A district judge invalidated a valuable Exxon patent in what experts believe is a first-of-its-kind ruling based on a recent decision by the U.S. Court of Appeals for the Federal Circuit.

The decision Nov. 30 by U.S. District Judge Vanessa Gilmore in Exxon Corp., et al. v. Phillips Petroleum Co., a patent infringement case, is significant because it voids one of Exxon’s most prized patents � certain metallocene catalysts used to manufacture plastics.