Tire for heavy-duty vehicles including a novel tread

Abstract

The tire for carrying heavy-duty vehicles comprises a tread having at least a rubber composition, the rubber composition containing: at least one elastomeric matrix, which comprises as the main component a copolymer based on styrene and butadiene with a glass transition temperature Tg strictly higher than -65°C and not exceeding -30°C; a reinforcing filler, which comprises silica as the main component; a chemical crosslinking system; a coupling agent for coupling between the elastomeric matrix and the reinforcing filler; a plasticizing system, which comprises 2 to 15 phr of at least one plasticizing resin, the plasticizing resin having a glass transition temperature Tg of at least 20°C, the total share of the plasticizing system in the composition being 2 to 17 phr; and a modifier for modifying the styrene and butadiene copolymer, the modifier optionally having been grafted onto the copolymer, the modifier being a 1,3-dipolar compound having the general formula (I): A-E-D(I). The symbol D is a functional group containing at least one nitrogen atom, which is capable of being bound to the copolymer by a [3+2] type cycloaddition on the carbon-carbon double bond of the copolymer chain; the symbol E is a divalent spacer group connecting the group D to the group A; A is a functional group selected from the following: C1-C 20 Alkyl, C7‑C 18 Alkylaryl, C7‑C 18 Arylalkyl, optionally substituted nitrogen-based heterocyclic ring having 5 to 6 atoms, optionally substituted sulfur-based heterocyclic ring having 5 to 6 atoms, ester group, phosphate group, dialkylamino group, and associative groups containing at least one nitrogen atom.

Description

Technical Field

[0001] The field of the invention is that of tyres for vehicles of the heavy-duty type, in particular heavy vehicles, buses, civil engineering vehicles and the like. Background Art

[0002] Tires intended for heavy-duty vehicles have specific dimensions, robustness and structural characteristics that distinguish them from other tires, especially those intended to equip passenger vehicles. Their treads must meet a large number of often contradictory technical performance qualities, in particular high wet grip, low rolling resistance and good wear resistance.

[0003] In particular, certain heavily loaded vehicles are intended to travel longer and longer distances due to improvements in the road network and the expansion of the global motorway network. For safety reasons, wet grip must be high. In addition, wear on the tread of these tires must be as low as possible, as must the energy losses associated with rolling.

[0004] However, it is well known to those skilled in the art that improvements in one performance quality of a tire are often achieved at the expense of other performance qualities.

[0005] For example, one way to give a tire high wet grip is to use a rubber composition with good hysteresis potential for the tread. However, at the same time, this tread must promote rolling resistance as low as possible to limit the energy losses associated with rolling, that is, it must have as little hysteresis as possible.

[0006] Another example of contradictory performance qualities is as follows. In order to improve the wear resistance, the skilled person knows that the tread must have good stiffness. This stiffness can be obtained in particular by increasing the content of reinforcing fillers in the rubber composition constituting these treads. However, increasing this content of reinforcing fillers causes an increase in the hysteresis of the tire, thereby creating a risk of impairing the rolling resistance performance.

[0007] Therefore, there is a continuing need to provide a tire for heavy-duty vehicles having a tread with high wet grip without compromising rolling resistance and wear resistance. Summary of the invention

[0008] In light of the foregoing, one object is to provide a tire intended to equip vehicles of the heavy load-carrying type, comprising a tread satisfying a compromise of wet grip / rolling resistance / wear strength performance qualities.

[0009] The Applicant has discovered in the course of his studies that a specific combination of a copolymer based on styrene and butadiene, said copolymer being modified by a specific modifier, a reinforcing filler mainly comprising silica and a specific content of a plasticizing system makes it possible to obtain a rubber composition which solves this problem and which can be used in the tread of tires for vehicles carrying heavy loads.

[0010] The present invention therefore relates to a tyre intended to be fitted to vehicles of the heavy load-carrying type, comprising a tread comprising at least one rubber composition based on at least:

[0011] - an elastomeric matrix mainly comprising a copolymer based on styrene and butadiene having a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C,

[0012] - a reinforcing filler mainly comprising silicon dioxide,

[0013] -Chemical cross-linking system,

[0014] - agents for coupling between the elastomeric matrix and the reinforcing filler,

[0015] a plasticizing system comprising 2 to 15 phr, preferably 2 to 10 phr, of at least one plasticizing resin having a glass transition temperature Tg greater than or equal to 20° C., and the total content of the plasticizing system in the composition is from 2 to 17 phr, preferably from 2 to 12 phr, and

[0016] - an agent for modifying said copolymer based on styrene and butadiene, said agent optionally having been grafted onto said copolymer, said modifying agent being a 1,3-dipolar compound of general formula (I):

[0017] AED (I)

[0018] o The symbol D represents a functional group comprising at least one nitrogen atom, said functional group being capable of binding to said copolymer by a [3+2] type cycloaddition on a carbon-carbon double bond of the chain of said copolymer,

[0019] o Symbol E represents a divalent spacer group connecting group D to group A,

[0020] o A represents a functional group selected from the following: C 1 -C 20 Alkyl, C 7 -C 18 Alkyl aryl, C 7 -C 18Arylalkyl, optionally substituted nitrogen-based heterocyclic ring having 5 to 6 atoms, optionally substituted sulfur-based heterocyclic ring having 5 to 6 atoms, ester group, phosphate group, dialkylamino group, and associative groups containing at least one nitrogen atom.

[0021] Preferably, the functional group D of the modifier comprises a nitrile oxide functional group, a nitrone functional group or a nitrile imine functional group.

[0022] Preferably, the spacer group E is a linear or branched C 1 -C 24 Preferred C 1 -C 10 An alkyl chain optionally comprising one or more heteroatoms selected from nitrogen, sulfur and oxygen atoms.

[0023] Preferably, the group D of the modifier is a group having formula (II):

[0024]

[0025] in:

[0026] -R1, R2, R3, R4, R5 may be the same or different and represent a hydrogen atom, a halogen atom, a C 1 -C 5 Alkyl, C 1 -C 5 Alkoxy or a covalent bond capable of connecting to a spacer group E;

[0027] - provided that at least one of R1, R2, R3, R4 and R5 represents said covalent bond.

[0028] Preferably, group A is an associative group comprising at least one nitrogen atom, said associative group being selected from the following formulae (IV) to (VIII):

[0029]

[0030] in:

[0031] -R11 represents a hydrocarbon group which may optionally contain heteroatoms,

[0032] -Q represents an oxygen atom or a sulfur atom or NH, preferably an oxygen atom, and

[0033] -The symbol * indicates the connection to the spacer group E.

[0034] Preferably, the modifier is selected from compounds having the following formulae (IX) to (XVIII) and their meso forms:

[0035]

[0036]

[0037] More preferably, the modifying agent is selected from compounds having formula (XIII), (XIV), (XV) and (XVII) and their meso forms.

[0038] Preferably, the content of the modifier having formula (I) in the composition is 0.01 mol % to 50 mol %, preferably 0.01 mol % to 5 mol %, more preferably 0.01 mol % to 3 mol %.

[0039] Preferably, the copolymer based on styrene and butadiene has a glass transition temperature of -60°C to -40°C.

[0040] Preferably, the copolymer based on styrene and butadiene consists of styrene monomers and butadiene monomers.

[0041] Preferably, the elastomeric matrix also comprises at least one second diene elastomer different from the copolymer based on styrene and butadiene.

[0042] Preferably, the second diene elastomer is chosen from polybutadienes, natural rubber, synthetic isoprenes, butadiene copolymers other than butadiene-styrene copolymers, isoprene copolymers and mixtures of these polymers and copolymers; preferably, the second diene elastomer is polybutadiene.

[0043] Preferably, the content of second diene elastomer ranges from 5 to 49 phr, preferably from 15 to 35 phr.

[0044] Preferably, the composition further comprises carbon black.

[0045] Preferably, the content of reinforcing filler is from 55 to 200 phr, preferably from 55 to 150 phr, more preferably from 55 to 80 phr.

[0046] Preferably, the plasticizing resin has a glass transition temperature Tg greater than or equal to 30°C, preferably from 30 to 100°C.

[0047] Preferably, the plasticizing resin is selected from cyclopentadiene homopolymer or copolymer resin, dicyclopentadiene homopolymer or copolymer resin, terpene homopolymer or copolymer resin, C 5 Fraction homopolymer or copolymer resin, C 9 Fraction homopolymer or copolymer resin, C 5 Fraction homopolymer or copolymer resin and C 9 Mixtures of fraction homopolymer or copolymer resins, alpha-methylstyrene homopolymer or copolymer resins and mixtures of these resins.

