Rubber composition

Abstract

The present invention relates to a rubber composition comprising at least - an elastomer matrix predominantly comprising a highly saturated diene elastomer, which functionalised highly saturated diene elastomer is a copolymer comprising ethylene units and units of a 1,3-diene in which the ethylene units represent at least 50 mol% of the monomer units of the copolymer, preferably at least 60 mol%, - a reinforcing filler containing silica, - a coupling agent, - a crosslinking system and - a liquid polymer of butadiene functionalised by at least one alkoxysilyl function, having a number-average molar mass (Mn) of greater than or equal to 1000 g / mol.

Description

[0001] Rubber composition

[0002] Technical field

[0003] The field of the present invention is that of rubber compositions based on highly saturated diene elastomer intended for use in a tire, in particular in its tread.

[0004] Prior art

[0005] The use of highly saturated diene elastomer is known in the manufacture of tires. For example, the Applicant has described copolymers of ethylene and 1,3-butadiene and their application in a tire tread in document WO2014114607A1. This document indicates that the use of these copolymers in the tread has the effect of conferring good wear resistance and rolling resistance properties to the tire.

[0006] Tire manufacturers are always looking for ways to improve tire performance. This research involves continuously improving the properties of the rubber compounds used to make tires. The compounds that make up tires generally represent compromises between performance properties that are difficult to reconcile simultaneously. Therefore, it is a constant goal for tire manufacturers to find formulas that improve the balance between all these performance properties.

[0007] In the field discussed above of tires comprising a highly saturated diene elastomer in the tread, there is a need, particularly in certain heavy load transport conditions, to have rubber compositions which give the tire good wear resistance without penalizing road behavior.

[0008] It is known to those skilled in the art that the addition of low molar mass plasticizers improves the tear resistance property, a descriptor directly linked to wear resistance. However, the rigidity of the composition is then lowered, and road behavior is impacted.

[0009] Common methods used to stiffen a rubber compound are vulcanization and the addition of reinforcing fillers. However, these methods can also lead to a reduction in wear resistance.

[0010] Continuing its efforts, the Applicant has found a rubber composition which makes it possible to meet this need in the field of application of highly saturated diene elastomers to rubber compositions for tires, and in particular for the tread. In particular, the Applicant has found, against all expectations, a rubber composition which combines the use of a highly saturated diene elastomer with the use of a liquid butadiene polymer functionalized by at least one alkoxysilyl function, and which makes it possible to significantly improve the tear resistance while maintaining, or even increasing, the rigidity of the composition compared to compositions using a non-functional liquid polybutadiene or not using a low molar mass plasticizer.These properties promise to give the tire good wear resistance properties while providing good resistance to external aggressions, particularly when transporting heavy loads.

[0011] Thus, a first object of the invention is such a rubber composition based on at least one elastomer matrix comprising mainly a highly saturated functionalized diene elastomer, and a liquid butadiene polymer functionalized by at least one alkoxysilyl function.

[0012] Another subject of the invention is a pneumatic or non-pneumatic tire which comprises a rubber composition according to the invention, preferably in its tread.

[0013] Summary of the invention

[0014] The invention, described in more detail below, relates to at least one of the embodiments listed in the following points:

[0015] 1. Rubber composition comprising at least

[0016] - an elastomer matrix comprising predominantly a functionalized highly saturated diene elastomer, which functionalized highly saturated diene elastomer is a copolymer comprising ethylene units and units of a 1,3-diene in which the ethylene units represent at least 50 mol% of the monomer units of the copolymer,

[0017] - a reinforcing filler containing silica,

[0018] - a coupling agent,

[0019] - a crosslinking system and

[0020] - a liquid polymer of butadiene functionalized by at least one alkoxysilyl function, having a number-average molar mass (Mn) greater than or equal to 1000 g / mol.

[0021] 2. Rubber composition according to embodiment 1, in which the ethylene units represent from 50% to 95% by mole of the monomer units of the copolymer.

[0022] 3. Rubber composition according to any one of the preceding embodiments, in which the ethylene units represent at least 60 mol% of the monomer units of the copolymer of ethylene and a 1,3-diene, preferably from 60% to 90 mol% of the monomer units of the copolymer.

[0023] 4. A rubber composition according to any one of the preceding embodiments wherein the functionalized highly saturated diene elastomer contains from 60% to 80% by mole of ethylene units.

[0024] 5. A rubber composition according to any one of the preceding embodiments, wherein the 1,3-diene is 1,3-butadiene, isoprene, myrcene or p-farnesene, or a mixture of myrcene and -farnesene, preferably 1,3-butadiene.

[0025] 6. A rubber composition according to any preceding embodiment, wherein the functionalized highly saturated diene elastomer is a copolymer of ethylene and 1,3-butadiene. 7. A rubber composition according to any preceding embodiment, wherein the functionalized highly saturated diene elastomer is a copolymer of ethylene and 1,3-butadiene and further contains 1,2-cyclohexanediyl units.

[0026] 8. Rubber composition according to any one of the preceding embodiments, in which the functionalized highly saturated diene elastomer is random.

[0027] 9. A rubber composition according to any one of the preceding embodiments wherein the functionalized highly saturated diene elastomer has a glass transition temperature of less than -35°C.

[0028] 10. A rubber composition according to any one of the preceding embodiments wherein the functionalized highly saturated diene elastomer has a glass transition temperature of between -70°C and -35°C.

[0029] 11. Rubber composition according to any one of the preceding embodiments, in which the functionalized highly saturated diene elastomer carries at least one silanol or alkoxysilyl function.

[0030] 12. Rubber composition according to any one of the preceding embodiments in which the functionalized highly saturated diene elastomer carries at least one silanol or alkoxysilyl function attached directly to the terminal unit of the copolymer by the silicon atom of the function.

[0031] 13. Rubber composition according to any one of the preceding embodiments, in which the functionalized highly saturated diene elastomer carries at least one silanol or alkoxysilyl function and one amine function.

[0032] 14. Rubber composition according to any one of the preceding embodiments, in which the functionalized highly saturated diene elastomer carries at least one silanol or alkoxysilyl function and one tertiary amine function.

[0033] 15. Rubber composition according to any one of the preceding embodiments, in which the functionalized highly saturated diene elastomer carries at least one silanol or alkoxysilyl function attached directly to the terminal unit of the copolymer by the silicon atom of the function, which function corresponds to formula (1)

[0034] - If(OR 1 ) 3-y -z(R 2 ) y (R)z (1) in which the symbols R 1, identical or different, represent a hydrogen atom or an alkyl group, the symbols R 2 , identical or different, represent a hydrogen atom or an alkyl group, the symbol R representing a hydrocarbon chain substituted by an amine function, preferably a tertiary amine, y being an integer ranging from 0 to 1, z being an integer ranging from 0 to 1.

