Hollow fiber membrane preparation method and hollow fiber membrane

Abstract

The invention discloses a preparation method of a hollow fiber membrane, which comprises the following steps of: reacting a monomer C with neopentyl of which the quaternary carbon atom is connected with carboxyl and the primary carbon atom is connected with hydroxyl with a monomer A with a phosphorylcholine branched chain and a monomer B with methylacryloyl in the hollow fiber membrane; the prepared hollow fiber membrane has alkali-resistant and heat-resistant characteristics after being applied to an ultrafiltration device, and can meet the requirement of frequent disinfection of the ultrafiltration device.

Description

Technical Field

[0001] This invention relates to the field of filtration materials technology, specifically to a method for preparing a hollow fiber membrane and the hollow fiber membrane itself. Background Technology

[0002] Hydrophilicity is a key performance characteristic of ultrafiltration membranes, significantly impacting their separation efficiency, antifouling ability, and operational stability. Hydrophilic membrane surfaces can form hydrogen bonds with water molecules, lowering the contact angle of water and thus reducing the energy barrier for water permeation, thereby increasing water flux. Under the same operating conditions, hydrophilic membranes typically exhibit higher pure water flux and permeate efficiency. Furthermore, hydrophilic surfaces effectively inhibit the adsorption of hydrophobic contaminants (such as proteins, oils, and colloidal particles), mitigating membrane fouling. The fouling layer is weaker on hydrophilic membrane surfaces, making it easier to remove through physical backwashing or chemical cleaning, thus extending cleaning cycles and membrane lifespan. Simultaneously, hydrophilic surfaces inhibit microbial adhesion, helping to reduce biofilm formation and lower the risk of biofouling. During long-term operation, hydrophilic membranes, due to their lower degree of fouling and less pore blockage, can more stably maintain their retention performance for target solutes (such as proteins and polysaccharides), ensuring continuous and efficient operation of the separation process.

[0003] However, when hydrophilic ultrafiltration membranes are used in ultrafiltration devices, they need to undergo periodic or irregular disinfection. Disinfection typically involves introducing strong alkalis such as sodium hydroxide to remove endotoxins from the ultrafiltration unit, and often uses high temperatures for sterilization to inactivate harmful microorganisms. In actual operation, as the usage time increases, the hydrophilic properties gradually decline, leading to increased membrane fouling, decreased flux, and affecting the long-term stable operation of the system. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art. To solve the above-mentioned technical problem, the technical solution of the present invention provides: A method for preparing a hollow fiber membrane includes the following steps: A film-forming solution is formed by mixing a monomer A with a phosphorylcholine branch, a monomer B with a methacryloyl group, a monomer C with a neopentyl group attached to a quaternary carbon atom and a hydroxyl group attached to a primary carbon atom, and a film-forming polymer. The film-forming solution is then used to prepare a hollow fiber membrane through a film-forming process.

[0005] A method for preparing a hollow fiber membrane includes the following steps: S1: Mix monomer A with phosphorylcholine side chain, monomer B with methacrylamide group and film-forming polymer to form film-forming solution, and prepare hollow fiber base membrane by film-forming process; S2: Prepare an alkaline solution by using a C monomer with a carboxyl group attached to a quaternary carbon atom and a hydroxyl group attached to a primary carbon atom, and coat the alkaline solution onto the hollow fiber base membrane.

[0006] Preferably, the pH of the alkaline solution is 8-13, the C monomer content in the alkaline solution is 30% (V / V), and the temperature of the solution is higher than 50°C when the alkaline solution is coated onto the hollow fiber base membrane.

[0007] Preferably, the alkaline solution is heated to 80°C, the hollow fiber membrane is immersed in the alkaline solution and kept for more than 20 minutes, and the immersed hollow fiber membrane is removed from the alkaline solution, drained, and placed in a negative pressure environment.

[0008] Preferably, monomer A is one of 2-methacryloyloxyethyl phosphorylcholine and ammonium methacrylate sulfonate, monomer B is one of methyl methacrylate or its salt, ethyl methacrylate or its salt, propyl methacrylate or its salt, the molar ratio of monomer A to monomer B is 1:(5-9), and monomer C is 2,2-dimethylolpropionic acid.

[0009] Preferably, the film-forming polymer is selected from one of polypropylene, polyethylene, polyacrylonitrile, polysulfone, polyethersulfone, polyester, polyvinyl chloride, and polyvinylidene fluoride.

[0010] Furthermore, the present invention also provides a hollow fiber membrane, which is prepared according to the aforementioned hollow fiber membrane preparation method.

[0011] Preferably, the hollow fiber membrane has a thickness of 80-150 μm and a diameter of 500-1000 μm.

