Preparation method and application of polymer membrane based on solvent in-situ functionalization enhancement

Abstract

The invention discloses a preparation method and application of a polymer membrane based on solvent in-situ functionalization enhancement. The method comprises the following steps: dissolving a polymer raw material by adopting a polymerizable solvent to form a homogeneous membrane casting solution; then synchronously carrying out ultraviolet light induced polymerization on the residual solvent in the membrane in the membrane casting liquid phase separation forming process by utilizing a constant-temperature circulating coagulating bath carrying an ultraviolet light illumination system; performing drying treatment to obtain a flat plate / hollow fiber composite membrane; the method is applied to the aspects of seawater desalination, wastewater treatment, food processing, biological medicine, energy chemical industry and the like. By utilizing dual functions of the solvent, polymerized solvent molecules and macromolecular chains form a stable cross-linked interpenetrating network structure, functional design of the membrane is realized through customizability of the solvent, functionalization enhancement of the membrane is realized while the process is simplified, ultraviolet polymerization synchronously optimizes phase separation kinetics, and the performance of the membrane is improved. Uniform surface pore size distribution and efficient mass transfer channels are formed, and the advantages of high efficiency and customizability are shown.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material preparation, in particular to a polymer membrane preparation method based on in-situ functionalization enhanced by solvents and applications. BACKGROUND

[0002] In recent years, membrane separation technology has been widely used in seawater desalination, wastewater treatment, food processing, biomedicine and energy chemical industry due to its advantages of high efficiency, energy saving, simple operation and environmental friendliness. This technology realizes material separation through selective permeation mechanism, which can effectively solve the problems of high energy consumption, serious pollution and low efficiency in traditional processes. According to statistics, the global membrane separation market size has an average annual growth rate of more than 8%, which has become a key support for promoting industrial upgrading and environmental protection.

[0003] Polymer materials have become the mainstream of the current separation membrane material market (accounting for more than 85%) due to their strong controllability, flexible processing and low cost. However, conventional polymer membranes usually face many inherent defects in use, such as product retention rate fluctuation and selectivity decline caused by insufficient separation precision, inherent contradiction between high flux demand and transmembrane mass transfer resistance, irreversible reduction of permeation flux and life decay caused by membrane pollution in dynamic operation, and structural instability and performance degradation of membrane materials in extreme operating environment. These challenges restrict the industrialization process of membrane separation technology in various fields, and need to be further optimized and developed. In order to overcome the above limitations, it is usually necessary to functionalize the membrane material to enhance its structural strength, anti-pollution, separation precision and flux.

[0004] The Chinese patent document with publication number CN109847603A discloses a method for improving the hydrophilicity and anti-pollution of polymer separation membrane by surface glycosylation, which includes the following steps: dissolving bioactive molecule glycolipid in phosphate PBS buffer to prepare a glycolipid solution with a concentration of 0.05-4 g / L, then immersing dry polymer separation membrane in the glycolipid solution, and placing it in a shaker with a rotation speed of 50-200 rpm and a temperature of 25-50 ℃. After a certain time of static adsorption, it is taken out, washed several times with deionized water, and dried at room temperature to obtain a polymer separation membrane modified by surface glycosylation. The polymer separation membrane prepared by the present application not only retains the original excellent bulk properties of the polymer separation membrane, but also has excellent hydrophilicity and anti-pollution performance. Its adsorption capacity for bovine serum albumin (BSA) is less than 5 μg / cm2, and it has good application value in water treatment and biochemical separation.

[0005] The Chinese patent document with publication number CN118512930B discloses a hydrophilic modified polyvinylidene fluoride microfiltration membrane and its preparation method, which includes the following steps: preparing monomer solutions with a mass fraction of 5-20%, initiator solutions with a mass fraction of 6-20%, and crosslinking agent solutions with a mass fraction of 0.6-1.2%, respectively; immersing a pre-wetted polyvinylidene fluoride membrane in the monomer solution, the initiator solution, and the crosslinking agent solution in sequence, and finally washing with water and drying to obtain the polyvinylidene fluoride microfiltration membrane. The hydrophilic modified polyvinylidene fluoride microfiltration membrane can be completely wetted within 1 second, and the protein recovery rate is ≥99%, with the characteristics of high flow rate, high bubble point, and low protein adsorption.

