JP7815240B2 - Rubber composition for tire tread - Google Patents

Description

The present invention relates to tires with a tread, in particular a snow tread, a winter tread or an all-season tread, capable of running on snow-covered ground (also called "snow tires", "winter tires" or "all-season tires"). As is known, these snow tires, identified by the letters M+S or M.S. or M&S on their sidewalls, are characterized by a tread design and structure intended to ensure better performance, especially in mud and fresh or melted snow, than that of road-type tires designed for running on non-snow-covered ground.

Snow-covered ground, known as white ground, is characterized by a low coefficient of friction, which has led to the development of snow tires with treads based on diene rubber compositions with low glass transition temperatures (Tg). However, the grip performance of these tires on wet ground is generally inferior to that of road tires, especially road tires whose treads are based on rubber compositions of different formulations with high Tg. To address this issue, patent application WO 2012/069565 proposes a tread whose composition comprises at least one diene elastomer having a functional group SiOR, where R is a hydrogen atom or a hydrocarbon-based radical, in combination with a high content of reinforcing inorganic fillers and a special plasticizing system.
Additionally, as fuel economy and environmental protection needs have become priorities, it is desirable to have available rubber compositions that can be used to manufacture various semi-finished products involved in forming tire casings that have reduced rolling resistance. However, reduced rolling resistance is often inconsistent with improved grip on both wet and snow-covered surfaces.
Additionally, because snow treads or winter treads generally have a more flexible tread pattern and/or are constructed of softer rubber compositions than "summer" treads, their wear resistance often proves to be lower as a result. It is also important to maintain or even improve the wear resistance of snow treads or winter treads as much as possible.
Manufacturers are therefore constantly searching for solutions to further improve the compromise between the rolling resistance, grip on snowy ground and wear resistance properties of tire treads intended in particular for driving on snowy ground.

During the continuation of its research, the Applicant has unexpectedly discovered that special rubber compositions make it possible to further improve the above-mentioned performance compromise. One subject of the present invention is therefore a rubber composition based on:
an elastomeric matrix comprising 25 to 95 parts by weight per 100 parts by weight of elastomer having a glass transition temperature of less than −64° C., phr, of a copolymer based on butadiene and styrene, and 5 to 75 phr of polybutadiene modified with functional groups capable of interacting with silica;
at least one reinforcing filler comprising silica,
at least one agent for coupling silica to diene elastomers,
25 to 100 phr of at least one plasticizing resin having a glass transition temperature above 20° C., and a crosslinking system.

I - Definitions The expression "composition based on" should be understood to mean a composition comprising a mixture and/or product of the in situ reaction of the various components used, some of which can and/or are intended to at least partially react with one another during the various stages of the preparation of the composition; the composition is therefore optionally fully or partially crosslinked or non-crosslinked.

For the purposes of the present invention, the expression "parts by weight per hundred parts by weight of elastomer" (or phr) should be understood to mean "parts by mass per hundred parts by mass of elastomer".
In this document, all percentages (%) given are percentages (%) by weight unless otherwise specified.
Furthermore, any interval of values expressed by the expression "between a and b" means a range of values extending from greater than a to less than b (i.e., the limits a and b are excluded), while any interval of values expressed by the expression "from a to b" means a range of values extending from a to b (i.e., including the narrow limits a and b). In this document, when an interval of values is expressed by the expression "from a to b", the interval expressed by the expression "between a and b" is also preferably expressed.

When referring to a "major" compound, this should be understood to mean that, for the purposes of the present invention, this compound is predominant among compounds of the same type in the composition, i.e., the compound that accounts for the largest amount by weight among compounds of the same type. Thus, for example, a primary elastomer is the elastomer that accounts for the largest amount by weight relative to the total weight of elastomers in the composition. Similarly, a "major" filler is the filler that accounts for the largest amount by weight among the fillers in the composition. For example, in a system containing only one elastomer, this single elastomer is predominant for the purposes of the present invention, and in a system containing two elastomers, the primary elastomer accounts for more than half of the elastomer's weight. Preferably, the term "major" should be understood to mean that it is present in more than 50%, preferably more than 60%, 70%, 80%, 90%, for example 100%.
The carbon-containing compounds referred to herein may be of fossil or bio-origin. If bio-origin, they may be partially or completely derived from biomass or may be obtained from renewable raw materials derived from biomass. This particularly relates to polymers, plasticizers, fillers, etc.
All values of glass transition temperature "Tg" given in this document are measured in known manner by DSC (Differential Scanning Calorimetry) according to ASTM standard D3418 (1999).

II - DESCRIPTION OF THE INVENTION II-1 Elastomeric Matrix According to the present invention, the elastomeric matrix of the composition comprises 25 to 95 phr of a copolymer based on butadiene and styrene, having a glass transition temperature of less than -64°C, and 5 to 75 phr of polybutadiene modified with functional groups capable of interacting with silica.

For the purposes of the present invention, the expression "copolymers based on butadiene and styrene" refers to any copolymer obtained by copolymerization of one or more styrene compounds with one or more butadienes. The following are particularly suitable as styrene monomers: styrene, methylstyrene, para-(tert-butyl)styrene, methoxystyrene and chlorostyrene. As the butadiene monomer, 1,3-butadiene is particularly suitable. These elastomers can have any microstructure, which depends on the polymerization conditions used, in particular the presence or absence of modifiers and/or randomizers, and the amount of modifiers and/or randomizers employed. The elastomers can be, for example, block, random, sequenced or microsequenced elastomers.
Advantageously, the copolymer based on butadiene and styrene is a butadiene-styrene copolymer (SBR). It should be noted that the SBR can be prepared in emulsion (ESBR) or solution (SSBR). Whether ESBR or SSBR, the SBR may have any microstructure compatible with a glass transition temperature of less than -70°C. In particular, the butadiene/styrene copolymer may have a styrene content by mass between 1% and 15%, and more particularly between 1% and 5%, and a 1,2-bond content (mol %) of the butadiene moiety between 4% and 25%.
Advantageously, the copolymer based on butadiene and styrene is SSBR.
Advantageously, the copolymer based on butadiene and styrene has a glass transition temperature in the range ranging from -105°C to -70°C, preferably from -100°C to -80°C, preferably between -95°C to -85°C, more preferably between -95°C to -86°C.

Preferably, the copolymer based on butadiene and styrene is a styrene-butadiene copolymer exhibiting any one, advantageously a combination of two or three, and even more advantageously all, of the following properties:
- styrene/butadiene copolymers (SSBR) prepared in solution,
its styrene content by weight is between 1% and 10%, preferably between 1% and 4%, relative to the total weight of the styrene/butadiene copolymer;
the vinyl bond content of the butadiene moiety is between 4% and 25%, preferably between 10% and 15%;
its Tg is in the range extending from -105°C to -70°C, preferably in the range between -95°C and -86°C;

Advantageously, the butadiene and styrene based copolymer comprises in its structure at least one alkoxysilane group and at least one other functional group, the silicon atom of which is attached to the elastomer chain, and the alkoxysilane group may be partially or completely hydrolyzed to give a silanol.
In the present description, the term "alkoxysilane group" in the structure of the elastomer refers to a group whose silicon atom is located in the polymer backbone and directly connected to the polymer backbone. This position in the structure also includes the polymer chain end. Therefore, the term "terminal group" is included. The alkoxysilane group is not a pendant group.
When the alkoxysilane groups are located at the chain ends, the diene elastomer is said to be chain end functionalized.
When the alkoxysilane group is located on the main elastomer chain, the diene elastomer is coupled or functionalized mid-chain, as opposed to at a "chain end" position, but the group is not exactly in the center of the elastomer chain. The silicon atom of this functional group bonds to two branches of the diene elastomer main chain.

A diene elastomer is said to be star-branched when it has a silicon atom in a central position to which at least three elastomeric branches are attached, forming a star-branched structure of the elastomer. Thus, the silicon atom is substituted with at least three branches of the diene elastomer.
It should be noted that it is known to those skilled in the art that when an elastomer is modified by the reaction of a functionalizing agent with a living elastomer resulting from an anionic polymerization step, a mixture of modified entities of this elastomer is obtained, the composition of which depends on the modification reaction conditions, in particular the ratio of reactive sites of the functionalizing agent to the number of living elastomer chains, and this mixture can include chain end functionalized, coupled, star-branched and/or non-functionalized entities.
Advantageously, the copolymer based on butadiene and styrene comprises, as the main entity, a diene elastomer functionalized mid-chain with alkoxysilane groups attached via silicon atoms to two of its branched chains, the alkoxy radicals being optionally partially or completely hydrolyzed to give hydroxyls. Even more particularly, the diene elastomer functionalized mid-chain with alkoxysilane groups accounts for 70% by weight of the copolymer based on butadiene and styrene.

In the alkoxysilane group, the alkoxyl radical, which may be partially or completely hydrolyzed to give hydroxyl, may comprise a _C1 - _C10 , or even a _C1 - _C8 , preferably a _C1 - _C4 alkyl radical; more preferentially the alkoxyl radical is methoxy or ethoxy.
The other functional groups are preferably functional groups containing at least one heteroatom selected from N, S, O or P. Among these functional groups, mention may be made by way of example of cyclic or acyclic primary, secondary or tertiary amines, isocyanates, imines, cyanos, thiols, carboxylates or primary, secondary or tertiary phosphines.

The copolymer based on butadiene and styrene advantageously comprises at least one functional group containing a nitrogen atom. The copolymer based on butadiene and styrene advantageously comprises in its structure at least one alkoxysilane group bonded to the elastomer via a silicon atom and a functional group containing a nitrogen atom.
This functional group containing a nitrogen atom may be located at the chain end and directly attached to the elastomer via a covalent bond or a hydrocarbon-based group.
The nitrogen-containing functional group may also be advantageously carried by an alkoxysilane group. The nitrogen-containing functional group may be carried by the silicon of the alkoxysilane group directly or via a spacer group. The spacer group may be an atom, particularly a heteroatom, or a group of atoms.
The spacer group may be a saturated or unsaturated, cyclic or acyclic, straight or branched chain, divalent aliphatic C ₁ -C ₁₈ hydrocarbon-based radical or a divalent aromatic C ₆ -C ₁₈ hydrocarbon-based radical, and may contain one or more aromatic groups and/or one or more heteroatoms. The hydrocarbon-based group may be optionally substituted.

Advantageously, the spacer group is a straight or branched chain divalent aliphatic C ₁ -C ₁₈ hydrocarbon-based radical, more preferentially a divalent aliphatic C ₁ -C ₁₀ , even more preferentially a C ₃ -C ₈ hydrocarbon-based radical, even more preferentially a straight chain divalent C ₃ hydrocarbon-based radical.
The butadiene and styrene based copolymer may contain additional functional groups within the elastomer (i.e., functional groups different from those described above), although this is not preferred.
The butadiene and styrene based copolymer may be a blend of several butadiene and styrene based copolymers.

The alkoxysilane group containing a functional group containing a nitrogen atom has the following formula (*-) _a Si(OR') _b R _c X
It can be expressed as:
(In the formula,
- *- represents a bond to the elastomer chain;
the R radical represents a substituted or unsubstituted C ₁ -C ₁₀ , or even C ₁ -C ₈ alkyl radical, preferably a C ₁ -C ₄ alkyl radical, more preferentially methyl and ethyl;
in an alkoxyl radical of formula —OR′, which may be partially or completely hydrolyzed to give hydroxyl, R′ represents a substituted or unsubstituted C ₁ -C ₁₀ , or even C ₁ -C ₈ alkyl radical, preferably a C ₁ -C ₄ alkyl radical, more preferentially methyl and ethyl;
X represents a group containing a nitrogen-based functionality;
a is 1 or 2, b is 1 or 2, and c is 0 or 1, provided that a+b+c=3.

Those skilled in the art will understand that the value of a depends on the position of the alkoxysilane group within the structure of the elastomer: when a is 1, the group is located at the end of the chain; when a is 2, the group is located in the middle of the chain.
As the functional group containing a nitrogen atom, mention may be made of an amine functional group. Particularly preferred are a primary amine which may be protected by a protecting group, a secondary amine which may be protected by a protecting group, or a tertiary amine.

Thus, as secondary or tertiary amine functions, mention may be made of amines substituted with C ₁ -C ₁₀ alkyl, preferably C ₁ -C ₄ alkyl radicals, more preferentially methyl or ethyl radicals, or cyclic amines forming a heterocycle containing a nitrogen atom and at least one carbon atom, preferably 2 to 6 carbon atoms, such as methylamino, dimethylamino, ethylamino, diethylamino, propylamino, dipropylamino, butylamino, dibutylamino, pentylamino, dipentylamino, hexylamino, dihexylamino or hexamethyleneamino, preferably diethylamino and dimethylmethylamino. When the amine is cyclic, the following groups are also suitable: morpholine, piperazine, 2,6-dimethylmorpholine, 2,6-dimethylpiperazine, 1-ethylpiperazine, 2-methylpiperazine, 1-benzylpiperazine, piperidine, 3,3-dimethylpiperidine, 2,6-dimethylpiperidine, 1-methyl-4-(methylamino)piperidine, 2,2,6,6-tetramethylpiperidine, pyrrolidine, 2,5-dimethylpyrrolidine, azetidine, hexamethyleneimine, heptamethyleneimine, 5-benzyloxyindole, 3-azaspiro[5.5]undecane, 3-azabicyclo[3.2.2]nonane, carbazole, bistrimethylsilylamine, pyrrolidine and hexamethyleneamine, preferably pyrrolidine and hexamethyleneamine groups.
The amine functionality is preferably a tertiary amine functionality, preferably diethylamine or dimethylamine.

