Process for the large-scale synthesis of a perfluoropolyether oil and a production system therefor

Abstract

The application discloses a large-scale synthesis preparation process and a production system of perfluoropolyether oil, and belongs to the technical field of fluorine chemical industry, and comprises the following steps: neutralization reaction is carried out on perfluoropolyether acyl fluoride and / or perfluoropolyether carboxylic acid and an alkaline compound to generate perfluoropolyether carboxylate intermediate I; decarboxylation reaction is carried out on the perfluoropolyether carboxylate intermediate I under the action of a reaction promoter to generate hydrogen-terminated fluorine-containing polyether intermediate II, wherein the reaction promoter comprises water or a compound with active protons; fluorination capping reaction is carried out on the hydrogen-terminated fluorine-containing polyether intermediate II to obtain perfluoropolyether oil products. The application sequentially passes through three steps of neutralization and salification, reaction promoter decarboxylation and fluorination capping, and systematically completes the conversion and stabilization of unstable end groups. Compared with the existing fluorination process, the process significantly reduces fluorine gas consumption, improves utilization efficiency, and has good engineering adaptability and large-scale production prospects.

Description

Technical Field

[0001] This invention relates to a large-scale synthesis preparation process and production system for perfluoropolyether oil, specifically to a large-scale synthesis preparation process for perfluoropolyether oil by stabilizing the end groups of unstable perfluoropolyether through a three-step reaction, and the production system used in conjunction with it, belonging to the field of fluorochemical technology. Background Technology

[0002] Perfluoropolyethers are a class of fluorinated polymer materials that combine excellent high and low temperature resistance, non-flammability, high heat and oxygen resistance, high chemical inertness, low volatility, excellent dielectric properties, non-toxicity, and excellent viscosity-temperature characteristics. They are widely used in aerospace, defense equipment, electronics, and nuclear energy fields as lubricants, greases, high-vacuum pump oils, heat transfer fluids, insulating fluids, and coolants. In existing technologies, whether it's Solvay's Fomblin Y-type and Z-type perfluoropolyethers, Chemours' Krytox (K-type), or Daikin Industries' Demnum (D-type) perfluoropolyethers, they all originate from polyether fluoride or polyether carboxylic acid with highly reactive end groups on their molecular chains. During production, polyether fluoride or polyether carboxylic acid must be converted into a stable molecular chain end group structure through a fluorination process to meet performance requirements.

[0003] Currently, there are three main process technologies successfully applied to fluorination treatment. The first is Simons electrolytic fluorination technology, which uses anhydrous hydrogen fluoride as both a solvent and a fluorine source. The material to be fluorinated is dissolved in anhydrous hydrogen fluoride and then electrolyzed in an electrolytic cell using direct current. Due to the limited solubility of anhydrous hydrogen fluoride, electrolytic fluorination technology is more commonly used for fluorinating small molecule compounds. Furthermore, the use of large quantities of anhydrous hydrogen fluoride poses significant safety risks and requires complex separation and purification processes. Therefore, its application in stabilizing the end groups of unstable perfluoropolyethers faces challenges. The second is fluorinated salt catalytic fluorination technology, using fluorinated salts such as CoF3, AlF3, and SbF5 as fluorinating agents. This technology generally requires high temperatures of 270–400°C to achieve good fluorination results. High-temperature fluorination presents challenges and difficulties in process control and the investment in supporting equipment. Moreover, these fluorinating agents are expensive, difficult to separate, and their product quality is hard to guarantee. The third method involves elemental fluorination using fluorinating agents, including fluorine gas, SF4, SF6, and BF3. This technology offers advantages such as simple post-processing and high product purity. However, because fluorinating agents like fluorine gas are gases with low solubility in perfluoropolyethers, the reaction is a gas-liquid heterogeneous process, often resulting in uneven dispersion and insufficient gas-liquid contact. This leads to low fluorinating agent utilization efficiency (the actual amount used is often more than 10 times the theoretical amount), excessively long reaction time, high costs, large exhaust gas volume, and significant environmental pressure.

[0004] To address the aforementioned issues, some patents have attempted to propose improvement solutions. For example, Chinese patent CN106633023A discloses a method for preparing perfluoropolyethers. This method uses fluoropolyether oligomers as raw materials and fluorine gas as a fluorinating agent, employing a two-step fluorination process to convert unstable end groups into stable perfluoroalkyl groups at 200–250°C and 0.01–0.02 MPa, aiming to reduce impurity residues and improve conversion rates. However, this process requires direct introduction of fluorine gas at high temperatures, resulting in significant material entrainment and vaporization, leading to substantial material losses. Furthermore, maintaining the high temperature requires high energy consumption, posing a significant challenge to the process's economic viability and hindering large-scale production.

