Hollow fiber membrane, method for producing the same, and use thereof

Abstract

This application discloses a hollow fiber membrane, its preparation method, and its application. The preparation method includes: co-extruding a casting solution and a core solution, followed by a preliminary phase inversion to obtain nascent membrane fibers; and subjecting the nascent membrane fibers to a second phase inversion to obtain a hollow fiber membrane. The core solution comprises, by mass, 40 to 46.3 parts water, 1.6 to 3.5 parts concentrated hydrochloric acid, 1 to 2.2 parts sodium chloride, 1.5 to 3.5 parts amino-cationic polymer, 0.5 to 0.8 parts hydrophilic nanomaterials, and 43.7 to 55.4 parts organic solvent. This application uses a core solution containing an amino-containing cationic polymer and hydrophilic nanomaterials to directionally modify the inner wall of the hollow fiber membrane. A stable hydrophilic modified layer is constructed by electrostatic adsorption generated from the negative charge on the membrane surface. In-situ functionalization can be achieved in a single spinning step, resulting in a simple process and a uniform and firmly adhered modified membrane layer.

Description

Technical Field

[0001] This application relates to the field of polymer membranes, and more particularly to a hollow fiber membrane, its preparation method, and its application. Background Technology

[0002] Membrane separation technology boasts advantages such as high sieving precision, no phase change, low energy consumption, environmental friendliness, and scalability. It is widely used in the purification of industrial wastewater and drinking water, as well as in the separation, concentration, and purification processes of biopharmaceuticals, pharmaceuticals, and the food industry. Sulfonated polysulfone materials possess a negatively charged backbone, high mechanical strength, good chemical stability, and resistance to acids, alkalis, and solvents. They exhibit excellent film-forming properties, resulting in membranes with controllable pore size and stable sieving and separation performance. These membranes are suitable for preparing high-precision, multifunctional separation membranes and are widely used in water treatment, biopharmaceuticals, and fine food separation, showing promising industrialization prospects.

[0003] Unmodified sulfonated polysulfone membranes have weak hydrophilicity and poor surface uniformity, limiting their applications. During water treatment, the membrane surface easily adsorbs organic matter, colloids, and microorganisms from the water, causing pore blockage, flux reduction, and decreased precision, shortening membrane lifespan, increasing maintenance and replacement costs, and making it difficult to meet the requirements for long-term stable operation of water purification. In the biological, pharmaceutical, and food fields, membrane materials exhibit severe non-specific adsorption, easily retaining proteins, peptides, active components, and functional ingredients in pharmaceuticals and food. This not only reduces material recovery rates and product purity but also easily leads to material deterioration and cross-contamination, failing to meet the production standards for high-precision purification and concentration.

[0004] Currently, the industry generally employs two methods to improve the hydrophilic and antifouling properties of membranes: one is post-modification of the finished membrane surface; the other is blending in the casting solution, including polymer blending and hydrophilic nanomaterial doping, among which hydrophilic nanomaterial doping modification is the most widely used. However, traditional hydrophilic nanomaterial doping modification has significant drawbacks. Hydrophilic nanomaterials have high surface energy, making them prone to agglomeration, sedimentation, and uneven dispersion in the casting system, thus failing to fully realize the modification effect. Furthermore, agglomerated particles can introduce microscopic defects into the membrane, damaging its structural integrity and reducing sieving stability and mechanical properties. In addition, directly mixing hydrophilic nanomaterials into the casting solution alters the system's viscosity, rheological properties, and phase separation kinetics, easily causing fiber breakage, membrane collapse, uneven membrane size, and micropore defects, resulting in low membrane yield and poor batch consistency.

[0005] In the blending modification of casting solutions, functional components are randomly distributed inside the membrane and cannot be directionally enriched at the membrane separation interface, resulting in the ineffective loss of a large number of components. High addition amounts are required to achieve the modification effect, which is costly. On the other hand, post-modification methods such as surface coating and chemical grafting are complicated processes with long production cycles. They require adjustment or modification of equipment and processes, cannot be directly adapted to existing mature spinning production lines, and are difficult to scale up for mass production, thus limiting their industrialization and promotion.

[0006] Therefore, there is an urgent need in this field to develop a sulfonated polysulfone-based multifunctional separation membrane modification technology that is simple to process, highly efficient in modification, structurally stable, and capable of large-scale production, in order to overcome the shortcomings of existing technologies. Summary of the Invention

[0007] In view of this, this application provides a hollow fiber membrane and its preparation method. The preparation method provided by this application uses an amino-containing cationic polymer and a core liquid of hydrophilic nanomaterials to directionally modify the inner wall of the hollow fiber membrane. The membrane surface is negatively charged to generate electrostatic adsorption to construct a stable hydrophilic modified layer. In-situ functionalization can be achieved in one spinning step. The process is simple and the resulting membrane modified layer is uniform and firmly attached.

[0008] This application provides a method for preparing a hollow fiber membrane, comprising: The casting solution and the core solution are co-extruded and, after preliminary phase inversion, primary membrane fibers are obtained. The nascent membrane fibers are subjected to a second phase transformation to obtain a hollow fiber membrane; The casting solution comprises, by weight, 15 to 20 parts of negatively charged polymer, 0.5 to 2.5 parts of water, and 77.5 to 84.5 parts of organic solvent; The core fluid comprises, by weight, 40 to 46.3 parts water, 1.6 to 3.5 parts concentrated hydrochloric acid, 1 to 2.2 parts sodium chloride, 1.5 to 3.5 parts amino cationic polymer, 0.5 to 0.8 parts hydrophilic nanomaterials, and 43.7 to 55.4 parts organic solvent.

[0009] In some specific implementations, the amino-cationic polymer includes one or more of polyethyleneimine, polyallylamine hydrochloride, polyamide-amine dendritic macromolecules, and polylysine.

[0010] In some specific implementations, the number-average molecular weight of the polyethyleneimine is between 22,000 and 27,000; The polyallylamine hydrochloride has a number-average molecular weight of 15,000 to 20,000; The polyamide-amine dendritic macromolecule is a second-generation (G2) or third-generation (G3). The polylysine has a number-average molecular weight of 15,000 to 30,000.

[0011] And / or, the organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylacetamide and N,N-dimethylformamide.

[0012] In some specific implementations, the hydrophilic nanomaterials include one or both of carbon-based nanomaterials and inorganic hydrophilic nanomaterials.

[0013] In some specific implementations, the carbon-based hydrophilic nanomaterials include one or more of hydroxylated carbon nanotubes, carboxylated carbon nanotubes, and graphene oxide; The inorganic hydrophilic nanomaterials include one or more of the following: silica nanoparticles, titanium dioxide nanoparticles, alumina nanoparticles, zinc oxide nanoparticles, and hydroxyapatite nanorods.

[0014] In some specific implementations, the particle size of the hydrophilic nanomaterial is 10 nm to 50 nm.

[0015] In some specific implementations, the negatively charged polymer includes one or more of sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyphenylenesulfone, sulfonated polyetheretherketone, and sulfonated polyaryletherketone; And / or, the organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylacetamide and N,N-dimethylformamide; And / or, the weight-average molecular weight of the negatively charged polymer is 50,000 to 100,000.

