WO2004090023A1

WO2004090023A1 - Metal/rubber composite for tyre

Info

Publication number: WO2004090023A1
Application number: PCT/EP2004/003715
Authority: WO
Inventors: Christiane Blanchard; Emmanuel Custodero; Marc Greiveldinger
Original assignee: Societe De Technologie Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2003-04-09
Filing date: 2004-04-07
Publication date: 2004-10-21
Also published as: FR2853660A1

Abstract

The invention concerns a metal/rubber composite comprising a diene elastomer matrix reinforced by a metal reinforcement adhering to the elastomer matrix via an adhesive intermediate phase based on a coupling agent of formula (RO)2 (Q) (Z)y Sx (Z)5 P (Q) (OR)2, wherein: the symbols R, identical or different, represent each a monovalent hydrocarbon group, hydrogen or an alkali metal selected between Na and K; the symbols Q, identical or different, represent oxygen or sulphur; the symbols Z, identical or different, are divalent binding groups containing 1 to 18 carbon atoms; each y is equal to 0 or 1; y is an integer or a fraction. The invention also concerns the use of such a composite for grip systems for motor vehicles, in particular tyres.

Description

COMPOSITE METAL / RUBBER FOR PNEUMATIC

The present invention relates to metal / rubber composites and in particular adhesive interphases providing, in such composites, the bond between metal and rubber.

It relates in particular to steel / rubber crosslinkable to sulfur composites and usable for the manufacture of ground connection systems of motor vehicles, in particular tires.

Pneumatic metal / rubber composites are well known, they generally consist of a rubber matrix comprising metal reinforcing elements (or "reinforcements"), most often in the form of son or wire assemblies.

Subject to very significant constraints during the rolling of the tires, in particular to repeated compressions, flexions or curvature variations, these composites must in a known manner satisfy a large number of technical criteria, sometimes contradictory, such as uniformity, flexibility, endurance in flexion and compression, tensile, wear and corrosion resistance, and maintain these performances at a very high level as long as possible. It is easily understood that the adhesive interiphase between rubber and metal plays a major role in the durability of these performances.

The traditional method for bonding the rubber compositions, in particular to carbon steel, consists in coating the surface of the steel with brass (copper-zinc alloy), the bond between the steel and the composition being provided by sulfurization of the steel. brass during vulcanization. To ensure optimum adhesion, an adhesion promoter additive such as a cobalt salt is also frequently used in the rubber composition.

The brass coating has the known disadvantage that the adhesion between the carbon steel and the rubber matrix is likely to weaken over time, due to the progressive evolution of the sulfides under the effect of different stresses encountered, in particular thermal and / or mechanical. In addition, the presence of moisture in the tires plays an important role in accelerating the degradation process above. Finally, the use of cobalt salt renders the rubber compositions more susceptible to oxidation and significantly increases the cost thereof.

To overcome these disadvantages of brass, have been proposed new adhesive interphases likely to improve the overall performance in adhesion of metal / rubber composites used in tires.

Application WO02 / 10265, in particular, describes such composites whose metal / rubber adhesive interface comprises an intermediate metal layer carrying oxides or hydroxides of aluminum, itself covered with an organosilane film ensuring that coupling agent is the bond between metal and rubber. Compared with conventional reinforced brass-coated composites, the composites described in this application WO02 / 10265 are characterized by a metal-rubber adhesive interphase providing an initial adhesion level at least as good, with significantly improved performance after wet-type aging. and / or corrosive. The longevity of the tires is thus substantially improved, in particular that of tires for industrial vehicles usually comprising metal carcass reinforcement subjected to particularly severe driving conditions, in particular in a humid and corrosive atmosphere.

Continuing our research, the Applicant has found a new metal / rubber composite which, thanks to a particular adhesive interphase, is also likely to constitute a substitution solution to conventional composites using brass as an adhesive bond.

Accordingly, a first object of the invention is a metal / rubber composite having a matrix of diene elastomer reinforced by a metal reinforcement adhered to said matrix via an adhesive interphase based on at least one compound to the formula:

(D

(RO) ₂ (Q) P - (Z) _y - S _x - (Z) _y - P (Q) (OR) ₂

in which :

the symbols R, identical or different, each represent a monovalent hydrocarbon group, hydrogen or an alkali metal chosen from Na and K; the symbols Q, identical or different, represent oxygen or sulfur; the symbols Z, which are identical or different, are divalent linking groups comprising from 1 to 18 carbon atoms; each y is equal to 0 or 1;

- x is an integer or fractional number.

The invention also relates to the use of such a composite for the manufacture or reinforcement of ground connection systems of motor vehicles, such as pneumatic tires, internal safety supports for tires, wheels, rubber springs, elastomeric joints, other suspension and anti-vibratory elements, or semi-finished rubber products intended for such ground connection systems.

The composite according to the invention is particularly intended for reinforcements reinforcing the crown, the carcass or the bead zone of tires intended for passenger vehicles or industrial vehicles chosen from light trucks, "heavy vehicles" - the., Metro, buses, road transport vehicles (trucks, tractors, trailers), off-the-road vehicles -, agricultural or engineering machinery, aircraft, other transport or handling vehicles. It is more advantageously used in the carcass reinforcement of tires for industrial vehicles such as vans or heavy trucks, as well as in the reinforcements of top tires for both passenger vehicles and industrial vehicles.

