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    • 专利摘要:
    The invention relates to a tire whose tread comprises a rubber composition based on at least 90 to 100 phr of one or more diene elastomers known as very low glass transition temperature (Tg) having a Tg included in a ranging from -110 ° C to -80 ° C, selected from butadiene homopolymers, copolymers of butadiene and vinylaromatic monomer, having a vinylaromatic unit level of between 0 and 5% by weight, and mixtures of these last ; a reinforcing filler, said reinforcing filler comprising predominantly by weight a so-called low surface area silica, having a CTAB specific surface area of between 50 and 100 m 2 / g; a coupling agent providing the bond between the silica and the diene elastomer; a plasticizer system, said plasticizer system comprising at least more than 15 phr (parts by weight per hundred parts by weight of elastomer) of a so-called high Tg hydrocarbon resin having a Tg greater than 20 ° C; and a crosslinking system.
    公开号:FR3045631A1
    申请号:FR1562820
    申请日:2015-12-18
    公开日:2017-06-23
    发明作者:Floriandre Voisin；Christine Nourry；Karine Longchambon
    申请人:Michelin Recherche et Technique SA Switzerland ；Compagnie Generale des Etablissements Michelin SCA；Michelin Recherche et Technique SA France；
    IPC主号:
    专利说明:

    [001] The invention relates to tires, in particular to tire treads and more particularly to tire tread compositions.
    [002] Since fuel savings and the need to protect the environment have become a priority, it has been necessary to produce tires with reduced rolling resistance while retaining the other properties of the tire.
    [003] In the field of reinforcing fillers, this has been made possible in particular by the use, in the treads of these tires, of new rubber compositions reinforced with inorganic fillers, in particular specific silicas of the highly dispersible type. , capable of competing from the reinforcing point of view with a conventional pneumatic grade carbon black, while offering these compositions a lower hysteresis, synonymous with a lower rolling resistance for the tires comprising them, as well as adhesion improved on wet, snowy or icy ground.
    In parallel with silicas of high specific surface area, used for several years in the tire, silicas of low specific surface area have been described for their use in tire composition in the document WO2003 / 002649, which describes compositions using a silica of low specific surface area, in compositions in which the majority elastomer has Tg customary tire, including a styrene-butadiene copolymer of Tg -29 ° C.
    [005] At present, the applicants have shown that the combined use of a low specific surface silica with a very low Tg diene elastomer and a plasticizer system comprising a thermoplastic resin makes it possible to obtain a new balance between the difficult performances. to reconcile, rolling resistance, wet grip and cohesion of the mixture. This performance offset is expressed in particular by a very significant decrease in the rolling resistance of the tires while retaining good cohesion properties of the mixture and adhesion on wet ground.
    [006] The invention therefore relates to a tire whose tread comprises a rubber composition based on at least 90 to 100 phr of one or more diene elastomers so-called very low glass transition temperature (Tg) having a Tg ranging from -110 ° C to -80 ° C, selected from homopolymers of butadiene, copolymers of butadiene and vinylaromatic monomer, having a vinylaromatic unit level of between 0 and 5% by weight, and mixtures of these; a reinforcing filler, said reinforcing filler comprising predominantly by weight a so-called low surface area silica, having a CTAB specific surface area of between 50 and 100 m 2 / g; a coupling agent providing the bond between the silica and the diene elastomer; a plasticizer system, said plasticizer system comprising at least more than 15 phr (parts by weight per hundred parts by weight of elastomer) of a so-called high Tg hydrocarbon resin having a Tg greater than 20 ° C; and a crosslinking system.
    [007] Preferably, the tire according to the invention will be selected from tires intended to equip a two-wheeled vehicle, a passenger vehicle, or a vehicle called "heavyweight" (that is to say, subway, bus , off-the-road vehicles, road transport equipment such as trucks, tractors, trailers), or aircraft, civil engineering, agrarian, or handling equipment. I-Constituents of the Composition [008] The tire tread compositions according to the invention are based on at least 90 to 100 phr of one or more diene elastomers known as very low glass transition temperature (Tg). having a Tg ranging from -110 ° C to -80 ° C, selected from butadiene homopolymers, copolymers of butadiene and vinylaromatic monomer, having a vinylaromatic unit level of between 0 and 5% by weight , and mixtures thereof; a reinforcing filler, said reinforcing filler comprising predominantly by weight a so-called low surface area silica, having a CTAB specific surface area of between 50 and 100 m 2 / g; a coupling agent providing the bond between the silica and the diene elastomer; a plasticizer system, said plasticizer system comprising at least more than 15 phr (parts by weight per hundred parts by weight of elastomer) of a so-called high Tg hydrocarbon resin having a Tg greater than 20 ° C; and a crosslinking system. These various essential elements and the preferred embodiments are detailed in the following.
    By the term "composition based on" is meant a composition comprising the mixture and / or the reaction product in situ of the various basic constituents used, some of these constituents being able to react and / or being intended to react. between them, at least partially, during the various phases of manufacture of the composition, or during the subsequent firing, modifying the composition as it was initially prepared. Thus, the compositions as implemented for the invention may be different in the uncrosslinked state and in the crosslinked state.
    In the present description, unless otherwise expressly indicated, all the percentages (%) indicated are percentages by weight. On the other hand, any range of values designated by the expression "between a and b" represents the range of values from more than a to less than b (i.e. terminals a and b excluded) while any range of values designated by the term "from a to b" means the range from a to b (i.e., including the strict limits a and b).
    When reference is made to a "majority" compound, for the purposes of the present invention, it is understood that this compound is predominant among the compounds of the same type in the composition, that is to say that it is the one which represents the largest quantity in mass among the compounds of the same type. Thus, for example, a majority polymer is the polymer representing the largest mass relative to the total mass of the polymers in the composition. In the same way, a so-called majority charge is that representing the largest mass among the charges of the composition. For example, in a system comprising a single polymer, it is the majority within the meaning of the present invention; and in a system comprising two polymers, the majority polymer accounts for more than half of the mass of the polymers. In contrast, a "minor" compound is a compound that does not represent the largest mass fraction among compounds of the same type.
    In the present application, when reference is made to a ratio of the amounts of a compound A and a compound B, or a ratio between the level of a compound A and the level of a compound B it is always the ratio in the mathematical sense of the amount of compound A over the amount of compound B.
    In the present description, Tg is understood to mean the glass transition temperature of a compound, in particular of the very low Tg diene elastomer of the invention, measured according to the ASTM D3418 standard. 1-1 Diene Elastomer The composition of the tread of the tire according to the invention may contain a single diene elastomer or a mixture of several diene elastomers.
    By elastomer (or "rubber", the two terms being considered synonymous) of the "diene" type, it is recalled here that must be understood in a known manner (one or more elastomers) at least in part ( ie, a homopolymer or copolymer) of diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or otherwise).
    The diene elastomers can be classified in two categories: "essentially unsaturated" or "essentially saturated". The term "essentially unsaturated" is generally understood to mean a diene elastomer derived at least in part from conjugated diene monomers, having a level of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%); Thus, diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins of the EPDM type do not fall within the above definition and may in particular be described as "essentially saturated" diene elastomers ( low or very low diene origin, always less than 15%). In the category of "essentially unsaturated" diene elastomers, the term "highly unsaturated" diene elastomer is particularly understood to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.
    These definitions being given, and as is well known to those skilled in the art, the term diene elastomer is more particularly understood to mean: (a) any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms; carbon; (b) any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms; (c) a ternary copolymer obtained by copolymerization of ethylene, an α-olefin having 3 to 6 carbon atoms with a non-conjugated diene monomer having from 6 to 12 carbon atoms, for example elastomers obtained from ethylene, propylene with a nonconjugated diene monomer of the aforementioned type such as in particular 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene; (d) a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated versions, in particular chlorinated or brominated, of this type of copolymer.
    For the purposes of the invention, the composition of the tread comprises, at a rate in a range from 90 to 100 phr, one or more diene elastomers said to be very low Tg, that is to say having a Tg ranging from -110 ° C to -80 ° C, the latter being chosen from butadiene homopolymers, copolymers of butadiene and vinylaromatic monomer, having a vinylaromatic unit level of between 0 and 5 % by weight, and mixtures thereof. Thus, the butadiene and vinylaromatic monomer copolymers may contain from 95 to less than 100% by weight of diene units and from more than 0 to 5% by weight of vinylaromatic units.
