| 摘要 |
PURPOSE:To obtain the title composition excellent in electrical insulation properties and thermal conductivity and causing neither abrasion nor corrosion of the sealed element or wire by mixing an alkenylated organopolysiloxane with an organophydrogenpolysiloxane, a platinum metal catalyst and a filler in a specified ratio. CONSTITUTION:The title composition is prepared by mixing an alkenylated organopolysiloxane (A) containing at least 0.5 alkenyl group on the average per molecule with an organohydrogenpolysiloxane (B) containing at least two Si-bonded hydrogen atoms in the molecule, a platinum metal catalyst (C), and at least one member (D) selected between an alumina powder and a silica powder each being in the form of spherical particles having a mean particle diameter of 50mum or below and an aspect ratio of 1.0-1.4 and having an alkali metal ion content and a halide ion content each of which is 10ppm or below when 5g of the powder is extracted with 50ml of water at 121 deg.C for 20hr, wherein component D is present in an amount of 25-90wt.% based on the total composition, and the ratio of the hydrosilyl groups of component B to the alkenyl groups of component A is 0.5/1-1.5/1. |
