Rubber composition

Abstract

This invention relates to rubber compositions based on: - at least one elastomer matrix comprising at least one polyisoprene at 45 phr to 80 phr and at least one highly saturated diene elastomer at 20 phr to 55 phr, - an aliphatic diacid dialkyl ester plasticizer, - carbon black, and - a crosslinking system, wherein the highly saturated diene elastomer is a copolymer of ethylene and 1,3-diene.

Description

Technical Field

[0001] The field of the present invention is a rubber composition reinforced with carbon black and containing a highly saturated diene elastomer, said rubber composition being particularly intended for use in tires, and more particularly for tire sidewalls. Background Technology

[0002] A tire typically comprises two beads intended to contact the 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. The sidewall is an elastomeric layer disposed outside the carcass reinforcement relative to the tire cavity, located between the crown and the beads, to completely or partially cover the area of ​​the carcass reinforcement extending from the crown to the beads.

[0003] In conventional tire manufacturing, the various components that make up the tread, carcass reinforcement, bead, and sidewall are assembled to form the tire outer casing. Following the assembly step and preceding the curing step is a shaping process that forms the outer casing to give the components a ring-shaped form.

[0004] Tires (especially the sidewalls) are subjected to numerous mechanical stresses that cycle repeatedly during rolling. These stresses (in the form of bending and compressive stresses) test the tire's durability and can shorten its lifespan. One way to improve tire durability is to enhance the fatigue resistance of the rubber composition that makes up the tire. For example, patents EP 722 977B1 and EP547 344B1 describe the use of rubber compositions with a generally less than 125 μm... 2 / g, or even much less than 100m 2 The low surface area of ​​silica ( / g) is beneficial for fatigue resistance.

[0005] Furthermore, tire sidewalls are also exposed to ozone. Deformation cycles combined with ozone exposure can cause cracks or fissures in the sidewalls, rendering the tire unusable without tread wear. Therefore, there is a need for highly cohesive rubber compositions, for example, those capable of withstanding large deformations without breaking, to form tire sidewalls.

[0006] To minimize the effects of ozone on rubber compositions, a known practice is to use copolymers with reduced oxidation sensitivity, such as highly saturated diene elastomers containing ethylene units in a molar content greater than 50 mol% of the elastomer monomer units. For example, copolymers of ethylene and 1,3-diene containing more than 50 mol% ethylene, particularly copolymers of ethylene and 1,3-butadiene, can be mentioned. For instance, WO 2014114607A1 describes the use of such ethylene and 1,3-butadiene copolymers in tire treads, which impart good rolling resistance and abrasion resistance to the tire. Similarly, EP 2 682 423 A1 describes the use of ethylene and 1,3-diene copolymers in sidewall compositions to increase resistance to ozone action.

[0007] Meanwhile, some literature, such as WO 2020011003 A1, mentions the use of aliphatic dialkyl diacid ester plasticizer (diisooctyl sebacate) as a possible plasticizer in polyethylene compositions without discussing any specific effects associated with the use of the plasticizer.

[0008] In the field of tires containing highly saturated diene elastomers, there is still a need to further improve the balance between the durability, deformability and hysteresis properties of rubber compositions (especially those used for tire sidewalls).

[0009] During the research, the applicant discovered that the use of specific plasticizers in rubber compositions containing highly saturated copolymers based on ethylene and diene units can improve the balance between the composition's durability, deformability, and hysteresis properties. Summary of the Invention

[0010] Therefore, the first subject of the present invention is a rubber composition based on at least one elastomer matrix comprising at least one polyisoprene at 45 phr to 80 phr and at least one highly saturated diene elastomer at 20 phr to 55 phr; an aliphatic diacid dialkyl ester plasticizer, carbon black and a crosslinking system; wherein the highly saturated diene elastomer is a copolymer of ethylene and 1,3-diene.

[0011] Another subject of the invention is a pneumatic or non-pneumatic tire that comprises a composition according to the invention, preferably comprising the composition according to the invention in at least one sidewall of the pneumatic or non-pneumatic tire.

