WO2024023465A1

WO2024023465A1 - Tire with radial carcass reinforcement

Info

Publication number: WO2024023465A1
Application number: PCT/FR2023/051200
Authority: WO
Inventors: Katia BARAN; Catherine MOUGIN
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2022-07-29
Filing date: 2023-07-28
Publication date: 2024-02-01
Also published as: FR3138352A1

Abstract

The present invention relates to a tire with radial carcass reinforcement. The tire comprises, between the reinforcing elements of the carcass reinforcement and the cavity of the tire, a rubber blend comprising a composition based on: an isoprene elastomer; 40 to 70 phr reinforcing fillers, including at least 10 phr pyrolytic carbon black, preferably at least 30 phr pyrolytic carbon black; a crosslinking system; and less than 0.07 g of metal from a pro-oxidant metal salt per 100 g of composition.

Description

DESCRIPTION

TITLE: Pneumatic with radial carcass reinforcement

FIELD OF INVENTION

The present invention relates to a tire with a radial carcass reinforcement, more particularly a tire intended to equip vehicles carrying heavy loads and traveling at sustained speed, such as for example trucks, tractors, trailers and road buses.

TECHNOLOGICAL BACKGROUND

Generally, a tire comprises a tread, intended to come into contact with a ground via a rolling surface, the two axial ends of which are connected via two sidewalls to two beads ensuring the connection mechanics between the tire and the rim on which it is intended to be mounted. A radial tire further comprises a reinforcing reinforcement, consisting of a crown reinforcement, radially internal to the tread, and a carcass reinforcement, radially internal to the crown reinforcement.

The rubber mixture, located between the carcass reinforcement and the tire cavity, more precisely between the carcass reinforcement and the tire sealing layer, must be both a chemical and physical barrier to oxygen in order to limit the diffusion of oxygen inside the tire. The rubbery mixture must therefore be able to react with oxygen by trapping it (chemical barrier) and be impermeable to oxygen (physical barrier).

By limiting the diffusion of oxygen in the lower zone and/or in the top of the tire, this rubber mixture contributes to the endurance of the tire.

A known and commonly used formulation lever to increase reactivity with oxygen is to use a pro-oxidant agent in the rubber mixture. Generally, a metallic salt such as a cobalt salt is used. This compound, however, has a very significant impact on the cost of the mixture. Furthermore, as the regulatory requirements linked to the use of this type of compound tend to become tougher, it would be advisable to be able to do without their use in rubber mixtures.

It is known to those skilled in the art that the reduction in the metal salt content in a mixture results in a reduction in the reactivity with oxygen, therefore a degradation of the endurance of the tire and a reduction in the cooking tO of the mixture with an increased risk of nodule formation during shaping of the mixture. One way to compensate for the decrease in reactivity with oxygen would be to increase the sulfur content, but as a result there would be an increased risk of nodule formation when shaping the mixture due to a decrease in tO cooking of the mixture.

The problem to be solved today is therefore to try to free ourselves from the use of metallic salts in rubber mixtures without degrading other performances such as endurance and shaping.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a tire with a radial carcass reinforcement consisting of at least one layer of reinforcing elements, the tire comprising a crown reinforcement, itself capped radially with a tread, the tread being joined to two beads via two sidewalls, characterized in that the tire comprises, between the reinforcing elements of the carcass reinforcement and the cavity of the tire, a rubbery mixture, said rubbery mixture comprising a composition based on :

- an isoprene elastomer;

- 40 to 70 phr of reinforcing fillers, including at least 10 phr of pyrolysis carbon black, preferably at least 30 phr of pyrolysis carbon black;

- a crosslinking system; And

- less than 0.07 g of metal from a pro-oxidant metal salt per 100 g of composition.

Other aspects of the invention are as described below and in the claims.

DEFINITIONS

By the expression "composition based on", is meant 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 less partially, during the different phases of manufacturing the composition; the composition can thus be in the totally or partially crosslinked state or in the non-crosslinked state. By the expression "part by weight per hundred parts by weight of elastomer" (or pce), is meant the part, by mass per hundred parts by mass of elastomer or rubber, the two terms being synonymous.

Herein, unless expressly stated otherwise, all percentages (%) shown are percentages (%) by mass.

On the other hand, any interval of values designated by the expression "between a and b" represents the range of values going from more than a to less than b (that is to say limits a and b excluded) while any interval of values designated by the expression "from a to b" means the range of values going from a to b (that is to say including the strict limits a and b). In the present, when we describe an interval of values by the expression "from a to b", we also and preferentially describe the interval represented by the expression "between a and b".

The expression “radial” refers to a radius of the tire. It is in this sense that we say of a point P1 that it is “radially interior” to a point P2 (or “radially inside” the point P2) if it is closer to the axis rotation of the tire than point P2. Conversely, a point P3 is said to be “radially external to” a point P4 (or “radially external” to point P4) if it is further from the axis of rotation of the tire than point P4. We will say that we advance “radially inwards (or outwards)” when we advance in the direction of the smaller (or larger) rays. When talking about radial distances, this meaning of the term also applies.

