Rubber composition for tire tread and pneumatic tire using the same
A rubber composition for a tire tread is disclosed, which provides a tire excellent in wet grip performance at low temperatures and wet grip performance at high temperatures. The rubber composition for a tire tread includes, per 100 parts by mass of diene-based rubbers including (a) 30 to 50 parts by mass of a styrene butadiene rubber having a glass transition point of −35° C. or more, (b) 20 to 40 parts by mass of a styrene butadiene rubber having a glass transition point of −45° C. or more and less than −35° C., and (c) 10 to 30 parts by mass of a styrene butadiene rubber having a glass transition point of −65° C. or more and less than −45° C.: 80 to 140 parts by mass of silica; and 15 to 50 parts by mass of a thermoplastic resin having a softening point of 40° C. or more.
1 . A rubber composition for a tire tread, comprising, per 100 parts by mass of diene-based rubbers including
(a) 30 to 50 parts by mass of a styrene butadiene rubber having a glass transition point of −35° C. or more,
(b) 20 to 40 parts by mass of a styrene butadiene rubber having a glass transition point of −45° C. or more and less than −35° C., and
(c) 10 to 30 parts by mass of a styrene butadiene rubber having a glass transition point of −65° C. or more and less than −45° C.:
80 to 140 parts by mass of silica; and
15 to 50 parts by mass of a thermoplastic resin having a softening point of 40° C. or more.
2 . The rubber composition for a tire tread according to claim 1 , wherein the styrene butadiene rubber (a) and the styrene butadiene rubber (b) each have a styrene content of 30 mass % or more.
3 . The rubber composition for a tire tread according to claim 1 , wherein the thermoplastic resin is a styrene-based resin or a terpene-based resin.
4 . The rubber composition for a tire tread according to claim 2 , wherein the thermoplastic resin is a styrene-based resin or a terpene-based resin.
5 . The rubber composition for a tire tread according to claim 1 , having a storage modulus at −5° C. of 150 MPa or less.
6 . The rubber composition for a tire tread according to claim 2 , having a storage modulus at −5° C. of 150 MPa or less.
7 . The rubber composition for a tire tread according to claim 1 , comprising 5 to 20 parts by mass of a protected mercaptosilane per 100 parts by mass of silica.
8 . The rubber composition for a tire tread according to claim 2 , comprising 5 to 20 parts by mass of a protected mercaptosilane per 100 parts by mass of silica.
9 . A pneumatic tire using the rubber composition according to claim 1 in a tread thereof.
10 . A pneumatic tire using the rubber composition according to claim 2 in a tread thereof.