A hydrophilic polytetrafluoroethylene separation membrane, a preparation method and application thereof
Patent Information
- Application Number
- CN202211421572.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-14
- Publication Date
- 2026-09-18
- Estimated Expiration
- 2042-11-14
AI Technical Summary
[0007]本申请针对PTFE分离膜的亲水改性困难的问题，提供了一种亲水性聚四氟乙烯分离膜及其制备方法和应用，采用可以发生快速交联反应的单体溶液分别浸润聚四氟乙烯分离膜，使交联反应在聚四氟乙烯分离膜的表面和孔道内部同时发生，形成超薄和完整的亲水性交联层
[0038] Optionally, the polytetrafluoroethylene separation membrane includes a flat sheet membrane or a hollow fiber membrane.
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Figure CN118059700B_ABST
Abstract
Description
Technical Field
[0001] This application relates to a hydrophilic polytetrafluoroethylene separation membrane, its preparation method and application, belonging to the field of polymer separation membrane technology. Background Technology
[0002] Membrane bioreactors (MBRs) are the most widely used and typical membrane-based water treatment technology. In my country, the annual consumption of MBR membranes reaches tens of millions of square meters, making it the most widely used field in water treatment membranes, generating an annual output value of nearly 100 billion yuan. Membrane materials are crucial in determining the performance of water treatment separation membranes. With the development of membrane separation technology, existing separation membrane materials such as polysulfone, polyvinylidene fluoride, and polypropylene are insufficient in mechanical strength and solvent resistance, severely limiting the application of membrane-based water treatment technologies. Therefore, there is an urgent need to develop high-performance separation membranes.
[0003] Polytetrafluoroethylene (PTFE), known as the "king of plastics," possesses excellent chemical stability, solvent resistance, and mechanical properties, making it an ideal organic membrane material. Companies like Sumitomo in Japan, Gore in the US, and domestic water treatment companies have shifted their research focus to PTFE water treatment separation membranes, successively launching several commercial products that have demonstrated their advantages in water treatment processes. However, PTFE's low surface energy and high hydrophobicity result in high water production pressure, continuous flux decline, and poor fouling resistance during water treatment, severely limiting its application. Furthermore, MBRs require low-pressure water production, while PTFE membranes have high water penetration pressure, necessitating ethanol pre-wetting in the MBR process to achieve water production, leading to secondary pollution in the water treatment process.
[0004] Studies have shown that hydrophilic surfaces are more conducive to water permeation through membranes, and hydrophilic modification is an effective means to improve the flux and antifouling performance of water treatment separation membranes. However, the low surface energy of PTFE makes it difficult for hydrophilic modification materials to adsorb onto the membrane surface, posing a significant challenge to the hydrophilic modification of PTFE separation membranes. Furthermore, it is generally speculated that the continuous decline in water flux of PTFE membranes is related to bubble blockage within the pores, but the mechanisms of bubble formation and elimination have not been systematically studied, limiting the application of PTFE separation membranes in water treatment processes such as MBR.
[0005] To suppress membrane fouling, MBRs employ aeration and low-pressure suction of permeate water. The feed water contains a large amount of air bubbles, necessitating high-pressure backwashing to remove contaminants. Researchers have conducted extensive studies on MBR fouling and cleaning, but existing research is largely based on traditional membrane materials such as polyvinylidene fluoride (PVDF) and polysulfone, primarily considering the sludge fouling process. In PTFE membrane separation, gaseous fouling is also a significant cause of water flux decline. Therefore, it is necessary to examine the mechanism of flux decline and membrane cleaning strategies during MBR membrane separation, taking into account the inherent properties of hydrophilic PTFE membranes, to provide technical support for the application of PTFE separation membranes in MBR processes.