[0016] In some specific implementations, the preparation method of the core fluid includes: Water, sodium chloride, and concentrated hydrochloric acid are mixed to obtain an acidic aqueous solution; Water and amino cationic polymer are mixed to obtain an amino cationic polymer solution; An acidic aqueous solution was added dropwise to an amino cationic polymer solution for amino protonation, followed by the addition of hydrophilic nanomaterials, stirring and ultrasonic dispersion, and then mixing with an organic solvent to obtain a core solution. The pH of the solution after mixing the acidic aqueous solution with the amino cationic polymer solution is 2.8 to 3.5.

[0017] This application also provides a hollow fiber membrane prepared according to the preparation method described above.

[0018] This application also provides a blood purifier, including the hollow fiber membrane as described above.

[0019] This application co-modifies the inner wall of hollow fiber membranes by blending amino-cationic polymers with hydrophilic nanomaterials in the core solution of spinning. This method not only targets the inner wall of the membrane, avoiding the problems of pore blockage, flux reduction, and deterioration of membrane mechanical properties caused by the mixing of the entire casting solution, but also promotes the protonation of the amino-cationic polymer by regulating the acidity of the system, which leads to electrostatic association with the hydrophilic nanomaterials and intermolecular hydrogen bonding, thus pre-forming a composite modified component. This modified component is bonded to the inner wall of the hollow fiber membrane by electrostatic interaction and is also synergistically fixed to the inner wall by hydrogen bonding. Compared with simple physical blending, the modified layer is more firmly bonded and less prone to detachment and loss. At the same time, this application can significantly reduce the amount of functional raw materials used and reduce production costs, with minimal impact on the overall film rheological properties and spinning formation. While ensuring the original structural strength and screening performance of the membrane matrix, it can significantly improve the hydrophilicity and antifouling ability of the inner wall of the membrane, with stronger targeted modification and better stability in use.

[0020] (1) In this application, the amino groups of the amino cationic polymer are electrostatically associated with the hydroxyl and carboxyl groups on the surface of the hydrophilic nanomaterial in the aqueous core liquid and in the early stage, and the nanomaterial is uniformly coated by the polymer chain, thereby inhibiting the aggregation and sedimentation of the nanomaterial at the molecular level. (2) This application relies on the electrostatic adsorption effect between the negative charge of the membrane surface of sulfonated polysulfone, sulfonated polyethersulfone and other amino cationic polymers and the cations of amino cationic polymers to drive the amino cationic polymer-nanomaterial composite system to be directionally enriched and aggregated on the inner surface of the membrane during the phase separation molding process. The modified components are concentrated on the membrane separation interface, and a small amount of addition can achieve a significant modification effect, which saves materials and has a higher modification efficiency. (3) All hydrophilic modification components in this application are added only to the core solution of spinning and do not enter the casting system. They will not change the inherent viscosity, rheological properties and phase separation behavior of the casting solution, and will not cause problems such as spinning breakage, hollow collapse, uneven inner diameter and film formation defects. There is no need to adjust the existing mature spinning equipment and production parameters, and no need to add post-modification process. It can be directly connected to the existing hollow fiber membrane production line. The process is simple and the mass production difficulty is low. (4) In this application, a composite modified component is first formed by electrostatic association and intermolecular hydrogen bonding between amino cationic polymer and hydrophilic nanomaterial. The modified component is then combined with the inner wall of the hollow fiber membrane by electrostatic interaction and synergistic fixation by hydrogen bonding to construct a multi-stable interface structure. The nanomaterial is firmly anchored, resistant to erosion, operation, and has a longer service life. (5) The integrated molding process of this application is short, the amount of reagents can be controlled, the modified layer is not easy to fall off, and there are no obvious harmful substances left, which is more in line with the green application requirements of water treatment membranes. Attached Figure Description

[0021] Figure 1This is a topographic image of the inner surface of the hollow fiber membrane provided in Embodiment 1 of this application; Figure 2 This is an interface morphology diagram of the hollow fiber membrane provided in Embodiment 1 of this application; Figure 3 This is an image showing the inner surface morphology of the hollow fiber membrane provided in Embodiment 2 of this application; Figure 4 This is an interface morphology diagram of the hollow fiber membrane provided in Embodiment 2 of this application; Figure 5 This is an image showing the inner surface morphology of the hollow fiber membrane provided in Example 3 of this application; Figure 6 This is an interface morphology diagram of the hollow fiber membrane provided in Embodiment 3 of this application; Figure 7 The inner surface morphology of the hollow fiber membrane provided in Comparative Example 1 of this application is shown in the figure. Figure 8 The image shows the interface morphology of the hollow fiber membrane provided in Comparative Example 1 of this application. Figure 9 The inner surface morphology of the hollow fiber membrane provided in Comparative Example 2 of this application is shown in the figure. Figure 10 This is an image showing the interface morphology of the hollow fiber membrane provided in Comparative Example 2 of this application. Figure 11 The inner surface morphology of the hollow fiber membrane provided in Comparative Example 3 of this application is shown in the figure. Figure 12 The image shows the interface morphology of the hollow fiber membrane provided in Comparative Example 3 of this application. Figure 13 This is a diagram showing the inner surface morphology of the hollow fiber membrane provided in Comparative Example 4 of this application. Figure 14 This is an image showing the interface morphology of the hollow fiber membrane provided in Comparative Example 4 of this application. Figure 15 This is a diagram showing the inner surface morphology of the hollow fiber membrane provided in Comparative Example 5 of this application. Figure 16 This is an image showing the interface morphology of the hollow fiber membrane provided in Comparative Example 5 of this application. Detailed Implementation

[0022] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0023] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0024] It should be understood that the order of steps or the sequence of actions is not important as long as this application remains operational. Furthermore, two or more steps or actions can be performed simultaneously.

[0025] The use of any and all instances or exemplary language such as “e.g.” or “include” in this document is intended merely to better illustrate the application and does not constitute a limitation on the scope of the application. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.

[0026] Furthermore, the numerical ranges and parameters used to define this application are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any numerical value inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.

[0027] This application provides a method for preparing a hollow fiber membrane, comprising: The casting solution and the core solution are co-extruded and, after preliminary phase inversion, primary membrane fibers are obtained. The nascent membrane fibers are subjected to a second phase transformation to obtain a hollow fiber membrane; The casting solution comprises, by weight, 15 to 20 parts of negatively charged polymer, 0.5 to 2.5 parts of water, and 77.5 to 84.5 parts of organic solvent; The core fluid comprises, by weight, 40 to 46.3 parts water, 1.6 to 3.5 parts concentrated hydrochloric acid, 1 to 2.2 parts sodium chloride, 1.5 to 3.5 parts amino cationic polymer, 0.5 to 0.8 parts hydrophilic nanomaterials, and 43.7 to 55.4 parts organic solvent.

[0028] This application is based on the dry-wet phase inversion spinning process. By introducing amino cationic polymers and hydrophilic nanomaterials into the spinning core solution of hollow fiber membranes, and relying on multiple effects such as electrostatic interaction and intermolecular hydrogen bonding, the microporous structure and surface properties of the inner surface of the hollow fiber membrane are directionally regulated. This optimizes the membrane's permeation filtration and sieving separation performance from the source, significantly improves the hydrophilicity and antifouling ability of the inner wall of the membrane, and the modified components are not easy to fall off, resulting in better long-term stability.

