Appeal No. 2006-2694
Application No. 09/910,968
monomer, increased energy cost, and equipment fouling “owing to the
deposition of polymer in or on the equipment being used.” (Specification 1.)
“A wide variety of compounds has been proposed and used for
inhibiting uncontrolled and undesired polymerization of ethylenically
unsaturated monomers.” (Specification 2.) The Specification discloses that
“nitroxyl radicals are highly efficient polymerization inhibitors under normal
use, providing better performance than most other inhibitors on the
market . . . .” (Specification 5.)
Many manufacturers improve the economics of producing monomers
by recycling and reusing the polymerization inhibitor. (Specification 13.)
“It is known in the industry that the recycling of streams utilizing nitroxyls
as polymerization inhibitors in plants employing temperatures in excess of
about 115° C causes loss of inhibitor efficiency, such that the tar recycle
leads to a higher polymer content than would be expected or desirable.”
(Specification 13.)
DISCUSSION
1. CLAIM CONSTRUCTION
Claims 1, 2, 9, and 17-26 are pending and on appeal. We will focus
on claims 1, 2, 9, and 18, which read as follows:
1. In a process for the production and purification of unsaturated
monomers employing distillation means and a nitroxyl-containing
polymerization inhibitor of said monomers, wherein a process stream
containing the nitroxyl-containing inhibitor is removed downstream of the
distillation means and returned to the process ahead of the distillation means,
the improvement which comprises recycling said stream containing the
nitroxyl-containing inhibitor into the distillation means, wherein the
temperature in the distillation means is no higher than about 110° C and the
pressure is less than 760 mm Hg.
2
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