FR3081162A1 - PNEUMATIC ROLLER BAND HAVING A CROSSLINKING SYSTEM BASED ON ORGANIC PEROXIDE - Google Patents

Abstract

The invention relates to a tread for a tire comprising a rubber composition based on at least 50 to 100 phr of a first diene elastomer, the first diene elastomer being a polybutadiene elastomer modified with a functional group capable of to interact with silica as a reinforcing filler; optionally from 0 to 50 phr of a second diene elastomer; between 150 and 220 phr of silica as a reinforcing filler; a coupling agent; a plasticizer system comprising a plasticizing resin having a glass transition temperature above 20 ° C; a crosslinking system based on organic peroxide; the total content of the first diene elastomer and the second diene elastomer in the composition being in a range from 80 to 100 phr.

Description

TIRE TREAD OF WHICH THE CROSSLINKING SYSTEM IS BASED ON ORGANIC PEROXIDE

The invention relates to tire treads intended in particular for passenger vehicles.

Tire treads must comply with a large number of technical requirements, often contradictory, among which are in particular rolling resistance, grip, wear, stiffness of cooked compositions (associated with road behavior and comfort conduct), at the same time as the cooking properties and the viscosity of the compositions in the raw state (associated with the ease of industrial implementation of the compositions, or processability).

Thus, tire designers are constantly looking for solutions which make it possible to develop the existing property compromise by improving at least one property of the tire, without penalizing the others.

To improve the adhesion compromise on wet and dry soil, it has been proposed to in application WO 2017/095563, a composition comprising a crosslinking system based on peroxide in an elastomeric matrix comprising from 80 to 100 phr of '' an elastomer based on functionalized polybutadiene comprising from 8 to 15% by weight of vinyl units and at least 30% by weight of trans bond, and whose glass transition temperature is between -100 ° C and -80 ° C .

However, there is always an advantage in further improving wet grip and dry grip.

Continuing her research, the Applicant has surprisingly discovered that a specific composition makes it possible to meet these needs. The Applicant has also found that this composition also improves the resistance to severe wear of the treads comprising this composition.

Thus, the subject of the present invention is in particular a tread for a tire comprising a rubber composition based on at least:

from 50 to 100 phr of a first diene elastomer, the first diene elastomer being a polybutadiene-based elastomer, modified with a functional group capable of interacting with silica as a reinforcing filler, optionally from 0 to 50 phr '' a second diene elastomer different from the first diene elastomer, between 150 and 220 phr of silica as reinforcing filler, a coupling agent, a plasticizing system comprising a plasticizing resin having a glass transition temperature above 20 ° C, a system crosslinking based on organic peroxide, the total level of the first diene elastomer and of the second diene elastomer in the composition being within a range from 80 to 100 phr.

The present invention also relates to a tire provided with a tread according to the invention.

The invention as well as its advantages will be easily understood in the light of the description and of the exemplary embodiments which follow.

I- DEFINITIONS

By the expression part by weight per hundred parts by weight of elastomer (or phr), it is meant within the meaning of the present invention, the part, by mass per hundred parts by mass of elastomers, whether they are thermoplastic or no. In other words, thermoplastic elastomers are elastomers.

In the present document, unless expressly indicated otherwise, all the percentages (%) indicated are percentages (%) by mass.

On the other hand, any range of values designated by the expression between a and b represents the range of values going from more than a to less than b (i.e. limits a and b excluded) while any range of values designated by the expression from a to b signifies the range of values going from a to b (that is to say including the strict limits a and b). In the present, when we designate a range of values by the expression from a to b, we also and preferably designate the range represented by the expression between a and b.

In the present, by the expression composition based on, is meant a composition comprising the mixture and / or the reaction product of the various constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the various stages of manufacturing the composition.

When reference is made to a majority compound, it is understood within the meaning of the present invention, that this compound is predominant among the compounds of the same type in the composition, that is to say that it is that which represents the most large amount by mass among the compounds of the same type, for example more than 50%, 60%, 70%, 80%, 90%, or even 100% by weight relative to the total weight of the type of compound. Thus, for example, a majority reinforcing filler is the reinforcing filler representing the largest mass relative to the total mass of the reinforcing fillers in the composition.

In the context of the invention, the compounds comprising carbon mentioned in the description, can be of fossil origin or bio-based. In the latter case, they can be, partially or totally, from biomass or obtained from renewable raw materials from biomass. Are concerned in particular polymers, plasticizers, fillers, etc.

All the glass transition temperature values “Tg” described herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to standard ASTMD3418 (1999).

II- DESCRIPTION OF THE INVENTION

Π-l Elastomeric matrix

According to the invention, the composition of the tread of the tire comprises at least 50 to 100 phr of a first diene elastomer, the first diene elastomer being a polybutadiene-based elastomer, modified with a functional group capable of interacting with silica as reinforcing filler, and optionally from 0 to 50 phr of a second diene elastomer, it being understood that the total level of the first diene elastomer and of the second diene elastomer in the composition being within a range from 80 at 100 pce.

II-l.l First diene elastomer

In the present document, unless the expression “first diene elastomer” is used, reference is made to an elastomer based on polybutadiene, modified with a functional group capable of interacting with silica as a reinforcing filler. . Such elastomers and their process for obtaining are described in particular in US patent documents 5,977,238, WO 2009/133068, EP 0 778 311 Bl, WO 2008/141702, WO 2006/050486, EP 0877 047 Bl, EP 1 400 559 Bl , JP 63-215701, JP 62-227908 or US 5,409,969. The first diene elastomer can also be a mixture of two or more elastomers based on polybutadiene, modified with a functional group capable of interacting with silica as a reinforcing filler.

Advantageously, the functional group capable of interacting with silica as a reinforcing filler of the first diene elastomer is at least one (that is to say one or more) alkoxysilane group linked to the elastomer by its atom of silicon. In the present application, the term "the alkoxysilane group" is used to designate at least, that is to say one or more, alkoxysilane group linked to the elastomer by its silicon atom.

According to the invention, the alkoxysilane group of the first diene elastomer can be located at the end of the elastomer chain.

Alternatively, and advantageously, the alkoxysilane group is located inside (or “in”) the elastomer chain, it will then be said that the first diene elastomer is coupled (or even functionalized) in the middle of the chain, in contrast to the position at the end of the chain, although the grouping is not located precisely in the middle (or "in the center") of the elastomer chain. The silicon atom of this function links the two main branches of the elastomer chain of the first diene elastomer.

The alkoxysilane group can carry another function preferably carried by the silicon of the alkoxysilane group, directly (that is to say via a covalent bond) or via a spacer group defined as being a atom or a divalent hydrocarbon radical, linear or branched, aliphatic in Ci-Cis, saturated or not, cyclic or not, or a divalent aromatic hydrocarbon radical in Cô-Cis.

The other function is preferably a function comprising at least one heteroatom chosen from N, S, O, P. By way of example, mention may be made, among these functions, of primary, secondary or tertiary amines, cyclic or not, isocyanates, imines, cyano, thiols, carboxylates, epoxides, primary, secondary or tertiary phosphines.

Thus, as secondary or tertiary amine function, mention may be made of amines substituted by C 1 -C 10 alkyl radicals, preferably C 1 -C 4 alkyl radicals, more preferably a methyl or ethyl radical, or else the cyclic amines forming a heterocycle containing a nitrogen atom and at least one carbon atom, preferably from 2 to 6 carbon atoms. For example, the groups metylamino-, dimethylamino-, ethylamino-, diethylamino-, propylamino-, dipropylamino-, butylamino-, dibutylamino-, pentylamino-, dipentylamino-, hexylamino-, dihexylamino-, hexamethyleneamino- groups are suitable. - and dimethylamino-.

