FR3159554A1 - TYRE COMPRISING AT LEAST ONE WORKING PLY WITH AN IMPROVED COMPROMISE OF PROPERTIES - Google Patents

Abstract

The invention relates to a tire comprising at least one working ply comprising metal reinforcing elements embedded in a rubber composition based on at least one diene elastomer and from 0.5 to 15 phr of a processing agent.

Description

TYRE COMPRISING AT LEAST ONE WORKING PLY WITH AN IMPROVED COMPROMISE OF PROPERTIES Technical field of the invention

The present invention relates to the field of vehicle tires.

Prior art

The performance of a vehicle tire, whether pneumatic, i.e. capable of supporting the vehicle load by means of a pressurized gas, or non-pneumatic, i.e. capable of supporting the vehicle load without the use of a pressurized gas, for example by means of stays, is partly linked to the rigidity properties of some of its constituents. Indeed, resistance to deformation is an important characteristic enabling it to respond to the stresses to which these objects are subjected. This need for rigidity is particularly essential in the calendered plies of crown plies, in particular working plies, and vehicle tires.

The required stiffness levels can be achieved through several levers, such as the use of reinforcing fillers such as carbon black and silica.

However, increasing the reinforcing filler content and the nature of this filler can lead to difficulties in the processability of raw mixes, particularly due to the increase in raw stiffness and the possible appearance of a decohesion phenomenon. Raw processability, in particular the viscosity of the mix, can be adjusted using additives known as "processing agents" but which are not without influence on the stiffness properties of crosslinked mixes. In addition, it is important to maintain properties specific to compositions intended for calendering reinforcing elements, such as adhesion to the reinforcing elements as well as crack resistance. Thus, the compromise of properties is complex to adjust.

WO2023/275494, in the field of tread compositions, aims to achieve a good compromise between processability and cured properties of the compositions such as grip, stiffness and rolling resistance and discloses that processing agents that improve the cured properties influence the stiffness properties of the crosslinked compositions. A good compromise is achieved by using an unusual content of coupling agent for inorganic fillers to elastomers.

Continuing its research, the applicant discovered that a composition comprising a specific implementation agent in association with other characteristics, in particular a blend of reinforcing fillers, makes it possible to obtain a good compromise of properties when this composition is used in working plies of vehicle tires.

Detailed description of the invention

The invention relates to a tire comprising at least one working ply comprising metal reinforcing elements embedded in a rubber composition based on at least one diene elastomer, from 10 to 70 parts by weight per hundred parts of elastomers, abbreviated phr, of reinforcing filler, said reinforcing filler comprising from 2 to 60 phr of carbon black and from 8 to 60 phr of reinforcing inorganic filler, and a crosslinking system, said crosslinking system comprising at least 4 phr of sulfur, a metal oxide, stearic acid or one of its salts and a vulcanization accelerator, the mass ratio of metal oxide to stearic acid or one of its salts being strictly greater than 4, said rubber composition comprising at least one agent for coupling the reinforcing inorganic filler to the diene elastomer, the content of coupling agent representing at most 10% by weight relative to the weight of the reinforcing inorganic filler, and from 0.5 to 15 pce of an implementing agent, the implementing agent consisting essentially of a mixture of at least one carboxylic acid comprising from 4 to 28 carbon atoms and at least one aliphatic polyol comprising from 2 to 22 carbon atoms, the melting temperature of the implementing agent being less than 80°C.

Definitions

The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. Obviously, the compounds mentioned may also come from the recycling of materials already in use, that is to say, they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes in particular polymers, plasticizers, fillers, etc.

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.

By the expression “part by weight per hundred parts by weight of elastomer” (or pce), it is meant in this description, the part, by mass per hundred parts by mass of elastomer.

In this document, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

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, excluding the limits a and b) 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 limits a and b).

In this description, the term "tire" (in English "tyre" or "tire") means a vehicle tire, whether this tire is pneumatic, that is to say supporting the load of the vehicle by means of a pressurized gas, or a non-pneumatic tire, that is to say supporting the load of the vehicle by a means other than a pressurized gas, for example by means of stays.

Diene elastomer

The tire according to the invention comprises at least one working ply comprising metal reinforcing elements embedded in a rubber composition based on at least one diene elastomer.

By “diene” elastomer (or indistinctly rubber), whether natural or synthetic, must be understood in a known manner an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers carrying two carbon-carbon double bonds, conjugated or not).

These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". "Essentially unsaturated" generally means a diene elastomer derived at least in part from conjugated diene monomers, having a content of units or patterns of diene origin (conjugated dienes) which is greater than 15% (mol %); thus, diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins such as EPDM do not fall within the previous definition and can be described in particular as "essentially saturated" diene elastomers (low or very low content of patterns of diene origin, always less than 15 mol %).

In the present application, the diene elastomers are by definition non-thermoplastic and are preferably homopolymers or random copolymers.

• tout homopolymère d’un monomère diène, conjugué ou non, ayant de 4 à 18 atomes de carbone ;
• tout copolymère d'un diène, conjugué ou non, ayant de 4 à 18 atomes de carbone et d’au moins un autre monomère.

The term diene elastomer capable of being used in the compositions in accordance with the invention is particularly understood to mean:

• any homopolymer of a diene monomer, conjugated or not, having from 4 to 18 carbon atoms;
• any copolymer of a diene, conjugated or not, having from 4 to 18 carbon atoms and at least one other monomer.