[0048] Preferably, the plasticizing system comprises from 0 to 2 phr of at least one plasticizer which is liquid at room temperature.

[0049] Preferably, the composition does not contain plasticizers that are liquid at room temperature.

[0050] Preferably, the tyre as defined above is intended to equip heavy vehicles or buses. DETAILED DESCRIPTION

[0051] I-Detailed Description of the Invention

[0052] The present invention relates to a tyre intended to be fitted to vehicles of the heavy load-carrying type, comprising a tread comprising at least one rubber composition based on at least:

[0053] - an elastomeric matrix essentially comprising a copolymer based on styrene and butadiene having a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C,

[0054] - a reinforcing filler mainly comprising silicon dioxide,

[0055] -Chemical cross-linking system,

[0056] - agents for coupling between the elastomeric matrix and the reinforcing filler,

[0057] a plasticizing system comprising 2 to 15 phr, preferably 2 to 10 phr, of at least one plasticizing resin having a glass transition temperature Tg greater than or equal to 20° C., and the total content of the plasticizing system in the composition is from 2 to 17 phr, preferably from 2 to 12 phr, and

[0058] - an agent for modifying said copolymer based on styrene and butadiene, said agent optionally having been grafted onto said copolymer, said modifying agent being a 1,3-dipolar compound of general formula (I):

[0059] AED (I)

[0060] o The symbol D represents a functional group comprising at least one nitrogen atom, said functional group being capable of binding to said copolymer by a [3+2] type cycloaddition on a carbon-carbon double bond of the chain of said copolymer,

[0061] o Symbol E represents a divalent spacer group connecting group D to group A,

[0062] o A represents a functional group selected from the following: C 1 -C 20 Alkyl, C 7 -C 18 Alkyl aryl, C 7 -C 18Arylalkyl, optionally substituted nitrogen-based heterocyclic ring having 5 to 6 atoms, optionally substituted sulfur-based heterocyclic ring having 5 to 6 atoms, ester group, phosphate group, dialkylamino group, and associative groups containing at least one nitrogen atom.

[0063] In the present specification, unless otherwise expressly indicated, all percentages (%) shown are percentages by weight.

[0064] In addition, any numerical range expressed by the expression "between a and b" represents a numerical range extending from greater than "a" to less than "b" (i.e., excluding the end values ​​a and b), while any numerical range expressed by the expression "a to b" means a numerical range extending from "a" to "b" (i.e., including the strict end values ​​a and b).

[0065] The abbreviation “phr” (per hundred parts of rubber) means parts by weight per 100 parts of elastomer (or the sum of the elastomers, if several are present) or rubber present in the rubber composition.

[0066] The term "tyre intended to fit a vehicle of the heavy load-carrying type" generally means any tyre intended to fit a heavy vehicle, a bus, a civil engineering vehicle, an agricultural vehicle or an aircraft. The invention is particularly well suited to tyres intended to fit a heavy vehicle or a bus.

[0067] The term "rubber composition based on" is understood to mean that the rubber composition comprises a mixture and / or reaction products of the various components used, some of these essential components being able or intended to react at least partially with one another during the various stages of the preparation of the composition, in particular during its crosslinking or vulcanization.

[0068] The terms "elastomeric matrix" or "elastomeric matrix" mean all elastomers present in the rubber composition.

[0069] The term "elastomer" (or equivalently rubber), whether natural or synthetic, is understood to mean an elastomer composed at least in part (i.e. a homopolymer or a copolymer) of diene monomers (i.e. monomers bearing two conjugated or non-conjugated carbon-carbon double bonds). These elastomers are also known as diene elastomers.

[0070] These diene elastomers can be divided into two categories: “essentially unsaturated” or “essentially saturated”. “Essentially unsaturated” generally refers to a diene elastomer that is at least partially derived from conjugated diene monomers and has a content of units of diene origin (conjugated dienes) greater than 15% (mol%); thus diene elastomers such as butyl rubber or EPDM-type copolymers of dienes and α-olefins do not fall within the aforementioned definition but may in particular be referred to as “essentially saturated” diene elastomers (low or very low content of units of diene origin, always less than 15 mol%). In the category of “essentially unsaturated” diene elastomers, the term “highly unsaturated” diene elastomer refers in particular to a diene elastomer having a content of units of diene origin (conjugated dienes) greater than 50% (mol%).

[0071] Taking these definitions into account, the term “diene elastomer usable in the composition according to the invention” means more particularly:

[0072] (a) any homopolymer of a conjugated diene monomer, especially any homopolymer obtained by polymerization of a conjugated diene monomer containing 4 to 12 carbon atoms;

[0073] (b) - any copolymer obtained by copolymerization of one or more conjugated dienes with one another or with ethylene monomers or with one or more vinyl aromatic compounds containing from 8 to 20 carbon atoms;

[0074] (c) terpolymers obtained by copolymerization of ethylene and α-olefins containing from 3 to 6 carbon atoms with nonconjugated diene monomers containing from 6 to 12 carbon atoms, for example elastomers obtained from ethylene and propylene with nonconjugated diene monomers of the abovementioned type, such as, in particular, 1,4-hexadiene, ethylidene norbornene or dicyclopentadiene;

[0075] (d) - Copolymers of isobutylene and isoprene (butyl rubber), and also halogenated forms of such copolymers, in particular chlorinated or brominated forms.

[0076] Although the present invention is applicable to any type of diene elastomer, a person skilled in the art will understand that the present invention is preferably implemented using essentially unsaturated diene elastomers, in particular diene elastomers of type (a) or (b) above.

[0077] The diene elastomers may have any microstructure, which depends on the polymerization conditions used, in particular on the presence or absence of modifiers and / or randomizers and on the amount of modifiers and / or randomizers used. The diene elastomers may, for example, be block, random, sequential or microsequential elastomers and may be prepared in dispersion or in solution; they may be coupled and / or star-branched or functionalized by coupling and / or star-branching or functionalizing agents. For coupling to reinforcing inorganic fillers such as silica, mention may be made of, for example, silanol functional groups or polysiloxane functional groups with silanol endcapping (as described, for example, in FR2740778 or US6013718 and WO2008 / 141702), alkoxysilane groups (as described, for example, in FR2765882 or US5977238), carboxyl groups (as described, for example, in WO01 / 92402 or US6815473, WO2004 / 096865 or US2006 / 0089445), or polyether groups (as described, for example, in EP1127909 or US6503973, WO2009 / 000750 and WO2009 / 000752).

[0078] As functional diene elastomers, mention may also be made of those prepared using functional initiators, in particular those carrying amine functions or tin functions (see, for example, WO 2010 / 072761).

[0079] As other examples of functionalized diene elastomers, mention may also be made of elastomers of the epoxidized type (for example BR, NR or IR).

[0080] For the purposes of the present invention, the term "predominant" means that the compound is predominant among the compounds of the same type in the composition, that is, it is the one that represents the largest amount by mass among the compounds of the same type. In other words, the mass of the compound represents at least 51% of the total mass of the compounds of the same type in the composition. For example, in a system comprising only one elastomer, the elastomer is predominant within the meaning of the present invention, whereas in a system comprising two elastomers, the predominant elastomer represents more than half of the mass of the total elastomer, in other words, the mass of the elastomer represents at least 51% of the mass of the total elastomer. In the same way, a "predominant" filler is the filler that represents the largest mass among the fillers of the composition. In other words, the mass of the filler represents at least 51% of the mass of the total fillers in the composition.

[0081] The term "minor" refers to a compound that does not account for the largest mass fraction among compounds of the same type.

[0082] All glass transition temperature "Tg" values ​​are determined in a known manner by DSC (Differential Scanning Calorimetry) according to Standard ASTM D3418 (1999).

[0083] The term "free of compound X" means that compound X cannot be detected by measures known to those skilled in the art, or that compound X is present in an amount so small as to represent an impurity (ie, ppm (parts per million)).

[0084] In the context of the present invention, the carbon-based products mentioned in the specification may be fossil or biogenic. In the latter case, they may be produced in part or in whole from biomass, or obtained from renewable raw materials derived from biomass. Of particular interest are compounds (e.g., monomers, polymers), reagents and other ingredients mentioned in the specification, such as plasticizers, fillers, etc.

