Temperature-sensitive dynamic pore-adjustable hollow fiber membrane and preparation method thereof

Abstract

The invention relates to the technical field of hollow fiber membranes, in particular to a preparation method of a temperature-sensitive dynamic pore-adjustable hollow fiber membrane, which comprises the following steps: S1, carrying out plasma treatment or alkali liquor soaking treatment on a substrate polymer; s2, dissolving the base material polymer, the temperature-sensitive copolymer, the pore-foaming agent and the ultraviolet cross-linking agent treated in the step S1 in a solvent to form a homogeneous spinning solution; s3, extruding the spinning solution into a coagulating bath through an annular spinning nozzle for curing, and synchronously performing ultraviolet radiation crosslinking to form a three-dimensional interpenetrating network structure; s4, removing the pore-foaming agent through water washing to form a gap, and drying to obtain the hollow fiber membrane. According to the invention, through bulk dispersion and temperature response of the temperature-sensitive polymer poly (N-isopropylacrylamide-co-polyethylene glycol diacrylate), continuous and reversible regulation and control of the pore size of the hollow fiber membrane are realized. Due to the dynamic pore adjusting capability, the single membrane can meet the separation requirements of substances with different molecular weights, and a membrane assembly does not need to be frequently replaced.

Description

Technical Field

[0001] The present invention relates to the technical field of hollow fiber membranes, and in particular to a temperature-sensitive hollow fiber membrane with adjustable dynamic pores and a preparation method thereof. Background Art

[0002] Hollow fiber membranes have been widely used in sewage treatment, biopharmaceutical separation, chemical catalysis and other fields due to their high specific surface area, high-efficiency separation performance and modular design advantages. Traditional hollow fiber membranes rely on porogens to form a static pore structure, and their pore size is fixed after preparation. This fixed pore characteristic makes it impossible for a single membrane component to adapt to dynamically changing separation needs. For example, when treating sewage with complex components, membrane components with different pore sizes need to be frequently replaced to meet the retention requirements of pollutants with different molecular weights, which significantly increases equipment costs and operational complexity. In addition, in the face of seasonal water quality fluctuations or sudden pollutant events, traditional membranes lack intelligent response capabilities and are difficult to achieve efficient and adaptive on-demand separation, which seriously limits the expansion of their application scenarios.

[0003] In recent years, the introduction of thermosensitive materials has provided new insights into the dynamic pore control of fiber membranes. Existing thermosensitive membrane technologies primarily include surface-grafted thermosensitive polymer membranes, thermosensitive microsphere composite membranes, and multilayer thermosensitive composite membranes. However, these technologies still have significant drawbacks: surface-grafted membranes achieve limited pore control through changes in the hydrophilicity and hydrophobicity of the surface layer, resulting in slow response rates and insufficient mechanical strength, making them susceptible to structural fatigue with long-term use; thermosensitive microsphere composite membranes indirectly control pores by embedding hydrogel microspheres, but uneven microsphere distribution can lead to a fragile membrane structure, poor interfacial bonding between the microspheres and the substrate, and low cyclic stability; and multilayer composite membranes achieve phased response by stacking thermosensitive layers with different lower critical solution temperatures (LCSTs). However, this process is complex and costly, and the multilayer interface is prone to mass transfer resistance and contamination accumulation. Summary of the Invention

[0004] In order to solve the problems in the background technology, the present invention proposes a preparation method and a hollow fiber membrane with temperature-sensitive dynamic pore adjustment, which realizes continuous and reversible regulation of the pore size of the hollow fiber membrane through the bulk dispersion and temperature response of the thermosensitive polymer poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate).

