Process for manufacture of aqueous dispersions comprising fluorinated polymer (F) particles

Abstract

The present invention relates to a process for the manufacture of an aqueous dispersion comprising particles of a fluorinated polymer (F) comprising at least repeating units derived from a C2-C3 hydrofluoroolefin (HFO), said process comprising the radical polymerization of at least one C2-C3 hydrofluoroolefin (HFO) in an aqueous medium in the presence of at least one partially fluorinated surfactant (S), and to a latex obtained by said process.

Description

[0001] This application claims priority to European patent application filed in Europe on June 23, 2022 under number 22180673.0, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to a process for the manufacture of an aqueous dispersion comprising particles of a fluorinated polymer (F) using at least one partially fluorinated surfactant (S) and to a latex obtained by such a process.

[0003] Known methods for preparing fluorinated polymers are aqueous polymerizations involving fluorinated surfactants. For exemplary purposes only, such methods are described in WO 2018 / 189091 and WO 2018 / 189092 of Solvay Specialty Polymers Italy Spa.

[0004] It is well known that the use of certain fluorinated surfactants may be limited for environmental reasons due to non-biodegradability within an acceptable range of time or conditions. Therefore, there is a continuing need for new surfactants suitable for use in the preparation of fluorinated polymers by aqueous polymerization processes in the presence or absence of nucleating agents, having improved biodegradability characteristics.

[0005] Non-fluorinated surfactants such as alkyl phosphates, alkyl sulfonates, alkyl sulfates, or alkyl carboxylates are generally unsuitable for aqueous free radical polymerization of fluorinated or partially fluorinated monomers because they carry H atoms that can be abstracted by free radical species during the polymerization process. These transfer reactions lead to fluorinated polymers with low molecular weight and therefore impaired properties.

[0006] Therefore, there is a need for new surfactants which are suitable for preparing fluorinated polymers by aqueous free radical polymerization processes in the presence or absence of nucleating agents, which undergo only limited transfer reactions and which ensure good stability of the resulting aqueous dispersions of fluorinated polymers.

[0007] It has surprisingly been found that the partially fluorinated surfactants according to the present invention are highly degradable while being suitable for the manufacture of aqueous dispersions comprising fluorinated polymer particles by an aqueous free radical polymerization process.

[0008] The present invention relates to a process for producing an aqueous dispersion comprising particles of a fluorinated polymer (F) comprising at least repeating units derived from C2-C3 hydrofluoroolefins (HFO), said process comprising the step of adding a prepolymer selected from the group consisting of: n-CFX-P (II), and a partially fluorinated surfactant (S) of the group consisting of a compound of formula (III) R-CF (-P) 2, wherein at least one C2-C3 hydrofluoroolefin (HFO) is free radically polymerized in an aqueous medium,

[0009] -R is an optionally branched C3-C 16 an alkyl or alkenyl chain, which optionally contains one or more than one catenary heteroatoms selected from N, O and S, optionally contains a carbonyl group, optionally contains one or more than one halogen atom selected from Cl, Br and I, and optionally contains a C3-C8 aliphatic ring,

[0010] -n is an integer from 2 to 16

[0011] --P represents -COO-M, -SO3-M or -PO3-M, wherein M is H, or an alkali metal, or an ammonium group N(R')4, wherein R' is the same or different at each occurrence and is a hydrogen atom or a C1-C6 hydrocarbon group, preferably an alkyl group, and

[0012] -X is H or F.

[0013] Typically, the surfactant (S) conforms to the formula (I) R-CFX-P (I), the formula (II) P-CFX-(CH2) n -CFX-P(II), or formula (III) R-CF(-P)2, wherein

[0014] -R is an optionally branched C3-C 16 an alkyl or alkenyl chain, which optionally contains one or more than one catenary heteroatoms selected from N, O and S, optionally contains a carbonyl group, optionally contains one or more than one halogen atom selected from Cl, Br and I, and optionally contains a C3-C8 aliphatic ring,

[0015] -n is an integer from 2 to 16,

[0016] --P represents -COO-M, -SO3-M or -PO3-M, wherein M is H, or an alkali metal, or an ammonium group N(R')4, wherein R' is the same or different at each occurrence and is a hydrogen atom or a C1-C6 hydrocarbon group, preferably an alkyl group, and

[0017] -X is H or F.

[0018] In some embodiments, M is an ammonium group, more preferably an NH 4 group.

[0019] In some preferred embodiments, -P represents -COO-M and in more preferred embodiments, -P represents -COO-NH4.

[0020] In some embodiments, R is a linear C3-C 16 Fully hydrogenated alkyl chains.

[0021] In some other embodiments, R is an optionally branched C3-C 16 An alkyl or alkenyl chain comprising a carbonyl group.

[0022] In still other embodiments, R is an optionally branched C3-C 16 An alkyl or alkenyl chain comprising one or more than one catenary heteroatom selected from N, S and S, for example R comprises one or more than one ether group, R comprises one or more than one thioether group or R comprises one or more than one amine group.

[0023] In some embodiments, R is an optionally branched C3-C 16 An alkyl or alkenyl chain comprising catenary N atoms and a carbonyl group, for example R comprises an amide group.

[0024] In some other embodiments, R is an optionally branched C3-C 16 an alkyl or alkenyl chain comprising a linear O atom and a carbonyl group, for example R comprises an ester group,

[0025] In still other embodiments, R is an optionally branched C3-C 16 An alkyl or alkenyl chain comprising one or more than one halogen atom selected from Cl, Br and I.

[0026] In some embodiments, R is an optionally branched C3-C 16 An alkyl or alkenyl chain comprising a C3-C8 aliphatic ring, for example, comprising a C6 aliphatic ring. In some embodiments, the surfactant (S) is selected from the group consisting of: R-CFH-COO-NH4, 4HN-OOC-CFH-(CH2) n -CFH-COO-NH4 and R-CFH-(COO-NH4)2, wherein R and n are as described above.

[0027] Good results were obtained using a surfactant (S) of CH3(CH2)7CFHCOO-NH4.

[0028] In some embodiments, the surfactant (S) is selected from the group consisting of: R-CFH-COO-NH4 and R-CFH-(COO-NH4)2, wherein R is as described above and R comprises a carbonyl group.

[0029] In some preferred embodiments, the surfactant (S) is CH3-CO-(CH2)7CFHCOO-NH4.

[0030] For illustrative purposes, the surfactant (S) according to the present invention can be synthesized according to the following reaction scheme:

[0031]

[0032] wherein X is H or F, R0′ is a C1-C3 hydrogenated alkyl chain, preferably ethyl, and R0 is a C1-C 14 A hydrogenated optionally branched alkyl chain which optionally comprises a carbonyl group.

