WO2013068270A1

WO2013068270A1 - Rubber composition containing a high level of elastomer with a low polydispersity index

Info

Publication number: WO2013068270A1
Application number: PCT/EP2012/071438
Authority: WO
Inventors: Stéphanie CAMBON; Anne Veyland
Original assignee: Compagnie Generale Des Etablissements Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2011-11-10
Filing date: 2012-10-30
Publication date: 2013-05-16
Also published as: FR2982614A1; FR2982614B1

Abstract

The invention relates to a rubber composition that can be used for producing tyres, based on at least one or a plurality of functionalised diene elastomers, at a level higher than or equal to 40 parts by weight per hundred parts (pce) by weight of elastomer, carbon black as the majority by weight of reinforcing filler, zinc at a level within a range from 0 to 1 pce, and a sulphur-based cross-linking system and an accelerator such that the ratio between the level of sulphur in pce and the level of accelerator in pce is strictly greater than 1, the functionalised diene elastomer or elastomers being composed of a particular diene elastomer functionalised at the end of the chain or in the middle of the chain by a tin function, and of a particular non-functional tin elastomer to a level of less than 15% by weight relative to the total weight of the functionalised diene elastomer.

Description

RUBBER COMPOSITION WITH HIGH ELASTOMER RATE

LOW POLYDISPERSITY INDEX

The present invention relates to rubber compositions for use in the manufacture of various semi-finished products used in the construction of tires, such as for example treads, in particular for heavy goods vehicles, making it possible to obtain pneumatic tires having good wear resistance without degradation of endurance and tire resistance.

Indeed, the tires that equip, in particular, heavy vehicles are generally subjected to severe stresses such as shocks against the sidewalk, climbs and curbs, penalizing the endurance of the tire. These strong stresses result in very large deformations of the tire which cause a decrease in the resistance to aggression and / or the endurance of the tire, the damage being able to go from a crack until the tearing off of a part of the tire. the tread. In known manner, the use of one or more non-isoprenic synthetic diene elastomers (for example styrene-butadiene copolymers or polybutadienes) in the rubber compositions for example for tread leads to an improvement in the resistance to abrasion. material wear, but unfortunately can be accompanied by a penalty of the implementation of these compositions in the unvulcanized state (and therefore the productivity in industry) compared to compositions containing predominantly natural rubber, and can also result in a degradation of the properties at break of the compositions that can induce a degradation of the resistance to severe aggression and endurance of finished products comprising such compositions, for example treads. Thus, particularly in heavy weight, the level of non-isoprene diene synthetic elastomer in the compositions usually used is most often less than or equal to 40 parts by weight per hundred parts of elastomer (pce) in vehicle tires. heavy weight, because of the severe stresses encountered by these tires, in particular in parking maneuver on asphalt or more generally on aggressive soil. There is therefore an industrial need to find compositions that provide good wear resistance products comprising such compositions, without degradation of the resistance to attack and endurance of these products, while obtaining a implementation of these compositions in the unvulcanized state (thus productivity in industry) satisfactory. In addition, it is also of interest for manufacturers to reduce the rolling resistance of tires, in order to reduce the fuel consumption of vehicles equipped with these tires.

Continuing its research, the Applicant has surprisingly discovered a composition to meet this need by combining a high level of one or more functionalized diene elastomers, a low zinc content and a so-called "conventional" vulcanization system. the functionalized diene elastomer (s) being composed of a specific diene elastomer functionalized at the chain end or in the middle of the chain by a tin function, and of a content of less than 15% by weight relative to the total weight of the elastomer functionalized diene of a particular non-functional tin elastomer, made it possible to achieve these objectives.

Thus, the invention relates to a rubber composition based on at least one or more functionalized diene elastomers at a total content greater than or equal to 40 parts by weight per hundred parts by weight of elastomer (phr), carbon black as majority reinforcing filler by weight, zinc at a rate within a range of 0 to 1 phr, and a sulfur-based crosslinking system and an accelerator such as the ratio of sulfur in phr and the accelerator rate in phr is strictly greater than 1; said functionalized diene elastomer (s) being composed of: a) a functional diene elastomer at the chain end or in the middle of the chain with a tin function and corresponding to the following formula: M.- - ^[ ,

where n and m are integers greater than or equal to 0 such that n + m = 1 or 2, b) a level of less than 15% by weight relative to the total weight of the functionalized diene elastomer of a non-elastomer functional tin corresponding to the following formula:

[ ^L A] ^J or. : - A is a diene elastomer, the A blocks being identical to each other

X is a group containing tin,

the elastomer A has a monomodal molecular weight distribution before possible functionalization and a polydispersity index before possible functionalization less than or equal to 1.3.

At the level of the tire comprising such a composition, this composition makes it possible to improve the wear resistance without degrading the endurance and the resistance to attack while obtaining an implementation of these compositions in the non state. vulcanized (therefore productivity in industry) satisfactory. Moreover, such a composition makes it possible to reduce the rolling resistance.

It also has the advantage of being substantially free of zinc or zinc derivative, which leads to a reduction in the cost of this rubber composition and a reduction in the known environmental impact of these compounds, in particular vis-à-vis water and aquatic organisms. Preferably, the invention relates to a composition as defined above in which the functionalized diene elastomer comprises a tin diene elastomer (c) having the following formula:

where - o and p are integers greater than or equal to 0 and such that o + p> 3, and o + p <6

A is the diene elastomer as defined in claim 1, it being understood that it has a monomodal molecular weight distribution before staring and a polydispersity index before staring less than or equal to 1.3,

Y is a group containing tin. In addition, the invention preferably relates to a composition as defined above in which the functionalized diene elastomer comprises from 5% to 45% by weight, preferably from 10% to 30% by weight relative to the total weight of the functionalized diene elastomer of said tin stellate elastomer c).

[0012] Preferably also, the invention relates to a composition as defined above in which the functionalized diene elastomer according to the invention comprises a level strictly greater than 0% by weight and less than 10% by weight, and more preferably, a level of less than 5% by weight relative to the total weight of the functionalized diene elastomer of said non-functional tin elastomer b).

[0013] Preferably, the invention relates to a composition as defined above in which the functionalization of the diene elastomer a) is obtained with a mono-halo-tin or di-halo-tin functionalization agent; and preferably also, wherein the stellar of the diene elastomer c) can be obtained with a tri or tetrahalogenotin starring agent.

