Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
  • B60C1/0016—Compositions of the tread
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
  • C08C19/00—Chemical modification of rubber
  • C08C19/22—Incorporating nitrogen atoms into the molecule
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
  • C08C19/00—Chemical modification of rubber
  • C08C19/25—Incorporating silicon atoms into the molecule
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F136/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds
  • C08F136/02—Homopolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds
  • C08F136/04—Homopolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds conjugated
  • C08F136/08—Isoprene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L15/00—Compositions of rubber derivatives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08L9/06—Copolymers with styrene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
  • C08K2003/2296—Oxides; Hydroxides of metals of zinc
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend

Definitions

• the present invention relates to tires with a tread, in particular with a snow, winter or all-season tread, suitable for driving on ground covered with snow (in English called “snow tires”, “winter tires” or “ garlic season ”).
• snow tires marked with an M + S or MS or even M&S inscription, marked on their sidewalls, are characterized by a tread pattern and a structure intended above all to ensure in mud and fresh snow. or melting behavior better than that of road type tires (in English called "road type tire”) designed to run on ground without snow.
• Snow-covered soils known as white soils, have the characteristic of exhibiting a low coefficient of friction, which has led to the development of snow tires comprising treads based on diene rubber compositions having a low glass transition temperature, Tg.
• Tg glass transition temperature
• the wet grip performance of these tires comprising such treads is generally lower than that of road tires, the treads of which are generally based on rubber compositions of different formulations, in particular at a higher Tg.
• application WO 2012/069565 proposes a tread whose composition comprises a diene elastomer bearing at least one SiOR function, R being a hydrogen or a hydrocarbon radical in combination with a high level of reinforcing inorganic filler and of 'a specific plasticizer system.
• snow or winter treads are generally provided with softer tread patterns and / or made of a softer rubber composition than so-called "summer" treads, their abrasion resistance is often found to be reduced. Also, it is important to keep as much as possible, or even improve, the abrasion resistance of snow or winter treads.
• the subject of the invention is a tire, the tread of which comprises a rubber composition based on:
• an elastomeric matrix comprising from 25 to 95 phr of butadiene and styrene-based copolymer having a glass transition temperature of less than - 70 ° C, and from 5 to 75 phr of polybutadiene, the elastomeric matrix comprising less than 15 phr isoprene elastomer,
• the expressions "the composition” or “the composition according to the invention” denote the composition of the tread according to the invention.
• composition based on is meant a composition comprising the mixture and / or the reaction product in situ of the various constituents used, some of these constituents being able to react and / or being intended to react with each other, less partially, during the various phases of manufacture of the composition; the composition may thus be in the fully or partially crosslinked state or in the non-crosslinked state.
• part by weight per hundred parts by weight of elastomer (or phr), it is meant within the meaning of the present invention, the part, by mass per hundred parts by mass of elastomer.
• any interval of values designated by the expression "between a and b” represents the range of values going from more than a to less than b (that is to say limits a and b excluded) while any range of values designated by the expression “from a to b” signifies the range of values going from a to b (that is to say including the strict limits a and b).
• the interval represented by the expression "between a and b" is also and preferably described.
• a “majority” compound it is meant, within the meaning of the present invention, that this compound is the majority among the compounds of the same type in the composition, that is to say that it is the one which represents the greatest amount by mass among compounds of the same type.
• a major elastomer is the elastomer representing the greatest mass relative to the total mass of the elastomers in the composition.
• a so-called majority filler is that representing the greatest mass among the fillers of the composition.
• majority elastomer represents more than half of the mass of elastomers.
• majority is meant present at more than 50%, preferably more than 60%, 70%, 80%, 90%, for example 100%.
• the compounds comprising carbon mentioned in the description can be of fossil origin or biobased. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. This concerns in particular polymers, plasticizers, fillers, etc.
• the glass transition temperatures (Tg) of the elastomers are determined using a differential scanning calorimeter ("differential scanning calorimeter”), according to ASTM E1356-08, which dates from 2014.
• the elastomeric matrix of the composition of the tire tread comprises from 25 to 95 phr of copolymer based on butadiene and on styrene having a glass transition temperature of less than -70 ° C, from 5 to 75 phr of polybutadiene, and less than 15 phr of isoprene elastomer.
• the term “copolymer based on butadiene and on styrene” refers to any copolymer obtained by copolymerization of one or more styrene compounds with one or more butadiene (s).
• Suitable styrene monomers are especially styrene, methylstyrenes, para-tert-butylstyrene, methoxystyrenes and chlorostyrenes.
• Suitable butadiene monomers are in particular 1,3-butadiene.
• elastomers can have any microstructure which depends on the polymerization conditions used, in particular on the presence or absence of a modifying and / or randomizing agent and the amounts of modifying and / or randomizing agent used.
• the elastomers can be for example block, statistical, sequenced, microsequenced.
• the copolymer based on butadiene and on styrene is a butadiene-styrene (SBR) copolymer.
• SBR butadiene-styrene
• the SBR can be prepared in emulsion (ESBR) or in solution (S SBR). Whether it is ESBR or S SBR, the SBR can be any microstructure compatible with a glass transition temperature below -70 ° C.
• the butadiene-styrene copolymer may have a styrene content of between 1% and 15% by weight and more particularly between 1% and 5%, a content (mol%) of -1.2 bonds of the butadiene part of between 4% and 25%.
• the copolymer based on butadiene and on styrene is an S SBR.
• the copolymer based on butadiene and on styrene has a glass transition temperature within a range ranging from -105 ° C to -70 ° C, preferably from -100 ° C to - 80 ° C, preferably between - 95 ° C and -85 ° C, more preferably between -95 ° C and -86 ° C.
• the butadiene-styrene-based copolymer is a styrene-butadiene copolymer having any one, preferably the combination of two or three, even more
• styrene-butadiene copolymer prepared in solution (SSBR)
• its styrene mass content relative to the total weight of the styrene-butadiene copolymer is between 1 and 10%, preferably between 1 and 4%
• its Tg is within a range from -105 ° C to -70 ° C, preferably between -95 ° C and -86 ° C.
• the butadiene and styrene-based copolymer comprises within its structure at least one alkoxysilane group and at least one other function, the silicon atom of the alkoxysilane group being bonded to the elastomeric chain (s), the alkoxysilane group being optionally partially or totally hydrolyzed to silanol.
