Surfactant and use thereof, preparation method for fluoropolymer, and fluoropolymer composition

Abstract

A surfactant and the use thereof, a preparation method for a fluoropolymer, and a fluoropolymer composition. The surfactant comprises a monophosphate, wherein the monophosphate contains an arylphenolic group having an alkyl chain substituent, and does not contain methyl, methylene or methine directly linked to an aromatic ring group. The surfactant does not contain methine. The methylene content of the surfactant is less than 20% in terms of the number of carbon atoms. The surface tension of a neutral aqueous solution containing 1 wt% of the surfactant is 26 mN / m to 31 mN / m.

Description

Surfactants and uses thereof, method for preparing fluorine-containing polymers, fluorine-containing polymer composition

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. 202411352400.9, filed on September 26, 2024, entitled “A low-tension surfactant and uses thereof” and Chinese Patent Application No. 202411352461.5, filed on September 26, 2024, entitled “A method for preparing fluorine-containing polymers”, the contents of which are hereby incorporated by reference in their entirety. TECHNICAL FIELD

[0003] The present application relates to the field of surfactants, in particular to a surfactant and uses thereof, a method for preparing fluorine-containing polymers, and a fluorine-containing polymer composition. BACKGROUND

[0004] Fluorine-containing surfactants, such as PFAS surfactants (PFAS corresponds to the Chinese full name of Per-and polyfluoroalkyl substances, the English full name of Per-and polyfluoroalkyl substances), have extremely low surface tension (<25 mN / m) and high bond energy (>480 kJ / mol). Compared with non-fluorine surfactants, they play an irreplaceable role in high-end application fields such as semiconductor manufacturing, fluorine-containing polymer synthesis, aerospace firefighting, advanced electroplating, and functional fabric finishing. However, PFAS surfactants have persistence, bioaccumulation, and high toxicity, which have caused serious environmental problems and attracted widespread attention from the public and regulatory agencies. Since 2021, the United States, the European Union, and China have successively announced action plans to restrict the use of PFAS substances. Therefore, it is of great significance to explore new non-fluorine surfactants to replace PFAS surfactants.

[0005] Phosphate surfactants are a class of surfactants containing phosphate groups, with a lower lower limit of surface tension, as low as 25 mN / m, and are widely used in coatings, inks, daily chemicals, papermaking, and pesticides. Special octyl phenol phosphate ester, bis-p- special octyl phenol phosphate ester is mainly used in metal ion extraction (Nippon Kogyo Kaishi 1988, 104, 601-605), lubrication (US3174932), cleaning (US5868799A), and ion-selective electrode (Analytica Chimica Acta 1976, 85, 261-276). In addition, phosphate surfactants generally have good biodegradability, can be quickly degraded in the natural environment, reduce pollution to the environment, and have the potential to become an environmentally friendly substitute for PFAS.

[0006] However, the carbon-hydrogen bond energy of the mainstream phosphate surfactant is generally low, which is difficult to cover the application scene requirements of PFAS surfactant. Therefore, it is necessary to further study the phosphate surfactant.

[0007] Further, fluoropolymers are mainly prepared by heterogeneous polymerization in aqueous systems, such as emulsion polymerization, suspension polymerization and microemulsion polymerization, etc. As one of the most commonly used synthesis methods of fluoropolymers, emulsion polymerization usually needs to add surfactants for dispersing and stabilizing fluorine-containing monomers and fluorine-containing polymerization products in the aqueous phase, therefore, the selection of surfactants is very important. At present, the most commonly used surfactants in the synthesis process of fluoropolymers are PFOA (Chinese full name is perfluorooctanoic acid, English full name is Perfluorooctanoic Acid) and GenX (Chinese full name is hexafluoropropylene oxide dimer acid ammonium salt, English full name is Hexafluoropropylene oxide dimer acid ammonium salt). These two types of surfactants have highly fluorinated structures, and the bond energy of C-F bond is as high as 480 kJ / mol, which inhibits the chain transfer reaction between the growing high activity free radicals at the end of the polymer chain and the surfactants. In addition, fluorinated surfactants have lower surface tension, which can effectively stabilize the emulsion in the polymerization system and prevent coagulation and demulsification during the polymerization reaction or after the polymerization is completed. Although fluorinated surfactants have the advantages of low surface tension and high stability, their ultra-long degradation half-life will circulate in the ecosystem and accumulate in the human body, seriously endangering ecological safety and human health. Since 2004, the European Union has issued a PFAS (Perfluorinated and Polyfluorinated Alkyl Compounds) proposal, and more and more fluorinated compounds have been included in it. Therefore, it is of great significance for environmental protection to replace fluorinated surfactants with low-toxicity and easily degradable non-fluorinated surfactants for the synthesis of fluoropolymers.

[0008] At present, the existing patents disclose the technology of synthesizing fluorine-containing polymers with non-fluorine-containing surfactants. The patent CN113490717A of Wu Yu Company synthesizes a vinylidene fluoride polymer composition by using non-fluorine-containing surfactants. The non-fluorine-containing surfactants contain polyethylene glycol segments and polypropylene glycol segments, which can maintain good polymerization stability and improve the polymerization yield in the synthesis of the vinylidene fluoride polymer. The vinylidene fluoride polymer composition is not easy to produce foaming when used, and is convenient to operate. The patent CN103717624A of Arkema Company synthesizes fluorine-containing polymers by using one or more alkyl sulfate non-fluorine-containing surfactants. In addition, the patent CN101243108B of Arkema Company discloses a method for synthesizing fluorine-containing polymers by using polyvinyl phosphoric acid, polyacrylic acid and polyvinyl sulfonic acid as surfactants in the aqueous phase free radical polymerization of fluorine-containing monomers. Both of the two patents mention that the use amount of non-fluorine-containing surfactants can be reduced in the synthesis of fluorine-containing polymers. The patent CN110446723A of Daikin Company synthesizes fluorine-containing polymers by using alkyl carboxylate or alkyl sulfonate as surfactants in the aqueous phase polymerization of fluorine-containing monomers.