[0035] 16. Rubber composition according to any one of the preceding embodiments, in which the functionalized highly saturated diene elastomer is obtained by functionalization with a functionalizing agent of formula (2) Si(OR 1 ) 3-a -b (R 2 )a(R)b (2) the symbols R 1 , identical or different, representing an alkyl group, the symbols R 2, identical or different, representing a hydrogen atom or an alkyl group, the symbol R representing a divalent hydrocarbon group substituted by an amine function, preferably a tertiary amine, a being an integer ranging from 0 to 1, b being an integer ranging from 0 to 1.

[0036] 17. Rubber composition according to the preceding embodiment in which the symbols R 1 are each a methyl or an ethyl, the symbols R 2 are methyl or ethyl and R is a 1,3-propanediyl group carrying a tertiary amine function.

[0037] 18. Rubber composition according to any one of the preceding embodiments, in which the level of functionalized highly saturated diene elastomer varies in a range from 60 to 100 phr, preferably from 80 to 100 phr and very preferably from 90 to 100 phr.

[0038] 19. Composition according to any one of the preceding embodiments in which the liquid butadiene polymer is a liquid polybutadiene functionalized by at least one alkoxysilyl function, which alkoxysilyl function is a trialkoxysilyl function, optionally totally or partially hydrolyzed, corresponding to the formula - Si(OR)3, in which R denotes a C1-C10 alkyl, preferably C1-C4.

[0039] 20. Composition according to any one of the preceding embodiments in which the alkoxysilyl function is a trimethoxysilyl or triethoxysilyl function, optionally totally or partially hydrolyzed.

[0040] 21. Composition according to any one of the preceding embodiments in which the functionalized liquid butadiene polymer carries at least one pendant alkoxysilyl function along the chain.

[0041] 22. Composition according to any one of the preceding embodiments in which the functionalized liquid butadiene polymer carries an alkoxysilyl function on at least one of the two ends of the main chain.

[0042] 23. Composition according to any one of the preceding embodiments in which the liquid butadiene polymer carries an alkoxysilyl function on each of the two ends of the main chain.

[0043] 24. Composition according to any one of the preceding embodiments in which the level of functionalized liquid butadiene polymer is within a range from 0.5 to 25 pce, preferably from 1 to 20 pce, more preferably from 5 to 15 pce.

[0044] 25. Composition according to any one of the preceding embodiments in which the liquid butadiene polymer has a Tg comprised in a range from -100°C to -60°C, more preferably from -90°C to -70°C.

[0045] 26. Composition according to any one of the preceding embodiments in which the liquid butadiene polymer has a number-average molar mass in a range from 1000 g / mol to 50000 g / mol, preferably in a range from 1000 g / mol to 30000 g / mol, even more preferably in a range from 1000 g / mol to 10000 g / mol, measured by SEC.

[0046] 27. Composition according to any one of the preceding embodiments in which the liquid butadiene polymer has a number-average molar mass in a range from 2000 g / mol to 5000 g / mol; more preferably in a range from 2000 g / mol to 4000 g / mol.

[0047] 28. Composition according to any one of the preceding embodiments in which the reinforcing filler comprises a silica as the majority reinforcing filler.

[0048] 29. Composition according to any one of the preceding embodiments in which the level of reinforcing filler is within a range from 10 to 70 pce.

[0049] 30. Composition according to any one of the preceding embodiments in which the silica content is within a range from 10 to 70 pce.

[0050] 31. Finished or semi-finished product comprising a rubber composition as defined in any one of the preceding embodiments.

[0051] 32. A tire comprising a rubber composition as defined in any one of embodiments 1 to 30.

[0052] 33. A tire whose tread comprises a rubber composition as defined in any one of embodiments 1 to 30.

[0053] Definitions

[0054] By the expression "part by weight per hundred parts by weight of elastomer" (or pce), it is meant, within the meaning of the present invention, the part, by mass per hundred parts by mass of elastomer.

[0055] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the range of values ​​from more than a to less than b (i.e., excluding the limits a and b), while any interval of values ​​designated by the expression "from a to b" means the range of values ​​from a to b (i.e., including the strict limits a and b). In this document, when an interval of values ​​is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also designated.

[0056] In the present application, the term "all the monomer units of the elastomer" or "the totality of the monomer units of the elastomer" means all the repeating units constituting the elastomer which result from the insertion of the monomers into the elastomer chain by polymerization. Unless otherwise indicated, the contents of a monomer unit or repeating unit in the highly saturated diene elastomer are given as a molar percentage calculated on the basis of all the monomer units constituting the elastomer.

[0057] When a "majority" compound is referred to, within the meaning of the present invention, this compound is the majority among the compounds of the same type in the composition, that is to say that it is the one which represents the largest quantity by mass among the compounds of the same type. Thus, for example, a majority elastomer is the elastomer representing the largest mass relative to the total mass of the elastomers in the composition. In the same way, a so-called majority filler is the one representing the largest mass among the fillers in the composition. For example, in a system comprising a single elastomer, this is the majority within the meaning of the present invention; and in a system comprising two elastomers, the majority elastomer represents more than half of the mass of the elastomers. On the contrary, a "minority" compound is a compound which does not represent the largest mass fraction among the compounds of the same type.Preferably, by majority, we mean a mass proportion of more than 50%; when the compound represents 100% by mass, it is also referred to as "majority".

[0058] By "alkoxy" we mean a radial -OR in which R represents an alkyl radical.

[0059] By "alkyl" is meant a saturated, linear or branched hydrocarbon radical comprising from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms, for example the methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl radicals.

[0060] By "divalent hydrocarbon group" is meant a divalent, saturated or unsaturated, linear or branched group comprising from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms, more preferably from 1 to 6 carbon atoms, the methanediyl, ethanediyl group, the propanediyl, butanediyl, pentanediyl, hexanediyl radicals.

[0061] The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already in use, i.e. they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes, in particular, polymers, plasticizers, fillers, etc.

[0062] Detailed description of the invention

[0063] 1 Elastomer matrix

[0064] By "elastomer matrix" we mean all the elastomers in the composition.

[0065] According to the invention, the elastomer matrix predominantly comprises at least one functionalized highly saturated diene elastomer, namely a functionalized copolymer containing ethylene units and 1,3-diene units (hereinafter referred to as "the copolymer").