[0012] I-Definition

[0013] The statement “composition based” should be understood to mean that the composition comprises a mixture of various basic ingredients used and / or in-situ reaction products, some of which are capable of reacting with each other at least partially and / or intended to react with each other at various stages of the composition’s manufacture; thus the composition may be in a fully or partially crosslinked state or in a non-crosslinked state.

[0014] For the purposes of this invention, the expression “parts by weight / 100 parts by weight elastomer” (or phr) should be understood as representing parts by weight per 100 parts by mass of elastomer.

[0015] In this document, all percentages (%) shown are mass percentages (%) unless otherwise explicitly stated.

[0016] Furthermore, any numerical range expressed as "between a and b" represents a range of values ​​extending from greater than a to less than b (i.e., excluding the limits a and b), while any numerical range expressed as "a to b" represents a range of values ​​extending from a to b (i.e., including the strict limits a and b). In this document, when a numerical range is expressed as "a to b," it is also preferable to express a range expressed as "between a and b."

[0017] In this application, the expression "all monomer units of the elastomer" or "total amount of elastomer monomer units" refers to all repeating units of the elastomer produced by the polymerization of monomers into the elastomer chain. Unless otherwise stated, the content of monomer units or repeating units in a highly saturated diene elastomer is expressed as a molar percentage calculated based on all monomer units of the elastomer.

[0018] For the purposes of this invention, when referring to a "major" compound, it should be understood to mean that among compounds of the same type in the composition, this compound is dominant, that is, it is the compound that accounts for the largest amount by mass among compounds of the same type. Thus, for example, a major elastomer is the elastomer that accounts for the largest mass relative to the total mass of elastomers in the composition. Similarly, a "major" filler is the filler that accounts for the largest mass of the fillers in the composition. For example, in a system containing only one elastomer, said elastomer is dominant for the purposes of this invention; in a system containing two elastomers, the major elastomer accounts for more than half the mass of the elastomer. Conversely, a "minor" compound is a compound that does not account for the largest mass fraction among compounds of the same type. Preferably, the term "major" means present in more than 50%, more preferably more than 60%, 70%, 80%, or 90%, and more preferably, the "major" compound accounts for 100%.

[0019] The compounds mentioned in this specification may be fossil-derived or bio-based. In the case of bio-based compounds, the compounds may be partially or wholly derived from biomass, or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also be derived from the recycling of used materials, i.e., they may be partially or wholly derived from the recycling process, or obtained from raw materials that are themselves derived from the recycling process. Polymers, plasticizers, fillers, etc., are particularly relevant.

[0020] Unless otherwise stated, the glass transition temperature “Tg” described herein is measured in a known manner by DSC (differential scanning calorimetry) in accordance with standard ASTM D3418 (1999).

[0021] II - Description of the Invention

[0022] II-1 Elastomer Matrix

[0023] The term "elastomer matrix" refers to all the elastomers in the composition.

[0024] According to the present invention, the elastomer matrix comprises at least one polyisoprene at 45 phr to 80 phr and at least one highly saturated diene elastomer at 20 phr to 55 phr, said highly saturated diene elastomer being a copolymer of ethylene and 1,3-diene (hereinafter referred to as "copolymer").

[0025] The term "copolymer comprising ethylene units and 1,3-diene units" refers to any copolymer whose structure contains at least ethylene units and 1,3-diene units. Therefore, copolymers can contain monomer units other than ethylene and 1,3-diene units. For example, copolymers can also contain α-olefin units, particularly α-olefin units containing 3 to 18 carbon atoms, advantageously α-olefin units containing 3 to 6 carbon atoms. For example, α-olefin units can be selected from propylene, butene, pentene, hexene, or mixtures thereof.

[0026] In a known manner, the term "ethylene unit" refers to the -(CH2-CH2)- unit formed by the insertion of ethylene into an elastomer chain.

[0027] The term "1,3-diene unit" refers to a monomer unit derived from the insertion of a monomer unit by the polymerization of a 1,3-diene monomer. Specifically, the 1,3-diene unit of the copolymer can be a 1,3-diene unit containing 4 to 12 carbon atoms, such as a 1,3-butadiene or 2-methyl-1,3-butadiene unit. More preferably, the 1,3-diene unit is primarily a 1,3-butadiene unit, or even more preferably only a 1,3-butadiene unit.