The invention further relates to the ground connection systems and the semi-finished rubber products themselves, when they comprise a composite according to the invention. The invention shows in particular its interest in the carcass reinforcement tires for heavy-duty vehicles which are expected today, thanks to the technical progress of retreading, they are able to endure over a million kilometers .

The invention also relates, per se, to a metal reinforcement coated with an adhesive layer capable of adhering to a rubber matrix based on diene elastomer, said adhesive layer being based on at least one compound or coupling agent of formula (I) above.

The invention as well as its advantages will be readily understood in the light of the description and the following exemplary embodiments, as well as the schematic figure relating to these examples, which represents a radial section of a carcass reinforcement truck tire. radial.

I. DETAILED DESCRIPTION OF THE INVENTION

The metal / rubber composite of the invention consists of a rubber matrix reinforced with at least one metal body. The metal-rubber adhesive interface is based on at least one bifunctional phosphorus coupling agent having the formula (I) above. By the term "interphase-based", it is of course understood an interphase comprising said coupling agent or its reaction product in situ (in the composite), its reactive functions (denoted X and Y below) being in effect likely to, or intended to react at least in part with metal and rubber, during the various phases of manufacture of the composite, especially during its vulcanization.

In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are% by weight.

1-1. Rubber matrix

The matrix is a rubber composition based (ie, formed) of at least one diene elastomer and comprising, in addition to this diene elastomer, all the usual ingredients such as reinforcing filler, crosslinking system and other additives for use in rubber compositions for ground-engaging systems of motor vehicles such as pneumatic tires, or semi-finished rubber products for such ground-engaging systems. A) Diene elastomer

By "diene" elastomer is meant in known manner an elastomer derived at least in part (ie a homopolymer or a copolymer) of monomers dienes that is to say monomers carrying two carbon-carbon double bonds, conjugated or not .

In general, the term "diene elastomer" is used herein 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% (%). in moles). Thus, 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 in particular be described as "essentially 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%.

Given these definitions, the elastomer of the composite according to the invention may be any diene elastomer, it being understood that the latter is preferentially chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, the various copolymers of butadiene, the various isoprene copolymers, and mixtures of these elastomers.

Among the polybutadienes, those having a content of -1.2 units of between 4% and 80% or those having a cis-1,4 content of greater than 80% are particularly suitable. Of the synthetic polyisoprenes, cis-1,4-polyisoprenes are preferred, preferably those having a cis-1,4 bond ratio of greater than 90%. Among the copolymers of butadiene or isoprene, is meant in particular the copolymers obtained by copolymerization of at least one of these two monomers with one or more vinyl-aromatic compounds having from 8 to 20 carbon atoms. Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the "vinyl-toluene" commercial mixture, para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene and divinylbenzene. vinyl naphthalene. The copolymers may contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinyl aromatic units. Among the butadiene or isoprene copolymers above, mention will preferably be made of butadiene-styrene copolymers, isoprene-butadiene copolymers, isoprene-styrene copolymers or isoprene-butadiene-styrene copolymers.

In summary, a diene elastomer selected from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene-styrene copolymers (SBR), copolymers of isoprene-butadiene (BIR), isoprene-styrene copolymers (SIR), butadiene-styrene-isoprene copolymers (SBIR) and mixtures of these elastomers. The composites in accordance with the invention are preferentially intended for tires, in particular for carcass reinforcement of tires for industrial vehicles such as vans or heavy goods vehicles, as well as for tire crown reinforcement intended both for passenger vehicles and for passenger vehicles. industrial vehicles.

It is then preferable to use matrices based on natural rubber or synthetic polyisoprene. By this is meant rubber matrices in which the diene elastomer is predominantly (i.e., greater than 50% by weight) made of natural rubber, synthetic polyisoprene or a mixture of these elastomers. Advantageously, the diene elastomer consists exclusively of natural rubber, synthetic polyisoprene or a mixture of these elastomers.

But it is also possible to use, according to another advantageous embodiment of the invention, blends (blends) of these polyisoprenes with other highly unsaturated diene elastomers, in particular with SBR or BR elastomers as mentioned above.

The rubber matrices of the composites of the invention may contain one or more elastomer (s) diene (s), which (s) last (s) may (s) used in combination with any type of synthetic elastomer other than diene, or even with polymers other than elastomers, for example thermoplastic polymers.

B) Other constituents

The rubber matrices of the composites according to the invention also comprise all or part of the additives normally used in rubber matrices intended for the manufacture of ground connection systems of motor vehicles such as tires, such as, for example, reinforcing fillers. such as carbon black or silica, anti-aging agents, antioxidants, extension oils, plasticizers or agents facilitating the use of the compositions in the green state, a crosslinking system based on either sulfur, either of sulfur and / or peroxide donors, accelerators, vulcanization activators or retarders, anti-eversion agents, methylene acceptors and donors, resins, known RFS-type adhesion promoter systems ( resorcinol-formaldehyde-silica) or metal salts, especially cobalt salts.

