RUBBER COMPOSITION BASED ON A MODIFIED DIENE LASTOMER

Description

Technical field

[0001] The invention relates to a rubber composition comprising a modified diene elastomer and silica as a reinforcing filler. Prior art

[0002] Since fuel savings and the need to preserve the environment have become a priority, it is desirable to produce mixtures having as low a hysteresis as possible in order to be able to implement them in the form of rubber compositions usable for the manufacture of various semi-finished products used in the composition of tires, such as for example underlayers, sidewalls, treads, and in order to obtain tires having reduced rolling resistance.

[0003] Ideally, for example, a tire tread must meet a large number of often conflicting technical requirements, including high wear resistance while providing the tire with low rolling resistance.

[0004] Furthermore, the reduction of the hysteresis of the mixtures, which guarantees a reduction in rolling resistance, must also be done while maintaining intact the suitability for use, particularly when raw, of the mixtures, while maintaining the creep resistance of the elastomers.

[0005] To achieve the objective of reducing hysteresis, many solutions have already been tested. In particular, we can cite the modification of the structure of polymers and diene copolymers at the end of polymerization by means of functionalization, coupling or star-forming agents in order to obtain a good interaction between the polymer thus modified and the filler, whether it is carbon black or a reinforcing inorganic filler.

[0006] In the context of mixtures containing a reinforcing inorganic filler such as silica, it has been proposed to use diene polymers functionalized by alkoxysilane derivatives, in particular by combining or not the functionalization by alkoxysilane functions with the functionalization by other functions, in particular amine, imine, epoxy or even thiol functions.

[0007] Functionalization by alkoxysilane compounds bearing an amine function has been widely described in the patent literature. Elastomers functionalized at the chain end by alkoxysilane functions bearing an amine group have been associated with both silica and carbon black, or even a mixture of these two fillers, in rubber compositions intended for the manufacture of tires.

[0008] The Applicant has described, in document WO 2009133068 A1, a functionalized diene elastomer essentially consisting of the coupled species of an elastomer having within the chain a group carrying an alkoxysilane function and an amine function, the silicon atom of this group linking the two parts of the diene elastomer chain. This elastomer functionalized in the middle of the chain gives the composition containing it improved mechanical and dynamic properties, in particular improved hysteresis, while retaining satisfactory raw processing, particularly with a view to use in tire treads.

[0009] Documents EP 2 003 146 A2, US 2014 / 0243476A1 describe diene elastomers modified with functionalizing agents having both at least one silicon atom and at least one nitrogen atom. JP 2016017097A describes diene elastomers modified with functionalizing agents having both at least one silicon atom and at least one nitrogen atom, carrying at the end of the chains not linked to the functionalizing agent, an amine functional group. These documents propose improving the mechanical and dynamic properties of rubber compositions having low levels of reinforcing filler and intended for tire application, and highlight in particular gains in wet grip, improved heat dissipation, gains in rolling resistance or even abrasion.

[0010] Applications WO2009 / 000750 and WO 2015 / 044225 describe compositions comprising an SBR diene elastomer modified by means of a modifying agent poly(oxy-1,2-ethanediyl)-α-[3-(dichloromethylsilyl)propyl]-ω-[3-(dichloromethylsilyl)propoxy]. In these compositions, the level of branched macromolecules is less than 20%.

[0011] In order to achieve certain tire performances, it may be necessary to use more or less reinforcing filler in the rubber compositions that make up the different parts of the tire. However, the use of a large quantity of filler to achieve some of these performances is, however, contradictory to the desired reduction in rolling resistance. Indeed, the use of a high level of reinforcing filler in the mixture used to manufacture the tread frequently penalizes, often in a prohibitive manner, the rolling resistance properties, being accompanied by a significant increase in the hysteretic losses of the rubber composition.

[0012] The technical problem which the present invention seeks to solve is to mitigate the effect of increasing the reinforcing filler content on the dynamic properties of rubber compositions and their implementation with a view to using these compositions for the manufacture of tires having reduced rolling resistance.

[0013] Continuing its research, the Applicant discovered that the use of certain particular modified diene elastomers in rubber compositions makes it possible to reduce the impact of the increase in the level of reinforcing fillers on the processing / hysteresis compromise. It is thus possible to provide tire rubber compositions comprising a high level of reinforcing fillers while minimizing the effect of this high level on the hysteresis and processing properties of the compositions. Statement of the invention

[0014] The subject of the invention is therefore a rubber composition based at least on one reinforcing filler and an elastomer matrix comprising a modified diene elastomer, characterized in that the reinforcing filler content is greater than or equal to 80 phr, the modified diene elastomer content is greater than or equal to 75 phr, and the modified diene elastomer comprises macromolecules comprising a linear or branched polyether block comprising at each end of the block a branching point to which is bonded up to three diene elastomer blocks and up to three -OR groups, R representing, independently of each other, a C1-C8 alkyl substituent or a hydrogen atom, a - the copolymer having a Mooney viscosity of at least 40 and at most 100, b - the copolymer being composed of at least 20%, preferably 30%, of branched macromolecules comprising the polyether block to which are bonded at least three diene elastomer blocks, of at most 80%, preferably 70%, of linear macromolecules, c - the polyether block having a number-average molecular mass varying from 150 g / mol to 5000 g / mol,and d - each of the branching points being made up of a silicon atom, the branched macromolecules corresponding to the formula I: , in which, R 1< represents a divalent, linear or branched, C 1 -C 10 hydrocarbon group, in particular a group - CH(R') - CH(R'') - in which R' and R" are, independently of each other, a hydrogen atom or a C 1 -C 4 alkyl substituent, preferably R 1< is a C 1 -C 4 alkanediyl group, more preferably a 1,2- or 1,3- ethanediyl or propanediyl group, the R 2< represent, independently of each other, a divalent hydrocarbon group, preferably a linear or branched or cyclic, saturated or unsaturated aliphatic group having 1 to 50 carbon atoms, preferably a linear aliphatic group, preferably saturated, preferably having 1 to 15 carbon atoms, preferably 2 to 10, preferably 3 to 8;the Y represent, identically or differently, a halogen atom or a group of formula - OR 4< in which the R 4< represent, independently of one another, a hydrogen atom, a C 1 -C 8 alkyl substituent, preferably the R 4< represent a hydrogen atom or a C 1 -C 4 alkyl substituent, preferably methyl or ethyl, i and j are numbers each independently of the other being 1, 2 or 3, provided that (i+j) varies from 3 to 6, and P represents a diene elastomer block; and the linear block macromolecules corresponding to the formula II: ; in which, R 1< represents a divalent, linear or branched, C 1 -C 10 hydrocarbon group, in particular a group - CH(R') - CH(R'') - in which R' and R'' are, independently of each other, a hydrogen atom or a C 1 -C 4 alkyl substituent, preferably R 1< is a C 1 -C 4 alkanediyl group, more preferably a 1,2- or 1,3- ethanediyl or propanediyl group, the R 2< represent, independently of each other, a divalent hydrocarbon group, preferably a linear or branched or cyclic, saturated or unsaturated aliphatic group having 1 to 50 carbon atoms, preferably a linear aliphatic group, preferably saturated, preferably having 1 to 15 carbon atoms, preferably 2 to 10, of preference 3 to 8;the Y represent, identically or differently, a halogen atom or a group of formula - OR 4< in which the R 4< represent, independently of one another, a hydrogen atom, a C 1 -C 8 alkyl substituent, preferably the R 4< represent a hydrogen atom or a C 1 -C 4 alkyl substituent, preferably methyl or ethyl, k and 1 are numbers each independently of the other being 0 or 1, provided that (k+1) is 1 or 2, and P represents a diene elastomer block. ; Detailed description

[0015] In this specification, unless expressly stated otherwise, all percentages (%) indicated are % by mass. Furthermore, any interval 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., excluding the limits a and b), while any interval of values ​​designated by the expression "from a to b" means the range of values ​​from a to b (i.e., including the strict limits a and b). In this specification, when a range of values ​​is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also designated.

