Rubber composition based on highly saturated diene elastomer

Abstract

This invention relates to rubber compositions exhibiting improved stiffness and hysteresis, and tires comprising such compositions. The rubber compositions are based on at least one elastomer matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, wherein the ethylene units in the copolymer comprise between 50 mol% and 95 mol% of the monomer units of the copolymer; reinforcing fillers; a crosslinking system; and processing aids comprising at least one carboxylic acid containing 4 to 28 carbon atoms and / or at least one carboxylic acid ester containing 4 to 28 carbon atoms and at least one aliphatic alcohol containing 2 to 22 carbon atoms.

Description

Technical Field

[0001] This invention relates to rubber compositions intended specifically for use in the manufacture of tires or tire semi-finished products. Background Technology

[0002] Tires must meet a number of often conflicting technical requirements in a known manner, including low rolling resistance, high wear resistance, and high wet and dry grip.

[0003] From an environmental perspective, rolling resistance and abrasion resistance have proven to be the most important of these properties, as they can reduce fuel consumption and extend tire life, respectively.

[0004] Diene rubber compositions commonly used in tires are rubber compositions reinforced with highly unsaturated diene elastomers, such as polybutadiene, polyisoprene, and copolymers of butadiene and styrene. In particular, the use of copolymers of ethylene and 1,3-butadiene (EBR) in rubber compositions for tires has been proposed in document WO 2014 / 114607 A1. Rubber compositions reinforced with copolymers of ethylene and 1,3-butadiene are specifically described for improving the trade-off between tire performance qualities of abrasion resistance and rolling resistance. These diene rubber compositions, after crosslinking, exhibit significantly higher stiffness than conventionally used diene rubber compositions, and therefore may sometimes prove unsuitable for certain applications.

[0005] Therefore, it is necessary to reduce the cured stiffness of rubber compositions containing ethylene-based diene rubbers. One known approach is to reduce the crosslinking density of the rubber composition. However, this approach is accompanied by increased hysteresis in the rubber composition, which is detrimental to rolling resistance. Document WO 2021 / 053296 A1 addresses this need by providing a rubber composition containing a copolymer of ethylene and a 1,3-diene with the molecular formula CH=CR-CH=CH (where R represents a hydrocarbon chain having 3 to 20 carbon atoms).

[0006] In fact, it remains advantageous to find ways to reduce the stiffness of the copolymer of ethylene and 1,3-diene in rubber compositions while reducing hysteresis, that is, to improve the rolling resistance of tires containing these compositions. Summary of the Invention

[0007] The applicant company unexpectedly discovered, through ongoing research, that the use of specific processing aids typically used to improve the rheological properties of raw materials in rubber compositions containing highly saturated diene elastomers could simultaneously improve stiffness and hysteresis.

[0008] Therefore, the subject of this 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, wherein the ethylene units in the copolymer comprise between 50 mol% and 95 mol% of the monomer units of the copolymer. - Reinforcing filler, - Crosslinking system, and - A processing aid comprising at least one carboxylic acid containing 4 to 28 carbon atoms and / or at least one carboxylic acid ester containing 4 to 28 carbon atoms and at least one aliphatic alcohol containing 2 to 22 carbon atoms.

[0009] Another subject of the present invention is a tire comprising a composition according to the present invention.

[0010] I – Definition The statement “composition based” should be understood to mean that the composition comprises a mixture of various components used and / or in-situ reaction products, some of which are capable of reacting with each other and / or intended to react with each other (at least partially) during various stages of the composition’s manufacture; thus the composition may be in a fully cross-linked or partially cross-linked state or in a non-cross-linked state.

[0011] The term "elastomer matrix" should be understood to refer to all elastomers in the composition, including copolymers as defined below.

[0012] Unless otherwise stated, the content of units resulting from the insertion of monomers into a copolymer is expressed as a molar percentage relative to all monomer units in the copolymer.

[0013] Within the meaning of this invention, the expression "parts by weight / 100 parts by weight elastomer" (or phr) should be understood to refer to parts by weight / 100 parts of elastomer present in the rubber composition under consideration.

[0014] In this document, all percentages (%) indicated are weight percentages (%) unless otherwise expressly stated.

[0015] Furthermore, any numerical interval represented by the expression "between a and b" represents a range of values ​​from greater than a to less than b (i.e., excluding the endpoints a and b), while any numerical interval represented by the expression "from a to b" means a range of values ​​from a to b (i.e., including the strict endpoints a and b). In this document, when a numerical interval is represented by the expression "from a to b," it is also preferable to represent the interval represented by the expression "between a and b."

[0016] The compounds mentioned in the specification can be fossil-derived or bio-based. In the latter case, they can be produced partly or entirely from biomass, or obtained from renewable raw materials derived from biomass. Similarly, the mentioned compounds can also originate from the recycling of previously used materials; that is, they can be produced partly or entirely by a recycling process, or obtained from starting materials themselves derived from a recycling process. Polymers, plasticizers, fillers, etc., are particularly relevant.

[0017] Unless otherwise stated, all glass transition temperature “Tg” values ​​described herein were measured in a known manner by DSC (differential scanning calorimetry) in accordance with standard ASTM D3418 (1999).

[0018] II - Description of the Invention II-1 Elastomer Matrix According to the present invention, the elastomer matrix comprises at least one copolymer containing ethylene units and 1,3-diene units, wherein the ethylene units in the copolymer account for between 50 mol% and 95 mol% of the monomer units of the copolymer (hereinafter referred to as the "copolymer").

