A tire comprising a sidewall with at least one high-contrast sidewall element

Abstract

The present invention relates to a tire (1) for a vehicle, comprising at least one sidewall (2) with at least one high-contrast sidewall element (3) consisting of a texture having a first brightness L*1 of at least 1 and at most 15, any adjacent portion of sidewall surface (21) having a second brightness L*2 of at least L*1+5. The invention describes a sidewall rubber composition (2) exhibiting a good compromise between tear resistance and rolling resistance. According to the invention, the weight ratio between the reinforcing filler and the plasticizing agent is at most 4.50, the sum of the reinforcing filler and the rubber powder content is at least 30 parts per million and at most 70 parts per million, and the weight ratio between the rubber powder content and the reinforcing filler is at least 0.20 and at most 2.50. Figure for the summary: Fig.1

Description

Title of the invention: Tire comprising a sidewall with at least one high-contrast sidewall element

[0001] The present invention relates to a tire for a vehicle, comprising a sidewall with at least one high-contrast sidewall element.

[0002] A tire comprises two sidewalls, one sidewall being the portion of the tire connecting one end of the tread, intended to come into contact with a ground, to a bead, intended to be mounted on a rim.

[0003] In what follows, the external surface of a side panel, in contact with the atmosphere, is referred to, more simply, as the "side panel surface." A side panel surface generally includes at least one graphic element and / or, possibly, an aesthetic element. A graphic element, usually called a marking and comprising letters, numbers, or symbols, is generally intended to communicate technical, commercial, or legal information.

[0004] By definition, a high-contrast side element refers to a side surface element consisting of a specific texture different from that of the most often smooth side surface. This texture gives said high-contrast side element a darker appearance than that of any adjacent side surface portion, such that this high-contrast side element can be visually distinguished from any adjacent side surface portion. A high-contrast side element may consist of either a graphic or aesthetic element, or a portion of the side surface surrounding said graphic or aesthetic element, which makes said graphic or aesthetic element particularly visible on the side surface.

[0005] Thus, whether for the enhancement of graphic elements or aesthetic elements of sidewall surface, there is a constant concern among tire designers to produce sidewall elements with high contrast.

[0006] The contrast between a high-contrast flank element and a portion of flank surface adjacent to said high-contrast flank element is due to a difference in brightness between the two areas. An adjacent surface portion, which may be smooth or have a different texture, has a higher brightness than the texture of said high-contrast flank element; that is, it appears visually brighter. This texture is made of a rubbery material, also called a rubber compound or elastomeric compound, identical to that of the portion of flank in contact with atmospheric air, since this texture is made of the same material as the flank.

[0007] Brightness can be quantified by luminous luminance, expressed in candelas / m², which measures the luminous flux from an illuminated surface that is reflected into the observer's eye. However, the relationship between luminous luminance and the visual perception of brightness is not linear and is complex. Therefore, for practical purposes, the International Commission on Illumination (CIE) defined the luminous intensity L*, a parameter that characterizes the ability of a surface to reflect light, based on the luminous intensity of light produced by a primary or secondary source, expressed in candelas per square meter (cd / m²), relative to the luminous intensity of white taken as a reference. Thus, in what follows, the luminous intensity L* is expressed on a scale from 0 to 100 in accordance with the L*a*b* colorimetric model adopted in 1976 by the International Commission on Illumination.The value 100 represents white or total reflection, and the value 0 represents black or total absorption.

[0008] To calculate the difference between a first brightness L*1 of the texture of a high-contrast flank element and a second brightness L*2 of an adjacent flank surface portion, the first brightness L*1 and the second brightness L*2 must be measured respectively using a spectrophotometer, for example, a KONICA-MINOLTA CM 700D spectrophotometer. To measure the first brightness L*1 of the texture, the spectrophotometer is positioned on the texture and this measurement is performed with the SCI mode (including specular reflection mode) set to an angle of 8° and with a light setting of type D65 (setting defined according to CIE). Similarly, to measure the second brightness L*2 of an adjacent flank surface portion, the spectrophotometer is positioned on said flank surface portion.To improve the determination of this second brightness L*2, it is possible to perform a plurality of brightness measurements on several adjacent flank surface portions, and then deduce an associated average brightness.

[0009] High-contrast flank elements, having a brightness difference substantially less than that of an adjacent flank surface portion, were described in documents WO 2016005572 A1 and WO 2011036061 A1 and WO 20174919 A1

[0010] It has been observed, on tire sidewall surfaces comprising high contrast sidewall elements, that there is an evolution over time in the visual appearance of the texture of said high contrast sidewall elements, which may in particular result from the appearance of cracks or micro-cracks, related both to the conditions of use of the tire and the aging of the material.

[0011] It is therefore necessary, in order to obtain a sidewall element with high and lasting contrast throughout the life of the tire, to be able to reduce these cracks, or at least It delays the onset of cracking, but with a limited impact on the hysteresis of the sidewall material, and therefore on the tire's rolling resistance. It is indeed known that crack resistance (or tearability) and the hysteresis of a rubber compound are linked.

[0012] Increasing the durability of a high-contrast sidewall element is indeed a significant commercial challenge for a tire manufacturer. For example, when a user replaces only the tires mounted on the front of their vehicle, they may notice a significant difference in appearance between the new front tires and the worn rear tires. This difference in appearance between the front and rear tires may be considered unacceptable by the user, especially if their vehicle is a sports or luxury vehicle.

