A small aperture enhanced polyfluoroethylene propylene separation membrane and a preparation method thereof

Abstract

The application discloses a small-aperture reinforced polyfluoroethylene propylene separation membrane and a preparation method thereof, and the preparation method comprises the following steps: carrying out ultrasonic pretreatment on a stainless steel mesh with a specific mesh number in acetone-anhydrous ethanol-deionized water; dissolving polyfluoroethylene propylene emulsion and polyvinyl alcohol aqueous solution in deionized water to uniformly mix, obtaining a casting solution, coating the casting solution on the stainless steel mesh after defoaming and ultrasonic oscillation, and obtaining a nascent separation membrane through a rapid heat setting forming method; and sintering in a heat treatment device to obtain the small-aperture reinforced polyfluoroethylene propylene separation membrane. The prepared separation membrane is resistant to temperature and chemical reagents, can be self-cleaned, is thin-walled, and has a high flux, improves service stability of the separation membrane material, prolongs a service life, is easy to backwash and reusable in actual application; raw materials selected by the method are cheap and easy to obtain, a preparation process is simple, the method is a low-energy-consumption and green and environment-friendly membrane preparation mode, and is favorable for industrialized mass production.

Description

Technical Field

[0001] This invention belongs to the field of membrane materials, specifically relating to a small-pore reinforced polytetrafluoroethylene propylene separation membrane and its preparation method. Background Technology

[0002] With the accelerated development of modern industry, and to meet the needs of national economic growth and people's production and daily life, the discharge of industrial oily wastewater continues to rise. It is estimated that by 2024, the scale of my country's waste oil industry will gradually reach approximately 15 billion tons. Meanwhile, with the continuous increase in global resource consumption, waste oil recycling is of great significance for energy conservation and emission reduction. Compared with traditional waste oil regeneration technologies, membrane separation technology has become the best choice for waste oil treatment due to its advantages such as less pollution, higher waste oil treatment efficiency, ease of operation, and smaller footprint. Among them, separation membranes are widely used in industrial waste oil recycling and treatment because of their high flux, ease of maintenance and cleaning, and scalability.

[0003] When treating oily wastewater, because waste oil usually contains a large amount of oily and hydrophobic substances, oleophilic membranes have excellent selectivity and higher oleophilicity, enabling them to efficiently adsorb and separate waste oil. On the other hand, protecting the quality of the oil is a key point in the waste oil regeneration process. Hydrophilic membranes may interact with components in the water, which may damage the quality of the waste oil. Industrial production needs to select appropriate film-forming materials and treatment methods based on the specific composition of the waste oil, process requirements, and treatment objectives. Although hydrophilic membranes have a wide range of applications in other industrial production, oleophilic membranes are generally used in industrial treatment to better meet the properties and treatment requirements of industrial waste oil. Enhanced separation membranes are widely used in actual industry.

[0004] Substrate materials used for separation membranes are generally divided into organic and inorganic materials. Organic materials suffer from poor mechanical strength and are prone to deformation and damage during long-term operation, resulting in a shorter service life. Chinese invention patent publication number CN107243260A discloses a superhydrophobic polypropylene modified ultrafiltration membrane, its preparation method, and its application. Although the process for preparing the oil-water separation membrane is simple and does not involve toxic reagents, the membrane's poor mechanical properties make it unsuitable for long-term, low-frequency operation. Compared to organic materials, inorganic materials, such as stainless steel metal substrates, are common materials with excellent physical properties, including corrosion resistance and temperature resistance. They also have the advantages of thin walls and easy backwashing. Metal substrates, as ultrathin support layers, are suitable for long-term stable operation. At the same time, the preparation cost of stainless steel materials is relatively economical, which is particularly important in large-scale industrial applications.