[0033] ICFXCOORO' can be prepared from the bromide or chloride analog (BrCFXCOORO' or ClCFXCOORO') according to the reaction pathways described in Journal American Chemical Society, 2001, Vol. 123, No. 30, pp. 7207-7219 or Journal of Chemical Society, Perkin Trans. 1, 1996, 1741-47.

[0034] The addition of the iodinated derivative to the unsaturated compound as shown in step 1) of reaction (i) can be carried out using Fe in tetrahydrofuran as described in Journal of Chemical Society, Perkin Trans. 1, 1996, 1741-47. Other methods can be used, such as methods involving the use of sodium dithionite Na2S2O4, as described in Journal of Fluorine Chemistry, 2005, 126, pp. 63-67. Examples of syntheses involving unsaturated compounds containing electron withdrawing groups such as carbonyl groups can be found in Journal of Chemical Society, Perkin Trans. 1, 1996, 1741-47.

[0035] Further reduction by Zn in acetic acid as shown in i) step 2) is described in Journal of Chemical Society, Perkin Trans. 1, 1996, 1741-47 or Journal of Fluorine Chemistry, 1992, Vol. 59, pp. 9-14.

[0036] The recovery of carboxylic acids from alkyl esters (eg ethyl esters) as shown in (ii) is described, for example, in Tetrahedron, 1994, Vol. 50, No. 33, pp. 9847-9864.

[0037] The preparation of ammonium carboxylate salts as described in (iii) is well known to those skilled in the art.

[0038] Other methods may be used to prepare the surfactant (S). Without limitation and for illustrative purposes, a route to the preparation of the intermediate ethyl ester of formula R-CH2CH2CFXCOOEt that does not involve the use of ICFXCOOEt can be found in Tetrahedron, 1994, Vol. 50, No. 33, pp. 9847-9864.

[0039] The biodegradability of the surfactant (S) is evaluated according to the carbon dioxide (CO2) evolution test (reference TG301 B) described by the OECD (Organization for Economic Co-operation and Development) in the "OECD Guideline for testing of chemicals No. 301B": https: / / read.oecd-ilibrary.org / environment / test-no-301-ready-biodegradability_9789264070349-en#page18.

[0040] According to this method, a solution of the test substance in a mineral medium is inoculated into activated sludge and incubated under aerobic conditions. Degradation is then determined by measuring the actual CO2 production compared to the theoretical CO2 that would be produced if the test compound were fully mineralized. CO2 measurements are made at a frequency that allows the start and end of biodegradation to be identified.

[0041] Reference compounds known to be biodegradable were run in parallel to check the validity of the procedure. The mean value of biodegradation was calculated based on the results obtained from 4 replicates.

[0042] According to "Guidelines for the testing of chemicals. Revised introduction to the OECD guidelines for testing of chemicals, Section 3, Part 1, Chapter 2.3 (adopted on March 23, 2006)":

[0043] A single-ingredient chemical is found to be readily biodegradable if the following two conditions are met:

[0044] 1) It produces at least 60% biodegradation within 28 days;

[0045] 2) Achieving the pass level within 10 days after achieving 10% biodegradation (10-day window).

[0046] Chemicals that produced at least 60% biodegradation results within 28 days but did not meet the 10-day window criterion were concluded to be not readily biodegradable, however they were still considered ultimately biodegradable, meaning they were expected to be fully mineralized in the environment.

[0047] For chemicals that do not achieve 60% biodegradation within 28 days, the enhanced ready biodegradability test is expected to extend the test time to up to 60 days (see ECHA Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7b: Endpoint specific guidance Version 4.0 (June 2017) and ECHA Guidance on Information Requirements and Chemical Safety Assessment - Chapter R.11: PBT / vPvB assessment Version 3.0, June 2017). A result of at least 60% biodegradation within 60 days is part of the evidence that the tested item is not persistent. Chemicals that do not produce a result of at least 60% biodegradation within 60 days are potentially persistent and require further evaluation to conclude on their persistence properties.

[0048] Typically, the partially fluorinated surfactants according to the present invention at least meet the pass level criterion of 60% biodegradation, which supports the absence of persistence.

[0049] Surprisingly, the partially fluorinated surfactants carrying -CHF- groups according to the present invention meet both of the above conditions, namely at least 60% biodegradation within 28 days and the 10-day window criterion.

[0050] Furthermore, it has been found that the partially fluorinated surfactants (S) according to the invention are very suitable for use in a process for the manufacture of an aqueous dispersion comprising particles of a fluorinated polymer (F) comprising at least repeating units derived from a C2-C3 hydrofluoroolefin (HFO), said process comprising the free radical polymerization of at least one C2-C3 hydrofluoroolefin (HFO) in an aqueous medium.

[0051] Without being bound by any theory, it seems that the one or more F atoms on the alpha carbon of the salt of the polar acidic group of the surfactant (S) according to the invention tend on the one hand to limit transfer reactions during the free radical polymerization of the fluorinated monomer and on the other hand to allow the surfactant (S) to stabilize the aqueous dispersion of the fluorinated polymer (F).

[0052] One or more surfactants (S) as defined above may be added to the aqueous free-radical polymerization medium of the process of the invention in a total amount advantageously ranging from 0.001 to 20% by weight, based on the weight of the aqueous polymerization medium.

[0053] Typically, the fluorinated polymer (F) comprises at least recurring units derived from a C2-C3 hydrofluoroolefin (HFO) and is obtained by free radical polymerization of at least one C2-C3 hydrofluoroolefin (HFO) in an aqueous medium.

[0054] The C2-C3 hydrofluoroolefin (HFO) according to the present invention is typically selected from the group consisting of vinylidene fluoride (VDF), vinyl fluoride, cis-1,2-difluoroethylene, trans-1,2-difluoroethylene, trifluoroethylene, 2,3,3,3-tetrafluoropropylene, cis-1,3,3,3-tetrafluoropropylene, trans-1,3,3,3-tetrafluoropropylene, cis-1,2,3,3-tetrafluoropropylene, trans-1,2,3,3-tetrafluoropropylene, 1,1,3,3-tetrafluoropropylene, 1,1,2,3-tetrafluoropropylene, 1,1,2,3-tetrafluoropropylene, 1,1,2,3-tetrafluoropropylene, 1,1,2,3-tetrafluoropropylene, 1,1,2,3-tetrafluoropropylene, 1,1,2,3-tetrafluoropropylene, 1,1,2,3-tetrafluoropropylene, 1,3 ... Fluoropropylene, cis-1,2,3,3,3-pentafluoropropylene, trans-1,2,3,3,3-pentafluoropropylene, 1,1,3,3,3-pentafluoropropylene, 1,1,2,3,3-pentafluoropropylene, 3,3,3-trifluoropropylene, 2,3,3-trifluoropropylene, cis-1,3,3-trifluoropropylene, trans-1,3,3-trifluoropropylene, cis-1,2,3-trifluoropropylene, trans-1,2,3-trifluoropropylene, 1,1,3-trifluoropropylene, 1,1,2-trifluoropropylene and mixtures thereof.

