EP2572029B1 - Method for the production of a three-layer metal cord of the type that is rubberised in situ - Google Patents

Description

The present invention relates to processes and devices for manufacturing metal cables with three concentric layers, M + N + P construction, used in particular for the reinforcement of rubber articles, in particular tires.

It is more particularly related to processes and devices for manufacturing metal cables of the type "gummed in situ", that is to say, gummed from the inside, during their manufacture itself, by rubber or a rubber composition, in to improve their resistance to corrosion and consequently their endurance in particular in carcass reinforcement of tires for industrial vehicles.

A radial tire comprises in known manner a tread, two inextensible beads, two flanks connecting the beads to the tread and a belt circumferentially disposed between the carcass reinforcement and the tread. This carcass reinforcement is constituted in known manner by at least one ply (or "layer") of rubber reinforced by reinforcement elements ("reinforcements") such as cords or monofilaments, generally of the metal type in the case of pneumatic tires for industrial vehicles carrying heavy loads.

For the reinforcement of the above carcass reinforcements, use is generally made of steel wires ( "steel cords") called "layers" ( "layered cords") consisting of a core layer and one or more layers of concentric wires arranged around this central layer. The most used three-layer cables are essentially M + N + P construction cables, formed of a central layer of M wire (s), M varying from 1 to 4, surrounded by an intermediate layer of N wires, N typically ranging from 5 to 15, itself surrounded by an outer layer of P son, P typically ranging from 10 to 22, the assembly may be optionally shrunk by an outer hoop thread wound helically around the outer layer .

In a well-known manner, these layered cables are subjected to considerable stresses during the rolling of the tires, in particular to repeated flexures or variations of curvature inducing at the level of the strands of friction, in particular as a result of the contacts between adjacent layers, and therefore of wear, as well as fatigue; they must therefore have a high resistance to phenomena known as "fatigue-fretting".

It is particularly important that they are impregnated as much as possible by the rubber, that this material penetrates the best in all spaces between the son constituting the cables. Indeed, if this penetration is insufficient, then forms of empty channels or capillaries, along and inside the cables, and corrosive agents such as water or even oxygen in the air, likely to penetrate the tires for example as a result of cuts in their band running along these empty channels into the carcass of the tire. The presence of this moisture plays an important role in causing corrosion and accelerating the degradation processes above (phenomena known as "fatigue-corrosion"), compared to use in a dry atmosphere.

All these phenomena of fatigue that are generally grouped under the generic term "fatigue-fretting-corrosion" are at the origin of a gradual degeneration of the mechanical properties of the cables and can affect, for the most severe driving conditions , the life of these.

To overcome the above disadvantages, the demand WO 2005/071157 proposed cables with three layers of 1 + N + P construction, in particular of construction 1 + 6 + 12, one of the essential characteristics is that a sheath consisting of a diene rubber composition covers at least the intermediate layer constituted M son, the core (or unit wire) of the cable may itself be covered or not rubber. Thanks to this specific architecture and at least partial filling by the rubber of the capillaries or interstices which results from it, not only an excellent penetrability by the rubber is obtained, limiting the problems of corrosion, but also the endurance properties in fatigue-fretting are significantly improved over the cables of the prior art. The longevity of the tires and that of their carcass reinforcement are thus very significantly improved.

However, the processes described for the manufacture of these cables, as well as the cables that come from them, are not without drawbacks.

First of all, these three-layer cables are obtained in several steps which have the disadvantage of being discontinuous, firstly by producing an intermediate cable 1 + N (in particular 1 + 6), then by sheathing via an extrusion head of this intermediate cable or core strand, finally by a final operation of wiring the P remaining son around the core strand and sheathed, for forming the outer layer. To avoid the problem of "green sticky" or parasitic stickiness inherent in the diene rubber sheath in the green state, before wiring the outer layer around the core strand, must be used further a plastic interlayer film during intermediate operations of winding and unwinding. All these successive manipulations are penalizing from the industrial and antinomic point of view of the search for high production rates.

On the other hand, if one wants to be able to guarantee a high penetration rate by the rubber inside the cable to obtain an air permeability of the cable, along its axis, which is As low as possible, it has been necessary according to these prior art methods to use relatively large amounts of rubber during sheathing. Such quantities lead to a spurious overflow, more or less pronounced, of the raw rubber at the periphery of the finished cable manufacturing.

However, as already mentioned above, because of the high stickiness of diene rubbers in the green state, such parasitic overflow in turn generates significant drawbacks during the subsequent handling of the cable, in particular during calendering operations which will follow for the incorporation of the cable to a band of rubber rubber itself in the green state, before the final operations of manufacturing the tire and final baking.

All the disadvantages described above, of course, slow industrial speeds and penalize the final cost of the cables and tires they reinforce.

Continuing their research, the Applicants have discovered an improved manufacturing process, using a specific rubber, which overcomes the aforementioned drawbacks.

• une étape d'assemblage des N fils de la deuxième couche (C2) autour du noyau (C1), pour formation en un point, dit «point d'assemblage » d'un câble intermédiaire dit « toron d'âme » de construction M+N ;
• respectivement en amont et/ou en aval dudit point d'assemblage, une étape de gainage du noyau et/ou du toron d'âme par ledit caoutchouc ou ladite composition de caoutchouc, par passage à travers au moins une tête d'extrusion ;
• une étape d'assemblage des P fils de la troisième couche (C3) autour du toron d'âme (M+N) pour formation du câble de construction M+N+P ainsi gommé de l'intérieur,

et étant caractérisé en ce que ledit caoutchouc est un élastomère thermoplastique insaturé extrudé à l'état fondu.Accordingly, the invention relates to a method for manufacturing a metal cable with three concentric layers (C1, C2, C3), of M + N + P construction, of the type gummed in situ, that is to say gummed with inside, even during its manufacture, with rubber or a rubber composition, said cable having a first layer or core (C1) consisting of diameter d _c of M wire (s) of diameter d _1, core around which are surrounded helical assembly in a pitch p ₂ , in a second layer (C2), N son of diameter d ₂ , second layer around which are helically wound together in a pitch p ₃ , in a third layer (C3), P wire of diameter d ₃ , said method comprising at least the following steps:

• a step of assembling the N son of the second layer (C2) around the core (C1), for formation at a point, called "assembly point" of an intermediate cable called "core strand" of construction M + N;
• respectively upstream and / or downstream of said assembly point, a step of sheathing the core and / or the core strand by said rubber or said rubber composition, by passing through at least one extrusion head;
• a step of assembling the P son of the third layer (C3) around the core strand (M + N) for forming the construction cable M + N + P thus gummed from the inside,

and being characterized in that said rubber is an unsaturated thermoplastic elastomer extruded in the molten state.

This method of the invention makes it possible to manufacture, in line and continuously, a cable with three concentric layers which, in comparison with the in situ three-layered gummed cables of the prior art, has the notable advantage that the rubber used as rubber of filling is an elastomer of the thermoplastic type and no longer diene, by definition thermofusible and therefore easier to implement, the amount of which can be easily controlled; it is thus possible, by adjusting the operating temperature of the thermoplastic elastomer, to evenly distribute the latter within each of the interstices of the cable, giving the latter optimum impermeability along its longitudinal axis.

