An electrospinning method for batch production of nanofiber membranes

Abstract

The application discloses a kind of electrospinning methods for batch preparation nanofiber membrane, comprising the following steps: S1, the preparation of spinning solution: polymer material is dissolved in organic solvent, then benzyl triethylammonium chloride and modified nanosilica sol are added in polymer solution, and spinning solution is prepared after being dissolved sufficiently;S2, spinning solution is nanofiber spinning by nozzleless electrospinning method to spinning solution;The application is by being provided with the microwell plate with multiple round holes on the surface in liquid storage tank, not only can reduce the rate of solvent volatilization, and under the blowing action of gas, multiple uniform size bubbles can be generated in the round holes on the microwell plate, to make the diameter of nanofiber more uniform, in addition, by changing the number of round holes on the microwell plate, the size of pore diameter, the formation and distribution of nanofiber can be changed, not only can improve the filtration effect of nanofiber membrane, but also can greatly improve the preparation yield of nanofiber membrane, realize batch production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrospinning, in particular to a method for batch preparation of nanofiber membrane by electrospinning. BACKGROUND

[0002] Nanofiber membrane materials prepared by electrospinning technology have very important application value in many fields such as biomedicine, filtration, catalysis and energy, etc. due to their excellent properties such as ultra-high specific surface area, high porosity and excellent mechanical properties. Compared with traditional single-structure nanofibers, composite-structure nanofibers have greater advantages in research and development of functionality, diversity and bionics, etc. and have received extensive attention.

[0003] In the prior art, electrospinning technology is generally divided into needle electrospinning and nozzle-free electrospinning. Needle electrospinning is to apply high voltage to a metal needle, which is connected to a syringe containing a spinning solution. When the voltage is high enough, a droplet of the spinning solution will be formed at the tip of the needle, and the droplet will be stretched into a nanofiber under the action of the electric field and deposited on a collecting substrate. Although this needle electrospinning method is simple to operate, only one droplet can be formed at the tip of one metal needle, and there are technical problems of slow spinning efficiency and low yield. Nozzle-free electrospinning does not use a metal needle to generate a droplet, and compared with conventional needle electrospinning technology, nozzle-free electrospinning can greatly improve the yield of nanofibers. However, the current nozzle-free electrospinning technology still has many problems, such as the nozzle of nozzle-free electrospinning exposes a large surface of the solution, and the evaporation of solvents of different raw materials may change the properties of the solution, thereby affecting the quality stability of the nanofibers and the adhesion to the substrate. In addition, the droplets generated by the nozzle-free electrospinning method are usually uneven in size and uncontrollable in size, resulting in large fluctuations in the diameter of the nanofibers formed by stretching, and thus affecting the filtration performance.

[0004] Therefore, the prior art has defects and needs to be improved. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a method for batch preparation of nanofiber membrane by electrospinning, which has high spinning yield, stable quality of nanofibers and good filtration performance.

[0006] To achieve this purpose, the present application adopts the following technical solutions:

[0007] A method for batch preparation of nanofiber membrane by electrospinning, comprising the following steps:

[0008] S1, preparation of the spinning solution: the polymer material is dissolved in an organic solvent to obtain a 18-24wt% polymer solution, then benzyltriethylammonium chloride is added to the polymer solution and dissolved at room temperature by magnetic stirring for 1-2h, and the spinning solution is prepared after sufficient dissolution, and the addition amount of benzyltriethylammonium chloride is 0.2-2% of the total mass of the spinning solution;

[0009] S2, after the spinning solution is placed and defoamed, filtered, and the spinning solution is nanofiber spinning by the nozzle-free electrospinning method, wherein the spinning step of the nozzle-free electrospinning method is:

[0010] S21, the spinning solution prepared in step S1 is placed in a liquid storage tank;

[0011] S22, a microporous plate with a plurality of round holes on the surface is covered on the liquid surface of the spinning solution, the density of the microporous plate is less than the density of the spinning solution, and the pore size of the round hole is 0.2-2mm;

[0012] S22, the receiving substrate is placed above the liquid storage tank, and the receiving substrate is grounded, and the distance between the liquid surface of the spinning solution and the receiving substrate is 15-25cm;

[0013] S23, a gas guide pipe made of metal is placed into the liquid storage tank, the gas guide pipe can move up and down along the height direction of the liquid storage tank, so that the gas outlet of the gas guide pipe and the liquid level of the spinning solution are kept at 1-4cm;

[0014] S24, the positive electrode of the high-voltage generator is connected with the gas guide pipe, and the gas pump communicating with the gas guide pipe is opened to introduce gas into the spinning solution in the liquid storage tank, so that the spinning solution uniformly generates bubbles in the round holes of the microporous plate;

[0015] S25, the high-voltage generator is started to stretch and break the bubbles by electric field force and generate jet, and the jet is then stretched and refined into Taylor cone and deposited on the receiving substrate above to form a nanofiber membrane.