The other monomer can be an olefin or a diene, conjugated or not.

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

Suitable olefins are vinyl aromatic compounds with 8 to 20 carbon atoms and aliphatic alpha-monoolefins with 3 to 12 carbon atoms.

Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene.

Suitable aliphatic alpha-monoolefins are, in particular, acyclic aliphatic alpha-monoolefins with 3 to 12 carbon atoms.

• tout homopolymère d’un monomère diène conjugué, notamment tout homopolymère obtenu par polymérisation d'un monomère diène conjugué ayant de 4 à 12 atomes de carbone;
• tout copolymère obtenu par copolymérisation d'un ou plusieurs diènes conjugués entre eux ou avec un ou plusieurs composés vinylaromatiques ayant de 8 à 20 atomes de carbone;
• un copolymère d'isobutène et d'isoprène (caoutchouc butyle), ainsi que les versions halogénées, en particulier chlorées ou bromées, de ce type de copolymère.
• tout copolymère obtenu par copolymérisation d'un ou plusieurs diènes, conjugués ou non, avec une alpha-monooléfine.

More specifically, the diene elastomer is:

• any homopolymer of a conjugated diene monomer, in particular any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;
• any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinylaromatic compounds having from 8 to 20 carbon atoms;
• a copolymer of isobutene and isoprene (butyl rubber), as well as halogenated, particularly chlorinated or brominated, versions of this type of copolymer.
• any copolymer obtained by copolymerization of one or more dienes, conjugated or not, with an alpha-monoolefin.

Preferably, the diene elastomer is chosen from the group consisting of natural rubber, synthetic isoprene elastomers, synthetic butadiene elastomers and the mixture of these elastomers, preferably chosen from the group consisting of natural rubber, synthetic polyisoprene elastomers and their mixture.

By "isoprene synthetic elastomer" is meant, in a known manner, a homopolymer or a copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of synthetic polyisoprenes (IR), the various isoprene copolymers and the mixtures of these elastomers. Among the isoprene copolymers, mention will be made in particular of isobutene-isoprene (butyl rubber - IIR) or isoprene-styrene (SIR) copolymers. This isoprene elastomer is preferably a synthetic cis-1,4 polyisoprene; more preferably still a synthetic polyisoprene having a rate (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%.

The term "butadiene elastomer" is understood to mean, in a known manner, a homopolymer or copolymer of butadiene, in particular a diene elastomer chosen from the group consisting of polybutadienes (BR), the various copolymers of butadiene and mixtures of these elastomers. Among the copolymers of butadiene, mention will be made in particular of copolymers of butadiene-styrene (SBR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR).

The rubber composition of the at least one working ply of the tire according to the invention may also contain, in a minor manner, any type of synthetic elastomer other than diene, or even polymers other than elastomers, for example thermoplastic polymers. Preferably, the rubber composition of the at least one working ply of the tire according to the invention does not comprise any elastomer other than an elastomer chosen from the group consisting of natural rubber, isoprene synthetic elastomers and their mixture.

Reinforcing charge

The tire according to the invention comprises at least one working ply comprising metal reinforcing elements embedded in a rubber composition based on 10 to 70 parts by weight per hundred parts of elastomers, abbreviated pce, of reinforcing filler, said reinforcing filler comprising from 2 to 60 pce of carbon black and from 8 to 60 pce of reinforcing inorganic filler.

A reinforcing filler is known for its ability to strengthen a rubber composition that can be used in the manufacture of tires.

The rubber composition of the tire according to the invention comprises a blend of a reinforcing filler of carbon black type and an inorganic reinforcing filler. Indeed, the use of a blend of fillers makes it possible, in association with the other characteristics of the rubber composition, to achieve a compromise of raw/cooked properties that the use of a single type of filler, in particular a single organic filler, does not allow.

Any type of so-called reinforcing filler, known for its ability to reinforce a rubber composition suitable for use in particular in the manufacture of tires, can be used, for example a filler such as carbon black and a reinforcing inorganic filler such as silica.

Preferably, the reinforcing filler consists of 2 to 60 phr of carbon black and 8 to 60 phr of reinforcing inorganic filler, and preferably comprises at least 3 phr of carbon black, preferably at least 4 phr of carbon black, very preferably at least 5 phr of carbon black, very preferably at least 7 phr of carbon black.

Suitable carbon blacks are all carbon blacks, including those conventionally used in tires or their treads. Among the latter, we will 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). These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a carrier for some of the rubber additives used. 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 WO99/16600-A1).

By "reinforcing inorganic filler" is meant here any inorganic or mineral filler, whatever its color and 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. As is known, certain reinforcing inorganic fillers can be characterized in particular by the presence of hydroxyl groups (-OH) on their surface.

Suitable reinforcing inorganic fillers are, in particular, mineral fillers of the siliceous type, preferably silica (SiO2) or of the aluminous type, in particular alumina (Al2O3). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET specific surface area and a CTAB specific surface area both less than 450 m2/g, preferably within a range from 30 to 400 m2/g, in particular from 60 to 300 m2/g.

Precipitated silica can be produced from raw materials derived from inorganic sand (silicon dioxide from inorganic sand), recycled material such as glass, especially soda-lime glass, or bio-based raw materials such as organic waste from plants such as bamboo leaves, corn cobs, sugarcane bagasse, rice, wheat, mustard, especially rice husks, wheat husks, mustard husks.