• an alkoxysilane group located within the structure of the elastomer is understood as a group in which the silicon atom is located in the backbone of the polymer and directly linked to it. This positioning within the structure includes the ends of polymer chains. Thus, the terminal grouping is included in this notion.
• the alkoxysilane group is not a pendant group.
• the diene elastomer is functionalized at the end or end of the chain.
• the diene elastomer is coupled or else functionalized in the middle of the chain, as opposed to the position "at the end of the chain” and although the group is not located. precisely in the middle of the elastomer chain.
• the silicon atom of this function links the two branches of the main chain of the diene elastomer.
• the diene elastomer is star shaped.
• the silicon atom is thus substituted by at least three branches of the diene elastomer.
• the copolymer based on butadiene and on styrene comprises, as the majority species, the diene elastomer functionalized in the middle of the chain with an alkoxysilane group linked to the two branches of the diene elastomer via the silicon atom. , the alkoxy radical optionally being partially or totally hydrolyzed to hydroxyl. More particularly again, the diene elastomer functionalized in the middle of the chain with an alkoxysilane group represents 70% by weight of the copolymer based on butadiene and on styrene.
• the alkoxyl radical in the alkoxysilane group, the alkoxyl radical, optionally partially or totally hydrolyzed to hydroxyl, the alkoxyl radical can comprise a C 1 -C 10 or even C 1 -C 8 alkyl radical, preferably C 1 -C 4 , more preferably the alkoxyl radical is a methoxy or an ethoxy.
• the other function is preferably a function comprising at least one heteroatom chosen from N, S, O, P. It is possible, by way of example, to cite among these functions, primary, secondary or tertiary amines, cyclic or not, isocyanates, imines, cyano, thiol, carboxylates, epoxides, primary, secondary or tertiary phosphines.
• the copolymer based on butadiene and on styrene advantageously comprises at least one function comprising a nitrogen atom.
• the butadiene-styrene-based copolymer advantageously comprises within its structure at least one alkoxysilane group bonded to the elastomer via the silicon atom, and a function comprising a nitrogen atom.
• This function comprising a nitrogen atom can be located at the end of the chain and be directly linked to the elastomer via a covalent bond or a hydrocarbon group.
• This function comprising a nitrogen atom can also, and advantageously, be carried by the alkoxysilane group.
• the function comprising a nitrogen atom can be carried by the silicon of the alkoxysilane group, directly or through a spacer group.
• the spacer group can be an atom, in particular a heteroatom, or a group of atoms.
• the spacer group can be a divalent hydrocarbon radical, linear or branched, aliphatic C 1 -C 18 , saturated or not, cyclic or not, or a divalent aromatic hydrocarbon radical in Cr, -C 1 s and can contain one or more radicals aromatic and / or one or more heteroatoms.
• the hydrocarbon radical can optionally be substituted.
• the spacer group is a divalent, linear or branched, Ci-Cis aliphatic hydrocarbon radical, more preferably a divalent C 1 -C 10 aliphatic hydrocarbon radical, more preferably still C 3 -C 8 , more preferably still a hydrocarbon radical linear divalent in C 3 .
• the butadiene-styrene-based copolymer may also include another function (i.e., a function different from those mentioned above) within the elastomer, but this is not preferable.
• the copolymer based on butadiene and styrene can also be a mixture of several copolymers based on butadiene and styrene.
• the alkoxysilane group comprising a function comprising a nitrogen atom can be represented by the formula (* -) a Si (OR ') bR c X in which:
• * - represents the bond to an elastomeric chain
• the radical R represents a substituted or unsubstituted alkyl radical, being C 1 -C 10, or even C 1 -C 8, preferably a C 1 -C 4 alkyl radical, more preferably methyl and ethyl;
• R' represents an alkyl radical, substituted or unsubstituted, being in C1-C10, or even in C1-Cs, preferably an alkyl radical in C1- C4, more
• X represents a group comprising the nitrogen function
• a is lou 2
• b is 1 or 2
• a is a function of the positioning of the alkoxysilane group within the structure of the elastomer. When a is 1, the group is located at the end of the chain. When a is 2, it is located in the middle of the chain.
• Primary amines, protected or not by a protective group, secondary, protected or not by a protective group, or tertiary amines are particularly suitable.
• amines substituted by C 1 -C 10 alkyl radicals preferably C 1 -C 4 alkyl, more preferably a methyl or ethyl radical, or else amines.
• suitable groups methylamino-, dimethylamino-, ethylamino-, diethylamino-, propylamino-, dipropylamino-, butylamino-, dibutylamino-, pentylamino-, dipentylamino-, hexylamino-, dihexylamino-, hexamethyleneamino-, preferably the groups - and
• amine dimethylamino-.
• amine is cyclic
• morpholine piperazine, 2,6-dimethylmorpholine, 2,6-dimethylpiperazine, 1-ethylpiperazine, 2-methylpiperazine,
• hexamethyleneamine preferably pyrrolidine and hexamethyleneamine groups.
• the amine function is a tertiary amine function, preferably diethylamine or dimethylamine.
• At least two, preferably at least three, preferably at least four, more preferably all of the following characteristics are observed:
• the function comprising a nitrogen atom is a tertiary amine, more particularly a diethylamino- or dimethylamino- group,
• the function comprising a nitrogen atom is carried by the alkoxysilane group via a spacer group defined as a hydrocarbon radical C 1 -C 10 aliphatic, more preferably a C 3 -C 6 aliphatic hydrocarbon radical, more preferably still the linear C 3 hydrocarbon radical,
• the alkoxysilane group is a methoxysilane or an ethoxysilane, optionally partially or totally hydrolyzed to silanol,
• the copolymer based on butadiene and on styrene is a butadiene-styrene copolymer prepared in solution
• the copolymer based on butadiene and styrene is mainly functionalized in the middle of the chain with an alkoxysilane group linked to the two branches of the copolymer based on butadiene and styrene via the silicon atom,
• the copolymer based on butadiene and on styrene has a glass transition temperature in a range ranging from -105 ° C to -70 ° C.
• At least two, preferably at least three, preferably at least four, more preferably all of the following characteristics are observed:
• the function comprising a nitrogen atom is a tertiary amine, more particularly a diethylamino- or dimethylamino- group,
• the function comprising a nitrogen atom is carried by the alkoxysilane group via a linear C3 aliphatic hydrocarbon radical,
• the alkoxysilane group is methoxysilane or G ethoxysilane, optionally partially or totally hydrolyzed to silanol,
• the copolymer based on butadiene and on styrene is a butadiene-styrene copolymer prepared in solution
• the copolymer based on butadiene and styrene is mainly functionalized in the middle of the chain with an alkoxysilane group linked to the two branches of the copolymer based on butadiene and styrene via the silicon atom,
• the copolymer based on butadiene and on styrene has a glass transition temperature in a range between -95 ° C and -86 ° C.