[0005] Another Chinese patent, CN119529262A, discloses a method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether. This method first converts the impurities (trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride) into their corresponding carboxylates using a metal compound. These are then decomposed by heating to generate trace amounts of olefins. Finally, under the action of a fluorinating agent diluted with a protective gas, the olefins are converted into perfluoropolyether oil, thereby solving the problems of trace acid and "acid backflow" in the product. However, this method still has the following shortcomings in terms of industrial applicability: First, its applicability is extremely limited, only able to handle trace impurities with acid values ​​in the range of 0.01 to 1.0 mg KOH / g, and cannot handle intermediates with high acid values ​​in the original polymerization solution; Second, the decarboxylation step generates olefin intermediates with unsaturated double bonds (-CF=CF2), resulting in insufficient product stability; Third, the process is cumbersome, requiring the use of large amounts of alkali (such as a 300 kg Na2CO3 fixed bed) and strict maintenance of anhydrous conditions, which not only generates solid waste but also makes operation difficult; At the same time, the generated olefins are highly reactive, and if not properly controlled, polymerization can easily occur, leading to increased system viscosity or gel formation, affecting product quality.

[0006] It is evident that although various improved fluorination treatment schemes have been disclosed in existing technologies, they still have significant shortcomings in terms of processing efficiency, energy consumption, material loss, applicable targets, product stability, and process operability. Therefore, there is an urgent need to develop a new method that can efficiently, economically, and on a large scale achieve end-group stabilization of perfluoropolyethers. Summary of the Invention

[0007] The purpose of this invention is to provide a large-scale synthesis process and production system for perfluoropolyether oil, aiming to achieve the efficient conversion of unstable perfluoropolyether acyl fluoride and / or perfluoropolyether carboxylic acid into perfluoropolyether oil through an end-group stabilization reaction. This method sequentially completes the conversion and stabilization of unstable end groups through three steps: neutralization and salt formation, decarboxylation with a reaction promoter, and fluorination end-capping. Compared with existing fluorination processes, this process significantly reduces fluorine gas consumption, improves utilization efficiency, and possesses good engineering adaptability and prospects for large-scale production.

[0008] This invention is achieved through the following technical solution: a large-scale synthesis and preparation process for perfluoropolyether oil, comprising the following steps: S1. Neutralize perfluoropolyether acyl fluoride and / or perfluoropolyether carboxylic acid with an alkaline compound to generate perfluoropolyether carboxylate intermediate I; S2. The perfluoropolyether carboxylate intermediate I is subjected to a decarboxylation reaction under the action of a reaction promoter to generate a hydrogen-terminated fluorinated polyether intermediate II, wherein the reaction promoter includes water or a compound with active protons, and the amount of the reaction promoter added is 1-5% of the mass of the perfluoropolyether carboxylate intermediate I; S3. Fluoride-capping reaction is carried out on hydrogen-terminated fluorinated polyether intermediate II to obtain perfluorinated polyether oil product.

[0009] Preferably, the alkaline compound is an inorganic alkaline compound or an organic alkaline compound.

[0010] Preferably, the molar ratio of the basic compound to the acyl fluoride group and / or carboxyl group is 1:1 to 1.1:1.

[0011] Preferably, during the neutralization reaction, the reaction temperature is controlled at 30–50°C, and the reaction is stirred for 1–2 hours.

[0012] Preferably, the reaction promoter is selected from one or more alcohol compounds and / or amine compounds.

[0013] Preferably, the decarboxylation reaction is carried out at a temperature of 120–250°C.

[0014] Preferably, the hydrogen-terminated fluorinated polyether intermediate II is subjected to a fluorination-end-capping reaction with a fluorinating agent gas under UV irradiation or heating conditions, with the temperature of the fluorination-end-capping reaction controlled at 120-160°C, the pressure at 0.1-0.3 MPa, and the reaction time at 10-50 h.

[0015] Preferably, the fluorinating agent gas is a mixture of F2 and N2, and the volume concentration of F2 in the mixture is 20-50%.

[0016] Another technical solution of the present invention is to provide a production system for perfluoropolyether oil, used in the above-mentioned large-scale synthesis preparation process, which is provided with at least a neutralization unit, a decarboxylation unit and a fluorination end-capping unit connected in sequence.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) This invention aims to solve the technical problems of high cost and large tail gas treatment volume caused by the low solubility of fluorine gas in the liquid phase and poor gas-liquid contact efficiency when directly fluorinating a large number of unstable acyl fluoride (-COF) or carboxylic acid (-COOH) end groups in traditional fluorination processes. This invention is the first to adopt a three-step process of "neutralization and salt formation - decarboxylation of reaction promoter - fluorination and end-capping". First, the unstable end groups are converted into hydrogen-containing end groups (-CF2H, etc.), and then the more reactive CH bonds are selectively fluorinated. This path significantly reduces the amount of fluorine gas required in the fluorination step, significantly improves the utilization efficiency of fluorine gas, thereby reducing raw material costs and safety risks, and at the same time reducing the burden of tail gas treatment, which has good economic and environmental benefits.

