A modified polysulfone membrane and its preparation method

Abstract

The present invention provides a modified polysulfone membrane and a preparation method thereof. The present invention prepares a polysulfone ultrafiltration membrane with a dense hydrophilic surface and a loose hydrophobic interior by a one-step molding method. Due to the dense and hydrophilic surface, the membrane has excellent retention performance and anti-protein adsorption performance for large molecular glucose and proteins, thereby improving the anti-pollution performance of the membrane surface layer for proteins; the hydrophobicity of the internal channel reduces the adsorption of small molecular glucose that penetrates on the inner wall of the channel. In addition, the membrane obtained by the preparation method of the present invention has a significantly increased thickness of the hydrophilic layer and has excellent wear resistance. The modified polysulfone membrane of the present invention with a dense hydrophilic exterior and a loose hydrophobic interior has obvious advantages in the field of sugar-protein separation.

Description

Technical Field

[0001] The invention relates to a modified polysulfone membrane with high flux, anti-pollution and excellent wear resistance and a preparation method thereof, belonging to the technical field of membrane materials. Background Art

[0002] Dextran is a carbohydrate formed by multiple monosaccharide molecules linked together by glycosidic bonds, with the chemical formula (C6H 10 O5) n Dextran, with molecular weights ranging from a few hundred to several million kDa, offers advantages such as safety, non-toxicity, and excellent biocompatibility. Different molecular weights of dextran have different applications in related industries such as medicine, food, and biochemistry. Low-molecular-weight dextran is highly valued for its pharmaceutical applications. It is typically prepared by microbial fermentation of sucrose to a high molecular weight, followed by further decomposition. Traditional processes utilize hydrochloric acid hydrolysis followed by alcohol precipitation for fractional separation. This process is energy-intensive, results in significant equipment loss, low yields, and a wide product molecular weight distribution.

[0003] In recent years, biosynthesis through biological metabolic catalysis has attracted considerable attention. New biosynthesis-based processes allow the hydrolysis of low-molecular-weight dextran using corresponding enzymes, offering mild reaction conditions, rapid reaction rates, low energy consumption, and minimal pollution. However, separation and purification of the product present technical challenges due to its similar properties and molecular weight to the substance being separated. Currently, the main separation techniques used include extraction and membrane separation.

[0004] Membrane separation technology uses the different particle sizes of a mixture at the molecular level to achieve selective separation. It is a physical separation without any chemical or phase changes, and has attracted people's attention.

[0005] In a new process designed using membrane separation technology, an ultrafiltration membrane is used to retain enzyme proteins and large molecular weight dextran, which are then recycled to a bioreactor for reuse. Low molecular weight byproducts are also separated, resulting in low energy consumption, high yield, and a narrow product molecular weight distribution. This process uses this membrane as the research target, specifically to separate low molecular weight dextran (<8 kDa) from large molecular weight dextran (>8 kDa) and dextranase protein. The filtrate contains dextran of varying molecular weights, dextran protein, and some inorganic salts. The membrane must possess anti-fouling, corrosion resistance, and chemical stability. Therefore, the process uses a polysulfone-based membrane, which is chemically stable, heat-resistant, and resistant to acid and alkali corrosion. However, polysulfone-based materials have a low pure water flux, and contaminants easily adsorb and deposit on the surface and internal pores, degrading membrane performance. Therefore, modification of polysulfone membranes has become a research priority.

[0006] Currently, the commonly used methods for modifying polymer materials can be divided into co-modification and surface coating based on the interaction between the modifying substance and the membrane and the distribution position of the modifying substance in the membrane, and bulk modification and surface grafting based on chemical bonds. Co-modification is to mix the modifying substance and the membrane material in the casting solution and cast the membrane together. Surface coating is to adhere the modifying substance to the membrane surface through intermolecular interaction. There are problems such as poor compatibility between the modifying substance and the membrane material with different hydrophilic and hydrophobic properties and weak intermolecular interaction. In actual use, the modifying substance is easy to gradually dissolve or fall off. In bulk modification and surface grafting, the modifying substance and the membrane material are connected by chemical bonds and are not easily denatured. The difference is that bulk modification is to modify the membrane material before preparing the casting solution, and the overall hydrophilicity and hydrophobicity of the finished membrane are consistent; surface grafting is to modify the surface of the finished membrane and has no effect on the structure of the membrane itself.

[0007] Patent document 1 discloses a method for preparing a modified blood purification membrane, wherein the polymer is first modified by chloromethylation, and the first reactant is obtained by filtration, washing, and drying; the polymer is then dissolved for nucleophilic substitution, and the modified resin is obtained by filtration, washing, and drying, and finally dissolved to prepare a casting solution, and the membrane is cast by a non-solvent-induced phase inversion method. This method undergoes two steps of reaction in different systems and a casting solution of a third solvent system, and the prepared membrane is hydrophilically modified as a whole, and the surface and internal properties are the same. Patent document 2 discloses a method of preparing a casting solution using chloromethyl polysulfone, chloromethyl polyethersulfone or chloromethyl polyetheretherketone as the base membrane material, and using a non-solvent-induced phase inversion method to prepare a chloromethylated polymer membrane, and utilizing the nucleophilic substitution reaction between the chloromethyl group on the membrane surface and the amino-terminated polyether to graft the amino-terminated polyol to the polymer membrane surface, thereby preparing a polysulfone membrane with a hydrophilic surface and a hydrophobic interior. Patent Document 2 first modifies polysulfone resin to synthesize chloromethylated polysulfone, then replaces the solvent to prepare the casting solution to form a membrane, and then performs a grafting reaction on the surface of the finished membrane. This method undergoes chloromethylation in one solvent system, casting in a second solvent system, and surface reaction in a third solvent system. The surface and interior of the prepared membrane have different hydrophilic and hydrophobic properties.

[0008] The aforementioned two-step reaction modification patents all require at least two organic solvent systems and a purification step for the intermediate product, resulting in lengthy, complex, and difficult-to-control processes. Furthermore, in the dextran separation process employed, the separation of sugars and proteins occurs primarily in the dense layer. Improving the hydrophilicity of the membrane surface alone is insufficient to prevent protein contamination; the entire dense layer must be hydrophilic. Furthermore, the modified membrane described in Patent 2 undergoes hydrophilic modification only on the membrane surface, at an atomic level of approximately 0.1 to 0.2 nm, making it susceptible to wear during use. Furthermore, to prevent contamination from interactions between polymers and sugars within the finger-like pores as sugars pass through them, the pores must be hydrophobic. However, the relevant patents do not report structures in which the dense layer is hydrophilic and the finger-like pores are hydrophobic. How to modify the polysulfone material while simplifying the preparation process and more conveniently producing a high-throughput, anti-fouling polysulfone membrane has become a challenge for those skilled in the art.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: CN114177778A

[0012] Patent Document 2: CN113274896A Summary of the Invention

[0013] Problems to be solved by the invention

[0014] In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide a modified polysulfone membrane with high flux, excellent wear resistance and anti-fouling properties, and a preparation method thereof.

