CN114761445A

CN114761445A - Dispersible particles of perfluorosulfonic acid ionomers

Info

Publication number: CN114761445A
Application number: CN202080084434.8A
Authority: CN
Inventors: 克劳斯·辛策; 阿尔内·塔勒; 科里纳·施泰宁格; 费·泽恩缇司; 马克·W·慕格利; 丹尼斯·杜谢恩; 格雷格·D·达尔克; 利萨·P·陈
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2019-12-02
Filing date: 2020-12-02
Publication date: 2022-07-15
Anticipated expiration: 2040-12-02
Also published as: EP4069755A1; JP2023504273A; WO2021111342A1; CN114761445B

Abstract

The invention describes a polymer having a molecular weight of at least 0.1g/m²PFSA ionomer particles of BET surface area. The PFSA ionomer comprises (i) Tetrafluoroethylene (TFE) derived material and represented by the formula- [ CF ]₂‑CF₂]A divalent unit represented by-and (ii) a divalent unit represented by formula (I), (I) wherein a represents 0 or 1, b is an integer of 2 to 8, c is an integer of 0 to 2, and e is an integer of 1 to 8, and X represents an OH group or a group OZ, wherein O is an oxyanion, and Z represents a counter cation other than a hydrogen cation. Also described are methods of making such particles, and dispersions and compositions comprising such particlesThe method is carried out.

Description

Dispersible particles of perfluorosulfonic acid ionomers

Background

Copolymers of Tetrafluoroethylene (TFE) and monomers having pendent sulfonic acid groups are known for use in the manufacture of membranes for use in electrical and fuel cells. Typically, such films are prepared by: a copolymer of TFE and monomers having pendant sulfonyl fluoride groups (also referred to as a "sulfonyl fluoride polymer" or "precursor polymer") is first produced and the sulfonyl groups are then hydrolyzed. The resulting sulfonate groups are then converted to sulfonic acid groups, for example by treatment with acid or by ion exchange with a cation exchange resin, to produce perfluorosulfonic acid polymers, also known as "PFSA ionomers". Compositions comprising the resulting PFSA ionomers can be used to make films as described, for example, in WO2004/062019a1(Hamrock et al).

It is desirable to provide the PFSA ionomer in dry form rather than in solution or dispersion form. The dried PFSA ionomer particles are more stable upon storage and easier to handle during storage than the corresponding liquid compositions. The dried PFSA ionomer particles are redispersed in a liquid to prepare a dispersion that can be used, for example, in the manufacture of membranes, catalyst inks, or binder materials for batteries and electrodes. In U.S. Pat. No. 10,189,927(Ino et al), a sulfonyl fluoride precursor polymer is hydrolyzed by aqueous base, then treated with hydrochloric acid to give a perfluorosulfonic acid polymer, and the resulting composition is dried. To make the film, the dried composition is redispersed in a liquid by subjecting the mixture to elevated pressure and temperature in an autoclave, and then processed to make a film. However, it has been found that dry PFSA ionomer compositions may be difficult to redisperse in water or water-solvent mixtures at ambient conditions, or that only fairly viscous compositions may be obtained. For coating applications such as for making catalyst inks or binder materials for batteries and electrodes, and for making films, low viscosity liquid compositions are generally easier to apply than viscous compositions. However, diluting the viscous PFSA ionomer composition reduces the PFSA ionomer content, which is generally undesirable. Processing dilute compositions results in increased costs because more solvent must be removed, recovered, or discarded.

Disclosure of Invention

It has now been found that PFSA ionomer particles can be prepared that can be dispersed in a liquid to form a low viscosity PFSA ionomer dispersion. Advantageously, the particles may be dispersed to provide a dispersion having a substantially constant viscosity over a wide range of shear rates, for example the ratio of the viscosity of the dispersion measured at a shear rate of 1/s to the viscosity of the dispersion measured at a shear rate of 1000/s is about 0.9-1.20, preferably between 0.9 and 1.1. Such dispersions can be processed within a wide processing window and are useful, for example, in the production of membranes, catalyst inks or binder materials for electrodes or batteries.

Thus, in one aspect, there is provided particles comprising a PFSA ionomer, wherein the composition has at least 0.1g/m²Wherein the PFSA ionomer comprises (i) Tetrafluoroethylene (TFE) derived and has the formula- [ CF [ ]₂-CF₂]Watch with watch tableThe divalent unit shown and (ii) the divalent unit represented by the formula (I),

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 (hydroxyl) group or a group OZ, wherein O is an oxyanion, and Z represents a counter cation other than a hydrogen cation.

In another aspect, a dispersion obtained by combining particles with a liquid is provided.

In another aspect, a method of preparing a dispersion is provided, the method comprising combining particles with a liquid, preferably a liquid comprising water or an aliphatic alcohol having 1 to 5C atoms or a combination thereof.

Further, a process for preparing the composition is provided, said process comprising subjecting an aqueous PFSA ionomer composition to a process comprising a drying step selected from freeze drying, freeze granulation, spray drying or a combination thereof, to provide a composition comprising a copolymer having at least 0.1g/m²The BET surface area of (a).

Drawings

Figure 1 is an electron microscope picture of PFSA granules according to the present disclosure obtained by a freeze granulation process.

Detailed Description

When the amounts of ingredients of a composition are expressed as weight percentages (also referred to herein as "wt%" 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 be 100% by weight unless otherwise specified. Likewise, when the amount of an ingredient is identified as% mole (or "% mole" or "mol%"), the amount of all ingredients is 100% mole unless otherwise specified.

If the description refers to standards such as DIN, ASTM, ISO, etc., and if the year in which the standard was issued is not indicated, the version in effect in 2018 is meant. If no version takes effect in 2018, e.g., the criteria have expired, then the reference date is closest to the version that took effect in 2018.

PFSA ionomer dispersion

In one aspect, perfluorosulfonic acid (PFSA) ionomer particles provided by the present disclosure may be dispersed in a liquid to produce a liquid dispersion having low viscosity at both low and high shear rates, for example a dispersion having a viscosity of less than 400 millipascal-seconds (mPa-s), preferably less than 150 mPa-s, and most preferably less than 100 mPa-s at a shear rate of 1/s and a viscosity of less than 400 mPa-s, preferably less than 150 mPa-s, and most preferably less than 100 mPa-s at a shear rate of 1000/s. In some embodiments, PFSA ionomer particles may be dispersed in a liquid to produce a dispersion of low viscosity, wherein the viscosity is substantially the same when measured at a shear rate of 1/s or at a shear rate of 1000/s. For example, the particles may be dispersed to provide a dispersion having a viscosity of less than 400mPa · s at both a shear rate of 1/s and a shear rate of 1000/s, preferably having a viscosity of less than 150mPa · s at both a shear rate of 1/s and a shear rate of 1000/s, and more preferably having a viscosity of less than 100mPa · s at both a shear rate of 1/s and a shear rate of 1000/s. In some embodiments, the PFSA ionomer particles may be dispersed to provide a dispersion having a calculated ratio of viscosity at 1/s to viscosity at 1000/s of about 0.9 to 1.20, preferably about 0.9 to 1.1. This means that the viscosity remains constant over a wide range of shear rates, allowing for a wide processing window.

Preferably, the liquid is selected from water; a protic solvent having at least one hydroxyl functional group and preferably having 1 to 5 carbon atoms; and combinations thereof. The protic solvent comprises C₁To C₅Alkanols, for example methanol, ethanol, isopropanol, n-propanol, tert-butanol, n-butanol, pentanol and pentanol. Preferably, the protic solvent is selected from the group consisting of ethanol, n-propanol, isopropanol, and combinations thereof. The liquid may comprise a mixture of water and one or more protic solvents, preferably in a ratio of water to protic solvent of about 100:1 to 1:100 wt.%, preferably 10:1 to 1:10 wt.%. The liquid may also be water only or water onlyIs a protic solvent or a combination of several protic solvents.

One advantage of PFSA particles according to the present disclosure is that they may be dispersed in environmentally safe and easy to handle liquids, e.g. liquids containing at least 30 wt%, preferably at least 50 wt% or at least 80 wt% or even 95 wt% or even 100 wt% water as described above, at a concentration of at least 5 wt% and up to, e.g. 35 wt% or e.g. up to 50 wt%. The PFSA ionomer particles according to the present disclosure may be mixed with the above-described liquid to produce a low viscosity liquid dispersion by mixing the PFSA ionomer composition and the liquid at room temperature and ambient pressure over 24 hours, for example by stirring the mixture on a roller set at 45rpm to 65rpm for 24 hours.

In some embodiments, the PFSA ionomer particles may be dispersed in the liquid in an amount of at least 5 wt%, 10 wt%, 15 wt%, or even 20 wt%, based on the total weight of the dispersion. In some embodiments, the PFSA ionomer particles may be dispersed in the liquid in an amount of up to 50 wt%, for example up to 40 wt%, based on the total weight of the dispersion. In some embodiments, the dispersion comprises 5 to 10 wt% PFSA ionomer particles based on the total weight of the dispersion, for example, when used to form an electrode ink or other composition with high loading of other solids. In some embodiments, the dispersion comprises from 10 wt% to 50 wt%, such as from 15 wt% to 40 wt%, or even from 20 wt% to 30 wt%, of PFSA ionomer particles based on the total weight of the dispersion. These higher concentrations can be used, for example, to make membranes.

The PFSA ionomer particles according to the present disclosure may be obtained by subjecting an aqueous composition comprising a PFSA ionomer to a treatment comprising a drying step selected from spray drying, freeze granulation and combinations thereof. Preferably, the drying is performed by a low temperature process, i.e. by freeze drying or freeze granulation. More preferably, the drying is performed by using freeze granulation.

Spray drying is known in the art and produces dry powders from liquids or slurries by rapid drying with hot air. Preferably, the spray drying is carried out at a temperature below 220 ℃. Spray dryers use a device, typically an atomizer or spray nozzle, to disperse a liquid or slurry into a spray of controlled droplet size. Spray dryers are commercially available.

Freeze-drying is a known low temperature dehydration process that involves freezing the composition, reducing the pressure, and removing the frozen water by sublimation. Freeze dryers are commercially available.

