Application and preparation method of polyfluorinated epoxy carboxylate

Abstract

The invention discloses an application of a polyfluorinated epoxy carboxylate as a surfactant, the structure of the polyfluorinated epoxy carboxylate is as shown in formula (I), R1 is independently selected from one of F and C1-C3 fluorine-containing alkyl groups, and M is selected from one of Na, K or NH4. The carbon chain length of the fluorine-containing epoxy carboxylate is less than 6, and the fluorine-containing epoxy carboxylate is excellent in surface activity, green and environment-friendly, can be used as a surfactant to replace PFOA / PFOS to be applied to the industries of fire fighting, textile and the like, and can be degraded under an acidic condition, and a degradation product is environment-friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical synthesis, in particular to the application of a polyfluorinated epoxy carboxylate and a preparation method thereof. BACKGROUND

[0002] Due to the restriction of new pollutant regulations, PFAS compounds are facing ban, and surfactant PFOA and its salts have been banned in many countries. PFOA is widely used and urgently needs to be replaced. Studies have shown that the inclusion of oxygen atoms in the carbon chain can increase the degradation rate of the compound, and reducing the fluorine content of the compound can significantly reduce its biological toxicity. Therefore, the industry has begun to use perfluoropolyether carboxylic acid (PFECA), but as research deepens, the bioaccumulation and potential toxicity of PFECA have attracted attention. Studies have shown that the length of the fluorocarbon chain of perfluoropolyether carboxylic acid is positively correlated with its biological toxicity, and when the carbon chain length is > 6, the biological toxicity of perfluoropolyether carboxylic acid will increase significantly. Since the cyclic fluorine-containing surfactant shortens the length of the fluorocarbon chain due to its cyclic structure, it also introduces better degradation performance, so it is of great significance to develop new cyclic fluorine-containing surfactants.

[0003] Regarding the cyclic fluorine-containing surfactant, Solvay discloses a fluorine-containing epoxy carboxylate salt in patent WO2011003575, which uses fluorine-containing oxolane as raw material, adds methanol, acylates and esterifies to obtain a cyclic fluorine-containing polyether ester, and then fluorinates to obtain a cyclic perfluoropolyether ester. After acidolysis and alkali treatment, a cyclic perfluoropolyether carboxylate emulsifier is obtained. However, this reaction route has six related reactions involving multiple different reaction types, and the synthesis process is complex. In addition, the starting material fluorine-containing oxolane (PDD) is expensive, which is not conducive to industrial scaling. In addition, its main carbon chain is still perfluoropolyether carboxylic acid structure, which still has not low biological toxicity.

[0004]

[0005] The document "Macromolecules, 2005, 38, 4237" mentions a method for generating fluorine-containing epoxy carboxylate by reacting trifluoroacetone ester and chlorohydrin. The fluorine-containing epoxy carboxylate synthesized by this method can be hydrolyzed to an epoxy carboxylate salt, but since the substrate selected for this reaction does not contain fluorine-containing alkyl branches, the fluorine-containing epoxy carboxylate salt obtained ultimately has poor surface activity and is not suitable for application in the field of surfactants.

[0006] In summary, the epoxy carboxylate salt in the prior art is not suitable for use as a surfactant due to insufficient surface performance caused by too few branched chains, or has certain biological toxicity due to a complex process and a main chain still retaining a perfluoropolyether carboxylic acid structure. Therefore, it is necessary to develop a brand new fluorine-containing epoxy carboxylate surfactant with high surface activity and a more green degradation product to replace the existing PFOS / PFOA fluorocarbon surfactant. SUMMARY

[0007] In order to solve the above technical problems, the present application provides a new type of polyfluoro epoxy carboxylate salt which has excellent surface activity and is green and environmentally friendly, and can be used as a surfactant to replace PFOA / PFOS in the fields of firefighting, textiles and the like.

[0008] The object of the present application is achieved by the following technical solutions.

[0009] The application of a polyfluoro epoxy carboxylate salt as a surfactant, which has a structure as shown in formula (I), wherein R1 is independently selected from one of F, C1-C3 fluorine-containing alkyl groups, and M is selected from one of Na, K or NH4.