By “radial section” or “radial section” we mean here a cut or a section along a plane which contains the axis of rotation of the tire.

An “axial” direction is a direction parallel to the axis of rotation of the tire. A point P5 is said to be “axially interior” to a point P6 (or “axially inside” the point P6) if it is closer to the median plane of the tire than the point P6. Conversely, a point P7 is said to be “axially external to” a point P8 (or “axially external” to point P8) if it is further from the median plane of the tire than point P8. The “median plane” of the tire is the plane which is perpendicular to the axis of rotation of the tire and which is located equidistant from the annular reinforcement structures of each bead.

A “circumferential” direction is a direction that is perpendicular to both a radius of the tire and the axial direction.

The compounds comprising carbon mentioned in the description may be of fossil or biosourced origin. In the latter case, they can be, partially or totally, derived from biomass or obtained from raw materials renewables from biomass. This concerns in particular polymers, plasticizers, fillers, etc.

The cooking temperature of a rubbery mixture designates the time allowing the processability of the mixture before the formation of crosslinking bridges (induction time).

DETAILED DESCRIPTION OF THE INVENTION

Surprisingly, the inventors have discovered that the use of pyrolysis carbon black in a rubbery mixture makes it possible to reduce the metal salt content without degrading the reactivity properties with oxygen and this while increasing the cooking tO of the blend. The proposed solution makes it possible to generally improve the impact on the environment and reduce the cost of mixtures.

Thus, the present invention relates to a tire with a radial carcass reinforcement consisting of at least one layer of reinforcing elements, the tire comprising a crown reinforcement, itself radially capped with a tread, the tread of bearing being joined to two beads via two sidewalls, characterized in that the tire comprises, between the reinforcing elements of the carcass reinforcement and the cavity of the tire, a rubbery mixture, said rubbery mixture comprising, or consisting of in, a composition based on:

- an isoprene elastomer;

- a crosslinking system; And

- less than 0.07 g of metal coming from a pro-oxidant metal salt per 100g of composition, preferably less than 0.05g, or even less than 0.02g or less than 0.01g, of metal coming from a pro-oxidant metal salt per 100g of composition, even more preferably 0g of metal coming from a pro-oxidant metal salt.

The composition may also include usual additives and processing agents.

The different constituents of the composition may be as described below. Elastomer

The composition useful in the context of the present invention is based on an isoprene elastomer.

By “isoprene elastomer” is meant in a known manner an isoprene homopolymer or copolymer, in other words an elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), copolymers isoprenes (e.g. copolymer of isobutene and isoprene) and their mixtures. Preferably, the composition useful in the context of the present invention is based on an isoprene elastomer chosen from the group consisting of natural rubber, synthetic polyisoprenes and their mixtures. The elastomer is then typically made up of 70 to 100 phr of natural rubber and 0 to 30 phr of synthetic polyisoprenes.

In certain embodiments, the composition useful in the context of the present invention is based on natural rubber. In other words, the composition does not include other elastomers.

The composition useful in the context of the present invention comprises from 40 to 70 phr of reinforcing fillers, including at least 10 phr of pyrolysis carbon black, preferably at least 30 phr of pyrolysis carbon black.

The term “reinforcing filler” designates any type of filler known for its capacity to reinforce a rubber composition usable in particular for the manufacture of tires, for example organic fillers such as carbon black or pyrolysis carbon black, or inorganic fillers such as silica or alumina. In addition to pyrolysis carbon black, the composition can therefore also comprise an inorganic reinforcing filler (e.g. silica or alumina) or an organic reinforcing filler such as carbon black so as to achieve a total content of reinforcing fillers ranging from 40 to 70 p.c.

In certain embodiments, the composition comprises from 40 to 70 phr of reinforcing fillers, the reinforcing fillers being pyrolysis carbon black. It must then be understood that the composition comprises pyrolysis carbon black as the only reinforcing fillers (the composition therefore does not include inorganic reinforcing fillers and other organic reinforcing fillers).

The reinforcing fillers can be as described below. Pyrolysis Carbon Black

The composition useful in the context of the invention comprises at least 10 phr of pyrolysis carbon black, preferably at least 30 phr of pyrolysis carbon black.

In certain embodiments, the composition comprises from 40 to 70 phr of pyrolysis carbon black.

By “pyrolysis carbon black”, for the purposes of the present invention is meant a carbon black resulting from a pyrolysis process of a material comprising at least one carbonaceous polymer and a carbon black, hereinafter the material to be pyrolyze, for example in the context of recycling such a material. The physical state in which the material to be pyrolyzed is in is irrelevant, whether in the form of powder, granules, strips, or any other form, in the crosslinked or non-crosslinked state.