[0015] Solutions for solving problems

[0016] The present inventors conducted intensive research to solve the above-mentioned problems and found that by using the same solvent as both the polysulfone polymer modification reaction solvent and the casting solution solvent, and performing a side group reaction after coating and before curing in pure water, the side chain hydrophobic groups of the polysulfone polymer are converted into hydrophilic groups, thereby obtaining a modified polysulfone membrane with a hydrophilic exterior and a hydrophobic interior.

[0017] Furthermore, the present invention adopts a modification method of curing while reacting. The reaction layer is the curing layer, and the polymer has a certain degree of mobility. Compared with the modification after casting in the prior art, the method according to the present invention has high reaction activity and can be carried out under mild conditions. In addition, the thickness of the reaction layer can be controlled by controlling the length of time the casting liquid stagnates in the reaction liquid, so that the hydrophilic layer of the modified polysulfone membrane obtained has a certain thickness. The hydrophilic layer of the existing modified polysulfone membrane is usually only the thickness of one group on the surface, about 0.1 to 0.2 nm. The thickness of the hydrophilic dense layer in the modified polysulfone membrane of the present invention is 2 to 3 μm, which can significantly improve the wear resistance. The modified polysulfone membrane of the present invention has excellent wear resistance.

[0018] That is, the present invention is as follows.

[0019] [1]. A method for preparing a modified polysulfone membrane, wherein the preparation method comprises:

[0020] Step A: mixing a polysulfone polymer, a first solvent, and a first reactant to perform a graft reaction to obtain a first reaction solution;

[0021] Step B: adding a porogen to the first reaction solution and coating it into a liquid film;

[0022] Step C: placing the liquid film in a side group reaction liquid to carry out side group reaction and partially solidify; and

[0023] Step D: placing the membrane obtained in step C in water for complete solidification to obtain a modified polysulfone membrane;

[0024] Wherein, the first reactant comprises a chloroalkane compound, an acyl chloride compound or a chloromethyl ether compound,

[0025] The side group reaction solution comprises a second reactant,

[0026] The second reactant comprises a catalyst for a hydrolysis reaction, a catalyst for an aminolysis reaction, or a catalyst for an oxidation reaction.

[0027] [2] The preparation method according to [1], wherein the step A comprises:

[0028] Step A1: dissolving the polysulfone polymer in the first solvent; and

[0029] Step A2: adding the first reactant and the catalyst to the solution obtained in step A1 to carry out a grafting reaction to obtain a first reaction solution.

[0030] [3] The preparation method according to [1] or [2], wherein the step A, step A1 or step A2 satisfies at least one of the following characteristics (a) to (h):

[0031] (a) the weight average molecular weight of the polysulfone polymer is 40,000 to 120,000;

[0032] (b) the first solvent comprises a chlorine-containing low-boiling point organic solvent and a sulfone-based solvent;

[0033] The chlorine-containing low-boiling point organic solvent comprises dichloromethane or chloroform;

[0034] The sulfone solvent comprises sulfolane or dimethyl sulfoxide;

[0035] The mass ratio of the sulfone solvent to the chlorine-containing low-boiling-point organic solvent is 1:1 to 3:1;

[0036] (c) the mass ratio of the polysulfone polymer to the first solvent is 1:4 to 1:6;

[0037] (d) the first reactant comprises ethyl 4-chloroacetoacetate, ethyl 2-chloroacetoacetate, ethyl chlorooxalyl, benzyl chloromethyl ether, 1,1-dichloromethyl ether or chloromethyl ethyl ether;

[0038] (e) the catalyst comprises at least one member selected from the group consisting of tin tetrachloride, ferric chloride and aluminum chloride;

[0039] (f) the mass ratio of the polysulfone polymer to the catalyst is 100:1 to 500:1;

[0040] (g) the mass ratio of the polysulfone polymer to the first reactant is 1:1 to 4:1;

[0041] (h) The grafting reaction temperature is 10 to 60° C., and the grafting reaction time is 12 to 48 hours.

[0042] [4] The preparation method according to any one of [1] to [3], wherein the step B comprises:

[0043] Step B1: adding a porogen to the first reaction solution to obtain a casting solution; and

[0044] Step B2: applying the casting solution on a substrate to form a liquid film.

[0045] [5] The preparation method according to [4], wherein step B, step B1 or step B2 satisfies at least one of the following characteristics (i) to (j):

[0046] (i) the porogen comprises polyethylene glycol 200, polyethylene glycol 400 or polyethylene glycol 600;

[0047] (j) The mass ratio of the porogen to the polysulfone polymer is 1:3 to 1:6.

[0048] [6] The production method according to any one of [1] to [5], wherein the step C or step D satisfies at least one of the following characteristics (k) to (n):

[0049] (k) the pendant group reaction solution comprises a second reactant and a second solvent;

[0050] The second reactant comprises sodium hydroxide, dilute sulfuric acid or N-aminoethylpiperazine;

[0051] The second solvent comprises acetone, ethanol or water;

[0052] (1) the side group reaction solution is a sodium hydroxide aqueous solution saturated with acetone;

[0053] (m) The side group reaction time is 5 to 30 minutes;

[0054] (n) The curing time in water is 24 to 48 hours.

[0055] [7] The preparation method according to any one of [1] to [6], wherein the preparation method further comprises:

[0056] Step E: subjecting the polysulfone membrane obtained in step D to at least one of a water bath soak, an acid solution wash, and a pore preservation treatment;

[0057] Preferably, the step E satisfies at least one of the following characteristics (o) to (p):

[0058] (o) the acid solution is dilute sulfuric acid or dilute hydrochloric acid;

[0059] (p) The concentration of the acidic solution is 0.1 to 2M.

[0060] [8] A modified polysulfone membrane having an external hydrophilic and internal hydrophobic structure, wherein the modified polysulfone membrane comprises a lower layer and a dense layer located on the lower layer,

[0061] The dense layer is hydrophilic and has a thickness of 2 to 3 μm.

[0062] The lower layer has an internal finger-shaped pore structure and is hydrophobic.

[0063] [9] The modified polysulfone membrane according to [8], wherein the modified polysulfone membrane is obtained according to the preparation method described in any one of [1] to [7];

[0064] Preferably, the average pore size of the modified polysulfone membrane is 0.01 to 0.04 μm;

[0065] Preferably, the pure water flux of the modified polysulfone membrane is 50 to 150 L / m2 ·h·bar.