[0029] The core fluid, serving as the core medium for hollow fiber membrane cavity formation and inner surface modification, is no longer limited to traditional forming and pore control functions, but also includes functional modification roles. The core functional component, an amino-cationic polymer, is a highly reactive cationic polymer with two or three active amino groups (primary, secondary, and tertiary amines) evenly distributed on its molecular chain, exhibiting extremely strong chemical reactivity and charge characteristics. In the homogeneous core fluid system, the active amino groups of the amino-cationic polymer can interact with the hydroxyl and carboxyl polar functional groups enriched on the surface of hydrophilic nanomaterials through intermolecular hydrogen bonding and electrostatic association, forming a stable structure. This interaction firmly fixes the hydrophilic nanomaterials onto the amino-cationic polymer molecular chain, effectively solving the industry pain points of easy agglomeration, uneven dispersion, and easy sedimentation of nanomaterials, ensuring the overall homogeneity and stability of the core fluid system, and laying the foundation for uniform membrane modification.

[0030] During the membrane fiber phase transformation process, the system charge effect plays a key modifying role. Sulfonated polysulfone / polyethersulfone and other polymer substrates themselves carry a negative charge, while the amino-cationic polymer molecules loaded with hydrophilic nanomaterials are strongly positively charged. Based on the principle of electrostatic adsorption of positive and negative charges, the amino-cationic polymer-nanocomposite system uniformly dispersed in the core fluid will actively accumulate and adhere to the inner surface of the membrane nascent body, achieving a tight bond between the nano-modified material and the polymer substrate. This avoids the problem of the modified components only physically adhering and easily falling off and failing, and significantly improves the adhesion and durability of the modified layer.

[0031] Hydrophilic nanomaterials possess structural advantages such as large specific surface area, high porosity, and abundant surface active sites, making them core functional fillers for regulating the microporous structure of membrane inner surfaces. In actual process control, by precisely optimizing the particle size and doping content of hydrophilic nanomaterials in the core fluid system, the pure water flux and small molecule solute permeation efficiency of the membrane can be improved, ensuring mass transfer efficiency during dialysis and filtration. Simultaneously, the introduction of hydrophilic nanomaterials can also optimize the hydrophilicity of the membrane surface, reduce the membrane fouling rate, and comprehensively improve the overall performance and service life of sulfonated polymer hollow fiber dialysis membranes.

[0032] This application utilizes amino-containing cationic polymers such as polyethyleneimine (PEI) and hydrophilic nanomaterials in a core solution to directionally modify the inner wall of hollow fiber membranes. A stable hydrophilic modified membrane inner surface is constructed by electrostatic adsorption generated from the negative charge of the sulfonated membrane surface. In-situ functionalization can be achieved in a single spinning step, resulting in a simple process. The modified components of the resulting membrane adhere firmly and exhibit superior hydrophilic properties. By precisely controlling the nanomaterial dosage and the pH range of the core solution, defects such as nanomaterial aggregation, increased contact angle, decreased flux, and increased flux decay rate are avoided, thus obtaining a highly hydrophilic, high-flux, and antifouling hollow fiber membrane.

[0033] Specifically, this application first provides a core solution and a casting solution. Water, sodium chloride, and concentrated hydrochloric acid are mixed to obtain an acidic aqueous solution; water and an amino-cationic polymer are mixed to obtain an amino-cationic polymer solution; the acidic aqueous solution is added dropwise to the amino-cationic polymer solution for amino protonation, hydrophilic nanomaterials are added, and the mixture is stirred and ultrasonically dispersed, then mixed with an organic solvent to obtain the core solution. In some specific implementations, the pH of the mixture of the acidic aqueous solution and the amino-cationic polymer solution is 2.8 to 3.5; the amino protonation time is 25 min to 35 min, preferably 30 min. The concentrated HCl-NaCl-pure water system can regulate the core solution to an acidic environment, which can both promote the full protonation of the amino-cationic polymer to enhance its electrostatic association ability and improve its interfacial bonding efficiency with various nanofunctional fillers. The specific steps for preparing the core solution include: adding NaCl to pure water and stirring to dissolve; slowly adding concentrated HCl dropwise at room temperature to prepare an acidic HCl-NaCl aqueous solution; adding an amino-cationic polymer to pure water and stirring to dissolve to prepare an amino-cationic polymer solution; then slowly adding the HCl-NaCl acidic aqueous solution dropwise to the amino-cationic polymer solution to control the pH of the solution system at 2.8-3.5, and stirring to complete the amino protonation; adding hydrophilic nanomaterials in small amounts multiple times, stirring at high speed and supplementing with ultrasonic dispersion; finally, slowly adding an organic solvent under low-speed stirring at room temperature, and stirring at a constant temperature for 1-2 hours to obtain a clear solution, which is the core solution. In some specific implementations, the amino-cationic polymer includes, but is not limited to, one or more of polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polyamide-amine dendrimer (PAMAM), and polylysine (PLL). The hydrophilic nanomaterials include one or both of carbon-based nanomaterials and inorganic hydrophilic nanomaterials, preferably one or more of hydroxylated carbon nanotubes, carboxylated carbon nanotubes, graphene oxide, silica nanoparticles, titanium dioxide nanoparticles, nano-alumina, nano-zinc oxide, and hydroxyapatite nanorods. The particle size of the hydrophilic nanomaterials is 10 nm to 50 nm; the concentrated hydrochloric acid is commercially available standard concentrated hydrochloric acid; the organic solvent includes, but is not limited to, one or more of N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide, and this application does not have special requirements for the selection of organic solvents. The number average molecular weight of the polyethyleneimine is 22,000 to 27,000; the number average molecular weight of the polyallylamine hydrochloride is 15,000 to 20,000; the polyamide-amine dendritic macromolecule is second-generation (G2) or third-generation (G3); and the number average molecular weight of the polylysine is 15,000 to 30,000. If the proportion of hydrophilic nanomaterials in the core fluid is less than 0.5%, the loading is too low, and the improvement in hydrophilicity and anti-fouling is not significant; if it is higher than 0.8%, the concentration of nanoparticles is too high, which makes them prone to agglomeration, clogging the flow channels and causing defects in the fiber walls.When the proportion of amino-cationic polymer in the core solution is less than 1.5%, the system lacks sufficient amino active sites and positive charge density, making it difficult to fully interact with various functional nanomaterials and unable to stably adhere to the inner wall of the negatively charged membrane substrate through electrostatic interactions. When the proportion is higher than 3.5%, the viscosity of the core solution increases, resulting in poor fiber output during spinning, easy fiber breakage, and affecting the inner diameter formation and flowability of hollow fibers. The weight percentage ratio of amino-cationic polymer to hydrophilic nanomaterials should be 3:1 to 5:1.

