Tyre having an outer sidewall based on a composition comprising pyrolysis carbon black and carbon nanotubes

Abstract

The present invention relates to a tyre that has an outer sidewall, the outer sidewall comprising at least one elastomeric composition based on: (1) at least one elastomer; (2) reinforcing fillers comprising: (a) predominantly pyrolysis carbon black; and (b) at least 1.0 phr of carbon nanotubes; and (3) a crosslinking system.

Description

[0001] DESCRIPTION

[0002] TIRE WITH AN OUTER SIDEWALL MADE FROM A COMPOSITION COMPRISING PYROLYTIC CARBON BLACK AND CARBON NANOTUBE

[0003] FIELD OF INVENTION

[0004] The present invention relates to the field of elastomeric compositions, in particular intended for the manufacture of the sidewalls of a tire, that is to say, by definition, to the elastomeric layers located radially on the outside of the tire, which are in contact with the ambient air.

[0005] STATE OF THE ART

[0006] In recent years, limiting the environmental impact of tire manufacturing and use has become a major challenge for industry players. Research and development initiatives to produce tires with elastomeric compounds made from recycled or bio-based materials have proliferated. For example, it has been proposed to use pyrolysis carbon black as a total or partial replacement for conventional carbon black used as a reinforcing filler in tire elastomeric compounds; conventional carbon black being obtained from non-renewable raw materials of petroleum or fossil origin, such as tars, oils, and / or gases.However, this partial or total substitution of conventional carbon blacks with pyrolysis carbon blacks comes with several drawbacks, including an increase in the Mooney viscosity of the elastomeric compositions. An increase in Mooney viscosity translates into a decrease in the industrial performance of the elastomeric compositions (calandrability and extrudability), in other words, a decrease in their processability. It has also been observed that the partial or total substitution of conventional carbon blacks with pyrolysis carbon blacks is accompanied by a decrease in the ozone resistance of the elastomeric compositions. Ozone is known to have detrimental effects on rubber products, typically producing glazing and / or cracking on their surface.Good ozone resistance is particularly desirable when the compounds are intended for use in the outer sidewalls of tires. The outer sidewall of a tire is the elastomeric layer in contact with the ambient air, located outside the carcass reinforcement relative to the internal cavity of the tire, between the crown and the bead, so as to completely or partially cover the area of ​​the carcass reinforcement extending from the crown to the bead. Furthermore, a tire sidewall must exhibit numerous other characteristics, including resistance to fatigue cracking caused by continuous flexing of the tire sidewall under operating conditions. It has also been observed that the partial or complete substitution of conventional carbon blacks with pyrolysis carbon blacks results in a decrease in fatigue crack resistance.Reconciling all the characteristics that elastomeric compositions for sidewalls must meet therefore proves particularly difficult when developing new compositions.

[0007] Thus, there remains a need for the provision of elastomeric compositions that meet an increasingly present need to limit the environmental impact of the manufacture and use of tires and that offer both good processability, good fatigue resistance and good ozone resistance, in particular without penalizing other properties of the outer sidewall such as rigidity.

[0008] SUMMARY OF THE INVENTION

[0009] The present invention relates to a tire having an outer sidewall, the outer sidewall comprising at least one elastomeric composition based on:

[0010] (1) of at least one elastomer;

[0011] (2) of reinforcing charges comprising:

[0012] (a) predominantly pyrolysis carbon black; and

[0013] (b) at least 1.0 part per annum of carbon nanotubes; and

[0014] (3) of a crosslinking system.

[0015] Other aspects of the invention are as defined below.

[0016] DEFINITIONS

[0017] The expression "composition based on" means a 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 composition; the composition can thus be in a totally or partially crosslinked state or in a non-crosslinked state.

[0018] By the expression "part by weight per hundred parts by weight of elastomer" (or pce), we must understand the part, by mass per hundred parts by mass of elastomer or rubber, the two terms being synonymous.

[0019] In this document, unless expressly stated otherwise, all percentages (%) shown are percentages (%) by mass.

[0020] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​going from more than a to less than b (that is, bounds a and b excluded) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (that is, including the strict bounds a and b).

[0021] The compounds mentioned in the description can be of fossil origin, derived from biomass. Obviously, the compounds mentioned can also come from the recycling of previously used materials; that is, they can be partially or totally derived from a recycling process, or even obtained from raw materials themselves derived from a recycling process. This includes, in particular, polymers, plasticizers, reinforcing fillers, etc.

[0022] By "elastomeric matrix" or "elastomeric matrix", we mean the entire set of elastomer(s) present in the elastomeric composition.

[0023] For the purposes of this invention, "majority" or "majority" means that the compound is the major component among the compounds of the same type in the composition; that is, it is the one that represents the largest quantity by mass among the compounds of the same type. In other words, the mass of this compound represents more than 50% of the total mass of the compounds of the same type in the composition, for example, at least 51%. By way of example, in a system comprising a single elastomer, this compound is the major component within the meaning of this invention; and in a system comprising two elastomers, the major elastomer represents more than half of the total mass of the elastomers; in other words, the mass of this elastomer represents more than 50%, for example, at least 51%, of the total mass of the elastomers. Similarly, a so-called major component is the one representing the largest mass among the components in the composition.In other words, the mass of this filler represents more than 50%, for example at least 51%, of the total mass of fillers in the composition.

[0024] All glass transition temperature (Tg) values ​​are measured using a known method by differential scanning calorimetry (DSC) according to ASTM D3418 (2008). DETAILED DESCRIPTION OF THE INVENTION

[0025] Surprisingly, the inventors discovered that adding carbon nanotubes to an elastomeric composition primarily composed of pyrolysis carbon black as a reinforcing filler meets the stated requirement. The proposed compositions reduce the environmental footprint of tires by incorporating recycled materials. With the same rigidity as conventional compositions, they offer a good compromise between processability, fatigue resistance, and ozone resistance, making them particularly well-suited for use in tire sidewalls.