To further enhance the performance of the composite of the invention, a preferred embodiment of the invention is to incorporate, to the rubber matrices, a bismaleimide compound. This type of compound, usable without hardener, has a cooking kinetics well adapted to that of tires, it is likely to activate the kinetics of adhesion and further improve, in the composites according to the invention, the endurance in wet aging conditions of adhesive interphases.

It is recalled that the bismaleimides respond, in known manner, to the following formula:

wherein R 'is a substituted or unsubstituted hydrocarbon, aromatic or aliphatic, cyclic or acyclic radical, such radical may include a heteroatom selected from O, N and S; this radical R 'preferably comprises from 2 to 24 carbon atoms.

More preferred is a bismaleimide selected from the group consisting of N, N'-ethylene-bismaleimides, N, N'-hexamethylene-bismaleimides, N, N '- (m-phenylene) -bismaleimides, N, N' - ( p-phenylene) -bismaleimides, N, N '- (p-tolylene) -bismaleimides, N, N'- (methylenedi-p-phenylene) -bismaleimides, N, N' - (oxydi-p-phenylene) -bismaleimides and mixtures of these compounds. Such bismaleimides are well known to those skilled in the art and have been described for example in FR-A-2,611,209 or US-A-4,818,601, EP-A-0 345 825 or US-A-4,803,250. , EP-A-0 564 966, US-A-5,300,585.

In the case where a reinforcing resin or a bismaleimide is used, it is present in the composite of the invention at a preferred level of between 0.1 and 20%, more preferably between 1 and 8% by weight of rubber composition. For levels above the maximum indicated, there is more or less exposure to the risks of excessive stiffening of the compositions, and therefore to embrittlement of the composites; for rates below the indicated minima, the intended technical effect may be insufficient.

1-2. Metal reinforcement

By "body" or "reinforcement" is meant here, in known manner, any reinforcing element capable of reinforcing the rubber matrix. This reinforcement can be in various forms, preferably in the form of a wire (monofilament), a film (for example a strip or a tape) or a son assembly, these wires are twisted between them ( for example, in the form of a cable) or substantially parallel to each other (for example in the form of a son packet, a continuous fiber or a set of short fibers).

In the composites and tires of the invention, this reinforcement is more preferably in the form of a unitary yarn or an assembly of yarns, for example a cable or a strand manufactured with devices and methods of cabling or stranding known to those skilled in the art, which are not described here for the simplicity of the presentation.

"Metal" reinforcement means any reinforcement, whether it is entirely metallic or not, of which at least the surface or external part intended to come into contact with the rubber, is made of metal.

The metal, or surface metal if appropriate, of the metal reinforcement is preferably selected from Fe, Cu, Zn, Al, Sn, Ni, Co, Cr, Mn, the oxides, hydroxides and alloys of these elements, more preferably from Fe, Cu, Zn, Al, Sn, their oxides, hydroxides and alloys. The invention is preferably implemented with a reinforcement made of steel, in particular carbon pearlitic (or feπito-pearlitic) steel, hereinafter referred to as "carbon steel", or else stainless steel (by definition, steel comprising at least 11% of chromium and at least 50% of iron) as described for example in applications EP-A-648 891 or WO98 / 41682. But it is of course possible to use other steels or other alloys.

When a carbon steel is used, its carbon content is preferably between 0.35% and 1.2%, especially between 0.5% and 1.1% (% by weight of steel); it is more preferentially between 0.6% and 1.0%, even more preferentially between 0.68% and 0.95%; these levels represent a good compromise between the mechanical properties required for the tire and the feasibility of the wires. It should be noted that in applications where the highest mechanical strengths are not necessary, it is advantageous to use carbon steels whose carbon content is between 0.50% and 0.70%, especially varies from 0, 55% to 0.60%, such steels being ultimately less expensive because easier to draw.

The person skilled in the art knows how to adapt the composition of the steel according to his own particular needs, for example by using microalloyed carbon steels containing specific addition elements such as Cr, Ni, Co, V, or various other known elements (see, for example, Research Disclosure 34984 - "Micro-alloyed steel cord constructions for tires" - May 1993, Research Disclosure 34054 - "High tensile strength steel cord constructions for tires" - August 1992).

As indicated above, the metal or steel used, whether in particular carbon steel or stainless steel, may itself be coated with an intermediate metal layer improving for example the properties implementation of the metal reinforcement and / or its constituent elements, or the use properties of the reinforcement and / or the composite themselves such as adhesion properties, corrosion resistance or resistance to aging .

According to a preferred embodiment, the steel used is covered with an intermediate layer of aluminum, zinc, copper, oxide and / or hydroxide or an alloy of these elements.

Among the aluminum alloys, those selected from Al-Mg, Al-Cu, Al-Ni and Al-Zn binary alloys and the ternary alloys of Al and two of the elements Mg, Cu and Ni are preferably used. Zn, more particularly an Al-Zn alloy.

Among the zinc alloys, those selected from among the Zn-Cu, Zn-Al, Zn-Mg, Zn-Co, Zn-Mo, Zn-Fe, Zn-Ni and Zn-Sn alloy alloys and alloys are preferably used. ternary Zn and two of the elements (for example Zn-Cu-Ni or Zn-Cu-Co), more particularly a Zn-Cu alloy (brass) or a Zn-Al alloy as mentioned above.