• the level of copolymer based on butadiene and on styrene in the composition of the tread of the tire according to the invention can advantageously be in a range ranging from 65 to 95 phr, preferably between 66 and 90 phr.
• Such copolymers based on butadiene and on styrene can be obtained by a process as described below.
• the first step of a process for preparing the butadiene-styrene-based copolymer is the anionic polymerization of at least one conjugated diene monomer or the polymerization of at least one conjugated diene monomer and one vinyl aromatic monomer, in the presence of a polymerization initiator.
• the monomers are as described above.
• the polymerization initiator any known mono-functional anionic initiator can be used. However, an initiator containing an alkali metal such as lithium is preferably used.
• Suitable organolithium initiators in particular are those comprising a carbon-lithium bond.
• Representative compounds are aliphatic organolithiums such as ethyllithium, n-butyllithium (n-BuLi), isobutyllithium, etc.
• the polymerization initiator is, for example, polymerization initiators with an amine function which lead to living chains having an amine group at the non-reactive end of the chain.
• lithium amides reaction products of an organolithium compound, preferably alkyllithium, and of an acyclic or cyclic secondary amine, preferably cyclic.
• secondary amine which can be used to prepare the initiators, mention may be made of dimethylamine, diethylamine, dipropylamine, di-n-butylamine, di-sec-butylamine, dipentylamine, dihexylamine, di-n-octylamine, di- (2-ethylhexyl ) amine, di-cyclohexylamine, N-methylbenzylamine, diallylamine, morpholine, piperazine, 2,6-dimethylmorpholine, 2,6-dimethylpiperazine, 1-ethylpiperazine, 2-methylpiperazine, 1 -benzylpiperazine, piperidine, 3,3-dimethylpiperidine, 2 , 6-dimethylpiperidine, 1- methyl-4- (methylamino) piperidine, 2,2,6,6-tetramethylpiperidine, pyrrolidine, 2,5-dimethylpyrrolidine, azetidine, hexamethyleneimine, h
• the alkyl lithium compound is preferably ethyllithium, n-butyllithium (n-BuLi), isobutyllithium, etc.
• the polymerization is preferably carried out in the presence of an inert hydrocarbon solvent which can be for example an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, iso-octane, cyclohexane, methylcyclohexane or a hydrocarbon.
• aromatic such as benzene, toluene, xylene.
• the microstructure of the elastomer can be determined by the presence or absence of a modifying and / or randomizing agent and the amounts of modifying and / or randomizing agent employed.
• a polar agent is used during the polymerization step in amounts such that it promotes the statistical distribution of the vinyl aromatic along the polymer chains. .
• the living diene elastomer resulting from the polymerization is then functionalized by means of a functionalizing agent capable of introducing an alkoxysilane group within the polymer structure to prepare the copolymer based on butadiene and styrene comprising within its structure at least one alkoxysilane group bonded to the elastomer via the silicon atom, and a function comprising a nitrogen atom.
• a functionalizing agent capable of introducing an alkoxysilane group within the polymer structure to prepare the copolymer based on butadiene and styrene comprising within its structure at least one alkoxysilane group bonded to the elastomer via the silicon atom, and a function comprising a nitrogen atom.
• the modification reaction of the living diene elastomer, obtained at the end of the first step, can take place at a temperature between -20 ° C and 100 C, by addition to the living polymer chains or conversely of an agent.
• of non-polymerizable functionalization capable of forming an alkoxysilane group, the silicon atom being integrated within the elastomer chain, carrying or not a function comprising a nitrogen atom. It is particularly a functionalization agent carrying functions reactive with respect to the living elastomer, each of these functions being directly linked to the silicon atom.
• the functionalizing agent corresponds to the formula (OR ') d Si (R) c X, in which:
• R' represents an alkyl radical, substituted or unsubstituted Ci-Cio, or Ci-C8, preferably C1-C4, more preferably methyl and ethyl;
• R represents a substituted or unsubstituted, C1-C10, or even C1 -Cl, alkyl radical, preferably a C1-C4 alkyl group, more preferably methyl and ethyl;
• X represents a group including a function comprising a nitrogen atom
• d 2 or 3
• c 0 or 1
• proviso that d + c 3.
• the function comprising a nitrogen atom is as defined above.
• the function comprising a nitrogen atom can be a primary amine, protected or not, secondary, protected or not, or tertiary.
• the nitrogen atom can then be substituted by two groups, identical or different, which may be a trialkyl silyl radical, the alkyl group having 1 to 4 carbon atoms, or a C1-C10 alkyl radical, preferably C1 alkyl. -C4, more preferably a methyl or ethyl radical, or else the two nitrogen substituents form with the latter a heterocycle containing a nitrogen atom and at least one carbon atom, preferably from 2 to 6 carbon atoms .
• the divalent hydrocarbon group making it possible to link the amine function to the trialkoxysilane group is the spacer group as described above, preferably aliphatic in C 1 -C 10 , more particularly linear in C 2 or C 3 .
• the functionalizing agent can be chosen from 3- (N, N-dimethylaminopropyl) trimethoxysilane, 3- (N, N-dimethylaminopropyl) triethoxysilane, 3- (N, N-diethylaminopropyl) trimethoxysilane, 3- (N , N-diethylaminopropyl) triethoxysilane, 3- (N, N-dipropylaminopropyl) trimethoxysilane, 3- (N, N-dipropylaminopropyl) triethoxysilane, 3- (N, N-dibutylaminopropyl) trimethoxysilane, 3- (N, N -dibutylaminopropyl) triethoxysilane, 3- (N, N-dipentylaminopropyl) trimethoxysilane, 3- (N, N-dipentylaminopropyl) triethoxysilane,
• the functionalizing agent can be chosen from 3- (N, N-methyltrimethylsilylaminopropyl) trimethoxysilane, 3- (N, N-methyltrimethylsilylaminopropyl) triethoxysilane, 3- (N, N-ethyltrimethylsilylaminopropyl) trimethoxysilane, 3- (N-methylsilylaminopropyl) , N-ethyltrimethylsilylaminopropyl) triethoxysilane, 3- (N, N-propyltrimethylsilylaminopropyl) trimethoxysilane, 3- (N, N-propyltrimethylsilylaminopropyl) triethoxysilane. More preferably, the functionalizing agent is 3- (N, N-methyltrimethylsilylaminopropyl) trimethoxysilane.