[0016] In the above technical solution, the polymer material is one of PE, PS, PES, PVA or PVDF.

[0017] In the above technical solution, the organic solvent is one or more of N-N-dimethylformamide, N-methylpyrrolidone, acetone, tetrahydrofuran, 1,4-dioxane, toluene.

[0018] In the above technical solution, the receiving substrate is one of filter paper substrate, melt-blown non-woven fabric substrate or filter felt substrate.

[0019] The organic solvent is a mixed solvent of N-N-dimethylformamide and 1,4-dioxane, and the solvent ratio of N-N-dimethylformamide to 1,4-dioxane is 20:80.

[0020] According to the technical scheme, in step S1, after adding benzyl triethyl ammonium chloride into the polymer solution, the modified nano-silica sol is added dropwise and stirred uniformly, and the addition amount of the modified nano-silica sol is 6-18% of the total mass of the spinning solution.

[0021] According to the technical scheme, the preparation process of the modified nano-silica sol is as follows.

[0022] The ammonia water, anhydrous ethanol and deionized water are uniformly stirred and mixed under water bath condition to obtain a mixed solution, then the methyl silicate is added dropwise into the mixed solution, and after sufficient stirring, the mixture is left to stand to obtain a nano-silica sol, then the divinyl tetramethyl disilazane is added dropwise into the nano-silica sol, and the mixture is fully stirred under oil bath condition, and after standing, the modified nano-silica sol is obtained.

[0023] The molar ratio of the ammonia water, the anhydrous ethanol, the deionized water, the methyl silicate and the divinyl tetramethyl disilazane is 0.05:7:2.5:1:0.05.

[0024] According to the technical scheme, in step S24, the spouting gas in the gas guide pipe is nitrogen, and the spouting flow rate of the nitrogen is 0.4-1.2 L / min.

[0025] According to the technical scheme, the bottom of the gas guide pipe is provided with a lifting device, the lifting device is used to control the up and down movement of the gas guide pipe along the height direction of the liquid storage tank, and a pressure sensor is arranged on the side wall of the nozzle of the gas guide pipe, the pressure sensor is connected with the lifting device through a controller, the pressure sensor is used to detect the water pressure change caused by the liquid level change of the spinning solution, and the water pressure change information is fed back to the controller, the controller can calculate the height difference of the spinning solution according to the water pressure change, and sends an instruction to the lifting device to act, so as to adjust the height of the gas guide pipe, and keep the distance between the nozzle of the gas guide pipe and the liquid level of the spinning solution constant.

[0026] According to the technical scheme, in step S2, the process parameters of the nozzle-free electrospinning are as follows: the environmental humidity is 40-60%, the temperature is 22-30℃, the spinning voltage is 65-85 kV, and the spinning time is 30-60 min.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] The application adds benzyl triethyl ammonium chloride and modified nano-silica sol in the spinning solution, the benzyl triethyl ammonium chloride is used as a surface surfactant, the viscosity and the surface tension of the spinning solution can be changed, the spinning solution can be more easily formed into nanofibers through the spinning process, meanwhile, the benzyl triethyl ammonium chloride can also increase the conductivity of the spinning solution, so that a more stable jet can be generated in the electrospinning process, thereby forming more uniform and finer nanofibers, and the modified nano-silica sol can form nano-silica particles in the spinning solution, the silica particles can be contained in the nanofibers in the spinning process, thereby improving the strength and rigidity of the nanofibers, achieving the effect of improving the mechanical properties of the nanofibers, and because the nano-silica particles are attached to the surface of the nanofibers, the roughness of the surface of the nanofibers can be increased, thereby improving the capture capacity of fine particulate matter, and the filtration performance is high, the nozzle-free electrospinning method of the application does not need to be heated and pressed or an adhesive to be added during preparation, the three-dimensional form of the nanofibers is maintained, thereby improving the filtration performance and the gas flowability, by arranging the microwell plate with a plurality of round holes on the surface in the liquid storage tank, the rate of solvent evaporation can be reduced, and a plurality of uniform-sized bubbles can be generated in the round holes on the microwell plate under the blowing action of the gas, thereby making the diameter of the nanofibers more uniform, and each generated bubble can be stretched and refined to form nanofibers, greatly improving the output efficiency of the nanofiber membrane, in addition, by changing the number and size of the round holes on the microwell plate, the number and direction of the generated jets can be controlled, so as to change the formation and distribution of the nanofibers, the method can not only improve the filtration effect of the nanofiber membrane, but also greatly improve the preparation yield of the nanofiber membrane, thereby realizing batch production. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is the schematic diagram of the instrument used in the preparation method of the nozzle-free electrospun nanofiber composite filter material provided by the application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application.

