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

Abstract

The present invention relates to a reinforced product based on at least one metal 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 compound and an alkaline earth metal, the rubber composition having a content of ascorbate compound at least equal to 0.5 phr and a molar ratio of ascorbate to alkaline earth metal ranging from 0.7 to 2.5.

Description

[Technical Field]

[0001] 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 products. [Background technology]

[0002] The reinforcing plies of pneumatic tires or reinforced rubber articles contain a rubber composition, commonly referred to as a skim rubber composition, and textile or metal reinforcing cords. It is understood that these plies must be particularly resistant to the phenomenon of separation or cracking of the ends of the cross plies in the "shoulder" regions of the tire, a problem known by the term "splitting," especially because of the sometimes particularly severe running conditions, for example, when the tire is running in a wet and corrosive atmosphere, and are subjected to significant stresses. This condition requires that the rubber compositions, especially those involved in forming the belts of the tire, have very high resistance to crack propagation and thermal oxidation, as well as favorable rupture properties. Many studies have been conducted by pneumatic tire manufacturers to improve one or more of these performance characteristics, particularly by adding additives to rubber compositions. Thus, U.S. Patent No. 5,859,101 describes tire compositions containing 0.05 to 5 phr of a compound selected from ascorbic acid and its derivatives, tocopherol, citric acid and its derivatives, which can improve the abrasion resistance, crack resistance, and fatigue strength of rubber compositions usable in skim compositions. This document does not address the issue of adhesion to reinforcing elements.

[0003] Document EP 3167110 discloses an in situ rubberized cord in which the rubber composition contains an antioxidant such as ascorbic acid to improve the durability of the adhesion of the composition to the metal reinforcement without degrading the initial adhesion. US Patent No. 3,903,026 teaches that the addition of magnesium oxide to a composition containing cobalt carboxylate can improve adhesion to zinc or zinc alloy coated metal reinforcements. The properties of the composition at break are not mentioned. During the course of research, the applicant discovered that rubber compositions containing an ascorbate compound and an alkaline earth metal, when used to skim coat metal reinforcing elements, exhibited both improved adhesion properties and improved resistance to crack propagation properties without degrading break properties. Summary of the Invention

[0004] The present invention relates to at least one of the following embodiments: 1. A reinforced product based on at least one metal reinforcing element and a rubber composition based on at least one diene elastomer, a reinforcing filler and a sulfur-based crosslinking system, wherein the rubber composition comprises at least one alkaline earth metal and a compound of the general formula (I): [ka] (I) (wherein R1 represents a hydrogen atom H or a group selected from alkyl groups containing 1 to 18 carbon atoms, alkylcarbonyl and alkenyl groups containing 2 to 18 carbon atoms, and alkenylcarbonyl groups containing 3 to 18 carbon atoms). wherein the rubber composition has a content of the ascorbate compound equal to at least 0.5 phr and a molar ratio of the ascorbate compound to the alkaline earth metal in the range of 0.7 to 2.5.

[0005] 2. The rubber composition comprises a rubber compound represented by general formula (II):

number

[0006] 7. Fortified product according to embodiment 1, in which the ascorbate compound is selected from ascorbic acid, calcium ascorbate and magnesium ascorbate, preferentially magnesium ascorbate and calcium ascorbate, preferably calcium ascorbate. 8. The reinforced product of any one of the preceding embodiments, wherein the rubber composition further comprises an oxide or hydroxide of an alkaline earth metal, preferentially an oxide of an alkaline earth metal. 9. The reinforced product of the preceding embodiment, wherein the oxide of an alkaline earth metal is selected from magnesium oxide, calcium oxide, and mixtures of these oxides. 10. The reinforced product of embodiment 1, wherein the rubber composition comprises ascorbic acid and an alkaline earth metal oxide, preferably selected from calcium oxide and magnesium oxide, and preferably magnesium oxide. 11. The reinforced product according to any one of the preceding embodiments, wherein the content of the ascorbate compound of general formula (I) in the rubber composition is at most 3 phr, preferably in the range of 1 to 3 phr. 12. The reinforced product of any one of the preceding embodiments, wherein the reinforcing filler of the rubber composition comprises carbon black, silica, or a mixture of carbon black and silica.

[0007] 13. The reinforced product of any one of the preceding embodiments, wherein the reinforcing filler of the rubber composition comprises silica and a coupling agent, and the content of the coupling agent ranges from 5% by mass to 15% by mass relative to the amount of silica. 14. The reinforced product of any one of the preceding embodiments, wherein the reinforcing filler content is between 10 and 200 phr. 15. The reinforced product of any one of the preceding embodiments, wherein the content of the cobalt salt in the rubber composition is in the range of 0.5 to 2 phr, preferably 0.5 to 1 phr. 16. Reinforced product according to any one of the preceding embodiments, wherein the rubber composition comprises at least 3 phr zinc oxide, preferentially at least 5 phr zinc oxide. 17. The reinforced article of any one of the preceding embodiments, wherein the rubber composition comprises a diene elastomer selected from the group consisting of polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. 18. Reinforced product according to any one of the preceding embodiments, wherein the rubber composition comprises at least 50 phr, preferentially at least 70 phr, preferably at least 85 phr of at least one isoprene elastomer.