By way of imine function, mention may be made of ketimines. For example, the groups (1,3-dimethylbutylidene) amino-, (ethylidene) amino-, (1methylpropylidene) amino-, (4-N, N-dimethylaminobenzylidene) amino-, (cyclohexylidene) amino-, dihydroimidazole and imidazole are suitable.

Thus, as the carboxylate function, mention may be made of acrylates or methacrylates. Such a function is preferably a methacrylate.

As epoxy function, mention may be made of epoxy or glycidyloxy groups.

By way of secondary or tertiary phosphine function, mention may be made of phosphines substituted by C1-C10 alkyl radicals, preferably C1-C4 alkyl radicals, more preferably a methyl or ethyl radical, or then diphenylphosphine. For example, the methylphosphino-, dimethylphosphino-, ethylphosphino-, diethylphosphino, ethylmethylphosphino- and diphenylphosphino- groups are suitable.

In a particularly advantageous manner, the alkoxysilane group carries an amine function. In this case, the alkoxysilane group can also be called “alkoxysilane group carrying an amine function” or “amino-alkoxysilane group”, the two expressions having the same meaning. The amine function can be a primary, secondary or tertiary amine function. Preferably, the amine function is a tertiary amine function, preferably chosen from diethylamine and dimethylamine.

The primary, secondary or tertiary amine function can be carried, directly (by a covalent bond) by the silicon atom of the alkoxysilane group of the first diene elastomer, or by means of a spacer group. The spacer group may in particular be a divalent, linear or branched hydrocarbon radical, Cmo alkyl, C 18 aryl or C 7-18 aralkyl. Preferably the spacer group is a linear C2-3 hydrocarbon radical.

According to the invention, the alkoxysilane group carrying the primary, secondary or tertiary amine function can correspond to one of the following formulas (I) to (III):

Formula (I) Formula (II) Formula (ΠΙ) in which:

E denotes the first diene elastomer,

Ri and Rs, identical or different, denote the first diene elastomer or an oxygen atom substituted by a hydrogen atom or an alkyl radical, linear or branched, Cmo, C5-18 cycloalkyl, Cs-is aryl or C7-18 aralkyl;

R ₂ is a divalent linear or branched hydrocarbon radical of Cmo alkyl, C6-18 aryl or C7-18 aralkyl;

R3 and R4, identical or different, represent a hydrogen atom or a Cmo alkyl radical, provided that when one of R3 and R4 represents a hydrogen atom the other is different, or then R3 and R4 form with N to which they are linked a heterocycle containing a nitrogen atom and at least one carbon atom;

R5 represents an alkylidene radical, linear or branched, in Cmo;

the symbols A denote, independently of one another, a nitrogen atom or a carbon atom, provided that at least one of the symbols A denotes a nitrogen atom.

Advantageously, the alkoxysilane group carrying the primary, secondary or tertiary amine function corresponds to one of the formulas (I) to (III) above in which:

Ri represents an oxygen atom substituted by a methyl or ethyl radical; and or

R2 represents the ethane-1,2-diyl or propane-1,3-diyl radical; and or,

R3 and R4, identical or different, represent a methyl or ethyl radical; and or

Rs represents a linear or branched C 4-6 alkylidene radical; and / or a single A denotes a nitrogen atom and is located in the meta or para position of the ring with respect to -R2; and or

Rs denotes the first diene elastomer.

The first diene elastomer carrying an amino-alkoxysilane group linked to the diene elastomer by the silicon atom as defined herein, can be prepared by techniques known to those skilled in the art, for example according to an appropriate process described in WO 2009/133068 or WO 2017/060395.

The process for preparing the first diene elastomer carrying an aminoalkoxysilane group linked to the diene elastomer by the silicon atom as defined herein, can in particular comprise a stripping step in order to recover the elastomer in dry form. This stripping step can have the effect of hydro lysing all or part of the hydrolysable alkoxysilane functions of said copolymer to transform them into silanol functions. For example, at least 50 mol% of the functions can thus be hydrolyzed.

Thus, according to the invention, the alkoxysilane group of the first diene elastomer carrying an amino-alkoxysilane group linked to the diene elastomer by the silicon atom as defined herein, can be partially or completely hydrolyzed to silanol.

According to the invention, the functional group capable of interacting with silica as a reinforcing filler of the first diene elastomer can also be at least one SiOR function, R being hydrogen or a hydrocarbon radical, in particular an alkyl, preferably having 1 to 12 carbon atoms, in particular methyl or ethyl. In the present application, the term “the SiOR function” is used to designate at least one SiOR function, that is to say one or more SiOR functions.

The term “hydrocarbon radical” is understood to mean a monovalent group essentially consisting of carbon and hydrogen atoms, such a group possibly comprising at least one heteroatom, knowing that the group consisting of carbon and hydrogen atoms represents the numerical fraction majority in the hydrocarbon radical.

The hydrocarbon radical can be an alkyl, branched or linear or alternatively cyclic, having 1 to 12 carbon atoms, more preferably from 1 to 6 carbon atoms, even more preferably from 1 to 4 carbon atoms, in particular a methyl or a ethyl. The radical R can also be an alkoxyalkyl, more particularly having 2 to 8 carbon atoms.

The SiOR function carried by the first diene elastomer can be located along the elastomer chain as a pendant group, at one end of the elastomer chain or even inside the elastomer chain. In the case where there are several SiOR functions carried by the elastomer, they can occupy one or other of the above configurations.

Advantageously, the radical R of the SiOR function carried by the first diene elastomer is a hydrogen atom (so-called “silanol” function of formula SiOH). . The silanol SiOH function is preferably located at the chain end of the diene elastomer, in particular in the form of a dimethylsilanol group -SiMe2SiOH.

The silanol function can be linked to a polysiloxane which constitutes one of the blocks of a block copolymer also comprising a polydiene block, as for example described in patent EP 0 778 311 B1. It can also be linked to a polyether constituting the one of the blocks of a block copolymer also comprising a polydiene block, as described for example in application WO 2009/000750.

Whatever the functional group capable of interacting with silica as a reinforcing filler of the first diene elastomer, the first diene elastomer can also have additional star formation by reaction with a star-forming agent known per se, for example based on tin or silicon. Preferably, the copolymer based on styrene and butadiene is functionalized with tin (Sn), that is to say that they contain a C-Sn bond (also called Sn functionalization). They can be simply functionalized (CSn bond at the end of the chain), coupled (Sn atom between two chains) and / or starred (Sn atom between 3 or more chains) with a functionalization, coupling and / or star-forming agent. Generically speaking, we are talking about bringing together all these elastomers linked to tin, elastomers functionalized with tin. These elastomers are known to those skilled in the art, for example those described in application WO 2011/042507.

Particularly advantageously, the first diene elastomer is a copolymer based on styrene and butadiene.

Within the meaning of the present invention, a copolymer based on styrene and butadiene is any copolymer obtained by copolymerization of one or more styrene compounds with one or more butadiene (s). As styrene monomers suitable in particular are styrene, methylstyrenes, para-tertiobutylstyrene, methoxystyrenes, chlorostyrenes. As butadiene monomers suitable in particular are 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C1-C6 alkyl) -1,3-butadiene such as for example 2 , 3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1, 3butadiene and an aryl-1,3-butadiene. These elastomers may have any microstructure which is a function of the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and the quantities of modifying and / or randomizing agent used. The elastomers can be, for example, block, statistical, sequenced, microsequenced.

