodiment, the invention also relates to a method as defined above which comprises the following steps:

to incorporate in a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, between 1 and 20 phr of an epoxy resin and a polycarboxylic acid of general formula (I) such that defined above, thermomechanically kneading the whole until reaching a maximum temperature between 1 10 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

then incorporate, during a second step (called "productive"), a crosslinking system and an imidazole of general formula (II) as defined above;

knead to a maximum temperature below 1 10 ° C. According to an eighth embodiment, the invention also relates to a method as defined above which comprises the following steps:

to incorporate in a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, and an imidazole of general formula (II) as defined above, by thermomechanically kneading the whole until reach a maximum temperature of between 110 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

then incorporate, during a second stage (called "productive"), a crosslinking system, between 1 and 20 phr of an epoxy resin and a polycarboxylic acid of general formula (I) as defined above ;

knead to a maximum temperature below 1 10 ° C.

The tires according to the invention are particularly intended for passenger vehicles such as two-wheeled vehicles (motorcycle, bicycle), industrial vehicles chosen from vans, "heavy-goods vehicles" - ie, subway, bus, transport vehicles road transport (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 easily understood in light of the description and examples of embodiments which follow.

I. Tests

The rubber compositions are characterized, before and after firing, as indicated below.

1.1. Mooney viscosity (or Mooney plasticity)

An oscillometric consistometer is used as described in the French standard NF T 43-005 (1991). The Mooney plasticity measurement is carried out according to the following principle: the raw composition (i.e., before firing) is molded in a cylindrical chamber heated to 100 ° C. After one minute of preheating, the rotor rotates within the test tube at 2 revolutions / minute and the useful torque is measured to maintain this movement after 4 minutes of rotation. Mooney plasticity (ML 1 +4) is expressed in "Mooney unit" (UM, with 1 UM = 0.83 Newton meter).

I.2. Dynamic Properties

The dynamic properties G ^* (10%) and tan (δ) max at 40 ° C are measured on a viscoanalyzer (Metravib VA4000), according to the ASTM D 5992-96 standard. The response of a sample of vulcanized composition is recorded (4 mm cylindrical specimen of thickness and 400 mm ² of section), subjected to a sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under normal temperature conditions (23 ° C) according to ASTM D 1349-99, or according to cases at a different temperature. A strain amplitude sweep of 0.1 to 50% (forward cycle) and then 50% to 1% (return cycle) are performed. The results exploited are the complex dynamic shear modulus G ^* and the loss factor tan (δ). For the return cycle, the maximum value of tan (δ) observed, denoted tan (δ) max, as well as the complex dynamic shear modulus G ^* (10%) at 10% deformation, at 40 ° C are indicated.

It is recalled that, in a manner well known to those skilled in the art, the value of tan (δ) max at 40 ° C is representative of the hysteresis of the material and thus the rolling resistance: plus tan (ô) max at 40 ° C is low, the lower the rolling resistance is reduced.

II. Conditions of realization of the invention

The rubber composition according to the invention is based on at least one diene elastomer, a reinforcing filler, a crosslinking system, an epoxy resin, at a rate in a range from 1 to 20 phr, an 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, 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 elastomer is the elastomer representing the largest mass relative to the total mass of the elastomers in the composition. In the same way, a so-called majority charge is that representing the largest mass among the charges of the composition. By way of example, in a system comprising a single elastomer, the latter has a majority within the meaning of present invention; and in a system comprising two elastomers, the majority elastomer represents more than half of the mass of the elastomers.

On the contrary, a "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. Diene elastomer

The rubber composition according to the invention comprises a diene elastomer.

By elastomer or "diene" rubber, must be understood in a known way (one means one or more) elastomer derived at least in part (ie, a homopolymer or a copolymer) of monomers dienes (monomers carrying two double bonds carbon-carbon, conjugated or not).

These diene elastomers can be classified in two categories: "essentially unsaturated" or "essentially saturated". The term "essentially unsaturated" is generally 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%); Thus, diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins of the EPDM type do not fall within the above definition and may in particular be described as "essentially saturated" diene elastomers ( low or very low diene origin, always less than 15%). 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%.

These definitions being given, the term diene elastomer can be understood more particularly to be used in the compositions according to the invention:

any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;

any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms; a ternary copolymer obtained by copolymerization of ethylene, of an α-olefin having 3 to 6 carbon atoms with a non-conjugated diene monomer containing from 6 to 12 carbon atoms, for example elastomers obtained from ethylene propylene with a non-conjugated diene monomer of the aforementioned type, such as in particular hexadiene-1,4, ethylidene norbornene, dicyclopentadiene;

a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated versions, in particular chlorinated or brominated, of this type of copolymer.

Although it applies to any type of diene elastomer, the person skilled in the art of the tire will understand that the present invention is preferably implemented with essentially unsaturated diene elastomers, in particular of the type (a) or (b) above.