[0008] 19. The reinforced article of the preceding embodiment, wherein the isoprene elastomer is selected from the group consisting of natural rubber, synthetic polyisoprene, isoprene copolymers, and mixtures thereof. 20. The reinforced product of any one of the preceding embodiments, wherein the reinforcing element comprises a metal surface. 21. A reinforced product according to the preceding embodiment, wherein the metal surface of said reinforcing element 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, preferentially iron, copper, tin, zinc, or alloys comprising at least one of these metals. 22. The reinforced product of any one of embodiments 20 and 21, wherein the metal of the metal surface is brass or steel. 23. A finished or semi-finished product comprising the reinforced product of any one of embodiments 1 to 22. 24. A pneumatic or non-pneumatic tire comprising a reinforcement product according to one of embodiments 1 to 22.

[0009] 25. A tire according to any preceding embodiment, comprising a reinforcing layer made of the reinforcing product according to one of embodiments 1-22 selected from a carcass ply, a crown ply, a bead filler, and combinations of these reinforcing layers. 26. A tire according to the previous embodiment, comprising a crown reinforcement formed from two crown plies of reinforcing elements and covered by a tread, two beads intended to come into contact with the rim, each comprising a circumferential reinforcing element, and two sidewalls, each extending radially inward from the axial end of the crown to the bead, wherein the tire further comprises a carcass reinforcement fixed to each of the beads and extending through the sidewalls from the bead to the crown, and wherein at least one of the two crown plies of reinforcing elements consists of a reinforcing product according to one of embodiments 1 to 22. DETAILED DESCRIPTION OF THE INVENTION

[0010] definition The expression "based on" should be understood to mean a product or composition comprising a mixture and / or product of the in situ reaction of the various components used, some of which can and / or are intended to at least partially react with one another during the various stages of the preparation of the composition, and thus the product or composition can be in a fully or partially crosslinked or non-crosslinked state. The expression "phr" is to be understood for the purposes of the present invention to mean parts by weight per hundred parts by weight of elastomer. In this document, all percentages (%) given are percentages (%) by weight unless expressly indicated otherwise. Furthermore, any interval of values ​​expressed by the expression "between a and b" denotes a range of values ​​extending from greater than a to less than b (i.e., excluding the limits a and b), while any interval of values ​​expressed by the expression "a to b" means a range of values ​​extending from a to at most b (i.e., including the strict limits a and b). The carbon-containing compounds referred to herein may be of fossil or biological origin. In the latter case, they may be derived partially or completely from biomass or may be obtained from renewable starting materials derived from biomass. These are in particular polymers, plasticizers, fillers, etc.

[0011] Reinforcement Products The reinforced product according to the invention is based on at least one metal 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 alkaline earth metal and a compound represented by the general formula (I): [ka] (I) (wherein R1 represents a hydrogen atom H or a group selected from alkyl groups containing 1 to 18 carbon atoms, alkylcarbonyl and alkenyl groups containing 2 to 18 carbon atoms, and alkenylcarbonyl groups containing 3 to 18 carbon atoms). and the rubber composition has a content of the ascorbate compound equal to at least 0.5 phr and a molar ratio of the ascorbate compound to the alkaline earth metal in the range of 0.7 to 2.5. An alkenyl group is understood to mean a monovalent hydrocarbon group containing at least one unsaturation. A carbonyl group is understood to mean a -CO- divalent group.

[0012] Ascorbate and alkaline earth metals The rubber composition of the reinforced product according to the present invention comprises at least one alkaline earth metal and one ascorbate compound of general formula (I), with a content of the ascorbate compound of general formula (I) at least equal to 0.5 phr and a molar ratio of the ascorbate compound of general formula (I) to the alkaline earth metal ranging from 0.7 to 2.5. Alkaline earth metals are understood to mean metals selected from the group consisting of beryllium, magnesium, calcium, strontium, barium and radium. The molar ratio of the ascorbate compound to the alkaline earth metal in the rubber composition ranges from 0.7 to 2.5. In combination with other features of the present invention, a molar ratio less than 0.7 results in a decrease in adhesive strength, while a ratio greater than 2.5 results in a decrease in elongation at break. The ascorbate compound of general formula (I) may be any type of ascorbate compound corresponding to this formula. Preferably, the rubber composition of the reinforced article according to the invention has the general formula (II):

number

[0013] Preferably, R1 represents a hydrogen atom or a group selected from alkyl groups containing 1 to 5 carbon atoms, preferentially 1 to 3 carbon atoms, alkylcarbonyl and alkenyl groups containing 2 to 5 carbon atoms, preferably 2 to 4 carbon atoms, and alkenylcarbonyl groups containing 3 to 5 carbon atoms, preferably 3 to 4 carbon atoms. In a particularly preferred embodiment, the R1 group is an alkyl group containing preferentially 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms, or an alkenyl group containing 2 to 5 carbon atoms, preferably 2 to 4 carbon atoms. In another preferred embodiment, the R1 group is a group selected from alkylcarbonyl groups containing preferentially 2 to 5 carbon atoms, preferably 2 to 4 carbon atoms, and alkenylcarbonyl groups containing 3 to 5 carbon atoms, preferably 3 to 4 carbon atoms. In another preferred embodiment, R1 represents a hydrogen atom. The R2 group is preferentially selected from alkaline earth metals, preferably magnesium and calcium. Preferably, the ascorbate compound is selected from ascorbic acid, calcium ascorbate and magnesium ascorbate, preferentially from magnesium ascorbate and calcium ascorbate, preferably calcium ascorbate.

