Rubber composition for tyres with low rolling resistance and good winter properties
The present invention relates to a cross-linkable rubber composition, a cross-linked rubber composition obtained by cross-linking such a rubber composition, a method of preparing a tyre and a tyre. In a cross-linkable rubber composition the cross-linkable rubber composition comprises, per hundred parts by weight of rubber (phr): ≤50 phr of a first rubber, the first rubber being a solution polymerized styrene-butadiene rubber (SSBR) comprising an alkoxysilane group and a primary amino group; ≥20 phr of a second rubber; and a coupling agent, a filler, and a resin, wherein the rubber composition comprises ≥15 phr of a third rubber; and ≥10 phr of a fourth rubber; 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 a range of ≥2:1 to ≤10:1.
1 . A cross-linkable rubber composition, the cross-linkable rubber composition comprising, per hundred parts by weight of rubber (phr):
≥10 phr to ≤40 phr of a first rubber, the first rubber being a solution polymerized styrene-butadiene rubber (SSBR) comprising an alkoxysilane group and a primary amino group;
≥20 phr to ≤40 phr of a second rubber, the second rubber being a butadiene rubber (BR) with a cis group content, as determined by infrared spectroscopy (IR), of ≥90%;
≥15 phr to ≤30 phr of a third rubber, the third rubber being a solution polymerized styrene-butadiene rubber (SSBR) having a glass transition temperature Tg of ≥−120° C. to ≤−40° C., the glass transition temperature Tg being measured by differential scanning calorimetry (DSC) according to ISO 22768; and
≥10 phr to ≤20 phr of a fourth rubber, the fourth rubber being a natural rubber; and a coupling agent, a filler, and a resin,
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 a range of ≥2:1 to ≤10:1.
2 . The rubber composition according to claim 1 , wherein the second and the fourth rubber have a glass transition temperature Tg of ≥−120° C. to ≤−40° C., the glass transition temperature Tg being measured by differential scanning calorimetry (DSC) according to ISO 22768.
3 . The rubber composition according to claim 1 , wherein the second coupling agent is selected from disulfide silanes, tetrasulfide silanes or a combination thereof.
4 . The rubber composition according to claim 1 , wherein the composition comprises ≥1 phr of an aliphatic or aromatic resin.
5 . The rubber composition according to claim 1 , wherein the composition comprises ≥60 phr≤130 phr of silica.
6 . A cross-linked rubber composition, characterised in that it is obtained by cross-linking a rubber composition according to claim 1 .
7 . The cross-linked rubber composition according to claim 6 , with a tan delta at 0° C. of ≥0.2 to ≤0.5 (determined from dynamic mechanical analysis (DMA) measurements according to ISO 4664-1, frequency 10 Hz, 0.1% dynamic strain) and a tan delta at 70° C. of ≥0.05 to ≤0.15 (determined from DMA measurements according to ISO 4664-1, frequency 10 Hz, 6% dynamic strain).
8 . The cross-linked rubber composition according to claim 6 , having a rebound at 70° C., determined according to ISO 4662, of ≥60% to ≤75%.
9 . A method of preparing a tyre, comprising the steps of:
providing a tyre assembly comprising a rubber composition according to claim 1 ;
cross-linking at least the rubber composition in the tyre assembly.
10 . A tyre comprising a tyre tread, characterised in that the tyre tread comprises a cross-linked rubber composition according to claim 6 .