Appeal No. 2006-2694
Application No. 09/910,968
reusing the inhibitor in the manner taught by Higgins would have provided a
cost benefit.
Higgins also teaches that the process of preparing styrene monomer
which includes an inhibitor recycling step “can be operated on . . . a
continuous . . . basis” (Higgins col. 3, ll. 32-33), as recited in claim 9.
Regarding the use of a blend of two nitroxyl inhibitors, Arhancet
discloses that a plurality of nitroxyl inhibitors is useful in preparing styrene
monomers. (Arhancet, col. 2, ll. 3-7 and 28-52.) Because one of ordinary
skill would have recognized that a combination of two of Arhancet’s
nitroxyl inhibitors would effectively inhibit polymerization, we agree with
the Examiner that claim 18 would have been obvious.
Thus, taken together, Arhancet and Higgins would have suggested
performing the steps recited in claims 1, 2, 9, and 18, at the temperatures and
pressures recited in those claims.
Appellants argue that because the dinitrophenol polymerization
inhibitor recycled in Higgins’ styrene monomer production process is not a
nitroxyl-containing compound, Higgins does not suggest the problems of
“using nitroxyl-containing compounds as inhibitors, nor does it suggest that
problems involved in using nitroxyl-containing compounds as inhibitors can
be overcome by recycling a stream containing such inhibitors at
temperatures no higher than about 110°C and at pressures below 760 mm
Hg, as required by the present claims.” (Br. 6.) Rather, Appellants urge,
Higgins discloses operation of the distillation column at an overhead
pressure of 414 mm Hg, resulting in a bottoms temperature of about 131°C,
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