Granted Patent
Utility
US 4,276,215 · App. 05/818,564
Purification of pyrrolidone
Inventors:
Eugene V. Hort, Waldo De Thomas
Patented Case
View Patent ↗
Granted: Jun 30, 1981
Filed: Jul 25, 1977
Inventors
Eugene V. Hort
Waldo De Thomas
Assignee (at issue)
GAF 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.