Polymerization process of sulphonic monomers

Details Polymerization process of sulphonic monomers Polymerization process of sulphonic monomers

2002-12-20

2003-10-28

Pezzuto, Helen L. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S805000, C524S817000

Reexamination Certificate

active

06639011

ABSTRACT:

The invention relates to a polymerization process to obtain sulphonic fluorinated ionomers with high productivity.
Specifically, the invention relates to a polymerization process in emulsion to obtain sulphonic fluorinated-ionomers, said process characterized by high productivity and by operating conditions such to minimize the coagulum formation during the polymerization and the reactor corrosion.
The polymerization of fluorinated monomers in emulsion is known in the prior art. However the productivity data are much lower compared with the polymerization in microemulsion by using ammonium perfluorooctanoate which is the industrially commonly used surfactant for the polymerization in aqueous emulsion of fluorinated monomers. It shows a series of drawbacks with respect to the polymerization in microemulsion. Higher polymerization yields are obtained by using the microemulsion.
The need was therefore felt to have available a polymerization process to obtain sulphonic fluorinated ionomers, said process characterized by high productivity, absence of coagulum formation during the polymerization and minimal reactor corrosion.
An object of the present invention is 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 —SO
2
F;
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
f
—X
−
M
+
 wherein
X is equal to —COO, —SO
3
;
M is selected from H, NH
4
, alkaline metal;
R
f
represents a (per)fluoropolyether chain, preferably having number average molecular weight comprised between about 230 and about 1,800, preferably from 300 to 750, said (per)fluoropolyether chain comprising repeating units selected from one or more of the following:a)
a) —(C
3
F
6
O)—;
b) —(CF
2
CF
2
O)—;
c) —(CFL
0
O)—, wherein L
0
=—F, —CF
3
;
d) —CF
2
(CF
2
)
z′
CF
2
O—, wherein z′ is an integer 1 or 2;
e) —CH
2
CF
2
CF
2
O—.
R
f
is monofunctional, and has a (per)fluorooxyalkyl end group T, for example CF
3
O—, C
2
F
5
O—, C
3
F
7
O—; optionally in the (per)fluoroalkyl end groups one fluorine atom can be substituted by one chlorine or hydrogen 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 (H) and of chain transfer agents.
Preferably during the polymerization the monomer (II) is added by steps.
Examples of end groups containing chlorine or hydrogen atoms are Cl(C
3
F
6
O)—, H(C
3
F
6
O)—. The unit a) C
3
F
6
O is —CF
2
—CF(CF
3
)O— or —CF(CF
3
)CF
2
O
−
.
In particular R
f
has preferably one of the following structures:
1) T—(CF
2
O)
a
—(CF
2
CF
2
O)
b
—CF
2
— with b/a comprised between 0.3 and 10, extremes included, a being an integer different from 0;
2) T—(CF
2
—(CF
2
)
z′
—CF
2
O)
b′
—CF
2
— wherein z′ is an integer equal to 1 or 2;
3) T—(C
3
F
6
O)
r
—(C
2
F
4
O)
b
—(CFL
0
O)
t
—CF
2
— 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.
The compounds wherein R
f
has the following formula are still more preferred:
T—(CF
2
CF(CF
3
)O)
m
(CF
2
O)
n
—CF
2
—
wherein m
=1-30;
wherein T=—OCF
3
or —OCF
2
Cl,
X is a carboxylic group and M is NH
4
, K.
Mixtures of one or more surfactants of the above classes can be used.
The (per)fluoropolyethers R
f
are obtainable with the well known processes of the prior art, see for example the following patents herein incorporated by reference: U.S. Pat. Nos. 3,665,041, 2,242,218, 3,715,378, and the European patent EP 239,123. The functionalized fluoropolyethers with hydroxyl termination are obtained for example according to patents EP 148,482, U.S. Pat. No. 3,810,874, from which the functional groups X are obtained with the processes mentioned in said patents.
