Melt-processable fluoropolymer composition, preparation methods and uses thereof

Abstract

Melt-processable compositions comprising a fluorinated polymer comprising a plurality of –SO2F groups, a fluorinated polymeric dispersant comprising a plurality of ionic groups and an azole compound are disclosed. The compositions are melt- processable and easy to extrude into films.

Description

DescriptionMelt-processable fluoropolymer composition, preparation methods and uses thereofReference to related applications

[0001] This application claims priority from European patent application EP24174569 filed on May 07, 2024, the whole content of this application being incorporated herein by reference for all purposesTechnical Field

[0002] The present invention relates to a melt-processable fluoropolymer composition, preparation method and uses thereof. More specifically, the present invention relates to a melt-processable composition comprising a fluorinated polymer comprising a plurality of sulfonyl fluoride groups and a fluorinated polymeric dispersant, a method of preparation thereof and to an extruded article comprising the composition.Background Art

[0003] Proton exchange membrane fuel cell (PEMFC) technology has been widely considered as the next revolution in renewable energy due to its high theoretical energy efficiency and zero carbon emissions at the point of use. Cost and durability of the proton exchange membrane have so far contributed to limit the large-scale implementation of fuel cell technology for use in transportation applications. To date, dispersion-cast perfluorosulfonic acid proton exchange membranes, typically reinforced with polytetrafluoroethylene support, have been the most widely used membranes for PEMFCs. Melt processes, however, might represent one of the most interesting technologies for the mass production of homogeneous thin polymer films at low cost. Melt processes have the advantage of eluding the safety and environmental concerns related to the mass production of membranes by dispersion-casting. Fluorosulfonic acid polymers are generally melt processed in their non-ionic forms, that is in their sulfonylfluoride form. Indeed, the strong ionic associations in the ionic form of the polymer increase both melt-viscosity and relaxation times, resulting in materials that are very difficult to melt-process.

[0004] In order to use the extruded polymers as proton exchange materials, therefore, post-extrusion treatments are needed. These treatments generally include hydrolysation of the polymer extruded in the sulfonyl fluoride form by treatment with a strong basic solution (e.g. NaOH or KOH) to convert it in its salt form (e.g. -SOsNa or -SO3K) followed by conversion of the salt form into the acid form (i.e. -SO3H) for example by treatment with an aqueous acid solution (e.g. H2SO4 or HNO3).

[0005] Fluorosulfonic acid polymers, i.e. fluorinated polymer comprising a plurality of sulfonyl fluoride groups, are generally prepared via the aqueous emulsion polymerization of one or more fluorinated monomers. In the polymerization process high molecular weight fluorinated polymeric dispersants comprising ionic groups (e.g. -SOsXa and -COOXa groups, wherein Xa is H; an ammonium group or a monovalent metal), such as those disclosed in WO 2018 / 167190A1 and WO 2023 / 165912, can be advantageously used as dispersing agents in replacement of environmentally hazardous non- polymeric (i.e., low molecular weight) surfactants. The polymerization process employing such fluorinated polymeric dispersants therefore allows the preparation of fluorosulfonic acid polymers with reduced environmental impact. Moreover, the fluorinated polymeric dispersants have a molecular weight comparable to that of the fluorosulfonic acid polymer, which makes the removal of the dispersants from the polymer at the end of the polymerization process unnecessary.

[0006] Unexpectedly, however, the Applicant has observed that melt-processing of the fluorinated polymers in non-ionic form (i.e. SO2F form) prepared using the fluorinated polymeric dispersants is hardly feasible, notwithstanding the absence of acid groups, leading to very low-quality melt-processed materials.

[0007] US9543607 and US9941538 disclose melt-processing a mixture of a perfluorosulfonic acid ionomer in its acid form and an additive comprising certain azoles that are water soluble, non-volatile, and thermally stable atprocessing temperatures, with a boiling point higher than the melt processing temperature to form a film having a thickness of from 3 to 200 microns. These patents, however, mainly aim at providing methods for manufacturing ion-exchange membranes by melt-extrusion starting from granules of the ionomer in acid form in order to avoid the aforementioned post-extrusion treatments and do not address the technical problem of improving the extrusion of a perfluorosulfonic acid ionomer in non-ionic form, let alone those obtainable in emulsion polymerization methods that rely on the use of the aforementioned fluorinated polymeric dispersants.

[0008] The need is therefore felt for compositions and methods having improved melt-processability, which can provide high-quality melt-processed articles, such as extruded ion-exchange membranes.

[0009] It has now been found that it is possible to improve the melt-processability of a composition comprising a fluorinated polymer comprising a plurality of sulfonyl fluoride groups and a fluorinated polymeric dispersant comprising a plurality of ionic groups by adding to the composition compounds of the azole family under certain conditions.

[0010] The invention described herein, therefore, allows melt-processing sulfonyl fluoride functionalized fluorinated polymers in their non-ionic form even if they are prepared by means of an aqueous emulsion polymerization process that uses fluorinated polymeric dispersants.Disclosure of Invention

[0011] According to a first aspect, therefore, the present invention relates to a melt-processable composition (MC) comprising:(i) a fluorinated polymer comprising a plurality of -SO2F groups [polymer (P)];(ii) a fluorinated polymeric dispersant [dispersant (D)] comprising: (a) a backbone chain comprising recurring units deriving from one or more fluorinated ethylenically unsaturated monomers, and (b) a plurality of ionic groups selected from: -SO3H, -PO3H, -COOH and a combination thereof; and(iii) an azole compound [compound (AZ)].

[0012] The Applicant has surprisingly found that the addition of the azole compound (AZ) to the polymer (P), when the polymer (P) is in combination with dispersant (D), leads to an optimal melt-processing of the composition thereof. Dispersant (D) used in the aqueous emulsion polymerization process for the preparation of polymer (P) may have the ionic groups - SOsXa either in acidic form (Xa = H) or in a salified form (Xa = NH4+or monovalent metal ion). In the latter case, prior to being combined with the azole compound to form the melt-processable composition, the blend comprising the polymer (P) and the dispersant (D) is treated with an acid to convert the ionic groups originally present into the corresponding acidic groups -SO3H, -PO3H and -COOH.

[0013] Advantageously, the melt-processing of the composition comprising the polymer (P) in its non-ionic form according to the present invention may be carried out at the conditions (e.g. temperature) generally required for meltprocessing the fluorosulfonic acid polymers (P) in non-ionic form prepared through emulsion polymerization process using conventional low-molecular weight, non-polymeric surfactants.

[0014] Without wishing to be bound to any theory, it is believed that the improvement of the melt-processability of the polymer (P) in non-ionic form may be due to the interaction of the acidic groups of the dispersant (D) with the azole compounds (AZ) resulting in a stabilisation of the composition at the melt-processing temperatures.

[0015] Advantageously, the dispersant (D) has a weight-average molecular weight (Mw) of at least 15000 and at most 800000.

[0016] Advantageously, the dispersant (D) has a molecular weight distribution such that it is substantially free from fractions having molecular weight (Mw) of less than 3000.

[0017] Preferably, the ionic groups in the dispersant (D) are in an amount of at least 1 .00 meq / g, with respect to the weight of the dispersant (D).

[0018] Preferably, the dispersant (D) is present in the melt-processable composition (MC) in an amount from 0.01 wt% to 15.0 wt%, preferably from 0.5 wt% to 10.0 wt%, based on the total weight of the polymer (P) and the dispersant (D).

[0019] As it will be detailed below, the polymer (P) and the dispersant (D), each independently, may both comprise a backbone chain comprising recurring units deriving from one or more fluorinated ethylenically unsaturated monomers.

[0020] In an advantageous embodiment of the invention, the dispersant (D) comprises the same recurring units as the polymer (P), the difference being the presence of ionic groups -SO3H in dispersant (D) in place of sulfonyl fluoride groups -SO2F in the polymer (P).