Advantageously, at least two, preferably at least three, preferably at least four, more preferably all of the following characteristics are observed:
the functional group containing a nitrogen atom is a tertiary amine, more particularly a diethylamino or dimethylamino group;
the functional group containing a nitrogen atom is carried by the alkoxysilane group via a spacer group defined as an aliphatic C ₁ -C ₁₀ hydrocarbon-based radical, more preferentially an aliphatic C ₃ -C ₈ hydrocarbon-based radical, and even more preferentially a linear C ₃ hydrocarbon-based radical;
the alkoxysilane groups are methoxysilanes or ethoxysilanes which may be partially or completely hydrogenated to give silanols;
- the copolymer based on butadiene and styrene is a butadiene-styrene copolymer prepared in solution;
the butadiene and styrene-based copolymer is functionalized mid-chain by an alkoxysilane group attached via a silicon atom to the two branched chains of the butadiene and styrene-based copolymer,
- Copolymers based on butadiene and styrene have glass transition temperatures in the range extending from -105°C to -70°C.

Particularly preferably, at least two, preferably at least three, preferably at least four, more preferably all of the following characteristics are observed:
the functional group containing a nitrogen atom is a tertiary amine, more particularly a diethylamino or dimethylamino group;
the functional group containing a nitrogen atom is carried by an alkoxysilane group via a linear _C3 hydrocarbon-based radical,
the alkoxysilane groups are methoxysilanes or ethoxysilanes, which may be partially or fully hydrogenated to give silanols;
- the copolymer based on butadiene and styrene is a butadiene-styrene copolymer prepared in solution;
the butadiene and styrene-based copolymer is functionalized mid-chain by an alkoxysilane group attached via a silicon atom to the two branched chains of the butadiene and styrene-based copolymer,
- Copolymers based on butadiene and styrene have glass transition temperatures in the range between -95°C and -86°C.

The content of copolymer based on butadiene and styrene in the composition according to the invention may advantageously be in a range extending from 65 to 95 phr, preferably between 66 and 90 phr.
Such copolymers based on butadiene and styrene can be obtained by the process described below.
The first step in the process for preparing copolymers based on butadiene and styrene is the anionic polymerization of at least one conjugated diene monomer or the polymerization of at least one conjugated diene monomer and a vinyl aromatic monomer in the presence of a polymerization initiator, the monomers being as described above.
As polymerization initiator, any known monofunctional anionic initiator can be used, however, preference is given to initiators containing an alkali metal such as lithium.
Organolithium initiators containing a carbon-lithium bond are particularly suitable. Representative compounds are aliphatic organolithium compounds such as ethyllithium, n-butyllithium (n-BuLi), isobutyllithium, and the like.
According to embodiments of the present invention where other functional groups are directly attached to the elastomeric chains, this can be provided by a polymerization initiator, such as an amine-functional polymerization initiator that results in living chains with an amine group at the non-reactive end of the chain.
As polymerization initiators containing an amine function, mention may be made preferably of lithium amides, which are reaction products of organolithium compounds, preferably alkyllithium compounds, with acyclic or cyclic, preferably cyclic, secondary amines.

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

The alkyllithium compound is preferably ethyllithium, n-butyllithium (n-BuLi), isobutyllithium, or the like.
The polymerization is preferably carried out in the presence of an inert hydrocarbon-based solvent, which may be, for example, an aliphatic or cycloaliphatic hydrocarbon, such as pentane, hexane, heptane, isooctane, cyclohexane or methylcyclohexane, or an aromatic hydrocarbon, such as benzene, toluene or xylene.
The microstructure of the elastomer can be determined by the presence or absence of modifiers and/or randomizers and the amount of modifiers and/or randomizers utilized. Preferentially, when the diene elastomer is based on a diene and a vinyl aromatic, a polar agent is used during the polymerization step in an amount that promotes random distribution of the vinyl aromatic along the polymer chain.
Advantageously, the living diene elastomer resulting from the polymerization is then functionalized with a functionalizing agent capable of introducing alkoxysilane groups into the polymer structure to prepare a butadiene and styrene-based copolymer containing in its structure at least one alkoxysilane group and a functional group containing a nitrogen atom, bound to the elastomer via a silicon atom.

The modification reaction of the living diene elastomer obtained as a result of the first step can occur at temperatures between -20°C and 100°C by the addition of a non-polymerizable functionalizing agent capable of forming alkoxysilane groups to the living polymer chain, or vice versa, thereby incorporating silicon atoms into the elastomer chain, which may or may not have functional groups containing nitrogen atoms. This is a functionalizing agent with functional groups that are particularly reactive toward living elastomers, each of which is directly bonded to a silicon atom.

The functionalizing agent has the formula (OR') _d Si(R) _c X
Corresponds to.
(In the formula,
in the alkoxyl radical of formula —OR′, which may be partially or completely hydrolyzable, R′ represents a substituted or unsubstituted C ₁ -C ₁₀ , or even C ₁ -C ₈ alkyl radical, preferably a C ₁ -C ₄ alkyl group, more preferentially methyl and ethyl;
R' represents a substituted or unsubstituted C ₁ -C ₁₀ , or even C ₁ -C ₈ alkyl radical, preferably a C ₁ -C ₄ alkyl radical, more preferentially methyl and ethyl;
X represents a group containing a functional group containing a nitrogen atom;
- d is 2 or 3, c is 0 or 1, provided that d + c = 3

The functional group containing a nitrogen atom is as defined above.
The functional group containing a nitrogen atom may be a protected or unprotected primary amine, a protected or unprotected secondary amine, or a tertiary amine. The nitrogen atom may then be substituted with two identical or different groups, which may be a trialkylsilyl radical, the alkyl group of which has 1 to 4 carbon atoms, or a _C1 - _C10 , preferably a _C1 - _C4 alkyl group, more preferentially a methyl or ethyl radical, or the two substituents of the nitrogen atom together form a heterocycle containing the nitrogen atom and at least one carbon atom, preferably 2 to 6 carbon atoms.
As functionalizing agents, mention may be made, for example, of (N,N-dialkylaminoalkyl)trialkoxysilanes, (N-alkylaminoalkyl)trialkoxysilanes, in which the secondary amine function is protected by a trialkylsilyl group and an (aminoalkyl)trialkoxysilane, the primary amine function is protected by two trialkylsilyl groups, and the divalent hydrocarbon-based group making it possible to link the amine function to the trialkoxysilane group is preferentially aliphatic C ₁ -C ₁₀ , more particularly the linear C ₂ or C ₃ spacer group mentioned above.

Functionalizing agents include (3-N,N-dimethylaminopropyl)trimethoxysilane, (3-N,N-dimethylaminopropyl)triethoxysilane, (3-N,N-diethylaminopropyl)trimethoxysilane, (3-N,N-diethylaminopropyl)triethoxysilane, (3-N,N-dipropylaminopropyl)trimethoxysilane, (3-N,N-dipropylaminopropyl)triethoxysilane, (3-N,N-dibutylaminopropyl)trimethoxysilane, (3-N,N-dibutylaminopropyl)triethoxysilane, (3-N,N-dipentylaminopropyl )trimethoxysilane, (3-N,N-dipentylaminopropyl)triethoxysilane, (3-N,N-dihexylaminopropyl)trimethoxysilane, (3-N,N-dihexylaminopropyl)triethoxysilane, (3-hexamethyleneaminopropyl)trimethoxysilane, (3-hexamethyleneaminopropyl)triethoxysilane, (3-morpholinopropyl)trimethoxysilane, (3-morpholinopropyl)triethoxysilane, (3-piperidinopropyl)trimethoxysilane, or (3-piperidinopropyl)triethoxysilane. More preferentially, the functionalizing agent is (3-N,N-dimethylaminopropyl)trimethoxysilane.

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

The functionalizing agent can be chosen from (3-N,N-bistrimethylsilylaminopropyl)trimethoxysilane and (3-N,N-bistrimethylsilylaminopropyl)triethoxysilane. More preferentially, the functionalizing agent is (3-N,N-bistrimethylsilylaminopropyl)trimethoxysilane.
The functionalizing agent is advantageously chosen from (N,N-dialkylaminoalkyl)trialkoxysilanes; more particularly here, the functionalizing agent is (3-N,N-dimethylaminopropyl)trimethoxysilane.
It should be noted that it is known to those skilled in the art that when an elastomer is modified by the reaction of a functionalizing agent with a living elastomer resulting from an anionic polymerization step, a mixture of entities modifying this elastomer is obtained, the composition of which depends in particular on the ratio of reactive sites of the functionalizing agent to the number of living elastomer chains, and which may include chain end functionalized, coupled, star-branched and/or non-functionalized entities.

The molar ratio of functionalizing agent to initiator metal essentially depends on the type of copolymer desired based on butadiene and styrene. Therefore, at ratios ranging from 0.40 to 0.75, or even from 0.45 to 0.65, or even from 0.45 to 0.55, coupling entities are advantageously formed in the modified elastomer, with the alkoxysilane groups located mid-chain. Similarly, at ratios ranging from 0.15 to 0.40, or even from 0.20 to 0.35, or even from 0.30 to 0.35, star-branched (tri-arm) entities are predominantly formed in the modified elastomer. At ratios of 0.75 or greater, or even greater than 1, entities functionalized at the chain ends are predominantly formed.

Advantageously, the molar ratio between the functionalizing agent and the polymerization initiator varies from 0.35 to 0.65, preferentially from 0.40 to 0.60, and even more preferentially from 0.45 to 0.55.
In this case, the butadiene and styrene-based copolymer can comprise, as the main entity, a diene elastomer functionalized mid-chain with alkoxysilane groups bonded via silicon atoms to two of its branched chains, and even more specifically, the diene elastomer functionalized mid-chain with alkoxysilane groups accounts for 70% by weight of the butadiene and styrene-based copolymer.
Advantageously, the alkoxysilane group comprises an alkoxy radical which may be partially or fully hydrolyzed to give a hydroxyl.
Alternatively, the alkoxysilane group advantageously has a functional group containing a nitrogen atom as defined above, which is preferably a tertiary amine functional group as defined above, in particular a diethylamino or dimethylamino functional group, preferably linked to the silicon atom via a spacer group as defined above, in particular a divalent linear _C2 or _C3 hydrocarbon-based radical.
If the functionalizing agent has a protected functional group, the synthetic process can be continued by a deprotection step of this functional group, which is carried out after the modification reaction and is well known to those skilled in the art.

The synthesis process may also include a step of hydrolysis of the hydrolyzable alkoxyl functions by addition of acidic, basic or neutral compounds, as described in document EP 2 266 819 A1, which are then converted into hydroxyl functions.
The process for the synthesis of copolymers based on butadiene and styrene can be continued, in a manner known per se, by a step of recovery of the copolymers based on butadiene and styrene.
These steps may include stripping steps, in particular for the purpose of recovering the elastomer obtained from the previous step. These stripping steps may have the effect of hydrolyzing all or part of the hydrolyzable functional groups of the butadiene and styrene-based copolymer. Advantageously, in this case, at least 50 mol % to 70 mol % of these functional groups may be hydrolyzed.
In accordance with the present invention, the elastomeric matrix of the composition comprises 5 to 75 phr of polybutadiene, also referred to herein as "modified polybutadiene," that has been modified with functional groups capable of interacting with silica.

The term "polybutadiene" (abbreviated as "BR") is understood to mean that it may be one or more types of polybutadiene. Polybutaene is a well-known rubber produced by polymerizing (typically homopolymerizing) 1,3-butadiene monomer in a solution polymerization process using a suitable catalyst known to those skilled in the art. Due to the two double bonds present in the butadiene monomer, the resulting polybutadiene can consist of three different forms: cis-1,4-polybutadiene, trans-1,4-polybutadiene, and vinyl-1,2-polybutadiene. Cis-1,4-elastomers and trans-1,4-elastomers are formed by monomers that connect one end to the other, while 1,2-vinyl elastomers are formed by monomers that connect end to end. Catalyst selection and process temperature are known variables commonly used to control the cis-1,4-bond content of polybutadiene.
Advantageously, the polybutadiene has a content (mol %) of cis-1,4-linkages greater than 90%, more preferentially greater than 95%.

