Don’t Forget the Reliable Old Non-Obviousness Arguments in the MPEP

Ex parte Slark, is a recent decision of the Patent Trial and Appeal Board (PTAB) addressing whether the changes to a prior art composition that would result from an examiner’s proposed modification were sufficiently dramatic to negate obviousness.

In Ex parte Slark, the claim at issue was directed to a hot melt adhesive composition. The relevant claim recited:

A non-reactive hot melt adhesive composition comprising two thermoplastic polyurethane copolymers (A) and (B), wherein

the thermoplastic polyurethane copolymer (A) comprises a reaction product of at least one polyester polyol, and at least one polyisocyanate, and has a number average molecular weight (M_n) of at least 25,000 g/mol;

the thermoplastic polyurethane copolymer (B) comprises a reaction product of at least one polyester polyol, and at least one polyisocyanate, and has a number average molecular weight (M_n) of less than 25,000 g/mol; and

wherein the hot melt adhesive composition has a melt viscosity of 1,000 to 100,000 mPas at 160 °C and

wherein both thermoplastic polyurethane copolymers (A) and (B) are essentially free of NCO groups.

The examiner cited a primary reference that disclosed a solvent-free hot melt adhesive composition including two thermoplastic polyurethane copolymers, each copolymer being a reaction product of at least one polyester polyol and at least one polyisocyanate. The examiner acknowledged that the primary reference failed to disclose that the hot melt adhesive was non-reactive or that the polyurethane copolymers were essentially free of NCO groups. The examiner noted particularly that the preferred ratio of NCO groups to OH groups in the copolymers of the primary reference (>1) would not result in a “non-reactive” composition in which the copolymers were “essentially free of NCO groups.”

To address this deficiency, the examiner turned to a secondary reference. The secondary reference disclosed a solvent-free hot melt adhesive composition including a polyurethane obtained from a polyester polyol and an isocyanate, in which the ratio of NCO groups to OH groups in the polyurethane (~1) resulted in a “non-reactive” composition in which the polyurethane was “essentially free of NCO groups.” The examiner asserted that it would have been obvious to modify the polyurethanes of the primary reference to have the NCO:OH ratio of the polyurethane of the secondary reference, because the secondary reference disclosed that the ratio was suitable for reacting a polyester polyol with a polyisocyanate such that the resulting hot melt adhesive would be essentially free of NCO groups and nonreactive.

Applicant argued over the rejection by relying on two non-obviousness arguments that are explicitly identified in the MPEP: (1) modifying the composition of the primary reference as proposed by the examiner would render the composition “unsatisfactory for its intended purpose” (MPEP 2143.01.V); and (2) modifying the composition of the primary reference as proposed by the examiner would “change the principle of operation” of the composition (MPEP 2143.01.VI).

With respect to (1), applicant argued that the primary reference was directed to a reactive thermoset hot melt adhesive composition – not a non-reactive thermoplastic composition as required by the claims. Applicant noted that the purpose of the primary reference was to provide a moisture reactive polyurethane hot melt adhesive having a particular cured strength and excellent adhesion to metals. Applicant argued that the examiner’s proposed modification would eliminate essentially all of the isocyanate moieties in the prepolymers, rendering them non-reactive and unsatisfactory for the intended purpose of the primary reference. With respect to (2), applicant similarly argued that, because the examiner’s proposed modification involved eliminating the isocyanate groups from the prepolymers, the principle of operation of the composition of the primary reference would be different – the composition would no longer be a reactive, moisture-curable thermosetting polyurethane adhesive composition.

The PTAB agreed with applicant. The PTAB indicated that the “intended purpose” and “principle of operation” of the adhesive composition of the primary reference were intertwined. The examiner attempted to broadly characterize the composition of the primary reference as involving adhesion – an intended purpose and principle of operation that would be preserved even if the examiner’s proposed modification was made. However, the PTAB indicated that the examiner should have considered the contribution of the primary reference to the art when identifying the intended purpose and principle of operation. The PTAB noted that the primary reference expressly stated that mixtures of isocyanate-terminated polyurethanes provide good adhesion to metal substrates by achieving an initial bond strength upon cooling on a substrate and eventually achieving an ultimate bond strength when cured with ambient moisture. The PTAB agreed with applicant that the examiner’s proposed modification would render the composition of the primary reference unsatisfactory for its intended purpose and would change the principle of operation.

Takeaway: When facing obviousness rejections of chemical compositions, it can be difficult to persuade an examiner that he or she has failed to make a prima facie case. Absent a plain oversight by the examiner regarding the scope of the claims or prior art, it is often necessary to significantly narrow the scope of the claims and/or rely on experimental evidence of unexpected results. However, there are legal arguments that can be effective in overcoming obviousness arguments without amendments or experimental results – and the MPEP remains a great source for identifying compelling reasoning for arguing over obviousness rejections.

Judges: Hanlon, Housel, Inglese