[0005] The technical solution adopted by the present invention to solve its technical problems is: to provide a method for preparing a temperature-sensitive hollow fiber membrane with adjustable dynamic pores, comprising the following steps: S1, performing surface activation treatment on a substrate polymer; S2, dissolving the substrate polymer treated with S1, a temperature-sensitive copolymer, a porogen and an ultraviolet crosslinking agent in a solvent to form a homogeneous spinning solution; S3, extruding the spinning solution through an annular spinneret into a coagulation bath for solidification, and simultaneously performing ultraviolet radiation crosslinking to form a three-dimensional interpenetrating network structure; S4, removing the porogen by water washing to form voids, and drying to obtain a hollow fiber membrane.

[0006] Furthermore, S1 surface activation treatment includes plasma treatment or alkali solution soaking treatment;

[0007] Furthermore, the plasma treatment generates at least one active group of hydroxyl and carboxyl on the surface of the substrate through plasma bombardment in an atmosphere of an inert gas or an oxygen-containing gas.

[0008] Furthermore, the alkali solution soaking conditions are: NaOH solution concentration 1-3wt%, soaking temperature 25-40°C, and soaking time 30-60min.

[0009] Furthermore, the spinning solution composition in S2 includes, by mass percentage, 15-20 wt % of substrate polymer, 10-30 wt % of thermosensitive copolymer, 10-15 wt % of porogen, 1-3 wt % of ultraviolet crosslinking agent, and the balance being solvent.

[0010] Furthermore, the substrate polymer includes polyethersulfone, polysulfone, polyvinylidene fluoride or polytetrafluoroethylene; the temperature-sensitive copolymer is poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate) with a molecular weight of 10,000-20,000 Da; the porogen includes polyethylene glycol 6000 or polyvinyl pyrrolidone; the UV crosslinker includes benzophenone or ammonium persulfate; and the solvent is N,N-dimethylacetamide.

[0011] Furthermore, the coagulation bath in S3 is a mixture of water and ethanol in a volume ratio of (7-9): (1-3), and the temperature is controlled at 5-10°C; the ultraviolet irradiation conditions are a wavelength of 365nm, an intensity of 50-100mW / cm², and an irradiation time of 5-10min.

[0012] Furthermore, the conditions for removing the porogen in S4 are washing with water at 50-60° C. for 6-12 hours; and drying at 25-35° C. for 24-48 hours.

[0013] A hollow fiber membrane prepared by the above preparation method has a lower critical transition temperature of 30-40°C, a surface porosity decreases by 30-50% when the temperature is higher than the lower critical transition temperature, and a water flux attenuation rate of ≤40%.

[0014] The invention discloses an application of a hollow fiber membrane prepared by using a method for preparing a temperature-sensitive dynamic pore-adjustable hollow fiber membrane in sewage treatment.

[0015] A hollow fiber membrane prepared by a method for preparing a temperature-sensitive, dynamically pore-adjustable hollow fiber membrane is used in the removal of cell debris in the biopharmaceutical field.

[0016] The invention discloses an application of a hollow fiber membrane prepared by a method for preparing a temperature-sensitive dynamically pore-adjustable hollow fiber membrane in protein separation and purification.

[0017] The beneficial effects of the present invention are:

[0018] (1) The present invention achieves continuous and reversible regulation of the pore size of hollow fiber membranes through the bulk dispersion and temperature response of the thermosensitive polymer poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate). When the temperature is below the lower critical transition temperature (LCST), the membrane material expands due to hydrophilicity, and the pores expand. When the temperature is above the LCST, the membrane material contracts due to hydrophobicity, and the pores shrink. This dynamic pore regulation capability enables a single membrane to adapt to the separation requirements of substances with different molecular weights, eliminating the need for frequent replacement of membrane components.

[0019] (2) The present invention uses a UV-synchronized cross-linking process to construct a three-dimensional interpenetrating network structure within the membrane, significantly improving the membrane's mechanical strength and cyclic stability. Experimental data show that after 50 cycles, the flux retention rate of the thermosensitive membrane still reached 88%, while the flux retention rate of the traditional membrane was only 45%. The membrane's dynamic pore regulation ability reduces the risk of contaminant clogging, extends the service life of the membrane assembly, and reduces replacement frequency and waste generation.