Also preferably, the invention relates to a composition as defined above in which the diene diene elastomer c) is a star-shaped elastomer 4 branches. Preferably, the invention relates to a composition as defined above in which the diene elastomer is chosen from polybutadienes, random copolymers or butadiene-styrene block, random copolymers or butadiene-isoprene block, copolymers statistics or butadiene-styrene-isoprene block, random copolymers or styrene-isoprene block and synthetic polyisoprene. According to a preferred embodiment, the invention relates to a composition as defined above in which the diene elastomer [A] - has the following formula:

or :

the block B consists of a polyisoprene or a polybutadiene,

the block C consists of a diene elastomer whose molar content of units derived from conjugated dienes is greater than 15%,

the number-average molecular mass Mn1 of block B varies from 2,500 to 20,000 g / mol, the number-average molecular mass Mn2 of block C varies from 80,000 to 350,000 g / mol,

the rate of 1,2 chains in block B is between 1 and 20% in the case where B is a polybutadiene block,

the rate of chains 3,4 in each block B is between 1 and 25% in the case where B is a polyisoprene block,

the copolymer B-C has a monomodal molecular weight distribution before optional functionalization and possible starter and a polydispersity index before possible functionalization and possible starter less than or equal to 1.3.

Preferably, according to this embodiment, the ratio of the number-average molecular weight Mn1 of each end-B polybutadiene or polyisoprene block to the number-average molecular weight Mn2 of each of the C blocks varies from 5 to 20%; and preferably also, the block C is chosen from copolymers of styrene and butadiene, copolymers of styrene and isoprene, copolymers of butadiene and isoprene, styrene / butadiene / isoprene copolymers, polyisoprene when the neighboring B block is a polybutadiene, and the polybutadiene when the neighboring B block is a polyisoprene.

[0018] Preferably, the invention relates to a composition as defined above in which, alternatively or simultaneously, the diene elastomer a) comprises an amino function at one or all ends of non-functionalized tin chains; the diene elastomer b) comprises an amino function at one of the chain ends; the diene elastomer c) comprises an amino function at the ends of non-starred tin chains.

Also preferably, the invention relates to a composition as defined above in which the carbon black content is in a range of more than 30 to 90 phr.

[0020] Preferably also, the invention relates to a composition as defined above in which the reinforcing filler is a blend of carbon black and silica.

Preferably, the invention relates to a composition as defined above in which the reinforcing filler comprises a carbon black surface specific CTAB greater than or equal to 90 m ² / g. [0022] Preferably also, the invention relates to a composition as defined above in which the level of zinc is in a range of 0 to 0.7 phr; and more preferably the level of zinc is in a range from 0.1 to 0.5 phr.

Preferably, the invention relates to a composition as defined above in which the ratio between the sulfur content in phr and the accelerator content in phr is greater than or equal to 2, and more preferably greater than or equal to 3.

The invention also relates to:

a semi-finished article for a tire comprising a composition as defined above, or a tire tread made of a composition as defined above, or

a tire equipped with a semi-finished article as defined above or a tread as defined above.

I-Description of the Invention The object of the invention therefore relates to a rubber composition that can be used for the manufacture of tires, based on at least one or more functionalized diene elastomers, at a rate greater than or equal to 40 parts by weight per hundred parts by weight of elastomer (phr), carbon black as majority reinforcing filler by weight, zinc at a level ranging from 0 to 1 phr, and a crosslinking system based on sulfur and an accelerator such that the ratio between the sulfur content in phr and the accelerator content in phr is strictly greater than 1, the said functionalized diene elastomer (s) being composed of a particular diene elastomer functionalized with chain end or in the middle of the chain by a tin function, and a content of less than 15% by weight relative to the total weight of the functionalized diene elastomer of a non-elastomer functional particular tin.

By the expression "composition based on" is meant a composition comprising the mixture and / or the reaction product in situ of the various basic constituents used, some of these constituents being able to react and / or being intended to react. between them, at least partially, during the different phases of manufacture of the composition, or during the subsequent cooking, modifying the composition as originally prepared. Thus, the compositions as implemented for the invention may be different in the uncrosslinked state and in the crosslinked state.

In an equivalent manner, the invention preferably relates to a composition as defined above, in which the composition is in the uncrosslinked state or in the crosslinked state.

In the present description, unless otherwise expressly indicated, all the percentages (%) indicated are% 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).

1-1 Elastomer or rubber

In the usual way, the terms "elastomer" and "rubber" that are interchangeable are used interchangeably in the text.

I-I-a Functionalized Dienic Elastomers

For the purposes of the present invention, one or more functionalized diene elastomers are used, the functionalized diene elastomer (s) being composed of: (a) a diene elastomer functionalized at the chain end or in the middle of the chain by a tin function and having the following formula:

where n and m are integers greater than or equal to 0 such that n + m = 1 or 2, b) a level of less than 15% by weight relative to the total weight of the functionalized diene elastomer of a non-elastomer functional tin corresponding to the following formula: Or

- A is a diene elastomer, the A blocks being identical to each other

X is a group containing tin,

According to a preferred embodiment, the functionalized diene elastomer according to the invention comprises a tin diene elastomer c) having the following formula:

or

o and p are integers greater than or equal to 0 and such that o + p> 3 and o + p <6,

- A is the diene elastomer as defined above, it being understood that it has a monomodal molecular weight distribution before staring and a polydispersity index before staring less than or equal to 1.3, - Y is a group containing the tin.

Preferably, the functionalized diene elastomer according to the invention comprises from 5% to 45% by weight, preferably from 10% to 30% by weight relative to the total weight of the functionalized diene elastomer of said star-shaped elastomer. tin c).

Preferably, the functionalized diene elastomer according to the invention comprises a level strictly greater than 0% by weight and less than 10% by weight, and more preferentially a content of less than 5% by weight relative to the weight. total functionalized diene elastomer of said non-functional tin elastomer b).

In the present description, the term functionalized diene elastomer a diene elastomer which comprises a group comprising one or more heteroatoms. This group can be at the end of the chain. It will then be said that the diene elastomer is functionalized at the end of the chain or at the end of the chain. This is generally an elastomer obtained by reaction of a living elastomer with a functionalizing agent, that is to say any molecule at least mono functional, the function being any type of chemical group known to those skilled in the art for react with a piece of living chain.

This group may be in the linear main elastomeric chain. It will be said that the diene elastomer is coupled or functionalized in the middle of the chain, as opposed to the position "at the end of the chain" and although the group is not precisely in the middle of the elastomeric chain. It is generally an elastomer obtained by reaction of a living elastomer on a coupling agent, that is to say any molecule at least difunctional, the function being any type of chemical group known to those skilled in the art to react. with a piece of living chain.