Of the copper alloys, the preferred binary alloys are those of Cu-Zn (above-mentioned brass) and Cu-Sn (bronze). Furthermore, oxides and / or hydroxides of aluminum which can be used have for example been described in the above-mentioned application WO02 / 10265, in particular Al ₂ O ₃ aluminas, aluminum oxide-hydroxides [Al (OH) _a O _b with 0 <a <3 and b = (3-a) / 2], aluminum trihydroxides Al (OH) ₃ , and any mixture of such oxides or hydroxides. Among the oxides and / or hydroxides of zinc, there will be mentioned in particular ZnO and Zn (OH) ₂ . Oxides and / or hydroxides of iron can also be considered, such as Fe ₂ O ₃ , Fe O and FeO (OH).

When an intermediate metal layer is deposited on the metal reinforcement or on the individual elements constituting this reinforcement, in particular when it is an assembly, it is possible to use any deposition method capable of applying, continuously or discontinuous, a metal coating on a metal substrate. For example, a simple run-in dipping technique is used, in a bath containing the metal or alloy in the liquid state, an electrolytic deposition technique or else by spraying.

In the most frequent case where the reinforcement used is a cable consisting of fine wires, the intermediate metal layer will preferably be deposited on the wires, and not on the final cable. In such a case, in particular to facilitate the drawing operations, the deposit will advantageously be made on a so-called "intermediate" diameter wire, for example of the order of a millimeter, at the outlet of the last heat treatment (patenting) preceding the step wet final wire drawing for obtaining the fine wire having the final diameter referred to.

When the composites of the invention are used to reinforce carcass reinforcement or crown reinforcement of radial tires, the reinforcements used are preferably assemblies (strands or cables) of fine carbon steel or stainless steel wires having:

a tensile strength greater than 2000 MPa, more preferably greater than 2500 MPa, in particular greater than 3000 MPa; the person skilled in the art knows how to manufacture fine threads having such strength, by adjusting in particular the composition of the steel and the final work hardening rates of these threads; for a good compromise strength / flexural strength / feasibility, a diameter φ between 0.12 and 0.40 mm, more preferably in a range from 0.15 to 0.26 mm when the composite is intended to strengthen a carcass reinforcement, in a range from 0.20 to 0.35 mm when the composite is intended to reinforce a crown reinforcement.

When the composites of the invention are used to reinforce tire bead zones, the reinforcements may be in particular in the form of rods consisting of carbon steel or stainless steel son, unitary or assembled, these son having:

a tensile strength greater than 1500 MPa, more preferably greater than 2000 MPa; a diameter φ (or a characteristic dimension, if it is a wire other than cylindrical) between 0.5 and 3 mm, more preferably between 0.8 and 2.2 mm. 1-3. Phosphorus coupling agent

It is recalled here that, by "coupling agent" metal-rubber, must be understood in known manner an agent capable of establishing a sufficient connection, chemical and / or physical, between the metal and the rubber. Such a coupling agent, therefore at least bifunctional, has for example as simplified general formula "Y-T-X", in which:

Y represents a functional group ("Y" function) which is capable of bonding physically and / or chemically to the surface metal of the metal reinforcement in question;

X represents a functional group ("X" function) capable of bonding physically and / or chemically to the rubber composition, for example to the diene elastomer via a sulfur atom;

T represents a divalent group making it possible to connect Y and X.

As indicated above, the polyfunctional coupling agent for the composite of the invention has the formula:

(I) (RO) ₂ (Q) P - (Z) _y - S _x - (Z) _y - P (Q) (OR) ₂

in which (according to the usual nomenclature, P = phosphorus and S = sulfur):

the symbols R, identical or different, each represent a monovalent hydrocarbon group, hydrogen or an alkali metal selected from Na and K;

the symbols Q, identical or different, represent oxygen or sulfur; the symbols Z, which are identical or different, are divalent linking groups comprising from 1 to 18 carbon atoms;

each y is equal to 0 or 1 (both of which may be different from each other); - x is an integer or fractional number.

Preferably, R is chosen from linear or branched C ₁ -C ₈ alkyls, C ₅ -C ₁₀ cycloalkyls, C ₆ -Cι ₈ aryls, C ₆ -Cι ₈ aryl- (Cι) -C ₈ ) alkyl, hydrogen or an alkali metal selected from Na and K. More preferably, R is chosen from alkyls, linear or branched, having from 1 to 6 carbon atoms and the phenyl radical, especially from methyl, ethyl, propyl and isopropyl.

On the other hand, according to another preferred embodiment of the invention, the following characteristics are verified:

Q represents oxygen;

- Z is a Cι-C ₈ alkylene group, preferably Cι-C;

each y is equal to 1, that is to say that there exists a "spacer" Z between the polysulfide group S _x and each phosphorus functional group; x is an integer or fractional number in a range from 2 to 8. Z chains may include, or be interrupted by, a heteroatom such as for example S, O or N.

Compounds of formula (I) above are known as well as their methods of synthesis; they have been described, for example, in GB-A-1 189 304 as lubricating additives.

