RUBBER COMPOSITION BASED ON HIGHLY SATURATED DIENE ELASTOMER

Abstract

The present invention relates to a rubber composition having improved rigidity and hysteresis, as well as to a tire comprising this composition. The rubber composition based on at least one elastomer matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing between 50% and 95% by mole of the monomer units of the copolymer; a reinforcing filler; a crosslinking system; and a processing agent comprising a mixture of at least one carboxylic acid comprising from 4 to 28 carbon atoms and / or at least one carboxylic acid ester comprising from 4 to 28 carbon atoms and at least one aliphatic alcohol comprising from 2 to 22 carbon atoms.

Description

Title of the invention: RUBBER COMPOSITION BASED ON HIGHLY SATURATED DIENE ELASTOMER

[0001] The present invention relates to rubber compositions intended in particular for the manufacture of tires or semi-finished products for tires.

[0002] A tire must comply in a known manner with a large number of technical requirements, often contradictory, including low rolling resistance, high wear resistance, as well as high grip on both dry and wet roads.

[0003] Among these properties, rolling resistance and wear resistance prove to be the most important from an environmental point of view because they respectively allow fuel consumption to be reduced and the life of the tires to be extended.

[0004] The diene rubber compositions traditionally used in tires are rubber compositions reinforced with highly unsaturated diene elastomers such as polybutadienes, polyisoprenes, butadiene and styrene copolymers. It has been proposed, in particular in document WO 2014 / 114607 A1, to use copolymers of ethylene and 1,3-butadiene (EBR) in rubber compositions for tires. The rubber compositions reinforced with copolymer of ethylene and 1,3-butadiene are described in particular for improving the performance compromise of a tire, namely wear resistance and rolling resistance. These diene rubber compositions, once crosslinked, have a much higher rigidity than the diene rubber compositions traditionally used and may therefore sometimes prove unsuitable for certain applications.

[0005] There is therefore a need to reduce the cured stiffness of such rubber compositions comprising an ethylene-based diene rubber. For this, it is known to reduce the crosslinking density of the rubber composition. However, this solution is accompanied by an increase in the hysteresis of the rubber composition, which is detrimental to rolling resistance. Document WO 2021 / 053296 A1 addressed the aforementioned need by providing rubber compositions which comprise a copolymer of ethylene and a 1,3-diene of formula CH=CR-CH=CH, the symbol R representing a hydrocarbon chain having 3 to 20 carbon atoms.

[0006] However, it is always interesting to find solutions to reduce rigidity. of ethylene and 1,3-diene copolymers in rubber compositions, while reducing hysteresis, i.e. improving the rolling resistance of a tire comprising these compositions.

[0007] Continuing its research, the Applicant unexpectedly discovered that the use of particular processing agents, conventionally used to improve the raw rheological properties of rubber compositions, in rubber compositions comprising a highly saturated diene elastomer, makes it possible to improve both the rigidity and the hysteresis.

[0008] Thus, the subject of the invention is a rubber composition based on at least: - an elastomer matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing between 50% and 95% by mole of the monomer units of the copolymer, - a reinforcing filler, - a crosslinking system, and - an implementing agent comprising a mixture of at least one carboxylic acid comprising from 4 to 28 carbon atoms and / or at least one carboxylic acid ester comprising from 4 to 28 carbon atoms and at least one aliphatic alcohol comprising from 2 to 22 carbon atoms.

[0009] It also relates to a tire comprising a composition according to the invention. I- DEFINITIONS

[0010] By the expression "composition based on", we mean a composition comprising the mixture and / or the in situ reaction product of the different constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacture of the composition; the composition thus being able to be in the totally or partially crosslinked state or in the non-crosslinked state.

[0011] By “elastomer matrix” is meant all of the elastomers in the composition, including the copolymer defined below.

[0012] Unless otherwise indicated, the rates of the units resulting from the insertion of a monomer into a copolymer are expressed as a molar percentage relative to the total of the monomer units of the copolymer.

[0013] By the expression "part by weight per hundred parts by weight of elastomer" (or pce), it is meant, within the meaning of the present invention, the part, by mass per hundred parts of elastomer present in the rubber composition considered.

[0014] Herein, unless expressly indicated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0015] On the other hand, any interval of values ​​designated by the expression "between a and b" is represents the range of values ​​from more than a to less than b (i.e., excluding the limits a and b), while any range of values ​​designated by the expression "from a to b" means the range of values ​​from a to b (i.e., including the strict limits a and b). In this document, when we designate an interval of values ​​by the expression "from a to b", we also and preferentially designate the interval represented by the expression "between a and b".

[0016] The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. In the same way, 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. This concerns in particular polymers, plasticizers, fillers, etc.

[0017] Unless otherwise indicated, all glass transition temperature "Tg" values ​​described herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to ASTM D3418 (1999). II- DESCRIPTION OF THE INVENTION II-1 Elastomeric matrix

[0018] According to the invention, the elastomer matrix comprises at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer represent between 50% and 95% by mole of the monomer units of the copolymer (hereinafter referred to as "the copolymer").

[0019] By "copolymer containing ethylene units and 1,3-diene units" is meant any copolymer comprising, within its structure, at least ethylene units and 1,3-diene units. The copolymer may thus comprise monomer units other than the ethylene units and the 1,3-diene units. For example, the copolymer may also comprise alpha-olefin units, in particular alpha-olefin units having from 3 to 18 carbon atoms, advantageously having 3 to 6 carbon atoms. For example, the alpha-olefin units may be chosen from the group consisting of propylene, butene, pentene, hexene or mixtures thereof.

