Rubber composition comprising a highly saturated diene elastomer

Abstract

The present invention relates to a rubber composition based on an elastomeric matrix comprising at least one highly saturated diene elastomer, carbon black, and an aliphatic diacid dialkyl ester, wherein the highly saturated diene elastomer is a copolymer of ethylene and a 1,3-diene, and wherein the ethylene units account for at least 50 mol% of the copolymer monomer units.

Description

Field of the Invention

[0001] The field of the invention is rubber compositions based on highly saturated diene elastomers, which are intended for use in tires, in particular for their treads. Background Art

[0002] The use of highly saturated diene elastomers is known in the prior art. For example, copolymers of ethylene and 1,3 - butadiene and their application in tire treads are described in WO 2014114607A1. It is stated in the said document that the use of these copolymers results in tires having good abrasion resistance and rolling resistance.

[0003] At the same time, certain documents such as WO 2020011003 A1 mention in a list the use of aliphatic diacid dialkyl esters plasticizers (diisooctyl sebacate) in polyethylene compositions as possible plasticizers without discussing any specific effects associated with the use of this plasticizer.

[0004] In the above - mentioned field of tires whose treads contain highly saturated diene elastomers, there is still a need for rubber compositions having an improved balance between the glass transition temperature characteristics of the mixture (which characteristics are important for optimizing the grip of the tire on the ground) and the stiffness.

[0005] It is known to those skilled in the art that the grip of a tire is adjusted by the glass transition temperature of the mixture according to the use temperature. In particular, in cold weather, as compared with the glass transition temperature of the mixture used in hot weather, those skilled in the art must lower the glass transition temperature of the mixture. To lower the glass transition temperature of the mixture, those skilled in the art can add an oil having a low glass transition temperature to the composition. However, the use of oil causes polymer dilution and results in a decrease in the stiffness of the mixture. The decrease in the stiffness of the mixture has an adverse effect on the tire behavior and increases tread wear. The problem to be solved by those skilled in the art is to be able to lower the glass transition temperature of the mixture without excessively reducing the stiffness of the said mixture. Summary of the Invention

[0006] The applicant has found a rubber composition that can meet this need in the field of applying highly saturated diene elastomers to tires, in particular to treads.

[0007] Thus, a first subject of the invention is a rubber composition based on at least one elastomeric matrix mainly containing highly saturated diene elastomers, carbon black, and aliphatic diacid dialkyl esters; the highly saturated diene elastomer is a copolymer of ethylene and 1,3 - diene, wherein the ethylene units account for at least 50 mol% of the copolymer monomer units.

[0008] Another subject of the present invention is a pneumatic or non-pneumatic tyre casing, which comprises a rubber composition according to the invention, preferably in the tread, a rubber composition according to the invention.

[0009] I - Definitions

[0010] The expression "the composition is based on" should be understood to mean that the composition comprises a mixture of the various basic components used and / or in-situ reaction products, some of which components are capable of reacting with each other at least partially during the various manufacturing stages of the composition and / or are intended to react with each other; thus the composition may be in a fully or partially crosslinked state or in a non-crosslinked state.

[0011] For the purposes of the present invention, the expression "parts by weight per 100 parts by weight of elastomer" (or phr) should be understood to mean parts by mass per 100 mass parts of elastomer.

[0012] In the present text, unless otherwise clearly stated, all percentages (%) shown are percentages by mass (%).

[0013] Furthermore, any numerical range represented by the expression "between a and b" represents a numerical range extending from greater than a to less than b (i.e., excluding the limits a and b), while any numerical range represented by the expression "a to b" represents a numerical range extending from a up to b (i.e., including the strict limits a and b). In this document, when a numerical range is represented by the expression "a to b", the range represented by the expression "between a and b" is also preferably represented.

[0014] In the present patent application, the expression "all monomer units of the elastomer" or "total amount of elastomer monomer units" means all the constitutive repeating units of the elastomer resulting from the insertion of monomers into the elastomer chains by polymerization. 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.