[0014] Preferably, the content of ascorbate compound of general formula (I) in the rubber composition is a maximum of 3 phr. It has been observed that when the content of ascorbate compound is less than 0.5 phr, the adhesive performance and elongation at break, which are other features of the present invention, deteriorate. A content of more than 3 phr may shorten the fixation time, which must be taken into account when processing reinforced products, and may affect the processability of the composition. Therefore, a content of ascorbate compound of general formula (I) in the range of 0.5 to 3 phr, preferably 1 to 3 phr, is an excellent compromise between uncured properties, i.e., properties before crosslinking, and cured properties. The rubber composition of the reinforced product according to the invention preferably further comprises an alkaline earth metal oxide or hydroxide, preferentially an alkaline earth metal oxide, which is comprised in the rubber composition of the reinforced product according to the invention both from the ascorbate-based compound of general formula (II) when the group R2 is selected from alkaline earth metals, and from the alkaline earth metal oxide or hydroxide, when alkaline earth metal oxide or hydroxide is present in the rubber composition.

[0015] In a preferred configuration, the rubber composition of the reinforced product according to the invention comprises ascorbic acid and an alkaline earth metal oxide, preferably selected from calcium oxide and magnesium oxide, preferably magnesium oxide, the combination of which exhibits particularly advantageous performance properties. In another preferred configuration, the rubber composition of the reinforced product according to the invention comprises calcium ascorbate and magnesium oxide. Preferably, the alkaline earth metal oxide is selected from magnesium oxide, calcium oxide and mixtures of these oxides. Preferably, the alkaline earth metals contained in the rubber composition of the reinforced product according to the invention are selected from calcium and magnesium.

[0016] Diene Elastomer The term "diene" elastomer (or, without distinction, rubber) should be understood to mean, in a known manner, an elastomer composed at least in part (i.e., homopolymer or copolymer) of diene monomer units (monomers having two conjugated or non-conjugated carbon-carbon double bonds), whether natural or synthetic. These diene elastomers can be divided into two categories: "essentially unsaturated" or "essentially saturated." The term "essentially unsaturated" is generally understood to mean a diene elastomer obtained at least in part from conjugated diene monomers having a content of units of diene origin (conjugated dienes) of more than 15% (mol%). This means that diene elastomers, such as butyl rubber or copolymers of dienes and α-olefins of the EPDM type, do not fall within the above definition and may in particular be described as "essentially saturated" diene elastomers (with a low or very low content of units of diene origin, always less than 15 mol%). The diene elastomers contained in the composition according to the invention are preferentially essentially unsaturated.

[0017] The term "diene elastomers that can be used in the compositions according to the invention" refers in particular to: (a) any homopolymer of conjugated or non-conjugated diene monomers containing from 4 to 18 carbon atoms; (b) any copolymer of a conjugated or non-conjugated diene containing from 4 to 18 carbon atoms and at least one other monomer; means. The other monomer may be ethylene, an olefin or a conjugated or non-conjugated diene. Suitable conjugated dienes include those containing from 4 to 12 carbon atoms, especially 1,3-dienes, particularly, for example, 1,3-butadiene and isoprene. Suitable olefins include vinyl aromatic compounds containing from 8 to 20 carbon atoms and aliphatic alpha-monoolefins containing from 3 to 12 carbon atoms. Suitable vinyl aromatic compounds include, for example, styrene, ortho-, meta-, or para-methylstyrene, the commercial mixture of "vinyltoluene," or para-(tert-butyl)styrene. Suitable aliphatic α-monoolefins include, in particular, acyclic aliphatic α-monoolefins containing from 3 to 18 carbon atoms.

[0018] Preferentially, the diene elastomer is selected from the group consisting of polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. The butadiene copolymers are in particular selected from the group consisting of butadiene / styrene copolymers (SBR). Preferably, the diene elastomer is an isoprene elastomer. The term "isoprene elastomer" is understood in a known manner to mean an isoprene homopolymer or copolymer, in other words a diene elastomer selected from the group consisting of natural rubber (NR), synthetic polyisoprene (IR), various isoprene copolymers, and mixtures of these elastomers. Among the isoprene copolymers, particular mention is made of isobutene / isoprene (butyl rubber - IIR), isoprene / styrene (SIR), isoprene / butadiene (BIR), or isoprene / butadiene / styrene (SBIR) copolymers. This isoprene elastomer is preferably selected from the group consisting of natural rubber, synthetic cis-1,4-polyisoprene, and mixtures thereof; among these synthetic polyisoprenes, polyisoprenes with a cis-1,4 bond content (mol %) of more than 90%, and even more preferentially more than 98%, are preferably used. Preferably, and according to any one of the provisions of this document, the diene elastomer is natural rubber.

[0019] Preferentially, the content of diene elastomer, preferably isoprene elastomer, preferably natural rubber, is between 50 and 100 phr, more preferentially between 70 and 100 phr, even more preferentially between 80 and 100 phr, and very preferentially between 90 and 100 phr. In particular, the content of diene elastomer, preferably isoprene elastomer, more preferably natural rubber, is very preferentially 100 phr. Whether the composition contains only one diene elastomer or a mixture of diene elastomers, the rubber composition according to the invention may, in a few embodiments, contain any kind of synthetic elastomer other than diene elastomers, even non-elastomeric polymers, such as thermoplastic polymers. Preferably, the rubber composition according to the invention contains no synthetic elastomers other than diene elastomers, or non-elastomeric polymers, or contains less than 20 phr, preferably less than 15 phr, of them.

