Rubber composition comprising a specific antioxidant

Abstract

The invention relates to a rubber composition based on at least one diene elastomer, a reinforcing filler comprising silica, 0.5 to 1.2 phr of wax, a crosslinking system and a compound of general formula (I). The invention also relates to a tread comprising the composition, to a carcass ply and / or an outer sidewall comprising the composition, to a tire comprising the composition and to a bicycle tire comprising the composition.

Description

[0001] Description

[0002] Title: RUBBER COMPOSITE CONTAINING A SPECIFIC ANTIOXIDANT

[0003] The present invention relates to rubber compositions comprising a specific antioxidant intended in particular for the manufacture of tires or semi-finished products for tires.

[0004] A tire must comply in a known way with a large number of technical requirements, often contradictory, among which is good resistance to ozone, measured statically and dynamically, without staining effect and without wax efflorescence.

[0005] Indeed, ozone is known to have detrimental effects on rubber products, typically causing glazing and / or cracking on their surface. In the case of tires, this cracking can negatively impact tire performance, particularly durability, potentially reducing tire lifespan, and also affecting the ability to maintain proper inflation pressure.

[0006] Traditionally, 6PPD (N-(1,3-dimethylbutyl-N'-phenyl-pp-phenylenediamine)) has been used to prevent the harmful effects of ozone. However, during its degradation, this molecule produces staining byproducts and a byproduct suspected of having a negative impact on the environment. Therefore, alternatives to 6PPD are currently being sought.

[0007] Document W02018 / 163041 describes tire compounds based on a diene elastomer filled with carbon black and a phenolic antioxidant-based protective system, containing neither 6PPD nor wax, thus improving resistance to dynamic ozone without causing staining. The results are measured by dynamic ozone resistance tests.

[0008] However, manufacturers are still looking for solutions to improve the trade-off between properties such as efflorescence performance and ozone resistance, under dynamic stress and static elongation.

[0009] Continuing its research, the Applicant unexpectedly discovered that the combined use of wax in the presence of a specific antioxidant in a composition based on at least one diene elastomer filled with silica substantially improves the aforementioned performance trade-off. Thus, the invention relates to a rubber composition based on at least: a. a diene elastomer, b. a reinforcing filler comprising silica, c. 0.5 to 1.2 parts per liter of wax, d. a crosslinking system, e. a compound of general formula I: in which:

[0010] RI, R4 and R5 are identical or different groups, chosen independently from each other from linear or branched alkyl groups,

[0011] R2 and R3 are identical or different groups, chosen independently of each other from linear or branched alkylene groups.

[0012] It also relates to a tread comprising the composition according to the invention, but also to a carcass ply and / or an outer sidewall comprising the composition according to the invention, also a tire comprising the composition according to the invention and a bicycle tire comprising the composition according to the invention.

[0013] In this document, unless otherwise indicated, the expressions "the composition" or "the composition according to the invention" refer to the tread composition according to the invention.

[0014] I- DEFINITIONS

[0015] The term "composition based on" refers to a composition comprising a mixture and / or the in situ reaction product of the various constituents used, some of which may react and / or are intended to react with each other, at least partially, during the different stages of manufacturing the composition; the composition may thus be in a fully or partially crosslinked state or in a non-crosslinked state. The term "elastomeric matrix" refers to all the elastomers in the composition, including the copolymer defined below.

[0016] Unless otherwise stated, the rates of units resulting from the insertion of a monomer into a copolymer are expressed as a mole percentage relative to the total monomer units of the copolymer.

[0017] The expression "part by weight per hundred parts by weight of elastomer" (or pce) is to be understood in the context of the present invention as the part, by mass per hundred parts of elastomer present in the rubber composition under consideration.

[0018] In this document, unless expressly stated otherwise, all percentages (%) shown are percentages (%) by mass.

[0019] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​from greater than a to less than b (that is, excluding the bounds a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from a to b (that is, including the strict bounds a and b). In this context, when an interval of values ​​is designated by the expression "from a to b," it also and preferably refers to the interval represented by the expression "between a and b."

[0020] When referring to a "major" compound, for the purposes of this invention, it is understood that this compound is the majority among the compounds of the same type in the composition; that is, it is the one that represents the largest quantity by mass among the compounds of the same type. Thus, for example, a major elastomer is the elastomer representing the greatest mass relative to the total mass of the elastomers in the composition. Similarly, a major filler is the one representing the greatest mass among the fillers in the composition. For example, in a system comprising a single elastomer, this elastomer is the major component for the purposes of this invention; and in a system comprising two elastomers, the major elastomer represents more than half the mass of the elastomers. Conversely, a "minor" compound is a compound that does not represent the largest mass fraction among the compounds of the same type.Preferably by majority, we mean present at more than 50%, preferably more than 60%, 70%, 80%, 90%, and most preferably the "majority" compound represents 100%.

[0021] The compounds mentioned in the description may be of fossil origin or bio-based.

[0022] In the latter case, they may be partially or entirely derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of previously used materials; that is, they may be partially or entirely produced through a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes, in particular, polymers, plasticizers, fillers, etc.

[0023] Unless otherwise stated, all glass transition temperature "Tg" values ​​described herein are measured in a known manner by DSC (Differential Scanning Calorimetry) according to ASTM D3418 (1999).

[0024] II- DESCRIPTION OF THE INVENTION

[0025] II- 1 Elastomer Matrix

[0026] The rubber composition according to the invention comprises at least one diene elastomer.

[0027] By "dienic" elastomer (or indistinctly rubber), whether natural or synthetic, should be understood in a known way as an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not).

[0028] These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". Generally, "essentially unsaturated" refers to a diene elastomer derived at least in part from conjugated diene monomers, having a proportion of diene-derived motifs or units (conjugated dienes) greater than 15% (mole percent); thus, diene elastomers such as butyl rubbers or EPDM-type diene-alpha-olefin copolymers do not fall under the previous definition and can be described as "essentially saturated" diene elastomers (low or very low proportion of diene-derived motifs, always less than 15%). In the category of "essentially unsaturated" diene elastomers, a "highly unsaturated" diene elastomer is defined in particular as a diene elastomer having a rate of diene origin motifs (conjugated dienes) which is greater than 50%.

[0029] The term diene elastomer specifically refers to a type of elastomer suitable for use in compositions according to the invention:

[0030] (a) - any homopolymer of a diene monomer, conjugated or not, having from 4 to 18 carbon atoms; (b) - any copolymer of a diene, conjugated or not, having from 4 to 18 carbon atoms and at least one other monomer.

[0031] The other monomer can be ethylene, an olefin or a diene, conjugated or not.

[0032] Suitable conjugated dienes are those with 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and isoprene.

[0033] Suitable as unconjugated dienes are unconjugated dienes having 6 to 12 carbon atoms, such as 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene.

