WO2018109376A1

WO2018109376A1 - Tyre provided with a composition comprising a diene elastomer, a zinc acrylate, a peroxide and a specific anti-oxidant

Info

Publication number: WO2018109376A1
Application number: PCT/FR2017/053540
Authority: WO
Inventors: Delphine NAYRAT
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2016-12-14
Filing date: 2017-12-13
Publication date: 2018-06-21
Also published as: FR3060012A1

Abstract

The invention concerns a tyre comprising a rubber composition having improved cohesion and crack propagation resistance, said composition being made from at least a diene elastomer; a peroxide; a zinc diacrylate derivative in the form of a specific zinc salt; a specific phenolic derivative; a metal oxide chosen from the group consisting of oxides of the metals from groups II, IV, V, VI, VII and VIII, and the mixtures of same; the levels of zinc diacrylate derivative and peroxide being such that the ratio of the level of peroxide and the level of zinc diacrylate derivative is less than or equal to 0.09.

Description

PNEUMATIC HAVING A COMPOSITION COMPRISING DIENE ELASTOMER, ZINC ACRYLATE, PEROXIDE AND ANTIOXIDANT

SPECIFIC The invention relates to tires and more particularly to those whose composition of an inner layer comprises a zinc diacrylate derivative, a peroxide and a specific antioxidant.

Tire layers such as the tread or the inner layers must obey a large number of technical, often antinomic, requirements including good rigidity, good cohesion and good resistance to crack propagation.

Tire designers are constantly looking for a solution to change the existing property compromise by improving at least one property of the tire, without penalizing others.

Systems commonly used to stiffen a rubber mixture are on the one hand vulcanization and on the other hand the introduction of reinforcing filler. However, these solutions can induce a decrease in cohesion and resistance to cracking.

It is in this context that the Applicant has surprisingly discovered that the use of a derivative of zinc diacrylate and a peroxide in combination with a specific phenolic derivative antioxidant improves the cohesion and resistance to crack propagation, without penalizing rigidity.

Thus, the present invention particularly relates to a tire comprising a rubber composition based on at least:

a diene elastomer,

a peroxide,

a zinc diacrylate derivative in the form of a zinc salt of formula (I)

(|)

in which R 1, R ₂ and R ₃ represent, independently of one another, a hydrogen atom or a C ₁ -C ₇ hydrocarbon-based group chosen from linear, branched or cyclic alkyl groups, aralkyl groups, alkylaryl groups and aryl groups, and optionally interrupted by one or more heteroatoms, R ₂ and R ₃ may together form a non-aromatic ring,

a phenol derivative of formula (II)

in which :

o represents a linear or branched C ₁ -C ₄ alkyl group optionally substituted by a carboxylate of a hydrocarbon group comprising 1 to 60 carbon atoms and optionally oxygen atoms;

A ₂ represents a hydrogen atom or a linear or branched C ₁ -C ₄ alkyl group;

A ₃ represents a hydrogen atom or a linear or branched C ₁ -C ₄ alkyl group optionally substituted by a phenolic group

in which the arrow (->) represents the point of attachment of the phenolic group to the alkyl group of the radical A ₃ ; Z represents a hydrogen atom or a phosphorus atom, Z comprising p valence (s) free (s), p having a value of 1 or 3;

it being understood that A ₂ and A ₃ do not both represent a hydrogen atom;

it being understood that A ₁ and A ₃ are not both substituted; and a metal oxide selected from the group consisting of Group II, IV, V, VI, VII and VIII metal oxides, and mixtures thereof;

the levels of zinc diacrylate derivative and of peroxide being such that the ratio of the level of peroxide and the level of zinc diacrylate derivative is less than or equal to 0.09.

I- DEFINITIONS

By the expression "part by weight per hundred parts by weight of elastomer" (or phr) is meant for the purposes of the present invention, the part, by mass per hundred parts by weight of elastomer or rubber.

In the present, unless expressly indicated otherwise, all the rates indicated are pce; and all percentages (%) indicated are percentages (%) by mass.

On the other hand, any range of values designated by the expression "between a and b" represents the range of values from more than a to less than b (i.e. terminals a and b excluded) while any range of values designated by the term "from a to b" means the range from a to b (i.e., including the strict limits a and b). In the present invention, when a range of values is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also designated and preferentially.

As used herein, "composition based on" is understood to mean a composition comprising the mixture and / or the reaction product of the various constituents used, some of these basic constituents being capable of or intended to react between they, at least in part, during the various phases of manufacture of the composition, in particular during its crosslinking or vulcanization. By way of example, a composition based on an elastomeric and sulfur matrix comprises the elastomeric matrix and the sulfur before firing, whereas after firing the sulfur is no longer detectable because the latter has reacted with the elastomeric matrix in forming sulfur bridges (polysulfides, disulfides, mono-sulphide). When reference is made to a "majority" compound, in the sense of the present invention, it is understood that this compound is predominant among the compounds of the same type in the composition, that is to say that it is the one which represents the largest amount by mass among the compounds of the same type, for example more than 50%, 60%, 70%, 80%, 90% or even 100% by weight relative to the total weight of the type of compound. Thus, for example, a majority reinforcing filler is the reinforcing filler representing the largest mass relative to the total weight of the reinforcing fillers in the composition. In contrast, a "minor" compound is a compound that does not represent the largest mass fraction among compounds of the same type.

In the context of the invention, the carbonaceous products mentioned in the description may be of fossil origin or biobased. In the latter case, they can be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. These include polymers, plasticizers, fillers, etc.

II- DESCRIPTION OF THE INVENTION

11-1 Diene Elastomer

The rubber compositions of the tire of the invention may contain a single diene elastomer or a mixture of several diene elastomers.