[0031] Example 1

[0032] The electrospinning method for batch preparation of nanofiber membranes provided in Example 1 of the application,

[0033] comprising the following steps:

[0034] S1, preparation of the spinning solution: PVDF was dissolved in organic solvent to obtain a 16wt% PVDF solution, then benzyltriethylammonium chloride and modified nano-silica sol were added into the PVDF solution and dissolved at room temperature by magnetic stirring for 2h. The spinning solution was prepared after complete dissolution. In this embodiment, benzyltriethylammonium chloride as a cationic surfactant can change the viscosity and surface tension of the spinning solution, making the spinning solution more easily form nanofibers through the spinning process; and benzyltriethylammonium chloride can also increase the conductivity of the spinning solution, so that a more stable jet can be generated in the electrospinning process, thereby forming more uniform and finer nanofibers. Specifically, benzyltriethylammonium chloride as a quaternary ammonium salt contains a positively charged nitrogen atom and three ethyl (-CH2-CH3) groups, as well as a benzyl (-C6H5-CH2-) group in its molecular structure. This structure makes benzyltriethylammonium chloride have a certain polarity, which can form ions in the solution. These ions form ionic bridges between polymer chains, increasing the viscosity of the spinning solution, making it easier to form nanofibers during the spinning process; in addition, the ions formed by benzyltriethylammonium chloride in the solution can also increase the conductivity of the spinning solution. The added modified nano-silica sol will form nano-silica particles in the spinning solution, which will be contained in the nanofibers during the spinning process, thereby improving the strength and stiffness of the nanofibers, achieving the effect of improving the mechanical properties of the nanofibers. In addition, the nano-silica particles attached to the surface of the nanofibers can increase the roughness of the nanofiber surface, thereby increasing the specific surface area of the fiber, thereby improving the filtration performance of the nanofibers.

[0035] The organic solvent is a mixed solvent of N-N-dimethylformamide and 1,4-dioxane, and the solvent ratio of N-N-dimethylformamide to 1,4-dioxane is 20:80.

[0036] In this embodiment, PVDF is a difficult-to-dissolve high polymer material, and N-N-dimethylformamide and 1,4-dioxane are selected to prepare a mixed solvent, which can improve the dissolution effect of PVDF. In addition, the volatilization rate of the solvent has a great influence on the formation of nanofibers during the spinning process. Specifically, when the solvent volatilizes quickly from the jet, the nanofibers will solidify quickly, which will cause the surface morphology of the nanofibers to be irregular, such as cracking. On the contrary, if the solvent volatilizes slowly, the jet may break before solidification, resulting in poor continuity of the fiber. Therefore, the volatilization rate of the solvent can make the nanofibers maintain good morphology during the solidification process. In this embodiment, N-N-dimethylformamide and 1,4-dioxane are selected as the mixed solvent, and the ratio is set to 20:80. The volatilization rate of the solvent can be effectively controlled by adjusting the ratio of the two organic solvents, so as to optimize the formation process of the nanofibers.

[0037] The benzyltriethylammonium chloride is added in an amount of 0.8% of the total mass of the spinning solution, and the modified nano-silica sol is added in an amount of 12% of the total mass of the spinning solution.