[0034] A casting solution is obtained by mixing water, an organic solvent, and a negatively charged polymer. In some specific implementations, the mixing time is 8 to 12 hours, preferably 10 hours; the mixing temperature is 60°C to 90°C, preferably 80°C. The specific operation for preparing the casting solution includes adding pure water to an organic solvent and stirring at room temperature for 0.5 hours; then adding the negatively charged polymer and stirring to obtain the casting solution. The negatively charged polymer is selected from one or more of the following negatively charged polymers: sulfonated polysulfone (SPSU), sulfonated polyethersulfone (SPES), sulfonated polyphenylene sulfone (SPPSU), sulfonated polyether ether ketone (SPEEK), and sulfonated polyarylether ketone (SPAEK), with sulfonated polysulfone (SPSU) and sulfonated polyethersulfone (SPES) being preferred. The weight-average molecular weight of the negatively charged polymer is selected to be between 50,000 and 100,000. The organic solvent includes, but is not limited to, one or more of N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; this application does not have special requirements for the selection of organic solvents.

[0035] This application then co-extrudes the casting solution and core solution, undergoing a preliminary phase inversion to obtain primary membrane filaments. Specifically, the casting solution and core solution are extruded together from a spinneret, with the core solution extruded from the inside of the spinneret needle core and the casting solution extruded from the outside of the spinneret needle core, then entering an air gap, where the preliminary phase inversion to obtain primary membrane filaments is completed. In some specific implementations, the flow rate of the core solution during co-extrusion is 10 mL / min to 15 mL / min; the flow rate of the casting solution during co-extrusion is 5 mL / min to 10 mL / min. In some specific implementations, the height of the air gap is 100 mm to 400 mm; the temperature of the air gap is 50°C to 60°C.

[0036] This application then performs a second phase inversion on the nascent membrane filaments to obtain a hollow fiber membrane. In some specific implementations, the second phase inversion includes the nascent membrane filaments entering a coagulation bath and being washed with water; the coagulation bath is composed of water; the temperature of the coagulation bath is 50°C to 60°C. The nascent membrane filaments enter the coagulation bath through an air gap, the coagulation bath is composed of pure water, and then enter a water washing tank. After washing, they are dried in an oven and then wound up to obtain a hollow fiber membrane; the drying temperature is 130-150°C, and the drying time is 40-60 seconds.

[0037] Current mainstream methods for hydrophilic modification of hollow fiber membranes mainly fall into two categories: one is to directly blend hydrophilic nanomaterials and hydrophilic polymeric additives in the casting solution; the other is to perform post-modification treatments such as surface immersion, coating, and grafting after the membrane preparation is completed. Compared with the above-mentioned traditional modification methods, this application adopts a core liquid pre-composite amino-cationic polymer-nano system, combined with electrostatic adsorption to assist intermolecular hydrogen bonding to achieve integrated molding modification, which has the following outstanding advantages: (1) In this application, the amino groups of the amino cationic polymer are first used to form intermolecular hydrogen bonds and electrostatic associations with the hydroxyl and carboxyl groups on the surface of the nanomaterial in the aqueous core liquid, so that the nanomaterial is uniformly coated by the polymer chain, thereby inhibiting the aggregation and sedimentation of the nanomaterial at the molecular level. (2) This application relies on the electrostatic adsorption effect between the negative charge of the membrane surface of sulfonated polysulfone, sulfonated polyethersulfone and other amino cationic polymers and the cations of amino cationic polymers to drive the amino cationic polymer-nanomaterial composite system to be directionally enriched and aggregated on the inner surface of the membrane during the phase separation molding process. The modified components are concentrated on the membrane separation interface, and a small amount of addition can achieve a significant modification effect, which saves materials and has a higher modification efficiency. (3) All hydrophilic modification components in this application are added only to the core solution of spinning and do not enter the casting solution system. They will not change the inherent viscosity, rheological properties and phase separation behavior of the casting solution, and will not cause problems such as spinning breakage, hollow collapse, uneven inner diameter and film formation defects. There is no need to adjust the existing mature spinning equipment and production parameters, and no need to add post-modification process. It can be directly connected to the existing hollow fiber membrane production line. The process is simple and the mass production difficulty is low. (4) In this application, a composite modified component is first formed in advance by electrostatic association and intermolecular hydrogen bonding between amino cationic polymer and hydrophilic nanomaterial. The modified component is then combined with the inner wall of the hollow fiber membrane by electrostatic interaction and synergistic fixation by hydrogen bonding to construct a multi-stable interface structure. The nanomaterial is firmly anchored, resistant to erosion, operation, and has a longer service life.

[0038] (5) The integrated molding process of this application is short, the amount of reagents can be controlled, the modified layer is not easy to fall off, and there are no obvious harmful substances left, which is more in line with the green application requirements of water treatment membranes.

[0039] This application also provides a hollow fiber membrane prepared according to the above preparation method.

[0040] The hollow fiber membrane described in this application can be used in the separation, concentration and purification of biological products, pharmaceutical products and food industry, as well as in the purification and treatment of industrial wastewater and drinking water.

[0041] This application also provides a blood purifier, including the hollow fiber membrane as described above.

[0042] In some specific implementations, the blood purifier includes a hemodialyzer, a hemofilter, a hemodialysis filter, or a plasma separator.

[0043] The present application is further illustrated below with reference to embodiments. The scope of protection of the present application is not limited to the following embodiments.

[0044] Example 1

[0045] This embodiment provides a hollow fiber membrane, the preparation method of which includes: Step 1: Prepare casting solution and core solution. The casting solution includes, by mass percentage: 15% sulfonated polysulfone, 0.5% pure water, and 84.5% N-methylpyrrolidone. Preparation of casting solution: Dissolve 50g of pure water in 8450g of N-methylpyrrolidone and stir at room temperature for 0.5h. Then add 1500g of sulfonated polysulfone and stir at 60℃ for 8h. The molecular weight of the sulfonated polysulfone is 85,000.

[0046] The core fluid, by mass percentage, comprises: 46.3% pure water, 1.7% 36% concentrated hydrochloric acid, 1.0% NaCl, 1.5% PEI, 0.5% hydroxylated carbon nanotubes, and 49% N-methylpyrrolidone. Preparation of the core solution: 100g NaCl was added to 2000g of pure water and stirred to dissolve. At room temperature, 170g of concentrated HCl was slowly added dropwise to prepare an acidic HCl-NaCl aqueous solution. 150g PEI was added to 2630g of water and stirred to dissolve, preparing a PEI solution. The acidic aqueous solution was then slowly added dropwise to the PEI solution to maintain the pH of the solution at 3.3-3.5, and the mixture was stirred for 30 min to complete the amino protonation. 50g of hydroxylated carbon nanotubes were added in small, repeated additions, with high-speed stirring and ultrasonic dispersion. Finally, 4900g of N-methylpyrrolidone was slowly added under low-speed stirring at room temperature, and the mixture was stirred at a constant temperature for 1-2 h to obtain a clear solution. The PEI had a molecular weight of 22,000, and the hydroxylated carbon nanotubes had a particle size of 10 nm.

[0047] Step 2: The casting solution and core solution are extruded together from the spinneret, with the core solution being extruded from the inside of the spinneret needle core and the casting solution from the outside. The flow rate of the core solution is 10 mL / min, and the flow rate of the casting solution is 6 mL / min.