[0009] However, the above-mentioned non-fluorine-containing surfactants still have the problem of chain transfer in the preparation of fluorine-containing polymers, so it is necessary to develop non-fluorine-containing surfactants suitable for fluorine-containing polymers. SUMMARY

[0010] In order to meet the low surface tension while improving the comprehensive bond energy, the inventors of the present application increase the number of methyl groups as much as possible in the molecular structure design of phosphate surfactants, while reducing the content of methylene and methine. The theoretical basis is that methyl is the best group in the non-fluorine organic group in terms of surface performance (Physicochem. Eng. Aspects 1996.114, 321-335), and the carbon-hydrogen bond energy of methyl is about 423 kJ / mol, which is the highest among all sp 3 carbon-hydrogen bonds.

[0011] The phosphate surfactant of the present application refers to a compound containing methyl groups.

[0012] It is particularly noted that the phosphate ester of the present application contains H connected with -P-O- bond or does not contain H connected with -P-O- bond, when containing H connected with -P-O- bond, the H can be substituted by alkali metal, alkali earth metal, ammonium group or substituted ammonium group, alkyl quaternary ammonium, alkyl amine group, pyridine group, imidazole group, the surface tension of the phosphate ester after substitution is almost unchanged, the H after being substituted by alkali metal, alkali earth metal, ammonium group or substituted ammonium group, alkyl quaternary ammonium, alkyl amine group, pyridine group, imidazole group is still phosphate ester in the present application.The phosphate ester of the present application includes phosphate ester containing H connected with -P-O- bond and phosphate ester containing H connected with -P-O- bond substituted by alkali metal, alkali earth metal, ammonium group or substituted ammonium group, alkyl quaternary ammonium, alkyl amine group, pyridine group, imidazole group.

[0013] The technical scheme of the present application is as follows:

[0014] In the first aspect, the present application provides a kind of surfactant, the surfactant includes monophosphate, the monophosphate contains alkyl chain substituent aromatic phenolic group;The monophosphate does not contain methyl, methylene, methine directly connected with aromatic ring group;The surfactant does not contain methine;The methylene content of the surfactant is less than 20% in terms of carbon atom number;The surface tension of neutral aqueous solution containing 1wt% of the surfactant is 26mN / m-31mN / m.

[0015] Further, the structure of the monophosphate is shown in formula (1),

[0016] R1 is C1~C 10 alkyl group;Ar1 is selected from phenyl, diphenyl ether group, biphenyl, pyridyl, pyrrole group, thiophene group, naphthyl, anthracene group;X1 is selected from hydrogen, alkali metal atom, alkali earth metal atom, ammonium group or substituted ammonium group, pyridine group, imidazole group. From the perspective of reducing surface tension, solubility, preferably, R1 is selected from C1-C4 alkyl group;Ar1 is selected from phenyl, diphenyl ether group;X1 is selected from hydrogen, alkali metal atom, alkali earth metal atom, ammonium group or substituted ammonium group, pyridine group, imidazole group. More preferably, R1 is methylene;Ar1 is phenyl;X1 is selected from hydrogen, alkali metal atom, alkali earth metal atom, ammonium group or substituted ammonium group, pyridine group, imidazole group. More preferably, the monophosphate is selected from p-tocotyl phenol phosphate.

[0017] Further, the surfactant further comprises a bisphosphate, the bisphosphate contains alkyl chain substituent aromatic phenolic group;The bisphosphate does not contain methyl, methylene, methine directly connected with aromatic ring group.

[0018] Further, the structure of the bisphosphate is shown in formula (2),

[0019] R2 is C1-C 10 The alkyl group; Ar2 is selected from phenyl, diphenyl ether, biphenyl, pyridinyl, pyrroleyl, thiophene, naphthyl, anthraceneyl; X2 is selected from hydrogen, alkali metal atom, alkaline earth metal atom, ammonium or substituted ammonium group, pyridinium group, imidazolium group. From the perspective of reducing surface tension and solubility, preferably, R2 is selected from C1-C4 alkyl groups; Ar2 is selected from phenyl, diphenyl ether; X2 is selected from hydrogen, alkali metal atom, alkaline earth metal atom, ammonium or substituted ammonium group, pyridinium group, imidazolium group. More preferably, R2 is methylene; Ar2 is phenyl; X2 is independently selected from hydrogen, alkali metal atom, alkaline earth metal atom, ammonium or substituted ammonium group, pyridinium group, imidazolium group. Even more preferably, the bisphosphate is selected from bis-p-tert-octylphenol phosphate.

[0020] Furthermore, the molar ratio of the monophosphate to the bisphosphate is 100:0-70:30, i.e., ≥2.3; preferably, the molar ratio of the monophosphate to the bisphosphate is 95:5-70:30. Surfactants within this molar ratio range have low surface tension.

[0021] Furthermore, the surfactant is composed of monophosphate and diphosphate.

[0022] The monophosphate ester may also be selected from the following compounds:

[0023] n1≥0.

[0024] The bisphosphate may also be selected from the following compounds:

[0025] n2≥0、

[0026] Where n3≥0, m3>1,

[0027] Where n4≥0 and m4>1.

[0028] Furthermore, the surfactant is composed of p-tert-octylphenol phosphate and bis-tert-octylphenol phosphate.

[0029] Furthermore, the molar ratio of p-tert-octylphenol phosphate to bis-tert-octylphenol phosphate is 100:0-70:30, i.e., ≥2.3; preferably, the molar ratio of p-tert-octylphenol phosphate to bis-tert-octylphenol phosphate is 95:5-70:30. Surfactants within this molar ratio range have low surface tension.

[0030] The characteristic peak position of the p-t-octyl phenol phosphate and bis-p-t-octyl phenol phosphate composition on the nuclear magnetic hydrogen spectrum (DMSO-d6) is 0.65-0.69, 1.25-1.28, 1.64-1.65, 6.95-7.03, 7.12-7.19, and the characteristic peak position on the phosphorus spectrum is -4.8--6.2, -10--12.

[0031] The surface active agent has little effect on the surface tension of the solution.

[0032] Further, the surface active agent is an environmentally friendly substitute for PFAS substances.

[0033] The application also provides a surface active agent as an emulsifier for preparing a fluorine-containing polymer.

[0034] Compared with the prior art, the application has the following beneficial effects:

[0035] The neutral aqueous solution containing 1wt% of the surface active agent provided by the application not only has a low surface tension of 26mN / m-31mN / m, but also has an environmentally friendly performance.

[0036] The surface active agent provided by the application can still maintain excellent surface performance under strong acid and strong base conditions.

