High-strength composite spinning ultrafiltration membrane and preparation method thereof
Through composite materials and process optimization, high-strength composite spinning ultrafiltration membranes were prepared, which solved the contradiction between high flux and mechanical strength of ultrafiltration membranes and achieved stable operation and efficient separation under harsh conditions.
Patent Information
- Application Number
- CN202510893966.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-30
- Publication Date
- 2025-10-10
AI Technical Summary
Existing ultrafiltration membranes have difficulty improving mechanical strength while maintaining high flux. They are prone to deformation, breakage or chemical degradation, especially under harsh working conditions, and are difficult to meet the selectivity and anti-pollution requirements of different application scenarios.
A high-strength composite spinning ultrafiltration membrane was prepared using a composite material of polyvinylidene fluoride, polyethersulfone, N,N-dimethylacetamide, polyvinyl pyrrolidone, glycerol phosphate, glutaraldehyde and polyacrylonitrile nanofibers through electrospinning and phase separation processes to form a multilayer structure, including a support layer, a transition layer and a functional layer, combined with biaxial stretching treatment to improve the comprehensive performance of the membrane.
It achieves a balance between high strength, porosity and anti-pollution, improves the tensile strength and separation performance of the membrane, is suitable for high-pressure and high-pollution environments, and expands the application scope of ultrafiltration technology.
Smart Images
Figure CN120754718A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of membrane separation technology, in particular to a high-strength composite spinning ultrafiltration membrane and a preparation method thereof. Background Art
[0002] Ultrafiltration membranes play a key role in water treatment and separation technologies, but conventional ultrafiltration membranes face a significant technical challenge in practical applications: how to maintain high flux while simultaneously improving their mechanical strength. This problem stems from the conflict between the membrane's porous structure and its material strength. Increasing porosity improves membrane flux, but this also reduces its mechanical strength, making it difficult to withstand high-pressure operation and frequent cleaning. Conversely, increasing material strength often leads to a decrease in porosity, compromising the membrane's separation performance. This conflict is particularly acute under demanding operating conditions, such as high temperature, high pressure, and strong acid and alkaline environments, where membrane materials are prone to deformation, fracture, or chemical degradation, severely impacting the stable operation and service life of the equipment. Furthermore, different application scenarios impose specific requirements on membrane properties such as selectivity and anti-fouling properties, further complicating material design and process optimization. Striking a balance between multiple performance indicators to develop ultrafiltration membranes that combine high strength with excellent separation performance has become a core technical challenge urgently needed in this field. Solving this problem not only affects the expansion of the application scope of ultrafiltration technology but also directly impacts the economic benefits and sustainable development of related industries. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a high-strength composite spinning ultrafiltration membrane with high strength, high porosity and pollution resistance, as well as a preparation method thereof. The preparation method is simple in steps and easy to operate.
[0004] The technical solution adopted by the high-strength composite spinning ultrafiltration membrane of the present invention is a high-strength composite spinning ultrafiltration membrane, which comprises the following components by weight percentage: Polyvinylidene fluoride 25-35wt%; polyethersulfone 15-20wt%; N,N-dimethylacetamide 45-50wt%; polyvinylpyrrolidone 3-5wt%; Glycerol phosphate 1-2 wt%; glutaraldehyde 0.5-1 wt%; and 5-8 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 50-100 nm and a length of 10-20 μm.
[0005] Furthermore, the ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 25wt%; Polyethersulfone 15wt%; N,N-dimethylacetamide 50wt%; polyvinylpyrrolidone 3wt%; Glycerol phosphate 1.5wt%; glutaraldehyde 0.5wt%; and 5 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 75 nm and a length of 15 μm.
[0006] or, The ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 27wt%; Polyethersulfone 17wt%; N,N-dimethylacetamide 45wt%; polyvinylpyrrolidone 4wt%; Glycerol phosphate 1wt%; glutaraldehyde 0.8wt%; and 5.2 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 80 nm and a length of 16 μm.
[0007] Or, The ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 25wt%; Polyethersulfone 16.5wt%; N,N-dimethylacetamide 46wt%; polyvinylpyrrolidone 3wt%; Glycerol phosphate 1wt%; glutaraldehyde 0.5wt%; and 8 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 90 nm and a length of 18 μm.