[0015] For the purposes of the present invention, when referring to a "major" compound, it is to be understood as meaning that among the compounds of the same type in the composition, this compound is the major one, i.e., the compound that represents the largest amount by mass among the compounds of the same type. Thus, for example, the major elastomer is the elastomer that represents the largest mass relative to the total mass of the elastomers in the composition. In the same way, the "major" filler is the filler that represents the largest mass among the fillers of the composition. For example, in a system containing only one elastomer, said elastomer is major for the purposes of the present invention, and in a system containing two elastomers, the major elastomer represents more than half of the mass of the elastomers. Conversely, a "minor" compound is a compound that does not represent the largest mass fraction among the compounds of the same type. Preferably, the term "major" means present in more than 50%, preferably more than 60%, 70%, 80%, 90%, and more preferably, the "major" compound represents 100%.

[0016] The compounds mentioned in this specification can be of fossil origin or can be bio-based. In the bio-based case, the compounds can be partially or completely derived from biomass, or can be obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned can also be derived from the recycling of used materials, i.e., they can be partially or wholly derived from a recycling process, or obtained from raw materials that themselves are derived from a recycling process. Particular mention is made of polymers, plasticizers, fillers, etc.

[0017] Unless otherwise stated, in the following examples, the values of the glass transition temperature "Tg" described in this document were measured in a known manner by DSC (Differential Scanning Calorimetry) according to standard ASTM D3418 (1999).

[0018] II - Description of the Invention

[0019] II-1 Elastomeric matrix

[0020] The term "elastomer matrix" denotes all the elastomers in the composition.

[0021] According to the present invention, the elastomer matrix mainly comprises at least one highly saturated diene elastomer, i.e., a copolymer comprising ethylene units and diene units (hereinafter referred to as "copolymer").

[0022] The highly saturated diene elastomer for the purposes of the present invention is a copolymer comprising ethylene units formed by the polymerization of ethylene, preferably a random copolymer. In a known manner, the term "ethylene unit" denotes a -(CH2-CH2)- unit formed by the insertion of ethylene into the elastomer chain.

[0023] The highly saturated diene elastomer is rich in ethylene units, since the ethylene units represent at least 50 mol% of all the monomer units of the elastomer.

[0024] Preferably, the highly saturated diene elastomer contains at least 65 mol% of ethylene units. In other words, the ethylene units preferably account for at least 65 mol% of all the monomer units of the highly saturated diene elastomer. More preferably, the highly saturated diene elastomer contains 65 mol% to 90 mol% of ethylene units, the mole percentage being calculated based on all the monomer units of the highly saturated diene elastomer.

[0025] Since the highly saturated diene elastomer is a copolymer of ethylene and 1,3-diene, it also contains 1,3-diene units formed by the polymerization of 1,3-diene. In a known manner, the expression "1,3-diene unit" means, in the case of isoprene, the unit formed by the insertion of 1,3-diene by 1,4 addition, 1,2 addition or 3,4 addition. The 1,3-diene unit is, for example, a unit of a 1,3-diene containing 4 to 12 carbon atoms (such as 1,3-butadiene, isoprene, 1,3-pentadiene or aryl-1,3-butadiene). Preferably, the 1,3-diene is 1,3-butadiene, in which case the highly saturated diene elastomer is a copolymer of ethylene and 1,3-butadiene, preferably a statistical copolymer.

[0026] The highly saturated diene elastomer useful for the purposes of the present invention can be obtained according to various synthesis methods known to those skilled in the art, in particular according to the target microstructure of the highly saturated diene elastomer. Generally, it can be prepared by copolymerization of at least one 1,3-diene (preferably 1,3-butadiene) and ethylene according to known synthesis methods (in particular in the presence of a catalytic system comprising a metallocene complex). In this regard, mention may be made of catalytic systems based on metallocene complexes, which are described in EP 1 092 731, WO 2004035639, WO 2007054223 and WO2007054224 in the name of the applicant. The highly saturated diene elastomer (including the case of random elastomers) can also be prepared by a method using a preformed catalytic system (such as described in WO 2017093654 A1, WO 2018020122 A1 and WO 2018020123 A1).