[0021] When both the polymer (P) and the dispersant (D) comprise recurring units deriving from one or more fluorinated ethylenically unsaturated monomers comprising sulfonyl fluoride groups and one or more fluorinated ethylenically unsaturated monomers free from sulfonyl fluoride groups, the molar ratio of the two types of monomers in the polymer (P) and the dispersant (D) may be the same or different, preferably the same or approximately the same.

[0022] Advantageously, the compound (AZ) has a solubility in water of at least 1 .0 g / L at 20°C.

[0023] Advantageously, the compound (AZ) when dissolved in water generates a solution having a pH in the range of 7.0 to 10.0.

[0024] Definitions

[0025] The expression “fluorinated” or “fluoro-", referred to a polymer, monomer, etc., is hereby intended to denote that they comprise at least one fluorine atom. Analogously, the term ’’perfluorinated” or ’’perfluoro-” refers to compounds that are fully fluorinated. In the present invention, the term ’’(per)fluorinated” or ’’(per)fluoro-” refer to both partially fluorinated and perfluorinated compounds.

[0026] The expression “azole compound” is used herein to refer to any compound comprising at least one five-membered heterocyclic moiety containing in the ring one nitrogen atom and at least one other non-carbon atom, the latter being selected from: nitrogen atom, sulfur atom or oxygen atom.

[0027] As used herein, the term "polymer" embraces the terms "homopolymer", "copolymer", “terpolymer” as well as polymeric compounds prepared by copolymerization of four or more types of monomers.

[0028] Herein, the molecular weight of a polymer is expressed as weight average molecular weight (Mw) or number average molecular weight (Mn). Mw and Mn are determined by Gel Permeation Chromatography analysis with respect to polystyrene standards, using dimethylacetamide as eluent and a Refractive Index detector (concentration of the polymer in the testing solution was 0.5% wt / vol).

[0029] For the purposes of the present description:- the expression “comprising a” should be understood as meaning “comprising at least one”. The expression “a” or “an” should be understood as meaning “at least one”;- the expression such as “Object P comprises at least the elements p1 , p2... pi” should also be understood as encompassing explicitly the embodiment wherein Object P consists essentially of the elements p1 , p2 ... pi;- “essentially” in this context means that some impurities, undesired species, unintentional compounds or the like could be present in Object P without impacting its targeted function and effect in the framework of the present invention; when used in respect of a polymer composition, including dispersant (D), is meant to indicate that said polymer contains no more than 1 mol% with respect to total moles of recurring units, of end-groups, impurities, defects and other spurious recurring units in addition to the listed recurring units;- the expression “comprised between ... and ...” or “ranging from ... to... ” and the like should be understood as including the limits;

[0030] Polymer (P)

[0031] The polymer (P) is a fluorosulfonic acid polymer in the sulfonyl fluoride form. That is, it is a fluorinated polymer comprising a plurality of sulfonyl fluoride groups -SO2F. The -SO2F groups are part of pendant side chains that are covalently bound to the backbone chain.

[0032] The polymer (P), therefore, is in non-ionic form, namely it does not contain functional groups that can be directly ion-exchanged with cations (e.g. protons, ammonium group or alkali metal), that is the -SO2F groups cannotbe converted into ionic groups without being hydrolysed beforehand, for example with a strong base, such as NaOH or KOH.

[0033] Preferably, the polymer (P) is “highly fluorinated”, namely at least 90% of the total number of univalent atoms in the polymer are fluorine. Most preferably, the polymer (P) is perfluorinated.

[0034] Preferably, the polymer (P) comprises recurring units deriving from at least one ethylenically unsaturated fluorinated monomer comprising at least one sulfonyl halide group, preferably sulfonyl fluoride group -SO2F, hereinafter referred to as [monomer (A)].

[0035] Non limiting examples of suitable monomers (A) are selected from the group consisting of:- sulfonyl halide fluoroolefins of formula: CF2=CF(CF2)PSO2X, with X being halogen, preferably F or Cl, more preferably F, wherein p is an integer between 0 and 10, preferably between 1 and 6, more preferably p is equal to 1 , 2 or 3;- sulfonyl halide fluorovinyl ethers of formula: CF2=CF-O-(CF2)mSO2X, with X being halogen, preferably F or Cl, more preferably F, wherein m is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;- sulfonyl halide fluoroallyl ethers of formula: CF2=CF-CF2-O- (CF2)nSO2X, with X being halogen, preferably F or Cl, more preferably F, wherein n is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;- sulfonyl halide fluoroalkoxyvinyl ethers of formula: CF2=CF-(OCF2CF(RFI ))W-O-CF2(CF(RF2))YSO2X, with X being halogen, preferably F or Cl, more preferably F, wherein w is an integer between 0 and 2, RFI and RF2, equal or different from each other, are independently F, Cl or a C1-C10 fluoroalkyl group, optionally substituted with one or more ether oxygen atoms, y is an integer between 0 and 6; preferably w is 1 , RFI is -CF3, y is 1 and RF2 is F;- sulfonyl halide aromatic fluoroolefins of formula CF2=CF-Ar-SO2X with X being halogen, preferably F or Cl, more preferably F, wherein Ar is a C5-C15 aromatic or heteroaromatic group.

[0036] Preferably monomer (A) is selected from the group of the sulfonyl fluoride fluorovinyl ethers of formula CF2=CF-O-(CF2)m-SO2F, wherein m is an integer between 1 and 6, preferably between 2 and 4.

[0037] More preferably monomer (A) is CF2=CFOCF2CF2-SO2F (perfluoro-5- sulfonylfluoride-3-oxa-1 -pentene).

[0038] The polymer (P), in addition to monomer (A), may comprise recurring units deriving from ethylenically unsaturated fluorinated monomers different from monomer (A), which are hereinafter referred to as monomer (B).

[0039] Non limiting examples of suitable monomers (B) are:C2-C8 perfluoroolefins, such as tetrafluoroethylene, hexafluoropropylene, perfluoroisobutylene;- C2-C8 hydrogen-containing fluoroolefins, such as trifluoroethylene, vinylidene fluoride, vinyl fluoride, pentafluoropropylene, and hexafluoroisobutylene;- C2-C8 chloro- and / or bromo- and / or iodo-containing fluoroolefins, such as chlorotrifluoroethylene and bromotrifluoroethylene;- fluoroalkylvinyl ethers of formula CF2=CFORfi , wherein Rn is a C1-Ce fluoroalkyl, e.g. -CF3, -C2F5, -C3F7;- fluorooxyalkylvinyl ethers of formula CF2=CFOXo, wherein Xo is a C1- C12 fluorooxyalkyl group comprising one or more than one ethereal oxygen atom, including notably fluoromethoxyalkylvinylethers of formulaRf3 / Rf4 HP R f5 f6CF2=CFOCF2ORf2, with Rf2 being a C1-C3 fluoro(oxy)alkyl group, such as - CF2CF3, -CF2CF2-O-CF3 and -CF3- fluorodioxoles of formula: wherein each of Rf3, Rf4, Rfs, Rf6, equal or different each other, is independently a fluorine atom, a Ci-Ce fluoro(halo)fluoroalkyl, optionally comprising one or more oxygen atom, e.g. -CF3, -C2F5, -C3F7, -OCF3, - OCF2CF2OCF3.

[0040] The polymer (P) typically comprises recurring units deriving from at least one monomer (A) as detailed above and from at least one ethylenically unsaturated fluorinated monomer different from monomer (A) selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, vinyl fluoride, vinylidene fluoride. Preferably, the polymer (P) is a copolymer of at least one monomer (A) and tetrafluoroethylene.