[0013] The inventors have therefore set themselves the objective, for a tire comprising a sidewall with at least one high-contrast sidewall element, of increasing the durability of the visual appearance of said high-contrast sidewall element, using a suitable rubber composition for the sidewall, particularly near the sidewall surface, presenting a satisfactory compromise between tear resistance and hysteresis.

[0014] This objective has been achieved by a tire for a vehicle, comprising a sidewall with at least one high-contrast sidewall element: -the high-contrast flank element being made up of a texture having a first luminance L*1 of at least 1 and at most 15, -any portion of flank surface adjacent to the high-contrast flank element, having a second brightness L*2 at least equal to L*l+5, -the sidewall comprising a rubber composition based on an elastomeric matrix, at least one reinforcing filler, at least one crosslinking system, at least one plasticizing agent and at least one rubber powder, -the weight ratio between the rate of reinforcing filler, expressed in parts per annum, and the rate of plasticizing agent, expressed in parts per annum, being at most equal to 4.50, -the sum of the rate of reinforcing filler, expressed in pc, and the rate of rubber powder, expressed in pc, being at least equal to 30 pc and at most equal to 70 pc, -and the weight ratio between the rate of rubber powder, expressed in pc, and the rate of reinforcing filler, expressed in pc, being at least equal to 0.20 and at most equal to 2.50.

[0015] According to the invention, the high contrast flank element consists of a texture having a first brightness L*1 of at least 1 and at most 15.

[0016] The lower the brightness of the high-contrast sidewall element when the tire is new, the greater the contrast for a given brightness of a The higher the initial brightness (L*1) of the sidewall texture, the more significant this contrast will remain over time on the aging tire. Indeed, over time, this initial brightness (L*1) of the high-contrast sidewall element's texture tends to increase due to factors such as dust, dirt, and material aging. Furthermore, within this brightness range, there is good contrast with any adjacent sidewall surface, which, in typical tire designs, most often has a brightness between 24 and 28. It should be noted that a texture with an initial brightness (L*1), typically at least equal to 9, is easier to produce, but the contrast is lower.

[0017] According to the invention, any portion of flank surface adjacent to the high contrast flank element has a second brightness L*2 at least equal to L*l+5.

[0018] The greater the difference in brightness between the high-contrast sidewall element and any adjacent sidewall surface area, the greater the contrast. The greater this difference in brightness is on a new tire, the more significant it will remain over time on an aging tire.

[0019] According to the invention, the sidewall comprises a rubber composition based on an elastomer matrix, at least one reinforcing filler, at least one crosslinking system, at least one plasticizing agent, and at least one rubber powder.

[0020] The expression "rubber composition based on" means a rubber composition comprising the mixture and / or the in situ reaction product of the different constituents used, some of these constituents being able to react and / or intended to react with each other, at least partially, during the different phases of manufacturing the rubber composition, the rubber composition thus being able to be in a totally or partially crosslinked state or in a non-crosslinked state.

[0021] A rubber composition comprises at least one and often several elastomers, in particular several diene elastomers. This mixture of elastomers, particularly diene elastomers, is called an elastomeric matrix. Preferably, the elastomeric matrix comprises at least two different diene elastomers.

[0022] The term "elastomer" means a polymer, that is, a homopolymer or a copolymer, exhibiting elastic properties obtained after cross-linking. The term rubber is a common synonym for elastomer.

[0023] The term "diene elastomer" or, interchangeably, "diene rubber," whether natural or synthetic, refers to an elastomer composed at least in part of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not). Diene elastomers are non-thermoplastic.

[0024] Diene elastomers can be classified into two categories: "essentially unsaturated" diene elastomers and " "Essentially saturated." A "simply unsaturated" diene elastomer is 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, in particular, as "simply saturated" diene elastomers (low or very low proportion of diene-derived motifs, always less than 15%).

[0025] The term diene elastomer suitable for use in rubber compositions according to the invention is particularly understood to mean: 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; the other being ethylene, an olefin or a diene, conjugated or not.

[0026] Suitable conjugated dienes are conjugated dienes having 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and T isoprene.

[0027] Suitable as unconjugated dienes are unconjugated dienes having 6 to 12 carbon atoms, such as 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene.

[0028] Suitable olefins are vinylaromatic compounds having 8 to 20 carbon atoms and aliphatic α-monoolefins having 3 to 12 carbon atoms.

[0029] Suitable examples of vinylaromatic compounds include styrene, ortho-, meta-, para-methylstyrene, the commercial "vinyl-toluene" mixture, para-tert-butylstyrene.

[0030] As aliphatic α-monoolefins, acyclic aliphatic α-monoolefins having from 3 to 18 carbon atoms are particularly suitable.

[0031] More specifically, diene telatomer is: 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; b. Any copolymer obtained by copolymerization of one or more dienes conjugated together or with one or more vinylaromatic compounds having 8 to 20 carbon atoms; 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, for example, elastomers obtained from ethylene, propylene with an unconjugated diene monomer of the aforementioned type.

[0032] A reinforcing filler, intended to strengthen a rubber composition, can be an organic filler such as carbon black, or an inorganic filler such as silica or alumina in combination with a coupling agent between the inorganic filler and the diene elastomer, or even a mixture of these types of fillers.

