Claims
- 1. A tire tread rubber composition which is comprised of (1) from about 20 phr to about 60 phr of an asymmetrically tin-coupled polybutadiene rubber, (2) from about 20 phr to about 60 phr of a rubber selected from the group consisting of natural rubber and synthetic polyisoprene, (3) from about 5 phr to about 40 phr of high vinyl polybutadiene rubber having a vinyl content of at least about 80 percent, wherein the high vinyl polybutadiene rubber is a high vinyl polybutadiene rubber other than said asymmetrically tin-coupled polybutadiene rubber, (4) from about 10 phr to about 250 phr of silica, (5) from about 5 phr to about 80 phr of carbon black and (6) a silica coupling agent.
- 2. A tire tread rubber composition as specified in claim 1 wherein the silica and the silica coupling agent are mixed into the composition utilizing a thermomechanical mixing technique wherein the rubber composition is maintained at a temperature which is within the range of about 145.degree. C. to about 180.degree. C. for about 4 minutes to about 12 minutes.
- 3. A tire tread rubber composition as specified in claim 2 wherein the total quantity of the silica and the carbon black is at least about 30 phr.
- 4. A tire tread rubber composition as specified in claim 3 wherein said tin-coupled polybutadiene rubber has a Mooney ML 1+4 viscosity at 100.degree. C. which is within the range of about 60 to about 120.
- 5. A tire tread rubber composition as specified in claim 3 wherein said asymmetrically tin-coupled polybutadiene rubber is tin-coupled in a continuous process.
- 6. A tire tread rubber composition as specified in claim 3 wherein said high vinyl polybutadiene rubber has a Mooney ML 1+4 viscosity at 100.degree. C. which is within the range of about 30 to about 100.
- 7. A tire tread rubber composition as specified in claim 4 wherein said member selected from the group consisting of natural rubber and synthetic polyisoprene is natural rubber.
- 8. A tire tread rubber composition as specified in claim 4 wherein said member selected from the group consisting of natural rubber and synthetic polyisoprene is synthetic polyisoprene rubber.
- 9. A tire tread rubber composition as specified in claim 6 wherein the tire tread rubber composition contains from about 25 phr to about 55 phr of the asymmetrically tin-coupled polybutadiene rubber, from about 25 phr to about 55 phr of the rubber selected from the group consisting of natural rubber and synthetic polyisoprene, from about 10 phr to about 30 phr of the high vinyl polybutadiene rubber, from about 15 phr to about 80 phr of the silica and from about 10 phr to about 40 phr of the carbon black.
- 10. A tire tread rubber composition as specified in claim 9 wherein the total quantity of the silica and the carbon black present is within the range of about 45 phr to about 130 phr.
- 11. A tire tread rubber composition as specified in claim 10 wherein the tire tread rubber composition contains from about 30 phr to about 50 phr of the asymmetrically tin-coupled polybutadiene rubber, from about 30 phr to about 50 phr of the rubber selected from the group consisting of natural rubber and synthetic polyisoprene and from about 15 phr to about 25 phr of the high vinyl polybutadiene rubber.
- 12. A tire tread rubber composition as specified in claim 11 wherein the silica has a Bet surface area which is within the range of about 40 to about 600 m.sup.2 /g.
- 13. A tire tread rubber composition as specified in claim 12 wherein the silica has an average particle size which is within the range of 0.01 microns to 0.05 microns as determined with an electron microscope.
- 14. A tire tread rubber composition as specified in claim 13 wherein the high vinyl polybutadiene rubber has a Mooney ML 1+4 viscosity at 100.degree. C. which is within the range of about 60 to about 80.
- 15. A tire tread rubber composition as specified in claim 14 wherein said asymmetrically tin-coupled polybutadiene rubber has a Mooney ML 1+4 viscosity at 100.degree. C. which is within the range of about 75 to about 110.
- 16. A tire tread rubber composition as specified in claim 14 wherein said asymmetrically tin-coupled polybutadiene rubber has a Mooney ML 1+4 viscosity at 100.degree. C. which is within the range of about 80 to about 100.
- 17. A tire tread rubber composition as specified in claim 15 wherein said asymmetrically tin-coupled polybutadiene is of the structural formula: ##STR5## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 can be the same or different and are selected from the group consisting of alkyl groups and polybutadiene arms, with the proviso that at least three members selected from the group consisting of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are polybutadiene arms, with the proviso that at least one member selected from the group consisting of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is a low molecular weight polybutadiene arm having a number average molecular weight of less than about 40,000, with the proviso that at least one member selected from the group consisting of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is a high molecular weight polybutadiene arm having a number average molecular weight of greater than about 80,000 and with the proviso that the ratio of the weight average molecular weight to the number average molecular weight of the asymmetrical tin-coupled polybutadiene rubber is within the range of about 2 to about 2.5.
- 18. A tire tread rubber composition as specified in claim 17 wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are all polybutadiene arms.
- 19. A tire tread rubber composition as specified in claim 17 wherein the low molecular weight polybutadiene arm has a number average molecular weight of less than about 30,000.
- 20. A tire tread rubber composition as specified in claim 19 wherein the high molecular weight polybutadiene arm has a number average molecular weight of greater than about 90,000.
- 21. A tire tread rubber composition as specified in claim 17 wherein the silica and the silica coupling agent are mixed into the composition in the thermomechanical mixing technique while the rubber composition is maintained at a temperature which is within the range of about 155.degree. C. to about 170.degree. C. for about 5 minutes to about 10 minutes.
- 22. A tire tread rubber composition as specified in claim 1 wherein the silica coupling agent is present at a level which is within the range of about 0.01 to about 1.0 parts by weight per part by weight of the silica.
- 23. A tire tread rubber composition as specified in claim 9 wherein the silica coupling agent is present at a level which is within the range of about 0.02 to about 0.4 parts by weight per part by weight of the silica.
- 24. A tire tread rubber composition as specified in claim 17 wherein the silica coupling agent is present at a level which is within the range of about 0.05 to about 0.25 parts by weight per part by weight of the silica.
Parent Case Info
This is a Divisional of application Ser. No. 08/935,172, filed on Sep. 22, 1997, presently pending.
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Number |
Name |
Date |
Kind |
4482678 |
Furukawa et al. |
Nov 1984 |
|
4647614 |
Takao et al. |
Mar 1987 |
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5512626 |
Matsuo et al. |
Apr 1996 |
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Foreign Referenced Citations (2)
Number |
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EPX |
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FRX |
Divisions (1)
|
Number |
Date |
Country |
Parent |
935172 |
Sep 1997 |
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