Oil degassing composite membrane as well as preparation method and application thereof

Abstract

The invention discloses an oil degassing composite membrane as well as a preparation method and application thereof, and belongs to the field of gas-liquid membrane separation. The oil degassing composite membrane comprises a supporting base membrane and a separation layer, the separation layer is attached to the surface of the supporting base membrane; the supporting base membrane is of a porous structure, and the separation layer is a fluorine-containing polymer; the thickness of the supporting base membrane is 10-60 [mu] m, and the molecular weight cut-off is 10-200 KDa; the thickness of the separation layer is 0.3-5 [mu] m; the O2 permeation rate of the oil degassing composite membrane is 100 to 3000 GPU (Graphics Processing Unit). The preparation method comprises the following steps: coating the fluorine-containing polymer coating liquid on the supporting base membrane, drying, and carrying out plasma treatment. A mixed solvent of a high-boiling-point fluorine-containing solvent and a low-boiling-point fluorine-containing solvent is utilized, so that defects on the surface of the composite membrane are prevented, the permeability of the membrane is ensured, fluorine-containing plasmas are utilized for treating the surface of a separation layer of the composite membrane, the defects are repaired quickly and effectively, and meanwhile, a flat membrane assembly prepared from the oil degassing composite membrane has the advantages of low cost and high efficiency. Proper specifications can be selected according to degassing requirements, and the adaptability is high.

Description

Technical Field

[0001] This application relates to an oil-degassing composite membrane, its preparation method, and its application, belonging to the field of gas-liquid membrane separation. Background Technology

[0002] Oil products often experience increased dissolved gas content during production and use due to factors such as contact with air, equipment aging, and localized overheating. These dissolved gases significantly impact the oil's performance. For example, dissolved fault characteristic gases (H2, CH4, C2H2, etc.) in transformer oil are early indicators of insulation faults; direct detection without degassing can lead to delayed response and misjudgments by online monitoring instruments, and in severe cases, equipment explosions. Dissolved air (mainly O2 and N2) in hydraulic oil can cause cavitation, leading to pump component wear, pressure fluctuations, and reduced system rigidity, which is particularly dangerous in high-pressure, high-temperature environments such as aviation and metallurgy (e.g., air bubbles in aviation hydraulic oil can cause control failure). Dissolved gases and microbubbles in lubricating oil reduce its oxidative stability, affecting its fluidity and lubricity. Air bubbles in fuel oil (especially aviation fuel) reduce combustion efficiency, cause fuel supply fluctuations, and promote microbial growth that clogs filter elements. Therefore, degassing oil products is crucial.

[0003] Currently, commonly used oil degassing methods include vacuum degassing, centrifugal degassing, heating degassing, and membrane separation degassing. Among these, membrane separation degassing technology has attracted much attention due to its advantages such as high efficiency, energy saving, environmental friendliness, and ease of operation. This technology utilizes the difference in permeation rates of gas and liquid molecules through a membrane to separate dissolved gases in the oil from one side of the membrane to the other. However, existing oil degassing membranes still face a series of severe challenges in practical applications, especially when dealing with complex oil environments. First, degassing efficiency and gas selectivity are limited. Although most existing membrane materials exhibit good gas permeability in oil, their selectivity for specific gases (such as H2 and CO) is often insufficient in complex multi-component gas mixtures, leading to incomplete degassing or low efficiency. Second, membranes generally have poor resistance to fouling and poor long-term stability. Actual oil products inevitably contain trace amounts of water, solid particles (such as wear particles and oxidation products), gums, and various functional additives. These impurities are easily adsorbed, condensed, or clogged on the membrane surface, causing membrane fouling, which leads to a sharp drop in membrane flux and a decrease in degassing performance. Finally, some high-performance degassing membrane materials have low mechanical strength and are prone to tearing, deformation, or damage when faced with harsh operating conditions such as high oil flow rates, pump pressure fluctuations, or vibrations, affecting the reliability and safety of the membrane module.

[0004] Therefore, it is crucial to develop an oil-degassing composite membrane for complex oil products. This membrane needs to possess good mechanical strength, not only to withstand the corrosion and contamination from impurities in the oil, but also to maintain long-term separation performance and stability. Summary of the Invention

[0005] To achieve the above objectives, this invention proposes an oil-degassing composite membrane, its preparation method, and its applications. The preparation method involves coating a fluoropolymer-containing coating liquid onto a supporting substrate membrane, followed by plasma treatment to obtain an oil-degassing composite membrane with high gas permeation rate and strong fouling resistance. Another objective of this invention is to propose using fluorine-containing gas for plasma treatment to repair defects in the separation layer. This invention also provides a process flow for removing dissolved gases from complex oil products using a flat-sheet membrane module prepared with the oil-degassing composite membrane.

