Peroxide brightening of mechanical pulps
CA 2081002 C · Owner: Pacifica Papers Inc. · Inventors: Eadie, Donald Thomas; Turnbull, James K.; Hetzler, Bernard H.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A method of brightening mechanical pulps by chelating and thickening to reduce the manganese content of the pulp to less than 30 parts per million (Cu less than 1 parts per million) adding ions preferably magnesium ions (e.g. magnesium sulphate MgSO4,) in the amount of 400 to 3,000 ppm Mg ions retained by the pulp based on the oven dry weight of the pulp and thereafter applying a bleaching liquor composed of peroxide (e.g. hydrogen peroxide) and an alkali (e.g. sodium hydroxide) having a ratio of alkali to peroxide of between 1-1 and 2-1 in an amount to apply between 1 to 8 percent peroxide based on the oven dry weight of the pulp and containing no added sodium silicate. Preferably the …
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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 October 20, 1992 and granted March 25, 2003. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended October 20, 2012.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by October 20, 2014.
- 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
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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.