By way of conjugated dienes 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C 1 -C 5 alkyl) -1,3-butadienes, such as for example 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl 1,3-butadiene, aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene. Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the "vinyl-toluene" commercial mixture, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene.

The copolymers may contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinylaromatic units. The elastomers may have any microstructure which is a function of the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and the amounts of modifying and / or randomizing agent used. The elastomers can 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. For coupling with carbon black, there may be mentioned for example functional groups comprising a C-Sn bond or amino functional groups such as benzophenone for example; for coupling to a reinforcing inorganic filler such as silica, mention may be made, for example, of silanol or polysiloxane functional groups having a silanol end (as described, for example, in FR 2,740,778 or US Pat. No. 6,013,718), alkoxysilane groups (such as as described for example in FR 2,765,882 or US 5,977,238), carboxylic groups (as described for example in WO 01/92402 or US 6,815,473, WO 2004/096865 or US 2006/0089445) or groups polyethers (as described for example in EP 1 127 909 or US Pat. No. 6,503,973). As other examples of functionalized elastomers, mention may also be made of elastomers (such as SBR, BR, NR or IR) of the epoxidized type.

Polybutadienes and in particular those having a content (mol%) in units -1, 2 of between 4% and 80% or those having a content (mol%) of cis-1, 4 of greater than 80%, are suitable. polyisoprenes, butadiene-styrene copolymers and in particular those having a Tg (glass transition temperature (Tg, measured according to ASTM D3418) between 0 ° C. and -70 ° C. and more particularly between -10 ° C. and -60 ° C. ° C, a styrene content of between 5% and 60% by weight and more particularly between 20% and 50%, a content (mol%) of -1,2 bonds of the butadiene part of between 4% and 75%, a content (mol%) of trans-1,4 bonds of between 10% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 90% by weight and a Tg of -40 At -80 ° C., the isoprene-styrene copolymers and in particular 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 of 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 (mol%) in units -1, 2 of the butadiene part of between 4% and 85%, a content (mol%) in trans-1,4 units of the butadiene part of between 6% and 80%, a content (mol%) in units -1, 2 plus -3 , 4 of the isoprenic part of between 5% and 70% and a content (mol%) in trans units -1, 4 of the isoprenic part of between 10% and 50%, and more generally any butadiene-styrene-isoprene copolymer having a Tg ranging from -20 ° C to -70 ° C.

In summary, the diene elastomer of the composition according to the invention is preferably selected from the group of highly unsaturated diene elastomers consisting of polybutadienes (abbreviated as "BR"), synthetic polyisoprenes (IR), natural rubber (NR), butadiene copolymers, 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) and isoprene-copolymers. butadiene-styrene (SBIR).

According to a particular embodiment, the diene elastomer is predominantly (ie, for more than 50 phr) an SBR, whether it is an emulsion prepared SBR ("ESBR") or a prepared SBR. in solution ("SSBR"), or a blend (mixture) SBR / BR, SBR / NR (or SBR / IR), BR / NR (or BR / IR), or SBR / BR / NR (or SBR / BR / IR). In the case of an SBR elastomer (ESBR or SSBR), an SBR having an average styrene content, for example between 20% and 35% by weight, or a high styrene content, for example 35 to 35% by weight, is used in particular. 45%, a vinyl ring content of the butadiene part of between 15% and 70%, a content (mol%) of trans-1,4 bonds of between 15% and 75% and a Tg of between -10 ° C. and - 55 ° C; such an SBR can be advantageously used in admixture with a BR preferably having more than 90% (mol%) of cis-1,4 bonds.

By "isoprene elastomer" is meant in known manner a homopolymer or copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR) which can be plasticized or peptized, the synthetic polyisoprenes (IR), the various isoprene copolymers and the mixtures of these elastomers. Among the isoprene copolymers, mention will in particular be made of copolymers of isobutene-isoprene (butyl rubber - IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR). This isoprene elastomer is preferably natural rubber or a synthetic cis-1,4 polyisoprene; of these synthetic polyisoprenes, polyisoprenes having a level (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%, are preferably used.

Preferably according to the invention, the elastomers are chosen from the isoprenic elastomers described above, and more preferably, the composition according to the invention comprises predominantly natural rubber (NR), alone, or in a blend with a or several other diene elastomers.

According to another preferred embodiment of the invention, the rubber composition comprises a blend of one (or more) diene elastomer said "high Tg" having a Tg between - 70 ° C and 0 ° C and a (one or more) diene elastomers called "low Tg" between -1 10 ° C and -80 ° C, more preferably between - 105 ° C and -90 ° C. The high Tg elastomer is preferably selected from the group consisting of S-SBR, E-SBR, natural rubber, synthetic polyisoprenes (having a molar ratio (% molar) of cis-1,4 preferably greater than 95%), BIRs, SIRs, SBIRs, and mixtures of these elastomers. The low Tg elastomer preferably comprises butadiene units at a level (mol%) of at least 70%; it consists preferably of a polybutadiene (BR) having a content (mol%) of cis-1,4 chains greater than 90%.

