US Patent 10519280 Process for preparing SiC-Bonded polyethersiloxanes

A process for preparing SiC-bonded polyethersiloxanes by precious metal-catalysed addition of olefinically unsaturated polyethers onto siloxanes having SiH groups is described, in which, prior to commencement of reaction, the siloxane having SiH groups is mixed together with a polyethersiloxane, preferably by stirring, and then, in a second step, this preliminary mixture is contacted with an olefinically unsaturated polyether and with a precious metal catalyst and optionally further additives, preferably with further stirring, and the SiC bond formation reaction is conducted up to an SiH conversion, determined by gas-volumetric means, of at least 97%.