Process to synthesize ab-pbo monomer and phosphate salts thereof
CA 2021159 A1 · Owner: Lysenko, Zenon · Inventors: Harris, William J.; Lysenko, Zenon; Hurtig, Carl W.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
AB-polybenzoxazole monomer, such as 3-amino-4- -hydroxybenzoic acid, can be synthesized in high yields from a hydroxy-benzoic acid or related compound in a three-step process of (1) nitration, (2) hydrolysis of the ester, and (3) reduction of the nitro moiety. The monomer is conveniently recovered as a phosphate salt in high purity by precipitating and recrystallizing from a phosphoric acid solution. The monomer may be polymerized in high concentrations in polyphosphoric acid containing high levels of P2O5 to yield a high molecular weight polymer wihout dehydrohalogenation.
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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 July 13, 1990. No grant is recorded for it in Canada; had it been granted, its 20-year term would have ended July 13, 2010.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by July 13, 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
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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.