Nanofiber membrane for oil / water filtration as well as preparation method and application of nanofiber membrane

Abstract

The invention discloses a nanofiber membrane for oil / water filtration and a preparation method and application thereof, and belongs to the technical field of filtration. The preparation method comprises the following steps: dispersing a polyurethane polymer into an organic solvent, stirring to obtain a spinning solution, then determining a receiving base material, and carrying out electrostatic spinning by using the spinning solution to obtain the nanofiber membrane for oil / water filtration. Due to the unique structure, the nanofiber membrane for oil / water filtration has the advantages of large specific surface area, high porosity, high filtration efficiency and low filtration resistance, is uniform in filtration effect, has hydrophilic and lipophilic properties, can be used for filtration of oily particles, water-based particles and salt particles, and is simple in structure and easy to implement. The filter is easy to manufacture and has a wide application prospect in the field of filtration.

Description

Technical Field

[0001] The invention relates to the field of filtration technology, and in particular to a nanofiber membrane for oil / water filtration and a preparation method and application thereof. Background Art

[0002] Traditional filtration membrane materials play a vital role in the industrial and environmental fields, especially when dealing with liquid and gas mixtures. However, the preparation processes of these materials, such as coating-drying and biaxial stretching, although still widely used in some applications, have some inherent limitations in performance.

[0003] The coating-drying process usually involves evenly coating a solution or suspension containing a polymer on a support material, and then removing the solvent or water by heating or natural drying to form a solid membrane layer. This method is relatively low-cost and easy to operate, but the membrane materials it prepares often have low porosity, which means that the number of pores inside the membrane material is small, thereby limiting the permeability of the fluid. The problem of larger pore size may lead to insufficient filtration accuracy and inability to effectively intercept smaller particles or molecules, which is an obvious defect for application scenarios that require high-precision filtration.

[0004] The biaxial stretching process improves the structure of the membrane material by physically stretching the polymer film to increase its density and uniformity. Although this method can improve the mechanical properties of the membrane to a certain extent, it also faces the problem of non-uniformity in the preparation process, which may cause the thickness of the membrane to vary significantly in different areas. The uneven thickness not only affects the mechanical strength of the membrane, but may also lead to non-uniformity in the filtration process, such as the filtration effect in some areas may be far worse than in other areas.

[0005] In addition, when traditional membrane materials are used to process mixtures containing oil and water, it is often difficult to effectively filter both oil and water at the same time. This is because the physical properties of oil and water are quite different, such as surface tension, viscosity, and density, which requires that membrane materials must have specific pore sizes and surface characteristics to simultaneously meet the requirements for filtering oil and water. However, membrane materials prepared by traditional processes often find it difficult to simultaneously meet these requirements, resulting in low filtration efficiency, increased filtration resistance, and uneven filtration effects.

[0006] To solve these problems, researchers are exploring more advanced membrane material preparation technologies. For example, nanotechnology can be used to prepare membrane materials with smaller pore sizes and higher porosity, which not only improves filtration efficiency but also enhances the interception capacity of particles of different sizes. In addition, by precisely controlling the coating process and post-processing steps of the polymer solution, the unevenness of the membrane material thickness can be reduced, thereby improving its overall performance.

[0007] In terms of material selection, new polymers or composite materials are developed, which not only have good filtration performance, but also have excellent chemical stability and durability, which is crucial for long-term operation of filtration systems. At the same time, through surface modification technology, specific surface properties such as hydrophilicity or hydrophobicity can be given to membrane materials to improve their filtration efficiency for oil and water.

[0008] In summary, although traditional filtration membrane materials still have application value in some aspects, with the advancement of technology and the development of new materials, future filtration membrane materials are expected to achieve significant improvements in performance and better meet the needs of industry and environmental protection. Summary of the invention

[0009] The main purpose of the present invention is to provide a nanofiber membrane for oil / water filtration and its preparation method and application, so as to solve the technical problems in the prior art that the filtration membrane is difficult to filter oil and water at the same time and the oil / water filtration effect is not ideal.

[0010] To achieve the above object, the present invention provides a method for preparing a nanofiber membrane for oil / water filtration, comprising the following steps:

[0011] S10: dispersing the polyurethane polymer in an organic solvent and stirring to obtain a spinning solution;

[0012] S20: determining a receiving substrate, and using the spinning solution to perform electrospinning to obtain a nanofiber membrane for oil / water filtration;

[0013] Wherein, the polyurethane polymer includes at least one of polyurethane and thermoplastic polyurethane.

[0014] In some embodiments of the present invention, the polyurethane polymer is hydrophilic and / or lipophilic.

