Composite material for rubber products

Abstract

The invention relates to a composite material comprising at least one reinforcing element embedded in a rubber composition based on at least one isoprene elastomer, up to 50 phr of a copolymer of ethylene and 1, 3-diene, at least 30 phr of a reinforcing inorganic filler, and a cross-linking system, the ethylene units in the copolymer comprise more than 50 mol% of the monomeric units of the copolymer.

Description

Field of the Invention

[0001] The present invention relates to the field of reinforced rubber compositions, and more particularly to plies comprising metal or fabric reinforcements embedded in a rubber composition, these plies being intended in particular for vehicle tires, conveyor belts or belts. Background of the Invention

[0002] The performance of vehicle tires (whether pneumatic tires (i.e., capable of supporting the load of a vehicle by pressurized gas) or non-pneumatic tires (i.e., capable of supporting the load of a vehicle, for example, by struts without using pressurized gas)), conveyor belts or belts is partly related to the stiffness of some of their components. Specifically, the resistance to deformation is an important property for coping with the stresses to which these objects are subjected.

[0003] This stiffness requirement is particularly important in the calendered plies of the crown ply of vehicle tires or in the bottom area (which is the area close to the rim). In addition to stiffness, the compounds in question must also meet a wider range of specifications, including low hysteresis, adhesion to the reinforcement, and as low an evolution as possible in the uncured state (i.e., before crosslinking the rubber composition) and in the cured state (i.e., after crosslinking).

[0004] The required level of stiffness can be achieved by two main means:

[0005] Increasing the content of reinforcing fillers (carbon black or silica),

[0006] Using a thermosetting resin, which forms a secondary network interpenetrating with the filler - elastomer - vulcanization network.

[0007] However, increasing the content of reinforcing fillers may lead to an increase in the hysteresis of the uncured compound and a decrease in processability, especially due to the increase in the stiffness of the uncured compound and the possible occurrence of depolymerization. In addition, the use of thermosetting resins may constitute an additional source of dissipation, which may have an adverse effect on the hysteresis performance. In addition, it is known that certain resin - hardener systems used in tires release formaldehyde and must therefore be treated using special measures.

[0008] Other avenues have been explored to increase the stiffness of the composition. For example, document WO2014 / 114607 teaches the use of highly saturated diene elastomers to increase the stiffness of rubber compositions without having an adverse effect on the hysteresis properties. Since these compositions are mainly intended for tire treads, this document neither solves the adhesion problem of such compositions nor their crack resistance. However, the presence of reinforcing elements, and thus the interface between elements with very different mechanical stiffnesses and behaviors (the reinforcing element and the rubber composition), may lead to unpredictable phenomena, especially in terms of crack propagation, energy dissipation or adhesion properties.

[0009] Document WO2020 / 074806 teaches the use of blends of natural rubber and copolymers of ethylene and 1,3-dienes with carbon black to obtain good cohesion and ozone resistance properties, which are highly sought after when used in the sidewalls of vehicle tires.

[0010] In the course of further research, the applicant has found that a composite material comprising at least one reinforcing element embedded in a rubber composition is capable of achieving a very good expression of the stiffness / hysteresis compromise without adversely affecting other performance properties (in particular grip and crack resistance) desired for the composition used in the carcass ply, said rubber composition being based on at least one isoprene elastomer, at most 50 phr of a copolymer of ethylene and 1,3-diene, at least 30 phr of a reinforcing inorganic filler, and a crosslinking system, the ethylene units in the copolymer accounting for more than 50 mol% of the monomer units of the copolymer. Summary of the Invention

[0011] The present invention relates to a composite material comprising at least one reinforcing element embedded in a rubber composition based on at least one isoprene elastomer, at most 50 phr of a copolymer of ethylene and 1,3-diene, at least 30 phr of a reinforcing inorganic filler, and a crosslinking system, the ethylene units in the copolymer accounting for more than 50 mol% of the monomer units of the copolymer.

[0012] Preferably, the rubber composition contains a metal oxide and a stearic acid derivative, and the ratio of the content (in phr) of the metal oxide to the stearic acid derivative is greater than 2.

[0013] Preferably, the rubber composition contains less than 10 phr, preferably less than 5 phr of a plasticizer.

[0014] Preferably, the copolymer of ethylene and 1,3-diene contains at least 60 mol% of ethylene units, preferably contains at least 65 mol% of ethylene units, and more preferably contains at least 70 mol% of ethylene units.

[0015] Preferably, the 1,3-diene units of the copolymer of ethylene and 1,3-diene are 1,3-diene units of a 1,3-diene having 4 to 12 carbon atoms, preferably 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-diene units of aryl-1,3-butadiene and mixtures of these units.

[0016] Preferably, the reinforcing inorganic filler of the rubber composition is silica.

[0017] Preferably, the rubber composition contains 30 phr to 150 phr of silica.

[0018] Preferably, the rubber composition does not contain carbon black, or contains less than 10 phr, preferably less than 5 phr of carbon black.

[0019] Preferably, the reinforcing element includes a fabric filamentary element or a metallic filamentary element.

[0020] Preferably, the metallic filamentary element is a metallic elementary monofilament or an assembly of a plurality of metallic elementary monofilaments.

[0021] Preferably, the reinforcing element includes a fabric filamentary element made of a thermoplastic polymer material or a non-thermoplastic polymer material.

[0022] The present invention also relates to a vehicle tire comprising the composite material according to the present invention. Detailed Description

[0023] Definitions

[0024] The carbon-containing compounds mentioned in the specification may be compounds of fossil origin or of bio-based origin. In the case where the carbon-containing compounds are compounds of bio-based origin, they may be partially or completely derived from biomass, or may be obtained from renewable starting materials derived from biomass. This particularly relates to polymers, plasticizers, fillers, etc.

