| 摘要 |
A new process for the production of very pure 4,4'-diisocyanatodiphenylmethane is disclosed, in which diisocyanatodiphenylmethane isomers which are obtained by distillation from the phosgenation products of aniline/formaldehyde condensates are initially freed from 2,2'- and 2,4'-isomers under certain distillation conditions and are then further worked-up by distillation, in that in a first final stage, from 50 to 90%, by weight of the diisocyanate freed from 2,2'- and 2,4'-isomers is isolated as the head product in the form of pure 4,4'-diisocyanatodiphenylmethane and in a second final stage, another quantity of pure 4,4'-diisocyanatodiphenylmethane is separated as the head product from the distillation of the sump of the first final stage. |
