Method for making caprolactam from impure ACN wherein ammonia and water are removed from crude caprolactam in a simple separation step and then THA is removed from the resulting caprolactam melt

Granted: Apr 6, 2004 Filed: Jun 17, 2003

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.