Reinforced product comprising a rubber composition based on a polyphenol compound, a guanidine and at least one peroxide compound

Abstract

The invention relates to a reinforced product based on at least one metal reinforcement embedded in a rubber composition based on at least one diene elastomer, a reinforcing filler essentially comprising silica, a crosslinking system based on at least one peroxide compound, at least one non-elastomeric polyphenol compound comprising at least three benzene rings each bearing at least two vicinal hydroxyl groups, and at least one compound from the guanidine family. The invention also relates to a rubber article comprising such a reinforced product.

Description

Technical Field

[0001] This invention relates to reinforced products based on elastomer compositions, and also to articles comprising such reinforced products. Background Technology

[0002] Many rubber-based products, such as pneumatic tires, non-pneumatic tires (i.e., tires that maintain their shape through means other than pressurized gas, such as supports), or conveyor belts, use reinforcing products, which are combinations of a rubber composition and reinforcing cables, typically metal with a brass coating. Because the reinforcing elements are usually arranged parallel to each other and coated with the rubber composition, these reinforcing products are often referred to as ply layers. Since these ply layers are subjected to high stresses during tire travel or conveyor belt operation, they must meet many sometimes contradictory criteria, such as high adhesion between the reinforcement and the composition, good crack resistance, low rolling or movement resistance of the rubber product, and good resistance to external erosion, particularly corrosion.

[0003] The adhesive properties of rubber compositions typically require specific formulations, particularly high levels of sulfur and zinc oxide, small amounts of stearic acid, the presence of cobalt salts, and the use of accelerators with long delayed phases. However, these high-sulfur vulcanization systems pose a major limitation during the manufacture of semi-finished products, especially to avoid premature crosslinking.

[0004] Therefore, manufacturers of reinforced rubber products are seeking formulations of rubber compositions that can reduce or even eliminate sulfur content in the reinforced product while still allowing it to adhere well to the reinforced cable, regardless of whether the cable is covered with a specific metal or alloy.

[0005] Documents WO 2017 / 081387 and WO 2017 / 081388 disclose a rubber composition and a composite based on a polymer matrix comprising a functionalized "grafted" diene polymer, and teach methods for its preparation. The functionalized diene polymer has at least one aromatic group substituted with at least two hydroxyl functional groups. Crosslinking of the rubber composition is carried out via a vulcanization system or a system based on one or more peroxide compounds. Good adhesion properties to metals are obtained from the rubber composition, but the use of a grafted polymer is required.

[0006] Patent application JP 2011252107 describes a rubber composition exhibiting good adhesion to metals, comprising a diene elastomer and a cobalt salt. Gallic acid or gallic acid hydrate promotes the dissolution of the cobalt salt. The composition is crosslinked using a sulfur-based system. Despite its good adhesive properties, this composition utilizes both sulfur and a cobalt salt.

[0007] Patent applications JP2009007408 and JP2008291173 disclose calendering compositions containing silica as a reinforcing filler, using conventional sulfur crosslinking systems and high zinc oxide content. Patent application JP2012229282 describes a calendering composition containing low sulfur and zinc oxide content. However, this composition uses a specific epoxide-functionalized elastomer.

[0008] During the ongoing research, the applicant discovered a reinforcing product comprising a diene elastomer, a reinforcing filler primarily comprising silica, a specific polyphenol compound, a peroxide-based crosslinking system, and at least one guanidine compound, the reinforcing product exhibiting excellent adhesion and durability properties. Summary of the Invention

[0009] The present invention relates to reinforced products based on at least one metal reinforcing element embedded in a rubber composition, rubber articles including such reinforced products, and pneumatic tires including such reinforced products.

[0010] definition

[0011] The statement “composition based” should be understood to mean that the composition comprises a mixture of various components used and / or in-situ reaction products, some of which are capable of reacting and / or intended to react with each other at least partially during various manufacturing stages of the composition; therefore, the composition may be in a fully or partially crosslinked state or in a non-crosslinked state.

[0012] For the purposes of this invention, the expression "parts by weight / hundred parts by weight elastomer" (or phr) should be understood as referring to parts by mass / hundred parts by mass elastomer.

[0013] In this invention, unless otherwise expressly stated, all percentages (%) shown are mass percentages (%).

[0014] Furthermore, any numerical interval expressed as "between a and b" represents a range of values ​​from greater than a to less than b (i.e., excluding the limits a and b), while any numerical interval expressed as "a to b" means a range of values ​​from a to b (i.e., including the strict limits a and b).

[0015] The carbon-containing compounds mentioned in the specification can be of fossil or bio-based origin. In the case of bio-based origin, they can be produced partially or entirely from biomass, or obtained from renewable feedstocks derived from biomass. This particularly relates to polymers, plasticizers, fillers, etc.

[0016] Therefore, the present invention relates to at least one of the following embodiments:

[0017] A reinforcing product based on at least one metal reinforcing element embedded in a rubber composition, the rubber composition being based on at least one diene elastomer, a reinforcing filler comprising primarily silica, a crosslinking system based on at least one peroxide compound, at least one non-elastomeric polyphenol compound, and at least one guanidine compound, the non-elastomeric polyphenol compound comprising at least three benzene rings, each benzene ring having at least two hydroxyl groups.

[0018] An enhanced product, wherein the molar mass of the polyphenol compound is preferably greater than 600 g / mol.

[0019] An enhanced product, wherein the polyphenolic compound is preferably selected from gallantanine, more preferably from esters of gallic acid and polyols, wherein the polyols are selected from pentoses and hexoses.