[0066]

[10] . A composite membrane comprising the modified polysulfone membrane according to [8] or [9].

[0067] Effects of the Invention

[0068] The polysulfone membrane with hydrophilic surface and hydrophobic interior prepared according to the preparation method of the present invention has excellent hydrophilicity, high water flux, excellent wear resistance, excellent anti-fouling and excellent mechanical properties, and can be used in sewage separation, biological separation and other fields.

[0069] In addition, according to the preparation method of the present invention, a thicker hydrophilic dense layer can be obtained. The thickness of the hydrophilic dense layer in the modified polysulfone membrane of the present invention is 2 to 3 μm. Compared with the thickness of the existing modified polysulfone membrane (about 0.1 to 0.2 nm), the thickness of the hydrophilic dense layer can be significantly increased, thereby significantly improving the wear resistance. The modified polysulfone membrane of the present invention has excellent wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Schematic flow chart of the preparation method of the modified polysulfone membrane of the present invention.

[0071] Figure 2 The figure is a schematic diagram for schematically illustrating the resin solution conversion process of Example 1 of the present invention.

[0072] Figure 3 Schematic diagram of the structure of the modified polysulfone membrane prepared according to Example 1.

[0073] Figure 4 Schematic diagram of EDS element characterization at various locations on the cross section of the modified polysulfone membrane prepared according to Example 1.

[0074] Figure 5 The infrared spectra of the modified polysulfone membranes prepared according to Example 1, Example 4 and Comparative Example 1 are shown.

[0075] Figure 6 Schematic diagram of SEM characterization of the surface structure of the polysulfone membrane prepared according to Example 1 and Comparative Example 4. DETAILED DESCRIPTION

[0076] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or preferred over other embodiments.

[0077] In addition, numerous specific details are provided in the following detailed description to better illustrate the present invention. Those skilled in the art will appreciate that the present invention can be practiced without certain specific details. In other instances, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of the present invention.

[0078] Unless otherwise stated, the units used in this specification are international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0079] In this specification, the use of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0080] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "embodiments," etc., mean that the specific elements (e.g., features, structures, properties, and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0081] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.

[0082] <Method for preparing modified polysulfone membrane>

[0083] The preparation method of the modified polysulfone membrane of the present invention comprises:

[0084] Step A: mixing a polysulfone polymer, a first solvent, and a first reactant to perform a graft reaction to obtain a first reaction solution;

[0085] Step B: adding a porogen to the first reaction solution and coating it into a liquid film;

[0086] Step C: placing the liquid film in a side group reaction liquid to carry out side group reaction and partially solidify; and

[0087] Step D: placing the membrane obtained in step C in water for complete solidification to obtain a modified polysulfone membrane;

[0088] Wherein, the first reactant comprises a chloroalkane compound, an acyl chloride compound or a chloromethyl ether compound,

[0089] The side group reaction solution comprises a second reactant,

[0090] The second reactant comprises a catalyst for a hydrolysis reaction, a catalyst for an aminolysis reaction, or a catalyst for an oxidation reaction.

[0091] The present invention adopts a mixed solvent to dissolve a polysulfone polymer into a homogeneous solution, and then carries out a grafting reaction to introduce a side group with high reactivity into the long chain of the polysulfone polymer molecule. After sufficient reaction, the above solution is directly coated on a substrate as a casting liquid, and a modified polysulfone membrane is prepared through a two-step non-solvent-induced phase transition.

[0092] Figure 1 FIG. 1 is a schematic flow chart of the method for preparing the modified polysulfone membrane of the present invention. Figure 1 As shown, the preparation method of the present invention includes: dissolving a polysulfone polymer in a first solvent and performing a side chain grafting reaction with a first reactant, mixing the solution obtained after the side chain grafting reaction with a porogen to prepare a casting liquid; coating the casting liquid on a substrate to form a film; placing the liquid film in a side group reaction liquid to perform a side group reaction; solidifying the liquid film obtained after the side group reaction in pure water and washing it to obtain a modified polysulfone membrane.

[0093] (Process A)

[0094] In some preferred embodiments, step A comprises:

[0095] Step A1: dissolving a polysulfone-based polymer in a first solvent; and

[0096] Step A2: adding the first reactant and the catalyst to the solution obtained in step A1 to carry out a grafting reaction to obtain a first reaction solution.

[0097] [Process A1]

[0098] A polysulfone polymer is a polymer having an aromatic ring, a sulfonyl group, and an ether group in its main chain. The polysulfone polymer may comprise repeating units of the following formula (1) and / or (2), and may be copolymerized with other monomers or modified to the extent that the effects of the present invention are not impaired, but is not limited thereto.

[0099]

[0100] In some embodiments, the polysulfone-based polymer includes at least one of a carboxylated polysulfone-based polymer, an aminated polysulfone-based polymer, and a sulfonated polysulfone-based polymer.

[0101] In some preferred embodiments, the weight-average molecular weight of the polysulfone polymer is preferably 40,000 to 120,000, more preferably 80,000 to 100,000. Adjusting the weight-average molecular weight of the polysulfone polymer to this range facilitates membrane formation and improves membrane strength and particle retention. The weight-average molecular weight can be measured, for example, by gel permeation chromatography (GPC).

[0102] When the weight-average molecular weight of the polysulfone polymer is less than 40,000, the viscosity of the resulting casting solution is too low, which is not conducive to membrane formation and the membrane strength is low. When the weight-average molecular weight of the polysulfone polymer is greater than 120,000, the pore size distribution of the membrane surface cortex increases, resulting in a decrease in the particle retention rate.

[0103] The first solvent includes a chlorine-containing low-boiling-point organic solvent and a sulfone-based solvent.

[0104] The chlorine-containing low-boiling-point organic solvent is preferably a chlorine-containing organic solvent having a boiling point of 62° C. or lower, and more preferably a chlorine-containing low-boiling-point organic solvent such as dichloromethane or chloroform.

[0105] As the sulfone-based solvent, sulfolane, dimethyl sulfoxide, and the like are preferred.

[0106] In the present invention, the first solvent serves as both the modification reaction solvent for the polysulfone polymer and the casting solution solvent described below, requiring only a single organic solvent system. The chlorine-containing, low-boiling-point organic solvent in the first solvent effectively lowers the dissolution temperature of the polysulfone polymer, allowing the solution to be liquid at a relatively low temperature, which facilitates the occurrence and forward progress of subsequent reactions. The sulfone solvent also increases the solubility of the polysulfone polymer without interfering with the side-chain grafting reaction between the polysulfone polymer and the first reactant.