[0006] The hydrophobic properties of PTFE and the water treatment process require a hydrophilic modification layer that penetrates deep into the pores of the PTFE membrane, and this hydrophilic layer should be relatively thin to inhibit pore blockage. Interfacial polymerization is a classic method for preparing reverse osmosis membranes, characterized by rapid reaction speed and strong self-inhibition, and it can form a thin cross-linked layer, potentially creating a hydrophilic layer inside the PTFE membrane pores. This project selects a solvent system capable of wetting PTFE to achieve overall hydrophilic modification of the separation membrane pores. Regarding the decrease in PTFE membrane flux, the growth mechanism of oil droplets in coalescing materials is used to explain the decrease in water flux caused by the coalescence of bubbles within the PTFE membrane pores during water treatment. By combining the hydrophilic modification of the PTFE membrane with changes in operating conditions, stable operation of the PTFE membrane in MBR (membrane bioreactor) processes can be achieved. Summary of the Invention
[0007] This application addresses the difficulty of hydrophilic modification of PTFE separation membranes by providing a hydrophilic polytetrafluoroethylene separation membrane, its preparation method, and its application. The method involves impregnating the polytetrafluoroethylene separation membrane with a monomer solution capable of rapid crosslinking, allowing the crosslinking reaction to occur simultaneously on the surface and inside the pores of the polytetrafluoroethylene separation membrane, thus forming an ultrathin and complete hydrophilic crosslinked layer.
[0008] According to one aspect of this application, a hydrophilic polytetrafluoroethylene (PTFE) separation membrane is provided, comprising a PTFE separation membrane and a hydrophilic functional layer, wherein the hydrophilic functional layer is attached to the surface and the interior of the pores of the PTFE separation membrane, and the hydrophilic functional layer is formed by crosslinking a hydrophilic monomer and a crosslinking agent.
[0009] Optionally, the thickness of the hydrophilic functional layer is 20–400 nm.
[0010] Optionally, the hydrophilic monomer is selected from at least one of glycerol, ethylene glycol, ethylenediamine, hexamethylenediamine, m-phenylenediamine, and piperazine.
[0011] Optionally, the crosslinking agent is a polyacrylamide chloride.
[0012] According to another aspect of this application, a method for preparing a hydrophilic polytetrafluoroethylene separation membrane is provided, comprising the following steps:
[0013] a) The polytetrafluoroethylene separation membrane was placed in a hydrophilic monomer solution, impregnated with I, and dried to obtain the polytetrafluoroethylene separation membrane precursor;
[0014] b) The polytetrafluoroethylene separation membrane precursor was placed in a crosslinking agent solution, impregnated with II, and dried to obtain a hydrophilic polytetrafluoroethylene separation membrane.
[0015] This application utilizes hydrophilic monomers and crosslinking agents that can undergo rapid crosslinking reactions with each other. Corresponding solvents are selected based on the hydrophilic monomers and crosslinking agents, ensuring sufficient wetting of the PTFE separation membrane while exhibiting low solubility for the other monomer. First, the hydrophilic monomer solution is used to wet the PTFE separation membrane. After drying, the dissolved hydrophilic monomers are adsorbed onto the surface and pores of the PTFE separation membrane. Then, a crosslinking agent solution is used to wet the PTFE separation membrane. After removal and heating, the hydrophilic monomers and crosslinking agents undergo in-situ crosslinking reactions at the interface between the crosslinking agent solution and the PTFE separation membrane, rapidly forming an ultrathin hydrophilic functional layer, thus achieving hydrophilic modification of the PTFE separation membrane.
[0016] Optionally, the hydrophilic monomer solution comprises a hydrophilic monomer and solvent I;
[0017] The hydrophilic monomer is a hydrophilic compound containing at least one functional group selected from hydroxyl, primary amino, and secondary amino groups;
[0018] Solvent I is selected from alcohols or esters.
[0019] Optionally, the hydrophilic monomer is selected from at least one of glycerol, ethylene glycol, ethylenediamine, hexamethylenediamine, m-phenylenediamine, and piperazine.
[0020] Optionally, solvent I is selected from at least one of methanol, ethanol, propanol, and ethyl acetate.