[0027] The highly saturated diene elastomer in the composition of the present invention preferably contains units of formula (I) [Chemical formula 1] or units of formula (II) [Chemical formula 2].

[0028] [Chemical formula 1]

[0029]

[0030] [Chemical formula 2]

[0031] -CH2-CH(CH=CH2)- (II)

[0032] The reason for the presence of the saturated six-membered ring unit (1,2-cyclohexylene diyl) of formula (I) in the copolymer may be that ethylene and 1,3-butadiene are inserted into the polymer chain in a very specific series during the growth of the polymer chain. When the highly saturated diene elastomer contains the unit of formula (I) or the unit of formula (II), the molar percentages (o and p respectively) of the unit of formula (I) and the unit of formula (II) in the highly saturated diene elastomer preferably satisfy the following formula (Formula 1), more preferably Formula (Formula 2), still more preferably Formula (Formula 3), and o and p are calculated based on all monomer units of the highly saturated diene elastomer.

[0033] [Formula 1]

[0034] 0 < o + p ≤ 35 [Formula 1]

[0035] [Formula 2]

[0036] 0 < o + p ≤ 25 [Formula 2]

[0037] [Formula 3]

[0038] 0 < o + p < 20 [Formula 3]

[0039] The highly saturated diene elastomer useful for the purposes of the present invention may consist of a mixture of highly saturated diene elastomers with different microstructures or macrostructures from each other.

[0040] According to the present invention, the content of the highly saturated diene elastomer in the rubber composition is at least 50 parts by weight per 100 parts by weight of elastomer of the rubber composition (phr). Preferably, the content of the highly saturated diene elastomer in the rubber composition varies in the range of 80 phr to 100 phr. More preferably, it varies in the range of 90 phr to 100 phr.

[0041] In addition, the elastomeric matrix of the composition of the present invention may contain a small amount of any type of elastomer. Particular attention may be paid to the diene elastomers known to those skilled in the art for use in the tire field.

[0042] II-2 Specific plasticizer

[0043] According to the present invention, the rubber composition is based on at least one aliphatic diacid dialkyl ester plasticizer.

[0044] Preferably, for the purposes of the present invention, the aliphatic diacid dialkyl ester plasticizer is present in the composition in an amount of 5 phr to 50 phr, preferably 7 phr to 40 phr, more preferably 8 phr to 30 phr. Most preferably, the content of the aliphatic diacid dialkyl ester plasticizer is in the range of 8 phr to 15 phr.

[0045] Preferably, the aliphatic diacid dialkyl ester plasticizer is a compound of the formula ROOC-(CH2)n-COOR, where R is a straight-chain or branched-chain alkyl group and n represents an integer from 4 to 20.

[0046] Preferably, the group R is an alkyl group containing 4 to 20 carbon atoms, preferably 6 to 12 carbon atoms and more preferably 6 to 10 carbon atoms.

[0047] Preferably, the group R is a branched-chain alkyl group, and very preferably, R is isooctyl.

[0048] Preferably, for the purposes of the present invention, n represents an integer from 4 to 12, preferably an integer from 6 to 10. Very preferably, n is equal to 8.

[0049] Very preferably, the aliphatic diacid dialkyl ester plasticizer is diisooctyl sebacate of the following [Chemical Formula 3].

[0050] [Chemical Formula 3]

[0051]

[0052] The glass transition temperature of diisooctyl sebacate with a CAS number of 122-62-3 is -104 °C and it is sold, for example, under the name Plasthall DOS by Hallstar.

[0053] Furthermore, the composition according to the present invention advantageously does not contain any plasticizer other than the above-mentioned specific plasticizer, or contains less than 15 phr, preferably less than 10 phr, preferably less than 5 phr of any plasticizer other than the above-mentioned specific plasticizer.