[0066] The functionalized highly saturated diene elastomer useful for the purposes of the invention is a copolymer, preferably a statistical copolymer carrying at least one function. The term "statistical copolymer" is understood in a known manner to mean a copolymer in which the sequential distribution of the monomer units obeys a known statistical law.

[0067] The functionalized highly saturated diene elastomer useful for the purposes of the invention is a copolymer which comprises ethylene units resulting from the polymerization of ethylene. As is known, the expression "ethylene unit" refers to the unit

[0068] -(CH2-CH2)- resulting from the insertion of ethylene into the elastomer chain. The highly saturated diene elastomer is rich in ethylene units, since the ethylene units represent at least 50 mol% of all the monomer units of the elastomer. The maximum proportion of ethylene units is fixed by the elastomeric nature of the polymer, this proportion is preferably at most 95 mol%, more preferably at most 90 mol%. Thus, preferably, the highly saturated diene elastomer comprises from 50% to 95 mol% of ethylene units relative to all the monomer units of the copolymer.

[0069] According to embodiments of the invention, the copolymer comprises at least 60 mol% of ethylene units. In other words, according to these embodiments, the ethylene units represent at least 60 mol% of all the monomer units of the copolymer.

[0070] According to these embodiments of the invention, the highly saturated diene elastomer preferably comprises from 60% to 90% mol of ethylene units, more preferably 60% to 80% mol, molar percentage calculated on the basis of all the monomer units of the copolymer.

[0071] The highly saturated diene elastomer functionalized according to the invention also comprises 1,3-diene units resulting from the polymerization of at least one 1,3-diene. As is known, the expression "1,3-diene unit" refers to the units resulting from the insertion of the 1,3-diene.

[0072] The 1,3-diene units are those for example of a 1,3-diene having 4 to 24 carbon atoms, preferably of a 1,3-diene having 4 to 15 carbon atoms, more preferably of a 1,3-diene having 4 to 12 carbon atoms.

[0073] Suitable 1,3-dienes include butadiene, isoprene, 2,3-di(C 1 -C 5 alkyl)-1,3-butadiene such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene or 2-methyl-3-isopropyl-1,3-butadiene, aryl-1,3-butadiene such as phenyl-1,3-butadiene, 1,3-pentadiene. Also suitable as 1,3-diene is a 1,3-diene of formula CH2=CR-CH=CH2, in which R represents a hydrocarbon chain having 3 to 20 carbon atoms, such as for example a linear monoterpene (CioHis), like myrcene, a linear sesquiterpene (C15H24), like p-farnesene etc....

[0074] The functionalized highly saturated diene elastomer is preferably a copolymer of ethylene and a 1,3-diene from among 1,3-butadiene, isoprene, myrcene, -farnesene and a mixture of myrcene and p-farnesene.

[0075] According to embodiments of the invention, the 1,3-diene units are derived from 1,3-butadiene or isoprene, more preferably from 1,3-butadiene, in which case the highly saturated diene elastomer is a copolymer of ethylene and 1,3-butadiene, preferably a random copolymer of ethylene and 1,3-butadiene.

[0076] According to the invention, when the highly saturated diene elastomer comprises 1,3-diene units derived from 1,3-butadiene, the highly saturated diene elastomer may further contain units

[0077] 1,2-cyclohexanediyl. The presence of these cyclic structures in the copolymer results from a very specific insertion of ethylene and 1,3-butadiene during polymerization. The content of 1,2-cyclohexanediyl units in the copolymer varies according to the respective contents of ethylene and

[0078] 1,3-butadiene in the copolymer. The copolymer preferably contains less than 15 mol% of 1,2-cyclohexanediyl unit units. The highly saturated diene elastomer useful for the purposes of the invention can be obtained according to different synthesis methods known to those skilled in the art, in particular depending on the targeted microstructure of the highly saturated diene elastomer. Generally, it can be prepared by copolymerization of at least one 1,3-diene, preferably 1,3-butadiene, and ethylene and according to known synthesis methods, in particular in the presence of a catalytic system comprising a metallocene complex. In this respect, mention may be made of catalytic systems based on metallocene complexes, which catalytic systems are described in documents EP 1092731, WO 2004035639, WO 2007054223 and WO 2007054224, as well as WO2020070442, WO2020070443 and WO2020074804 in the name of the Applicant.The highly saturated diene elastomer, including when it is random, can also be prepared by a process using a preformed type catalytic system such as those described in documents WO 2017093654 Al, WO 2018020122 Al and WO 2018020123 Al.

[0079] According to embodiments of the invention, the functionalized highly saturated diene elastomer has a glass transition temperature of less than -35°C, more particularly between -70°C and -35°C, the glass transition temperature being measured in a known manner by DSC (Differential Scanning Calorimetry) according to standard ASTM D3418 (1999).

[0080] According to the invention, the term “functionalized highly saturated diene elastomer useful for the purposes of the invention” means a highly saturated diene elastomer carrying at least one function. In the context of the invention, the term “function” means a function capable of interacting with the reinforcing filler comprising silica, i.e. a function capable of forming, within a rubber composition reinforced by means of the filler, a physical or chemical bond with said filler. This interaction can be established for example by means of covalent, hydrogen, ionic and / or electrostatic bonds between said function and functions present on the filler, in particular silica. This function is preferably an alkoxysilyl or silanol function. The silanol or alkoxysilyl function is then very preferably attached directly to the terminal unit of the copolymer by the silicon atom of the function.

[0081] According to preferred embodiments of the invention, the functionalized highly saturated diene elastomer carries at least one silanol or alkoxysilyl function and one amine function. The silanol or alkoxysilyl function is then very preferably attached directly to the terminal unit of the copolymer by the silicon atom of the function and carrying the amine function. The amine function may be primary, protected or not, secondary, protected or not, or tertiary. The amine function is preferably tertiary.

[0082] According to these preferred embodiments, the functionalized highly saturated diene elastomer carries at least one functional group comprising a silanol or alkoxysilyl function and an amine function, which group can be represented by the formula (1)

[0083] - If(OR 1 ) 3-y -z(R 2 ) y (R)z (1) in which the symbols R 1, identical or different, represent a hydrogen atom or an alkyl group, the symbols R 2 , identical or different, represent a hydrogen atom or an alkyl group, the symbol R representing a hydrocarbon chain substituted by an amine function, y being an integer ranging from 0 to 1, z being an integer ranging from 0 to 1. The highly saturated diene elastomer functionalized according to the invention can be obtained by adding a functionalizing agent at the end of polymerization instead of adding an alcohol usually used to stop the polymerization. A functionalized polymer is then recovered.

