Heat-resistant anti-fouling polyether sulfone hollow fiber membrane and preparation method thereof

Abstract

The application belongs to the technical field of fiber membranes, and particularly relates to a heat-resistant and anti-pollution polyether sulfone hollow fiber membrane and a preparation method thereof. The application uses a functional macromolecular reagent as an additive. The aromatic ring contained in the structure of the functional macromolecular reagent can produce pi-pi conjugation with the aromatic ring in the polyether sulfone structure. Therefore, the molecular chains of the two can form a three-dimensional structure of mutual entanglement and interweaving. The cross-linking structure can limit the movement of the polyether sulfone molecular chain, thereby improving the stability of the fiber membrane under high-temperature conditions and being beneficial to enhancing the heat-resistant performance of the fiber membrane. In addition, the functional macromolecular reagent structure contains rich hydrophilic sulfonic acid groups and secondary amine groups, which can greatly improve the hydrophilicity of the fiber membrane, thereby improving the anti-pollution performance of the fiber membrane.

Description

Technical Field

[0001] This invention belongs to the field of fiber membrane technology, specifically relating to a heat-resistant and anti-fouling polyethersulfone hollow fiber membrane and its preparation method. Background Technology

[0002] Polyethersulfone (PES), a high-performance engineering plastic, is widely used in the preparation of separation membranes such as microfiltration, ultrafiltration, and nanofiltration due to its excellent film-forming properties, mechanical strength, chemical stability, and wide pH range. It plays a particularly important role in water treatment, biomedicine, food and beverage, and industrial wastewater treatment. Hollow fiber membranes, in particular, have become one of the main product forms in membrane separation technology due to their high packing density, good self-support, and ease of modularization. However, in practical applications, PES hollow fiber membranes often face the following two key problems: Firstly, its heat resistance is insufficient. Although polyethersulfone itself has a high glass transition temperature, under long-term high-temperature operation or online steam / hot water sterilization, ordinary polyethersulfone hollow fiber membranes are prone to structural densification, pore size shrinkage, or creep deformation, leading to a significant decrease in membrane flux and even loss of separation performance. This limits its application in high-temperature material processing (such as dairy product sterilization, fermentation broth filtration, and high-temperature industrial wastewater reuse).

[0003] Secondly, its antifouling ability is limited. Polyethersulfone materials have strong hydrophobicity, with a pure water contact angle typically exceeding 70°–80°. This makes the membrane surface and pore walls prone to adsorption of organic pollutants such as proteins, polysaccharides, oils, and humic acids, leading to irreversible membrane fouling. Frequent chemical cleaning is required after fouling, increasing operating costs and shortening membrane lifespan. Especially in complex feed systems such as oily wastewater and protein solutions, the antifouling performance of ordinary polyethersulfone membranes is particularly inadequate.

[0004] To improve the aforementioned properties of polyethersulfone hollow fiber membranes, some attempts have been made in the prior art. For example, inorganic nanoparticles or hydrophilic polymers (such as polyvinylpyrrolidone PVP and polyethylene glycol PEG) are introduced through blending to enhance the membrane's hydrophilicity and antifouling ability; or the structural stability of the membrane is improved through post-crosslinking, heat treatment, etc. However, these methods often suffer from the problem of easy loss of modifiers, and cannot guarantee the membrane's performance in the long term.

[0005] Therefore, developing a polyethersulfone hollow fiber membrane with both excellent heat resistance and antifouling ability is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a heat-resistant and anti-fouling polyethersulfone hollow fiber membrane and its preparation method.

[0007] A first aspect of the present invention provides a heat-resistant and anti-fouling polyethersulfone hollow fiber membrane, made from the following raw materials measured in parts by weight: Polyethersulfone: 65-82 parts; Functional macromolecular reagents: 3.5-6.5 parts; Pore-forming agent: 20-30 parts; Organic solvent: 200-240 parts; The functional macromolecular reagent is prepared by a substitution reaction of 6,6'-(ethylene-1,2-diyl)bis(3-aminobenzenesulfonic acid) and a chain extender.