[0006] The Chinese patent document with publication number CN118320629A discloses a modification method of a self-polymerized microporous polymer gas separation membrane, which includes the following steps: placing the gas separation membrane to be modified in a plasma excitation reaction chamber, vacuumizing the plasma excitation reaction chamber; then filling a gas source (H-2, Ar, SF-6, O-2, or NH-3) into the plasma excitation reaction chamber; and exciting the gas source into plasma through an electric field to modify the gas separation membrane. The present application utilizes the plasma generated by gas excitation to control the micropores of the polymer membrane material and construct efficient gas selective transmission channels, thereby significantly improving the diffusion selectivity of the gas separation membrane for oxygen / nitrogen.

[0007] The reported functional modification process of membrane materials mainly introduces functional groups through grafting or blending, which can improve the performance of the membrane to some extent, but usually requires the additional introduction of functional reagents such as nanofillers and grafting monomers, and involves multiple pretreatment procedures in the modification process, which not only leads to a sharp increase in energy consumption and complex process, but also aggravates the environmental burden. In addition, the modified layer of the membrane material obtained by the above modification method has weak interfacial bonding force with the substrate, which is prone to peeling failure and performance degradation problems during long-term operation. At the same time, the modification process may have adverse effects on the structure of the membrane material. These technical bottlenecks seriously restrict the large-scale application of high-performance membranes, and innovative strategies that can simplify the process and synergistically improve the performance are urgently needed. SUMMARY

[0008] To solve the problems in the background art, the present application provides a polymer membrane preparation method based on in-situ functionalization enhancement of solvents and its application. This method has the advantages of process simplification, performance synergistic improvement, long-term operation stability, etc., and does not require the additional introduction of functional reagents and multiple pretreatment procedures.

[0009] The technical solution adopted by the present application is as follows: I. A polymer membrane preparation method based on in-situ functionalization enhancement of solvents The method includes the following steps: Step (1): A certain amount of raw material is added to the polymerizable solvent under the preset temperature condition, and then stirred to obtain a homogeneous casting solution; The step (1) is specifically: A certain amount of raw material is added to the polymerizable solvent under the preset temperature condition of 0-90℃, and stirred at a speed of 200-1000 rpm for 1-48 hours to obtain a homogeneous casting solution; The raw material in the step (1) is one or more combinations of cellulose and its derivatives, polyether sulfone (PES), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyamidoxime (PAO), polyacrylonitrile (PAN), polylactic acid (PLA), polymethyl methacrylate (PMMA) and polystyrene (PS) and other high molecular polymers; The polymerizable solvent in the step (1) is one or more combinations of ionic liquid (1-allyl-3-methylimidazolium chloride AMIMCl), eutectic solvent (ZnCl2 / H2O / AA), N-vinyl pyrrolidone (NVP), hydroxyethyl methacrylate (HEMA), acrylic acid (AA), acrylamide (AM) and methyl methacrylate (MMA) and other solvents.

[0010] Step (2): A certain amount of crosslinking agent and photoinitiator are added to the homogeneous casting solution, and after the crosslinking agent and photoinitiator are completely dissolved, centrifugation is performed to remove all bubbles in the mixed solution composed of the homogeneous casting solution, the crosslinking agent and the photoinitiator, thereby obtaining a homogeneous casting mixed solution, specifically, after the polymerizable solvent is determined, the matching crosslinking agent and photoinitiator are selected according to the polymerizable solvent; The step (2) is specifically: A certain amount of crosslinking agent and photoinitiator are added to the homogeneous casting solution, and the crosslinking agent and photoinitiator are completely dissolved by blending at a speed of 200-1000 rpm for 0.5-5 hours, and then all bubbles in the solution mixed with the crosslinking agent, the photoinitiator and the homogeneous casting solution are removed by centrifugation at 3000-8000 rpm for 5-20 minutes, thereby obtaining a homogeneous casting mixed solution; The mass ratio of the crosslinking agent to the homogeneous casting solution is 0.5-15 wt%, and the mass ratio of the photoinitiator to the homogeneous casting solution is 0.5-15 wt%; The crosslinking agent in the step (2) is one or more combinations of N,N'-methylenebisacrylamide (MBA), ethylene glycol dimethacrylate (EGDMA), polyethylene glycol diacrylate (PEGDA), pentaerythritol tetraacrylate (PETTA) and trimethylolpropane triacrylate (TMPTA); The photoinitiator in the step (2) is one or more combinations of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (2959), 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173), 2,2-dimethoxy-2-phenylacetophenone (DMPA), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO), and benzotriazole (BTA), etc.

