Aperture-adjustable brominated polyaryl sulfone ultrafiltration membrane and preparation method thereof

Abstract

The invention belongs to the technical field of separation membrane preparation, and particularly relates to an aperture-adjustable brominated polyaryl sulfone ultrafiltration membrane and a preparation method thereof. The preparation method comprises the following steps: forming a membrane from a membrane casting solution, and standing in air for air bath; and finally, immersing in a coagulating bath for phase inversion to obtain the brominated polyaryl sulfone ultrafiltration membrane with adjustable aperture. The membrane material comprises one or more of brominated polyaryl sulfone copolymers, the good solvent comprises a volatile organic solvent and a non-volatile organic solvent, the volume ratio of the non-volatile organic solvent to the volatile organic solvent is 1: 0.1-1: 10, and the air bath time is 1-120 s. The brominated polyaryl sulfone ultrafiltration membrane is prepared by a non-solvent induced phase inversion method, the preparation method is simple and easy to implement and low in cost, and has the characteristics of large-scale expansion and easy popularization, and the brominated polyaryl sulfone ultrafiltration membrane prepared by the method has the advantages of high flux and stable chemical performance, and can be widely applied to the fields of biology, medicine, food, water treatment and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of separation membrane preparation, and particularly relates to a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size and a preparation method thereof. Background Art

[0002] Polyarylsulfone polymers, such as polysulfone and polyethersulfone, are widely used as raw materials for polymer membranes (such as dialysis membranes or ultrafiltration membranes) due to their mechanical properties, chemical stability, and thermal stability. These polymer membranes are used in separation processes in medical applications, food technology, biotechnology, the pharmaceutical industry, and water treatment.

[0003] However, the pore size of traditional polyarylsulfone separation membranes is above 20 nm, which makes it difficult to effectively regulate the pore size range directly through phase inversion methods. It is also difficult to effectively retain low molecular weight materials, especially materials in the range of 1 to 3 kDa.

[0004] Related art provides an ultrafiltration membrane and a method for adjusting its pore size. The method involves immersing the membrane in a predetermined concentration of a moisturizer solution and then drying it based on drying parameters to obtain a pore-adjusted ultrafiltration membrane. However, this method is complex and difficult to control, making it difficult to accurately and effectively adjust the pore size of the ultrafiltration membrane. Summary of the Invention

[0005] The present invention aims to provide a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size and a preparation method thereof. The preparation method provided by the present invention can obtain a brominated polyaryl sulfone ultrafiltration membrane with a desired pore size, has excellent permeability and chemical stability, and can be widely used in biological and medical separation and purification and water treatment processes.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size, comprising the following steps:

[0008] The casting liquid is formed into a film, and then allowed to stand in the air for an air bath; finally, it is immersed in a coagulation bath for phase inversion to obtain the brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size; the casting liquid includes a membrane material, a good solvent and a water-soluble porogen, the membrane material includes one or more brominated polyaryl sulfone copolymers, the good solvent includes a volatile organic solvent and a non-volatile organic solvent, the boiling point of the volatile organic solvent is lower than the boiling point of the non-volatile organic solvent, the volume ratio of the non-volatile organic solvent to the volatile organic solvent is 1:0.1 to 1:10, the air bath time is 1 to 120 seconds, and the coagulation bath contains water.

[0009] Preferably, the volatile organic solvent includes one or more of acetone, tetrahydrofuran, 1,2-dichloroethane, 1,4-dioxane, ethyl acetate and methyl acetate.

[0010] Preferably, the low-volatile organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane and tetramethyl sulfoxide.

[0011] Preferably, the water-soluble porogen comprises a water-soluble polymer and / or an inorganic chloride salt;

[0012] The mass content of the water-soluble porogen in the casting solution is 0.5-20 wt %.

[0013] Preferably, the water-soluble polymer comprises one or more of polyvinyl pyrrolidone, polyethylene oxide, polypropylene oxide and polyethylene glycol; or the water-soluble polymer comprises one or more of a copolymer of at least two of polyvinyl pyrrolidone, polyethylene oxide, polypropylene oxide and polyethylene glycol;

[0014] The inorganic chloride salt includes one or more of lithium chloride, potassium chloride, sodium chloride and zinc chloride.

[0015] Preferably, the mass content of the membrane material in the casting solution is 10-30%.

