High-performance true nanoscale fiber membrane as well as preparation method and application thereof

Abstract

The invention discloses a high-performance true nanoscale fiber membrane as well as a preparation method and application thereof, and belongs to the technical field of nanofiber air filtering materials. The preparation method comprises the following steps: by taking water as a solvent, dissolving a dimethyl diallyl ammonium chloride monomer in deionized water, adding ammonium persulfate and azodiisobutyronitrile as initiators to prepare poly dimethyl diallyl ammonium chloride, then dissolving the poly dimethyl diallyl ammonium chloride and nylon 66 particles in an organic solvent 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3 A spinning precursor solution is prepared in 1, 2, 2-trifluoroethanol, and the fiber membrane with a real nanoscale fiber structure is prepared from the spinning precursor solution through an electrostatic spinning technology and a one-step method. Compared with an existing preparation process, the preparation method has the advantages that the process is simple and easy to operate, the production efficiency is high, and the fibrous membrane with the real nanoscale fibers shows excellent filtering performance on fine particulate matters with different particle sizes and shows excellent application potential in the fields of air purification, environmental protection, industrial waste gas treatment and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanofiber air filtration materials, and particularly relates to a high-performance true nano-scale fiber membrane, a preparation method thereof, and an application thereof. Background Art

[0002] With the acceleration of the urbanization process and the increase in industrial activities, the problem of air pollution has become increasingly severe, posing a huge threat to human health and the ecological environment. Globally, especially in developing countries, the rapid growth of the population and the rapid development of the economy have exerted great pressure on air quality. The expansion of cities and the advancement of industrialization not only increase energy consumption but also exacerbate the quantity of pollutants emitted, resulting in an increasing amount of harmful substances in the atmosphere. Particulate matter PM 0.3 As the most penetrable ultrafine particulate matter, it has extremely strong diffusivity and permeability, can spread over long distances and carry various harmful substances (such as viruses and bacteria), posing a major threat to human health, the ecological environment, and climate change. Therefore, there is an urgent need to develop high-performance personal protective materials.

[0003] Currently, the filtration materials for ultrafine particulate matter (such as PM 0.3 ) mainly rely on melt-blown nonwovens, commercial nanofiber membranes, and traditional electrospun materials. Among them, micron-scale fibers (1 - 5 μm) are prepared by the melt-blown process, and particulate matter is intercepted by fiber gaps (such as medical mask materials). However, its filtration efficiency is positively correlated with the pressure drop. The pressure drop of high-efficiency melt-blown cloth (such as N95) is as high as over 200 Pa, and the comfort during long-term wearing is poor. Although the commercial nanofiber membrane ePTFE membrane can efficiently filter PM 0.3 , it relies on complex stretching processes and perfluorinated materials, with high costs and difficulty in biodegradation. Sub-micron-scale fibers (300 - 800 nm) can be prepared using raw materials such as polyacrylonitrile (PAN) and polylactic acid (PLA), but it is still difficult to stably obtain true nano-scale fibers (<100 nm). In addition, conventional electrospinning solutions need to add inorganic salts (such as NaCl) or surfactants to regulate the conductivity, resulting in a decrease in the mechanical strength of the fiber membrane. Moreover, it is difficult for traditional materials to balance high efficiency and low resistance. Therefore, the development of high-performance protective filtration materials is particularly important and urgent. Summary of the Invention

[0004] To solve the above problems, the present invention provides a high-performance true nano-scale fiber membrane, its preparation method and application. First, a strong cationic polyelectrolyte poly(dimethyldiallylammonium chloride) (PDADMAC) is used to regulate the physical and chemical properties of the nylon 66 spinning solution. The addition of PDADMAC can significantly increase the conductivity and viscosity of the spinning solution. Through electrospinning technology, charged jets can be fully stretched to significantly refine the fiber diameter, thus forming a true nano-scale fiber structure. The design of the true nano-scale fiber structure can significantly increase the specific surface area and porosity of the fibers, thereby improving the filtration efficiency and air permeability of the air filtration material. The nylon 66 true nano-scale fiber membrane prepared by the one-step electrospinning technology of the present invention solves the problem that it is difficult to balance the filtration efficiency and pressure drop of electrospun fibers, and at the same time has excellent filtration stability, and can be widely used in air filtration fields such as personal protective masks and anti-haze window screens, with great practical application value.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A preparation method of a high-performance true nano-scale fiber membrane: Using water as a solvent, dimethyldiallylammonium chloride (DADMAC) is synthesized into a strong cationic polyelectrolyte poly(dimethyldiallylammonium chloride) (PDADMAC) under the action of an initiator. Subsequently, the poly(dimethyldiallylammonium chloride) and nylon 66 particles are dissolved in an organic solvent and mixed to prepare a spinning precursor solution, and the spinning precursor solution is prepared into a fiber membrane with a true nano-scale fiber structure by one-step electrospinning technology.