[0020] An enhanced product wherein the polyphenol compound is preferably selected from esters of glucose and gallic acid, preferably from polygalloglucose containing 3 to 10 galloyl units, and more preferably from polygalloglucose containing 5 to 10 galloyl units.

[0021] An enhanced product, wherein the polyphenolic compound is preferably selected from trigalloyl glucose, pentagalloyl glucose, decagalloyl glucose and mixtures thereof, and more preferably selected from 1,2,6-trigalloyl glucose, 1,3,6-trigalloyl glucose, 1,2,3,4,6-pentagalloyl glucose, tannic acid and mixtures thereof.

[0022] An enhanced product wherein the content of polyphenolic compounds in the rubber composition preferably ranges from 0.1 phr to 30 phr, more preferably from 5 phr to 20 phr, and most preferably from 5 phr to 15 phr.

[0023] An enhanced product, wherein the guanidine compound is preferably diphenylguanidine.

[0024] An enhanced product, wherein the content of the guanidine compound preferably ranges from 0.5 phr to 3 phr, more preferably from 0.5 phr to 2.5 phr, and even more preferably from 0.5 phr to 2 phr.

[0025] An enhanced product wherein the rubber composition preferably contains less than 5 phr of a functionalized elastomer, more preferably less than 1 phr of a functionalized elastomer, and very preferably does not contain a functionalized elastomer.

[0026] An enhanced product wherein the rubber composition preferably does not contain cobalt salt, or contains less than 2 phr, preferably less than 1 phr, more preferably less than 0.5 phr, and very preferably less than 0.1 phr of cobalt salt.

[0027] A preferred reinforced product, wherein the rubber composition does not contain molecular sulfur, or contains molecular sulfur of less than 1 phr.

[0028] A preferred reinforced product, wherein the rubber composition does not contain stearic acid or its derivatives, or contains less than 2 phr, preferably less than 1 phr, more preferably less than 0.5 phr, and very preferably less than 0.1 phr of stearic acid or its derivatives.

[0029] A preferred reinforced product, wherein the rubber composition contains no zinc or zinc oxide, or contains only a very small amount of zinc or zinc oxide, preferably less than 1 phr, more preferably less than 0.5 phr, and more preferably less than 0.2 phr.

[0030] A preferred reinforced product, wherein the rubber composition comprises 10 phr to 200 phr of reinforcing filler.

[0031] A preferred reinforced product, wherein the rubber composition comprises a reagent selected from reagents for coupling silica and reagents for coating silica, and mixtures thereof, wherein the content of the reagent is in the range of 5% to 20% by weight relative to the amount of silica, preferably in the range of 6% to 18% by weight relative to the amount of silica.

[0032] A preferred reinforced product, wherein the diene elastomer of the rubber composition is selected from polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymers, isoprene copolymers, and mixtures of these elastomers, preferably selected from natural rubber and synthetic polyisoprene.

[0033] A preferred reinforced product, wherein the rubber composition comprises 0.01 phr to 10 phr of a peroxide compound, preferably 1 phr to 5 phr of a peroxide compound.

[0034] A preferred reinforcing product, wherein the crosslinking system comprises a peroxide compound selected from organic peroxides.

[0035] A preferred reinforcing product, wherein the metal reinforcing element includes a metal surface, the metal of which is selected from iron, copper, tin, zinc, and alloys containing at least one of these metals, preferably selected from steel and brass.

[0036] A rubber article comprising the reinforced product according to any of the above embodiments.

[0037] According to the rubber product described in the previous embodiment, the rubber product is preferably selected from pneumatic tires and non-pneumatic tires, conveyor belts and tracks.

[0038] Diene elastomers

[0039] The reinforced product according to the present invention comprises at least one diene elastomer.

[0040] As is known, a "diene" elastomer (or indistinguishable rubber) (whether natural or synthetic) means an elastomer that is at least partially (i.e., a homopolymer or copolymer) composed of diene monomer units (monomers with two conjugated or non-conjugated carbon-carbon double bonds).

[0041] These diene elastomers can be classified into two categories: "substantially unsaturated" or "substantially saturated." The term "substantially unsaturated" is generally understood to mean a diene elastomer that is at least partially derived from a conjugated diene monomer and has a diene source (conjugated diene) unit content greater than 15% (mol%); thus, diene elastomers such as butyl rubber or EPDM-type copolymers of dienes with α-olefins do not fall into the aforementioned definition, but can be specifically described as "substantially saturated" diene elastomers (with low or very low diene source unit content, always less than 15%). The diene elastomers included in the compositions according to the invention are preferably substantially unsaturated.

[0042] The term "dien elastomer that can be used in compositions according to the invention" specifically means:

[0043] (a) Any homopolymer containing 4 to 18 carbon atoms of conjugated or non-conjugated diene monomers;

[0044] (b) Any copolymer of a conjugated or non-conjugated diene containing 4 to 18 carbon atoms with at least one other monomer.

[0045] Other monomers can be ethylene, olefins, or conjugated or non-conjugated dienes.

[0046] Suitable conjugated dienes are those with 4 to 12 carbon atoms, especially 1,3-dienes, such as 1,3-butadiene and isoprene.

[0047] Suitable alkenes are vinyl aromatic compounds with 8 to 20 carbon atoms and aliphatic α-monoolefins with 3 to 12 carbon atoms.

[0048] Suitable examples of vinyl aromatic compounds include styrene, o-, m-, or p-methylstyrene, "vinyltoluene" commercial mixtures, or p-(tert-butyl)styrene.

[0049] Suitable as aliphatic α-monoolefins, especially acyclic aliphatic α-monoolefins having 3 to 18 carbon atoms.

[0050] Preferably, the diene elastomer is selected from polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. The butadiene copolymer is particularly selected from butadiene / styrene copolymer (SBR).