[0020] (3) The present invention enhances the surface activity of the substrate by plasma treatment or alkali solution immersion, and combines ultraviolet radiation cross-linking and porogen removal processes. The preparation process is simple and controllable, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an SEM image of the membrane surface of the polyethersulfone-based hollow fiber membrane prepared in Example 1 of the present invention at 20°C;

[0022] Figure 2 This is an SEM image of the membrane surface of the polyethersulfone-based hollow fiber membrane prepared in Example 1 of the present invention at 50°C. DETAILED DESCRIPTION

[0023] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the invention. It should be understood that the specific embodiments described herein are only used to illustrate the present invention and are not intended to limit the present invention. It should also be noted that for ease of description, the drawings only show parts relevant to the present invention, not all structures.

[0024] Example 1: Preparation of polyethersulfone-based hollow fiber membrane (plasma treatment).

[0025] S1: substrate polymer pretreatment;

[0026] Plasma treatment: The polyethersulfone substrate was placed in a plasma treatment device, oxygen was introduced, the power was set to 150 W, and the treatment time was 3 minutes to introduce hydroxyl active groups on the surface of the substrate to enhance the adhesion of subsequent temperature-sensitive materials.

[0027] S2: Prepare a homogeneous spinning solution according to the following mass percentages:

[0028] Base polymer: polyethersulfone, 18 wt%;

[0029] Thermosensitive copolymer: poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate), molecular weight 15000 Da, 25 wt%;

[0030] Porogen: polyethylene glycol 6000, 12wt%;

[0031] UV crosslinker: benzophenone, 2wt%;

[0032] Solvent: N,N-dimethylacetamide, 43 wt%.

[0033] The above components were added into a stirring kettle and stirred at a constant temperature of 60°C for 6 hours until they were completely dissolved to form a transparent homogeneous solution.

[0034] S3: The spinning solution is extruded through an annular spinneret into a coagulation bath for curing. Simultaneously, UV crosslinking is performed to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol in a volume ratio of 8:2, and the temperature is controlled at 8°C. UV irradiation parameters: A UV lamp with a wavelength of 365nm, an irradiation intensity of 80mW / cm², and an irradiation time of 8 minutes is used to trigger the gradient crosslinking of the thermosensitive copolymer and the substrate, forming a three-dimensional interpenetrating network structure.

[0035] S4: Soak the cured hollow fiber membrane in deionized water at 55°C for 10 hours to fully wash out the porogen and form a uniform microporous structure. Dry the membrane in an oven at 30°C for 36 hours to obtain a finished hollow fiber membrane.

[0036] like Figure 1 and Figure 21 and 2 are SEM images of the hollow fiber membrane of Example 1 at 20° C. and 50° C. As can be seen from the figure, at 20° C., the pores of the hollow fiber membrane become larger; at 50° C., the pores of the hollow fiber membrane shrink.

[0037] Example 2: Preparation of polyethersulfone-based hollow fiber membrane (alkaline solution immersion treatment).

[0038] Step 1: Substrate Polymer Pretreatment

[0039] Alkali solution immersion: Immerse the polyethersulfone substrate in 1wt% NaOH solution at 25℃ for 60 minutes, rinse and dry.

[0040] Step 2: Prepare a homogeneous spinning solution according to the following mass percentages:

[0041] Base polymer: polyethersulfone, 17 wt%;

[0042] Thermosensitive copolymer: poly (N-isopropylacrylamide-co-polyethylene glycol diacrylate), molecular weight 10000 Da, 30 wt%;

[0043] Porogen: polyethylene glycol 6000, 11 wt%;

[0044] UV crosslinker: benzophenone, 1wt%;

[0045] Solvent: N,N-dimethylacetamide, 41 wt%.

[0046] The above components were added into a stirring kettle and stirred at a constant temperature of 50°C for 9 hours until they were completely dissolved to form a transparent homogeneous solution.

