Rubber composition

Abstract

The invention relates to a rubber composition comprising more than 90 parts per million (ppm) of a highly saturated diene elastomer that is a copolymer of ethylene and 1,3-butadiene and contains more than 50 mole percent of ethylene units, between 30 and 55 ppm of a reinforcing filler that contains more than 50 mass percent of carbon black, and more than 1 part to less than 15 ppm of 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. The composition, particularly when used in a tire tread for heavy-duty vehicles, exhibits good crack propagation resistance properties.

Description

Title of the invention: 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 copolymers with lower oxidation sensitivity in tire rubber compositions, such as highly saturated diene elastomers, namely ethylene-1,3-butadiene copolymers containing more than 50 mole percent ethylene. The use of these ethylene-1,3-butadiene copolymers in a tire tread is described, for example, in document WO 2014114607 A1 and results in 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 speeds, as described, for example, in document WO 2016012259 A1.

[0003] It is also important to have rubber compounds that exhibit good cohesion, particularly good resistance to crack propagation. Indeed, during rolling, a tire tread is subjected to mechanical stresses and aggressions resulting from direct contact with the ground. This leads to the formation of crack initiators. As they propagate on the surface or within the tread, these crack initiators can damage the tread material. This damage to the tread reduces the tire's tread life.Since the mechanical stresses and aggressions experienced by the tire are amplified by the weight it carries, good cohesion is particularly desirable for a compound intended for use as the tread of a tire mounted on a vehicle carrying heavy loads, such as a tire for a heavy goods vehicle or construction equipment. To increase the crack propagation resistance of a carbon black-reinforced rubber compound containing such a highly saturated diene elastomer, the Applicant described in document WO 2020053520 A1 the use of sulfur in the rubber compound at a rate of less than 1 part per annum and also lower than that of accelerators.

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

[0005] Thus, a first object of the invention is a rubber composition comprising more than 90 parts of a highly saturated diene elastomer which is a copolymer of ethylene and 1,3-butadiene and which contains more than 50 mole percent of ethylene units, between 30 parts and 55 parts of a reinforcing filler which contains more than 50 mass percent of a carbon black, more than 1 part but less than 15 parts of a hydrocarbon plasticizing resin which is selected from the group consisting of C5 cutting homopolymer resins, C5 cutting copolymer resins, C9 cutting homopolymer resins and C9 cutting copolymer resins.

[0006] Another object of the invention is a tire comprising a tread, the portion of which intended to be in contact with the road surface being made entirely or partially of a rubber composition according to 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., bounds a and b excluded) 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 bounds a and b).

[0008] The abbreviation "pce" means parts by weight per hundred parts of elastomer (of the total elastomers if several elastomers are present).

[0009] The compounds mentioned in the description may be of fossil origin or bio-based. 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 used, 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 "pneumatic" (in English, "tire") refers to a pneumatic or non-pneumatic tire. A pneumatic tire typically comprises two beads intended to contact a rim, a crown consisting of at least one crown reinforcement and a tread, and two sidewalls. The tire is reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic tire, on the other hand, typically 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 dimples. This structure is disposed between the base and the top. Such non-pneumatic bandages do not necessarily include a sidewall. Non-pneumatic bandages are described, for example, in documents WO 03 / 018332 and FR2898077. According to any one of the embodiments of the invention, the pneumatic according to the invention is preferably a pneumatic bandage.

[0011] Unless otherwise indicated, the rates of the 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. As is known, an ethylene unit is a monomer unit with the motif -(CH2-CH2)-. Also as is known, a butadiene unit is a monomer unit with the motif -CH2-CH(CH=CH2)- (unit 1,2) or -CH2-CH=CH-CH2- (unit 1,4) 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. The highly saturated diene elastomer contains more than 50 mole percent of 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 60% to 80 mol% ethylene units, particularly 60% to 75 mol% ethylene units, more particularly 65% ​​to 75 mol% ethylene units, molar percentage calculated on the basis of all monomer units of the highly saturated diene elastomer.