[0048] Step 3: Preliminary Phase Transformation. The casting solution and core solution enter the air gap together, where the preliminary phase transformation is completed to obtain the primary film fibers. The height of the air gap is 150 mm, and the temperature of the air gap is 50 °C.

[0049] Step 4: Second phase transformation. The nascent membrane fibers enter the coagulation bath through the air gap, then enter the water washing tank for washing, and after washing, they enter the drying oven for drying, followed by the fiber winding operation. The coagulation bath consists of pure water, the coagulation temperature is 50℃, the drying temperature is 130℃, and the drying time is 60s.

[0050] The inner surface morphology of the hollow fiber membrane provided in Example 1 is shown in the figure below. Figure 1 As shown, the interface morphology diagram of the hollow fiber membrane provided in Example 1 is as follows. Figure 2 As shown.

[0051] Example 2

[0052] This embodiment provides a hollow fiber membrane, the preparation method of which includes: Step 1: Prepare casting solution and core solution. The casting solution includes, by mass percentage: 18% sulfonated polyphenylene sulfone, 2% pure water, and 80% N,N-dimethylacetamide. Preparation of casting solution: Dissolve 200g of pure water in 8000g of N,N-dimethylacetamide and stir at room temperature for 0.5h. Then add 1800g of sulfonated polyphenylsulfone and stir at 70℃ for 8.5h. The molecular weight of sulfonated polyphenylsulfone is 50,000.

[0053] The core fluid, by mass percentage, comprises: 43.4% pure water, 2.6% concentrated hydrochloric acid (36%), 1.5% NaCl, 2.5% polyallylamine hydrochloride (PAH), 0.7% silica nanoparticles, and 49.3% N,N-dimethylacetamide. Preparation of the core solution: Add 150g NaCl to 2000g pure water and stir to dissolve; at room temperature, slowly add 260g concentrated HCl dropwise to prepare an HCl-NaCl acidic aqueous solution; add 250g PAH to 2340g water and stir to dissolve to prepare a PAH solution; then slowly add the acidic aqueous solution dropwise to the PAH solution to control the pH of the solution system at 3.0-3.2, and stir for 30min to complete the amino protonation; add 70g of silica nanoparticles in small amounts several times, stirring at high speed and supplemented with ultrasonic dispersion; finally, slowly add 4930g N,N-dimethylacetamide under low-speed stirring at room temperature, and stir at a constant temperature for 1-2h to obtain a clear solution. The PAH molecular weight is 15,000, and the silica nanoparticles have a particle size of 30nm.

[0054] Step 2: The casting solution and core solution are extruded together from the spinneret, with the core solution being extruded from the inside of the spinneret needle core and the casting solution from the outside. The flow rate of the core solution is 12 mL / min, and the flow rate of the casting solution is 8 mL / min.

[0055] Step 3: Preliminary Phase Transformation. The casting solution and core solution enter the air gap together, where the preliminary phase transformation is completed to obtain the primary film fibers. The height of the air gap is 300 mm. The temperature of the air gap is 55℃.

[0056] Step 4: Second phase transformation. The nascent membrane fibers enter the coagulation bath through the air gap, then are washed in a water washing tank, dried in an oven, and then wound up. The coagulation bath consists of pure water, the coagulation temperature is 55℃, the drying temperature is 140℃, and the drying time is 50s.

[0057] The inner surface morphology of the hollow fiber membrane provided in Example 2 is shown in the figure below. Figure 3 As shown, the interface morphology diagram of the hollow fiber membrane provided in Example 2 is as follows. Figure 4 As shown.

[0058] Example 3

[0059] This embodiment provides a hollow fiber membrane, the preparation method of which includes: Step 1: Prepare casting solution and core solution. The casting solution includes, by mass percentage: 20% sulfonated polyethersulfone, 1% pure water, and 79% N,N-dimethylformamide. Preparation of casting solution: Dissolve 100g of pure water in 7900g of N,N-dimethylformamide and stir at room temperature for 0.5h. Then add 2000g of sulfonated polyethersulfone and stir at 90℃ for 12h. The molecular weight of the sulfonated polyethersulfone is 100,000.

[0060] The core fluid, by mass percentage, comprises: 40.2% pure water, 3.5% 36% concentrated hydrochloric acid, 2.2% NaCl, 3.5% polyamide-amine dendritic macromolecules (PAMAM), 0.8% nano titanium dioxide, and 49.8% N,N-dimethylformamide. Preparation of the core solution: Add 220g NaCl to 2000g pure water and stir to dissolve; at room temperature, slowly add 350g concentrated HCl to prepare an acidic HCl-NaCl aqueous solution; add 350g polyamide-amine dendrimer (PAMAM) to 2020g water and stir to dissolve to prepare a PAMAM solution; then slowly add the acidic aqueous solution to the PAMAM solution to control the pH of the solution system at 2.8-3.0, and stir for 30min to complete the amino protonation; add 80g nano titanium dioxide in small amounts several times, stirring at high speed and supplemented with ultrasonic dispersion; finally, slowly add 4980g N,N-dimethylformamide under low-speed stirring at room temperature, and stir at constant temperature for 1-2h to obtain a clear solution. The polyamide-amine dendrimer (PAMAM) is second generation (G2), and the nano titanium dioxide particle size is 50nm.

[0061] Step 2: The casting solution and core solution are extruded together from the spinneret, with the core solution being extruded from the inside of the spinneret needle core and the casting solution from the outside. The flow rate of the core solution is 15 mL / min, and the flow rate of the casting solution is 10 mL / min.

[0062] Step 3: Preliminary Phase Transformation. The casting solution and core solution enter the air gap together, where the preliminary phase transformation is completed to obtain primary film fibers. The height of the air gap is 400 mm, and the temperature of the air gap is 60℃.

[0063] Step 4: Second phase transformation. The nascent membrane fibers enter the coagulation bath through the air gap, then are washed in a water washing tank, dried in an oven, and then wound up. The coagulation bath consists of pure water, the coagulation temperature is 60℃, the drying temperature is 150℃, and the drying time is 40s.

[0064] The inner surface morphology of the hollow fiber membrane provided in Example 3 is shown in the figure below. Figure 5 As shown, the interface morphology diagram of the hollow fiber membrane provided in Example 3 is as follows. Figure 6 As shown.

[0065] Comparative Example 1

[0066] This comparative example provides a hollow fiber membrane, the preparation method of which includes: Step 1: Prepare casting solution and core solution. The casting solution includes, by mass percentage: 15% sulfonated polysulfone, 0.5% pure water, 0.5% hydroxylated carbon nanotubes, and 84% N-methylpyrrolidone. Preparation of the casting solution: 50g of hydroxylated carbon nanotubes were added to 50g of pure water in small batches, stirred at high speed and dispersed by ultrasonication; then, 8400g of N-methylpyrrolidone was slowly added under low-speed stirring at room temperature, and stirred for 0.5h. Next, 1500g of sulfonated polysulfone was added, and the mixture was stirred at 60℃ for 8h. The sulfonated polysulfone had a molecular weight of 85,000. The hydroxylated carbon nanotubes had a particle size of 10nm.

[0067] The core fluid, by mass percentage, comprises: 46.3% pure water and 53.7% N-methylpyrrolidone; Preparation of core solution: Add 5370g of N-methylpyrrolidone to 4630g of pure water and stir at a constant temperature for 1~2h to obtain a clear solution.

