Method of bleaching pulp with chlorine-free chemicals wherein a complexing agent is added immediately after an ozone bleach stage
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United States of America Patent
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-
Jan 4, 2000
Issued Date -
N/A
app pub date -
Sep 15, 1997
filing date -
Mar 3, 1993
priority date (Note) -
Expired
status (Latency Note)
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Abstract
Kraft pulp is bleached to an acceptable brightness (e.g. 86 ISO or more) without using chlorinated organic compounds, yet the strength of the produced pulp remains commercially acceptable. In the manufacture of pulp, the pulp which is cooked and oxygen delignified to a kappa number of 14 or less, and then is bleached with ozone at a medium consistency. After the ozone treatment, heavy metals are removed from the pulp, and then the pulp is led to oxygen and/or peroxide treatment, which is followed by a second ozone bleaching stage. The sequence (ZT) (EOP) (ZP) is preferred.
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