[0005] Conventional membrane materials are limited in their application in waste oil recycling due to factors such as high oil viscosity, susceptibility to contamination, and low temperature and pressure resistance. Fluoropolymers, with their strong CF bonds, exhibit superior thermal and chemical stability, are less prone to adhesion to liquids and other substances, and possess good self-cleaning capabilities. Perfluoroethylene propylene (PFEP) combines excellent temperature and chemical resistance with good melt processing properties, along with hydrophobic and oleophilic characteristics. These superior properties make this invention suitable for waste oil treatment scenarios requiring the handling of high-temperature liquids or gases, making it an ideal membrane material for waste oil processing. However, no methods for preparing small-pore reinforced PFEP separation membranes via thermosetting molding and sintering have been reported. Summary of the Invention

[0006] In response to the problem of industrial waste oil recycling and treatment, one objective of this invention is to provide a method for preparing a small-pore reinforced polytetrafluoroethylene propylene (PTFE) separation membrane that is pressure-resistant, wear-resistant, thin-walled, simple to prepare, uses inexpensive and readily available materials, and is easy to mass-produce.

[0007] Another object of the present invention is to provide a small-pore reinforced polytetrafluoroethylene propylene separation membrane prepared by the above method.

[0008] Therefore, the present invention adopts the following technical solution:

[0009] A method for preparing a small-pore reinforced polytetrafluoroethylene propylene (PTFE) separation membrane includes the following steps:

[0010] S1, Pre-treatment of stainless steel mesh to remove surface stains and dry it;

[0011] S2, Preparation of casting solution: Stir a 70wt% aqueous solution of perfluoroethylene propylene and a 60-70wt% aqueous solution of polyvinyl alcohol in deionized water at 60-90℃ to obtain a casting solution; then vacuum degas the prepared casting solution for 3 hours and then ultrasonically treat it for 30 minutes.

[0012] S3, Preparation of small-pore reinforced polytetrafluoroethylene propylene separation membrane: The casting solution obtained in step S2 is uniformly coated onto the upper surface of the stainless steel mesh treated in step S1, and then spread in a vacuum hot air box at 60-90℃ for 1-3 minutes. The mesh is then placed vertically in the vacuum hot air box to dry and thermoset. After the moisture has completely evaporated, the membrane is removed to obtain the nascent reinforced polytetrafluoroethylene propylene separation membrane.

[0013] S4, Preparation of small-pore reinforced poly(perfluoroethylene propylene) separation membrane: The nascent reinforced poly(perfluoroethylene propylene) separation membrane is placed in a muffle furnace, heated in a gradient to 270-330℃, and sintered for 5-15 minutes to obtain a small-pore reinforced poly(perfluoroethylene propylene) separation membrane.

[0014] Preferably, the stainless steel mesh in step S1 has a mesh count of 1000-2000.

[0015] The pretreatment method in step S1 is as follows: the stainless steel mesh is ultrasonically cleaned for 30 minutes each in an acetone-anhydrous ethanol solution and in deionized water; the drying method is as follows: the cleaned stainless steel mesh is dried in a 50°C vacuum hot air oven for 3-6 minutes. Preferably, the volume percentage concentration of ethanol in the acetone-anhydrous ethanol mixed solution is 50-80%.

[0016] Preferably, in the casting solution described in step S2, the concentration of perfluoroethylene propylene is 10-30 wt%, and the concentration of polyvinyl alcohol is 5-8 wt%. The stirring is performed by magnetic stirring at a speed of 120-240 r / min for 3 hours.

[0017] In step S3, the directional spreading angle is 0-75° with the horizontal direction.

[0018] Preferably, the gradient temperature increase in step S4 is 5-10℃ / min.

[0019] A small-pore reinforced poly(perfluoroethylene propylene) separation membrane prepared by the above-described method comprises an outer poly(perfluoroethylene propylene) separation membrane layer and an inner stainless steel mesh reinforcement. The thickness of the poly(perfluoroethylene propylene) separation membrane layer is 100-200 μm, and the thickness of the stainless steel mesh reinforcement is 0.2-0.5 mm. The kerosene flux of the small-pore reinforced poly(perfluoroethylene propylene) separation membrane is 75-1325 L·m³. -2 ·h -1 The bar has a pore size range of 10-400nm and a contact angle of 95-120°; after 10-30 tape peels, the water contact angle is 93-118°.

