RUBBER COMPOSITION

Description

[0001] The field of the present invention is that of rubber compositions based on diene elastomers, reinforcing fillers and organic cobalt salts; these rubber compositions being intended in particular for the manufacture of reinforced products and the manufacture of tires.

[0002] Rubber compositions based on diene elastomers, carbon black and organic cobalt salts are commonly used in rubber articles such as tires, conveyor belts, transmission belts because they have good adhesive power to the metallic elements present in these articles. In tires, these rubber compositions are used in particular in the constitution of various internal layers such as reinforced plies and can also be called coating composition.

[0003] In particular, it is known that the various reinforced plies constituting in particular the belt of radial tires include metal reinforcements in the form of steel cables made up of fine wires assembled together by cabling or twisting; these metal reinforcements being covered on the surface with brass.

[0004] To effectively fulfill their function of reinforcing radial tire belts, which are known to be subject to very high stresses when the tires are running, these steel cords must meet a very large number of technical criteria, sometimes contradictory, such as high compressive strength, high tensile strength, wear and corrosion resistance, strong adhesion to the surrounding rubber, and be able to maintain these performances at a very high level for as long as possible. It is easy to understand that the adhesive interphase between the rubber and the metal plays a major role in the durability of these performances.

[0005] The adhesion between the rubber composition and the metal reinforcing elements is created via the phenomenon of sulfurization of the metal surface, particularly the brass-plated surface, of the cable. However, the rubber composition, like the bonds created, can change under the effect of humidity, temperature or corrosive elements and their combined effects, for example the combined effect of oxidation and heat (thermo-oxidation) encountered in tires. In the long term, these effects can lead to the appearance of cracks in these rubber compositions which can lead to the separation of the different plies constituting the tire belt. It is therefore important that the rubber composition of the reinforced products has good resistance to cracking and has good adhesion to the steel reinforcing element.

[0006] Furthermore, this rubber composition must also have good cohesion while having the lowest possible hysteresis to obtain a reduction in rolling resistance.

[0007] Rubber compositions are known from the prior art that meet the criteria listed above. These compositions comprise a diene elastomer, in particular natural rubber, carbon black, an organic cobalt salt and a vulcanization system comprising sulfur, zinc oxide, stearic acid and vulcanization accelerators.

[0008] However, tire designers are constantly looking for solutions to improve the property compromise of these existing coating compositions by improving at least one property without penalizing the others.

[0009] In particular, nowadays, given that fuel economy and the need to preserve the environment have become a priority, it is desirable to produce rubber compositions with as low hysteresis as possible.

[0010] To achieve the objective of reducing hysteresis, many solutions have already been tested. In particular, we can cite reducing the amount of reinforcing fillers in rubber compositions. However, this reduction in the level of reinforcing fillers is accompanied by a deterioration in the cohesion of the rubber compositions.

[0011] In view of the above, there is therefore still a need to provide rubber compositions, particularly for reinforced products, which satisfy a compromise of complex and acceptable properties, particularly for use in tires.

[0012] This is why an aim of the present invention is to provide a rubber composition, in particular for a reinforced product, having improved crack resistance while having acceptable hysteresis properties and without its adhesion and cohesion properties being degraded.

[0013] Continuing his research, the applicant discovered that the addition of a reinforcing inorganic filler and a plasticizing resin in a rubber composition based on a diene elastomer, carbon black and cobalt salt having a good dispersion of the reinforcing filler in its elastomeric matrix makes it possible, surprisingly, to significantly improve the crack resistance and cohesion of this rubber composition without degrading its adhesion properties and its hysteresis.

[0014] Thus, an object of the present invention relates to a rubber composition, in particular for a reinforced product, based on at least one elastomeric matrix comprising at least one diene elastomer, at least one reinforcing filler comprising mainly carbon black and at least one reinforcing inorganic filler, at least one plasticizing resin having a glass transition temperature greater than or equal to 20°C, at least one cobalt salt and at least one vulcanization system, said rubber composition having a dispersion score Z of the reinforcing filler in the elastomeric matrix greater than or equal to 85, preferably greater than or equal to 90.

[0015] Another subject of the present invention relates to a reinforced product comprising at least one steel reinforcing element coated at least in part with a metallic coating and a rubber composition as defined above, said reinforcing element being embedded in said rubber composition.

[0016] Another subject of the present invention relates to a tire comprising at least one rubber composition as defined previously or comprising at least one reinforced product as defined previously.

[0017] In this description, unless expressly indicated otherwise, all percentages (%) indicated are % by mass.

[0018] The abbreviation "pce" (usually "phr" in English) means parts by weight per hundred parts of elastomer or rubber (of the total of elastomers if several elastomers are present). It should be noted that in the concept of pce "parts by weight per hundred parts of elastomer", all the elastomers present in the final composition are taken into consideration.

[0019] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​going from more than a to less than b (i.e., excluding the limits a and b) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (i.e., including the strict limits a and b).

[0020] The expression "composition based on" means a composition comprising the mixture and / or the in situ reaction product of the different basic constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacture of the composition, or during subsequent cooking, modifying the composition as it is initially prepared. Thus, the compositions as implemented for the invention may be different in the non-crosslinked state and in the crosslinked state.

[0021] When a “majority” compound is referred to, within the meaning of the present invention, this compound is the majority among the compounds of the same type in the composition, i.e. it is the one that represents the largest quantity by mass among the compounds of the same type. Thus, for example, a majority polymer is the polymer representing the largest mass relative to the total mass of the polymers in the composition. In the same way, a so-called majority filler is the one representing the largest mass among the fillers in the composition. For example, in a system comprising a single polymer, this is the majority within the meaning of the present invention; and in a system comprising two polymers, the majority polymer represents more than half of the mass of the polymers. On the contrary, a “minority” compound is a compound that does not represent the largest mass fraction among the compounds of the same type.The words "majority" and "majority" are synonymous and equivalent. The words "minority" and "minority" are synonymous and equivalent.

[0022] The carbon-containing compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. This includes, in particular, polymers, plasticizers, fillers, etc.

[0023] As seen previously, the rubber composition of the present invention, in particular for a reinforced product, is based on at least one elastomeric matrix comprising at least one diene elastomer, at least one reinforcing filler comprising mainly carbon black and at least one reinforcing inorganic filler, at least one cobalt salt, at least one plasticizing resin having a glass transition temperature greater than or equal to 20°C and at least one vulcanization system, said rubber composition having a dispersion score Z of the reinforcing filler in the elastomeric matrix greater than or equal to 85, preferably greater than or equal to 90.

[0024] The rubber composition of the invention comprises at least one elastomeric matrix comprising at least one diene elastomer.

[0025] For the purposes of the present invention, the term "elastomeric matrix" means all the elastomers (rubbers) in the rubber composition. Thus, the elastomeric matrix may in particular consist of a single elastomer but also of a blend of two or more elastomers.

[0026] By "diene" elastomer (or indistinctly rubber), whether natural or synthetic, must be understood in a known manner an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers carrying two carbon-carbon double bonds, conjugated or not).

[0027] Diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". "Essentially unsaturated" generally means a diene elastomer derived at least in part from conjugated diene monomers, having a content of units or motifs of diene origin (conjugated dienes) which is greater than 15% (mol %); thus, diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins such as EPDM do not fall within the previous definition and can be described in particular as "essentially saturated" diene elastomers (low or very low content of motifs of diene origin, always less than 15 mol %).In the category of "essentially unsaturated" diene elastomers, a "highly unsaturated" diene elastomer is understood to mean in particular a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50% by mole.

[0028] The term diene elastomer capable of being used in the context of the present invention is understood more particularly to mean: any homopolymer of a diene monomer, conjugated or not, having from 4 to 12 carbon atoms; any copolymer of a diene, conjugated or not, having from 4 to 18 carbon atoms and at least one other monomer.

[0029] The other monomer can be ethylene, an olefin, or a diene, conjugated or not.

[0030] Suitable conjugated dienes are conjugated dienes having 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and 2-methyl-1,3-butadiene (or isoprene).

[0031] Suitable olefins are vinylaromatic compounds with 8 to 20 carbon atoms and aliphatic α-monoolefins with 3 to 12 carbon atoms.

[0032] Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene.

[0033] Suitable aliphatic α-monoolefins are, in particular, acyclic aliphatic α-monoolefins having from 3 to 18 carbon atoms.