[0085] Copolymers based on styrene and butadiene

[0086] The elastomeric matrix of the rubber composition in the tire according to the invention consists essentially of a copolymer based on styrene and butadiene having a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C. In other words, the mass of the copolymer based on styrene and butadiene having a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C represents at least 51% of the total mass of the elastomeric matrix.

[0087] The term "copolymer based on styrene and butadiene" means herein a copolymer of at least one styrene monomer and at least one butadiene monomer having a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C (and of course also any mixtures of such copolymers); in other words, said copolymer based on styrene and butadiene comprises by definition at least styrene units (derived from styrene monomer) and butadiene units (derived from butadiene monomer) and has a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C.

[0088] The following are particularly suitable as butadiene monomers: 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C 1 -C 5 alkyl)-1,3-butadiene (e.g., 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene), aryl-1,3-butadiene.

[0089] The following are particularly suitable as styrene monomers: styrene, methylstyrene, p-tert-butylstyrene, methoxystyrene or chlorostyrene.

[0090] Among the copolymers based on styrene and butadiene, mention may in particular be made of those having a styrene content between 5% and 60% by weight and more particularly between 20% and 50% by weight, a 1,2-bond molar content (mol %) in the butadiene portion between 4% and 75% and a trans-1,4-bond molar content (mol %) in the butadiene portion between 10% and 80%. The styrene weight content, the molar content of 1,2-bonds in the butadiene portion and the molar content of trans-1,4-bonds are determined by techniques known to those skilled in the art.

[0091] In one embodiment, the copolymer based on styrene and butadiene is composed of styrene monomers and butadiene monomers, that is, the sum of the mole percentages of styrene monomers and butadiene monomers is equal to 100%.

[0092] In the remainder of the present specification, for the sake of simplicity, the expression "copolymer based on styrene and butadiene" is used to indicate a copolymer comprising or consisting of a styrene monomer and a butadiene monomer.

[0093] Copolymers based on styrene and butadiene can have any microstructure depending on the polymerization conditions used.

[0094] Preferably, the copolymer based on styrene and butadiene may be obtained by solution polymerization. It should advantageously be noted that the rubber composition of the tyre according to the invention may not contain or may contain very small amounts of extended copolymers based on styrene and butadiene; in other words, the content of extended copolymers based on styrene and butadiene, if copolymers of this type are present, may be less than or equal to 2 phr, so that this content may preferably correspond to impurities. More particularly, the rubber composition of the tyre according to the invention may be free of extended copolymers based on styrene and butadiene. The term "extended copolymer" means a copolymer extended and stabilized with an oil, in particular an oil of the paraffinic, naphthenic or aromatic type.

[0095] Preferably, the glass transition temperature Tg of the copolymer based on styrene and butadiene may be from -60° C. to -40° C. Those skilled in the art know how to modify the microstructure of the copolymer based on styrene and butadiene in order to adjust its Tg, in particular by modifying the content of 1,2-bonds in the styrene, butadiene part or trans-1,4-bonds in the butadiene part.

[0096] Preferably, the content of the copolymer based on styrene and butadiene in the rubber composition of the tire according to the invention may range from 51 to 100 phr, preferably from 60 to 100 phr and more preferably from 60 to 85 phr.

[0097] The copolymers based on styrene and butadiene can advantageously be used in a blend (mixture) with one or more other diene elastomers different from said copolymers based on styrene and butadiene. In the case of a blend, it is particularly understood that the sum of the various elastomers used is equal to 100 phr.

[0098] Thus, in one embodiment of the tire according to the invention, the above-mentioned copolymer based on styrene and butadiene may be optionally combined with at least one second diene elastomer different from the copolymer based on styrene and butadiene; that is to say, the second diene elastomer does not contain any units originating from styrene and butadiene. When it is present, the second diene elastomer may be chosen from polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymers different from butadiene-styrene copolymers, isoprene copolymers and mixtures of these polymers and copolymers. Preferably, the second diene elastomer may be polybutadiene (BR). When it is present, the content of the second diene elastomer may be at most equal to 49 phr, preferably at most equal to 35 phr. Preferably, the content of the second diene elastomer may range from 5 to 49 phr (as a reminder, the term “phr” means parts by weight per 100 parts of elastomer (that is to say the total amount of elastomer present in the tread)), preferably from 15 to 35 phr.

[0099] In another embodiment of the tire according to the invention, the copolymer based on styrene and butadiene may be optionally combined with at least one second diene elastomer, different from said copolymer based on styrene and butadiene (that is to say not comprising any units derived from styrene and butadiene), a third elastomer different from said copolymer based on styrene and butadiene and also different from the second diene elastomer. Preferably, the third diene elastomer may be an isoprene elastomer. Preferably, the second diene elastomer may be chosen from polybutadienes (BR) and butadiene copolymers different from butadiene-styrene copolymers; and the third diene elastomer may be chosen from natural rubber (NR), synthetic isoprene (IR), isoprene copolymers and mixtures of these polymers and copolymers. Preferably, the second diene elastomer may be butadiene and the third diene elastomer may be natural rubber or synthetic isoprene. Preferably, the content of the second elastomer may be 0.5 to 35 phr, and the content of the third elastomer may be 0.5 to 35 phr; more preferably, the content of the second elastomer may be 9 to 31 phr, and the content of the third elastomer may be 4 to 24 phr.

[0100] Among the polybutadienes or butadiene copolymers used in the above-mentioned blends, those particularly suitable for use are: polybutadienes with a content (mol %) of 1,2-units between 4% and 80% or those with a content (mol %) of cis-1,4-units greater than 80%, more particularly greater than 90%, butadiene-isoprene copolymers, especially those with an isoprene content between 5% and 90% by weight and a Tg of -40°C to -80°C, or isoprene-styrene copolymers, especially those with a styrene content between 5% and 50% by weight and a Tg between -25°C and -50°C. In the case of butadiene-styrene-isoprene copolymers, those having a styrene content of between 5% and 50% by weight and more particularly between 10% and 40% by weight, an isoprene content of between 15% and 60% by weight and more particularly between 20% and 50% by weight, a butadiene content of between 5% and 50% by weight and more particularly between 20% and 40% by weight, a content of 1,2-units in the butadiene part and a content of 1,2-units in the butadiene part and a content of 2,3-dimethylformamide ...2,3-dimethylformamide in the butadiene part and a content of 2,3-dimethylformamide in the butadiene part and a content of 2,3-dimethylformamide in the butadiene part and a content of 2,3-dimethylformamide in the butadiene part and a content of 2,3-dimethylformamide in the butadiene The invention relates to butadiene-styrene-isoprene copolymers having a content (mol %) of between 4% and 85%, a content (mol %) of trans-1,4-units in the butadiene part between 6% and 80%, a content (mol %) of 1,2-plus 3,4-units in the isoprene part between 5% and 70% and a content (mol %) of trans-1,4-units in the isoprene part between 10% and 50%, more typically any butadiene-styrene-isoprene copolymer having a Tg between -20°C and -70°C.

[0101] Among the isoprene elastomers (i.e. isoprene homopolymers or copolymers) used in the above blends, mention will be made in particular of NR, IR, or isoprene copolymers such as isobutylene-isoprene (butyl rubber or IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR) copolymers. Among the synthetic polyisoprenes, it may be preferred to use polyisoprenes having a cis-1,4-linkage content (mol %) greater than 90%, even more preferably greater than 98%.

[0102] The previously described diene elastomers may also be combined in smaller amounts with synthetic elastomers other than diene elastomers or even with non-elastomeric polymers, such as thermoplastic polymers.

[0103] Reagents for modifying copolymers based on styrene and butadiene

[0104] As previously stated, the rubber composition used in the tire of the invention comprises at least one agent for modifying a copolymer based on styrene and butadiene, said agent optionally having been grafted onto said copolymer, said modifier being a 1,3-dipolar compound of general formula (I):

[0105] AED (I)

[0106] o The symbol D represents a functional group comprising at least one nitrogen atom, said functional group being capable of binding to said copolymer by a [3+2] type cycloaddition on a carbon-carbon double bond of the chain of said copolymer,

[0107] o The symbol E represents a divalent spacer group connecting the functional group D to the functional group A,

[0108] o A represents a functional group selected from the following: C 1 -C 20 Alkyl, C 7 -C 18 Alkyl aryl, C 7 -C 18 Arylalkyl, optionally substituted nitrogen-based heterocyclic ring having 5 to 6 atoms, optionally substituted sulfur-based heterocyclic ring having 5 to 6 atoms, ester group, phosphate group, dialkylamino group, and associative groups containing at least one nitrogen atom.

