Aus der Chemie der Silikone

Abstract

Silicones or organopolysiloxanes are defined as being substances which on the one hand are containing Si–C linkages and on the other hand Si–O–Si bridges. It is easy to obtain Si–O–Si bridges by intermolecular condensation of organosilanoles, which therefore are applied as monomerous intermediate products for the synthesis of silicones. The functionality of the organosilanoles applied and their reciprocal proportion during the condensation reaction are determinative for the structure and state of the resulting organopolysiloxanes (silicone oils, silicone rubber, silicone resins, etc.).
In general the organosilanoles are not isolated in the course of a silicone synthesis, in most cases they are rather formed by reaction of water on hydrolysable silicon-functional organo-Si-compounds, especially organosiliconchlorides, and introduced immediately into the condensation reaction. The organo-siliconchlorides are the real initial products of a silicone synthesis which are to be prepared in as pure a form as possible; of the methods for producing organosilicon-chlorides there are discussed the “direct synthesis”, the Grignard synthesis and the synthesis by reaction of carbon compounds with Si-H groups.
The organopolysiloxane mixtures obtained by hydrolysis of organosiliconchlorides and subsequent condensation of organosilanoles frequently are reaching the end stage necessary for their practical application only by an aftertreatment (“equilibration” of silicone oils, curing of silicone resins).