[0034] More specifically, the diene elastomer is: any homopolymer of a conjugated diene monomer, in particular any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms; any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinylaromatic compounds having from 8 to 20 carbon atoms; any copolymer obtained by copolymerization of one or more dienes, conjugated or not, with ethylene, an α-monoolefin or their mixture such as for example elastomers obtained from ethylene, propylene with a non-conjugated diene monomer of the aforementioned type.

[0035] The diene elastomer usable in the context of the present invention can therefore be a natural rubber or a synthetic diene elastomer.

[0036] Synthetic diene elastomers can have any microstructure which depends on the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and the quantities of modifying and / or randomizing agent used. These elastomers can be, for example, block, random, sequenced, microsequenced, and be prepared in dispersion or in solution; they can be coupled and / or star-shaped or even functionalized with a coupling and / or star-shaping or functionalizing agent.For coupling to carbon black, examples that may be mentioned are functional groups comprising a C-Sn bond or amine functional groups such as aminobenzophenone for example; for coupling to a reinforcing inorganic filler such as silica, examples that may be mentioned are silanol or polysiloxane functional groups having a silanol end (as described for example in FR 2 740 778, US 6 013 718 and WO 2008 / 141702), alkoxysilane groups (as described for example in FR 2 765 882 or US 5 977 238), carboxylic groups (as described for example in WO 01 / 92402 or US 6 815 473, WO 2004 / 096865 or US 2006 / 0089445) or polyether groups (as described for example in EP 1 127 909, US 6 503 973, WO 2009 / 000750 and WO 2009 / 000752). Other examples of functionalized elastomers include elastomers (such as SBR, BR, NR or IR) of the epoxidized type.These functionalized elastomers can be used in blends with each other or with non-functionalized elastomers. For example, a silanol or polysiloxane functionalized elastomer having a silanol end can be used in blend with a tin-coupled and / or star-shaped elastomer (described in WO 11 / 042507), the latter representing a rate of 5 to 50%, for example 25 to 50%.

[0037] Suitable diene elastomers that can be used in the context of the present invention are polybutadienes and in particular those having a content (mol%) of -1,2 units of between 4% and 80% or those having a content (mol%) of cis-1,4 greater than 80%, polyisoprenes, butadiene-styrene copolymers and in particular those having a Tg (glass transition temperature (Tg, measured according to ASTM D3418-1999) of between 0°C and -90°C and more particularly between -10°C and -70°C, a styrene content of between 1% and 60% by weight and more particularly between 20% and 50%, a content (mol%) of -1,2 bonds of the butadiene part of between 4% and 75%, a content (mol%) of trans-1,4 between 10% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content between 5% and 90% by weight and a Tg of - 40°C to - 80°C,isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg of between -5°C and -50°C. In the case of butadiene-styrene-isoprene copolymers, those having a styrene content of between 5% and 50% by weight and more particularly between 10% and 40%, an isoprene content of between 15% and 60% by weight and more particularly between 20% and 50%, a butadiene content of between 5% and 50% by weight and more particularly between 20% and 40%, a content (mol%) of -1,2 units in the butadiene part of between 4% and 85%, a content (mol%) of trans -1,4 units in the butadiene part of between 6% and 80%, a content (mol%) of -1,2 plus -3,4 units in the isoprene part of between 5% and 70% and a content (mol%) of trans -1,4 units in the isoprene part of between 5% and 70% between 10% and 50%,and more generally any butadiene-styrene-isoprene copolymer having a Tg between - 5°C and - 70°C.,

[0038] Preferably, the diene elastomer(s) usable in the context of the present invention are preferably chosen from the group consisting of polybutadienes (abbreviated as (BR)), synthetic polyisoprenes (IR), natural rubber (NR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR), isoprene-butadiene-styrene copolymers (SBIR), butadiene-acrylonitrile copolymers (NBR), butadiene-styrene-acrylonitrile copolymers (NSBR) or a mixture of two or more of these polymers.

[0039] Even more preferably, the diene elastomer(s) usable in the context of the present invention are preferably chosen from the group consisting of natural rubber, synthetic polyisoprenes and mixtures of these elastomers.

[0040] The composition according to the invention comprises at least one reinforcing filler comprising mainly carbon black and at least one reinforcing inorganic filler. The reinforcing filler is therefore a blend of a carbon black and a reinforcing inorganic filler in which the carbon black is in the majority and the reinforcing inorganic filler is in the minority.

[0041] Reinforcing fillers are known for their ability to strengthen a rubber composition suitable for tire manufacturing.

[0042] By "a reinforcing filler consisting mainly of carbon black" or by "carbon black is predominant" is meant, within the meaning of the present invention, that the carbon black represents the largest quantity by mass or by weight of the reinforcing fillers in the rubber composition. In other words, the mass of the carbon black is strictly greater than 50% of the total mass, preferably greater than 60% of the total mass of the reinforcing fillers in the rubber composition.

[0043] Suitable carbon blacks are all carbon blacks, including those conventionally used in tires or their treads. Among the latter, we will particularly mention the reinforcing carbon blacks of the 100, 200, 300 series, or the blacks of the 500, 600 or 700 series (ASTM D-1765-2017 grades), such as for example blacks N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772. These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a carrier for some of the rubber additives used.

[0044] Preferably, the carbon black has a Compressed Oil Absorption Number (COAN) of greater than or equal to 60 ml / 100 g, preferably a COAN number in the range of 65 to 130 ml / 100 g. The COAN, or Compressed Oil Absorption Number (COAN) of the carbon black is measured according to ASTM D3493-2016.

[0045] Preferably, the carbon black has a BET specific surface area greater than or equal to 30 m 2 < / g; preferably greater than or equal to 60 m 2 < / g, more preferably still within a range from 60 to 150 m 2 < / g. The BET specific surface area of ​​the carbon black is measured according to standard D6556-2010 [multipoint method (at least 5 points) - gas: nitrogen - relative pressure range P / P0: 0.1 to 0.3].

[0046] More preferably still, the carbon black has a compressed sample oil absorption index (COAN) in the range of 65 to 130 ml / 100 g and a BET specific surface area in the range of 60 to 150 m 2 < / g.

[0047] The carbon black content can be in the range of 10 to 80 phr. Below 10 phr, it has been observed that the rigidity of the rubber composition begins to no longer be sufficient, negatively impacting endurance, while above 80 phr, rolling resistance performance begins to deteriorate. Advantageously, the carbon black content is in the range of 30 to 70 phr, even more preferably 35 to 65 phr.

[0048] The rubber composition of the invention comprises as reinforcing filler, in addition to carbon black, at least one reinforcing inorganic filler. This reinforcing inorganic filler is in the minority compared to the carbon black, that is to say that it does not represent the largest mass fraction among the reinforcing fillers. In other words, the mass of the reinforcing inorganic filler is strictly less than 50% of the total mass, preferably less than 40% of the total mass of the reinforcing fillers in the rubber composition.

[0049] By "reinforcing inorganic filler" is meant here any inorganic or mineral filler, whatever its color and origin (natural or synthetic), also called "white" filler, "clear" filler or even "non-black" filler as opposed to carbon black, capable of reinforcing on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires. As is known, certain reinforcing inorganic fillers can be characterized in particular by the presence of hydroxyl groups (-OH) on their surface.

[0050] Suitable inorganic reinforcing fillers are, in particular, mineral fillers of the siliceous type, preferably silica (SiO 2 ), or of the aluminous type, in particular alumina (Al 2 O 3 ).

[0051] Preferably, the reinforcing inorganic filler comprises a silica. Even more preferably, the inorganic reinforcing filler consists, in particular essentially, of silica.

[0052] The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET specific surface area and a CTAB specific surface area both less than 450 m 2 < / g, preferably within a range from 30 to 400 m 2 < / g, in particular from 60 to 300 m 2 < / g.

[0053] In this presentation, the BET specific surface area of ​​the reinforcing inorganic filler is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, page 309, February 1938), and more precisely according to a method adapted from the NF ISO 5794-1 standard, annex E of June 2010 [multipoint volumetric method (5 points) - gas: nitrogen - vacuum degassing: one hour at 160°C - relative pressure range p / po: 0.05 to 0.17].

