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Abstract

A polyorganosiloxane composition for molding includes: (A) a straight-chain polyorganosiloxane having two or more alkenyl groups and having a viscosity (25° C.) of 10,000 to 500,000 mPa·s; (B) 30 to 80 mass % of a resinoid polyorganosiloxane including M, D, and Q units, at a molar ratio of a:b:c, on average (0.3≤a≤0.6, 0≤b≤0.1, 0.4≤c≤0.7, and a+b+c=1), and having two or more alkenyl groups; (C) an amount of a polyorganohydrogensiloxane having Si-bonded hydrogen atoms, an average degree of polymerization of 10 or more, a content of the Si-bonded hydrogen atoms of 5.0 mmol/g or more and 11.0 mmol/g or less, and a mass decrease rate up to 140° C. by TGA of 2.0 mass % or less so that an amount of the (Si-bonded hydrogen atoms/alkenyl groups) is 1.0 to 3.0 mol; and (D) a hydrosilylation reaction catalyst. A cured product excellent in mold release property is obtained and contamination of a metal mold is prevented.

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First Claim