[0018] (2) This invention completely converts the perfluoropolyether carboxylate intermediate into a hydrogen-terminated fluorinated polyether through a thorough decarboxylation reaction, and then obtains stable perfluoroalkyl end groups (-CF3, -C2F5, -C3F7, etc.) through fluorination end-capping. This fundamentally eliminates the product acid value problem caused by residual acyl fluoride or carboxylic acid, as well as the "backflow" phenomenon during use. The product acid value can be stably controlled at ≤0.03 mg KOH / g, reaching the international top level and meeting the stringent requirements of high-end fields such as aerospace, electronics, and semiconductors for ultra-pure and ultra-stable lubricating media.

[0019] (3) This invention is based on a reaction promoter as the key component for deacidification. Unlike existing methods (such as CN119529262A) that can only handle trace impurities (acid value 0.01-1.0 mg KOH / g), this invention is not limited by the initial acid value of the raw materials and can directly stabilize the high-acid-value perfluoropolyether acyl fluoride / carboxylic acid in the original polymerization solution on a large scale. The key is that an appropriate amount of reaction promoter (water or compounds with active protons, such as alcohols and amines) is introduced in the decarboxylation step to efficiently and controllably complete decarboxylation at 120-250°C, generating stable terminal hydrogen intermediates instead of unstable olefins (-CF=CF2). This avoids the risk of increased viscosity or gel formation caused by olefin polymerization and ensures the consistency and high quality of product batches.

[0020] (4) Compared with patent CN119529262A, this invention has significant advantages in terms of process simplicity and ease of operation. This patent requires the use of a large amount of alkali (e.g., a 300 kg Na2CO3 fixed bed), strict maintenance of anhydrous conditions, and complex solid waste treatment issues. In contrast, the process flow of this invention is simpler, with mild operating conditions for each unit (neutralization, decarboxylation, and fluorination end-capping) (neutralization 30–50°C, decarboxylation 120–250°C, fluorination 120–160°C), and conventional reaction equipment can be used. Especially in the decarboxylation step, an anhydrous environment is not required, and the amount of reaction promoter added is only 1–5% of the intermediate mass, greatly reducing the difficulty of operation and the consumption of auxiliary materials. The entire process is not only suitable for batch production but also easy to design for continuous production, possessing good prospects for engineering scale-up and industrialization.

[0021] (5) In the fluorination end-capping step of this invention, UV irradiation is preferably used, which can efficiently complete the perfluorination of terminal hydrogen groups under conditions of 120-160℃ and 0.1-0.3MPa with a fluorine-nitrogen mixed gas (F2 volume concentration of 20-50%). UV excitation increases the fluorination reaction rate of CH bonds, shortens the reaction time (10-50h), and reduces the required fluorine partial pressure and temperature, further improving process safety. Compared with addition fluorination that relies solely on heat (such as the treatment of trace olefins in CN119529262A), this method is more efficient and has better control in large-scale production.

[0022] In summary, this invention provides an efficient, economical, and scalable process and production system for the synthesis of perfluoropolyether oils. It successfully overcomes many bottlenecks in existing technologies in terms of fluorine utilization, raw material applicability, product stability, and engineering feasibility, opening up a new technical path for the industrial production of high-performance perfluoropolyether oils. Attached Figure Description

[0023] Figure 1 The image shows the infrared spectrum of the perfluoropolyether carboxylic acid in Example 2.

[0024] Figure 2 The infrared spectrum of the hydrogen-terminated fluorinated polyether intermediate in Example 2 is shown.

[0025] Figure 3 The image shows the infrared spectrum of the perfluoropolyether oil product in Example 2. Detailed Implementation

[0026] The invention's objective, technical solution, and beneficial effects will be further explained in detail below.

[0027] It should be noted that the following detailed description is exemplary and intended to provide further illustration of the claimed invention. Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] This invention achieves efficient stabilization of unstable end groups of perfluoropolyether acyl fluoride and / or perfluoropolyether carboxylic acid through a three-step reaction involving neutralization, decarboxylation, and fluorination end-capping. The process pathway is clear and the conversion is thorough, enabling the production of high-purity perfluoropolyether oil products while significantly improving fluorine gas utilization efficiency. This provides a novel technical route for the industrial production of perfluoropolyether oil that combines economic efficiency and safety.

[0029] The following is a detailed summary of the process flow and equipment of this invention: Step 1: Neutralization and Salt Formation Reaction An alkaline compound and perfluoropolyether acyl fluoride and / or perfluoropolyether carboxylic acid are added to a reactor equipped with a stirrer. The molar ratio of the alkaline compound to the acyl fluoride group and / or carboxyl group is controlled to be 1:1 to 1.1:1. The neutralization reaction is carried out at 30 to 50°C. After stirring for 1 to 2 hours, perfluoropolyether carboxylate intermediate I is generated.

