Fluoroelastomers

Abstract

VDF-based curable fluoroelastomers having glass transition temperature lower than −35° C. and an amount of —COF end groups in the polymer lower than the sensitivity limit of the method using the FT-IR spectroscopy described in the present application.

1 . A process to obtain the monomer CF 3 OCF 2 OCF═CF 2  comprising the following steps:
 I obtainment of the fluoroformate CF 3 OCOF;   II reaction of the fluoroformate CF 3 OCOF with elemental fluorine and olefinic compounds having formula:
   CAF═CA′F  (IV) 
 for obtaining the fluorohalogenether of formula
   CF 3 OCF 2 OCFACF 2 A′  (V) 
 
 wherein A and A′, equal to or different the one from the other, are H, Cl or Br, with the proviso that both are not H; 
 the temperature being between −120° C. and −20° C.; 
   III removal of the substituents A and A′ from the fluorohalogenether (V).   
   
   
       2 . A process according to  claim 1 , wherein in step I the fluoroformate CF 3 OCOF is prepared by reaction of CF 3 OF with CO at temperatures between 80° C. and 250° C. 
   
   
       3 . A process according to  claim 1 , wherein in step I the temperature ranges from 120° C. to 230° C. 
   
   
       4 . A process according to  claim 1 , wherein in step I the temperature ranges from 150° C. to 200° C. 
   
   
       5 . A process according to  claim 1 , wherein in step I the molar ratio CF 3 OF/CO is between 0.1 and 10. 
   
   
       6 . A process according to  claim 1 , wherein in step I the molar ratio CF 3 OF/CO is between 0.2 and 5. 
   
   
       7 . A process according to  claim 1 , wherein in step I the molar ratio CF 3 OF/CO is between 0.5 and 2. 
   
   
       8 . A process according to  claim 1 , wherein in step II it is operated in the presence of a perhalogenated solvent, liquid and inert under the reaction conditions. 
   
   
       9 . A process according to  claim 8 , wherein the perhalogenated solvent is an organic compound containing fluorine and/or chlorine. 
   
   
       10 . A process according to  claim 8 , wherein the perhalogenated solvent contains one or more oxygen atoms in the chain and/or aminic groups as end group. 
   
   
       11 . A process according to  claim 8 , wherein the perhalogenated solvent is perfluorinated. 
   
   
       12 . A process according to  claim 11 , wherein the perfluorinated solvent is selected from perfluorocarbons, perfluoroethers, perfluoropolyethers or perfluoroamines, and mixtures thereof. 
   
   
       13 . A process according to  claim 1 , wherein in step II fluorine is diluted with an inert gas. 
   
   
       14 . A process according to  claim 13 , wherein the inert gas is selected from nitrogen or helium. 
   
   
       15 . A process according to  claim 1 , wherein in step I the reaction mixture containing CF 3 OCOF is directly fed, without separation of the mixture components, into the reactor of step II. 
   
   
       16 . A process according to  claim 1 , wherein the reactor used in step I is made of glass, inert perfluorinated plastics, or of metal alloys coated inside with glass or with perfluorinated plastics. 
   
   
       17 . A process according to  claim 16 , wherein the perfluorinated plastics are selected from PTFE, PFA.