[0051] Preferably, the diene elastomer is an isoprene elastomer.

[0052] As is known, "isoprene elastomer" is understood to mean isoprene homopolymers or copolymers, in other words, diene elastomers selected from natural rubber (NR), synthetic polyisoprene (IR), various isoprene copolymers, and mixtures of these elastomers. Among isoprene copolymers, isobutylene / isoprene (butyl rubber-IIR) copolymers, isoprene / styrene (SIR) copolymers, isoprene / butadiene (BIR) copolymers, or isoprene / butadiene / styrene (SBIR) copolymers will be specifically mentioned. The isoprene elastomer is preferably selected from natural rubber, synthetic cis-1,4-polyisoprene, and mixtures thereof; among these synthetic polyisoprene, it is preferred to use polyisoprene with a cis-1,4-bond content (mol%) greater than 90%, and more preferably greater than 98%. Preferably, and according to any arrangement of the invention, the diene elastomer is natural rubber.

[0053] Preferably, the content of the diene elastomer (preferably isoprene elastomer, more preferably natural rubber) is 50 phr to 100 phr, more preferably 60 phr to 100 phr, even more preferably 70 phr to 100 phr, still more preferably 80 phr to 100 phr, and very preferably 90 phr to 100 phr. In particular, the content of the diene elastomer (preferably isoprene elastomer, more preferably natural rubber) is very preferably 100 phr.

[0054] Whether containing only one 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 the diene elastomer, or even polymers other than elastomers, such as thermoplastic polymers. Preferably, the rubber composition according to the invention does not contain any synthetic elastomers other than the diene elastomer or polymers other than elastomers, or contains less than 10 phr, preferably less than 5 phr, of synthetic elastomers other than the diene elastomer or polymers other than elastomers.

[0055] Preferably, the rubber composition contains less than 5 phr of a functionalized elastomer, more preferably less than 1 phr of a functionalized elastomer, and most preferably does not contain a functionalized elastomer.

[0056] The term "functionalization" is understood to mean that an elastomer has functional groups, such as groups containing conjugated diene functional groups, epoxide functional groups, carbonyl functional groups, acid anhydride functional groups, or acid ester functional groups.

[0057] Therefore, the rubber composition is preferably composed of an epoxide-functionalized elastomer containing less than 5 phr, more preferably containing an epoxide-functionalized elastomer containing less than 1 phr, and most preferably not containing an epoxide-functionalized elastomer.

[0058] Crosslinking system

[0059] The rubber composition of the reinforced product according to the present invention is based on a crosslinking system, said crosslinking system being based on at least one peroxide compound.

[0060] The peroxide compound accounts for 0.01 phr to 10 phr of the rubber composition, preferably 1 phr to 5 phr.

[0061] As a peroxide that can be used according to the present invention, any peroxide known to those skilled in the art can be used.

[0062] Preferably, the peroxide is selected from organic peroxides.

[0063] The term "organic peroxide" refers to an organic compound (i.e., a carbon-containing compound) that contains an -OO- group (two oxygen atoms linked by a single covalent bond).

[0064] During the cross-linking process, organic peroxides decompose at their unstable O-O bonds to generate free radicals. These free radicals enable the formation of cross-linking bonds.

[0065] According to one embodiment, the organic peroxide is selected from dialkyl peroxides, monoperoxycarbonates, diacyl peroxides, peroxyketals, peroxide esters, and mixtures thereof.

[0066] Preferably, the dialkyl peroxide is selected from dicumyl peroxide, di(tert-butyl) peroxide, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-pentylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne, 2,5-dimethyl-2,5-di(tert-pentylperoxy)hex-3-yne, α,α'-di[(tert-butylperoxy)isopropyl]benzene, α,α'-di[(tert-pentylperoxy)isopropyl]benzene, di(tert-pentyl) peroxide, 1,3,5-tris[(tert-butylperoxy)isopropyl]benzene, 1,3-dimethyl-3-(tert-butylperoxy)butanol, 1,3-dimethyl-3-(tert-pentylperoxy)butanol, and mixtures thereof.

[0067] Some monoperoxy carbonates, such as OO-tert-butyl-O-(2-ethylhexyl) monoperoxy carbonate, OO-tert-butyl-O-isopropyl monoperoxy carbonate, OO-tert-pentyl-O-(2-ethylhexyl) monoperoxy carbonate and mixtures thereof, can also be used.

[0068] Among diacyl peroxides, benzoyl peroxide is the preferred peroxide.

[0069] In the peroxy ketal, the preferred peroxide is selected from 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 4,4-di(tert-butylperoxy)valerate n-butyl ester, 3,3-di(tert-butylperoxy)butyrate ethyl ester, 2,2-di(tert-amylperoxy)propane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (or cyclic trimer of methyl ethyl ketone peroxide), 3,3,5,7,7-pentamethyl-1,2,4-tricyclooxyhexane, 4,4-bis(tert-amylperoxy)valerate n-butyl ester, 3,3-di(tert-amylperoxy)butyrate ethyl ester, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-amylperoxy)cyclohexane and mixtures thereof.

[0070] Preferably, the peroxide ester is selected from tert-butyl peroxide, tert-butyl peroxide-2-ethylhexanoate, tert-butyl peroxide-3,5,5-trimethylhexanoate, and mixtures thereof.