According to the invention, the first diene elastomer is advantageously a styrene butadiene copolymer (SBR).

Preferably, the styrene-butadiene-based copolymer consists of styrene monomers and butadiene monomers, that is to say that the sum of the molar percentages of styrene monomers and butadiene monomers is equal to 100%.

It should be noted that the SBR can be prepared in emulsion (ESBR) or in solution (SSBR). Whether ESBR or SSBR, the SBR can be of any microstructure. One can in particular use an SBR having a low styrene content, for example comprised of more than 0 to 10%, an average styrene content, for example comprised between 10% and 35% by weight, or a high styrene content, for example example from 35 to 55%, a content of vinyl bonds in the butadiene part of between 4% and 70%, and a Tg of less than -40 ° C, preferably less than -50 ° C.

Preferably, the first diene elastomer is a styrene-butadiene copolymer exhibits any one, advantageously the combination of two or three, even more advantageously all, of the following characteristics:

it is a styrene-butadiene copolymer prepared in solution (SSBR), its mass content of styrene relative to the total weight of the styrene butadiene copolymer is between 1 and 15%, preferably between 1 and 4%, its content of vinyl bonds of the butadiene part between 4 and 25%, preferably between 10 and 15%, its Tg is less than -60 ° C, preferably between -100 ° C and -80 ° C.

Advantageously, the level of the first diene elastomer in the composition of the tread of the tire according to the invention is within a range ranging from 80 to 100 phr. It can for example be from 80 to 95 phr, for example from 80 to 90 phr.

II-1.2 Second diene elastomer

Although this is not necessary for the implementation of the present invention, the elastomeric matrix of the composition of the tread according to the invention may contain in a minority one or more different diene elastomers (hereinafter called "second diene elastomer ”(for the sake of simplification of drafting) of the first diene elastomer used in the context of the present invention. For example, the second diene elastomer can be chosen, for example, from the group of highly unsaturated diene elastomers constituted by polybutadienes (abbreviated BR) different from the first diene elastomer used in the context of the present invention, natural rubber (NR ), synthetic polyisoprene (IR), butadiene copolymers, isoprene copolymers (other than RR) and mixtures of these elastomers. Such copolymers can for example be chosen from the group consisting of butadiene-styrene copolymers (SBR) different from the first diene elastomer used in the context of the present invention, isoprene-butadiene copolymers (BIR), copolymers of isoprene-styrene (SIR), isoprene-butadiene-styrene copolymers (SBIR), butadiene-acrylonitrile copolymers (NBR), butadiene-styrene-acrylonitrile copolymers or a mixture of two or more these compounds. Advantageously, the second diene elastomer is a polybutadiene. Also advantageously, the second diene elastomer is natural rubber, a synthetic polyisoprene or their mixtures, preferably natural rubber.

Advantageously, the level of the second diene elastomer in the composition of the tread of the tire according to the invention is within a range ranging from 0 to 20 phr. It can be, for example, from 5 to 20 phr, for example from 10 to 20 phr.

The elastomeric matrix can also contain in a minority any type of synthetic elastomer other than diene, or even with polymers other than elastomers, for example thermoplastic polymers. Preferably, the elastomeric matrix does not contain synthetic elastomer other than diene nor of polymer other than elastomers or contains less than 10 phr, preferably less than 5 phr.

In a particularly advantageous manner, the composition of the tread according to the invention does not comprise butyl rubber or comprises less than 10 pce, preferably less than 5 pce.

Preferably, the level of the first diene elastomer in the composition is within a range from 80 to 100 phr, and the level of the second diene elastomer in the composition is within a range from 0 to 20 phr.

Advantageously, the total level of the first diene elastomer and of the second diene elastomer in the composition of the tread of the tire according to the invention is included in a range ranging from 80 to 100 phr, preferably 90 to 100 phr, more preferably from 95 to 100 pce.

In a particularly advantageous manner, the total rate of the first diene elastomer and of the second diene elastomer in the composition of the tread of the tire according to the invention is 100 phr.

Π-2 Strengthening charge

The composition of the tread according to the invention has the essential characteristic of containing between 150 and 220 phr of silica as a reinforcing filler and a coupling agent.

By silica as reinforcing filler, should be understood here silica (SiO ₂ ), capable of reinforcing on its own, without other means than an intermediate coupling agent, a rubber composition intended for the manufacture of pneumatic tires; such a charge is generally characterized, in a known manner, by the presence of hydroxyl groups (-OH) on its surface.

The silica used can be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface as well as a CTAB specific surface, both less than 450 m ² / g, preferably from 30 to 400 m ² / g, in particular between 60 and 300 m ² / g. As highly dispersible precipitated silicas (called HDS), mention may be made for example of the “Ultrasil” 7000 and “Ultrasil” 7005 silicas from the company

Degussa, the 1165MP, 1135MP and 1115MP “Zeosil” silicas from the company Rhodia, the “Hi-Sil” EZ150G silica from the company PPG, the “Zeopol” silicas 8715, 8745 and 8755 from the Huber company, the high-surface silicas specific as described in application WO 03/16387. Preferably, the silica content in the composition of the tread is between 150 and 200 phr, preferably between 155 and 180 phr.

To couple the reinforcing inorganic filler to the diene elastomer, use is made in a well known manner of a coupling agent (or binding agent) at least bifunctional intended to ensure a sufficient connection, of chemical and / or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. In particular organosilanes or polyorganosiloxanes which are at least bifunctional are used.

Those skilled in the art can find examples of coupling agent in the following documents: WO 02/083782, WO 02/30939, WO 02/31041, WO 2007/061550,

WO 2006/125532, WO 2006/125533, WO 2006/125534, US 6,849,754, WO 99/09036, WO 2006/023815, WO 2007/098080, WO 2010/072685 and WO 2008/055986.

The coupling agent may in particular be an organosilane coupling agent having no sulfur atom, having a disulfide, trisulfide or tetrasulfide group, or having a mercapto group. For example, the coupling agent can be chosen from the group comprising or consisting of 3.3′-bis disulfide (triethoxysilylpropyl), 3.3′-bis disulfide (tri-tbutoxysilylpropyl), disulfide of 3.3 '-bis (propyl-diethoxysilylpropyl), 2,2'-bis (dimethylmethoxysilylethyl) disulfide, and mixtures thereof. The coupling agent can also be chosen from the group consisting of or comprising 3-mercaptopropyltrimethoxysilane, 2mercaptoethyltrimeth-oxysilane, 2-mercaptodimethylmethoxysilane and their mixtures. It can also be chosen from the group consisting of or comprising 3-glycidoxypropyl methyldimethoxy silane, vinyltrimethoxysilane, 3-methacryloxypropyl methyldimethoxysilane and their mixtures.

The content of coupling agent advantageously represents from 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler, preferably from 4 to 12%, more preferably from 6 to 10% by weight relative to the amount of reinforcing inorganic filler. The level of coupling agent is preferably within a range ranging from 9 to 22 phr, preferably from 9 to 18 phr. This level can easily be adjusted by a person skilled in the art according to the level of inorganic filler used in the composition.

The rubber composition of the tire according to the invention may also contain, in addition to the coupling agents, coupling activators, agents for recovery of inorganic charges or more generally agents for aid in use which are susceptible in known manner. , thanks to an improvement in the dispersion of the filler in the rubber matrix and to a lowering of the viscosity of the compositions, to improve their ability to be used in the raw state, these agents being for example hydrolysable silanes such as alkylalkoxysilanes (in particular alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines (for example trialkanol-amines), hydroxylated or hydrolyzable POSs, for example α, ω- dihydroxy-polyorganosiloxanes (in particular α, ω-dihydroxypolydimethylsiloxanes), fatty acids such as, for example, stearic acid.

