Granted Patent
Utility
US 4,720,571 · App. 06/875,831
Polyols from scrap polyethylene terephthalate and dimethyl terephthalate process residue
Inventor:
John M. Trowell
Patented Case
View Patent ↗
Granted: Jan 19, 1988
Filed: Jun 18, 1986
Inventor
John M. Trowell
Assignee (at issue)
HERCULES LLC
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.