[0010]

[0011] Preferably, in the formula (I), R1 is independently selected from C1-C3 fluorine-containing alkyl groups.

[0012] The number of fluorine atoms in the polyfluoro epoxy carboxylate salt should account for 80% or more of the total number of fluorine atoms and hydrogen atoms.

[0013] The polyfluoro epoxy carboxylate salt contains oxygen between carbon chains, is easy to degrade, has relatively low environmental migration and pollution compared with perfluorocarbon chain compounds without oxygen atoms. The main structure of the fluorine-containing epoxy carboxylate salt is an acetal structure (five-membered ring), the carboxylate end at the top of the five-membered ring is a hydrophilic group, and the alkyl group at the bottom of the five-membered ring and the five-membered ring structure together constitute a fluorocarbon hydrophobic chain as a hydrophobic and oleophobic end. Therefore, the fluorine-containing epoxy carboxylate salt has good surface activity, with a minimum surface tension of 22 mN / m, and can be used as a surfactant in the fields of chemical industry, oil field, firefighting, textiles and papermaking. In addition, the fluorine-containing epoxy carboxylate salt has an acid-resistant cyclic acetal structure, and the five-membered ring will directly degrade into aldehyde and alcohol structures under acidic conditions, which is environmentally friendly.

[0014] The present application also provides a preparation method of any one of the polyfluoro epoxy carboxylate salts, which specifically comprises the following steps:

[0015] S1. In an aprotic solvent, trifluoroacetone acid ester and chlorohydrin react under the action of an organic base to generate a fluorine-containing epoxy carboxylate ester;

[0016] S2. The fluorinated epoxy carboxylic acid ester reacts with fluorine gas in a microchannel reactor to generate a polyfluorinated epoxy carboxylic acid ester;

[0017] S3. The polyfluoroepoxycarboxylic acid ester undergoes a hydrolysis reaction under the action of a hydrolysis catalyst to generate polyfluoroepoxycarboxylic acid;

[0018] S4. The polyfluoroepoxycarboxylic acid undergoes a salt-forming reaction in the presence of an inorganic base to generate a polyfluoroepoxycarboxylic acid salt.

[0019] This invention selects trifluoropyruvate as the substrate molecule for cyclization reaction. Compared with fluorine-free substrate molecules, trifluoropyruvate contains trifluoromethyl, which greatly increases the electrophilicity of the ortho-carbonyl group, thus significantly improving the reaction yield. Furthermore, depending on the different substrates R1 and R2, groups with different alkyl chain lengths can be introduced.

[0020] In step S1, in an aprotic solvent, the trifluoroacetone ester of formula (II) and the chloroalcohol of formula (III) react under the action of an organic base to generate a fluorinated epoxy carboxylic acid ester of formula (IV). The reaction is shown in reaction formula 1:

[0021]

[0022] R2 is independently selected from H, F, or a C1-C4 alkyl group.

[0023] Specifically, the molar ratio of the trifluoropyruvate, chloroalcohol and organic base is 1:(1-10):(0.1-1); preferably 1:(1-3):(0.1-0.3).

[0024] The aprotic solvent described in this invention is readily miscible with organic bases and must meet the requirement of a low boiling point, not exceeding 100°C. Specifically, the aprotic solvent is selected from at least one of acetonitrile, toluene, acetone, tetrahydrofuran, and dioxane; preferably, the aprotic solvent is selected from at least one of acetonitrile, acetone, or tetrahydrofuran. The molar ratio of the trifluoropyruvate ester to the aprotic solvent is 1:(10-20), preferably 1:(15-20). The organic base is selected from any one of triethylamine, trimethylamine, N,N-dimethylethylamine, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).

[0025] The reaction temperature is -10 to 80°C, and the reaction time is 1 to 24 hours; preferably, the reaction temperature is -10 to 50°C, and the reaction time is 1 to 3 hours.