[0016] The expression "based on" composition means a composition comprising the mixture and / or the reaction product of the different constituents used, some of these basic constituents being capable of, or intended to, react with each other, at least in part, during the different phases of manufacture of the composition, in particular during its crosslinking or vulcanization.

[0017] In this description, the abbreviation "pce" means parts by weight per hundred parts by mass of elastomers present in the elastomer matrix, the elastomer matrix designating all of the elastomers present in the rubber composition.

[0018] In the present application, by "predominantly" or "majority" in connection with a compound, it is meant that this compound is in the majority among the compounds of the same type in the composition, that is to say that it is the one which represents the largest weight fraction among the compounds of the same type. In the same way, a functional species of a modified diene elastomer called majority is that representing the largest weight fraction among the functionalized species constituting the diene elastomer, relative to the total weight of the modified diene elastomer. In a system comprising a single compound of a certain type, this is in the majority within the meaning of the present invention.

[0019] In the present description, Mooney viscosity means the Mooney viscosity ML(1+4)100°C of a compound, in particular of the modified diene elastomer of the invention, measured according to the ASTM D1646 standard.

[0020] In the present description, the term "functional polyether" means a difunctional polyether. The functional polyether may be linear or branched and has a main chain comprising at each of the two ends a silicon atom, each substituted by three alkoxyl functions or by three halogen atoms. A linear polyether comprises at both ends of the polymer chain a silicon atom, each substituted by three alkoxyl functions or by three halogen atoms. A branched polyether comprises a main linear chain of which all or some of the repeating units are branched. A branched polyether comprises at each of the two ends of the main chain a silicon atom, each substituted by three alkoxyl functions or by three halogen atoms. The branches are hydrocarbon-based, preferably aliphatic, and do not comprise a silicon atom.

[0021] In the present description, the term “modified diene elastomer” means a mixture of macromolecules resulting from the reaction with a functional polyether comprising six reactive trialkoxysilyl or trihalosilyl functions.

[0022] The person skilled in the art will understand that a modification reaction with a compound comprising more than one reactive function with respect to the living elastomer results in a mixture of linear macromolecules and macromolecules branched with at least three branches and at most as many branches as there are reactive functions of the functional polyether. Depending on the operating conditions, mainly the molar ratio of the number of reactive functions of the functional polyether to the living chains, certain macromolecules are more or less present in the mixture.

[0023] In this description, the expression "monomer unit", whether diene or otherwise, is understood as a repeating unit of the polymer derived from the monomer in question.

[0024] It should be noted that in the context of the invention, the monomers used may be of fossil or bio-sourced origin. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass.

[0025] Thus the invention relates to a rubber composition based at least on one reinforcing filler comprising silica and an elastomer matrix comprising a modified diene elastomer, characterized in that the silica content is greater than or equal to 80 phr, the modified diene elastomer content is greater than or equal to 75 phr, and the modified diene elastomer comprises macromolecules comprising within their structure a polyether block, linear or branched, comprising at both ends of the block a branching point to which are bonded up to three diene elastomer blocks and up to three -OR groups, R representing, independently of each other, a C1-C8 alkyl substituent or a hydrogen atom, a- the copolymer having a Mooney viscosity of at least 40 and at most 100, b- the copolymer being composed of at least 20%, preferably at least 30%, of branched macromolecules comprising a polyether block to which are bonded at least three diene elastomer blocks, of at most 80%, preferably at most 70%, of linear macromolecules, c- the polyether block having a number-average molecular mass varying from 150 to 5000 g / mol,and d- each of the branching points being made up of a silicon atom, the branched macromolecules corresponding to formula I: , in which, R 1< represents a divalent, linear or branched, C 1 -C 10 hydrocarbon group, in particular a group - CH(R') - CH(R") - in which R' and R" are, independently of each other, a hydrogen atom or a C 1 -C 4 alkyl substituent, preferably R 1< is a C 1 -C 4 alkanediyl group, more preferably a 1,2- or 1,3- ethanediyl or propanediyl group, the R 2< represent, independently of each other, a divalent hydrocarbon group, preferably a linear or branched or cyclic, saturated or unsaturated aliphatic group having 1 to 50 carbon atoms, preferably a linear aliphatic group, preferably saturated, preferably having 1 to 15 carbon atoms, preferably 2 to 10, preferably 3 at 8;the Y represent, identically or differently, a halogen atom or a group of formula - OR 4< in which the R 4< represent, independently of one another, a hydrogen atom, a C 1 -C 8 alkyl substituent, preferably the R 4< represent a hydrogen atom or a C 1 -C 4 alkyl substituent, preferably methyl or ethyl, i and j are numbers each independently of the other being 1, 2 or 3, provided that (i+j) varies from 3 to 6, and P represents a diene elastomer block; and the linear block macromolecules corresponding to the formula II: ; in which, R 1< represents a divalent, linear or branched, C 1 -C 10 hydrocarbon group, in particular a group - CH(R') - CH(R'') - in which R' and R" are, independently of each other, a hydrogen atom or a C 1 -C 4 alkyl substituent, preferably R 1< is a C 1 -C 4 alkanediyl group, more preferably a 1,2- or 1,3- ethanediyl or propanediyl group, the R 2< represent, independently of each other, a divalent hydrocarbon group, preferably a linear or branched or cyclic, saturated or unsaturated aliphatic group having 1 to 50 carbon atoms, preferably a linear aliphatic group, preferably saturated, preferably having 1 to 15 carbon atoms, preferably 2 to 10, preferably 3 to 8;the Y represent, identically or differently, a halogen atom or a group of formula - OR 4< in which the R 4< represent, independently of one another, a hydrogen atom, a C 1 -C 8 alkyl substituent, preferably the R 4< represent a hydrogen atom or a C 1 -C 4 alkyl substituent, preferably methyl or ethyl, k and 1 are numbers each independently of the other being 0 or 1, provided that (k+1) is 1 or 2, and P represents a diene elastomer block. ;

[0026] By diene elastomer capable of being used as the modified diene elastomer in the compositions in accordance with the invention, must be understood in a known manner a synthetic elastomer consisting at least in part of diene monomer units, conjugated or not.

[0027] More specifically, synthetic diene elastomer means: (a) - any homopolymer of a diene monomer, particularly a conjugated diene monomer, in particular any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms; (b) - any copolymer obtained by copolymerization of one or more diene monomers with each other or with one or more vinylaromatic monomers.

[0028] In the case of copolymers (b), these contain from 20 to 99% by weight of diene units and from 1 to 80% by weight of units derived from vinylaromatic monomers.

[0029] Suitable conjugated dienes include, in particular, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-di(C1-C5 alkyl)-1,3-butadienes such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, an aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene. Preferably, the conjugated diene is a derivative of 1,3-butadiene, more preferably 1,3-butadiene.

[0030] Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene. Preferably, the vinyl aromatic compound is styrene.

[0031] Preferably, the diene elastomer is chosen from the group consisting of polybutadienes (BR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and blends of these elastomers. Such copolymers are more preferably chosen from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene-butadiene-styrene copolymers (SBIR). According to a variant of the invention, the diene elastomer is more particularly a butadiene-styrene copolymer (SBR) or a polybutadiene (BR).

[0032] The diene elastomer can have any microstructure which depends on the polymerization conditions used.

[0033] The diene elastomer can be block, statistical, sequenced, microsequenced...

[0034] According to a variant of the invention, the number-average molar mass of the elastomeric branches of the modified diene elastomer is less than 150,000 g / mol, preferably at least 40,000 g / mol and at most 100,000 g / mol.

[0035] According to a variant of the invention, the end of the elastomer branches of the block copolymer, not linked to a silicon atom, may carry a function comprising a nitrogen atom, preferably a cyclic or acyclic amine function. Preferably, the ends of the elastomer branches of the block copolymer are functionalized to at least 70 mol%, relative to the number of moles of elastomer branches, by a cyclic or acyclic amine function.

