A device and method for continuous fluorination of perfluoropolyether end groups

Abstract

A device and method for continuous fluorination of perfluoropolyether end groups, belonging to the technical field of fluorine chemical industry. In the device, an ultraviolet mercury lamp (9) is placed in a cold trap (8), the cold trap (8) is placed in a liquid storage tank (6), the volute mixer (3) is connected to a tubular reactor (7), the tubular reactor (7) is spirally wound around the cold trap (8), and the liquid storage tank (6) is filled with pure water. The method steps are as follows: pure water is introduced into the liquid storage tank (6), and the ultraviolet mercury lamp (9) is turned on; a mixed gas of perfluoropolyether with unsaturated groups and fluorine gas is introduced into the volute mixer (3); under the ultraviolet irradiation condition of the ultraviolet mercury lamp (9), the material fully mixed by the volute mixer (3) enters the tubular reactor (7) for fluorination end-capping reaction. The present invention improves the yield and production efficiency of saturated perfluoropolyether, reduces energy consumption, has a simple process, and is suitable for industrial large-scale production.

Description

Technical Field

[0001] The invention discloses a device and method for continuous fluorination of perfluoropolyether end groups, belonging to the technical field of fluorine chemical industry. Background Art

[0002] Perfluoropolyether is a fluorinated polymer. Due to its excellent resistance to extreme high temperatures, wide operating temperature range, excellent oxidation resistance and chemical corrosion resistance, wide material compatibility, excellent electrical insulation properties, excellent film-forming properties, excellent load-bearing and lubrication properties, it has extremely wide applications in cutting-edge scientific fields such as military industry, aerospace and nuclear industry.

[0003] There are two main methods for preparing perfluoropolyethers. One is anionic ring-opening polymerization using hexafluoropropylene oxide as raw material, and the other is photo-oxidative polymerization using tetrafluoroethylene or hexafluoropropylene as raw material. The perfluoropolyethers obtained by these two methods have active unsaturated groups at the ends, and their end groups need to be stabilized to obtain perfluoropolyethers with excellent performance. End fluorination is currently the best choice for stabilizing the end groups of perfluoropolyethers, and is also a common method for preparing perfluoropolyethers.

[0004] At present, there are two main methods for fluorination of perfluoropolyether end groups. One is to use fluorinating agents such as AlF3 and SbF5 to react under high temperature conditions. The fluoride used in this method is relatively expensive and the product separation is difficult. Another method is the direct fluorination method using fluorine gas, such as the method described in Chinese patent CN106397761A, but the main disadvantage of this method is that direct fluorination of fluorine gas generally requires high temperature, usually above 150°C, low molecular weight perfluoropolyether has a low boiling point, and is prone to loss during fluorination. For high molecular weight perfluoropolyether, the gas-liquid contact is poor, the fluorination efficiency is low, the reaction time is long, and high-temperature fluorination has high requirements for equipment materials, which is not conducive to industrial production. Patent CN103111253A discloses a reactor that allows fluorine gas to circulate with materials through a stirring paddle to improve the utilization rate of the fluorinating agent, but this method cannot carry out continuous fluorination reaction, and the reaction equipment is complex and the maintenance cost is relatively high.

[0005] Patent CN 112876669A discloses a method of using ultraviolet light to irradiate a mixture of fluorine gas and an inert gas for activation, and then feeding the activated mixture into a reactor containing perfluoropolyether for reaction to obtain a perfluoropolyether with terminal fluorination. This method reduces the reaction temperature, but the device is complex and continuous fluorination cannot be achieved, which is not conducive to industrial production. The photoinduced perfluoropolyether fluorination end-capping is mainly affected by the following factors:

[0006] The intensity of ultraviolet radiation is proportional to the distance from the ultraviolet lamp. The closer the distance to the ultraviolet lamp, the greater the intensity of ultraviolet radiation, and the easier the fluorination capping reaction is to proceed.

