Methods for preparing functionalized polymers

Abstract

The present invention relates to a compound represented by formula (I) [Formula 1] The present invention provides compounds comprising a fluoroallyl xanthate group of formula (I) TIFF2025505991000028.tif17170. The present invention also relates to processes for making these compounds and to the use of said compounds as chain transfer agents or monomers. The present invention also relates to polymers, including copolymers, comprising units derived from the compound of formula (I).

Description

[Technical field]

[0001] REFERENCE TO RELATED APPLICATIONS This application claims priority from European Patent Application Publication No. 22155260.7, filed February 4, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention provides compounds that contain fluoroallyl xanthate groups. The present invention also relates to processes for producing these compounds and the use of said compounds as chain transfer agents or monomers. The present invention also relates to polymers, including copolymers, that contain repeat units derived from compounds that contain fluoroallyl xanthate groups. [Background technology]

[0003] In certain cases it may be beneficial to provide the polymer with functional groups.

[0004] Polymers with attached functional groups can be prepared directly by polymerization of functional monomers. Oligomers and polymers prepared by controlled polymerization processes can have functional groups at specific positions along the chain and in specific amounts. For example, functional monomers can be periodically placed along the polymer chain, initiators can have added functionality, or groups that make the polymerization controlled can be removed and replaced with the desired functional group. However, there are some functional monomers that cannot be directly copolymerized by polymerization processes. Furthermore, monomers with the desired functional group may not be copolymerized in the desired manner using the selected polymerization process.

[0005] For example, it is very difficult to introduce monomers with side chain functionalities that are -CF2SO3H and -CF2SH.

[0006] In the field of fuel cells and electrolysis applications, the availability of polymers with very short side chains carrying -CF2SO3H groups would lead to systems, e.g. membranes, with higher electrochemical performance and better mechanical properties than current technology.

[0007] The applicant has discovered novel monomers, more specifically monomers containing fluoroallyl xanthates, which can be used to synthesize polymers with pendant functional groups that can be suitably converted to multiple functional groups in post-polymerization processes. The resulting polymers can be tailored for a variety of applications.

[0008] Alkyl xanthates are compounds with the general formula ROC(=S)SR'. They are widely used in engineering applications, such as as chain transfer agents in flotation and controlled radical polymerization, and are generally prepared by the substitution reaction of xanthates with chloroalkyl compounds. Summary of the Invention

[0009] Therefore, a first object of the present invention is to provide a compound of formula (I): [ka] (In the formula, R a is a (per)fluoroallyl group, and R b is a straight or branched alkyl group. The compound (AX) conforms to the following formula: R b is C1~C 12 It is a straight-chain or branched alkyl group of the formula, typically a C1 to C8 straight-chain or branched alkyl group, and preferably a C1 to C6 straight-chain or branched alkyl group.

[0010] The present invention also relates to a process for preparing the compound (AX) according to the first object.

[0011] Another object of the invention is a polymer (P) comprising recurring units derived from a compound (AX) of formula (I) as defined above.

[0012] The present invention also relates to a process for the manufacture of a polymer (P) comprising recurring units derived from a compound (AX) of formula (I) as defined above.

[0013] -S(=S)OR present in the repeating unit derived from compound (AX) b The polymer (P) can be appropriately chemically transformed in order to convert the groups into different functional groups, resulting in a further functionalized polymer.

[0014] In a further object, the present invention relates to the use of compounds (AX) of formula (I) as defined above as chain transfer agents in controlled radical polymerization. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] In this application: - any description, even if made in relation to a particular embodiment, is applicable to and interchangeable with other embodiments of the present disclosure; - when an element or component is said to be included in and / or selected from a list of enumerated elements or components, in the relevant embodiments expressly contemplated herein, it is to be understood that the element or component may be any one of the individual enumerated elements or components, or may also be selected from the group consisting of any two or more of the explicitly enumerated elements or components, and that any element or component enumerated in a list of elements or components may be omitted from such list; - any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited range, as well as the endpoints of the range, and equivalents thereof; - the use of parentheses "(...)" around a symbol or a number identifying a formula or part of a formula has the sole purpose of better distinguishing the symbol or number from the rest of the sentence, and therefore said parentheses may also be omitted.

[0016] For the purposes of the present invention, the term "(per)fluoroallyl group" is intended to denote a partially or fully fluorinated allyl group, i.e. an allyl group in which all or only a portion of the hydrogen atoms of the hydrocarbon allyl structure are replaced by fluorine atoms bonded to unsaturated and / or saturated carbons. If the allyl group is fully fluorinated, the term perfluoro is used.

[0017] R a is preferably a perfluoroallyl group.

[0018] The compound (AX) of the present invention preferably has the formula (II): [ka] In accordance with the formula, b is as defined above.

[0019] R b Non-limiting examples include ethyl, isopropyl, n-butyl, isobutyl, n-pentyl and isopentyl groups, among others.

[0020] Particularly preferred is the formula (III): [ka] The compound (AX) is hereinafter referred to as "FAX".