[0047] S3: The spinning solution is extruded through an annular spinneret into a coagulation bath for curing. Simultaneously, UV crosslinking is performed to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol in a volume ratio of 8:2, and the temperature is controlled at 6°C. UV irradiation parameters: A UV lamp with a wavelength of 365nm, an irradiation intensity of 60mW / cm², and an irradiation time of 9 minutes is used to trigger the gradient crosslinking of the thermosensitive copolymer and the substrate, forming a three-dimensional interpenetrating network structure.

[0048] S4: Soak the cured hollow fiber membrane in deionized water at 52°C for 7 hours to fully wash out the porogen and form a uniform microporous structure. Dry the membrane in an oven at 28°C for 42 hours to obtain a finished hollow fiber membrane.

[0049] Example 3: Preparation of polysulfone-based hollow fiber membrane (water:ethanol=8:2).

[0050] S1: substrate polymer pretreatment;

[0051] Alkali solution soaking: Immerse the polysulfone substrate in 1.5wt% NaOH solution at 30℃ for 50 minutes, rinse and dry.

[0052] S2: Prepare the spinning solution according to the following mass percentages:

[0053] Base polymer: polysulfone, 16 wt%;

[0054] Thermosensitive copolymer: poly (N-isopropylacrylamide-co-polyethylene glycol diacrylate), molecular weight 18000 Da, 28 wt%;

[0055] Porogen: polyvinyl pyrrolidone, 13 wt%;

[0056] UV crosslinker: ammonium persulfate, 1.5wt%;

[0057] Solvent: N,N-dimethylacetamide, 41.5 wt%.

[0058] The above components were added into a stirring kettle and stirred at a constant temperature of 55°C for 7 hours until they were completely dissolved to form a transparent homogeneous solution.

[0059] S3: The spinning solution is extruded through an annular spinneret into a coagulation bath for curing. Simultaneously, UV crosslinking is performed to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol in a volume ratio of 8:2, and the temperature is controlled at 10°C. UV irradiation parameters: A UV lamp with a wavelength of 365nm, an irradiation intensity of 70mW / cm², and an irradiation time of 10 minutes is used to trigger the gradient crosslinking of the thermosensitive copolymer and the substrate, forming a three-dimensional interpenetrating network structure.

[0060] S4: Soak the cured hollow fiber membrane in deionized water at 60°C for 8 hours to fully wash out the porogen and form a uniform microporous structure. Dry the membrane in an oven at 28°C for 40 hours to obtain a finished hollow fiber membrane.

[0061] Example 4: Preparation of polysulfone-based hollow fiber membrane (water:ethanol = 7:3) S1: Pretreatment of substrate polymer;

[0062] Alkali solution soaking: Immerse the polysulfone substrate in 1.5wt% NaOH solution at 30℃ for 50 minutes, rinse and dry.

[0063] S2: Prepare the spinning solution according to the following mass percentages:

[0064] Base polymer: polysulfone, 16 wt%;

[0065] Thermosensitive copolymer: poly (N-isopropylacrylamide-co-polyethylene glycol diacrylate), molecular weight 18000 Da, 28 wt%;

[0066] Porogen: polyvinyl pyrrolidone, 13 wt%;

[0067] UV crosslinker: ammonium persulfate, 1.5wt%;

[0068] Solvent: N,N-dimethylacetamide, 41.5 wt%.

[0069] The above components were added into a stirring kettle and stirred at a constant temperature of 55°C for 7 hours until they were completely dissolved to form a transparent homogeneous solution.

[0070] S3: The spinning solution is extruded through an annular spinneret into a coagulation bath for curing. Simultaneously, UV crosslinking is performed to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol in a volume ratio of 7:3, and the temperature is controlled at 10°C. UV irradiation parameters: A UV lamp with a wavelength of 365nm, an irradiation intensity of 70mW / cm², and an irradiation time of 10 minutes is used to trigger the gradient crosslinking of the thermosensitive copolymer and the substrate, forming a three-dimensional interpenetrating network structure.