[0037] The surface active agent provided by the application can still maintain excellent surface performance under high electrolyte concentration.

[0038] In the second aspect, the application also provides a preparation method of a fluorine-containing polymer, the preparation method comprising the step of water-based emulsion polymerization of one or more fluorinated monomers, wherein the water-based emulsion polymerization is carried out in the presence of at least one surface active agent, and the surface active agent is the surface active agent of the first aspect.

[0039] The addition amount of the surface active agent in the water-based emulsion polymerization reaction meets the emulsion stabilization effect and does not produce or produces little demulsification phenomenon.

[0040] The fluorinated monomer according to the present application is a fluorine-containing compound that can participate in a polymerization reaction. Preferably, the fluorinated monomer is selected from at least one of vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, tetrafluoropropylene, trifluorochloroethylene, 1,1-difluorochloroethylene, 1,2-difluorochloroethylene, perfluoroalkyl ethylene, perfluoroalkyl vinyl ether, perfluoro-n-propyl vinyl ether, perfluoro-methyl vinyl ether, and perfluoro(2,2-dimethyl-1,3-dioxolene); more preferably, the fluorinated monomer is selected from at least one of vinyl fluoride, vinylidene fluoride, trifluoroethylene, hexafluoropropylene, trifluorochloroethylene, 1,1-difluorochloroethylene, perfluoro-n-propyl vinyl ether, perfluoro-methyl vinyl ether, and perfluoro(2,2-dimethyl-1,3-dioxolene). The perfluoroalkyl vinyl ether mentioned above can be selected from perfluoro-methyl vinyl ether, perfluoro-ethyl vinyl ether, perfluoro-n-propyl vinyl ether, and perfluoro-butyl vinyl ether.

[0041] The fluorine-containing polymer according to the present application can further comprise a non-fluorine-containing compound structural unit selected from at least one of ethylene, acrylate, methyl acrylate, methacrylate, methyl methacrylate, vinyl ether, vinyl acetate, acrylonitrile, butadiene, isoprene, styrene, maleic anhydride, and itaconic acid. In terms of molar amount, the fluorinated monomer accounts for 50% to 100% of the total amount of polymerized monomers, and the non-fluorine-containing compound accounts for 0 to 50% of the total amount of polymerized monomers.

[0042] The fluorine-containing polymer according to the present application is a polymer containing fluorine atoms, and preferably, the fluorine-containing polymer is selected from one of polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, polytrifluorochloroethylene, polytetrafluoroethylene, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trifluorochloroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene-trifluorochloroethylene copolymer, vinylidene fluoride-trifluoroethylene-fluorochloroethylene copolymer, ethylene-trifluorochloroethylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer.

[0043] The fluorine-containing polymer prepared by the aqueous emulsion polymerization reaction according to the present application has a solid content of greater than or equal to 20% by mass; preferably, greater than or equal to 25%; more preferably, greater than or equal to 30%; and more preferably, greater than or equal to 40%.

[0044] The fluorine-containing polymer prepared by the aqueous emulsion polymerization reaction according to the present application has a demulsification amount of less than or equal to 0.1% by mass; preferably, less than or equal to 0.05%; and more preferably, less than or equal to 0.01%.

[0045] The emulsion particle size of the fluorine-containing polymer according to the present application is 100 nm to 300 nm.

[0046] The aqueous emulsion polymerization reaction of the present application is initiated by an initiator, which is commonly used in the field of fluorinated monomer polymerization, for example, the initiator includes persulfate salt, such as ammonium persulfate or potassium persulfate. The initiator can also include azo initiator, such as 2,2'-azobis-(2,4-dimethyl-4-methoxy valeronitrile) or azobis isobutyronitrile (English abbreviation: AIBN). The initiator can also include organic peroxide, such as alkyl peroxide, dialkyl peroxide, diacyl peroxide, peroxy ester and peroxy dicarbonate; such as 2,5-bis(tert-butyl peroxy)-2,5-dimethyl hexane, benzoyl peroxide and its derivatives, tert-butyl peroxy pivalate, tert-amyl peroxy pivalate, bis(4-tert-butyl cyclohexyl) peroxy dicarbonate, sodium peroxy dicarbonate or di(n-alkyl) peroxy dicarbonate, di-peroxy tert-butyl, peroxy succinic acid, di-n-propyl peroxy dicarbonate, diisopropyl peroxy dicarbonate. The amount of initiator used is 0.005% to 2.5% of the total amount of polymerized monomers, based on the mass.

[0047] The aqueous emulsion polymerization reaction of the present application can also add a chain transfer agent for adjusting the molecular weight of the fluorinated polymer. The chain transfer agent is commonly used in the field of fluorinated monomer polymerization, and the chain transfer agent is selected from at least one of alcohol small molecule compounds, ether small molecule compounds, ester small molecule compounds, thiol small molecule compounds, halogen-containing organic compounds. The amount of chain transfer agent used in the aqueous emulsion polymerization reaction is 0.005% to 5% of the total amount of polymerized monomers, based on the mass.

[0048] In the aqueous emulsion polymerization reaction of the present application, the reaction temperature is generally 5°C to 130°C, and the reaction pressure is 0.05 MPa to 10 MPa; preferably, the reaction temperature is 60°C to 100°C, and the reaction pressure is 1 MPa to 6 MPa. The reaction temperature and the reaction pressure are appropriately determined according to the type of fluorinated monomer used, the molecular weight of the target fluorinated polymer, and the reaction rate.

[0049] The aqueous emulsion polymerization reaction of the present application is carried out under stirring, and the stirring rate is 50 rpm to 700 rpm. The stirring mode is preferably magnetic stirring or mechanical stirring, and other stirring modes that can achieve the corresponding stirring function can also be selected.

[0050] The fluorinated polymer prepared by the present application, the content of the surfactant is 0.1 ppm to 5% (i.e. 10 -7 -0.05), further, 0.1 ppm to 2%, more further, 0.01% to 0.2%, more more further, 0.1 ppm to 1000 ppm (i.e. 10 -7 -10 -3Preferably, it is 100 ppm (i.e., 10). -4 ) or less, more preferably, 10 ppm (i.e., 10 -5 , 0.001%) or less.

[0051] The surfactant described in this invention can be used together with initiators, chain transfer agents, and detergents commonly used in the field of polymerization, and will not decompose under the reaction temperature and reaction pressure of aqueous emulsion polymerization.

