Preparation method of fluorinated polyether type surfactant

Abstract

The invention belongs to the technical field of fine chemical synthesis, belongs to a nonionic short fluorine chain surfactant, and relates to a preparation method of a fluorinated polyether surfactant. The preparation method comprises the following steps: reacting trimethylolethane with a hydrogen bromide acetic acid solution to prepare an intermediate 1; reacting the intermediate 1 in an alkaline environment without an organic solvent to prepare an intermediate 2; reacting the intermediate 2 with pentafluoropropanol under the action of potassium hydroxide and a catalyst 1 to prepare a fluorinated monomer; finally, the fluorinated monomer is subjected to ring opening polymerization under the action of an initiator and a catalyst 2, and the fluorinated polyether type surfactant is prepared. The method has the advantages of easily available raw materials, mild reaction conditions, simple synthesis, low cost, high yield and short fluorine chain of the product, can replace a long-chain fluorine-containing surfactant which is difficult to degrade, and can be used as an additive in the fields of photoresists, coatings, adhesives and the like. The surface tension can be obviously reduced, the surface defects of a coating can be reduced, and the appearance can be improved by adding a very small amount of the surface tension reducing agent.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical synthesis technology, specifically to nonionic short-chain fluorinated surfactants, and relates to a method for preparing a fluorinated polyether surfactant. Background Technology

[0002] Surfactants are an extremely important class of "industrial MSG." Through their unique "amphiphilic" structure, they play a role at the interface, achieving a variety of key functions such as cleaning, emulsification, dispersion, and wetting. They are an indispensable part of modern chemical industry and daily life.

[0003] If conventional surfactants are "all-purpose helpers," then fluorinated surfactants are "special forces," exhibiting irreplaceable roles under extreme or harsh conditions. Fluorinated surfactants are a class of surfactants in which all or part of the hydrogen atoms in the hydrophobic tail chain are replaced by fluorine atoms. Their hydrophobic tail chain is not a typical hydrocarbon chain (-CH2-CH2-), but a fluorinated carbon chain (-CF2-CF2-). This seemingly minor structural change endows them with unparalleled properties. While ordinary surfactants are "hydrophilic and oleophobic," fluorinated surfactants, due to their unique carbon-fluorine bonds, exhibit "double-repellent" properties, making them "outliers" in the surfactant family and resulting in the following superior properties: extremely high surface activity, extremely high chemical and thermal stability, and excellent water, oil, and stain resistance. Due to their superior performance and higher cost, fluorinated surfactants are mainly used in high-end and specialty fields, such as electroplating and electronics industries, aerospace, coatings and inks, fire extinguishing agents, polymerization reactions, textiles, and leather.

[0004] A crucial issue unavoidable with fluorinated surfactants is that when the carbon chain length is greater than 8, these substances are difficult to degrade in the natural environment and can persist and accumulate in water, soil, and organisms for extended periods. They exhibit bioaccumulation and potential toxicity, and are associated with health risks such as cancer, endocrine disruption, and immune system impacts. Given these environmental and health risks, global regulation and restrictions on certain long-chain fluorinated surfactants are being strengthened. The chemical industry is also actively developing and promoting short-chain fluorinated surfactants, which have lower bioaccumulation rates compared to long-chain substances; and novel environmentally friendly alternatives, researching degradable, fluorine-free, or low-toxicity alternatives. However, this remains a significant challenge in terms of performance and cost. Therefore, short-chain fluorinated surfactants (currently C3, C5, and C7) are considered by the industry as an important transitional solution to the ban on long-chain PFAS. They are not a perfect answer to the environmental problems of PFAS, but rather a necessary and important advancement under current technological conditions.

[0005] Short-chain fluorinated surfactants are a molecularly designed solution that balances the superior performance of fluorinated surfactants with their environmental friendliness. By shortening the fluorocarbon chain, they reduce environmental persistence and bioaccumulation while maintaining sufficient application performance. This can be simply understood as trading a small performance loss for a huge improvement in environmental safety.

[0006] There are two main approaches to preparing short-chain fluorinated surfactant monomers: The first approach involves first preparing an alcoholic oxetane, then brominating it to obtain brominated oxetane, which is then reacted with a fluoride to obtain the monomer. Patent CN103772347 A uses diethyl carbonate to react with trimethylolethane to prepare 3-hydroxymethyl-3-methyloxetane, but this method involves high reaction temperatures, high product boiling points, difficulty in distillation, and the generation of byproducts, resulting in low yields. Furthermore, the synthesis of intermediate 2 requires the use of hazardous chemicals such as triphenylphosphine, liquid bromine, and diethyl ether, making the process complex, dangerous, and costly.