    As vinylaromatic compounds are suitable for example styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene.
    The 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 amounts of modifying and / or randomizing agent used. The elastomers can be, for example, block, random, sequenced, microsequenced, and be prepared in dispersion or in solution. In the case of a copolymer based on a diene and a vinyl aromatic, in particular containing butadiene and styrene, preferably the two monomers are statistically distributed.
    Said diene elastomer of very low Tg may be coupled and / or star-shaped or functionalized by a group introduced via a coupling agent and / or starring or functionalization known to those skilled in the art. This grouping can be at the end of the linear main elastomer chain. It will then be said that the diene elastomer is functionalized at the end or end of the chain. This is generally an elastomer obtained by reacting a living elastomer with a functionalizing agent, that is to say any molecule that is at least monofunctional, the function being any type of chemical group known to those skilled in the art for reacting with a piece of living chain.
    This group may be in the linear elastomeric main chain. It will be said that the diene elastomer is coupled or functionalized in the middle of the chain, as opposed to the position "at the end of the chain" and although the group is not precisely in the middle of the elastomeric chain. It is generally an elastomer obtained by reaction of two chains of the elastomer living on a coupling agent, that is to say any molecule at least difunctional, the function being any type of chemical group known by the man of the art to react with a piece of living chain.
    This group can be central to which n elastomer chains (n> 2) are linked forming a star structure. It will then be said that the diene elastomer is starred. It is generally an elastomer obtained by reaction of n chains of the elastomer living on a staring agent, that is to say any multifunctional molecule, the function being any type of chemical group known to those skilled in the art to react with a piece of living chain.
    Those skilled in the art will understand that a functionalization reaction with an agent comprising more than one reactive function vis-à-vis the living elastomer, results in a mixture of functionalized end-of-pipe species and mid-chain, constituting the linear chains of the functionalized elastomer, as well as, if appropriate, of star-shaped species. Depending on the operating conditions, mainly the molar ratio of the functionalizing agent to the living chains, certain species are in the majority in the mixture.
    Preferably for the purposes of the invention, said very low Tg diene elastomer has a Tg ranging from -100 ° C to -80 ° C, preferably from -95 ° C to -80 ° C. .
    Also preferably, said diene elastomer of very low Tg has a Mooney viscosity in a range from 50 to 80. In the present description, by Mooney viscosity, Mooney viscosity means the Mooney ML (1 + 4) 100 ° viscosity. C of a compound, especially the modified diene elastomer of the invention, measured according to ASTM D1646.
    According to a preferred embodiment, said very low Tg diene elastomer comprises a copolymer of butadiene and vinylaromatic monomer, preferably styrene, having a vinylaromatic unit level of between 0 and 5% by weight, preferably from 1 to 4% by weight, as well as a proportion of vinylic unit relative to the diene portion ranging from 8 to 15% by weight, preferably from 10 to 15% by weight, relative to the total weight of the diene elastomer.
    Preferably, at least 70% by weight of said butadiene and vinylaromatic monomer copolymer is functionalized, preferably with an alkoxysilane group, optionally partially or completely hydrolysed to silanol, the alkoxysilane group carrying, or not, another function capable of interacting with a reinforcing filler the alkoxysilane group being bonded to the diene elastomer via the silicon atom. Preferably, said copolymer of butadiene and vinylaromatic monomer is functionalized mainly in the middle of the chain. The microstructure of these elastomers can be determined by the presence or absence of a polar agent and the amounts of polar agent employed in the anionic polymerization step. Preferably, when the diene elastomer is based on a diene and styrene, a polar agent is used during the polymerization step in such amounts as to promote the statistical distribution of styrene along the polymer chains while retaining the ratio of -1,2 bonds preferably between 8% and 15%, preferably 10 to 15%.
    The term "alkoxysilane group interacting in a privileged manner with the reinforcing filler" or "function capable of interacting with a reinforcing filler", any alkoxysilane group or other function, preferably amine, capable of forming, within a reinforced rubber composition by means of a filler, a physical or chemical bond with said filler. This interaction can be established for example by means of covalent, hydrogen, ionic and / or electrostatic bonds between said function and functions present on charges.
    The alkoxy radical of the alkoxysilane group may be of formula R'O-, where R 'represents a substituted or unsubstituted C1-C10 or even C1-C8 alkyl group, preferably a C1-C8 alkyl group. C4, more preferably methyl and ethyl.
    In a very preferred manner according to this second variant, the other function capable of interacting with a reinforcing filler is a primary, secondary or tertiary amine. This variant of the invention is particularly advantageous because of the improvement of the hysteretic properties.
    In the present description, the term "primary or secondary amine" means a primary or secondary amine protected or not by a protective group known to those skilled in the art.
    As secondary or tertiary amine functional groups, mention may be made of amines substituted with C 1 -C 10 alkyl radicals, preferably C 1 -C 4 alkyl radicals, more preferably methyl or ethyl radicals, or else 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 methylamino-, dimethylamino-, ethylamino-, diethylamino-, propylamino-, dipropylamino-, butylamino-, dibutylamino-, pentylamino-, dipentylamino-, hexylamino-, dihexylamino-, hexamethyleneamino- groups, preferably the diethylamino groups, are suitable. and dimethylamino- [0034] Preferably, the function capable of interacting with a reinforcing filler is a tertiary amine function, preferably diethylamine or dimethylamine.
    According to a variant of the invention, the function, preferably primary amine, secondary or tertiary, capable of interacting with a reinforcing filler is directly related to the silicon atom itself directly linked to the diene elastomer.
    According to another variant of the invention, the function, preferably primary, secondary or tertiary amine, capable of interacting with a reinforcing filler and the silicon atom bonded to the diene elastomer, are connected to each other by a grouping. spacer which can be an atom or a group of atoms. The spacer group may be a divalent hydrocarbon radical, linear or branched, aliphatic C1-C18, saturated or unsaturated, cyclic or not, or a divalent aromatic hydrocarbon radical C6-C18 and may contain one or more aromatic radicals and / or a or more heteroatoms. The hydrocarbon radical may optionally be substituted.
    Preferably, said butadiene and vinylaromatic monomer copolymer comprises more than 0 and up to 30% by weight (more preferably between 0 and 20%), relative to the total weight of copolymer of butadiene and vinylaromatic monomer, a copolymer of butadiene and vinylaromatic star monomer.
    Preferably, said copolymer of butadiene and vinylaromatic monomer is present at a level in a range from 50 to 100 phr, preferably from 70 to 100 phr, very preferably from 90 to 100 phr.
    According to a preferred embodiment, said very low Tg diene elastomer comprises a homopolymer of butadiene, preferably at a level in a range from 1 to 50 phr, preferably from 1 to 30 phr, very preferably from 1 to 10 pce.
    According to another preferred embodiment, said copolymer of butadiene and vinylaromatic monomer is present at a level of 100 phr.
    Preferably, the composition of the tread of the tire according to the invention comprises a total content of diene elastomers of very low Tg of 95 to 100 phr, preferably 100 phr.
    When the composition comprises, the complementary elastomers of the diene elastomers of very low Tg may be all elastomers known to those skilled in the art. 1-2 Reinforcing Charge and Silica With a Low Specific Surface [0043] The composition of the tread of the tire of the invention comprises, as majority reinforcing filler, a silica with a low specific surface area as defined below. In addition, the composition may comprise another reinforcing filler, as a minority reinforcing filler.
    Characterization of silicas The silicas described below consist, in a known manner, of agglomerates of particles capable of disaggregating into these particles under the effect of an external force, for example under the action of mechanical work. or ultrasound. The term "particle" used in the present application must be understood in its usual generic sense of aggregate (also called "secondary particle"), and not in that of elementary particle (also called "primary particle") which may form, the where appropriate, part of that aggregate; by "aggregate" is meant in known manner the whole non-breaking (ie, which can not be cut, divided, shared) that is produced during the synthesis of the load, usually formed of elementary (primary) particles aggregated between they. These silicas are characterized as indicated below.