[0030] The reaction equation is as follows (taking metal oxide MOH as an example): Rf1O[CF(CF3)CF2O] m [CF2CF2O] n [CF2O] q Rf2+MOH →Rf'1O[CF(CF3)CF2O] m [CF2CF2O] n [CF2O] q Rf'2+H2O(1) Where m, n, and q represent the number of repeating units; Rf1 and Rf2 can be structural units with -CF3, -C2F5, or -C3F7 groups at one end or with -COF, -CF2COF, -CF(CF3)COF, -COOH, -CF2COOH, or -CF(CF3)COOH groups at both ends; Rf'1 and Rf'2 are structural units with -CF3, -C2F5, or -C3F7 groups or -COOM, -CF2COOM, or -CF(CF3)COOM.

[0031] As an example, the basic compound can be an inorganic basic compound or an organic basic compound. Inorganic basic compounds can be selected from basic substances such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, aluminum hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate, aluminum carbonate, sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, aluminum bicarbonate, and ammonia. Organic basic compounds can be selected from amine compounds, such as methylamine, ethylamine, propylamine, ethylenediamine, and ethanolamine. Preferably, the basic compound can be selected from readily available sources such as sodium hydroxide, potassium hydroxide, and ammonia.

[0032] During the neutralization reaction, the molar ratio of the basic compound to the acyl fluoride group and / or carboxyl group is 1:1 to 1.1:1. The reaction temperature is controlled in the range of 30 to 50°C. The reaction is stirred for 1 to 2 hours to ensure that the acid and base react completely to obtain perfluoropolyether carboxylate intermediate I. The obtained perfluoropolyether carboxylate intermediate I can directly enter the next step of the reaction.

[0033] Step 2: Decarboxylation reaction The perfluoropolyether carboxylate intermediate I obtained from the first step of neutralization and salt formation reaction is fed into a decarboxylation reactor, which can be a reaction vessel or a reactive distillation column. The decarboxylation reaction is carried out under the action of a reaction promoter. The reaction process needs to be carried out under heating conditions, and the reaction temperature is usually controlled at 120-250℃ to generate hydrogen-terminated fluorinated polyether intermediate II.

[0034] The reaction equation is as follows (taking water as an accelerator as an example): Rf'1O[CF(CF3)CF2O] m [CF2CF2O] n [CF2O] q Rf'2+H2O

[0035] Rf''1O[CF(CF3)CF2O] m [CF2CF2O] n [CF2O] q Rf''2+ CO2↑+MOH (2) Among them, Rf''1 and Rf''2 are structural units of groups such as -CF3, -C2F5, and -C3F7, or structural units of groups such as -CF2H, -CF2CF2H, and -CFH(CF3).

[0036] The reaction accelerator can be water or a compound with active protons, such as one or more alcohols and / or amines. The amount of reaction accelerator added is 1 to 5% of the mass of perfluoropolyether carboxylate intermediate I. A single type of accelerator, a composite composition of two to three types, or a mixture with water can be used.

[0037] When using accelerators such as alcohols and amines, compounds with boiling points above 120°C are preferred. For example, alcohols such as ethylene glycol, glycerol, ethylene glycol ether, and ethylene glycol ether can be used; amines such as primary and secondary amines, including hexylamine, octylamine, tripropylamine, tributylamine, and ethanolamine, can be used.

[0038] Step 3: Fluorination capping reaction The hydrogen-terminated fluorinated polyether intermediate II obtained from the second decarboxylation reaction is fed into a fluorination reactor. Under UV irradiation or heating conditions, the hydrogen-containing end groups (such as -CF2H) of the hydrogen-terminated fluorinated polyether intermediate II are fluorinated and capped by fluorinating agent gas to finally obtain a completely stable perfluorinated polyether oil product.

[0039] The reaction process is as follows: Rf''1O[CF(CF3)CF2O] m [CF2CF2O] n [CF2O] q Rf''2+F2

[0040] Rf'''1O[CF(CF3)CF2O] m [CF2CF2O] n [CF2O] q Rf'''2+HF(3) Among them, Rf'''1 and Rf'''2 are saturated and stable structural units such as -CF3, -C2F5, and -C3F7 groups.

[0041] During the fluorination end-capping reaction, the reaction temperature is typically controlled at 120–160℃, the pressure at 0.1–0.3 MPa, and the reaction time at 10–50 h. When using UV irradiation, the reaction temperature is also controlled at 120–160℃, and the preferred UV wavelength range is 185–300 nm. UV excitation can significantly increase the fluorination rate of CH bonds, shorten the reaction time, reduce dependence on high temperature and high pressure, and improve process safety.

