Classifications

• • 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
• • 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
  • C08C19/30—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule
  • C08C19/42—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule reacting with metals or metal-containing groups
  • C08C19/44—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule reacting with metals or metal-containing groups of polymers containing metal atoms exclusively at one or both ends of the skeleton
• • 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
  • C08F136/06—Butadiene
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
  • Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction 

Definitions

• the present invention relates to tires with tread, in particular with snow, winter or all-season tread, suitable for running on snow-covered ground (in English called “snow tires”, “winter tires” or “ all season”).
• snow tires marked with an M+S or M.S. or even M&S inscription, marked on their sidewalls are characterized by a tread design and a structure intended above all to belay in mud and fresh snow. or melting behavior better than that of road type tires (in English called “road type tyre”) designed to run on non-snow-covered ground.
• Snow-covered soils known as white soils, have the characteristic of having 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 grip performance on wet ground of these tires comprising such treads is generally lower than that of road tires whose treads are generally based on rubber compositions of different formulations, in particular with a higher Tg.
• application WO 2012/069565 proposes a tread whose composition comprises a diene elastomer carrying at least one SiOR function, R being a hydrogen or a hydrocarbon radical in combination with a high rate of reinforcing inorganic filler and a specific plasticizing system.
• snow or winter treads are generally provided with more flexible tread patterns and/or consist of a softer rubber composition than so-called “summer” treads, their resistance to abrasion often turns out to be reduced. Also, it is important to keep as much as possible, or even improve, the abrasion resistance of snow or winter treads. Thus, manufacturers are always looking for solutions to further improve a compromise of properties which are rolling resistance, grip on snowy ground and resistance to abrasion of the tread of tires intended to run in particular on snowy ground.
• the subject of the invention is a rubber composition based on:
• an elastomer matrix comprising from 25 to 95 parts by weight per hundred parts by weight of elastomer, phr, of copolymer based on butadiene and styrene having a glass transition temperature below -64° C., and from 5 to 75 phr of polybutadiene modified with a functional group capable of interacting with silica,
• composition based on means a composition comprising the mixture and/or the in situ reaction product of the various constituents used, some of these constituents being able to react and/or being intended to react with one another, less partially, during the various phases of manufacture of the composition; the composition thus possibly being in the totally or partially crosslinked state or in the non-crosslinked state.
• part by weight per hundred parts by weight of elastomer (or phr) is meant within the meaning of the present invention, the part, by mass per hundred parts by mass of elastomer.
• any interval of values denoted by the expression “between a and b” represents the domain of values going from more than a to less than b (i.e. limits a and b excluded) while any interval of values denoted 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 in 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 majority 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 the one representing the greatest mass among the fillers of the composition.
• the majority elastomer represents more than half of the mass of the 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 can be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. This concerns in particular polymers, plasticizers, fillers, etc.
• Glass transition temperature “Tg” values described herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to standard ASTM D3418 (1999).
• the elastomeric matrix of the composition comprises from 25 to 95 phr of copolymer based on butadiene and styrene having a glass transition temperature below -64° C., from 5 to 75 phr of polybutadiene modified with a functional capable of interacting with silica.
• the term “copolymer based on butadiene and styrene” is used to refer to any copolymer obtained by copolymerization of one or more styrenic compounds with one or more butadiene(s).
• Suitable styrene monomers include styrene, methylstyrenes, para-tert-butylstyrene, methoxystyrenes and chlorostyrenes.
• 1,3-butadiene is particularly suitable.
• elastomers can have any microstructure which depends on the polymerization conditions used, in particular on the presence or not 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 styrene is a butadiene-styrene copolymer (SBR).
• SBR can be prepared in emulsion (ESBR) or in solution (SSBR). Whether it is ESBR or SSBR, the SBR can be of 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 (% molar) of ⁇ 1,2 bonds of the butadiene part comprised between 4% and 25%.
• the copolymer based on butadiene and styrene is an SSBR.
• the copolymer based on butadiene and styrene has a glass transition temperature comprised in 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 copolymer based on butadiene and styrene is a styrene-butadiene copolymer exhibiting any one, advantageously the combination of two or three, even more advantageously all, of the following characteristics:
• - its Tg is within a range ranging from -105°C to -70°C, preferably between -95°C and -86°C.
• the copolymer based on butadiene and styrene 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 elastomer chain(s), the alkoxysilane group being optionally partially or completely hydrolyzed to silanol.
• an alkoxysilane group located within the structure of the elastomer is understood as a group whose silicon atom is located in the backbone of the polymer and directly connected thereto. This positioning within the structure includes the ends of polymer chains. Thus, the terminal group is included in this notion.
• the alkoxysilane group is not a pendent group.
• the diene elastomer is functionalized at the end or end of the chain.
• the diene elastomer is coupled or even 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 styrene comprises as majority species the diene elastomer functionalized in the middle of the chain by an alkoxysilane group bonded to the two branches of the diene elastomer via the silicon atom , the alkoxy radical optionally being partially or completely hydrolyzed to hydroxyl. 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 styrene.
• the alkoxyl radical may comprise a Ci-Cio or even Ci-Cs alkyl radical, preferably C1-C4, 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.
• the copolymer based on butadiene and styrene advantageously comprises at least one function comprising a nitrogen atom.
• the copolymer based on butadiene and styrene 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 via 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 in Ci-C 18, saturated or not, cyclic or not, or an aromatic divalent hydrocarbon radical in C6-CIS and can contain one or more aromatic radicals and/or one or more heteroatoms.
• the hydrocarbon radical may optionally be substituted.
• the spacer group is a divalent hydrocarbon radical, linear or branched, aliphatic in Ci-Cis, more preferentially a divalent aliphatic hydrocarbon radical in Ci-Cio, more preferentially still in C3-Cs, more preferentially still a linear divalent hydrocarbon radical in C3 .
• the copolymer based on butadiene and styrene can also comprise another function (that is to say 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:
• the radical R represents a substituted or unsubstituted alkyl radical, being Ci-Cio, or even Ci-Cs, preferably a C1-C4 alkyl radical, more preferentially methyl and ethyl;
• R' represents an alkyl radical, substituted or unsubstituted, being C1-C10, or even Ci-Cs, preferably an alkyl radical in C1-C4, more preferably methyl and ethyl;
• - X represents a group comprising the nitrogen function
• 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.
• amines substituted by C1-C10 alkyl radicals preferably C1-C4 alkyl, more preferably a methyl or ethyl radical, or cyclic amines forming a heterocycle containing a nitrogen atom and at least one carbon atom, preferably 2 to 6 carbon atoms.
• methylamino-, dimethylamino-, ethylamino-, diethylamino-, propylamino-, dipropylamino-, butylamino-, dibutylamino-, pentylamino-, dipentylamino-, hexylamino-, dihexylamino-, hexamethyleneamino- groups are suitable, preferably diethylamino groups. - and dimethylamino-.
• amine is cyclic
• morpholine piperazine, 2,6-dimethylmorpholine, 2,6-dimethylpiperazine, 1-ethylpiperazine, 2-methylpiperazine, 1-benzylpiperazine, piperidine, 3,3-dimethylpiperidine, 2,6- dimethylpiperidine, l-methyl-4-(methylamino)piperidine, 2,2,6,6-tetramethylpiperidine, pyrrolidine, 2,5-dimethylpyrrolidine, azetidine, hexamethyleneimine, heptamethyleneimine, 5-benzyloxyindole, 3-azaspiro[5,5]undecane , 3-aza-bicycle[3.2.2]nonane, carbazole, bistrimethylsilylamine, pyrrolidine and hexamethyleneamine, preferably pyrrolidine groups and hexamethyleneamine.
• the amine function is a tertiary amine function, preferably diethylamine or dimethylamine.
• 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 met:
• 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 an aliphatic hydrocarbon radical in Ci-Cio, more preferentially an aliphatic hydrocarbon radical in C3-C8, more preferentially still the C3 linear hydrocarbon radical,
• the alkoxysilane group is a methoxysilane or an ethoxysilane, optionally partially or totally hydrolyzed to silanol,
• the copolymer based on butadiene and 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 by 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 styrene has a glass transition temperature comprised 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 met:
• 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 C3 linear aliphatic hydrocarbon radical,
• the alkoxysilane group is methoxysilane or ethoxysilane, optionally partially or totally hydrolyzed to silanol,
• the copolymer based on butadiene and 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 by 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 styrene has a glass transition temperature comprised in a range comprised between -95°C and -86°C.
