Appeal No. 1997-0090
Application No. 08/083,183
subjecting a chemical paper pulp to a sequence of
treatment steps including purification prior to a final stage
so that its manganese content does not exceed 3 ppm by weight
with respect to the solids, and delignification prior to a
final stage to a kappa number (measured according to the SCAN
standard C1-59) not exceeding 5, said sequence of treatment
stages thereafter including a final stage with hydrogen
peroxide in an alkaline medium, said final stage with hydrogen
peroxide carried out in the presence of at least one
stabilising agent, at a consistency of at least 25% by weight
of solids.
6. The process according to claim 1, wherein the
bleaching is carried out in a treatment sequence consisting
of, other than intermediate stages with a wash composed of
water, a four-stage treatment sequence selected from the group
consisting of O C/D Ep, P, O D Ep P, Q Paa Ep P, and Q C Ep
A
P,
wherein:
O stands for a stage with gaseous oxygen under pressure,
D stands for a stage with chlorine dioxide,
C/D stands for a stage with chlorine and with chlorine
dioxide applied as a mixture,
E [sic. Ep] stands for a stage of alkaline extraction in
p
the presence of hydrogen peroxide,
P stands for a stage with hydrogen peroxide in an
alkaline medium,
C stands for a stage with peroxomonosulfuric acid or one
A
of its salts,
Paa stands for a stage with peracetic acid, and
Q stands for a stage with an acid or a sequestering acid.
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