Pneumatics comprising at least one ultra-thin shrink-fit layer to prevent creep of the protective layers

Abstract

The invention relates to a tire comprising a crown reinforcement comprising a shrink-fit reinforcement comprising at least one shrink-fit layer (19) comprising an elastomer matrix (Ma) and at least a plurality of shrink-fit reinforcement elements (48), in which: - the shrink-fit reinforcement elements (48) are embedded in the elastomer matrix (Ma), the shrink-fit reinforcement elements (48) extending along a direction (Z1) and being arranged side by side along a principal direction (X1) perpendicular to the direction (Z1), each shrink-fit reinforcement element (48) comprising several multifilament strands; - each shrink-fit reinforcement element (48) has an average size D along the principal direction (X1) and the average distance L separating two successive reinforcement elements along the principal direction (X1) is such that the ratio R=D / L is strictly greater than 4.5;and- the shrink-fit layer (19) has a filling coefficient CR greater than or equal to 80%, with CR = dx D, with d the density of shrink-fit reinforcement element (48) in the shrink-fit layer (19). Figure for the abbreviation: Fig.2;

Description

Title of the invention: A pneumatic system comprising at least one ultra-thin shrink-fit layer for preventing creep of the protective layers

[0001] The present invention relates to a tire comprising at least one ultra-thin shrink-wrapping layer.

[0002] A 245 / 45 RI8 type tire belonging to the Primacy 4 range for passenger vehicles is known from the prior art, comprising a carcass reinforcement anchored in two beads and radially surmounted by a crown reinforcement itself surmounted by a tread which is joined to the beads by two sidewalls.

[0003] In such a tire, the crown reinforcement comprises a shrinkage reinforcement and a working reinforcement. The shrinkage reinforcement is radially interposed between the tread and the working reinforcement. The shrinkage reinforcement comprises shrinkage reinforcement elements made of two strands of 94 tex nylon at 320 rpm coated in the ply at a density of 120 threads / dm, with a reinforcement element diameter D = 0.54 mm and a distance L between two adjacent reinforcement elements of 0.3 mm, i.e., a D / L ratio = 1.8.

[0004] A tire comprising a thin shrink-wrapped layer is known from the prior art and in particular from document EP 3740385.

[0005] We also know of the prior art document EP908329 which discloses a tire comprising reinforcement elements of shrinkage made up of two 55 tex PEN yarns embedded in the web at a density of 224 yarns / dm, with a diameter of reinforcement element D= 0.35 mm and a distance L between two adjacent reinforcement elements of L=0.08mm, i.e. a ratio D / L of 4.4.

[0006] Such tires with a thinner reinforcement layer certainly reduce the tire's weight, but they do not address the problem of migration of the elastomeric matrix present in the protective layers to the reinforcement layer. Creep is detrimental to the very functioning of the layers because the elastomeric matrix is ​​displaced between the reinforcing elements, and the behavior of the layer can be altered.

[0007] Thus, the invention aims to find a tire that solves the problems mentioned above.

[0008] To this end, the invention relates to a tire comprising a top reinforcement comprising a shrink-fit reinforcement comprising at least one ply a shrink-fitting system comprising an elastomer matrix (Ma) and at least a plurality of shrink-fitting reinforcement elements, wherein: - the shrink-fitting reinforcement elements are embedded in the elastomer matrix, the shrink-fitting reinforcement elements extending along a direction (Zl) and being arranged side by side along a principal direction (XI) perpendicular to the direction (Zl), each shrink-fitting reinforcement element comprising several multifilamentary strands; - each reinforcement element in the shrink-fit system has an average overall length D along the principal direction (XI), and the average distance L separating two successive reinforcement elements along the principal direction (XI) is such that the ratio R=D / L is strictly greater than 4.5; and - the shrink-fitting layer has a filling coefficient CR greater than or equal to 80%, with CR = dx D, with d the density of shrink-fitting reinforcement element in the shrink-fitting layer.

[0009] By elastomer matrix, we mean a matrix 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.

[0010] Preferably, the elastomer matrix comprises a diene elastomer.

