Background

Copolymers of tetrafluoroethylene (TFE) and monomers having sulfonic acid pendant groups are known for making membranes for electrical cells and fuel cells (see, for example, U.S. Pat. Nos.

3,282,875 (Connolly), 3,718,627 (Grot), 4,267,364 (Grot), 4,273,729 (Krespan), 8,227,139 (Watakabe), International Pat. Appl. Pub. No. WO 00/24709 (Famham et ak), European Patent No. EP 2913347 B1 (Saito et ak), U.S. Pat. Appl. Pub. Nos. 2017/0183435 (Ino), 2013/0253157 (Takami), 2013/0245219 (Perry), 2013/0252134 (Takami) and U.S. Pat. No. 8,470,943 (Watakabe)). Typically, such membranes are prepared by first generating a copolymer of TFE and a monomer having pendent sulfonyl fluoride groups (also referred to as“sulfonyl fluoride polymer” or“sulfonyl fluoride precursor polymer”) and subsequently hydrolyzing the sulfonyl groups. The resulting sulfonate groups are then converted into sulfonic acid groups, for example by treatment with acids or by ion exchange with cation exchange resins, to produce a perfluorosulfonic acid polymer, also referred to as“PFSA ionomer”. The resulting PFSA ionomer compositions, can be used to make membranes, as described for example in W02004/062019 A1 (Hamrock et ak).

There is not only a need to provide PFSA ionomer membranes or sulfonyl precursor polymers but also to provide the PFSA ionomers in a dried form, for example as a raw material for making membranes, catalyst inks or binder materials for batteries and electrodes. The dried PFSA ionomer compositions are easier to store and handle than liquid compositions. To make membranes, inks or binder materials, the dried PFSA ionomers can be re-dispersed in a liquid and processed as solution or dispersion. In United States Patent No. 10,189,927 (Ino et ak) a sulfonyl fluoride precursors polymer was hydrolyzed by an aqueous base and then treated with hydrochloric acid to provide a perfluorosulfonic acid polymer and the resulting composition was dried. For making a membrane the dried composition was re-dispersed in a liquid by subjecting the mixture to elevated pressure and temperature in an autoclave before processed it for making a membrane. The viscosity of the re-dispersed ionomer composition is not disclosed.

It has been found that dried PFSA ionomer compositions may be difficult to re-disperse in aqueous based solvents at ambient conditions or provide rather viscous compositions. For coating applications, for example when using the PFSA ionomer to make catalysts inks or binder materials for batteries and electrodes, liquid compositions of low viscosity are often advantageous. Liquid

compositions of low viscosity are also advantageous when making thin membranes. Diluting viscous PFSA ionomer compositions would reduce the PFSA ionomer content. Processing diluted compositions, however, leads to increased manufacturing costs because more solvent would have to be removed, recycled or discarded.

Therefore, there is a need to provide PFSA ionomer compositions that can be dispersed easily in water or water- miscible solvents to make liquid compositions having low viscosities at low and high shear rates. Summary

It has now been found that PFSA ionomer compositions can be prepared that can be dispersed in a liquid to form PFSA ionomer dispersions of low viscosity. Such compositions may be useful, for example, for producing membranes, catalyst inks or binder materials for electrodes or batteries.

Therefore, in one aspect, the present disclosure provides a method of making a dispersible solid perfluorosulfonic acid ionomer (PFSA ionomer)., The method includes providing an aqueous composition of a PFSA ionomer comprising divalent units derived from tetrafluoroethene (TFE) represented by formula -[CF2-CF2]- and divalent units represented by formula (I),

and divalent units derived from formula (II),

wherein a represents 0 or 1, b is an integer from 2 to 8, c is an integer from 0 to 2, and e is an integer from 1 to 8 and X represents an OH group and wherein m’ is 0 or 1 and Rf _| is selected from a linear or branched perfluoroalkyl group having from 1 to 12 carbon atoms that can be interrupted once or more than once by an (ether) oxygen atom. The method further includes drying the aqueous composition of the ionomer to a moisture content of no less than 2 wt.% and no greater than 15 wt.% water based on the total weight of the composition; wherein the aqueous composition of the ionomer is dried at a temperature of no greater than T(a) + 20 °C.

Detailed Description

When the amounts of ingredients of a composition are indicated by weight percentages, (also referred to herein as“% by weight” or“% wt” or“wt %”) the weight percentages are based on the total weight of the composition, i.e. the amounts of all ingredients of the composition will give 100 % wt, unless specified otherwise. Likewise, when the amounts of ingredients are identified by % mole (or“% mole” or“mole %”) the amount of all ingredients gives 100% mole unless specified otherwise.

In case the description refers to standards like DIN, ASTM, ISO etc and in case the year that standard was issued is not indicated, it is referred to the version that was in force in 2018. In case no version was in force in 2018 anymore, for example the standard has expired, the version that was in force at the date closest to 2018 is referred to.

PFSA ionomer compositions

In one aspect PFSA ionomer compositions are provided by the present disclosure that can be dispersed in a liquid to produce liquid compositions of low viscosity, for example compositions having a viscosity of less than 400 mPas at a shear rate of 1/s, more preferably less than 350 mPas at a shear rate 1/s and most preferably less than 300 mPas at a shear rate of 1/s. Preferably, the liquid compositions have a viscosity of less than 400 mPas at a shear rate of 1000/s, more preferably less than 350 mPas at a shear rate of 1000/s and most preferably less than 300 mPas at a shear rate of 1000/s. The dispersible PFSA ionomer composition can be directly dispersed in the liquid in amounts to provide compositions with a PFSA ionomer concentration of at least 10, 15, 20, or 25 percent by weight, for example 10 to 50 % by weight or from about 15 to about 40 % by weight, or from about 15 to 35% by weight based on the total weight of the composition.

Preferably, the liquid is selected from water, a protic solvent having at least one hydroxyl functionality and, preferably, having from 1 to 5 carbon atoms and combinations thereof. Protic solvents include C \ to C5 alkanols, for example methanol, ethanol, isopropanol, n-propanol, tert-butanol, n- butanol, pentanol, amylalcohol. Preferably, the protic solvent is selected from ethanol, n-propanol, iso propanol and combinations thereof. The liquid may include mixtures of water and one or more protic solvent, preferably in a ratio of water to protic solvent(s) from about 100 : 1 to 1 : 100 % by weight, preferably from 10 : 1 to 1 : 10 by weight. The liquid may also be only water or only the protic solvent or a combination of several protic solvents. Preferably, the protic solvent is selected from n-propanol, iso propanol and the combination thereof. It is an advantage of the dispersible PFSA compositions according to the present disclosure herein that they can be dispersed at concentrations of at least 10% by weight and up to for example 35% by weight, or for example up to 50% by weight in a liquid that is environmentally safe and easy to handle, for example a liquid as described above containing at least 30% by weight preferably at least 50% by weight or at least 80% by weight or even 95% or even 100% by weight of water. The PFSA ionomer compositions according to the present disclosure can be combined with the liquid described above to produce the liquid compositions of low viscosity by mixing the PFSA ionomer composition and the liquid at room temperature and ambient pressure within a period of 24 hours, for example by agitating the mixture on a roller set at 45 to 65 rpm for a period of 24 hours.

The dispersible PFSA ionomer composition according to the present disclosure can be obtained by drying an aqueous composition comprising the PFSA ionomer at a temperature that is not higher than 20°C above the T alpha temperature to reduce the moisture of that composition to below 15% by weight but above at least 1% by weight, preferably above at least 2 % by weight, for example above at least 3.1% by weight or above at least 3.9 % by weight. The aqueous composition to be subjected to the drying treatment can be obtained by hydrolyzing the corresponding sulfonylfluoride precursor polymer, preferably with an aqueous composition comprising a base preferably an alkali base selected from a Li, Na, or K base or a combination thereof and converting it into its sulfonic acid form, preferably by subjecting it to cation-exchange with at least one cation-exchange resin. Preferably, the sulfonyl fluoride precursor polymer has been subjected to a fluorination treatment to reduce the amount of carboxylic acid end groups prior to hydrolysis, preferably to below 150 carboxylic acid end groups per lO^ carbon atoms. Preferably, the sulfonyl fluoride polymer has been obtained by a polymerization comprising polymerizing tetrafluoroethene (TFE) with the one or more perfluorinated sulfonyl fluoride monomers and preferably the at least one or more perfluorinated ether monomers that will be described below. Preferably, the sulfonyl fluoride precursor polymer has a glass transition temperature (Tg) of up to 25 °C, 20 °C, 15 °C, or 10 °C. Preferably, the sulfonyl fluoride precursor polymer has a melt flow index (MFI, e.g., 265 °C/5 kg) of at least 1 gram per 10 minutes and up to 100, preferably up to 80 grams per 10 minutes, for example between 5 and 55 grams per 10 minutes.

The PFSA ionomers according to the present disclosure typically exhibit a thermal transition between a state in which the ionic clusters are closely associated and a state in which the interactions between those clusters have been weakened. This transition is described as an alpha transition, and the transition temperature is T(a) or T alpha. In some embodiments, the PFSA ionomers have a T(a) of from 70°C and up to 135°C. In some embodiments, the PFSA ionomers have a T(a) in the range from 75 °C to 125 °C or 80 °C to 120°C.