This group may be central to which n chains or elastomer branches (n> 2) are bonded forming a star structure of the elastomer. It will then be said that the diene elastomer is starred with n branches. It is generally an elastomer obtained by reaction of a living elastomer on a starzing agent, that is to say any multifunctional molecule, the function being any type of chemical group known to those skilled in the art to react with a piece of living chain.

For the purposes of the invention, the term "polydispersity index" refers to the ratio by weight average molecular weight / number average molecular weight. The minimum theoretical value being 1.

As explained above, the diene elastomer a) is functionalized at the end or in the middle of the chain by a tin function. The functionalization may be obtained with a mono- halo-tin or di-halo-tin functionalization agent capable of satisfying the general formula Pv4- _x SnX ° _x , where x represents an integer of value 1 or 2, R represents an alkyl, cycloalkyl or aryl radical. , alkaryl or vinyl having 1 to 12 carbon atoms, preferably butyl, and X ° is a halogen atom, preferably chlorine. As a preferred functionalizing agent include tributyltin monochloride or dichloride, dibutyltin _^. In the same way, the functionalization can be obtained with a functionalization agent derived from tin which can respond to the general formula (X'yR ¹ B-ySnVO-CSnP zX'z) or R ^1- _y Sn) -0- (CH ₂₎ _e -0- (SnR ¹ 3_ X _z ¹ _z), where y and z represent integers between 0 and 2 and y + z equal to 1 or 2, R ¹ represents an alkyl, cycloalkyl, aryl, alkaryl or vinyl radical having 1 to 12 carbon atoms, preferably butyl, X ¹ is a halogen atom, preferably chlorine, and e represents an integer of 1 to 20, preferably 4. [0040] The diene elastomer c), when it is present, is starred by a tin function. Starring may be obtained with a tri or tetrahalogenotin starring agent which may correspond to the general formula R ² _q SnX ² ₄ _q , where q represents an integer of value 0 or 1, R ² represents an alkyl radical, cycloalkyl, aryl, alkaryl or vinyl having 1 to 12 carbon atoms, preferably butyl, and X ² is a halogen atom, preferably chlorine. As a preferred starch agent, mention may be made of butyl tin trichloride or tin tetrachloride. In the same way, the starring can be obtained with a functionalization agent derived from tin which can meet the general formula (X ³ _k R ³ ₃ - _k Sn) -O- (SnR ³ ₃ -iX ³ i) or ( X ³ R ³ _k ₃ - _k Sn) -0- (CH2) 0- (SnR ³ ₃ ³ _iX i), where k and 1 are integers between 0 and 3, k + 1 integers from 3 and 6, R ³ represents an alkyl, cycloalkyl, aryl, alkaryl or vinyl radical having from 1 to 12 carbon atoms, preferably butyl, X ³ is a halogen atom, preferably chlorine and f represents an integer of value from 1 to 20 preferably 4.

According to a preferred embodiment, the diene elastomer a) is a diene elastomer functionalized with a tin function in the middle of the chain. According to another preferred embodiment, the diene elastomer c) is a star-branched diene elastomer with 4 branches.

According to another preferred embodiment, the diene elastomer a) is a diene elastomer functionalised by a tin function in the middle of the chain and the diene elastomer c) is a tin diene elastomer with 4 branches. According to the invention, the diene elastomer b) is non-functional tin. Said elastomer can be obtained during functionalization.

According to the invention, as explained above, the diene elastomer a) functionalized at the chain end or in the middle of the chain by a tin function, has a monomodal molecular weight distribution before functionalization and a polydispersity index before lower functionalization. or equal to 1.3. Similarly, as explained above, the diene diene elastomer c), when present, has a monomodal molecular weight distribution before staring and a polydispersity index before staring less than or equal to 1.3.

By diene elastomer is meant according to the invention any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms, or any block copolymer, random, sequential or microsequenced, obtained by copolymerization of a or more dienes conjugated to each other or to one or more vinylaromatic compounds having 8 to 20 carbon atoms. In the case of copolymers, these contain from 20% to 99% by weight of diene units, and from 1 to 80% by weight of vinylaromatic units.

By way of conjugated diene monomers which can be used in the process according to the invention, 1,3-butadiene, 2-methyl-1,3-butadiene and 2,3-di (C 1 to C 5) alkyl are especially suitable. 1,3-butadiene, such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene and 2-methyl-3-ethyl-1,3-butadiene. 2-methyl-3-isopropyl-1,3-butadiene, phenyl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene.

As vinylaromatic compounds are especially suitable styrene, ortho-, meta, para-methylstyrene, the commercial mixture "vinyltoluene", para-tert-butylstyrene, methoxy styrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, etc. .

Preferably, the diene elastomer is chosen from polybutadienes, random copolymers or butadiene-styrene block, random copolymers or butadiene-isoprene block, random copolymers or butadiene-styrene-isoprene block, statistical copolymers or styrene-isoprene block and synthetic polyisoprene.

As such are suitable polybutadienes and in particular those having a content (mol%) in -1,2 units of between 4% and 80%, 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., a styrene content of between 5% and 60%> by weight and more particularly between 20% and 50%, a content (mol%) in -1,2 bonds of the butadiene part of between 4%> and 75%>, a content (%> molar) in trans-1 bonds , 4 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 ° C. to -80 ° C., isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg of between 5 ° C. and -55 ° C. In the case of butadiene-styrene-isoprene copolymers, those having a styrene content of between 5% and 50% by weight and more particularly of between 10% and 40%, and an isoprene content of between 15%, are especially suitable. 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 units -1.4 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 isoprene part of between 10% and 50%, and more generally any copolymer butadiene-styrene-isoprene having a Tg between -5 ° C and -70 ° C.

According to a first particular embodiment, the diene elastomer [A] ^" can satisfy the following formula:

or :

the block B consists of a polyisoprene or a polybutadiene,

block C consists of a diene elastomer whose molar level of units derived from conjugated dienes is greater than 15%,

the number-average molecular mass Mn1 of block B varies from 2,500 to 20,000 g / mol,

the number-average molecular mass Mn2 of block C varies from 80,000 to 350,000 g / mol,

the rate of chains 3,4 in each block B is between 1 and 25% in the case where B is a polyisoprene block, the copolymer BC has a monomodal molecular weight distribution before possible functionalization or possible star-spiking and a polydispersity index before possible functionalization or possible star-ringing less than or equal to 1.3.