[0026] Thus, the present invention relates to a tire having an outer sidewall, the outer sidewall comprising at least one elastomeric composition based on:

[0027] (1) of at least one elastomer;

[0028] (2) of reinforcing charges comprising:

[0029] (a) predominantly pyrolysis carbon black; and

[0030] (b) at least 1.0 pc of carbon nanotubes; and

[0031] (3) of a crosslinking system.

[0032] The different constituents of the elastomeric composition can be as described below.

[0033] Elastomer

[0034] The elastomeric composition of the present invention is based on at least one elastomer (or indistinctly rubber).

[0035] The elastomer or each elastomer can be chosen from the group consisting of diene elastomers and mixtures thereof.

[0036] By "diene" elastomer, whether natural or synthetic, should be understood in a known way as an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not).

[0037] These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". Generally, "essentially unsaturated" refers to a diene elastomer derived at least in part from conjugated diene monomers, with a proportion of diene motifs or units (conjugated dienes) greater than 15% (mole percent). Thus, diene elastomers such as butyl rubbers or EPDM-type diene-alpha-olefin copolymers do not fall under the previous definition and can be described as "essentially saturated" diene elastomers (low or very low proportion of diene motifs, always less than 15%).

[0038] Specifically, a diene elastomer that can be used is understood to mean:

[0039] (a) - any homopolymer obtained by polymerization of a diene monomer, conjugated or not, having from 4 to 18 carbon atoms;

[0040] (b) - any copolymer obtained by copolymerization of a diene, conjugated or not, having from 4 to 18 carbon atoms and at least one other monomer.

[0041] The other monomer can be ethylene, an olefin or a diene, conjugated or not.

[0042] Suitable conjugated dienes are those with 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and isoprene.

[0043] Suitable olefins include vinylaromatic compounds with 8 to 20 carbon atoms and aliphatic α-monoolefins with 3 to 12 carbon atoms.

[0044] Examples of suitable vinylaromatic compounds include styrene, ortho-, meta-, para-methylstyrene, the commercial "vinyl-toluene" mixture, and para-tert-butylstyrene.

[0045] Acyclic a-monoolefins with 3 to 18 carbon atoms are particularly suitable as aliphatic α-monoolefins.

[0046] More specifically, the diene elastomer that can be used in the compositions may be:

[0047] (a') - any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;

[0048] (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;

[0049] (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.

[0050] The diene elastomer can be modified, that is to say either coupled and / or star-shaped, or functionalized, or coupled and / or star-shaped and simultaneously functionalized.

[0051] Thus, the diene elastomer can be coupled and / or star-shaped, for example by means of a silicon or tin atom which links the elastomer chains together.

[0052] The diene elastomer can be functionalized simultaneously or alternatively and comprise at least one functional group. A functional group is defined as a group comprising at least one heteroatom selected from Si, N, S, O, or P. Particularly suitable functional groups include those comprising at least one function such as silanol, an alkoxysilane, a primary, secondary, or tertiary amine, cyclic or non-cyclic, a thiol, or an epoxide. The composition useful within the scope of the invention may contain a single diene elastomer or a mixture of several diene elastomers.

[0053] Preferably, the diene elastomer is chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. Butadiene copolymers are particularly chosen from the group consisting of butadiene-styrene copolymers (SBR).

[0054] In some embodiments, the rubber composition useful within the framework of the invention comprises one or more elastomers, it may thus comprise from 15 to 75 parts natural rubber or synthetic polyisoprene and from 25 to 85 parts at least one polybutadiene (BR), preferably from 30 to 60 parts natural rubber or synthetic polyisoprene and from 40 to 70 parts at least polybutadiene (BR).

[0055] In some embodiments, the rubber composition useful in the context of the invention comprises, as an elastomer, a mixture of natural rubber (NR) and at least one polybutadiene (BR). Preferably, the mixture consists of 35 to 50 parts natural rubber (NR) and 50 to 65 parts polybutadiene (BR).

[0056] The elastomeric composition includes reinforcing fillers.

[0057] The term "reinforcing filler" refers to any type of filler known for its ability to reinforce an elastomeric composition usable in particular for the manufacture of tires, such as virgin carbon black, pyrolysis carbon black, carbon nanotubes, siliceous or aluminous mineral fillers, etc.

[0058] In particular, the elastomeric composition includes, as reinforcing fillers:

[0059] (a) predominantly pyrolysis carbon black; and

[0060] (b) at least 1.0 pc, preferably at least 1.5 pc of carbon nanotubes.

[0061] In some embodiments, the carbon nanotube content varies from 1.5 to 20 parts per annum or from 2 to 10 parts per annum.

[0062] In some embodiments, the elastomeric composition comprises:

[0063] (a) 10 to 100 parts per annum, preferably 20 to 70 parts per annum, more preferably 20 to 60 parts per annum or 30 to 60 parts per annum, of pyrolysis carbon black; and / or

[0064] (b) at least 1.5 parts per cubic centimeters, preferably at least 2 parts per cubic centimeters, preferably from 1.5 to 20 parts per cubic centimeters, more preferably from 2 to 10 parts per cubic centimeters, and even more preferably from 5 to 10 parts per cubic centimeters or from 5 to 8 parts per cubic centimeters, of carbon nanotubes. These embodiments make it possible to obtain, in particular, elastomeric compositions having a good compromise between processability, fatigue resistance, and ozone resistance, making them particularly suitable for use in the sidewall of a tire.

[0065] The total reinforcing filler content of the composition typically varies from 20 to 110 parts per million (ppm), more preferably from 30 to 80 ppm, and even more preferably from 40 to 70 ppm. Thus, the reinforcing fillers may also include, in smaller quantities, virgin carbon black and / or siliceous or aluminous mineral fillers.

[0066] In some embodiments, the elastomeric composition comprises pyrolysis carbon black and carbon nanotubes as the only reinforcing fillers.

