CN113039074A

CN113039074A - Rubber composition for tire tread

Info

Publication number: CN113039074A
Application number: CN201980074837.1A
Authority: CN
Inventors: F·瓦赞
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2018-11-15
Filing date: 2019-11-14
Publication date: 2021-06-25
Also published as: EP3880489A1; CA3117748A1; FR3088644A3; JP2022507330A; FR3088643A1; WO2020099789A1; FR3088643B1

Abstract

The invention relates to a tire having an improved balance of properties, the tread of which comprises a rubber composition based on at least one elastomer matrix, a reinforcing filler and a vulcanization system, wherein the elastomer matrix comprises 35 to 95 parts by weight per hundred parts by weight of elastomer (phr) of a first diene elastomer which is a copolymer based on butadiene and styrene, said copolymer comprising within its structure at least one alkoxysilane group attached to the elastomer via a silicon atom and at least one function comprising a nitrogen atom and having a glass transition temperature of less than-70 ℃, and 5phr to 40phr of a second elastomer which is an isoprene elastomer.

Description

Rubber composition for tire tread

Technical Field

The present invention relates to a tire having a tread, and particularly to a tire having a snow tread, a winter tread, or a four season tread (referred to as a "snow tire", "winter tire", or "four season tire") that can run on snow-covered ground. It is known that these snow tires (identified by the marks M + S or m.s. or M & S marked on their sidewalls) are characterized by a tread design and structure which is intended in particular to ensure a behaviour in mud, snow or snow slush that is superior to that of tires of the type of road designed for running on ground without snow cover.

Background

Snow-covered ground, known as white ground, is characterized by a low coefficient of friction, which has led to the development of snow tires comprising a tread based on a diene rubber composition having a low glass transition temperature Tg. However, the grip performance on wet ground of these tires comprising such a tread is generally lower than that of road tires, the treads of which are generally based on rubber compositions having different formulations (in particular those having a higher Tg). In order to solve this problem, application WO 2012/069565 proposes a tread whose composition comprises a diene elastomer bearing at least one functional SiOR (R being a hydrogen atom or a hydrocarbon radical) in combination with a high content of reinforcing inorganic filler and a specific plasticizing system.

Furthermore, as fuel economy and the need to protect the environment have become priorities, it has been desirable to use rubber compositions that can be used to manufacture various semi-finished products involved in forming tire casings with reduced rolling resistance. However, a reduction in rolling resistance is generally contradictory to an improvement in grip on wet ground and snow-covered ground.

Furthermore, the snow or winter tread generally has a reduced wear resistance, since it is generally provided with a more flexible tread pattern and/or is composed of a softer rubber composition than a "summer" tread. It is also important to preserve or even improve the wear resistance of the snow tread or winter tread as much as possible.

Therefore, manufacturers are always seeking solutions for further improving the compromise in terms of properties of rolling resistance of the tyre tread, in particular intended to run on snow-covered ground, grip on wet ground and wear resistance.

Disclosure of Invention

In the course of continuing research, the applicant has surprisingly found that the use of certain functional diene elastomers in combination with isoprene elastomers enables a further improvement in the above performance compromise.

The subject of the present invention is therefore a tire, the tread of which comprises a rubber composition based on at least one elastomeric matrix, a reinforcing filler and a vulcanization system, wherein the elastomeric matrix comprises:

-35 to 95 parts by weight per hundred parts by weight of elastomer (phr) of a first diene elastomer, said first diene elastomer being a copolymer based on butadiene and styrene comprising within its structure at least one alkoxysilane group bonded to the elastomer through a silicon atom and at least one function comprising a nitrogen atom and having a glass transition temperature of less than-70 ℃,

-from 5phr to 40phr of a second elastomer, the second diene elastomer being an isoprene elastomer, and

-optionally from 0 to 40phr of a third diene elastomer.

In the present application, unless otherwise specified, the expression "composition" or "composition according to the invention" denotes the composition of the tread according to the invention.

I-DingYi (Chinese character)

The expression "composition based on" is understood to mean that the composition comprises a mixture and/or an in situ reaction product of the various components used, some of which are capable of (and/or intended to) at least partially react with each other during the various manufacturing stages of the composition; thus, the composition may be in a fully or partially crosslinked state or in an uncrosslinked state.

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

In the present application, all percentages (%) shown are mass percentages (%), unless explicitly stated otherwise.

Furthermore, any numerical interval denoted by the expression "between a and b" means a numerical range from greater than a to less than b (i.e. limits a and b are not included), whereas any numerical interval denoted by the expression "from a to b" means a numerical range extending from a up to b (i.e. including the strict limits a and b). In the present application, when numerical intervals are described by the expression "from a to b", intervals represented by the expression "between a and b" are also preferably described.

When referring to a "primary" compound, for the purposes of the present invention it is understood to mean that, among the same type of compounds of the composition, the compound is primary, i.e. the compound which makes up the greatest amount by mass among the compounds of the same type. Thus, for example, the predominant elastomer is the elastomer that has taken the greatest mass relative to the total mass of elastomers in the composition. In the same way, the "predominant" filler is the filler that makes up the greatest mass of the fillers in the composition. For example, in a system comprising only one elastomer, which for the purposes of the present invention is predominant, in a system comprising two elastomers, the predominant elastomer represents more than half the mass of the elastomer. Preferably, the term "primary" is understood to mean present at more than 50%, preferably more than 60%, 70%, 80%, 90%, more preferably the "primary" compound makes up 100%.

The carbon-containing compounds mentioned in the description may be of fossil or bio-based origin. In the case of bio-based sources, they may be partially or completely derived from biomass or obtained by renewable starting materials derived from biomass. In particular to polymers, plasticizers, fillers, and the like.

The glass transition temperature (Tg) of the elastomer was determined by means of a differential calorimeter (differential scanning calorimeter) according to the standard ASTM E1356-08 (2014).

II-description of the invention

II-1 elastomeric matrix

According to the invention, the elastomeric matrix of the composition of the tire tread comprises:

-35 to 95phr of a first diene elastomer, said first diene elastomer being a butadiene and styrene based copolymer comprising within its structure at least one alkoxysilane group bonded to the elastomer through a silicon atom and at least one function comprising a nitrogen atom and having a glass transition temperature of less than-70 ℃,

-optionally from 0 to 40phr of a third diene elastomer.

"diene" elastomer (or rubber without distinction), whether natural rubber or synthetic rubber, is understood in a known manner to mean an elastomer which is at least partially (i.e. a homopolymer or a copolymer) composed of diene monomer units (monomers bearing two conjugated or non-conjugated carbon-carbon double bonds).

The first diene elastomer is a copolymer based on butadiene and styrene.

Within the meaning of the present invention, styrene-and butadiene-based copolymers mean any copolymer obtained by copolymerization of one or more styrene compounds with one or more butadiene compounds. The following are particularly suitable as styrene monomers: styrene, methyl styrene, p- (tert-butyl) styrene, methoxy styrene and chlorostyrene. The following are particularly suitable as butadiene monomers: 1, 3-butadiene, 2-methyl-1, 3-butadiene, 2, 3-di (C)₁-C₅Alkyl) -1, 3-butadienes (e.g., 2, 3-dimethyl-1, 3-butadiene, 2, 3-diethyl-1, 3-butadiene, 2-methyl-3-ethyl-1, 3-butadiene, or 2-methyl-3-isopropyl-1, 3-butadiene) and aryl-1, 3-butadienes. These elastomers may have any microstructure depending on the polymerization conditions used, in particular the presence or absence of the modifying and/or randomizing agent and the amount of modifying and/or randomizing agent used. The elastomer may for example be a block elastomer, a random elastomer, a sequential elastomer or a microsequential elastomer.

The first diene elastomer is advantageously a butadiene/styrene copolymer (SBR).

It should be noted that SBR may be prepared in Emulsion (ESBR) or in solution (SSBR). Whether it is ESBR or SSBR, SBR may have any microstructure compatible with a glass transition temperature of less than-70 ℃. In particular, the butadiene/styrene copolymer may have a styrene content of between 1% and 60% by weight, more particularly between 10% and 50%, a1, 2-bond content (mol%) of the butadiene moiety of between 4% and 75% and a trans-1, 4-bond content (mol%) of between 10% and 80%.

Advantageously, the first diene elastomer has a glass transition temperature in the range-105 ℃ to-70 ℃, preferably-100 ℃ to-75 ℃, preferably-95 ℃ to-80 ℃.

Preferably, the first diene elastomer is a styrene/butadiene copolymer having any one, advantageously two or three in combination, still more advantageously all of the following characteristics:

it is a styrene/butadiene copolymer (SSBR) prepared in solution,

-the mass content of styrene is between 1% and 15%, preferably between 1% and 5%, relative to the total weight of the styrene/butadiene copolymer,

the vinyl bond content of the butadiene moiety is between 4% and 25%, preferably between 10% and 15%.

The first diene elastomer comprises within its structure at least one alkoxysilane group bonded to the elastomer through a silicon atom and a function comprising a nitrogen atom.

In the present description, the concept of alkoxysilane groups located within the elastomeric structure is understood to be groups in which the silicon atom is located in and directly attached to the backbone of the polymer. Such locations within the structure include polymer chain ends. Thus, the concept includes end groups. The alkoxysilane groups are not pendant groups.

When the alkoxysilane groups are located at the chain ends, it can be said that the diene elastomer is functionalized at the chain ends.