Preferably, the ratio of the number-average molecular weight Mn1 of each end-B polybutadiene or polyisoprene block to the number-average molecular weight Mn2 of each of the C blocks varies from 5 to 20%.

Preferably, the block or blocks C are chosen from copolymers of styrene and butadiene, copolymers of styrene and isoprene, copolymers of butadiene and isoprene, copolymers of styrene / butadiene / isoprene, polyisoprene when the neighboring B block is a polybutadiene, and polybutadiene when the neighboring B block is a polyisoprene. And more preferably, the block or blocks C are chosen from copolymers of styrene and butadiene.

According to a particularly preferred sub-embodiment, B is polyisoprene, C is a copolymer of styrene and butadiene, the block copolymer a) being functionalized with the dibutyltin dichloride functionalizing agent (Bu ₂ SnCl ₂ ) and the block copolymer c) being starred by the tin tetrachloride staining agent (SnCl ₄ ).

According to another particularly preferred sub-embodiment, B is polybutadiene, C is a copolymer of styrene and butadiene, the block copolymer a) being functionalized with the functionalizing agent dibutyltin dichloride (Bu ₂ SnCl ₂ ) and the block copolymer c) being starred by the tin tetrachloride staring agent (SnCl ₄ ).

According to a second particular embodiment of the invention, the diene elastomer a) may comprise an amine function at one or all ends of the non-functionalized tin chain. Similarly, the optionally present diene elastomer c) may comprise an amine function at the ends of the non-starred tin chains. Similarly, the non-functional tin diene elastomer b) may comprise an amine function at one end of the chain.

The polymerization of diene monomers is initiated by an initiator. As a polymerization initiator, any known mono functional anionic initiator can be used. However, an initiator containing an alkali metal such as lithium is used in a preferred manner. As organolithium initiators are particularly suitable those having a carbon-lithium bond. Preferably, use will be made of an organolithium hydrocarbon initiator having no heteroatom. Representative compounds are aliphatic organoliths such as ethyllithium, n-butyllithium (n-BuLi), isobutyl lithium. According to a particular embodiment of the invention, when the diene elastomer comprises an amino function at one or all of the ends of the chain, mention may also be made of organolithium compounds comprising a nitrogen-lithium bond, such as the compounds corresponding to the formula Li (NR ₁ R ₂ ) _a (NR 3) b (R 4) _c , in which R 1 and R ₂ denote an alkyl, cycloalkyl or aryl radical containing from 1 to 20 carbon atoms, R ₃ a cyclic alkyl radical, branched or unbranched, containing from 3 to 16 carbon atoms, R ₄ an alkyl, cycloalkyl, aryl radical containing from 1 to 20 carbon atoms, and a, b and c are integers between 0 and 4 provided that a + b + c = 4 and a + b> 1.

The polymerization is, as known per se, preferably carried out in the presence of an inert solvent which may be for example an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane or isooctane, cyclohexane or an aromatic hydrocarbon such as benzene, toluene, xylene.

The polymerization can be carried out continuously or batchwise, preferably batchwise. The polymerization is generally carried out at a temperature of between 20 ° C. and 120 ° C. and preferably in the region of 30 ° C. to 90 ° C. It is of course also possible to add at the end of the polymerization a transmetallation agent for modifying the reactivity of the living-chain end.

The living diene elastomer resulting from the polymerization is then functionalized to prepare the functionalized diene elastomer according to the invention.

According to a mode of preparation of the functionalized diene elastomer according to the invention when [A] - = [B-C] -, the block copolymer at the end of a living chain can be prepared in different stages:

[0065] the preparation of the polyisoprene or polybutadiene end block which is alive, and

- The preparation of the essentially unsaturated diene elastomer used to obtain said block other than the polybutadiene or polyisoprene block. According to this method of preparation, the polymerization of diene monomers, isoprene or butadiene, is initiated by said organolithium initiators to obtain a polyisoprene diene homopolymer or living polybutadiene. The living diene homopolymer thus obtained is then used as an initiator (initiator) for the preparation of the diene elastomer to obtain a living block copolymer. The discerning reader would understand that during the second stage of preparation, adequate working conditions must be put in place in order to limit the formation of dead or deactivated polyisoprene or polybutadiene diene homopolymer thus generating low molecular weight chains. An amount greater than 1% by weight of these polyisoprene or polybutadiene chains could penalize the properties of the functionalized diene elastomer according to the invention.

The living block copolymer resulting from the polymerization is then functionalized to prepare the functionalized diene elastomer according to the invention.

According to a first variant of preparation of the functionalized diene elastomer present in the composition according to the invention, the functionalized diene elastomer a) and the optional diene diene elastomer c) are mixed in the proportions necessary to minimize the elastomer content b).

The functionalized diene elastomer a) can be obtained in a manner known per se by reaction of a tin derivative on the living diene elastomer resulting from the polymerization. The optional star-shaped elastomer c) can be obtained in a manner known per se by reacting a tin-containing star-forming agent on the living diene elastomer resulting from the polymerization.

The two elastomers can be mixed in an inert solvent, for example an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, isooctane, cyclohexane or an aromatic hydrocarbon such as benzene, toluene, xylene, which may be the same as the polymerization solvent. The mixing is then carried out at a temperature of preferably between 20 ° C and 120 ° C, preferably in the region of 30 ° C to 90 ° C.

According to a second variant of preparation of the functionalized diene elastomer present in the composition according to the invention, in the case where the diene diene elastomer c) is present, the living diene elastomer from the polymerization step is subjected to the reaction of a starter agent and that of a functionalizing agent.

Thus, for example, the functionalization of the living diene elastomer resulting from the polymerization step can be carried out at a temperature ranging from 30 to 120 ° C., in the presence initially of an appropriate amount of a staring agent for staring preferably from 5 to 45% by weight of the living elastomer. Then, in a second step, the remaining living chains of the diene elastomer obtained after the first step are functionalized by adding a functionalization agent to tin, which can introduce at the end of the chain or in the middle of the chain a tin function. The functionalization reaction of the diene elastomer is then stopped by the deactivation of the remaining living chains.

The informed reader would understand that during the steps of preparation of the functionalized diene elastomers a) and c), in the case where the diene diene elastomer c) is present, suitable conditions of implementation must be put in place to to limit the formation of diene elastomer b) non-functionalized tin.

