Tyre comprising a sidewall with at least one high-contrast sidewall element

Abstract

The present invention relates to a vehicle tyre (1), the tyre comprising at least one sidewall (2) with at least one high-contrast sidewall element (3) consisting of a texture having a first luminosity L*1 of at least 1 and at most 15, wherein any adjacent sidewall surface portion (21) has a second luminosity L*2 of at least L*1+5. The invention discloses a rubber composition of the sidewall (2) that exhibits a good trade-off between tear strength and rolling resistance. According to the invention, the weight ratio of the reinforcing filler content to the plasticiser content is at most 4.50, the sum of the reinforcing filler content and the crumb rubber content is at least 30 phr and at most 70 phr, and the weight ratio of the crumb rubber content to the reinforcing filler content is at least 0.20 and at most 2.50.

Description

A 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 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 sidewall element is a sidewall surface element with a specific texture that differs from the typically smooth surface of the sidewall. This texture gives the high-contrast sidewall element a darker appearance than any adjacent sidewall surface, allowing it to be visually distinguished from any adjacent sidewall surface. A high-contrast sidewall element can be either a graphic or aesthetic element, or a portion of the sidewall surface surrounding that graphic or aesthetic element, making it particularly prominent on the sidewall surface.

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

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

[0007] Brightness can be quantified by luminous luminance, expressed in candela / m². 2 Luminance measures the luminous flux from an illuminated surface that is reflected into the observer's eye. However, the relationship between luminous flux and the visual perception of brightness is not linear and is complex. Therefore, for practical purposes, the International Commission on Illumination (CIE) defined luminance L*, a parameter that characterizes a surface's ability to reflect light, based on the luminous flux of the light produced by a primary or secondary source, expressed in candelas per square meter (cd / m²). 2), relative to the luminous luminance of white taken as a reference. Thus, in what follows, the luminance 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 area, the first brightness L*1 and 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 the measurement is taken in 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 area, the spectrophotometer is positioned on that portion of the flank surface.In order to improve the determination of this second brightness L*2, it is possible to carry out a plurality of brightness measurements on several adjacent flank surface portions, and then deduce an associated average brightness.

[0009] High-contrast flank features, having a significantly lower brightness difference than an adjacent flank surface portion, were described in documents WO 2016005572 Al, WO 2011036061 Al, and WO 20174919 AL

[0010] It has been observed that on tire sidewall surfaces containing high-contrast sidewall elements, 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] Therefore, to obtain a sidewall element with high contrast that lasts throughout the tire's lifespan, it is necessary to reduce these cracks, or at least delay their appearance, but with a limited impact on the sidewall material's hysteresis, and thus on the tire's rolling resistance. It is well known that crack resistance (or tear resistance) and the hysteresis of a rubber compound are linked.

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

[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 was 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 first and second luminances (L*1, L*2) being expressed according to a scale ranging from 0 to 100 in accordance with the L*a*b* colorimetric model adopted in 1976 by the International Commission on Illumination, -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 level of an adjacent sidewall surface area, and 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, good contrast is achieved with any adjacent sidewall surface area, which, in typical tire designs, most often has a brightness level 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, 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 being 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, including several diene elastomers. This mixture of elastomers, particularly diene elastomers, is called the elastomer matrix. Preferably, the elastomer matrix comprises at least two different diene elastomers.

[0022] The term "elastomer" refers to 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 simply "diene rubber," whether natural or synthetic, refers to an elastomer composed at least partially 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" diene elastomers. An "essentially unsaturated" diene elastomer is a diene elastomer derived at least in part from conjugated diene monomers, with a proportion of diene-derived motifs or units (conjugated dienes) greater than 15% (mole percent). Thus, diene elastomers such as butyl rubbers or diene-alpha-olefin copolymers like EPDM do not fall under the previous definition and can be classified as "essentially 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 means in particular: 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 those with 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and 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 include vinylaromatic compounds with 8 to 20 carbon atoms and aliphatic α-monoolefins with 3 to 12 carbon atoms.

