CA1289291C - Fluoropolymer solutions - Google Patents

Abstract

ABSTRACT

The invention is a solution composition comprising a fluorinated polymer containing sites convertible to ion exchange groups dissolved in a solvent, wherein the densities of the fluorinated polymer and solvent are balanced. The most preferred solvent is 1,2-dibromotetrafluoroethane and has a boiling point of less than 110°C; and a solubility parameter of from greater than 7.1 to 8.2 hildebrands.
The composition can be used to make ion exchange media, films and articles for use in electrolytic cells, fuel cells and gas or liquid permeation units.

Description

9~1 NOVEL FLUOROPOLYMER SOLUTIONS- --Ion exchange active fluoropolymer films or sheets have been widely used in industry, particu-larly as ion exchange membranes in chlor-alkali cells.
Such membranes are made from fluorinated polymers having ion exchange active groups attached to pendant groups on the polymeric backbone.

Such polymers are usually thermoplastic and may be fabricated into films or sheets while in their molten form ~sing mechanical extrusion equipment.
However, such equipment is operated in the temperature region near the crystalline melting point of the polymer, which is commonly near the decomposition temperature of some of the polymers. Thus, decomposition may be a problem when some polymers are formed into films by conventional methods. Likewise, it is difficult to make such polymers into films thinner than about lO
microns using such techni~ues. In addition, it is difficult to make films of consistent thickness. It would therefore be highly desirable to be able to make films having a consistent thickness.

32,176-F -1-1289~9.

Forming membrane structures and support structures into multiple layers is the subject of several patents and applications includi~g U.S. Patent Nos. 3,925,135; 3,909,378; 3,770,567; and 4,341,605.
However, these methods use complicated procedures and equipment including such things as vacuum manifolds, - rolls.and release media.

Prior art methods ~for fabricating films from perfluorinated polymers have been limited by the solu-bility of the polymers and the temperature-dependent viscosity shear rate behavior of the polymers. To overcome these characteristics of perfluorinated car-boxylic ester polymers, workers have tried to swell the polymers using various types of swelling agents and to reduce the fabrication temperatures of the polymers to practical ranges by extraction. Extractions methods have been taught in, for example, U.S. Patent No.
4,360,601. There, low molecular weight oligomers were removed from carboxylic ester polymers. Polymer "fluff"
29 was extracted in a Soxhlet device at atmospheric pres-sure for 24 hours (see Examples 1 and 3 of U.S. Patent No. 4,360,601). Such treatment has been found to make some fluorinated carboxylic ester copolymers more processible and operate more efficiently in a chlor--alkali cell when in a hydrolyzed form. such extrac-tions modify the fabricated polymer article, for example, by forming a grease of .the polymer as shown in Example 3 of U.S. Patent No. 4,360,601.

In addition, such extractions seem to lower processing temperatures of carboxylic ester polymers after isolation. Isolation means separation from the 32,176-F -2-39~91 polymerization latex by conventional methods of deacti-vating the surfactant such as freezing, heating, shear-ing, salting out or pH adjustment.

British Patent No. 1,286,859 teaches that highly polar organic "solvents" dissolve small amounts of a fluorinated vinyl ether/tetrafluoroethyl-ene copolymer in its thermoplastic form. Thermoplastic form means the polymer i-s in a for~ which can be molded or processed above some transition temperature (such as the glass transition temperature or the melting point) without altering its chemical structure or composition.
The patent teaches the use of "solvents" including butanol, ethanol, N,N-dimethylacetamide, and N,N-dimethylaniline.

Similar approaches have been used to swell membranes in their ionic forms. Ionic forms of mem-branes are membranes which have been converted from their thermoplastic form (-SO2F or -COOCH3j to their ionic forms (-SO3M or -COOM where M is H , K , Na , or NH4 or other metal ion.

Prior art workers have used highly polar solvents or mixtures of solvents on substantially perfluorinated polymers and less polar solvents on fluorinated polymers containing hydrocarbon components . 25 as co-monomers, ter-monomers or crosslinking agents.