[0007] The second approach involves first preparing brominated acetate, and then generating brominated oxobutane through intramolecular etherification. US5807977A first prepared intermediate 1 by reacting trimethylolethane with glacial acetic acid, sodium bromide, and concentrated sulfuric acid for 48 hours. This reaction was time-consuming, costly, and hazardous. Intermediate 1 was then reacted with a catalyst, sodium hydroxide, and carbon tetrachloride for 24 hours to obtain intermediate 2. This reaction also took a long time, and the solvent carbon tetrachloride has been strictly restricted or banned due to its extreme toxicity and environmental hazards. Summary of the Invention

[0008] To overcome the problems existing in the prior art, the present invention provides a method for preparing fluorinated polyether surfactants.

[0009] To achieve the above objectives, the specific technical solution of the present invention is as follows: A method for preparing a fluorinated polyether surfactant involves reacting trimethylolethane with a solution of hydrogen bromide and acetic acid to obtain intermediate 1; reacting intermediate 1 in an alkaline environment without organic solvents to obtain intermediate 2; reacting intermediate 2 with pentafluoropropanol in the presence of potassium hydroxide and catalyst 1 to obtain a fluorinated monomer; and finally, ring-opening polymerization of the fluorinated monomer in the presence of an initiator and catalyst 2 to obtain a fluorinated polyether surfactant.

[0010] To elaborate further, Step 1: Trimethylolethane and acetic acid solution of hydrogen bromide are reacted by a step-by-step heating method. After the reaction, the organic phase and the aqueous phase are separated. The organic phase is collected to obtain 3-bromo-2-bromomethyl-2-methylpropyl acetate (intermediate 1). Intermediate 1 can be directly carried out in the next step of the reaction without purification. Step 2: The intermediate 1 obtained in Step 1 is directly subjected to intramolecular etherification and cyclization reaction under the action of an alkaline environment and a catalyst. The reaction is controlled by gas chromatography until the reaction of the raw materials is complete. After post-reaction processing, the crude product is purified to obtain 3-methyl-3-bromomethyloxetane (intermediate 2). Step 3: Intermediate 2 and pentafluoropropanol react in an alkaline environment and in the presence of a catalyst. After the reaction is completed, the short-chain fluorinated monomer (short chain of C3) is obtained through post-treatment and purification. Step 4: Under inert gas protection, the above-mentioned short-chain fluorinated monomers are added dropwise to the reaction system of initiator and catalyst 2 to carry out ring-opening polymerization. After the reaction is completed, the fluorinated polyether surfactant is obtained by post-treatment and purification.

[0011] The reaction of trimethylolethane and hydrogen bromide acetic acid solution is carried out by a stepwise temperature increase, and gas chromatography is used for intermediate control until the reaction of the raw materials is complete. Ice water is added to the cooled reaction solution for quenching, and the organic phase and aqueous phase are separated. The organic phase is washed with sodium hydroxide solution until neutral, and then washed with saturated brine to obtain 3-bromo-2-bromomethyl-2-methylpropyl acetate (intermediate 1). The mass fraction of hydrogen bromide in the hydrogen bromide acetic acid solution is 30-50%, and the molar ratio of trimethylolethane to hydrogen bromide is 1:2-4.

[0012] The temperature rise in stages is as follows: first, the temperature is raised to 50-75℃ and held for 0.5-2 hours; then, the temperature is raised to 75-95℃ and held for 0.5-2 hours; and then, the temperature is raised to 95-120℃ and held for 6-10 hours, with a total reaction time of 7-14 hours.

[0013] Step two involves directly subjecting intermediate 1 obtained in step one to an intramolecular etherification and cyclization reaction at 60-90°C for 0.5-3 hours under alkaline conditions and with the aid of a catalyst. The reaction is controlled by gas chromatography until the reactants are completely reacted. After the reaction, the organic phase is extracted with an extractant and washed three times with deionized water and saturated brine. Finally, the organic phase is dried with anhydrous magnesium sulfate and then distilled under reduced pressure at a vacuum of 1.5-3 kPa. The distillate is collected at 50-65°C to obtain intermediate 2.

[0014] The molar ratio of intermediate 1, base, and catalyst is 1:1-5:0.01-0.1, wherein the base is sodium hydroxide or potassium hydroxide with a mass fraction of 5-20%, and the catalyst is benzyltriethylammonium chloride, tetrabutylammonium bromide, or tetrabutylammonium chloride.