• the content of copolymer based on butadiene and styrene, in the composition according to the invention, can advantageously be within a range ranging from 65 to 95 phr, preferably between 66 and 90 phr.
• Such copolymers based on butadiene and styrene can be obtained by a process as described below.
• the first step of a process for the preparation of the copolymer based on butadiene and styrene is the anionic polymerization of at least one conjugated diene monomer or the polymerization of at least one conjugated diene monomer and a vinylaromatic monomer, in the presence of a polymerization initiator.
• the monomers are as described above.
• any known monofunctional anionic initiator can be used.
• an initiator containing an alkali metal such as lithium is preferably used.
• Suitable organolithium initiators are in particular those comprising a carbon-lithium bond.
• Representative compounds are aliphatic organolithiums such as ethyllithium, n-butyllithium (n-BuLi), isobutyllithium, etc...
• the other function is directly linked to the elastomer chain
• this can be provided by the polymerization initiator.
• Such initiators are, 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 products of the reaction of an organolithium compound, preferably alkyllithium, and an acyclic or cyclic secondary amine, preferably cyclic.
• a 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, l-methyl-4-(methylamino)piperidine, 2,2,6,6-tetramethylpiperidine, pyrrolidine, 2,5-dimethylpyrrolidine, azetidine, hexamethyleneimine,
• the alkyllithium 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 may for example be an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, iso-octane, cyclohexane, methylcyclohexane or a hydrocarbon aromatic like benzene, toluene, xylene.
• an inert hydrocarbon solvent which may for example be an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, iso-octane, cyclohexane, methylcyclohexane or a hydrocarbon aromatic like 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 quantities of modifying and/or randomizing agent used.
• a polar agent is used during the polymerization step in quantities such that it promotes the statistical distribution of the vinylaromatic 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 at within its structure at least one alkoxysilane group linked 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 at within its structure at least one alkoxysilane group linked 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 vice versa of an agent non-polymerizable functionalization capable of forming an alkoxysilane group, the silicon atom being integrated within the elastomer chain, whether or not carrying a function comprising a nitrogen atom. It is particularly a functionalizing agent carrying reactive functions 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 a substituted or unsubstituted, Ci-Cio or even Ci-Cs alkyl radical, preferably a C1-C4 alkyl group, more preferably methyl and ethyl;
• - R represents an alkyl radical, substituted or unsubstituted, Ci-Cio, or even Ci-Cs, preferably a C1-C4 alkyl group, more preferably methyl and ethyl;
• - X represents a group including a function comprising a nitrogen atom
• 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 can 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 the two nitrogen substituents together form 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 C1-C10, more particularly linear in C2 or C3.
• 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 is 3-(N,N-dimethylaminopropyl)trimethoxysilane.
• the functionalizing agent can be chosen from 3-(N,N-methyltrimethylsilylaminopropyl)trimethoxysilane, 3-(N,N-methyltrimethylsilylaminopropyl)triethoxysilane, 3-(N,N-ethyltrimethylsilylaminopropyl)trimethoxysilane, 3-(N ,N-ethyltrimethylsilylaminopropyl)triethoxysilane, 3-(N,N-propyltrimethylsilylaminopropyl)trimethoxysilane, 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 preferentially, 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 copolymer based on butadiene and styrene desired. Thus, with a ratio ranging from 0.40 to 0.75, or even from 0.45 to 0.65, or even from 0.45 to 0.55, the formation of coupled species within the elastomer is preferred. 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, stellate species are mainly formed (3 branches) in the within the modified elastomer.
• the molar ratio between the functionalizing agent and the polymerization initiator varies from 0.35 to 0.65, preferentially from 0.40 to 0.60 and even more preferentially from 0.45 to 0.55.
• the copolymer based on butadiene and styrene may comprise as majority species the diene elastomer functionalized in the middle of the chain by an alkoxysilane group linked to the two branches of the diene elastomer via the intermediary of 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 styrene.
• the alkoxysilane group advantageously comprises an alkoxy radical, optionally partially or totally hydrolyzed to hydroxyl.
• the alkoxysilane group advantageously bears 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-, bonded 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 continue with a step of deprotection of this function. This step is implemented after the modification reaction and is well known to those skilled in the art.
• the synthesis process may also comprise a step of hydrolysis of the hydrolyzable alkoxyl functions, by adding an acid, basic or neutral compound as described in document EP 2 266 819 AL.
• the hydrolyzable functions are then transformed into hydroxyl function.
• the process for synthesizing the copolymer based on butadiene and styrene can be continued in a manner known per se by the steps for recovering the copolymer based on butadiene and styrene.
• these steps may in particular comprise a stripping step with a view to recovering the elastomer resulting from the previous steps.
• This stripping step can have the effect of hydrolyzing all or part of the hydrolysable functions of the copolymer based on butadiene and styrene.
• at least 50 to 70 molar % of these functions can thus be hydrolyzed.
• the elastomeric matrix of the composition according to the invention comprises from 5 to 75 phr of polybutadiene modified with a functional group capable of interacting with silica, also referred to as “modified polybutadiene” herein.
• polybutadiene (abbreviated to “BR”), it will be understood that it may be one or more polybutadienes.
• BR polybutadiene
• Polybutadiene is a well-known rubber which is made by polymerizing 1,3-butadiene monomer (typically homopolymerization) in a solution polymerization process using suitable catalysts known to those skilled in the art. Due to the two double bonds present in the butadiene monomer, the resulting polybutadiene can comprise 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.
• Catalyst choice and process temperature are known as the variables generally used to control the cis-1,4 bond content of polybutadiene.
• the polybutadiene has a rate (% molar) of cis-1,4 linkages greater than 55%, preferably greater than 90%, more preferably greater than 95%.
• the modified polybutadiene can be obtained by a process comprising the following steps:
• halogen donor comprising an alkylaluminum halide
• said salt is in suspension or in solution in at least one inert and saturated hydrocarbon solvent of the aliphatic or alicyclic type;
• step (b) adding to the pseudo-living elastomer formed in step (a) a polyfunctional compound, comprising at least three functional groups, said functional group being capable of reacting with the reactive end of the pseudo-living elastomer;
• step (c) adding to the mixture formed in step (b) a functionalizing agent corresponding to the formula A-Ri-B with A denoting a group capable of reacting with the reactive end of the pseudo-living elastomer, Ri denoting an atom or a group of atoms forming a bond between A and B, and B designating a function capable of reacting with a reinforcing charge;
• modified polybutadiene has all or part of these reactive chain ends, in particular with respect to functionalizing agents.
• rare earth means a metal chosen from yttrium, scandium and the lanthanides, metals having an atomic number ranging from 57 to 71 included in the periodic table of the elements of Mendele ⁇ ev.
• the rare earth metal is chosen from lanthanides, neodymium being more particularly preferred.
• Steps (a), (b), (c) and (d) of the process for obtaining the modified polybutadiene are described below.
• the catalytic system is advantageously a "preformed" type catalytic system based on at least:
• alkylating agent comprising aluminium, the "alkylating agent"/"rare earth salt” molar ratio having a value between 1 and 5, and
• halogen donor comprising an alkyl aluminum halide.
• the catalytic system can be prepared batchwise or continuously.
• the catalytic system can be introduced directly into the reactor or be mixed beforehand with at least one of the other components which supply the polymerization reactor.
• the inert hydrocarbon solvent in which said rare earth salt is in suspension or in solution is advantageously an aliphatic or alicyclic solvent of low molecular weight, such as cyclohexane, methylcyclohexane, n-heptane, pentane, or a mixture of these solvents.
• An important characteristic of the process for obtaining the modified polybutadiene is the "aluminum"/"rare earth salt" molar ratio.
• the total molar quantity of aluminum is such that the “aluminum/rare earth salt” molar ratio, in particular the “aluminum/neodymium salt” molar ratio, has a value between 1 and 5, advantageously between 1 and 4, more advantageously ranging from 2.5 to 3.8.
