Cross-linked sulphonated polymers and their preparation process

Details Cross-linked sulphonated polymers and their preparation process Cross-linked sulphonated polymers and their preparation process

2002-03-08

2003-11-18

Lipman, Bernard (Department: 1713)

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

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S326200, C525S353000, C525S366000, C525S367000, C525S378000

Reexamination Certificate

active

06649703

ABSTRACT:

FIELD OF INVENTION
The present invention is concerned with cationic ion-exchange resins, particularly in the form of membranes, preferably partially or completely fluorinated, their applications, in particular in electrochemical applications such as fuel cells, alkali-chloride processes, electrodialysis, ozone production, as well as any other application related to the dissociation of anionic centers linked to the membrane, such as heterogeneous catalysis in organic chemistry.
BACKGROUND OF THE INTENTION
Because of their chemical inertia, ion-exchange membranes partially or completely fluorinated are usually chosen for alkali-chloride processes or fuel cells consuming hydrogen or methanol. Such membranes are commercially available under trade names like Nafion™, Flemion™, Dow™. Other similar membranes are proposed by Ballard Inc. in application WO 97/25369 that describes copolymers of tetrafluoroethylene and perfluorovinylethers or trifluorovinylstyrene. The active monomers from which these copolymers are obtained bear chemical functions that are the precursors of ionic groups of the sulfonate or carboxylate type. Example of such precursors are:
wherein
X is F, Cl or CF
3
;
n is 0 to 10 inclusively; and
p is 1 or 2.
Aromatic polymers of the polyimide or sulfonated polyether sulfone type have also been considered, for example:
Once obtained, the copolymer containing the above precursors is molded, for example in the form of sheets, and converted into an ionic form through hydrolysis, to give species of the sulfonate or carboxylate type. The cation associated to the sulfonate and carboxylate anion include the proton, an alkali metal cation (Li
+
, Na
+
, K
+
); an alkaline-earth metal cation (Mg
2+
, Ca
2+
, Ba
2+
); a transition metal cation (Zn
2+
, Cu
2+
); Al
3+
; Fe
3+
; a rare earth cation (Sc
3+
, Y
3+
, La
3+
); an organic cation of the “onium” type, such as oxonium, ammonium, pyridinium, guanidinium, amidinium, sulfonium, phosphonium, these organic cations being optionally substituted by one or more organic radicals; an organometallic cation such as metallocenium, arene-metallocenium, alkylsilyl, alkylgermanyl or alkyltin.
Such membranes suffer from many important disadvantages.
A) Although the copolymers forming the membrane are insoluble in their ionic form, the membrane does not have a good dimensional stability and swells significantly in water or polar solvents. These copolymers form inverted micellia only when heated at high temperatures in a specific mixture water-alcohol that, after evaporation, allows the production of a film. However, this film regenerated in the solid form does not have good mechanical properties.
B) Tetrafluoroethylene (TFE) is a hazardous product to handle, because its polymerisation is performed under pressure and can cause uncontrolled reactions, particularly in the presence of oxygen. Because of the difference of boiling points between the two monomers forming the copolymer, as well as their polarity difference, it is difficult to obtain a statistical copolymer corresponding to the addition rate of each monomer.
C) The ionic groups in high concentration on the chain have a tendency to cause solubilisation of the copolymer. To prevent this phenomenon, the concentration of ionic groups is kept fairly low by adding an important molar fraction of TFE monomers and/or by increasing the secondary chains length (n>1), with the end result that the concentration of the exchangeable ion groups are less than 1 milliequivalent per gram. Consequently, the conductivity is relatively low and highly sensitive to the water content of the membrane, particularly when the latter is acidified for applications in a fuel cell.
D) The penetration of methanol and oxygen through the membrane is high, because the perfluorocarbonated portion of the polymer allows an easy diffusion of the molecular species, which will chemically react at the opposite electrode and cause a loss of faradic efficiency, mainly in methanol fuel cells.
