Method for the preparation of organopolysiloxanes

摘要

A highly efficient method for preparing an organopolysiloxane which contains minimal amounts of low molecular weight organosiloxane is disclosed, said method comprising: (I) polymerizing (A) cyclic trisiloxane having the formula <CHEM> wherein R is a monovalent hydrocarbon radical, excluding aryl radical, using as a polymerization initiator (B) a lithium compound having the formula <CHEM> in which R' is independently selected from monovalent hydrocarbon radicals, X and X' are selected from hydrogen atom or lithium, with the proviso that one of X and X' must be lithium, and m is an integer having a value of at least 1, optionally, in the presence of (C) a molecular-weight regulator selected from water or a compound having the formula <CHEM> in which R' has its previously defined meaning and p is an integer having a value of at least 1, said polymerization taking place in the presence of both (D) a nitrile compound and (E) an active hydrogen-free polar solvent; and (II) terminating the polymerization reaction product from step (I) with a neutralizing agent selected from an acid or an organohalosilane.