[0067] For the purposes of this invention, "pyrolysis carbon black" means carbon black obtained by pyrolyzing a material comprising at least one carbon polymer and carbon black, hereinafter referred to as the material to be pyrolyzed, for example, in the context of recycling such a material. The physical state of the material to be pyrolyzed is irrelevant, whether it is in the form of powder, granules, strips, or any other form, and whether it is cross-linked or non-cross-linked.

[0068] Preferably, the material to be pyrolyzed can be recovered from manufactured articles or products generated during their manufacture / production (such as by-products or scrap); these manufactured articles can be selected from the group consisting of pneumatic tires, non-pneumatic tires, industrial conveyor belts, transmission belts, rubber seals, rubber hoses, shoe soles, and windshield wipers. More preferably still, the pyrolysis carbon black usable within the scope of the present invention is a carbon black obtained from a pyrolysis process in which the material to be pyrolyzed is derived from manufactured articles selected from the group consisting of pneumatic and non-pneumatic tires.

[0069] Pyrolysis, as defined in the present invention, means any type of thermal decomposition in the absence of oxygen, where the raw material is the material to be pyrolyzed as defined above. Pyrolysis carbon blacks are therefore distinguished from virgin carbon blacks, also known as industrial and / or ASTM grade carbon blacks, in that the carbonaceous raw material used for pyrolysis is a material comprising at least one carbon polymer and a carbon black, and not materials derived from petroleum fractions, coal, natural oils, or oils obtained from recycling processes (such as pyrolysis oil). The pyrolysis carbon blacks usable within the scope of the present invention are distinguished from known carbon blacks, such as industrial carbon blacks, particularly so-called "furnace" carbon blacks, notably by a higher ash content.

[0070] Preferably, the pyrolysis carbon black usable within the framework of the present invention has an ash content in the range of 5 to 30% by weight, more preferably in the range of 8 to 25% by weight, more preferably in the range of 10% to 22% by weight, relative to the total weight of the pyrolysis carbon black.

[0071] Preferably, the pyrolysis carbon black usable within the framework of the present invention has a sulfur content greater than 2% by weight, preferably 2.5 to 5% by weight, relative to the total weight of the pyrolysis carbon black.

[0072] Preferably, the pyrolysis carbon black usable within the framework of the present invention has a zinc content greater than or equal to 2% by weight, preferably 2.5 to 8% by weight, relative to the total weight of the pyrolysis carbon black.

[0073] Preferably, the pyrolysis carbon black usable within the scope of the present invention has a specific surface area (STSA) measured according to ASTM D 6556-2021 within a range of 20 to 200 m² 2 / g, more preferentially ranging from 30 to 90 m 2 / g.

[0074] Preferably, the pyrolysis carbon black usable within the framework of the present invention has a void volume measured according to ASTM D7854-21 and at a pressure of 50 MPa within a range of 30 to 60 ml / 100g, more preferably within a range of 35 to 55 ml / 100g.

[0075] The ash content is determined by calcination in platinum capsules in a muffle furnace at 825°C according to the following protocol. A capsule is identified before each series of measurements and tared to the nearest 0.1 mg; its mass is noted as PO. Five grams of pyrolysis carbon black sample are introduced into the capsule and weighed precisely to the nearest 0.1 mg; this mass is noted as P1. The capsule and its contents are pre-calcined using a Bunsen burner until fumes appear and the product ignites. Once the product has completely burned, the capsule and its contents are placed in a muffle furnace heated to 825°C for 1 hour. After 1 hour, the capsule is removed from the furnace and immediately placed in a desiccator at room temperature. When the capsule and the ash have returned to room temperature, the capsule is weighed again to obtain mass P2.Finally, it is possible to obtain the ash content (% ash) using the formula below: [Math 1].

[0076] % ash 100 The zinc content in pyrolysis carbon black is determined after calcination of the sample, followed by resuspension of the ash in an acidic medium and analysis by ICP-AES (inductively coupled plasma atomic emission spectroscopy). The ash is obtained using the protocol described above. Approximately 100 mg of ash (test sample) is taken and placed in a PFA (perfluoroalkoxy) tube for use with a HotBiock hot plate. Then, 8 mL of 37% concentrated hydrochloric acid, 3 mL of 65% concentrated nitric acid, and 0.5 mL of 40% hydrofluoric acid are added. The tube is then capped and heated at 130°C for 2 hours. After cooling, the contents are then transferred using ultrapure water into a 100 mL PTFE (polytetrafluoroethylene) volumetric flask already containing 2 g of boric acid (to neutralize the hydrofluoric acid). Ultrapure water is then added to the calibration mark.The resulting solution is diluted 100-fold by taking 1 mL from a 100 mL PTFE flask previously containing 8 mL of 37% concentrated hydrochloric acid, 3 mL of 65% concentrated nitric acid, 0.5 mL of 40% hydrofluoric acid, and 2 g of boric acid. This diluted solution is then filtered through a 0.45 µm GHP syringe filter before being analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). Prior to the analysis of the diluted solution, at least five standards are analyzed by ICP-AES at zinc concentrations of 0, 0.5, 1, 2, and 5 mg / L. These standards were prepared in 100 mL volumetric flasks by diluting a commercially available solution certified to a zinc concentration of 1 g / L.