[0007] The cold trap material and tubular reactor material have an important influence on the UV transmittance. The better the UV transmittance of the material, the higher the UV radiation intensity in the reaction zone. At the same time, the tubular reactor material must have excellent corrosion resistance and not react with acyl fluoride and fluorine gas.

[0008] The light transmittance of heat transfer media such as heat medium also has an important influence on the intensity of ultraviolet radiation. It is very important to select heat medium with good light transmittance and reasonable economy.

[0009] The mixing effect of the perfluoropolyether and fluorine gas mixture affects the concentration distribution and temperature distribution of the reaction solution, and has an important influence on the yield and selectivity of the fluorinated end-capped product.

[0010] Process selection has an important influence on fluorination reaction. Intermittent process is highly dangerous and inefficient, while continuous process is safe and stable, has small scale-up effect and high time-space yield.

[0011] In summary, it is urgent to develop a method for fluorination of perfluoropolyether end groups to improve the fluorination and capping efficiency of perfluoropolyether, reduce safety risks, and facilitate industrial-scale production. Summary of the invention

[0012] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a device and method for continuous fluorination of perfluoropolyether end groups with high yield, low energy consumption and simple process.

[0013] The technical solution adopted by the present invention to solve its technical problems is: the perfluoropolyether continuous fluorination end-capping device includes an ultraviolet mercury lamp, a cold trap, a volute-type mixer, a tubular reactor and a liquid storage tank, and is characterized in that: the ultraviolet mercury lamp is placed in the cold trap, the cold trap is placed in the liquid storage tank, the volute-type mixer is connected to the tubular reactor, the tubular reactor is spirally wound around the cold trap, and the liquid storage tank is filled with pure water.

[0014] The present invention arranges a volute-type mixer at the front end of a photochemical tubular reactor, which can efficiently mix perfluoropolyether and fluorine gas. The ultraviolet light provided by the ultraviolet mercury lamp can reduce the reaction temperature. After application, the device has high fluorination efficiency, safe and stable operation, simple device structure, and can continuously fluorinate and cap the end groups of perfluoropolyether, and is suitable for industrial large-scale production.

[0015] A preferred perfluoropolyether continuous fluorination end-capping device, the cold trap is made of quartz, and the cold trap wall thickness is 1mm to 3mm. The liquid storage tank is made of 304 stainless steel or 316 stainless steel, and the heat transfer medium in the liquid storage tank is pure water, and the pure water temperature is 30°C to 80°C. The material of the tubular reactor is quartz or FEP, and the more preferred material of the tubular reactor is FEP material. The tubular reactor made of FEP material has better corrosion resistance during fluorination reaction.

[0016] A preferred perfluoropolyether continuous fluorination end-capping device, the volute-type mixer is made of silicon carbide or Hastelloy, and the volute-type mixer is composed of 3 to 10 volutes connected in series. When the volute-type mixer is composed of 3 to 10 volutes, the raw materials can be fully mixed to meet the subsequent end-capping reaction.

[0017] A method for continuous fluorination and end-capping of perfluoropolyether using the above device comprises the following steps:

[0018] 1) Pour pure water into the liquid storage tank and turn on the ultraviolet mercury lamp;

[0019] 2) introducing a mixed gas of perfluoropolyether with unsaturated groups and fluorine gas into a volute mixer;

[0020] 3) Under the ultraviolet irradiation condition of the ultraviolet mercury lamp, the materials fully mixed by the volute mixer enter the tubular reactor for fluorination capping reaction.

[0021] In the method of the present invention, pure water of a certain temperature is first introduced into the liquid storage tank to maintain the tubular reactor immersed in the pure water at a suitable reaction temperature. The ultraviolet mercury lamp is turned on, and after the irradiation intensity of the mercury lamp is stabilized, a mixed gas of perfluoropolyether and fluorine gas is introduced into the volute mixer, and after the reaction is completed, the end-group fluorinated perfluoropolyether is collected. The present invention improves the yield and production efficiency of saturated perfluoropolyether, reduces energy consumption, has a simple process, and is suitable for industrial large-scale production.