[0084] According to preferred embodiments of the invention, the functionalized highly saturated diene elastomer is obtained by adding at the end of polymerization a functionalizing agent of formula (2), SijOR 1 )^ ( R 2 )a( R)b (2) the symbols R 1, identical or different, representing an alkyl group, the symbols R 2 , identical or different, representing a hydrogen atom or an alkyl group, the symbol R representing a hydrocarbon chain substituted by an amine function, a being an integer ranging from 0 to 1, b being an integer ranging from 0 to 1.

[0085] In formulas (1) and (2),

[0086] - the alkyl group represented by the symbol R 1 is Ci-Cio, preferably Ci-C4, more preferably methyl or ethyl;

[0087] - the alkyl group represented by the symbol R 2 is Ci-Cio, preferably Ci-C4, more preferably methyl or ethyl;

[0088] - the hydrocarbon chain substituted by an amine function represented in the symbol R is preferably a C1-C10 alkanediyl chain, preferably comprising at most 6 carbon atoms, more preferably the 1,3-propanediyl group.

[0089] The amine function useful for the purposes of the invention and in particular designated in the symbol R in formulae (1) and (2), is a protected primary amine function, a protected secondary amine function or a tertiary amine function. As protecting groups for the primary and secondary amine functions, mention may be made of silyl groups, for example trimethylsilyl and tert-butyldimethylsilyl groups. Preferably, the amine function is a tertiary amine function. Advantageously, the amine function is a tertiary amine function of formula - N ( R')z in which each R' represents an alkyl, preferably a methyl or an ethyl.

[0090] As functionalizing agent for preparing a polymer bearing an amine function according to the first variant, mention may be made of the compounds (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)methyldiethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyl-diethoxysilane, (N,N-dimethylaminopropyl)trimethoxysilane, (N,N-dimethylaminopropyl)triethoxysilane and (N-(3-trimethoxysilyl)propyl)-N-(trimethylsilyl)silanamine, (N-(3-triethoxysilyl)propyl)-N-(trimethyl-silyl)silanamin, preferably (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldimethoxysilane, (N,N-dimethylaminopropyl)trimethoxysilane and (N-(3-trimethoxysilyl)-propyl)-N-(trimethylsilyl)silanamine, more preferably (N,N-dimethylaminopropyljtrimethoxysilane and (N-(3-trimethoxysilyl)propyl)-N-(trimethylsilyl)-silanamine.

[0091] The functionalizing agent is typically added to the polymerization medium. It is typically added to the polymerization medium at a monomer conversion rate chosen by a person skilled in the art according to the desired macrostructure of the copolymer. Since the polymerization step is generally carried out under ethylene pressure, degassing of the polymerization reactor may be carried out before adding the functionalizing agent. The functionalizing agent is added under inert and anhydrous conditions to the polymerization medium, maintained at the polymerization temperature. 0.25 to 10 moles of functionalizing agent are typically used per 1 mole of cocatalyst, preferably 2 to 4 moles of functionalizing agent per 1 mole of cocatalyst. The functionalizing agent is brought into contact with the polymerization medium for a sufficient time to allow the functionalization reaction.This contact time is judiciously chosen by the person skilled in the art depending on the concentration of the reaction medium and the temperature of the reaction medium. Typically, the functionalization reaction is carried out with stirring, at a temperature ranging from 17 to 80°C, for 0.01 to 24 hours.

[0092] When the functionalizing agent carries a protected function as described above, the polymer functionalization step can be followed by a hydrolysis reaction to form a copolymer carrying a deprotected function, such as a primary amine or a secondary amine.

[0093] A hydrolysis reaction can also follow the polymer functionalization reaction. Hydrolysis of the polymer bearing an alkoxysilyl function leads to the preparation of a polymer bearing a silanol function.

[0094] The highly saturated diene elastomer useful for the purposes of the invention may consist of a mixture of highly saturated diene elastomers which differ from one another by their microstructures or by their macrostructures.

[0095] According to the invention, the level of the highly saturated diene elastomer in the rubber composition is preferably at least 50 parts by weight per hundred parts of elastomer of the rubber composition (phr). More preferably, the level of the highly saturated diene elastomer in the rubber composition varies in a range from 60 to 100 phr, preferably 80 to 100 phr. More preferably, it varies in a range from 90 to 100 phr.

[0096] Additionally, the elastomer matrix of the composition of the invention may comprise at least one other elastomer, in a minority. Particularly noteworthy are the diene elastomers known to those skilled in the art for their use in the field of tires, such as a polybutadiene (abbreviated as "BR"), a synthetic polyisoprene (IR), natural rubber (NR), a butadiene copolymer such as a butadiene-styrene copolymer (SBR), an isoprene copolymer and mixtures of these elastomers.

[0097] 2 Liquid polymer of functionalized butadiene

[0098] The term "butadiene polymer" means a homopolymer or copolymer of butadiene, in other words a diene polymer selected from the group consisting of polybutadienes, the various copolymers of butadiene and mixtures of these polymers. Among the copolymers of butadiene, mention will be made in particular of copolymers of butadiene and of a vinylaromatic monomer, preferably styrene. Among the copolymers, those having at least 80% by weight of units derived from butadiene are suitable. Preferably, the liquid polymer of butadiene is a liquid polybutadiene.

[0099] According to the invention, the liquid butadiene polymer is liquid at room temperature (around 23°C at 1 atm); that is to say, as a reminder, substances having the capacity to eventually take the shape of their container. Its Tg is preferably less than -20°C, more preferably less than -40°C. According to one embodiment of the invention, the liquid butadiene polymer has a Tg of less than -60°C, for example within a range from -100°C to -60°C, preferably within a range from -95°C to -65°C, more preferably within a range from -90°C to -70°C.

[0100] According to the invention, the liquid polymer of butadiene functionalized along the chain has a number-average molar mass (Mn) greater than or equal to 1000 g / mol and preferably less than or equal to 50000 g / mol, more preferably less than or equal to 30000 g / mol, more preferably still less than or equal to 10000 g / mol. Thus, according to certain embodiments, the liquid polymer of butadiene functionalized along the chain has a number-average molar mass (Mn) within a range from 1000 g / mol to 10000 g / mol.

[0101] According to other embodiments of the invention, the liquid butadiene polymer has a number-average molar mass (Mn) greater than or equal to 1000 g / mol and preferably less than or equal to 6000 g / mol, more preferably less than or equal to 5500 g / mol, more preferably within a range from 1000 g / mol to 5000 g / mol, more preferably within a range from 2000 g / mol to 4000 g / mol.