[0026] In step S2, the fluorinated epoxy carboxylic ester represented by formula (Ⅳ) is mixed with fluorine gas and reacted in a microchannel reactor to generate the polyfluorinated epoxy carboxylic ester represented by formula (Ⅴ). The molar ratio of fluorine gas to fluorinated epoxy carboxylic ester is 8.0:5.0 to 0.5:1.0, the reaction temperature is 30 to 100°C, and the reaction pressure is 0 to 1.0 MPa.

[0027]

[0028] In step S3, the fluorinated epoxy carboxylic acid ester undergoes a hydrolysis reaction under the action of a hydrolysis catalyst to generate a polyfluorinated epoxy carboxylic acid as shown in formula (VI). The reaction is shown in reaction formula 3:

[0029]

[0030] The hydrolysis reaction involves the alkaline hydrolysis of a polyfluoroepoxycarboxylic acid ester using a hydrolysis catalyst, followed by reaction with an aqueous acid solution to generate a polyfluoroepoxycarboxylic acid. Specifically, the hydrolysis catalyst is an aqueous inorganic base selected from at least one of NaOH, KOH, NH3·H2O, K2CO3, and Na2CO3. Specifically, the molar ratio of the polyfluoroepoxycarboxylic acid ester to the hydrolysis catalyst is 1:(1-10); preferably, the molar ratio is 1:(8-10). The aqueous acid solution is selected from any one of HCl, H2SO4, H3PO4, and HNO3, and the molar ratio of the polyfluoroepoxycarboxylic acid ester to the aqueous acid solution is 1:(1-3); preferably, the molar ratio is 1:(1.5-3).

[0031] The reaction temperature is -10 to 80°C, and the hydrolysis reaction time is 12 to 32 hours; preferably, the reaction temperature is -10 to 50°C, and the hydrolysis reaction time is 14 to 22 hours.

[0032] In step S4, the salt formation reaction is shown in reaction formula 4:

[0033]

[0034] The salt-forming reaction involves further neutralizing the polyfluoroepoxycarboxylic acid with an inorganic base, introducing the cation onto the carboxyl group to generate the target compound, the polyfluoroepoxycarboxylate. The inorganic base is selected from at least one of NaOH, KOH, NH3·H2O, K2CO3, and Na2CO3, and the molar ratio of the polyfluoroepoxycarboxylic acid to the inorganic base is 1:(1–3).

[0035] The reaction temperature is -10 to 80°C, and the salt formation reaction time is 1 to 24 hours; preferably, the reaction temperature is -10 to 50°C, and the salt formation reaction time is 1 to 3 hours.

[0036] In one specific embodiment, the preparation method of the polyfluoroepoxycarboxylate of the present invention specifically includes the following steps:

[0037] S1. After adding trifluoropyruvate, aprotic solvent and organic base to the reaction vessel, slowly add chlorohydrin reagent at a temperature of -10 to 10°C. After the addition is complete, react at a temperature of -10 to 80°C. After the reaction is complete, wash the reaction solution with water, let it stand to separate into layers, take the lower layer, and further distill to obtain fluorinated epoxy carboxylic acid ester, and recover the solvent and organic base used.

[0038] S2. After adding a fluorinated epoxy carboxylic acid ester to a specific container, a 20 mol% fluorine-nitrogen mixed gas is introduced into the reaction vessel at a temperature of 30–100°C. The feed rate is 4.01 g / min, the molar ratio of fluorine gas to epoxy carboxylic acid ester is 8.0:5.0–0.5:1.0, and the reaction pressure is 0.1 MPa. The crude product is collected after quenching, and the tail gas is absorbed by a solid alkali. The crude product is the fluorinated polyfluoroepoxy carboxylic acid ester.

[0039] S3. Add the polyfluoroepoxycarboxylic acid ester and aqueous solvent to the reaction vessel, then add the hydrolysis catalyst, and react at a temperature of 0-50°C. After the reaction is complete, add an aqueous acid solution to adjust the pH of the reaction solution to 4.0-6.0, then extract with an organic solvent, wash, dry, and further rotary evaporate to obtain fluorinated epoxycarboxylic acid.