[0071] Particularly preferred, the organic peroxide is selected from dicumyl peroxide, aryl or diaryl peroxide, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl) peroxide, tert-butylcumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, 4,4'-di(tert-butylperoxy)valerate, OO-(tert-butyl)-O-(2-ethylhexyl)monoperoxycarbonate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxybenzoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, 1,3(4)-bis( The mixture comprises tert-butylperoxyisopropylbenzene, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane and mixtures thereof, more preferably selected from dicumyl peroxide, 4,4'-di(tert-butylperoxy)valerate, OO-(tert-butyl)-O-(2-ethylhexyl)monoperoxycarbonate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxybenzoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, 1,3(4)-bis(tert-butylperoxyisopropylbenzene), 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane and mixtures thereof.

[0072] Reinforced packing

[0073] The rubber composition of the reinforced product of the present invention comprises reinforcing filler, which mainly comprises silica.

[0074] The term "major" is understood to mean that silica accounts for at least 50% by weight of the reinforcing filler in the rubber composition, preferably at least 70% by weight, and more preferably at least 90% by weight.

[0075] In addition to silica, any type of reinforcing filler known to be able to reinforce rubber compositions that can be specifically used in the manufacture of tires may be used, such as reinforcing organic fillers (e.g., carbon black), reinforcing inorganic fillers, or mixtures of both.

[0076] Preferably, the rubber composition contains up to 10 phr of carbon black, more preferably up to 5 phr, and very preferably up to 1 phr of carbon black. Very preferably, apart from unavoidable impurities, the rubber composition does not contain carbon black, independent of other characteristics of the rubber composition.

[0077] The silica used can be any reinforced silica known to those skilled in the art, especially with a BET specific surface area and a CTAB specific surface area both less than 450 m². 2 / g, preferably at 30m 2 / g to 400m 2 Within the range of / g, especially 60m 2 / g to 300m 2 / g of any precipitated silica or pyrolytic silica. Any type of precipitated silica can be used, particularly highly dispersible silica (HDS). These precipitated silicas (which may be highly dispersible or not) are well known to those skilled in the art. References may be made to silica described, for example, in patent applications WO 03 / 016215-A1 and WO03 / 016387-A1. In commercial HDS silica, particularly those from Evonik can be used. 5000GR and 7000GR silica or from Solvay 1085GR 1115MP 1165MP Premium200MP and HRS1200MP silica. As a non-HDS silica, the following commercial silica can be used: from Evonik... VN2GR and VN3GR silica, from Solvay 175GR silica or Hi-Sil EZ120G(-D), Hi-Sil EZ160G(-D), Hi-Sil EZ200G(-D), Hi-Sil243LD, Hi-Sil 210 and Hi-Sil HDP 320G silica from PPG.

[0078] In this application, the BET specific surface area was determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, p. 309, February 1938), and more specifically according to the method adapted by Annex E of standard NF ISO 5794-1, June 2010 [multi-point (5-point) volumetric method - gas: nitrogen - degassing under vacuum: 1 hour at 160°C - relative pressure p / p0 range: 0.05 to 0.17].

[0079] For inorganic fillers such as silica, the CTAB specific surface area value is determined according to the standard NFISO 5794-1, Annex G, June 2010. This method is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "outer" surface of the reinforcing filler.

[0080] Suitable carbon blacks include all carbon blacks, especially those conventionally used in tires or their treads. More specifically, the 100, 200, and 300 series of reinforcing carbon blacks, or the 500, 600, or 700 series (ASTM D-1765-2017 grade) carbon blacks, such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772 carbon blacks, will be mentioned. These carbon blacks can be used in commercially available isolated forms or in any other form, such as as a carrier for some rubber engineering additives. Carbon blacks can be incorporated, for example, into diene elastomers, particularly isoprene elastomers, in the form of masterbatches (see, for example, patent applications WO 97 / 36724-A2 and WO 99 / 16600-A1).

[0081] For carbon black, the specific surface area of ​​STSA is determined according to standard ASTM D6556-2016.

[0082] It is not important what physical state the reinforcing inorganic filler is provided in, whether it is in the form of powder, microspheres, granules, beads, or any other suitable densification form. Of course, the term "reinforcing inorganic filler" also refers to mixtures of different reinforcing inorganic fillers, particularly mixtures of silica as described above.

[0083] Those skilled in the art will know how to adjust the total content of reinforcing filler according to the intended use (particularly according to the type of tire involved, such as tires for motorcycles, passenger vehicles, or multi-purpose vehicles such as vans or heavy-duty vehicles)). Preferably, the total content of reinforcing filler (such as reinforcing inorganic filler such as silica and / or carbon black) is between 10 phr and 200 phr, more preferably between 25 phr and 180 phr, and in a known manner, the optimal value varies depending on the specific target application.

[0084] To couple reinforcing inorganic fillers (particularly silica) to diene elastomers, at least bifunctional coupling agents (or binders) designed to provide a satisfactory chemical and / or physical connection between the inorganic filler (its particle surface) and the diene elastomer can be used in known ways. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. The term "bifunctional" 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 bifunctional compound may contain a first functional group containing silicon atoms and a second functional group containing sulfur atoms, the first functional group being capable of interacting with the hydroxyl groups of the inorganic filler and the second functional group being capable of interacting with the diene elastomer.

[0085] Preferably, the organosilane is selected from 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, and terminal mercaptosilanes (such as S-(3-(triethoxysilyl)propyl)octanethioate sold by Momentive under the name "NXT Silane"). More preferably, the organosilane is an organosilane polysulfide.

[0086] The coupling agent content in the compositions of the present invention is preferably less than or equal to 35 phr, which is understood to mean that it is generally desirable to use as little coupling agent as possible. Typically, the coupling agent content is from 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler. Its content is preferably in the range of 0.5 phr to 20 phr, more preferably in the range of 3 phr to 10 phr. The content of the reinforcing inorganic filler used in the compositions according to the present invention can be easily adjusted by those skilled in the art.

