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.
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.
JACOBS JAN
SEYFERT WILFRIED
SCHWARZ HANS VOLKMAR
SCHWEERS OLAF
SCHARR VOLKER
PENZEL ULRICH
| JP2002502838A | 2002-01-29 | |||
| JPS4911863A | 1974-02-01 | |||
| JPH07316122A | 1995-12-05 | |||
| JPH04253952A | 1992-09-09 | |||
| JPH10508859A | 1998-09-02 | |||
| JPS5365860A | 1978-06-12 | |||
| JPS4815862A | ||||
| JP2002502838A | 2002-01-29 | |||
| JPS4911863A | 1974-02-01 | |||
| JPH07316122A | 1995-12-05 | |||
| JPH04253952A | 1992-09-09 | |||
| JPH10508859A | 1998-09-02 | |||
| JPS5365860A | 1978-06-12 | |||
| JPS4815862A |
| WO1996016028A1 | 1996-05-30 | |||
| WO1996016028A1 | 1996-05-30 |