In some embodiments, the PFSA ionomers according to the present disclosure have up to 150 carboxylic acid end groups per lO^ carbon atoms, preferably up to 100 or up to 50, for example between 1 and 45 or between 10 and 90 carboxylic acid end groups per lO^ carbon atoms.

In some embodiments, the PFSA ionomers according to the present disclosure have an -SO3H equivalent weight of up to 2000. In some embodiments, the copolymer has an -SO3H equivalent weight of at least 300. In some embodiments, the copolymer has an -SO3H equivalent weight in a range from 300 to 1400, or 600 to 1200, or 350 to 1250, or from 400 to 800.

Preferably the dispersible PFSA ionomer composition according to the present disclosure is a solid composition, preferably a composition of solid particles. The particles may be soft or hard. The particles may be friable. The particle may be comminuted, for example, by hand, or they can be milled into smaller particles. The particles may be of regular or irregular shape or a combination thereof. The particles may be in the form of, for example, chunks, lumps, flakes, granules or small particles. The particles may have a size smaller than 12 cm, preferably smaller than 8 cm or even smaller than 5 cm and more preferably smaller than 3 cm. The size is determined by the longest axis of the particle (for example its diameter or its length). In case the particle is irregular, the longest axis is the longest dimension of the particle. For example, in one embodiment the particles have a size of from 0.01 mm to 5 cm. Particle size may be determined by sieving or image analysis.

The dispersible PFSA ionomer composition according to the present disclosure contains at least 50% by weight, preferably at least 80% by weight, more preferably at least 85% by weight of PFSA ionomer. In one embodiment the PFSA ionomer composition has a moisture content from 1 to 15% by weight, preferably from 3 to 13 % and more preferably from 3.9 to 12 % by weight based the total weight of the dispersible composition is 100% by weight, preferably based on the weight of the PFSA ionomer.

In one embodiment the PFSA ionomer composition contains at least 50% by weight, preferably at least 80% by weight, more preferably at least 85% by weight of PFSA ionomer. has a moisture content of from 3.1 % by weight to less than 15% by weight, preferably less than 12 % by weight and more preferably less than 10.0 % by weight based on the weight of the dispersible composition, preferably based on the weight of the PFSA ionomer, and the PFSA ionomer has an EW of from about 750 to about 2000, preferably 750 to 1200.

In one embodiment the PFSA composition of the present disclosure contains at least 50% by weight, preferably at least 80% by weight, more preferably at least 85% by weight of PFSA ionomer and has a moisture content of from 3.9 % by weight to less than 15% by weight, preferably less than 12 % by weight and more preferably less than 10.0 % by weight based on the weight of the dispersible composition, preferably based on the weight of the PFSA ionomer, and the PFSA ionomer has an EW of from about 750 to about 300, preferably 750 to 600.

The PFSA ionomer according to the present disclosure is a copolymer of tetrafluoroethene (TFE) and at least one, preferably at least two comonomers. Consequently, the copolymer contains units derived from TFE. Such units include divalent units represented by formula -[CF2-CF2]-. Typically, the PFSA ionomer according to the present disclosure contains at least 60 mole % of divalent units represented by formula -[CF2-CF2]-, based on the polymer (100 mole %). In some embodiments, the PFSA ionomer comprises at least 65, 70, 75, 80, or 90 mole % of divalent units represented by formula -[CF2-CF2]-, based on the polymer (100%).

The ionomer according to the present disclosure further includes divalent units independently represented by formula (I):

In formula (I), a represents 0 or 1, b is an integer from 2 to 8, c is an integer from 0 to 2, and e is an integer from 1 to 8 and X represents an OH group, i.e., the pending ionomer side group terminates a perfluorosulfonic acid group (-SO3H). C _e F2 _e may be linear or branched and preferably is linear. may be linear or branched and preferably is branched. In some embodiments, b is a number from 2 to 6 or 2 to 4. In a preferred embodiment a is 0. In another preferred embodiment a and c are both 0, and e is 3 to 8, preferably 3 to 6, more preferably 3 to 4, and most preferably 4. Typically, the PFSA ionomer according to the present disclosure contains from 10 to 40 mole % of divalent units represented by formula (I) based on the polymer (100 mole %). In some embodiments, the PFSA ionomer comprises from 15 to 25 mole % of units represented by formula (I) based on the total units of the polymer (100 mole %).

Ionomers having divalent units represented by formula (I) can be most conveniently prepared by copolymerizing the corresponding sulfonyl fluoride, e.g. a compound represented by formula

CF2=CF(CF2) _a -(0C¾F2b) _c -0-(C _e F2 _e )-S02X’, in which a, b, c, and e are as defined above and X’ is F. The sulfonylfluoride will then be hydrolyzed to produce the sulfonic acid salt, i.e. a compound represented by formula CF2=CF(CF2) _a -(0C _j3 F2 _j3 ) _c -0-(C _c F2 _c )-S02X . X” represents OZ and each Z is a cation, preferably an alkali metal cation or a quaternary ammonium cation. The quaternary ammonium cation can be substituted with any combination of hydrogen and alkyl groups, in some embodiments, alkyl groups independently having from one to four carbon atoms. In some preferred embodiments, Z is an alkali-metal cation, preferably a sodium or lithium cation.

Preferred sulfonyl fluoride monomers include CF2=CF-0-(CF2) _e -S02F with e = 1-8,

CF ₂ =CF-0-CF2CF(CF ₃ )0(CF2)e-S02F with a = 1-8, CF ₂ =CF[0CF ₂ CF(CF ₃ )] _c -S02F with c = 1-5. Particular examples include CF2=CF0CF2CF2S02F, CF2=CF0CF2CF2CF2CF2S02F,

CF2=CF0CF ₂ CF2CF ₂ S02F, CF2=CF0CF ₂ CF(CF ₃ )0CF2CF ₂ S02F,

CF ₂ =CF0CF2CF(CF ₃ )0CF2CF2CF ₂ S02F, CF ₂ =CF0CF ₂ CF(CF ₃ )S0 ₂ F, CF2=CF-CF ₂ -0-CF ₂ CF2- SO2F. More preferred sulfonyl fluoride monomers include CF2=CF0CF2CF2S02F,

CF ₂ =CF0CF2CF2CF2CF ₂ S02F, CF2=CF0CF ₂ CF(CF ₃ )0CF2CF ₂ S02F. Most preferred is

CF ₂ =CF0CF2CF2CF2CF ₂ S02F.

The PFSA ionomer according to the present disclosure further comprises divalent units independently represented by formula (II):

In formula (II), m’ is 0 or 1, and Rf _| is a linear or branched perfluoroalkyl group having from 1 to

12 carbon atoms that can be interrupted once or more than once by an (ether) oxygen atom, in which case Rfl is a perfluoroalkoxyalkyl group. Typically, the PFSA ionomer according to the present disclosure contains from 0 to 15 mole % units represented by formula (II) based on the polymer (100 mole %). In some embodiments, the PFSA ionomer comprises from 3 to 15 mole %, preferably from 5 to 10 mole% of units represented by formula (II).

Ionomers having divalent units represented by formula (II) can be most conveniently prepared by copolymerizing a monomer represented by C F2=C F-(C F2 ) _m‘ -O- Rf i with m’ and Rf _[ being the same as described above. For example, in case m’ is 0, the unit represented by formula (II) is derived from a perfluoroalkyl or perfluoroalkoxy alkyl vinyl ether comonomer. For example, using CF2=CF-0-C3F7

(PPVE-1) as comonomer will lead to a unit according to formula (II) with m’ being 0, and Rfl being C3F7.

In case m’ is 1, the unit is derived from a perfluoroalkyl or perfluoroalkoxyalkyl allyl ether comonomer. For example, using CF2=CF-CF2-0-C3F7 (PPAE-1) as comonomer will lead to a unit according to formula (II) wherein m’ is 1 and Rfl is C3F7.

Examples of suitable perfluoroalkyl vinyl ether and perfluoroalkyl allyl ethers inclde but are not limited to compounds according to the formula CF2=CFORfl and CF2=CFCF20Rfl with Rfl being methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl. Preferably, Rfl is linear.