When the alkoxysilane groups are located in the main elastomer chain, the diene elastomer can be said to be coupled or functionalized in the middle of the chain, compared to the position "at the chain ends", although said groups are not located exactly in the middle of the elastomer chain. The functional silicon atom bonds two branches of the main chain of the diene elastomer.

A diene elastomer can be said to be star-branched when the silicon atom is in a central position bonded to at least three elastomer branches forming the star-branched structure of the elastomer. The silicon atoms are thus substituted by at least three branches of the diene elastomer.

It should be noted that, as known to the person skilled in the art, when modifying an elastomer by reaction of a functionalizing agent with a living elastomer resulting from an anionic polymerization step, a mixture of modified species of this elastomer is obtained, the composition of said mixture depending on the modification reaction conditions, in particular the ratio of the reactive sites of the functionalizing agent with respect to the number of living elastomer chains. The mixture includes species functionalized, coupled, star-branched, and/or unfunctionalized at the chain ends.

Advantageously, the first diene elastomer comprises, as the main species, a diene elastomer functionalized in the middle of the chain by alkoxysilane groups bonded to the two branches of the diene elastomer by silicon atoms, the alkoxy groups optionally being partially or completely hydrolyzed to hydroxyl groups. Still more particularly, the diene elastomer functionalized in the middle of the chain by means of alkoxysilane groups represents 70% by weight of the first diene elastomer.

Alkoxysilyl groups in which the alkoxy group is optionally partially or completely hydrolysed to hydroxylThe clique may include C₁-C₁₀Alkyl, or even C₁-C₈Alkyl, preferably C₁-C₄Alkyl, more preferably alkoxy, is methoxy or ethoxy.

The first diene elastomer further comprises at least one functional group comprising a nitrogen atom.

The nitrogen atom containing functionality may be located at the chain end and attached directly to the elastomer by a covalent bond or a hydrocarbyl group.

The nitrogen atom-containing function may also advantageously be carried by an alkoxysilane group. The function comprising a nitrogen atom may be carried by the silicon of the alkoxysilane group directly or via a spacer group. The spacer group may be an atom (particularly a heteroatom) or a group of atoms.

The spacer group may be a saturated or unsaturated, cyclic or acyclic, linear or branched divalent aliphatic C₁-C₁₈Hydrocarbyl or divalent aromatic C₆-C₁₈Hydrocarbyl, and may contain one or more aromatic groups and/or one or more heteroatoms. The hydrocarbyl group may be optionally substituted.

Advantageously, the spacer group is a linear or branched divalent aliphatic C₁-C₁₈A hydrocarbon group, more preferably a divalent aliphatic C₁-C₁₀Hydrocarbyl, still more preferably linear divalent C₂Or C₃A hydrocarbyl group.

The first diene elastomer may also contain another functionality within the elastomer (i.e., a functionality different from the above), but this is not preferred.

The first diene elastomer may also be a mixture of a plurality of first diene elastomers.

The alkoxysilane groups may be represented by the formula:

(*—)_aSi(OR’)_bR_cX

wherein:

-;

the radical R represents a substituted or unsubstituted C₁-C₁₀Alkyl, or even C₁-C₈Alkyl, preferably C₁-C₄Alkyl, more preferably methylA group and an ethyl group;

in the alkoxy group of formula-OR '(optionally partially OR completely hydrolysed to hydroxyl), R' represents a substituted OR unsubstituted C₁-C₁₀Alkyl, or even C₁-C₈Alkyl, preferably C₁-C₄Alkyl, more preferably methyl and ethyl;

-X represents a group comprising a nitrogen-based function;

-a is 1 or 2, b is 1 or 2, c is 0 or 1, with the proviso that a + b + c is 3.

It will be appreciated by those skilled in the art that the value of a depends on the position of the alkoxysilane groups within the elastomer structure. When a is 1, the group is located at the chain end. When a is 2, the group is located in the middle of the chain.

As the function containing a nitrogen atom, an amine function may be mentioned. Primary (optionally protected by a protecting group), secondary (optionally protected by a protecting group) or tertiary amines are particularly suitable.

As secondary or tertiary amine functions, mention may thus be made of₁-C₁₀Alkyl, preferably C₁-C₄Alkyl, more preferably methyl or ethyl, or a cyclic amine forming a heterocycle comprising a nitrogen atom and at least one carbon atom, preferably 2 to 6 carbon atoms. For example, suitable are methylamino, dimethylamino, ethylamino, diethylamino, propylamino, dipropylamino, butylamino, dibutylamino, pentylamino, dipentylamino, hexylamino, dihexylamino or hexamethyleneamino groups, preferably diethylamino and dimethylamino groups. When the amine is a cyclic amine, the following groups are also suitable: morpholine, piperazine, 2, 6-dimethylmorpholine, 2, 6-dimethylpiperazine, 1-ethylpiperazine, 2-methylpiperazine, 1-benzylpiperazine, piperidine, 3-dimethylpiperidine, 2, 6-dimethylpiperidine, 1-methyl-4- (methylamino) piperidine, 2,6, 6-tetramethylpiperidine, pyrrolidine, 2, 5-dimethylpyrrolidine, azetidine, hexamethyleneimine, heptamethyleneimine, 5-benzyloxyindole, 3-azaspiro [ 5.5.5 ]]Undecane, 3-azabicyclo [3.2.2]Nonane, carbazole, bistrimethylsilylamines, pyrrolidine and hexamethyleneamine, preferably the group pyrrolidine andhexamethylene amine.

The amine function is preferably a tertiary amine function, preferably diethylamine or dimethylamine.

Advantageously, at least two, preferably at least three, preferably at least four, more preferably all of the following features are observed:

the nitrogen atom-containing function is a tertiary amine, more particularly a diethylamino or dimethylamino group,

the function comprising a nitrogen atom is carried by the alkoxysilane group via a spacer group, said spacer group being defined as aliphatic C₁-C₁₀Hydrocarbyl, still more preferably linear C₂Or C₃A hydrocarbon group,

the alkoxysilane groups are methoxysilanes or ethoxysilanes, optionally partially or completely hydrolyzed to silanols,

-the first diene elastomer is a butadiene/styrene copolymer,

-the first diene elastomer is mainly functionalized in the middle of the chain by means of alkoxysilane groups bonded to the two branches of the first diene elastomer by means of silicon atoms,

-the glass transition temperature of the first diene elastomer is in the range of-105 ℃ to-70 ℃.

Particularly preferably, at least two, preferably at least three, preferably at least four, more preferably all of the following features are observed:

the nitrogen atom-containing function being derived from an alkoxysilane group via a linear aliphatic C₃The hydrocarbon group carries a radical of a hydrogen atom,

-the first diene elastomer is a butadiene/styrene copolymer,

-the glass transition temperature of the first diene elastomer is in the range of-95 ℃ to-80 ℃.

The content of the first diene elastomer in the composition of the tire tread according to the invention is advantageously in the range from 40phr to 80 phr.

The first diene elastomer may be obtained by the process described below.

The first step of the process for preparing the first diene elastomer is to anionically polymerize at least one conjugated diene monomer or to polymerize at least one conjugated diene monomer with a vinyl aromatic monomer in the presence of a polymerization initiator. The monomers are as described above.

As polymerization initiator, any known monofunctional anionic initiator can be used. However, it is preferred to use initiators comprising alkali metals, such as lithium.

Organolithium initiators containing carbon-lithium bonds are particularly suitable. Representative compounds are aliphatic organolithium compounds such as ethyllithium, n-butyllithium (n-BuLi), isobutyllithium, and the like.

Based on the embodiment according to the invention in which the other functions are directly bonded to the elastomer chain, said functions can be provided by a polymerization initiator. Such initiators are, for example, polymerization initiators comprising amine functions, which generate living chains with amino groups at the unreacted chain ends.

As the polymerization initiator containing an amine function, lithium amide (a reaction product of an organolithium compound (preferably an alkyllithium compound) and an acyclic or cyclic (preferably cyclic) secondary amine) can be preferably mentioned.

As secondary amines which can be used for preparing the initiator, mention may be made of dimethylamine, diethylamine, dipropylamine, di (N-butyl) amine, di (sec-butyl) amine, dipentylamine, dihexylamine, di (N-octyl) amine, di (2-ethylhexyl) amine, dicyclohexylamine, N-methylbenzylamine, diallylamine, morpholine, piperazine, 2, 6-dimethylmorpholine, 2, 6-dimethylpiperazine, 1-ethylpiperazine, 2-methylpiperazine, 1-benzylpiperazine, piperidine, 3-dimethylpiperidine, 2, 6-dimethylpiperidine, 1-methyl-4- (methylamino) piperidine, 2,6, 6-tetramethylpiperidine, pyrrolidine, 2, 5-dimethylpyrrolidine, azetidine, hexamethyleneimine, heptamethyleneimine, 5-benzyloxyindole, 3-azaspiro [5.5] undecane, 3-azabicyclo [3.2.2] nonane, carbazole, bistrimethylsilylamine, pyrrolidine and hexamethyleneamine. When the secondary amine is a cyclic secondary amine, it is preferably selected from pyrrolidine and hexamethyleneamine.

The alkyllithium compound is preferably ethyllithium, n-butyllithium (n-BuLi), isobutyllithium or the like.

The polymerization is preferably carried out in the presence of an inert hydrocarbon solvent, which may be, for example, an aliphatic or alicyclic hydrocarbon (e.g., pentane, hexane, heptane, isooctane, cyclohexane or methylcyclohexane) or an aromatic hydrocarbon (e.g., benzene, toluene or xylene).

