A temperature-sensitive hollow fiber membrane with adjustable dynamic pore size and its preparation method

Abstract

This invention relates to the field of hollow fiber membrane technology, and particularly to a method for preparing a temperature-sensitive, dynamically tunable hollow fiber membrane, comprising the following steps: S1, plasma treatment or alkaline immersion treatment of the substrate polymer; S2, dissolving the substrate polymer treated in S1, the temperature-sensitive copolymer, the pore-forming agent, and the UV 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, simultaneously performing UV irradiation crosslinking to form a three-dimensional interpenetrating network structure; S4, removing the pore-forming agent by washing with water to form voids, and drying to obtain the hollow fiber membrane. This invention achieves continuous and reversible control of the pore size of the hollow fiber membrane through the bulk dispersion and temperature response of the temperature-sensitive polymer poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate). This dynamic pore adjustment capability allows a single membrane to adapt to the separation requirements of substances with different molecular weights, eliminating the need for frequent membrane module replacements.

Description

Technical Field

[0001] This invention relates to the field of hollow fiber membrane technology, and in particular to a temperature-sensitive hollow fiber membrane with adjustable dynamic pore size and its preparation method. Background Technology

[0002] Hollow fiber membranes, with their high specific surface area, high separation efficiency, and modular design, have been widely used in wastewater treatment, biopharmaceutical separation, and chemical catalysis. Traditional hollow fiber membranes rely on pore-forming agents to create a static pore structure, with pore sizes remaining fixed after fabrication. This fixed pore size characteristic means that a single membrane module cannot adapt to dynamically changing separation requirements. For example, when treating wastewater with complex compositions, it is necessary to frequently replace membrane modules with different pore sizes to meet the retention requirements of pollutants with varying molecular weights, significantly increasing equipment costs and operational complexity. Furthermore, in the face of seasonal water quality fluctuations or sudden pollutant events, traditional membranes lack intelligent response capabilities, making it difficult to achieve efficient, adaptive, on-demand separation, severely limiting the expansion of their application scenarios.

[0003] In recent years, the introduction of thermosensitive materials has provided new ideas for the dynamic porosity control of fiber membranes. Existing thermosensitive membrane technologies mainly 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 only achieve limited porosity control through changes in the hydrophilicity and hydrophobicity of the surface layer, resulting in slow response rates and insufficient mechanical strength, making them prone to structural fatigue after long-term use; thermosensitive microsphere composite membranes indirectly control porosity by embedding hydrogel microspheres, but uneven distribution of microspheres easily leads to fragile membrane structures, and the poor bonding force between the microspheres and the matrix results in low cycle stability; multilayer composite membranes achieve staged response by stacking thermosensitive layers with different low critical solution temperatures (LCST), but the process is complex and costly, and the multilayer interface easily leads to mass transfer resistance and contamination accumulation. Summary of the Invention

[0004] To address the problems in the background art, this invention proposes a method for preparing a temperature-sensitive, dynamically adjustable hollow fiber membrane and the hollow fiber membrane itself. By utilizing the bulk dispersion and temperature response of the temperature-sensitive polymer poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate), the pore size of the hollow fiber membrane can be continuously and reversibly controlled.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: a method for preparing a temperature-sensitive, dynamically adjustable hollow fiber membrane, comprising the following steps: S1, surface activation treatment of the substrate polymer; S2, dissolving the substrate polymer treated in S1, the temperature-sensitive copolymer, the pore-forming agent, and the 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 irradiation crosslinking to form a three-dimensional interpenetrating network structure; S4, removing the pore-forming agent by washing with water to form voids, and drying to obtain a hollow fiber membrane.

[0006] Furthermore, the S1 surface activation treatment includes plasma treatment or alkaline immersion treatment;

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

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

[0009] Furthermore, the spinning solution composition in S2 comprises, by mass percentage: 15-20 wt% of the base polymer, 10-30 wt% of the thermosensitive copolymer, 10-15 wt% of the pore-forming agent, 1-3 wt% of the UV crosslinking agent, and the balance being solvent.