In addition, the thermoplastic elastomer above does not pose a problem of parasitic tights in case of a slight overflow outside the cable after manufacture. Finally, the unsaturated and therefore (co) vulcanizable nature of this unsaturated thermoplastic elastomer offers the cable excellent compatibility with matrices of unsaturated diene rubbers such as natural rubber, usually used as calendering gum in metal fabrics for reinforcing tires. .

• un exemple de dispositif de retordage et gommage in situ utilisable pour la fabrication d'un câble à trois couches selon un procédé conforme à l'invention (Fig. 1) ;
• en coupe transversale, un exemple de câble de construction 1+6+12 du type compact, , gommé in situ, susceptible d'être fabriqué par le procédé de l'invention (Fig. 2) ;
• en coupe transversale, un câble de construction 1+6+12 conventionnel, également du type compact, non gommé in situ (Fig. 3).

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 Figures 1 to 3 relating to these examples which schematize, respectively:

• an example of an in situ twisting and scrubbing device that can be used for the manufacture of a three-layer cable according to a method according to the invention ( Fig. 1 );
• in cross-section, an example of a construction cable 1 + 6 + 12 of the compact type, gummed in situ, which can be manufactured by the process of the invention ( Fig. 2 );
• in cross-section, a conventional 1 + 6 + 12 construction cable, also of the compact type, not gummed in situ ( Fig. 3 ).

I. DETAILED DESCRIPTION OF THE INVENTION

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

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).

• tout d'abord, une étape d'assemblage des N fils de la deuxième couche (C2) autour du noyau (C1), pour formation en un point, dit « point d'assemblage » d'un câble intermédiaire dit « toron d'âme » de construction M+N (ou C1+C2) ;
• respectivement en amont et/ou en aval dudit point d'assemblage, une étape de gainage du noyau et/ou du toron d'âme par un caoutchouc (ou composition de caoutchouc) spécifique (dénommé « gomme de remplissage ») qui est extrudé à l'état fondu par passage à travers une ou plusieurs tête(s) d'extrusion ;
• puis une étape d'assemblage des P fils de la troisième couche (C3) autour du toron d'âme (M+N) pour formation du câble de construction M+N+P ainsi gommé de l'intérieur.

The method of the invention is therefore intended for the manufacture of a metal cable with three concentric layers (C1, C2, C3), of construction M + N + P, comprising a first layer or core (C1) of diameter of M wire (s) of diameter d ₁ , core around which are surrounded together in a helix in a pitch p ₂ , in a second layer (C2), N son of diameter d ₂ , second layer around which are helically wound together in a step p ₃ , in a third layer (C3), P son of diameter d ₃ , said method comprising at least the following steps:

• first, a step of assembling the N son of the second layer (C2) around the core (C1), for formation at a point, called "assembly point" of an intermediate cable called "strand of soul "of construction M + N (or C1 + C2);
• respectively upstream and / or downstream of said assembly point, a step of sheathing the core and / or the core strand with a specific rubber (or rubber composition) (called "filling rubber") which is extruded at the molten state by passage through one or more extrusion heads;
• then a step of assembling the P son of the third layer (C3) around the core strand (M + N) for forming the construction cable M + N + P and gummed from the inside.

By definition, in the present application, the first layer or central layer (C1) is also called the core (" core ") of the cable, while the first (C1 and second (C2) layers once assembled (C1 + C2 ) are what is commonly called the cable strand.

When M is greater than 1, it should of course be understood that the method of the invention comprises a prior assembly step (whatever the direction S, or Z) of the core wires (C1). The diameter d _c of the core (C1) then represents the diameter of the cylinder of imaginary revolution (or size) which surrounds the M central threads of diameter d ₁ .

According to a preferred embodiment, the P son of the third layer (C3) are helically wound at the same pitch and in the same direction of torsion as the N son of the second layer (C2) and the M son of the first layer (C1) when M is greater than 1.

In the process of the invention, the so-called filling gum is thus introduced in situ in the cable during manufacture, by sheathing either the core alone, or the core strand alone, or both the core and the strand. core, said cladding in itself being operated in a known manner for example by passing through at least one (that is to say one or more) extrusion head (s) delivering the filling rubber in the state molten.

• soit par câblage : dans un tel cas, les fils ne subissent pas de torsion autour de leur propre axe, en raison d'une rotation synchrone avant et après le point d'assemblage ;
• soit par retordage : dans un tel cas, les fils subissent à la fois une torsion collective et une torsion individuelle autour de leur propre axe, ce qui génère un couple de détorsion sur chacun des fils et sur le câble lui-même.

It will be recalled here that there are two possible techniques for assembling metal wires:

• or by wiring: in such a case, the wires are not twisted around their own axis, due to a synchronous rotation before and after the assembly point;
• or by twisting: in such a case, the son undergo both a collective twist and an individual twist around their own axis, which generates a torque of detorsion on each of the son and on the cable itself.

Both of the above techniques are applicable, although a twisting step is preferably used for each of the above assembly steps.

According to a preferred embodiment, the step of assembling the M son of the first layer (C1) when M is greater than 1, the step of assembling the N son of the second layer (C2) and the step of the P-threads of the first layer (C3) are made by twisting.

Downstream of the "assembly point" defined above, the tension stress exerted on the core strand is preferably between 10 and 25% of its breaking force.

The head or each extrusion head is brought to a suitable temperature, easily adjustable according to the specific nature of the TPE elastomer used and its thermal properties. Preferably, the extrusion temperature of the unsaturated TPE elastomer is between 100 ° C and 250 ° C, more preferably between 150 ° C and 200 ° C. Typically, the extrusion head defines a cladding zone having for example the shape of a cylinder of revolution whose diameter is preferably between 0.15 mm and 1.2 mm, more preferably between 0.20 and 1, 0 mm, and whose length is preferably between 1 and 10 mm.

The amount of filling gum delivered by the extrusion head is adjusted to a preferred range of 5 to 40 mg per gram of final cable (i.e., finished in manufacture, gummed in situ). Below the indicated minimum, it is more difficult to guarantee that the filling compound is present, at least in part, in each of the interstices or capillaries of the cable, while beyond the maximum indicated, one is exposed to a risk of overflowing of the filling rubber at the periphery of the cable. For all these reasons, it is preferred that the level of gum filling is between 5 and 35 mg, especially between 5 and 30 mg, more particularly in a range of 10 to 25 mg per gram of cable.

The unsaturated thermoplastic elastomer in the molten state thus covers the core and / or core strand by means of the cladding head, at a running speed typically of a few meters to a few tens of m / min, for a flow rate extrusion pump typically from several cm ³ / min to several tens of cm ³ / min. Core or core strand, as applicable, is advantageously preheated before passing through the extrusion head, for example by passing through an HF generator or through a heating tunnel.

According to a first preferred embodiment, the cladding is performed on the core (C1) alone, that is to say upstream of the assembly point of the N son of the second layer (C2) around the core; in such a case, the core once sheathed is covered with a minimum thickness of unsaturated TPE elastomer which is preferably greater than 20 μm, typically between 20 and 100 μm, in sufficient quantity to be able to coat the wires of the second layer (C2) of the cable once this second layer is in place.

Then the N son of the second layer (C2) are wired or twisted together (direction S or Z) around the core (C1) for formation of the core strand (C1 + C2), in a manner known per se; the son are delivered by supply means such as coils, a distribution grid, coupled or not to a connecting grain, intended to converge around the core N son in a common point of torsion (or point d 'assembly).

