Appeal No. 1998-0119 Page 6
Application No. 08/466,171
polysiloxane was known at the time of the invention as evidenced by the fact that appellant
uses a commercially available product.” See Answer, pages 5 and 7 respectively.
The Encyclopedia of Polymer Science and Engineering article directed to Polymers
for Co-extruded Films provides a general discussion regarding the selection of polymers as
individual layers of a co-extruded multilayer film. See pages 116 to 119. The discussion
therein contains measurements of properties including Oxygen Permeabilities, Table 1,
Water Vapor Transmission Rates, Table 2 and Qualitative Degree of Adhesion between
Resin, Table 3. There is however, no specific suggestion or motivation to substitute any
specific polymer for another polymer in the formation of a multilayer film. Indeed, the
article cautions us throughout that, “layer interactions can greatly influence mechanical
behavior of composites,” page 117, and that, “[u]nfavorable layer interactions can lead
to mutual interlayer destruction ie, failure in one layer leads to premature failure in
normally ductile layers, causing catastrophic failure of an entire composite.” Id. Indeed it
is concluded that although calculations may be used to estimate strength, “it is inadequate
for predicting layer interactions and ultimate film performance.” Id. Accordingly, we
conclude that one skilled in the art cannot simply substitute high density polyethylene for
polypropylene with a reasonable expectation of success in obtaining a film having
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