• the aluminum is provided by the catalytic system and also, where appropriate, by an additional addition to the alkyl aluminum polymerization medium as described below. Surprisingly, it was found that this “aluminum”/“rare earth salt” molar ratio influenced the average percentage of functionalized chains.
• the catalytic system is such that said rare earth salt has a mass content of rare earth metal ranging from 12.0% to 13.5%, determined both by the technique of complexometric titration in return by acid tetraacetic diethylene diamine (EDTA for short) and by the technique of atomic emission spectrometry coupled with an induced plasma (ICP/AES for short).
• said rare earth salt has a mass content of rare earth metal ranging from 12.5% to 13.2%.
• the rare earth organic phosphoric acid salt is advantageously a rare earth tris(organophosphate), it being possible for the organophosphate to be chosen from among the phosphoric acid diesters of general formula (R'O)(R"O)PO(OH ), in which R′ and R′′, identical or different, represent an alkyl, aryl or alkylaryl radical.
• neodymium tris [dibutyl phosphate], neodymium tris [dipentyl phosphate], neodymium tris [dioctyl phosphate], neodymium tris [bis(2-ethylhexyl) phosphate], neodymium tris[bis(1-methylheptyl)phosphate], neodymium tris[bis(p-nonylphenyl)phosphate], neodymium tris[butyl(2-ethylhexyl)phosphate], tris[(1-methylheptyl) ( neodymium 2-ethylhexyl)phosphate], neodymium tris[(2-ethylhexyl)(p-nonylphenyl)phosphate], neodymium tris[bis(2-ethylhexyl)phosphate], tris[[[2-ethylhex
• rare earth salt a tris[bis(2-ethylhexyl)phosphate] of said rare earth metal(s) is used as rare earth salt.
• said rare earth salt is neodymium tris[bis(2-ethylhexyl)phosphate].
• conjugated diene monomer which can be used to preform the catalytic system
• 1,3-butadiene on a preferential basis.
• alkylating agent which can be used in the catalytic system, mention may be made of alkylaluminums chosen from trialkylaluminums of formula Al(Rf) or dialkylaluminum hydrides of formula HA1(R)2.
• the alkyl group, R advantageously comprises 1 to 20 carbon atoms, more advantageously from 1 to 12 carbon atoms.
• As tri(alkylaluminum) mention may be made of triethylaluminum, tri-isopropylaluminum, tri-isobutylaluminum, tributylaluminum or trioctylaluminum.
• di(alkylaluminum hydride) mention may be made of diisobutylaluminum hydride.
• halogen donor which can be used in the catalytic system according to the invention, mention may be made of using an alkyl halide, an alkyl aluminum halide or an alkyl aluminum sesquihalide.
• An alkyl aluminum halide is preferably used, the alkyl group comprising from 1 to 8 carbon atoms. Of these, diethylaluminum chloride is preferred.
• the rare earth metal or metals are present in the catalytic system in a concentration equal to or greater than 0.005 mol/l and, preferably, ranging from 0.010 to 0.1 mol/l and more particularly ranging from 0.02 mol/l /1 to 0.08 mol/1.
• the "alkylating agent"/"salt of rare earth(s)" molar ratio in said catalytic system can advantageously have a value ranging from 1 to 2.
• the "halogen donor"/"rare earth salt” molar ratio may advantageously have a value ranging from 2 to 3.6 and even more preferentially from 2.4 to 3.2, even more preferentially ranging from 2.5 to 3.
• the “preformation monomer”/“salt of rare earth(s)” molar ratio may advantageously have a value ranging from 15 to 70, or even from 25 to 50.
• alkylaluminums such as:
• - trialkylaluminums such as for example trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, tri-t-butylaluminum, triisobutylaluminum, tri-n-pentylaluminum, tri- n-hexylaluminum, tricyclohexylaluminum, preferably triisobutylaluminum, or
• dialkylaluminum hydrides such as, for example, diethylaluminum hydride, diisopropylaluminum hydride, di-n-propylaluminum hydride, diisobutylaluminum hydride, di-n-octylaluminum hydride, di-n-butylaluminum, preferably diisobutylaluminum hydride.
• the molar ratio "alkylaluminum compound added offset" / "alkylaluminum in the catalytic system” varies from 1/20 to 50/1, preferentially varies from 1/15 to 30/1 and even more preferentially from 1/10 to 20 /1.
• the amount of aluminum alkyl added is such that in the polymerization medium, the molar ratio of the total molar amount of aluminum, relative to the molar amount of rare earth salt, in particular neodymium salt, is always included in the previously defined range.
• the polymerization can be carried out in bulk. In this case there is no addition of polymerization solvent.
• the polymerization can alternatively be carried out in solution or in semi-mass.
• the medium then comprises an inert hydrocarbon polymerization solvent, preferably aliphatic or alicyclic of low molecular mass, in particular for environmental reasons.
• an inert hydrocarbon polymerization solvent preferably aliphatic or alicyclic of low molecular mass, in particular for environmental reasons.
• Mention may be made, by way of example, of n-pentane, isopentane, isoamylenes (2-methyl-2-butene, 2-methyl-1-butene and 3-methyl-1-butene), 2,2- dimethylbutane, 2,2-dimethyl-propane (neopentane), n-heptane, n-octane, iso-octane, cyclopentane, cyclohexane, n-hexane, methylcyclopentane and methylcyclohexane, as well as mixtures of these compounds
• mass polymerization means a polymerization carried out in a reaction medium not comprising any organic solvent.
• polymerization in solution means a polymerization carried out in a reaction medium comprising from 70% to 99% by weight of an organic solvent, relative to the total weight of the monomers and of said organic solvent.
• si-mass polymerization means a polymerization carried out in a reaction medium comprising between 0% and 70% by weight of an organic solvent, relative to the total weight of the monomers and of said organic solvent.
• the solvent can be introduced directly into the reactor. It can also be mixed beforehand with at least one other of the components introduced into the polymerization reactor, in particular with the monomer to be polymerized.
• the polymerization temperature is between 40°C and 90°C, preferably between 40°C and 80°C, preferably between 45°C and 75°C, and preferably between 50°C and 70°C.
• the polyfunctional compound added to the pseudo-living elastomer formed in step (a) comprises at least three functional groups and will thus make it possible to link several polybutadiene chains together.
• this polyfunctional compound comprises at least four functional groups.
• This polyfunctional compound may be a small molecule bearing at least three, advantageously at least four, functional groups or a polymer bearing these at least three, advantageously at least four, functional groups.
• the functional groups are advantageously identical.
• the functional groups are advantageously identical to the functional group A of the functionalizing agent described below.
• the polyfunctional compound advantageously corresponds to the formula (E) n -Rj, with n denoting an integer greater than or equal to 3, E denoting said functional group, Rj denoting an atom or a group of atoms bearing the n groups E.
• Rj is a linear, branched or cyclic hydrocarbon radical, and may contain one or more aromatic radicals, and/or one or more heteroatoms.
• Rj comprises one or more aromatic radicals.
• said Rj radical may optionally be substituted, provided that the other substituents are inert with respect to the reactive ends of the pseudo-living elastomer.
• Rj is a polymeric hydrocarbon chain.
• Rj does not include any Si-O-Si sequence.
• the functional group E is advantageously chosen from epoxides, glycidyloxy, glycidylamino, isocyanates, imines, aziridines, imidazoles. More advantageously, the functional group E is chosen from glycidylamino, isocyanates, imines and imidazoles.
• the polyfunctional compound is advantageously chosen from triglycidylaminophenol, tetraglycidylaminodiphenylmethane (TGMDA), N,N-Diglycidyl-4-glycidyloxyaniline, Tris(4-hydroxyphenyljmethane triglycidyl ether, l,3-bis(N,N'-diglycidylaminomethyl) cyclohexane, tetraglycidylxylenediamine, polymethylenepolyphenylpolyisocyanate, tetra(isocyanato)silane (CAS No: 3410-77-3), phenyltris(methylethylketoximio)silane (CAS No: 34036-80-1), poly[[l, 3-bis[3-(4,5-dihydro-1H-imidazol-1-yl)propyl]-1,3:1,3-disiloxanedylidene]
• the “polyfunctional compound”/“aluminum” molar ratio is advantageously less than 0.3, more advantageously between 0.01 and 0.3.