Freeze granulation is another low temperature dehydration process. It involves pumping a composition through a device (typically an atomizer or spray nozzle or a combination thereof) to disperse a liquid or slurry into a controlled droplet size spray, and freezing the spray, for example, by exposing the spray to liquid nitrogen. The freezing medium is removed (evaporated) to provide a dry powder. The freeze granulation equipment is commercially available.

Preferably, the moisture content of the dried ionomer particles is less than 15 wt%, but residual amounts of moisture may remain in the PFSA ionomer particles. For example, in some embodiments, the moisture content of the particles may be at least 1 wt%, such as at least 2 wt%, at least 3 wt%, or even at least 4 wt%.

The aqueous ionomer composition to be subjected to drying treatment can be obtained, for example, by hydrolyzing the corresponding sulfonyl fluoride precursor polymer with an aqueous composition comprising a base (e.g., an alkali metal base selected from Li, Na, or K base, or a combination thereof) and converting it to its sulfonic acid form (e.g., by cation exchanging it with at least one cation exchange resin). In some embodiments, the sulfonyl fluoride precursor polymer has been fluorinated to reduce the amount of carboxylic acid end groups prior to hydrolysis, preferably to less than every 10⁶Carbon atom 150 carboxylic acid end groups. In some embodiments, the sulfonyl fluoride polymer has been obtained by polymerizing Tetrafluoroethylene (TFE) with one or more perfluorinated sulfonyl fluoride monomers. In some embodiments, the sulfonyl fluoride precursor polymer has a glass transition temperature (Tg) of up to 25 ℃, 20 ℃, 15 ℃, or 10 ℃. In some embodiments, the melt flow index (MFI, e.g., 265 ℃/5kg) of the sulfonyl fluoride precursor polymer is at least 1 gram/10 minutes and up to 100, preferably up to 10080 grams more per 10 minutes, for example between 5 and 55 grams per 10 minutes.

PFSA ionomers according to the present disclosure typically exhibit a thermal transition between a state in which ion clusters are closely associated and a state in which the interactions between those clusters have been weakened. The transition is described as an alpha transition and the transition temperature is either T (alpha) or T alpha. In some embodiments, the T (α) of the PFSA ionomer (free acid form) is 70 ℃ and up to 150 ℃, such as, but not limited to, 75 ℃ to 135 ℃. In some embodiments, the T (α) of the PFSA ionomer ranges from 75 ℃ to 125 ℃ or 80 ℃ to 120 ℃.

Preferably, the PFSA ionomer according to the present disclosure has per 10⁶Carbon atoms up to 150 carboxylic acid end groups, preferably per 10⁶Up to 100 or up to 50 carbon atoms, for example from 1 to 45 or from 10 to 90 carboxylic acid end groups.

PFSA ionomers according to the present disclosure typically have equivalent weights (EW or-SO) of up to 2000₃H equivalent weight). In some embodiments, the copolymer has an EW in the range of 600 to 1400, preferably from about 650 to about 1200, and more preferably from about 700 to about 1000.

The ionomer particles may be soft or hard. These particles may be friable. The particles may be in the form of, for example, lumps, flakes, granules. Preferably, the particles are spherical or substantially spherical (i.e. they may best approximate a spherical shape). The particles may generally have a size of 2.0mm or less (i.e., D100 of less than or equal to 2.0mm), or a size of 1.0mm or less (i.e., D100 of equal to or less than 1.0 mm). Preferably, at least 90% of the particles (D90) have a particle size of 2.0mm or less or preferably 1.0mm or less. In one embodiment, the particles have an average particle size (D50) in a range from about 5 μm to 500 μm or from about 25 μm to 350 μm. The granularity may be determined by image analysis. Sieving can be used to exclude particles above or below a certain threshold.

The PFSA ionomer particles according to the present disclosure have a high BET surface area, i.e., at least 0.1g/m²BET surface area of (a). In some embodiments, the ionomer particles have a BET surface area of at least 0.3g/m²E.g. at least 0.5g/m²Or even at least 1.0g/m². In some embodiments, the BET surface area of the PFSA ionomer particles is from 0.3 to 10g/m²E.g. 0.5 to 10g/m²Or even 1g/m²To 9g/m²。

The PFSA ionomer particles according to the present disclosure comprise at least 50 wt%, preferably at least 80 wt%, more preferably at least 85 wt% of PFSA ionomer. In some embodiments, the PFSA ionomer composition has a moisture content of 1 to 15 wt%, preferably 3 to 13 wt%, and more preferably 3.9 to 12 wt%, based on the total weight of the composition being 100 wt%, preferably based on the weight of the PFSA ionomer.

The PFSA ionomers according to the present disclosure are copolymers of Tetrafluoroethylene (TFE) and at least one, preferably at least two, comonomers. Thus, the copolymer contains units derived from TFE. Such units include those of the formula- [ CF ]₂-CF₂]-the bivalent unit of the representation. Typically, the PFSA ionomers according to this disclosure comprise at least 60 mole%, based on polymer (100 mole%), of a copolymer represented by the formula- [ CF₂-CF₂]-the bivalent unit of the representation. In some embodiments, the PFSA ionomer comprises at least 65 mole%, 70 mole%, 75 mole%, 80 mole%, or 90 mole% based on the polymer (100%) of a polymer of the formula- [ CF: (l-CF-l-CF-l-r-l-₂-CF₂]-a divalent unit of the formula.

Ionomers according to the present disclosure also include 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 (hydroxyl) group, i.e., a pendant ionomer pendant-terminating perfluorosulfonic acid group (-SO)₃H) Or X represents a group OZ in which O represents an oxyanion and Z represents a counter cation, i.e. with a perfluorosulfonate group (-SO) as pendant group₃Z) is terminated. Z preferably represents an alkali metal cation or a quaternary ammonium cation. The quaternary ammonium cation can be substituted by hydrogen and alkylAny combination of substituent groups, in some embodiments, the alkyl groups independently have one to four carbon atoms. In some preferred embodiments, Z is an alkali metal cation, preferably a sodium or lithium cation. Preferably, however, X represents OH.

C_eF_2eMay be linear or branched, and is preferably linear. C_bF_2bMay be linear or branched, and is preferably branched. In some embodiments, b is a number from 2 to 6 or from 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 comprises 10 to 40 mol% of divalent units represented by formula (I) based on the polymer (100 mol%). In some embodiments, the PFSA ionomer comprises 15 to 25 mol% of the unit represented by formula (I) based on the total units of the polymer (100 mol%).

Ionomers having divalent units represented by formula (I) can most conveniently be prepared by copolymerizing the corresponding sulfonyl fluoride, for example, of formula CF₂＝CF(CF₂)_a-(OC_bF_2b)_c-O-(C_eF_2e)-SO₂X 'wherein a, b, c and e are as defined above, and X' is F. The sulfonyl fluoride is then hydrolyzed to produce the sulfonate, i.e., from the formula CF₂＝CF(CF₂)_a-(OC_bF_2b)_c-O-(C_eF_2e)-SO₂X' represents a compound. X "represents OZ, and each Z is a cation as described above, preferably an alkali metal cation or a quaternary ammonium cation. The quaternary ammonium cation may be substituted with any combination of hydrogen and alkyl groups, in some embodiments, the alkyl groups independently have 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-O-(CF₂)_e-SO₂F (wherein e is 1-8), CF₂＝CF-O-CF₂CF(CF₃)O(CF₂)_e-SO₂F (wherein a is 1-8), CF₂＝CF[OCF₂CF(CF₃)]_c-SO₂F (wherein c is 1-5). Specific examples include CF₂＝CFOCF₂CF₂SO₂F、CF₂＝CFOCF₂CF₂CF₂CF₂SO₂F、CF₂＝CFOCF₂CF₂CF₂SO₂F、CF₂＝CFOCF₂CF(CF₃)OCF₂CF₂SO₂F、CF₂＝CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F、CF₂＝CFOCF₂CF(CF₃)SO₂F、CF₂＝CF-CF₂-O-CF₂CF₂-SO₂F. More preferred sulfonyl fluoride monomers include CF₂＝CFOCF₂CF₂SO₂F、CF₂＝CFOCF₂CF₂CF₂CF₂SO₂F、CF₂＝CFOCF₂CF(CF₃)OCF₂CF₂SO₂F. Most preferred is CF₂＝CFOCF₂CF₂CF₂CF₂SO₂F。

In a preferred embodiment, 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 Rf₁Is a linear or branched perfluoroalkyl group having 1 to 12 carbon atoms, which may be interrupted once or more than once by an (ether) oxygen atom, in which case Rf1 is a perfluoroalkoxyalkyl group. Typically, the PFSA ionomer according to the present disclosure comprises 0 to 15 mol% of units represented by formula (II) based on the polymer (100 mol%). In some embodiments, the PFSA ionomer comprises from 3 to 15 mole%, preferably from 5 to 10 mole% of a monomer of formula (la)A unit represented by (II).

Ionomers having divalent units represented by formula (II) can be most conveniently polymerized from CF by copolymerization₂＝CF-(CF₂)_m’-O-Rf₁Wherein m' and Rf₁As described above. For example, in the case where m' is 0, the unit represented by formula (II) is derived from a perfluoroalkyl or perfluoroalkoxyalkylvinylether comonomer. For example, using CF₂＝CF-O-C₃F₇(PPVE-1) as comonomer will give units according to formula (II) wherein m' is 0 and Rf1 is C₃F₇。

In the case where m' is 1, the unit is derived from a perfluoroalkyl or perfluoroalkoxyalkylallyl ether comonomer. For example, using CF₂＝CF-CF₂-O-C₃F₇(PPAE-1) as comonomer will give units according to formula (II) wherein m' is 1 and Rf1 is C₃F₇。

Examples of suitable perfluoroalkyl vinyl ethers and perfluoroalkyl allyl ethers include, but are not limited to, those according to formula CF₂CFORf1 and CF₂＝CFCF₂A compound of ORf1, wherein Rf1 is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl. Preferably, Rf1 is linear.