[0038] The preparation process of the modified nano-silica sol is as follows:

[0039] The ammonia water, the anhydrous ethanol and the deionized water are uniformly stirred and mixed under water bath conditions to obtain a mixed solution, then the tetramethyl orthosilicate is added dropwise into the mixed solution, and after sufficient stirring, the solution is left to stand to obtain a nano-silica sol, then the divinyltetramethyldisilazane is added dropwise into the nano-silica sol, and the solution is stirred sufficiently under oil bath conditions, and after standing, the modified nano-silica sol is obtained, and the molar ratio between the ammonia water, the anhydrous ethanol, the deionized water, the tetramethyl orthosilicate and the divinyltetramethyldisilazane is 0.05:7:2.5:1:0.05. In the preparation process, the ammonia water acts as an alkaline catalyst to promote the hydrolysis and condensation reaction of the tetramethyl orthosilicate to generate nano-silica particles. In this process, the anhydrous ethanol and the deionized water act as reaction media to effectively control the reaction speed and the generation process of the nano-silica particles, so that the nano-silica sol with good dispersibility and stability is obtained. The divinyltetramethyldisilazane is a coupling agent containing silane groups and vinyl groups, which can react with the hydroxyl groups on the surface of the nano-silica particles through the silane groups to replace the hydrophilic hydroxyl groups in the sol with hydrophobic groups, so that the modified nano-silica sol with hydrophobic groups on the surface is prepared.

[0040] S2, after the spinning solution is left to stand and defoamed and filtered, the spinning solution is subjected to nanofiber spinning through a nozzle-free electrospinning method, and the spinning step of the nozzle-free electrospinning method is as follows:

[0041] S21, the spinning solution obtained in step S1 is placed in a liquid storage tank 1;

[0042] S22, a microporous plate 2 with a plurality of circular holes 20 on the surface is covered on the liquid surface of the spinning solution, the density of the microporous plate 2 is less than the density of the spinning solution, and the diameter of the circular holes 20 is 1 mm;

[0043] In this embodiment, the circular holes 20 on the microporous plate 2 can make the spinning solution form uniform bubbles under the action of gas blowing, and these bubbles will be stretched and broken to form jets under the action of a high-voltage electric field; at the same time, the number and the size of the circular holes 20 on the microporous plate 2 can control the number and the direction of the generated jets, so as to change the formation and distribution of the nanofibers;

[0044] In addition, the arrangement of the microporous plate 2 can also avoid the rapid evaporation of the spinning solution under the high-voltage electric field; the density of the microporous plate 2 is set to be less than the density of the spinning solution, so that the microporous plate 2 can float on the surface of the spinning solution to float down with the consumption of the spinning solution.

[0045] S22, place the receiving substrate 4 above the liquid storage tank 1, and ground the receiving substrate 4, the distance between the liquid level of the spinning solution and the receiving substrate 4 is 20 cm; in this embodiment, the receiving substrate 4 is a melt-blown non-woven fabric substrate.

[0046] S23, place the air guide pipe 3 made of metal into the liquid storage tank 1, the air guide pipe 3 can move up and down along the height direction of the liquid storage tank 1, so that the height difference between the air outlet of the air guide pipe 3 and the liquid level of the spinning solution is kept at 1 cm; and a lifting device 7 is arranged at the bottom of the air guide pipe 3, the lifting device is used to control the air guide pipe 3 to move up and down along the height direction of the liquid storage tank 1, and a pressure sensor 6 is arranged on the side wall of the air guide pipe 3, the pressure sensor 6 is connected with the lifting device 7 through a controller, the pressure sensor 6 is used to detect the change of water pressure caused by the change of the liquid level of the spinning solution, and feed back the information of the change of water pressure to the controller, the controller can calculate the height difference of the spinning solution according to the change of water pressure, and send instructions to the lifting device 7 to act, so as to adjust the height of the air guide pipe 3, so that the distance between the air outlet of the air guide pipe 3 and the liquid level of the spinning solution is kept constant.

[0047] S24, connect the positive electrode of the high-voltage generator 5 with the air guide pipe 3, open the air pump connected with the air guide pipe 3, and introduce gas into the spinning solution in the liquid storage tank 1, so that the spinning solution generates bubbles uniformly in the round holes 20 of the microporous plate 2; in this embodiment, the gas sprayed in the air guide pipe 3 is nitrogen, and the flow rate of the nitrogen is 0.4 L / min. When the nitrogen is sprayed out of the air guide pipe 3, bubbles can be generated in the round holes 20 of the microporous plate 2, at this time, the flow rate of the nitrogen is 0.4 L / min. It should be noted that when the flow rate of the nitrogen is too large, the speed of bubble generation and the speed of jet flow formed by the bubbles will be too fast, which will affect the quality of the nanofiber because the nanofiber cannot be stretched sufficiently; when the flow rate of the nitrogen is too small, it is difficult to form enough bubbles for spinning.