[0033] The crosslinking system can be any type of system known to those skilled in the art in the field of tire rubber compounds. It can, in particular, be sulfur-based, and / or peroxide-based, and / or bismaleimide-based. Preferably, the crosslinking system is sulfur-based: this is then referred to as a vulcanization system. The sulfur can be supplied in any form, in particular as molecular sulfur, or as a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally and also preferably, various known vulcanization activators can be used, such as zinc oxide, stearic acid, or an equivalent compound such as stearic acid salts and transition metal salts, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retardants.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.

[0034] A plasticizing agent is a common processing agent, known to those skilled in the art and usually used in rubber compositions. A plasticizing agent may be selected from the group consisting of plasticizing oils, high-temperature glass transition (Tg) plasticizing resins, and combinations thereof.

[0035] Any extending oil, whether aromatic or non-aromatic, known for its plasticizing properties with respect to elastomers, is suitable. At room temperature (23°C), these oils, which vary in viscosity, are liquids (that is, substances capable of eventually taking the shape of their container), unlike, in particular, high-Tg hydrocarbon resins, which are solid at room temperature. The plasticizing oil generally has a glass transition temperature (Tg) below -20°C, preferably below -40°C. The glass transition temperature (Tg) of the plasticizing oil is measured according to ASTM D3418 (2008).

[0036] By definition, a hydrocarbon resin with a high Tg, typically at least equal to 30°C, is solid at ambient temperature and pressure (23°C, 1 atm), while a Plasticizing oil is liquid at room temperature, while a low-Tg hydrocarbon resin is viscous at room temperature. Hydrocarbon resins, also called hydrocarbon plasticizing resins, are polymers well known to those skilled in the art, primarily carbon- and hydrogen-based but potentially containing other types of atoms, such as oxygen. They are particularly useful as plasticizing or tackifying agents in polymer matrices. By nature, they are at least partially miscible (i.e., compatible) at the ratios used with the polymer compositions for which they are intended, so as to act as true diluents. It is well known that these hydrocarbon resins can also be described as thermoplastic resins in that they soften upon heating and can thus be molded.The glass transition temperature Tg of the plasticizing resin is measured according to ASTM D3418 (2008).

[0037] A rubber composition, particularly in contact with atmospheric air, such as a tire sidewall rubber composition, may also contain anti-ozone waxes, such as, for example, paraffinic waxes, microcrystalline waxes or mixtures of paraffinic and microcrystalline waxes.

[0038] These waxes consist of a mixture of linear and non-linear alkanes (isoalkanes, cycloalkanes, branched alkanes) obtained from petroleum refining or the catalytic hydrogenation of carbon monoxide (Fisher-Tropsch process), predominantly comprising chains of at least 20 carbon atoms. The alkane distribution is determined by gas chromatography coupled with a flame ionization detector (GC-FID). The chromatogram is analyzed according to the EWF (European Wax Federation) method.

[0039] All known ozone-blocking waxes can be used, including natural waxes such as, for example, candelilla wax or carnauba wax. These waxes can also be used in cutting processes.

[0040] Anti-ozone waxes are commercially available such as, by way of example, “Varazon 4959”, “Varazon 6500” and “Varazon 6810” from Sasol, “Ozoace 0355” from Nippon Seiro, “Negozone 9343” from H&R and “H3841” from Yanggu Huatai.

[0041] In the invention, the rubber composition comprises, in addition to the elastomer matrix, a rubber powder (also called "crumb rubber" in English) which is in the form of granules, possibly in the form of a rubber sheet, and which is a recycled product.

[0042] Most often these rubber powders are obtained from grinding or micronizing vulcanized rubber compositions already used for a Their first application, for example, is in tires, shoe soles, and seals. They are therefore a recycled product of these materials.

[0043] In a known manner, rubber powders can be obtained more particularly by reducing used tires into granules from which reinforcing materials such as steels or textile fibers have been removed.

[0044] Rubber powders can be prepared by cryogenic grinding of used tires, for example according to the process described in US patent 7,445,170, comprising successive and independent steps of granulation, separation of metal and textile reinforcements, cooling, and micronization to obtain a coarse distribution of micron-sized particles of vulcanized compound (also called microparticles). This micronization can be carried out using a conical impact mill as described in US patent 7,861,958. The cryogenically cooled incoming material enters the mill (for example, the Netzsch CUM150 or Alpine CW250 mills can be used), and is then transferred by gravity to a high-speed rotating rotor. The cryogenically cooled incoming material is thus repeatedly projected against the walls of the rotor chamber, leading to its micronization.The particles can then pass through a series of two vibrating sieves of the same size to separate any remaining non-vulcanized mixture elements. This yields a crude distribution of micron-sized vulcanized mixture particles. "Microparticles" are defined as particles with a size—namely their diameter in the case of spherical particles, or their largest dimension in the case of anisometric particles—of a few tens or hundreds of microns. The size of microparticles can be determined using techniques known to those skilled in the art, such as microscopy. Rubber powders are commercially available from suppliers such as Lehigh Technology.

[0045] Rubber powders can be simple rubber granules or micronized materials, without further processing. However, it is also known that rubber powders can undergo processing to modify them. This processing can consist of chemical modification through functionalization or devulcanization. It can also involve thermomechanical, thermochemical, or biological treatment.

[0046] According to a first essential feature of the invention, the weight ratio between the rate of reinforcing filler, expressed in pc, and the rate of plasticizing agent, expressed in pc, is at most equal to 4.50.