[0020] As is known, the expression “ethylene unit” refers to the -(CH2-CH 2)- motif resulting from the insertion of ethylene into the elastomer chain.

[0021] As is known, the expression “1,3-diene unit” refers to the units resulting from the insertion of the 1,3-diene by a 1,4 addition, a 1,2 addition or a 3,4 addition in the case of a substituted diene such as isoprene for example.

[0022] Preferably, the 1,3-diene units are chosen from the group consisting of butadiene units, isoprene units and mixtures of these 1,3-diene units. In particular, the 1,3-diene units of the copolymer may be 1,3-diene units having 4 to 12 carbon atoms, for example 1,3-butadiene, 2-methyl-1,3-butadiene (or isoprene) units. More preferably, the 1,3-diene units are for more than 50%, by mole, or even preferably exclusively, 1,3-butadiene units.

[0023] In the copolymer, the ethylene units represent between 50% and 95% by mole of the monomer units of the copolymer. Advantageously, the ethylene units in the copolymer represent between 55% and 90%, preferably from 60% to 90%, preferably from 70% to 85%, by mole of the monomer units of the copolymer.

[0024] Advantageously, the copolymer is a copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene), that is to say, according to the invention, a copolymer consisting exclusively of ethylene units and 1,3-diene units (preferably 1,3-butadiene).

[0025] When the copolymer is a copolymer of ethylene and a 1,3-diene, it advantageously contains units of formula (I) and / or (II). The presence of a saturated 6-membered cyclic unit, 1,2-cyclohexanediyl, of formula (I) as a monomeric unit in the copolymer may result from a series of very specific insertions of ethylene and 1,3-butadiene into the polymer chain during its growth. -CH2-CH(CH=CH2)- (II)

[0026] For example, the copolymer of ethylene and a 1,3-diene may be devoid of units of formula (I). In this case, it preferably contains units of formula (V).

[0027] When the copolymer of ethylene and a 1,3-diene comprises units of formula (I) or units of formula (II) or units of formula (I) and units of formula (II), the molar percentages of the units of formula (I) and the units of formula (II) in the copolymer, respectively o and p, preferably satisfy the following equation (eq. 1), more preferably equation (eq. 2), o and p being calculated on the basis of all the monomer units of the copolymer. 0 < o+p < 25 (eq. 1) 0 < o+p < 20 (eq. 2)

[0028] According to the invention, the copolymer, preferably the copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene), is a random copolymer.

[0029] Advantageously, the number average mass (Mn) of the copolymer, preferably of the copolymer of ethylene and a 1,3-diene (preferably 1,3-butadiene) is within a range of 100,000 to 300,000 g / mol, preferably 150,000 to 250,000 g / mol.

[0030] The Mn of the copolymer is determined in a known manner, by size exclusion chromatography (SEC) as described in point IV-1 below.

[0031] The copolymer can be obtained according to different synthesis methods known to those skilled in the art, in particular depending on the targeted microstructure of the copolymer. Generally, it can be prepared by copolymerization of at least one diene, preferably a 1,3-diene, more preferably 1,3-butadiene, and ethylene and according to known synthesis methods, in particular in the presence of a catalytic system comprising a metallocene complex. Mention may be made, in this respect, of catalytic systems based on metallocene complexes, which catalytic systems are described in documents EP 1 092 731, WO 2004035639, WO 2007054223 and WO 2007054224 in the name of the Applicant. The copolymer, including when it is random, can also be prepared by a process using a preformed type catalytic system such as those described in documents WO 2017093654 A1, WO 2018020122 A1 and WO 2018020123 A1.

[0032] The copolymer may consist of a mixture of copolymers containing ethylene units and 1,3-diene units which differ from each other by their microstructures and / or by their macrostructures.

[0033] According to the invention, the elastomer matrix may comprise at least one other diene elastomer, which is not the copolymer as defined above, but this is not necessary. Preferably, the content of the at least one copolymer is within a range from more than 50 to 100 phr, preferably from 60 to 100 phr, preferably from 80 to 100 phr. Advantageously, the at least one copolymer containing ethylene units and 1,3-diene units is the only elastomer in the composition, i.e. it represents 100% by mass of the elastomer matrix.

[0034] By "diene" elastomer (or indistinctly rubber), whether natural or synthetic, must be understood in a known manner an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers carrying two carbon-carbon double bonds, conjugated or not). This definition includes the copolymer containing ethylene units and 1,3-diene units.

[0035] When the elastomer matrix comprises at least one other diene elastomer, which is not the copolymer containing ethylene units and 1,3-diene units, the at least one other elastomer may be, for example, chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. The butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR). II-2 Reinforcing charge

[0036] The rubber composition according to the invention advantageously comprises a reinforcing filler, known for its ability to reinforce a rubber composition usable for the manufacture of tires. Such a reinforcing filler typically consists of particles whose average size (by mass) is less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, in particular and more preferably between 20 and 150 nm.

[0037] The reinforcing filler may comprise carbon black, silica or a mixture thereof. Advantageously, the reinforcing filler of the composition according to the invention comprises more than 50% by weight, preferably more than 80% by weight, of silica, relative to the total weight of the reinforcing filler.