[0107] In some preferred embodiments, the mass ratio of the sulfone solvent to the chlorine-containing low-boiling-point organic solvent is 1:1 to 3:1.

[0108] In some specific embodiments, the mass ratio of the sulfone solvent to the chlorine-containing low-boiling point organic solvent is 1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3:1.

[0109] In some preferred embodiments, the first solvent comprises chloroform and sulfolane, and the mass ratio of sulfolane to chloroform is preferably 2:1 to 3:1, more preferably 2.3:1 to 3:1.

[0110] In some preferred embodiments, the mass ratio of the polysulfone polymer to the first solvent is 1: 4 to 1: 6. By setting the mass ratio within the above range, the polysulfone polymer can be fully dissolved in the first solvent.

[0111] In some specific embodiments, the mass ratio of the polysulfone-based polymer to the first solvent is 1:4, 1:4.5, 1:5, 1:5.5 or 1:6.

[0112] In some preferred embodiments, the dissolution temperature is preferably 20 to 70°C, more preferably 30 to 50°C. In some specific embodiments, the dissolution temperature is 20°C, 30°C, 40°C, 50°C, 60°C, or 70°C. By setting the dissolution temperature within the above range, the polysulfone polymer can be fully and gently dissolved in the first solvent. If the dissolution temperature is greater than 70°C, the solvent tends to boil too violently, which can easily lead to safety accidents. If the dissolution temperature is less than 20°C, the dissolution rate is too slow, and the dissolution process is inefficient.

[0113] [Process A2]

[0114] In step A2, the first reactant and the catalyst are added to the solution obtained in step A1 to carry out a grafting reaction, thereby introducing active side chains having hydrophilic or hydrophobic groups into the polysulfone polymer molecular chain.

[0115] In some preferred embodiments, the first reactant preferably comprises ethyl 4-chloroacetoacetate, ethyl 2-chloroacetoacetate, ethyl chloride oxalyl ester, benzyl chloromethyl ether, 1,1-dichloromethyl ether, or chloromethyl ethyl ether.

[0116] The catalyst is preferably at least one selected from the group consisting of tin tetrachloride, ferric chloride, and aluminum chloride, and more preferably aluminum chloride.

[0117] In some preferred embodiments, the mass ratio of the polysulfone polymer to the first reactant is 1: 1 to 4: 1. In some specific embodiments, the mass ratio of the polysulfone polymer to the first reactant is 1: 1, 1.3: 1, 1.5: 1, 1.7: 1, 1.9: 1, 2: 1, 2.1: 1, 2.2: 1, 2.3: 1, 2.4: 1, 2.5: 1, 2.6: 1, 2.7: 1, 2.8: 1, 2.9: 1, 3: 1, 3.2: 1, 3.4: 1, 3.5: 1, 3.6: 1, 3.8: 1 or 4: 1.

[0118] In some preferred embodiments, the mass ratio of the polysulfone polymer to the catalyst is 100: 1 to 500: 1. In some specific embodiments, the mass ratio of the polysulfone polymer to the catalyst is 100: 1, 150: 1, 200: 1, 220: 1, 240: 1, 250: 1, 260: 1, 280: 1, 300: 1, 350: 1, 400: 1, 450: 1 or 500: 1.

[0119] In the present invention, when the components are mixed in the above mass ratio, the grafting reaction can be more advantageously performed, thereby more advantageously introducing side groups with high reactivity into the long molecular chain of the polysulfone-based polymer.

[0120] In some preferred embodiments, the reaction temperature is preferably 10-60°C, more preferably 30-50°C. In some specific embodiments, the reaction temperature is 10°C, 20°C, 30°C, 40°C, 50°C, or 60°C. When the reaction temperature is within this range, the grafting reaction can proceed sufficiently, thereby better introducing active side chains into the polysulfone polymer molecular chain. If the reaction temperature is greater than 60°C, the solvent approaches boiling point, and the reactants are easily volatile. If the reaction temperature is less than 10°C, the reaction rate is too slow, and the reaction efficiency is low.

[0121] In the present invention, the reaction time is 12 to 48 hours, preferably 24 to 36 hours. In some specific embodiments, the reaction time is 12 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours or 48 hours. When the reaction time is within the above range, the grafting reaction can be fully carried out, and active side chains can be introduced into the polysulfone polymer molecular chain. When the reaction time is less than 12 hours, the progress of the grafting reaction is affected, the reaction degree is low, the number of grafted active groups is small, and the modification effect is poor. When the reaction time is greater than 48 hours, the reaction degree does not change much over time.

[0122] (Process B)

[0123] In some preferred embodiments, step B comprises:

[0124] Step B1: adding a porogen to the first reaction solution to obtain a casting solution; and

[0125] Step B2: The casting liquid is applied on a substrate to form a liquid film.

[0126] [Process B1]

[0127] Polyethylene glycol is a preferred porogen. The molecular weight of polyethylene glycol is preferably 200 to 100,000, more preferably 200 to 600. When the molecular weight of polyethylene glycol exceeds 100,000, the membrane's outer separation layer becomes thicker, affecting the water production efficiency of the polysulfone membrane. When the molecular weight of polyethylene glycol is less than 200, the viscosity of the casting solution is low, and the pressure at the spinneret outlet is too low, making stable spinning impossible.

[0128] In some preferred embodiments, the porogen comprises polyethylene glycol 200, polyethylene glycol 400, or polyethylene glycol 600.

[0129] In some preferred embodiments, the mass ratio of the porogen to the polysulfone polymer is 1:3 to 1:6. In some specific embodiments, the mass ratio of the porogen to the polysulfone polymer is 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6.

[0130] In some preferred embodiments, the first reaction solution and the porogen are mixed at room temperature (23-25° C.).

[0131] There are no particular limitations on the mixing method, and conventional mixing methods such as a stirrer or a magnetic stirrer may be used.

[0132] [Process B2]

[0133] In some preferred embodiments, the casting liquid is coated on the substrate using a coating apparatus to form a liquid film.

[0134] The coating substrate temperature is 15-55°C, preferably 20-30°C. When the temperature is lower than 15°C, the casting solution has poor fluidity and is difficult to coat onto the substrate into a uniform film. When the temperature is higher than 55°C, the solvent approaches its boiling point, causing the casting solution to slightly boil and generate bubbles.

[0135] (Process C and Process D)

[0136] In the present invention, a substrate formed with a liquid film is placed in a side group reaction liquid, so that the active side groups of the polysulfone polymer in the surface portion of the liquid film react with the second reactant in the side group reaction liquid and partially solidify. Then, the above-mentioned substrate is removed and placed in pure water, so that the casting liquid is completely solidified and falls off from the substrate, thereby forming a polysulfone membrane with a hydrophilic surface and a hydrophobic interior through a two-step non-solvent-induced phase transition.