[0015] In some embodiments of the present invention, the mass percentage of the polyurethane polymer in the spinning solution is 15% to 38%.

[0016] In some embodiments of the present invention, the mass percentage of the organic solvent in the spinning solution is 62% to 85%.

[0017] In some embodiments of the present invention, the receiving substrate includes at least one of non-woven fabric and needle-punched cotton.

[0018] In some embodiments of the present invention, the organic solvent includes N,N-dimethylformamide.

[0019] In some embodiments of the present invention, in step S10, the polyurethane polymer is dispersed in an organic solvent and is further subjected to a heating treatment at a temperature of 60°C to 75°C.

[0020] In some embodiments of the present invention, the voltage range of the electrospinning is +35kv to +85kv, -15kv to -65kv;

[0021] And / or, the liquid supply speed of the electrospinning is 800ml / h to 2000ml / h;

[0022] And / or, the winding speed of the electrospinning is 0 to 4 m / min;

[0023] And / or, the coating speed of the electrospinning is 0 to 200 mm / s;

[0024] And / or, the coating stroke of the electrospinning is 0 to 1600 mm;

[0025] And / or, the temperature of the electrospinning is 50°C to 100°C;

[0026] And / or, the humidity of the electrospinning is 10% to 30%.

[0027] The present invention also provides a nanofiber membrane for oil / water filtration prepared by the method for preparing the nanofiber membrane for oil / water filtration as described above.

[0028] The present invention also provides an application of the nanofiber membrane for oil / water filtration as described above, wherein the nanofiber membrane for oil / water filtration is used to filter salt particles, oily particles and water particles.

[0029] The beneficial effects that can be achieved by the present invention are:

[0030] The present invention combines a spinning solution prepared from a polyurethane polymer with an electrostatic spinning process. During the electrostatic spinning process, the spinning solution overcomes the surface tension of the droplets under the action of the electric field force to form a jet stream. As the solvent of the stream evaporates during the jetting process, fibers with nanometer size are obtained at the microscopic level. These fibers cross and stack with each other to form a fiber membrane similar to a non-manufactured cloth on a receiving substrate. These fiber membranes, due to their unique structure, show a large specific surface area and high porosity, have the advantages of high filtration efficiency and low filtration resistance, have a relatively uniform filtration effect, are hydrophilic and lipophilic, can be used for filtering oily particles, water particles and salt particles, and have a simple structure and are easy to manufacture, and have broad application prospects in the field of filtration. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0032] Figure 1 This is a SEM image of a nanofiber membrane for oil / water filtration according to an embodiment of the present invention.

[0033] Figure 2 This is a graph showing the water contact angle of the nanofiber membrane used in oil / water filtration according to Example 1 of the present invention.

[0034] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0035] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0038] Traditional filtration membrane materials use processes such as coating-drying and biaxial stretching. The membrane materials prepared by this process have the characteristics of low porosity, large pore size, and uneven thickness, which leads to low filtration efficiency, large filtration resistance, and uneven filtration of the membrane material.

[0039] In view of this, the present invention provides a nanofiber membrane for oil / water filtration and a preparation method thereof, the preparation method comprising the following steps:

[0040] S10: dispersing the polyurethane polymer in an organic solvent and stirring to obtain a spinning solution;

[0041] S20: determining a receiving substrate, and using the spinning solution to perform electrospinning to obtain a nanofiber membrane for oil / water filtration;

[0042] Wherein, the polyurethane polymer includes at least one of polyurethane and thermoplastic polyurethane.

[0043] The present invention combines a spinning solution prepared from a polyurethane polymer with an electrostatic spinning process. During the electrostatic spinning process, the spinning solution overcomes the surface tension of the droplets under the action of the electric field force to form a jet stream. As the solvent of the stream evaporates during the jetting process, fibers with nanometer size are obtained at the microscopic level. These fibers cross and stack with each other to form a fiber membrane similar to a non-manufactured cloth on a receiving substrate. These fiber membranes, due to their unique structure, show a large specific surface area and high porosity, have the advantages of high filtration efficiency and low filtration resistance, have a relatively uniform filtration effect, are hydrophilic and lipophilic, can be used for filtering oily particles, water particles and salt particles, and have a simple structure and are easy to manufacture, and have broad application prospects in the field of filtration.