[0019] The term "copolymer containing ethylene units and 1,3-diene units" is understood to refer to any copolymer whose structure contains at least ethylene units and 1,3-diene units. Therefore, the copolymer may contain monomer units other than ethylene and 1,3-diene units. For example, the copolymer may also contain α-olefin units, particularly α-olefin units having 3 to 18 carbon atoms, advantageously having 3 to 6 carbon atoms. For example, the α-olefin units may be selected from propylene, butene, pentene, hexene, and mixtures thereof.

[0020] In a known manner, the term "ethylene unit" refers to the -(CH2-CH2)- unit generated by inserting ethylene into an elastomer chain.

[0021] In a known manner, a “1,3-diene unit” is defined as a unit produced by inserting a 1,3-diene into a substituted diene, such as isoprene, via 1,4-addition, 1,2-addition, or 3,4-addition.

[0022] Preferably, the 1,3-diene units are selected from butadiene units, isoprene units, and mixtures of these 1,3-diene units. In particular, the 1,3-diene units of the copolymer can be 1,3-diene units having 4 to 12 carbon atoms, such as 1,3-butadiene or 2-methyl-1,3-butadiene (or isoprene) units. More preferably, more than 50 mol% of the 1,3-diene units are 1,3-butadiene units, and indeed even more preferably, the 1,3-diene units are only 1,3-butadiene units.

[0023] In the copolymer, ethylene units account for between 50 mol% and 95 mol% of the copolymer monomer units. Advantageously, the ethylene units in the copolymer account for between 55 mol% and 90 mol% of the copolymer monomer units, preferably between 60 mol% and 90 mol%, and more preferably between 70 mol% and 85 mol%.

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

[0025] When the copolymer is a copolymer of ethylene and 1,3-diene, the copolymer advantageously comprises units of formula (I) and / or (II). The saturated six-membered ring unit (1,2-cyclohexanediyl) of formula (I) present as a monomer unit in the copolymer can be generated by a series of very specific insertions of ethylene and 1,3-butadiene into the polymer chain during the growth of the polymer chain.

[0026] (I) -CH2-CH(CH=CH2)-(II) For example, copolymers of ethylene and 1,3-diene may not contain units of formula (I). In this case, they preferably contain units of formula (V).

[0027] When the copolymer of ethylene and 1,3-diene comprises units of formula (I), or units of formula (II), or units of both formula (I) and formula (II), the molar percentages of units of formula (I) and units of formula (II) in the copolymer are o and p, respectively, which preferably satisfy the following formula 1, more preferably formula 2, where o and p are calculated based on all monomer units of the copolymer: 0 < o+p ≤ 25 (Formula 1) 0 < o+p < 20 (Formula 2) According to the present invention, the copolymer, preferably a copolymer of ethylene and 1,3-diene (preferably 1,3-butadiene), is a random copolymer.

[0028] Advantageously, the number-average molar mass (Mn) of the copolymer, preferably the copolymer of ethylene and 1,3-diene (preferably 1,3-butadiene), is in the range of 100,000 to 300,000 g / mol, preferably 150,000 to 250,000 g / mol.

[0029] The Mn of the copolymer was determined in a known manner by size exclusion chromatography (SEC), as described in point IV-1 below.

[0030] The copolymer can be obtained, in particular, according to the target microstructure of the copolymer, by various synthetic methods known to those skilled in the art. Typically, it can be prepared by copolymerizing at least a diene (preferably 1,3-diene, more preferably 1,3-butadiene) and ethylene, particularly in the presence of a catalytic system containing a metallocene complex, according to known synthetic methods. In this regard, references can be made to metallocene-based catalytic systems described in the applicant's documents EP 1 092 731, WO 2004 / 035639, WO 2007 / 054223 and WO 2007 / 054224. The copolymer (including when it is random) can also be prepared by using a pre-formed type of catalytic system (e.g., those methods described in documents WO2017 / 093654 A1, WO 2018 / 020122 A1 and WO 2018 / 020123 A1).

[0031] The copolymers can consist of a mixture of copolymers containing ethylene units and 1,3-diene units, which differ from each other in their microstructure and / or their macrostructure.

[0032] According to the invention, the elastomer matrix may contain at least one other diene elastomer that is not a copolymer as defined above, but this is not required. Preferably, the content of at least one copolymer is in the range of greater than 50 phr to 100 phr, more preferably 60 phr to 100 phr, and more preferably 80 phr to 100 phr. Advantageously, at least one copolymer containing ethylene units and 1,3-diene units is the only elastomer in the composition, that is, it accounts for 100% by weight of the elastomer matrix.

[0033] The term "diene" elastomer (or, indiscriminately, rubber), whether natural or synthetic, should be understood in a known manner as an elastomer at least partially (i.e., homopolymer or copolymer) composed of diene monomer units (monomers with two conjugated or non-conjugated carbon-carbon double bonds). This definition includes copolymers containing ethylene units and 1,3-diene units.

[0034] When the elastomer matrix comprises at least one diene elastomer that is not a copolymer containing ethylene units and 1,3-diene units, said at least one other elastomer may be selected, for example, polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. Butadiene copolymers are particularly selected from styrene-butadiene copolymers (SBR).

[0035] II-2 Reinforced Packing The rubber composition according to the invention advantageously includes a reinforcing filler, which is known to strengthen rubber compositions that can be used to manufacture tires. Such reinforcing filler typically consists of particles with an average size (by weight) of less than one micrometer, typically less than 500 nanometers, most commonly between 20 and 200 nanometers, and particularly and more preferably between 20 and 150 nanometers.