[0020] Crosslinked system The rubber composition of the reinforced article according to the invention comprises a sulfur-based crosslinking system, which in this case is called a vulcanization system. The sulfur may be provided in any form, in particular in the form of molecular sulfur or a sulfur donor. At least one vulcanization accelerator is also preferably present, and if necessary and preferentially, various known vulcanization activators may be used, such as zinc oxide, stearic acid or equivalent compounds, such as stearates and salts of transition metals, guanidine derivatives (in particular diphenylguanidine), or known sulfuration retarders. Sulphur is used in a preferred content of between 0.5 and 12 phr, in particular between 1 and 10 phr. Vulcanisation accelerators are used in a preferred content of between 0.5 and 10 phr, more preferably between 0.5 and 5 phr, very preferably between 0.5 and 3 phr.

[0021] Preferably, the rubber composition of the reinforced product according to the invention comprises at least 3 phr of zinc oxide, preferentially at least 5 phr of zinc oxide.Preferentially, the rubber composition of the reinforced product according to the invention comprises at most 15 phr of zinc oxide, preferentially at most 12 phr of zinc oxide. As accelerators, any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used, in particular accelerators of the thiazole type and also of its derivatives, or accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type. As examples of such accelerators, the following compounds may be mentioned in particular: 2-mercaptobenzothiazyl 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 sulfenimide ("TBSI"), tetrabenzyl thiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC"), and mixtures of these compounds.

[0022] Reinforcing filler The rubber composition includes one or more reinforcing fillers. Any type of "reinforcing" filler known for its ability to reinforce rubber compositions usable in particular in the manufacture of tires may be used, such as organic fillers, e.g., carbon black, inorganic fillers, e.g., silica, or a mixture of these two fillers. All carbon blacks are suitable, especially those conventionally used in tires or their treads. Among them, 100, 200, and 300 series reinforcing carbon blacks, or 500, 600, or 700 series blacks (ASTM D-1765-2017 grades), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772 blacks, may be mentioned in more detail. These carbon blacks can be used in a commercially available separated state or in any other form, for example, as a support for some rubber additives. Carbon black can, for example, already be incorporated into diene elastomers, especially isoprene elastomers, in the form of masterbatches (see, for example, WO 97 / 36724 and WO 99 / 16600). Even more preferred are carbon blacks obtained from recycled tires, such as blacks obtained from the pyrolysis of pneumatic tires, such as Enviro CB P550 black from the 500 series manufactured by Scandinavian Enviro Systems.

[0023] Examples of organic fillers other than carbon black may include functionalized polyvinyl organic fillers described in applications WO 2006 / 069792, WO 2006 / 069793, WO 2008 / 003434, and WO 2008 / 003435. The term "reinforcing inorganic filler" should be understood herein to mean any inorganic or mineral filler, whatever its color and origin (natural or synthetic), also called "white" filler, "transparent" filler or even "non-black" filler, in contrast to carbon black, capable of reinforcing rubber compositions intended for the manufacture of tires by itself, without other means than intermediate coupling agents. In a known manner, certain reinforcing inorganic fillers may be characterized in particular by the presence of hydroxyl groups (-OH) on their surface.

[0024] Particularly suitable as reinforcing inorganic fillers are mineral fillers of the siliceous type, preferentially silica (SiO2), or mineral fillers of the aluminous type, in particular alumina (Al2O3). The silica used may be any reinforcing silica known to those skilled in the art, in particular any of the 450m 2 / g or less, preferably 30 to 400m 2 / g, especially 60-300m 2 The silica may be any precipitated or fumed silica exhibiting a BET specific surface area and a CTAB specific surface area ranging from 0.1 to 0.1 / g. Any type of precipitated silica may be used, in particular highly disperse precipitated silica (referred to as "HDS" for "highly disperse" or "highly disperse silica"). These precipitated silicas, which may or may not be highly disperse, are well known to those skilled in the art. For example, mention may be made of the silicas described in applications WO 03 / 016215 and WO 03 / 016387. Among commercial HDS silicas, Ultrasil® 5000GR and Ultrasil® 7000GR silicas manufactured by Evonik, or Zeosil® 1085GR, Zeosil® 1115MP, Zeosil® 1165MP, Zeosil® Premium 200MP, and Zeosil® HRS 1200 MP silicas manufactured by Solvay, may be used in particular. As non-HDS silicas, the following commercial silicas may be used: Ultrasil® VN2GR and 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 and Hi-Sil HDP 320G silicas from PPG, or K-160 from Wilmar.

[0025] In the present disclosure, the BET specific surface area 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), more specifically according to the method derived from standard NF ISO 5794-1, June 2010, Appendix E [Multipoint (5-point) volumetric method - Gas: Nitrogen - Degassed under vacuum: 160°C for 1 hour - Relative pressure p / po range: 0.05-0.17]. In the case of inorganic fillers such as silica, for example, CTAB specific surface area values ​​were determined according to standard NF ISO 5794-1, Appendix G, of June 2010. The process is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) onto the "external" surface of the reinforcing filler. In the case of carbon black, the STSA specific surface area is determined according to standard ASTM D6556-2016.

