| 摘要 |
A process is described for the selective removal of 2,2'- and 2,4'-diaminodiphenylmethane from mixtures thereof with the corresponding 4,4'-isomer by heating the mixture of isomers in the presence of a 1,3,5-tri-arylhexahydro-1,3,5-triazine and a catalyst (aqueous mineral acid). The process is particularly useful in facilitating the isolation of substantially pure 4,4'-isomer from the aniline-formaldehyde condensation. The pure 4,4'-isomer is a valuable intermediate for polyamides as well as for the corresponding diisocyanate. The by-products of the reaction are oligomeric polymethylene polyphenyl polyamines which are also useful as curing agents and intermediates for polymethylene polyphenyl polyisocyanates and the like.
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