Appeal No. 1997-3118
Application No. 08/372,083
Appellants’ most preferred multivalent cation is aluminum,
particularly aluminum supplied by alum (specification, page
13, lines 1-3).
Strazdins discloses making paper having good strength
without the need for alum by adding to unbleached pulp 1) a
polysalt composed of specified water insoluble anionic and
water soluble cationic polymers, and 2) an ionization
suppressor (i.e., an acid which has a pH of less than 3 and is
compatible with the polysalt) (col. 1, lines 57-58; col. 1,
line 66 - col. 2, line 2; col. 2, lines 3-20 and 48-56; col.
4, lines 27-39). “The [polysalt-ionization suppressor]
compositions can be successfully added to furnishes which
contain alum in normal amount and which thus have a pH in the
range of 4-6. This secures the full benefit of the alum
present and incorporates alum into the paper, and when one or
both of the polymers carries aldehyde thermosetting
substituents, best wet strength is obtained” (col. 5, lines
16-46). Appellants indicate that the amount of alum normally
used with unbleached pulps is less than 1% (specification,
page 4, lines 13-15), and in Strazdins’ examples the amount
used is 1% (col. 7, line 4; col. 9, line 61).
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