[0036] The alkoxy groups substituting the silicon atom may be, according to certain variants of the invention, partially or totally hydrolyzed to hydroxyl. According to these variants, all or at least 50 mol% of the alkoxy groups carried by the modified diene elastomer are hydrolyzed to hydroxyl. In particular, at least 80 mol% of the alkoxy functions carried by the modified diene elastomer are hydrolyzed to hydroxyl, or even 100%.

[0037] The alkyl substituents of the alkoxy groups substituting the silicon atoms are, independently of one another, chosen from C1-C10, or even C1-C8 alkyl substituents, preferably from C1-C4 alkyl substituents, more preferably from methyl and ethyl.

[0038] According to a variant of the invention, the polyether block is a block consisting of - (OR)- units, in which R is a divalent hydrocarbon group, preferably an aliphatic group, linear or branched, having 1 to 10 carbon atoms, in particular a - CH(R') - CH(R") - group in which R' and R" are, independently of one another, a hydrogen atom or a C1-C4 alkyl substituent, preferably R is a C1-C4 alkanediyl group, more preferably a 1,2- or 1,3-ethanediyl or propanediyl group.

[0039] Mention may thus be made, as polyether block suitable for the invention, of polyoxymethylene, poly(ethylene oxide), poly(propylene oxide), or polytetrahydrofuran, preferably the polyether block is a poly(ethylene oxide) or poly(propylene oxide) block.

[0040] The polyether block has a number-average molecular mass of approximately 150 to 5000 g / mol and preferably 200 to 3000 g / mol. The number-average molecular mass is calculated using the SEC (Size Exclusion Chromatography) technique, which separates macromolecules in solution according to their size using columns filled with a porous gel. The method is explained further in the text.

[0041] According to the invention, the branching points of the block copolymer to which the diene elastomer chains are linked are silicon atoms. There are two branching points located at each end of the linear polyether block.

[0042] Thus, a branch point can link up to three diene elastomer blocks to the polyether block.

[0043] According to the invention, the linear macromolecules consist of elastomer chains not linked to a polyether block, of macromolecules each branching point of which is linked to a diene elastomer block (linear triblock copolymer) and of macromolecules a single branching point of which is linked to a diene elastomer block (linear diblock copolymer). Their mass content is at most 80%, preferably at most 70% and even more preferably at most 65% relative to the total weight of the block copolymer.

[0044] According to the invention, the branched macromolecules consist of macromolecules whose entire branching points are linked to at most three diene elastomer blocks. For reasons of feasibility and technical reality, these macromolecules preferably have a distribution of the diene elastomer blocks on either side of the polyether block, on the branching points, i.e. all the elastomer blocks are not linked to the same branching point but distributed over the two branching points.Thus, when the polyether block is linear, the three-branched macromolecules may comprise two elastomeric branches at one end of the polyether block and one elastomeric branch at the other end, the four-branched macromolecules may comprise two elastomeric branches at one end of the polyether block and two elastomeric branches at the other end or three elastomeric branches at one end of the polyether block and one elastomeric branch at the other end, and so on. The mass content of the branched macromolecules is at least 20%, preferably at least 30%, more preferably at least 35% relative to the total weight of the block copolymer.

[0045] When the branch points, which are silicon atoms, are not linked to three diene elastomer blocks, they are substituted by one, two or three hydroxyl or C1-C8 alkoxy substituents, preferably C1-C4, more preferably methoxy or ethoxy.

[0046] The alkoxy groups substituting the silicon atom may be, according to certain variants of the invention, partially or completely hydrolyzed to hydroxyl. According to these variants, all or at least 50 mol% of the alkoxy functions carried by the modified diene elastomer are hydrolyzed to hydroxyl. In particular, at least 80 mol% of the alkoxy functions carried by the modified diene elastomer are hydrolyzed to hydroxyl, or even 100%.

[0047] The block macromolecules composing the diene block copolymer are represented by the following formulas I and II: branched macromolecules corresponding to the formula I: in which, R1 represents a divalent hydrocarbon group, preferably a linear or branched aliphatic group, having 1 to 10 carbon atoms, in particular a group - CH(R') - CH(R") - , in which R' and R" are, independently of each other, a hydrogen atom or a C1-C4 alkyl substituent, preferably R1 is a C1-C4 alkanediyl group, more preferably a 1,2- or 1,3-ethanediyl or propanediyl group, the R2 represent, independently of each other, a divalent hydrocarbon group, preferably a linear or branched or cyclic, saturated or unsaturated aliphatic group, having 1 to 50 carbon atoms, preferably a linear aliphatic group, preferably saturated, preferably having 1 to 15 carbon atoms, preferably 2 to 10, the Y represent, identically or differently, a group of formula -OR4 in which the R4s represent, independently of each other, a hydrogen atom,a C1-C18 alkyl, C5-C18 cycloalkyl or C6-C18 aryl substituent, preferably R4 represents a hydrogen atom or a C1-C8 alkyl substituent, more preferably C1-C4, more preferably methyl or ethyl. i and j are numbers each independently of the other being 1, 2 or 3, provided that (i+j) varies from 3 to 6, and P represents a diene elastomer block; linear block macromolecules corresponding to formula II: , in which, R1 represents a divalent hydrocarbon group, preferably a linear or branched, saturated or unsaturated aliphatic group having 1 to 10 carbon atoms, in particular a group - CH(R') - CH(R") - , in which R' and R" are, independently of each other, a hydrogen atom or a C1-C4 alkyl substituent, preferably R1 is a C1-C4 alkanediyl group, more preferably a 1,2- or 1,3-ethanediyl or propanediyl group, R2 represent, independently of each other, a divalent hydrocarbon group, preferably a linear or branched or cyclic, saturated or unsaturated aliphatic group having 1 to 50 carbon atoms, preferably a linear, preferably saturated aliphatic group, preferably having 1 to 15 carbon atoms, preferably 2 to 10;the Ys represent, identically or differently, a group of formula - OR4 in which the R4s represent, independently of one another, a hydrogen atom, a C1-C18 alkyl, C5-C18 cycloalkyl or C6-C18 aryl substituent, preferably the R4s represent a hydrogen atom or a C1-C8 alkyl substituent, preferably C1-C4, more preferably methyl or ethyl, k and 1 are numbers each independently of the other being 0 or 1, provided that (k+1) is 1 or 2, and P represents a diene elastomer block. ;

[0048] According to variants of the invention which can be combined with the previous ones, P represents a diene elastomer branch carrying at the end of the chain a group comprising a nitrogen atom, more particularly an amine function, cyclic or acyclic.

[0049] The modified diene elastomer according to a preferred embodiment of the invention comprises at least 50% by weight of branched macromolecules relative to the total weight of the modified diene elastomer, preferably at least 80% by weight, the branched macromolecules being all of the macromolecules with at least three branches of the modified diene elastomer, that is to say that they consist of a polyether block to which at least three diene elastomer blocks are linked.

[0050] The reader will understand that, the macromolecules of the modified diene elastomer corresponding to formulas I and II, according to this variant, at least 50% by weight of branched macromolecules relative to the total weight of the modified diene elastomer, preferably at least 80% by weight, correspond to formula I.

[0051] According to another variant, which can be combined with the previous one, at most 25% by weight of the total weight of the modified diene elastomer may consist of macromolecules comprising a polyether block to which four or more diene elastomer blocks are linked.

[0052] The reader will understand that, the macromolecules of the modified diene elastomer corresponding to formulas I and II, according to this variant, at most 25% by weight of branched macromolecules relative to the total weight of the modified diene elastomer, preferably at least 80% by weight, correspond to formula I for which i+j is 4 or more.