[0020] This invention uses stainless steel mesh as the substrate material and perfluoroethylene propylene, which is resistant to temperature and chemical reagents, as the film-forming material to develop an enhanced separation membrane for treating complex waste oil.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention creatively employs a specific adhesive, PVA, and uses a coating-thermosetting method to rapidly fix the film-forming polymer onto a smooth stainless steel mesh, enhancing the adhesion between the membrane layer and the stainless steel mesh, improving the stability of the separation membrane material during service, and extending its service life. The use of PVA as an adhesive mainly involves two factors: the preparation of the casting solution and pore formation. On the one hand, the stainless steel mesh is very smooth, and FEP solution alone is difficult to adhere to its smooth surface. Using PVA as an adhesive not only effectively disperses FEP but also increases the overall viscosity of the solution, allowing FEP to adhere better to the stainless steel mesh. On the other hand, the decomposition temperature of PVA is lower than that of FEP, meaning that PVA can decompose while FEP is in a molten state, and its decomposed volatile substances can escape onto the surface of the molten FEP, forming surface pores.

[0023] 2. The separation membrane prepared by the method of the present invention has a thin wall (0.3-0.7 mm) and a high flux (kerosene flux is 75-1325 L·m). -2 ·h -1 bar);

[0024] 3. The separation membrane prepared by the method of the present invention has the characteristics of self-cleaning, high temperature resistance, chemical reagent resistance, and excellent wear resistance;

[0025] 4. The separation membrane prepared by the method of the present invention is easy to clean and can be reused;

[0026] 5. The raw materials selected by the method of the present invention are cheap and readily available, and the preparation process is simple. It is a low-energy-consumption, green and environmentally friendly film-making method, which is conducive to large-scale industrial production. Attached Figure Description

[0027] Figure 1 This is an enlarged structural schematic diagram of the 1000-mesh stainless steel mesh used in Embodiment 1 of the present invention;

[0028] Figure 2 This is an electron microscope image of the surface morphology of the small-pore reinforced polytetrafluoroethylene propylene separation membrane prepared in Example 1 of the present invention;

[0029] Figure 3 This is a cross-sectional electron microscope image of the small-pore reinforced polytetrafluoroethylene propylene separation membrane prepared in Example 1 of the present invention. Detailed Implementation

[0030] The preparation method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] Example 1

[0032] A method for preparing a small-pore reinforced polytetrafluoroethylene propylene (PTFE) separation membrane, comprising the following steps:

[0033] S1, Pre-treatment of stainless steel mesh:

[0034] 1000-mesh stainless steel mesh was selected as the reinforcement. The stainless steel mesh was placed in acetone-anhydrous ethanol solution (where the concentration of anhydrous ethanol was 50% (v / v)) and deionized water in sequence, and ultrasonically treated for 30 min each time. After washing, it was placed in a vacuum hot air oven at 50℃ and dried for 5 min.

[0035] S2, Preparation of casting solution: A 70wt% aqueous solution of perfluoroethylene propylene (FEP) and a 60wt% aqueous solution of polyvinyl alcohol (PVA) as a binder were magnetically stirred in deionized water at 90°C for 3 hours at 120 rpm to obtain a homogeneous casting solution. The concentration of FEP in the casting solution was 10wt%, and the concentration of PVA was 5wt%. The casting solution was then subjected to vacuum degassing at 90°C for 3 hours, followed by ultrasonic treatment for 30 minutes.

[0036] S3, Preparation of nascent reinforced polytetrafluoroethylene propylene (PTFE) separation membrane: The casting solution obtained in S2 is uniformly coated onto the upper surface of the stainless steel mesh obtained in S1, and horizontally spread in a 60℃ vacuum hot air box for 1 min. The mesh is then vertically placed in the vacuum hot air box for drying and thermosetting to improve the uniformity of the casting solution. After the moisture has completely evaporated, the nascent reinforced PTFE separation membrane is obtained.

