Enhanced hollow fiber porous composite membrane and method of making the same

Abstract

This invention belongs to the technical field of polymer separation membranes, specifically relating to an enhanced hollow fiber porous composite membrane and its preparation method. The inner reinforcing material used in this porous composite membrane is a woven tube; the polymer membrane material used in casting forms a separation skin layer on the outer wall of the woven tube, while a sponge layer is formed on the pinholes and / or inner wall of the woven tube. The separation skin layer and the sponge layer form an embedded anchoring structure for the woven tube. The preparation method of the enhanced hollow fiber porous composite membrane includes the following steps: (1) preparing the casting solution; (2) wet spinning; (3) post-treatment of the membrane fibers. The porous composite membrane has high mechanical properties, greatly avoiding the risk of peeling during use. The preparation method can be directly operated on existing wet spinning equipment, without requiring complex pretreatment processes such as corona treatment and degreasing of the inner reinforcing material, and without requiring extensive modification of the wet spinning equipment.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer separation membranes, specifically relating to an enhanced hollow fiber porous composite membrane and its preparation method. Background Technology

[0002] Polymer porous membranes are widely used in water treatment fields such as industrial and municipal wastewater treatment, drinking water purification, and greywater reuse due to their asymmetric structure and the ability to control the pore size according to the formulation and production process. Currently, the more mature membrane fabrication methods are Thermally Induced Phase Separation (TIPS) and Non-Solvent-Induced Phase Separation (NIPS). TIPS-processed porous membranes have high strength and high flux, but lack a dense separation layer, resulting in lower separation accuracy. NIPS, on the other hand, has a simple process and produces membranes with high separation accuracy and good hydrophilicity, but its low mechanical strength leads to problems such as membrane breakage, effluent deterioration, and reduced filtration efficiency when hollow fiber membranes operate in harsh water environments for extended periods.

[0003] To address the strength issues of fiber membranes, research on reinforced hollow fiber composite membranes is increasing, and their applications are becoming more widespread. Currently, the main method employed is long fiber and braided fabric reinforcement. This involves using materials such as polyester fibers, polyamide fibers, polyolefin fibers, and polyacrylonitrile fibers to create braided tubes as inner reinforcing materials. A spinneret is then used to uniformly coat the surface of the braided tubes to form a separation layer. The membrane is then formed using the NIPS method. The resulting hollow fiber porous composite membranes are widely used in municipal wastewater treatment processes such as MBR (membrane bioreactor) and submerged ultrafiltration.

[0004] The tensile breaking strength of reinforced hollow fiber membranes depends on the breaking strength of the inner lining reinforcement material. Although current technology using braided tubes as reinforcement support tubes can meet the breaking strength requirements, the service life of porous membranes largely depends on the interfacial bonding strength between the membrane's separation layer and the support layer of the support tube. High bonding strength improves the stability of the fiber membrane. However, due to the high braiding density of the braided tubes, the casting solution is difficult to penetrate, resulting in insufficient bonding between the separation layer formed on the surface of the braided tube and the braided tube support layer. As a result, the separation layer of the braided tube reinforced porous membrane is prone to peeling during operation, ultimately leading to substandard effluent.

[0005] To address the interfacial bonding strength issue between the separation layer and the support layer in braided tube reinforced porous membranes, existing technologies employ the following methods:

[0006] (1) Modify the surface of the braided tubing, specifically in the following ways:

[0007] Patent CN104117289A discloses an enhanced composite support hollow fiber membrane and its preparation method. The method involves corona treatment of the braided tube to roughen its surface, followed by heat setting at 150-250℃ and then spinning using the NIPS method to increase the bonding force between the transition layer and the support tube.

[0008] Patent CN101357303A discloses a method for preparing a polyvinylidene fluoride hollow fiber composite microporous membrane with strong interfacial bonding. The method involves first coating a braided tube with a dilute polymer solution of 3%-10% (amphiphilic or neutral), then drying the treated braided tube at a temperature of 40-80℃, and finally coating the dried braided tube a second time with a casting solution and then gelling it in a coagulation bath to form a film.

[0009] Patents CN102430348A and CN102512992A, among others, involve degreasing and chemically modifying braided tubing. This method requires strong alkali treatment, which can damage the braided tubing, reduce the strength of the membrane fibers during breakage, and shorten the service life of the membrane fibers. Furthermore, the operation process is relatively complex.

[0010] As can be seen from the above, the surface modification of braided tubes makes the fiber membrane preparation process relatively complex, which is not conducive to large-scale industrial production.

[0011] (2) Use other solutions to fill the inside of the braided tubing, as follows:

[0012] Patent CN104888621A discloses a braided tube homogeneous reinforced polyvinylidene fluoride hollow fiber membrane and its preparation method. The method involves soaking a braided support tube in a low-concentration PVDF solution, allowing the PVDF to penetrate into the inner side of the support tube. Then, a high-concentration casting solution is applied to coat the soaked support tube. Since both materials are the same (high and low concentrations), this method utilizes the principle of homogeneous reinforcement to enhance adhesion, resulting in a hollow fiber membrane with high adhesion and resistance to peeling. However, if the braided tube is not properly selected during the membrane preparation process, the casting solution may seep into the hollow fiber tube, blocking the water passages and causing quality defects.

[0013] Patent CN101254420A first uses a soluble polymer solution with a certain viscosity as the core fluid to block the tube wall and central hole of the braided tube. Then, a casting solution is coated on the outside of the braided tube, and the membrane fibers are prepared using the NIPS process. This method also has the problem that if the viscosity of the casting solution and the process are not properly matched, too much casting solution will seep into the support tube before gelation during the spinning process, leading to blockage of the water production channel and causing quality defects. Moreover, this method is also relatively complex.

[0014] It is evident that while the above methods can improve the bonding strength between the polymer separation layer and the braided tube support layer, they can affect the flux of the hollow fiber membrane, and the preparation process of the fiber membrane is relatively complex.

[0015] Therefore, there is an urgent need for an enhanced hollow fiber porous composite membrane that can ensure the strength of the composite membrane without affecting its permeation flux. Summary of the Invention

[0016] One objective of this invention is to provide an enhanced hollow fiber porous composite membrane. This composite membrane uses a woven tube as the inner reinforcing material, and the polymer membrane material used for casting permeates into the pinholes of the woven tube or onto the inner wall surface of the woven tube. In this way, the polymer membrane material not only forms a dense separation skin layer on the outer wall of the woven tube, but also forms a loose sponge layer on the pinholes or inner wall surface of the woven tube. This dense separation skin layer and loose sponge layer form an embedded anchoring structure for the woven tube, thereby creating a bond with high peel strength between the separation skin layer and the support interface of the woven tube, making it difficult for the separation skin layer to detach. At the same time, the polymer membrane material only permeates into the pinholes of the woven tube, at most onto the inner wall surface of the woven tube, without blocking the water production channels inside the woven tube. This results in a high permeation flux of the composite membrane, making it suitable for industrial production.

