Rubber composition

Abstract

The invention relates to a rubber composition which comprises more than 90 phr of a highly saturated diene elastomer which is a copolymer of ethylene and 1,3-butadiene and contains more than 50 mol% of ethylene units, between 30 phr and 55 phr of a reinforcing filler containing more than 50% by weight of a carbon black, and more than 1 phr to less than 15 phr of a plasticizing hydrocarbon resin which is selected from the group consisting of C5-cut homopolymer resins, C5-cut copolymer resins, C9-cut homopolymer resins and C9-cut copolymer resins. The composition, in particular used in a tread for a tyre for a vehicle carrying heavy loads, has good crack propagation resistance properties.

Description

Rubber composition

[0001] The field of the present invention is that of rubber compositions reinforced with carbon black and rich in a highly saturated diene elastomer. These rubber compositions are particularly intended for use in a tire.

[0002] It is known to use in tire rubber compositions copolymers having a lower sensitivity to oxidation, such as for example highly saturated diene elastomers that are copolymers of ethylene and 1,3-butadiene which contain more than 50 mol% of ethylene unit. The use of these copolymers of ethylene and 1,3-butadiene in a tire tread is for example described in document WO 2014114607 A1 and has the effect of giving the tire an improved performance compromise between rolling resistance and wear resistance. It is also known to use such copolymers in aircraft tire treads to increase wear resistance at high speed, as is for example described in document WO 2016012259 A1.

[0003] It is also important to have rubber compositions that exhibit good cohesion, including good resistance to crack propagation. During rolling, a tire tread is subjected to mechanical stresses and attacks resulting from direct contact with the ground. This results in the formation of cracks. As they propagate on the surface or inside the tread, the crack incipients can damage the material that makes up the tread. This damage to the tread reduces the tire's tread life.Since the mechanical stresses and the attacks suffered by the tire are amplified under the effect of the weight carried by the tire, good cohesion is particularly sought for a composition intended to be used as a tread of a tire mounted on a vehicle carrying heavy loads, such as a tire for a heavy goods vehicle or civil engineering vehicle. To increase the resistance to crack propagation of a rubber composition reinforced with a carbon black and containing such a highly saturated diene elastomer, the Applicant has described in document WO 2020053520 A1 the use in the composition of sulfur rubber at a rate of less than 1 phr and also lower than that of the accelerators.

[0004] Continuing its efforts, the Applicant has developed a new rubber composition rich in a highly saturated diene elastomer and reinforced mainly with carbon black which has further improved crack propagation resistance properties.

[0005] Thus, a first subject of the invention is a rubber composition which comprises more than 90 phr of a highly saturated diene elastomer which is a copolymer of ethylene and 1,3-butadiene and which contains more than 50 mol% of ethylene units, between 30 phr and 55 phr of a reinforcing filler which contains more than 50% by mass of a carbon black, more than 1 phr to less than 15 phr of a hydrocarbon plasticizing resin which is selected from the group consisting of C5 cut homopolymer resins, C5 cut copolymer resins, C9 cut homopolymer resins and C9 cut copolymer resins.

[0006] Another subject of the invention is a tire which comprises a tread, the portion of which intended to be in contact with the rolling ground is made up entirely or in part of a rubber composition in accordance with the invention. Detailed description

[0007] Any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​greater than "a" and 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 domain of values ​​from "a" to "b" (i.e., including the strict limits a and b).

[0008] The abbreviation "pce" means parts by weight per hundred parts of elastomer (of the total elastomers if more than one elastomer is present).

[0009] 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, that is to say, they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0010] In the present invention, the term "tyre" means a pneumatic or non-pneumatic tire. A pneumatic tire usually comprises two beads intended to come into contact with a rim, a crown composed of at least one crown reinforcement and a tread, two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic tire, for its part, usually comprises a base, designed for example for mounting on a rigid rim, a crown reinforcement, ensuring the connection with a tread and a deformable structure, such as spokes, ribs or cells, this structure being arranged between the base and the crown. Such non-pneumatic tires do not necessarily comprise a sidewall. Non-pneumatic tires are described for example in documents WO 03 / 018332 and FR2898077.According to any one of the embodiments of the invention, the tire according to the invention is preferably a pneumatic bandage.

[0011] Unless otherwise indicated, the rates of units resulting from the insertion of a monomer into a copolymer such as the highly saturated diene elastomer useful for the purposes of the invention are expressed as a molar percentage relative to the total monomer units of the copolymer.

[0012] The highly saturated diene elastomer useful for the purposes of the invention is a copolymer of ethylene and 1,3-butadiene, preferably a random copolymer, which implies that the monomer units of the copolymer are those resulting from the copolymerization of ethylene and 1,3-butadiene. The copolymer therefore contains ethylene units and butadiene units. In a known manner, an ethylene unit is a monomer unit of the unit -(CH2-CH2)-. Also in a known manner, a butadiene unit is a monomer unit of the unit -CH2-CH(CH=CH2)- (1,2 unit) or -CH2- CH=CH-CH2- (1,4 unit) depending on whether the 1,3-butadiene monomer is inserted into the polymer chain during the polymerization reaction by a 2,1 or 1,4 addition. Highly saturated diene elastomer contains more than 50 mol% ethylene units.