[0055] Preferably, the C2-C3 hydrofluoroolefin (HFO) is vinylidene fluoride (VDF) or 2,3,3,3-tetrafluoropropene, preferably it is vinylidene fluoride (VDF).

[0056] In some embodiments, the fluorinated polymer (F) consists essentially of repeating units derived from vinylidene fluoride (VDF).

[0057] In some other embodiments, the fluorinated polymer (F) further comprises repeating units derived from at least one additional fluorinated monomer and is thus obtained by free radical polymerization of at least one C2-C3 hydrofluoroolefin (HFO) and the at least one additional fluorinated monomer in an aqueous medium.

[0058] By additional fluorinated monomer is meant an ethylenically unsaturated monomer comprising at least one fluorine atom. The choice of such additional fluorinated monomer is not particularly limited and any fluorinated monomer may be used.

[0059] The additional fluorinated monomers may further comprise one or more other halogen atoms (Cl, Br, I) and may be partially or fully halogenated.

[0060] Non-limiting examples of additional (per)fluorinated monomers include:

[0061] - C2-C8 perfluoroolefins, such as tetrafluoroethylene (TFE) or hexafluoropropylene (HFP);

[0062] - C2-C8 hydrogenated fluoroolefins, such as vinyl fluoride, 1,2-difluoroethylene and trifluoroethylene (TrFE), hexafluoroisobutylene (HFIB),

[0063] - a perfluoroalkylethylene of the formula CH2=CH-Rf0, wherein Rf0 is a C1-C6 perfluoroalkyl group;

[0064] - chloro- and / or bromo- and / or iodo-C2-C6-fluoroolefins, such as chlorofluoroethylene (CFE) or chlorotrifluoroethylene (CTFE);

[0065] - perfluoroalkyl vinyl ether (PAVE) of the formula CF2=CF-O-Rf1, wherein Rf1 is a C1-C6 perfluorinated alkyl group, such as CF3, C2F5, C3F7;

[0066] - partially fluorinated alkyl vinyl ethers of the formula CF2=CF-O-Rf2, wherein Rf2 is a C1-C6 partially fluorinated alkyl group;

[0067] - perfluoroalkoxyalkyl vinyl ether (PAAVE) of the formula CF2=CF-O-X0, wherein X0 is C1-C 12 Perfluorinated alkoxyalkyl;

[0068] - partially fluorinated alkoxyalkyl vinyl ether of the formula CF2=CF-O-X1, wherein X1 is C1-C 12 Partially fluorinated alkoxyalkyl;

[0069] - partially fluorinated fluoroalkoxyalkyl vinyl ether of the formula CF2=CF-O-X2, wherein X2 is C1-C12 Alkoxyalkyl;

[0070] - hydrofluoroalkyl vinyl ethers of the formula CH2=CF-OY, wherein Y is a C1-C6 fluoro- or perfluoroalkyl group, for example -CF3, -C2F5, -C3F7;

[0071] - fluorodioxole, preferably perfluorodioxole;

[0072] - (per)fluoro-methoxy-vinyl ether (MOVE, hereinafter) having the formula:

[0073] CFZ=CZ-O-CF2-O-Rf3

[0074] Wherein, Rf3 is selected from linear or branched C1-C6 (per)fluoroalkyl; C5-C6 cyclic (per)fluoroalkyl; and linear or branched C2-C6 (per)fluorooxyalkyl containing 1 to 3 chain oxygen atoms, and Z = F, H; preferably Z is F, and Rf3 is -CF2CF3 (MOVE1); -CF2CF2OCF3 (MOVE2); or -CF3 (MOVE3).

[0075] In some preferred embodiments, the fluorinated polymer (F) further comprises repeating units derived from at least one monomer selected from the group consisting of cis-1,2-difluoroethylene, trans-1,2-difluoroethylene, trifluoroethylene (TrFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), chlorofluoroethylene (CFE), chlorotrifluoroethylene (CTFE) and perfluoroalkyl vinyl ether (PAVE) of formula CF2=CF-O-Rf1, wherein Rf1 is a C1-C6 perfluorinated alkyl group.

[0076] Perfluoroalkyl vinyl ether (PAVE) is preferably selected from the group consisting of perfluoromethyl vinyl ether (PMVE) of formula CF2=CF-O-CF3, perfluoroethyl vinyl ether (PEVE) of formula CF2=CF-O-CF2-CF3 and perfluoropropyl vinyl ether (PPVE) of formula CF2=CF-O-CF2-CF2-CF3. Mixtures of different PAVEs can also be used herein.

[0077] In some embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of, repeating units derived from:

[0078] -VDF and TFE;

[0079] -VDF, TFE and CTFE;

[0080] -VDF, TFE and PAVE;

[0081] -VDF, TFE and HFP;

[0082] -VDF, TFE, HFP and PAVE;

[0083] -VDF and TrFE;

[0084] -VDF, TrFE and CFE;

[0085] -VDF, TrFE and CTFE;

[0086] -VDF, TrFE and HFP;

[0087] -VDF and CFE;

[0088] -VDF and CTFE;

[0089] -VDF and HFP;

[0090] - VDF, HFP and PAVE; or

[0091] -VDF, HFP and CTFE.

[0092] In some embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of (in mol %, relative to the total moles of repeating units):

[0093] - 5 to 95% by mole of repeating units derived from vinylidene fluoride (VDF); and

[0094] - 5 to 95% by mole of repeating units derived from at least one further fluorinated monomer.

[0095] In some other embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of:

[0096] - 15 to 35% by mole of repeating units derived from vinylidene fluoride (VDF); and

[0097] - 65 to 85% by mole of repeating units derived from at least one further fluorinated monomer.

[0098] In still some other embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of:

[0099] - 60 to 90% by mole of repeating units derived from vinylidene fluoride (VDF); and

[0100] - 10 to 40% by moles of repeating units derived from at least one further fluorinated monomer.

[0101] In some embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of:

[0102] - 60 to 80% by mole of repeating units derived from vinylidene fluoride (VDF);

[0103] - 15 to 25% by mole of repeating units derived from hexafluoropropylene (HFP); and

[0104] - 5 to 15% by mole of repeating units derived from tetrafluoroethylene (TFE).