The microstructure of the elastomer can be determined by the presence or absence of the modifier and/or randomizer and the amount of modifier and/or randomizer used. Preferably, when the diene elastomer is based on a diene and a vinyl aromatic compound, the amount of polar agent used in the polymerization step is such that said polar agent promotes the random distribution of the vinyl aromatic compound along the polymer chain.

Advantageously, the living diene elastomer resulting from the polymerization is subsequently functionalized by a functionalizing agent capable of introducing alkoxysilane groups into the polymer structure, thus preparing a first diene elastomer.

The reaction for modifying the living diene elastomer obtained at the end of the first step can be carried out at a temperature of between-20 ℃ and 100 ℃ by adding a living polymer chain or, conversely, a non-polymerizable functionalizing agent capable of forming alkoxysilane groups, silicon atoms being incorporated into the elastomer chain with or without the functionality comprising nitrogen atoms. It is in particular a functionalizing agent bearing functions reactive with respect to the reactive elastomer, each of these functions being directly bonded to a silicon atom.

The functionalizing agent corresponds to the formula:

(OR’)_dSi(R)_cX

wherein:

■ alkoxy at formula-ORIn the radical (which may optionally be partially or completely hydrolysed), R' represents a substituted or unsubstituted C₁-C₁₀Alkyl, or even C₁-C₈Alkyl, preferably C₁-C₄Alkyl groups, more preferably methyl and ethyl;

■ R represents a substituted or unsubstituted C₁-C₁₀Alkyl, or even C₁-C₈Alkyl, preferably C₁-C₄Alkyl, more preferably methyl and ethyl;

■ X represents a group containing a functional group containing a nitrogen atom;

■ d is 2 or 3 and c is 0 or 1, provided that d + c is 3.

The functions comprising nitrogen atoms are as defined above.

The function comprising a nitrogen atom may be a protected or unprotected primary amine, a protected or unprotected secondary amine or a tertiary amine. The nitrogen atom may then be substituted by two identical or different radicals, which may be trialkylsilyl (alkyl having from 1 to 4 carbon atoms) or C₁-C₁₀(preferably C)₁-C₄) Alkyl (more preferably methyl or ethyl), or two substituents of nitrogen form with the nitrogen a heterocyclic ring comprising a nitrogen atom and at least one carbon atom (preferably 2 to 6 carbon atoms).

As functionalizing agents there may be mentioned, for example, (N, N-dialkylaminoalkyl) trialkoxysilanes, (N-alkylaminoalkyl) trialkoxysilanes, secondary amine functions protected by trialkylsilyl groups, (aminoalkyl) trialkoxysilanes, primary amine functions protected by two trialkylsilyl groups, divalent hydrocarbon groups capable of bonding an amine function to a trialkoxysilane group being a spacer group as described above (preferably aliphatic C)₁-C₁₀More particularly linear C₂Or C₃)。

The functionalizing agent may be selected from (3-N, N-dimethylaminopropyl) trimethoxysilane, (3-N, N-dimethylaminopropyl) triethoxysilane, (3-N, N-diethylaminopropyl) trimethoxysilane, (3-N, N-diethylaminopropyl) triethoxysilane, (3-N, N-dipropylaminopropyl) trimethoxysilane, (3-N, N-dipropylaminopropyl) triethoxysilane, (3-N, N-dibutylaminopropyl) trimethoxysilane, (3-N, N-dibutylaminopropyl) triethoxysilane, (3-N, N-dipentylaminopropyl) trimethoxysilane, (3-N, N-dipentylaminopropyl) triethoxysilane, and mixtures thereof, (3-N, N-dihexylaminopropyl) trimethoxysilane, (3-N, N-dihexylaminopropyl) triethoxysilane, (3-hexamethyleneaminopropyl) trimethoxysilane, (3-hexamethyleneaminopropyl) triethoxysilane, (3-morpholinopropyl) trimethoxysilane, (3-morpholinopropyl) triethoxysilane, (3-piperidinopropyl) trimethoxysilane or (3-piperidinopropyl) triethoxysilane. More preferably, the functionalizing agent is (3-N, N-dimethylaminopropyl) trimethoxysilane.

The functionalizing agent may be selected from (3-N, N-methyltrimethylsilylaminopropyl) trimethoxysilane, (3-N, N-methyltrimethylsilylaminopropyl) triethoxysilane, (3-N, N-ethyltrimethylsilylaminopropyl) trimethoxysilane, (3-N, N-ethyltrimethylsilylaminopropyl) triethoxysilane, (3-N, N-propyltrimethylsilylaminopropyl) trimethoxysilane or (3-N, N-propyltrimethylsilylaminopropyl) triethoxysilane. More preferably, the functionalizing agent is (3-N, N-methyltrimethylsilylaminopropyl) trimethoxysilane.

The functionalizing agent may be selected from (3-N, N-bistrimethylsilylaminopropyl) trimethoxysilane and (3-N, N-bistrimethylsilylaminopropyl) triethoxysilane. More preferably, the functionalizing agent is (3-N, N-bistrimethylsilylaminopropyl) trimethoxysilane.

The functionalizing agent is advantageously chosen from (N, N-dialkylaminoalkyl) trialkoxysilanes; more particularly herein, the functionalizing agent is (3-N, N-dimethylaminopropyl) trimethoxysilane.

It should be noted that, as known to the person skilled in the art, when modifying an elastomer by reaction of a functionalizing agent with a living elastomer resulting from an anionic polymerization step, a mixture of modified species of this elastomer is obtained, the composition of said mixture depending in particular on the ratio of the reactive sites of the functionalizing agent with respect to the number of living elastomer chains. The mixture comprises species functionalized, coupled, star-branched and/or unfunctionalized at the chain ends.

The molar ratio of functionalizing agent to metal of the polymerization initiator depends substantially on the type of first diene elastomer desired. Thus, in the ratio range of 0.40 to 0.75, or even 0.45 to 0.65, or 0.45 to 0.55, the formation of the coupling species (alkoxysilane group in the middle of the chain) in the modified elastomer is facilitated. In the same way, in the ratio range from 0.15 to 0.40, or even from 0.20 to 0.35, or from 0.30 to 0.35, star-branched (three-branched) species are predominantly formed within the modified elastomer. At ratios greater than or equal to 0.75, or even greater than 1, species functionalized at the chain ends are predominantly formed.

Advantageously, the molar ratio between the functionalizing agent and the polymerization initiator varies from 0.35 to 0.65, preferably from 0.40 to 0.60, still more preferably from 0.45 to 0.55.

Thus, the first diene elastomer may comprise, as the main species, a diene elastomer functionalized in the middle of the chain by an alkoxysilane group bonded to the two branches of the diene elastomer by a silicon atom. Still more particularly, the diene elastomer functionalized in the middle of the chain by means of alkoxysilane groups represents 70% by weight of the first diene elastomer.

Advantageously, the alkoxysilane groups advantageously comprise alkoxy groups, which are optionally partially or completely hydrolyzed to hydroxyl groups.

Alternatively, the alkoxysilane groups advantageously carry a functionality as defined above comprising a nitrogen atom. The function is preferably via a spacer group (in particular divalent linear C) as defined above₂Or C₃Hydrocarbyl group) to a silicon atom, a tertiary amine function as defined above (in particular a diethylamino or dimethylamino group).

When the functionalizing agent bears a protected functionality, the synthetic method may be followed by a deprotection step for that functionality. This step is carried out after the modification reaction and is well known to the person skilled in the art.

The synthesis process may also comprise a step of hydrolysis of the hydrolysable alkoxy function by addition of an acid, a base or a neutral compound, as described in document EP 2266819 a 1. The hydrolyzable functionality is then converted to a hydroxyl functionality.

The process of synthesizing the first diene elastomer may be followed by a step of recovering the first diene elastomer in a manner known per se.

These steps may in particular comprise a stripping step for the purpose of recovering the elastomer obtained from the preceding step. The effect of this stripping step is to fully or partially hydrolyze the hydrolyzable functionality of the first diene elastomer. Advantageously, at least 50 to 70 mol% of these functions can be hydrolyzed thereby.

As indicated above, the second diene elastomer is an isoprene elastomer.

The term "isoprene elastomer" is understood in a known manner to mean an isoprene homopolymer or copolymer, in other words a diene elastomer selected from Natural Rubber (NR), synthetic polyisoprenes (IR), various isoprene copolymers and mixtures of these elastomers. Among the isoprene copolymers, mention will in particular be made of isobutene/isoprene (butyl rubber-IIR) copolymers, isoprene/Styrene (SIR) copolymers, isoprene/Butadiene (BIR) copolymers or isoprene/butadiene/Styrene (SBIR) copolymers. The isoprene elastomer is preferably natural rubber or synthetic cis-1, 4-polyisoprene; among these synthetic polyisoprenes, preference is given to using polyisoprenes having a cis-1, 4-linkage content (mol%) of greater than 90%, and more preferably still greater than 98%.

Advantageously, the second elastomer is a polyisoprene having a mass content of cis-1, 4-linkages of at least 90% of the mass of the polyisoprene. Preferably, the second elastomer is selected from the group consisting of natural rubber, synthetic polyisoprene, and mixtures thereof. More preferably, the polyisoprene is natural rubber.