[0077] These volumetric flasks initially contain 8 mL of 37% concentrated hydrochloric acid, 3 mL of 65% concentrated nitric acid, 0.5 mL of 40% hydrofluoric acid, and 2 g of boric acid. The standard solutions are analyzed by ICP-AES at a wavelength of ΔZn = 202.613 nm. For each standard concentration (c), the zinc signal intensity IZn is plotted on a graph IZn = f(c), which corresponds to the calibration curve (of the type y = ax + b). The sample solution (diluted solution) of unknown concentration is then measured under the same conditions as the standards. The measured intensity is related to the concentration using the calibration curve obtained previously. The ash concentration (c) in mass percent is thus obtained directly by the software, since the sample size and volume have been previously recorded. The concentration of zinc in pyrolysis black [c]black in mass % is obtained by the following equation: [Math 2]

[0078] [c ]black = [ C Ashes * 100 * % Ashes

[0079] The determination of sulfur content in pyrolysis carbon black is carried out using a LECO furnace. LECO sulfur analyzers are designed to measure, in particular, the sulfur content in organic and / or inorganic materials by combustion and non-dispersive infrared detection. Before measuring the sulfur content of the sample, the sampling chambers are cleaned and the furnace is calibrated. The LECO furnace chambers are cleaned beforehand: the empty chamber is analyzed under the same conditions as the samples. The calibration curve is prepared using a commercial standard called "BBOT" with a purity greater than 99.99% and a guaranteed carbon (C), hydrogen (H), nitrogen (N), oxygen (O), and sulfur (S) content. This content is as follows: C%: 72.52; H%: 6.09; N%: 6.51; O%: 7.43; and S%: 7.44. We weigh approximately exactly 10 ± 3, 20 ± 3 and 40 ± 3 mg of BBOT in a capsule.The standard / pod assembly is introduced into the combustion furnace, regulated at 1350 °C under pure oxygen. The combination of the furnace temperature and the analysis flow rate causes the sample to burn and releases sulfur and / or carbon as SO2(g). After 20 seconds, oxygen begins to flow through the lance to accelerate the combustion of materials that are difficult to burn. The sulfur and / or carbon, in the form of SO2(g), are carried by an oxygen flow through the infrared detection cells. The instrument software plots a line connecting the introduced standard mass and the observed response (area) on the detector. This yields a calibration curve. After thoroughly cleaning the sampling equipment, approximately 80 ± 5 mg of pyrolysis carbon black is weighed and introduced into a LECO furnace pod.The area of ​​the observed SO2 peak is related to the concentration using the calibration curve. The instrument's software then calculates the mass percentage of sulfur in the sample based on the mass of sample introduced into the capsule.

[0080] Pyrolysis carbon blacks are marketed, for example, by Scandinavian Enviro Systems under the reference "P550 HD" or by Bolder Industries under the reference BolderBlack

[0081] Carbon nanotubes

[0082] Carbon nanotubes are allotropes of carbon that exhibit a unique atomic structure composed of covalently bonded carbon atoms arranged in long cylinders.

[0083] The carbon nanotubes useful in the context of the present invention may be made of one or more rolled graphite sheets. The nanotubes may be of the single-walled (SWNT) or multi-walled (MWNT) type.

[0084] The carbon nanotubes useful in the context of the present invention typically have an average diameter ranging from 0.1 to 200 nm, preferably from 0.1 to 100 nm, more preferably from 0.4 to 50 nm, and even better, from 1 to 30 nm, or even from 10 to 15 nm, and advantageously an average length of more than 0.1 pm, advantageously from 0.1 to 20 pm, preferably from 0.1 to 10 pm, for example, about 6 pm. Their length-to-diameter ratio is advantageously greater than 10 and most often greater than 100. The average length and average diameter of the carbon nanotubes can be conventionally determined by transmission electron microscopy (TEM). The average diameter is the average value of all the diameters measured using nm as the unit. The average length is determined by the average value of all the lengths measured.

[0085] The carbon nanotubes useful in the context of the present invention can have closed and / or open ends. These nanotubes are generally obtained by chemical vapor deposition. Their specific surface area, for example, ranges from 100 to 300 m². 2 / g, advantageously from 200 to 300 m 2 / g. Their apparent density can range from 0.01 to 0.5 g / cm³. 3 and more preferably from 0.07 to 0.2 g / cm² 3 Multi-walled carbon nanotubes can, for example, comprise 5 to 15 layers and more preferably 7 to 10 layers.

[0086] Carbon nanotubes can in particular be manufactured from a renewable source (bio-ethylene derived from bioethanol).

[0087] An example of carbon nanotubes that can be used in the context of the invention is, in particular, the commercial reference Graphistrength® C100 from the company Arkema.

[0088] Virgin carbon black

[0089] The elastomeric composition may also include a carbon black different from pyrolysis carbon black; this carbon black is also called "virgin carbon black" because it is not produced from materials that already contain carbon black. Virgin carbon black is produced from materials derived from petroleum fractions or coal, or from natural oils or oils obtained through recycling processes (such as pyrolysis oil).

[0090] As virgin carbon blacks, all carbon blacks are suitable, including carbon blacks conventionally used in tires or their treads, especially industrial carbon blacks, more specifically so-called "furnace" carbon blacks.

[0091] Among virgin carbon blacks, special mention should be made of reinforcing virgin carbon blacks of the 100, 200, 300 series, or blacks of the 500, 600 or 700 series (ASTM grades D-1765-23b published on December 15, 2023), such as for example blacks N115, N 134, N234, N326, N330, N339, N347, N375, N550, N683, N772.

[0092] Virgin carbon blacks can be used in their isolated state, as commercially available, or in any other form, for example as a carrier for certain rubberizing additives used. Virgin carbon blacks could, for example, already be incorporated into diene elastomers, particularly isoprene elastomers, in the form of a masterbatch (see, for example, applications WO97 / 36724-A2 or W099 / 16600-A1).

[0093] Siliceous or aluminous mineral fillers

[0094] Suitable inorganic reinforcing fillers include mineral fillers of the siliceous type, preferably silica (SiCh), or of the aluminous type, particularly alumina (Al2O3). The silica used can be any reinforcing silica known to those skilled in the art, including precipitated or fumed silica. Precipitated silica can be produced from non-renewable raw materials, notably those derived from inorganic sand (silicon dioxide from inorganic sand), recycled materials such as foundry sands, end-of-life tires, and in particular the treads of end-of-life tires, which consist mainly of silica as a reinforcing filler, or from bio-based raw materials such as organic waste from plants, preferably inedible organic waste from plants.