[0041] The polymer (P) is preferably selected from polymers comprising, consisting essentially of, or consisting of:- 50 to 99 mol%, preferably 50 to 98 mol%, even 50 to 95 mol%, with respect to the total number of moles of units constituting the polymer (P), of recurring units deriving from tetrafluoroethylene (TFE) (monomer (B));- 1 to 50 mol%, preferably 2 to 50 mol%, even 5 to 50 mol%, with respect to the total number of moles of units constituting the polymer (P), of recurring units deriving from at least one monomer (A) selected from the group consisting of:(j) sulfonyl halide fluorovinyl ethers of formula: CF2=CF-O- (CF2)mSO2X, with X being halogen, preferably F or Cl, more preferably F, wherein m is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;(jj) sulfonyl halide fluoroallyl ethers of formula: CF2=CFCF2-O- (CF2)nSO2X, with X being halogen, preferably F or Cl, more preferably F, wherein n is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;(jjj) sulfonyl halide fluoroalkoxyvinyl ethers of formula: CF2=CF- (OCF2CF(RFI ))W-O-CF2(CF(RF2))YSO2X with X being halogen, preferably F or Cl, more preferably F, wherein w is an integer between 0 and 2, RFI and RF2, equal or different from each other, are independently F, Cl or a C1-C10 fluoroalkyl group, optionally substituted with one or more ether oxygen atoms, y is an integer between 0 and 6; preferably w is 1 , RFI is -CF3, y is 1 and RF2 is F; and(jv) mixtures thereof; and- 0 to 45 mol%, preferably 0 to 40 mol%, even 0 to 25 mol%, withrespect to the total number of moles of units constituting the polymer (P), of recurring units deriving from at least one monomer (B) different from TFE, preferably a perfluorinated monomer, generally selected from the group consisting of hexafluoropropylene, perfluoroalkylvinyl ethers of formula CF2=CFOR’fi, wherein R’n is a Ci-Ce perfluoroalkyl, e.g. -CF3, -C2F5, -C3F7; perfluoro-oxyalkylvinyl ethers of formula CF2=CFOR’OI , wherein R’01 is a C2- C12 perfluoro-oxyalkyl having one or more ether groups, including e.g. perfluoroalkyl-methoxy-vinyl ethers of formula CF2=CFOCF2OR’f2 in which R’f2 is a Ci-Ce perfluoroalkyl, e.g. -CF3, -C2F5, -C3F7 or a Ci-Ce perfluoro- oxyalkyl having one or more ether groups, like -C2F5-O-CF3; fluorodioxoles, of formula:wherein each of Rf3, Rf4, Rfs, Rf6, equal or different each other, is independently a fluorine atom, a Ci-Ce (halo)fluoroalkyl, optionally comprising one or more oxygen atom, e.g. -CF3, -C2F5, -C3F7, -OCF3, - OCF2CF2OCF3, preferably -OCF3.

[0042] Preferably, the polymer (P) comprises, consists essentially of, or consists of (mol% referred to the total number of moles of units constituting the polymer (P)):(1 ) from 50 to 95 mol%, preferably from 55 to 93 mol% of recurring units deriving from TFE (monomer (B));(2) from 5 to 50 mol%, preferably from 7 to 45 mol% of recurring units deriving from one or more than one monomer (A) comprising -SO2X groups, with X being halogen, preferably F or Cl, more preferably F;(3) from 0 to 25 mol%, preferably from 0 to 20 mol% of recurring units deriving from one or more than one monomers (B) different from TFE, selected from the groups of (j), (jj), (jjj) and (jv) as detailed above.

[0043] Advantageously, the polymer (P) comprises, consists essentially of, or consists of (mol% referred to the total number of moles of units constituting the polymer (P)):(1 ) from 50 to 95 mol%, preferably from 55 to 93 mol% of recurring units deriving from TFE (monomer (B));(2) from 5 to 50 mol%, preferably from 7 to 45 mol% of recurring units deriving from CF2=CFOCF2CF2-SO2F;(3) from 0 to 25 mol%, preferably from 0 to 20 mol% of recurring units deriving from fluorinated one or more monomers (B)) different from TFE , selected from the groups of (j), (jj), (jjj) and (jv) as detailed above.

[0044] The polymer (P) generally possess a weight average molecular weight (Mw) of at least 50000, preferably of at least 85000 more preferably of at least 100000.

[0045] The weight-average molecular weight (Mw) of polymer (P) is generally of at most 700000, preferably at most 600000, more preferably at most 500000. Suitable ranges for most applications of the polymer (P) are for instance from 150000 to 600000, preferably from 180000 to 500000.

[0046] Preferably, the polymer (P) has a number-average molecular weight of at least 50000, preferably of at least 90000 and / or advantageously of at most 500000, preferably of at most 450000.

[0047] Dispersant (D)

[0048] In the melt-processable composition of the invention, the fluorinated polymeric dispersant (D) comprises a backbone chain comprising recurring units deriving from one or more ethylenically unsaturated monomers, and a plurality of ionic groups selected from: -SO3H, -PO3H, -COOH and a combination thereof. As said, however, the fluorinated polymeric dispersant used in the process for the preparation of polymer (P) may contain ionic groups that may be selected from -SOsXa, -POsXa, -COOXa and a combination thereof, wherein Xa is H, an ammonium group or a monovalent metal ion. The monovalent metal ion is typically a monovalent alkali metal ion, preferably selected from lithium, sodium and potassium ions.

[0049] Herein, therefore, the composition of the polymeric dispersant (D) is disclosed with reference to the polymer in the form suitable for use in the preparation of the polymer (P) via emulsion polymerization.

[0050] As said, the presence of the azole compound in the extrudable composition (EC) improves the melt-processing properties of polymer (P) provided that the ionic groups of the dispersant (D) are in acid form. Therefore, if the polymer (P) is in combination with a dispersant (D) in which the ionic groups are not in such form, i.e. they are -SOsXa, -PC Xa or -COOXa groups wherein Xa is an ammonium group or a monovalent metal ion, then these ionic groups have to be converted into the acid form (i.e. -SO3H, -PO3H or -COOH)) according to methods known in the art, for example by treatment of the dispersant (D) with an aqueous solution of an acid, prior to being combined with the azole compound (AZ). Non-limiting examples of acids that can be used are nitric acid and sulfuric acid, typically in the form of aqueous solutions. For the conversion into the acid form, a liquid dispersion comprising the polymer (P) and the dispersant (D) may also be treated on a proton-exchange resin.

[0051] Advantageously, the dispersant (D) does not contain unsaturated carboncarbon bonds.

[0052] Preferably, the dispersant (D) has a weight average molecular weight (Mw) of at least 15000.

[0053] The weight average molecular weight of dispersant (D) is generally at most 800000, at most 600000, preferably at most 500000, more preferably at most 400000.

[0054] Preferably dispersant (D) has a weight average molecular weight of at least 20000, preferably of at least 25000, advantageously of at least 50000, at least 100000 or even at least 150000.

[0055] Particularly good results have been obtained with dispersants having a weight average molecular weight of from 50000 to 400000, even 150000 to 400000.

[0056] The dispersant (D) may advantageously have a number average molecular weight (Mn) of 7000 to 500000, preferably from 25000 to 400000, even from 50000 to 250000.

[0057] Advantageously, the dispersant (D) is a polymer having a molecular weight and a molecular weight distribution such that dispersant (D) is substantially free from fractions having molecular weight Mw and Mn of less than 3000.

[0058] The expression “substantially free” in connection with dispersant (D) and fractions having molecular weight of less than 3000 is intended to mean that said fractions are present in an amount of at most 0.03 wt%, preferably at most 0.01 wt%, based on the weight of the dispersant (D).

[0059] Preferably, the amount of ionic groups in dispersant (D) is at least 1.00 meq / g, preferably at least 1.10 meq / g, more preferably at least 1 .20 meq / g, even more preferably at least 1 .30 meq / g, with respect to the weight of the dispersant (D). The amount of ionic groups in the dispersant (D) is generally at most 2.50 meq / g, preferably at most 2.20 meq / g, more preferably at most 2.00 meq / g.