The content of the second diene elastomer in the composition for a tire tread according to the invention is preferably in the range from 10phr to 35phr, preferably from 10phr to 30 phr.

The composition of the tire tread according to the invention may optionally comprise a third diene elastomer, for example in a content ranging from 0 to 40 phr.

The third diene elastomer is, of course, different from the first diene elastomer and the second diene elastomer described in the present application.

Advantageously, the third diene elastomer is chosen from polybutadienes (BR), butadiene copolymers and mixtures thereof.

The content of third diene elastomer in the composition for a tire tread according to the invention is preferably in the range from 5phr to 35phr, preferably from 10phr to 30 phr.

The composition of the tire tread according to the invention may also comprise another diene elastomer, but this is not preferred. Advantageously, therefore, the total content of the first diene elastomer, of the second diene elastomer and of the third diene elastomer in the composition for a tire tread according to the invention is in the range 80phr to 100phr, preferably 90phr to 100phr, more preferably 100 phr.

Advantageously, the total content of the first diene elastomer and of the second diene elastomer in the composition for a tire tread according to the invention is in the range 80phr to 100phr, preferably 90phr to 100phr, more preferably 100 phr.

The composition of the tire tread according to the invention may also comprise small amounts of any type of synthetic elastomer other than diene elastomers, or even polymers other than elastomers, such as thermoplastic polymers. Preferably, the elastomeric matrix does not comprise a synthetic elastomer other than a diene elastomer or a polymer other than an elastomer, or comprises less than 10phr, preferably less than 5phr, of a synthetic elastomer other than a diene elastomer or a polymer other than an elastomer.

II-2 reinforcing fillers

The composition of the tire tread according to the invention additionally comprises reinforcing fillers known for their ability to reinforce rubber compositions that can be used for the manufacture of tires.

The reinforcing filler may comprise carbon black, a reinforcing inorganic filler or a mixture thereof.

The carbon black that may be used in the context of the present invention may be any carbon black conventionally used in tires or treads therefor ("tire grade" carbon black). Among the "tire grade" blacks, mention will be made more particularly of reinforcing blacks of the series 100, 200 and 300, or blacks of the series 500, 600 or 700 (ASTM grades), such as, for example, the blacks N115, N134, N234, N326, N330, N339, N347, N375, N550, N683 and N772. These carbon blacks may be used in a separate state as is commercially available, or in any other form (e.g., as a carrier for some of the rubber additives used). The carbon black may, for example, have been incorporated into diene elastomers, in particular isoprene elastomers, in the form of a masterbatch (see, for example, applications WO 97/36724 or WO 99/16600).

As examples of organic fillers other than carbon black, mention may be made of functionalized polyvinyl organic fillers as described, for example, in applications WO 2006/069792, WO 2006/069793, WO 2008/003434 and WO 2008/003435.

According to standard D6556-10[ multipoint (at least 5 points) method-gas: nitrogen-relative pressure P/P0 range: 0.1 to 0.3] measuring the BET specific surface area of the carbon black.

The silica which can be used in the context of the present invention may be any silica known to the person skilled in the art, in particular having a BET surface area and a CTAB specific surface area both of which are less than 450m²A/g, preferably of 30m²G to 400m²(ii) any precipitated silica or fumed silica per gram.

The BET specific surface area of The silica is determined in a known manner by gas adsorption using The Brunauer-Emmett-Teller method described in The Journal of The American Chemical Society (vol.60, p.309, month 2 1938), more particularly according to French Standard NF ISO 9277 (multipoint (5 points) volumetric method-gas: nitrogen-degassing: 1 hour at 160 ℃ C. -relative pressure p/p)₀The range is as follows: 0.05 to 0.17). The CTAB specific surface area of the silica was determined according to French standard NF T45-007 (method B) at 11 months 1987.

Preferably, the silica has less than 200m²BET specific surface area/g and/or less than 220m²CTAB specific surface area/g, preferably of 125m²G to 200m²In the range of/gAnd/or at 140m²G to 170m²CTAB specific surface area in the range of/g.

As silicas that can be used in the context of the present invention, mention will be made, for example, of the highly dispersible precipitated silicas from Evonik (known as "HDS") Ultrasil 7000 and Ultrasil 7005, the silicas Zeosil 1165MP, 1135MP and 1115MP from Rhodia, the silica Hi-Sil EZ150G from PPG, the silicas Zeopol 8715, 8745 and 8755 from Huber or the silicas with high specific surface area as described in application WO 03/16837.

For coupling the reinforcing silica to the diene elastomer, use is made, in a known manner, of an at least bifunctional coupling agent (or bonding agent) aimed at providing a linkage of satisfactory chemical and/or physical characteristics between the silica (on the surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used.

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

Mention may in particular be made of alkoxysilane polysulfide compounds, in particular bis (trialkoxysilylpropyl) polysulfide, very particularly bis (3-triethoxysilylpropyl) disulfide (abbreviated to "TESPD") and bis (3-triethoxysilylpropyl) tetrasulfide (abbreviated to "TESPT"). It should be remembered that TESPD (formula [ (C)₂H₅O)₃Si(CH₂)₃S]₂) In particular sold by Degussa under the name Si266 or Si75 (in the second case in the form of a mixture of disulfides (75% by weight) and polysulfides). TESPT (chemical formula is [ (C)₂H₅O)₃Si(CH₂)₃S]₂) Sold in particular by Degussa under the name Si69 (or X50S when it is supported on carbon black at 50% by weight) and is the polysulfide S_x(wherein x has an average value of about 4).

Advantageously, the reinforcing filler comprises mainly a reinforcing inorganic filler, preferably silica.

The content of reinforcing inorganic filler, preferably silica, in the composition for a tire tread according to the invention may range from 90phr to 200phr, preferably from 95phr to 180phr, preferably from 100phr to 150 phr.

Furthermore, the content of carbon black in the composition for a tire tread according to the invention may range from 0 to 40phr, preferably from 1phr to 20phr, preferably from 2phr to 10 phr.

II-3 vulcanization system

The vulcanization system preferably comprises molecular sulfur and/or at least one sulfur donor. Also preferably present is at least one vulcanization accelerator, and optionally, also preferably, various known vulcanization activators such as zinc oxide, stearic acid or equivalent compounds (e.g., stearates and transition metal salts), guanidine derivatives (especially diphenylguanidine), or known vulcanization retarders may be used.

Sulfur is used in an amount of preferably between 0.5phr and 12phr, in particular between 1phr and 10 phr. Vulcanization accelerators are used in amounts preferably between 0.5phr and 10phr, more preferably between 0.5phr and 5.0 phr.

As accelerators, any compound capable of acting as vulcanization accelerator for diene elastomers in the presence of sulfur can be used, in particular accelerators of the thiazole type and their derivatives, or of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type. As examples of such accelerators, the following compounds may be mentioned in particular: 2-mercaptobenzothiazole disulfide (abbreviated MBTS), N-cyclohexyl-2-benzothiazolesulfenamide (CBS), N-dicyclohexyl-2-benzothiazolesulfenamide (DCBS), N- (tert-butyl) -2-benzothiazolesulfenamide (TBBS), N- (tert-butyl) -2-benzothiazolesulfenimide (TBSI), tetrabenzylthiuram disulfide (TBZTD), zinc dibenzyldithiocarbamate (ZBEC) and mixtures of these compounds.

II-4 plasticizing System

The rubber composition of the tire tread according to the invention may additionally comprise a plasticizing system comprising a plasticizing resin having a glass transition temperature greater than 20 ℃ (referred to as "high Tg") (which is also denoted as "plasticizing resin" in the present application for the sake of brevity).

II-4.1 plasticizing resin

The name "resin" is retained in the present patent application according to a definition known to a person skilled in the art as a compound that is solid at ambient temperature (23 ℃), unlike a liquid plasticizing compound (e.g. an oil).

Plasticizing resins are polymers well known to those skilled in the art, which are based primarily on carbon and hydrogen, but may also contain other types of atoms, which may be used as plasticizers or tackifiers, particularly in polymer matrices. The plasticizing resin is generally substantially miscible (i.e., compatible) at the level used with the polymer composition in which it is intended to be used, thereby acting as a true diluent. It has been described, for example, in an article entitled "Hydrocarbon Resins" by R.Mildenberg, M.Zander and G.Collin (New York, VCH,1997, ISBN 3-527-. It may be of the aliphatic, cycloaliphatic, aromatic, hydroaromatic, or aliphatic/aromatic type (i.e. based on aliphatic and/or aromatic monomers). It may be natural or synthetic, and may or may not be petroleum-based (if petroleum-based, it is also referred to as petroleum resin). Its Tg is preferably greater than 20 deg.C (generally between 30 deg.C and 95 deg.C).

In a known manner, these plasticizing resins can also be described as thermoplastic resins, since they soften when heated and can therefore be molded. It may also be defined by a softening point. The softening point of the plasticized resin is typically about 50 ℃ to 60 ℃ higher than its Tg value. The softening point is measured according to standard ISO 4625 (ring and ball method). The macrostructures (Mw, Mn and PDI) were determined by Size Exclusion Chromatography (SEC) as shown below.

