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(11) | EP 0 716 182 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Chlorine-free organosolv pulps |
| (57) This invention provides for a batch and continuous process with countercurrent recycle
of bleaching filtrates for the delignification and bleaching of organosolv pulp. Oxygen
delignification of organosolv pulp is achieved in excess of from about 50% to about
76% as measured by kappa numbers, while the pulp viscosity is minimally decreased
in the range of from about 2 to about 5 cps. Bleaching of delignified pulp is achieved
with peroxy compounds and ozone and pulp brightness of from about 82 to 88 ISO can
be achieved with pulp containing zero level TOX from chlorine based bleaching chemicals
and zero level of AOX in the bleach effluents. Higher brightness of from about 90
to about 92 ISO can also be achieved by addition of very low levels of chlorine based
bleaching chemicals. Corresponding bleach effluents contain less than 200 ppm AOX.
Bleaching filtrates can be recycled for pulp washing and for use with an organosolv
pulping process which results in significant energy savings and mitigation if not
elimination of pollution typically associated with chlorine based bleaching. This
invention also relates to bleach pulp product derived from the process. |