Any type of precipitated silica can be used, in particular highly dispersible precipitated silicas (known as “HDS”). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. Examples include the silicas described in applications WO03/016215-A1 and WO03/016387-A1. Among the commercial HDS silicas, it is possible to use in particular 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 company Solvay. As non-HDS silica, the following commercial silicas can be used: silicas “Ultrasil ® VN2GR”, “Ultrasil ® VN3GR” from Evonik, silica “Zeosil® 175GR” from Solvay, silicas “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

As other examples of reinforcing inorganic fillers that can be used in the rubber compositions of the invention, mention may also be made of mineral fillers of the aluminous type, in particular alumina (Al2O3), aluminum oxides, aluminum hydroxides, aluminosilicates, titanium oxides, silicon carbides or nitrides, all of the reinforcing type as described, for example, in applications WO99/28376-A2, WO00/73372-A1, WO02/053634-A1, WO2004/003067-A1, WO2004/056915-A2, US6610261-B1 and US6747087-B2. Examples include the aluminas “Baikalox A125” or “CR125” (Baïkowski company), “APA-100RDX” (Condéa), “Aluminoxid C” (Evonik) or “AKP-G015” (Sumitomo Chemicals).

Preferably, the reinforcing inorganic filler in the rubber composition of the invention is a silica, preferably a precipitated silica.

The physical state in which the reinforcing inorganic filler is presented is indifferent, 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, provided that this reinforcing filler of another nature is covered with an inorganic layer such as silica, or else 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. By way of example, mention may be made of carbon blacks partially or completely covered with silica, or carbon blacks modified with silica, such as, without limitation, the “Ecoblack®” type fillers of the CRX2000 series or the “CRX4000” series from Cabot Corporation.

The person skilled in the art will be able to adapt the total reinforcing charge rate 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.

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

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

Coupling agent of reinforcing inorganic filler to diene elastomer

The tire according to the invention comprises at least one working ply comprising metallic reinforcing elements embedded in a rubber composition comprising at least one agent for coupling the reinforcing inorganic filler to the diene elastomer, the content of coupling agent representing at most 10% by weight relative to the weight of the reinforcing inorganic filler.

To couple the inorganic reinforcing filler to the diene elastomer, an at least bifunctional coupling agent (or bonding agent) is used in a well-known manner, intended to ensure a sufficient connection, of a chemical and/or physical nature, between the inorganic filler (surface of its aggregates) and the diene elastomer. 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 filler and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the diene elastomer.

The coupling agent content represents at most 10% by weight relative to the weight of the reinforcing inorganic filler. A higher content does not improve the raw/cooked compromise of the compositions used in the tire according to the invention.

Preferably, the agent for coupling the reinforcing inorganic filler to the diene elastomer is chosen from polysulfide silanes, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, mercaptosilane dimers, blocked mercaptosilane dimers, mercaptosilane oligomers, blocked mercaptosilane oligomers and mixtures thereof.

Even more preferably, the coupling agent of the reinforcing inorganic filler to the diene elastomer is a polysulfide silane.

More particularly, polysulfide silanes, called “symmetrical” or “asymmetrical” depending on their particular structure, can be used, as described for example in applications WO03/002648 (or US 2005/016651) and WO03/002649 (or US 2005/016650).

Preferably, polysulfurized silanes corresponding to the following general formula (II) are particularly suitable, without the following definition being limiting:

Z - A - Sx - A - Z (II) ,

• x est un entier de 2 à 8 (de préférence de 2 à 5) ;
• les symboles A, identiques ou différents, représentent un radical hydrocarboné divalent (de préférence un groupement alkylène en C1-C18 ou un groupement arylène en C6-C12, plus particulièrement un alkylène en C1-C10, notamment en un alkylène en C1-C4, en particulier le propylène) ;
• les symboles Z, identiques ou différents, répondent à l'une des trois formules ci-après:

in which:

• x is an integer from 2 to 8 (preferably from 2 to 5);
• the symbols A, identical or different, represent a divalent hydrocarbon radical (preferably a C1-C18 alkylene group or a C6-C12 arylene group, more particularly a C1-C10 alkylene, in particular a C1-C4 alkylene, in particular propylene);
• the symbols Z, identical or different, correspond to one of the three formulas below:

• les radicaux R^a, substitués ou non substitués, identiques ou différents entre eux, représentent un groupe alkyle en C1-C18, un groupe cycloalkyle en C5-C18 ou un groupe aryle en C6-C18 (de préférence des groupes alkyle en C1-C6, le cyclohexyle ou le phényle, notamment des groupes alkyle en C1-C4, plus particulièrement le méthyle et/ou l'éthyle).
• les radicaux R^b, substitués ou non substitués, identiques ou différents entre eux, représentent un groupe alkoxyle en C1-C18 ou un groupe cycloalkoxyle en C5-C18 (de préférence un groupe choisi parmi les alkoxyles en C1-C8 et les cycloalkoxyles en C5-C8, plus préférentiellement encore un groupe choisi parmi les alkoxyles en C1-C4, en particulier le méthoxyle et l’éthoxyle), ou un groupe hydroxyle, ou tel que 2 radicaux R^breprésentent un groupe dialkoxyle en C3-C18.