[0054] For inorganic reinforcing fillers such as silica, for example, the CTAB specific surface area values ​​were determined according to standard NF ISO 5794-1, annex G of June 2010. The process is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "external" surface of the reinforcing filler.

[0055] Any type of precipitated silica may be used, in particular highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. Examples include the silicas described in applications WO03 / 016215-A1 and WO03 / 016387-A1. Among the commercial HDS silicas, we can notably use the silicas “Ultrasil ®< 5000GR”, “Ultrasil ®< 7000GR” from the company Evonik, the silicas “Zeosil ®< 1085GR”, “Zeosil ®< 1115 MP”, “Zeosil ®< 1165MP”, “Zeosil ®< Premium 200MP”, “Zeosil ®< HRS 1200 MP” from the company Solvay.As non-HDS silica, the following commercial silicas can be used: silicas “Ultrasil ®< VN2GR”, “Ultrasil ®< VN3GR” from Evonik, silica “Zeosil ®< 175GR” from Solvay, silicas “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

[0056] The physical state in which the reinforcing inorganic filler is present is indifferent, whether in the form of powder, microbeads, granules, or even beads or any other suitable densified form. Of course, the term reinforcing inorganic filler also means mixtures of different reinforcing inorganic fillers, in particular mixtures of silicas as described above.

[0057] Those skilled in the art will understand that, as a replacement for the reinforcing inorganic filler described above, a reinforcing filler of another nature could be used, provided that this reinforcing filler of another nature is covered with an inorganic layer such as silica, or else has functional sites on its surface, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between this reinforcing filler and the diene elastomer. By way of example, mention may be made of carbon blacks partially or completely covered with silica, or carbon blacks modified with silica, such as, without limitation, the “Ecoblack®” type fillers of the CRX2000 series or the “CRX4000” series from Cabot Corporation.

[0058] To couple the reinforcing inorganic filler to the diene elastomer, it is possible to use, in a well-known manner, an at least bifunctional coupling agent (or bonding agent) intended to ensure a sufficient connection, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. In a known manner, the level of coupling agent of the reinforcing inorganic filler with the diene elastomer may preferably represent from 0.5% to 15% by weight relative to the quantity of reinforcing inorganic filler.

[0059] As an agent for coupling the reinforcing inorganic filler with the diene elastomer, at least bifunctional organosilanes or polyorganosiloxanes are used in particular. By "bifunctional" is meant 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 comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic filler and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

[0060] Preferably, the organosilanes are chosen from the group consisting of polysulfurized organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, marketed under the name “Si69” by the company Evonik or bis-(triethoxysilylpropyl) disulfide, abbreviated to TESPD, marketed under the name “Si75” by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate marketed by the company Momentive under the name “NXT Silane”. More preferably, the organosilane is a polysulfurized organosilane.

[0061] The level of reinforcing inorganic filler in the rubber composition may be less than or equal to 50 phr, preferably within a range from 0.5 phr to 50 phr. Below 0.5 phr, it has been observed that the adhesion of the rubber composition begins to no longer be sufficient, whereas above 50 phr, the rolling resistance performance begins to deteriorate. Advantageously, this level is within a range from 2 to 40 phr, more preferably still from 4 to 25 phr.

[0062] Preferably, the total reinforcing filler content (carbon black and reinforcing inorganic filler) is within a range of 20 to 130 phr, more preferably is within a range of 30 to 120 phr, even more preferably within a range of 30 to 95 phr.

[0063] According to a preferred embodiment of the invention, the carbon black content is within a range from 30 to 70 phr and the content of the reinforcing inorganic filler is within a range from 2 to 40 phr.

[0064] According to a preferred embodiment of the invention, the carbon black content is within a range from 30 to 70 phr and the content of the reinforcing inorganic filler is within a range from 4 to 25 phr.

[0065] According to another preferred embodiment of the invention, the carbon black content is within a range from 35 to 65 phr and the content of the reinforcing inorganic filler is within a range from 2 to 40 phr.

[0066] According to another embodiment of the invention, the carbon black content is within a range from 35 to 65 pce and the content of the reinforcing inorganic filler is within a range from 4 to 25 pce.

[0067] As seen previously, the rubber composition of the invention comprises a plasticizing resin having a glass transition temperature (Tg) greater than or equal to 20°C, also called high Tg plasticizing resin. The Tg is measured according to the ASTM D3418 (1999) standard.

[0068] A high Tg hydrocarbon resin is, by definition, a solid, at room temperature and pressure (20°C, 1 atm).

[0069] Plasticizing resins, also called hydrocarbon plasticizing resins, are polymers well known to those skilled in the art and can be used in particular as plasticizing agents or tackifying agents in polymer matrices. They are essentially based on carbon and hydrogen but may contain other types of atoms, for example oxygen. They are by nature at least partially miscible (i.e., compatible) at the rates used with the polymer compositions for which they are intended, so as to act as true diluting agents. They have been described, for example, in the work entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9), chapter 5 of which is devoted to their applications, in particular in pneumatic rubber (5.5. "Rubber Tires and Mechanical Goods").As is known, these hydrocarbon resins can also be described as thermoplastic resins in the sense that they soften upon heating and can thus be molded.

[0070] Preferably, the high Tg plasticizing resin has a softening temperature less than or equal to 170°C, more preferably less than or equal to 140°C. The softening point of hydrocarbon resins is measured according to standard ISO 4625-2004 (“Ring and Ball” method).

[0071] High Tg plasticizing resins can be aliphatic, aromatic, or aliphatic / aromatic, i.e., based on aliphatic and / or aromatic monomers and mixtures of these resins. They can be natural or synthetic, petroleum-based or not (if so, also known as petroleum resins).

[0072] Suitable aromatic monomers include, for example, styrene, alpha-methylstyrene, indene, ortho-, meta-, para-methylstyrene, vinyl toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, any vinylaromatic monomer from a C9 fraction (or more generally from a C8 to C10 fraction). Preferably, the vinylaromatic monomer is styrene or a vinylaromatic monomer from a C9 fraction (or more generally from a C8 to C10 fraction). Preferably, the vinylaromatic monomer is the minor monomer, expressed as a molar fraction, in the copolymer in question.

[0073] According to a particularly preferred embodiment, the high Tg plasticizing resin is chosen from the group consisting of cyclopentadiene (abbreviated CPD) or dicyclopentadiene (abbreviated DCPD) homopolymer or copolymer resins, terpene homopolymer or copolymer resins, terpene phenol homopolymer or copolymer resins, C5 cut homopolymer or copolymer resins, C9 cut homopolymer or copolymer resins, alpha-methyl-styrene homopolymer and copolymer resins and mixtures of these resins.

[0074] The term "terpene" here commonly refers to the monomers alpha-pinene, betapinene and limonene; the limonene monomer commonly occurring in the form of three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or dipentene, the racemate of the dextrorotatory and levorotatory enantiomers. Among the above hydrocarbon plasticizing resins, mention may be made in particular of homo- or copolymer resins of alphapinene, betapinene, dipentene or polylimonene.

[0075] Even more preferably, the high Tg plasticizing resin is chosen from the group consisting of cyclopentadiene or dicyclopentadiene homopolymer or copolymer resins, C5 cut homopolymer or copolymer resins (in particular C5 / vinylaromatic cut copolymer resins), C9 cut homopolymer or copolymer resins and mixtures of these resins.

[0076] More preferably still, the high Tg plasticizing resin is a C5 / vinylaromatic cut copolymer resin.

[0077] Preferably, the high Tg plasticizing resin has at least any one of the following characteristics: a glass transition temperature greater than or equal to 30°C; a number-average molecular mass (Mn) between 300 and 2000 g / mol, more preferably between 400 and 1500 g / mol; a polymolecularity index (Ip) less than 3, more preferably less than 2 (reminder: Ip = Mw / Mn with Mw weight-average molecular mass).

[0078] More preferably, this high Tg plasticizing resin has all of the above preferential characteristics.

[0079] The macrostructure (Mw, Mn and Ip) of the hydrocarbon resin is determined by size exclusion chromatography (SEC): tetrahydrofuran solvent; temperature 35°C; concentration 1 g / l; flow rate 1 ml / min; solution filtered on a 0.45 µm porosity filter before injection; Moore calibration with polystyrene standards; set of 3 “WATERS” columns in series (“STYRAGEL” HR4E, HR1 and HR0.5); detection by differential refractometer (“WATERS 2410”) and its associated operating software (“WATERS EMPOWER”).