[0028] In the copolymer, ethylene units advantageously account for between 50 mol% and 95 mol% of the copolymer monomer units, i.e., between 50 mol% and 95 mol% of the copolymer monomer units. Advantageously, ethylene units in the copolymer account for more than 60 mol% of the copolymer monomer units, preferably more than 70 mol%. Also advantageously, in the copolymer, ethylene units account for no more than 90 mol% of the copolymer monomer units, preferably no more than 85 mol%.

[0029] Advantageously, the copolymer (i.e., as a reminder, at least one copolymer comprising ethylene units and diene units) is a copolymer of ethylene and 1,3-diene (preferably 1,3-butadiene), that is, according to the invention, a copolymer consisting only of ethylene units and 1,3-diene (preferably 1,3-butadiene) units, more preferably a random copolymer of ethylene and 1,3-diene (preferably 1,3-butadiene).

[0030] When the copolymer is a copolymer of ethylene and 1,3-diene, it advantageously contains units of formula (I) [Chemical Formula 1] and / or formula (II) [Chemical Formula 2]. The reason for the presence of the saturated 6-membered ring unit (1,2-cyclohexadiyl) of formula (I) as a monomer unit in the copolymer may be due to the very specific insertion of ethylene and 1,3-butadiene into the polymer chain during polymer chain growth.

[0031] [Chemical Formula 1]

[0032]

[0033] [Chemical Formula 2]

[0034] -CH2-CH(CH=CH2)- (II)

[0035] For example, copolymers of ethylene and 1,3-diene may not contain units of formula (I). In this case, it is preferable to include units of formula (II).

[0036] When the copolymer of ethylene and 1,3-diene contains units of formula (I) or formula (II), the molar percentages (o and p, respectively) of the units of formula (I) and formula (II) in the highly saturated diene elastomer preferably satisfy the following formula 1 (formula 1) [mathematical formula 1], more preferably formula 2 (formula 2) [mathematical formula 2], more preferably formula 3 (formula 3) [mathematical formula 3], where o and p are calculated based on all monomer units of the highly saturated diene elastomer.

[0037] [Mathematical Expression 1]

[0038] 0 < o + p ≤ 35 [Equation 1]

[0039] [Mathematical Expression 2]

[0040] 0 < o + p ≤ 25 [Equation 2]

[0041] [Mathematical Expression 3]

[0042] 0 < o + p < 20 [Equation 3]

[0043] According to the present invention, the copolymer is preferably a copolymer of ethylene and 1,3-diene (preferably 1,3-butadiene) and is a random copolymer.

[0044] Advantageously, the copolymer is preferably a copolymer of ethylene and 1,3-diene (preferably 1,3-butadiene) with a number average mass (Mn) in the range of 100,000 g / mol to 300,000 g / mol, preferably 150,000 g / mol to 250,000 g / mol.

[0045] The Mn of the copolymer was determined in a known manner by size exclusion chromatography (SEC) as described below:

[0046] Size exclusion chromatography (SEC) separates macromolecules in solution based on their size using a column packed with porous gel. Macromolecules are separated according to their hydrodynamic volume, with the largest eluting first. SEC is not an absolute method, but it helps to understand the molar mass distribution of polymers. Various number-average molar masses (Mn) and weight-average molar masses (Mw) can be determined from commercial standards, and the polydispersity index (Ip = Mw / Mn) can be calculated using molar calibration. No special treatment is required for the polymer sample before analysis. The polymer sample is prepared at approximately 1 g / L... -1 The concentration was simply dissolved in the elution solvent. The solution was then filtered through a filter with a porosity of 0.45 μm before injection. The equipment used was a Waters Acquity or Waters Alliance chromatography chain. The elution solvent was tetrahydrofuran containing 250 ppm BHT (butylated hydroxytoluene) as an antioxidant, and the flow rate was 1 mL / min. -1 The column temperature was 35°C, and the analysis time was 40 minutes. A set of three Agilent columns, commercially available as InfinityLab PolyPore, was used. The injected sample solution volume was 100 μL. The detector was either a Waters 2410 or an Acquity differential refractometer, and the software used to process the chromatographic data was the Waters Empower system. The calculated average molar mass is relative to a calibration curve generated from polystyrene standards.

