Granted Patent
Utility
US 4,255,315 · App. 06/023,227
Method of making a high impact polystyrene
Inventor:
Harry D. Anspon
Patented Case
View Patent ↗
Granted: Mar 10, 1981
Filed: Mar 23, 1979
Inventor
Harry D. Anspon
Assignee (at issue)
United States Steel 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.