[0048] S25, start the high-voltage generator 5 to stretch and break the bubbles by electric field force and generate jet flow, the jet flow is then stretched and refined into Taylor cone and deposited on the receiving substrate 4 above to form nanofiber, so as to obtain the finished PVDF nanofiber / melt-blown non-woven fabric composite filter material. The process parameters of the nozzle-free electrospinning are as follows: the environmental humidity is 40%, the temperature is 22℃, the spinning voltage is 80kV, and the spinning time is 45 min.

[0049] Example 2

[0050] Embodiment 2 of the present application provides an electrospinning method for batch preparation of nanofiber membranes,

[0051] comprising the following steps:

[0052] S1, preparation of the spinning solution: PES is dissolved in an organic solvent to obtain a 24wt% PES solution, then benzyltriethylammonium chloride and modified nanosilica sol are added to the PES solution, and dissolved by magnetic stirring at room temperature, the stirring time is 2h, and the spinning solution is prepared after sufficient dissolution;

[0053] The organic solvent is a mixed solvent of N-N-dimethylformamide and 1,4-dioxane, and the solvent ratio of N-N-dimethylformamide to 1,4-dioxane is 20:80;

[0054] Among them, the addition amount of benzyltriethylammonium chloride is 2% of the total mass of the spinning solution, and the addition amount of modified nanosilica sol is 8% of the total mass of the spinning solution;

[0055] The preparation process of the modified nanosilica sol is:

[0056] The ammonia water, anhydrous ethanol and deionized water are uniformly stirred and mixed under water bath conditions to obtain a mixed solution, then the methyl silicate is added dropwise to the mixed solution, stirred thoroughly and then placed to obtain the nanosilica sol, then the divinyltetramethyldisilazane is added dropwise to the nanosilica sol, and the mixture is stirred thoroughly under oil bath conditions, and then placed to obtain the modified nanosilica sol;

[0057] The molar ratio among the ammonia water, anhydrous ethanol, deionized water, methyl silicate and divinyltetramethyldisilazane is 0.05:7:2.5:1:0.05.

[0058] S2, after the spinning solution is placed and defoamed, filtered, the nanofiber spinning of the spinning solution is carried out by the nozzle-free electrospinning method, and the spinning step of the nozzle-free electrospinning method is:

[0059] S21, the spinning solution prepared in step S1 is placed in a liquid storage tank 1;

[0060] S22, a microporous plate 2 with a plurality of circular holes 20 on the surface is covered on the liquid surface of the spinning solution, the density of the microporous plate 2 is less than the density of the spinning solution, and the pore size of the circular hole 20 is 2mm;

[0061] S22, the receiving substrate 4 is arranged above the liquid storage tank 1, and the receiving substrate 4 is grounded, the distance between the liquid surface of the spinning solution and the receiving substrate 4 is 25cm; in this embodiment, the receiving substrate 4 is a filter paper substrate.

[0062] S23, the metal-made air guide pipe 3 is placed into the liquid storage tank 1, the air guide pipe 3 can move up and down along the height direction of the liquid storage tank 1, so that the air outlet of the air guide pipe 3 and the liquid level difference of the spinning solution are kept at 2cm; and a lifting device 7 is arranged at the bottom of the air guide pipe 3, the lifting device is used to control the air guide pipe 3 to move up and down along the height direction of the liquid storage tank 1, and a pressure sensor 6 is arranged on the side wall of the pipe mouth of the air guide pipe 3, the pressure sensor 6 is connected with the lifting device 7 through a controller, the pressure sensor 6 is used to detect the change of water pressure caused by the change of liquid level of the spinning solution, and feedback the water pressure change information to the controller, the controller can calculate the height difference of the spinning solution according to the change of water pressure, and send instructions to the lifting device 7 to act, so as to adjust the height of the air guide pipe 3, so that the distance between the pipe mouth of the air guide pipe 3 and the liquid level of the spinning solution is kept constant.

[0063] S24, the positive electrode of the high-voltage generator 5 is connected with the air guide pipe 3, and the air pump communicating with the air guide pipe 3 is opened, so that the gas is introduced into the spinning solution in the liquid storage tank 1, so that the spinning solution uniformly generates bubbles in the round hole 20 of the microporous plate 2; wherein the jet gas in the air guide pipe 3 is nitrogen, and the jet flow rate of nitrogen is 0.4L / min.