[0016] Preferably, the preparation method of the brominated polyaryl sulfone copolymer comprises the following steps:

[0017] Mixing bis(4-fluorophenyl)sulfone, bis(4-hydroxyphenyl)sulfone, a methyl-containing monomer, a deacidifying agent, and an organic solvent to obtain a mixed solution; dehydrating the mixed solution and then performing a polymerization reaction to obtain a methylated random polyarylsulfone polymer;

[0018] The methylated random polyarylsulfone polymer, a brominating agent, an initiator and an organic solvent are mixed to carry out a bromination reaction to obtain the brominated polyarylsulfone copolymer.

[0019] Preferably, the methyl-containing monomer includes one or more of 3,3',5,5'-tetramethylbiphenyl-4,4'-diol, tetramethylbisphenol A, 2-methylhydroquinone and methylbisphenol fluorene, and the molar amount of the methyl-containing monomer accounts for 10 to 60% of the total molar amount of the bis(4-fluorophenyl)sulfone, bis(4-hydroxyphenyl)sulfone and the methyl-containing monomer; the deacidification agent is an alkali metal carbonate, the dehydration temperature is 120 to 150° C., and the polymerization reaction temperature is 160 to 180° C.;

[0020] The brominating agent is N-bromosuccinimide, the initiator is azoisobutyronitrile, and the temperature of the bromination reaction is 75-85°C.

[0021] Preferably, the coagulation bath is water or a mixture of water and the non-volatile organic solvent.

[0022] The present invention provides a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size prepared by the preparation method described in the above technical solution.

[0023] The present invention provides a method for preparing a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size, comprising the following steps: forming a membrane from a casting solution, then allowing it to stand in air for an air bath; and finally immersing it in a coagulation bath for phase inversion to obtain the brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size; the casting solution comprises a membrane material, a good solvent, and a water-soluble porogen, the membrane material comprises one or more of a brominated polyaryl sulfone copolymer, the good solvent comprises a volatile organic solvent and a less volatile organic solvent, the boiling point of the volatile organic solvent is lower than the boiling point of the less volatile organic solvent, the volume ratio of the less volatile organic solvent to the volatile organic solvent is 1:0.1 to 1:10, the air bath time is 1 to 120 seconds, and the coagulation bath contains water. The preparation method provided by the present invention uses both a volatile organic solvent and a less volatile organic solvent as good solvents, and the membrane pores are controlled by adjusting the volume ratio of the two solvents and the air bath time to obtain brominated polyaryl sulfone ultrafiltration membranes with different molecular weight cut-offs. The preparation method provided by the present invention can obtain a brominated polyaryl sulfone ultrafiltration membrane with a controllable molecular weight cutoff within the range of 1 to 10 kDa. The present invention prepares the membrane by a non-solvent-induced phase transformation method, which is simple and easy to implement, low in cost, and has the characteristics of scalability and easy promotion. The brominated polyaryl sulfone ultrafiltration membrane prepared by the present invention has the advantages of high flux and stable chemical properties, and can be widely used in the fields of biology, medicine, food, water treatment, etc.

[0024] At the same time, the membrane material used in the present invention includes one or more brominated polyaryl sulfone copolymers. In the prepared brominated polyaryl sulfone ultrafiltration membrane, the bromine element as a reactive active site can not only provide a chemical pathway for further modification, but the halogen can also enhance the anti-pollution ability of the ultrafiltration membrane.

[0025] Furthermore, in the present invention, the mass content of the membrane material in the casting solution is 10 to 30% and the mass content of the water-soluble porogen in the casting solution is 0.5 to 20% by weight. The preparation method provided by the present invention simultaneously optimizes the contents of the membrane material and the water-soluble porogen in the casting solution, thereby more effectively regulating the pore size of the brominated polyaryl sulfone ultrafiltration membrane and achieving pore size adjustability of the brominated polyaryl sulfone ultrafiltration membrane.

[0026] The present invention provides a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size, prepared by the preparation method described in the above technical solution. The brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size provided by the present invention has a multilayer structure, comprising a finger-shaped pore support layer, a sponge pore transition layer, and a dense separation layer stacked in sequence. The multilayer structure of the brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size provided by the present invention is formed according to the following principle: during an air bath, the volatile organic solvent evaporates, causing a polymer phase to aggregate on the surface along with the volatile organic solvent to form a polymer-rich phase, making the membrane surface dense. The membrane is then immersed in a coagulation bath, where the casting liquid undergoes a phase transformation, i.e., from a liquid phase to a solid phase. During the phase inversion process, the water-soluble porogen will dissolve in the coagulation bath and then diffuse from the casting liquid into the coagulation bath; at the same time, due to the concentration difference, the good solvent in the membrane diffuses into the coagulation bath, and the water in the coagulation bath will also diffuse into the membrane. Due to the diffusion of solvent-non-solvent, a delayed phase inversion occurs in the coagulation bath, so the membrane surface is a dense separation layer structure, and a transition layer of sponge pore structure is formed under the surface; and a support layer of finger-like pore structure is formed synchronously in the membrane. This three-layer structure is formed synchronously in the coagulation bath, and is the result of the interaction between solvent evaporation-induced phase inversion and non-solvent-induced phase inversion. The brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size provided by the present invention forms a three-layer structure, which has the advantages of high flux and stable chemical properties, and can be widely used in biology, medicine, food, water treatment and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an electron microscope image of the brominated polyaryl sulfone ultrafiltration membrane prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size, comprising the following steps:

[0029] The casting liquid is formed into a film, and then allowed to stand in the air for an air bath; finally, it is immersed in a coagulation bath for phase inversion to obtain the brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size; the casting liquid includes a membrane material, a good solvent and a water-soluble porogen, the membrane material includes one or more brominated polyaryl sulfone copolymers, the good solvent includes a volatile organic solvent and a non-volatile organic solvent, the boiling point of the volatile organic solvent is lower than the boiling point of the non-volatile organic solvent, the volume ratio of the non-volatile organic solvent to the volatile organic solvent is 1:0.1 to 1:10, the air bath time is 1 to 120 seconds, and the coagulation bath contains water.

[0030] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0031] In the present invention, the membrane material is preferably one or more of brominated polyaryl sulfone copolymers.

[0032] In the present invention, the preparation method of the brominated polyaryl sulfone copolymer preferably comprises the following steps:

[0033] Mixing bis(4-fluorophenyl)sulfone, bis(4-hydroxyphenyl)sulfone, a methyl-containing monomer, a deacidifying agent, and an organic solvent to obtain a mixed solution; dehydrating the mixed solution and then performing a polymerization reaction to obtain a methylated random polyarylsulfone polymer;

[0034] The methylated random polyarylsulfone polymer, a brominating agent, an initiator and an organic solvent are mixed to carry out a bromination reaction to obtain the brominated polyarylsulfone copolymer.

[0035] The present invention comprises mixing bis(4-fluorophenyl)sulfone, bis(4-hydroxyphenyl)sulfone, a methyl-containing monomer, a deacidifying agent, and an organic solvent to obtain a mixed solution; the mixed solution is dehydrated and then subjected to a polymerization reaction to obtain a methylated random polyarylsulfone polymer. In the present invention, the methyl-containing monomer preferably includes 3,3',5,5'-tetramethylbiphenyl-4,4'-diol and / or other bisphenol monomers containing a benzyl ring methyl group, and more preferably includes one or more of 3,3',5,5'-tetramethylbiphenyl-4,4'-diol, tetramethylbisphenol A, 2-methylhydroquinone, and methylbisphenol fluorene. In embodiments, the deacidifying agent may be 3,3',5,5'-tetramethylbiphenyl-4,4'-diol. The deacidifying agent is preferably an alkali metal carbonate, more preferably potassium carbonate, and in embodiments, anhydrous potassium carbonate. The molar amount of the methyl-containing monomer is preferably 10-60%, more preferably 20-40%, of the total molar amount of the bis(4-fluorophenyl)sulfone, bis(4-hydroxyphenyl)sulfone, and methyl-containing monomer. In an embodiment, the molar ratio of bis(4-fluorophenyl)sulfone to bis(4-hydroxyphenyl)sulfone is 2.5:1. The molar ratio of bis(4-fluorophenyl)sulfone to the methyl-containing monomer is 5:3. The molar ratio of bis(4-fluorophenyl)sulfone to the deacidifying agent is 1:1.05. The organic solvent preferably comprises N-methylpyrrolidone (NMP) and toluene. In an embodiment, the volume ratio of NMP to toluene is preferably 2:1. The mixing preferably comprises the following steps: in a nitrogen atmosphere, sequentially adding bis(4-fluorophenyl)sulfone, bis(4-hydroxyphenyl)sulfone, and the methyl-containing monomer to the organic solvent, stirring and dissolving to obtain a premixed solution; and then adding the deacidifying agent to the premixed solution in a nitrogen atmosphere. In the present invention, the dehydration is carried out in a nitrogen atmosphere, the dehydration temperature is preferably 120-150°C, and the dehydration time is preferably 2-6 hours. The polymerization reaction is preferably carried out in a nitrogen atmosphere, the polymerization temperature is preferably 160-180°C, and the polymerization time is preferably 12-24 hours. After the polymerization reaction is completed, the temperature is lowered to room temperature to obtain a polymerization reaction system; the polymerization reaction system is mixed with a hydrochloric acid solution for precipitation to obtain a filamentous polymer product; the filamentous polymer product is washed with water and dried in sequence to obtain the methylated random polyarylsulfone polymer. In the present invention, the pH value of the hydrochloric acid solution is preferably 1 to 2. Deionized water is preferably used for washing. The drying is preferably vacuum drying, and the temperature of the vacuum drying is preferably 60 to 65°C. In the present invention, the methylated random polyarylsulfone polymer contains units containing methyl monomers. The molar content of the units containing methyl monomers in the methylated random polyarylsulfone polymer is 10 to 60%, more preferably 20 to 40%.