[0071] S4: Soak the cured hollow fiber membrane in deionized water at 60°C for 8 hours to fully wash out the porogen and form a uniform microporous structure. Dry the membrane in an oven at 28°C for 40 hours to obtain a finished hollow fiber membrane.

[0072] At low temperature (20°C), the average pore size is 82 nm and the lysozyme retention rate is 83%;

[0073] At high temperature (50°C), the average pore size is 43 nm and the BSA retention rate is 91%;

[0074] The ethanol proportion was increased to 30%, which enhanced the solidification rate, made the membrane surface denser, and achieved a circulation flux retention rate of 89%.

[0075] Example 5: Preparation of polyvinylidene fluoride-based hollow fiber membrane (water:ethanol=8:2).

[0076] S1: substrate polymer pretreatment;

[0077] Alkali solution soaking: Immerse the polyvinylidene fluoride substrate in 3wt% NaOH solution, treat at 40℃ for 30 minutes, and rinse until neutral.

[0078] S2: Prepare the spinning solution according to the following mass percentages;

[0079] Base polymer: polyvinylidene fluoride, 20wt%;

[0080] Thermosensitive copolymer: poly (N-isopropylacrylamide-co-polyethylene glycol diacrylate), molecular weight 12000 Da, 20 wt%;

[0081] Porogen: polyvinyl pyrrolidone, 10 wt%;

[0082] UV crosslinker: benzophenone, 3wt%;

[0083] Solvent: N,N-dimethylacetamide, 47 wt%.

[0084] The above components were added into a stirring kettle and stirred at a constant temperature of 65°C for 5 hours until they were completely dissolved to form a transparent homogeneous solution.

[0085] S3: The spinning solution is extruded through an annular spinneret into a coagulation bath for curing. Simultaneously, UV crosslinking is performed to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol in a volume ratio of 8:2, and the temperature is controlled at 5°C. UV irradiation parameters: A UV lamp with a wavelength of 365nm, an irradiation intensity of 100mW / cm², and an irradiation time of 6 minutes is used to trigger the gradient crosslinking of the thermosensitive copolymer and the substrate, forming a three-dimensional interpenetrating network structure.

[0086] S4: Soak the cured hollow fiber membrane in deionized water at 50°C for 12 hours to fully wash out the porogen and form a uniform microporous structure. Dry the membrane in an oven at 25°C for 48 hours to obtain a finished hollow fiber membrane.

[0087] Example 6: Preparation of polyvinylidene fluoride-based hollow fiber membrane (water:ethanol=9:1).

[0088] S1: substrate polymer pretreatment;

[0089] Alkali solution soaking: Immerse the polyvinylidene fluoride substrate in 3wt% NaOH solution, treat at 40℃ for 30 minutes, and rinse until neutral.

[0090] S2: Prepare the spinning solution according to the following mass percentages;

[0091] Base polymer: polyvinylidene fluoride, 19wt%;

[0092] Thermosensitive copolymer: poly (N-isopropylacrylamide-co-polyethylene glycol diacrylate), molecular weight 12000 Da, 22 wt%;

[0093] Porogen: polyvinylpyrrolidone, 11 wt%;

[0094] UV crosslinker: benzophenone, 2.5wt%;

[0095] Solvent: N,N-dimethylacetamide, 45.5 wt%.

[0096] The above components were added into a stirring kettle and stirred at a constant temperature of 65°C for 5 hours until they were completely dissolved to form a transparent homogeneous solution.

[0097] S3: The spinning solution is extruded through an annular spinneret into a coagulation bath for curing and simultaneous UV crosslinking to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a 9:1 volume ratio of water and ethanol, and the temperature is controlled at 10°C. UV irradiation parameters: A UV lamp with a wavelength of 365nm, an irradiation intensity of 90mW / cm², and an irradiation time of 7 minutes is used to trigger the gradient crosslinking of the thermosensitive copolymer and the substrate, forming a three-dimensional interpenetrating network structure.