According to another particular embodiment of the invention, the rubber composition comprises, for example, from 30 to 100 phr, in particular from 50 to 100 phr, of a high Tg elastomer in a blend with 0 to 70 phr, in particular from 0 to 50 phr, of a low Tg elastomer; according to another example, it comprises for all 100 pce one or more SBR prepared (s) in solution.

According to another particular embodiment of the invention, the diene elastomer of the composition according to the invention comprises a cleavage of a BR (as low elastomer Tg) having a molar ratio (mol%) of cis-1, 4 chains higher than 90%, with one or more S-SBR or E-SBR (as elastomer (s) high Tg).

The compositions of the invention may contain a single diene elastomer or a mixture of several diene elastomers, or the diene elastomers may be used in combination with any type of synthetic elastomer other than diene, or with polymers other than elastomers, for example thermoplastic polymers.

11.2. Reinforcing charge

It is possible to use 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, 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 black type HAF, ISAF, SAF conventionally used in tires (so-called pneumatic grade black). Among these, mention will be made more particularly of reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as, for example, N 1 15 blacks,

N134, N234, N326, N330, N339, N347, N375, or, depending on the intended applications, black 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 "non-black filler", as opposed to carbon black, capable of reinforcing on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires, in other words capable of replacing, in its reinforcing function, a conventional carbon black of 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 / boy Wut. As highly dispersible precipitated silicas (called "HDS"), there may be mentioned for example the silicas "Ultrasil 7000" and "Ultrasil 7005" from the company Evonik or Degussa, the silicas "Zeosil 1 165MP", "1 135MP" and " 1 1 15MP "of the company Rhodia, the silica" Hi-Sil EZ150G "from the company PPG, the silicas" Zeopol 8715 "," 8745 "and" 8755 "from the company Huber, the silicas with high specific surface area 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 content of total reinforcing filler (carbon black and / or reinforcing inorganic filler such as silica) is between 20 and 200 phr, more preferably between 30 and 150 phr, the optimum being in a known manner. different depending on the particular 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 Trucks.

According to a preferred embodiment of the invention, a reinforcing filler comprising between 30 and 150 phr, more preferably between 50 and 120 phr, is used. organic filler, especially carbon black, and optionally silica; the silica, 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). This preferred embodiment is particularly preferred when the majority elastomer of the composition is an isoprene rubber, more particularly natural rubber.

Alternatively, according to another preferred embodiment of the invention, a reinforcing filler comprising between 30 and 150 phr is used, more preferably between 50 and 120 phr of inorganic filler, particularly silica, 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). This preferred embodiment is particularly preferred when the rubber composition comprises a blend of one (or more) diene elastomer called "high Tg" having a Tg between -70 ° C and 0 ° C and a one or more) diene elastomers called "low Tg" between -1 10 ° C and -80 ° C.

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

In particular, polysulphurized silanes, called "symmetrical" or "asymmetrical" silanes, are used according to their particular structure, as described for example in the applications WO03 / 002648 (or US 2005/016651) and WO03 / 002649 (or US 2005 / 016650).

In particular, the following definition is not limiting, so-called "symmetrical" polysulfide silanes corresponding to the following general formula (I):

(I) Z - A - Sx - A - Z, wherein:

x is an integer of 2 to 8 (preferably 2 to 5);

- A is a divalent hydrocarbon radical (preferably C 1 -C 18 alkylene groups or C 6 -C 12 arylene groups, more particularly C 1 -C 10 alkylenes, especially C 1 -C 4 alkylenes, in particular propylene);

Z is one of the following formulas:

R1 R1 R2

-Si-R1; - Si- R2; - Si- R2,

R2 R2 in which:

the radicals R1, which may be substituted or unsubstituted, which are identical to or different from one another, represent a C1-C18 alkyl, C5-C18 cycloalkyl or C6-C18 aryl group (preferably C1-C6 alkyl, cyclohexyl or phenyl groups, especially C1-C4 alkyl groups, more particularly methyl and / or ethyl).

the radicals R2, substituted or unsubstituted, which are identical to or different from each other, represent a C 1 -C 18 alkoxyl or C 5 -C 18 cycloalkoxyl group (preferably a group chosen from C 1 -C 8 alkoxyls and C 5 -C 8 cycloalkoxyls, more preferably still, a group chosen from C 1 -C 4 alkoxyls, in particular methoxyl and ethoxyl).

In the case of a mixture of polysulfurized alkoxysilanes corresponding to the formula (I) above, in particular common commercially available mixtures, the average value of the "x" is a fractional number preferably between 2 and 5. more preferably close to 4. However, the invention can also be advantageously used for example with disulfide alkoxysilanes (x = 2).