[0013] The highly saturated diene elastomer preferably comprises at least 60 mol% of ethylene units, more preferably at least 65 mol% of ethylene units. In other words, the ethylene units preferably represent at least 60 mol% of all the monomer units of the highly saturated diene elastomer, more preferably at least 65 mol% of all the monomer units of the highly saturated diene elastomer. Preferably, the ethylene units represent at most 80 mol% of all the monomer units of the highly saturated diene elastomer. More preferably, the ethylene units represent at most 75 mol% of all the monomer units of the highly saturated diene elastomer.Advantageously, the highly saturated diene elastomer comprises from 60% to 80% mol of ethylene unit, particularly from 60% to 75% mol of ethylene unit, more particularly from 65% to 75% mol of ethylene unit, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer.

[0014] The highly saturated diene elastomer 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 1,3-butadiene and ethylene and according to known synthesis methods, in particular in the presence of a catalytic system comprising a metallocene complex. Mention may be made in this respect of catalytic systems based on metallocene complexes, which catalytic systems are described in patent applications EP 1 092731, WO 2004035639, WO 2007054223 and WO 2007054224 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 patent applications WO 2017093654 A1, WO 2018020122 A1 and WO 2018020123 A1.Advantageously, the diene elastomer is statistical and is preferably prepared according to a semi-continuous or continuous process. as described in patent applications WO 2017103543 A1, WO 201713544 A1, WO 2018193193 and WO 2018193194.

[0015] The highly saturated diene elastomer preferably contains units of formula (I) or units of formula (II), unit 1,2. -CH2-CH(CH=CH2)- (II)

[0016] The presence of 6-membered saturated cyclic unit, 1,2-cyclohexane unit, of formula (I) in the copolymer may result from a series of very specific insertions of ethylene and 1,3-butadiene into the polymer chain during its growth. When the highly saturated diene elastomer comprises units of formula (I) or units of formula (II), the molar percentages of the units of formula (I) and the units of formula (II) in the highly saturated diene elastomer, respectively o and p, preferably satisfy the following equation (eq. 1) or equation (eq. 2), o and p being calculated on the basis of all the monomer units of the highly saturated diene elastomer. 0 < o+p < 30 (eq. 1) 0 < o+p < 25 (eq. 2)

[0017] Preferably, the highly saturated diene elastomer comprises units of formula (I) in a molar ratio greater than 0% and less than 15%, more preferably less than 10% mol, molar percentage calculated on the basis of all the monomer units of the highly saturated diene elastomer.

[0018] According to a particularly preferred embodiment, the highly saturated diene elastomer contains 1,4-units of trans configuration (1,4-trans units). When the diene elastomer contains 1,4-trans units, the 1,4-trans units represent more than 50 mol% of the 1,4-units of the highly saturated diene elastomer, preferably more than 80 mol% of the 1,4-units of the highly saturated diene elastomer.

[0019] The highly saturated diene elastomer can consist of a mixture of highly saturated diene elastomers which differ from each other in their microstructures or in their macrostructures.

[0020] The content of the highly saturated diene elastomer in the rubber composition is greater than 90 parts by weight per hundred parts of elastomer of the rubber composition (pce). In the case where the highly saturated diene elastomer consists of a mixture of highly saturated diene elastomers which differ from each other by their microstructures or by their macrostructures, the level of highly saturated diene elastomer in the rubber composition refers to the mixture of highly saturated diene elastomers.

[0021] The rubber composition may contain, in addition to the highly saturated diene elastomer, a second diene elastomer at a mass content of less than 10 phr. A diene elastomer is understood to mean an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not). The second elastomer may be chosen from the group of highly unsaturated diene elastomers consisting of polymers containing 1,3-butadiene units or isoprene units such as polybutadienes, butadiene copolymers, isoprene copolymers. A highly unsaturated diene elastomer is an elastomer which contains more than 50 mol% of diene units.

[0022] The rate of highly saturated diene elastomer in the rubber composition is preferably greater than 95 pce, advantageously equal to 100 pce. The higher the rate of highly saturated diene elastomer in the rubber composition, the greater the intended technical effect.

[0023] The rubber composition comprises any type of so-called reinforcing filler, known for its ability to reinforce a rubber composition, in particular usable for the manufacture of a tire tread. Such a reinforcing filler typically consists of nanoparticles whose average size (by mass) is less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, in particular and more preferably between 20 and 150 nm. The rate of the reinforcing filler is between 30 pce and 55 pce, preferably varies from 35 pce to 50 pce, more preferably varies from 35 pce to 45 pce.

[0024] The reinforcing filler has the essential characteristic of containing more than 50% by mass up to 100% by mass of a carbon black, mass percentages calculated relative to the mass of the reinforcing filler of the rubber composition. Preferably, the mass content of the carbon black is greater than 95% of the mass of the reinforcing filler and less than or equal to 100% of the mass of the reinforcing filler. When the mass content of carbon black in the rubber composition is less than 100% of the mass of the reinforcing filler, the reinforcing filler may therefore comprise any type of filler other than carbon black which is also known for its ability to reinforce a rubber composition usable for the manufacture of tires, for example a reinforcing inorganic filler such as silica with which a coupling agent is associated in a known manner.Advantageously, the mass rate of carbon black is equal to 100% of the mass of the reinforcing filler.

[0025] Suitable carbon blacks are all reinforcing carbon blacks, including those conventionally used in tires or their treads (so-called tire-grade blacks). These include: more particularly reinforcing carbon blacks of the 100, 200, 300 series, or blacks of the 500, 600 or 700 series (ASTM grades), such as for example blacks N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772). When the rubber composition in accordance with the invention is used in a tread, the carbon black is preferably a carbon black of the 100 or 200 series.