[0060] The dispersant (D) comprises the ionic groups as pendant groups covalently bound through side-chains to recurring units deriving from an ethylenically unsaturated functional monomer [monomer (X)].

[0061] Advantageously, the dispersant (D) may consist essentially of recurring units deriving from one or more than one fluorinated monomer (X) or it can be a copolymer comprising recurring units deriving from one or more than one fluorinated monomer (X) and recurring units deriving from one or more than one additional monomer different from monomer (X) (hereinafter monomer (Y)).

[0062] Advantageously, the dispersant (D) is a polymer comprising a plurality of - SOsXa groups, wherein Xa is H, an ammonium group or a monovalent alkali metal, preferably it is a polymer comprising a plurality of -SO3H or -SO3M groups, wherein M is Na or K.

[0063] The dispersant (D) may consist essentially of recurring units deriving from one or more than one monomer (X) comprising a -SOsXa group, wherein Xa is H, an ammonium group or a monovalent alkali metal. Alternatively, dispersant (D) may comprise recurring units deriving from one or more than one monomer (X) comprising a -SOsXa group, wherein Xa is H, an ammonium group or a monovalent alkali metal, and recurring units derivingfrom one or more than one monomer (Y) which does not contain a -SChXa group.

[0064] The expression “recurring units deriving from” in connection with a monomer (X) comprising a -SOsXa group is intended to encompass both: i) recurring units as directly obtained from polymerizing said monomer (X) comprising a -SOsXa group, and ii) recurring units obtained from polymerizing a monomer (X) comprising a functional group precursor to a -SOsXa group followed by modification and / or post-treatment of the polymer, e.g. by hydrolysis.In other terms, a dispersant (D) comprising recurring units deriving from one or more than one monomer (X) comprising a -SOsXa group, may be obtained by polymerizing monomers comprising -SO2X groups, where X is halogen, preferably F or Cl, followed by hydrolysis of the same.

[0065] Suitable dispersants (D) comprising a plurality of -SOsXa groups, wherein Xa is H, an ammonium group or a monovalent metal ion, are polymers comprising recurring units deriving from:- at least one ethylenically unsaturated fluorinated monomer (X) containing at least one -SC Xa group; and- recurring units deriving from at least one ethylenically unsaturated fluorinated monomer (Y) free from -SC Xa group, wherein Xa is H, an ammonium group or a monovalent metal ion.

[0066] Ethylenically unsaturated fluorinated monomers (X) containing at least one -SC Xa group suitable for the preparation of the dispersant (D) may be selected from the list of monomers (A) detailed above for polymer (P).

[0067] The expression “at least one monomer” is used herein with reference to monomers of certain (e.g. (A), (B), ... ) to indicate that one or more than one monomer of each type can be present in the dispersant (D). Herein the term monomer is used to refer to both one and more than one monomer of a given type.

[0068] Suitable ethylenically unsaturated fluorinated monomers (Y) may be selected from the list of monomers (B) detailed above for the polymer (P).

[0069] Non-limiting examples of monomers (Y) are: C2-C8 perfluoroolefins, such as tetrafluoroethylene,hexafluoropropylene, perfluoroisobutylene;- C2-C8 hydrogen-containing fluoroolefins, such as trifluoroethylene, vinylidene fluoride, vinyl fluoride, pentafluoropropylene, and hexafluoroisobutylene;- C2-C8 chloro- and / or bromo- and / or iodo-containing fluoroolefins, such as chlorotrifluoroethylene and bromotrifluoroethylene;- fluoroalkylvinyl ethers of formula CF2=CFORfi , wherein Rn is a C1-Ce fluoroalkyl, e.g. -CF3, -C2F5, -C3F7;- fluorooxyalkylvinyl ethers of formula CF2=CFOXo, wherein Xo is a C1- C12 fluoro-oxyalkyl group comprising one or more than one ethereal oxygen atom, including notably fluoromethoxyalkylvinyl ethers of formula CF2=CFOCF2ORf2, with Rf2 being a C1-C3 fluoro(oxy)alkyl group, such as - CF2CF3, -CF2CF2-O-CF3 and -CF3- fluorodioxoles, of formula:wherein each of Rf3, Rf4, Rfs, Rf6, equal or different each other, is independently a fluorine atom, a Ci-Ce (halo)fluoroalkyl, optionally comprising one or more oxygen atom, e.g. -CF3, -C2F5, -C3F7, -OCF3, - OCF2CF2OCF3.

[0070] Preferably monomer (Y) is selected among:- C2-C8 perfluorolefins selected from tetrafluoroethylene and / or hexafluoropropylene;- C2-C8 hydrogen-containing fluoroolefins, selected from trifluoroethylene, vinylidene fluoride, and vinyl fluoride; and- mixtures thereof.

[0071] More preferably, monomer (Y) is tetrafluoroethylene.

[0072] In a preferred embodiment, the dispersant (D) is a fluorinated polymer comprising a plurality of -SOsXa functional groups, and consistingessentially of, or consisting of, recurring units deriving from at least one fluorinated monomer (X) containing at least one -SOsXa group, wherein Xa is H, an ammonium group or a monovalent metal ion, and from at least one ethylenically unsaturated fluorinated monomer (Y).

[0073] According to certain embodiments, the at least one monomer (Y) of the dispersant (D) is tetrafluoroethylene.

[0074] Preferred dispersants (D) are selected from the group consisting of polymers comprising, or essentially consisting of:- 50 to 99 mol%, preferably 50 to 98 mol%, even 50 to 95 mol%, with respect to the total number of moles of units constituting the dispersant (D), of recurring units deriving from tetrafluoroethylene (monomer (Y));- 1 to 50 mol%, preferably 2 to 50 mol%, even 5 to 50 mol%, with respect to the total number of moles of units constituting the dispersant (D), of recurring units deriving from at least one monomer (Y) selected from the group consisting of:(j) sulfonyl halide fluorovinyl ethers of formula: CF2=CF-O- (CF2)mSO2X, with X being OXa, with Xa as above detailed or X is halogen, preferably F or Cl, more preferably F, wherein m is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;(jj) sulfonyl halide fluoroallyl ethers of formula: CF2=CFCF2-O- (CF2)nSO2X, with X being OXa, with Xa as above detailed or X is halogen, preferably F or Cl, more preferably F, wherein n is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;(jjj) sulfonyl halide fluoroalkoxyvinyl ethers of formula: CF2=CF- (OCF2CF(RFI ))W-O-CF2(CF(RF2))YSO2X, with X being OXa, with Xa as above detailed or X is halogen, preferably F or Cl, more preferably F, wherein w is an integer between 0 and 2, RFI and RF2, equal or different from each other, are independently F, Cl or a C1-C10 fluoroalkyl group, optionally substituted with one or more ether oxygen atoms, y is an integer between 0 and 6; preferably w is 1 , RFI is -CF3, y is 1 and RF2 is F; and(jv) mixtures thereof; and- 0 to 45 mol%, preferably 0 to 40 mol%, even 0 to 25 mol%, with respect to total number of moles of units constituting the dispersant (D), of recurring units deriving from at least one hydrogenated and / or fluorinated monomer different from TFE, preferably a perfluorinated monomer, generally selected from the group consisting of hexafluoropropylene, perfluoroalkylvinylethers of formula CF2=CFOR’fi , wherein R’n is a Ci-Ce perfluoroalkyl, e.g. -CF3, -C2F5, -C3F7; perfluoro-oxyalkylvinylethers of formula CF2=CFOR’OI , wherein R’01 is a C2-C12 perfluoro-oxyalkyl having one or more ether groups, including e.g. perfluoroalkyl-methoxy-vinylethers of formula CF2=CFOCF2OR’f2 in which R’f2 is a Ci-Ce perfluoroalkyl, e.g. - CF3, -C2F5, -C3F7 or a Ci-Ce perfluorooxyalkyl having one or more ether groups, like -C2F5-O-CF3.

