RUBBER COMPOSITION AND A TIRE

Abstract

In a first aspect, the present invention is directed to a rubber composition comprising 70 phr to 90 phr of styrene butadiene rubber, wherein said styrene butadiene rubber comprises a first styrene butadiene rubber having a glass transition temperature within a range of −49° C. to −15° C. and a second styrene butadiene rubber having a glass transition temperature within a range of −50° C. to −89° C. Furthermore, the rubber composition comprises from 10 phr to 30 phr of one or more of natural rubber and synthetic polyisoprene rubber, 100 phr to 200 phr of silica, and at least 25 phr of at least one terpene resin having a weight average molecular weight (Mw) of at most 1000 g/mol. Moreover, the invention is directed to a tire comprising such a rubber composition, in particular in the tread of the tire.

Claims

1. A rubber composition comprising: 70 phr to 90 phr of styrene butadiene rubber comprising a first styrene butadiene rubber having a glass transition temperature within a range of −49° C. to −15° C. and a second styrene butadiene rubber having a glass transition temperature within a range of −50° C. to −89° C.; 10 phr to 30 phr of one or more of natural rubber and synthetic polyisoprene; 100 phr to 200 phr of silica; and at least 25 phr of at least one terpene resin having a weight average molecular weight of at most 1000 g/mol.

2. The rubber composition according to claim 1 wherein the resin has a softening point within a range of 100° C. to 150° C. and a weight average molecular weight within a range of 500 g/mol to 1000 g/mol.

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

4. The rubber composition according to claim 1 wherein the silica comprises a BET surface area within a range of 150 m.sup.2/g to 190 m.sup.2/g.

5. The rubber composition according to claim 1 wherein the rubber composition comprises from 115 phr to 145 phr of the silica.

6. 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.

7. The rubber composition according to claim 1 comprising at most 9 phr of liquid plasticizers.

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

9. The rubber composition according claim 1 comprising from 1 phr to 7 phr of oil.

10. The rubber composition according to claim 1 wherein said styrene butadiene rubber comprises at least 10 phr more of the second styrene butadiene rubber than of the first styrene butadiene rubber, and at least 20 phr of the first styrene butadiene rubber.

11. The rubber composition according to claim 1 comprising 15 phr to 25 phr of natural rubber or synthetic polyisoprene.

12. The rubber composition according to claim 1 wherein one or more of the first styrene butadiene rubber and the second styrene butadiene rubber comprises at least one functional group configured for the coupling to the silica.

13. The rubber composition according to claim 1 wherein 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 at 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, at least one of its ends, with an amino siloxane group.

15. The rubber composition of claim 1 wherein the first styrene butadiene rubber has a glass transition temperature within a range of −25° 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 of claim 1 comprising from 30 phr to 50 phr of the resin.

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

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

19. The tire of claim 18, wherein the tire comprises a tread including said rubber composition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] 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:

[0054] FIG. 1 is a schematic cross section of a tire comprising a tread and further rubber components.

DETAILED DESCRIPTION OF THE INVENTION

[0055] 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 to a position to anchor each axial end portion 6. 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 embodiments of the invention.

[0056] 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.

[0057] 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 to 3 in comparison with a Comparative Example (not in accordance with the present invention). In the lower section of TABLE 1, test results are shown for tires having the different rubber compositions of the Comparative Example and the Inventive Examples in a tire tread of tires with same construction. The tire test results for rolling resistance, wet braking, dry braking and wet handling have been normalized to the respective performance of the Comparative Example.

[0058] As shown in the upper section of TABLE 1, the comparative sample comprises a low Tg solution polymerized styrene butadiene rubber in combination with a natural rubber. The rubber matrix of the Inventive Examples is based on a combination of a low Tg solution polymerized styrene butadiene rubber in combination with a high Tg solution polymerized styrene butadiene rubber. In particular, such a combination helps to achieve a higher compound Tg which supports an advanced wet performance. Moreover, having two SBRs with high Tg and low Tg helps to obtain a good abrasion resistance compared to the use of a single higher Tg rubber, in particular a high Tg SBR. Inventive Examples 1 and 2 comprise a silica with a higher surface area in comparison with the Comparative Example 1 and the Inventive Example 3. Moreover, all Inventive Examples include increased amounts of silane compared to the Comparative Example, which is deemed to further increase the rolling resistance performance in view of the utilized silane 1. While the Comparative Example relies on an aromatic modified petroleum hydrocarbon resin, the Inventive Examples use a terpene resin which has been found to further improve the rolling resistance performances. Moreover, it has been found that the low Mw of such resins helps to improve the wet performance and rolling resistance balance, in particular in the relatively high amounts used. Also, such a resin has a good miscibility whereas higher Mw resins may result in a phase separation which is deemed detrimental to rolling resistance performance. BDBzTH is not deemed to have an impact on the rolling resistance or wet and dry performances discussed herein but has rather been used with regards to advance wear properties, in particular to improve abrasion resistance. Remarkably, all Examples comprise limited amounts of oil (some including extension oil) which helps to improve tensile properties.

