Rubber composition for tire tread and pneumatic tire
View Patent ↗A rubber composition for a tire tread of the present technology comprises a rubber component containing not less than 30 mass % of a conjugated diene-based rubber (A), a silica (B), and a predetermined alkyltriethoxysilane (C), the conjugated diene-based rubber (A) containing not less than 5 mass % of a specified structural member (a), the silica (B) having a nitrogen adsorption specific surface area (N 2 SA) from 194 to 225 m 2 /g and a CTAB adsorption specific surface area (CTAB) from 180 to 210 m 2 /g, a content of the silica (B) being from 60 to 150 parts by mass per 100 parts by mass of the rubber component, and a content of the alkyltriethoxysilane (C) being from 2.5 to 8.0 mass % relative to the silica (B).
1. A rubber composition for a tire tread comprising:
a rubber component containing not less than 30 mass % of a conjugated diene-based rubber (A);
a silica (B); and
an alkyltriethoxysilane (C) represented by the following formula (I),
wherein R is an alkyl group having from 8 to 18 carbons,
the conjugated diene-based rubber (A) containing not less than 5 mass % of a structural member (a), in which not less than three conjugated diene-based polymer chains (a1) are bonded via a modifier (a2), obtained by a reaction of the conjugated diene-based polymer chains (a1) and the modifier (a2);
the conjugated diene-based polymer chain (a1) including an isoprene block containing not less than 70 mass % of isoprene units on one terminal and containing an active terminal on the other terminal;
the modifier (a2) including at least one group selected from an epoxy group and a hydrocarbyloxysilyl group, a total number of the epoxy groups and hydrocarbyloxy groups contained in the hydrocarbyloxysilyl group being not less than three;
the silica (B) having a nitrogen adsorption specific surface area from 194 to 225 m 2 /g and a cetyl trimethyl ammonium bromide (CTAB) adsorption specific surface area from 180 to 210 m 2 /g;
a content of the silica (B) being from 60 to 150 parts by mass per 100 parts by mass of the rubber component; and
a content of the alkyltriethoxysilane (C) being from 3.0 to 7.0 mass % relative to the silica (B).
2. The rubber composition for a tire tread according to claim 1 , wherein the modifier (a2) is a polyorganosiloxane.
3. The rubber composition for a tire tread according to claim 2 , wherein a vinyl bond content derived from an isoprene unit in the isoprene block is from 21 to 85 mass %.
4. The rubber composition for a tire tread according to claim 1 , wherein a vinyl bond content derived from an isoprene unit in the isoprene block is from 21 to 85 mass %.
5. The rubber composition for a tire tread according to claim 1 , wherein the composition contains bis(3-triethoxysilylpropyl)tetrasulfide as a silane coupling agent.
6. The rubber composition for a tire tread according to claim 1 , wherein the alkyltriethoxysilane (C) comprises octyltriethoxysilane.
7. The rubber composition for a tire tread according to claim 1 , wherein the rubber component contains 30 to 90 mass % of the conjugated diene-based rubber (A).
8. The rubber composition for a tire tread according to claim 7 , wherein the composition contains bis(3-triethoxysilylpropyl)tetrasulfide as a silane coupling agent.
9. The rubber composition for a tire tread according to claim 7 , wherein the silica (B) has a nitrogen adsorption specific surface area from 213 to 225 m 2 /g.
10. The rubber composition for a tire tread according to claim 9 , wherein the composition contains bis(3-triethoxysilylpropyl)tetrasulfide as a silane coupling agent.
11. The rubber composition for a tire tread according to claim 1 , wherein the silica (B) has a nitrogen adsorption specific surface area from 213 to 225 m 2 /g.
12. The rubber composition for a tire tread according to claim 11 , wherein the composition contains bis(3-triethoxysilylpropyl)tetrasulfide as a silane coupling agent.
13. The rubber composition for a tire tread according to claim 1 , wherein the nitrogen adsorption specific surface area of the silica (B) is 213 m 2 /g.
14. A pneumatic tire comprising a tire tread formed using the rubber composition for a tire tread described in claim 1 .
15. A pneumatic tire comprising a tire tread formed using the rubber composition for a tire tread described in claim 2 .
16. A pneumatic tire comprising a tire tread formed using the rubber composition for a tire tread described in claim 4 .