    Specific surface area: The BET specific surface area ("mass area") is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" Vol. 60, page 309, February 1938), more precisely according to the French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points) - gas: nitrogen - degassing: 1 hour at 160 ° C - relative pressure range p / po : 0.05 to 0.17] The specific surface CTAB is the external surface determined according to the French standard NF T 45-007 of November 1987 (method B).
    Granulometry: The average size (in mass) of the particles, denoted dw, is measured in a conventional manner after dispersion, by deagglomeration with ultrasound, of the charge to be analyzed in water. The measurement is carried out using an XDC X-ray centrifugal sedimentometer ("X-rays Disk Centrifuge"), marketed by Brookhaven Instruments, according to the following procedure.
    A suspension of 3.2 g of silica sample to be analyzed in 40 ml of water, per action for 8 minutes, at 60% power (60% of the maximum position of the "output control"). a 1500 W ultrasonic probe (3/4 inch Vibracell sonifier marketed by Bioblock); after sonification, 15 ml of the suspension is introduced into the rotating disc; after sedimentation for 120 minutes, the mass distribution of the particle sizes is calculated by the XDC sedimentometer software. The geometric mean mass of particle sizes ("mean geometry (Xg)" according to the software name), denoted dw, is computed by the software from the following equation, in which mi represents the mass of the set of objects in the di diameter class.
    Deagglomeration rate a: The deagglomeration rate noted a is measured by means of an ultrasonic deagglomeration test, at 100% power of a 600 W (watt) probe, operating here in pulsed mode (either : 1 second ON, 1 second OFF) to avoid excessive heating of the ultrasonic probe during measurement. This known test, in particular the subject of the patent application WO99 / 28376 (see also WO99 / 28380, WO00 / 73372, WO00 / 73373), makes it possible to continuously measure the evolution of the average size (in volume) of the agglomerates of particles during sonication, as indicated below.
    The assembly used consists of a laser granulometer (type "Mastersizer S", marketed by Malvern Instruments - He-Ne laser source emitting in the red, wavelength 632.8 nm) and its preparer (" Malvern Small Sample Unit MSX1 "), between which was interposed a continuous flow treatment unit (Bioblock M72410) equipped with an ultrasonic probe (1/2 inch Vibracell type sonifier type 600 W marketed by the company Bioblock).
    A small amount (150 mg) of silica to be analyzed is introduced into the preparator with 160 ml of water, the circulation rate being set at its maximum. At least three consecutive measurements are carried out to determine, according to the known Fraunhofer calculation method (Malvern 3 $$ D calculation matrix), the average initial diameter (in volume) of the agglomerates, denoted dv [0]. The sonification (pulsed mode: 1 s ON, 1 s OFF) is then established at a power of 100% (ie 100% of the maximum position of the "tip amplitude") and the evolution of the average diameter is followed for about 8 minutes. in volume dv [t] as a function of time "t" at the rate of one measurement every 10 seconds approximately. After an induction period (about 3-4 minutes), it is observed that the inverse of the volume mean diameter 1 / dv [t] varies linearly, or substantially linearly, with time "t" (steady state deagglomeration). The deagglomeration rate a is calculated by linear regression of the evolution curve of 1 / dv [t] as a function of time "t", in the zone of stable deagglomeration regime (in general, between 4 and 8 minutes approximately) . It is expressed in pm '1 / min.
    The above-mentioned application W099 / 28376 describes in detail a measuring device that can be used for carrying out this ultrasound disagglomeration test. This device, it is recalled, consists of a closed circuit in which a flow of agglomerates of particles suspended in a liquid can flow. This device essentially comprises a sample preparer, a laser granulometer and a treatment cell. Atmospheric pressure, at the level of the sample preparer and the treatment cell itself, allows the continuous removal of air bubbles that form during sonication (action of the ultrasound probe).
    The sample preparer ("Malvern Small Sample Unit MSX1") is intended to receive the test silica sample (in suspension in the liquid 3) and to circulate it through the circuit at the preset speed ( potentiometer - maximum speed of about 3 l / min), in the form of a liquid suspension stream. This preparer is simply a receiving tank which contains, and through which circulates, the suspension to be analyzed. It is equipped with a stirring motor, at variable speed, in order to avoid sedimentation of the particle agglomerates of the suspension; a centrifugal mini-pump is intended to ensure the circulation of the suspension in the circuit; the inlet of the preparator is connected to the open air via an opening intended to receive the test sample to be tested and / or the liquid used for the suspension.
    To the preparator is connected a laser granulometer ("Mastersizer S") whose function is to measure continuously, at regular time intervals, the average volume size "dv" agglomerates, the passage of the flow, thanks to a measuring cell to which the automatic recording and calculating means of the granulometer are coupled. It will be briefly recalled here that the laser granulometers use, in a known manner, the principle of diffraction of light by solid objects suspended in a medium whose refractive index is different from that of the solid. According to Fraunhofer's theory, there is a relation between the size of the object and the diffraction angle of light (the smaller the object, the higher the angle of diffraction). In practice, it is sufficient to measure the amount of light diffracted for different diffraction angles in order to determine the size distribution (in volume) of the sample, dv corresponding to the average volume size of this distribution (dv = Σ (ni di4 ) / Σ (ni di3) with neither number of objects of the size class or diameter di).
    Interlaced between the preparator and the laser granulometer is finally a treatment cell equipped with an ultrasonic probe, which can operate in continuous or pulsed mode, intended to continuously break the particle agglomerates at the passage of the flow. This flow is thermostatically controlled by means of a cooling circuit arranged at the level of the cell in a double envelope surrounding the probe, the temperature being controlled for example by a temperature probe immersed in the liquid at the level of the preparer.
    The tread of the tire according to the invention has the essential feature of being reinforced by a reinforcing filler, said reinforcing filler comprising predominantly by weight a so-called low surface area silica (denoted by LS), having a specific surface area. CTAB between 50 and 100 m2 / g.
    Silicles with a small CTAB surface that can meet this definition are known and have been described in particular in applications EP 157 703, EP 396 450 and EP 722 977. Their known application in pneumatic tires has hitherto been mainly in parts. tire other than its tread, especially in internal mixtures used for example for calendering crown or carcass reinforcement plies. Also, the document WO2003 / 002649 discussed above proposes their use in compositions in which the majority elastomer has conventional Tg in a tire, in particular a styrene-butadiene copolymer of Tg -29.degree.
    It is recalled that by "reinforcing inorganic filler" must be understood in known manner an inorganic or mineral filler, regardless of its color and its origin (natural or synthetic), also called "white" charge or sometimes charge " as opposed to carbon black, capable of reinforcing on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires, in other words able to replace, in its function reinforcement, a conventional load of pneumatic grade carbon black.
    This silica specific "LS" (for "Low Surface") has first an unusual CTAB surface for a tread application, between 50 and 100 m2 / g. For a CTAB surface of less than 50 m 2 / g, the rubber compositions have a facilitated implementation as well as a reduced hysteresis, but there is a deterioration of the properties at break and a wear resistance, in tire, which decreases significantly. For a CTAB surface greater than 100 m 2 / g, in particular between 150 and 250 m 2 / g, there is the disadvantage of the usual high surface area silicas for treads of "Green Tires", namely on the one hand a reduced dispersibility in the rubbery matrix and difficulties of implementation in the raw state, due to parasitic interactions with certain other ingredients of the rubber compositions (in particular vulcanization system), on the other hand the need to use a higher coupling agent level. Preferably, the low surface area specific silica has a CTAB specific surface area of between 55 and 95 m 2 / g, and more preferably within a range of 60 to 90 m 2 / g.
    Silica LS preferably has a dw size of between 50 and 350 nm. For high dw sizes, greater than 350 nm, the particles may behave as defects that could decrease wear resistance, while very small dw sizes, less than 50 nm, could make it more difficult to implement. in the raw state and the dispersion of the load during this implementation. Preferably, the low surface area specific silica has a dw particle size between 90 and 300 nm, a dw particle size in a range of 100 to 250 nm.