[0064] S25, start the high-voltage generator 5 to stretch and break the bubbles by electric field force and generate jet, then the jet is stretched and refined into Taylor cone and deposited on the receiving substrate 4 above to form nanofibers, so as to obtain the finished PES nanofiber / filter paper composite filter material. The process parameters of nozzle-free electrospinning are: the environmental humidity is 60%, the temperature is 30℃, the spinning voltage is 85kV, and the spinning time is 60min.

[0065] Comparative Example 1

[0066] The difference between the electrospinning method for batch preparation of nanofiber membrane of the comparative example 1 and the example 1 is that in step S2, the needle type electrospinning method is used for nanofiber spinning.

[0067] Comparative Example 2

[0068] The difference between the electrospinning method for batch preparation of nanofiber membrane of the comparative example 2 and the example 1 is that in step S22, the microporous plate 2 is not arranged on the surface of the spinning solution in the liquid storage tank 1.

[0069] Comparative Example 3

[0070] The difference between the electrospinning method for batch preparation of nanofiber membrane of the comparative example 3 and the example 1 is that in step S1, the benzyl triethyl ammonium chloride is not added in the spinning solution.

[0071] Comparative Example 4

[0072] The difference between the electrospinning method for batch preparation of nanofiber membranes of Comparative Example 4 and Example 1 is that in step S1, no modified nanosilica sol is added to the spinning solution.

[0073] Comparative Example 5

[0074] The difference between the electrospinning method for batch preparation of nanofiber membranes of Comparative Example 5 and Example 1 is that in step S1, the amount of modified nanosilica sol added is 2% of the total mass of the spinning solution.

[0075] Comparative Example 6

[0076] The difference between the electrospinning method for batch preparation of nanofiber membranes of Comparative Example 6 and Example 1 is that in step S1, the amount of modified nanosilica sol added is 35% of the total mass of the spinning solution.

[0077] Comparative Example 7

[0078] The difference between the electrospinning method for batch preparation of nanofiber membranes of Comparative Example 7 and Example 1 is that in step S24, the jet flow rate of nitrogen is 4 L / min.

[0079] The following experiments were conducted on the above-mentioned Examples 1-2 and Comparative Examples 1-7 to verify or understand their performance. The nanofiber composite filtration material prepared in the above-mentioned Examples 1-2 and Comparative Examples 1-7 was tested for gas filtration efficiency and resistance (pressure drop in millimeters of water column height) at room temperature. In this test, sodium chloride aerosol was used as the filtration medium, the effective area was 100 cm 2 , the flow rate was 32±0.1 L / min, the sample was tested 5 times, and the average value was taken. The filtration resistance performance test values of the nanofiber composite filtration material are shown in Table 1 below.

[0080] No. Flow rate (L / min) Air resistance (Pa) 0.3 μm (%) 0.5 μm (%) Yield (g / h) Example 1 32 24.7 97.6 98.3 8.63 Example 2 32 56.3 95.3 96.7 8.45 Comparative Example 1 32 23.4 97.8 98.6 1.32 Comparative Example 2 32 38.6 89.7 91.3 4.67 Comparative Example 3 32 33.7 88.6 90.2 6.72 Comparative Example 4 32 28.9 90.5 91.8 6.83 Comparative Example 5 32 32.7 91.3 93.2 7.24 Comparative Example 6 32 35.6 93.7 95.2 5.94 Comparative Example 7 32 34.2 87.2 89.6 6.58

[0081] Table 1 Comparison of nanofiber composite filtration material filtration resistance performance test of each example and comparative example

[0082] According to Table 1 above, it can be seen that:

[0083] In Comparative Example 1, although the prepared filtration material has high filtration performance and low filtration resistance, and the comprehensive performance is the best, it is prepared by needle-type electrospinning method, and the metal needle tip of the needle-type electrospinning method can only form one droplet at a time, which has the defects of slow spinning efficiency and low yield, and cannot meet the demand of rapid batch production.

[0084] In Comparative Example 2, the micro-hole plate 2 is not arranged on the surface of the spinning solution in the storage tank 1, so that the bubble diameter generated by the action of the gas flow is uneven during the spinning process, resulting in large fluctuations in the diameter of the nanofiber and irregular morphology, and uniform and fine nanofibers cannot be obtained, thereby affecting the filtration resistance performance of the nanofiber composite filtration material; at the same time, since the micro-hole plate 2 is not arranged, the volatilization rate of the solvent is fast during the spinning process, which also affects the formation effect of the nanofiber.