[0047] The copolymer can be obtained according to various synthetic methods known to those skilled in the art, particularly based on the target microstructure of a highly saturated diene elastomer. Typically, it can be prepared by copolymerization of at least one diene (preferably 1,3-diene, more preferably 1,3-butadiene) and ethylene according to known synthetic methods (especially in the presence of a catalytic system containing a metallocene complex). In this regard, reference can be made to catalytic systems based on metallocene complexes, described in EP 1 092 731, WO 2004035639, WO 2007054223 and WO 2007054224 under the applicant's name. The copolymer (including the case of random copolymers) can also be prepared by using pre-formed catalytic systems (e.g., described in WO2017093654A1, WO 2018020122 A1 and WO 2018020123 A1).

[0048] The copolymer may consist of a mixture of copolymers containing ethylene units and diene units (the microstructures and / or macrostructures of these copolymers are different from each other).

[0049] As described above, the elastomeric matrix of the composition according to the invention further comprises polyisoprene. Polyisoprene can be an elastomer having any microstructure.

[0050] Advantageously, the polyisoprene (preferably containing at least 90% by mass of the 1,4-cis bond) is natural rubber, synthetic polyisoprene, or a mixture thereof. More preferably, the polyisoprene (preferably containing at least 90% by mass of the cis-1,4- bond) is natural rubber.

[0051] The copolymer, preferably a copolymer of ethylene and 1,3-diene (preferably 1,3-butadiene), may be present in the composition in the range of 20 phr to 50 phr, preferably in the range of 20 phr to less than 45 phr, and more preferably in the range of 20 phr to 40 phr.

[0052] Furthermore, the content of polyisoprene (preferably natural rubber) in the composition can be in the range of 50 phr to 80 phr, preferably in the range of greater than 55 phr to 80 phr, and more preferably in the range of 60 phr to 80 phr.

[0053] According to the present invention, the elastomer matrix may contain at least one other elastomer that is neither polyisoprene nor a copolymer containing ethylene units and diene units, but this is not mandatory. Therefore, preferably, at least one polyisoprene and at least one copolymer containing ethylene units and diene units are the only elastomers in the composition, i.e., they constitute 100% by mass of the elastomer matrix.

[0054] When the elastomer matrix contains at least one other elastomer that is neither polyisoprene nor a copolymer containing ethylene units and diene units, said at least one other elastomer may constitute less than 50% by mass of the elastomer matrix, preferably less than 40% by mass, preferably less than 30% by mass, preferably less than 20% by mass, and preferably less than 10% by mass. The other elastomer may be any diene elastomer well known to those skilled in the art that is neither polyisoprene nor a copolymer containing ethylene units and diene units.

[0055] II-2 Specific Plasticizers

[0056] According to the present invention, the rubber composition is based on at least one aliphatic dialkyl diacid plasticizer.

[0057] Preferably, for the purposes of this invention, the aliphatic diacid dialkyl ester plasticizer is present in the composition at a content of 5 phr to 50 phr, more preferably 7 phr to 40 phr, and more preferably 8 phr to 30 phr. Very preferably, the content of the aliphatic diacid dialkyl ester plasticizer is in the range of 10 phr to 25 phr.

[0058] Preferably, the aliphatic diacid dialkyl ester plasticizer is a compound of the formula ROOC-(CH2)n-COOR, wherein R is a straight-chain or branched alkyl group and n represents an integer from 4 to 20.

[0059] Preferably, the group R is an alkyl group containing 4 to 20 carbon atoms, more preferably 6 to 12 carbon atoms, and more preferably 6 to 10 carbon atoms.

[0060] Preferably, the group R is a branched alkyl group, and very preferably, R is an isooctyl group.