According to another preferred embodiment, the cladding is performed on the core strand (C1 + C2) itself, that is to say downstream (and no longer upstream) of the N-joint point. wires of the second layer (C2) around the core; in such a case, the core strand once sheathed is covered with a minimum thickness of unsaturated thermoplastic elastomer which is preferably greater than 5 microns, typically between 5 and 30 microns.

Thus, in the two preferential cases above (sheathing either of the core or the core strand), the filling compound can be delivered at a fixed point, unique and compact, by means of a head of single extrusion.

However, the in-situ scrubbing of the cable according to the invention could also be carried out in two successive cladding operations, a first cladding operation on the core (thus upstream of the assembly point) and a second sheathing operation on the strand. of soul (thus downstream of the point of assembly).

Preferably, all the steps of the method of the invention are operated online and continuously, regardless of the type of cable manufactured (compact cable as cable with cylindrical layers), all this at high speed. The above method can be implemented at a speed (running speed of the cable on the production line) greater than 50 m / min, preferably greater than 70 m / min, especially greater than 100 m / min.

But it is of course also possible to manufacture the cable according to the invention in a discontinuous manner, for example by pre-sheathing of the core strand (C1 + C2), solidification of the filling compound, and then winding and storage of the latter before final operation assembling the third and last layer (C3); the solidification of the elastomeric sheath is easy, it can be conducted by any suitable cooling means, for example by cooling in air or water, followed in the latter case by a drying operation.

During a third step, the final assembly is carried out by wiring or twisting (S or Z direction) of the P wires of the third or outer layer (C3) around the core strand (M + N). or C1 + C2). During this final assembly, the P son come to rely on the filling rubber in the molten state, to become embedded in the latter. The filling rubber, moving under the pressure exerted by these outer P son, then has a natural tendency to penetrate into each of the interstices or cavities left empty by the son, between the core strand (C1 + C2) and the layer external (C3).

At this stage, the manufacture of the cable according to the invention is complete. However, when, according to a preferred embodiment of the invention, the different layers of the cable are assembled by twisting, it is then preferred to add a torsion balancing step to obtain a so-called balanced (or stabilized) cable. twist; "Torsional balancing" here means, in a known manner, the cancellation of the residual torsional torques (or of the elastic recoil of detorsion) acting on the cable. Torsion balancing tools are well known to those skilled in the art of twisting; they may consist for example of trainers and / or twisters and / or twister-trainers consisting of either pulleys for twisters, or small diameter rollers for trainers, pulleys and / or rollers through which the cable runs.

Preferably, in this finished cable, the thickness of filling rubber between two adjacent wires of the cable, whatever they are, varies from 1 to 10 microns. This cable can be wound on a receiving reel, for storage, before being processed for example through a calendering plant, for preparing a metal-diene rubber composite fabric that can be used, for example, as a carcass reinforcement, or else crown reinforcement of a tire.

This cable made according to the process of the invention can be described as gummed cable in situ, that is to say that it is gummed from the inside, during its manufacture itself, by rubber or a rubber composition called (e) filling rubber.

In other words, in the raw state of manufacture, its "capillaries" or "interstices" (the two terms, interchangeable, denoting the empty spaces, free, formed by adjacent son, in the absence of filling rubber ), for a part or preferably all of them, situated on the one hand between the one or more M wire (s) core (C1) and N son of the second layer (C2), on the other hand between N son of the second layer (C2) and the P son of the third layer (C3), or even between the M core threads themselves when M is greater than 1, already include a specific rubber as filling rubber which at least partially fills said interstices, continuously or not along the axis of the cable. By cable in the raw state of manufacture, of course means a cable which has not yet been brought into contact with a diene rubber matrix (eg natural rubber) of a semi-finished product or an article rubber finish such as a tire, that said cable would be intended to reinforce later.

This specific rubber is an unsaturated thermoplastic elastomer, used alone or with any additives (that is to say in this case in the form of an unsaturated thermoplastic elastomer composition) to form the filling rubber.

It will be recalled here firstly that thermoplastic elastomers (abbreviated as "TPE") are thermoplastic elastomers in the form of block copolymers based on thermoplastic blocks. Of intermediate structure between thermoplastic polymers and elastomers, they consist in a known manner of rigid thermoplastic blocks, in particular polystyrene, linked by flexible elastomer blocks, for example polybutadiene or polyisoprene for unsaturated TPEs or poly (ethylene / butylene) for saturated TPEs. .

This is the reason why, in known manner, the above TPE block copolymers are generally characterized by the presence of two glass transition peaks, the first peak (lowest temperature, generally negative) being relative to the elastomer sequence of the TPE copolymer, the second peak (highest temperature, positive, typically greater than 80 ° C for preferred elastomers TPS type) being relative to the thermoplastic part (eg styrene blocks) of the TPE copolymer.

These TPE elastomers are often triblock elastomers with two rigid segments connected by a flexible segment. The rigid and flexible segments can be arranged linearly, star or connected. These TPE elastomers may also be diblock elastomers with a single rigid segment connected to a flexible segment. Typically, each of these segments or blocks contains at least more than 5, usually more than 10 base units (e.g., styrene units and isoprene units for a styrene / isoprene / styrene block copolymer).

This being recalled, an essential characteristic of the TPE elastomer used in accordance with the invention is that it is unsaturated. By unsaturated TPE elastomer is meant by definition and well known manner a TPE elastomer which is provided with ethylenic unsaturations, that is to say which has carbon-carbon double bonds (conjugated or not); reciprocally, a saturated TPE elastomer is of course a TPE elastomer which is free of such double bonds.

The unsaturated nature of the unsaturated TPE elastomer causes the latter to be (co) crosslinkable, (co) vulcanizable with sulfur, which makes it advantageously compatible with matrices of unsaturated diene rubbers, such as those based on natural rubber, used usually as a calendering rubber in metal fabrics for reinforcing tires. Thus, any overflow of the filling rubber outside the cable, during the manufacture of the latter, will not be detrimental to its subsequent adhesion to the calendering gum of said metal fabric, this defect being indeed susceptible of be corrected during the final firing of the tire by the possible co-crosslinking between the unsaturated TPE elastomer and the diene elastomer of the calendering gum.

Preferably, the unsaturated TPE elastomer is a styrenic thermoplastic elastomer (abbreviated as "TPS"), that is to say comprising, as thermoplastic blocks, styrene blocks (polystyrene).

More preferably, the unsaturated TPS elastomer is a copolymer comprising polystyrene blocks (that is to say formed from polymerized styrene monomer) and polydiene blocks (that is to say formed from polymerized diene monomer), preferably from the latter polyisoprene blocks and / or polybutadiene blocks.

By polydiene blocks, in particular polyisoprene blocks and polybutadiene blocks, is also meant by extension, in the present application, blocks of random diene copolymer, in particular of isoprene or butadiene, for example blocks of styrene / isoprene random copolymer (SI) or styrene-butadiene (SB), these polydiene blocks being particularly associated with polystyrene thermoplastic blocks to form the preferred unsaturated TPS elastomers which have been described previously.