They can be prepared according to methods known to those skilled in the art, for example those for which Q = oxygen, by reaction of a hydrocarbon dihalide with a trialkyl phosphite to form intermediately the corresponding halogenated dialkylphosphonate. Sulfurization of the latter with an alkali metal polysulfide followed by oxidation leads to the compound (I) of the polysulfide type.

By way of preferred examples of polysulfides corresponding to formula (I) above, mention may be made in particular of the polysulfides of particular formulas (II) to (IV) below:

O O

II (EtO) ₂ P ^• (CH ₂ ) ₄ S x- (CH ₂ ) ₄ ^• P (OEt) ₂

(H)

O O

II

(HO) ₂ P (CH ₂ ) ₄ - S x- (CH ₂ ) ₄ P (OH) ₂

(Πi)

O O

(NaO) ₂ P (CH ₂₎ ₄ Sx (CH ₂₎ ₄ P (ONa) ₂

(IV)

for which, therefore:

- Q = O (oxygen);

- y = 1; - Z = (CH ₂ ) ₄ (butylene);

- R = Et (ethyl), H or Na;

x is in a range from 2 to 8, preferably from 2 to 5.

In formula (I) above (and more particularly in formulas (II) to (IV) above), in the case where the synthesis route of the compound in question can give rise to only one kind of polysulfide group, the number x is then an integer, preferably in a range from 2 to 8, more preferably from 2 to 5; this is the case for example disulfide compounds (x = 2) or tetrasulfides (x = 4). However, those skilled in the art will readily understand that this number may be a fractional average number when the synthesis route gives rise to a mixture of polysulfide groups each having a different number of sulfur atoms; in such a case, the polysulfide group synthesized consists in fact of a distribution of polysulphides, ranging for example from disulfide S to heavier polysulphides, centered on a mean value (in mole) of "x" (fractional number) included between 2 and 8, more preferably between 2 and 5.

1-4. Treatment of the metallic reinforcement by the phosphorus coupling agent

The phosphorus coupling agent is preferably deposited directly on the surface of the metal reinforcement used. This deposition may be carried out by any known method, batchwise or continuously, for example by application with a brush, by dipping, by spraying, the coupling agent being used pure or diluted in a solvent such as toluene.

If the selected coupling agent is used in solution, for example in toluene, the concentration of the coupling agent in the solution is preferably between 0.001% and 15%, more preferably between 0.001% and 5%.

Before contact with the coupling agent, the surface of the metal reinforcement may be previously cleaned and / or activated in various ways known in the art, for example by washing with hot water, by treatment with an acidic or basic aqueous solution. , with optional rinsing and drying steps, or by plasma treatment.

As an indication, the layer of coupling agent thus deposited preferably represents less than 50 mg, more preferably less than 5 mg of phosphorus coupling agent per 100 g of reinforcement, which is equivalent to a thickness generally of between 10 and 100 nm (nanometers), depending on the type of process used for the deposit.

After the application of the coupling agent, the surface of the reinforcement may be dried, for example in ambient air, or preferably heat-treated, by heating in an oven or in a tunnel, the heating being obtained, for example, by conduction on contact with hot gas, or electrically, in particular by Joule effect or by induction. This heat treatment allows the departure of the solvent or solvents, as well as the reaction, partial or total depending on the intensity of the treatment, the phosphorus coupling agent with the metal surface.

1-5. Composite of the invention

The metal reinforcement thus prepared can be put directly in contact with the rubber composition, in order to manufacture the composite of the invention.

This composite may be in various forms, for example in the form of a sheet, a strip, tape or a rubber block in which is incorporated the metal reinforcement using various means known to the user. skilled in the art, such as, for example, molding, calendering or coiling means. Of course, the invention relates to composites in the green state (ie, before baking or crosslinking) as in the cooked state (ie, after crosslinking). In this composite, the final adhesion between the metal and the rubber composition, via the adhesive inteiphase, is obtained at the end of the firing of the finished article, for example the tire, comprising the composite. Preferably, this cooking is operated under pressure.

The composites according to the invention are preferably intended for tires, in particular for radial tires to form all or part of the crown reinforcement, of the carcass reinforcement or the reinforcement of the bead zone of such tires.

By way of example, the appended figure schematically represents a radial section of a heavy-weight tire 1 with a radial carcass reinforcement that may or may not conform to the invention, in this general representation. This tire 1 comprises a crown 2, two sidewalls 3, two beads 4, a carcass reinforcement 7 extending from one bead to the other. The top 2, surmounted by a tread (not shown in this schematic figure, for simplification), is in a manner known per se reinforced by a crown reinforcement 6 constituted for example by at least two superimposed crossed vertex plies (plies so-called "working" top), optionally covered with at least one protective crown ply, all these plies being able to be reinforced by metal ropes. The carcass reinforcement 7 is wound around the two rods 5 in each bead 4, the upturn 8 of this armature 7 being for example disposed towards the outside of the tire 1 which is shown here mounted on its rim 9. The armature of carcass 7 consists of at least one ply reinforced by so-called "radial" metal cables, that is to say that these cables are arranged substantially parallel to each other and extend from one bead to the other so as to form an angle between 80 ° and 90 ° with the median circumferential plane (plane perpendicular to the axis of rotation of the tire which is located halfway between the two beads 4 and passes through the middle of the armature of summit 6).