[0034] Suitable olefins include vinylaromatic compounds with 8 to 20 carbon atoms and aliphatic α-monoolefins with 3 to 12 carbon atoms.

[0035] Examples of suitable vinylaromatic compounds include styrene, ortho-, meta-, para-methyl styrene, the commercial mixture "vinyl-toluene", and para-tert-butylstyrene.

[0036] Acyclic a-monoolefins with 3 to 18 carbon atoms are particularly suitable as aliphatic a-monoolefins.

[0037] More specifically, diene elastomer is:

[0038] (a') - 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;

[0039] (b') - any copolymer obtained by copolymerization of one or more dienes conjugated together or with one or more vinylaromatic compounds having from 8 to 20 carbon atoms;

[0040] (c') - any copolymer obtained by copolymerization of one or more dienes, conjugated or not, with ethylene, an α-monoolefin or a mixture thereof, such as elastomers obtained from ethylene, propylene with a non-conjugated diene monomer of the aforementioned type,

[0041] The diene elastomer can in particular be an isoprene elastomer or a butadien elastomer.

[0042] The term "isoprene elastomer" is commonly understood to mean a homopolymer or copolymer of isoprene, in other words, a diene elastomer selected from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), various isoprene copolymers, and mixtures of these elastomers. Among the isoprene copolymers, particular examples include isobutene-isoprene (butyl rubber - IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR), and isoprene-butadiene-styrene (SBIR). This isoprene elastomer is preferably natural rubber or a synthetic cis-1,4 polyisoprene; among these synthetic polyisoprenes, polyisoprenes with a molar percentage of cis-1,4 bonds greater than 90% are preferred, and even more preferably greater than 98%.

[0043] The term "butadiene elastomer" is commonly understood to mean a homopolymer or copolymer of butadiene, in particular a diene elastomer selected from the group consisting of polybutadienes (BR), various butadiene copolymers, and mixtures of these elastomers. Among the butadiene copolymers, butadiene-styrene (SBR), isoprene-butadiene (BIR), and isoprene-butadiene-styrene (SBIR) copolymers are particularly noteworthy. This butadiene elastomer is preferably a cis-1,4 polybutadiene; among these polybutadienes, those with a cis-1,4 bond percentage (molar %) greater than 90% are preferred, and even more preferably, those greater than 96%.

[0044] Advantageously, the rubber composition comprises a substantially saturated diene elastomer. In particular, any ethylene-diene monomer (EPDM) rubber can be used in the context of the present invention. Indeed, the use of ethylene-diene monomer (EPDM) rubber can be advantageous in the context of the present invention. The ethylene-diene monomer (EPDM) rubber can be a single EPDM rubber or a blend of several EPDM rubbers.

[0045] Preferably, the diene elastomer is chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, ethylene-diene monomer rubbers (EPDM), and blends of these elastomers. Advantageously, the butadiene copolymers are chosen from the group consisting of butadiene-styrene copolymers (SBR).

[0046] Suitable materials include polybutadienes, particularly those with a -1,2 unit content (molar %) between 4% and 80% or those with a cis-1,4 unit content (molar %) greater than 80%; polyisoprenes; butadiene-styrene copolymers, particularly those with a glass transition temperature (Tg, measured according to ASTM D3418-99) between 0°C and -90°C, and more specifically between -10°C and -70°C; a styrene content between 1% and 60% by weight, and more specifically between 20% and 50%; a -1,2 unit content (molar %) of the butadiene portion between 4% and 75%; and a trans-1,4 unit content (molar %) between 10% and 80%. butadiene-isoprene 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 between 5% and 50% by weight and a Tg between -5°C and -50°C.In the case of butadiene-styrene-isoprene copolymers, those with a styrene content between 5% and 50% by weight, and more particularly between 10% and 40%, are particularly suitable; those with an isoprene content between 15% and 60% by weight, and more particularly between 20% and 50%, a butadiene content between 5% and 50% by weight, and more particularly between 20% and 40%, a butadiene fraction (molar %) in -1.2 units of between 4% and 85%, a trans-1.4 unit (molar %) of between 6% and 80%, an isoprene fraction (molar %) in between -1.2 and -3.4 units of between 5% and 70%, and a trans-1.4 unit (molar %) of between 5% and 70%. Isoprene content between 10% and 50%, and more generally any butadiene-styrene-isoprene copolymer with a Tg between -5°C and -70°C. Note that SBR can be prepared as an emulsion (ESBR) or as a solution (S SBR).

[0047] The diene elastomer can be modified, that is to say either coupled and / or star-shaped, or functionalized, or coupled and / or star-shaped and simultaneously functionalized.

[0048] Thus, the diene elastomer can be coupled and / or star-shaped, for example by means of a silicon or tin atom which links the elastomer chains together.

[0049] The diene elastomer can be simultaneously or alternatively functionalized and comprise at least one functional group. By functional group is meant a group comprising at least one heteroatom chosen from Si, N, S, O, P. Particularly suitable as functional groups are those comprising at least one function such as: silanol, an alkoxysilane, a primary, secondary or tertiary amine, cyclic or non-cyclic, a thiol, an epoxide.

[0050] In the context of functionalized elastomers, that is to say, those comprising at least one functional group:

[0051] - The functional group can be located at the end of the elastomer chain, we will then say that the diene elastomer is functionalized at the end or end of the chain.

[0052] - The functional group can be located in the main linear elastomer chain, we will then say that the diene elastomer is coupled or functionalized in the middle of the chain, as opposed to the "end of the chain" position and although the group is not located precisely in the middle of the main elastomer chain.

[0053] - The functional group can be central and link n elastomer chains (n>2), the elastomer being star-shaped or branched.

[0054] - The diene elastomer may have several functional groups, pendant or not, distributed along the main chain of the elastomer, we will then say that the diene elastomer is functionalized along the chain.

[0055] Functionalized elastomers are suitable if prepared using a functional initiator, particularly those bearing an amine group. Such functional elastomers and their production methods are known to those skilled in the art.

[0056] Also suitable as functionalized elastomers are those obtained by copolymerization of at least one diene monomer and a monomer carrying a function.

[0057] Functionalized elastomers also include those obtained by post-polymerization modification through reaction with a functionalizing agent that introduces at least one functional group into the elastomer structure. Such functionalized elastomers and their production methods are known to those skilled in the art. Such functionalization can be classically achieved through various reactions, for example, by radical grafting onto the diene elastomer, by 1,3-dipolar reaction on the diene elastomer, or by reaction of the (pseudo)living diene elastomer obtained after coordination or anionic polymerization with a functionalizing agent.

[0058] The rubber composition of the invention may contain a single diene elastomer or a mixture of several diene elastomers.

[0059] Advantageously, the percentage of butadiene-styrene copolymer (SBR) in the composition according to the invention is in the range of 0 to 100 parts per cent, the percentage of polybutadiene (BR) is in the range of 0 to 50 parts per cent, the percentage of natural rubber (NR) is in the range of 0 to 100 parts per cent, and the percentage of ethylene-diene-monomer rubber (EPDM) is in the range of 0 to 45 parts per cent.

