RUBBER COMPOSITION AND A TIRE

Abstract

In a first aspect, the present invention is directed to a rubber composition comprising 70 phr to 95 phr of styrene butadiene rubber comprising at least 5 phr of a first styrene butadiene rubber having a glass transition temperature within a range of −49° C. to −15° C. and at least 45 phr of a second styrene butadiene rubber having a glass transition temperature within a range of −50° C. to −89° C., wherein the rubber composition comprises more of the second styrene butadiene rubber than of the first styrene butadiene rubber. Moreover, the rubber composition comprises 5 phr to 30 phr of one or more of natural rubber and synthetic polyisoprene; 135 phr to 200 phr of silica; and at least 55 phr of at least one hydrocarbon resin comprising at least one terpene resin having a glass transition temperature of at least 30° C.

Claims

1. A rubber composition comprising: 70 phr to 95 phr of styrene butadiene rubber comprising at least 5 phr of a first styrene butadiene rubber having a glass transition temperature within a range of −49° C. to −15° C. and at least 45 phr of a second styrene butadiene rubber having a glass transition temperature within a range of −50° C. to −89° C., wherein the rubber composition comprises more of the second styrene butadiene rubber than of the first styrene butadiene rubber; 5 phr to 30 phr of at least one member selected from the group consisting of natural rubber and synthetic polyisoprene rubber; 135 phr to 200 phr of silica; and at least 55 phr of at least one hydrocarbon resin comprising at least one terpene resin which has a glass transition temperature of at least 30° C.

2. The rubber composition according to claim 1, wherein the rubber composition comprises at least 60 phr of the at least one hydrocarbon resin.

3. The rubber composition according to claim 1, wherein the terpene resin is an alpha pinene based terpene resin.

4. The rubber composition according to claim 1, wherein said terpene resin has one or more of: i) a softening point within a range of 100° C. to 150° ; ii) a glass transition temperature within a range of 35° C. and 90° C.; and iii) a weight average molecular weight Mw within a range of 500 g/mol to 1000 g/mol.

5. The rubber composition according to claim 1, wherein the terpene resin is one or more of i) non-hydrogenated, and ii) free of aromatic modifications.

6. The rubber composition according to claim 1, comprising from 140 phr to 200 phr of the silica.

7. The rubber composition according to claim 1, wherein the first and the second styrene butadiene rubbers are solution polymerized styrene butadiene rubbers.

8. The rubber composition according to claim 1, wherein the second styrene butadiene rubber has a glass transition temperature higher than −70° C.

9. The rubber composition according to claim 1, wherein the silica has a BET surface area within a range of 150 m.sup.2/g to 220 m.sup.2/g.

10. The rubber composition according to claim 1, further comprising one or more of: from 0.1 phr to 10 phr of carbon black; from 10 phr to 20 phr of silane; from 10 phr to 20 phr of a blocked mercapto silane; and from 0 phr to 9 phr of liquid plasticizers.

11. The rubber composition according to claim 1, further comprising from 8 phf to 15 phf of a blocked mercapto silane.

12. The rubber composition according claim 1, comprising from 1 phr to 7 phr of a vegetable oil.

13. The rubber composition according to claim 1, wherein one or both of the first styrene butadiene rubber and the second styrene butadiene rubber comprise at least one functional group configured for the coupling to the silica.

14. The rubber composition according to claim 1, wherein one of the first styrene butadiene rubber and the second styrene butadiene rubber is end chain functionalized with an amino silane group on at least one of its ends, and wherein the other one of the first styrene butadiene rubber and the second styrene butadiene rubber is end chain functionalized on at least one of its ends with an amino siloxane group.

15. The rubber composition according to claim 1, wherein the first styrene butadiene rubber has a glass transition temperature within a range of −20° C. to −40° C. and the second styrene butadiene rubber has a glass transition temperature within a range of −55° C. and −69° C.

16. The rubber composition according to claim 1, wherein the glass transition temperature of the rubber composition is within a range of −25° C. and −15° C.

17. A tire comprising the rubber composition according to claim 1.

18. The tire according to claim 17, wherein the tire comprises a tread including said rubber composition.

19. The tire according to claim 17, wherein the tire is a summer tire.

20. The tire according to claim 17, wherein the tire has a speed symbol selected from W and Y.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The structure, operation, and advantages of the invention will become more apparent upon contemplation of the following description taken in conjunction with the accompanying drawing, wherein:

[0061] FIG. 1 is a schematic cross section of a tire comprising a tread and further rubber components.

DETAILED DESCRIPTION OF THE INVENTION

[0062] FIG. 1 is a schematic cross-section of a tire 1. The tire 1 has a tread 10, an inner liner 13, a belt structure comprising four belt plies 11, a carcass ply 9, two sidewalls 2, and two bead regions 3 comprising bead filler apexes 5 and beads 4. The example tire 1 is suitable, for example, for mounting on a rim of a vehicle, e.g. a truck or a passenger car. As shown in FIG. 1, the belt plies 11 may be covered by an overlay ply 12. The carcass ply 9 includes a pair of axially opposite end portions 6, each of which is associated with a respective one of the beads 4. Each axial end portion 6 of the carcass ply 9 may be turned up and around the respective bead 4 in a position to anchor each axial end portion 6 of the carcass ply 9. The turned-up portions 6 of the carcass ply 9 may engage the axial outer surfaces of two flippers 8 and axial inner surfaces of two chippers 7. As shown in FIG. 1, the example tread 10 may have four circumferential grooves, each groove essentially defining a U-shaped opening in the tread 10. The tread 10 comprises one or more tread compounds as described herein in accordance with various embodiments of the invention.