Examples of suitable perfluoroalkoxyalkyl vinyl ethers include but are not limited to

CF ₂ =CFOCF ₂ OCF ₃ , CF2=CFOCF ₂ OCF ₂ CF3, CF2=CFOCF ₂ CF ₂ OCF3, CF ₂ =CF0CF2CF2CF ₂ 0CF3, CF ₂ =CF0CF2CF2CF2CF ₂ 0CF3, CF ₂ =CF0CF2CF20CF ₂ CF3, CF ₂ =CF0CF2CF2CF20CF ₂ CF3, CF ₂ =CF0CF2CF2CF2CF20CF ₂ CF3, CF ₂ =CF0CF2CF20CF ₂ 0CF3,

CF ₂ =CF0CF2CF20CF2CF ₂ 0CF3, CF ₂ =CF0CF2CF20CF2CF2CF ₂ 0CF3,

CF2=CF0CF2CF20CF2CF2CF2CF ₂ 0CF3, CF2=CF0CF2CF20CF2CF2CF2CF2CF ₂ 0CF3,

CF ₂ =CF0CF ₂ CF2(0CF2)30CF3, CF ₂ =CF0CF2CF2(0CF ₂ )40CF3,

CF2=CF0CF2CF20CF20CF20CF3, CF2=CF0CF2CF20CF2CF ₂ CF3

CF2=CF0CF2CF20CF2CF20CF2CF ₂ CF3, CF ₂ =CF0CF ₂ CF(CF3)-0-C3F7 (PPVE-2),

CF ₂ =CF(0CF2CF(CF3))2-0-C ₃ F7 (PPVE-3), and CF ₂ = CF(0CF ₂ CF(CF3))3-0-C ₃ F7 (PPVE-4). Such vinyl ethers can be prepared according to the methods described in U.S. Pat. Nos. 6,255,536 (Worm et al.) and 6,294,627 (Worm et al.) or other methods known in the art and some of these ethers are commercially available. Also the corresponding allyl ethers are useful. Such allyl ethers can be prepared, for example, according to the methods described in U.S. Pat. No. 4,349,650 (Krespan) or other methods known in the art. Some of these ethers are also commercially available. Particular examples of suitable comonomers leading to a unit according to formula (II) include but are not limited to (i) perfluoroalkyl vinyl ethers including: CF2=CF-0-CF3 (PMVE),

CF ₂ =CF-0-CF ₂ CF ₃ (PEVE), CF ₂ =CF-0-CF ₂ CF ₂ CF ₃ (PPVE-1), CF ₂ =CF-0-CF(CF ₃ )CF ₃ ;

(ii) perfluoroalkyl allyl ethers including: F ₂ C=CF-CF ₂ -0-CF ₃ (MAI), F ₂ C=CF-CF ₂ -0-CF ₂ CF ₃ (MA2), F ₂ C=CF-CF ₂ -0-CF ₂ CF ₂ CF ₃ (MA3), F ₂ C=CF-CF ₂ -0-CF ₂ CF ₂ CF ₂ CF ₃ (MA4);

(iii) perfluoroalkoxy alkyl vinyl ethers including: CF ₂ =CF-(0-CF ₂ -CF(CF ₃ ))-0-CF ₂ CF ₂ CF ₃ (PPVE-2), CF ₂ =CF-(0-CF ₂ -CF(CF ₃ )) ₂ -0-CF ₂ CF ₂ CF ₃ (PPVE-3), CF ₂ =CF(0CF ₂ CF(CF ₃ )) ₃ -0-C ₃ F ₇ (PPVE-4); CF ₂ =CF-0-(CF ₂ ) ₃ -0CF ₃ (MV31), CF ₂ =CF-0-(CF ₂ ) ₂ -0CF ₃ (MV21), CF ₂ =CF-0-(CF ₂ ) ₄ -0CF ₃ (MV41), CF ₂ =CF-0-CF ₂ -0CF ₃ (MV11);

(iv) perfluoroalkoxy alkyl allyl ethers including F ₂ C=CF-CF ₂ -0-(CF ₂ ) ₃ -0-CF ₃ (MA31), F ₂ C=CF-CF ₂ - 0-CF ₂ ) ₂ -0-CF ₃ (MA21), F ₂ C=CF-CF ₂ -0-CF ₂ -0-CF ₃ (MA11), F ₂ C=CF-CF ₂ -0-(CF ₂ ) ₄ -0-CF ₃ (MA41).

Particular examples also include combination of one or more of the monomers within each group (i), (ii), (iii) and (iv). Particular examples also include combinations of one or more of (i) with (ii), (i) with (iii), (i) with (iv), (ii) with (iii), (ii) with (iv) and (iii) with (iv).

Other optional comonomers

Although not necessary and less preferred the PFSA ionomers according to the present disclosure may also include units derived from other optional comonomers, in addition to or as alternative to the optional comonomers above providing units according to formula (II). Such other optional comonomers include, for example, fluorinated olefins, non-fluorinated olefins and modifiers and cross-linkers, typically bisolefins. Typically, the ionomers according to the present disclosure contain less than 20% by weight of units derived from optional comonomers and, preferably less than 5% and more preferably 0% by weight based on the total weight of the ionomer.

Fluorinated olefins

In some, less preferred, embodiments the PFSA ionomer according to the present disclosure contain divalent units derived from at least one other fluorinated olefin independently represented by formula C(R) ₂ =CF-Rf ₂ . These fluorinated divalent units are represented by formula -[CR ₂ -CFRf ₂ ]-. In formulas C(R) ₂ =CF-Rf ₂ and -[CR ₂ -CFRf ₂ ]-, Rf ₂ is fluorine or a perfluoroalkyl having from 1 to 8, in some embodiments 1 to 3, carbon atoms, and each R is independently hydrogen, fluorine, or chlorine. Some examples of fluorinated olefins useful as components of the polymerization include,

hexafluoropropylene (HFP), trifluorochloroethylene (CTFE), and partially fluorinated olefins (e.g., vinylidene fluoride (VDF), tetrafluoropropylene (R1234yf), pentafluoropropylene, and trifluoroethylene). Preferably, however, the PFSA ionomers according to the present disclosure do not contain any units derived from any other fluorinated olefin.

Bisolefins

The PFSA ionomers of the present disclosure can also include units derived from one or more bisolefins represented by formula X2C=CY-(CW2) _m -(0) _n -R -(0) ₀ -(CW2)p-CY=CX2· In this formula, each of X, Y, and W is independently fluoro, hydrogen, alkyl, alkoxy, polyoxyalkyl, perfluoroalkyl, perfluoroalkoxy or perfluoropolyoxyalkyl, m and p are independently an integer from 0 to 15, and n, o are independently 0 or 1. In some embodiments, X, Y, and W are each independently fluoro, CF3, C2F5, C3F7, C4F9, hydrogen, CH3, C2H5, C3H7, C4H9. In some embodiments, X, Y, and W are each fluoro (e g., as in CF ₂ =CF-0-R _F -0-CF=CF ₂ and CF2=CF-CF ₂ -0-R _F -0-CF2-CF=CF ₂ ). In some

embodiments, n and o are 1, and the bisolefins are divinyl ethers, diallyl ethers, or vinyl -allyl ethers. Rp represents linear or branched perfluoroalkylene or perfluoropolyoxyalkylene or arylene, which may be non-fluorinated or fluorinated. In some embodiments, Rp is perfluoroalkylene having from 1 to 12, from

2 to 10, or from 3 to 8 carbon atoms. The arylene may have from 5 to 14, 5 to 12, or 6 to 10 carbon atoms and may be non-substituted or substituted with one or more halogens other than fluoro, perfluoroalkyl (e.g. -CF3 and -CF2CF3), perfluoroalkoxy (e.g. -O-CF3, -OCF2CF3), perfluoropolyoxyalkyl (e.g., -

OCF2OCF3; -CF2OCF2OCF3), fluorinated, perfluorinated, or non-fluorinated phenyl or phenoxy, which may be substituted with one or more perfluoroalkyl, perfluoroalkoxy, perfluoropolyoxyalkyl groups, one or more halogens other than fluoro, or combinations thereof. In some embodiments, Rp is phenylene or mono-, di-, tri- or tetrafluoro-phenylene, with the ether groups linked in the ortho, para or meta position. In some embodiments, Rp is CF2; (CF2)q wherein q is 2, 3, 4, 5, 6, 7 or 8; CF2-O-CF2; CF2-O-CF2- CF ₂ ; CF(CF ₃ )CF ₂ ; (CF ₂ )2-0-CF(CF3)-CF ₂ ; CF(CF ₃ )-CF2-0-CF(CF3)CF ₂ ; or

(CF ₂ )2-0-CF(CF3)-CF2-0-CF(CF3)-CF2-0-CF ₂ .

When used in low amounts, for example less than 2% by weight, preferably less than 1% by weight the bisolefins can introduce long chain branches as described in U.S. Pat. Appl. Pub. No.

2010/0311906 (Lavallee et al.). When used in greater amounts the bisolefins can cross-link the ionomer. The bisolefins, described above in any of their embodiments, may be present in the components to be polymerized in any useful amount. In a preferred embodiment, the ionomers do not contain any units derived from bisolefins or contain such units in amounts of from about 0% by weight to about 5% by weight.

The PSFA-ionomer according to the present disclosure is preferably not cross-linked.

Non-fluorinated comonomers

The PFSA ionomers of the present disclosure can also include units derived from non-fluorinated monomers. Examples of suitable non-fluorinated monomers include ethylene, propylene, isobutylene, ethyl vinyl ether, vinyl benzoate, ethyl allyl ether, cyclohexyl allyl ether, norbomadiene, crotonic acid, an alkyl crotonate, acrylic acid, an alkyl acrylate, methacrylic acid, an alkyl methacrylate, and hydroxybutyl vinyl ether. Any combination of these non-fluorinated monomers may be useful. In some embodiments, the components to be polymerized further include acrylic acid or methacrylic acid, and the copolymer of the present disclosure includes units derived from acrylic acid or methacrylic acid. Preferably, the PFSA ionomers according to the present disclosure do not contain units derived from a non-fluorinated comonomer or contains units derived from a non-fluorinated comonomer in an amount of from 0 to 10% by weight (based on the total weight of the ionomer which is 100% by weight).