[0008] A method for preparing the high-strength composite spinning ultrafiltration membrane as described above comprises the following steps: a. Preparation of casting solution: Dissolve polyvinylidene fluoride and polyethersulfone in N,N-dimethylacetamide by weight percentage, add polyvinyl pyrrolidone and glycerol phosphate, and stir for 6 to 8 hours until completely dissolved to form a homogeneous casting solution; b. Preparation of support layer by electrospinning: The casting solution is passed through an electrospinning device to prepare a porous support layer, wherein the spinneret aperture is 0.5-1 mm and the ambient humidity is 30-50%; c. Phase separation to form a transition layer: immersing the support layer in a coagulation bath to induce non-solvent phase separation to form a transition layer; d. Functional layer coating and crosslinking: polyacrylonitrile nanofibers are dispersed in N,N-dimethylacetamide, glutaraldehyde solution is added, and the mixture is coated on the surface of the transition layer. The mixture is heat-treated at 60-80°C for 1-2 hours to form a crosslinked functional layer. e. Post-treatment: After washing and drying the film formed in step d, it is subjected to biaxial stretching treatment at 60-80°C to obtain the final film product.
[0009] More specifically, in step b, the operating voltage of the electrospinning device is 15 to 20 kV, and the receiving distance is 15 to 25 cm.
[0010] In the step c, the volume ratio of water to ethanol in the coagulation bath is 3:1, and the temperature is 25-35°C.
[0011] In the step e, the specific ratio of biaxial stretching of the film is: 5% in the longitudinal direction and 3% in the transverse direction.
[0012] In the step d, the cross-linking degree of the formed cross-linked functional layer is 60-75%.
[0013] In the step e, the final membrane product obtained has no rupture under a pressure of 0.2 MPa.
[0014] The beneficial effects of the present invention are as follows: in the present invention, polyvinylidene fluoride and polyethersulfone are used as main components, and a uniform solution is formed by dissolving them in N,N-dimethylacetamide solvent. The ratio of the polyvinylidene fluoride and polyethersulfone is adjusted to optimize the mechanical properties and chemical stability of the membrane. The main components are ensured to be fully mixed with the solvent by stirring to obtain a casting solution suitable for subsequent processes, and the casting solution is the basis for forming the support layer; polyvinyl pyrrolidone is used as a porogen, glycerol phosphate is used as a stabilizer, and glutaraldehyde is used as a cross-linking agent. The porogen is used to regulate the pore size distribution of the membrane, and the stabilizer is used to reduce the surface roughness of the membrane. The surface can reduce pollution, the cross-linking agent is used to enhance the mechanical strength of the membrane, and the auxiliary materials are added to the casting solution and fully mixed to ensure that the auxiliary materials are evenly distributed during the membrane formation process, thereby improving the comprehensive performance of the ultrafiltration membrane; polyacrylonitrile nanofibers are used as a reinforcing skeleton, and a network structure is formed through a specific process. The polyacrylonitrile nanofibers are dispersed in the solution and incorporated into the functional layer to enhance the deformation resistance of the ultrafiltration membrane. By adjusting the size and distribution density of the reinforcing fibers, the tensile strength and structural stability of the ultrafiltration membrane are optimized, ensuring that the reinforcing fibers are effectively combined with the multi-layer structure. In the preparation method of the present invention, a porous structure is prepared by an electrospinning process, and a support layer is formed by a casting liquid under a specific voltage and receiving distance. The pore structure of the support layer provides basic support for subsequent layers, and the uniformity and stability of the support layer are ensured by controlling environmental conditions. The support layer serves as the basic part of the multilayer structure and provides support for the formation of the transition layer and the functional layer; the transition layer is formed by a non-solvent-induced phase separation process and is prepared in a specific coagulation bath. The phase separation process is controlled by adjusting the composition and temperature of the coagulation bath to obtain the transition layer with a porous structure. The transition layer connects the support layer and the functional layer to ensure close bonding and pore transition between the multilayer structure, thereby improving the ultrafiltration The overall performance and stability of the membrane are enhanced. The functional layer is formed through a coating and cross-linking process, with reinforcing fibers and a cross-linking agent solution applied to the surface of the transition layer. A heat treatment is then performed to achieve a cross-linking reaction, resulting in a dense functional layer with a high retention rate. The degree of cross-linking in the functional layer is optimized to balance flux and separation efficiency, ensuring that the ultrafiltration membrane has good rupture resistance under high pressure. Residual solvent and impurities are removed through washing and drying. The ultrafiltration membrane is then subjected to a biaxial stretching treatment, which applies transverse and longitudinal stresses to orient the molecular chains, thereby improving the tensile strength and structural stability of the ultrafiltration membrane. The post-processing step ensures tight bonding between the layers of the multilayer structure, optimizing the ultimate performance of the ultrafiltration membrane. Therefore, the present invention effectively improves the strength, porosity, and pollution resistance of the ultrafiltration membrane. Its preparation method is simple and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION
[0016] The high-strength composite spinning ultrafiltration membrane of the present invention comprises the following components by weight percentage: Polyvinylidene fluoride 25-35wt%; polyethersulfone 15-20wt%; N,N-dimethylacetamide 45-50wt%; polyvinylpyrrolidone 3-5wt%; Glycerol phosphate 1-2 wt%; glutaraldehyde 0.5-1 wt%; and 5-8 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 50-100 nm and a length of 10-20 μm.