[0006] The above preparation method of a high-performance true nano-scale fiber membrane specifically includes the following steps: (1) Dissolve dimethyldiallylammonium chloride (DADMAC) monomer in deionized water, and add ammonium persulfate and azobisisobutyronitrile as initiators to the dimethyldiallylammonium chloride water (DADMAC) solution to react to prepare poly(dimethyldiallylammonium chloride) (PDADMAC); (2) Dissolve the PDADMAC in step (1) and nylon 66 particles in the organic solvent 2,2,2-trifluoroethanol. A large number of quaternary ammonium salt groups in the PDADMAC molecular chain ionize to generate free ions, which can significantly enhance the charge density of the jet under the high-voltage electric field, promote the stretching and splitting of the jet, and refine the fiber diameter to less than 100 nm; after the mixed solution is stirred evenly, a precursor solution is prepared; (3) Place the precursor solution in step (2) in a syringe, and use electrospinning technology to prepare a nylon 66 true nano-scale fiber membrane.

[0007] Further, the mass fraction of the dimethyldiallylammonium chloride aqueous solution in step (1) is 20 wt%.

[0008] Furthermore, the amount of ammonium persulfate used in the initiator solution in step (1) is calculated based on 1 wt% of the mass of the DADMAC monomer, and the amount of azobisisobutyronitrile is calculated based on 0.5 wt% of the mass of the DADMAC monomer; the calculated amount of ammonium persulfate is made into a 1 wt% solution, and the calculated amount of azobisisobutyronitrile is made into a 0.5 wt% anhydrous ethanol solution, and they are successively added to the aqueous solution of dimethyldiallylammonium chloride in step (1).

[0009] Furthermore, the final concentration range of the PDADMAC in step (2) is 0 - 100 wt%.

[0010] Furthermore, the final concentration of the nylon 66 in step (2) is 3 - 9 wt%.

[0011] Furthermore, the relevant parameters of the electrospinning in step (3) are: the injection rate is 0.8 - 1.0 ml h -1 , the roller rotation speed is 200 rpm, the receiving distance is 12 - 15 cm, the applied voltage is 19 - 27 kV, the spinning time is 10 - 30 min, the ambient temperature is 20 - 30 °C, and the humidity is 40 - 60 %RH.

[0012] A true nano-scale fiber membrane prepared by the above method.

[0013] Application of the above true nano-scale fiber membrane in protective filtration products.

[0014] Technical principle of the present invention: First, the strong cationic polyelectrolyte PDADMAC is used to regulate the physical and chemical properties of the nylon 66 spinning solution. The addition of PDADMAC can significantly increase the conductivity and viscosity of the spinning solution, increase the electric field force on the jet under the high-voltage electric field, and at the same time increase the stability of the jet, making it easier for the jet to form fine fibers; then through the electrospinning technology, with the non-woven fabric as the receiving substrate, the charged jet is fully stretched to significantly refine the fiber diameter, and a nylon 66 fiber membrane with a true nano-scale fiber structure is prepared in one step. The design of the true nano-scale fiber structure can significantly increase the specific surface area and porosity of the fiber, thereby improving the filtration efficiency and air permeability of the air filtration material, having high filtration efficiency, low pressure drop and excellent filtration stability. It can be widely used in air filtration fields such as personal protective masks and anti-haze window screens, and has great practical application value.

[0015] Advantages of the present invention: (1) One-step electrospinning forming: PDADMAC and nylon 66 are co-dissolved in 2,2,2-trifluoroethanol, and by optimizing the spinning parameters, a true nano-scale fiber membrane can be directly obtained without subsequent modification or composite processes.

[0016] (2)The prepared nylon 66 true nano - scale fiber membrane has a high filtration efficiency. The filtration efficiency for PM 0.3 is as high as over 99%, while the pressure drop is only less than 50 Pa. The design of the true nano - scale fiber structure enables the fiber membrane to effectively capture fine particles only through physical interception, and it has excellent filtration stability in complex environments such as high - humidity environments.

