Appeal No. 2001-0098 8
Application No. 08/875,424
EP’491 is directed to a method for bleaching cellulose pulp wherein prior to the
bleaching the pulp is subjected to acid treatment at a pH of up to about 5 (steps a and c)
and treated with a complexing agent (step e). See Abstract and page 2, lines 1-3 and 43-
48. We find that the treatment with a complexing agent may be carried out in a separate
stage after the acid treatment (step e). See page 3, lines 19-20. We find that the
treatment with a complexing agent and magnesium and calcium compounds take place in a
single step after the acid treatment (step e). We note in this respect that the specification
likewise provides for the addition of calcium and magnesium. See specification, page 5,
lines 20-21. See page 3, lines 24-25 of EP ‘491. We find that after the pretreatment the
pulp is suitably dewatered or washed and is then bleached with a peroxide containing
compound at an alkaline pH (steps f and g). See page 3, lines 26-27, and page 4, lines 4-
5. We find that the acid treatment is performed at a pH of up to about 5 and preferably
from a pH of from 2 to 3 in the presence of hydrochloric or sulfuric acid (steps a and c).
See page 4, lines 12-17. We find that the acid treatment and the treatment with a
complexing agent are carried out at a temperature of from about 10oC to about 100oC
and for a time of from about 1 minute to 600 minutes (steps c and e). See page 5, lines
27-30. We find that the peroxide used maybe hydrogen peroxide (step g) or a mixture
of hydrogen peroxide and oxygen. See page 5, lines 35-39.
Example 1, page 6 discloses the treatment of pulp having a kappa number of 15.7
with sulfuric acid at a pH of 2.0 for 30 minutes. Although the temperature is only 50oC,
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