[0042] The fluorinating agent gas used is fluorine gas (F2) diluted with a protective gas. A mixture of F2 and N2 is usually used, with the volume concentration of F2 controlled between 20% and 50%, preferably 20%. The reaction tail gas is treated by alkaline absorption before being discharged.

[0043] The specific implementation of the present invention will be described below with reference to the embodiments. Of course, the scope of protection of the present invention is not limited to the following embodiments.

[0044] Example 1: Intermittent Take 10 kg of perfluoropolyether acyl fluoride (average molecular weight about 1000) with an initial acid value of 105 mg KOH / g and add it to a 20 L stainless steel reactor. Add 1.16 kg of potassium hydroxide (KOH) (molar ratio 1:1.1), control the temperature at 50℃, and stir the reaction for 2 h to obtain the perfluoropolyether carboxylate potassium salt intermediate.

[0045] 0.56 kg of ethylene glycol (approximately 5% of the intermediate mass) was added to the above reaction vessel, the temperature was raised to 250°C, and the reaction was carried out for 5 hours. After the reaction was completed, a hydrogen-terminated fluorinated polyether intermediate was obtained, and the terminal groups were mainly -CF2H.

[0046] The above intermediate was transferred to a fluorination reactor, and a mixture of F2 and N2 (F2 volume concentration of 20%) was introduced. The reaction temperature was controlled at 120℃, the pressure at 0.3MPa, and the reaction was carried out under UV irradiation at a wavelength of 254nm for 20 h. After the reaction, residual fluorine and HF were removed by nitrogen purging, yielding 8.25 kg of colorless and transparent perfluorinated polyether oil product, with a yield of 93%. The acid value of the product was determined by extraction acid value titration, and the actual amount of fluorine used was ≤0.03 mgKOH / g, with an actual fluorine consumption of 0.84 kg.

[0047] Example 2: Intermittent Take a perfluoropolyether carboxylic acid with an initial acid value of 100 mg KOH / g (e.g.) Figure 1 10 kg of sodium hydroxide (NaOH) with an average molecular weight of approximately 1100 was added to a 20L stainless steel reactor. 0.79 kg of NaOH (molar ratio 1:1.1) was added, and the temperature was controlled at 30℃. The mixture was stirred for 2 h to obtain a sodium perfluoropolyether carboxylate intermediate.

[0048] 0.38 kg of ethylene glycol (3.5% of the intermediate mass) was added to the above reaction vessel, the temperature was raised to 200℃, and the reaction was carried out for 5 hours. After the reaction was completed, a hydrogen-terminated fluorinated polyether intermediate was obtained. The terminal groups were mainly -CF2H (e.g., ...). Figure 2 ).

[0049] The above intermediate was transferred to a fluorination reactor, and a mixture of F2 and N2 (F2 volume concentration of 20%) was introduced. The reaction temperature was controlled at 130℃, the pressure at 0.2 MPa, and the reaction was carried out under UV irradiation at a wavelength of 254 nm for 15 h. After the reaction was completed, nitrogen was used to purge and remove residual fluorine and HF, yielding 8.06 kg of colorless and transparent perfluorinated polyether oil product (e.g., ...). Figure 3 The yield was 94%. The acid value of the product was determined by extraction acid value titration to be ≤0.03 mg KOH / g, and the actual amount of fluorine gas used was 0.78 kg.

[0050] Infrared spectroscopy analysis was performed on the products of each stage mentioned above, and the results are as follows: Figure 1 The image shows the infrared spectrum of the perfluoropolyether carboxylic acid in Example 2. Figure 1 It can be seen that 1776cm -1 A characteristic absorption peak for carbonyl groups (C=O) appears at 979 cm⁻¹. -1 This corresponds to the absorption of asymmetric stretching vibrations of COC at 1118 cm. -1 The corresponding symmetrical / asymmetric stretching vibration absorption of the CF structure is 1224 cm. -1 Corresponding to the -CF2 / -CF3 structural stretching vibration absorption; 3000~3250cm -1 The test sample exhibits proton vibration absorption within the specified range. These characteristics indicate that the sample is a perfluoropolyether carboxylic acid with an unsaturated carbonyl group.

[0051] Figure 2 This is the infrared spectrum of the hydrogen-terminated fluorinated polyether intermediate in Example 2. Figure 2 It can be seen that 900.76cm -1 The presence of a proton vibration absorption peak for the terminal hydrogen-containing fluorinated polyether indicates that the decarboxylation reaction successfully introduced a hydrogen-containing terminal group (-CF2H).

[0052] Figure 3 The image shows the infrared spectrum of the perfluoropolyether oil product from Example 2. Figure 3 As can be seen, 1776.4cm -1 The characteristic absorption peak of the carbonyl group at 900.76 cm⁻¹ -1 The proton vibration absorption peaks of the terminal hydrogen fluorinated polyether have completely disappeared, indicating that the unstable end groups have been completely transformed into stable perfluoroalkyl structures, achieving complete end group stabilization.