[0068] Step 2: The casting solution and core solution are extruded together from the spinneret, with the core solution being extruded from the inside of the spinneret needle core and the casting solution from the outside. The flow rate of the core solution is 10 mL / min, and the flow rate of the casting solution is 6 mL / min.

[0069] Step 3: Preliminary Phase Transformation. The casting solution and core solution enter the air gap together, where the preliminary phase transformation is completed to obtain the primary film fibers. The height of the air gap is 150 mm, and the temperature of the air gap is 50 °C.

[0070] Step 4: Second phase transformation. The nascent membrane fibers enter the coagulation bath through the air gap, then enter the water washing tank for washing, and after washing, they enter the drying oven for drying, followed by the fiber winding operation. The coagulation bath consists of pure water, the coagulation temperature is 50℃, the drying temperature is 130℃, and the drying time is 60s.

[0071] The inner surface morphology of the hollow fiber membrane provided in Comparative Example 1 is shown in the figure below. Figure 7 As shown in the figure, the interface morphology of the hollow fiber membrane provided in Comparative Example 1 is as follows: Figure 8 As shown.

[0072] Comparative Example 2

[0073] This comparative example provides a hollow fiber membrane, the preparation method of which includes: Step 1: Prepare casting solution and core solution. The casting solution includes, by mass percentage: 18% sulfonated polyphenylene sulfone, 2% pure water, 0.7% silica nanoparticles, and 79.3% N,N-dimethylacetamide. Preparation of the casting solution: 70g of silica nanoparticles were added to 200g of pure water in small batches, stirred at high speed and dispersed by ultrasonication. Then, 7930g of N,N-dimethylacetamide was slowly added under low-speed stirring at room temperature, and the mixture was stirred for 0.5h. Next, 1800g of sulfonated polyphenylene sulfone was added, and the mixture was stirred at 70℃ for 8.5h. The molecular weight of the sulfonated polyphenylene sulfone was 50,000. The particle size of the silica nanoparticles was selected to be 30nm.

[0074] The core fluid, by weight percentage, comprises: 43.4% pure water and 56.6% N,N-dimethylacetamide; Preparation of core solution: Add 5660g of N,N-dimethylacetamide to 4340g of pure water and stir at a constant temperature for 1~2h to obtain a clear solution.

[0075] Step 2: The casting solution and core solution are extruded together from the spinneret, with the core solution being extruded from the inside of the spinneret needle core and the casting solution from the outside. The flow rate of the core solution is 12 mL / min, and the flow rate of the casting solution is 8 mL / min.

[0076] Step 3: Preliminary Phase Transformation. The casting solution and core solution enter the air gap together, where the preliminary phase transformation is completed to obtain the primary film fibers. The height of the air gap is 300 mm. The temperature of the air gap is 55℃.

[0077] Step 4: Second phase transformation. The nascent membrane fibers enter the coagulation bath through the air gap, then enter the water washing tank for washing, and after washing, they enter the drying oven for drying, followed by the fiber winding operation. The coagulation bath consists of pure water, the coagulation temperature is 55℃, the drying temperature is 140℃, and the drying time is 50s.

[0078] The inner surface morphology of the hollow fiber membrane provided in Comparative Example 2 is shown in the figure below. Figure 9 As shown in the figure, the interface morphology diagram of the hollow fiber membrane provided in Comparative Example 2 is as follows. Figure 10 As shown.

[0079] Comparative Example 3

[0080] This comparative example provides a hollow fiber membrane, the preparation method of which includes: Step 1: Prepare casting solution and core solution. The casting solution includes, by mass percentage: 20% sulfonated polyethersulfone, 1% pure water, 0.8% nano titanium dioxide, and 78.2% N,N-dimethylformamide. Preparation of the casting solution: 80g of nano-titanium dioxide was added to 100g of pure water in small batches, stirred at high speed and dispersed by ultrasonication. 7820g of N,N-dimethylformamide was slowly added under low-speed stirring at room temperature, and the mixture was stirred for 0.5h. Then, 2000g of sulfonated polyethersulfone was added, and the mixture was stirred at 90℃ for 12h. The sulfonated polyethersulfone had a molecular weight of 100,000. The nano-titanium dioxide was selected with a particle size of 50nm.

[0081] The core fluid, by weight percentage, comprises: 40.2% pure water and 59.8% N,N-dimethylformamide; Preparation of core solution: Add 5980g of N,N-dimethylformamide to 4020g of pure water and stir at a constant temperature for 1~2h to obtain a clear solution.

[0082] Step 2: The casting solution and core solution are extruded together from the spinneret, with the core solution being extruded from the inside of the spinneret needle core and the casting solution from the outside. The flow rate of the core solution is 15 mL / min, and the flow rate of the casting solution is 10 mL / min.

[0083] Step 3: Preliminary Phase Transformation. The casting solution and core solution enter the air gap together, where the preliminary phase transformation is completed to obtain primary film fibers. The height of the air gap is 400 mm, and the temperature of the air gap is 60℃.

[0084] Step 4: Second phase transformation. The nascent membrane fibers enter the coagulation bath through the air gap, then enter the water washing tank for washing, and after washing, they enter the drying oven for drying, followed by the fiber winding operation. The coagulation bath consists of pure water, the coagulation temperature is 60℃, the drying temperature is 150℃, and the drying time is 40s.

[0085] The inner surface morphology of the hollow fiber membrane provided in Comparative Example 3 is shown in the figure below. Figure 11 As shown in the figure, the interface morphology of the hollow fiber membrane provided in Comparative Example 3 is as follows. Figure 12 As shown.

[0086] Comparative Example 4

[0087] This comparative example provides a hollow fiber membrane. The difference between the preparation method of the hollow fiber membrane and that of Example 3 is that the proportion of nano-titanium dioxide in the core liquid is 0.2%, and the proportion of N,N-dimethylformamide is 50.4%.

[0088] The inner surface morphology of the hollow fiber membrane provided in Comparative Example 4 is shown in the figure below. Figure 13 As shown in the figure, the interface morphology of the hollow fiber membrane provided in Comparative Example 4 is as follows. Figure 14 As shown.

[0089] Comparative Example 5

[0090] This comparative example provides a hollow fiber membrane. The difference between the preparation method of the hollow fiber membrane and that of Example 3 is that the proportion of nano-titanium dioxide in the core liquid is 2.0%, and the proportion of N,N-dimethylformamide is 48.6%.

[0091] The inner surface morphology of the hollow fiber membrane provided in Comparative Example 5 is shown in the figure below. Figure 15 As shown in the figure, the interface morphology of the hollow fiber membrane provided in Comparative Example 5 is as follows. Figure 16 As shown.

[0092] The surface hydrophilicity, solute sieving ability, antifouling and mechanical properties of the hollow fiber membranes prepared in Examples 1-3 and Comparative Examples 1-5 were tested respectively. The characterization indicators included surface contact angle, small molecule toxin removal rate, flux attenuation rate, elongation at break and maximum load.

[0093] Performance testing: 1. Membrane inner surface and interface morphology: The Nova NanoSEM 450 FEI field emission scanning electron microscope was used.