[0017] The specific technical solution is as follows:

[0018] An enhanced hollow fiber porous composite membrane has a hollow tubular structure. The inner reinforcing material used in the enhanced hollow fiber porous composite membrane is a hook-woven tube. The polymer membrane material used in the casting forms a separation skin layer on the outer wall of the hook-woven tube, and a sponge layer is formed on the pinholes and / or inner wall of the hook-woven tube. The separation skin layer and the sponge layer form an embedded anchoring structure for the hook-woven tube.

[0019] A woven tube is a hollow fiber support tube produced by weaving fibers. Each bundle of fibers in a woven tube has a certain number of pinholes due to variations in the weaving process; this number is known as the mesh count of the woven tube. Figure 1 As shown, the woven tube plays a major reinforcing role in the composite membrane, the relatively dense separation skin structure formed by the polymer membrane material plays a separating role, while the loose sponge layer structure plays an auxiliary reinforcing role. Unlike the large cavity or finger-like pore structure of existing reinforced composite membranes, the loose sponge layer in this composite membrane has a sponge-like pore structure, which can not only improve the pressure resistance of the composite membrane, but also effectively reduce the defects of large pores in the hollow fiber membrane caused by improper spinning process control or burrs on the woven tube.

[0020] Furthermore, the outer diameter of the woven tubes in the enhanced hollow fiber porous composite membrane is 1.0-3.0 mm; the mesh count of the woven tubes is 25-40 mesh. The mesh count of the woven tube refers to the number of pinholes within a 25.4 mm long woven tube. The number of pinholes reflects the weaving density of the woven tube; the fewer the pinholes, the denser the weaving.

[0021] Preferably, the outer diameter of the crocheted tube is 1.2-2.5 mm.

[0022] Furthermore, the hooked fibers of the hooked tubes in the reinforced hollow fiber porous composite membrane are selected from one of polyester fiber, polyamide fiber, polyolefin fiber or polyacrylonitrile fiber.

[0023] Furthermore, the polymer membrane material used in the casting of the enhanced hollow fiber porous composite membrane is selected from one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluorochloroethylene P (VDF-CTFE), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polysulfone (PSF), or polyethersulfone (PES).

[0024] Furthermore, the thickness of the casting solution coating forming the separation skin layer in the enhanced hollow fiber porous composite membrane is 40-150 μm. Here, the thickness refers only to the coating thickness of the casting solution applied to the outer wall of the woven tube.

[0025] The separation skin is ultimately formed by polymers, such as polyvinylidene fluoride, polyvinylidene fluoride-chlorotrifluoroethylene, polyvinyl chloride, polyacrylonitrile, polysulfone, or polyethersulfone. These high molecular weight polymers are insoluble in water and form the framework of the separation skin. Other additives, solvents, and non-solvents mainly function to form pores, adjust the viscosity of the casting solution, and control the phase separation rate. Some of these components enter the coagulation bath after phase inversion, while others remain in the polymer pores and are gradually lost during membrane use. The final thickness of the separation skin refers to the thickness of the dry film as seen under an optical microscope or electron microscope. Figure 3 The thickness is indicated by g in the figure.

[0026] Furthermore, the porosity of the aforementioned reinforced hollow fiber porous composite membrane is 55%-80%; its burst strength is 0.4-0.9 MPa; its ethanol bubble point pressure is 0.05-0.21 MPa; and the pure water flux of the composite membrane under conditions of 0.1 MPa and 25°C is 800-1600 L / (㎡·h). Generally, hollow fiber membranes with a burst strength of 0.2 MPa or higher and a pure water flux of 400 L / (㎡·h or higher under conditions of 0.1 MPa and 25°C can meet the requirements for membrane use in the water treatment field.

[0027] The magnitude of the ethanol bubble point pressure indirectly reflects the pore size and the number of defects in the membrane; that is, the higher the ethanol bubble point pressure, the smaller the pore size of the membrane. Porosity, on the other hand, indirectly reflects the degree of looseness of the membrane. The flux of a fiber membrane is related not only to the density of the separation layer of the fiber membrane but also to the porosity of the fiber membrane. Generally, the higher the porosity of the membrane, the greater the flux of the fiber membrane.

[0028] Another objective of this invention is to provide a method for preparing the above-mentioned reinforced hollow fiber porous composite membrane. This method eliminates the need for any pretreatment of the inner reinforcing material hook tube, and the embedded anchoring structure of the hook tube can be obtained directly through wet spinning.

[0029] The specific technical solution is as follows:

[0030] The preparation method of the above-mentioned reinforced hollow fiber porous composite membrane includes the following steps:

[0031] (1) Preparation of casting solution: First, mix the solvent, additives and non-solvent evenly, then add the polymer membrane material and mix and stir, and heat to 50-90℃ to dissolve the polymer membrane material and stir evenly to form a casting solution; vacuum and let stand to remove bubbles, and set aside for later use; after the polymer membrane material is stirred and swollen, the polymer molecular chains can be relaxed and can be dissolved better.

[0032] (2) Wet spinning: First, the inner lining reinforcement material hook tube and the casting solution obtained in step (1) are extruded together through the spinneret in the wet spinning equipment to obtain nascent film fibers, wherein the viscosity of the casting solution is controlled at 20,000-100,000 mPa·s; then, after passing through the air section, the nascent film fibers enter the coagulation bath vertically, and the immersion depth of the nascent film fibers in the coagulation bath is 60-180 cm; after reaching the immersion depth, the nascent film fibers enter the rinsing tank for rinsing, and after rinsing, they are wound and cut by a winding machine; the cut film fibers are soaked in pure water.

[0033] The immersion depth refers to the distance between the surface of the coagulation bath and the first guide roller after the nascent membrane fibers enter the coagulation bath. The immersion depth can be adjusted and controlled by moving the guide rod connected to the first guide roller up and down.

[0034] (3) Post-treatment of membrane fibers: First, take out the membrane fibers soaked in pure water in step (2) and drain them. Then, soak the drained membrane fibers in a protective solution and take them out to dry, thus obtaining the reinforced hollow fiber porous composite membrane.

[0035] Firstly, the reinforcing material selected for the inner lining in this invention is a woven tube. Unlike braided tubes, which have a high braiding density, woven tubes have high porosity. This makes it extremely easy for material to seep into the woven tube, clogging the internal water production channels. To address the severe material seepage problem in woven tubes, existing technologies have either significantly increased the viscosity of the casting solution (typically 60,000-120,000 mPa·s during spinning) to reduce seepage and prevent clogging of the water production channels, but this greatly limits the range of usable casting solutions; or increased polymer content to increase the viscosity of the casting solution, which not only increases the film-making cost but also reduces the adhesion between the casting solution and the woven tube, making it prone to peeling; and reduces the porosity of the hollow fiber membrane, thus lowering the flux.