[0061] Preferably, for the purposes of this invention, n represents an integer from 4 to 12, more preferably an integer from 6 to 10. Very preferably, n equals 8.

[0062] Very preferably, the aliphatic diacid dialkyl ester plasticizer is diisooctyl sebacate [Chemical Formula 3].

[0063] [Chemical Formula 3]

[0064]

[0065] Diisooctyl sebacate with CAS number 122-62-3 has a glass transition temperature of -104°C, and is marketed by Hallstar, for example, under the name Plasthall DOS.

[0066] Furthermore, the compositions according to the invention advantageously do not contain any plasticizer other than the specific plasticizers described above, or contain less than 15 phr, preferably less than 10 phr, and more preferably less than 5 phr of any plasticizer other than the specific plasticizers described above.

[0067] II-3 Reinforced Filler

[0068] Another key feature of the rubber composition according to the invention is that it contains reinforcing fillers, including carbon black.

[0069] The rubber composition may contain any other type of "reinforcing" filler known to enhance rubber compositions that can be used to manufacture tires, such as organic fillers other than carbon black, reinforcing inorganic fillers such as silica, and coupling agents bonded to them in a known manner. Such reinforcing fillers typically consist of nanoparticles with an average (mass) size of less than one micrometer, typically less than 500 nm, generally between 20 nm and 200 nm, and particularly preferably between 20 nm and 150 nm.

[0070] All carbon blacks, especially those conventionally used in tires or their treads, are suitable for use as carbon black. More particularly mentioned among carbon blacks are the 100, 200, and 300 series reinforcing carbon blacks or the 500, 600, or 700 series carbon blacks (ASTM D-1765-2017 grade), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772 carbon blacks. These carbon blacks can be used in commercially available single forms or any other form, for example, as a carrier for some rubber engineering additives used. For example, carbon black can already be incorporated into diene elastomers, particularly isoprene elastomers, in the form of masterbatches (see, for example, patent applications WO 97 / 36724-A2 and WO 99 / 16600-A1).

[0071] Advantageously, carbon black has a BET specific surface area of ​​30 m². 2 / g to 100m 2 / g, preferably 33m 2 / g to 70m 2 / g, more preferably 35m 2 / g to 50m 2 Within the range of / g. The BET specific surface area can be measured according to standard ASTM D6556-09 [Multi-point method (5 points) - Gas: Nitrogen - Relative pressure range P / P0: 0.05 to 0.30].

[0072] Advantageously, the reinforcing filler mainly comprises carbon black, preferably only carbon black. In particular, the reinforcing filler preferably comprises at least 80% by weight, more preferably at least 90% by weight, of carbon black. Particularly preferably, the reinforcing filler comprises only carbon black, i.e., 100% by weight, of carbon black.

[0073] In the compositions according to the invention, the carbon black content is preferably in the range of 15 phr to 65 phr, more preferably 20 phr to 45 phr. The carbon black can be a mixture of different carbon blacks, in which case the carbon black content involves all types of carbon black.

[0074] II-4 crosslinking system

[0075] The crosslinking system can be any type of system known to those skilled in the art in the field of tire rubber compositions. It can be, in particular, based on sulfur and / or peroxides and / or bismaleimides.

[0076] Preferably, the crosslinking system is based on sulfur; it is then referred to as a vulcanization system. Sulfur can be provided in any form, particularly as molecular sulfur or a sulfur donor. It is also preferred to have at least one vulcanization accelerator, and optionally, various known vulcanization activators are also preferred, such as zinc oxide, stearic acid or equivalent compounds, such as stearates and transition metal salts, guanidine derivatives (especially diphenylguanidine), or known vulcanization inhibitors.

[0077] Sulfur is preferably used at a concentration between 0.2 phr and 10 phr, more preferably between 0.3 phr and 5 phr. The main vulcanization accelerator is preferably used at a concentration between 0.5 phr and 10 phr, more preferably between 0.5 phr and 5 phr.

