Tire fabric comprising reinforcing elements including an assembly made of two multifilament strands of polyamide 5,6

Abstract

The invention relates to an elastomeric composite (35) comprising at least one reinforcing element (45) embedded in an elastomeric composition, the reinforcing element (45) comprising an assembly of at least two multifilament strands of aliphatic polyamide 5,6 (46), and the strands (46) being wound together helically to form a layer, and the reinforcing element (45) being torsionally balanced, the torsion factor K of the reinforcing element (45) ranging from 110 to 220, and the density of reinforcing elements (45) in the composite (35) ranging from 80 to 145 reinforcing elements per decimeter of composite. Figure for the abstract: Fig 3

Description

Title of the invention: Tire fabric comprising reinforcing elements including an assembly made of two multifilament strands of polyamide 5,6

[0001] The present invention relates to a tire composite comprising reinforcement elements comprising an assembly made of two multifilament strands of polyamide 5,6. The invention also relates to a tire comprising a shrink-fit layer obtained from this composite.

[0002] Prior art is known of a tire fabric intended for use on passenger vehicles marketed under the MICHELIN brand and belonging to the PRIMACY 4 range, with the following dimensional characteristics: 225 / 45R17 94W XL TL. Such a tire comprises a tread and a reinforcing reinforcement extending into the crown in a circumferential direction of the tire. The reinforcing reinforcement comprises a reinforcing layer including several reinforcing elements arranged side by side substantially parallel to each other and forming an angle of less than or equal to 10° with the circumferential direction of the tire.

[0003] Such a prior art tire comprises a shrink-fit layer comprising a composite comprising reinforcing elements comprising an assembly made of two multifilament strands of polyamide 6,6, the two strands being helically wound around each other at a twist of 250 turns per meter. Each multifilament strand has a fiber count of 140 tex.

[0004] The invention aims to find an elastomer composite that provides a tire reinforcement layer with sufficient breaking strength to withstand road hazards, and comprising reinforcing elements with strength and torsional characteristics that allow the tire designer to adapt tire performance, for example, the durability and compressive fatigue resistance of the reinforcing elements. The invention also aims to reduce the proportion of petroleum-based multifilament fibers in the tire by increasing the proportion of durable material in the multifilament fibers.

[0005] To this end, the invention relates to an elastomeric composite comprising a plurality of substantially parallel, parallel, wire-like reinforcing elements extending along a principal direction, each reinforcing element being embedded in an elastomeric composition, the reinforcing element comprising an assembly made up of at least two multifilamentary strands of aliphatic polyamide 5,6, and The strands are wound together in a helix to form a layer, and the reinforcing element is torsionally balanced, with the torsion factor K of the reinforcing element ranging from 110 to 220, where K is defined by the formula K = T x [(Title / (1000.p)]1 / 2 where T is the twist of the reinforcing element expressed in turns per meter, Title is the sum of the titles of the multifilamentary strands of the reinforcing element in tex, p is the average density of the multifilamentary strands in g / cm3 weighted by the respective titles of the constituent materials of the multifilamentary strands, and the density of reinforcing elements in the composite ranging from 80 to 145 reinforcing elements per decimeter of composite measured along a transverse direction perpendicular to the principal direction of the reinforcing elements.

[0006] An aliphatic polyamide strand is defined as a set of filaments made up of linear macromolecules of polymers or copolymers containing amide functional groups without aromatic rings and which can be synthesized by polycondensation between a carboxylic acid and an amine. Among the 5,6-aliphatic polyamides, PA 5,6 polyamides may be cited, which comprise at least 30% by mass of bio-based material, and in particular Bio-Nylon 56 from the company OTIZ.

