METHOD OF PREPARING A CURABLE POLYORGANOSILOXANE COMPOSITION

摘要

A method of preparing a curable polyorganosiloxane composition including kneading a uniform mixture of an alkenyl group-containing polyorganosiloxane, a polyorganohydrogensiloxane, and a platinum group metal compound, and defoaming the kneaded mixture under reduced pressure, the alkenyl group-containing polyorganosiloxane includes a linear polyorganosiloxane of the formula (I):;;, R is R1 or R2, and at least two Rs are R1; R1 is C2-C6 alkenyl; R2 is C1-C6 alkyl; and n is a value that yields a viscosity at 23° C. of 10 to 10,000 cPs, a branched polyorganosiloxane containing SiO4/2 and R′3SiO1/2 units, optionally a R′2SiO and/or a R′SiO3/2, R′ represents a monovalent aliphatic or alicyclic, and at least three R′ groups per molecule are alkenyls, the alkenyl group-containing polyorganosiloxane having a weight ratio of the branched to linear polyorganosiloxane of 1 to 5; and a number of hydrogens bonded to a silicon atom of the polyorganohydrogensiloxane exceeds 2.

主权项

1. A method of preparing a curable polyorganosiloxane composition, the method comprising:
(a) kneading a uniform mixture of an alkenyl group-containing polyorganosiloxane, a polyorganohydrogensiloxane, and a platinum group metal compound, and (b) defoaming the resultant kneaded mixture from step (a) under reduced pressure, wherein (A) the alkenyl group-containing polyorganosiloxane comprises (i) a linear polyorganosiloxane represented by a formula (I) as follows:, wherein each R group is independently a R1 group or a R2 group, and at least two R groups are R1 groups; each R1 group is independently a C2-C6 alkenyl group; each R2 group is independently a C1-C6 alkyl group; and n is a value that yields a viscosity at 23° C. of 10 to 10,000 cPs, and
(ii) a branched polyorganosiloxane comprising a SiO4/2 unit and a R′3SiO1/2 unit, and optionally a R′2SiO unit and/or a R′SiO3/2 unit, wherein each R′ group independently represents an unsubstituted or substituted, monovalent aliphatic group or alicyclic group, and at least three R′ groups per molecule are alkenyl groups, the alkenyl group-containing polyorganosiloxane having a weight ratio of the branched polyorganosiloxane to the linear polyorganosiloxane of 1 to 5, and, when the optional R′SiO3/2 unit is present in the branched polyorganosiloxane, a weight ratio of the SiO4/2 unit and the R′SiO3/2 unit is 25 to 50% by weight based on the total weight of the linear polyorganosiloxane and the branched polyorganosiloxane; and (B) a number of hydrogen atoms bonded to a silicon atom of the polyorganohydrogensiloxane exceeds 2.