[0053] Example 3: Continuous A continuous production system consisting of a neutralization reactor, a decarboxylation reaction tower, and a fluorination end-capping reactor connected in sequence was employed. Perfluoropolyether carboxylic acid (average molecular weight approximately 1000) with an initial acid value of 105 mg KOH / g and ammonia water were continuously fed into the neutralization reactor at a carboxyl group:NH3 molar ratio of 1:1.1, with the temperature controlled at 35°C and the reaction held for 1.5 h with stirring. The neutralization product was continuously fed into the decarboxylation reaction tower, with 5% (by mass) of tripropylamine added as a reaction promoter. The tower temperature was 150°C, and the reaction was held for 1 h. The decarboxylation product was continuously fed into the fluorination end-capping reactor. Under UV light (wavelength 265 nm), a mixture of F2 and N2 (F2 volume concentration 20%) was introduced, with the reaction temperature at 120°C and the pressure at 0.3 MPa, and the reaction held for 15 h, yielding a colorless and transparent perfluoropolyether oil product. The system operated continuously for 20 h, ultimately yielding 26 kg of perfluoropolyether oil product, with a yield of 95%. The acid value of the final product was determined by extraction acid value titration method to be ≤0.03mgKOH / g, and the actual amount of fluorine gas used was 2.7kg.

[0054] Comparative Example 1: Traditional Fluorination Process A one-step elemental fluorination process was employed. 10 kg of perfluoropolyether fluoride (average molecular weight approximately 1000), with an initial acid value of 105 mg KOH / g (same as in Example 1), was added to a 20 L stainless steel reactor and heated to 130 °C. A mixture of F2 and N2 (F2 volume concentration 20%) was directly introduced, and the reaction was carried out continuously at 0.3 MPa for 50 h. After the reaction, nitrogen was used for purging, yielding 5500 g of perfluoropolyether oil product, with a yield of 62%. The acid value of the product was determined by extraction acid value titration to be 0.12 mg KOH / g, and the actual amount of fluorine used was 1.5 kg.

[0055] Comparative Example 2: CN106633023A Method Following the process described in the embodiment of Chinese Patent CN106633023A, a bubbler was added to the bottom of the stainless steel reactor (with a stirrer) in Embodiment 1 of the present invention, and the process was reproduced. The specific steps are as follows: Step 1: Add 20% of the raw material to stainless steel reactor I, heat to 200℃, start stirring (400 rpm), and then introduce fluorine gas at an unpredictable flow rate to keep the pressure inside the reactor at 0.01 MPa.

[0056] Step 2: When the fluorine gas flow rate is reduced to 0 and the pressure inside the reactor remains at 0.01 MPa and no longer decreases, the temperature is increased to 250°C at a rate of 20°C / h and held for 30 minutes.

[0057] Step 3: Add the remaining 80% of the raw materials to another stainless steel reactor II, heat to 250°C, and purge with nitrogen until the gauge pressure reaches 0.1 MPa.

[0058] Step 4: Open the valve connecting the bottom of the two stainless steel reactors to allow the liquid in stainless steel reactor II to flow into stainless steel reactor I. Close the valve when the flow rate reaches 250 mL.

[0059] Step 5: Repeat Step 4 every 15 minutes until all the liquid in stainless steel reactor II has been transferred.

[0060] Step 6: When the fluorine gas flow rate is reduced to 0 again and the pressure inside the stainless steel reactor I remains at 0.01 MPa and no longer decreases, turn off the fluorine gas and cool the reactor. Then, put the fluorinated product into the receiver through the valve at the bottom of the reactor.

[0061] The raw materials used in this comparative example were perfluoropolyether fluoride with the same initial acid value as in Example 1, and the amount of raw materials used was the same. 5300g of perfluoropolyether product was obtained, with a yield of 59%. The acid value of the product was determined by extraction acid value titration: 0.15 mgKOH / g, and the actual amount of fluorine gas used was 1.7kg.

[0062] Comparative Example 3: CN119529262A Method Referring to the method described in the embodiment of Chinese Patent CN119529262A, and based on the reaction equipment provided in Embodiment 2 of this invention, the preparation process is reproduced, and the specific steps are as follows: Take 10 kg of perfluoropolyether carboxylic acid (average molecular weight about 1100) with an initial acid value of 100 mg KOH / g and add it to a 20 L stainless steel reactor. Add 2.1 kg of Na2CO3 in a 5-fold molar ratio and carry out a neutralization and decarboxylation reaction at 250 °C to generate an intermediate with an unsaturated double bond structure.