[0007] By balanced in torsions, it is understood that the two multifilamentary strands are wound with a substantially identical twist and that the twist of the monofilaments of each multifilamentary strand, that is to say the twist of the monofilaments of the aliphatic polyamide multifilamentary strand and the twist of the monofilaments of the aliphatic polyamide strand is substantially zero.Indeed, the manufacturing process of these reinforcement elements, well known in the state of the art, includes a first step during which each strand of monofilaments (in English "yam") is first individually twisted on itself (according to an initial twist RI' and R2' with R1'=R2') in a given direction D'=D1'=D2' (respectively direction S or Z, according to a recognized nomenclature designating the orientation of the turns according to the crossbar of an S or a Z), to form a strand in which the monofilaments are subjected to a helical deformation around the axis of the strand. Then, in a second step, the two strands are then twisted together according to a final twist R3 such that R3=R1'=R2' in direction D3 opposite to the direction D'=D1'=D2' (respectively direction Z or S), to obtain the reinforcing element (in English "cord").This reinforcing element is then said to be torsionally balanced because the monofilaments of the two strands exhibit, in the final reinforcing element, the same residual torsion since R1'=R2'. This residual torsion is zero or practically zero because R3=R1'=R2' and the direction D'=D1'=D2' is opposite to the direction D3. By. residual torsion substantially zero, it is understood that the residual torsion is strictly less than 2.5% of the R3 torsion.

[0008] By elastomer composition, we mean a composition comprising an elastomer, preferably diene, for example natural rubber, a reinforcing filler, for example carbon black and / or silica and a crosslinking system, for example a vulcanizing system, preferably comprising sulfur.

[0009] By "assembly constituted", it is understood that the assembly does not include any other multifilamentary strand than at least the two multifilamentary strands of aliphatic polyamide.

[0010] Within the selected torsion factor range, for a given title, the composite comprising an assembly made up of at least two multifilamentary strands of aliphatic polyamide 5,6 exhibits improved endurance.

[0011] The multifilamentary strands of aliphatic polyamide are wound together in a helix to form a layer.

[0012] The torsion factor K is related to the torsion T according to the following known relationship: K = T x [(Title / (1000.p)]1 / 2 in which the twist T of the elementary filaments is expressed in turns per meter, the Title is expressed in tex (weight in grams of 1000 meters of the reinforcing element), and finally p is the density or specific gravity (in g / cm3) of the material (for example, about 1.50 g / cm3 for cellulose, 1.44 g / cm3 for aramid, 1.38 g / cm3 for a polyester such as PET, 1.14 g / cm3 for polyamide 5,6); in the case of a hybrid cable, p is of course an average of the densities weighted by the respective titles of the materials of the reinforcing element. As an example, for the first embodiment of a reinforcement element comprising an assembly made of two multifilament strands of polyamide 5.6 with a fiber count of 140 tex and whose reinforcement element has a twist of 250 turns per meter, the calculation of K is as follows: K = 250 x [(140 + 140) / (1000 x (140 x 1.14 + 140 x 1.14) / (140 + 140))]1 / 2 K = 124

[0013] The measurement of the torsion T of the reinforcing element can be carried out by any method known to the person skilled in the art, for example in accordance with ASTM D 885 / D 885M - 10a of 2014.

[0014] The count (or linear density) of each strand is determined according to the ASTM D1423 standard. The count is given in tex (weight in grams of 1000 m of product - reminder: 0.111 tex equals 1 denier).

[0015] Advantageously, the reinforcing element has a torsion factor K such that it must have a sufficient value to have a good compromise between, on the one hand the The modulus of extension and breaking strength, and on the other hand, the compressive fatigue resistance. Thus, the tire will have a good compromise between lateral stiffness and durability.

[0016] The count (or linear density) of each strand is determined according to the ASTM D1423 standard. The count is given in tex (weight in grams of 1000 m of product - reminder: 0.111 tex equals 1 denier).

[0017] In an advantageous embodiment, the reinforcing element also comprises a layer of an adhesive composition coating the assembly formed by the two strands. Such an adhesive composition is, for example, of the RFL type (acronym for Resorcinol-Formaldehyde-Latex) but also adhesive compositions as described in WO2015118041.