[0052] The method for testing the surface tension of the phosphate ester surfactant composition of the present invention is as follows: under constant temperature of 25°C, the phosphate ester surfactant composition to be tested is prepared into an aqueous solution with a mass fraction of 1 wt%, and the surface tension is tested by the pendant drop method. The average value is taken after three tests.

[0053] Thirdly, the present invention also provides a fluoropolymer composition obtained by the preparation method of the second aspect, comprising a fluoropolymer and at least one surfactant.

[0054] Furthermore, based on the mass of the fluoropolymer, the content of the surfactant is 0.1 ppm to 5% (i.e., 10 ppm) on a mass basis. -7 -0.05), further, 0.1ppm-2%, even further, 0.01%-0.2%, and even further, 0.1ppm-1000ppm (i.e., 10 -7 -10 -3 Preferably, it is 100 ppm (i.e., 10). -4 ) or less, more preferably, 10 ppm (i.e., 10 -5 , 0.001%) or less.

[0055] The monophosphate and diphosphate esters described in this invention can be prepared by reacting alkylphenols with a phosphorylating agent. For details, please refer to the article "Investigation of the hydrogen bonding properties of a series of monosaccharides in aqueous media by..." 1 The sample was prepared using the method described in "H NMR and IR spectroscopy" (Eur JOC. 2002, 12, 1925-1936).

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The surfactant used in the application solves the environmental pollution problem caused by fluorine-containing surfactants, and has low surface tension and low chain transfer property, and can effectively improve the polymerization reaction rate, has good emulsion stability and high emulsion solid content when used as a surfactant in the preparation of fluorine-containing polymers. BRIEF DESCRIPTION OF DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the disclosed drawings.

[0059] Figure 1 is the nuclear magnetic hydrogen spectrum of the p-t-octyl phenol phosphate and bis-p-t-octyl phenol phosphate composition in the preparation of PVDF in Example 19 of the present application.

[0060] Figure 2 is the nuclear magnetic phosphorus spectrum of the p-t-octyl phenol phosphate and bis-p-t-octyl phenol phosphate composition in the preparation of PVDF in Example 19 of the present application. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0062] Test method of surface tension of the present application:

[0063] Instrument: Dataphysics contact angle system OCA 20;

[0064] Mode: pendant drop method;

[0065] Test method: adjust the room temperature to 25℃, prepare a 1wt% neutral aqueous solution of the surfactant to be tested, and suck the prepared solution into a syringe with a needle diameter of 1.65mm, and test after emptying the air bubbles. In the software test interface, select the "pendant drop" mode, set the needle diameter, sample density, ambient temperature and other parameters, and start testing.

[0066] The test method of the micelle particle size of the present application is as follows:

[0067] Instrument: HORIBA / SZ100Z2 nanoparticle size analyzer;

[0068] Test temperature: 25℃

[0069] Test parameter setting: polydispersity

[0070] Solvent medium: water

[0071] Test method: 1wt% content of surfactant neutral aqueous solution 3mL, added to plastic cuvette. The cuvette was placed in the sample tank, closed the cover to start the test, test three times to get the average value.

[0072] The test method of the emulsion particle size of the present application is as follows:

[0073] Instrument: dynamic light scattering nanoparticle size analyzer (DLS).

[0074] Test method: test angle is 90°, test three times to get the average value.

[0075] The results of DLS test emulsion particle size are generally 30-50nm larger than the results of SEM observation emulsion particle size.

[0076] In the present application, Mn refers to the number average molecular weight of the polymer; PDI refers to the polymer dispersity index, the larger the PDI, the wider the molecular weight distribution; the smaller the PDI, the more uniform the molecular weight distribution.

[0077] PLURONIC 31R1: a double functional block copolymer surfactant with terminal secondary hydroxyl, a nonionic surfactant, non-toxic, from BASF.

[0078] Method for determining the presence of surfactant in fluoropolymer composition: 10g fluoropolymer was soaked in 100g isopropanol for 12h, the filtrate was dried and dissolved in DMSO-d6 for NMR analysis.

[0079] The following examples will specifically illustrate the surfactant.

[0080] Example 1

[0081] P-tert-octylphenol phosphate (1.15g, 4mmol) was dissolved in 115g water, and sodium hydroxide was added to neutralize the solution to pH 7. The surface tension was measured to be 30.13mN / m using the pendant drop method, and the micelle particle size was 8.9nm tested by nanoparticle size analyzer.

[0082] Example 2

[0083] P-tert-octylphenol phosphate (1.15g, 4mmol) and bis-p-tert-octylphenol phosphate (0.05g, 0.1mmol) were dissolved in 120g water, and sodium hydroxide was added to neutralize the solution to pH 7. The surface tension was measured to be 27.62mN / m using the pendant drop method, and the micelle particle size was 157.7nm tested by nanoparticle size analyzer.

[0084] Example 3

[0085] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.10 g, 0.2 mmol) were dissolved in 125 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 27.11 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 155.2 nm.

[0086] Example 4

[0087] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.14 g, 0.3 mmol) were dissolved in 129 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.92 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 166.9 nm.

[0088] Example 5

[0089] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.19 g, 0.4 mmol) were dissolved in 134 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.52 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 191.8 nm.

[0090] Example 6

[0091] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.24 g, 0.5 mmol) were dissolved in 139 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.55 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 180.4 nm.

[0092] Example 7

[0093] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.28 g, 0.6 mmol) were dissolved in 143 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.65 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 212.2 nm.

[0094] Example 8

[0095] p-Terxtylphenol phosphate (1.15 g, 4 mmol) and bis-p-terxtylphenol phosphate (0.33 g, 0.7 mmol) were dissolved in 148 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.49 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 226.4 nm.

[0096] Example 9

[0097] p-Terxtylphenol phosphate (1.15 g, 4 mmol) and bis-p-terxtylphenol phosphate (0.38 g, 0.8 mmol) were dissolved in 153 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.58 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 247.6 nm.

[0098] Example 10

[0099] p-Terxtylphenol phosphate (1.15 g, 4 mmol) and bis-p-terxtylphenol phosphate (0.43 g, 0.9 mmol) were dissolved in 158 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.47 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 241.2 nm.