[0017] (3)The ultra - thin thickness (the fiber membrane thickness ranges from 200 to 500 nm) brought by the <100 nm nano - scale fibers in the prepared nylon 66 true nano - scale fiber membrane endows the fiber membrane with excellent air permeability.

[0018] (4)It can be applied to air - filtration fields such as personal protective masks and anti - haze window screens. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below.

[0020] Figure 1 Shows the scanning electron micrograph (left) and fiber diameter graph (right) of the fiber membrane in Example 1.

[0021] Figure 2 Shows the scanning electron micrograph of the fiber membrane in Comparative Example 1.

[0022] Figure 3 Shows the scanning electron micrograph (left) and fiber diameter graph (right) of the fiber membrane in Comparative Example 2.

[0023] Figure 4 Shows the scanning electron micrograph (left) and fiber diameter graph (right) of the fiber membrane in Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention provides a method for preparing a high - performance true nano - scale fiber membrane, which includes the following steps: Step 1: Preparation of polyelectrolyte PDADMAC: In one embodiment, this step can be specifically carried out as follows: Mix DADMAC particles and deionized water at a mass ratio of 1:4 to form a monomer solution. Subsequently, add ammonium persulfate (APS, pre-prepared as a 1 wt% aqueous solution) equivalent to 1% of the mass of DADMAC monomer and 0.5% of azobisisobutyronitrile (AIBN, pre-prepared as a 0.5 wt% absolute ethanol solution). Stir until the initiator is completely dissolved to form a homogeneous system. Pass nitrogen into the solution for 30 min to remove oxygen in the system and heat up to 70 °C, turn on mechanical stirring (rotation speed: 300 rpm), and continue the reaction for 12 h. Cool the reaction solution to room temperature, transfer it to a dialysis bag, and dialyze it in deionized water for 72 h (change the water every 6 h) to remove unreacted monomers and small molecule impurities; the solution after dialysis is freeze-dried (-50 °C, 24 h) to obtain PDADMAC.

[0026] Step Two: Preparation of electrospinning precursor solution: In one embodiment, this step can be specifically carried out as follows: Add 0 - 100 wt% PDADMAC and 3 - 9 wt% polylactic acid to 2,2,2-trifluoroethanol, and magnetically stir at room temperature until completely dissolved to obtain a precursor solution.

[0027] Step Three: Preparation of nylon 66 true nano-scale fiber membrane: In one embodiment, this step can be specifically carried out as follows: Transfer the precursor spinning solution into a syringe, use a spunbond non-woven fabric as the receiving substrate, set the injection rate to 0.8 - 1.0 ml h -1 , the roller rotation speed is 200 rpm, the receiving distance is 12 cm, the applied voltage is 19 - 27 kV, the spinning time is 10 - 30 min, the ambient temperature is 20 - 30 °C, and the humidity is 40 - 60 %RH.

[0028] As used herein, "one embodiment" or "an embodiment" refers to specific features, structures, or characteristics that may be included in at least one implementation manner of the present invention. The "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selectively mutually exclusive embodiment with other embodiments.

[0029] The specific operation method of the filtration experiment in the present invention is as follows: Test conditions for the filtration performance of the sample: Use an LZC-K1 automatic filter material instrument to test the filtration performance of the prepared electrospun composite membrane. The number of salt particles with a particle size of about 300 nm generated by the aerosol generator is approximately 125,000, the wind speed is 32 L / min, and the test area is 100 cm 2Each sample was tested 3 times, and the average values of the pressure drop and filtration efficiency were calculated. The quality factor (QF) reflecting the comprehensive filtration performance was calculated as follows: where represents the filtration efficiency, and Δp represents the pressure drop.

[0030] Air permeability test of the sample: The YG461E-III fabric air permeability tester was used for the test. The test area was 100 cm 2 , the pressure difference was set at 200 Pa, the test mode was set to the automatic mode, the number of tests was 10 times, and the average value was taken.

[0031] The specific operation method of the actual applicability test in the present invention is as follows: The LZC-K1 filter material comprehensive performance test platform was used to test the filtration efficiency and pressure drop of the fiber membrane and the control sample at different low and high wind speeds to evaluate the actual applicability of the fiber membrane.

[0032] The specific operation method of the filtration stability test under high humidity conditions in the present invention is as follows: The fiber membrane and the control sample were placed in a constant temperature and humidity chamber. The temperature was set at 25°C and the humidity was set at 90%RH. After being placed in the chamber for 48 h, they were taken out and the LZC-K1 filter material comprehensive performance test platform was used to test the changes in the filtration efficiency and pressure drop of the fiber membrane before and after treatment.