By way of examples of polysulphide silanes, mention may be made more particularly of polysulfides (in particular disulfides, trisulphides or tetrasulfides) of bis (C 1 -C 4 alkoxyl) -alkyl (C 1 -C 4) alkyl-silyl (C 1 -C 4) )), such as polysulfides of bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl). Among these compounds, bis (3-triethoxysilylpropyl) tetrasulfide, abbreviated TESPT, of formula [(C2H50) 3Si (CH2) 3S2] 2 or bis (triethoxysilylpropyl) disulfide, abbreviated as TESPD, is especially used. formula [(C2H50) 3Si (CH2) 3S] 2. Mention may also be made, by way of preferred examples, of polysulphides (in particular disulfides, trisulphides or tetrasulfides) of bis- (monoalkoxyl (C1 -C4) -dialkyl (C1 -C4) silylpropyl), more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide, as described above. in the patent application WO 02/083782 (or US 2004/132880).

As a coupling agent other than polysulfurized alkoxysilane, there may be mentioned in particular bifunctional POS (polyorganosiloxanes) or polysulfides of hydroxysilane (R 2 = OH in formula I above) as described in the patent applications. WO 02/30939 (or US Pat. No. 6,774,255) and WO 02/31041 (or US 2004/051210), or alternatively silanes or POS bearing azo-dicarbonyl functional groups, as described, for example, in the patent applications WO 2006 / 125532, WO 2006/125533, WO 2006/125534. In the rubber compositions according to the invention, the content of coupling agent is preferably between 4 and 12 phr, more preferably between 4 and 8 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, especially 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. Epoxy resin

The epoxy resins that are used in the present invention include all polyepoxide compounds, such as aromatic epoxide compounds, alicyclic epoxy compounds, and aliphatic epoxide compounds. Especially among the aromatic epoxide compounds are preferred novolak epoxy resins, 2,2 bis [4- (glycidyloxy) phenyl] propane, poly [o-cresylglycidyl ether] -co-formaldehyde] and the mixtures of these compounds. By way of example, mention may be made of the "ECN1273", "ECN1280", "ECN1299" and "ECN 951 1" resins marketed by Huntsman or the "DER 332", "DER 354", "DER 383" and "DEN" resins. 425 "," DEN 431 "," DEN 438 "," DEN 439 "marketed by Dow Chemicals.

The degree of epoxidation or epoxidation rate, represented by the average molar mass of resin per epoxy function (EEW = Epoxy Equivalent Weigth), can vary for example from 50 to 1000 g / equivalent. For the purposes of the invention, it is preferred that the epoxidation rate be within a range of from 100 to 600 g / equivalent, preferably from 150 to 300 g / equivalent.

The amount of epoxy resin is in a range from 1 to 20 phr; below the minimum indicated, the technical effect is insufficient, while beyond the maximum indicated, there is a risk of excessive increase in rigidity and excessive penalty of hysteresis. For all these reasons, an amount in a range from 3 to 20 phr is preferably chosen, and more preferably from 5 to 18 phr.

II.4. Poly-acid and imidazole system

The resin described above is associated with a polycarboxylic acid of general formula (I) and an imidazole of general formula (II), capable of crosslinking or hardening. The crosslinking of the resin is caused during the firing of the rubber matrix, by formation of covalent bonds between the resin and the acid functions of the polycarboxylic acid of general formula (I), also called the hardener, thanks to an imidazole activation of general formula (II), also called the activator.

The poly-acid and imidazole system therefore 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).

Il.4.a. 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, preferably from 2 to 300 carbon atoms, more preferably from 2 to 300 carbon atoms. 100 carbon atoms, and very preferably from 2 to 50 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 50 carbon atoms, preferentially from 4 to 30 carbon atoms, more preferably from 4 to 20 carbon atoms.

[0087] Preferably, in the poly-acid of general formula (I), A may be a divalent aliphatic or aromatic group 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 poly-carboxylic acid content is in a range from 0.2 to 4 molar equivalents, and preferably from 0.3 to 3 molar equivalents, relative to the epoxide functional groups present on the epoxy resin. Preferably, this level is in a range from 0.5 to 2 molar equivalents, and preferably from 0.5 to 1.5 molar equivalents, relative to the epoxide functional groups present on the epoxy resin. Below 0.2 molar equivalents of poly-acid, the effect of the crosslinking is not appreciable, whereas above 4 molar equivalents of poly-acid no additional benefit is observed compared to lower rates.

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 commercially available poly-acids 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) cyclopentane carboxylic acid.

Il.4.b. imidazole

The imidazole useful for the tire crosslinking system of 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 (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 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 5 to 12 carbon atoms, preferably 5 or 6 carbon atoms.