[0100] Example 11

[0101] p-Terxtylphenol phosphate (1.15 g, 4 mmol) and bis-p-terxtylphenol phosphate (0.47 g, 1.0 mmol) were dissolved in 162 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.5 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 290.1 nm.

[0102] Example 12

[0103] p-Terxtylphenol phosphate (1.15 g, 4 mmol) and bis-p-terxtylphenol phosphate (0.52 g, 1.1 mmol) were dissolved in 167 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.44 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 314.7 nm.

[0104] Example 13

[0105] p-Terxtylphenol phosphate (1.15 g, 4 mmol) and bis-p-terxtylphenol phosphate (0.57 g, 1.2 mmol) were dissolved in 172 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.44 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 350.3 nm.

[0106] Example 14

[0107] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.62 g, 1.3 mmol) were dissolved in 177 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.44 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 440.5 nm.

[0108] Example 15

[0109] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.66 g, 1.4 mmol) were dissolved in 181 g water and neutralized to a solution pH of 7 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.54 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 443.7 nm.

[0110] Example 16

[0111] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.66 g, 1.4 mmol) were dissolved in 181 g water and neutralized to a solution pH of 14 with sodium hydroxide. The surface tension was measured using the pendant drop method to be 26.68 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 188.3 nm.

[0112] Example 17

[0113] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.66 g, 1.4 mmol) were dissolved in 181 g water and neutralized to a solution pH of 1 with phosphoric acid. The surface tension was measured using the pendant drop method to be 27.01 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 787.3 nm.

[0114] Example 18

[0115] P-tert-octylphenol phosphate (1.15 g, 4 mmol) and bis-p-tert-octylphenol phosphate (0.66 g, 1.4 mmol) were dissolved in 181 g water and neutralized to a solution pH of 7 with sodium hydroxide and 1.81 g of NaCl solids were added. The surface tension was measured using the pendant drop method to be 27.02 mN / m and the micelle size was tested by a nanoparticle size analyzer to be 833.0 nm.

[0116] Comparative Example 1

[0117] p-Terxtylphenol sulfate (1 g) was dissolved in 100 g of water and neutralized with sodium hydroxide to a solution pH of 7. The surface tension was measured using the pendant drop method to be 58.12 mN / m and the micelle size was measured by a nanoparticle size analyzer to be 8.2 nm.

[0118] Comparative Example 2

[0119] Tergitol Triton X (1 g) was dissolved in 100 g of water and neutralized with sodium hydroxide to a solution pH of 7. The surface tension was measured using the pendant drop method to be 30.41 mN / m.

[0120] Table 1 Surface Tension and Micelle Size of Surfactants of Examples 1-18 and Comparative Examples 1-2

[0121] As can be seen from Table 1, the data of Examples 15-18 show that the pH value has little effect on the surface tension of the surfactants. The data of the examples and comparative examples show that the surface tension of the surfactants of the present application is greatly reduced.

[0122] The following examples will describe the preparation of fluoropolymers in detail.

[0123] The surfactant A was prepared by the following method:

[0124] p-Terxtylphenol phosphate (1.15 g, 4 mmol) and bis-p-terxtylphenol phosphate (0.47 g, 1 mmol) were dissolved in 162 g of water and neutralized with sodium hydroxide to a solution pH of 7. The surface tension was measured using the pendant drop method to be 26.5 mN / m and the micelle size was measured by a nanoparticle size analyzer to be 290.1 nm.

[0125] The surfactant B was prepared by the following method:

[0126] p-Terxtylphenol phosphate (1.15 g, 4 mmol) was dissolved in 115 g of water and neutralized with sodium hydroxide to a solution pH of 7. The surface tension was measured using the pendant drop method to be 30.13 mN / m and the micelle size was measured by a nanoparticle size analyzer to be 8.9 nm.

[0127] Example 19 - Preparation of PVDF

[0128] Into a 3.4 L polymerization kettle was added purified water (1800 g). After the kettle was assembled, the oil seal vacuum pump was used to continuously pull a vacuum for 5 minutes, after which the kettle was backfilled with high purity nitrogen to 0.15 MPa. This procedure was repeated three times, after which the final vacuum was pulled and vinylidene fluoride (150 g) was added from a high pressure cylinder, a solution of surfactant A (100 g, 0.4 wt% surfactant, 0.2 wt% ethyl acetate) was added from a plunger pump, and the mixture was heated to 80 °C with stirring (700 rpm) turned on. After the temperature was stable for 5 minutes, vinylidene fluoride (50 g) was added from a high pressure cylinder to a pressure of 4.50 MPa, and ammonium persulfate solution (100 g, 0.8 wt%) was added from a plunger pump to initiate the polymerization. The temperature in the kettle was maintained (80 ± 0.5 °C) and vinylidene fluoride was added to maintain the pressure (4.25 ± 0.25 MPa) during the polymerization until the target amount of vinylidene fluoride (650 g) was reached. The stirring was stopped and the pressure relief valve was opened, and the emulsion (2602 g, 25.2 wt% solids) was collected after the pressure dropped to ambient. The total amount of emulsion breaker was 0.01 wt% based on the mass of the polymer. The resulting polyvinylidene fluoride had an average emulsion particle size of 237 nm as measured by DLS, and a viscosity of 2765 cP (shear rate of 2.325 s -1 ) for a 7 wt% NMP solution.

[0129] After the emulsion was spray dried, the amount of phosphate ester in the fluoropolymer was measured. 10 g of the fluoropolymer was soaked in 100 g of isopropyl alcohol for 12 h with stirring, and the resulting filtrate was dried and dissolved in DMSO-d6. The resulting solution was analyzed by 400 MHz NMR. The results are shown in FIG. 1 and FIG. 2. The molar ratio of p-t-octylphenol phosphate ester to bis-p-t-octylphenol phosphate ester was 4.06:1, and the corresponding mass ratio was 2.45:1.