[0085] In Comparative Example 3, no benzyltriethylammonium chloride is added to the spinning solution. The benzyltriethylammonium chloride acts as a cationic surfactant in the spinning solution, which can change the viscosity and surface tension of the spinning solution, so that the spinning solution is more easily formed into nanofibers through the spinning process. In addition, benzyltriethylammonium chloride can also increase the conductivity of the spinning solution, so that a more stable jet can be generated during the electrospinning process, thereby forming more uniform and finer nanofibers. However, in Comparative Example 3, no benzyltriethylammonium chloride is added, which affects the quality of the nanofiber formation and thus the filtration resistance performance.

[0086] In Comparative Example 4, no modified nanosilica sol is added to the spinning solution. The nanosilica particles can adhere to the surface of the nanofiber to increase the roughness of the nanofiber surface, thereby increasing the specific surface area of the fiber and improving the filtration performance of the nanofiber. However, in Comparative Example 4, no modified nanosilica sol is added, which affects the filtration performance of the nanofiber. However, combined with the filtration resistance data, it is shown that the effect of the modified nanosilica sol on the quality of the nanofiber formation is less than that of the benzyltriethylammonium chloride.

[0087] In Comparative Examples 5 and 6, it is shown that the addition amount of the modified nanosilica particles also affects the filtration resistance performance of the nanofiber composite filtration material. Excessive or insufficient addition amount will have an effect, and it is not a simple linear relationship. Therefore, when preparing the nanofiber composite filtration material, the addition amount of the modified nanosilica particles needs to be controlled to ensure that the best filtration resistance performance is obtained within the appropriate range.

[0088] In Comparative Example 7, the nitrogen gas flow rate during the spinning process is 4 L / min. Too fast nitrogen gas flow rate will cause the bubbles generated by the solution in the round hole 20 of the micro-hole plate 2 to be too large or too fast, thereby causing unstable solution spraying, affecting the spinning effect of the nanofiber, and too fast nitrogen gas flow rate will cause the stretching speed of the nanofiber to be too fast, so that the fiber cannot be fully stretched and solidified during the formation process, thereby affecting the quality and performance of the nanofiber.

[0089] In summary, by adding benzyl triethyl ammonium chloride and modified nano-silica sol in the spinning solution, the benzyl triethyl ammonium chloride can change the viscosity and surface tension of the spinning solution as a surface surfactant, so that the spinning solution can be more easily formed into nanofibers through the spinning process; at the same time, the benzyl triethyl ammonium chloride can also increase the conductivity of the spinning solution, so that a more stable jet can be generated in the electrospinning process, thereby forming more uniform and finer nanofibers; and the modified nano-silica sol in the spinning solution will form nano-silica particles, which will be contained in the nanofibers during the spinning process, thereby improving the strength and stiffness of the nanofibers, achieving the effect of improving the mechanical properties of the nanofibers, and because the nano-silica particles are attached to the surface of the nanofibers, the roughness of the nanofiber surface can be increased, thereby improving the capture ability of fine particulate matter, and the filtration performance is high; the nozzle-free electrospinning method of the present application does not need to be heated and pressed or add a binder during preparation, so that the three-dimensional morphology of the nanofibers is maintained, thereby improving the filtration performance and the flowability of the gas; by arranging the microwell plate with multiple round holes on the surface in the liquid storage tank, not only the rate of solvent evaporation can be reduced, but also multiple uniform-sized bubbles can be generated in the round holes on the microwell plate under the blowing action of the gas, thereby making the diameter of the nanofibers more uniform, and each generated bubble can be stretched and refined to form a nanofiber, greatly improving the output efficiency of the nanofiber membrane; in addition, by changing the number and size of the round holes on the microwell plate, the number and direction of the generated jets can be controlled to change the formation and distribution of the nanofibers; the method not only can improve the filtration effect of the nanofiber membrane, but also can greatly improve the preparation yield of the nanofiber membrane, thereby realizing mass production.