The overall rate of diene functionalized elastomers as defined above introduced into the rubber composition must be within a range from 40 phr to 100 phr, preferably 41 to 99 phr, more preferably 45 to 95 phr. more preferably from 50 to 95 phr and very preferably from 55 to 90 phr. Below 40 phr, the use of such elastomers is of less interest with regard to the rubber properties concerned.

I-l-b Other elastomers of the composition

When the rubber composition comprises a functionalized diene elastomer level as defined above less than 100 phr, the elastomeric matrix of the composition is then a diene (s) elastomer (s) cut (s) functionalized with at least one (i.e. one or more) elastomer not belonging to the category of functionalized diene elastomers as defined above. In other words, the composition may contain a level of elastomer different from a functionalized diene elastomer as defined above, in a range from 0 to 60 phr, preferably from 1 to 59 phr, more preferably from 5 to 60 phr. at 55, still more preferably from 5 to 50 phr and very preferably from 10 to 45 phr. For example, this or these different diene elastomers of the functionalized diene elastomer as defined above may be chosen from diene elastomers conventionally used in tires, such as natural rubber or a synthetic elastomer, or a other functionalized or star-shaped elastomer. Preferably, this elastomer is natural rubber.

1-2 Reinforcing filler

Carbon black is used as the majority reinforcing filler by weight (that is to say, it represents the highest content in phr among the reinforcing fillers of the composition, and preferably, it represents more than 50% of the reinforcing filler), known for its ability to reinforce a rubber composition that can be used for the manufacture of tires, alone or in a blend with a reinforcing inorganic filler such as silica.

As carbon blacks are suitable for all black carbon, 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 such as "CRX1346" from Cabot, or blacks from the 100 or 200 series (ASTM grades), such as blacks NI 15, NI 34, N220, or N234, or, depending on the intended applications, blacks of higher series (for example N326, N330, N339, N347, N375, N660, N683, N772). The carbon blacks could for example already be incorporated into the elastomer in the form of a masterbatch (see for example WO 97/36724 or WO 99/16600).

As carbon blacks are preferentially suitable reinforcing carbon blacks having a specific surface CTAB (determined according to the French standard NF T 45-007 of November 1987, method B) greater than or equal to 90 m ² / g, which corresponds to in particular to carbon blacks 100, 200 series (ASTM grades), as mentioned above. More preferably, the carbon blacks will have a specific surface area greater than 120 m ² / g, more preferably in a range from 120 m ² / g to 180 m 2 / g.

Other types of reinforcing filler may be used in blending with carbon black, in particular other reinforcing organic fillers or reinforcing inorganic fillers. As examples of organic fillers other than carbon blacks, mention may be made of the organic functionalized polyvinylaromatic fillers as described in applications WO-A-2006/069792 and WO-A-2006/069793.

By "reinforcing inorganic filler" must be understood in the present application, by definition, any inorganic or mineral filler (whatever its color and its origin (natural or synthetic), also called "white" charge, charge "clear" or "non-black filler" as opposed to carbon black, capable of reinforcing on its own, with no other means than an intermediate coupling agent, a rubber composition for manufacturing tire, in other words able to replace, in its reinforcing function, a conventional carbon black pneumatic grade, such a charge is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) at its area.

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 appropriate densified form. Of course, the term "reinforcing inorganic filler" also refers to mixtures of different reinforcing inorganic fillers, in particular highly dispersible siliceous and / or aluminous fillers as described below.

As reinforcing inorganic fillers are particularly suitable mineral fillers of the siliceous type, in particular of silica (SiO ₂ ), or of the aluminous type, in particular of alumina (Al ₂ O ₃ ). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface and a CTAB specific surface both less than 450 m ² / g, preferably from 30 to 400 m ² / g. As highly dispersible precipitated silicas (referred to as "HDS"), mention may be made, for example, of the silicas "Ultrasil 7000" and "Ultrasil 7005" from the company Degussa, the silicas "Zeosil 1165MP", "1135MP" and "1115MP" of the Rhodia company, the "Hi-Sil EZ150G" silica of the PPG company, the "Zeopol 8715", "8745" and "8755" silicas of the Huber Company, the high surface area silicas as described in the application WO 03 / 16837.

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

In particular, polysulfide 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).

As examples of polysulphurized silanes, mention may be made more particularly of the polysulfides (in particular disulphides, trisulphides or tetrasulfides) of bis- (C ₁ -C ₄ ) alkoxyl-C ₁ -C ₄ alkylsilyl-alkyl (C ₁ -C ₄ ) C4)), such as polysulfides of bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl). Among these compounds, bis (3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, of formula [(C ₂ H ₅ O) ₃ Si (CH ₂ ) 3 S 2] 2 or bis (triethoxysilylpropyl) disulfide, in abbreviated form, is especially used. TESPD, of formula [(C ₂ H ₅ O) 3 Si (CH 2) 3 S] 2. Mention may also be made, by way of preferred examples, of polysulfides (in particular disulphides, trisulphides or tetrasulfides) of bis (monoalkoxyl (Ci-C ₄ ) -dialkyl (Ci-C ₄ ) silylpropyl), more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide. as described in patent application WO 02/083782 (or US 2004/132880).

As coupling agent other than polysulfurized alkoxysilane, there may be mentioned in particular bifunctional POS (polyorganosiloxanes) or polysulfides of hydroxysilane (R 2 = OH in formula III 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.

When the rubber compositions in accordance with the invention contain coupling agents, in a known manner, their level is adjusted according to the level of silica, it is preferably in a range from 0.1 to 10 phr, more preferably from 0.2 to 8 and even more preferably from 0.5 to 5 phr.

Those skilled in the art 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 have on its surface functional sites, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between the filler and the elastomer.

The person skilled in the art knows how to adapt according to a part of the specific surface of the reinforcing filler and secondly according to the particular applications referred to, the total rate of total reinforcing filler (carbon black and reinforcing inorganic filler). such as silica). Indeed, the optimum is known in different ways depending on the specific applications targeted: the level of reinforcement expected on a bicycle tire, for example, is of course less than that required on a tire capable of driving at high speed in a sustained manner, for example a motorcycle tire, a tire for a passenger vehicle or for a commercial vehicle such as a truck. Preferably, this level is in a range from 30 to 90 phr, preferably from 30 to 70 phr, more preferably from 40 to 60 phr. For the purposes of the invention, the reinforcing filler mainly contains, by weight, carbon black, that is to say that it represents the highest content in phr of the reinforcing fillers of the composition, preferentially the carbon represents more than 50% of the reinforcing filler, for example at a level within a range of 30 to 90 phr, preferably 30 to 70 phr, more preferably 40 to 60 phr.