[0026] Other examples of inorganic fillers that may be used in the rubber composition of the present invention include aluminous mineral fillers, in particular alumina (AlO), aluminum oxide, aluminum hydroxide, aluminosilicates, titanium oxide, silicon carbide or silicon nitride, such as all of the reinforcing types described in applications WO 99 / 28376, WO 00 / 73372, WO 02 / 053634, WO 2004 / 003067, WO 2004 / 056915, U.S. Patent No. 6,610,261, and U.S. Patent No. 6,747,087. In particular, mention may be made of alumina Baikalox A125 or CR125 (Baikowski), APA-100RDX (Condea), Aluminoxide C (Evonik) or AKP-G015 (Sumitomo Chemical Co., Ltd.). The physical state in which the reinforcing inorganic filler is provided is not important, whether in the form of powder, micropearls, granules or beads, or any other suitable densified form. Naturally, reinforcing inorganic filler is also understood to mean mixtures of different reinforcing inorganic fillers, in particular the silicas mentioned above. Those skilled in the art will understand how to adjust the total content of reinforcing fillers depending on the use involved, in particular depending on the type of tire involved, for example a tire for a motorcycle, a passenger car or a utility vehicle, for example a van or a heavy vehicle. Preferentially, the total content of reinforcing fillers (reinforcing inorganic fillers such as carbon black and / or silica) is between 10 and 200 phr, more preferentially between 25 and 180 phr, the optimum values ​​varying in a known manner depending on the specific application targeted.

[0027] To couple the reinforcing inorganic filler to the diene elastomer, at least difunctional coupling agents (or bonding agents) may be used in a known manner, intended to provide a good connection of chemical and / or physical properties between the inorganic filler (the surface of its particles) and the diene elastomer. In particular, at least difunctional organosilanes or polyorganosiloxanes are used. The term "difunctional" is understood to mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer. For example, such a difunctional compound may contain a first functional group containing a silicon atom, capable of interacting with the hydroxyl groups of the inorganic filler, and a second functional group containing a sulfur atom, capable of interacting with the diene elastomer. Preferably, the organosilane is selected from the group consisting of organosilane polysulfides (symmetrical or asymmetrical), such as bis(3-triethoxysilylpropyl)tetrasulfide, abbreviated as TESPT, sold by Evonik under the name "Si69", or bis(triethoxysilylpropyl)disulfide, abbreviated as TESPD, sold by Evonik under the name "Si75", polyorganosiloxanes, mercaptosilanes, block mercaptosilanes, such as S-(3-(triethoxysilyl)propyl)octanethioate, sold by Momentive under the name "NXT Silane". More preferentially, the organosilane is an organosilane polysulfide.

[0028] The content of the coupling agent in the composition of the present invention is preferably 35 phr or less, and it is generally understood that it is desirable to use as little of it as possible. Typically, the content of the coupling agent is 0.5% to 15% by weight, preferably 5% to 15% by weight, based on the amount of the reinforcing inorganic filler. The content is preferentially in the range of 0.5 to 20 phr, more preferentially in the range of 3 to 10 phr. This content can be easily adjusted by those skilled in the art according to the content of the reinforcing inorganic filler used in the composition of the present invention. Those skilled in the art will understand that alternative reinforcing fillers to the inorganic reinforcing fillers described above can be used, but that these fillers are either covered with an inorganic layer such as silica or contain functional sites, especially hydroxyl sites, on their surface, necessitating the use of a coupling agent to establish a bond between the reinforcing filler and the diene elastomer. Examples include carbon black partially or completely covered with silica, or carbon black modified with silica, such as, but not limited to, Ecoblack® type fillers of the CRX2000 series or CRX4000 series from Cabot Corporation.

[0029] additives The rubber composition of the reinforced product according to the invention may also comprise all or some of the common additives and processing aids known to those skilled in the art and customarily 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, for example reclaimed or desulphurized crumb obtained from recycling pneumatic tires), pigments, protective agents such as antiozonant waxes, chemical antiozonants or antioxidants, antifatigue agents, reinforcing resins (for example as described in application WO 02 / 10269), for example sulphur and other vulcanizing agents, and / or crosslinking systems based on peroxides and / or bismaleimides. The use of ascorbate compounds and alkaline earth metals under the conditions of the present invention allows the amount of cobalt salt present in the rubber composition of the reinforced product to be minimized. Thus, in a preferred configuration, the content of cobalt salt in the rubber composition of the reinforced product according to the present invention is in the range of 0.5 to 2 phr, preferably 0.5 to 1 phr.

[0030] Reinforcing elements The reinforced product according to the invention is based on at least one metal reinforcing element and a rubber composition. The expression "based on at least metal reinforcing elements and a rubber composition" should be understood to mean that the reinforced product comprises reinforcing elements and said composition, and that the composition has been able to react with the surface of the reinforcing elements during the various stages of the manufacture of the reinforced product, in particular during crosslinking of the composition or during the manufacture of the reinforced product before crosslinking of the composition. The metallic reinforcing elements are tread-like elements. The metallic reinforcing elements may be entirely or partly made of metal. In a particular configuration, the reinforcing element comprises a metal surface. The metallic surface of the reinforcing element constitutes at least part, and preferentially all, of the surface of said element and is intended to be in direct contact with the rubber composition. Preferably, the reinforcing element is metallic, i.e. formed from a metallic material. The rubber composition coats at least a portion of the reinforcing elements, preferentially all of said elements.

[0031] According to a first variant of the invention, the metal surface of the reinforcing element is made from a material different from the rest of the reinforcing element. In other words, the reinforcing element is made from a material that is at least partially, preferentially completely, covered with a metal layer that constitutes the metal surface. The material that is at least partially, preferentially completely covered with the metal surface can be metallic or non-metallic, preferably essentially metallic. According to a second variant of the invention, the reinforcing elements are made from one and the same material, in this case the reinforcing elements are made from the same metal as that of the metal surface. The metal surface may for example be able to improve the processing properties of the reinforcing element or the use properties of the reinforced product and / or the pneumatic tire itself, such as adhesion, corrosion resistance or ageing resistance properties. According to one embodiment of the present invention, the metal 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 alloy may be, for example, a binary or ternary alloy, such as steel, bronze, or brass. Preferably, the metal of the metal surface is iron, copper, tin, zinc, or an alloy comprising at least one of these metals. More preferentially, the metal of the metal surface is steel, brass (Cu-Zn alloy), zinc, or bronze (Cu-Sn alloy), even more preferably brass or steel, and very preferably brass.