[0090] The above examples are only used to illustrate the technical solutions of the present application, but not limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrospinning method for batch production of nanofiber membranes, characterized by, The method comprises the following steps: S1, preparation of the spinning solution: dissolving the polymer material in the organic solvent to obtain a 18-24wt% polymer solution, then adding benzyltriethylammonium chloride in the polymer solution and dissolving at room temperature by magnetic stirring for 1-2h, and preparing the spinning solution after sufficient dissolution, the addition amount of the benzyltriethylammonium chloride is 0.2-2% of the total mass of the spinning solution; S2, after the spinning solution is placed and defoamed, filtered, the spinning solution is nanofiber spinning by nozzle-free electrospinning method, wherein the spinning step of the nozzle-free electrospinning method is: S21, placing the spinning solution prepared in step S1 in a liquid storage tank; S22, covering the liquid surface of the spinning solution with a microporous plate having a plurality of round holes on the surface, the density of the microporous plate is less than the density of the spinning solution, and the pore size of the round hole is 0.2-2mm; S22, placing the receiving substrate above the liquid storage tank and grounding the receiving substrate, the distance between the liquid surface of the spinning solution and the receiving substrate is 15-25cm; S23, placing a gas guide pipe made of metal into the liquid storage tank, the gas guide pipe can move up and down along the height direction of the liquid storage tank, so that the height difference between the gas outlet of the gas guide pipe and the liquid surface of the spinning solution is kept at 1-4cm; S24, connecting the positive electrode of the high-voltage generator with the gas guide pipe, opening the air pump connected with the gas guide pipe to introduce gas into the spinning solution in the liquid storage tank, so that the spinning solution uniformly generates bubbles in the round holes of the microporous plate; The gas ejected in the gas guide pipe is nitrogen, and the ejection flow rate of the nitrogen is 0.4-1.2L / min, the bottom of the gas guide pipe is provided with a lifting device for controlling the gas guide pipe to move up and down along the height direction of the liquid storage tank, and a pressure sensor is arranged on the side wall of the pipe mouth of the gas guide pipe, the pressure sensor is connected with the lifting device through a controller, the pressure sensor is used for detecting the change of water pressure caused by the change of the liquid surface of the spinning solution and feeding back the water pressure change information to the controller, the controller can calculate the height difference of the spinning solution according to the change of the water pressure and send instructions to the lifting device to act, so as to adjust the height of the gas guide pipe and keep the distance between the pipe mouth of the gas guide pipe and the liquid surface of the spinning solution constant; S25, starting the high-voltage generator to stretch and break the bubbles by electric field force and generate jet, the jet is then stretched and refined into Taylor cone and deposited on the receiving substrate above to form a nanofiber membrane.

2. The electrospinning method for mass production of nanofiber membranes according to claim 1, characterized by, The polymer material is one of PE, PS, PES, PVA or PVDF.

3. The electrospinning method for mass production of nanofiber membranes according to claim 1, wherein, The organic solvent is one or more of N-N-dimethylformamide, N-methylpyrrolidone, acetone, tetrahydrofuran, 1,4-dioxane and toluene.

4. The electrospinning method for mass production of nanofiber membranes according to claim 1, wherein, The receiving substrate is one of filter paper substrate, melt-blown non-woven fabric substrate or filter felt substrate.

5. The electrospinning method for mass production of nanofiber membranes according to claim 3, wherein The organic solvent is a mixed solvent of N-N-dimethylformamide and 1,4-dioxane, and the solvent ratio of N-N-dimethylformamide to 1,4-dioxane is 20:

80.

6. The electrospinning process for mass production of nanofibrous membranes according to claim 1, wherein, In step S1, after adding benzyltriethylammonium chloride into the polymer solution, it is also necessary to drop and stir uniformly the modified nano-silica sol, and the adding amount of the modified nano-silica sol is 6-18% of the total mass of the spinning solution.

7. The electrospinning process for batch production of nanofibrous membranes according to claim 6, characterized in that, The preparation process of the modified nano-silica sol is as follows: The ammonia water, anhydrous ethanol and deionized water are uniformly stirred and mixed under water bath condition to obtain a mixed solution, then the tetramethyl orthosilicate is added dropwise into the mixed solution, after fully stirring, it is placed to obtain a nano-silica sol, then the divinyltetramethyldisilazane is added dropwise into the nano-silica sol, and fully stirred under oil bath condition, and after standing, the modified nano-silica sol is obtained. The molar ratio among the ammonia water, the anhydrous ethanol, the deionized water, the tetramethyl orthosilicate and the divinyltetramethyldisilazane is 0.05:7:2.5:1:0.

05.

8. The electrospinning process for mass production of nanofibrous membranes according to claim 1, wherein, In step S2, the process parameters of the nozzle-free electrospinning are as follows: the environmental humidity is 40-60%, the temperature is 22-30℃, the spinning voltage is 65-85kV, and the spinning time is 30-60min.

Images