[0036] After obtaining the methylated random polyarylsulfone polymer, the present invention mixes the methylated random polyarylsulfone polymer, a brominating agent, an initiator and an organic solvent to carry out a bromination reaction to obtain the brominated polyarylsulfone copolymer. In the present invention, the brominating agent is preferably N-bromosuccinimide (NBS). The initiator is preferably azoisobutyronitrile (AIBN). The organic solvent is preferably 1,2-dichloroethane. The molar ratio of the brominating agent to the methylated random polyarylsulfone polymer is preferably 0.13 to 1.2:1, more preferably 1:1. The present invention preferably controls the degree of bromination of the methylated random polyarylsulfone polymer by controlling the molar ratio of the brominating agent to the methylated random polyarylsulfone polymer.

[0037] In an embodiment of the present invention, the mass ratio of the methylated random polyarylsulfone polymer to the brominating agent is preferably 40:28.8. The mass ratio of the methylated random polyarylsulfone polymer to the initiator is preferably 10:1. The bromination reaction is preferably carried out in a nitrogen atmosphere at a temperature of 75-85°C. The bromination reaction is preferably carried out under reflux conditions for a duration of 12-24 hours. After the bromination reaction is completed, the temperature is cooled to room temperature to obtain a bromination reaction system; the bromination reaction system is subjected to solid-liquid separation to obtain a liquid product; the liquid product is mixed with ethanol and subjected to alcohol precipitation to obtain a solid product; and the solid product is dried to obtain the brominated polyarylsulfone copolymer. In the present invention, the solid-liquid separation is preferably performed by filtration. The ethanol is preferably anhydrous ethanol. The volume ratio of the liquid product to ethanol is preferably 1:1. The alcohol precipitation preferably comprises: adding the liquid product to ethanol, stirring and mixing until the solid product is completely precipitated, and then maintaining the mixture at this temperature with stirring to obtain an alcohol precipitation reaction solution; and solid-liquid separation of the alcohol precipitation reaction solution to obtain a solid product. The temperature of the ethanol used for the alcohol precipitation is preferably 60-80°C, and the time of the heat preservation and stirring is preferably 1.5-2 hours. The specific method of solid-liquid separation of the alcohol precipitation reaction liquid is preferably filtration. The drying is preferably vacuum drying, and the temperature of the vacuum drying is preferably 60-65°C; and the time is preferably 24-32 hours.

[0038] In the present invention, the mass content of the membrane material in the casting solution is preferably 10 to 30%, more preferably 15 to 25%.

[0039] In the present invention, the volatile organic solvent is preferably an organic solvent that can volatilize at room temperature (20 to 30° C.).

[0040] In the present invention, the volatile organic solvent preferably includes one or more of acetone, tetrahydrofuran (THF), 1,2-dichloroethane, 1,4-dioxane, ethyl acetate and methyl acetate, more preferably THF or 1,4-dioxane.

[0041] In the present invention, the low-volatile organic solvent includes one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane (Ts) and tetramethyl sulfoxide, more preferably NMP.

[0042] In the present invention, the volume ratio of the less volatile organic solvent to the volatile organic solvent in the casting solution is preferably 1:0.1 to 1:10, more preferably 1:1 to 8, and even more preferably 1:2 to 6.

[0043] In the present invention, the water-soluble porogen preferably includes a water-soluble polymer and / or an inorganic chloride salt. The water-soluble polymer preferably includes one or more of polyvinyl pyrrolidone (PVP), polyethylene oxide, polypropylene oxide, and polyethylene glycol. Alternatively, the water-soluble polymer preferably includes one or more copolymers of at least two of polyvinyl pyrrolidone, polyethylene oxide, polypropylene oxide, and polyethylene glycol. The water-soluble polymer is more preferably PVP or polyethylene glycol. The inorganic chloride salt preferably includes one or more of lithium chloride, potassium chloride, sodium chloride, and zinc chloride. In the present invention, the PVP is preferably PVP-K30. The molecular weight (Mw) of the polyethylene glycol is preferably 400 g / mol.

