Branched organopolysiloxanes

摘要

The invention relates to branched organopolysiloxanes and to their preparation and use. A branched organopolysiloxane is prepared by the reaction of an alkoxysilane with a substantially linear organopolysiloxane containing at least one hydroxyl or hydrolysable group bonded to silicon, in the presence of a phosphazene catalyst. The branched organopolysiloxanes obtained can be suitable for use in a moisture curable sealant composition capable of curing to a high modulus seal, with less tendency to gel than when using other siloxane polycondensation catalysts. Phosphazene catalysts also have the advantage that the content of undesired low molecular weight cyclic silicones in the polymerization product is low.

主权项

1. A process for the preparation of a branched organopolysiloxane comprising reacting an alkoxysilane with a substantially linear organopolysiloxane containing at least one hydroxyl or hydrolysable group bonded to silicon, wherein the reaction is carried out in the presence of a phosphazene catalyst and a diluent selected from a hydrocarbon oil comprising from 5 to 25 carbon atoms per molecule, where the amount of diluent used in the process is 5 to 70% of the combined weight of alkoxysilane, substantially linear organopolysiloxane and diluent.