[0137] In the present invention, a second reactant dissolved in a non-solvent is introduced during the non-solvent-induced phase inversion process, and solidification occurs during the reaction.

[0138] Generally, in the steps of preparing modified membranes by non-solvent-induced phase separation, all modification steps are carried out before casting the membrane, such as Patent Document 1, which requires continuous replacement of the reaction solution system; or after the casting of the membrane is completed by solvent extraction in pure water, the completely solidified membrane is modified, such as Patent Document 2. Since the reaction activity of the completely solidified membrane is low, the second step reaction usually requires a long reaction time or more intense conditions, which can easily damage the membrane structure; at the same time, the reaction is carried out after the casting is completed, and the hydrophilic layer obtained is usually only as thick as one group on the surface, about 0.1 to 0.2 nm, which makes the layer very easy to wear during actual use.

[0139] The present invention adopts a modification method of curing while reacting. The reaction layer is the curing layer, and the polymer has a certain degree of mobility. Compared with modification after casting, the method according to the present invention has high reaction activity and can be carried out under relatively mild conditions. The thickness of the reaction layer can be controlled by controlling the length of time the casting solution is stagnant in the reaction solution, so that the hydrophilic layer of the modified polysulfone membrane has a certain thickness, thereby improving the wear resistance of the hydrophilic layer in subsequent use. The second reactant is insoluble in the casting solution, and the polymer in the casting solution that has not yet penetrated the non-solvent does not react. Therefore, a modified membrane with different hydrophilic and hydrophobic properties on the surface and inside can be prepared.

[0140] The reaction involved in the side group reaction solution occurs in the active side chains of the polysulfone polymer, converting the hydrophobic groups of the side chains into hydrophilic groups. The reaction involved can be a hydrolysis reaction, an aminolysis reaction, or an oxidation reaction, preferably a hydrolysis reaction, because the generated oxygen-containing groups have high polarity and strong hydrophilicity. The hydrolysis reaction can be acid-catalyzed using dilute sulfuric acid as a catalyst, base-catalyzed using sodium hydroxide as a catalyst, or heated catalysis, preferably base-catalyzed using sodium hydroxide as a catalyst.

[0141] In some preferred embodiments, the side group reaction solution comprises a second reactant and a second solvent.

[0142] The second reactant is preferably a catalyst for hydrolysis, an aminolysis or an oxidation reaction, and more preferably dilute sulfuric acid, sodium hydroxide or N-aminoethylpiperazine.

[0143] As the second solvent, acetone, ethanol or water is preferably contained.

[0144] In some preferred embodiments, an aqueous sodium hydroxide solution saturated with acetone is preferably used as the side group reaction liquid, and the mass ratio of water to sodium hydroxide is preferably 5:1 to 20:1, more preferably 10:1 to 18:1.

[0145] The reaction time of the side group liquid is preferably 5 to 30 minutes, more preferably 5 to 25 minutes, and even more preferably 10 to 20 minutes. When the reaction time is less than 5 minutes, the surface reaction degree is low, the hydrophilicity is poor, the pure water flux is low, and the thickness of the hydrophilic dense layer is thin. When the reaction time is greater than 30 minutes, the membrane is completely solidified and falls off the substrate, and the entire membrane reacts with the reaction liquid, resulting in hydrophilic membrane pores and poor anti-fouling properties.

[0146] In some preferred embodiments, the curing time in water is preferably 24 to 48 hours.

[0147] (Process E)

[0148] In some preferred embodiments, step E includes: soaking the polysulfone membrane obtained in the above step D in a water bath at a temperature of 0 to 30°C for 24 to 48 hours, extracting the solvent to completely solidify the membrane; using an acidic solution to clean inorganic oxides and hydroxides that may be attached to the surface, and using pure water to clean the residual acidic solution; and placing the polysulfone membrane in a pore-preserving agent for pore-preserving treatment.

[0149] The acidic solution is preferably dilute sulfuric acid. The concentration of the acidic solution is preferably 0.1 to 2 M, more preferably 0.5 to 1 M. If the concentration of the acidic solution is less than 0.1 M, it will be difficult to clean particles such as metal oxides and hydroxides attached to the polysulfone membrane surface. If the concentration of the acidic solution is greater than 2 M, the membrane structure may be damaged.

[0150] Examples of the pore-retaining agent used in the pore-retaining treatment include aqueous solutions of ethylene glycol and glycerol. The mass concentration of the pore-retaining agent is preferably 30 to 40%, and the pore-retaining time is preferably 12 to 24 hours.

[0151] <Modified polysulfone membrane with external hydrophilic and internal hydrophobic structure>

[0152] The present invention also provides a modified polysulfone membrane having an external hydrophilic and internal hydrophobic structure, wherein the modified polysulfone membrane comprises a lower layer and a dense layer located on the lower layer.

[0153] The dense layer is hydrophilic and has a thickness of 2 to 3 μm.

[0154] The lower layer has an internal finger-shaped pore structure and is hydrophobic.

[0155] The modified polysulfone membrane of the present invention has the characteristics of surface hydrophilicity and internal hydrophobicity. The polysulfone membrane with hydrophilic surface and internal hydrophobicity has excellent hydrophilicity, water flux and anti-pollution performance, and can be used in the fields of sewage separation, biological separation, etc.

[0156] The modified polysulfone membrane of the present invention has excellent retention and protein resistance for large-molecule glucose and proteins due to its dense, hydrophilic surface, improving the membrane's surface resistance to protein contamination. The hydrophobic nature of the internal channels reduces the adsorption of small-molecule glucose that permeates onto the channel walls. The modified polysulfone membrane of the present invention, with its dense, hydrophilic exterior and loose, hydrophobic interior, offers significant advantages in the field of sugar-protein separation.

[0157] The modified polysulfone membrane of the present invention has a small pore size on the membrane surface, with an average pore size of 0.01 to 0.04 μm, and a finger-shaped pore structure inside.

[0158] The present invention has an excellent separation effect on dextran 2 and dextran 20.

[0159] The pure water flux of the modified polysulfone membrane of the present invention is 50 to 150 L / m2·h·bar.

[0160] In addition, the hydrophilic layer of existing modified polysulfone membranes is only as thick as one surface group, approximately 0.1 to 0.2 nm. This relatively thin layer is easily abraded during actual use. The hydrophilic dense layer in the modified polysulfone membrane of the present invention has a thickness of 2 to 3 μm, which significantly improves wear resistance. The modified polysulfone membrane of the present invention has excellent wear resistance.