In a particularly advantageous method, the modified polybutadiene is prepared by the following steps:
(a) homopolymerizing butadiene to form a pseudo-living elastomer with a catalyst system comprising at least:
conjugated diene monomers,
one or more rare earth metal salts of organic phosphoric acids,
an aluminium-containing alkylating agent, and a halogen donor comprising an alkylaluminium halide,
It is based on
- the salt is in suspension or solution in at least one saturated inert hydrocarbon-based solvent of the aliphatic or cycloaliphatic type;
(b) adding a multifunctional compound containing at least three functional groups to the pseudo-living elastomer formed in step (a), wherein the functional groups are capable of reacting with the reactive ends of the pseudo-living elastomer;
(c) adding a functionalizing agent corresponding to the formula A-Ri-B to the mixture formed in step (b), wherein A represents a group capable of reacting with the reactive end of the pseudo-living elastomer, Ri represents an atom or group of atoms that form a bond between A and B, and B represents a functional group capable of reacting with the reinforcing filler;
(d) recovering the modified polybutadiene;
and
In this process, the total molar amount of aluminum in the polymerization medium has an "aluminum/rare earth salt" molar ratio between 1 and 5, and the polymerization is carried out at a temperature between 40°C and 90°C.

The term "quasi-living" in reference to modified polybutadiene means that the modified polybutadiene has all or a portion of its chain ends reactive, particularly with respect to functionalizing agents.
The term "rare earth" is understood to mean metals selected from yttrium, scandium and the lanthanides, metals having atomic numbers in the Mendeleev periodic table ranging from 57 to 71. The rare earth metals are preferably selected from the lanthanides, with neodymium being more particularly preferred.
Steps (a), (b), (c) and (d) of the process for obtaining the modified polybutadiene are described below.

Step (a)
Catalyst System The catalyst system advantageously comprises at least one conjugated diene monomer,
salts of one or more rare earth metals of organic phosphoric acid, said salts being in suspension or solution in at least one saturated inert hydrocarbon-based solvent of aliphatic or cycloaliphatic type,
an alkylating agent comprising aluminum, the molar ratio of "alkylating agent"/"rare earth salt" being between 1 and 5, and a halogen donor comprising an alkylaluminum halide;
It is a "preformed" type catalyst system based on

The catalyst system can be prepared batchwise or continuously. The catalyst system can be introduced directly into the reactor or can be premixed with at least one of the other components fed to the polymerization reactor.
The inert hydrocarbon-based solvent in which the rare earth salt is in suspension or solution is advantageously an aliphatic or alicyclic low molecular weight solvent, such as cyclohexane, methylcyclohexane, n-heptane, pentane, or a mixture of these solvents.
An important feature of the process for obtaining modified polybutadiene is the "aluminum"/"rare earth salt" molar ratio. The total molar amount of aluminum in the polymerization medium is such that the "aluminum"/"rare earth salt" molar ratio, in particular the "aluminum"/"neodymium salt" molar ratio, has a value between 1 and 5, preferably between 1 and 4, and more preferably in the range of 2.5 to 3.8. Aluminum is provided by the catalyst system and, where appropriate, by supplemental addition of alkylaluminum to the polymerization medium, as explained below. Surprisingly, it has been found that this "aluminum"/"rare earth salt" molar ratio influences the average percentage of functionalized chains.
Advantageously, the catalytic system is such that the rare earth salt has a rare earth metal mass content ranging from 12.0% to 13.5%, as measured by both complexation back titration with diethylenediaminetetraacetic acid (abbreviated as EDTA) and inductively coupled plasma/optical emission spectroscopy (abbreviated as ICP/AES), and preferably has a rare earth metal content ranging from 12.5% to 13.2%.

The rare earth organophosphate is preferably a rare earth tris(organophosphate), which may be selected from phosphoric acid diesters of the general formula (R'O)(R"O)PO(OH), where R' and R" may be the same or different and represent alkyl, aryl or alkylaryl radicals. As examples, mention may be made of neodymium tris[dibutyl phosphate], neodymium tris[dipentyl phosphate], neodymium tris[dioctyl phosphate], neodymium tris[bis(2-ethylhexyl)phosphate], neodymium tris[bis(1-methylheptyl)phosphate], neodymium tris[bis(p-nonylphenyl)phosphate], neodymium tris[butyl(2-ethylhexyl)phosphate], neodymium tris[(1-methylheptyl)(2-ethylhexyl)phosphate], neodymium tris[(2-ethylhexyl)(p-nonylphenyl)phosphate], neodymium tris[bis(2-ethylhexyl)phosphate], neodymium tris[bis(oleyl)phosphate] or neodymium tris[bis(linelyl)phosphate].

In particular, tris[bis(2-ethylhexyl)phosphates] of said rare earth metals are used as rare earth salts, and even more preferentially, said rare earth salt is neodymium tris[bis(2-ethylhexyl)phosphate].
As a conjugated diene monomer that can be used to preform the catalyst system, preference can be given to 1,3-butadiene.

Mention may also be made of 2-methyl-1,3-butadiene (or isoprene), 2,3-di(C ₁ -C ₅ alkyl)-1,3-butadiene, such as 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, phenyl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene, or other conjugated dienes having between 4 and 8 carbon atoms.

As the alkylating agent that can be used in the catalyst system, mention may be made of an alkylaluminum selected from a trialkylaluminum of formula Al(R) ₃ or a dialkylaluminum hydride of formula HAl(R) ₂ . The alkyl group R preferably contains 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms. As the tri(alkylaluminum), mention may be made of triethylaluminum, triisopropylaluminum, triisobutylaluminum, tributylaluminum or trioctylaluminum. As the di(alkylaluminum) hydride, mention may be made of diisobutylaluminum hydride.
As halogen donors that can be used in the catalyst system according to the invention, mention can be made of alkyl halides, alkylaluminum halides or alkylaluminum halides. Alkylaluminum halides are preferentially used, the alkyl group containing 1 to 8 carbon atoms. Of these, diethylaluminum chloride is preferred.
Advantageously, the rare earth metal is present in the catalytic system in a concentration greater than or equal to 0.005 mol/l, preferably in the range from 0.010 to 0.1 mol/l, more particularly in the range from 0.02 mol/l to 0.08 mol/l.
The molar ratio of "alkylating agent"/"salt of rare earth" in said catalytic system can advantageously have a value ranging from 1 to 2.
The molar ratio "halogen donor"/"rare earth salt" may advantageously have a value ranging from 2 to 3.6, more preferentially from 2.4 to 3.2, and even more preferentially from 2.5 to 3.
The molar ratio "preformed monomer"/"salt of rare earth" may advantageously have a value ranging from 15 to 70, or even from 25 to 50.
A process for preparing such a catalyst system is described, for example, in patent application WO 02/38636.

Alternating Addition of Alkylaluminum In a stream independent from the introduction of the catalyst system used in the polymerization reaction, it is possible to introduce into the polymerization reactor a predetermined amount of at least one alkylaluminum compound of formula Al(R) ₃ or HAl(R) ₂ or (R'''') _nAl (R''') _3-n , where R and R''' represent optionally saturated alkyl groups of 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, R'''' represents an allyl group, and n is an integer of 1 to 3.

Examples of alkylaluminum compounds include alkylaluminums, such as trialkylaluminums, for example, trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, tri-(t-butyl)aluminum, triisobutylaluminum, tri-n-pentylaluminum, tri-n-hexylaluminum, tricyclohexylaluminum, preferably triisobutylaluminum, or dialkylaluminum hydrides, for example, diethylaluminum hydride, diisopropylaluminum hydride, di-n-propylaluminum hydride, diisobutylaluminum hydride, di-n-octylaluminum hydride, di-n-butylaluminum hydride, preferably diisobutylaluminum hydride,
can be mentioned.
Advantageously, the molar ratio of "alternately added alkylaluminum compound"/"alkylaluminum in the catalytic system" ranges from 1/20 to 50/1, preferentially from 1/15 to 30/1, and even more preferentially from 1/10 to 20/1.
The amount of alkylaluminum added is such that the molar ratio of the total amount of aluminum to the amount of rare earth salt, in particular neodymium salt, in the polymerization medium is always within the range defined above.

Polymerization Solvent The polymerization can be carried out under bulk conditions, in which case there is no added polymerization solvent.
Alternatively, the polymerization can be carried out in solution or under semi-bulk conditions. In this case, the medium comprises an inert hydrocarbon-based polymerization solvent, which is preferably an aliphatic or cycloaliphatic low-molecular-weight solvent, particularly for environmental reasons. Examples that may be mentioned include n-pentane, isopentane, isoamylene (2-methyl-2-butene, 2-methyl-1-butene, and 3-methyl-1-butene), 2,2-dimethylbutane, 2,2-dimethylpropane (neopentane), n-heptane, n-octane, isooctane, cyclopentane, cyclohexane, n-hexane, methylcyclopentane, and methylcyclohexane, as well as mixtures of these compounds, with n-pentane being particularly preferred. Solvents that may also be mentioned include aromatic hydrocarbons, such as benzene or toluene.
The term "bulk polymerization" is understood to mean a polymerization carried out in a reaction medium free from organic solvents.
The term "solution polymerization" is understood to mean a polymerization carried out in a reaction medium comprising from 70% to 99% by weight of an organic solvent relative to the total weight of the monomers and said organic solvent.
The term "semi-bulk polymerization" is understood to mean a polymerization carried out in a reaction medium comprising between 0% and 70% by weight of an organic solvent relative to the total weight of the monomers and said organic solvent.
The solvent can be introduced directly into the reactor or can be premixed with at least one of the other components introduced into the polymerization reactor, in particular the monomers to be polymerized.

Polymerization Temperature Another important feature of the process for obtaining modified polybutadiene is the polymerization temperature of above 40°C, which makes the process suitable for implementation on an industrial scale. The polymerization temperature is between 40°C and 90°C, preferably between 40°C and 80°C, preferably between 45°C and 75°C, and preferably between 50°C and 70°C.

Step (b)
The polyfunctional compound added to the pseudo-living elastomer formed in step (a) contains at least three functional groups, thus making it possible to link several polybutadiene chains together. Advantageously, the polyfunctional compound contains at least four functional groups.

The polyfunctional compound may be a small molecule having at least three, preferably at least four, functional groups, or a polymer having at least three, preferably at least four, functional groups.
In the polyfunctional compound, the functional groups are advantageously identical. In addition, the functional groups are advantageously identical to the functional group A of the functionalizing agent described below.
The polyfunctional compound advantageously corresponds to the formula (E) _n -Rj, where n represents an integer greater than or equal to 3, E represents said functional group and Rj represents an atom or group of atoms carrying n groups E.
In a first embodiment, Rj is a linear, branched, or cyclic hydrocarbon-based radical and may contain one or more aromatic radicals and/or one or more heteroatoms. Advantageously, Rj comprises one or more aromatic groups. In addition to the n substituents E, the Rj group may be optionally substituted, provided that the other substituents are inert toward the reactive end of the pseudo-living elastomer.
In a second embodiment, Rj is a polymeric hydrocarbon chain.
Advantageously, in any of these embodiments, Rj does not include Si-O-Si chains.
The functional group E is preferably selected from epoxide, glycidyloxy, glycidylamino, isocyanate, imine, aziridine and imidazole, and more preferably selected from glycidylamino, isocyanate, imine and imidazole.

The polyfunctional compound is advantageously selected from triglycidylaminophenol, tetraglycidylaminodiphenylmethane (TGMDA), N,N-diglycidyl-4-glycidyloxyaniline, tris(4-hydroxyphenyl)methane triglycidyl ether, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, tetraglycidylxylenediamine, polymethylene polyphenyl polyisocyanate, tetra(isocyanato)silane (CAS No.: 3410-77-3), phenyltris(methylethylketoximio)silane (CAS No.: 34036-80-1), poly[[1,3-bis[3-(4,5-dihydro-1H-imidazol-1-yl)propyl]-1,3:1,3-disiloxanedylidene]-1,3-bis(oxy)] (CAS No.: 1325615-33-5). Preferably, the polyfunctional compound is advantageously selected from triglycidylaminophenol and tetraglycidylaminodiphenylmethane (TGMDA).
The molar ratio of "polyfunctional compound" to "aluminum" is advantageously less than 0.3, and more advantageously between 0.01 and 0.3.
Here too, the amount of aluminum corresponds to the total amount of aluminum present in the reaction medium, taking into account the aluminum contained in the catalyst system and, where appropriate, the aluminum contained in additional alkylaluminum compounds added alternately to the catalyst system.
Step (b) of reacting at least one multifunctional compound with the pseudo-living elastomer solution is preferably carried out at a temperature ranging from 40°C to 90°C, more preferably from 40°C to 80°C, even more preferably from 45°C to 75°C, and preferably from 50°C to 70°C.

Step (c)
The functionalizing agent introduced in step (c) capable of reacting with the pseudo-living elastomer of step (b) corresponds to the formula A-Ri-B, where A represents a group capable of reacting with the reactive end of the pseudo-living elastomer, Ri represents an atom or group of atoms that form a bond between A and B, and B represents a functional group capable of reacting with the reinforcing filler.