[0025] Any numerical interval represented by the expression "between a and b" represents a numerical range greater than "a" and less than "b" (i.e., the limits a and b are not included), while any numerical interval represented by the expression "from a to b" means a numerical range extending from "a" to "b" (i.e., the strict limits a and b are included). The abbreviation "phr" means parts by weight per hundred parts of elastomer (if there are multiple elastomers, the sum of the elastomers).

[0026] In the present specification, the expression "the composition is based on" should be understood to mean that the composition contains a mixture of the various components used and / or an in-situ reaction product, and some of these basic components (such as elastomers, fillers, components of the vulcanization system, or other additives conventionally used in rubber compositions intended for the manufacture of tires) are liable (or intended) to react at least partially together during the various manufacturing stages of the composition intended for the manufacture of vehicle tires.

[0027] In the present application, the expression "all monomer units of the elastomer" or "the total amount of monomer units of the elastomer" means all the constituent repeating units of the elastomer produced by inserting monomers into the elastomer chain by polymerization. Unless otherwise stated, the content of monomer units or repeating units in a highly saturated diene elastomer is given as a mole percentage calculated based on all monomer units of the elastomer.

[0028] Copolymer of ethylene and 1,3-diene

[0029] The rubber composition of the composite material according to the invention comprises at most 50 phr of a copolymer of ethylene and a 1,3-diene, wherein the ethylene units in the copolymer account for more than 50 mol% of the monomer units of the copolymer.

[0030] The copolymer of ethylene and a 1,3-diene is a highly saturated diene elastomer, which is preferably random and contains ethylene units resulting from the polymerization of ethylene. In a known manner, the expression "ethylene units" means the -(CH2-CH2)-subunits obtained by inserting ethylene into the elastomer chain. The copolymer of ethylene and a 1,3-diene is rich in ethylene units since the ethylene units account for more than 50 mol% of all the monomer units of the elastomer.

[0031] Preferably, the copolymer of ethylene and a 1,3-diene contains at least 60 mol% of ethylene units, preferably contains at least 65 mol% of ethylene units, more preferably contains at least 70 mol% of ethylene units. In other words, the ethylene units in the copolymer of ethylene and a 1,3-diene preferably account for at least 60 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene, more preferably account for at least 65 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene. Even more preferably, the ethylene units account for at least 70 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene.

[0032] Preferably, the ethylene units in the copolymer of ethylene and a 1,3-diene account for at most 90 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene. More preferably, the ethylene units account for at most 85 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene. Even more preferably, the ethylene units account for at most 80 mol% of all the monomer units of the copolymer of ethylene and a 1,3-diene.

[0033] According to an advantageous embodiment, the copolymer of ethylene and a 1,3-diene contains 60 mol% to 90 mol% of ethylene units, in particular 60 mol% to 85 mol% of ethylene units, calculated as a mole percentage based on all the monomer units of the copolymer of ethylene and a 1,3-diene. More advantageously, the copolymer of ethylene and a 1,3-diene contains 60 mol% to 80 mol% of ethylene units, calculated as a mole percentage based on all the monomer units of the copolymer of ethylene and a 1,3-diene.

[0034] According to another advantageous embodiment, the copolymer of ethylene and a 1,3-diene contains 65 mol% to 90 mol% of ethylene units, in particular 65 mol% to 85 mol% of ethylene units, calculated as a mole percentage based on all the monomer units of the copolymer of ethylene and a 1,3-diene. More advantageously, the copolymer of ethylene and a 1,3-diene contains 65 mol% to 80 mol% of ethylene units, calculated as a mole percentage based on all the monomer units of the copolymer of ethylene and a 1,3-diene.

[0035] According to another advantageous embodiment of the present invention, the copolymer of ethylene and 1,3-diene comprises from 70 to 90 mol% of ethylene units, in particular from 70 to 85 mol% of ethylene units, based on all the monomer units of the copolymer of ethylene and 1,3-diene, in terms of mole percentage. More advantageously, the copolymer of ethylene and 1,3-diene comprises from 70 to 80 mol% of ethylene units, based on all the monomer units of the copolymer of ethylene and 1,3-diene, in terms of mole percentage.

[0036] Since the copolymer of ethylene and 1,3-diene is a copolymer of ethylene and 1,3-diene, it also comprises 1,3-diene units resulting from the polymerization of 1,3-diene. In a known manner, the expression "1,3-diene unit" or "diene unit" denotes a unit resulting from the insertion of 1,3-diene by 1,4-addition, 1,2-addition or 3,4-addition (for example in the case of isoprene). The 1,3-diene unit is, for example, a 1,3-diene unit of a 1,3-diene having from 4 to 12 carbon atoms (for example, 1,3-butadiene, isoprene, 1,3-pentadiene, or aryl-1,3-butadiene). Preferably, the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes (one of which is 1,3-butadiene). More preferably, the 1,3-diene is 1,3-butadiene, in which case the copolymer of ethylene and 1,3-diene is preferably a random copolymer of ethylene and 1,3-butadiene.

[0037] Copolymers of ethylene and 1,3-dienes can be obtained according to various synthesis methods known to those skilled in the art, particularly based on the target microstructure of the copolymers of ethylene and 1,3-dienes. Generally, they can be prepared, in particular, by copolymerization of at least one 1,3-diene (preferably 1,3-butadiene) with ethylene in the presence of a catalytic system comprising a metallocene complex according to known synthesis methods. In this regard, mention may be made of the catalytic systems based on metallocene complexes described in the documents EP 1092731, WO 2004 / 035639, WO2007 / 054223 and WO 2007 / 054224 in the name of the applicant. Copolymers of ethylene and 1,3-dienes (including when they are random copolymers) can also be prepared by using a method of a preformed type of catalytic system (such as the catalytic systems described in the documents WO 2017 / 093654A1, WO 2018 / 020122 A1 and WO 2018 / 020123 A1). Advantageously, the copolymer of ethylene and 1,3-diene is random and is preferably prepared according to a semi-continuous or continuous method as described in the documents WO 2017 / 103543 A1, WO 2017 / 13544A1, WO 2018 / 193193 and WO 2018 / 193194.

