Process for preparing neutral and functional perfluoropolyethers with controlled molecular weight

Claim 1

A process for the scission of perfluoropolyethers selected from those having one of the following general formulae: ##STR10## in which A is --CF 3 ; --C 2 F 5 ; --C 3 F 7 and Z is A or an acid group --COF or a derivative thereof, or the group --CO--CF 3 ; the monomeric units with indexes m, n and r are randomly distributed along the chain of the perfluoropolyether, m, n and r are integers from 0 to 200, and the value of m+n+r being always greater than zero; B--O(--CF.sub.2 CF.sub.2 --O).sub.p --(CF.sub.2).sub.q --Z (II) in which B is --CF 3 , C 2 F 5 ; and Z is B or an acid group --COF or a derivative thereof, the monomeric units with indexes p and q are randomly distributed along the chain of the perfluoropolyether, p and q are integers and p/q is from 0.5 to 2, extremes included; ##STR11## in which Y is an acyl fluoride group --CF(CF 3 )COF and m is an integer greater than zero; said process comprising heating the perfluoropolyether at a temperature from 150° C. to 380° C. in the presence of a catalyst comprising a fluoride and/or oxyfluoride of a metal selected from the group consisting of aluminum, titanium, vanadium, cobalt, nickel and mixtures thereof, in amounts corresponding to 0.1% to 2% by weight on the perfluoropolyether, to obtain the corresponding compounds having a lower molecular weight.