• the functionalizing agent can be chosen from 3- (N, N-bistrimethylsilylaminopropyl) trimethoxysilane and 3- (N, N-bistrimethylsilylaminopropyl) triethoxysilane. More preferably, the functionalizing agent is 3- (N, N-bistrimethylsilylaminopropyl) trimethoxysilane.
• the functionalizing agent is advantageously chosen from (N, N-dialkylaminoalkyl) trialkoxysilanes; more particularly then the functionalizing agent is 3- (N, N-dimethylaminopropyl) trimethoxysilane.
• the molar ratio of the functionalizing agent to the metal of the polymerization initiator depends essentially on the type of butadiene-styrene-based copolymer desired. Thus, with a ratio ranging from 0.40 to 0.75, or even from 0.45 to 0.65, or alternatively from 0.45 to 0.55, the formation of coupled species within the elastomer is favored. modified, the alkoxysilane group then being located in the middle of the chain. In the same way, with a ratio ranging from 0.15 to 0.40, or even from 0.20 to 0.35, or even from 0.30 to 0.35, mainly stellate species (3 branches) are formed in the within the modified elastomer. With a ratio greater than or equal to 0.75, or even greater than 1, mainly functionalized species at the end of the chain are formed.
• polymerization varies from 0.35 to 0.65, preferably from 0.40 to 0.60 and even more
• the copolymer based on butadiene and on styrene can comprise, as the majority species, the diene elastomer functionalized in the middle of the chain with an alkoxysilane group linked to the two branches of the diene elastomer via the atom of silicon. More particularly still, the diene elastomer functionalized in the middle of the chain with an alkoxysilane group represents 70% by weight of the copolymer based on butadiene and on styrene.
• the alkoxysilane group advantageously comprises an alkoxy radical
• the alkoxysilane group advantageously carries a function comprising a nitrogen atom as defined above.
• This function is preferably a tertiary amine function as defined above, in particular diethylamino- or dimethylamino-, linked to the silicon atom preferably via a spacer as defined above, in particular a divalent hydrocarbon radical. linear in C2 or C3.
• the synthesis process can be continued with a step of deprotection of this function. This step is carried out after the modification reaction and is well known to those skilled in the art.
• the synthesis process can also comprise a step of hydrolysis of the hydrolyzable alkoxyl functions, by adding an acidic, basic or neutral compound as described in document EP 2 266 819 A1.
• the hydrolyzable functions are then transformed into hydroxyl functions.
• the process for the synthesis of the copolymer based on butadiene and on styrene can be continued in a manner known per se with the stages of recovering the copolymer based on butadiene and on styrene.
• These steps can in particular include a stripping step in order to recover the elastomer from the previous steps.
• This stripping step can have the effect of hydrolyzing all or part of the hydrolyzable functions of the copolymer based on butadiene and styrene.
• at least 50 to 70 mol% of these functions can thus be hydrolyzed.
• the elastomeric matrix of the composition of the tire tread according to the invention comprises 5 to 75 phr of polybutadiene.
• polystyrene (abbreviated "BR)
• BR polybutadiene
• Polybutadienes are polybutadienes.
• Polybutadiene is a well-known rubber that is made by polymerizing 1,3 -butadiene monomer (typically a homopolymerization) in a process of
• the resulting polybutadiene can have three different forms: cis-1,4, trans-1,4 and vinyl-1,2 polybutadiene.
• the cis-1,4 and trans-1,4 elastomers are formed by the monomers connecting end to end, while the vinyl-1,2 elastomer is formed by the monomers connecting between the ends of the monomer.
• the choice of catalyst and the temperature of the process are known as the variables generally used to control the content of cis-1,4 bonds in polybutadiene.
• the polybutadiene has a rate (mol%) of cis-1,4 linkages greater than 90%, more preferably greater than 95%.
• polybutadienes can be produced using a neodymium catalyst in a manner well known to those skilled in the art, for example according to a process described in document JP 60/23406 A and WO 03/097708 A1.
• polybutadienes can also commercially available, for example, Buna ® CB 22 sold by Lanxess.
• the glass transition temperature of the polybutadiene is within a range ranging from -110 ° C to -80 ° C, preferably from -108 ° C to -100 ° C.
• the level of polybutadiene in the composition of the tread of the tire according to the invention is within a range ranging from 5 to 35 phr, preferably between 10 and 34 phr.
• the elastomeric matrix of the tread of the tire according to the invention advantageously comprises from 65 to 95 phr of copolymer based on butadiene and styrene and from 5 to 35 phr of polybutadiene, preferably 66 90 phr of copolymer based on butadiene and styrene and 10 and 34 phr of polybutadiene.
• the elastomeric matrix of the composition of the tire tread according to the invention comprises less than 15 phr of isoprene elastomer.
• isoprene elastomer in a known manner a homopolymer or a copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), various isoprene copolymers and mixtures of these elastomers.
• NR natural rubber
• IR synthetic polyisoprenes
• isoprene copolymers there may be mentioned in particular the copolymers of isobutene-isoprene (butyl rubber - IIR), of isoprene-styrene (SIR), of isoprene-butadiene (BIR) or of isoprene-butadiene-styrene (SBIR).
• This isoprene elastomer is preferably natural rubber or a synthetic cis-1,4 polyisoprene; among these synthetic polyisoprenes, use is preferably made of polyisoprenes having a content (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%.
• the level of isoprene elastomer in the composition of the tire tread according to the invention is preferably less than 14 phr, preferably less than 10 phr, preferably less than 5 phr, preferably less than 4 phr.
• the composition of the tread of the tire according to the invention is devoid of isoprene elastomer.
• the total level of copolymer based on butadiene and on styrene and on polybutadiene, in the composition of the tread of the tire is 100 phr.
• composition of the tread of the tire according to the invention further comprises a reinforcing filler, known for its capacity to reinforce a rubber composition which can be used for the manufacture of tires.
• the reinforcing filler can comprise a carbon black, an inorganic reinforcing filler or a mixture thereof.
• the reinforcing filler mainly comprises a reinforcing inorganic filler, preferably a silica.
