A method for hydrophilic modification of PVDF membrane with low protein adsorption capacity and cross-linked network and application thereof

Abstract

The application belongs to the technical field of separation membranes, and particularly relates to a PVDF membrane hydrophilic modification method with low protein adsorption and a crosslinked network and application. Methyl methacryl dopamine, an organic compound monomer containing an electron-withdrawing group, and a thermal free radical initiator are copolymerized in water, the polymer solution is diluted, a PVDF hydrophobic membrane pre-wetted by an organic solvent is immersed in the solution, and then the modified membrane is obtained by crosslinking through a crosslinking agent solution, and cleaning. The application forms a dense network structure through copolymerization and crosslinking, weakens the interaction between the membrane and the protein from the structure and electrostatic interaction, and greatly reduces the protein adsorption. The hydrophilic coating is firmly combined with the membrane substrate, and the finished product membrane can be directly modified. The process is mild and safe to operate. The modified membrane has good hydrophilicity and water flux, and is suitable for high-value protein filtration and concentration fields.

Description

Technical Field

[0001] This invention belongs to the field of separation membrane technology, specifically relating to a method and application of hydrophilic modification of PVDF membranes with low protein adsorption capacity and cross-linked network. Background Technology

[0002] Polyvinylidene fluoride (PVDF) membranes are widely used in separation and filtration processes in biopharmaceuticals, food processing, and environmental monitoring due to their excellent chemical stability, mechanical strength, temperature resistance, and solvent resistance. They are particularly favored as a substrate for filter devices, especially in the filtration and concentration of high-value proteins. However, PVDF is a highly hydrophobic polymer. When filtering protein solutions, the hydrophobic effect leads to severe protein adsorption on the membrane surface, significantly reducing the protein solution recovery rate. Furthermore, the adsorbed protein easily causes membrane pore blockage, affecting the membrane's filtration flux and reusability, thus limiting its further application in protein separation and purification.

[0003] To address the hydrophobicity of PVDF membranes, various hydrophilic modification methods have been developed in the industry. Among them, modification techniques based on dopamine and its derivatives have become a research hotspot due to their relatively simple operation and significant hydrophilication effect. In existing technologies, some methods involve immersing the PVDF membrane in a dopamine aqueous solution, utilizing the oxidative self-polymerization of dopamine to form a polydopamine coating to achieve hydrophilicity. While this method can impart hydrophilicity to the PVDF membrane, the bond between polydopamine and the PVDF membrane relies solely on non-covalent bonds with low bond energy, leading to easy detachment of the hydrophilic coating. Furthermore, the oxidative polymerization of dopamine easily forms particles with uneven particle sizes, making precise control of the coating thickness difficult. Excessive coating thickness or large particles further increases the risk of detachment. Detached coatings can contaminate the filtered products, causing excessive leaching and seriously affecting safety and user experience.

[0004] Another technique involves the direct oxidative polymerization of dopamine compounds in the casting solution, or the prior oxidative polymerization followed by the addition of the product to the casting solution to prepare PVDF films. While these methods enhance the non-covalent bonding between the hydrophilic components and the PVDF matrix to some extent, they still fail to overcome the inherent limitations of non-covalent bond energy. Therefore, the improvement in coating adhesion is limited, and the problem of coating detachment cannot be fundamentally solved. The core principle of the aforementioned dopamine modification techniques relies on the oxidation of catechol from dopamine to a quinone structure, followed by a disproportionation reaction to generate semi-quinone free radicals, which then couple to form cross-links. This singular reaction mechanism leads to inherent defects in the modification effect.

[0005] In addition, there are technologies that use acrylic acid with electron-withdrawing groups to react with PVDF powder to prepare block copolymers, which reduce protein adsorption and coagulation of the membrane by means of electrostatic effect. However, this requires the pretreatment of PVDF powder with concentrated alkali, which poses safety hazards in the operation process. Moreover, the process steps are complicated and have high requirements for equipment and operating conditions. It cannot directly modify the prepared PVDF hydrophobic membrane, thus limiting its applicability and making it difficult to meet the actual needs of direct modification of existing PVDF membrane substrates in industrial production.

