Granted Patent
Utility
US 4,994,499 · App. 07/560,946
Method of adding flame retardant to vinyl aromatic polymers made in a one-step process
Inventors:
Fred Sonnenberg, Dennis M. Hajnik
Patented Case
View Patent ↗
Granted: Feb 19, 1991
Filed: Jul 31, 1990
Inventors
Fred Sonnenberg
Dennis M. Hajnik
Assignee (at issue)
Arco Chemical Technology, L.P.
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.