Typical PFSA ionomers

Preferred embodiments of PFSA ionomers according to the present disclosure contain at least 60 mole %, preferably from 65 to 90 mole %, of units derived from TFE, i.e., units represented by formula - [CF2-CF2]- and from 10 to 40 mole %, preferably from 15 to 25 % by mole of units represented by formula (I). The PFSA ionomer according to the present disclosure may contain from 0 to 15 mole %, preferably 5 to 10 mole% of units represented by formula (II) and from 0 to 30% by mole of units derived from other comonomers including the other optional comonomers described above.

The PFSA ionomer according to the present disclosure may contain from 5 to 50 % by weight, for example from 10 to 40 % by weight of units according to formula (I). The PFSA ionomer according to the present disclosure may contain from 30 to 95 % by weight, for example from 45 to 90 % by weight of units represented by formula -[CF2-CF2]- and units represented by formula (II). Preferably, the PFSA ionomer according to the present disclosure may contain from 30 to 95 % by weight, for example from 45 to 90 % by weight, of units represented by formula -[CF2-CF2]- and units represented by formula (II) and the molar ratio of units represented by formula -[CF2-CF2]- derived to units according to formula (II) is from 90 : 1 to 4 : 1. The total weight of the polymer is 100 % by weight.

Preferably, the PFSA ionomer is perfluorinated which means it is obtained by using only perfluorinated monomers and no partially or non-fluorinated polymers. A partially fluorinated monomer contains C-F bonds and C-H bonds, a perfluorinated monomer contains C-F bonds but does not contain C-H bonds and a non-fluorinated monomer contains no C-F bonds but C-H bonds.

Preparation of the PFSA ionomers

The PFSA ionomers of the present disclosure can be prepared by copolymerizing the

comonomers, i.e. TFE, and comonomers giving the divalent units of formula (I) and, optionally, the comonomers giving the units of formula (II) and, optionally, copolymerizing optional comonomers for example the optional comonomers described above.

The monomers are charged to the reaction in proportions and amounts to give the final polymer with the desired comonomer units in the desired amounts. Differing incorporation speeds have to be taken into account when selecting the monomer feed. The monomers may be charged continuously or intermittently, for example as a batch polymerization. They may be charged continuously with the same amounts and speed or with varying amounts and feeding speeds depending on the polymer architecture to be created, i.e. core-shell polymers, random polymers or heterogenous polymers, for example bimodal or polymodal polymers.

The polymerization can be carried out by free-radical polymerization. Reaction equipment is used that is appropriate for handling corrosive substances including exposure to HF. The reaction equipment may allow handling under inert gases or purging with inert gases. Typically, stainless steel vessels are used but if appropriate the vessels can be made of other materials or may contain an inert protective lining, for example a PTFE lining. Samples or materials may be stored in stainless steel containers or in HDPE containers or other appropriate containers. The vessels and other equipment, for example stirring equipment, may vary in dimensions and design depending on the polymers to be produced.

Concentrations of ingredients may be determined on line, for example, by using pressure, pH, or other appropriate indicators, or samples may be taken intermittently and actual amounts of ingredients may be measured off line, for example, by gas chromatography, mass spectrometry, pH electrodes, F-electrodes or other appropriate analytical devices and methods. Free radical polymerization includes radical aqueous emulsion polymerization, which is preferred, suspension polymerization and solvent polymerization. Aqueous emulsion polymerization typically produces polymer particles of about 50 to 500 nm dispersed in the aqueous phase, also referred to in the art as“polymer latex”. Suspension polymerization will typically produce particle sizes up to several millimeters. Solvents for solvent polymerization include chlorofluorocarbon, hydrochlorofluorocarbon, hydrofluorocarbon, hydrofluoroether or the like, more preferably hydrofluorocarbon or hydrofluoroether which will not damage the ozone layer. Suitable hydrofluorocarbons may have from 4 to 10 carbon atoms. The hydrofluorocarbon preferably has a ratio of the number of hydrogen atoms/the number of fluorine atoms (hereinafter referred to as H/F) on a molar basis from 0.05 to 20. The hydrofluorocarbon may be linear or branched. Examples of suitable hydrofluoroethers CF3CH2OCF2CF2H, CHF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CF2H and CF3CH2OCF2CF2H.

The polymerization initiator to start the polymerization may, for example, be a diacyl peroxide (such as disuccinic acid peroxide, benzoyl peroxide, perfluoro-benzoyl peroxide, lauroyl peroxide or bis(pentafluoropropionyl) peroxide), an azo compound (such as 2,2'-azobis(2-amidinopropane) hydrochloride, 4,4'-azobis(4-cyanovalerianic acid), dimethyl 2,2'-azobisisobutyrate or

azobisisobutyronitrile), a peroxyester (such as t-butyl peroxyisobutyrate ort-butyl peroxypivalate), a peroxydicarbonate (such as diisopropyl peroxydicarbonate or bis(2-ethylhexyl)peroxydicarbonate), a hydroperoxide (such as diisopropylbenzene hydroperoxide or t-butyl hydroperoxide), or a dialkyl peroxide (such as di -t-butyl peroxide or perfluoro-di -t-butyl peroxide). Also a water-soluble initiator (for example inorganic initiators, e.g., potassium permanganate or a peroxy sulfuric acid salt) can be useful to start the polymerization process. Salts of peroxy sulfuric acid, such as ammonium persulfate or potassium persulfate, can be applied either alone or in the presence of a reducing agent, such as bisulfites or sulfmates (e.g., fluorinated sulfmates disclosed in U.S. Pat. Nos. 5,285,002 and 5,378,782, both to Grootaert) or the sodium salt of hydroxy methane sulfmic acid (sold under the trade designation “RONGALIT”, BASF Chemical Company, New Jersey, USA). The concentration range for the initiators and reducing agent can vary from 0.001% to 5% by weight based on the polymerization medium.

Most of the initiators described above and any emulsifiers that may be used in the polymerization have an optimum pH-range where they show most efficiency. For these reasons, buffers may be useful. Buffers include phosphate, acetate, oxalate or carbonate (e.g., (NH^CC^ or NaHCC^) buffers or any other acid or base, such as ammonia or alkali-metal hydroxides. In some embodiments, the

copolymerizing is carried out at a pH of lower than pH 9. The concentration range for the initiators and buffers can vary from 0.01% to 5% by weight based on the aqueous polymerization medium. In some embodiments, ammonia is added to the reaction mixture in an amount to adjust the pH if the pH is too acidic.

Typical chain-transfer agents like ¾, lower alkanes (e.g. n-pentane, n-hexane or cyclohexane), alcohols (e.g. such as methanol, ethanol, 2,2,2-trifhioroethanol, 2,2,3,3-tetrafhioropropanol, 1, 1,1, 3,3,3- hexafluoroisopropanol or 2,2,3,3,3-pentafluoropropanol), ethers (e.g. diethyl ether or methyl ethyl ether), esters (e.g. methyl acetate or ethyl acetate), and CH2CI2 may be useful in the preparation of the polymers according to the present disclosure. Termination primarily via chain-transfer results in a polydispersity of about 2.5 or less. In some embodiments of the method according to the present disclosure, the polymerization is carried out without any chain-transfer agents. A lower polydispersity can sometimes be achieved in the absence of chain-transfer agents. Recombination typically leads to a polydispersity of about 1.5 for small conversions. The amount of the molecular weight-controlling agent if used may be from 0.0001 to 50, or from 0.001 to 10 parts per 100 parts of monomers.

Useful polymerization temperatures can range from 20 °C to 150 °C. Typically, polymerization is carried out in a temperature range from 30 °C to 120 °C, 40 °C to 100 °C, or 50 °C to 90 °C. The polymerization pressure is usually in the range of 0.4 MPa to 2.5 MPa, 0.6 to 1.8 MPa, 0.8 MPa to 1.5 MPa, and in some embodiments is in the range from 1.0 MPa to 2.0 MPa.