[0008] As a preferred embodiment of the present invention, the functional macromolecular reagent is prepared by the following method: 6,6'-(ethylene-1,2-diyl)bis(3-aminobenzenesulfonic acid) and dimethyl sulfoxide were added to a nitrogen-filled reactor. After the addition was complete, stirring was started until a homogeneous reaction solution was formed. Chain extender and alkaline catalyst were then added to the reaction solution. After the addition was complete, the temperature was raised to 60-70℃ at a rate of 3-5℃ / min and held for 1-2 hours. Then the temperature was raised to 80-90℃ and stirred continuously for 12-24 hours. The solvent was evaporated, and the crude product was collected for purification to obtain a functional macromolecular reagent.

[0009] As a preferred embodiment of the present invention, the molar ratio of 6,6'-(ethylene-1,2-diyl)bis(3-aminobenzenesulfonic acid) to the chain extender is 1:0.95-0.98.

[0010] As a preferred embodiment of the present invention, the chain extender is 2,2'-dibromodiethyl ether or dichloroethyl ether.

[0011] As a preferred embodiment of the present invention, the alkaline catalyst is potassium carbonate or cesium carbonate.

[0012] It should be noted that in the above technical solution, 6,6'-(ethylene-1,2-diyl)bis(3-aminobenzenesulfonic acid) is used as a raw material. The primary amine group in its structure can undergo a continuous substitution reaction with the halogen substituent in the chain extender structure under the action of an alkaline catalyst to obtain a macromolecular substance with alternating aminobenzenesulfonic acid-ether segments, i.e., a functional macromolecular reagent.

[0013] As a preferred embodiment of the present invention, the pore-forming agent is any one of polyvinylpyrrolidone-K30, polyvinylpyrrolidone-K60, or polyvinylpyrrolidone-K90.

[0014] As a preferred embodiment of the present invention, the organic solvent is at least one of N,N-dimethylformamide or N,N-dimethylacetamide.

[0015] A second aspect of the present invention provides a method for preparing a heat-resistant and anti-fouling polyethersulfone hollow fiber membrane, comprising the following steps: Step 1: Weigh each raw material according to the weight proportions, then add the organic solvent to the mixing tank and mechanically stir and mix evenly at a temperature of 40-50℃. Then continue to add polyethersulfone, functional macromolecular reagent and pore-forming agent to the mixing tank. After the addition is complete, raise the temperature to 90-100℃ and keep it warm and stirring for 1-2 hours. Adjust the temperature to 40-45℃ and vacuum stir for 10-12 hours to obtain the precursor liquid. The second step is to filter the precursor solution, let it stand to remove bubbles, and form a casting solution. The third step involves controlling the temperature of the spinneret to 55-65℃, the temperature of the casting solution to 40-50℃, and the air humidity to 60±5%. The casting solution and core solution are then injected into metering pumps and ejected through two concentric hollow nozzles. The casting solution pressure is controlled at 0.1-0.2MPa, the winding speed at 10-20m / min, and the flow rate at 2-3g / min. The ejected solution forms a fibrous tubular liquid surface, thus producing a polyethersulfone hollow fiber membrane.

[0016] As a preferred technical solution of the present invention, in the third step, the core fluid is an aqueous solution of N,N-dimethylformamide or an aqueous solution of N,N-dimethylacetamide, with a volume fraction of 20-30%.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The functional macromolecular reagent prepared in this invention contains aromatic rings, which can undergo π-π conjugation with the aromatic rings in the polyethersulfone structure. Therefore, the molecular chains of the two can form an intertwined three-dimensional structure. This cross-linking structure restricts the movement of the polyethersulfone molecular chains, thus improving the stability of the fiber membrane under high-temperature conditions and enhancing its heat resistance. Furthermore, the functional macromolecular reagent structure contains abundant hydrophilic sulfonic acid groups and secondary amine groups, which significantly increases the hydrophilicity of the fiber membrane, thereby improving its antifouling properties. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is an infrared analysis test image of a functional macromolecular reagent. Detailed Implementation

