Making a well-understood tradeoff between two variables to achieve the same end-product is generally obvious. Here, for example, decreasing an annealing temperate while increasing a corresponding annealing time was found to be obvious in view of the well-known Arrhenius equation describing the relationship between the two. This would be a good case to consult before responding to an obviousness rejection in a highly predictable technology.
Background / Facts: The patent on appeal here from rejection at the PTO as part of reexamination proceedings is directed to ultra-high molecular weight polyethylene (“UHMWPE”) with improved properties for use in medical implants. The specification sets forth a two-step process, whereby a polymer is first irradiated and then heat treated. The prior art inherently discloses the claimed properties, but only by annealing above the temperature range claimed.
Issue(s): Whether a skilled artisan, with an understanding of the Arrhenius equation, would have reasonably expected decreasing the annealing temperature to still generate the same product, i.e., irradiated UHMWPE with the properties recited.
Holding(s): Yes. “This is a crowded art detailing a well-known problem and solution: the annealing of irradiated polyethylene to improve oxidation resistance. … [A]ccording to the Arrhenius equation, an increase in the heating temperature requires a lower heating time to achieve the same or a similar reaction time. [] Thus, a skilled artisan, armed with that understanding, would appreciate that a specific product can be generated by annealing at any point along the temperature/time spectrum. … The record overwhelmingly establishes that a skilled artisan would understand that modifying the annealing temperature of [the primary reference], as set forth in [another reference], would generate the same end-product, as long as the annealing time was also modified.”