[0075] Preferred dispersant (D) comprises, essentially consists of, or consists of (mol% referred to the total number of moles of units constituting the dispersant (D):- from 50 to 95 mol%, preferably from 55 to 93 mol% of recurring units deriving from TFE (monomer (Y);- from 5 to 50 mol%, preferably from 7 to 45 mol% of recurring units deriving from one or more than one fluorinated monomer (X) containing - SO2X groups, wherein X is either F, OH or OXa where Xa is an ammonium group or a monovalent metal ion;- from 0 to 25 mol%, preferably from 0 to 20 mol% of recurring units deriving from one or more than one fluorinated monomer (Y) different from TFE.

[0076] Advantageously, the dispersant (D) comprises, consists essentially of, or consists of (mol% referred to the total number of moles of units constituting the dispersant (D):(1 ) from 50 to 95 mol%, preferably from 55 to 93 mol% of recurring units deriving from TFE (monomer (Y));(2) from 5 to 50 mol%, preferably from 7 to 45 mol% of recurring units deriving from CF2=CFOCF2CF2-SO2X, wherein X is either F, OH or OXa where Xa is an ammonium group or a monovalent metal ion;(3) from 0 to 25 mol%, preferably from 0 to 20 mol% of recurring unitsderiving from one or more than one fluorinated monomer (Y) different from TFE, as detailed above.

[0077] In certain embodiments of the invention, dispersant (D) has the same monomer composition as polymer (P), except for the fact that polymer (P) is in the sulfonyl fluoride form whereas dispersant (D) is in the ionic form.

[0078] The dispersant (D) and the polymer (P) may be prepared by any polymerization process known in the art without particular limitations. Suitable processes for the preparation of such polymers are for instance those described in US 4940525, EP 1323751A, EP1172382A.

[0079] Compositions comprising polymer (P) and dispersant (D) may be prepared according to the process described in WO2023 / 165912A1 which is incorporated herein by reference.

[0080] Compound (AZ)

[0081] Compound (AZ) is an azole compound, that is a compound comprising at least one five-membered heterocyclic moiety containing in the ring one nitrogen atom and at least one other non-carbon atom, the latter being selected from: nitrogen atom, sulfur atom or oxygen atom.

[0082] Compound (AZ) is preferably selected from the compounds of general formula (I):in which:-X can be a nitrogen atom or a -CR3 group, wherein R3 is selected from H or a C1-C12 alkyl group, optionally fluorinated and / or optionally unsaturated, and R3 may form part of an aliphatic or aromatic ring structure with R1 ;-Y can be a -CR4 group or a nitrogen atom, wherein R4 may be H or a C1-C12 alkyl group, optionally fluorinated and / or optionally unsaturated; and-Ri and R2 may, independently of each other, be H or a C1-C12 alkyl or C6-C12 aryl and wherein R1 may form part of an aliphatic or aromatic ring structure with R3.

[0083] Non-limiting examples of suitable compounds of formula (I) are for instance: triazole, alkyl triazole, vinyl-triazole, fluoro-alkyl triazole, fluoro-vinyl triazole, pyrazole, alkyl pyrazole, vinyl pyrazole, fluoro-alkyl pyrazole, fluoro-vinyl pyrazole, substituted tetrazole (especially 5-aminotetrazole), benzimidazole, alkyl benzimidazole, vinyl benzimidazole, fluoro-alkyl benzimidazole, fluoro-vinyl benzimidazole, thiazole, indazole.

[0084] Advantageously, compound (AZ) has a solubility in water at 20°C of at least 1 .0 g / L at 20°C, even at least 1 .5 g / L. The solubility in water may be up to 100.0 g / L, typically up to 50.0 g / L. The solubility in water of compound (AZ) may conveniently be from 1 .0 to 50.0 g / L, from 1 .5 to 40.0 g / L at 20°C.

[0085] Advantageously, compound (AZ) when dissolved in water generates a solution having a pH in the range of 7.0 to 10.0. The pH of the solution of compound (AZ) in water at 20°C is preferably in the range of 7.0 to 9.5, even in the range of 7.0 to 9.0.

[0086] Among compounds of formula (I) whose solution in water at 20°C has a pH in the range of 7.0 to 10.0 mention may be made of benzimidazole, imidazole, pyrazole, thiazole and indazole.

[0087] In a preferred embodiment compound (AZ) is benzimidazole.

[0088] Melt-processable Composition (MC)

[0089] The melt-processable composition (MC) comprises the polymer (P), the dispersant (D) and the azole compound (AZ).

[0090] The polymer (P) is generally present in the composition (MC) in an amount of from 85.0 to 99.9 wt% with respect to the total weight of the polymer (P) and dispersant (D), preferably from 90.0 to 99.5, even more preferably from 95.0 to 99.0.

[0091] In certain embodiments, the dispersant (D) is present in an amount from 0.1 wt% to 15.0 wt%, with respect to the weight of the polymer (P), more preferably from 0.5 wt% to 10.0 wt%, even more preferably from 1 .0 wt% to 5.0 wt%.

[0092] Preferably, the dispersant (D) is present in an amount from 0.1 wt% to 15.0 wt%, with respect to the total weight of the polymer (P) and dispersant (D), more preferably from 0.5 wt% to 10.0 wt%, even more preferably from 1.0 wt% to 5.0 wt.

[0093] Preferably, the polymer (P) and the dispersant (D) are obtained in the form of a composition as the product of an aqueous polymerization process to prepare the polymer (P) that uses the dispersant (D) in the absence of other surfactants or dispersant, especially in the absence of non-polymeric surfactants.

[0094] The compound (AZ) is present in the composition (MC) in an amount which is calculated on the basis of the moles of ionic groups present in the dispersant (D). Preferably, the amount of compound (AZ) is such that the ratio between the moles of compound (AZ) and the moles of ionic groups in the dispersant (D) in the composition is between 0.5 and 2.5, more preferably between 1 .0 and 2.0, even more preferably between 1 .0 and 1 .5, even more preferably between 1.0 and 1.3.

[0095] According to another aspect, the present invention relates to a process for the preparation of the melt-processable composition (MC) described above. The process comprises the steps of:(a) contacting in an aqueous medium the polymer (P), the dispersant (D) and the compound (AZ) to obtain an aqueous dispersion;(b) separating the composition (MC) comprising the polymer (P), the dispersant (D) and the compound (AZ) in solid form from the aqueous medium.

[0096] As per the aqueous medium, water may be used alone or as a mixture with an organic liquid, such as an alcohol (e.g. C1-C4 alkyl alcohol).

[0097] In the process, the step (b) of separating the composition (MC) in solid form may comprise a solid / liquid separation, for instance by subjecting the aqueous dispersion obtained at the end of step (a) to filtration or centrifugation.

[0098] Alternatively, the step (b) of separating the composition (MC) in solid form may comprise spray drying or lyophilization of the aqueous dispersion obtained at the end of step (a).

[0001] Processes for the recovery of the composition (MC) as a solid from the aqueous dispersion are described for instance in W02020 / 094563A1 or WO2022 / 224105A1 , both incorporated herein by reference.

[0099] Advantageously, the composition (MC) is in solid form, such as pellets, preferably having shape and size suitable for subsequent melt-processing.

[0100] The composition (MC) is typically characterised by a melt flow rate at 280 °C that does not exceed 55 g / 10 min, preferably it does not exceed 50 g / 10 min. The melt flow rate of the composition (MC) is at least 1 g / 10 min, preferably at least 6 g / 10 min, more preferably at least 7 g / 10 min.