[0021] Optionally, the mass concentration of the hydrophilic monomer in the hydrophilic monomer solution is 0.1% to 15%.
[0022] Optionally, the mass concentration of the hydrophilic monomer in the hydrophilic monomer solution is selected from any value or a range between two values from 0.1%, 0.5%, 1%, 3%, 5%, 7%, 10%, 12.5%, and 15%.
[0023] Optionally, the crosslinking agent solution comprises a crosslinking agent and solvent II;
[0024] The crosslinking agent is a polyacryl chloride;
[0025] Solvent II is an alkane and / or a benzene.
[0026] Optionally, the polyacryl chloride is selected from at least one of isophthaloyl chloride, terephthaloyl chloride, and trimesoyl chloride.
[0027] Optionally, solvent II is selected from at least one of n-hexane, cyclohexane, toluene, and xylene.
[0028] Optionally, the mass concentration of the crosslinking agent in the crosslinking agent solution is 0.1% to 5%.
[0029] Optionally, the mass concentration of the crosslinking agent in the crosslinking agent solution is selected from any value or a range between two values from 0.1%, 0.5%, 1%, 2%, 3%, 4%, and 5%.
[0030] Optionally, the immersion time for I is 5 to 120 minutes.
[0031] Optionally, the immersion time I is any value or a range between two values from 5 min, 10 min, 20 min, 25 min, 40 min, 60 min, 80 min, and 120 min.
[0032] Alternatively, the drying method is natural air drying.
[0033] Optionally, the immersion time II is 1 to 60 minutes.
[0034] Optionally, the immersion time II is any value among 1 min, 5 min, 20 min, 30 min, and 60 min, or a range between two values.
[0035] Optionally, the drying temperature is 40–100°C, and the drying time is 2–100 min.
[0036] Optionally, the drying temperature is any value or a range between two of 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C.
[0037] Optionally, the drying time is selected from any value of 2 min, 5 min, 10 min, 50 min, 75 min, 100 min, or a range between two values.
[0038] Optionally, the polytetrafluoroethylene separation membrane includes a flat sheet membrane or a hollow fiber membrane.
[0039] According to another aspect of this application, a membrane bioreactor is provided, comprising the above-described polytetrafluoroethylene separation membrane or the polytetrafluoroethylene separation membrane obtained by the above preparation method.
[0040] The beneficial effects that this application can produce include:
[0041] 1) The hydrophilic polytetrafluoroethylene separation membrane provided in this application can improve the hydrophilicity and water flux of the PTFE separation membrane and reduce the penetration pressure by attaching a hydrophilic functional layer to the surface and pores of the PTFE separation membrane.
[0042] 2) The preparation method of the hydrophilic polytetrafluoroethylene separation membrane provided in this application uses a solvent system with good wettability to the PTFE separation membrane. The hydrophilic modified material can be fully wetted into the surface and pores of the PTFE separation membrane, forming a complete hydrophilic modified layer in the membrane pores, effectively inhibiting gas embolism in the membrane pores and reducing the water penetration pressure of the PTFE separation membrane.
[0043] 3) The method for preparing the hydrophilic polytetrafluoroethylene separation membrane provided in this application utilizes the interfacial polymerization reaction mechanism. The hydrophilic monomer reacts rapidly with the crosslinking agent to quickly form a crosslinked layer, inhibiting the occurrence of subsequent crosslinking reactions. This method can form an ultrathin hydrophilic modified layer within the pores of the PTFE separation membrane, effectively suppressing the problem of membrane pore blockage caused by the swelling of the hydrophilic layer during water treatment and improving the water flux of the PTFE separation membrane.