[0011] Step (3): according to one of the following two polymer film preparation processes: The first preparation method S1: the homogeneous casting film mixture obtained in step (2) is prepared into a solvent in-situ functionalized enhanced hollow fiber composite membrane by using a dry-wet spinning process in a constant temperature circulating coagulation bath equipped with an ultraviolet light system; The second preparation method S2: the homogeneous casting film mixture obtained in step (2) is coated on a glass substrate by using a doctor blade, and then a solvent in-situ functionalized enhanced flat plate composite membrane is prepared in a constant temperature circulating coagulation bath equipped with an ultraviolet light system.

[0012] The step (3) is specifically: The first preparation method S1 is specifically: the homogeneous casting film mixture obtained in step (2) is placed in a nitrogen pressurized system, the pressure is controlled so that the homogeneous casting film mixture is extruded through the outer layer of a double-layer coaxial needle at 0~90℃, at the same time, the inner layer of the needle is used to introduce core fluid at a certain speed, the distance between the coaxial needle and the coagulation bath liquid surface is 0~30 cm, the extruded homogeneous casting film mixture is simultaneously contacted with air and core fluid to obtain nascent fibers, the nascent fibers are drawn into the constant temperature circulating coagulation bath equipped with an ultraviolet light system at a drawing speed of 0.1~100 m / min under the traction of a winding device, the polymerizable solvent is cured under the ultraviolet light system, the nascent fibers are preliminarily cured in the constant temperature circulating coagulation bath equipped with an ultraviolet light system, the residual solvent in the membrane is simultaneously subjected to ultraviolet light induced polymerization in the casting film liquid phase separation forming process, then the nascent fibers are immersed in water to fully phase separate and cure, and after drying treatment under certain conditions, a solvent in-situ functionalized enhanced hollow fiber composite membrane is obtained; The second preparation method S2 is specifically: a doctor blade with a thickness of 100-1000 μm is used to uniformly coat the homogeneous casting film mixture obtained in step (2) on a glass substrate, then the glass substrate is immersed in a constant temperature circulating coagulation bath equipped with an ultraviolet light system for preliminary curing, wherein the raw material is preliminarily cured in the constant temperature circulating coagulation bath equipped with an ultraviolet light system, the polymerizable solvent is cured under the ultraviolet light system, the residual solvent in the membrane is simultaneously subjected to ultraviolet light induced polymerization in the casting film liquid phase separation forming process, the glass substrate is taken out after 5~120 seconds, immersed in water to fully phase separate and cure the raw material, and after drying treatment under certain conditions, a solvent in-situ functionalized enhanced flat plate composite membrane is obtained.

[0013] The core fluid of the step S1 is one or more combinations of deionized water, ethanol, acetone, dimethyl sulfoxide, N,N-dimethylformamide and calcium chloride aqueous solution, etc. The coagulation bath in the step S1 and the step S2 is one or more combinations of deionized water, ethanol, acetone, dimethyl sulfoxide, N,N-dimethylformamide and calcium chloride aqueous solution, etc. The drying treatment mode in the step S1 and the step S2 is one or more combinations of vacuum oven drying, normal pressure oven drying, normal temperature drying, freeze drying and supercritical drying, etc.

[0014] In the step S1, the pressure range of the nitrogen pressurization system is 0.1-8 MPa, the inlet speed range of the core fluid is 1-20 mL / min, and the traction speed range of the winding device is 0.1-100 m / min. In the step S1 and the step S2, the ultraviolet light intensity range of the ultraviolet light irradiation system is 500-10000 W / m 2 The temperature range of the coagulation bath is 0-60 ℃.

[0015] II. A polymer membrane based on solvent in-situ functionalization enhancement The polymer membrane is prepared by the above preparation method. The prepared polymer membrane based on solvent in-situ functionalization enhancement can be crosslinked with other substances, or grafted with other functional groups on the surface, or loaded with polymers, etc., to realize the optimization of separation performance and the diversification of material functions.

[0016] III. Application of a polymer membrane based on solvent in-situ functionalization enhancement In gas separation, sewage treatment, protein separation, food processing, antibiotic purification, virus filtration and precious metal recovery, etc.