[0026] Preferably, the carbon black has a BET specific surface area greater than 90 m 2 / g. more preferably, the BET specific surface area of ​​carbon black is greater than 100 m 2 / g. Preferably, the carbon black has a BET specific surface area of ​​less than 145 m 2 / g. Carbon black more preferably has a BET specific surface area of ​​less than 130 m 2 / g.

[0027] The BET specific surface area is typically measured according to ASTM D6556-09 [multipoint method (5 points) - gas: nitrogen - relative pressure range P / PO: 0.05 to 0.30],

[0028] Another essential feature of the rubber composition is to contain a hydrocarbon plasticizing resin selected from the group consisting of C5-cut homopolymer resins, C5-cut copolymer resins, C9-cut homopolymer resins and C9-cut copolymer resins.

[0029] As is known, the term C5 (or for example respectively C9) cut is understood to mean any fraction resulting from a process originating from petrochemistry or oil refining, any distillation cut containing mainly compounds having 5 (or respectively 9 in the case of a C9 cut) carbon atoms; C5 cuts for example may contain, by way of illustration and without limitation, the following compounds whose relative proportions may vary depending on the production process, for example the origin of the naphtha and the steam cracking process: 1,3-butadiene, butene-1,2-butenes, 1,2-butadiene, 3-methyl-1-butene, 1,4-pentadiene, 1-pentene, 2-methyl-1-butene, 2-pentenes, isoprene, cyclopentadiene which may be present in the form of its dimer dicyclopentadiene, piperylenes, cyclopentene, 1-methyl-cyclopentene, 1-hexene, methylcyclopentadiene, cyclohexene.These cuts can be obtained by all chemical processes known in the petroleum and petrochemical industry. As non-limiting examples, mention may be made of naphtha steam cracking processes or fluid catalytic cracking processes for gasoline, these processes being able to be associated with all possible chemical treatments for transforming these cuts, known to those skilled in the art, such as hydrogenation and dehydrogenation.

[0030] Hydrocarbon resins, also called hydrocarbon plasticizing resins, are polymers well known to those skilled in the art, essentially based on carbon and hydrogen atoms but which may contain other types of atoms, for example oxygen, which can be used in particular as plasticizing agents or tackifying agents in polymer matrices. They are by nature at least partially miscible (i.e., compatible) at the levels 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 book "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9) whose chapter 5 is devoted to their applications, particularly in pneumatic rubber (5.5. "Rubber Tires and Mechanical Goods"). As is known, these hydrocarbon resins can also be described as thermoplastic resins in the sense that they soften upon heating and can therefore be molded. The softening point of hydrocarbon resins is measured according to ISO 4625 ("Ring and Bail" method). The Tg is measured according to ASTM D3418 (1999).The macrostructure (Mw, Mn and Ip) of the hydrocarbon resin is determined by size exclusion chromatography (SEC): tetrahydrofuran solvent; temperature 35°C; concentration 1 g / l; flow rate 1 ml / min; solution filtered on 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").

[0031] Hydrocarbon resins can be aliphatic, aromatic, or aliphatic / aromatic, i.e., based on aliphatic and / or aromatic monomers. They can be natural or synthetic, petroleum-based or not (if so, also known as petroleum resins). Preferably, the plasticizing hydrocarbon resin has a glass transition temperature above 20°C.

[0032] Advantageously, the hydrocarbon resin has at least one of the following characteristics, more preferably all of them: - a Tg greater than 30°C; - a number-average molecular mass (Mn) of between 300 and 2000 g / mol, more preferably between 400 and 1500 g / mol; - a polymolecularity index (Ip) less than 3, more preferably less than 2 (reminder: Ip = Mw / Mn with Mw average molecular mass by weight).

[0033] The content of the hydrocarbon plasticizing resin in the rubber composition is greater than 1 pce and less than 15 pce. Below the minimum indicated, the intended technical effect is insufficient, whereas from 15 pce the hysteresis of the rubber composition becomes too great for use of the rubber composition in a tread of a tire for a vehicle intended to carry heavy loads. Preferably, the content of the hydrocarbon plasticizing resin is 2 to 10 pce.

[0034] According to a particularly preferred embodiment of the invention, the mass ratio between the level of reinforcing filler and the level of plasticizing hydrocarbon resin is greater than 3.

[0035] Preferably, the hydrocarbon plasticizing resin is a resin of a C5 fraction and C9 fraction copolymer.

[0036] The rubber composition may contain a plasticizer other than the hydrocarbon plasticizing resin. This other plasticizer may be a liquid plasticizer or a hydrocarbon resin other than a C5-cut homopolymer resin, a C5-cut copolymer resin, a C9-cut homopolymer resin, or a C9-cut copolymer resin. A substance is described as liquid when, at room temperature (23°C), the substance, which is more or less viscous, is liquid, that is to say, as a reminder, a substance having the capacity to eventually take the shape of its container, in contrast in particular to hydrocarbon plasticizing resins which are by nature solid at room temperature.Examples of liquid plasticizers that may be mentioned include oils commonly used in tire rubber compositions such as paraffinic oils, MES oils (“Medium Extracted Solvates”), TDAE oils (“Treated Distillate Aromatic Extracts”), TRAE oils (“Treated Residual Aromatic Extract”), SRAE oils (“Safety Residual Aromatic Extract oils”), mineral oils and mixtures thereof.