[0038] The copolymer of ethylene and 1,3-diene preferably contains units of formula (I) or units of formula (II).

[0039]

[0040] -CH2-CH(CH=CH2)- (II)

[0041] The presence of the saturated six-membered ring units (1,2-cyclohexanediyl) of formula (I) in the copolymer may be caused by a series of very specific insertions of ethylene and 1,3-butadiene in the polymer chain during the growth of the polymer chain. When the copolymer of ethylene and 1,3-diene contains units of formula (I) or units of formula (II), the mole percentages (o and p respectively) of the units of formula (I) and the units of formula (II) in the highly saturated diene elastomer preferably satisfy the following equation (Equation 1) or equation (Equation 2), calculating o and p based on all monomer units of the copolymer of ethylene and 1,3-diene.

[0042] 0 < o + p ≤ 30 (Equation 1)

[0043] 0 < o + p < 25 (Equation 2)

[0044] Preferably, the copolymer of ethylene and 1,3-diene comprises units of formula (I) in a molar content greater than 0 mol% and less than 15 mol%, more preferably less than 10 mol%, calculated as a molar percentage based on all monomer units of the copolymer of ethylene and 1,3-diene.

[0045] Isoprene elastomer

[0046] The rubber composition of the composite material according to the invention is essentially characterized in that it comprises at least one isoprene elastomer.

[0047] The term "isoprene elastomer" is understood to mean an isoprene homopolymer or copolymer, in other words, a diene elastomer selected from natural rubber (NR) (which may be plasticized or peptized), synthetic polyisoprene (IR), various isoprene copolymers (in particular isoprene / styrene (SIR) copolymers, isoprene / butadiene (BIR) copolymers or isoprene / butadiene / styrene (SBIR) copolymers) and mixtures of these elastomers.

[0048] Preferably, the isoprene elastomer is selected from synthetic polyisoprene, natural rubber, isoprene copolymers and mixtures thereof, preferably from natural rubber, polyisoprene containing a cis-1,4 bond in a weight content of at least 90%, more preferably at least 98% relative to the weight of the isoprene elastomer, and mixtures thereof. Very preferably, the isoprene elastomer is natural rubber.

[0049] Preferably, the rubber composition of the composite material according to the invention comprises at least 50 phr of isoprene elastomer. Preferably, the content of isoprene elastomer in the rubber composition is greater than 55 phr and less than or equal to 70 phr.

[0050] The content of the copolymer of ethylene and 1,3-diene (in particular the copolymer of ethylene and 1,3-butadiene) for the purposes of the present invention in the rubber composition preferably varies in the range from 10 phr to 40 phr.

[0051] Advantageously, the rubber composition comprises from 10 phr to 40 phr of a copolymer of ethylene and 1,3-diene (in particular a copolymer of ethylene and 1,3-butadiene) and from 60 phr to 90 phr of an isoprene elastomer.

[0052] Inorganic filler

[0053] The rubber composition of the composite material according to the invention comprises at least 30 phr of reinforcing inorganic filler.

[0054] In the present patent application, by definition, the term "reinforcing inorganic filler" is to be understood as meaning any inorganic filler or mineral filler (irrespective of its color and its origin, natural or synthetic), which is also called "white filler", "transparent filler" and in fact even "non-black filler" with respect to carbon black and which is capable of reinforcing alone a rubber composition intended for the manufacture of tires without a method other than an intermediate coupling agent, in other words, which can replace conventional tire-grade carbon black in terms of reinforcing action; in a known manner, such fillers are generally characterized by the presence of hydroxyl (-OH) groups on their surface.

[0055] Mineral fillers of the siliceous type (in particular silica (SiO2)) or of the aluminous type (in particular alumina (Al2O3)) are particularly suitable as reinforcing inorganic fillers.

[0056] Preferably, the reinforcing inorganic filler is silica. The silica used can be any reinforcing silica known to those skilled in the art, in particular any precipitated silica or pyrogenic silica with a BET specific surface area and a CTAB specific surface area both less than 450 m 2 / g, preferably from 30 m 2 / g to 400 m 2 / g. As highly dispersible precipitated silica ("HDS"), mention will be made, for example, of Ultrasil 7000 and Ultrasil 7005 silica from Degussa, Zeosil 1165MP, 1135MP and 1115MP silica from Rhodia, Hi-Sil EZ150G silica from PPG, Zeopol 8715, 8745 and 8755 silica from Huber or silica with a high specific surface area as described in application WO 03 / 16837.

[0057] It is not important in what physical state the reinforcing inorganic filler is provided, whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the term "reinforcing inorganic filler" is also understood to mean a mixture of different reinforcing inorganic fillers, in particular a mixture of highly dispersible siliceous fillers and / or aluminous fillers.

[0058] The BET specific surface area of the reinforcing inorganic filler used (in particular if it is silica) is preferably between 45 m 2 / g and 400 m 2 / g, more preferably between 60 m 2 / g and 300 m 2 / g.

[0059] Preferably, the rubber composition of the composite material according to the present invention comprises 30 phr to 150 phr, preferably 35 phr to 100 phr of silica.

[0060] In order to couple the reinforcing inorganic filler to the elastomer, at least a bifunctional coupling agent (or binder) intended to provide satisfactory chemical and / or physical properties connection between the inorganic filler (on the surface of its particles) and the elastomer can be optionally used in a known manner, in particular a bifunctional silane or a polyorganosiloxane.