[0060] Advantageously, the percentage of butadiene-styrene copolymer (SBR) in the composition according to the invention is in the range of 40 to 60 parts per annum, the percentage of polybutadiene (BR) is in the range of 30 to 50 parts per annum, and the percentage of natural rubber (NR) is in the range of 5 to 15 parts per annum. II-2 Reinforcing Filler

[0061] The rubber composition according to the invention comprises at least one reinforcing filler comprising silica.

[0062] By charge, we mean here any type of charge, whether it is reinforcing, non-reinforcing or inert.

[0063] • Reinforcing charges

[0064] The rubber composition of the invention may include one or more reinforcing fillers.

[0065] Any type of reinforcing filler, known for its ability to strengthen a rubber composition suitable for tire manufacturing, can be used. Examples include organic fillers such as carbon black, inorganic fillers such as silica, or a mixture of both. Such reinforcing fillers typically consist of particles with an average size (by mass) of less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, and particularly and preferentially between 20 and 150 nm.

[0066] According to the invention, the reinforcing filler comprises silica. It may further comprise another reinforcing filler, in particular carbon black.

[0067] All carbon blacks are suitable, including those conventionally used in tires or their treads. Among these, particularly the reinforcing carbon blacks of the 100, 200, and 300 series, or the 500, 600, and 700 series (ASTM D-1765-2017 grades), such as NI 15, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772. These carbon blacks can be used on their own, as commercially available, or in other forms, for example, as a carrier for certain rubber compound additives. Carbon blacks could for example already be incorporated into the diene elastomer, in particular isoprene in the form of a masterbatch (see for example applications WO97 / 36724-A2 or W099 / 16600-A1).

[0068] Examples of organic fillers other than carbon blacks include functionalized polyvinyl organic fillers as described in applications W02006 / 069792-A1, W02006 / 069793-A1, W02008 / 003434-A1 and W02008 / 003435-A1.

[0069] The term "reinforcing inorganic filler" here refers to any inorganic or mineral filler, regardless of its color or origin (natural or synthetic), also called "white" filler, "light" filler, or even "non-black" filler (as opposed to carbon black), capable of reinforcing, on its own and without the need for an intermediate coupling agent, a rubber compound intended for tire manufacturing. As is known, some reinforcing inorganic fillers are characterized, in particular, by the presence of hydroxyl groups (-OH) on their surface.

[0070] Suitable inorganic reinforcing fillers include mineral fillers of the siliceous type, preferably silica (SiCl) or of the aluminous type, in particular alumina (Al2O3).

[0071] The silica used can be any reinforcing silica known to a person skilled in the art, including any precipitated or pyrogenated silica.

[0072] Precipitated silica can be produced from non-renewable raw materials, including those derived from inorganic sand (silicon dioxide from inorganic sand), recycled materials such as foundry sands, end-of-life tires and in particular the treads of end-of-life tires which mainly contain silica as a reinforcing filler, or from bio-based raw materials such as organic waste from plants, preferably inedible organic waste from plants.

[0073] Non-renewable raw materials are defined as raw materials that do not regenerate on a human timescale. These are therefore exhaustible resources. Examples include minerals such as stones or sand, metals, gas, and oil.

[0074] Among the plants that have silicon dioxide in their tissues are mustard, grasses, corn, sugar cane bagasse, rice, wheat and in particular mustard husks, bamboo leaves, ears of corn, rice husks, wheat husks.

[0075] Silica derived from non-renewable raw materials such as natural inorganic sand is usually obtained by heating sand in a glass furnace in the presence of sodium carbonate. The resulting sodium silicate is then dissolved in water, possibly in the presence of a base such as sodium hydroxide. Precipitated synthetic silica is formed from this aqueous solution by controlled treatment of the silicate with an acid (e.g., a mineral acid and / or an acidifying gas such as carbon dioxide). Sometimes, an electrolyte (e.g., sodium sulfate) may be present to promote the formation of precipitated silica particles. The recovered precipitated silica is amorphous.

[0076] Silica derived from bio-based raw materials such as those mentioned above can, for example, be obtained by burning the bio-based raw material in order to recover the ash of this bio-based material which contains mainly silicon dioxide.For example, with rice husks, and in a process equivalent to the one described above for silicas based on non-renewable or recycled mineral raw materials, rice husk ash is generally treated with a strong base such as sodium hydroxide to form an aqueous silicate solution (e.g., sodium silicate). Following this, precipitated synthetic silica is formed by the controlled addition of an acid (e.g., a mineral acid and / or an acidifying gas such as carbon dioxide) in which an electrolyte (e.g., sodium sulfate) may be present to promote the formation of precipitated silica particles derived from rice husks. The recovered precipitated silica is amorphous precipitated silica. Silica derived from rice husk ash is commonly referred to as RHA silica (Rice Husk Ash Silica).Bio-based silicas are available, for example, from suppliers such as Solvay, Evonik, Quechen, Wilmar International, Wuxi...

[0077] In summary, the synthesis of a precipitated silica usable within the framework of the invention can be carried out from a sodium silicate entirely obtained from bio-based, recycled or non-renewable raw materials, but also from a mixture of bio-based and / or recycled and / or non-renewable raw materials.

[0078] Preferably, precipitated silica, whether obtained from mineral, non-renewable, recycled or bio-based raw materials, has a specific surface area BET and a specific surface area CTAB, both less than 450 m². 2 / g, preferably within a range of 30 to 400 m 2 / g, particularly from 60 to 300 m 2 / g.

[0079] Any type of precipitated silica can be used, including highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art.

[0080] Examples include the silicas described in applications W003 / 016215-A1 and W003 / 016387-A1. Among the commercial HDS silicas, the following can be used: “Ulsil ® 5000GR”, “Ulsil ® 7000GR” from Evonik, “Zeosil ® 1085GR”, “Zeosil® 1115 MP”, “Zeosil® 1165MP”, “Zeosil® Premium 200MP”, “Zeosil® HRS 1200 MP” from Solvay. As non-HDS silica, the following commercial silicas may be used: “Ultrasil® VN2GR”, “Ultrasil® VN3GR” silicas from Evonik, “Zeosil® 175GR” silica from Solvay, “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” silicas from PPG, “K160”, “K185”, “K195” silicas from Wilmar International.

[0081] Other examples of inorganic fillers that could be used in the rubber compositions of the invention may also be cited: mineral fillers of the aluminous type, in particular alumina (Al2O3), aluminum oxides, aluminum hydroxides, aluminosilicates, titanium oxides, silicon carbides or nitrides, all of the reinforcing type as described for example in applications WO99 / 28376-A2, WOOO / 73372-A1, WO02 / 053634-A1, W02004 / 003067-A1, W02004 / 056915-A2, US6610261-B1 and US6747087-B2. Examples include the aluminas “Baikalox A125” or “CR125” (Baïkowski company), “APA-100RDX” (Condéa), “Aluminoxid C” (Evonik) or “AKP-G015” (Sumitomo Chemicals).