[0036] The reinforcing filler may include one of carbon black, silica, or mixtures 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.

[0037] Any type of precipitated silica, particularly highly dispersible precipitated silica (referred to as "HDS"), can be suitable for use as silica. These precipitated silicas (whether highly dispersible or not) are well known to those skilled in the art. For example, references may be made to the silica described in applications WO03 / 016215-A1 and WO03 / 016387-A1. Among commercially available HDS silicas, Ultrasil® 5000GR and Ultrasil® 7000GR silica from Evonik, or Zeosil® 1085GR, Zeosil® 1115 MP, Zeosil® 1165MP, Zeosil® Premium 200MP, and Zeosil® HRS 1200 MP silica from Solvay, may be used in particular. As non-HDS silica, the following commercially available silicas can be used: Ultrasil® VN2GR and Ultrasil® VN3GR silicas from Evonik, Zeosil® 175GR silicas from Solvay, or Hi-Sil EZ120G(-D), Hi-Sil EZ160G(-D), Hi-Sil EZ200G(-D), Hi-Sil 243LD, Hi-Sil 210 and Hi-Sil HDP 320G silicas from PPG.

[0038] To couple silica to a diene elastomer, a coupling agent (or binder) that is at least bifunctional is used in a known manner to provide a satisfactory chemical and / or physical bond between the inorganic filler (its particulate surface) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. The term "bifunctional" is understood to mean that the compound has 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 contain a first functional group containing silicon atoms and a second functional group containing sulfur atoms, the first functional group being capable of interacting with the hydroxyl groups of the inorganic filler and the second functional group being capable of interacting with the diene elastomer.

[0039] Preferably, the organosilane is selected from organosilane polysulfides (which are symmetrical or asymmetrical), such as bis(3-triethoxysilylpropyl)tetrasulfide sold by Evonik under the name Si69 with the abbreviation TESPT, or bis(triethoxysilylpropyl)disulfide sold by Evonik under the name Si75 with the abbreviation TESPD, polyorganosiloxanes, mercaptosilanes, and terminally capped mercaptosilanes, such as 3-octanoylthiopropyltriethoxysilane sold by Momentive under the name NXT silane. More preferably, the organosilane is an organosilane polysulfide.

[0040] Those skilled in the art can readily adjust the content of the coupling agent. Typically and preferably, the content of the coupling agent is 0.5% to 15% by weight relative to the amount of silica.

[0041] Those skilled in the art can easily adjust the content of reinforcing filler according to the intended use of the rubber composition. Advantageously, the content of reinforcing filler in the compositions according to the invention is in the range of 20 phr to less than 200 phr, preferably 25 phr to 150 phr, and more preferably 30 phr to 100 phr.

[0042] Preferably, the composition according to the invention comprises 20 phr to less than 200 phr, preferably 25 phr to 150 phr, more preferably 30 phr to 100 phr of silica, and 0.5 phr to 10 phr, more preferably less than 1 phr to 5 phr of carbon black.

[0043] The carbon black that can be used in the context of this invention can be any carbon black conventionally used in tires or their treads (“tire-grade” carbon black). More specifically, reference will be made to 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. These carbon blacks can be used alone (e.g., in a commercially available state) or in any other form (e.g., as a carrier for some rubber additives used). Carbon black can, for example, be incorporated into diene elastomers in masterbatch form, particularly isoprene elastomers (see, for example, applications WO 97 / 36724 and WO 99 / 16600).

[0044] II-3 Processing aids It is known that "processing aids" are used to improve the rheological properties of rubber compositions containing reinforcing fillers in the untreated state, particularly the Mooney index, thereby improving their processability.

[0045] Surprisingly, the applicant company noted that in the presence of copolymers containing ethylene units and 1,3-diene units in the rubber composition (where the ethylene units in the copolymer account for between 50 mol% and 95 mol% of the copolymer monomer units), the use of certain processing aids can improve the hysteresis of the composition while reducing its stiffness.

[0046] Therefore, the rubber composition of the present invention has the following essential characteristics: it contains at least one processing aid, which comprises, preferably, a mixture of at least one carboxylic acid containing 4 to 28 carbon atoms and / or at least one carboxylic acid ester containing 4 to 28 carbon atoms and at least one aliphatic alcohol containing 2 to 22 carbon atoms.

[0047] As an example of a commercially available processing aid that can be used in the context of this invention, Aflux 37 or Aflux 42, obtained from Rhein Chemie, may be mentioned, for example.

[0048] In the context of this specification, the term "consistently composed of" means that, in addition to carboxylic acids (and / or carboxylic esters containing 4 to 28 carbon atoms) and aliphatic alcohols containing 2 to 22 carbon atoms, the processing aid may contain other components in proportions that do not affect the properties and function of the processing aid, i.e., its ability to improve the processability of a rubber composition reinforced with at least one reinforcing filler. Other components that may be present in the processing aid may be, for example, ethylene glycol, polyethylene glycol, dioxins, polyethylene waxes, antioxidants, or mixtures of these compounds. Preferably, the other components that may optionally be present in the processing aid constitute less than 10% by weight of the total weight of the processing aid, more preferably less than 6% by weight of the total weight of the processing aid.

[0049] Preferably, carboxylic acids (and / or carboxylic esters) and alcohols account for more than 50% by weight of all components of the processing aid, more preferably more than 90% by weight of all components of the processing aid, and more preferably more than 94% by weight of all components of the processing aid.