[0015] In step three, intermediate 2 and pentafluoropropanol react at 70-90°C for 2-5 hours in an alkaline environment and in the presence of a catalyst. After the reaction, the reaction mixture is poured into a separatory funnel and extracted with dichloromethane. The organic layer is washed with deionized water and saturated brine and dried with anhydrous magnesium sulfate. The purification method is vacuum distillation at a vacuum degree of 1-3 kPa and a distillation temperature of 55-70°C to obtain the fluorinated monomer.

[0016] The molar ratio of pentafluoropropanol, intermediate 2, base and catalyst is 1: 1-1.2: 1-2: 0.01-0.1. The base is sodium hydroxide or potassium hydroxide with a mass fraction of 20-50%. The catalyst is benzyltriethylammonium chloride, tetrabutylammonium bromide or tetrabutylammonium chloride.

[0017] In step four, the above-mentioned fluorinated monomer is added dropwise to the reaction system of initiator and catalyst 1 under inert gas protection and subjected to ring-opening polymerization at 20-40°C for 3-8 hours. Dichloromethane is added to the mixture after the reaction to fully dissolve it. The organic phase is washed with 3-5% hydrochloric acid and saturated brine, dried with anhydrous magnesium sulfate, and the solvent is removed by vacuum distillation. Finally, it is vacuum dried at 60-70°C for 8-12 hours to obtain the fluorinated polyether surfactant.

[0018] The inert gas is argon or nitrogen; catalyst 1 is boron trifluoride diethyl ether complex or boron trifluoride tetrahydrofuran complex; the initiator is one of 1,4-butanediol, 1,5-pentanediol, neopentanediol or 1,6-hexanediol; the molar ratio of initiator, fluorinated monomer and catalyst is 1: 4-30: 0.05-0.5.

[0019] The viscosity of the fluorinated polyether surfactant product is 5000-15000 mPa·s, and the testing instrument used is a Brookfield cone-plate viscometer at a test temperature of 25℃. The average molecular weight is 1500-7200 g / mol, and the testing instrument used is an APC gel chromatograph. The density is 1.2680-1.3150 g / mL, and the testing instrument used is a Mettler densitometer at a test temperature of 20℃.

[0020] The fluorinated polyether surfactant prepared in this invention has the following beneficial effects in practical applications: (1) Using pentafluoropropanol as a raw material greatly reduces the length of the fluorocarbon chain, giving the product a better environmental fate, lower bioaccumulation, and faster degradation in the environment.

[0021] (2) The preparation route is innovative. Intermediate 1 is prepared by using a staged heating method, which greatly shortens the reaction time. Intermediate 1 is directly synthesized into intermediate 2 without purification, which greatly simplifies the process, reduces production costs, and increases the yield. Intermediate 2 is prepared by reacting without organic solvents, which greatly reduces the huge toxicity and environmental hazards caused by organic solvents.

[0022] (3) In line with regulatory trends, with the strict prohibition and restriction of long-chain products globally, short-chain fluorocarbon products have become a compliant alternative for many existing applications.

[0023] (4) It retains the core function. Although its surface activity may be slightly inferior to long fluorocarbon chain products, its "double hydrophobic" (waterproof and oilproof) performance is still excellent and sufficient to meet most application needs. Attached Figure Description

[0024] Figure 1 The 1H NMR spectrum of the fluorinated polyether surfactant prepared in Example 1 is shown. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection of the claims of the present invention.

[0026] The preparation method of this invention uses readily available raw materials, mild reaction conditions, simple synthesis, low cost, high yield, high selectivity, and produces a product with a short fluorine chain. This product can replace long-chain fluorinated surfactants that are difficult to degrade and can be used as an additive in photoresists, coatings, adhesives, and lubricants. It exhibits high thermal and chemical stability, good compatibility, and even a very small amount can significantly reduce surface tension, effectively reducing surface defects in coatings and improving their appearance.

[0027] In the following examples, the content of trimethylolethane is greater than 97%, the content of pentafluoropropanol is greater than 99%, and the content of initiator is greater than 99%.

[0028] Example 1 20.62 g of trimethylolethane and 100 mL of 33% (w / w) hydrogen bromide acetic acid solution were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The stirrer and condenser were turned on, and the temperature was raised to 55 °C and held for 1 h. Then the temperature was raised to 85 °C and held for 1.5 h. Finally, the temperature was raised to 112 °C and held for the reaction. The reaction was monitored by gas chromatography. After 8 h of reaction at this temperature, the gas chromatography showed that the raw material was completely exhausted. After cooling to room temperature, the mixture was quenched with deionized water, and the organic phase was separated. It was washed with 1 mol / L sodium hydroxide solution until neutral, and then washed with saturated brine to obtain 46.52 g of 3-bromo-2-bromomethyl-2-methylpropyl acetate (hereinafter referred to as intermediate 1), with a normalized gas phase purity of 96.22%. It was directly used for the next reaction without further purification.