[0082] The physical state of the reinforcing inorganic filler is irrelevant, whether it be in the form of powder, microbeads, granules, spheres, or any other suitable densified form. Of course, the term "reinforcing inorganic filler" also refers to mixtures of different reinforcing inorganic fillers, particularly silicas as described above.

[0083] Those skilled in the art will understand that, in place of the inorganic reinforcing filler described above, a reinforcing filler of another nature could be used, provided that this reinforcing filler of another nature is coated with an inorganic layer such as silica, or has functional sites on its surface, particularly hydroxyl sites, requiring the use of a coupling agent to establish the bond between this reinforcing filler and the diene elastomer. Examples include carbon blacks partially or fully coated with silica, or carbon blacks modified with silica, such as, but not limited to, the "Ecoblack®" fillers of the CRX2000 series or the "CRX4000" series from Cabot Corporation.

[0084] A person skilled in the art will be able to adapt the total reinforcing load rate according to the use concerned, in particular according to the type of tire concerned, for example tire for bicycle, for motorcycle, for passenger vehicle or even for utility vehicle such as van or heavy goods vehicle.

[0085] Preferably, the reinforcing filler consists mainly of an inorganic reinforcing filler, preferably silica.

[0086] Preferably also, the silica content is in the range of 30 to 140 pc, preferably 30 to 120 pc, more preferably 35 to 110 pc; the optimum being known to differ according to the particular applications intended.

[0087] Preferably, carbon black is used at a rate of 10 parts per cubic centimeter (ppm) or less, preferably less than 5 ppm, more preferably less than 1 ppm, and even more preferably, the composition does not include any carbon black. Within the indicated ranges, the coloring (black pigmenting agent) and UV-resistant properties of carbon black are utilized without compromising the typical performance provided by the reinforcing inorganic filler.

[0088] In this presentation, the specific surface area BET is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, page 309, February 1938), and more specifically according to a method adapted from the standard NF ISO 5794-1, Annex E of June 2010 [multipoint volumetric method (5 points) - gas: nitrogen - degassing under vacuum: one hour at 160°C - relative pressure range w / in: 0.05 to 0.17],

[0089] For inorganic fillers such as silica, for example, the CTAB specific surface area values ​​were determined according to the NF ISO 5794-1 standard, Annex G of June 2010. The process is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "external" surface of the reinforcing filler.

[0090] For carbon blacks, the STSA specific surface area is determined according to ASTM D6556-2016. Coupling agents:

[0091] To couple the reinforcing inorganic filler to the diene elastomer, a well-known coupling agent (or bonding agent) can be used to ensure sufficient chemical and / or physical connection between the inorganic filler (the surface of its particles) and the diene elastomer. Organosilanes or polyorganosiloxanes, at least bifunctional, are particularly suitable. "Bifunctional" refers to a compound possessing a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer.For example, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being able to interact with the hydroxyl groups of an inorganic charge and a second functional group comprising a sulfur atom, said second functional group being able to interact with the diene elastomer.

[0092] Preferably, organosilanes are chosen from the group consisting of polysulfide organosilanes (symmetric or asymmetric) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated TESPT and marketed under the name "Si69" by Evonik, or bis-(3-triethoxysilylpropyl) disulfide, abbreviated TESPD and marketed under the name "Si75" by Evonik, polyorganosiloxanes, mercaptosilanes, and blocked mercaptosilanes, such as octanethioate of

[0093] S-(3-(triethoxysilyl)propyl) marketed by the company Momentive under the name "NXT Silane". More preferably, the organosilane is a polysulfide organosilane.

[0094] Of course, mixtures of the coupling agents described above could also be used.

[0095] The coupling agent content in the composition of the invention is advantageously less than or equal to 5 parts per million (ppm), it being understood that it is generally desirable to use as little as possible. Typically, the coupling agent content represents 5% to 16% by weight relative to the amount of reinforcing inorganic filler. Its content is preferably within a range of 1.5% to 22 ppm, preferably 1.5% to 19 ppm, and more preferably within a range of 2% to 12 ppm. This content is easily adjusted by a person skilled in the art according to the amount of reinforcing inorganic filler used in the composition of the invention. [The following appears to be unrelated and possibly a separate entry: o The covering agents

[0096] Rubber compositions may also contain coating agents for the reinforcing inorganic filler when a reinforcing inorganic filler is used, thereby improving their workability in the raw state. These recovery agents are well known (see for example patent applications WO2006 / 125533-A1, W02007 / 017060-A1 and W02007 / 003408-A1), examples include hydrolyzable silanes such as hydroxysilanes (see for example W02009 / 062733-A2), alkylalkoxysilanes, polyols (for example diols or triols), polyethers (for example polyethylene glycols), primary, secondary or tertiary amines, hydroxylated or hydrolyzable polyorganosiloxanes (for example α,co-dihydroxy-polyorganosilanes (see for example EP0784072-A1).

[0097] • Additional charges

[0098] The composition of the invention may further comprise an additional filler such as an inert filler, for example, a semi-reinforcing filler such as graphite, or a mixture of these two types of fillers. Semi-reinforcing fillers

[0099] Semi-reinforcing fillers are not capable of reinforcing a rubber composition intended for the manufacture of tires on their own; in other words, they are not suitable for replacing, in its reinforcing function, a conventional tire-grade carbon black. However, they allow an increase in the tensile modulus of a rubber composition in which they are incorporated, which is why they are called "semi-reinforcing".

[0100] Graphite may be mentioned as a semi-reinforcing filler that may be present in the composition of the present invention.

[0101] Graphite is generally understood to mean a set of stacked graphene planes, graphene being a sheet of atomic thickness in which carbon atoms are organized in an essentially hexagonal network.

[0102] Having given these definitions, the term graphite, which is suitable for use in the context of the invention, is understood more specifically to mean:

[0103] (a) any natural graphite, associated with rocks affected by metamorphism, after separation of impurities accompanying the graphite veins and after grinding;

[0104] (b) any thermally expandable natural graphite, i.e. in which a chemical compound in liquid form, for example an acid, is intercalated between its graphene planes; (c) any expanded natural graphite, the latter being produced in two stages: intercalation of a chemical compound in liquid form, for example an acid, between the graphene planes of a natural graphite by chemical treatment and expansion at high temperature;

[0105] (d) any synthetic graphite.

[0106] The usable rubber composition according to the invention may contain a single graphite or a mixture of several graphites, thus for example one may have a cut of natural graphite and / or expanded graphite and / or synthetic graphite.

[0107] Graphite, as defined above, can be found morphologically in a lamellar or non-lamellar form.