• the level of reinforcing inorganic filler, preferably silica, in the composition of the tread of the tire according to the invention can be within a range ranging from 80 to 200 phr, preferably from 90 to 180 phr, preferably from 100 to 160 pc.
• the level of carbon black in the composition of the tread of the tire according to the invention may be within a range ranging from 0 to 40 phr, preferably from 1 to 20 phr, preferably from 2 to 10 pc.
• the blacks that can be used in the context of the present invention can be any black conventionally used in tires or their treads (so-called tire grade blacks).
• tire grade blacks there will be mentioned more particularly the reinforcing carbon blacks of the 100, 200, 300 series, or the blacks of the 500, 600 or 700 series (ASTM grades), such as for example the blacks NI 15, NI 34, N234, N326 , N330, N339, N347, N375, N550, N683, N772).
• These carbon blacks can be used in the isolated state, as available commercially, or in any other form, for example as a support for some of the rubber additives used.
• the carbon blacks could, for example, already be incorporated into the diene elastomer, in particular isoprene, in the form of a masterbatch (see for example applications WO 97/36724 or WO 99/16600).
• organic fillers other than carbon blacks
• the BET specific surface area of carbon blacks is measured according to standard D6556-10 [multi-point method (at least 5 points) - gas: nitrogen - relative pressure range R / R0: 0.1 to 0.3]
• the reinforcing inorganic fillers preferably silicas, which can be used in the context of the present invention can be any silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface as well as a CTAB specific surface area, both of which are lower. to 450 m2 / g, preferably 30 to 400 m2 / g.
• the BET specific surface area of the reinforcing inorganic filler preferably silica
• the BET specific surface area of the reinforcing inorganic filler is determined in a known manner by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society” Vol. . 60, page 309, February 1938, 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 / in: 0.05 to 0.17).
• the CTAB specific surface of silica is determined according to the French standard
• the reinforcing inorganic filler preferably silica
• silicas which can be used in the context of the present invention, mention will be made, for example, of highly dispersible precipitated silicas (called “HDS”).
• HDS highly dispersible precipitated silicas
• an at least bifunctional coupling agent intended to ensure a sufficient connection, of a chemical and / or physical nature, between the filler. inorganic (surface of its particles) and the diene elastomer.
• an at least bifunctional coupling agent intended to ensure a sufficient connection, of a chemical and / or physical nature, between the filler. inorganic (surface of its particles) and the diene elastomer.
• bifunctional is meant a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer.
• a bifunctional compound can comprise a first functional group comprising a silicon atom, the said first functional group being able to interact with the hydroxyl groups of an inorganic charge and a second functional group comprising a sulfur atom, the said second functional group being able to interact with the diene elastomer.
• the organosilanes are chosen from the group consisting of polysulfurized organosilanes (symmetrical or asymmetrical) such as bis (3-triethoxysilylpropyl) tetrasulfide, in short TESPT marketed under the name “Si69” by the company Evonik or bis disulfide.
• polysulfurized organosilanes symmetrical or asymmetrical
• bis (3-triethoxysilylpropyl) tetrasulfide in short TESPT marketed under the name “Si69” by the company Evonik or bis disulfide.
• the organosilane is a polysulfurized organosilane.
• the vulcanization system preferably comprises molecular sulfur and / or at least one sulfur donor agent.
• At least one vulcanization accelerator is also preferably present, and, optionally, also preferentially, one can use various known vulcanization activators such as zinc oxide, stearic acid or equivalent compound such as the salts of stearic acid and salts. of transition metals, guanide derivatives (in particular
• diphenylguanidine or also known vulcanization retarders.
• Sulfur is used at a preferential rate of between 0.5 and 12 phr, in particular between 1 and 10 phr.
• the vulcanization accelerator is used at a preferential rate of between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr.
• MBTS 2-mercaptobenzothiazyl disulfide
• CBS N-cyclohexyl-2-benzothiazyl sulfenamide
• DCBS N-dicyclohexyl- 2-Benzothiazyl sulfenamide
• TBBS N-ter-butyl-2-benzothiazyl sulfenamide
• TZTD tetrabenzylthiuram disulfide
• ZBEC zinc dibenzyldithiocarbamate
• the rubber composition for the tread of the tire according to the invention further comprises from 25 to 100 phr of at least one plasticizing resin having a glass transition temperature greater than 20 ° C., called “high Tg”, (also referred to herein as “plasticizing resin” for the sake of editorial simplicity ”).
• resin is reserved in the present application, by definition known to those skilled in the art, for a compound which is solid at room temperature (23 ° C.), as opposed to a liquid plasticizer compound such as an oil.
• Plasticizing resins are polymers which are well known to those skilled in the art, essentially based on carbon and hydrogen but which may contain other types of atoms, which can be used in particular as plasticizing agents or tackifying agents in polymer matrices. They are generally by nature miscible (i.e., compatible) at the rates used with the polymer compositions for which they are intended, so as to act as true diluents.
• these plasticizing resins can also be qualified as thermoplastic resins in that they soften on heating and can thus be molded. They can also be defined by a softening point or temperature (in English, "softening point”).
• the softening temperature of a plasticizing resin is generally approximately 50 to 60 ° C. greater than its value of Tg.
• the softening point is measured according to the ISO 4625 standard (“Ring and Bail” method).
• the macrostructure (Mw, Mn and Ip) is determined by size exclusion chromatography (SEC) as indicated below.
• SEC analysis for example, consists in separating the macromolecules in solution according to their size through columns filled with a porous gel; molecules are separated according to their hydrodynamic volume, the larger ones being eluted first.
• the sample to be analyzed is simply solubilized beforehand in an appropriate solvent, tetrahydrofuran at a
• the solution is then filtered through a filter with a porosity of 0.45 mih, before injection into the apparatus.
• the apparatus used is, for example, a "Waters Alliance" chromatographic line under the following conditions:
• elution solvent is tetrahydrofuran
• the plasticizing resin exhibits at least any one, preferably 2 or 3, more preferably all of the following characteristics: a Tg greater than 25 ° C (in particular between 30 ° C) C and 100 ° C), more
• a softening point greater than 50 ° C (in particular between 50 ° C and 150 ° C); a number-average molar mass (Mn) of between 300 and 2000 g / mol,
• C5 cut / vinylaromatic copolymer resins in particular C5 cut / styrene 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 the name “Wingtack Extra”, by Kolon under the names “Hikorez Tl 095" and “Hikorez Tl 100", 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".
