PNEUMATIC TIRE COMPRISING A RUBBER COMPOSITION BASED ON EPOXIDIZED POLYISOPRENE AND A THERMOPLASTIC POLYURETHANE

Abstract

A tire having improved mechanical properties comprises a rubber composition based on at least one epoxidized polyisoprene having a molar degree of epoxidation ranging from 5% to 85%, at least one thermoplastic polyurethane, and a crosslinking system.

Claims

1.-15. (canceled)

16. A tire comprising a rubber composition based on: at least one epoxidized polyisoprene having a molar degree of epoxidation ranging from 5% to 85%; at least one thermoplastic polyurethane; and a crosslinking system.

17. The tire according to claim 16, wherein the at least one epoxidized polyisoprene predominantly comprises an epoxidized natural rubber.

18. The tire according to claim 16, wherein the molar degree of epoxidation of the at least one epoxidized polyisoprene is within a range extending from 10% to less than 50%.

19. The tire according to claim 16, wherein the molar degree of epoxidation of the at least one epoxidized polyisoprene is within a range extending from 40% to 80%.

20. The tire according to claim 16, wherein the at least one epoxidized polyisoprene has a Mooney viscosity (ML 1+4) at 100° C., measured according to Standard ASTM D1646 (1999), within a range extending from 30 to 150.

21. The tire according to claim 16, wherein a content of the at least one epoxidized polyisoprene, in the rubber composition, is within a range extending from 20 to 90 parts by weight per hundred parts by weight of elastomer, phr.

22. The tire according to claim 16, wherein a content of the at least one thermoplastic polyurethane, in the rubber composition, is within a range extending from 10 to 80 phr.

23. The tire according to claim 16, wherein the at least one thermoplastic polyurethane comprises at least one flexible segment and at least one rigid segment, the flexible segment resulting from a reaction of a polyisocyanate with a polyol, the molecular weight of the hydrocarbon-based chain of which is between 600 and 2500 g/mol, and the rigid segment resulting from a reaction of a polyisocyanate with a diol or triol, the molecular weight of which is in a range extending from 40 to 350 g/mol.

24. The tire according to claim 16, wherein the rubber composition comprises from 5 to 150 phr of at least one reinforcing filler.

25. The tire according to claim 16, wherein the rubber composition does not comprise a reinforcing filler or comprises less than 5 phr of a reinforcing filler.

26. The tire according to claim 24, wherein the at least one reinforcing filler comprises carbon black, a reinforcing inorganic filler or a mixture thereof.

27. The tire according to claim 24, wherein the at least one reinforcing filler predominantly comprises carbon black.

28. The tire according to claim 16, wherein the crosslinking system is based on molecular sulfur, a sulfur-donating agent, or both molecular sulfur and a sulfur-donating agent.

29. The tire according to claim 16, wherein the rubber composition is present in a tread of the tire.

30. The tire according to claim 16, wherein the tire is a tire for civil engineering, agricultural or heavy-duty vehicles.

Description

III—EXAMPLES

III-1 Measurements and Tests Used

[0102] Dynamic Properties (after Curing): Tensile Test

[0103] These tensile tests make it possible to determine the elasticity stresses and the properties at break. Unless otherwise indicated, they are carried out in accordance with French Standard NF T 46-002 of September 1988. Processing the tensile recordings also makes it possible to plot the curve of modulus as a function of the elongation. The modulus used here is the true secant modulus measured in first elongation, calculated by normalizing to the true cross section of the test specimen at any moment of the test. The nominal secant moduli (or apparent stresses, in MPa) are measured in first elongation at 50%, 100% and 300% elongation, respectively denoted M50, M100 and M300. The MSV300/MSV100 ratio is an indicator of the reinforcement of the rubber composition. The high this ratio, the stronger the reinforcement of the composition.

[0104] The elongation at break (EB %) and breaking stress (BS) tests are based on Standard NF ISO 37 of December 2005 on an H2 dumbbell specimen and are measured at a tensile speed of 500 mm/min. The elongation at break is expressed as a percentage of elongation. The breaking stress is expressed in MPa.

[0105] All these tensile measurements are carried out under the standard conditions of temperature (23±2° C.) and hygrometry (50±5% relative humidity), according to French Standard NFT 40-101 (December 1979).