Preferably, the material to be pyrolyzed can be recovered from manufactured articles or products generated during their manufacturing/production (such as by-products or scraps); these manufactured articles may 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. Even more preferably, the pyrolysis carbon black usable in the context of the present invention is a carbon black obtained from a pyrolysis process in which the material to be pyrolyzed comes from manufactured articles chosen from the group consisting of pneumatic tires and non-pneumatic tires.

Pyrolysis in the context of the present invention means any type of thermal decomposition in the absence of oxygen and the raw material of which is the material to be pyrolyzed as defined above. Pyrolysis carbon blacks are therefore distinguished from so-called industrial and/or ASTM grade carbon blacks in that the carbonaceous raw material used for pyrolysis is a material comprising at least one carbonaceous polymer and one carbon black and not materials from petroleum cuts or from coal or even from oils of natural origin.

The pyrolysis carbon blacks usable in the context of the present invention differ from known carbon blacks such as industrial carbon blacks, in particular so-called “furnace” carbon blacks, in particular by a higher ash content.

Preferably, the pyrolysis carbon black usable in the context of the present invention has an ash content ranging from 5 to 30% by weight, more preferably ranging from 8 to 25% by weight, even more preferably ranging from 10% to 22% by weight, relative to the total weight of the pyrolysis carbon black.

Preferably, the pyrolysis carbon black usable in the context of the present invention has a sulfur content greater than 2% by weight, preferably ranging from 2.5 to 5% by weight, relative to the total weight of the carbon black. pyrolysis.

Preferably, the pyrolysis carbon black usable in the context of the present invention has a zinc content greater than or equal to 2% by weight, preferably ranging from 2.5 to 8% by weight, relative to the total weight of the black. of pyrolysis carbon.

Preferably, the pyrolysis carbon black usable in the context of the present invention has a specific surface area STSA measured according to standard ASTM D 6556-2021 included in a range ranging from 20 to 200 m ² /g, more preferably ranging from 30 to 90 m ² /g.

Preferably, the pyrolysis carbon black usable in the context of the present invention has an empty volume measured according to standard ASTM D7854 (2018) and at a pressure of 50 MPa included in a range ranging from 30 to 60 ml/100g, more preferably ranging from 35 to 55 ml/100g.

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 previously identified before each series of measurements and is tared to the nearest 0.1 mg and the mass is noted PO. 5 g of sample of pyrolysis carbon black are introduced into the capsule, which is weighed precisely to the nearest 0.1 mg; this mass is denoted P1. The capsule and its contents are pre-calcined using a Bunsen burner until smoke appears and the product ignites. Once the product has completely burned, the capsule and its contents are introduced into a muffle furnace heated to 825°C for 1 hour. After 1 h, the capsule was removed from the oven and immediately introduced into a desiccator at room temperature. When the capsule and the ashes have returned to room temperature, the capsule is weighed again to obtain the mass P2. Finally, it is possible to obtain the ash rate (% ash) using the formula below:

P 2 - PO ashes ~ - - - x 100

PI - PO

The zinc content in the pyrolysis carbon black is carried out after calcination of the sample, then recovery of the ashes in an acidic medium and determination by ICP-AES (inductively coupled plasma atomic emission spectroscopy). The ashes are obtained by carrying out the protocol above. Approximately exactly 100 mg of ash is taken (test portion) which is introduced into a PFA (perfluoroalkoxy) tube for HotBIock hot plate. 8 mL of 37% concentrated hydrochloric acid, 3 mL of 65% concentrated nitric acid and 0.5 mL of 40% hydrofluoric acid are then added. The tube is closed with its cap and heated to 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). Top up with ultrapure water up to the mark. The solution obtained is diluted by 100, by taking 1 mL into a 100 mL PFTE flask, previously containing 8 mL of hydrochloric acid concentrated at 37%, 3 mL of nitric acid concentrated at 65%, 0.5 mL of 40% hydrofluoric acid and 2g of boric acid. This diluted solution is then filtered through a 0.45 pm 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 5 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 dilution of a certified commercial solution to a zinc concentration of 1 g/L.

These volumetric flasks previously contain 8 mL of hydrochloric acid concentrated at 37%, 3 mL of nitric acid concentrated at 65%, 0.5 mL of hydrofluoric acid at 40% and 2g of boric acid. The standard solutions are analyzed by ICP-AES at a wavelength of ÀZn = 202.613 nm. For each standard concentration (c), the intensity of the zinc signal IZn is plotted on a graph IZn = f(c), which corresponds to the calibration line (of 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 linked to the concentration using the calibration line obtained previously. We thus obtain the concentration [cjashes in % by mass directly by the software, because the test portion and the volume have been previously recorded. The zinc concentration in the pyrolysis black [c]black in % by mass is obtained by the following equation:

ashes The determination of the sulfur content in the pyrolysis carbon blacks is carried out by a LECO oven. 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 level on the sample, the nacelles are cleaned and the oven is calibrated. The LECO oven pods are cleaned beforehand: this involves analyzing the empty pod, under the same conditions as the samples. The preparation of the calibration curve is done using a commercial standard called “BBOT” whose purity is greater than 99.99% and whose content of carbon (C), hydrogen (H), nitrogen (N ), oxygen (O) and sulfur (S) is guaranteed. This content is as follows C%: 72.52; H% 6.09; N% 6.51; 0% 7.43 and S% 7.44. We weigh approximately exactly 10 ± 3, 20 ± 3 and 40 ± 3 mg of BBOT in a basket. The standard/nacelle assembly is introduced into the combustion furnace, regulated at 1350 C under pure oxygen. The combination of oven temperature and analysis flow rate causes the sample to burn and the sulfur and/or carbon to be released in the form of SO2(g). After a time of 20 s, oxygen begins to circulate through the “lance” to accelerate the combustion of difficult-to-burn materials. Sulfur and/or carbon, in the form of SC>2(g), are carried by a flow of oxygen through the infrared detection cells. The instrument software draws a line connecting the introduced standard mass and the observed response (area) on the detector. We thus obtain a calibration line. After carefully cleaning the sampling equipment, approximately exactly 80 ± 5 mg of pyrolysis carbon black is weighed out and introduced into a LECO tower gondola. The area of the observed SO2 peak is linked to the concentration using the calibration line. The instrument software then calculates, using the mass of the sample introduced into the nacelle, the % by mass of sulfur in the sample.

Pyrolysis carbon blacks are marketed for example by the company BlackBear under the reference “BBCT30” or by the company Scandinavian Enviro Systems under the reference “P550”.

Carbon black

The composition useful in the context of the invention may comprise carbon black.

As carbon blacks, all carbon blacks are suitable, in particular blacks conventionally used in tires or their treads, in particularly industrial carbon blacks, more specifically so-called “furnace” carbon blacks.

Among the carbon blacks, we will more particularly mention the reinforcing carbon blacks of the 100, 200, 300 series, or the blacks of the 500, 600 or 700 series (ASTM D-1765-2017 grades), such as for example blacks N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, N772. Preferably, the carbon blacks are selected from the group consisting of 300, 500, 600 and 700 series blacks.

Carbon blacks can be used in isolated state, as commercially available, or in any other form, for example as a support for some of the rubber additives used. The carbon blacks could for example already be incorporated into the diene elastomer, in particular isoprene in the form of a masterbatch (see for example applications WO97/36724-A2 or W099/16600-A1).

Reinforcing inorganic filler

The composition useful in the context of the invention may comprise a reinforcing inorganic filler.

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

As reinforcing inorganic fillers suitable in particular are mineral fillers of the siliceous type, preferably silica (SiC>2) or of the aluminous type, in particular alumina (AI2O3). The silica used can be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET specific surface as well as a CTAB specific surface both less than 450 m ² /g, preferably included in a range ranging from 30 to 400 m ² /g, in particular from 60 to 300 m ² /g.

Any type of precipitated silica can be used, in particular highly dispersible precipitated silicas (called “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. We can cite, for example, the silicas described in the applications W003/016215-A1 and W003/016387-A1. Among the commercial HDS silicas, one can in particular use the silicas “Ultrasil ® 5000GR”, “Ultrasil ® 7000GR” from the company Evonik, the silicas “Zeosil ® 1085GR”, “Zeosil® 1115 MP”, “Zeosil® 1165MP”, “ Zeosil® Premium 200MP”, “Zeosil® HRS 1200 MP” from the Solvay Company. As non-HDS silica, the following commercial silicas can be used: “Ultrasil ® VN2GR” silicas, “Ultrasil ® VN3GR” silicas from the company Evonik, “Zeosil® 175GR” silica from the company Solvay, “Hi -Sil EZ120G(-D)”, “Hi-Sil EZ160G(- D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

The BET specific surface area of silica is determined in a known manner by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" Vol. 60, page 309, February 1938, more precisely according to the French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points) - gas: nitrogen - degassing: 1 hour at 160°C - relative pressure range p/in: 0.05 to 0.17). The CTAB specific surface area of the silica is determined according to the French standard NF T 45-007 of November 1987 (method B).

As other examples of inorganic fillers capable of being used in the compositions, mineral fillers of the aluminous type may also be cited, in particular alumina (Al2O3), aluminum oxides, aluminum hydroxides, aluminosilicates, titanium oxides, silicon carbides or nitrides, all of the reinforcing type as described for example in applications WO99/28376-A2, WOOO/73372-A1, WO02/053634-A1, WO2004/003067-A1 , W02004/056915-A2, US6610261-B1 and US6747087-B2. We can cite in particular the aluminas “Baikalox A125” or “CR125” (Baïkowski company), “APA-100RDX” (Condéa), “Aluminoxid C” (Evonik) or “AKP-G015” (Sumitomo Chemicals).