[0047] According to a second essential feature of the invention, the sum of the reinforcing filler rate, expressed in pc, and the rubber powder rate, expressed in pc, is at least equal to 30 pc and at most equal to 70 pc.

[0048] According to a third essential feature of the invention, the weight ratio between the percentage of rubber powder, expressed in pc, and the percentage of reinforcing filler, expressed in pc, is at least equal to 0.20 and at most equal to 2.50.

[0049] The proportions of the various constituents are expressed in "parts per hundred" (ph). The unit "parts per hundred" or "parts per hundred of elastomer" represents the mass part per hundred mass parts of elastomer or rubber. In English, this unit is translated as "phr" ("parts per hundred of rubber"). The elastomers in the rubber powder are excluded from the mass of elastomer being considered.

[0050] The combination of these essential characteristics of the rubber composition gives the sidewall, and in particular any high contrast sidewall element, satisfactory tear resistance, combined with low hysteresis contributing to low rolling resistance of the tire.

[0051] Advantageously the weight ratio between the rate of reinforcing filler, expressed in pc, and the rate of plasticizing agent, expressed in pc, is at least equal to 1.50, preferably at least equal to 2.00 and at most equal to 4.00, and more preferably at least equal to 2.00 and at most equal to 3.50.

[0052] Also advantageously the sum of the reinforcing filler rate, expressed in pc, and the rubber powder rate, expressed in pc, is at least equal to 35 pc and at most equal to 65 pc, preferably at least equal to 35 pc and at most equal to 63 pc, and more preferably at least equal to 40 pc and at most equal to 63 pc.

[0053] Even more advantageously, the weight ratio between the percentage of rubber powder, expressed in pc, and the percentage of reinforcing filler, expressed in pc, is at least equal to 0.25 and at most equal to 1.50.

[0054] Preferably the reinforcing load ratio is at least equal to 5 pc and at most equal to 70 pc, preferably at least equal to 5 pc and at most equal to 60 pc, more preferably at least equal to 5 pc and at most equal to 55 pc, even more preferably at least equal to 10 pc and at most equal to 50 pc, and even more preferably at least equal to 20 pc and at most equal to 45 pc.

[0055] More preferably the reinforcing filler comprises mainly carbon black.

[0056] When reference is made to a "major" compound, this means, for the purposes of the present invention, that this compound is the majority among the compounds of the same type in the composition; that is to say, it is the one that represents the greatest quantity by weight among the compounds of the same type, and preferably more than 50% by weight, more preferably more than 75% by weight. Thus, a "major" filler is the one that represents the greatest weight among the fillers in the composition.

[0057] Preferably the plasticizing agent rate is at least equal to 2 pc and at most equal to 28 pc, preferably at least equal to 7 pc and at most equal to 24 pc, and more preferably at least equal to 10 pc and at most equal to 20 pc.

[0058] More preferably Pau at least one plasticizing agent is chosen from the group consisting of plasticizing oils, high Tg plasticizing resins, and their combinations.

[0059] Even more preferably the plasticizing agent is a plasticizing oil selected from the group consisting of naphthenic oils, paraffinic oils, naphthenic oils, DAE oils, polyolefinic oils, MES oils, TDAE oils, RAE oils, TRAE oils, SRAE oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these oils, more preferably is an oil selected from the group consisting of MES oils, TDAE oils, RAE oils, TRAE oils, SRAE oils, mineral oils, vegetable oils and mixtures of these plasticizing oils.

[0060] Preferably the elastomer matrix comprises at least one isoprene elastomer and at least one butadien elastomer.

[0061] The term "isoprene elastomer" is commonly understood to mean a homopolymer or copolymer of isoprene. In other words, an isoprene elastomer may be 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) copolymers. Preferably, an isoprene elastomer may be selected from the group consisting of natural rubber, synthetic cis-1,4 polyisoprenes, and combinations thereof.Even more preferably, the isoprene elastomer is chosen from the group consisting of natural rubber, synthetic polyisoprenes having a molar percentage of cis-1,4 bonds greater than 90% (even more preferably greater than 98%), and combinations of these elastomers.

[0062] The term "butadiene elastomer" is commonly understood to mean a homopolymer or copolymer of butadiene. In other words, a butadiene elastomer can be selected from the group consisting of polybutadienes (BR), various butadiene copolymers, and mixtures of these elastomers. Among the butadiene copolymers, butadiene-styrene (SBR) and ethylene-butadiene (EBR) copolymers are particularly noteworthy. Preferably, the butadiene elastomer can be a cis-1,4 polybutadiene; in particular, a polybutadiene having a cis-1,4 bonding percentage (molar %) greater than 90%, and even more preferably greater than 96%.

[0063] More preferably the elastomer matrix comprises at least one isoprene elastomer at a rate of at least 20% and at most 80%, preferably at least 30% and at most 70%, more preferably at least 35% and at most 65%, and at least one butadiene elastomer at a rate of at least 20% and at most 80%, preferably at least 30% and at most 70%, more preferably at least 35% and at most 65%.

[0064] Preferably the percentage of rubber powder is at least equal to 2 pc and at most equal to 35 pc, preferably at least equal to 5 pc and at most equal to 33 pc, more preferably at least equal to 6 pc and at most equal to 32 pc, even more preferably at least equal to 7 pc and at most equal to 31 pc, and even more preferably at least equal to 8 pc and at most equal to 30 pc.