[0087] Those skilled in the art will understand that reinforcing fillers with other properties can be used as alternatives to the aforementioned reinforcing inorganic fillers, provided that such reinforcing fillers with other properties are covered with an inorganic layer such as silica, or that their surface contains functional sites, particularly hydroxyl sites, that require the use of a coupling agent to form bonds between the reinforcing filler and the diene elastomer. For example, carbon black partially or completely covered with silica, or silica-modified carbon black, such as, but not limited to, the “CRX2000” or “CRX4000” series from Cabot Corporation, can be mentioned. Type of packing.

[0088] Polyphenol compounds

[0089] The compositions according to the invention comprise at least one non-elastomeric polyphenol compound, said non-elastomeric polyphenol compound comprising at least three benzene rings, each benzene ring having at least two hydroxyl groups.

[0090] The term "adjoint" is understood to mean that two hydroxyl groups carried by an aromatic ring are in adjacent positions relative to each other.

[0091] The term "benzene ring" is understood to refer to a substituted aromatic ring containing six carbon atoms.

[0092] The molar mass of the polyphenol compound is preferably greater than 600 g / mol, more preferably greater than 800 g / mol, more preferably greater than 1000 g / mol, and more preferably greater than 1200 g / mol.

[0093] Preferably, the polyphenolic compound is selected from gallic tannins, i.e., esters of gallic acid and polyols, wherein the polyols are preferably selected from pentoses and hexoses. Preferably, the polyphenolic compound is selected from esters of glucose and gallic acid, more preferably from polygalloglucose containing 3 to 10 galloyl units, and more preferably from polygalloglucose containing 5 to 10 galloyl units. Preferably, the polyphenolic compound is selected from trigalloylglucose, pentagalloylglucose, and decagalloylglucose, and mixtures thereof, and more preferably from 1,2,6-trigalloylglucose, 1,3,6-trigalloylglucose, 1,2,3,4,6-pentagalloylglucose, tannic acid (or β-D-glucose penta(3,4-dihydroxy-5-((3,4,5-trihydroxybenzoyl)oxy)benzoate), and mixtures thereof. Very preferably, the polyphenolic compound is tannic acid. Due to their complex structure, such compounds are introduced into the rubber composition in this form and cannot be the product of chemical reactions (especially esterification reactions) between the various components of the rubber composition.

[0094] In particular, due to the presence of polyphenolic compounds combined with the main silica reinforcing filler and at least one guanidine compound, the rubber compositions according to the invention have particularly advantageous adhesion properties to metal reinforcing elements (for the composition of reinforcing products, most particularly for reinforcing products intended for use in tires), regardless of whether the reinforcing elements are covered with a particular metal or alloy.

[0095] The rubber composition according to the invention preferably contains 0.1 phr to 30 phr of polyphenolic compound, more preferably 5 phr to 20 phr, and very preferably 5 phr to 15 phr. Below 0.1 phr, the polyphenolic compound has no significant effect on the adhesive properties of the rubber composition according to the invention. Above 30 phr, no significant gain is observed.

[0096] Surprisingly, excellent adhesion of the rubber composition to metal-reinforced cables was achieved without the use of cobalt salts, stearic acid, or zinc oxide. Therefore, as those skilled in the art will know, the compositions according to the invention are preferably free of cobalt salts (whose known effects are improved adhesion and durability), or contain less than 1 phr, preferably less than 0.5 phr, more preferably less than 0.2 phr, and most preferably less than 0.1 phr of cobalt salt.

[0097] Guanidine compounds

[0098] The rubber composition of the reinforced product according to the invention comprises at least one guanidine compound. These compounds are typically used in conjunction with a sulfur-based crosslinking system (referred to as a vulcanization system) as a vulcanization accelerator. It has now been observed that the presence of at least one guanidine compound can significantly improve the properties of the reinforced product according to the invention, in conjunction with reinforcing fillers mainly comprising silica, polyphenolic compounds, and a crosslinking system based on at least one peroxide compound.

[0099] Preferably, the content of guanidine compounds in the rubber composition ranges from 0.5 phr to 3 phr, more preferably from 0.5 phr to 2.5 phr, and even more preferably from 0.5 phr to 2 phr.

[0100] Preferably, the guanidine compound is diphenylguanidine.

[0101] Various additives

[0102] The rubber composition according to the invention may also contain all or part of conventional additives known to those skilled in the art and commonly used in tire (particularly the inner layer as defined below in this patent application) rubber compositions, such as plasticizers (plasticizing oils and / or plasticizing resins), reinforcing or non-reinforcing fillers other than the reinforcing fillers described above, pigments, protective agents (e.g., anti-ozone waxes, chemical anti-ozone agents, antioxidants), anti-fatigue agents, or reinforcing resins (such as those described, for example, in patent application WO 02 / 10269).

[0103] Preferably, independent of other features of the invention, the rubber composition of the reinforced product according to the invention is free of reinforcing resin, or contains less than 5 phr, preferably less than 1 phr, of reinforcing resin.

[0104] In addition to optional coupling agents, these compositions may also contain coupling activators, agents for coating inorganic fillers, or more generally processing aids that can improve the processability of the composition in its uncured state by improving the dispersion of the filler in the rubber matrix and reducing the viscosity of the composition in a known manner. These agents are, for example, hydrolyzable silanes (e.g., alkylalkoxysilanes (e.g., octyltriethoxysilane or octyltriethoxysilane)), polyols, polyethers, or hydroxylated or hydrolyzable polyorganosiloxanes.