[0109] For the purposes of the present invention, the term "modifier" means an electrically neutral compound with at least one dipole (i.e., a positive charge and a negative charge in one of its main standard formulas) and capable of forming a [1,3] dipolar cycloaddition on an unsaturated carbon-carbon bond. In other words, the modifier is a 1,3-dipolar compound. Those skilled in the art can refer to the definition of this compound given by IUPAC (International Union of Pure and Applied Chemistry) in the table of class names of organic compounds and reactive intermediates based on structure (IUPAC Recommendations 1995, PAC, 1995, 67, 1307).

[0110] The functional group D comprises at least one nitrogen atom and is capable of binding to the chain of the copolymer based on styrene and butadiene by a [3+2] type cycloaddition on the carbon-carbon double bonds of the chain of said copolymer.

[0111] Preferably, the functional group D comprises a nitrile oxide functional group, a nitrone functional group or a nitrile imine functional group.

[0112] For the purposes of the present invention, the term "nitrile oxide" means a dipole corresponding to the formula -C≡N→O, including its meso form.

[0113] For the purposes of the present invention, the term "nitrile imine" means a dipole corresponding to the formula -C≡N→N, including its meso form.

[0114] For the purposes of the present invention, the term "nitrone" means a dipole corresponding to the formula -C=N(→O)-, including its meso form.

[0115] Preferably, the functional group D comprises a nitrile oxide functional group.

[0116] Preferably, the functional group D comprises a nitrile oxide functional group and is a group having the formula (II):

[0117]

[0118] in:

[0119] -R1, R2, R3, R4, R5 may be the same or different and represent a hydrogen atom, a halogen atom, a C 1 -C 5 Alkyl, C 1 -C 5 Alkoxy or a covalent bond capable of connecting to a spacer group E;

[0120] - provided that at least one of R1, R2, R3, R4 and R5 represents said covalent bond.

[0121] Among the ester groups, those corresponding to the formula C(O)-O-R6, in which R6 represents C 1 -C 20 Hydrocarbyl groups, preferably C 1 -C 12 A hydrocarbon group, more preferably a C 1 -C 6 Preferably, R6 is C 1 -C 6 Alkyl, more preferably R6 is methyl or ethyl.

[0122] Among the phosphate groups, those corresponding to the formula -O-P(O)(OR7)(OR8) are particularly suitable for use, wherein R7 and R8 may be identical or different and represent a hydrogen atom, an alkyl group, an aryl group or an alkylaryl group. Preferably, R7 and R8 are identical and are C 1 -C 12 Alkyl, preferably C 1 -C 6 The alkyl group is preferably a methyl group or an ethyl group.

[0123] Among the dialkylamino groups, those corresponding to the formula -NR9R10, in which R9 and R10 may be identical or different, are particularly suitable for use. 1 -C 6 Alkyl. Mention may be made, for example, of an N,N-dimethylamino group, an N,N-diethylamino group or an N-ethyl-N-propylamino group. Preferably, R9 and R10 are identical and are methyl.

[0124] The term "associative groups comprising at least one nitrogen atom" means groups which are able to associate with each other via hydrogen bonds, ionic bonds and / or hydrophobic bonds and which contain one or more nitrogen atoms. They are especially groups which are able to associate via hydrogen bonds.

[0125] When the associative groups are capable of associating via hydrogen bonding, each associative group comprises at least one donor "site" and one acceptor site with respect to hydrogen bonding, such that two identical associative groups are self-complementary and can associate together by forming at least two hydrogen bonds.

[0126] The associative groups according to the invention are also capable of associating via hydrogen bonds, ionic bonds and / or hydrophobic bonds with functional groups present on the fillers present in the composition.

[0127] The spacer group E is a divalent group which allows the attachment of at least one functional group D and / or at least one functional group A, especially when the functional group A is an associative group, and can therefore be of any type known per se. However, the spacer group E must not interfere with the functional groups D and A of the modifier, or must interfere very little, especially when the functional group A is an associative group.

[0128] The spacer group E is therefore considered to be a divalent group which is inert relative to the functional group D. The spacer group E is preferably a linear, branched or cyclic hydrocarbon chain which may contain one or more aromatic groups and / or one or more heteroatoms. The chain may optionally be substituted, provided that the substituents are inert relative to the functional group D.

[0129] According to a preferred embodiment, the spacer group E is a linear or branched C 1 -C 24 Preferred C 1 -C 10 Alkyl chain, more preferably linear C 1 -C 6 An alkyl chain optionally comprising one or more heteroatoms selected from nitrogen, sulfur and oxygen atoms.

[0130] The compound according to the present invention comprising a functional group D, a spacer group E and a functional group A (especially an associative group) can be represented, for example, by the following formula (IIIa):

[0131] AED (IIIa)

[0132] The compound according to the invention comprising a functional group D, a spacer group E and two functional groups A (especially two associative groups) can be represented, for example, by the following formula (IIIb):

[0133]

[0134] Similarly, the compound according to the invention comprising two functional groups D, a spacer group E and a functional group A (especially an associative group) can be represented, for example, by the following formula (IIIc):

[0135]

[0136] According to the same principle, the compound according to the present invention comprising two functional groups D, a spacer group E and two functional groups A (especially two associative groups) can be represented by the following formula (IIId), for example:

[0137]

[0138] Preferably, the functional group A is an associative group comprising at least one nitrogen atom and is selected from the following formulae (IV) to (VIII):

[0139]

[0140]

[0141] in:

[0142] -R11 represents a hydrocarbon group which may optionally contain heteroatoms,

[0143] -Q represents an oxygen atom or a sulfur atom or NH, preferably an oxygen atom, and

[0144] -The symbol * indicates the connection to the spacer group E.

[0145] Preferably, the modifier to be grafted or the modifier grafted onto the copolymer based on styrene and butadiene can be selected from the following compounds (IX) to (XVIII):

[0146]

[0147]

[0148] Even more preferably, the modifier is selected from compounds having formula (XIII), (XIV), (XV) and (XVII) above and their meso forms.

[0149] The modifying agent of general formula (I) used in the present invention, if not commercially available, can be prepared by any method known to those skilled in the art. For example, the synthesis method described in WO 2012 / 007441 can be used.

[0150] In the remainder of this document, the term "content of modifier" present in the rubber composition (expressed as mole percentage) means the number of moles of said modifier present in the composition per 100 units of the copolymer based on styrene and butadiene in the composition, whether these units are diene units or non-diene units.

[0151] For example, if the modifier is present at 0.20 mol% on a copolymer based on styrene and butadiene, this means that for every 100 styrene and butadiene units of the copolymer, there will be 0.20 units derived from the modifier.

[0152] Preferably, the content of the modifier is 0.01 to 50 mol %, preferably 0.01 to 5 mol %.

[0153] The grafting of copolymers based on styrene and butadiene having a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C is carried out by reacting said copolymers with functional groups D carried by a modifier as defined above. During this reaction, the functional groups D or these functional groups D form covalent bonds with the elastomer chains.

[0154] More precisely, the grafting of the modifier is accomplished by a [3+2] cycloaddition of the functional group D of the modifier as defined above to one or more carbon-carbon double bonds of the chain of the copolymer based on styrene and butadiene. The cycloaddition mechanism is well known to those skilled in the art and can be illustrated by the following general reaction scheme:

[0155] Cycloaddition of the nitrile oxide to the unsaturated groups or double bonds of the polymer (in this case the isoprene units)

[0156]

[0157] Cycloaddition of the nitrone to an unsaturated group or double bond of the polymer (in this case the isoprene unit)

[0158]

[0159] Cycloaddition of the nitrile imine with the unsaturated groups or double bonds of the polymer (in this case the isoprene units)

[0160]

[0161] The modifier (or preferred modifiers) of formula (I) as defined above can be grafted in bulk, for example in an internal mixer or an open mixer (e.g. an open mill). The grafting is then carried out at a temperature of less than 60° C. in an open mixer or an internal mixer, followed by a grafting reaction step in a press or furnace at a temperature of 80° C. to 200° C. or at a temperature of more than 60° C. in an open mixer or an internal mixer, without subsequent heat treatment.

[0162] The grafting process can also be carried out in solution, continuously or batchwise.The copolymer thus modified can be isolated from its solution by any type of method known to those skilled in the art, in particular by stripping operations.

[0163] Reinforcement filler

[0164] The rubber composition used in the tire of the present invention comprises at least one reinforcing filler, the reinforcing filler mainly comprises silica, that is, the mass of silica accounts for at least 51% of the total mass of the reinforcing filler component. Preferably, the mass of silica accounts for more than 60% of the total reinforcing filler mass, preferably more than 70%.