[0050] Preferably, the processing aid comprises, and more preferably consists of, a mixture of at least one carboxylic acid containing 4 to 28 carbon atoms and at least one aliphatic alcohol containing 2 to 22 carbon atoms.

[0051] The carboxylic acid in the processing aid preferably contains 6 to 22 carbon atoms, more preferably 8 to 20 carbon atoms, and even more preferably 14 to 20 carbon atoms. Advantageously, the carboxylic acid in the processing aid is a mixture of several carboxylic acids having 14 to 18 carbon atoms.

[0052] Preferably, the carboxylic acid in the processing aid is a fatty acid containing preferably 6 to 22 carbon atoms, preferably 8 to 20 carbon atoms, preferably 14 to 20 carbon atoms, and preferably 14 to 18 carbon atoms.

[0053] The carboxylic acid ester of the processing aid may contain 6 to 22 carbon atoms, preferably 8 to 20 carbon atoms, and more preferably 14 to 20 carbon atoms. The carboxylic acid ester of the processing aid may be a mixture of several carboxylic acid esters having 14 to 18 carbon atoms.

[0054] The carboxylic acid ester can be a fatty acid ester containing preferably 6 to 22 carbon atoms, preferably 8 to 20 carbon atoms, preferably 14 to 20 carbon atoms, and preferably 14 to 18 carbon atoms.

[0055] Preferably, the aliphatic alcohol in the processing aid is an aliphatic polyol containing 2 to 22 carbon atoms, more preferably 2 to 15 carbon atoms, and even more preferably 2 to 10 carbon atoms.

[0056] The aliphatic alcohol in the processing aid may be selected from aliphatic polyols including 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, galactitol, mannitol, inositol, and mixtures thereof. Preferably, the aliphatic alcohol in the processing aid is selected from aliphatic polyols including 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 in the processing aid is trimethylolpropane.

[0057] Preferably, in the processing aid, the weight ratio of the aliphatic alcohol to the carboxylic acid or the carboxylic acid ester is in the range of 1:20 to 10:1, more preferably 1:10 to 5:1.

[0058] Preferably, the processing aid comprises, and more preferably consists of, a carboxylic acid containing 14 to 20 carbon atoms, more preferably containing 14 to 18 carbon atoms, and an aliphatic polyol selected from 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 and trimethylolpropane.

[0059] Particularly advantageously, the processing aid consists essentially of at least one carboxylic acid containing 14 to 18 carbon atoms and trimethylolpropane. Such processing aids are commercially available, for example, from Rhein Chemie under the trade name Aflux 37.

[0060] Preferably, the content of the processing aid in the rubber composition is in the range of 1 to 15 phr, more preferably 3 to 10 phr.

[0061] II-4 Crosslinking System The crosslinking system can be any type of system known to those skilled in the art in the field of rubber compositions for tires. It can be particularly based on sulfur and / or peroxides and / or bismaleimide.

[0062] Preferably, the crosslinking system is based on sulfur; it is thus referred to as a vulcanization system. Advantageously, the vulcanization system contains molecular sulfur and / or at least one sulfur donor. It is also preferred that at least one vulcanization accelerator is present, and optionally, it is also preferred that various known vulcanization activators can be used, such as zinc oxide, stearic acid or equivalent compounds (e.g., salts of stearic acid) and salts of transition metals, guanidine derivatives (especially diphenylguanidine), or known vulcanization inhibitors.

[0063] The preferred sulfur content is between 0.5 phr and 12 phr, particularly between 1 phr and 10 phr. A vulcanization accelerator is used at a preferred content between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr.

[0064] As accelerators, any compound capable of acting as an accelerator for sulfur 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 dithiuram (ZBEC), and mixtures of these compounds.

[0065] Particularly advantageously, the crosslinking system comprises sulfur and a vulcanization accelerator, and the weight ratio of sulfur content to vulcanization accelerator content is in the range of 0.4 to 1.5, preferably 0.7 to 1.5, and more preferably 0.9 to 1.1.

[0066] II-5 Plasticizing System Although not essential for the implementation of the present invention, the plasticizing system of the rubber composition according to the present invention may include a plasticizing resin with a glass transition temperature greater than 20°C, referred to as "high Tg" (for simplicity, it is also referred to as "plasticizing resin" herein).

[0067] In this patent application, the term "resin" is retained, according to the definition known to those skilled in the art, to refer to a compound that is solid at ambient temperature (23°C), as opposed to a liquid plasticizing compound (e.g., oil).

[0068] Plasticizing resins are polymers known to those skilled in the art, which are essentially based on carbon and hydrogen but may contain other types of atoms, and can be used in particular as plasticizers or tackifiers in polymer matrices. They are generally naturally miscible (i.e., compatible) with the polymer compositions to which they are intended at the concentrations used, thus acting as true diluents. They have been described, for example, in the work of R. Mildenberg, M. Zander, and G. Collin entitled "..." Hydrocarbon ResinsIn the book "..." (New York, VCH, 1997, ISBN 3-527-28617-9), Chapter 5 of the book discusses their applications, particularly in the field of tire rubber (5.5.). Rubber Tires and Mechanical Goods These can be aliphatic, alicyclic, aromatic, hydrogenated aromatic, or aliphatic / aromatic types, i.e., based on aliphatic and / or aromatic monomers. They can be natural or synthetic and can be petroleum-based or not (if petroleum-based, they are also called petroleum resins). Their Tg is preferably greater than 20°C (typically between 30°C and 95°C).