[0014] The highly saturated diene elastomer can be obtained by various synthetic methods known to those skilled in the art, particularly depending on the desired microstructure of the highly saturated diene elastomer. Generally, it can be prepared by copolymerization of 1,3-butadiene and ethylene and by methods of known syntheses, particularly in the presence of a catalytic system comprising a metallocene complex. Examples include catalytic systems based on metallocene complexes, which are described in patent applications EP 1 092 731, WO 2004035639, WO 2007054223, and WO 2007054224 filed by the Applicant. Highly saturated diene elastomers, including statistically saturated ones, can also be prepared by a process using a preformed catalytic system such as those described in the patent applications. WO 2017093654 Al, WO 2018020122 Al and WO 2018020123 Al. Advantageously, the diene elastomer is statistically significant and is preferably prepared by a semi-continuous or continuous process as described in the patent applications. WO 2017103543 Al, WO 201713544 Al, 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=CHJ- (h)

[0016] The presence of a saturated 6-member cyclic motif, 1,2-cyclohexane motif, of formula (I) in the copolymer can result from a series of very specific insertions of ethylene and 1,3-butadiene in 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 units of formula (I) and 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% molar, 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% by mole of the 1,4 units of the highly saturated diene elastomer, preferably more than 80% by mole of the 1,4 units of the highly saturated diene elastomer.

[0019] The highly saturated diene elastomer can be made up of a mixture of highly saturated diene elastomers which differ from each other by their microstructures or by their macrostructures.

[0020] The proportion of highly saturated diene elastomer in the rubber composition is greater than 90 parts by weight per hundred parts of elastomer in the rubber composition (pw). In the case where the highly saturated diene elastomer consists of a mixture of highly saturated diene elastomers that differ from one another by their microstructures or by their macrostructures, the proportion 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 in a mass percentage of less than 10 parts per mole. A diene elastomer is defined as an elastomer composed 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 selected from the group of highly unsaturated diene elastomers consisting of polymers containing 1,3-butadiene units or isoprene units, such as polybutadienes, butadiene copolymers, and isoprene copolymers. A highly unsaturated diene elastomer is defined as an elastomer containing more than 50 mole percent diene units.

[0022] The percentage of highly saturated diene elastomer in the rubber composition is preferably greater than 95 parts per million, advantageously equal to 100 parts per million. The greater the percentage 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 strengthen a rubber composition, particularly useful for manufacturing tire treads. 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, and more preferably between 20 and 150 nm. The reinforcing filler content is between 30 and 55 parts per cubic centimeter, preferably from 35 to 50 parts per cubic centimeter, and more preferably from 35 to 45 parts per cubic centimeter.

[0024] The reinforcing filler has the essential characteristic of containing more than 50% in up to 100% by mass of carbon black, mass percentages calculated relative to the mass of the reinforcing filler in the rubber compound. Preferably, the mass percentage 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. When the mass percentage of carbon black in the rubber compound 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 that is also known for its ability to reinforce a rubber compound suitable for tire manufacturing, for example, an inorganic reinforcing filler such as silica combined with a known coupling agent. Advantageously, the mass percentage of carbon black is equal to 100% of the mass of the reinforcing filler.

[0025] All reinforcing carbon blacks are suitable, particularly those conventionally used in tires or their treads (so-called tire-grade blacks). Among these, reinforcing carbon blacks of the 100, 200, and 300 series, or those of the 500, 600, or 700 series (ASTM grades), such as NI 15, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772, are particularly suitable. When the rubber compound according to the invention is used in a tread, the carbon black is preferably a carbon black from the 100 or 200 series.

[0026] Preferably, carbon black has a specific surface area BET greater than 90 m² / g. More preferably, the specific surface area BET of carbon black is greater than 100 m² / g. Preferably, carbon black has a specific surface area BET less than 145 m² / g. More preferably, carbon black has a specific surface area BET less than 130 m² / g.

