Reinforced product based on at least one metal reinforcing element and on a rubber composition

Abstract

The invention relates to a reinforced product based on at least one metal reinforcing element and on a rubber composition based on at least one diene elastomer, a reinforcing filler and a sulfur-based crosslinking system, the rubber composition comprising at least one ascorbate derivative of general formula (I), wherein n is an integer equal to 1 or 2, A- is an ascorbate compound and B is a hydrogen atom or an alkali or alkaline-earth metal, the rubber composition comprising a thiosulfate salt and at most 0.1 phr of a salt of a transition metal.

Description

[0001] Reinforced product based on at least one metallic reinforcing element and a rubber composition.

[0002] Technical field of the invention

[0003] The present invention relates to the field of reinforced rubber products, in particular for pneumatic or non-pneumatic tires, as well as to articles comprising such reinforced products.

[0004] Previous art

[0005] Reinforcing plies in tires or rubber-reinforced articles typically comprise a calendered rubber compound and textile or metallic reinforcing cords. Since these plies are subjected to significant stresses during tire operation, particularly due to potentially harsh driving conditions such as humid and corrosive environments, it is essential that the rubber compounds used in their construction possess not only good adhesion properties to the reinforcements but also good deformation-at-break properties, even under severe conditions.

[0006] Numerous studies have been conducted by tire manufacturers to improve one or more of these performance characteristics, notably through the addition of additives to rubber compounds. For example, US patent 5,859,101 describes a tire compound comprising 0.05 to 5 parts per liter of a selected compound, including ascorbic acid and its derivatives, tocopherol, and citric acid and its derivatives, designed to improve the abrasion resistance, crack resistance, and fatigue resistance of rubber compounds suitable for calendering. This patent does not address the issue of adhesion to reinforcing elements.

[0007] Adhesion to reinforcements, particularly metallic ones, is improved by the use of cobalt salts. However, recent years have seen a sharp increase in pressure on cobalt, and efforts are underway to limit the use of these salts as much as possible.

[0008] Document WO2015 / 135847 aims to replace cobalt salts while maintaining good rubbery properties and high adhesion, particularly in hot and humid environments. This document proposes using a combination of a thiosulfate salt, a reduced zinc oxide content, and a salt of an alkali earth, alkali, or lanthanide metal, specifically an acetylacetonate of an alkali earth, alkali, or lanthanide metal. Document WO2021 / 123587 teaches the use of an ascorbate compound and an alkali earth metal to improve initial adhesion and crack propagation resistance without degrading fracture properties. However, this document does not describe the combination of an ascorbate derivative with a thiosulfate compound.

[0009] Continuing her research, the applicant discovered that a rubber composition comprising an ascorbate derivative and a thiosulfate salt exhibited both adhesion properties, particularly after aging, and deformation at break that were maintained, or even improved, when the composition was used in calendering a metal reinforcement element.

[0010] Detailed description of the invention

[0011] The invention relates to at least one reinforced product based on at least one metallic reinforcing element and a rubber composition based on at least one diene elastomer, a reinforcing filler and a sulfur-based crosslinking system, the rubber composition comprising at least one ascorbate derivative of general formula (l) ■ [d-] n [B n+ ] (I) in which n is an integer equal to 1 or 2, A~ represents an ascorbate compound of general formula (II) in which Ri represents a hydrogen atom or a group selected from alkyl groups comprising 1 to 18 carbon atoms, alkylcarbonyl and alkenyl groups comprising 2 to 18 carbon atoms, and alkenylcarbonyl groups comprising 3 to 18 carbon atoms, and B represents a hydrogen atom or an alkali or alkaline earth metal, said rubber composition comprising a thiosulfate salt and at most 0.1 pc of a transition metal salt.

[0012] Definitions

[0013] The term "based on" refers to a product or composition comprising a mixture and / or the in situ reaction product of the various constituents used, some of which may react and / or are intended to react with each other, at least partially, during the different stages of manufacturing the composition; the product or composition may thus be in a fully or partially crosslinked state or in a non-crosslinked state. The term "part by weight per hundred parts by weight of elastomer" (or pw) refers, for the purposes of this invention, to the part, by mass, per hundred parts by mass of elastomer.

[0014] In this document, unless expressly stated otherwise, all percentages (%) shown are percentages (%) by mass.

[0015] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​going from more than a to less than b (that is, bounds a and b excluded) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (that is, including the strict bounds a and b).

[0016] The carbon-containing compounds mentioned in the description may be of fossil or bio-based origin. In the latter case, they may be partially or entirely derived from biomass or obtained from renewable raw materials derived from biomass. This includes, in particular, polymers, plasticizers, fillers, etc.