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

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

Those skilled in the art will know how to adapt the total rate of reinforcing load according to the use concerned, in particular according to the type of tires concerned, for example tires for motorcycles, for passenger vehicles or even for utility vehicles such as vans or heavy goods vehicles.

To couple the reinforcing inorganic filler to the diene elastomer, it is possible to use in a well-known manner an at least bifunctional coupling agent (or bonding agent) intended to ensure a sufficient connection, of a chemical and/or physical nature, between the filler. inorganic (surface of its particles) and diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. By “bifunctional” we mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer. For example, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic charge and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

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

Those 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, 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. The content of coupling agent preferably represents 0.5% to 15% by weight relative to the quantity of reinforcing inorganic filler, preferably 4 to 12%, more preferably 6 to 10% by weight relative to the quantity of reinforcing inorganic filler. Typically, the level of coupling agent is less than 20 phr, preferably included in a range ranging from 6 to 17 phr, preferably from 8 to 15 phr. This rate can easily be adjusted by those skilled in the art according to the rate of inorganic filler used in the composition.

The composition may also contain, in addition to the coupling agents, coupling activators, inorganic charge recovery agents or more generally processing aids capable in a known manner, thanks to an improvement in dispersion. of the filler in the rubber matrix and a lowering of the viscosity of the compositions, to improve their ability to be used in the raw state, these agents being for example hydrolysable silanes such as alkylalkoxysilanes (in particular alkyltriethoxysilanes) , polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines (for example trialkanol amines), hydroxylated or hydrolysable POS, for example a,co-dihydroxy-polyorganosiloxanes (in particular a, co-dihydroxy-polydimethylsiloxanes), fatty acids such as for example stearic acid.

Other organic loads

The composition useful in the context of the invention may comprise a reinforcing organic filler of functionalized polyvinyl type as described in applications WO 2006/069792-A1, WO 2006/069793-A1, WO 2008/003434-A1 and WO 2008/ 003435-A1.

Reticulation system

The composition useful in the context of the invention comprises a crosslinking system.

The crosslinking system can be any type of system known to those skilled in the art in the field of rubber compositions for tires. It may in particular be based on sulfur, and/or peroxide and/or bismaleimides.

Preferably, the crosslinking system is based on sulfur, we then speak of a vulcanization system. The sulfur can be provided in any form, in particular in the form of molecular sulfur, or of a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and, optionally, also preferentially, various known vulcanization activators can be used such as zinc oxide, stearic acid or equivalent compound such as the salts stearic acid and transition metal salts, guanidic derivatives (in particular diphenylguanidine), or even known vulcanization retarders.

Sulfur is used at a preferential rate of between 0.5 and 12 phr, in particular between 1 and 10 phr, preferably between 2 and 9 phr.

The vulcanization accelerator is used at a preferential rate of between 0.1 and 10 phr, more preferably between 0.3 and 1.0 phr.

The vulcanization activator is used at a preferential rate of between 1 and 10 phr, more preferably between 3.3 and 10 phr.

Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur can be used as an accelerator, in particular accelerators of the thiazole type as well as their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. As examples of such accelerators, the following compounds may be cited in particular: 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl- 2-benzothiazyl sulfenamide ("DCBS"), N-ter-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-ter-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD") , zinc dibenzyldithiocarbamate (“ZBEC”) and mixtures of these compounds.

Pro-oxidant metal salts

The composition useful in the context of the present invention comprises less than 0.07g of metal originating from a pro-oxidant metal salt per 100g of composition, preferably less than 0.05g, or even less than 0.02g or less than 0. .01g, of metal from a pro-oxidant metal salt per 100g of composition, even more preferably 0g of metal from a pro-oxidant metal salt.

A pro-oxidant metal salt accelerates oxygen fixation by catalyzing oxidation. Such salts are well known to those skilled in the art. Examples of pro-oxidant metal salts include, without limitation, cobalt salts, in particular cobalt salts chosen from the group consisting of abietates, acetylacetonates, tallates, naphthenates, resinates and their mixtures, salts manganese or iron salts (e.g. iron III salts as described in WO 99/24502 or WO 00/68309).

Preferably, the metal salt is a cobalt salt. Thus, the composition useful in the context of the present invention then comprises less than 0.07g of cobalt coming from a pro-oxidant cobalt salt per 100g of composition, preferably less than 0.05g, or even less than 0.02g or less than 0.01g, of cobalt from a pro-cobalt salt oxidant per 100g of composition, even more preferably 0 g of cobalt coming from a pro-oxidant cobalt salt.

Preferably, the composition is free of pro-oxidant metal salts.

Common additives and processing agents

The composition useful in the context of the invention may also comprise all or part of the usual additives and processing agents, known to those skilled in the art and usually used in rubber compositions for tires, such as for example plasticizers (such as plasticizing oils and/or plasticizing resins), non-reinforcing fillers, pigments, raw stickiness promoting agents (i.e. tackifying agent, for example rosin), protective agents such as anti-ozone waxes , chemical anti-ozonants, antioxidants, anti-fatigue agents, reinforcing resins (as described for example in application WO 02/10269).