[0006] In summary, existing methods for hydrophilic modification of PVDF membranes all have varying degrees of shortcomings, such as low coating adhesion and easy detachment, complex processes and poor safety, inability to directly modify finished PVDF membranes, and the continued high protein adsorption capacity of the modified membranes. Therefore, developing a simple, safe, and direct method for modifying finished hydrophobic PVDF membranes, resulting in a strong membrane layer bond and low protein adsorption capacity, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the problems mentioned in the background art, this invention proposes a hydrophilic modification method and application for PVDF membranes with low protein adsorption capacity and cross-linked networks. The method involves copolymerizing methacryloyldopamine with an organic compound monomer containing electron-withdrawing groups, followed by cross-linking to form a dense network structure. This weakens the interaction between the membrane and protein molecules from both structural and electrostatic dimensions. The modified PVDF membrane exhibits significantly lower protein adsorption capacity compared to the unmodified membrane, effectively reducing protein adsorption loss and significantly improving the recovery rate during protein solution filtration and concentration processes, thus meeting the core application needs of the biopharmaceutical field.

[0008] The technical solution adopted by this invention to solve its technical problem is: to provide a method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network, comprising the following steps:

[0009] S1. Preparation of copolymerization solution: Add methacrylamide, an organic monomer containing an electron-withdrawing group, and a thermal free radical initiator to water, and heat to carry out the copolymerization reaction;

[0010] S2. Dilute the polymer solution obtained in step S1 with water;

[0011] S3. Immerse the PVDF hydrophobic membrane in the diluted polymer solution. Before immersion, pre-wet the PVDF hydrophobic membrane with an organic solvent and complete the full material exchange.

[0012] S4. Take out the PVDF hydrophobic membrane, remove excess liquid from the membrane surface, transfer it to the crosslinking agent solution, and heat it to carry out the crosslinking reaction.

[0013] S5. The PVDF membrane that has completed the cross-linking reaction is cleaned to obtain the hydrophilic modified PVDF membrane.

[0014] The PVDF hydrophobic membrane refers to a hydrophobic microfiltration or ultrafiltration membrane prepared by phase inversion or electrospinning with a pore size range of 0.1-10 μm and a porosity of 60-90%.

[0015] Further, in step 1), the mass concentration of methacrylamide in water is 1%-5%, the mass concentration of the organic compound monomer containing electron-withdrawing groups in water is 0.1%-2.5%, and the mass ratio of methacrylamide to the organic compound monomer containing electron-withdrawing groups is 1:0.1-0.5.

[0016] Further, in step 1), the mass concentration of the thermal free radical initiator in water is 0.5%-5%, the copolymerization temperature is 50-100℃, and the reaction time is 5-10 hours.

[0017] Further, in step 2), the polymer solution is diluted with water by 2-10 times.

[0018] Furthermore, in step 4), the cross-linking reaction temperature is 60-100℃, and the cross-linking reaction time is 5-20 minutes.

[0019] Furthermore, the organic compound monomer containing electron-withdrawing groups includes one or more of acrylic acid and acrylates, methacrylic acid and methacrylates, acrylamide and its derivatives, N,N-dimethylacrylamide, vinylpyrrolidone, vinylpyridine, maleic anhydride, sodium styrenesulfonate, and styrenesulfonic acid.

[0020] Furthermore, the thermal free radical initiator includes one or more of persulfate, azo compounds, and persulfate / bisulfite redox systems; the persulfate includes ammonium persulfate and potassium persulfate, and the azo compounds include azobisisobutylamidine hydrochloride.

[0021] Furthermore, the organic solvent includes one or more of ethanol, isopropanol, and acetic acid, or an aqueous solution of any one of ethanol, isopropanol, and acetic acid with a mass concentration of 30% or more.

[0022] Further, the crosslinking agent includes one or more of dialdehyde compounds and diisocyanate compounds; the dialdehyde compounds include butanaldehyde, glutaraldehyde, and hexamethylenedialdehyde; and the diisocyanate compounds include toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0023] The application of a PVDF membrane prepared by a hydrophilic modification method with low protein adsorption capacity and cross-linked network in the field of high-value protein filtration and concentration.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) This invention uses methacrylamide to copolymerize with an organic compound monomer containing an electron-withdrawing group and cross-link it to form a dense network structure. This weakens the interaction between the membrane and protein molecules from both structural and electrostatic dimensions. The protein adsorption capacity of the modified PVDF membrane is significantly reduced compared with the unmodified membrane, effectively reducing protein adsorption loss and significantly improving the recovery rate in the process of protein solution filtration and concentration, which meets the core application needs of the biopharmaceutical field.

