US 12,187,894 B2
Rubber composition and pneumatic tire
Ryota Kitago, Kobe (JP); Rie Yasuda, Kobe (JP); and Shogo Hirao, Kobe (JP)
Assigned to Sumitomo Rubber Industries, Ltd., Hyogo (JP)
Appl. No. 17/291,382
Filed by Sumitomo Rubber Industries, Ltd., Hyogo (JP)
PCT Filed Oct. 15, 2019, PCT No. PCT/JP2019/040356
§ 371(c)(1), (2) Date May 5, 2021,
PCT Pub. No. WO2020/100492, PCT Pub. Date May 22, 2020.
Claims priority of application No. 2018-212210 (JP), filed on Nov. 12, 2018.
Prior Publication US 2022/0017729 A1, Jan. 20, 2022
Int. Cl. C08L 9/06 (2006.01); B60C 1/00 (2006.01); C08K 3/04 (2006.01); C08K 3/36 (2006.01); C08L 15/00 (2006.01); C08L 91/00 (2006.01)
CPC C08L 9/06 (2013.01) [B60C 1/0016 (2013.01); C08K 3/04 (2013.01); C08K 3/36 (2013.01); C08L 15/00 (2013.01); C08L 91/00 (2013.01)] 16 Claims
 
1. A rubber composition, comprising a rubber component that includes a copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound,
the rubber composition comprising, per 100 parts by mass of the rubber component therein, 30 parts by mass or more of at least two different softeners, and
the rubber composition contains 5 parts or less by mass of an oil per 100 parts by mass of the rubber component,
the rubber composition having a heat aging resistance index defined by the following equation (1) of 10 or less,
Heat aging resistance index=[(Hardness of rubber composition after heat treatment)−(Hardness of rubber composition before heat treatment)]/(Hardness of rubber composition before heat treatment)×100  (1)
wherein each hardness represents the JIS-A hardness at 25° C. of the corresponding rubber composition, and the heat treatment involves allowing the rubber composition to stand at a temperature of 90° C. and an oxygen concentration of 20% for 336 hours.