[0017] like Figure 1 As shown, the preparation method of the above-mentioned high-strength composite spinning ultrafiltration membrane includes the following steps: a. Preparation of casting solution: Dissolve polyvinylidene fluoride and polyethersulfone in N,N-dimethylacetamide by weight percentage, add polyvinyl pyrrolidone and glycerol phosphate, and stir for 6 to 8 hours until completely dissolved to form a homogeneous casting solution; b. Preparation of support layer by electrospinning: The casting solution is passed through an electrospinning device to prepare a porous support layer, wherein the spinneret aperture is 0.5-1 mm and the ambient humidity is 30-50%; c. Phase separation to form a transition layer: immersing the support layer in a coagulation bath to induce non-solvent phase separation to form a transition layer; d. Functional layer coating and crosslinking: polyacrylonitrile nanofibers are dispersed in N,N-dimethylacetamide, glutaraldehyde solution is added, and the mixture is coated on the surface of the transition layer. The mixture is heat-treated at 60-80°C for 1-2 hours to form a crosslinked functional layer. e. Post-treatment: After washing and drying the film formed in step d, it is subjected to biaxial stretching treatment at 60-80°C to obtain the final film product.
[0018] Specifically, in step b, the operating voltage of the electrospinning device is 15-20 kV, and the receiving distance is 15-25 cm. In step c, the volume ratio of water to ethanol in the coagulation bath is 3:1, and the temperature is 25-35°C. In step e, the membrane is biaxially stretched at a specific ratio of 5% in the longitudinal direction and 3% in the transverse direction. In step d, the crosslinking degree of the crosslinked functional layer formed is 60-75%. In step e, the final membrane product obtained does not crack under a pressure of 0.2 MPa.
[0019] In this invention, PVP acts as a porogen to regulate the membrane's pore size distribution (5-20 nm) and enhance hydrophilicity. Glycerol phosphate reduces the membrane's surface energy, reducing pollutant adsorption. Glutaraldehyde cross-links with the hydroxyl and amino groups of PVDF and PPSU, enhancing mechanical strength. PAN nanofibers act as a reinforcing framework, forming a network structure through electrospinning to inhibit membrane deformation. Furthermore, in the composite electrospinning process, the PVDF / PPSU casting solution and PAN nanofibers are simultaneously spun to form a porous structure. Lateral and longitudinal tensile stresses are applied during post-processing to orient the molecular chains and enhance tensile strength.
[0020] Three embodiments of the present invention are as follows: Example 1: The ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 25wt%; Polyethersulfone 15wt%; N,N-dimethylacetamide 50wt%; polyvinylpyrrolidone 3wt%; Glycerol phosphate 1.5wt%; glutaraldehyde 0.5wt%; and 5 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 75 nm and a length of 15 μm.
[0021] The ultrafiltration membrane prepared by the method of the present invention has the following properties after testing: Tensile strength 11.2N, porosity 78%, flux 1200 L / (m²·h)·0.1MPa.
[0022] Example 2: The ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 27wt%; Polyethersulfone 17wt%; N,N-dimethylacetamide 45wt%; polyvinylpyrrolidone 4wt%; Glycerol phosphate 1wt%; glutaraldehyde 0.8wt%; and 5.2 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 80 nm and a length of 16 μm.
[0023] The ultrafiltration membrane prepared by the method of the present invention has the following properties after testing: Tensile strength 11.8N, porosity 79%, flux 1250 L / (m²·h)·0.1MPa.
[0024] Example 3: The ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 25wt%; Polyethersulfone 16.5wt%; N,N-dimethylacetamide 46wt%; polyvinylpyrrolidone 3wt%; Glycerol phosphate 1wt%; glutaraldehyde 0.5wt%; and 8 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 90 nm and a length of 18 μm.
[0025] The ultrafiltration membrane prepared by the method of the present invention has the following properties after testing: Tensile strength 12.5N, porosity 82%, flux 1300 L / (m²·h)·0.1MPa.