However, each of the prior art methods for swelling, dispersing or extracting the polymers has certain shortcomings which are known to those practi-cing the art. Polar solvents have the potential for .

32,176-F -3-,, 9~91 water absorption or reactivity with the functional groups during subsequent fabrication operations, thus making poor coatings, films, etc. High boiling solvents are difficult to remove and frequently exhibit toxic or flammability properties. Functional forms (ionic forms) of the polymers can react with solvents. (See Analyt-- - ical Chem., 1982, Volume 54,-pages 1639-1641).

- -~ The more polar of the solvents such as meth-anol, butanol esters, and ketones as disclosed in U.S.
Patent No. 3,740,369; British Patent No. 1,286,859; and Chemical Abstracts 7906856, have high vapor pressures at ambient conditions, which is desirable for solvent removal; however, they tend to absorb water. Their water content is undesirable because it causes problems in producing continuous coatings and films of hydropho-bic polymers. In addition, polar solvents frequently leave residues which are incompatible with the polymers.
Also, they frequently leave residues which are reactive during subsequent chemical or thermal operations if they are not subsequently removed.

Another approach taken by the prior art workers to form films from fluoropolymers include the use of high molecular weight "solvents" which have been produced by halogenating vinyl ether monomers. (See British Patent No. 2,066,824).
.
The swelling of the functional (ionic) forms of the fluoropolymers by polar or hydrophilic agents has been known for some time. In addition, the solvent solubility parameters were compared to the swelling effect of 1200 equivalent weight Nafion ion exchange 32,176-F -4-~ 3 ~

membrane (available from E. I. DuPont Company) by Yeo at Brookhaven Laboratory (see PolYmer, 1980, Volume 21, page 432).

The swelling was found to be proportional to two different ranges of the solubility parameter and a calculation was developed for optimi~ing ratios of solvent mixtures. Ionic forms of functional fluoro-- polymers may be treated in such a manner,-however,-the --subsequent physical forming or manipulation of the polymers into usable configurations by any thermal operation is limited when the polymers are in the functional forms. In addition, non-ionic forms of polymers treated in this manner are also limited in the thermoplastic processing range by the stability of-the 15 functional group bonds. -.

Other solvation methods have used temperatures near the crystalline melting points of the polymers being solvated, thus requiring either high boiling point "solvents" or high pressure vessels to maintain the system in a solid~liquid state. See Analytical Chem., 1982, Volume 54, pages 1639-1641.

Burrell states the theory of Bagley [J. Paint Tech., Volume 41, page 495 (1969)] predicts a non-crystal-line polymer will dissolve in a solvent of similar solubility parameter without chemical similarity, association, or any intermolecular force. However, he fails to mention anything about the solubility of polymers demonstrating crystallinity.

More particularly, the invention resides in a-solution comprising a perfluorinated polymer 32,176-F -5-1289Z9~

containing sites convertible to ion exchange groups dissolved in a solvent wherein the fluorinated polymer is a copolymer comprising a first monomer represented by the general formula;

CF2=CZZ' where:
Z and Z' are independently selected from -H,--Cl, -F, and CF3;
and a second monomer represented by the general formula;
Y-(CF2)a-(CFRf)b-(CFRf.)~-O-[CF(CF2X)-CF2-O]n-CF=CF2(II) where Y is selected from -SO2Z, -CN, -COZ, and C(R3f)(R4f)OH;
Z is selected from I, Br, Cl, F, OR and NRlR2;
R is selected from a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
R3f and R4f are independently selected from perfluoroalkyl radicals having from 1 to 10 carbon ; atoms;
Rl and R2 are independently selected from H, a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;

32,176-F -6-39~91 -6a-a is 0-6;
b is 0-6i c is 0 or 1;
provided a+b+c is not equal to 0;
x is selected from Cl, Br, F, and mixtures thereof when n>l;
n is 0 to 6; and Rf and Rf. are independently selected from F, Cl, perfluoroalkyl radicals having from 1 to 10 carbon atoms and fluorochloroalkyl radicals having from 1 to 10 carbon atoms, and wherein the solvent is represented by the general formula:

XCF2-CYZX ' wherein:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, 0 Cl, Br, I and R';
R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms, said solvent having a boiling point less than 110C; an25 a solubility parameter of from greater than 7.1 up to 8.2 hildebrands.
The most preferred solvent is 1,2-dibromo- 0 tetrafluoroethane (commonly known as FREON 114 B 2) BrCF2-CF2Br and 1,1,3-trichlorotrifluoroethane (commonly known as Freon 113):
ClF2C-CCl2F

32,176-F -6a-~2~39~

-6b-of these two, 1,2-dibromotetrafluoroethane is the most preferred solvent. It has a boiling point of about 47.3C, a density of about 2.156 grams per cubic centimeter, and a solubility parameter of about 7.2 hildebrands.
The present invention also comprises a method for dissolving a fluorinated polymer containing sites convertible to ion exchange groups, comprising the steps of contacting the polymer with a solvent for a time and at a temperature sufficient to dissolve at least a portion of the polymer in the solvent. The fluorinated polymer and the solvent being the specific polymer and solvent hereinbefore defined.

32,176-F -6b-1~3929~

The present invention can be used to make ion exchange media, films and articles for use in electro-lytic cells, fuel cells and gas or liquid permeation units.

Non-ionic forms of perfluorinated polymers described in the foll~wing U.S. patents are suitable for use in the present invention: 3,282,875; 3,909,378;
4,025,405; 4,065,366; 4,116,~8`8; 4,123,336; 4,126,588;
4,151,052; 4,176,215; 4,178,218; 4.192,725; 4,209,635;
4,212,713; 4,251,333; 4,270,996; 4,329,435; 4,330,654;
4,337,137; 4,337,211; 4,340,680; 4,357,218; 4,358,412;
4,358,545; 4,417,969; 4,462,877; 4,470,889; and 4,478,695; and European Publication No. 0,027,009.
Such polymers usually have equivalent weights in the range of from 500 to 2000.

Particularly preferred are copolymers of monomer I with monomer II (as defined below). Option-ally, a third type of monomer may be copolymerized with I and II.

The first type of monomer is represented by the general formula:

CF2=CZZ' (I) ~ where: .}
Z and Z' are independently selected from of -H, -Cl, -F, and CF3.

The second monomer consists of one or more monomers selected from compounds represented by the general formula:

32,176-F -7-~9~91 Y-(cF2)a~(cFRf)b-(cFRfl)c-o-[cF(cF~x)-cF2-o]n-cF=cF2 (II) where:
Y is selected from -so2Z, -CN, -CoZ, and C(R3f~(R4f)OH;
Z is selected from I, Br, Cl, F, OR, and NRl R2 i ` - -R is selected from a branched or linear alkyl - radical having from-1 to 10 carbon atoms and an aryl radical;
R3f and R4f are independently selected from perfluoroalkyl radicals having from 1 to 10 carbon atoms;
Rl and R2 are independently selected from H, a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
a is 0-6;
b is 0-6;
c is 0 or 1;
provided a+b+c is not equal to 0;
X is selected from Cl, Br, F, and mixtures thereof when n>1;
n is 0 to 6; and Rf and Rf, are independently selected from F, Cl, perfluoroalkyl radicals having from 1 to 10 car-bon atoms, and fluorochlororadicals having from 1 to 10 carbon atoms. . . .

Particularly preferred is when Y is -SO2F or -COOCH3; n is 0 or 1; Rf and Rf, are F; X is Cl or F;
and a+b+c is 2 or 3.

32,176-F -8-~ ~9291 g .

The third and optional monomer suitable is one or more monomers selected from the compounds repre-sented by the general formula:

- Y ~(CF2)al-(CFRf)bl-(CFRfl )C,-O-[CF(CF2X' )-CF2-O]n,-CF=CF2 (III) where:
~ - Y' is selected from F, Cl and Br;
a' and b' are independently 0-3;
c is 0 or 1;
provided a'+b'+c' is not equal to 0;
n' is 0-6;
Rf and Rf, are independently selected from Br, Cl, F, perfluoroalkyl radicals having from 1 to 10 carbon atoms, and chloroperfluoroalkyl radicals having from 1 to 10 carbon atoms; and X' is selected from F, Cl, Br, and mixtures thereof when n'>1.