[0018] Advantageously, the assembly consists of two multifilamentary strands of aliphatic polyamide 5,6.

[0019] Preferably, the assembly consists of two multifilament strands of aliphatic polyamide 5,6; the strands being wound together helically to form a layer. The term "assembly" means that the assembly does not include any multifilament strands other than the two multifilament strands of aliphatic polyamide 5,6.

[0020] Advantageously, the torsion factor K of the reinforcing element ranges from 120 to 150.

[0021] Advantageously, the density of reinforcing elements in the composite ranges from 90 to 130 reinforcing elements per decimeter of composite, preferably from 95 to 125 reinforcing elements per decimeter of composite. The density of reinforcing elements in the composite is the number of reinforcing elements per decimeter of the composite in the direction perpendicular to the direction in which the reinforcing elements extend parallel to each other. Within these reinforcing element density ranges, the composite exhibits relatively high breaking strength and a relatively low cost, enabling its use in tires suitable for most applications.

[0022] Advantageously, the torsion of the reinforcing element ranges from 200 to 500 revolutions per meter and preferably from 250 to 490 revolutions per meter. For a given strength, within this torsion range, the reinforcing element exhibits sufficient endurance for use in a tire suitable for most current applications and a relatively low risk of dispersion of its breaking strength.

[0023] Advantageously, the number of the multifilament strand of polyamide 5,6 ranges from 60 to 160 tex and preferably from 70 to 140 tex.

[0024] Advantageously, the initial tensile modulus of the reinforcing element ranges from 1 to 5 cN / tex and preferably from 2 to 5 cN / tex. The initial modulus is relative to certain performance of the reinforcement element under small deformations, particularly when the tire's shrink-wrapping layer is flattened.

[0025] Advantageously, the final modulus ranges from 5 to 18 cN / tex and preferably from 5 to 12 cN / tex. The final modulus is related to certain performance characteristics of the reinforcing element under large deformations; for example, for a shrink-fit application, stiffness tendencies under large deformations have little impact on pneumatic performance.

[0026] The initial modulus is defined as the slope at the origin of the linear portion of the Force-Elongation curve that occurs immediately after a standard pretension of 0.5 cN / tex. The final modulus is defined as the slope at the point corresponding to 80% of the breaking force on the Force-Elongation curve. The Force-Elongation curve is obtained by measurement in a known manner using an INSTRON tensile testing machine equipped with 4D grippers. The tested samples are subjected to tension over an initial length of 400 mm at a nominal speed of 200 mm / min, under a standard pretension of 0.5 cN / tex.

[0027] Thus, for example, for an assembly made up of two multifilamentary strands of 5.6 to 94 tex aliphatic polyamide, the initial modulus is the slope of the Force-Elongation curve between 1000 cN and 2000 cN and the final modulus is the slope of the Force-Elongation curve between 4000 cN and 11000 cN.

[0028] And, for example, for an assembly made up of two multifilamentary strands of 5.6 to 140 tex aliphatic polyamide, the initial modulus is the slope of the Force-Elongation curve between 1000 cN and 4000 cN and the final modulus is the slope of the Force-Elongation curve between 6000 cN and 18000 cN.

[0029] Advantageously, the ratio of the diameter of the reinforcing element to the thickness of the composite is strictly less than 0.90, preferably less than or equal to 0.80.

[0030] Advantageously, the diameter of the reinforcing element is less than or equal to 0.95 mm, preferably less than or equal to 0.80 mm, more preferably less than or equal to 0.70 mm. The reinforcing element according to the invention extends along a general direction G, and the diameter of this reinforcing element is the diameter in which this reinforcing element is inscribed in a cutting plane perpendicular to the direction G.

[0031] Advantageously, the thickness of the composite is less than or equal to 1.45 mm, preferably less than or equal to 1.30 mm, more preferably less than or equal to 1.20 mm. The thickness of the composite is the shortest distance between the two external surfaces of the composite, that is to say, the distance measured along a direction perpendicular to the two external surfaces of the composite.