[0044] The present invention selects polyurethane polymers to prepare the spinning solution, such as polyurethane and thermoplastic polyurethane, which have good mechanical strength and flexibility. The nanofiber membrane prepared by combining the electrospinning process inherits the above characteristics, so that the obtained nanofiber membrane for oil / water filtration has good tensile and compression resistance, maintains good filtration pores, and ensures the filtration effect. In addition, polyurethane and thermoplastic polyurethane also have good chemical stability, can resist the erosion of various chemical substances, and improve the service life of the nanofiber membrane.

[0045] In some embodiments, the polyurethane polymer is hydrophilic and / or lipophilic, for example, the polyurethane includes lipophilic polyurethane and / or hydrophilic polyurethane; the thermoplastic polyurethane includes lipophilic thermoplastic polyurethane and / or hydrophilic thermoplastic polyurethane; the prepared nanofiber membrane can also be hydrophilic and / or lipophilic, thereby achieving oil / water filtration.

[0046] In the present invention, polyurethane can be dispersed in an organic solvent to obtain a spinning solution, thermoplastic polyurethane can be dispersed in an organic solvent to obtain a spinning solution, or polyurethane and thermoplastic polyurethane can be compounded to prepare a spinning solution.

[0047] In some embodiments, polyurethane and thermoplastic polyurethane are compounded and dispersed in an organic solvent to prepare a spinning solution, which is beneficial to adjust the rheological properties of the spinning solution, making it more compatible with the electrospinning process, improving processing efficiency, and obtaining a more uniform nanofiber membrane. The compounding of polyurethane and thermoplastic polyurethane can also reduce the fiber adhesion phenomenon that occurs during the electrospinning process, thereby obtaining a nanofiber membrane with a uniform and continuous fiber structure, while optimizing the fiber diameter and morphology, and improving the hydrophilic and lipophilic effects of the nanofiber membrane.

[0048] In some embodiments, polyurethane and thermoplastic polyurethane are compounded to prepare a spinning solution, and the mass ratio of polyurethane to thermoplastic polyurethane is 1:1 to 22:25. Under the above ratio conditions, it is beneficial to improve the hydrophilicity and lipophilicity of the nanofiber membrane and improve the filtration effect.

[0049] In some embodiments, the mass percentage of polyurethane in the spinning solution is 15% to 38%, and can be any value in the range of 15%, 18%, 20%, 25%, 28%, 30%, 33%, 35%, 38%, etc.

[0050] In some embodiments, the mass percentage of the organic solvent in the spinning solution is 62% to 85%.

[0051] In some embodiments, the organic solvent includes N,N-dimethylformamide, which has a good dissolving effect on polar polymer materials such as polyurethane and thermoplastic polyurethane, to obtain a uniformly dispersed spinning solution, thereby weaving nano-scale fibers with the help of an electrospinning process, and interweaving and stacking to obtain a uniform and continuous nanofiber membrane.

[0052] In some embodiments, a solid polyurethane polymer may be first dissolved in an organic solvent to obtain a spinning solution.

[0053] In some embodiments, liquid polyurethane polymers and organic solvents can be mixed and the liquid polyurethane polymers can be diluted with organic solvents. This is beneficial for obtaining a uniform spinning solution with good fluidity, reducing the risk of thread adhesion during the electrospinning process, and facilitating the acquisition of nanoscale fibers and the preparation of a nanofiber membrane with a continuous structure.

[0054] In some embodiments, in step S10, after the polyurethane polymer is dispersed in the organic solvent, it is also subjected to a heating treatment, and the heating temperature is 60°C to 75°C, and can be any value in the range of 60°C to 75°C, such as 60°C, 65°C, 75°C, etc. Under the above heating temperature conditions, it is beneficial to increase the dissolution rate of the polyurethane polymer in the organic solvent, reduce the viscosity of the solvent, and improve the fluidity of the spinning solution. In conjunction with the electrospinning process, it is beneficial to obtain nano-scale fiber filaments, prevent adhesion, and obtain a nanofiber membrane with a continuous structure.

[0055] During the electrospinning process, the polymer solution overcomes the surface tension of the droplets under the action of the electric field force to form a jet stream. As the solvent evaporates during the jetting process, a nanofiber membrane with a large specific surface area and high porosity is finally formed on the receiving substrate. Therefore, the process conditions of electrospinning also affect the quality of the nanofiber membrane.

[0056] In some embodiments, the voltage range of electrospinning is +35 kv to +85 kv, -15 kv to -65 kv.

[0057] In some embodiments, the liquid supply rate of electrospinning is 800ml / h to 2000ml / h. At the above liquid supply rate, the fibers formed by the spinning solution have shorter stretching and solidification times during flight, which helps to reduce the adhesion of the fibers on the receiving substrate, is beneficial to obtaining nano-scale fibers, and improves the mechanical properties of the fibers.