[0029] Examples of suitable vinylaromatic compounds include styrene, ortho-, meta-, para-methyl styrene, the commercial mixture "vinyl-toluene", para-tert-obuty styrene.

[0030] As suitable aliphatic a-monoolefins, acylic aliphatic a-monoolefins having 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 from 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 their mixture, such as, for example, elastomers obtained from ethylene, propylene with a non-conjugated 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 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 may 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, including molecular sulfur or a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and optionally, various known vulcanization activators may be used, 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 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 chosen 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 high-Tg hydrocarbon resins, which are solid at room temperature. 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 high Tg hydrocarbon resin, typically at least 30°C, is solid at room temperature and pressure (23°C, 1 atm), while a plasticizing oil is liquid at room temperature and 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.These hydrocarbon resins are known to be thermoplastic resins because they soften upon heating and can therefore 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 nonlinear alkanes (isoalkanes, cycloalkanes, branched alkanes) derived from petroleum refining or the catalytic hydrogenation of carbon monoxide (Fisher-Tropsch process), predominantly containing 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-reducing waxes can be used, including natural waxes such as candelilla wax or carnauba wax. These waxes can also be used in blending.

[0040] Anti-ozone waxes are commercially available such as, for 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, optionally in the form of a rubber sheet, and which is a recycled product.

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

[0043] As is known, rubber powders can be obtained in particular 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. A crude distribution of micron-sized vulcanized mixture particles is obtained. "Microparticles" refers to particles that have a specific size, namely their diameter in the case of spherical particles, or their largest dimension in the case of non-spherical particles. These particles are anisometric, ranging in size from a few tens to hundreds of microns. The size of the 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 powders, without any 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 pieces per annum, and the percentage of reinforcing filler, expressed in pieces per annum, is at least equal to 0.20 and at most equal to 2.50.

[0049] The proportions of the various constituents are expressed in "pc." The unit "pc," or "parts per hundred of elastomer," represents the mass fraction 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 parts per annum, and the rate of plasticizing agent, expressed in parts per annum, 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 pieces per annum, and the percentage of reinforcing filler, expressed in pieces per annum, 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% and at most equal to 70%, preferably at least equal to 5% and at most equal to 60%, more preferably at least equal to 5% and at most equal to 55%, even more preferably at least equal to 10% and at most equal to 50%, and even more preferably at least equal to 20% and at most equal to 45%.

[0055] Preferably the reinforcing filler consists mainly of 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] Preferably 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 chosen 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 chosen 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 isoprenoid 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 can 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). Preferably, an isoprene telatomer can be selected from the group consisting of natural rubber, synthetic cis-1,4 polyisoprenes, and combinations thereof.More preferably, isoprene telatomer is chosen from the group consisting of natural rubber, synthetic polyisoprenes having a molar percentage of cis-1,4 bonds greater than 90% (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, a butadiene elastomer can be a cis-1,4 polybutadiene; specifically, a polybutadiene with a cis-1,4 bond 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 rate of rubber dust 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 this invention, 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 exhibits 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 exhibits 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 with such a distribution, an additional sieving step based on a size criterion was carried out. Sieving can be performed using various technologies (vibration, centrifugation, aspiration) known to those skilled in the art. Preferably, this sieving step is carried out 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 The particles retained on the sieve pass through to the next stage. Those skilled in the art will understand that the distributions considered subsequently can be composed of all the particles passing through a given sieve or of all the particles retained between two stages.

[0068] Preferably the rubber powder exhibits 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, rubber powder is 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 of at least 1 and at most 15, any portion of sidewall surface adjacent to the high contrast sidewall element, having a second brightness L*2 of at least L*1+5.