[0017] Reinforced product

[0018] The reinforced product according to the invention is based on at least one metallic reinforcing element and a rubber composition based on at least one diene elastomer, a reinforcing filler and a sulfur-based crosslinking system, the rubber composition comprising at least one ascorbate derivative of general formula (l) ■ [ -] n [B n+ ] (I) in which n is an integer equal to 1 or 2, A~ represents an ascorbate compound of general formula (II) in which Ri represents a hydrogen atom or a group selected from alkyl groups comprising 1 to 18 carbon atoms, alkylcarbonyl and alkenyl groups comprising 2 to 18 carbon atoms, and alkenylcarbonyl groups comprising 3 to 18 carbon atoms, and B represents a hydrogen atom or an alkali or alkaline earth metal, said rubber composition comprising a thiosulfate salt and at most 0.1 pc of a transition metal salt.

[0019] An alkenyl group is understood to be a monovalent hydrocarbon group comprising at least one unsaturation.

[0020] Ascorbate and alkaline earth metal

[0021] The rubber composition of the reinforced product according to the invention comprises at least one ascorbate derivative of general formula (l), and has an ascorbate derivative of general formula (l) content preferably ranging from 0.5 pc to 10 pc, preferably ranging from 1 to 8 pc.

[0022] Alkaline earth metal is defined as a metal chosen from the group consisting of berillium, magnesium, calcium, strontium, barium and radium.

[0023] The ascorbate compound of general formula (l) can be any type of ascorbate derivative corresponding to this formula.

[0024] Preferably, Ri represents a hydrogen atom or a group selected from alkyl groups comprising 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms, alkylcarbonyl and alkenyl groups comprising 2 to 5 carbon atoms and preferably 2 to 4 carbon atoms, and alkenylcarbonyl groups comprising 3 to 5 carbon atoms and preferably 3 to 4 carbon atoms.

[0025] In particular, in one preferred arrangement, the Ri group is preferentially a group selected from alkyl groups comprising 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms, and alkenyl groups comprising 2 to 5 carbon atoms, and preferably 2 to 4 carbon atoms. In another preferred arrangement, the Ri group is preferentially a group selected from alkylcarbonyl groups comprising 2 to 5 carbon atoms, and preferably 2 to 4 carbon atoms, and alkenylcarbonyl groups comprising 3 to 5 carbon atoms, and preferably 3 to 4 carbon atoms.

[0026] In another preferred arrangement, Ri represents the hydrogen atom.

[0027] Group B preferably represents a hydrogen atom or a metal chosen from magnesium, calcium, and sodium, and preferably is a hydrogen atom. Preferably, the ascorbate derivative of general formula (l) is chosen from ascorbic acid, calcium ascorbate, sodium ascorbate, and magnesium ascorbate, preferably from magnesium ascorbate and ascorbic acid, and preferably is ascorbic acid.

[0028] The rubber composition of the reinforced product according to the invention comprises 0.5 to 10 pc, preferably 0.5 to 4 pc and more preferably 1 to 3 pc of a thiosulfate salt.

[0029] Thiosulfate salt can be used in its hydrated or non-hydrated form.

[0030] Preferably, the thiosulfate salt is a salt of hexamethylene 1,6-bisthiosulfate, preferably sodium hexamethylene 1,6-bisthiosulfate. Other salts of hexamethylene 1,6-bisthiosulfate may be used, for example, potassium or calcium salts.

[0031] Preferably, the rubber composition of the reinforced product according to the invention comprises at least 8 parts per cubic meter of zinc oxide. This zinc oxide content ensures the properties of the reinforced product according to the invention.

[0032] Dienic elastomer

[0033] By "dienic" elastomer (or indistinctly rubber), whether natural or synthetic, should be understood in a known way as an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not).

[0034] These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated." Generally, "essentially unsaturated" refers to a diene elastomer derived at least in part from conjugated diene monomers, having a proportion of diene-derived motifs or units (conjugated dienes) greater than 15% (mole percent). Thus, diene elastomers such as butyl rubbers or EPDM-type diene-alpha-olefin copolymers do not fall under the preceding definition and can be described, in particular, as "essentially saturated" diene elastomers (low or very low proportion of diene-derived motifs, always less than 15%). The diene elastomers included in the composition according to the invention are preferably essentially unsaturated. The term diene elastomer specifically refers to a diene elastomer that can be used in compositions according to the invention.

[0035] (a) any homopolymer of a conjugated or unconjugated diene monomer having from 4 to 18 carbon atoms;

[0036] (b) any copolymer of a diene, conjugated or not, having from 4 to 18 carbon atoms and at least one other monomer.

[0037] The other monomer can be ethylene, an olefin or a diene, conjugated or not.

[0038] Suitable conjugated dienes are those having 4 to 12 carbon atoms, in particular 1,3'dienes, such as 1,3'butadiene and isoprene.

[0039] Suitable olefins include vinylaromatic compounds with 8 to 20 carbon atoms and aliphatic chromoolefins with 3 to 12 carbon atoms.