[0038] Any type of precipitated silica may be suitable as silicas, in particular highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. Examples that may be mentioned are the silicas described in applications WO03 / 016215-A1 and WO03 / 016387-A1. Among the commercial HDS silicas, we can notably use the silicas “Ultrasil ® 5000GR”, “Ultrasil ® 7000GR” from the company Evonik, the silicas “Zeosil ® 1085GR”, “Zeosil® 1115 MP”, “Zeosil® 1165MP”, “Zeosil® Premium 200MP”, “Zeosil® HRS 1200 MP” from the company Solvay.As non-HDS silica, the following commercial silicas can be used: silicas “Ultrasil ® VN2GR”, “Ultrasil ® VN3GR” from Evonik, silica “Zeosil® 175GR” from Solvay, silicas “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

[0039] To couple the silica to the diene elastomer, an at least bifunctional coupling agent (or bonding agent) is used in a well-known manner, intended to ensure a sufficient connection, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. By "bifunctional", we mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer. For example, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic filler and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

[0040] Preferably, the organosilanes are chosen from the group consisting of the or- polysulfurized ganosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated TESPT marketed under the name “Si69” by the company Evonik or bis-(triethoxysilylpropyl) disulfide, abbreviated TES PD marketed under the name “Si75” by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate marketed by the company Momentive under the name “NXT Silane”. More preferably, the organosilane is a polysulfurized organosilane.

[0041] The coupling agent content can easily be adjusted by a person skilled in the art. Typically and preferably, the coupling agent level represents from 0.5% to 15% by weight relative to the quantity of silica.

[0042] The level of reinforcing filler can easily be adjusted by a person skilled in the art depending on the use of the rubber composition. Advantageously, the level of reinforcing filler, in the composition according to the invention, is within a range from 20 to less than 200 phr, preferably from 25 to 150 phr, preferably from 30 to 100 phr.

[0043] Preferably, the composition according to the invention comprises from 20 to less than 200 pce, preferably from 25 to 150 pce, preferably from 30 to 100 pce of silica, and from 0.5 to 10 pce, preferably less than 1 to 5 pce of carbon black.

[0044] The blacks that can be used in the context of the present invention can be any black conventionally used in tires or their treads (so-called tire-grade blacks). Among the latter, mention will be made more particularly of reinforcing carbon blacks of the 100, 200, 300 series, or blacks of the 500, 600 or 700 series (ASTM grades), such as for example blacks NI 15, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772). These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a support for certain of the rubber additives used. Carbon blacks could, for example, already be incorporated into the diene elastomer, in particular isoprene, in the form of a masterbatch (see, for example, applications WO 97 / 36724 or WO 99 / 16600). II-3 Implementation agent

[0045] "Processing agents" are known to improve the raw rheological properties, in particular the Monney index, and therefore capable of improving the processability of a rubber composition comprising a reinforcing filler. These compounds are also called "processing aids" in English.

[0046] Surprisingly, the Applicant has noticed that the use of certain specific processing agents, in the presence of a copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer re having between 50% and 95% by mole of the monomer units of the copolymer in a rubber composition, makes it possible to improve the hysteresis of the composition while reducing its rigidity.

[0047] Thus, the rubber composition of the invention has the essential characteristic of comprising at least one processing agent comprising, preferably consisting essentially of, a mixture of at least one carboxylic acid comprising from 4 to 28 carbon atoms and / or at least one carboxylic acid ester comprising from 4 to 28 carbon atoms and at least one aliphatic alcohol comprising from 2 to 22 carbon atoms.

[0048] As an example of an implementing agent which can be used in the context of the present invention and is commercially available, mention may be made, for example, of “Aflux 37” or “Aflux 42” from the company Rhein Chemie.

[0049] By "consisting essentially of" in the sense of the present description, it is meant that the processing agent may contain, in addition to the carboxylic acid having from 4 to 28 carbon atoms (and / or the carboxylic acid ester having from 4 to 28 carbon atoms) and the aliphatic alcohol having from 2 to 22 carbon atoms, other ingredients in proportions which do not affect the characteristics and function of the processing agent, namely its capacity to improve the processability of a rubber composition reinforced by at least one reinforcing filler. The other ingredients which may be present in the processing agent may be, for example, ethylene glycol, polyethylene glycol, polyethylene wax dioxin, antioxidants or a mixture of these compounds.Preferably, the other ingredients which may optionally be present in the implementing agent represent less than 10% by weight of the total weight of the implementing agent, more preferably represent less than 6% by weight of the total weight of the implementing agent.

[0050] Preferably, the carboxylic acid (and / or the carboxylic acid ester) and the alcohol represent more than 50% by weight of the total ingredients of the processing agent, preferably more than 90% by weight of the total ingredients of the processing agent, preferably more than 94% by weight of the total ingredients of the processing agent.

[0051] Preferably, the implementing agent comprises, preferably consists essentially of, a mixture of at least one carboxylic acid comprising from 4 to 28 carbon atoms and at least one aliphatic alcohol comprising from 2 to 22 carbon atoms.

[0052] The carboxylic acid of the processing agent preferably comprises from 6 to 22 carbon atoms, preferably from 8 to 20 carbon atoms, preferably from 14 to 20 carbon atoms. Advantageously, the carboxylic acid of the processing agent implementation is a mixture of several carboxylic acids having 14 to 18 carbon atoms.

[0053] Preferably, the carboxylic acid of the implementing agent is a fatty acid preferably comprising from 6 to 22 carbon atoms, preferably from 8 to 20 carbon atoms, preferably from 14 to 20 carbon atoms, preferably from 14 to 18 carbon atoms.

