Granted Patent
Utility
US 5,690,793 · App. 08/509,793
Purification process for cyclic formals
Inventor:
Hubert H. Thigpen
Patented Case
View Patent ↗
Granted: Nov 25, 1997
Filed: Aug 1, 1995
Inventor
Hubert H. Thigpen
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.