TIRE PROVIDED WITH AN OUTER SIDEWALL, THE COMPOSITION OF WHICH CONTAINS A THERMOPLASTIC ELASTOMER AND A POLYETHYLENE OXIDE

Abstract

A tire is provided with an outer sidewall, said outer sidewall comprising at least one composition based on at least one thermoplastic elastomer comprising at least one elastomer block and at least one thermoplastic block, a butadiene elastomer, 10 to 100 phr of carbon black, 0.6 to 1.9 phr of polyethylene oxide with a weight-average molecular weight Mw within a range extending from 250 to 550 g/mol, and a crosslinking system.

Claims

1.-15. (canceled)

16. A tire provided with an outer sidewall, the outer sidewall comprising at least one composition based on: at least one thermoplastic elastomer comprising at least one elastomer block and at least one thermoplastic block; a butadiene elastomer; 10 to 100 phr of carbon black; 0.6 to 1.9 phr of polyethylene oxide with a weight-average molecular weight Mw within a range extending from 250 to 550 g/mol; and a crosslinking system.

17. The tire according to claim 16, wherein the at least one thermoplastic elastomer comprises a non-hydrogenated or partially hydrogenated unsaturated elastomer block selected from the group consisting of polyisoprenes, polybutadienes, copolymers of styrene and of butadiene, and mixtures thereof.

18. The tire according to claim 16, wherein the at least one thermoplastic elastomer comprises a thermoplastic block selected from the group consisting of polyolefins, polyurethanes, polyamides, polyesters, polyacetals, polyethers, polyphenylene sulfides, polyfluorinated compounds, polystyrenes, polycarbonates, polysulfones, poly(methyl methacrylate), polyetherimide, thermoplastic copolymers, and mixtures thereof.

19. The tire according to claim 16, wherein the at least one thermoplastic elastomer is selected from the group consisting of styrene/butadiene/styrene, styrene/isoprene/styrene and styrene/optionally partially hydrogenated butadiene-styrene copolymer/styrene block copolymers, and mixtures thereof.

20. The tire according to claim 16, wherein the at least one thermoplastic elastomer is selected from the group consisting of styrene/butadiene/styrene and styrene/partially hydrogenated butadiene-styrene copolymer/styrene block copolymers, and mixtures thereof.

21. The tire according to claim 16, wherein a content of the at least one thermoplastic elastomer is within a range extending from 5 to 45 phr.

22. The tire according to claim 16, wherein a content of butadiene elastomer is within a range extending from 55 to 95 phr.

23. The tire according to claim 16, wherein the butadiene elastomer is selected from the group consisting of polybutadienes, butadiene/styrene copolymers and mixtures thereof.

24. The tire according to claim 16, wherein the butadiene elastomer is selected from the group consisting of polybutadienes and mixtures thereof.

25. The tire according to claim 16, wherein the total amount of carbon black is within a range extending from 20 to 60.

26. The tire according to claim 16, wherein the weight-average molecular weight Mw of the polyethylene oxide is within a range extending from 300 to 500 g/mol.

27. The tire according to claim 16, wherein the amount of polyethylene oxide is within a range extending from 0.7 to 1.8 phr.

28. The tire according to claim 16, wherein the at least one composition further comprises an anti-ozone wax in an amount within a range extending from 0.2 to 10 phr.

29. The tire according to claim 28, wherein the anti-ozone wax contains from 50% to 75% of linear alkanes comprising 30 carbon atoms to 38 carbon atoms, relative to a total amount of linear alkanes.

30. The tire according to claim 16, wherein the at least one composition of the outer sidewall further comprises a hydrocarbon-based resin.

Description

EXAMPLES OF IMPLEMENTATION OF THE INVENTION

[0145] The outer sidewall described above can advantageously be used in pneumatic tyres for all types of vehicles, in particular passenger vehicles or industrial vehicles, such as heavy-duty vehicles.

[0146] By way of example, the single appended figure represents very diagrammatically (without observing a specific scale) a radial section of a pneumatic tyre in accordance with the invention.

[0147] This pneumatic tyre 1 comprises a crown 2 reinforced by a crown reinforcement or belt 6, two outer sidewalls 3 and two beads 4, each of these beads 4 being reinforced with a bead wire 5. The crown 2 is surmounted by a tread, not represented in this diagrammatic figure. A carcass reinforcement 7 is wound around the two bead wires 5 in each bead 4, the turn-up 8 of this reinforcement 7 being, for example, positioned towards the outside of the tyre 1, which is represented here fitted onto its wheel rim 9. The carcass reinforcement 7 is, in a manner known per se, formed of at least one ply reinforced with “radial” cords, for example made of textile or metal, that is to say that these cords are positioned virtually parallel to each other and extend from one bead to the other so as to form an angle of between 80° and 90° with the median circumferential plane (plane perpendicular to the axis of rotation of the tyre which is located midway between the two beads 4 and passes through the middle of the crown reinforcement 6).