[0040] S4. Add polyfluoroepoxycarboxylic acid and inorganic base to the reaction vessel and react at a temperature of 0-50°C. Monitor the reaction progress with a pH meter. After complete neutralization, the reaction is complete, and the target product, the fluorinated surfactant polyfluoroepoxycarboxylic acid salt, is obtained.

[0041] The aqueous solvent is selected from distilled water, deionized water, or ultrapure water.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] 1. The fluorinated epoxy carboxylate of the present invention has a carbon chain length of less than 6, excellent surface activity, and is environmentally friendly. It can be used as a surfactant to replace PFOA / PFOS in industries such as fire protection and textiles.

[0044] 2. The preparation method of the present invention can achieve the construction of fluorinated epoxy carboxylic acid esters without the use of high-boiling-point solvents, which helps solvent recovery after process scale-up and saves production costs;

[0045] 3. The preparation method of the present invention uses fluorine gas fluorination to obtain high-performance polyfluorinated epoxy carboxylate surfactants, which not only have the high surface activity of fluorinated cyclic emulsifiers, but also decompose easily under acidic conditions, thus having better environmental friendliness. Attached Figure Description

[0046] Figure 1 The hydrogen spectrum of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester prepared in Example 1;

[0047] Figure 2 The fluorine spectrum of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester prepared in Example 1. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0049] The organic solvents used in this invention are all solvents with boiling points below 110°C. When distilling polyfluoroepoxycarboxylic acid esters, the solvents can also be recovered through the distillation apparatus, and no solid waste is generated, making it suitable for industrial-scale production.

[0050] In this embodiment of the invention, gas chromatography was used for analysis. The analytical instrument was a Shimadzu GC-2014; the chromatographic column was SH-1301 (inner diameter 0.25 mm, length 60 m). GC analysis method: high-purity nitrogen and hydrogen were used as carrier gases; detector temperature 250℃, vaporization chamber temperature 220℃; column temperature: 33℃ (10 min) 10℃ / min 200℃ (5 min); carrier gas (nitrogen) flow rate 30 mL / min, air flow rate 400 mL / min, hydrogen flow rate 40 mL / min, injection port split ratio 30.0, and injection volume 0.1 μL.

[0051] In this embodiment of the invention, liquid chromatography was used for analysis. The analytical instrument was an Agilent 1260 Infinity II; the chromatographic column was a Dionex. C18 (4.6mm×100mm, 5μm, LC analysis method: mobile phase: acetonitrile and water volume ratio 94:6, flow rate (mL / min): 0.4, constant gradient time (min): 7, column temperature (°C): 35, differential refractive index detector temperature (°C): 35, differential refractive index detector signal polarity: negative, injection volume (μL): 10.

[0052] In this embodiment of the invention, a pH meter was used for analysis, and the analytical instrument was a Leici PHSJ-3F+962246 hydrofluoric acid resistant pH electrode. Analytical method: direct testing.

[0053] In this embodiment of the invention, a surface tension meter was used for analysis. The analytical instrument was a KINO A101 surface tension meter. The surface tension analysis method was the Wilhelmy Plate method, the temperature (°C) was 25, and the sample volume was 5 mL.

[0054] Example 1

[0055] Synthesis of compound 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium

[0056] Preparation of S1,4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester

[0057]

[0058] 1.0 mol of methyl trifluoropyruvate (156 g) and 5.0 mol of CH3CN (205 g) were added to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser. After cooling the reaction system to 0 °C, 0.4 mol of triethylamine (40 g) was added, followed by the slow addition of 1.0 mol of 1-chloro-2-propanol reagent (94 g). After 30 min, the mixture was slowly restored to room temperature and stirred for 2 h. After the reaction was completed, the product was obtained by direct distillation: 0.9 mol of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester (224 g) with a yield of 96%. Acetonitrile and triethylamine were recovered and reused.

[0059] The 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester was subjected to... 1 HNMR (400MHz, CDCl3), 19 FNMR (376MHz, CDCl3) was performed to obtain the proton spectrum. Figure 1 Fluorine spectrum Figure 2 .