[0033] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with specific embodiments.

[0034] Example 1 Preparation of a high-performance true nano-scale fiber membrane, including the following steps: (1) Preparation of polyelectrolyte PDADMAC: DADMAC particles and deionized water were mixed at a mass ratio of 1:4 to form a monomer solution. Subsequently, ammonium persulfate (APS, pre-prepared as a 1 wt% aqueous solution) equivalent to 1% of the mass of the DADMAC monomer and 0.5% of azobisisobutyronitrile (AIBN, pre-prepared as a 0.5 wt% absolute ethanol solution) were added, and stirred until completely dissolved to form a homogeneous solution. Nitrogen was introduced into the solution for 30 min to remove the oxygen in the system and the temperature was raised to 70°C. Mechanical stirring was started (rotation speed: 300 rpm), and the reaction continued for 12 hours. The reaction solution was cooled to room temperature, transferred to a dialysis bag, and dialyzed in deionized water for 72 h (changing the water every 6 h) to remove unreacted monomers and small molecule impurities; the dialyzed solution was freeze-dried (-50°C, 24 h) to obtain PDADMAC.

[0035] (2) Preparation of electrospinning precursor solution: Weigh 0.15 g of PDADMAC prepared in step (1) into a small glass bottle, add 4.85 g of the organic solvent 2,2,2-trifluoroethanol, stir magnetically at room temperature until completely dissolved, and then add 0.15 g of nylon 66 and stir until completely dissolved to prepare a nylon 66 spinning solution.

[0036] (3) Preparation of nylon 66 true nano-fiber membrane: Inject the spinning solution into a 10 mL syringe, install a 20 G needle, and set the electrospinning parameters: voltage 25 kV, injection rate 1.0 mL h -1 , receiving distance 12 cm, roller speed 200 rpm, ambient temperature 20 - 30 °C, ambient humidity 40 - 60% RH, spinning time 20 min. After completion, a nylon 66 true nano-fiber membrane is obtained.

[0037] In Figure 1 it can be observed that there are no beaded fibers in the nylon 66 true nano-fiber membrane, and the presented fiber diameter is at the nano-scale, with an average fiber diameter of 44.5 nm. The nylon 66 true nano-fiber membrane has a filtration efficiency for PM 0.3 of over 99%, and the pressure drop is only about 45 Pa. It still has a high filtration efficiency at high wind speeds and can maintain excellent filtration performance even in a high-humidity environment.

[0038] Comparative Example 1 Control group of electrospun fibers at different voltages Weigh 0.15 g of PDADMAC prepared in Example 1 and 0.15 g of nylon 66 particles into a small glass bottle, add 4.85 g of the organic solvent 2,2,2-trifluoroethanol, and stir magnetically at room temperature until completely dissolved to prepare a nylon 66 spinning solution.

[0039] Inject the spinning solution into a 10 mL syringe, install a 20 G needle, and set the electrospinning parameters: voltage 19 kV, injection rate 1.0 mL h -1 , receiving distance 12 cm, roller speed 200 rpm, ambient temperature 20 - 30 °C, ambient humidity 40 - 60% RH, spinning time 20 min. After completion, a nylon 66 fiber membrane is obtained.

[0040] In Figure 2 it can be observed that there are beaded fibers in the nylon 66 fiber membrane prepared in Comparative Example 1, the fiber diameter distribution is uneven, and there are sub-micron and nano-scale fibers in the fiber diameter. From the filtration performance test, the filtration efficiency of the nylon 66 fiber membrane for PM 0.3 is only about 95%, and it cannot efficiently capture PM 0.3 .

[0041] Comparative Example 2 Fiber control group with different concentrations of polymer nylon 66 Weigh 0.15 g of PDADMAC prepared in Example 1 and 0.45 g of nylon 66 particles into a small glass bottle, add 4.65 g of organic solvent 2,2,2-trifluoroethanol, and stir magnetically at room temperature until fully dissolved to prepare a nylon 66 spinning solution.

[0042] Inject the spinning solution into a 10 mL syringe, install a 20 G needle, and set the electrospinning parameters: voltage 25 kV, injection rate 1.0 mL h -1 , receiving distance 12 cm, roller speed 200 rpm, ambient temperature 20 - 30 °C, ambient humidity 40 - 60%RH, spinning time 20 min. After completion, a nylon 66 fiber membrane is obtained.

