[Old Professer]

It wasn’t so much that the patent would run out or that duPont was the sole vendor, it was the fact that the die had been cast and R-12 was about to be banned and that dupont was one of the first to develop an acceptable replacement, R-134A; the history of the invention, patenting and widespread use is covered well by the historic background part of the ozone story released by NOAA:

http://www.esrl.noaa.gov/gmd/hats/publictn/elkins/cfcs.html

[Toddsterpatriot]

It wasn’t so much that the patent would run out

Yeah, that's what I thought. LOL!

Thanks.