Method for preparation of derivatives of polyvinylidene fluoride
View Patent ↗The invention relates to a method for preparation of a polymer from monomers comprising polyvinylidene fluoride, trifluoroethylene and a third monomer, the method successively comprising: injection of all the monomers to react into a reactor; initiation of a polymerization of the monomers; a continuation step (a) of the polymerization of the monomers, during which a drop in pressure in the reactor is compensated.
1. A method for preparing a polymer starting from monomers comprising vinylidene fluoride, trifluoroethylene and a third monomer, the method comprising, successively:
injecting all the monomers to be reacted into a reactor;
initiating polymerization of the monomers;
(a) continuing the polymerization of the monomers, during which the pressure in the reactor is kept constant by injecting into the reactor a stream of liquid which is immiscible with the monomers and inert with regard to the polymerization, whereby pressure in the reactor is kept about equal to a reference value of 50-130 bar absolute.
2. The method as claimed in claim 1 , in which the pressure is kept constant during (a) by injecting a stream of water into the reactor.
3. The method as claimed in claim 1 , in which, during (a), the pressure in the reactor is kept substantially equal to a reference value of 85 to 95 bar absolute.
4. The method as claimed in claim 1 , further comprising, after (a):
(b) continuing the polymerization of the monomers, during which the temperature inside the reactor increases.
5. The method as claimed in claim 4 , wherein the temperature inside the reactor increases during (b) up to a value of greater than or equal to 50° C.
6. The method as claimed in claim 1 , wherein the temperature inside the reactor during (a) is less than or equal to 55° C.
7. The method according to claim 6 , wherein the temperature inside the reactor during a) is 35°−50° C.
8. The method as claimed in claim 1 , in which a molar proportion of at least 60% of the monomers are consumed during (a).
9. The method as claimed in claim 1 , wherein the third monomer is a haloalkene.
10. The method according to claim 9 , wherein the haloalkene is 2,3,3,3-tetrafluoropropene, 2-chloro-3,3,3-trifluoropropene, 1-chloro-2-fluoroethylene, 3,3,3-trifluoropropene, 1,1,3,3,3-pentafluoropropene, 1,2,3,3,3-pentafluoropropene, 1-chloro-2,2-difluoroethylene, 1-bromo-2,2-difluoroethylene, bromotrifluoroethylene, fluoroethylene, tetrafluoroethylene or hexafluoropropene.
11. The method as claimed in claim 1 , wherein the third monomer is a perfluoroalkyl vinyl ether.
12. The method according to claim 11 , wherein the third monomer is PPVE (perfluoropropyl vinyl ether) or PMVE (perfluoromethyl vinyl ether).
13. The method as claimed in claim 1 , wherein the third monomer is chlorotrifluoroethylene or 1,1-chlorofluoroethylene.
14. The method as claimed in claim 1 , wherein the relative molar proportions of the monomers injected into the reactor, based on the total amount of monomers injected, are:
from 50 to 80% of vinylidene fluoride;
from 15 to 40% of trifluoroethylene; and
from 1 to 15% of third monomer.
15. A polymer able to be obtained according to the method of claim 1 , having a melting point of greater than or equal to 145° C.
16. A film comprising the polymer able to be obtained according to the method of claim 1 , said polymer having a melting point of greater than or equal to 145° C., said film having a thickness from 1 to 5 μm and a dielectric constant of less than 40.