[0011] By definition, the overall size D of the reinforcement element is the diameter in which this reinforcement element is inscribed in a cutting plane perpendicular to the direction (Zl).

[0012] The density of reinforcing elements in the layer d is the number of reinforcing elements taken on one decimeter of the layer along the direction perpendicular to the direction along which the reinforcing elements extend parallel to each other.

[0013] 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 (vans, trucks, tractors, trailers), off-road vehicles, agricultural or civil engineering vehicles.

[0014] Preferably, the tires can be intended for motor vehicles of the passenger car, 4x4, "SUV" (Sport Utility Vehicles) type.

[0015] The compounds mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already used, that is to say, they may be partially or totally derived from a recycling process, or obtained from materials These are themselves derived from a recycling process. This includes filaments, fibers, polymers, plasticizers, fillers, etc.

[0016] The inventors of the invention demonstrate that by selecting at least one shrink-fit layer with a D / l ratio strictly greater than 4.5 and a filling coefficient greater than or equal to 80%, it is possible to block the fineness of the mixture of the working layers towards the top block and to obtain a protective screen allowing to limit deep indentations and to block the phenomenon of oxidation.

[0017] Advantageously, the ratio R=D / L is strictly greater than 5.0 and more preferably greater than or equal to 6.0.

[0018] In an advantageous embodiment, the ratio R=D / L is strictly greater than 10.1.

[0019] Preferably, each shrink-fit reinforcement element comprises an assembly made up of two multifilament strands, the two strands being wound helix around each other.

[0020] By "constituted assembly", it is understood that the assembly does not include any other multifilamentary strands than the two multifilamentary strands.

[0021] Advantageously, in a first embodiment, each shrink-fit reinforcement element comprises an assembly consisting of: of a multifilament strand of aromatic polyamide or aromatic copolyamide, and a multifilament strand of polyester, the two strands being wound helically around each other and the reinforcing element being torsionally balanced.

[0022] By aromatic polyamide strand or aromatic copolyamide, it is well known that it is a set of filaments made up of linear macromolecules formed of aromatic groups linked together by amide bonds of which at least 85% are directly linked to two aromatic nuclei, and more particularly of poly (p-phenylene terephthalamide) (or PPTA) fibers, manufactured for a very long time from optically anisotropic spinning compositions.Among the aromatic polyamides or aromatic copolyamides, we can mention polyarylamides (or PAA, notably known under the trade name Ixef from the company Solvay), poly(metaxylylene adipamide), polyphthalamides (or PPA, notably known under the trade name Amodel from the company Solvay), amorphous semi-aromatic polyamides (or PA 6-3T, notably known under the trade name Trogamid from the company Evonik), meta-aramids (or poly(metaphenylene isophthalamide or PA MPD-I notably known under the trade name Nomex from the company Du Pont de Nemours) or para-aramids (or poly(paraphenylene terephthalamide or PA PPD-T. notably known under the trade name Kevlar from the company Du Pont de Nemours or Twaron from the company Teijin).

[0023] A polyester strand, it should be noted, is a collection of filaments made up of linear macromolecules formed from groups linked together by ester bonds. Polyesters are manufactured by polycondensation, by esterification between a dicarboxylic acid or one of its derivatives, a diol. For example, polyethylene terephthalate can be manufactured by polycondensation of terephthalic acid and ethylene glycol. Among the known polyesters, we can mention polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene naphthalate (PBN), polypropylene terephthalate (PPT), and polypropylene naphthalate (PPN).

[0024] By balanced in twists, it is understood that the two multifilamentary strands are wound with a substantially identical twist and that the twist of the filaments of each multifilamentary strand, i.e. the twist of the filaments of the polyamide or aromatic copolyamide multifilamentary strand and the twist of the filaments of the polyester 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 yarn of filaments (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 or surtors (in English "strand") in which the filaments 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 filaments 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 practically zero residual torsion, we mean that the residual torsion is strictly less than 2.5% of the torsion R3.

[0025] Preferably, the strand count of the aromatic polyamide or aromatic copolyamide ranges from 10 to 50 tex, preferably from 10 to 30 tex, more preferably from 15 to 25 tex and in which the strand count of the polyester ranges from 10 to 50 tex, preferably from 10 to 30 tex, more preferably from 15 to 25 tex.