[0036] Another existing technical approach is to pre-treat the woven tube by soaking it in a solution to fill some of the surface pores of the woven tube, thereby reducing the porosity and reducing material penetration. This avoids severe material penetration during the subsequent wet spinning process, which could cause blockage of the water production channel of the woven tube. However, this is similar to the process of braided tubes, making the fiber membrane process relatively complex.

[0037] This invention eliminates the need for any pretreatment of the woven tube. Instead, it directly regulates the penetration of the polymer membrane material into the woven tube during the wet spinning process of existing wet spinning equipment by synergistically adjusting the viscosity of the casting solution and the depth of water penetration. This ensures that the material penetrates into the pinholes of the woven tube or, in a small amount, to the inner wall surface, thus preventing blockage of the water production holes and rendering the fiber membrane unusable. This invention follows the necessary steps of existing wet spinning processes without adding additional steps, thereby avoiding increased production costs, including time, labor, and raw material costs. Furthermore, it eliminates the need for a specific viscosity limit for the casting solution; using a low-viscosity solution can avoid severe material leakage, thus expanding the types and varieties of casting solutions that can be used.

[0038] Even more unexpectedly, the perfect synergistic effect between the viscosity of the casting solution and the immersion depth allows the polymer membrane material to form a separation skin on the outer wall of the hook tube, while simultaneously forming a sponge layer on the pinholes and / or inner wall of the hook tube. The separation skin and the sponge layer form an embedded anchoring structure for the hook tube, thus achieving a composite membrane structure in which the polymer membrane material anchors the hook tube, solving the problem of weak bonding between the separation layer and the support interface.

[0039] Furthermore, in step (1) of the method for preparing the enhanced hollow fiber porous composite membrane, the casting solution contains 51%-73.5 wt% solvent, 10%-30 wt% additives, 0.5%-4 wt% non-solvent, and 15%-25 wt% polymer membrane material.

[0040] Furthermore, in step (1) of the method for preparing the enhanced hollow fiber porous composite membrane, the solvent is one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N-methylpyrrolidone (NMP);

[0041] The additive consists of at least polyethylene glycol (PEG), Tween, and polyvinylpyrrolidone (PVP). The membrane fibers, after coagulation bath, rinsing tank, pure water immersion, and protective solution treatment, still contain mostly PVP, with small amounts of PEG and Tween.

[0042] Preferably, the number-average molecular weight of the polyethylene glycol is 200-20000; more preferably, the polyethylene glycol is at least one of PEG400, PEG1000, PEG2000 and PEG8000.

[0043] Preferably, the Tween is Tween 80.

[0044] Preferably, the number-average molecular weight of the polyvinylpyrrolidone is 10,000-650,000; more preferably, the polyvinylpyrrolidone is at least one of PVPK17, PVPK30, and PVPK90. The molecular weight of PVPK90 is generally 630,000.

[0045] The non-solvent is glycerol or deionized water;

[0046] Furthermore, in step (2) of the method for preparing the enhanced hollow fiber porous composite membrane, the viscosity of the casting solution is controlled at 25000-50000 mPa·s.

[0047] In step (2), the spinning temperature through the spinneret is 50-75℃; the spinning speed is 15-35m / min. This spinning speed takes into account both the membrane pore structure and the yield, ensuring a certain yield while also ensuring that the membrane gels in the coagulation bath to form the required pore structure.

[0048] Spinning speed and spinning temperature are interdependent process parameters. When the spinning temperature is low, the viscosity of the casting solution is high, and the speed needs to be slower; otherwise, the casting solution will have difficulty penetrating into the needle holes of the hook tube. When the spinning temperature is high, the viscosity of the casting solution is low, and the casting solution can penetrate into the needle holes more easily, so the spinning speed can be relatively faster.

[0049] Furthermore, in step (2) of the method for preparing the enhanced hollow fiber porous composite membrane, the height of the air section through which the nascent membrane fibers pass is 10-30 cm. According to the mechanism of solvent evaporation forming pores, the height of the air section affects the porosity of the membrane surface.

[0050] Furthermore, in step (2) of the method for preparing the enhanced hollow fiber porous composite membrane, the coagulation bath is water or an aqueous solution of solvent with a mass fraction ≤50%, wherein the solvent is the same as the solvent of the casting solution. According to the solvent phase inversion method (NIPS) membrane formation mechanism, the coagulation bath and the casting solution work synergistically to regulate the pore structure and permeation separation performance of the composite membrane.

[0051] Furthermore, in step (2) of the method for preparing the enhanced hollow fiber porous composite membrane, the temperature of the coagulation bath is 35-60℃.

[0052] Furthermore, in step (2) of the method for preparing the enhanced hollow fiber porous composite membrane, the rinsing solution in the rinsing tank is pure water; the temperature of the rinsing solution in the rinsing tank is 30-45℃.

[0053] Furthermore, the protective solution for the post-treatment of the membrane fibers in step (3) of the method for preparing the enhanced hollow fiber porous composite membrane consists of the following components: water; glycerol with a mass concentration of 15%-35% and the bactericide Kathon with a mass concentration of 50-100ppm.

[0054] The beneficial effects of this invention are as follows:

[0055] The reinforced hollow fiber porous composite membrane of this invention uses woven tubes as the inner reinforcing material, which greatly improves the mechanical properties of the composite membrane, achieving a burst strength of 0.9 MPa. The density of the woven tubes is lower than that of the braided tubes, contributing to energy conservation and emission reduction during water treatment. The polymer membrane material used forms an embedded anchoring effect on the woven tubes, significantly improving the bonding force between the two materials. The high burst strength of the membrane fibers greatly avoids the risk of peeling during use of the hollow fiber porous composite membrane.

[0056] Meanwhile, the hollow fiber porous composite membrane of the present invention has a large permeation flux, and the pure water flux under the conditions of 0.1MPa and 25℃ can reach 1600L / (㎡·h), which is 2-4 times higher than the requirements for water treatment fiber membranes.

[0057] The method for preparing the hollow fiber porous composite membrane described in this invention can be directly operated on existing wet spinning equipment, eliminating the need for complex pretreatment processes such as corona treatment and degreasing of the inner lining reinforcement material, and also eliminating the need for extensive modifications to the wet spinning equipment. This reduces pretreatment costs and simplifies the spinning process.

[0058] The preparation method achieves a perfect match between the immersion depth of the nascent membrane fibers in the coagulation bath and the viscosity of the casting solution, thereby adjusting the balance between hydrostatic pressure and phase separation rate. This allows for precise control of the depth of the casting solution penetrating into the hook tube and the thickness of the coating on the outer wall of the hook tube. As a result, the formation of polymer membrane material anchors the hook tube structure without affecting the permeation flux of the hollow fiber membrane or the coating thickness of the casting solution, which is beneficial for large-scale continuous production. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the internal structure of the hook-and-weave tube of the present invention.