By elastomer (or "rubber", the two terms being considered synonymous) of the "diene" type, it will be recalled here that it is to be understood in known manner that one or more elastomers derived from at least a part (ie, a homopolymer or copolymer) of diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or otherwise).

The diene elastomers can be classified into two "essentially unsaturated" or "essentially saturated" categories. The term "essentially unsaturated" is generally understood to mean a diene elastomer derived at least in part from conjugated diene monomers, having a level of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%); for example, diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins of the EPDM type do not fall within the above definition and may to be especially qualified as "substantially saturated" diene elastomers (low or very low diene origin, always less than 15%). In the category of "essentially unsaturated" diene elastomers, the term "highly unsaturated" diene elastomer is particularly understood to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.

These definitions being given, the term "diene elastomer" can be understood more particularly to mean the rubber compositions of the tire according to the invention: a) any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms ;

b) any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms;

c) a ternary copolymer obtained by copolymerization of ethylene, an oolefin having 3 to 6 carbon atoms with a non-conjugated diene monomer having from 6 to 12 carbon atoms, for example elastomers obtained from ethylene, propylene with a non-conjugated diene monomer of the aforementioned type, such as in particular hexadiene-1,4, ethylidene norbornene, dicyclopentadiene;

d) a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated versions, in particular chlorinated or brominated, of this type of copolymer.

Although it applies to any type of diene elastomer, the person skilled in the tire art will understand that the present invention is preferably implemented with essentially unsaturated diene elastomers, in particular of the type (a) or (b). ) above.

As conjugated dienes 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C 1 -C ₅ alkyl) -1,3-butadienes, such as for example 2, are particularly suitable. 3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3 butadiene, aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene. Examples of suitable vinylaromatic compounds are styrene, ortho-, meta-, para-methylstyrene, "vinyl-toluene" commercial mixture, para-tertiarybutylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene. The copolymers may contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinylaromatic units. The elastomers may have any microstructure which is a function of the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and the amounts of modifying and / or randomizing agent used. The elastomers can be for example block, statistical, sequenced, microsequenced, and be prepared in dispersion or in solution; they may be coupled and / or starred or functionalized with a coupling agent and / or starring or functionalization. For coupling with carbon black, there may be mentioned, for example, functional groups comprising a C-Sn bond or amine functional groups such as aminobenzophenone for example; for coupling to a reinforcing inorganic filler such as silica, mention may be made, for example, of silanol or polysiloxane functional groups having a silanol end (as described, for example, in FR 2,740,778, US 6,013,718 and WO 2008/141702), alkoxysilane groups (as described for example in FR 2 765 882 or US Pat. No. 5,977,238), carboxylic groups (as described for example in WO 01/92402 or US Pat. No. 6,815,473, WO 2004/096865 or US 2006/0089445). ) or polyether groups (as described for example in EP 1 127 909, US 6,503,973, WO 2009/000750 and WO 2009/000752). As other examples of functionalized elastomers, mention may also be made of elastomers (such as SBR, BR, NR or IR) of the epoxidized type.

In summary, the diene elastomer of the composition is preferably chosen from the group of highly unsaturated diene elastomers consisting of polybutadienes (abbreviated "BR"), synthetic polyisoprenes (IR), natural rubber (NR), copolymers butadiene, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR), isoprene-copolymers of butadiene-styrene (SBIR), butadiene-acrylonitrile copolymers (NBR), butadiene-styrene-acrylonitrile copolymers (NSBR) or a mixture of two or more of these compounds. According to a particular preferential embodiment, the diene elastomer is a predominantly isoprene elastomer (that is to say whose mass fraction of isoprene elastomer is the largest, compared to the mass fraction of other elastomers). By "isoprene elastomer" is meant in known manner a homopolymer or copolymer of isoprene, in other words a diene elastomer selected from the group consisting of natural rubber (NR) which can be plasticized or peptized, the polyisoprenes of synthesis (IR), the various isoprene copolymers and the mixtures of these elastomers. Among the isoprene copolymers, mention will in particular be made of copolymers of isobutene-isoprene (butyl rubber IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene ( SBIR). This isoprene elastomer is preferably natural rubber or a synthetic cis-1,4 polyisoprene; of these synthetic polyisoprenes, polyisoprenes having a level (mol%) of cis 1,4 bonds greater than 90%, more preferably still greater than 98%, are preferably used. Preferably, according to this embodiment, the level of isoprene diene elastomer is more than 50 phr (that is to say 50 to 100 phr), more preferably at least 60 phr (that is, 60 to 100 phr), more preferably at least 70 phr (that is to say from 70 to 100 phr), more preferably still at least 80 phr (i.e. from 80 to 100 phr) and very preferably at least 90 phr (that is to say from 90 to 100 phr). In particular according to this embodiment, the level of isoprene diene elastomer is very preferably 100 phr.

II-2 Derivative of zinc diacrylate

The composition of the tire according to the invention is based on a derivative of zinc diacrylate

wherein R 1, R ₂ and R ₃ independently represent a hydrogen atom or a C ₁ -C ₇ hydrocarbon group selected from linear, branched or cyclic alkyl groups, aralkyl groups, alkylaryl groups and aryl groups, and optionally interrupted by one or more heteroatoms, R ₂ and R ₃ may together form a non-aromatic ring.

By cyclic alkyl group is meant an alkyl group comprising one or more rings.

