Peroxide bleach sequence including an acidic bleach stage and including a wash stage
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United States of America Patent
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Aug 12, 2003
Grant Date -
N/A
app pub date -
Mar 28, 1994
filing date -
Oct 1, 1993
priority date (Note) -
Expired
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Abstract
A method and device for bleaching chemical paper pulp or dissolving wood pulp, which has been cooked and delignified without employing chlorine-containing chemicals, comprising a bleaching sequence which comprises optionally a first stage comprising a chelation treatment step; 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 less than 12 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 second step.
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