Patent ID: 8664346
Filing Date: 2014-03-04
Classification: C08G

Abstract:
1. A process for the production of an organopolysiloxane of a targeted molecular weight, comprising: providing a continuous, two-stage reactor for the preparation of the organopolysiloxane, and in the reactor a) in a first step, continuously reacting one or more chlorosilanes with from 0.002 to 0.6 mol of water per mole of hydrolyzable chlorine and 0.3 to 1.6 mol alcohol per mole of hydrolyzable chlorine at a temperature and a pressure, such that gaseous hydrogen chloride is evolved, to produce a partial hydrolysate, b) in a second step, optionally mixing the partial hydrolysate with a water-insoluble organic solvent having a density of less than 0.9 g/ml, and metering in water in an amount of from 0.2 to 100 mol per mole of hydrolyzable chlorine in the chlorosilane(s); and c) in a third step, separating an aqueous alcoholic phase from a phase containing the organopolysiloxane product of said targeted molecular weight; the process further comprising first preparing a first organopolysiloxane having a first molecular weight in the reactor by the above steps, and measuring the molecular weight of the first organopolysiloxane; and comparing the first molecular weight to the targeted molecular weight and if the first molecular weight is not the targeted molecular weight, regulating the molecular weight of an organopolysiloxane product later isolated to the target molecular weight by adjusting at least one of the temperature and pressure, an increased pressure elevating the molecular weight and an increased temperature lowering the molecular weight.