By group or hydrocarbon chain (e) interrupted by one or more heteroatoms is meant a group or chain comprising one or more heteroatoms, each heteroatom being between two carbon atoms of said group or said chain, or between an atom carbon of said group or said chain and another heteroatom of said group or said chain or between two other hetero atoms of said group or said chain. The heteroatom (s) may be a nitrogen, sulfur or oxygen atom. Preferentially, R 1, R ₂ and R ₃ independently represent a hydrogen atom or a methyl group. More preferably, R ₂ and R ₃ each represent a hydrogen atom. More preferably, R 1 represents a methyl group. Even more advantageously, R ₂ and R ₃ each represent a hydrogen atom, and R 1 represents a methyl group.

In the rubber composition of the tire according to the invention, the amount of zinc diacrylate derivative is preferably in a range from 5 to 40 phr, preferably from 7 to 35 phr, or from 5 to 30 phr, preferably from 5 to 20 phr, preferably from 5 to 10 phr. Beyond a rate of 40 phr, the dispersion is less good and the properties of the composition may degrade while below a level of 5 phr, the effect of the zinc diacrylate derivative is less significant on stiffening and reinforcement.

By way of example, there are commercially available zinc diacrylate derivatives such as zinc diacrylate (ZDA) "Dimalink 633" from Cray Valley or zinc dimethacrylate (ZDMA) "Dimalink 634" from the company Cray Valley.

11-3 Peroxide

In addition to the above-described elastomeric matrix and zinc diacrylate derivative, the rubber composition of the tire of the invention utilizes a peroxide, which may be any peroxide known to those skilled in the art. Among the peroxides, well known to those skilled in the art, it is preferable to use for the invention a peroxide chosen from the family of organic peroxides. Preferably, the peroxide is an organic peroxide selected from the group consisting of or consisting of dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, ditertbutyl peroxide. tertbutylcumylperoxide, 2,5-bis (tertbutylperoxy) -2,5-dimethylhexane, and mixtures thereof. There are various packaged products commercially known under their trademarks; we can mention: -the "Dicup" from Hercules Powder Co., the "Perkadox Y12" from Noury van der Lande, the "Peroximon F40" from Montecatini Edison SpA, the "Trigonox" from Noury van der Lande, the "Varox" from RTVanderbilt Co., or the "Luperko" from Wallace & Tiernan, Inc.

Preferably, the amount of peroxide to be used for the purposes of the invention is less than or equal to 3 phr. Preferably, the amount of peroxide in the composition is in a range from 0.1 to 3 phr. Indeed, below an amount of 0.1 phr, the effect of the peroxide is not noticeable whereas beyond 3 phr, the properties of elongation rupture and therefore resistance of the composition are decreased . More preferably, the amount of peroxide in the composition is in a range from 0.2 to 2.5 phr, preferably from 0.25 to 1.8 phr. Regardless of the amounts of zinc diacrylate derivative and peroxide, it is important for the invention that the ratio of the peroxide level to the level of zinc diacrylate derivative is less than or equal to 0.09. Preferably, the ratio of the peroxide level to the level of zinc diacrylate derivative is between 0.01 and 0.09; preferably between 0.03 and 0.09 and more preferably between 0.05 and 0.08.

II-4 Phenolic derivative

The rubber composition of the tire of the invention also has the essential characteristic of containing a phenol derivative of formula (II)

in which :

Α-ι represents a linear or branched C1-C4 alkyl group optionally substituted by a carboxylate of a hydrocarbon group comprising 1 to 60 carbon atoms and optionally oxygen atoms;

A ₂ represents a hydrogen atom or a linear or branched alkyl group in dC ₄ ;

A ₃ represents a hydrogen atom or a linear or branched alkyl group in dC ₄ optionally substituted by a phenolic group

in which the arrow (->) represents the point of attachment of the phenolic group to the alkyl group of the radical A ₃ ;

Z represents a hydrogen atom or a phosphorus atom, Z comprising p valence (s) free (s), p having a value of 1 or 3;

it being understood that A ₂ and A ₃ do not both represent a hydrogen atom;

it being understood that A ₁ and A ₃ are not both substituted. By the expression "being understood that A-ι and A ₃ are not both substituted", it is well understood by those skilled in the art that this means that when A-ι is substituted by a carboxylate of a hydrocarbon group comprising 1 to 60 carbon atoms and optionally oxygen atoms, then As is not substituted by the phenolic group, and conversely, when A ₃ is substituted by the phenolic group, then A 1 is not substituted by a carboxylate a hydrocarbon group comprising 1 to 60 carbon atoms and optionally oxygen atoms. Thus, according to the invention, it is clear that A-ι and A ₃ may simultaneously represent a linear or branched C ₁ -C ₄ alkyl group. By "linear or branched C ₁ -C ₄ alkyl group" is meant, in the sense of the present invention, a monovalent hydrocarbon chain, linear or branched, having 1 to 4 carbon atoms. By way of example, mention may in particular be made of methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl groups. According to the invention, the linear or branched alkyl group at dC ₄ of the radicals A ₁ , A ₂ and A ₃ is preferably chosen from the group consisting of methyl, ethyl and tert-butyl groups.

More preferably, A ₁ is methyl or tert-butyl; A ₂ and A ₃ represent, independently of one another, a hydrogen atom or a tert-butyl group.

For example, the compound of formula (II) may be the compound below:

This compound is also known as 2,6-di-tert-butyl-4-methylphenol or BHT. This compound is commercially available, especially under the name "Vulkanox BHT" from Lanxess.