[0165] In the present description, the BET specific surface area is determined in a known manner by gas adsorption using the Brunauer-Emmett-Teller method described in The Journal of the American Chemical Society, Vol. 60, p. 309, February 1938, more particularly according to the French standard NF ISO 9277 of December 1996 (volumetric (5-point) method - gas: nitrogen - degassing: 1 hour at 160° C. - relative pressure p / po range: 0.05 to 0.17). The CTAB specific surface area is the external surface area determined according to the French standard NF T45-007 of November 1987 (method B).

[0166] The term "reinforcing inorganic filler" is understood here to mean any inorganic or mineral filler, whatever its color and its origin (natural or synthetic), which is also called "white filler", "transparent filler" or even "non-black filler" in comparison with carbon black; this inorganic filler is capable of reinforcing the rubber composition intended for the manufacture of tires alone without any means other than an intermediate coupling agent, in other words, this inorganic filler is capable of replacing conventional tire-grade carbon black in its reinforcing effect. Such fillers are generally characterized in a known manner by the presence of hydroxyl (-OH) groups on their surface, which, in order to be used as reinforcing fillers, require the use of coupling agents or systems intended to provide stable chemical bonds between the filler and the elastomeric matrix.

[0167] Siliceous mineral fillers, preferably silicon dioxide (SiO 2 ) is particularly suitable for use as an inorganic reinforcing filler. The silica used may be any reinforcing silica known to those skilled in the art, in particular, one having a BET specific surface area and a CTAB specific surface area of ​​less than 450 m 2 / g, preferably 30 to 400m 2 / g, especially at 60 and 300m 2As highly dispersible precipitated silicas ("HDS"), mention may be made of, for example, Ultrasil 7000 and Ultrasil 7005 silicas from Evonik, Zeosil 1165MP, 1135MP and 1115MP silicas and Zeosil Premium 200 silica from Solvay, Hi-Sil EZ150G silica from PPG, Zeopol 8715, 8745 and 8755 silicas from Huber or silicas with a high specific surface area as described in patent application WO 03 / 016837.

[0168] Of course, the term "reinforcing inorganic filler" is also understood to mean mixtures of various reinforcing inorganic fillers, in particular mixtures of highly dispersible silica or siliceous type inorganic fillers as described above with non-siliceous inorganic fillers. As non-siliceous inorganic fillers, mention may be made of mineral fillers of the aluminous type, in particular alumina (Al 2 O 3 ) or aluminum (oxide) hydroxide, or reinforcing titanium oxide, for example as described in US 6 610 261 and US 6 747 087. When present, the non-siliceous inorganic filler is a minor component of the reinforcing filler.

[0169] It is not important in what physical state the inorganic reinforcing filler is provided, whether it is in the form of a powder, microspheres, granules or beads.

[0170] According to one embodiment, the content of reinforcing filler in the rubber composition of the tyre according to the invention may range from 55 to 200 phr, preferably from 55 to 150 phr, more preferably from 55 to 80 phr. These preferred ranges apply to any embodiment of the invention.

[0171] It will be appreciated by those skilled in the art that reinforcing fillers of another nature, in particular organic nature, such as carbon black, can be used as fillers equivalent to the reinforcing inorganic fillers described in this section, provided that the reinforcing filler is covered with an inorganic layer such as silica, or contains functional sites, in particular hydroxyl sites, on its surface that require the use of a coupling agent to form a bond between the filler and the elastomer. By way of example, mention may be made of carbon blacks such as those used in tires, as described in, for example, patent documents WO 96 / 37547 and WO 99 / 28380.

[0172] Carbon Black :

[0173] According to one embodiment of the tire of the present invention, the rubber composition may further contain carbon black.

[0174] When present, carbon black may preferably be used in an amount less than or equal to 10 phr, preferably less than or equal to 5 phr. Preferably, the amount of carbon black may be from 0.5 to 4 phr. These preferred ranges apply to any embodiment of the present invention.

[0175] Any carbon black, in particular the carbon black conventionally used in tires or their treads ("tire grade" carbon black) is suitable for use as carbon black. Among the latter, the reinforcing carbon blacks of the 100, 200 and 300 series, or the carbon blacks of the 500, 600 or 700 series (ASTM grade), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683 and N772 carbon blacks, will be more particularly mentioned. These carbon blacks can be used in a separate form as commercially available, or can be used in any other form, for example as a support for some rubber additives used.

[0176] Coupling agent

[0177] In order to couple the reinforcing inorganic filler to the elastomeric matrix (that is to say to the copolymer based on styrene and butadiene modified by the modifier, and to the diene elastomer when present), use may be made in a known manner of at least bifunctional coupling agents (or binders) intended to provide a connection of satisfactory chemical and / or physical nature between the inorganic filler (the surface of its particles) and the elastomeric matrix. Use may in particular be made of at least bifunctional organosilanes or polyorganosiloxanes.

[0178] Use is made in particular of silane polysulfides which, depending on their specific structure, are referred to as “symmetrical” or “asymmetrical”, as described, for example, in patent applications WO 03 / 002648 (or US 2005 / 016651) and WO 03 / 002649 (or US 2005 / 016650).

[0179] Particularly suitable, but not limited to the following, are silane polysulfides corresponding to the following general formula (XVIII):

[0180] ZB x -BZ

[0181] (XVIII)

[0182] in:

[0183] -x is an integer from 2 to 8 (preferably from 2 to 5);

[0184] - Symbol B, which may be the same or different, represents a divalent hydrocarbon group (preferably C 1 -C 18 Alkylene or C 6 -C 12Arylene, more particularly C 1 -C 10 , especially C 1 -C 4 Alkylene, especially propylene);

[0185] - The symbols Z, which may be the same or different, correspond to one of the following three formulae:

[0186]

[0187] in:

[0188] -R 12 The groups may be substituted or unsubstituted and may be identical or different from each other, indicating that C 1 -C 18 Alkyl, C 5 -C 18 Cycloalkyl or C 6 -C 18 Aryl (preferably C 1 -C 6 Alkyl, cyclohexyl or phenyl, especially C 1 -C 4 alkyl, more particularly methyl and / or ethyl),

[0189] -R 13 The groups may be substituted or unsubstituted and identical or different from each other, indicating that C 1 -C 18 Alkoxy or C 5 -C 18 Cycloalkoxy (preferably selected from C 1 -C 8 Alkoxy and C 5 -C 8 The cycloalkoxy group is even more preferably selected from C 1 -C 4 alkoxy radicals, in particular methoxy and ethoxy).

[0190] In the case of mixtures of alkoxysilane polysulfides corresponding to the above formula (XVIII), in particular the conventional commercially available mixtures, the average value of the "x" index is preferably a fraction between 2 and 5, more preferably a fraction of approximately 4. However, the invention can also be advantageously carried out using, for example, alkoxysilane disulfides (x=2).

[0191] As examples of silane polysulfides, mention will be made more particularly of bis((C 1 -C 4 ) alkoxy (C 1 -C 4 )alkylsilyl(C 1 -C4 )alkyl) polysulfides (especially disulfides, trisulfides or tetrasulfides), for example bis(3-trimethoxysilylpropyl) or bis(3-triethoxysilylpropyl) polysulfides. Among these compounds, the formula [(C 2 H 5 O) 3 Si(CH 2 ) 3 S 2 ] 2 Bis(3-triethoxysilylpropyl)tetrasulfide, or TESPD, of the formula [(C 2 H 5 O) 3 Si(CH 2 ) 3 S] 2 As preferred examples, mention will also be made of bis(mono(C 1 -C 4 ) alkoxydi(C 1 -C 4 )alkylsilylpropyl)polysulfide (especially disulfide, trisulfide or tetrasulfide), more especially bis(monoethoxydimethylsilylpropyl)tetrasulfide, as described in the above-mentioned patent application WO 02 / 083782 (or US Pat. No. 7,217,751).

[0192] As examples of coupling agents other than alkoxysilane polysulfides, mention will be made in particular of bifunctional POS (polyorganosiloxane) or hydroxysilane polysulfide (in the above formula (XVIII), R 2 =OH), as described, for example, in patent applications WO 02 / 30939 (or US 6774255), WO 02 / 31041 (or US 2004 / 051210) and WO 2007 / 061550, or silanes or POS carrying an azodicarbonyl function, as described, for example, in patent applications WO 2006 / 125532, WO 2006 / 125533, WO 2006 / 125534.

