Prior Art Disclosure of Interchangeable Chemical Species Insufficient to Teach Their Combination

On April 2, 2020, the Patent Trial and Appeal Board issued a decision in Ex parte Humphrey reversing an Examiner’s obviousness rejection because the Examiner’s factual finding that a prior art method involving the reaction of a chain extender suggested a reaction involving a combination of different chain extenders was erroneous. No. 2019-004118 (P.T.A.B. Apr. 2, 2020) (non-precedential).

The primary reference relied on by the Examiner in the obviousness rejection (U.S. Patent No. US 5,824,738 (“US ‘738”)) related urethane thermoplastic elastomers obtained by reacting a polyether/polyol, a diisocyanate, and a chain extender. See US ‘738, 3:22–27. With respect the chain extender, US ‘738 stated:

Chain extending agents which may be employed in the preparation of the urethane thermoplastic elastomer of the present invention include aromatic secondary or aliphatic primary or secondary diamines, all of which are well known in the art.

Chain extenders such as ethylene glycol, diethylene glycol, propylene glycol, pentane diol, 3-methylpentane-1,5-diol, hexane diol, HQEE [hydroquinone bis(2-hydroxyethyl)ether], CHDM (1,4-cyclohexanedimethanol), or HBPA (hydrogenated bisphenol A) could also be used.

In the preferred embodiment, the chain extender is 1,4-butanediol.

Ex parte Humphrey, Decision at 5 (quoting US ‘738).

According to the Examiner, it would have been obvious to use a combination of the diamine chain extending agents with one of the alternative chain extending agents such as ethylene glycol “based upon a rationale in KSR (MPEP [§] 2143, rationale (B),”; namely, as a simple substitution of one known element for another to obtain predictable results. Id. at 5. The Applicant disagreed, stating that the recitation of possible alternatives for the chain extender was not a disclosure to use more than one chain extender, the preferred embodiment involved a single chain extender, and the compositions in the examples only used one chain extender. Id. at 4.

The Board found that the Applicant was on better footing because the different chain extenders were disclosed as alternatives in different paragraphs, the preferred chain extender was a single chain extender, and the Examiner’s simple substitution rationale “would have resulted in a composition having only one chain extender.” Id. at 6.

Takeaways: This decision shows the importance of challenging erroneous applications of the KSR rationales summarized in MPEP § 2143. And in the context of the obviousness, this decision shows that while it is generally “prima facie obvious to combine two compositions each of which is taught by the prior art to be useful for the same purpose, in order to form a third composition to be used for the very same purpose,” it is a fact specific inquiry where the lack of an express disclosure to use more than one species may support a finding of nonobviousness for the use of a combination of species. In re Kerkhoven, 626 F.2d 846, 850 (CCPA 1980).

Judges: M. Colaianni, G. Best, D. Dennet