[0094] 2. Hydrophilicity (contact angle): The static water contact angle was measured using a German dataphysics OCA25 video optical contact angle meter. The smaller the contact angle, the better the hydrophilicity.

[0095] 3. Mechanical properties: The mechanical properties (maximum load and elongation at break) of hollow fiber membranes were determined using a Shimadzu EZ-LX universal tensile testing machine. Maximum load refers to the maximum tensile force a single hollow fiber membrane can withstand before breaking, commonly measured in Newtons (N), and is a core indicator of mechanical performance. Elongation at break refers to the percentage elongation of a single hollow fiber membrane relative to its original gauge length when stretched to break, characterizing its toughness and resistance to deformation. Higher maximum load and elongation at break indicate better mechanical properties of the hollow fiber membrane.

[0096] Elongation at break (E) b The formula for calculating (%) is as follows: ; Where: L0: initial gauge length; L: total length at break; 4. Solute sieving performance (small molecule removal rate): To evaluate the solute sieving performance (small molecule clearance rate) of hollow fiber membranes, urea and creatinine were used as small molecule solutes for testing. The experimental temperature was set at 37±0.5℃, and the system pH was controlled at 7.2~7.4. Simulated solutions were prepared with 10 mmol / L urea and 0.2 mmol / L creatinine. A double-sided countercurrent circulation method was used for testing. The flow rate of the simulated solution inside the hollow fiber membrane was 150 mL / min, while the flow rate of dialysis fluid or physiological saline outside the membrane was 300 mL / min. The transmembrane pressure difference was maintained at 35 mmHg. After the membrane module was fully wetted with pure water, it was connected to the pipeline. After the system ran stably for 20 min, liquid samples were collected from the inlet and outlet of the membrane module. The solute concentration was measured using a UV spectrophotometer, and the clearance rate was calculated. A higher clearance rate indicates a higher solute sieving efficiency.

[0097] Small molecule clearance rate (CL, mL / min) is the core evaluation indicator, and the calculation formula is as follows: ; In the formula: C in The solute concentration at the inlet of the membrane module is expressed in mL / min. C out The solute concentration at the membrane module outlet is expressed in mL / min. Q b The simulated fluid flow rate inside the membrane is expressed in mL / min.

[0098] Antifouling performance (flux attenuation rate): To evaluate the flux attenuation rate of hollow fiber membranes, the test procedures are as follows: Using the assembled hollow fiber membrane module, under constant operating pressure of 0.1 MPa and 25°C, the module was first pre-pressurized with pure water until the flux stabilized using internal pressure and cross-flow filtration. The initial pure water flux J0 was measured. Subsequently, the solution was replaced with 1 g / L BSA simulated pollutant, and continuous filtration was performed at constant temperature and pressure for 120 min. The flux J at this point was measured. t Calculate the membrane flux decay rate using the following formula. The smaller the flux decay rate, the stronger the membrane's antifouling performance.

[0099] ; In the formula: J0 - Initial stable pure water flux, LMH / bar; J t - The flux during 120 minutes of operation, LMH / bar; the test results are shown in Table 1.

[0100] Table 1

[0101] In conjunction with Examples 1-3 Figure 1-6 The test results show that, in this application, the composite component of amino-cationic polymer and hydrophilic nanomaterials is added to the spinning core solution. Through intermolecular hydrogen bonding and electrostatic association, the composite component pre-forms a modified composite component. This modified component is then directionally enriched on the inner surface of the hollow fiber membrane through electrostatic adsorption and intermolecular hydrogen bonding. As the amount of hydrophilic nanomaterials added to the core solution gradually increases within the limits specified in this application, the loading of the modified component on the inner surface of the membrane increases uniformly. The overall cross-sectional structure of the membrane remains intact, without abnormal morphologies such as filament deformation or microporous defects, and the membrane matrix structure exhibits excellent stability. When the proportion of nanomaterials in the core solution is too low (Comparative Example 4), Figure 13 , 14 The amount of nanomaterials fixed on the inner surface of the membrane decreases as the concentration of nanomaterials in the core fluid increases (Comparative Example 5). Figure 15 , 16 Nanoparticles aggregate and adhere to the inner surface of the membrane, thereby blocking the membrane pore channels and destroying the inherent sieving pore structure of the membrane.

[0102] Scanning electron microscopy Figure 1-16As can be seen, the membrane micropore structures of Examples 1-3 and Comparative Example 4 are complete and regular. Because all the modified components of this application are added to the core liquid system, they do not interfere with the inherent viscosity, rheological properties, or phase separation behavior of the casting liquid. The spinning process is stable, without defects such as broken fibers, hollow collapse, or uneven membrane diameter. The membrane micromorphology of Comparative Example 5 has slight defects because excessive hydrophilic nanomaterials cause local agglomeration, slightly affecting the core liquid flow and membrane pore formation. Comparative Examples 1-3 have significant defects in their microstructure. After the hydrophilic nanomaterials are directly incorporated into the casting liquid, they form agglomerates. Due to the high surface energy of the hydrophilic nanomaterials, agglomeration and uneven dispersion occur within the casting system. The agglomerated particles are distributed throughout the membrane matrix, resulting in numerous micropore defects on the inner surface of the membrane. Simultaneously, the nanoagglomerates disrupt the rheological properties and phase separation behavior of the casting liquid, leading to structural defects such as flattened fibers and filament distortion in the membrane cross-section. This severely damages the structural integrity of the hollow fiber membrane matrix, significantly reducing the yield of the formed membrane.

[0103] In Examples 1-3, under the control of an acidic core fluid environment (pH 2.8-3.5), the mass ratio of amino-cationic polymer to hydrophilic nanomaterials increased, and the contact angle of the membrane inner surface gradually decreased from 54.6°±0.8° to 44.2°±0.9°, indicating a continuous improvement in the membrane's hydrophilicity. This is because the acidic system promotes the full protonation of the amino-cationic polymer, increasing the positive charge density of the system and increasing the directional loading of the amino-cationic polymer-hydrophilic nanocomposite system on the membrane inner surface, thus increasing the loading of hydrophilic functional groups.

[0104] In Comparative Example 4, the proportion of hydrophilic nanomaterials was too low, resulting in insufficient effective hydrophilic functional fillers. The membrane contact angle increased to 67.8°±1.0°, and the hydrophilic performance significantly decreased. In Comparative Example 5, the proportion of hydrophilic nanomaterials was too high, leading to nanoparticle aggregation and covering of hydrophilic functional groups. The membrane contact angle increased to 65.2°±0.8°, and the hydrophilic performance significantly decreased. Comparative Examples 1-3 used a traditional casting solution blending process, resulting in nanomaterial aggregation and disordered distribution. The effective hydrophilic component content on the inner surface of the membrane was low, and the contact angles were all greater than 65°, indicating hydrophilic performance far inferior to the scheme in this application.

