Patent ID: 8969461
Filing Date: 2015-03-03
Classification: B60C,C08K,C08L

Abstract:
1. A rubber composition comprising: (A) a rubber component containing 10% by mass or more of at least one kind of rubber selected from diene rubber synthesized by emulsion polymerization and natural rubber and 90% by mass or less of another kind of diene rubber; (B) a silica having a n-hexadecyltrimethylammonium bromide (CTAB) adsorption specific surface area of not less than 180 m 2 /g measured according to a method described in ASTM D3765-92; (C) at least one silane coupling agent selected from a polysulfide compound and a thioester compound; and (D) a vulcanization accelerator, the rubber composition after vulcanization having an average aggregated aggregate area (nm 2 ) of the silica of 1,900 or less, measurement method of average aggregated aggregate area: an upper surface of a specimen of the rubber composition after vulcanization is cut in a direction making an angle of 38° with respect to the upper surface of the specimen with a focused ion beam; then a smooth surface of the specimen formed by cutting is imaged with a scanning electron microscope at an acceleration voltage of 5 kV in a direction perpendicular to the smooth surface; the resulting image is converted to a binarized image of a rubber portion and a silica portion as a filler of the specimen by the Otsu's method; an aggregated aggregate area of the silica portion is obtained based on the resulting binarized image; and the average aggregated aggregate area of the silica portion is calculated in terms of number average (arithmetic average) per unit area (3 μm×3 μm) from a total surface area of the silica portion and the number of aggregated aggregates, provided that in the calculation, a particle that is in contact with an edge of the image is not counted, and a particle of 20 pixels or less is assumed to be noise and is not counted.