[0020] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0021] Preparation Example Preparation of functional macromolecular reagents: 1.2 g of 6,6'-(ethylene-1,2-diyl)bis(3-aminobenzenesulfonic acid) and dimethyl sulfoxide were added to a nitrogen-filled reactor. After the addition was complete, stirring was started until a homogeneous reaction solution was formed. Then, 0.72 g of 2,2'-dibromodiethyl ether and potassium carbonate were added to the reaction solution. After the addition was complete, the temperature was raised to 65°C at a rate of 3°C / min and held for 1.5 h. Then, the temperature was raised to 85°C and held for stirring for 16 h. The solvent was evaporated, and the crude product was collected for purification to obtain a functional macromolecular reagent.

[0022] Figure 1 This is the infrared analysis spectrum of this functional macromolecular reagent, where 3456 cm⁻¹... -1 and 3384cm -1 The characteristic absorption peak appearing at 1274 cm⁻¹ is the characteristic absorption peak of NH. -1 The characteristic absorption peak appearing at 1038 cm⁻¹ is the characteristic absorption peak of the S=O group of the sulfonic acid group. -1 The characteristic absorption peak appearing at the position is the characteristic absorption peak of CO in ether bonds, and no obvious C-Br characteristic absorption peak was observed in the figure.

[0023] Example 1 This embodiment provides a heat-resistant and anti-fouling polyethersulfone hollow fiber membrane, which is made from the following raw materials measured in parts by weight: Polyethersulfone: 65 parts; Functional macromolecular reagents: 3.5 parts; Polyvinylpyrrolidone-K30: 20 parts; N,N-Dimethylformamide: 200 parts; The method for preparing the fiber membrane includes the following steps: Step 1: Weigh each raw material according to the weight proportions, then add N,N-dimethylformamide to the mixing tank and mechanically stir and mix evenly at 40°C. Then continue to add polyethersulfone, functional macromolecular reagent and polyvinylpyrrolidone-k30 to the mixing tank. After the addition is complete, raise the temperature to 95°C and keep stirring for 1 hour. Adjust the temperature to 40°C and stir under vacuum for 12 hours to obtain the precursor liquid. The second step is to filter the precursor solution, let it stand to remove bubbles, and form a casting solution. The third step involves controlling the temperature of the spinneret to 60℃, the temperature of the casting solution to 45℃, and the air humidity to 60%. The casting solution and a 30% N,N-dimethylformamide aqueous solution are injected into metering pumps and sprayed out through two concentric hollow nozzles. The casting solution pressure is controlled at 0.1MPa, the winding speed at 15m / min, and the flow rate at 2.5g / min. The sprayed solution forms a fibrous tubular liquid surface, thus producing a polyethersulfone hollow fiber membrane.

[0024] The preparation methods for functional macromolecular reagents are shown in the preparation examples, and the same applies to the following methods.

[0025] Example 2 This embodiment provides a heat-resistant and anti-fouling polyethersulfone hollow fiber membrane, which is made from the following raw materials measured in parts by weight: Polyethersulfone: 70 parts; Functional macromolecular reagents: 6 parts; Polyvinylpyrrolidone-K60: 25 parts; N,N-Dimethylformamide: 220 parts; The method for preparing the fiber membrane includes the following steps: Step 1: Weigh each raw material according to the weight proportions, then add N,N-dimethylformamide to the mixing tank and mechanically stir and mix evenly at 40°C. Then continue to add polyethersulfone, functional macromolecular reagent and polyvinylpyrrolidone-K60 to the mixing tank. After the addition is complete, raise the temperature to 95°C and keep stirring for 1 hour. Adjust the temperature to 40°C and stir under vacuum for 12 hours to obtain the precursor liquid. The second step is to filter the precursor solution, let it stand to remove bubbles, and form a casting solution. The third step involves controlling the temperature of the spinneret to 60℃, the temperature of the casting solution to 45℃, and the air humidity to 60%. The casting solution and a 30% N,N-dimethylformamide aqueous solution are injected into metering pumps and sprayed out through two concentric hollow nozzles. The casting solution pressure is controlled at 0.1MPa, the winding speed at 15m / min, and the flow rate at 2.5g / min. The sprayed solution forms a fibrous tubular liquid surface, thus producing a polyethersulfone hollow fiber membrane.