A is preferably selected from epoxide, glycidyloxy, glycidylamino, isocyanate, imine, aziridine and imidazole, and more preferably selected from glycidylamino, isocyanate, imine and imidazole.
B is preferably a dialkoxysilane, advantageously a diethoxysilane.
The Ri group is preferably a linear, branched, or cyclic hydrocarbon-based divalent radical, which may contain one or more aromatic radicals and/or one or more heteroatoms. The Ri radical may be optionally substituted, provided that other substituents are inert toward the reactive end of the pseudo-living elastomer. According to a preferred variant, the Ri group represents a saturated or unsaturated, cyclic or acyclic aliphatic divalent _C1 - _C18 , advantageously _C1 - _C10 , more advantageously _C1 - _C6 , and even more advantageously _C1 - _C3 or _C2 - _C8 hydrocarbon-based radical, which may contain one or more aromatic radicals. In particular, Ri is an aliphatic divalent _C1 - _C3 radical. In particular, Ri is an aliphatic divalent _C2 - _C8 radical.

The expression "groups capable of reacting with the reactive end of a pseudo-living elastomer" is understood to mean preferentially groups selected in particular from epoxide, glycidyloxy, glycidylamino, isocyanate, imine, aziridine and imidazole. More preferably, the groups capable of reacting with the reactive end of a pseudo-living elastomer are selected from glycidylamino, isocyanate, imine and imidazole.
The term "functional group capable of interacting with the reinforcing filler" is understood to mean a functional group that preferably comprises one or more functional groups selected from tertiary, protected or unprotected secondary, or protected or unprotected primary amine, imine, imide, amide, nitrile, azo, carbamate, methacrylate, methacrylamide, hydroxyl, carbonyl, carboxyl, epoxy, glycidyloxy, thiol, sulfide, disulfide, thiocarbonyl, thioester, sulfonyl, silane, silanol, alkoxysilane, alkoxydialkylsilane, dialkoxysilane, dialkoxyalkylsilane, trialkoxysilane, stannyl, tin halides, alkyltin halides, aryltin halides, polyethers, nitrogen-containing heterocycles, oxygen-containing heterocycles, sulfur-containing heterocycles, and aromatic groups substituted with the above groups.

For example, dialkoxysilane functional groups, especially diethoxysilane functional groups, and especially dialkoxyalkylsilanes, such as diethoxyalkylsilanes, may be preferred as functional groups capable of interacting with the reinforcing filler.
The various preferred or non-preferential aspects described above, particularly with regard to the nature of the A, Ri and B groups, can be combined with one another. Thus, depending on the synthesis difficulty and commercial availability, but especially on the type of reinforcing filler envisaged in combination with the modified polybutadiene, a person skilled in the art will know which combinations, and in particular which of the above-mentioned combinations of A and B groups, are particularly advantageous.
As examples of these variants, mention may be made of functionalizing agents such as (3-glycidyloxypropyl)methyldiethoxysilane, N-(3-diethoxy(methyl)silylpropyl)-4,5-dihydroimidazole, 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane, tris(3-diethoxy(methyl)silylpropyl)isocyanurate, and 3-isocyanatopropylmethyldiethoxysilane. Among these functionalizing agents, (3-glycidyloxypropyl)methyldiethoxysilane and 3-isocyanatopropylmethyldiethoxysilane are particularly advantageous.

The molar ratio "functionalizing agent"/"aluminium" is advantageously at least 1. Preferably, the molar ratio "functionalizing agent"/"aluminium" is at least 1/1 and at most 10/1, preferentially at most 5/1, or even at most 2/1.
Thus, relative to aluminum, there is a deficiency of the polyfunctional compound, while the functionalizing agent is in an equimolar amount or excess.
Here too, the amount of aluminum corresponds to the total amount of aluminum present in the reaction medium, taking into account the aluminum contained in the catalyst system and, where appropriate, the aluminum contained in additional alkylaluminum compounds added alternately to the catalyst system.
Another important feature of the process for obtaining modified polybutadiene is the order of addition of the polyfunctional compound and the functionalizing agent: the polyfunctional compound is added before the introduction of the functionalizing agent.
The functionalization step (c) is preferably carried out at a temperature in the range of between 40°C and 90°C, more preferably between 40°C and 80°C, even more preferably between 45°C and 75°C, and preferably between 50°C and 70°C.

Step (d)
At this stage, according to a variant of the invention, the process of synthesizing the modified polybutadiene can continue in a manner known per se. Thus, according to one embodiment, it is possible to inject the terminator and antioxidant at this step.
The process then continues in a manner known per se, with the separation and recovery of the modified polybutadiene prepared. Unreacted butadiene and/or solvent can be removed according to methods known to those skilled in the art.
The modified polybutadiene recovered at the end of these various steps can be packaged in a manner known per se, for example in the form of balls.
Therefore, the modified polybutadiene of the composition according to the present invention, which can be obtained by the above process, contains free polybutadiene chains which have reacted only with the functionalizing agent and polybutadiene chains which are linked via the polyfunctional compound.

The modified polybutadiene advantageously has a Mooney viscosity ML(1+4) at 100° C. of 40 or more, in particular in the range of 40-80.
The modified polybutadiene also advantageously exhibits reduced flowability, which can be characterized in particular by the modified polybutadiene having a cold flow CF(1+6) value at 100°C of less than 1 g, more advantageously less than 0.5 g, and even more advantageously less than 0.2 g.

Preferably, the modified polybutadiene simultaneously has:
a molar content of cis-1,4 unit bonds of at least 55%, preferably at least 90%, relative to the polybutadiene;
- a polydispersity index of less than 2.3,
- an average percentage of functionalized chains greater than 25%;
a Mooney viscosity ML(1+4) at 100° C. greater than or equal to 40, and a cold flow value CF(1+6) at 100° C. less than 1 g, preferably less than 0.5 g.

In this document, "functionalized chain" refers to a polybutadiene chain that has been reacted with a functionalizing agent of formula A-R _i -B as defined below.
The average percentage of functionalized chains is the ratio of the mass of modified polybutadiene chains to the total mass of polybutadiene chains. It is determined by multiplying the number of functional groups, _CH2 -Si/PB, in moles per unit mass of polymer by the number-based molar mass of the polymer. The number of functional groups, in moles per unit mass of polymer, is determined by ^1H NMR according to the protocol described at the beginning of the examples.
Advantageously, the modified polybutadiene has an average content of functionalized chains between 25% and 80%. In one embodiment, the modified polybutadiene has an average percentage of functionalized chains between 25% and 60%. In another embodiment, the modified polybutadiene has an average percentage of functionalized chains between 40% and 80%, advantageously between 40% and 70%.
Furthermore, the modified polybutadiene advantageously has a glass transition temperature (Tg) of less than -100°C, preferably less than -105°C, preferably between -110°C and -105°C.
Advantageously, the content of modified polybutadiene in the composition according to the invention is in a range extending from 5 to 35 phr, preferably between 10 and 34 phr.

Thus, according to the invention, the composition according to the invention advantageously comprises from 65 to 95 phr of copolymer based on butadiene and styrene and from 5 to 35 phr of polybutadiene, preferably from 66 to 90 phr of copolymer based on butadiene and styrene and from 10 to 34 phr of polybutadiene.
Advantageously, the elastomeric matrix of the composition according to the invention comprises less than 15 phr of isoprene elastomer.

The term "isoprene elastomer" is used to mean, as is known, an isoprene homopolymer or copolymer, in other words a diene elastomer selected from the group consisting of natural rubber (NR), synthetic polyisoprene (IR), various isoprene copolymers and mixtures of these elastomers. Among the isoprene copolymers, particular mention will be made of isobutene/isoprene (butyl rubber - IIR), isoprene/styrene (SIR), isoprene/butadiene (BIR) or isoprene/butadiene/styrene (SBIR) copolymers. This isoprene elastomer is preferably natural rubber or synthetic cis-1,4-polyisoprene; among these synthetic polyisoprenes, preference is given to using polyisoprenes with a content (mol %) of cis-1,4 bonds greater than 90%, and even more preferentially greater than 98%.
The content of isoprene elastomer in the composition according to the invention is preferably less than 14 phr, preferably less than 10 phr, preferably less than 5 phr, preferably less than 4 phr.

The total content of butadiene and styrene based copolymer and modified polybutadiene in the composition is advantageously in the range extending from 85 phr to 100 phr, preferably from 86 to 100 phr, preferably from 90 phr to 100 phr, preferably from 95 to 100 phr, preferably from 96 to 100 phr.
Particularly preferably, the composition according to the invention is devoid of isoprene elastomers. Advantageously, the total content of butadiene and styrene-based copolymer and polybutadiene in the composition according to the invention is therefore 100 phr.

II-2 Reinforcing Filler The composition according to the present invention also contains a reinforcing filler known for its ability to reinforce rubber compositions that can be used in the manufacture of tires. This reinforcing filler includes silica.
Silicas that can be used in connection with the present invention can be any silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface area and a CTAB specific surface area both less than 450 m ² /g, preferably between 30 and 400 m ² /g.
The BET specific surface area of the silica is determined in a known manner by gas adsorption using the Brunauer-Emmett-Teller method described in The Journal of the American Chemical Society, Vol. 60, page 309, February 1938, and more particularly according to the French standard NF ISO 9277 of December 1996 (multipoint (5-point) volumetric method - gas: nitrogen - degassing: 1 hour at 160°C - relative pressure p/p ₀ range: 0.05 to 0.17). The CTAB specific surface area of the silica is determined according to the French standard NF T 45-007 of November 1987 (method B).

Preferably, the silica has a BET specific surface area between 100 and 250 m ² /g, preferably in the range extending from 105 to 200 m ² /g, preferably in the range extending from 125 to 180 m ² /g.
Also preferably, the silica has a CTAB specific surface area between 105 and 220 m ² /g, preferably in the range extending from 110 to 200 m ² /g, preferably in the range extending from 140 to 170 m ² /g.
As reinforcing inorganic fillers, preferably silicas, that can be used in connection with the present invention, mention may be made, for example, of highly disperse precipitated silicas (called "HDS"), Ultrasil 7000 and Ultrasil 7005 from Evonik, Zeosil 1165MP, 1135MP and 1115MP from Rhodia, Hi-Sil EZ150G silica from PPG, Zeopol 8715, 8745 and 8755 silica from Huber, and silicas with a high specific surface area as described in patent application WO 03/16837.

To bond the reinforcing silica to the diene elastomer, known methods may be used, utilizing at least difunctional coupling agents (or binders) designed to provide a satisfactory connection between the silica (its particle surface) and the diene elastomer, chemical and/or physical properties. In particular, at least difunctional organosilanes or polyorganosiloxanes are used. The term "difunctional" is understood to mean a compound having a first functional group capable of interacting with the silica and a second functional group capable of interacting with the diene elastomer. For example, such a difunctional compound may contain a first functional group containing a silicon atom, which is capable of interacting with the hydroxyl groups of the inorganic filler (e.g., silica), and a second functional group containing a sulfur atom, which is capable of interacting with the diene elastomer.

Preferably, the organosilane is selected from the group consisting of organosilane polysulfides (symmetrical or asymmetrical), such as bis(3-triethoxysilylpropyl)tetrasulfide, abbreviated as TESPT and sold by Evonik under the trade name Si69, or bis(triethoxysilylpropyl)disulfide, abbreviated as TESPD and sold by Evonik under the trade name Si75, polyorganosiloxanes, mercaptosilanes, block mercaptosilanes, such as S-(3-(triethoxysilyl)propyl)octanethioate, abbreviated as NXT silane, sold by Momentive. More preferably, the organosilane is an organosilane polysulfide.

Advantageously, the reinforcing filler mainly comprises silica. The silica content in the composition according to the invention may be in a range extending from 80 to 200 phr, preferably from 100 to 180 phr, preferably from 105 to 145 phr.
The reinforcing filler may also include carbon black. The carbon black content in the composition according to the invention may range from 0 to 40 phr, preferably from 1 to 20 phr, preferably from 2 to 10 phr.
The blacks that can be used in the context of the present invention can be any blacks conventionally used in tires or their treads ("tire-grade" blacks). Among the latter, more particular mention will be made of the 100, 200, and 300 series reinforcing carbon blacks, or the 500, 600, or 700 series blacks (ASTM grades), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772 blacks. These carbon blacks can be used alone, as commercially available, or in any other form, for example, as a support for some of the rubber additives used. The carbon black can, for example, already be incorporated in a diene elastomer, in particular an isoprene elastomer, in the form of a masterbatch (see, for example, patent applications WO 97/36724 or WO 99/16600).
The content of coupling agent in the compositions of the present invention is advantageously 35 phr or less, although it is understood that it is generally desirable to use as little of it as possible.
Typically, the content of the coupling agent corresponds to 0.5 to 15% by mass relative to the amount of silica. The content is preferably in the range of 0.5 to 20 phr, more preferably in the range of 1 to 3 phr. This content can be easily adjusted by those skilled in the art according to the content of silica used in the composition of the present invention.

