Cotelomers and a process for making them.

摘要

A cotelomer of -CH2CF2- (VDF) units and CF2CF(CF3)- (HFP) units characterised in that the VDF units comprise at least 33% of all VDF and HFP units in the cotelomer combined. Also claimed is a process for preparing a cotelomer in the liquid state comprising reacting (A) a bromine geminal telogen having the general formula RC(R')Br2 wherein R and R' are selected from the group consisting of F and perfluorinated alkyl radicals having 1 to 8 carbon atoms; (B) 1,1-difluoroethene, and (C) hexafluoropropene, the molar ratio of said components (A):(B):(C) being x:1:1 to x:1:5, in which x is 1 to 5.