[0026] Example 3 This embodiment provides a heat-resistant and anti-fouling polyethersulfone hollow fiber membrane, which is made from the following raw materials measured in parts by weight: Polyethersulfone: 82 parts; Functional macromolecular reagents: 6.5 parts; Polyvinylpyrrolidone-K90: 30 parts; N,N-Dimethylformamide: 240 parts; The method for preparing the fiber membrane includes the following steps: Step 1: Weigh each raw material according to the weight proportions, then add N,N-dimethylformamide to the mixing tank and mechanically stir and mix evenly at 40°C. Then continue to add polyethersulfone, functional macromolecular reagent and polyvinylpyrrolidone-k90 to the mixing tank. After the addition is complete, raise the temperature to 95°C and keep stirring for 1 hour. Adjust the temperature to 40°C and stir under vacuum for 12 hours to obtain the precursor liquid. The second step is to filter the precursor solution, let it stand to remove bubbles, and form a casting solution. The third step involves controlling the temperature of the spinneret to 60℃, the temperature of the casting solution to 45℃, and the air humidity to 60%. The casting solution and a 30% N,N-dimethylformamide aqueous solution are injected into metering pumps and sprayed out through two concentric hollow nozzles. The casting solution pressure is controlled at 0.1MPa, the winding speed at 15m / min, and the flow rate at 2.5g / min. The sprayed solution forms a fibrous tubular liquid surface, thus producing a polyethersulfone hollow fiber membrane.

[0027] Comparative Example 1 The difference between this comparative example and Example 2 is that the functional macromolecular reagent has been removed; otherwise, they are the same.

[0028] The fiber membranes provided in the above embodiments and comparative examples were subjected to performance tests, and the test methods are as follows: (1) Heat resistance test First, the original pure water flux of the membrane was tested under the conditions of 0.1 MPa and 25°C. Then, the fiber membrane was placed in a temperature environment of 100°C and left to stand for 24 hours before being taken out. After the fiber membrane cooled down, the pure water flux was tested again under the same conditions. The decrease rate of pure water flux before and after heat treatment was calculated to evaluate the heat resistance of the fiber membrane. Generally speaking, the lower the decrease rate, the better the heat resistance, and vice versa. (2) Water flux recovery rate test First, the initial pure water flux of the membrane was tested under conditions of 0.1 MPa and 25°C. Then, threonine feed solution was filtered using a fiber membrane with the inlet pressure set at 1.2 MPa and the outlet pressure at 0.8 MPa. After 50 repeated filtrations, the fiber membrane was intermittently cleaned at room temperature using 0.01 mol / L NaOH, 0.1 mol / L HCl, and tap water. Then, it was circulated and cleaned for 30 minutes using 40°C hot water at 0.8 MPa. After rinsing until neutral, the flux was restored. The pure water flux of the fiber membrane was tested again under conditions of 0.1 MPa and 25°C. The membrane water flux recovery rate was obtained by comparing it with the initial pure water flux of the membrane, which evaluated the antifouling performance of the fiber membrane. Generally speaking, the higher the recovery rate, the better the antifouling performance, and vice versa. The threonine feed solution was obtained by adding activated carbon to the threonine fermentation broth and then separating it by high-speed centrifugation. The threonine fermentation broth was purchased from Ningbo Zhenhai Haide Biochemical Technology Co., Ltd., and the amount of activated carbon added was 1% of the total mass of the threonine fermentation broth.

[0029] The performance test data above are shown in Table 1.