Examples of suitable perfluoroalkoxyalkylvinylethers include, but are not limited to, CF₂＝CFOCF₂OCF₃、CF₂＝CFOCF₂OCF₂CF₃、CF₂＝CFOCF₂CF₂OCF₃、CF₂＝CFOCF₂CF₂CF₂OCF₃、CF₂＝CFOCF₂CF₂CF₂CF₂OCF₃、CF₂＝CFOCF₂CF₂OCF₂CF₃、CF₂＝CFOCF₂CF₂CF₂OCF₂CF₃、CF₂＝CFOCF₂CF₂CF₂CF₂OCF₂CF₃、CF₂＝CFOCF₂CF₂OCF₂OCF₃、CF₂＝CFOCF₂CF₂OCF₂CF₂OCF₃、CF₂＝CFOCF₂CF₂OCF₂CF₂CF₂OCF₃、CF₂＝CFOCF₂CF₂OCF₂CF₂CF₂CF₂OCF₃、CF₂＝CFOCF₂CF₂OCF₂CF₂CF₂CF₂CF₂OCF₃、CF₂＝CFOCF₂CF₂(OCF₂)₃OCF₃、CF₂＝CFOCF₂CF₂(OCF₂)₄OCF₃、CF₂＝CFOCF₂CF₂OCF₂OCF₂OCF₃、CF₂＝CFOCF₂CF₂OCF₂CF₂CF₃CF₂＝CFOCF₂CF₂OCF₂CF₂OCF₂CF₂CF₃、CF₂＝CFOCF₂CF(CF₃)-O-C₃F₇(PPVE-2)、CF₂＝CF(OCF₂CF(CF₃))₂-O-C₃F₇(PPVE-3) and CF₂＝CF(OCF₂CF(CF₃))₃-O-C₃F₇(PPVE-4). Such vinyl ethers may 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. The corresponding allyl ethers are also 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.

Specific examples of suitable comonomers to produce units according to formula (II) include, but are not limited to

(i) A perfluoroalkyl vinyl ether comprising: CF₂＝CF-O-CF₃(PMVE)、CF₂＝CF-O-CF₂CF₃(PEVE)、CF₂＝CF-O-CF₂CF₂CF₃(PPVE-1)、CF₂＝CF-O-CF(CF₃)CF₃；

(ii) Perfluoroalkyl allyl ethers including: f₂C＝CF-CF₂-O-CF₃(MA1)、F₂C＝CF-CF₂-O-CF₂CF₃(MA2)、F₂C＝CF-CF₂-O-CF₂CF₂CF₃(MA3)、F₂C＝CF-CF₂-O-CF₂CF₂CF₂CF₃(MA4)；

(iii) Perfluoroalkoxyalkyl vinyl ethers comprising: CF (compact flash)₂＝CF-(O-CF₂-CF(CF₃))-O-CF₂CF₂CF₃(PPVE-2)、CF₂＝CF-(O-CF₂-CF(CF₃))₂-O-CF₂CF₂CF₃(PPVE-3)、CF₂＝CF(OCF₂CF(CF₃))₃-O-C₃F₇(PPVE-4)；CF₂＝CF-O-(CF₂)₃-OCF₃(MV31)、CF₂＝CF-O-(CF₂)₂-OCF₃(MV21)、CF₂＝CF-O-(CF₂)₄-OCF₃(MV41)、CF₂＝CF-O-CF₂-OCF₃(MV11)；

(iv) Perfluoroalkoxyalkylallyl ethers of the formula₂C＝CF-CF₂-O-(CF₂)₃-O-CF₃(MA31)、F₂C＝CF-CF₂-O-CF₂)₂-O-CF₃(MA21)、F₂C＝CF-CF₂-O-CF₂-O-CF₃(MA11)、F₂C＝CF-CF₂-O-(CF₂)₄-O-CF₃(MA41)。

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

Other optional comonomers

Although not required and less preferred, PFSA ionomers according to the present disclosure may also comprise units derived from other optional comonomers, in addition to or as an alternative to the optional comonomers provided above for units according to formula (II). Such other optional comonomers include, for example, fluorinated olefins, non-fluorinated olefins and modifiers and crosslinking agents, typically diolefins. Typically, ionomers according to the present disclosure comprise less than 20 wt%, and preferably less than 5 wt%, and more preferably 0 wt% of units derived from optional comonomers, based on the total weight of the ionomer.

Fluorinated olefins

In some less preferred embodiments, PFSA ionomers according to the present disclosure comprise a homopolymer derived from at least one monomer independently represented by formula c (r)₂＝CF-Rf₂Divalent units of other fluorinated olefins are indicated. These fluorinated divalent units are represented by the formula- [ CR ]₂-CFRf₂]-represents. In the formula C (R)₂＝CF-Rf₂And- [ CR ]₂-CFRf₂]In (a) to (b), Rf₂Is fluorine or perfluoroalkyl having 1 to 8 carbon atoms, in some embodiments 1 to 3 carbon atoms, and each R is independently hydrogen, fluorine, or chlorine. Some examples of fluorinated olefins that may be used as components of the polymerization include Hexafluoropropylene (HFP), Chlorotrifluoroethylene (CTFE), and partially fluorinated olefins such as vinylidene fluoride (VDF), tetrafluoropropene (R1234yf), pentafluoropropene, and trifluoroethylene. Preferably, however, the PFSA ionomer according to the present disclosure does not comprise any units derived from any other fluorinated olefin.

Diolefins (dienes)

The PFSA ionomers of the present disclosure may also comprise a polymer derived from one or more of formula X₂C＝CY-(CW₂)_m-(O)_n-R_F-(O)_o-(CW₂)_p-CY＝CX₂Units of diolefin are shown. In the formula, each of X, Y and W is independently fluorine, hydrogen, alkyl, alkoxy, polyoxyalkyl, perfluoroalkyl, perfluoroalkoxy, or perfluoropolyoxyalkyl, m and p are independently integers from 0 to 15, and n, o are independentlyIs 0 or 1. In some embodiments, X, Y and W are each independently fluorine, CF₃、C₂F₅、C₃F₇、C₄F₉Hydrogen, CH₃、C₂H₅、C₃H₇、C₄H₉. In some embodiments, X, Y and W are each fluorine (e.g., as in CF)₂＝CF-O-R_F-O-CF＝CF₂And CF₂＝CF-CF₂-O-R_F-O-CF₂-CF＝CF₂In (1). In some embodiments, n and o are 1, and the diolefin is divinyl ether, diallyl ether, or vinyl-allyl ether. R_FDenotes linear or branched perfluoroalkylene or perfluoropolyoxyalkylene or arylene, which may be non-fluorinated or fluorinated. In some embodiments, R_FIs a perfluoroalkylene group having 1 to 12, 2 to 10, or 3 to 8 carbon atoms. The arylene group can have 5 to 14, 5 to 12, or 6 to 10 carbon atoms, and can be unsubstituted or substituted with one or more halogens other than fluorine, perfluoroalkyl (e.g., -CF)₃and-CF₂CF₃) Perfluoroalkoxy (e.g., -O-CF)₃、-OCF₂CF₃) Perfluoropolyoxyalkyl radicals (e.g. OCF)₂OCF₃；-CF₂OCF₂OCF₃) Fluorinated, perfluorinated or non-fluorinated phenyl or phenoxy substituted; the phenyl or phenoxy group may be substituted with one or more perfluoroalkyl groups, perfluoroalkoxy groups, perfluoropolyoxyalkyl groups, one or more halogens other than fluorine, or a combination thereof. In some embodiments, R_FIs phenylene or monofluorophenylene, difluorophenylene, trifluorophenylene or tetrafluorophenylene, to which an ether group is bonded in the ortho-, para-or meta-position. In some embodiments, R_FIs CF₂；(CF₂)_qWherein q is 2,3, 4,5, 6,7 or 8; CF (compact flash)₂-O-CF₂；CF₂-O-CF₂-CF₂；CF(CF₃)CF₂；(CF₂)₂-O-CF(CF₃)-CF₂；CF(CF₃)-CF₂-O-CF(CF₃)CF₂(ii) a Or (CF)₂)₂-O-CF(CF₃)-CF₂-O-CF(CF₃)-CF₂-O-CF₂。

When used in low amounts (e.g., less than 2 wt%, preferably less than 1 wt%), the diolefins may incorporate long chain branching as described in U.S. patent application publication No. 2010/0311906 (Lavallee et al). When used in greater amounts, the diolefins may crosslink the ionomer. The diolefins described above in any embodiment of the diolefins may be present in the component to be polymerized in any useful amount. In a preferred embodiment, the ionomer does not contain any units derived from diolefins or contains such units in an amount of about 0 wt% to about 5 wt%.

The PSFA-ionomers according to the present disclosure are preferably not crosslinked.

Non-fluorinated comonomers

The PFSA ionomers of the present disclosure may also comprise 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, norbornadiene, crotonic acid, alkyl crotonate, acrylic acid, alkyl acrylate, methacrylic acid, alkyl methacrylate, and hydroxybutyl vinyl ether. Any combination of these non-fluorinated monomers may be useful. In some embodiments, the component to be polymerized further comprises acrylic acid or methacrylic acid, and the copolymers of the present disclosure comprise units derived from acrylic acid or methacrylic acid. Preferably, the PFSA ionomers according to the present disclosure contain no units derived from non-fluorinated comonomers or contain units derived from non-fluorinated comonomers in an amount of from 0 wt% to 10 wt% (100 wt% based on the total weight of the ionomer).

Typical PFSA ionomers

Preferred embodiments of PFSA ionomers according to this disclosure comprise at least 60 mol%, preferably from 65 mol% to 90 mol%, of units derived from TFE (i.e., represented by the formula [ CF)₂-CF₂]-units represented by) and 10 to 40 mol%,Preferably 15 to 25 mol% of the unit represented by the formula (I). The PFSA ionomer according to the present disclosure may comprise 0 to 15 mol%, preferably 5 to 10 mol%, of units represented by formula (II) and 0 to 30 mol% of units derived from other comonomers including the other optional comonomers described above.

The PFSA ionomer according to the present disclosure may comprise 5 to 50 wt%, for example 10 to 40 wt% of units according to formula (I). The PFSA ionomers according to the present disclosure may comprise from 30 wt% to 95 wt%, for example from 45 wt% to 90 wt%, of a copolymer of formula [ CF₂-CF₂]-a unit represented by formula (II). Preferably, the PFSA ionomers according to the present disclosure may comprise from 30 wt% to 95 wt%, for example from 45 wt% to 90 wt%, of a copolymer of the formula- [ CF%₂-CF₂]A unit represented by the formula (II) and a unit represented by the formula- [ CF ]₂-CF₂]The molar ratio of the units represented by (a) to the units according to formula (II) is from 90:1 to 4: 1. The total weight of the polymer is 100 wt.%.

