Granted Patent
Utility
US 4,987,258 · App. 07/017,062
4,4'-diaminodiphenyl compounds, process for their preparation and their use
Inventors:
Klaus Hunger, Heinrich Frolich, Kurt Habig
Patented Case
View Patent ↗
Granted: Jan 22, 1991
Filed: Feb 20, 1987
Inventors
Klaus Hunger
Heinrich Frolich
Kurt Habig
Assignee (at issue)
Hoechst GmbH
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.