Conversion-of Y to ion exchange groups is well known in the art and consists of reaction with an alkaline solution.

It has been discovered that certain perhalo-genated solvents have a surprising effect of dissolving the polymers defined above, especially when the polymers are in a finely divided state.

It is important that the solvent has a boil-ing point of from 30C to 110C. The ease of removal of the solvent and the degree of solvent removal is important in the production of various films, coatings 32,176-F -9-~39~91 and the like, without residual solvent; hence a reason-able boiling point at atmospheric pressure allows con-venient handling at ambient temperature conditions yet effective solvent removal by atmospheric drying or mild warming.

It was discovered that in the prior art no recognition and thus no attempt was made to balance - density. The prior art was only interested in forming - -solutions and solutions do not separate.

Solubility parameters are related to the cohesive energy density of compounds. Calculating solubility parameters is discussed in U.S. Patent No.
4,348,310.

It is important that the solvent has a solu-bility parameter of from greater than 7.1 and up to 8.2hildebrands. The similarity in cohesive energy den-sities between the solvent and the polymer determine the likelihood of dissolving and swelling the polymer in the solvent.

It is preferable that the solvent has a vapor pressure of up to about 760 mm Hg at the specified temperature limits at the point of solvent removal.
The solvent should be conveniently removed without the necessity of higher temperatures or reduced pressures 25- involving extended heating such as would be necessary in cases similar to U.S. Patent No. 3,692,569 or the examples in British Patent No. 2,066,824 in which low pressures (300 millimeters) had to be employed as well as non-solvents to compensate for the higher boiling points and low vapor pressures of the complex solvents.

32,176-F -10-, 12~ 9~L

It has been found that solvents represented by the following general formula are par-ticularly preferred provided they also meet the charac-teristics discussed above (boiling point and solubility parameter):

XCF2-CYZ-X ' wherein: ~
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms.

The most preferred solvents are 1,2-dibromo-tetrafluoroethane (commonly known as Freon~114 B 2):

BrCF2-CF2Br and 1,2,3-trichlorotrifluoroethane (commonly known as Freon 113):

ClF2C-CCl2F

Of these.two solvents 1,2-dibromotetrafluoro-ethane is the most preferred. It has a boiling point of about 47.3C, a density of about 2.156 grams per cubic centimeter, and a solubility parameter of about 7.2 hildebrands.

:
e~ k 32,176-F -11-. -:, !: ~

29~

1,2-d~bromotetrafluoroethane is thought to work particularly well because, though not directly polar, it is highly polarizable. Thus, when 1,2-dibromo-tetrafluoroethane is associated with a polar molecule, its electron density shifts and causes it to behave as a polar molecule. Yet, when 1,2-dibromotetrafluoro-ethane is in contact with a non-polar molecule, it behaves as a non-polar solvent. Thus, 1,2-dibromo-- tetrafluoroethane tènds to dissolve the non-polar backbone of polytetrafluoroethylene and also the polar, ion-exchange-containing pendant groups. The solubility parameter of 1,2-dibromotetrafluoroethane is calculated to be from 7.13 to 7.28 hildebrands.

It is surprising that an off-the-shelf, readily-available compound such as 1,2-dibromotetra-fluoroethane would act as a solvent for the fluoro-polymers described above. It is even more surprising that 1,2-dibromotetrafluoroethane happens to have a boiling point, a density, and a solubility parameter such that it is particularly suitable for use as a solvent in the present invention.

In practicing the present invention, the polymer may be in any physical form. However, it is preferably in the form of fine particles to speed dissolution of the particles into the solvent.
Preferably, the particle size-of the polymers is from : 0.01 microns to 840 microns. More preferably, the particle size is less than 250 microns.