1-3 Crosslinking system

The crosslinking system is preferably a vulcanization system, that is to say a system based on sulfur (that is to say sulfur or a sulfur donor agent) and a vulcanization accelerator. To this basic vulcanization system are added, incorporated during the first non-productive phase and / or during the production phase as described later, various known vulcanization activators such as the zinc compounds defined below. stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine). Among the sulfur-donor agents, there may be mentioned, for example, 2-mercaptobenzothiazyl (abbreviated as "MBTS"), or tetrabenzylthiuram disulphide (TBZTD).

Sulfur is used at a preferential rate of between 0.5 and 12 phr, in particular between 1 and 10 phr, if a sulfur donor is used, its rate is adjusted so as to obtain such a sulfur content of vulcanization. The vulcanization accelerator is used at a preferential rate of between 0.2 and 10 phr, more preferably between 0.3 and 6.0 phr. Any compound (or mixture of compounds) capable of acting as an accelerator for vulcanizing diene elastomers in the presence of sulfur, especially thiazole accelerators and their derivatives, type accelerators, may be used as accelerator. thiurams, zinc dithiocarbamates. These accelerators are for example selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), tetrabenzylthiuram disulfide (TBZTD), N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), N, N-dicyclohexyl-2 benzothiazyl sulfenamide (DCBS), N-tert-butyl-2-benzothiazylsulphenamide (TBBS), N-tert-butyl-2-benzofhiazylsulphenide (TBSI), zinc dibenzyldithiocarbamate (ZBEC) and mixtures thereof. For the purposes of the present invention, the crosslinking system is such that the ratio between the sulfur content (that is to say the degree of vulcanization sulfur) in phr and the accelerator rate in phr. (that is to say the sum of accelerator rates if there are several) is strictly greater than 1 (so-called "conventional" vulcanization system), preferably greater than or equal to 2, more preferably greater than or equal to at 3, very preferably in a range from 3 to 12 and more preferably from 3 to 10.

1-4 Zinc compounds

As vulcanization activators, zinc-based compounds can be used. Among these compounds, there are, for example, zinc oxide (ZnO), zinc carboxylates such as zinc ethyl hexanoate (ZEH), zinc acetate or salts of zinc fatty acids, for example , zinc laurate or zinc stearate. Such compounds are more fully described in WO 2008/080582 or K-10-2004-0105992.

Other zinc compounds such as zinc dithiocarbamates, for example zinc dibenzyldithiocarbamate (ZBEC), may also be present as vulcanization accelerators.

For the purposes of the present invention, the level of zinc compounds introduced into the composition will be such that the total zinc level is less than 1 phr, preferably less than 0.7 phr, and most preferably within a range of 0.1 to 0.5 phr. In the case where zinc oxide is used, it is well known to those skilled in the art that it is useful to add a fatty acid, such as stearic acid, at a specific rate. preferably between 0.1 and 3 phr.

1-5 Various additives [00103] The rubber compositions in accordance with the invention may also comprise all or part of the usual additives normally used in elastomer compositions intended for the manufacture of tires, in particular treads, such as Examples of plasticizers or extension oils, whether these are of aromatic or non-aromatic nature, pigments, protective agents such as anti-ozone waxes, chemical antiozonants, anti-oxidants, anti-fatigue agents , reinforcing resins, acceptors (for example phenolic novolac resin) or methylene donors (for example HMT or H3M) as described for example in the application WO 02/10269, vulcanization activators provided of course in the case zinc-based activators to meet the recommended maximum zinc level. Preferably, these compositions comprise, as preferential non-aromatic or very weakly aromatic plasticizing agent, at least one compound chosen from the group consisting of naphthenic, paraffinic oils, MES oils, TDAE oils, and esters (in particular glycerol particular trioleates), the hydrocarbon plasticizing resins having a high Tg preferably greater than 30 ° C, and mixtures of such compounds. These compositions may also contain, in addition to the coupling agents, coupling activators, reinforcing inorganic filler recovery agents or, more generally, processing aid agents that are capable in a known manner, thanks to an improvement of the dispersion of the inorganic 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 (in particular alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines (for example trialkanol amines), hydroxylated or hydrolyzable POSs, for example α, ω -dihydroxy- polyorganosiloxanes (especially α, ω-dihydroxy-polydimethylsiloxanes), fatty acids, for example stearic acid. II- Preparation of compositions

The rubber compositions of the invention are manufactured in appropriate mixers, using two successive preparation phases according to a general procedure well known to those skilled in the art: a first phase of work or thermo-mechanical mixing (sometimes referred to as a "non-productive" phase) at a high temperature, up to a maximum temperature of between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C, followed by a second mechanical working phase ( sometimes referred to as a "productive" phase) at a lower temperature, typically less than 120 ° C., for example between 60 ° C. and 100 ° C., a finishing phase during which the crosslinking or vulcanization system is incorporated.

According to a preferred embodiment of the invention, all the basic constituents of the compositions of the invention, with the exception of the vulcanization system, namely the reinforcing filler, the coupling agent, if appropriate, are intimately incorporated, by kneading, with the diene elastomer during the so-called non-productive first phase, that is to say that is introduced into the mixer and which is thermomechanically kneaded, in a or several steps, at least these different basic constituents until reaching the maximum temperature between 130 ° C and 200 ° C, preferably between 145 ° C and 185 ° C.

For example, the first phase (non-productive) is conducted in a single thermomechanical step during which is introduced into a suitable mixer such as a conventional internal mixer, all the necessary constituents, the possible additional coating or processing agents and other miscellaneous additives, with the exception of the vulcanisation system. The total mixing time in this non-productive phase is preferably between 1 and 15 minutes. After cooling the mixture thus obtained during the first non-productive phase, the vulcanization system is then incorporated at low temperature, generally in an external mixer such as a roll mill; the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.

The final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for a characterization in the laboratory, or extruded, to form for example a rubber profile used for the manufacture semi-finished products such as treads. The crosslinking (or vulcanization or cooking) is conducted in a known manner at a temperature generally between 130 ° C and 200 ° C, under pressure, for a sufficient time which may vary for example between 5 and 90 minutes depending in particular the firing temperature, the crosslinking system adopted, the kinetics crosslinking of the composition in question or the size of the tire.