[0102] The Tg of the liquid polymer is measured according to ASTM D3418 (1999). The macrostructure (Mw, Mn and IP) of the liquid polymer is determined by size exclusion chromatography (SEC): tetrahydrofuran solvent; temperature 35°C; concentration 1 g / l; flow rate 1 ml / min; solution filtered through a 0.45 pm porosity filter before injection; Moore calibration with polystyrene standards; set of 3 "WATERS" columns in series ("STYRAGEL" HR4E, HR1 and HR0.5); detection by differential refractometer ("WATERS 2410") and its associated operating software ("WATERS EMPOWER").

[0103] According to the invention, the liquid butadiene polymer is functionalized by at least one alkoxysilyl function. By "functionalized polymer" is meant a polymer comprising at least one alkoxysilyl functional group attached to the main chain of the polymer, this at least one group being able to be pendant along the main chain of the polymer or located at one of its two ends. By "by at least one alkoxysilyl function" is meant one or more alkoxysilyl functions.

[0104] The polymer thus comprises an average number of at least 1 function per chain, preferably at least 1.3, more preferably at least 2.0. The average functionality can be calculated via the number-average molar mass (Mn) of the liquid butadiene polymer and the number of alkoxysilyl functions.

[0105] By "alkoxysilyl function" we mean a function corresponding to the formula - Si(0R) nR3-n, each R, independently of each other, represents a C1-C10 alkyl radical, preferably C1-C4, and n is an integer from 1 to 3. Preferably, the alkoxysilyl function is a trialkoxysilyl function corresponding to the formula - Si(OR)3- More preferably still the alkoxysilyl function is a trimethoxysilyl or triethoxysilyl function. Depending on the medium in which the liquid polymer of functionalized butadiene is used, a person skilled in the art will understand that the alkoxysilyl functions can be partially or totally hydrolyzed. All the preferential and advantageous aspects concerning the liquid polymer of functionalized butadiene are combinable according to the invention.

[0106] According to embodiments of the invention, the liquid polymer of functionalized butadiene is functionalized at each chain end by an alkoxysilyl function. Preferably according to this embodiment, the liquid polymer of functionalized butadiene is a functionalized liquid polybutadiene carrying at each chain end a trialkoxysilyl function, preferably trimethoxysilyl or triethoxysilyl. Such polymers can be obtained in a simple and known manner by functionalization of a liquid telechelic polymer of butadiene carrying -OH functions at the chain ends, obtained by radical polymerization, with a functionalization agent of alkoxysilane type capable of reacting with the -OH functions of the polymer. Mention may be made of alkoxysilane compounds carrying an isocyanate function as functionalization agent. Such polymers and their synthesis are for example described in document WO2016180649A1.According to these embodiments, the at least one alkoxysilyl function can be linked to the butadiene polymer directly by a covalent bond or via a hydrocarbon group which can comprise one or more heteroatoms chosen from N and O.

[0107] According to embodiments of the invention, the liquid polymer of functionalized butadiene is functionalized along the chain and carries one or more pendant alkoxysilyl functions. Preferably according to this embodiment, the liquid polymer of functionalized butadiene is a functionalized liquid polybutadiene carrying one or more trialkoxysilyl functions, preferably trimethoxysilyl or triethoxysilyl, along the chain. Obtaining pendant alkoxysilyl functions along the chain can be carried out in a simple and known manner by hydrosilylation of the pendant carbon-carbon double bonds of the 1,2-vinyl units of the butadiene part of a liquid polymer of butadiene. Such polymers are for example described in documents EP3466996A1 and EP3293217A1.

[0108] Liquid butadiene polymers useful for the purposes of the invention can be found commercially under the name, for example, "POLYVEST EP ST-E 60" and "POLYVEST EP ST-E 100" marketed by the company EVONIK, and X-12-1267B, X-12-1267B-ES and X-12-1287A marketed by the company Shin-Etsu.

[0109] According to any one of the embodiments of the invention, the liquid polymer content of the functionalized butadiene is advantageously greater than or equal to 0.5 phr, preferably within a range from 0.5 phr to 25 phr, preferably from 1 to 20 phr, more preferably from 5 phr to 15 phr.

[0110] The liquid butadiene polymer functionalized by at least one alkoxysilyl function may be a mixture of several liquid butadiene polymers functionalized by at least one alkoxysilyl function as described above.

[0111] 3 Reinforcing charge

[0112] The composition according to the invention comprises a reinforcing filler comprising silica.

[0113] In addition to silica, at least one other reinforcing filler known for its ability to reinforce a rubber composition suitable for the manufacture of tires may also be used, for example an organic filler such as carbon black, a reinforcing inorganic filler other than silica, such as alumina, or a blend of these two types of filler. More particularly, if the reinforcing filler comprises a filler other than silica, it comprises a carbon black.

[0114] Suitable carbon blacks are all carbon blacks, in particular so-called pneumatic grade blacks. Among the latter, we will mention in particular the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as blacks N115, N134, N234, N326, N330, N339, N347, N375, or, depending on the intended applications, blacks of higher series (for example N660, N683, N772). The carbon blacks could, for example, already be incorporated into an isoprene elastomer in the form of a masterbatch (see for example applications WO 97 / 36724 or WO 99 / 16600).

[0115] Examples of organic fillers other than carbon blacks include functionalized polyvinyl organic fillers as described in applications WO-A-2006 / 069792, WO-A-2006 / 069793, WO-A-2008 / 003434 and WO-A-2008 / 003435.

[0116] The composition may contain one type of silica or a blend of several silicas. The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface area and a CTAB specific surface area both less than 450 m 2 / g, preferably 30 to 400 m 2 / g. As highly dispersible precipitated silicas (called "HDS"), mention may be made, for example, of the silicas "Ultrasil 7000" and "Ultrasil 7005" from the company Degussa, the silicas "Zeosil" 1165MP, 1135MP and 1115MP from the company Solvay, the silica "Hi-Sil EZ150G" from the company PPG, the silicas "Zeopol" 8715, 8745 and 8755 from the company Huber, treated precipitated silicas such as, for example, the silicas "doped" with aluminium described in application EP-A-0735088 or the silicas with a high specific surface area as described in application WO 03 / 16837.

[0117] According to one embodiment of the invention, the reinforcing filler is predominantly silica, i.e. it preferably comprises more than 50% by weight of silica relative to the total weight of the reinforcing filler. Optionally, according to this variant, the reinforcing filler also comprises carbon black.