By styrene monomer is meant any styrene-based monomer, unsubstituted as substituted; among the substituted styrenes may be mentioned, for example, methylstyrenes (for example o-methylstyrene, m-methylstyrene or p-methylstyrene, alpha-methylstyrene, alpha-2-dimethylstyrene, alpha-4- dimethylstyrene or diphenylethylene), para-tert-butylstyrene, chlorostyrenes (for example o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene or , 4,6-trichlorostyrene), bromostyrenes (eg, o-bromostyrene, m-bromostyrene, p-bromostyrene, 2,4-dibromostyrene, 2,6-dibromostyrene or 2,4,6-dibromostyrene). tribromostyrene), fluorostyrenes (eg, o-fluorostyrene, m-fluorostyrene, p-fluorostyrene, 2,4-difluorostyrene, 2,6-difluorostyrene or 2,4,6-trifluorostyrene), para hydroxy-styrene, and mixtures of such monomers.

The term "diene monomer" should be understood to mean any monomer bearing two carbon-carbon double bonds, conjugated or otherwise, in particular any conjugated diene monomer having from 4 to 12 carbon atoms chosen in particular from the group constituted by isoprene, butadiene, 1-methylbutadiene, 2-methylbutadiene, 2,3-dimethyl-1,3-butadiene, 2,4-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3 -pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 2,5-dimethyl-1,3-pentadiene , 1,3-hexadiene, 2-methyl-1,3-hexadiene, 3-methyl-1,3-hexadiene, 4-methyl-1,3-hexadiene, 5-methyl-1,3-hexadiene, hexadiene, 2,5-dimethyl-1,3-hexadiene, 2-neopentylbutadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-vinyl-1,3-cyclohexadiene, and mixtures of such monomers .

Such an unsaturated TPS elastomer is chosen in particular from the group consisting of styrene / butadiene (SB), styrene / isoprene (SI), styrene / butadiene / butylene (SBB), styrene / butadiene / isoprene (SBI), styrene block copolymers. butadiene / styrene (SBS), styrene / butadiene / butylene / styrene (SBBS), styrene / isoprene / styrene (SIS), styrene / butadiene / isoprene / styrene (SBIS) and mixtures of these copolymers.

More preferably still, this unsaturated TPS elastomer is a copolymer comprising at least three blocks, this copolymer being more particularly chosen from the group consisting of styrene / butadiene / styrene (SBS), styrene / butadiene / butylene / styrene block copolymers (SBBS) styrene / isoprene / styrene (SIS), styrene / butadiene / isoprene / styrene (SBIS) and mixtures of these copolymers.

According to a particular and preferred embodiment of the invention, the styrene content in the unsaturated TPS elastomer above is between 5 and 50%. Below 5%, the thermoplastic character of the TPS elastomer may be insufficient while above 50% there is a risk of excessive stiffening of the latter and of a part of decreased ability to (co) crosslink.

According to another particular and preferred embodiment of the invention, the number-average molecular weight (denoted Mn) of the TPE elastomer (in particular TPS) is preferably between 5,000 and 500,000 g / mol, more preferably between The number average molecular weight (Mn) of the TPS elastomers is determined in known manner by size exclusion chromatography (SEC). The sample is solubilized beforehand in tetrahydrofuran at a concentration of approximately 1 g / l; then the solution is filtered on a 0.45 μm porosity filter before injection. The equipment used is a chromatographic chain "WATERS alliance". The elution solvent is tetrahydrofuran, the flow rate 0.7 ml / min, the system temperature 35 ° C and the analysis time 90 min. A set of four WATERS columns in series, of trade names "STYRAGEL"("HMW7","HMW6E" and two "HT6E") is used. The injected volume of the solution of the polymer sample is 100 μl. The detector is a differential refractometer "WATERS 2410" and its associated software for the exploitation of chromatographic data is the "WATERS MILLENIUM" system. The calculated average molar masses relate to a calibration curve made with polystyrene standards.

According to another particular and preferred embodiment of the invention, the Tg of the unsaturated TPE elastomer (in particular TPS) (as a reminder, first Tg relative to the elastomer block) is less than 0 ° C., more particularly less than - 15 ° C, this quantity being measured in a known manner by DSC ( Differential Scanning Calorimetry ), for example according to the ASTM D3418-82 standard.

According to another particular and preferred embodiment of the invention, the Shore A hardness (measured according to ASTM D2240-86) of the unsaturated TPE elastomer (in particular TPS) is between 10 and 100, more particularly included in a range of 20 to 90.

Unsaturated TPS elastomers such as, for example, SB, SI, SBS, SIS, SBBS or SBIS are well known and commercially available, for example from Kraton under the name "Kraton D" (eg, products D1161, D1118, D1116, D1163), from Dynasol under the name "Calprene" (eg, products C405, C411, C412), from Polimeri Europa under the name "Europrene" (eg, product SOLT166), from BASF under denomination "Styroflex" (eg, product 2G66), or from Asahi under the name "Tuftec" (eg, product P1500).

The unsaturated thermoplastic elastomer previously described is sufficient on its own for the filling rubber to fully fulfill its function of closing off the capillaries or interstices of the cable according to the invention. However, various other additives may be added, typically in small amounts (preferably at weight ratios of less than 20 parts, more preferably less than 10 parts per 100 parts of unsaturated thermoplastic elastomer), for example plasticizers, reinforcing fillers such as carbon black or silica, non-reinforcing or inert fillers, lamellar fillers, protective agents such as antioxidants or anti-ozonants, various other stabilizers, coloring agents intended for example to color the gum filling. The filling rubber could also comprise, in a minority weight fraction relative to the unsaturated thermoplastic elastomer fraction, polymers or elastomers other than unsaturated thermoplastic elastomers.

By wire rope, is meant by definition in the present application a cable formed of son constituted mainly (that is to say for more than 50% in number of these son) or integrally (for 100% son) a metallic material. Regardless of one of the other and from one layer to another, the wire or the M son of the core (C1), the N son of the second layer (C2) and P son of the third layer (C3) are preferably steel, more preferably carbon steel. But it is of course possible to use other steels, for example a stainless steel, or other alloys. When a carbon steel is used, its carbon content (% by weight of steel) is preferably between 0.2% and 1.2%, especially between 0.5% and 1.1%; 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 a carbon content of between 0.5% and 0.6% makes such steels ultimately less expensive because easier to draw. Another advantageous embodiment of the invention may also consist, depending on the applications concerned, of using steels with a low carbon content, for example between 0.2% and 0.5%, in particular because of a cost lower and easier to draw.

The metal or steel used, whether it is in particular a carbon steel or a stainless steel, may itself be coated with a metal layer improving for example the properties of implementation of the wire rope and / or its constituent elements, or the properties of use of the cable and / or the tire themselves, such as adhesion properties, corrosion resistance or resistance to aging. According to a preferred embodiment, the steel used is covered with a layer of brass (Zn-Cu alloy) or zinc; it is recalled that during the wire manufacturing process, the coating of brass or zinc facilitates the drawing of the wire, as well as the bonding of the wire with the rubber. But the son could be covered with a thin metal layer other than brass or zinc, for example having the function of improving the resistance to corrosion of these son and / or their adhesion to rubber, for example a thin layer of Co, Ni, Al, an alloy of two or more compounds Cu, Zn, Al, Ni, Co, Sn.

The cables produced according to the process of the invention are preferably made of carbon steel and have a tensile strength (Rm) preferably greater than 2500 MPa, more preferably greater than 3000 MPa. The total elongation at break (At) of the cable, the sum of its structural, elastic and plastic elongations, is preferably greater than 2.0%, more preferably at least 2.5%.