[0161] In addition, the surface of the modified polysulfone membrane of the present invention can further undergo interfacial polymerization reaction to prepare a composite membrane with specific properties.

[0162] Example

[0163] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be obtained commercially.

[0164] Example 1

[0165] Preparation of the side group reaction solution: Dissolve 60 g of sodium hydroxide in 800 mL of pure water, then add 200 mL of acetone, stir until fully mixed, and retain the lower layer of sodium hydroxide aqueous solution saturated with acetone as the side group reaction solution.

[0166] Preparation of dilute sulfuric acid: Take 20mL of concentrated sulfuric acid and dilute it to 500mL with pure water for later use.

[0167] (1) 24 g of polysulfone resin particles (manufactured by Solvay, USA) were dispersed in a mixed solvent of 30 g of chloroform and 70 g of sulfolane, and magnetically stirred at 50°C for 1.5 h until completely dissolved.

[0168] (2) Add 0.1 g of aluminum chloride to the solution obtained in step (1), add 10 g of 1,1-dichloromethyl ether dropwise, and stir the mixture at 30° C. for 24 h.

[0169] (3) Add 8 g of polyethylene glycol 400 (PEG-400) to the reaction solution obtained in step (2), stir magnetically to mix evenly, and then let it stand until the bubbles disappear to obtain a casting solution.

[0170] The substrate temperature of the coating apparatus was set to 25° C., the scraper height was set to 150 μm, and the casting solution was coated on the substrate to form a liquid film.

[0171] (4) The substrate coated with the liquid film is placed in the above-prepared side group reaction solution for 15 minutes, then taken out and placed in pure water to solidify until it is detached from the substrate. The water is then changed every 8 hours. After changing the water twice, the modified polysulfone membrane is taken out and placed in dilute sulfuric acid for ultrasonic treatment for 150 minutes, rinsed with pure water three times, and then placed in pure water for ultrasonic treatment for 150 minutes, and placed in a 30% mass concentration ethylene glycol solution for pore preservation treatment.

[0172] Example 2

[0173] A modified polysulfone membrane was obtained in the same manner as in Example 1 except that the time for which the substrate coated with the liquid film was placed in the pendant group reaction liquid in the above step (4) was changed to 20 minutes.

[0174] Example 3

[0175] A modified polysulfone membrane was obtained in the same manner as in Example 1 except that the time for which the substrate coated with the liquid film was placed in the pendant group reaction solution in the above step (4) was changed to 10 minutes.

[0176] Example 4

[0177] A modified polysulfone membrane was obtained in the same manner as in Example 1 except that the mixed solvent in the above step (1) was changed to 30 g of dichloromethane and 70 g of sulfolane.

[0178] Example 5

[0179] A modified polysulfone membrane was obtained in the same manner as in Example 1 except that 8 g of polyethylene glycol 400 (PEG-400) added in the above step (3) was changed to 8 g of polyethylene glycol 200 (PEG-200).

[0180] Comparative Example 1

[0181] Preparation of the reaction solution: Dissolve 60 g of sodium hydroxide in 800 mL of pure water, then add 200 mL of acetone, stir until fully mixed, and retain the lower layer of sodium hydroxide aqueous solution saturated with acetone as the reaction solution.

[0182] Preparation of dilute sulfuric acid: Take 20mL of concentrated sulfuric acid and dilute it to 500mL with pure water for later use.

[0183] (1) 24 g of polysulfone resin particles (manufactured by Solvay, USA) were dispersed in a mixed solvent of 30 g of chloroform and 70 g of sulfolane, and magnetically stirred at 50°C for 1.5 h until completely dissolved.

[0184] (2) Add 0.1 g of aluminum chloride to the solution obtained in step (1), add 10 g of 1,1-dichloromethyl ether dropwise, and stir the mixture at 30° C. for 24 h.

[0185] (3) Add 8 g of polyethylene glycol 400 (PEG-400) to the reaction solution obtained in step (2), stir magnetically to mix evenly, and then let it stand until the bubbles disappear to obtain a casting solution.

[0186] The substrate temperature of the coating apparatus was set to 25° C., the scraper height was set to 150 μm, and the casting liquid was coated on the substrate to form a liquid film.

[0187] (4) The above liquid film is placed in pure water for solidification, and the water is changed every 8 hours. After two changes, the polysulfone membrane is taken out and then placed in the above reaction solution. The reaction is carried out under ultrasonic conditions for 180 minutes. After the reaction is completed, the modified polysulfone membrane is taken out and placed in dilute sulfuric acid for ultrasonication for 150 minutes. The membrane is rinsed three times with pure water, and then placed in pure water for ultrasonication for 150 minutes. The membrane is then placed in a 30% mass concentration ethylene glycol solution for pore preservation treatment.

[0188] Comparative Example 2

[0189] Preparation of dilute sulfuric acid: Take 20mL of concentrated sulfuric acid and dilute it to 500mL with pure water for later use.

[0190] (1) 24 g of polysulfone resin particles (manufactured by Solvay, USA) were dispersed in a mixed solvent of 30 g of chloroform and 70 g of sulfolane, and magnetically stirred at 50°C for 1.5 h until completely dissolved.

[0191] (2) 0.1 g of aluminum chloride was added to the solution obtained in step (1), 10 g of 1,1-dichloromethyl ether was added dropwise, and the mixture was stirred at 30° C. for 24 h. Subsequently, 10 g of sodium hydroxide was added and the mixture was stirred for 24 h.

[0192] (3) Add 8 g of polyethylene glycol 400 (PEG-400) to the reaction solution obtained in step (2), stir magnetically to mix evenly, and then let it stand until the bubbles disappear to obtain a casting solution.

[0193] The substrate temperature of the coating apparatus was set to 25° C., the scraper height was set to 150 μm, and the casting solution was coated on the substrate.

[0194] During the film-forming process, when step (2) is implemented, solid sodium hydroxide is difficult to dissolve in the system, resulting in the reaction solution obtained in step (2) containing too many solid impurities, making it impossible to form a film in step (3).

[0195] Comparative Example 3

[0196] (1) 24 g of polysulfone resin particles (manufactured by Solvay, USA) were dispersed in a mixed solvent of 30 g of chloroform and 70 g of sulfolane, and magnetically stirred at 50°C for 1.5 h until completely dissolved.

[0197] (2) Add 0.1 g of aluminum chloride to the solution obtained in step (1), add 10 g of 1,1-dichloromethyl ether dropwise, and stir the mixture at 30° C. for 24 h.

[0198] (3) Add 8 g of polyethylene glycol 400 (PEG-400) to the reaction solution obtained in step (2), stir magnetically to mix evenly, and then let it stand until the bubbles disappear to obtain a casting solution.