Although this is not necessary for the implementation of the present invention, the rubber composition of the tread of the tire according to the invention, may include carbon black. According to the invention, the composition of the tread does not comprise carbon black, or comprises less than 50 phr, preferably, less than 20 phr, more preferably still less than 10 phr (for example between 0.5 and 20 pce, in particular between 1 and 10 pce, for example between 2 and 5 pce). Within the indicated intervals, the coloring properties (black pigmentation agent) and anti-UV properties of the carbon blacks are benefited, without, however, penalizing the typical performances provided by the reinforcing inorganic filler.

The blacks which can be used in the context of the present invention may be any black conventionally used in tires or their treads (so-called pneumatic grade blacks). Among the latter, there may be mentioned more particularly the reinforcing carbon blacks of the 100, 200, 300 series, or the blacks of the 500, 600 or 700 series (grades AS TM), such as, for example, the blacks NI 15, NI34, N234, N326. , N330, N339, N347, N375, N550, N683, N772). These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a support for some of the rubber additives used. The carbon blacks could for example already be incorporated into the diene elastomer, in particular isoprene, in the form of a masterbatch (see for example applications WO 97/36724 or WO 99/16600). The BET specific surface area of carbon blacks is measured according to standard D6556-10 [multipoint method (at least 5 points) - gas: nitrogen - relative pressure range Ρ / Ρ0: 0.1 to 0.3],

In a particularly advantageous manner, the total rate of reinforcing filler is between 150 and 240 phr, preferably between 155 and 180 phr.

Π-3 Plasticizer system

The rubber composition of the tread of the tire according to the invention further comprises a plasticizer system comprising a plasticizer resin having a glass transition temperature above 20 ° C, called "high Tg" (also called "plasticizer resin" in the present for the sake of simplification of drafting ”).

II-3.1 Plasticizing resin

The name "resin" is reserved in the present application, by definition known to those skilled in the art, to a compound which is solid at room temperature (23 ° C), in contrast to a liquid plasticizing compound such as an oil.

Plasticizing resins are polymers well known to those skilled in the art, essentially based on carbon and hydrogen but which may contain other types of atoms, which can be used in particular as plasticizing agents or tackifying agents in polymeric matrices.

They are generally by nature miscible (i.e., compatible) at the levels used with the polymer compositions for which they are intended, so as to act as true diluents. They have been described for example in the work entitled Hydrocarbon Resins by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9), Chapter 5 of which is devoted to their applications, especially in pneumatic rubber (5.5. Rubber Tires and Mechanical Goods). They can be aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, of the aliphatic / aromatic type, that is to say based on aliphatic and / or aromatic monomers. They can be natural or synthetic, based on petroleum or not (if this is the case, also known as petroleum resins). Their Tg is preferably greater than 20 ° C (most often between 30 ° C and 95 ° C).

In known manner, these plasticizing resins can also be qualified as thermoplastic resins in the sense that they soften by heating and can thus be molded. They can also be defined by a softening point or temperature (in English, softeningpoint). The softening temperature of a plasticizing resin is generally about 50 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 Ip) is determined by steric exclusion chromatography (SEC) as indicated below.

As a reminder, the SEC analysis, for example, consists in separating the macromolecules in solution according to their size through columns filled with a porous gel; the molecules are separated according to their hydrodynamic volume, the largest being eluted first. The sample to be analyzed is simply dissolved beforehand in an appropriate solvent, tetrahydrofuran at a concentration of 1 g / liter. The solution is then filtered on a filter with a porosity of 0.45 μm, before injection into the apparatus. The apparatus used is for example a Waters alliance chromatographic chain according to the following conditions:

elution solvent is tetrahydrofuran, temperature 35 ° C .;

concentration 1 g / liter;

flow rate: 1 ml / min;

volume injected: 100 μΐ;

Moore calibration with polystyrene standards;

- set of 3 Waters columns in series (Styragel HR4E, Styragel HR1 and Styragel HR0.5);

detection by differential refractometer (for example WATERS 2410) which can be equipped with operating software (for example Waters Millenium).

A Moore calibration is carried out with a series of commercial standards of low Ip polystyrene (less than 1.2), of known molar masses, covering the range of masses to be analyzed. We deduce from the recorded data (mass distribution curve of molar masses) the mass-average molar mass (Mw), the number-average molar mass (Mn), as well as the polymolecularity index (Ip = Mw / Mn).

All the molar mass values indicated in the present application therefore relate to calibration curves carried out with polystyrene standards.

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

a Tg greater than 25 ° C (in particular between 30 ° C and 100 ° C), more preferably 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) of between 300 and 2000 g / mol, preferably between 400 and 1500 g / mol;

a polymolecularity index (Ip) of less than 3, preferably of 2 (reminder: Ip = Mw / Mn with Mw average molar mass by weight).

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

polylimonene resins: by the company DRT under the name Dercolyte L120 (Mn = 625 g / mol; Mw = 1010 g / mol; Ip = 1.6, Tg = 72 ° C) or by the company ARIZONA under the name Sylvagum TR7125C ( Mn = 630 g / mol; Mw = 950 g / mol; Ip = 1.5, Tg = 70 ° C);

copolymer resins cut C5 / vinyl aromatic, in particular cut C5 / styrene or cut C5 / cut C9: by Neville Chemical Company under the names Super Nevtac 78, Super Nevtac 85 or Super Nevtac 99, by Goodyear Chemicals under the name Wingtack Extra, by Kolon under names Hikorez Tl095 and Hikorez Tl 100, by Exxon under names Escorez 2101 and Escorez 1273; limonene / styrene copolymer resins: by DRT under the name Dercolyte T S 105 from the company DRT, by ARIZONA Chemical Company under the names ZT115LT and ZT5100.

According to the invention, the plasticizing resin having a glass transition temperature above 20 ° C. can be chosen from the group comprising or consisting of cyclopentadiene homopolymer or copolymer resins (abbreviated as CPD), homopolymer or copolymer resins of dicyclopentadiene (abbreviated as DCPD), terpene homopolymer or copolymer resins, C5 cut homopolymer or copolymer resins, C9 cut homopolymer or copolymer resins, alpha homopolymer or copolymer resins -methyl-styrene and mixtures thereof. Preferably, the plasticizing resin is chosen from the group comprising or consisting of the copolymer (D) CPD / vinyl aromatic resins, the copolymer resins (D) CPD / terpene, the terpene phenol copolymer resins, the copolymer resins (D ) CPD / C5 cut, copolymer resins (D) CPD / C9 cut, terpene / vinylaromatic copolymer resins, terpene / phenol copolymer resins, C5 / vinylaromatic cut copolymer resins, and mixtures thereof.

The term terpene groups together here in a known manner the alpha-pinene, beta-pinene and limonene monomers; a limonene monomer is preferably used, a compound which is known in the form of three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or else dipentene, racemic of dextrorotatory and levorotatory enantiomers . As vinyl aromatic monomer, for example, styrene, alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyl-toluene, para-tertiobutylstyrene, methoxystyrenes, chlorostyrenes are suitable. hydroxystyrenes, vinyl mesitylene, divinylbenzene, vinylnaphthalene, any vinyl aromatic monomer resulting from a C9 cut (or more generally from a C "to Cio cut).

More particularly, mention may be made of the plasticizing resins chosen from the group consisting of homopolymer resins (D) CPD, copolymer resins (D) CPD / styrene, polylimonene resins, limonene / styrene copolymer resins, limonene / D copolymer resins (CPD), C5 cut / styrene copolymer resins, C5 cut / C9 cut copolymer resins, and mixtures of these resins.