To dissolve the polymer particles into the solvent, the polymer particles are placed in contact with the solvent of choice and intimately mixed. The - 32,176-F -12-9~9~

polymer and the solvent may be mixed by any of several means including, but not limited to, shaking, stirring, milling or ultra sonic means. Thorough, intimate contact between the polymer and the solvent is needed for optimum dissolution.

The polymers of the present invention are dissolved into the solvent at concentrations up to 0.5 -weight percent of polymer to solvent. At concen-trations below 0.1 weight percent, there is insuffi-cient polymer dissolved to be effective as a medium for coating of articles or forming films within a reasonable number of repetitive operations. Conversely, the amount of polymer that dissolves is about 0.5 weight percent polymer. Higher concentrations of polymers in - 15 solutions can be obtained by evaporating solvent from the above solutions until the solubility limits of the polymers are approached.

Dissolving of the polymer into the solvent can be conducted at room temperature conditions.
20 However, the optimum solution effects are best achieved at temperatures from 10C to 50C. At temperatures above 50C the measures for dissolving the polymer have to include pressure confinement for the preferred solvents or method of condensing the solvents. Con-versely, at temperatures below 10C many of thepolymers of the present invention are below their glass transition temperatures thus causing their solutions to be difficult to form at reasonable conditions of mixing, stirring, or grinding.

Dissolving the polymers of the present inven-tion into the solvent are best conducted at atmospheric '.
32,176-F -13-"
:
,, ~' .
: - , ~, ~
~ ~ .
:. . .
., pressure. However, solution effects can be achieved at pressures from 760 to 15,000 mm Hg or greater. At pressures below 760 mm Hg, the operation of the appar-atus presents no advantage in dissolving polymers, rather hindering permeation into the polymers and thus preventing forming of the solutions.
, Conversely, pressures above 760 mm Hg aid in dissolving polymers very little compared to the di-f-iculty and complexity of the operation. Experiments have shown that at about 20 atmospheres the amount of polymer dissolved in the solvent is not appreciably greater.

After the polymer compositions of the present invention have been formed, they may be fixed to other polymer films or substrates by sintering or compression to fix the polymer from the solution to the substrate.

The following methods are suitable for fixing the solution of the present invention to a substrate.
Dipping the substrate into the solution followed by air drying and sintering at the desired temperature with sufficient repetition to build the desired thickness.
Spraying the solution onto the substrate is used to advantage for covering large or irregular shapes.
Pouring the solution onto the substrate is sometimes used. Painting the solution with brush or roller has been successfully employed. In addition, coatings may be easily applied with metering bars, knives or rods.
Usually, the coatings or films are built up to the thickness desired by repetitive drying and sintering.

32,176-F -14-~9~

The type of substrate upon which the solution of the present invention may be applied can include such things as glass, polytetrafluoroethylene tapes, or sheets, expanded mesh metal electrodes, scrim materials made of, for example, fibers selected from carbon-, PTFE
and metal, metal foil or sheets, or other polymer films or o~jects.

The substrate upon which the sol~tion is to be deposited is cleaned or treated in such a way as to assure uniform contact with the solution. The sub-strate can be cleansed by washing with a degreaser or solvent followed by drying to remove any dust or oils from objects to be used as substrates. Metals should usually be acid etched, then washed with a solvent to promote adhesion, if desired, unless the metal is new in which case degreasing is sufficient.

After being cleaned, the substrates may be pre-conditioned by heating or vacuum drying prior to contact with the solution in the coating operation.
Temperatures and pressures in the following ranges are preferably used: about 20 mm Hg at about 110C is sufficient in all cases; however, mild heat is usually adequate when applied at a temperature of about 50C at atmospheric pressure.

After preparation, the substrates are coated with the solution by any of several means including, but not limited to, dipping, spraying, brushing, pour-ing. Then the solution may be evened out using scrap-ing knives, rods, or other suitable means. The solu-tion can be applied in a single step or in several steps depending on the concentration of the polymer in 32,176-F -15-9Z~3~

the solution and the desired thickness of the coating or film.