[0101] The melt flow rate of composition (C) is measured according to ASTM D1238-04 at 280°C / 5 kg.

[0102] According to a further aspect, the present invention relates to a process for the preparation of an article comprising the step of melt-processing a composition (MC).

[0103] Melt-processing techniques are generally known in the art and include, for example, melt-extrusion, melt-casting and melt-blowing. Melt processing involves preferably extrusion or injection moulding.

[0104] The article comprises the composition (MC), namely it comprises at least the polymer (P), the dispersant (D) and the azole compound (AZ).

[0105] Advantageously, the process may comprise an intermediate step in which the composition (MC) is formed into pellets, which are then further processed into the final article. The process accordingly comprises the steps of:(a) providing the composition (MC) as defined above;(b) melt-processing the composition (MC) to provide pellets; and(c) forming the pellets made of composition (MC) into an article.

[0106] Preferably, step (c) is performed by extrusion. The conditions for the extrusion can be selected by the person skilled in the art of thermoplastic polymer processing in view of the nature of polymer (P) and of the article to be prepared.

[0107] Typically the composition (MC) may be melt-processed at temperatures of 200 to 280°C, preferably from 220 to 260°C.

[0108] It has been found that the composition (MC) may be easily extruded into pellets or other shapes at the same conditions used for the processing of the polymer (P) only, without the formation of bubbles or other defects such as the discoloration of the polymer.

[0109] In a preferred embodiment of the invention the composition (MC) is used in the preparation of a film that can be converted into a membrane for use in an electrochemical device.

[0110] Accordingly, further objects of the present invention are a film made of the composition (MC) as well as a proton exchange membrane comprising said film in hydrolysed form, i.e. comprising -SO3H groups.

[0111] Typically the film has a thickness of less than 250 pm, preferably in the range from 1 to 150 pm, more preferably from 3 to 100 pm, even more preferably from 5 to 60 pm.

[0112] The film, which can be obtained for example by extrusion, can subsequently be converted into a proton exchange membrane by hydrolysis, i.e. by converting the sulfonyl fluoride groups of the polymer (P) to the sulfonic acid form, according to methods known in the art. Notably, this step may remove the compound (AZ) from the hydrolysed film, although its removal may not be required for the correct functioning of the membrane in an electrolysis device.

[0113] A further object of the present invention is therefore a process for preparing a proton exchange membrane, the process comprising:- melt-processing a melt-processable composition (MC) to form a film;- hydrolysing the sulfonyl fluoride groups of the polymer (P) to sulfonic acid groups.

[0114] Notable non-limiting examples where the proton exchange membranes may be used as components of electrochemical devices, such as fuel cells, water electrolysers, redox flow batteries and chloro-alkali cells.

[0115] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0116] The invention will be now explained in more detail with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.

[0117] Preparative Example 1 - Preparation of Dispersant (D) by polymerization of tetrafluoroethylene (TFE) and perfluoro-5- sulfonylfluoride-3-oxa-1 -pentene (SFVE) and successive hydrolysis

[0118] Step 1 - Polymerization

[0119] A fluorinated polymeric dispersant (D) was prepared as described below.

[0120] In a 5 L autoclave the following reagents were charged: 1.8 L of demineralized water;533 g of the monomerwith formula: CF2=CF-O-CF2CF2-SO2F (SFVE); 89 g of a 46 wt% aqueous solution of the ammonium salt of the fluorocompound of formula:with Xa being NF .The autoclave, stirred at 650 rpm, was heated at 58°C. A water based solution with 16 g / L of ammonium persulfate was added in a quantity of 90 mL. The pressure was maintained at a value of 8.5 bar (abs.) by 8.2 bar of feeding tetrafluoroethylene (TFE). After the initial addition of 83 g, SFVE was added portionwise (23 g) each 5 wt% of TFE converted. The reaction was stopped after 200 min by stopping the stirring, cooling the autoclave and reducing the pressure by venting the TFE; a total of 340 g of TFE was fed into the autoclave. Overall, 0.12 grams of surfactant for each gram of converted TFE were used.The latex thus obtained was degassed for 48 h with air flow to remove monomer’s residuals and then coagulated through freeze-thawing. The powder was washed with deionized water (4 x 1 L) for 30 min and dried in a vent oven at 120°C overnight.A copolymer was obtained, said copolymer having an equivalent weight (EW) of 720 g / mol and possessing the following composition: TFE: 81.5 mol%; SFVE: 18.5 mol% as determined by FT-IR measurements.The polymer had a number-average molecular weight (Mn) of 93000 and a weight-average molecular weight (Mw) of 241000. Substantially no fraction having a molecular weight below 3000 was detected by GPC.

[0121] Step 2 - Hydrolysis and Dissolution in water

[0122] 250 g of the powder obtained in Step 1 was treated at 70°C with a mixture of 10 L / h of fluorine and 4 L / h of nitrogen for 3 h end-capping the backbone with -CF3functional groups and removing the undesired carboxylic acid groups. The powder was treated under stirring with a 1.5 L solution of NaOH / H2O (20 wt%) and heated at 80°C. Complete conversion of the originally comprised -SO2F groups to ionic -SOsNa groups was confirmed by solid state NMR. The amount of ionic groups in the polymer was 1.39 meq / g. After 10 h the powder was washed under stirring with deionized water (4x 1 L) for 30 min and dissolved in deionized water in a pressurised vessel heated at 250°C.

[0123] Example 1 - Preparation of a blend (B1) of polymer (P) and dispersant (D)

[0124] In a 22 L autoclave the following reagents were charged:- 8.5 L of demineralized water;- 800 g of a 25 wt% aqueous dispersion of the polyfunctional polymeric dispersant prepared under preparative example 1 (after thermal concentration).The autoclave, stirred at 470 rpm, was heated at 55°C. A water based solution containing 16 g / L of sodium persulfate was added in a quantity of 90 mL. The pressure was maintained at a value of 14.3 bar (abs.) by feeding tetrafluoroethylene (TFE). 700 g of SFVE were fed in the reactor and the pressure of the autoclave was maintained at constant value of 14.5 bar by feeding TFE and feeding SFVE portionwise. After 85 minutes, when a quantity of 3200 grams of TFE and 2600 g of SFVE were fed, the TFE feeding was stopped. By keeping constant stirring of 50 rpm the autoclave was cooled to ambient temperature the latex was discharged after beingkept under air bubbling for 48 hours to strip away residual monomers from the polymerization, and then stored in a plastic tank. The latex so produced was freeze-thawed and the powder obtained (4170 g) was washed with deionized water (3 x 10 L) and then dried in a vent oven for 48 h at 120°C. The powder thus obtained was a blend (B1 ) of the polymer (P) and the dispersant (D), with dispersant (D) being in a concentration of 4.8 wt% based on the weight of the dry blend. The blend (B1 ) had an equivalent weight (EW), measured through FT-IR, of 1045 g / mol corresponding to a composition of TFE: 88.4 mol% and SFVE: 11.6 mol%. Melt Flow Index (MFI), measured with a load of 5 Kg at 280°C was 5 g / 1 O’.

[0125] Example 2 - Extrusion of blend (B1)

[0126] The polymer blend (B1 ) of Example 1 was extruded using a conical twin screws extruder having a rod-shaped head with a diameter of 3 mm. The temperature profile along the extruder was set from 250°C (hopper) to 289°C (die) and the screw rotation was set at 5 rpm.

[0127] The extrudate had a very poor quality as it contained many bubbles resembling a polymer foam. No further processing was therefore possible on such material.