[0044] In the present invention, the mass content of the water-soluble porogen in the casting solution is preferably 0.5 to 20 wt %, more preferably 1 to 16 wt %, and even more preferably 5 to 12 wt %.

[0045] In the present invention, the method for preparing the casting solution preferably includes: premixing a water-soluble porogen with a good solvent to obtain a premixed solution; heating the premixed solution and the membrane material to dissolve the premixed solution to obtain a mixed solution; and sequentially allowing the mixed solution to stand at room temperature and degassing the solution to obtain the casting solution. The dissolution temperature is preferably 55-60°C. The present invention has no particular requirements for the specific method of degassing.

[0046] In the present invention, the film forming preferably comprises the following steps: casting the film casting solution on a base material, and then scraping the film with a doctor blade. In the present invention, the base material is preferably a non-woven fabric.

[0047] In the present invention, the time of the air bath is preferably 5 to 120 seconds, more preferably 5 to 60 seconds. The present invention has no special requirements for the relative humidity of the air bath, and a relative humidity of 30 to 60% can be used.

[0048] In the present invention, the coagulation bath is water or a mixture of water and the non-volatile organic solvent, more preferably water. The water is preferably deionized water. The mixture of water and the non-volatile organic solvent is preferably a mixture of water and NMP, and the volume content of water in the mixture is preferably 30-35%. The temperature of the coagulation bath is preferably room temperature (20-30°C), more preferably 25°C. The time for the Xining phase transformation in the coagulation bath is preferably ≤10min. After the coagulation bath ends, an initial brominated polyaryl sulfone ultrafiltration membrane is obtained. The present invention preferably further comprises immersing the initial brominated polyaryl sulfone ultrafiltration membrane in water to remove residual solvent in the membrane to obtain a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size. The water is preferably deionized water. The immersion temperature is preferably room temperature, and the immersion time is preferably 12-24h.

[0049] The pore-adjustable brominated polyaryl sulfone ultrafiltration membrane prepared by the present invention comprises, from bottom to top, a support layer, a transition layer, and a dense separation layer stacked in sequence. The support layer has a finger-like pore structure, and the transition layer has a sponge pore structure. The support layer is the surface layer formed on the side of the brominated polyaryl sulfone ultrafiltration membrane that contacts the substrate during preparation. The pore size of the dense separation layer is preferably ≤10 nm.

[0050] The present invention provides a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size prepared by the preparation method described in the above technical solution.

[0051] The present invention provides a method for preparing a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size. Specifically, brominated polyaryl sulfone ultrafiltration membranes with different molecular weight cutoffs are prepared by regulating the volume ratio of a volatile organic solvent to a non-volatile organic solvent in a good solvent and the air bath time during the membrane preparation process. The brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size provided by the present invention is prepared by non-solvent-induced phase transformation and has a multilayer structure comprising a finger-like pore support layer, a sponge pore transition layer, and an extremely thin and dense separation layer. The molecular weight cutoff of the brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size provided by the present invention is preferably 1 to 10 kDa. The molecular weight cutoff of the brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size provided by the present invention is effectively controllable within the range of 1 to 10 kDa. The preparation method provided by the present invention is simple, easy to implement, low-cost, scalable, and easily disseminated. The resulting brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size has high flux and good chemical stability, and can be widely used in the fields of biology, medicine, food, water treatment, etc.

[0052] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] The membrane material used in the following examples and comparative examples is a brominated polyarylsulfone copolymer, named PES-Br-20.

[0054] The preparation method of PES-Br-20 is as follows:

[0055] To a 1L three-necked flask, add 560mL of NMP and 280mL of toluene. N2 was purged three times. Then, 70.0g of bis(4-fluorophenyl)sulfone, 41.34g of bis(4-hydroxyphenyl)sulfone, and 26.68g of 3,3',5,5'-tetramethylbiphenyl-4,4'-diol were added sequentially to the flask, stirred to dissolve, and N2 was purged three times. 39.95g of anhydrous potassium carbonate was added, a water separator was installed, and N2 was purged three times. The system was heated to 140°C and maintained for 4 hours to remove water from the reaction system. After the water was removed, the system was heated to 170°C to remove toluene from the system, and then maintained at 170°C for 12 hours. After the reaction is completed, the temperature is lowered to room temperature, and the system is placed in a hydrochloric acid aqueous solution with a pH of 2 to precipitate a filamentous polymer. The polymer is rinsed with deionized water several times to remove the residual solvent and vacuum dried at 65°C for 24 hours to obtain a methylated (-CH3) random polyarylsulfone polymer, named PES-CH-20.

