Appeal No. 1997-4290
Application No. 08/218,647
BACKGROUND
The invention is directed to a chlorine free bleaching process for paper pulp
or dissolving wood pulp. According to Appellants the claimed invention results in
substantial environmental benefits. (Brief, p. 2). Claim 18 which is representative
of the invention is reproduced below:
18. A method of bleaching chemical paper pulp or dissolving wood
pulp, which has been cooked and delignified without employing
chlorine- containing chemicals, comprising a bleaching sequence for
bleaching chemical pulp which comprises at least 4 stages,
a first stage comprising a chelation treatment stage;
a second stage comprising a first peroxide treatment stage, wherein
said first peroxide treatment stage is a delignifying peroxide treatment
stage, in which the amount of peroxide is between 2 and 8 kilo/bone
dry metric tons,
a third stage comprising an acidic delignifying treatment stage,
following said second stage and including a wash, and
a fourth stage comprising a second peroxide treatment stage, following
said third stage and including a wash, wherein said second peroxide
treatment stage is a bleaching peroxide treatment, in which the amount
of peroxide exceeds 3 kilo/bone dry metric tons and exceeds the
amount of peroxide employed in said first peroxide stage.
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