[0037] S4, Preparation of small-pore reinforced poly(perfluoroethylene propylene) separation membrane: The obtained nascent reinforced poly(perfluoroethylene propylene) separation membrane is placed in a muffle furnace and heated to 290°C at a gradient rate of 5°C / min, and held for 15 min to obtain a small-pore reinforced poly(perfluoroethylene propylene) separation membrane composed of a stainless steel mesh substrate and a poly(perfluoroethylene propylene) separation layer.

[0038] The surface morphology of the prepared small-pore reinforced polytetrafluoroethylene propylene separation membrane was scanned by electron microscopy, and the results are as follows: Figure 2 As shown. The small-pore reinforced polytetrafluoroethylene propylene separation membrane has a separation layer thickness of 120 μm, a stainless steel mesh thickness of 0.2 mm, a static water contact angle of 120°, and a kerosene flux of 1325 L·m. -2 ·h -1 The bar has an average pore size of 400 nm and a static water contact angle of 118° after 10 tape peels.

[0039] After filtering kerosene, the above-mentioned small-pore reinforced polytetrafluoroethylene propylene separation membrane was placed in anhydrous ethanol and subjected to room temperature sonication for 30 minutes, and the flux recovery rate was 79%.

[0040] Example 2

[0041] A method for preparing a small-pore reinforced polytetrafluoroethylene propylene (PTFE) separation membrane, comprising the following steps:

[0042] S1, Pre-treatment of stainless steel mesh:

[0043] A 1500-mesh stainless steel mesh was selected as the reinforcement. The stainless steel mesh was sequentially placed in an acetone-anhydrous ethanol solution (where the concentration of anhydrous ethanol was 55% (v / v)) and then in deionized water, and ultrasonically treated for 30 minutes each time. After washing, it was placed in a 50°C vacuum hot air oven to dry for 5 minutes.

[0044] S2, Preparation of casting solution: A 70wt% aqueous solution of perfluoroethylene propylene and a 65wt% aqueous solution of polyvinyl alcohol were magnetically stirred at 150 rpm in deionized water at 90°C until homogeneous, yielding a uniform casting solution. The concentration of perfluoroethylene propylene in the casting solution was 15wt%, and the concentration of polyvinyl alcohol was 6wt%. The prepared casting solution was then subjected to vacuum degassing at 90°C for 3 hours, followed by ultrasonic treatment for 30 minutes.

[0045] S3, Preparation of nascent reinforced poly(perfluoroethylene propylene) separation membrane: The casting solution obtained in S2 is uniformly coated onto the upper surface of a stainless steel mesh, spread at a 75° angle to the horizontal direction, and placed in a 70°C vacuum hot air box for 1.5 min. The mesh is then vertically placed in the vacuum hot air box for drying and thermosetting to improve the uniformity of the casting solution. After the moisture has completely evaporated, the membrane is removed, yielding the nascent reinforced poly(perfluoroethylene propylene) separation membrane.

[0046] S4, Preparation of small-pore reinforced poly(perfluoroethylene propylene) separation membrane: The obtained nascent reinforced poly(perfluoroethylene propylene) separation membrane is placed in a muffle furnace and heated to 310℃ at a gradient rate of 6℃ / min, and held for 10min to obtain a small-pore reinforced poly(perfluoroethylene propylene) separation membrane composed of a stainless steel mesh substrate and a poly(perfluoroethylene propylene) separation layer.

[0047] The prepared small-pore reinforced polytetrafluoroethylene propylene separation membrane has a separation layer thickness of 140 μm, a stainless steel mesh thickness of 0.3 mm, a static water contact angle of 108°, and a kerosene flux of 750 L·m. -2 ·h -1 The bar has an average pore size of 250nm and a static water contact angle of 105° after 15 tape peels.