[0069] In a known manner, these plasticized resins can also be referred to as thermoplastic resins in the sense that they soften upon heating and thus can be molded. They can also be defined by their softening point. The softening point of a plasticized resin is typically about 50°C to 60°C higher than its Tg value. The softening point is measured according to standard ISO 4625 (“Ring and Sphere Method”). The macrostructure (Mw, Mn, and PI) is determined by size exclusion chromatography (SEC) as described below.

[0070] It should be noted that SEC analysis, for example, involves separating macromolecules in solution based on their size using a column packed with a porous gel; molecules are separated according to their hydrodynamic volume, with the largest eluting first. The sample to be analyzed is pre-dissolved simply in a suitable solvent, tetrahydrofuran, at a concentration of 1 g / L. The solution is then filtered through a filter with a porosity of 0.45 µm before injection into the instrument. The instrument used is, for example, a WatersAlliance chromatogram under the following conditions: - Elution solvent: tetrahydrofuran; - Temperature: 35℃; - Concentration: 1 g / L; - Flow rate: 1 ml / min; - Injection volume: 100 microliters; - Molar calibration using polystyrene standards: - A set of three Waters columns connected in series (Styragel HR4E, Styragel HR1 and Styragel HR0.5); - Detection is performed using a differential refractometer (e.g., Waters 2410) with operating software (e.g., Waters Millenium).

[0071] Molar calibration was performed using a series of commercially available polystyrene standards with low polydispersity index (PI) (less than 1.2) and known molar masses covering the mass range to be analyzed. Weight-average molar mass (Mw), number-average molar mass (Mn), and polydispersity index (PI = Mw / Mn) were derived from recorded data (weight distribution curves of molar mass).

[0072] Therefore, all molar mass values ​​shown in this patent application are relative to a calibration curve generated using polystyrene standards.

[0073] Plasticized resins can exhibit at least one of the following properties, preferably two or three, and more preferably all of the following properties: - Tg greater than 25°C (especially between 30°C and 100°C), more preferably greater than 30°C (especially between 30°C and 95°C); - Softening point greater than 50°C (especially between 50°C and 150°C); - Number-average molar mass (Mn) between 300 and 2000 g / mol, preferably between 400 and 1500 g / mol. - The polydispersity index (PI) should be less than 3, preferably less than 2 (Note: PI = Mw / Mn, where Mw is the weight-average molar mass).

[0074] The preferred high-Tg plasticizing resins described above are known to those skilled in the art and are commercially available, for example, regarding the sale of the following resins: - Polylimonene resin: sold by DRT under the name Dercolyte L120 (Mn = 625 g / mol; Mw = 1010 g / mol; PI = 1.6; Tg = 72°C), or by Arizona Chemical Company under the name Sylvagum TR7125C (Mn = 630 g / mol; Mw = 950 g / mol; PI = 1.5; Tg = 70°C); - C5 fraction / vinyl aromatic copolymer resins, especially C5 fraction / styrene or C5 fraction / C9 fraction copolymer resins: sold by Neville Chemical Company under the names Super Nevtac 78, Super Nevtac 85 and Super Nevtac 99, by Goodyear Chemicals under the name Wingtack Extra, by Kolon under the names Hikorez T1095 and Hikorez T1100, or by Exxon under the names Escorez 2101 and Escorez 1273; - Limonene / styrene copolymer resin: sold by DRT under the name Dercolyte TS 105, or by Arizona Chemical Company under the names ZT115LT and ZT5100.

[0075] Plasticizing resins with a glass transition temperature greater than 20°C can be selected from cyclopentadiene (CPD) homopolymers or copolymers, dicyclopentadiene (DCPD) homopolymers or copolymers, terpene homopolymers or copolymers, C5 fraction homopolymers or copolymers, C9 fraction homopolymers or copolymers, α-methylstyrene homopolymers or copolymers, and mixtures thereof. Preferably, the plasticizing resin is selected from (D)CPD / vinyl aromatic copolymers, (D)CPD / terpene copolymers, terpene / phenol copolymers, (D)CPD / C5 fraction copolymers, (D)CPD / C9 fraction copolymers, terpene / vinyl aromatic copolymers, terpene / phenol copolymers, C5 fraction / vinyl aromatic copolymers, and mixtures thereof.

[0076] The term "terpene" here refers in a known manner to include α-pinene, β-pinene, and limonene monomers; preferably, limonene monomers are used, which are known to exist in three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or dipentene (i.e., a racemic mixture of the dextrorotatory and levorotatory enantiomers). Suitable vinyl aromatic monomers include, for example: styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, p-(tert-butyl)styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinyltrimethylbenzene, divinylbenzene, vinylnaphthalene, or derived from C9 fractions (or more generally from C8 to C9 fractions). 10 Any vinyl aromatic monomer (distillate).

[0077] More specifically, reference may be made to plasticizing resins selected from the following: (D)CPD homopolymer resins, (D)CPD / styrene copolymer resins, polylimonene resins, limonene / styrene copolymer resins, limonene / D(CPD) copolymer resins, C5 fraction / styrene copolymer resins, C5 fraction / C9 fraction copolymer resins, and mixtures thereof.