The invention particularly relates to the use of a rubber composition according to the invention for the manufacture of tires or semi-finished rubber products for these tires, these semi-finished products being in particular chosen from the group constituted by the treads, the sub-layers intended for example to be placed under these treads, the crown plies, the sidewalls, the carcass plies, the heels, the protectors, the inner tubes and the waterproof inner tires for tire without a chamber.

The composition according to the invention is particularly suitable for the manufacture of treads of tires intended to equip passenger vehicles, vans, 4x4 vehicles (4-wheel drive), two wheels, "heavy vehicles" ( that is, metro, bus, road transport vehicles (trucks, tractors, trailers), off-the-road vehicles), aircraft, civil engineering, agrarian, or handling equipment, these treads being able to be used in the manufacture of new tires or for the retreading of used tires. The invention relates to these tires and treads both in the green (i.e., before firing) and the fired (i.e., after crosslinking or vulcanization) state. The tread according to the invention is particularly suitable for tires intended to equip heavy-duty motor vehicles.

The invention as well as its advantages will be readily understood in light of the detailed description which follows. III- Examples

III- 1 Characterization of rubber compositions III-1-a Fixing time (or roasting time)

The measurements are carried out at 130 ° C., in accordance with the French NF standard.

T 43-005. The evolution of the consistometric index as a function of time allows determine the toasting time of the rubber compositions, evaluated according to the above-mentioned standard by parameter T5 (case of a large rotor), expressed in minutes, and defined as being the time necessary to obtain an increase in the consistometric index ( expressed in MU) of 5 units above the minimum value measured for this index. ΠΙ-1-b Traction tests

These tensile tests make it possible to determine the properties at break: elongation at break (in%). All these tensile measurements are carried out at 60 ° C, according to the French standard NF T 40-101 (December 1979).

III-l-c Dynamic Shear Properties The dynamic property G * is measured on a viscoanalyzer (Metravib

VA4000), according to ASTM D 5992-96. The response of a sample of vulcanized composition (cylindrical specimen 4 mm in height and 400 mm ² in section), subjected to a sinusoidal stress in alternating simple shear, at the frequency of 10 Hz, at 60 ° C., is recorded. A strain amplitude sweep is performed from 0.1% to 100% (forward cycle) and then from 100% to 0.1% (return cycle). The results exploited are the complex dynamic shear modulus G * and the loss factor tan (δ). For the forward cycle, the maximum value of tan (δ) observed, denoted tan (δ) _max , as well as the value of the complex modulus at 50%> of peak-to-peak deformation denoted G * 50% _{cc are indicated} .

ΠΙ-1-d Mooney Viscosity [00117] An oscillating consistometer is used as described in the French NF standard

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. The Mooney plasticity (ML 1 + 4) is expressed in "Mooney unit" (UM, with 1 UM = 0.83 Newton.meter).

III-2 Examples of compositions

The examples presented below are prepared as indicated above, their composition is given in Table 1, in phr. Table 1

(1) natural rubber (plasticized, peptized) (Tg = -65 ° C)

(2) polybutadiene with 2.5% 1,4-trans; 92.5% of 1,4-cis; 5.0% 1-2 (Tg = -105 ° C)

(3) Standard TPE functional SBR with high polydispersity index: polystyrene butadiene with the following mass ratios: 50%> 1,4-trans BR; 26%> 1,4-cis BR; 24%> of BR

1,2; 15.5%) of styrene (Tg = -65 ° C). The molecular weight Mn of this polymer, determined by the SEC technique, is 145,000 g / mol, the Ip is 1.7.

(4) tin-coupled SBR with a low polydispersity index, according to the invention: styrene-butadiene copolymer with the following mass ratios: 45.2% of 1,4-trans BR; 30.5% of 1,4-cis BR; 24.3% of BR 1,2; 15.5% styrene (Tg = -65 ° C). The molecular weight Mn of this polymer, determined by the SEC technique, is 194,000 gmol ^-1 , the Ip is 1.18.

(5) N234 for composition A0 and N134 for compositions A1 to A5

(6) N-1,3-dimethylbutyl N-phenylparaphenylenediamine (6-PPD)

(7) N-cyclohexyl-2-benzothiazylsulfenamide (CBS) The compositions A0, Al, A2, A3, A4 and A5 are distinguished from each other in particular by the type of cutting and the nature of the elastomers, the oxide content zinc, the sulfur content and the accelerator rate in Table 1. The rubber composition A0 is the control, corresponding to the composition used in the usual way in the treads of heavy weight. It contains 40 phr of synthetic elastomer conventionally used and usual rates of zinc oxide, sulfur and accelerator. It also contains 3 phr of an implementing agent, the "AFLUX 42" marketed by Rhein Chemie, which is necessary because of its cutting of elastomers and 0.5 phr of hardener and 0.25 phr of hardening resin. . The compositions Al, A2, A3, and A4 contain an NR / BR / SBR blend (15/10/75) and are distinguished from each other by the zinc oxide (ZnO), sulfur and accelerator content.

The composition A5 is the composition according to the invention and differs from A4 only by the nature of the SBR elastomer. The level of 0.5 phr of ZnO corresponds to a level of 0.4 phr of zinc in this composition, the molar mass of ZnO being 83 g / mol, including 65 g / mol for zinc.

III-3 Properties of the compositions

The properties of the compositions presented above are presented in Table 2 below.

Table 2

The comparison between the compositions A0 and Al highlights the expected fact that the G * modulus increases between A0 and Al, with the level of synthetic elastomer, which can result in an improvement in wear resistance. . Moreover, the increase in the level of synthetic elastomer penalizes the breaking properties of a rubber composition and thus decreases the endurance of the tread. Indeed there is a significant decrease in the elongation elongation of Al relative to AO. Mooney plasticity increases sharply.

The comparison between the compositions A0 and A2 demonstrates the fact that the reduction of the ZnO content from 3 phr to 0.5 phr, combined with the increase in the level of synthetic elastomers, also penalizes the properties at break. of a rubber composition conventionally used, even if the elongation of rupture is slightly improved with respect to Al. Mooney plasticity increases sharply.

The comparison between the compositions A0 and A3 highlights the fact that the modification of the sulfur content and the CBS content, so that the sulfur / CBS ratio changes from 1 (Al) to 4 (A3), combined. the increase in the level of synthetic elastomers does not make it possible to find as good a property at break as that of the control A0, even if the elongation of rupture is slightly improved with respect to Al. The Mooney plasticity increases strongly.