All of the above plasticizing resins are well known to a person skilled in the art and are commercially available, for example sold by the company DRT under the name Dercolyte with regard to the polylimonene resins, by the company Neville Chemical Company under the name Super Nevtac, by Kolon under the name Hikorez or by the company Exxon Mobil under the name Escorez for C5 / styrene resins or C5 / C9 cut resins, or by the company Struktol under the name 40 MS or 40 NS (mixtures of aromatic resins and / or aliphatic).

Advantageously, the level of plasticizing resin having a glass transition temperature greater than 20 ° C. in the composition of the tread according to the invention is included in a range ranging from 35 to 220 phr, preferably from 50 to 200 phr, preferably still from 60 to 180 pce.

II-3.2 Plasticizer liquid at 23 ° C

Although this is not necessary for the implementation of the present invention, the plasticizer system of the rubber composition of the tread of the tire according to the invention may comprise a plasticizer liquid at 23 ° C, called "low" Tg ", that is to say which by definition has a Tg of less than -20 ° C, preferably less than -40 ° C. According to the invention, the composition can optionally comprise from 0 to 110 phr of a plasticizer liquid at 23 ° C.

When a liquid plasticizer at 23 ° C is used, its level in the composition of the tread according to the invention can be included in a range ranging from 5 to 110 phr, preferably from 30 to 90 phr.

Any plasticizer liquid at 23 ° C (or extension oil), whether of an aromatic or nonaromatic nature, known for its plasticizing properties with respect to diene elastomers, can be used. At room temperature (23 ° C), these plasticizers or these oils, more or less viscous, are liquids (that is to say, substances having the capacity to eventually take the form of their container) , as opposed in particular to plasticizing resins which are by nature solid at room temperature.

Particularly suitable are plasticizers liquid at 23 ° C chosen from the group comprising or consisting of liquid diene polymers, polyolefin oils, naphthenic oils, paraffinic oils, DAE oils, MES oils (Medium Extracted Solvates), TDAE oils (Treated Distillate Aromatic Extracts), RAE oils (Residual Aromatic Extract oils), TRAE oils (Treated Residual Aromatic Extract) and SRAE oils (Safety Residual Aromatic Extract oils), mineral oils, vegetable oils, plasticizers ethers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these plasticizers liquid at 23 ° C.

For example, the plasticizer liquid at 23 ° C can be a petroleum oil, preferably non-aromatic. A liquid plasticizer is qualified as non-aromatic when it has a content of polycyclic aromatic compounds, determined with the extract in DMSO according to the IP 346 method, of less than 3% by weight, relative to the total weight of the plasticizer. .

The plasticizer liquid at 23 ° C. can also be a liquid polymer resulting from the polymerization of olefins or dienes, such as polybutenes, polydienes, in particular polybutadienes, polyisoprenes (also known under the name "LIR") or butadiene and isoprene copolymers, or butadiene or isoprene and styrene copolymers or mixtures of these liquid polymers. The number-average molar mass of such liquid polymers preferably ranges from 500 g / mol to 50,000 g / mol, preferably from 1,000 g / mol to 10,000 g / mol. By way of example, the "RICON" products from SARTOMER can be cited.

When the liquid plasticizer at 23 ° C is a vegetable oil, it can for example be an oil chosen from the group comprising or consisting of linseed, safflower, soybean, corn, cotton, rape, castor oil, abrasive oils , pine, sunflower, palm, olive, coconut, peanut, grape seed and mixtures of these oils. Vegetable oil is preferably rich in oleic acid, that is to say that the fatty acid (or all of the fatty acids if several are present) from which it is derived, comprises oleic acid according to a mass fraction. at least equal to 60%, even more preferably according to a mass fraction at least equal to 70%. As vegetable oil, a sunflower oil is advantageously used which is such that all of the fatty acids from which it is derived comprises oleic acid according to a mass fraction equal to or greater than 60%, preferably 70% and, according to a particularly advantageous embodiment of the invention, according to a mass fraction equal to or greater than 80%.

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

As an example of phosphate plasticizers, mention may be made of those which contain between 12 and 30 carbon atoms, for example trioctyl phosphate. Mention may in particular be made, as examples of plasticizers of esters of carboxylic acid, of the compounds chosen from the group consisting of trimellitates, pyromellitates, phthalates, 1,2-cyclohexane dicarboxylates, adipates, azelates, sebacates , glycerol triesters and mixtures of these compounds. Among the above triesters, mention may in particular be made of glycerol triesters, preferably consisting mainly (for more than 50%, more preferably for more than 80% by weight) of an unsaturated Cis fatty acid, that is to say ie chosen from the group consisting of oleic acid, linoleic acid, linolenic acid and mixtures of these acids. The glycerol triester is preferred. More preferably, whether it is of synthetic or natural origin (case for example of vegetable oils of sunflower or rapeseed), the fatty acid used is constituted for more than 50% by weight, more preferably still for more than 80 % by weight of oleic acid. Such triesters (trioleates) with a high oleic acid content are well known, they have been described for example in application WO 02/088238, as plasticizers in tire treads.

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

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

II-3.3 Viscous plasticizing resin at 20 ° C

Although this is not necessary for the implementation of the present invention, the plasticizer system of the rubber composition of the tread of the tire according to the invention may comprise a viscous plasticizer resin at 20 ° C, called "de low Tg ", that is to say which by definition has a Tg comprised in a range from -40 ° C. to 20 ° C. According to the invention, the composition can optionally comprise, in addition to or in substitution for all or part of the plasticizer liquid at 23 ° C, from 0 to 110 phr of viscous plasticizer resin at 20 ° C.

Preferably, the viscous plasticizing resin at 20 ° C. exhibits at least any one, preferably 2 or 3, preferably all, of the following characteristics:

a Tg of between -40 ° C and 0 ° C, more preferably between -30 ° C and 0 ° C and more preferably still between -20 ° C and 0 ° C;

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

a softening point in a range from 0 to 50 ° C, preferably from 0 to 40 ° C, more preferably from 10 to 40 ° C, preferably from 10 to 30 ° C;

a polymolecularity index (Ip) less than 3, more preferably less than 2 (reminder: Ip = Mw / Mn with Mw average molecular weight by weight).

The viscous plasticizing resins above preferential at 20 ° C. are well known to those skilled in the art and are commercially available, for example sold with regard to:

aliphatic resin: by CRAY VALLEY under the name "Wingtack 10" (Mn = 480 g / mol; Mw = 595 g / mol; Ip = 1.2; SP = 10 ° C; Tg = -28 ° C), coumarone resins indene: by the company Rütgers Chemicals under the name "Novares C30" (Mn = 295 g / mol; Mw = 378 g / mol; Ip = 1.28; SP = 25 ° C; Tg = 19 ° C);

C9 cutting resins: by the company Rütgers Chemicals under the name "Novares TT30" (Mn = 329 g / mol; Mw = 434 g / mol; Ip = 1.32; SP = 25 ° C; Tg = 12 ° C).

When a viscous plasticizing resin at 20 ° C. is used, its content in the composition of the tread according to the invention can be included in a range ranging from 5 to 110 phr, preferably from 30 to 90 phr.

Very advantageously, the total level of liquid plasticizer at 23 ° C and viscous plasticizer resin at 20 ° C is within a range from 5 to 110 phr, preferably from 20 to 100 phr, preferably from 30 to 90 phr.

II-3.4 Tg of the composition

A person skilled in the art knows how to adapt the Tg of the rubber composition by adjusting the level of the plasticizer system.