[0017] The present application is based on the reaction of polymer raw materials and polymerizable solvents to prepare a homogeneous casting solution, then immerse the casting solution in a constant temperature circulating coagulation bath equipped with an ultraviolet light irradiation system, utilize the dual function (dissolution and in-situ utilization) of the solvent, simultaneously induce in-situ polymerization of the residual solvent in the membrane during phase separation molding, make the polymerized solvent molecules and polymer chains form a crosslinked interpenetrating network structure, and then realize functional modification in one body. Then dry the material, and the obtained material is a solvent in-situ functionalization enhanced polymer membrane material. By controlling the types of polymer raw materials and polymerizable solvents, the solid content of the casting solution, the light intensity, the dry-wet spinning parameters and spinning conditions, the types of coagulation bath, the structure and performance of the solvent in-situ functionalization enhanced polymer membrane material can be adjusted.

[0018] This invention, for the first time, utilizes the dual function of solvents (dissolution and in-situ utilization). By simultaneously inducing UV-induced in-situ polymerization of residual solvent within the membrane during phase separation and molding, the polymerized solvent molecules and polymer chains form a cross-linked interpenetrating network structure, thereby achieving stable functional modification in an integrated manner. This completely eliminates the need for additional functionalizing reagents and multiple pretreatment steps required by traditional modification methods such as grafting and blending, avoiding damage to the original membrane structure during subsequent modification. It enhances the stability of the modified structure, ensuring long-term operational durability. Furthermore, by simultaneously regulating phase separation kinetics through UV polymerization, it forms a uniform surface pore size distribution and efficient mass transfer channels, significantly improving separation accuracy and throughput, achieving synergistic performance optimization. It exhibits excellent performance in the field of membrane modification and has broad application prospects.

[0019] The method of this invention is simple, requiring no additional functionalizing reagents (such as nanofillers or grafted monomers) or post-processing steps, thus improving solvent utilization and significantly reducing energy consumption and environmental burden. Utilizing the dual functions of solvent dissolution and in-situ utilization, the prepared polymer film undergoes direct UV-induced polymerization during phase separation via in-situ solvent functionalization, forming a cross-linked interpenetrating network structure. This significantly enhances mechanical strength and structural stability while achieving functional enhancement, perfectly solving the problems of weak interfacial bonding, performance degradation, and structural damage in traditional modification processes.

[0020] Furthermore, by simultaneously regulating phase separation kinetics through UV polymerization, the membrane pore formation process can be precisely controlled, synergistically optimizing the separation performance and structural precision of the polymer membrane, thus overcoming the inherent contradiction between traditional high-throughput requirements and transmembrane resistance. This provides a new, efficient, and sustainable strategy for the field of separation membrane modification.

[0021] The polymer membrane material prepared by the method of this invention exhibits excellent performance in separation, filtration and purification processes, and has the advantages of high efficiency and customizability. It has great application prospects in the fields of seawater desalination, wastewater treatment, food processing, biomedicine and energy chemical industry.

[0022] The beneficial effects of the present invention are: the modification method of the present invention has simple steps, significant modification effect, wide applicability, and has the potential for large-scale production.

[0023] This invention utilizes the dual function of solvents to enable polymerized solvent molecules to form a stable cross-linked interpenetrating network structure with polymer chains. The customizability of the solvent enables the functional design of the membrane, simplifying the process while enhancing the functionality of the membrane. The UV polymerization simultaneously optimizes phase separation kinetics, forming a uniform surface pore size distribution and efficient mass transfer channels, demonstrating high efficiency and customizability.

[0024] (1) Integrated functional modification, significantly simplifying the process flow: Traditional modification requires the additional introduction of functional reagents (such as nano-fillers, grafting monomers) and multiple pre-treatment processes. This invention utilizes the dual function of solvents (dissolution and in-situ polymerization) to directly complete UV-induced polymerization during phase separation molding, eliminating additional modification steps such as grafting and blending, reducing raw material costs, and improving solvent utilization. This completely solves the problems of high energy consumption, complex process flow, and large environmental burden in traditional modification processes, achieving "one-step" efficient modification, with green economic advantages, conducive to promoting the large-scale application of high-performance membrane materials, and in line with the trend of sustainable manufacturing.