[0021] The compound (AX) of the present invention may be prepared by a process comprising the following steps a) and b): a) Formula (IV): [ka] (In the formula, R b is as defined above, and M + is a monovalent cation) providing a xanthate salt of b) reacting the xanthate salt provided in step a) with a compound of formula (V): R a-OSO2X (V) (In the formula, R a is a (per)fluoroallyl group, and X is a halogen atom. with (per)fluoroallyl fluorosulfate.

[0022] In formula (IV), M + is preferably selected from alkali metal cations, more preferably M + is Na + , K + , Cs + and Li + and even more preferably selected from M + is K + It is.

[0023] Among the (per)fluoroallyl fluorosulfates, perfluoroallyl fluorosulfate of the formula CF2=CFCF2OSO2F (hereinafter referred to as "FAFS") is particularly preferred.

[0024] In step b), the reaction is preferably carried out at room temperature.

[0025] The reaction in step b) is typically carried out in the presence of a solvent. Suitable solvents for the reaction in step b) are polar aprotic solvents, in particular glycol ethers, ethers, nitriles. Preferably, the solvent is acetonitrile.

[0026] The reaction time of step b) is suitably from 1 to 5 hours.

[0027] At the end of step b), the solid FSO3M by-product is filtered off from the reaction mixture and compound (AX) is recovered in powder form after evaporation of the solvent.

[0028] The compound (AX) of the present invention can be used to prepare polymers. Advantageously, the repeating units derived from the compound (AX) can serve as precursors for other protective and / or reactive functional groups, such as -CF2SO3 and -CF2SH.

[0029] A further object of the invention is therefore a polymer (P) comprising repeat units derived from compound (AX).

[0030] The polymer (P) may be a homopolymer, i.e. it may consist of repeat units derived from the compound (AX).

[0031] Alternatively, the polymer (P) may be a copolymer comprising repeat units derived from compound (AX) and repeat units derived from one or more ethylenically unsaturated monomers.

[0032] The polymer (P) according to the invention is preferably a copolymer.

[0033] More preferably, the polymer (P) is a copolymer comprising repeat units derived from a compound (AX) as defined above and repeat units derived from at least one fluoromonomer [fluoromonomer (FM)]. The expression "fluoromonomer" is used herein according to its usual meaning, i.e. to denote an ethylenically unsaturated monomer containing at least one fluorine atom.

[0034] In a preferred embodiment of the present invention, the polymer (P) comprises 85 to 5 mol % of repeating units derived from the compound (AX) relative to the total number of moles of repeating units of the polymer (P) and 15 to 95 mol % of repeating units derived from at least one fluoromonomer (FM) relative to the total number of moles of repeating units of the polymer (P).

[0035] The polymer (P) may contain at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 35%, at least 45%, at least 50%, or even at least 60% or at least 70% of the compound (AX) relative to the total number of moles of the repeating units of the polymer (P). The polymer (P) may contain less than 80%, less than 75%, less than 65%, or even less than 50%, less than 45%, or less than 30% of the compound (AX) relative to the total number of moles of the repeating units of the polymer (P). The remaining repeating units in the polymer (P) are derived from one or more fluoromonomers (FM).

[0036] The fluoromonomer (FM) is typically selected from the group consisting of: - C2-C8 perfluoroolefins such as tetrafluoroethylene and hexafluoropropene, - C2-C8 hydrogen-containing fluoroolefins such as vinyl fluoride, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, pentafluoropropylene and hexafluoroisobutylene; - Formula CH2=CH-R f0 (In the formula, R f0 is C1-C6 (per)fluoroalkyl or C1-C6 (per)fluorooxyalkyl having one or more ether groups, - chloro- and / or bromo- and / or iodo-C2-C6 fluoroolefins, such as chlorotrifluoroethylene; - Formula CF2=CFOR f1 (In the formula, R f1 is C1-C6 fluoro or perfluoroalkyl, for example -CF3, -C2F5, -C3F7), - Formula CH2=CFOR f1 (In the formula, R f1 is C1-C6 fluoro or perfluoroalkyl, for example -CF3, -C2F5, -C3F7), - Formula CF2 = CFOX0 (wherein X0 is C1 to C 12C1-C with one or more ether groups, such as oxyalkyl or perfluoro-2-propoxy-propyl 12 (per)fluorooxyalkyl; - Formula CF2=CFOCF2OR f2 (In the formula, R f2 is C1-C6 fluoro or perfluoroalkyl, for example C1-C6 (per)fluorooxyalkyl having one or more ether groups, such as -CF3, -C2F5, -C3F7 or -C2F5-O-CF3, - Formula CF2 = CFOY0 (wherein Y0 is C1 to C 12 Alkyl or (per)fluoroalkyl or C1-C 12 Oxyalkyl or C1-C 12 (per)fluorooxyalkyl, said Y0 group containing a carboxylic acid group or a sulfonic acid group in its acid, acid halide or salt form; - Formula: [ka] (In the formula, R f3 , R f4 , R f5 , R f6 are equal to or different from each other and are independently a C1-C6 fluoro or per(halo)fluoroalkyl containing a fluorine atom, optionally one or more oxygen atoms, e.g., -CF3, -C2F5, -C3F7, -OCF3, -OCF2CF2OCF3). of fluorodioxole.