[0065] It should be noted that, for the purposes of the present invention, the rubber powder is not considered a reinforcing filler. Consequently, the proportion of rubber powder is not included in the proportion of the reinforcing filler.

[0066] Advantageously, the rubber powder has a microparticle size distribution such that it comprises less than 1% by mass of particles not retained through a 600 µm sieve and less than 10% by mass of microparticles not retained through a 105 µm sieve, relative to the total mass of the rubber powder microparticles. Preferably, the rubber powder has a microparticle size distribution such that it comprises less than 1% by mass of microparticles not retained through a 600 µm sieve and less than 10% by mass of microparticles not retained through a 177 µm sieve, relative to the total mass of the rubber powder microparticles. The distribution of the rubber powder microparticles is determined according to ASTM D5644-01 (2013).

[0067] To obtain such a rubber powder exhibiting such distributions, an additional sieving step based on a size criterion was performed. Sieving can be carried out using various technologies (vibration, centrifugation, aspiration) known to those skilled in the art. Preferably, this sieving step is performed using a series of sieves stacked in order of size (sieves with calibrated mesh sizes, such as the commercial products from Gericke, for example). Thus, the largest particles are retained on the sieve while the smaller ones pass to the next lower sieve. Those skilled in the art will understand that the distributions considered hereafter can be composed of all the particles passing through a given sieve or of all the particles retained between two sieves.

[0068] Preferably the rubber powder has a microparticle size distribution such that it comprises less than 1% by mass of microparticles not retained through a 250 pm sieve and less than 10% by mass of microparticles not retained through a 177 pm sieve, relative to the total mass of rubber powder microparticles.

[0069] Advantageously, the rubber powder is a rubber powder that has not undergone any modification by a treatment chosen from the group consisting of thermal, mechanical, biological and chemical treatments and their combinations.

[0070] The rubber composition described above, with all its embodiments, is, in particular, the constituent material of the high contrast sidewall element, made of material with the sidewall and consisting of a texture having a first brightness L*1 at least equal to 1 and at most equal to 15, any portion of sidewall surface adjacent to the high contrast sidewall element, having a second brightness L*2 at least equal to L*1+5.

[0071] Advantageously the high contrast flank element is made up of a texture having a first brightness L*1 of at least 4 and at most 13.

[0072] Also advantageously any portion of flank surface adjacent to the high contrast flank element has a second brightness L*2 at least equal to L*l+10, preferably at least equal to L*l+12.

[0073] Advantageously, any portion of flank surface adjacent to the high-contrast flank element has a second brightness L*2 of at least 18, preferably at least 22.

[0074] According to a first and second preferred embodiment, the high contrast flank element consists of a texture comprising protuberances, raised in relation to a flank surface, in contact with atmospheric air, and / or cavities, recessed in relation to the flank surface.

[0075] According to a first variant of the first preferred embodiment, the high-contrast flank element consists of a texture comprising strand-shaped protuberances.

[0076] According to a second variant of the first preferred embodiment, the high-contrast flank element consists of a texture comprising blade-shaped protuberances.

[0077] The texture of a high-contrast sidewall element, according to the first and second preferred embodiments, is most often produced by molding during the tire curing process. The corresponding mold element, intended to produce the texture of the high-contrast sidewall element, is manufactured, by way of non-exhaustive examples, by machining or laser engraving. The texture of a high-contrast sidewall element This can also be achieved directly on the tire sidewall surface after curing, for example by laser engraving. The texture is therefore made of the same material as the rest of the sidewall.

[0078] The texture of the high-contrast side elements, comprising strand- or blade-shaped protrusions, absorbs a large portion of the incident light rays after one or more successive reflections off the walls of the protrusions. This gives the texture a darker appearance and, consequently, improves its contrast and therefore its visibility compared to any adjacent portion of the side surface. Furthermore, this particular texture provides a pleasant, velvety feel to the side surface. Finally, the texture has a water-repellent and slightly hydrophobic effect. In a particular embodiment, the texture can be positioned on a surface recessed from the side surface, so that it is embedded in the side, which has the advantage of protecting it, for example, against wear caused by the side surface rubbing against a curb.

[0079] Similarly, the texture of the high-contrast sidewall elements, comprising recesses relative to the sidewall surface, allows for the absorption of a large portion of the incident light rays after one or more successive reflections off the cavity walls. This specific texture has the advantage of being recessed relative to the sidewall surface, which ensures the durability of said texture by protecting it against wear caused by the sidewall surface rubbing against a curb. It also has the advantage of not disrupting the aerodynamic airflow near the sidewall surface during tire rolling.

[0080] The rubber composition described within the scope of the present invention is illustrated by the following non-limiting examples.

[0081] In order to confirm the properties of the rubber composition of the present invention, eleven rubber compositions (C1, C2, C3, C4, C5 and C6: examples according to the invention, T1: reference, and T2, T3, T4 and T5: comparative examples) were used. Each of the formulations of the rubber compositions is presented in Table 1 with the quantities of the various ingredients expressed in parts per kilogram (pwc).