[0032] Another object of the invention is a tire comprising a shrink-fitting frame comprising at least one shrink-fitting layer, in which the shrink-fitting layer comprises an elastomer composite as described above.

[0033] The tires of the invention, in particular, can be intended for motor vehicles of the passenger car type, 4x4, "SUV" (Sport Utility Vehicles), but also for two-wheeled vehicles such as motorcycles, or for industrial vehicles such as subways, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles, agricultural or civil engineering vehicles.

[0034] Preferably, the tires can be intended for motor vehicles of the passenger car, 4x4, "SUV" (Sport Utility Vehicles) type.

[0035] The invention will be better understood in the light of the following description, given solely by way of non-limiting example and made with reference to the drawings in which: - Fig. 1 is a view, in a meridian cross-section, of a tire 10 according to the invention, -Fig.2 illustrates a composite 35 allowing to obtain a shrink-fitting sheet of the tire of [Fig.1]; - [Fig.3] is a cross-sectional view along plane III-IIF of the composite 35 of [Fig.2]; and - [Fig.4] is an enlargement of a cross-sectional view of the reinforcing element 45 according to the invention.

[0036] In using the term "radial," it is important to distinguish several different uses of the word by those skilled in the art. First, the expression refers to a radius of the tire. It is in this sense that a point A is said to be "radially inside" a point B (or "radially inside" point B) if it is closer to the axis of rotation of the tire than point B. Conversely, a point C is said to be "radially outside" a point D (or "radially outside" point D) if it is farther from the axis of rotation of the tire than point D. One says that one is moving "radially inward (or outward)" when moving in the direction of smaller (or larger) radii. When referring to radial distances, this sense of the term also applies.

[0037] By "radial cut" or "radial section" we mean here a cut or section along a plane which includes the axis of rotation of the tire.

[0038] The "median circumferential plane" M of the tire is the plane which is normal to the axis of rotation of the tire and which is located equidistant from the annular reinforcement structures of each bead.

[0039] The "median tangential plane" TT of the tire is the plane which is perpendicular to the "median circumferential plane" M.

[0040] An “axial” direction is a direction parallel to the axis of rotation of the tire.

[0041] A “circumferential” direction is a direction that is perpendicular to both a radius of the tire and the axial direction.

[0042] EXAMPLE OF A PNEUMATIC ACCORDING TO THE INVENTION

[0043] In the figures, we have represented a frame X, Y, Z corresponding to the usual directions respectively axial (X), radial (Y) and circumferential (Z) of a tire.

[0044] A radial cross-sectional view of a tire according to a first embodiment of the invention and designated by the general reference 10 is schematically represented in [Fig. 1]. The tire 10 is substantially of revolution about an axis substantially parallel to the axial direction X. The tire 10 is here intended for a passenger vehicle.

[0045] The tire 10 comprises a crown 12 including a crown reinforcement 14 comprising a working reinforcement 15 comprising two working layers 16, 18 of working reinforcement elements and a shrink-fit reinforcement 17 comprising a shrink-fit layer 19 of shrink-fit reinforcement elements. The crown reinforcement 14 is surmounted by a tread 20 arranged radially outside the crown reinforcement 14. Here, the shrink-fit reinforcement 17, the shrink-fit layer 19, is radially interposed between the working reinforcement 15 and the tread 20.

[0046] The tire also includes two sidewalls 22 extending radially inwards from the top 12. The tire 10 further includes two beads 24 radially inward to the sidewalls 22, each comprising an annular reinforcing structure 26, in this case a bead 28, surmounted by a bead-filling rubber mass 30, as well as a radial carcass reinforcement 32.