[0071] Advantageously, the high-contrast flank element consists 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 protrusions, 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 created by molding during the tire curing process. The corresponding mold element, intended to create the texture of the high-contrast sidewall element, is produced, by way of non-exhaustive examples, by machining or laser engraving. The texture of a high-contrast sidewall element can also be created 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 sidewall elements, featuring strand-like or blade-like protrusions, absorbs a significant portion of the incident light rays after one or more successive reflections off the protrusion walls. This gives the texture a darker appearance, thereby improving its contrast and visibility compared to any adjacent sidewall surface. Furthermore, this particular texture provides a pleasant, velvety feel to the sidewall surface. Finally, the texture has a water-repellent and slightly hydrophobic effect. In one particular embodiment, the texture can be positioned on a recessed surface relative to the sidewall, so that it is embedded within the sidewall, which has the advantage of protecting it, for example, from wear caused by the sidewall surface rubbing against a curb.

[0079] Similarly, the texture of high-contrast flank elements, featuring recesses relative to the flank surface, absorbs 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 set back from the flank surface, thus ensuring its longevity by protecting it against The wear caused by the sidewall rubbing against a curb. It also has the advantage of not disrupting the aerodynamic airflow near the sidewall when the tire is rolling.

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

[0081] 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 formulation of the rubber compositions is presented in Table 1 with the quantities of the various ingredients expressed in parts per kilogram (pc).

[0082] Each rubber compound was produced as follows: the reinforcing filler, elastomer matrix, rubber powder, plasticizer, and various other ingredients such as ozone-suppressing 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 was 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 mixture thus obtained was recovered 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 whole being mixed (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 achieve failure (FRD, in MPa (in N / mm)) is determined, and the strain at failure (DRD, in %) is measured at 100°C. A notched specimen measuring 10 x 145 x 2.5 mm is used for this purpose. Three notches, 3 mm deep, are made at the center of its length to induce fracture. This allows us to determine the energy required to fracture the specimen (fracture energy), which is the product of the force required for fracture (FRD) and the deformation at fracture (DRD). The force required to achieve fracture and the deformation at fracture are measured on a specimen stretched at 375 mm / min to induce fracture.

[0085] Tear resistance performance results are expressed as a base of 100, with 100 representing the tear energy of the reference rubber compound (Tl). The tear energy values, also expressed as a base of 100, of the tested rubber compounds are presented in Table 2. The higher the value—that is, the greater the difference in tear energy compared to the reference—the higher the relative tear resistance, and therefore the better the tear resistance performance.

[0086] To measure the hysteresis of a rubber compound, a crucial parameter for rolling resistance, it is necessary to measure the dynamic properties of the rubber compound. 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) using bonded specimens of vulcanized rubber compounds. 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). 2), the thickness "L" of each test specimen is 2 mm, giving a ratio "d / L" of 5 (as opposed to the ISO 2856 standard, 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 shear modulus (G) and the viscous shear modulus (G") on the reverse cycle, as well as the loss factor (tan θ), which corresponding to the ratio G" / G', have been calculated. Similarly, the complex modulus (G*) is defined as the absolute value of the complex sum of the elastic modulus (G) and the viscous modulus (G"): G* = (G2 + 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 assigned to the reference rubber composition (Tl). The hysteresis performance results for the examples (Cl, C2, C3, C4, C5, and C6) according to the invention and for the comparative examples (T2, T3, T4, and T5) are presented in Table 2. The values ​​shown 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, with all quantities expressed in pieces: [Table 1] (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 mol%; (3) Carbon black of ASTM N550 grade according to ASTM D1765-14 having an STSA measured according to ASTM D6556-10 equal to 39 m 2 / g, a COAN 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, the percentage of rubber powder microparticles retained by a 250 pm sieve is less than 1% by weight, measured according to ASTM D5644-01 (2013), and 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: [Table 2]

[0092] The results in Table 2 show that the rubber compositions according to the invention (Cl to C6) have both the best tearability and hysteresis performance compared to the reference rubber composition Tl 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 with a good compromise of performance properties in terms of tear resistance and hysteresis, which allows for a high-contrast marking that lasts over time, throughout the life of the tire.

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

[0095] Figure 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] Figure 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 Figure 3.