[0105] Preparation of rubber composition

[0106] The rubber composition according to the invention is manufactured in a suitable mixer using preparation stages known to those skilled in the art:

[0107] - A thermomechanical processing or kneading stage, which can be carried out in a single thermomechanical step, in which all necessary components (particularly the elastomer matrix, polyphenolic compounds, fillers, and optionally various other additives) are introduced into a suitable mixer, such as a standard closed mixer (e.g., a 'Banbury' type). The introduction of fillers into the elastomer can be done once or multiple times, simultaneously with thermomechanical kneading. Where the filler (particularly carbon black) has been wholly or partially introduced into the elastomer in masterbatch form (as described, for example, in patent applications WO 97 / 36724 and WO 99 / 16600), what is introduced is a directly kneaded masterbatch and other elastomers or fillers (where appropriate) present in the composition that are not in masterbatch form, as well as optionally various other additives.

[0108] Thermomechanical kneading is carried out at a high temperature between 110°C and 200°C, preferably between 130°C and 185°C, typically for a time between 2 and 10 minutes.

[0109] -Then a second stage of machining can be carried out in an open mixer (e.g., an open mill) after the mixture obtained in the first stage is cooled to a lower temperature (typically less than 120°C, for example, between 40°C and 100°C).

[0110] During the first or second stage, when the second stage is performed, a crosslinking system is added based on the knowledge of those skilled in the art. Typically, a peroxide- or sulfur-based crosslinking system is added during the second stage.

[0111] The resulting final composition is then calendered, for example, into sheets or plates, particularly for laboratory characterization, or extruded as a rubber semi-finished product (or molding element).

[0112] The composition can be in an uncured state (before crosslinking or vulcanization) or in a cured state (after crosslinking or vulcanization), and can be a semi-finished product that can be used in tires.

[0113] Curing is carried out under pressure at a temperature typically between 130°C and 200°C for a sufficient time (e.g., between 5 minutes and 90 minutes) in a manner known to those skilled in the art, the time of which may vary particularly depending on the curing temperature, the crosslinking system employed, the crosslinking kinetics of the composition under consideration, or the size of the tire.

[0114] The statement "based on at least a metal reinforcing element and a rubber composition" should be understood to mean a reinforcing product that includes a reinforcing element and the composition, wherein the composition may react with the surface of the reinforcing element during various manufacturing stages of the reinforcing product, particularly during the crosslinking of the composition or during the manufacturing of the reinforcing product prior to the crosslinking of the composition.

[0115] The metal reinforcing element is a filamentous element. The reinforcing element is metallic, that is, it is made of metallic material.

[0116] The rubber composition of the reinforcing product according to the invention is coated on at least a portion of the reinforcing element, preferably the entire element.

[0117] According to a first variant of the invention, the metal 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 metallic material that is at least partially, preferably completely, covered by the metal layer constituting the metal surface.

[0118] According to a second variant of the invention, the metal reinforcing element is made of the same material, in which case the reinforcing element is made of the same metal as the metal surface.

[0119] According to one embodiment of the invention, the metal surface comprises a metal selected from 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, and brass. Preferably, the metal on the metal surface is iron, copper, tin, zinc, or an alloy comprising at least one of these metals. More preferably, the metal on 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.

[0120] When the metal 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 wt% and 1.2 wt%, or between 0.05 wt% and 1.2 wt%, or between 0.2 wt% and 1.2 wt%, particularly between 0.4 wt% and 1.1 wt%. When the steel is stainless steel, it preferably contains at least 11% chromium and at least 50% iron.

[0121] According to a preferred embodiment, the reinforcing product comprises a plurality of reinforcing elements as defined above and calendered rubber in which the reinforcing elements are embedded, said calendered rubber being composed of a rubber composition of the reinforcing product according to the invention. According to this embodiment, the reinforcing elements are typically arranged side-by-side along a main direction. For the envisioned application in tires, the reinforcing product can therefore constitute a tire reinforcement.

[0122] The reinforced product according to the invention can be in an uncured state (before the rubber composition crosslinks) or in a cured state (after the rubber composition crosslinks). The reinforced product is cured after the reinforcing element is brought into contact with the rubber composition according to the invention.

[0123] The reinforced product can be manufactured using a method that includes the following steps:

[0124] - To manufacture two layers of a rubber composition.

[0125] - The reinforcing element is sandwiched between two layers by placing the reinforcing element between the two layers.

[0126] - Where appropriate, cure the reinforced product.

[0127] Alternatively, reinforced products can be manufactured by placing the reinforcing element on a portion of the layer and then folding the layer itself to cover the reinforcing element, thereby clamping the reinforcing element over the entire or part of the length of the layer.

[0128] These layers can be produced through calendering. During the curing process of the reinforced product, the rubber composition is cross-linked.

[0129] When a reinforcing product is intended to be used as a reinforcement in a tire, the curing of the reinforcing product typically takes place during the curing of the outer tire.

[0130] pneumatic tires

[0131] Pneumatic tires (another subject of the invention) have the basic characteristic of including a reinforcing product according to the invention. The tire can be in an uncured state (before the rubber composition crosslinks) or in a cured state (after the rubber composition crosslinks). Typically, during tire manufacturing, the uncured reinforcing product (i.e., before the rubber composition crosslinks) is arranged in the tire's structure before the step of curing the tire.

[0132] The present invention particularly relates to pneumatic tires intended for use with passenger vehicles, SUVs (sports utility vehicles), two-wheeled vehicles (especially motorcycles), aircraft, or industrial vehicles selected from trucks, heavy-duty vehicles (i.e., subways, buses, heavy road transport vehicles (trucks, tractors, trailers) or off-road vehicles (e.g., heavy agricultural vehicles or earthmoving equipment)).