[0060] Figure 2 This is a diagram of the wet spinning process apparatus used in an embodiment of the present invention.

[0061] Figure 3 The image shows the overall cross-sectional morphology of the PVDF ultrafiltration membrane based on the hooked tube prepared in Example 1 of this invention.

[0062] Figure 4 This is an electron microscope image of a partial cross-sectional morphology of the PVDF ultrafiltration membrane of Embodiment 1 of the present invention.

[0063] Figure 5 This is an electron microscope image of the overall cross-sectional morphology of the PVDF ultrafiltration membrane based on braided tube, which is Comparative Example 2 of the present invention.

[0064] Figure 6 This is an electron microscope image of a partial cross-sectional morphology of the PVDF ultrafiltration membrane based on braided tube, which is Comparative Example 3 of the present invention.

[0065] Among them, 1 is the weaving tube, 2 is the spinneret, 3 is the metering pump, 4 is the casting liquid container, 5 is the air section, 6 is the water immersion depth, 7 is the guide wheel, 8 is the guide rod, 9 is the coagulation bath, 10 is the rinsing tank, 11 is the winding machine, and 12 is the hollow fiber porous composite membrane. Detailed Implementation

[0066] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0067] 1. Test method for porosity of hollow fiber porous composite membrane: The gravimetric method is used to determine the pore volume V of the membrane based on the weight change before and after immersion in water. 孔 The membrane skeleton volume V 膜骨架 The porosity of the membrane can be obtained from the density of the membrane raw materials and the weight of the dry membrane; therefore, the porosity of the membrane is ε = V. 孔 / (V 孔 +V 膜骨架 ).

[0068] 2. Test method for ethanol bubble point pressure: Place the prepared reinforced hollow fiber porous composite membrane in anhydrous ethanol and soak it at 25℃ for 10 minutes; place the pre-wetted sample in the tester of the bubble point pressure-flow tester, immerse the membrane fibers in anhydrous ethanol, adjust the pressure of the tester, and stop increasing the pressure when the first continuous bubble appears in the tester. Record the pressure value at this time, which is the ethanol bubble point pressure.

[0069] 3. Thickness of the dry film separation layer: The thickness of the dry film separation layer was measured using an optical microscope.

[0070] 4. Test method for pure water flux of composite porous membrane: When measuring pure water flux, pure water passes through the porous membrane at a pressure of 0.1 MPa and a temperature of 25℃. The total volume of pure water passing through the porous membrane per unit time and per unit area is measured using a bubble point pressure-flow tester.

[0071] The pure water flux is calculated using the formula J = Q / A·t.

[0072] In the formula, J is the fluid flux (L / m²·h), Q is the sample test flux (L), and A is the sample area (m²). 2 t - Sample testing time, h.

[0073] 5. Test method for membrane burst pressure: The membrane burst pressure is measured by internal pressure dead-end filtration. High-pressure gas is pumped in reverse to measure the pressure at which the membrane ruptures, i.e., the burst pressure of the membrane.

[0074] Example 1

[0075] Selection of the inner lining reinforcement material: 1.30mm outer diameter, 32 mesh needle holes of polyester fiber woven tube.

[0076] The method for preparing the enhanced hollow fiber porous composite membrane includes the following steps:

[0077] (1) Preparation of casting solution: First, 3025g (60.5wt%) of solvent NMP, 19wt% of additives consisting of 250g PEG400, 150g PEG2000, 500g PVPK17 and 50g Tween 80, and 75g (1.5wt%) of non-solvent deionized water were added sequentially to a 10L stirred tank. After stirring for 15min, 950g (19wt%) of polymer membrane material PVDF powder was added and stirred for 30min. Then, the heating switch of the stirred tank was turned on, and the heating temperature was set to 80℃. The mixture was stirred until a homogeneous solution was formed. The stirring speed was reduced, a vacuum was drawn, and the mixture was allowed to stand and be kept warm to remove bubbles, thus obtaining the casting solution for later use.

[0078] (2) Wet spinning:

[0079] First, the parameters are set as follows: the spinneret heating jacket is set to 70℃ (controlled by the circulating water heating jacket outside the spinneret); at this temperature, the viscosity of the casting solution is 41000 mPa·s; the coagulation bath is a 50wt% NMP solution with a temperature of 40℃; the spinning speed is set to 20 m / min; the air section height is adjusted to 15 cm; the water immersion depth is set to 120 cm; and the rinsing solution in the rinsing tank is pure water with a temperature of 40℃.

[0080] Then, after all parameters are set and the set conditions are met, the valves and metering pumps are turned on to start spinning:

[0081] The woven tube and casting solution are extruded together to obtain the nascent membrane filaments;

[0082] The nascent membrane filaments enter the coagulation bath vertically after passing through the air section;

[0083] After reaching the water depth, the nascent membrane fibers enter the rinsing tank for rinsing.

[0084] After rinsing, the filaments are wound and cut using a winding machine; the wound and cut membrane filaments are then rinsed in pure water at 35°C for 24 hours.

[0085] (3) Post-treatment of membrane fibers: First, the membrane fibers soaked in pure water are taken out and drained; then the drained membrane fibers are soaked in an aqueous solution composed of 20wt% glycerol and 50ppm Kathon for 4h, with the temperature of the protective solution being 35℃. After soaking, the membrane fibers are taken out and dried to obtain hollow fiber porous composite membrane.

[0086] like Figure 3 and Figure 4 As shown, a is the hollow fiber porous composite membrane obtained in this embodiment, b is the conductive adhesive used to fix the hollow fiber membrane when taking electron microscope images, c is the polymer coating formed after the casting solution is extruded together with the hook tube and then sequentially passed through a coagulation bath, rinsing tank, winding machine, soaking solution and drying, d is the hook tube, e is the hook fiber, f is the pinhole of the hook tube, and g is the thickness of the dry film separation skin layer.

[0087] Example 2

[0088] Selection of the inner lining reinforcement material: 1.45mm outer diameter, 25 mesh needle count polyamide fiber woven tube.

[0089] The method for preparing the enhanced hollow fiber porous composite membrane includes the following steps:

[0090] (1) Preparation of casting solution: First, 2975g (51.7wt%) of solvent DMAc, 30wt% of additives consisting of 1000g PEG1000, 600g PVPK30, 50g PVPK90 and 75g Tween 80, and 150g (2.6wt%) of non-solvent glycerol were added sequentially to a 10L stirred tank and stirred for 15min. Then, 900g (15.7wt%) of polymer membrane material PVDF powder was added and stirred for 30min. The heating switch of the stirred tank was then turned on and the heating temperature was set to 80℃. The mixture was stirred until a homogeneous solution was formed. The stirring speed was reduced, a vacuum was drawn, and the mixture was allowed to stand and be kept warm to remove bubbles, thus obtaining the casting solution for later use.