Preferably, the PFSA ionomer is perfluorinated, meaning that it is obtained by using only perfluorinated monomers and not partially or non-fluorinated polymers. The partially fluorinated monomers contain C-F bonds and C-H bonds, the perfluorinated monomers contain C-F bonds but no C-H bonds, and the non-fluorinated monomers contain no C-F bonds but no C-H bonds.

In a preferred embodiment, the PFSA ionomer is as described above, wherein in formula (I) a is 1 or 0, C is 0, C_eF_2eIs straight-chain and e is 2,3 or 4, more preferably in formula (I) a is 1 or 0, C is 0, C_eF_2eIs straight-chain and e is 4.

In another preferred embodiment, a PFSA ionomer is described above, wherein the PFSA ionomer comprises units according to formula (II), and wherein in formula (II) m' is 0 and Rf is selected from CF₃、C₂F₅、C₃F₇Preferably CF₂CF₂CF₃。

In another preferred embodiment, the foregoing has been describedA PFSA ionomer is described, wherein the PFSA ionomer comprises units according to formula (II) and wherein in formula (II) m' is 1 and Rf is selected from CF₃、C₂F₅、C₃F₇Preferably CF₂CF₂CF₃。

In another preferred embodiment, a PFSA ionomer is described above, wherein the PFSA ionomer comprises units according to formula (II), and wherein in formula (II) m' is 1 and Rf is selected from (CF)₂)_nOCF₃And n is 1, 2,3 or 4, preferably n is 3.

In another preferred embodiment, a PFSA ionomer is described above, wherein the PFSA ionomer comprises units according to formula (II), and wherein in (I) m' is 0 and Rf is selected from (CF)₂)_nOCF₃And n is 1, 2,3 or 4, preferably n is 3.

In another preferred embodiment, a PFSA ionomer is described above, wherein the PFSA ionomer, wherein in formula (I) a is 0, C is_eF_2eIs linear and e is 4, and the PFSA ionomer comprises units according to formula (II), and in formula (II) m' is 0, and Rf is selected from CF₃、C₂F₅、C₃F₇Preferably CF₂CF₂CF₃。

In another preferred embodiment, a PFSA ionomer is described above wherein in formula (I) a is 0, C is_eF_2eIs linear and e is 4, and m' is 1 in formula (II) and Rf is selected from CF₃、C₂F₅、C₃F₇Preferably CF₂CF₂CF₃。

In another preferred embodiment, the PFSA ionomer is as described above, and wherein in formula (I) a is 0, C is_eF_2eIs linear and e is 4, and m' is 0 in formula (II), and Rf is selected from (CF)₂)_nOCF₃And n is 1, 2,3 or 4, preferably n is 3.

In yet another preferred embodiment, PFSA ionomersAs described above, wherein a is 0, C is 0, C in formula (I)_eF_2eIs linear and e is 4, and m' is 1 in formula (II), and Rf is selected from (CF)₂)_nOCF₃And n is 1, 2,3 or 4, preferably n is 3.

Preparation of PFSA ionomer

The PFSA ionomers of the present disclosure may be prepared by copolymerizing the comonomers, i.e., TFE, and a comonomer that yields a divalent unit of formula (I) and optionally a comonomer that yields a unit of formula (II) and optionally copolymerizing the optional comonomers, such as the optional comonomers described above.

The monomers are added to the reaction in proportions and amounts to give the final polymer with the desired amount of the desired comonomer units. In selecting the monomer feed, different incorporation rates must be considered. The monomers may be added continuously or intermittently, for example as a batch polymerization. Depending on the polymer structure to be produced, i.e. the core-shell polymer, the random polymer or the heterogeneous polymer, for example bimodal or multimodal, they can be added continuously in the same amount and rate or in different amounts and feed rates.

The polymerization may be carried out by radical polymerization. Reaction equipment suitable for handling corrosive materials, including exposure to HF, is used. The reaction equipment may be allowed to treat under inert gas or purged with inert gas. Typically, a stainless steel container is used, but if appropriate, the container may be made of other materials, or may contain an inert protective liner, such as a PTFE liner. The sample or material may be stored in a stainless steel container or HDPE container or other suitable container. The vessels and other equipment, such as agitation equipment, may vary in size and design depending on the polymer to be produced. The concentration of the component can be determined online, for example, by using pressure, pH, or other suitable indicators, or can be sampled intermittently, and the actual amount of the component can be measured offline, for example, by gas chromatography, mass spectrometry, pH electrodes, F electrodes, or other suitable analytical devices and methods. Free radical polymerization includes free radical aqueous emulsion polymerization (which is preferred), suspension polymerization, and solvent polymerization. Water (W)Aqueous emulsion polymerization typically produces about 50nm to 500nm of polymer particles, also referred to in the art as "polymer latex," dispersed in an aqueous phase. Suspension polymerization will generally produce particle sizes of up to a few millimeters. The solvent used for the solvent polymerization includes chlorofluorocarbon, hydrochlorofluorocarbon, hydrofluorocarbon, hydrofluoroether and the like, and hydrofluorocarbon or hydrofluoroether which does not damage the ozone layer is more preferable. Suitable hydrofluorocarbons may have from 4 to 10 carbon atoms. The hydrofluorocarbons preferably have a molar ratio of the number of hydrogen atoms/the number of fluorine atoms (hereinafter referred to as H/F) of 0.05 to 20. The hydrofluorocarbons may be straight chain or branched. An example of a suitable hydrofluoroether is CF₃CH₂OCF₂CF₂H、CHF₂CF₂CH₂OCF₂CF₂H、CF₃CF₂CH₂OCF₂CF₂H and CF₃CH₂OCF₂CF₂H。

The polymerization initiator to start the polymerization may be, for example, a diacyl peroxide such as disuccinic acid peroxide, benzoyl peroxide, perfluorobenzoyl peroxide, lauroyl peroxide or bis (pentafluoropropionyl) peroxide, an azo compound such as 2,2' -azobis (2-amidinopropane) hydrochloride, 4' -azobis (4-cyanovaleric acid), dimethyl 2,2' -azobisisobutyrate or azobisisobutyronitrile, a peroxyester such as t-butyl peroxyisobutyrate or t-butyl peroxypivalate, peroxydicarbonates such as diisopropyl peroxydicarbonate or bis (2-ethylhexyl) peroxydicarbonate, hydroperoxides such as diisopropylbenzene hydroperoxide or tert-butyl hydroperoxide, dialkyl peroxides such as di-tert-butyl peroxide or perfluoro-di-tert-butyl peroxide. Water-soluble initiators (e.g., inorganic initiators such as potassium permanganate or peroxysulfate) can also be used to start the polymerization process. Salts of peroxysulfuric acid, such as ammonium persulfate or potassium persulfate, may be used alone or in the presence of a reducing agent such as a bisulfite or sulfinate (e.g., fluorinated sulfinate as disclosed in U.S. Pat. Nos. 5,285,002 and 5,378,782, both to Grootaert) or the sodium salt of hydroxymethanesulfinic acid (sold under the trade designation "RONGALIT" by BASF Chemical Company, New Jersey, USA, N.J.). The concentration of the initiator and reducing agent can range from 0.001 wt% to 5 wt% based on the polymerization medium.

Most of the initiators mentioned above and any emulsifiers that may be used in the polymerization have an optimum pH range in which they show the highest efficiency. For these reasons, buffers may be useful. Buffers include phosphates, acetates, oxalates, or carbonates (e.g., (NH)₄)₂CO₃Or NaHCO₃) A buffer or any other acid or base, such as ammonia or an alkali metal hydroxide. In some embodiments, the copolymerization is carried out at a pH below pH 9. The concentration ranges of initiator and buffer may vary from 0.01 to 5 wt% based on the aqueous polymerization medium. In some embodiments, if the pH is too acidic, ammonia is added to the reaction mixture in an amount to adjust the pH.

Typical chain transfer agents are for example H₂Lower alkanes (e.g. n-pentane, n-hexane or cyclohexane), alcohols (e.g. methanol, ethanol, 2,2, 2-trifluoroethanol, 2,2,3, 3-tetrafluoropropanol, 1,1,1,3,3, 3-hexafluoroisopropanol or 2,2,3,3, 3-pentafluoropropanol), ethers (e.g. diethyl ether or methylethyl ether), esters (e.g. methyl acetate or ethyl acetate) and CH₂Cl₂Can be used to prepare polymers according to the present disclosure. Termination via chain transfer leads to a polydispersity of about 2.5 or less. In some embodiments of the methods according to the present disclosure, the polymerization is carried out in the absence of any chain transfer agent. Lower polydispersity can sometimes be achieved in the absence of chain transfer agents. For small conversions, recombination typically results in a polydispersity of about 1.5. If used, the amount of molecular weight control agent can range from 0.0001 to 50 or 0.001 to 10 parts per 100 parts monomer.

