Process for producing diphenylsiloxane / dimethylsiloxane copolymer

摘要

PURPOSE: To obtain the copolymer having a narrow mol.wt. distribution and a controlled molecular structure by copolymerizing a specific cyclic trisiloxane mixture in the absence or presence of a lithium compd. and a mol.wt. modifier in a nitrile compd. and a polar solvent having no active hydrogen atom. ;CONSTITUTION: This copolymer represented by formula V (wherein B is II or an organosilyl; n₁ and n₂ are each 1 or higher; and 1 is O or higher) is obtd. by polymerizing a cyclic trisiloxane mixture comprising hexamethylcyclotrisiloxane represented by formula I (wherein Me is methyl) and 50mol% or lower hexaphenylcyclotrisiloxane represented by formula II (wherein Ph is phenyl) in the absence or presence of a lithium compd. represented by formula III (wherein R is a monovalent hydrocarbon group; X and X' are each Li or H provided at least one of them is Li; and m is 1 or higher) as the polymn. initiator and a compd. represented by formula IV (wherein p is 0 or higher) as the mol.wt. modifier in a nitrile compd. and a polar solvent having no active hydrogen atom and adding an acid or an organohalogenosilane to the polymn. system to stop the polymn.;COPYRIGHT: (C)1996,JPO