[0063] The above intermediate was transferred to a fluorination reactor, and a mixture of F2 and N2 (F2 volume concentration of 20%) was introduced. The reaction temperature was controlled at 130℃, the pressure at 0.2 MPa, and the reaction was carried out under UV irradiation at a wavelength of 254 nm for 15 h. After the reaction, nitrogen was used to purge residual fluorine and HF, yielding 5250 g of colorless and transparent perfluoropolyether oil product, with a yield of 59%. The acid value of the product was determined by extraction acid value titration: 0.23 mg KOH / g, and the actual amount of fluorine used was 1.64 kg.

[0064] Comparative Example 4: No reaction accelerator This comparative example is based on Example 2, except that the reaction promoter (ethylene glycol) is omitted, while the remaining process steps and operating parameters are exactly the same as in Example 2. 3550g of perfluoropolyether product was obtained, with a yield of 40%. The acid value of the product was determined by extraction acid value titration: 0.25 mgKOH / g, and the actual amount of fluorine gas used was 1.2kg.

[0065] Comparative Example 5: Excess Reaction Accelerator Referring to the material ratio of perfluoropolyether potassium carboxylate (1681g, 5.58mol) and ethylene glycol (907g, 14.6mol) used to prepare perfluoropolyether hydrogen-capped compounds in Chinese patent CN117362627A, the amount of ethylene glycol added in Example 1 was adjusted.

[0066] In the preparation process, a perfluoropolyether potassium carboxylate intermediate (perfluoropolyether potassium carboxylate) was prepared in the same manner as in Example 1. Then, 6.08 kg of ethylene glycol (54% of the mass of perfluoropolyether potassium carboxylate) was added, the temperature was raised to 250°C, and the reaction was carried out for 5 hours. After the reaction, a terminal hydrogen-containing fluorinated polyether intermediate was obtained. This intermediate was then transferred to a fluorination reactor, and 5.24 kg of perfluoropolyether oil product was prepared in the same manner as in Example 1, with a yield of 65%. The acid value of the product was determined by extraction acid value titration, and the actual amount of fluorine gas used was ≤0.17 mgKOH / g.

[0067] Comparative Example 6: Excess Reaction Accelerator Referring to the material ratio of sodium perfluoropolyether carboxylate (210g, 0.625mol) and ethylene glycol (130g, 2.0mol) used to prepare perfluoropolyether hydrogen-capped compounds in Chinese patent CN117362627A, the amount of ethylene glycol added in Example 2 was adjusted.

[0068] In the preparation process, a sodium perfluoropolyether carboxylate intermediate (sodium perfluoropolyether carboxylate) was prepared in the same manner as in Example 2. Then, 6.5 kg of ethylene glycol (62% of the mass of sodium perfluoropolyether carboxylate) was added, the temperature was raised to 200°C, and the reaction was carried out for 5 hours. After the reaction, a fluorinated polyether intermediate with terminal hydrogen was obtained. This intermediate was then transferred to a fluorination reactor, and 4.5 kg of perfluoropolyether oil product was prepared in the same manner as in Example 2, with a yield of 50.7%. The acid value of the product was ≤0.21 mg KOH / g by extraction acid value titration, and the actual amount of fluorine gas used was 1.95 kg.

[0069] [Product Performance Testing] The main performance indicators of the perfluoropolyether oil products prepared in the above examples and comparative examples were tested.

[0070] The extraction acid value is in accordance with GB / T 264; the breakdown voltage (2.5 mm interval) is in accordance with GB / T 507; the dielectric constant (25℃ & 1MHz) is in accordance with GB / T 1409-2006; the kinematic viscosity (25℃) is in accordance with GB / T 265; and the non-volatile residues (ppm) are in accordance with GB / T 6324.2-2004.

[0071] The test results are shown in Table 1 below: Table 1. Main performance indicators of perfluoropolyether oil products

[0072] As shown in Table 1, the perfluoropolyether fluid prepared by the process route of this invention has a lower extraction acid value, non-volatile residues, higher breakdown voltage, and better dielectric properties. The results indicate that the perfluoropolyether oil prepared by this invention fully meets the requirements of aerospace, electronics, semiconductor and other fields for ultrapure and highly stable lubricating media.

[0073] By comparing the process route of the present invention with Comparative Examples 1 to 6, it can be seen that: (1) This invention achieves a highly efficient and controllable decarboxylation reaction by strictly controlling the amount of reaction promoter added in the decarboxylation step to 1-5% of the intermediate mass. The yields of Examples 1-2 are as high as 93-94%, and the acid values ​​of the products are all controlled below 0.03 mg KOH / g. However, in Comparative Example 4, after completely eliminating the reaction promoter, the yield plummeted to 40%, and the acid value increased to 0.25 mg KOH / g. In addition, when Comparative Examples 5 and 6 used excess ethylene glycol (more than 50%) according to the prior art (CN117362627A), although decarboxylation could be completed, the final yield was low, and the consumption of fluorine gas was significantly increased. This shows that this invention, by using a low amount of promoter, can not only maintain a high yield (≥93%), but also has economic and operational convenience, and has practical application value.