According to another preferred embodiment, the core or central layer (C1) of diameter d _c consists of 1 to 4 wires of diameter d ₁ (that is to say that M is included in a range 1 to 4) N is within a range of 5 to 15, and P is in a range from 10 to 22. More preferably, M is 1, N is in a range of 5 to 7, and P is included in a domain of 10 to 14.

When the core (C1) consists of a single wire (M equal to 1), the diameter d ₁ of the core wire is then preferably within a range of 0.08 to 0.40 mm.

• 0,08 ≤ d₁ ≤ 0,40 ;
• 0,08 ≤ d₂ ≤ 0,35 ;
• 0,08 ≤ d₃ ≤ 0,35 ;
• 5 π (d₁ + d₂) < p₂ ≤ p₃ < 10 π (d₁ + 2d₂ + d₃).

According to another preferred embodiment, the following characteristics are satisfied (d ₁ , d ₂ , d ₃ , p ₂ and p ₃ being expressed in mm):

• 0.08 ≤ d ₁ ≤ 0.40;
• 0.08 ≤ d ₂ ≤ 0.35;
• 0.08 ≤ d ₃ ≤ 0.35;
• Π (d ₁ + d ₂ ) <p ₂ ≤ p ₃ <10 π (d ₁ + 2d ₂ + d ₃ ).

The core (C1) of the cable according to the invention is preferably made of a single single wire or at most 2 or 3 son, the latter may for example be parallel or twisted together. However, more preferably, the core (C1) of the cable according to the invention consists of a single wire, N is in a range of 5 to 7, and P is in a range of 10 to 14.

It will be recalled here that in a known manner the pitch "p" represents the length, measured parallel to the axis of the cable, at the end of which a wire having this pitch performs a complete revolution about said axis of the cable.

• 0,10 ≤ d₁ ≤ 0,35;
• 0,10 ≤ d₂ ≤ 0,30;
• 0,10 ≤ d₃ ≤ 0,30.

For an optimized compromise between strength, feasibility, rigidity and bending endurance of the cable, it is preferred that the diameters of the wires of the layers C1, C2 and C3, whether these wires have an identical diameter or not from one layer to another, check the following relations (d ₁ , d ₂ , d ₃ being expressed in mm):

• 0.10 ≤ d ₁ ≤ 0.35;
• 0.10 ≤ d ₂ ≤ 0.30;
• 0.10 ≤ d ₃ ≤ 0.30.

• 0,10 ≤ d₁ ≤ 0,28;
• 0,10 ≤ d₂ ≤ 0,25 ;
• 0,10 ≤ d₃ ≤ 0,25.

More preferably still, the following relationships are verified:

• 0.10 ≤ d ₁ ≤ 0.28;
• 0.10 ≤ d ₂ ≤ 0.25;
• 0.10 ≤ d ₃ ≤ 0.25.

• pour N = 5 : 0,6 < (d₁ / d₂) < 0,9 ;
• pour N = 6 : 0,9 < (d₁ / d₂) < 1,3 ;
• pour N = 7 : 1,3 < (d₁ / d₂) < 1,6.

According to another particular embodiment, the following characteristics are verified:

• for N = 5: 0.6 <(d ₁ / d ₂ ) <0.9;
• for N = 6: 0.9 <(d ₁ / d ₂ ) <1.3;
• for N = 7: 1.3 <(d ₁ / d ₂ ) <1.6.

The wires of the layers C2 and C3 may have an identical diameter or different from one layer to another; wires of the same diameter are preferably used from one layer to another (ie d ₂ = d ₃ ), which simplifies in particular the manufacture and reduces the cost of the cables.

Preferably, we have the following relation which is verified: $$\mathrm{5}\mathrm{\pi }\left({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{1}}+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{2}}\right)<{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="imgf0002.png"\; state="\{\{state\}\}">p</figure-callout>}}_{\mathrm{2}}\le {\mathrm{p}}_{\mathrm{3}}<\mathrm{5}\mathrm{\pi }\left({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{1}}+\mathrm{2}{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{2}}+{\mathrm{d}}_{\mathrm{3}}\right)\mathrm{.}$$

The steps p ₂ and p ₃ are chosen more preferably in a range from 5 to 30 mm, more preferably still in a range from 5 to 20 mm, in particular when d ₂ = d ₃ .

According to another preferred embodiment, the diameter d ₂ is within a range of 0.08 to 0.35 mm and the twisting pitch p ₂ is within a range of 5 to 30 mm.

According to another preferred embodiment, the diameter d ₃ is within a range of 0.08 to 0.35 mm and the twisting pitch p ₃ is greater than or equal to p ₂ .

According to another preferred embodiment, the p ₂ and p ₃ are equal. This is the case in particular for cables with layers of the compact type as schematized for example at the figure 2 , in which the two layers C2 and C3 have the other characteristic of being wound in the same direction of torsion (S / S or Z / Z). In such cables with so-called compact layers, the compactness is very high, such that the cross-section of these cables has an outline that is polygonal and non-cylindrical, as illustrated by way of example in FIG. figure 2 compact cable 1 + 6 + 12 according to the invention) or figure 3 (compact cable 1 + 6 + 12 control, that is to say, not gummed in situ).

When the core (C1) consists of more than one wire (M different from 1), the M son are preferably assembled, in particular twisted, in a step p ₁ which is more preferably in a range of 3 to 30 mm , in particular in a range of 3 to 20 mm.

The third or outer layer C3 has the preferential characteristic of being a saturated layer, that is to say that, by definition, there is not enough room in this layer to add at least one (P _max +1) th wire diameter d ₃ , P _max representing the maximum number of windable son in a layer around the second layer C2. This construction has the significant advantage of further limiting the risk of overfilling gum filling at its periphery and offer, for a given diameter of the cable, a higher strength.

Thus, the number P of wires can vary to a very large extent according to the particular embodiment of the invention, it being understood that the maximum number of wires P will be increased if their diameter d ₃ is reduced compared to the diameter d ₂ of the son of the second layer, in order to preferentially keep the outer layer in a saturated state.

According to a particularly preferred embodiment, the first layer (C1) comprises a single wire (M equal to 1), the second layer (C2) has 6 wires (N equal to 6) and the third layer (C3) comprises 11 or 12 wires (P equal to 11 or 12); in other words, the cable according to the invention has the preferred constructions 1 + 6 + 11 or 1 + 6 + 12. Among these cables are in particular those consisting of wires having substantially the same diameter of the second layer (C2) to the third layer (C3) (ie d ₂ = d ₃ ).

The cable manufactured according to the method of the invention, like all layered cables, can be of two types, namely of the type with compact layers or of the type with cylindrical layers.

Preferably, the two layers C2 and C3, as well as the layer C1 in the case where M is greater than 1, are wound in the same direction of torsion, that is to say in the direction S (arrangement "S / S ") or in the Z direction (" Z / Z "arrangement). Coiling in the same direction of these layers advantageously allows to minimize the friction between these two layers and therefore the wear of the son that constitute them. More preferably, they are wound in the same direction of torsion and at the same pitch (ie p ₂ = p ₃ or p ₁ = p ₂ = p ₃ if M is greater than 1), to obtain a cable of the type compact as represented for example in the figure 2 .

