Process for bleaching of chemical cellulose pulp
CA 2032315 C · Owner: Samuelson, Hans Olof · Inventors: Samuelson, Hans Olof; Larsson, Per Olof
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Up to now, full scale use of the from the environmental point of view excellent bleaching agent ozone has been, hampered e.g. by the comparatively large amounts required and the excessive depolymerization of the pulp. The present invention aims at solving these problems and relates to a three-step method for bleaching chemical pulp with a lignin content corresponding to a kappa number not exceeding 10. This method is characterized in that the bleaching begins with a chlorine dioxide step at a comparatively high pulp consistency, and that the pulp, after the bulk of chlorine dioxide has been consumed, is intimately contacted with an ozone-containing aqueous solution and brought to react with …
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Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Filed December 14, 1990 and granted April 15, 1997. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended December 14, 2010.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by December 14, 2012.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
Timeline From CIPO dates
Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.