[0037] According to a particularly preferred embodiment of the invention, the rubber composition contains 0 to less than 3 pce of plasticizer chosen from liquid plasticizers and plasticizing resins other than C5 cut homopolymer resins, C5 cut copolymer resins, C9 cut homopolymer resins and C9 cut copolymer resins.

[0038] According to a particularly preferred embodiment of the invention, in particular for the use of the rubber composition in a tread of a tire for a vehicle carrying heavy loads, the rubber composition does not contain any plasticizer other than a hydrocarbon plasticizing resin chosen from the group consisting of C5-cut homopolymer resins, C5-cut copolymer resins, C9-cut homopolymer resins and C9-cut copolymer resins, in particular other than a resin of a C5-cut and C9-cut copolymer.

[0039] Embodiments in which the liquid plasticizer content is less than 3 phr are preferred to further optimize tear resistance and are even more preferred when the liquid plasticizer content is 0.

[0040] The rubber composition may also include all or part of the usual additives normally used in elastomer compositions intended to constitute treads, such as, for example, crosslinking agents, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants.

[0041] The rubber composition preferably contains a vulcanization system. The vulcanization system typically comprises sulfur and a vulcanization accelerator.

[0042] Sulfur is typically supplied in the form of molecular sulfur or a sulfur-donating agent, preferably in molecular form. Sulfur in molecular form is also referred to as molecular sulfur. This refers to sulfur donor any compound that releases sulfur atoms, combined or not in the form of a polysulfide chain, capable of being inserted into the polysulfide chains formed during vulcanization and bridging the elastomer chains. The sulfur content in the rubber composition is preferably less than 2 pce, preferably between 0.3 and 1.5 pce.

[0043] Any compound capable of acting as a vulcanization accelerator (primary or secondary) which can act as a vulcanization accelerator for diene elastomers in the presence of sulfur may be used, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide type for primary accelerators, and accelerators of the guanidine, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type for secondary accelerators. Guanidine is understood to mean any compound which contains the divalent radical -HN-C(=NH)-NH-. Guanidine is preferably diphenylguanidine. The vulcanization accelerator is used at a preferential rate of between 0.3 and 5 pce, more preferably between 0.5 and 2.5 pce.

[0044] Examples of primary accelerators include sulfenamide compounds such as N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), and mixtures of these compounds. The primary accelerator is preferably a sulfenamide, more preferably N-cyclohexyl-2-benzothiazyl sulfenamide.

[0045] Examples of secondary accelerators include thiuram polysulfides, preferably thiuram disulfides such as tetraethylthiuram disulfide, tetrabutylthiuram disulfide ("TBTD"), tetrabenzylthiuram disulfide ("TBZTD") and mixtures of these compounds. The secondary accelerator is preferably a thiuram disulfide, more preferably tetrabenzylthiuram disulfide.

[0046] The primary accelerator is preferably a sulfenamide. When the primary vulcanization accelerator is a sulfenamide, it is preferably N-cyclohexyl-2-benzothiazyl sulfenamide.

[0047] The vulcanization accelerator is preferably a mixture of a primary accelerator and a secondary accelerator. The term "a primary accelerator" designates a single primary accelerator or a mixture of primary accelerators. Similarly, the term "a secondary accelerator" designates a single secondary accelerator or a mixture of secondary accelerators. When the vulcanization accelerator is a mixture of a primary accelerator and a secondary accelerator, the vulcanization accelerator is preferably a mixture of a sulfenamide and a thiuram disulfide or a mixture of a sulfenamide, a thiuram disulfide and a guanidine, the sulfenamide preferably being N-cyclohexyl-2-benzothiazyl sulfenamide, the thiuram disulfide being preferentially tetrabenzylthiuram disulfide, guanidine being preferentially diphenylguanidine.

[0048] As is well known, the vulcanization system may also comprise vulcanization activators such as metal oxides such as zinc oxide or fatty acids such as stearic acid.

[0049] The rubber composition may be manufactured in suitable mixers, using two successive preparation phases according to a general procedure well known to those skilled in the art: a first thermo-mechanical working or kneading phase (sometimes referred to as the "non-productive" phase) at high temperature, up to a maximum temperature of between 110°C and 190°C, preferably between 130°C and 180°C, followed by a second mechanical working phase (sometimes referred to as the "productive" phase) at a lower temperature, typically below 110°C, for example between 40°C and 100°C, a finishing phase during which the sulfur or sulfur donor and the vulcanization accelerator are incorporated. For example, the first (non-productive) phase is carried out in a single thermomechanical step during which all the necessary constituents, any additional processing agents and other various additives, with the exception of the sulfur and the vulcanization accelerator, are introduced into a suitable mixer such as a conventional internal mixer. The total mixing time in this non-productive phase is preferably between 1 and 15 min. After cooling the mixture thus obtained during the first non-productive phase, the sulfur and the vulcanization accelerator are then incorporated at low temperature, generally in an external mixer such as a roller mixer, and the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.