The method of the invention makes it possible to manufacture cables which can be, according to a particularly preferred embodiment, without or almost no filling rubber at their periphery; by such an expression, it is meant that no particle of filling compound is visible, with the naked eye, at the periphery of the cable, that is to say that the person skilled in the art does not make any difference at the output of manufacture, with the naked eye and at a distance of three meters or more, between a cable reel manufactured in accordance with the invention and a conventional cable reel not gummed in situ.

However, as indicated above, a possible overflow of the filling rubber at the periphery of the cable will not be detrimental to its subsequent adhesion to a metal fabric calendering rubber, thanks to the co-crosslinkable nature of the unsaturated thermoplastic elastomer and the diene elastomer of said calendering rubber.

The method of the invention is of course applicable to the manufacture of compact type cables (for recall and by definition, those whose layers C1 (if M is greater than 1), C2 and C3 are wound at the same step and in the same meaning) as for the manufacture of cables of the type with cylindrical layers (for recall and by definition, those whose layers C1 (if M is greater than 1), C2 and C3 are wound either at different steps (whatever their senses of torsion, identical or not), or in opposite directions (whatever their steps, identical or different)).

• des moyens d'alimentation d'une part du fil ou des M fils de la première couche ou noyau (C1), d'autre part des N fils de la deuxième couche (C2) ;
• des premiers moyens d'assemblage des N fils pour mise en place de la deuxième couche (C2) autour de la première couche (C1), en un point dit « point d'assemblage », pour formation d'un câble intermédiaire dit « toron d'âme » de construction M+N ;
• des seconds moyens d'assemblage des P fils autour du toron d'âme ainsi gainé, pour mise en place de la troisième couche (C3) ;
• des moyens d'extrusion délivrant l'élastomère thermoplastique à l'état fondu, disposés respectivement en amont et/ou en aval des premiers moyens d'assemblage, pour gainage du noyau et/ou du toron d'âme M+N.

An assembly and scrubbing device preferably used for implementing the method of the invention described above, is a device comprising upstream downstream, according to the direction of advancement of a cable being formed:

• feed means on the one hand of the wire or M son of the first layer or core (C1), on the other hand N son of the second layer (C2);
• first means for assembling the N wires for placing the second layer (C2) around the first layer (C1), at a point called "assembly point", for forming an intermediate cable called "strand" soul "of construction M + N;
• second means for assembling the P wires around the core strand thus sheathed, for placing the third layer (C3);
• extrusion means delivering the thermoplastic elastomer in the molten state, disposed respectively upstream and / or downstream of the first assembly means, for cladding the core and / or the core strand M + N.

Of course, when M is greater than 1, the above device also comprises means for assembling the M son of the central layer (C1), arranged between the feeding means of these M son and the assembly means N son of the second layer (C2). In the case of a double cladding (core and core), the extrusion means are therefore arranged both upstream and downstream of the first assembly means.

We see on the figure 1 attached an example of device (10) for assembly by twisting, of the fixed feed and rotary receiving type, usable for the manufacture of a cable of the compact type (p ₂ = p ₃ and the same direction of twist of the layers C2 and C3). In this device (10), supply means (110) deliver, around a single core wire (C1), N wires (11) through a grid (12) distribution (axisymmetric splitter), coupled or not to a connecting grain (13), gate beyond which converge the N (for example six) wires of the second layer at an assembly point (14), for formation of the core strand (C1 + C2 ) of construction 1 + N (eg 1 + 6).

The core strand (C1 + C2), once formed, then passes through a cladding zone consisting for example of a single extrusion head (15) constituted for example by a twin-screw extruder (fed by a hopper containing the TPE elastomer in the form of granules) feeding a calibration die via a pump. The distance between the point of convergence (14) and the sheathing point (15) is for example between 50 cm and 1 m. Around the strand of soul thus gummed (16) and progressing in the direction of the arrow, are then assembled by twisting the P son (17) of the outer layer (C3), for example twelve in number, delivered by supply means (170). The final cable (C1 + C2 + C3) thus formed is finally collected on the rotary reception (19), after passing through the torsion balancing means (18) consisting for example of a trainer and / or a twister-trainer.

It will be recalled here that, in a manner well known to those skilled in the art, for the manufacture of a cable of the type with cylindrical layers (different pitch p ₂ and p ₃ and / or different direction of torsion of the layers C2 and C3), we use a device comprising two rotating organs (feeding or receiving), and not just one as described above ( Fig. 3 ) for exemple.

The figure 2 schematically, in section perpendicular to the axis of the cable (assumed rectilinear and at rest), an example of a preferred cable 1 + 6 + 12 gummed in situ, obtainable using the method according to the previously described invention.

This cable (noted C-1) is of the compact type, that is to say that its second and third layers (respectively C2 and C3) are wound in the same direction (S / S or Z / Z according to a recognized nomenclature ) and moreover at the same step (p ₂ = p ₃ ). This type of construction has the consequence that the wires (21, 22) of these second and third layers (C2, C3) form around the core or first layer (C1) two substantially concentric layers which each have a contour (E) (shown in FIG. dotted) which is substantially polygonal (more precisely hexagonal) and non-cylindrical as in the case of cables with so-called cylindrical layers.

This cable C-1 can be described as cable gummed in situ: each of the capillaries or interstices (empty spaces in the absence of filling rubber) formed by the adjacent wires, taken three by three, of its three layers C1, C2 and C3, is filled, at least in part (continuously or not along the axis of the cable), by the filling rubber such that for any cable length of 2 cm, each capillary comprises at least one rubber stopper .

More specifically, the filling rubber (23) fills each capillary (24) (symbolized by a triangle) formed by the adjacent wires (taken three to three) of the various layers (C1, C2, C3) of the cable, by discarding them very slightly. We see that these capillaries or interstices are naturally formed either by the core wire (20) and the son (21) of the second layer (C2) surrounding it, or by two son (21) of the second layer (C2) and a wire (23) of the third layer (C3) which is immediately adjacent thereto, or else by each wire (21) of the second layer (C2) and the two wires (22) of the third layer (C3) which are immediately adjacent; a total of 24 capillaries or interstices (24) are thus present in this cable 1 + 6 + 12.

According to a preferred embodiment, in this cable M + N + P, the filling rubber extends in a continuous manner around the second layer (C2) which it covers.

Thus prepared, the cable M + N + P can be qualified as airtight: at the air permeability test described in paragraph II-1-B which follows, it is characterized by an average air flow rate. which is preferably less than 2 cm ³ / min, more preferably less than or equal to 0.2 cm ³ / min.

For comparison, the figure 3 recalls the section of a cable 1 + 6 + 12 (noted C-2) conventional (ie, not gummed in situ), also of the compact type. The absence of filling rubber makes practically all the son (30, 31, 32) are in contact with each other, which leads to a particularly compact structure, moreover very difficult to penetrate (not to say impenetrable) from the outside by rubber. The characteristic of this type of cable is that the various wires form three to three of the channels or capillaries (34) which for a large number of them remain closed and empty and thus conducive, by "wicking" effect, to the propagation corrosive environments such as water.

II. EXAMPLES OF CARRYING OUT THE INVENTION

The following tests demonstrate the ability of the invention to provide three-layer cables which, compared with prior art in-situ gelled three-layer cables with conventional (non-heat-fusible) diene rubber, have the significant advantage of have a reduced and controlled amount of filling rubber, which guarantees them a better compactness, this gum being moreover preferentially distributed uniformly inside the cable, in particular inside each of its capillaries, thus conferring on them a optimal longitudinal impermeability; in addition, this filling gum has the essential advantage of being free of unwanted cling in the green (i.e., uncrosslinked) state.