[0106] The dynamic properties G*(25%) are measured on a viscosity analyser (Metravib VA4000) according to Standard ASTM D 5992-96. The response of a sample of crosslinked composition (cylindrical test specimen with a thickness of 4 mm and a cross section of 400 mm.sup.2), subjected to a simple alternating sinusoidal shear stress, at a frequency of 10 Hz, under the defined conditions of temperature, for example at 60° C., according to Standard ASTM D 1349-99 or, as the case may be, at a different temperature, is recorded. A strain amplitude sweep is carried out from 0.1% to 50% (outward cycle) and then from 50% to 1% (return cycle). The results made use of are the complex dynamic shear modulus G*. For the return cycle, the complex dynamic shear modulus G* at 25% strain, at 60° C., is shown.

III-2 Preparation of the Compositions

[0107] The tests which follow are carried out in the following way: the thermoplastic polyurethane then the elastomer and also the various other ingredients, with the exception of the crosslinking system, are successively introduced into a blade mixer (final degree of filling: approximately 70% by volume), the initial vessel temperature of which is approximately 175° C. Thermomechanical working (non-productive phase) is then carried out in one step, which lasts in total approximately from 5 to 8 min, until a maximum “dropping” temperature of 175° C. is reached.

[0108] The mixture thus obtained is recovered and cooled and then the crosslinking system is incorporated on a mixer (homofinisher) at 23° C. or 50° C., respectively, everything being mixed (productive phase) in a roll mill for an appropriate time (for example between 5 and 12 min).

[0109] The compositions thus obtained are subsequently calendered, either in the form of plaques (thickness of 2 to 3 mm) or of thin sheets of rubber, for the measurement of their physical or mechanical properties, or extruded in the form of a profiled element.

[0110] The samples thus produced were cured for 20 minutes at 170° C. in a bell press. The samples were analysed after having been cooled at ambient temperature for 24 hours.

III-3 Tests on Rubber Compositions

[0111] The examples presented in Table 1 are intended to compare the mechanical properties and the reinforcement of compositions in accordance with the invention (C1, C2, C3 and C4) with those of control compositions (T1, T2 and T3) which differ from the compositions in accordance with the invention in that they do not comprise epoxidized polyisoprene and thermoplastic polyurethane concomitantly. The control compositions T4 and T5 differ from the compositions in accordance with the invention C2 and C3 respectively in that the is natural rubber is not epoxidized. The formulations (in phr) and the properties thereof have been summarized in Table 1 below.

TABLE-US-00001 TABLE 1 T1 T2 T3 C1 T4 C2 C3 T5 C4 NR (1) 100 — — — 60 — — 40 — ENR50 (2) — 100 — 60 — — 40 — 80 ENR25 (3) — — — — — 60 — — — TPU (4) — — 100 40 40 40 60 60 20 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 CBS (5) 1 1 1 1 1 1 1 1 1 ZnO (6) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Stearic acid (7) 1 1 1 1 1 1 1 1 1 MSV 300/100 100 95 93 127 118 99 135 101 103 MSV rupture 100 48 1376 1345 365 555 680 418 148 % EB 100 79 145 174 113 174 142 113 109 (1) Natural rubber (2) Epoxidized natural rubber at 50 mol % (Epoxyprene 50 from the company Guthrie) (3) Epoxidized natural rubber at 25 mol % (Epoxyprene 25 from the company Guthrie) (4) Thermoplastic polyurethane (Desmopan 3378A from the company Bayer) (5) N-Cyclohexyl-2-benzothiazolesulfenamide (Santocure CBS from Flexsys) (6) Zinc oxide (industrial grade-Umicore) (7) Stearin (Pristerene 4931 from Uniqema)

[0112] These results show that the compositions in accordance with the invention all make it possible to improve the compromise in mechanical properties without penalizing the reinforcement of the composition. The use of an epoxidized polyisoprene having a molar degree of epoxidation of 50% also makes it possible to improve the reinforcement of the composition. Finally, it is observed that the performance compromise is greatly improved when an epoxidized polyisoprene is used instead of a non-epoxidized polyisoprene.