[0105] Good results were obtained with a fluorinated polymer (F) consisting of:

[0106] - 70% by mole of repeating units derived from vinylidene fluoride (VDF);

[0107] - 19% by mole of repeating units derived from hexafluoropropylene (HFP); and

[0108] - 11 % by mole of repeating units derived from tetrafluoroethylene (TFE).

[0109] Optionally, the fluorinated polymer (F) of the present invention further comprises repeating units derived from a diene [diene (OF)] having the following general formula:

[0110]

[0111] wherein R1, R2, R3, R4, R5 and R6 are the same or different from each other and are H or C1-C5 alkyl; Z is a linear or branched, optionally containing an oxygen atom, preferably at least partially fluorinated C1-C 18 A hydrocarbon group (including an alkylene group or a cycloalkylene group), or a (per)fluoropolyoxyalkylene group, for example, as described in EP 661304A.

[0112] The diene (OF) is preferably selected from the group consisting of dienes conforming to formula (OF-1), (OF-2) and (OF-3):

[0113] (OF-1)

[0114]

[0115] wherein j is an integer between 2 and 10, preferably between 4 and 8, and R1, R2, R3, R4 are the same as or different from each other and are H, F or C 1-5 Alkyl or (per)fluoroalkyl;

[0116] (OF-2)

[0117]

[0118] wherein each A is the same as or different from each other and, at each occurrence, is independently selected from F, Cl and H; each B is the same as or different from each other and, at each occurrence, is independently selected from F, Cl, H and OR B , where R B is a branched or straight chain alkyl group which may be partially, substantially or completely fluorinated or chlorinated; E is an optionally fluorinated divalent group having 2 to 10 carbon atoms which may be interrupted by an ether bond; preferably, E is -(CF2) m -group, wherein m is an integer from 3 to 5; a preferred diene of type (OF-2) is F2C=CF-O-(CF2)5-O-CF=CF2.

[0119] (OF-3)

[0120]

[0121] wherein E, A and B have the same meanings as defined above; R5, R6, R7 are the same as or different from each other and are H, F or C 1-5 Alkyl or (per)fluoroalkyl.

[0122] Good results were obtained using a diene of the (OF-1) type having the formula H2C=CH-(CF2)6-CH=CH2.

[0123] In some other embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of (in mol %, relative to the total moles of repeating units) the following monomer composition:

[0124] (i) Vinylidene fluoride (VDF) 35%-85%, hexafluoropropylene (HFP) 10%-45%, tetrafluoroethylene (TFE) 0-30%, (per)fluoroalkyl vinyl ether (PAVE) 0-15%; diene (OF): 0-5%;

[0125] (ii) vinylidene fluoride (VDF) 50%-80%, (per)fluoroalkyl vinyl ether (PAVE) 5%-50%, tetrafluoroethylene (TFE) 0-20%, diene olefin (OF): 0-5%;

[0126] (iii) vinylidene fluoride (VDF) 20%-30%, C2-C8 non-fluorinated olefin (Ol) 10%-30%, hexafluoropropylene (HFP) and / or (per)fluoroalkyl vinyl ether (PAVE) 18%-27%, tetrafluoroethylene (TFE) 10%-30%; diene olefin (OF): 0-5%;

[0127] (iv) tetrafluoroethylene (TFE) 45%-65%, C2-C8 non-fluorinated olefin (Ol) 20%-55%, vinylidene fluoride 5%-30%; diene olefin (OF): 0-5%;

[0128] (v) tetrafluoroethylene (TFE) 33%-75%, (per)fluoroalkyl vinyl ether (PAVE) 15%-45%, vinylidene fluoride (VDF) 5%-30%, hexafluoropropylene HFP 0-30%; diene olefin (OF): 0-5%;

[0129] (vi) vinylidene fluoride (VDF) 35%-85%, (per)fluoro-methoxy-vinyl ether (MOVE) 5%-40%, (per)fluoroalkyl vinyl ether (PAVE) 0-30%, tetrafluoroethylene (TFE) 0-40%, hexafluoropropylene (HFP) 0-30%; diene (OF): 0-5%;

[0130] Optionally, the fluorinated polymer (F) of the present invention further comprises iodine and / or bromine cure sites.

[0131] These iodine and / or bromine cure sites may be included as pendant groups attached to the backbone of the fluorinated polymer (F) chain or may be included as terminal groups of said polymer chain.

[0132] According to a first embodiment, the iodine and / or bromine cure sites are included as pendant groups attached to the backbone of the fluorinated polymer (F) chain; the fluorinated polymer (F) according to this embodiment typically comprises repeating units derived from brominated and / or iodinated cure site comonomers selected from:

[0133] - bromine and / or iodine alpha-olefins containing 2 to 10 carbon atoms, such as bromotrifluoroethylene or bromotetrafluorobutene as described, for example, in US 4,035,565 (DuPont) 12 / 07 / 1977, or other bromine and / or iodine alpha-olefins disclosed in US 4,694,045 (DuPont) 15 / 09 / 1987;

[0134] - iodo and / or bromofluoroalkyl vinyl ethers (as described notably in patents US 454662, US 4564662 (MINNESOTA MINING) 14.01.1986 and EP 199138 A (DAIKIN IND LTD) 29.10.1986).

[0135] According to a second embodiment, iodine and / or bromine cure sites, preferably iodine cure sites, are included as end groups of the fluorinated polymer (F) chain; the fluorinated polymer according to this embodiment is typically obtained by adding at least one of the following to the polymerization medium during the manufacture of the fluorinated polymer (F):

[0136] - one or more iodinated and / or brominated chain transfer agents; suitable chain transfer agents are typically of the formula Rf4(I) x (Br) y Those wherein Rf4 is a (per)fluoroalkyl or (per)fluorochloroalkyl group containing 1 to 8 carbon atoms, and x and y are integers between 0 and 2, wherein 1≤x+y≤2 (see, for example, patents US 4243770 (Daikin Industries, Ltd.) 6 / 01 / 1981 and US 4943622 (NIPPON MEKTRON KK) 24 / 07 / 1990); and

[0137] - Alkali metal or alkaline earth metal iodides and / or bromides, as notably described in patent US Pat. No. 5,173,553 (AUSIMONT SRL) of 22 / 12 / 1992.

[0138] Advantageously, to ensure acceptable reactivity, it is generally understood that the iodine and / or bromine content in the fluorinated polymer (F) should be at least 0.05% wt, preferably at least 0.06% wt relative to the total weight of the fluorinated polymer (F).