[0130] Example 20 - Preparation of PVDF

[0131] A 3.4 L polymerization vessel was charged with purified water (1800 g). After the vessel was closed, the oil-sealed vacuum pump was used to continuously pull a vacuum for 5 minutes, after which the vessel was backfilled to 0.15 MPa with high purity nitrogen. This procedure was repeated three times, and after the final pull of vacuum, vinylidene fluoride (150 g) was added from a high pressure cylinder, a solution of Surfactant A (100 g, 1.2 wt% Surfactant, 0.2 wt% ethyl acetate) was added from a syringe pump, and the mixture was heated to 80 °C with stirring (700 rpm) turned on. After the temperature had stabilized for 5 minutes, vinylidene fluoride (50 g) was added from a high pressure cylinder to a pressure of 4.50 MPa, and the polymerization was initiated by adding ammonium persulfate solution (100 g, 0.8 wt%) from a syringe pump. The temperature in the vessel (80 ± 0.5 °C) was maintained during the polymerization, and vinylidene fluoride was added to maintain the pressure (4.25 ± 0.25 MPa) until the total target amount of vinylidene fluoride (700 g) was reached. The stirring was stopped and the pressure relief valve was opened, and the emulsion (2790 g, 30.3 wt% solids) was collected after the pressure had dropped to ambient. The total breaker material content was 0.01 wt% based on the mass of the polymer. The resulting polyvinylidene fluoride had an average emulsion particle size of 245 nm as measured by DLS, and a 7 wt% NMP solution viscosity of 2895 cP (shear rate of 2.325 s -1 ) at 25 °C.

[0132] Example 21 - Preparation of PVF

[0133] A 3.4 L polymerization vessel was charged with purified water (1800 g). After the vessel was closed, the oil-sealed vacuum pump was used to continuously pull a vacuum for 5 minutes, after which the vessel was backfilled to 0.15 MPa with high purity nitrogen. This procedure was repeated three times, and after the final pull of vacuum, vinyl fluoride (80 g) was added from a compressor, a solution of Surfactant A (100 g, 0.4 wt% Surfactant) was added from a syringe pump, and the mixture was heated to 80 °C with stirring (700 rpm) turned on. After the temperature had stabilized for 5 minutes, vinyl fluoride (150 g) was added from a compressor to a pressure of 2.75 MPa, and the polymerization was initiated by adding ammonium persulfate solution (100 g, 0.8 wt%) from a syringe pump. The temperature in the vessel (80 ± 0.5 °C) was maintained during the polymerization, and vinyl fluoride was added to maintain the pressure (2.75 ± 0.25 MPa) until the total target amount of vinyl fluoride (400 g) was reached. The stirring was stopped and the pressure relief valve was opened, and the emulsion (2213 g, 15.6 wt% solids) was collected after the pressure had dropped to ambient. The total breaker material content was 0.01 wt% based on the mass of the polymer. The resulting polyvinyl fluoride had an average emulsion particle size of 218 nm as measured by DLS.

[0134] Example 22 - Preparation of PCTFE

[0135] Add 1800g of pure water to a 3.4L polymerization reactor. After merging the reactor, continuously evacuate for 5 minutes using an oil-sealed vacuum pump, then backfill with high-purity nitrogen to 0.15MPa. Repeat this operation three times. After the last evacuation, add 400g of trifluorochloroethylene using a high-pressure gas cylinder, and add 100g of a solution prepared with surfactant A (0.4wt% surfactant content) using a plunger pump. Start stirring (700rpm) and heat the mixture to 80°C. After the temperature stabilizes for 5 minutes, add 100g of ammonium persulfate solution (0.8wt%) using a plunger pump to initiate the polymerization reaction. Maintain the reactor temperature (80±0.5°C) during the polymerization reaction until the pressure drops to 2.5MPa. Stop stirring and open the pressure relief valve. After the pressure drops to atmospheric pressure, collect the emulsion (2253g, solid content 15.1wt%). The total demulsified material content is 0.01wt% based on the polymer mass. The average particle size of the polyvinylidene fluoride emulsion observed by DLS was 223 nm.

[0136] Example 23 - Preparation of PVDF-HFP

[0137] Add 1800g of pure water to a 3.4L polymerization reactor. After merging the reactor, continuously evacuate for 5 minutes using an oil-sealed vacuum pump, then backfill with high-purity nitrogen to 0.15MPa. Repeat this operation three times. After the last evacuation, add 40g of hexafluoropropylene using a high-pressure gas cylinder, and add 100g of a solution prepared with surfactant A (0.4wt% surfactant content, 0.2wt% ethyl acetate content) using a plunger pump. Start stirring (700rpm) and heat the mixture to 80°C. After the temperature stabilizes for 5 minutes, add 180g of vinylidene fluoride to 4.50MPa using a high-pressure gas cylinder, and add 100g of ammonium persulfate solution (0.8wt%) using a plunger pump to initiate the polymerization reaction. During the polymerization reaction, maintain the reactor temperature (80±0.5°C) and add vinylidene fluoride to maintain the pressure (4.25±0.25MPa) until the total monomer feed target (650g) is reached. Stop stirring and open the pressure relief valve. Collect the emulsion (2605 g, solid content 25.9 wt%) after the pressure drops to atmospheric pressure. The total demulsified material content is 0.01 wt% based on polymer mass. The average particle size of the obtained polyvinylidene fluoride copolymer emulsion, as observed by DLS, is 253 nm, and its 7 wt% NMP solution viscosity is 1480 cp (shear rate 2.325 s). -1 ).

[0138] Example 24 - Preparation of ECTFE

[0139] Into a 3.4 L polymerization kettle was added purified water (1800 g). After the kettle was closed, vacuum was applied for 5 minutes using an oil-sealed vacuum pump, and then high purity nitrogen was used to backfill the kettle to 0.15 MPa. This procedure was repeated three times, and after the final vacuum was applied, ethylene (35 g) and chlorotrifluoroethylene (300 g) were added from a high pressure cylinder, a solution of surfactant A (100 g, 0.4 wt% surfactant, 0.2 wt% ethyl acetate) was added from a piston pump, and the mixture was heated to 80 °C with stirring (700 rpm) turned on. After the temperature was stable for 5 minutes, ethylene (25 g) and chlorotrifluoroethylene (200 g) were added from a high pressure cylinder to 3.80 MPa, and an ammonium persulfate solution (100 g, 0.8 wt%) was added from a piston pump to initiate the polymerization. The temperature in the kettle was maintained at (80 ± 0.5 °C) during the polymerization, and ethylene and chlorotrifluoroethylene were added to maintain the pressure at (3.80 ± 0.20 MPa) until the total monomer target (500 g) was reached. The stirring was turned off and the pressure relief valve was opened, and the emulsion (2237 g, 17.8 wt% solids) was collected after the pressure dropped to atmospheric pressure. The total amount of emulsion breaker material was 0.01 wt% based on the mass of the polymer. The resulting poly-ECTFE had an average emulsion particle size of 236 nm as measured by DLS.

