Process for preparing perfluoroethers by fluorination with elemental fluorine

Claim 1

A process for preparing compounds having general formula: ##STR10## wherein: R 1 is a perfluoroalkyl containing 1 to 10 carbon atoms or an perfluoroalkylether containing 2 to 10 carbon atoms: R 2 and R 3 either equal to or different from each other, can be fluorine or perfluoroalkyl containing 1 to 10 carbon atoms or perfluoroalkylether containing 2 to 10 carbon atoms; R 4 is fluorine or fluoroalkyl containing 2 to 10 carbon atoms, either or not containing halogen atoms other than fluorine; R 1 and R 2 being susceptible of forming, together, a divalent perfluoroalkyl radical containing 2 carbon atoms, optionally comprising 1 to 2 oxygen atoms in the chain; comprising reacting elemental fluorine with an at least partially hydrogenated ether compound, in the presence of a reaction solvent consisting of a perfluoropolyether, and of an alkaline metal fluoride in an amount ranging from 1 to 10 moles per hydrogen atom of the starting product, at a temperature ranging from 20° to 150° C.