| 摘要 |
PROBLEM TO BE SOLVED: To provide hydrated silicic acid as a reinforcing filler which imparts suitable tensile strength, elongation, tear strength, reinforcing properties such as resilience, dynamic fatigue resistance, etc., to a silicone rubber while providing a kneaded silicone rubber stock having a suitable hardness and viscosity and which hardly causes dusting and exhibits suitable workability and processibility. SOLUTION: This reinforcing filler is hydrated silicic acid which has an average particle size (D50 ) [of particle size distribution (wt. distribution) by a laser method] of 8.0μm or higher but lower than 14.0μm, a content of particles having particle sizes less than 6.0μm of 15.0% or lower, and a content of particles having particle sizes of 27.0μm or higher of 8.0% or lower. Pref., the bulk density of the filler at a water adsorption of 3% or higher but lower than 8% is higher than 80 g/l but lower than 150 g/l.
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