[0037] The polymer (P) may contain repeat units derived from at least one additional monomer different from the fluoromonomer (FM), i.e. a monomer not containing fluorine, otherwise generally called hydrogen-containing monomer [monomer (HM)]. Examples of hydrogen-containing monomers (HM) are, inter alia, C2-C8 non-fluorinated olefins, in particular C2-C8 non-fluorinated α-olefins, including ethylene, propylene, 1-butene; diene monomers; styrene monomers. The monomer (HM) is preferably selected from C2-C8 α-olefins.

[0038] In one preferred embodiment of the invention, the polymer (P) is a copolymer comprising repeating units derived from the compound (AX) defined above, repeating units derived from at least one C2-C8 perfluoroolefin, and repeating units derived from at least one functional fluoro-alkylvinyl ether of formula CF2=CFOY0 defined above.

[0039] The C2-C8 perfluoroolefin is preferably tetrafluoroethylene. The functional fluoro-alkyl vinyl ether of formula CF2=CFOY0 is preferably a C1-C perfluoroolefin, where Y0 contains a sulfonic acid group in the acid, acid halide or salt form. 12 The (per)fluorooxyalkyl group is selected from fluoroalkyl vinyl ethers.

[0040] The functional fluoro-alkyl vinyl ether of formula CF2=CFOY0 is preferably selected from the group consisting of: (j) Formula: CF2 = CF-O-(CF2) m’ SO2X', where m' is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, and even more preferably m' is equal to 2, and X' is selected from among the halogens (Cl, F, Br, I), preferably F, or -O - M' + and M' + is H + , NH4 + , K + , Li+ , Na + or a mixture thereof, preferably M' + is H + and (jj) Formula: CF2 = CF-(OCF2CF(R F1 )) w -O-CF2(CF(R F2 )) y SO2X', where X' is selected from among halogens (Cl, F, Br, I), preferably F, or -O - M' + and M' + is H + , NH4 + , K + , Li + , Na + or a mixture thereof, preferably M' + is H + where w is an integer from 0 to 2, and R F1 and R F2 are equal to or different from each other and independently represent C optionally substituted with F, Cl or one or more ether oxygens; 1~ C 10 is a fluoroalkyl group, y is an integer from 0 to 6, and preferably w is 1; R F1 is -CF3, y is 1, and R F2 is F) sulfonyl fluoride fluoroalkoxy vinyl ether.

[0041] Even more preferably, the at least one functional fluoro-alkyl vinyl ether has the formula (FM1): [ka] (In the formula, m' is an integer of 1 to 10, preferably 1 to 6, more preferably 2 to 4, and X' is selected from halogens (Cl, F, Br, I), preferably F, -O - M' + and M' + is H+ , NH4 + , K + , Li + , Na + or a mixture thereof, preferably M' + is H + is) is a sulfonated perfluorovinyl ether.

[0042] Advantageously, the sulfonated perfluorovinyl ethers of formula (FM1) are of the formulae (FM1-A), (FM1-B) and (FM1-C): [ka] (wherein X' has the same meaning as defined above). The compound is selected from the group consisting of:

[0043] The sulfonated perfluorovinyl ether preferably has the formula (FM1-D): [ka] Perfluoro-5-sulfonyl fluoride-3-oxa-1-pentene (hereinafter referred to as "VEFS"), which may be in its -SO2F form as shown above, or in its -SO3X form, where X is H, or an alkali metal, or NH 4+ It is.

[0044] Advantageously, the polymer (P) has formula (VI): [ka] (wherein n, m and p are each independently an integer greater than 0 and together represent the mole fraction of each monomer in the polymer (P). Typically, n is 0.50 to 0.75, m is 0.10 to 0.30, and p is 0.05 to 0.40.

[0045] In the above notation for copolymer, the n, m and p units may appear in any order. Formula (VI) is intended only to define the relative proportions of monomer units, and is not intended to define the exact order in the copolymer, which is random. Similarly, the tail-to-tail pattern repeat unit orientation in formula (VI) is merely a guideline and is not intended to limit the structure of the polymer. The repeat units in polymer (P) of formula (VI) may be in head-to-head, tail-to-tail or head-to-tail configuration.

[0046] In a preferred embodiment of the present invention, the polymer (P) is - 5 to 25 mol %, 10 to 20 mol % of repeating units derived from compound (AX); - 45 to 85 mol %, 60 to 70 mol % of repeating units derived from tetrafluoroethylene; - 10 to 30 mol %, 15 to 25 mol % of repeating units derived from a functional fluoro-alkyl vinyl ether of formula (FM1-D) where the molar amount relates to the total number of moles of repeating units of the polymer (P).

[0047] The polymer (P) is reacted in the presence of at least a free radical initiator and optionally at least one surfactant, (i) at least one compound (AX) as defined above, (ii) at least one fluoromonomer (FM) as defined above The polymerization may be carried out in an aqueous emulsion.

[0048] The monomer mixture (MM) may optionally contain the following monomers: (iii) at least one monomer different from the fluoromonomer (FM), ie the monomer (HM) defined above.

[0049] A monomer mixture (MM) comprising a compound (AX), one or more fluoromonomers (FM) and, optionally, a monomer (HM) is usually used in the preparation of the polymer (P) of the invention.