[0025] (2) Zero-damage to the base structure and high customizability: By omitting the post-treatment modification step, the physical and chemical damage to the original membrane structure caused by traditional processes is avoided. At the same time, by directly regulating the cross-linked network characteristics through customizable solvents (such as selecting polymerizable solvents containing functional groups), the flexibility of functional design of polymer membranes, such as hydrophilicity, anti-pollution, and mechanical strength, is achieved, meeting the differentiated needs of various scenarios (such as environmental governance and biomedicine).

[0026] (3) Enhancing structural stability and long-term durability: By in-situ polymerization of solvent molecules to form a cross-linked interpenetrating network structure, the functional components are tightly combined with the polymer matrix. This breakthrough in the weak interfacial bonding in traditional modification avoids the peeling failure and performance degradation of the modified layer during long-term operation, significantly improving the structural stability and service life of the membrane in extreme operating environments (such as high pressure and high pollution conditions).

[0027] (4) Synergistic optimization of separation performance and structural precision: In addition to the functional enhancement brought by in-situ polymerization of solvent molecules, UV polymerization simultaneously regulates the phase separation kinetics, precisely controlling the membrane pore formation process, which is beneficial to the formation of uniform surface pore size distribution, solving the problem of fluctuation in retention rate caused by insufficient separation precision of traditional membranes; and constructing efficient mass transfer channels, breaking through the inherent contradiction between high flux and transmembrane mass transfer resistance, and simultaneously improving the separation efficiency of polymer membranes. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Schematic diagram for the preparation of hollow fiber composite membrane for solvent in-situ functional enhancement; Figure 2 Schematic diagram for the formation of cross-linked interpenetrating network structure by in-situ polymerization of solvent molecules and high molecular weight materials after UV polymerization; Figure 3 Comparison of molecular weight retention and permeation flux of hollow fiber membranes prepared in Example 1 and Comparative Example 1; Figure 4 Comparison of molecular weight retention and permeation flux of flat sheet membranes prepared in Example 2 and Comparative Example 2; Figure 5Molecular weight cut-off and permeate flux of hollow fiber composite membranes prepared using different mass percentages of crosslinking agent; Figure 6 Molecular weight cut-off and permeate flux of hollow fiber composite membranes prepared using different mass percentages of photoinitiator; Figure 7 Molecular weight cut-off and permeate flux of hollow fiber composite membranes prepared using different UV light intensities; Figure 8 Molecular weight cut-off and permeate flux of flat composite membranes prepared using different UV light intensities. DETAILED DESCRIPTION

[0029] The application will be described in further detail below with reference to the drawings and specific embodiments.

[0030] The application will be described in further detail below with reference to the drawings and specific embodiments.

[0031] The application will be described in further detail below with reference to the drawings and specific embodiments. Example 1 Cellulose was selected as the raw material required for the reaction and added to the ionic liquid AMIMCl, and oil bath heating was performed at a temperature of 80 °C, and stirring was performed at 600 rpm for 48 h, to configure a homogeneous casting solution with a cellulose mass fraction of 9 wt%; 3 wt% MBA crosslinking agent and 2 wt% 2959 photoinitiator were added to the homogeneous casting solution and blended for 30 minutes to make them completely dissolved; the homogeneous casting solution was centrifuged at 5000 rpm for 10 minutes to remove all air bubbles in the solution. Subsequently, a dry-wet spinning process was used to prepare a hollow fiber membrane: the obtained homogeneous casting solution was placed in a nitrogen pressurization system, the pressure was controlled to be 3 MPa, and the temperature was set to be 80 °C, so that the casting solution was extruded through the outer layer of a coaxial needle, while deionized water was introduced into the inner layer of the needle at a flow rate of 3 mL / min as the core fluid, and the distance between the coaxial needle and the liquid surface of the coagulation bath was 15 cm; the extruded nascent fiber was drawn into a constant-temperature circulating water coagulation bath equipped with a UV light irradiation system at a speed of 0.2 m / min under the traction of a winding device, the UV light intensity was set to be 2000 W / m 2 , and the water coagulation bath temperature was set to be 25 °C; the obtained hollow fiber was immersed in water to allow it to be fully phase-separated and solidified, and then treated by CO2 supercritical drying, to finally obtain a solvent in-situ functionalized enhanced cellulose hollow fiber composite membrane (the preparation process is shown in Figure 1 and Figure 2 ).