[0063] While the embodiment of FIG. 1 suggests a plurality of tire components including for instance apexes 5, chippers 7, flippers 8 and an overlay 12, such components are not mandatory for the invention. Also, the turned-up end of the carcass ply 9 is not necessary for the invention or may pass on the opposite side of the bead area 3 and end on the axially inner side of the bead 4 instead of the axially outer side of the bead 4. The tire could also have for instance more or less than four grooves. The present invention shall not be limited to the example of the tire 1 depicted and described in accordance with FIG. 1.

[0064] Preferred examples of a rubber composition, such as for a tire tread, which are in accordance with preferred embodiments of the invention are shown in the upper section of TABLE 1 as Inventive Examples 1 and 2 in comparison with a Comparative Example (not in accordance with the present invention).

[0065] In the lower section of TABLE 1, test results are shown for tires having one of the rubber compositions according to the Comparative Example and the Inventive Examples in the tire tread, wherein the tested tires have the same tire construction. The tire test results for rolling resistance, wet braking, and treadwear have been normalized to the respective performance of the Comparative Example.

[0066] As shown in the upper section of TABLE 1, the Inventive Examples comprise a polymer matrix based on a high glass transition temperature and solution-polymerized styrene butadiene rubber and a low glass transition temperature, solution-polymerized styrene butadiene rubber together with natural rubber, whereas the Comparative Example comprises one solution polymerized styrene butadiene rubber with a relatively high glass transition temperature in combination with a lower glass transition temperature polybutadiene and natural rubber. Moreover, the silica and silane contents of the Inventive Examples are higher than the silica content of the Comparative Example. Remarkably, the resin level of the Inventive Examples is considerably higher than the resin level in the Comparative Example.

[0067] As indicated in the lower section of TABLE 1, rolling resistance, wet braking and tread wear have been significantly improved for the Inventive Examples compared to the Comparative Example. While the values for rolling resistance and wet braking are even better for Inventive Example 2 compared to Inventive Example 1, the tread wear is significantly better in Inventive Example 1 than in Inventive Example 2. Thus, Inventive Example 1 has a good balance of said three properties with an emphasis on tread wear, whereas Inventive Example 2 has advantages over Inventive Example 1 in wet braking. Nevertheless, both Inventive Examples have an overall good balance of the three determined properties.

TABLE-US-00001 TABLE 1 Comparative Inventive Inventive Example Example 1 Example 2 phr Materials PBD.sup.1 10 0 0 SBR 1.sup.2 110 0 0 SBR 2.sup.3 0 70 53 SBR 3.sup.4 0 10 27 NR.sup.5 10 20 20 Silica.sup.6 130 145 145 Oil 1.sup.7 4 0 0 Oil 2.sup.8 0 3 4 Silane 1.sup.9 10.5 14.5 14.5 Silane 2.sup.10 1 1 1 Tackifyer.sup.11 2 0 0 Resin 1.sup.12 22 63 20 Resin 2.sup.13 0 0 43 Antidegradants.sup.14 4.6 5.5 5.5 Rosin 2 0 0 Waxes 1.5 3 2 Sulfur 0.7 1 1 Vulcanization agents.sup.15 4.3 5.9 5.9 Stearic Acid 1 2.5 2.5 Zinc soap 2 2 2 Zinc Oxide 1 1.1 1.1 Carbon black 1 1 1 Properties Rolling Resistance .sup.a 100 107 108 Wet Braking .sup.b 100 108 111 Tread wear .sup.c 100 122 117 .sup.1Polybutadiene rubber as Budene ™ 1223 from Goodyear .sup.2SSBR as SLR6430 from Trinseo, including 20 phr of TDAE extension oil in the 110 phr listed here, having a Tg of about −36° C. .sup.3Thio-functionalized, solution-polymerized styrene butadiene rubber as SLR3402 from Trinseo, having a Tg of −62° C. .sup.4Amino silane-functionalized, solution-polymerized styrene butadiene rubber as HPR355H from JSR, having a Tg of −27° C. .sup.5Natural rubber .sup.6Precipitated silica as Zeosil ™ 1165 MP with a BET surface area of about 160 m.sup.2/g .sup.7TDAE oil .sup.8Sunflower oil .sup.93-Octanoylthio-1-propyltriethoxysilane as NXT ™ from Momentive .sup.10Bis-triethoxysilylpropyl tetrasulfide as SI 69 from Evonik .sup.11SP 1068 from Akrochem .sup.12Alpha pinene based terpene resin as Dercolyte ™ A115 from DRT .sup.13C9 modified C5 resin as Oppera ™ PR 373 from Exxon Mobil .sup.14P-phenylene diamines and dihydroquinolines .sup.15including benzothiazolesulfenamides, diphenylguanidine, BDBzTH, N-cyclohexylthiophthalimide .sup.a Relative tire test results, normalized to the Comparative Example (higher is better) .sup.b Relative tire test results, normalized to the Comparative Example (higher is better) .sup.c Relative tire test results, normalized to the Comparative Example (higher is better)

[0068] While certain representative embodiments, examples and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the invention. It is, therefore, to be understood that changes may be made in the particular example embodiments described which will be within scope of the invention as defined by the following appended claims. In any case, the above described embodiments and examples shall not be understood in a limiting sense.