[0048] After filtering kerosene, the above-mentioned small-pore reinforced polytetrafluoroethylene propylene separation membrane was placed in anhydrous ethanol and subjected to room temperature ultrasonication for 60 minutes, and the flux recovery rate was 82%.

[0049] Example 3

[0050] A method for preparing a small-pore reinforced polytetrafluoroethylene propylene (PTFE) separation membrane, comprising the following steps:

[0051] S1, Pre-treatment of stainless steel mesh:

[0052] 2000-mesh stainless steel mesh was selected as the reinforcement. The stainless steel mesh was sequentially placed in an acetone-anhydrous ethanol solution (where the concentration of anhydrous ethanol was 60% (v / v)) and then in deionized water, and ultrasonically treated for 30 min in each solution. After washing, it was placed in a 50℃ vacuum hot air oven to dry for 5 min.

[0053] S2, Preparation of casting solution: A 70wt% aqueous solution of perfluoroethylene propylene and a 65wt% aqueous solution of polyvinyl alcohol were magnetically stirred at 180 r / min in deionized water at 90°C to obtain a uniform casting solution; the casting solution contained 20wt% perfluoroethylene propylene and 7wt% polyvinyl alcohol. The prepared casting solution was then subjected to vacuum degassing at 90°C for 3 hours, followed by ultrasonic treatment for 30 minutes.

[0054] S3, Preparation of nascent reinforced polytetrafluoroethylene propylene separation membrane: The casting solution obtained in S2 is uniformly coated onto the upper surface of a stainless steel mesh and spread at a 45° angle to the horizontal direction in an 80° vacuum hot air box for 2 minutes. Then, the mesh is vertically placed in the vacuum hot air box to dry and thermoset to improve the uniformity of the casting solution. After the moisture is completely evaporated, it is taken out to obtain the nascent reinforced polytetrafluoroethylene propylene separation membrane.

[0055] S4, Preparation of small-pore reinforced poly(perfluoroethylene propylene) separation membrane: The obtained nascent reinforced poly(perfluoroethylene propylene) separation membrane is placed in a muffle furnace and heated to 330°C at a gradient rate of 7°C / min, and held for 5 min to obtain a small-pore reinforced poly(perfluoroethylene propylene) separation membrane composed of a stainless steel mesh substrate and a poly(perfluoroethylene propylene) separation layer.

[0056] The prepared small-pore reinforced polytetrafluoroethylene propylene separation membrane has a separation layer thickness of 160 μm, a stainless steel mesh thickness of 0.4 mm, a static water contact angle of 102°, and a kerosene flux of 327 L·m³. -2 ·h -1 The bar has an average pore size of 110 nm and a static water contact angle of 101° after 20 tape peels.

[0057] After filtering kerosene, the above-mentioned small-pore reinforced polytetrafluoroethylene propylene separation membrane was placed in anhydrous ethanol and subjected to room temperature ultrasonication for 90 minutes, and the flux recovery rate was 83%.

[0058] Example 4

[0059] The preparation steps of a small-pore reinforced polytetrafluoroethylene propylene separation membrane are as follows:

[0060] S1, Pre-treatment of stainless steel mesh:

[0061] 1500-mesh stainless steel mesh was selected as the reinforcement. The stainless steel mesh was sequentially placed in an acetone-anhydrous ethanol solution (where the concentration of anhydrous ethanol was 70% (v / v)) and then in deionized water, and ultrasonically treated for 30 min each time. After washing, it was placed in a 50℃ vacuum hot air oven to dry for 5 min.

[0062] S2, Preparation of casting solution: Poly(tetrafluoroethylene) propylene solution (70wt%) and polyethylene solution (70wt%) are magnetically stirred evenly in deionized water at 90℃ at a speed of 210r / min to obtain casting solution; the concentration of poly(tetrafluoroethylene) propylene solution in the casting solution is 25wt% and the concentration of polyvinyl alcohol is 8wt%. Then the prepared casting solution is subjected to constant temperature vacuum degassing treatment at 90℃ for 3h and then ultrasonic treatment for 30min.