II-3 Crosslinking System The crosslinking system can be of any type known to those skilled in the art of rubber compositions for tires. It may in particular be based on sulfur and/or peroxides and/or bismaleimides.
Preferably, the crosslinking system is sulfur-based; it is called a vulcanization system. Advantageously, the vulcanization system comprises molecular sulfur and/or at least one sulfur donor. Preferentially, at least one vulcanization accelerator is also present, and preferentially, various known vulcanization activators may be utilized, such as zinc oxide, stearic acid or equivalent compounds, such as stearates, and salts of transition metals, guanidine derivatives (especially diphenylguanidine), or other known vulcanization retarders.

Sulphur is used in a preferred content of between 0.5 and 12 phr, in particular between 1 and 10 phr. Vulcanisation accelerators are used in a preferential content of between 0.5 and 10 phr, more preferentially between 0.5 and 5.0 phr.
As accelerators, any compound capable of acting as an accelerator of the vulcanization of diene elastomers in the presence of sulfur may be used, in particular accelerators of the thiazole type and also their derivatives, or accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type. In particular, the following compounds may be mentioned as examples of such accelerators: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazole sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazole sulfenamide ("DCBS"), N-(tert-butyl)-2-benzothiazole sulfenamide ("TBBS"), N-(tert-butyl)-2-benzothiazole sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC"), and mixtures of these compounds.

II-4 Plasticizing System The rubber composition according to the present invention also comprises 25 to 100 phr of at least one plasticizing resin (for simplicity of language, also referred to in this document as "plasticizing resin") having a glass transition temperature above 20°C, known as "high Tg".

II-4.1 Plasticizing Resins The term "resin" is reserved in the present patent application for compounds that are solid at ambient temperature (23°C), according to the definition known to those skilled in the art, as opposed to liquid plasticizing compounds such as oils.
Plasticizing resins are polymers well known to those skilled in the art that are essentially based on carbon and hydrogen, but can contain other types of atoms, and can be used, among other things, as plasticizers or tackifiers in polymer matrices. Plasticizing resins are generally essentially miscible (i.e., compatible) with the intended polymer composition at the levels they are used in, so that they act as true diluents. They are described, for example, in the study entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander, and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9), whose Chapter 5 is specifically devoted to their application in the tire rubber field (5.5. "Rubber Tires and Mechanical Goods"). They may be aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, or aliphatic/aromatic, i.e., based on aliphatic and/or aromatic monomers. They may be natural or synthetic, and may or may not be petroleum-based (if so, they are also known as petroleum resins). Their Tg is preferably above 20°C (generally between 30°C and 95°C).

As is known, these plasticized resins can also be described as thermoplastic resins, meaning that they soften and can be molded when heated. They may also be defined by their softening point. The softening point of a plasticized resin is generally approximately 50°C to 60°C higher than its Tg value. The softening point is measured according to ISO standard 4625 (ring and ball method). The macrostructure (Mw, Mn, and PDI) is determined by size exclusion chromatography (SEC) as shown below.

As a reminder, SEC analysis consists of separating macromolecules in a solution according to their size, for example, by passing them through a column packed with porous gel; the molecules are separated by their hydrodynamic volume, with the bulkiest molecules eluting first. The sample to be analyzed is briefly dissolved in advance in a suitable solvent, tetrahydrofuran, at a concentration of 1 g/liter. The solution is then filtered through a filter with a porosity of 0.45 μm before injection into the device. The device used is, for example, a Waters Alliance chromatographic line, according to the following conditions:
the elution solvent is tetrahydrofuran;
- Temperature: 35℃;
concentration: 1 g/liter;
- Flow rate: 1ml/min;
- Injection volume: 100μl;
- Moore calibration with polystyrene standards;
- a set of three "Waters" columns in series (Styragel HR4E, Styragel HR1 and Styragel HR 0.5);
Detection by means of a differential refractometer (for example WATERS 2410) which may be equipped with operating software (for example Waters Millennium).

Moore calibration is performed using a series of commercially available polystyrene standards with low PDI (<1.2) and known molar masses covering the mass range to be analyzed. The mass-average molar mass (Mw), number-average molar mass (Mn) and polydispersity index (PDI = Mw/Mn) are also estimated from the recorded data (molar mass distribution curve).
Therefore, all molar mass values given in this patent application relate to calibration curves generated using polystyrene standards.

According to a preferred embodiment of the present invention, the plasticized resin exhibits at least one, preferably two or three, and more preferentially all, of the following properties:
a Tg greater than 25°C (in particular between 30°C and 100°C), more preferentially greater than 30°C (in particular between 30°C and 95°C);
a softening point above 50°C (in particular between 50°C and 150°C);
a number-average molar mass (Mn) between 300 and 2000 g/mol, preferentially between 400 and 1500 g/mol;
a polydispersity index (PDI) of less than 3, preferentially less than 2 (as a reminder: PDI=Mw/Mn, Mw being the weight-average molar mass).

Such preferred high Tg plasticizing resins are well known to those skilled in the art and are commercially available, for example, as sold as:
- polylimonene resins: DRT under the name Dercolyte L120 (Mn=625 g/mol; Mw=1010 g/mol; PDI=1.6; Tg=72°C) or Arizona under the name Sylvagum TR7125C (Mn=630 g/mol; Mw=950 g/mol; PDI=1.5; Tg=70°C);
_C5 /vinyl aromatic copolymer resins, in particular _C5 /styrene or _C5 / _C9 copolymer resins: from Neville Chemical Company under the names Super Nevtac 78, Super Nevtac 85 and Super Nevtac 99, from Goodyear Chemicals under the name Wingtack Extra, from Kolon under the names Hikorez T1095 and Hikorez T1100 or from Exxon under the names Escorez 2101 and Escorez 1273;
Limonene/styrene copolymer resins: from DRT under the name Dercolyte TS 105 or by Arizona Chemical Company under the names ZT115LT and ZT5100.

According to the present invention, the plasticizing resin having a glass transition temperature above 20°C can be selected from the group comprising or consisting of cyclopentadiene (abbreviated as CPD) homopolymer or copolymer resin, dicyclopentadiene (abbreviated as DCPD) homopolymer or copolymer resin, terpene homopolymer or copolymer resin, _C5 fraction homopolymer or copolymer resin, _C9 fraction homopolymer or copolymer resin, α-methylstyrene homopolymer or copolymer resin, and mixtures thereof. Preferably, the plasticizing resin can be selected from the group comprising or consisting of (D) CPD/vinyl aromatic copolymer resin, (D) CPD/terpene copolymer resin, terpene/phenol copolymer resin, (D) CPD/ _C5 fraction copolymer resin, (D) CPD/C9 fraction copolymer resin, terpene/vinyl aromatic copolymer resin, terpene/phenol copolymer resin, _C5 fraction/vinyl aromatic copolymer resin, and mixtures thereof.
The term "terpene" here refers, as is known, to the α-pinene, β-pinene and limonene monomers; the limonene monomer is preferably used, which is a compound that, as is known, exists in three possible isomeric forms: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer) or dipentene, a racemate of the levorotatory and dextrorotatory enantiomers. Suitable vinyl aromatic monomers are, for example, styrene, α-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyltoluene, para-(tert-butyl)styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinylmesitylene, divinylbenzene, vinylnaphthalene or any vinyl aromatic monomer originating from the _C9 fraction (or more generally from the _C8 - _C10 fraction).
More specifically, mention may be made of plasticizing resins selected from the group consisting of (D)CPD homopolymer resins, (D)CPD/styrene copolymer resins, polylimonene resins, limonene/styrene copolymer resins, _limonene /D(CPD) copolymer resins, _C5 fraction/styrene copolymer resins, C5 fraction/ _C9 fraction copolymer resins and mixtures of these resins.

All the above plasticizing resins are well known to those skilled in the art and are commercially available, for example the polylimonene resins sold by DRT under the name Dercolyte, the _C5 /styrene or _C5 / _C9 resins sold by Neville Chemical Company under the name Super Nevtac, or by ExxonMobil under the name Escorez, or by Struktol under the name 40 MS or 40 NS (mixtures of aromatic and/or aliphatic resins).
Advantageously, the content of plasticizing resin with a glass transition temperature above 20° C. in the composition according to the invention is between 50 and 150 phr, preferably between 55 and 100 phr, particularly advantageously between 65 and 90 phr.

II-4.2 Plasticizers that are liquid at 23° C. Although this is not essential to the practice of the present invention, the plasticizing system of the rubber composition according to the present invention can comprise what are called "low Tg" plasticizers, i.e., by definition, have a Tg of less than −20° C., preferably less than −40° C. According to the present invention, the composition can optionally contain 0 to 60 phr of a plasticizer that is liquid at 23° C.
When a plasticizer that is liquid at 23° C. is used, its content in the composition of the tread according to the invention may range from 1 to 40 phr, preferably from 2 to 20 phr, more preferably from 3 to 14 phr.

Any plasticizer (or extending oil), whether aromatic or non-aromatic in nature, that is liquid at 23° C. and known for its plasticizing properties with respect to diene elastomers can be used. These plasticizers or these oils, which are more or less viscous at ambient temperature (23° C.), are liquids (i.e., substances that, for the record, have the ability to ultimately assume the shape of their container), in contrast to plasticizing resins, which are essentially solid at ambient temperature.
Particularly preferred are plasticizers that are liquid at 23°C selected from the group consisting of or including liquid diene polymers, polyolefin oils, naphthalene oils, paraffin oils, DAE oils, MES (Medium Extracted Solvates) oils, TDAE (Treated Distillate Aromatic Extracts) oils, RAE (Residual Aromatic Extract) oils, TRAE (Treated Residual Aromatic Extract) oils, SRAE (Safe Residual Aromatic Extract) oils, mineral oils, vegetable oils, ether-based plasticizers, ester-based plasticizers, phosphate ester-based plasticizers, sulfonate ester-based plasticizers, and mixtures of these plasticizers that are liquid at 23°C.
For example, a plasticizer that is liquid at 23° C. may be a petroleum oil, which is preferably non-aromatic. A liquid plasticizer is described as non-aromatic if it exhibits a content of polycyclic aromatic compounds of less than 3% by weight, relative to the total weight of the plasticizer, determined on an extract in DMSO according to the IP 346 method.

Plasticizers that are liquid at 23°C can also be liquid polymers resulting from the polymerization of olefins or dienes, such as polybutene, polydienes, especially polybutadiene, polyisoprene (also known by the name LIR), or copolymers of butadiene and isoprene, or copolymers of butadiene and styrene or isoprene and styrene, or mixtures of these liquid polymers. The number-average molar mass of such liquid polymers is preferably in the range from 500 g/mol to 50,000 g/mol, preferably from 1,000 g/mol to 10,000 g/mol. As an example, mention may be made of Ricon products from Sartomer.

If the plasticizer liquid at 23°C is a vegetable oil, it may be, for example, an oil selected from the group consisting of linseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rapeseed oil, castor oil, tung oil, pine oil, sunflower oil, palm oil, olive oil, coconut oil, peanut oil, grapeseed oil, and mixtures of these oils. The vegetable oil is preferentially rich in oleic acid, i.e., the fatty acid from which it is derived (or the fatty acid mixture, if several fatty acids are present) contains at least 60% by mass of oleic acid, and even more preferentially at least 70% by mass. Advantageously, sunflower oil is used as the vegetable oil, the fatty acid mixture from which it is derived contains at least 60%, preferably at least 70%, by mass of oleic acid, and according to a particularly advantageous embodiment of the invention, at least 80% by mass of oleic acid.

According to another particular embodiment of the invention, the liquid plasticizer is a triester selected from the group consisting of carboxylic acid triesters, phosphoric acid triesters, sulfonic acid triesters and mixtures of these triesters.
Examples of phosphate ester plasticizers include those containing 12 to 30 carbon atoms, such as trioctyl phosphate. Examples of carboxylic acid ester plasticizers include trimellitates, pyromellitates, phthalates, 1,2-cyclohexanedicarboxylic acid esters, adipates, azelates, sebacates, glycerol triesters, and mixtures of these compounds. Among these triesters, particular mention may be made of glycerol triesters, which are preferably composed mainly (more than 50% by weight, more preferably 80% by weight) of unsaturated _C18 fatty acids, i.e., fatty acids selected from the group consisting of oleic acid, linoleic acid, linolenic acid, and mixtures of these acids. Glycerol triesters are preferred. More preferentially, the fatty acids used, whether of synthetic or natural origin (in this case, for example, from sunflower oil or rapeseed oil), are composed of more than 50% by weight, even more preferentially 80% by weight, of oleic acid. Such triesters (trioleates) with a high content of oleic acid are well known; they are described, for example, in patent application WO 02/088238 as plasticizers in tire treads.