[0050] When the vulcanization system comprises a primary accelerator and a secondary accelerator, the rubber composition is preferably manufactured by a process which comprises a first step, step a), during which the constituents of the rubber composition are mixed by kneading, in particular thermomechanical kneading, with the exception of the sulfur and the primary accelerator, and a second step, step b), during which the sulfur and the primary accelerator are incorporated into the kneaded mixture comprising the elastomer, the reinforcing filler and the secondary accelerator. During step a), the elastomer, the reinforcing filler and the secondary accelerator are kneaded together, typically in a suitable mixer such as a conventional internal mixer. The kneading temperature in step a) is greater than 110°C, preferably between 110°C and 190°C, advantageously greater than 130°C and less than 180°C.The temperature ranges between 110°C and 190°C and between 130°C and 180°C correspond to maximum temperature values ​​reached by the kneaded mixture in the mixer during step a). Typically, the kneading during step a) is continued until the kneaded mixture reaches the maximum kneading temperature before being extracted. of the mixer. The total mixing time in step a) is preferably between 1 and 15 minutes. The mixture prepared at the end of step a) is recovered and then cooled to be able to proceed to step b), which is carried out at a lower temperature, in this case at a temperature below 110°C, preferably between 40°C and 100°C. During step b), the incorporation of the sulfur and the primary accelerator into the rubber composition is typically carried out by mixing in an external mixer such as a roller mixer, generally for a time between 2 and 15 minutes. The mixing in step b) is carried out at a temperature below 110°C, preferably between 40°C and 100°C.

[0051] Preferably, the rubber composition is extruded to form all or part of a profile of a tread of a tire. Then during the assembly of a tire usually comprising, radially from the outside to the inside, a tread, a crown reinforcement and a carcass reinforcement, the tread is laid radially outside the crown reinforcement. Radially means in a known manner in a radial direction relative to the axis of rotation of the tire.

[0052] The tire may be in the raw state (i.e. before the tire curing step) or in the cured state (i.e. after the tire curing step). The tire is preferably a tire for a vehicle carrying heavy loads, in particular a tire for a heavy goods vehicle or a tire for a civil engineering vehicle, preferably a tire for a heavy goods vehicle.

[0053] In summary, the invention may be implemented according to any of the following embodiments 1 to 29:

[0054] Mode 1: A rubber composition which comprises more than 90 phr of a highly saturated diene elastomer which is a copolymer of ethylene and 1,3-butadiene and which contains more than 50 mol% of ethylene units, between 30 phr and 55 phr of a reinforcing filler which contains more than 50% by mass of a carbon black, more than 1 phr to less than 15 phr of a hydrocarbon plasticizing resin which is selected from the group consisting of C5-cut homopolymer resins, C5-cut copolymer resins, C9-cut homopolymer resins and C9-cut copolymer resins.

[0055] Mode 2 Rubber composition according to mode 1 in which the highly saturated diene elastomer comprises at least 60 mol% of ethylene unit.

[0056] Mode 3: Rubber composition according to mode 1 or 2 in which the highly saturated diene elastomer comprises at least 65 mol% of ethylene unit.

[0057] Mode 4: Rubber composition according to any one of modes 1 to 3 in which the highly saturated diene elastomer comprises at most 80 mol% of ethylene unit.

[0058] Mode 5: Rubber composition according to any one of modes 1 to 4 in which the highly saturated diene elastomer comprises at most 75 mol% of ethylene unit.

[0059] Mode 6: Rubber composition according to any one of modes 1 to 5 in which the highly saturated diene elastomer contains units of formula (I) or units of formula (II). -CH2-CH(CH=CH2)- (II)

[0060] Mode 7: Rubber composition according to mode 6 in which the highly saturated diene elastomer comprises units of formula (I) in a molar ratio greater than 0% and less than 15%.

[0061] Mode 8: A rubber composition according to any one of modes 1 to 7 in which the highly saturated diene elastomer is a random copolymer.

[0062] Method 9: Rubber composition according to any one of methods 1 to 8 in which the content of the hydrocarbon plasticizing resin varies from 2 to 10 pce.

[0063] Mode 10: Rubber composition according to any one of modes 1 to 9 in which the rate of reinforcing filler varies from 35 pce to 50 pce.

[0064] Mode 11: Rubber composition according to any one of modes 1 to 10 in which the rate of the reinforcing filler varies from 35 pce to 45 pce.

[0065] Mode 12: Rubber composition according to any one of modes 1 to 11 in which the mass ratio between the rate of the reinforcing filler and the rate of the hydrocarbon plasticizing resin is greater than 3.

[0066] Mode 13: Rubber composition according to any one of modes 1 to 12 in which the mass content of carbon black is greater than 95% of the mass of the reinforcing filler and less than or equal to 100% of the mass of the reinforcing filler.

[0067] Mode 14: Rubber composition according to any one of modes 1 to 13 wherein the hydrocarbon plasticizing resin is a resin of a C5 fraction and C9 fraction copolymer.

[0068] Mode 15: Rubber composition according to any one of modes 1 to 14 in which the carbon black has a BET specific surface area greater than 90 m 2 / g.

[0069] Mode 16: Rubber composition according to any one of modes 1 to 15 wherein the carbon black has a BET specific surface area greater than 100 m 2 / g.

[0070] Mode 17: Rubber composition according to any one of modes 1 to 16 in which the carbon black has a BET specific surface area of ​​less than 145 m 2 / g.

[0071] Mode 18: A rubber composition according to any one of modes 1 to 17 wherein the carbon black has a BET specific surface area of ​​less than 130 m 2 / g.

[0072] Mode 19: Rubber composition according to any one of modes 1 to 18, which composition contains 0 to less than 3 pce of a plasticizer selected from liquid plasticizers and plasticizing resins other than C5-cut homopolymer resins, C5-cut copolymer resins, C9-cut homopolymer resins and C9-cut copolymer resins.

