Appeal No. 2001-0098 2
Application No. 08/875,424
THE INVENTION
The invention is directed to a method of treating cellulose pulp by substantially
sequentially acid treating the pulp at a pH of 2-6 under specified conditions so as to
decrease the Kappa number by 1-9 units, the acid treating step designated as D. The pulp
is thereafter treated in a second stage with a complexing or sequestering agent at a pH of
4-9, the treatment with a complexing agent designated as Q. After a washing step, the
pulp is bleached with hydrogen peroxide, the peroxide treatment designated as P.
Accordingly, the sequence of steps may be described as D QP. Additional limitations are
described in the following illustrative claims.
THE CLAIMS
Claims 16 and 36 are illustrative of appellants’ invention and are reproduced below:
16. A method of pre-treating, prior to bleaching with peroxide, cellulose
pulp, to improve bleachability of the pulp, using an acid tower, and a tower in a
second treatment stage, comprising the steps of substantially sequentially:
(a) if necessary, adjusting the pH of the pulp to between 2-6 by adding
aminic acid, sulfuric acid, hydrochloric acid or another acid which does not contain
oxidizing perhydroxyl ions;
(b) feeding the pulp to the acid tower;
(c) treating the pulp in the acid tower at substantially the pH, between 2-6,
to which it has been adjusted in step (a), at a pressure of 0-20 bar, at a
temperature of 75-130oC, and for 20-240 minutes, so that acid treatment
decreases the kappa number by 1-9 units;
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