[0054] II-3 Reinforcing filler

[0055] A basic feature of the rubber composition according to the present invention also lies in the inclusion of a reinforcing filler, which includes carbon black.

[0056] The reinforcing filler generally consists of nanoparticles with an average (mass average) size of less than one micron, usually less than 500 nm, usually between 20 nm and 200 nm, and particularly more preferably between 20 nm and 150 nm.

[0057] Any carbon black, especially carbon black conventionally used in tires or their treads ("tire-grade" carbon black), is suitable for use as the carbon black. Among carbon blacks, mention is made more particularly of reinforcing carbon blacks of the 100, 200 and 300 series or carbon blacks of the 500, 600 or 700 series (ASTM grades), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683 and N772 carbon blacks. When the rubber composition according to the invention is used in the tread, the carbon black is preferably a carbon black of the 100 or 200 series.

[0058] The content of carbon black can vary within a wide range and is adjusted by those skilled in the art according to the intended use of the rubber composition (especially in the tire industry). For the application of the rubber composition in the tread (especially a vehicle tread intended to carry heavy loads), the content of carbon black in the rubber composition is preferably between 15 phr and 65 phr. For applications in the heavy goods vehicle industry, below 15 phr the rubber composition may have insufficient reinforcement level, and above 65 phr it may exhibit excessive hysteresis. Preferably, the carbon black content in the rubber composition is in the range of 20 phr to 45 phr.

[0059] II-4 Crosslinking system

[0060] 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 in particular be based on sulfur and / or peroxides and / or bismaleimides.

[0061] Preferably, the crosslinking system is based on sulfur; it is then called a vulcanization system. Sulfur can be provided in any form, especially in the form of molecular sulfur or sulfur donors. It is also preferred to have at least one vulcanization accelerator, and optionally it is also preferred to use various known vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, such as stearates and salts of transition metals, guanidine derivatives (especially diphenylguanidine), or known vulcanization retarders.

[0062] Sulfur is preferably used in an amount between 0.2 phr and 10 phr, more preferably between 0.3 phr and 5 phr. The vulcanization accelerator or accelerator mixture is preferably used in an amount between 0.5 phr and 10 phr, more preferably between 0.5 phr and 5 phr.

[0063] As accelerators, any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur can be used, in particular thiazole-type accelerators and their derivatives, or accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate types. As examples of such accelerators, the following compounds can be specifically mentioned: 2-mercaptobenzothiazole disulfide (abbreviated as "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 sulfimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC"), and mixtures of these compounds.

[0064] II-5 Possible additives

[0065] The rubber composition according to the invention may also optionally contain all or some of the common additives usually used in tire elastomer compositions, such as plasticizers (such as plasticizing oils and / or plasticizing resins), pigments, protective agents (such as antiozonant waxes, chemical antiozonants, antioxidants, antifatigue agents), reinforcing resins (as described, for example, in patent application WO 02 / 10269).

[0066] However, in a particularly advantageous manner, the composition according to the invention does not contain any plasticizer other than the above-mentioned plasticizers, or contains less than 20 phr, preferably less than 10 phr, more preferably less than 5 phr of any plasticizer other than the above-mentioned plasticizers.

[0067] Advantageously, the composition according to the invention does not contain any plasticized hydrocarbon resin.

[0068] II-6 Preparation of rubber composition

[0069] The composition according to the invention is prepared in a suitable mixer using two consecutive preparation stages known to those skilled in the art:

[0070] - The first stage of thermomechanical processing or kneading (“non-production” stage), which can be carried out in a single thermomechanical step in which all the necessary components (in particular the elastomeric matrix, reinforcing fillers and various other optional additives apart from the crosslinking system) are introduced into a suitable mixer, such as a standard closed mixer (e.g., Banbury type). Optional fillers can be introduced into the elastomer one or more times during thermomechanical kneading. In the case where the fillers have been introduced into the elastomer in whole or in part in the form of masterbatches (e.g., as described in patent applications WO 97 / 36724 or WO 99 / 16600), it is the masterbatch that is directly kneaded, and if appropriate, fillers in non-masterbatch form present in other elastomers or compositions, as well as various other optional additives apart from the crosslinking system, are introduced. The non-production stage can be carried out at a high temperature, with the maximum temperature reached being between 110 °C and 200 °C, preferably between 130 °C and 185 °C, and usually lasting for a time between 2 and 10 minutes;