[0027] The specific surface area BET is typically measured according to ASTM D6556-09 [multipoint method (5 points) - gas: nitrogen - relative pressure range P / P0: 0.05 to 0.30],

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

[0029] In a known manner, a C5 cut (or, for example, C9) is understood to mean any fraction obtained from a petrochemical or petroleum refining process, any distillation cut containing predominantly compounds having 5 (or 9 in the case of a C9 cut) carbon atoms; C5 cuts, for example, may contain, by way of illustration and not limitation, the following compounds, the relative proportions of which may vary depending on the production process, for example, of The origin of naphtha and the steam cracking process: 1,3-butadiene, butene-1,2-butenes, 1,2-butadiene, 3-methyl-l-butene, 1,4-pentadiene, 1-pentene, 2-methyl-l-butene, 2-pentenes, isoprene, cyclopentadiene (which may be present as its dimer dicyclopentadiene), piperylenes, cyclopentene, 1-methylcyclopentadiene, 1-hexene, methylcyclopentadiene, cyclohexene. These fractions can be obtained by all known chemical processes in the petroleum and petrochemical industries. By way of non-limiting examples, we can cite the steam cracking processes of naphtha or the fluid catalytic cracking processes of gasoline, these processes being able to be associated with all possible chemical treatments for the transformation of these fractions, known to the person 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, and are particularly useful as plasticizing or tackifying agents in polymer matrices. By nature, they are at least partially miscible (i.e., compatible) at the rates used with the polymer compositions for which they are intended, so as to act as true diluents. They have been described, for example, in the book entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander, and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9), Chapter 5 of which 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 classified as thermoplastic resins in that they soften upon heating and can thus 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 through a 0.45 µm 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 of the aliphatic / aromatic type, i.e., based on aliphatic and / or aromatic monomers. They can be natural or synthetic, petroleum-based or non-petroleum-based (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; - an average number molecular mass (Mn) 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 percentage of hydrocarbon plasticizing resin in the rubber composition is greater than 1 part per million (ppm) and less than 15 ppm. Below the stated minimum, the intended technical effect is insufficient, while above 15 ppm, the hysteresis of the rubber composition becomes too significant for its use in the tread of a tire for a vehicle designed to carry heavy loads. Preferably, the percentage of hydrocarbon plasticizing resin is between 2 and 10 ppm.

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

[0035] Preferably, the hydrocarbon plasticizing resin is a resin of a C5-cut and C9-cut 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 homopolymer resin, a C5 copolymer resin, a C9 homopolymer resin, or a C9 copolymer resin. A substance is considered liquid when, at room temperature (23°C), the substance, more or less viscous, is liquid; that is to say, a substance having the capacity to eventually take the shape of its container, in contrast to hydrocarbon plasticizing resins, which are by nature solid at room temperature.Examples of liquid plasticizers 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), mineral oils and mixtures thereof.

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

[0038] According to a particularly preferred embodiment of the invention, especially 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 selected from the group consisting of C5 cutting homopolymer resins, C5 cutting copolymer resins, C9 cutting homopolymer resins and C9 cutting copolymer resins, in particular other than a resin of a C5 cutting and C9 cutting copolymer.

[0039] Embodiments in which the liquid plasticizer content is less than 3 parts per annum are preferred to further optimize tear resistance and are preferred even more as the liquid plasticizer content is equal to 0.

[0040] The rubber composition may also include all or part of the usual additives commonly used in elastomer compositions intended to constitute treads, such as 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. Molecular sulfur is also referred to as molecular sulfur. A sulfur donor is defined as any compound that releases sulfur atoms, whether or not combined in a polysulfide chain, capable of inserting themselves into the polysulfide chains formed during vulcanization and bridging the elastomeric chains. The sulfur content in the rubber composition is preferably less than 2 parts per million (ppm), preferably between 0.3 and 1.5 ppm.