[0063] S3, Preparation of nascent reinforced polytetrafluoroethylene propylene separation membrane: The casting solution obtained in S2 is uniformly coated onto the upper surface of a stainless steel mesh and spread at a 45° angle to the horizontal direction in an 80° vacuum hot air box for 2.5 min. Then the mesh is vertically placed in the vacuum hot air box to dry and thermoset to improve the uniformity of the casting solution. After the moisture is completely evaporated, it is taken out to obtain the nascent reinforced polytetrafluoroethylene propylene separation membrane.

[0064] S4, Preparation of small-pore reinforced poly(perfluoroethylene propylene) separation membrane: The obtained nascent reinforced poly(perfluoroethylene propylene) separation membrane is placed in a muffle furnace and heated to 330°C at a gradient rate of 8°C / min, and held for 10 min to obtain a small-pore reinforced poly(perfluoroethylene propylene) separation membrane composed of a stainless steel mesh substrate and a poly(perfluoroethylene propylene) separation layer.

[0065] The prepared small-pore reinforced polytetrafluoroethylene propylene separation membrane has a separation layer thickness of 120 μm, a stainless steel mesh thickness of 0.5 mm, a static water contact angle of 98°, and a kerosene flux of 178 L·m³. -2 ·h -1 The bar has an average pore size of 50 nm and a static water contact angle of 93° after 20 tape peels.

[0066] After filtering kerosene, the above-mentioned small-pore reinforced polytetrafluoroethylene propylene separation membrane was placed in anhydrous ethanol and subjected to room temperature sonication for 120 minutes, and the flux recovery rate was 85%.

[0067] Example 5

[0068] The preparation steps of a small-pore reinforced polytetrafluoroethylene propylene separation membrane are as follows:

[0069] S1, Pre-treatment of stainless steel mesh:

[0070] 2000-mesh stainless steel mesh was selected as the reinforcement. The stainless steel mesh was sequentially placed in an acetone-anhydrous ethanol solution (where the concentration of anhydrous ethanol was 80% (v / v)) and then in deionized water, and ultrasonically treated for 30 minutes each time. After washing, it was placed in a 50℃ vacuum hot air oven to dry for 5 minutes.

[0071] S2, Preparation of casting solution: The aqueous solutions of poly(perfluoroethylene propylene) (70wt%) and polyvinyl alcohol (70wt%) were magnetically stirred at 240r / min in deionized water at 90℃ to obtain a uniform casting solution; the concentration of poly(perfluoroethylene propylene) in the casting solution was 30wt% and the concentration of polyvinyl alcohol was 6wt%. Then the prepared casting solution was subjected to vacuum degassing treatment at 90℃ for 3h and then ultrasonic treatment for 30min.

[0072] S3, Preparation of nascent reinforced polytetrafluoroethylene propylene separation membrane: The casting solution is uniformly coated onto the upper surface of a stainless steel mesh and spread at a 20° angle to the horizontal direction in an 80° vacuum hot air box for 3 minutes. Then, the mesh is vertically placed in the vacuum hot air box to dry and thermoset to improve the uniformity of the casting solution. After the moisture is completely evaporated, it is taken out to obtain the nascent reinforced polytetrafluoroethylene propylene separation membrane.

[0073] S4, Preparation of small-pore reinforced poly(perfluoroethylene propylene) separation membrane: The obtained nascent reinforced poly(perfluoroethylene propylene) separation membrane is placed in a muffle furnace and heated to 330°C at a gradient rate of 10°C / min, and held for 5 min to obtain a small-pore reinforced poly(perfluoroethylene propylene) separation membrane composed of a stainless steel mesh substrate and a poly(perfluoroethylene propylene) separation layer.