[0050] The polymerization initiator used in the process of the present invention is organic or inorganic. Organic initiators can include, for example, diisopropyl peroxydicarbonate (IPP) or di-tert-butyl peroxide (DTBP). Inorganic radical initiators are preferably used, such as ammonium and / or potassium and / or sodium salts of persulfate, optionally combined with iron, copper or silver salts. The supply procedure of the initiator can be continuous or added at once at the beginning of the polymerization.

[0051] Optionally, a surfactant may be used. The surfactant may be a fluorinated surfactant or a non-fluorinated surfactant.

[0052] Among the fluorinated surfactants, mention may be made of functional (per)fluoropolyether compounds comprising at least one (per)fluoropolyoxyalkylene chain and at least one functional end group selected from carboxylic, phosphonic and sulfonic acid groups, as well as cyclic fluoro compounds, such as those described in WO 2010 / 00392.

[0053] In a typical polymerization process, a mixture comprising water, optional surfactant, and monomers ((i), (ii) and optionally (iii)) is formed in a reaction vessel at the polymerization temperature, and the polymerization reaction is initiated by the addition of a free radical initiator. In an emulsion polymerization process, a surfactant is usually present in the mixture, thereby forming an emulsion.

[0054] The polymerization reaction is usually carried out at a temperature in the range of from 25° C. to 130° C. The polymerization is typically carried out at atmospheric pressure or under elevated pressure, for example from 2 bar to 60 bar.

[0055] Preferably, the polymerization reaction is usually carried out at a temperature between 40° C. and 70° C., preferably between 50° C. and 60° C., and at a pressure up to 20 bar, preferably above 5 bar.

[0056] A polymerized latex or suspension containing the polymer dispersed in an aqueous liquid phase is obtained at the end of the process. The polymer (P) can be recovered from said polymerized latex using well-known techniques such as freeze-thaw coagulation or by the addition of electrolytes such as aluminum sulfate or nitric acid.

[0057] Further treatments can be carried out on such coagulum before isolating the polymer (P) in powder form, such as purification of the latex or suspension, washing from contaminants and drying.

[0058] Advantageously, the polymer (P) of the invention is obtained by a process comprising polymerizing a monomer mixture (MM) comprising a compound (AX) of formula (III) as defined above, tetrafluoroethylene and a fluoromonomer (FM) of formula (FM1-D), as a result of which a polymer (P) of formula (VI) as defined above is obtained.

[0059] Chemical transformations can be carried out on the polymer (P) according to the invention.

[0060] Advantageously, the -S(=S)OR group present in the repeat unit derived from compound (AX) b The groups can be converted into different functional groups.

[0061] Thus, in a further aspect, the present invention provides a process for the chemical conversion of a repeat unit derived from compound (AX) of a polymer (P) into a different functional group.

[0062] According to a first embodiment of the present invention, the process comprises: [ka] This involves chemically hydrolyzing the moiety to the group -SH.

[0063] Chemical hydrolysis of the xanthate moieties to sulfhydryl groups -SH can be suitably carried out in the presence of an acidic or basic aqueous solution. Thus, the process involves reacting the polymer (P) with an acid or base in an aqueous solution.

[0064] Suitable aqueous acidic solutions are especially those containing HCl, HBr or H3PO4.

[0065] Suitable aqueous basic solutions are especially those containing NaOH or KOH.

[0066] The reaction is usually carried out at a temperature in the range of 25°C to 100°C.

[0067] -S(=S)OR b The conversion of the group to a -SH group can be monitored by analytical techniques such as infrared spectroscopy.

[0068] According to a further embodiment of the present invention, the process of chemical transformation applied to the polymer (P) is carried out by converting the xanthate moieties of the repeating units derived from the compound (AX), i.e. [ka] The aim of this study is to convert the site of 3H to the group -SO3H by chemical oxidation.

[0069] The chemical oxidation of the xanthate moieties to sulfonic acid groups -SO3H may be suitably carried out in the presence of an oxidizing agent such as hydrogen peroxide. Thus, the process comprises reacting the polymer (P) with an oxidizing agent, preferably hydrogen peroxide.

[0070] The reaction is usually carried out at a temperature in the range of 25°C to 100°C.

[0071] -S(=S)OR b The conversion of the group to a -SO3H group can be observed by analytical techniques such as infrared spectroscopy.

[0072] Thus, a further object of the present invention is to provide a compound of formula (VII): [ka] (wherein w is either 0 or 1, Q is an integer from 1 to 4, preferably 1 or 2, and X' is selected from halogens (Cl, F, Br, I), preferably F or -O - M' + and M' + is H + , NH4 + , K + , Li + , Na + or a mixture thereof, preferably M' + is H + where n and p are, independently of one another, integers greater than 0, m is greater than 0, and m, n, and p represent the mole fraction of each monomer in the polymer. Polymer (P ox ). Typically, n is 0.50 to 0.75, m is 0 to 0.30, and p is 0.05 to 0.50. In formula (VII), n is 0.60 to 0.70, m is 0.10 to 0.30, and p is 0.10 to 0.20.