[0148] The internal wall of the pneumatic tyre 1 comprises an airtight layer 10, for example with a thickness equal to approximately 0.9 mm, on the side of the internal cavity 11 of the pneumatic tyre 1.

[0149] The pneumatic tyre according to the invention can use, for example for the composition of its outer sidewall as defined above, a composition in accordance with the present invention.

[0150] The tyre provided with its outer sidewall as described above is preferably produced before crosslinking (or curing). The crosslinking is subsequently carried out conventionally.

[0151] An alternative manufacturing form which is advantageous, for a person skilled in the art of pneumatic tyres, will consist, for example during a first step, in depositing the airtight layer flat directly on a tyre-building drum, in the form of a skim of suitable thickness, before covering the latter with the remainder of the structure of the pneumatic tyre, according to manufacturing techniques well known to a person skilled in the art.

[0152] Tests

[0153] The properties of the elastomer compositions and of some of their constituents are characterized as indicated below.

[0154] The ozone resistance of the materials is measured according to the following method: after curing, the B15 test specimens are prepared. The “B15” test specimens result from an MFTR (known as Monsanto) plaque, the two beads of which located at the ends are used to hold the test specimen. The “B15” test specimens have the following dimensions 78.5 mm×15 mm×1.5 mm. After 240 hours of exposure to a temperature of 38° C. and an ozone level of 50pphm (parts per hundred million), the test specimens are placed on a trapezium-shaped support, and the maximum extension, beyond which the sample breaks, is measured in steps of 10% elongation. The result used is the maximum extension that the samples withstood without breaking during exposure to ozone. The higher this extension, the better the resistance of the material.

[0155] Measurement of the dynamic properties (after curing) The dynamic properties G* and G″ are measured on a viscosity analyser (Metravib V A4000), according to Standard ASTM D 5992-96. The response of a sample of vulcanized composition (cylindrical test specimen with a thickness of 2 mm and a cross section of 78.5 mm.sup.2), subjected to a simple alternating sinusoidal shear stress, at a frequency of 10 Hz, at a temperature of 23° C. and according to Standard ASTM D 1349-99, is recorded. A peak-to-peak strain amplitude sweep is performed from 0.1% to 50% (outward cycle) and then from 50% to 1% (return cycle). For the return cycle, the value of G* at 20% strain and also the value of G″ at 20% strain are indicated. The results used are the complex dynamic shear modulus (G*), which indicates the stiffness and a reduced value of which represents better stiffness performance in the case of an FE mixture; and the loss modulus (G″), which indicates the hysteresis and an increased value of which represents increased hysteresis and decreased performance. For greater readability, the results will be shown in terms of performance in base 100, the value 100 being assigned to the control. A result of less than 100 indicates a decreased performance and, conversely, a result of greater than 100 will indicate an improved performance.

[0156] Tests

[0157] Outer sidewall compositions containing customary elastomers, reinforcing fillers and additives not in accordance with the invention (C1 and C2, Table 1) were prepared according to the methods known to those skilled in the art and similarly to the preparation of the compositions of the invention described above. These control compositions were compared with a composition (C3 of Table 1) in accordance with the invention.

[0158] Table 1 shows all of the compositions prepared. The contents are all expressed in phr.

TABLE-US-00001 TABLE 1 Compositions C1 C2 C3 Natural rubber (NR) (1) 35 0 0 Polybutadiène (BR) (2) 65 75 75 SBS (3) 0 25 25 Carbon black (4) 50 25 25 PEG (5) 0 0 1.5 Wax (6) 1 1 1 Oil (7) 20 15 15 Antioxidants (8) 3 3 3 Stearic acid 1 1 1 Zinc oxide 3 2.5 2.5 Sulfur 1.4 1.2 1.2 Accelerator (9) 1.4 1.2 1.2 Table 1 references: (1) NR Natural rubber (2) Butadiene Rubber Nd (3) SBS block copolymer, “D1101” from Kraton (4) Carbon black N550 (5) PEG-400, “Pluriol FT E 400” from BASF (6) Anti-ozone wax, “Varazon 4959” from Sasol Wax (7) MES oil from Exxon Mobil (8) Antioxidants: Santoflex 6PPD from Solutia and Vulkanox IPPD from Bayer (9) N-Cyclohexyl-2-benzothiazolesulfenamide, Santocure CBS from Solutia

[0159] The compositions were tested according to the tests described above for performance in terms of resistance to ozone, stiffness (G*) and hysteresis (G″).

[0160] Table 2 shows all of the results of the compositions tested.

TABLE-US-00002 TABLE 2 Compositions C1 C2 C3 Maximum extension 50% 100% No break after 240 h ozone G″ MAX return at 23° C. 100 169 169 G* at 10% of def at 23° C. 100 100 100

[0161] The results presented in Table 2 show that only composition C3, in accordance with the invention, makes it possible to prevent breaking of the samples subjected to an ozone attack and therefore exhibits very good resistance to ozone. The composition also exhibits an improved balance between stiffness performance and hysteresis performance.