Of course, this tire 1 also comprises, in a known manner, an inner rubber or elastomer layer (commonly known as "inner liner") which defines the radially inner face of the tire and which is intended to protect the carcass reinforcement from the diffusion of the tire. air from the interior space to the tire. Advantageously, it further comprises an intermediate reinforcing elastomer layer which is located between the carcass reinforcement and the inner layer, intended to reinforce the inner layer and, consequently, the carcass reinforcement, also intended to partially relocate the stresses. undergone by the carcass reinforcement.

The tire according to the invention has the essential characteristic of comprising in its structure at least one metal / rubber composite in accordance with the invention, this composite possibly being, for example, a portion of the bead zone 4 comprising the bead wire 5, a cross-ply web or a protective ply of the crown reinforcement 6, a ply forming all or part of the carcass reinforcement 7.

As indicated above, the composite of the invention is advantageously usable for constituting a carcass reinforcement ply 7 of a tire for an industrial vehicle such as than Heavyweight. Preferably, in such a case, its rubber composition has, in the vulcanized state (ie, after firing), a secant modulus in extension at 10% elongation (denoted "E10") which is less than 9 MPa. more preferably between 4 and 9 MPa.

But the composite of the invention can have an equally advantageous use in the crown reinforcement of all types of tires, for example for passenger vehicles, vans or heavy vehicles. Preferably, in such a case, its rubber composition has in the vulcanized state a modulus E10 which is greater than 9 MPa, more preferably between 9 and 20 MPa.

II. EXAMPLES OF CARRYING OUT THE INVENTION

II- 1. Dynamometric measurements

For metal reinforcements (wire or cable), the breaking force measurements denoted Fm (maximum load in N), breaking strength denoted Rm (in MPa) and elongation at break denoted At ( total elongation in%) are made in tension according to ISO 6892 of 1984. As regards the rubber compositions, the modulus measurements are carried out in tension, unless otherwise indicated according to ASTM D 412 of 1998 (test piece "C "): the secant modules are measured in second elongation (that is to say after an accommodation cycle), that is to say, brought back to the real section of the test tube at 10% elongation, noted E10 and expressed in MPa (normal temperature and humidity conditions according to ASTM D 1349 of 1999).

U-2. Nature and properties of reinforcements used

For the production of examples of composites in accordance with the invention, the following are used as metallic reinforcements: cables consisting of fine carbon steel wires, coated or not, suitable for reinforcing carcass reinforcement of heavy-duty tires or reinforcements tourism tire crowns, ie large diameter elementary threads that can be used for reinforcing low tire areas, especially in the form of rods.

The fine carbon steel wires are prepared starting from, for example, machine wires (diameter 5 to 6 mm) that are first cold-worked by rolling and / or drawing to an intermediate diameter of about 1 mm. or starting directly from commercial intermediate threads whose diameter is close to 1 mm. The steel used is a known carbon steel, for example of the USA AISI 1069 type, the carbon content of which is approximately 0.7%, comprising approximately 0.5% manganese and 0.2% silicon, the remainder being made of iron and the usual unavoidable impurities associated with the steelmaking process. The intermediate diameter son then undergo a degreasing treatment and / or pickling, before further processing. After optional depositing of a metal coating on these intermediate son (for example, brass, zinc or aluminum alloy), is carried out on each wire a so-called "final" hardening (ie, implemented after the last heat treatment of patenting), by cold drawing in a wet medium with a drawing lubricant which is, for example, in the form of an aqueous emulsion.

The cables used are for example layered cables of known construction [3 + 9], fretted, formed of 12 wires of diameter equal to about 0.225 mm (Fm = 131 daN, Rm ≈ 2685 MPa, At = 2.75%) . These cables comprise a core of 3 wires wound together in a helix (direction S) in a pitch of 6.3 mm, this core being in contact with an outer layer of 9 wires themselves wound together in a helix (direction S) around of the core, in a pitch of 12.5 mm, the whole being shrunk by a 0.15 mm hoop wire with a pitch of 3.5 mm (Z direction). Other cables used are, for example, stranded cables of known construction [3 × 2], not fretted, formed of 6 wires of diameter equal to about 0.225 mm (Fm = 66 daN, Rm = 2700 MPa, At = 2.7% ); these cables comprise three strands wound together in a helix (direction S) in a pitch of 12.5 mm, each strand consisting of two son themselves wound together helically (Z direction) at the same pitch of 12.5 mm.

In these cables, each carbon steel wire may be either "clear" steel (that is to say uncoated), or coated with an aluminum-zinc alloy interlayer (about 5% by weight aluminum), or a flash of zinc. The thickness of the Al-Zn alloy coating, deposited "by dipping" before final wet drawing, is of the order of one micrometer after drawing (ie about 1.6 g of aluminum alloy per 100 g of wire) . The thickness of the zinc flash deposited electrolytically before final wet drawing, is of the order of 0.002 microns after wire drawing (ie about 4 mg of zinc per 100 g of wire).