[0078] All of the above-mentioned plasticizing resins are well known to those skilled in the art and are commercially available, such as polylimonene resin sold by DRT under the name Dercolyte, C5 fraction / styrene resin or C5 fraction / C9 fraction resin sold by Neville Chemical Company under the name Super Nevtac, sold by Kolon under the name Hikorez, or sold by Exxon Mobil under the name Escorez, or mixtures of aromatic and / or aliphatic resins sold by Struktol under the names 40 MS or 40 NS.

[0079] In the compositions according to the invention, the content of plasticizing resin with a glass transition temperature greater than 20°C can be in the range of 10 to 120 phr, preferably 20 to 110 phr, preferably 30 to 80 phr, and preferably 40 to 75 phr.

[0080] While not essential for the implementation of this invention, the plasticizing system of the rubber composition according to the invention may include a plasticizer known as "low Tg" that is liquid at 23°C, i.e., by definition exhibiting a Tg below -20°C, preferably below -40°C. According to the invention, the composition may optionally contain a plasticizer that is liquid at 23°C with a concentration of 0 to 60 phr.

[0081] When a plasticizer that is liquid at 23°C is used, its content in the composition according to the invention can be in the range of 1 to 120 phr, preferably 2 to 80 phr, more preferably 3 to 40 phr.

[0082] Any plasticizer (or oil) that is liquid at 23°C, whether aromatic or non-aromatic, can be used, provided that it is known to have plasticizing properties for diene elastomers. At ambient temperature (23°C), these plasticizers or these oils (which are more or less viscous) are liquids (i.e., substances capable of ultimately taking the shape of their containers), which is particularly in contrast to plasticized resins that are naturally solid at ambient temperature.

[0083] Particularly suitable plasticizers that are liquid at 23°C are selected from: liquid diene polymers, polyolefin oils, naphthenic oils, paraffin oils, DAE oils, MES (medium-extracted solvates) oils, TDAE (treated distilled aromatic extracts) oils, RAE (residual aromatic extracts) oils, TRAE (treated residual aromatic extracts) oils, SRAE (safe residual aromatic extracts) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate ester plasticizers, sulfonate plasticizers, and mixtures of these plasticizers that are liquid at 23°C.

[0084] Preferably, the plasticizer that is liquid at 23°C is selected from MES oil, TDAE oil, naphthenic oil, vegetable oil, and mixtures of these plasticizers that are liquid at 23°C.

[0085] Advantageously, the composition according to the invention contains, in the above-described amounts, both a plasticizing resin with a glass transition temperature greater than 20°C as defined above and a plasticizer that is liquid at 23°C.

[0086] II-6 Possible Additives The rubber composition according to the invention may also optionally include all or part of the common additives commonly used in elastomer compositions for tires, such as fillers (reinforcing or non-reinforcing fillers other than those mentioned above), pigments, or protective agents (e.g., anti-ozone waxes, chemical anti-ozone agents, or antioxidants).

[0087] Preparation of II-7 Composition The rubber composition according to the invention can be manufactured in a suitable mixer using two consecutive preparation stages known to those skilled in the art: - The first stage of thermomechanical processing or kneading (“non-production” stage), which can be carried out in a single thermomechanical stage, involves the introduction of all necessary components, except for the crosslinking system, amine-based hardener, and optional condensation accelerator, particularly the elastomer matrix, reinforcing filler, epoxy resin, and various other optional additives, into a suitable mixer, such as a standard closed mixer (e.g., of the Banbury type). Fillers can be introduced into the elastomer in one or multiple stages by thermomechanical kneading. Where the filler has already been fully or partially introduced into the elastomer in masterbatch form (as described, for example, in patent applications WO 97 / 36724 and WO 99 / 16600), the masterbatch is kneaded directly, and, where appropriate, other elastomers or fillers not in masterbatch form present in the composition, as well as various other optional additives besides the crosslinking system, are introduced. The non-production stage can be carried out at high temperatures, typically for a period of 2 to 10 minutes, with a maximum temperature between 110°C and 200°C, preferably between 130°C and 185°C. - The second stage of machining (“production” stage) can be 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.

[0088] Such stages have been described, for example, in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO 00 / 05300, and WO 00 / 05301.

[0089] The resulting final composition is then calendered, for example, into sheets or plates for laboratory characterization, or extruded (or co-extruded with another rubber composition) into a rubber semi-finished product (or molded part) that can be used, for example, as an inner layer of a tire. These products can then be used to manufacture tires according to techniques known to those skilled in the art.

[0090] The composition can be in an untreated state (before crosslinking or vulcanization) or in a cured state (after crosslinking or vulcanization), and can be a semi-finished product that can be used in tires.

[0091] Crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example, under pressure at a temperature between 130°C and 200°C.

[0092] II-8 Rubber Products Another subject of the invention is a rubber article comprising at least one composition according to the invention. Preferably, the rubber article is a tire.

[0093] In this invention, "tire" is understood to refer to either a pneumatic tire or a non-pneumatic tire. A pneumatic tire typically includes two beads intended to contact a rim, a crown consisting of at least one crown reinforcement and a tread, and two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic tire typically includes a base designed for, for example, mounting on a rigid rim, a crown reinforcement ensuring connection to the tread, and deformable structures such as spokes, ribs, or cells arranged between the base and the crown. Such a non-pneumatic tire does not necessarily include sidewalls. Non-pneumatic tires are described, for example, in documents WO 03 / 018332 and FR 2 898 077. Advantageously, the tire according to the invention is preferably a pneumatic tire.

[0094] More particularly, another subject of the invention is 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 can form part or all of the tire tread.