[0073] In a particularly preferred embodiment of the present invention, the polymer (P) of formula (VI) defined above is post-treated by chemical oxidation with hydrogen peroxide to give the polymer of formula (VIII): [ka] where n, m, and p are each independently an integer greater than 0 and represent the mole fraction of each monomer in the polymer. The post-treated polymer (P ox) is obtained. Typically, n can be 0.50 to 0.65, m can be 0.10 to 0.30, and p can be 0.05 to 0.40. In formula (VIII), n is 0.60 to 0.70, m is 0.10 to 0.30, and p is 0.10 to 0.20.

[0074] In the above notation for copolymers, the n, m and p units can appear in any order. Formulas (VII) and (VIII) are intended only to define the relative proportions of monomer units, and are not intended to define the exact order in the copolymer, which is random. Similarly, the tail-to-tail pattern of repeat unit orientation in formulas (VII) and (VIII) is merely a guide and is not intended to limit the structure of the polymer. The repeat units in the polymers of formulas (VII) and (VIII) can be in head-to-head, tail-to-tail or head-to-tail configuration.

[0075] The polymers (P), such as those of formula (VII) or (VIII), obtained by the process of the present invention ox ) are ion-conducting polymers or precursors thereof. They are particularly suitable for use in electrochemical applications. The polymers of formula (VII) or (VIII) can be used to prepare membranes for electrochemical applications such as membranes for fuel cells, e.g. chloro-soda cells, lithium batteries, etc. They can further be used as membranes for electrodialysis applications and reactors in which membranes made of the polymers act as superacid catalysts.

[0076] Sulfonic acid type perfluorinated ion-conducting polymers are currently considered as benchmark materials for fuel cells (mainly low-temperature fuel cells for transportation) and electrolyzers (producing so-called green hydrogen from renewable energies) due to their combination of chemical stability in harsh environments and good proton conductivity in a wide range of humidity conditions. Commercially available perfluorinated ion-conducting polymers are copolymers of tetrafluoroethylene and vinyl ethers of different lengths with -SO3H groups. The ion-conducting polymer with the shortest side chains (two -CF2- groups) currently available on the market is Solvay's Aquivion® ion-conducting polymer, while the ion-conducting polymer with the longest side chains is Chemours' Nafion®. Obtaining ion-conducting polymers with shorter side chains would have a significant impact on improving electrochemical performance and mechanical strength.

[0077] Thus, the present invention provides perfluorinated ion-conducting polymers having side chains containing only one -CF2- group, such as polymers of formula (VII) or (VIII): b The polymer (P) in which the groups are oxidized to -SO3H groups has the advantages of having higher proton conductivity, higher crystallinity and higher mechanical strength than commercially available perfluorinated ion-conducting polymers.

[0078] Thus, a further object of the present invention is to provide a polymer (P) or a polymer (P ox The article may be in the form of a membrane, such as an ion-conducting membrane. ox Ion conducting membranes comprising cations such as Cr, Cl, and Hf may be used in electrolysis or fuel cell applications.

[0079] In another aspect of the invention there is provided the use of a compound (AX) of formula (I) as defined above as a chain transfer agent in a controlled radical polymerization.

[0080] Among the controlled radical polymerization techniques, reversible addition-fragmentation chain transfer (RAFT) and polymer design by interconversion of xanthate compounds (MADIX) can be mentioned.

[0081] RAFT / MADIX agents can act as reversible chain transfer agents in free radical polymerizations, thereby inducing reversible addition-fragmentation transfer reactions to result in an equilibrium between a growing radical (i.e., a growing polymer chain) and so-called dormant species (containing chain transfer agent fragments) that can become active again.

[0082] The Applicant has surprisingly found that compound (AX) can be suitably used as a RAFT / MADIX agent in the emulsion polymerization of fluoromonomers to control the polymer microstructure.

[0083] Thus, in a further aspect, the present invention provides a method for emulsion polymerizing at least one fluoromonomer, comprising the steps of: (i) at least one fluoromonomer [monomer (F)] and a compound of formula (I): [ka] (In the formula, R a is a (per)fluoroallyl radical group, R b is a linear or branched alkyl radical group. providing at least one aqueous emulsion comprising a monomer mixture comprising at least one compound (AX) of the formula (I) and optionally at least one surfactant; (ii) adding at least one radical initiator to initiate polymerization of the monomer mixture in the aqueous emulsion; (iii) continuing the polymerization by adding additional amounts of said at least one monomer (F) and / or said compound (AX) until a target amount of said monomer mixture is converted; (iv) terminating the polymerization and recovering the latex of the fluoropolymer [polymer (F)]; The present invention provides a method comprising:

[0084] The expression "fluoromonomer" is used herein according to its ordinary meaning, i.e. to denote an ethylenically unsaturated monomer that contains at least one fluorine atom.

[0085] The fluoromonomer (F) may in particular be a fluoromonomer (FM) as defined above.

[0086] The process of the present invention is suitable for the production of a variety of fluoropolymers, including, inter alia, non-melt processable tetrafluoroethylene polymers (such as PTFE homopolymers and copolymers thereof containing small amounts of perfluoro comonomers), thermoplastic fluoropolymers (e.g., vinylidene fluoride homopolymers and plastomeric copolymers thereof, copolymers of ethylene and chlorotrifluoroethylene, thermoplastic copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ethers, thermoplastic copolymers of tetrafluoroethylene and hexafluoropropylene), and fluoroelastomers.