Particularly advantageously, if any of the radicals A ₁ or A ₃ represents a linear or branched alkyl group in d ₄ which is substituted, then Z represents a hydrogen atom. According to a first particularly advantageous embodiment of the invention, the radical Z of the phenolic derivative of formula (II) represents a hydrogen atom. According to this first embodiment, the phenolic derivative of formula (II) can be for example a compound of general formula (IIa)

wherein A ₃ 'represents a linear or branched alkylene group -C _4, preferably a linear alkylene group -C _4. By "linear or branched alkylene in dC ₄ " is meant, in the sense of the present invention, a bivalent hydrocarbon chain, linear or branched, having 1 to 4 carbon atoms. By way of example, mention may in particular be made of the groups - (CH ₂ ) -, - (CH ₂ ) 2 -, - (CH ₂ ) ₃ -, - (CH ₂ ) ₄ -, -CH ₂ -CH (CH ₂ ) ₃ ) -, -CH (CH ₃ ) -CH (CH ₃ ) -, - (CH ₂ ) ₂ -CH (CH ₃ ) - and -CH ₂ -CH (CH ₃ ) -CH ₂ -.

Preferably, in the compound of general formula (IIa), A- _\ is methyl or tert-butyl; A ₂ is methyl or tert-butyl and A ₃ 'is methylene or ethylene. More preferably, the compound of general formula (II) is the compound below:

OH OH

This compound is also known as 2,2'-methylene-bis (4-methyl-6-tert-butylphenol) or BPH. This compound is commercially available, in particular under the name "Vulkanox BKF" from Lanxess.

According to the first embodiment, the phenol derivative of formula (II) can also be for example a compound of general formula (Mb)

in which Ai 'represents a linear or branched C1-C4 alkylene, preferably linear C1-C4 alkylene, and A4 represents a linear or branched C ₂ 0 alkyl group, preferably a linear or branched C ₆ - alkyl group; Ci ₅ .

Preferably, in this compound of general formula (Mb), A 1 represents a methylene or ethylene group; A ₂ and A ₃ represent, independently of one another, a methyl or tert-butyl group; A4 represents a branched C ₆ -C ₁₅ alkyl group. More preferably, the compound of general formula (II) is the compound below:

This compound is also known under the name lsotridecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate or AO 1077. This compound is commercially available, in particular under the name "Songnox 1077 LQ". the company Songwon. According to the first embodiment, the phenol derivative of formula (II) can also be for example a compound of general formula (I le)

wherein Ai represents a linear or branched C1-C4 alkylene, preferably linear alkylene C 1 -C 4, and A ₅ represents a linear or branched alkylene group -C _6, preferably linear alkylene -C _6. More preferably A ₅ represents a methylene or ethylene group.

Preferably, in this compound of general formula (IIc), represents a methylene or ethylene group; A ₂ and A ₃ represent, independently of one another, a methyl or tert-butyl group; A ₅ represents a linear C 1 -C 4 alkyl group. . More preferably, the compound of general formula (II) is the compound below:

The compound is also known as Tetrakis [methylene-3 (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate] methane. This compound is commercially available, in particular under the name "AO-1010" from Akrochem Corporation or "Songnox 1010" from Songwon.

According to a second embodiment of the invention, the radical Z of the phenolic derivative of formula (II) represents a phosphorus atom. According to this second embodiment, the phenol derivative of formula (II) may advantageously be a compound of general formula (IId)

More preferably, the compound of general formula (II) is the compound below

The compound is also known as 2,2,4-trimethyl-1,2-dihydroquinoline. This compound is commercially available, especially under the name "IRGAFOS 168" from Ciba.

According to the invention, the level of the phenolic derivative of formula (II) is in a range from 0.5 to 5 phr, preferably from 1 to 4 phr, or 0.5 to 3 phr, more preferably from 1 to 2.5 phr. 11-5 Reinforcing filler

The elastomer, the zinc diacrylate derivative, the peroxide and the antioxidant are sufficient on their own for the invention to be carried out. Nevertheless, the composition of the tire according to the invention may comprise a reinforcing filler known for its ability to reinforce a rubber composition that can be used for the manufacture of tires.

The reinforcing filler, when present, of the rubber composition of the tire according to the invention advantageously comprises mainly carbon black. The reinforcing filler may comprise, for example, from 50 to 100% by weight of carbon black, preferably from 55 to 90% by weight, preferably from 60 to 80% by weight. Particularly advantageously, the reinforcing filler comprises exclusively carbon black. The reinforcing filler may also further comprise a reinforcing inorganic filler. Preferably, the reinforcing inorganic filler is a silica.

Such a reinforcing filler typically consists of particles whose average size (in mass) is less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, in particular and more preferably between 20 and 150 nm.

The volume fraction of reinforcing filler in the rubber composition is defined as the ratio of the volume of the reinforcing filler to the volume of all the constituents of the composition, it being understood that the volume of all the constituents is calculated in adding the volume of each of the constituents of the composition. The volume fraction of reinforcing filler in a composition is therefore defined as the ratio of the volume of the reinforcing filler to the sum of the volumes of each of the constituents of the composition, and preferably this volume fraction is between 5% and 20%. preferably between 5% and 15%. In a preferentially equivalent manner, the total reinforcing filler content (carbon black and optionally silica) is less than 65 phr, preferably 5 to 60 phr, more preferably 10 to 50 phr, and very preferably from 20 to 40 phr. Whatever the amounts of zinc diacrylate derivative and filler, it is advantageous for the invention that the ratio of the filler rate to the level of zinc diacrylate derivative is less than or equal to 4. Preferably, preferably , the ratio of the charge rate and the level of zinc diacrylate derivative is in a range from 0.15 to 3, preferably from 1.5 to 3. Alternatively and preferably also, the ratio of the charge ratio and the level of zinc diacrylate derivative is in a range from 0.7 to 1.3.

