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.