The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 07, 1977
Filed:
Aug. 18, 1975
Adnan A Sayigh, North Haven, CT (US);
Kwok K Sun, Hamden, CT (US);
Henri Ulrich, Northford, CT (US);
The Upjohn Company, Kalamazoo, MI (US);
Abstract
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.