As a reminder, SEC analysis, for example, involves separating macromolecules in solution according to their size through a column filled with a porous gel; the molecules are separated according to their hydrodynamic volume, with the largest volume being eluted first. The sample to be analyzed was simply dissolved in advance in a suitable solvent (tetrahydrofuran) at a concentration of 1 g/l. The solution was then filtered through a filter with a porosity of 0.45 μm before injection into the instrument. The instrument used is for example a Waters Alliance colour line according to the following conditions:

-the elution solvent is tetrahydrofuran;

-a temperature of 35 ℃;

-concentration 1 g/l;

-flow rate: 1 ml/min;

-an injection volume: 100 mul;

molar calibration with polystyrene standards:

a set of 3 "Waters" columns in series (Styragel HR4E, Styragel HR1 and Styragel HR 0.5);

detection is carried out by means of a differential refractometer (e.g. Waters 2410) which can be equipped with operating software (e.g. Waters Millennium).

Molar calibration was performed using a series of commercial polystyrene standards with a low PDI (abbreviated Ip in french) (less than 1.2), known molar masses and covering the mass range to be analyzed. From the recorded data (mass distribution curve of molar masses), the weight-average molar mass (Mw), the number-average molar mass (Mn) and the polydispersity index (PDI ═ Mw/Mn) were derived.

Thus, all molar mass values shown herein are relative to a calibration curve generated from polystyrene standards.

According to a preferred embodiment of the invention, the plasticizing resin has at least one, preferably 2 or 3, more preferably all of the following features:

-a Tg greater than 25 ℃ (in particular between 30 ℃ and 100 ℃), more preferably greater than 30 ℃ (in particular between 30 ℃ and 95 ℃);

-a softening point greater than 50 ℃ (in particular between 50 ℃ and 150 ℃);

a number-average molar mass (Mn) of between 300g/mol and 2000g/mol, preferably between 400g/mol and 1500 g/mol;

-a polydispersity index (PDI) of less than 3, preferably less than 2 (as a reminder: PDI. Mw/Mn, where Mw is the weight average molar mass).

The preferred high Tg plasticizing resins described above are well known to those skilled in the art and are commercially available, for example, sold in the following areas:

-a poly-limonene resin: sold by DRT under the name dersolve L120(Mn 625 g/mol; Mw 1010 g/mol; PDI 1.6; Tg 72 ℃) or by Arizona under the name Sylvagum TR7125C (Mn 630 g/mol; Mw 950 g/mol; PDI 1.5; Tg 70 ℃);

-C₅distillate/vinyl aromatic copolymer resin (especially C)₅Fraction/styrene or C₅fraction/C₉Distillate copolymer resin): sold by Neville Chemical Company under the names Super Nevtac 78, Super Nevtac 85 and Super Nevtac 99, by Goodyear Chemicals under the name Wingtack Extra, by Kolon under the names Hikorez T1095 and Hikorez T1100 or by Exxon under the names Escorez 2101 and Escorez 1273;

-limonene/styrene copolymer resin: sold under the name Dercolyte TS 105 by DRT or under the names ZT115LT and ZT5100 by Arizona Chemical Company.

According to the invention, the plasticizing resin having a glass transition temperature greater than 20 ℃ may be selected from the group comprising or consisting of: cyclopentadiene (abbreviated as CPD) homopolymer or copolymer resin, dicyclopentadiene (abbreviated as DCPD) homopolymer or copolymer resin, terpene homopolymer or copolymer resin, C₅Fraction homopolymer or copolymer resin, C₉A distillate homopolymer or copolymer resin, an alpha-methylstyrene homopolymer or copolymer resin, and mixtures thereof. Preferably, the plasticizing resin is selected from the group comprising or consisting of: (D) CPD/vinyl aromatic copolymer resin, (D) CPD/terpene copolymer resin, terpene/phenol copolymer resin, and (D) CPD/C₅A distillate copolymer resin, (D) CPD/C₉Fractional copolymer resin, terpene/vinyl aromatic copolymer resin, terpene/phenol copolymer resin, C₅Distillate/vinyl aromatic copolymer resins and mixtures thereof.

The term "terpene" group is used herein in a known manner to group the α -pinene, β -pinene and limonene monomers; preference is given to using limonene monomers, which in a known manner exist in three possible isomeric forms: l-limonene (levo isomer), D-limonene (dextro isomer) or dipentene (racemate of levo and dextro isomers). Suitable as vinylaromatic monomers are, for example: styrene, alpha-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluenes, p- (tert-butyl) styrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes, vinylmesitylenes, divinylbenzene, vinylnaphthalene or mixtures derived from C₉Fraction (or more generally from C)₈To C₁₀Fractions) of any vinyl aromatic monomer.

More particularly, mention may be made of resins selected from (D) CPD homopolymer resin, (D) CPD/styrene copolymer resin, polycitratene resin, limonene/styrene copolymer resin, limonene/D (CPD) copolymer resin, C₅Fraction/styrene copolymer resin, C₅fraction/C₉Distillate copolymer resins and mixtures of these resins.

All the above plasticizing resins are well known to those skilled in the art and are commercially available, for example the poly-limonene resin sold under the name Dercolyte by DRT, the Super Nevtac name by Neville Chemical Company, the Hikorez name by Kolon or the Escorez name by Exxon Mobil₅Fraction/styrene resin or C₅fraction/C₉Distillate resins, or sold under the name 40MS or 40NS by Struktol (mixture of aromatic and/or aliphatic resins).

Advantageously, the content of plasticizing resin having a glass transition temperature greater than 20 ℃ in the composition of the tread according to the invention is in the range from 10phr to 50phr, preferably from 20phr to 45 phr.

II-4.2 plasticizers which are liquid at 23 ℃

Although not essential to the practice of the present invention, the plasticizing system of the rubber composition of the tire tread according to the present invention may comprise a plasticizer that is liquid at 23 ℃ (referred to as "low Tg"), i.e., by definition, a plasticizer having a Tg of less than-20 ℃, preferably less than-40 ℃. According to the invention, the composition may optionally comprise from 0 to 50phr of a plasticizer which is liquid at 23 ℃.

When a plasticizer that is liquid at 23 ℃ is used, its content in the composition of the tread according to the invention may range from 10phr to 45phr, preferably from 15phr to 30 phr.

Any plasticizer (or extender oil) that is liquid at 23 ℃ that is known for its plasticizing properties relative to diene elastomers, whether aromatic or non-aromatic, may be used. At ambient temperature (23 ℃), these plasticizers or these oils (more or less viscous) are liquids (what is meant here, i.e. substances with the ability to finally assume the shape of their container), in particular in contrast to plasticizing resins that are natural solids at ambient temperature.

Plasticizers which are liquid at 23 ℃ selected from the group comprising or consisting of: liquid diene polymers, polyolefin oils, naphthenic oils, paraffin oils, DAE oils, MES (medium extraction solvates) oils, TDAE (treated distilled aromatic extract) oils, RAE (residual aromatic extract) oils, TRAE (treated residual aromatic extract) oils, SRAE (safe residual aromatic extract) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these plasticizers which are liquid at 23 ℃.

For example, the plasticizer which is liquid at 23 ℃ may be a petroleum, preferably non-aromatic. Liquid plasticizers are described as non-aromatic liquid plasticizers when the content of polycyclic aromatic compounds relative to the total weight of the plasticizer, determined with an extract in DMSO according to the IP 346 method, is less than 3% by weight.

The plasticizer which is liquid at 23 ℃ may also be a liquid polymer derived from the polymerization of olefins or dienes, for example polybutene, polydienes, in particular polybutadiene, polyisoprene (also known as LIR), copolymers of butadiene and isoprene, copolymers of butadiene or isoprene and styrene or mixtures of these liquid polymers. The number-average molar mass of such liquid polymers is preferably in the range from 500g/mol to 50000g/mol, preferably from 1000g/mol to 10000 g/mol. By way of example, mention may be made of the Ricon product from Sartomer.

When the plasticizer which is liquid at 23 ℃ is a vegetable oil, it may for example be an oil selected from the group comprising or consisting of: linseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rapeseed oil, castor oil, tung oil, pine oil, sunflower oil, palm oil, olive oil, coconut oil, peanut oil, grape seed oil and mixtures of these oils. The vegetable oil is preferably rich in oleic acid, i.e. the fatty acids from which the vegetable oil is derived (if a plurality of fatty acids are present, the combined fatty acids) comprise a mass fraction of oleic acid at least equal to 60%, more preferably still at least equal to 70%. As vegetable oil, use is advantageously made of sunflower oil in which the combined fatty acids from which the vegetable oil derives comprise oleic acid in a mass fraction equal to or greater than 60%, preferably 70%, and according to a particularly advantageous embodiment of the invention in a mass fraction equal to or greater than 80%.

According to another particular embodiment of the invention, the liquid plasticizer is a triester selected from the group consisting of carboxylic triesters, phosphoric triesters, sulfonic triesters and mixtures of these triesters.

As an example of the phosphate ester plasticizer, mention may be made of phosphate ester plasticizers containing between 12 and 30 carbon atoms, such as trioctyl phosphate. As examples of carboxylate plasticizers, mention may in particular be made of compounds selected from trimellitate, pyromellitate, phthalate, 1, 2-cyclohexanedicarboxylate, adipate, azelate, sebacate, triglyceride and mixtures of these compounds. Among the above triesters, mention may be made in particular of C preferably predominantly (more than 50% by weight, more preferably more than 80% by weight) bound to unsaturation₁₈Triglycerides of fatty acids, i.e. fatty acids selected from oleic acid, linoleic acid, linolenic acid and mixtures of these acids. Triglycerides are preferred. More preferably, the fat used is of synthetic or natural origin (for example in the case of sunflower or rapeseed plant oil)The acid consists of more than 50 wt.%, even more preferably more than 80 wt.% oleic acid. Such triesters (trioleate) with high content of oleic acid are well known; which is described, for example, in application WO 02/088238 as a plasticizer for tire treads.