[0078] As accelerators, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used, particularly thiazole-type accelerators and their derivatives, or accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate types. Examples of such accelerators include, in particular, 2-mercaptobenzothiazole disulfide (abbreviated “MBTS”), N-cyclohexyl-2-benzothiazole sulfenamide (“CBS”), N,N-dicyclohexyl-2-benzothiazole sulfenamide (“DCBS”), N-(tert-butyl)-2-benzothiazole sulfenamide (“TBBS”), N-(tert-butyl)-2-benzothiazole sulfenimide (“TBSI”), tetrabenzylthiuram disulfide (“TBZTD”), zinc dibenzyl dithiocarbamate (“ZBEC”), and mixtures of these compounds.

[0079] II-5 Possible Additives

[0080] The rubber composition according to the invention may optionally contain all or some of the commonly used additives typically used in tire elastomer compositions, such as pigments, protective agents (e.g., anti-ozone waxes, chemical anti-ozone agents, antioxidants, anti-fatigue agents), and reinforcing resins (e.g., as described in patent application WO 02 / 10269).

[0081] Advantageously, the compositions according to the invention do not contain hydrocarbon plasticizers.

[0082] Preparation of II-6 Rubber Composition

[0083] The composition according to the invention is prepared in a suitable mixer using two consecutive preparation stages known to those skilled in the art:

[0084] - The first stage of thermomechanical processing or kneading (“non-production” stage), which can be carried out in a single thermomechanical step, in which all necessary components (particularly the elastomer matrix, reinforcing fillers, and various other optional additives besides the crosslinking system) are introduced into a suitable mixer, such as a standard closed mixer (e.g., a Banbury type). Optional fillers can be introduced into the elastomer once or multiple times during thermomechanical kneading. Where the filler has already been introduced into the elastomer in whole or in part as a masterbatch (e.g., described in patent applications WO 97 / 36724 or WO 99 / 16600), the masterbatch is kneaded directly, and, if appropriate, fillers in non-masterbatch forms present in other elastomers or compositions, as well as various other optional additives besides the crosslinking system, are introduced. The non-production stage can be carried out at high temperatures, with the highest temperatures reached between 110°C and 200°C, preferably between 130°C and 185°C, typically lasting between 2 and 10 minutes.

[0085] - The second stage of machining (the "production" stage) is carried out in an open mixer (e.g., a two-roll mill) after the mixture obtained in the first non-production stage has been cooled to a lower temperature (typically less than 120°C, for example, between 40°C and 100°C). The crosslinking system is then introduced, and the combined mixture is then mixed for several minutes, for example, between 5 and 15 minutes.

[0086] The stage is described, for example, in patent applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300, or WO 00 / 05301.

[0087] The resulting final composition is then calendered, for example, in the form of sheets or plates, particularly for laboratory characterization, or extruded (or co-extruded with another rubber composition) in the form of a rubber semi-finished product (or molding element) that can be used, for example, as a tire sidewall. These products can then be used in the manufacture of tires according to techniques known to those skilled in the art.

[0088] The composition can be in an unprocessed state (before crosslinking or vulcanization) or a cured state (after crosslinking or vulcanization), or it can be a semi-finished product used in tires.

[0089] Crosslinking (or curing) (or, where appropriate, vulcanization) is carried out in a known manner at a temperature typically between 130°C and 200°C for a sufficient time, said time which may vary, for example, between 5 minutes and 90 minutes, depending in particular on the curing temperature, the crosslinking system used, and the crosslinking kinetics of the composition under consideration.

[0090] II-7 tires

[0091] The subject of this invention also includes tires comprising the rubber composition according to the invention.

[0092] Preferably, the composition according to the invention is present at least in the sidewall of the tire according to the invention. Advantageously, the composition is present only in the sidewall of the tire.