[0082] Each rubber composition was produced as follows: the reinforcing filler, the elastomer matrix, the rubber powder, the plasticizing agent, and various other ingredients such as the ozone-blocking wax, with the exception of the vulcanizing system, were successively introduced into an internal mixer with an initial tank temperature of 60°C, the Banbury-type internal mixer being filled to approximately 70% of its volume. The thermomechanical work (non-productive phase) was then carried out in a single step lasting 3 to 4 minutes, until a maximum "drop" temperature of 165°C was reached. The resulting mixture was collected and cooled, then the vulcanizing agent (sulfur) and the vulcanizing accelerator (N-cyclohexyl-2-benzothiazolesulfenamide) of the crosslinking system were incorporated on an external mixer (homo-finisher) at a temperature of 30°C, the mixture being blended (productive phase) for a period of more than 5 minutes and less than 12 minutes.

[0083] The rubber compositions thus obtained were then calendered into sheets for the measurement of their tear resistance and rolling resistance properties according to the protocols below.

[0084] Regarding the tear resistance test, the measurement of tear resistance is carried out as follows. At 100°C, the force required to cause failure (FRD, in MPa (in N / mm)) is determined, and the strain at failure (DRD, in %) is measured at 100°C. A specimen measuring 10 x 145 x 2.5 mm is used, notched along its length with three notches to a depth of 3 mm to induce fracture. The energy required to cause fracture (fracture energy) of the specimen, which is the product of FRD and DRD, can thus be determined. The force required to cause failure and the strain at failure are measured on a specimen stretched at 375 mm / min to induce fracture.

[0085] The tear resistance performance results are expressed on a scale of 100, with 100 being assigned to the tear resistance energy of the reference rubber composition (Tl). The tear resistance energy values, on a scale of 100, of the tested rubber compositions are presented in Table 2. The higher the value, i.e., the greater the difference in tear resistance energy compared to the reference, the higher the relative tear resistance, i.e., the higher the tear resistance performance.

[0086] To measure the hysteresis of a rubber composition, an essential parameter with respect to rolling resistance, it is necessary to measure the dynamic properties of the rubber composition. Dynamic properties, such as the dynamic shear modulus (or dynamic modulus) G', the viscous shear modulus G”, the loss factor tan θ, and the complex dynamic modulus G*, are obtained from measurements performed on a viscoanalyzer (Metravib VA4000) with bonded specimens of vulcanized rubber compositions. The specimens used are described in ASTM D 5992-96 (the version published in September 2006 but initially approved in 1996 is used) in Figure X2.1 (circular specimens). The diameter “d” of each specimen is 10 mm (the circular cross-section is thus 78.5 mm²), the thickness “L” of each specimen is 2 mm, giving a “d / L” ratio of 5 (as opposed to the standard ISO 2856, mentioned in paragraph X2.4 of the ASTM standard, which recommends a d / L value of 2).

[0087] The response of a vulcanized rubber compound specimen subjected to sinusoidal alternating simple shear loading at a frequency of 10 Hz and a temperature of 23°C is recorded. A strain amplitude sweep is performed from 0.1% to 50% (peak-to-peak on the forward cycle, i.e., 12 measurement points), then from 50% to 0.1% (peak-to-peak on the reverse cycle, i.e., 11 measurement points). After each data acquisition, the dynamic elastic shear modulus (G1) and the viscous shear modulus (G") on the reverse cycle, as well as the loss factor (tan θ), which corresponds to the ratio G" / G', were calculated. Similarly, the complex modulus (G*) is defined as the absolute value of the complex sum of the elastic modulus (G1) and the viscous modulus (G"): G* = (G'2 +G"2)0.5.

[0088] Each value of tan ô at 10 Hz and at 23°C is representative of the hysteresis of the corresponding rubber composition, therefore of the contribution of the rubber composition to the rolling resistance of a tire.

[0089] The hysteresis performance results are expressed as a base of 100, with the value 100 being assigned to the reference rubber composition (Tl). The hysteresis performance results of the examples (Cl, C2, C3, C4, C5 and C6) according to the invention and of the comparative examples (T2, T3, T4 and T5) are presented in Table 2. The values ​​indicated correspond to the ratio between the loss factor of the reference composition Tl and that of the rubber composition X: tan θ (Tl, 10 Hz, 23°C) / tan θ (X, 10 Hz, 23°C) x 100, where X represents one of the rubber compositions Cl, C2, C3, C4, C5, C6, T2, T3, T4 and T5. The higher the value, the lower the loss factor of the rubber composition, relative to that of the reference, the better the hysteresis performance, therefore the lower the contribution of the rubber composition to the rolling resistance, and thus the rolling resistance.