[0010] Further, the substrate polymer includes polyethersulfone, polysulfone, polyvinylidene fluoride, or polytetrafluoroethylene; the thermosensitive 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 polyvinylpyrrolidone; the UV crosslinking agent 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℃; 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℃ for 6-12 hours; and drying at 25-35℃ for 24-48 hours.

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

[0014] Application of a hollow fiber membrane prepared using a method for preparing a temperature-sensitive, dynamically adjustable pore hollow fiber membrane in wastewater treatment.

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

[0016] Application of a hollow fiber membrane prepared using a method for preparing a temperature-sensitive, dynamically adjustable pore hollow fiber membrane in protein separation and purification.

[0017] The beneficial effects of this invention are:

[0018] (1) This invention achieves continuous and reversible control of the pore size of hollow fiber membranes through the bulk dispersion and temperature response of the temperature-sensitive polymer poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate). When the temperature is below the lower critical transition temperature (LCST), the membrane material hydrophilically expands, and the pores enlarge; when the temperature is above the LCST, the membrane material hydrophobically shrinks, and the pores shrink. This dynamic pore adjustment capability allows a single membrane to adapt to the separation requirements of substances with different molecular weights without the need for frequent replacement of membrane modules.

[0019] (2) This invention constructs a three-dimensional interpenetrating network structure inside the membrane through a UV synchronous crosslinking process, which significantly improves the mechanical strength and cycle stability of the membrane. Experimental data show that after 50 cycles, the flux retention rate of the temperature-sensitive membrane still reaches 88%, while the flux retention rate of the traditional membrane is only 45%. The dynamic pore adjustment capability of the membrane reduces the risk of clogging by pollutants, extends the service life of the membrane module, and reduces the frequency of replacement and waste generation.

[0020] (3) The present invention enhances the surface activity of the substrate by plasma treatment or alkaline immersion, and combines ultraviolet irradiation crosslinking and pore-forming agent removal processes. The preparation process is simple and controllable, and is suitable for large-scale industrial production. Attached Figure Description

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

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

[0023] The technical solutions of the embodiments of the invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely for explaining the invention and not for limiting the invention. Furthermore, it should be noted that, for ease of description, only the parts related to the invention are shown in the accompanying drawings, not all of the structures.

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

[0025] S1: Substrate polymer pretreatment;

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

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

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

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

[0030] Pore-forming agent: Polyethylene glycol 6000, 12 wt%;

[0031] UV crosslinking agent: benzophenone, 2wt%;

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

[0033] Add the above components to a stirred tank and stir at 60°C for 6 hours until completely dissolved to form a transparent homogeneous solution.

[0034] S3: The spinning solution is extruded through a ring spinneret into a coagulation bath for solidification, while simultaneously undergoing ultraviolet irradiation crosslinking to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol at a volume ratio of 8:2, with the temperature controlled at 8℃. Ultraviolet irradiation parameters: A 365nm ultraviolet lamp is used, with an irradiation intensity of 80mW / cm² and an irradiation time of 8 minutes, triggering gradient crosslinking between the temperature-sensitive copolymer and the substrate to form a three-dimensional interpenetrating network structure.

[0035] S4: Immerse the cured hollow fiber membrane in deionized water at 55℃ for 10 hours to fully wash away the pore-forming agent and form a uniform microporous structure. Dry in an oven at 30℃ for 36 hours to obtain the finished hollow fiber membrane.

[0036] like Figure 1 and Figure 2The figure shows SEM images of the hollow fiber membrane of Example 1 at 20°C and 50°C. As can be seen from the figure, the pores of the hollow fiber membrane increase at 20°C and decrease at 50°C.

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

[0038] Step 1: Substrate polymer pretreatment

[0039] Alkaline immersion: Immerse the polyethersulfone substrate in a 1 wt% NaOH solution and treat at 25°C for 60 minutes, then rinse and dry.