[0199] The substrate temperature of the coating apparatus was set to 25° C., the scraper height was set to 150 μm, and the casting liquid was coated on the substrate to form a liquid film.

[0200] (4) The substrate coated with the liquid film is placed in pure water for solidification, and the water is changed every 8 hours. After three changes, the modified polysulfone membrane is taken out, rinsed three times with pure water, and then placed in pure water for ultrasonic treatment for 150 minutes, and then placed in a 30% mass concentration ethylene glycol solution for pore preservation treatment.

[0201] Comparative Example 4

[0202] Except for replacing step (3) in the above-mentioned embodiment 1 with the following step (3), the rest of the process was carried out in the same manner as in embodiment 1 to obtain a modified polysulfone membrane.

[0203] (3) The reaction solution obtained in step (2) is allowed to stand until it is defoamed to obtain a casting solution.

[0204] The substrate temperature of the coating apparatus was set to 25° C., the scraper height was set to 150 μm, and the casting liquid was coated on the substrate to form a liquid film.

[0205] <Evaluation Test>

[0206] (1) Determination of pure water flux

[0207] (Experimental setup)

[0208] The experimental setup includes the following components:

[0209] 1. Cross-flow membrane separation unit: comprising the polysulfone membrane prepared in the above embodiment or comparative example, a water inlet, a water outlet and a concentrated water outlet.

[0210] 2. Water inlet system: includes pure water storage tank, pump and flow control device, used to provide a constant flow of pure water.

[0211] 3. Pressure control system: includes pressure gauge and regulating valve, used to control the operating pressure on both sides of the membrane.

[0212] 4. Measurement system: includes flow meter and timer, used to measure the amount of water passing through the membrane and the time.

[0213] 5. Analytical system: including a total organic carbon (TOC) analyzer to measure the concentration of glucan in the influent and permeate.

[0214] (Operation steps)

[0215] 1. Preparation: Introduce pure water from the pure water storage tank into the cross-flow membrane separation unit through the water inlet system; adjust the pump and flow control device so that the pure water enters the polysulfone membrane prepared in the above embodiment or comparative example at a set flow rate; adjust the pressure control system so that the operating pressure reaches the preset value of 0.2 MPa.

[0216] 2. Measurement process: Start the device and run it for a period of time (about 10 to 15 minutes) to ensure that the system reaches a stable state. During this period, monitor and record the operating pressure P and temperature T. After stable operation, the volume of liquid permeating V1 within a certain period of time t1 is recorded by the measurement system.

[0217] A 1 g / L dextran 2 solution was introduced into the cross-flow membrane separation unit through the water inlet system to displace pure water. The pressure control system was adjusted to make the operating pressure reach P (0.2 MPa). After the system reached a stable state, the inlet water sample and the permeate sample were collected, and the dextran 2 concentrations C1 and C2 in the inlet water sample and the permeate sample were measured using a TOC analyzer.

[0218] Pure water is introduced into the cross-flow membrane separation unit through the water inlet system for pure water cross-flow cleaning for 1 hour. Then the pressure control system is adjusted to make the operating pressure reach P (0.2MPa). After stable operation, the permeate volume V2 within a certain time t2 is recorded by the measurement system;

[0219] A 1 g / L dextran 20 solution was introduced into the cross-flow membrane separation unit through the inlet system to displace pure water. The pressure control system was then adjusted to make the operating pressure reach P (0.2 MPa). After the system reached a stable state, the inlet and permeate samples were collected, and the dextran 20 concentrations C3 and C4 in the inlet and permeate samples were measured using a TOC analyzer.

[0220] Pure water is introduced into the cross-flow membrane separation unit through the water inlet system for pure water cross-flow cleaning, which lasts for 1 hour. Then the pressure control system is adjusted to make the operating pressure reach P (0.2MPa). After stable operation, the permeate liquid volume V3 within a certain time t3 is recorded by the measurement system.

[0221] The above steps were repeated three times.

[0222] (Data Processing)

[0223] The pure water flux J is calculated according to the following formula w1 ,J w2 ,J w3 :

[0224]

[0225]

[0226] Wherein, A is the effective area of ​​the polysulfone membrane, and P is the operating pressure (0.2 MPa).

[0227] The retention rate R1 of dextran 2, the retention rate R2 of dextran 20 and the retention difference ΔR were calculated according to the following formula:

[0228]

[0229] ΔR=R2-R1

[0230] The flux recovery rate FRR1 of dextran 2 and the flux recovery rate FRR2 of dextran 20 were calculated according to the following formula:

[0231]

[0232] Table 1

[0233] <![CDATA[Pure water flux J w1 (L / m 2 ·bar·h)]]> Example 1 157.5 Example 2 117.5 Example 3 67.6 Example 4 163.5 Example 5 146.7 Comparative Example 1 0.19 Comparative Example 3 0.58 Comparative Example 4 40.9

[0234] Table 2

[0235]

[0236] Table 1 shows the pure water flux of the modified polysulfone membranes prepared according to Examples 1 to 5 and Comparative Examples 1, 3 to 4. As shown in Table 1, Examples 1 to 5 can all make the membrane porous and obtain high pure water flux. However, the pure water flux of the polysulfone membranes of Comparative Examples 1, 3 to 4 is low. The polysulfone membrane prepared in Comparative Example 3 does not have a hydrophilic upper layer and has a pure water flux of only 0.58 L / m 2 ·bar·h.

[0237] Table 2 shows the retention rate R1 of dextran 2, the retention rate R2 of dextran 20, the retention difference ΔR, the flux recovery rate FRR1 of dextran 2, and the flux recovery rate FRR2 of dextran 20 for the modified polysulfone membranes prepared according to Examples 1-3 and Comparative Example 4. As shown in Table 2, Examples 1-3 all achieved good separation of dextran 2 and dextran 20, with a large retention difference and excellent flux recovery, i.e., the membrane's anti-fouling properties. However, the retention performance of Comparative Example 4 was poor. The polysulfone membrane prepared in Comparative Example 4 did not contain a porogen, resulting in large pores on the membrane surface. The retention rate R2 of dextran 20 was only 3.5%.

[0238] Figure 2 Schematic diagram of the resin solution conversion process of Example 1 of the present invention. Figure 2As shown, a substrate formed with a liquid film is placed in a side group reaction liquid, so that the active side groups of the polysulfone polymer in the surface part of the liquid film react with the second reactant in the side group reaction liquid, so that the hydrophobic groups of the side chains of the polysulfone polymer are converted into hydrophilic groups. Then, the above-mentioned substrate is taken out from the side group reaction liquid and placed in pure water, so that the casting liquid is completely solidified and falls off from the substrate, thereby forming a polysulfone membrane with a hydrophilic surface and a hydrophobic interior through a two-step non-solvent-induced phase transition.

