Pre-treatment of sulfite pulp before bleaching with oxygen containing chemicals
CA 2121969 C · Owner: Garrood, Bernard Frederick · Inventors: Sen, Ben; Becker, Edward; Garrood, Bernard Frederick
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
This invention relates to the pre-treatment of sulfite pulp. More particularly, this invention relates to a novel process for caustic extraction of unbleached sulfite pulp to reduce metallic impurities in the pulp. The process of reducing metallic impurities in unbleached sulfite pulp comprises subjecting the pulp to caustic extraction.
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 April 22, 1994 and granted November 4, 1997. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended April 22, 2014.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by April 22, 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.