[0095] Non-renewable raw materials are defined as raw materials that do not regenerate on a human timescale. These are therefore exhaustible resources. Examples include minerals such as stones or sand, metals, gas, and oil.

[0096] Among the plants that have silicon dioxide in their tissues are mustard, grasses, corn, sugar cane bagasse, rice, wheat and in particular mustard husks, bamboo leaves, ears of corn, rice husks, wheat husks.

[0097] Silica derived from non-renewable raw materials such as natural inorganic sand is usually obtained by heating sand in a glass furnace in the presence of sodium carbonate. The resulting sodium silicate is then dissolved in water, possibly in the presence of a base such as sodium hydroxide. Precipitated synthetic silica is formed from this aqueous solution by controlled treatment of the silicate with an acid (e.g., a mineral acid and / or an acidifying gas such as carbon dioxide). Sometimes, an electrolyte (e.g., sodium sulfate) may be present to promote the formation of precipitated silica particles. The recovered precipitated silica is amorphous.

[0098] Silica derived from bio-based raw materials such as those mentioned above can, for example, be obtained by burning the bio-based raw material in order to recover the ash of this bio-based material which contains mainly silicon dioxide.For example, with rice husks, and in a process equivalent to the one described above for silicas based on non-renewable or recycled mineral raw materials, rice husk ash is generally treated with a strong base such as sodium hydroxide to form an aqueous silicate solution (e.g., sodium silicate). Following this, precipitated synthetic silica is formed by the controlled addition of an acid (e.g., a mineral acid and / or an acidifying gas such as carbon dioxide) in which an electrolyte (e.g., sodium sulfate) may be present to promote the formation of precipitated silica particles derived from rice husks. The recovered precipitated silica is amorphous precipitated silica. Silica derived from rice husk ash is commonly referred to as RHA silica (Rice Husk Ash Silica).Bio-based silicas are available, for example, from suppliers such as Solvay, Evonik, Quechen, Wilmar International, Wuxi.

[0099] In summary, the synthesis of a precipitated silica usable within the framework of the invention can be carried out from a sodium silicate entirely obtained from bio-based, recycled or non-renewable raw materials, but also from a mixture of bio-based and / or recycled and / or non-renewable raw materials.

[0100] Preferably, precipitated silica, whether obtained from mineral, non-renewable, recycled or bio-based raw materials, has a specific surface area and a CTAB specific surface area both below 450 m² 2 / g, preferably within a range of 30 to 400 m 2 / g, particularly from 60 to 300 m 2 / g..

[0101] Any type of precipitated silica can be used, including highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art.

[0102] Examples include the silicas described in applications W003 / 016215-A1 and W003 / 016387-A1. Among the commercial HDS silicas, the following can be used: “Ulsil ® 5000GR”, “Ulsil ® 7000GR” from Evonik, “Zeosil ® 1085GR”, “Zeosil® 1115 MP”, “Zeosil® 1165MP”, “Zeosil® Premium 200MP”, “Zeosil® H RS 1200 MP” from Solvay. As non-HDS silica, the following commercial silicas may be used: “Ultrasil® VN2GR”, “Ultrasil® VN3GR” silicas from Evonik, “Zeosil® 175GR” silica from Solvay, “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” silicas from PPG, “K160”, “K185”, “K195” silicas from Wilmar International.Other examples of inorganic fillers that may be used in compositions include mineral fillers of the aluminous type, in particular alumina (Al2O3), aluminum oxides, aluminum hydroxides, aluminosilicates, titanium oxides, silicon carbides or nitrides, all of the reinforcing type as described for example in applications WO 99 / 28376-A2, WO 00 / 73372-A1, WO 02 / 053634-A1, WO 2004 / 003067-A1, WO 2004 / 056915-A2, US 6 610 261-B1 and US 6 747087-B2. Examples include the aluminas “BaikaloxA125” or “CR125” (Baïkowski company), “APA-100RDX” (Condéa), “Aluminoxid C” (Evonik) or “AKP-G015” (Sumitomo Chemicals).

[0103] The physical state of the reinforcing inorganic filler is irrelevant, whether it be in the form of powder, microbeads, granules, spheres, or any other suitable densified form. Of course, the term "reinforcing inorganic filler" also refers to mixtures of different reinforcing inorganic fillers, particularly silicas as described above.

[0104] Those skilled in the art will understand that, in place of the inorganic reinforcing filler described above, a reinforcing filler of another nature could be used, provided that this reinforcing filler of another nature is covered with an inorganic layer such as silica, or has functional sites on its surface, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between this reinforcing filler and the diene elastomer.

[0105] To couple the reinforcing inorganic filler to the diene elastomer, a well-known coupling agent (or bonding agent) can be used to ensure sufficient chemical and / or physical connection between the inorganic filler (the surface of its particles) and the diene elastomer. Organosilanes or polyorganosiloxanes, at least bifunctional, are particularly suitable. "Bifunctional" refers to a compound possessing a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer.For example, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being able to interact with the hydroxyl groups of an inorganic charge and a second functional group comprising a sulfur atom, said second functional group being able to interact with the diene elastomer.

[0106] Preferably, organosilanes are chosen from the group consisting of polysulfide organosilanes (symmetric or asymmetric) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated TESPT and marketed under the name "Si69" by Evonik, or bis-(triethoxysilylpropyl) disulfide, abbreviated TESPD and marketed under the name "Si75" by Evonik; polyorganosiloxanes; mercaptosilanes; and blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate, marketed by Momentive under the name "NXT Silane". More preferably, the organosilane is a polysulfide organosilane.