[0030] Table 1 Performance Test Results

[0031] As can be seen from the above, the fiber membrane prepared in the embodiments of the present invention has good heat resistance and antifouling properties. After the functional macromolecular reagent is removed, the heat resistance and antifouling properties of the fiber membrane decrease significantly, indicating that the addition of functional macromolecular reagent has a great positive effect on the heat resistance and antifouling properties of the fiber membrane.

[0032] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A heat-resistant and anti-fouling polyethersulfone hollow fiber membrane, characterized in that, It is made from the following raw materials, measured in parts by weight: Polyethersulfone: 65-82 parts; Functional macromolecular reagents: 3.5-6.5 parts; Pore-forming agent: 20-30 parts; Organic solvent: 200-240 parts; The functional macromolecular reagent is prepared by a substitution reaction of 6,6'-(ethylene-1,2-diyl)bis(3-aminobenzenesulfonic acid) and a chain extender; The functional macromolecular reagent is prepared using the following method: 6,6'-(ethylene-1,2-diyl)bis(3-aminobenzenesulfonic acid) and dimethyl sulfoxide were added to a nitrogen-filled reactor. After the addition was complete, stirring was started until a homogeneous reaction solution was formed. Chain extender and alkaline catalyst were then added to the reaction solution. After the addition was complete, the temperature was raised to 60-70℃ at a rate of 3-5℃ / min and held for 1-2 hours. Then the temperature was raised to 80-90℃ and stirred for 12-24 hours. The solvent was evaporated, and the crude product was collected for purification to obtain a functional macromolecular reagent. The molar ratio of 6,6'-(ethylene-1,2-diyl)bis(3-aminobenzenesulfonic acid) to the chain extender is 1:0.95-0.98; The chain extender is 2,2'-dibromodiethyl ether or dichloroethyl ether.

2. The heat-resistant and anti-fouling polyethersulfone hollow fiber membrane according to claim 1, characterized in that, The alkaline catalyst is potassium carbonate or cesium carbonate.

3. The heat-resistant and anti-fouling polyethersulfone hollow fiber membrane according to claim 1, characterized in that, The pore-forming agent is any one of polyvinylpyrrolidone-K30, polyvinylpyrrolidone-K60, or polyvinylpyrrolidone-K90.

4. The heat-resistant and anti-fouling polyethersulfone hollow fiber membrane according to claim 1, characterized in that, The organic solvent is at least one of N,N-dimethylformamide or N,N-dimethylacetamide.

5. A method for preparing a heat-resistant and anti-fouling polyethersulfone hollow fiber membrane as described in claim 1, characterized in that, Includes the following steps: Step 1: Weigh each raw material according to the weight proportions, then add the organic solvent to the mixing tank and mechanically stir and mix evenly at a temperature of 40-50℃. Then continue to add polyethersulfone, functional macromolecular reagent and pore-forming agent to the mixing tank. After the addition is complete, raise the temperature to 90-100℃ and keep it warm and stirring for 1-2 hours. Adjust the temperature to 40-45℃ and vacuum stir for 10-12 hours to obtain the precursor liquid. The second step is to filter the precursor solution, let it stand to remove bubbles, and form a casting solution. The third step involves controlling the temperature of the spinneret to 55-65℃, the temperature of the casting solution to 40-50℃, and the air humidity to 60±5%. The casting solution and core solution are then injected into metering pumps and ejected through two concentric hollow nozzles. The casting solution pressure is controlled at 0.1-0.2MPa, the winding speed at 10-20m / min, and the flow rate at 2-3g / min. The ejected solution forms a fibrous tubular liquid surface, thus producing a polyethersulfone hollow fiber membrane.

6. The method for preparing a heat-resistant and anti-fouling polyethersulfone hollow fiber membrane according to claim 5, characterized in that, In the third step, the core fluid is an aqueous solution of N,N-dimethylformamide or an aqueous solution of N,N-dimethylacetamide, with a volume fraction of 20-30%.

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