[0118] In this presentation, the BET specific surface area is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, page 309, February 1938), and more precisely according to a method adapted from the standard NF ISO 5794-1, annex E of June 2010 [multipoint volumetric method (5 points) - gas: nitrogen - vacuum degassing: one hour at 160°C - relative pressure range p / in: 0.05 to 0.2], The CTAB specific surface area values ​​were determined according to the standard NF ISO 5794-1, annex G of June 2010. The method is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "external" surface of the reinforcing filler.

[0119] The person skilled in the art will understand that, as a filler equivalent to silica, a reinforcing filler of another nature, in particular organic, could be used, provided that this reinforcing filler is covered with a layer of silica, or else has functional sites on its surface, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between the filler and the elastomer. The physical state in which the reinforcing filler is present is immaterial, whether in the form of powder, microbeads, granules, beads or any other suitable densified form.

[0120] For the purposes of the invention, the level of total reinforcing filler (silica and optionally carbon black and / or reinforcing inorganic filler other than silica) is preferably 10 to 100 phr, more preferably 15 to 70 phr. Below 10 phr of filler, the composition may not be sufficiently reinforced.

[0121] According to one embodiment of the invention, silica is used as the majority filler, preferably at a rate ranging from 10 to 100 phr, more preferably from 15 to 70 phr, and, optionally, carbon black. Carbon black, when present, is then used in a minor manner, preferably at a rate in a range ranging from 0.1 to 20 phr, more preferably from 0.5 to 10 phr, in particular from 1 to 5 phr. In the indicated ranges, the coloring (black pigmenting agent) and anti-UV properties of carbon blacks are benefited from, without otherwise penalizing the typical performances provided by the reinforcing inorganic filler.

[0122] To couple the silica to the diene elastomer, according to the invention and in a well-known manner, an at least bifunctional coupling agent is used intended to ensure a sufficient connection, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. By "bifunctional", we mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer. For example, 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 and a second functional group comprising a sulfur atom, said second functional group capable of interacting with the diene elastomer.

[0123] Preferably, the coupling agents are chosen from the group consisting of polysulfurized organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, marketed under the name "Si69" by the company Evonik or bis-(triethoxysilylpropyl) disulfide, abbreviated to TESPD, marketed under the name "Si75" by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked or partially blocked mercaptosilanes, such as "NXT-Silane" or "NXT-Z45 Silane" marketed by the company Momentive. Of course, mixtures of these coupling agents could also be used.

[0124] Those skilled in the art will understand that the coupling agent content is dependent on the amount of reinforcing inorganic filler to be coupled to the elastomer. Typically, the coupling agent content represents from 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler, in particular silica.

[0125] The composition according to the invention may optionally also contain coupling activators, agents for covering inorganic fillers or more generally processing aids capable, in a known manner, thanks to an improvement in the dispersion of the filler in the rubber matrix and a reduction in the viscosity of the composition, of improving its processability in the raw state, these agents being known elsewhere.

[0126] 4 Crosslinking system

[0127] The crosslinking system may be any type of system known to those skilled in the art in the field of tire rubber compositions. It may in particular be based on sulfur, and / or peroxide and / or bismaleimides.

[0128] Preferably, the crosslinking system is sulfur-based, in which case it is referred to as a vulcanization system. The sulfur can be provided in any form, in particular in the form of molecular sulfur, or a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally, also preferably, various known vulcanization activators can be used, such as zinc oxide, stearic acid or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders.

[0129] Sulphur is used at a preferential rate of between 0.2 pce and 10 pce, more preferably between 0.3 and 5 pce. The vulcanisation accelerator or accelerator mixture is used at a preferential rate of between 0.5 and 10 pce, more preferably between 0.5 and 5 pce.

[0130] Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0131] 5 Possible Additives

[0132] The rubber composition according to the invention may optionally also comprise all or part of the usual additives usually used in elastomer compositions for tires, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents, plasticizers other than the liquid butadiene polymer, reinforcing resins (as described for example in application WO 02 / 10269).

[0133] It goes without saying that the invention relates to the rubber compositions previously described both in the so-called "raw" or uncrosslinked state (i.e., before curing) and in the so-called "cured" or crosslinked state (i.e., after crosslinking or vulcanization). of the rubber composition

[0134] The 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: - a first working phase or thermomechanical mixing (so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents are introduced into a suitable mixer such as a conventional internal mixer (for example of the 'Banbury' type), in particular the elastomeric matrix, the liquid polybutadiene polymer, the reinforcing filler, any other various additives, with the exception of the crosslinking system. The incorporation of the optional filler into the elastomer can be carried out in one or more times by thermomechanical mixing.In the case where the filler is already incorporated in whole or in part into the elastomer in the form of a masterbatch as described for example in applications WO 97 / 36724 or WO 99 / 16600, it is the masterbatch which is directly mixed and where appropriate the other elastomers or fillers present in the composition which are not in the form of a masterbatch are incorporated, as well as any other various additives other than the crosslinking system. 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.

[0135] - 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 crosslinking system is then incorporated, and everything is then mixed for a few minutes, for example between 5 and 15 min.

[0136] Such phases are well known to those skilled in the art.

[0137] The final composition thus obtained is then calendered, for example, in the form of a sheet or plate, in particular for characterization in the laboratory, or extruded (or co-extruded with another rubber composition) in the form of a semi-finished (or profiled) rubber usable in a tire, for example as a tread. These products can then be used for the manufacture of tires, according to techniques known to those skilled in the art.

[0138] The composition can be either in the raw state (before crosslinking or vulcanization), or in the cooked state (after crosslinking or vulcanization), can be a semi-finished product which can be used in a tire.

[0139] Crosslinking (or curing), and where appropriate vulcanization, is carried out in a known manner at a temperature generally between 130°C and 200°C, for a sufficient time which may vary, for example, between 5 and 90 min depending in particular on the curing temperature, the crosslinking system adopted and the crosslinking kinetics of the composition in question.

[0140] 7 Semi-finished product and tire

[0141] The rubber composition according to the invention has good tear resistance and rigidity suitable for use in the manufacture of tires. Thus, a tire comprising such a composition in its tread provides good wear resistance properties while providing good road behavior, particularly when transporting heavy loads. This is why another subject of the present invention relates to a semi-finished article, in particular for a tire, comprising at least one rubber composition in accordance with the invention and as defined above.

[0142] The semi-finished article may be any article that can be used for the manufacture of a finished rubber article such as a tire. Preferably, the semi-finished article for a tire is a tread. The semi-finished articles are obtained by methods well known to those skilled in the art.

[0143] Another subject of the present invention relates to a tire comprising at least one rubber composition in accordance with the invention and as described above or comprising at least one semi-finished article for a tire as described above, in particular the tread. The tires of the invention are obtained by methods well known to those skilled in the art.