in which:

• the radicals R ^a , substituted or unsubstituted, identical or different from each other, represent a C1-C18 alkyl group, a C5-C18 cycloalkyl group or a C6-C18 aryl group (preferably C1-C6 alkyl groups, cyclohexyl or phenyl, in particular C1-C4 alkyl groups, more particularly methyl and/or ethyl).
• the radicals R ^b , substituted or unsubstituted, identical or different from each other, represent a C1-C18 alkoxyl group or a C5-C18 cycloalkoxyl group (preferably a group chosen from C1-C8 alkoxyls and C5-C8 cycloalkoxyls, more preferably still a group chosen from C1-C4 alkoxyls, in particular methoxyl and ethoxyl), or a hydroxyl group, or such that 2 radicals R ^b represent a C3-C18 dialkoxyl group.

In the case of a mixture of polysulfurized alkoxysilanes corresponding to formula (II) above, in particular usual commercially available mixtures, the average value of "x" is a fractional number preferably between 2 and 5, more preferably close to 4. But the rubber composition can advantageously comprise, for example, disulfurized alkoxysilanes (x = 2).

Examples of polysulfurized silanes include bis-(alkoxyl(C1-C4)-alkyl(C1-C4)silyl-alkyl(C1-C4)) polysulfides (especially disulfides, trisulfides or tetrasulfides), such as bis(3-trimethoxysilylpropyl) or bis(3-triethoxysilylpropyl) polysulfides. Among these compounds, bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, of formula [(C2H5O)3Si(CH2)3S2]2 or bis-(triethoxysilylpropyl) disulfide, abbreviated to TESPD, of formula [(C2H5O)3Si(CH2)3S]2. Mention will also be made, as preferred examples, of polysulfides (in particular disulfides, trisulfides or tetrasulfides) of bis-(monoalkoxyl(C1-C4)-dialkyl(C1-C4)silylpropyl), more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide as described in patent application WO02/083782 (or US7217751).

Preferably, the agent for coupling the reinforcing inorganic filler to the diene elastomer corresponds to formula (II) with x being an integer from 2 to 8 (preferably from 2 to 5), the symbols A, identical or different, represent a C1-C10 alkylene group, preferably a C1-C4 alkylene, more preferably propylene, the symbols Z, identical or different, correspond to the formula Si(R ^b ) ₃ with R ^b , identical or different from each other, representing a C1-C4 alkoxyl group, in particular methoxyl and ethoxyl.

Even more preferably, the coupling agent of the inorganic reinforcing filler to the diene elastomer is chosen from the group consisting of bis(triethoxysilylpropyl) tetrasulfide, bis(trimethoxysilylpropyl) tetrasulfide, bis-(triethoxysilylpropyl) disulfide and bis-(trimethoxysilylpropyl) disulfide, more preferably is chosen from the group consisting of bis(triethoxysilylpropyl) tetrasulfide and bis(trimethoxysilylpropyl) tetrasulfide.

Examples of coupling agents other than a polysulfurized alkoxysilane include bifunctional POS (polyorganosiloxanes) or hydroxysilane polysulfides (Rb = OH in formula I above) as described, for example, in patent applications WO02/30939-A1 (or US6774255-B1), WO02/31041-A1 (or US2004/051210-A1), and WO2007/061550-A1, or silanes or POS bearing azo-dicarbonyl functional groups, as described, for example, in patent applications WO2006/125532-A1, WO2006/125533-A1, WO2006/125534-A1.

Examples of other sulfurized silanes include, for example, silanes carrying at least one thiol function (-SH) (called mercaptosilanes) and/or at least one blocked thiol function, such as, for example, “NXT-Silane” marketed by the company Momentive, the dimers or oligomers of these silanes, as described, for example, in patents or patent applications US6849754, WO99/09036, WO2006/023815, WO2007/098080, WO2007/98120, EP1994038, EP2079793, WO2010/072685 and WO2008/055986.

Crosslinking system

The crosslinking system is a sulfur-based system. This is called a vulcanization system. The sulfur can be provided in any form, including molecular sulfur or a sulfur-donating agent. The crosslinking system also includes a metal oxide, stearic acid or one of its salts, and a vulcanization accelerator.

The crosslinking system may also include guanidine derivatives (in particular diphenylguanidine) as vulcanization activators, or even known vulcanization retarders.

Sulphur is used at a rate of at least 4 pce. Below this rate, the rubber composition less well meets the criteria required for a calendering composition for metallic elements.

Any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur may be used as an accelerator, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. Examples of such accelerators include, but are not limited to, the following compounds: 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-tert-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

The mass ratio of metal oxide to stearic acid or one of its salts in the crosslinking system is strictly greater than 4. When this ratio is less than 4, the properties of the rubber-metal composite, in particular the adhesion of the rubber composition to the metal, are less satisfactory.

Implementation Agent

The rubber composition of the at least one working ply of the tire according to the invention comprises from 0.5 to 15 pce of an implementing agent, the implementing agent consisting essentially of a mixture of at least one carboxylic acid comprising from 4 to 28 carbon atoms and at least one aliphatic polyol comprising from 2 to 22 carbon atoms, the melting temperature of the implementing agent being less than 80°C.