• the plasticizing resin having a glass transition temperature greater than 20 ° C. can be chosen from the group comprising or consisting of cyclopentadiene homopolymer or copolymer resins (abbreviated CPD), homopolymer or copolymer resins. dicyclopentadiene (abbreviated DCPD), terpene homopolymer or copolymer resins, C5-cut homopolymer or copolymer resins, C9-cut homopolymer or copolymer resins, alpha homopolymer or copolymer resins -methyl-styrene and mixtures thereof.
• CPD cyclopentadiene homopolymer or copolymer resins
• DCPD dicyclopentadiene
• terpene homopolymer or copolymer resins C5-cut homopolymer or copolymer resins
• C9-cut homopolymer or copolymer resins alpha homopolymer or copolymer resins -
• the plasticizing resin is chosen from the group comprising or consisting of CPD / vinylaromatic copolymer (D) resins, CPD / terpene copolymer (D) resins, terpene phenol copolymer resins, copolymer resins (D ) CPD / C5 cut, (D) CPD / C9 cut copolymer resins, terpene / vinylaromatic copolymer resins, terpene / phenol copolymer resins, C5 cut / vinyl aromatic copolymer resins, and mixtures thereof.
• CPD / vinylaromatic copolymer (D) resins CPD / terpene copolymer (D) resins, terpene phenol copolymer resins, C5 cut / vinyl aromatic copolymer resins, and mixtures thereof.
• pene includes here in a known manner the alpha-pinene, beta-pinene and limonene monomers;
• a limonene monomer is used, a compound which is presented in a known manner in the form of three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or else dipentene, racemic of the dextrorotatory and levorotatory enantiomers .
• Suitable vinyl aromatic monomers are, for example, styrene, alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyl-toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, any vinylaromatic monomer obtained from a C 9 cut (or more generally from a CL to Cio cut).
• plasticizing resins chosen from the group consisting of CPD homopolymer (D) resins, CPD / styrene copolymer (D) resins, polylimonene resins, limonene / styrene copolymer resins, copolymer resins limonene / D (CPD), C5 cut / styrene copolymer resins, C5 cut / C9 cut copolymer resins, and mixtures of these resins.
• CPD homopolymer (D) resins CPD / styrene copolymer (D) resins
• polylimonene resins limonene / styrene copolymer resins
• copolymer resins limonene / D C5 cut / styrene copolymer resins
• C5 cut / C9 cut copolymer resins and mixtures of these resins.
• plasticizing resins above are well known to those skilled in the art and available commercially, for example sold by the company DRT under the name “Dercolyte” with regard to the polylimonene resins, by the company Neville Chemical Company under the name “Super Nevtac “, by Kolon under the name” Hikorez “or by the company Exxon Mobil under the name” Escorez "as regards the C 5 cut / styrene resins or C 5 cut / C 9 cut resins, or else by the company Struktol under designation "40 MS” or "40 NS” (mixtures of aromatic and / or aliphatic resins).
• the level of plasticizing resin exhibiting a glass transition temperature greater than 20 ° C. in the composition of the tread according to the invention is between 50 and 100 phr, preferably between 55 and 90 phr.
• the total level of plasticizing resin exhibiting a glass transition temperature greater than 20 ° C. is within a range ranging from 25 to 100 phr, preferably between 50 and 100 phr, preferably between 55 and 90 phr.
• the plasticizer system for the rubber composition of the tread of the tire according to the invention may comprise a liquid plasticizer at 23 ° C., called “low. Tg ”, that is to say which by definition has a Tg of less than -20 ° C, preferably less than -40 ° C.
• the composition can optionally comprise from 0 to 60 phr of a liquid plasticizer at 23 ° C.
• the level in the composition of the tread according to the invention may be within a range ranging from 10 to 60 phr, preferably from 15 to 40 phr.
• the total level of liquid plasticizer at 23 ° C. is within a range ranging from 0 to 60 phr, preferably 10 to 60 phr, preferably 15 to 40 phr.
• any liquid plasticizer at 23 ° C. (or extender oil), whether of an aromatic or non-aromatic nature, known for its plasticizing properties vis-à-vis diene elastomers, can be used.
• these plasticizers or these oils, more or less viscous are liquids (that is to say, as a reminder, substances having the capacity to eventually take the shape of their container) , as opposed in particular to plasticizing resins which are by nature solid at room temperature.
• Liquid plasticizers at 23 ° C chosen from the group comprising or consisting of liquid diene polymers, polyolefinic oils, naphthenic oils, paraffinic oils, DAE oils, MES oils (Medium Extracted Solvates), TDAE oils are particularly suitable. (Treated Distillate Aromatic Extracts), RAE (Residual Aromatic Extract oils), TRAE (Treated Residual Aromatic Extract) oils and SRAE (Safety Residual Aromatic Extract) oils oils), mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these liquid plasticizers at 23 ° C.
• the plasticizer liquid at 23 ° C can be a petroleum oil, preferably non-aromatic.
• a liquid plasticizer is qualified as non-aromatic when it has a content of polycyclic aromatic compounds, determined with the extract in DMSO according to the IP 346 method, of less than 3% by weight, relative to the total weight of the plasticizer .
• the plasticizer that is liquid at 23 ° C. can also be a liquid polymer resulting from the polymerization of olefins or dienes, such as polybutenes, polydienes, in particular polybutadienes, polyisoprenes (also known under the name “LIR”) or copolymers of butadiene and isoprene, or also copolymers of butadiene or isoprene and styrene or mixtures of these liquid polymers.
• the number-average molar mass of such liquid polymers is preferably within a range ranging from 500 g / mol to 50,000 g / mol, preferably from 1,000 g / mol to 10,000 g / mol.
• the plasticizer which is liquid at 23 ° C. is a vegetable oil
• it may be, for example, an oil chosen from the group comprising or consisting of linseed, safflower, soybean, corn, cotton, rape, castor and abrasin oils. , pine, sunflower, palm, olive, coconut, peanut, grape seed and mixtures of these oils.
• Vegetable oil is preferably rich in oleic acid, that is to say that the fatty acid (or all the fatty acids if several are present) from which it is derived, contains oleic acid according to a mass fraction at least equal to 60%, even more preferably according to a mass fraction at least equal to 70%.
• a sunflower oil is advantageously used which is such that the set of fatty acids from which it is derived comprises oleic acid in a mass fraction equal to or greater than 60%, preferably 70% and, according to a particularly advantageous embodiment of the invention, according to a mass fraction equal to or greater than 80%.