[0140] Example 25 - Preparation of PTFE

[0141] Into a 3.4 L polymerization kettle was added purified water (1800 g). After the kettle was closed, vacuum was applied for 5 minutes using an oil-sealed vacuum pump, and then high purity nitrogen was used to backfill the kettle to 0.15 MPa. This procedure was repeated three times, and after the final vacuum was applied, tetrafluoroethylene (150 g) was added from a high pressure cylinder, a solution of surfactant A (100 g, 0.2 wt% surfactant, 0.2 wt% isopropyl alcohol) was added from a piston pump, and the mixture was heated to 80 °C with stirring (700 rpm) turned on. After the temperature was stable for 5 minutes, tetrafluoroethylene (50 g) was added from a high pressure cylinder to 3.80 MPa, and an ammonium persulfate solution (100 g, 0.8 wt%) was added from a piston pump to initiate the polymerization. The temperature in the kettle was maintained at (80 ± 0.5 °C) during the polymerization, and tetrafluoroethylene was added to maintain the pressure at (3.80 ± 0.20 MPa) until the total monomer target (300 g) was reached. The stirring was turned off and the pressure relief valve was opened, and the emulsion (2057 g, 8.3 wt% solids) was collected after the pressure dropped to atmospheric pressure. The total amount of emulsion breaker material was 1.5 wt% based on the mass of the polymer. The resulting poly-ECTFE had an average emulsion particle size of 233 nm as measured by DLS.

[0142] Example 26 - Preparation of PVDF

[0143] A 3.4 L polymerization vessel was charged with purified water (1800 g). After the vessel was closed, vacuum was applied for 5 minutes using an oil-sealed vacuum pump, and then high purity nitrogen was used to backfill the vessel to 0.15 MPa. This procedure was repeated three times, and after the final vacuum application, hexafluoropropene (150 g) was added using a high pressure cylinder, a solution of surfactant B (100 g, 0.4 wt% surfactant, 0.2 wt% ethyl acetate) was added using a syringe pump, and the mixture was heated to 80 °C with stirring (700 rpm) turned on. After the temperature had stabilized for 5 minutes, hexafluoropropene (50 g) was added using a high pressure cylinder to a pressure of 4.50 MPa, and an ammonium persulfate solution (100 g, 0.8 wt%) was added using a syringe pump to initiate the polymerization. The temperature in the vessel was maintained at (80 ± 0.5 °C) during the polymerization, and hexafluoropropene was added to maintain the pressure at (4.25 ± 0.25 MPa) until the total target amount of hexafluoropropene (650 g) was reached. The stirring was stopped and the pressure relief valve was opened, and the emulsion (2629 g, 25.7 wt% solids) was collected after the pressure had returned to ambient. The total amount of emulsion breaker material was 0.02 wt% based on the mass of the polymer. The resulting polyvinylidene fluoride had an average emulsion particle size of 218 nm as measured by DLS, and a 7 wt% NMP solution viscosity of 2234 cp (shear rate of 2.325 s -1 ) at 25 °C.

[0144] Comparative Example 3 - PVDF prepared using PFOA as emulsifier

[0145] A 3.4 L polymerization vessel was charged with purified water (1800 g). After the vessel was closed, vacuum was applied for 5 minutes using an oil-sealed vacuum pump, and then high purity nitrogen was used to backfill the vessel to 0.15 MPa. This procedure was repeated three times, and after the final vacuum application, hexafluoropropene (150 g) was added using a high pressure cylinder, a solution of surfactant B (100 g, 0.4 wt% surfactant, 0.2 wt% ethyl acetate) was added using a syringe pump, and the mixture was heated to 80 °C with stirring (700 rpm) turned on. After the temperature had stabilized for 5 minutes, hexafluoropropene (50 g) was added using a high pressure cylinder to a pressure of 4.50 MPa, and an ammonium persulfate solution (100 g, 0.8 wt%) was added using a syringe pump to initiate the polymerization. The temperature in the vessel was maintained at (80 ± 0.5 °C) during the polymerization, and hexafluoropropene was added to maintain the pressure at (4.25 ± 0.25 MPa) until the total target amount of hexafluoropropene (650 g) was reached. The stirring was stopped and the pressure relief valve was opened, and the emulsion (2629 g, 25.7 wt% solids) was collected after the pressure had returned to ambient. The total amount of emulsion breaker material was 0.02 wt% based on the mass of the polymer. The resulting polyvinylidene fluoride had an average emulsion particle size of 218 nm as measured by DLS, and a 7 wt% NMP solution viscosity of 2234 cp (shear rate of 2.325 s -1 ) at 25 °C.

[0146] Comparative Example 4 - PVDF prepared using a block copolymer as emulsifier

[0147] Into a 3.4 L polymerization kettle was added purified water (1400 g). After the kettle was assembled, the vacuum pump was used to continuously pull a vacuum for 5 minutes, then high purity nitrogen was used to backfill the kettle to 0.15 MPa. This was repeated three times, after the final pull of the vacuum, vinylidene fluoride monomer (180 g) was added from a high pressure cylinder, a PLURONIC 31R1 dilution solution (150 g, 0.6 wt% active, 0.05 wt% ethyl acetate) was added from a syringe pump, and the mixture was heated to 80 °C with stirring (700 rpm) turned on. After the temperature was stable for 5 minutes, vinylidene fluoride monomer (82 g) was added from a high pressure cylinder to 4.50 MPa, and an ammonium persulfate solution (50 g, 1 wt%) was added from a syringe pump to initiate the polymerization. The temperature in the kettle was maintained (80 ± 0.5 °C) and vinylidene fluoride monomer was added to maintain the pressure (4.25 ± 0.25 MPa) during the polymerization until the total monomer target (600 g) was reached. The stirring was turned off and the pressure relief valve was opened, and the emulsion (2002 g, 23.2 wt% solids) was collected after the pressure dropped to ambient. The total coagulum content was 1.2 wt% based on the mass of the polymer. The resulting PVDF had an average emulsion particle size of 198 nm as observed by SEM, and a 7 wt% NMP solution viscosity of 1152 cp (shear rate of 2.325 s -1 ) at 25 °C.