[0071] - The second stage of mechanical processing (“production” stage), which is carried out in an open mixer (e.g., a mill) after cooling the mixture obtained in the first non-production stage to a lower temperature (usually less than 120 °C, e.g., between 40 °C and 100 °C). Then the crosslinking system is introduced, and then the combined mixture is mixed for several minutes, e.g., between 5 minutes and 15 minutes.

[0072] This stage is described, for example, in patent applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO 00 / 05301.

[0073] The final composition thus obtained is then calendered, for example, in the form of sheets or plates, especially 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, for example, be used as a tire tread. These products can then be used in the manufacture of tires according to techniques known to those skilled in the art.

[0074] The composition can be in an unprocessed state (before crosslinking or vulcanization) or in a cured state (after crosslinking or vulcanization), and can be a semi-finished product used in tires.

[0075] Crosslinking (or curing) (or vulcanization, where appropriate) is carried out in a known manner at a temperature usually between 130 °C and 200 °C for a sufficient time, which can vary, for example, between 5 minutes and 90 minutes, depending in particular on the curing temperature, the crosslinking system employed and the crosslinking kinetics of the composition under consideration.

[0076] II-7 Tire

[0077] The subject of the present invention also relates to a tire comprising a rubber composition according to the invention.

[0078] Preferably, the composition according to the invention is present at least in the tread of a tire according to the invention.

[0079] The tire according to the invention may be intended for fitting to a motor vehicle of the passenger vehicle type, an SUV (sport utility vehicle), a two-wheeled vehicle (in particular a motorcycle), an aircraft, or an industrial vehicle selected from trucks, heavy vehicles (i.e. subway, bus, heavy road transport vehicle (truck, tractor, trailer) or off-road vehicle) such as a heavy agricultural vehicle or a construction vehicle, etc.

[0080] The above and other features of the present invention will be more clearly understood by reading the description of several embodiments of the present invention given below by way of non-limiting illustration. Detailed description

[0081] III. Embodiments for carrying out the present invention

[0082] III.1 Tests and measurements:

[0083] III.1-1 Determination of elastomeric microstructure:

[0084] When the resolution of the 1H NMR spectrum cannot assign and quantify all entities, the microstructure of the elastomer is determined by combining 1H NMR analysis with 13C NMR analysis. Measurements are carried out using a Bruker 500 MHz NMR spectrometer, with a frequency of 500.43 MHz for proton observation and 125.83 MHz for carbon observation.

[0085] For insoluble elastomers capable of swelling in a solvent, proton observation and carbon observation are carried out in proton decoupling mode using a 4 mm z-level HRMAS probe. Spectra are acquired at a spinning speed of 4000 Hz to 5000 Hz.

[0086] For the measurement of soluble elastomers, proton observation and carbon observation are carried out in proton decoupling mode using a liquid NMR probe.

[0087] The preparation of insoluble samples is carried out in a rotor filled with the analytical material and a deuterated solvent capable of swelling (usually deuterated chloroform (CDCl3)). The solvent used must always be deuterated, and its chemical properties can be adjusted by those skilled in the art. The amount of material used can be adjusted to obtain spectra with sufficient sensitivity and resolution.

[0088] Dissolve the soluble sample in a deuterated solvent (about 25 mg of elastomer in 1 mL). The deuterated solvent is typically deuterated chloroform (CDCl3). The solvent or solvent blend used must always be deuterated, and its chemistry can be adjusted by those skilled in the art.