Perfluorinated or partially fluorinated emulsifiers may be used in the polymerization. Generally, these fluorinated emulsifiers may be present in a range from about 0.02% to about 3% by weight with respect to the polymer. Polymer particles produced with a fluorinated emulsifier typically have an average diameter, as determined by dynamic light scattering techniques, in range of about 10 nanometers (nm) to about 500 nm, and in some embodiments in range of about 50 nm to about 300 nm. Examples of suitable emulsifiers include perfluorinated and partially fluorinated emulsifier having the formula

[Rf-0-U-COO-]iX ⁱ⁺ wherein L represents a linear partially or fully fluorinated alkylene group or an aliphatic hydrocarbon group, Rf represents a linear partially or fully fluorinated aliphatic group or a linear partially or fully fluorinated aliphatic group interrupted with one or more oxygen atoms, X' ⁺ represents a cation having the valence i and i is 1, 2 or 3. (See, e.g., U.S. Pat. No. 7,671,112 to Hintzer et al.). Additional examples of suitable emulsifiers also include perfluorinated polyether emulsifiers having the formula CF3-(OCF2) _x -

O-CF2-X’, wherein x has a value of 1 to 6 and X’ represents a carboxylic acid group or salt thereof, and the formula CF3-0-(CF2)3-(0CF(CF3)-CF2)y-0-L-Y’ wherein y has a value of 0, 1, 2 or 3, L represents a divalent linking group selected from -CF(CF3)-, -CF2-, and-CF2CF2-, and Y’ represents a carboxylic acid group or salt thereof (See, e.g., U.S. Pat. Publ. No. 2007/0015865 to Hintzer et al.). Other suitable emulsifiers include those described in U.S. Pat. Publ. No. 2006/0199898 to Funaki et al.), U.S. Pat. Publ. No. 2007/0117915 to Funaki et al., U.S. Pat. No. 6,429,258 to Morgan et al., U.S. Pat. No. 4,621,116 to Morgan, U.S. Pat. Publ. No. 2007/0142541 to Hintzer et al., U.S. Pat. Publ. Nos. 2006/0223924, 2007/0060699, and 2007/0142513 each to Tsuda et al. and 2006/0281946 to Morita et al. and U.S. Pat. No. 2,559,752 to Berry). However, conveniently, in some embodiments, the polymerization may be conducted in the absence of any of these emulsifiers or with no fluorinated emulsifier.

The monomers may be charged all at once, or they may be charged continuously or

intermittently. Perfhioroalkoxyalkyl vinyl ethers and perfluoroalkoxyalkyl allyl ethers are typically liquids and may be sprayed into the reactor or added directly, as liquid or vaporized, or atomized. It can be useful to feed the compound represented by formula CF2=CF(CF2) _a -(0C¾F2b) _c -0-(C _e F2 _e )-S02X” and the other comonomers leading to units according to formula (II) as a homogenous mixture or emulsion to the polymerization. It may be useful to use one or more of the emulsifiers described above to prepare such pre-emulsion. It may also be useful to hydrolyze some of the C F2=C F(C F2 ) _a -(OC’b F2b ) _c -0-

(C _e F2e)-S02F by an aqueous base to obtain an“in situ”-emulsifier as for example described in

W02005/044878 (Thaler et al).

If fluorinated emulsifiers are used, the emulsifiers can be removed or recycled from the fhioropolymer latex, if desired, as described in U.S. Pat. Nos. 5,442,097 to Obermeier et al., 6,613,941 to Felix et al., 6,794,550 to Hintzer et al., 6,706,193 to Burkard et al., and 7,018,541 to Hintzer et al.

Alternatively, the emulsifiers may also be removed by heat-treatment (for example evaporation or treatment with carrier gas streams or steam) and subsequently be thermally degraded or recovered and recycled.

Preferably, the sulfonyl fluoride precursor polymer has a glass transition temperature (Tg) of up to 25 °C, 20 °C, 15 °C, or 10 °C. The Tg of the polymer can be influenced by the monomer compositions. Typically, side chains with perfluoralkoxy groups reduce the Tg of the polymer. Preferably, the sulfonyl fluoride precursor polymer has a melt flow index (MFI, e.g., 265 °C/5 kg) of at least 1 gram per 10 minutes and up to 100, preferably up to 80 grams per 10 minutes, for example an MFI between 5 and 55 grams per 10 minutes. The MFI of the copolymer can be adjusted by adjusting the amount of the initiator and/or chain-transfer agent used during polymerization, both of which affect the molecular weight and molecular-weight distribution of the copolymer. MFI can also be controlled by the rate of addition of initiator to the polymerization. Variations in the monomer composition can also affect the MFI The S02F-comonomers may be less reactive than the other comonomers. Therefore, it can be useful to feed these monomers to the polymerization system in excess (for example in an amount greater than 30% than the expected final amount in the polymer) to obtain the desired incorporation into the polymer. To remove and recover excess SC^F-monomer, the reaction mixture can be coagulated and unreacted monomer can be recovered from the coagulate, for example by evaporation. The reaction mixture may or may not be diluted prior to the coagulation or solvents or other liquids that allow recovery of the unreacted monomer may be added prior to the coagulation. The coagulation and monomer recovery can be done in the same reaction vessel or the reaction mixture can be transferred to a different reaction vessel. The reaction mixture can be transferred all at once and then be subjected to an evaporation treatment, or it can be transferred continuously or intermittently in portions. Evaporation may be carried out by heat-treatment, for example in a reactor with an external heating jacket or by using a carrier medium, for example steam, or both. The carrier medium may also be used to heat the reactor, for example when steam is used as carrier medium or a heated carrier gas is used. In case of using a carrier medium the reactor may contain one or more nozzles through which the carrier medium can enter and exit. The reactor may contain one or more stirrer, for example an impeller stirrer or a helical ribbon stirrer, or the reactor can be a fluidized bed reactor. The unreacted monomer can be recovered by condensation and/or other separation from the carrier medium. To coagulate the obtained copolymer latex, any coagulant which is commonly used for coagulation of a fluoropolymer latex may be used, and it may, for example, be a water-soluble salt (e.g., calcium chloride, magnesium chloride, aluminum chloride or aluminum nitrate), an acid (e.g., nitric acid, hydrochloric acid or sulfuric acid), or a water- soluble organic liquid (e.g., alcohol or acetone. The amount of the coagulant to be added may be in a range of 0.001 to 20 parts by mass, for example, in a range of 0.01 to 10 parts by mass per 100 parts by mass of the latex. For example, 341 kg of a polymer dispersion with a solid content of 29 % to which 200 kg deionized water is added can be charged into a stainless steel reactor having an internal capacity of 800 1 equipped with a stirrer, a high speed agitator“TURRAX” and steam nozzles for heating up the reactor. While the stirrer of the reactor was rotated at 100 rpm and the high-speed agitator at 600 rpm 65 wt-% nitric acid (28,2 kg) can be fed continuously in the reactor to precipitate the polymer at room temperature and agitation can be continued for lh. This can lead to almost complete coagulation with a solid content of less than 1% in the resulting water phase. Alternatively, or additionally, the latex may be frozen for coagulation or mechanically coagulated, for example, with a homogenizer as described in U.S. Pat. No. 5,463,021 (Beyer et ah). Alternatively, or additionally, the latex may be coagulated by adding polycations. It may be useful to avoid using salts as coagulants to avoid introducing metal contaminants. To avoid coagulation altogether and any contaminants from coagulants, spray drying the latex after polymerization and optional ion-exchange purification may be useful to provide solid precursor polymer.

The coagulated precursor polymer can be collected by filtration and washed with water. The washing water may, for example, be ion-exchanged water, pure water, or ultrapure water. The amount of the washing water may be from 1 to 5 times by mass to the precursor polymer, whereby the amount of the emulsifier attached to the polymer can be sufficiently reduced by one washing. The precursor polymer can be dried with drying equipment as known in the art, for example by a fluidized bed dryer or a tumble drier or simply an oven, to a water content of for example 0.1% by weight or less, preferably less than 0.05%wt. Depending on the nature of the polymerization initiator (e.g. KIVInOq) a cation-exchange process might be beneficial prior to the comonomer recovery process. Useful cation exchange resins include polymers (typically cross-linked) that have a plurality of pendant anionic or acidic groups such as, for example, polysulfonates or polysulfonic acids, polycarboxylates or poly carboxylic acids. Examples of useful sulfonic acid cation exchange resins include sulfonated styrene-divinylbenzene copolymers, sulfonated crosslinked styrene polymers, phenol-formaldehyde-sulfonic acid resins, and benzene- formaldehyde-sulfonic acid resins. Preferably, the cation exchange resin is an organic acid cation exchange resin, such as carboxylic acid cation exchange resin. Cation exchange resins are available commercially from a variety of sources. Cation exchange resins are commonly supplied commercially in either their acid or their sodium form. If the cation exchange resin is not in the acid form (i.e., protonated form) it may be at least partially or fully converted to the acid form in order to avoid the generally undesired introduction of other cations into the dispersion. This conversion to the acid form may be accomplished by means well known in the art, for example by treatment with any adequately strong acid. The ion-exchange process may be carried out in a continuous mode using fixed bed columns, for example a column with a length to diameter ratio of 20 : 1 to 7 : 1 at a flow rate of 1 bed volume/h. The process can be monitored on line or offline by pH-meter, metal -analyzer (for example if the hydrolyzation is carried out Li-salts, the lithium content can be measured) or other techniques (e.g. conductivity etc.). The ion-exchange resin can be a multimodal resin or a monomodal resin and it can have a broad or narrow particle size distribution. Commercially available cation exchange resins include but are not limited to those available under the trade designation LEWATIT MONO PLUS S 100, AMBERLITE IR-120(Plus) or PUROLITE 150C TLH.

If purification of the fluoropolymer dispersion is carried out using both anion and cation exchange processes, the anion exchange resin and cation exchange resin may be used individually or in combination as, for example, in the case of a mixed resin bed having both anion and cation exchange resins.

