Patent ID: 7179935

Claim:
A process for the preparation of isocyanates from carbamic esters, comprising: (i) continuously passing a mixture comprising a monofunctional or polyfunctional carbamic ester into a cleavage reactor or a cascade of two or more cleavage reactors, (ii) subjecting the carbamic ester to a thermal cleavage to obtain a cleavage gas comprising isocyanate and alcohol, (iii) cooling and at least partly condensing the cleavage gas, which comprises the isocyanate, the alcohol, any uncleaved and/or partly cleaved carbamic ester and byproducts, escaping from the cleavage reactor or reactors by bringing the cleavage gas into contact with a liquid coolant and a condensing agent, and (iv) obtaining the isocyanate and the alcohol from the cooled cleavage gas and the condensate in a rectification column, wherein a part-stream of the alcohol obtained is used as the liquid coolant and the condensing agent for cooling and condensing the cleavage gas.