[0026] (2) This invention abandons the traditional dopamine modification method that relies solely on non-covalent bonding. It first achieves the initial adhesion of hydrophilic polymers to PVDF membranes through hydrogen bonding and Π-Π stacking. Then, the polymers are crosslinked to form a three-dimensional network crosslinked structure through a crosslinking agent, which tightly binds the hydrophilic coating to the membrane substrate as a whole. This completely solves the problems of easy peeling of traditional modified hydrophilic coatings and excessive leaching leading to product contamination, and greatly improves the safety and reliability of membrane use.

[0027] (3) This invention does not require pretreatment of PVDF powder with concentrated alkali, nor does it require complex polymerization in casting solution. It can directly modify the finished PVDF hydrophobic membrane to adapt to microfiltration / ultrafiltration membranes with different pore sizes and porosities. The whole process uses water as the main reaction medium, the reaction conditions are mild and easy to control, and organic solvents are only used for low-toxicity pre-wetting. The operation is safe and the equipment requirements are low, making it more suitable for industrial mass production.

[0028] (4) The modified PVDF membrane of this invention has extremely fast wetting speed in pure water and cold brine, which thoroughly improves the hydrophobic properties and avoids membrane pore blockage. The cross-linked network makes the hydrophilic properties durable and can still maintain good wetting effect after repeated use. Under the premise of low protein adsorption, the membrane still maintains a high water flux, which takes into account the filtration efficiency and extends the actual service life of the membrane. Attached Figure Description

[0029] Figure 1 Here is the chemical reaction equation for Example 1. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1:

[0032] like Figure 1 As shown, the copolymerization solution was prepared by adding 2g of methacrylamide, 1g of acrylic acid, and 2g of ammonium persulfate to a flask, then adding 95g of deionized water, mixing well, heating to 80℃, and stirring at a constant temperature for 8 hours to complete the copolymerization reaction.

[0033] Dilute the polymer solution: Add deionized water to the polymer solution prepared above and dilute to a total mass of 500g. Stir well and set aside for later use.

[0034] Immersion modification of membrane: The 0.22μm PVDF hydrophobic membrane was pre-wetted with anhydrous ethanol. After the mass exchange was fully completed, the membrane was immersed in the diluted polymer solution for 10 min.

[0035] Crosslinking reaction: Take out the PVDF membrane, blow off the excess liquid on the membrane surface with compressed air, and then transfer it to a 1% glutaraldehyde aqueous solution. Heat to 80℃ and keep the temperature constant for 5 minutes to complete the crosslinking.

[0036] Post-processing: The cross-linked PVDF membrane is removed, and the surface residual reagents are repeatedly washed with deionized water. After drying, the modified PVDF membrane is obtained.

[0037] The modified membrane was tested for performance, and the results were as follows: pure water wetting speed < 1s, wetting speed of 0℃ supersaturated sodium chloride cold brine 3-5s, and water flux 13mL / min / cm. 2 @-70KPa, protein adsorption capacity 2.2mg / cm 2 .

[0038] Example 2:

[0039] Preparation of copolymerization solution: Add 4g of methacrylamide, 1g of acrylic acid, and 2g of ammonium persulfate to a flask, then add 93g of deionized water, mix well, heat to 80℃, and stir at a constant temperature for 8 hours to complete the copolymerization reaction;

[0040] Dilute the polymer solution: Add deionized water to the above polymer solution to dilute to a total mass of 500g, stir well and set aside for use;

[0041] Immersion modification of membrane: 0.22μm PVDF hydrophobic membrane was pre-wetted with anhydrous ethanol, and after sufficient mass exchange, it was immersed in diluted polymer solution for 10 min.

[0042] Crosslinking reaction: Dry the excess liquid on the membrane surface with compressed air, transfer the membrane to a 1% glutaraldehyde aqueous solution, and crosslink at 80℃ for 5 minutes.