• the quantity of aluminum corresponds to the total quantity of aluminum present in the reaction medium, taking into account the aluminum included in the catalytic system and, where appropriate, the aluminum included in the additional alkylaluminum compound added offset from the catalytic system.
• Step (b) of reacting at least one polyfunctional compound with the solution of pseudoliving elastomer is advantageously carried out at a temperature between 40° C. and 90° C., more advantageously between 40° C. and 80° C. C, even more advantageously between 45°C and 75°C, and advantageously varying from 50°C to 70°C.
• the functionalizing agent capable of reacting with the pseudo-living elastomer of step (b), introduced in step (c), corresponds to the formula A-Ri-B with A denoting a group capable of reacting on the reactive end of the pseudo-living elastomer, R denoting an atom or a group of atoms forming a bond between A and B and B denoting a function capable of reacting with a reinforcing charge.
• A is advantageously chosen from epoxides, glycidyloxy, glycidylamino, isocyanates, imines, aziridines, imidazoles. More advantageously, A is chosen from glycidylamino, isocyanates, imines and imidazoles.
• B is preferably a di-alkoxysilane, advantageously a diethoxy-silane.
• the Ri group is preferably a divalent hydrocarbon radical, linear, branched or cyclic, and can contain one or more aromatic radicals, and/or one or more heteroatoms. Said radical Ri may optionally be substituted, provided that the substituents are inert with respect to the reactive ends of the pseudo-living elastomer.
• the group Ri denotes a divalent aliphatic hydrocarbon radical Ci-Cis, advantageously Ci-Cio, more advantageously Ci-C ⁇ , more advantageously C1-C3 or C2-C8, saturated or not, cyclic or no, which may contain one or more aromatic radicals.
• Ri is a C1-C3 aliphatic divalent radical.
• Ri is a C2-C8 aliphatic divalent radical.
• Group capable of reacting with the reactive end of the pseudo-living elastomer preferably means a group chosen from in particular epoxides, glycidyloxys, glycidylaminos, isocyanates, imines, aziridines, imidazoles. More advantageously, the group capable of reacting with the reactive end of the pseudo-living elastomer is chosen from glycidylamino, isocyanates, imines and imidazoles.
• the term "function capable of interacting with a reinforcing charge” preferably means a functional group comprising one or more functions chosen from a protected or unprotected primary amine, a protected or unprotected secondary or tertiary amine, an imine, an imide, an amide, a nitrile, azo, carbamate, methacrylate, methacrylamide, hydroxyl, carbonyl, carboxyl, epoxy, glycidyloxy, thiol, sulfide, disulfide, thiocarbonyl, thioester, sulfonyl, silane, silanol, alkoxysilane, alkoxydi-alkylsilane, di-alkoxysilane, di-alkoxyalkylsilane, tri-alkoxysilane, stannyl, tin halide, tin halide alkyl, tin halide aryl tin, a poly
• di-alkoxysilane function in particular diethoxysilane, in particular a di-alkoxyalkylsilane such as a diethoxyalkylsilane, as a function capable of interacting with a reinforcing filler.
• functionalizing agents such as (3-glycidyloxypropyl) methyldiethoxysilane, N-(3-diethoxy(methyl)silylpropyl)-4,5-dihydroimidazole, 2-(3 ,4-epoxycyclohexyl)ethyl methyldiethoxysilane, tris(3-diethoxy(methyl)silylpropyl)isocyanurate, 3-isocyanatopropylmethyldiethoxysilane.
• these functionalizing agents (3-glycidyloxypropyl) methyldiethoxysilane and 3-isocyanatopropylmethyldiethoxysilane are particularly advantageous.
• the "functionalization agent"/"aluminum” molar ratio is advantageously at least 1.
• the “functionalization agent”/"aluminum” molar ratio is at least 1/1 and at most 10/ 1, preferably at most 5/1, or even at most 2/1.
• the polyfunctional compound is lacking while the functionalizing agent is in an equimolar quantity or in excess.
• the quantity of aluminum corresponds to the total quantity of aluminum present in the reaction medium, taking into account the aluminum included in the catalytic system and, where appropriate, the aluminum included in the additional alkylaluminum compound added offset from the catalytic system.
• Another important characteristic of the process for obtaining the modified polybutadiene is the order of addition of the polyfunctional compound and the functionalizing agent: the polyfunctional compound is added before introducing the functionalizing agent.
• Functionalization step (c) is advantageously carried out at a temperature between 40°C and 90°C, more advantageously between 40°C and 80°C, even more advantageously between 45°C and 75°C. C, and advantageously varying from 50°C to 70°C.
• the method for synthesizing a modified polybutadiene can be continued in a manner known per se.
• the process then continues in a manner known per se with the separation and recovery of the modified polybutadiene prepared.
• the unreacted butadiene and/or the solvent can be removed, according to methods known to those skilled in the art.
• the modified polybutadiene recovered at the end of these various stages can then be packaged in a manner known per se, in the form of balls for example.
• the modified polybutadiene of the composition according to the invention capable of being obtained by the process described above, therefore comprises free polybutadiene chains having reacted only with the functionalizing agent and polybutadiene chains linked together via the polyfunctional compound.
• the modified polybutadiene advantageously has a Mooney viscosity ML(1+4) at 100° C. equal to or greater than 40, in particular ranging from 40 to 80.
• the modified polybutadiene also advantageously exhibits reduced creep, which may be characterized in particular by a cold-flow value (“cold-flow” in English) CF(l+6) at 100° C. of the modified polybutadiene of less than 1 g, more preferably less than 0.5 g, even more preferably less than 0.2 g.
• the modified polybutadiene has both:
• CF(1+6) at 100° C. of less than 1 g, preferably less than 0.5 g.
• the “functionalized chains” designate the polybutadiene chains having reacted with the functionalizing agent, of formula A-Ri-B, as defined below.
• the average percentage of functionalized chains is the ratio between the weight of the chains of the modified polybutadiene relative to the total weight of polybutadiene chains. It is determined by multiplying the number of functions, CFL—Si/PB, in moles per mass unit of the polymer, by the molar mass in number of said polymer. The number of functions, in mole per unit mass of the polymer, is determined by NMR following the protocol described in the introduction to the examples.
• the modified polybutadiene has an average content of functionalized chains of between 25% and 80%. In one embodiment, the modified polybutadiene has an average percentage of functionalized chains of between 25% and 60%. In another embodiment, the modified polybutadiene has an average percentage of functionalized chains of between 40% and 80%, advantageously between 40% and 70%.
• the modified polybutadiene advantageously has a glass transition temperature (Tg) below -100°C, preferably below -105°C, preferably between -110°C and -105°C.
• Tg glass transition temperature
• the content of modified polybutadiene, in the composition according to the invention is within a range ranging from 5 to 35 phr, preferably between 10 and 34 phr.
• the composition according to the invention advantageously comprises from 65 to 95 phr of copolymer based on butadiene and styrene and from 5 to 35 phr of polybutadiene, preferably from 66 to 90 phr of copolymer based on butadiene and styrene and 10 and 34 phr of polybutadiene.
• the elastomeric matrix of the composition according to the invention comprises less than 15 phr of isoprene elastomer.
• isoprene elastomer is understood to mean in known manner an isoprene homopolymer or copolymer, 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 mention will be made in particular of 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, are preferably used polyisoprenes having a rate (% molar) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%.
• the level of isoprene elastomer, in the composition according to the invention, is preferably less than 14 phr, preferably less than 10 phr, preferably less than 5 phr, preferably less than 4 phr.
• the total content of the copolymer based on butadiene and styrene and of the modified polybutadiene, in the composition is advantageously within a range ranging from 85 phr to 100 phr, preferably from 86 to 100 phr, preferably from 90 phr to 100 phr, preferably from 95 to 100 phr, preferably from 96 to 100 phr.
• the composition according to the invention is devoid of isoprene elastomer.
• the total content of copolymer based on butadiene and styrene and polybutadiene, in the composition according to the invention is 100 phr.