The comparison between the compositions A0 and A4 highlights the fact that the modification of the sulfur content and the CBS content, so that the sulfur / CBS ratio changes from 1 (Al) to 4 (A4) associated with the reduction of the ZnO level from 3 phr to 0.5 phr and combined with the increase in the level of synthetic elastomers makes it possible to find similar values of elongation of rupture and even leads to a slight improvement compared with the control A0. The value of max tanδ of the composition A4 is substantially identical to that of the composition A0, which corresponds to a rolling resistance of the tire similar to that of A0. Mooney plasticity increases sharply.

The comparison between the compositions A0 and A5 highlights the fact that the modification of the sulfur content and the CBS content, so that the sulfur / CBS ratio changes from 1 (Al) to 4 (A5) associated with the reduction of the ZnO level from 3 phr to 0.5 phr and combined with the increase in the level of functionalized diene elastomers specific as described for the purposes of the invention also makes it possible to find similar values of elongation of rupture and even leads to a slight improvement over witness A0. In addition, these properties are accompanied by a decrease in the level of tanδ max of the composition, which corresponds to an improvement in the rolling resistance of the tire, without significantly penalizing the implementation (Mooney plasticity) of the composition A5 and therefore the productivity with respect to the reference composition A0. Thus, these results show that it is possible to increase the level of functionalized diene elastomer as defined according to the invention, and therefore a priori to improve the wear resistance without degrading the endurance, by improving the rolling resistance. with a rubber composition which comprises a content of functionalized diene elastomer as defined according to the invention greater than 40 phr (75 phr in Example A5), a low level of zinc (0.4 in Example A5 ) and a sulfur content and accelerator characterized in that the ratio between sulfur content in pce and accelerator rate in pce is greater than 1 (4 in Example A5).

Claims

1. A rubber composition based on at least one or more functionalized diene elastomers at a total content greater than or equal to 40 parts by weight per hundred parts by weight of elastomer (phr), carbon black as a reinforcing filler predominant by weight, zinc at a rate within a range of 0 to 1 phr, and a sulfur-based crosslinking system and an accelerator such as the ratio between the sulfur content in phr and the rate of accelerator in pce is strictly greater than 1; said functionalized diene elastomer (s) being composed of: a) a functional diene elastomer at the chain end or in the middle of the chain with a tin function and corresponding to the following formula:

[ ^L A] ^J or. :

- A is a diene elastomer, the A blocks being identical to each other

X is a group containing tin, elastomer A has a monomodal molecular weight distribution before possible functionalization and a polydispersity index before possible functionalization less than or equal to 1.3.

2. Composition according to claim 1 characterized in that the functionalized diene elastomer comprises a diene elastomer c) stellar tin corresponding to the following formula: or

o and p are integers greater than or equal to 0 and such that o + p> 3, and o + p <6

Y is a group containing tin.

3. Composition according to claim 1 characterized in that the functionalized diene elastomer comprises from 5% to 45% by weight, preferably from 10% to 30% by weight relative to the total weight of the functionalized diene elastomer of said star-shaped elastomer. tin c).

4. Composition according to any one of claims 1, 2 or 3 characterized in that the diene functionalized elastomer according to the invention comprises a level strictly greater than 0%> by weight and less than 10%> by weight, and more preferentially a content of less than 5% by weight relative to the total weight of the functionalized diene elastomer of said non-functional tin elastomer b).

5. Composition according to any one of claims 1 to 4, characterized in that the functionalization of the diene elastomer a) is obtained with a mono-halo-tin or di-halo-tin functionalization agent.

6. Composition according to any one of claims 1 to 5, characterized in that the stellar diene elastomer c) can be obtained with a sorting agent tri or tetrahalo-tin.

7. Composition according to any one of claims 1 to 6, characterized in that the diene diene elastomer c) is a star-shaped elastomer 4 branches.

8. Composition according to any one of claims 1 to 7, characterized in that the diene elastomer is chosen from polybutadienes, random copolymers or butadiene-styrene block, random copolymers or butadiene-isoprene block, random copolymers or butadiene-styrene-isoprene block, random copolymers or styrene-isoprene block and synthetic polyisoprene.

9. Composition according to any one of claims 1 to 8, characterized in that the diene elastomer [A] - has the following formula: [B - C] - where:

the block B consists of a polyisoprene or a polybutadiene,

block C consists of a diene elastomer whose molar level of units derived from conjugated dienes is greater than 15%; the number-average molecular mass Mn1 of block B varies from 2500 to 20 000 g / mol,

10. Composition according to claim 9 characterized in that the ratio of the number-average molecular weight Mnl of each end-B polybutadiene or polyisoprene block to the number-average molecular mass Mn2 of each of the blocks C varies from 5 to 20%. .

11. Composition according to Claim 9 or 10, characterized in that the block C is chosen from copolymers of styrene and butadiene, copolymers of styrene and isoprene, copolymers of butadiene and isoprene, copolymers of styrene / butadiene / isoprene, polyisoprene when the neighboring B block is a polybutadiene, and polybutadiene when the neighboring B block is a polyisoprene.

12. Composition according to any one of claims 1 to 8 characterized in that the diene elastomer a) comprises an amine function at one or all ends of non-functionalized tin chains.

13. Composition according to any one of claims 1 to 8 characterized in that the diene elastomer b) comprises an amine function at one of the ends of chains.

14. Composition according to any one of claims 1 to 8 characterized in that the diene elastomer c) comprises an amine function at the ends of non-starred tin chains.

15. Composition according to any one of claims 1 to 14 characterized in that the carbon black content is in a range of more than 30 to 90 phr.

16. Composition according to any one of claims 1 to 15 characterized in that the reinforcing filler is a blend of carbon black and silica.

17. Composition according to any one of claims 1 to 16 characterized in that the reinforcing filler comprises a carbon black surface specific CTAB greater than or equal to 90 m ² / g.

18. Composition according to any one of claims 1 to 17 characterized in that the zinc level is in a range of 0 to 0.7 phr.

19. The composition of claim 18 characterized in that the zinc level is in a range of 0.1 to 0.5 phr.

20. Composition according to any one of claims 1 to 19 characterized in that the ratio between the sulfur content in pce and the accelerator rate in pce is greater than or equal to 2.

21. Composition according to claim 20 characterized in that the ratio between the sulfur content in pce and the accelerator rate in pce is greater than or equal to 3.

22. Tire tread characterized in that it consists of a composition according to any one of claims 1 to 21.