Appeal No. 1995-1915
Application No. 08/117,846
Sublett teaches that PET copolymers formed by
adding 25-5000 ppm sodium or potassium, prior to
polymerization, will form a final PET copolymer
composition with improved crystallization rates from
the glassy state during thermoforming due to polymer
salts formed in situ (p. 5, [lines] 10-30). It is
these polymer salts that act as nucleating agents
with the other polymerized PET at the thermoforming
step. The reference sets forth that crystallization
rates of ordinary PET copolymers are usually too
slow although the physical properties of such
copolymers are highly desirable in such applications
(p. 3, [lines] 17-31). [Emphasis added.]
In contrast to this teaching in Sublett, the invention of
claim 6 requires a "blend" of a thermoplastic crystallizable
or crystalline polyester base resin and an alkali metal salt
of a polyester polymer. Appellants argue (Brief, p. 3):
The PCT reference [Sublett] is distinguishable,
because it is directed to copolymerizing
terephthalate salts into a PET polymer. The present
invention is directed to blending polyester salts
with a polyester polymer. Applicant's blending is
not an obvious variation of the PCT reference's
copolymerizing, because the PCT reference
specifically teaches against blending . . . .
Sublett expressly teaches (p. 4, lines 13-16):
Adding the terephthalate salts to an already-formed
copolymer would cause breakdown of the polymer,
resulting in an undesirable decrease in molecular
weight and inherent viscosity.
4(...continued)
1342 n.3, 166 USPQ 406, 407 n.3 (CCPA 1970).
6
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