Process for alkaline peroxide bleaching of wood pulp using a quaternary amine as additive
CA 2029923 A1 · Owner: Littleton, Teresa · Inventors: Christiansen, Steven H.; Patton, Robert T.; Littleton, Teresa
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A process for alkaline hydrogen peroxide bleaching of mechanical wood pulp which employs a quaternary amine compound, such as (3-chloro-2-hydroxypropyl)trimethyl ammonium chloride, in the stabilized bleach solution. The brightness of the final paper product made from such bleached pulp shows marked improvement over that in which only chelating agents are employed to improve the brightness according to the known art. The process is useful in both silicate and silicate-free bleach solutions.
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 November 14, 1990. No grant is recorded for it in Canada; had it been granted, its 20-year term would have ended November 14, 2010.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by November 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.