[0056] To a 1L three-necked flask, add 800mL of 1,2-dichloroethane and displace the atmosphere with nitrogen three times. Then, add 40g of PES-CH-20 and stir to dissolve. Then, add 28.8g of NBS and 4.0g of AIBN, stirring to dissolve. Displace the atmosphere with nitrogen three times, then heat to 80°C and reflux for 12 hours. After the reaction, cool to room temperature and filter to remove insoluble impurities. The reaction mixture is then slowly added dropwise to an equal volume of anhydrous ethanol at 60°C with stirring, allowing the brominated polymer to precipitate. After complete precipitation, stir at this temperature for 2 hours, filter, and dry the solid at 65°C under vacuum for 24 hours to obtain a brominated polyarylsulfone copolymer, designated PES-Br-20.

[0057] Example 1:

[0058] PVP (K30) was placed in a co-solvent of NMP and THF, stirred and dissolved at room temperature, PES-Br-20 was added, and the temperature was raised to 60°C to dissolve to obtain a brown transparent solution. The solution was allowed to stand and degassed at room temperature to obtain a clear, uniform and stable casting solution, wherein the volume ratio of NMP:THF was 1:1, the mass content of PVP (K30) was 8%, and the mass content of PES-Br-20 was 20%.

[0059] The casting solution was cast onto a clean non-woven fabric. A doctor blade with a defined gap (150 μm) was used to scrape the membrane at a constant speed. After a 30-second air bath, the membrane was quickly immersed in a 25°C deionized water coagulation bath to complete phase inversion. Finally, the membrane was immersed in deionized water for at least 12 hours to ensure complete removal of any residual solvent from the membrane pores. This resulted in a brominated polyarylsulfone ultrafiltration membrane.

[0060] The brominated polyarylsulfone ultrafiltration membrane prepared in this example was tested and the pure water flux of the membrane was 73.58 L·m 2 ·h -1 bar -1 The retention rate of 10kDa PEG molecules is 94.58%.

[0061] Example 2:

[0062] PEG (Mw = 400 g / mol) was placed in a co-solvent of Ts and THF, stirred and dissolved at room temperature, PES-Br-20 was added, and the temperature was raised to 60°C to dissolve to obtain a brown transparent solution. The solution was allowed to stand at room temperature and degassed to obtain a clear, uniform, and stable casting solution, wherein the volume ratio of Ts:THF was 2:1, the mass content of PEG (Mw = 400 g / mol) was 8%, and the mass content of PES-Br-20 was 18%.

[0063] The casting solution was cast onto a clean non-woven fabric. The membrane was scraped at a constant speed using a doctor blade with a certain gap. After a 10-second air bath, the membrane was quickly immersed in a 25°C deionized water coagulation bath to complete the phase inversion. Finally, the membrane was soaked in deionized water for at least 12 hours to ensure that any residual solvent in the membrane pores was completely removed. This resulted in a brominated polyaryl sulfone ultrafiltration membrane.

[0064] The brominated polyarylsulfone ultrafiltration membrane prepared in this example was tested to have a pure water flux of 51.13 L·m 2 ·h -1 bar -1 The retention rate for 10 kDa PEG molecules is 95.32%.

[0065] Example 3:

[0066] PVP (K30) was placed in a co-solvent of NMP and THF, stirred and dissolved at room temperature, PES-Br-20 was added, and the temperature was raised to 60°C to dissolve to obtain a brown transparent solution. The solution was allowed to stand and degassed at room temperature to obtain a clear, uniform and stable casting solution, wherein the volume ratio of NMP:THF was 1:1.75, the mass content of PVP (K30) was 8%, and the mass content of PES-Br-20 was 22%.

[0067] The casting solution is cast onto a clean non-woven fabric. The membrane is scraped at a constant speed using a doctor blade with a certain gap. After a 30-second air bath, the membrane is quickly immersed in a 25°C deionized water coagulation bath to complete the phase inversion. Finally, the scraped membrane is soaked in deionized water for at least 12 hours to ensure that any residual solvent in the membrane pores is completely removed. This results in a brominated polyaryl sulfone ultrafiltration membrane.