[0144] The above-mentioned characteristics of the present invention, as well as others, will be better understood upon reading the following description of several exemplary embodiments of the invention, given for illustrative and non-limiting purposes.

[0145] EXAMPLES OF CARRYING OUT THE INVENTION

[0146] 1 Tests and measurements:

[0147] 1-1 Determination of the microstructure of elastomers

[0148] The microstructure of elastomers is determined by NMR analysis 1 H, supplemented by NMR analysis 13C when the resolution of the NMR spectra of the 1 H does not allow the attribution and quantification of all species. Measurements are carried out using a BRUKER 500MHz NMR spectrometer at frequencies of 500.43 MHz for proton observation and 125.83 MHz for carbon observation.

[0149] For non-soluble elastomers that have the ability to swell in a solvent, a 4mm z-grad HRMAS probe is used to observe the proton and carbon in proton-decoupled mode. Spectra are acquired at rotation speeds of 4000Hz to 5000Hz.

[0150] For measurements on soluble elastomers, a liquid NMR probe is used to observe the proton and carbon in proton-decoupled mode.

[0151] The preparation of insoluble samples is carried out in rotors filled with the analyzed material and a deuterated solvent allowing swelling, generally deuterated chloroform (CDCU). The solvent used must always be deuterated and its chemical nature can be adapted by the person skilled in the art. The quantities of material used are adjusted so as to obtain spectra with sufficient sensitivity and resolution.

[0152] Soluble samples are dissolved in a deuterated solvent (approximately 25 mg of elastomer in 1 mL), generally deuterated chloroform (CDCU). The solvent or solvent blend used must always be deuterated and its chemical nature can be adapted by those skilled in the art.

[0153] In both cases (soluble sample or swollen sample): For proton NMR, a single 30° pulse sequence is used. The spectral window is adjusted to observe all the resonance lines belonging to the molecules analyzed. The accumulation number is adjusted to obtain a sufficient signal-to-noise ratio for the quantification of each pattern. The recycling time between each pulse is adapted to obtain a quantitative measurement.

[0154] For carbon NMR, a single 30° pulse sequence is used with proton decoupling only during acquisition to avoid "Nuclear Overhauser" (NOE) effects and to remain quantitative. The spectral window is adjusted to observe all the resonance lines belonging to the analyzed molecules. The accumulation number is adjusted to obtain a sufficient signal-to-noise ratio for the quantification of each pattern. The recycling delay between each pulse is adapted to obtain a quantitative measurement.

[0155] NMR measurements are performed at 25°C.

[0156] 1-2 Determination of the Tg of elastomers

[0157] The glass transition temperature (Tg) values ​​described herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to ASTM D3418 (1999).

[0158] 1-3 Measurement of tearability

[0159] Tearability indices are measured at 100°C. In particular, the force required to achieve rupture (FRD, in MPa (in N / mm 2 )) and the strain at break (DRD, in %) is measured on a test piece of dimensions 10 x 85 x 2.5 mm notched in the center of its length by 3 notches to a depth of 3 mm, to cause the rupture of the specimen stretched at 375 mm / min. Thus we can determine the Energy to cause rupture (Rupture Energy) of the specimen which is the product of the FRD and the DRD.

[0160] 1-4 Measurement of dynamic properties

[0161] The dynamic properties G*(25%) at 60°C are measured on a viscoanalyzer (Metravib VA4000), according to the ASTM D 5992-96 standard. The response of a sample of crosslinked composition (cylindrical specimen 2 mm thick and 10 mm in diameter), subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under the defined temperature conditions, for example at 60°C according to the ASTM D 1349-99 standard, is recorded. A strain amplitude sweep is carried out from 0.1 to 50% (forward cycle), then from 50% to 1% (return cycle). The results used are the complex dynamic shear modulus G* at 25% strain, at 60°C.

[0162] The G* (25%) measurement is a descriptor of stiffness and therefore an indication of the wear resistance performance of the material. The value in base 100 is calculated according to the operation: (G* (25%) value at 60°C of the sample / G* (25%) value at 60°C of the control) * 100. In this way, a lower value than the control represents a decrease in stiffness, while a higher value represents a higher stiffness.

[0163] 2 Preparation of rubber compositions:

[0164] The rubber compositions, the formulation details of which are given in Table 1, were prepared as follows: The elastomer is introduced into an internal mixer (final filling rate: approximately 70% by volume), with an initial tank temperature of approximately 90°C. When the temperature reaches 100°C, the liquid butadiene polymer, silica, carbon black and coupling agent are introduced, as well as the various other ingredients except for the sulfur and vulcanization accelerators. Thermomechanical work (non-productive phase) is then carried out in one step, lasting a total of approximately 3 to 4 minutes, until a maximum "drop" temperature of 160°C is reached. The resulting mixture is recovered, cooled and then the sulfur and vulcanization accelerators are incorporated on a cylinder tool at 25°C, mixing everything (productive phase) for an appropriate time (e.g., 5 minutes).

[0165] The compositions thus obtained are then calendered either in the form of plates (thickness 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties. Crosslinking was then carried out at a temperature of 150°C, under pressure.

[0166] Preparation of the elastomer

[0167] The elastomer (EBR) is prepared according to the following procedure:

[0168] The EBR elastomer is prepared in the presence of a catalytic system based on a metallocene [Me2Si(Flu)2Nd(p-BH4hLi(THF)] and a co-catalyst, butyloctylmagnesium, according to the following procedure:

[0169] In a 90 L stainless steel reactor, 64 L of MCH and a solution of BOMAG (23 mmol) in methylcyclohexane (0.01 mol / L) are introduced. The reactor is heated to 80°C and the monomers are added at a controlled flow rate in order to maintain the composition of the monomer mixture in the polymerization medium constant. The ethylene flow rate is set at 40 g / min and the butadiene is injected independently and the flow rate is controlled by the ethylene flow rate according to the butadiene / ethylene mass ratio equal to 0.55. When the reactor reaches a pressure of 8 bars, the catalytic system (6.25 mmol of Nd) preformed at a concentration of 0.007 mol / L prepared according to the protocol described in application WO 2017093654 A1 is introduced into the polymerization medium.The chain termination reaction is carried out by a functionalization reaction described according to the functionalization procedure when 5 to 6 kg of polymer are formed: the polymer is recovered after a stripping step. The polymer is then dried on a screw machine equipped with a single screw at 150°C.