[0040] Examples of suitable vinylaromatic compounds include styrene, ortho-, mela-, para-methylstyrene, the commercial mixture "vinyl toluene", and para-tert-butylstyrene.

[0041] As suitable aliphatic chromoolefins, acyclic aliphatic chromoolefins having from 3 to 18 carbon atoms are particularly suitable.

[0042] Preferably, the diene elastomer is chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. Butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR).

[0043] Preferably, the diene elastomer is an isoprene elastomer.

[0044] The term "isoprene elastomer" is commonly understood to mean a homopolymer or copolymer of isoprene, in other words, a diene elastomer selected from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), various isoprene copolymers, and mixtures of these elastomers. Among the isoprene copolymers, particular examples include isobutene-isoprene (butyl rubber - IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR), and isoprene-butadiene-styrene (SBIR). This isoprene elastomer is preferably selected from the group consisting of natural rubber, synthetic cis-1,4 polyisoprenes, and mixtures thereof. among these synthetic polyisoprenes, polyisoprenes with a molar percentage of cis'1,4 bonds greater than 90% are preferred, and even more preferably greater than 98%.Preferably and according to any one of the arrangements herein, diene elastomer is natural rubber.

[0045] Preferably, the content of diene elastomer, preferably isoprene elastomer, preferably natural rubber, is 50 to 100 parts per cent, more preferably 70 to 100 parts per cent, even more preferably 80 to 100 parts per cent, and most preferably 90 to 100 parts per cent. In particular, the content of diene elastomer, preferably isoprene elastomer, preferably selected from the group consisting of natural rubber, synthetic polyisoprenes, and mixtures thereof, is most preferably 100 parts per cent.

[0046] Whether it contains a single diene elastomer or a mixture of several diene elastomers, the rubber composition according to the invention may also contain, in small amounts, any type of synthetic elastomer other than a diene elastomer, or even polymers other than elastomers, for example, thermoplastic polymers. Preferably, the rubber composition according to the invention contains no synthetic elastomer other than a diene elastomer or any polymer other than elastomers, or contains less than 20 parts per million, preferably less than 15 parts per million.

[0047] Crosslinking system

[0048] The rubber composition of the reinforced product according to the invention comprises a sulfur-based crosslinking system. This is referred to as a vulcanization system.

[0049] Sulfur can be supplied in any form, including molecular sulfur or a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and optionally, various known vulcanization activators such as zinc oxide, stearic acid or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (especially diphenylguanidine), or known vulcanization retardants may be used.

[0050] Sulfur is used at a preferential rate of between 0.5 and 12 parts per million (ppm), particularly between 1 and 10 ppm. The vulcanization accelerator is used at a preferential rate of between 0.5 and 10 ppm, more preferably between 0.5 and 5 ppm, and most preferably between 0.5 and 3 ppm. Preferably, the rubber composition of the reinforced product according to the invention comprises at most 15 ppm of zinc oxide, and preferably at most 12 ppm of zinc oxide.

[0051] Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used as an accelerator, including thiazole-type accelerators and their derivatives, sulfenamide-type accelerators, thiurams, dithiocarbamates, dithiophosphates, thioureas and xanthates. Examples of such accelerators include the following compounds: ■ 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-ter-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-ter-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0052] Reinforcing load

[0053] The rubber composition includes one or more reinforcing fillers.

[0054] Any type of so-called reinforcing filler can be used, known for its ability to strengthen a rubber composition usable in particular for the manufacture of tires, for example an organic filler such as carbon black, an inorganic filler such as silica or a mixture of these two types of fillers.

[0055] All carbon blacks are suitable, including those conventionally used in tires or their treads. Among these, particularly the reinforcing carbon blacks of the 100, 200, and 300 series, or the 500, 600, and 700 series (ASTM D-1765-2017 grades), such as NI 15, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772. These carbon blacks can be used on their own, as commercially available, or in other forms, for example, as a carrier for certain rubber compound additives. Carbon blacks could for example already be incorporated into the diene elastomer, in particular isoprene in the form of a masterbatch (see for example applications WO97 / 36724-A2 or W099 / 16600-A1).Also suitable are carbon blacks derived from tire recycling, such as blacks produced by the pyrolysis of tire treads, for example, EnviroCB P550 500 series black produced by Scandinavian Enviro Systems. Examples of organic fillers other than carbon blacks include functionalized polyvinyl organic fillers as described in applications W02006 / 069792-A1, W02006 / 069793-A1, W02008 / 003434-A1 and W02008 / 003435-A1.

[0056] The term "reinforcing inorganic filler" here refers to any inorganic or mineral filler, regardless of its color or origin (natural or synthetic), also called "white" filler, "light" filler, or even "non-black" filler (as opposed to carbon black), capable of reinforcing, on its own and without the need for an intermediate coupling agent, a rubber compound intended for tire manufacturing. It is known that some reinforcing inorganic fillers are characterized, in particular, by the presence of hydroxyl groups (-OH) on their surface. For the purposes of this definition, silica used alone, that is, without a coupling agent, is not considered a reinforcing filler.