[0012] Compared with the prior art, the advantages of the present invention are as follows: This invention involves reacting a C monomer with a carboxyl group attached to a quaternary carbon atom and a hydroxyl group attached to a primary carbon atom with an A monomer containing a phosphorylcholine branch and a B monomer containing a methacryloyl group, used in the preparation of hollow fiber membranes. This results in a hollow fiber membrane that exhibits alkali and heat resistance when applied in an ultrafiltration device, thus meeting the requirements for frequent sterilization of hollow fiber membranes in ultrafiltration devices. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the ultrafiltration device structure of the present invention. Figure 2 This is a graph showing the relationship between the number of sterilization cycles experienced by the hollow fiber column in this invention and the ultrafiltration coefficient.

[0014] Figure 3 , 4Figures 5 and 6 are microstructure diagrams of the fifth hollow fiber membrane in Embodiment 3 of the present invention.

[0015] The labels in the diagram represent: 1. Hollow fiber column, 2. Pump, 3. Feed tank, 4. First pressure gauge, 5. Second pressure gauge, 6. Reflux valve, 7. First permeation end, 8. Water bath, 9. Second permeation end. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0019] In this invention, unless otherwise explicitly specified and limited, the terms "assembly," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0020] Preparation of casting solution and core solution for hollow fiber ultrafiltration membrane in Example 1 Polyethersulfone, polyethylene glycol, lithium chloride, phosphate, anhydrous ethanol, N-methylpyrrolidone, 2-methacryloyloxyethylphosphonic choline, and methyl methacrylate are mixed in a certain proportion, heated and stirred, and allowed to stand to remove bubbles. The specific composition of the casting solution is shown in Table 1 below: Table 1. Proportioning of Components in Casting Solution

[0021] Core solution preparation: N-methylpyrrolidone, water, and lithium chloride were mixed and stirred in a certain proportion, heated, and then allowed to stand to remove bubbles; the specific composition of the core solution is shown in Table 2 below: Table 2

[0022] Example 2 Spinning Using a spinning device manufactured by Chutian Technology, the casting solution prepared in Example 1 was extruded through a spinneret, simultaneously extruding the core solution. Solvents in the casting solution diffused into the core solution, while non-solvents in the core solution diffused into the casting solution, resulting in the precipitation of polyethersulfone into a interconnected network of pores. This process was then followed by air gap and coagulation bath molding to form a hollow fiber membrane. Specific process parameters for the spinning device were set as follows: air gap 600 mm; spinning speed 30 m / min; casting solution temperature 60°C; coagulation bath temperature 5°C; air gap humidity 90%; washing tank temperature 5°C. The flow rates of the casting solution and core solution were adjusted to maintain a ratio of approximately 1:1, resulting in a hollow fiber membrane with an inner diameter of approximately 0.8 mm and a wall thickness of approximately 0.2 mm. The microstructure of the hollow fiber membrane is shown below. Figure 3 , 4 As shown in Figure 5.

[0023] Table 3 Casting solution and core solution for each membrane during the spinning process.

[0024] Example 3 Hollow Fiber Ultrafiltration Membrane Base Membrane Modification 2,2-Dimethylolpropionic acid and Na2HPO4 solution (pH=9) were mixed in a mass ratio of 3:7 to form a modified solution. The second hollow fiber membrane prepared in Example 2 was immersed in the modified solution. The modified solution was heated to 80°C and then circulated at a constant temperature for 2 hours. The ultrafiltration membrane was then removed, the water was drained, and residual chemical substances were removed by vacuum to obtain the fifth hollow fiber membrane.

[0025] Example 4: Ultrafiltration Membrane Sterilization Treatment The first, third, and fourth hollow fiber membranes prepared in Example 2, and the fifth hollow fiber membrane modified in Example 3, were each bundled in groups of 300, cut and aligned, and then fixed to the outer shell with sealant to prepare hollow fiber columns, as detailed below:

[0026] The hollow fiber columns prepared above are then processed according to... Figure 1 The ultrafiltration device is assembled in the following manner and then sterilized in the following order.

[0027] Process 1: Prepare a total of 4 liters of 1.0 mol / L NaOH solution and pour it into feed tank 1. Set the pumping speed of pump 2 to 4 L / min, adjust the opening of reflux valve 5 so that the pressure displayed on the second pressure gauge 5 is 1 bar, and the circulation flushing time is 0.5 h. Process 2: Set the temperature of water bath 8 to 80℃, set the pumping speed of pump 2 to 4 L / min, adjust the opening of reflux valve 5 so that the pressure displayed on the second pressure gauge 5 is 1 bar, and circulate and rinse for 1 hour before cooling naturally to room temperature.

[0028] Example 5 Performance Test of Ultrafiltration Device After sterilization, the ultrafiltration device equipped with the first, second, third, and fourth hollow fiber columns was tested. The specific tests are as follows: Test 1: Pour 100 EU / mL of endotoxin stock solution into feed tank 3, set pump 2 to pumping speed of 4 L / min, adjust reflux valve 6 until the pressure displayed on second pressure gauge 5 is about 1 bar, and take permeate after 10 min to detect endotoxin concentration.