[0074] It should be noted that, although the yields of Comparative Examples 5 and 6, which used excess ethylene glycol, were higher than those of Comparative Example 4 (which did not use any promoter), this was because the large amount of ethylene glycol, as a high-boiling-point solvent, improved the mass and heat transfer of the reaction system to some extent, thus playing an auxiliary role in decarboxylation. However, this method obviously cannot achieve the same high efficiency as that achieved in this application using a small amount of ethylene glycol (1-5%) as a reaction promoter.

[0075] More importantly, the excessive use of ethylene glycol in the existing technology (CN117362627A) actually conveys to those skilled in the art the technical instruction that "decarboxylation reactions require a large amount of solvent medium," without providing any inspiration or motivation for "efficiently catalyzing decarboxylation with a very small amount of active proton compounds." On the contrary, following this existing technical path will not only lead to a significant increase in the cost of auxiliary materials and complicate post-reaction processing (a large amount of high-boiling-point ethylene glycol needs to be recycled), but will also severely restrict large-scale application.

[0076] This invention overcomes the aforementioned technical biases by precisely controlling the amount of reaction promoter at 1-5%, successfully solving the economic and engineering challenges caused by excessive use, while maintaining excellent product yield and purity, thus achieving the best balance between efficiency, cost, and large-scale production.

[0077] (2) The perfluoropolyether oil product obtained by the process of this invention has excellent comprehensive performance: the product acid value is ≤0.03mgKOH / g, reaching the international top level; the non-volatile residue is only 25-28ppm, far lower than the 60-113ppm of the comparative examples; the breakdown voltage is ≥37.5kV, and the dielectric constant is as low as 2.01-2.05, which is better than the comparative examples. More importantly, this invention can directly process the original polymerization solution with an initial acid value as high as 100-105mgKOH / g without pre-purification, and realizes continuous production (Example 3, yield 95%), overcoming the inherent defects of existing technologies (such as CN119529262A) that can only handle trace impurities and generate unstable olefin intermediates.

[0078] In summary, this invention significantly improves the production efficiency, product purity, and fluorine utilization rate of perfluoropolyether oil by precisely controlling the type and amount of reaction promoter (1-5%) and combining it with UV-assisted fluorination end-capping. It overcomes the defects of existing technologies such as poor raw material adaptability, high fluorination cost, and unstable products, and achieves the best balance between efficiency, cost, and product quality, and has the prospect of large-scale application.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A process for the large-scale synthesis and preparation of perfluoropolyether oil, characterized in that: Includes the following steps: S1. Neutralize perfluoropolyether acyl fluoride and / or perfluoropolyether carboxylic acid with an alkaline compound to generate perfluoropolyether carboxylate intermediate I; S2. The perfluoropolyether carboxylate intermediate I is subjected to a decarboxylation reaction under the action of a reaction promoter to generate a hydrogen-terminated fluorinated polyether intermediate II, wherein the reaction promoter includes water or a compound with active protons, and the amount of the reaction promoter added is 1-5% of the mass of the perfluoropolyether carboxylate intermediate I; S3. Fluoride-capping reaction is carried out on hydrogen-terminated fluorinated polyether intermediate II to obtain perfluorinated polyether oil product.

2. The large-scale synthesis and preparation process according to claim 1, characterized in that: The alkaline compound is an inorganic alkaline compound or an organic alkaline compound.

3. The large-scale synthesis and preparation process according to claim 1, characterized in that: The molar ratio of the basic compound to the acyl fluoride group and / or carboxyl group is 1:1 to 1.1:

1.

4. The large-scale synthesis and preparation process according to claim 1, characterized in that: During the neutralization reaction, the reaction temperature is controlled at 30–50°C, and the reaction is stirred for 1–2 hours.

5. The large-scale synthesis and preparation process according to claim 1, characterized in that: The reaction promoter is selected from one or more alcohol compounds and / or amine compounds.

6. The large-scale synthesis and preparation process according to claim 1, characterized in that: During the decarboxylation reaction, the reaction temperature is controlled at 120–250°C.

7. The large-scale synthesis and preparation process according to claim 1, characterized in that: Under UV irradiation or heating conditions, the hydrogen-terminated fluorinated polyether intermediate II is subjected to a fluorination-end-capping reaction with a fluorinating agent gas. The temperature of the fluorination-end-capping reaction is controlled at 120–160°C, the pressure at 0.1–0.3 MPa, and the reaction time at 10–50 h.

8. The large-scale synthesis and preparation process according to claim 1, characterized in that: The fluorinating agent gas is a mixture of F2 and N2, and the volume concentration of F2 in the mixture is 20-50%.

9. A production system for perfluoropolyether oil, characterized in that: The process for large-scale synthesis preparation according to any one of claims 1 to 8 includes at least a neutralization unit, a decarboxylation unit, and a fluorination end-capping unit connected in sequence.

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