[0074] The prepared small-pore reinforced polytetrafluoroethylene propylene separation membrane has a separation layer thickness of 200 μm, a stainless steel mesh thickness of 0.5 mm, a static water contact angle of 110°, and a kerosene flux of 75 L·m. -2 ·h -1 The bar has an average pore size of 25nm and a static water contact angle of 107° after 30 tape peels.

[0075] After filtering kerosene, the above-mentioned small-pore reinforced polytetrafluoroethylene propylene separation membrane was placed in anhydrous ethanol and subjected to room temperature sonication for 150 min, and the flux recovery rate was 88%.

Claims

1. A method for preparing a small-pore reinforced polytetrafluoroethylene propylene (PTFE) separation membrane, characterized in that, Includes the following steps: S1, Pre-treatment of stainless steel mesh to remove surface stains and dry it; S2, Preparation of casting solution: Stir a 70wt% aqueous solution of perfluoroethylene propylene and a 60-70wt% aqueous solution of polyvinyl alcohol in deionized water at 60-90℃ to obtain a casting solution; then vacuum degas the prepared casting solution for 3 hours and then ultrasonically treat it for 30 minutes. S3, Preparation of small-pore reinforced polytetrafluoroethylene propylene separation membrane: The casting solution obtained in step S2 is uniformly coated onto the upper surface of the stainless steel mesh treated in step S1, and then spread in a vacuum hot air box at 60-90℃ for 1-3 minutes. The mesh is then placed vertically in the vacuum hot air box to dry and thermoset. After the moisture has completely evaporated, the membrane is removed to obtain the nascent reinforced polytetrafluoroethylene propylene separation membrane. S4, Preparation of small-pore reinforced poly(perfluoroethylene propylene) separation membrane: The nascent reinforced poly(perfluoroethylene propylene) separation membrane is placed in a muffle furnace, heated in a gradient to 270-330℃, and sintered for 5-15 minutes to obtain a small-pore reinforced poly(perfluoroethylene propylene) separation membrane.

2. The preparation method according to claim 1, characterized in that, The stainless steel mesh in step S1 has a mesh count of 1000-2000.

3. The preparation method according to claim 1, characterized in that, The pretreatment method in step S1 is as follows: the stainless steel mesh is ultrasonically cleaned for 30 minutes each in acetone-anhydrous ethanol solution and deionized water; the drying method is as follows: the cleaned stainless steel mesh is placed in a 50°C vacuum hot air box for 3-6 minutes.

4. The preparation method according to claim 3, characterized in that: In the acetone-anhydrous ethanol mixed solution, the volume percentage concentration of ethanol is 50-80%.

5. The preparation method according to claim 1, characterized in that: In the casting solution described in step S2, the concentration of perfluoroethylene propylene is 10-30 wt%, and the concentration of polyvinyl alcohol is 5-8 wt%.

6. The preparation method according to claim 1, characterized in that, The stirring described in step S2 is as follows: magnetic stirring at a speed of 120-240 r / min for 3 hours.

7. The preparation method according to claim 1, characterized in that, The directional spreading angle in step S3 is 0-75° with the horizontal direction.

8. The preparation method according to claim 1, characterized in that: The gradient temperature increase in step S4 is 5-10℃ / min.

9. The small-pore reinforced polytetrafluoroethylene propylene separation membrane prepared by the preparation method according to any one of claims 1-8, characterized in that: The membrane comprises an outer poly(perfluoroethylene propylene) separation membrane layer and an inner stainless steel mesh reinforcement. The thickness of the poly(perfluoroethylene propylene) separation membrane layer is 100-200 μm, and the thickness of the stainless steel mesh reinforcement is 0.2-0.5 mm. The kerosene flux of the small-pore reinforced poly(perfluoroethylene propylene) separation membrane is 75-1325 L·m³. -2 ·h -1 The bar has a pore size range of 10-400nm and a contact angle of 95-120°; after 10-30 tape peels, the water contact angle is 93-118°.

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