The blacks that can be used in the context of the present invention may be all black conventionally used in tires or their treads (so-called pneumatic grade blacks). Among these, the reinforcing carbon blacks of the series 100, 200, 300, or the series blacks 500, 600 or 700 (ASTM grades), for example the blacks N15, N134, N234, N326, will be mentioned more particularly. 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. 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 WO 97/36724 or WO 99/16600). The BET surface area of the carbon blacks is measured according to the D6556-10 standard [multipoint method (at least 5 points) - gas: nitrogen - relative pressure range Ρ / Ρ0: 0.1 to 0.3].

"Reinforcing inorganic filler" means any inorganic or mineral filler, irrespective of 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, with no other means than an intermediate coupling agent, a rubber composition intended for the manufacture of pneumatic tires, in other words able to replace, in its function of reinforcement, a conventional carbon black of pneumatic grade; such a filler is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface. In other words, without a coupling agent, the inorganic filler does not make it possible to reinforce or not sufficiently the composition and is therefore not included in the definition of "reinforcing inorganic filler". Suitable reinforcing inorganic fillers are in particular mineral fillers of the siliceous type, preferentially silica (SiO ₂ ). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface and a CTAB specific surface both less than 450 m ² / g, preferably from 30 to 400 m ² / g, especially between 60 and 300 m ² / g. As highly dispersible precipitated silicas (called "HDS"), mention may be made, for example, of the "Ultrasil" 7000 and "Ultrasil" 7005 silicas of Degussa, the "Zeosil" silicas 1 165MP, 1 135MP and 1 1 15MP of the Rhodia company, the "Hi-Sil" silica EZ150G from the company PPG, the "Zeopol" silicas 8715, 8745 and 8755 from the Huber Company, the high surface area silicas as described in the application WO 03/016387.

In the present description, with regard to silica, the BET surface area is determined in a known manner by gas adsorption using the method of Brunauer-Emmett-Teller described in "The Journal of the American Chemical Society" Flight . 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 / po: 0.05 to 0.17). The CTAB specific surface is the external surface determined according to the French standard NF T 45-007 of November 1987 (method B).

Reinforcing inorganic fillers are also suitable for mineral fillers of the aluminous type, in particular alumina (Al ₂ O ₃ ) or aluminum (oxide) hydroxides, or reinforcing titanium oxides, for example described in US Pat. No. 6,610,261 and US Pat. US 6,747,087.

The physical state in which the reinforcing inorganic filler is present is indifferent whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the term "reinforcing inorganic filler" also refers to mixtures of different reinforcing inorganic fillers, in particular highly dispersible siliceous and / or aluminous fillers as described above.

Those skilled in the art will understand that as an equivalent load of the reinforcing inorganic filler described in this paragraph, a reinforcing filler of another nature, especially organic, since this reinforcing filler would be covered with an inorganic layer such as silica, or would comprise on its surface functional sites, in particular hydroxyl sites, requiring the use of a surfactant; coupling to establish the connection between the load and the elastomer.

In order to couple the reinforcing inorganic filler to the diene elastomer, an at least bifunctional coupling agent (or bonding agent) is used in a well-known manner to ensure a sufficient chemical and / or physical connection between the inorganic filler (surface of its particles) and the diene elastomer. In particular, organosilanes or at least bifunctional polyorganosiloxanes are used.

Those skilled in the art can find examples of coupling agent 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 is advantageously less than 10 phr, it being understood that it is generally desirable to use as little as possible. Typically when a reinforcing inorganic filler is present, the level of coupling agent is from 0.5% to 15% by weight based on the amount of inorganic filler. Its level is preferably in a range from 0.5 to 7.5 phr. This level is easily adjusted by those skilled in the art according to the level of inorganic filler used in the composition.

The rubber composition of the tire according to the invention may also contain, in addition to the coupling agents, coupling activators, inorganic charge-covering agents or, more generally, processing aid agents capable in known manner. by improving the dispersion of the filler in the rubber matrix and lowering the viscosity of the compositions, to improve their ability to use in the green state, these agents being for example hydrolysable silanes such as alkylalkoxysilanes (especially alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines (for example trialkanol amines), hydroxylated or hydrolyzable POSs, for example α, ω- dihydroxy-polyorganosiloxanes (especially α, ω-dihydroxy-polydimethylsiloxanes), fatty acids such as stearic acid.

11-6 Metal Oxide

The composition of the tire according to the invention further comprises a metal oxide.

The metal oxide may be selected from the group consisting of Group II, IV, V, VI, VII and VIII metal oxides, and mixtures thereof. Preferably, the metal oxide is selected from the group consisting of oxides of zinc, magnesium, cobalt, nickel and mixtures thereof. More preferably, the metal oxide is a zinc oxide.

The metal oxide content of the composition of the tire according to the invention is advantageously greater than 5 phr. Preferably, this level is in a range from 5 to 20 phr, preferably from 7 to 15 phr.

As an example of commercially available metal oxides, mention may be made of industrial grade zinc or magnesium oxides from Umicore.

II-7 Vulcanization system

The composition of the tire according to the invention does not require a vulcanization system, which is one of its advantages since it simplifies the formula and the preparation of the composition. If however a vulcanization system is present in the composition, it is preferably in small amounts.

The vulcanization system itself is usually based on sulfur (or a sulfur-donor agent) and a primary vulcanization accelerator. To this basic vulcanization system are added, incorporated during the first non-productive phase and / or during the production phase as described later, various known secondary accelerators or vulcanization activators such as zinc oxide. stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine). Molecular sulfur (or equivalently the molecular sulfur donor agents), when it is used, is at a preferential rate of less than 0.5 phr,

Thus, very preferably, the composition does not contain molecular sulfur or sulfur-donor agent as vulcanizing agent or contains less than 0.5 phr, preferably less than 0.3 phr, preferably still less than 0.1 phr. More preferably, the composition of the tire according to the invention does not contain molecular sulfur or sulfur-donor agent as vulcanizing agent.