[0068] The pure water flux of the tested membrane in this example is 12.03 L·m 2 ·h-1 bar -1 The retention rate of 2kDa PEG molecules is 90.72%.

[0069] Example 4:

[0070] PVP (K30) was placed in a co-solvent of NMP and THF, stirred and dissolved at room temperature, PES-Br-20 was added, and the temperature was raised to 60°C to dissolve to obtain a brown transparent solution. The solution was allowed to stand and degassed at room temperature to obtain a clear, uniform and stable casting solution, wherein the volume ratio of NMP:THF was 1:2.25, the mass content of PVP (K30) was 4%, and the mass content of PES-Br-20 was 20%.

[0071] The casting solution was cast onto a clean non-woven fabric. The membrane was scraped at a constant speed using a doctor blade with a certain gap. After standing in an air bath for 45 seconds, the membrane was quickly immersed in a 25°C deionized water coagulation bath to complete the phase inversion. Finally, the scraped membrane was soaked in deionized water for at least 12 hours to ensure that any residual solvent in the membrane pores was completely removed, thus obtaining a brominated polyaryl sulfone ultrafiltration membrane.

[0072] The brominated polyarylsulfone ultrafiltration membrane prepared in this example was tested and the pure water flux of the membrane was 11.21 L·m 2 ·h -1 bar -1 The retention rate of 2kDa PEG molecules was 90.37%.

[0073] Figure 1 This is an electron microscope image of the brominated polyaryl sulfone ultrafiltration membrane prepared in Example 4, wherein: Figure 1 a is the surface electron microscope image of the film prepared in Example 4 (magnification is 50kx) Figure 1 b is a cross-sectional electron microscope image of the membrane prepared in Example 4 (magnification is 1kx), Figure 1 c is a further magnified electron microscope image of the dense separation layer in the cross section of the membrane prepared in Example 4 (magnification is 20kx), Figure 1 d in the figure is a further electron microscope image of the porous support layer in the cross section of the membrane prepared in Example 4 (magnification is 50kx).

[0074] Depend on Figure 1 It can be seen that the brominated polyaryl sulfone ultrafiltration membrane prepared in Example 4 has a three-layer structure, which includes a finger-like pore support layer, a sponge pore transition layer and a dense separation layer stacked in sequence, wherein the dense separation layer is an extremely thin layer structure.

[0075] Comparative Example 1:

[0076] 8% PVP (K30) was placed in a co-solvent of NMP and THF (with a volume ratio of 1:2) and the PVP (K30) content was 8%. Stirring was performed at room temperature to dissolve the mixture. Then, 20 wt% commercial PES (brand E6020 P) was added and the mixture was heated to 60°C for dissolution. However, the PES was insoluble, and membrane formation was unsuccessful.

[0077] Comparative Example 2:

[0078] PVP (K30) was placed in NMP solvent, stirred and dissolved at room temperature, PES-Br-20 was added, and the temperature was raised to 60°C to dissolve to obtain a brown transparent solution. The solution was allowed to stand at room temperature and degassed to obtain a clear, uniform and stable casting solution, in which the mass content of PVP (K30) was 12% and the mass content of PES-Br-20 was 20%.

[0079] The casting solution was cast onto a clean non-woven fabric. The membrane was scraped at a constant speed using a doctor blade with a certain gap. After a 10-second air bath, the membrane was quickly immersed in a 25°C deionized water coagulation bath to complete the phase inversion. Finally, the membrane was soaked in deionized water for at least 12 hours to ensure that any residual solvent in the membrane pores was completely removed. This resulted in a brominated polyaryl sulfone ultrafiltration membrane.

[0080] The brominated polyarylsulfone ultrafiltration membrane prepared in this comparative example was tested and the pure water flux of the membrane was 132.18 L·m 2 ·h -1 bar -1 The retention rate for 10 kDa PEG molecules was 28.07%.

[0081] Comparative Example 3:

[0082] PES-Br-20 was placed in a co-solvent of NMP and THF, heated to 60°C to dissolve, obtaining a brown transparent solution. The solution was allowed to stand at room temperature and degassed to obtain a clear, uniform, and stable casting solution, wherein the volume ratio of NMP to THF was 1:2 and the mass content of PES-Br-20 was 20%.