[0080] The above preferred high Tg plasticizing resins are well known to those skilled in the art and commercially available, for example sold as: polylimonene resins: by the company DRT under the name “Dercolyte L120” (Mn=625 g / mol; Mw=1010 g / mol; Ip=1.6; Tg=72°C) or by the company ARIZONA under the name “Sylvagum TR7125C” (Mn=630 g / mol; Mw=950 g / mol; Ip=1.5; Tg=70°C); C5 / vinylaromatic cut copolymer resins, in particular C5 / styrene cut or C5 / C9 cut: by Neville Chemical Company under the names “Super Nevtac 78”, “Super Nevtac 85” or “Super Nevtac 99”, by Goodyear Chemicals under the name “Wingtack Extra”, by Kolon under the names “Hikorez T1095” and “Hikorez T1100”, by Exxon under the names “Escorez 2101” and “Escorez 1273”; limonene / styrene copolymer resins: by DRT under the name “Dercolyte TS 105” of the company DRT, by ARIZONA Chemical Company under the names “ZT115LT” and “ZT5100”.

[0081] Examples of other preferred plasticizing resins that may also be mentioned are phenol-modified alpha-methyl-styrene resins. To characterize these phenol-modified resins, it is recalled that a so-called "hydroxyl index" (measured according to ISO 4326 standard and expressed in mg KOH / g) is used in a known manner. Alpha-methyl-styrene resins, in particular phenol-modified ones, are well known to those skilled in the art and are commercially available, for example sold by Arizona Chemical under the names "Sylvares SA 100" (Mn = 660 g / mol; Ip = 1.5; Tg = 53°C); "Sylvares SA 120" (Mn = 1030 g / mol; Ip = 1.9; Tg = 64°C); “Sylvares 540” (Mn = 620 g / mol; Ip = 1.3; Tg = 36°C; hydroxyl number = 56 mg KOH / g); “Silvares 600” (Mn = 850 g / mol; Ip = 1.4; Tg = 50°C; hydroxyl number = 31 mg KOH / g).

[0082] The level of high Tg plasticizing resin in the rubber composition may be in a range from 0.5 to 20 phr, preferably from 2 to 12 phr, more preferably still from 3 to 10 phr.

[0083] The rubber composition also comprises a cobalt salt, preferably an organic cobalt salt.

[0084] The rate of cobalt salt may for example be in a range from 0.1 pce to 6 pce, preferably from 0.5 pce to 5 pce, more preferably still from 0.6 pce to 3 pce.

[0085] Preferably, the cobalt salt is chosen from the group consisting of cobalt abietates, cobalt acetylacetonates, cobalt tallates, cobalt naphthenates, cobalt resinates and mixtures of these cobalt salts.

[0086] The vulcanization system of the rubber composition used in the context of the present invention is based on sulfur (or a sulfur donor agent).

[0087] Sulphur may be used at a preferential rate which is less than or equal to 10 pce, preferably within a range of 0.5 to 7 pce, more preferably within a range of 0.75 pce to 5.5 pce. Below 0.5 pce, the rubber composition may not be sufficiently vulcanised for its use, particularly in a reinforced product, while above 10 pce, the composition may have less resistance to thermo-oxidation.

[0088] To this basic vulcanization system may be added, incorporated during the first non-productive phase and / or during the productive phase as described later, various known vulcanization accelerators or activators as described below.

[0089] As vulcanization activators which can be used in the context of the invention, mention may be made, for example, of zinc oxide, stearic acid or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders.

[0090] In particular, any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0091] The rubber composition according to the invention may optionally also comprise all or part of the usual additives usually used in rubber compositions intended in particular for the manufacture of tires, such as for example pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, plasticizing oils, reinforcing resins, anti-reversion agents (for example hexamethylene 1,6-bisthiosulfate salts or 1,3-bis(citracoimidomethyl)benzene), acceptors (for example phenolic novolak resin) or methylene donors (for example HMT or H3M).

[0092] The rubber compositions according to the invention may also further comprise a second mineral salt different from the cobalt salt. Preferably, this mineral salt different from the cobalt salt is chosen from the group consisting of salts of an alkaline earth metal, salts of an alkali metal, lanthanide salts and mixtures of these mineral salts. Even more preferably, this mineral salt different from the cobalt salt is chosen from the group consisting of an acetylacetonate of an alkaline earth metal, acetylacetonate of an alkali metal, an acetylacetonate of a lanthanide metal.

[0093] The rubber composition of the invention has a Z score of dispersion of the reinforcing filler in the elastomeric matrix of the composition greater than or equal to 85, preferably greater than or equal to 90.

[0094] There are many methods for obtaining a rubber composition with good dispersion of the reinforcing filler in the elastomeric matrix.

[0095] Generally speaking, for a reinforcing filler to be well dispersed in the elastomeric matrix of the rubber composition, it is appropriate that this reinforcing filler be present in the elastomeric matrix of the composition in a final form which is both as finely divided as possible and distributed as homogeneously as possible.

[0096] To obtain a rubber composition with good dispersion of the reinforcing filler, we can cite, for example, techniques of mass mixing of the different constituents of the rubber composition.

[0097] Another solution for obtaining such a rubber composition with good dispersion of the reinforcing filler is to use a masterbatch of diene elastomer and carbon black. By "masterbatch" is meant a composite based on diene elastomer into which a filler and possibly other additives have been introduced.

[0098] Preferably, the rubber composition used in the context of the present invention is obtained from a masterbatch comprising at least the diene elastomer and the carbon black into which are then incorporated, in particular in an internal mixer, the minority reinforcing inorganic filler, the high Tg plasticizing resin, the cobalt salt and the other possible constituents of the rubber composition with the exception of the vulcanization system by thermomechanically kneading this mixture until reaching a maximum temperature in a range from 130°C to 200°C. Once this mixture has cooled to a temperature below 100°C, the vulcanization system is then incorporated and kneaded to a maximum temperature below 100°C.

[0099] More preferably still, said masterbatch is obtained by mixing in liquid phase from an aqueous dispersion of carbon black, that is to say a filler dispersed in water, commonly called "slurry", and a diene elastomer latex. The diene elastomer latex is a particular form of the diene elastomer which is in the form of diene elastomer particles dispersed in water.

[0100] Thus, to obtain the rubber composition usable in the context of the present invention, diene elastomer latexes will be preferentially used, the diene elastomers being those defined previously.

[0101] As a natural rubber (NR) latex which is particularly suitable for the invention, reference may be made to Chapter 3 “Latex concentrates: properties and composition”, by KF Gaseley, ADT Gordon and TD Pendle in “Natural Rubber Science and Technology”, AD Roberts, Oxford University Press - 1988.

[0102] More specifically, several forms of natural rubber latex are marketed: so-called "field" natural rubber latex, so-called "concentrated" natural rubber latex, epoxidized latex, deproteinized latex or prevulcanized latex. Field natural rubber latex is a latex to which ammonia has been added to prevent premature coagulation and concentrated natural rubber latex corresponds to a field latex that has undergone a treatment corresponding to washing followed by concentration. The different categories of concentrated natural rubber latex are listed in particular according to the ASTM D 1076-06 standard.Among these concentrated natural rubber latexes, we distinguish in particular concentrated natural rubber latexes of so-called "HA" ("high ammonia") quality and so-called "LA" ("low ammonia") quality; we will advantageously use concentrated natural rubber latexes of HA quality for the invention.

[0103] Natural rubber latex can be used directly or pre-diluted in water to facilitate its processing.

[0104] Thus, as a synthetic diene elastomer latex, the latex may in particular consist of a synthetic diene elastomer already available in emulsion form (for example a polybutadiene or a copolymer of butadiene and styrene, SBR, prepared in emulsion), or of a synthetic diene elastomer initially in solution (for example an SBR or a BR prepared in solution) which is emulsified in a mixture of organic solvent and water, generally by means of a surfactant.

[0105] Particularly suitable in the context of the present invention is an SBR latex, in particular an SBR prepared in emulsion (“ESBR”) or an SBR prepared in solution (“SSBR”), and more particularly an SBR prepared in emulsion.

