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. 14, 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'-diaminodiphenylmethanes from mixtures containing 2,2'-, 2,4'- and 4,4'-diaminodiphenylmethanes and polyamines by heating these mixtures in the presence of aqueous hydrochloric acid (55 to 95 percent by equivalents based on the total amine in the starting material) and formaldehyde. The process is particularly useful to facilitate the isolation of substantially pure 4,4'-isomer from aniline-formaldehyde condensation products. 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.