• the composition according to the invention further comprises a reinforcing filler, known for its ability to reinforce a rubber composition that can be used for the manufacture of tires.
• This reinforcing filler comprises silica.
• the silicas that 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 fumed silica having a BET surface area as well as a CTAB specific surface area both less than 450 m2/g, preferably from 30 to 400 m2/g.
• the BET specific surface of silica is determined in a known manner by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society” Vol. 60, page 309, February 1938, more specifically according to French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points) - gas: nitrogen - degassing: 1 hour at 160°C - relative pressure range p/po: 0.05 to 0.17).
• the CTAB specific surface of the silica is determined according to the French standard NF T 45-007 of November 1987 (method B).
• the silica has a BET specific surface of between 100 and 250 m 2 /g, preferably within a range ranging from 105 to 200 m 2 /g, preferably from 125 to 180 m 2 /g.
• the silica has a CTAB specific surface of between 105 and 220 m 2 /g, preferably within a range ranging from 110 to 200 m 2 /g, preferably from 140 to 170 m 2 /g.
• silicas which can be used in the context of the present invention, mention will be made, for example, of the highly dispersible precipitated silicas (known as "HDS") "Ultrasil 7000" and “Ultrasil 7005" from the company Evonik, “Zeosil 1165MP, 1135MP and 1115MP” silicas from Rhodia, “Hi-Sil EZ150G” silica from PPG, “Zeopol 8715, 8745 and 8755” silicas from Huber, high specific surface silicas such as as described in application WO 03/16837.
• 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 silica ( surface of its particles) and the diene elastomer.
• at least bifunctional organosilanes or polyorganosiloxanes are used. “Bifunctional” means a compound having a first functional group capable of interacting with silica and a second functional group capable of interacting with the diene elastomer.
• such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic filler (such as silica) and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.
• the organosilanes are chosen from the group consisting of polysulphide organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulphide, abbreviated as TESPT marketed under the name “Si69” by the company Evonik or bis disulphide -(triethoxysilylpropyl), abbreviated as TESPD marketed under the name “Si75” by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate marketed by the company Momentive under the name “NXT Silane”. More preferably, the organosilane is a polysulphide organosilane.
• the reinforcing filler mainly comprises silica.
• the silica content in the composition according to the invention may be within a range ranging from 80 to 200 phr, preferably from 100 to 180 phr, preferably from 105 to 145 phr.
• the reinforcing filler can also comprise carbon black.
• the content of carbon black in the composition 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 phr.
• 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 any black conventionally used in tires or their treads
• These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a carrier for some of the rubber additives used.
• the carbon blacks could for example already be incorporated into the diene elastomer, in particular isoprene in the form of a masterbatch (see for example applications WO 97/36724 or WO 99/16600).
• the content of coupling agent in the composition of the invention is advantageously less than or equal to 35 phr, it being understood that it is generally desirable to use as little as possible.
• the rate of coupling agent represents from 0.5% to 15% by weight relative to the amount of silica. Its content is preferably within a range ranging from 0.5 to 20 phr, more preferably within a range ranging from 1 to 3 phr. This rate is easily adjusted by a person skilled in the art according to the rate of silica used in the composition of the invention.
• the crosslinking system can be any type of system known to those skilled in the art in the field of rubber compositions for tires. It may in particular be based on sulfur, and/or peroxide and/or bismaleimides.
• the crosslinking system is sulfur-based, in which case we speak of a vulcanization system.
• the vulcanization system comprises molecular sulfur and/or at least one sulfur-donating agent.
• At least one vulcanization accelerator is also preferentially present, and, optionally, also preferentially, various known vulcanization activators such as zinc oxide, stearic acid or equivalent compound such as stearic acid salts and salts can be used. of transition metals, guanidine derivatives (in particular diphenylguanidine), or alternatively known vulcanization retarders.
• the 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 comprised between 0.5 and 10 phr, more preferentially comprised between 0.5 and 5.0 phr.
• Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used as an accelerator, in particular accelerators of the thiazole type as well as their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type.
• MBTS 2-mercaptobenzothiazyl disulphide
• CBS N-cyclohexyl-2-benzothiazyl sulfenamide
• DCBS N,N-dicyclohexyl- 2-Benzothiazyl sulfenamide
• TBBS N-ter-butyl-2-benzothiazyl sulfenamide
• TZTD tetrabenzylthiuram disulfide
• ZBEC zinc dibenzyldithiocarbamate
• the rubber composition according to the invention further comprises from 25 to 150 phr of at least one plasticizing resin having a glass transition temperature above 20° C., called “high Tg”, (also called “plasticizing resin” in the present for the sake of simplicity of drafting”).
• high Tg glass transition temperature above 20° C.
• plasticizing resin also called “plasticizing resin” in the present for the sake of simplicity of drafting”.
• resin is reserved in the present application, by definition known to those skilled in the art, for a compound which is solid at ambient temperature (23° C.), as opposed to a liquid plasticizing compound such as an oil.
• Plasticizing resins are polymers well known to those skilled in the art, essentially based on carbon and hydrogen but which may contain other types of atoms, which can be used in particular as plasticizing agents or tackifying agents in 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 diluting agents. They have been described for example in the work entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9) of which chapter 5 is devoted their applications, in particular in pneumatic rubber (5.5. "Rubber Tires and Mechanical Goods'”).
• They can be aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, of the aliphatic/aromatic type, that is to say based on aliphatic and/or aromatic monomers. They can be natural or synthetic, petroleum-based or not (if so, also known as petroleum resins). Their Tg is preferably greater than 20°C (usually between 30°C and 95°C).
• these plasticizing resins can also be qualified as thermoplastic resins in the sense that they soften on heating and can thus be molded. They can also be defined by a softening point or temperature.
• the softening temperature of a plasticizing resin is generally higher by around 50 to 60°C than its Tg value. softening is measured according to standard ISO 4625 (“Ring and Bail” method)
• the macrostructure (Mw, Mn and Ip) is determined by steric 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; the molecules are separated according to their hydrodynamic volume, the largest being eluted first.
• the sample to be analyzed is simply dissolved beforehand in an appropriate solvent, tetrahydrofuran at a concentration of 1 g/litre.
• the solution is then filtered through a filter with a porosity of 0.45 ⁇ m, before injection into the apparatus.
• the equipment used is, for example, a "Waters Alliance" chromatographic chain under the following conditions:
• differential refractometer for example "WATERS 2410" which can be equipped with operating software (for example “Waters Millenium”).
• the plasticizing resin has at least any one, preferably 2 or 3, more preferably all, of the following characteristics:
• Tg greater than 25°C (in particular between 30°C and 100°C), more preferably greater than 30°C (in particular between 30°C and 95°C);
• Mn number-average molar mass
• 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 (in abbreviated form CPD), homopolymer or copolymer resins dicyclopentadiene (abbreviated as DCPD), terpene homopolymer or copolymer resins, C5 cut homopolymer or copolymer resins, C9 cut homopolymer or copolymer resins, alpha -methyl-styrene and mixtures thereof.
• CPD cyclopentadiene homopolymer or copolymer resins
• DCPD homopolymer or copolymer resins dicyclopentadiene
• terpene homopolymer or copolymer resins C5 cut homopolymer or copolymer resins
• C9 cut homopolymer or copolymer resins alpha -methyl-styrene and mixtures thereof.
• the plasticizing resin is chosen from the group comprising or consisting of (D)CPD/vinyl aromatic copolymer resins, (D)CPD/terpene copolymer resins, terpene phenol copolymer resins, (D)CPD copolymer resins )CPD/C5 cut, (D)CPD/C9 cut copolymer resins, terpene/vinyl aromatic copolymer resins, terpene/phenol copolymer resins, C5 cut/vinyl aromatic copolymer resins, and mixtures thereof.
• terpene groups together here in a known manner the monomers alpha-pinene, beta-pinene and limonene; preferentially, 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 vinylaromatic 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 derived from a C9 cut (or more generally from a CL to Cio cut).
• plasticizing resins chosen from the group consisting of (D)CPD homopolymer resins, (D)CPD/styrene copolymer resins, polylimonene resins, limonene/styrene copolymer resins, limonene/D(CPD) copolymer resins, C5 cut copolymer/styrene resins, C5 cut/C9 cut copolymer resins, and mixtures of these resins.