The vulcanization system of the composition according to the invention may also comprise one or more additional accelerators, for example the compounds of the thiuram family, the zinc dithiocarbamate derivatives, the sulphenamides, the guanidines or the thiophosphates. In particular, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur, in particular thiazole type accelerators and their derivatives, thiuram type accelerators, zinc dithiocarbamates, may be used in particular. These accelerators are more preferably selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated "CBS"), N, N-dicyclohexyl-2-benzothiazyl sulphenamide (abbreviated "DCBS"), N-tert-butyl-2-benzothiazyl sulphenamide (abbreviated "TBBS"), N-tert-butyl-2-benzothiazyl sulphenimide (abbreviated "TBSI"), zinc dibenzyldithiocarbamate (in abbreviated "ZBEC") and mixtures of these compounds. Preferably, a primary accelerator of the sulfenamide type is used.

If an accelerator is used, it is at rates such as those practiced by those skilled in the art of vulcanized tire compositions. Nevertheless, the composition of the tire according to the invention is preferably devoid of any vulcanization accelerator.

1-8 Other possible additives

The rubber compositions of the tire according to the invention optionally also include all or part of the usual additives normally used in tire elastomer compositions, for example pigments, protective agents such as anti-ozone waxes, anti-ozonants chemical, plasticizing agents (such as a solid hydrocarbon resin (or plasticizing resin), an extender oil (or plasticizing oil), or a mixture of both), anti-fatigue agents, reinforcing resins, acceptors (for example novolac phenolic resin) or methylene donors (eg HMT or H3M).

11-9 Tires

The present invention also relates to a finished or semi-finished rubber article and a tire comprising a composition according to the present invention.

The invention particularly relates to tires intended to equip motor vehicles of the tourism type, SUV ("Sport Utility Vehicles"), or two wheels (in particular motorcycles), or planes, or industrial vehicles chosen from light trucks, "Poids- "heavy" - that is, metros, buses, road transport vehicles (trucks, tractors, trailers), off-the-road vehicles such as agricultural or civil engineering machinery, and others.

It is possible to define three types of zones within the tire:

• The radially outer zone and in contact with the ambient air, this zone consisting essentially of the tread and the outer side of the tire. An outer flank is an elastomeric layer disposed outside the carcass reinforcement with respect to the internal cavity of the tire, between the crown and the bead so as to completely or partially cover the region of the carcass reinforcement. extending from the top to the bead.

· The radially inner zone and in contact with the inflation gas, this zone being generally constituted by the inflation-gas-tight layer, sometimes called inner waterproof layer or inner liner ("inner liner" in English).

• The inner area of the tire, that is to say the area between the outer and inner zones. This zone includes layers or plies which are here called internal layers of the tire. These are, for example, carcass plies, tread sub-layers, tire belt plies or any other layer that is not in contact with the ambient air or the inflation gas of the tire. The composition defined in the present description is particularly well suited to the inner layers of tire.

Also, in the tire according to the present invention the composition may be present in at least one inner layer of the tire. According to the invention, the inner layer may be chosen from the group consisting of the carcass plies, the crown plies, the bead planks, the toe feet, the crown feet, the decoupling layers, the edge gums, the sub-ply tread layer and combinations of these inner layers. Preferably, the inner layer is selected from the group consisting of carcass plies, crown plies, bead fences, toe feet, decoupling layers and combinations of these inner layers.

The invention relates to tires and semi-finished products for tires previously described, rubber articles, both in the raw state (that is to say, before cooking) and in the cooked state (that is to say, before cooking). after crosslinking or vulcanization).

11-10 Preparation of rubber compositions

The compositions are manufactured in appropriate mixers, using two successive preparation phases well known to those skilled in the art: a first phase of work or thermomechanical mixing (sometimes called a "nonproductive" phase) at high temperature, up to a maximum temperature of between 110 ° C. and 190 ° C., preferably between 130 ° C. and 180 ° C., followed by a second mechanical working phase (sometimes referred to as a "productive" phase) at a lower temperature , typically less than 1 10 ° C, for example between 60 ° C and 100 ° C, finishing phase during which is incorporated the crosslinking system and in particular the peroxide compositions according to the invention; such phases have been described, for example, in EP-A-0501227, EP-A-0735088, EP-A-0810258, WO00 / 05300 or WO00 / 05301.

The first (non-productive) phase is preferably carried out in several thermomechanical steps. In a first step, the elastomers and the reinforcing fillers (and optionally the coupling agents and / or other ingredients) are introduced into a suitable mixer such as a conventional internal mixer at a temperature of between 20.degree. ° C and 100 ° C and preferably between 25 ° C and 100 ° C. After a few minutes, preferably from 0.5 to 2 min and a rise in temperature to 90 ° C to 100 ° C, the other ingredients (ie, those that remain if all were not put initially) are added at once or in parts, with the exception of the crosslinking system and in particular the peroxide during a mixing ranging from 20 seconds to a few minutes. The total mixing time in this non-productive phase is preferably between 2 and 10 minutes at a temperature of less than or equal to 180 ° C., and preferably less than or equal to 170 ° C.

After cooling the mixture thus obtained, the crosslinking system and in particular the peroxide are then incorporated at low temperature (typically below 100 ° C.), generally in an external mixer such as a roll mill; the whole is then mixed (productive phase) for a few minutes, for example between 5 and 15 min. The final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for a characterization in the laboratory, or extruded, to form for example a rubber profile used for the manufacture of semi-finished products. finished to obtain so-called "internal layers" products such as carcass ply, top plies (or tire belt), bead filler. These products can then be used for the manufacture of tires, according to the techniques known to those skilled in the art.