[0170] Functionalization procedure:

[0171] When the desired monomer conversion is reached (5 to 6 kg of polymer), the contents of the reactor are degassed, the functionalizing agent, N, N dimethylaminopropyl-methyldimethoxysilane, is introduced into the polymerization medium under inert atmosphere by overpressure at a rate of 4 equivalents relative to the number of moles of Nd and Mg introduced into the reactor. The reaction medium is stirred for 15 minutes at 80°C. The reaction medium is deactivated with methanol. The polymer is recovered after a stripping step. The polymer is then dried on a screw machine equipped with a single screw at 150°C. It is then analyzed by SEC (THF), NMR 1 H, 29 Yes. Table 1

[0172] (1) Copolymer of ethylene and 1,3-butadiene containing 75 mol% of ethylene unit, 16 mol% of butadiene unit in the form of 1,2 and 1,4 units and 9 mol% of 1,2-cyclohexanediyl unit functionalized at the chain end, functional level at 35%, functionalizing agent (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane

[0173] (2) “Zeosil 1165 MP” from Solvay-Rhodia in the form of microbeads

[0174] (3) Carbon black grade N 234 according to ASTM D-1765, from Cabot Company

[0175] (4) Silane Mercapto - Thiocarboxylate Oligomer (“NXT-Z45”) - CAS 922519-17-3 - Moment ive company

[0176] (5) “LBR-307”, Kuraray company, non-functional BR liquid with Tg -95°C and Mn 8000 g / mol

[0177] (6) “X-12-1267B-ES” from Shin-Etsu, BR functional liquid along the chain of Tg -90°C and Mn 4700 g / mol, of formula

[0178] (7) “POLYVEST ST E 100” from Evonik, BR functional triethoxysilyl liquid at each end of the chain, Tg -80°C and Mn 3300 g / mol

[0179] (8) Diphenylguanidine “Perkacit DPG” from Flexsys

[0180] (9) Anti-ozone wax “VARAZON 4959” from the company Sasol Wax

[0181] (10)N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine "Santoflex 6PPD" from Flexys

[0182] (11) Stearic acid “Pristerene 4931” from Unigema

[0183] (12) Industrial grade Zinc Oxide from Umicore (13) N-cyclohexyl-2-benzothiazol-sulfenamide “Santocure CBS” from Flexsys

[0184] 3 Results:

[0185] Composition T1 is the control without liquid butadiene polymer to evaluate the effect of the nature of the liquid butadiene polymer used in compositions C1 to C3 respectively. Compositions C2 and C3 are in accordance with the invention.

[0186] The results show that the composition according to the invention, with an elastomer matrix based on a functionalized EBR and a liquid polybutadiene functionalized by at least one alkoxysilyl function, whether along the chain or at the ends of the chain, makes it possible to significantly improve the tear resistance while maintaining or even improving the rigidity compared with a composition not comprising liquid polybutadiene. This effect is observed against all expectations since the joint use of a functionalized EBR and a non-functionalized liquid polybutadiene degrades the rigidity. The shift in tear resistance and rigidity performances predicts, for a tire comprising such a composition, an improvement in the wear resistance properties with unchanged or even improved road holding.

Claims

CLAIMS 1. Rubber composition based on at least - an elastomer matrix comprising predominantly a functionalized highly saturated diene elastomer, which highly saturated diene elastomer is a copolymer comprising ethylene units and units of a 1,3-diene in which the ethylene units represent at least 50 mol% of the monomer units of the copolymer, preferably at least 60 mol%, - a reinforcing filler containing silica, - a coupling agent, - a crosslinking system and - a liquid polymer of butadiene functionalized by at least one alkoxysilyl function, having a number-average molar mass (Mn) greater than or equal to 1000 g / mol.

2. A rubber composition according to claim 1, wherein the 1,3-diene is 1,3-butadiene, isoprene, myrcene or p-farnesene, or a mixture of myrcene and -farnesene, preferably 1,3-butadiene.

3. Rubber composition according to any one of the preceding claims, in which the functionalized highly saturated diene elastomer carries at least one silanol or alkoxysilyl function, preferably attached directly to the terminal unit of the copolymer by the silicon atom of the function.

4. Rubber composition according to any one of the preceding claims, in which the functionalized highly saturated diene elastomer carries an amine function, preferably a tertiary amine, and at least one alkoxysilyl or silanol function.

5. Rubber composition according to any one of the preceding claims, in which the functionalized highly saturated diene elastomer carries at least one silanol or alkoxysilyl function attached directly to the terminal unit of the copolymer by the silicon atom of the function, which function corresponds to formula (1) - If(OR 1 ) 3.y -z(R 2 ) y (R)z (1) in which the symbols R 1 , identical or different, represent a hydrogen atom or a C1-C10 alkyl group, preferably C1-C4, preferably a methyl or an ethyl, the symbols R 2, identical or different, represent a hydrogen atom or a C1-C10 alkyl group, preferably C1-C4, preferably methyl or ethyl, the symbol R representing a hydrocarbon chain substituted by an amine function, preferably a tertiary amine, y being an integer ranging from 0 to 1, z being an integer ranging from 0 to 1.

6. Rubber composition according to any one of the preceding claims, in which the level of functionalized highly saturated diene elastomer varies in a range from 60 to 100 phr, preferably from 80 to 100 phr and very preferably from 90 to 100 phr.

7. Rubber composition according to any one of the preceding claims in which the alkoxysilyl function of the liquid butadiene polymer is a trialkoxysilyl function, corresponding to the formula - Si(OR)3, in which R denotes a C1-C10 alkyl, preferably C1-C4, preferably a trimethoxysilyl function or a triethoxysilyl function.

8. Rubber composition according to any one of the preceding claims in which the functionalized liquid butadiene polymer carries at least one pendant alkoxysilyl function along the chain.

9. Rubber composition according to any one of the preceding claims in which the functionalized liquid butadiene polymer carries at at least one end of the main chain an alkoxysilyl function, preferably at both ends of the chain.

10. Rubber composition according to any one of the preceding claims in which the level of functionalized liquid butadiene polymer is within a range from 0.5 to 25 phr, preferably from 1 to 20 phr, more preferably from 5 to 15 phr.

11. Rubber composition according to any one of the preceding claims in which the reinforcing filler comprises silica as the majority reinforcing filler.

12. Rubber composition according to any one of the preceding claims in which the level of reinforcing filler is within a range from 10 to 100 phr.

13. Rubber composition according to any one of the preceding claims in which the silica content is within a range from 15 to 70 pce.

14. Finished or semi-finished product comprising a rubber composition as defined in any one of the preceding claims.

15. A tire comprising a rubber composition as defined in any one of claims 1 to 13.

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