[0029] In a four-necked flask equipped with a stirrer, thermometer, and condenser, 170 mL of the above intermediate 1, 3 mol / L sodium hydroxide solution, and 2.68 g of tetrabutylammonium bromide were added. The mixture was heated to 75 °C with stirring and controlled by gas chromatography. The reaction was completed after 1.5 h. After cooling to room temperature, the mixture was extracted with dichloromethane to separate the organic phase. The organic phase was washed three times with deionized water and saturated brine, respectively, and dried over anhydrous magnesium sulfate. The mixture was then distilled under reduced pressure at a vacuum of 1.8 kPa, and the fraction collected at 56-60 °C was used to prepare 23.68 g of 3-methyl-3-bromomethyloxetane (hereinafter referred to as intermediate 2). The normalized content in the gas phase was 99.10%, and the yield of the first two steps was 85.43%.

[0030] In a four-necked flask equipped with a stirrer, thermometer, and condenser, intermediate 2, 20.32 g of pentafluoropropanol, and 1.10 g of tetrabutylammonium bromide were added. The mixture was heated to 80 °C with stirring. 22.75 g of 40% potassium hydroxide solution was added dropwise to the reaction flask using a constant-pressure dropping funnel, controlling the dropping rate to maintain the reaction temperature at around 85 °C. The addition was completed in about 1 hour. The gas chromatograph showed that the reaction was basically complete after 3.5 hours. The reaction solution was cooled to room temperature and extracted with dichloromethane to separate the organic phase. The organic phase was washed with deionized water and saturated brine, dried over anhydrous magnesium sulfate, and distilled under reduced pressure at a vacuum of 2.2 kPa. The fraction collected at 62-66 °C yielded 28.96 g of fluorinated monomer with a normalized gas phase purity of 99.35% and a yield of 90.73%.

[0031] 0.65 g of neopentyl glycol, 0.35 g of boron trifluoride tetrahydrofuran complex, and 12 mL of dichloromethane were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The mixture was stirred for 20 min under nitrogen protection while the system was heated to 30 °C. Then, the above-mentioned fluorinated monomer was added dropwise, maintaining the temperature at around 35 °C. After the addition was complete, the reaction was continued at this temperature for 5.5 h. The reaction was then stopped, and 50 mL of dichloromethane was added to the system to completely dissolve the product. The product was then washed three times with 3% hydrochloric acid (100 mL each time), followed by two washes with saturated brine. Finally, the product was dried with anhydrous magnesium sulfate, and the dichloromethane was removed by vacuum distillation. The product was then dried under vacuum at 65 °C for 10 h to obtain 29.00 g of fluorinated polyether surfactant with a yield of 98.50%, a viscosity of 11500 mPa·s, an average molecular weight of 4758 g / mol, and a density of 1.3106 g / mL.

[0032] Example 2 20.62 g of trimethylolethane and 120 mL of 33% (w / w) hydrogen bromide acetic acid solution were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The stirrer and condenser were turned on, and the temperature was raised to 60 °C and held for 0.5 h. Then the temperature was raised to 80 °C and held for 2.0 h. Finally, the temperature was raised to 105 °C and held for the reaction. The reaction was monitored by gas chromatography. After 9 h of reaction at this temperature, the gas chromatography showed that the starting material was completely exhausted. After cooling to room temperature, the mixture was quenched with deionized water, and the organic phase was separated. It was washed with 1 mol / L sodium hydroxide solution until neutral, and then washed with saturated brine to obtain 45.86 g of intermediate 1 with a normalized gas phase purity of 96.57%. It was directly used for the next reaction without further purification.

[0033] In a four-necked flask equipped with a stirrer, thermometer, and condenser, the above intermediate 1, 165 mL of 3 mol / L sodium hydroxide solution, and 2.58 g of tetrabutylammonium bromide were added. The mixture was heated to 85 °C with stirring and controlled by gas chromatography. The reaction was completed after 1.0 h. After cooling to room temperature, the mixture was extracted with dichloromethane to separate the organic phase. The organic phase was washed three times with deionized water and saturated brine, respectively, and dried over anhydrous magnesium sulfate. The mixture was then distilled under reduced pressure at a vacuum of 1.5 kPa, and the fraction collected at 54-58 °C was used to obtain 23.21 g of intermediate 2 with a normalized gas phase content of 99.16% and a yield of 83.78% for the first two steps.