Fluoropolymers obtained by aqueous emulsion polymerization typically have a high number of carboxylic acid end groups (more than 200 carboxylic acid end groups per 10^ carbon atoms created, for example, by a side reaction of the polymerization initiator. Preferably, the copolymer has less than 150 carboxylic acid end groups per 10^ carbon atoms, preferably less than 100 or even less than 50, for example between 1 and 45 or between 10 and 90 carboxylic acid end groups per 10^ carbon atoms.

Reducing the number of carboxylic acid end groups can be accomplished by a fluorination treatment. Fluorination of the fluoropolymer converts unstable end groups to -CF3 end groups. The fluorination may be carried out in any convenient manner. The fluorination can be conveniently carried out with nitrogen/fluorine gas mixtures in ratios of 75 - 90 : 25 - 10 at temperatures between 20 °C and 250 °C, in some embodiments in a range of 150 °C to 250 °C or 70 °C to 120 °C, and pressures from 10 kPa to 1000 kPa. Reaction times can range from about four hours to about 16 hours. The fluorination can be carried out continuously or intermittently, for example by a sequence of fluorination and purging steps, and at the same temperature or at different temperature intervals. Purging is conveniently carried out by using nitrogen gas. Under these conditions, most unstable carbon-based end groups are removed, whereas the- SO2F groups survive. After completion of the reaction the reactor vessel is purged with nitrogen to remove the fluorine gas. The fluorination can be carried out, for example, in an appropriately equipped autoclave, tumble reactor or fluidized bed reactor or a combination thereof.

The S02F-copolymer is hydrolyzed to convert the SC^F-groups into -SO2OX” groups, “sulfonate groups”. X” represents OZ and each Z is a cation, preferably an alkali metal cation or a quaternary ammonium cation. The quaternary ammonium cation can be substituted with any combination of hydrogen and alkyl groups, in some embodiments, alkyl groups independently having from one to four carbon atoms. In some preferred embodiments, Z is an alkali-metal cation, preferably a sodium or lithium cation. The hydrolysis can be done by subjecting the SC^F-polymer to a treatment with an aqueous base.

The reaction can be done under pressure, for example in an autoclave, fluidized bed reactor or a stirred vessel. Typically, the hydrolysis is carried out at elevated temperature, for example at a temperature between 150°C -300°C. Reaction times may be from 0.5 to 10 hours. Preferably an alkaline base (for example but not limited to lithium hydroxide or lithium carbonate, an earth-alkali base or ammonia (NR4OH) or a combination thereof are used as base. The water amount may be chosen to give a solid content of 5 to 40% by weight. After the reaction is completed further salts forming poorly soluble fluoride salts (Al(OH)3, Ca(OH)2) or flocculants may be added to reduce the fluorine levels in the water phase. After the fluoride salts have been removed (for example by filtration, centrifugation or sedimentation) the -SO2OX” groups of the polymer are converted into the perfluorosulfonic acid form (-

SO3H form) by acid treatment or ion-exchange with a cation exchange resin. Cation exchange resins as described above may be used. The ion-exchange process may be carried out as described above, for example, in a continuous mode using fixed bed columns, for example a column with a length to diameter ratio of 20 : 1 to 7 : 1 at a flow rate of 1 bed volume/h. The process can be monitored on line or off line, for example, by pH-meter, metal-analyzer (for example if the hydrolyzation is carried out Li-salts, the lithium content can be measured) or other techniques (e.g. conductivity etc.) including those decribed above.

To create a dispersible PFSA composition according to the present disclosure the aqueous PFSA ionomer composition is subjected to drying. It has been found that the drying regime influences the viscosity of the resulting dispersions when re-dispersing the dried PFSA ionomer into a liquid, in particular liquids like water and water-alcohol mixtures, preferably water-alkanol mixtures, and in particular for ionomers with reduced carboxylic acid end group content. The drying is carried out at a temperature that is not higher than 20°C above the T alpha temperature of the perfluorosulfonic acid ionomer, i.e. the drying is carried out at a temperature below a temperature of T alpha + 20 °C. Drying at temperature at or above the T alpha temperature but below the T alpha + 20 °C threshold, is preferably only done for a short time, for example, for not more than 5 hours, preferably not more than 3 hours.

Preferably, the drying is carried out at temperatures below the T alpha temperature of the PFSA ionomer, for example at a temperature of 20°C below the T alpha temperature (“T alpha -20°C”) or even lower.

The drying period may depend on the final moisture content to be achieved and on the equivalent weight of the polymer. Drying at such temperatures can be carried out for a period of at least 24 hours or at least 48 hours or even 96 hours or longer. At equivalent weight of 800 or greater short drying intervals at a temperature interval of T alpha + 10 °C or T alpha - 10°C may be benefitial to reduce the viscosity to below 300 mPas but such intervals preferably should not exceed more than 4 hours. The drying regime can be carried out at constant temperature or at varying temperatures. For example, a short period at a temperature at or above the T alpha temperature but less than T alpha + 20°C (less than 4 hours, preferably less than 1 hour) and a longer period at temperatures below the T alpha temperature may be used, for example 24 hours to 96 hours. Also cycles of different temperature regimes may be used. The drying can be carried out continuously or intermittently. In some embodiments, the drying is preferably done at a temperature between 50°C to 100°C, more preferably between 50°C and 80°C, most preferably between 50°C and 75°C. Preferably, the drying is carried out for 24 hours to 96 hours or even up to 110 hours.

The drying can be carried out in drying equipment as known in the art but preferably in a vacuum oven, a circulated air oven or other drying equipment or simply by drying the ionomer dispersions on open trays in on oven.

Preferably, the drying is carried out at a temperature and for an effective time to reduce the moisture content of the aqueous PFSA ionomer composition, preferably the cation-exchanged composition, to a moisture content of less than 25 weight %, preferably less than 15 weight %, more preferably less than 12 weight % based on the weight of the composition. The drying preferably is carried out such that the moisture content does not decrease below the content described above and below, for example not below 2 weight %, preferably not below 3.1 weight % more preferably below 3.9 wt % (based on the weight of the composition).

The resulting PFSA ionomer compositions are dispersible and can be used to make the liquid compositions according to the present disclosure as described above and below. The dispersible compositions and may have the size and form as described above or may be brought into a size and shape as described above by comminuting them, for example by grinding or milling or simply by breaking them into smaller pieces by hand. The solid PFSA ionomer compositions typically have a total content of Na, K and Li ions of less than 100 ppm, preferably less than 50 ppm, or even less than 20 ppm, and one or more of all of these ions may actually be absent. The dispersible PFSA ionomer compositions typically have a heavy metal content (total content of Fe, Ni, Cu and Cr ions) of not greater than 100 ppm, preferably less than 20 ppm and more preferably the Fe content is below 5 ppm.

The PFSA ionomer compositions according to the present disclosure can typically be directly dispersed at a concentration of at least 10, 15, 20, or 25 percent by weight in a liquid, preferably the liquid selected from water and an organic protic solvent containing at least one hydroxyl functionality and from 1 to 5 carbon atoms as described above and below. In some embodiments, the copolymer disclosed herein can be directly dispersed at a concentration of up to 30, 40, or 50 percent by weight. The dispersible PFSA ionomer compositions can be dispersed in the liquid to provide a liquid composition having a viscosity of less than 400 mPas at a shear rate 1/s and at a shear rate at 1000/s, or even lower viscosities as described above and below. A useful method includes combining the components and mixing the components at ambient temperature and pressure to make the liquid composition. Mixing can be carried out by agitating the composition. Mild agitation conditions may be sufficient, for example placing the mixture on a roller that is set at 45 to 65 rpm for a period of 24 hours at room temperature and ambient pressure. Although the liquid compositions can be prepared at ambient conditions, they may also be prepared in other ways, for example by adding other solvents or operating at elevated temperatures or pressures but in many cases this may be disadvantageous and unnecessary.

The PFSA ionomer compositions of the present disclosure may be used, for example, in the manufacture of membranes, for example polymer electrolyte membranes for use in fuel cells or electrolyte membranes in an electrochemical cell, for example in a chlor-alkali membrane cell. The PFSA ionomer compositions are particularly suitable for making thin membranes, i.e. membranes having a thickness of less than 50 micrometer, preferably less than 30 micrometers, for example between 20 and 40 micrometers, or between 10 to 28 micrometers. The membranes are typically extended sheets and may have a length of greater than 12 cm. Typically, the membrane is cast from a liquid composition or a dispersion and then dried, annealed, or both. The membrane may be cast on a support. Typically, the supporting matrix is electrically non-conductive. Typically, the supporting matrix is composed of a fluoropolymer, which is more typically perfluorinated. Typical matrices include porous

polytetrafluoroethylene (PTFE), such as biaxially stretched PTFE webs. In another embodiment fdlers (e.g. fibers) might be added to the PFSA ionomer composition to reinforce the membrane. After forming, the membrane may be annealed, typically at a temperature of 120 °C or higher, more typically 130 °C or higher, most typically 150 °C or higher.