[0022] A preferred method for continuous fluorination end-capping of perfluoropolyether, wherein the molecular formula of the perfluoropolyether with unsaturated groups in step 2) is R f1 (CF2CF2O) m -(C2F4O) n -CF2)R f2 , R f1 (CF2CF(CF3) m (OCF2O) n R f2 or R f1 (CF(CF3)CF2O) m R f2 ; wherein m and n are 1 to 200 respectively, and m / n is between 0.1 and 10.

[0023] A preferred method for continuous fluorination and capping of perfluoropolyether, wherein the fluorine gas mixture in step 2) is a mixture of fluorine gas and at least one of nitrogen, helium, and hydrogen fluoride, and the molar concentration of fluorine gas in the fluorine gas mixture is 1% to 90%. The fluorine gas of the present invention enters the volute mixer in the form of a mixed gas to participate in the reaction, which can control the severity of the reaction and improve the utilization rate of fluorine gas.

[0024] A preferred method for continuous fluorination end-capping of perfluoropolyether is that the molar ratio of the perfluoropolyether with unsaturated groups to the fluorine gas mixture is 1:10 to 50. The preferred ratio of the perfluoropolyether to the fluorine gas mixture can control the reaction speed and perform the end-capping reaction at a lower temperature.

[0025] A preferred method for continuous fluorination and end-capping of perfluoropolyether, wherein the power of the ultraviolet mercury lamp (9) in step 1) is 200W to 1000W, and the effective ultraviolet wavelength is 200nm to 600nm. The heat released by the ultraviolet mercury lamp at the preferred power and wavelength is heat exchanged with the pure water in the liquid storage tank, providing a certain amount of energy for the fluorination and end-capping reaction. The use of the heat released by the mercury lamp is conducive to saving energy consumption, and at the same time, it can avoid the mercury lamp from working under high temperature conditions and extend the life of the mercury lamp. More importantly, the introduction of appropriately strong ultraviolet light can better activate the fluorine gas, which is conducive to improving the utilization rate of the fluorine gas and saving the cost of raw materials for fluorine gas end-capping.

[0026] A preferred method for continuous fluorination end-capping of perfluoropolyether, wherein the molar ratio of the unsaturated groups of the perfluoropolyether to the fluorine gas in the fluorine gas mixture is 2 to 5:1; the reaction temperature of the fluorination end-capping reaction is 20°C to 70°C, and the reaction pressure is 0 to 0.5MPa. The fluorine gas irradiated by ultraviolet light is activated into fluorine atoms, and the perfluoropolyether is fluorinated using highly active fluorine atoms, so that the fluorination process can be carried out at a relatively low temperature of 20°C to 70°C.

[0027] A preferred method for continuous fluorination and end-capping of perfluoropolyether, wherein the inner diameter of the tubular reactor is 1 mm to 5 mm, and the residence time of the material in the tubular reactor is 3 min to 15 min. The residence time of the material in the tubular reactor is the controlled fluorination and end-capping reaction time, and the fluorination process is carried out at a relatively low temperature of 20° C. to 70° C. Under the preferred reaction time, the fluorination and end-capping reaction can be completed more thoroughly.

[0028] The end-capping method of continuous photofluorination perfluoropolyether of the present invention solves the problems of high reaction temperature, low fluorine gas utilization rate and unsuitability for industrial production in the existing end-capping method, improves the yield and production efficiency of saturated perfluoropolyether, reduces energy consumption, has a simple process and is suitable for large-scale industrial production.

[0029] After the fluid enters the vortex mixer, the fluorine gas is mixed in the perfluoropolyether in the form of bubbles and is broken into a large number of small bubbles under the action of the fluid. The gas and liquid phases enter the tubular reactor after being fully mixed through multiple volutes.

[0030] The heat released by the ultraviolet mercury lamp exchanges heat with the pure water in the storage tank, providing a certain amount of energy for the fluorination capping reaction. The heat released by the mercury lamp is used to save energy, while avoiding the mercury lamp from working under high temperature conditions, thereby extending the life of the mercury lamp.