[0053] The modified diene elastomer according to another preferred embodiment of the invention, which can be combined with one or other of the two preceding embodiments or with the combination of the two, comprises at least 20%, preferably at least 35%, by weight of three-branched macromolecules, relative to the total weight of the modified diene elastomer, preferably at least 40%, the three-branched macromolecules consisting of a polyether block to which three diene elastomer blocks are linked.

[0054] The reader will understand that, the macromolecules of the modified diene elastomer corresponding to formulas I and II, according to this variant, at least 20%, preferably at least 35%, by weight of branched macromolecules relative to the total weight of the modified diene elastomer, preferably at least 40% by weight, correspond to formula I for which i+j is 3.

[0055] The different variants and preferred aspects concerning the nature of the modified diene elastomer, the functionalization of the elastomer branches, their Mn, the alkoxy function, the number of silicon atoms, the spacer group and the group comprising at least one nitrogen atom, the rate of branched macromolecules, the rate of three-branched macromolecules, etc. can be combined with each other subject to their compatibility.

[0056] According to advantageous variants of the invention, the modified diene elastomer comprising macromolecules comprising within their structure a linear or branched polyether block comprising at each chain end a branching point to which is linked up to three diene elastomer blocks and up to three -OR groups, R representing, independently of each other, a C1-C8 alkyl substituent or a hydrogen atom, is such that at least one of the following characteristics is respected, at least two, at least three, at least four, at least five, at least six, at least seven, and preferably all: the polyether block is made up of -(OR)- units, in which R is a C1-C4 alkanediyl group, more preferably a 1,2- or 1,3- ethanediyl or propanediyl group, the polyether block has a number-average molecular mass of substantially 200 to 3000 g / mol all or part, preferably at least 50 mol%, of the alkoxy functions substituting one or more silicon atoms is hydrolyzed to hydroxyl; the diene elastomer is a butadiene-styrene copolymer; all or part, preferably at least 70 mol%, of the ends of elastomer branches not linked to a silicon atom is functionalized relative to the number of moles of chain end, by an amine function; the average Mn of the elastomeric branches is less than 150,000 g / mol, preferably from 40,000 to 100,000 g / mol; the modified diene elastomer comprises at least 50% by weight of macromolecules branched to at least three branches;the modified diene elastomer comprises at least 20% by weight, preferably at least 35%, of three-branched macromolecules.;

[0057] According to these advantageous variants of the invention, the modified diene elastomer may comprise, according to a preferred aspect, at most 25% by weight of branched macromolecules with four or more branches.

[0058] The modified diene elastomer according to the invention can be obtained according to a synthesis process comprising the reaction of a living diene elastomer, resulting from the polymerization of at least one diene monomer, with a functional, linear or branched polyether, with a number-average molecular mass varying from 150 to 5000 g / mol comprising at each chain end a trifunctional group based on silicon, reactive with respect to the reactive end of the living elastomer, chosen from trialkoxysilyls or trihalosilyls.

[0059] The invention also relates to a rubber composition based at least on one reinforcing filler comprising a silica content greater than or equal to 80 phr, preferably greater than or equal to 100 phr, and an elastomer matrix comprising a content of a modified diene elastomer greater than or equal to 75 phr, the modified diene elastomer being obtained by this synthesis process including its particular, advantageous and preferential aspects described below.

[0060] The polymerization step according to the invention can be carried out by anionic polymerization initiated for example by means of an organic compound of an alkali or alkaline-earth metal. The polymerization of at least one conjugated diene monomer according to these different implementations generates elastomer chains having a reactive site at the chain end. This is then commonly referred to as a living elastomer or a living chain.

[0061] In the context of anionic polymerization, the polymerization initiator may be any known anionic initiator. However, an initiator containing an alkali metal such as lithium. An initiator containing an alkali metal such as lithium is preferably used. Suitable organolithium initiators include those comprising at least one carbon-lithium bond or at least one nitrogen-lithium bond. Representative compounds are aliphatic organolithium compounds such as ethyllithium, n-butyllithium (n BuLi), isobutyllithium, and lithium amides obtained from a cyclic secondary amine, such as pyrrolidine and hexamethyleneimine. Such anionic polymerization initiators are known to those skilled in the art.

[0062] The polymerization can be carried out in a manner known per se. The polymerization is generally carried out at temperatures between 0°C and 110°C and preferably from 40°C to 100°C, or even from 50°C to 90°C. The polymerization process can be carried out in solution, in a more or less concentrated or dilute medium. The polymerization solvent is preferably an inert hydrocarbon solvent which can be, for example, an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, isooctane, cyclohexane, methylcyclohexane or an aromatic hydrocarbon such as benzene, toluene, xylene.

[0063] The monomers that can be used in the context of the invention are described above.

[0064] In order to refine the microstructure of diene elastomers, a modifying and / or randomizing agent may or may not be added in appropriate quantities. This is within the general knowledge of those skilled in the art.

[0065] These variants concerning the polymerization step can be combined with the preferred or alternative variants and aspects described below.

[0066] The polymerization of at least one conjugated diene monomer according to the invention generates elastomeric chains having a reactive site at the chain end. These living chains, or living elastomers, then react with the functional polyether during the modification step. The functional polyether comprises groups that are reactive with respect to the reactive site of the elastomer, in this case alkoxy groups or halogen atoms substituting the silicon atoms.

[0067] The amount of functional polyether intended to react with the living diene elastomer essentially depends on the type of modified diene elastomer desired. Thus, according to certain variants of the modification step, the molar ratio of the functional polyether to the metal of the polymerization initiator is at least 0.1, preferably at least 0.15, more preferably at least 0.25, and at most 0.45, preferably at most 0.40, or even at most 0.35. Thus, according to a particularly advantageous variant of the modification step, the molar ratio of the functional polyether to the metal of the polymerization initiator has a value ranging from 0.25 to 0.40.

[0068] The conditions for adding and reacting the functional polyether to the elastomer are conventional in the field of modification in anionic polymerization and known to those skilled in the art. These conditions do not include any particular limitations.

[0069] For example, this reaction on the living diene elastomer can take place at a temperature between -20°C and 100°C, by adding the functional polyether to the living elastomer chains or vice versa. This reaction can of course be carried out with one or more different functional polyethers.

[0070] The mixing of the living elastomer with the functional polyether can be carried out by any suitable means, in particular using any mixer having static agitation and / or any dynamic mixer of the perfectly agitated type known to those skilled in the art. The latter determines the reaction time between the living diene polymer and the functional polyether, which can vary from a few minutes, for example 2 minutes, to several hours, for example 2 hours.

[0071] The functional polyether may be linear or branched. According to a variant of the invention, the functional polyether is a polymer comprising -(OR)- units, in which R is a divalent hydrocarbon group, preferably a linear or branched aliphatic group, having 1 to 10 carbon atoms, in particular a -CH(R')-CH(R")- group in which R' and R" are, independently of one another, a hydrogen atom or a C1-C4 alkyl substituent, preferably R is a C1-C4 alkanediyl group, more preferably a 1,2- or 1,3-ethanediyl or propanediyl group. Mention may thus be made of polyoxymethylene, poly(ethylene oxide), poly(propylene oxide), or polytetrahydrofuran, preferably the functional polyether is derived from a poly(ethylene oxide) or poly(propylene oxide).

[0072] The functional polyether according to the invention comprises at each of the two ends of the main chain, a trialkoxysilyl or trihalosilyl group.

[0073] When the groups at the end of the chains are trialkoxysilyls, the alkoxy groups are acyclic C1-C18 or cyclic C5-C18, or aryloxy C6-C18, preferably acyclic alkoxy substituents C1-C8, preferably C1-C4, more preferably methoxy or ethoxy.

[0074] When the chain end groups are trihalosilyls, the halogen atom is preferably chlorine.

[0075] Advantageously, the functional polyether has a number-average molecular mass of 150 to 5000 g / mol, preferably 150 to 3000 g / mol and more preferably 200 to 3000 g / mol. The number-average molecular mass is calculated by the SEC (Size Exclusion Chromatography) technique described below.