[0128] Example 3 - Preparation of a blend (B2) of polymer (P) and dispersant

[0129] In a 22 L autoclave the following reagents were charged:- 7.4 L of demineralized water;- 750 g of a 22.5 wt% aqueous dispersion of the polyfunctional polymeric dispersant prepared under preparative example 1 (after thermal concentration).The autoclave, stirred at 540 rpm, was heated at 58°C. A water based solution with 16 g / L of ammonium persulfate was added in a quantity of 90 mL. The pressure was maintained at a value of 10.9 bar (abs.) by feeding tetrafluoroethylene (TFE). 480 g of SFVE were fed in the reactor and the pressure of the autoclave was maintained at constant value of 11 .2 bar by feeding TFE and feeding SFVE portionwise. After 130 minutes, when a quantity of 1980 grams of TFE and 1890 g of SFVE were fed, the TFE feeding was stopped. The autoclave was cooled to ambient temperaturewithout stirring and the latex was discharged after being kept under air bubbling for 48 hours to strip away residual monomers from the polymerization, and then stored in a plastic tank. The latex so produced was freeze-thawed and the powder obtained (3100 g) was washed with deionized water (3 x 10 L) and then dried in a vent oven for 48 h at 120°C. The powder thus obtained was a blend (B2) of the polymer (P) and the dispersant (D), with dispersant (D) being in a concentration of 5.4 wt% based on the weight of the dry blend. The blend (B2) had an equivalent weight (EW), measured through FT-IR, of 900 g / mol corresponding to a composition of TFE: 86.1 mol% and SFVE: 13.9 mol%. Melt Flow Index (MFI), measured with a load of 5 Kg at 280°C was 16 g / 1 O’.

[0130] Although the dispersant (D) was prepared in a fully salified form (i.e., with - SOsNa groups), a further exchange with sodium ions was carried out to ensure that any hydrolysed functional groups that may have possibly originated during the preparation of the polymer were converted into Na form. The powder blend (B2) was thus treated with a solution of NaCI (520 g) in deionized water (8 L) under stirring and at room temperature for 1 h. The powder blend (B2) was then extensively washed for 1 h with deionized water (4 x 2 L) and finally dried in a vent oven at 120°C for 48 h.

[0131] Example 4 - Extrusion of blend (B2)

[0132] The polymer blend (B2) of Example 3 was extruded using a conical twin screws extruder having a rod-shaped head with a diameter of 3 mm. The temperature profile along the extruder was set from 250°C (hopper) to 290°C (die) and the screw rotation was set at 15 rpm generating a torque of about 70 Nm. Under these conditions polymer pellets of helicoidal shape, shark skin-like surface and containing some bubbles were obtained with a productivity of 3.3 Kg / h. The pellets were then melt-extruded in a single screw extruder equipped with a head having thickness of 0.5 mm and length of 100 mm. The temperature profile along the extruder was set from 240°C (hopper) to 340°C (die) and the screw rotation was set at 20 rpm generating a torque exceeding 65 Nm. The film produced was rubbery, showed many transversal fractures and, in general, had very low quality.The improved quality of the pellets of the blend (B2) compared to those ofthe blend (B1 ) suggests that some hydrolyzed functional groups were indeed present in the dispersant (D) after the polymerization reaction. The exchange with sodium ions carried out on the blend (B2), however, leads to an insufficient improvement of the melt-processability of the polymer (P).

[0133] Example 5 - Preparation of a blend (B3) of polymer (P) and dispersant (D) and of melt-processable composition (MC)

[0134] In a 22 L autoclave the following reagents were charged:- 7.4 L of demineralized water;- 750 g of a 22.5 wt% aqueous dispersion of polyfunctional polymeric dispersant prepared under preparative example 1 (after thermal concentration).The autoclave, stirred at 540 rpm, was heated at 58°C. A water based solution with 16 g / L of ammonium persulfate was added in a quantity of 90 mL. The pressure was maintained at a value of 9.3 bar (abs.) by feeding tetrafluoroethylene (TFE). 480 g of SFVE were fed in the reactor and the pressure of the autoclave was maintained at a constant value of 9.5 bar by feeding TFE and feeding SFVE portionwise. After 385 minutes, when a quantity of 1960 grams of TFE and 1890 g of SFVE were fed, the TFE feeding was stopped. The autoclave was cooled to ambient temperature without stirring and the latex was discharged after being kept under air bubbling for 48 hours to strip away residual monomers from the polymerization, and then stored in a plastic tank. The latex so produced was freeze-thawed and the powder obtained (3500 g) was washed with deionized water (3 x 10 L) and then dried in a vent oven for 48 h at 120°C. The powder thus obtained was a blend (B3) of the polymer (P) and the dispersant (D), with dispersant (D) being in a concentration of 4.8 wt% based on the weight of the dry blend. The blend (B3) had an equivalent weight (EW), measured through FT-IR, of 755 g / mol corresponding to a composition of TFE: 82.6 mol% and SFVE: 17.4 mol%. Melt Flow Index (MFI), measured with a load of 5 Kg at 280°C was 80 g / 1 O’.The hydrolyzable ionic groups of the dispersant (D) were converted into acid form by ion-exchanging them in an aqueous medium. The powder blend (B3) was treated with a solution of HNOs / deionized water (20 wt%, 25 L)under stirring and at room temperature for 30 min and then washed with deionized water (17 L) under stirring and at room temperature for 30 min. This procedure was repeated three times. In order to eliminate the residual acidity, the powder blend (B3) was washed with deionized water (4 x 50 L) under stirring and at room temperature for 30 min. The so-obtained powder blend (B3) containing the dispersant (D) in acid form was then treated with a solution of benzimidazole (27.7 g) in deionized water (25 L) at room temperature, under stirring for 30 min. The ratio between the number of moles of benzimidazole and the number of moles of ionic groups in the dispersant (D) was 1.00. The powder composition (MC) comprising the polymer (P), the dispersant (D) and benzimidazole (compound (AZ)) was then separated and rinsed with deionized water (3 x 20 L) at room temperature, under stirring and for 30 min. Finally the powder was dried in a vent oven at 120°C for 48 h. The final powder had MFI, measured with a load of 5 Kg at 280°C, of 41 g / 1 O’.

[0135] Example 6 - Extrusion of melt-processable composition (MC)

[0136] The melt-processable composition (MC) of Example 5 was extruded using a conical twin screws extruder having a rod-shaped head with a diameter of 3 mm. The temperature profile along the extruder was set from 230°C (hopper) to 255°C (die) and the screw rotation was set at 30 rpm generating a torque of about 25 Nm and a pressure of about 10 bar. Under these conditions clear and bubble-free polymer pellets were obtained with a productivity of 3.7 Kg / h. The pellets were then melt-extruded in a single screw extruder equipped with a head having thickness of 0.5 mm and length of 100 mm. The temperature profile along the extruder was set from 220°C (hopper) to 245°C (die) and the screw rotation was set at 30 rpm generating a torque of about 55 Nm. The film thus produced was clear, transparent and without visible defects.

Claims

Claims1 . A melt-processable composition comprising:(i) a fluorinated polymer comprising a plurality of -SO2F groups [polymer (P)];(ii) a fluorinated polymeric dispersant [dispersant (D)] comprising: (a) a backbone chain comprising recurring units deriving from one or more fluorinated ethylenically unsaturated monomers, and (b) a plurality of ionic groups selected from: -SO3H, -PO3H, -COOH and a combination thereof; and(iii) an azole compound [compound (AZ)].

2. The composition of any one of the preceding claims wherein the amount of the dispersant (D) is from 0.1 wt% to 15.0 wt%, based on the total weight of the polymer (P) and dispersant (D).

3. The composition of any one of the preceding claims in which the ratio between the number of moles of compound (AZ) and the number of moles of ionic groups in the dispersant (D) is between 0.5 and 2.5.

4. The composition of any one of the preceding claims, wherein the dispersant (D) is a polymer comprising recurring units deriving from at least one ethylenically unsaturated fluorinated monomer containing at least one group -SC Xa and recurring units deriving from at least one ethylenically unsaturated fluorinated monomer free from -SOsXa groups, wherein Xais H, an ammonium group or a monovalent alkali metal.