Preferably, R-ι represents a group chosen from alkyl groups having from 2 to 12 carbon atoms, or aralkyls having from 7 to 13 carbon atoms. carbon; 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 level of imidazole is preferably in a range from 0.01 to 2 molar equivalents, and preferably from 0.01 to 1, 2 molar equivalents, relative to carboxylic acid functions present on the polycarboxylic acid of general formula (I). Below 0.01 molar equivalents, there is no effect of the imidazole coagent with respect to the situation where the poly-acid is used alone while above a value of 1.2 molar equivalents, there is no additional benefit compared to lower rates. Thus, the level of imidazole is more preferably in a range from 0.01 to 0.8 molar equivalents, and preferably from 0.01 to 0.5 molar equivalents, relative to the carboxylic acid functions present on the poly carboxylic 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.4.C. Poly-acid and imidazole

[00102] Clearly, 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 for forming a salt between one or more acid functional groups of the poly-acid and respectively one or more imidazole nuclei.

11.5. Crosslinking system

The crosslinking system may be a vulcanization system, it is preferably based on sulfur or sulfur donors and primary vulcanization accelerator (preferably 0.5 to 10.0 pce primary accelerator). To this vulcanization system are optionally added, various known secondary accelerators or vulcanization activators such as zinc oxide (preferentially for 0.5 to 10.0 phr), stearic acid, guanidine derivatives (in particular diphenylguanidine), or others (preferably for 0.5 to 5.0 phr each). Sulfur is used at a preferential rate of between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr, for example between 0.5 and 3.0 phr, when the invention is applied to a strip. of tire rolling.

As accelerator (primary or secondary) can be used any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur, especially thiazole-type accelerators and their derivatives, thiuram type accelerators, dithiocarbamates of zinc. These accelerators are more preferably selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated "CBS"), N, N-dicyclohexyl-2-benzothiazyl sulfenamide (abbreviated "DCBS"), N-tert-butyl-2-benzothiazylsulfenamide (abbreviated "TBBS"), N-tert-butyl-2-benzothiazylsulfenimide (abbreviated "TBSI"), zinc dibenzyldithiocarbamate (in abbreviated "ZBEC") and mixtures of these compounds. Preferably, a primary accelerator of the sulfenamide type is used.

According to a particular embodiment of the invention, the composition of the invention is devoid of guanidine derivative or contains less than 0.5 phr. Preferably, the composition is either totally devoid of such compounds, or it contains less than 0.45 phr, preferably less than 0.4 phr, more preferably less than 0.3 phr, preferably less than 0, 2 phr and very preferably less than 0.1 phr. The term "guanidine derivative" is understood to mean the organic compounds bearing as their main function a guanidine function, such as those known in tire compositions, in particular as vulcanization accelerators, for example diphenylguanidine (DPG) or diorthotolylguanidine (DOTG).

According to another particular embodiment of the invention, in the tire according to the invention, the composition comprising the epoxy resin necessary for The invention also has no need for zinc or contains less than 0.5 phr, preferably less than 0.3 phr, more preferably less than 0.2 phr, and most preferably less than 0.1 phr.

11.6. Various additives

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

These compositions can also contain, in addition to the coupling agents, coupling activators, inorganic charge-covering agents or, more generally, processing aid agents that can be used in a known manner, by means of 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.

11.7. Preparation of rubber compositions

The compositions used in the treads of the invention 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 (phase so-called "non-productive") at a high temperature, up to a maximum temperature of between 1 10 ° C and 190 ° C, preferably between 130 ° C and 180 ° C, followed by a second phase of mechanical work (phase so-called "productive") to a lower temperature, typically below 1 10 ° C, for example between 40 ° C and 100 ° C, finishing phase during which the crosslinking system is incorporated.

The process for preparing such compositions comprises for example the following steps:

incorporating into a diene elastomer, during a first step (called "nonproductive"), a reinforcing filler, thermomechanically kneading the whole until a maximum temperature of between 110 ° C and 190 ° C; cool the assembly to a temperature below 100 ° C;

knead everything to a maximum temperature below 1 10 ° C;

it being understood that a polycarboxylic acid of general formula (I) as defined above, an imidazole of general formula (II) as defined above and between 1 and 20 phr of an epoxy resin, are also added independently of one another and indifferently during the first step, and / or during the second step.

For example, the non-productive phase is conducted in a single thermomechanical step during which is introduced, in a suitable mixer such as a conventional internal mixer, in the first place all the basic constituents necessary (a diene elastomer, reinforcing filler and the like), then in a second step, for example after one to two minutes of mixing, the other additives, any optional load-collecting or processing agents, with the exception of crosslinking system. The total mixing time in this non-productive phase is preferably between 1 and 15 minutes. During this phase, may optionally be added the epoxy resin, the hardener and the activator, or only the epoxy resin. If the epoxy resin and the poly-acid and imidazole system are not added during this phase, they should be added during the next phase below so that the epoxy resin and the poly-acid and imidazole system required for the purposes of the invention are present in the finished composition.

After cooling the mixture thus obtained, is then incorporated in an external mixer such as a cylinder mixer, maintained at low temperature (for example between 40 ° C and 100 ° C), the crosslinking system. The whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min. During this phase, the epoxy resin and the polyacid and imidazole system may be added, or only the polyacid and imidazole system if the epoxy resin has been added during the non-productive phase.