[0093] The tires according to the invention are intended to be fitted to passenger vehicles, SUVs (sports utility vehicles), two-wheeled vehicles (especially motorcycles), aircraft, or industrial vehicles such as heavy agricultural vehicles or construction vehicles selected from trucks, heavy vehicles (i.e., subways, buses, heavy road transport vehicles (trucks, tractors, trailers) or off-road vehicles). Detailed Implementation

[0094] III. Embodiments of the Invention

[0095] III.1 Testing and Measurement:

[0096] Dynamic properties:

[0097] Dynamic properties were measured according to standard ASTM D5992-96 using a viscosity analyzer (Metravib VA4000). The vulcanized composition sample (4 mm thickness, 400 mm² cross-sectional area) was recorded. 2The cylindrical specimen was subjected to a simple alternating sinusoidal shear stress at 10 Hz and 23 °C according to standard ASTM D 1349–99. Peak-to-peak strain amplitude scans were performed from 0.1% to 50% (outward cycle) and then from 50% to 0.1% (backward cycle). The results used are measurements of the modulus G' and G” at 23 °C and 10% strain in the backward cycle, representing the stiffness (and therefore deformability) and hysteresis of the composition, respectively.

[0098] To improve readability, results are displayed as a percentage of 100, with a value of 100 assigned to the control. A result greater than 100 indicates an improvement in the performance under consideration. For "G' with 10% return at 23°C", a result greater than 100 indicates a lower modulus, resulting in better deformability, which is an important characteristic for durability when used in tire sidewalls. For "G' with 10% return at 23°C", a result greater than 100 indicates reduced hysteresis, resulting in better rolling resistance performance when used in tires.

[0099] III.2 Preparation of Rubber Compositions:

[0100] The elastomer (EBR) is prepared according to the following procedure:

[0101] 30 mg of metallocene [{Me₂SiFlu₂Nd(μ-BH₄)₂Li(THF)}₂, denoted by Flu, representing a fluorene group of C₁₃H₈] was introduced into the first Steinnie flask in a glove box. The co-catalyst (pre-dissolved in 300 ml of methylcyclohexane in a second Steinnie flask) was introduced into the first Steinnie flask containing the metallocene at the following ratio: 0.00007 mol / L metallocene, 0.0004 mol / L co-catalyst. A catalytic solution was obtained after contacting at ambient temperature for 10 minutes. The catalytic solution was then introduced into the polymerization reactor. The temperature in the reactor was then raised to 80 °C. When this temperature was reached, the reaction was initiated by injecting a gas mixture of ethylene and 1,3-butadiene (80 / 20 mol%) into the reactor. The polymerization reaction was carried out at a pressure of 8 bar. The ratio of metallocene to co-catalyst was 0.00007 mol / L and 0.0004 mol / L, respectively. The polymerization reaction was stopped by cooling, reactor degassing, and the addition of ethanol. An antioxidant was added to the polymer solution. The copolymer was recovered by drying in a vacuum oven. Butyloctylmagnesium (BOMAG) was added to an 80°C reactor containing methylcyclohexane, ethylene, and butadiene (ethylene / butadiene ratio of 80 / 20 mol%) to neutralize impurities in the reactor, followed by the addition of a catalyst system. At this point, the reaction temperature was adjusted to 80°C, and the polymerization reaction began. The polymerization reaction was carried out at a constant pressure of 8 bar. During polymerization, ethylene and butadiene were supplied to the reactor in an 80 / 20 mol% (ethylene / butadiene) ratio. The polymerization reaction was stopped by cooling, reactor degassing, and the addition of ethanol. An antioxidant was added to the polymer solution. The copolymer was recovered by vacuum drying in an oven to constant weight.

[0102] The catalytic system is a preformed catalytic system. It is prepared in methylcyclohexane from a metallocene [Me₂Si(Flu)₂Nd(μ-BH₄)₂Li(THF)], a co-catalyst butyloctylmagnesium (BOMAG), and a preformed monomer 1,3-butadiene, with the following content: metallocene: 0.00007 mol / L, co-catalyst: 0.00036 mol / L. It is prepared according to the preparation method in paragraph II.1 of patent application WO 2017093654 A1.

[0103] In the examples below, the rubber composition was prepared as described in points II-6 above. Specifically, the "non-production" stage was carried out in a 0.4-liter mixer at an average paddle speed of 50 rpm for 6 minutes until the maximum discharge temperature of 160°C was reached. The "production" stage was carried out in a cylindrical tool at 23°C for 10 minutes.

[0104] The crosslinking of the composition was carried out under pressure at a temperature between 130°C and 200°C.