[0043] In Figure 3 it can be observed that the nylon 66 fiber membrane prepared in Comparative Example 2 has no beaded fibers and the fiber diameter distribution is uniform, but the fiber diameter exceeds 100 nm, and the average fiber diameter is 175 nm.

[0044] Comparative Example 3 Fiber control group with different PDADMAC concentrations Weigh 0.03 g of PDADMAC prepared in Example 1 and 0.15 g of nylon 66 particles into a small glass bottle, add 4.85 g of organic solvent 2,2,2-trifluoroethanol, and stir magnetically at room temperature until fully dissolved to prepare a nylon 66 spinning solution.

[0045] Inject the spinning solution into a 10 mL syringe, install a 20 G needle, and set the electrospinning parameters: voltage 25 kV, injection rate 1.0 mL h -1 , receiving distance 12 cm, roller speed 200 rpm, ambient temperature 20 - 30 °C, ambient humidity 40 - 60%RH, spinning time 20 min. After completion, a nylon 66 fiber membrane is obtained.

[0046] In Figure 4 it can be observed that although the fibers of the nylon 66 fiber membrane prepared in Comparative Example 3 reach the true nanoscale, there are a large number of beaded fibers. From the filtration performance test, the filtration efficiency of this nylon 66 fiber membrane for PM 0.3 is only about 39%, and it cannot efficiently capture PM 0.3 .

Claims

1. A method for preparing a high-performance true nano-scale fiber membrane, characterized in that: Using water as a solvent, dimethyldiallylammonium chloride is synthesized into a strong cationic polyelectrolyte, polydimethyldiallylammonium chloride, under the action of an initiator. Subsequently, polydimethyldiallylammonium chloride and nylon 66 particles are dissolved in an organic solvent and mixed to prepare a spinning precursor solution. The spinning precursor solution is prepared into a fiber membrane with a true nano-scale fiber structure by one-step electrospinning technology.

2. The preparation method of the high-performance true nano-scale fiber membrane according to claim 1, characterized in that: It includes the following steps: (1) Dimethyldiallylammonium chloride is dissolved in deionized water, and ammonium persulfate and azobisisobutyronitrile solution are added to the dimethyldiallylammonium chloride aqueous solution to react to prepare polydimethyldiallylammonium chloride; (2) The polydimethyldiallylammonium chloride obtained in step (1) and nylon 66 particles are dissolved in the organic solvent 2,2,2-trifluoroethanol. After the mixed solution is stirred evenly, a spinning precursor solution is obtained; (3) The spinning precursor solution obtained in step (2) is placed in a syringe, and a nylon 66 true nano-scale fiber membrane is prepared by electrospinning technology.

3. The preparation method of the high-performance true nano-scale fiber membrane according to claim 1, characterized in that, In step (1), the mass fraction of the dimethyldiallylammonium chloride aqueous solution is 20 wt%.

4. The preparation method of the high-performance true nano-scale fiber membrane according to claim 1, characterized in that In step (1), the amount of ammonium persulfate used in the initiator solution is calculated according to 1 wt% of the mass of the dimethyldiallylammonium chloride monomer, and the amount of azobisisobutyronitrile is calculated according to 0.5 wt% of the mass of the dimethyldiallylammonium chloride monomer; the calculated amount of ammonium persulfate is made into a 1 wt% solution, and the calculated amount of azobisisobutyronitrile is made into a 0.5 wt% absolute ethanol solution, and they are successively added to the dimethyldiallylammonium chloride aqueous solution in step (1).

5. The preparation method of the high-performance true nano-scale fiber membrane according to claim 1, characterized in that: The concentration range of the polydimethyldiallylammonium chloride described in step (2) is 0-100 wt%.

6. The preparation method of the high-performance true nano-scale fiber membrane according to claim 1, wherein, The concentration of nylon 66 described in step (2) is 3-9 wt%.

7. The preparation method of the high-performance true nano-scale fiber membrane according to claim 1, characterized in that, The electrospinning-related spinning parameters described in step (3) are as follows: the liquid injection speed is 0.8 to 1 ml / h -1 , the roller rotation speed is 200 rpm, the receiving distance is 12 to 15 cm, the applied voltage is 19 to 27 kV, the spinning time is 10 to 30 min, the ambient temperature is 20 to 30 °C, and the humidity is 40 to 60%RH.

8. A true nano-scale fiber membrane obtained by the method according to any one of claims 1-6.

9. Application of the true nano-scale fiber membrane according to claim 8 in protective filtration articles.

Images