[0098] S4: Soak the cured hollow fiber membrane in deionized water at 55°C for 10 hours to fully wash out the porogen and form a uniform microporous structure. Dry the membrane in an oven at 25°C for 48 hours to obtain a finished hollow fiber membrane.

[0099] Example 7: Preparation of polytetrafluoroethylene-based hollow fiber membrane.

[0100] S1: substrate polymer pretreatment;

[0101] Plasma treatment: Place the polytetrafluoroethylene substrate in a plasma treatment device, introduce oxygen, set the power to 200W, and treat for 2 minutes to introduce hydroxyl active groups on the surface of the substrate to enhance the adhesion of subsequent temperature-sensitive materials.

[0102] Step 2: Prepare the spinning solution according to the following mass percentages;

[0103] Base polymer: polytetrafluoroethylene, 15wt%;

[0104] Thermosensitive copolymer: poly (N-isopropylacrylamide-co-polyethylene glycol diacrylate), molecular weight 20000 Da, 30 wt%;

[0105] Porogen: polyvinyl pyrrolidone, 15 wt%;

[0106] UV crosslinker: ammonium persulfate, 2.5wt%;

[0107] Solvent: N,N-dimethylacetamide, 37.5 wt%.

[0108] The above components were added into a stirring kettle and stirred at a constant temperature of 70°C for 6 hours until they were completely dissolved to form a transparent homogeneous solution.

[0109] S3: The spinning solution is extruded through an annular spinneret into a coagulation bath for curing and simultaneous UV crosslinking to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol in a volume ratio of 8:2, and the temperature is controlled at 7°C. UV irradiation parameters: A UV lamp with a wavelength of 365nm, an irradiation intensity of 90mW / cm², and an irradiation time of 7 minutes is used to trigger the gradient crosslinking of the thermosensitive copolymer and the substrate, forming a three-dimensional interpenetrating network structure.

[0110] S4: Soak the cured hollow fiber membrane in deionized water at 58°C for 9 hours to fully wash out the porogen and form a uniform microporous structure. Dry the membrane in an oven at 32°C for 32 hours to obtain a finished hollow fiber membrane.

[0111] Comparative Example: Preparation of traditional static pore hollow fiber membrane.

[0112] Substrate pretreatment: The polysulfone substrate was immersed in 1.5 wt% NaOH solution at 30 °C for 50 minutes, rinsed and dried.

[0113] Spinning solution preparation: Mix the following components by mass percentage:

[0114] Base polymer: polysulfone, 18 wt%;

[0115] Porogen: polyvinyl pyrrolidone, 12 wt%;

[0116] Solvent: N,N-dimethylacetamide, 70 wt%.

[0117] The above components were added into a stirring kettle and stirred at a constant temperature of 55°C for 7 hours until they were completely dissolved to form a transparent homogeneous solution.

[0118] Spinning: The spinning solution is extruded through an annular spinneret into a coagulation bath for solidification. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol in a volume ratio of 8:2, and the temperature is controlled at 10°C.

[0119] Porogen Removal:

[0120] The cured hollow fiber membrane was immersed in deionized water at 60°C for 8 hours to fully wash out the porogen and form a uniform microporous structure. It was then dried in an oven at 28°C for 40 hours to obtain a conventional static pore polysulfone hollow fiber membrane.

[0121] Example 8: Hollow fiber membrane rejection test.

[0122] Table 1 is a test table of the retention rate test of the fiber membranes prepared in Examples 1-7.