[0239] Figure 3 Schematic diagram of the structure of the modified polysulfone membrane prepared according to Example 1. Figure 3 As shown, the modified polysulfone membrane of Example 1 comprises a lower layer 1 and a dense layer 2 located on the lower layer 1. The lower layer 1 has an internal finger-like pore structure and is hydrophobic. The dense layer 2 is hydrophilic and has a thickness of 2.6 μm, which can significantly improve the wear resistance of the modified polysulfone membrane.

[0240] Figure 4 Schematic diagram of EDS element characterization at various locations on the cross section of the modified polysulfone membrane prepared according to Example 1. Figure 4 As shown, the Cl% in the dense layer 2 is low, indicating that the hydrophobic groups in the side chains of the polysulfone-based polymer are converted into hydrophilic groups, and the dense layer 2 has hydrophilicity.

[0241] Figure 5 The infrared spectra of the modified polysulfone membranes prepared according to Example 1, Example 4 and Comparative Example 1 are shown. Figure 5 It can be seen that Example 1 and Example 4 have the same -1 There is one more absorption peak than that in Comparative Example 1, which is the stretching vibration peak of CO. This shows that the method of first preparing the membrane and then performing hydrophilic modification of the side branches in Comparative Example 1 cannot achieve the modification effect as that in Example 1 and Example 4.

[0242] Figure 6 Schematic diagram of SEM characterization of the surface structure of the polysulfone membrane prepared according to Example 1 and Comparative Example 4. Figure 6 It can be clearly seen that under the same magnification, the surface of the polysulfone membrane of Comparative Example 4 has many large holes, while the surface of the modified polysulfone membrane of Example 1 is smoother and denser, with almost no large pore defects. It can be seen that the addition of porogens can significantly reduce surface defects.

[0243] It should be noted that, although the technical solutions of the present invention are described with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0244] While various embodiments of the present invention have been described above, the above descriptions are intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a modified polysulfone membrane, characterized in that: The preparation method comprises: Step A: mixing a polysulfone polymer, a first solvent, and a first reactant to perform a graft reaction to obtain a first reaction solution; Step B: adding a porogen to the first reaction solution and coating it into a liquid film; Step C: placing the liquid film in a side group reaction solution to carry out side group reaction and partially solidify; Step D: placing the membrane obtained in step C in water for complete solidification to obtain a modified polysulfone membrane; Wherein, the first reactant comprises a chloroalkane compound, an acyl chloride compound or a chloromethyl ether compound, The side group reaction solution comprises a second reactant, The second reactant comprises a catalyst for a hydrolysis reaction, a catalyst for an aminolysis reaction, or a catalyst for an oxidation reaction.

2. The preparation method according to claim 1, characterized in that The process A comprises: Step A1: dissolving the polysulfone polymer in the first solvent; Step A2: adding the first reactant and the catalyst to the solution obtained in step A1 to carry out a grafting reaction to obtain a first reaction solution.

3. The preparation method according to claim 2, characterized in that The step A, step A1 or step A2 satisfies at least one of the following characteristics (a) to (h): (a) the weight average molecular weight of the polysulfone polymer is 40,000 to 120,000; (b) the first solvent comprises a chlorine-containing low-boiling point organic solvent and a sulfone-based solvent; The chlorine-containing low-boiling point organic solvent comprises dichloromethane or chloroform; The sulfone solvent comprises sulfolane or dimethyl sulfoxide; The mass ratio of the sulfone solvent to the chlorine-containing low-boiling-point organic solvent is 1:1 to 3:1; (c) the mass ratio of the polysulfone polymer to the first solvent is 1:4 to 1:6; (d) the first reactant comprises ethyl 4-chloroacetoacetate, ethyl 2-chloroacetoacetate, ethyl chlorooxalyl, benzyl chloromethyl ether, 1,1-dichloromethyl ether or chloromethyl ethyl ether; (e) the catalyst comprises at least one member selected from the group consisting of tin tetrachloride, ferric chloride and aluminum chloride; (f) the mass ratio of the polysulfone polymer to the catalyst is 100:1 to 500:1; (g) the mass ratio of the polysulfone polymer to the first reactant is 1:1 to 4:1; (h) The grafting reaction temperature is 10 to 60° C., and the grafting reaction time is 12 to 48 hours.

4. The preparation method according to any one of claims 1 to 3, characterized in that The process B comprises: Step B1: adding a porogen to the first reaction solution to obtain a casting solution; and Step B2: applying the casting solution on a substrate to form a liquid film.

5. The preparation method according to claim 4, characterized in that The step B, step B1 or step B2 satisfies at least one of the following characteristics (i) to (j): (i) the porogen comprises polyethylene glycol 200, polyethylene glycol 400 or polyethylene glycol 600; (j) The mass ratio of the porogen to the polysulfone polymer is 1:3 to 1:

6.

6. The preparation method according to any one of claims 1 to 3, characterized in that The process C or the process D satisfies at least one of the following characteristics (k) to (n): (k) the pendant group reaction solution comprises a second reactant and a second solvent; The second reactant comprises sodium hydroxide, dilute sulfuric acid or N-aminoethylpiperazine; The second solvent comprises acetone, ethanol or water; (1) the side group reaction solution is a sodium hydroxide aqueous solution containing acetone; (m) The side group reaction time is 5 to 30 minutes; (n) The curing time in water is 24 to 48 hours.

7. The preparation method according to any one of claims 1 to 3, characterized in that The preparation method further comprises: Step E: The polysulfone membrane obtained in the step D is subjected to at least one treatment selected from the group consisting of immersion in a water bath, cleaning with an acidic solution, and pore retention treatment.

8. The preparation method according to claim 7, characterized in that The process E satisfies at least one of the following characteristics (o) to (p): (o) the acidic solution is dilute sulfuric acid or dilute hydrochloric acid; (p) The concentration of the acidic solution is 0.1 to 2M.

9. A modified polysulfone membrane having an external hydrophilic and internal hydrophobic structure prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The modified polysulfone membrane comprises a lower layer and a dense layer located on the lower layer. The dense layer is hydrophilic and has a thickness of 2 to 3 μm. The lower layer has an internal finger-shaped pore structure and is hydrophobic.

10. The modified polysulfone membrane according to claim 9, characterized in that The average pore size of the modified polysulfone membrane is 0.01-0.04 μm.

11. The modified polysulfone membrane according to claim 9, characterized in that The pure water flux of the modified polysulfone membrane is 50 to 150 L / m 2 ·h·bar.

12. A composite membrane, characterized in that The composite membrane comprises the modified polysulfone membrane according to any one of claims 9 to 11.

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