For making a membrane a liquid PFSA ionomer composition according to the present disclosure may be used, for example obtained by dispersing the dispersible PFSA ionomer composition in the liquid as described above to produce a liquid composition of low viscosity. However, the dispersible PFSA ionomer composition may also be combined with other liquids to provide a dispersion or a solution. Additives may be added before the membrane is cast. The additives may be added to a composition obtained by combining the dispersible PFSA ionomer composition according to the present disclosure with a liquid, preferably the liquid described above for producing the liquid PFSA ionomer composition of low viscosity according to the present disclosure or with a different liquid. The additives may be added as solid materials or dissolved or dispersed in a liquid. The additives may also be combined directly with the dispersible PFSA ionomer composition according to the present disclosure and may be added as solids, for examples as powders, or they may be added as solution or dispersion in a liquid, which may be water or the protic organic solvent having at least one functional hydroxyl group as described above, or it may be a different liquid. In some embodiments the additive includes a salt of at least one of cerium, manganese or ruthenium or one or more cerium oxide or zirconium oxide compounds and is added to the PFSA ionomer before membrane formation. The salt of cerium, manganese, or ruthenium may comprise any suitable anion, including chloride, bromide, hydroxide, nitrate, sulfonate, acetate, phosphate, and carbonate. More than one anion may be present. Other salts may be present, including salts that include other metal cations or ammonium cations. Once cation exchange occurs between the transition metal salt and the acid form of the ionomer, it may be desirable for the acid formed by combination of the liberated proton and the original salt anion to be removed. Thus, it may be useful to use anions that generate volatile or soluble acids, for example chloride or nitrate. Manganese cations may be in any suitable oxidation state, including

Mh^+, Mrri ⁺ . and Mh^+, but are most typically h^+ Ruthenium cations may be in any suitable oxidation state, including Riri ⁺ and Ru^ ⁺ . but are most typically Riri ⁺ . Cerium cations may be in any suitable oxidation state, including Ce^ ⁺ and Ce^ ⁺ . Without wishing to be bound by theory, it is believed that the cerium, manganese, or ruthenium cations persist in the polymer electrolyte because they are exchanged with H ⁺ ions from the anion groups of the polymer electrolyte and become associated with those anion groups. Furthermore, it is believed that polyvalent cerium, manganese, or ruthenium cations may form crosslinks between anion groups of the polymer electrolyte, further adding to the stability of the polymer. In some embodiments, the salt may be present in solid form. The cations may be present in a combination of two or more forms including solvated cation, cation associated with bound anion groups of the polymer electrolyte membrane, and cation bound in a salt precipitate. The amount of salt added is typically between 0.001 and 0.5 charge equivalents based on the molar amount of acid functional groups present in the polymer electrolyte, more typically between 0.005 and 0.2, more typically between 0.01 and 0.1, and more typically between 0.02 and 0.05. Further details for combining an anionic copolymer with cerium, manganese, or ruthenium cations can be found in U.S. Pat. Nos. 7,575,534 and 8,628,871, each to Frey et al. The cerium oxide compound may contain cerium in the (IV) oxidation state, the (III) oxidation state, or both and may be crystalline or amorphous. The cerium oxide may be, for example, CeC>2 or Ce2C>3. The cerium oxide may be substantially free of metallic cerium or may contain metallic cerium. The cerium oxide may be, for example, a thin oxidation reaction product on a metallic cerium particle. The cerium oxide compound may or may not contain other metal elements. Examples of mixed metal oxide compounds comprising cerium oxide include solid solutions such as zirconia-ceria and multicomponent oxide compounds such as barium cerate. Without wishing to be bound by theory, it is believed that the cerium oxide may strengthen the polymer by chelating and forming crosslinks between bound anionic groups. The amount of cerium oxide compound added is typically between 0.01 and 5 weight percent based on the total weight of the PFSA ionomer, more typically between 0.1 and 2 weight percent, and more typically between 0.2 and 0.3 weight percent. The cerium oxide compound is typically present in an amount of less than 1% by volume relative to the total volume of the polymer electrolyte membrane, more typically less than 0.8% by volume, and more typically less than 0.5% by volume. Cerium oxide may be in particles of any suitable size, in some embodiments, between 1 nm and 5000 nm, 200 nm to 5000 nm, or 500 nm to 1000 nm. Further details regarding polymer electrolyte membranes including cerium oxide compounds can be found in U.S. Pat. No. 8,367,267 (Frey et al.).

The PFSA ionomer compositions of the present disclosure may also be used for making a catalyst ink composition. For making a catalyst ink the dispersible PFSA ionomer composition may be used to make the liquid composition of low viscosity according to the present disclosure and combining it with catalyst particles (e.g., metal particles or carbon-supported metal particles). However, the dispersible PFSA ionomer composition may also be combined with other liquids to provide a dispersion or a solution to which catalyst particles may be added. The catalyst particles may also be added directly to the dispersible PFSA ionomer composition and combined with it. The catalyst particles may be added as solid materials or dissolved or dispersed in a liquid, preferably water or the protic solvent having at least one hydroxyl functionality as described above. A variety of catalysts may be useful. Typically, carbon- supported catalyst particles are used. Typical carbon-supported catalyst particles are 50% to 90% carbon and 10% to 50% catalyst metal by weight, the catalyst metal typically comprising platinum for the cathode and platinum and ruthenium in a weight ratio of 2: 1 for the anode. However, other metals may be useful, for example, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys thereof. The ink may then be applied to a substrate, for example a membrane or an electrode. In one embodiment the catalyst particles or at least a part thereof is added to the dispersible PFSA ionomer composition prior to adding the liquid to form a liquid composition. Details concerning the preparation of catalyst inks and their use in membrane assemblies can be found, for example, in U.S. Pat. Publ. No. 2004/0107869 (Velamakanni et al.).

The PFSA ionomer dispersion according to the present disclosure may also be used for making a binder for an electrode or a battery (for example, lithium ion batteries). To make electrodes, powdered active ingredients can be dispersed with a solvent and added as solids, for example as powders, to the dispersible PFSA ionomer dispersion according to the present disclosure or to a composition obtained by combining the dispersible PFSA ionomer composition with a liquid. Preferably the liquid is water or the protic organic solvent having at least one functional hydroxyl group as described above. The binder composition may then be coated onto a substrate, for example a metal foil or a current collector. The resulting composite electrode contains the powdered active ingredient in the polymer binder adhered to the metal substrate. Useful active materials for making negative electrodes include alloys of main group elements and conductive powders such as graphite. Examples of useful active materials for making a negative electrode include oxides (tin oxide), carbon compounds (e.g., artificial graphite, natural graphite, soil black lead, expanded graphite, and scaly graphite), silicon carbide compounds, silicon-oxide compounds, titanium sulfides, and boron carbide compounds. Useful active materials for making positive electrodes include lithium compounds, such as Eί^T^^O Uf ^Og, U1V2O5, UiCoq 2^0 8^2· UiNi02, LiFcPOq. LiMnPOq. U1C0PO4, UilVh^Oq, and UiCoC^. The electrodes can also include electrically conductive diluents and adhesion promoters. In order that this disclosure can be more fully understood, the following examples are set forth. It should be understood that these examples are for illustrative purposes only and are not to be construed as limiting this disclosure in any manner.

EXAMPLES

Moisture content

The moisture content of the solid ionomer compositions was determined with a Mettler- Thermowaage HR73, HR83 (Halogen) by thermogravimetric analysis. 3 g of the product was weighed into the thermobalance. The thermobalance was run at 120°C for 30 minutes. The resulting solid content (%) was determined by the ratio of final weight/initial weight times 100. The moisture content (%) was calculated by: 100% - solid content (%).

Viscosity

The viscosities at a shear rate of 1/s and 1000/s were determined by rotational viscometry (rotational viscometer MCR 102 / cylinder system CC 27; Anton Paar Germany GmbH, Ostfildem- Schamhausen, Germany) at 20 °C. The solid samples were milled if necessary before the liquid was added. The liquid was added to the ionomer in amounts to give ionomer dispersion with the desired ionomer content. Unless stated otherwise 6 g of ionomer sample were used. The resulting mixture was placed on a roller box and was rolled for 24 hours at room temperature.

Solid Content

Solid content was usually calculated by the weight of the ingredient. It can be determined gravimetrically by placing samples of the dispersions on a heated balance and recording the mass before and after evaporation of solvent. The solid content is the ratio of the initial mass of the sample and the mass of the sample when the mass did not decrease further with continued heating. A thermobalance (Mettler-Thermowaage HR73, HR83 (Halogen)) was used for thermogravimetric analysis. Typically, 3 g of product was weighed into the thermobalance and the thermobalance was run at 120°C.

Equivalent Weight (EW)

The EW of the ionomer was calculated by the formula:

wherein M2 is the sulfonyl fluoride monomer and M3 is the optional vinyl ether or allyl ether monomer and M3 is 0 is the optional monomer is not present. ^F-NMR spectra can be used to determine the composition of the polymers. An NMR spectrometer available under the trade designation AVANCE II 300 from Bruker, Billerica, MA, USA with a 5 mm Broadband probe can be used. Samples of about 13 weight percent polymer dispersion should be measured at 60 °C.