[0107] A person skilled in the art can find examples of coupling agents in the following documents: WO 02 / 083782, WO 02 / 30939, WO 02 / 31041, WO 2007 / 061550,

[0108] WO 2006 / 125532, WO 2006 / 125533, WO 2006 / 125534, US 6,849,754, WO 99 / 09036, WO 2006 / 023815, WO 2007 / 098080, WO 2010 / 072685 and WO 2008 / 055986.

[0109] The coupling agent content preferably represents 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler, preferably 4% to 12%, and preferably 6% to 10% by weight relative to the amount of reinforcing inorganic filler. Typically, the coupling agent content is less than 20%, preferably within the range of 6% to 17%, and preferably 8% to 15%. This percentage can easily be adjusted by a person skilled in the art according to the amount of inorganic filler used in the composition.

[0110] The composition may also contain, in addition to coupling agents, coupling activators, inorganic filler covering agents or more generally processing aids which are known to improve the dispersion of the filler in the elastomer matrix and to lower the viscosity of the compositions, thereby improving their processing ability in the raw state, these agents being for example hydrolyzable silanes such as alkylalkoxysilanes (in particular alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines (for example trialcanol-amines), hydroxylated or hydrolyzable POS, for example α,ε-dihydroxy-polyorganosiloxanes (in particular α,ε-dihydroxy-polydimethylsiloxanes), fatty acids such as stearic acid.

[0111] Other organic charges

[0112] Examples of organic fillers other than carbon blacks and pyrolysis carbon blacks include functionalized polyvinyl organic fillers as described in applications WO 2006 / 069792-A1, WO 2006 / 069793-A1, WO 2008 / 003434-A1 and WO 2008 / 003435-A1.

[0113] Crosslinking system

[0114] The elastomeric composition of the invention includes a crosslinking system.

[0115] The crosslinking system can be any type of system known to those skilled in the art in the field of elastomeric compounds for tires. 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.

[0116] Sulfur can be supplied in any form, including as molecular sulfur, or as a sulfur donor agent.

[0117] A sulfur donor is defined as any compound that releases sulfur atoms, whether combined or not in the form of a polysulfide chain, capable of inserting themselves into the polysulfide chains formed during vulcanization and bridging the elastomeric chains. The sulfur content in the elastomeric composition is preferably less than 10 parts per million (ppm), preferably within the range of 1 to 8 ppm, and more preferably within the range of 1.5 to 6 ppm.

[0118] Any compound capable of accelerating the vulcanization of diene elastomers in the presence of sulfur may be used as a vulcanization accelerator (primary or secondary). This includes, in particular, thiazole-type accelerators and their derivatives, sulfenamide-type accelerators, guanidine-type accelerators, thiuram-type accelerators, dithiocarbamate-type accelerators, dithiophosphate-type accelerators, thiourea-type accelerators, and xanthate-type accelerators. The vulcanization accelerator may be used at a preferential rate in the range of 0.3 to 5 parts per million (ppm), more preferably from 0.5 to 3.5 ppm.

[0119] As is well known, the vulcanization system may also include vulcanization activators such as metal oxides like zinc oxide or fatty acids such as stearic acid.

[0120] Common additives and processing aids

[0121] The elastomeric composition of the invention may also include all or part of the usual additives and processing agents known to those skilled in the art and commonly used in elastomeric compositions for tires, such as plasticizing agents (such as plasticizing oils and / or plasticizing resins), non-reinforcing fillers, pigments, raw tack promoters (i.e., tackifying agents), pro-oxidant metallic salts, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents, reinforcing resins (such as described, for example, in application WO 02 / 10269).

[0122] Preferably, the rate of plasticizing agent(s) in the elastomeric composition is in a range of 0 to 20 pc, more preferably in a range of 0 to 10 pc.

[0123] Composition manufacturing

[0124] The elastomeric composition of the invention is manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: - a first thermomechanical working or mixing phase (the so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents are introduced into a suitable mixer such as a standard internal mixer (for example, of the 'Banbury' type), including the highly saturated diene elastomer as defined above, the reinforcing filler(s) including pyrolysis carbon black, and any other miscellaneous additives, with the exception of the crosslinking system. The incorporation of the reinforcing filler into the highly saturated diene elastomer can be carried out in one or more stages by thermomechanical mixing.The non-productive phase is carried out at high temperature, up to a maximum temperature within a range of 110°C to 200°C, for a duration generally within a range of 2 to 10 minutes;

[0125] - a second mechanical working phase (the so-called "productive" phase), which is carried out in an external mixer such as a roller mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 120°C, for example ranging from 40°C to 100°C. The crosslinking system is then incorporated, and the whole is then mixed for a few minutes, for example from 5 to 15 min.

[0126] The final elastomeric composition thus obtained is then calendered, for example in the form of a sheet or plate, particularly for characterization in the laboratory, or extruded in the form of a semi-finished (or profile) of rubber usable for an outer sidewall of a vehicle tire.

[0127] The elastomeric composition can be either in the raw state (before crosslinking or vulcanization), or in the cured state (after crosslinking or vulcanization), and can be a semi-finished product that can be used in a tire.

[0128] The crosslinking of the elastomeric composition can be carried out in a manner known to those skilled in the art, for example at a temperature within a range of 130°C to 200°C, preferably under pressure, for a sufficient time which can vary for example from 5 to 90 min.

[0129] TIRES

[0130] The tire according to the invention is intended for use on passenger cars, SUVs (Sport Utility Vehicles), two-wheeled vehicles (particularly motorcycles), aircraft, and industrial vehicles such as vans, heavy goods vehicles (i.e., subways, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles such as agricultural or construction equipment), and others. Preferably, the tire according to the invention is particularly suitable for use on passenger cars, vans, and SUVs. The tire has a conventional structure. Within a tire, three zones are typically distinguished: the outer radial zone in contact with the ambient air; the inner radial zone in contact with the inflation gas; and the inner zone of the tire.