[0139] On the other hand, the amount of iodine and / or bromine preferably does not exceed 7% wt, more specifically does not exceed 5% wt, or even does not exceed 4% wt, relative to the total weight of the fluorinated polymer (F), these amounts generally being chosen to avoid side reactions and / or adverse effects on thermal stability.

[0140] Typically, the amount of iodine in the fluorinated polymer (F) ranges from 0.05% wt to 7% wt, preferably 0.10% wt to 4.0% wt, relative to the total weight of the fluorinated polymer (F).

[0141] In some preferred embodiments, the iodinated chain transfer agent is of formula I-(CF2) k -I, where k is an integer between 2 and 10.

[0142] Good results were obtained using I-(CF2)4-I as the iodinated chain transfer agent.

[0143] In some embodiments, the fluorinated polymer (F) of the present invention comprises repeating units derived from a diene [diene (OF)] as previously described and an iodine atom as a terminal group.

[0144] Good results were obtained using dienes of the type (OF-1) H2C=CH-(CF2)6-CH=CH2 and I-(CF2)4-I as iodinated chain transfer agents.

[0145] In some embodiments, the process according to the present invention comprising the free radical polymerization of at least one C2-C3 hydrofluoroolefin (HFO) in an aqueous medium in the presence of at least one surfactant (S) is carried out in the presence of at least one non-functional perfluoropolyether (PFPE).

[0146] Any non-functional perfluoropolyether consisting of a sequence of perfluorooxyalkylene units can be advantageously utilized. Typically suitable perfluoropolyethers have neutral end groups and an average molecular weight ranging from 300 to 3000. For example, a suitable non-functional perfluoropolyether corresponds to the following formula:

[0147] i)R g O(CF(CF3)-CF2O) q (CFO(CF3)) r (CF2O) s R g ', having randomly distributed perfluorooxyalkylene units; or

[0148] ii) R g ”O(CF2CF2O) q (CFO(CF3)) r (CF2O) s R g '", where R g and R g ', respectively R g ” and R g '", are -CF3, -C2F5, -C3F7, similarly or differently from each other, and q, r, s, respectively q', r', s', have such values ​​that the above-mentioned conditions on the average molecular weight are satisfied.

[0149] Formula: CF3O (CF2-CF(CF3)O) o (CF2O) p CF3 (where o / p = 20), having an average molecular weight of 450, available from Solvay D02 obtained good results.

[0150] In some embodiments, the method according to the present invention comprising free radical polymerization of at least one C2-C3 hydrofluoroolefin (HFO) in an aqueous medium in the presence of at least one surfactant (S) is carried out in the presence of at least one nucleating agent. Nucleating agent means any agent suitable for promoting latex particle formation and allowing to obtain a fluorinated polymer having a smaller primary particle size than in the absence of the polymerization of the nucleating agent. Nucleating agents are well known to those skilled in the art. For exemplary purposes only, nucleating agents include perfluoropolyether (PFPE) acids or salts thereof and nonionic surfactants such as nonionic hydrocarbon surfactants. Using a nucleating agent corresponding to the formula C3F7O[CF(CF3)CF2O] t Good results have been obtained as nucleating agents with hexafluoropropylene oxide oligomers bearing carboxylic acid groups of CF(CF3)COOH (wherein t is such that the average molecular weight Mw of the oligomer is in the range of 1000 Da to 1500 Da, preferably 1100 Da to 1400 Da).

[0151] Depending on the chemical nature of the nucleating agent, it is usually used in an amount of: equal to or less than 1000 ppm; preferably equal to or less than 500 ppm; more preferably equal to or less than 100 ppm; sometimes equal to or less than 10 ppm (based on aqueous medium). Good results have been obtained using hexafluoropropylene oxide oligomers with carboxylic acid groups in an amount equal to or less than 100 ppm based on aqueous medium.

[0152] Use the available D02 and as previously defined corresponds to the formula C3F7O[CF(CF3)CF2O] t Hexafluoropropylene oxide oligomers with carboxylic acid groups of CF(CF3)COOH gave good results as nucleating agents.

[0153] The free-radical polymerization in aqueous medium is typically carried out at a pressure comprised between 10 and 40 bar, preferably between 11 and 25 bar.

[0154] The polymerization temperature generally depends on, inter alia, the nature of the free radical initiator used to initiate the free radical polymerization.Aqueous free radical polymerization is typically carried out at a temperature comprised between 50°C and 135°C, preferably between 55°C and 130°C.

[0155] Although the selection of free radical initiator is not particularly limited, it should be understood that, since the reaction is carried out in an aqueous medium, a water-soluble free radical initiator is preferably used to initiate and / or accelerate polymerization. However, initiators that are insoluble in water or have poor solubility can also be used in the present invention.

[0156] Both organic and inorganic free radical initiators can be used in the method of the present invention. Suitable inorganic free radical initiators include, but are not limited to, persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, and hydrogen peroxide.

[0157] In addition, organic free radical initiators can be used, and these organic free radical initiators include, but are not limited to: acetylcyclohexane persulfonic acid; diacetyl peroxydicarbonate; dialkyl peroxydicarbonate, such as diethyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate; tert-butyl peroxyneodecanoate; 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); tert-butyl perpivalate; dioctanoyl peroxide; dilauroyl peroxide; 2,2'-azobis(2,4-dimethyl tert-butylperoxy)butane; dicumyl peroxide; di-tert-amyl peroxide; di-tert-butyl peroxide (DTBP); p-methane hydroperoxide; pinane hydroperoxide; cumene hydroperoxide; and tert-butyl hydroperoxide.

[0158] Other suitable free radical initiators include notably halogenated free radical initiators such as chlorocarbon-based and fluoroalkane-based acyl peroxides such as trichloroacetyl peroxide, bis(perfluoro-2-propoxypropionyl) peroxide, [CF3CF2CF2OCF(CF3)COO]2, perfluoropropionyl peroxide, (CF3CF2CF2COO)2, (CF3CF2COO)2, {(CF3CF2CF2)[CF(CF3)CF2O] m CF(CF3)COO}2 (where m = 0-8), [ClCF2(CF2) n COO]2, and [HCF2(CF2) n COO]2 (where n = 0-8); perfluoroalkylazo compounds, such as perfluoroazoisopropane, [(CF3)2CFN=]2, R*N=NR* (where R* is a straight or branched perfluorocarbon group with 1-8 carbons); stable or hindered perfluoroalkyl radicals, such as hexafluoropropylene trimer radical, [(CF3)2CF]2(CF2CF2)C ● Free radicals and perfluoroalkanes.

[0159] Redox systems comprising at least two components forming a redox pair, such as oxalate-permanganate, dimethylaniline-benzoyl peroxide, diethylaniline-benzoyl peroxide and diphenylamine-benzoyl peroxide, can also be used as free radical initiators in the present invention.