[0044] 4) The preparation method, modification method and reaction conditions provided in this application are mild, the steps are simple, and they are easy to scale up industrially, and have good industrial application value. Attached Figure Description
[0045] Figure 1 This is a cross-sectional SEM image of the hydrophilic polytetrafluoroethylene separation membrane of Example 1 of this application; Detailed Implementation
[0046] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0047] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0048] Example 1
[0049] The hollow fiber polytetrafluoroethylene separation membrane has a water penetration pressure of 0.06 MPa and a water flux of 120 L / m³ at 0.1 MPa. 2 h, at 0.1 MPa, the water flux of bovine serum albumin (1 g / L) solution is 30 L / m 2 h, the bovine serum albumin retention rate was 15%.
[0050] Prepare a hydrophilic monomer modification solution by mixing 0.1g of glycerol and 99.9g of ethanol. Prepare a crosslinking agent solution by mixing 0.1g of isophthaloyl chloride and 99.9g of n-hexane. Immerse the PTFE separation membrane in the hydrophilic monomer solution for 5 minutes, then remove and air dry naturally. After drying, immerse the PTFE separation membrane in the crosslinking agent solution for 5 minutes, then remove and place it in an oven at 40℃ for 5 minutes to complete the preparation of the hydrophilic polytetrafluoroethylene separation membrane.
[0051] The obtained hydrophilic polytetrafluoroethylene separation membrane is as follows: Figure 1As shown, the hydrophilic polytetrafluoroethylene separation membrane is formed by the interlacing of multiple polymer fibers to create membrane pores, and a hydrophilic cross-linked layer is formed on the surface of the fibers.
[0052] The modified polytetrafluoroethylene (PTFE) separation membrane has a water penetration pressure reduced to 0.04 MPa, and a water flux of 80 L / m³ at 0.05 MPa. 2 h, the water flux is 180 L / m at 0.1 MPa. 2 h, the water flux of bovine serum albumin (1 g / L) solution is 50 L / m 2 h, the bovine serum albumin retention rate was 20%.
[0053] Example 2
[0054] The hollow fiber polytetrafluoroethylene separation membrane has a water penetration pressure of 0.06 MPa and a water flux of 120 L / m³ at 0.1 MPa. 2 h, at 0.1 MPa, the water flux of bovine serum albumin (1 g / L) solution is 30 L / m 2 h, the bovine serum albumin retention rate was 15%.
[0055] Prepare a hydrophilic monomer modification solution by mixing 2g of ethylenediamine and 98g of ethanol. Prepare a crosslinking agent solution by mixing 1g of trimesoyl chloride and 99g of n-hexane. Immerse the PTFE separation membrane in the hydrophilic monomer solution for 40 minutes, then remove and air-dry it naturally. After drying, immerse the PTFE separation membrane in the crosslinking agent solution for 40 minutes, then remove and place it in an oven at 60℃ for 40 minutes to complete the preparation of the hydrophilic polytetrafluoroethylene separation membrane.
[0056] The modified polytetrafluoroethylene (PTFE) separation membrane has a water penetration pressure reduced to 0.03 MPa, and a water flux of 120 L / m³ at 0.05 MPa. 2 h, the water flux is 280 L / m at 0.1 MPa. 2 h, the water flux of bovine serum albumin (1 g / L) solution is 60 L / m 2 h, the bovine serum albumin retention rate was 25%.
[0057] Example 3
[0058] The hollow fiber polytetrafluoroethylene separation membrane has a water penetration pressure of 0.06 MPa and a water flux of 120 L / m³ at 0.1 MPa. 2 h, at 0.1 MPa, the water flux of bovine serum albumin (1 g / L) solution is 30 L / m 2 h, the bovine serum albumin retention rate was 15%.
[0059] Prepare a hydrophilic monomer modification solution by mixing 5g of hexamethylenediamine and 95g of ethanol. Prepare a crosslinking agent solution by mixing 2g of trimesoyl chloride and 98g of n-hexane. Immerse the PTFE separation membrane in the hydrophilic monomer solution for 80 minutes, remove it and air dry it naturally. After drying, immerse the PTFE separation membrane in the crosslinking agent solution for 80 minutes, remove it and place it in an oven to heat at 80℃ for 60 minutes to complete the preparation of the hydrophilic polytetrafluoroethylene separation membrane.