Surprisingly, the applicant noticed that the use of a specific processing agent in the presence of a reinforcing filler comprising both a reinforcing inorganic filler and a reinforcing organic filler in a rubber composition makes it possible to achieve an unexpected compromise of properties and obtain a rubber composition exhibiting a good compromise between processability and cured rigidity.

For the purposes of the present invention, the term “processing agent” means any compound capable of lowering the Mooney index, and therefore capable of improving the processability, of a rubber composition comprising a reinforcing filler. These compounds are also called “processing aids” in English.

By "consisting essentially of" as used herein is meant that the processing agent may contain, in addition to the carboxylic acid having from 4 to 28 carbon atoms and the aliphatic polyol having from 2 to 22 carbon atoms, other ingredients in proportions which do not affect the characteristics and function of the processing agent, namely its ability to improve the processability of the rubber composition.

The other ingredients that may be present in the processing agent may be, for example, ethylene glycol, polyethylene glycol or dioxin. Preferably, the other ingredients that may optionally be present in the processing agent represent less than 10% by weight of the total weight of the processing agent, more preferably represent less than 6% by weight of the total weight of the processing agent.

The processing agent used in the compositions of the invention is therefore a mixture of two ingredients: a polyol as defined above and a carboxylic acid as defined above, these two ingredients representing more than 50% by weight of all the ingredients of the processing agent, more preferably more than 84% by weight of all the ingredients of the processing agent, more preferably still more than 90% by weight of all the ingredients of the processing agent. The carboxylic acid that can be used in the processing agent may be a mixture of carboxylic acids as defined in the present description.

Preferably, the aliphatic polyol of the processing agent comprises from 2 to 15 carbon atoms, preferably from 2 to 10 carbon atoms.

Preferably, the aliphatic polyol of the implementing agent is chosen from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane, erythritol, xylitol, sorbitol, dulcitol, mannitol, inositol and mixtures thereof.

Even more preferably, the aliphatic polyol of the implementing agent is chosen from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane and mixtures thereof.

Even more preferably, the aliphatic polyol of the implementing agent is trimethylolpropane.

Preferably, the carboxylic acid of the implementing agent comprises from 6 to 22 carbon atoms, preferably from 8 to 20 carbon atoms, even more preferably comprises from 14 to 20 carbon atoms.

Preferably, the carboxylic acid of the implementing agent is chosen from the group consisting of caprylic acid, lauric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid and mixtures thereof.

Preferably, the carboxylic acid of the implementing agent is a mixture of several carboxylic acids having from 16 to 18 carbon atoms.

Preferably, the implementing agent consists essentially of an aliphatic polyol chosen from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane and a carboxylic acid comprising 14-20 carbon atoms, more preferably comprising 16 to 18 carbon atoms.

Preferably, the implementing agent consists essentially of trimethylolpropane and a carboxylic acid comprising 16 to 18 carbon atoms.

Preferably, in the implementing agent, the weight ratio between said aliphatic polyol and said carboxylic acid is within a range from 1:20 to 10:1, preferably is within a range from 1:10 to 5:1.

Preferably, the implementing agent comprises at most 5% by weight of the implementing agent of fatty mono-alcohol.

The melting temperature of the processing agent is preferably less than 75°C, more preferably less than 70°C.

The rubber composition of the at least one working ply of the tire according to the invention preferably comprises from 0.5 to 10 phr of an implementing agent as described above, preferably from 0.5 to 6 phr of such an implementing agent, preferably from 1.0 to 6 phr, preferably from 1.5 to 6 phr and very preferably from 2.0 to 6 phr.

Preferably, the rubber composition of the at least one working ply of the tire according to the invention comprises less than 4 phr of processing agent whose melting temperature is greater than 70°C, preferably comprises less than 3 phr of processing agent whose melting temperature is greater than 70°C, preferably less than 2 phr of processing agent whose melting temperature is greater than 70°C and preferably less than 1 phr of processing agent whose melting temperature is greater than 70°C.

The implementing agents that can be used in the context of the invention are known and marketed. For example, mention may be made of the implementing agent marketed under the reference “Aflux 37”.

Various additives

The rubber composition of the tire according to the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended for the manufacture of tires, such as for example plasticizers or extender oils, whether the latter are of an aromatic or non-aromatic nature, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents, adhesion promoters such as cobalt salts.

Reinforcing element

The tire according to the invention comprises at least one working ply comprising metal reinforcing elements embedded in a rubber composition.

The working sheet is therefore a reinforced product comprising metal reinforcing elements and a rubber composition, the composition having been able to react with the surface of the reinforcing elements during the different phases of manufacturing the reinforced product, in particular during the crosslinking of the composition or during the manufacture of the reinforced product before crosslinking of the composition.

Metallic reinforcing elements are wire elements. By metallic, we mean that they are made of a metallic material. A wire element is an element extending in a main direction, its dimension in the main direction being much greater than the dimensions in directions perpendicular to the main direction. A wire element is flexible, that is, it can be wound elastically.

The metal reinforcing elements are embedded in the rubber composition, i.e. completely surrounded by the composition, with the possible exception of the cut areas of the ply.

According to a first variant, the metal surface of the reinforcing elements is made of a material different from the rest of the reinforcing elements. In other words, the reinforcing elements are made of a metal material which is at least partly, preferably totally, covered by a metal layer which constitutes the metal surface.

According to a second variant of the invention, the metal reinforcing elements are made of the same material, in which case the reinforcing elements are made of a metal which is identical to the metal of the metal surface.