[0123]

[0124] Table 1 shows the retention performance differences of the hollow fiber membranes of Examples 1-7 at different temperatures. All thermosensitive membranes exhibit dynamic pore control: at low temperatures (20°C), the pores expand, preferentially retaining small-molecule lysozyme (e.g., Example 4, with a lysozyme retention rate of 90%), while at high temperatures (50°C), the pores contract, effectively retaining large-molecule BSA (e.g., Example 1, with a BSA retention rate of 97%). Different substrates and preparation processes significantly influence performance: polyvinylidene fluoride (Example 4), due to its strong hydrophobicity, exhibits the most significant pore contraction at high temperatures, resulting in the highest BSA retention rate (98%). Polytetrafluoroethylene (Example 5), due to its chemical inertness, exhibits a slightly slower temperature-sensitive response and the smallest change in retention rate (BSA retention rate of 88%). Furthermore, plasma-treated polyethersulfone (Example 1) exhibits a high degree of crosslinking and more complete pore contraction, while alkaline-treated polyethersulfone (Example 2) exhibits slightly weaker interfacial bonding and a slightly lower retention rate.

[0125] Example 9: Hollow fiber membrane durability test table.

[0126] Table 2 is a test table of the durability test of the fiber membranes prepared in Examples 1-7 and the comparative example.

[0127]

[0128] Table 2 compares the cyclic stability of the thermosensitive membranes of Examples 1-5 and traditional polysulfone membranes. The flux retention rates of the thermosensitive membranes after 50 temperature cycles are significantly higher than those of the traditional membranes. Among them, the plasma-treated ·1 polyethersulfone of Example 1 has the highest flux retention rate due to the enhanced interface bonding due to the high degree of cross-linking; the polyvinylidene fluoride of Example 4 has excellent anti-pollution performance with a retention rate of 90% due to the synergistic effect of hydrophobicity and thermosensitivity. Although the polytetrafluoroethylene of Example 5 has high chemical stability, its flux retention rate is slightly lower due to its slow thermosensitive response rate. In contrast, the traditional membrane is prone to clogging due to the serious performance degradation due to the static pores. The results show that the thermosensitive membrane significantly improves the reliability and economy of long-term use through dynamic pore adjustment and structural optimization.

[0129] The hollow fiber membrane prepared by the present invention realizes dynamic reversible regulation of pores through the bulk dispersion and temperature response mechanism of the thermosensitive polymer poly (N-isopropylacrylamide-co-polyethylene glycol diacrylate. At a low temperature of 20°C, the membrane material expands its pores due to hydrophilic expansion. For example, in Example 4, the average pore diameter reaches 88nm, which can efficiently intercept small molecule lysozyme. At a high temperature of 50°C, the membrane material shrinks hydrophobically and the pores are significantly reduced. For example, in Example 1, the average pore diameter is reduced to 38nm, and the retention rate of the large molecule bovine serum albumin BSA is as high as 97%. This intelligent This adjustable capability allows a single membrane to adapt to the separation needs of substances with different molecular weights, eliminating the need for frequent replacement of membrane components and significantly reducing equipment costs and operational complexity. Furthermore, the three-dimensional interpenetrating network structure constructed through the UV synchronous cross-linking process significantly improves the membrane's mechanical strength and cyclic stability. After 50 temperature cycles, the flux retention rate remains at 88%-92%, far exceeding the 45% of traditional static pore membranes. Furthermore, by optimizing the substrate's surface activity through plasma treatment or alkaline solution immersion, it is compatible with a variety of materials, including polyethersulfone and polytetrafluoroethylene. The process parameters are clearly defined and controllable, making it suitable for large-scale industrial production.

[0130] The hollow fiber membrane of this application shows broad application potential in many fields. In sewage treatment, multi-stage separation can be achieved through temperature switching: large molecular oils and fats (>50kDa) can be intercepted at low temperatures, and soluble small molecular pollutants (<20kDa) can be removed at high temperatures, flexibly responding to water quality fluctuations and sudden pollution incidents. In the field of biopharmaceuticals, dynamic adjustment of the membrane pore size (30-40°C) can efficiently separate cell fragments (>1μm) and target proteins (such as antibodies), significantly improving product purity and yield. In addition, during the protein separation and purification process, its low critical transition temperature (LCST) characteristics can be utilized to allow large molecular impurities to pass through at low temperatures, and to intercept target small molecular proteins at high temperatures, simplifying the purification process. The intelligent response characteristics and structural innovations of the present invention provide efficient, economical and sustainable solutions for complex separation scenarios.