[0058] In some embodiments, winding can be performed simultaneously during the spinning process, and the winding speed is 0 to 4 m / min.

[0059] In some embodiments, the coating speed of electrospinning is 0 to 200 mm / s.

[0060] In some embodiments, the coating stroke of electrospinning is 0 to 1600 mm.

[0061] In some embodiments, the temperature of electrospinning is 50°C to 100°C. Under the above temperature conditions, it is beneficial to promote the rapid volatilization of the solvent in the spinning solution, promote the solidification and forming of the fiber, and help reduce the viscosity of the spinning solution, making the spinning solution easier to pass through the spinneret, thereby forming more uniform fibers.

[0062] In some embodiments, the humidity of electrospinning is 10% to 30%. Within the above humidity range, it helps to reduce fiber breakage during the formation process. In addition, a lower humidity environment can reduce the adhesion between fibers, making the fibers less likely to break. A lower humidity environment is also beneficial to increase the electrostatic repulsion between fibers, which helps reduce fiber aggregation during the collection process, thereby obtaining a more evenly distributed fiber network.

[0063] In some embodiments, the receiving substrate comprises at least one of non-woven fabric and needle-punched cotton.

[0064] In some embodiments, the nonwoven fabric includes a hydrophilic nonwoven fabric, and the needle-punched cotton includes a hydrophilic needle-punched cotton.

[0065] The nanofiber membrane for oil / water filtration prepared by the present invention has a unique structure, exhibits a large specific surface area and high porosity, has the advantages of high filtration efficiency and low filtration resistance, has a relatively uniform filtration effect, has hydrophilicity and lipophilicity, can be used for filtering oily particles, water particles and salt particles, and has a simple structure and is easy to manufacture, and has broad application prospects in the field of filtration.

[0066] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0067] Example 1

[0068] S10: Dissolve the hydrophilic TPU (thermoplastic polyurethane) in DMF to obtain a hydrophilic TPU solution with a mass fraction of 20%, dissolve the hydrophilic PU (polyurethane) in DMF to obtain a hydrophilic PU solution with a mass fraction of 20%, and then mix the hydrophilic TPU solution and the hydrophilic PU solution in a mass ratio of 1:1, stir for 2h, and prepare a spinning solution with a mass percentage of 20% of the polyurethane polymer and a mass percentage of 80% of the solvent DMF.

[0069] S20: Using hydrophilic PP non-woven fabric as the receiving substrate, the spinning solution in step S10 is used as the spinning material, and needle-free electrospinning is performed to prepare a nanofiber membrane for oil / water filtration. The spinning conditions are controlled as follows: spinning voltage is 70KV, -20KV, liquid supply speed is 800ml / h, winding speed is 2m / min, coating speed is 150, coating stroke is 1250mm, temperature is 85℃, and humidity is 10%.

[0070] Example 2

[0071] S10, dispersing the hydrophilic PU in the solvent DMF, stirring for 2 hours, and obtaining a spinning solution in which the mass percentage of the hydrophilic PU is 30% and the mass percentage of the solvent DMF is 70%.

[0072] S20, using the hydrophilic ES non-woven fabric as the receiving substrate, using the spinning solution of step S10 as the spinning material, and performing needle-free electrospinning to prepare a nanofiber membrane for oil / water filtration, the spinning conditions are controlled as follows: spinning voltage is 80KV, -25KV, liquid supply speed is 1200ml / h, winding speed is 4m / min, coating speed is 150, coating stroke is 1250mm. Temperature is 85°C, and humidity is 10%.

[0073] Example 3

[0074] S10: Disperse the lipophilic PU in DMF and stir for 2 hours to obtain a spinning solution in which the mass percentage of the lipophilic PU is 35% and the mass percentage of the solvent DMF is 65%.

[0075] S20: Using the hydrophilic PP non-woven fabric as the receiving substrate and the spinning solution of step S10 as the spinning material, needle-free electrospinning is performed to prepare a nanofiber membrane for oil / water filtration, and the spinning conditions are controlled as follows: spinning voltage is 75KV, -35KV, liquid supply speed is 1000ml / h, winding speed is 3m / min, coating speed is 150, coating stroke is 1250mm. Temperature is 85°C, and humidity is 10%.