[0031] Compared with the prior art, the device and method for continuous fluorination of perfluoropolyether end groups of the present invention have the following beneficial effects:

[0032] The invention discloses a method for continuous fluorination of perfluoropolyether end groups, wherein the perfluoropolyether R f1 (CF2CF2O) m -(C2F4O) n -CF2)R f2 , R f1 (CF2CF(CF3) m (OCF2O)R f2 or R f1 (CF(CF3) CF2O) m R f2 As raw material, under the condition of ultraviolet radiation, fluorine gas is continuously introduced into a photochemical tubular reactor to react and generate terminal fluorinated perfluoropolyether.

[0033] The present invention realizes efficient mixing of perfluoropolyether and fluorine gas by a volute mixer at the front end of a photochemical tubular reactor, and the introduction of ultraviolet light reduces the reaction temperature. The invention has the advantages of high fluorination efficiency, safe and stable process, and simple device structure, and realizes continuous fluorination of perfluoropolyether end groups, and is suitable for industrial large-scale production.

[0034] The present invention realizes the continuous fluorination and capping process of perfluoropolyether, the process is safe and controllable, there is no amplification effect, it is suitable for industrial large-scale production, and it is a green, environmentally friendly and efficient continuous production method.

[0035] The fluorination end-capping process of the perfluoropolyether of the present invention introduces ultraviolet light to activate the fluorine gas, thereby improving the utilization rate of the fluorine gas, saving the raw material cost of the fluorine gas end-capping and reducing the emission of waste gas, while lowering the fluorination temperature and reducing damage to equipment.

[0036] The present invention adopts a volute-type mixer to achieve full mixing of fluorine gas and perfluoropolyether, reduce the volume of bubbles, increase the mass transfer driving force, shorten the reaction time, and improve the reaction rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present invention. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0038] Figure 1 A schematic diagram of a perfluoropolyether fluorination end-capping device of the present invention

[0039] Among them, 1. fluorine gas mixed gas feed pipeline 2, perfluoropolyether feed pipeline 3, volute mixer 4, pure water supply pipeline 5, pure water return pipeline 6, liquid storage tank 7, tubular reactor 8, cold trap 9, ultraviolet mercury lamp 10, product outlet pipeline. DETAILED DESCRIPTION

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0042] See attached Figure 1 , a device for continuous fluorination of perfluoropolyether end groups provided in this embodiment comprises a vortex mixer 3 and a tubular reactor 7 connected in sequence by pipelines, the tubular reactor 7 is placed in a liquid storage tank 6, a cold trap 8 is placed in the center of the liquid storage tank 6, a mercury lamp 9 is placed in the cold trap 8, the tubular reactor 7 is arranged in a spiral shape around the outer periphery of the cold trap 8, and the outer wall of the tubular reactor 7 is 20 mm away from the outer wall of the cold trap 8. A fluorine gas mixed gas feed pipeline 1 and a perfluoropolyether feed pipeline 2 are arranged at the front end of the vortex mixer 3. The lower end of the liquid storage tank 6 is connected to the pure water supply pipeline 4, and the upper end of the liquid storage tank 6 is connected to the pure water return pipeline 5; the liquid storage tank 6 is filled with pure water as a heat transfer medium, and the pure water temperature is 30°C to 80°C. The cold trap 8 is made of quartz, and the wall thickness of the cold trap is 1 mm to 3 mm; the liquid storage tank 6 is made of 304 stainless steel or 316 stainless steel, and the tubular reactor is made of quartz or FEP; the volute mixer 3 is made of silicon carbide or Hastelloy, and the volute mixer 3 is composed of 3 to 10 volutes connected in series.

[0043] The present invention is further described below in conjunction with specific embodiments, wherein Embodiment 1 is the best implementation.