[0089] In both cases (soluble sample or swollen sample):

[0090] Use a 30° single-pulse sequence for proton NMR. Set the spectral window to observe all resonance lines belonging to the molecule being analyzed. The number of accumulations is set to obtain a signal-to-noise ratio sufficient to quantify each unit. The recycle delay between each pulse is adapted to obtain a quantitative measurement.

[0091] Use a 30° single-pulse sequence for carbon NMR, with only proton decoupling during acquisition to avoid nuclear overheating effects (NOE) and maintain quantification. Set the spectral window to observe all resonance lines belonging to the molecule being analyzed. The number of accumulations is set to obtain a signal-to-noise ratio sufficient to quantify each unit. The recycle delay between each pulse is adapted to obtain a quantitative measurement.

[0092] NMR measurements are performed at 25 °C.

[0093] III.1-2 Measurement of dynamic properties:

[0094] Dynamic properties

[0095] Measure the dynamic properties on a viscometer (Metravib VA4000) according to standard ASTM D5992-96. Record the response of a cylindrical specimen of the vulcanized composition sample (4 mm thick, cross-sectional area 400 mm 2 2) subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz according to standard ASTM D 1349-99.

[0096] The following results are based on measurements using a temperature scan at a given stress and a strain scan at a stress frequency of 10 Hz.

[0097] Stiffness: Stiffness is determined at 50% return strain during a strain scan from 0.1% to 100% peak-to-peak strain at 60 °C.

[0098] Glass transition temperature: The glass transition temperature is determined as the temperature at which the mixture has the maximum G” value in a forced stress shear test at 0.7 MPa.

[0099] III.2 Preparation of rubber composition:

[0100] The rubber composition is prepared in the following manner, and the details of the formulation are given in Table 1:

[0101] An elastomer, reinforcing fillers, and various other ingredients other than sulfur and vulcanization accelerators are introduced successively into an internal mixer (final filling rate: about 70% by volume), the initial tank temperature of which is about 90 °C. Oil is introduced at 115 °C. Then thermomechanical processing (non-production phase) is carried out in one step, for a total of about 3 to 4 minutes until a maximum "discharge" temperature of 160 °C is reached. The mixture thus obtained is recovered, cooled, and then sulfur and vulcanization accelerators are introduced into a mixer (homogenizer-trimmer) at 30 °C, and all substances are mixed for an appropriate time (e.g., about 10 minutes) (production phase).

[0102] Subsequently, the composition thus obtained is calendered into the form of a sheet (thickness 2 mm to 3 mm) or a rubber sheet for measuring their physical or mechanical properties, or extruded into the form of a tire tread.

[0103] The elastomer (EBR) is prepared according to the following procedure:

[0104] 30 mg of metallocene [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}2, where the symbol Flu represents a fluorenyl group of the formula C13H8] is introduced into the first Steinie bottle in a glove box. The cocatalyst (butyloctylmagnesium pre-dissolved in 300 ml of methylcyclohexane in the second Steinie bottle) is introduced into the first Steinie bottle containing the metallocene in the following ratio: 0.00007 mol / L of metallocene, 0.0004 mol / L of cocatalyst. A catalytic solution is obtained after 10 minutes of contact at ambient temperature. Then the catalytic solution is introduced into the polymerization reactor. Then the temperature in the reactor is raised to 80 °C. When this temperature is reached, the reaction is started by injecting a gas mixture of ethylene and 1,3-butadiene (80 / 20 mol%) into the reactor. The polymerization reaction is carried out at a pressure of 8 bar. The ratios of metallocene and cocatalyst are 0.00007 mol / L and 0.0004 mol / L, respectively. The polymerization reaction is stopped by cooling, degassing the reactor, and adding ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in a vacuum oven. Butyloctylmagnesium (BOMAG) is added to an 80 °C reactor containing methylcyclohexane, ethylene, and butadiene (ethylene / butadiene ratio 80 / 20 mol%) to neutralize impurities in the reactor, and then the catalytic system is added. At this time, the reaction temperature is adjusted to 80 °C and the polymerization reaction starts. The polymerization reaction is carried out at a constant pressure of 8 bar. Ethylene and butadiene in a ratio of 80 / 20 mol% (ethylene / butadiene) are supplied to the reactor during the polymerization. The polymerization reaction is stopped by cooling, degassing the reactor, and adding ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying to constant weight in a vacuum oven.

