Mixed polyimides and process for preparing them
CA 2021047 C · Owner: Imi-Tech Fibres Gmbh · Inventors: Seidl, Sigrid; Simharl, Reinhold; Weinrotter, Klaus
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
To produce mixed polyimides having structural units of the general formulae, (see fig. I), and (see fig. II), wherein n is an integer larger than 1 and R represents a divalent aromatic residue, a solution of an intramolecular tetracarboxylic acid dianhydride mixture including 50 to 99 % by mol benzophenone-3,3',4,4'tetracraboxylic acid dianhydride and 50 to 1 % by mol pyromellitic acid dianhydride is heated in a polar aprotic solvent and is admixed with an altogether equimolar amount of 2,4- and/or 2,6-toluenediisocyanate and/or methylenebis(phenylisocyanate). The mixed polyimides according to the invention are readily soluble in organic solvents, are flame-retardant and exhibit a good …
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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 12, 1990 and granted May 11, 1999. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended July 12, 2010.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by July 12, 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.