The final 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 used for manufacturing of a tire. The invention relates to tires and semi-finished products for tires previously described, rubber articles both in the raw state (that is, before cooking) and in the cooked state (c '). that is, after crosslinking or vulcanization).

11 - Pneumatic of the invention

The rubber composition according to the invention can be used in different parts of the tire, in particular in the crown, the zone of the bead, the zone of the sidewall and the tread (in particular in the underlayer of the tire strip). rolling).

According to a preferred embodiment of the invention, the rubber composition described above can be used in the tire as a rigid 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 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 according to the invention can 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 according to 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 of the invention may be the use of the composition according to 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. III. EXAMPLES OF CARRYING OUT THE INVENTION

111.1. Preparation of compositions

The following tests are carried out as follows: one introduces into an internal mixer (final filling ratio: approximately 70% by volume), the initial tank temperature of which is approximately 60 ° C., diene elastomer, the reinforcing filler and the epoxy resin, as well as the various other ingredients with the exception of the vulcanization system, the hardener and the activator. Thermomechanical work (non-productive phase) is then carried out in one step, which lasts in total about 3 to 4 min, until a maximum temperature of "fall" of 180 ° C is reached.

The mixture thus obtained is recovered, cooled and then sulfur is incorporated, a sulfenamide type accelerator and the poly-acid and imidazole system on a mixer (homo-finisher) at 30 ° C, mixing all (phase). productive) for a suitable time (for example between 5 and 12 min).

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, or extruded in the form of a profile.

111.2. Testing of rubber compositions

This test illustrates rubber compositions which can be used in particular in the underlayer, or in the low tire zone, areas requiring high rigidity at low deformation. These compositions exhibit superior stiffness to a conventional rubber composition (including a phenolic resin and HMT as a methylene donor), while maintaining a similar and acceptable level of hysteresis, otherwise processability, and safety at the same time. The roasting of the compositions of the invention is markedly improved over compositions comprising an epoxy resin and a polyacid and imidazole system.

For this purpose, rubber compositions were prepared as indicated above, composition C1 and C2 being a control composition and compositions C3 to C6 being in accordance with the invention (see Table 1).

The properties of compositions C1 to C6 were measured as indicated above and the results are shown in Table 2.

It is noted that the replacement of the formo-phenolic resin / hardener (s) HMT couple by an epoxy resin, a poly-carboxylic acid and an imidazole in the compositions of the invention C3 to C6 provides a significant improvement the processability of the compositions, represented by lowered Mooney values. Of moreover, a complex dynamic shear modulus G ^* (10%) at 40 ° C equivalent to or greater than that of the control composition, representative of an increase in the low-deformation rigidity of the compositions according to the invention, is noted, while limiting the increase of the loss factor to 40 ° C (noted tan (δ) max), that is to say keeping a hysteresis which remains acceptable.

In summary, the results of these tests demonstrate that the use of an epoxy resin and a poly-carboxylic acid hardener in the compositions of the invention makes it possible to obtain rubber compositions with improved processability. a rigidity at low deformation equivalent to or greater than that of a conventional composition (here control composition), synonymous with an improvement in road behavior, while maintaining an acceptable hysteresis, particularly in certain areas of the tire, especially in the area low and in the underlayer.

Table 1

(1) Natural rubber;

(2) Carbon black N326 (designation according to ASTM D-1765);

(3) Zinc oxide (industrial grade - Umicore company);

(4) Stearin ("Pristerene 4931" from Uniqema);

(5) N-1,3-dimethylbutyl-N-phenylparaphenylenediamine (Santoflex 6-PPD from Flexsys);

(6) Insoluble sulfur at 80%;

(7) Acc: N-cyclohexyl-2-benzothiazyl sulfenamide (Santocure CBS from Flexsys); (8) Resin 1: formophenolic novolac resin ("Peracit 4536K" from Perstorp);

(9) Resin 2: epoxy resin "DEN 439" from Dow Chemical Co.

(10) Resin 3: epoxy resin "ECN 1273" from the company Huntsman

(1 1) Hardener 1: p-xylylene diamine (from Sigma Aldrich)

(12) Hardener 2: Hexamethylenetetramine (from the company Degussa)

(13) Hardener 3: Adipic acid (CAS 124-04-9), from Sigma-Aldrich;

(14) Hardener 4: Terephthalic acid (CAS 100-21 -0), from Sigma-Aldrich;

(15) 1-Benzyl-2-methylimidazole (CAS 13750-62-4), from Sigma-Aldrich.

