Patent ID: 7776988
Filing Date: 2010-08-17
Classification: C08G

Abstract:
1. A process for the preparation of polyorganosiloxanes by ring-opening polymerization and/or redistribution polymerization of cyclic polyorganosiloxanes and of linear and/or nonlinear polyorganosiloxanes, said process comprising the following steps: a) polymerizing the cyclic polyorganosiloxanes and the linear and/or nonlinear polyorganosiloxanes, by the steps of: (i) at least 20% by weight with respect to the total weight of the composition of at least one cyclic siloxane of following formula (I): in which: n=3, 4, 5, 6, 7 or 8; R R (ii) optionally up to 80% by weight with respect to the total weight of the composition of at least one polyorganosiloxane comprising siloxyl units, which are identical to or different from one another, of general formula (II): in which: w and z=0, 1, 2 or 3 and w+z ≦3; R R b) neutralizing the reaction mixture; and c) optionally devolatilizing the reaction mixture; wherein for the alkaline catalyst (III), the number of mmol x used meets the following criterion: 0.005≦x≦5 mmol per 500 g of cyclic siloxane (I), and for the cryptand (IV), the number of mmol y used meets the criterion defined by the molar ratio y/x<0.040.