Organofunktionelle Silikone

Abstract

The introduction of electronegative substituents into the alkylgroups of the organopolysiloxanes generally affects the properties being in principal the basis for the technical use of silicones. Therefore the organofunctional silicon compounds are found mainly in fields of application being quite unusual for silicones. In the conventional range of application for silicones they can be made useful by inserting the organofunctional units, statistically distributed to a relative small extent, into a methyl siloxane system. In this way it is possible to change the properties of the methyl siloxanes in a directed manner. As the most important case there is discussed the synthesis of organofunctional silicon compounds by addition of substituted olefines to Si–H linkages. Various transformations at the organofunctional groups are frequently following this base synthesis, so that one silicon compound may become the clue for a whole family of novel compounds. This is made clear by the example of the β-cyanoethyl-methyldichlorosilane, with reference to the various possibilities of application. –  Further examples are selected from the research work of Th. Goldschmidt AG: γ-acetoxypropylmethyldichlorosilane can react with chlorosulphonic acid forming a polymeric sulphuric acid ester having the structure [–Si(CH₃)Cl–(CH₂)₃–O–SO₂–O–]_n . By acid saponification of this ester one obtains aqueous solutions of the γ-oxypropylmethylsilandiol which in a certain range of concentration is found on equilibrium conditions in the monomeric state. The silanol can be used – especially in combinations with unsaturated acids, e.g. maleic acid – as coupling agent for glass fiber reinforced plastics. The reaction of the polymeric sulphuric acid ester with alcohol and amines results in the production of wetting agents which can be easily destroyed by hydrolytic cleavage of the Si–O–C linkages. If an equilibration with dimethylsiloxanes is preceeding this reaction Si-organic emulsifiers are obtained which, for example, are particularly suitable for the production of emulsions of waterrepellents.