Following the application of the solution, the solvent is removed by any of several methods including, but not limited to, evaporation or extrac-tion. Extraction is the use of some agent which selec-tively dissolves or mixes with the solvent but not the polymer. - -These removal means should be employed until a uniform deposition of polymer is obtained and acontinuous film is formed.

The solvent removal is typically carried out by maintaining the coated substrate at temperatures ranging from 10C to 110C, with the preferred heating range being from 20C to 100C. The temperature selec-ted depends upon the boiling point of the solvent.

Heating temperatures are customarily in the range of from 20C to 50C for 1,2-dibromotetrafluoro-ethane.
.

The pressures employed for the removal of the solvent from the coated substrate can range from 20 mm Hg to 760 mm Hg depending on the nature of the solvent, although pressures are typically in the range of from 300 mm Hg to 760 mm Hg for 1,2-dibromotetrafluoroethane.

The forming of the coating or film can be carried out as part of the polymer deposition and solvent removal process or as a separate step by adjusting the thermal and pressure conditions 32,176-F -16-~, i "

~289~91 associated with the separation of the polymer from the solvent. If the solution is laid down in successive steps, a continuous film or coating free from pinholes can be formed without any subsequent heating above ambient temperature by control of the rate of evapor-ation. This can be done by vapor/liquid equilibrium in - a con~tainer or an enclosure; therefore, the solvent removal step can be merely a drying step or a control-~ - led process for forming a coating or film. If the solvent is removed as by flash evaporation, a film will not form without a separate heating step.

After the solvent has been removed, -the residual polymer, as a separate step, is preferably . subjected to a heat source at a temperature of from 15 250C to 380C for a period of time ranging from 10 seconds to 120 minutes, depending upon the thermo-plastic properties of the polymers. The polymers having melt viscosities on the order of 5 x 105 poise at about 300C at a shear rate of l sec. 1, as measured by a typical capillary rheometer, would require the longer times and higher temperatures within the limits . of the chemical group stability. Polymers with viscosi-ties on the order of 1 poise at ambient temperatures would require no further treatment.

The most preferred treatment temperatures are from 270C to 350C and a time of from 0.2 to 45 m~nutes for the most preferred polymers for use in the present invention. Such polymers form continuous films under the conditions described above.

32,176-F -17-~2~9~9~

Films of varying thicknesses can be easily produced by the methods and means described above.
Such films are suitable as membranes when in their ionic forms for use in electrochemical cells. They are particularly useful for the electrolysis of sodium chloride brine solutions to produce chlorine gas and sodium hydroxide solutions. Membranes prepared accord-ing to the present invention have surprisingly good curreht efficiencies when used in chlor-alkali ce~ls. ~

EXAMPLES
Exam~le 1 A terpolymer solution was prepared from mon-omers represented by general formulas I; II, and III
set forth hereinafter: -.

CF2=CF-0-CF2-CF2-CF2-Cl; (I) CF2=CF-O-CF2-CF2-CO-0-CH3, (II) and CF2=CF2 (III) The terpolymer solution was prepared by the following techniques: 7.0 grams of monomer I and 14 grams of monomer II was added to 400 ml of deoxygenated water containing 3 grams of K2S2O8, 1.5 grams of Na2HPO~
and 3.5 grams of C7Fl5CO2K under a positive pressure of monomer III in a 1 liter glass-lined reactor at a temperature of 25C and 70 psig (482 kPa) pressure with stirring for 105 minutes. The reactor was then vented and the contents were acidified with 50 ml of concen-trated hydrochloric acid to coagulate the latex. The polymer was vigorously washed to remove residual salts -~ 30 and soap and monomers. Some of the terpolymer was ~; ' .

32,176-F -18-.
. ~ ~

- . .