[0044] Example 1

[0045] In this embodiment, the volute mixer 3 is made of silicon carbide and is composed of 6 volutes connected in series, the tubular reactor 7 is made of FEP, the cold trap 8 is made of quartz, and the liquid storage tank 6 is made of 316L stainless steel. The tubular reactor has a length of 2000 mm, an inner diameter of 5 mm, and a wall thickness of 1 mm.

[0046] The process flow of preparing terminal fluorinated perfluoropolyether by using the device of this embodiment is as follows: pure water is introduced into the liquid storage tank 6 through the pure water supply pipe 4, and the ultraviolet mercury lamp 9 is turned on. The power of the ultraviolet mercury lamp 9 is 300W, and the effective ultraviolet wavelength is 300nm-500nm. Fluorine gas mixture and perfluoropolyether COF (CF2CF2O) are introduced into the volute mixer 3 through the fluorine gas mixture feed pipe 1 and the perfluoropolyether feed pipe 2. m -(C2F4O) n -CF2COF. The fluorine gas mixture consists of fluorine gas and nitrogen gas, wherein the molar percentage of fluorine gas is 10%. The molecular weight of perfluoropolyether is 20000, wherein m / n is 1.6. The molar ratio of perfluoropolyether to fluorine gas mixture is 1:25. The temperature of the tubular reactor is maintained at 50°C and the pressure is 1.0 bar.

[0047] After the reaction was completed, the production capacity of the terminal fluorinated perfluoropolyether was 34.2 g / min, and the yield was 95%. Infrared detection showed that the terminal groups of the perfluoropolyether were completely fluorinated.

[0048] Example 2

[0049] In this embodiment, the volute mixer 3 is made of silicon carbide and is composed of 7 volutes connected in series, the tubular reactor 7 is made of FEP, the cold trap 8 is made of quartz, and the liquid storage tank 6 is made of 316L stainless steel. The tubular reactor has a length of 2000 mm, an inner diameter of 3 mm, and a wall thickness of 1 mm.

[0050] The process flow of preparing terminal fluorinated perfluoropolyether by using the device of this embodiment is as follows: pure water is introduced into the liquid storage tank 6 through the pure water supply pipe 4, and the ultraviolet mercury lamp 9 is turned on. The power of the ultraviolet mercury lamp 9 is 500W, and the effective ultraviolet wavelength is 300nm-500nm. The fluorine gas mixture and the perfluoropolyether COF (CF2CF2O) are introduced into the volute mixer 3 through the fluorine gas mixture feed pipe 1 and the perfluoropolyether feed pipe 2 respectively. m -(C2F4O) n -CF2COF, maintain the temperature of the tubular reactor at 30°C and the pressure at 1.0 bar. The fluorine gas mixture consists of fluorine gas and nitrogen gas, wherein the molar percentage of fluorine gas is 10%. The molecular weight of perfluoropolyether is 20,000, wherein m / n is 1.6. The molar ratio of perfluoropolyether to fluorine gas mixture is 1:30.

[0051] The output of the terminal fluorinated perfluoropolyether is 81.9 g / min, and the yield is 91%. According to infrared detection, the terminal groups of the perfluoropolyether are completely fluorinated.

[0052] Example 3

[0053] In this embodiment, the volute mixer 3 is made of silicon carbide and is composed of five volutes connected in series, the tubular reactor 7 is made of FEP, the cold trap 8 is made of quartz, and the liquid storage tank 6 is made of 316L stainless steel. The tubular reactor has a length of 2000 mm, an inner diameter of 5 mm, and a wall thickness of 1 mm.

[0054] The process flow of preparing terminal fluorinated perfluoropolyether by using the device of this embodiment is as follows: temperature pure water is introduced into the liquid storage tank 6 through the pure water supply pipe 4, and the ultraviolet mercury lamp 9 is turned on. The power of the ultraviolet mercury lamp 9 is 500W, and the effective ultraviolet wavelength is 200nm-400nm. The fluorine gas mixture and the perfluoropolyether COF (CF2CF (CF3)) are introduced into the volute mixer 3 through the fluorine gas mixture feed pipe 1 and the perfluoropolyether feed pipe 2 respectively. m (OCF2O) n -CF2COOH, maintain the temperature of the tubular reactor at 50°C and the pressure at 1.0 bar. The fluorine gas mixture consists of fluorine gas and nitrogen gas, wherein the molar percentage of fluorine gas is 5%. The molecular weight of perfluoropolyether is 6000, wherein m / n is 1.6. The molar ratio of perfluoropolyether to fluorine gas mixture is 1:25.