In certain embodiments, the composition useful in the context of the invention comprises more than 0 to 5 phr of a raw tack promoting agent, for example 1 to 5 phr of a raw tack promoting agent.

In certain embodiments, the composition useful in the context of the invention comprises from 0.3% to 4% by mass relative to the total mass of the composition of one or more antioxidant agent(s). ), preferably from 0.5% to less than 0.7% by mass relative to the total mass of the composition of one or more antioxidant agent(s).

The antioxidant agent can be of the amine, phenol, imidazole, para-phenylene diamine(s) and/or dihydrotrimethylquinoline(s), polymerized quinine, wax or any other antioxidant type usually used in elastomer formulations.

As a specific example, we can cite: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6-PPD, marketed for example under the brands ANTIGENE® 6C by Sumitomo Chemical Co., Ltd NOCLAC® 6C by Ouchi Shinko Chemical Industrial Co., Ltd.), the product "Ozonon" 6C marketed by Seiko Chemical Co., Ltd., polymerized 1,2-dihydro-2,2,4-trimethyl quinoline (TMQ , marketed for example under the brand Agerite Resin D, by R. T. Vanderbilt), butylated hydroxytoluene (BHT), and butylated hydroxyanisole (BHA).

The antioxidant agent is advantageously an N-alkyl-N'-phenyl-paraphenyldiamine corresponding to formula (I):

in which R ¹ represents an alkyl group, linear or branched, having from 1 to 12 carbon atoms or a cycloalkyl group having from 5 to 8 carbon atoms.

Preferably, R ¹ represents an alkyl having from 2 to 8 carbon atoms, preferably chosen from the group consisting of ethyl, propyl (ie, n-propyl, iso-propyl), butyl (ie, n-butyl, sec-butyl and tert-butyl), pentyl, hexyl, heptyl and octyl, or a cycloalkyl group having 5 to 8 carbon atoms (cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl), more preferably a cyclohexyl group.

We more preferably use compounds whose R ¹ groups are branched, of formulas (I -bis) below:

- in which R ⁴ , R ⁵ , identical or different from each other, each represent an alkyl group whose number of carbon atoms conforms to the preferential definitions given above for R ¹ .

As more preferential examples of branched R ¹ radicals, mention will be made in particular of isopropyl, 1,3-dimethylbutyl and 1,4-dimethylpentyl.

The compounds of formula (l-bis) above are well known to those skilled in the art. They have been used for a very long time as anti-aging protective agents in rubber compositions for tires, particularly in the belts of such tires, and belong to the family of paraphenylenediamine derivatives ("PPD") such as for example N-isopropyl-N'-phenyl-paraphenylenediamine ("l-PPD")

or Nl,3-dimethylbutyl-N'-phenyl-paraphenylenediamine ("6-PPD")

(see for example applications WO 2004/033548, WO 2005/063510, WO 2005/133666).

In certain embodiments, the composition useful in the context of the invention is a composition based on:

- an isoprene elastomer;

- a crosslinking system, preferably the crosslinking system (e.g., a vulcanization system) comprising:

- between 0.5 and 12 phr, in particular between 1 and 10 phr, preferably between 2 and 9 phr, of sulfur;

- between 0.1 and 10 pce, preferably between 0.3 and 1.0 pce of one or more vulcanization accelerators;

- between 1 and 10 phr, preferably between 3.3 and 10 phr, of one or more vulcanization activators;

- less than less than 0.07g of metal coming from a pro-oxidant metal salt per 100g of composition, preferably less than 0.05g, or even less than 0.02g or less than 0.01g of metal coming from a pro-oxidant metal salt per 100g of composition, even more preferably 0g of metal coming from a pro-oxidant metal salt; And

- 0.3 to 4% by mass relative to the total mass of the composition of one or more antioxidant agent(s), preferably from 0.5 to less than 0.7% by mass. Manufacturing of compositions

The composition useful in the context of the invention is manufactured in appropriate mixers, using two successive preparation phases well known to those skilled in the art:

- a first working phase or thermomechanical mixing (so-called "nonproductive" phase), which can be carried out in a single thermomechanical step during which one introduces into a suitable mixer such as a usual internal mixer (for example of the 'type Banbury'), all the necessary constituents, in particular the elastomeric matrix, the fillers, any other various additives, with the exception of the crosslinking system. The incorporation of the filler into the elastomer can be carried out in one or several times by thermomechanical mixing. In the case where the filler is already incorporated in whole or in part into the elastomer in the form of a masterbatch as described for example in applications WO 97/36724 or WO 99 /16600, it is the masterbatch which is directly kneaded and if necessary the other elastomers or fillers present in the composition which are not in the form of masterbatch are incorporated, as well as any other various additives other than the reticulation system.