[0060] Preparation of S2 4-trifluoromethyl-2-(trifluoromethyl)-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ester

[0061]

[0062] 224 g of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester was added to a 100 ml reactor with a tetrafluoroethylene liner. A 20 mol% fluorine-nitrogen mixture was introduced into the reaction vessel at a feed rate of 4.01 g / min for 30 min. The molar ratio of fluorine to raw material was 5.0:1.0, and the reaction pressure was 0.1 MPa. After quenching, the crude product was distilled to collect the main components, yielding 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ester (281 g), with a yield of 88%.

[0063] Hydrolysis of S3,2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ester

[0064]

[0065] 0.9 mol of 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ester (281 g) and 22.5 mol of water (405 g) were added to a reaction vessel, followed by 4.5 mol of KOH (252 g). The reaction was carried out at room temperature (25 °C) with stirring for 18 h. After the reaction was completed, dilute sulfuric acid solution was added to adjust the pH to 4. After extraction, washing, and drying, the target product 0.8 mol of 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid (258 g) was obtained by rotary evaporation, with a yield of 96%.

[0066] Synthesis of S4,2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium

[0067]

[0068] 0.8 mol of 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid (258 g) and 0.8 mol of 25% ammonia solution (115 g) were added to a reaction vessel. The reaction was carried out at room temperature and stirred for 2 h. After the reaction was completed, the water was removed by rotary evaporation to obtain the target product 0.8 mol of 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium (287 g), with a yield of 98%.

[0069] The overall yield of the four-step reaction was calculated to be 81%.

[0070] Comparative Example 1

[0071] Synthesis of compound 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ammonium

[0072] Preparation of S1,4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester

[0073]

[0074] 1.0 mol of methyl trifluoropyruvate (156 g) and 15.0 mol of DMSO (1172 g) were added to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser. The reaction system was cooled to 0 °C, and then 0.2 mol of K₂CO₃ (28 g) was added. 1.0 mol of 1-chloro-2-propanol reagent (94 g) was slowly added dropwise. After 30 min, the mixture was slowly restored to room temperature and stirred for 2 h. After the reaction was completed, the supernatant was collected and distilled to obtain the target product 0.9 mol of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester (224 g), with a yield of 91%.

[0075] Hydrolysis of S2,4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester

[0076]

[0077] 0.9 mol of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ester (224 g) and 22.5 mol of water (405 g) were added to a reaction vessel, followed by 4.5 mol of KOH (252 g). The reaction was carried out at room temperature (25 °C) with stirring for 18 h. After the reaction was completed, dilute sulfuric acid solution was added to adjust the pH to 4. After extraction, washing, and drying, the target product 0.8 mol of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid (178 g) was obtained by rotary evaporation, with a yield of 93%.

[0078] Synthesis of S3,4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ammonium

[0079]

[0080] 0.8 mol of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid (178 g) and 0.8 mol of 25% ammonia solution (115 g) were added to a reaction vessel. The reaction was carried out at room temperature and stirred for 2 h. After the reaction was completed, the water was removed by rotary evaporation to obtain the target product 0.8 mol of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ammonium (207 g), with a yield of 94%.

[0081] The overall yield of the three-step reaction was calculated to be 85%.

[0082] Example 2

[0083] The operation in this embodiment is the same as in Example 1, except that the chloro alcohol reagent is replaced by 1-chloro-2-propanol with 1-chloro-2-pentanol. Other operations remain unchanged, and 0.54 mol of the target product 2-trifluoromethyl-4-heptafluoropropyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium (312 g) is obtained.

[0084]

[0085] The overall yield of the three-step reaction was calculated to be 82%.

[0086] Example 3

[0087] The operation in this embodiment is the same as in Example 1, except that the chloro alcohol reagent is replaced by 2-chloro-1-hydroxypropane instead of 1-chloro-2-propanol. All other operations remain the same, and 0.80 mol of the target product 2,5-bis(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ammonium (271 g) is obtained.

[0088] Calculations show that the overall yield of the three-step reaction is 80%.