[0054] The carboxylic acid ester of the processing agent may comprise from 6 to 22 carbon atoms, preferably from 8 to 20 carbon atoms, preferably from 14 to 20 carbon atoms. The carboxylic acid ester of the processing agent may be a mixture of several carboxylic acid esters having from 14 to 18 carbon atoms.

[0055] The carboxylic acid ester may be a fatty acid ester preferably comprising from 6 to 22 carbon atoms, preferably from 8 to 20 carbon atoms, preferably from 14 to 20 carbon atoms, preferably from 14 to 18 carbon atoms.

[0056] Preferably, the aliphatic alcohol of the processing agent is an aliphatic polyol comprising from 2 to 22 carbon atoms, preferably from 2 to 15 carbon atoms, preferably from 2 to 10 carbon atoms.

[0057] The aliphatic alcohol of the processing agent may be an aliphatic polyol selected from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane, erythritol, xylitol, sorbitol, dulcitol, mannitol, inositol and mixtures thereof. Preferably, the aliphatic alcohol of the processing agent is an aliphatic polyol selected from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane and mixtures thereof. Particularly advantageously, the aliphatic alcohol of the processing agent is trimethylolpropane.

[0058] Preferably, in the implementing agent, the weight ratio between said aliphatic alcohol and said carboxylic acid or said carboxylic acid ester is within a range from 1:20 to 10:1, preferably from 1:10 to 5:1.

[0059] Advantageously, the implementing agent comprises, preferably consists essentially of, a carboxylic acid comprising from 14 to 20 carbon atoms, more preferably comprising from 14 to 18 carbon atoms and an aliphatic polyol chosen from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane.

[0060] In a particularly advantageous manner, the implementing agent consists essentially of at least one carboxylic acid comprising from 14 to 18 atoms of carbon and trimethylolpropane. Such an implementing agent is commercially available, for example under the reference “Aflux 37” from the company Rhein Chemie.

[0061] Preferably, in the rubber composition, the level of the processing agent is within a range from 1 to 15 pce, preferably from 3 to 10 pce. II-4 Crosslinking system

[0062] The crosslinking system may be any type of system known to those skilled in the art in the field of tire rubber compositions. It may in particular be based on sulfur, and / or peroxide and / or bismaleimides.

[0063] Preferably, the crosslinking system is sulfur-based, in which case it is referred to as a vulcanization system. Advantageously, the vulcanization system comprises molecular sulfur and / or at least one sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally, also preferably, various known vulcanization activators may be used, such as zinc oxide, stearic acid or equivalent compound such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders.

[0064] Sulphur is used at a preferential rate of between 0.5 and 12 pce, in particular between 1 and 10 pce. The vulcanisation accelerator is used at a preferential rate of between 0.5 and 10 pce, more preferably between 0.5 and 5.0 pce.

[0065] Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0066] Particularly advantageously, the crosslinking system comprises sulfur and a vulcanization accelerator, and the mass ratio of the sulfur content to the vulcanization accelerator content is within a range from 0.4 to 1.5, preferably from 0.7 to 1.5, more preferably from 0.9 to 1.1. II-5 Plasticizing system

[0067] Although not necessary for the implementation of the present invention, the plasticizing system of the rubber composition according to the invention may comprise a plasticizing resin having a glass transition temperature above 20°C, known as “high Tg”, (also referred to herein as “plasticizing resin” for the sake of wording simplification).

[0068] The term “resin” is reserved in the present application, by definition known to those skilled in the art, for a compound which is solid at room temperature (23°C), as opposed to a liquid plasticizing compound such as an oil.

[0069] Plasticizing resins are polymers well known to those skilled in the art, essentially based on carbon and hydrogen but which may contain other types of atoms, usable in particular as plasticizing agents or tackifying agents in polymer matrices. They are generally by nature miscible (i.e., compatible) at the rates used with the polymer compositions for which they are intended, so as to act as true diluting agents. They have been described for example in the work entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9) of which chapter 5 is devoted to their applications, in particular in pneumatic rubber (5.5.). They can be aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, aliphatic / aromatic type, i.e. based on aliphatic and / or aromatic monomers.They can be natural or synthetic, petroleum-based or not (if so, also known as petroleum resins). Their Tg is preferably greater than 20°C (most often between 30°C and 95°C).

[0070] In a known manner, these plasticizing resins can also be described as thermoplastic resins in the sense that they soften upon heating and can thus be molded. They can also be defined by a softening point or temperature (in English, "softening point"). The softening temperature of a plasticizing resin is generally approximately 50 to 60°C higher than its Tg value. The softening point is measured according to ISO 4625 ("Ring and Bail" method). The macrostructure (Mw, Mn and Ip) is determined by size exclusion chromatography (SEC) as indicated below.

[0071] As a reminder, SEC analysis, for example, consists of separating macromolecules in solution according to their size through columns filled with a porous gel; the molecules are separated according to their hydrodynamic volume, the largest being eluted first. The sample to be analyzed is simply previously solubilized in an appropriate solvent, tetrahydrofuran at a concentration of 1 g / liter. Then the solution is filtered through a 0.45 pm porosity filter, before injection into the apparatus. The apparatus used is, for example, a "Waters alliance" chromatographic chain according to the following conditions: - elution solvent is tetrahydrofuran, - temperature 35°C; - concentration 1 g / liter; - flow rate: 1 ml / min; - injected volume: 100 ft; - Moore calibration with polystyrene standards; - set of 3 “Waters” columns in series (“Styragel HR4E”, “Styragel HR1” and “Styragel HR 0.5”); - detection by differential refractometer (for example "WATERS 2410") which can be equipped with operating software (for example "Waters Millennium").