[0043] Post-treatment: The membrane was repeatedly washed with deionized water and dried to obtain the modified PVDF membrane.

[0044] Performance test results: Pure water wetting rate < 1s, cold brine wetting rate < 1s, water flux 11mL / min / cm 2 @-70KPa, protein adsorption capacity 2.4mg / cm³ 2 .

[0045] Example 3:

[0046] Preparation of copolymerization solution: Add 4g of methacrylamide, 2g of acrylic acid, and 2g of ammonium persulfate to a flask, then add 92g of deionized water, and stir at 80℃ for 8 hours to complete the copolymerization reaction;

[0047] Dilute the polymer solution: Dilute with deionized water to a total mass of 500g and stir well;

[0048] Immersion modification of membrane: 0.22μm PVDF hydrophobic membrane was pre-wetted with anhydrous ethanol, and after sufficient mass exchange, it was immersed in polymer dilution solution for 10 min;

[0049] Crosslinking reaction: Dry off excess liquid, transfer to 1% glutaraldehyde aqueous solution, and crosslink at 80℃ for 5 minutes;

[0050] Post-processing: After washing with deionized water and drying, the modified PVDF membrane is obtained.

[0051] Performance test results: Pure water wetting speed < 1s, cold brine wetting speed < 1s, water flux 9mL / min / cm 2 @-70KPa, protein adsorption capacity 1.9mg / cm³ 2 .

[0052] Example 4:

[0053] Preparation of copolymerization solution: Add 4g of methacrylamide, 2g of acrylic acid, and 2g of potassium persulfate to a flask, then add 92g of deionized water, and stir at 80℃ for 8 hours to complete the copolymerization reaction;

[0054] Dilute the polymer solution: Dilute with deionized water to a total mass of 500g and stir well;

[0055] Immersion modification of membrane: 0.22μm PVDF hydrophobic membrane was pre-wetted with 50% isopropanol aqueous solution, and after sufficient mass exchange, it was immersed in polymer dilution solution for 10min;

[0056] Crosslinking reaction: Dry excess liquid with compressed air, transfer to 1% glutaraldehyde aqueous solution, and crosslink at 80℃ for 5 minutes;

[0057] Post-treatment: The membrane was repeatedly washed with deionized water and dried to obtain the modified PVDF membrane.

[0058] Performance test results: Pure water wetting speed < 1s, cold brine wetting speed < 1s, water flux 9mL / min / cm 2 @-70KPa, protein adsorption capacity 1.8mg / cm³ 2 .

[0059] Example 5:

[0060] Preparation of copolymerization solution: Add 4g of methacrylamide, 2g of acrylic acid, and 2g of potassium persulfate to a flask, then add 92g of deionized water, and stir at 80℃ for 8 hours to complete the copolymerization reaction;

[0061] Dilute the polymer solution: Dilute with deionized water to a total mass of 500g and stir well;

[0062] Immersion modification of membrane: 0.22μm PVDF hydrophobic membrane was pre-wetted with 50% isopropanol aqueous solution, and after sufficient mass exchange, it was immersed in polymer dilution solution for 10min;

[0063] Crosslinking reaction: Dry off excess liquid, transfer to a 2% (w / w) glutaraldehyde aqueous solution, and crosslink at 90°C for 10 minutes;

[0064] Post-processing: After washing with deionized water and drying, the modified PVDF membrane is obtained.

[0065] Performance test results: Pure water wetting speed < 1s, cold brine wetting speed < 1s, water flux 8 mL / min / cm 2 @-70KPa, protein adsorption capacity 1.9mg / cm³ 2 .

[0066] Example 6:

[0067] Preparation of copolymerization solution: Add 4g of methacrylamide, 0.4g of acrylic acid, and 2g of ammonium persulfate to a flask, then add 93.6g of deionized water, and stir at 80℃ for 8 hours to complete the copolymerization reaction;

[0068] Dilute the polymer solution: Dilute with deionized water to a total mass of 500g and stir well;

[0069] Immersion modification of membrane: 0.22μm PVDF hydrophobic membrane was pre-wetted with 50% isopropanol aqueous solution, and after sufficient mass exchange, it was immersed in polymer dilution solution for 10min;

[0070] Crosslinking reaction: Dry off excess liquid, transfer to 2% glutaraldehyde aqueous solution, and crosslink at 90℃ for 10 minutes;

[0071] Post-processing: After washing with deionized water and drying, the modified PVDF membrane is obtained.