Useful polymerization temperatures can range from 20 ℃ to 150 ℃. Typically, the polymerization is carried out at a temperature in the range of 30 ℃ to 120 ℃, 40 ℃ to 100 ℃, or 50 ℃ to 90 ℃. The polymerization pressure is typically in the range of from 0.4MPa to 2.5MPa, from 0.6MPa to 1.8MPa, from 0.8MPa to 1.5MPa, and in some embodiments, from 1.0MPa 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 of about 0.02% to about 3% by weight relative to the polymer. The polymer particles prepared with the fluorinated emulsifier typically have an average diameter in the range of about 10 nanometers (nm) to about 500nm, and in some embodiments, in the range of about 50nm to about 300nm, as determined by dynamic light scattering techniques. Examples of suitable emulsifiers include those having the formula

[R_f-O-L-COO^-]_iXⁱ⁺

Wherein L represents a linear partially or fully fluorinated alkylene group or an aliphatic hydrocarbon group, R_fDenotes a linear partially or fully fluorinated aliphatic group or a linear partially or fully fluorinated aliphatic group interrupted by one or more oxygen atoms, Xⁱ⁺Represents a cation having a 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: CF (compact flash)₃-(OCF₂)_x-O-CF₂-X ', wherein X has a value of 1 to 6, and X' represents a carboxylic acid group or a salt thereof; and CF₃-O-(CF₂)₃-(OCF(CF₃)-CF₂)_y-O-L-Y', wherein Y has a value of 0,1, 2 or 3 and L represents a group selected from-CF (CF)₃)-、-CF₂-and-CF₂CF₂-and Y' represents a carboxylic acid group or a salt thereof (see, e.g., U.S. patent publication No. 2007/0015865 to Hintzer et al). Other suitable emulsifiers include those described in U.S. patent publication No. 2006/0199898 to Funaki et al, U.S. patent publication No. 2007/0117915 to Funaki et al, U.S. patent No. 6,429,258 to Morgan et al, U.S. patent No. 4,621,116 to Morgan, U.S. patent publication No. 2007/0142541 to Hintzer et al, U.S. patent publications nos. 2006/0223924, 2007/0060699, and 2007/0142513 to Tsuda et al, and 2006/0281946 to Morita et al and U.S. patent No. 2,559,752 to Berry, respectively. Conveniently, however, in some embodiments, the polymerization may be in the absence of any of these emulsifiersWith or without fluorinated emulsifiers.

The monomers may be added all at once, or they may be added continuously or intermittently. Perfluoroalkoxyalkylvinyl ethers and perfluoroalkoxyalkylallyl ethers are typically liquids and may be sprayed into the reactor in liquid or vaporized or atomized form or added directly. It may be useful to synthesize a compound of formula CF₂＝CF(CF₂)_a-(OC_bF_2b)_c-O-(C_eF_2e)-SO₂The compound represented by X "and other comonomers yielding units according to formula (II) are fed as a homogeneous mixture to be polymerized. It may be useful to prepare such a pre-emulsion using one or more of the emulsifiers described above. It may also be useful to hydrolyze some of the CF by aqueous base₂＝CF(CF₂)_a-(OC_bF_2b)_c-O-(C_eF_2e)-SO₂F to obtain an "in situ" -emulsifier as described, for example, in WO2005/044878(Thaler et al).

If a fluorinated emulsifier is used, the emulsifier can be removed or recycled from the fluoropolymer latex, if desired, as described in U.S. Pat. No. 5,442,097 to Obermeier et al, U.S. Pat. No. 6,613,941 to Felix et al, U.S. Pat. No. 6,794,550 to Hintzer et al, U.S. Pat. No. 6,706,193 to Burkard et al, and U.S. Pat. No. 7,018,541 to Hintzer et al. Alternatively, it can also be removed by thermal treatment (e.g. evaporation or treatment with a carrier gas stream or steam) followed by thermal degradation or recovery and recycling of the emulsifier.

Preferably, the glass transition temperature (Tg) of the sulfonyl fluoride precursor polymer is up to 25 deg.C, 20 deg.C, 15 deg.C or 10 deg.C. The Tg of the polymer can be affected by the monomer composition. Typically, side chains with perfluoroalkoxy groups will lower the Tg of the polymer. Preferably, the melt flow index (MFI, e.g., 265 ℃/5kg) of the sulfonyl fluoride precursor polymer is at least 0.1 g/10min and at most 100, preferably at most 80 g/10min, e.g., MFI between 5 and 55 g/10 min. The MFI of the copolymer can be adjusted by adjusting the amount of initiator and/or chain transfer agent used during polymerization, both of which affect the molecular weight and molecular weight distribution of the copolymer. The MFI can also be controlled by the rate at which the initiator is added to the polymerization. Variations of the monomer composition may also affect the MFI.

SO₂The reactivity of the F-comonomer may be lower than that of the other comonomers. Thus, it may be useful to feed these monomers into the polymerization system in excess (e.g., in an amount 30% greater than the final amount expected in the polymer) to obtain the desired incorporation into the polymer. In order to remove and recover excess SO₂F-monomer, the reaction mixture can be condensed and unreacted monomer can be recovered from the condensate, for example by evaporation. The reaction mixture may or may not be diluted prior to coagulation, or a solvent or other liquid that allows recovery of unreacted monomer may be added prior to coagulation. The condensation and monomer recovery can be carried out in the same reaction vessel, or the reaction mixture can be transferred to a different reaction vessel. The reaction mixture may be transferred all at once and then subjected to an evaporation treatment, or may be transferred continuously or batchwise. The evaporation can be carried out by thermal treatment, for example in a reactor with an external heating jacket or by using a support medium such as steam, or both. The carrier medium can also be used for heating the reactor, for example when steam is used as carrier medium or a heated carrier gas is used. In case a carrier medium is used, the reactor may comprise one or more nozzles through which the carrier medium may enter and exit. The reactor may comprise one or more agitators, such as an impeller agitator or helical ribbon agitator, or the reactor may be a fluidized bed reactor. Unreacted monomer may be recovered by condensation and/or other separation from the support medium. In order to coagulate the obtained copolymer latex, any coagulant commonly used for coagulation of fluoropolymer latices may be used, and may be, for example, 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., ethanol or acetone). The amount of coagulant to be added may be in the range of 0.001 to 20 parts by mass, for example, 0.01 to 10 parts by mass, per 100 parts by mass of the latexInside the enclosure. For example, 341kg of a polymer dispersion having a solids content of 29%, to which 200kg of deionized water was added, may be charged into a stainless steel reactor having an internal capacity of 800l, which is equipped with a stirrer, a high-speed stirrer "TURRAX" and a steam nozzle for heating the reactor. While the agitator of the reactor was rotating at 100rpm and the high speed agitator was rotating at 600rpm, 65 wt% nitric acid (28,2kg) may be continuously fed into the reactor to precipitate the polymer at room temperature, and stirring may be continued for 1 h. This may lead to almost complete coagulation with a solids content of less than 1% in the resulting aqueous phase. Alternatively or additionally, the latex may be frozen, for example with a homogenizer, for coagulation or mechanical coagulation, as described in U.S. patent No. 5,463,021(Beyer et al). Alternatively or additionally, the latex may be coagulated by addition of a polycation. It may be useful to avoid the use of salts as coagulants to avoid the introduction of metal contaminants. To avoid complete coagulation and any contamination from the coagulant, spray drying the latex after polymerization and optional ion exchange purification can be used to provide a solid precursor polymer.

The coagulated precursor polymer may be collected by filtration and washed with water. The washing water may be, for example, ion-exchanged water, pure water, or ultrapure water. The amount of the washing water may be 1 to 5 times by mass of the precursor polymer, whereby the amount of the emulsifier attached to the polymer can be sufficiently reduced by one washing. The precursor polymer may be dried with drying equipment as known in the art, e.g. by a fluid bed dryer or a drum dryer or a simple oven, to a water content of e.g. 0.1 wt% or less, preferably below 0.05 wt%. Based on polymerization initiators (e.g. KMnO)₄) It may be beneficial to perform the cation exchange process prior to the comonomer recovery process. Useful cation exchange resins include polymers (typically crosslinked) having multiple pendant anionic or acidic groups, such as, for example, polysulfonates or polysulfonic acids, polycarboxylates or polycarboxylic 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. Preference is given toThe cation exchange resin is an organic acid cation exchange resin, such as a carboxylic acid cation exchange resin. Cation exchange resins are commercially available from a variety of sources. Cation exchange resins are generally commercially available in their acid or sodium salt form. If the cation exchange resin is not in the acid form (i.e., protonated form), it may be at least partially or completely converted to the acid form in order to avoid the generally undesirable introduction of other cations into the dispersion. This conversion to the acid form can be achieved by means well known in the art, for example by treatment with any sufficiently strong acid. The ion exchange process may be carried out in a continuous mode using a fixed bed column, for example a column having a length to diameter ratio of 20:1 to 7:1 and a flow rate of 1 bed volume/h. The process can be monitored online or offline by pH meters, metal analyzers (e.g., lithium content can be measured if hydrolysis is performed in Li salts), or other techniques (e.g., conductivity, etc.). The ion exchange resin may be a multimodal resin or a unimodal resin, and it may have a broad or narrow particle size distribution. Commercially available cation exchange resins include, but are not limited to, those available under the tradenames LEWATIT MONO PLUS S100, AMBERLITE IR-120(PLUS), or PUROLITE 150C TLH.

If both anion exchange and cation exchange processes are used for the purification of the fluoropolymer dispersion, the anion exchange resin and the cation exchange resin can be used alone or in combination as, for example, in the case of a mixed resin bed with both anion exchange resin and cation exchange resin.

Fluoropolymers obtained by aqueous emulsion polymerization typically have a large number of carboxylic acid end groups (e.g., every 10 produced by side reaction of the polymerization initiator)⁶More than 200 carboxylic acid end groups). Preferably, the copolymer has a molecular weight of every 10⁶Less than 150 carboxylic acid end groups of carbon atoms, preferably per 10⁶Less than 100 or even less than 50 carbon atoms, for example 1 to 45 or 10 to 90 carboxylic acid end groups. Reducing the number of carboxylic acid end groups can be achieved by fluorination treatment. Fluorination of fluoropolymers to convert unstable end groups to-CF₃An end group. Fluorination may be carried out in any convenient manner. Fluorination may conveniently be at between 20 deg.CAnd 250 ℃, in some embodiments at a temperature in the range of from 150 ℃ to 250 ℃ or from 70 ℃ to 120 ℃ and a pressure of from 10kPa to 1000kPa, wherein the ratio of nitrogen/fluorine gas mixture is from 75-90: 25-10. The reaction time may range from about four hours to about 16 hours. The fluorination may be carried out continuously or intermittently, for example by a series of fluorination and purging steps, at the same temperature or at different temperature intervals. Purging is conveniently performed by using nitrogen. Under these conditions, the least stable carbon-based end groups, however, -SO, were removed₂The F group remains. After the reaction was complete, the reactor vessel was purged with nitrogen to remove fluorine gas. The fluorination can be carried out, for example, in suitably equipped autoclaves, drum reactors or fluidized bed reactors or combinations thereof.