[0091] (2) Wet spinning:

[0092] First, the parameters are set as follows: the spinneret heating jacket is set to 60℃ (controlled by the circulating water heating jacket outside the spinneret); at this temperature, the viscosity of the casting solution is 38500 mPa·s; the coagulation bath is a 30wt% DMAc solution with a temperature of 45℃; the spinning speed is set to 25 m / min; the air section height is adjusted to 10 cm; the water immersion depth is set to 180 cm; and the rinsing solution in the rinsing tank is pure water with a temperature of 40℃.

[0093] Then, after all parameters are set and the set conditions are met, the valves and metering pumps are turned on to start spinning:

[0094] The woven tube and casting solution are extruded together to obtain the nascent membrane filaments;

[0095] The nascent membrane filaments enter the coagulation bath vertically after passing through the air section;

[0096] After reaching the water depth, the nascent membrane fibers enter the rinsing tank for rinsing.

[0097] After rinsing, the filaments are wound and cut using a winding machine; the wound and cut membrane filaments are then rinsed in pure water at 35°C for 24 hours.

[0098] (3) Post-treatment of membrane fibers: First, the membrane fibers soaked in pure water are taken out and drained; then the drained membrane fibers are soaked in an aqueous solution composed of 15wt% glycerol and 100ppm Kathon for 4h, with the temperature of the protective solution being 35℃. After soaking, the membrane fibers are taken out and dried to obtain hollow fiber porous composite membrane.

[0099] Example 3

[0100] The selection of the inner lining reinforcement material hook tube: a polyolefin fiber hook tube with an outer diameter of 2.5mm and a needle hole count of 35 is selected.

[0101] The method for preparing the enhanced hollow fiber porous composite membrane includes the following steps:

[0102] (1) Preparation of casting solution: First, 3275g (65.5wt%) of solvent DMAc, 15.5wt% of additives consisting of 250g PEG400, 200g PEG8000, 250g PVPK30 and 75g Tween 80, and 100g (2.0wt%) of non-solvent glycerol were added sequentially to a 10L stirred tank. After stirring for 15min, 850g (17.0wt%) of polymer membrane material P (VDF-CTFE) powder was added and stirred for 30min. Then, the heating switch of the stirred tank was turned on and the heating temperature was set to 80℃. The mixture was stirred until a homogeneous solution was formed. The stirring speed was reduced, a vacuum was drawn, and the mixture was allowed to stand and be kept warm to remove bubbles, thus obtaining the casting solution for later use.

[0103] (2) Wet spinning:

[0104] First, the parameters are set as follows: the spinneret heating jacket is set to 55℃ (controlled by the circulating water heating jacket outside the spinneret); at this temperature, the viscosity of the casting solution is 25500 mPa·s; the coagulation bath is a 40wt% DMAc solution with a temperature of 45℃; the spinning speed is set to 15m / min; the air section height is adjusted to 20cm; the water immersion depth is set to 150cm; and the rinsing solution in the rinsing tank is pure water with a temperature of 40℃.

[0105] Then, after all parameters are set and the set conditions are met, the valves and metering pumps are turned on to start spinning:

[0106] The woven tube and casting solution are extruded together to obtain the nascent membrane filaments;

[0107] The nascent membrane filaments enter the coagulation bath vertically after passing through the air section;

[0108] After reaching the water depth, the nascent membrane fibers enter the rinsing tank for rinsing.

[0109] After rinsing, the filaments are wound and cut using a winding machine; the wound and cut membrane filaments are then rinsed in pure water at 35°C for 24 hours.

[0110] (3) Post-treatment of membrane fibers: First, the membrane fibers soaked in pure water are taken out and drained; then the drained membrane fibers are soaked in an aqueous solution composed of 25wt% glycerol and 60ppm Kathon for 4h, with the temperature of the protective solution being 35℃. After soaking, the membrane fibers are taken out and dried to obtain hollow fiber porous composite membrane.

[0111] Example 4

[0112] Selection of the inner lining reinforcement material: 1.8mm outer diameter, 30 mesh needle holes of polyacrylonitrile fiber woven tube.

[0113] The method for preparing the enhanced hollow fiber porous composite membrane includes the following steps:

[0114] (1) Preparation of casting solution: First, 3025g (60.5wt%) of solvent DMF, 19.0wt% of additives consisting of 250g PEG400, 400g PEG2000, 250g PVPK30 and 50g Tween 80, and 25g (0.5wt%) of non-solvent deionized water were added sequentially to a 10L stirred tank. After stirring for 15min, 1000g (20.0wt%) of polymer film material PAN powder was added and stirred for 30min. Then, the heating switch of the stirred tank was turned on and the heating temperature was set to 80℃. The mixture was stirred until a homogeneous solution was formed. The stirring speed was reduced, a vacuum was drawn, and the mixture was allowed to stand and be kept warm to remove bubbles, thus obtaining the casting solution for later use.

[0115] (2) Wet spinning:

[0116] First, the parameters are set as follows: the spinneret heating jacket is set to 60℃ (controlled by the circulating water heating jacket outside the spinneret); at this temperature, the viscosity of the casting solution is 32000 mPa·s; the coagulation bath is a 40wt% DMF solution with a temperature of 45℃; the spinning speed is set to 20m / min; the air section height is adjusted to 25cm; the water immersion depth is set to 80cm; and the rinsing solution in the rinsing tank is pure water with a temperature of 40℃.

[0117] Then, after all parameters are set and the set conditions are met, the valves and metering pumps are turned on to start spinning:

[0118] The woven tube and casting solution are extruded together to obtain the nascent membrane filaments;

[0119] The nascent membrane filaments enter the coagulation bath vertically after passing through the air section;

[0120] After reaching the water depth, the nascent membrane fibers enter the rinsing tank for rinsing.

[0121] After rinsing, the filaments are wound and cut using a winding machine; the wound and cut membrane filaments are then rinsed in pure water at 35°C for 24 hours.

[0122] (3) Post-treatment of membrane fibers: First, the membrane fibers soaked in pure water are taken out and drained; then the drained membrane fibers are soaked in an aqueous solution composed of 25wt% glycerol and 60ppm Kathon for 4h, with the temperature of the protective solution being 35℃. After soaking, the membrane fibers are taken out and dried to obtain hollow fiber porous composite membrane.

[0123] Because the braided tube and the coating material are the same, the polymer and the braided tube are bonded more tightly, which greatly increases the burst pressure.

[0124] Example 5

[0125] Selection of the inner lining reinforcement material: 1.8mm outer diameter, 30 mesh needle holes of polyacrylonitrile fiber woven tube.

