Patent ID: 7776988

Claim:
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: a-1) preparing a reaction composition at ambient temperature, where the reaction composition comprises: (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 1 is a hydrogen atom, an optionally substituted, linear or branched, C 1 -C 12 alkyl radical, an alkenyl radical, an optionally substituted C 5 -C 10 cycloalkyl radical, an optionally substituted C 6 -C 18 aryl radical or an optionally substituted aralkyl radical, and R 2 is a radical R 1 or an —OR 3 radical, with R 3 being a hydrogen atom or an optionally substituted, linear or branched, C 1 -C 12 alkyl radical; and (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): (R 3 ) w (R 4 ) z SiO (4-w-z)/2 in which: w and z=0, 1, 2 or 3 and w+z ≦3; R 3 is a hydrogen atom, a linear or branched C 1 -C 12 alkyl radical which is optionally substituted by chlorine and/or fluorine, an optionally substituted C 1 -C 12 alkenyl radical, an optionally substituted C 1 -C 12 haloalkyl radical, an optionally substituted C 1 -C 12 haloalkenyl radical, an optionally substituted C 3 -C 8 cycloalkyl radical, an optionally substituted C 3 -C 8 cycloalkenyl radical, an optionally substituted C 3 -C 4 cyanoalkyl radical or an optionally substituted C 6 -C 12 phenyl, alkylphenyl or phenylalkyl radical; and R 4 is a radical R 3 or an —OR 5 radical with R 5 having the same definition as R 3 ; a-2) adding a catalytic system to the reaction composition, wherein the catalytic system is composed of x mmol of at least one alkaline catalyst (III) and y mmol of at least one cryptand (IV) which is a macroheterobicyclic diamine, and a-3) adjusting the temperature of the reaction mixture to a temperature of between 100° C. to 190° C.; 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.