[0059] As shown in the lower section of TABLE 1, all three Inventive Examples result in improved rolling resistance test results. In addition the first and the third Inventive Example result also in better wet and dry braking performances, whereas Inventive Example 2 remains at the same level as the Comparative Example. Despite the advance wet and dry braking performance of the first and the third inventive examples, the wet handling performance of the first Inventive Example is on a lower level than the same performance of the Comparative Example 1. I n the present comparison only the third Inventive Example maintains also the wet handling performance on the same level as the Comparative Example. Overall, all inventive examples show an improved balance of rolling resistance combined with wet and dry braking performance.

TABLE-US-00001 TABLE 1 Rubber Compositions Comparative Inventive Inventive Inventive Example 1 Example 1 Example 2 Example 3 Ingredient phr SSBR.sup.1 80 0 0 0 Natural Rubber 20 20 20 20 SSBR.sup.2 0 10 0 0 SSBR.sup.3 0 0 30 30 SSBR.sup.4 0 73.5 52.5 52.5 Silica 1.sup.5 0 125 110 0 Silica 2.sup.6 120 0 0 120 Silane 1.sup.7 12 15 13.2 14.4 Silane 2.sup.8 1 1 1 1 Resin 1.sup.9 38 0 0 0 Resin 2.sup.10 0 43 39 39 BDBzTH.sup.11 0 1.5 2.2 2.2 Antidegradants.sup.12 5.5 5.5 5.5 5.5 Oil 4 0 0 2 Waxes 2.25 2.25 2.25 2.25 Sulfur 0.8 0.8 0.6 0.6 Accelerators.sup.13 3.5 2.2 2.2 2.2 Stearic Acid 2.5 2.5 2.5 2.5 Zinc soap 2 2 2 2 Zinc Oxide 1.1 1 1.1 1.1 Tire test results Rolling 100 104 107 106 WET Braking.sup.b 100 103 100 106 DRY Braking.sup.c 100 102 100 103 WET Handling.sup.d 100 93 95 100 .sup.1Thio-functionalized, solution-polymerized styrene butadiene rubber as SLR3402 from Trinseo, having a Tg of −62° C. .sup.2Amino silane-functionalized, solution-polymerized styrene butadiene rubber as HPR355H from JSR, having a Tg of −27° C. .sup.3Amino silane-functionalized, solu tion-polymerized styrene butadiene rubber as SOL 5251H from KKPC, havii ig a Tg of −34° C. .sup.4Amino siloxane-functionalized, solution-polymerized styrene butadiene rubber as F1038 from LG Chem, having a Tg of −62° C., with 5% oil extension by weight .sup.5Precipitated silica as Zeosil ™ Premium 200MP with a BET surface area of about 215 m.sup.2/g .sup.6 Precipitated silica as Zeosil ™ 1165 MP with a BET surface area of about 160 m.sup.2/g .sup.73-Octanoylthio-l-propyltriethoxysilane as NXT from Momentive .sup.7Bis-triethoxysilylpropyl tetrasulfide as SI 69 from Evonik .sup.850% bis-triethoxysilylpropyl tetrasulfide on 50% N330 carbon black carrier, as X50S from Evonik .sup.9Aromatic modified petroleum hydrocarbon resin as Oppera ™ PR373 from Exxon Mobile, having a weight average molecular weight of 1500 g/mol .sup.10Alpha pinene based terpene resin as Dercolyte Al 15 from DRT, having a weight average molecular weight of about 600 g/mol .sup.111,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane as Vulcuren ™ from Lanxess .sup.12Mixed p-phenylene diamine type .sup.13Sulfenamide and guanidine types .sup.aRelative tire test results, normalized to Comparative Example 1 (higher is better) .sup.bRelative tire test results, normalized to Comparative Example 1 (higher is better) .sup.cRelative tire test results, normalized to Comparative Example 1 (higher is better) .sup.dRelative tire test results, normalized to Comparative Example 1 (higher is better)

[0060] Variations in the present invention are possible in light of the provided description. 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.