    Finally, for applications where the highest level of reinforcement is targeted, the silica LS used will also have, preferably, a high intrinsic dispersibility, illustrated by a deagglomeration rate greater than 5.10'3 pm'Vmin , more preferably at least equal to 1.10'2 pm'Vmin. For such a deagglomeration rate, it has been found that the silica LS has a very high dispersibility, that is to say that few micron agglomerates are observed by reflection under optical microscopy on a section of rubber composition prepared according to the rules. art.
    Silica LS preferably has a BET specific surface area of between 50 and 140 m 2 / g, more preferably in a range from 60 to 120 m 2 / g, and even more preferably from 60 to 100 m 2 / g.
    The physical state under which the silica LS may be indifferent, whether in the form of powder, microbeads, granules, pellets, beads or any other densified form; it may be a precipitated silica such as a pyrolysis silica. Its BET / CTAB surface ratio is preferably in a range from 1.0 to 1.5, more preferably from 1.0 to 1.2.
    The silica LS above can advantageously constitute all of the reinforcing inorganic filler.
    However, to this silica LS, may be optionally associated with another reinforcing inorganic filler, for example a conventional reinforcing silica with a higher specific surface area.
    The silica LS may also be associated with a conventional carbon black of pneumatic grade, selected in particular from the blacks of the HAF, ISAF, SAF type conventionally used in tire treads (for example, blacks N115, N134, N234, N330, N339, N347, N375). This carbon black is then preferably used in a small proportion, at a level preferably between 2 and 20 phr, more preferably in a range of 5 to 15 phr. In the intervals indicated, it benefits from the coloring properties (black pigmentation agent) and anti-UV carbon blacks, without otherwise penalizing the typical performance provided by silica LS.
    Finally, those skilled in the art will understand that, as the equivalent load of a reinforcing inorganic filler, could be used a reinforcing filler of the organic type, in particular a carbon black for a tire, covered at least in part with an inorganic layer, especially silica, requiring the use of a coupling agent to ensure the connection with the elastomer.
    Preferably, the level of total reinforcing filler (including the silica with a very high specific surface area) is 30 to 200 phr, more preferably 45 to 170 phr, and very preferably 50 to 150 phr. . Below 30 pce of load, the composition could be less effective in wear resistance while above 200 pce of load, the composition could be less effective in rolling resistance.
    Preferably, silica content of low specific surface area is in a range from 25 to 180 phr, preferably from 40 to 160 phr, more preferably from 50 to 140 phr.
    According to one embodiment, the composition comprises carbon black, as a minority charge. In this case, the black level is preferably between 0 and 30 phr. In this embodiment, the black level is preferably in a range from 1 to 10 phr, preferably from 1 to 5 phr. I-3. Coupling Agents [0071] The tread compositions of the tire of the invention comprise a coupling agent to bond the silica to the elastomers.
    These coupling agents, which are well known to those skilled in the art, may be, for example, hydrolysable silanes such as alkylalkoxysilanes, or hydroxylated or hydrolysable polyorganosiloxanes.
    In particular, polysulfide silanes, called "symmetrical" or "asymmetrical" silanes according to their particular structure, are used, as described for example in the applications W003 / 002648 (or US 2005/016651) and W003 / 002649 (or US 2005 / 016650).
    In particular, the following definition is not limiting, so-called "symmetrical" polysulfide silanes corresponding to the following general formula (III): (III) ZA-Sx-AZ, in which: - x is a integer from 2 to 8 (preferably from 2 to 5); A is a divalent hydrocarbon radical (preferably C 1 -C 18 alkylene groups or C 6 -C 12 arylene groups, more particularly C 1 -C 10 alkylenes, especially C 1 -C 4 alkylenes, in particular propylene); Z is one of the following formulas:
    in which: the radicals R1, substituted or unsubstituted, identical or different from each other, represent a C1-C18 alkyl, C5-C18 cycloalkyl or C6-C18 aryl group (preferably C1-C6 alkyl groups, cyclohexyl or phenyl, especially C1-C4 alkyl groups, more particularly methyl and / or ethyl). the radicals R2, substituted or unsubstituted, which are identical to or different from one another, represent a C1-C18 alkoxyl or a C5-C18 cycloalkoxyl group (preferably a group chosen from C1-C8 alkoxyls and C5-C8 cycloalkoxyls, plus still more preferably a group chosen from C1-C4 alkoxyls, in particular methoxyl and ethoxyl).
    In the case of a mixture of polysulfurized alkoxysilanes corresponding to the formula (III) above, in particular common commercially available mixtures, the average value of "x" is a fractional number preferably between 2 and 5 more preferably close to 4. However, the invention can also be advantageously used for example with disulfide alkoxysilanes (x = 2).
    By way of examples of polysulphurized silanes, mention may be made more particularly of the polysulfides (in particular disulfides, trisulphides or tetrasulfides) of bis (C 1 -C 4 alkoxy) -alkyl (C 1 -C 4) silyl-C 1 -C 4 alkyl. )), such as polysulfides of bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl). Among these compounds, bis (3-triethoxysilylpropyl) tetrasulfide, abbreviated TESPT, of formula [(C2H50) 3Si (CH2) 3S2] 2 or bis (triethoxysilylpropyl) disulfide, abbreviated as TESPD, is especially used. formula [(C2H50) 3Si (CH2) 3S] 2. Mention may also be made, by way of preferred examples, of polysulfides (in particular disulphides, trisulphides or tetrasulfides) of bis- (monoalkoxyl (C1-C4) -dialkyl (C1-C4) silylpropyl), more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide, as described above. in the patent application WO 02/083782 (or US 2004/132880).
    As coupling agent other than polysulfurized alkoxysilane, mention may also be made of bifunctional POS (polyorganosiloxanes) or hydroxysilane polysulfides (R 2 = OH in formula III above) as described in the patent applications. WO 02/30939 (or US Pat. No. 6,774,255) and WO 02/31041 (or US 2004/051210), or alternatively silanes or POS bearing azo-dicarbonyl functional groups, as described, for example, in the patent applications WO 2006 / 125532, WO 2006/125533, WO 2006/125534.
    In the rubber compositions according to the invention, the content of coupling agent is preferably between 2 and 20 phr, more preferably between 3 and 15 and even more preferably between 4 and 12 phr. Crosslinking System [0079] The composition of the tread of the tire of the invention comprises a crosslinking system, which may be any type of crosslinking system known to those skilled in the art. In particular, this crosslinking system may be based on sulfur; this is called a vulcanization system.
    The vulcanization system itself is based on sulfur (or a sulfur donor agent) and a primary vulcanization accelerator. To this basic vulcanization system are added, incorporated during the first non-productive phase and / or during the production phase as described later, various known secondary accelerators or vulcanization activators such as zinc oxide. stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine).
    Sulfur is used at a preferential rate of between 0.5 and 10 phr, more preferably between 0.5 and 5 phr, in particular between 0.5 and 3 phr.
    The vulcanization system of the tread composition of the tire of the invention may also comprise one or more additional accelerators, for example the compounds of the thiuram family, the zinc dithiocarbamate derivatives, the sulphenamides, the guanidines or thiophosphates. In particular, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur, in particular thiazole type accelerators and their derivatives, thiuram type accelerators, zinc dithiocarbamates, may be used in particular. These accelerators are more preferably selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated "CBS"), N, N-dicyclohexyl-2-benzothiazyl sulphenamide (abbreviated "DCBS"), N-tert-butyl-2-benzothiazyl sulphenamide (abbreviated "TBBS"), N-tert-butyl-2-benzothiazyl sulphenimide (abbreviated "TBSI"), zinc dibenzyldithiocarbamate (in abbreviated "ZBEC") and mixtures of these compounds. Preferably, a primary accelerator of the sulfenamide type is used. 1-5 Plasticizer System [0083] The tread composition of the tire of the invention further comprises a combination of plasticizers or plasticizer system. This combination of plasticizer is composed of at least one hydrocarbon resin of high Tg. In addition to this first plasticizer, the composition may optionally comprise a hydrocarbon resin of high Tg and / or a plasticizing oil, the latter being preferably absent. or at a low level in the tread composition of the tire of the invention.