[0029] Test 2: Add sufficient purified water to feed tank 3, adjust the flow rate of pump 2 and the opening of reflux valve 6 to maintain the value of the second pressure gauge 5 at about 1 bar, close the first permeation end 7, and after 10 minutes, use a measuring cylinder to measure and record the flow rate and velocity of the permeate flowing out of the second permeation end 9 to calculate the ultrafiltration coefficient.

[0030] The results of Test 1 showed that after 40 sterilization treatments, the endotoxin concentration of the first and second hollow fiber columns was still below the detection limit (0.00739 EU / ml). This indicates that the hollow fiber membrane obtained by reacting 2,2-dimethylolpropionic acid (C monomer) with 2-methacryloyloxyethylphosphorylcholine (A monomer) and methyl methacrylate (B monomer) used to prepare the hollow fiber membrane can withstand frequent strong alkali and high temperature sterilization treatments, and can ensure the retention capacity of the hollow fiber membrane for small molecules after sterilization treatment.

[0031] The results of test 2 are as follows Figure 2As shown in the test results, the first and second hollow fiber columns prepared by reacting 2,2-dimethylolpropionic acid (C monomer) with 2-methacryloyloxyethyl phosphorylcholine (A monomer) and methyl methacrylate (B monomer) for preparing hollow fiber membranes remained relatively stable after more than 28 sterilization treatments. However, the third and fourth hollow fiber columns, which were not treated with 2,2-dimethylolpropionic acid (C monomer), showed a gradually increasing ultrafiltration coefficient after more than 28 sterilization treatments. The ultrafiltration coefficient is a key indicator of ultrafiltration membrane stability; an increase in the ultrafiltration coefficient indicates a decrease in membrane stability. Therefore, it can be seen that using 2,2-dimethylolpropionic acid (C monomer) improves the stability of the hydrophilic membrane prepared using 2-methacryloyloxyethyl phosphorylcholine (A monomer) and methyl methacrylate (B monomer). The inventors believe that the neopentyl structure of 2,2-dimethylolpropionic acid (C monomer) enables C monomer to form a stable compound after reacting with the groups on 2-methacryloyloxyethylphosphorylcholine (A monomer) and methyl methacrylate (B monomer) used in the preparation of hollow fiber membranes. This maintains the stability of the ultrafiltration membrane, allowing it to maintain high stability even after multiple sterilization processes, thus exhibiting a relatively stable ultrafiltration coefficient.

[0032] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for producing a hollow fiber membrane, characterized by, The method comprises the following steps: The A monomer with phosphorylcholine branch, the B monomer with methacryl group, the C monomer with neopentyl group having carboxyl connected to quaternary carbon atom and hydroxyl connected to primary carbon atom and a film-forming polymer are mixed to form a film-forming solution, and the film-forming solution is prepared into a hollow fiber membrane through a film-forming process.

2. A hollow fiber membrane production method characterized by, The method comprises the following steps: S1: The A monomer with phosphorylcholine branch, the B monomer with methacryl group and a film-forming polymer are mixed to form a film-forming solution, and the film-forming solution is prepared into a hollow fiber base membrane through a film-forming process; S2: The C monomer with neopentyl group having carboxyl connected to quaternary carbon atom and hydroxyl connected to primary carbon atom is prepared into a basic solution, and the basic solution is coated on the hollow fiber base membrane.

3. The method for producing a hollow fiber membrane according to claim 2, characterized by, The pH of the basic solution is 8-13, the content of the C monomer in the basic solution is 30% (V / V), and the temperature of the solution when the basic solution is coated on the hollow fiber base membrane is higher than 50℃.

4. The method for producing a hollow fiber membrane according to claim 2, characterized by, The basic solution is heated to 80℃, the hollow fiber base membrane is immersed in the basic solution and kept for more than 20 min, and then the immersed hollow fiber base membrane is taken out from the basic solution and drained and placed in a negative pressure environment.

5. The method for producing a hollow fiber membrane according to any one of claims 1 to 4, characterized by, The A monomer is one of 2-methacryloyloxyethyl phosphorylcholine and methacrylic acid sulfonic acid inner ammonium salt, the B monomer is one of methyl methacrylate or its salt, ethyl methacrylate or its salt, and propyl methacrylate or its salt, the molar ratio of the A monomer and the B monomer is 1: (5-9), and the C monomer is 2,2-dimethylol propionic acid.

6. The method for producing a hollow fiber membrane according to any one of claims 1 to 4, characterized by, The film-forming polymer is selected from one of polypropylene, polyethylene, polyacrylonitrile, polysulfone, polyethersulfone, polyester, polyvinyl chloride, and polyvinylidene fluoride.

7. A hollow fiber membrane, characterized by, The hollow fiber membrane is prepared according to the method for preparing the hollow fiber membrane according to any one of claims 1-6.

8. The hollow fiber membrane according to claim 7, characterized in that, The thickness of the hollow fiber membrane is 80-150 μm, and the diameter of the hollow fiber membrane is 500-1000 μm.

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