Abstract:
PROBLEM TO BE SOLVED: To provide a method for producing methylenedianiline (MDA) by reacting aniline with formaldehyde in the presence of acid catalysts while minimizing the N-methyl-MDA content as an undesirable by-product. SOLUTION: The semicontinuous method for producing MDA includes: introducing aniline with or without the acid catalyst; feeding formaldehyde with or without the acid catalyst through a mixing means into a circuit in which aniline with or without the acid catalyst and with or without previously added formaldehyde is circulated; and heating a reaction mixture to a temperature above 75°C after feeding in at least 50% of the total amount of formaldehyde to be fed. There is also provided a method for producing polyisocyanates by phosgenation of amines obtainable in such a manner. MDA is used for production of methylene-bis(phenyl isocyanate) (MDI) having a low chlorine content and/or a light color. COPYRIGHT: (C)2011,JPO&INPIT
Abstract:
Process for preparing organic isocyanates, which comprises the steps (a) making available a first partial amount of chlorine, with the chlorine of this first partial amount having a content of free and bound bromine and iodine of
Abstract:
Procedimiento para producir isocianatos orgánicos con los pasos (a) aportación de una primera cantidad parcial de cloro, en donde el cloro de la primera cantidad parcial presenta un contenido de bromo y yodo libre o enlazado