[0057] Suitable inorganic reinforcing fillers include mineral fillers of the siliceous type, preferably silica (SiO₂), or of the aluminous type, particularly alumina (Al₂O₃). The silica used may be any reinforcing silica known to those skilled in the art, including any precipitated or fumed silica with a specific surface area (BET) and a specific surface area (CTAB) both below 450 m². 2 / g, preferably within a range of 30 to 400 m 2 / g, particularly from 60 to 300 m 2 / g. Any type of precipitated silica may be used, including highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. Examples include the silicas described in applications W003 / 016215-A1 and W003 / 016387-A1. Among commercial HDS silicas, the following may be used: "Ultrasil® 5000GR" and "Ultrasil® 7000GR" from Evonik, and "Zeosil® 1085GR", "Zeosil® 1115 MP", "Zeosil® 1165 MP", "Zeosil® Premium 200 MP", and "Zeosil® HRS 1200 MP" from Solvay.As non-HDS silica, the following commercial silicas can be used: ■ “Ultrasil ® VN2GR”, “Ultrasil ® VN3GR” silicas from Evonik, “Zeosil® 175GR” silica from Solvay, “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(- D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” silicas from PPG and “K- 160” from Wilmar.

[0058] In this presentation, the specific surface area BET is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, page 309, February 1938), and more specifically according to a method adapted from the standard NF ISO 5794-1, Annex E of June 2010 [multipoint volumetric method (5 points) - gas: nitrogen - degassing under vacuum: one hour at 160°C - relative pressure range w / in: 0.05 to 0.17].

[0059] For inorganic fillers such as silica, for example, the CTAB specific surface area values ​​were determined according to the NF ISO 5794-1 standard, Annex G of June 2010. The process is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "external" surface of the reinforcing filler.

[0060] For carbon blacks, the STSA specific surface area is determined according to ASTM D6556-2016.

[0061] Other examples of inorganic fillers that could be used in the rubber compositions of the invention may also be cited: mineral fillers of the aluminous type, in particular alumina (Al2O3), aluminum oxides, aluminum hydroxides, aluminosilicates, titanium oxides, silicon carbides or nitrides, all of the reinforcing type as described for example in applications WO99 / 28376-A2, WOOO / 73372-A1, WO02 / 053634-A1, W02004 / 003067-A1, W02004 / 056915-A2, US6610261-B1 and US6747087-B2. Examples include the aluminas “Baikalox A125” or “CR125” (Baïkowski company), “APA-100RDX” (Condéa), “Aluminoxid C” (Evonik) or “AKP-G015” (Sumitomo Chemicals).

[0062] The physical state of the reinforcing inorganic filler is irrelevant, whether it be in the form of powder, microbeads, granules, spheres, or any other suitable densified form. Of course, the term "reinforcing inorganic filler" also refers to mixtures of different reinforcing inorganic fillers, particularly silicas as described above.

[0063] A skilled professional will know how to adjust the total reinforcing filler content according to the intended use, particularly the type of tire, for example, motorcycle tires, passenger car tires, or commercial vehicle tires such as vans or trucks. Preferably, the total reinforcing filler content (carbon black and / or inorganic reinforcing filler such as silica) is between 10 and 200 parts per cubic meter (ppm), more preferably between 25 and 180 ppm, with the optimum being known to vary depending on the specific application.

[0064] To couple the reinforcing inorganic filler to the diene elastomer, a well-known coupling agent (or bonding agent) can be used to ensure sufficient chemical and / or physical connection between the inorganic filler (the surface of its particles) and the diene elastomer. Organosilanes or polyorganosiloxanes, at least bifunctional, are particularly suitable. "Bifunctional" refers to a compound possessing a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer.For example, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being able to interact with the hydroxyl groups of an inorganic charge and a second functional group comprising a sulfur atom, said second functional group being able to interact with the diene elastomer.

[0065] Preferably, organosilanes are chosen from the group consisting of polysulfide organosilanes (symmetric or asymmetric) such as bis(3) tetrasulfide _triethoxysilylpropyl), abbreviated TESPT and marketed under the name "Si69" by Evonik, or bis-(triethoxysilylpropyl) disulfide, abbreviated TESPD and marketed under the name "Si75" by Evonik, polyorganosiloxanes, mercaptosilanes, and blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl octanethioate) marketed by Momentive under the name "NXT Silane". More preferably, the organosilane is a polysulfide organosilane.