When the plasticizer which is liquid at 23 ℃ is an ether plasticizer, it may be, for example, polyethylene glycol or polypropylene glycol.

Preferably, the plasticizer which is liquid at 23 ℃ is selected from the group comprising or consisting of: MES oils, TDAE oils, naphthenic oils, vegetable oils and mixtures of these plasticizers which are liquid at 23 ℃. More preferably, the plasticizer which is liquid at 23 ℃ is a vegetable oil, preferably sunflower oil.

Advantageously, the composition of the tread according to the invention does not comprise a plasticizer that is liquid at 23 ℃.

II-3.3 plasticizing resins viscous at 20 ℃

Although not essential to the practice of the present invention, the plasticizing system of the rubber composition of the tire tread according to the present invention may comprise a plasticizing resin that is viscous at 20 ℃ (referred to as "low Tg"), i.e., a plasticizing resin having a Tg, by definition, in the range of-40 ℃ to-20 ℃. According to the invention, the composition may optionally comprise, in addition to all or part of the plasticizer which is liquid at 23 ℃ or its substitutes, from 0 to 140phr of a plasticizing resin which is viscous at 20 ℃.

Preferably, the plasticizing resin which is viscous at 20 ℃ has at least one, preferably 2 or 3, preferably all of the following characteristics:

-a Tg between-40 ℃ and 0 ℃, more preferably between-30 ℃ and 0 ℃, still more preferably between-20 ℃ and 0 ℃;

-a number average molecular weight (Mn) of less than 800g/mol, preferably less than 600g/mol, more preferably less than 400 g/mol;

-a softening point in the range of 0 ℃ to 50 ℃, preferably 0 ℃ to 40 ℃, more preferably 10 ℃ to 40 ℃, preferably 10 ℃ to 30 ℃;

-a polydispersity index (PDI) of less than 3, more preferably less than 2 (as a reminder: PDI. Mw/Mn, where Mw is the weight average molecular weight).

The above preferred plasticizing resins which are tacky at 20 ℃ are well known to those skilled in the art and are commercially available, for example, sold in the following respects:

-aliphatic resins: sold by Cray Valley under the name wintack 10(Mn 480 g/mol; Mw 595 g/mol; PDI 1.2; SP 10 ℃; Tg-28 ℃);

-coumarone/indene resin: sold by Ratgers Chemicals under the name Novares C30 (Mn: 295 g/mol; Mw: 378 g/mol; PDI: 1.28; SP: 25 ℃; Tg: 19 ℃);

-C₉fraction resin: sold by Ratgers Chemicals under the name Novares TT30(Mn 329 g/mol; Mw 434 g/mol; PDI 1.32; SP 25 ℃; Tg-12 ℃).

When a plasticizing resin that is viscous at 20 ℃ is used, its content in the composition of the tread according to the invention is in the range from 20phr to 120phr, preferably from 40phr to 90 phr.

Very advantageously, the total content of plasticizer liquid at 23 ℃ and of plasticizing resin viscous at 20 ℃ is in the range 0 to 50phr, preferably 10phr to 45phr, preferably 15phr to 30 phr.

II-5 other possible additives

The rubber composition of the tire tread according to the invention may also optionally comprise all or part of the usual additives usually used in tire elastomer compositions, such as plasticizers (for example plasticizing oil and/or plasticizing resin), pigments, protective agents (for example antiozone waxes, chemical antiozonants, antioxidants), antifatigue agents, reinforcing resins (such as the reinforcing resins described in application WO 02/10269).

Preparation of II-6 rubber composition

The compositions according to the invention can be manufactured in a suitable mixer using two successive preparation stages known to those skilled in the art:

a first stage of thermomechanical working or kneading ("non-productive" stage), which can be carried out in a single thermomechanical step, during which all the necessary components (in particular the elastomeric matrix, the optional fillers and the optional other various additives) except the vulcanization system are introduced into a suitable mixer, for example a standard internal mixer (for example of the 'Banbury' type). When thermomechanically kneaded, the optional filler may be incorporated into the elastomer in one portion or in batches. The non-productive phase can be carried out at high temperature, with a maximum temperature of between 110 ℃ and 200 ℃, preferably between 130 ℃ and 185 ℃, for a duration generally between 2 minutes and 10 minutes;

a second stage of mechanical processing in an open mixer (e.g. open mill) (the "production" stage) after cooling the mixture obtained during the first non-production stage to a lower temperature (typically less than 120 ℃, for example between 40 ℃ and 100 ℃). The vulcanization system is then introduced and the combined mixture is mixed for several minutes, for example between 5 and 15 minutes.

This stage is described, for example, in patent applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO 00/05300 or WO 00/05301.

The final composition thus obtained is then calendered, for example in the form of a sheet or plate (in particular for laboratory characterization), or extruded in the form of a semifinished (or shaped) element of rubber that can be used, for example, as a tread for a passenger vehicle tire. These products can then be used to manufacture tyres according to techniques known to those skilled in the art.

The composition may be in the green state (before vulcanization) or in the cured state (after vulcanization) and may be a semi-finished product useful for tires.

The vulcanization of the composition can be carried out under pressure in a manner known to the person skilled in the art, for example at a temperature between 130 ℃ and 200 ℃.

II-7 Tread and tire

In a known manner, the tread of a tire (whether it is intended to fit a passenger vehicle or other vehicle) comprises a tread surface intended to come into contact with the ground when the tire is rolling. The tread is provided with a tread pattern comprising in particular tread pattern elements or basic blocks defined by various main grooves, longitudinal or circumferential, transverse or even inclined, which may additionally comprise various cuts or thinner strips. The grooves form channels intended to drain water when driving on wet ground and, depending on the direction of bending, the walls of these grooves define the leading and trailing edges of the tread pattern elements.

According to the invention, the tread may consist of one and the same composition. Advantageously, it may also comprise a plurality of portions (or layers), for example two, overlapping in the radial direction. In other words, the portions (or layers) are at least substantially parallel to each other and to a tangential (or longitudinal) plane, which is defined as being orthogonal to the radial direction.

Thus, the composition according to the invention may be present throughout the tread according to the invention.

Preferably, the tread comprises at least one radially inner portion and one radially outer portion, the composition according to the invention being advantageously present in the radially inner portion of the tread of the tire according to the invention. In this case, the radially outer portion of the tread is preferably formed from a composition different from the composition according to the invention. The tread may also comprise two compositions different from each other but both according to the invention, one present in the radially external portion of the tread and the other present in the radially internal portion.

Since the geometry of a tire exhibits rotational symmetry about the axis of rotation, it is generally described in a meridian plane containing the axis of rotation of the tire. For a given meridian plane, the radial direction, the axial direction and the circumferential direction respectively denote a direction perpendicular to the rotation axis of the tyre, a direction parallel to the rotation axis of the tyre and a direction perpendicular to the meridian plane. By convention, the expressions "radially inside" and respectively "radially outside" mean "closer to" and respectively "further away" from the axis of rotation of the tyre. "axially on the inside" and respectively "axially on the outside" are understood to mean "closer to" and respectively "further away from" the equatorial plane of the tyre, which is the plane passing through the middle of the tread surface of the tyre and perpendicular to the rotation axis of the tyre.

Preferably, the tire tread according to the invention:

has an axial width L and is formed by the radial superposition of a first portion and of a second portion radially external to said first portion,

the first part consisting of a single layer C₁The method comprises the steps of (1) forming,

layer C₁Having a radial thickness E₁Said radial thickness E₁Measured in the equatorial plane (XZ) of the tyre and substantially constant over at least 80% of the axial width L of the tread, said layer C₁Is formed from the composition according to the present invention,

the second part consisting of a single layer C₂The method comprises the steps of (1) forming,

layer C₂Having a radial thickness E₂Said radial thickness E₂Measured in the equatorial plane (XZ) of the tyre and substantially constant over at least 80% of the axial width L of the tread, said layer C₂From a rubber composition C different from the composition according to the invention₂And (4) forming.

By definition, the radially inner portion of the tread is not in contact with the ground when the tire is new or when the radially outer portion of the tread is not sufficiently worn. On the other hand, the radially inner portion of the tread is intended to be in contact with the ground after the radially outer portion of the tread has worn. It has therefore been understood by those skilled in the art that the radially outermost portion of the radially inner portion of the tread according to the invention is advantageously located above the wear indicator of the tire tread.

Advantageously, the radial thickness E of the second portion of the tyre₂In the range of 4mm to 8mm, preferably 4.5mm to 7.5 mm.

Furthermore, the radial thickness E of the first portion of the tyre₁In the range of 1mm to 5mm, preferably 1.5mm to 4.5 mm.

The invention relates in particular to tyres intended for fitting motor vehicles of the passenger type and of the SUV ("sport utility vehicle") type.

The present invention relates to tires in a green state (i.e. before curing) and in a cured state (i.e. after curing).

Drawings

III-brief description of the Individual figures

Fig. 1 shows a meridian section through the crown of a tyre 1, said tyre 1 comprising a tread 2, said tread 2 being intended to be in contact with the ground. The directions XX ', YY ' and ZZ ' are the circumferential, axial and radial directions of the tire, respectively. The plane XZ is the equatorial plane of the tyre. The tread with axial width L is formed by the radial superposition of a first portion 21 and of a second portion 22 radially external to said first portion 21.

