Granted Patent
Utility
US 4,803,295 · App. 07/100,493
Purification of diphenyl phthalates
Inventors:
A. Lee Stautzenberger, Robert Kunkel
Patented Case
View Patent ↗
Granted: Feb 7, 1989
Filed: Sep 24, 1987
Inventors
A. Lee Stautzenberger
Robert Kunkel
Assignee (at issue)
Hoechst Celanese Corporation
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.