[0073] Mode 20: Rubber composition according to any one of modes 1 to 19, in which the liquid plasticizer content is less than 3 pce.

[0074] Mode 21: Rubber composition according to any one of modes 1 to 20, which composition does not contain a liquid plasticizer.

[0075] Mode 22: Rubber composition according to any one of modes 1 to 21, which composition does not contain a plasticizer other than a hydrocarbon plasticizing resin selected from the group consisting of C5 cut homopolymer resins, C5 cut copolymer resins, C9 cut homopolymer resins and C9 cut copolymer resins.

[0076] Mode 23: Rubber composition according to any one of modes 1 to 22, which composition does not contain a plasticizer other than a resin of a C5- and C9-fraction copolymer.

[0077] Mode 24: Rubber composition according to any one of modes 1 to 23 in which the content of highly saturated diene elastomer is greater than 95 pce, is preferably equal to 100 pce.

[0078] Mode 25: Rubber composition according to any one of modes 1 to 24, which composition contains a vulcanization system.

[0079] Mode 26: Rubber composition according to any one of modes 1 to 25, wherein the highly saturated diene elastomer contains 1,4-units of trans configuration which represent more than 50 mole % of the 1,4-units of the highly saturated diene elastomer.

[0080] Mode 27: Rubber composition according to any one of modes 1 to 26, wherein the highly saturated diene elastomer contains 1,4-units of trans configuration which represent more than 80 mole % of the 1,4-units of the highly saturated diene elastomer.

[0081] Mode 28: Tire which comprises a tread, the portion of which intended to be in contact with the rolling ground consists entirely or partly of a rubber composition defined according to any one of modes 1 to 27.

[0082] Mode 29: Tire according to mode 28, which tire is a heavy goods vehicle tire or a civil engineering vehicle tire.

[0083] 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 purposes. Examples [000841 Determination of the microstructure of elastomers by nuclear magnetic resonance (NMR): Ethylene and 1,3-butadiene copolymers are characterized by NMR spectrometry 1 H, 13 C. NMR spectra are recorded on a Brüker Avance III 500 MHz Spectrometer equipped with a BBIz-grad 5 mm “broadband” cryoprobe. The NMR experiment 1Quantitative H, uses a single 30° pulse sequence and a 5-second repetition delay between each acquisition. 64 to 256 accumulations are performed. The NMR experiment 13 Quantitative C uses a 30° single-pulse sequence with proton decoupling and a 10-second repetition delay between each acquisition. 1024 to 10240 accumulations are performed. Two-dimensional experiments 1 H / 13 C are used for the purpose of determining the structure of polymers. The determination of the microstructure of copolymers is defined in the literature, according to the article by Llauro et al., Macromolecules 2001, 34, 6304-6311. NMR measurements are carried out at 25°C. The copolymers are dissolved in a deuterated solvent (approximately 25 mg of elastomer in 1 mL), generally deuterated chloroform (CDCI3).

[0085] Glass transition temperature of polymers: The glass transition temperature (Tg) is measured using a differential scanning calorimeter according to ASTM D3418 (1999).

[0086] Mooney Viscosity: Mooney viscosity is measured using an oscillating consistometer as described in ASTM D1646 (1999). The measurement is carried out according to the following principle: the sample analyzed in the raw state (i.e., before curing) is molded (shaped) in a cylindrical enclosure heated to a given temperature (100°C). After 1 minute of preheating, the rotor rotates within the specimen at 2 revolutions / minute and the torque needed to maintain this movement is measured after 4 minutes of rotation. Mooney viscosity (ML) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Newton meters).

[0087] Size exclusion chromatography (SEC / RI): Size exclusion chromatography (SEC) allows the fractionation of polymer chains in a solvent according to their hydrodynamic volume. Like any chromatographic system, the technique is based on the elution of a solute (the polymer) through a column containing a stationary phase. The system is composed in this order: a solvent reservoir, a pumping system, an injector, a set of columns and detectors. The measurement chain is equipped with a Waters Alliance e2695 module and a Waters fRI410 refractometer. The mobile phase is eluted with a flow rate of 1 mL / min. The polymer is solubilized in THF at a concentration of 1 g / L. A volume of 100 pL is injected through a set of 3 AGILENT size exclusion chromatography columns (MIXED B LS). The columns are thermostated in an oven at 35°C. The stationary phase of the columns is based on a polystyrene divinylbenzene gel with controlled porosity. The polymer chains are separated according to the hydrodynamic volume they occupy when they are solubilized in the solvent. The larger the volume, the less accessible the column pores are and the shorter their elution time. Detection is ensured by a refractometer (RI) thermostated at 35°C. Each elution volume is associated with a mass via Moore calibration (certified standard passage: standard polystyrenes from Polymer Standard Service (Mainz). The WATERS: EMPOWER software is used for data acquisition and analysis. It is then possible to determine the number-average molar masses (Mn), the mass-average molar masses (Mw) as well as the dispersity (D = Mw / Mn).