In a particularly advantageous manner, the plasticizer system is present in an amount such that the glass transition temperature (Tg) of the composition is within a range from -45 ° C to 0 ° C, preferably from -25 ° C to -5 ° C.

The glass transition temperature Tg of the compositions according to the invention is determined on a viscoanalyzer (Metravib VA4000), according to standard ASTM D 5992-96. The dynamic properties are measured on a crosslinked composition sample, that is to say cooked to a conversion rate of at least 90%, the sample having the shape of a cylindrical test piece having a thickness equal to 2 mm and a section equal to 78.5 mm ² . The response of the elastomeric mixture sample to a sinusoidal stress in alternating single shear is recorded, having a peak-peak amplitude equal to 0.7 MPa and a frequency equal to 10 Hz. A temperature scan is carried out at rising speed at a constant temperature of + 1.5 ° C / min. The results used are generally the complex dynamic shear modulus G *, comprising an elastic part G 'and a viscous part G ”, and the dynamic loss tanô, equal to the ratio G” / G'. The glass transition temperature Tg is the temperature at which the dynamic loss tanô reaches a maximum during the temperature sweep.

Π-4 Crosslinking system

II-4-1 Organic peroxide

According to the invention, the rubber composition of the tread comprises at least one organic peroxide. The organic peroxide used in the process according to the invention can be any organic peroxide known to those skilled in the art.

The organic peroxide is preferably chosen from the group comprising or consisting of dialkyl peroxides, monoperoxycarbonates, diacyl peroxides, peroxyketals or peroxy esters.

Preferably, the dialkyl peroxides are chosen from the group comprising or consisting of dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, 2,5dimethyl-2,5-di (t-butylperoxy ) hexane, 2,5-dimethyl-2,5-di (t-amylperoxy) -hexane, 2,5dimethyl-2,5-di (t-butylperoxy) hexyne-3, 2,5-dimethyl-2 , 5-di (t-amylperoxy) hexyne-3, α, α'di - [(t-butyl-peroxy) isopropyl] benzene, le a, a'-di - [(t-amyl-peroxy) isopropyl] benzene , di-t-amyl peroxide, 1,3,5-tri - [(t-butylperoxy) isopropyl] benzene, 1,3-dimethyl-3- (tbutylperoxy) butanol, and 1,3-dimethyl -3- (t -amylperoxy) butanol.

Certain monoperoxycarbonates such as OO-tert-butyl-O- (2-ethylhexyl) monoperoxycarbonate, OO-tert-butyl-O-isopropyl monoperoxycarbonate and OO-tert-amyl-O2-ethyl hexyl monoperoxycarbonate, can also be used.

Among the diacyl peroxides, the preferred peroxide is benzoyl peroxide.

Among the peroxyketals, the preferred peroxides are chosen from the group comprising or consisting of 1,1-di- (t-butylperoxy) -3,3,5-trimethylcyclohexane, 4,4-di- (tbutylperoxy) valerate of n -butyl, ethyl 3,3-di- (t-butylperoxy) butyrate, 2,2-di- (tamylperoxy) -propane, 3,6,9-triethyl-3,6,9-trimethyl- 1,4,7-triperoxynonane (or cyclic trimer methyl ethyl ketone peroxide), 3,3,5,7,7-pentamethyl-1,2,4-trioxepane, 4,4-bis (tamylperoxy) valerate n-butyl, ethyl 3,3-di (t-amylperoxy) butyrate, 1,1-di (t butylperoxy) cyclohexane, 1,1-di (t-amylperoxy) cyclohexane and mixtures thereof. Preferably, the peroxyesters are chosen from the group consisting of tertbutylperoxybenzoate, tert-butyleperoxy-2-ethylhexanoate and tert-butyleperoxy-3,5,5trimethylhexanoate.

In summary, the organic peroxide is, in a particularly preferred manner, chosen from the group consisting of dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, peroxide ditertbutyl, tertbutylcumyle peroxide, 2,5-bis (tertbutylperoxy) -2,5-dimethylhexane, n-butyl4,4'-di (tert-butylperoxy) valerate, OO- (t-butyl) -O - (2-ethylhexyl) monoperoxycarbonate, tert-butyl peroxyisopropylcarbonate, tertio-butyl peroxybenzoate, tert-butyl peroxy3,5,5-trimethylhexanoate, l, 3 (4) -bis (tert-butylperoxyisopropyl) benzene and their mixtures . More preferably, the organic peroxide is chosen from the group consisting of from the group consisting of dicumyl peroxide, n-butyl-4,4'-di (tert-butylperoxy) -valerate, OO- (t-butyl) O- (2-ethylhexyl) monoperoxycarbonate, tert-butyl peroxyisopropylcarbonate, tertio-butyl peroxybenzoate, tert-butyl peroxy-3,5,5trimethylhexanoate, 1,3 (4) -bis (tert-butylperoxyisopropyl) benzene and their mixtures.

The level of peroxide in the composition can be included in a range ranging from 0.2 to 10 phr. More preferably, the amount of peroxide in the composition is within a range from 1 to 8, preferably from 0.8 to 8 phr, more preferably from 2 to 6 phr.

II-4-2 Sulfur

Furthermore, the rubber composition according to the invention is advantageously free of sulfur as vulcanizing agent, or contain less than 0.3 phr and preferably less than 0.1 phr. The sulfur can be molecular sulfur or come from a sulfur donor, such as alkyl phenol disulfides (APDS). Very advantageously, the composition of the tread according to the invention is free of sulfur as a vulcanizing agent.

II-4-3 Acrylate derivative

Furthermore, the rubber composition of the tread according to the invention is advantageously free of acrylate derivative of formula (I):

[X] p A (i) in which, o [X] p corresponds to a radical of formula (II):

P (II) in which,

Ri, R ₂ and R3 independently represent a hydrogen atom or a Ci-Cg hydrocarbon group chosen from the group consisting of linear, branched or cyclic alkyl groups, alkylaryl groups, aryl groups and aralkyls, and optionally interrupted by one or more heteroatoms, R ₂ and R3 can together form a non-aromatic ring, (*) represents the point of attachment of the radical of formula (II) to A, where A represents an atom belonging to the group consisting of alkaline earth metals or the transition metals, a carbon atom or a Ci-Cg hydrocarbon group, o A comprising p free valences, p having a value ranging from 2 to 4, o it being understood that the 2 to 4 radicals X are identical or different , or contains less than 1 pce, preferably less than 0.8 pce. Very advantageously, the composition of the tread according to the invention is free from the acrylate derivative of formula (I) above.

Π-5 Miscellaneous additives

The rubber composition of the tread of the tire according to the invention may also comprise all or part of the usual additives usually used in elastomer compositions for tires, such as, for example, reinforcing resins, fillers other than those mentioned above, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, anti-oxidants, anti-fatigue agents, well known to those skilled in the art.

Π-6 Preparation of rubber compositions

The rubber composition of the tread according to the invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art:

a first thermomechanical working phase or kneading (so-called “nonproductive” phase), which can be carried out in a single thermomechanical step during which one introduces, into a suitable mixer such as a usual internal mixer (for example of the 'Banbury type '), all the necessary constituents, in particular the elastomeric matrix, silica, any other miscellaneous additives, with the exception of peroxide. The incorporation of the filler into the elastomer, when it is present, can be carried out in one or more times by thermomechanically kneading. The non-productive phase is carried out at high temperature, up to a maximum temperature between 110 ° C and 200 ° C, preferably between 130 ° C and 185 ° C, for a period generally between 2 and 10 minutes.

a second mechanical working phase (so-called "productive" phase), which is carried out in an external mixer such as a cylinder mixer, after cooling of the mixture obtained during the first non-productive phase to a lower temperature , typically below 120 ° C, for example between 40 ° C and 100 ° C. The peroxide is then incorporated, and the whole is then mixed for a few minutes, for example between 2 and 15 min.