Table 2

C1 C2 C3 C4 C5 C6

Mooney 77 140 70 71 67 69

G ^* 10% 40 ° C 6.5 7.8 8.8 6 7.5 7

Tan d max 40 ° C 0.23 0.33 0.31 0.31 0.30 0.29

Claims

claims

1. A tire comprising a rubber composition based on at least one diene elastomer, a reinforcing filler, a crosslinking system, an epoxy resin, at a level ranging from 1 to 20 phr, a polycarboxylic acid of formula general (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,

2. A tire comprising a rubber composition according to claim 1 wherein A represents a covalent bond or a divalent hydrocarbon group having 1 to 1800 carbon atoms, preferably 2 to 300 carbon atoms.

3. A tire comprising a rubber composition according to any one of claims 1 or 2 wherein A represents a divalent hydrocarbon group having 2 to 100 carbon atoms, preferably 2 to 50 carbon atoms.

4. A tire comprising a rubber composition according to any one of claims 1 to 3 wherein A represents a divalent hydrocarbon group having from 3 to 50 carbon atoms.

5. A tire comprising a rubber composition according to any one of claims 1 to 4 wherein A represents a divalent hydrocarbon group having from 4 to 30 carbon atoms, preferably from 10 to 40 carbon atoms.

6. A tire comprising a rubber composition according to any one of claims 1 to 5 wherein A is a divalent group of aliphatic or aromatic type or a group having at least one aliphatic portion and an aromatic portion.

7. A tire comprising a rubber composition according to any one of claims 1 to 6 wherein A is a divalent group of the aliphatic type, or a group having at least one aliphatic portion and an aromatic portion.

8. A tire comprising a rubber composition according to any one of claims 1 to 7 wherein A is a divalent group of saturated or saturated aliphatic type.

9. A tire comprising a rubber composition according to any one of claims 1 to 8 wherein A is an alkylene group.

10. A tire comprising a rubber composition according to any one of claims 1 to 9 wherein A is interrupted by at least one heteroatom selected from oxygen, nitrogen and sulfur, preferably oxygen.

1 1. A tire comprising a rubber composition according to any one of claims 1 to 10 wherein A is substituted with at least one radical selected from alkyl, cycloalkylalkyl, aryl, aralkyl, hydroxyl, alkoxy, amino and carbonyl radicals.

12. A tire comprising a composition according to any one of claims 1 to 1 1, wherein A is substituted with one or more carboxylic acid functions and / or with one or more hydrocarbon radicals selected from alkyl, cycloalkyl, cycloalkylalkyl, aryl radicals. aralkyl, themselves substituted by one or more carboxylic acid functions.

13. A tire comprising a composition according to any one of claims 1 to 1 1, wherein the radical A has no other carboxylic acid function.

14. A tire comprising a rubber composition according to any one of the preceding claims, wherein the polycarboxylic acid content is in a range from 0.2 to 4 molar equivalents, and preferably from 0.3 to 3. molar equivalents, relative to the epoxide functions present on the epoxy resin.

15. A tire comprising a rubber composition according to any one of the preceding claims, wherein the polycarboxylic acid content is in a range from 0.5 to 2 molar equivalents, and preferably from 0.5 to 1 molar equivalents. , 5 molar equivalents, relative to the epoxide functions present on the epoxy resin.

Pneumatic tire comprising a rubber composition according to any one of the preceding claims, wherein

17. A tire comprising a rubber composition according to any one of claims 1 to 16, 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.

18. A tire comprising a rubber composition according to any one of claims 1 to 17, wherein R 1 represents an aralkyl group having from 7 to 13 carbon atoms optionally substituted and R ₂ represents an alkyl group having 1 to 12 carbon atoms.

19. A tire comprising a rubber composition according to any one of claims 1 to 18, wherein R 1 represents an aralkyl group having 7 to 9 carbon atoms optionally substituted and R ₂ represents an alkyl group having from 1 to 4 carbon atoms. carbon.

20. A tire comprising a rubber composition according to one of the preceding claims, wherein R ₃ and R ₄ independently represent identical or different groups chosen from hydrogen or alkyl groups having from 1 to 12 carbon atoms, cycloalkyl having from 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.

21. Tire comprising a rubber composition according to one of Claims 1 to 19, in which R ₃ and R ₄ represent, with the carbon atoms of the imidazole ring to which they are attached, a phenyl, cyclohexene or cyclopentene ring.

22. A tire comprising a rubber composition according to any one of the preceding claims, wherein the imidazole content is in a range from 0.01 to 2 molar equivalents, and preferably from 0.01 to 1, 2 molar equivalents, relative to the carboxylic acid functions present on the polycarboxylic acid of general formula (I).

23. A tire comprising a rubber composition according to any one of the preceding claims, wherein the imidazole content is in a range from 0.01 to 0.8 molar equivalents, and preferably from 0.01 to 0. , 5 molar equivalents, relative to the carboxylic acid functions present on the polycarboxylic acid of general formula (I).

24. A tire comprising a rubber composition according to any of claims 1 to 23, wherein the diene elastomer is selected from the group consisting of natural rubber, synthetic polyisoprenes, polybutadienes, butadiene copolymers, copolymers of isoprene and mixtures of these elastomers.