[0193] As examples of other silane sulfides, mention will be made of, for example, silanes carrying at least one mercapto (—SH) function (called mercaptosilanes) and / or at least one masked mercapto function, as described, for example, in patents or patent applications US Pat. No. 6,849,754, WO 99 / 09036, WO 2006 / 023815, WO 2007 / 098080, WO 2010 / 072685 and WO 2008 / 055986.

[0194] Of course, it is also possible to use mixtures of the abovementioned coupling agents, as described in particular in the abovementioned patent application WO 2006 / 125534.

[0195] The content of coupling agent is advantageously less than 20 phr, it being understood that it is generally desirable to use as little coupling agent as possible. Typically, the content of coupling agent accounts for 0.5% to 15% by weight of the amount of inorganic filler. Its content is preferably between 0.5 and 12 phr, more preferably in the range of 3 to 10 phr. This content is easily adjusted by those skilled in the art according to the content of inorganic filler used in the composition. These preferred ranges apply to any embodiment of the present invention.

[0196] Covering agent :

[0197] In addition to the coupling agents, these compositions may also contain coupling activators, agents for coating the inorganic fillers or, more generally, processing aids which are able to improve, in a known manner, the processability of the composition in the untreated state, owing to improved dispersion of the filler in the rubber matrix and to a reduction in the viscosity of the composition, such agents as, for example, hydrolyzable silanes such as alkylalkoxysilanes, polyols, polyethers, primary, secondary or tertiary amines or hydroxylated or hydrolyzable polyorganosiloxanes.

[0198] Plasticizing system

[0199] The rubber composition of the tire according to the invention comprises 2 to 17 phr of a plasticizing system comprising: 2 to 15 phr of at least one plasticizing resin having a glass transition temperature Tg greater than or equal to 20° C. and preferably 0 to 2 phr of a plasticizer that is liquid at room temperature.

[0200] As known to the person skilled in the art, the term "resin" is reserved by definition in this patent application for compounds that are solid at room temperature (23° C.), in contrast to plasticizers, such as oils, which are liquid at room temperature.

[0201] Plasticizing resins are polymers well known to those skilled in the art. These are hydrocarbon-based resins that are essentially based on carbon and hydrogen but may contain other types of atoms, which can be used in particular as plasticizers or tackifiers in polymer matrices. They are miscible (i.e. compatible) with the diene elastomer compositions for which they are intended in terms of properties at the content used, thus acting as real diluents. They have been described in, for example, the publication entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9), the 5th chapter of which relates to their applications, in particular in the field of tire rubbers (5.5. "Rubber Tires and Mechanical Goods"). They can be aliphatic, alicyclic, aromatic, hydrogenated aromatic, or aliphatic / aromatic type, that is, based on aliphatic and / or aromatic monomers. They can be natural or synthetic, and based or not based on petroleum (in the case of being based on petroleum, they are also referred to as petroleum resins). Their Tg is preferably greater than 0°C, especially greater than 20°C (most usually between 30°C and 95°C).

[0202] In a known manner, these plasticized resins can also be referred to as thermoplastic resins in terms of the meaning that plasticized resins soften when heated and can therefore be molded. They can also be defined by softening point or softening temperature. The softening point of plasticized resins is usually about 50 to 60 ° C higher than its Tg value. Softening point is measured according to standard ISO 4625 (ring and ball method). Macrostructure (Mw, Mn and PDI) is determined by size exclusion chromatography (SEC) as described below.

[0203] As a reminder, the SEC analysis consists, for example, in separating macromolecules in solution according to their size by means of a column 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 a concentration of 1 g / l in a suitable solvent, tetrahydrofuran. The solution is then filtered through a filter with a porosity of 0.45 μm before injection into the instrument. The instrument used is, for example, a "Waters Alliance" chromatographic line according to the following conditions: elution solvent: tetrahydrofuran; temperature 35° C.; concentration 1 g / l; flow rate: 1 ml / min; injection volume: 100 μl; molar calibration with polystyrene standards; a set of 3 "Waters" columns in series ("Styragel HR4E", "Styragel HR1" and "Styragel HR 0.5"); detection is carried out by a differential refractometer (for example "Waters 2410") which may be equipped with operating software (for example "Waters Millenium").

[0204] The molar calibration was performed using the following series of commercial polystyrene standards with low PDI (less than 1.2) and known molar masses covering the mass range to be analyzed. The weight-average molar mass (Mw), number-average molar mass (Mn) and polydispersity index (PDI=Mw / Mn) were derived from the recorded data (mass distribution curve of molar masses). Therefore, all values ​​of molar masses shown in this patent application are relative to the calibration curve generated with polystyrene standards.

[0205] According to a preferred embodiment of the present invention, the plasticized resin may have at least any one of the following characteristics:

[0206] - Tg greater than or equal to 20°C (in particular between 30°C and 100°C), more preferably greater than or equal to 30°C (in particular between 30°C and 95°C);

[0207] - a softening point greater than or equal to 40° C. (in particular between 40° C. and 150° C.);

[0208] - a number average molar mass (Mn) between 400 and 2000 g / mol, preferably between 500 and 1500 g / mol;

[0209] The polydispersity index (PDI) is less than 3, preferably less than 2 (reminder: PDI=Mw / Mn, where Mw is the weight-average molar mass).

[0210] More preferably, the plasticizing resin may have all of the above-mentioned preferred characteristics.

[0211] As examples of such plasticizing resins, mention may be made of those selected from the group consisting of cyclopentadiene (abbreviated as CPD) homopolymer or copolymer resins, dicyclopentadiene (abbreviated as DCPD) homopolymer or copolymer resins, terpene homopolymer or copolymer resins, C 5 Fraction homopolymer or copolymer resin, C 9 Fraction homopolymer or copolymer resin, C 5 Fraction homopolymer or copolymer resin and C 9 Mixtures of fraction homopolymer or copolymer resins, alpha-methylstyrene homopolymer or copolymer resins, and mixtures of these resins.

[0212] Among the above copolymer resins, mention may be made more particularly of those selected from the group consisting of CPD / vinyl aromatic copolymer resins, DCPD / vinyl aromatic copolymer resins, CPD / terpene copolymer resins, DCPD / terpene copolymer resins, terpene / phenol copolymer resins, CPD / C 5 Distillate copolymer resin, DCPD / C 5 Fraction copolymer resin, CPD / C9 Distillate copolymer resin, DCPD / C 9 Fraction copolymer resin, C 5 A mixture of fractions and C9 fraction resins, terpene / vinyl aromatic copolymer resins, terpene / phenol copolymer resins, C 5 distillate / vinyl aromatic copolymer resins, and mixtures of these resins.

[0213] The term "terpene" here in a known manner combines the monomers α-pinene, β-pinene and limonene; preference is given to using the limonene monomer, which compound exists in a known manner in the form of three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer) or dipentene (racemate of dextrorotatory and levorotatory enantiomers). Suitable vinyl aromatic monomers are, for example: styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, p-(tert-butyl)styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinyl mesitylene, divinylbenzene, vinylnaphthalene or tert-butylstyrene derived from C 9 fraction (or more usually from C 8 To C 10 fraction).

[0214] More particularly, mention may be made of a resin selected from the group consisting of CPD homopolymer resins, DCPD homopolymer resins, CPD / styrene copolymer resins, DCPD / styrene copolymer resins, polylimonene resins, limonene / styrene copolymer resins, limonene / CPD copolymer resins, limonene / DCPD copolymer resins, CPD / styrene ... 5 Fraction / styrene copolymer resin, C 5 Fraction / C 9 Fraction copolymer resins, and mixtures of these resins.

[0215] All of the above resins are known to the person skilled in the art and are commercially available, for example, in the case of polylimonene resins, they are sold under the name Dercolyte by the company DRT and in the case of C 5 Fraction / Styrene resin or C 5 Fraction / C 9 The fraction resins are sold under the name Super Nevtac by the company Neville Chemical Company, under the name Hikorez by Kolon or under the name Escorez by the company Exxon Mobil, or under the name 40MS or 40NS by the company Struktol (mixtures of aromatic and / or aliphatic resins).

[0216] According to one embodiment of the invention, the plasticizing system may also comprise a plasticizer that is liquid at room temperature (at 23° C.), said plasticizer being present in a content less than or equal to 2 phr.