    Preferably, the total level of plasticizer in the composition is in a range from 20 to 120 phr, preferably from 50 to 110 phr, preferably from 60 to 100 phr. Below 20 phr, and especially below 50 phr of plasticizer, the composition could be less efficient in terms of industrial processability. High Tg Resin [0085] The plasticizer combination comprises a thermoplastic hydrocarbon resin, referred to as high Tg resin, whose Tg is greater than 20 ° C. This resin is a solid at room temperature (23 ° C), as opposed to a liquid plasticizer such as an oil or viscous such as a low Tg resin.
    Preferably, the thermoplastic hydrocarbon plasticizing resin has at least one of the following characteristics: a Tg greater than 30 ° C; a number-average molecular weight (Mn) of between 400 and 2000 g / mol, more preferentially between 500 and 1500 g / mol; a polymolecularity index (Ip) of less than 3, more preferably less than 2 (booster: Ip = Mw / Mn with Mw weight average molecular weight).
    More preferably, this thermoplastic hydrocarbon plasticizing resin has all of the above preferred characteristics.
    The macrostructure (Mw, Mn and Ip) of the hydrocarbon resin is determined by steric exclusion chromatography (SEC): tetrahydrofuran solvent; temperature 35 ° C; concentration 1 g / l; flow rate 1 ml / min; filtered solution on 0.45 μm porosity filter before injection; Moore calibration with polystyrene standards; set of 3 "WATERS" columns in series ("STYRAGEL" HR4E, HR1 and HR0.5); differential refractometer detection ("WATERS 2410") and its associated operating software ("WATERS EMPOWER").
    The thermoplastic hydrocarbon resins may be aliphatic or aromatic or aliphatic / aromatic type that is to say based on aliphatic and / or aromatic monomers. They may be natural or synthetic, whether or not based on petroleum (if so, also known as petroleum resins).
    As aromatic monomers are suitable for example styrene, alpha-methylstyrene, ortho-, meta-, para-methylstyrene, vinyl-toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene , divinylbenzene, vinylnaphthalene, any vinylaromatic monomer from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinylaromatic monomer is styrene or a vinylaromatic monomer derived from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinylaromatic monomer is the minor monomer, expressed as a mole fraction, in the copolymer under consideration.
    According to a particularly preferred embodiment, the plasticizing hydrocarbon resin is selected from the group consisting of homopolymer resins or copolymers of cyclopentadiene (abbreviated CPD) or dicyclopentadiene (abbreviated DCPD), homopolymer resins or terpene copolymers, terpene phenol homopolymer or copolymer resins, homopolymer resins or C5 cutting copolymers, C9 homopolymer or copolymer resins, alpha-methyl-styrene homopolymer and copolymer resins, and mixtures of these resins, used alone or in combination with a liquid plasticizer, for example a MES oil or TDAE, or a vegetable oil. The term "terpene" here combines in a known manner the alpha-pinene, beta-pinene and limonene monomers; preferably, a limonene monomer is used which is present in a known manner in the form of three possible isomers: L-limonene (laevorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or the dipentene, racemic of the dextrorotatory and levorotatory enantiomers. . Among the above-mentioned hydrocarbon plasticizing resins, there may be mentioned resins of homo- or copolymers of alphapinene, betapinene, dipentene or polylimonene.
    The preferred resins above 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 Mw = 1010 g / mol, lp = 1.6, Tg = 72 ° C.) or by ARIZONA under the name "Sylvagum TR7125C" (Mn = 630 g / mol, Mw = 950 g / mol; = 1.5, Tg = 70 ° C); C5 / vinylaromatic cut copolymer resins, in particular C5 / styrene cut or C5 cut / C9 cut: by Neville Chemical Company under the names "Super Nevtac 78", "Super Nevtac 85" or "Super Nevtac 99", by Goodyear Chemicals under denomination "Wingtack Extra", by Kolon under the names "Hikorez T1095" and "Hikorez T1100", by Exxon under the names "Escorez 2101" and "Escorez 1273"; Limonene / styrene copolymer resins: by DRT under the name "Dercolyte TS 105" from the company DRT, by ARIZONA Chemical Company under the names "ZT115LT" and "ZT5100".
    As examples of other preferred resins, mention may also be made of alpha-methyl-styrene resins modified phenol. To characterize these phenol-modified resins, it is recalled that a so-called "hydroxyl number" index (measured according to ISO 4326 and expressed in mg KOH / g) is used in a known manner. The alpha-methyl-styrene resins, in particular those modified phenol, are well known to those skilled in the art and commercially available, for example sold by Arizona Chemical under the names "Sylvares SA 100" (Mn = 660 g / mol; Ip = 1.5, Tg = 53 ° C); "Sylvares SA 120" (Mn = 1030 g / mol, Ip = 1.9, Tg = 64 ° C); "Sylvares 540" (Mn = 620 g / mol, Ip = 1.3, Tg = 36 ° C, hydroxyl number = 56 mg KOH / g); "Silvares 600" (η = 850 g / mol, Ip = 1.4, Tg = 50 ° C., hydroxyl number = 31 mg KOH / g).
    According to a particular embodiment of the invention, the level of hydrocarbon plasticizing resin of high Tg is in a range from 20 to 120 phr, preferably from 50 to 110 phr. Preferably, the level of hydrocarbon resin of high Tg is in a range from 60 to 100 phr. Indeed, below 20 phr of high Tg resin, the composition could have sticky problems and / or industrial processability. Low Tg resin [0095] Optionally, the combination of plasticizer may also contain a so-called "low Tg" thermoplastic hydrocarbon resin, that is to say which, by definition, has a Tg in a range of -40 ° C. at 20 ° C.
    Preferably, when it is present, the low Tg hydrocarbon plasticizing resin has at least one of the following characteristics: a Tg of between -40 ° C. and 0 ° C., more preferably between -30 ° C. and 0 ° C. ° C and more preferably still between -20 ° C and 0 ° C; a number-average molecular weight (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 0 to 40 ° C, more preferably 10 to 40 ° C, preferably 10 to 30 ° C; a polymolecularity index (Ip) of less than 3, more preferably less than 2 (booster: Ip = Mw / Mn with Mw weight average molecular weight).
    More preferably, this low Tg hydrocarbon plasticizing resin has all of the above preferred characteristics.
    The softening point is measured according to ISO 4625 ("Ring and Bail" method). Tg is measured according to ASTM D3418 (1999). The macrostructure (Mw, Mn and Ip) of the hydrocarbon resin is determined by steric exclusion chromatography (SEC): solvent tetrahydrofuran; temperature 35 ° C; concentration 1 g / l; flow rate 1 ml / min; filtered solution on 0.45 μm porosity filter before injection; Moore calibration with polystyrene standards; set of 3 "WATERS" columns in series ("STYRAGEL" HR4E, HR1 and HR0.5); differential refractometer detection ("WATERS 2410") and its associated operating software ("WATERS EMPOWER").
    The thermoplastic hydrocarbon resins may be aliphatic or aromatic or alternatively of the aliphatic / aromatic type, that is to say based on aliphatic and / or aromatic monomers. They may be natural or synthetic, whether or not based on petroleum (if so, also known as petroleum resins).
    As aromatic monomers are suitable for example styrene, alpha-methylstyrene, ortho-, meta-, para-methylstyrene, vinyl-toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene , divinylbenzene, vinylnaphthalene, any vinylaromatic monomer from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinylaromatic monomer is styrene or a vinylaromatic monomer derived from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinylaromatic monomer is the minor monomer, expressed as a mole fraction, in the copolymer under consideration.
    According to a particularly preferred embodiment, the plasticizing hydrocarbon resin is selected from the group consisting of homopolymer resins or copolymers of cyclopentadiene (abbreviated CPD) or dicyclopentadiene (abbreviated DCPD), homopolymer resins or terpene copolymers, terpene phenol homopolymer or copolymer resins, C5 resins of homopolymers or copolymers, C9 resins of homopolymers or copolymers, and mixtures of these resins, which may be used alone or in combination with a plasticizer liquid, for example a MES oil or TDAE, or a vegetable oil. The term "terpene" here combines in a known manner the alpha-pinene, beta-pinene and limonene monomers; preferably, a limonene monomer is used which is present in a known manner in the form of three possible isomers: L-limonene (laevorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or the dipentene, racemic of the dextrorotatory and levorotatory enantiomers. . Among the above-mentioned hydrocarbon plasticizing resins, there may be mentioned resins of homo- or copolymers of alphapinene, betapinene, dipentene or polylimonene.