[0061] Particularly, silane polysulfides, which are called "symmetric" or "asymmetric" according to their specific structure, can be used, for example, the silane polysulfides described in applications WO 03 / 002648 (or US2005 / 016651) and WO 03 / 002649 (or US2005 / 016650).

[0062] As an example of silane polysulfides, polysulfides of bis(C1-C4 alkoxy-C1-C4 alkyl) silyl-C1-C4 alkyl) (especially disulfide, trisulfide or tetrasulfide) can be more particularly mentioned, for example, bis(3-trimethoxysilylpropyl) polysulfide or bis(3-triethoxysilylpropyl) polysulfide. Among these compounds, bis(3-triethoxysilylpropyl) tetrasulfide (abbreviated as TESPT) having the formula [(C2H5O)3Si(CH2)3S2]2 or bis(3-triethoxysilylpropyl) disulfide (abbreviated as TESPD) having the formula [(C2H5O)3Si(CH2)3S]2 are particularly used. As a preferred example, polysulfides of bis(mono(C1-C4) alkoxy di(C1-C4) alkyl silylpropyl) (especially disulfide, trisulfide or tetrasulfide) will also be mentioned, more particularly bis(monoethoxydimethylsilylpropyl) tetrasulfide, for example, as described in patent application US2004 / 132880.

[0063] As a coupling agent other than alkoxysilane polysulfides, bifunctional POS (polyorganosiloxane) or hydroxy silane polysulfides (for example, as described in patent applications WO 02 / 30939 and WO 02 / 31041) or silanes or POS with azodicarbonyl functional groups (for example, as described in patent applications WO 2006 / 125532, WO 2006 / 125533 and WO2006 / 125534) will be particularly mentioned.

[0064] In the elastomeric composition according to the invention, the content of the coupling agent is preferably in the range of 5% to 60% by weight, preferably in the range of 15% to 50% by weight, preferably in the range of 20% to 40% by weight, relative to the amount of silica. These contents have been shown to be particularly advantageous for obtaining the properties of the composite material according to the invention.

[0065] The rubber composition of the composite material according to the invention may also contain carbon black.

[0066] All carbon blacks (in particular carbon blacks of the HAF, ISAF or SAF types conventionally used in tires ("tire-grade" carbon blacks)) are suitable for use as carbon black. Among the "tire-grade" carbon blacks, reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades) (such as N115, N134, N234, N326, N330, N339, N347 and N375 carbon blacks), or higher series carbon blacks depending on the target application (such as N660, N683 or N772) will be more particularly mentioned. The carbon black may for example already have been introduced into an isoprene elastomer in the form of a masterbatch (see for example applications WO 97 / 36724 and WO 99 / 16600). The BET specific surface area of the carbon black is measured according to standard D6556-10 [multi-point (at least 5 points) method - gas: nitrogen - relative pressure p / p0 range: 0.1 to 0.3].

[0067] Preferably, the rubber composition of the composite material according to the invention does not contain carbon black, or contains less than 10 phr, preferably less than 5 phr of carbon black.

[0068] Crosslinking system

[0069] The rubber composition of the composite material according to the invention contains a crosslinking system.

[0070] The crosslinking system may be based on sulfur or sulfur donors and / or peroxides and / or bismaleimides. Preferably, the crosslinking system is a vulcanization system, i.e., a system based on sulfur (or sulfur donor) and a vulcanization accelerator. As the vulcanization accelerator, any compound capable of acting as a vulcanization accelerator for a diene elastomer in the presence of sulfur can be used, in particular accelerators of the thiazole type and their derivatives or accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. As examples of such accelerators, the following sulfenamide compounds can be particularly mentioned: N-cyclohexyl-2-benzothiazole sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazole sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazole sulfenamide ("TBBS") and mixtures of these compounds.

[0071] Sulfur is used in an amount preferably between 0.3 phr and 10 phr, more preferably between 0.3 phr and 5 phr. The main vulcanization accelerator is used in an amount preferably between 0.5 phr and 10 phr, more preferably between 0.5 phr and 5 phr.

[0072] Preferably, the composition of the composite material according to the invention comprises a metal oxide and a stearic acid derivative, and the ratio of the content (in phr) of the metal oxide to the stearic acid derivative is greater than 2. This preferred content allows for good adhesion to the reinforcing elements embedded in the rubber composition. The metal oxide is preferably zinc oxide.

[0073] The rubber composition of the composite material according to the invention preferably comprises a vulcanization accelerator. The content of the vulcanization accelerator used is preferably such that the sulfur / vulcanization accelerator weight ratio is less than or equal to 5, preferably less than or equal to 4.

[0074] As the accelerator, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used, in particular accelerators of the thiazole type and their derivatives, or sulfenamides, thiurams, dithiocarbamates, dithiophosphates, thioureas, and xanthates. As examples of such accelerators, the following compounds can be particularly mentioned: 2-mercaptobenzothiazole disulfide (abbreviated as MBTS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazole sulfenamide (DCBS), N-(tert-butyl)-2-benzothiazole sulfenamide (TBBS), N-(tert-butyl)-2-benzothiazole sulfimide (TBSI), tetrabenzylthiuram disulfide (TBZTD), zinc dibenzyldithiocarbamate (ZBEC), and mixtures of these compounds.

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

[0076] Various additives

[0077] The rubber composition of the composite material according to the invention can also comprise all or part of the common additives usually used in elastomeric compositions intended for vehicle tires, conveyor belts, or plies, such as processing aids, plasticizers, pigments, protective agents (such as antiozonant waxes, chemical antiozonants, antioxidants).

[0078] Suitable plasticizers are all the plasticizers commonly used in tires. In this regard, mention may be made of oils (which are preferably non-aromatic or very weakly aromatic and are selected from naphthenic oils, paraffin oils, MES oils, TDAE oils, vegetable oils), ether plasticizers, ester plasticizers.