The non-productive phase is carried out at high temperature, up to a maximum temperature between 130°C and 170°C, for a duration generally between 2 and 10 minutes.

- a second phase of mechanical work (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 110°C, for example between 40°C and 100°C. The crosslinking system is then incorporated, and everything is then mixed for a few minutes, for example between 1 and 30 min.

The final composition thus obtained is then calendered for example in the form of a sheet or a plate, in particular for characterization in the laboratory, or even extruded in the form of a semi-finished (or profile) of rubber usable by example as an internal layer in a tire.

The composition can be either in the raw state (before crosslinking or vulcanization), or in the cooked state (after crosslinking or vulcanization), and can be a semi-finished product which can be used in a tire. The crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 130°C and 200°C, preferably under pressure, for a sufficient time which can vary for example between 5 and 200°C. 90 mins.

TIRES

The compositions described above are particularly useful for forming the internal wall of a tire with a radial carcass reinforcement, more particularly for being placed between the reinforcing elements of the carcass reinforcement and the cavity of the tire, even more precisely between the reinforcing elements of the carcass reinforcement and the sealing layer of the tire.

In certain embodiments, the tire of the present invention as described above is characterized in that the rubber mixture between the cavity of the tire and the reinforcing elements of the carcass reinforcement consists of at least two layers of mixture rubbery, the rubbery mixture layer, radially adjacent to the radially innermost rubbery mixture layer, comprising, or consisting of, a composition as described above. In other words, the rubbery mixture layer comprising, or consisting of, a composition as described above is located between the carcass reinforcement and the sealing layer of the tire (radially furthest rubbery mixture layer). 'interior). The tires covered by the invention are therefore tires comprising, in addition to the carcass reinforcement and the sealing layer, an additional layer of rubber mixture as described above. Thus, this layer is not in direct contact with the air.

The tire of the present invention can be as described with reference to the figures which follow.

- Figure 1 a, a meridian view of a diagram of a tire according to one embodiment of the invention,

- Figure 1b, an enlarged partial view of part of the diagram in Figure 1a. The figures are not represented to scale to simplify understanding. In Figure 1a and Figure 1b, the tire 1, of dimension 315/70 R 22.5, comprises a radial carcass reinforcement 2 anchored in two beads 3, around rods 4. The carcass reinforcement 2 is formed of a single layer of metal cables 11 and two layers of calendering 13. The carcass reinforcement 2 is hooped by a crown reinforcement 5, itself covered with a tread 6. Figure 1 b illustrates an enlargement of zone 7 of Figure 1 a and indicates in particular the thickness E of rubber mixture between the inner surface 10 of the cavity 8 of the tire and the point 12 of a reinforcing element 11 the most close to said surface 10. This thickness E is equal to the length of the orthogonal projection of the point 12 of a reinforcing element 11 closest to said surface 10 on the surface 10. This thickness E is the sum of the thicknesses of the different rubbery mixtures placed between said reinforcing element 11 of the carcass reinforcement 2; this is on the one hand the thickness of the calendering layer 13 radially interior of the carcass reinforcement and on the other hand, the thicknesses e1, e2 of the different layers 14, 15 of rubber mixture forming the internal wall of the tire 1. These thicknesses e1, e2 are also equal to the length of the orthogonal projection of a point of one surface on the other surface of the layer concerned respectively 14 or 15.

The compositions described above are particularly useful for forming the rubber mixture layer 14 (rubber mixture layer, radially adjacent to the radially innermost rubber mixture layer 15).

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

EXAMPLES

Measuring method

Rheometry:

The measurements are carried out at 140°C with an oscillating chamber rheometer, according to standard DI N 53529 - part 3 (June 1983). The evolution of the rheometric torque as a function of time describes the evolution of the stiffening of the composition following the vulcanization reaction. The measurements are processed according to standard DIN 53529 - part 2 (March 1983). tO is the induction time, that is to say the time necessary for the start of the vulcanization reaction. ta is the time necessary to achieve a conversion of a%, that is to say a% of the difference between the minimum and maximum couples of the crosslinked composition. t99 is therefore the time required to reach 99% of the conversion. Oxygen reactivity measurements:

7 samples of mixtures 6/ ^10th of a mm thick are baked at 140°C for a duration corresponding to t99.

The level of oxygen initially contained in this sample is measured.

The remaining 6 samples are placed in a study in air at 85°C for the following aging times respectively: 3, 5, 7, 10, 12 and 14J.

The oxygen level contained in each of the 6 aged samples is then measured. For each of the 7 samples, the fixed oxygen level is calculated: oxygen level measured in the aged sample - oxygen level measured in the initial sample.

The reactivity with oxygen of the mixture then corresponds to the slope of the line linking the fixed oxygen level (in % mass) to the number of days of aging at 85°C in air (in days).