The second portion 21 consists of a single layer C₁Form the layer C₁Having a radial thickness E₁Said radial thickness E₁Measured in the equatorial plane XZ of the tyre and substantially constant over at least 80% of the axial width L of the tread 2, said layer C₁Formed of a polymeric material 1.

The second portion 22 is formed of a single layer C₂Form the layer C₂Having a radial thickness E₂Said radial thickness E₂Measured in the equatorial plane XZ of the tyre and substantially constant over at least 80% of the axial width L of the tread 2.

Radially inside the first radially inner portion 21, a crown block 3 is shown, said crown block 3 comprising two crown layers comprising preferably textile reinforcements. Radially inside the crown reinforcement 3, a carcass reinforcement 4 is shown, said carcass reinforcement 4 comprising a carcass layer.

Detailed Description

IV-preferred embodiments

In light of the foregoing description, preferred embodiments of the invention are described as follows:

A. tyre, the tread of which comprises a rubber composition based on at least one elastomeric matrix, a reinforcing filler and a vulcanization system, wherein the elastomeric matrix comprises:

-optionally from 0 to 40phr of a third diene elastomer.

B. The tire of embodiment a, wherein the first diene elastomer is a butadiene/styrene copolymer.

C. The tire of any of the preceding embodiments, wherein the alkoxysilane group comprises C₁-C₁₀Alkoxy, or even C₁-C₈Alkoxy, preferably C₁-C₄Alkoxy groups, more preferably methoxy and ethoxy groups, which are optionally partially or completely hydrolyzed to hydroxyl groups.

D. The tire of any one of the preceding embodiments, wherein the nitrogen atom-containing functionality is located at the chain end and is directly attached to the elastomer via a covalent bond or a hydrocarbyl group.

E. The tire according to any one of the preceding embodiments, wherein the nitrogen atom-containing functionality is carried by the silicon of the alkoxysilane group, directly or through a spacer group defined as an atom or a saturated or unsaturated, cyclic or acyclic, linear or branched divalent aliphatic C₁-C₁₈Hydrocarbyl or divalent aromatic C₆-C₁₈A hydrocarbyl group, the spacer group optionally comprising one or more aromatic groups and/or one or more heteroatoms.

F. The tire of any of the preceding embodiments, wherein the alkoxysilane group is represented by the formula

(*—)_aSi(OR’)_bR_cX

Wherein:

-;

the radical R represents a substituted or unsubstituted C₁-C₁₀Alkyl, or even C₁-C₈Alkyl, preferably C₁-C₄Alkyl, more preferably methyl and ethyl;

-X represents a group comprising a function comprising a nitrogen atom;

-a is 1 or 2, b is 1 or 2, c is 0 or 1, with the proviso that a + b + c is 3.

G. The tire according to any one of the preceding embodiments, wherein the nitrogen atom-containing functionality is selected from a protected or unprotected primary amine, a protected or unprotected secondary amine, or a cyclic or acyclic tertiary amine.

H. The tire of any one of embodiments a through F, wherein the nitrogen atom-containing functionality is a tertiary amine functionality, preferably diethylamine or dimethylamine.

I. The tire according to any one of the preceding embodiments, wherein the first diene elastomer is functionalized in the middle of the chain predominantly by alkoxysilane groups bonded to both branches of the first diene elastomer through silicon atoms, the alkoxy groups optionally being partially or fully hydrolyzed to hydroxyl groups.

J. The tire of any of the preceding embodiments, wherein the first diene elastomer has a glass transition temperature in the range of from-105 ℃ to-70 ℃, preferably from-100 ℃ to-75 ℃, preferably from-95 ℃ to-80 ℃.

K. The tire according to any one of the preceding embodiments, wherein at least two, preferably at least three, preferably at least four of the following features are observed:

-the nitrogen atom-containing function is a tertiary amine, more particularly a diethylamino or dimethylamino group,

-the first diene elastomer is a butadiene/styrene copolymer,

L. the tire according to any one of embodiments a to J, wherein all of the following features are observed:

-the first diene elastomer is a butadiene/styrene copolymer,

M. the tire of any of the preceding embodiments, wherein the amount of the first diene elastomer in the composition is in a range from 40phr to 80 phr.

N. the tire of any one of the preceding embodiments, wherein the second elastomer is a polyisoprene having a mass content of cis-1, 4-linkages of at least 90% of the mass of the polyisoprene.

O. the tire of embodiment N, wherein the polyisoprene is selected from the group consisting of natural rubber, synthetic polyisoprene, and mixtures thereof.

P. the tire of embodiments N or M, wherein the polyisoprene is natural rubber.

Q. the tire of any one of the preceding embodiments, wherein the amount of the second diene elastomer in the composition is in the range of 10phr to 35 phr.

R. the tire of any one of the preceding embodiments, wherein the third diene elastomer is selected from the group consisting of polybutadiene, butadiene copolymers, and mixtures thereof.

S. the tire of any of the preceding embodiments, wherein the content of the third diene elastomer in the composition is in the range of 5phr to 35 phr.

T. the tire according to any one of the preceding embodiments, wherein the total content of the first diene elastomer, the second diene elastomer and the third diene elastomer (preferably the first diene elastomer and the second diene elastomer) in the composition is in the range of from 80phr to 100phr, preferably from 90phr to 100phr, more preferably 100 phr.

U. the tire according to any one of the preceding embodiments, wherein the reinforcing filler comprises carbon black, a reinforcing inorganic filler, or a mixture thereof.

V. the tire according to any one of the preceding embodiments, wherein the reinforcing filler comprises predominantly a reinforcing inorganic filler.

W. the tire according to embodiment U or V, wherein the reinforcing inorganic filler is silica.

X. the tire according to any one of embodiments U to W, wherein the content of reinforcing inorganic filler in the composition is in the range of from 90phr to 200phr, preferably from 95phr to 180phr, preferably from 100phr to 150 phr.

Y. the tire of any one of embodiments U through X, wherein the amount of carbon black in the composition is in the range of 0 to 40phr, preferably 1phr to 20phr, preferably 2phr to 10 phr.

Z. the tire according to any one of the preceding embodiments, wherein the curing system is based on sulfur or a sulfur donor.

A tire according to any one of the preceding embodiments, wherein the composition further comprises at least one plasticizing resin having a glass transition temperature greater than 20 ℃.

BB. the tire according to embodiment AA, wherein the plasticizing resin having a glass transition temperature greater than 20 ℃ is selected from the group consisting of a cyclopentadiene homopolymer or copolymer resin, a dicyclopentadiene homopolymer or copolymer resin, a terpene homopolymer or copolymer resin, C₅Fraction homopolymer or copolymer resin, C₉A distillate homopolymer or copolymer resin, an alpha-methylstyrene homopolymer or copolymer resin, and mixtures thereof.

The tire according to embodiment AA or BB, wherein the content of plasticizing resin having a glass transition temperature greater than 20 ℃ in the composition is in the range from 10phr to 45phr, preferably from 15phr to 30 phr.

DD. the tire according to any one of the preceding embodiments, wherein the composition further optionally comprises 0 to 50phr of a plasticizer that is liquid at 23 ℃.

The tire of embodiment DD, wherein the plasticizer that is liquid at 23 ℃ is selected from the group consisting of liquid diene polymers, polyolefin oils, naphthenic oils, paraffin oils, DAE oils, MES oils, TDAE oils, RAE oils, TRAE oils, SRAE oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers, and mixtures thereof.

FF. the tire according to any one of the preceding embodiments, wherein the tread includes at least one radially inner portion and one radially outer portion, the composition being present in the radially inner portion of the tread.

Gg. the tire of embodiment FF, wherein the radially outer portion has a radial thickness E₂In the range of 4mm to 8mm, preferably 4.5mm to 7.5 mm.

HH. A tire according to embodiment FF or GG, wherein the radially inner portion has a radial thickness E₁In the range of 1mm to 5mm, preferably 1.5mm to 4.5 mm.

The tire according to any one of embodiments FF to HH, wherein the radially outer portion comprises a rubber composition that is different from the composition of the radially inner portion.

V examples

Measurement and testing of V-1 usage

Dynamic properties:

the dynamic properties G and tan (δ) Max were measured on a viscosity analyzer (Metravib VA4000) according to the standard ASTM D5992-96. According to the standard ASTM D1349-09, samples of the vulcanized composition (thickness 2mm, cross-section 79 mm) subjected to a simple alternating sinusoidal shear stress at a frequency of 10Hz either at standard temperature conditions (23 ℃) or at 0 ℃ (for measuring tan (delta) Max) or at-20 ℃ (for measuring G ℃) are recorded²Cylindrical sample of (d). The strain amplitude scan was performed from 0.1% to 50% (outward cycle) and then from 50% to 0.1% (return cycle). The maximum value of tan δ (noted tan (δ) max) observed for the return cycle is shown, as well as the complex modulus difference (Δ G) between the values at 0.1% strain and 50% strain (Payne effect).

The results used are the loss factors tan (δ) Max at 0 ℃ and 23 ℃ and the complex dynamic shear modulus G at-20 ℃.

The results of tan (. delta.) Max at 0 ℃ are expressed in base number 100, and the control is assigned a value of 100. Results above 100 indicate improved performance, i.e. the composition of the example under consideration reflects better grip on wet ground for treads comprising this composition.