[0079] Preferably, the rubber composition comprises less than 10 phr, preferably less than 5 phr of plasticizer.

[0080] The rubber composition can be manufactured in a suitable mixer using two successive preparation stages according to general procedures known to those skilled in the art: a first stage of thermomechanical working or kneading at a high temperature (sometimes called the "non-production" stage), the maximum temperature of which is between 110 °C and 190 °C, preferably between 130 °C and 180 °C, followed by a second stage of mechanical working at a low temperature (usually below 110 °C, for example between 40 °C and 100 °C) (sometimes called the "production" stage), during which sulfur or a sulfur donor and a vulcanization accelerator are added during the course of the finishing stage.

[0081] By way of example, the (non-production) first stage is carried out in a single thermomechanical step during which all the necessary components except sulfur and the vulcanization system, optional additional processing aids and various other additives are introduced into a suitable mixer (such as a standard closed mixer). The total duration of kneading in this non-production stage is preferably between 1 minute and 15 minutes. After cooling the mixture thus obtained in the first non-production stage, sulfur and a vulcanization accelerator are then usually introduced at a low temperature in an open mixer (such as a mill); then, all the substances are mixed (production stage) for a few minutes, for example between 2 minutes and 15 minutes.

[0082] The final composition thus obtained is then calendered (especially for laboratory characterization) in the form of sheets or plates, for example, or extruded to form rubber molding elements, for example, for manufacturing semi-finished products (such as the reinforcing ply of a tire).

[0083] Reinforcing element

[0084] The composite material according to the invention comprises at least one reinforcing element embedded in the rubber composition.

[0085] "Embedded" means that the reinforcing element is completely covered by the rubber composition, except possibly in the cut areas of the composite material.

[0086] A reinforcing element is understood to be an element that provides mechanical reinforcement to the matrix in which the reinforcing element is intended to be embedded. The reinforcing element includes filamentous elements.

[0087] The filamentary element can be a metallic filamentary element or a fabric filamentary element. A filamentary element is understood to be an element whose length is at least 10 times greater than the maximum dimension of its cross-section, regardless of the shape of this cross-section: circular, oval, rectangular, polygonal (in particular rectangular or square) or ovoid. In the case of a rectangular cross-section, the filamentary element has a ribbon shape.

[0088] The metallic filamentary element can be a metallic elementary monofilament. Such a metallic elementary monofilament comprises a steel core, which is optionally coated with one or more coatings, which coatings can be metallic and / or based on a non-metallic binder composition.

[0089] The metallic coating comprises a metal selected from zinc, copper, tin, cobalt and alloys of these metals. Examples of alloys of these metals include brass and bronze. The steel of the core is carbon steel, which comprises between 0.1% by weight and 1.2% by weight of carbon, at most 11% by weight of chromium and less than 1% by weight of each of the following elements: manganese, silicon, aluminium, boron, cobalt, copper, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium, phosphorus, sulphur and nitrogen, the balance being made up of iron and inevitable impurities resulting from the preparation. The steel can have a pearlitic, ferritic, austenitic, bainitic or martensitic microstructure, or a microstructure resulting from a mixture of these microstructures.

[0090] The mechanical strength of the metallic elementary monofilament ranges from 1000 MPa to 5000 MPa. This mechanical strength corresponds to the steel grades commonly used in the tyre field, namely steel grades NT (Normal Tensile), HT (High Tensile), ST (Super Tensile), SHT (Super High Tensile), UT (Ultra Tensile), UHT (Ultra High Tensile) and MT (Mega Tensile). The use of a high mechanical strength can optionally improve the reinforcement of the matrix in which the reinforcing element is intended to be embedded and reduce the weight of the matrix thus reinforced.

[0091] If the metallic elementary monofilaments have a circular cross-section, the diameter of these metallic elementary monofilaments preferably ranges from 0.05 mm to 0.50 mm.

[0092] The metallic filamentary element can be an assembly of a plurality of metallic elementary monofilaments as described above, which are assembled spirally, for example by cabling or twisting the metallic elementary monofilaments, so as to form, for example, a laminated cord or a stranded cord comprising a plurality of concentric layers of metallic elementary monofilaments, each strand comprising a plurality of concentric layers of metallic elementary monofilaments. Optionally and as described in WO2005071157, such a metallic filamentary element comprises a layer based on a polymer composition, preferably based on a composition comprising an elastomer, which layer is located between two layers of metallic elementary monofilaments of the strands of the laminated cord or the stranded cord.

[0093] The fabric filamentary element can be a fabric elementary monofilament, which is optionally coated with one or more coatings based on an adhesive composition. Such a fabric elementary monofilament is obtained, for example, by melt spinning, solution spinning or gel spinning. Each fabric elementary monofilament is made of an organic material (especially a polymeric material) or an inorganic material (such as glass or carbon). The polymeric material can be of the thermoplastic type, such as aliphatic polyamides (especially polyamide 6,6) and polyesters (especially polyethylene terephthalate). The polymeric material can be of the non-thermoplastic type, such as aromatic polyamides (especially aramid) and cellulose (natural or synthetic, especially rayon).

[0094] The fabric filamentary element can be an assembly of a plurality of fabric elementary monofilaments as defined above. In a first variant, the assembly comprises from 2 to 7 fabric elementary monofilaments, each fabric elementary monofilament having a substantially circular cross-section with a diameter in the range, for example, of 0.10 mm to 0.50 mm. In a second variant, the assembly comprises more than 10 fabric elementary monofilaments, preferably more than 100 fabric elementary monofilaments, more preferably more than 500 fabric elementary monofilaments, each fabric elementary monofilament having a substantially circular cross-section with a diameter in the range, for example, of 2 μm to 100 μm. In the first variant and the second variant, the formed assembly is generally referred to as a strand.