[0106] There are two main types of emulsion copolymerization processes for styrene and butadiene, one of which, or hot process (carried out at a temperature close to 50°C), is suitable for the preparation of highly branched SBRs while the other, or cold process (carried out at a temperature ranging from 15°C to 40°C), makes it possible to obtain more linear SBRs.

[0107] In the case of an SBR elastomer (ESBR or SSBR), use is made in particular of an SBR having a medium styrene content, for example between 20% and 35% by weight, or a high styrene content, for example between 35 and 45%, a vinyl bond content of the butadiene part of between 15% and 70%, a content (mol%) of trans-1,4 bonds of between 15% and 75% and a Tg of between -10°C and -55°C; such an SBR can advantageously be used in a mixture with a BR preferably having more than 90% (mol%) of cis-1,4 bonds.

[0108] It should be noted that it is possible to consider using one or more natural rubber latexes in blending, one or more synthetic rubber latexes in blending or blending one or more natural rubber latexes with one or more synthetic rubber latexes.

[0109] Preferably, the diene elastomer masterbatch is obtained according to the following process steps: feeding a continuous flow of a diene elastomer latex to a mixing zone of a coagulation reactor defining an elongated coagulation zone extending between the mixing zone and an outlet, feeding a continuous flow of a fluid comprising the aqueous dispersion of carbon black under pressure into the mixing zone of a coagulation reactor to form a coagulated mixture (also called coagulum) drying the coagulum obtained previously in order to recover the first master batch

[0110] The steps of this process as well as the coagulation reactor are described in detail in document US6929783B2, in particular in columns 16 to 18. The process in particular, as described in this document, makes it possible to obtain a masterbatch of diene elastomer and carbon black having very good dispersion of the carbon black in the diene elastomer.This method consists in particular of incorporating a continuous flow of a first fluid consisting of a diene elastomer latex into the mixing zone of a coagulation reactor, of incorporating a second continuous flow of a second fluid consisting of an aqueous dispersion of carbon black under pressure into the mixing zone to form a mixture with the elastomer latex; the mixing of these two fluids being sufficiently energetic to allow the elastomer latex to be almost completely coagulated with the carbon black before the outlet orifice of the coagulation reactor and then of drying the coagulum obtained to obtain the masterbatch.

[0111] Once the master batch of diene elastomer and carbon black has been obtained, the minor reinforcing inorganic filler, the high Tg plasticizing resin, the cobalt salt and any other constituents of the rubber composition, with the exception of the vulcanization system, are incorporated therein, in particular in an internal mixer, and a first phase of thermomechanical working or mixing is carried out up to a maximum temperature in a range from 130°C to 200°C. This first mixing step in the internal mixer is referred to as the “non-productive” phase. The total mixing time in this non-productive phase is preferably in a range from 1 to 15 min.

[0112] After cooling the mixture thus obtained during this first non-productive phase, the low-temperature vulcanization system is then incorporated, generally in an external mixer such as a roller mixer. This is the phase often referred to as "productive", which takes place for a few minutes, for example between 2 and 15 min, and at a temperature typically below 120°C, preferably in a range of 60°C to 100°C.

[0113] The final rubber composition thus obtained is then calendered, for example, in the form of a sheet or plate, in particular for laboratory characterization, or calendered or extruded in the form of a sheet or layer of rubber usable for the manufacture of a reinforced product according to the invention as described below or for the manufacture of an internal layer in a tire.

[0114] Crosslinking (or curing) is carried out in a known manner at a temperature generally between 130°C and 200°C, for a sufficient time which may vary, for example, between 5 and 90 min depending in particular on the curing temperature, the crosslinking system adopted and the crosslinking kinetics of the composition considered.

[0115] Preferably, the rubber composition may be used in the tire in the form of a layer, in particular in the form of an inner layer. By layer is meant any three-dimensional element, of any shape and thickness, in particular in sheet, strip or other element of any cross section, for example rectangular or triangular.

[0116] Another subject of the present invention relates to a reinforced product comprising at least one steel reinforcing element coated at least in part with a metallic coating and a rubber composition as defined above, said reinforcing element being embedded in said rubber composition.

[0117] By "steel reinforcing element" is meant an element, consisting mainly (i.e. for more than 50% of its mass) or entirely (for 100% of its mass), of steel allowing the mechanical reinforcement of a rubber composition in which this reinforcing element is intended to be embedded.

[0118] The steel reinforcing element may comprise, in one embodiment, a single wire reinforcing element, also called an elementary monofilament, the core of which is made of steel.

[0119] The term "wire reinforcement element" means an elongated element of great length relative to its cross-section, whatever the shape of the latter, for example circular, elliptical, oblong, polygonal, in particular rectangular, square or oval. In the case of a rectangular section, the wire element has the shape of a strip. When it is circular in shape, the diameter of the wire reinforcement element is preferably less than 5 mm, more preferably within a range from 0.05 to 2 mm.

[0120] The steel wire reinforcement element can be straight or non-straight, for example twisted or corrugated. The wire reinforcement element can also be in the form of strips or bands that have a large length in relation to their thickness.

[0121] The steel wire reinforcement element may have a mechanical strength ranging from 1000 MPa to 5000 MPa. Such mechanical strengths correspond to the steel grades commonly encountered in the tire field, namely, the NT (Normal Tensile), HT (High Tensile), ST (Super Tensile), SHT (Super High Tensile), UT (Ultra Tensile), UHT (Ultra High Tensile) and MT (Mega Tensile) grades, the use of high mechanical strengths possibly allowing improved reinforcement of the rubber composition in which the reinforcement element is intended to be embedded and a lightening of the rubber composition thus reinforced.

[0122] In another embodiment, the steel reinforcing element may comprise an assembly of several elementary steel monofilaments (or several steel wire reinforcing elements) as described above, assembled together in a helix, for example by cabling or twisting the elementary steel monofilaments to form, for example, layered cables comprising several concentric layers of elementary steel monofilaments or stranded cables, each strand comprising several concentric layers of elementary steel monofilaments.

[0123] The steel core of the reinforcing element is monolithic, i.e. it is, for example, made from material or cast.

[0124] Steel can have a pearlitic, ferritic, austenitic, bainitic, martensitic microstructure or a microstructure resulting from a mixture of these microstructures.

[0125] Preferably, the steel is a pearlitic carbon steel known as “carbon steel”. In particular, when a carbon steel is used, its carbon content is preferably in a range from 0.1% to 1.2% by mass and more preferably from 0.3% to 1.1% by mass relative to the mass of steel.

[0126] It is also possible to use a steel known as “stainless steel”, this steel comprising at least 0.5% by mass, preferably at least 5% by mass and more preferably at least 15% by mass of chromium relative to the mass of steel.

[0127] By "steel reinforcing element partially coated with a metallic coating" is meant that the steel wire reinforcing element is directly covered at least over part of the steel core with a metallic coating. The metallic coating promotes the adhesion of the reinforcing element to the rubber composition in which it is embedded.

[0128] Preferably, the metal coating covers the entire steel core of the reinforcing element. This metal coating can be made of a metal identical to or different from the steel, preferably the metal of the coating is different from the steel.

[0129] Preferably, the metal coating comprises a metal selected from zinc, copper, tin, cobalt and alloys of these metals. Examples of alloys of these metals include brass and bronze. Preferably, the metal coating is an alloy of metals, more preferably brass.

[0130] By "directly covered" is meant that the metal coating is in contact with the reinforcing element without any other object, in particular another layer or another coating, being interposed between the reinforcing element and the metal coating.

[0131] The coating of the steel reinforcing element is carried out by any technique well known to those skilled in the art, in particular by any known coating technique such as, for example, spraying, impregnation by dipping, rolling in a bath or other equivalent technique of depositing a thin or ultra-thin film or composition, or by a combination of one or more of these techniques.

[0132] The reinforced product according to the invention can be prepared according to a process comprising at least the following steps: producing two layers of the rubber composition according to the invention and as previously described; combining at least a portion of at least one steel reinforcing element coated at least in part with a metallic coating with the rubber composition from the previous step to form a reinforced product; crosslinking by baking, preferably under pressure, the reinforced product thus formed.

[0133] The combination of the steel reinforcing element coated at least in part with a metallic coating with the rubber composition can be carried out for example by sandwiching the reinforcing element(s) in the two layers of the rubber composition according to the invention by depositing it / them between the two layers.

