A process for producing thiourea dioxide and a process for bleaching pulp for papermaking by the use of thiourea dioxide obtained by said production process
CA 2113642 C · Owner: Kimura, Akiko · Inventors: Koshitsuka, Tetsuo; Kanada, Toshiaki; Shimpo, Masafumi
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
There are disclosed a process for producing a thiourea dioxide fluid by mixing thiourea and a per-oxide, or thiourea, a peroxide and a reaction catalyst or thiourea, a peroxide, a reaction catalyst and a chelating agent, in the absence or presence of pulp and a process for bleaching pulp by the use of the thiourea dioxide fluid produced by the above process economically advantageously with a small chemicals loss and by small consumption of energy
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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 June 8, 1993 and granted November 9, 1999. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended June 8, 2013.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by June 8, 2015.
- 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.