[0217] In addition to the plasticizing resin, it is also possible to use any extender oil, whether aromatic or non-aromatic, or any plasticizer that is liquid at room temperature (known for its plasticizing properties with respect to diene elastomers). These plasticizers or these oils (more or less viscous) are liquids (that is to say, substances that have the ability to finally take on the shape of their container) at room temperature (23° C.), in particular in contrast to the plasticized hydrocarbon resins that are naturally solid at room temperature.

[0218] As plasticizers that are liquid at room temperature, there can be mentioned in particular liquid diene polymers, polyolefin oils, naphthenic oils, paraffinic oils, DAE (distilled aromatic extract) oils, MES (solvate extracted by medium) oils, TDAE (treated distilled aromatic extract) oils, RAE (residual aromatic extract) oils, TRAE (treated residual aromatic extract) oils, SRAE (safe residual aromatic extract) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these compounds. According to a more preferred embodiment, the plasticizer that is liquid at room temperature is selected from MES oils, TDAE oils, naphthenic oils, vegetable oils and mixtures of these oils.

[0219] In one embodiment, the rubber composition of the tire according to the invention may comprise 2 to 12 phr of a plasticizing system comprising: 2 to 10 phr of at least one plasticizing resin having a glass transition temperature Tg greater than or equal to 20° C., and preferably 0 to 2 phr of a plasticizer that is liquid at room temperature (23° C.). The preferred features of the plasticizing resin as described above and of the plasticizer that is liquid at room temperature (when it is present) apply to this embodiment.

[0220] In another embodiment, the rubber composition of the tire according to the invention may be free of plasticizers that are liquid at room temperature (23° C.). In this case, the rubber composition of the tire according to the invention may contain 2 to 10 phr of a plasticizing system consisting of 2 to 10 phr of at least one plasticizing resin having a glass transition temperature Tg greater than or equal to 20° C.

[0221] Various additives

[0222] The rubber composition of the tyre according to the invention may also contain all or some of the usual additives usually used in elastomeric compositions intended to constitute the outer mix of a finished rubber article, such as a tyre, in particular a tread, such as protective agents such as anti-ozone waxes (for example paraffin waxes), chemical antiozonants, antioxidants, anti-fatigue agents, pigments.

[0223] Cross-linking system

[0224] The crosslinking system is preferably a vulcanization system, i.e. a system based on sulfur (or on a sulfur donor) and a primary vulcanization accelerator. Various known secondary vulcanization accelerators or vulcanization activators (e.g. zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (particularly diphenylguanidine)), or known vulcanization retarders can be added to the basic vulcanization system, introduced in the first non-production stage and / or during the production stage, as described later.

[0225] When sulfur is used, it is used in a preferred content of between 0.5 and 12 phr, in particular between 1 and 10 phr. These preferred ranges apply to any embodiment of the present invention. The primary vulcanization accelerator is used in a preferred content of between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr. These preferred ranges apply to any embodiment of the present invention.

[0226] The sulphur content used in the rubber composition of the tread according to the invention is most generally between 0.5 and 3.0 phr, and the content of primary accelerator is between 0.5 and 5.0 phr. These preferred ranges apply to any one of the embodiments of the invention.

[0227] As (primary or secondary) accelerator, any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used, in particular accelerators of the thiazole type and derivatives thereof, and accelerators of the thiuram and zinc dithiocarbamate type. These accelerators are chosen, for example, from 2-mercaptobenzothiazole disulfide (abbreviated to MBTS), tetrabenzylthiuram disulfide (TBZTD), N-cyclohexyl-2-benzothiazolesulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolesulfenamide (DCBS), N-(tert-butyl)-2-benzothiazolesulfenamide (TBBS), N-(tert-butyl)-2-benzothiazolesulfenimide (TBSI), zinc dibenzyldithiocarbamate (ZBEC) and mixtures of these compounds.

[0228] Composition and tire preparation

[0229] The rubber composition can be prepared in a suitable mixer according to general procedures well known to those skilled in the art using two consecutive preparation stages: a first stage of thermomechanical processing or kneading at high temperature (up to a maximum temperature of between 130° C. and 200° C., preferably between 145° C. and 185° C.) (sometimes called the “non-preparation” stage), followed by a second stage of mechanical processing at a lower temperature, generally below 120° C., for example between 60° C. and 100° C. (sometimes called the “preparation” stage), during which the crosslinking or vulcanization system is introduced.

[0230] According to a first embodiment of the invention, before preparing the rubber composition, the copolymer based on styrene and butadiene as defined above is grafted with a modifier having formula (I) as defined above (or a plurality of preferred modifiers as defined above). In this case, it is therefore a grafted copolymer based on styrene and butadiene, having a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C, which is introduced during the "non-preparative" first stage. Therefore, according to this first embodiment of the method, the method comprises the following steps:

[0231] - modifying said copolymer based on styrene and butadiene in a post-polymerization or in solution or in bulk by grafting with a modifier of formula (I) as defined above (or a plurality of preferred modifiers as defined above),

[0232] - introducing the reinforcing filler, the plasticizing system and all the other essential components of the composition except the chemical crosslinking system into said copolymer based on styrene and butadiene grafted with said modifier (or preferred modifiers as defined above), kneading everything thermomechanically one or more times until reaching a maximum temperature of between 130° C. and 200° C., preferably between 145° C. and 185° C.,

[0233] - cooling the combined mixture to a temperature below 100°C,

[0234] -Then introduce a chemical cross-linking agent,

[0235] - kneading all the materials until the maximum temperature is less than 120°C,

[0236] - Extruding or calendering the rubber composition thus obtained.

[0237] According to a second embodiment of the invention, the grafting of a copolymer based on styrene and butadiene with a modifier of formula (I) (or a plurality of preferred modifiers as defined above) can be carried out simultaneously with the preparation of the rubber composition, the copolymer having a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C. In this case, both the copolymer based on styrene and butadiene, which has not yet been grafted, and the modifier of formula (I) (or a plurality of preferred modifiers as defined above) are introduced during a first "non-preparation" stage. Preferably, the reinforcing filler is then subsequently added during this same non-preparation stage to prevent any side reactions with the modifier of formula (I) (or with a plurality of preferred modifiers as defined above).

[0238] Therefore, according to this second embodiment of the method, the method comprises the following steps:

[0239] - introducing into a copolymer based on styrene and butadiene having a glass transition temperature Tg strictly above -65°C and below or equal to -30°C: a modifier of formula (I) as described above (or a plurality of preferred modifiers as defined above) is introduced at a temperature and for a duration such that the grafting rate is preferably greater than 60%, more preferably greater than 80%, followed by preferably reinforcing fillers, plasticizing system and all the essential components of the composition except the chemical crosslinking system, by one or more thermomechanical kneading of all the substances until a maximum temperature of between 130°C and 200°C, preferably between 145°C and 185°C is reached,

[0240] - cooling the combined mixture to a temperature below 100°C,

[0241] -Then a chemical cross-linking agent is introduced,

[0242] - kneading all the materials until the maximum temperature is less than 120°C,

[0243] - Extruding or calendering the rubber composition thus obtained.

[0244] The final composition thus obtained can subsequently be calendered, for example, into the form of sheets or plates, in particular for laboratory characterizations, or extruded to form rubber profiles for use, for example, as treads for tires intended for vehicles of the load-bearing type, in particular for heavy vehicles or civil engineering vehicles.

[0245] The tyre according to the invention is preferably a tyre intended to equip vehicles of the heavy load-carrying type (for example heavy vehicles, buses, civil engineering vehicles).Preferably, the tyre according to the invention is a tyre intended to equip heavy vehicles.

[0246] The tire may be prepared according to any method known to those skilled in the art.

[0247] The above-mentioned and other characteristics of the invention will be more clearly understood on reading the following description of several embodiments of the invention which are described by way of illustration and not by way of limitation.

[0248] II - Embodiments of the Invention

[0249] II-1. Measurements and tests used:

[0250] Dynamic performance

[0251] The dynamic properties, in particular tan (δ), were measured on a viscoanalyzer (Metravib VA4000) according to standard ASTM D 5992-96. max , which represents the hysteresis. Record the vulcanized composition sample (thickness 4 mm, cross section 400 mm) subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz 2 The response of a cylindrical test specimen.

[0252] For the modulus G at 50% strain * (G * 50％ ) and tan(δ) max The measurements were performed at 60°C with a strain amplitude from 0.1% to 100% peak-to-peak (outward cycle) and then from 100% to 0.1% peak-to-peak (return cycle). The result used is the composite dynamic shear modulus (G * ) and the loss factor tan(δ). For the outward cycle, the maximum observed tan(δ) is shown (tan(δ) ma ), the maximum value is between the values ​​at 0.1% strain and 100% strain.