[0134] Alternatively, the reinforced product may be manufactured by depositing the steel reinforcing element coated at least in part with a metal coating on a portion of a layer obtained in the previous step, the layer is then folded back on itself to cover said reinforcing element which is then thus sandwiched over its entire length or part of its length.

[0135] The reinforced product of the invention can advantageously be used for reinforcing tires. Among these tires, the invention relates in particular to tires intended to equip passenger car motor vehicles, SUVs ("Sport Utility Vehicles"), two-wheelers (in particular bicycles, motorcycles), airplanes, such as industrial vehicles chosen from vans, "Heavy Goods Vehicles" i.e. metro, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles such as agricultural or civil engineering vehicles, other transport or handling vehicles. Also, the reinforced product of the invention can be used for the manufacture of rubber belts or for conveyor belts such as treadmills.

[0136] As already indicated previously, the reinforced product of the invention may be presented in various forms, in a unitary form (with a single reinforcing element) or in the form of a sheet or a layer, a strip, a strip or a block of rubber in which are incorporated, for example by calendering, several reinforcing elements made of steel coated at least in part with a metallic coating. The definitive adhesion between the reinforcing element made of steel coated at least in part with a metallic coating and the rubber composition according to the invention described above may be obtained after curing, preferably under pressure, the finished article for which the reinforced product of the invention is intended.

[0137] Preferably, the reinforced product is a straight reinforced sheet or an angled reinforced sheet.

[0138] In one embodiment, in which each reinforcing element is a reinforcing filamentary element, the reinforcing filamentary elements are arranged parallel to one another and embedded, for example by calendering, in the rubber composition described above. A so-called straight ply is then obtained, in which the reinforcing filamentary elements of the ply are parallel to one another and are parallel to a main direction of the ply. Then, if necessary, portions of each straight ply are cut at a cutting angle and these portions are joined together so as to obtain a so-called angled ply in which the reinforcing filamentary elements of the ply are parallel to one another and form an angle with the main direction of the angled ply, the angle formed with the main direction then being equal to the cutting angle.

[0139] The reinforced product can be a carcass ply, a working crown ply, a hooping crown ply, a protective crown ply, etc.

[0140] The invention also relates to a tire comprising at least one rubber composition according to the invention as defined above and / or at least one reinforced product as defined above.

[0141] It is possible to define three types of zones within the tire: the outer zone and in contact with the ambient air, this zone being essentially made up of the tread and an external sidewall of the tire, this external sidewall is an elastomeric layer arranged outside the carcass reinforcement relative to the internal cavity of the tire, between the crown and the bead so as to totally or partially cover the area of ​​the carcass reinforcement extending from the crown to the bead; the inner zone and in contact with the inflation gas when the tire is mounted on a rim, this zone generally being made up of a layer impervious to inflation gases, sometimes called an inner waterproof layer or inner rubber (“inner liner” in English); the internal zone of the tire, that is to say that between the outer zone and the inner zone. This zone includes layers or plies which are called herein internal layers of the tire.These are, for example, carcass plies, tread underlays, tire belt plies or any other layer that is not in contact with the ambient air or the tire inflation gas.

[0142] The rubber composition according to the invention, as defined above, is particularly well suited to internal layers, in particular to reinforced internal layers or as an internal layer adjacent to a reinforced internal layer.

[0143] More preferably, the tire of the invention comprises at least one rubber composition as defined above. According to another embodiment, the tire of the invention comprises at least one reinforced product as defined above or comprises at least one rubber composition as defined above constituting at least one internal layer of the tire. Preferably, this internal layer is adjacent to a reinforced product of the tire.

[0144] The inner layer adjacent to a reinforced product of the tire can be a decoupling rubber, an edge rubber, the bead fillers...

[0145] Of course, the invention relates to the objects previously described, namely the rubber composition, the reinforced product and the tire comprising them, both in the raw state (before crosslinking) and in the cooked state (after crosslinking).

[0146] The invention will be better understood upon reading the following description, given solely as a non-limiting example and with reference to the drawings in which: there figure 1 is a section of a tire according to the invention comprising an internal layer adjacent to a reinforced product. The figure 1 without respecting any specific scale, schematically represents a radial section of a tire in accordance with the invention for a passenger vehicle. figure 2 is a schematic section of an example of a reinforced product according to the invention forming a reinforced sheet.

[0147] In the following, the expressions "radially inside" and "radially outside" or "radially outside" mean respectively "closer to the axis of rotation of the tire, in the radial direction, than" and "further from the axis of rotation of the tire, in the radial direction, than".

[0148] There figure 1 represents only a half-view of a tire which extends symmetrically with respect to the XX' axis which represents the circumferential median plane or equatorial plane of the tire.

[0149] On the figure 1 , the tire 1 comprises a radial carcass reinforcement composed of a single ply 2 of steel metal cables, said carcass reinforcement being anchored in each bead; said beads are not shown on the figure 1 The carcass reinforcement is radially on the outside surmounted by a crown reinforcement 3 comprising radially from the inside to the outside: a first crown ply 30 called triangulation and formed of steel metal cables, a first working crown ply 31 formed of steel metal cables, then a second working crown ply 32 formed of steel metal cables identical to those of the first working crown ply 31; and radially interposed between the ends of the working crown plies 31, 32 an edge rubber P, comprising at least one composition according to the invention and as described above, which extends partly parallel to the ply 2, and a decoupling rubber B comprising at least one composition according to the invention as described above, covering the end of said working ply 30.

[0150] On the figure 2 , there is shown a sectional view of a reinforced product according to the invention, designated by the general reference 33 forming a reinforced ply, in particular a working ply of the tire of the figure 1The reinforced sheet 33 comprises reinforcing elements 34, for example steel monofilaments 35 coated at least in part with a metallic coating, embedded in the rubber composition 36 as described above. 5. EXAMPLES 5.1 Z-score measurement

[0151] In a known manner, the filler dispersion in an elastomeric matrix can be represented by the Z grade, which is measured, after crosslinking, according to the method described by S. Otto et al in Kautschuk Gummi Kunststoffe, 58 Jahrgang, NR 7-8 / 2005, in accordance with ISO 11345-2006.

[0152] The calculation of the Z grade is based on the percentage of surface in which the charge is not dispersed (“% undispersed surface”), as measured by the “disperGRADER+” device supplied with its operating mode and its “disperDATA” operating software by the Dynisco company according to the equation: Z = 100 − % surface non dispersée / 0,35

[0153] The percentage of undispersed surface is measured using a camera observing the surface of the sample under incident light at 30°. The light spots are associated with filler and agglomerates, while the dark spots are associated with the rubber matrix; digital processing transforms the image into a black and white image, and allows the determination of the percentage of undispersed surface, as described by S.Otto in the aforementioned document.

[0154] The higher the Z score, the better the dispersion of the filler in the elastomeric matrix (a Z score of 100 corresponds to perfect dispersion and a Z score of 0 to poor dispersion). A Z score greater than or equal to 80 will be considered to correspond to a surface with very good dispersion of the filler in the elastomeric matrix. 5.2 Measurement of fracture energy.

[0155] The breaking energy is measured at 100°C on a specimen stretched at 500 mm / min to cause the rupture of a tensile specimen. This specimen consists of a parallelepiped-shaped rubber plate with dimensions of 10 x 145 x 2.5 mm in which 3 notches of 3 mm length and a depth of 5 mm are made using a razor blade, at mid-height and spaced 6 mm apart parallel to the width of the specimen, before starting the test. The force (N / mm) to be exerted to obtain rupture (FRD in N / mm) is determined and the strain at rupture (DRD, in %) is measured. Thus, the energy to cause rupture (fracture energy) of the specimen can be determined, which is the product of the FRD and DRD. The breaking energy is a descriptor of the cohesion of the material. The higher the fracture energy value, the better the cohesion of the rubber composition.For greater readability, the results will be indicated on a base of 100, with the value 100 being arbitrarily assigned to the control. A result below 100 indicates a decrease in the cohesion performance of the mixture, and conversely, a result above 100 indicates an increase in this performance. 5.3 Dynamic Properties.