[0060] The modified polytetrafluoroethylene (PTFE) separation membrane has a water penetration pressure reduced to 0.01 MPa, and a water flux of 150 L / m³ at 0.05 MPa. 2 h, the water flux is 320 L / m at 0.1 MPa. 2 h, the water flux of bovine serum albumin (1 g / L) solution is 70 L / m 2 h, the bovine serum albumin retention rate was 28%.
[0061] Example 4
[0062] The hollow fiber polytetrafluoroethylene separation membrane has a water penetration pressure of 0.06 MPa and a water flux of 120 L / m³ at 0.1 MPa. 2 h, at 0.1 MPa, the water flux of bovine serum albumin (1 g / L) solution is 30 L / m 2 h, the bovine serum albumin retention rate was 15%.
[0063] Prepare a hydrophilic monomer modification solution by mixing 10g of m-phenylenediamine and 90g of ethanol. Prepare a crosslinking agent solution by mixing 4g of trimesoyl chloride and 96g of n-hexane. Immerse the PTFE separation membrane in the hydrophilic monomer solution for 100 minutes, remove it and air dry it naturally. After drying, immerse the PTFE separation membrane in the crosslinking agent solution for 100 minutes, remove it and place it in an oven to heat at 100℃ for 100 minutes to complete the preparation of the hydrophilic polytetrafluoroethylene separation membrane.
[0064] The modified polytetrafluoroethylene (PTFE) separation membrane has a water penetration pressure reduced to 0.005 MPa, and a water flux of 180 L / m³ at 0.05 MPa. 2 h, the water flux is 420 L / m at 0.1 MPa. 2 h, the water flux of bovine serum albumin (1 g / L) solution is 90 L / m 2 h, the bovine serum albumin retention rate was 31%.
[0065] Example 5
[0066] The flat-plate PTFE separation membrane has a water penetration pressure of 0.04 MPa and a water flux of 180 L / m³ at 0.1 MPa. 2 At 0.1 MPa, the water flux of bovine serum albumin (1 g / L) solution is 50 L / m.2 h, the bovine serum albumin retention rate was 15%.
[0067] Prepare a hydrophilic monomer modification solution by mixing 15g of piperazine and 85g of ethanol. Prepare a crosslinking agent solution by mixing 5g of trimesoyl chloride and 95g of n-hexane. Immerse the PTFE separation membrane in the hydrophilic monomer solution for 120 minutes, then remove and air-dry it naturally. After drying, immerse the PTFE separation membrane in the crosslinking agent solution for 120 minutes, then remove and place it in an oven to heat at 100℃ for 100 minutes to complete the preparation of the hydrophilic polytetrafluoroethylene separation membrane.
[0068] The modified polytetrafluoroethylene (PTFE) separation membrane has a water penetration pressure reduced to 0.005 MPa, and a water flux of 240 L / m³ at 0.05 MPa. 2 h, the water flux is 530 L / m at 0.1 MPa. 2 h, the water flux of bovine serum albumin (1 g / L) solution is 120 L / m 2 h, the bovine serum albumin retention rate was 28%.
[0069] Example 6
[0070] The flat-plate PTFE separation membrane has a water penetration pressure of 0.04 MPa and a water flux of 180 L / m³ at 0.1 MPa. 2 At 0.1 MPa, the water flux of bovine serum albumin (1 g / L) solution is 50 L / m. 2 h, the bovine serum albumin retention rate was 15%.
[0071] Prepare a hydrophilic monomer modification solution using 12g of ethylene glycol and 88g of ethanol. Prepare a crosslinking agent solution using 5g of trimesoyl chloride and 95g of n-hexane. Immerse the PTFE separation membrane in the hydrophilic monomer solution for 120 minutes, then remove and air-dry it naturally. After drying, immerse the PTFE separation membrane in the crosslinking agent solution for 120 minutes, then remove and place it in an oven at 100℃ for 120 minutes to complete the preparation of the hydrophilic polytetrafluoroethylene separation membrane.
