Patent ID: 7393893

Claim:
A curable organopolysiloxane composition comprising: (A) 100 parts by mass of an organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms within each molecule, (B) an organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms within each molecule, in sufficient quantity to provide from 0.4 to 5.0 mols of hydrogen atoms bonded to silicon atoms for each 1 mol of alkenyl groups bonded to silicon atoms within said composition, (C) 5 to 50 parts by mass of a finely powdered silica with a specific surface area measured by nitrogen gas absorption of at least 50 m 2 /g, (D) 0.1 to 50 parts by mass of heavy calcium carbonate with a specific surface area measured by air permeability of 0.5 to 2.5 m 2/ g, the surface of which has been treated with a paraffin-based compound, and (E) an effective quantity of a platinum group metal-based catalyst.