[0090] The formulations of the various rubber compositions are presented in Table 1 below, all quantities being expressed in pieces: [Tables 1] Composition Tl Cl C2 T2 C3 T3 C4 T4 C5 T5 C6 Elastomer (1) 53 53 53 53 53 53 53 53 53 53 53 Elastomer (2) 47 47 47 47 47 47 47 47 47 47 47 47 Reinforcing filler (3) - A 57 36 36 13 29 29 29 10 45 17 29 Rubber powder (4) -B (-) 21 10 33 17 5 30 17 17 10 17 Anti-ozone wax (5) 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 Agent Plasticizer (6) - C 12 12 12 12 12 12 12 12 12 12 12 Antioxidant (7) 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 Stearic acid (8) 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Zinc oxide (9) 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Vulcanization accelerator (10) 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 Sulfur 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 Weight ratio A / C 4.75 3.00 3.00 1.08 2.42 2.42 2.42 0.83 3.75 1.42 2.42 Sum A + B 57 57 46 46 46 34 59 27 62 27 46 Weight ratio B / A 0 0.58 0.28 2.54 0.59 0.17 1.03 1.70 0.38 0.59 0.59 1. Isoprene elastomer: natural rubber; 2. Butadiene elastomer: cis-1,4 polybutadiene synthesized with a neodymium catalyst having a cis-1,4 bonding ratio of at least 98% molar; 3. ASTM N550 grade carbon black according to ASTM D1765-14 having an STSA measured according to ASTM D6556-10 equal to 39 m2 / g, a CO AN index measured according to ASTM D3493-16 equal to 85 ml / 100g; 4. Rubber powder obtained by recycling (micronization of used tires), and marketed by Lehigh Technology, of which the percentage of rubber powder microparticles retained by a 250 µm sieve is less than 1% by weight, measured according to ASTM D5644-01 (2013), and of which the percentage of rubber powder particles retained by a 177 µm sieve is less than 10% by weight, relative to the total weight of the rubber powder particles, the rubber powder being unmodified; 5. Anti-ozone wax marketed by Sasol under the commercial reference "Varazon 4959"; 6. TDAE oil marketed by H&R under the commercial reference "VivaTec 500"; 7. Mixture of 2 antioxidants: ((N-(l,3-dimethylbutyl) -N-phenyl-para-phenylenediamine marketed by Flexsys under the reference "Santaflex 6-PPD" and 2,2,4-trimethyl-l,2-dihydroquinolone marketed by Lanxess; 8. Stearic acid marketed by Uniquema under the reference "Pristerene 4931"; 9. Zinc oxide: commercial grade, marketed by Umicore; 10. N-dicyclohexyl-2-benzothiazolesulfenamide marketed by Flexsys under the reference “Sancure CBS”. Weight ratio A / C: ratio between the rate of reinforcing filler, expressed in parts per annum, and the rate of plasticizing agent, expressed in parts per annum; Sum A + B: sum of the reinforcing charge rate, expressed in pcs, and the rubber powder rate, expressed in pcs; Weight ratio B / A: ratio between the percentage of rubber powder, expressed in pieces, and the percentage of reinforcing filler expressed in pieces.

[0091] The results of the respective performance in tearability and hysteresis are presented in Table 2 below: [Tables 2] Composition Tl Cl C2 T2 C3 T3 C4 T4 C5 T5 C6 Tear resistance performance 100 186 125 61 109 64 170 46 196 56 110 Hysteresis performance 100 122 129 122 139 154 122 160 110 164 127

[0092] The results in Table 2 show that the rubber compositions according to the invention (C1 to C6) have both the best tearability and hysteresis performance compared to the reference rubber composition T1 and compared to the comparative rubber compositions (T2 to T5).

[0093] In conclusion, the rubber composition according to the invention makes it possible to obtain a sidewall exhibiting a good compromise of performance properties in terms of tearability and hysteresis, which allows for a high-contrast marking that is permanent over time, throughout the life of the tire.

[0094] The characteristics of a high-contrast sidewall element according to the invention are illustrated by the schematic Figures 1 to 5, which are not drawn to scale: - [Fig. 1]: Perspective view of a portion of a tire comprising a sidewall with high-contrast elements, -[Fig.2]: Meridional half-section of a tire including a sidewall with a high-contrast element, -[Fig.3]: Texture of a high-contrast element comprising strand-like protuberances, according to a first variant of the first preferred embodiment of the texture, -[Fig.4]: Texture of a high-contrast element comprising blade-like protrusions, according to a second variant of the first preferred embodiment of the texture, -[Fig.5]: Texture of a high-contrast element including cavities, according to the second preferred embodiment of the texture.

[0095] Fig. 1 is a perspective view of a portion of a tire 1 comprising a sidewall 2 with high-contrast elements 3. Among the high-contrast elements 3 are two graphic elements 31, intended to communicate technical, commercial or legal information, and one aesthetic element 32.

[0096] Fig. 2 is a meridional half-section of a tire 1 comprising a sidewall 2 with a high-contrast element 3 consisting of a texture comprising protrusions 3, raised in relief from the surface of the sidewall 21. The protrusions 4 have a strand-like shape as shown in Fig. 3.

[0097] Fig. 3 is a texture of a high-contrast element 3 comprising strand-shaped protrusions 4, according to a first variant of the first preferred embodiment of the texture. The strand-shaped protrusions 4, raised against a flank surface, have an average height H4. Average height is understood to be the arithmetic mean of the heights of all the protrusions. The strand-shaped protrusions 4 are spaced at an average pitch P4. The strand-shaped protrusions 4, having a diameter varying along the entire height of the strand, have an average diameter D4. In the embodiment shown, the 4-strand-shaped protuberances have a diameter that decreases from a strand base, at the interface with the flank surface, and a free strand apex.

[0098] Figure 4 is a texture of a high-contrast element 3 comprising blade-shaped protrusions 5, according to a second variant of the first preferred embodiment of the texture. The blade-shaped protrusions 5, raised against a flank surface, have an average height H5. Average height is understood to be the arithmetic mean of the heights of all the protrusions. The blade-shaped protrusions 5 are spaced at a pitch P5. The blade-shaped protrusions 5, having a width that varies along the entire height of the blade, have an average width D5. In the embodiment shown, the blade-shaped protrusions 5 have a width that decreases from a blade base, at the interface with the flank surface, and a free blade apex.