[0034] In a four-necked flask equipped with a stirrer, thermometer, and condenser, intermediate 2, 20.52 g of pentafluoropropanol, and 1.54 g of tetrabutylammonium bromide were added. The mixture was heated to 85 °C with stirring. 20.43 g of 45% potassium hydroxide solution was added dropwise to the reaction flask using a constant-pressure dropping funnel, controlling the dropping rate to maintain the reaction temperature at around 90 °C. The addition was completed in about 1 hour. The gas chromatograph showed that the reaction was basically complete after 3.0 hours. After cooling the reaction solution to room temperature, it was extracted with dichloromethane to separate the organic phase. The organic phase was washed with deionized water and saturated brine, dried over anhydrous magnesium sulfate, and distilled under reduced pressure at a vacuum of 1.6 kPa. The fraction collected at 57-61 °C yielded 28.88 g of fluorinated monomer with a normalized gas phase purity of 99.28% and a yield of 89.54%.

[0035] 0.81 g of neopentyl glycol, 0.54 g of boron trifluoride tetrahydrofuran complex, and 12 mL of dichloromethane were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The mixture was stirred for 20 min under nitrogen protection while the system was heated to 35 °C. Then, the above-mentioned fluorinated monomer was added dropwise, maintaining the temperature at around 40 °C. After the addition was complete, the reaction was continued at this temperature for 4.5 h. The reaction was then stopped, and 50 mL of dichloromethane was added to the system to completely dissolve the product. The product was then washed three times with 3% hydrochloric acid (100 mL each time), followed by two washes with saturated brine. Finally, the product was dried with anhydrous magnesium sulfate, and the dichloromethane was removed by vacuum distillation. The product was then dried under vacuum at 70 °C for 8 h to obtain 28.96 g of fluorinated polyether surfactant with a yield of 98.23%, a viscosity of 10600 mPa·s, an average molecular weight of 3855 g / mol, and a density of 1.3029 g / mL.

[0036] Example 3 20.62 g of trimethylolethane and 110 mL of 33% (w / w) hydrogen bromide acetic acid solution were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The stirrer and condenser were turned on, and the temperature was raised to 65 °C and held for 0.5 h. Then the temperature was raised to 85 °C and held for 1.0 h. Finally, the temperature was raised to 115 °C and held for the reaction. The reaction was monitored by gas chromatography. After 7 h of reaction at this temperature, the gas chromatography showed that the starting material was completely exhausted. After cooling to room temperature, the mixture was quenched with deionized water, and the organic phase was separated. It was washed with 1 mol / L sodium hydroxide solution until neutral, and then washed with saturated brine. 46.52 g of intermediate 1 was obtained, with a normalized gas phase purity of 95.87%. It was directly used for the next reaction without further purification.

[0037] In a four-necked flask equipped with a stirrer, thermometer, and condenser, intermediate 1, 175 mL of 3 mol / L sodium hydroxide solution, and 3.06 g of tetrabutylammonium bromide were added. The mixture was heated to 70 °C with stirring and controlled by gas chromatography. The reaction was completed after 2.0 h. The mixture was cooled to room temperature, extracted with dichloromethane, and the organic phase was separated. The organic phase was washed three times with deionized water and saturated brine, respectively, and dried over anhydrous magnesium sulfate. The mixture was then distilled under reduced pressure at a vacuum of 2.0 kPa, and the fraction collected at 59–62 °C was used to obtain 22.96 g of intermediate 2 with a normalized gas phase content of 98.92% and a yield of 82.69% for the first two steps.

[0038] In a four-necked flask equipped with a stirrer, thermometer, and condenser, intermediate 2, 18.96 g of pentafluoropropanol, and 2.02 g of tetrabutylammonium bromide were added. The mixture was heated to 85 °C with stirring. 23.30 g of 45% potassium hydroxide solution was added dropwise to the reaction flask using a constant-pressure dropping funnel, controlling the dropping rate to maintain the reaction temperature at around 90 °C. The addition was completed in about 1 hour. The gas chromatograph showed that the reaction was basically complete after 2.5 hours. The reaction solution was cooled to room temperature and extracted with dichloromethane to separate the organic phase. The organic phase was washed with deionized water and saturated brine, dried over anhydrous magnesium sulfate, and distilled under reduced pressure at a vacuum of 2.0 kPa. The fraction collected at 60-63 °C yielded 26.26 g of fluorinated monomer with a normalized gas phase purity of 98.86% and a yield of 88.61%.