According to one embodiment of the invention, the metal surface comprises a metal selected from the group consisting of iron, copper, zinc, tin, aluminum, cobalt, nickel and alloys comprising at least one of these metals. The alloys may be, for example, binary or ternary alloys, such as steel, bronze and brass. Preferably, the metal of the metal surface is iron, copper, tin, zinc or an alloy comprising at least one of these metals. More preferably, the metal of the metal surface is steel, brass (Cu-Zn alloy), zinc or bronze (Cu-Sn alloy), even more preferably brass or steel, and very preferably brass.

When the metal surface is made of steel, the steel is preferably a carbon steel or a stainless steel. When the steel is a carbon steel, its carbon content, by weight, is preferably between 0.01% and 1.2% or between 0.05% and 1.2%, or even between 0.2% and 1.2%, in particular between 0.4% and 1.1%. When the steel is stainless, it preferably comprises at least 11% chromium and at least 50% iron.

The metal reinforcing elements are arranged side by side in a main direction.

Preparation of rubber compositions

• une première phase de travail ou malaxage thermomécanique (phase dite « non-productive »), qui peut être conduite en une seule étape thermomécanique au cours de laquelle on introduit, dans un mélangeur approprié tel qu'un mélangeur interne usuel (par exemple de type « Banbury »), tous les constituants nécessaires, notamment le ou les élastomères diéniques, la ou les charges renforçantes dont la charge inorganique renforçante, l’agent de couplage de la charge inorganique renforçante à l’élastomère diénique, l’agent de mise œuvre spécifique, les éventuels autres additifs divers, à l'exception du système de réticulation. L’incorporation de la charge renforçante à l’élastomère peut être réalisée en une ou plusieurs fois en malaxant thermomécaniquement. Dans le cas où la charge est déjà incorporée en totalité ou en partie à l’élastomère sous la forme d’un mélange-maître (« masterbatch » en anglais) comme cela est décrit par exemple dans les demandes WO 97/36724 ou WO 99/16600, c’est le mélange-maître qui est directement malaxé et le cas échéant on incorpore les autres élastomères ou charges présents dans la composition qui ne sont pas sous la forme de mélange-maître, ainsi que les éventuels autres additifs divers autres que le système de réticulation.
• une seconde phase de travail mécanique (phase dite « productive »), qui est réalisée dans un mélangeur externe tel qu'un mélangeur à cylindres, après refroidissement du mélange obtenu au cours de la première phase non-productive jusqu'à une plus basse température, typiquement inférieure à 120°C, par exemple entre 40°C et 100°C.On incorpore alors le système de réticulation, et le tout est alors mélangé pendant quelques minutes, par exemple entre 5 et 15 min.

The rubber composition used in 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 (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 conventional internal mixer (for example of the "Banbury" type), in particular the diene elastomer(s), the reinforcing filler(s) including the reinforcing inorganic filler, the agent for coupling the reinforcing inorganic filler to the diene elastomer, the specific processing agent, any other various additives, with the exception of the crosslinking system. The incorporation of the reinforcing filler into the elastomer can be carried out in one or more stages 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 mixed and where appropriate the other elastomers or fillers present in the composition which are not in the form of a masterbatch are incorporated, as well as any other various additives other than the crosslinking system.
• a second phase of mechanical work (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 between 40°C and 100°C. The crosslinking system is then incorporated, and everything is then mixed for a few minutes, for example between 5 and 15 min.

The non-productive phase can be carried out at high temperature, up to a maximum temperature between 110°C and 200°C, preferably between 130°C and 185°C, for a duration generally between 2 and 10 minutes.

The final composition thus obtained is then calendered, for example, in the form of a sheet or plate, in particular for laboratory characterization, or extruded in the form of a semi-finished (or profiled) rubber. The rubber composition is calendered, then the metal reinforcing elements are embedded by incorporation between two strips of rubber composition in order to form the at least one working ply of the tire according to the invention.

The composition can be either in the raw state (before crosslinking or vulcanization), or in the cooked state (after crosslinking or vulcanization).

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

Pneumatic

A tire having a geometry of revolution relative to an axis of rotation, its geometry is usually described in a meridian plane containing the axis of rotation of the tire. For a given meridian plane, the radial, axial and circumferential directions respectively designate the directions perpendicular to the axis of rotation of the tire, parallel to the axis of rotation of the tire and perpendicular to the meridian plane. By convention, the expressions "radially inward, respectively radially outward" mean "closer, respectively further from the axis of rotation of the tire". By "axially inward, respectively axially outward" is meant "closer, respectively further from the equatorial plane of the tire", the equatorial plane of the tire being the plane passing through the middle of the tire's rolling surface and perpendicular to the axis of rotation of the tire.

The tire of the invention is preferably intended to equip passenger car and SUV (“Sport Utility Vehicles”) type motor vehicles.

In this application, the term "tire" (in English "tyre" or "tire") means a pneumatic or non-pneumatic tire.

The term "pneumatic tire" means a tire intended to form a cavity by cooperating with a support element, for example a rim, this cavity being capable of being pressurized to a pressure higher than atmospheric pressure.

In contrast, a "non-pneumatic tire" means a tire that is not suitable for being pressurized.

