A method of bleaching pulp
CA 2132056 C · Owner: Ronkonharju, Hannu · Inventors: Pikka, Olavi; Nummenaho, Matti; Ronkonharju, Hannu
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
The present invention relates to a method of bleaching pulp to a brightness of at least ISO 80 by utilizing at least two of the following bleaching agents: oxygen ozone, peroxide. The invention is characterized of cooking the pulp, treating the pulp with at least one of the following agents or manners: acidifying EDTA and DTPA, for removing heavy metals delignifying pulp in a, pressurized, two-step oxygen stage and bleaching the pulp, with at least one of the following agents: O2 O3, ClO2, H2O2.
Read the whole patent
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 September 14, 1994 and granted November 24, 1998. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended September 14, 2014.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by September 14, 2016.
- 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.