CONTINUOUS PLURAL STAGE HEATED VAPOR INJECTION PROCESS FOR RECOVERING LUBE OIL BASE STOCKS FROM USED MOTOR OIL FORMULATIONS, AND ASPHALT BLEND COMPOSITIONS CONTAINING USED MOTOR OIL BOTTOMS FROM SAID PROCESS

Granted: Sep 10, 2002 Filed: May 19, 2000

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.