II-1. Measurements and tests used II-1-A. Dynamometric measurements

For metal wire and cable, the breaking force measurements denoted Fm (maximum load in N), tensile strength Rm (in MPa) and elongation at break denoted At (total elongation in %) are made in tension according to ISO 6892 of 1984.

With regard to the diene rubber compositions, the modulus measurements are made in tension, unless otherwise indicated according to ASTM D 412 of 1998 ("C" test specimen): the secant modulus "true" (i.e., brought back to the actual section of the specimen) is measured at the second elongation (i.e., after an accommodation cycle) at 10% elongation , noted E10 and expressed in MPa (normal temperature and humidity conditions according to ASTM D 1349 of 1999).

II-1-B. Test of air permeability

This test makes it possible to determine the longitudinal permeability to the air of the cables tested, by measuring the volume of air passing through a specimen under constant pressure for a given time. The principle of such a test, well known to those skilled in the art, is to demonstrate the effectiveness of the treatment of a cable to make it impermeable to air; it has been described for example in ASTM D2692-98.

The test is here performed either on cables extracted from tires or rubber sheets that they reinforce, so already coated from the outside by the rubber in the fired state, or on raw cables manufacturing.

In the second case, the raw cables must be previously embedded, coated from the outside by a so-called coating gum. For this, a series of 10 cables arranged in parallel (inter-cable distance: 20 mm) is placed between two skims (two rectangles of 80 × 200 mm) of a diene rubber composition in the raw state, each skim having a 3.5 mm thick; the whole is then locked in a mold, each of the cables being kept under a sufficient tension (for example 2 daN) to ensure its straightness during the establishment in the mold, using clamping modules; then the vulcanization (baking) is carried out for 40 min at a temperature of 140 ° C and a pressure of 15 bar (rectangular piston 80 x 200 mm). After which, the assembly is demolded and cut 10 pieces of cables thus coated, in the form of parallelepipeds of dimensions 7x7x20 mm, for characterization.

A conventional rubber composition for tires based on natural rubber (peptized) and carbon black N330 (65 phr), comprising the following usual additives: sulfur (7 phr), sulfenamide accelerator, is used as a coating rubber. (1 phr), ZnO (8 phr), stearic acid (0.7 phr), antioxidant (1.5 phr), cobalt naphthenate (1.5 phr); the E10 module of the coating gum is approximately 10 MPa.

The test is carried out on 2 cm of cable length, thus coated by its surrounding rubber composition (or coating gum) in the fired state, as follows: air is sent to the cable inlet at a pressure of 1 bar, and the volume of air at the outlet is measured using a flow meter (calibrated for example from 0 to 500 cm ³ / min). During the measurement, the cable sample is blocked in a compressed seal (eg a dense foam or rubber seal) in such a way that only the amount of air passing through the cable from one end to the other, along its longitudinal axis, is taken into account by the measure; a leakproofness test of the seal is made using a solid rubber specimen, ie without cable.

The measured flow rate is lower as long as the longitudinal imperviousness of the cable is high. As the measurement is made with an accuracy of ± 0.2 cm ³ / min, measured values equal to or less than 0.2 cm ³ / min are considered to be zero; they correspond to a cable that can be described as airtight along its axis (ie, in its longitudinal direction).

II-1-C. Rate gum filling

The amount of filling compound is measured by difference between the weight of the initial cable (thus erased in situ) and the weight of the cable (and therefore that of its threads) whose filling compound has been eliminated by a treatment in a solvent of appropriate extraction.

For example, the procedure is as follows. A sample of cable of a given length (for example one meter), coiled on itself to reduce its bulk, is placed in a sealed bottle containing one liter of toluene. Then the bottle is stirred (125 round-trip per minute) for 24 hours at room temperature (20 ° C.), using a "Ping-Pong 400" agitator from the company. Fischer Scientific); after removal of the solvent, the operation is repeated once. The thus treated cable is recovered and the residual solvent evaporated under vacuum for 1 hour at 60 ° C. Then the cable thus freed of its filling rubber is weighed. From this calculation, the filling rate in the cable, expressed in mg (milligram) of filling rubber per g (gram) of initial cable, is calculated and averaged over 10 measurements (i.e. total cable meters).

II-2. Cable manufacturing and tests

In the following tests, 1 + 6 + 12 layered wires made of brass-coated carbon steel thin wires are manufactured.

The carbon steel wires are prepared in a known manner, for example starting from machine wires (diameter 5 to 6 mm) which are first cold-rolled, by rolling and / or drawing, to a neighboring intermediate diameter. of 1 mm. The steel used is a known carbon steel (USA AISI 1069 standard) with a carbon content of 0.70%. The intermediate diameter son undergo a degreasing treatment and / or pickling, before further processing. After deposition of a brass coating on these intermediate son, is carried on each wire a so-called "final" work hardening (ie, after the last patenting heat treatment), by cold drawing in a moist medium with a drawing lubricant which is for example in the form of an emulsion or an aqueous dispersion. The brass coating that surrounds the son has a very small thickness, significantly less than one micrometer, for example of the order of 0.15 to 0.30 microns, which is negligible compared to the diameter of the steel son.

The steel wires thus drawn have the following diameter and mechanical properties: <b> Table 1 </ b> Steel φ (mm) Fm (N) Rm (MPa) NT 0.18 68 2820 NT 0.20 82 2620

These wires are then assembled in the form of 1 + 6 + 12 layer cables, the construction of which is in accordance with the representation of the figure 1 and whose mechanical properties are given in Table 2. <b> Table 2 </ b> Cable p ₂ (mm) p ₃ (mm) Fm (daN) Rm (MPa) At (%) C-1 10 10 120 2550 2.4

The cables according to the invention 1 + 6 + 12 (C-1), as schematized in FIG. Fig. 1 , are therefore formed of 19 son in total, a core wire of diameter 0.20 mm and 18 son around, all of diameter 0.18 mm, which were wound in two concentric layers at the same pitch (p ₂ = p ₃ = 10.0 mm) and in the same direction of torsion (S / S) to obtain a cable of the compact type. The rate of filling rubber, measured according to the method indicated previously in paragraph I-3, is equal to about 18 mg per g of cable. This filling rubber is present in each of the 24 capillaries or interstices formed by the various son taken three to three, that is to say that it fills all or at least partly each of these capillaries in such a way that there is at least, on any length of cable of length equal to 2 cm, a rubber stopper in each capillary or interstice.

For the manufacture of these cables, a device was used as described previously and schematized in FIG. figure 1 , sheathing the core strand (1 + 6) and then twisting the outer layer of the 12 strands onto the sheathed core strand. The core strand was thus covered with a TPS elastomer layer of about 15 microns. The filling gum consisted of an unsaturated TPS elastomer which was extruded at a temperature of about 180 ° C by means of a twin-screw extruder (length 960 mm, L / D = 40) feeding a sizing die. 0.570 mm in diameter by means of a pump; the core strand (1 + 6) was moving during its sheathing perpendicular to the extrusion direction and straight.

Three unsaturated TPS elastomers (commercial products) were tested in these tests: one SBS block copolymer (styrene-butadiene-styrene blocks), an SIS block copolymer (styrene-isoprene-styrene blocks) and an S (SB) S block copolymer (styrene-butadiene-styrene blocks) whose central polydiene block (denoted SB) was a styrene-butadiene random diene copolymer) of Shore A hardness of about 70, 25 and 90, respectively.