[0131] The radially outer area in contact with the ambient air is essentially made up of the tread and the outer sidewall of the tire. An outer sidewall is an elastomeric layer positioned outside the carcass reinforcement relative to the internal cavity of the tire, between the crown and the bead, so as to cover totally or partially the area of ​​the carcass reinforcement extending from the crown to the bead.

[0132] The radially inner area in contact with the inflation gas is generally made up of the layer that is airtight against the inflation gas, sometimes called the inner rubber (“inner liner” in English).

[0133] The inner zone of the tire is the area between the outer and inner zones. This zone includes layers or plies, which are referred to here as the tire's inner layers. These include, for example, carcass plies, tread sub-layers, tire belt plies, or any other layer that is not in contact with ambient air or the tire's inflation gas.

[0134] The following examples are given for illustrative purposes only. They should in no way be considered as limiting the present invention.

[0135] EXAMPLES

[0136] 1. Measurement Method

[0137] 1.1 Mooney viscosity (ML 1+4)

[0138] The Mooney viscosity measurement is performed according to the following principle and in accordance with ASTM D-1646 (1999). The composition being analyzed in its raw state (i.e., before baking) is molded in a cylindrical chamber heated to a given temperature, usually 100°C. After one minute of preheating, an L-type rotor rotates within the specimen at 2 revolutions per minute, and the torque required to maintain this rotation is measured after 4 minutes of rotation. The Mooney viscosity (ML 1+4) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Newton-meters). As is well known to those skilled in the art, the lower the Mooney viscosity, the easier the material is to work.

[0139] All values ​​are expressed as a base of 100 relative to the given control. A value lower than that of the control indicates an improved result, i.e., better processability. 1.2 Dynamic Properties

[0140] Dynamic properties are measured on a viscoanalyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a sample of the vulcanized composition (cylindrical specimens 2 mm thick and 10 mm in diameter, subjected to sinusoidal loading in simple alternating shear, at the frequency 1OHz, at a temperature of 23°C) is recorded.

[0141] For the measurements of the complex dynamic shear modulus (G*) and the loss factor tan(delta), a strain amplitude sweep is performed from 0.1% to 100% peak-to-peak (forward cycle), then from 100% to 0.1% peak-to-peak (return cycle). For the return cycle, the maximum observed tan(delta) value, denoted tan(delta)max, is recorded, as well as the modulus G* at 10% strain, denoted G*10%.

[0142] The G*10% values ​​measured at 23°C are representative of the stiffness, which must be close to the reference value to ensure a good level of fatigue resistance in order to guarantee good tire endurance.

[0143] All values ​​are given as a base of 100 relative to a given reference.

[0144] 1.3 Measurement of ozone resistance

[0145] The susceptibility of an elastomeric composition to stress cracking in the presence of ozone (or ozone resistance) is measured using the following method: after baking and then drying at 77°C in air for 28 days, 10 B15 specimens are placed on a trapezoid at various elongations ranging from 10% to 100% in 10% elongation increments along the specimen's major axis (specimen length). These B15 specimens are made from an MFTR plate (known as Monsanto), the two end ridges of which serve to hold the specimen in place. The B15 specimens have the following dimensions: 78.5 mm x 15 mm x 1.5 mm. After aging the specimens under the conditions described above, they are placed in an oven at a temperature of 38°C and an ozone concentration of 50 ppm (parts per hundred million) for 3 days. After 2, 5 or 7 days of exposure, each face is visually analyzed via photo with a binocular magnifying glass.Each test specimen is scored out of 20 based on its color: all black = score of 20 (each specimen (10% elongation, 20% elongation... to 100% elongation) is intact), specimen breakage = score of 0 (all specimens (10% elongation, 20% elongation... to 100% elongation) have broken), and between these two extremes, the number and depth of cracks assign shades of gray to the specimen (measured using computer processing). An intermediate score will show an increasing number of cracks with deformation until failure occurs at higher deformation levels. This 20-point scale takes into account all specimens at different deformation levels. The higher the score, the better the ozone performance.

[0146] All values ​​are expressed as a percentage of 100 relative to a given reference value. A value higher than the reference value indicates an improved result, i.e., better resistance to ozone.

[0147] 1.4 Fatigue Test

[0148] Fatigue resistance, expressed in number of cycles or in relative unit (ur), is measured in a known manner on 12 specimens subjected to repeated low-frequency tensile stresses up to an elongation of 110%, at 23°C, using a Monsanto apparatus (type "MFTR", cam 16) until the specimen breaks, according to ASTM D4482-85 and ISO 6943 standards.

[0149] The result is expressed in relative units (ur). A value higher than that of the control, arbitrarily set at 100, indicates an improved result, i.e., better fatigue resistance of the rubber samples.

[0150] 2. Preparation of compositions

[0151] The compositions are prepared as follows: the diene elastomer(s), the reinforcing filler(s), and the various other ingredients, with the exception of the vulcanizing system, are successively introduced into an internal mixer (final filling rate: approximately 70% by volume), whose initial tank temperature is approximately 90°C. A thermomechanical process (non-productive phase) is then carried out in a single step, lasting approximately 3 to 4 minutes in total, until a maximum "drop" temperature of 165°C is reached.

[0152] The mixture thus obtained is collected, cooled, and then sulfur and an accelerator (sulfenamide) are incorporated on a mixer (homo-finisher) at 40°C by mixing (productive phase) for 5 to 12 min.

[0153] The elastomeric compositions thus obtained are then calendered into plates (2 to 3 mm thick) for the measurement of their physical or mechanical properties.

[0154] 3. Tests

[0155] The purpose of these tests is to demonstrate the improved compromise in properties obtained with the compositions of the invention compared to a conventional control composition used in a tire sidewall. The ingredients of the different compositions are listed in Table 1 below, and the quantity of these ingredients is expressed in parts per hundred by weight of elastomer.

[0156] Table 1: Elastomeric compositions for tire sidewalls

[0157] The rate of reinforcing fillers was adjusted so that the elastomeric compositions exhibit the same curing stiffness and their mechanical properties can be compared.