[0006] According to the first aspect of this application, an oil degassing composite membrane is provided.

[0007] An oil degassing composite membrane, the oil degassing composite membrane comprising a supporting base membrane and a separation layer; The separation layer is attached to the surface of the supporting base membrane; The supporting base membrane has a porous structure, and the separation layer is a fluoropolymer. The thickness of the supporting base film is 10~60μm, and the molecular weight cutoff is 10~200KDa; The thickness of the separation layer is 0.3~5μm; The O2 permeation rate of the oil-degassing composite membrane is 100~3000 GPU.

[0008] Preferably, the thickness of the supporting base film is 25~45μm, and the molecular weight cutoff is 20~100KDa; The thickness of the separation layer is 0.5~2μm.

[0009] Optionally, the O2 / N2 separation coefficient of the oil degassing composite membrane is α(O2 / N2) of 2.00~2.80.

[0010] According to a second aspect of this application, a method for preparing an oil-degassing composite membrane is provided. The method involves coating a fluoropolymer-containing coating liquid onto a supporting substrate membrane, drying it, and then subjecting it to plasma treatment. Using a mixed solvent of a certain proportion of high-boiling-point and low-boiling-point fluoropolymers prevents the generation of surface defects in the composite membrane while ensuring its permeability. Furthermore, fluoropolymer plasma treatment of the composite membrane's separation layer surface quickly and effectively repairs defects.

[0011] The preparation method of the oil-degassing composite membrane described above includes: (1) Preparation of the supporting base film: A uniform casting solution is prepared by mixing polymer, solvent and additives. The casting solution is coated onto a nonwoven fabric and dried. After drying, it is treated in a gelling agent to obtain a supporting base film. (2) Preparation of fluoropolymer coating liquid: Fluoropolymer powder is dissolved in a fluorine-containing mixed solvent and dispersed evenly to obtain a homogeneous coating liquid; (3) Preparation of oil-degassing composite membrane The coating liquid obtained in step (2) is coated onto the support base film obtained in step (1), dried, and then subjected to plasma treatment to obtain an oil-degassed composite film.

[0012] Optionally, in step (1), the content of the polymer is 12~30wt%, the content of the solvent is 60~87wt%, and the content of the additive is 0.1~10wt%.

[0013] Optionally, the polymer is at least one selected from polysulfone, polyethersulfone, polyimide, polyamide-imide, polyetherimide, polyacrylonitrile, polyvinylidene fluoride, and polyetheretherketone. The solvent is at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and tetrahydrofuran; The additive is at least one of sulfolane, γ-butyrolactone, lithium nitrate, lithium chloride, calcium bromide, tetraethylene glycol dimethyl ether, n-butanol, and glycerol.

[0014] Optionally, in step (2), the fluorinated mixed solvent is composed of a high-boiling-point fluorinated solvent with a boiling point of 100~250℃ and a low-boiling-point fluorinated solvent with a boiling point of less than 100℃. Optionally, the mass ratio of the high-boiling-point fluorinated solvent to the low-boiling-point fluorinated solvent is 1:9~19.

[0015] Optionally, the fluorinated solvent may be any one of perfluoropolyether, hydrofluoroalkane, hydrofluoroolefin, perfluoroalkane, perfluoroolefin, perfluorobenzene, and perfluoroalcohol.

[0016] Optionally, in step (2), the concentration of the fluoropolymer in the coating liquid is 0.5~10wt%, preferably 0.8~2.0wt%.

[0017] Optionally, in step (2), the structural formula of the fluoropolymer is: ; Where a, b, and c are the degrees of polymerization, and a and b are not both 0; a = 0~800, b = 0~800, c = 1~400; Monomers X and Y are selected from compounds with the following structures: , , , , , , , , , , , ; Monomer Z is selected from compounds with the following structures: , ; R1 and R2 are each independently selected from H, F, Cl or Br; The values ​​of m, n, k, t, d, and q are integers from 0 to 6.

[0018] Optionally, monomers X and Y are selected from compounds with the following structures: , , , , , , , ; The monomer Z is selected from compounds with the following structures: , , , , , , , .

[0019] Optionally, in step (3), the gas used for plasma treatment is at least one of CF4 and SF6; The power supply has a radio frequency of 40KHz, 13.56MHz, or 2.54GHz, preferably 13.56MHz; and a processing time of 5~100s, preferably 15~30s.

[0020] Optionally, in step (3), the coating method is any one of dip coating, slot coating, or cast coating.