[0026] The count (or linear mass) of each strand is determined according to the ASTM D1423 standard. The count is given in tex (mass in grams of 1000 m of product - reminder: 0.111 tex equals 1 denier).

[0027] Advantageously, in a second embodiment, each shrink-fit reinforcement element comprises an assembly made up of two multifilament polyester strands, the two strands being wound helix around each other and the shrink-fit reinforcement element being torsionally balanced.

[0028] Preferably, the count of each of the polyester strands ranges from 10 to 100 tex, preferably from 30 to 70 tex, more preferably from 40 to 60 tex.

[0029] The following features apply to both embodiments described above.

[0030] Advantageously, the twist of each strand of the reinforcing element ranges from 100 to 1000 turns per meter, preferably from 250 to 500 turns per meter.

[0031] The measurement of the torsion of the reinforcing element can be carried out by any method known to a person skilled in the art, for example in accordance with ASTM D1423 or ASTM D 885 / D 885MA of January 2010 (paragraph 30), for example using a torsiometer.

[0032] Advantageously, the density d ranges from 180 to 350 reinforcement elements per decimeter of layer and preferably from 200 to 300 reinforcement elements per decimeter of layer.

[0033] Advantageously, the overall size D of the reinforcement elements of the shrinkage is less than or equal to 0.54 mm and preferably less than 0.40 mm.

[0034] Preferably, the sum of the titles of the multifilament strands is less than or equal to 110 tex.

[0035] Advantageously, the average minimum thickness of elastomer L separating two successive shrink-fit reinforcement elements along the main direction (XI) is strictly less than 0.05 mm and preferably less than or equal to 0.03 mm.

[0036] The closer the reinforcement elements of the shrink sleeve are, the more effectively the shrink sleeve acts as a protective barrier in case of puncture. This limits the thinning of the protective layers and helps to protect the tire.

[0037] Preferably, the average minimum thickness E of the shrink-wrapping layer is less than or equal to 0.77 mm.

[0038] Reducing the thickness of the shrink-fit layer has the advantage of lightening the tire.

[0039] While having a reduced thickness and a high density of shrinkage reinforcements, the shrinkage layer according to the invention makes it possible to reduce the oxidation of the working layers and to block the fining of the mixture of the latter in the shrinkage layer.

[0040] Advantageously, the porosity surface of each shrink-fit reinforcement element is less than or equal to 20,000 pm2 with the calculation of the porosity surface being carried out using a measuring device allowing the geometries on scanned and calibrated images from an optics and light systems allowing the porosity surface of the shrink-fit reinforcement element to be revealed.

[0041] Preferably, the less porous the reinforcing elements are, the less capacity they have to transmit water and the more protective they are against oxidation of the working layers.

[0042] The invention will be better understood upon reading 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 shrink-fitting sheet 19 of the tire of [Fig.1]; - [Fig. 3] is a photograph of the apex armature 14 according to a second variant of the invention; and - [Fig.4] is a photograph of a shrink-fit reinforcement element 48 according to a second variant of the invention according to the invention and of the prior art reinforcement element in the shrink-fit layer.

[0043] 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 will say 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.

[0044] 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.

[0045] The "circumferential median 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.

[0046] The "median tangential plane" TT of the tire is the plane which is perpendicular to the "median circumferential plane" M.

[0047] An “axial” direction is a direction parallel to the axis of rotation of the tire.

[0048] A “circumferential” direction is a direction that is perpendicular to both a radius of the tire and the axial direction.

[0049] EXAMPLE OF A PNEUMATIC ACCORDING TO THE INVENTION

[0050] In the figures, a reference frame X, Y, Z has been represented corresponding to the usual directions respectively axial (X), radial (Y) and circumferential (Z) of a tire.

[0051] 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.