[0160] Among the inorganic free radical initiators, particular preference is given to inorganic persulfates, and in particular potassium persulfate and / or ammonium persulfate. Good results have been obtained with ammonium persulfate (APS).

[0161] Among the organic free radical initiators, particular preference is given to peroxides having a self-accelerating decomposition temperature (SADT) above 50° C., such as, for example: di-tert-butyl peroxide (DTBP), di-tert-butyl peroxyisopropyl carbonate, tert-butyl (2-ethylhexyl) peroxycarbonate, tert-butyl peroxy-3,5,5-trimethylhexanoate.

[0162] One or more free-radical initiators as defined above may be added to the aqueous polymerization medium of the process of the invention in a total amount advantageously ranging from 0.001 to 20% by weight, based on the weight of the aqueous polymerization medium.

[0163] Typically a small amount of initiator is introduced into the reactor at the beginning of the polymerization process to get it started, and then additional amounts of initiator are added to the reactor continuously or stepwise until the polymerization reaction is complete.

[0164] In some embodiments, the aqueous dispersion comprising particles of fluorinated polymer (F) containing repeating units derived from at least one C2-C3 hydrofluoroolefin (HFO) obtained by the process according to the invention is in the form of an aqueous latex obtained thereby by aqueous emulsion polymerization.

[0165] The present invention therefore also relates to an aqueous latex obtainable by the process according to the invention as previously described.

[0166] The invention also relates to an aqueous latex comprising at least one fluorinated polymer (F) and at least one partially fluorinated surfactant selected from the group consisting of compounds of formula (I), formula (II) and formula (III) as previously described.

[0167] Typically, the aqueous latex obtained by the process according to the invention comprises from 10 to 30% by weight of a fluorinated polymer (F) as previously described, relative to the total weight of the aqueous latex.

[0168] Typically, the aqueous latex obtained by the process according to the invention comprises the fluorinated polymer (F) in the form of primary particles having an average primary particle size of from 50 to 350 nm as measured according to ISO 22412 (2017).

[0169] "Average primary particle size" means the average size of primary particles of the fluorinated polymer (F) obtainable by aqueous emulsion polymerization.

[0170] For the purposes of the present invention, "primary particles" of fluorinated polymer (F) are intended to be distinguishable from agglomerates of primary particles. An aqueous latex comprising primary particles of fluorinated polymer (F) is advantageously obtainable by a process according to the present invention comprising aqueous emulsion polymerization. Agglomerates of primary particles of fluorinated polymer (F) are typically obtainable by recovery and conditioning steps of fluorinated polymer (F) manufacture such as concentration and / or coagulation of aqueous fluorinated polymer (F) latex and subsequent drying and homogenization to provide fluorinated polymer (F) powder.

[0171] As explained previously, in some embodiments the fluorinated polymer (F) of the present invention comprises iodine and / or bromine curing sites, typically in an amount ranging from 0.05% wt to 7% wt, preferably from 0.10% wt to 4.0% wt relative to the total weight of the fluorinated polymer (F). Such iodine-containing fluorinated polymer (F) can be cured in the presence of at least one peroxide (P) capable of generating free radicals at relatively low temperatures with suitable kinetics.

[0172] Another object of the present invention is therefore the use of the aqueous latex obtained by the process according to the invention in coating applications, for example as a dielectric coating for capacitors or transistors.

[0173] Yet another object of the present invention is the use of the aqueous latex obtained by the process according to the invention in sealing or gasketing applications, for example for automobiles.

[0174] Should the disclosure of any patents, patent applications, and publications incorporated herein by reference conflict with the description of the present application to the extent that it might render a term unclear, the present description shall take precedence.

[0175] Examples

[0176] Preparation of ICHFCOOEt(a)

[0177] At room temperature, ethyl bromofluoroacetate (0.24 mol, 1 equivalent) was added to a stirred solution of anhydrous sodium iodide (0.29 mol, 1.2 equivalents) in anhydrous acetone (240 cm3) in 1 h. After the addition was complete, the reaction mixture was stirred at room temperature overnight. The suspension was diluted with diethyl ether (150 cm3) and filtered with a 0.45 μm PVDF membrane, and the residual solid was filtered with a 2x25 cm 3 The filtered solution was evaporated under vacuum and the residual red oil was dissolved in 150 cm 3 of diethyl ether and 150 cm 3 The organic phase was separated and washed again with demineralized water, then it was separated and dried over Na2SO4.

[0178] The organic phase was distilled under reduced pressure to obtain 50 g of pure ethyl fluoroiodoacetate.

[0179] Ethyl fluoroiodoacetate (90%). Oil, 63°C-70°C, at 11 / 14 Torr.

[0180] Preparation of ethyl 2-fluorodecanoate (b)

[0181] Iron powder (0.06 mol, 0.3 eq.), 1-octene (0.78 mmol, 4 eq.), ethyl fluoroiodoacetate (a) (45 g, 0.19 mol, 1 eq.) and THF (490 cm 3 The heterogeneous mixture of ) was stirred at 70°C-80°C (water bath temperature) under nitrogen for 15 h until the fluoroiodoacetate was completely converted. After cooling to room temperature, zinc (0.29 mol, 1.5 eq.), ethanol (160 cm 3 ) and acetic acid (69cm 3 ), and the reaction was refluxed for another 2 h. The suspension was cooled, filtered on a Gauche D filter, and the solid residue was washed with 2 x 30 cm 3 The filtered solution was concentrated under vacuum to obtain a viscous light yellow oil, which was washed with 300 cm 3 10% NaHCO3 and 300cm 3 The organic layer was separated and then filtered again with 300 cm 3 The aqueous phase was washed with diethyl ether.

[0182] The combined organic layers were washed twice with 10% aqueous NaHCO 3 solution and water, and then dried over Na 2 SO 4 . The solvent was removed under vacuum, and the desired product (b) was isolated as a light yellow oil in 70% yield.

[0183] Preparation of 2-fluorodecanoic acid (c)

[0184] A 1 M solution of ethyl 2-fluorodecanoate (b) (25 g, 0.12 mol, 1 eq.) in methanol was added dropwise to a 150 cm 3 After addition, the solution was stirred at room temperature for 2 h. Methanol was removed under vacuum to obtain a dispersion of a white solid in water, which was filtered on a 0.45 μm PVDF membrane. The collected white solid was filtered using a 2x100 cm 3The isolated white solid was treated with 1.2 equivalents of diluted HCl (11% in water) for 1 h under stirring. Diethyl ether was added to the resulting mixture until 2-fluorodecanoic acid was completely dissolved. After separation, 2x70cm 3 The aqueous phase was extracted with diethyl ether and the collected organic layers were dried over Na2SO4. The solvent was removed under vacuum to give a white crystalline solid in an overall yield of 94%. 1 H and 19 F NMR confirmed it to be the desired product (c).