[0097] Figure 3 shows 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 LL. Average height is defined as 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 that varies along the entire height of the strand, have an average diameter D4. In the embodiment shown, the strand-shaped protrusions 4 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 relative 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 within 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

Claims 1. Tire (1) for a vehicle comprising a sidewall (2) with at least one high-contrast sidewall element (3): -the high-contrast flank element (3) being constituted by a texture having a first brightness L*1 at least equal to 1 and at most equal to 15, -any portion of flank surface (21) adjacent to the high-contrast flank element (3), having a second brightness L*2 at least equal to L*l+5, -the first and second brightnesses (L*l, L*2) being expressed according to a scale ranging from 0 to 100 in accordance with the colorimetric model L*a*b* adopted in 1976 by the International Commission on Illumination, -the sidewall (2) comprising 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 crumb, characterized in that the weight ratio between the reinforcing filler content, expressed in pce, and the plasticizing agent content, expressed in pce, is at most equal to 4.50, in that the sum of the reinforcing filler content, expressed in pce, and the rubber crumb content, expressed in pce, is at least equal to 30 pce and at most equal to 70 pce, and in that the weight ratio between the rubber crumb content, expressed in pce, and the reinforcing filler content, expressed in pce, is at least equal to 0.20 and at most equal to 2.

50.

2. Tire (1) according to claim 1, in which the weight ratio between the level of reinforcing filler, expressed in pce, and the level of plasticizing agent, expressed in pce, 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. Tire (1) according to one of claims 1 or 2, in which the sum of the reinforcing filler content, expressed in pce, and the rubber crumb content, expressed in pce, is at least equal to 35 pce and at most equal to 65 pce, preferably at least equal to 35 pce and at most equal to 63 pce, and more preferably at least equal to 40 pce and at most equal to 63 pce.

4. Tire (1) according to any one of claims 1 to 3, in which the weight ratio between the rate of rubber crumb, expressed in pce, and the rate of reinforcing filler, expressed in pce, is at least equal to 0.25 and at most equal to 1.

50.

5. Tire (1) according to any one of claims 1 to 4, in which the reinforcing filler rate is at least equal to 5 pce and at most equal to 70 pce, preferably at least equal to 5 pce and at most equal to 60 pce, more preferably at least equal to 5 pce and at most equal to 55 pce, even more preferably at least equal to 10 pce and at most equal to 50 pce, and even more preferably at least equal to 20 pce and at most equal to 45 pce.

6. Tire (1) according to any one of claims 1 to 5, in which the reinforcing filler mainly comprises carbon black.

7. Tire (1) according to any one of claims 1 to 6, in which the level of plasticizing agent is at least equal to 2 pce and at most equal to 28 pce, preferably at least equal to 7 pce and at most equal to 24 pce, and more preferably at least equal to 10 pce and at most equal to 20 pce.

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

9. Tire according to any one of claims 1 to 8, in which the rubber crumb content is at least equal to 2 pce and at most equal to 35 pce, preferably at least equal to 5 pce and at most equal to 33 pce, more preferably at least equal to 6 pce and at most equal to 32 pce, even more preferably at least equal to 7 pce and at most equal to 31 pce, and even more preferably at least equal to 8 pce and at most equal to 30 pce.

10. A tire according to any one of claims 1 to 9, wherein the rubber crumb has a microparticle size distribution such that it comprises less than 1% by mass of unretained microparticles through a 250 μm sieve and less than 10% by mass of unretained microparticles. through a 177 pm sieve, relative to the total mass of rubber crumb microparticles.

11. Tire (1) according to any one of claims 1 to 10, in which the high-contrast sidewall element (3) consists of a texture having a first brightness L*1 at least equal to 4 and at most equal to 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 at least equal to 18, preferably at least equal to 22.

14. Tire (1) according to any one of claims 1 to 13, in which the high-contrast sidewall element (3) is constituted by a texture comprising protuberances (4, 5), in relief relative to a sidewall surface (21), in contact with atmospheric air, and / or cavities (6), hollow relative to the sidewall surface (21).

15. A tire (1) according to any one of claims 1 to 14, wherein the high-contrast sidewall element (3) is constituted by a texture comprising strand-shaped protrusions (4).

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

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