[0052] 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 two shrink-fit layers 19, 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 and the shrink-fit layer 19 are radially interposed between the working reinforcement 15 and the tread 20.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] Each working layer 16, 18, shrink-fit layer 19 and carcass layer 34 comprises a polymer composition in which reinforcement elements of the layer are embedded corresponding. Each polymer composition, here an elastomeric composition, of the working layers 16, 18, of the shrinkage layer 19 and of the carcass layer 34 is made in a conventional composition for calendering of reinforcing elements comprising classically 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.

[0057] EXAMPLE OF A SHRINK-BRACING PLATE ACCORDING TO THE INVENTION

[0058] We will now describe, with reference to figures 2 and 3, the shrink-fitting sheet 19 according to a second variant of the invention.

[0059] In Figures 2 and 3, the shrink-fit layer 19 and the reinforcing elements 48 are shown in a coordinate system XI, Y1, ZI in which the direction Y1 is substantially parallel to the radial direction Y. In these Figures 2 and 3, the reinforcing elements 48 of the shrink-fit layer 19 are arranged side by side along the principal direction XI. The reinforcing elements 48 extend parallel to each other. Each reinforcing element 48 comprises at least two wire elements extending along the direction ZI, which, when inside the tire 10, forms an angle of 0° with the circumferential direction Z of the tire 10.

[0060] The density d of the shrink-fitting reinforcement elements 48 in the shrink-fitting layer 19 ranges from 180 to 350 shrink-fitting reinforcement elements per decimeter of layer and preferably from 200 to 300 shrink-fitting reinforcement elements per decimeter of layer. Here d = 250 shrink-fitting reinforcement elements per decimeter of layer.

[0061] The average minimum thickness of elastomer L separating two successive reinforcing elements along the main direction XI is strictly less than 0.05 mm and preferably less than or equal to 0.03 mm. Here, L = 0.03 mm.

[0062] The average minimum thickness E of the shrink-fit layer 19 is less than or equal to 0.77 mm. Here, E = 0.55 mm.

[0063] EXAMPLE OF A REINFORCING ELEMENT ACCORDING TO THE INVENTION

[0064] We will now describe, with reference to the photograph in [Fig.4], a reinforcement element of the shrinkage 48 according to the second variant of the invention.

[0065] Each reinforcing element 48 comprises a wire element assembly. Each wire element comprises an assembly consisting of two multifilament polyester strands, the two strands being wound helically around each other and the reinforcing element being torsionally balanced.

[0066] The count of each of the polyester strands ranges from 10 to 100 tex, preferably from 30 to 70 tex, more preferably from 40 to 60 tex. Here it is 55 tex.

[0067] The overall size D of the reinforcement elements of the shrinkage 48 is less than or equal to 0.54 mm and preferably less than 0.40 mm. Here D = 0.37 mm.

[0068] The sum of the counts of the multifilament strands is less than or equal to 110 tex. Here, it is 110 tex.

[0069] The porosity area of ​​each reinforcement element 48 is less than or equal to 20,000 pm2. Here, the porosity area is equal to 15,700 pm2.

[0070] METHOD FOR MANUFACTURING THE TIRE ACCORDING TO THE INVENTION

[0071] 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.

[0072] Comparative Measurements and Tests

[0073] Table 1 summarizes the characteristics of the tires according to the first and second variants of the invention and of a prior art tire of type 245 / 45 RI8 belonging to the Primacy 4 range.

[0074] [Tables 1] TEDT Tl T2 Pneumatic Shrink Wrap NEDT 19' 19 REDT - 48 Strand Type / Tires (tex) / Number Nylon / 94 / 2 Aramid22 / PET22.5 PET / 55 / 2 Twist (turns / m) 320 / 320 1000 / 1000 500 / 500 D (mm) 0.54 0.25 0.37 Surface Porosity (pm) 24,400 - 15,700 L (mm) 0.3 0.04 0.03 D / L 1.8 6.4 12 CR 64.8 86.6 93.0 Density d (threads / dm) 120 340 250 E (mm) 0.77 0.42 0.55 Wrap Strength (daN / dm) 1800 1836 1810 Creep ++ - -

[0075] It is observed that in the Tl and T2 tires according to the invention with a D / l ratio strictly greater than 4.5 and a CR filling coefficient greater than or equal to 80%, it is possible to block the fineness of the mixture of the working plies towards the top block and to obtain a protective screen allowing to limit deep indentations and to block the phenomenon of oxidation.