[0126] The method for preparing the enhanced hollow fiber porous composite membrane includes the following steps:

[0127] (1) Preparation of casting solution: First, 3100g (62wt%) of solvent DMSO, 18.0wt% of additives consisting of 250g PEG400, 500g PVPK17, 50g PVPK90 and 100g Tween 80, and 50g (1.0wt%) of non-solvent deionized water were added sequentially to a 10L stirred tank. After stirring for 15min, 950g (19.0wt%) of polymer film material PVC powder was added and stirred for 30min. Then, the heating switch of the stirred tank was turned on, and the heating temperature was set to 80℃. The mixture was stirred until a homogeneous solution was formed. The stirring speed was reduced, a vacuum was drawn, and the mixture was allowed to stand and be kept warm to remove bubbles, thus obtaining the casting solution for later use.

[0128] (2) Wet spinning:

[0129] First, the parameters are set as follows: the spinneret heating jacket is set to 50℃ (controlled by the circulating water heating jacket outside the spinneret); at this temperature, the viscosity of the casting solution is 35400 mPa·s; the coagulation bath is a 35wt% DMSO solution with a temperature of 55℃; the spinning speed is set to 25 m / min; the air section height is adjusted to 20 cm; the water immersion depth is set to 170 cm; and the rinsing solution in the rinsing tank is pure water with a temperature of 40℃.

[0130] Then, after all parameters are set and the set conditions are met, the valves and metering pumps are turned on to start spinning:

[0131] The woven tube and casting solution are extruded together to obtain the nascent membrane filaments;

[0132] The nascent membrane filaments enter the coagulation bath vertically after passing through the air section;

[0133] After reaching the water depth, the nascent membrane fibers enter the rinsing tank for rinsing.

[0134] After rinsing, the filaments are wound and cut using a winding machine; the wound and cut membrane filaments are then rinsed in pure water at 35°C for 24 hours.

[0135] (3) Post-treatment of membrane fibers: First, the membrane fibers soaked in pure water are taken out and drained; then the drained membrane fibers are soaked in an aqueous solution composed of 30wt% glycerol and 75ppm Kathon for 4h, with the temperature of the protective solution being 35℃. After soaking, the membrane fibers are taken out and dried to obtain hollow fiber porous composite membrane.

[0136] Example 6

[0137] Selection of the inner lining reinforcement material: 1.5mm outer diameter, 40 mesh needle holes of polyester fiber woven tube.

[0138] The method for preparing the enhanced hollow fiber porous composite membrane includes the following steps:

[0139] (1) Preparation of casting solution: First, 2700g (54wt%) of solvent DMAc, 20.0wt% of additives consisting of 400g PEG400, 150g PEG8000, 350g PVPK30 and 100g Tween 80, and 150g (3.0wt%) of non-solvent deionized water were added sequentially to a 10L stirred tank. After stirring for 15min, 1150g (23.0wt%) of polymer film material PS powder was added and stirred for 30min. Then, the heating switch of the stirred tank was turned on, and the heating temperature was set to 80℃. The mixture was stirred until a homogeneous solution was formed. The stirring speed was reduced, a vacuum was drawn, and the mixture was allowed to stand and be kept warm to remove bubbles, thus obtaining the casting solution for later use.

[0140] (2) Wet spinning:

[0141] First, the parameters are set as follows: the spinneret heating jacket is set to 50℃ (controlled by the circulating water heating jacket outside the spinneret); at this temperature, the viscosity of the casting solution is 21500 mPa·s; the coagulation bath is pure water, and the temperature is set to 45℃; the spinning speed is set to 30 m / min; the air section height is adjusted to 15 cm; the water immersion depth is set to 60 cm; and the rinsing solution in the rinsing tank is pure water, and the temperature is 40℃.

[0142] Then, after all parameters are set and the set conditions are met, the valves and metering pumps are turned on to start spinning:

[0143] The woven tube and casting solution are extruded together to obtain the nascent membrane filaments;

[0144] The nascent membrane filaments enter the coagulation bath vertically after passing through the air section;

[0145] After reaching the water depth, the nascent membrane fibers enter the rinsing tank for rinsing.

[0146] After rinsing, the filaments are wound and cut using a winding machine; the wound and cut membrane filaments are then rinsed in pure water at 35°C for 24 hours.

[0147] (3) Post-treatment of membrane fibers: First, the membrane fibers soaked in pure water are taken out and drained; then the drained membrane fibers are soaked in an aqueous solution composed of 20wt% glycerol and 75ppm Kathon for 4h, with the temperature of the protective solution being 35℃. After soaking, the membrane fibers are taken out and dried to obtain hollow fiber porous composite membrane.

[0148] Example 7

[0149] Selection of the inner lining reinforcement material: 1.3mm outer diameter, 35 mesh needle holes of polyamide fiber woven tube.

[0150] The method for preparing the enhanced hollow fiber porous composite membrane includes the following steps:

[0151] (1) Preparation of casting solution: First, 3000g (58.8wt%) of solvent DMAc, 19.6wt% of additives consisting of 500g PEG400, 250g PEG8000, 200g PVPK30 and 50g Tween 80, and 150g (2.9wt%) of non-solvent glycerol were added sequentially to a 10L stirred tank. After stirring for 15min, 950g (18.6wt%) of polymer membrane material PES powder was added and stirred for 30min. Then, the heating switch of the stirred tank was turned on and the heating temperature was set to 80℃. The mixture was stirred until a homogeneous solution was formed. The stirring speed was reduced, a vacuum was drawn, and the mixture was allowed to stand and be kept warm to remove bubbles, thus obtaining the casting solution for later use.

[0152] (2) Wet spinning:

[0153] First, the parameters are set as follows: the spinneret heating jacket is set to 65℃ (controlled by the circulating water heating jacket outside the spinneret); at this temperature, the viscosity of the casting solution is 24500 mPa·s; the coagulation bath is a 30% DMAc solution with a temperature of 55℃; the spinning speed is set to 25 m / min; the air section height is adjusted to 15 cm; the water immersion depth is set to 90 cm; and the rinsing solution in the rinsing tank is pure water with a temperature of 40℃.

[0154] Then, after all parameters are set and the set conditions are met, the valves and metering pumps are turned on to start spinning:

[0155] The woven tube and casting solution are extruded together to obtain the nascent membrane filaments;

[0156] The nascent membrane filaments enter the coagulation bath vertically after passing through the air section;

[0157] After reaching the water depth, the nascent membrane fibers enter the rinsing tank for rinsing.

[0158] After rinsing, the filaments are wound and cut using a winding machine; the wound and cut membrane filaments are then rinsed in pure water at 35°C for 24 hours.

[0159] (3) Post-treatment of membrane fibers: First, the membrane fibers soaked in pure water are taken out and drained; then the drained membrane fibers are soaked in an aqueous solution composed of 25wt% glycerol and 75ppm Kathon for 4h, with the temperature of the protective solution being 35℃. After soaking, the membrane fibers are taken out and dried to obtain hollow fiber porous composite membrane.

[0160] Comparative Example 1

[0161] Selection of the inner lining reinforcement material: 1.30mm outer diameter, 32 mesh needle holes of polyester fiber woven tube.