[0105] III.3 Rubber Tests:

[0106] The examples given below are intended to compare the performance balance between deformability and hysteresis of two compositions (C1 and C2) according to the present invention with two control compositions (T1 and T2).

[0107] Table 1 shows the compositions tested (in phr), and Table 2 shows the results obtained, with a baseline of 100.

[0108] [Table 1]

[0109] formula T1 C1 T2 C2 NR(1) 50 50 60 60 EBR(2) 50 50 40 40 Carbon black (3) 29 29 29 29 Plasticizer 1(4) 20 - 20 - Plasticizer 2(5) - 20 - 20 wax 1 1 1 1 TMQ(6) 1 1 1 1 6PPD(7) 3 3 3 3 CBS(8) 0.9 0.9 0.9 0.9 ZnO 3 3 3 3 stearic acid 2 2 2 2 sulfur 1.75 1.75 1.75 1.75

[0110] (1) Natural rubber

[0111] (2) EBR, Mooney 85, ethylene content: 77%

[0112] (3) N550 grade carbon black from Cabot Corporation, conforming to standard ASTM D-1765.

[0113] (4) Tudalen 1968 liquid paraffin from Klaus Dahleke

[0114] (5) Plasthall DOS oil from Hallstar

[0115] (6) 2,2,4-Trimethyl-1,2-dihydroquinoline, from Pilnox TMQ by Nocil.

[0116] (7) N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine, from Flexsys' Santoflex 6-PPD

[0117] (8) N-cyclohexyl-2-benzothiazole sulfonamide, from Santocure CBS of Flexsys.

[0118] [Table 2]

[0119] T1 C1 T2 C2 10% of G' returned at 23℃ 100 99 100 108 10% of G returned at 23℃ 100 114 100 123

[0120] The results shown in Table 2 above indicate that the composition according to the present invention improves the balance between deformability and hysteresis properties compared to the control composition.

Claims

1. A rubber composition, which is based at least on: - An elastomer matrix comprising at least one polyisoprene at 45 phr to 80 phr and at least one highly saturated diene elastomer at 20 phr to 55 phr. - Dialkyl aliphatic diacid ester plasticizer -Carbon black, and - Crosslinking system, The highly saturated diene elastomer is a copolymer of ethylene and 1,3-diene.

2. The rubber composition according to claim 1, wherein the ethylene units in the copolymer account for between 50 mol% and 95 mol% of the copolymer monomer units.

3. The rubber composition according to any one of the preceding claims, wherein the 1,3-diene is 1,3-butadiene.

4. The rubber composition according to claim 1, wherein the copolymer is a random copolymer.

5. The rubber composition according to claim 1, wherein the content of the copolymer comprising ethylene units and diene units is in the range of 20 phr to 50 phr.

6. The rubber composition according to claim 1, wherein the polyisoprene is natural rubber, synthetic polyisoprene, or a mixture thereof.

7. The rubber composition according to claim 1, wherein the polyisoprene content is in the range of 50 phr to 80 phr.

8. The rubber composition according to claim 1, wherein the content of the aliphatic diacid dialkyl ester plasticizer is in the range of 5 phr to 50 phr.

9. The rubber composition according to claim 1, wherein the aliphatic diacid dialkyl ester plasticizer is a compound of the formula ROOC-(CH2)n-COOR, wherein R is a straight-chain or branched alkyl group and n represents an integer from 4 to 20.

10. The rubber composition according to claim 9, wherein group R is an alkyl group comprising 4 to 20 carbon atoms.

11. The rubber composition according to any one of claims 9 and 10, wherein the group R is a branched alkyl group.

12. The rubber composition according to claim 9, wherein n represents an integer from 4 to 12.

13. The rubber composition according to claim 1, wherein the aliphatic diacid dialkyl ester plasticizer is diisooctyl sebacate.

14. The rubber composition according to claim 1, wherein the total carbon black content is in the range of 15 phr to 65 phr.

15. A pneumatic or non-pneumatic tire carcass comprising a rubber composition as defined in any one of claims 1 to 14.

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