[0089] Application Example 1

[0090] The surface activity of compound 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium prepared in Example 1 was tested.

[0091] Thoroughly clean and dry the platinum plate and watch glass used for testing. Heat the platinum plate with an alcohol lamp until red-hot and then cool it. Add 5 mL of deionized water to the watch glass; the surface tension value is 72 mN / m. Pour out the deionized water and dry the watch glass. Add 5 mL of a 5% aqueous solution of 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium prepared in Example 1 to the watch glass; the surface tension value is 25 mN / m. Pour out the 5% aqueous solution of 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium and dry the watch glass. Add 5 mL of a 10% aqueous solution of 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium to this watch glass; the surface tension value is 28 mN / m.

[0092] The test results showed that the lowest surface tension of the aqueous solution of 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid was 28 mN / m.

[0093] Application Example 2

[0094] The surface activity of compound 2-trifluoromethyl-4-heptafluoropropyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium prepared in Example 2 was tested.

[0095] Thoroughly clean and dry the platinum plate and watch glass used for testing. Heat the platinum plate with an alcohol lamp until red-hot and then cool it. Add 5 mL of deionized water to the watch glass; the surface tension value is 72 mN / m. Pour out the deionized water and dry the watch glass. Add 5 mL of a 5% aqueous solution of 2-trifluoromethyl-4-heptafluoropropyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium prepared in Example 2 to the watch glass; the surface tension value is 22 mN / m. Pour out the 5% aqueous solution of 2-trifluoromethyl-4-heptafluoropropyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium and dry the watch glass. Add 5 mL of a 10% aqueous solution of 2-trifluoromethyl-4-heptafluoropropyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium to this watch glass; the surface tension value is 22 mN / m.

[0096] The test results showed that the lowest surface tension of the aqueous solution of 2-trifluoromethyl-4-heptafluoropropyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylic acid ammonium was 22 mN / m.

[0097] Application Comparative Example 1

[0098] The surface activity of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ammonium prepared in Comparative Example 1 was tested.

[0099] Thoroughly clean and dry the platinum plate and watch glass used for testing. Heat the platinum plate with an alcohol lamp until red-hot and then cool it. Add 5 mL of deionized water to the watch glass; the surface tension value is measured to be 72 mN / m. Pour out the deionized water and dry the watch glass. Add 5 mL of a 5% aqueous solution of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ammonium prepared in Comparative Example 1 to the watch glass; the surface tension value is measured to be 35 mN / m. Pour out the 5% aqueous solution of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ammonium and dry the watch glass. Add 5 mL of a 10% aqueous solution of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ammonium to this watch glass; the surface tension value is measured to be 35 mN / m. The test results show that the lowest surface tension of the 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid ammonium aqueous solution is 35 mN / m.

[0100] As can be seen from Comparative Example 1, since the five-membered ring of 4-methyl-2-(trifluoromethyl)-1,3-dioxolane-2-carboxylate ammonium is entirely composed of carbon-hydrogen bonds and has only one trifluoromethyl branch, its minimum surface tension, while somewhat improved compared to hydrocarbon surfactants, is significantly inferior to that of fluorinated cyclic surfactants compared to the compounds 2,4-trifluoromethyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylate ammonium and 2-trifluoromethyl-4-heptafluoropropyl-4,5,5-trifluoro-1,3-dioxolane-2-carboxylate ammonium prepared in Examples 1 and 2 of this invention. For surfactants, the surface tension reduction of fluorocarbon chains at the same carbon chain length is far better than that of hydrocarbon chains.

Claims

1. An application of a polyfluorinated epoxy carboxylate as a surfactant, characterized in that: The structure of the polyfluoroepoxycarboxylate is shown in formula (I), wherein R1 is selected from F or one of C1 to C3 fluorinated alkyl groups, and M is selected from Na, K or NH4.

2. The application of the polyfluorinated epoxy carboxylate as a surfactant according to claim 1, characterized in that: The number of fluorine atoms in the polyfluorinated epoxy carboxylate should be 80% or more of the total number of fluorine and hydrogen atoms.

