Method of preparation of the fluids of polydiorganosiloxane to termination triorganosiloxy with a low content of silanol.

摘要

Are prepared with a linear polydiorganosiloxane triorganosiloxy having a silanol content of less than about 200 ppm by condensing of the linear polydiorganosiloxanediols upper molar mass having a hydroxyl group linked to if, in each pattern terminal and a silanol content is preferably greater than about 1 000, in two distinct stages, using a fixed bed of a solid form of a catalyst of the conventional balance and the other using a condensation catalyst / dismutation, for example a halide phosphonitrilic or oligomer or the product of reaction with water, an alcohol, an acid or a siloxane or a silane, until the polydiorganosiloxane has reached the desired content of the silanol groups, for example less than 200 ppm by weight. It is possible to carry out the two steps in any order and a conventional monofunctional chain limiting agent may be present in one or other of steps or in the two. The process does not increase the content of the products under -.