[0072] The modified polytetrafluoroethylene (PTFE) separation membrane has a water penetration pressure reduced to 0.002 MPa, and a water flux of 280 L / m³ at 0.05 MPa. 2 h, the water flux is 600 L / m at 0.1 MPa. 2 h, the water flux of bovine serum albumin (1 g / L) solution is 120 L / m 2 h, the bovine serum albumin retention rate was 32%.
[0073] Data on water flux and bovine serum albumin rejection rate of the polytetrafluoroethylene (PTFE) separation membranes and modified PTFE separation membranes in Examples 1 to 6 show that by attaching a hydrophilic functional layer to the surface and pores of the PTFE separation membrane, the hydrophilicity and water flux of the PTFE separation membrane can be improved, and the penetration pressure can be reduced.
[0074] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A hydrophilic polytetrafluoroethylene separation membrane, characterized in that, It includes a polytetrafluoroethylene (PTFE) separation membrane and a hydrophilic functional layer, wherein the hydrophilic functional layer is attached to the surface and the interior of the pores of the PTFE separation membrane, and the hydrophilic functional layer is formed by crosslinking hydrophilic monomers and crosslinking agents; The hydrophilic monomer is selected from at least one of glycerol, ethylene glycol, ethylenediamine, hexamethylenediamine, m-phenylenediamine, and piperazine; The crosslinking agent is a polyacryl chloride; The hydrophilic polytetrafluoroethylene separation membrane needs to be placed in a hydrophilic monomer solution during its preparation. The hydrophilic monomer solution comprises a hydrophilic monomer and solvent I; Solvent I is selected from at least one of methanol, ethanol, propanol, and ethyl acetate.
2. The hydrophilic polytetrafluoroethylene separation membrane according to claim 1, characterized in that, The thickness of the hydrophilic functional layer is 20~400nm.
3. A method for preparing the hydrophilic polytetrafluoroethylene separation membrane according to claim 1 or 2, characterized in that, Includes the following steps: a) The polytetrafluoroethylene separation membrane is placed in a hydrophilic monomer solution, impregnated with I, and dried to obtain the polytetrafluoroethylene separation membrane precursor; b) The polytetrafluoroethylene separation membrane precursor was placed in a crosslinking agent solution, impregnated with II, and dried to obtain a hydrophilic polytetrafluoroethylene separation membrane.
4. The preparation method according to claim 3, characterized in that, The mass concentration of the hydrophilic monomer in the hydrophilic monomer solution is 0.1% to 15%.
5. The preparation method according to claim 3, characterized in that, The crosslinking agent solution comprises a crosslinking agent and solvent II; Solvent II is an alkane and / or a benzene; The crosslinking agent is selected from at least one of isophthaloyl chloride, terephthaloyl chloride, and trimesoyl chloride; Solvent II is selected from at least one of n-hexane, cyclohexane, toluene, and xylene; The crosslinking agent solution contains a crosslinking agent concentration of 0.1% to 5% by mass.
6. The preparation method according to claim 3, characterized in that, The immersion time for I is 5-120 minutes; The drying method is natural air drying.
7. The preparation method according to claim 3, characterized in that, The immersion time for the second stage is 1 to 60 minutes; The drying temperature is 40~100℃, and the drying time is 2~100min.
8. The preparation method according to claim 3, characterized in that, The polytetrafluoroethylene separation membrane includes a flat sheet membrane or a hollow fiber membrane.
9. A membrane bioreactor, characterized in that, The hydrophilic polytetrafluoroethylene separation membrane includes the hydrophilic polytetrafluoroethylene separation membrane according to claim 1 or 2, or the hydrophilic polytetrafluoroethylene separation membrane obtained by any one of the preparation methods of claims 3 to 8.