[0158] (1): Natural rubber

[0159] (2): Polybutadiene obtained by synthesis with a neodymium catalyst, polybutadiene having a 1,2 unit content of 0.5%, a 1,4-cis unit content of 98% and a 1,4-trans unit content of 1.5%, of Tg = -108°C and exhibiting a Mooney (1+4) viscosity at 100°C of 63.

[0160] (3): Liquid plasticizer: TDAE oil from Grupa LOTOS SA, Tg= 85°C (TDAE: "Treated Distillate Aromatic Extract")

[0161] (4): Antioxidant: ((N-(1,3-dimethylbutyl)-N-phenyl-para-phenylenediamine) marketed under the reference "Santaflex 6-PPD" by Flexsys (5): Anti-ozone wax "Varazon 4959" by Sasol Wax

[0162] (6): Stearic acid marketed under the reference "Pristerene 4931" by the company Uniqema

[0163] (7) Industrial grade zinc oxide marketed by Umicore

[0164] (8): N-cyclohexyl-2-benzothiazyl-sulfenamide: “Santicure CBS” from Flexsys / (9): Virgin carbon black (also called conventional carbon black) of ASTM N683 grade (ASTM D1765-17) produced from petroleum-derived raw materials and having an ash content of less than 1% by weight and a sulfur content of less than 2% by weight, relative to the total weight of the virgin carbon black, the ash and sulfur content being obtained according to the methods described above

[0165] (10): Pyrolysis carbon black “P550 HD” from Scandinavian Enviro Systems obtained by pyrolysis of end-of-life tires. The ash content is 18.5% by weight, the sulfur content is 3% by weight; the zinc content is 4.5% by weight (% by weight relative to the weight of the pyrolysis carbon black); the STSA specific surface area is 56 m² 2 / g (ASTM D6556-2021); the vacuum volume at 50M Pa is 44ml / 100g (ASTM D7854-21), the ash content, sulfur content and zinc content being obtained according to the methods described above

[0166] (11): Carbon nanotubes marketed under the reference "Graphistrength® C100" by Arkema, having an average diameter of 12 nm, an average length ranging from 1 to 10 pm and a specific surface area ranging from 200 to 250 m² 2 / g

[0167] (12) ASTM N550 grade carbon black (ASTM D1765-17) produced from petroleum-derived raw materials and having an ash content of less than 1% by weight and a sulfur content of less than 2% by weight, relative to the total weight of virgin carbon black, the ash content and sulfur content being obtained according to the methods described above

[0168] The properties of these compositions are measured after cooking at 160°C for 15 minutes and are presented in Table 2 below.

[0169] Table 2. The data presented show that the use of pyrolysis carbon black as a reinforcing filler negatively affects the processability of the compositions (Mooney plasticity) (B2 versus B1). It is observed that the compositions according to the invention (B3 to B6) exhibit better processability (Mooney plasticity) than a composition comprising only pyrolysis carbon black as a reinforcing filler (B2). The compositions according to the invention therefore offer a better compromise between curing stiffness and processability than compositions comprising only pyrolysis carbon black as a reinforcing filler.

[0170] Furthermore, the compositions of the present invention exhibit better resistance to ozone than a composition comprising only pyrolysis carbon black as reinforcing fillers (B3 to B6 versus B2).

[0171] It is also observed that the addition of carbon nanotubes at concentrations greater than or equal to 5 pce, by allowing a significant decrease in pyrolysis carbon black content, makes it possible to achieve ozone resistances equivalent to or greater than those of a composition without pyrolysis carbon black (B4 and B6 versus B1).

Claims

DEMANDS 1. A tire having an outer sidewall, the outer sidewall comprising at least one elastomeric composition based on: (1) of at least one elastomer; (2) of reinforcing charges comprising: (a) predominantly pyrolysis carbon black; and (b) at least 1.0 pc of carbon nanotubes; and (3) of a crosslinking system.

2. Pneumatic according to claim 1, wherein the elastomer is a diene elastomer or a mixture of diene elastomers.

3. Pneumatic according to claim 1 or 2, wherein the or each elastomer is a diene elastomer selected from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers.

4. Pneumatic according to claim 1 or 2, wherein the elastomeric composition comprises 15 to 75 parts per annum of natural rubber or synthetic polyisprone and 25 to 85 parts per annum of at least one polybutadiene.

5. Pneumatic according to any one of claims 1 to 4 wherein the elastomeric composition comprises from 10 to 100 parts per annum of pyrolysis carbon black.

6. Pneumatic according to any one of claims 1 to 5 wherein the reinforcing fillers further comprise in a minority of virgin carbon black and / or siliceous or aluminous mineral fillers.

7. Pneumatics according to any one of claims 1 to 5 wherein the reinforcing fillers consist of pyrolysis carbon black and carbon nanotubes.

8. Pneumatic according to any one of claims 1 to 7 wherein the elastomeric composition comprises at least 1.5 parts per 1000 of carbon nanotubes, preferably from 1.5 to 20 parts per 1000 of carbon nanotubes.

9. A tire according to any one of claims 1 to 8, wherein the pyrolysis carbon black has an ash content of 5 to 30% by weight, preferably 8 to 25% by weight, relative to the total weight of the pyrolysis carbon black.

10. A tire according to any one of claims 1 to 9, wherein the pyrolysis carbon black has a sulfur content greater than 2% by weight, preferably 2.5 to 5% by weight, relative to the total weight of the pyrolysis carbon black.

11. Pneumatic according to any one of claims 1 to 10, wherein the crosslinking system is a vulcanizing system based on molecular sulfur and / or a sulfur-donating agent.

12. Pneumatic according to any one of claims 1 to 11, wherein the composition further comprises one or more agents selected from the group consisting of plasticizers, non-reinforcing fillers, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents and reinforcing resins.

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