SO₂F-copolymer hydrolysis, SO₂Conversion of F-group to-SO₂An OX "group, i.e., a" sulfonate group ". X "represents OZ, and each Z is a cation, preferably an alkali metal cation or a quaternary ammonium cation. The quaternary ammonium cation may be substituted with any combination of hydrogen and alkyl groups, in some embodiments, the alkyl groups independently have from one to four carbon atoms. In some preferred embodiments, Z is an alkali metal cation, preferably a sodium or lithium cation. The hydrolysis may be carried out by reacting SO₂The F-polymer is subjected to an aqueous base treatment. The reaction can be carried out under pressure, for example in an autoclave, a fluidized bed reactor or a stirred vessel. Typically, the hydrolysis is carried out at elevated temperatures, for example at temperatures between 150 ℃ and 300 ℃. The reaction time may be 0.5 to 10 hours. Preferably, an alkali metal base (such as, but not limited to, lithium hydroxide or lithium carbonate), an alkaline earth metal base, or ammonia (NR) is used₄OH) or a combination thereof as a base. The amount of water may be selected to give a solids content of 5 to 40 wt.%. After completion of the reaction, a fluoride salt (Al (OH)) which is hardly soluble may be added₃、Ca(OH)₂) To reduce the fluorine content in the aqueous phase. After removal of fluoride salt (e.g. by filtration, centrifugation or sedimentation), the-SO of the polymer₂Conversion of OX "groups to perfluorosulfonic acids by acid treatment or ion exchange with cation exchange resinsForm (-SO)₃H form). Cation exchange resins as described above may be used. The ion exchange process may be carried out in a continuous mode as described above, for example using a fixed bed column, for example a column having a length to diameter ratio of 20:1 to 7:1, at a flow rate of 1 bed volume/h. The process may be monitored online or offline, for example, by a pH meter, a metal analyzer (e.g., lithium content may be measured if hydrolysis is performed in Li salt), or other techniques including those described above (e.g., conductivity, etc.).

To produce dispersible PFSA ionomer particles, the aqueous PFSA ionomer composition is dried. Preferably, the drying is carried out at a temperature and for a time effective to reduce the moisture content of the aqueous PFSA ionomer composition to a moisture content of less than 25 wt%, preferably less than 15 wt%, more preferably less than 12 wt%, based on the weight of the composition. Drying is preferably carried out so that the moisture content does not decrease below the levels described above and below, for example not less than 2% by weight, preferably not less than 3.1% by weight, more preferably not less than 3.9% by weight (based on the weight of the composition).

Preferably, the drying process is carried out such that the temperature of the composition does not exceed 220 ℃ or 200 ℃ or even 100 ℃. More preferably, the drying is performed by a low temperature process, i.e. a process comprising freezing the dispersion.

In some embodiments, the aqueous PFSA-composition is obtained by a process comprising spray drying. Typically, the spray drying process produces particles having a particle size of about 10 μm to 300 μm. These particle sizes may be D50 values or may be maximum particle sizes. The use of a sieve ensures that particles having a diameter exceeding the above-mentioned size are removed from the composition. The particles are generally spherical or substantially spherical, which means that the particles are not completely spherical in shape, but their geometry may best approximate a sphere.

In other embodiments, the PFSA-composition according to the present disclosure is dried by a method comprising freeze-drying. Freeze drying produces a flake-like material, typically with a maximum dimension between 5 μm and 1000 μm. The flakes may be comminuted into smaller particles. In some embodiments, the foam is generated from an aqueous composition and frozenAnd (5) drying. The foam may be produced, for example, by subjecting the aqueous composition to ultrasonic radiation, by subjecting a gas such as CO₂Injected into the dispersion, or produced by mechanical force, for example by subjecting the aqueous composition to one or more high speed stirrers. Combinations of the above steps may also be used.

In other embodiments, the PFSA ionomer particles are obtained by a process comprising freeze granulation, preferably freeze granulation with liquid nitrogen. Typically, freeze granulation produces spherical particles with a size between 10 μm and 500 μm. These particle sizes may be D50 values or may be maximum particle sizes. The use of a sieve ensures that particles having a diameter exceeding the above-mentioned size are removed from the composition. The granules obtained by freeze granulation are usually porous. They are usually spherical or substantially spherical, which means that the particles are not completely spherical, but their geometry can best be approximated as spherical.

The solid PFSA ionomer particles typically have a total content of Na, K and Li ions of less than 100ppm, preferably less than 50ppm or even less than 20ppm, and one or more of all of these ions may be practically absent. The dispersible PFSA ionomer particles typically have a heavy metal content (total content of Fe, Ni, Cu and Cr ions) of no more than 100ppm, preferably less than 20ppm, more preferably an Fe content of less than 5 ppm.

The PFSA ionomer particles may generally be dispersed directly in a liquid, preferably a liquid selected from the group consisting of water and organic protic solvents containing at least one hydroxyl functional group and 1 to 5 carbon atoms, at a concentration of at least 10 wt%, 15 wt%, 20 wt% or 25 wt%, as described above and below. In some embodiments, the ionomer particles may be directly dispersed at a concentration of up to and including 30 wt%, preferably up to and including 40 wt% or even 50 wt%. The PFSA ionomer particles may be dispersed in a liquid to provide a liquid composition having a viscosity of less than 300mPas, preferably less than 100mPas, or even lower at a shear rate of 1/s and a shear rate of 1000/s, as described above and below.

The PFSA ionomer particles can be easily dispersed in water or a water-miscible solvent to produce a liquid composition having a low viscosity at low and high shear rates and preferably even at fairly high PFSA ionomer concentrations, for example, up to at least 20 wt% of the PFSA ionomer, or at least up to at least 30 wt% of the PFSA ionomer or even up to 40 wt% of the PFSA ionomer or greater. Another advantage of PFSA ionomer particles is that they can be used to prepare dispersions with low viscosity that remain substantially constant over a wide range of shear rates. For example, the ratio of the viscosities of such PFSA dispersions measured at a low shear rate, e.g., 1/s, and a high shear rate, e.g., 1000/s, is equal to or near 1, e.g., between and including 0.9 and 1.20. This allows for a wide processing window of the dispersions obtained from the PFSA ionomers and ionomer compositions provided in this disclosure.

A useful method for preparing such dispersions includes combining the components and mixing the components at ambient temperature and pressure to prepare a liquid dispersion of ionomer particles. The mixing may be performed by stirring the composition. Mild stirring conditions may be sufficient, for example placing the mixture on a roller set at 45 to 65rpm for 24 hours at room temperature and ambient pressure. Although liquid compositions may be prepared at ambient conditions, they may also be prepared in other ways, for example by addition of other solvents or by operating at elevated temperature or pressure, but in many cases this is disadvantageous and unnecessary.

The PFSA ionomer dispersions of the present disclosure may be used, for example, to make membranes, such as polymer electrolyte membranes for fuel cells or electrolyte membranes in electrochemical cells, such as chlor-alkali membrane cells. PFSA ionomer dispersions are particularly suitable for making thin films, i.e. membranes having a thickness of less than 50 microns, preferably less than 30 microns, for example between 20 and 40 microns, or between 10 and 28 microns. The film is typically an extended sheet and may have a length of greater than 12 cm. Typically, films are cast from a liquid composition or dispersion and then dried, annealed, or both. The film may be cast on a support. Typically, the support matrix is non-conductive. Typically, the support matrix is comprised of a fluoropolymer, which is more typically perfluorinated. Typical substrates include porous Polytetrafluoroethylene (PTFE), such as biaxially stretched PTFE webs. In another embodiment, fillers (e.g., fibers) may be added to the PFSA ionomer composition to reinforce the membrane. After formation, the film may be annealed, typically at a temperature of 120 ℃ or greater, more typically 130 ℃ or greater, and most typically 150 ℃ or greater.

To prepare the membrane, a liquid PFSA ionomer dispersion is obtained by dispersing a dispersible PFSA ionomer composition in a liquid as described above to produce a low viscosity liquid composition. However, the dispersible PFSA ionomer particles may also be mixed with other liquids to provide a dispersion or solution. Additives may be added prior to casting the film. Additives may be added to the composition obtained by combining dispersible PFSA ionomer particles with a liquid (preferably the liquid described above for producing a low viscosity liquid PFSA ionomer dispersion) or with a different liquid. The additive may be added as a solid material or dissolved or dispersed in a liquid. The additives may also be combined directly with the dispersible PFSA ionomer particles according to the present disclosure and may be added as a solid, for example as a powder, or they may be added as a solution or dispersion in a liquid, which may be water or a 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 comprises a salt of cerium, manganese, or ruthenium or at least one of one or more cerium oxide or zirconium oxide compounds, and is added to the PFSA ionomer prior to 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 containing other metal cations or ammonium cations. When cation exchange is performed between a transition metal salt and an acid form ionomer, it may be desirable to remove the acid formed by the combination of the liberated proton and the original salt anion. Thus, it may be useful to use anions which generate volatile or soluble acids, e.g.Chloride ion or nitrate ion. The manganese cation may be in any suitable oxidation state, including Mn²⁺、Mn³⁺And Mn⁴⁺But most typically Mn²⁺. The ruthenium cation may be in any suitable oxidation state, including Ru³⁺And Ru⁴⁺But most typically Ru³⁺. The cerium cation may be in any suitable oxidation state, including Ce³⁺And Ce⁴⁺. While not wishing to be bound by theory, it is believed that the cerium, manganese, or ruthenium cations remain in the polymer electrolyte because they interact with H in the anionic groups of the polymer electrolyte⁺Ion exchanged and associated with those anionic groups. Furthermore, it is believed that multivalent cerium, manganese, or ruthenium cations can form crosslinks between anionic groups of the polymer electrolyte, further increasing the stability of the polymer. In some embodiments, the salt may be present in a solid form. The cations may be present in a combination of two or more forms, including solvated cations, cations associated with bound anionic groups of the polymer electrolyte membrane, and cations bound in salt precipitates. The amount of salt added is typically between 0.001 and 0.5, 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 charge equivalents based on the molar amount of acid functional groups present in the polymer electrolyte. Additional details regarding the combination of anionic copolymers 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 (IV) cerium in an oxidation state, (III) cerium in an oxidation state, or both, and may be crystalline or amorphous. The cerium oxide may be, for example, CeO₂Or Ce₂O₃. The cerium oxide may be substantially free of or may contain metallic cerium. The cerium oxide may be, for example, a thin oxidation reaction product on metallic cerium particles. The cerium oxide compound may or may not contain other metal elements. Examples of mixed metal oxide compounds including cerium oxide include solid solutions (such as zirconia-ceria) and multicomponent oxide compounds (such as barium cerate). While not wishing to be bound by theory, it is believed that cerium oxide may be formed by incorporating an anionic groupThe groups chelate with each other and form crosslinks to strengthen the polymer. The amount of cerium oxide compound added is typically between 0.01 and 5 wt%, more typically between 0.1 and 2 wt%, and more typically between 0.2 and 0.3 wt%, based on the total weight of the PFSA. The cerium oxide compound is typically present in an amount of less than 1 volume percent, more typically less than 0.8 volume percent, and more typically less than 0.5 volume percent, relative to the total volume of the polymer electrolyte membrane. The cerium oxide may be particles of any suitable size, in some embodiments, particles of a size between 1nm and 5000nm, 200nm to 5000nm, or 500nm to 1000 nm. Additional details regarding polymer electrolyte membranes comprising cerium oxide compounds may be found in U.S. patent 8,367,267(Frey et al).