[0032] Comparative Example 1 Cellulose was selected as the raw material for the reaction and added to the ionic liquid AMIMCI. The mixture was heated in an oil bath at 80 °C and stirred at 600 rpm for 48 h to prepare a homogeneous casting solution with a cellulose mass fraction of 9 wt%. 3 wt% MBA crosslinking agent and 2 wt% 2959 photoinitiator were added to the homogeneous casting solution and blended for 30 min to ensure complete dissolution. The homogeneous casting solution was centrifuged at 5000 rpm for 10 min to remove all air bubbles in the solution. A dry-wet spinning process was then used to prepare the hollow fiber membrane: the obtained homogeneous casting solution was placed in a nitrogen pressurized system, the pressure was controlled at 3 MPa, and the temperature was set at 80 °C. The casting solution was extruded through the outer layer of a coaxial needle, while deionized water was introduced into the inner layer of the needle at a flow rate of 3 mL / min as the core fluid. The distance between the coaxial needle and the coagulation bath was 15 cm. The extruded nascent fiber was directly introduced into a 25 °C constant temperature circulating water coagulation bath at a speed of 0.2 m / min under the traction of a winding device. The obtained hollow fiber was then immersed in water to allow it to fully phase separate and solidify. Finally, the hollow fiber was treated by CO2 supercritical drying to obtain a conventional cellulose hollow fiber membrane, which was used as the comparative example 1 of example 1.

[0033] The molecular weight cut-off (MWCO) and permeation flux of the hollow fiber membranes prepared in example 1 and comparative example 1 were tested, and the results are shown in table 1 and Figure 3

[0034] Table 1 The results show that the solvent in-situ functionalized enhanced cellulose hollow fiber composite membrane has a lower molecular weight cut-off (MWCO) and a higher permeation flux than the conventional cellulose hollow fiber membrane (see Figure 3 ).

[0035] Example 2 Cellulose was selected as the raw material for the reaction and added to the ionic liquid AMIMCI. The mixture was heated in an oil bath at 80 °C and stirred at 600 rpm for 48 h to prepare a homogeneous casting solution with a cellulose mass fraction of 9 wt%. 3 wt% MBA crosslinking agent and 2 wt% 2959 photoinitiator were added to the homogeneous casting solution and blended for 30 min to ensure complete dissolution. The homogeneous casting solution was centrifuged at 5000 rpm for 10 min to remove all air bubbles in the solution. A dry-wet spinning process was then used to prepare the hollow fiber membrane: the obtained homogeneous casting solution was placed in a nitrogen pressurized system, the pressure was controlled at 3 MPa, and the temperature was set at 80 °C. The casting solution was extruded through the outer layer of a coaxial needle, while deionized water was introduced into the inner layer of the needle at a flow rate of 3 mL / min as the core fluid. The distance between the coaxial needle and the coagulation bath was 15 cm. The extruded nascent fiber was directly introduced into a 25 °C constant temperature circulating water coagulation bath at a speed of 0.2 m / min under the traction of a winding device. The obtained hollow fiber was then immersed in water to allow it to fully phase separate and solidify. Finally, the hollow fiber was treated by CO2 supercritical drying to obtain a conventional cellulose hollow fiber membrane, which was used as the comparative example 1 of example 1. 2 ​The coagulation bath temperature was set to 25 °C; after 20 s, the membrane was taken out of the coagulation bath and immersed in water to allow it to fully phase separate and solidify; finally, the membrane was treated by CO2 supercritical drying to obtain the solvent in situ functionalized reinforced cellulose flat composite membrane.

[0036] Comparative Example 2 Cellulose was selected as the raw material required for the reaction and added to the ionic liquid AMIMCl, and oil bath heating was carried out at a temperature of 80 °C, and stirring was carried out at 600 rpm for 48 h, to configure a homogeneous casting solution with a cellulose mass fraction of 9 wt%; 3 wt% MBA crosslinking agent and 2 wt% 2959 initiator were added to the homogeneous casting solution and blended for 30 minutes to allow them to fully dissolve; the homogeneous casting solution was centrifuged at 5000 rpm for 10 minutes to remove all air bubbles in the solution; then the obtained homogeneous casting solution was uniformly scraped onto a glass substrate using a scraper with a thickness of 500 μm, and immersed in a constant temperature circulating water coagulation bath at 25 °C, after 20 s, the membrane was taken out of the coagulation bath and immersed in water to allow it to fully phase separate and solidify; finally, the membrane was treated by CO2 supercritical drying to obtain a conventional cellulose flat membrane.