[0088] Mechanical resistance in the presence of crack initiation (tearability): The force and tear deformation are measured on a specimen stretched at 375 mm / min to cause the specimen to break. The tensile specimen consists of a parallelepiped-shaped rubber plate, 2.5 mm thick, 84 mm long and 10 mm wide. 3 very fine notches, 3 mm long, are made using a razor blade, halfway along and aligned in the width direction of the specimen, before starting the test. The force (N / mm) to be exerted to achieve rupture is determined and the elongation at break is measured. The Energy to cause rupture ("Tearability") of the specimen can be determined, which is the product of the force and the elongation at break. The test was conducted in air at a temperature of 100°C. High values ​​indicate good cohesion of the rubber composition although there are signs of cracking.

[0089] Dynamic properties: The dynamic properties are measured on a viscoanalyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a sample of the vulcanized composition (cylindrical specimens 4 mm thick and 400 mm2 in cross-section), subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, is recorded. For the measurements of dynamic complex shear modulus (G*) and the tanô loss factor, a strain amplitude sweep is carried out from 0.1% to 100% peak-peak (forward cycle), then from 100% to 0.1% peak-peak (return cycle) at 60°C. For the forward cycle, the maximum tanô value observed is indicated, noted tanô(max). The greater the value of tanô(max), the greater the hysteresis, which leads to higher rolling resistance of a tire containing the rubber composition.

[0090] Preparation of rubber compositions: It is introduced into an internal mixer of volume: 3300 cm 3 (final filling rate: approximately 70% by volume), whose initial tank temperature is approximately 50°C, successively the elastomer, the reinforcing filler, if applicable the plasticizing hydrocarbon resin, the secondary accelerators as well as the various other ingredients with the exception of the sulfur and the primary accelerator. A thermomechanical work is then carried out (non-productive phase) in one step, which lasts a total of approximately 3 to 4 minutes, until a maximum "drop" temperature of 160°C is reached. The mixture thus obtained is recovered, cooled and then the sulfur and the accelerator are incorporated primary on an external mixer (roller mixer) at 30°C, mixing everything (productive phase) for 10 minutes.

[0091] The details of the formulations of the compositions are shown in Table 1.

[0092] The compositions thus obtained are then calendered, either in the form of plates (with a thickness ranging from 2 to 3 mm) or thin sheets of rubber, for the measurement of their physical or mechanical properties after vulcanization at 140°C (cooked state), or in the form of profiles which can be used directly, after cutting and / or assembly to the desired dimensions, for example as semi-finished products for tires.

[0093] The copolymer of ethylene and 1,3-butadiene, elastomer El, is synthesized according to the procedure described below. All reagents are obtained commercially except for the metallocene which can be prepared according to the procedure described in WO 2007054224. Butyloctylmagnesium BOMAG (20% in heptane, C = 0.88 mol.L -1) comes from Chemtura and is transferred and stored in a Schlenk tube under an inert atmosphere. The ethylene, N35 grade, comes from Air Liquide and is used without prior purification. The polymerization of ethylene and 1,3-butadiene is carried out according to a continuous process in solution in methylcyclohexane at 80°C under 10 bar in the presence of a catalytic system (195 pmoles Nd per 100 g of monomers), the mass concentration of monomer feed in the reactor being 7%, the mass ratio 1,3-butadiene / ethylene being 0.79, the molar ratio active Mg / Nd being 2.7. The additional Mg to reach a ratio of 2.7 is provided by an addition of BOMAG in the polymerization medium. At the desired conversion (83%, 120 minutes) to reach an Mn of approximately 160,000 g / mol, the polymerization is stopped at the line outlet using a solution of antioxidants in methylcyclohexane (0.8 pce of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 0.7 pce of 2,2'-methylene-bis(4-methyl-6-tertbutylphenol, pce: part by weight per hundred parts of elastomer). The copolymer is recovered by a steam distillation process called "stripping" well known to those skilled in the art, then dried on a worm machine equipped with a single screw.

[0094] The copolymer contains 69% ethylene unit, 23% butadiene unit (1,2 unit and 1,4 unit which is more than 80% in the form of 1,4-trans) and 8% cyclic unit (1,2-cyclohexane unit). Its transition temperature is -43°C (AT of 5°C, the AT being the temperature difference between the beginning of the glass transition and its end), its Mn of 157700 g / mol, its ML (1+4) at 100°C of 69.

[0095] The catalytic system is a preformed catalytic system. It is prepared in methylcyclohexane from a metallocene, [Me2Si(Flu)2Nd(p-BH4)2Li(THF)] at 0.0065 mol / L, a co-catalyst, butyloctylmagnesium (BOMAG) whose BOMAG / Nd molar ratio is equal to 2.2, and a preformed monomer, 1,3-butadiene whose 1,3-butadiene / Nd molar ratio is equal to 90. The medium is heated to 80°C for a period of 5h. It is prepared according to a preparation method in accordance with paragraph 11.1 of patent application WO 2017093654 Al.

[0096] Results : The results are shown in Tables 2 and 3. The results are expressed on a base of 100 relative to a control ([value of the composition considered / value of the control composition]xl00). A value greater than 100 indicates a value higher than that of the control.

[0097] Compositions C1 to C3, which contain a highly saturated diene elastomer, a carbon black, and a hydrocarbon plasticizing resin, a C5- and C9-fraction copolymer resin, are all in accordance with the invention. Composition C0, which differs from compositions C1 to C3 in that it does not contain the hydrocarbon plasticizing resin, is a control composition of C1 to C3. Composition C4, which also does not contain the hydrocarbon plasticizing resin, is a composition not in accordance with the invention. It differs from C0 in that the carbon black is an N134 grade carbon black instead of an N234 grade carbon black. Due to its higher specific surface area, the N134 grade is known to be more reinforcing than an N234 grade.

