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Abstract

This is to provide a curable polyorganosiloxane composition which gives a cured product excellent in cold resistance. This relates to a curable polyorganosiloxane composition which comprises (A) an alkenyl group-containing polyorganosiloxane comprising (A1) a linear polyorganosiloxane represented by the formula (1) (wherein Rs independently represent R¹ or R², and among Rs, at least two of which are R₁s, R¹s independently represent a C₂-C₆ alkenyl group, R²s independently represent a C₁-C₆ alkyl group, n is a number which makes a viscosity at 23° C. 10 to 10,000 cP), and (A2) a branched polyorganosiloxane comprising a SiO_4/2 unit and a R′₃SiO_1/2 unit, and further optionally a R′₂SiO unit and/or a R′SiO_3/2 unit (wherein R′s each independently represent an unsubstituted or substituted, monovalent aliphatic group or alicyclic group), at least three R′s are alkenyl groups per one molecule, a weight ratio of (A2) based on (A1) is 1 to 5, a weight ratio of the SiO_4/2 unit and the optionally existing R′SiO_3/2 unit based on the total weight of (A1) and (A2) is 20 to 60% by weight; (B) a polyorganohydrogensiloxane having hydrogen atoms bonded to a silicon atom in a number of exceeding 2 in the molecule; and (C) a platinum group metal compound.

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First Claim