[0087] The invention will now be described with reference to the following examples, the purposes of which are illustrative only and are not intended to limit the scope of the invention. EXAMPLES

[0088] Example 1: Synthesis of FAX A three-necked round bottom flask equipped with a thermometer, condenser, and dropping funnel was charged with 109.20 g of CF2=CFCF2OSO2F (FAFS) under nitrogen. Then, 70.57 g of potassium ethyl xanthate dissolved in 1482 ml of acetonitrile was added dropwise at room temperature over 25 minutes. After stirring for 2 hours, the reaction was complete and a white solid (FSO3K) precipitated. The white solid was filtered and the resulting clear solution was washed three times with distilled water (1:1 volume with respect to the organic phase). The organic phase was separated and vacuum distilled to obtain 82.73 g of pure CF2=CFCF2S(C=S)OCH2CH3 (FAX).

[0089] In acetone 19F NMR (HFMX standard): -82 ppm (m; 2F; -SCF2CF=CF2); -93.5 ppm (m; 1F; cis-SCF2CF=CF2); -105 ppm (m; 1F; trans-SCF2CF=CF2); -184 ppm (m; 1F; -SCF2CF=CF2). 1 H NMR (TMS standard): +4.8ppm(q;2H;-OCH2CH3);+1.5ppm(m;3H;-OCH2CH3).

[0090] Example 2: Polymerization of TFE+VEFS+FAX Deionized water (1.8 L), VEFS (212 g) and an aqueous solution of Fluorolink 7800 (540 g, 5 wt%) were placed in a 5 L reactor, then pressurized with 7.5 bar of TFE and the system was heated to 50° C. with stirring. After feeding potassium persulfate solution (concentration 10.5 g / L, 200 mL), the reaction took place. For every 10% conversion of TFE, 45 g of VEFS and 50 g of a solution of VEFS (90 wt%) and FAX (10 wt%) were fed. The reaction was stopped when 4.95 g of FAX and 257 g of VEFS were added, cooled and the pressure was reduced by removing the TFE. The polymer latex thus obtained was freeze-thawed and the polymer was recovered as a yellowish powder.

[0091] FT-IR: 970cm-1 (combination of symmetric stretching of CF and COC); 1150cm-1 (combination of asymmetric stretching of COC and stretching vibration of CF bond); 1020cm -1 (C=S telescopic);1220cm -1 (CF2 symmetric and asymmetric stretching); 1470 cm-1 (SF bond motion); 2365 cm -1 (CF overtone / composite band); 2705cm -1 (SF overtones).

[0092] Example 3 (Comparative): Polymerization of TFE+VEFS Deionized water (1.8 L), VEFS (212 g) and an aqueous solution of Fluorolink 7800 (540 g, 5 wt%) were placed in a 5 L reactor, then pressurized with 7.5 bar of TFE and the system was heated to 50° C. with stirring. After feeding potassium persulfate solution (concentration 10.5 g / L, 200 mL), the reaction took place. 45 g of VEFS were fed for every 10% conversion of TFE. When 707 g of VEFS had been added, the reaction was stopped, cooled and the pressure was reduced by removing the TFE. The polymer latex thus obtained was freeze-thawed and the polymer was recovered as a white powder. The powder was washed 4 times with demineralized water (1 L) at room temperature with stirring and then dried overnight at 80° C. in a vented oven.

[0093] FT-IR: 970cm-1 (combination of CF and COC symmetric stretching); 1150cm -1 (combination of asymmetric stretching of COC and stretching vibration of CF bond); 1220cm -1 (CF2 symmetric and asymmetric stretching); 1470cm -1 (SF coupled motion);2365cm -1 (CF overtone / composite band); 2705cm -1 (SF overtones).

[0094] Example 4: Conversion of xanthate groups to -SO3H groups The polymer of Example 2 was washed 4 times with demineralized water (1 L each) and ethyl acetate (0.5 L). The washing was carried out at room temperature with stirring. The powder was then dried overnight at 80° C. in a vented oven. The polymer was stirred for 8 hours at 45° C. in a solution of H2O2 (15%, 200 mL) and H2SO4 (0.5 M, 2 mL) with a pH of about 4. The powder thus obtained was washed 4 times (1 L each) with distilled water with stirring at room temperature and finally dried overnight at 80° C. in a vented oven.

[0095] FT-IR: 515 cm-1 (CS deformation of CF2-SO3); 634 cm-1 (S-OH deformation of SO3H); 970 cm-1 (combined symmetric stretching of CF and COC); 1057 cm-1 (symmetric stretching of SO3); 1154 cm-1 (combined symmetric stretching of COC and SO3 and stretching vibration of CF bond); 1220 cm-1 (symmetric and asymmetric stretching of CF2); 1300 cm-1 (symmetric and asymmetric stretching of SO3); 1470 cm-1 (SF bond motion); 2365 cm-1 (CF overtone / combined band); 2705 cm-1 (SF overtone).

[0096] Example 5 (Comparative): Conversion of -SO2F groups to -SO3H groups The polymer of Comparative Example 3 was treated with a solution of NaOH in demineralized water (20% by weight, 1 L) with stirring at 80° C. After 8 hours, the powder was washed 4 times with demineralized water (1 L each) with stirring at room temperature, then treated twice with a solution of HNO3 in distilled water (20% by weight, 1 L each) with stirring at room temperature. The polymer was washed with distilled water (4×1 L) with stirring at room temperature, then dried in a vented oven (80° C., overnight).