[0108] Preferably, the graphite usable according to the invention is in lamellar form.

[0109] Preferably, the content of the semi-reinforcing filler(s), particularly graphite, in the rubber composition of the invention is in the range of 0 to 35 parts per cubic centimeter, preferably from 1 to 35 parts per cubic centimeter, and even more preferably from 1 to 20 parts per cubic centimeter. Inert fillers

[0110] Inertial charges are defined as non-reinforcing charges.

[0111] Among the inert fillers well known to those skilled in the art, we will mention in particular those chosen from the group consisting of natural (chalk) or synthetic calcium carbonate microparticles, synthetic or natural silicates (such as kaolin, talc, mica, vermiculite), aluminosilicates (clay, bentonite, montmorillonite), glass microbeads, glass flakes, and a mixture of these compounds.

[0112] Preferably, the content of the inert filler(s) in the rubber composition of the invention is in a range from 0 to 120 parts per annum, preferably from 10 to 80 parts per annum, and even more preferably from 20 to 70 parts per annum.

[0113] The aforementioned inert fillers are indeed particularly interesting because they allow for the improvement of the impermeability of the compositions in which they are dispersed at an appropriate rate.

[0114] • Focus on lamellar mineral charges

[0115] Silicon-based lamellar mineral fillers are particularly suitable as inert fillers. In particular, phyllosilicates, especially those belonging to the group consisting of smectites, kaolin, talc, mica, and vermiculite, are suitable among silicon-based lamellar mineral fillers.

[0116] Among the phyllosilicates suitable for the invention are functionalized phyllosilicates, and in particular organo-modified phyllosilicates. According to a particular embodiment, the organic structure to which the inert filler is associated is a surfactant with the formula: -M+R c R d R e - , where M represents a nitrogen, sulfur, phosphorus, or pyridine atom and where R c , R d , and R e represents a hydrogen atom, an alkyl group, an aryl group, or an allyl group, R c, R d , and R e being identical or different.

[0117] In particular, organo-modified montmorillonites are suitable for the invention.

[0118] Thus, montmorillonites modified with a surfactant such as a quaternary ammonium salt dioctadecyldimethyl-dihydrogenated. Such an organo-modified montmorillonite is marketed notably by Southern Clay Products under the trade names "CLOISITE 6A" and "CLOISITE 20A".

[0119] Other surfactants based on quaternary ammonium salts can still be used to modify phyllosilicates as described in patent application W02006 / 047509-A2.

[0120] Reinforcing inorganic fillers such as alumina, titanium oxide or inert fillers such as kaolin can be used instead of silica.

[0121] II-3 Wax

[0122] Ozone-blocking waxes are well known to those in the trade. These waxes are used to combat the harmful effects of ozone, such as glazing and / or cracking, which typically occur on the surface of rubber articles.

[0123] For the purposes of the invention, the composition comprises 0.5 to 1.2 pieces of wax.

[0124] Any wax known to a person skilled in the art can be used.

[0125] Preferably, the waxes used are C28 to C38 waxes, more preferably C32 to C36 and even more preferably a blend of C32 to C36 waxes.

[0126] Such waxes are available from suppliers H&R or SASOL. For example, SASOL's C32 "Varazon 4959" wax and SASOL's C36 "Varazon 6810" wax can be used.

[0127] II-4 Antioxidant

[0128] As an antioxidant agent, the composition according to the invention comprises at least one compound of general formula I

[0129] in which:

[0130] RI, R4 and R5 are identical or different groups, chosen independently from each other from linear or branched alkyl groups,

[0131] R2 and R3 are identical or different groups, chosen independently from each other from linear or branched alkylene groups.

[0132] Advantageously, in formula (I), RI and R4 are identical groups, chosen from among linear alkyl groups,

[0133] R5 is chosen from among the linear alkyl groups,

[0134] R2 and R3 are identical groups selected from linear alkylene groups. Advantageously, R1 and R4 are selected from C4-C12 alkyl groups, preferably C6-C10, preferably C8; R5 is a C1-C4 alkyl group, preferably a methyl group; and R2 and R3 are selected from C1-C4 alkyl groups, preferably C1-C2; R2 and R3 are preferably methylenes (Cl). Advantageously, compound I is 4,6-bis(octylthiomethyl)-o-cresol (commercially known as Irganox 1520L), supplied, for example, by BASF.

[0135] Antioxidants are known to those skilled in the art to prevent or limit the aging of the composition attributable to the action of oxygen.

[0136] In the rubber composition according to the invention, preferably the proportion of compound I is in the range of 4 to 12 parts per annum, preferably 5 to 10 parts per annum.

[0137] The rubber composition according to the invention may further comprise another antioxidant agent. This antioxidant may be selected from the group consisting of substituted p-phenylenediamines, substituted diphenylamines, substituted triphenylamines, quinoline derivatives, antioxidant phenolic compounds, and mixtures thereof. More preferably, the antioxidant may be selected from the group consisting of substituted p-phenylenediamines and mixtures thereof.

[0138] However, advantageously, the composition according to the invention does not comprise substituted p-phenylenediamine (abbreviated "PPD" or "PPDA"), preferably the composition according to the invention does not comprise Nl,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (better known by the abbreviated term "6-PPD"), or when the composition comprises a substituted p-phenylenediamine (abbreviated "PPD" or "PPDA"), in particular Nl,3-dimethylbutyl-N'-phenyl-p-phenylenediamine, it comprises less than 1 pc.

[0139] Advantageously also, the composition according to the invention does not comprise 2,2,4-trimethyl-l,2-dihydroquinoline (TMQ) or comprises less than 1 pc.

[0140] II-5 Crosslinking System

[0141] The composition according to the invention comprises at least one crosslinking system.

[0142] The crosslinking system can be any type of system known to those skilled in the art in the field of tire rubber compounds. It may, in particular, be sulfur-based, and / or peroxide-based, and / or bismaleimide-based.

[0143] Preferably, the crosslinking system is sulfur-based; this is then referred to as a vulcanization system. Advantageously, the vulcanization system comprises molecular sulfur and / or at least one sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and optionally, various known vulcanization activators such as zinc oxide, stearic acid, or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or known vulcanization retarders may be used.

[0144] Sulfur is used at a preferential rate of between 0.3 and 12 parts per thousand (ppm), particularly between 0.3 and 10 ppm. The vulcanization accelerator is used at a preferential rate of between 0.3 and 10 ppm, more preferably between 0.3 and 5.0 ppm.

[0145] Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used as an accelerator, including thiazole-type accelerators and their derivatives, sulfenamide-type accelerators, thiurams, dithiocarbamates, dithiophosphates, thioureas and xanthates. Examples of such accelerators include the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-ter-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-ter-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0146] II-6 Plasticizing system The rubber composition according to the invention may preferably further comprise a plasticizing system, comprising a plasticizing resin having a glass transition temperature above 20°C, referred to as "high Tg", (also referred to as "plasticizing resin" in the present for the sake of simplification of drafting).