[0055] The output of the terminal fluorinated perfluoropolyether is 83.7 g / min, and the yield is 93%. According to infrared detection, the terminal groups of the perfluoropolyether are completely fluorinated.

[0056] Example 4

[0057] In this embodiment, the volute mixer 3 is made of silicon carbide and is composed of 8 volutes connected in series, the tubular reactor 7 is made of FEP, the cold trap 8 is made of quartz, and the liquid storage tank 6 is made of 316L stainless steel. The tubular reactor has a length of 2000 mm, an inner diameter of 5 mm, and a wall thickness of 1 mm.

[0058] The process flow of preparing terminal fluorinated perfluoropolyether by using the device of this embodiment is as follows: pure water is introduced into the liquid storage tank 6 through the pure water supply pipe 4, and the ultraviolet mercury lamp 9 is turned on. The power of the ultraviolet mercury lamp 9 is 300W, and the effective ultraviolet wavelength is 300nm-400nm. The fluorine gas mixture and the perfluoropolyether CF3 (CF2CF (CF3)) are introduced into the volute mixer 3 through the fluorine gas mixture feed pipe 1 and the perfluoropolyether feed pipe 2 respectively. m (OCF2O) n -CF2COOH, maintain the temperature of the tubular reactor at 50°C and the pressure at 1.0 bar. The fluorine gas mixture consists of fluorine gas and nitrogen gas, wherein the molar percentage of fluorine gas is 5%. The molecular weight of perfluoropolyether is 6500, wherein m / n is 1.6. The molar ratio of perfluoropolyether to fluorine gas mixture is 1:25.

[0059] The output of the terminal fluorinated perfluoropolyether is 83.7 g / min, and the yield is 93%. According to infrared detection, the terminal groups of the perfluoropolyether are completely fluorinated.

[0060] Example 5

[0061] In this embodiment, the volute mixer 3 is made of Hastelloy, and is composed of 10 volutes connected in series, the tubular reactor 7 is made of FEP, the tubular reactor 7 is made of Hastelloy, the cold trap 8 is made of quartz, and the liquid storage tank 6 is made of 304 stainless steel. The tubular reactor has a length of 2000 mm, an inner diameter of 1 mm, and a wall thickness of 1 mm.

[0062] The process flow of preparing terminal fluorinated perfluoropolyether by using the device of this embodiment is as follows: pure water is introduced into the liquid storage tank 6 through the pure water supply pipe 4, and the ultraviolet mercury lamp 9 is turned on. The power of the ultraviolet mercury lamp 9 is 200W, and the effective ultraviolet wavelength is 400nm-600nm. Fluorine gas mixture and perfluoropolyether COF (CF (CF3) CF2O) are introduced into the volute mixer 3 through the fluorine gas mixture feed pipe 1 and the perfluoropolyether feed pipe 2. m -CF2COF. The fluorine gas mixture consists of fluorine gas and hydrogen fluoride, wherein the molar percentage of fluorine gas is 90%. The molecular weight of perfluoropolyether is 3350, wherein m is 20. The molar ratio of perfluoropolyether to fluorine gas mixture is 1:10. The temperature of the tubular reactor is maintained at 70°C and the pressure is 0.5MPa.

[0063] After the reaction was completed, the production capacity of the terminal fluorinated perfluoropolyether was 18.2 g / min, and the yield was 95%. Infrared detection showed that the terminal groups of the perfluoropolyether were completely fluorinated.