[0021] As a preferred embodiment, the method for preparing the oil-degassing composite membrane includes: (1) Preparation of the supporting base film: The polymer, solvent and additives are prepared into a uniform casting solution. The treated casting solution is coated onto the nonwoven fabric by a film scraper. After drying in the air, it is treated in a gelling agent to obtain the supporting base film. (2) Preparation of fluoropolymer coating liquid: Dissolve the fluoropolymer powder in a fluorine-containing mixed solvent, and disperse it evenly by ultrasonication to obtain a homogeneous coating liquid; (3) Preparation of oil degassing composite membrane: The coating liquid obtained in step (2) is coated onto the support base membrane obtained in step (1), dried, and then subjected to plasma treatment to obtain oil degassing composite membrane.

[0022] According to a third aspect of this application, an application of an oil degassing composite membrane is provided. This oil degassing composite membrane can be used in the degassing of complex oil products and has the advantages of high gas permeation rate and strong resistance to fouling. Furthermore, the flat sheet membrane module prepared from the oil degassing composite membrane can be selected with appropriate specifications according to degassing requirements, demonstrating strong adaptability.

[0023] The application of the oil degassing composite membrane described above in oil degassing.

[0024] Optionally, the oil is transformer oil, hydraulic oil, lubricating oil, or fuel oil. The beneficial effects that this application can produce include: (1) Compared with traditional oil degassing technology, membrane degassing process is simple, energy-efficient, and occupies a small area, and can be integrated into compact system equipment according to needs; (2) The oil-degassing composite membrane is prepared by coating a fluoropolymer onto a supporting substrate membrane. On the one hand, the high bond energy of the CF bond in the fluoropolymer improves the fouling resistance of the oil-degassing composite membrane; on the other hand, the cyclic structure in the fluoropolymer increases the gas permeation rate. (3) Using a certain proportion of high-boiling-point fluorinated solvent and low-boiling-point fluorinated solvent can, on the one hand, prevent the solvent boiling point from being too low, which would cause the solvent to evaporate quickly and generate defects on the surface of the composite membrane; on the other hand, it can also prevent the solvent boiling point from being too high, which would cause the residual solvent to be unable to be removed and affect the membrane permeation performance. (4) Using a high-voltage power supply to discharge CF4 or SF6 gas, the generated fluorine-containing plasma is used to treat the surface of the composite membrane separation layer, repairing defects quickly and effectively; (5) Flat sheet membrane modules prepared using oil-degassing composite membranes can be selected according to the degassing requirements, and have strong adaptability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the oil-degassing composite membrane; Figure 2 It is a process flow that uses an oil degassing membrane module to remove gas from complex oil products; Figure 3 This is a cross-sectional view of the membrane module degassing process; Figure 4 This is a SEM image of the surface of the oil-degassing composite membrane in Example 4; Figure 5 This is a photo of the nonwoven fabric side of the degassing membrane in a 4-inch roll-to-roll membrane assembly.

[0026] Reference numerals: 1. Separation layer; 2. Supporting membrane; 3. Nonwoven fabric; 4. Oil tank; 5. Oil pump; 6. Gas source; 7. Pressure regulating valve; 8. Gas-liquid mixing tank; 9. Ball valve; 10. Membrane module; 11. Pressure gauge; 12. Flow regulating valve; 13. Vacuum gauge; 14. Vacuum pump; 101. Oil inlet; 102. Oil outlet; 103. Gas outlet; 104. Feed mesh; 105. Oil degassing composite membrane; 106. Permeate mesh; 107. Oil; 108. Gas. Detailed Implementation

[0027] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0028] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0029] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0030] The thicknesses of the supporting substrate membrane and the separation layer of the oil-degassing composite membrane prepared in this embodiment of the invention were measured using a field emission scanning electron microscope (Zeiss Sigma HD).

[0031] In this embodiment of the invention, the molecular weight cutoff of the supporting membrane was determined by gel permeation chromatography (GPC), and the specific steps are as follows: A dextran aqueous solution was prepared, wherein the concentrations of Dextran T-10, Dextran T-40, Dextran T-70, and Dextran T-500 were 0.25 wt%, 0.1 wt%, 0.1 wt%, and 0.2 wt%, respectively. The solution was filtered using a static cup apparatus at a pressure of 0.1 MPa. The chromatographic peaks of the filtered solution and the initial solution were then determined by liquid chromatography. Since the peak area is linearly related to the concentration of different molecular weights, the rejection rate R was calculated using the following formula: R = (1 - area of ​​the membrane fluid / area of ​​the initial fluid) × 100% Based on the retention rates of these four dextrans, the molecular weight cut-off curve of the membrane was plotted and the molecular weight cut-off of the membrane was determined. The molecular weight cut-off is generally defined as the molecular weight of the dextran when the retention rate is greater than or equal to 90%.

