Continuous process for the preparation of isocyanates.

摘要

Organic mono- and di-isocyanates are prepared by decomposition of the corresponding urethanes, by means of a continuous process in which: (a) a urethane is continuously fed to a decomposition reactor containing a liquid mixture composed of a high boiling inert organic solvent, urethane and isocyanate, kept at the boiling point of the solvent and at a temperature suitable for decomposing the urethane and evaporating the alcohol which is the other product of the reaction; (b) the liquid mixture is continuously withdrawn from the reactor of (a) and is fed to a flash evaporator kept at an operating temperature lower than the decomposition temperature of the urethane, where the isocyanate is partially evaporated and the residual liquid mixture is recycled to the reactor of (a); and (c) the vapor generated in (b) is distilled to separate the isocyanate in pure of substantially pure form. p