[0066] The coupling agent content in the composition of the invention is preferably less than or equal to 35 parts per liter (ppm), it being understood that it is generally desirable to use as little as possible. Typically, the coupling agent content represents 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler, preferably 5% to 15% by weight. Its content is preferably in the range of 0.5% to 20 parts per liter, more preferably in the range of 3% to 10%. This content is readily adjusted by a person skilled in the art according to the amount of reinforcing inorganic filler used in the composition of the invention.

[0067] Those skilled in the art will understand that, in place of the inorganic reinforcing filler described above, a reinforcing filler of another nature could be used, provided that this reinforcing filler of another nature is coated with an inorganic layer such as silica, or has functional sites on its surface, particularly hydroxyl sites, requiring the use of a coupling agent to establish the bond between this reinforcing filler and the diene elastomer. Examples include carbon blacks partially or fully coated with silica, or carbon blacks modified with silica, such as, but not limited to, the "Ecoblack®" fillers of the CRX2000 series or the "CRX4000" series from Cabot Corporation.

[0068] Preferably, the reinforcing filler in the rubber composition comprises silica and at most 4 parts carbon black. Most preferably, the reinforcing filler in the rubber composition comprises 20 to 80 parts silica and at most 4 parts carbon black. The combination of a silica reinforcing filler with at most 4 parts carbon black, an ascorbate derivative, and a thiosulfate salt, in a composition not containing a transition metal salt, yields particularly advantageous adhesion and deformation-at-break properties.

[0069] Additives

[0070] The rubber compositions of the reinforced product according to the invention may also include all or part of the usual additives and processing agents known to those skilled in the art and commonly used in rubber compositions for pneumatic tires, such as plasticizers (such as plasticizing oils and / or plasticizing resins), fillers (reinforcing or non-reinforcing / other than those mentioned above such as, for example, regenerated or devulcanized powders from the recycling of pneumatic tires), pigments, protective agents such as antrozone waxes, chemical antrozonants, antioxidants, anti-fatigue agents, reinforcing resins (such as described, for example, in application WO 02 / 10269), a crosslinking system, for example based on sulfur and other vulcanizing agents, and / or peroxide and / or bismaleimide.

[0071] The use of an ascorbate derivative and a thiosulfate salt, preferably with a zinc oxide content of at least 8 parts per million (ppm), minimizes the amount of cobalt salts present in the rubber composition of the reinforced product, or even eliminates the need for such salts altogether. Thus, the transition metal salt content, particularly cobalt salts, in the rubber composition of the reinforced product according to the invention is at most 0.1 ppm, preferably at most 0.05 ppm, and most preferably at most 0.01 ppm.

[0072] Reinforcing element

[0073] The reinforced product according to the invention is based on at least one metallic reinforcing element and a rubber composition.

[0074] The expression "based on at least one metallic reinforcing element and a rubber composition" means a reinforced product comprising the reinforcing element and said composition, the composition having been able to react with the surface of the reinforcing element during the different phases of manufacture of the reinforced product, in particular during the crosslinking of the composition or during the manufacture of the reinforced product before crosslinking of the composition.

[0075] The said metallic reinforcement element is a wire element. It can be entirely or partially metallic.

[0076] In a particular arrangement, said reinforcing element includes a metallic surface.

[0077] The metallic surface of the reinforcing element constitutes at least part, and preferably all, of the surface of said element and is intended to come into direct contact with the rubber composition. Preferably, the reinforcing element is metallic, that is to say, made of a metallic material.

[0078] The rubber compound coats at least part of the reinforcing element, preferably the entire element.

[0079] According to a first embodiment of the invention, the metallic surface of the reinforcing element is made of a material different from the rest of the reinforcing element. In other words, the reinforcing element is made of a material that is at least partially, preferably totally, covered by a metallic layer that constitutes the metallic surface. The material at least partially, preferably totally, covered by the metallic surface is metallic or non-metallic, preferably metallic.

[0080] According to a second variant of the invention, the reinforcing element is made of the same material, in which case the reinforcing element is made of a metal that is identical to the metal of the metallic surface.

[0081] The metallic surface can, for example, improve the implementation properties of the reinforcing element, or the usage properties of the reinforced product and / or the pneumatic tire itself, such as adhesion properties, corrosion resistance or resistance to aging.

[0082] According to one embodiment of the invention, the metallic surface comprises a metal selected from the group consisting of iron, copper, zinc, tin, aluminum, cobalt, nickel, and alloys comprising at least one of these metals. The alloys may be, for example, binary or ternary alloys, such as steel, bronze, and brass. Preferably, the metal of the metallic surface is iron, copper, tin, zinc, or an alloy comprising at least one of these metals. More preferably, the metal of the metallic surface is steel, brass (Cu-Zn alloy), zinc, or bronze (Cu-Sn alloy); even more preferably, brass or steel; and most preferably, brass.

[0083] Since some metals are subject to oxidation when in contact with ambient air, the metal may be partially oxidized.

