TIRE PROVIDED WITH AN OUTER SIDEWALL, THE COMPOSITION OF WHICH COMPRISES A DERIVATIVE OF POLYETHYLENE OXIDE

Abstract

A tire is provided with an external sidewall, the said external sidewall comprising at least one composition based on at least from 15 to 70 phr of isoprene elastomer, from 25 to 85 phr of butadiene elastomer, from 10 to 100 phr of carbon black, from 0.75 to 2.7 phr of polyethylene oxide derivative of general formula (Chem 1) below, in which n is a number within a range extending from 20 to 25, and m is a number within a range extending from 13 to 17, from 0.5 to 10 phr of antiozone wax, and a crosslinking system

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Claims

1.-10. (canceled)

11. A tire provided with an external sidewall, the external sidewall comprising at least one composition based on at least: from 15 to 70 phr of isoprene elastomer; from 25 to 85 phr of butadiene elastomer; from 10 to 100 phr of carbon black; from 0.75 to 2.7 phr of polyethylene oxide derivative of general formula (Chem 1) ##STR00005## in which n is a number within a range extending from 20 to 25, and m is a number within a range extending from 13 to 17; from 0.5 to 10 phr of antiozone wax; and a crosslinking system.

12. The tire according to claim 11, wherein the content of isoprene elastomer is within a range extending from 30 to 60 phr.

13. The tire according to claim 11, wherein the content of butadiene elastomer is within a range extending from 40 to 70 phr.

14. The tire according to claim 11, wherein the total amount of carbon black is within a range extending from 20 to 60 phr.

15. The tire according to claim 11, wherein the polyethylene oxide derivative exhibits a number-average molecular mass Mn within a range extending from 1080 to 1412 g/mol.

16. The tire according to claim 11, wherein the polyethylene oxide derivative is such that n is a number within a range extending from 20 to 23.

17. The tire according to claim 11, wherein the polyethylene oxide derivative is such that m is equal to 15.

18. The tire according to claim 11, wherein the antiozone wax contains from 50% to 75% of linear alkanes comprising from 30 carbon atoms to 38 carbon atoms, with respect to a total amount of linear alkanes.

19. The tire according to claim 11, wherein the amount of antiozone wax is within a range extending from 0.7 to 5 phr.

20. The tire according to claim 11, wherein the at least one composition of the external sidewall further comprises a hydrocarbon resin.

21. The tire according to claim 11, wherein the polyethylene oxide derivative exhibits a number-average molecular mass Mn within a range extending from 1080 g/mol to 1200 g/mol.

22. The tire according to claim 11, wherein the polyethylene oxide derivative is such that n is equal to 20.

23. The tire according to claim 11, wherein the polyethylene oxide derivative has an HLB value of greater than 14.

24. The tire according to claim 11, wherein the polyethylene oxide derivative has an HLB value in the range extending from 14 to 20.

25. The tire according to claim 11, wherein the polyethylene oxide derivative has an HLB value in the range extending from 15 to 17.

Description

[0112] This pneumatic tyre 1 comprises a crown 2 reinforced by a crown reinforcement or belt 6, two external 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 way known per se, formed of at least one ply reinforced by “radial” cords, for example made of textile or metal, that is to say that these cords are positioned virtually parallel to one another 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).

[0113] 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.

[0114] The pneumatic tyre according to the invention can use, for example for the composition of its external sidewall as defined above, a composition in accordance with the present invention.

[0115] The tyre provided with its external sidewall as described above is preferably produced before crosslinking (or curing). The crosslinking is subsequently carried out conventionally.

[0116] An alternative manufacturing form which is advantageous, for a person skilled in the art of pneumatic tyres, will consist, for example during a first stage, 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.

[0117] Tests

[0118] The properties of the elastomer compositions and of some of their constituents are characterized as indicated below.

[0119] Measurement of Ozone Resistance

[0120] The ozone resistance of the materials is measured according to the following method: after curing, 10 test specimens are placed on a trapezium at different elongations ranging from 10% to 100% in steps of 10% elongation. 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 “B 15” test specimens have the following dimensions 78.5 mm*15 mm*1.5 mm. After exposure for 192 hours to a temperature of 38° C. and to an ozone content of 50 pphm (parts per hundred million), each facies is graded as a function of the number and of the depth of the cracks. This subjective grading ranges from 0 to 5 (0: no cracks; 1 to 4: presence of increasingly large and deep cracks; 5: breaking of the test specimen). The mean of the gradings of all the deformations (the lower the mean, the better the ozone performance) is selected as classification criterion.

[0121] Measurement of the Efflorescence Performance

[0122] After an operation of cutting out from the plaques of cured mixture, the test specimens with a thickness of 2.5 mm are stoved at 70° C. under air for 12 h. They are subsequently stoved at 40° C. under air for 4 weeks. After exiting from the stove and exposing to ambient temperature for 15 min, a mechanical stimulus is applied so as to reveal the efflorescence of the wax. In the present case, the mechanical stimulus consists of an operation of scraping the test specimen with a metal blade. The extent of the efflorescence phenomenon (white colouration of the surface) is subsequently evaluated by means of a subjective scale of values which is representative of the final appearance of the samples. The values of this subjective scale which were respectively obtained for the tested samples can vary from 0 to 3 and correspond to the “efflorescence grading”. These values, ranging from 0 to 3, correspond to the following aspects for the samples:

[0123] 0: No efflorescence. The scraped surface remains black.

