RUBBER COMPOSITION FOR TYRE TREAD

Abstract

The present invention relates to a a cross-linkable rubber composition, the cross-linkable rubber composition comprising, based upon parts by weight per 100 parts by weight rubber (phr): ≥60 phr to ≤80 phr of a butadiene rubber, a syndiotactic 1,2-polybutadiene, coupling agent, a filler, and a resin, wherein the composition co?prises ≥10 phr to ≤20 phr of the sy?diotactic 1,2-polybutadiene, and wherein the composition comprises ≥1 phr to ≤20 phr of at least two coupling agents wherein one of the coupling agents is or comprises a mercapto based silane and wherein the ratio of the mercapto based silane to the second coupling agent is in the range of ≥2:1 to ≤:10:1.

Claims

1. A cross-linkable rubber composition, the cross-linkable rubber composition comprising, based upon parts by weight per 100 parts by weight rubber (phr): ≥60 phr to ≤80 phr of a butadiene rubber, a syndiotactic 1,2-polybutadiene, coupling agent, a filler, and a resin, wherein the composition comprises ≥0 phr to ≤20 phr of the syndiotactic 1,2-polybutadiene, and wherein the composition comprises ≥1 phr to ≤20 phr of at least two coupling agents wherein one of the coupling agents is or comprises a mercapto based silane and wherein the ratio of the mercapto based silane to the second coupling agent is in the range of ≥2:1 to ≤10:1.

2. The rubber composition according to claim 1, wherein the second coupling agent is selected from disulfide silanes, tetrasulfide silanes or a combination thereof.

3. The rubber composition according to claim 1, wherein the butadiene rubber is selected from polybutadiene, functionalized polybutadiene rubber, ESBR, SSBR, functionalized SSBR, or a combination thereof.

4. The rubber composition according to claim 1, wherein the butadiene rubber is present in an amount of ≥70 to ≤80 phr.

5. The rubber composition according to claim 1, wherein the composition further comprises ≥10 phr to ≤20 phr of a natural rubber.

6. The rubber composition according to claim 1, wherein the filler is selected from carbon blacks, silica, surface treated silica, surface treated carbon blacks or a combination thereof.

7. The rubber composition according to claim 1, wherein the resin is selected from polyterpene resins, terpene phenolic resins, alpha methyl styrene resins or a combination thereof.

8. The rubber composition according to claim 1, wherein the resin is present in an amount ranging from ≥1 to ≤30 phr.

9. A cross-linked rubber composition, wherein it is obtained by cross-linking a rubber composition according to claim 1.

10. The cross-linked rubber composition according to claim 9 with a G′ at 0° C. (measured by DMA as per ISO 4664-1) ranging from 22 to 38 MPa.

11. The cross-linked rubber composition according to claim 9 with a rebound value at 23° C. (as per ISO 4662) ranging from ≥8% to ≤15%.

12. A method of preparing a tyre, comprising the steps of: providing a tyre assembly comprising a cross-linkable rubber composition according to claim 1; and cross-linking at least the cross-linkable rubber composition in the tyre assembly.

13. A tyre comprising a tread, wherein the tread comprises a cross-linked rubber composition according to claim 9.

14. Use of the cross-linked rubber composition according to claim 9 for increasing the wet grip of a tyre.

15. Use of a syndiotactic 1,2-polybutadiene and at least two coupling agents wherein one of the coupling agents is or comprises a mercapto based silane for increasing the wet grip of a tyre.

Description

EXAMPLE 1

[0052] The table below shows the composition I1 in comparison to a reference composition R1 wherein the Nd-Butadiene rubber was replaced with a syndiotactic 1,2-butadiene rubber and the compositions had a high loading of silica.

TABLE-US-00001 Reference R1 I1 amount Components (PHR) (PHR) NR 15.00 15.00 Nd-BR 15.00 0.00 Syndiotactic 1,2-butadiene 0.00 15.00 BR 70.00 70.00 Filler 80.00 80.00 Coupling Agent 1 8.00 8.00 Coupling agent 2 2.00 2.00 Resin 15.00 15.00

[0053] The following table shows the results obtained from the cured compositions of table 1:

TABLE-US-00002 Result R1 I1 Hardness (median) ° Sh A 67.00 77.70 M25% MPa 1.49 2.45 M100% MPa 5.76 7.64 Rebound (23° C.) % 18.00 11.50 G′ (0° C.) MPa 11.50 36.48 Tan (70° C.) .08 .08

[0054] The results show a reduction in rebound at 23 degrees from 18.00 to 11.50 and increase in G′ at 0° C. from 11.50 to 36.50. The reduction in rebound and increase in G′ are well known indicators of increase in the wet grip in the tyre industry.

[0055] Improvement was also observed in compound consistency during dump after mixing in Banbury mixer in the form of lumps and not in crumb or small pieces of compound. For sheeting at the mill no bagging at the mill nip and no holes in band were formed on mill roller with good sheet surface.

[0056] Increase in the stiffness of the cured rubber was also observed by measuring modulus M25% and M100% (static stiffness) and DMA G′ (0° C.) and G′ (70° C.) (dynamic stiffness). Further, the replacement of Nd-Butadiene rubber with a syndiotactic 1,2-butadiene rubber resulted in an increase in hardness.

[0057] The hysteresis of compound was measured using DMA and values of tan δ @70° C. indicates that the hysteresis is maintained after addition of syndiotactic 1,2-butadiene polymer.

EXAMPLE 2

[0058] The table below shows the composition I2 in comparison to a reference composition R2 wherein the Nd-Butadiene rubber was replaced with a syndiotactic 1,2-butadiene rubber and the amount of silica had been reduced in both the compositions.

TABLE-US-00003 Reference R2 I2 amount Components (PHR) (PHR) NR 15.00 15.00 Nd-BR 15.00 0.00 Syndiotactic 1,2-butadiene 0.00 15.00 BR 70.00 70.00 Filler 55.00 55.00 Coupling Agent 1 5.50 5.50 Coupling agent 2 2.00 2.00 Resin 15.00 15.00

[0059] The following table shows the results obtained from the cured compositions of the table 3:

TABLE-US-00004 Result R2 I2 Hardness (median) ° Sh A 60.40 70.60 M25% MPa 0.99 1.83 M100% MPa 3.43 6.04 Rebound (23° C.) % 22.90 11.60 G′ (0° C.) MPa 5.61 23.68 Tan (70° C.) .06 .06

[0060] As can be seen from this table, results were better for the rubber composition when Nd-Butadiene rubber was replaced with a syndiotactic 1,2-butadiene rubber.

[0061] Such cross-linked rubber compositions are particularly usable for manufacturing a tyre tread compounds. These compositions can further be used to manufacture tread cap compounds or secondary tread compounds.