[0039] 0.97 g neopentyl glycol, 0.39 g boron trifluoride tetrahydrofuran complex, and 15 mL dichloromethane were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The mixture was stirred for 30 min under nitrogen protection while the system was heated to 25 °C. Then, the above-mentioned fluorinated monomer was added dropwise, maintaining the temperature at around 30 °C. After the addition was complete, the reaction was continued at this temperature for 6.0 h. The reaction was then stopped, and 50 mL of dichloromethane was added to the system to completely dissolve the product. The product was then washed three times with 3% hydrochloric acid (100 mL each time), followed by two washes with saturated brine. Finally, the product was dried with anhydrous magnesium sulfate, and the dichloromethane was removed by vacuum distillation. The product was then dried under vacuum at 70 °C for 8 h to obtain 26.22 g of fluorinated polyether surfactant with a yield of 97.50%, a viscosity of 9250 mPa·s, an average molecular weight of 2896 g / mol, and a density of 1.2946 g / mL.

[0040] Example 4 20.62 g of trimethylolethane and 150 mL of 33% (w / w) hydrogen bromide acetic acid solution were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The stirrer and condenser were turned on, and the temperature was raised to 75 °C and held for 0.5 h. Then the temperature was raised to 95 °C and held for 0.5 h. Finally, the temperature was raised to 115 °C and held for the reaction. The reaction was monitored by gas chromatography. After 7 h of reaction at this temperature, the gas chromatography showed that the starting material was completely exhausted. After cooling to room temperature, the mixture was quenched with deionized water, and the organic phase was separated. It was washed with 1 mol / L sodium hydroxide solution until neutral, and then washed with saturated brine to obtain 45.94 g of intermediate 1 with a normalized gas phase purity of 95.18%. It was directly used for the next reaction without further purification.

[0041] In a four-necked flask equipped with a stirrer, thermometer, and condenser, the above intermediate 1, 200 mL of 3 mol / L sodium hydroxide solution, and 1.35 g of tetrabutylammonium bromide were added. The mixture was heated to 70 °C with stirring and controlled by gas chromatography. The reaction was completed after 3.0 h. After cooling to room temperature, the mixture was extracted with dichloromethane to separate the organic phase. The organic phase was washed three times with deionized water and saturated brine, respectively, and dried over anhydrous magnesium sulfate. The mixture was then distilled under reduced pressure at a vacuum of 2.0 kPa, and the fraction collected at 59-62 °C was used to obtain 22.69 g of intermediate 2. The normalized gas phase content was 98.74%, and the yield of the first two steps was 81.57%.

[0042] In a four-necked flask equipped with a stirrer, thermometer, and condenser, intermediate 2, 19.41 g of pentafluoropropanol, and 1.51 g of tetrabutylammonium bromide were added. The mixture was heated to 75 °C with stirring. 26.63 g of 40% potassium hydroxide solution was added dropwise to the reaction flask using a constant-pressure dropping funnel, controlling the dropping rate to maintain the reaction temperature at approximately 80 °C. The addition was completed in about 1 hour. Gas chromatography showed that the reaction was essentially complete after 4.0 hours. The reaction solution was cooled to room temperature and extracted with dichloromethane to separate the organic phase. The organic phase was washed with deionized water and saturated brine, dried over anhydrous magnesium sulfate, and distilled under reduced pressure at a vacuum of 1.4 kPa. The fraction collected at 57-60 °C yielded 27.27 g of fluorinated monomer with a normalized gas phase purity of 99.02% and a yield of 90.06%.

[0043] 1.52 g of neopentyl glycol, 0.92 g of boron trifluoride tetrahydrofuran complex, and 15 mL of dichloromethane were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The mixture was stirred for 30 min under nitrogen protection while the system was heated to 35 °C. Then, the above-mentioned fluorinated monomer was added dropwise, maintaining the temperature at around 40 °C. After the addition was complete, the reaction was continued at this temperature for 4.0 h. The reaction was then stopped, and 50 mL of dichloromethane was added to the system to completely dissolve the product. The product was then washed three times with 3% hydrochloric acid (100 mL each time), followed by two washes with saturated brine. Finally, the product was dried with anhydrous magnesium sulfate, and the dichloromethane was removed by vacuum distillation. The product was then dried under vacuum at 65 °C for 11 h to obtain 27.88 g of fluorinated polyether surfactant with a yield of 97.83%, a viscosity of 7400 mPa·s, an average molecular weight of 1992 g / mol, and a density of 1.2781 g / mL.

[0044] Example 5 20.62 g of trimethylolethane and 80 mL of 48% (w / w) hydrogen bromide acetic acid solution were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The stirrer and condenser were turned on, and the temperature was raised to 55 °C and held for 1.0 h. Then the temperature was raised to 80 °C and held for 1.0 h. Finally, the temperature was raised to 115 °C and held for the reaction. The reaction was monitored by gas chromatography. After 8.5 h of reaction at this temperature, the gas chromatography showed that the starting material was completely exhausted. After cooling to room temperature, the mixture was quenched with deionized water, and the organic phase was separated. It was washed with 1 mol / L sodium hydroxide solution until neutral, and then washed with saturated brine to obtain 46.33 g of intermediate 1 with a normalized gas phase purity of 95.27%. It was directly used for the next reaction without further purification.