[0162] The method for preparing the enhanced hollow fiber porous composite membrane includes the following steps:

[0163] (1) Preparation of casting solution (excluding non-solvents): First, 3200g (64wt%) of solvent NMP and an additive (19wt%) consisting of 250g PEG400, 150g PEG2000, 500g PVPK17, and 50g Tween 80 were added sequentially to a 10L stirred tank and stirred for 15min. Then, 850g (17wt%) of polymer film material PVDF powder was added and stirred for 30min. The heating switch of the stirred tank was then turned on, and the heating temperature was set to 80℃. The mixture was stirred until a homogeneous solution was formed. The stirring speed was reduced, a vacuum was drawn, and the mixture was allowed to stand and be kept warm to remove bubbles, thus obtaining the casting solution for later use.

[0164] (2) Wet spinning:

[0165] First, the parameters are set as follows: the spinneret heating jacket is set to 70℃ (controlled by the circulating water heating jacket outside the spinneret); at this temperature, the viscosity of the casting solution is 40500 mPa·s; the coagulation bath is a 50wt% NMP solution with a temperature of 40℃; the spinning speed is set to 20 m / min; the air section height is adjusted to 15 cm; the water immersion depth is set to 105 cm; and the rinsing solution in the rinsing tank is pure water with a temperature of 40℃.

[0166] Then, after all parameters are set and the set conditions are met, the valves and metering pumps are turned on to start spinning:

[0167] The woven tube and casting solution are extruded together to obtain the nascent membrane filaments;

[0168] The nascent membrane filaments enter the coagulation bath vertically after passing through the air section;

[0169] After reaching the water depth, the nascent membrane fibers enter the rinsing tank for rinsing.

[0170] After rinsing, the filaments are wound and cut using a winding machine; the wound and cut membrane filaments are then rinsed in pure water at 35°C for 24 hours.

[0171] (3) Post-treatment of membrane fibers: First, the membrane fibers soaked in pure water are taken out and drained; then the drained membrane fibers are soaked in an aqueous solution composed of 20wt% glycerol and 50ppm Kathon for 4h, with the temperature of the protective solution being 35℃. After soaking, the membrane fibers are taken out and dried to obtain hollow fiber porous composite membrane.

[0172] Comparative Example 2

[0173] The difference between Comparative Example 2 and Example 1 is that an unmodified braided tube made of polyester fiber is used as the inner lining reinforcement material.

[0174] Everything else is the same as in Example 1, including the membrane fiber formulation and process parameter settings.

[0175] Depend on Figure 5It can be seen that the polymer membrane material of the hollow fiber membrane obtained in Comparative Example 2 is basically on the outer wall of the braided tube and does not form an anchoring structure with the braided tube.

[0176] Comparative Example 3

[0177] The difference between Comparative Example 3 and Example 2 is that an unmodified braided tube made of polyamide fibers is used as the inner lining reinforcement material.

[0178] Everything else is the same as in Example 2, including the membrane fiber formulation and process parameter settings.

[0179] Depend on Figure 6 It is evident that in Comparative Example 3, the polymer and braided tube in the cross-section of the hollow fiber membrane do not form an anchoring structure. The braided tube has a high braiding density, and the polymer coating is basically on the outside of the braided tube, resulting in lower flux and burst strength compared to the braided tube. This further demonstrates that the hollow fiber porous membrane of the present invention has the advantages of high membrane flux and burst pressure.

[0180] Comparative Example 4

[0181] The difference between Comparative Example 4 and Example 3 is that the immersion depth is 210cm.

[0182] Everything else is the same as in Example 3, including the membrane fiber formulation and process parameter settings.

[0183] When the water depth is 210cm, normal membrane fibers cannot be prepared, the inside of the hook tube is completely blocked by permeate, and the pure water flux is 0.

[0184] Comparative Example 5

[0185] The difference between Comparative Example 5 and Example 5 is that the immersion depth is 50cm.

[0186] Everything else is the same as in Example 5, including the membrane fiber formulation and process parameter settings.

[0187] Compared with Example 5, due to the shallow water immersion depth, less casting solution penetrates into the gaps of the hook-and-loop tube, resulting in lower bonding strength and reduced burst strength.

[0188] The depth of immersion in water mainly affects the static pressure of the coagulation liquid on the nascent membrane fibers in the coagulation bath. If the nascent membrane fibers are immersed too deeply in the coagulation bath or come into contact with the guide wheel before they solidify, severe material leakage will occur, which will block the water production pores of the hollow fiber and lead to spinning failure. It can be seen that controlling the phase separation rate and immersion depth of the formulation system can effectively prevent the phenomenon of material leakage blocking the water production pores.

[0189] Comparative Example 6

[0190] Selection of the inner lining reinforcement material: 1.30mm outer diameter, 32 mesh needle holes of polyester fiber woven tube.

[0191] The method for preparing the enhanced hollow fiber porous composite membrane includes the following steps:

[0192] (1) Preparation of casting solution: First, 3212.5g (64.25wt%) of solvent NMP, 19wt% of additives consisting of 250g PEG400, 150g PEG2000, 500g PVPK17 and 50g Tween 80, and 12.5g (0.25wt%) of non-solvent deionized water were added sequentially to a 10L stirred tank. After stirring for 15min, 825g (16.5wt%) of polymer membrane material PVDF powder was added and stirred for 30min. Then, the heating switch of the stirred tank was turned on, and the heating temperature was set to 70℃. The mixture was stirred until a homogeneous solution was formed. The stirring speed was reduced, a vacuum was drawn, and the mixture was allowed to stand and be kept warm to remove bubbles, thus obtaining the casting solution for later use.

[0193] (2) Wet spinning:

[0194] First, the parameters are set as follows: the spinneret heating jacket is set to 70℃ (controlled by the circulating water heating jacket outside the spinneret); at this temperature, the viscosity of the casting solution is 19000 mPa·s; the coagulation bath is a 50wt% NMP solution with a temperature of 40℃; the spinning speed is set to 20 m / min; the air section height is adjusted to 15 cm; the water immersion depth is set to 120 cm; and the rinsing solution in the rinsing tank is pure water with a temperature of 40℃.

[0195] Then, after all parameters are set and the set conditions are met, the valves and metering pumps are turned on to start spinning:

[0196] The woven tube and casting solution are extruded together to obtain the nascent membrane filaments;

[0197] The nascent membrane filaments enter the coagulation bath vertically after passing through the air section;

[0198] After reaching the water depth, the nascent membrane fibers enter the rinsing tank for rinsing.

[0199] After rinsing, the filaments are wound and cut using a winding machine; the wound and cut membrane filaments are then rinsed in pure water at 35°C for 24 hours.