[0043] Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used as a vulcanization accelerator (primary or secondary). Examples include thiazole-type accelerators and their derivatives, sulfenamide-type accelerators for primary accelerators, and guanidine, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate-type accelerators for secondary accelerators. Guanidine is defined as any compound containing the divalent radical -HN-C(=NH)-NH-. Preferably, diphenylguanidine is the guanidine. The vulcanization accelerator is used at a preferential rate of between 0.3 and 5 parts per liter (ppw), more preferably between 0.5 and 2.5 ppw.

[0044] Examples of primary accelerators include sulfenamide compounds such as N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-ter-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] By way of example of secondary accelerators, thiuram polysulfides may be cited, 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-cy-clohexyl-2-benzothiazyl sulfenamide.

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

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

[0049] The rubber composition can 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 thermomechanical working or mixing phase (sometimes referred to as the "non-productive" phase) at high temperature, up to a maximum temperature 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 sulfur or the sulfur donor and vulcanization accelerator. As an 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 miscellaneous additives, with the exception of sulfur and the vulcanization accelerator, are introduced into a suitable mixer, such as a standard internal mixer. The total mixing time in this non-productive phase is preferably between 1 and 15 minutes. After the mixture obtained in the first non-productive phase has cooled, the sulfur and the vulcanization accelerator are then incorporated at low temperature, generally in an external mixer such as a roller mixer. The mixture is then blended (productive phase) for a few minutes, for example, between 2 and 15 minutes.

[0050] When the vulcanization system includes a primary accelerator and a secondary accelerator, the rubber compound is preferably manufactured by a process comprising a first step, step a), in which the constituents of the rubber compound, with the exception of sulfur and the primary accelerator, are mixed by kneading, in particular thermomechanical kneading, and a second step, step b), in which the sulfur and the primary accelerator are incorporated into the kneaded mixture comprising the elastomer, the reinforcing filler, and the secondary accelerator. In 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 above 110°C, preferably between 110°C and 190°C, advantageously above 130°C and below 180°C.The temperature ranges between 110°C and 190°C and between 130°C and 180°C correspond to the maximum temperatures reached by the mixed mixture in the mixer during step a). Typically, mixing during step a) is continued until the mixed mixture reaches the maximum mixing temperature before being removed from 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 collected and then cooled to allow for step b), which is carried out at a lower temperature, in this case below 110°C, preferably between 40°C and 100°C. During step b), the incorporation of sulfur and primary accelerator into the rubber composition is typically carried out by kneading in an external mixer such as a roller mixer, usually for a period of 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 compound is extruded to form all or part of a tire tread profile. Then, during assembly In a tire typically comprising, radially from the outside in, a tread, a crown reinforcement, and a carcass reinforcement, the tread is laid radially on the outside of the crown reinforcement. Radially means in a known radial direction relative to the tire's axis of rotation.

[0052] The tire may be in its raw state (i.e., before the tire curing stage) or in its cured state (i.e., after the tire curing stage). 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 construction equipment, preferably a tire for a heavy goods vehicle.

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

[0054] Mode 1: Rubber composition comprising more than 90 parts per annum of a highly saturated diene elastomer which is a copolymer of ethylene and 1,3-butadiene and which contains more than 50 mole percent of ethylene units, between 30 parts per annum and 55 parts per annum of a reinforcing filler which contains more than 50 mass percent of a carbon black, more than 1 part per annum of a hydrocarbon plasticizing resin which is selected from the group consisting of C5 cutting homopolymer resins, C5 cutting copolymer resins, C9 cutting homopolymer resins and C9 cutting copolymer resins.

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

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

[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% ethylene units.

[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% ethylene units.

[0059] Mode 6: Rubber composition according to any one of modes 1 to 5 in which the highly saturated diene elastomer contains formula units (I) or formula units (II). -CH2-CH(CH=CH2)- (11)

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

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

[0062] Mode 9: Rubber composition according to any one of modes 1 to 8 in which the rate of hydrocarbon plasticizing resin varies from 2 to 10 parts per cent.