    The preferred resins above are well known to those skilled in the art and commercially available, for example sold with regard to: aliphatic resins: by the company CRAY VALLEY under the name "Wingtack 10" (Mn = 480 g / mol, Mw = 595 g / mol, lp = 1.2, SP = 10 ° C., Tg = -28 ° C.), coumarone indene resins: by Rütgers Chemicals under the name "Novares C30" (Mn = 295 g Mw = 378 g / mol, lp = 1.28, SP = 25 ° C, Tg = -19 ° C); aliphatic and aromatic C9 cut resins: by Rütgers Chemicals under the name "Novares TT30" (Mn = 329 g / mol, Mw = 434 g / mol, Ip = 1.32, SP = 25 ° C, Tg = -12 °) VS).
    According to a particular embodiment of the invention, when it is included in the composition, the level of low Tg resin is in a range from 5 to 80 phr, preferably from 7 to 70 phr, still more preferably from 10 to 50 phr.
    Plasticizing Oil Optionally, the plasticizer combination of the composition of the invention may comprise an extender oil (or plasticizing resin) that is liquid at 20 ° C., referred to as "low Tg", that is to say which by definition has a Tg lower than -20 ° C, preferably lower than -40 ° C.
    [00105] Preferably, the plasticizer system does not include a plasticizing oil or comprises less than 15 phr, preferably less than 10 phr. When the plasticizer system comprises a plasticizing oil, the plasticizer system comprises 1 to 10 phr, preferably 1 to 8 phr of plasticizing oil. Indeed, above 15 phr of oil, the composition could be less effective in adhesion, with a Tg of the mixture too low.
    Any extender oil, whether of aromatic or non-aromatic nature known for its plasticizing properties vis-à-vis diene elastomers, is usable. At ambient temperature (20 ° C), these oils, more or less viscous, are liquids (that is to say, as a reminder, substances having the ability to eventually take the shape of their container), as opposed in particular to hydrocarbon plasticizing resins which are inherently solid at room temperature.
    [00107] Particularly suitable extension oils selected from the group consisting of naphthenic oils (low or high viscosity, especially hydrogenated), paraffinic oils, oils MES (Medium Extracted Solvates), oils TDAE (Treated Distillate Aromatic Extracts), mineral oils, vegetable oils, ethers plasticizers, ester plasticizers, phosphate plasticizers, sulphonate plasticizers and mixtures of these compounds. For example, there may be mentioned those containing between 12 and 30 carbon atoms, for example trioctyl phosphate. By way of examples of non-aqueous and non-water-soluble ester plasticizers, mention may be made in particular of compounds selected from the group consisting of trimellitates, pyromellitates, phthalates, 1,2-cyclohexane dicarboxylates, adipates, azela- sebacates, glycerol triesters and mixtures of these compounds. Among the triesters above, mention may be made in particular of glycerol triesters, preferably consisting mainly (for more than 50%, more preferably for more than 80% by weight) of a C18 unsaturated fatty acid, that is, that is to say chosen from the group consisting of oleic acid, linoleic acid, linolenic acid and mixtures of these acids. More preferably, whether of synthetic or natural origin (for example vegetable oils of sunflower or rapeseed), the fatty acid used is more than 50% by weight, more preferably still more than 80% by weight. % by weight of oleic acid. Such high oleic acid triesters (trioleates) are well known and have been described, for example, in application WO 02/088238, as plasticizers in tire treads. I-6 Other possible additives [00108] The tread compositions of the tires according to the invention optionally also include all or part of the usual additives usually used in elastomer compositions intended in particular for the production of treads, such as for example pigments, protective agents such as anti-ozone waxes, chemical antiozonants, anti-oxidants, plasticizers other than those previously described, anti-fatigue agents, reinforcing resins, acceptors (for example resin phenolic novolak) or methylene donors (eg HMT or H3M).
    Of course, the tread compositions of the tire of the invention can be used alone or in cutting (i.e., mixed) with any other rubber composition usable for the manufacture of tires.
    It goes without saying that the invention relates to the previously described rubber compositions both in the so-called "raw" or non-crosslinked state (ie, before cooking) in the so-called "cooked" or crosslinked state, or still vulcanized (ie, after crosslinking or vulcanization).
    II-Preparation of Rubber Compositions [00111] The compositions are manufactured in appropriate mixers, using two successive preparation phases well known to those skilled in the art: a first phase of work or thermomechanical mixing (sometimes called phase "non-productive") at high temperature, up to a maximum temperature of between 110 ° C and 190 ° C, preferably between 130 ° C and 180 ° C, followed by a second mechanical working phase (sometimes referred to as "productive" phase) at a lower temperature, typically below 110 ° C, for example between 60 ° C and 100 ° C, finishing phase during which is incorporated the crosslinking system or vulcanization; such phases have been described, for example, in EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.
    The first phase (non-productive) is preferably carried out in several thermomechanical steps. In a first step, the elastomers, the reinforcing fillers, the combination of plasticizers (and optionally the coupling agents and / or other ingredients at the same time) are introduced into a suitable mixer such as a conventional internal mixer. exception of the vulcanization system), at a temperature of between 20 ° C and 100 ° C and preferably between 25 ° C and 100 ° C. After a few minutes, preferably from 0.5 to 2 min and a rise in temperature to 90 ° C to 100 ° C, the other ingredients (ie, those that remain if all were not put initially) are added at once or in portions, except for the vulcanization system during mixing ranging from 20 seconds to a few minutes. The total mixing time, in this non-productive phase, is preferably between 2 and 10 minutes at a temperature of less than or equal to 180 ° C, and preferably less than or equal to 170 ° C.
    After cooling the mixture thus obtained, the vulcanization system is then incorporated at low temperature (typically below 100 ° C), generally in an external mixer such as a roll mill; the whole is then mixed (productive phase) for a few minutes, for example between 5 and 15 min.
    The final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for a characterization in the laboratory, or extruded, for example to form a rubber profile used for the manufacture. semi-finished to obtain products such as a tread. These products can then be used for the manufacture of tires, according to the techniques known to those skilled in the art.
    The vulcanization (or baking) is conducted in a known manner at a temperature generally between 130 ° C and 200 ° C, under pressure, for a sufficient time which may vary for example between 5 and 90 min depending in particular on the cooking temperature, the vulcanization system adopted, the kinetics of vulcanization of the composition in question or the size of the tire.
    The examples which follow illustrate the invention without however limiting it. III-Examples of embodiment of the invention 111-1 Preparation of Examples [00117] In the examples which follow, the rubber compositions were produced as described previously. III-2 Characterization of the Examples [00118] In the examples, the rubber compositions are characterized before and / or after cooking as indicated below. Tensile tests (after firing): These tensile tests make it possible to determine the modulus of elasticity and the properties at break and are based on the NF ISO 37 standard of December 2005. It is measured at 23.degree. second elongation (ie, after an accommodation cycle at the extension rate provided for the measurement itself) the nominal secant modulus (or apparent stress, in MPa, referred to deformation, without unit) at 100% elongation (noted MA100) and / or 300% elongation (noted MA300). True stress at break (in MPa) and elongation at break (in%) can also be measured.
    The value of MA300 measured at 23 ° C is a good indicator of the cohesion of the mixture, the higher the value, the better the cohesion. For more readability the results will be indicated according to the performance, in base 100, the value 100 being attributed to the witness. A result less than 100 indicating a decrease in the cohesion performance of the mixture (decrease in the value of MA300), and conversely, a result greater than 100, will indicate an increase in the performance (increase of the value of MA300). Dynamic properties (after firing): The dynamic properties G * and tan (5) max are measured on a viscoanalyzer (Metravib V A4000), according to the ASTM D 5992 - 96 standard. The response of a sample is recorded. of vulcanized composition (cylindrical specimen 4 mm thick and 400 mm 2 section) subjected to a sinusoidal stress in alternating simple shear, at the frequency of 10 Hz, under the variable temperature conditions, in particular at 0 ° C. and 23 ° C according to ASTM D 1349-99. A peak to peak strain sweep of 0.1 to 50% (forward cycle) followed by 50% to 1% (return cycle) was performed. The results exploited are the complex dynamic shear modulus (G *) and the loss factor (tan δ). For the return cycle, the maximum value of tan δ observed (tan (δ) max) and the complex modulus difference (AG *) between the values at 0.1% and at 50% of deformation (effect Payne).