[0200] (3) Post-treatment of membrane fibers: First, the membrane fibers soaked in pure water are taken out and drained; then the drained membrane fibers are soaked in an aqueous solution composed of 20wt% glycerol and 50ppm Kathon for 4h, with the temperature of the protective solution being 35℃. After soaking, the membrane fibers are taken out and dried to obtain hollow fiber porous composite membrane.

[0201] Compared with Example 1, the ethanol bubble point pressure, pure water flux, and burst strength of the membrane fiber in Comparative Example 6 were all reduced. It can be seen that when the polymer content is too low, the viscosity of the casting solution is too low, and the non-solvent content in the formula is too low, the phase separation rate of the casting solution is slow. The coating under the spinning conditions is thinner and cannot coat a thicker polymer. The seepage will be more serious and spinning will not be possible.

[0202] The performance indicators of the hollow fiber porous composite membranes obtained in each embodiment and comparative example are summarized in Table 1 below.

[0203] Table 1 Performance indicators of various hollow fiber porous composite membranes

[0204]

[0205]

[0206] (1) Compared with Example 1, the pure water flux of the porous membrane in Comparative Example 1 was reduced by 7.5%, and the burst strength was reduced by 19.0%.

[0207] (2) Compared with Example 1, the pure water flux of the porous membrane in Comparative Example 2 was reduced by 12.3%, and the burst strength was reduced by 30.2%.

[0208] (3) Compared with Example 2, the pure water flux of the porous membrane in Comparative Example 3 was reduced by 10.4%, and the burst strength was reduced by 17.7%.

[0209] (4) Compared with Example 5, the pure water flux of the porous membrane in Comparative Example 5 was reduced by 33.5%, and the burst strength was reduced by 32.8%.

[0210] (5) Compared with Example 1, the pure water flux of the porous membrane in Comparative Example 6 was reduced by 28.5%, and the burst strength was reduced by 33.3%.

Claims

1. An enhanced hollow fiber porous composite membrane having a hollow tubular structure, characterized by, The inner lining reinforcing material of the reinforced hollow fiber porous composite membrane is a hook-knitted tube; the polymer membrane material used for casting forms a separation skin layer on the outer wall of the hook-knitted tube, and a sponge layer on the needle holes and / or inner wall of the hook-knitted tube, and the separation skin layer and the sponge layer form an embedded anchoring structure for the hook-knitted tube; The reinforced hollow fiber porous composite membrane is prepared by the following steps: (1) Preparation of casting solution: first, mix and stir the solvent, additives and non-solvent uniformly, then add the polymer membrane material and mix and stir, and heat to 50-90℃ to dissolve the polymer membrane material, stir uniformly to form a casting solution; vacuumize and stand to remove bubbles, ready for use; (2) Wet spinning: first, the inner lining reinforcing material hook-knitted tube and the casting solution prepared in step (1) are extruded through the spinneret in the wet spinning equipment to obtain a nascent membrane filament, wherein the viscosity of the casting solution is controlled at 20000-100000 mPa·s; Then, the nascent membrane filament vertically enters the coagulation bath after passing through the air section, and the water entry depth of the nascent membrane filament in the coagulation bath is 60-180 cm; wherein the water entry depth refers to the distance between the coagulation bath water surface and the first godet after the nascent membrane filament enters the coagulation bath; The coagulation liquid in the coagulation bath is a solvent aqueous solution with a mass fraction of ≤50%, wherein the solvent is the same as that of the casting solution; After reaching the water entry depth, the nascent membrane filament enters the rinsing tank for rinsing, and is collected by the winding machine and cut after rinsing; the cut membrane filament is soaked in pure water; (3) Membrane filament post-treatment: first, take out the membrane filament soaked in pure water in step (2) and drain; then soak the drained membrane filament in a protective solution, take it out and dry, to obtain the reinforced hollow fiber porous composite membrane.

2. The reinforced hollow fiber porous composite membrane of claim 1, wherein, The outer diameter of the hook-knitted tube is 1.0-3.0 mm; the hook-knitted tube has a mesh number of 25-40.

3. The reinforced hollow fiber porous composite membrane of claim 2, wherein, The outer diameter of the hook-knitted tube is 1.2-2.5 mm.

4. The reinforced hollow fiber porous composite membrane of claim 1, wherein, The hook-knitted fibers of the hook-knitted tube are selected from one of polyester fibers, polyamide fibers, polyolefin fibers or polyacrylonitrile fibers.

5. The reinforced hollow fiber porous composite membrane of claim 1, wherein, The polymer membrane material is selected from one of polyvinylidene fluoride, polyvinylidene fluoride-trifluorochloroethylene, polyvinyl chloride, polyacrylonitrile, polysulfone or polyethersulfone.

6. The reinforced hollow fiber porous composite membrane of claim 1, wherein, The coating thickness of the casting solution forming the separation skin layer is 40-150 μm.

7. The reinforced hollow fiber porous composite membrane of any one of claims 1-6, wherein, The porosity of the composite membrane is 55%-80%; the burst strength is 0.4-0.9 MPa; the ethanol bubble point pressure is 0.05-0.21 MPa; the pure water flux of the composite membrane under the condition of 0.1 MPa and 25℃ is 800-1600 L / (㎡•h).

8. The reinforced hollow fiber porous composite membrane of claim 1, wherein, The casting solution in step (1) contains 51%-73.5wt% of solvent, 10%-30wt% of additives, 0.5%-4wt% of non-solvent and 15%-25wt% of polymer membrane material; The solvent is one of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide and N-methyl pyrrolidone; The additives are at least composed of polyethylene glycol, Tween and polyvinylpyrrolidone; The non-solvent is glycerol or deionized water.

9. The reinforced hollow fiber porous composite membrane of claim 8, wherein, The number average molecular weight of the polyethylene glycol is 200-20000; the Tween is Tween 80; the number average molecular weight of the polyvinylpyrrolidone is 10000-650000.

10. The reinforced hollow fiber porous composite membrane of claim 9, wherein, The polyethylene glycol is at least one of PEG400, PEG1000, PEG2000 and PEG8000; the polyvinylpyrrolidone is at least one of PVPK17, PVPK30 and PVPK90.

11. The reinforced hollow fiber porous composite membrane of claim 1, wherein, The viscosity of the casting solution in the preparation step (2) is controlled to be 25000-50000 mPa·s; The spinning temperature in step (2) is 50-75℃ by the spinneret; the spinning speed is 15-35 m / min.

12. The reinforced hollow fiber porous composite membrane of claim 1, wherein, The height of the air section through which the nascent membrane filament passes in the preparation step (2) is 10-30 cm; The temperature of the coagulation bath in step (2) is 35-60℃; The rinsing liquid of the rinsing tank in step (2) is pure water; the temperature of the rinsing liquid in the rinsing tank is 30-45℃; The protective liquid for the post-treatment of the membrane filament in step (3) is composed of water, glycerol with a mass concentration of 15%-35% and a bactericide, Karson, with a concentration of 50-100 ppm.

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