The PFSA ionomer particles and dispersions of the present disclosure may also be used to prepare catalyst ink compositions. To prepare the catalyst ink, dispersible PFSA ionomer particles can be used to prepare and combine a low viscosity liquid composition according to the present disclosure with catalyst particles (e.g., metal particles or carbon-supported metal particles). However, the dispersible PFSA ionomer particles may also be mixed with other liquids to provide a dispersion or solution to which catalyst particles may be added. The catalyst particles may also be added directly to and mixed with the dispersible PFSA ionomer particles. The catalyst particles may be added as a solid material or dissolved or dispersed in a liquid, preferably water or a protic solvent having at least one hydroxyl functional group as described above. A variety of catalysts may be useful. Carbon supported catalyst particles are typically used. Typical carbon-supported catalyst particles are 50 to 90 weight percent carbon and 10 to 50 weight percent catalyst metal, which typically comprises platinum as the cathode and 2:1 weight ratio of platinum and ruthenium as the anode. However, other metals may be useful, such as 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, such as a membrane or an electrode. In one embodiment, the catalyst particles, or at least a portion thereof, are added to the dispersible PFSA ionomer composition prior to the addition of liquid to form a liquid composition. Details regarding the preparation of catalyst inks and their use in membrane modules can be found, for example, in U.S. patent publication 2004/0107869 (Velamarkanni et al).

PFSA ionomer particles and dispersions according to the present disclosure may also be used to make binders for electrodes or batteries (e.g., lithium ion batteries). To manufacture the electrode, the powdered active ingredient may be dispersed with a solvent and added in solid form, for example in powder form, 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 a protic organic solvent having at least one functional hydroxyl group as described above. The adhesive composition may then be coated onto a substrate such as a metal foil or current collector. The resulting composite electrode contains a powdered active ingredient in a polymeric binder that adheres to the metal substrate. Useful active materials for preparing the negative electrode include alloys of main group elements and conductive powders such as graphite. Examples of usable active materials for preparing the negative electrode include oxides (tin oxide), carbon compounds (e.g., artificial graphite, natural graphite, soil black lead, expanded graphite, and flake graphite), silicon carbide compounds, silicon oxide compounds, titanium sulfide, and boron carbide compounds. Useful active materials for preparing the positive electrode include lithium compounds, such as Li_4/3Ti_5/3O₄、LiV₃O₈、LiV₂O₅、LiCo_0.2Ni_0.8O₂、LiNiO₂、LiFePO₄、LiMnPO₄、LiCoPO₄、LiMn₂O₄And LiCoO₂. The electrode may also include a conductive diluent and an adhesion promoter.

In order that the disclosure may 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 way.

Examples

Moisture content method：

The moisture content of the solid ionomer composition was determined by thermogravimetric analysis using Mettler-Thermowaage HR73, HR83 (halogen). 3g of the product are weighed into a thermobalance. The thermobalance was run at 120 ℃ for 30 minutes. The resulting solids content (%) was determined by multiplying the ratio of the final weight/initial weight by 100. The moisture content (%) was calculated by 100% -solid content (%).

Viscosity method：

The viscosity is determined at 20 ℃ by means of a rotational viscometer (rotational viscometer MCR 102/cylinder system CC 27; Ostfildenden-Toppa Germany (Anton Paar Germany GmbH, Ostfildern-Scharnhausen, Germany)) at shear rates of 1/s and 1000/s. If necessary, the solid sample is ground before adding the liquid. The liquid is added to the ionomer in an amount to give an ionomer dispersion having the desired ionomer content. Unless otherwise stated, a 6g ionomer sample was used. The resulting mixture was placed on a roller box and rolled at room temperature for 24 hours.

Solids content method：

The solids content is generally calculated as the weight of the ingredients. The solid content can be determined gravimetrically by placing a sample of the dispersion on a heated balance and recording the mass before and after evaporation of the solvent. The solids content is the ratio of the initial mass of the sample to the mass of the sample when the mass does not decrease further with continued heating. Thermogravimetric analysis was performed using thermobalances (Mettler-Thermowaage HR73, HR83 (halogen)). Typically, 3g of the product is weighed into a thermobalance and the thermobalance is operated at 120 ℃.

Equivalent Weight (EW) process：

The EW of the ionomer is calculated by the following formula:

wherein M2 is a sulfonyl fluoride monomer and M3 is an optional vinyl ether or allyl ether monomer, and M3 is 0 meaning that no optional monomer is present. Can use¹⁹F-NMR spectroscopy was used to determine the composition of the polymer. Can be used forAn NMR spectrometer with a 5mm bandwidth probe, available from Bruker, Billerica, MA, USA under the trade name AVANCE II 300, was used. A sample of about 13 wt% polymer dispersion should be measured at 60 ℃. SO (SO)₃H-EW is EW (SO) in free acid form₃H-form).

Determination of the amount of carboxyl end groups：

Determination of every 10 in copolymer using Fourier transform Infrared Spectroscopy (FT-IR) measurements⁶The number of carboxyl end groups of C atoms. The measurement is carried out by FT-IR in transmission technique. The measured sample had a film thickness of 100 μm. The wavenumber of the COOH peak of interest was 1775cm^-1And 1808cm^-1. To determine the amount of carboxyl end groups in the polymer, two IR spectra were collected. One from the carboxyl group containing sample and one from the reference sample (no carboxyl groups). The reference material was TFE/MV 4S-copolymer which had been fluorinated for a period of time at 1775 and 1808cm^-1No peaks appear anymore.

Every 10 th⁶The number of terminal groups of carbon atoms can be determined by F₁And F₂Equations 1 and 2 of (a) calculate:

(Peak height. times.F)₁) Thickness of film [ mm ]](1)

(Peak height. times.F)₂) Thickness of film [ mm ]](2)

Wherein the peak heights are at 1775 and 1808cm^-1(ii) the difference between the peak height of the sample and the peak height of the reference sample;

F₁: 1775cm with upsilon from U.S. Pat. No. 4,675,380(Buckmaster et al), incorporated herein by reference^-1The associated calculation factor (320);

F₂: from U.S. Pat. No. 4,675,380(Buckmaster et al), incorporated herein by reference, and υ 1808cm^-1The associated calculation factor (335).

The sum of the results from equations 1 and 2 is every 10⁶The number of carboxyl end groups of carbon atoms.

Particle size method for solid composition：

The particle size of the solid composition was determined optically using a scanning electron microscope from the Phenom G2 Pure SEM from ThermoFischer Scientific. The size of the particles was measured manually using imaging software from a Phenom SEM. D10, D50, D90 (i.e., the diameter of spherical particles or the maximum size of plate-like particles for which 10%, 50% and 90% of the particles were smaller than the corresponding values, respectively) were determined. Preferably, the sample size comprises 100 particles.

Melt flow index process：

The Melt Flow Index (MFI) can be measured according to a similar procedure described in DIN EN ISO 1133-1, using a GOETTFERT MPD, MI-Robo, MI4 melt indexer (Buhen, Germany) at a load bearing of 5.0kg and a temperature of 265 ℃ and is reported in g/10 min. The MFI can be obtained using a standard extrusion die of 2.1mm diameter and 8.0mm length.

T (alpha) measuring method：

The T (. alpha.) of the polymer samples can be measured using a TA Instruments AR2000 EX rheometer. The sample was heated at 2 deg.C/min under a temperature ramp of-100 deg.C to about 125 deg.C. The measurements were performed at a frequency of one hertz.

Glass transition temperature method：

The glass transition temperature (Tg) of a polymer sample can be measured using a TA Instruments Q2000 DSC. The sample was heated at 10 ℃/min under a temperature ramp of-50 ℃ to about 200 ℃. The transition temperature was analyzed on the second heating.

Method for metal content：

The metal ion content of the ionomer can be measured by inductively coupled plasma emission spectroscopy (ICP-OES, also known as ICP-AES, ICP atomic Spectroscopy) in a Thermo Scientific ICP-OES-ICAP 7400, CCD detector according to DIN EN ISO 11885. For quantitative determination, the sample can be incinerated (e.g., in a quartz glass container, in an electric furnace at a temperature of 550 ℃ for 30 minutes) and the residue absorbed in an acid solution (e.g., in aqueous HCl (35% HCl); ultra-pure grade) and analyzed with ICP-OES.

BET surface area method：

Specific surface area per unit of nitrogen adsorption was determined according to the BET method using a surface area analyzer SA 3100 from Beckman Coulter (Beckman Coulter) according to DIN 9277:2010 (dynamic volume method using Polytetrafluoroethylene (PTFE) TF2071Z available from 3M company of St.Paul, Minn., USA as reference substance TF2071Z has 9.9M²/g+/-0.4m²Surface area in g).