[0076] According to a variant of the invention, the functional polyether can be represented by the following formula III: in which, R1 represents a divalent hydrocarbon group, preferably a linear or branched aliphatic group, C1-C10, in particular a group - CH(R') - CH(R'') - in which R' and R" are, independently of each other, a hydrogen atom or a C1-C4 alkyl substituent, preferably R1 is a linear C1-C4 alkanediyl group, more preferably a 1,2- or 1,3-ethanediyl or propanediyl group, R2 represent, independently of each other, a divalent hydrocarbon group, preferably a linear or branched or cyclic, saturated or unsaturated aliphatic group having 1 to 50 carbon atoms, preferably a linear aliphatic group, preferably saturated, preferably having 1 to 15 carbon atoms, preferably 2 to 10, preferably 3 to 8, the X represent, identically or differently, a halogen atom, preferably Cl,or a group of formula - OR3 in which the R3s represent, independently of one another, a C1-C18 alkyl, C5-C18 cycloalkoxyl or C6-C18 aryl substituent, preferably the R3s represent a C1-C8 alkyl substituent, preferably C1-C4, more preferably methyl or ethyl, n is a number greater than 1, so that the polyether block has a number-average molecular mass of substantially 150 to 5000 g / mol, preferably 150 to 3000 g / mol and more preferably 200 to 3000 g / mol.

[0077] Among the functional polyethers corresponding to formula III, mention may be made, for example, of poly(oxy-1,2-ethanediyl)-α-[3-(triethoxysilyl)propyl]-ω-[3-(triethoxysilyl)propoxy], poly(oxy-1,2-ethanediyl)-α-[3-(trimethoxysilyl)propyl]-ω-[3-(trimethoxysilyl)propoxy], poly[oxy(methyl-1,2-ethanediyl)]-α-[3-(trichlorosilyl)propyl]-ω-[3-(trichlorosilyl)propoxy].

[0078] The functional polyether can either be found commercially or prepared according to methods described in the literature consisting for example of carrying out a first allylation reaction of a polyethylene glycol in the presence of allyl bromide and a base such as potassium hydroxide, either in aqueous solution, or in a two-phase medium or even in an organic solvent such as tetrahydrofuran then a hydrosilylation reaction for example using a platinum catalyst such as the platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex or hexachloroplatinic acid, in the presence of a trihalosilane such as in particular trichlorosilane or a trialkoxysilane such as in particular trimethoxysilane or triethoxysilane, in the presence or absence of solvent.

[0079] When the silicon atoms of the functional polyether carry halogenated reactive sites, the process for synthesizing the modified diene copolymer according to the invention generally continues with a hydrolysis or alcoholysis step known per se making it possible to generate silanol Si-OH or alkoxysilane Si-OR functions from these halogenated active sites which have not reacted with the living elastomer. This hydrolysis or alcoholysis step can be carried out by adding the polymer solution to an aqueous solution or to a solution containing an alcohol or, conversely, by adding the water or the alcohol to the polymer solution. This step may or may not be carried out in the presence of a base or a buffer. For example, an amine such as triethylamine may be used.

[0080] When the silicon atoms of the functional polyether carry alkoxysilyl reactive sites, the method for synthesizing the modified diene copolymer according to the invention may comprise a step of hydrolysis of the hydrolyzable alkoxysilyl functions which have not reacted with the living elastomer, by adding an acidic, basic or neutral compound as described in document EP 2 266 819 A1. The hydrolyzable alkoxysilyl functions are then transformed into silanol functions.

[0081] The process for synthesizing the modified diene copolymer can continue in a manner known per se with the steps of recovering the copolymer.

[0082] These steps may include a stripping step to recover the modified diene copolymer from the previous steps in dry form. This stripping step may have the effect of hydrolyzing all or part of the residual hydrolyzable alkoxysilyl functions of the block copolymer to transform them into silanol functions. Advantageously, at least 50 to 70 mol% of the residual hydrolyzable alkoxysilyl functions may thus be hydrolyzed.

[0083] According to the invention, the rubber composition comprises an elastomer matrix comprising at least 75 phr of modified diene elastomer as described above, preferably at least 80 phr, and more preferably still 100 phr of modified diene elastomer. The modified diene elastomer may consist of a mixture of several modified diene elastomers as described above.

[0084] According to a variant of the invention, the elastomer matrix may also comprise less than 25 phr, preferably less than 20 phr, of at least one diene elastomer different from the modified diene elastomer described above. As a complementary diene elastomer, mention may be made of any diene elastomer, whether natural or synthetic. In particular, the diene elastomer may be chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. The butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR).

[0085] In accordance with the invention, the rubber composition also comprises at least 80 phr of silica, preferably at least 100 phr, and preferably at most 200 phr, more preferably at most 150 phr, the optimal rate being different in a known manner depending on the particular applications targeted.

[0086] The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface area and a CTAB specific surface area both less than 450 m2 / g, preferably from 30 to 400 m2 / g, in particular between 60 and 300 m2 / g, even more preferably between 130 and 300 m2 / g, or even between 130 and 250 m2 / g.

[0087] In addition to silica, any other type of reinforcing filler known for its ability to reinforce a rubber composition suitable for the manufacture of tire treads may be used, for example carbon black or another reinforcing inorganic filler, or a mixture of these fillers.

[0088] Suitable carbon blacks are all carbon blacks, used individually or in the form of mixtures, in particular HAF, ISAF, SAF type blacks conventionally used in tire treads (so-called tire grade blacks). Among the latter, we will particularly mention the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as for example blacks N115, N134, N234, N326, N330, N339, N347, N375.

[0089] As a reinforcing inorganic filler, it is understood in the present application, by definition, any inorganic or mineral filler whatever its color and origin (natural or synthetic), capable of reinforcing on its own, without any means other than an intermediate coupling agent, a rubber composition intended for the manufacture of tires; such a filler is generally characterized, in a known manner, by the presence of hydroxyl groups (-OH) on its surface.

[0090] Suitable reinforcing inorganic fillers are, in particular, mineral fillers of the siliceous type, in addition to silica (SiO2), or of the aluminous type or even reinforcing titanium oxides, for example described in US 6,610,261 and US 6,747,087. Among the mineral fillers of the aluminous type, mention may be made in particular of alumina (Al2O3) or aluminium (oxide)hydroxides.

[0091] Other reinforcing fillers, in particular carbon black, are also suitable as reinforcing fillers, provided that these reinforcing fillers are covered with a siliceous layer, or have functional sites on their surface, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between the filler and the elastomer. By way of example, mention may be made, for example, of carbon blacks for tires as described, for example, in patent documents WO 96 / 37547, WO 99 / 28380.

[0092] The physical state in which the reinforcing inorganic filler, including silica, is present is immaterial, whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, reinforcing filler also means mixtures of different reinforcing fillers, in particular highly dispersible siliceous fillers as described above.

[0093] According to an advantageous variant of the invention, the reinforcing filler is mainly silica, preferably it comprises more than 50% by weight of the total weight of the silica reinforcing filler.

[0094] According to this variant, when carbon black is also present, it can be used at a rate of less than 20 pce, more preferably less than 10 pce, and at a rate of greater than 0.5 pce, in particular greater than or equal to 1.

[0095] The use of silica as a reinforcing filler may require the use of a coupling agent to establish the bond between the filler and the elastomer. In this case, organosilanes, in particular polysulfurized alkoxysilanes or mercaptosilanes, or at least bifunctional polyorganosiloxanes, may be used as coupling agents.

[0096] When the composition according to the invention comprises a coupling agent, its quantity depends on that of the reinforcing inorganic filler. Its level is easily adjusted by a person skilled in the art according to the level of this filler; it is typically of the order of 0.5% to 15% by weight relative to the quantity of reinforcing inorganic filler other than carbon black, preferably 6% to 12% by weight.