DD-3. Phosphorus coupling agent

The coupling agent used is a bis (butyldiethylphosphonate) polysulfide corresponding to the above-mentioned formula (U):

O O

(EtO) ₂ (CH ₂₎ ₄ Sx (CH ₂₎ ₄ P (OEt) ₂

This coupling agent was obtained in two steps: an Arbusov reaction making it possible to obtain bromobutyldiethylphosphonate, followed by a sulfurization reaction, as indicated in the reaction scheme below (Et = ethyl):

O

P (OEt) ₃

Br (CH ₂ ) ₄ Br (EtO) ₂ P (CH ₂ ) ₄ Br

Na ₂ S _x (Na ₂ S.9H ₂ O + S ₈₎ H ₂ 0 + NaCl Toluene TBAB

O

(EtO) ₂ P (CH ₂ ) ₄ S x (CH ₂ ) ₄ P (OEt) ₂ A) Synthesis of 4-bromobutyldiethylphosphonate:

In a three-necked 100 ml equipped with a magnetic bar and an ascending condenser, introduced 26.98 g (0.125 mol) of 1,4-dibromobutane. The mixture is heated to 90 ° C. before the addition of triethyl phosphite (8.31 g, 0.05 mol) is begun. Temperature and stirring are maintained for 24 hours (monitoring by gas chromatography makes it possible to control the progress of the reaction). The mixture is distilled under vacuum in a bulb oven (1.7 mm Hg, temperature 65 ° C.). 10.61 g of product are thus collected.

B) Synthesis of bis (butyldiethylphosphonate) polysulfide

In a second step, the target polysulfide is formed by the action of the sodium polysulfide generated in situ with 4-bromobutyldiethylphosphonate, using a known technique of phase transfer catalysis (see for example US 5,468,893).

In a three-neck topped with a condenser, are introduced 0.51 g (15.7 mmol) of sulfur and 1.27 g (5.3 mmol) of Na ₂ S (taken under argon) to which are added 8 ml of saturated water in NaCl and 3 ml of toluene. The solution is heated to 80 ° C. The yellow reaction medium first turns red, then a solution containing 90 mg of TBAB (tetrabutylammonium bromide), 2.80 g of 4-bromobutyldiethylphosphonate (10 mmol) and 3 ml of toluene is added dropwise. The initially red aqueous phase is discolored in favor of the colorless toluene phase which becomes yellow. The toluene phase is isolated and the aqueous phase is extracted with toluene. The organic phases are joined and concentrated.

2.44 g of product of formula (II) above is thus obtained, as attested by NMR analysis (yield 92%). This product actually consists of a distribution of polysulfides, ranging essentially from disulfide (x = 2) to hexasulfide (x = 6), centered on a mean value of x which is close to 4.

It will be understood that modified synthesis conditions would make it possible to obtain other distributions of polysulphides, with average values of x variables but preferably between 2 and 8, more preferably between 2 and 5.

II-4. Cable treatment

For the treatment of cables with this coupling agent, the procedure is as follows: the reinforcement is first treated by passing through a hot water bath at 60 ° C., the residence time being approximately 10 seconds ; in the case of Zn-flashed light steel, this step is preceded by 10 s pickling in an acid bath at 60 ° C (Condat's "Allmet" degreaser product, diluted to 10% in water). ). Then, the reinforcement is sent into the bath of phosphorus coupling agent at 20 ° C containing, depending on the case, 0.01 or 0.05 mol of phosphorus coupling agent diluted in toluene (residence time: 5 or 15 minutes). , According to the case). After application of the coupling agent, the surface of the reinforcement is dried by passing through a heating oven at a temperature of 100 ° C for 60 s. An ultra-thin phosphor coupling agent film, estimated at less than 5 mg of coupling agent per 100 g of reinforcement, is thus targeted. π-5. Composites and tires of the invention

For the manufacture of the composites and tires of the invention, the previously described cables of construction [3x2] are incorporated by calendering with a rubberized fabric formed of a known composition based on natural rubber and carbon black as a reinforcing filler. , conventionally used for the manufacture of crown reinforcement plies for radial tires (ElO module equal to about 18 MPa, after firing). This composition essentially comprises, in addition to the elastomer and the reinforcing filler, an antioxidant, stearic acid, a reinforcing resin (phenolic resin plus methylene donor), cobalt naphthenate as adhesion promoter, finally a vulcanization system (sulfur, accelerator, ZnO). In the rubber fabric, the cables are arranged parallel in a known manner, according to a determined cable density, for example about 70 cables per dm of web, which, given the diameter of the cables, equals a width of the bridges. of rubber, between two adjacent cables, about 0.65 mm.

Those of construction [3 + 9] are used to reinforce another fabric formed of a similar rubber matrix, based on natural rubber and carbon black, conventionally used for the manufacture of carcass reinforcement plies of radial tires. Heavy-weight type (ElO module equal to about 6 MPa, after cooking). In this other fabric, the cables are arranged in parallel according to a cable density of about 60 cables per dm of web (width of the rubber bridges of about 0.5 mm).