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

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

[0065] Mode 12: Rubber composition according to any one of modes 1 to 11 in which the mass ratio between the rate of reinforcing filler and the rate of 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 percentage 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 in which the hydrocarbon plasticizing resin is a resin of a C5-cut and C9-cut copolymer.

[0068] Mode 15: Rubber composition according to any one of modes 1 to 14 in which the carbon black has a specific surface area BET greater than 90 m2 / g.

[0069] Mode 16: Rubber composition according to any one of modes 1 to 15 in which the carbon black has a specific surface area BET greater than 100 m2 / g.

[0070] Mode 17: Rubber composition according to any one of modes 1 to 16 in which the carbon black has a specific surface area BET of less than 145 m2 / g.

[0071] Mode 18: Rubber composition according to any one of modes 1 to 17 in which the carbon black has a specific surface area BET of less than 130 m2 / g.

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

[0073] Mode 20: Rubber composition according to any one of modes 1 to 19, wherein the liquid plasticizer content is less than 3 parts per cent.

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

[0075] Mode 22: Rubber composition according to any one of modes 1 to 21, which composition does not contain any 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 any plasticizer other than a resin of a C5-cut and C9-cut copolymer.

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

[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 trans configuration units that represent more than 50% by 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 trans configuration units that represent more than 80% by mole of the 1,4 units of the highly saturated diene elastomer.

[0081] Mode 28: Tire which includes a tread, the portion of which is intended to be in contact with the road surface being made up of all or part of a rubber composition defined according to any one of modes 1 to 27.

[0082] Mode 29: Pneumatic according to mode 28, which pneumatic is a heavy vehicle pneumatic or a construction vehicle pneumatic.

[0083] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of several examples of embodiments of the invention, given by way of illustration. Examples

[0084] Determination of the microstructure of elastomers by nuclear magnetic resonance (NMR): Ethylene-1,3-butadiene copolymers are characterized by ¹H and ¹³C NMR spectroscopy. NMR spectra are recorded on a Brüker Avance III 500 MHz spectrometer equipped with a 5 mm BBIz-grad "broadband" cryo-probe. The quantitative ¹H NMR experiment uses a single 30° pulse sequence and a 5-second repetition delay between acquisitions. 64 to 256 accumulations are performed. The quantitative ¹³C NMR experiment uses a single 30° pulse sequence with proton decoupling and a 10-second repetition delay between acquisitions. 1024 to 10240 accumulations are performed. The two-dimensional ¹H / ¹³C experiments are used to determine the polymer structure. 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 performed at 25°C. The copolymers are in solution in a deuterated solvent (approximately 25mg of elastomer in ImL), generally deuterated chloroform (CDC13).

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

[0086] Moonev viscosity: Mooney viscosity is measured using an oscillating consistometer as described in ASTM D1646 (1999). The measurement is performed according to the following principle: the sample being analyzed in its raw state (i.e., before cooking) is molded (shaped) in a cylindrical chamber heated to a given temperature (100°C). After 1 minute of preheating, the rotor rotates inside the specimen at 2 revolutions per minute, and the torque required to maintain this rotation 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 consists, in this order, of 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 at 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 three AG1LENT (MIXED B LS) size-exclusion chromatography columns is used. The columns are temperature-controlled 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 dissolved in the solvent. The larger the volume, the less accessible the column pores are to them, and the shorter their elution time. Detection is performed using a refractometer (RI) temperature-controlled at 35°C. Each elution volume is associated with a mass via Moore calibration (certified standard: Polymer Standard Service (Mainz) standard polystyrenes). 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 a crack initiation point (tearability): The force and tear strength are measured on a specimen stretched at 375 mm / min to induce fracture. The tensile specimen consists of a parallelepiped-shaped rubber plate, 2.5 mm thick, 84 mm long, and 10 mm wide. Three very fine notches, 3 mm long, are made with a razor blade, at mid-length and aligned across the width of the specimen, before the test begins. The force (N / mm) required to induce fracture is determined, and the elongation at break is measured. The energy required to cause fracture ("tear strength") of the specimen, which is the product of the force and the elongation at break, can then be determined. The test was conducted in air at a temperature of 100°C. High values ​​indicate good cohesion of the rubber composition, although showing signs of cracking.