[0072] A Moore calibration is carried out with a series of commercial polystyrene standards with low Ip (less than 1.2), of known molar masses, covering the range of masses to be analyzed. The mass average molar mass (Mw), the number average molar mass (Mn), as well as the polymolecularity index (Ip = Mw / Mn) are deduced from the recorded data (molar mass distribution curve).

[0073] All the molar mass values ​​indicated in the present application are therefore relative to calibration curves produced with polystyrene standards.

[0074] The plasticizing resin may have at least one, preferably 2 or 3, more preferably all, of the following characteristics: - a Tg greater than 25°C (in particular between 30°C and 100°C), more preferably greater than 30°C (in particular between 30°C and 95°C); - a softening point above 50°C (in particular between 50°C and 150°C); - a number-average molar mass (Mn) between 300 and 2000 g / mol, preferably between 400 and 1500 g / mol; - a polymolecularity index (Ip) less than 3, preferably 2 (reminder: Ip = Mw / Mn with Mw average molar mass by weight).

[0075] The above preferred high Tg plasticizing resins are well known to those skilled in the art and commercially available, for example sold as: - polylimonene resins: by the company DRT under the name "Dercolyte L120" (Mn=625 g / mol; Mw=1010 g / mol; Ip=1.6; Tg=72°C) or by the company ARIZONA under the name "Sylvagum TR7125C" (Mn=630 g / mol; Mw=950 g / mol; Ip=1.5; Tg=70°C); - C5 / vinylaromatic cut copolymer resins, in particular C5 / styrene cut or C5 / C9 cut: by Neville Chemical Company under the names "Super Nevtac 78", "Super Nevtac 85" or "Super Nevtac 99", by Goodyear Chemicals under the name "Wingtack Extra", by Kolon under the names "Hikorez T1095" and "Hikorez Tl 100", by Exxon under the names "Escorez 2101" and "Escorez 1273" ; - limonene / styrene copolymer resins: by DRT under the name "Dercolyte TS 105" from the company DRT, by ARIZONA Chemical Company under the names "ZT115LT" and "ZT5100".

[0076] The plasticizing resin having a glass transition temperature above 20°C may be chosen from the group comprising or consisting of cyclopentadiene homopolymer or copolymer resins (abbreviated CPD), dicyclopentadiene homopolymer or copolymer resins (abbreviated DCPD), terpene homopolymer or copolymer resins, C5-cut homopolymer or copolymer resins, C9-cut homopolymer or copolymer resins, alpha-methyl-styrene homopolymer or copolymer resins and mixtures thereof.Preferably, the plasticizing resin is selected from the group comprising or consisting of (D)CPD / vinylaromatic copolymer resins, (D)CPD / terpene copolymer resins, terpene phenol copolymer resins, (D)CPD / C5 cut copolymer resins, (D)CPD / C9 cut copolymer resins, terpene / vinylaromatic copolymer resins, terpene / phenol copolymer resins, C5 cut / vinylaromatic copolymer resins, and mixtures thereof.

[0077] The term "terpene" here groups together in a known manner the alpha-pinene, beta-pinene and limonene monomers; preferably a limonene monomer is used, a compound which is present in a known manner in the form of three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or dipentene, racemic of the dextrorotatory and levorotatory enantiomers. Suitable vinylaromatic monomers are, for example, styrene, alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyltoluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, any vinylaromatic monomer from a C9 cut (or more generally from a C8 to C10 cut).

[0078] More particularly, mention may be made of plasticizing resins chosen from the group consisting of (D)CPD homopolymer resins, (D)CPD / styrene copolymer resins, polylimonene resins, limonene / styrene copolymer resins, limonene / D(CPD) copolymer resins, C5 / styrene cut copolymer resins, C5 / C9 cut copolymer resins, and mixtures of these resins.

[0079] All of the above plasticizing resins are well known to those skilled in the art and commercially available, for example sold by the company DRT under the name "Dercolyte" for polylimonene resins, by the company Neville Chemical Company under the name "Super Nevtac", by Kolon under the name mination "Hikorez" or by the company Exxon Mobil under the name "Escorez" for C5 / styrene cut resins or C5 / C9 cut resins, or by the company Struktol under the name "40 MS" or "40 NS" (mixtures of aromatic and / or aliphatic resins).

[0080] The level of plasticizing resin having a glass transition temperature above 20°C in the composition according to the invention may be within a range from 10 to 120, preferably from 20 to 110 pce, preferably from 30 to 80 pce, preferably from 40 to 75 pce.

[0081] Although this is not necessary for the implementation of the present invention, the plasticizing system of the rubber composition according to the invention may comprise a plasticizer which is liquid at 23°C, known as “low Tg”, i.e. which by definition has a Tg of less than -20°C, preferably less than -40°C. According to the invention, the composition may optionally comprise from 0 to 60 pce of a plasticizer which is liquid at 23°C.

[0082] When a liquid plasticizer at 23°C is used, its level in the composition according to the invention can be within a range from 1 to 120 pce, preferably from 2 to 80 pce, more preferably from 3 to 40.