[0047] The frame reinforcement 32 comprises at least one frame layer including several reinforcing elements, the layer being anchored to each of the ribs 24 by a bend around the rod 28, so as to form in each rib 24 a forward strand 38 extending from the ribs through the sides towards the top 12, and a return strand 40, the radially outer end 42 of the return strand 40 being radially outside the annular reinforcing structure 26. The frame reinforcement 32 thus extends from the ribs 24 through the sides 22 to the top 12. The frame reinforcement 32 is arranged radially inside the top reinforcement 14 and the shrink-fit reinforcement 17. The frame reinforcement 32 comprises a single frame layer 34.

[0048] The tire 10 also includes an internal sealing layer 43, preferably made of butyl, axially internal to the sidewalls 22 and radially internal to the top reinforcement 14 and extending between the two beads 24.

[0049] Each working layer 16, 18, shrink-fit layer 19, and frame layer 34 comprises a polymer composition in which reinforcing elements of the corresponding layer are embedded. Each polymer composition, here an elastomeric composition, of the working layers 16, 18, shrink-fit layer 19, and frame layer 34 is made in a conventional composition for calendering reinforcing elements classically comprising a diene elastomer, for example natural rubber, a reinforcing filler, for example carbon black and / or silica, a crosslinking system, for example a vulcanization system, preferably comprising sulfur, stearic acid and zinc oxide, and possibly a vulcanization accelerator and / or retarder and / or various additives.

[0050] EXAMPLE OF A COMPOSITE ACCORDING TO THE INVENTION

[0051] We will now describe, with reference to figures 2 and 3, a composite from which the shrink-fitting sheet 19 is obtained.

[0052] The composite comprises reinforcing elements 45 embedded in an elastomer composition. The reinforcing elements 45 are substantially parallel to each other and along a principal direction D substantially perpendicular to the general direction G along which the reinforcing elements of the shrink-fit layer extend, the general direction G making an angle greater than or equal to 45°, preferably ranging from 80° to 110° and here equal to 90°.

[0053] Nature of the strands of each reinforcing element

[0054] As schematically represented in [Fig. 3], each reinforcing element 45 comprises several multifilament strands and includes an assembly consisting of two multifilament strands of aliphatic polyamide, the two strands being helically wound around each other. Here, the aliphatic polyamide is Polyamide 5,6. Each reinforcing element is torsionally balanced. For the sake of clarity, [Fig. 4] is a cross-sectional view of the reinforcing element 45 in which the filaments 46 of each of the strands are visible.

[0055] Title of each reinforcement element

[0056] The fiber count of the aliphatic polyamide multifilament strand of the warp reinforcement element ranges from 60 to 160 tex and preferably from 70 to 140 tex. Here, the fiber count of each 5,6 aliphatic polyamide multifilament strand of the warp reinforcement element is 94 tex.

[0057] Torsion of each reinforcing element

[0058] The torsion of each reinforcing element 45 ranges from 200 to 500 turns per meter and preferably from 250 to 490 turns per meter. Here, it is equal to 250 turns per meter.

[0059] Torsion factor of each reinforcing element

[0060] The torsion factor K of each reinforcing element 45 ranges from 110 to 220 and preferably from 120 to 150. Here K=124.

[0061] Initial and final modules of each reinforcement element

[0062] The initial tensile modulus of each reinforcement element ranges from 1 to 5 cN / tex and preferably from 2 to 5 cN / tex. Here it is 4.9 cN / tex.

[0063] And, the final modulus ranges from 5 to 18 cN / tex and preferably from 5 to 12 cN / tex. Here it is 11.4 cN / tex.

[0064] Geometric characteristics of the composite

[0065] Returning to [Fig. 3], each composite 35 has a thickness E and each reinforcing element 45 has a diameter d. The diameter d corresponds to the diameter of the theoretical circle in which the reinforcing element is inscribed. In this [Fig. 3], the representation of each strand is intentionally schematic for the sake of simplifying the description.

[0066] The diameter of each reinforcing element 45 is less than or equal to 0.95 mm, preferably less than or equal to 0.80 mm, more preferably less than or equal to 0.70 mm. Here, d = 0.65 mm.