When the plasticizer that is liquid at 23° C. is an ether plasticizer, it can be, for example, polyethylene glycol or polypropylene glycol.
Preferably, the plasticizer that is liquid at 23° C. is selected from the group comprising or consisting of MES oil, TDAE oil, naphthenic oil, vegetable oil and mixtures of these plasticizers that are liquid at 23° C. More preferably, the plasticizer that is liquid at 23° C. is a vegetable oil, preferably sunflower oil.
Also advantageously, the composition according to the invention does not contain any liquid polymers.
Advantageously, the composition according to the invention comprises from 10 to 60 phr, preferably from 15 to 40 phr, of vegetable oil, preferably sunflower oil.

II-5 Other Possible Additives The rubber composition according to the present invention may contain all or some of the usual additives commonly used in elastomer compositions for tires, such as plasticizers (e.g., plasticizing oils and/or plasticizing resins), pigments, protective agents such as anti-ozone waxes, chemical antiozonants, antioxidants, anti-fatigue agents, reinforcing resins, etc. (e.g., as described in patent application WO 02/10269).

II-6 Preparation of the Rubber Composition The compositions according to the invention can be prepared in a suitable mixer using two successive preparation steps well known to those skilled in the art:
a first thermochemical operation or kneading stage ("non-productive" stage) which can be carried out in a single thermochemical step, during which all the necessary components, in particular the elastomeric matrix, any fillers and any other various additives, except the vulcanization system, are introduced into a suitable mixer, for example a standard internal mixer (for example of the "Banbury" type). Any fillers can be incorporated into the elastomer in one or several batches while being thermochemically kneaded. The non-productive stage can be carried out at elevated temperatures up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C, for a time generally between 2 and 10 minutes;
- a second mechanical working stage ("productive" stage) carried out in an external mixer, for example an open mill, after cooling the mixture obtained during the first non-productive stage to a lower temperature, typically below 120°C, for example between 40°C and 100°C. The vulcanization system is then incorporated and this combined mixture is then mixed for a few minutes, for example between 5 and 15 minutes.
Such steps are described, for example, in patent applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO 00/05300 or WO 00/05301.

The final compositions thus obtained are subsequently calendered, for example in the form of sheets or plaques, in particular for laboratory characterization, or extruded in the form of semi-finished (or profiled) rubber elements that can be used, for example, as tire treads for passenger cars. These products can then be used to manufacture tires, according to techniques known to those skilled in the art.
The composition may be in either the raw state (before vulcanization) or the cured state (after vulcanization), and may be a semi-finished product that can be used in tires.
Vulcanization of the composition can be carried out by methods known to those skilled in the art, for example at temperatures between 130°C and 200°C under pressure.

II-7 Rubber Articles and Tires Another subject of the present invention is a finished or semi-finished rubber article comprising a composition according to the invention.
Advantageously, the rubber article is a pneumatic or non-pneumatic tire, preferably a pneumatic tire. Furthermore, as examples of non-pneumatic tires known to those skilled in the art, mention may be made in particular of those described in patent applications WO 03/18332 and WO 2013/095499.
The present invention also relates to a pneumatic or non-pneumatic tire, preferably a pneumatic tire, comprising a composition according to the invention, or to a semi-finished rubber article according to the invention.
In a known manner, the tread of a pneumatic or non-pneumatic tire comprises a tread surface intended to come into contact with the ground when the tire is rolling, the tread being provided with a tread pattern comprising in particular tread pattern elements or basic blocks separated by various longitudinal or circumferential, transverse or even oblique main grooves, the basic blocks possibly further comprising various incisions or finer sipes.

Advantageously, the composition according to the invention is present in the tread of the tire, preferably in the radially outer portion of the tread intended to come into contact with the ground when the tire is rolling.
The invention relates in particular to tires intended to fit automobiles of the passenger car, SUV ("Sport Utility Vehicles") and light truck type, and in particular automobiles of the passenger car and SUV type.
The present invention relates to tires in both the raw state (i.e., before curing) and the cured state (i.e., after vulcanization).

III - PREFERRED EMBODIMENTS In light of the above, preferred embodiments of the present invention are described below:
1. A rubber composition based on:
an elastomeric matrix comprising 25 to 95 parts by weight per 100 parts by weight of elastomer having a glass transition temperature of less than −64° C., phr, of a copolymer based on butadiene and styrene, and 5 to 75 phr of polybutadiene modified with functional groups capable of interacting with silica;
at least one reinforcing filler comprising silica,
at least one agent for coupling silica to diene elastomers,
25 to 150 phr of at least one plasticizing resin having a glass transition temperature above 20° C., and a crosslinking system.

2. The composition of embodiment 1, wherein the butadiene and styrene based copolymer has a glass transition temperature in the range spanning from -105°C to -70°C, preferably between -95°C to -86°C.
3. A composition according to any one of the previous embodiments, wherein the copolymer based on butadiene and styrene comprises within its structure at least one alkoxysilane group bonded to the elastomer via a silicon atom and at least one functional group comprising a nitrogen atom.
4. Copolymers based on butadiene and styrene, having the following characteristics:
the functional group containing a nitrogen atom is a tertiary amine, more particularly a diethylamino or dimethylamino group;
the functional group containing a nitrogen atom is carried by the alkoxysilane group via a spacer group defined as an aliphatic C ₁ -C ₁₀ hydrocarbon-based radical, more preferentially a linear C ₃ hydrocarbon-based radical;
The alkoxysilane groups are methoxysilanes or ethoxysilanes, which may be partially or fully hydrogenated to give silanols.
- Copolymers based on butadiene and styrene are butadiene-styrene copolymers prepared in solution.
the butadiene and styrene-based copolymer is functionalized mid-chain by an alkoxysilane group attached via a silicon atom to the two branched chains of the butadiene and styrene-based copolymer,
- copolymers based on butadiene and styrene have glass transition temperatures in the range extending from -105°C to -70°C;
4. The composition of embodiment 3, wherein at least two, preferably at least three, preferably at least four of the following are observed:

5. Copolymers based on butadiene and styrene, having the following characteristics:
the functional group containing a nitrogen atom is a tertiary amine, more particularly a diethylamino or dimethylamino group;
the functional group containing a nitrogen atom is carried by an alkoxysilane group via a linear _C3 hydrocarbon-based radical,
the alkoxysilane groups are methoxysilanes or ethoxysilanes, which may be partially or fully hydrogenated to give silanols;
- the copolymer based on butadiene and styrene is a butadiene-styrene copolymer prepared in solution;
the butadiene and styrene-based copolymer is functionalized mid-chain by an alkoxysilane group attached via a silicon atom to the two branched chains of the butadiene and styrene-based copolymer,
- copolymers based on butadiene and styrene have a glass transition temperature between -95°C and -86°C;
4. The composition of embodiment 3, wherein all of the following are observed:

6. The composition of any one of the previous embodiments, wherein the modified polybutadiene has a molar content of cis-1,4 unit bonds of at least 55%, preferably at least 90%.
7. The modified polybutadiene is prepared by the following steps:
(a) homopolymerizing butadiene to form a pseudo-living elastomer with a catalyst system comprising at least:
one conjugated diene monomer,
one or more rare earth metal salts of organic phosphoric acids,
an aluminium-containing alkylating agent, and a halogen donor comprising an alkylaluminium halide,
It is based on
- the salt is in suspension or solution in at least one saturated inert hydrocarbon-based solvent of the aliphatic or cycloaliphatic type;
(b) adding a multifunctional compound containing at least three functional groups to the pseudo-living elastomer formed in step (a), wherein the functional groups are capable of reacting with the reactive ends of the pseudo-living elastomer;
(c) adding a functionalizing agent corresponding to the formula A-Ri-B to the mixture formed in step (b), wherein A represents a group capable of reacting with the reactive end of the pseudo-living elastomer, Ri represents an atom or group of atoms that form a bond between A and B, and B represents a functional group capable of reacting with the reinforcing filler;
(d) recovering the modified polybutadiene;
wherein the total molar amount of aluminum in the polymerization medium has an "aluminum/rare earth salt" molar ratio of between 1 and 5, and the polymerization is carried out at a temperature of between 40°C and 90°C.
8. The composition according to embodiment 7, wherein in the catalytic system of the process for obtaining modified polybutadiene, the molar ratio of "aluminum"/"rare earth salt" has a value between 1 and 4, advantageously in the range of 2.5 to 3.8.
9. The composition of any one of embodiments 7 and 8, wherein the polymerization of the process to obtain the modified polybutadiene is carried out at a temperature between 45°C and 75°C.

10. The composition of any one of embodiments 7 to 9, wherein in the catalyst system of the process for obtaining modified polybutadiene, the salt is neodymium tris[bis(2-ethylhexyl)phosphate].
11. The composition according to any one of embodiments 7 to 10, wherein the “functionalizing agent”/“aluminum” molar ratio of the process for obtaining the modified polybutadiene is advantageously at least 1.
12. The composition of any one of embodiments 7 to 11, wherein for the functionalizing agent of formula A-Ri-B in the process for obtaining modified polybutadiene, A is selected from glycidylamino, isocyanate, imine, and imidazole.
13. The composition of any one of embodiments 7 to 12, wherein for the functionalizing agent of formula A-Ri-B in the process for obtaining modified polybutadiene, B is a dialkoxysilane, preferably a diethoxysilane.

14. The composition of any one of embodiments 7 to 13, wherein for the functionalizing agent of formula A-Ri-B in the process for obtaining modified polybutadiene, Ri is a divalent aliphatic C ₁ -C ₁₀ radical.

15. The composition of any one of embodiments 7 to 14, wherein the process for obtaining the modified polybutadiene has a "polyfunctional compound"/"aluminum" molar ratio of less than 0.3.
16. The composition of any one of embodiments 7 to 15, wherein the polyfunctional compound of the process for obtaining the modified polybutadiene corresponds to the formula (E) _n -Rj, where n represents an integer equal to or greater than 3, E represents the functional group, and Rj represents an atom or group of atoms bearing n groups E.
17. The composition of any one of embodiments 7 to 16, wherein in the multifunctional compound of the process for obtaining modified polybutadiene, the functional groups are selected from glycidylamino, isocyanate, imine, and imidazole.
18. The composition of any one of embodiments 7 to 17, wherein the polyfunctional compound of the process for obtaining modified polybutadiene is tetraglycidylaminodiphenylmethane.
19. The composition of any one of embodiments 7 through 18, wherein the modified polybutadiene comprises free polybutadiene chains that have reacted only with a functionalizing agent and polybutadiene chains that are linked via a multifunctional compound.

20. The composition of any one of embodiments 7 to 19, wherein the modified polybutadiene has a cold flow value CF(1+6) at 100° C. of less than 1 g, preferably less than 0.5 g.
21. The modified polybutadiene is
a molar content of cis-1,4 unit bonds of at least 90% relative to the polybutadiene;
- a polydispersity index of less than 2.3,
- an average percentage of functionalized chains greater than 25%;
- a Mooney viscosity ML(1+4) at 100°C greater than or equal to 40, and - a cold flow value CF(1+6) at 100°C less than 1 g, preferably less than 0.5 g,
21. The composition of any one of embodiments 7 to 20, having
22. The composition of any one of embodiments 7 through 21, wherein the modified polybutadiene has a glass transition temperature of less than −100° C., preferably less than −105° C.
23. The composition of any one of embodiments 7 to 22, wherein the modified polybutadiene has an average content of functionalized chains between 25% and 80%, preferably between 25% and 60%.
24. The composition of any one of embodiments 7 to 22, wherein the modified polybutadiene has an average content of functionalized chains between 40% and 80%.

25. The composition of any one of the preceding embodiments, wherein the content of the butadiene and styrene-based copolymer in the composition is in a range ranging from 65 to 95 phr, and the content of the modified polybutadiene in the composition is in a range ranging from 5 to 35 phr.
26. The composition of any one of embodiments 1 through 27, wherein the elastomeric matrix comprises less than 15 phr of isoprene elastomer.
27. The composition of any one of embodiments 1 to 28, wherein the content of isoprene elastomer in the composition is less than 14 phr, preferably less than 10 phr, preferably less than 5 phr.
28. The composition of any one of the previous embodiments, wherein the total content of the butadiene and styrene-based copolymer and modified polybutadiene in the composition is in the range extending from 85 to 100 phr, preferably from 90 to 100 phr.
29. The composition of any one of the previous embodiments, wherein the total content of butadiene and styrene-based copolymer and modified polybutadiene in the composition is 100 phr.

30. The composition of any one of the previous embodiments, wherein the reinforcing filler comprises primarily silica.
31. The composition of any one of the previous embodiments, wherein the silica has a BET specific surface area in the range extending between 100 and 250 m ² /g, preferably 105 to 200 m ² /g, preferably 125 to 180 m ² /g.
32. The composition of any one of the previous embodiments, wherein the silica has a CTAB specific surface area in the range extending between 105 and 220 m ² /g, preferably 110 to 200 m ² /g, preferably 140 to 170 m ² /g.
33. The composition of any one of the previous embodiments, wherein the content of silica in the composition is in the range extending from 80 to 200 phr, preferably from 100 to 180 phr, and more preferably from 105 to 145 phr.
34. The composition of any one of the previous embodiments, wherein the content of plasticizing resin exhibiting a glass transition temperature above 20°C in the composition is in the range extending from 50 to 150 phr, preferably from 55 to 100 phr, and more preferably from 65 to 90 phr.