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

[0090] Preparation of rubber compositions: The elastomer, reinforcing filler, and, if applicable, hydrocarbon plasticizing resin, secondary accelerators, and various other ingredients (excluding sulfur and the primary accelerator) are successively introduced into an internal mixer with a volume of 3300 cm³ (final filling rate: approximately 70% by volume), whose initial tank temperature is approximately 50°C. A single-stage thermomechanical process (non-productive phase) is then carried out, lasting approximately 3 to 4 minutes, until a maximum "drop" temperature of 160°C is reached. The resulting mixture is collected, cooled, and then the sulfur and primary accelerator are incorporated into an external mixer (roller mixer) at 30°C, where the mixture is blended for 10 minutes (productive phase).

[0091] The details of the composition formulations 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 (cured state), or in the form of profiles directly usable, after cutting and / or assembly to the desired dimensions, for example as semi-finished products for tires.

[0093] The ethylene and 1,3-butadiene copolymer, El elastomer, is synthesized according to the procedure described below. All reagents are commercially available except for metallocene, which can be prepared according to the procedure described in document WO 2007054224. Butylloctylmagnesium BOMAG (20% in heptane, C = 0.88 mol / L*) is sourced from Chemtura and is transferred and then stored in a Schlenk tube under an inert atmosphere. The N35 grade ethylene is sourced from Air Liquide and is used without prior purification. The polymerization of ethylene and 1,3-butadiene is carried out by 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 into the reactor being 7%, the mass ratio of 1,3-butadiene / ethylene being 0.79, the molar ratio of active Mg / Nd being 2.7. The additional Mg to reach a ratio of 2.7 is provided by the addition of BOMAG in the polymerization medium. At the desired conversion (83%, 120 minutes) to achieve a Mn of approximately 160,000 g / mol, polymerization is stopped at the line outlet using an antioxidant solution in methylcyclohexane (0.8 wt. of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 0.7 wt. of 2,2'-methylene-bis(4-methyl-6-tert-butylphenol, wt.: wt. part by weight per percent parts). of elastomer). The copolymer is recovered by a steam entrainment process called "stripping" well known to those skilled in the art, then dried on a screw conveyor equipped with a single screw.

[0094] The copolymer contains 69% ethylene units, 23% butadiene units (1,2-unit and 1,4-unit, the latter being more than 80% in the 1,4-trans form) and 8% cyclic units (1,2-cyclohexane motif). Its transition temperature is -43°C (AT of 5°C, AT being the temperature difference between the beginning and end of the glass transition), its Mn is 157,700 g / mol, and its ML (1+4) at 100°C is 69.

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

[0096] Results: The results are shown in Tables 2 and 3. Results are expressed as a percentage of 100 relative to a control ([value of the composition considered / value of the control composition]x00). 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, carbon black, and a hydrocarbon plasticizing resin, a C5-cut copolymer resin, and a C9-cut 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 N134 grade carbon black instead of N234 grade carbon black. Due to its higher specific surface area, N134 grade is known to be more reinforcing than N234 grade.

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

[0099] Table 3 shows that the addition of the hydrocarbon plasticizing resin to a carbon black-reinforced rubber composition containing an elastomer Highly saturated diene elastomer significantly increases tear resistance performance: +39 points for C2 and +81 points for C3. This technical effect of adding hydrocarbon plasticizing resin to the rubber composition containing highly unsaturated diene elastomer is not observed: the addition of 6 parts hydrocarbon plasticizing resin results in a tear resistance performance index of 98 for T2 compared to 100 for T1 (Table 2). From a tear resistance performance standpoint, an unexpected synergy is therefore observed when using hydrocarbon plasticizing resin and highly saturated diene elastomer together in a carbon black-reinforced rubber composition.