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

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

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

[0043] Pore-forming agent: Polyethylene glycol 6000, 11 wt%;

[0044] UV crosslinking agent: benzophenone, 1 wt%

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

[0046] Add the above components to a stirred tank and stir at 50°C for 9 hours until completely dissolved to form a transparent homogeneous solution.

[0047] S3: The spinning solution is extruded through a ring spinneret into a coagulation bath for solidification, while simultaneously undergoing ultraviolet irradiation crosslinking to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol at a volume ratio of 8:2, with the temperature controlled at 6℃. Ultraviolet irradiation parameters: A 365nm ultraviolet lamp is used, with an irradiation intensity of 60mW / cm² and an irradiation time of 9 minutes, triggering gradient crosslinking between the temperature-sensitive copolymer and the substrate to form a three-dimensional interpenetrating network structure.

[0048] S4: Immerse the cured hollow fiber membrane in deionized water at 52℃ for 7 hours to fully wash away the pore-forming agent and form a uniform microporous structure. Dry in an oven at 28℃ for 42 hours to obtain the finished hollow fiber membrane.

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

[0050] S1: Substrate polymer pretreatment;

[0051] Alkaline immersion: Immerse the polysulfone substrate in a 1.5wt% NaOH solution and treat at 30°C for 50 minutes, then rinse and dry.

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

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

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

[0055] Porcelain pore-forming agent: polyvinylpyrrolidone, 13 wt%;

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

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

[0058] Add the above components to a stirred tank and stir at 55°C for 7 hours until completely dissolved to form a transparent homogeneous solution.

[0059] S3: The spinning solution is extruded through a ring spinneret into a coagulation bath for solidification, while simultaneously undergoing ultraviolet irradiation crosslinking to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol at a volume ratio of 8:2, with the temperature controlled at 10℃. Ultraviolet irradiation parameters: A 365nm ultraviolet lamp is used, with an irradiation intensity of 70mW / cm² and an irradiation time of 10 minutes, triggering gradient crosslinking between the temperature-sensitive copolymer and the substrate to form a three-dimensional interpenetrating network structure.

[0060] S4: Immerse the cured hollow fiber membrane in deionized water at 60℃ for 8 hours to fully wash away the pore-forming agent and form a uniform microporous structure. Dry in an oven at 28℃ for 40 hours to obtain the finished hollow fiber membrane.

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

[0062] Alkaline immersion: Immerse the polysulfone substrate in a 1.5wt% NaOH solution and treat at 30°C for 50 minutes, then rinse and dry.

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

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

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

[0066] Porcelain pore-forming agent: polyvinylpyrrolidone, 13 wt%;

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

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

[0069] Add the above components to a stirred tank and stir at 55°C for 7 hours until completely dissolved to form a transparent homogeneous solution.

[0070] S3: The spinning solution is extruded through a ring spinneret into a coagulation bath for solidification, while simultaneously undergoing ultraviolet irradiation crosslinking to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol at a volume ratio of 7:3, with the temperature controlled at 10℃. Ultraviolet irradiation parameters: A 365nm ultraviolet lamp is used, with an irradiation intensity of 70mW / cm² and an irradiation time of 10 minutes, triggering gradient crosslinking between the temperature-sensitive copolymer and the substrate to form a three-dimensional interpenetrating network structure.

[0071] S4: Immerse the cured hollow fiber membrane in deionized water at 60℃ for 8 hours to fully wash away the pore-forming agent and form a uniform microporous structure. Dry in an oven at 28℃ for 40 hours to obtain the finished hollow fiber membrane.

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

[0073] At high temperature (50℃), the average pore size is 43 nm, and the BSA rejection rate is 91%.

[0074] The ethanol ratio was increased to 30%, which enhanced the coagulation rate, made the membrane surface more dense, and maintained the circulation flux at 89%.