[0097] FT-IR: 515cm -1 (CS deformation of CF2-SO3); 634cm -1 (S-OH transformation of SO3H); 970cm -1 (CF and COC symmetric stretching combined); 1057cm -1 (SO3 symmetric stretching); 1154cm -1 (combination of symmetric stretching vibrations of COC and SO3 and C—F bond stretching vibrations); 1220 cm -1 (symmetric and asymmetric stretching of CF2); 1300cm -1 (Symmetric and asymmetric stretching of SO3).

Claims

1. Formula (I): 【Chemistry 1】 (In the formula, R ａ is a (per)fluoroallyl group, and R ｂ is a linear or branched alkyl group, preferably C １ ~C １２ is a straight-chain or branched alkyl group Compound (AX).

2. Formula (II): 【Chemistry 2】 (In the formula, R ｂ is selected from the group consisting of ethyl, isopropyl, n-butyl, isobutyl, n-pentyl and isopentyl groups. The compound (AX) according to claim 1 .

3. Formula (III) 【Transformation 3】 The compound (AX) according to claim 1,

4. A process for preparing the compound (AX) according to claim 1, comprising the following steps a) and b): a) Formula (IV) 【Chemistry 4】 (In the formula, R ｂ is a linear or branched alkyl group, and M ＋ is preferably a monovalent cation selected from alkali metal cations, more preferably M ＋ is Na ＋ , K. ＋ , Cs ＋ and Li ＋ and even more preferably selected from M ＋ Is, K ＋ is) providing a xanthate salt of b) reacting the xanthate salt provided in step a) with a compound of formula (V): R ａ —OSO ２ X (V) (In the formula, R ａ is a (per)fluoroallyl group, and X is a halogen atom. with (per)fluoroallyl fluorosulfate A process involving:

5. 5. The process according to claim 4, wherein step b) is carried out in the presence of a polar aprotic solvent, preferably in acetonitrile.

6. Formula (I) 【Transformation 5】 (In the formula, R ａ is a (per)fluoroallyl group, and R ｂ is a linear or branched alkyl group) A polymer (P) comprising a repeating unit derived from a compound (AX) of the formula:

7. The polymer (P) according to claim 6, which is a copolymer comprising a repeating unit derived from the compound (AX) and a repeating unit derived from at least one ethylenically unsaturated monomer containing at least one fluorine atom [fluoromonomer (FM)].

8. The polymer (P) according to claim 7, comprising 85 to 5 mol% of repeating units derived from the compound (AX), based on the total number of moles of repeating units in the polymer (P), and 15 to 95 mol% of repeating units derived from the at least one fluoromonomer (FM), based on the total number of moles of repeating units in the polymer (P).

9. The fluoromonomer (FM) is - C such as tetrafluoroethylene and hexafluoropropene ２ ~C ８ perfluoroolefins, - C such as vinyl fluoride, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, pentafluoropropylene and hexafluoroisobutylene ２ ~C ８ hydrogen-containing fluoroolefins, - Formula CH ２ =CH-R ｆ０ (In the formula, R ｆ０ is C １ ~C ６ (Per)fluoroalkyl or C having one or more ether groups １ ~C ６ (per)fluoroalkylethylene according to the formula (per)fluorooxyalkyl), chloro-, and / or bromo-, and / or iodo-C, such as chlorotrifluoroethylene; ２ ~C ６ fluoroolefins, - Formula CF ２ =CFOR ｆ１ (In the formula, R ｆ１ is C １ ~C ６ Fluoro or perfluoroalkyl, such as —CF ３ , -C ２ F ５ , -C ３ F ７ fluoroalkyl vinyl ethers according to - Formula CH ２ =CFOR ｆ１ (In the formula, R ｆ１ is C １ ~C ６ Fluoro or perfluoroalkyl, such as —CF ３ , -C ２ F ５ , -C ３ F ７ a hydrofluoroalkyl vinyl ether according to - Formula CF ２ =CFOX ０ (In the formula, X ０ is C １ ~C １２ C having one or more ether groups, such as oxyalkyl or perfluoro-2-propoxy-propyl １ ~C １２ fluoro-oxyalkyl vinyl ethers according to the formula (I), wherein the fluoro-oxyalkyl vinyl ether is (per)fluorooxyalkyl; - Formula CF ２ = CFOCF ２ OR ｆ２ (In the formula, R ｆ２ is C １ ~C ６ Fluoro or perfluoroalkyl, such as —CF ３ , -C ２ F ５ , -C ３ F ７ or -C ２ F ５ -O-CF ３ C having one or more ether groups, such as １ ~C ６ fluoroalkyl-methoxy-vinyl ethers according to the formula (I), wherein the fluoroalkyl-methoxy-vinyl ether is (per)fluorooxyalkyl; - Formula CF ２ =CFOY ０ (In the formula, Y ０ is C １ ~C １２ Alkyl or (per)fluoroalkyl or C １ ~C １２ Oxyalkyl or C １ ~C １２ (per)fluorooxyalkyl, ０ groups containing carboxylic acid or sulfonic acid groups in their acid, acid halide or salt form), - Formula: 【Transformation 6】 (In the formula, R ｆ３ , R ｆ４ , R ｆ５ , R ｆ６ are equal to or different from each other and independently comprise a C containing a fluorine atom, optionally one or more oxygen atoms. １ ~C ６ Fluoro or per(halo)fluoroalkyl, such as —CF ３ , -C ２ F ５ , -C ３ F ７ , -OCF ３ , -OCF ２ CF ２ OCF ３ is) Fluorodioxole The polymer (P) according to claim 7, selected from the group consisting of:

10. A repeating unit derived from compound (AX) and at least one C ２ ~C ８ a repeating unit derived from a perfluoroolefin, preferably tetrafluoroethylene, and a repeating unit of formula CF ２ =CFOY ０ and repeat units derived from at least one functional fluoro-alkyl vinyl ether of (j) Formula: CF ２ =CF-O-(CF ２ ) ｍ’ SO ２ X', where m' is an integer from 1 to 10, preferably from 1 to 6, more preferably from 2 to 4, even more preferably m is equal to 2, and X' is selected from among the halogens (Cl, F, Br, I), preferably F, -O － M' ＋ and M' ＋ Is, H ＋ , N.H. ４ ＋ , K. ＋ , Li ＋ , Na ＋ or a mixture thereof, preferably M' ＋ Is, H ＋ a sulfonyl halide fluorovinyl ether of the formula (jj) Formula: CF ２ =CF-(OCF ２ CF (R Ｆ１ )) ｗ -O-CF ２ (CF(R Ｆ２ )) ｙ SO ２ X' (wherein X' is selected from halogens (Cl, F, Br, I), preferably F, -O － M' ＋ and M' ＋ Is, H ＋ , N.H. ４ ＋ , K. ＋ , Li ＋ , Na ＋ or a mixture thereof, preferably M' ＋ Is, H ＋ where w is an integer from 0 to 2, and R Ｆ１ and R Ｆ２ are equal to or different from each other and independently represent C optionally substituted with F, Cl or one or more ether oxygens; １ ~C １０ fluoroalkyl group, y is an integer from 0 to 6, preferably w is 1, and R Ｆ１ is -CF ３ y is 1, and R Ｆ２ is F) The polymer (P) according to claim 6, selected from the group consisting of:

11. The at least one functional fluoro-alkyl vinyl ether has the formula (FM1): 【Transformation 7】 (wherein m' is an integer of 1 to 10, preferably 1 to 6, more preferably 2 to 4, and X' is a halogen (Cl, F, Br, I), -O － M' ＋ and M' is selected from ＋ Is, H ＋ , N.H. ４ ＋ , K. ＋ , Li ＋ , Na ＋ or a mixture thereof, preferably X'=-O － H) 11. The polymer (P) according to claim 10, selected from:

12. - 10 to 20 mol % of repeating units derived from compound (AX), - 60 to 70 mol % of repeat units derived from tetrafluoroethylene, 15 to 25 mol % of formula (FM1-D): 【Transformation 8】 and a repeating unit derived from a functional fluoro-alkyl vinyl ether of The polymer (P) according to claim 6, comprising:

13. 7. A process for producing the polymer (P) according to claim 6, comprising the steps of: (i) at least one compound (AX) according to claim 1, (ii) at least one fluoromonomer (FM); A process comprising polymerizing a monomer mixture (MM) comprising:

14. 7. A process for chemically modifying a polymer (P) according to claim 6, comprising: modifying the xanthate moiety of the repeating unit derived from a compound (AX), i.e., a compound of the formula 【Chemistry 9】 to the group -SH.

15. 15. The process according to claim 14, wherein the hydrolysis is carried out by reacting the polymer (P) with an acid or a base in an aqueous solution.

16. 7. A process for chemically modifying a polymer (P) according to claim 6, comprising: modifying the xanthate moiety of the repeating unit derived from a compound (AX), i.e., a compound of the formula 【Chemistry 10】 The site is a group -SO ３ A process comprising oxidation to H.

17. 17. The process according to claim 16, wherein the oxidation is carried out by reacting the polymer (P) with an oxidizing agent, preferably hydrogen peroxide.

18. Formula (VII): 【Chemistry 11】 wherein w is either 0 or 1, Q is an integer from 1 to 4, preferably 1 or 2, and X' is selected from halogens, preferably F or -O. － M' ＋ and M' ＋ Is, H ＋ , N.H. ４ ＋ , K. ＋ , Li ＋ , Na ＋ or a mixture thereof, preferably M' ＋ Is, H ＋ wherein n and p are, independently of one another, integers greater than 0, m is greater than or equal to 0, and m, n, and p represent the mole fraction of each monomer in the polymer. Polymer (P ｏｘ ).

19. The polymer (P) according to claim 6 or the polymer (P) according to claim 18 ｏｘ ) items.

20. 20. The article of claim 19, which is a membrane for use in an electrolysis cell or a fuel cell.

21. Formula (I): 【Chemistry 12】 (In the formula, R ａ is a (per)fluoroallyl group, and R ｂ is a linear or branched alkyl group) Use of the compound (AX) of formula (I) as a chain transfer agent in controlled radical polymerization.

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