25. A tire comprising a rubber composition according to any one of claims 1 to 24, wherein the epoxy resin content is in a range from 3 to 20 phr.

26. A tire comprising a rubber composition according to any one of claims 1 to 25, wherein the epoxy resin content is in a range from 5 to 18 phr.

27. A tire comprising a rubber composition according to any one of claims 1 to 26, wherein the reinforcing filler comprises carbon black, silica or a mixture of carbon black and silica.

28. A tire comprising a rubber composition according to any one of claims 1 to 27, wherein the amount of reinforcing filler is between 20 and 200 phr.

29. Process for preparing a tire comprising a rubber composition according to any one of claims 1 to 28, characterized in that it comprises the following steps:

cool the assembly to a temperature below 100 ° C;

knead everything to a maximum temperature below 1 10 ° C;

characterized in that between 1 and 20 phr of an epoxy resin, a polycarboxylic acid of general formula (I) as defined in claims 1 to 15, and an imidazole of general formula (II) as defined in Claims 16 to 23 are also added independently of each other and indifferently during the first step, and / or during the second step.

30. The method of claim 29, characterized in that it comprises the following steps:

incorporating in a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, between 1 and 20 phr of an epoxy resin, a polycarboxylic acid of general formula (I) such that defined in claims 1 to 15, and an imidazole of general formula (II) as defined in claims 16 to 23, thermomechanically kneading the whole until a maximum temperature of between 1 10 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C; then incorporate, during a second step (called "productive"), a crosslinking system;

knead to a maximum temperature below 1 10 ° C.

31. Process according to Claim 29, characterized in that it comprises the following steps:

cool the assembly to a temperature below 100 ° C;

then incorporate, during a second stage (so-called "productive"), a crosslinking system, between 1 and 20 phr of an epoxy resin, a polycarboxylic acid of general formula (I) as defined in the claims 1 to 15, and an imidazole of the general formula (II) as defined in claims 16 to 23;

knead to a maximum temperature below 1 10 ° C.

32. The method of claim 29, characterized in that it comprises the following steps:

cool the assembly to a temperature below 100 ° C;

then, during a second (so-called "productive") step, incorporate a crosslinking system, a polycarboxylic acid of general formula (I) as defined in claims 1 to 15, and an imidazole of general formula ( II) as defined in claims 16 to 23;

knead to a maximum temperature below 1 10 ° C.

33. The method of claim 29, characterized in that it comprises the following steps:

incorporating in a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, a polycarboxylic acid of general formula (I) as defined in claims 1 to 15, and an imidazole of general formula (II) as defined in claims 16 to 23, by kneading thermomechanically all until reaching a maximum temperature between 1 10 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

knead to a maximum temperature below 1 10 ° C.

34. The method of claim 29, characterized in that it comprises the following steps:

- Incorporating into a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, between 1 and 20 phr of an epoxy resin and an imidazole of general formula (II) as defined in claims 16 to 23, thermomechanically kneading the whole until reaching a maximum temperature of between 110 ° C and 190 ° C;

- cool all at a temperature below 100 ° C;

then, during a second (so-called "productive") step, incorporate a crosslinking system, and a polycarboxylic acid of general formula (I) as defined in claims 1 to 15;

knead to a maximum temperature below 1 10 ° C.

35. Method according to claim 29, characterized in that it comprises the following steps:

to incorporate in a diene elastomer, during a first step (called "nonproductive"), a reinforcing filler, a polycarboxylic acid of general formula (I) as defined in claims 1 to 15, by thermomechanically kneading all until reaching a maximum temperature of between 110 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

then incorporate, during a second stage (called "productive"), a crosslinking system, between 1 and 20 phr of an epoxy resin and an imidazole of general formula (II) as defined in claims 16 to 23 ;

knead to a maximum temperature below 1 10 ° C.

36. The method of claim 29, characterized in that it comprises the following steps:

to incorporate in a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, between 1 and 20 phr of an epoxy resin and a polycarboxylic acid of general formula (I) such that defined in claims 1 to 15, thermomechanically kneading the whole until reaching a maximum temperature of between 1 10 ° C and 190 ° C;

cool the assembly to a temperature below 100 ° C;

then incorporate, during a second step (called "productive"), a crosslinking system and an imidazole of general formula (II) as defined in claims 16 to 23;

knead to a maximum temperature below 1 10 ° C.

37. The method of claim 29, characterized in that it comprises the following steps:

to incorporate in a diene elastomer, during a first step (called "non-productive"), a reinforcing filler, and an imidazole of general formula (II) as defined in claims 16 to 23, by thermomechanically mixing the whole until reaching a maximum temperature of between 110 ° C and 190 ° C; cool the assembly to a temperature below 100 ° C;

then incorporate, during a second stage (called "productive"), a crosslinking system, between 1 and 20 phr of an epoxy resin and a polycarboxylic acid of general formula (I) as defined in the claims 1 to 15;

knead to a maximum temperature below 1 10 ° C.