Abstract: The present invention relates to a hydrous silica for rubber reinforcing fillers having CTAB specific surface area in the range of 220 to 350 m2/g and a pore volume over the range of pore radius 1.9 to 100 nm measured by mercury press-in method in the range of 1.7 to 2.0 cm3/g, wherein a volume average particle diameter D50 in a volume particle size distribution measured by laser diffraction method for the slurry obtained by dispersing 50 ml of a hydrous silica slurry adjusted to 4 mass % with an ultrasonic homogenizer at an output of 140 W for 10 minutes is in the range of 5.0 to 12.0 ?m, and a cumulative value of hydrous silica particles over the range of 4.0 to 35.0 ?m in the volume particle size distribution is 80% or more. The present invention also relates to a rubber composition containing the above-mentioned hydrous silica and a rubber component containing a natural rubber.

Abstract: The present invention pertains to a hydrous silica for rubber-reinforcing filler, having a BET specific surface area ranging from 230 to 350 m2/g; the volume average particle diameter (D50) measured by the laser diffraction method after dispersing 50 ml of a hydrous silica slurry adjusted to 4% by weight with an ultrasonic homogenizer having an output of 140 W for 10 minutes is 3.0 ?m or less; and the top 10% of particles (D90) in the particle size distribution is 10.0 ?m or less. This invention provides a hydrous silica capable of further improving reinforcing properties of a rubber, particularly the wear resistance by improving dispersibility of the hydrous silica in the rubber in addition to rubber reinforcing properties obtained by a high BET specific surface area.

Abstract: The present invention pertains to a hydrous silica for rubber-reinforcing filler, having a BET specific surface area ranging from 230 to 350 m2/g, and satisfies the following: a) the pore volume of 1.9 nm to 100 nm pore radius measured by the mercury press-in method (VHP-Hg) ranges from 1.40 to 2.00 cm3/g; b) total pore volume in the range of 1.6 nm to 100 nm pore radius by the nitrogen adsorption/desorption method (VN2) ranges from 1.60 to 2.20 cm3/g; and c) the pore volume ratio of (a) and (b) VHP-Hg/VN2 ranges from 0.70 to 0.95. This invention provides a hydrous silica capable of further improving reinforcing properties of a rubber, particularly the wear resistance by improving dispersibility of the hydrous silica in the rubber in addition to rubber reinforcing properties obtained by a high BET specific surface area.