[0095] The fabric filamentary element can be an assembly of a plurality of assemblies or strands as defined above. In one variant, the fabric elementary monofilaments of each assembly or strand are made of the same material. In another variant, the fabric elementary monofilaments of each assembly or strand are made of different materials, and the fabric filamentary element is generally referred to as a hybrid fabric filamentary element.

[0096] In one embodiment, in the case of both the metallic filamentary element and the fabric filamentary element, the layer based on the non-metallic adhesive composition is formed by a layer of an adhesion primer capable of improving the adhesion of the filamentary element, for example, to an elastomeric matrix. Such an adhesion primer is an adhesion primer commonly used by those skilled in the art for pore filling treatment of certain fabric fibers (especially fibers made of polyester (such as PET), aramid or aramid / nylon). For example, epoxy-based primers, especially polyglycerol polyglycidyl ether-based primers, can be used. Blocked isocyanate-based primers can also be used.

[0097] In another embodiment, in the case of both the metallic filamentary element and the fabric filamentary element, the layer based on the non-metallic adhesive composition is formed by a layer based on a resin and an elastomeric latex. Adhesive compositions of the RFL (resorcinol-formaldehyde-latex) type can be mentioned, but adhesive compositions described, for example, in WO 2015 / 118041 can also be mentioned.

[0098] In another embodiment, whether in the case of a wire-like element or a fabric-like element, the wire-like element can be coated with a layer of an adhesive primer as described above, and the adhesive primer layer itself is coated with a layer of a latex based on a resin and one or more elastomers as described above.

[0099] In one embodiment, the reinforcing element includes a wire-like element and an optional sheath, and the sheath independently coats the wire-like element or jointly coats a plurality of wire-like elements. The sheath can include one or more layers, each layer based on a polymer composition, such as a thermoplastic composition or a composition described in WO2010 / 136389, WO2010 / 105975, WO2011 / 012521, WO2011 / 051204, WO2012 / 016757, WO2012 / 038340, WO2012 / 038341, WO2012 / 069346, WO2012 / 104279, WO2012 / 104280 and WO2012 / 104281. In this embodiment, the polymer composition of each layer of the sheath is different from the composition based on the matrix intended to embed the sheathed wire-like element.

[0100] In another embodiment, the reinforcing element can be a knitted fabric or a woven fabric.

[0101] A knitted fabric is an assembly of wire-like elements as defined above and includes stitches formed by one or more of these wire-like elements. Each stitch includes a loop interlaced with another loop. For example, for a weft knitted fabric, mention may be made of a knitted fabric having a plain structure or an English rib structure, and for a warp knitted fabric, mention may be made of a knitted fabric having a tricot structure or a double warp satin structure.

[0102] A woven fabric is an assembly of a first group of wire-like elements (becoming warp wire-like elements, which are substantially parallel to each other) and a second group of wire-like elements (called weft wire-like elements, which are substantially parallel to each other). Preferably, the first group of wire-like elements is substantially perpendicular to the second group of wire-like elements.

[0103] In an embodiment of the composite material (where each reinforcing element is a wire-like reinforcing element), the wire-like reinforcing elements are arranged parallel to each other and are embedded in a rubber composition, for example, by calendering. Then a ply called a straight ply is obtained, where the wire-like reinforcing elements of the ply are parallel to each other and parallel to the main direction of the ply. Then, if necessary, a part of each straight ply is cut along a cutting angle and these parts are butt-jointed to each other to obtain a ply called an angled ply, where the wire-like reinforcing elements of the ply are parallel to each other and form an angle with the main direction of the angled ply, and the angle formed with the main direction is equal to the cutting angle.

[0104] Tire

[0105] A vehicle tire (another subject of the present invention) comprises a composite material according to the present invention. Preferably, the tire comprises a reinforcing ply made of the composite material according to the present invention.

[0106] The composite material and the tire according to the present invention can be in an uncured state (i.e., before crosslinking) or in a cured state (i.e., after crosslinking).

[0107] Examples

[0108] Preparation of rubber compositions

[0109] Seven rubber compositions C-1 to C-17 were prepared as follows, and the formulation details are shown in Tables 1 and 2:

[0110] Elastomers, organic fillers or inorganic fillers (carbon black or silica), and various other components, except for sulfur and vulcanization accelerators, were continuously introduced into a closed mixer with an initial vessel temperature of about 80 °C (final filling degree: about 70% by volume). Then, thermomechanical processing (non-production stage) was carried out in one step, which lasted for about 3 to 4 minutes in total until a maximum "discharge" temperature of 165 °C was reached. The mixture thus obtained was recovered and cooled, and then sulfur and vulcanization accelerators were introduced into a mixer (homogenizing finisher) at 30 °C, and all substances were mixed for an appropriate time (e.g., about 10 minutes) (production stage).

[0111] Then, the composition thus obtained was calendered in the form of rubber sheets (with a thickness of 2 mm to 3 mm) or rubber thin sheets (for measuring its physical properties or mechanical properties) or extruded to form, for example, a shaped element for a tire.

[0112] Except for compositions C-1, C-6, and C-10, the rubber compositions comprise a highly saturated diene elastomer with an ethylene molar content greater than 50% and natural rubber, which in this case contains 74 mol% of ethylene units.

[0113] Testing and measurement

[0114] Measurement of Mooney viscosity (or Mooney plasticity)

[0115] Use an oscillating consistency meter as described in French Standard NF T 43-005 (1991). Measure the Mooney plasticity according to the following principle: Mold the composition in the uncured state (i.e., before curing) in a cylindrical chamber heated to 100 °C. After preheating for one minute, the rotor rotates within the specimen at 2 revolutions per minute, and after 4 minutes of rotation, measure the working torque required to maintain this motion. The Mooney plasticity (ML 1+4) is expressed in "Mooney units" (MU, 1 MU = 0.83 Newton·meter). The smaller the Mooney value, the lower the viscosity before curing, and the better the processability of the composition.

