Teaching away is an important concept when considering the obviousness of a patent claim. The Federal Circuit’s recent decision in Chemours v. Daikin makes it easier to find that a reference teaches away from an invention, potentially increasing the difficulty of invalidating a patent claim for being obvious. There, the Circuit reversed the Patent Trial and Appeal Board’s obviousness ruling, holding that it failed to adequately explain why a skilled artisan would modify a reference when doing so involved changing its inventive concept.
The patents in Chemours related to polymers used in insulating communication cables by pulling wires through melted polymer to coat and insulate wires – a process known as “extrusion.” Reference Kaulbach disclosed a melt flow rate of 24 g/10 min, while the claimed rate was 30 ±3 g/10 min. Notably, Kaulbach suggested having a “narrow” rather than a “broad” molecular weight distribution polymer, in contrast to the prior art. The Board found that a skilled artisan would have been motivated to increase the melt flow rate to be within the claimed range in order to coat wires faster.
The Federal Circuit disagreed, stating the Board did not adequately grapple with why a skilled artisan would find it obvious to increase Kaulbach’s melt flow rate to the claimed range, while retaining its critical “very narrow molecular-weight distribution.” As the Circuit noted, Kaulbach appeared to teach away from broadening molecular weight distribution and the known methods for increasing melt flow rate. In the words of Judge Dyk’s dissenting opinion, the Chemours decision “expands the teaching away doctrine such that it encompasses a reference’s mere preference for a particular alternative.”
Of course, the teaching away doctrine is not without its mixed history. For example, the Federal Circuit opined in Gurley that “[a] reference may be said to teach away when a person of ordinary skill, upon reading the reference, would be discouraged from following the path set out in the reference, or would be led in a direction divergent from the path that was taken by the applicant.”
Later, the teaching away standard calcified into a more rigid test bearing little resemblance to the principles laid out in Gurley. In Fulton, the Circuit considered whether a reference that disclosed alternatives to the claimed elements could be regarded as teaching away from the claimed combination. The Circuit answered no, but in so doing, it also held that “because such disclosure does not criticize, discredit, or otherwise discourage the solution claimed in the” subject application, it does not teach away from the purported combination.
The Chemours decision seems to be more in line with the spirit and flexibility of Gurley rather than with the rigidity of Fulton. As a matter of practicality, the Chemours decision should ease the burden of arguing that a reference teaches away from a claimed combination.
 Chemours Company FC, LLC v. Daikin Industries, Ltd., No. 20-1289, Slip Op. (Fed. Cir. Jul. 22, 2021).
 In re Gurley, 27 F.3d 551 (Fed. Cir. 1994).
 In re Fulton, 391 F.3d 1195 (Fed. Cir. 2004).
 Emphasis added.