[0083] Any liquid plasticizer at 23°C (or extending oil), whether aromatic or non-aromatic, known for its plasticizing properties with respect to diene elastomers, can be used. At room temperature (23°C), these plasticizers or these oils, more or less viscous, are liquids (that is to say, as a reminder, substances having the capacity to eventually take the shape of their container), in contrast in particular to plasticizing resins which are by nature solid at room temperature.

[0084] Particularly suitable are liquid plasticizers at 23°C chosen from the group comprising or consisting of liquid diene polymers, polyolefin oils, naphthenic oils, paraffinic oils, DAE oils, MES (Medium Extracted Solvated) oils, TDAE (Treated Distillate Aromatic Extracts) oils, RAE (Residual Aromatic Extract) oils, TRAE (Treated Residual Aromatic Extract) oils and SRAE (Safety Residual Aromatic Extract) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these plasticizers which are liquid at 23°C.

[0085] Preferably, the plasticizer which is liquid at 23°C is chosen from the group comprising or consisting of MES oils, TDAE oils, naphthenic oils, vegetable oils and mixtures of these plasticizers which are liquid at 23°C.

[0086] Advantageously, the composition according to the invention comprises both a plasticizing resin having a glass transition temperature greater than 20°C and a liquid plasticizer at 23°C as defined previously at the aforementioned levels. II-6 Possible additives

[0087] The rubber compositions according to the invention may optionally also comprise all or part of the usual additives usually used in elastomer compositions for tires, such as, for example, fillers (reinforcing or non-reinforcing / other than those mentioned above), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants. II-7 Preparation of the compositions

[0088] The rubber compositions in accordance with the invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: - a first working phase or thermomechanical mixing (so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents are introduced into a suitable mixer such as a conventional internal mixer (for example of the "Banbury" type), in particular the elastomeric matrix, the reinforcing filler, the epoxy resin, any other various additives, with the exception of the crosslinking system, the amine hardener and the possible condensation accelerator. The incorporation of the filler into the elastomer can be carried out in one or more times by thermomechanical mixing.In the case where the filler is already incorporated in whole or in part into the elastomer in the form of a masterbatch as described for example in applications WO 97 / 36724 or WO 99 / 16600, it is the masterbatch which is directly kneaded and where appropriate the other elastomers or fillers present in the composition which are not in the form of a masterbatch are incorporated, as well as any other various additives other than the crosslinking system. The non-productive phase can be carried out at high temperature, up to a maximum temperature of between 110°C and 200°C, preferably between 130°C and 185°C, for a duration generally of between 2 and 10 minutes. - a second phase of mechanical work (so-called "productive" phase), which can be carried out in an external mixer such as a roller mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 120°C, for example between 40°C and 100°C. The crosslinking system is then incorporated, and everything is then mixed for a few minutes, for example between 5 and 15 min.

[0089] Such phases have been described for example in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.

[0090] The final composition thus obtained is then calendered, for example, in the form of a sheet or a plate, in particular for characterization in the laboratory, or further extruded (or co-extruded with another rubber composition) in the form of a semi-finished (or profiled) rubber usable for example as an internal layer of a tire. These products can then be used for the manufacture of tires, according to techniques known to those skilled in the art.

[0091] The composition may be either in the raw state (before crosslinking or vulcanization), or in the cured state (after crosslinking or vulcanization), and may be a semi-finished product which may be used in a tire.

[0092] The crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 130°C and 200°C, under pressure. II-8 Rubber article

[0093] The present invention also relates to a rubber article comprising at least one composition according to the invention. Preferably, the rubber article is a tire.

[0094] In the present invention, the term "tyre" means a pneumatic or non-pneumatic bandage. A pneumatic bandage usually comprises two beads intended to come into contact with a rim, a crown composed of at least one crown reinforcement and a tread, two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic bandage, for its part, usually comprises a base, designed for example for mounting on a rigid rim, a crown reinforcement, ensuring the connection with a tread and a deformable structure, such as spokes, ribs or cells, this structure being arranged between the base and the crown. Such non-pneumatic bandages do not necessarily comprise a sidewall. Non-pneumatic bandages are described for example in documents WO 03 / 018332 and FR2898077.Advantageously, the tire according to the invention is preferably a pneumatic bandage.

[0095] More particularly, the invention also relates to a tire comprising a composition according to the invention. The composition according to the invention is preferably present in the tread of the tire. It may constitute part or all of the tread of the tire.

[0096] The tire according to the invention can be intended to equip any type of vehicle, in particular motor vehicles, without any particular limitation. III- EXAMPLES III-1 Measurements and tests used

[0097] Dynamic properties (after curing): Tensile test

[0098] The dynamic properties are measured on a viscoanalyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a sample of vulcanized composition (cylindrical specimen 4 mm thick and 400 mm2 in cross-section) is recorded, subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, during a temperature sweep, under a fixed stress of 0.7 MPa, the complex dynamic shear modulus G* is recorded, at 60°C. The same sample is also subjected, at a temperature of 40°C, to a strain amplitude sweep from 0.1% to 100% (forward cycle), then from 100%> to 1% (return cycle). The non-linearity (noted NL or AG*) is the difference in shear modulus between 0.1% and 100% of strain in MPa.

[0099] For greater readability, the results are indicated on a base of 100 (percentage), the value 100 being assigned to the control T1. For G*, a result greater than 100 reflects a reduction in rigidity, which in this case constitutes an improvement in rigidity compared to the control composition. For non-linearity, a result greater than 100 reflects a reduction in hysteresis and therefore an improvement in the rolling resistance of the composition considered compared to the control composition.