Then the C-1 cables thus manufactured were subjected to the air permeability test described in paragraph II-1, by measuring the volume of air (in cm ³ ) passing through the cables in 1 minute (average of 10 measurements per minute). each cable tested).

For each cable C-1 tested and for 100% of the measurements (ie ten test pieces out of ten), regardless of the unsaturated TPS elastomer tested, a flow rate of zero or less than 0.2 cm ³ / min was measured; in other words, the cables prepared according to the process of the invention can be qualified as airtight along their longitudinal axis.

On the other hand, control gummed in situ cables, of the same construction as the previous C-1 cables, but gummed in situ by a conventional diene rubber composition (based on natural rubber), were prepared according to the method described in FIG. Requirement WO 2005/071557 mentioned above, in several discontinuous steps, by sheathing via an extrusion head of the intermediate core strand 1 + 6, then in a second step by wiring the remaining 12 wires around the core thus sheathed, for forming the outer layer . These control cables were then subjected to the air permeability test of section 1-2.

It was found first of all that none of these control cables showed 100% of the measurements (ie ten test pieces out of ten) with a flow rate of zero or less than 0.2 cm ³ / min, in other words that no these control cables could not be qualified as airtight (totally airtight) along its axis. It has been observed, on the other hand, that among these control cables, those having the best impermeability results (ie an average flow rate of approximately 2 cm ³ / min) all had a relatively large amount of filling rubber (diene rubber). ) parasite overflowing at their periphery, rendering them unsuitable for a satisfactory calendering operation in industrial conditions, because of the raw sticky problem mentioned in the introduction of this memoir.

In conclusion, the cables prepared according to the process according to the invention thus have an optimal penetration rate by the unsaturated thermoplastic elastomer, with a controlled amount of filling compound, which guarantees the presence of internal partitions (continuous or discontinuous in the case of the invention). cable axis) or gum plugs in the capillaries or interstices in a sufficient number; thus, the cable becomes impervious to the propagation, along the cable, of any corrosive fluid such as water or oxygen from the air, thereby eliminating the wicking effect described in the introduction of this memo. In addition, the thermoplastic elastomer used does not pose a problem of parasitic tights in case of a slight overflow outside the cable after its manufacture due to its unsaturated character and therefore (co) vulcanizable with an unsaturated diene rubber matrix such as natural rubber.

Of course, the invention is not limited to the previously described embodiments.

For example, the core (C1) of the cables could consist of a non-circular section wire, for example plastically deformed, in particular a wire of substantially oval or polygonal section, for example triangular, square or rectangular; the core could also consist of a preformed wire, of circular section or not, for example a corrugated wire, twisted, twisted helical or zig-zag. In such cases, it must of course be understood that the diameter d _c of the core (C1) represents the diameter of the cylinder of imaginary revolution which surrounds the central wire (encumbrance diameter), and no longer the diameter (or any other size). transversal, if its section is not circular) of the central wire itself.

For reasons of industrial feasibility, cost and overall performance, however, it is preferred to implement the invention with a single conventional linear (C1) linear core wire of circular section.

On the other hand, the central wire is less stressed during the manufacture of the cable than the other son, given its position in the cable, it is not necessary for this wire to use for example steel compositions offering high torsional ductility; advantageously any type of steel may be used, for example a stainless steel.

In addition, a (at least one) linear yarn of one of the other two layers (C2 and / or C3) could also be replaced by a preformed or deformed yarn, or more generally by a yarn of section different from that of the other yarns of diameter d ₂ and / or d ₃ , so as to further improve the penetrability of the cable by the rubber or other material, the overall size of this replacement wire may be smaller, equal to or greater than the diameter ( d ₂ and / or d ₃ ) other constituent son of the layer (C2 and / or C3) concerned.

Without the spirit of the invention being modified, a portion of the son constituting the cable could be replaced by son other than son steel, metal or not, including son of mineral or organic material with high mechanical strength, by example of mono-filaments organic polymers liquid crystal.

Claims (15)

1. Method for manufacturing a metal cord with three concentric layers (C1, C2, C3), of M+N+P construction, of the type "rubberized in situ", that is to say a cord that is rubberized from the inside, during its actual manufacture, with rubber or a rubber composition, the said cord comprising a first layer or core (C1) of diameter d_c made up of M wire(s) of diameter d₁, around which core are wound together as a helix at a pitch p₂, as a second layer (C2), N wires of diameter d₂, around which second layer are wound together as a helix at a pitch p₃, as a third layer (C3), P wires of diameter d₃, the said method comprising at least the following steps:

   - an assembling step of assembling the N wires of the second layer (C2) around the core (C1) in order to form, at a point called "assembling point", an intermediate cord called "core strand" of M+N construction;

   - respectively upstream and/or downstream of the said assembling point, a sheathing step in which the core and/or the core strand is sheathed with the said rubber or the said rubber composition by passing through at least one extrusion head;

   - then an assembling step in which the P wires of the third layer (C3) are assembled around the core strand (M+N) to form a cord of M+N+P construction thus rubberized from the inside,

   characterized in that the said rubber is an unsaturated thermoplastic elastomer extruded in the molten state.
2. Method according to Claim 1, in which the unsaturated thermoplastic elastomer is a thermoplastic styrene (TPS) elastomer.
3. Method according to Claim 2, in which the unsaturated TPS elastomer comprises polystyrene blocks and polydiene blocks.
4. Method according to Claim 3, in which the polydiene blocks are selected from the group consisting of polyisoprene blocks, polybutadiene blocks and mixtures of such blocks.
5. Method according to Claim 4, in which the TPS elastomer is a copolymer selected from the group consisting of styrene/butadiene/styrene (SBS), styrene/butadiene/butylene/styrene (SBBS), styrene/isoprene/styrene (SIS) and styrene/butadiene/isoprene/styrene (SBIS) block copolymers and blends of these copolymers.
6. Method according to any one of Claims 2 to 5, in which the content of TPS elastomer delivered during sheathing is comprised between 5 and 40 mg per gram of finished cord.
7. Method according to any one of Claims 1 to 6, in which the tensile stress applied to the core strand downstream of the assembling point is comprised between 10 and 25% of its breaking strength.
8. Method according to any one of Claims 1 to 7, in which the temperature at which the thermoplastic elastomer is extruded is comprised between 100°C and 250°C.
9. Method according to any one of Claims 1 to 8, in which the sheathing is performed on the core.
10. Method according to Claim 9, in which after sheathing, the core is covered with a minimum thickness of unsaturated thermoplastic elastomer which exceeds 20 µm.
11. Method according to any one of Claims 1 to 8, in which the sheathing is performed on the core strand.
12. Method according to Claim 11, in which, after sheathing, the core strand is covered with a minimum thickness of unsaturated thermoplastic elastomer which exceeds 5 µm.
13. Method according to any one of Claims 1 to 12, in which the sheathing is performed on both the core and the core strand.
14. Method according to any one of Claims 1 to 13, in which M is comprised in a range from 1 to 4, N is comprised in a range from 5 to 15, and P is comprised in a range from 10 to 22.
15. Method according to Claim 14, in which M is equal to 1, N is comprised in a range from 5 to 7, and P is comprised in a range from 10 to 14.

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