[0084] When the metallic surface is made of steel, the steel is preferably carbon steel or stainless steel. When the steel is carbon steel, its carbon content is preferably between 0.01% and 1.2%, or between 0.05% and 1.2%, or between 0.2% and 1.2%, particularly between 0.4% and 1.1%. When the steel is stainless steel, it preferably contains at least 11% chromium and at least 50% iron.

[0085] The invention applies in particular to normal tensile (NT) or high tensile (HT) steel cords, where the second and third carbon steel reinforcements have a tensile strength (Rm) preferably greater than 2000 MPa, and more preferably greater than 2500 MPa. The invention also applies to super high tensile (SHT) and ultra high tensile (UHT or MT) steel cords, where the second and third carbon steel reinforcements have a tensile strength (Rm) preferably greater than 3000 MPa, and more preferably greater than 3500 MPa. The total elongation at break (At) of these reinforcements, the sum of the elastic elongation and the plastic elongation, is preferably greater than 2.0%.

[0086] The measurements of breaking strength, breaking resistance noted Rm (in MPa) and elongation at break noted At (total elongation in %) are carried out in tension according to the ISO 6892 standard of 1984.

[0087] According to a preferred embodiment, the reinforced product of the invention comprises several reinforcing elements as defined above and a calendered rubber in which the reinforcing elements are embedded, the calendered rubber being the rubber composition of the reinforced product of the invention. In this embodiment, the reinforcing elements are generally arranged side by side along a principal direction. For a envisaged application in the tire industry, the reinforced product of the invention can therefore constitute a reinforcing reinforcement for the tire.

[0088] The reinforced product according to the invention can be in its raw state (before crosslinking of the rubber composition) or in its cured state (after crosslinking of the rubber composition). The reinforced product according to the invention is cured after the reinforcing element(s) have been brought into contact with the rubber composition.

[0089] The reinforced product according to the invention can be manufactured by a process which comprises the following steps :

[0090] • Apply two layers of the rubber compound,

[0091] • Sandwich the reinforcement element(s) between the two layers by placing it / them between the two layers,

[0092] • If necessary, cook the product reinforced according to the invention.

[0093] Alternatively, the reinforced product according to the invention can be manufactured by depositing the reinforcing element on a portion of a layer, the layer is then folded over itself to cover the reinforcing element which is thus sandwiched along its entire length or part of its length.

[0094] The layers can be produced by calendering. During the curing of the reinforced product according to the invention, the rubber composition is cross-linked.

[0095] When the reinforced product according to the invention is intended to be used as a reinforcing reinforcement in a pneumatic tire, the curing of the reinforced product according to the invention generally takes place during the curing of the tire.

[0096] Finished or semi-finished article and pneumatic

[0097] The invention also relates to a finished or semi-finished article comprising a reinforced product according to the invention. The finished or semi-finished article may be any article comprising a reinforced product. Examples, without limitation, include balloons, conveyor belts, shoe soles, and pneumatic or non-pneumatic bandages.

[0098] The pneumatic or non-pneumatic bandage, another object of the invention, has as its essential characteristic the inclusion of the reinforced product according to the invention. The bandage may be in its raw state (before cross-linking of the rubber composition) or in its cured state (after cross-linking of the rubber composition). Generally, during the manufacture of the bandage, the reinforced product is deposited in its raw state (i.e., before cross-linking of the rubber composition) within the bandage structure prior to the curing stage.

[0099] The tire according to the invention comprises a reinforced layer made of a reinforced product according to the invention, preferably selected from carcass plies, crown plies, bead-fillers, and combinations of these reinforced layers. Furthermore, the rubber composition of the reinforced product according to the invention could be used as an inner layer in a pneumatic or non-pneumatic tire, an inner layer being a layer of the tire that is neither in contact with ambient air nor with the inflation gas. Such inner layers are, for example, crown-foot layers, decoupling layers, edge rubbers, and combinations of these inner layers. In the present context, "edge rubber" means a layer positioned within the tire directly in contact with the end of a reinforced layer, the end of a reinforcing element, or another edge rubber.

[0100] The invention relates particularly to tires intended to equip motor vehicles of the passenger car type, SUVs ("Sport Utility Vehicles"), or two wheels (in particular motorcycles), or aircraft, or even industrial vehicles chosen from among vans, "Heavy Goods Vehicles", i.e. metro, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles such as agricultural or civil engineering vehicles, and others.

[0101] Thus, the invention relates in particular to a pneumatic or non-pneumatic tire comprising a crown including a crown reinforcement formed of two crown layers of reinforcing elements and surmounted by a tread, two beads intended to come into contact with a rim each comprising a circumferential reinforcing element and two sidewalls each extending radially inwards from an axial end of the crown to the beads, said tire further comprising a carcass reinforcement anchored to each of the beads and extending from the beads through the sidewalls towards the crown, at least one of the two crown layers of reinforcing elements being made of a reinforced product according to the invention.