• the liquid plasticizer is a triester selected from the group consisting of triesters of carboxylic acid, phosphoric acid, sulfonic acid and mixtures of these triesters.
• phosphate plasticizers By way of example of phosphate plasticizers, mention may be made of those which contain between 12 and 30 carbon atoms, for example trioctyl phosphate.
• carboxylic acid ester plasticizers mention may in particular be made of the compounds chosen from the group consisting of trimellitates, pyromellitates, phthalates, 1, 2-cyclohexane dicarboxylates, adipates, azelates and sebacates. , glycerol triesters and mixtures of these compounds.
• glycerol triesters preferably consisting mainly (for more than 50%, more preferably for more than 80% by weight) of an unsaturated C 8 fatty acid, that is, that is to say selected from the group consisting of oleic acid, linoleic acid, linolenic acid and mixtures of these acids.
• the glycerol triester is preferred. More preferably, whether it is of synthetic or natural origin (case for example of vegetable oils of sunflower or rapeseed), the fatty acid used consists for more than 50% by weight, more preferably still for more than 80% by weight of oleic acid.
• Such triesters (trioleates) with a high level of oleic acid are well known; they have been described for example in application WO 02/088238, as plasticizers in treads for tires.
• liquid plasticizer at 23 ° C is an ether plasticizer, it may be, for example, polyethylene glycol or polypropylene glycol.
• the plasticizer which is liquid at 23 ° C. is chosen from the group comprising or constituted by MES oils, TDAE oils, naphthenic oils, vegetable oils and mixtures of these plasticizers which are liquid at 23 ° C. More preferably, the plasticizer which is liquid at 23 ° C. is a vegetable oil, preferably a sunflower oil.
• composition of the tire tread according to the invention does not include liquid polymer.
• composition of the tread according to the invention comprises 10 to 60 phr, preferably 15 to 40 phr, of vegetable oil, preferably of sunflower oil.
• the plasticizing system of the rubber composition of the tread of the tire according to the invention may comprise a plasticizing resin which is viscous at 20 ° C., called “de. low Tg ”, that is to say which by definition has a Tg within a range from -40 ° C to -20 ° C.
• the composition can optionally comprise, in addition to or in substitution for all or part of the plasticizer which is liquid at 23 ° C, from 0 to 140 phr of viscous plasticizer resin at 20 ° C.
• the viscous plasticizing resin at 20 ° C exhibits at least any one, preferably 2 or 3, preferably all, of the following characteristics:
• Tg of between -40 ° C and 0 ° C, more preferably between -30 ° C and 0 ° C and more preferably still between -20 ° C and 0 ° C;
• Mn a number-average molecular mass (Mn) of less than 800 g / mol, preferably less than 600 g / mol and more preferably less than 400 g / mol;
• composition of the tread according to the invention can be within a range ranging from 20 to 120 phr, preferably from 40 to 90 phr.
• the total level of plasticizer which is liquid at 23 ° C. and of viscous plasticizing resin at 20 ° C. is within a range ranging from 0 to 50 phr, preferably from 10 to 45 phr, preferably from 15 to 30 phr.
• the rubber compositions for the tread of the tire according to the invention may optionally also include all or part of the usual additives usually used in elastomer compositions for tires, such as for example plasticizers (such as plasticizing oils and / or plasticizing resins), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, anti-oxidants, anti-fatigue agents, reinforcing resins (such as described for example in application WO 02/10269) .
• plasticizers such as plasticizing oils and / or plasticizing resins
• protective agents such as anti-ozone waxes, chemical anti-ozonants, anti-oxidants, anti-fatigue agents, reinforcing resins (such as described for example in application WO 02/10269) .
• composition in accordance with the invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art:
• thermomechanical working or mixing phase which can be carried out in a single thermomechanical step during which is introduced, into an appropriate mixer such as a usual internal mixer (for example of the 'Banbury'), all the necessary constituents, in particular the elastomeric matrix, any fillers, any other various additives, with the exception of the vulcanization system.
• an appropriate mixer such as a usual internal mixer (for example of the 'Banbury')
• all the necessary constituents in particular the elastomeric matrix, any fillers, any other various additives, with the exception of the vulcanization system.
• the incorporation of the optional filler into the elastomer can be carried out one or more times by mixing thermomechanically.
• the non-productive phase can be carried out at high temperature, up to a maximum temperature between 110 ° C and 200 ° C, preferably between 130 ° C and 185 ° C, for a period generally between 2 and 10 minutes a second phase of mechanical work (so-called “productive” phase), which is carried out in an external mixer such as a roller mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 120 ° C, for example between 40 ° C and 100 ° C.
• the vulcanization system is then incorporated, and the whole is then mixed for a few minutes, for example between 5 and 15 min.
• Such phases have been described for example in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.
• the final composition thus obtained is then calendered, for example in the form of a sheet or of a plate, in particular for a characterization in the laboratory, or else extruded in the form of a semi-finished (or profile) of rubber which can be used by example such as a passenger vehicle tire tread.
• These products can then be used for the manufacture of tires, according to techniques known to those skilled in the art.
• the composition can be either in the raw state (before vulcanization) or in the cured state (after vulcanization), can be a semi-finished product which can be used in a tire.
• the vulcanization of the composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 130 ° C and 200 ° C, under pressure.
• the tread of a tire comprises a tread surface intended to be in contact with the ground when the tire is rolling.
• the tread is provided with a tread comprising in particular tread elements or elementary blocks delimited by various main grooves, longitudinal or circumferential, transverse or even oblique, the elementary blocks possibly further comprising various incisions or finer lamellae.
• the grooves constitute channels intended to evacuate water when driving on wet ground and the walls of these grooves define the leading and trailing edges of the tread elements, depending on the direction of the turn.
• a tire having a geometry of revolution relative to an axis of rotation its geometry is usually described in a meridian plane containing the axis of rotation of the tire.
• the radial, axial and circumferential directions respectively denote the directions perpendicular to the axis of rotation of the tire, parallel to the axis of rotation of the tire and perpendicular to the meridian plane.
• the expressions "radially inner, respectively radially outer” mean “closer, respectively further away from the axis of rotation of the tire”.
• axially inner, respectively axially outer is meant “closer to, respectively further away from the equatorial plane of the tire", the equatorial plane of the tire being the plane passing through the middle of the tread surface of the tire and perpendicular to the tire. axis of rotation of the tire.
• the tread can consist of one and the same composition. It can also, and advantageously, comprise several portions (or layers), for example two, superimposed in the radial direction.