35. The composition of any one of the previous embodiments, wherein the plasticizing resin exhibiting a glass transition temperature greater than ₂₀ °C is selected from the group consisting of cyclopentadiene homopolymer or copolymer resins, dicyclopentadiene homopolymer or copolymer resins, terpene homopolymer or copolymer resins, C5 cut homopolymer or copolymer resins, _C9 cut homopolymer or copolymer resins, α-methylstyrene homopolymer or copolymer resins, and mixtures thereof.
The composition of any one of the previous embodiments may comprise 36.0 to 60 phr of a plasticizer that is liquid at 23°C.
37. The composition of any one of the preceding embodiments comprising 1 to 40 phr, preferably 2 to 20 phr, preferably 3 to 14 phr, of a plasticizer that is a liquid at 23° C.
38. The composition of embodiment 36 or 37, wherein the plasticizer that is liquid at 23°C is selected from the group consisting of liquid diene polymers, polyolefin oils, naphthalene oils, paraffin oils, DAE oils, MES oils, TDAE oils, RAE oils, TRAE oils, SRAE oils, mineral oils, vegetable oils, ether-based plasticizers, ester-based plasticizers, phosphate ester-based plasticizers, sulfonate ester-based plasticizers, and mixtures thereof.
39. The composition of embodiment 36 or 37, wherein the plasticizer that is liquid at 23°C is selected from the group consisting of MES oils, TDAE oils, naphthenic oils, vegetable oils and mixtures of these plasticizers that are liquid at 23°C, preferably vegetable oils, preferably sunflower oil.

40. The composition of any one of the preceding embodiments, wherein the crosslinking system is a vulcanization system comprising molecular sulfur and/or at least one sulfur donor.
41. A finished or semi-finished rubber article comprising the composition of any one of embodiments 1 to 40.
42. A pneumatic or non-pneumatic tire comprising the rubber composition of any one of embodiments 1-40.
43. The pneumatic or non-pneumatic tire of embodiment 42, wherein the composition of any one of embodiments 1 to 40 is present in the tread of the tire.

IV - Example IV-1 Measurements and Tests Used Dynamic Properties:
The dynamic properties G* and tan(δ)Max are measured with a viscometer (Metravib VA4000) according to ASTM standard D5992-96. The response of a sample of the vulcanized composition (cylindrical specimen with a thickness of 2 mm and a cross-sectional area of 79 mm2 ⁾ subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz is recorded under standard temperature conditions (23°C) or at 0°C for the measurement of tan(δ)Max, according to ASTM standard D1349-09, or at -20°C for the measurement of G*. A strain amplitude sweep is performed from 0.1% to 50% (outward cycle), followed by a return cycle from 50% to 0.1%. For the return cycle, the maximum value of tan δ observed (tan(δ)max) and the difference in complex modulus (ΔG*) between the values at 0.1% strain and at 50% strain (Payne effect) are shown.

The results used are the loss factor tan(δ)Max at 0°C and 23°C, and the complex dynamic shear modulus G* at -20°C.
The results for tan(δ)Max at 0°C are expressed on a base 100 basis, with the control assigned a value of 100. A result greater than 100 indicates an improvement in performance, i.e., the composition of the example under consideration, reflecting a better grip on wet ground of a tread containing such a composition.
The results for tan(δ)Max at 23°C and G* at -20°C are expressed on a base 100 basis, with the control assigned a value of 100. A result less than 100 indicates an improvement in performance, i.e., the composition of the example under consideration, reflecting better rolling resistance and better grip, respectively, on snow-covered ground for a tread comprising such composition.

Abrasion Resistance The abrasion resistance is measured by determining the volume loss due to abrasion according to NF ISO standard 4649 of November 2010, which is based on determining the volume loss of a sample after a linear movement of 40 meters on standardized abrasive paper.
More specifically, the volume loss due to abrasion is determined using an abrasion tester in which a cylindrical specimen is subjected to the action of an abrasive sheet of P60 coarseness attached to the surface of a rotating drum over a course of 40 m under a contact pressure of 5 N (N = Newton), in accordance with the instructions of NF ISO standard 4649 (Method B) of November 2010. The mass loss of the sample is measured and the volume loss is calculated depending on the density (ρ) of the material constituting the specimen, which is obtained in a conventional manner based on the mass fraction of each component of the material and their respective densities (ρ).
Results are expressed on a 100 basis. The arbitrary value of 100 assigned to the control composition allows for comparison of the material volume loss of the various test compositions. The value expressed on a 100 basis for the tested composition is calculated according to the following formula: (measured material volume loss of the control composition/measured material volume loss of the test composition) x 100. Thus, a result greater than 100 indicates reduced volume loss, and thus improved abrasion resistance, which corresponds to improved abrasion performance. Conversely, a result less than 100 indicates increased volume loss, and thus decreased abrasion resistance, which corresponds to decreased abrasion performance.

Mooney Viscosity The Mooney viscosity ML(1+4) at 100°C is measured for polymer and rubber compositions according to ASTM standard D1646 (December 2015).
A vibration consistency meter is used as described in ASTM standard D1646. Mooney plasticity measurements are carried out according to the following principle: the elastomer or composition in its raw state (i.e., before curing) is molded in a cylindrical chamber heated to 100°C. After 1 minute of preheating, a rotor is rotated in the test specimen at 2 revolutions per minute, and after 4 minutes of rotation, the operating torque required to maintain this movement is measured. Mooney plasticity ML(1+4) is expressed in "Mooney units" (MU, 1 MU = 0.83 N.m).
The difference between the Mooney viscosity of the composition and the Mooney viscosity of the elastomer makes it possible to measure the raw processability or processing: the smaller this difference, the better the raw material processing.

Differential Calorimetry The glass transition temperature (Tg) of an elastomer is determined using a differential calorimeter ("differential scanning calorimeter") at a scan rate of 20°C/min.

Near Infrared (NIR) Spectroscopy The microstructure of elastomers is characterized by near infrared (NIR) spectroscopy.
Near-infrared (NIR) spectroscopy is used to quantitatively determine the mass content of styrene in elastomers and their microstructure (the relative distribution of 1,2-butadiene, trans-1,4-butadiene, and cis-1,4-butadiene units). The principle of this method is based on the Beer-Lambert law generalized to multicomponent systems. Because this method is indirect, it involves a multivariate calibration performed using standard elastomers whose compositions are determined by ^13C NMR [Vilmin, F., Dussap, C., and Coste, N., Applied Spectroscopy, 2006, 60, 619-29]. The microstructure is then calculated from the NIR spectrum of an approximately 730 μm thick elastomer film. Spectra are acquired in transmission mode between 4000 and 6200 cm ⁻¹ with a resolution of 2 cm ⁻¹ using a Bruker Tensor37 Fourier transform near-infrared spectrometer equipped with a Peltier-cooled InGaAs detector.

Intrinsic Viscosity The intrinsic viscosity of an elastomer at 25° C. is determined from a 0.1 g.dl ⁻¹ solution of the elastomer in toluene according to the following principle.
The intrinsic viscosity is determined by measuring the flow time t of the polymer solution and the flow time t ₀ of toluene in a capillary tube.
The flow times of toluene and of 0.1 g.dl ^-1 polymer solutions are measured in Ubbelohde tubes (capillary diameter 0.46 mm, volume 18-22 ml) placed in a thermostatically controlled bath at 25±0.1°C.
The intrinsic viscosity is determined by the following relationship:

is obtained by
where C is the concentration of the polymer solution in toluene in ^g.dl
t: flow time of the polymer solution in toluene in seconds,
t ₀ : flow time of toluene in seconds;
η _inh : intrinsic viscosity expressed in dl. g ⁻¹ units

Cold flow (CF(1+6) 100°C)
This consists in measuring the mass of elastomer extruded through a calibrated die under constant conditions (T=100° C.) for a given time (6 hours). The die is 6.35 mm in diameter and 0.5 mm thick and is placed at the bottom and center of a hollow cylindrical dish with a diameter of 52 mm.
40±4 g of elastomer, previously formed into a pellet (2 cm thick and 52 mm in diameter), is placed in the apparatus. A calibrated piston with a mass of 1 kg (±5 g) is placed on the elastomer pellet. The assembly is then placed in an oven at 100±0.5°C.
At t=1 hour the extruded product is cut and discarded as conditions are not stable during the first hour in the oven.
Measurements are then continued for 6 hours ± 5 minutes, during which time the product is left in the oven. After 6 hours, a sample of the extruded product is cut and weighed. The result is the weight of the weighed elastomer, expressed in grams. The smaller this result, the more resistant the elastomer is to cold flow.

Determination of the number of functional groups in moles per unit mass of polymer: Determination of the amount of (3-glycidyloxypropyl)methyldiethoxysilane (GMDE) grafted onto the polybutadiene obtained a) Principle:
This determination is made by NMR analysis of a coagulated sample.
Spectra are acquired on a Bruker Avance III HD 500 MHz spectrometer equipped with a Bruker cryo-BBFO z-grad 5 mm probe.
1D ¹ H NMR spectra are recorded using a single pulse experiment with a tilt angle of 30°, a repetition rate of 128, and a recycle delay of 5 seconds. The experiment is carried out at 25°C.
b) Sample preparation:
25 mg of sample is dissolved in 1 ml of carbon disulfide (CS ₂ ); 70 μl of deuterated cyclohexane (C ₆ D ₁₂ ) is added to the polymer solution for field frequency locking.
c) Characterization:
The NMR spectrum contains signals characteristic of the butadiene units (BR1-4 and BR1-2). In addition to these, isolated signals (of low intensity) are observed that are due to the functionalizing agent, in this case the GMDE molecule. The 1H chemical shifts of the characteristic signals of this molecule in a BR matrix are shown below:
δ1H (ppm) Attribute 5.45 -CH=CH ₂ BR1-2
5.23 -CH=CH- BR1-4
4.85 -CH=CH ₂ BR1-2
3.61 -O-CH ₂ -CH ₃ (GMDE)
0.00 -Si-CH ₃ (GMDE)
0.46 -Si-CH ₂ - (GMDE)
Quantification was performed from integration of 1D ¹ H NMR spectra using Topspin software.

The integral zones considered for the quantification are:
A: between 5.5 ppm and 5.0 ppm, corresponding to two protons from BR1-4 and one proton from BR1-2;
- B: Between 5.5 and 4.75 ppm, corresponding to the two protons of BR1-2 - C: Between 3.66 and 3.56 ppm, corresponding to the two protons of GMDE (-O-CH ₂ -CH ₃ unit) - D: Between 0.02 and -0.10 ppm, corresponding to the three protons of GMDE (-Si-CH ₃ unit)

The microstructure can be quantified in mole percentage as follows:
Mol% of unit = ^1H integral of unit × 100/Σ ( ^1H integral of each unit)
(In the formula,
- ^1H integral of BR1-4 units = (A-(B/2))/2
- ^1H integral of BR1-2 units = B/2
- -O-CH ₂ -CH ₃ ¹ H integral of GMDE unit = C/2
- -Si-CH ₃ GMDE unit ¹ H integral = D/3)

Integration of the 1D ¹ H NMR spectrum of a purified portion of the sample can be used to quantify the grafted GMDE units as mole percentages as described above.
Determination of the molar mass distribution of polybutadiene obtained by size exclusion chromatography (SEC) technique a) Principle of measurement:
Size exclusion chromatography, or SEC, allows the separation of macromolecules in solution according to their size through a column filled with porous gel: the macromolecules are separated according to their hydrodynamic volume, with the bulkiest eluting first.
Although not an absolute method, SEC provides insight into the molar mass distribution of polymers. From commercially available standards, various number average molecular weights (Mn) and weight average molecular weights (Mw) can be measured, and via "Moore" calibration, the polydispersity index (PDI = Mw/Mn) can be calculated.

b) Preparation of the polymer:
The polymer samples undergo no special treatment before analysis: they are simply dissolved in tetrahydrofuran at a concentration of approximately 1 g/l.

c) SEC analysis:
Case c1) The equipment used is a Waters Alliance chromatographic line. The elution solvent is tetrahydrofuran, the flow rate is 1 ml/min, the system temperature is 35°C, and the analysis time is 30 minutes. Two Waters columns with the trade name "Styragel HT6E" are used.
The injection volume of the polymer sample solution is 100 μl. The detector is a Waters 2140 differential refractometer and the software for utilizing the chromatographic data is a Waters Millennium system.