[0076] Example 4

[0077] S10: dissolving the lipophilic PU in DMF to obtain a lipophilic PU solution with a mass fraction of 22%, dissolving the lipophilic TPU in DMF to obtain a lipophilic TPU solution with a mass fraction of 25%, and then mixing the lipophilic PU solution and the lipophilic TPU solution in a mass ratio of 1:1, stirring for 2h, and preparing a spinning solution in which the mass percentage of the polyurethane polymer is 23.5% and the mass percentage of the solvent DMF is 76.5%.

[0078] S20: Using the hydrophilic ES non-woven fabric as the receiving substrate and the spinning solution in step S10 as the spinning material, needle-free electrospinning is performed to prepare a nanofiber membrane for oil / water filtration, and the spinning conditions are controlled as follows: spinning voltage is 80KV, -30KV, liquid supply speed is 1000ml / h, winding speed is 2m / min, coating speed is 150, coating stroke is 1250mm. Temperature is 85°C, and humidity is 10%.

[0079] Performance Testing

[0080] 1. Morphology test: The nanofiber membrane for oil / water filtration prepared in Example 1 was observed using a scanning electron microscope. Figure 1 ,like Figure 1 As shown, the interlaced and stacked fibers form a nanofiber membrane.

[0081] 2. Water contact angle test: Test the water contact angle of the nanofiber membrane of Example 1. Figure 2 As shown, the water contact angle of the nanofiber membrane is 38.8°, which has good hydrophilicity.

[0082] 3. Filtration test: The nanofiber membranes prepared in Examples 1 to 4 were tested for filtration efficiency and filtration resistance of salt particles, oily particles and aqueous particles. The test results are shown in Table 1.

[0083] 4. Air permeability test: The sample fiber membrane is made into a disc with a diameter of 20 cm, and the air permeability of the sample is measured using a fully automatic air permeability meter, with the pressure drop value set to 100 Pa.

[0084] Table 1

[0085]

[0086] It can be seen from Table 1 that the nanofiber membranes prepared by combining polyurethane solution with electrospinning technology in Examples 1 to 4 have good filtering effects on salt particles, oily particles and water particles.

[0087] Table 2

[0088]

[0089]

[0090] It can be seen from Table 2 that the nanofiber membranes prepared by combining the polyurethane solution with the electrospinning technology in Examples 1 to 4 have good air permeability, and the samples still have good air permeability after filtration.

[0091] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a nanofiber membrane for oil / water filtration, characterized in that: The following steps are involved: S10: dispersing the polyurethane polymer in an organic solvent and stirring to obtain a spinning solution; S20: determining a receiving substrate, and using the spinning solution to perform electrospinning to obtain a nanofiber membrane for oil / water filtration; Wherein, the polyurethane polymer includes at least one of polyurethane and thermoplastic polyurethane.

2. The method for preparing a nanofiber membrane for oil / water filtration according to claim 1, characterized in that: The polyurethane polymer has hydrophilicity and / or lipophilicity.

3. The method for preparing a nanofiber membrane for oil / water filtration according to claim 1, characterized in that: The mass percentage of the polyurethane polymer in the spinning solution is 15% to 38%.

4. The method for preparing a nanofiber membrane for oil / water filtration according to claim 1, characterized in that: The mass percentage of the organic solvent in the spinning solution is 62% to 85%.

5. The method for preparing a nanofiber membrane for oil / water filtration according to claim 1, characterized in that: The receiving substrate includes at least one of non-woven fabric and needle-punched cotton.

6. The method for preparing a nanofiber membrane for oil / water filtration according to claim 1, characterized in that: The organic solvent includes N,N-dimethylformamide.

7. The method for preparing a nanofiber membrane for oil / water filtration according to claim 1, characterized in that: In the step S10, the polyurethane polymer is dispersed in an organic solvent and is further heated at a temperature of 60°C to 75°C.

8. The method for preparing a nanofiber membrane for oil / water filtration according to claim 1, characterized in that: The voltage range of the electrospinning is +35kv to +85kv, -15kv to -65kv; And / or, the liquid supply speed of the electrospinning is 800ml / h to 2000ml / h; And / or, the winding speed of the electrospinning is 0 to 4 m / min; And / or, the coating speed of the electrospinning is 0 to 200 mm / s; And / or, the coating stroke of the electrospinning is 0 to 1600 mm; And / or, the temperature of the electrospinning is 50°C to 100°C; And / or, the humidity of the electrospinning is 10% to 30%.

9. A nanofiber membrane for oil / water filtration prepared by the method for preparing a nanofiber membrane for oil / water filtration according to any one of claims 1 to 8.

10. An application of the nanofiber membrane for oil / water filtration according to claim 9, characterized in that: The nanofiber membrane for oil / water filtration is used for filtering salt particles, oily particles and water particles.

Images