[0032] The permeation rate and separation performance of the oil-degassing composite membrane prepared in this embodiment of the invention are evaluated by the permeation rate J of pure O2 and N2 and the O2 / N2 separation coefficient α (O2 / N2).

[0033] In this invention, the oil tolerance of the membrane is achieved through... Figure 2The process flow test involved encapsulating the oil-degassing composite membrane into a flat sheet membrane module and running it continuously for 60 days. No oil permeated through the permeate side of the module, indicating that the prepared oil-degassing composite membrane has excellent tolerance to complex oils.

[0034] like Figure 1 The diagram shows the structure of the oil-degassing composite membrane. Separation layer 1 is attached to the surface of the supporting base membrane 2. Separation layer 1 is a fluoropolymer, and the supporting base membrane 2 has a porous structure. The supporting base membrane 2 is attached to the surface of the nonwoven fabric 3.

[0035] like Figure 2 As shown, this is a process flow for removing gas from complex oil products using an oil degassing membrane module. The oil tank 4 is connected to the gas-liquid mixing tank 8 via the oil pump 5. The gas source 6 is connected to the gas-liquid mixing tank 8 via the regulating valve 7. The gas-liquid mixing tank 8 is connected to the membrane module 10 via the ball valve 9. The membrane module 10 is connected to the vacuum pump 14 and the oil tank 4 respectively. A vacuum gauge 13 is installed on the pipeline between the membrane module 10 and the vacuum pump 14. A flow regulating valve 12 and a pressure gauge 11 are installed on the pipeline between the membrane module 10 and the oil tank 4.

[0036] like Figure 3 The diagram shows a cross-sectional view of the membrane module degassing process. Oil enters the membrane module 10 through the oil inlet 101. The oil degassing membrane module consists of a raw material mesh 104, an oil degassing composite membrane 105, and a permeate mesh 106 stacked in sequence. The degassed gas 108 is discharged through the gas outlet 103, and the degassed oil is discharged from the oil outlet 102.

[0037] Comparative Example 1 10g of polysulfone, 89g of N-methylpyrrolidone and 1g of sulfolane were prepared into a uniform casting solution. The treated casting solution was coated onto a nonwoven fabric by a coating machine. After drying in the air, it was treated in a gelling agent to obtain a supporting base film. 0.8 g of the copolymer fluoropolymer powder was dissolved in 9.92 g of Solvay Galden (boiling point 135 °C). ® SV135 and 89.28g Solvay Galden with a boiling point of 55°C ® In SV55 mixed solvent, a homogeneous coating liquid is obtained by uniformly dispersing the mixture using ultrasound; wherein, the monomer of the copolymer fluoropolymer is: and ; The obtained coating liquid was applied to the supporting substrate film and dried to obtain the initial composite film. Subsequently, CF4 gas was subjected to high-voltage discharge using a power supply with a radio frequency of 40KHz, and the generated plasma was used to treat the initial composite film for 15s to obtain the final oil-degassed composite film.

[0038] The thickness of the supporting base membrane is 25 μm, the molecular weight cutoff is 200 kDa, and the thickness of the separation layer is 0.5 μm.

[0039] At 25℃ and 1 bar, the O2 permeation rate of the oil-degassing composite membrane was 4000 GPU, and α(O2 / N2) = 1.3. The molecular weight cutoff of the supporting base membrane was too large, resulting in poor coating performance, large defects in the separation layer, and poor selectivity.

[0040] Comparative Example 2 A uniform casting solution was prepared by mixing 15g of polyamide-imide, 5g of polyether-imide, 70g of N,N-dimethylacetamide, and 10g of tetraethylene glycol dimethyl ether. The treated casting solution was then coated onto a nonwoven fabric using a coating machine. After drying in the air, the fabric was treated in a gelling agent to obtain a supporting base film. 1.2 g of the copolymer fluoropolymer powder was dissolved in 7.06 g of Chemours Opteon SF10 (boiling point 110 °C) and 91.74 g of Chemours Vertrel (boiling point 55 °C). TM In an XF mixed solvent, a homogeneous coating liquid is obtained by uniformly dispersing the mixture using ultrasound; wherein, the monomer of the copolymer fluoropolymer is: and ; The obtained coating liquid is cast onto the supporting base film and dried to obtain an oil-degassed composite film.

[0041] The thickness of the supporting base membrane is 35 μm, the molecular weight cutoff is 60 kDa, and the thickness of the separation layer is 1 μm.

[0042] At 25℃ and 1 bar, the O2 permeation rate of the oil degassing composite membrane was 3600 GPU and α(O2 / N2) = 1.8. The oil degassing composite membrane without plasma treatment had a few defects in the separation layer and could not be used for the oil degassing process.