[0097] The rubber composition according to the invention may also contain, in addition to the coupling agents, coupling activators, filler recovery agents or more generally processing aids capable, in a known manner, thanks to an improvement in the dispersion of the filler in the elastomer matrix and a reduction in the viscosity of the composition, of improving its processability in the raw state, these agents being, for example, hydrolyzable silanes such as alkylalkoxysilanes, polyols, polyethers, primary, secondary or tertiary amines, hydroxylated or hydrolyzable polyorganosiloxanes.

[0098] The rubber compositions in accordance with the invention may also contain reinforcing organic fillers which may replace all or part of the carbon blacks or other reinforcing inorganic fillers described above. Examples of reinforcing organic fillers include functionalized polyvinyl organic fillers as described in applications WO-A-2006 / 069792, WO-A-2006 / 069793, WO-A-2008 / 003434 and WO-A-2008 / 003435.

[0099] The rubber composition according to the invention may also contain at least one plasticizer. In a manner known to those skilled in the art of tire rubber compositions, this plasticizer is preferably chosen from high glass transition temperature (Tg) hydrocarbon resins, low Tg hydrocarbon resins, plasticizing oils, and mixtures thereof. Preferably, the plasticizer is chosen from high Tg hydrocarbon resins, plasticizing oils, and mixtures thereof.

[0100] According to an advantageous variant of the invention, the total level of plasticizer in the composition is greater than or equal to 20 pce, more preferably greater than or equal to 50 pce, and advantageously at most 100 pce.

[0101] By definition, a high Tg hydrocarbon resin is by definition a solid at room temperature and pressure (20°C, 1 atm), while a plasticizing oil is liquid at room temperature and a low Tg hydrocarbon resin is viscous at room temperature. Tg is measured according to ASTM D3418 (1999).

[0102] As is known, high Tg hydrocarbon resins are thermoplastic hydrocarbon resins with a Tg greater than 20°C. The preferred high Tg hydrocarbon resins that can be used in the context of the invention are well known to those skilled in the art and are commercially available. The plasticizer may also contain a plasticizing oil (or extending oil) that is liquid at 20°C, known as “low Tg”, i.e. which by definition has a Tg lower than 20°C, preferably lower than 40°C.

[0103] Any extender oil, whether aromatic or non-aromatic, known for its plasticizing properties towards elastomers, can be used. At room temperature (20°C), these oils, more or less viscous, are liquids (that is to say, as a reminder, substances having the capacity to eventually take the shape of their container), in contrast in particular to high Tg hydrocarbon resins which are by nature solid at room temperature.

[0104] Particularly suitable are plasticizing oils chosen from the group consisting of naphthenic oils (low or high viscosity, in particular hydrogenated or not), paraffinic oils, MES oils (Medium Extracted Solvates), TDAE oils (Treated Distillate Aromatic Extracts), RAE oils (Residual Aromatic Extract oils), TRAE oils (Treated Residual Aromatic Extract) and SRAE oils (Safety Residual Aromatic Extract oils), mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these compounds.

[0105] The rubber composition in accordance with the invention may also comprise all or part of the usual additives and processing agents, known to those skilled in the art and usually used in rubber compositions for tires, in particular tread rubber compositions, such as, for example, non-reinforcing fillers, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents, reinforcing resins (as described, for example, in application WO 02 / 10269), a crosslinking system, for example based on sulfur and other vulcanizing agents, and / or peroxide and / or bismaleimide.

[0106] The rubber composition in accordance with the invention is manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first working phase or thermomechanical mixing (so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents, in particular the elastomer matrix, the fillers, any other various additives, with the exception of the crosslinking system, are introduced into a suitable mixer such as a conventional internal mixer (for example of the 'Banbury' type). The incorporation of the filler into the elastomer can be carried out in one or more stages by thermomechanical mixing. The non-productive phase is carried out at high temperature, up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C, for a duration generally of between 2 and 10 minutes.a second phase of mechanical work (so-called "productive" phase), which is carried out in an external mixer such as a roller mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 120°C, for example between 40°C and 100°C. The crosslinking system is then incorporated, and everything is then mixed for a few minutes, for example between 5 and 15 min.

[0107] The final composition thus obtained is then calendered, for example, in the form of a sheet or plate, in particular for characterization in the laboratory, or extruded in the form of a semi-finished (or profiled) rubber usable, for example, as a vehicle tire tread.

[0108] The composition can be either in the raw state (before crosslinking or vulcanization) or in the cooked state (after crosslinking or vulcanization), can be a semi-finished product that can be used in a tire

[0109] The crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 130°C and 200°C, under pressure.

[0110] Due to the maintenance of the compromise of hysteresis properties / raw implementation despite a high load rate which characterizes a reinforced rubber composition according to the invention, it will be noted that such a composition can constitute any semi-finished product of the tire and in particular the tread, notably reducing its rolling resistance, while improving its performance linked to the high reinforcing load rate.

[0111] The invention therefore finally relates to a tire comprising a semi-finished article consisting in whole or in part of a composition according to the invention, in particular a tread.

[0112] The above-mentioned characteristics of the present invention, as well as others, will be better understood upon reading the following description of several exemplary embodiments of the invention, given for illustrative and non-limiting purposes. Examples I - Measurements and tests used Determination of the Mn value of the branch before coupling or star formation by size exclusion chromatography

[0113] The SEC (Size Exclusion Chromatography) technique separates macromolecules in solution according to their size through columns filled with a porous gel. Macromolecules are separated according to their hydrodynamic volume, with the largest being eluted first.

[0114] Although not an absolute method, SEC allows us to understand the distribution of molar masses of a polymer. From commercial standard products, the different number-average (Mn) and weight-average (Mw) molar masses can be determined and the polymolecularity index (Ip = Mw / Mn) calculated via a so-called MOORE calibration.

[0115] There is no special treatment of the polymer sample before analysis. It is simply solubilized in the elution solvent at a concentration of approximately 1 gL-1. The solution is then filtered through a 0.45µm porosity filter before injection.

[0116] The equipment used is a "WATERS alliance" chromatographic chain. The elution solvent is tetrahydrofuran, the flow rate is 1 mL.min-1, the system temperature is 35°C and the analysis time is 30 min. A set of two WATERS columns with the trade name "STYRAGEL HT6E" is used. The injected volume of the polymer sample solution is 100 µL. The detector is a "WATERS 2410" differential refractometer and the chromatographic data processing software is the "WATERS EMPOWER" system.

[0117] The calculated average molar masses are relative to a calibration curve produced for SBRs with the following microstructure: 25% by mass of styrene-type units, 23% by mass of type 1-2 units and 50% by mass of type 1-4 trans units.

[0118] Determination of the levels of linear and branched macromolecules by the high-resolution size exclusion chromatography (high-resolution SEC) technique.

[0119] The high-resolution SEC technique is used to determine the mass percentages of the different chain populations present in a polymer sample.

[0120] There is no special treatment of the polymer sample before analysis. It is simply solubilized in the elution solvent at a concentration of approximately 1 gL-1. The solution is then filtered through a 0.45 µm porosity filter before injection.

[0121] The apparatus used is a "WATERS alliance 2695" chromatographic chain. The elution solvent is tetrahydrofuran, the flow rate is 0.2 ml.min-1, the system temperature is 35 °C. A set of three identical columns in series is used (Shodex, length 300 mm, diameter 8 mm). The number of theoretical plates in the column set is greater than 22,000. The injected volume of the polymer sample solution is 50 µL. The detector is a "WATERS 2414" differential refractometer and the chromatographic data processing software is the "WATERS EMPOWER" system.

[0122] The calculated molar masses are relative to a calibration curve produced for SBRs with the following microstructure: 25% by mass of styrene-type units, 23% by mass of 1,2-type units and 50% by mass of 1,4-trans-type units. Determination of Mooney viscosity

[0123] For polymers and rubber compounds, Mooney viscosities ML(1+4)100 °C are measured according to ASTM D-1646.