[0148] The properties of the fluoropolymers prepared in Examples 19-26 and Comparative Examples 3-4 are shown in Table 2.

[0149] Table 2 Properties of fluoropolymers prepared in Examples 19-26 and Comparative Examples 3-4

[0150] As can be seen from Table 2, the fluoropolymers of Examples 19-26 used the surfactants of the present application in amounts of 0.01-0.3% by mass of the polymer produced, and the resulting PVDF, PVF, PCTFE, PVDF-HFP, and ECTFE emulsions had high solids content, low coagulum, and short induction periods. Comparative Example 3 used nearly 5 times the amount of PFOA (by mass of polymer produced) as Example 19, and yet had similar solids content, coagulum, and induction period. Example 20 had a solids content of 30.3% which was higher than Comparative Example 3, even though the same amount of surfactant was used. Comparative Example 4 used a non-fluorinated surfactant, and used more than 3 times the amount of PLURONIC 31R1 (by mass of polymer produced) as Example 19, and had a long induction period and 120 times the coagulum of Example 19.

[0151] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, it is to be understood that the application embraces all such possible combinations.

[0152] The above-described embodiments only express several implementation manners of the application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be pointed out that, for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the application, and these all belong to the protection scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims.

Claims

1. A surfactant characterized in that, said surfactant comprises a mono-phosphate ester, said mono-phosphate ester comprises an aromatic phenolic group substituted with an alkyl chain; said mono-phosphate ester does not comprise a methyl group, a methylene group, a methine group directly linked to the aromatic ring group; said surfactant does not comprise a methine group; said surfactant has a methylene group content lower than 20% by number of carbon atoms; a neutral aqueous solution comprising 1 wt% of said surfactant has a surface tension comprised between 26 mN / m and 31 mN / m.

2. The surfactant of claim 1, wherein, The structure of the monophosphate ester is shown in formula (1), R1is a C1-C 10 alkyl group; Ar1is selected from phenyl, diphenyloxide, biphenyl, pyridyl, pyrrolyl, thienyl, naphthyl, anthryl; X1is selected from hydrogen, an alkali metal atom, an alkaline earth metal atom, an ammonium or substituted ammonium group, a pyridinium group, an imidazolium group.

3. The surfactant according to claim 2, wherein: R1 is selected from a C1-C4 alkyl group; Ar1 is selected from a phenyl group, a diphenyloxide group; X1 is selected from a hydrogen, an alkali metal atom, an alkaline earth metal atom, an ammonium group or a substituted ammonium group, a pyridinium group, an imidazolium group.

4. The surfactant of claim 3, wherein, R1 is a methylene group; Ar1 is a phenyl group; X1 is selected from a hydrogen, an alkali metal atom, an alkaline earth metal atom, an ammonium group or a substituted ammonium group, a pyridinium group, an imidazolium group.

5. The surfactant of any one of claim 14, characterized in that, said surfactant further comprises a di-phosphate ester, said di-phosphate ester comprises an aromatic phenolic group substituted with an alkyl chain; said di-phosphate ester does not comprise a methyl group, a methylene group, a methine group directly linked to the aromatic ring group.

6. The surfactant of claim 5, wherein, The structure of the bisphosphate is shown in formula (2), R2is a C1-C 10 R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R2is a C1-C R 7. The surfactant of claim 6, wherein, R2 is selected from a C1-C4 alkyl group; Ar2 is selected from a phenyl group, a diphenyloxide group; X2 is selected from a hydrogen, an alkali metal atom, an alkaline earth metal atom, an ammonium group or a substituted ammonium group, a pyridinium group, an imidazolium group.

8. The surfactant of claim 7, wherein, R2 is a methylene group; Ar2 is a phenyl group; X2 is independently selected from a hydrogen, an alkali metal atom, an alkaline earth metal atom, an ammonium group or a substituted ammonium group, a pyridinium group, an imidazolium group.

9. The surfactant of claim 5, wherein, said mono-phosphate ester and said di-phosphate ester are present in a molar ratio comprised between 100:0 and 70:

30.

10. The surfactant of claim 9, wherein, said mono-phosphate ester and said di-phosphate ester are present in a molar ratio comprised between 95:5 and 70:

30.

11. The surfactant of claim 5, wherein, said mono-phosphate ester is selected from a p-tert-octyl phenol phosphate ester; said di-phosphate ester is selected from a bis-p-tert-octyl phenol phosphate ester.

12. The surfactant of claim 5, wherein, said surfactant consists of a mono-phosphate ester and a di-phosphate ester.

13. Use of a surfactant as claimed in any one of claims 1 to 12, characterised in that, said surfactant is used as an emulsifier for the preparation of a fluoropolymer.

14. A process for the preparation of a fluoropolymer, said process comprising the step of aqueous emulsion polymerization of one or more fluorinated monomers, said aqueous emulsion polymerization being carried out in the presence of at least one surfactant, characterized in that, said surfactant is the surfactant according to any one of claims 1 to 12.

15. The process for producing a fluoropolymer according to claim 14, characterized in that, said surfactant is added to the aqueous emulsion polymerization reaction in an amount comprised between 0.001% and 5% by mass of the fluoropolymer produced.

16. The process for producing a fluoropolymer according to claim 15, characterized in that, said surfactant is added to the aqueous emulsion polymerization reaction in an amount comprised between 0.01% and 0.2% by mass of the fluoropolymer produced.

17. The process for producing a fluoropolymer according to claim 14, characterized in that, said fluorinated monomer is selected from at least one of vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, -tetrafluoropropylene, chlorotrifluoroethylene, 1,1-difluorochloroethylene, 1,2-difluorochloroethylene, perfluoroalkylethylene, perfluoroalkyl vinyl ether, perfluoro-n-propyl vinyl ether, perfluoro-methyl vinyl ether and perfluoro(2,2-dimethyl-1,3-dioxole).

18. The process for producing a fluoropolymer according to claim 17, characterized in that, said fluorinated monomer is present in an amount comprised between 50% and 100% by moles of the total amount of polymerized monomers.

19. A fluoropolymer composition obtainable by the process according to any one of claims 14 to 18, characterized in that, comprises a fluoropolymer and at least one surfactant.

20. The fluoropolymer composition of claim 19, wherein, said surfactant is present in an amount comprised between 0.1 ppm and 5% by mass of the fluoropolymer.

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