[0083] The casting solution was cast onto a clean non-woven fabric. The membrane was scraped at a constant speed using a doctor blade with a defined scraping gap. After a 5-second air bath, the membrane was quickly immersed in a 25°C deionized water coagulation bath to complete phase inversion. The membrane was then immersed in deionized water for at least 12 hours to ensure complete removal of any residual solvent from the membrane pores. This resulted in a brominated polyaryl sulfone ultrafiltration membrane. Testing of the brominated polyaryl sulfone ultrafiltration membrane prepared in this comparative example revealed no pure water flux.

[0084] The above examples demonstrate that the present invention provides a method for preparing a high-throughput, pore-adjustable, dense brominated polyaryl sulfone ultrafiltration membrane. The membrane material used in the preparation method provided herein has good solubility in volatile organic solvents. The membrane pore size is regulated by adjusting the volume ratio of the volatile organic solvent to the less volatile organic solvent and the air bath time to produce a dense brominated polyaryl sulfone ultrafiltration membrane with a desired pore size. The preparation method provided by the present invention enables the precise customization of separation membranes for materials of varying separation sizes.

[0085] At the same time, the bromine in the membrane material used in the present invention as a reactive active site can not only provide a chemical pathway for further modification, but the halogen also enhances the anti-pollution ability of the membrane.

[0086] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size, characterized in that: The following steps are involved: The casting liquid is formed into a film, and then allowed to stand in the air for an air bath; finally, it is immersed in a coagulation bath for phase inversion to obtain the brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size; the casting liquid includes a membrane material, a good solvent and a water-soluble porogen, the membrane material includes one or more brominated polyaryl sulfone copolymers, the good solvent includes a volatile organic solvent and a non-volatile organic solvent, the boiling point of the volatile organic solvent is lower than the boiling point of the non-volatile organic solvent, the volume ratio of the non-volatile organic solvent to the volatile organic solvent is 1:0.1 to 1:10, the air bath time is 1 to 120 seconds, and the coagulation bath contains water.

2. The preparation method according to claim 1, characterized in that The volatile organic solvent includes one or more of acetone, tetrahydrofuran, 1,2-dichloroethane, 1,4-dioxane, ethyl acetate and methyl acetate.

3. The preparation method according to claim 1 or 2, characterized in that The low-volatile organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane and tetramethyl sulfoxide.

4. The preparation method according to claim 1, characterized in that The water-soluble porogen includes a water-soluble polymer and / or an inorganic chloride salt; The mass content of the water-soluble porogen in the casting solution is 0.5-20 wt %.

5. The preparation method according to claim 4, characterized in that The water-soluble polymer includes one or more of polyvinyl pyrrolidone, polyethylene oxide, polypropylene oxide and polyethylene glycol; or the water-soluble polymer includes one or more of a copolymer of at least two of polyvinyl pyrrolidone, polyethylene oxide, polypropylene oxide and polyethylene glycol; The inorganic chloride salt includes one or more of lithium chloride, potassium chloride, sodium chloride and zinc chloride.

6. The preparation method according to claim 1, characterized in that The mass content of the membrane material in the membrane casting solution is 10-30%.

7. The preparation method according to claim 1 or 6, characterized in that The preparation method of the brominated polyaryl sulfone copolymer comprises the following steps: Mixing bis(4-fluorophenyl)sulfone, bis(4-hydroxyphenyl)sulfone, a methyl-containing monomer, a deacidifying agent, and an organic solvent to obtain a mixed solution; dehydrating the mixed solution and then performing a polymerization reaction to obtain a methylated random polyarylsulfone polymer; The methylated random polyarylsulfone polymer, a brominating agent, an initiator and an organic solvent are mixed to carry out a bromination reaction to obtain the brominated polyarylsulfone copolymer.

8. The preparation method according to claim 7, characterized in that The methyl-containing monomer includes one or more of 3,3',5,5'-tetramethylbiphenyl-4,4'-diol, tetramethylbisphenol A, 2-methylhydroquinone and methylbisphenol fluorene, and the molar amount of the methyl-containing monomer accounts for 10-60% of the total molar amount of the bis(4-fluorophenyl)sulfone, bis(4-hydroxyphenyl)sulfone and the methyl-containing monomer; the deacidification agent is an alkali metal carbonate, the dehydration temperature is 120-150° C., and the polymerization reaction temperature is 160-180° C.; The brominating agent is N-bromosuccinimide, the initiator is azoisobutyronitrile, and the temperature of the bromination reaction is 75-85°C.

9. The preparation method according to claim 1, characterized in that The coagulation bath is water or a mixture of water and the non-volatile organic solvent.

10. A brominated polyaryl sulfone ultrafiltration membrane with adjustable pore size prepared by the preparation method according to any one of claims 1 to 9.

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