    For the value of tan (5) max at 0 ° C, the higher the value, the more the composition will allow good adhesion on wet ground. For more readability the results will be indicated according to the performance, in base 100, the value 100 being attributed to the witness. A result lower than 100 indicating a decrease in wet grip performance (decrease in the value of tan (5) max at 0 ° C), and conversely, a result greater than 100, will indicate an increase in performance ( increase of the value of tan (5) max at 0 ° C).
    For the value of tan (5) max at 23 ° C, the lower the value, the lower the composition will have a low hysteresis and therefore a low rolling resistance. For more readability the results will be indicated according to the performance, in base 100, the value 100 being attributed to the witness. A result lower than 100 indicating a decrease in the rolling resistance performance (increase of the value of tan (5) max at 23 ° C), and inversely, a result greater than 100, will indicate an increase of the performance (decrease of the value of tan (5) max at 23 ° C). III-3 Examples
    EXAMPLE 1 Preparation of a functional aminoalkoxysilane functional SBR of Tq -88 ° C.
    In a continuously stirred reactor of 32 L, assumed perfectly stirred according to the skilled person, are continuously introduced methylcyclohexane, butadiene, styrene and tetrahydrofurfuryl ethyl ether, in the following proportions: flow rate mass butadiene = 4.013 kg.h-1, styrene mass flow rate = 0.122 kg.h-1, mass concentration of monomer = 9.75 wt%, 15 ppm tetrahydrofurfuryl ethyl ether. N-Butyllithium (n-BuLi) is introduced in sufficient quantity to neutralize the practical impurities introduced by the various constituents present at the inlet of the first reactor; 850 pmol of n-BuLi per 100 g of monomer are introduced.
    The different flow rates are calculated so that the average residence time in the reactor is 35 min. The temperature is maintained at 95 ° C. At the outlet of the polymerization reactor, a sample of polymer solution is made. The polymer thus obtained is subjected to an antioxidant treatment with the addition of 0.4 phr of 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol) and 0.2 phr of N- (1,3 dimethylbutyl) -N'-phenyl-p-phenylenediamine. The polymer thus treated is then separated from its solution by a stripping operation with steam, and then dried on a roll tool at 100 ° C. The "initial" inherent viscosity measured is 1.98 dLg -1. The number-average molecular weight, Mn, determined by the SEC technique, is 90,000 g / mol-1 and the polymolecularity index, Ip, is 1.90. At the outlet of the polymerization reactor, 440 pmol per 100 g of monomer of 3- (N, N-dimethylaminopropyl) trimethoxysilane (coupling agent and starch AdC) in solution in methylcyclohexane are added to the solution of living polymer (AdC / Li = 0.52).
    The polymer thus obtained is subjected to an antioxidant treatment with addition of 0.4 phr of 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol) and 0.2 phr of N- ( 1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine. The polymer thus treated is then separated from its solution by a stripping operation with steam, and then dried on a roll tool at 100 ° C.
    The "final" inherent viscosity measured is 2.52 dL.g-1. The viscosity jump, defined as the ratio of said "final" viscosity to said "initial" viscosity, is here 1.27. The Mooney viscosity of this polymer A is 70. The number-average molecular weight, Mn, determined by the SEC technique, is 168,600 g.mol-1 and the polymolecularity index, Ip, is 1.68. . The microstructure of this polymer is determined by the NIR method. The level of 1,2 units is 12.7% relative to the butadiene units. The mass content of styrene is 2.1%. The glass transition temperature of this polymer is -88 ° C. The CF (1 + 6) cold flow of 100 ° C of the polymer is 0.52. The distribution of the species after functionalization is given with the modeling method described above: 86% functional chains of which 77% are functional in the middle of the chain and 14% of nonfunctional starred chains.
    Example 2 - Compositions [00128] The compositions are manufactured with an introduction of all the constituents on an internal mixer, with the exception of the vulcanization system. The vulcanizing agents (sulfur and accelerator) are introduced on an external mixer at low temperature (the constituent rolls of the mixer being at about 30 ° C.).
    The examples presented in Table 1 are intended to compare the different rubber properties of control compositions (T1 and T2) compositions C1 to C3 according to the invention.
    In comparison with the control compositions, it is noted that the compositions of the tread of the tire of the invention have the best performance compromise between the Tan (δ) max measurements at 23 ° C., at 0 ° C. and the MA300. These results show that the compositions of the invention make it possible to very significantly improve the rolling resistance of the tires, while retaining good properties on the essential aspects of the cohesion of the mixture and the adhesion on wet ground. None of the control compositions allow such a good compromise of all these performances at the same time.
    Table 1
    * Calculated average performance, assigning a double coefficient to the performance sought primarily as a reduction in rolling resistance. (1) SBR with 44% of styrene unit and 41% of 1,2 unit of butadiene (Tg = -12 ° C); (2) SBR of Tg = -88 ° C of Example 1; (3) BR: polybutadiene with 0.5% of 1-2 unit; 1.2% trans-1-4; 98.3% cis-1-4 unit (Tg = -108 ° C); (4) ASTM grade N234 (Cabot company); (5) "Zeosil 1165 MP" silica of the company Solvay type "H DS"; (6) "Zeosil 1085GR" silica from Solvay (BET = 85 m 2 / g, CTAB = 80 m 2 / g, Dw = 110 nm); (7) High Tg hydrocarbon resin, C5 / C9 "Wingtack STS" cut from Cray Valley; (8) Glycerol trioleate, sunflower oil 85% by weight of oleic acid "Lubrirob Tod 1880" from Novance; (9) coupling agent: "Si69" from Evonik - Degussa; (10) N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine (Santoflex 6-PPD) from Flexsys and Anti-Ozone Wax; (11) N-cyclohexyl-2-benzothiazol sulfenamide ("Santocure CBS" from Flexsys); (12) Diphenylguanidine "Perkacit DPG" from Flexsys Company.
    权利要求:
    Claims (32)
    [1" id="c-fr-0001]
    1. A tire whose tread comprises a rubber composition based on at least: 90 to 100 phr of one or more diene elastomers of a very low glass transition temperature (Tg) having a Tg included in a range ranging from -110 ° C to -80 ° C, chosen from butadiene homopolymers, copolymers of butadiene and vinylaromatic monomer, having a vinylaromatic unit level of between 0 and 5% by weight, and mixtures thereof. a reinforcing filler, said reinforcing filler comprising predominantly by weight a so-called low surface area silica, having a CTAB specific surface area of between 50 and 100 m 2 / g, a coupling agent ensuring the bond between the silica and the diene elastomer, a plasticizer system, said plasticizer system comprising at least more than 15 phr (parts by weight per hundred parts by weight of elastomer) of a hydrocarbon resin known as e high Tg with a Tg greater than 20 ° C, a crosslinking system.
    [2" id="c-fr-0002]
    2. A tire according to claim 1, wherein said very low Tg diene elastomer is present at a total content of 95 to 100 phr, preferably 100 phr.
    [3" id="c-fr-0003]
    A tire according to any one of the preceding claims, wherein said very low Tg diene elastomer has a Tg in the range of -100 ° C to -80 ° C, preferably -95 ° C to -80 ° C ° C.
    [4" id="c-fr-0004]
    4. A tire according to any one of the preceding claims wherein said very low Tg diene elastomer has a Mooney viscosity in a range from 50 to 80.
    [5" id="c-fr-0005]
    5. A tire according to any one of the preceding claims wherein said very low Tg diene elastomer comprises a copolymer of butadiene and vinylaromatic monomer, preferably styrene, having a vinylaromatic unit level of between 0 and 5% by weight. preferably from 1 to 4% by weight, as well as a proportion of vinylic unit relative to the diene portion ranging from 8 to 15% by weight, preferably from 10 to 15% by weight, relative to the weight total diene elastomer.