[0099] Figure 5 is a texture of a high-contrast element 3 comprising cavities 6, according to the second preferred embodiment of the texture. The cavities 6, recessed with respect to a flank surface, have an average depth. By average depth, we mean the arithmetic mean of the depths of all the cavities. A cavity 6 consists of a cavity interior 62, formed in the thickness of the flank, and an opening 61, opening onto the surface of the flank. The openings 61 on the flank surface are spaced at a pitch P6. The openings 61 on the flank surface have an average diameter D6. By average diameter, we mean an arithmetic mean of the diameters, not necessarily identical, of the openings on the flank surface.

Claims

Demands

1. A tire (1) for a vehicle comprising a sidewall (2) with at least one high-contrast sidewall element (3): - the high-contrast sidewall element (3) being made of a texture having a first brightness L*1 of at least 1 and at most 15, - any portion of the sidewall surface (21) adjacent to the high-contrast sidewall element (3) having a second brightness L*2 of at least L*1+5, - the first and second brightnesses (L*1, L*2) being expressed on a scale from 0 to 100 in accordance with the L*a*b* colorimetric model adopted in 1976 by the International Commission on Illumination, - the sidewall (2) comprising a rubber composition based on an elastomeric matrix, at least one reinforcing filler, at least one crosslinking system, at least one plasticizing agent, and at least one rubber powder, characterized in that the weight ratio between the reinforcing load rate, expressed in pc,and the plasticizing agent content, expressed in parts per annum, is at most 4.50, in that the sum of the reinforcing filler content, expressed in parts per annum, and the rubber powder content, expressed in parts per annum, is at least 30 parts per annum and at most 70 parts per annum, and in that the weight ratio between the rubber powder content, expressed in parts per annum, and the reinforcing filler content, expressed in parts per annum, is at least 0.20 and at most 2.

50.

2. Pneumatic (1) according to claim 1, wherein the weight ratio between the rate of reinforcing filler, expressed in pc, and the rate of plasticizing agent, expressed in pc, is at least equal to 1.50, preferably at least equal to 2.00 and at most equal to 4.00, and more preferably at least equal to 2.00 and at most equal to 3.

50.

3. Pneumatic (1) according to any one of claims 1 or 2, wherein the sum of the reinforcing charge rate, expressed in pc, and the rubber powder rate, expressed in pc, is at least equal to 35 pc and at most equal to 65 pc, preferably at least equal to 35 pc and at most equal to 63 pc, and more preferably at least equal to 40 pc and at most equal to 63 pc.

4. Pneumatic (1) according to any one of claims 1 to 3, wherein the weight ratio between the percentage of rubber powder, expressed in pcs, and the percentage of reinforcing filler, expressed in pcs, is at least equal to 0.25 and at most equal to 1.

50.

5. Pneumatic (1) according to any one of claims 1 to 4, wherein the reinforcing load ratio is at least equal to 5 pc and at most equal to 70 pc, preferably at least equal to 5 pc and at most equal to 60 pc, more preferably at least equal to 5 pc and at most equal to 55 pc, even more preferably at least equal to 10 pc and at most equal to 50 pc, and even more preferably at least equal to 20 pc and at most equal to 45 pc.

6. Pneumatic (1) according to any one of claims 1 to 5, wherein the reinforcing filler comprises predominantly carbon black.

7. Pneumatic (1) according to any one of claims 1 to 6, wherein the plasticizing agent content is at least 2 pc and at most 28 pc, preferably at least 7 pc and at most 24 pc, and more preferably at least 10 pc and at most 20 pc.

8. Pneumatic (1) according to any one of claims 1 to 7, wherein at least one plasticizing agent is selected from the group consisting of plasticizing oils, high Tg plasticizing resins, and combinations thereof.

9. A tire according to any one of claims 1 to 8, wherein the proportion of rubber powder is at least 2 pc and at most 35 pc, preferably at least 5 pc and at most 33 pc, more preferably at least 6 pc and at most 32 pc, even more preferably at least 7 pc and at most 31 pc, and even more preferably at least 8 pc and at most 30 pc.

10. Pneumatic according to any one of claims 1 to 9, wherein the rubber powder has a microparticle size distribution such that it comprises less than 1% by mass of microparticles not retained through a 250 pm sieve and less than 10% by mass of microparticles not retained through a 177 pm sieve, relative to the total mass of rubber powder microparticles.

11. Tire (1) according to any one of claims 1 to 10, wherein the high contrast sidewall element (3) is made up of a texture having a first brightness L*1 of at least 4 and at most 13.

12. Tire (1) according to any one of claims 1 to 11, wherein any portion of sidewall surface (21) adjacent to the high contrast sidewall element (3) has a second brightness L*2 at least equal to L*1+10, preferably at least equal to L*1+12.

13. Tire (1) according to any one of claims 1 to 12, wherein any portion of sidewall surface (21) adjacent to the high contrast sidewall element (3) has a second brightness L*2 of at least 18, preferably at least 22.

14. Pneumatic (1) according to any one of claims 1 to 13, wherein the high contrast sidewall element (3) is made up of a texture comprising protrusions (4, 5), raised in relation to a sidewall surface (21), in contact with atmospheric air, and / or cavities (6), recessed in relation to the sidewall surface (21).

15. Tire (1) according to any one of claims 1 to 14, wherein the high contrast sidewall element (3) is made up of a texture comprising strand-like protrusions (4).

16. Pneumatic (1) according to any one of claims 1 to 14, wherein the high contrast sidewall element (3) is made up of a texture comprising blade-shaped protrusions (4).

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