3. A method for preparing a polyfluoroepoxycarboxylate, characterized in that: The preparation method specifically includes the following steps: S1. In an aprotic solvent, trifluoropyruvate and chloroalcohol react under the action of an organic base to form a fluorinated epoxy carboxylic acid ester; S2. The fluorinated epoxy carboxylic acid ester reacts with fluorine gas in a microchannel reactor to generate a polyfluorinated epoxy carboxylic acid ester; S3. The polyfluoroepoxycarboxylic acid ester undergoes a hydrolysis reaction under the action of a hydrolysis catalyst to generate polyfluoroepoxycarboxylic acid; S4. The polyfluoroepoxycarboxylic acid undergoes a salt-forming reaction in the presence of an inorganic base to generate a polyfluoroepoxycarboxylic acid salt.

4. The method for preparing polyfluoroepoxycarboxylate according to claim 3, characterized in that: S1. In an aprotic solvent, methyl trifluoropyruvate of formula (II) and chloroalcohol of formula (III) react under the action of an organic base at a reaction temperature of -10 to 80°C for 1 to 24 hours to produce a fluorinated epoxy carboxylic acid ester of formula (IV), as shown in reaction formula 1: R2 is selected from H, F, or one of C1 to C3 alkyl groups; S2. The fluorinated epoxy carboxylic ester represented by formula (Ⅳ) is mixed with fluorine gas and reacted in a microchannel reactor to generate the polyfluorinated epoxy carboxylic ester represented by formula (Ⅴ). The molar ratio of fluorine gas to the fluorinated epoxy carboxylic ester is 8.0:5.0 to 0.5:1.0, the reaction temperature is 30 to 100°C, and the reaction pressure is 0 to 1.0 MPa. The reaction is shown in reaction formula 2. S3. The polyfluoroepoxycarboxylic acid ester represented by formula (V) undergoes hydrolysis reaction at a reaction temperature of -10 to 80°C for 12 to 32 hours under the action of a hydrolysis catalyst to generate a polyfluoroepoxycarboxylic acid represented by formula (VI). The hydrolysis catalyst is selected from at least one of NaOH, KOH, NH3·H2O, K2CO3, and Na2CO3. The reaction is shown in reaction formula 3. S4. The polyfluoroepoxycarboxylic acid represented by formula (VI) undergoes a salt-forming reaction for 1–24 h in the presence of an inorganic base at a reaction temperature of -10–80 °C to produce the polyfluoroepoxycarboxylic acid salt represented by formula (I):

5. The method for preparing polyfluoroepoxycarboxylate according to claim 3, characterized in that: In step S1, the aprotic solvent is selected from at least one of acetonitrile, toluene, acetone, tetrahydrofuran, and dioxane, and the molar ratio of the trifluoroacetate ester to the aprotic solvent is 1:(10-20).

6. The method for preparing polyfluoroepoxycarboxylate according to claim 3, characterized in that: In step S1, the organic base is selected from any one of triethylamine, trimethylamine, DBU, N,N-dimethylethylamine, etc., and the molar ratio of trifluoropyruvate, chloroalcohol and organic base is 1:(1~10):(0.1~1).

7. The method for preparing polyfluoroepoxycarboxylate according to claim 3, characterized in that: In step S3, the molar ratio of the fluorinated epoxy carboxylic acid ester to the hydrolysis catalyst is 1:(1-10).

8. The method for preparing polyfluoroepoxycarboxylate according to claim 3, characterized in that: In step S3, the aqueous acid solution is selected from any one of HCl, H2SO4, H3PO4, and HNO3, and the molar ratio of the polyfluoroepoxycarboxylic acid ester to the aqueous acid solution is 1:(1-3).

9. The method for preparing polyfluoroepoxycarboxylate according to claim 3, characterized in that: In step S4, the inorganic base is selected from at least one of NaOH, KOH, NH3·H2O, K2CO3, and Na2CO3, and the molar ratio of the polyfluoroepoxycarboxylic acid to the inorganic base is 1:(1-3).

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