The cooking is carried out in a known manner at a temperature generally of between 130 ° C. and 200 ° C., under pressure, for a sufficient time which may vary, for example, between 5 and 90 min, depending in particular on the cooking temperature, vulcanization adopted, the vulcanization kinetics of the composition in question or the size of the tire.

III- EXAMPLES

111-1 Measurements and tests used

Dynamic properties (after cooking): Tensile test

These tensile tests make it possible to determine the elastic stress and the properties at break. Unless otherwise indicated, they are carried out in accordance with the French standard NF T 46-002 of September 1988. Traction data processing also makes it possible to trace the module curve as a function of elongation. The module used here is the nominal secant modulus (or apparent) measured in first elongation, calculated by reducing to the initial section of the specimen. The nominal secant modulus (or apparent stresses, in MPa) is measured at first elongation at 23 ° C. at 100% elongation denoted M100.

The breaking elongation (AR%) and breaking stress (CR) tests are based on the NF ISO 37 standard of December 2005 on a dumbbell test piece of the H2 type and are measured at a pulling speed of 500 mm / min. The elongation rupture is expressed in% elongation. The breaking stress is expressed in MPa.

The tensile strength and deformation are measured on a specimen drawn at 500 mm / min to cause the test piece to rupture. The tensile test piece consists of a parallelepiped-shaped rubber plate, for example of thickness between 1 and 2 mm, of length between 130 and 170 mm and of width between 10 and 15 mm, the two lateral edges being each lengthwise covered with a cylindrical rubber bead (diameter 5 mm) allowing anchoring in the jaws of the traction machine. 3 very fine cuts of between 15 and 20 mm in length are made using a razor blade, at mid-width and aligned along the length of the test piece, one at each end and one in the center of the latter, before starting the test. The force (N / mm) to be exerted to obtain the rupture is determined and the elongation at break and the breaking stress are measured. The product of the tear strength and the deformation (elongation break) of tearability gives the tearing energy which is a cohesive descriptor of the material to resist cracking.

All these tensile measurements are carried out under normal conditions of temperature (23 ± 2 ° C.) and hygrometry (50 ± 5% relative humidity), according to the French standard NF T 40-101 (December 1979). III-2 Preparation of compositions

In the following examples, the rubber compositions were made as described above. 111-3 Testing of rubber compositions

Three compositions (denoted hereinafter B, D and F) according to the invention in that they comprise an antioxidant which is a phenolic derivative of formula (II), and three compositions (denoted hereinafter C, E and G ) not in accordance with the invention in that they comprise an antioxidant which is not a phenolic derivative of formula (II) have been compared to a control composition A which does not include an antioxidant. Their formulations (in phr) have been summarized in Table I below.

In a first step, the M100 rigidities of the compositions were measured. In a second step, the crack propagation resistance cohesion properties were measured for compositions with little or no rigidity degradation with respect to control A. The results are shown in Table II and III below. . The results of stiffness (M100), rupture elongation (AR%), fracture stress, tear strength, tearability deformation and tearing energy are presented in "base 100" with respect to the control composition. The higher the value, the better the result.

Table I

(1) Natural rubber

(2) Carbon black N234 (designation according to ASTM D-1765)

(3) Zinc oxide (industrial grade - Umicore company)

(4) Zinc dimethacrylate ("Dimalink 634" from Cray Valley Corporation)

(5) Dicumyl peroxide ("Dicup" from the company Hercules) (6) 2,6-di-tert-butyl-4-methylphenol ("Vulkanox BHT" from the company Lanxess)

(7) 2,2,4-trimethyl-1,2-dihydroquinoline ("TMQ" from the company Nocil)

(8) Tris (2,4-di-tert-butylphenyl) phosphite ("Irgafos 168" from the company Ciba)

(9) dilaurylthidipropionate ("BNX DL TDP" from the company Mayzo)

(10) 2,2'-methylene-bis (4-methyl-6-tert-butylphenol) ("Vulkanox BPH" from the company Lanxess)

(1 1) N-1,3-dimethylbutyl-N-phenylparaphenylenediamine ("Santoflex 6-PPD" from the company Flexsys)

Table II

Table III

These results show that the only compositions according to the present invention comprising a phenol derivative of formula (II) make it possible to improve both the cohesion and tear-resistance properties, without penalizing the rigidity of the composition.

Claims

A tire comprising a rubber composition based on at least: a diene elastomer,

a peroxide,

a zinc diacrylate derivative in the form of a zinc salt of formula (I)

in which R 1, R ₂ and R ₃ independently of one another represent a hydrogen atom or a C ₁ -C ₇ hydrocarbon group selected from linear, branched or cyclic alkyl groups, aralkyl groups, alkylaryl groups and aryl groups, and optionally interrupted by one or more heteroatoms, R ₂ and R ₃ may together form a non-aromatic ring,

a phenol derivative of formula II)

in which :

o A-i represents a linear or branched C 1 -C 4 alkyl group optionally substituted by a carboxylate of a hydrocarbon group comprising 1 to 60 carbon atoms and optionally oxygen atoms;

o A ₂ represents a hydrogen atom or a linear or branched alkyl group in dC ₄ ;

it being understood that A ₂ and A ₃ do not both represent a hydrogen atom;

the levels of zinc diacrylate derivative and of peroxide being such that the mass ratio of the peroxide level and the level of zinc diacrylate derivative is less than or equal to 0.09.

