Granted Patent
Utility
US 4,599,431 · App. 06/627,776
Process for the preparation of naphthalene-1,4,5,8-tetracarboxylic acid and its 1,8-monoanhydride in a high degree of purity
Inventors:
Siegfried Schiessler, Ernst Spietschka
Patented Case
View Patent ↗
Granted: Jul 8, 1986
Filed: Jul 5, 1984
Inventors
Siegfried Schiessler
Ernst Spietschka
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.