[0045] In a four-necked flask equipped with a stirrer, thermometer, and condenser, the above intermediate 1, 180 mL of 3 mol / L sodium hydroxide solution, and 1.55 g of tetrabutylammonium bromide were added. The mixture was heated to 85 °C with stirring and controlled by gas chromatography. The reaction was completed after 2.5 h. After cooling to room temperature, the mixture was extracted with dichloromethane to separate the organic phase. The organic phase was washed three times with deionized water and saturated brine, respectively, and dried over anhydrous magnesium sulfate. The mixture was then distilled under reduced pressure at a vacuum of 1.7 kPa, and the fraction collected at 57-60 °C was used to obtain 23.50 g of intermediate 2 with a normalized gas phase content of 98.55% and a yield of 84.29% for the first two steps.

[0046] In a four-necked flask equipped with a stirrer, thermometer, and condenser, intermediate 2, 20.35 g of pentafluoropropanol, and 2.16 g of tetrabutylammonium bromide were added. The mixture was heated to 85 °C with stirring. 21.78 g of 45% potassium hydroxide solution was added dropwise to the reaction flask using a constant-pressure dropping funnel, controlling the dropping rate to maintain the reaction temperature at around 90 °C. The addition was completed in about 1 hour. The gas chromatograph showed that the reaction was basically complete after 3.0 hours. After cooling the reaction solution to room temperature, it was extracted with dichloromethane to separate the organic phase. The organic phase was washed with deionized water and saturated brine, dried over anhydrous magnesium sulfate, and distilled under reduced pressure at a vacuum of 1.5 kPa. The fraction collected at 58-60 °C yielded 28.16 g of fluorinated monomer with a normalized gas phase purity of 98.52% and a yield of 88.24%.

[0047] 0.52 g of neopentyl glycol, 0.28 g of boron trifluoride tetrahydrofuran complex, and 12 mL of dichloromethane were added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The mixture was stirred for 20 min under nitrogen protection while the system was heated to 35 °C. Then, the above-mentioned fluorinated monomer was added dropwise, maintaining the temperature at around 40 °C. After the addition was complete, the reaction was continued at this temperature for 6.0 h. The reaction was then stopped, and 50 mL of dichloromethane was added to the system to completely dissolve the product. The product was then washed three times with 3% hydrochloric acid (100 mL each time), followed by two washes with saturated brine. Finally, the product was dried with anhydrous magnesium sulfate, and the dichloromethane was removed by vacuum distillation. The product was then dried under vacuum at 70 °C for 9 h to obtain 27.76 g of fluorinated polyether surfactant with a yield of 98.22%, a viscosity of 12700 mPa·s, an average molecular weight of 5721 g / mol, and a density of 1.3127 g / mL.

[0048] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and cannot limit the scope of protection of the present invention. For those skilled in the art, equivalent substitutions or modifications made according to the technical solutions of the present invention are all within the scope of protection of the present invention.

Claims

1. A method for preparing a fluorinated polyether surfactant, characterized in that, Intermediate 1 was prepared by reacting trimethylolethane with a solution of hydrogen bromide and acetic acid; intermediate 1 was reacted in an alkaline environment without organic solvents to prepare intermediate 2; intermediate 2 was reacted with pentafluoropropanol in the presence of potassium hydroxide and catalyst 1 to prepare a fluorinated monomer; finally, the fluorinated monomer was subjected to ring-opening polymerization in the presence of an initiator and catalyst 2 to prepare a fluorinated polyether surfactant.

2. The method for preparing fluorinated polyether surfactant according to claim 1, characterized in that, Step 1: Trimethylolethane and hydrogen bromide acetic acid solution are reacted by a step-by-step heating method. After the reaction, the organic phase and the aqueous phase are separated. The organic phase is collected to obtain 3-bromo-2-bromomethyl-2-methylpropyl acetate (intermediate 1), which is directly used for the next step of the reaction. Step 2: The intermediate 1 obtained in Step 1 is directly subjected to intramolecular etherification and cyclization reaction under the action of an alkaline environment and a catalyst. The reaction is controlled by gas chromatography until the reaction of the raw materials is complete. After post-reaction processing, the crude product is purified to obtain 3-methyl-3-bromomethyloxetane (intermediate 2). Step 3: Intermediate 2 and pentafluoropropanol react in an alkaline environment and in the presence of a catalyst. After the reaction is complete, the organic phase is collected and purified to obtain a short-chain fluorinated monomer. Step 4: Under inert gas protection, the above-mentioned short-chain fluorinated monomers are added dropwise to the reaction system of initiator and catalyst 2 to carry out ring-opening polymerization. After the reaction is completed, the organic phase is purified to obtain fluorinated polyether surfactant.