[0105] The catalytic system is a preformed catalytic system. It is prepared in methylcyclohexane from the metallocene [Me2Si(Flu)2Nd(μ-BH4)2Li(THF)], the cocatalyst butyloctylmagnesium (BOMAG), and the preformed monomer 1,3-butadiene, with the following contents: metallocene: 0.00007 mol / L, cocatalyst: 0.00036 mol / L. It is prepared according to the preparation method in paragraph II.1 of patent application WO 2017093654 A1.

[0106] The rubber composition C3 is according to the present invention. The rubber compositions C1 and C2 do not conform to the present invention because they do not contain the specific plasticizing system required by the present invention.

[0107] [Table 1]

[0108] Components C1 C2 C3 EBR(1) 100 100 100 Carbon black(2) 42 42 42 Oil 1(3) - 11 - Oil 2(4) - - 11 Wax(5) 1 1 1 Antioxidant(6) 2 2 2 Stearic acid 1.5 1.5 1.5 ZnO 2.5 2.5 2.5 Diphenylguanidine 0.5 0.5 0.5 Accelerator(7) 0.8 0.8 0.8 Sulfur 0.4 0.4 0.4

[0109] (1) EBR, Mooney 85, ethylene content: 77%,

[0110] (2) Carbon black, ASTM N234 from Cabot Corporation,

[0111] (3) Liquid paraffin "Extensoil 51" from Repsol,

[0112] (4) Oil "Plasthall DOS" from Hallstar,

[0113] (5) Antiozonant wax C32 ST,

[0114] (6) Santoflex 6PPD from Flexsys,

[0115] (7) Accelerators: cyclohexylbenzothiazole sulfenamide CBS and tetrabenzylthiuram disulfide TBzTD from Akrochem.

[0116] III.3 Results:

[0117] The results are given in Table 2.

[0118] [Table 2]

[0119] MDC measurement C1 C2 C3 Stiffness at 60 °C (G*50% return) 1.25 0.92 1.24 Glass transition temperature (T G”max) -39.45 -43.47 -46.93

[0120] The results show that the compositions according to the present invention can simultaneously lower the glass transition temperature of the mixture while maintaining a high level of stiffness, and are suitable for tire treads. The reduction of the glass transition temperature of the mixture enables the formulation to be used at lower temperatures, and the lower reduction of stiffness enables good tire performance to be maintained as well as acceptable wear of the composition in the tread.

Claims

1. A rubber composition, said rubber composition being based on an elastomeric matrix comprising at least one highly saturated diene elastomer, carbon black, an aliphatic diacid dialkyl ester plasticizer and a crosslinking system; said highly saturated diene elastomer being a copolymer of ethylene and a 1,3-diene, wherein the ethylene units account for at least 50 mol% of the copolymer monomer units.

2. The rubber composition according to claim 1, wherein the ethylene units are 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 ethylene units account for at least 65 mol% of the copolymer monomer units.

4. The rubber composition according to claim 1, wherein the 1,3-diene is 1,3-butadiene.

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

6. The rubber composition according to claim 1, wherein the content of the highly saturated diene elastomer in the rubber composition varies in the range of 80 phr to 100 phr.

7. 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.

8. 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-chain alkyl group and n represents an integer from 4 to 20.

9. The rubber composition according to claim 8, wherein R is an alkyl group containing 4 to 20 carbon atoms.

10. The rubber composition according to claim 8, wherein the group R is a branched-chain alkyl group.

11. The rubber composition according to claim 8, wherein n represents an integer from 4 to 12.

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

13. The rubber composition according to claim 1, wherein the carbon black content is between 15 phr and 65 phr.

14. A pneumatic or non-pneumatic tire carcass comprising the rubber composition according to any one of claims 1 to 13.

Images