Method for the preparation of an organopolysiloxane containing tetrafunctional siloxane units

摘要

An efficient and economically advantageous method is proposed for the preparation of an organopolysiloxane comprising tetrafunctional siloxane units, i.e. Q units, and, typically, monofunctional siloxy units, i.e. M units, and useful as a reinforcing agent in silicone rubbers. The method comprises the steps of: mixing the reactants for providing the Q and M units, such as ethyl orthosilicate and trimethyl methoxy silane, in a desired molar ratio; and heating the mixture at a temperature higher by at least 10 DEG C. than the boiling point of the mixture under normal pressure in a closed vessel in the presence of water and a catalyst such as a sulfonic acid group-containing compound. In addition to the greatly shortened reaction time and remarkably decreased contents of residual alkoxy groups and gelled matter in the product, the method is advantageous also in respect of the absence of the problems caused by the disposal of the waste water as well as the corrosiveness of hydrogen chloride unavoidably produced in the conventional prior art methods.