[0095] The tires according to the invention can be designed to fit any type of vehicle, particularly motor vehicles, without any particular limitation. Detailed Implementation

[0096] III-Example Measurements and tests used in III-1 Kinetic properties (after curing): Tensile test Kinetic properties were measured using a viscosity analyzer (Metravib VA4000) according to standard ASTM D 5992-96. The response of samples of the vulcanized composition (cylindrical test specimens with a thickness of 4 mm and a cross-sectional area of ​​400 mm²) to simple alternating sinusoidal shear stress at a frequency of 10 Hz during a temperature scan under a fixed stress of 0.7 MPa; the complex kinetic shear modulus G at 60 °C was also recorded. * At 40°C, the same sample was also subjected to strain amplitude scans from 0.1% to 100% (outward cycle) and then from 100% to 0.1% (backward cycle). Nonlinearity (labeled NL or AG) * () refers to the difference in shear modulus between 0.1% and 100% strain, expressed in MPa.

[0097] For better readability, the results (percentages) are displayed in base 100, with the value 100 assigned to control T1. For G... * A result greater than 100 indicates a decrease in stiffness, which in this case is considered an improvement in stiffness relative to the control composition. For nonlinearity, a result greater than 100 indicates a decrease in hysteresis, thus indicating an improvement in rolling resistance of the composition under consideration compared to the control composition.

[0098] The microstructure of the elastomer was determined using nuclear magnetic resonance (NMR): pass 1 H and 13 C10 NMR spectroscopy was used to characterize the copolymer of ethylene and 1,3-butadiene. NMR spectra were recorded on a Brüker Avance III 500 MHz spectrometer equipped with a BBI Z-grade 5 mm "broadband" cryoprobe. 1 1H NMR quantification experiments used a simple 30° pulse sequence and a 5-second repetition time between each acquisition. Accumulations were performed from 64 to 256. 13 Quantitative C NMR experiments were performed using a simple 30° pulse sequence with proton decoupling and a 10-second repetition time between each acquisition. Accumulations were performed from 10²⁴ to 10²⁴⁰. 1 H / 13 Two-dimensional experiments were used to determine the structure of polymers. According to an article by Llauro et al. Macromolecules (2001, 34, 6304-6311), in which the determination of the microstructure of the copolymer was specified.

[0099] NMR measurements were performed at 25°C, with the copolymer dissolved in a deuterated solvent (approximately 25 mg of elastomer per mL), typically deuterated chloroform (CDCl3).

[0100] The macroscopic structure of the polymer was determined by size exclusion chromatography (SEC): Size exclusion chromatography (SEC) separates polymer chains in a solvent based on their hydrodynamic volume. Like any chromatographic system, this technique is based on the elution of a solute (polymer) through a column containing a stationary phase. The system consists of a solvent reservoir, pump system, syringe, column assembly, and detector. Measurement lines are equipped with a Waters Alliance e2695 module and a Waters fRI410 refractometer.

[0101] The mobile phase was eluted at a flow rate of 1 mL / min. The polymer was dissolved in THF at a concentration of 1 g / L in the presence of 1% diisopropylamine and 1% triethylamine. A 100 μL volume was injected through a set of three Agilent size exclusion columns (MIXED-B LS). The columns were maintained at 35°C in an oven. The stationary phase was based on a porosity-controlled polystyrene / divinylbenzene gel. Polymer chains were separated based on the hydrodynamic volume occupied by the polymer chains when dissolved in the solvent. The larger the volume occupied by the polymer chain, the fewer pores it can enter, and the shorter the elution time. Detection was performed using a refractometer (RI) maintained at 35°C. Each elution volume was molar-calibrated and mass-dependent (using certified standards: polystyrene standards obtained from Polymer Standard Service (Mainz)). Data were acquired and analyzed using Waters Empower software. Then the number-average molar mass (Mn), weight-average molar mass (Mw), and dispersion (PI = Mw / Mn) can be determined.

[0102] Determination of Mooney viscosity ML 1+4 For polymer and rubber compositions, Mooney viscosity ML(1+4) at 100°C is measured using an oscillating consistency meter according to standard ASTM D-1646 (1999). Mooney plasticity is measured based on the following principle: the untreated composition (i.e., before curing) is molded in a cylindrical chamber heated to 100°C. After 1 minute of preheating, a rotor is rotated within the test specimen at 2 revolutions per minute, and the working torque used to maintain this motion is measured after 4 minutes of rotation. Mooney plasticity ML(1+4) is expressed in Mooney units (MU, 1 MU = 0.83 Nm).

[0103] Synthesis of copolymer E1 of III-2: Elastomer E1 (EBR) was prepared according to the following procedure in the presence of a metallocene-based catalytic system [Me2Si(Flu)2Nd(μ-BH4)2Li(THF)] and a cocatalyst, butyloctylmagnesium.

[0104] A co-catalyst (0.36 mmol / L) was added to a reactor containing methylcyclohexane, followed by the addition of metallocene (0.07 mmol / L). The alkylation reaction lasted for 10 minutes at a temperature of 20°C. Subsequently, ethylene and 1,3-butadiene were continuously added to the reactor in molar amounts of 80% and 20%, respectively. The polymerization reaction was carried out at 80°C under a pressure of 8 bar. The polymerization reaction was stopped by cooling, degassing the reactor, and adding ethanol. An antioxidant was added to the polymer solution. The copolymer was recovered by drying it to constant weight in a vacuum oven according to the method described in application WO2020 / 212184A1.

