E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC, decided April 17, 2019, Claim Interpretation

U.S. Patent No. 8,607,926 is directed to a composite flame barrier laminate for a blanket (page 2). The claim recites three layers where one layer comprises platelets in an amount of 100% by weight (page 3). The parties dispute whether the “100% by weight” allows for any residual dispersant due to incomplete drying (page 5). The specification teaches 85%, 90%, 95%, or 100% platelets and notes in a following sentence that the layer may comprise some residual dispersant (page 5). The “100% by weight” was added in prosecution to overcome a prior art reference teaching less than 100% (pages 6-7). The claim language was changed to “platelets in the amount of 100% by weight . . . and a residual moisture content of no greater than 10%” (page 7). The claim reciting the moisture content up to 10% by weight in addition to the 100% by weight platelets indicates that the 100% may allow for other content in the layer (page 11). The specification teaching some residual dispersant after stating the various percentages including 100% indicates that 100% platelets allows for residual dispersant (pages 11-12). The examples in the specification all had 0% residual dispersant but other materials were taught that did not (page 12). The specification further teaches that 100% is relative to carrier material (page 13). The amendment to 100% was done to indicate no need for a carrier used in the 70% embodiment of the prior art (pages 16-17). “100% by weight” requires no other carrier material but allows for residual dispersant (page 18).

Hindsight: The claim language could have related the 100% to the carrier material as opposed to just the layer. In general, reciting an absolute (e.g., 100%) in a claim should be avoided. It is not clear why 100% was chosen over any of the other listed percentages (85% and up) where the prior art was 70%, but using one of the lesser percentages could have avoided this dispute. Perhaps the Examiner would consider anything less than 100% as obvious. Alternative materials taught in the specification helped.