[0102] Examples

[0103] Preparation of rubber compositions

[0104] The following tests are conducted as follows: ■ The diene elastomer, the reinforcing filler, and the various other ingredients, with the exception of the vulcanization system, are successively introduced into an internal mixer (final fill level approximately 70% by volume), whose initial tank temperature is approximately 60°C. A single-stage thermomechanical process (non-productive phase) is then carried out, lasting approximately 3 to 4 minutes in total, until a maximum "drop" temperature of 165°C is reached.

[0105] The mixture thus obtained is collected, cooled, and then sulfur and an accelerator (sulfenamide) are incorporated on a mixer (homo-finisher) at 30 °C, mixing everything (productive phase) for an appropriate time (for example between 5 and 12 min).

[0106] The compositions thus obtained are then calendered into plates (2 to 3 mm thick) or thin sheets of rubber and then subjected to a baking stage before their physical or mechanical properties are measured.

[0107] Measurement methods

[0108] Traction tests

[0109] These tensile tests determine the breaking properties of rubber compounds. The tests were carried out in accordance with the French standard NF T 46-002 of September 1988. Elongations at break (in %) are measured at 100°C.

[0110] The results are expressed as a base of 100, with the value 100 being assigned to the control composition T1 for Table 1, and T2 for Table 2. A result greater than 100 indicates that the composition of the example considered has a greater elongation at break than the control.

[0111] Adhesion test

[0112] Preparing the test tubes

[0113] The rubber compositions thus prepared are used to make a composite in the form of a test specimen according to the following protocol.

[0114] The metal / rubber composite used in this test is a block of rubber compound, consisting of two plates measuring 200 mm by 12.5 mm and 3.5 mm thick, applied one on top of the other before curing; the resulting block is then 7 mm thick. During the preparation of this block, the reinforcements, for example twelve in number, are sandwiched between the two raw plates. Only a specific length of reinforcement, for example 12.5 mm, is left exposed to come into contact with the rubber compound, to which this reinforcement will bond during curing; the remaining length of the reinforcements is insulated from the rubber compound (for example, using a plastic or metallic film) to prevent any adhesion outside the defined contact area.Each reinforcement passes through the rubber block from one side to the other, with at least one of its free ends being kept of sufficient length (at least 5 cm, for example between 5 and 10 cm) to allow subsequent pulling of the reinforcement.

[0115] For the tests in Table 1, each metal reinforcement consists of 1 steel wire, 32 / 100ths of a millimeter in diameter, coated with a brass coating comprising 63% copper.

[0116] For the tests in Table 2, each metal reinforcement consists of 19 steel wires, 18 / 100ths of a millimeter in diameter, made up of three layers: a first central layer consisting of one wire, a second layer consisting of 6 wires wound helically around the central wire, and a third layer consisting of 12 wires wound helically around the second layer, each wire being coated with brass, the brass comprising 63% copper.

[0117] The block containing the twelve reinforcements is then placed in a suitable mold and then baked for 50 minutes at 140°C for the compositions in Table 1 and 15 minutes at 160°C for the compositions in Table 2, under a pressure of approximately 11 bar.

[0118] After baking the block, the following accelerated aging conditions are applied, allowing the resistance of the samples to the combined action of heat and humidity to be determined ■ the rubber blocks are placed in an oven at a temperature of 55°C, for 7 days and under a relative humidity of 95%.

[0119] Measurement of pull-out forces

[0120] Following the curing and aging process described above, the block is cut into test specimens, each containing a reinforcement which is pulled out of the rubber block using a tensile testing machine according to the method described in the standard.

[0121] ASTM D 2229-02; the tensile speed is 100 mm / min; adhesion is thus characterized by the force required to pull the reinforcement out of the specimen, at a temperature of 60°CJ the pull-out force represents the average of the 15 measurements corresponding to the 15 reinforcements of the composite.

[0122] The higher the force value, the greater the adhesion between the cable and the rubber compound. The results are expressed as a base of 100 relative to a control specimen containing metallic reinforcements of the same type as the tested specimen and containing the rubber compound "T1" for Table 1, and "T5" for Table 2. A value higher than that of the control specimen, arbitrarily set at 100, indicates an improved result, i.e., a pull-out force greater than that of the control specimen.

[0123] The compositions of the different test specimens tested and the results obtained are presented in Tables 1 and 2.