[0043] Comparative Example 3 A uniform casting solution was prepared by mixing 25g of polyacrylonitrile, 73g of N,N-dimethylformamide, 1g of calcium bromide and 1g of glycerol. The treated casting solution was coated onto a nonwoven fabric by a coating machine, dried in the air and then treated in a gelling agent to obtain a supporting base film. 1.5 g of homopolymer fluoropolymer powder was dissolved in 6.16 g of 3M Fluorinert FC40 (boiling point 165 °C) and 92.34 g of 3M Novec (boiling point 61 °C). TM In a 7100 mixed solvent, a homogeneous coating liquid is obtained by uniformly dispersing the mixture using ultrasound; wherein, the monomer of the homopolymer fluoropolymer is: ; The obtained coating liquid was cast onto the supporting substrate and dried to obtain the initial composite film. Subsequently, N2 gas was subjected to high-voltage discharge using a power supply with a radio frequency of 13.56MHz. The generated plasma was used to treat the initial composite film for 27s to obtain the final oil-degassed composite film.

[0044] The thickness of the supporting base membrane is 40 μm, the molecular weight cutoff is 40 kDa, and the thickness of the separation layer is 1.5 μm.

[0045] At 25℃ and 1 bar, the O2 permeation rate of the oil-degassing composite membrane was 3200 GPU and α(O2 / N2) = 1.75. When the oil-degassing composite membrane was treated with N2 gas plasma, the separation layer had a few defects and could not be used for the oil degassing process.

[0046] Comparative Example 4 A uniform casting solution was prepared by mixing 25g of polyethersulfone, 5g of polyvinylidene fluoride, 52g of N-methylpyrrolidone, 15g of tetrahydrofuran and 3g of n-butanol. The treated casting solution was coated onto a nonwoven fabric by a coating machine, dried in the air and then treated in a gelling agent to obtain a supporting base film. Dissolve 2.0 g of the copolymer fluoropolymer powder in 93.1 g of 3M Fluorinert FC70 (boiling point 215℃) and 4.9 g of 3M Novec (boiling point 98℃). TM In a 7300 mixed solvent, a homogeneous coating liquid was obtained by uniformly dispersing the mixture using ultrasound; wherein, the monomer of the copolymer fluoropolymer is: , and ; The obtained coating liquid was slit-coated onto the supporting substrate membrane and dried to obtain the initial composite membrane. Subsequently, a high-voltage discharge of a mixture of 1 mL CF4 and 4 mL SF6 gas was performed using a power supply with a radio frequency of 13.56 MHz. The generated plasma was used to treat the initial composite membrane for 30 s to obtain the final oil-degassed composite membrane.

[0047] The thickness of the supporting base membrane is 45 μm, the molecular weight cutoff is 20 kDa, and the thickness of the separation layer is 2 μm.

[0048] At 25℃ and 1 bar, the O2 permeation rate of the oil-degassing composite membrane was 10 GPU, and α(O2 / N2) = 1.20. When the content of the high-boiling-point fluorinated solvent 3M Fluorinert FC70 was too high, a large amount of solvent remained in the oil-degassing composite membrane, resulting in very low selectivity and gas flux.

[0049] Example 1 12g of polysulfone, 87g of N-methylpyrrolidone and 1g of sulfolane were prepared into a uniform casting solution. The treated casting solution was coated onto a nonwoven fabric by a coating machine. After drying in the air, it was treated in a gelling agent to obtain a supporting base film. 0.8 g of the copolymer fluoropolymer powder was dissolved in 9.92 g of Solvay Galden (boiling point 135 °C). ® SV135 and 89.28g Solvay Galden with a boiling point of 55°C ® In SV55 mixed solvent, a homogeneous coating liquid is obtained by uniformly dispersing the mixture using ultrasound; wherein, the monomer of the copolymer fluoropolymer is: and ; The obtained coating liquid was applied to the supporting substrate film and dried to obtain the initial composite film. Subsequently, CF4 gas was subjected to high-voltage discharge using a power supply with a radio frequency of 40KHz, and the generated plasma was used to treat the initial composite film for 15s to obtain the final oil-degassed composite film.

[0050] The thickness of the supporting base membrane is 25 μm, the molecular weight cutoff is 100 kDa, and the thickness of the separation layer is 0.5 μm.

[0051] At 25℃ and 1 bar, the O2 permeation rate of the oil degassing composite membrane was 3000 GPU and α(O2 / N2) = 2.00, which is comparable to the intrinsic properties of fluoropolymers. This indicates that the separation layer is defect-free and can be used in the oil degassing process.