[0124] 1: Light efflorescence.

[0125] 2: Moderate efflorescence.

[0126] 3: Total efflorescence. The scraped surface is white.

[0127] The lower the value, the better the appearance of the efflorescence performance, that is to say the weaker the efflorescence.

[0128] Evaluation of the Feeling to the Touch

[0129] The feeling to the touch is evaluated by means of a scale of values which is representative of the final appearance of the samples on conclusion of the preceding test. The values of this scale which were respectively obtained for the samples tested can vary from 0 to 3. These values ranging from 0 to 3 correspond to the following appearances for the samples:

[0130] 0: The surface is non-tacky and non-greasy

[0131] 1: The surface is slightly greasy

[0132] 2: The surface is greasy and tacky

[0133] 3: The surface is excessively greasy and tacky: the appearance is totally unacceptable

[0134] The lower the value, the better the feeling to the touch.

Tests

[0135] External sidewall compositions containing ordinary elastomers, reinforcing fillers and additives corresponding to the controls (C1 to C11, Table 1) were prepared according to the methods known to a person skilled in the art and similarly to the preparation of the compositions of the invention described above. These control compositions were compared with compositions (I1 and I2 of Table 1) in accordance with the invention.

[0136] All of the compositions prepared are presented in Table 1. The contents are all expressed in phr.

TABLE-US-00001 TABLE 1 Composition C1 C2 I1 I2 C3 C4 C5 C6 C7 C8 C9 C10 C11 NR (1) 50 50 50 50 50 50 50 50 50 50 50 50 50 BR (2) 50 50 50 50 50 50 50 50 50 50 50 50 50 Carbon black 50 50 50 50 50 50 50 50 50 50 50 50 50 (3) Oil (4) 20 20 20 20 20 20 20 20 20 20 20 20 20 Anti-ozone wax 2 2 2 2 2 2 2 2 2 2 2 2 2 (5) Product 1 (6) — 0.5 1.0 2.5 3.0 — — — — — — — — Product 2 (7) — — — — — 1.0 — — — — — — — Product 3 (8) — — — — — — 1.0 — — — — — — Product 4 (9) — — — — — — — 1.0 — — — — — Product 5 (10) — — — — — — — — 1.0 — — — — Product 6 (11) — — — — — — — — — 1.0 Product 7 (12) — — — — — — — — — — 3.0 5.0 — Product 8 (13) — — — — — — — — — — — — 1.0 Antioxidant (14) 3 3 3 3 3 3 3 3 3 3 3 3 3 Stearic acid 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 Zinc oxide 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Accelerator (15) 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 Sulfur 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 Table 1 references: (1) NR Natural rubber (2) Nd Butadiene rubber (3) Carbon black N683 (BET equal to 36 m.sup.2/g; COAN 85 ml/100 g) (4) MES oil from Exxon Mobil (5) Antiozone wax, “Varazon 4959” from Sasol (6) Product 1: Polyoxyethylene 20 cetyl ether, “Brij C20” from Croda, the HLB value of which is 15.7 and the molar mass of which is 1124 g/mol (7) Product 2: Polyoxyethylene 10 cetyl ether,” Brij C10” from Croda, the HLB value of which is 12.9 and the molar mass of which is 683 g/mol (8) Product 3: Polyoxyethylene 2 cetyl ether, “Brij C2” from Croda, the HLB value of which is 5.3 and the molar mass of which is 330 g/mol (9) Product 4: Polyoxyethylene (9) of C.sub.13-C.sub.15 alcohols, “Synperonic A9” from Croda, the HLB value of which is 12.5 and the average molar mass of which is substantially equal to 610 g/mol (10) Product 5: Polyoxyethylene (11) of C.sub.13-C.sub.15 alcohols, “Synperonic A11” from Croda, the HLB value of which is 13.9 and the average molar mass of which is substantially equal to 698 g/mol (11) Product 6: Polyoxyethylene (40) monostearate, “Myrj S40” from Croda, the HLB value of which is 16.9 and the molar mass of which is 2044 g/mol (12) Product 7: Poly(α-olefin), Vybar 103 from Baker Hughes (13) Product 8: PEG-600, Pluriol E 600 from BASF (14) 6PPD: N-(1,3-Dimethylbutyl)-N′-phenyl-para-phenylenediamin (15) N-Cyclohexyl-2-benzothiazolesulfenamide, Santocure CBS from Solutia

[0137] The compositions were tested according to the tests described above for ozone, efflorescence and touch performance.

[0138] All of the results of the compositions tested are presented in Table 2. nm* indicates values not measured.

TABLE-US-00002 TABLE 2 Performance C1 C2 I1 I2 C3 C4 C5 C6 C7 C8 C9 C10 C11 Ozone 0.0 0.0 0.0 0.0 0.0 nm* nm* nm* nm* nm* nm* 4.8 0.0 Efflorescence 3 3 1 0 0 2 3 3 3 3 2 0 2 Touch 0 0 0 1 3 0 0 0 0 0 0 0 0

[0139] The results presented in Table 2 show that only the compositions I1 and I2 in accordance with the invention make it possible to prevent the efflorescence and the impairment of touch, while exhibiting a very good ozone resistance.