[0072] Performance test results: Pure water wetting rate < 1s, cold brine wetting rate < 1s, water flux 12mL / min / cm 2 @-70KPa, protein adsorption capacity 5.6mg / cm³ 2 .

[0073] Example 7:

[0074] Preparation of copolymerization solution: Add 4g of methacrylamide, 0.4g of acrylamide, and 2g of ammonium persulfate to a flask, then add 93.6g of deionized water, and stir at 80℃ for 8 hours to complete the copolymerization reaction;

[0075] Dilute the polymer solution: Dilute with deionized water to a total mass of 500g and stir well;

[0076] Immersion modification of membrane: 0.22μm PVDF hydrophobic membrane was pre-wetted with 50% isopropanol aqueous solution, and after sufficient mass exchange, it was immersed in polymer dilution solution for 10min;

[0077] Crosslinking reaction: Dry off excess liquid, transfer to 2% glutaraldehyde aqueous solution, and crosslink at 90℃ for 10 minutes;

[0078] Post-processing: After washing with deionized water and drying, the modified PVDF membrane is obtained.

[0079] Performance test results: Pure water wetting rate < 1s, cold brine wetting rate < 1s, water flux 10mL / min / cm 2 @-70KPa, protein adsorption capacity 6.1mg / cm³ 2 .

[0080] Example 8:

[0081] Preparation of copolymerization solution: Add 4g of methacrylamide dopamine, 0.4g of styrene sulfonic acid, and 2g of ammonium persulfate to a flask, then add 93.6g of deionized water, and stir at 80℃ for 8 hours to complete the copolymerization reaction;

[0082] Dilute the polymer solution: Dilute with deionized water to a total mass of 500g and stir well;

[0083] Immersion modification of membrane: 0.22μm PVDF hydrophobic membrane was pre-wetted with 50% isopropanol aqueous solution, and after sufficient mass exchange, it was immersed in polymer dilution solution for 10min;

[0084] Crosslinking reaction: Dry off excess liquid, transfer to 2% glutaraldehyde aqueous solution, and crosslink at 90℃ for 10 minutes;

[0085] Post-processing: After washing with deionized water and drying, the modified PVDF membrane is obtained.

[0086] Performance test results: Pure water wetting rate < 1s, cold brine wetting rate < 1s, water flux 10mL / min / cm 2 @-70KPa, protein adsorption capacity 2.7mg / cm³ 2 .

[0087] Example 9:

[0088] Preparation of copolymerization solution: Add 4g of methacrylamide dopamine, 0.4g of styrene sulfonic acid, and 2g of ammonium persulfate to a flask, then add 93.6g of deionized water, and stir at 80℃ for 8 hours to complete the copolymerization reaction;

[0089] Dilute the polymer solution: Dilute with deionized water to a total mass of 500g and stir well;

[0090] Immersion modification of membrane: 0.22μm PVDF hydrophobic membrane was pre-wetted with 50% isopropanol aqueous solution, and after sufficient mass exchange, it was immersed in polymer dilution solution for 10min;

[0091] Crosslinking reaction: Dry off excess liquid, transfer to a 2% (w / w) succinaldehyde aqueous solution, and crosslink at 90℃ for 10 minutes;

[0092] Post-treatment: The membrane was repeatedly washed with deionized water and dried to obtain the modified PVDF membrane.

[0093] Performance test results: Pure water wetting rate < 1s, cold brine wetting rate < 1s, water flux 10mL / min / cm 2 @-70KPa, protein adsorption capacity 2.8mg / cm³ 2 .

[0094] Performance Testing Specifications

[0095] Cold brine wetting rate: A drop test was conducted using a supersaturated sodium chloride solution stored at 0℃, and the time required for the membrane to be completely wetted was recorded;

[0096] Water flux: The amount of pure water per minute per unit area of ​​the membrane under a pressure of -70 kPa.

[0097] Protein adsorption capacity: Dead-end filtration was performed on a 10 mm circular modified membrane using 1 g / L pancreatic soy peptone. The protein adsorption capacity on the membrane surface was deduced by measuring the absorbance of the solution before and after filtration.