[0052] Example 2 A uniform casting solution was prepared by mixing 15g of polyimide, 80g of N,N-dimethylformamide, 4g of γ-butyrolactone and 1g of lithium nitrate. The treated casting solution was coated onto a nonwoven fabric by a coating machine, dried in the air and then treated in a gelling agent to obtain a supporting base film. Dissolve 1.0 g of the copolymer fluoropolymer powder in 8.25 g of Solvay Galden (boiling point 110℃). ® SV110 and 90.75g Solvay Galden with a boiling point of 80°C ® In SV80 mixed solvent, a homogeneous coating liquid is obtained by uniformly dispersing the mixture using ultrasound; wherein, the monomer of the copolymer fluoropolymer is: and ; The obtained coating liquid was slit-coated onto the supporting substrate membrane and dried to obtain the initial composite membrane. Subsequently, SF6 gas was subjected to high-voltage discharge using a power supply with a radio frequency of 13.56MHz, and the generated plasma was used to treat the initial composite membrane for 19s to obtain the final oil-degassed composite membrane.

[0053] The thickness of the supporting base membrane is 30 μm, the molecular weight cutoff is 80 kDa, and the thickness of the separation layer is 0.8 μm.

[0054] At 25℃ and 1 bar, the O2 permeation rate of the oil degassing composite membrane was 2600 GPU and α(O2 / N2) = 2.20, which is comparable to the intrinsic properties of fluoropolymers. This indicates that the separation layer is defect-free and can be used in the oil degassing process.

[0055] Example 3 A uniform casting solution was prepared by mixing 15g of polyamide-imide, 5g of polyether-imide, 70g of N,N-dimethylacetamide, and 10g of tetraethylene glycol dimethyl ether. The treated casting solution was then coated onto a nonwoven fabric using a coating machine. After drying in the air, the fabric was treated in a gelling agent to obtain a supporting base film. 1.2 g of the copolymer fluoropolymer powder was dissolved in 7.06 g of Chemours Opteon SF10 (boiling point 110 °C) and 91.74 g of Chemours Vertrel (boiling point 55 °C). TM In an XF mixed solvent, a homogeneous coating liquid is obtained by uniformly dispersing the mixture using ultrasound; wherein, the monomer of the copolymer fluoropolymer is: and ; The obtained coating liquid was cast onto the supporting substrate film and dried to obtain the initial composite film. Subsequently, CF4 gas was subjected to high-voltage discharge using a power supply with a radio frequency of 2.54 GHz, and the generated plasma was used to treat the initial composite film for 23 seconds to obtain the final oil-degassed composite film.

[0056] The thickness of the supporting base membrane is 35 μm, the molecular weight cutoff is 60 kDa, and the thickness of the separation layer is 1 μm.

[0057] At 25℃ and 1 bar, the O2 permeation rate of the oil degassing composite membrane was 2000 GPU and α(O2 / N2) = 2.40, which is comparable to the intrinsic properties of fluoropolymers. This indicates that the separation layer is defect-free and can be used in the oil degassing process.

[0058] Example 4 A uniform casting solution was prepared by mixing 25g of polyacrylonitrile, 73g of N,N-dimethylformamide, 1g of calcium bromide and 1g of glycerol. The treated casting solution was coated onto a nonwoven fabric by a coating machine, dried in the air and then treated in a gelling agent to obtain a supporting base film. 1.5 g of homopolymer fluoropolymer powder was dissolved in 6.16 g of 3M Fluorinert FC40 (boiling point 165 °C) and 92.34 g of 3M Novec (boiling point 61 °C). TM In a 7100 mixed solvent, a homogeneous coating liquid is obtained by uniformly dispersing the mixture using ultrasound; wherein, the monomer of the homopolymer fluoropolymer is: ; The obtained coating liquid was cast onto the supporting substrate film and dried to obtain the initial composite film. Subsequently, SF6 gas was subjected to high-voltage discharge using a power supply with a radio frequency of 13.56MHz, and the generated plasma was used to treat the initial composite film for 27s to obtain the final oil-degassed composite film.

[0059] The thickness of the supporting base membrane is 40 μm, the molecular weight cutoff is 40 kDa, and the thickness of the separation layer is 1.5 μm.

[0060] Tested at 25℃ and 1 bar, the O2 permeation rate of the oil-degassing composite membrane was 1400 GPU, and α(O2 / N2) = 2.60, which is comparable to the intrinsic properties of fluoropolymers. It can also be obtained through… Figure 4 The separation layer is free of defects and can be used in oil degassing processes.