3. The method for preparing fluorinated polyether surfactant according to claim 2, characterized in that, The reaction of trimethylolethane and hydrogen bromide acetic acid solution is carried out by a stepwise temperature increase, and gas chromatography is used for intermediate control until the reaction of the raw materials is complete. Ice water is added to the cooled reaction solution for quenching, and the organic phase and aqueous phase are separated. The organic phase is washed with sodium hydroxide solution until neutral, and then washed with saturated brine to obtain 3-bromo-2-bromomethyl-2-methylpropyl acetate (intermediate 1). The mass fraction of hydrogen bromide in the hydrogen bromide acetic acid solution is 30-50%, and the molar ratio of trimethylolethane to hydrogen bromide is 1:2-4.

4. The method for preparing fluorinated polyether surfactant according to claim 2 or 3, characterized in that, The temperature rise in stages is as follows: first, the temperature is raised to 50-75℃ and held for 0.5-2 hours; then, the temperature is raised to 75-95℃ and held for 0.5-2 hours; and then, the temperature is raised to 95-120℃ and held for 6-10 hours, with a total reaction time of 7-14 hours.

5. The method for preparing fluorinated polyether surfactant according to claim 2, characterized in that, Step two involves directly subjecting intermediate 1 obtained in step one to an intramolecular etherification and cyclization reaction at 60-90°C for 0.5-3 hours under alkaline conditions and with the aid of a catalyst. The reaction is controlled by gas chromatography until the reactants are completely reacted. After the reaction, the mixture is extracted with an extractant to separate the organic phase. The organic phase is washed three times with deionized water and saturated brine, and finally dried with anhydrous magnesium sulfate. After drying, the mixture is distilled under reduced pressure at a vacuum of 1.5-3 kPa, and the distillate is collected at 50-65°C to obtain intermediate 2.

6. The method for preparing fluorinated polyether surfactant according to claim 5, characterized in that, The molar ratio of intermediate 1, base, and catalyst is 1:1-5:0.01-0.1, wherein the base is sodium hydroxide or potassium hydroxide with a mass fraction of 5-20%, and the catalyst is benzyltriethylammonium chloride, tetrabutylammonium bromide, or tetrabutylammonium chloride.

7. The method for preparing fluorinated polyether surfactant according to claim 2, characterized in that, In step three, intermediate 2 and pentafluoropropanol react at 70-90°C for 2-5 hours in an alkaline environment and in the presence of a catalyst. After the reaction, the reaction mixture is poured into a separatory funnel and extracted with dichloromethane. The organic layer is washed with deionized water and saturated brine and dried with anhydrous magnesium sulfate. The purification method is vacuum distillation at a vacuum degree of 1-3 kPa and a distillation temperature of 55-70°C to obtain the fluorinated monomer.

8. The method for preparing fluorinated polyether surfactant according to claim 7, characterized in that, The molar ratio of pentafluoropropanol, intermediate 2, base and catalyst is 1: 1-1.2: 1-2: 0.01-0.

1. The base is sodium hydroxide or potassium hydroxide with a mass fraction of 20-50%. The catalyst is benzyltriethylammonium chloride, tetrabutylammonium bromide or tetrabutylammonium chloride.

9. The method for preparing fluorinated polyether surfactant according to claim 2, characterized in that, In step four, the above-mentioned fluorinated monomer is added dropwise to the reaction system of initiator and catalyst 1 under inert gas protection and subjected to ring-opening polymerization at 20-40°C for 3-8 hours. Dichloromethane is added to the mixture after the reaction to fully dissolve it. The organic phase is washed with 3-5% hydrochloric acid and saturated brine, dried with anhydrous magnesium sulfate, and the solvent is removed by vacuum distillation. Finally, it is vacuum dried at 60-70°C for 8-12 hours to obtain the fluorinated polyether surfactant.

10. The method for preparing fluorinated polyether surfactant according to claim 9, characterized in that, The inert gas is argon or nitrogen; catalyst 1 is boron trifluoride diethyl ether complex or boron trifluoride tetrahydrofuran complex; the initiator is one of 1,4-butanediol, 1,5-pentanediol, neopentanediol or 1,6-hexanediol; the molar ratio of initiator, fluorinated monomer and catalyst is 1:4-30:0.05-0.5.

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