[0067] The thickness E of each composite 35 is less than or equal to 1.45 mm, preferably less than or equal to 1.30 mm, more preferably less than or equal to 1.20 mm. Here, E=0.86.

[0068] Thus, the ratio d / E is strictly less than 0.90, preferably less than or equal to 0.80. Here, d / E=0.76.

[0069] Density of the reinforcing elements in the composite

[0070] The density of the reinforcing elements in the composite ranges from 80 to 145 reinforcing elements per decimeter of composite, here it is 98 threads per dm of composite.

[0071] METHOD FOR MANUFACTURING THE REINFORCING ELEMENT

[0072] As described previously, each reinforcing element 45 is twist-balanced, meaning that the two multifilament strands are wound with substantially identical twist and the twist of the monofilaments in each multifilament strand is substantially zero. In a first step, each strand of monofilaments is first individually twisted around itself with an initial twist of 485 turns per meter in a given direction, here the Z direction, to form a strand. Then, in a second step, the two strands are twisted together with a final twist of 485 turns per meter in the S direction to obtain the assembly of the reinforcing element (cord).

[0073] In subsequent steps, each assembly is coated with an adhesive composition, for example an RFL (Resorcinol-Formaldehyde-Latex) type adhesive composition and undergoes heat treatment steps in order to crosslink, at least partially, the adhesive composition.

[0074] METHOD FOR MANUFACTURING THE COMPOSITE ACCORDING TO THE INVENTION

[0075] Each composite 35 is manufactured by embedding several reinforcing elements 45 in the elastomer composition, for example by calendering. During such a calendering step, well known to those skilled in the art, reinforcing elements are passed through Two strips made of an elastomer composition, called skims, are placed on either side of the reinforcing elements so as to sandwich the reinforcing elements between the two skims. The reinforcing elements are thus embedded in the elastomer composition.

[0076] METHOD FOR MANUFACTURING THE TIRE SEEON OF INVENTION

[0077] The tire manufacturing process is that conventionally used by those skilled in the art. During this process, and as described above, various plies and composites are successively arranged in a first series of assembly steps. The resulting blank is then shaped. Next, other plies and composites are arranged to form the crown 12 of the tire 10, including the composite according to the invention intended to form the shrink-fit plies 19 of the tire 10. Finally, the resulting blank is vulcanized to obtain the tire 10.

[0078] Comparative Measurements and Tests

[0079] By way of comparative example, a prior art composite designated by the general reference NT of a prior art tire was chosen. The NT composite comprises ET reinforcement elements, each consisting of an assembly of two multifilament strands of polyamide 6,6 joined together and wound helically around each other at a twist of 250 turns per meter. Each ET reinforcement element is torsionally balanced. Each multifilament strand of the ET reinforcement element has a fiber count of 140 tex.

[0080] As another comparative example, a reference composite designated by the general reference T of a PT tire was chosen. The composite T comprises reinforcement elements RT, each consisting of an assembly of two multifilament strands of polyamide 6,6 joined together and wound helically around each other at a twist of 485 turns per meter. Each reinforcement element T is torsionally balanced. Each multifilament strand of the reinforcement element T has a fiber count of 94 tex.

[0081] Comparison of reinforcement elements

[0082] Table 1 summarizes the characteristics of the reinforcement element 45 of the tire 10 according to the invention, the reinforcement element 45' according to the invention, a reference reinforcement element T, and a prior art reinforcement element ET. The tensile strength measurements were performed according to ISO 6892:1984.