[0061] Example 5 A uniform casting solution was prepared by mixing 25g of polyethersulfone, 5g of polyvinylidene fluoride, 52g of N-methylpyrrolidone, 15g of tetrahydrofuran and 3g of n-butanol. The treated casting solution was coated onto a nonwoven fabric by a coating machine, dried in the air and then treated in a gelling agent to obtain a supporting base film. 2.0 g of the copolymer fluoropolymer powder was dissolved in 4.9 g of 3M Fluorinert FC70 (boiling point 215°C) and 93.1 g of 3M Novec (boiling point 98°C). TM In a 7300 mixed solvent, a homogeneous coating liquid was obtained by uniformly dispersing the mixture using ultrasound; wherein, the monomer of the copolymer fluoropolymer is: , and ; The obtained coating liquid was slit-coated onto the supporting substrate membrane and dried to obtain the initial composite membrane. Subsequently, a high-voltage discharge of a mixture of 1 mL CF4 and 4 mL SF6 gas was performed using a power supply with a radio frequency of 13.56 MHz. The generated plasma was used to treat the initial composite membrane for 30 s to obtain the final oil-degassed composite membrane.

[0062] The thickness of the supporting base membrane is 45 μm, the molecular weight cutoff is 20 kDa, and the thickness of the separation layer is 2 μm.

[0063] At 25℃ and 1 bar, the O2 permeation rate of the oil degassing composite membrane was 100 GPU and α(O2 / N2) = 2.80, which is comparable to the intrinsic properties of fluoropolymers. This indicates that the separation layer is defect-free and can be used in the oil degassing process.

[0064] Example 6 use Figure 2 The process flow shown involves encapsulating the oil degassing composite membranes from Examples 1-5 into 6-inch spiral wound membrane modules. Transformer oil is added to the oil tank, and oxygen is used as the gas source. The pressure gauge reading is 1 bar. A vacuum is drawn on the permeate side of the membrane module, and the vacuum gauge reading is -0.9 bar. After continuous operation for 60 days, the module is disassembled. No transformer oil permeates through the permeate side of the module. Random oil degassing composite membrane sheets are taken for cleaning and drying. The membrane performance is then tested. The selectivity and gas flux show almost no change, indicating that the prepared oil degassing composite membrane has excellent transformer oil tolerance.

[0065] Example 7 use Figure 2 The process flow shown describes the encapsulation of the oil-degassing composite membranes from Examples 1-5 into 4-inch spiral wound membrane modules. No. 15 aviation hydraulic oil is added to the oil tank, and oxygen is used as the gas source. The pressure gauge reading is 8.5 bar. A vacuum is applied to the permeate side of the membrane module, and the vacuum gauge reading is -0.9 bar. The module is run continuously for 60 days. Then, the module is disassembled, as shown... Figure 5 As shown, no No. 15 aviation hydraulic oil permeated the nonwoven fabric of the permeation side membrane of the component. Randomly selected oil-degassing composite membranes were cleaned and dried before testing the membrane performance. The selectivity and gas flux showed almost no change, indicating that the prepared oil-degassing composite membrane has excellent hydraulic oil resistance.

[0066] Example 8 use Figure 2The process flow shown involves encapsulating the oil-degassing composite membranes from Examples 1-5 into 4-inch spiral wound membrane modules. No. 15 aviation hydraulic oil is added to the oil tank, and oxygen is used as the gas source. The pressure gauge reading is 25 bar. A vacuum is applied to the permeate side of the membrane module, and the vacuum gauge reading is -0.1 bar. After 60 days of continuous operation, the module is disassembled. No No. 15 aviation hydraulic oil permeates the permeate side. Randomly selected oil-degassing composite membrane sheets are cleaned and dried before testing the membrane performance. The selectivity and gas flux show almost no change, indicating that the prepared oil-degassing composite membrane has excellent hydraulic oil tolerance.

[0067] Example 9 use Figure 2 The process flow shown involves encapsulating the oil-degassing composite membranes of Examples 1-5 into 10-panel membrane modules. Lubricating oil is added to the oil tank, and oxygen is used as the gas source. The pressure gauge reading is 5 bar. The permeate side of the membrane module is evacuated, and the vacuum gauge reading is -0.9 bar. After continuous operation for 60 days, the module is disassembled. No lubricating oil permeates through the permeate side of the module. Random oil-degassing composite membrane sheets are taken for cleaning and drying. The membrane performance is tested, and the selectivity and gas flux show almost no change, indicating that the prepared oil-degassing composite membrane has excellent lubricant oil tolerance.

