CA2414506A1 - Polymerization process of sulphonic monomers - Google Patents

Abstract

A polymerization process in aqueous emulsion of:
(I) one or more fluorinated monomers containing at least one ethylene unsaturation;

(II) one or more fluorinated monomers containing sulphonyl groups -SO2F;
said process comprising the use of a surfactant having the formula:
R~- X-M' wherein X is equal to -COO, -S03;
M is selected from H, NH4, alkaline metal;
- R~ represents a (per)fluoropolyether chain, preferably having number average molecular weight comprised between about 230 and about 1,800.

Claims (10)

1. A polymerization process in aqueous emulsion of:
(I) one or more fluorinated monomers containing at least one ethylene unsaturation;
(II) one or more fluorinated monomers containing sul-phonyl groups -SO2F;
said process comprising:
reactor purging, monomer (II) introduction in liquid form into the reactor, reactor pressurization with gaseous monomers (I); addition of at least one surfactant of formula:
R~-X-M' wherein:
X is equal to -COO, -SO3;
M is selected from H, NH4, alkaline metal;
R~ represents a (per)fluoropolyether chain, prefe-rably having number average molecular weight comprised between about 230 and about 1,800, preferably from 300 to 750, said (per)fluoropoly-ether chain comprising repeating units selected from one or more of the following:
a) - (C3F6O) -;
b) - (CF2CF2O) -;
c) - (CFL0O) -, wherein L0 = -F, -CF3;

d) -CF2(CF2)2,CF2O-, wherein z' is an integer 1 or 2;

e) -CH2CF2CF2O-.

R f is monofunctional, and has a (per)fluorooxyalkyl end group T, optionally in the (per)fluoroalkyl end groups one fluorine atom is substituted by one chlorine or hydr-ogen atom;

addition of the initiator, and during the polymerization feeding of monomers (I) so as to maintain constant the reactor pressure; optionally further addition of monomer (II) and chain transfer agents.

2. A process according to claim 1, wherein the monomer (II) is added by steps.

3. A process according to claims 1-2, wherein R f has one of the following structures:

1) T-(CF2O)a-(CF2CF2O)b-CF2-with b/a comprised between 0.3 and 10, extremes in-cluded, a being an integer different from 0;

2) T-(CF2-(CF2)z'-CF2O)b'-CF2-wherein z' is an integer equal to 1 or 2;

3) T-(C3F6O)r-(C2F4O)b-(CFL0O)t-CF2-with r/b = 0.5-2.0 (r+b)/t = 10-30, b and t being integers different from 0 when all the units with indexes r, b, and t are present; or b=t=0, or b=0;

a, b, b', r, t, are integers, whose sum is such that R f has the above values of number average molecular weight.

4. A process according to claims 1-3, wherein the fluorinated monomers of type (I) are selected from:

- vinylidene fluoride (VDF);

- C2-C8 perfluoroolefins, preferably tetrafluoroethy-lene (TFE);

- C2-C8 chloro- and/or bromo- and/or iodo- fluoroole-fins, such as chlorotrifluoroethylene (CTFE) and bromotrifluoroethylene;

- (per)fluoroalkylvinylethers (PAVE) CF2=CFOR f, wherein R f is a C1-C5 (per)fluoroalkyl, for example trifluo-romethyl, bromo difluoromethyl, pentafluoropropyl;

- perfluoro-oxyalkylvinylethers CF2=CFOX, wherein X is a C2-C12 perfluoro-oxyalkyl having one or more ether groups, for example perfluoro-2-propoxy-propyl;

the fluorinated monomers of type (II) are selected from:

- F2C=CF-O-CF2-CF2-SO2F (vinylsulphonylfluoride);

- FCC=CF-O-(CF2-CXF-O]n-CF2-CF2-SO2F

wherein X = Cl, F or CF3; n = 1-10;

- F2C=CF-O-CF2-CF2-CF2-SO2F;

- F2C=CF-Ar-SO2F.

. A process according to claims 1-4 , wherein in the polyme-rization process comonomers in an amount in the range 0.01-5% by moles, bis olefins of formula:

R1R2C=CH-(CF2)m-CH=CR5R6 (III) are used, wherein:
m = 2-10, preferably 4-8;
R1, R2, R5, R6, equal to or different from each other, are H or C1-C5 alkyl groups.

6. A process according to claims 1-5, wherein in the polyme-rization process brominated and/or iodinated "cure-site"
comonomers are fed; alternatively or also in combination with the "cure-site" comonomers, it is possible to introduce in the end groups iodine and/or bromine atoms by addition to the reaction mixture of iodinated and/or brominated chain transfer agents or chain transfer agents containing hydrogen, such as hydrocarbons, alcohols, in particular ethyl acetate and ethane.

7. A process according to claims 1-6, wherein in the pol-ymerization process as comonomers are used:

- TFE;

- CF2=CF-O-CF2CF2SO2F;
optionally a bis-olefin of formula (III) , wherein R1, R2, R5, R5 are H and m = 6 or 8.

8. A process according to claims 1-7, wherein the sulphonic fluorinated ionomers have equivalent weight comprised between 300 and 1,700.

9. A process according to claims 1-8, wherein the polyme-rization is carried out at temperatures in the range 25°-130°C, at atmospheric pressure or under pressure, prefe-rably from 2 bar up to 60 bar.

10. A process according to claim 9, wherein the temperature is in the range 50°-70°C, preferably 50°-60°C, under pressure up to 30 bar, preferably higher than 8.