[0133] Three types of areas can be defined within an inflatable tire:

[0134] • The radially outer region in contact with ambient air, which is essentially composed of the tire tread and the outer sidewall. The outer sidewall is an elastomeric layer located on the outside of the carcass reinforcement relative to the tire's inner cavity, between the crown and the bead, thereby completely or partially covering the area of ​​the carcass reinforcement extending from the crown to the bead.

[0135] • The radially inner region in contact with the inflating gas, which typically consists of a gas-tight layer (sometimes called an inner gas-tight layer or liner) that is airtight to the inflating gas.

[0136] • The inner region of a tire, that is, the region between the outer region and the inner region. This region includes layers or plies referred to herein as the inner layers of the tire. These layers or plies are, for example, carcass plies, tread plies, tire belt plies, or any other layers that do not come into contact with ambient air or the inflation gas of the tire.

[0137] The reinforced products according to the invention are particularly suitable as reinforcing ply layers for pneumatic or non-pneumatic tires or for reinforcing rubber articles such as conveyor belts or tracks. The term "non-pneumatic tire" is understood to mean a tire intended to be mounted on a vehicle and to maintain its shape by means other than pressurized gas. Detailed Implementation

[0138] Example

[0139] To prepare various rubber compositions (the compositions of which are shown below), the following steps are taken. In the first stage, the elastomer, followed by all other components of the mixture except the crosslinking system, are sequentially introduced into a closed mixer (final fill factor: approximately 70% by volume), the initial container temperature of which is approximately 60°C. Then, thermomechanical processing is performed in a step until a maximum "discharge" temperature of 150°C is reached. The resulting mixture is then recovered. In the second stage, it is cooled to 30°C in an open mixer (homogeneous finishing machine), and a peroxide-based or sulfur-based crosslinking system is added.

[0140] The adhesion quality between the rubber composition and the metal reinforcement element is determined by measuring the force required to extract a segment of the metal reinforcement from the cross-linked rubber composition. For this purpose, a reinforced product is prepared in the form of a specimen consisting of a metal reinforcement element and a rubber composition.

[0141] Sample preparation

[0142] The rubber composition is used to prepare reinforced products in sample form according to the following scheme:

[0143] A rubber block consisting of two sheets bonded together before curing is prepared. Both sheets of the block are composed of the same rubber composition. During the preparation of the block, metal reinforcing elements are embedded at equal intervals between the two uncured sheets, with the ends of the reinforcing elements extending sufficiently beyond the sides of these sheets for subsequent tensile testing. The block, including the reinforcement, is then cured. For example, in the current case, the block is cured at 160°C for 5 to 40 minutes (depending on the composition) under a pressure of 5.5 tons.

[0144] The individual wires of the metal reinforcement element are light steel wires coated with brass. The metal reinforcement element is an assembly of two individual wires with a diameter of 0.30 mm (“2.30” cord), which is typically used in the production of the working cord layer of tires for passenger vehicles; the thickness of the brass coating ranges from 50 nm to 300 nm.

[0145] Adhesion test

[0146] At the end of curing, the specimen, which consists of the cross-linked block and metal reinforcement elements, is placed in the jaws of a tensile testing machine, and the jaws of the tensile testing machine are adjusted so that each segment can be tested individually at a given speed and a given temperature (e.g., in the current case, at 100 mm / min and ambient temperature).

[0147] The adhesion level is characterized by measuring the "peeling" force that separates a segment from the sample.

[0148] The results are expressed as a base of 100 relative to a control sample, which includes a metal reinforcement element that is identical in nature to the tested sample. The control sample is made from composition "T1".

[0149] A value greater than that of the control sample (arbitrarily set to 100) indicates an improved result, i.e., a greater peel force than the sample.

[0150] The reinforced product according to the invention has a value greater than 100 in the adhesion test, thus exhibiting improved peel resistance after the sample is cured (i.e., at t=0), and its durability is also improved after the sample is aged (i.e., after 21 days at 95% relative humidity and 55°C).

[0151] Tensile test

[0152] These tensile tests determine the elastic stress and fracture properties of the rubber composition. Tests were conducted according to French standard NF T 46-002 of September 1988. Elongation at break (in percentage) was measured at 23°C.

[0153] The elongation at break was measured at t=0 days and then 21 days later at 55°C and 95% relative humidity.

[0154] Results are expressed as a base of 100, assigning a value of 100 to the elongation at break of the sample T1 under consideration at day t=0. A result greater than 100 indicates that the composition under consideration has a greater elongation at break than the same composition at day t=0.

[0155] Compared with the control composition, the composition according to the invention has a greater elongation at break.

[0156] Rolling resistance index

[0157] The rolling resistance caused by the test composition is estimated by measuring the energy loss of the sample after the sixth rebound when initial energy is applied at a temperature of 60°C, as described, for example, in standard DIN 53-512 of April 2000. This measurement is expressed as P60 and is calculated as follows: P60(%) = 100 × (E0 - E1) / E0, where E0 represents the initial energy and E1 represents the recovered energy.

[0158] Losses at 60°C were measured in air at 77°C at t=0 and 21 days later. Air humidity was not controlled and corresponded to ambient air humidity (i.e., between 30% and 50%).

[0159] The results are expressed as a base of 100, assigning a value of 100 to the loss of sample T1 at 60°C on day t=0. A result greater than 100 indicates that the composition under consideration has a greater loss at 60°C than the same composition at day t=0, resulting in greater rolling resistance.

[0160] It was observed that, compared with the control composition, the composition according to the invention exhibits less loss at 60°C and considerable scalability over time.

