Gel-forming composition based on a cellulose ether, process for preparing a gel, process for the reversible destruction of this gel and its use in secondary oil recuperation

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Listed from its EPO record in Patent Yard's archive of European patents past their term. Its claims, description and drawings are in the EPO PDF and on Google Patents, and the Claude kit works from them.

Why it's free to use

• Filed March 22, 1982 and granted January 2, 1985. A European patent lasts at most 20 years from filing, so its term ended March 22, 2002.
• A supplementary protection certificate, which can extend a medicine or crop-protection patent, adds at most five and a half years, so even that would have ended by September 22, 2007.
• We check European rights only. A US or other national patent in its family could still be in force: check its family on Espacenet or Google Patents.