[0105] The hollow fiber membranes prepared in Examples 1-3 exhibited stable maximum loads of 1.62 N-1.70 N and elongation at break of 52.60%-54.36%, demonstrating excellent mechanical properties with minimal parameter fluctuations. Because the modified components acted only directionally on the inner surface of the membrane, the sulfonated polysulfone membrane matrix framework was not disrupted. Furthermore, the composite modified layer formed by intermolecular hydrogen bonding combined with electrostatic adsorption further maintained the membrane structural stability. In contrast, Comparative Examples 1-3, which used direct blending of nanomaterials in a casting solution, resulted in nanoagglomerates causing numerous microscopic defects within the membrane, leading to filament deformation. The maximum load decreased to 0.54 N-0.84 N, and the elongation at break was only 23.27%-30.49%, resulting in a significant deterioration in mechanical properties. Comparative Example 4, due to its low content of hydrophilic nanomaterials, did not produce agglomeration defects, and its mechanical properties were basically the same as those of the embodiments in this application. In Comparative Example 5, the excessive agglomeration of nanomaterials damaged the inner wall structure of the membrane, the maximum load dropped to 1.01N, the elongation at break dropped to 40.72%, and the mechanical properties decreased significantly.

[0106] In Examples 1-3, with the optimization of the ratio of amino-cationic polymer to hydrophilic nanomaterials, the urea removal rate increased from 198.45 mL / min to 245.85 mL / min, and the creatinine removal rate increased from 195.05 mL / min to 242.55 mL / min, indicating a gradual improvement in membrane sieving and mass transfer performance. The hydrophilic nanomaterials were uniformly loaded on the inner surface of the membrane, optimizing the membrane's microstructure and improving material transfer efficiency without pore blockage. In Comparative Examples 1-3, the nanomaterials aggregated inside the membrane matrix and blocked the mass transfer channels, hindering material flow. The urea and creatinine removal rates were only 163.64 mL / min-173.84 mL / min, resulting in severely insufficient sieving performance. In Comparative Examples 4 and 5, due to the functional component ratio deviating from the preferred range of this application, insufficient modification and membrane pore blockage occurred, respectively, causing the urea and creatinine removal rates to fall back to the 180 mL / min-185 mL / min range, significantly reducing sieving and separation performance.

[0107] In Examples 1-3, the flux decay rate gradually decreased from 35% to 22%, indicating a continuous improvement in membrane fouling resistance. The improved hydrophilicity of the membrane inner surface effectively inhibited the non-specific adsorption of pollutants such as proteins and organic colloids. Simultaneously, the modified components were firmly anchored through a combination of intermolecular hydrogen bonding and electrostatic adsorption, making the modified layer less prone to detachment and further ensuring the membrane's long-term antifouling effect. In Comparative Examples 1-3, the membranes exhibited poor hydrophilicity and numerous pore defects, leading to easy adsorption and accumulation of pollutants on the membrane surface and within the pores, resulting in flux decay rates as high as 59%-63% and extremely poor fouling resistance. In Comparative Examples 4 and 5, the unbalanced component ratios caused a decrease in membrane hydrophilicity and localized pore blockage, increasing the flux decay rate to 50%-53%, highlighting the significant flux decay problem during long-term membrane operation.

[0108] In summary, compared to existing technologies that directly blend hydrophilic nanomaterials in the casting solution for modification, this application employs an in-situ modification method that introduces an amino-cationic polymer-hydrophilic nanocomposite system into the spinning core solution. This fundamentally solves the technical defects of nanomaterials, such as easy agglomeration, structural defects in the membrane, poor film-forming properties, and decreased mechanical properties. Furthermore, it requires no modification to existing spinning equipment and process parameters, making it suitable for large-scale industrial production. The hollow fiber membrane prepared in this application possesses high strength, high hydrophilicity, high sieving efficiency, and strong resistance to fouling. The modified layer is firmly bonded with no component leaching, making it widely applicable in water treatment, biomedicine, food separation, and other fields, demonstrating significant industrialization value. The blood purifier prepared in this application exhibits high sieving efficiency.

[0109] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and application concept of this application, should be included within the scope of protection of this application.

Claims

1. A method for preparing a hollow fiber membrane, characterized in that, include: The casting solution and the core solution are co-extruded and, after preliminary phase inversion, primary membrane fibers are obtained. The nascent membrane fibers are subjected to a second phase transformation to obtain a hollow fiber membrane; The casting solution comprises, by weight, 15 to 20 parts of negatively charged polymer, 0.5 to 2.5 parts of water, and 77.5 to 84.5 parts of organic solvent; The core fluid comprises, by weight, 40 to 46.3 parts water, 1.6 to 3.5 parts concentrated hydrochloric acid, 1 to 2.2 parts sodium chloride, 1.5 to 3.5 parts amino cationic polymer, 0.5 to 0.8 parts hydrophilic nanomaterials, and 43.7 to 55.4 parts organic solvent.

2. The preparation method according to claim 1, characterized in that, The amino-cationic polymer includes one or more of polyethyleneimine, polyallylamine hydrochloride, polyamide-amine dendritic macromolecules, and polylysine.

3. The preparation method according to claim 2, characterized in that, The number-average molecular weight of the polyethyleneimine is between 22,000 and 27,000; The polyallylamine hydrochloride has a number-average molecular weight of 15,000 to 20,000; The polyamide-amine dendritic macromolecule is a second-generation (G2) or third-generation (G3). The polylysine has a number-average molecular weight of 15,000 to 30,000.

4. The preparation method according to claim 1, characterized in that, The hydrophilic nanomaterials include one or both of carbon-based nanomaterials and inorganic hydrophilic nanomaterials; The organic solvent in the core fluid includes one or more of N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide.

5. The preparation method according to claim 4, characterized in that, The carbon-based hydrophilic nanomaterials include one or more of hydroxylated carbon nanotubes, carboxylated carbon nanotubes, and graphene oxide. The inorganic hydrophilic nanomaterials include one or more of the following: silica nanoparticles, titanium dioxide nanoparticles, alumina nanoparticles, zinc oxide nanoparticles, and hydroxyapatite nanorods.

6. The preparation method according to claim 1, characterized in that, The hydrophilic nanomaterial has a particle size of 10 nm to 50 nm.

7. The preparation method according to claim 1, characterized in that, The negatively charged polymer includes one or more of sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyphenylsulfone, sulfonated polyetheretherketone, and sulfonated polyaryletherketone; And / or, the organic solvent in the casting solution includes one or more of N-methylpyrrolidone, N,N-dimethylacetamide and N,N-dimethylformamide; And / or, the weight-average molecular weight of the negatively charged polymer is 50,000 to 100,000.

8. The preparation method according to claim 1, characterized in that, The method for preparing the core fluid includes: Water, sodium chloride, and concentrated hydrochloric acid are mixed to obtain an acidic aqueous solution; Water and amino cationic polymer are mixed to obtain an amino cationic polymer solution; An acidic aqueous solution was added dropwise to an amino cationic polymer solution for amino protonation, followed by the addition of hydrophilic nanomaterials, stirring and ultrasonic dispersion, and then mixing with an organic solvent to obtain a core solution. The pH of the solution after mixing the acidic aqueous solution with the amino cationic polymer solution is 2.8 to 3.

5.

9. A hollow fiber membrane, characterized in that, Prepared according to the preparation method described in any one of claims 1 to 8.

10. A blood purifier, characterized in that, Includes the hollow fiber membrane as described in claim 9.

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