Thus, a pneumatic tire usually comprises two beads intended to come into contact with a rim, a crown composed of at least one crown reinforcement and a tread, two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads. The crown reinforcement comprises at least one working ply comprising metal reinforcing elements arranged parallel to each other and forming with the circumferential plane an angle at least equal to 10°.

The pneumatic tires according to the invention are intended to equip in particular vehicles of all types such as passenger vehicles, two-wheeled vehicles, heavy goods vehicles, agricultural vehicles, civil engineering vehicles or aircraft or, more generally, any rolling device.

A non-pneumatic tire is a toric body made of at least one polymeric material, intended to perform the function of a tire but without being subjected to inflation pressure. A non-pneumatic tire may be solid or hollow. A hollow non-pneumatic tire may contain air, but at atmospheric pressure, i.e. it does not have pneumatic rigidity provided by an inflation gas at a pressure higher than atmospheric pressure. Thus, a non-pneumatic tire usually comprises a base, designed for example for mounting on a rigid rim, a crown reinforcement, ensuring the connection with a tread and a deformable structure, such as spokes, ribs or cells, this structure being arranged between the base and the crown. Such non-pneumatic tires do not necessarily include a sidewall. Non-pneumatic tires are described for example in documents WO 03/018332 and FR2898077. Non-pneumatic tires are intended to equip passenger vehicles or two-wheelers in particular.

The invention relates to tires both in the raw state (i.e., before curing) and in the cured state (i.e., after vulcanization).

Examples Preparation of rubber compositions

The following tests are carried out as follows: the diene elastomer, the reinforcing filler and the various other ingredients, with the exception of the vulcanisation system, are successively introduced into an internal mixer (final filling rate: approximately 70% by volume), whose initial tank temperature is approximately 60°C. Thermomechanical work (non-productive phase) is then carried out in one step, lasting a total of approximately 3 to 4 minutes, until a maximum "drop" temperature of 165°C is reached.

The mixture thus obtained is recovered, cooled and then sulfur and an accelerator (sulfenamide) are incorporated, on a mixer (homo-finisher) at 30°C, mixing everything (productive phase) for an appropriate time (for example between 5 and 12 min).

The crosslinking of the composition was carried out at a temperature of 160°C, under pressure for 10 to 15 min.

Measurement methods

Mooney Plasticity

The Mooney plasticity measurement is carried out according to the following principle and in accordance with ASTM D-1646. The raw mixture 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 needed to maintain this movement is measured after 4 minutes of rotation. The Mooney plasticity (ML 1+4) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Newton.meters).

The results are expressed in base 100, a value greater than 100 meaning a Mooney plasticity of lower value than that of the reference mixture, while a value less than 100 means a Mooney plasticity of higher value than that of the reference mixture.

Dynamic properties G*

The dynamic properties are measured on a Metravib viscoanalyzer, according to the ASTM D 5992-96 standard. The response of a crosslinked composition sample (cylindrical specimen 4 mm thick and 400 mm² in cross-section) is recorded, subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz at 60 ° C. A strain amplitude sweep is carried out from 0.1 to 100% (forward cycle), then from 100% to 0.1% (return cycle). The results used are the dynamic complex shear modulus G*. For the return cycle, the dynamic complex shear modulus G* (50%) at 50% strain, at 60 ° C and the dynamic complex shear modulus G* (20%) at 20% strain, at 60 ° C are indicated.

The results are expressed in base 100, a value greater than 100 meaning a complex dynamic shear modulus greater than the modulus of the reference mixture, while a value less than 100 means a modulus less than the modulus of the reference mixture.

Elongation modulus

This is the elastic modulus of the mixture measured during a uniaxial tensile experiment, at an elongation value of 0.5 (i.e. 50% elongation, expressed as a percentage). A constant uniaxial tensile speed is imposed on the specimen, and its elongation and stress are measured. The measurement is carried out using an INSTRON type tensile testing machine, at a temperature of 23°C, and a relative humidity of 50% (ISO 23529 standard). The measurement conditions and the exploitation of the results to determine the elongation and the stress are as described in the NF ISO 37: 2012-03 standard. The stress is determined for an elongation of 0.5 and the elastic modulus at 50% is calculated by calculating the ratio of this stress value to the elongation value. The person skilled in the art will know how to choose and adapt the dimensions of the test piece according to the quantity of mixture accessible and available, particularly in the case of taking samples from a finished product such as a tire.

These values are determined immediately after crosslinking of the mixture, then after 7 days and 14 days of aging in an oven at a temperature of 77°C in air. The results are noted respectively M50 0 days, M50 7 days and M50 14 days. They are expressed on a base of 100, a value greater than 100 meaning a modulus greater than the modulus of the reference mixture, while a value less than 100 means a modulus less than the modulus of the reference mixture.

The melting temperature can be measured by differential scanning calorimetry (DSC) as described in ISO 11357-3 of March 2018.

The different compositions presented in Table 1 are prepared. Mixture T1 is the reference mixture for compositions C1 and C2. Mixture T2 is the reference mixture for compositions C3 and C4. Mixture T3 is the reference mixture for compositions C5, C6 and C7. Mixture T4 is the reference mixture for compositions C8 and C9. Mixture T5 is the reference mixture for compositions C10 and C11.

It is observed that the use of an implementing agent in accordance with the invention, here Aflux 37, makes it possible to maintain, or even reduce, the Mooney plasticity of the raw mixes while increasing the G* rigidity of the crosslinked mixes. The elongation moduli are also at least maintained, with good resistance to aging.

