Method of isolation of 4,4 '- diaminodiphenylmethane of a mixture of pure isomers

摘要

A process is described for the isolation of 4,4'-diaminodiphenylmethane in substantially pure form (of the order of purity of at least 95%) from admixtures thereof with the corresponding 2,4'-isomer and 2,2'-isomer. The isomeric mixture of diamines is heated, optionally in the presence of an inert organic solvent, with at least two equivalents, per mole of said diamine mixture, of a phenol or bisalkylidenephenol. The 4,4'-diaminodiphenylmethane forms a complex with said phenol and the 4,4'-isomer of the diamine is isolated therefrom in substantially pure form by treatment with alkali or by heating to dissociate. The isomeric mixture of diamines used as starting material can be employed in the form of a mixture of polymethylene polyphenyl polyamines containing a major portion of said diamines.