[0076] In [Fig.4], it can be seen that the elastomeric matrix of the tire in the state The technology has shifted while that of the T2 tire has remained in place and forms this protective screen allowing to limit deep indentations and block the phenomenon of oxidation.

[0077] The invention is not limited to the embodiments described above.

[0078] 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. Pneumatic (10) comprising a top reinforcement (14) comprising a shrink-fit reinforcement (17) comprising at least one shrink-fit layer (19) comprising an elastomer matrix (Ma) and at least a plurality of shrink-fit reinforcement elements (48), characterized in that: - the shrink-fit reinforcement elements (48) are embedded in the elastomer matrix (Ma), the shrink-fit reinforcement elements (48) extending along a direction (Zl) and being arranged side by side along a principal direction (XI) perpendicular to the direction (Zl), each shrink-fit reinforcement element (48) comprising several multifilamentary strands; - each reinforcement element of the shrinkage (48) has an average size D along the main direction (XI) and the average distance L separating two successive reinforcement elements along the main direction (XI) is such that the ratio R=D / L is strictly greater than 4.5;and - the shrink-fit layer (19) has a filling coefficient CR greater than or equal to 80%, with CR = dx D, with d the density of shrink-fit reinforcement element (48) in the shrink-fit layer (19).;

2. Pneumatic (10) according to claim 1, wherein each shrink-fit reinforcement element (48) comprises an assembly consisting of two multifilament strands, the two strands being helically wound around each other.

3. Pneumatic (10) according to claim 2, wherein each shrink-fitting reinforcement element (48) comprises an assembly consisting of: a multifilament strand of aromatic polyamide or aromatic copolyamide, and a multifilament strand of polyester, the two strands being wound helically around each other and the shrink-fitting reinforcement element being torsionally balanced.

4. Pneumatic (10) according to claim 2, wherein each shrink-fit reinforcement element (48) comprises an assembly made up of two multifilament polyester strands, the two strands being helically wound around each other and the shrink-fit reinforcement element being torsionally balanced.

5. Pneumatic (10) according to claim 3 wherein the strand count of aromatic polyamide or aromatic copolyamide ranges from 10 to 50 tex, preferably from 10 to 30 tex, more preferably from 15 to 25 tex and wherein the strand count of polyester ranges from 10 to 50 tex, preferably from 10 to 30 tex, more preferably from 15 to 25 tex.

6. Pneumatic (10) according to claim 4 wherein the count of each of the polyester strands ranges from 10 to 100 tex, preferably from 30 to 70 tex, more preferably from 40 to 60 tex.

7. Pneumatic (10) according to any one of the preceding claims, wherein d ranges from 180 to 350 shrink-fitting reinforcement elements (48) per decimeter of web and preferably from 200 to 300 shrink-fitting reinforcement elements (48) per decimeter of web.

8. Pneumatic (10) according to any one of the preceding claims, wherein the size D of the shrink-fitting reinforcement elements (48) is less than or equal to 0.54 mm and preferably less than 0.40 mm.

9. Pneumatic (10) according to any one of the preceding claims, wherein the sum of the multifilament strand counts is less than or equal to 110 tex.

10. Pneumatic (10) according to any one of the preceding claims, wherein the average minimum thickness of elastomer L separating two successive shrink-fit reinforcement elements (48) along the main direction (XI) is strictly less than 0.05 mm and preferably less than or equal to 0.03 mm.

11. Pneumatic (10) according to any one of the preceding claims, wherein the average minimum thickness E of the shrink-wrapping layer (19) is less than or equal to 0.77 mm.

12. Pneumatic (10) according to any one of the preceding claims, wherein the porosity area of ​​each shrink-fit reinforcement element (48) is less than or equal to 20,000 pm2 with the calculation of the porosity area being carried out using a measuring device enabling the measurement of geometries on scanned and calibrated images from an optics and light systems enabling the porosity area of ​​the reinforcement element to be revealed.

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