Determination of amount of carboxyl end groups

A Fourier transform infrared spectroscopy (FT-IR) measurement was used to determine the number of carboxyl endgroups per 10^ C-atoms in the copolymer. The measurement was performed by FT-IR in a transmission technique. The measured sample had a fdm thickness of 100 pm. The wave numbers of the COOH peaks of interest are 1775 cm * and 1808 cm l. To quantify the amount of carboxyl endgroups of the polymer two IR spectra are taken. One from the carboxyl containing sample and one from a reference sample (without carboxyl groups). The reference material was a TFE/MV4S- copolymer that was subjected to a fluorination treatment for such a period of time that peaks at 1775 and 1808 cm l were no longer observed.

The number of endgroups per 10^ carbon atoms can be calculated via equation 1 and 2 for F _| and F2:

(peak height F _| ) / fdm thickness [mm] (1)

(peak height ^c F2) / fdm thickness [mm] (2)

with the peak height being the difference of the peak height of the sample and the peak height of the reference sample at 1775 and 1808 cm l;

F calculated factor (= 320) related to u = 1775 cm l f _rom pjS patent No. 4,675,380 (Buckmaster et al) incorporated herein by reference;

F2: calculated factor (= 335) related to u = 1808 cm l f _rom pjS patent No. 4,675,380 (Buckmaster et al) incorporated herein by reference.

The sum of the results from the equations 1 and 2 yield the number of carboxyl end groups per 10^ carbon atoms.

Particle Size by Dynamic Light Scattering

The particle size determination can be conducted by dynamic light scattering according to ISO 13321 (1996). A Zeta Sizer Nano ZS, available from Malvern Instruments Ltd, Malvern, Worcestershire, UK, equipped with a 50 mW laser operating at 532 nm can be used for the analysis. 12 mm square glass cuvettes with round aperture and cap (PCS 8501, available from Malvern Instruments Ltd) can be used to mount a sample volume of 1 mL. Since light scattering of surfactants is extremely sensitive to the presence of larger particles, e.g. dust particles, the presence of contaminants can be minimized by thoroughly cleaning the cuvettes before the measurements. The cuvettes can be washed with freshly- distilled acetone for 8 h in a cuvette washing device. Dust discipline should also be applied to the samples by centrifuging the surfactant solutions in a laboratory centrifuge at 14,500 G (142,196 N/kg) for 10 min prior to the measurements. The measuring device can be operated at 25 °C in 173° backscattering mode.

Low correlation times of t < 1 ^ sec are enabled by the research tool (the research tool is a software up grade of the standard instrument provided by the supplier). In order to exploit the complete scattering ability of the sample volume, the following settings can be applied in all cases:“attenuator,” 11;

“measurement position,” 4.65 mm (center of the cell). Under these conditions, the baseline scattering of pure water (reference) is around 250 kcps. Each measurement consisting of 10 sub-runs can be repeated for five times. The particle sizes can be expressed as D50 value.

Melt Flow Index

The melt flow index (MFI), reported in g/10 min, was measured with a Goettfert MPD, MI-Robo, MI4 melt indexer (Buchen, Germany) following a similar procedure to that described in DIN EN ISO 1133-1 at a support weight of 5.0 kg and a temperature of 265 °C. The MFI was obtained with a standardized extrusion die of 2.1 mm in diameter and a length of 8.0 mm.

T(a) Measurement

A TA Instruments AR2000 EX rheometer was used to measure the T(a) of the polymer samples. Samples were heated on a temperature ramp from -100 °C to about 125 °C at 2 °C per minute.

Measurements were made at a frequency of one hertz.

Glass Transition Temperature

A TA Instruments Q2000 DSC can be used to measure the glass transition temperature (Tg) of the polymer samples. Samples were heated on a temperature ramp from -50 °C to about 200 °C at 10 °C per minute. Transition temperatures were analyzed on the second heats.

Metal Content

The metal ion content of the ionomer was measured by Inductively coupled plasma optical emission spectrometry (ICP-OES, also known as ICP-AES, ICP atomic spectrometry) in a Thermo Scientific ICP-OES-ICAP 7400; CCD-detector according to DIN EN ISO 11885. For the quantitative determination the sample was incinerated (for example in a quartz glass container at a temperature of 550°C for 30 minutes in an electric oven) and the residue was taken up in an acid solution (for example in aqueous HC1 solution (35% HC1); ultra pure grade) and analyzed with ICP-OES.

Example 1 (EX-1)

2 perfluorosulfonic acid (PFSA) ionomer aqueous dispersions of the same chemical composition (TFE-MV4S) but different equivalent weight (EW) were prepared. Perfluorosulfonyl fluoride precursor polymers were prepared by polymerizing TFE and F2C=CF-0-CF2CF2CF2CF2S02F (MV4S) in aqueous emulsion polymerization (KMNO4 initiator, partially fluorinated carboxylic acid es emulsifier) to produce a sulfonyl fluoride copolymer (19.7 mol% units derived from MV4S) with an MFI at 265°C and at a 5kg load of 10 / 10 minutes and a fluoride sulfonyl copolymer (22.4 mol% units derived from MV4S) with an MFI (265/5) of 17 g / 10 minutes. The sulfonyl fluoride copolymers were dried and then fluorinated to reduce the carboxylic and groups, hydrolyzed with lithium hydroxide/lithium carbonate solutions and cation-exchanged to produce the sulfonic acid form. The resulting PFSA ionomers had an equivalent weight of 725 and 800. The 725 EW PFSA ionomer had a T alpha of 114°C, and an COOH end group content of 22 per 10^ carbon atoms. The 800 EW PFSA ionomer had a T alpha of 118°C and an COOH end group content of 77 per 10^ carbon atoms.

The solutions were kept in open HDPE bottles and were dried at different temperatures and periods to different moisture levels as indicated in table 1. The resulting friable PFSA solids were re dispersed in n-propanol/water (60% wt / 40% wt) in a concentration to give 20% wt of ionomer content and the viscosity of the resulting dispersion was measured. The results are also shown in table 1.

Table 1:

n.d. = not determinec

Example 2

A dispersible perfluorosulfonic acid was prepared by first preparing a perfluorosulfonyl fluoride precursor polymer by aqueous polymerization of TFE, F2C=CF-0-CF2CF2CF2CF2S02F (MV4S) and CF2=CF-0-(CF2)3-0CF3 (MV31) using KMn04 as initiator and partially fluorinated carboxylic acid as emulsifier to produce a polymer latex with polymer particles of an average size of 126 nm and a solid content of 23.2% after a reaction time of 249 minutes. MV4S was prepared according to the method described in U.S. Pat. No. 6,624,328 (Guerra). MV31 was prepared according to the method described in U.S. Pat. Nos. 6,255,536 (Worm et al.) The perfluorosulfonyl polymer was coagulated with aqueous HNO3 and the coagulate was dried to a moisture content below 0.1 % by weight and then subjected to fluorination by treatment with seven F2/N2 cycles to reduce the number of carboxylic end groups to less than 100 per 10^ carbon atoms. The resulting perfluorosulfonyl precursor polymer (70 mole % TFE, 25 mole% MV4S and 5 mole% MV31) had an MFI (265 °C/5 kg) of 41 g/10 min. The sulfonyl fluoride precursor polymer was subsequently hydrolyzed using a combination of FiOH and F12CO3 and water. The resulting dispersion was ion-exchanged (cation exchange) to obtain the perfluorosulfonic acid ionomer. The ion-exchanged dispersion was dried in a vacuum oven at 0.15 bar and at a temperature between 70°C and 80°C for 16 to 20 hours to achieve a moisture content below 9% by weight. The total Fi, Na and K content was below 5 ppm (1.2 ppm) and the total Fe, Ni, Cu and Cr content was also below 5 ppm (3.2 ppm). The EW was between 720 and 760 and the T alpha temperature was between 90 andl 10°C. The PFSA was in the form of a friable solid. To 15g of the solid a water-n-propanol mixture (water and n-propanol; 60%wt propanol and 40% water) was added in an amount to give a dispersion with a PFSA ionomer content of about 20% by weight. The mixture was put on a roller box for 12 hours which resulted in a homogenous and clear dispersion that had a viscosity of 195 mPas at a shear rate of 1/s and a viscosity of 150 mPas at a shear rate of 1000/s.

Comparative Example 1

Example 2 was repeated except that the ion-exchanged dispersion was dried at around 100°C. Clear dispersions were obtained when redispersing the dried PFSA ionomer but the viscosity of the resulting dispersion was greater than 800 mPas at both shear rates of 1/s and 1000/s. Example 3

An Ion-exchanged PFSA dispersion was obtained in a similar way as described in Example 2 with comonomer ratios resulting in an EW of about 725. The ion-exchanged dispersion was dried in a circulated air oven for 100 hours at 60°C to give a friable solid (moisture content was 7.3%). The solid composition was redispersed in the same way as described in example 2 but with the exception that only distilled water (18.2 MOhm · cm resistivity) was used as liquid. The ionomer content in the dispersion was 27.8% by weight (based on the total weight of the dispersion) and the resulting viscosities of the clear compositions were below 100 mPas as shown in table 2. Table 2