5. The composition of any one of the preceding claims wherein the polymer (P) and / or the dispersant (D) comprise recurring units deriving from at least one ethylenically unsaturated fluorinated monomer containing at least one -SO2X group which is selected from the group consisting of:- sulfonyl halide fluoroolefins of formula: CF2=CF(CF2)PSO2X; wherein in dispersant (D) X is OXa, with Xa being H, an ammonium group or a monovalent metal and in polymer (P) X is a halogen, preferably F or Cl, more preferably F, wherein p is an integer between 0 and 10, preferably between 1 and 6, more preferably p is equal to 1 , 2 or 3;- sulfonyl halide fluorovinyl ethers of formula: CF2=CF-O-(CF2)mSO2X, wherein in dispersant (D) X is OXa, with Xa being H, an ammonium group or amonovalent metal and in polymer (P) X is a halogen, preferably F or Cl, more preferably jF, wherein m is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;- sulfonyl halide fluoroallyl ethers of formula: CF2=CFCF2-O-(CF2)nSO2X, wherein in dispersant (D) X is OXa, with Xa being H, an ammonium group or a monovalent metal and in polymer (P) X is a halogen, preferably F or Cl, more preferably F, wherein n is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;- sulfonyl halide fluoroalkoxyvinyl ethers of formula: CF2=CF-(OCF2CF(RFI ))W-O-CF2(CF(RF2))ySO2X wherein in dispersant (D) X is OXa, with Xabeing H, an ammonium group or a monovalent metal and in polymer (P) X is a halogen, preferably F or Cl, more preferably F, wherein w is an integer between 0 and 2, RFI and RF2, equal or different from each other, are independently F, Cl or a C1-C10 fluoroalkyl group, optionally substituted with one or more ether oxygens, y is an integer between 0 and 6; preferably w is 1 , RFI is -CF3, y is 1 and RF2 is F;- sulfonyl halide aromatic fluoroolefins of formula CF2=CF-Ar-SO2X wherein in dispersant (D) X is OXa, with Xabeing H, an ammonium group or a monovalent metal and in polymer (P) X is a halogen, preferably F or Cl, more preferably F, wherein Ar is a C5-C15 aromatic or heteroaromatic group.

6. The composition of any one of the preceding claims wherein the polymer (P) and / or the dispersant (D) comprise:- 50 to 99 mol%, with respect to the total number of moles of units constituting the polymer (P) or the dispersant (D), of recurring units deriving from tetrafluoroethylene;- 1 to 50 mol%, with respect to total number of moles of units constituting the polymer (P) or the dispersant (D), of recurring units deriving from at least one monomer selected from the group consisting of:(j) sulfonyl halide fluorovinyl ethers of formula: CF2=CF-O-(CF2)mSO2X, wherein in dispersant (D) X is OXa, with Xabeing H, an ammonium group or a monovalent metal and in polymer (P) X is a halogen, preferably F or Cl, morepreferably F, wherein m is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;(jj) sulfonyl halide fluoroallyl ethers of formula: CF2=CFCF2-O-(CF2)nSO2X, wherein in dispersant (D) X is OXa, with Xabeing H, an ammonium group or a monovalent metal and in polymer (P) X is a halogen, preferably F or Cl, more preferably F, wherein n is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably m equals 2;(jjj) sulfonyl halide fluoroalkoxyvinyl ethers of formula: CF2=CF- (OCF2CF(RFi))w-O-CF2(CF(RF2))ySO2X with X being OXa, wherein in dispersant (D) X is OXa, with Xabeing H, an ammonium group or a monovalent metal and in polymer (P) X is a halogen, preferably F or Cl, more preferably F, wherein w is an integer between 0 and 2, RFI and RF2, equal or different from each other, are independently F, Cl or a Ci- C10 fluoroalkyl group, optionally substituted with one or more ether oxygen atoms, y is an integer between 0 and 6; preferably w is 1 , RFI is -CF3, y is 1 and RF2 is F; and(jv) mixtures thereof; and- 0 to 45 mol%, with respect to the total number of moles of units constituting the polymer (P) or the dispersant (D), of recurring units deriving from at least one hydrogenated and / or fluorinated monomer different from tetrafluoroethylene, preferably a perfluorinated monomer selected from the group consisting of hexafluoropropylene, perfluoroalkylvinyl ethers of formula CF2=CFOR’fi, wherein R’n is a Ci-Ce perfluoroalkyl; perfluoro-oxyalkylvinylethers of formula CF2=CFOR’OI , wherein R’01 is a C2-C12 perfluoro-oxyalkyl having one or more ether groups, including perfluoroalkyl-methoxy-vinylethers of formula CF2=CFOCF2OR’f2 in which R’f2 is a Ci-Ce perfluoroalkyl, or a Ci-Ce perfluorooxyalkyl having one or more ether groups; fluorodioxoles, of formula:wherein each of Rf3, Rf4, Rfs, Rf6, equal or different from each other, is independently a fluorine atom, a Ci-Ce (halo)fluoroalkyl, optionally comprising one or more oxygen atoms.

7. The composition of any one of the preceding claims wherein the compound (AZ) is selected from the compounds of general formula (I):in which:-X can be a nitrogen atom or a -CR3 group, wherein R3 is selected from H or a C1-C12 alkyl group, optionally fluorinated and / or optionally unsaturated, and R3 may form part of an aliphatic or aromatic ring structure with R1 ;-Y can be a -CR4 group or a nitrogen atom, wherein R4 may be H or a C1- C12 alkyl group, optionally fluorinated and / or optionally unsaturated; and-Ri and R2 may, independently of each other, be H or a C1-C12 alkyl or Ce- C12 aryl and wherein R1 may form part of an aliphatic or aromatic ring structure with R3.

8. The composition of any one of the preceding claims, which has a melt flow rate, measured according to ASTM D1238-04 at 280°C / 5 kg, that does not exceed 55 g / 10 min.

9. A process for preparing a melt-processable composition of any one of the preceding claims, said process comprising the steps:(a) contacting in an aqueous medium a polymer (P), a dispersant (D) and a compound (AZ) as defined in any one of claims 1 to 10 to obtain an aqueous dispersion;(b) separating the melt-processable composition comprising the polymer (P), the dispersant (D) and the compound (AZ) in solid form from the aqueous medium.

10. The process for preparing a melt-processable composition according to claim 9, wherein separating the melt-processable composition in solid form comprisessubjecting the aqueous dispersion obtained at the end of step (a) to at least one of: spray-drying, lyophilization, filtration or centrifugation.11 . The process of claim 10, which comprises, before step (a):- providing a fluorinated polymeric dispersant (D) comprising: (a) a backbone chain comprising recurring units deriving from one or more fluorinated ethylenically unsaturated monomers, and (b) a plurality of ionic groups selected from: -SOsXa, -POsXa, -COOXa and a combination thereof, wherein Xa is an ammonium group or a monovalent metal ion;- converting the hydrolyzable ionic groups of the dispersant (D) into acid form.

12. The process of claim 10 or 11 , wherein the polymer (P) and the dispersant (D) are the product of an aqueous polymerization process to prepare the polymer (P) that uses the dispersant (D) in the absence of non-polymeric surfactants.

13. A process for the preparation of an article comprising the melt-processable composition of any one of claims 1 to 8, the process comprising the step of meltprocessing the melt-processable composition.

14. A film comprising a melt-processable composition of any one of claims 1 to 8.

15. A proton exchange membrane comprising the film of claim 14, in which the polymer (P) comprises sulfonic acid groups.

16. A process for preparing a proton exchange membrane, the process comprising:- melt-processing a melt-processable composition (MC) to form a film;- hydrolysing the sulfonyl fluoride groups of polymer (P) to sulfonic acid groups.

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