[0131] The present invention has been described in detail above with reference to the embodiments and comparative examples. However, the present invention is not limited to the above embodiments. Various modifications can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Any content not described in detail in the present invention may be adapted from existing technologies.

Claims

1. A method for preparing a temperature-sensitive, dynamically pore-adjustable hollow fiber membrane, characterized in that: The following steps are involved: S1. Surface activation treatment is performed on the substrate polymer; S2. The substrate polymer treated in S1, the thermosensitive copolymer, the porogen, and the UV crosslinking agent are dissolved in a solvent to form a homogeneous spinning solution; S3. The spinning solution is extruded through an annular spinneret into a coagulation bath for solidification, and simultaneously crosslinked by UV radiation to form a three-dimensional interpenetrating network structure; S4. The porogen is removed by water washing to form voids, and the hollow fiber membrane is obtained by drying.

2. The method for preparing a temperature-sensitive, dynamically pore-adjustable hollow fiber membrane according to claim 1, characterized in that: S1 surface activation treatment includes plasma treatment or alkaline solution soaking treatment.

3. The method for preparing a temperature-sensitive hollow fiber membrane with dynamically adjustable pores according to claim 2, characterized in that: The plasma treatment generates at least one active group of hydroxyl and carboxyl on the surface of the substrate through plasma bombardment in an atmosphere of an inert gas or an oxygen-containing gas.

4. The method for preparing a temperature-sensitive, dynamically pore-adjustable hollow fiber membrane according to claim 2, wherein: The alkali solution soaking conditions are: NaOH solution concentration 1-3wt%, soaking temperature 25-40°C, and time 30-60min.

5. The method for preparing a temperature-sensitive, dynamically pore-adjustable hollow fiber membrane according to claim 1, wherein: The spinning solution composition in S2 includes, by mass percentage, 15-20 wt % of a substrate polymer, 10-30 wt % of a thermosensitive copolymer, 10-15 wt % of a porogen, 1-3 wt % of a UV crosslinker, and the remainder being a solvent.

6. The method for preparing a temperature-sensitive hollow fiber membrane with dynamically adjustable pores according to claim 1, characterized in that: The substrate polymer includes polyethersulfone, polysulfone, polyvinylidene fluoride or polytetrafluoroethylene; the temperature-sensitive copolymer includes poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate) with a molecular weight of 10,000-20,000 Da; the porogen includes polyethylene glycol 6000 or polyvinyl pyrrolidone; the ultraviolet crosslinker includes benzophenone or ammonium persulfate; and the solvent includes N,N-dimethylacetamide.

7. The method for preparing a temperature-sensitive, dynamically pore-adjustable hollow fiber membrane according to claim 1, characterized in that: The coagulation bath in S3 is a mixture of water and ethanol in a volume ratio of (7-9):(1-3), and the coagulation bath temperature is 5-10°C; the ultraviolet irradiation conditions are a wavelength of 360-370nm, an intensity of 50-100mW / cm², and an irradiation time of 5-10min.

8. The method for preparing a temperature-sensitive, dynamically pore-adjustable hollow fiber membrane according to claim 1, characterized in that: The conditions for removing the porogen in S4 are washing with water at 50-60°C for 6-12 hours; and drying at 25-35°C for 24-48 hours.

9. A hollow fiber membrane prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The lower critical transition temperature of the hollow fiber membrane is 30-40° C. When the temperature is higher than the lower critical transition temperature, the surface porosity decreases by 30-50%, and the water flux attenuation rate is ≤40%.

10. Use of a hollow fiber membrane prepared by the method for preparing a temperature-sensitive, dynamically pore-adjustable hollow fiber membrane according to any one of claims 1 to 8 in sewage treatment.

Images