[0032] Certain metals are subject to oxidation when in contact with ambient air, which may result in the metal being partially oxidized. If the metal surface is made of steel, the steel is preferentially carbon steel or stainless steel. If 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%, in particular between 0.4% and 1.1%. If the steel is stainless steel, it contains at least 11% chromium and at least 50% iron. The invention applies in particular to steels of normal tensile (NT) or high tensile (HT) steel cord type, in which the carbon steel reinforcement preferably has a tensile strength (Rm) higher than 2000 MPa, more preferentially higher than 2500 MPa. The invention also applies to steels of super high tensile (SHT), ultra high tensile (UHT) or mega tensile (MT) steel cord type, in which the carbon steel reinforcement preferably has a tensile strength (Rm) higher than 3000 MPa, more preferentially higher than 3500 MPa. The total elongation at break (At) of these reinforcements, which is the sum of the elastic and plastic elongations, is preferably greater than 2.0%.

[0033] Measurements of the force at break, the tensile strength expressed in Rm (in MPa), and the elongation at break expressed in At (total elongation in %) are carried out under tension according to ISO standard 6892 of 1984. According to a preferred embodiment, the reinforced product according to the invention comprises a plurality of reinforcing elements as defined above and skim rubber in which the reinforcing elements are embedded, the skim rubber consisting of the rubber composition of the reinforced product according to the invention. According to this embodiment, the reinforcing elements are generally arranged side by side along a main direction. In the case of the application envisaged for a tire, the reinforced product according to the invention may therefore constitute the reinforcement of the tire. The reinforced product according to the invention may be in the green state (before the rubber composition has been crosslinked) or in the cured state (after the rubber composition has been crosslinked). The reinforced product according to the invention is cured after contacting the reinforcing element with the rubber composition. The reinforced product according to the invention may be manufactured by a method comprising the following steps: - producing two layers of rubber composition, - sandwiching the two layers by depositing a reinforcing element between the two layers; - If appropriate, the reinforced product according to the invention is cured.

[0034] Alternatively, the reinforced product according to the invention may be produced by depositing the reinforcing element on part of a layer and then folding the layer back over the reinforcing element, thereby sandwiching the reinforcing element over its entire length or part of its length. The layers may be produced by calendering.During the curing of the reinforced product according to the invention, the rubber composition is crosslinked. If the reinforcement product according to the invention is intended to be used as reinforcement for pneumatic tires, the curing of the reinforcement product according to the invention generally takes place during the curing of the tire. Finished or semi-finished products and tires Another subject of the invention is a finished or semi-finished product comprising a reinforced product according to the invention. The finished or semi-finished product may be any article comprising a reinforced product. Non-limiting examples that may be mentioned include balls, conveyor belts, shoe soles, and pneumatic or non-pneumatic tires. Another subject of the present invention is a pneumatic or non-pneumatic tire, which has the essential feature of comprising a reinforcing product according to the invention. The tire may be in the green state (before the rubber composition has been crosslinked) or in the cured state (after the rubber composition has been crosslinked). Generally, during the manufacture of the tire, the reinforcing product is deposited in the green state (i.e. before the rubber composition has been crosslinked) on the structure of the tire, before the tire's curing step.

[0035] The tire according to the invention comprises a reinforcing layer made of the reinforcing product of the invention, preferentially selected from the carcass ply, crown ply, bead filler and a combination of these reinforcing layers. Furthermore, the rubber composition of the reinforced product according to the invention can be used as an inner layer in a pneumatic or non-pneumatic tire, that is, a layer of the tire that is not in contact with the ambient air or with the inflation gas. Such inner layers are, for example, a crown bottom layer, a decoupling layer, an edge rubber and a combination of these inner layers. In this document, the term "edge rubber" is understood to mean a layer that is placed in the tire in direct contact with the end of a reinforcing layer, the end of a reinforcing element or another edge rubber. The invention relates in particular to tyres intended to equip passenger car-type motor vehicles, SUVs ("sports utility vehicles"), or two-wheeled vehicles (especially motorcycles), or aircraft, or industrial vehicles such as vans, heavy vehicles, i.e. metro trains, buses, heavy road transport vehicles (trucks, tractors, trailers) or off-road vehicles, for example large agricultural vehicles, or construction vehicles. The present invention therefore particularly relates to a pneumatic or non-pneumatic tire comprising a crown reinforcement formed from two crown plies of reinforcing elements and covered by a tread, two beads intended to come into contact with the rim, each comprising a circumferential reinforcing element, and two sidewalls each extending radially inward from the axial end of the crown to the bead, said tire further comprising a carcass reinforcement fixed to each of the beads and extending through the sidewalls from the bead to the crown, at least one of the two crown plies of reinforcing elements consisting of a reinforcing product according to the invention. [Example]

[0036] Preparation of Rubber Composition The following tests are carried out in the following way: the diene elastomer, the reinforcing filler and the various other ingredients, excluding the vulcanization system, are successively introduced into an internal mixer (final filling level: approximately 70% by volume) with an initial container temperature of approximately 60°C. Then, the thermomechanical work (non-productive phase) is carried out in one step, which lasts approximately 3-4 minutes in total, until a maximum "drop" temperature of 165°C is reached. The mixture thus obtained is recovered and cooled, after which sulfur and an accelerator (sulfenamide) are mixed in a mixer (homofinisher) at 30°C, and the whole is mixed for an appropriate time (for example, between 5 and 12 minutes) (production stage). The composition thus obtained is then calendered into a slab (2-3 mm thick) or thin rubber sheet and subjected to a curing step at 150°C for 25 minutes, after which its physical or mechanical properties are measured.

