PURPOSE:To prepare the title foam excellent in qualities and properties with a homogeneous cell structure at a high productivity by treating a specific silicone rubber compsn. under specified conditions and then foaming and simultaneously completely curing the compsn. CONSTITUTION:A semi-curable organopolysiloxane compsn. mainly comprising an organopolysiloxane having org. peroxide-curable functional groups (e.g. a dimethylpolysiloxane having both molecular ends blocked with dimethylvinylsiloxy groups) is compounded with an org. peroxide having an activation energy of 25-41kcal/mol [e.g. 2,5-dimethyl-2,5-di(t-butylperoxy)hexane] and a blowing agent (e.g. 4,4'-oxybisbenzenesulfonyl hydrazide) to give a silicone rubber compsn., which is formed into particles and treated below 100 deg.C to give an intermediate molding material which comprises spherical particles in a semi- cured state and in which the activity of the peroxide and the blowing capability of the blowing agent are fully retained and the functional groups of the organopolysiloxane still remains. The intermediate material is foamed and simultaneously completely cured at above 100 deg.C.
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