The results of tan (δ) Max at 23 ℃ and G at-20 ℃ are expressed in base 100 and the control is assigned a value of 100. Results of less than 100 indicate improved performance, i.e. the compositions of the examples considered reflect respectively better rolling resistance and better grip on the ground covered by snow of the treads comprising the compositions.

Wear resistance

The abrasion resistance obtained by determining the volume loss of abrasion was measured according to standard NF ISO 4649 of 11 months 2010, which consists in determining the volume loss of a sample after a linear displacement of 40 meters on a standard sandpaper.

More specifically, the volume loss of wear was determined using a wear tester according to the instructions of standard NF ISO 4649 (method B) on month 11 2010, in which a cylindrical test piece was subjected to the action of P60 grit abrasive sheets attached to the surface of a rotating drum at a contact pressure of 5N (N ═ newton) for a course of 40 m. The mass loss of the sample is measured, and the volume loss is calculated from the density (. rho.) of the material constituting the specimen. The density (ρ) of the material constituting the specimen is generally obtained based on the mass fraction of each component of the material and its respective density (ρ).

The results are expressed in base 100. Any value of 100 assigned to the control composition allows comparison of the material volume loss for each composition tested. The values expressed in base 100 of the tested compositions were calculated according to the following operations: (measurement of material volume loss for control composition/measurement of material volume loss for tested composition) × 100. In this way, results greater than 100 indicate a reduction in volume loss and therefore an improvement in wear resistance, which corresponds to an improvement in wear resistance performance. Conversely, results less than 100 indicate an increase in volume loss and therefore a decrease in wear resistance, which corresponds to a decrease in wear resistance performance.

Preliminary tack (or tack):

tack is the ability of a component of the uncured mixture to withstand tear stress.

The preliminary tack (tack) was measured using a test apparatus (ASTM D2979-95) inspired by a probe tack tester. An Instron tensile tester was used that included a fixed metal jaw and a moving metal jaw. A first test specimen consisting of a 3mm thick film of the mixture was adhered to the fixed jaw. A second sample consisting of a 3mm thick film of the mixture was adhered to the moving jaw. By means of double-sided adhesive tapes (

4970) A thin film of the mixture was adhered to the surface of the metal jaw.

To prepare a sample of the mixture, a thin film of the mixture was obtained by calendering at a thickness of 3 mm. The sample was sheared by a punch having a diameter of 1 cm.

The measurement principle consists in bringing the two mixture films into contact for 5 seconds by applying a compressive force of 40N. After this contact phase, the crosshead of the tensile tester was driven to separate it. The displacement speed of the crosshead in this tearing phase was 1 mm/s. The displacement and force of the crosshead are measured continuously as a function of time during the contact phase and the tearing phase.

The preliminary tack result is a measure of the maximum force (in newtons (N)) achieved during tearing. Values of 9N or higher are desirable for the present invention.

The preliminary sticky result is expressed in base 100 and the control is assigned a value of 100. Results above 100 indicate improved performance, i.e. better adhesion of the composition to its support.

Preparation of V-2 composition

In the following examples, rubber compositions were prepared as described above in point II-6. In particular, the "non-productive" phase is carried out in a 0.4 liter mixer with an average blade speed of 50 revolutions per minute for 3.5 minutes until a maximum discharge temperature of 160 ℃ is reached. The "production" stage was carried out on a mill at 23 ℃ for 5 minutes.

Testing of V-3 rubber composition

The examples shown below are intended to compare the performance compromise between rolling resistance, grip on wet ground, grip on snow-covered ground, abrasion resistance and preliminary adhesion of seven compositions according to the invention (C1 to C7) and five control compositions (T1 to T5).

The formulations tested each comprised an elastomer matrix (the characteristics and contents of which are shown in table 1 below), 120phr of "HDS" -type Zeosil 1165MP from Rhodia, 9.6phr of TESPT liquid silane (Si 69 from Degussa) as an agent for coupling silica to elastomers, 4phr of ASTM N234 grade carbon black from Cabot, 19phr of Lubrirob Tod 1880 triolein (sunflower oil with 85 wt% oleic acid) from novances, 2phr of ozone resistant Wax (VARAZON 4959 from Sasol Wax), 3phr of antioxidant (N- (1, 3-dimethylbutyl) -N-phenyl-p-phenylenediamine, Santoflex 6-PPD from Flexsys), 47phr of PPD resin (C1, 3-phr of plasticized plasticizing plasticizer-p-phenylenediamine, Santoflex 6-PPD from Flexsys), 47phr of PPD resin (C)₅/C₉Resin fromECR-373 resin from ExxonMobil), 3phr of stearic acid (Pristerene 4931 from Uniqema), 2phr of Perkacit DPG diphenylguanidine from Flexsys, 1.4phr of sulfur, 1.6phr of N-cyclohexyl-2-benzothiazolesulfenamide (Santocure CBS from Flexsys) as a vulcanization accelerator, and 1.5phr of technical grade zinc oxide (Umicore). The properties of these formulations are also shown in table 1 below.

The control composition differs from composition C1 only by the nature of the butadiene and styrene based copolymer.

Compositions C2 to C4 were able to study the effect of the respective contents of butadiene and styrene based copolymer and polyisoprene in the compositions according to the invention on the above performance compromise.

Compositions C5 to C7 show the effect of adding polybutadiene to the compositions according to the invention.

TABLE 1

a) Natural rubber

b) SBR No. 1: 1, 2-units having 3% of styrene units and 13% of butadiene moieties and carrying an amino-alkoxysilane-functional SBR (Tg-88 ℃ C.) in the middle of the elastomer chain

c) SBR 2: 1, 2-units having 15.5% of styrene units and 24% of butadiene moieties and bearing silanol-functional SBR (Sn star-branched) at the end of the elastomer chain (Tg-65 ℃ C.)

d) SBR No. 3: 1, 2-units having 25% of styrene units and 24% of butadiene moieties and carrying an amino-alkoxysilane-functional SBR (Tg-65 ℃ C.) in the middle of the elastomer chain

e) SBR No. 4: 1, 2-units having 26% of styrene units and 24% of butadiene moieties and bearing silanol-functional SBR (Sn star-branched) at the end of the elastomer chain (Tg-48 ℃ C.)

f) SBR 5: 1, 2-units having 25% of styrene units and 58% of butadiene moieties and bearing silanol-functional SBR (Sn star-branched) at the end of the elastomer chain (Tg-24 ℃ C.)

g) SBR 6: SBR (3-tris (di-tert-butylphenyl) phosphite star-branched) unfunctionalized with 1, 2-units having 26.5% of styrene units and 24% of butadiene moieties (Tg-48 ℃ C.)

h) BR: polybutadiene having 0.5% of 1, 2-unit and 97% of cis-1, 4-unit (Tg-108 ℃ C.)

These results show that the substitution of the styrene-and butadiene-based copolymer according to the invention with a copolymer based on styrene and butadiene not according to the invention in a composition also comprising polyisoprene systematically leads to a loss of properties in terms of abrasion resistance, grip on snow-covered ground and possible rolling resistance.

Furthermore, it was observed that when the composition comprises 5phr of polyisoprene, the preliminary tack properties are acceptable limits for use in the radially inner portion of the tread. Furthermore, at 40phr of polyisoprene, a compromise in performance is still observed, but not optimal.

Finally, the experiments carried out made it possible to observe that the addition of polybutadiene to the composition according to the invention enables a further improvement in the above performance compromise, in particular in terms of grip on snow-covered ground and initial tackiness.

Claims

1. Tyre, the tread of which comprises a rubber composition based on at least one elastomeric matrix, a reinforcing filler and a vulcanization system, wherein the elastomeric matrix comprises:

-35 to 95 parts by weight per hundred parts by weight of elastomer, phr of a first diene elastomer, said first diene elastomer being a copolymer based on butadiene and styrene comprising within its structure at least one alkoxysilane group bonded to the elastomer through a silicon atom and at least one function comprising a nitrogen atom and having a glass transition temperature of less than-70 ℃,

-optionally from 0 to 40phr of a third diene elastomer.

2. Tyre according to claim 1, wherein at least two, preferably at least three, preferably at least four, of the following characteristics are observed:

-the first diene elastomer is a butadiene/styrene copolymer,

3. Tyre according to any one of the preceding claims, wherein said second elastomer is selected from natural rubber, synthetic polyisoprene and mixtures thereof.

4. Tyre according to any one of the preceding claims, wherein said third diene elastomer is selected from polybutadiene, butadiene copolymers and mixtures thereof.

5. Tyre according to any one of the preceding claims, wherein the total content of first diene elastomer, second diene elastomer and third diene elastomer, preferably first diene elastomer and second diene elastomer, in the composition is 100 phr.

6. Tyre according to any one of the preceding claims, wherein said reinforcing filler comprises carbon black, a reinforcing inorganic filler or a mixture thereof.

7. Tyre according to claim 6, wherein said reinforcing filler mainly comprises a reinforcing inorganic filler.

8. Tyre according to claim 6 or 7, wherein the content of reinforcing inorganic filler in the composition is in the range from 90phr to 200phr, preferably from 95phr to 180phr, preferably from 100phr to 150 phr.

9. Tire according to any one of the preceding claims, wherein the tread comprises at least one radially inner portion and one radially outer portion, said composition being present in the radially inner portion of the tread.

10. The tire of claim 9, wherein the radially outer portion comprises a rubber composition different from the composition of the radially inner portion.