[0037] The molecular weight cut-off (MWCO) and permeation flux of the flat membranes prepared in Example 2 and Comparative Example 2 were tested, and the results are shown in Table 2 and Figure 4 .

[0038] Table 2 The results show that the solvent in situ functionalized reinforced cellulose flat composite membrane has a lower molecular weight cut-off (MWCO) and a higher permeation flux than the conventional cellulose flat membrane (see Figure 4 ).

[0039] Examples 3-6 The mass percentage of crosslinking agent in the casting solution was 1 wt%, 2 wt%, 4 wt%, and 5 wt%, respectively, and the other conditions were the same as in Example 1. The results are shown in Table 3 and Figure 5 .

[0040] Table 3 The results show that as the mass percentage of crosslinking agent increases, the molecular weight cut-off of the hollow fiber membrane decreases, and when the mass percentage of crosslinking agent in the casting solution is 1 wt%, the permeation flux of the hollow fiber membrane is the largest (see Figure 5 ).

[0041] Examples 7-10 The mass percentage of photoinitiator in the casting solution was 0.5 wt%, 1 wt%, 3 wt%, 4 wt%, respectively, and the rest of the conditions were the same as in Example 1. The results are shown in Table 4 and Figure 6 .

[0042] Table 4 The results show that, with the increase of the mass percentage of photoinitiator, the molecular weight cut-off of the hollow fiber membrane decreases, and when the mass percentage of photoinitiator in the casting solution is 3 wt%, the permeate flux of the hollow fiber membrane is the largest (see Figure 6 ).

[0043] Examples 11-14 The ultraviolet light intensity of the ultraviolet light irradiation system was 500 W / m 2 , 1000 W / m 2 , 3000 W / m 2 , 4000 W / m 2 , respectively, and the rest of the conditions were the same as in Example 1. The results are shown in Table 5 and Figure 7 .

[0044] Table 5 The results show that, with the increase of the ultraviolet light intensity, the molecular weight cut-off of the hollow fiber membrane decreases, and when the ultraviolet light intensity is 1000 W / m 2 , the permeate flux of the hollow fiber membrane is the largest (see Figure 7 ).

[0045] Examples 15-18 The ultraviolet light intensity of the ultraviolet light irradiation system was 500 W / m 2 , 1000 W / m 2 , 2000 W / m 2 , 2500 W / m 2 , respectively, and the rest of the conditions were the same as in Example 3. The results are shown in Table 6 and Figure 8 .

[0046] Table 6 The results show that, with the increase of the ultraviolet light intensity, the molecular weight cut-off of the hollow fiber membrane decreases, and when the ultraviolet light intensity is 500 W / m 2 , the permeate flux of the hollow fiber membrane is the largest (see Figure 8 ).

Claims

1. A method for preparing polymer films based on solvent in-situ functionalization enhancement, characterized in that: The method includes the following steps: Step (1): Under preset temperature conditions, add the raw materials to the polymerizable solvent and then stir to obtain a homogeneous casting solution; Step (2): Add crosslinking agent and photoinitiator to the homogeneous casting solution respectively. After the crosslinking agent and photoinitiator are dissolved, centrifuge to remove air bubbles, thereby obtaining a homogeneous casting solution. Step (3): Proceed according to one of the following two polymer film preparation processes: The first preparation method S1: The homogeneous casting mixture obtained in step (2) is used to prepare a solvent-in-situ functionalized hollow fiber composite membrane in a constant temperature circulating coagulation bath equipped with an ultraviolet light system using a dry-wet spinning process. The second preparation method S2: The homogeneous casting mixture obtained in step (2) is applied to a glass substrate using a scraper, and then a solvent-functionalized and enhanced flat composite film is prepared in a constant temperature circulating coagulation bath equipped with an ultraviolet light system.

2. The method for preparing a polymer film based on in-situ solvent functionalization enhancement according to claim 1, characterized in that, The specific steps (1) are as follows: Under a preset temperature of 0–90°C, 5–15 wt% of raw materials, accounting for a mass ratio of the polymerizable solvent, are added to the polymerizable solvent and stirred at a speed of 200–1000 rpm for 1–48 hours to obtain a homogeneous casting solution.