[0147] The term "resin" is reserved in this application, by definition known to those skilled in the art, for a compound which is solid at room temperature (23 °C), as opposed to a liquid plasticizing compound such as an oil.

[0148] Plasticizing resins are polymers well known to those skilled in the art, primarily carbon- and hydrogen-based but potentially containing other types of atoms. They are particularly useful as plasticizing or tackifying agents in polymer matrices. They are generally inherently miscible (i.e., compatible) with the polymer compositions for which they are intended, acting as true diluents. They were described, for example, in the book "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, particularly in pneumatic rubber (5.5. "Rubber Tires and Mechanical Goods"). They can be aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, of the aliphatic / aromatic type, i.e. based on aliphatic and / or aromatic monomers.They can be natural or synthetic, petroleum-based or not (if so, also known as petroleum resins). Their Tg is preferably above 20°C (most often between 30°C and 95°C).

[0149] These plasticizing resins are known to be thermoplastic resins because they soften upon heating and can therefore be molded. They can also be defined by their softening point or temperature. The softening temperature of a plasticizing resin is generally about 50 to 60°C higher than its Tg value. The softening point is measured according to ISO 4625 (Ring and Bail method). The macrostructure (Mw, Mn, and Ip) is determined by size exclusion chromatography (SEC) as described below.

[0150] As a reminder, SEC analysis, for example, involves separating macromolecules in solution according to their size using columns filled with a porous gel; the molecules are separated according to their hydrodynamic volume, with the largest being eluted first. The sample to be analyzed is simply pre-solubilized in a suitable solvent, tetrahydrofuran, at a concentration of 1 g / liter. The solution is then filtered through a 0.45 µm porosity filter before being injected into the instrument. The instrument used is, for example, a Waters Alliance chromatographic system under the following conditions:

[0151] - the elution solvent is tetrahydrofuran;

[0152] - temperature 35°C;

[0153] - concentration 1 g / litre;

[0154] - flow rate: 1 ml / min;

[0155] - injected volume: 100 pl;

[0156] - Moore calibration with polystyrene standards;

[0157] -set of 3 "Waters" columns in series ("Styragel HR4E", "Styragel HR1" and "Styragel HR 0.5");

[0158] - detection by differential refractometer (for example "WATERS 2410") which can be equipped with operating software (for example "Waters Millennium").

[0159] A Moore calibration is performed using a series of commercial polystyrene standards with a low Ip value (less than 1.2) and known molar masses, covering the range of masses to be analyzed. From the recorded data (mass distribution curve of molar masses), the mass average molar mass (Mw), the number average molar mass (Mn), and the polymolecularity index (Ip = Mw / Mn) are deduced.

[0160] All molar mass values ​​indicated in this application are therefore relative to calibration curves made with polystyrene standards.

[0161] The plasticizing resin may exhibit at least one, preferably two or three, and more preferably all of the following characteristics:

[0162] - a Tg greater than 25°C (in particular between 30°C and 100°C), more preferably greater than 30°C (in particular between 30°C and 95°C);

[0163] - a softening point above 50°C (in particular between 50°C and 150°C);

[0164] - an average number molar mass (Mn) between 300 and 2000 g / mol, preferably between 400 and 1500 g / mol;

[0165] - a polymolecularity index (Ip) less than 3, preferably 2 (reminder: Ip = Mw / Mn with Mw average molar mass by weight).

[0166] The above-mentioned preferred high Tg plasticizing resins are well known to those skilled in the art and are commercially available, for example, sold with regard to:

[0167] - 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);

[0168] - C5 / vinylaromatic copolymer resins, in particular C5 / styrene or C5 / C9: 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 Koi on under the names "Hikorez T1095" and "Hikorez T1100", by Exxon under the names "Escorez 2101" and "Escorez 1273";

[0169] - limonene / styrene copolymer resins: by DRT under the name "Dercolyte TS 105" of the DRT company, by ARIZONA Chemical Company under the names "ZT115LT" and "ZT5100".

[0170] The plasticizing resin having a glass transition temperature above 20°C may be selected from the group comprising or consisting of cyclopentadiene homopolymer or copolymer resins (abbreviated CPD), dicyclopentadiene homopolymer or copolymer resins (abbreviated DCPD), terpene homopolymer or copolymer resins, C5-cut homopolymer or copolymer resins, C9-cut homopolymer or copolymer resins, alpha-methyl-styrene homopolymer or copolymer resins and their mixtures. Preferably, the plasticizing resin is chosen from the group consisting of terpene homopolymer or copolymer resins, C5-cut homopolymer or copolymer resins or C9-cut homopolymer or copolymer resins, preferably the plasticizing resin is chosen from the group consisting of terpene homopolymer or copolymer resins.

[0171] The term "terpene" here includes the known monomers alpha-pinene, beta-pinene and limonene; preferentially, a limonene monomer is used, a compound known to exist in the form of three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or dipentene, a racemic of the dextrorotatory and levorotatory enantiomers. Suitable vinylaromatic monomers include, for example, styrene, alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyl-toluene, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene, and any vinylaromatic monomer derived from a C9 cut (or more generally from a Cs to C10 cut).

[0172] In particular, we can mention the plasticizing resins chosen from the group consisting of homopolymer (D)CPD resins, (D)CPD / styrene copolymer resins, polylimonene resins, limonene / styrene copolymer resins, limonene / D(CPD) copolymer resins, C5 / styrene copolymer resins, C5 / C9 copolymer resins, and mixtures of these resins.

[0173] All the above plasticizing resins are well known to those skilled in the art and are commercially available, for example sold by DRT under the name "Dercolyte" for polylimonene resins, by Neville Chemical Company under the name "Super Nevtac", by Kolon under the name "Hikorez" or by Exxon Mobil under the name "Escorez" for C5 / styrene cut resins or C5 / C9 cut resins, by Struktol under the name "40 MS" or "40 NS" (mixtures of aromatic and / or aliphatic resins), or by Kraton under the name "Sylvatraxx 8125", a polyterpene-based resin.

[0174] According to the invention, the proportion of the plasticizing resin having a glass transition temperature above 20°C in the composition according to the invention is within a range of 0% to 30% by weight, relative to the total weight of the rubber composition according to the invention. Preferably, this proportion is within a range of 15% to 25% by weight, and more preferably 18% to 22% by weight, relative to the total weight of the rubber composition.

[0175] The proportion of the plasticizing resin having a glass transition temperature above 20°C in the composition according to the invention can be in a range from 0 to 40 parts per cent, preferably from 11 to 30 parts per cent.