[0105] Preparation of III-3 Composition In the following examples, the rubber composition was prepared as described in points II-7 above. Specifically, the "non-production" stage was carried out in a 0.4-liter mixer for 3.5 minutes (with an average blade speed of 60 revolutions per minute) until the maximum discharge temperature of 165°C was reached. The "production" stage was carried out in an open mill at 40°C for 5 minutes.

[0106] The composition was crosslinked under pressure at a temperature of 150°C.

[0107] III-4 Tests on Rubber Compositions The purpose of the following examples is to compare the stiffness and hysteresis performance of the compositions (C1 to C3) according to the invention with control compositions (T1 and T2).

[0108] The tested compositions (in phr) and the results obtained are presented in Table 1.

[0109] The only difference between compositions C1, C2, C3, and T2 and control composition T1 is the presence of specific processing aids, wherein the volume fraction of silica remains constant in the composition, and the content of the coupling agent remains constant relative to the amount of silica. The processing aids used in compositions C1, C2, and C3 conform to the present invention. The processing aids used in composition T2 do not conform to the present invention.

[0110] [Table 1] (1) Elastomer E1, obtained by the method described in point III-2 above, (2) Silica, obtained from Solvay's Zeosil 1165MP, (3) Triethoxysilylpropyltetrasulfide (TESPT) liquid silane, obtained from Evonik's Si69, (4) Carbon black, obtained from Cabot's ASTM N234, (5) Polylimonene resin, obtained from DRT's Dercolyte L120 (Tg = 72℃). (6) TDAE oil, obtained from British Petroleum's Vivatec 500, (7) Processing aid, Aflux 37 from Rhein Chemie (specifically containing C 14 To C 18 A mixture of fatty acids and trimethylolpropane. (8) Processing aid, Aflux 42 from Rhein Chemie (specifically containing C 12 To C 18 Fatty acid esters and C 18 (a mixture of alcohols) (9) Processing aids, obtained from Struktol 40MS (specifically containing a mixture of aliphatic and aromatic hydrocarbon resins). (10) N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, obtained from Flexsys' Santoflex 6-PPD, (11) Stearic acid, obtained from Pristerene 4931 of Uniqema. (12) Zinc oxide, industrial grade, obtained from Umicore. (13) N-cyclohexyl-2-benzothiazole sulfenamide, obtained from Santocure CBS of Flexsys.

[0111] The results presented in Table 1 above demonstrate that the combination of the copolymer according to the invention with a specific processing aid according to the invention allows for simultaneous improvement of the composition's hysteresis (and thus rolling resistance) and stiffness. This effect is particularly pronounced when the processing aid comprises a mixture of at least one carboxylic acid containing 4 to 28 carbon atoms and at least one aliphatic polyol containing 2 to 22 carbon atoms.

Claims

1. A rubber composition based on at least: - An elastomer matrix comprising at least one copolymer containing ethylene units and 1,3-diene units, wherein the ethylene units in the copolymer comprise between 50 mol% and 95 mol% of the monomer units of the copolymer. - Reinforcing filler, - Crosslinking system, and - A processing aid comprising: at least one carboxylic acid containing 4 to 28 carbon atoms and / or at least one carboxylic acid ester containing 4 to 28 carbon atoms and at least one aliphatic alcohol containing 2 to 22 carbon atoms.

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

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 any one of the preceding claims, wherein, The content of the at least one copolymer containing ethylene units and 1,3-diene units is in the range of 50 phr to 100 phr, preferably 80 phr to 100 phr.

5. The rubber composition according to any one of the preceding claims, wherein, The processing aid comprises, preferably, a mixture of at least one carboxylic acid containing 4 to 28 carbon atoms and at least one aliphatic alcohol containing 2 to 22 carbon atoms.

6. The rubber composition according to any one of the preceding claims, wherein, The carboxylic acid in the processing aid contains 6 to 22 carbon atoms, preferably 8 to 20 carbon atoms, and more preferably 14 to 20 carbon atoms.

7. The rubber composition according to any one of the preceding claims, wherein, The carboxylic acid in the processing aid is a fatty acid containing 14 to 20 carbon atoms, preferably 14 to 18 carbon atoms.

8. The rubber composition according to any one of the preceding claims, wherein, The aliphatic alcohol in the processing aid is an aliphatic polyol containing 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms.

9. The rubber composition according to any one of the preceding claims, wherein, The aliphatic alcohol in the processing aid is selected from the following aliphatic polyols: 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, galactitol, mannitol, inositol, and mixtures thereof, preferably selected from the following aliphatic polyols: 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. The rubber composition according to any one of the preceding claims, wherein, The processing aid comprises, preferably, essentially, a carboxylic acid containing 14 to 20 carbon atoms, more preferably containing 14 to 18 carbon atoms, and an aliphatic polyol selected from 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, and trimethylolpropane.

11. The rubber composition according to any one of the preceding claims, wherein, The content of the processing aid is in the range of 1 phr to 15 phr, preferably 3 phr to 10 phr.

12. The rubber composition according to any one of the preceding claims, 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. The rubber composition according to any one of the preceding claims, wherein, The content of the reinforcing filler is in the range of 20 phr to less than 200 phr, preferably 30 phr to 100 phr.

14. The rubber composition according to any one of the preceding claims, wherein, The crosslinking system is a vulcanization system based on molecular sulfur and / or based on sulfur donor.

15. A tire comprising the composition as defined in any one of claims 1 to 14, wherein the composition is preferably present in the tread of the tire.

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