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

[0076] S1: Substrate polymer pretreatment;

[0077] Alkaline soaking: Immerse the polyvinylidene fluoride material in a 3wt% NaOH solution, treat at 40°C for 30 minutes, and rinse until neutral.

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

[0079] Substrate polymer: Polyvinylidene fluoride, 20 wt%

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

[0081] Pore-forming agent: Polyvinylpyrrolidone, 10 wt%;

[0082] UV crosslinking agent: benzophenone, 3 wt%;

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

[0084] Add the above components to a stirred tank and stir at 65°C for 5 hours until completely dissolved to form a transparent homogeneous solution.

[0085] S3: The spinning solution is extruded through a ring spinneret into a coagulation bath for solidification, while simultaneously undergoing ultraviolet irradiation crosslinking to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol at a volume ratio of 8:2, with the temperature controlled at 5℃. Ultraviolet irradiation parameters: A 365nm ultraviolet lamp is used, with an irradiation intensity of 100mW / cm² and an irradiation time of 6 minutes, triggering gradient crosslinking between the temperature-sensitive copolymer and the substrate to form a three-dimensional interpenetrating network structure.

[0086] S4: Immerse the cured hollow fiber membrane in deionized water at 50℃ for 12 hours to fully wash away the pore-forming agent and form a uniform microporous structure. Dry in an oven at 25℃ for 48 hours to obtain the finished hollow fiber membrane.

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

[0088] S1: Substrate polymer pretreatment;

[0089] Alkaline soaking: Immerse the polyvinylidene fluoride material in a 3wt% NaOH solution, treat at 40°C for 30 minutes, and rinse until neutral.

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

[0091] Substrate polymer: Polyvinylidene fluoride, 19 wt%;

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

[0093] Porcelain pore-forming agent: polyvinylpyrrolidone, 11 wt%;

[0094] UV crosslinking agent: benzophenone, 2.5 wt%;

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

[0096] Add the above components to a stirred tank and stir at 65°C for 5 hours until completely dissolved to form a transparent homogeneous solution.

[0097] S3: The spinning solution is extruded through a ring spinneret into a coagulation bath for solidification, while simultaneously undergoing ultraviolet irradiation 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, with the temperature controlled at 10℃. Ultraviolet irradiation parameters: A 365nm ultraviolet lamp is used, with an irradiation intensity of 90mW / cm² and an irradiation time of 7 minutes, triggering gradient crosslinking between the temperature-sensitive copolymer and the substrate to form a three-dimensional interpenetrating network structure.

[0098] S4: Immerse the cured hollow fiber membrane in deionized water at 55℃ for 10 hours to fully wash away the pore-forming agent and form a uniform microporous structure. Dry in an oven at 25℃ for 48 hours to obtain the finished hollow fiber membrane.

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

[0100] S1: Substrate polymer pretreatment;

[0101] Plasma treatment: The polytetrafluoroethylene material is placed in a plasma treatment device, oxygen is introduced, the power is set to 200W, and the treatment time is 2 minutes, so as to introduce hydroxyl active groups on the surface of the substrate and enhance the adhesion of subsequent temperature-sensitive materials.

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

[0103] Substrate polymer: Polytetrafluoroethylene, 15 wt%;

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

[0105] Pore-forming agent: Polyvinylpyrrolidone, 15 wt%;

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

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

[0108] Add the above components to a stirred tank and stir at 70°C for 6 hours until completely dissolved to form a transparent homogeneous solution.

[0109] S3: The spinning solution is extruded through a ring spinneret into a coagulation bath for solidification, while simultaneously undergoing ultraviolet irradiation crosslinking to form a three-dimensional interpenetrating network structure. Coagulation bath conditions: The coagulation bath consists of a mixture of water and ethanol at a volume ratio of 8:2, with the temperature controlled at 7℃. Ultraviolet irradiation parameters: A 365nm ultraviolet lamp is used, with an irradiation intensity of 90mW / cm² and an irradiation time of 7 minutes, triggering gradient crosslinking between the temperature-sensitive copolymer and the substrate to form a three-dimensional interpenetrating network structure.