[0176] Although not necessary for the implementation of the present invention, the plasticizing system of the rubber composition according to the invention may include a liquid plasticizer at 23°C, referred to as a "low Tg" plasticizer, that is to say, one which by definition has a Tg below -20°C, preferably below -40°C. According to the invention, the composition may optionally comprise from 0 to 30 parts per cent of a liquid plasticizer at 23°C or from 0% to 20% by weight relative to the total weight of the composition according to the invention.

[0177] When a liquid plasticizer at 23°C is used, its concentration in the composition according to the invention can range from 4 to 20 parts per cent, or from 5% to 15% by weight relative to the total weight of the rubber composition according to the invention. Any liquid plasticizer at 23°C (or extending oil), whether aromatic or non-aromatic, known for its plasticizing properties with respect to diene elastomers, is suitable. At room temperature (23°C), these plasticizers or oils, with varying degrees of viscosity, are liquids (that is, substances capable of eventually taking the shape of their container), unlike plasticizing resins, which are solid at room temperature.

[0178] Particularly suitable are liquid plasticizers at 23°C selected from the group comprising or consisting of liquid diene polymers, polyolefinic oils, naphthenic oils, paraffinic oils, DAE oils, MES (Medium Extracted Solvates) oils, TDAE (Treated Distillate Aromatic Extracts) oils, RAE (Residual Aromatic Extract) oils, TRAE (Treated Residual Aromatic Extract) oils and SRAE (Safety Residual Aromatic Extract) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and their mixtures C.

[0179] II-7 Possible Additives

[0180] The rubber compositions according to the invention may optionally also include all or part of the usual additives commonly used in elastomer compositions for tires, pigments, other protective agents, anti-fatigue agents, reinforcing resins (such as described for example in application WO 02 / 10269).

[0181] II-8 Preparation of rubber compositions

[0182] The compositions according to the invention can be manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art:

[0183] - a first thermomechanical working or mixing phase (the so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents, including the elastomeric matrix, the reinforcing filler, and any other miscellaneous additives, with the exception of the crosslinking system, are introduced into a suitable mixer such as a standard internal mixer (for example, a "Banbury" type mixer). The incorporation of any telastomer filler can be carried out in one or more stages by thermomechanical mixing.If the filler is already fully or partially incorporated into Telastomer as a masterbatch, as described, for example, in applications WO 97 / 36724 or WO 99 / 16600, the masterbatch is mixed directly. If necessary, other elastomers or fillers present in the composition that are not in masterbatch form are then incorporated, along with any other miscellaneous additives other than the crosslinking system. The non-productive phase can be carried out at high temperature, up to a maximum temperature between 110°C and 200°C, preferably between 130°C and 185°C, for a duration generally between 2 and 10 minutes.

[0184] - a second mechanical working phase (the so-called "productive" phase), which can be carried out in an external mixer such as a roller mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 120°C, for example between 40°C and 100°C. The crosslinking system is then incorporated, and the whole is then mixed for a few minutes, for example between 5 and 15 min.

[0185] Such phases have been described for example in applications EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.

[0186] The resulting final composition is then calendered, for example, into a sheet or plate, particularly for laboratory characterization, or extruded (or co-extruded with another rubber compound) into a semi-finished product (or profile) of rubber usable, for example, as a tire tread, carcass ply, and / or sidewall. These products can then be used for tire manufacturing, according to techniques known to those skilled in the art.

[0187] The composition can be either in its raw state (before crosslinking or vulcanization), or in its cooked state (after crosslinking or vulcanization), and can be a semi-finished product that can be used in a tire.

[0188] The crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 130°C and 200°C, under pressure.

[0189] II-9 Rubber Article

[0190] The present invention also relates to a rubber article comprising at least one composition according to the invention. The rubber article may be selected from the group consisting of tires, tracks, conveyor belts, belts, and anti-vibration articles. Preferably, the rubber article is selected from the group consisting of tires and conveyor belts. Preferably, the rubber article is a tire.

[0191] In the present invention, the term "pneumatic" (in English, "tire") refers to a pneumatic or non-pneumatic tire. A pneumatic tire typically comprises two beads for contact with a rim, a crown consisting of at least one crown reinforcement and a tread, and two sidewalls. The tire is reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic tire typically comprises a base, designed, for example, for mounting on a rigid rim, a crown reinforcement connecting to a tread, and a deformable structure, such as spokes, ribs, or dimples, this structure being positioned between the base and the crown. Such non-pneumatic tires do not necessarily include sidewalls. Non-pneumatic tires are described, for example, in documents WO 03 / 018332 and FR2898077.According to any one of the embodiments of the invention, the tire according to the invention is preferably a pneumatic tire.

[0192] It is possible to define three types of zones within the tire:

[0193] • The radially outer area in contact with the ambient air, this area being essentially made up of the tread and the outer sidewall of the tire. An outer sidewall is an elastomeric layer positioned 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.

[0194] • The radially inner area in contact with the inflation gas, this area generally being made up of the layer that is airtight to the inflation gas, sometimes called the inner rubber (“inner liner” in English).

[0195] • The inner zone of the tire, that is, the area between the outer and inner zones. This zone includes layers or plies which are referred to here as the inner layers of the tire. These are, for example, carcass plies, tread sub-layers, tire belt plies, or any other layer that is not in contact with the ambient air or the tire inflation gas.

[0196] More specifically, the invention also relates to a tire having a tread, a carcass ply, and / or an outer sidewall comprising a composition according to the invention. The composition according to the invention may constitute part or all of the tread, the carcass ply, and / or the outer sidewall of the tire.

[0197] The tire according to the invention can be intended to equip any type of vehicle, in particular bicycles, without any particular limitation.

[0198] III- EXAMPLES

[0199] III- 1 Measurements and tests used The performance of the invention is evaluated by measurements under dynamic stress (continuous cyclic tensile stress), under static elongation (stress with imposed deformation) and in efflorescence.

[0200] III-1. Static ozone resistance measurements

[0201] The ozone resistance of materials is measured using the trapezoidal stress test, where cracking is determined after the sample is stretched under static conditions. Samples subjected to stress are more likely to crack. After firing, three specimens are placed on the support at different elongations: 10%, 20%, and 30%. The B15 specimens are made from an MFTR plate (known as Monsanto), the two ridges at the ends of which serve to hold the specimen in place. The B15 specimens have the following dimensions: 75.8 mm x 15 mm x 1.5 mm. After 24, 48, and 72 hours of exposure to a temperature of 38°C and an ozone concentration of 50 ppm (parts per hundred million), each surface is recorded based on the number and depth of the cracks. This subjective rating ranges from 0 to 5 (0: no cracks; 1 to 4: presence of increasingly large and deep cracks; 5: breakage of the specimen).The average of the scores for all deformations is used as the classification criterion. The lower the average, the better the ozone performance under static loading.