The tires, manufactured in known manner, are as schematized in the appended figure, already commented. Their radial carcass reinforcement 7 consists of a single radial ply formed of the previously described rubberized fabric according to the invention, comprising the metal cables [3 + 9] arranged at an angle of approximately 90 ° with the median circumferential plane. As for the crown reinforcement 6, it consists of two crossed superimposed working plies, reinforced with metal cables inclined by 22 degrees, these two working plies being covered by a protective crown ply reinforced with conventional elastic metal cables inclined by 22 degrees. Each of the two working plies is formed of the rubberized fabric or composite previously described according to the invention, reinforced by the cables [3 × 2].

Claims

A metal / rubber composite comprising a matrix of diene elastomer reinforced by a metal reinforcement adhered to said matrix via an adhesive interphase based on a compound having the formula:

(RO) ₂ (Q) P - (Z) _y - S _x - (Z) _y - P (Q) (OR) ₂

in which :

the symbols R, identical or different, each represent a monovalent hydrocarbon group, hydrogen or an alkali metal chosen from Na and K;

each y is equal to 0 or 1;

- x is an integer or fractional number.

2. The composite of claim 1, wherein R is selected from alkyl, linear or branched Cι-C ₈ cycloalkyl, C ₅ -Cιo, aryls C ₆ -Cι _8, the (C ₆ - Cι ₈ ) aryl- (Cι-C ₈ ) alkyl, hydrogen or an alkali metal selected from Na and K.

3. Composite according to claim 2, wherein R is selected from linear or branched alkyls having from 1 to 6 carbon atoms and the phenyl radical.

4. Composite according to any one of claims 1 to 3, wherein:

Q represents oxygen; - Z is a Cι-C ₈ alkylene group, preferably -; each y is 1;

x is an integer or fractional number in a range from 2 to 8.

5. Composite according to any one of claims 1 to 4, the diene elastomer being selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and blends. of these elastomers.

6. Composite according to claim 5, the diene elastomer being selected from the group consisting of natural rubber, synthetic polyisoprenes, isoprene copolymers and mixtures of these elastomers.

7. Composite according to claim 6, the diene elastomer being natural rubber.

8. Composite according to any one of claims 1 to 7, the surface metal of the metal body being selected from Fe, Cu, Zn, Al, Ni, Co, Cr, Mn, Sn, oxides, hydroxides and alloys thereof. elements.

9. Composite according to claim 8, the surface metal being selected from Fe, Cu, Zn, Al, Sn, the oxides, hydroxides and alloys of these elements.

10. Composite according to any one of claims 1 to 9, the metal of the metal body being steel.

11. Composite according to claim 10, the steel being a stainless steel or a carbon steel.

12. Composite according to claim 11, the steel being a carbon steel having a carbon content of between 0.35% and 1.20%, preferably between 0.5% and

1.1%.

13. Composite according to any one of claims 10 to 12, the steel being covered with an intermediate layer of aluminum, zinc, or an alloy thereof.

14. Composite according to any one of claims 1 to 13, the metal body being selected from son, yarn assemblies and films.

15. Use of a composite according to any one of claims 1 to 14 for the manufacture or reinforcement of a ground connection system of a motor vehicle or a semi-finished rubber product for such a system.

16. Use according to claim 15, the ground connection system being a tire.

17. Use according to claim 16, the composite being used for reinforcing a crown reinforcement, a carcass reinforcement or the bead zone of a tire.

18. Use according to claim 17, the composite being used for the reinforcement of a tire carcass reinforcement for a heavy vehicle vehicle.

19. A ground connection system or semi-finished rubber product incorporating a composite according to any one of claims 1 to 14.

20. Ground connection system according to claim 19, consisting of a tire.

21. A tire according to claim 20, the composite being present in the armature of the bead zone of the tire.

22. A tire according to claim 20, the composite being present in the carcass reinforcement of the tire.

23. A tire according to claim 20, the composite being present in the crown reinforcement of the tire.

24. Metal reinforcement coated with an adhesive layer capable of adhering to a rubber matrix based on diene elastomer, said adhesive layer being based on at least one compound corresponding to the formula:

(RO) ₂ (Q) P - (Z) _y - S _x - (Z) _y - P (Q) (OR) ₂

in which :

the symbols R, identical or different, each represent a monovalent hydrocarbon group, hydrogen or an alkali metal chosen from Na and K; the symbols Q, identical or different, represent oxygen or sulfur; the symbols Z, which are identical or different, are divalent linking groups comprising from 1 to 18 carbon atoms;

each y is equal to 0 or 1;

- x is an integer or fractional number.

25. metal reinforcement according to Claim 24 wherein R is selected from alkyl, linear or branched Cι-C ₈ cycloalkyl, C ₅ -Cιo, aryls C ₆ -Cι _8, the (C ₆ - Cι ₈ ) aryl- (Cι-C ₈ ) alkyl, hydrogen or an alkali metal selected from Na and K.

26. Metal reinforcement according to claim 25, wherein R is selected from alkyls, linear or branched, having from 1 to 6 carbon atoms and the phenyl radical.

Metal reinforcement according to any of claims 24 to 26, wherein:

Q represents oxygen;

Z is a Cι-C ₈ alkylene group, preferably a Cι-C ₄ alkylene group;

each y is 1;

x is an integer or fractional number in a range from 2 to 8.

28. Metal reinforcement according to any one of claims 24 to 27, said reinforcement being selected from son, yarn assemblies and films.