[0110] S4: Immerse the cured hollow fiber membrane in deionized water at 58℃ for 9 hours to fully wash away the pore-forming agent and form a uniform microporous structure. Dry in an oven at 32℃ for 32 hours to obtain the finished hollow fiber membrane.

[0111] Comparative example: Preparation of traditional static porous hollow fiber membranes.

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

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

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

[0115] Pore-forming agent: Polyvinylpyrrolidone, 12 wt%;

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

[0117] Add the above components to a stirred tank and stir at 55°C for 7 hours until completely dissolved to form a transparent homogeneous solution.

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

[0119] Pore-forming agent removal:

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

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

[0122] Table 1 shows the test results for the retention rate of the fiber membranes prepared in Examples 1-7.

[0123]

[0124] Table 1 shows the differences in retention performance of the hollow fiber membranes of Examples 1-7 at different temperatures. All temperature-sensitive membranes exhibited dynamic pore regulation capabilities: at low temperatures (20°C), the pores expanded, preferentially retaining small molecule lysozyme (e.g., the lysozyme retention rate in Example 4 reached 90%), while at high temperatures (50°C), the pores contracted, efficiently retaining large molecule BSA (e.g., the BSA retention rate in Example 1 reached 97%). Different substrates and preparation processes significantly affected the performance: polyvinylidene fluoride (Example 4), due to its strong hydrophobicity, showed the most significant pore contraction at high temperatures, resulting in the highest BSA retention rate (98%); polytetrafluoroethylene (Example 5), due to its chemical inertness, exhibited a slightly slower temperature-sensitive response and the smallest change in retention rate (BSA retention rate 88%). In addition, plasma-treated polyethersulfone (Example 1) had a high degree of crosslinking and more thorough pore contraction, while alkali-treated polyethersulfone (Example 2) had slightly weaker interfacial bonding and a slightly lower retention rate.

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

[0126] Table 2 shows the durability test results for the fiber membranes prepared in Examples 1-7 and the comparative examples.

[0127]

[0128] Table 2 compares the cycling stability of the temperature-sensitive membranes in Examples 1-5 with that of the conventional polysulfone membrane. After 50 temperature cycles, the flux retention rate of the temperature-sensitive membranes was significantly higher than that of the conventional membranes. Among them, the plasma-treated polyethersulfone of Example 1 exhibited the highest flux retention rate due to its high degree of cross-linking and enhanced interfacial bonding. The polyvinylidene fluoride of Example 4, with its excellent antifouling properties and synergistic effect of hydrophobicity and temperature sensitivity, maintained a 90% flux retention rate. Although the polytetrafluoroethylene of Example 5 had high chemical stability, its flux retention rate was slightly lower due to its slower temperature response rate. In contrast, the conventional membranes suffered from severe performance degradation due to the susceptibility to static pore clogging. The results indicate that the temperature-sensitive membranes, through dynamic pore adjustment and structural optimization, significantly improved the reliability and economy of long-term use.

[0129] The hollow fiber membrane prepared in this invention achieves dynamic and reversible pore size control through the bulk dispersion and temperature-responsive mechanism of the temperature-sensitive polymer poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate). At a low temperature of 20°C, the membrane material expands its pores due to hydrophilic swelling; for example, in Example 4, the average pore size reaches 88 nm, enabling efficient retention of small molecule lysozyme. Conversely, at a high temperature of 50°C, the membrane material shrinks hydrophobically, significantly reducing the pore size; for example, in Example 1, the average pore size decreases to 38 nm, while maintaining a retention rate of up to 97% for large molecule bovine serum albumin (BSA). This intelligent… The adaptability allows a single membrane to be adapted to the separation needs of substances with different molecular weights, eliminating the need for frequent membrane module replacements and significantly reducing equipment costs and operational complexity. Simultaneously, the three-dimensional interpenetrating network structure constructed by the UV-synchronous crosslinking process significantly improves the membrane's mechanical strength and cycling stability; after 50 temperature cycles, the flux retention rate still reaches 88%-92%, far exceeding the 45% of traditional static porous membranes. Furthermore, by optimizing the substrate surface activity through plasma treatment or alkaline immersion, it is compatible with various materials such as polyethersulfone and polytetrafluoroethylene, with clearly defined and controllable process parameters, making it suitable for large-scale industrial production.