[0037] Measurement method Tensile test These tensile tests make it possible to determine the elastic modulus and the properties at break of a rubber composition. The tests were carried out in accordance with French standard NF T 46-002 of September 1988. The elongation at break (in %) is measured at 100°C. The results are expressed on a scale of 100, with a value of 100 being assigned to the control composition T1. A result greater than 100 indicates that the example composition under consideration has a greater elongation at break than the control. Adhesion Test Preparation of test specimens The rubber composition thus prepared is used to prepare a composite in the form of a test specimen according to the following protocol.

[0038] The metal / rubber composite used in this test is a block of rubber composition consisting of two sheets, each measuring 200 mm x 12.5 mm (millimeters) and 3.5 mm thick, glued together before curing. The resulting block is therefore 7 mm thick. During production of this block, for example, 12 reinforcements are enclosed between the two uncured sheets. Only a given length of the reinforcement, for example, 12.5 mm, is left in free contact with the rubber composition to which it will bond during curing. The remainder of the reinforcement length is separated from the rubber composition (e.g., using a plastic or metal film) to prevent adhesion outside the given contact area. Each reinforcement penetrates the rubber block, and at least one sufficient length (at least 5 cm, e.g., between 5 and 10 cm) of its free end is retained to allow subsequent tensile testing of the reinforcement. Each metal reinforcement consists of two twisted threads of 30 / 100 mm diameter made from steel containing 0.7% carbon, and a brass coating containing 63% copper. The block containing 12 reinforcements is then placed in a suitable mould and cured at 160° C. for 15 minutes under a pressure of approximately 11 bar. After the blocks have hardened, the following accelerated ageing conditions are applied, making it possible to determine the resistance of the samples to the combined action of heat and humidity: the rubber blocks are placed in an oven at a temperature of 55° C. for 28 days and a relative humidity of 95%.

[0039] Tear Force Measurement After the above-mentioned curing and aging are completed, the block is cut into specimens that serve as samples, each containing a reinforcement to be pulled out of the rubber block, using a tensile testing machine according to the method described in standard ASTM D 2229-02. The pull-out speed is 100 mm / min. The adhesion is therefore characterized by the force required to pull the reinforcement out of the specimen at a temperature of 60°C. The tear force represents the average of 12 measurements corresponding to the 12 reinforcements of the composite. The higher the force value, the greater the adhesion between the cord and the rubber composition. Results are expressed on a scale of 100 relative to a control specimen containing metal reinforcement of the same nature as that of the specimen tested and containing the "T1" rubber composition. Values ​​higher than the control specimen value, which was arbitrarily set to 100, indicate improved results, i.e., higher tear forces than that of the control specimen.

[0040] Crack propagation resistance test As described below, crack rates were measured for specimens of rubber compositions T-1 to T-19 using a cyclic fatigue device, model 381 from MTS (Elastomer Test System). Crack resistance is measured using repeated tensile tests on specimens that are initially restrained (after the first tensile cycle) and then notched. The tensile specimens consist of a parallelepiped-shaped rubber sheet, e.g., between 1 and 2 mm thick, between 130 and 170 mm long, and between 10 and 15 mm wide, with two side edges secured to the jaws of a tensile tester. The specimens thus prepared are tested after 14 days of accelerated aging at 77°C in a ventilated chamber. Testing was carried out at 60°C in air. After restraint, three very thin notches, each between 15 and 20 mm long, are made in the center of the specimen's width using a razor blade, aligned along the length of the specimen, one at each end and one in the center. After each tensile cycle, the strain of the specimen is measured to determine the energy release level (the amount of energy released during crack propagation) of approximately 1000 J / m. 2 The crack propagation rate is measured every cycle and expressed in nanometers. Clearly, a lower value indicates better resistance to crack propagation. The results are expressed on a scale of 100 relative to the control rubber composition T1. A value lower than that of the control specimen indicates an improved result, i.e. a crack propagation rate lower than that of the control specimen.

[0041] Measuring scorch time The measurements are carried out at 130°C on uncured rubber compositions, i.e. before curing or crosslinking, in accordance with French Standard NF T 43-005 (1991). The change in the consistency index as a function of time is evaluated in accordance with said standard by the parameter T5 (for large rotors), expressed in minutes, and makes it possible to determine the scorch time of the rubber composition, defined as the time necessary to obtain an increase in the consistency index (expressed in MU or Mooney units, 1 MU = 0.83 Newton meters) of 5 units higher than the lowest value measured for the consistency index. The results are expressed relative to the control rubber composition T1 on a scale of 100. Values ​​lower than those of the control specimen indicate shorter scorch times than the control specimen. The compositions of the various specimens tested and the results obtained are shown in Table 1. It is observed that only the specimens according to the invention have better adhesion to the metal reinforcement and higher tear strength than the control, while at the same time having maintained elongation at break and improved crack resistance.