[0100] Moreover, these gains are achieved with a particular trade-off between tear resistance and hysteresis performance. In the case of the highly unsaturated elastomer, the use of the hydrocarbon plasticizing resin not only fails to improve tear resistance but also increases hysteresis. In the case of the highly saturated elastomer, the addition of the hydrocarbon plasticizing resin at 3 parts per cubic centimeter (ppc) makes it possible to achieve a performance trade-off between tear resistance and hysteresis comparable to that obtained with a rubber composition containing a more reinforcing carbon black (C4 composition), and this trade-off is even improved with the addition of 6 ppc.

[0101] [Tables 1] Composition T0 Tl CO Cl C2 C3 C4 SBR(l) 80 80 BR (2) 20 20 EBR (3) 100 100 100 100 100 Carbon black (4) 58 58 40 Carbon black (5) 40 40 40 40 Ozone-blocking wax (6) 1 1 1 1 1 1 1 Antioxidant (7) 2 2 2 2 2 2 2 Hydrocarbon plasticizing resin (8) 6 3 6 9 Stearic acid (9) 2 2 2 2 2 2 2 ZnO (10) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Primary accelerator (H) 1.1 1.1 0.5 0.5 0.5 0.5 0.5 Secondary accelerator (12) 0.8 0.8 0.8 0.8 0.8 Sulfur 1.1 1.1 0.5 0.5 0.5 0.5 0.5 (1) SBR containing 26.5% styrene motif (% mass) and 24% 1,2 motif of the butadiene part (Tg = - 48°C) (2) BR Neodymium containing 98% of 1,4-cis butadiene motif (Tg = -108°C) (3) Elastomer (4) Carbon black N134 (BET of 145 m2 / g) (5) Carbon black N234 (BET of 120 m2 / g) (6) Anti-ozone wax “VARAZON 4959” from the company Sasol Wax (7) N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine “Santaflex 6PPD” from the company Flexys (8) C5 / C9 cutting resin “THER 8644” with a Tg of 44°C, marketed by the Cray Valley company (9) Stearine “Pristerene 4931” from the company Uniqema (10) Industrial grade zinc oxide from Umicore (11) N-cyclohexyl-2-benzothiazyl sulfenamide “Santocure CBS” from the company Flexys (12) Tetrabenzylthiuram disulfide (0.3 pc, “Perkacit TBZTD” of the company

[0102] Flexsys) and diphenylguanidine (0.5 pc, [Tables 2] “Perkacit DPG” from Flexsys) Composition TO Tl Tearability 100 98 tanô(max) 100 107

[0103] [Tables3] Composition CO Cl C2 C3 C4 Tearability 100 139 181 278 145 tanô(max) 100 102 107 114 107

Claims

1.

2.

3.

4.

5.

6.

7.

8.

9.

10. Claims 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. Rubber composition according to claim 1 wherein the highly saturated diene elastomer comprises at least 60 mol% of ethylene unit, preferably at least 65 mol% of ethylene unit. Rubber composition according to claim 1 or 2 in which the highly saturated diene elastomer is a random copolymer. 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. Rubber composition according to any one of claims 1 to 4 in which the level of reinforcing filler varies from 35 pce to 50 pce, preferably from 35 pce to 45 pce. 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. 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. A rubber composition according to any one of claims 1 to 7 wherein the hydrocarbon plasticizing resin is a resin of a C5- and C9-fraction copolymer. 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 m2 / g, preferably greater than 100 m2 / g. A rubber composition according to any one of claims 1 to 9 wherein the carbon black has a BET specific surface area in-

11.

12.

13.

14.

15. lower than 145 m2 / g. 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 m2 / g. Rubber composition according to any one of claims 1 to 11 in which the content of highly saturated diene elastomer is greater than 95 pce, and is preferably equal to 100 pce. 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 consists entirely or partly of a rubber composition defined according to any one of claims 1 to 13. A tire according to claim 14, which tire is a heavy goods vehicle tire or a civil engineering vehicle tire.