[0083] [Tables 1] ET T 45 45' Nature of strands Polyamide 6.6 / Poly amide6.6 Polyamide 6.6 / Poly amide6.6 Polyamide 5.6 / Poly amide5.6 Polyamide 5.6 / Poly amide5.6 Initial modulus at 20°C (cN / tex) 4.9 3.3 4.9 2.7 Final modulus at 20°C (cN / tex) 13.6 9.3 11.4 6.8 Torsion (t / m) 250 485 250 485 Strand count (tex) 140 / 140 94 / 94 140 / 140 94 / 94 Torsion factor K 124 197 124 197 Breaking strength (daN) 23.09 14.2 22.04 13.8

[0084] It is noted that the reinforcement element 45 has an initial modulus equivalent to that of the prior art reinforcement element ET and a final modulus significantly lower than that of the prior art reinforcement element ET and that the reinforcement element 45' has an initial modulus equivalent to the control reinforcement element T and a final modulus significantly lower than that of the control reinforcement element T. For the application in a hoop, the stiffness tendencies at high deformations have a low impact on the performance of the tire.

[0085] Comparison of composites

[0086] The composite 35 according to the invention comprising reinforcing elements 45 was compared to a prior art NT composite comprising ET reinforcing elements. The geometric characteristics of these composites are summarized in Table 2 below.

[0087] [Tables2] Composite NT 35 Reinforcement element ET 45 Density (reinforcement elements / dm²) 98 98 Diameter d of the reinforcing element (mm) 0.65 0.65 Thickness E of the composite (mm) 0.86 0.86 Ratio d / E 0.76 0.76 Fracture strength of the composite (da N / cm) 226.2 215.9

[0088] Endurance of the reinforcing elements

[0089] The endurance of the reinforcement element 45 was compared to that of the prior art reinforcement element ET. The reinforcement element 45 conforms to the invention. The prior art reinforcement element ET does not conform to the invention. To evaluate the endurance, reinforcement elements were embedded in an elastomer composition to form a test specimen in the form of a strip 2 mm thick, which was then cycled around a cylindrical bar 15 mm in diameter. After 190,000 cycles, the final breaking strength of each reinforcement element was measured. The decay, corresponding to the percentage loss of breaking strength after the 190,000 cycles, was then calculated. The higher the decay, the lower the endurance. The test results and the characteristics of the tested reinforcement elements are summarized in Table 3 below.

[0090] [Tables3] Reinforcement element ET 45 Strand type Polyamide 6.6 Polyamide 5.6 Initial breaking strength (daN) 23 23.3 Final breaking strength (daN) 12 17.42 Depletion (%) 45 25

[0091] The endurance of the reinforcement element 45' was compared to that of a control reinforcement element T. The reinforcement element 45' conforms to the invention. The control reinforcement element T does not conform to the invention. To evaluate the endurance, reinforcement elements were embedded in an elastomer composition to form a test specimen in the form of a strip 2 mm thick, which was then cycled around a cylindrical bar 15 mm in diameter. After 800,000 cycles, the final breaking strength of each reinforcement element was measured. The decay, corresponding to the percentage loss of breaking strength after 800,000 cycles, was then calculated. The higher the decay, the lower the endurance. The test results and the characteristics of the tested reinforcement elements are summarized in Table 4 below.

[0092] [Tables4] Reinforcement element T 45' Strand type Polyamide 6.6 Polyamide 5.6 Initial breaking strength (daN) 15.1 13.2 Final breaking strength (daN) 11.3 11.22 Depletion (%) 25 15

[0093] These results show that, for strand types in aliphatic polyamide 5,6 and in the torsion factor range K from 110 to 220, it is observed that the endurance of the reinforcing elements and thus that of the composite according to the invention can be improved while reducing the proportion of petroleum-based materials, thereby increasing the rate of durable material.

[0094] The invention is not limited to the embodiments described above.

[0095] In the embodiment of the invention, the rod 28 is a braided rod made up of an assembly of metal wires coated with a zinc-based or copper alloy deposit which undergo a specific surface treatment, for example by heat treatment to allow adhesion to the elastomeric matrix.

