Patent ID: 7214833
Filing Date: 2007-05-08
Classification: C08G

Abstract:
1. A process to obtain perfluoropolyethers having a reduced absorption at wave lengths lower than 250 nm and having the formula: wherein: with the proviso that: wherein the chlorine atoms, determined by wherein said process comprises the following steps: a) synthesis of the peroxidic perfluoropolyether, carried out by one of the following reactions: a1) TFE photooxidation in the presence of UV light, at low temperature, generally from −40° C. to 100° C., in liquid solvents under the reaction conditions selected between perfluorocarbons and (mono)hydrofluorocarbons, represented by the following general formula:  wherein y is an integer from 2 to 4; x is an integer equal to 0 or 1;  in the presence of fluorine, as regulating agent of the molecular weight, diluted with an inert gas; or a2) TFE oxidation using as radical initiator fluorine or hypofluorites of formula  R b) thermal treatment of the peroxidic product obtained in step a) at a temperature from 150° C. to 250° C., optionally in the presence of a molecular weight regulator selected between fluorine or hypofluorite of formula (III); c) treatment with fluorine of the polymer obtained in step b) at temperatures from 100° C. to 250° C., or by treatment with fluorine in the presence of UV radiations, operating at temperatures from −50° C. to 120° C.