[0156] The dynamic properties, and in particular tan (δ)max, are measured on a viscoanalyzer (Metravib VA4000), according to the ASTM D 5992-96 standard. The response of a sample of vulcanized composition (cylindrical specimen 2.8 mm thick and 400 mm 2< in section) is recorded, subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz and a temperature of 100°C. A strain amplitude sweep is carried out from 0.1 to 100% peak-peak (forward cycle), then from 100% to 0.1% peak-peak (return cycle). The results used are the loss factor (tan δ). For the return cycle, the maximum value of tan δ observed, noted tan(δ) max at 100°C, is indicated.

[0157] The tan(δ) max results at 100°C are given in base 100 and are obtained as follows: the tan(δ) max result at 100°C obtained for a test sample is calculated in base 100 by assigning the arbitrary value 100 to the control:Tan(δ) max result at 100°C (base 100) = (tan(δ) max value at 100°C of the test sample × 100) / (tan(δ) max value at 100°C of the control). In this way, a result below 100 indicates a decrease in hysteresis (which is favorable for rolling resistance). 5.4 Crack propagation resistance test

[0158] Cracking rate (CR) was measured on rubber compound specimens using a cyclic fatigue machine (“Elastomer Test System”) type 381, from MTS, as explained below.

[0159] Cracking resistance is measured using repeated tractions on a specimen initially accommodated (after a first traction cycle), then notched. The tensile specimen consists of a parallelepiped-shaped rubber plate, with a thickness between 1 and 2 mm, a length between 130 and 170 mm and a width between 10 and 15 mm, the two lateral edges each being covered lengthwise with a cylindrical rubber bead (diameter 5 mm) allowing anchoring in the jaws of the tensile machine. The specimens thus prepared are tested in the new condition. The test was conducted under nitrogen, at a temperature of 100°C. After accommodations, 3 very fine notches of lengths between 15 and 20 mm are made using a razor blade, at half width and aligned in the direction of the length of the test piece, one at each end and one in the center of the test piece, before starting the test.At each tensile cycle, the strain rate of the specimen is automatically adjusted so as to maintain the energy release rate (amount of energy released during crack progression) constant at a value less than or equal to 3000 J / m 2 < . The crack propagation speed is measured in nanometers per cycle. The crack propagation resistance will be expressed in relative units (ur) by dividing the propagation speed of the control by that of the sample to be analyzed, the speeds being measured at the same energy release rate. A value lower than that of the control, arbitrarily set at 100, indicates an improved result, i.e. improved crack propagation resistance. 5.5. Adhesion test

[0160] The quality of the bond between the rubber composition and the reinforcing elements is assessed by an adhesion test in which the force required to extract these reinforcing elements from a vulcanized rubber composition is measured using adhesion test pieces.

[0161] To produce the adhesion test specimens, 15 identical reinforcing elements are used, the reinforcing element being a cable formed by 11 steel wires of diameter 35 mm coated with brass. A rubber block is made up of two raw plates measuring 200 mm by 12.5 mm and 7 mm thick, applied one on top of the other before curing (the thickness of the resulting block is then 14 mm). The two plates of the rubber block consist of the same rubber composition. It is during the production of the block that the reinforcing elements (15 in total) are trapped between the two plates of the rubber block in the raw state, at an equal distance and leaving one end of the reinforcing element protruding on either side of these plates of sufficient length for subsequent traction. The block containing the reinforcing elements is placed in a suitable mold and then cured at 110°C for 480 min under pressure of 15 bars (plate clamping force = 30 kN).After curing, the test piece made up of the vulcanized block and the 15 steel wires is placed in the jaws of a tensile testing machine (Intron Series 5000) to enable each steel wire to be tested at a speed of 100 mm / min and at a temperature of 23°C.

[0162] Adhesion levels are characterized by measuring the so-called tear force in N / mm 2< (denoted F max ) to tear the reinforcing elements from the specimen. A value higher than that of the control specimen, arbitrarily set at 100, indicates an improved result, i.e. a tear force greater than that of the control specimen. 5.6 : Essay

[0163] The purpose of this example is to demonstrate the improvement in the rolling resistance / cohesion / resistance to cracking rate / adhesion property compromise of a rubber composition used in a reinforced product according to the invention compared to rubber compositions used in control reinforced products.

[0164] For this, the following five rubber compositions are prepared: control composition T1 is a composition conventionally used and marketed for coating steel reinforcing elements. It therefore represents a compromise in rolling resistance / cohesion / resistance to cracking rate / adhesion performance for reinforcing elements and marketed reinforced products; it is based on natural rubber, carbon black, a cobalt salt and sulfur. It is prepared by mass mixing; composition T2, not in accordance with the invention, differs from composition T1 in that it further comprises a reinforcing inorganic filler and a plasticizing resin having a glass transition temperature greater than 20°C; composition T3, not in accordance with the invention, differs from composition T1 in that it is produced from a masterbatch obtained by liquid mixing;composition T4, not in accordance with the invention, differs from composition T3 in that it further comprises a plasticizing resin having a glass transition temperature greater than 20°C; composition T5, not in accordance with the invention, differs from composition T3 in that it further comprises a reinforcing inorganic filler; composition C1, in accordance with the invention, differs from composition T3 in that it further comprises a reinforcing inorganic filler and a plasticizing resin having a glass transition temperature greater than 20°C. ;

[0165] The formulation of these compositions is given in Table 1; the rate of the different products is expressed in pce (parts by weight per hundred parts by weight of elastomer). [Table 1] Compositions T1 T2 T3 T4 T5 C1 Elastomer (1) 100 100 (-) (-) (-) (-) Carbon black (2) 50 50 (-) (-) (-) (-) Masterbatch (3) (-) (-) 150 150 150 150 Reinforcing inorganic filler (4) (-) 6 (-) (-) 6 6 Coupling agent (5) (-) 0,85 (-) (-) 0,85 0,85 Plasticizing resin (6) (-) 6 (-) 6 (-) 6 Antioxidant 2 2 2 2 2 2 Zinc oxide (7) 7,5 7,5 7,5 7,5 7,5 7,5 Stearic acid (8) 0,9 0,9 0,9 0,9 0,9 0,9 Sulfur 5 5 5 5 5 5 Accelerator (9) 0,6 0,6 0,6 0,6 0,6 0,6 Cobalt salt (10) 1,12 1,12 1,12 1,12 1,12 1,12 (1): Natural rubber; (2): Carbon black of ASTM N347 grade (Cabot company) with a BET specific surface area of ​​90 m 2 < / g, COAN index of 100 g / 100 ml, the BET surface area and the COAN index are measured according to the methods described above; (3): Masterbatch: 100 pce of natural rubber and 50 pce of carbon black of ASTM N347 grade (Cabot company), the masterbatch is obtained by mixing in the liquid phase according to the process described in document US6929783 and below and from a natural rubber latex and an aqueous dispersion of said carbon black; (4): Silica “Zeosil 1165MP” marketed by the company Solvay; the BET specific surface area, measured according to the method described in the description, of this silica is equal to 160 m 2 < / g; (5): Bis[3-(triethoxysilyl)propyl] Tetrasulfide silane (TESPT) marketed by Evonik under the reference “Si69”;(6): Plasticizing resin: C5 / C9 cut marketed by Exxon Mobil under the reference “Escorez 2173”, whose Tg = 40°C measured according to the method described above, the softening temperature measured according to ASTM D3461-2014 is 90°C, Mn = 940 g / mol and Ip = 1.7 measured according to the method described above, (7): Industrial grade zinc oxide - Umicore company; (8): Stearin “Pristerene 4931” from Uniqema company; (9): N-ter-butyl-2-benzothiazyl sulfenamide (“Santocure TBBS” from Flexsys company) (10): Cobalt naphthenate “Product No. 60630” from Fluka company.; Production of compositions Composition T1 and T2:

[0166] For the manufacture of compositions T1 and T2, the procedure is as follows: the reinforcing filler (carbon black) and possibly the reinforcing inorganic filler when present, the natural rubber, as well as the various other ingredients, such as the plasticizing resin when present, with the exception of the crosslinking system, are successively introduced into an internal mixer, the initial tank temperature of which is approximately 50°C; the mixer is thus filled to approximately 70% by volume. Thermomechanical work is then carried out (non-productive phase) in one step of approximately 3 to 5 minutes, until a maximum "fall" temperature of 160°C is reached. The mixture thus obtained is recovered, cooled and then the sulfur and the vulcanization accelerator are incorporated into an external mixer (homo-finisher) at 40°C, mixing everything (productive phase) for a few minutes. Compositions T3 to T5 and C1

[0167] For compositions T3 to T5 and C1, the masterbatch is first manufactured in the following manner according to the method described in document US6929783. More particularly, an aqueous dispersion of carbon black N347 at a mass concentration of 14.5% is injected at a flow rate of 2512 kg / h into the mixing zone of a coagulation reactor as described in document US6929783 where it is mixed with the natural rubber latex which is a field latex having a mass concentration of 28% (field latex) and which arrives at a flow rate of 2580 kg / h in said mixing zone. The two dispersions coagulate in this device and form a coagulum. The coagulum obtained is then wrung out, dried and masticated according to the process described in patent US6929783 and the elastomer / carbon black masterbatch is obtained which contains 100 pce of natural rubber and 50 pce of carbon black N347.