[0096] In embodiments not described above, the tire may have a rod that is a sheathed rod, that is, one made of metal wires pre-coated with a polymer film or made of an assembly of metal wires coated with a polymer film. The rod's sheath is made of an extrudable thermoplastic, such as, for example, an aliphatic polyamide, and preferably aliphatic polyamide 6,6. To ensure the adhesion of the sheathed rod to the elastomeric composition, an adhesive composition, for example, of the RFL (Resorcinol-Formaldehyde-Latex) type, but also adhesive compositions such as those described in WO2015118041, is deposited at the sheath interface, thus avoiding the need for specific surface treatment of the metal wires.This sheathed rod, without requiring any specific treatment of the wires, ensures adhesion to the elastomeric matrix and protects the rod against corrosion in aggressive environments.

[0097] It will also be possible to combine the characteristics of the different embodiments and variants described or envisaged above, provided that these are compatible with each other.

Claims

Demands

1. Elastomeric composite (35), characterized in that it comprises a plurality of wire reinforcement elements substantially parallel to each other and extending along a principal direction, each reinforcement element (45) being embedded in an elastomeric composition, the reinforcement element (45) comprising an assembly made up of at least two multifilamentary strands of aliphatic polyamide 5,6 (46), and the strands (46) being wound together helically to form a layer and the reinforcement element (45) being torsionally balanced, the torsion factor K of the reinforcement element (45) ranging from 110 to 220 with K defined by the formula K = T x [(Title / (1000.p)]1 / 2 in which T is the torsion of the reinforcing element (45) expressed in turns per meter, Title is the sum of the titles of the multifilamentary strands of the reinforcing element in tex, p is the average density of the multifilamentary strands in g / cm3 weighted by the respective titles of the constituent materials of the multifilamentary strands, and the density of reinforcing elements (45) in the composite (35) ranging from 80 to 145 reinforcing elements per decimeter of composite measured along a transverse direction perpendicular to the principal direction of the reinforcing elements; and in which the initial tensile modulus of the reinforcing element (45) ranges from 1 to 5 cN / tex.

2. Elastomer composite (35) according to the preceding claim, wherein the assembly consists of two multifilamentary strands of aliphatic polyamide 5,6 (46).

3. Elastomer composite (35) according to any one of the preceding claims, wherein the torsion factor K of the reinforcing element (45) ranges from 120 to 150.

4. Elastomer composite (35) according to any one of the preceding claims, wherein the density of reinforcing elements (45) in the composite (35) ranges from 90 to 130 reinforcing elements per decimeter of composite, preferably from 95 to 125 reinforcing elements per decimeter of composite.

5. Elastomeric composite (35) according to any one of the preceding claims, wherein the torsion of the element of reinforcement (45) goes from 200 to 500 revolutions per meter and preferably from 250 to 490 revolutions per meter.

6. Elastomer composite (35) according to any one of the preceding claims, wherein the multifilament strand count of polyamide 5,6 (46) ranges from 60 to 160 tex and preferably from 70 to 140 tex.

7. Elastomer composite (35) according to any one of the preceding claims, wherein the initial tensile modulus of the reinforcing element (45) ranges from 2 to 5 cN / tex.

8. Elastomer composite (35) according to any one of the preceding claims, wherein the final tensile modulus of the reinforcing element (45) ranges from 5 to 18 cN / tex and preferably from 5 to 12 cN / tex.

9. Elastomer composite (35) according to any one of the preceding claims, wherein the ratio of the diameter of the reinforcing element (45) to the thickness of the composite is strictly less than 0.90, preferably less than or equal to 0.

80.

10. Elastomer composite (35) according to claim 9, wherein the diameter of the reinforcing element (45) is less than or equal to 0.95 mm, preferably less than or equal to 0.80 mm, more preferably less than or equal to 0.70 mm.

11. Elastomer composite (35) according to claim 9 or 10 wherein the thickness of the composite (35) is less than or equal to 1.45 mm, preferably less than or equal to 1.30 mm, more preferably less than or equal to 1.20 mm.

12. Pneumatic (10) comprising a shrink-fitting frame (17) comprising at least one shrink-fitting layer (19), characterized in that the shrink-fitting layer (19) comprises an elastomer composite (35) according to any one of the preceding claims.