[0124] An oscillating consistometer is used as described in ASTM D-1646. The Mooney plasticity measurement is carried out according to the following principle: the composition in its raw state (i.e. before curing) is molded in a cylindrical chamber heated to 100 °C. After one minute of preheating, the rotor rotates within the specimen at 2 revolutions / minute and the torque needed to maintain this movement after 4 minutes of rotation is measured. The Mooney plasticity ML(1+4) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Nm). Determination of the glass transition temperature of polymers

[0125] The glass transition temperatures (Tg) of elastomers are determined using a differential scanning calorimeter according to ASTM D3418. Dynamic properties

[0126] The dynamic properties, and in particular tan δ max, are measured on a viscoanalyzer (Metravib VA4000), according to the ASTM D 5992-96 standard. The response of a sample of vulcanized composition (cylindrical specimen 2 mm thick and 79 mm 2< in section) is recorded, subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under normal temperature conditions (23 ° C) according to the ASTM D 1349-99 standard. A strain amplitude sweep is carried out from 0.1% to 50% peak-peak (forward cycle), then from 50% to 0.1% peak-peak (return cycle). The result most particularly used is the loss factor tan δ. For the return cycle, the maximum value of tan δ observed is indicated, noted tan δ max. This value is representative of the hysteresis of the material and in this case of the rolling resistance: the lower the value of tan δ max, the lower the rolling resistance. II - Examples of preparation of elastomers Preparation of Polymer A: Diene Block Copolymer - witness

[0127] In a 90-liter reactor, maintained under a nitrogen pressure of approximately 2 bars, containing 44 kg of methylcyclohexane, 1.74 kg of styrene and 5.84 kg of butadiene are injected, as well as 1.07 L of a 0.36 mol.L-1 tetrahydrofuran solution in methylcyclohexane. After neutralizing the impurities in the solution to be polymerized by adding n-butyllithium, 716 mL of 0.06 mol.L-1 n-butyllithium in methylcyclohexane are added. The polymerization is carried out at 50 °C.

[0128] After 45 minutes, the monomer conversion rate reached 68%. This rate was determined by weighing a dried extract at 140 °C, under the reduced pressure of 200 mmHg. The value of the Mn branch before coupling determined by SEC RI was 120,000 g.mol-1. 1.19L of a solution of poly(oxy-1,2-ethanediyl)-α-[3-(triethoxysilyl)propyl]-ω-[3-(triethoxysilyl)propoxy] (CAS 666829-33-0) at 0.018 mol.L-1 in toluene are then added (npoly(oxy-1,2-ethanediyl)-α-[3-(triethoxysilyl)propyl]-m-[3-(triethoxysilyl)propoxy]) / n(n-butyllithium) = 0.5). The solution is stirred at a temperature of 50°C for 30 minutes. The solution is then antioxidized by adding 0.8 parts per hundred parts of elastomer (pce) of 4,4'-methylene-bis-2,6-tert-butylphenol and 0.2 parts per hundred parts of elastomer (pce) of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.The copolymer thus treated is separated from its solution by a steam stripping operation, then dried on cylinder tools at 100°C for 15 minutes.

[0129] The Mooney viscosity of the polymer is 70.

[0130] The distribution of 1-branch, 2-branch, 3-branch, 4-branch, 5-branch and 6-branch (1b / 2b / 3b / 4b / 5b / 6b) species determined by high-resolution SEC is as follows: 16 / 72 / 6 / 4 / 3 / 0.

[0131] The glass transition temperature of this copolymer is -63°C. Preparation of polymer B: Diene block copolymer according to the invention

[0132] In a 90-liter reactor, maintained under a nitrogen pressure of approximately 2 bars, containing 44 kg of methylcyclohexane, 1.74 kg of styrene and 5.84 kg of butadiene are injected, as well as 1.02 L of a 0.36 mol.L-1 tetrahydrofuran solution in methylcyclohexane. After neutralizing the impurities in the solution to be polymerized by adding n-butyllithium, 1.1 mL of 0.06 mol.L-1 n-butyllithium in methylcyclohexane are added. The polymerization is carried out at 50°C.

[0133] After 45 minutes, the monomer conversion rate reaches 70%. This rate is determined by weighing a dried extract at 140 °C, under the reduced pressure of 200 mmHg. 1. The value of the Mn branch before coupling determined by SEC RI is 81,000 g.mol-1. 37L of a solution of poly(oxy-1,2-ethanediyl)-α-[3-(triethoxysilyl)propyl]-ω-[3-(triethoxysilyl)propoxy] (CAS 666829-33-0) at 0.018 mol.L-1 in toluene are then added (npoly(oxy-1,2-ethanediyl)-α-[3-(triethoxysilyl)propyl]-ω-[3-(triethoxysilyl)propoxy]) / n(n-butyllithium) = 0.35). The solution is stirred at a temperature of 50°C for 15 minutes. The solution is then antioxidized by adding 0.8 parts per hundred parts of elastomer (pce) of 4,4'-methylene-bis-2,6-tert-butylphenol and 0.2 parts per hundred parts of elastomer (pce) of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.The copolymer thus treated is separated from its solution by a steam stripping operation, then dried on cylinder tools at 100°C for 15 minutes.

[0134] The Mooney viscosity of the polymer is 44.

[0135] The distribution of 1-branch, 2-branch, 3-branch, 4-branch, 5-branch and 6-branch (1b / 2b / 3b / 4b / 5b / 6b) species determined by high-resolution SEC is as follows: 12 / 29 / 21 / 38 / 0 / 0.

[0136] The glass transition temperature of this copolymer is -64°C. Examples of preparation of rubber compositions

[0137] Elastomers A and B were used for the preparation of tread-type rubber compositions, each comprising silica as a reinforcing filler in two different formulations.

[0138] Each of the following compositions is produced, initially, by thermomechanical work, then, in a second finishing stage, by mechanical work, according to standard processes for preparing rubber mixtures.

[0139] Into an internal laboratory mixer of the "Banbury" type, with a capacity of 400 cm3, which is 70% full and whose initial temperature is approximately 90°C, are successively introduced the elastomer, two-thirds of the silica, the black, the coupling agent and the oil, then, approximately one minute later, the remainder of the reinforcing filler, the resin, the antioxidant, the stearic acid and the anti-ozone wax, then, approximately two minutes later, the zinc monoxide.

[0140] The thermomechanical working stage is carried out for 4 to 5 minutes, until a maximum drop temperature of approximately 160°C is reached.

[0141] The first aforementioned stage of thermomechanical work is thus carried out, it being specified that the average speed of the pallets during this first stage is 50 rpm.

[0142] The mixture thus obtained is recovered, cooled and then, in an external mixer (homo-finisher), the sulphur and the accelerator are added at 30°C, mixing everything again for a period of 3 to 4 minutes (second stage of mechanical work mentioned above).

[0143] The compositions thus obtained are then calendered, either in the form of plates (with a thickness ranging from 2 to 3 mm) or thin sheets of rubber, for the measurement of their physical or mechanical properties, or in the form of profiles which can be used directly, after cutting and / or assembly to the desired dimensions, for example as semi-finished products for tires, in particular for treads.

[0144] Crosslinking is carried out at 150°C for 40 min.