    [6" id="c-fr-0006]
    The tire of claim 5 wherein at least 70% by weight of said butadiene copolymer and vinylaromatic monomer is functionalized.
    [7" id="c-fr-0007]
    7. A tire according to claim 6 wherein said copolymer of butadiene and vinylaromatic monomer is functionalized with an alkoxysilane group, optionally partially or completely hydrolysed to silanol, the alkoxysilane group carrying, or not, another function capable of interacting with a reinforcing filler the alkoxysilane group being bonded to the diene elastomer via the silicon atom.
    [8" id="c-fr-0008]
    8. A tire according to any one of claims 6 or 7 wherein said copolymer of butadiene and vinylaromatic monomer is functionalized mainly in the middle of the chain.
    [9" id="c-fr-0009]
    9. A tire according to any one of claims 5 to 8 wherein said copolymer of butadiene and vinylaromatic monomer comprises more than 0 and up to 30% by weight, based on the total weight of copolymer of butadiene and vinylaromatic monomer, a copolymer of butadiene and vinylaromatic star monomer.
    [10" id="c-fr-0010]
    10. The tire of claim 9 wherein said copolymer of butadiene and vinylaromatic monomer comprises between 0 and 20% by weight of a copolymer of butadiene and vinylaromatic star monomer.
    [11" id="c-fr-0011]
    11. A tire according to any one of the preceding claims wherein said copolymer of butadiene and vinylaromatic monomer is present at a level ranging from 50 to 100 phr, preferably from 70 to 100 phr.
    [12" id="c-fr-0012]
    12. A tire according to claim 11 wherein said copolymer of butadiene and vinylaromatic monomer is present at a level within a range from 90 to 100 phr, preferably 100 phr.
    [13" id="c-fr-0013]
    A tire according to any one of the preceding claims wherein said very low Tg diene elastomer comprises butadiene homopolymer.
    [14" id="c-fr-0014]
    14. A tire according to claim 13 wherein said homopolymer of butadiene is present at a level within a range of 1 to 50 phr, preferably 1 to 30 phr.
    [15" id="c-fr-0015]
    15. A tire according to any preceding claim wherein the reinforcing filler content is in a range from 30 to 200 phr, preferably from 45 to 170 phr, more preferably from 50 to 150 phr.
    [16" id="c-fr-0016]
    16. A tire according to any one of the preceding claims wherein the silica content of low specific surface area is in a range from 25 to 180 phr, preferably from 40 to 160 phr, more preferably from 50 to 140 phr.
    [17" id="c-fr-0017]
    A tire according to any one of the preceding claims wherein the low surface area silica has a CTAB specific surface area within a range of from 55 to 95 m 2 / g, preferably from 60 to 90 m 2 / g.
    [18" id="c-fr-0018]
    18. A tire according to any one of the preceding claims wherein the low surface area silica has an average particle size dw of between 50 and 350 nm, preferably between 90 and 300 nm, more preferably within a range of 100. at 250 nm.
    [19" id="c-fr-0019]
    Tire according to any one of the preceding claims, in which the silica having a very high specific surface area has a deagglomeration rate greater than 5 × 10 -3 μm -1, preferably at least 1 × 10 -2 μm -1.
    [20" id="c-fr-0020]
    20. A tire according to any one of the preceding claims wherein the low surface area silica has a BET specific surface area in a range from 50 to 140 m 2 / g, preferably from 60 to 120 m 2 / g.
    [21" id="c-fr-0021]
    21. A tire according to any one of the preceding claims comprising carbon black as a minority reinforcing filler.
    [22" id="c-fr-0022]
    22. A tire according to the preceding claim wherein the carbon black content is between 0 and 30 phr, preferably in a range from 1 to 10 phr, preferably from 1 to 5 phr.
    [23" id="c-fr-0023]
    23. A tire according to any one of the preceding claims wherein the level of hydrocarbon resin of high Tg is in a range from 20 to 120 phr, preferably from 50 to 110 phr.
    [24" id="c-fr-0024]
    24. A tire according to the preceding claim wherein the level of hydrocarbon resin of high Tg is in a range from 60 to 100 phr.
    [25" id="c-fr-0025]
    25. A tire according to any one of the preceding claims wherein the hydrocarbon resin of high Tg has a Tg greater than 30 ° C.
    [26" id="c-fr-0026]
    26. A tire according to any one of the preceding claims wherein the high Tg hydrocarbon resin has a number average molecular weight of between 400 and 2000 g / mol, preferably between 500 and 1500 g / mol.
    [27" id="c-fr-0027]
    27. A tire according to any one of the preceding claims wherein the hydrocarbon resin of high Tg has a polymolecularity index (Ip) of less than 3, preferably less than 2.
    [28" id="c-fr-0028]
    28. A tire according to any one of the preceding claims further comprising in the plasticizer system, a so-called low Tg resin, with a Tg of between -40 ° C and 20 ° C.
    [29" id="c-fr-0029]
    29. A tire according to any one of the preceding claims, in which the plasticizing system does not comprise a plasticizing oil or comprises less than 15 phr, preferably less than 10 phr.
    [30" id="c-fr-0030]
    30. A tire according to any preceding claim wherein the plasticizer system comprises 1 to 10 phr, preferably 1 to 8 phr of plasticizing oil.
    [31" id="c-fr-0031]
    31. Tire according to the preceding claim wherein the plasticizing oil is selected from the group consisting of naphthenic oils, paraffinic oils, oils MES (Medium Extracted Solvates), oils TDAE (Treated Distillate Aromatic Extracts), mineral oils , vegetable oils, ethers plasticizers, ester plasticizers, phosphate plasticizers, sulphonate plasticizers and mixtures of these compounds.
    [32" id="c-fr-0032]
    32. A tire according to any one of the preceding claims, in which the total level of plasticizers is in a range from 20 to 120 phr, preferably from 50 to 110 phr, preferably from 60 to 100 phr.
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    同族专利:
    公开号 | 公开日
    CA3005288A1|2017-06-22|
    FR3045631B1|2017-12-29|
    WO2017103386A1|2017-06-22|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    WO2003002649A1|2001-06-28|2003-01-09|Societe De Technologie Michelin|Tyre tread reinforced with silica having a very low specific surface area|
    EP2749404A1|2011-11-29|2014-07-02|Sumitomo Rubber Industries, Ltd.|Pneumatic tire and method for manufacturing same|
    JP2017075227A|2015-10-14|2017-04-20|住友ゴム工業株式会社|tire|
    JP6888948B2|2016-12-08|2021-06-18|Ｔｏｙｏ Ｔｉｒｅ株式会社|Rubber composition for tire tread and pneumatic tire|
    FR3098518A1|2019-07-09|2021-01-15|Compagnie Generale Des Etablissements Michelin|TIRE TREAD RUBBER COMPOSITION|
    法律状态:
    2016-12-22| PLFP| Fee payment|Year of fee payment: 2 |
    2017-06-23| PLSC| Publication of the preliminary search report|Effective date: 20170623 |
    2017-12-21| PLFP| Fee payment|Year of fee payment: 3 |
    2019-09-27| ST| Notification of lapse|Effective date: 20190906 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1562820A|FR3045631B1|2015-12-18|2015-12-18|RUBBER COMPOSITION COMPRISING SPECIFIC LOW-SURFACE SILICA AND DIENE ELASTOMER WITH LOW VITREOUS TRANSITION TEMPERATURE|FR1562820A| FR3045631B1|2015-12-18|2015-12-18|RUBBER COMPOSITION COMPRISING SPECIFIC LOW-SURFACE SILICA AND DIENE ELASTOMER WITH LOW VITREOUS TRANSITION TEMPERATURE|
    CA3005288A| CA3005288A1|2015-12-18|2016-12-08|Tyre, the tread of which comprises a rubber composition comprising a low specific surface area silica and a low glass transition temperature diene elastomer|
    PCT/FR2016/053282| WO2017103386A1|2015-12-18|2016-12-08|Tyre, the tread of which comprises a rubber composition comprising a low specific surface area silica and a low glass transition temperature diene elastomer|
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