2. A tire according to claim 1, wherein R 1, R ₂ and R ₃ independently represent a hydrogen atom or a methyl group.

3. A tire according to claim 1 or 2, wherein R ₂ and R ₃ each represent a hydrogen atom.

4. A tire according to any one of claims 1 to 3, wherein R 1 is a methyl group.

A tire according to any one of claims 1 to 4, wherein the amount of zinc diacrylate derivative in the composition is in a range from 5 to 40 parts by weight per hundred parts by weight of elastomer, preferably from 7 to 35 phr.

A tire according to any one of claims 1 to 5, wherein the linear or branched C ₁ -C ₄ alkyl group of the radicals A ₁ , A ₂ and A ₃ is selected from the group consisting of methyl, ethyl and tert-butyl groups. .

A tire according to any one of claims 1 to 6 wherein A 1 is methyl or tert-butyl; A ₂ and A ₃ represent, independently of one another, a hydrogen atom or a tert-butyl group.

8. A tire according to any one of claims 1 to 7, wherein Z represents a hydrogen atom.

9. A tire according to any one of claims 1 to 5, and 8, wherein the phenolic derivative of formula (II) is a compound of general formula (IIa)

(IIa) wherein A ₃ 'represents a linear or branched C ₁ -C ₄ alkylene group.

10. The tire of claim 9, wherein A-ι represents a methyl or tert-butyl group; A ₂ is methyl or tert-butyl and A ₃ 'is methylene or ethylene.

11. A tire according to any one of claims 1 to 5 and 8, in the phenolic derivative of formula (II) is a compound of general formula (Mb)

(Mb) in which Α-ι represents a linear or branched C ₁ -C ₄ alkylene, and A4 represents a linear or branched C ₆ -C ₂ alkyl group.

Pneumatic tire according to claim 11, wherein A 'is methylene or ethylene; A ₂ and A ₃ represent, independently of one another, a methyl or tert-butyl group; A4 represents a branched C ₆ -C ₁₅ alkyl group.

13. A tire according to any one of claims 1 to 5 and 8, wherein the phenolic derivative of formula (II) is a compound of general formula (Ile)

wherein A _{1 '} is a linear or branched C ₁ -C ₄ alkylene, and A ₅ is a linear or branched C ₁ -C ₆ alkylene group.

Tire according to claim 13, wherein A 'is methylene or ethylene; A ₂ and A ₃ represent, independently of one another, a methyl or tert-butyl group; A ₅ represents a linear C 1 -C 4 alkyl group.

15. A tire according to any one of claims 1 to 7, wherein Z represents a phosphorus atom.

16. A tire according to claim 15, wherein the phenol derivative formula (II) is a compound of general formula (IId)

17. A tire according to any one of claims 1 to 16, wherein the level of the phenolic derivative of formula (II) is in a range from 0.5 to 5 phr, preferably from 1 to 4 phr.

18. A tire according to any one of claims 1 to 17, wherein the peroxide in the composition is an organic peroxide.

The tire of claim 18, wherein the organic peroxide is selected from the group consisting of dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, ditertbutyl peroxide, tertbutylcumyl peroxide, 2,5-bis (tertbutylperoxy) -2,5-dimethylhexane, and mixtures thereof.

20. A tire according to any one of claims 1 to 19, wherein the amount of peroxide in the composition is less than or equal to 3 phr.

21. A tire according to any one of claims 1 to 20, wherein the amount of peroxide in the composition is in a range from 0.1 to 3 phr, preferably from 0.2 to 2.5 phr.

22. A tire according to any one of claims 1 to 21, wherein the ratio of the peroxide level to the level of zinc diacrylate derivative is between 0.01 and 0.09; preferably between 0.03 and 0.09 and more preferably between 0.05 and 0.08.

23. A tire according to any one of claims 1 to 22, wherein the diene elastomer is selected from the group consisting of polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, isoprene copolymers and mixtures of these elastomers.

24. The tire of claim 23, wherein the diene elastomer comprises predominantly at least one isoprene elastomer.

The tire of claim 24, wherein the isoprene elastomer is selected from the group consisting of natural rubber, synthetic polyisoprenes and mixtures of these elastomers.

26. A tire according to any one of claims 1 to 25, wherein said composition does not comprise a reinforcing filler or comprising less than 65 phr, the reinforcing filler predominantly consisting of carbon black.

27. A tire according to claim 26, wherein the level of reinforcing filler is in a range from 5 to 60 phr, preferably from 10 to 50 phr.

28. The tire of claim 26 or 27, wherein the reinforcing filler further comprises silica.

29. A tire according to any one of claims 26 to 28, wherein the ratio of the charge rate and the level of zinc diacrylate derivative is less than or equal to 4.

30. A tire according to any one of claims 26 to 29, wherein the ratio of the charge rate and the level of zinc diacrylate derivative is in a range from 0.15 to 3; preferably from 1.5 to 3.

31. The rubber composition according to any one of claims 1 to 30, wherein the metal oxide is a zinc oxide.

32. The rubber composition according to claim 31, wherein the metal oxide level is greater than 5 phr.

33. A rubber composition according to claim 31 or 32, wherein the metal oxide level is within a range of 5 to 20 phr, preferably 7 to 15 phr.

34. A tire according to any one of claims 1 to 33, wherein the composition does not contain molecular sulfur or sulfur-donor agent as vulcanizing agent or contains less than 0.5 phr thereof.

Tire according to any one of claims 1 to 34, wherein the composition does not contain molecular sulfur or sulfur-donor agent as vulcanizing agent or contains less than 0.3 phr and preferably less than 0.1 phr.

36. Tire according to one of the preceding claims, wherein the composition defined in any one of claims 1 to 35 is present in at least one inner layer of said tire.

The tire of claim 36, wherein the inner layer is selected from the group consisting of carcass plies, crown plies, bead fences, toe feet, decoupling layers, edge gums, sub-plywood tread layer and the combinations of these inner layers.