The sample container unit (consisting of a sample container with a volume of 12ml, a slide-in tube and a lid) is first weighed on an analytical balance at room temperature. A 2g to 3g sample of dried ionomer was then introduced into the sample container, inserted into the slide-in tube and capped. The sample container unit containing the ionomer sample was heated in the analyzer at 80 ℃ for 180 minutes and then weighed again to obtain the exact mass of degassed ionomer. Specific surface area analysis was performed by nitrogen adsorption (99.99% pure nitrogen) using a multi-point assay in a surface area analyzer SA 3100 at-196 ℃. Duplicate measurements were performed for each sample.

Example 1 (freeze granulation); EX1：

The aqueous PFSA ionomer dispersion (solids content 11.1 wt%) was freeze granulated.

Usually by polymerizing TFE and F in an aqueous emulsion polymerization₂C＝CF-O-CF₂CF₂CF₂CF₂SO₂F and subsequently hydrolyzing the sulfonyl polymer to give a free sulfonic acid polymer to obtain a dispersion. The monomers were used in an amount to yield an Equivalent Weight (EW) of 950. PFSA ionomer per 10⁶Carbon atoms have less than 100 unstable end groups (after fluorination). SO₂The MFI of the F precursor polymer at 265 ℃/5kg load (MFI 265/5) was 0.2g/10 min.

The frozen granulation was carried out using POWDERPRO cryogranulator LS-2 from PowderPro AB, Sweden. A1L beaker was filled with liquid nitrogen and stirred by a magnetic stirrer at 400 rpm. The ionomer suspension was atomized in a two-substance nozzle into a fine spray at a flow rate of 2 liters/hour and 0.2bar of nitrogen and then sprayed into stirred liquid nitrogen, where the droplets were instantaneously frozen. In a subsequent freeze-drying step, the frozen particles were dried by sublimation of ice under a vacuum of 1.5bar in an ALPHA2-4LSCplus freeze-dryer of ruin science limited, Germany (Martin Christ Gefriertrocknungsanlagen GmbH, Germany). The temperature was raised to 18 ℃ over 24 hours while maintaining a vacuum of 1.5 mbar. In the post-drying step, the temperature was increased from 18 ℃ to 22 ℃ over 6 hours, while the pressure was further reduced from 1.5mbar to 0.5 mbar. After a total of 30 hours of drying, the vacuum was released. The properties of the resulting material are shown in table 1. The resulting powder was suspended in n-propanol/water (60 wt%/40 wt%) at a concentration to give an ionomer content of 20 wt% and the viscosity of the resulting dispersion was measured. The results are shown in Table 1.

Example 2 (frozen granulation); EX2：

The aqueous PFSA ionomer dispersion (solids content 8.5 wt%) was subjected to the same treatment as described in example 1. PFSA ionomer was obtained as described in example 1, except that TFE was copolymerized with different comonomers: CF₂＝CF-O-CF₂CF(CF₃)-O-CF₂CF₂SO₂F. The monomer is used in an amount to give an EW of 1070. The resulting powder was suspended in n-propanol/water (60 wt%/40 wt%) at a concentration to give an ionomer content of 20 wt% and the viscosity of the resulting dispersion was measured. The results are shown in Table 1.

Example 3 (spray drying); EX3：

An aqueous PFSA ionomer dispersion was obtained as described in example 1, except that the monomers were used in an amount to provide an Equivalent Weight (EW) of 800. PFSA ionomer per 10⁶The carbon atoms have less than 100 unstable end groups. The MFI (265/5) of the sulfonyl fluoride precursor was 18g/10 min. The PFSA dispersion (solids content 13 wt%) was spray dried. Spray drying was performed using a glass co-current spray drying apparatus from ProCepT n.v. company (ProCepT n.v., Zelzate, Belgium) of beljakott. The ionomer dispersion was metered into the spray dryer at a rate of 5 g/min. A two-fluid nozzle having an internal diameter of 0.8mm and a nozzle gas (air) velocity of 4.2l/min was used. The feed dispersion was heated by hot air. Make the air equal to 0.4m³The metering was carried out at a rate of/min and the air inlet temperature was set to a temperature of 160 ℃. The outlet temperature was 80 ℃. The resulting powder was dispersed in n-propanol/water (60 wt%/40 wt%) at a concentration to give an ionomer content of 20 wt% and the viscosity of the resulting dispersion was measured at different shear rates. The results are shown in Table 1.

Example 4 (freeze-drying); EX4：

The ionomer dispersion of example 3 was freeze-dried. Freeze-drying was carried out using an ALPHA2-4LSCplus freeze-dryer from Martin ChristingFritchlonk agro mountain Ragan, Germany (Martin Christ Gefriertrocknungsanlagen GmbH). The sample pan was filled with ionomer dispersion to a level of about 10mm and placed in a freeze dryer to freeze the ionomer dispersion at a set shelf temperature of-65 ℃ for 19 hours. The frozen ionomer dispersion was dried by subliming ice under vacuum. At a shelf temperature set at-65 ℃, a vacuum of 1.5mbar was applied to reduce the pressure from 1bar to 0.2mbar within 10 minutes. The temperature was raised to 40 ℃ over 2 hours while maintaining a vacuum of 0.2 mbar. The temperature was maintained at 40 ℃ for 25 hours at 0.2 mbar. After drying for 27 hours, the vacuum was released. The resulting powder was dispersed in n-propanol/water (60 wt%/40 wt%) at a concentration to give an ionomer content of 20 wt% and the viscosity of the resulting dispersion was measured at different shear rates. The results are shown in Table 1.

Table 1: results of the examples.

Comparative example 1 (oven drying)

Perfluorosulfonic acid (PFSA) ionomer compositions are obtained by the following general method: polymerization of TFE and F in aqueous emulsion polymerization₂C＝CF-O-CF₂CF₂CF₂CF₂SO₂F, subsequent hydrolysis of the sulfonyl polymer to give the free sulfonic acid polymer (EW of 800, T.alpha.of 118 ℃ C., 10 ℃ C. each)⁶In the carbon atomLess than 100 unstable end groups (after fluorination)). The solution was stored in open HDPE bottles and dried at different temperatures and times to different moisture levels as shown in table 2. The resulting friable PFSA solid (pieces of about 5mm average particle size; BET surface area less than 0.001m²/g) were redispersed in n-propanol/water (60 wt%/40 wt%) at a concentration to give an ionomer content of 20 wt% and the viscosity of the resulting dispersion was measured. The results are also shown in Table 2.

Table 2: results of comparative example 1

n.d. ═ not determined

The examples show that PFSA ionomers according to the present disclosure can be easily resuspended and provide low viscosity suspensions at a wide range of different shear rates (1/s to 1000/s). The viscosity does not change much at different shear rates (the calculated viscosity ratio at 1/s to 1000/s is about 0.9 to about 1.20).

An easily dispersible PFSA-ionomer composition can also be prepared by a very specific and carefully controlled drying protocol as shown in comparative example 1, but the viscosity appears to be higher and the ratio of the viscosity at 1/s to 1000/s is 1.24 or more.

All methods recited in the claims below refer to the methods described in the examples section of this disclosure.

Claims

1. A particle comprising a perfluorosulfonic acid (PFSA) ionomer, wherein the particle has at least 0.1g/m measured according to the BET surface area method²Wherein the PFSA ionomer comprises (i) Tetrafluoroethylene (TFE) and has the formula- [ CF [ ]₂-CF₂]A divalent unit represented by (I) and (ii) a divalent unit represented by formula (I),

2. The particle of claim 1, wherein the PFSA ionomer further comprises (iii) a divalent unit represented by formula (II),

wherein m' is 0 or 1, and Rf₁Selected from linear or branched perfluoroalkyl groups having 1 to 12 carbon atoms which may be interrupted once or more than once by (ether) oxygen atoms.

3. The granule of any of the preceding claims wherein the granule has a moisture content of from 2% to 15% as measured according to the moisture content method.

4. The particles according to any of the preceding claims, wherein the particles have an average particle size (D50) in the range of 5 to 500 μ ι η, and at least 90% of the particles (D90) have a particle size of 2mm or less, measured according to the particle size method.

5. The particle of any of the preceding claims, wherein the PFSA ionomer has an equivalent weight of 300 to 2000, measured according to the equivalent weight method.

6. The particle of any of the preceding claims, wherein the BET surface area of the particle is at least 1g/m²。

7. The particle of any one of the preceding claims, wherein the PFSA ionomer has an equivalent weight of 600 up to 1400.

8. The granule according to any of the preceding claims, which is obtained by a process comprising freeze-drying, freeze-granulation, spray-drying or a combination thereof.

9. A composition comprising a dispersion of particles according to any one of claims 1 to 8 dispersed in a liquid comprising water, an aliphatic alcohol having 1 to 5 carbon atoms, or a combination thereof; wherein the dispersion comprises at least 5 wt% and not more than 50 wt% of the particles based on the total weight of the dispersion and has a viscosity of less than 400 mPa-s, both at a shear rate of 1/s and at a shear rate of 1000/s, measured according to the viscosity method at 20 ℃.

10. The composition of claim 9, wherein the dispersion has a viscosity of less than 150 mPa-s at both a shear rate of 1/s and a shear rate of 1000/s.

11. The composition of claim 9 or 10, wherein the dispersion comprises from 5 wt% to 10 wt% of the particles based on the total weight of the dispersion.

12. The composition of claim 9 or 10, wherein the dispersion comprises 20 to 30 wt% of the particles based on the total weight of the dispersion.

13. The composition of any one of the preceding claims, wherein the ratio of the viscosity at a shear rate of 1/s to the viscosity at a shear rate of 1000/s is from 0.9 to 1.2.

14. A catalyst ink comprising the composition of any one of claims 9 to 11 and at least one catalyst.

15. A binder for an electrode, the binder comprising the composition of any one of claims 9 to 11 and an active material for making a negative electrode or a positive electrode.

16. A method of making the particle of any one of claims 1 to 8, the method comprising subjecting an aqueous composition of the PFSA ionomer to a drying step selected from freeze drying, freeze granulation, spray drying, or a combination thereof.

17. The method of claim 14, wherein the drying step comprises freeze drying.

18. The method of claim 14, wherein the drying step comprises freeze granulation.

19. A method of making a film comprising combining the ionomer particles of any one of claims 1 to 8 with a liquid comprising water, an aliphatic alcohol having 1 to 5 carbon atoms, or a combination thereof to form a dispersion and casting the dispersion into a film.