• plasticizing resins chosen from the group consisting of (D)CPD homopolymer resins, (D)CPD/styrene copolymer resins, polylimonene resins, limonene/styrene copolymer resins, limonene/D(CPD) copolymer resins, C5 cut copolymer/styrene 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 commercially available, for example sold by the company DRT under the name “Dercolyte” as regards polylimonene resins, by the company Neville Chemical Company under name “Super Nevtac”, by Kolon under the name “Hikorez” or by the company Exxon Mobil under the name “Escorez” with regard to C5/styrene cut resins or C5/C9 cut resins, or by the company Struktol under the name "40 MS” or "40 NS” (mixtures of aromatic and/or aliphatic resins).
• the content of plasticizing resin having a glass transition temperature greater than 20° C. in the composition according to the invention is between 50 and 150 phr, preferably between 55 and 100 phr and in a particularly advantageous manner from 65 to 90 phr .
• the plasticizer system of the rubber composition according to the invention may comprise a plasticizer that is liquid at 23° C., referred to as “low Tg”, i.e. that is to say which by definition has a Tg of less than -20°C, preferably less than -40°C.
• the composition may optionally comprise from 0 to 60 phr of a liquid plasticizer at 23°C.
• a plasticizer that is liquid at 23° C. When a plasticizer that is liquid at 23° C. is used, its level in the composition according to the invention may be within a range ranging from 1 to 40 phr, preferably from 2 to 20 phr, more preferably from 3 to 14 phr. .
• any liquid plasticizer at 23° C. (or extender oil), whether aromatic or non-aromatic in nature, known for its plasticizing properties with respect to diene elastomers, can be used.
• these plasticizers or oils, more or less viscous are liquids (that is to say, as a reminder, substances having the capacity to take the shape of their container in the long term) , as opposed in particular to plasticizing resins which are by nature solid at room temperature.
• the plasticizers liquid at 23° C. chosen from the group comprising or consisting of liquid diene polymers, polyolefinic oils, naphthenic oils, paraffinic oils, DAE oils, MES (Medium Extracted Solvates') oils, oils TDAE (Treated Distillate Aromatic Extracts), RAE oils (Residual Aromatic Extract oils), TRAE oils (Treated Residual Aromatic Extract) and SRAE oils (Safety Residual Aromatic Extract oils), mineral oils, vegetable oils, ether plasticizers , ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these liquid plasticizers at 23°C. For example, the liquid plasticizer at 23° C.
• 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 liquid plasticizer 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 else copolymers of butadiene or isoprene and styrene or mixtures of these liquid polymers.
• the number-average molar mass of such liquid polymers preferably ranges from 500 g/mol to 50,000 g/mol, preferably from 1,000 g/mol to 10,000 g/mol.
• the “RICON” products from SARTOMER can be cited.
• the liquid plasticizer 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, cottonseed, rape, castor, tung , pine, sunflower, palm, olive, coconut, peanut, grapeseed and mixtures of these oils.
• the vegetable oil is preferentially rich in oleic acid, that is to say that the fatty acid (or all the fatty acids if several are present) from which it derives, comprises oleic acid according to a mass fraction at least equal to 60%, even more preferably according to a mass fraction at least equal to 70%.
• sunflower oil which is such that all the fatty acids from which it derives comprise oleic acid according to a mass fraction equal to or greater than 60%, preferably 70% and, according to a particularly advantageous embodiment of the invention, according to a mass fraction equal to or greater than 80%.
• the liquid plasticizer is a triester chosen from the group consisting of triesters of carboxylic acid, phosphoric acid, sulphonic 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 be made in particular of the compounds chosen from the group consisting of trimellitates, pyromellitates, phthalates, 1,2-cyclohexane dicarboxylates, adipates, azelates, sebacates , glycerol triesters and mixtures of these compounds.
• glycerol triesters preferably consisting mainly (for more than 50%, more preferably for more than 80% by weight) of an unsaturated Cis fatty acid, that is to say chosen from the group consisting of oleic acid, linoleic acid, l linolenic acid and mixtures of these acids.
• Glycerol triester is preferred. More preferentially, 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 preferentially still for more than 80 % by weight of oleic acid.
• Such triesters (trioleates) with a high oleic acid content are well known; they have been described for example in application WO 02/088238, as plasticizers in treads for tires.
• liquid plasticizer at 23°C is an ether plasticizer
• it may be, for example, polyethylene glycol or polypropylene glycol.
• the plasticizer that is liquid at 23°C is chosen from the group comprising or consisting of MES oils, TDAE oils, naphthenic oils, vegetable oils and mixtures of these plasticizers that are liquid at 23°C. More preferably, the liquid plasticizer at 23°C is a vegetable oil, preferably a sunflower oil.
• composition according to the invention does not comprise a liquid polymer.
• composition according to the invention comprises from 10 to 60 phr, preferably from 15 to 40 phr, of vegetable oil, preferably sunflower oil.
• the rubber compositions according to the invention may optionally also comprise 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, antioxidants, anti-fatigue agents, reinforcing resins (as described for example in application WO 02/10269).
• plasticizers such as plasticizing oils and/or plasticizing resins
• pigments such as for example plasticizing oils and/or plasticizing resins
• protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents, reinforcing resins (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 mixing (so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which, in a suitable mixer such as a usual internal mixer (for example type 'Banbury'), all necessary constituents, in particular the elastomeric matrix, any fillers, any other miscellaneous additives, with the exception of the vulcanization system.
• a suitable mixer such as a usual internal mixer (for example type 'Banbury')
• all necessary constituents in particular the elastomeric matrix, any fillers, any other miscellaneous additives, with the exception of the vulcanization system.
• the incorporation of the optional filler into the elastomer can be carried out in one or more stages by mixing thermomechanically.
• the non-productive phase can be carried out at high temperature, up to a maximum temperature of between 110° C. and 200° C., preferably between 130° C. and 185° C., for a duration generally of 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.
• the final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for characterization in the laboratory, or even extruded in the form of a semi-finished (or profiled) rubber that can be used by example as a passenger vehicle tire tread.
• a semi-finished (or profiled) rubber that can be used by example as a passenger vehicle tire tread.
• 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 of between 130° C. and 200° C., under pressure.
• the present invention also relates to a finished or semi-finished rubber article comprising a composition according to the invention.
• the rubber article is a pneumatic or non-pneumatic tire, preferably a pneumatic tire.
• a pneumatic or non-pneumatic tire preferably a pneumatic tire.
• a pneumatic or non-pneumatic tire comprising a composition according to the invention or a semi-finished rubber article according to the invention.
• the tread of a pneumatic or non-pneumatic tire comprises a rolling surface intended to be in contact with the ground when the tire is rolling.
• the tread is provided with a tread pattern comprising in particular tread pattern elements or elementary blocks delimited by various main, longitudinal or circumferential, transverse or even oblique grooves, the elementary blocks possibly also comprising various finer incisions or sipes.
• composition according to the invention is present in the tread of the tire, preferably in the radially outer part of the tread, intended to be in contact with the ground when the tire is rolling.
• the invention relates particularly to tires intended to be fitted to motor vehicles of the passenger car, SUV ("Sport Utility Vehicles") and light truck type, in particular motor vehicles of the passenger car and SUV type.
• the invention relates to tires both in the raw state (that is to say, before curing) and in the cured state (that is to say, after vulcanization).
• an elastomer matrix comprising from 25 to 95 parts by weight per hundred parts by weight of elastomer, phr, of copolymer based on butadiene and styrene having a glass transition temperature below -64° C., and from 5 to 75 phr of polybutadiene modified with a functional group capable of interacting with silica,
• composition according to any one of the preceding embodiments in which the copolymer based on butadiene and styrene comprises within its structure at least one alkoxysilane group bonded to the elastomer via the silicon atom, and at least one function comprising a nitrogen atom.