[0124] [Table 1]

[0125] (1) Natural rubber

[0126] (2) Carbon black, ASTM grade N326

[0127] (3) N-(1,3'-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (Santoflex 6) _ Flexsys' PPD")

[0128] (4) Cobalt acetylacetonate

[0129] (5) Stearine, "Pristerene 4931" from Uniqema

[0130] (6) Zinc oxide, industrial grade — Umicore

[0131] (7) DCBS (N,N-dicyclohexyl-2-benzothiazyl sulfenamide)

[0132] (8) Hexamethylene 1,6'-bisthiosulfate sodium from Nocil Mumbai Company

[0133] Removing the cobalt salt leads to a degradation of adhesion to the metal reinforcement after aging of nearly 15%. Adding a thiosulfate salt alone to this cobalt-free formula does not restore the adhesion and also significantly degrades the deformation at failure at 100°C.

[0134] Adding ascorbic acid alone to the same formula without cobalt salt does not restore the post-aging adhesion level of the mixture with cobalt salt. Combining a thiosulfate salt and an ascorbate derivative, in the absence of cobalt salt, provides similar post-aging adhesion properties and a deformation at break at 100°C, i.e., no less than 90% of the reference value with cobalt salt.

[0135] [Table 2]

[0136] (1) Natural rubber

[0137] (2) Silica Zeosil® HRS 1200 MP Solvay

[0138] (3) Coupling agent ■ “Si69” from Evonik — Degussa

[0139] (4) N-(1,3'-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (Santoflex 6) _ Flexsys' PPD")

[0140] (5) Cobalt acetylacetonate

[0141] (6) Diphenylguanidine, “Perkacit DPG” from Flexsys

[0142] (7) Stearine, “Pristerene 4931” from Uniqema

[0143] (8) Zinc oxide, industrial grade — Umicore

[0144] (9) TBBS (N-ter-butyF2-benzothiazyl sulfenamide)

[0145] (10) Hexamethylene 1,6'-bisthiosulfate sodium from Nocil Mumbai Company

[0146] The combination of a thiosulfate salt and an ascorbate derivative allows, in the absence of cobalt salt and in the presence of silica, to obtain adhesion and deformation at break properties superior to those of the control composition.

Claims

DEMANDS

1. Reinforced product based on at least one metallic reinforcing element and a rubber composition based on at least one diene elastomer, a reinforcing filler and a sulfur-based crosslinking system, the rubber composition comprising at least one ascorbate derivative of general formula (l) ■ [d-] n [B n+ ] (I) in which n is an integer equal to 1 or 2, A~ represents an ascorbate compound of general formula (II) in which Ri represents a hydrogen atom or a group selected from alkyl groups comprising 1 to 18 carbon atoms, alkylcarbonyl and alkenyl groups comprising 2 to 18 carbon atoms, and alkenylcarbonyl groups comprising 3 to 18 carbon atoms, and B represents a hydrogen atom or an alkali or alkaline earth metal, said rubber composition comprising a thiosulfate salt and at most 0.1 pc of a transition metal salt.

2. Reinforced product according to the preceding claim in which B represents a hydrogen atom or an alkali or alkaline earth metal selected from magnesium, calcium and sodium, and preferably is a hydrogen atom.

3. Reinforced product according to any one of the preceding claims wherein Ri represents a hydrogen atom or a group selected from alkyl groups comprising 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms, alkylcarbonyl and alkenyl groups comprising 2 to 5 carbon atoms and preferably 2 to 4 carbon atoms, and alkenylcarbonyl groups comprising 3 to 5 carbon atoms and preferably 3 to 4 carbon atoms.

4. Reinforced product according to claim 1 or 2 in which Ri represents a hydrogen atom.

5. Reinforced product according to claim 1 wherein the ascorbate derivative of general formula (l) is selected from ascorbic acid, calcium ascorbate, sodium ascorbate and magnesium ascorbate, preferably selected from magnesium ascorbate and ascorbic acid and preferably is ascorbic acid.

6. Reinforced product according to any one of the preceding claims, wherein the content of ascorbate derivative of general formula (l) in the rubber composition ranges from 0.5 to 10 pc, and preferably from 1 to 8 pc.

7. Enhanced product according to any one of the preceding claims wherein the thiosulfate salt is a hexamethylene 1,6-bisthiosulfate salt, preferably is sodium hexamethylene 1,6'bisthiosulfate.

8. Reinforced product according to any one of the preceding claims wherein the rubber composition comprises at least 8 parts of a zinc oxide.

9. Reinforced product according to any one of the preceding claims wherein the reinforcing filler of the rubber composition comprises carbon black, silica or a mixture of carbon black and silica.

10. Reinforced product according to any one of the preceding claims wherein the reinforcing filler of the rubber composition comprises silica and at most 4 parts carbon black.

11. Reinforced product according to any one of the preceding claims wherein the rubber composition comprises a diene elastomer selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers, and mixtures of these elastomers, and preferably selected from the group consisting of natural rubber, synthetic polyisoprenes, and mixtures thereof.

12. Finished or semi-finished article comprising a reinforced product according to any one of claims 1 to 11.

13. Pneumatic or non-pneumatic bandage comprising a reinforced product according to any one of claims 1 to 11.

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