Non-fluorinated systems like sulfonated polyimides or sulfonated polyether sulfones have the same drawbacks because one must compromise between the charged density, and thus the conductivity, and the solubility or excessive swelling.
SUMMARY OF THE INVENTION
The present invention concerns a sulfonated polymer comprising a fraction or all the sulfonyl groups cross-linked, and wherein at least one fraction of the cross-linking bonds bear an ionic charge. More specifically, the cross-linking bonds are of the type:
P—SO
2
—Y
−
(M
+
)—SO
2
—P′
P—SO
2
(M
+
)Y
−
SO
2
—(Q—SO
2
)
r
Y
−
(M
+
)SO
2
—P′
wherein
P and P′ are the same or different and are part of a polymeric chain;
Y comprises N or CR wherein R comprises H, CN, F, SO
2
R
3
, C
1-20
alkyl substituted or unsubstituted; C
1-20
aryl substituted or unsubstituted; C
1-20
alkylene substituted or unsubstituted, wherein the substituent comprises one or more halogen, and wherein the chain comprises one or more substituent F, SO
2
R, aza, oxa, thia ou dioxathia;
R
3
comprises F, C
1-20
alkyl substituted or unsubstituted; C
1-20
aryl substituted or unsubstituted; C
1-20
alkylene substituted or unsubstituted, wherein the substituent comprises one or more halogens;
M
+
comprises an inorganic or organic cation;
Q comprises a divalent radical C
1-20
alkyl, C
1-20
oxaalkyl, C
1-20
azaalkyl, C
1-20
thiaalkyl, C
1-20
aryl or C
1-20
alkylaryl, each being optionally substituted by one or more halogens, and wherein the chain comprises one or more substituents oxa, aza or thia; and
r is 0 or 1.
In a preferred embodiment, M+ comprises the proton, a metal cation, an organometallic cation or an organic cation, the latter 2 optionally substituted with one or more organic radicals comprising:
a proton, an alkyl, an alkenyl, an oxaalkyl, an oxaalkenyl, an azaalkyl, an azaalkenyl, a thiaalkyl, a thiaalkenyl, a dialkylazo, a silaalkyl optionally hydrolysable, a silaalkenyl optionally hydrolysable, each being straight, branched or cyclic and comprising from 1 to 18 carbon atoms;
a cyclic or heterocyclic aliphatic radical comprising from 4 to 26 carbon atoms optionally comprising at least one lateral chain comprising one or more heteroatoms such as nitrogen, oxygen or sulfur;
an aryl, an arylalkyl, an alkylaryl and an alkenylaryl of from 5 to 26 carbon atoms optionally comprising one or more heteroatoms in the aromatic nucleus or in a substituent.
The metal preferably comprises an alkaline metal, an alkaline-earth metal, a rare earth or a transition metal; the organometallic cation comprises a metallocenium, an arene-metallocenium, an alkylsilyl, an alkylgermanyl or an alkyltin, and the organic cation comprises R″O
+
(onium), NR″
+
(ammonium), R″C(NHR″)
2
+
(amidinium), C(NHR″)
3
+
(guanidinium), C
5
R″N
+
(pyridinium), C
3
R″N
2
+
(imidazolium), C
2
R″N
3
(triazolium), C
3
R″N
2
+
(imidazolinium), SR″
+
(sulfonium), PR″
+
(phosphonium), IR″
+
(iodonium), (C
6
R″)
3
C
+
(carbonium), wherein R″ is defined as an organic radical as defined above, and when an organic cation comprises at least two radicals R″ other than H, these radicals can form together a cycle, aromatic or not, eventually containing the center bearing the cationing charge.
In a further preferred embodiment, the divalent radical Q and the sulfonated polymer are partially or completely fluorinated.
The present invention further comprises a process for cross-linking sulfonyl groups of a sulfonated polymer wherein at least a fraction of the cross-linking bonds bear an ionic charge, the process comprising mixing the polymer with a cross-linking agent allowing the reaction between 2 sulfonyl groups from adjacent polymeric chains, to form the said cross-linking bonds. Preferred cross-linking agents are of formula
(M
+
)A
2
Y
−
;
(M
+
)AY
−
SO

Affiliated with

Also associated with

Rating

Cross-linked sulphonated polymers and their preparation process does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Cross-linked sulphonated polymers and their preparation process, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cross-linked sulphonated polymers and their preparation process will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3141256