[0116] Tensile test

[0117] Conduct the test according to French Standard NF T 46-002 of September 1988. Conduct all tensile measurements under standard temperature (23 ± 2 °C) and humidity (50% ± 5% relative humidity) conditions according to French Standard NF T 40-101 (December 1979).

[0118] In the second elongation (i.e., after conditioning), measure the nominal secant modulus (or apparent stress, in MPa) (denoted as MA 10 ) in a sample cured at 150 °C for 60 minutes at 10% elongation, which is calculated based on the initial cross-section of the specimen.

[0119] Dynamic properties (after curing)

[0120] Measure the dynamic property tan(δ)max at 23 °C on a viscosity analyzer (Metravib VA4000) according to Standard ASTM D 5992-96. Record the response of a sample of a crosslinked composition (with a thickness of 4 mm and a cross-section of 400 mm 2 of a cylindrical specimen) subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz under defined temperature conditions (e.g., at 23 °C) according to Standard ASTM D 1349-99. Conduct a strain amplitude sweep from 0.1% to 50% (outward cycle) and then from 50% to 1% (return cycle). The result used is the loss factor tan(δ). For the return cycle, mark the maximum value of the observed tan(δ), denoted as tan(δ)max.

[0121] It will be recalled that, in a manner well-known to those skilled in the art, the value of tan(δ)max at 23 °C represents the hysteresis of the material (and thus the rolling resistance): the smaller the tan(δ)max at 23 °C, the more the rolling resistance is reduced, and thus the greater the improvement in rolling resistance.

[0122] Adhesion test:

[0123] A strip composed of three metal wires with a diameter of 0.32 mm is manufactured. The metal wires are placed parallel to each other and embedded in a polyamide 6-6 sheath to obtain a strip with a thickness of 0.46 mm and a width of 1.45 mm.

[0124] The strip is covered with an RFL adhesive and then embedded in a test rubber composition.

[0125] To test the adhesion between the test rubber composition and the strip, measurements are carried out according to standard ASTM D2229.

[0126] The adhesion level is characterized by measuring the "pull-out" force (denoted as Fmax) for pulling the strip out of the specimen. The results are expressed on a scale of 100, where values greater than 100 indicate a pull-out force greater than that of the reference specimen.

[0127] Copolymer of ethylene and 1,3-diene

[0128] The copolymer of ethylene and 1,3-diene used in the following examples is prepared according to the following procedure:

[0129] A solution of butyloctylmagnesium (BOMAG) in methylcyclohexane and a catalytic system are added to a 70-liter reactor containing methylcyclohexane (64 liters), ethylene (5600 g), and 1,3-butadiene (2948 g). The Mg / Nd ratio is 6.2. The volume of the introduced catalytic system solution is 840 ml, and the concentration of Nd in the catalytic system solution is 0.0065 M. The reaction temperature is adjusted to 80 °C, and the polymerization reaction starts. The polymerization reaction is carried out at a constant pressure of 8.3 bar. Throughout the polymerization process, ethylene and 1,3-butadiene with a molar ratio of 73 / 27 are fed to the reactor. The polymerization reaction is terminated by cooling, degassing the reactor, and adding ethanol. An antioxidant is added to the polymer solution. After steam stripping and drying to a constant mass, the copolymer is recovered. The polymerization time is 225 minutes. The weighed mass (6.206 kg) enables the determination of the average catalytic activity of the catalytic system (expressed in kg of polymer synthesized per mole of neodymium metal per hour (kg / mol.h)). The ML(1+4) value of the copolymer at 100 °C is equal to 62.

[0130] The catalytic system is a preformed catalytic system. The catalytic system is prepared from metallocene [Me2Si(Flu)2Nd(μ-BH4)2Li(THF)] at a concentration of 0.0065 mol / l, cocatalyst butyloctylmagnesium (BOMAG) (the BOMAG / Nd molar ratio is equal to 2.2), and preformed monomer 1,3-butadiene (the 1,3-butadiene / Nd molar ratio is equal to 90) in methylcyclohexane. The medium is heated at 80 °C for 5 h. It is prepared according to the preparation method in Section II.1 of patent application WO 2017 / 093654 A1.

[0131] The obtained copolymer of ethylene and 1,3-diene (copolymer of ethylene and 1,3-butadiene) is an ethylene-butadiene elastomer (hereinafter referred to as "EBR").

[0132] Example 1

[0133] In this example, the proportion of EBR in the NR-EBR blend was varied. The way in which the stiffness / hysteresis compromise (MA 10 / tan(δ) ratio) changed was evaluated. The results are expressed on a scale of 100, with a value of 100 assigned to the stiffness / hysteresis compromise of the composition containing no EBR for each series containing a given silica content.

[0134] Results greater than 100 indicate that the composition of the example under consideration has a greater ratio than the control.

[0135] [Table 1]

[0136]

[0137] (1) Copolymer of ethylene and 1,3-butadiene, containing 74 mol% of ethylene units, 19 mol% of butadiene units in the form of 1,2-units and 1,4-units, and 7 mol% of 1,2-cyclohexanediyl units, Tg = -44 °C

[0138] (2) Zeosil 1165MP, precipitated silica in the form of microbeads with a CTAB of 160 m 2 / g from Solvay-Rhodia

[0139] (3) Triethoxysilylpropyltetrasulfide (TESPT) liquid silane, Si69 from Evonik

[0140] (4) Diphenylguanidine, Perkacit DPG from Flexsys

[0141] (5) N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, Santoflex 6PPD from Flexys

[0142] (6) Stearic acid, Pristerene 4931 from Uniqema

[0143] (7) Industrial grade zinc oxide from Umicore

[0144] (8) N-cyclohexyl-2-benzothiazolesulfenamide, Santocure CBS from Flexsys

[0145] It can be seen that the combination of the inorganic filler and the blend of natural rubber and EBR enables a very good expression of the stiffness / hysteresis trade-off, and the greater the content of the inorganic filler, the more obvious this expression is.