[0145] Each of the compositions has the following formulation (expressed in pce: parts per hundred parts of elastomer): Table 1 Ingredients Formulation 1 Formulation 2 Polymer 100 100 Silica 110 70 Carbon black 3 3 oil 13 0 Resin 59 46 Coupling agent 8.8 5.6 Stearic acid 3 3 Zinc oxide 1.5 1.5 DPG 2.3 1.5 Soluble sulfur 1 1 Accelerator 2.3 2.3 Antioxidant 3 3 Silica: Rhodia's "Zeosil 1165MP", HDS type. Carbon black: Cabot Corporation ASTM N234 grade Oil: Novance 85% oleic sunflower oil, "Lubrirob Tod 1880" Resin: ExxonMobil Escorez 5600 or PR383 aromatic DCPD resin Coupling agent: Degussa TESPT Si69 silane DPG: Diphenylguanidine ("Perkacit" DPG from Flexsys) Accelerator: CBS: N-cylohexyl-2-benzothiazol-sulfenamide ("Santocure CBS" from Flexsys) Antioxidant: Flexsys N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine Results:

[0146] The results presented in the table below show: - That the elastomer according to the invention improves the hysteresis / Mooney composition compromise compared to the reference elastomer, whether in one or other of the two Formulations. - That the elastomer according to the invention particularly improves the compromise when it is used in a composition containing a high level of silica (Formulation 1). Table 2 polymer formulation 1 tan delta max 23°C Mooney composition performance index A witness 100 100 1.0 B invention 102 65 1.5 Table 3 polymer formulation 2 tan delta max 23°C Mooney composition performance index A witness 100 100 1.0 B invention 112 64 1.4

[0147] In the table above, the tan delta or Mooney values ​​are expressed in base 100 relative to the control.

[0148] The performance index is calculated as: 10000 / (tan delta value * Mooney composition value). The lower the tan delta, the lower the Mooney composition, the better the rolling resistance / implementation performance compromise.

Claims

1. Rubber composition based at least on a reinforcing filler comprising silica and on an elastomer matrix comprising a modified diene elastomer, characterized in that: - the content of silica is greater than or equal to 80 phr, preferably greater than or equal to 100 phr, - the content of modified diene elastomer is greater than or equal to 75 phr, and - the modified diene elastomer comprises macromolecules comprising, within their structure, a linear or branched polyether block comprising, at each of the two ends of the block, a branch point to which up to three diene elastomer branches and up to three - OR groups are bonded, R representing, independently of one another, a C1-C8 alkyl substituent or a hydrogen atom, a- the copolymer exhibiting a Mooney viscosity of at least 30, preferably of at least 40, and of at most 100, b- the copolymer being composed: - of at least 20%, preferably at least 30%, of branched macromolecules comprising a polyether block to which at least three diene elastomer blocks are bonded, - of at most 80%, preferably at most 70%, of linear macromolecules, c- the polyether block exhibiting a number-average molecular weight varying from 150 to 5000 g / mol, and d- each of the branch points consisting of a silicon atom; the branched macromolecules corresponding to the formula I: in which: R1 represents a linear or branched divalent C1-C10 hydrocarbon group, in particular a - CH(R') - CH(R") - group, in which R' and R" are, independently of each other, a hydrogen atom or a C1-C4 alkyl substituent; preferably, R1 is a C1-C4 alkanediyl group, more preferentially a 1,2- or 1,3-ethanediyl or -propanediyl group, the R2 groups represent, independently of each other, a saturated or unsaturated, linear or branched or cyclic, divalent hydrocarbon group, preferably aliphatic group, having 1 to 50 carbon atoms, preferably a linear aliphatic group, which is preferably saturated, preferentially having 1 to 15 carbon atoms, preferably 2 to 10, preferably 3 to 8, the Y groups represent, identically or differently, a halogen atom or a group of formula -OR4 in which the R4 groups represent, independently of one another, a hydrogen atom or a C1-C8 alkyl substituent; preferably, the R4 groups represent a hydrogen atom or a C1-C4 alkyl substituent, preferably methyl or ethyl, i and j are numbers having, each independently of the other, the value 1, 2 or 3, with the proviso that (i + j) varies from 3 to 6, and P represents a diene elastomer block; and the linear block macromolecules corresponding to the formula II: in which: R1 represents a linear or branched divalent C1-C10 hydrocarbon group, in particular a - CH(R') - CH(R") - group, in which R' and R" are, independently of each other, a hydrogen atom or a C1-C4 alkyl substituent; preferably, R1 is a C1-C4 alkanediyl group, more preferentially a 1,2- or 1,3-ethanediyl or -propanediyl group, the R2 groups represent, independently of each other, a saturated or unsaturated, linear or branched or cyclic, divalent hydrocarbon group, preferably aliphatic group, having 1 to 50 carbon atoms, preferably a linear aliphatic group, which is preferably saturated, preferentially having 1 to 15 carbon atoms, preferably 2 to 10, preferably 3 to 8, the Y groups represent, identically or differently, a halogen atom or a group of formula -OR4 in which the R4 groups represent, independently of one another, a hydrogen atom or a C1-C8 alkyl substituent; preferably, the R4 groups represent a hydrogen atom or a C1-C4 alkyl substituent, preferably methyl or ethyl, k and l are numbers having, each independently of the other, the value 0 or 1, with the proviso that (k + 1) has the value 1 or 2, and P represents a diene elastomer block.

2. Composition according to Claim 1, characterized in that the modified diene elastomer is a polybutadiene or a butadiene copolymer, preferentially a butadiene / styrene copolymer.

3. Composition according to Claim 1 or 2, characterized in that the elastomer branches of the modified diene elastomer have a number-average molar mass (Mn) of at least 40 000 g / mol and of at most 100 000 g / mol.

4. Composition according to any one of Claims 1 to 3, characterized in that the end of the elastomer branches not bonded to a silicon atom bears a function comprising a nitrogen atom, preferably a cyclic or acyclic amine function.

5. Composition according to any one of Claims 1 to 4, characterized in that the polyether block is a polyoxymethylene, poly(ethylene oxide), poly(propylene oxide) or polytetrahydrofuran block, preferably a poly(ethylene oxide) or poly(propylene oxide) block.

6. Composition according to any one of Claims 1 to 5, characterized in that the copolymer comprises at least 50% by weight of branched macromolecules consisting of a polyether block to which at least three diene elastomer blocks are bonded.

7. Composition according to any one of Claims 1 to 6, characterized in that the copolymer comprises at least 20% by weight, preferably at least 35%, of branched macromolecules consisting of a polyether block to which three diene elastomer blocks are bonded.

8. Composition according to any one of Claims 1 to 7, characterized in that the copolymer comprises at most 25% of branched macromolecules consisting of a polyether block to which four or more diene elastomer blocks are bonded.

9. Composition according to any one of Claims 1 to 8, characterized in that at least one, at least two, at least three, at least four, at least five, at least six, at least seven and preferably all of the following characteristics is / are observed: - the polyether block is linear consisting of -(OR)- units, in which R is a C1-C4 alkanediyl group, more preferentially a 1,2- or 1,3-ethanediyl or -propanediyl group; - the polyether block exhibits a number-average molecular weight substantially of 150 to 5000 g / mol and preferentially of 200 to 3000 g / mol; - all or a part, preferably at least 50 mol%, of the alkoxy functions substituting one or more silicon atoms are hydrolysed to give hydroxyl groups; - the diene elastomer is a butadiene / styrene copolymer; - all or a part, preferably at least 70 mol%, of the ends of elastomer branches not bonded to a silicon atom are functionalized, with respect to the number of moles of chain end, by an amine function; - the mean Mn of the elastomer branches is less than 150 000 g / mol, preferably from 40 000 to 100 000 g / mol; - the modified diene elastomer comprises at least 50% by weight of branched macromolecules having at least three branches; - the modified diene elastomer comprises at least 20% by weight of branched macromolecules having three branches, preferably at least 35%.

10. Composition according to any one of Claims 1 to 9, characterized in that the content of silica is greater than or equal to 100 phr.

11. Composition according to any one of Claims 1 to 10, characterized in that it comprises 20 phr or more, preferably 50 phr or more, of at least one plasticizer.

12. Composition according to Claim 11, characterized in that the plasticizer is chosen from hydrocarbon resins with a high Tg, plasticizing oils and their mixtures.

13. Tyre comprising a semi-finished article constituted, in all or in part, by a composition according to any one of Claims 1 to 12.