Ester gp-contg. perfluorinated vinyl ethers having formula CF2=CFOCF2 (A)p (CF2)q COOR, (I), (where A is a divalent perfluorinated 1-10C gp. p is 0 or 1, q is 0 or 1-3 and R is an organic gp) are prepd. by (a) pyrolysing an asymmetric diacyl halide having formula FOC-CF(CF3)OCF2(A)p (CF2)q COX, (II), (where X is is F, Cl or Br), pref. a diacyl fluoride, to form a halocarbonyl gp. contg. perfluorinate vinyl ether having formula CF2=CFOCF2 (A)p (CF2)q COX, (III), and (b) esterification of (III) with an alcohol ROH, pref. at -20 to +40 degrees C. (I) can be copolymerised with other fluorinated monomers to form vulcanisable plastics and elastomers, and are used as monomers for introducing crosslinking positions into the polymer system. (I) can also be used in the prodn. of fluorinated cation exchanger membranes. (I) are obtd. in high yields. Yield in step (b) is 100%.
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