[0064] Example 6

[0065] In this embodiment, the volute mixer 3 is made of silicon carbide and is composed of three volutes connected in series, the tubular reactor 7 is made of FEP, the cold trap 8 is made of quartz, and the liquid storage tank 6 is made of 316L stainless steel. The tubular reactor has a length of 2000 mm, an inner diameter of 5 mm, and a wall thickness of 1 mm.

[0066] The process flow of preparing terminal fluorinated perfluoropolyether by using the device of this embodiment is as follows: pure water is introduced into the liquid storage tank 6 through the pure water supply pipe 4, and the ultraviolet mercury lamp 9 is turned on. The power of the ultraviolet mercury lamp 9 is 1000W, and the effective ultraviolet wavelength is 200nm-400nm. Fluorine gas mixture and perfluoropolyether COOH (CF (CF3) CF2O) are introduced into the volute mixer 3 through the fluorine gas mixture feed pipe 1 and the perfluoropolyether feed pipe 2. m-CF2COOH. The fluorine gas mixture consists of fluorine gas and helium gas, wherein the molar percentage of fluorine gas is 1%. The molecular weight of perfluoropolyether is 4000, wherein m is 23. The molar ratio of perfluoropolyether to fluorine gas mixture is 1:50. The temperature of the tubular reactor is maintained at 20°C and the pressure is 1.0 bar.

[0067] After the reaction was completed, the production capacity of the terminal fluorinated perfluoropolyether was 83.9 g / min, and the yield was 91%. Infrared detection showed that the terminal groups of the perfluoropolyether were completely fluorinated.

[0068] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for continuous fluorination and end-capping of perfluoropolyether, characterized in that: The end-capping device comprises an ultraviolet mercury lamp (9), a cold trap (8), a volute-type flow mixer (3), a tubular reactor (7) and a liquid storage tank (6), wherein the ultraviolet mercury lamp (9) is placed in the cold trap (8), the cold trap (8) is placed in the liquid storage tank (6), the volute-type flow mixer (3) is connected to the tubular reactor (7), the tubular reactor (7) is spirally wound around the cold trap (8), and the liquid storage tank (6) is filled with pure water; the volute-type flow mixer (3) is composed of 3 to 10 volutes connected in series; The following steps are involved: 1) Pure water is introduced into the liquid storage tank (6) and the ultraviolet mercury lamp (9) is turned on; 2) introducing a mixed gas of perfluoropolyether having unsaturated groups and fluorine gas into a volute-type mixer (3); 3) Under the ultraviolet irradiation condition of the ultraviolet mercury lamp (9), the materials fully mixed by the volute mixer (3) enter the tubular reactor (7) for fluorination and capping reaction.

2. A method for continuous fluorination and capping of perfluoropolyether according to claim 1, characterized in that: The fluorine gas mixture in step 2) is a mixture of fluorine gas and at least one of nitrogen gas, helium gas and hydrogen fluoride, and the molar concentration of fluorine gas in the fluorine gas mixture is 1% to 90%.

3. A method for continuous fluorination and capping of perfluoropolyether according to claim 1, characterized in that: The molar ratio of the perfluoropolyether with unsaturated groups to the fluorine gas mixture is 1:10-50.

4. A method for continuous fluorination and capping of perfluoropolyether according to claim 1, characterized in that: The power of the ultraviolet mercury lamp (9) in step 1) is 200W to 1000W, and the effective ultraviolet wavelength is 200nm to 600nm.

5. A method for continuous fluorination and capping of perfluoropolyether according to claim 1, characterized in that: The molar ratio of the unsaturated groups of the perfluoropolyether to the fluorine gas in the fluorine gas mixture is 2 to 5:1; The reaction temperature of the fluorination end-capping reaction is 20°C to 70°C, and the reaction pressure is 0 to 0.5 MPa.

6. A method for continuous fluorination and capping of perfluoropolyether according to claim 1, characterized in that: The inner diameter of the tubular reactor (7) is 1 mm to 5 mm, and the residence time of the material in the tubular reactor (7) is 3 min to 15 min.

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