[0161] Test of crack propagation resistance

[0162] The cracking rate was measured on a specimen of elastomer composition using a Model 381 cyclic fatigue apparatus (elastomer testing system) from MTS, as described below.

[0163] Crack resistance was measured by repeated tensile actions on a specimen that had been initially conditioned (after the first tensile cycle) and then scored. The tensile specimen consisted of a parallelepiped-shaped rubber sheet, for example, having a thickness between 0.5 mm and 1.5 mm, a length between 60 mm and 100 mm, and a width between 4 mm and 8 mm. Each of its two sides was covered along its length with a cylindrical rubber bead (5 mm in diameter) that could be anchored in the jaws of the tensile testing apparatus. The specimens thus prepared were tested after curing and accelerated aging in an oven at 77°C for 21 days in a ventilated chamber. The test was conducted in air at 60°C. After conditioning, before starting the test, four extremely fine cuts, each between 5 mm and 7 mm in length, were made at the center width using a razor blade. These cuts were aligned with the length of the specimen, with two cuts at each end and two cuts on either side of the center of the specimen. In each tensile cycle, the strain of the specimen is automatically adjusted to keep the energy recovery rate (the amount of energy released during crack propagation) constant at approximately 1500 J / m. 2 The crack propagation rate was measured in nanometers per cycle.

[0164] Results are expressed as a base of 100 relative to the unaged control sample of composition T1. Values ​​greater than those of the unaged sample (arbitrarily set to 100) indicate a worse result, i.e., a greater crack growth rate than the unaged control sample. When the sample fractures, the note "nm" indicating "unmeasurable" is displayed. This note indicates that the sample has lower crack growth resistance.

[0165] No measurements were taken of the sample containing composition C2.

[0166] It has been observed that the compositions according to the invention have a lower crack propagation rate (including aged samples).

[0167] Composition T0 is a composition commonly used in the prior art for calendering, as shown, for example, in documents WO2016 / 058943 and FR2981298, wherein composition T0 is crosslinked using a sulfur-based system.

[0168] Composition T1 corresponds to composition C-2 in document WO2020 / 058613. Composition T2 is similar to T1 but has a lower tannin content and exhibits better metal adhesion and lower elongation at break compared to T1. Composition T3 is a composition with similar adhesion properties to composition T2, which contains silica as a reinforcing filler. It can be seen that, contrary to the effects of silica known to those skilled in the art, composition T3 exhibits a greater loss of hysteresis compared to composition T2 in this system. Compositions C1 to C4 are compositions according to the present invention.

[0169] [Table 1]

[0170]

[0171]

[0172] (1) Natural rubber (gelling)

[0173] (2) ASTM grade N326 (Cabot);

[0174] (3) 160 MPa of silica, 1165 MPa of Zeosil from Rhodia;

[0175] (4) Si75 from Degussa;

[0176] (5) Si69 from Degussa;

[0177] (6) Industrial-grade zinc oxide from Umicore;

[0178] (7) Stearin, from Pristerene 4931 of Uniqema;

[0179] (8) N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (Santoflex 6-PPD) from Flexsys;

[0180] (9) CTP, N-(cyclohexylthio)phthalimide; sold by Lanxess under the name Vulkalent G or by Duslo under the name Duslin P;

[0181] (10) Luperox 231XL40 from Arkema

[0182] (11) N,N-Dicyclohexyl-2-benzothiazole sulfenamide (Santocure DCBS from Flexsys);

[0183] (12) Diphenylguanidine.

Claims

1. A reinforced product based on at least one metal reinforcing element embedded in a rubber composition, the rubber composition being based on at least one diene elastomer, a reinforcing filler comprising primarily silica, a crosslinking system based on at least one peroxide compound, at least one non-elastomeric polyphenol compound, and at least one guanidine compound, the non-elastomeric polyphenol compound comprising at least three benzene rings, each benzene ring having at least two hydroxyl groups.

2. The enhanced product according to the preceding claim, wherein, The molar mass of the polyphenol compound is greater than 600 g / mol.

3. The enhanced product according to any one of the preceding claims, wherein, The polyphenolic compound is selected from gallic tannins.

4. The enhanced product according to claim 1, wherein, The polyphenolic compound is selected from esters of glucose and gallic acid.

5. The enhanced product according to claim 1, wherein, The content of polyphenolic compounds in the rubber composition ranges from 0.1 phr to 30 phr.

6. The enhanced product according to claim 1, wherein, The guanidine compound is diphenylguanidine.

7. The enhanced product according to claim 1, wherein, The content of the guanidine compound ranges from 0.5 phr to 3 phr.

8. The enhanced product according to claim 1, wherein, The rubber composition contains a functionalized elastomer of less than 5 phr.

9. The enhanced product according to claim 1, wherein, The rubber composition does not contain molecular sulfur, or contains less than 1 phr of molecular sulfur.

10. The enhanced product according to claim 1, wherein, The rubber composition contains no zinc or zinc oxide, or contains only a very small amount of zinc or zinc oxide, less than 1 phr.

11. The enhanced product according to claim 1, wherein, The rubber composition comprises a reagent selected from reagents for coupling silica and reagents for coating silica, and mixtures thereof, wherein the content of the reagent is in the range of 5% to 20% by weight relative to the amount of silica.

12. The enhanced product according to claim 1, wherein, The rubber composition contains 0.01 phr to 10 phr of peroxide compound.

13. The enhanced product according to claim 1, wherein, The crosslinking system comprises a peroxide compound selected from organic peroxides.

14. A rubber article, comprising a reinforced product according to any one of claims 1 to 13.

15. The article of manufacture according to the preceding claim, wherein the article of manufacture is selected from pneumatic tires and non-pneumatic tires, conveyor belts and tracks.

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