• composition according to embodiment 3 in which, in the copolymer based on butadiene and styrene, at least two, preferably at least three, preferably at least four, 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 an aliphatic hydrocarbon radical in Ci-Cio, more preferably the linear hydrocarbon radical in C3,
• the alkoxysilane group is a methoxysilane or an ethoxysilane, optionally partially or totally hydrolyzed to silanol,
• the copolymer based on butadiene and 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 by 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 styrene has a glass transition temperature comprised in a range ranging from -105°C to -70°C.
• composition according to embodiment 3 in which, in the copolymer based on butadiene and styrene, 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 C3 linear aliphatic hydrocarbon radical,
• the alkoxysilane group is methoxysilane or ethoxysilane, optionally partially or totally hydrolyzed to silanol,
• the copolymer based on butadiene and 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 by 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 styrene has a glass transition temperature of between -95°C and -86°C.
• composition according to any one of the preceding embodiments in which the modified polybutadiene has a molar rate of linkage of 1,4-cis units of at least 55%, preferably of at least 90%.
• halogen donor comprising an alkylaluminum halide
• said salt is in suspension or in solution in at least one inert and saturated hydrocarbon solvent of the aliphatic or alicyclic type;
• step (b) adding to the pseudo-living elastomer formed in step (a) a polyfunctional compound, comprising at least three functional groups, said functional group being capable of reacting with the reactive end of the pseudo-living elastomer;
• step (c) adding to the mixture formed in step (b) a functionalizing agent corresponding to the formula A-Ri-B with A denoting a group capable of reacting with the reactive end of the pseudo-living elastomer, Ri denoting an atom or a group of atoms forming a bond between A and B, and B designating a function capable of reacting with a reinforcing charge;
• composition according to any one of embodiments 7 to 9 in which, in the catalytic system of the process for obtaining the modified polybutadiene, the said salt is neodymium tris[bis(2-ethylhexyl)phosphate].
• the “functionalizing agent”/“aluminum” molar ratio of the process for obtaining the modified polybutadiene is advantageously at least 1.
• CF(1+6) at 100° C. of less than 1 g, preferably less than 0.5 g.
• composition according to any one of the preceding embodiments in which the content of the copolymer based on butadiene and styrene, in the composition, is within a range ranging from 65 to 95 phr, and the content of the modified polybutadiene, in the composition, is included in a range ranging from 5 to 35 phr.
• composition according to any one of the preceding embodiments in which the elastomer matrix comprises less than 15 phr of isoprene elastomer.
• composition according to any one of the preceding embodiments, in which the level of isoprene elastomer, in the composition, is less than 14 phr, preferably less than 10 phr, preferably less than 5 phr.
• composition according to any one of the preceding embodiments in which the total content of the copolymer based on butadiene and styrene and of the modified polybutadiene, in the composition, is within a range ranging from 85 to 100 phr, preferably from 90 to 100 pc.
• composition according to any one of the preceding embodiments in which the total content of the copolymer based on butadiene and styrene and of the modified polybutadiene, in the composition, is 100 phr.
• composition according to any one of the preceding embodiments in which the silica has a BET specific surface area of between 100 and 250 m 2 /g, preferably within a range ranging from 105 to 200 m 2 /g, preferably of 125 to 180 m 2 /g.
• composition according to any one of the preceding embodiments in which the silica has a CTAB specific surface area of between 105 and 220 m 2 /g, preferably within a range ranging from 110 to 200 m 2 /g, preferably of 140 to 170 m 2 /g.
• composition according to any one of the preceding embodiments in which the level of silica in the composition is within a range ranging from 80 to 200 phr, preferably from 100 to 180 phr, preferably from 105 to 145 phr.
• the content of plasticizing resin having a glass transition temperature above 20° C. is included in a range ranging from 50 and 150 phr, preferably from 55 and 100 phr, more preferably from 65 to 90 phr.
• composition according to any one of the preceding embodiments in which the plasticizing resin having a glass transition temperature greater than 20° C. is chosen from the group consisting of cyclopentadiene homopolymer or copolymer resins, cyclopentadiene homopolymer resins resins or copolymer of dicyclopentadiene, resins of homopolymer or copolymer of terpene, resins of homopolymer or copolymer of Cs cut, resins of homopolymer or copolymer of C9 cut, resins of homopolymer or copolymer of alpha-methyl- styrene and mixtures thereof.
• the plasticizing resin having a glass transition temperature greater than 20° C. is chosen from the group consisting of cyclopentadiene homopolymer or copolymer resins, cyclopentadiene homopolymer resins resins or copolymer of dicyclopentadiene, resins of homopolymer or copolymer of
• composition according to any one of the preceding embodiments optionally comprising from 0 to 60 phr of liquid plasticizer at 23°C.
• composition according to any one of embodiments 1 to 35 comprising from 1 to 40 phr, preferably from 2 to 20 phr, preferably from 3 to 14 phr of liquid plasticizer at 23°C.
• composition according to embodiment 36 or 37 in which the liquid plasticizer at 23°C is chosen from the group consisting of liquid diene polymers, polyolefinic oils, naphthenic oils, paraffinic oils, DAE oils, MES oils , TDAE oils, RAE oils, TRAE oils, SRAE oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures thereof.
• composition according to embodiment 36 or 37 in which the liquid plasticizer at 23° C. is chosen from the group consisting of MES oils, TDAE oils, naphthenic oils, vegetable oils and mixtures of these liquid plasticizers at 23 ° C, preferably from the group consisting of vegetable oils, preferably sunflower.
• composition according to any one of the preceding embodiments in which the crosslinking system is a vulcanization system comprising molecular sulfur and/or at least one sulfur-donating agent.
• Finished or semi-finished rubber article comprising a composition according to any one of embodiments 1 to 40.
• Pneumatic or non-pneumatic tire comprising a rubber composition according to any one of embodiments 1 to 40.
• the dynamic properties G* and tan(8)Max are measured on a viscoanalyzer (Metravib VA4000), according to standard ASTM D5992-96.
• the response of a sample of vulcanized composition (cylindrical specimen 2 mm thick and 79 mm 2 in cross-section) is recorded, subjected to a sinusoidal stress in simple alternating shear, at a frequency of 10 Hz, under normal conditions of temperature (23°C) or at 0°C according to the ASTM D 1349-09 standard for the tan(8)Max measurements, or else at -20°C for the G* measurements.
• a deformation amplitude scan is carried out from 0.1% to 50% (go cycle), then from 50% to 0.1% (return cycle).
• the maximum value of tan 8 observed (tan(S)max) is indicated, as well as the difference in complex modulus (AG*) between the values at 0.1% and at 50% deformation (effect Payne).
• the results used are the loss factors tan(8)Max at 0°C and at 23°C, as well as the complex dynamic shear modulus G* at -20°C.
• results of tan(8)Max at 0° C. are expressed in base 100, the value 100 being assigned to the control.
• a result greater than 100 indicates improved performance, i.e. the composition of the example considered reflects better wet grip of the tread comprising such a composition.
• results of tan(8)Max at 23° C. and of G* at -20° C. are expressed in performance base 100, the value 100 being assigned to the control.
• a result greater than 100 indicates improved performance, that is to say that the composition of the example considered reflects respectively better rolling resistance and better grip on snowy ground of the tread comprising such a composition.
• the abrasion resistance obtained by determining the loss in volume by abrasion is measured according to the NF ISO 4649 standard of November 2010 which consists in determining the loss in volume of a sample after displacement of 40 linear meters on standardized abrasive paper. .
• a loss of mass of the sample is measured and the loss of volume is calculated according to the density (p) of the material constituting the specimen.
• 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 assigned to the control composition makes it possible to compare the volume of loss of substance 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 loss of substance of the control composition / measured value of the volume of loss of substance of the composition tested) X 100.
• a result greater than 100 will indicate a decrease in volume loss and therefore an improvement in abrasion resistance, which corresponds to an improvement in wear resistance performance.
• a result below 100 will indicate an increase in volume loss and therefore a decrease in abrasion resistance, which corresponds to a drop in wear resistance performance.
• Mooney viscosities ML(1+4) 100°C are measured according to standard ASTM D 1646 (December 2015).
• the Mooney plasticity measurement is carried out according to the following principle: the elastomer or the composition in the raw state (i.e. before curing) is molded in a cylindrical chamber heated to 100°C. After one minute of preheating, the rotor rotates within the specimen at 2 rpm and the torque needed to maintain this movement after 4 minutes of rotation is measured.