The final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for characterization in the laboratory, or else extradited in the form of a semi-finished (or profiled) rubber usable by example as a tire tread or as an inner tire layer.

Cooking can be carried out, in a manner known to a person skilled in the art, at a temperature generally between 130 ° C. and 200 ° C., under pressure, for a sufficient time which can vary for example between 5 and 90 min depending in particular the baking temperature, the crosslinking system adopted, the crosslinking kinetics of the composition under consideration or even the size of the tire.

Π-7 Tread and tire

In a known manner, the tread of a tire, whether it is intended to equip a passenger vehicle or other, comprises a rolling surface intended to be in contact with the ground when the tire is rolling. The tread is provided with a tread comprising in particular tread elements or elementary blocks delimited by various main grooves, longitudinal or circumferential, transverse or even oblique, the elementary blocks being able moreover to have various incisions or finer lamellae. The grooves constitute channels intended to evacuate the water during rolling on wet ground and the walls of these grooves define the leading and trailing edges of the tread elements, according to the direction of the turn.

The present invention also relates to a tire provided with a tread according to the invention.

The invention relates particularly to tires intended to equip motor vehicles of the tourism and SUV (Sport Utility Vehicles) type.

The invention relates to the tires and semi-finished products for tires described above, to rubber articles, both in the raw state (that is to say, before baking) and in the cooked state (that is to say , after crosslinking or vulcanization).

III- EXAMPLES

III-1 Measurements and tests used

Dynamic properties:

The dynamic properties G * and tan (ô) Max are measured on a viscoanalyzer (Metravib VA4000), according to standard ASTM D5992-96. The response of a sample of vulcanized composition (cylindrical specimen 2 mm thick and 79 mm ² in section) is recorded, subjected to a sinusoidal stress in alternating single shear, at the frequency of 10 Hz, under normal conditions of temperature (23 ° C), at 0 ° C or 100 ° C according to ASTM D 1349-09 for tan (ô) Max measurements, or at -10 ° C for G * measurements. A deformation amplitude sweep is carried out from 0.1% to 50% (outward cycle), then from 50% to 0.1% (return cycle).

The results used are the loss factors tan (ô) at 0 ° C and 100 ° C. On the return cycle, the loss factor is recorded, noted tan (ô) Max.

The results of tan (ô) Max at 0 ° C. are expressed in base 100, the value 100 being assigned to the control. A result greater than 100 indicates improved performance, that is to say that the composition of the example considered reflects better grip on wet ground of the tread comprising such a composition.

The results of tan (ô) Max at 100 ° C. are expressed in base 100, the value 100 being assigned to the control. A result greater than 100 indicates improved performance, that is to say that the composition of the example considered reflects better grip on dry ground of the tread comprising such a composition.

Tensile tests:

These tensile tests make it possible to determine the elastic moduli and the breaking properties and are based on the French standard NF T 46-002 of September 1988.

A processing of the traction records also makes it possible to plot the module curve as a function of the elongation. The module used here being the nominal (or apparent) secant module measured in first elongation, calculated by reducing to the initial section of the test piece. The first secant modules (or apparent stresses, in MPa) at 10%, 100% and 300% elongation, noted respectively MSA10, MSA100 and MSA300, are measured at first elongation at 100 ° C ± 2 ° C.

The results of MS A3 00 at 100 ° C. are expressed in base 100, the value 100 being assigned to the control. A result greater than 100 indicates improved performance, that is to say that the composition of the example considered reflects a resistance to severe wear of the tread comprising such a composition.

III-2 Preparation of the compositions

In the following examples, the rubber compositions were produced as described in point II.6 above. In particular, the “non-productive” phase was carried out in a 0.4 liter mixer for 3.5 minutes, for an average speed of pallets of 50 revolutions per minute until reaching a maximum drop temperature of 160 °. vs. The "productive" phase was carried out in a cylinder tool at 23 ° C for 5 minutes.

III-3 Tests of rubber compositions

The examples presented below are intended to compare the resistance to severe wear and the adhesion on dry and wet soil of a composition in accordance with the present invention (Cl) with a control composition (Tl) of 1 'prior art which differs from Cl only in the level of silica as reinforcing filler (the rate of coupling agent used is maintained at a content of 8% by weight relative to the weight of silica). Other compositions in accordance with the invention (C2, C3, C4, C5, C6) were also tested to determine the effect of different functionalized diene elastomers, the addition of liquid plasticizer and another blend of reinforcing filler. The formulations analyzed (in pce) and the results obtained are presented in Table 1 below.

Table 1

tl Cl C2 C3 C4 C5 C6 SBR 1 (a) 100 100 - 85 50 100 100 SBR 2 (b) - - 57 - - - - SBR 3 (c) - - - - 50 - - BR (d) - - 43 - - - - Natural rubber - - - 15 - - - Silica 110 170 170 170 170 170 160 Carbon black (f) 5 5 5 5 5 5 15 Plasticizing resin (g) 90 90 90 90 90 70 90 Liquid plasticizer (h) - - - - - 20 - Peroxide (i) 4 4 4 4 4 4 4 Antioxidant (j) 3.5 3.5 3.5 3.5 3.5 3.5 3.5 TMQ (k) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Anti-ozone wax (1) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Coupling agent (m) 8.8 13.6 13.6 13.6 13.6 13.6 12.8 DPG (n) 3.5 3.5 3.5 3.5 3.5 3.5 3.5 Ac. stearic (o) 3 3 3 3 3 3 3 ZnO (p) 1.2 1.2 1.2 1.2 1.2 1.2 1.2 MSA300 at 100 ° C 100 141 132 130 125 132 152 tan (ô) Max 100 ° C 100 132 144 135 153 134 140 tan (ô) Max 0 ° C 100 131 133 138 123 120 127

a) SBR 1: SBR with 3% of styrene unit and 13% of unit 1,2 of the butadiene part carrying an amino-alkoxysilane function in the middle of the elastomer chain (Tg -88C)

b) SBR2: SBR (starred Sn) with 26% of styrene unit and 24% of unit 1,2 of the butadiene part 10 carrying silanol function at the end of the elastomer chain (Tg -65 ° C)

c) SBR 3: SBR with 24.5% of styrene unit and 24% of unit 1,2 of the butadiene part carrying amino-alkoxysilane function in the middle of the elastomer chain (Tg -48 ° C)

d) BR: Polybutadiene with 0.5% of unit 1,2 and 97% of 1,4-cis (Tg = -108 ° C)

e) “Zeosil 1165 MP” silica from the company Rhodia of the “HDS” type

f) ASTM N234 grade (Cabot company)

g) C5 / C9 resin (“ECR-373 resin” from ExxonMobil)

h) TDAE oil ("Vivatec 500" from Klaus Dahleke)

i) 1,3 (4) -bis (tert-butylperoxyisopropyl) benzene "Luperox F40MG" from Arkema)

j) N-1,3-dimethylbutyl-N-phenylparaphenylenediamine (“Santoflex 6-PPD” from the company Flexsys)

k) 2,2,4-trimethyl-1,2-dihydroquinoline (“TMQ” from the company Lanxess)

l) Anti-ozone wax (“VARAZON 4959” from the company Sasol Wax)

m) TESPT (“Si69” from Degussa)

n) Diphenylguanidine (“Perkacit” DPG from the company Flexsys)

o) Stearin (“Pristerene 4931” from Uniqema)

p) Zinc oxide (industrial grade - Umicore company)

These results show that the increase in the amount of silica as reinforcing filler in compositions mainly comprising at least one elastomer based on polybutadiene, modified with a functional group capable of interacting with silica as reinforcing filler and a peroxide crosslinking system improves both resistance to severe wear and grip on dry and wet surfaces.