[0185] Preparation of 2-fluorodecanoic acid ammonium salt aqueous solution (d)

[0186] 2-Fluorodecanoic acid (13 g, 0.068 mol, 1 eq) was charged into a flask with 24 g of water (35% wt aqueous solution) at room temperature. The multiphase mixture was stirred vigorously. Ammonia solution (4.3 g, 0.075 mol, 1.1 eq, title 33%) was added dropwise until the solid residue was completely dissolved while monitoring the temperature and pH (pH = 7-8). 1 H NMR confirmed complete salification of the acid and the concentration of the final solution (35% wt).

[0187] Polymer Materials

[0188] - CH3(CH2)7CHFCOO-NH4 as surfactant was prepared as described above.

[0189] -C6O4 is a commercial perfluorinated surfactant consisting of a mixture of diastereoisomers of 2,2-difluoro-2-{[2,2,4,5-tetrafluoro-5-(trifluoromethoxy)-1,3-dioxolan-4-yl]oxy}ammonium acetate and was used as a comparative surfactant in this paper.

[0190] - The nucleating agent consists of an oligomer of hexafluoropropylene oxide with carboxylic acid groups, the oligomer corresponding to the formula C3F7O[CF(CF3)CF2O] n CF(CF3)COOH, has an average molecular weight Mw of 1300 Da.

[0191] - The nucleating agent and the surfactant are simultaneously introduced into the polymerization reactor in the form of solutions in water, these solutions respectively containing:

[0192] - 30 wt% CH3(CH2)7CHFCOO-NH4, 5 wt% nucleating agent and 65 wt% water; or

[0193] - 30 wt% of the ammonium salt of a perfluorinated C6O4 surfactant, 15 wt% of a nucleating agent and 55 wt% of water.

[0194] -1,4-diiodoperfluorobutane (C4F8I2) was used as a transfer agent in The 15 wt% solution in D02 was introduced into the polymerization reactor.

[0195] - a diene of the formula H2C=CH-(CF2)6-CH=CH2 is reacted with The 33 wt% solution in D02 was introduced into the polymerization reactor.

[0196] - Ammonium persulfate (APS) as initiator was introduced into the polymerization reactor in the form of a 4 wt% solution in demineralized water.

[0197] Example 1: Tripolymer VDF: 70% TFE: 11% HFP: 19% (nominal molar basis)

[0198] In an AISI 316 steel vertical autoclave equipped with baffles and a stirrer operating at 500 rpm, 3.3 1 of demineralized water were introduced. Then 6 ml of a 35% wt / wt aqueous solution of the surfactant CH3(CH2)7CHFCOO-NH4, which contained 5% wt / wt of the above nucleating agent, were introduced. Then 1.5 ml of a 33% vol. 1,4-diiodoperfluorobutane D02 solution, 2 ml of 15% vol. diene of formula H2C=CH-(CF2)6-CH=CH2 The D02 solution was introduced into the reactor. The temperature was then raised to a reaction temperature of 80°C and, when the latter was reached, HFP (hexafluoropropylene) was introduced to produce a pressure change of 12 bar (absolute). Next, a gas mixture of 70% VDF, 11% TFE and 19% HFP (by mole) was added by a compressor until a pressure of 30 bar (absolute) was reached.

[0199] Then, 24 ml of a 4 wt. % solution of ammonium persulfate (APS) in demineralized water were fed in. The polymerization pressure was maintained constant by feeding the above gas mixture.

[0200] When 140 g of the gas mixture was reached, 2 ml of 15% vol. diolefin was added. The D02 solution was introduced into the reactor and then up to 450 g per 120 g of the gas mixture.

[0201] When 390 g of the gas mixture was reached, 9 ml of 33% vol 1,4-diiodoperfluorobutane was added. The D02 solution and 8 ml of a 4 wt. % solution of ammonium persulfate (APS) in demineralized water were fed.

[0202] When 600 g of gas were fed, the reactor was cooled at room temperature, the resulting latex was stripped in an autoclave, and then discharged, degassed and worked up by coagulation.

[0203] The recovered polymer was washed with demineralized water and dried at 90°C for 16 hours.

[0204] Comparative Example 2: Tripolymer VDF: 70% TFE: 11% HPF: 19% (nominal molar basis)

[0205] The same procedure as in previous Example 1 was followed, but 6 ml of a 45% wt / wt aqueous solution of the ammonium salt of the perfluorinated surfactant C6O4 containing 15 wt.% of the above nucleating agent were introduced.

[0206] Coagulation procedure

[0207] Under stirring, 250 ml of latex was poured into 3 liters of 2 g / L Al2(SO4)3 aqueous solution using a dropping funnel. The latex was poured over 10 minutes, causing the water to become slightly opaque. After a few minutes nucleation occurred and larger particles were produced. The water began to become transparent and the particle size increased until the water became completely transparent. The water was then removed by filtration and the resulting flaky polymer was washed by stirring in another volume of water for 10 minutes. The polymer was filtered and washed 5 more times and then dried in an oven at 90°C overnight.

[0208] Table 1: Polymer characterization

[0209]

[0210] * Average particle diameter measured by dynamic light scattering (DLS) according to ISO 22412 (2017), specifically based on photon correlation spectroscopy

[0211] **Monomer composition by 19 F-NMR determination

[0212] ***Glass transition temperature Tg measured by differential scanning calorimetry (DSC)

[0213] **** Average molecular weights Mn (number) and Mw (weight) were measured by gel permeation chromatography (GPC).

[0214] *****Iodine percentage determined by X-ray fluorescence

[0215] From the results compiled in Table 1, it can be seen that the partially fluorinated surfactant CH3(CH2)7CHFCOO-NH4 according to the present invention is suitable for preparing aqueous dispersions of fluorinated polymer particles, which fluorinated polymer comprises repeating units derived from VDF, such as VDF-HFP-TFE copolymers, and whose characteristics such as composition, glass transition and molecular weight are similar to those obtained with fluorinated polymers synthesized using perfluorinated C6O4 surfactants.

[0216] In addition, the partially fluorinated surfactant CH3(CH2)7CHFCOO-NH4 was evaluated according to the carbon dioxide (CO2) release test (OECD / TG 301B). CH3(CH2)7CHFCOO-NH4 meets the definition of a readily biodegradable chemical as it achieves 60% degradation, meeting the 10-day window criterion. In addition, at the end of the test, i.e., 31 days, it showed an average degradation of 71% (see Table 2 below).