[0098] The rubber compositions T0 and T1 which do not contain a highly saturated diene elastomer, but a highly unsaturated diene elastomer, an SBR containing 26.5% styrene unit (% by mass), are not in accordance with the invention and are reference compositions. The composition T0 which differs from the composition T1 in that it does not contain the hydrocarbon plasticizing resin is the control composition for the composition T1.

[0099] Table 3 shows that the addition of the hydrocarbon plasticizing resin to a carbon black-reinforced rubber composition containing a highly saturated diene elastomer significantly increases the tear strength performance: +39 points for C2 and +81 points for C3. This technical effect of the addition of the hydrocarbon plasticizing resin to the rubber composition containing the highly unsaturated diene elastomer is not observed: the addition of 6 phr of the hydrocarbon plasticizing resin results in a tear strength performance index of 98 for T2 compared to 100 for T1 (Table 2). From the point of view of tear strength performance, a synergy is therefore unexpectedly observed in using the plasticizing hydrocarbon resin and the highly saturated diene elastomer together in the carbon black-reinforced rubber composition. [000100] Furthermore, these gains are obtained with a compromise between the performance of tear resistance and hysteresis which is particular. In the case of the highly unsaturated elastomer, the use of the hydrocarbon plasticizing resin not only does not improve the tear resistance, but causes an increase in hysteresis. In the case of the highly saturated elastomer, the addition of the hydrocarbon plasticizing resin at 3 pce makes it possible to achieve a compromise of performance between tear resistance and hysteresis comparable to that obtained with a rubber composition containing a more reinforcing carbon black (composition C4), and even this compromise is improved in the case of the addition of 6 pce. [000101] Table 1 (1) SBR containing 26.5% styrene unit (mass %) and 24% 1,2-unit of the butadiene part (Tg = - 48°C) (2) BR Neodymium containing 98% 1,4-cis butadiene unit (Tg = -108°C) (3) Elastomer El (4) Carbon black N134 (BET 145 m 2 / g) (5) Carbon black N234 (BET 120 m 2 / g) (6) Anti-ozone wax “VARAZON 4959” from the company Sasol Wax (7) N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine “Santoflex 6PPD” from Flexys (8) C5 cut / C9 cut resin “THER 8644” with a Tg of 44°C, marketed by the company Cray Valley (9) Stearin “Pristerene 4931” from Uniqema company (10) Industrial grade zinc oxide from Umicore (11) N-cyclohexyl-2-benzothiazyl sulfenamide “Santocure CBS” from Flexys (12) Tetrabenzylthiuram disulfide (0.3 pce, “Perkacit TBZTD” from Flexsys) and diphenylguanidine (0.5 pce, “Perkacit DPG” from Flexsys) [000102] Table 2 [000103] Table 3

Claims

Claims 1. A rubber composition which comprises more than 90 phr of a highly saturated diene elastomer which is a copolymer of ethylene and 1,3-butadiene and which contains more than 50 mol% of ethylene units, between 30 phr and 55 phr of a reinforcing filler which contains more than 50% by mass of a carbon black, more than 1 phr to less than 15 phr of a hydrocarbon plasticizing resin which is selected from the group consisting of C5-cut homopolymer resins, C5-cut copolymer resins, C9-cut homopolymer resins and C9-cut copolymer resins.

2. Rubber composition according to claim 1 in which the highly saturated diene elastomer comprises at least 60 mol% of ethylene unit, preferably at least 65 mol% of ethylene unit.

3. A rubber composition according to claim 1 or 2 wherein the highly saturated diene elastomer is a random copolymer.

4. Rubber composition according to any one of claims 1 to 3 in which the level of the hydrocarbon plasticizing resin varies from 2 to 10 pce.

5. Rubber composition according to any one of claims 1 to 4 in which the level of the reinforcing filler varies from 35 pce to 50 pce, preferably from 35 pce to 45 pce.

6. Rubber composition according to any one of claims 1 to 5 in which the mass ratio between the level of reinforcing filler and the level of plasticizing hydrocarbon resin is greater than 3.

7. Rubber composition according to any one of claims 1 to 6 in which the mass content of carbon black is greater than 95% of the mass of the reinforcing filler and less than or equal to 100% of the mass of the reinforcing filler.

8. Rubber composition according to any one of claims 1 to 7 in which the hydrocarbon plasticizing resin is a resin of a C5 cut and C9 cut copolymer.

9. A rubber composition according to any one of claims 1 to 8 wherein the carbon black has a BET specific surface area greater than 90 m 2 / g, preferably greater than 100 m 2 / g.

10. A rubber composition according to any one of claims 1 to 9 wherein the carbon black has a BET specific surface area of ​​less than 145 m 2 / g.

11. A rubber composition according to any one of claims 1 to 10 wherein the carbon black has a BET specific surface area of ​​less than 130 m 2 / g.

12. Rubber composition according to any one of claims 1 to 11 in which the content of the highly saturated diene elastomer is greater than 95 pce, is preferably equal to 100 pce.

13. A rubber composition according to any one of claims 1 to 12, which composition contains a vulcanization system. A tire which comprises a tread, the portion of which intended to be in contact with the rolling ground is made up entirely or in part of a rubber composition defined according to any one of claims 1 to 13. A tire according to claim 14, which tire is a tire for a heavy goods vehicle or a tire for a civil engineering vehicle.

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