[0026] Examples 1 to 3 are presented in the form of tables as follows:
[0027] In addition, the following table shows three comparative examples of the prior art:
[0028] By comparison, in the present invention, PAN nanofibers are formed into a skeleton through electrospinning, forming a strong interface bond with the PVDF / PPSU matrix; glutaraldehyde cross-links the PVDF / PPSU molecular chains to inhibit swelling; the PVP porogen cooperates with the phase separation process to form a pore structure, balancing flux and mechanical strength; compared with the three comparative examples, the present invention achieves high flux and porosity. The present invention significantly improves the mechanical properties of the membrane through material composite and process optimization, so that the tensile strength of the membrane is higher than 10N, while maintaining high separation efficiency, and is suitable for harsh scenarios such as highly polluted wastewater treatment and seawater desalination.
[0029] Finally, it should be emphasized that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A high-strength composite spinning ultrafiltration membrane, characterized in that: The ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 25-35wt%; polyethersulfone 15-20wt%; N,N-dimethylacetamide 45-50wt%; polyvinylpyrrolidone 3-5wt%; Glycerol phosphate 1-2 wt%; glutaraldehyde 0.5-1 wt%; and 5-8 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 50-100 nm and a length of 10-20 μm.
2. The high-strength composite spinning ultrafiltration membrane according to claim 1, characterized in that: The ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 25wt%; Polyethersulfone 15wt%; N,N-dimethylacetamide 50wt%; polyvinylpyrrolidone 3wt%; Glycerol phosphate 1.5wt%; glutaraldehyde 0.5wt%; and 5 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 75 nm and a length of 15 μm.
3. The high-strength composite spinning ultrafiltration membrane according to claim 1, characterized in that: The ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 27wt%; Polyethersulfone 17wt%; N,N-dimethylacetamide 45wt%; polyvinylpyrrolidone 4wt%; Glycerol phosphate 1wt%; glutaraldehyde 0.8wt%; and 5.2 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 80 nm and a length of 16 μm.
4. The high-strength composite spinning ultrafiltration membrane according to claim 1, characterized in that: The ultrafiltration membrane comprises the following components by weight percentage: Polyvinylidene fluoride 25wt%; Polyethersulfone 16.5wt%; N,N-dimethylacetamide 46wt%; polyvinylpyrrolidone 3wt%; Glycerol phosphate 1wt%; glutaraldehyde 0.5wt%; and 8 wt % of polyacrylonitrile nanofibers, wherein the polyacrylonitrile nanofibers have a diameter of 90 nm and a length of 18 μm.
5. A method for preparing a high-strength composite spinning ultrafiltration membrane according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: a. Preparation of casting solution: Dissolve polyvinylidene fluoride and polyethersulfone in N,N-dimethylacetamide by weight percentage, add polyvinyl pyrrolidone and glycerol phosphate, and stir for 6 to 8 hours until completely dissolved to form a homogeneous casting solution; b. Preparation of support layer by electrospinning: The casting solution is passed through an electrospinning device to prepare a porous support layer, wherein the spinneret aperture is 0.5-1 mm and the ambient humidity is 30-50%; c. Phase separation to form a transition layer: immersing the support layer in a coagulation bath to induce non-solvent phase separation to form a transition layer; d. Functional layer coating and crosslinking: polyacrylonitrile nanofibers are dispersed in N,N-dimethylacetamide, glutaraldehyde solution is added, and the mixture is coated on the surface of the transition layer. The mixture is heat-treated at 60-80°C for 1-2 hours to form a crosslinked functional layer. e. Post-treatment: After washing and drying the film formed in step d, it is subjected to biaxial stretching treatment at 60-80°C to obtain the final film product.
6. The preparation method according to claim 5, characterized in that: In the step b, the operating voltage of the electrospinning device is 15 to 20 kV, and the receiving distance is 15 to 25 cm.
7. The preparation method according to claim 5, characterized in that: In the step c, the volume ratio of water to ethanol in the coagulation bath is 3:1, and the temperature is 25-35°C.
8. The preparation method according to claim 5, characterized in that In the step e, the specific ratio of biaxial stretching of the film is: 5% in the longitudinal direction and 3% in the transverse direction.
9. The preparation method according to claim 5, characterized in that: In the step d, the cross-linking degree of the formed cross-linked functional layer is 60-75%.
10. The preparation method according to claim 5, characterized in that: In the step e, the final membrane product obtained has no rupture under a pressure of 0.2 MPa.