[0100] Determination of the microstructure of elastomers by nuclear magnetic resonance (NMR):

[0101] Ethylene and 1,3-butadiene copolymers are characterized by 'H, 13C NMR spectrometry. The NMR spectra are recorded on a Brüker Avance III 500 MHz Spectrometer equipped with a BBIz-grad 5 mm "broadband" cryoprobe. The quantitative 'H NMR experiment uses a 30° single pulse sequence and a 5 second repetition delay between each acquisition. 64 to 256 accumulations are performed. The quantitative 13C NMR experiment uses a 30° single pulse sequence with proton decoupling and a 10 second repetition delay between each acquisition. 1024 to 10240 accumulations are performed. The two-dimensional 'H / 13C experiments are used to determine the structure of the polymers. The determination of the microstructure of copolymers is defined in the literature, according to the article by Llauro et al., Macromolecules 2001, 34, 6304-6311.

[0102] The NMR measurements are carried out at 25°C. The copolymers are in solution in a deuterated solvent (approximately 25 mg of elastomer in 1 mL), generally deuterated chloroform (CDCl3).

[0103] Determination of the macrostructure of polymers by size exclusion chromatography (SEC):

[0104] Size exclusion chromatography (SEC) allows the fractionation of polymer chains in a solvent according to their hydrodynamic volume. Like any chromatographic system, the technique is based on the elution of a solute (the polymer) through a column containing a stationary phase. The system is composed in this order: a solvent reservoir, a pumping system, a injector, a set of columns and detectors. The measuring chain is equipped with a Waters Alliance e2695 module and a Waters fRI410 refractometer.

[0105] The mobile phase is eluted with a flow rate of 1 mL / min. The polymer is solubilized in THF in the presence of 1% by weight of diisopropylamine and 1% by weight of triethylamine at a concentration of 1 g / L. A volume of 100 pL is injected through a set of 3 AGILENT size exclusion chromatography columns (MIXED B LS). The columns are thermostated in an oven at 35°C. The stationary phase of the columns is based on a polystyrene divinylbenzene gel with controlled porosity. The polymer chains are separated according to the hydrodynamic volume they occupy when they are solubilized in the solvent. The larger the volume they occupy, the less accessible the pores of the columns are and the shorter their elution time. Detection is ensured by a refractometer (RI) thermostated at 35°C.Each elution volume is associated with a mass via Moore calibration (certified standard passage: standard polystyrenes from Polymer Standard Service (Mainz). The WATERS: EMPOWER software is used for data acquisition and analysis. It is then possible to determine the number-average molar masses (Mn), the mass-average molar masses (Mw) as well as the polydispersity (Ip = Mw / Mn). Determination of Mooney viscosity ML 1+4

[0106] For polymers and rubber compositions, the Mooney viscosities ML(l+4) at 100°C are measured using an oscillating consistometer according to ASTM D-1646 (1999). The Mooney plasticity measurement is carried out according to the following principle: the composition in the raw state (i.e. before curing) is molded in a cylindrical enclosure heated to 100°C. After one minute of preheating, the rotor rotates within the test piece at 2 revolutions / minute and the torque needed to maintain this movement after 4 minutes of rotation is measured. The Mooney plasticity ML(l+4) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Nm). III-2 Synthesis of copolymer El:

[0107] The elastomer El (EBR) is prepared in the presence of a catalytic system based on a metallocene [Me2Si(Flu)2Nd(q-BH4)2Li(THF)] and a co-catalyst, butyloctyl-magnesium, according to the following procedure.

[0108] In a reactor containing methylcyclohexane, the co-catalyst (0.36 mmol / L) is added, then the metallocene (0.07 mmol / L). The alkylation time is 10 minutes, the reaction temperature is 20 °C. Then, ethylene and 1,3-butadiene are added continuously in the respective molar quantities of 80% and 20% in the reactor. The polymerization is carried out at 80 °C under a pressure of 8 bars. The polymerization reaction is stopped by cooling, degassing the reactor and addition of ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in a vacuum oven to constant mass using a method in accordance with that described in application WO2020 / 212184A1. III-3 Preparation of compositions

[0109] In the following examples, the rubber compositions were produced as described in point 11-7 above. In particular, the “non-productive” phase was carried out in a 0.4 liter mixer for 3.5 minutes, for an average paddle speed of 60 revolutions per minute until a maximum drop temperature of 165°C was reached. The “productive” phase was carried out in a cylinder tool at 40°C for 5 minutes.

[0110] The crosslinking of the composition was carried out at a temperature of 150°C, under pressure. III-4 Rubber composition tests

[0111] The examples presented below aim to compare the compromise of performances, rigidity and hysteresis of compositions in accordance with the present invention (C1 to C3) with control compositions (T1 and T2).

[0112] Table 1 shows the compositions tested (in pce), as well as the results obtained.

[0113] Compositions C1, C2, C3 and T2 differ from the control composition T1, only by the presence of a particular processing agent with a constant volume fraction of silica in the composition and with a constant level of coupling agent relative to the quantity of silica. The processing agent used for compositions C1, C2 and C3 is in accordance with the invention. The processing agent used for composition T2 is not in accordance with the invention.