9~9~

dissolved in 150 milliliters of BrCF2CF2Br by stirring 20 grams of the polymer at a reflux temperature of 47.3C for 2 hours. At least a portion of the polymer dissolved in the solvent. The solution was analyzed by 5 evaporating a portion of the solution and weighing the polymer remaining in the container and found to contain 0.3 weight percent polyme . 50 Milliliters of this solution was poured into a petri dish and the solvent was allowed to evaporate. This yieldèd a continuous polymer film in the bottom of the dish. This film was hydrolyzed with a 15 percent weight percent KOH in methanol solution for 1 hour at a temperat~re of 50C.
The polymer thickness was measured and found to be 2 mils (50.8 micron) thick.

32,176-F -19-

Claims (10)

1. A solution composition comprising a fluorinated polymer containing sites convertible to ion exchange groups dissolved in a solvent wherein the fluorinated polymer is a copolymer comprising a first monomer represented by the general formula;

CF2=CZZ' (I) where:
Z and Z' are independently selected from -H,--Cl, -F, and CF3;
and a second monomer represented by the general formula;

Y-(CF2)a-(CFRf)b-(CFRf')c-O-[CF(CF2X)-CF2-O]n-CF=CF2(II) where Y is selected from -SO2Z, -CN, -COZ, and C(R3f)(R4f)OH;
Z is selected from I, Br, Cl, F, OR and NR1R2;
R is selected from a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;

32,176-F -20-R3f and R4f are independently selected from perfluoroalkyl radicals having from 1 to 10 carbon atoms;
R1 and R2 are independently selected from H, a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
a is 0-6;
b is 0-6;
c is 0 or 1;
provided a+b+c is not equal to 0;
X is selected from Cl, Br, F, and mixtures thereof when n>1;
n is 0 to 6; and Rf and Rf' are independently selected from F, Cl, perfluoroalkyl radicals having from 1 to 10 carbon atoms and fluorochloroalkyl radicals having from 1 to 10 carbon atoms, and wherein the solvent is represented by the general formula:

XCF2-CYZX' wherein:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms, said solvent having a boiling point less than 110°C; and a solubility parameter of from greater than 7.1 up to 8.2 hildebrands.
32,176-F -21-

2. The composition of Claim 1, wherein the solvent is selected from 1,2 dibromotetrafluoroethane or 1,2,3-trichlorotrifluoroethane and has a boiling point of from 30°C to 110°C.

3. The composition of Claim 1, wherein the solubility parameter of the solvent is from greater than 7.1 up to 7.5 hildebrands.

4. The composition of Claim 1, wherein X and X' in the solvent are Cl or Br.

5. The composition of Claim 1, wherein the fluorinated polymer is dissolved in the solvent at a concentration of less than about 0.5 weight percent.

6. The composition of Claim 1, wherein the fluorinated polymer is dissolved in the solvent at a concentration of from 0.1 to 0.3 weight percent.

7. The composition of Claim 1, wherein the fluorinated polymer includes a third monomer represented by the general formula:

Y'-(CF2)a'-(CFRf)b'-(CFR'f)c'-O-[CF(CF2X')-CF2-O]n'-CF=CF2 (III) where;
Y' is selected from F, Cl and Br;
a' and b' are independently 0-3;
c' is 0 or 1;
provided a'+b'+c' is not equal to 0;
n' is 0-6' Rf and R'f are independently selected from Br, Cl, F, perfluoroalkyl radicals having from 1 to 10 32,176-F -22-carbon atoms, and chloroperfluoroalkyl radicals having from 1 to 10 carbon atoms; and X' is selected from F, Cl, Br, and mixtures thereof when n'>1.

8. The composition of Claim 7, wherein Y is -SO2F or -COOCH3;
n is 0 or 1;
Rf and Rf' is F;
X' is Cl or F; and a+b+c = 2 or 3.

9. A method for dissolving a fluorinated polymer containing sites convertible to ion exchange groups, comprising the steps of contacting the polymer with a solvent for a time and at a temperature sufficient to dissolve at least a portion of the polymer in the solvent, wherein the fluorinated polymer and the solvent are as defined in Claims 1 or 7.

10. The method of Claim 9, wherein the solvent is selected from 1,2 dibromotetrafluoroethane and 1,2,3-trichlorotrifluoroethane.

32,176-F -23-