[0202] III-L2 Dynamic Ozone Resistance Measurements

[0203] The ozone resistance of materials under dynamic stress is tested according to ASTM D3395. After baking and stabilization for at least 24 hours at 23°C and 50% relative humidity, the specimens are subjected to elongation varying periodically from 0 to 25% at a frequency of 0.5 Hz under an ozone concentration of 50 ppm (parts per hundred million) at 38°C for 48 hours. The dimensions of each sample are 145 mm x 20 mm x 2.5 mm instead of the 100 mm x 10 mm dimensions specified in ASTM D3395. After 48 hours of exposure, each surface is rated according to the number and depth of cracks. This subjective rating ranges from 0 to 10 (0: no cracks; 1 to 10: presence of increasingly large and deep cracks). The lower the value, the better the ozone performance under dynamic stress.

[0204] III-L3 Efflorescence Measurements

[0205] After cutting the baked mixture plates, the 2.5 mm thick test specimens are cured at 70°C for 12 hours in air. They are then cured at 40°C in air for 4 weeks. After removal from the curing oven and exposure to room temperature for 15 minutes, two successive mechanical stimuli are applied to reveal wax efflorescence. In this case, the first mechanical stimulus consists of scraping the specimen with a metal blade. The second mechanical stimulus consists of elongating the specimen to 100% of its deformation. The extent of the efflorescence (white discoloration of the surface) is then assessed using a subjective scale that represents the final appearance of the samples. The values ​​on this subjective scale obtained for the tested samples range from 0 to 3 and correspond to the "efflorescence rating."These values ​​ranging from 0 to 3 correspond to the following aspects for the samples:

[0206] 0 - No efflorescence. The scraped surface remains black

[0207] 1 - Slight efflorescence.

[0208] 2 - Moderate efflorescence.

[0209] 3 - Total efflorescence. The scraped surface is white.

[0210] The lower the value, the better the aspect of performance in efflorescence, i.e., low efflorescence.

[0211] III-2 Preparation of compositions

[0212] In the following examples, the rubber compounds were prepared as described in section II.8 above. Specifically, the "non-productive" phase was carried out in a 0.4-liter mixer for 3.5 minutes, at an average paddle speed of 50 rpm, until a maximum drop temperature of 160°C was reached. The "productive" phase was carried out in a roller tool at 23°C for 5 minutes.

[0213] The crosslinking of the composition was carried out at a temperature between 130°C and 200°C, under pressure.

[0214] III-3 Tests of Rubber Compositions

[0215] The examples presented below are intended to compare the performance trade-off between static ozone, dynamic ozone and blooming of two compositions according to the present invention (E1 to E2) with four control compositions (T1 to T4).

[0216] Table 1 presents the compositions tested (in pieces), as well as the results obtained.

[0217] [Table 1]

[0218] (1) Natural rubber

[0219] (2) Neodymium polybutadiene 98% 1,4 cis - Tg = -108°C

[0220] (3) SBR 4602 from Synthos

[0221] (4) Silica (Ultrasil VN 3 GR, from the company Evonik (CT AB: 170 m 2 / g)) (5) Silane (Si 69 liquid silane from the Evonik company)

[0222] (6) Paraffin oil (Flexon 847, from ExxonMobil)

[0223] (7) Irganox 1520L from BASF

[0224] (8) Wax (1:1 mixture of C32 and C36 wax, “Varazon 4959” from SASOL, “Varazon 6810” from SASOL)

[0225] The results presented in Table 1 above show that, surprisingly, the performance in resistance to static ozone, dynamic ozone and efflorescence of the compositions El and E2, according to the invention, are much better compared to the controls, not according to the invention.

Claims

Demands 1. Rubber composition based on at least: a. a diene elastomer b. a reinforcing filler comprising silica c. 0.5 to 1.2 parts per liter of wax d. a crosslinking system e. a compound of general formula I in which: RI, R4 and R5 are identical or different groups, chosen independently from each other from linear or branched alkyl groups, R2 and R3 are identical or different groups, chosen independently from each other from linear or branched alkylene groups characterized in that the composition includes a substituted p-phenylenediamine, in particular N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine, it includes less than 1 pc.

2. Rubber composition according to claim 1, wherein RI and R4 are identical groups, chosen from among linear alkyl groups, R5 is chosen from among the linear alkyl groups, R2 and R3 are identical groups chosen from linear alkylene groups.

3. Rubber composition according to any one of claims 1 or 2, wherein RI and R4 are selected from C4-C12 alkyls preferably Ce-Cio, preferably Cs, R5 is a C1-C4 alkyl group and preferably R5 is a methyl, and R2 and R3 are selected from C1-C4 alkylenes preferably C1-C2, preferably R2 and R3 are methylenes.

4. Rubber composition according to any one of the preceding claims, wherein compound I is 4,6-bis(octylthiomethyl)-o-cresol.

5. Rubber composition according to any one of the preceding claims, wherein the content of compound I is in the range of 4 to 12 parts per annum, preferably 5 to 10 parts per annum.

6. A rubber composition according to any one of the preceding claims, wherein the composition does not comprise substituted p-phenylenediamine, preferably the composition according to the invention does not comprise N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine 7. Rubber composition according to any one of the preceding claims, wherein the composition does not comprise 2,2,4-trimethyl-1,2-dihydroquinoline or comprises less than 1 pc.

8. Rubber composition according to any one of the preceding claims, wherein the reinforcing filler comprises predominantly silica.

9. Rubber composition according to any one of the preceding claims, wherein the silica content is in the range of 30 to 140, preferably 30 to 120 pc, more preferably in the range of 35 to 110 pc.

10. Rubber composition according to any one of the preceding claims, wherein the reinforcing filler comprises less than 10 pc of carbon black, preferably less than 5 pc, more preferably less than 1 pc and more preferably the rubber composition does not comprise carbon black.

11. Rubber composition according to any one of the preceding claims, further comprising a plasticizing resin.

12. Rubber composition according to any one of the preceding claims, wherein the diene elastomer is selected from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, ethylene-diene-monomer rubber (EPDM) and mixtures of these elastomers; preferably the butadiene copolymers are selected from the group consisting of butadiene-styrene copolymers (SBR).

13. Rubber composition according to the preceding claim, wherein the percentage of butadiene-styrene copolymer (SBR) is in the range of 0 to 100 parts per annum, the percentage of polybutadiene (BR) is in the range of 0 to 50 parts per annum, the percentage of natural rubber (NR) is in the range of 0 to 100 parts per annum, the percentage of ethylene-diene-monomer rubber (EPDM) is in the range of 0 to 45 parts per annum.

14. Rubber composition according to the preceding claim, wherein the percentage of butadiene-styrene copolymer (SBR) is in the range of 40 to 60 parts per cent, and the percentage of polybutadiene (BR) is in the range of 30 to 50 pc, the natural rubber (NR) content is in a range of 5 to 15 pc.

15. Tire comprising a composition according to any one of claims 1 to 13, preferably in its tread, its carcass ply and / or its outer sidewall.

16. Tire according to the preceding claim, characterized in that it is a bicycle tire.

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