[0042] [Table 1] Preferred embodiments of the present invention are as follows. [1] A reinforced product based on at least one metal reinforcing element and a rubber composition based on at least one diene elastomer, a reinforcing filler and a sulfur-based crosslinking system, wherein the rubber composition comprises at least one alkaline earth metal and a compound of the general formula (I): TIFF0007734670000006.tif2649 (I) (In the formula, R 1 represents a hydrogen atom H or a group selected from alkyl groups containing 1 to 18 carbon atoms, alkylcarbonyl and alkenyl groups containing 2 to 18 carbon atoms, and alkenylcarbonyl groups containing 3 to 18 carbon atoms) wherein the rubber composition has a content of the ascorbate compound equal to at least 0.5 phr and a molar ratio of the ascorbate compound to the alkaline earth metal in the range of 0.7 to 2.5. [2] The rubber composition comprises a rubber compound represented by general formula (II): TIFF0007734670000007.tif6170 (In the formula, R 2 represents a hydrogen atom or an alkaline earth metal, n is an integer equal to 1 or 2, and A represents an ascorbate compound of general formula (I) The reinforcement product according to [1], comprising an ascorbate-based compound. 〔3〕R 1 represents a hydrogen atom or a group selected from alkyl groups containing 1 to 5 carbon atoms, preferentially 1 to 3 carbon atoms, alkylcarbonyl and alkenyl groups containing 2 to 5 carbon atoms, preferably 2 to 4 carbon atoms, and alkenylcarbonyl groups containing 3 to 5 carbon atoms, preferably 3 to 4 carbon atoms. The reinforced product according to [1] or [2] above. 〔4〕R 1 The reinforced product according to any one of the above [1] to [3], wherein represents a group selected from linear alkyl, alkenyl, alkylcarbonyl and alkenylcarbonyl groups. 〔5〕R 1 The reinforced product according to [1] or [2] above, wherein represents a hydrogen atom. 〔6〕R 2 The reinforced product according to any one of [2] to [5] above, wherein is selected from alkaline earth metals, and is preferentially selected from magnesium and calcium. [7] The fortified product according to [1], wherein the ascorbate compound is selected from ascorbic acid, calcium ascorbate and magnesium ascorbate, preferentially magnesium ascorbate and calcium ascorbate, and preferably calcium ascorbate. [8] The reinforced product according to any one of [1] to [7], wherein the rubber composition further contains an oxide or hydroxide of an alkaline earth metal, preferentially an oxide of an alkaline earth metal. [9] The reinforced product according to [8], wherein the alkaline earth metal oxide is selected from magnesium oxide, calcium oxide and mixtures of these oxides.

[10] The reinforced product according to [1], wherein the rubber composition contains ascorbic acid and an alkaline earth metal oxide, preferably selected from calcium oxide and magnesium oxide, and preferably magnesium oxide.

[11] The reinforced product according to any one of [1] to

[10] , wherein the content of the ascorbate compound of general formula (I) in the rubber composition is at most 3 phr, preferably in the range of 1 to 3 phr.

[12] The reinforced product according to any one of [1] to

[11] , wherein the reinforcing filler of the rubber composition contains carbon black, silica, or a mixture of carbon black and silica.

[13] The reinforced product according to any one of [1] to

[12] , wherein the rubber composition contains a diene elastomer selected from the group consisting of polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymer, isoprene copolymer, and a mixture of these elastomers.

[14] A finished or semi-finished product comprising the reinforced product according to any one of [1] to

[13] .

[15] A pneumatic or non-pneumatic tire comprising the reinforcement product according to any one of [1] to

[13] above.

Claims

1. 1. A reinforced product based on at least one metal reinforcing element and a rubber composition based on at least one diene elastomer, a reinforcing filler and a sulfur-based crosslinking system, said rubber composition comprising at least one alkaline earth metal and a compound of the general formula (I): 【Chemical 1】 (I) (In the formula, R 1 represents a hydrogen atom H or a group selected from alkyl groups containing 1 to 18 carbon atoms, alkylcarbonyl and alkenyl groups containing 2 to 18 carbon atoms, and alkenylcarbonyl groups containing 3 to 18 carbon atoms. wherein the rubber composition has a content of the ascorbate compound equal to at least 0.5 phr and a molar ratio of the ascorbate compound to the alkaline earth metal ranging from 0.7 to 2.

5.

2. The rubber composition comprises a compound represented by general formula (II): [Equation 1] (In the formula, R 2 represents a hydrogen atom or an alkaline earth metal, n is an integer equal to 1 or 2, and A represents an ascorbate compound of general formula (I).

10. The reinforced product of claim 1, comprising an ascorbate-based compound of formula:

3. R 1 Reinforced product according to claim 1 or 2, wherein represents a hydrogen atom.

4. R 2 4. Reinforced product according to claim 2 or 3, wherein is selected from alkaline earth metals.

5. 3. The reinforced product of claim 2, wherein the ascorbate-based compound is selected from ascorbic acid, calcium ascorbate, and magnesium ascorbate.

6. The reinforced product according to any one of claims 1 to 5, wherein the rubber composition further comprises an oxide or hydroxide of an alkaline earth metal.

7. 7. The reinforced product of claim 6, wherein the alkaline earth metal oxide is selected from magnesium oxide, calcium oxide and mixtures of these oxides.

8. The reinforced article according to any one of claims 1 to 7, wherein the content of the ascorbate compound of general formula (I) in the rubber composition is at most 3 phr.

9. 9. The reinforced article according to claim 1, wherein the rubber composition comprises a diene elastomer selected from the group consisting of polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymers, isoprene copolymers, and mixtures of these elastomers.

10. Pneumatic or non-pneumatic tire comprising a reinforcement product according to one of claims 1 to 9.

Images