• the portions (or layers) are at least substantially parallel to each other, as well as to the tangential (or longitudinal) plane, a plane defined as being orthogonal to the radial direction.
• composition according to the invention can be present in the whole of the tread according to the invention.
• the tread comprises at least a radially inner portion and a radially outer portion, the composition in accordance with the invention being advantageously present in a radially outer portion of the tread of the tire according to the invention.
• the radially inner portion of the tread is preferably formed by a composition different from that in accordance with the present invention.
• the tread may also comprise two compositions which are different from one another but both conform to the present invention, one being present in a radially outer portion of the tread, the other in a radially inner portion.
• the tread of the tire according to the invention is preferably:
• the first portion being constituted by a single layer Ci ,
• the layer Ci having a radial thickness Ei, measured in an equatorial plane (XZ) of the tire, substantially constant over at least 80% of the axial width L of the tread, and consisting of a composition different from the composition in accordance with the invention,
• the second portion being formed by a single layer C2
• the radially outer portion of the tread comes, by definition, in contact with the ground when the tire is new or when the radially outer portion of the tread is little worn.
• the radially inner portion of the tread is intended to be in contact with the ground after wear of the radially outer portion of the tread.
• a person skilled in the art therefore understands that the most radially outer part of the radially inner portion of the tread according to the invention is advantageously located above the wear indicator of the tire tread.
• the radial thickness E2 of the second portion of the tire is within a range ranging from 4 to 8 mm, preferably from 4.5 to 7.5 mm.
• the radial thickness Ei of the first portion of the tire is within a range ranging from 1 to 5 mm, preferably from 1.5 to 4.5 mm.
• the invention particularly relates to tires intended to be fitted to motor vehicles of the passenger car, SUV (“Sport Utility Vehicles”) and light-duty type, in particular motor vehicles of the passenger type and SUV.
• SUV Sport Utility Vehicles
• light-duty type in particular motor vehicles of the passenger type and SUV.
• the invention relates to tires both in the raw state (ie, before curing) and in the cured state (ie, after vulcanization).
• Dynamic properties The dynamic properties G * and tan (8) Max are measured on a viscoanalyst (Metravib VA4000), according to standard ASTM D5992-96.
• the response of a sample of vulcanized composition (cylindrical test piece 2 mm thick and 79 mm 2 in section) is recorded, subjected to a sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under normal conditions of temperature (23 ° C) or at 0 ° C according to standard ASTM D 1349-09 for measurements of tan (d) Max, or at -20 ° C for measurements of G *.
• a strain amplitude sweep is carried out from 0.1% to 50% (outward cycle), then from 50% to 0.1% (return cycle).
• tan (ô) max) we indicate the maximum value of tan d observed (tan (ô) max), as well as the difference in complex modulus (AG *) between the values at 0.1% and at 50% deformation (effect Payne).
• the abrasion resistance obtained by determining the loss in volume by abrasion is measured according to standard NF ISO 4649 of November 2010 which consists in determining the loss in volume of a sample after moving 40 linear meters on standardized abrasive paper .
• a mass loss of the sample is measured and the volume loss is calculated from the density (p) of the material constituting the test piece.
• the density (p) of the material constituting the specimen is conventionally obtained on the basis of the mass fractions of each constituent of the material and their respective density (p).
• the results are indicated in base 100.
• the arbitrary value 100 being attributed to the control composition makes it possible to compare the volume of substance loss of different compositions tested.
• the value expressed in base 100 for the composition tested is calculated according to the operation: (measured value of the volume of substance loss of the control composition / measured value of the volume of substance loss of the composition tested) X 100.
• a result greater than 100 will indicate a decrease in the loss in volume and therefore an improvement in abrasion resistance, which corresponds to an improvement in wear resistance performance.
• a result of less than 100 will indicate an increase in volume loss and therefore a decrease in abrasion resistance, which corresponds to a decrease in wear resistance performance.
• the rubber compositions were produced as described in point IL 6 above.
• the “non-productive” phase was carried out in a 0.4 liter mixer for 3.5 minutes, for an average pallet speed of 50 revolutions per minute until a maximum drop temperature of 160 ° was reached.
• the "productive” phase was carried out in a cylinder tool at 23 ° C for 5 minutes.
• the formulations tested all contain an elastomeric matrix, the nature and contents of which are shown in Table 1 below, 120 phr of silica “Zeosil 1165 MP" from the company Rhodia type “HDS”, 9.6 phr of liquid silane TESPT (“Si69” from the company Degussa) as coupling agent for silica to the elastomers, 4 phr of Grade ASTM N234 carbon black from the company Cabot, 12 phr of glycerol trioleate (sunflower oil at 85% in weight of oleic acid) “Lubrirob Tod 1880” from the company Novance, 2 pce of anti-ozone wax (“VARAZON 4959” from the company Sasol Wax), 3 pce of anti-oxidant (Nl, 3-dimethylbutyl-N -phenylparaphenylenediamine, “Santoflex 6-PPD” from the company Flexsys), 3 pce of stearic acid
• Table 1 The purpose of the tests presented in Table 1 is to demonstrate the effect of the elastomeric matrix, in particular the effect of the copolymer based on butadiene and styrene exhibiting a glass transition temperature below -70 ° C, on the properties. grip on snowy ground, abrasion resistance and rolling resistance.
• SBR SBR with 3% of moti ' styrene and 13% of unit 1, 2 of the butadiene part, and carrying an amino-alkoxysilane function in the middle of the elastomer chain (Tg -88C)
• compositions in accordance with the invention make it possible to improve the performance compromise of grip on snow-covered ground, abrasion resistance, rolling resistance and grip on wet ground. It is noted that the use of copolymer based on butadiene and styrene in accordance with the invention at levels of less than 65 phr (C4 and C5) gives rise to a further improvement in the adhesion on snow-covered ground and in abrasion resistance in the snow. detriment of rolling resistance.
• plasticizing resin having a Tg greater than 20 ° C at a rate less than 50 phr (C7) generates a further improvement in the grip on snow-covered ground and in abrasion resistance to the detriment of the grip on snow. wet ground.
• the compositions containing more than 65 phr of butadiene and styrene-based copolymer in accordance with the invention and more than 50 phr of plasticizing resin having a Tg greater than 20 ° C (Cl, C2 and C3) present the best compromise. overall between the properties of grip on snowy ground, abrasion resistance, rolling resistance and grip on wet ground.

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