[0098] Comparative example:

[0099] A 0.22 μm PVDF hydrophobic membrane without hydrophilic modification was tested under the same conditions. The results showed that it could not be naturally wetted by pure water or cold saline. After being wetted with ethanol, the water flux measured with water was 13 mL / min / cm. 2@-70KPa, protein adsorption capacity 23.7mg / cm³ 2 .

[0100] Table 1 shows the performance test results of Examples 1-9.

[0101] Dead-end filtration was performed on a 10 mm circular membrane using 1 g / L pancreatic soy peptone, and the amount of protein adsorbed was deduced by measuring the absorbance of the solution before and after filtration.

[0102]

[0103] As can be seen from the test results of the above embodiments and comparative examples, the PVDF membrane modified by the method of the present invention has excellent hydrophilic properties, and the protein adsorption capacity is significantly reduced compared with the unmodified membrane. Moreover, the water flux, protein adsorption capacity and other properties of the membrane can be precisely controlled by adjusting the raw material ratio and crosslinking process parameters according to actual application needs.

[0104] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network, characterized in that, Includes the following steps: S1. Preparation of copolymerization solution: Add methacrylamide, an organic monomer containing an electron-withdrawing group, and a thermal free radical initiator to water, and heat to carry out the copolymerization reaction; S2. Dilute the polymer solution obtained in step S1 with water; S3. Immerse the PVDF hydrophobic membrane in the diluted polymer solution. Before immersion, pre-wet the PVDF hydrophobic membrane with an organic solvent and complete the full material exchange. S4. Take out the PVDF hydrophobic membrane, remove excess liquid from the membrane surface, transfer it to the crosslinking agent solution, and heat it to carry out the crosslinking reaction. S5. The PVDF membrane that has completed the cross-linking reaction is cleaned to obtain the hydrophilic modified PVDF membrane.

2. The method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network according to claim 1, characterized in that, In step S1, the mass concentration of methacrylamide in water is 1%-5%, the mass concentration of the organic compound monomer containing electron-withdrawing groups in water is 0.1%-2.5%, and the mass ratio of methacrylamide to the organic compound monomer containing electron-withdrawing groups is 1:0.1-0.

5.

3. The method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network according to claim 1, characterized in that, In step S1, the mass concentration of the thermal free radical initiator in water is 0.5%-5%, the copolymerization temperature is 50-100℃, and the reaction time is 5-10 hours.

4. The method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network according to claim 1, characterized in that, In step S2, the polymer solution is diluted with water by 2-10 times.

5. The method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network according to claim 1, characterized in that, In step S4, the crosslinking reaction temperature is 60-100℃ and the crosslinking reaction time is 5-20 minutes.

6. The method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network according to claim 1, characterized in that, The organic compound monomers containing electron-withdrawing groups include one or more of acrylic acid and acrylates, methacrylic acid and methacrylates, acrylamide and its derivatives, N,N-dimethylacrylamide, vinylpyrrolidone, vinylpyridine, maleic anhydride, sodium styrenesulfonate, and styrenesulfonic acid.

7. The method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network according to claim 1, characterized in that, The thermal free radical initiator includes one or more of persulfate, azo compounds, and persulfate / bisulfite redox systems; the persulfate includes ammonium persulfate and potassium persulfate, and the azo compound includes azobisisobutylamidine hydrochloride.

8. The method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network according to claim 1, characterized in that, The organic solvent includes one or more of ethanol, isopropanol, and acetic acid, or an aqueous solution of any one of ethanol, isopropanol, and acetic acid with a mass concentration of 30% or more.

9. The method for hydrophilic modification of a PVDF membrane with low protein adsorption capacity and a cross-linked network according to claim 1, characterized in that, The crosslinking agent includes one or more of dialdehyde compounds and diisocyanate compounds; the dialdehyde compounds include butanaldehyde, glutaraldehyde, and hexamethylenedialdehyde; and the diisocyanate compounds include toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

10. The application of a PVDF membrane prepared by a hydrophilic modification method for a PVDF membrane with low protein adsorption capacity and cross-linked network in the field of high-value protein filtration and concentration.

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