Claims (23)

1. Tire tread comprising a rubber composition based on at least: from 50 to 100 phr of a first diene elastomer, the first diene elastomer being a polybutadiene-based elastomer, modified with a functional group capable of interacting with silica as a reinforcing filler, optionally from 0 to 50 phr '' a second diene elastomer different from the first diene elastomer, between 150 and 220 phr of silica as reinforcing filler, a coupling agent, a plasticizing system comprising a plasticizing resin having a glass transition temperature above 20 ° C, a system crosslinking based on organic peroxide, the total level of the first diene elastomer and of the second diene elastomer in the composition being within a range from 80 to 100 phr. 2. A tread according to claim 1, the functional group capable of interacting with silica as a reinforcing filler of the first diene elastomer is at least one alkoxysilane group linked to the elastomer by its silicon atom. 3. The tread according to claim 2, in which the alkoxysilane group of the first diene elastomer is disposed inside the elastomer chain of the first diene elastomer. 4. The tread according to claim 2 or 3, wherein the first diene elastomer further carries at least one primary, secondary or tertiary amine function. 5. A tread according to claim 4, in which the primary, secondary or tertiary amine function is carried, directly or by means of a spacer group, by the silicon atom of the alkoxysilane group of the first diene elastomer. 6. A tread according to claim 4 or 5, in which the alkoxysilane group carrying the primary, secondary or tertiary amine function corresponds to one of the following formulas (I) to (III):

Formula (III) Formula (I) Formula (II) in which: E denotes the first diene elastomer, Ri and Rs, identical or different, denote the first diene elastomer or an oxygen atom substituted by a hydrogen atom or an alkyl radical, linear or branched, Cmo, C5-18 cycloalkyl, C6-is aryl or C7-18 aralkyl; R ₂ is a divalent, linear or branched hydrocarbon radical of C1-10 alkyl, C6-aryl or C7-18 aralkyl; R3 and R4, identical or different, represent a hydrogen atom or a C1-10 alkyl radical, provided that when one of R3 and R4 represents a hydrogen atom the other is different, or then R3 and R4 form with N to which they are linked a heterocycle containing a nitrogen atom and at least one carbon atom; R5 represents an alkylidene radical, linear or branched, in Cmo; the symbols A denote, independently of one another, a nitrogen atom or a carbon atom, provided that at least one of the symbols A denotes a nitrogen atom. 7. A tread according to claim 6, in which: Ri represents an oxygen atom substituted by a methyl or ethyl radical; and or R2 represents the ethane-1,2-diyl or propane-1,3-diyl radical; and or, R3 and R4, identical or different, represent a methyl or ethyl radical; and / or Rs represents a linear or branched C 4-6 alkylidene radical; and / or a single A denotes a nitrogen atom and is located in the meta or para position of the ring with respect to -R2; and or R6 denotes the first diene elastomer. 8. A tread according to any one of the preceding claims, in which the first diene elastomer is a styrene-butadiene copolymer. 9. A tread according to claim 8, in which the first diene elastomer is a styrene-butadiene copolymer having at least one of the following properties: it is a styrene-butadiene copolymer prepared in solution (SSBR), its mass content of styrene relative to the total weight of the styrenebutadiene copolymer is between 1 and 15%, preferably between 1 and 4%, its molar content of vinyl bonds of the butadiene part is between 4 and 25%, preferably between 10 and 15%, its Tg is less than -60 ° C, preferably between -100 ° C and -80 ° C. 10. A tread according to any one of the preceding claims, in which the second diene elastomer is chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and mixtures of these elastomers. 11. A tread according to any one of the preceding claims, in which the level of the first diene elastomer in the composition is in a range from 80 to 100 phr, and the level of the second diene elastomer in the composition is in a range from 0 to 20 pce. 12. Tread according to any one of the preceding claims, in which the total level of the first diene elastomer and of the second diene elastomer in the composition is within a range ranging from 90 to 100 phr, preferably 100 phr. 13. A tread according to any one of the preceding claims, in which the plasticizing resin having a glass transition temperature greater than 20 ° C. is chosen from the group consisting of homopolymer or copolymer resins of cyclopentadiene, resins of homopolymer or copolymer of dicyclopentadiene, homopolymer or copolymer resins of terpene, homopolymer or copolymer resins of C5 cut, homopolymer or copolymer resins of C9 cut, homopolymer or copolymer resins of alpha- methyl styrene and mixtures thereof. 14. A tread according to any one of the preceding claims, in which the level of plasticizing resin having a glass transition temperature greater than 20 ° C. in the composition is within a range ranging from 35 to 220 phr, preferably from 50 to 200 pce. 15. A tread according to any one of the preceding claims, in which the plasticizer system optionally comprises from 0 to 110 phr of plasticizer at 23 ° C. 16. A tread according to claim 15, in which the level of liquid plasticizer at 23 ° C in the composition is in a range from 5 to 110 phr, preferably from 30 to 90 phr. 17. A tread according to claim 15 or 16, in which the plasticizer liquid at 23 ° C is chosen from the group consisting of liquid diene polymers, polyolefin oils, naphthenic oils, paraffinic oils, DAE oils, MES oils, TDAE oils, RAE oils, TRAE oils, SRAE oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures thereof 18. A tread according to any one of the preceding claims, in which the plasticizer system is present in an amount such that the glass transition temperature of the composition is within a range from -45 ° C to 0 ° C. 19. A tread according to any one of the preceding claims, in which the organic peroxide is chosen from the group consisting of dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, ditertbutyl peroxide, tertbutylcumyl peroxide, 2,5-bis (tertbutylperoxy) -2,5-dimethylhexane, n-butyl-4,4'-di (tert-butylperoxy) valerate, OO- (tbutyl) -O- (2-ethylhexyl) monoperoxycarbonate, tert-butyl peroxyisopropylcarbonate, tertio-butyl peroxybenzoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, l, 3 (4) -bis (tertbutylperoxyisopropyl) benzene and their mixtures. 20. A tread according to any one of the preceding claims, in which the level of organic peroxide in the composition is within a range ranging from 0.8 to 8 phr, preferably from 2 to 6 phr. 21. A tread according to any one of the preceding claims, in which the composition does not comprise an acrylate derivative of formula (I), or comprises less than 1 pce: [X] p A (i) in which, o [X] p corresponds to a radical of formula (II):

in which, Ri, R2 and R3 independently represent a hydrogen atom or a C1-Cg hydrocarbon group chosen from the group consisting of linear, branched or cyclic alkyl groups, alkylaryl groups, aryl groups and aralkyls, and optionally interrupted by one or more heteroatoms, R2 and R3 can together form a non-aromatic ring, (*) represents the point of attachment of the radical of formula (II) to A, where A represents an atom belonging to the group consisting of metals alkaline earth or transition metals, a carbon atom or a C1-Cg hydrocarbon group, o A comprising p free valences, p having a value ranging from 2 to 4, it being understood that the 2 to 4 radicals X are identical or different . 22. A tread according to any one of the preceding claims, in which the composition does not contain butyl rubber or comprises less than 10 phr, preferably less than 5 phr. 23. A tire provided with a tread according to any one of claims 1 to 22.