[0217] Table 2: Enhanced biodegradability test (OECD / TG 301B)

[0218]

[0219] *Individual results of 4 tests: A: 70%, B: 80%, C: 64%, D: 72%

[0220] Therefore, the partially fluorinated surfactant CH3(CH2)7CHFCOO-NH4 is suitable for preparing fluorinated polymers by free radical polymerization in aqueous media and stabilizing the dispersion of the resulting fluorinated polymer, while advantageously being a readily biodegradable chemical.

Claims

1. A method for producing an aqueous dispersion comprising particles of a fluorinated polymer (F) comprising repeating units derived from a C2-C3 hydrofluoroolefin (HFO), the method comprising adding a fluorinated polymer (F) to at least one of the following: n -CFX-P, and a partially fluorinated surfactant (S) of the group consisting of a compound of formula (III): R-CF(-P)2, wherein at least one C2-C3 hydrofluoroolefin (HFO) is free radically polymerized in an aqueous medium, -R is an optionally branched C3-C 16 an alkyl or alkenyl chain, which optionally contains one or more than one catenary heteroatoms selected from N, O and S, optionally contains a carbonyl group, optionally contains one or more than one halogen atom selected from Cl, Br and I, and optionally contains a C3-C8 aliphatic ring, -n is an integer from 2 to 16, --P represents -COO-M, -SO3-M or -PO3-M, wherein M is H, or an alkali metal, or an ammonium group N(R')4, wherein R' is the same or different at each occurrence and is a hydrogen atom or a C1-C6 hydrocarbon group, preferably an alkyl group, and -X is H or F.

2. The method according to claim 1, wherein: The C2-C3 hydrofluoroolefin (HFO) is selected from the group consisting of vinylidene fluoride (VDF), vinyl fluoride, cis-1,2-difluoroethylene, trans-1,2-difluoroethylene, trifluoroethylene, 2,3,3,3-tetrafluoropropylene, cis-1,3,3,3-tetrafluoropropylene, trans-1,3,3,3-tetrafluoropropylene, cis-1,2,3,3-tetrafluoropropylene, trans-1,2,3,3-tetrafluoropropylene, 1,1,3,3-tetrafluoropropylene, 1,1,2,3-tetrafluoropropylene , cis-1,2,3,3,3-pentafluoropropylene, trans-1,2,3,3,3-pentafluoropropylene, 1,1,3,3,3-pentafluoropropylene, 1,1,2,3,3-pentafluoropropylene, 3,3,3-trifluoropropylene, 2,3,3-trifluoropropylene, cis-1,3,3-trifluoropropylene, trans-1,3,3-trifluoropropylene, cis-1,2,3-trifluoropropylene, trans-1,2,3-trifluoropropylene, 1,1,3-trifluoropropylene, 1,1,2-trifluoropropylene and mixtures thereof.

3. The method according to claim 1 or 2, wherein: The C2-C3 hydrofluoroolefin (HFO) is vinylidene fluoride or 2,3,3,3-tetrafluoropropene, preferably vinylidene fluoride.

4. A method according to any one of the preceding claims, wherein: The partially fluorinated surfactant (S) is CH3(CH2)7CHFCOO-NH4 or CH3-CO-(CH2)7CFHCOO-NH4.

5. A method according to any one of the preceding claims, wherein: The fluorinated polymer (F) further comprises repeating units derived from at least one additional fluorinated monomer.

6. The method according to claim 5, wherein: The at least one additional fluorinated monomer is selected from the group consisting of cis-1,2-difluoroethylene, trans-1,2-difluoroethylene, trifluoroethylene (TrFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), chlorofluoroethylene (CFE), chlorotrifluoroethylene (CTFE) and a monomer of the formula CF2=CF-OR f1 Perfluorinated alkyl vinyl ether (PAVE), wherein R f1 It is a C1-C6 perfluorinated alkyl group.

7. A method according to any one of the preceding claims, wherein: The fluorinated polymer (F) consists essentially of repeating units derived from: -VDF and TFE; -VDF, TFE and CTFE; -VDF, TFE and PAVE; -VDF, TFE and HFP; -VDF, TFE, HFP and PAVE; -VDF and TrFE; -VDF, TrFE and CFE; -VDF, TrFE and CTFE; -VDF, TrFE and HFP; -VDF and CFE; -VDF and CTFE; -VDF and HFP; - VDF, HFP and PAVE; or -VDF, HFP and CTFE.

8. A method according to any one of the preceding claims, wherein: The fluorinated polymer (F) further comprises repeating units derived from at least one diene [diene (OF)] having the general formula: wherein R1, R2, R3, R4, R5 and R6 are the same or different from each other and are H or C1-C5 alkyl; Z is a linear or branched, optionally containing an oxygen atom, preferably at least partially fluorinated C1-C 18 A hydrocarbon group (including an alkylene group or a cycloalkylene group), or a (per)fluoropolyoxyalkylene group.

9. A method according to any one of the preceding claims, wherein: The fluorinated polymer (F) contains iodine.

10. The process according to any one of the preceding claims, which is carried out in the presence of at least one non-functional perfluoropolyether.

11. The process according to any one of the preceding claims, which is carried out in the presence of at least one nucleating agent.

12. A method according to any one of the preceding claims, wherein: The aqueous dispersion comprising the fluorinated polymer (F) particles is an aqueous latex.

13. An aqueous latex obtainable by a process according to any one of the preceding claims.

14. An aqueous latex comprising at least one fluorinated polymer (F) comprising repeating units derived from a C2-C3 hydrofluoroolefin (HFO) and at least one partially fluorinated surfactant (S) selected from the group consisting of: n -CFX-P(II), and a compound of formula (III) R-CF(-P)2, wherein -R is an optionally branched C3-C 16 an alkyl or alkenyl chain, which optionally contains one or more than one catenary heteroatoms selected from N, O and S, optionally contains a carbonyl group, optionally contains one or more than one halogen atom selected from Cl, Br and I, and optionally contains a C3-C8 aliphatic ring, -n is an integer from 2 to 16, --P represents -COO-M, -SO3-M or -PO3-M, wherein M is H, or an alkali metal, or an ammonium group N(R')4, wherein R' is the same or different at each occurrence and is a hydrogen atom or a C1-C6 hydrocarbon group, preferably an alkyl group, and -X is H or F.

15. The aqueous latex according to claim 13 or 14, wherein The fluorinated polymer (F) is in the form of primary particles having an average primary particle size as measured according to ISO 22412 of 50 to 350 nm.

16. Use of the aqueous latex according to any one of claims 13 to 15 in coating, sealing or gasketing applications.

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