| abstract |
The invention relates to a method, preferably a multistage method, for continuously producing organic polyisocyanates, preferably diisocyanates, particularly preferably aromatic, aliphatic, or cycloaliphatic diisocyanates, by reacting the corresponding organic polyamines with carbon dioxide and secondary amines into low-molecular monomeric polyureas and cleaving same. The invention further relates to a corresponding production method in which the produced polyisocyanates and unusable residue are separated at specified reaction stages, and reusable auxiliary and intermediate products are recirculated to the initial stages. |