[0168] Then, into an internal Banbury-type mixer (final filling rate: approximately 70% by volume), whose initial tank temperature is approximately 50°C, are introduced successively the masterbatch obtained in the previous step, where appropriate the plasticizing resin and / or the minor reinforcing inorganic filler as well as the various other ingredients with the exception of the crosslinking system; the mixer is thus filled to approximately 70% by volume. Thermomechanical work is then carried out (non-productive phase) in one step of approximately 3 to 5 min, until a maximum "drop" temperature of 160°C is reached.

[0169] The mixture thus obtained is recovered, cooled and then the crosslinking system is incorporated on an external mixer (homo-finisher) at 30°C, mixing everything (productive phase) for a few minutes. Rubber properties

[0170] The compositions T1 to T5 and C1 thus obtained are then calendered either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties, or extruded in the form of a profile. For the manufacture of reinforced products, the procedure is well known to those skilled in the art, by calendering the metal reinforcements between two layers of rubber composition in the raw state (unvulcanized) each having a desired thickness for the manufacture of the test pieces (see above).

[0171] For fracture energy measurements, dynamic properties and crack propagation resistance, the samples thus produced were cured for 360 min at 115°C in a bell press.

[0172] The properties of these different compositions and reinforced products were evaluated and are presented in Table 2 below. [Table 2] Compositions T1 T2 T3 T4 T5 C1 Note Z 87 78 94 95 90 92 Tan(δ) max at 100°C (base 100) 100 103 78 74 92 91 Breaking energy at 100°C (base 100) 100 268 100 191 163 215 Resistance to cracking rate (base 100) 100 81 97 94 80 38 Adhesion test on the reinforced product Fmax at 20°C after cooling after cooking (base 100) 100 91 81 93 72 100

[0173] It can be seen from Table 2 that when a reinforcing inorganic filler and a plasticizing resin are added to the control composition T1 to obtain the non-compliant composition T2, the rolling resistance / cohesion / resistance to cracking rate / adhesion compromise is not improved (comparison of compositions T1 and T2). Indeed, although the fracture energy and resistance to cracking rate are significantly improved, these improvements are made to the detriment of the hysteresis (Tan(δ) max at 100°C) (therefore the rolling resistance) and the adhesion properties (reduced F max).

[0174] When natural rubber, in the form of latex, and carbon black, in the form of an aqueous dispersion, are mixed by liquid mixing to obtain composition T3, it is found, in comparison with composition T1, that neither the cohesion of the rubber composition (fracture energy) nor the adhesion of the composition to the steel reinforcing elements have been improved. The compromise of properties is therefore not achieved.

[0175] When a plasticizing resin is added to the composition not in accordance with the invention T3 to obtain the composition not in accordance with the invention T4, an improvement in the hysteresis, the cohesion of the composition, as well as the resistance to the cracking rate of the composition T4 is observed compared to the composition T3 as well as a slight improvement in the adhesion properties but without however reaching for this property the values ​​of the control composition T1. The compromise of properties is therefore also not reached for the composition T4.

[0176] When a silica is added to the composition not in accordance with the invention T3 to obtain the composition not in accordance with the invention T5, an improvement in the cohesion of the composition T5 is observed compared to the cohesion of the composition T3, as well as an improvement in the resistance to the cracking rate compared to the composition T3, but also compared to the composition T1. On the other hand, a significant reduction in the adhesion properties of the composition T5 is observed. The property compromise is therefore also not achieved for the composition T5.

[0177] Surprisingly, when a silica and a high Tg plasticizing resin are added to composition T3 to obtain composition C1 according to the invention, a significant improvement in the cohesion, crack rate resistance and adhesion properties is observed compared to the control composition T3, but also compared to the non-compliant compositions T4 and T5. Composition C1 according to the invention also has significantly improved hysteresis, cohesion and crack rate resistance properties compared to the control composition T1 while retaining adhesion properties equivalent to those of composition T1. The compromise of rolling / cohesion / cracking rate resistance / adhesion properties is therefore improved for composition C1 according to the invention.Surprisingly, composition C1 according to the invention has the best crack resistance properties of all the non-compliant compositions T1 to T5 tested.

Claims

1. Rubber composition based on at least one elastomeric matrix comprising at least one diene elastomer, at least one reinforcing filler predominantly comprising carbon black and at least one reinforcing inorganic filler, at least one plasticizing resin having a glass transition temperature being measured according to the standard ASTM D3418 (1999) of greater than or equal to 20°C, at least one cobalt salt and at least one vulcanization system, said rubber composition exhibiting a Z score for dispersion of the reinforcing filler in the elastomeric matrix of greater than or equal to 85, the Z score being measured according to the method described into the paragraph 5.1.

2. Rubber composition according to Claim 1, in which the carbon black exhibits a compressed oil absorption number measured according to the standard ASTM D3493-2016 of greater than or equal to 60 ml / 100 g, preferably within a range extending from 65 to 130 ml / 100 g.

3. Reinforced rubber composition according to either one of Claims 1 and 2, in which the carbon black exhibits a BET specific surface measured according to the standard ASTM D6556-2010 of greater than or equal to 30 m2 / g, preferably of greater than or equal to 60 m2 / g, more preferentially still within a range extending from 60 to 150 m2 / g.

4. Rubber composition according to any one of the preceding claims, in which the content of carbon black is within a range extending from 10 to 80 phr, preferably from 30 to 70 phr, more preferentially still from 35 to 65 phr.

5. Rubber composition according to any one of the preceding claims, in which the content of reinforcing inorganic filler is less than or equal to 50 phr, preferably is within a range extending from 0.5 phr to 50 phr, more preferentially still is within a range extending from 2 to 40 phr, more preferentially still from 4 to 25 phr.

6. Rubber composition according to any one of the preceding claims, in which the reinforcing inorganic filler comprises a silica, more preferentially consists of silica.

7. Rubber composition according to any one of the preceding claims, in which the plasticizing resin is selected from the group consisting of aliphatic resins, aromatic resins, resins of aliphatic / aromatic type and the mixtures of these plasticizing resins.

8. Rubber composition according to any one of the preceding claims, in which the content of plasticizing resin is within a range extending from 0.5 to 20 phr, preferably from 2 to 12 phr, more preferentially still from 3 to 10 phr.

9. Rubber composition according to any one of the preceding claims, in which the rubber composition is obtained from a masterbatch of said diene elastomer and of said carbon black.

10. Rubber composition according to Claim 9, in which the masterbatch is obtained by liquid-phase compounding starting from a diene elastomer latex and from an aqueous dispersion of carbon black.

11. Rubber composition according to Claim 10, in which the masterbatch is obtained according to the following process stages: - feeding a continuous stream of a diene elastomer latex to a mixing region of a coagulation reactor defining an elongated coagulation region extending between the mixing region and an outlet, - feeding a continuous stream of a fluid comprising a filler under pressure to the mixing region of a coagulation reactor in order to form a coagulated mixture, - drying the coagulated mixture obtained above in order to recover the masterbatch.

12. Reinforced product comprising at least one steel reinforcing element coated at least in part with a metallic coating and a rubber composition as defined in any one of Claims 1 to 11, said reinforcing element being embedded in said rubber composition.

13. Reinforced product according to the preceding claim, in which the metal of the metallic coating of the reinforcing element is chosen from zinc, copper, tin, cobalt and the alloys of these metals.

14. Tyre comprising at least one rubber composition according to any one of Claims 1 to 11.

15. Tyre comprising at least one reinforced product as defined in Claim 12 or Claim 13.