For mixtures containing only carbon black, no impact on Mooney plasticity or gain in rigidity is observed. Comparison of Aflux 37 and Aflux 42 shows no influence on the elongation modulus.

Hybrid blends, containing both carbon black and silica, exhibit improved G* stiffness and elongation moduli that are not very sensitive to aging.

1. Natural rubber
2. Carbon black grade ASTM N326 (designation according to ASTM D-1765 standard);
3. Solvay-Rhodia's "Zeosil 1165 MP" in the form of microbeads, CTAB 160 m²/g, precipitated silica
4. Liquid silane triethoxysilylpropyltetrasulfide (TESPT) “Si69” from Evonik
5. Diphenylguanidine "Perkacit DPG" from Flexsys
6. Paraffinic oil "Extensoil 51" from Repsol YPF
7. Mixture of 25% by weight of trimethylolpropane, 70% by weight of carboxylic acids having 16 to 18 carbon atoms and 5% by weight of other ingredients, product marketed by Rheinchemie under the reference “Aflux 37”. Melting point 60°C
8. “Aflux 42” from Lanxess, Melting temperature 85°C
9. Oleic sunflower oil from CARGILL
10. N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine “Santoflex 6PPD” from Flexys
11. Stearic acid "Pristerene 4931" from Uniqema company
12. Industrial grade Zinc Oxide from Umicore
13. Cobalt naphthenate, product number 60830 from Fluka
14. N-Tert-Butyl-2-Benzothiazole sulfenamide
15. Sulfur

The compounds are identical to those in Table 1.

The compounds are identical to those in Table 1.

Claims (12)

A tire comprising at least one working ply comprising metal reinforcing elements embedded in a rubber composition based on at least one diene elastomer, from 10 to 70 parts by weight per hundred parts of elastomers, abbreviated pce, of reinforcing filler, said reinforcing filler comprising from 2 to 60 pce of carbon black and from 8 to 60 pce of reinforcing inorganic filler, and a crosslinking system, said crosslinking system comprising at least 4 pce of sulfur, a metal oxide, stearic acid or one of its salts and a vulcanization accelerator, the mass ratio of metal oxide to stearic acid or one of its salts being strictly greater than 4, said rubber composition comprising at least one agent for coupling the reinforcing inorganic filler to the diene elastomer, the content of coupling agent representing at most 10% by weight relative to the weight of the reinforcing inorganic filler, and from 0.5 to 15 pce of an implementing agent, the implementing agent consisting essentially of a mixture of at least one carboxylic acid comprising from 4 to 28 carbon atoms and at least one aliphatic polyol comprising from 2 to 22 carbon atoms, the melting temperature of the implementing agent being less than 80°C. Tire according to the preceding claim in which the content of processing agent in the rubber composition of the working ply ranges from 0.5 to 10 phr, preferably from 0.5 to 6 phr, more preferably from 1.0 to 6 phr, preferentially from 1.5 to 6 phr and very preferentially from 2.0 to 6 phr. Tire according to any one of the preceding claims in which the melting temperature of the processing agent is less than 75°C, preferably less than 70°C. Tire according to any one of the preceding claims in which the rubber composition of the at least one working ply comprises less than 4 phr of processing agent whose melting temperature is greater than 70°C, preferably comprises less than 3 phr of processing agent whose melting temperature is greater than 70°C, preferably less than 2 phr of processing agent whose melting temperature is greater than 70°C and preferentially less than 1 phr of processing agent whose melting temperature is greater than 70°C. A tire according to any one of the preceding claims, in which the aliphatic polyol of the processing agent comprises from 2 to 15 carbon atoms, preferably from 2 to 10 carbon atoms. A tire according to any preceding claim, wherein the aliphatic polyol of the processing agent is selected from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane, erythritol, xylitol, sorbitol, dulcitol, mannitol, inositol and mixtures thereof. A tire according to any preceding claim, wherein the aliphatic polyol of the processing agent is selected from the group consisting of 1,2-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-sec-butyl-2-methyl-1,3-propanediol, trimethylolpropane and mixtures thereof. A tire according to any preceding claim, wherein the carboxylic acid of the processing agent comprises from 6 to 22 carbon atoms, preferably from 8 to 20 carbon atoms, preferably from 14 to 20 carbon atoms. A tire according to any preceding claim, wherein the carboxylic acid of the processing agent is a mixture of several carboxylic acids having from 16 to 18 carbon atoms. A tire according to any preceding claim, wherein the processing agent comprises at most 5% by weight of the fatty monoalcohol agent. A tire according to any one of the preceding claims, wherein the diene elastomer of the rubber composition of the at least one working ply is selected from the group consisting of natural rubber, isoprene synthetic elastomers, butadiene synthetic elastomers and mixtures of these elastomers, preferably selected from the group consisting of natural rubber, isoprene synthetic elastomers and mixtures thereof. A tire according to any one of the preceding claims, wherein the reinforcing filler of the rubber composition of the at least one working ply consists of 2 to 60 phr of carbon black and 8 to 60 phr of reinforcing inorganic filler, and preferably comprises at least 3 phr of carbon black, preferably at least 4 phr of carbon black, very preferably at least 5 phr of carbon black, very preferably at least 7 phr of carbon black.