The results are expressed on a basis of 100 relative to the control (the value of 100 is given to the control).

Oxygen level measurements

The cooked mixture is introduced into a pyrolysis chamber at a temperature of around 1000°C, swept by a constant current of helium.

The pyrolyzate passes through a carbon reducer. Oxygen is transformed into carbon monoxide. The gases pass over soda ash and a desiccant to remove acidic vapors. Carbon monoxide is separated from other pyrolysis gases by a chromatographic column and detected by a catharometer.

The oxygen content in the cooked mixture is calculated via a calibration curve made with cholesterol. It is expressed in % by mass of the mixture.

Preparation of compositions

The compositions are manufactured in appropriate mixers, using two successive preparation phases well known to those skilled in the art: a first working phase or thermo-mechanical mixing (sometimes referred to as a "non-productive" phase) at high temperature, up to at a maximum temperature between 110°C and 200°C, preferably between 130°C and 180°C, followed by a second phase of mechanical work (sometimes referred to as the "productive" phase) at a lower temperature, typically lower at 110°C, for example between 60°C and 100°C, finishing phase at during which the crosslinking or vulcanization system is conventionally incorporated.

Cooking is carried out at 140°C for 50 min. Examples

The mixtures prepared are as described in Table 1 (components and content - unless otherwise indicated, the contents are expressed in pce).

Table 1: prepared mixtures

Mixtures ML1 and ML6 are control mixtures. The mixtures ML3, ML4 and ML5 are mixtures according to the invention.

The mixtures ML7, ML8 and ML9 are counterexamples without pyrolysis carbon black. They illustrate the effects of different contents of pro-oxidant metal salts (comparison with ML6).

Results :

The properties of the mixtures are presented in Table 2.

Table 2: properties of mixtures It can be observed that the use of pyrolysis carbon black in a rubber mixture makes it possible to reduce the metallic salt content without degrading the reactivity properties with oxygen, while increasing the cooking tO of the mixture.

Claims

1. Tire with radial carcass reinforcement consisting of at least one layer of reinforcing elements, the tire comprising a crown reinforcement, itself capped radially with a tread, the tread being joined to two beads by the intermediate of two sidewalls, characterized in that the tire comprises, between the reinforcing elements of the carcass reinforcement and the cavity of the tire, a rubber mixture, said rubber mixture comprising a composition based on:

- an isoprene elastomer;

- a crosslinking system; And

- less than 0.07g of metal from a pro-oxidant metal salt per 100g of composition.

2. Tire according to the preceding claim in which the isoprene elastomer is chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), isoprene copolymers and their mixtures.

3. Tire according to claim 1 or 2 in which the elastomer consists of 70 to 100 phr of natural rubber and 0 to 30 phr of synthetic polyisoprenes.

4. Tire according to any one of the preceding claims in which the pyrolysis carbon black has an ash content ranging from 5 to 30% by weight, preferably ranging from 8 to 25% by weight, more preferably ranging from 10 to 22 % by weight, relative to the total weight of the pyrolysis carbon black.

5. Tire according to any one of the preceding claims in which the pyrolysis carbon black has a sulfur content greater than 2% by weight, preferably ranging from 2.5 to 5% by weight, relative to the total weight of the pyrolysis carbon black.

6. Tire according to any one of the preceding claims in which the pyrolysis carbon black has a zinc content greater than or equal to 2% in weight, preferably ranging from 2.5 to 8% by weight, relative to the total weight of the pyrolysis carbon black.

7. Tire according to any one of the preceding claims in which the crosslinking system is a vulcanization system based on molecular sulfur and/or a sulfur donor agent.

8. Tire according to claim 7 in which the vulcanization system comprises between 0.5 and 12 phr of sulfur, preferably between 2 and 9 phr.

9. Tire according to claim 7 or 8 in which the vulcanization system comprises between 0.1 and 10 phr, preferably between 0.3 and 1.0 phr of one or more vulcanization accelerators.

10. Tire according to claim 7, 8 or 9 in which the vulcanization system comprises between 1 and 10 phr, preferably between 3.3 and 10 phr of one or more vulcanization activators.

11. Tire according to any one of the preceding claims in which the composition further comprises one or more agents selected from the group consisting of plasticizers, non-reinforcing fillers, pigments, raw stickiness promoting agents, protective agents such as anti-ozone waxes, chemical anti-ozonants, anti-oxidants, anti-fatigue agents and reinforcing resins.

12. Tire according to any one of the preceding claims in which the composition further comprises from 0.3% to 4% by mass relative to the total mass of the composition of one or more anti-oxidant agents.

13. Tire according to any one of the preceding claims in which the rubber mixture between the reinforcing elements of the carcass reinforcement and the cavity of the tire consists of at least two layers of rubber mixture, the layer of rubber mixture, radially adjacent to the radially innermost layer of rubbery mixture, comprising a composition as described in any one of claims 1 to 12.