• the difference between the Mooney viscosity of the composition and the Mooney viscosity of the elastomer makes it possible to measure the processability or raw implementation. The smaller this difference, the better the raw processing.
• the glass transition temperatures (Tg) of the elastomers are determined using a differential scanning calorimeter with a scanning speed of 20°C/min.
• NIR Near infrared
• NIR Near-infrared
• the principle of the method is based on the Beer-Lambert law generalized to a multicomponent system. The method being indirect, it calls upon a multivariate calibration [Vilmin, F.; Dussap, C.; Coste, N. Applied Spectroscopy 2006, 60, 619-29] carried out using standard elastomers with a composition determined by 13C NMR.
• the microstructure is then calculated from the NIR spectrum of an elastomer film approximately 730 ⁇ m thick. Spectrum acquisition is carried out in transmission mode between 4000 and 6200 cm-1 with a resolution of 2 cm-1, using a Broker Tensor 37 Fourier transform near-infrared spectrometer equipped with a cooled InGaAs detector by Peltier effect.
• the inherent viscosity of elastomers at 25°C is determined from a 0.1 g.dL-1 elastomer solution in toluene, according to the following principle.
• the inherent viscosity is determined by measuring the flow time t of the polymer solution and the flow time to of the toluene, in a capillary tube.
• the inherent viscosity is obtained by the following relationship: with: C: concentration of the polymer solution in toluene in g.dL 1 , t: flow time of the polymer solution in toluene in seconds, to: flow time of the toluene in seconds, r
• Cold-Flow CF(l+6) 100°C) (cold flow)
• the die is 6.35mm in diameter, 0.5mm thick and is located at the bottom and center of a hollowed cylindrical cup 52mm in diameter.
• the measurement is then continued for 6 hours ⁇ 5 min, during which the product is left in the oven. At the end of the 6 hours, the sample of extradited product is cut up and then weighed. The result of the measurement is the weighed mass of elastomer, expressed in g. The lower this result, the more the elastomer resists cold flow.
• This determination is carried out by an NMR analysis on coagulated samples.
• the spectra are acquired on a Braker Avance III HD 500 MHz spectrometer equipped with a Braker cryo-BBFO z-grad 5 mm probe.
• the NMR spectra contain the characteristic signals of the Butadiene units (BRI -4 and BRI -2). In addition to these, isolated (low intensity) signals attributed to the functionalizing agent, here the GMDE molecule, are observed.
• the 1H chemical shifts of the characteristic signals of this molecule in the BR matrix are shown below:
• the integration zones considered for the quantification are:
• the quantification of the grafted GMDE motif can be carried out in molar percentage as described above. Determination of the distribution of the molar masses of the polybutadienes obtained by the technique of steric exclusion chromatography (SEC). a) Principle of measurement:
• Steric exclusion chromatography or SEC size exclusion chromatography separates macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, the largest being eluted first.
• Case cl The equipment used is a “WATERS alliance” chromatographic chain.
• the elution solvent is tetrahydrofuran, the flow rate 1 ml/min., the system temperature 35°C and the analysis time 30 min.
• a set of two WATERS columns under the trade name “STYRAGEL HT6E” is used.
• the injected volume of the polymer sample solution is 100 ⁇ l.
• the detector is a "WATERS 2140" differential refractometer and the chromatographic data processing software is the “WATERS MILLENIUM” system.
• Case c2) The equipment used is a “WATERS alliance” chromatograph.
• the elution solvent is tetrahydrofuran, the flow rate 0.7 ml/min, the system temperature 35°C and the analysis time 90 min.
• the injected volume of the polymer sample solution is 100 ⁇ l.
• the detector is a "WATERS model RI32X” differential refractometer and the chromatographic data processing software is the “WATERS MILLENIUM” system.
• Nd/Bd/HDiBA/CDEA catalytic system diluted in MCH is synthesized according to the procedure described in WO-A-02/38636 (pages 8 to 11):
• the neodymium phosphate salt in powder form is introduced into a reactor previously cleaned of its impurities. This salt is then subjected to bubbling with nitrogen for 10 min in order to make the reaction medium inert. The following successive steps are then carried out:
• a solvent consisting of MCH previously distilled, purified on alumina and bubbled with nitrogen is introduced into the reactor.
• the duration and the contacting temperature of this solvent and the neodymium salt are 30 min at 30°C with stirring.
• the butadiene previously purified on alumina and bubbled with nitrogen is then introduced into the reactor at 30°C. This monomer will be used to preform the catalyst during the aging step.
• HDiBA in solution in MCH is then introduced into the reactor as an alkylating agent for the neodymium salt, at a concentration of approximately 1 mol/L.
• the duration of the alkylation is 15 min.
• the temperature of the alkylation reaction is equal to 30°C.
• the CDEA in solution in the MCH is then introduced into the reactor as a halogen donor, at a concentration of approximately 0.5 mol/L.
• the temperature of the reaction medium is brought to 60° C.
• the mixture thus obtained is aged by maintaining the temperature of 60° C. for a period of 50 min.
• the catalytic solution obtained is finally stored under a nitrogen atmosphere at a temperature between -15°C and -5°C.
• the catalytic system is characterized by its catalytic formula which is given in the form Nd/Monomer/Alkylating Agent/Halogenating Agent in molar ratios indexed on the neodymium salt.
• the neodymium concentration The catalytic formula is 1/36/3/2.6 with a concentration of 0.038 mol/L.
• Total Al defines the total amount of aluminum present in the reaction medium.
• Diisobutylaluminum hydride (HDIBA) was introduced in sufficient quantity in order to neutralize the protic impurities brought by the various constituents present in the inlet of the first reactor.
• HDIBA Diisobutylaluminum hydride
• a certain quantity of HDIBA per 100 g of butadiene and a certain quantity of the catalytic system described previously per 100 g of butadiene were introduced.
• the different flow rates are calculated so that the average residence time in the reactor is 25 min.
• the temperature is maintained at a given polymerization temperature.
• a sample of polymer solution is taken.
• the polymer thus obtained is subjected to an antioxidant treatment with the addition of 0.4 phr of 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol) and 0.2 phr of N-(1,3 -dimethylbutyl)-N'-phenyl-p-phenylenediamine.
• the polymer thus treated is then separated from its solution by a steam stripping operation, then dried on a roller tool at 100°C.
• a certain quantity per 100 g of butadiene of (3-glycidyloxypropyl) methyldiethoxysilane in solution in methylcyclohexane was added to the solution of living polymer according to a ((3-glycidyloxypropyl) methyldiethoxysilane)/(total Al) molar ratio of 2.5.
• the polymers thus obtained were subjected to an antioxidant treatment with the addition of 0.4 phr of 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol) and 0.2 phr of N-(1, 3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.
• the polymers thus treated were then separated from its solution by a steam stripping operation, then dried on a roller tool at 100°C.
• the “total Al” is calculated by taking into account the HDIBA of the catalyst (Nd/Al ratio of 3) and the HDIBA added in the polymerization reaction.
• the average percentage of functionalized chains (in %) is obtained by the formula: (CH2-Si/PB)*Mn*1.10-4 with CH2-Si/PB in mmol/Kg and Mn in g/mol.
• the rubber compositions were produced as described in point II.6 above.
• the "non-productive" phase was carried out in a 0.4 liter mixer for 3.5 minutes, for an average paddle speed of 50 revolutions per minute up to reach a maximum drop temperature of 160°C.
• the “productive” phase was carried out in a cylinder tool at 23°C for 5 minutes.
• the crosslinking of the composition was carried out at a temperature of between 130° C. and 200° C., under pressure.
• control compositions T1 to T4 with a control composition (C1) and a composition in accordance with the invention (II).
• the purpose of the tests presented in Table 2 is to demonstrate the effect of the elastomeric matrix, in particular the effect of the copolymer based on butadiene and styrene having a glass transition temperature below -64°C, on the properties snow grip, abrasion resistance and rolling resistance.
• SBR 1 SBR with 3% styrene unit and 13% 1,2 unit of the butadiene part, and carrying an amino-alkoxysilane function in the middle of the elastomer chain (Tg -88C)

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