Case c2) The equipment used is a Waters Alliance chromatograph. The elution solvent is tetrahydrofuran, the flow rate is 0.7 ml/min, the system temperature is 35°C, and the analysis time is 90 min. A set of four Waters columns in series is used, with the trade names "Styragel HMW7", "Styragel HMW6E", and two "Styragel HT6E".
The injection volume of the polymer sample solution is 100 μl. The detector is a Waters model RI32X differential refractometer and the software for utilizing the chromatographic data is a Waters Millennium system.

Synthesis of Nd/Bd/DIBALH/DEAC catalyst system The Nd/Bd/DIBALH/DEAC catalyst system diluted in MCH is synthesized according to the procedure described in WO-A-02/38636 (pages 8-11):
To obtain this catalyst, a neodymium phosphate salt in powder form is introduced into a reactor that has previously been purified. This salt is then bubbled with nitrogen for 10 minutes in order to inert the reaction medium. The following successive steps are then carried out:
- First step of solvation:
A solvent consisting of predistilled MCH, purified with alumina and bubbled with nitrogen is introduced into the reactor, and the time and temperature for contacting this solvent with the neodymium salt, taking into account the formation of a gel, is 30 minutes at 30°C with stirring.
- Second step of monomer addition:
Butadiene, previously purified on alumina and bubbled with nitrogen, is then introduced into the reactor at 30° C. This monomer is used to preform the catalyst during the aging step.
- Third step of alkylation:
Next, DIBALH in solution in MCH is introduced into the reactor as a reagent for alkylating the neodymium salt at a concentration of approximately 1 mol/l. The alkylation time is 15 minutes. The temperature of the alkylation reaction is 30°C.
- 4th halogenation step:
DEAC in solution in MCH is then introduced into the reactor as halogen donor at a concentration of approximately 0.5 mol/l. The temperature of the reaction medium is brought to 60°C.
- Fifth step of ageing:
The mixture thus obtained is aged by maintaining it at a temperature of 60° C. for 50 minutes.
The resulting catalyst solution is finally stored under a nitrogen atmosphere at a temperature between -15°C and -5°C.
The catalyst system is characterized by a catalyst formulation in the form Nd/monomer/alkylating agent/halogenating agent, with the molar ratios indexed to neodymium salts. In the example, the neodymium concentration catalyst formulation is 1/36/3/2.6, with a concentration of 0.038 mol/l.
"Total Al" defines the total amount of aluminum present in the reaction medium.

IV-2 Elastomer Testing Several polybutadienes (Comparative Examples EC1-EC8 and Examples I1-I4 according to the invention) were synthesized and compared according to the following process.
Methylcyclohexane and butadiene were continuously introduced into a 32 L continuously fed stirred reactor, assumed by those skilled in the art to be perfectly stirred. The mass flow rate of butadiene was 5.30 kg h ^-1 , and the mass concentration of butadiene in the methylcyclohexane/butadiene mixture was 9% by mass.
Diisobutylaluminum hydride (DIBALH) was introduced at the inlet of the first reactor in an amount sufficient to neutralize the protic impurities introduced by the various components present, at which reactor an amount of DIBALH per 100 g of butadiene and an amount of the above catalyst system per 100 g of butadiene were introduced.
The various flow rates are calculated so that the average residence time in the reactor is 25 minutes. The temperature is maintained at the desired polymerization temperature.
At the outlet of the polymerization reactor, a sample of the polymer solution is taken. The polymer thus obtained is subjected to an antioxidant treatment by adding 0.4 phr of 2,2'-methylenebis(4-methyl-6-(tert-butyl)phenol) and 0.2 phr of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. The polymer thus treated is subsequently separated from its solution by a steam stripping operation and then dried on an open mill at 100°C.

Upon exiting the polymerization reactor, a certain amount of (3-glycidyloxypropyl)methyldiethoxysilane in solution in methylcyclohexane was added per 100 g of butadiene at a temperature at least equal to the polymerization temperature, at a molar ratio of ((3-glycidyloxypropyl)methyldiethoxysilane)/(total Al) of 2.5. Optionally, prior to or simultaneously with the introduction of (3-glycidyloxypropyl)methyldiethoxysilane, a certain amount of 4,4'-methylenebis(N,N-diglycidylaniline) (or TGMDA) in solution in toluene was added to the living polymer solution at a molar ratio of (4,4'-methylenebis(N,N-diglycidylaniline))/(total Al) of 0.10 per 100 g of butadiene.

The polymer thus obtained was subsequently subjected to an antioxidant treatment by adding 0.4 phr of 2,2'-methylenebis(4-methyl-6-(tert-butyl)phenol) and 0.2 phr of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

The polymers thus treated were then separated from their solutions by a steam stripping operation and then dried at 100° C. on an open mill.
The amount of DIBALH (in μmol per 100 g of butadiene), the amount of catalyst system corresponding to the neodymium concentration (in μm cm), the polymerization temperature, the "initial" intrinsic viscosity, the number average molar mass, i.e., Mn, determined by SEC techniques, the polydispersity index, i.e., PDI, the amount of (3-glycidyloxypropyl)methyldiethoxysilane in solution in methylcyclohexane ("functionalizing agent" in μmol per 100 g of butadiene), the amount of 4,4'-methylenebis(N The amounts (in μmol of "multifunctional compound" per 100 g of butadiene) of (3-glycidyloxypropyl)methyldiethoxysilane) that may be used, and the time of introduction: either before (AV) or simultaneously with (EMT) the (3-glycidyloxypropyl)methyldiethoxysilane), the "final" intrinsic viscosity, the Mooney viscosity of these polymers, the content of cis-1,4 units relative to the mass of the polymer as determined by NIR methods, the glass transition temperature, or Tg, of these polymers, the cold flow CF(1+6) 100° C. of the polymers, and the number of functional groups as measured by ¹ H NMR, and also the average percentage of functionalized chains, are shown in Table 1 below.
In this table, "Total Al" is calculated taking into account the catalyst DIBALH (Nd/Al ratio is 3) and the DIBALH added in the polymerization reaction. **The average percentage (%) of functionalized chains is obtained by the formula: ( _CH2 -Si/PB) x Mn x ^1.10-4 , where _CH2 -Si/PB is in mmol/kg and Mn is in g/mol.

These results indicate that it is preferable to have the lowest possible total Al/Nd salt ratio, so that whatever the resulting molar mass, the higher the content of functionalized chains (see EC1 and EC2 compared to EC3 and EC4). Furthermore, it is advantageous to add a multifunctional compound before the functionalizing agent to increase the content of functionalized chains and decrease the flowability (see I1 compared to EC5). A comparison of EC1, EC6, EC7, and EC8 shows the influence of polymerization temperature on the content of functionalized chains. Finally, a comparison of EC1 with I3 or EC6 with I2 shows the beneficial effect of adding a multifunctional compound to decrease the flowability and maintain a high content of functionalized chains.
Thus, only the functionalized polybutadienes that can be used in connection with the present invention exhibit reduced cold flow, which is particularly advantageous for preserving or using polybutadiene in processes for making rubber compositions.

IV-3 Preparation of Compositions In the following examples, rubber compositions were prepared as described in II-6 above. In particular, the "non-productive" stage was carried out in a 0.4 liter mixer for 3.5 minutes at an average blade speed of 50 revolutions per minute until a maximum drop temperature of 160°C was reached. The "productive" stage was carried out on an open mill for 5 minutes at 23°C. Crosslinking of the compositions was carried out under pressure at temperatures between 130°C and 200°C.

IV-4 Tests on Rubber Compositions Four control compositions (T1 to T4) including a control composition (C1) and a composition according to the invention (I1).
All test formulations contained an elastomeric matrix, the nature and content of which are shown in Table 2 below, 120 phr "HDS" type Zeosil 1165 MP from Rhodia, 9.6 phr TESPT liquid silane (Si69 from Degussa) as an agent for coupling the silica to the elastomer, 4 phr ASTM N234 grade carbon black from Cabot, 73 phr C5/C9 resin "ECR-373 resin" (Tg=44°C) from ExxonMobil, 12 phr glyceryl trioleate (sunflower oil containing 85% by weight of oleic acid) "Lubrirob Tod 1880" from Novance, 2 phr ozone-resistant wax (Sasol The formulations contained 1.6 phr N-cyclohexyl-2-benzothiazole sulfenamide (Santocure CBS from Flexsys) as a vulcanization accelerator, and 1.5 phr technical grade zinc oxide (Umicore). The properties of these formulations are also shown in Table 2 below.

The purpose of the tests shown in Table 2 was to demonstrate the effect of the elastomeric matrix, in particular the effect of a butadiene and styrene-based copolymer having a glass transition temperature below -64°C, on the properties of grip on snow-covered ground, abrasion resistance and rolling resistance.

These results show that the use of a butadiene and styrene-based copolymer according to the present invention in a blend with polybutadiene can improve grip and abrasion resistance on snow-covered surfaces without excessively damaging rolling resistance. Conversely, replacing a butadiene and styrene-based copolymer according to the present invention with a butadiene and styrene-based copolymer not according to the present invention systematically results in a loss of performance in terms of abrasion resistance, grip force on snow-covered surfaces, and potentially rolling resistance. It should be noted that this performance loss can be further ameliorated by combining a butadiene and styrene-based copolymer according to the present invention with a polybutadiene according to the present invention.

Claims (9)

below:
an elastomeric matrix comprising 25 to 95 parts by weight per 100 parts by weight (i.e., phr) of a copolymer based on butadiene and styrene having a glass transition temperature of less than −64° C., and 5 to 75 phr of a modified polybutadiene modified with functional groups capable of interacting with silica;
at least one reinforcing filler comprising silica,
at least one agent for coupling silica to diene elastomers,
- 25 to 150 phr of at least one plasticizing resin having a glass transition temperature above 20°C, and - a crosslinking system,
A rubber composition based on
The modified polybutadiene is prepared by the following steps:
(a) homopolymerizing butadiene in a polymerization medium to form a pseudo-living elastomer with a catalyst system comprising at least:
one conjugated diene monomer,
neodymium tris[bis(2-ethylhexyl)phosphate],
an aluminium-containing alkylating agent, and a halogen donor comprising an alkylaluminium halide,
It is based on
- neodymium tris[bis(2-ethylhexyl)phosphate] is in suspension or solution in at least one saturated inert hydrocarbon-based solvent of the aliphatic or cycloaliphatic type;
(b) adding a multifunctional compound containing at least three functional groups to the pseudo-living elastomer formed in step (a), wherein the functional groups are capable of reacting with reactive ends of the pseudo-living elastomer;
(c) adding a functionalizing agent corresponding to the formula A-Ri-B to the mixture formed in step (b), wherein A represents a group capable of reacting with the reactive end of the pseudo-living elastomer, Ri represents an atom or group of atoms that form a bond between A and B, and B represents a functional group capable of reacting with a reinforcing filler;
(d) recovering the modified polybutadiene;
obtained by a process including
In this process, the total molar amount of aluminum in the polymerization medium has an "aluminum/rare earth salt" molar ratio between 1 and 5, and the homopolymerization is carried out at a temperature between 40°C and 90°C;
the modified polybutadiene comprises free polybutadiene chains reacted only with the functionalizing agent and polybutadiene chains linked via the polyfunctional compound;
The modified polybutadiene is
a molar content of cis-1,4 unit bonds of at least 90% relative to said modified polybutadiene;
- a polydispersity index of less than 2.3,
- an average percentage of functionalized chains greater than 25%;
- a Mooney viscosity ML(1+4) at 100°C greater than or equal to 40, and - a cold flow value CF(1+6) at 100°C less than 1 g,
The rubber composition has 2. The rubber composition of claim 1, wherein the copolymer based on butadiene and styrene has a glass transition temperature in the range extending from -105°C to -70°C. 3. The rubber composition according to claim 1, wherein the modified polybutadiene has a molar content of cis-1,4 unit bonds of at least 55%. The rubber composition according to any one of claims 1 to 3, wherein the content of the copolymer based on butadiene and styrene in the rubber composition is within a range of 65 to 95 phr, and the content of the modified polybutadiene in the rubber composition is within a range of 5 to 35 phr. The rubber composition according to any one of claims 1 to 4, wherein the reinforcing filler contains more than 50% by mass of silica. The rubber composition according to any one of claims 1 to 5, wherein the silica has a BET specific surface area between 100 and 250 m ² /g. The rubber composition according to any one of claims 1 to 6, wherein the content of silica in the rubber composition is within a range of 80 to 200 phr. The content of plasticizing resin exhibiting a glass transition temperature above 20°C is in the range of 50 to 150 phr,
The plasticizing resin exhibiting a glass transition temperature above 20°C is selected from the group consisting of cyclopentadiene homopolymer or copolymer resins, dicyclopentadiene homopolymer or copolymer resins, terpene homopolymer or copolymer resins, _C5 cut homopolymer or copolymer resins, _C9 cut homopolymer or copolymer resins, α-methylstyrene homopolymer or copolymer resins, and mixtures thereof.
The rubber composition according to any one of claims 1 to 7. A pneumatic or non-pneumatic tire comprising the rubber composition according to any one of claims 1 to 8.