[0146] For a lower content of the inorganic filler, the stiffness / hysteresis trade-off no longer changes substantially according to the ratio of NR and EBR in the NR / EBR blend.

[0147] Example 2

[0148] In this example, by varying the ratio of EBR in the NR / EBR blend of a set of compositions containing carbon black and a set of compositions containing silica, the way in which the stiffness / hysteresis trade-off (MA 10 / tan(δ) ratio) changes was evaluated. Compositions C-14 and C-17 were adjusted to have substantially the same stiffness MA 10 and substantially the same stiffness / hysteresis trade-off.

[0149] The results are expressed on a scale of 100, with the stiffness / hysteresis ratio and stiffness MA of Composition C-4 10 assigned a value of 100. Results greater than 100 indicate that the composition of the example under consideration has a greater stiffness (or a greater ratio) than the control.

[0150] [Table 2]

[0151]

[0152] (1) to (8) are the same as in Table 1

[0153] (9) Carbon black, ASTM N347 grade

[0154] (10) Cobalt salt

[0155] (11) Cyclohexylthiophthalimide (PVI)

[0156] (12) N-(tert-butyl)-2-benzothiazolesulfenamide from Flexsys

[0157] In Table 2, the composition was adjusted so that the stiffness (MA10) at 10% strain was similar for the silica-based mixture and the carbon black-based mixture. Based on Composition C-4, the results are expressed on a scale of 100.

[0158] It can be seen that the stiffness and stiffness / hysteresis trade-off at 10% strain of Composition C-14 (carbon black) and Composition C-4 (silica) are similar.

[0159] It has been observed that, compared with the combination of organic fillers and blends of natural rubber and EBR, the combination of inorganic fillers and blends of natural rubber and EBR allows a better expression of the stiffness / hysteresis compromise.

[0160] [Table 3]

[0161] <![CDATA[G (J / m 2 ) - base 100]]> C-1 C-2 C-3 C-4 C-5 300 100 100 100 100 100 500 171 138 250 227 606 1000 614 313 750 891 1618

[0162] The data shown in Table 3 also show in Figure 1 in.

[0163] The crack rate increases with the release energy. As long as the content of EBR is less than 50 phr, these crack rates increase significantly in the same way. When the content of EBR reaches 50 phr, the crack rate increases significantly faster.

[0164] Example 3

[0165] In this example, the adhesion properties of various compositions were evaluated. Various rubber blocks were tested using the compositions shown in Table 4.

[0166] For compositions C-1 to C-4, the reference specimen was a specimen made of a rubber composition (C-1) that did not contain any EBR. For compositions C-6 and C-8, the reference specimen was a specimen made of a rubber composition (C-6) that did not contain any EBR. For compositions C-14 and C-16, the reference specimen was a specimen made of rubber composition C-14.

[0167] [Table 4]

[0168] Composition C-1 C-2 C-4 C-6 C-8 C-14 C-16 Base 100 100 95 100 100 99 100 100

[0169] It has been observed that, for the compositions tested, the presence of EBR has no significant effect on the degree of adhesion.

Claims

1. A composite material, said composite material comprising at least one reinforcing element embedded in a rubber composition, said rubber composition being based on at least one isoprene elastomer, up to 50 phr of a copolymer of ethylene and a 1,3-diene, at least 30 phr of a reinforcing inorganic filler, and a crosslinking system, the ethylene units in the copolymer accounting for more than 50 mol% of the monomer units of the copolymer.

2. The composite material according to the previous claim, wherein, The rubber composition contains a metal oxide and a stearic acid derivative, and the ratio of the contents of the metal oxide and the stearic acid derivative in phr is greater than 2.

3. The composite material according to any one of the preceding claims, wherein, The rubber composition contains less than 10 phr, preferably less than 5 phr, of a plasticizer.

4. The composite material according to any one of the preceding claims, wherein, The copolymer of ethylene and a 1,3-diene contains at least 60 mol% of ethylene units, preferably contains at least 65 mol% of ethylene units, and more preferably contains at least 70 mol% of ethylene units.

5. The composite material according to any one of the preceding claims, wherein, The 1,3-diene units of the copolymer of ethylene and a 1,3-diene are 1,3-diene units of a 1,3-diene having 4 to 12 carbon atoms, preferably 1,3-diene units of 1,3-butadiene, isoprene, 1,3-pentadiene, aryl-1,3-butadiene, and mixtures of these units.

6. The composite material according to any one of the preceding claims, wherein, The reinforcing inorganic filler of the rubber composition is silica.

7. The composite material according to the preceding claim, wherein, The rubber composition contains 30 phr to 150 phr of silica.

8. The composite material according to any one of claims 6 and 7, wherein, The rubber composition contains a coupling agent, and the content of the coupling agent is in the range of 5 wt% to 60 wt% relative to the amount of silica, preferably in the range of 15 wt% to 50 wt% relative to the amount of silica, and preferably 20 wt% to 40 wt% relative to the amount of silica.

9. The composite material according to any one of the preceding claims, wherein, The rubber composition does not contain carbon black, or contains less than 10 phr, preferably less than 5 phr, of carbon black.

10. The composite material according to any one of the preceding claims, wherein, The reinforcing element includes a fabric filamentous element or a metal filamentous element.

11. The composite material according to the preceding claims, wherein, The metal filamentous element is a metal elementary monofilament or a assembly of multiple metal elementary monofilaments.

12. The composite material according to claim 10, wherein, The reinforcing element includes a fabric filamentous element made of a thermoplastic polymer material or a non-thermoplastic polymer material.

13. A vehicle tire, said vehicle tire comprising the composite material according to any one of the preceding claims.

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