[0068] Example 10 use Figure 2 The process flow shown involves encapsulating the oil-degassing composite membranes of Examples 1-5 into 20-panel membrane modules. Aviation fuel is added to the fuel tank, and oxygen is used as the gas source. The pressure gauge reading is 10 bar. The permeate side of the membrane module is evacuated, and the vacuum gauge reading is -0.2 bar. After continuous operation for 60 days, the module is disassembled. No aviation fuel permeates through the permeate side of the module. Random oil-degassing composite membrane sheets are taken for cleaning and drying. The membrane performance is tested, and the selectivity and gas flux show almost no change, indicating that the prepared oil-degassing composite membrane has excellent fuel tolerance.

[0069] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. An oil degassing composite membrane, characterized in that, The oil degassing composite membrane includes a supporting base membrane and a separation layer; The separation layer is attached to the surface of the supporting base membrane; The supporting base membrane has a porous structure, and the separation layer is a fluoropolymer. The thickness of the supporting base film is 10~60μm, and the molecular weight cutoff is 10~200KDa; The thickness of the separation layer is 0.3~5μm; The O2 permeation rate of the oil-degassing composite membrane is 100~3000 GPU.

2. The oil degassing composite membrane according to claim 1, characterized in that, The thickness of the supporting base film is 25~45μm, and the molecular weight cutoff is 20~100KDa; The thickness of the separation layer is 0.5~2μm; Preferably, the O2 / N2 separation coefficient of the oil degassing composite membrane is α(O2 / N2) of 2.00~2.

80.

3. The method for preparing the oil-degassing composite membrane according to claim 1 or 2, characterized in that, The preparation method includes: (1) Preparation of the supporting base film: A uniform casting solution is prepared by mixing polymer, solvent and additives. The casting solution is coated onto a nonwoven fabric and dried. After drying, it is treated in a gelling agent to obtain a supporting base film. (2) Preparation of fluoropolymer coating liquid: Fluoropolymer powder is dissolved in a fluorine-containing mixed solvent and dispersed evenly to obtain a homogeneous coating liquid; (3) Preparation of oil-degassing composite membrane The coating liquid obtained in step (2) is coated onto the support base film obtained in step (1), and after drying, it is subjected to plasma treatment to obtain an oil-degassed composite film.

4. The preparation method according to claim 3, characterized in that, In step (1), the content of the polymer is 12~30wt%, the content of the solvent is 60~87wt%, and the content of the additive is 0.1~10wt%. Preferably, the polymer is at least one selected from polysulfone, polyethersulfone, polyimide, polyamide-imide, polyetherimide, polyacrylonitrile, polyvinylidene fluoride, and polyetheretherketone. The solvent is at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and tetrahydrofuran; The additive is at least one of sulfolane, γ-butyrolactone, lithium nitrate, lithium chloride, calcium bromide, tetraethylene glycol dimethyl ether, n-butanol, and glycerol.

5. The preparation method according to claim 3, characterized in that, In step (2), the fluorinated mixed solvent is composed of a high-boiling-point fluorinated solvent with a boiling point of 100~250℃ and a low-boiling-point fluorinated solvent with a boiling point of less than 100℃. Preferably, the mass ratio of the high-boiling-point fluorinated solvent to the low-boiling-point fluorinated solvent is 1:9~19; Preferably, the fluorinated solvent is any one of perfluoropolyether, hydrofluoroalkane, hydrofluoroolefin, perfluoroalkane, perfluoroolefin, perfluorobenzene, and perfluoroalcohol.

6. The preparation method according to claim 3, characterized in that, In step (2), the concentration of fluoropolymer in the coating liquid is 0.5~10wt%, preferably 0.8~2.0wt%.

7. The preparation method according to claim 3, characterized in that, In step (2), the structural formula of the fluoropolymer is: ； Where a, b, and c represent the degree of polymerization, and a and b are not both 0; a = 0~800, b = 0~800, c = 1~400; Monomers X and Y are selected from compounds with the following structures: 、 、 、 、 、 、 、 、 、 、 、 ； Monomer Z is selected from compounds with the following structures: 、 ； R1 and R2 are each independently selected from H, F, Cl or Br; The values ​​of m, n, k, t, d, and q are integers ranging from 0 to 6.

8. The preparation method according to claim 7, characterized in that, Monomers X and Y are selected from compounds with the following structures: 、 、 、 、 、 、 、 ； The monomer Z is selected from compounds with the following structures: 、 、 、 、 、 、 、 。 9. The preparation method according to claim 3, characterized in that, In step (3), the gas used for plasma treatment is at least one of CF4 and SF6; The power supply has a radio frequency of 40KHz, 13.56MHz, or 2.54GHz; the processing time is 5~100s, preferably 15~30s.

10. The application of the oil degassing composite membrane according to claim 1 or 2 in oil degassing, characterized in that, The oil is transformer oil, hydraulic oil, lubricating oil, or fuel oil.

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