[0114] [Tables 1] Compositions Tl Cl C2 C3 T2 Elastomer El(l) 100 100 100 100 100 Silica(2) 85.5 86.5 88.0 88.0 87.5 Volume fraction of (2) 18% 18% 18% 18% 18% Coupling agent(3) 6.8 6.9 7.0 7.0 7.0 N234(4) 3.0 3.0 3.0 3.0 3.0 Plasticizing resin(5) 50 50 50 50 50 Liquid plasticizing agent(6) 22 22 22 22 22 Compound 1(7) - 2.0 5.0 - - Compound 2(8) - - - 5.0 - Compound 3(9) - - - - 5.0 6PPD(10) 2 2 2 2 2 Stearic acid(ll) 2 2 2 2 2 ZnO(12) 1 1 1 1 1 Sulfur 1 1 1 1 1 Accelerator(13) 2 2 2 2 2 Properties AG* at 40°C (base 100) 100 124 147 109 90 G* at 60°C (base 100) 100 125 205 103 101

[0115] (1) Elastomer El obtained by the process described in point III-2 above (2) Silica “Zeosil 1165MP” from Solvay (3) Liquid silane triethoxysilylpropyltetrasulfide (TESPT) “Si69” from Evonik (4) Cabot Company ASTM N234 Carbon Black (5) Polylimonene resin “Dercolite L120” from DRT (Tg = 72°C) (6) TDAE “Vivatec 500” oil from British Petroleum (7) Implementation agent “Aflux 37” from Rhein Chemie (mixture including in particular C14 to C18 fatty acids and trimethylolpropane) (8) Implementation agent “Aflux 42” from Rhein Chemie (mixture including in particular C12 to C18 fatty acid esters and a C18 alcohol) (9) Implementation agent “Struktol 40MS” from the company Struktol (mixture including in particular aliphatic and aromatic hydrocarbon resins) (10) Nl,3-dimethylbutyl-N-phenylparaphenylenediamine “Santoflex 6-PPD” from Flexsys (11) Stearic acid “Pristerene 4931” from Uniqema company (12) Industrial grade zinc oxide from Umicore (13) N-cyclohexyl-2-benzothiazyl sulfenamide “Santocure CBS” from Flexsys

[0116] The results presented in Table 1 above show that the combination of a copolymer according to the invention and a specific processing agent in accordance with the invention makes it possible to improve both the hysteresis, and therefore the rolling resistance, and the rigidity of the composition. This effect is particularly marked when the processing agent comprises a mixture of at least one carboxylic acid comprising from 4 to 28 carbon atoms and at least one aliphatic polyol comprising from 2 to 22 carbon atoms.

Claims

Claims

1. Rubber composition based on at least: - an elastomer matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, the ethylene units in the copolymer representing between 50% and 95% by mole of the monomer units of the copolymer, - a reinforcing filler, - a crosslinking system, and - an implementing agent comprising a mixture of at least one carboxylic acid comprising from 4 to 28 carbon atoms and / or at least one carboxylic acid ester comprising from 4 to 28 carbon atoms and at least one aliphatic alcohol comprising from 2 to 22 carbon atoms.

2. The rubber composition of claim 1, wherein the copolymer containing ethylene units and 1,3-diene units is a copolymer of ethylene and 1,3-diene.

3. A rubber composition according to any preceding claim, wherein the 1,3-diene is 1,3-butadiene.

4. Rubber composition according to any one of the preceding claims, in which the content of the at least one copolymer containing ethylene units and 1,3-diene units is within a range of 50 to 100 phr, preferably 80 to 100 phr.

5. A rubber composition according to any preceding claim, wherein the processing agent comprises, preferably consists essentially of, a mixture of at least one carboxylic acid having from 4 to 28 carbon atoms and at least one aliphatic alcohol having from 2 to 22 carbon atoms.

6. A rubber composition according to any preceding claim, wherein the carboxylic acid of the processing agent comprises from 6 to 22 carbon atoms, preferably from 8 to 20 carbon atoms, preferably from 14 to 20 carbon atoms.

7. A rubber composition according to any preceding claim, wherein the carboxylic acid of the processing agent is a fatty acid comprising from 14 to 20 carbon atoms, preferably from 14 to 18 carbon atoms.

8. A rubber composition according to any preceding claim, wherein the aliphatic alcohol of the processing agent is an aliphatic polyol having from 2 to 15 carbon atoms, preferably from 2 to 10 carbon atoms.

9. A rubber composition according to any preceding claim, wherein the aliphatic alcohol of the processing agent is an aliphatic polyol selected from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane, erythritol, xylitol, sorbitol, dulcitol, mannitol, inositol and mixtures thereof, preferably from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane and mixtures thereof.

10. Rubber composition according to any one of the preceding claims, wherein the processing agent comprises, preferably consists essentially of, a carboxylic acid comprising from 14 to 20 carbon atoms, more preferably comprising from 14 to 18 carbon atoms and an aliphatic polyol selected from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane.

11. A rubber composition according to any one of the preceding claims, wherein the level of the processing agent is within a range of 1 to 15 phr, preferably 3 to 10 phr.

12. A rubber composition according to any preceding claim, wherein the reinforcing filler comprises more than 50% by weight, preferably more than 80% by weight of silica, relative to the total weight of the reinforcing filler.

13. A rubber composition according to any one of the preceding claims, wherein the level of the reinforcing filler is in a range from 20 to less than 200 phr, preferably from 30 to 100 phr.

14. A rubber composition according to any one of claims preceding, wherein the crosslinking system is a molecular sulfur-based and / or sulfur-donating agent-based vulcanization system.

15. A tire comprising a composition as defined in any one of claims 1 to 14, the composition being preferentially present in the tread of the tire.