Appeal No. 1998-2077
Application 08/553,324
the description thereof in appellants’ specification (pages 2-4), including the affect of each of the Q, P
and Z stages with respect to the bleaching sequences QPZ and QPZP, on paper brightness, particularly
noting that in using the Z stage, the “lignin content of the pulp is decreased . . . [which] is important since
a pulp bleached with only peroxide or oxygen/peroxide still contains a relatively high content of lignin,
which affects the brightness revision tendency of the pulp” (col. 2, lines 22-34), and appellants
acknowledge that a reduction in lignin content is reflected in a reduced kappa number (specification,
pages 2-3). Backlund further states, with respect to the prior art, that is has been shown that “an ozone
stage after a peroxide stage increases the brightness of sulphite pulp,” that if “a peroxide stage is allowed
to follow the ozone stage, a further increase in brightness is obtained,” and that “this is also the case for
sulphate pulp” (col. 2, lines 35-41). In this respect, both appellants (specification, pages 1-2) and
Backlund (col. 2) refer to the “LIGNOX” bleaching method in “SE-A-8902058,” which foreign patent
document appears to correspond to Lundgren, wherein the bleaching method has the bleaching
sequence QP, and both describe other known bleaching methods in which the bleaching sequence of
“LIGNOX” was expand to the sequences QPZ and QPZP to increase brightness.
I find that Lundgren discloses that the Q stage is carried out under “neutral conditions,” that is, at
a pH of 3.1 to 9.0, and the P stage is carried at an alkaline pH, with the sequence QP being preferably4
used “where the bleaching sequence comprises an oxygen [delignification] stage . . . either immediately
after the delignification of the pulp, i.e., before an optional oxygen stage, or after the oxygen stage,” and
with “a washing stage between the two treatment stages, such that the complex bound metals are
removed from the pulp suspension before the peroxide stage” (col. 1, lines 7-22, and col. 3, line 17, to
col. 5, line 66). While Lundgren teaches that the pH of the Q stage should be adjusted, the reference
does not specifically disclose or claim how that must be accomplished, but does disclose the use of acid
for that purpose (col. 4, lines 30-32).
Similarly, the use of alkali in the P stage is disclosed. With respect to the expanded bleaching
sequences QPZ and QPZP based on this process known in the art as discussed above, I find that the
reference further discloses that “after this two-step treatment, the pulp may be subjected to a final
bleaching to obtain the desired brightness” (col. 4, lines 2-4). Lundgren further teaches that when “using
I note that Lindberg discloses that transition metals “precipitate out as solids if the pH is raised so that
the liquid containing the dissolved metals is sufficiently alkaline. Typically if the pH is greater than 9, and
preferably above 10.5, the metals precipitate out and can be readily filtered” (col. 1, lines 27-33).
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