[0253] To measure tan(δ) -20℃ , a temperature sweep was performed under a stress of 0.7 MPa and the tan(δ) values ​​observed at -20 °C were recorded.

[0254] II-2. Preparation of rubber composition:

[0255] The procedure for the following tests was as follows: The ungrafted diene elastomer was introduced into a 85 cm 3 In a Polylab internal mixer, the internal mixer is filled to 70% and has an initial container temperature of about 110° C. For the mixtures relating to the invention, the modifier of general formula (I) is introduced simultaneously with the diene elastomer, thermomechanical processing is carried out at 25° C. for 1 minute and 30 seconds, and everything is mixed (preparation phase) for about 5 to 6 minutes.

[0256] Next, for all compositions (control and inventive), the optional reinforcing filler, the optional coupling agent, and then, after kneading for 1 to 2 minutes, the various other ingredients except the vulcanizing system are introduced into the mixer. Thermomechanical processing (not preparation phase) is then carried out in one step (total duration of kneading equal to about 5 minutes), until a maximum "drip" temperature of 160° C. is reached. The mixture thus obtained is recovered and cooled, and then the vulcanizing system (sulphur) is added to an open mixer (homofinisher) at 25° C., mixing everything (preparation phase) for about 5 to 6 minutes.

[0257] The composition thus obtained is subsequently calendered into the form of plates (thickness 2 to 3 mm) or thin sheets of rubber for measuring their physical or mechanical properties, or into the form of molded parts that can be used directly, for example, as tire semi-finished products, in particular tire treads, after cutting and / or assembling to the desired dimensions.

[0258] II-3. Test A:

[0259] The purpose of this test is to demonstrate that the compositions according to the invention improve the compromise of wet grip / rolling resistance / abrasion strength performance qualities relative to compositions not complying with the invention.

[0260] For this purpose, four compositions were compared, which differed from each other essentially in the following technical characteristics:

[0261] - Composition T1 is a composition not in accordance with the invention, comprising SBR with a Tg of -65°C without the use of a modifier having the general formula (I);

[0262] Composition T2 is a composition not in accordance with the invention, comprising SBR with a Tg of -48°C without the use of a modifier having the general formula (I);

[0263] - Composition T3 is a composition not in accordance with the present invention, comprising SBR having a Tg of -65°C and a modifier having the general formula (I);

[0264] - Composition C1 is a composition according to the invention comprising SBR with Tg = -48°C and a modifier having the general formula (I).

[0265] Table 1 gives the formulations of the various compositions T1 to T3 and C1; the contents are expressed in phr. All the compositions (T1 to T3 and C1) comprise a crosslinking system commonly used in the preparation of tire treads; this crosslinking system comprises in particular sulphur, ZnO, stearic acid and an accelerator.

[0266] Table 1

[0267]

[0268]

[0269] (1) non-functional and non-extended solution SBR having 24% 1,2-polybutadiene units, 26.5% styrene units, and Tg = -48°C;

[0270] (2) non-functional and non-extended solution SBR having 24% 1,2-polybutadiene units, 15.5% styrene units, and Tg = -65°C;

[0271] (3) Neodymium polybutadiene having 98% cis-1,4-butadiene units and Tg = -108°C;

[0272] (4) Zeosil 1165MP silica of HDS type from Solvay;

[0273] (5) N134 carbon black;

[0274] (6)C 5 / C 9 A fraction resin sold by Cray Valley under the name THER 8644 resin (Tg = 44°C);

[0275] (7) A modifier having formula (I): 2,4,6-trimethyl-3-(2-(2-oxoimidazolidin-1-yl)ethoxy)nitrile oxide synthesized according to the protocol described in WO2012 / 007441

[0276] (8) Coupling agent: TESPT (Si69 from Degussa);

[0277] (9) diphenylguanidine (Perkacit DPG from Flexsys);

[0278] (10) N-(1,3-Dimethylbutyl)-N-phenyl-p-phenylenediamine, sold by Flexsys under the name Santoflex 6-PPD.

[0279] The properties of the compositions after curing at 150°C for 45 minutes are listed in Table 2 below.

[0280]

[0281] It can be seen from Table 2 that for the equivalent stiffness (G * 50% value), the composition T2 comprising an unmodified high Tg SBR not conforming to the invention makes the wet grip performance (tan(δ) -20℃The composition T2 shows a significant improvement in the wet grip / rolling resistance / abrasion resistance performance quality compromise relative to the composition T1 not in accordance with the invention.

[0282] Furthermore, it can be found that, for equivalent stiffness, the composition T3 not in accordance with the invention comprising a low Tg SBR modified by a modifier of general formula (I) leads to a significant improvement in rolling resistance performance relative to the composition T1 not in accordance with the invention comprising an unmodified low Tg SBR, but at the expense of wet grip performance. The composition T3 does not improve the compromise of wet grip / rolling resistance / abrasion resistance performance qualities relative to the composition T1 not in accordance with the invention.

[0283] Surprisingly, for equivalent stiffness, it can be found that the composition C1 according to the invention comprising a high Tg SBR modified by a modifier of general formula (I) leads to a significant improvement in both rolling resistance and wet grip performance relative to the composition T1 not conforming to the invention. Thus, surprisingly, the composition C1 according to the invention has an improved wet grip / rolling resistance / abrasion strength performance quality compromise relative to the composition T1 not conforming to the invention.

Claims

1. A tire intended to equip a vehicle of the heavy-duty type, comprising a tread comprising at least one rubber composition based on at least: - an elastomeric matrix consisting essentially of a glass transition temperature Tg strictly higher than -65°C and lower than or equal to -30°C based copolymers of styrene and butadiene, wherein the elastomeric matrix comprises at least one second diene elastomer other than the copolymer based on styrene and butadiene, chosen from polybutadiene, natural rubber, synthetic isoprene, butadiene copolymers other than butadiene-styrene copolymers, isoprene copolymers and mixtures of these polymers and copolymers, the content of said second diene elastomer being from 5 to 49 phr, - a reinforcing filler mainly comprising silicon dioxide, -Chemical cross-linking system, - agents for coupling between the elastomeric matrix and the reinforcing filler, a plasticizing system comprising from 2 to 15 phr of at least one plasticizing resin having a glass transition temperature Tg greater than or equal to 20° C., and the total content of the plasticizing system in the composition being from 2 to 17 phr, and - an agent for modifying said copolymer based on styrene and butadiene, said agent having been grafted onto said copolymer, said modifying agent being a 1,3-dipolar compound of general formula (I): AED(I) o The symbol D represents a functional group comprising at least one nitrogen atom, said functional group being capable of binding to said copolymer by a [3+2] type cycloaddition on a carbon-carbon double bond of the chain of said copolymer, o Symbol E represents a divalent spacer group connecting group D to group A, o A represents an associative group comprising at least one nitrogen atom, said associative group being selected from the following formulae (IV) to (VIII): in: -R11 represents a hydrocarbon group which may contain heteroatoms, -Q represents an oxygen atom or a sulfur atom or NH, and -The symbol * indicates the connection to the spacer group E.

2. The tire according to claim 1, wherein: The functional group D of the modifier comprises a nitrile oxide functional group, a nitrone functional group or a nitrile imine functional group.

3. The tire according to claim 1, wherein: The spacer group E is a linear or branched C1-C 24 An alkyl chain comprising one or more heteroatoms selected from nitrogen, sulfur and oxygen atoms.

4. The tire according to claim 1, wherein: The group D of the modifier is a group having the formula (II): in: - R1, R2, R3, R4, R5 can be the same or different and represent a hydrogen atom, a halogen atom, a C1-C5 alkyl group, a C1-C5 alkoxy group or a covalent bond that can be connected to the spacer group E; - provided that at least one of R1, R2, R3, R4 and R5 represents said covalent bond.

5. The tire according to claim 1, wherein: The modifier is selected from compounds having formula (XIII), (XIV), (XV), (XVII) and their meso forms, 6. The tire according to claim 1, wherein: The content of the modifier is 0.01 to 50 mol%.

7. The tire according to claim 1, wherein: The copolymer based on styrene and butadiene has a glass transition temperature of -60°C to -40°C.

8. The tire according to claim 1, wherein: The composition also includes carbon black.

9. The tire according to claim 1, wherein: The content of reinforcing fillers ranges from 55 to 200 phr.

10. The tire according to any one of claims 1 to 9, characterized in that The tire is intended to fit large passenger vehicles.

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