Appeal No. 1997-3118
Application No. 08/372,083
combination of alum with Smith’s cationic and anionic
polymers.
Economou discloses liquid water insoluble polysalt
coacervates formed by mixing a dilute aqueous solution of an
anionic polyelectrolyte with a dilute aqueous solution of a
cationic polyelectrolyte, and teaches that the coacervates are
“dry-strength agents which can be self-adsorbed by cellulose
fibers in aqueous suspension and which consequently do not
require the addition of alum or other fixing agent” (col. 1,
lines 31-35; col. 2, lines 64-67). Economou, however,
provides examples where the polysalts are used in aqueous
suspensions of bleached fibers containing up to 2% alum based
on the dry weight of the fibers (col. 9, lines 21-40; col. 12,
lines 40-56). In these examples the paper dry strength
increases as the alum is increased to 0.5 wt%, and then
decreases as the amount of alum is further increased.
The examiner argues that Economou “teaches that the
addition of alum improves the strength imparted to paper by
the polysalt formed by the addition of cationic and anionic
polymers to a pulp slurry” (answer, page 4). Economou,
however, does not disclose use of unbleached pulp. The
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