| 摘要 |
PROBLEM TO BE SOLVED: To provide a rubber composition for a tire tread, having low heat-generating properties compatible with wet performances at a high degree.SOLUTION: A rubber composition for a tire tread contains a rubber constituent comprising at least 2 kinds of styrene-butadiene copolymer rubbers having the different bonded styrene content and a filler, and the difference {St(A)-St(B)} between the bounded styrene content St(A) of the styrene-butadiene copolymer rubber (A) having high bounded styrene content and the bounded styrene content St(B) of the styrene-butadiene copolymer rubber (B) having low bounded styrene content is 6 to 22 mass%, tanδ at 0°C is 0.95 or more and a value obtained by dividing the absolute value of the difference between tanδ at -5°C and that at 5°C by the temperature difference between -5°C and 5°C, {|(tanδ at -5°C)-(tanδ at 5°C)|/10}(/°C) is 0.045/°C or lower. A measurement method of the bounded styrene content (mass%): it is calculated from an integration ratio ofH-NMR spectrum. A measurement method of tanδ: values of tanδ at -25°C to 80°C with the frequency of 52 Hz, the initial strain of 2%, the dynamic strain of 1%, and the rate of the temperature increase of 3°C/minute is measured by using a dynamic tension viscoelasticity measurement testing machine. |