[0130] The hollow fiber membrane of this application demonstrates broad application potential in multiple fields. In wastewater treatment, multi-stage separation can be achieved through temperature switching: large molecular lipids (>50kDa) are retained at low temperatures, while soluble small molecular pollutants (<20kDa) can be removed at high temperatures, flexibly responding to water quality fluctuations and sudden pollution events. In the biopharmaceutical field, dynamically adjusting the membrane pore size (30-40℃) can efficiently separate cell debris (>1μm) from target proteins (such as antibodies), significantly improving product purity and yield. Furthermore, in protein separation and purification processes, utilizing its low critical transition temperature (LCST) characteristic, large molecular proteins can permeate at low temperatures while retaining target small molecular proteins at high temperatures, simplifying the purification process. The intelligent response characteristics and structural innovation of this invention provide an efficient, economical, and sustainable solution for complex separation scenarios.

[0131] The present invention has been described in detail above with reference to embodiments and comparative examples. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. All contents not described in detail in the present invention can be derived from existing technologies.

Claims

1. A method for preparing a temperature-sensitive hollow fiber membrane with adjustable dynamic pore size, characterized in that, Includes the following steps: S1. Surface activation treatment is performed on the substrate polymer; S2. Dissolve the substrate polymer, thermosensitive copolymer, pore-forming agent and ultraviolet crosslinking agent treated in S1 in a solvent to form a homogeneous spinning solution; S3. The spinning solution is extruded through a ring spinneret into a coagulation bath for solidification, and ultraviolet irradiation crosslinking is carried out simultaneously to form a three-dimensional interpenetrating network structure. S4. The pore-forming agent is removed by washing with water, and the hollow fiber membrane is obtained by drying. In S3, the coagulation bath is a mixture of water and ethanol in a volume ratio of (7-9):(1-3), and the coagulation bath temperature is 5-10℃. The ultraviolet irradiation conditions are a wavelength of 360-370 nm and an intensity of 50-100 mW / cm². 2 Irradiation time: 5-10 minutes; The substrate polymer includes polyethersulfone, polysulfone, polyvinylidene fluoride or polytetrafluoroethylene; The thermosensitive copolymer includes poly(N-isopropylacrylamide-co-polyethylene glycol diacrylate) with a molecular weight of 10,000-20,000 Da; The pore-forming agent includes polyethylene glycol 6000 or polyvinylpyrrolidone; The ultraviolet crosslinking agent includes benzophenone or ammonium persulfate; The solvent includes N,N-dimethylacetamide.

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

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

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

5. The method for preparing a temperature-sensitive, dynamically adjustable pore hollow fiber membrane according to claim 1, characterized in that: The spinning solution composition described in S2, by mass percentage, includes: The substrate polymer is 15-20 wt%, the thermosensitive copolymer is 10-30 wt%, the pore-forming agent is 10-15 wt%, the UV crosslinking agent is 1-3 wt%, and the balance is solvent.

6. The method for preparing a temperature-sensitive, dynamically adjustable pore 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℃ for 6-12 hours; The drying conditions are 25-35℃ for 24-48 hours.

7. A hollow fiber membrane prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The hollow fiber membrane has a low critical transition temperature of 30-40℃. When the temperature is higher than the low critical transition temperature, the surface porosity decreases by 30-50%, and the water flux attenuation rate is ≤40%.

8. The application of a hollow fiber membrane prepared by the method for preparing a temperature-sensitive, dynamically adjustable pore hollow fiber membrane as described in any one of claims 1 to 6 in wastewater treatment.

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