At the end of the polymer process a latex is obtained. The latex discharged from the polymerization reactor can be subjected, if desired, to the usual post-treatments depending on the planned uses, in particular on the coagulation and drying process.
The fluorinated monomers of type (I) are selected from:
vinylidene fluoride (VDF);
C
2
-C
8
perfluoroolefins, preferably tetrafluoroethylene (TFE);
C
2
-C
8
chloro- and/or bromo- and/or iodo-fluoroolefins, such as chlorotrifluoroethylene (CTFE) and bromotrifluoroethylene;
(per)fluoroalkylvinylethers (PAVE) CF
2
═CFOR
f
, wherein R
f
is a C
1
-C
6
(per)fluoroalkyl, for example trifluoromethyl, bromo difluoromethyl, pentafluoropropyl;
perfluoro-oxyalkylvinylethers CF
2
═CFOX, wherein X is a C
1
-C
12
perfluoro-oxyalkyl having one or more ether groups, for example perfluoro-2-propoxy-propyl.
The fluorinated monomers of type (II) are selected from:
F
2
C═CF—O—CF
2
—CF
2
—SO
2
F (vinylsulphonylfluoride);
F
2
C═CF—O—[CF
2
—CXF—O]
n
—CF
2
—CF
2
—SO
2
F wherein X=Cl, F or CF
3
; n=1-10;
F
2
C═CF—O—CF
2
—CF
2
—CF
2
—SO
2
F;
F
2
C═CF—Ar—SO
2
F.
Optionally in the polymerization process of the present invention, besides the monomers of type (I) and (II) bis olefins of formula:
R
1
R
2
C═CH—(CF
2
)
m
—CH═CR
5
R
6
  (III)
can bemused as comonomers, in an amount in the range 0.01-5% by moles, wherein:
m=2-10, preferably 4-8;
R
1
, R
2
, R
5
, R
6
, equal to or different from each other, are H or C
1
-C
5
alkyl groups.
Optionally in the polymerization process of the present invention brominated and/or iodinated “cure-site” comonomers, can be fed, as bromo and/or iodo olefins having from 2 to 10 carbon atoms (as described for example in U.S. Pat. No. 4,035,565 and U.S. Pat. No. 4,694,045), or iodo and/or bromo fluoro-alkylvinylethers (as described in U.S. Pat. No. 4,745,165, U.S. Pat. No. 4,564,662 and EP 199,138), in such amounts whereby the “cure-site” comonomer content in the final product is generally comprised between 0.05 and 2 moles per 100 moles of the other basis monomeric units.
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, such for example the compounds of formula R
f
(I)
x
(Br)
y
, wherein R
f
is a (per)fluoroalkyl or a (per)fluorochloroalkyl having from 1 to 8 carbon atoms, while x and y are integers comprised between 0 and 2, with 1≦x+y≦2 (see for example U.S. Pat. No. 4,243,770 and U.S. Pat. No. 4,943,622). It is also possible to use as chain transfer agents iodides and/or bromides of alkaline or alkaline-earth metals, according to U.S. Pat. No. 5,173,553. Other usable chain transfer agents are molecules containing hydrogen, such as hydrocarbons, alcohols, in particular ethyl acetate and ethane.
The polymerization initiators used in the process of the present invention are organic or inorganic. As organic initiators, IPP, DTBP, etc. can for example be mentioned. Preferably radical inorganic initiators, such for example the ammonium and/or potassium and/or sodium persulphate, optionally in combination with ferrous, cupreous or silver salts, are used. The initiator feeding procedures can be in a continuous way or by a single addition at the polymerization starting.
Preferably in the polymerization process of the present invention are used as comonomers:
TFE;
CF
2
═CF—O—CF
2
CF
2
SO
2
F;
optionally a bis-olefin of formula (III), wherein R
1
, R
2
, R
5
, R
6
are H and m=6 or 8.
With the polymerization process of the invention it is possible to obtain sulphonic fluorinated ionomers having a high molecular weight and a good chemical and thermal

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