3. The method for preparing a polymer film based on in-situ solvent functionalization enhancement according to claim 2, characterized in that: The raw materials in step (1) are one or more combinations of cellulose and its derivatives, polyethersulfone, polytetrafluoroethylene, polyvinylidene fluoride, polyamine oxime, polyacrylonitrile, polylactic acid, polymethyl methacrylate and polystyrene. The polymerizable solvent in step (1) is one or a combination of ionic liquid, eutectic solvent, N-vinylpyrrolidone, hydroxyethyl methacrylate, acrylic acid, acrylamide and methyl methacrylate.

4. The method for preparing a polymer film based on solvent in-situ functionalization enhancement according to claim 1, characterized in that, Step (2) specifically involves: A certain amount of crosslinking agent and photoinitiator are added to the homogeneous casting solution, and the mixture is stirred at 200-1000 rpm for 0.5-5 hours to dissolve the crosslinking agent and photoinitiator. Then, the mixture is centrifuged at 3000-8000 rpm for 5-20 minutes to remove air bubbles from the solution containing the crosslinking agent, photoinitiator and homogeneous casting solution, thus obtaining a homogeneous casting solution. The crosslinking agent accounts for 0.5–15 wt% of the homogeneous casting solution by mass, and the photoinitiator accounts for 0.5–15 wt% of the homogeneous casting solution by mass.

5. The method for preparing a polymer film based on solvent in-situ functionalization enhancement according to claim 4, characterized in that: The crosslinking agent in step (2) is one or a combination of N,N′-methylenebisacrylamide, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, pentaerythritol tetraacrylate and trimethylolpropane triacrylate; The photoinitiator in step (2) is one or a combination of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,2-dimethoxy-2-phenylacetophenone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide and benzotriazole.

6. The method for preparing a polymer film based on solvent in-situ functionalization enhancement according to claim 1, characterized in that, The specific steps (3) are as follows: The first preparation method S1 is as follows: the homogeneous casting mixture obtained in step (2) is placed in a nitrogen pressurization system, so that the homogeneous casting mixture reacts with air and core fluid at 0 to 90°C to obtain nascent fibers. The nascent fibers enter a constant temperature circulating coagulation bath equipped with an ultraviolet irradiation system at a traction speed of 0.1 to 100 m / min. Then, they are immersed in water to separate and solidify the nascent fiber phases. After drying, a solvent-in-situ functionalized and enhanced hollow fiber composite membrane is obtained. The second preparation method S2 is as follows: the homogeneous casting mixture obtained in step (2) is scraped onto a glass substrate using a scraper, and then immersed in a constant temperature circulating coagulation bath equipped with an ultraviolet light irradiation system for preliminary curing. After 5 to 120 seconds, it is taken out, immersed in water for phase separation and curing, and then dried to obtain a solvent-in-situ functionalized enhanced flat composite film.

7. The method for preparing a polymer film based on solvent in-situ functionalization enhancement according to claim 6, characterized in that: The core fluid in step S1 is one or a combination of deionized water, ethanol, acetone, dimethyl sulfoxide, N,N-dimethylformamide and calcium chloride aqueous solution. The coagulation bath in steps S1 and S2 is one or a combination of deionized water, ethanol, acetone, dimethyl sulfoxide, N,N-dimethylformamide and calcium chloride aqueous solution. The drying methods in steps S1 and S2 are one or more combinations of vacuum oven drying, atmospheric pressure oven drying, room temperature drying, freeze drying, and supercritical drying.

8. The method for preparing a polymer film based on solvent in-situ functionalization enhancement according to claim 6, characterized in that: In step S1, the pressure range of the nitrogen pressurization system is 0.1~8 MPa. In steps S1 and S2, the ultraviolet light intensity range of the ultraviolet irradiation system is 500~10000 W / m. 2 The temperature range of the coagulation bath is 0~60 ℃.

9. A polymer film enhanced by in-situ solvent functionalization, characterized in that, It is prepared by any of the preparation methods described in claims 1-8.

10. An application of the polymer film based on solvent in-situ functionalization enhancement as described in claim 9, characterized in that: Applications in gas separation, wastewater treatment, protein separation, food processing, antibiotic purification, virus filtration, and precious metal recovery.

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