A high electrostatic cellulose acetate-based electret air filter material and a preparation method thereof

Abstract

The application discloses a high-static-acid cellulose-based electret air filter material and a preparation method thereof, and belongs to the field of air filter material preparation. The method is characterized in that: a mixed solution of acid cellulose and CuSO4 is electrospun under a voltage of 18-22 kV, the mass ratio of the acid cellulose and CuSO4 is 1: (0.01-0.04), and a composite nanofiber film is obtained; and the excess solvent in the composite nanofiber film is removed, so that the high-static-acid cellulose-based electret air filter material is obtained. The method solves the problem that the electrostatic enhancement effect of the acid cellulose-based electret air filter material is relatively weak, is simple, has low preparation cost, and greatly improves the filtering efficiency and service life of the acid cellulose-based electret air filter material.

Description

Technical Field

[0001] This invention belongs to the field of air filter material preparation, specifically a high electrostatic cellulose acetate-based electret air filter material and its preparation method. Background Technology

[0002] With industrialization, air pollution has become a serious environmental problem. Pollutants in the air, including toxic gases (ozone (O3), sulfur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOCs), particulate matter (PM), and viruses, not only affect air quality but also have severe negative impacts on ecosystems, climate change, and human health. Therefore, there is an urgent need to develop air filtration materials with high filtration efficiency and low resistance.

[0003] Currently, electrostatically reinforced synthetic fiber materials have become the mainstream air filtration materials (i.e., electret filtration materials) due to their advantages such as high charge storage stability, strong moisture resistance, and long service life. However, these materials are difficult to degrade and pose a threat to the ecological environment. Therefore, in order to protect the ecological environment, it is necessary to develop biodegradable air filtration materials based on this.

[0004] Cellulose acetate (CA) is an esterified derivative of cellulose. Due to its good biodegradability, biocompatibility, and absorbency, cellulose acetate has become one of the most promising raw materials for preparing air filtration materials. However, the numerous hydrogen bonds between CA molecules result in tightly connected molecular chains that are difficult to move. This makes it difficult for the internal dipoles to orient and polarize under an electric field, leading to relatively weak electrostatic enhancement effects in cellulose acetate-based electret air filtration materials. Furthermore, the strong hydrophilicity imparted by the polyhydroxyl structure on the fiber surface accelerates charge decay, which significantly reduces the filtration efficiency and lifespan of the material. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a high electrostatic cellulose acetate-based electret air filter material and its preparation method, thereby solving the problem of relatively weak electrostatic enhancement effect of cellulose acetate-based electret air filter materials. The method is simple, the preparation cost is low, and it greatly improves the filtration efficiency and service life of cellulose acetate-based electret air filter materials.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing a high-static cellulose acetate-based electret air filter material includes the following steps:

[0008] S1, a mixed solution of cellulose acetate and CuSO4 is electrospun at a voltage of 18~22 kV, with a mass ratio of cellulose acetate to CuSO4 of 1:(0.01~0.04), to obtain a composite nanofiber membrane;

[0009] S2, remove excess solvent from the composite nanofiber membrane to obtain a high electrostatic cellulose acetate-based electret air filter material.

[0010] A further improvement of the present invention is that:

[0011] The mixed solution described in S1 is obtained through the following process:

[0012] S1. Add cellulose acetate powder and CuSO4 powder to N,N-dimethylacetamide and acetone, and then stir at 5~45℃ for 6.5~7.5h until the cellulose acetate powder and CuSO4 powder are completely dissolved to obtain the mixed solution.

[0013] The mass ratio of N,N-dimethylacetamide to acetone is 1:1.

[0014] The total mass ratio of N,N-dimethylacetamide and acetone to cellulose acetate powder is 83:17.

[0015] The electrospinning described in S1 is at 25~30 o The experiment was conducted at a temperature of C and an ambient relative humidity of 30% to 40%.

[0016] S1. The mixed solution is loaded into an injection needle tube equipped with a metal needle. The opening of the injection needle tube is fixed horizontally on the spraying device. The positive electrode of the high voltage power supply of the electrospinning instrument is connected to the metal needle. Non-woven fabric is wrapped around the roller-shaped negative electrode. The injection needle tube is aligned with the center of the negative electrode. The working chamber of the electrospinning instrument is kept sealed before electrospinning.

[0017] The distance from the metal needle tip of the injection syringe to the center of the negative electrode is 16-18 cm.

[0018] The flow rate during S1 electrospinning is 0.015~0.018 ml / min.

[0019] S2 removes excess solvent from the composite nanofiber membrane by vacuum drying, which is carried out at 60°C for 3 hours.

[0020] A high electrostatic cellulose acetate-based electret air filter material obtained by the preparation method of the high electrostatic cellulose acetate-based electret air filter material described in any one of the above claims.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] This invention discloses a method for preparing a high-static cellulose acetate-based electret air filter material. By adjusting the ratio of cellulose acetate to CuSO4, Cu... 2+ Coordination with hydroxyl and ester groups on CA alters the crystal structure of the CA molecule, enhancing its activity and independent polarization properties. Electrospinning with a suitable voltage further improves the electrostatic construction effect. The elimination of polyhydroxyl structures on the fiber surface significantly reduces charge decay, greatly improving the material's filtration efficiency and lifespan. 2+ The coordination with oxygen-containing functional groups on CA alters the crystal structure of CA, thereby enhancing its activity and independent polarization properties, resulting in a prominent dipole moment (8.86 debye) and electrostatic building-up effect. The surface potential can reach a maximum of 12.52 kV, and the filtration efficiency for PM0.3 can reach 99.31%, which is 39.98% higher than that of CA membranes. The molecular chain spacing of CA is expanded, and a high-electrostatic cellulose-based air filter material is prepared. This invention overcomes the problems of non-degradability and environmental pollution caused by existing electret filter materials, and prepares a high-electrostatic cellulose acetate electret air filter material (CA-Cu) with copper ion assistance. 2+ Compared to CA membranes, electret filtration membranes have a significant electrostatic enhancement effect, resulting in a substantial improvement in filtration performance, and are expected to be applied in actual production. Attached Figure Description

[0023] Figure 1 The CA-Cu of this invention 2+ A schematic diagram of the preparation process of composite electret air filter material.

[0024] Figure 2 This is a SEM image of the CA film described in Comparative Example 1 of the present invention at a magnification of 5K.

[0025] Figure 3 This is a SEM image of the CA film described in Comparative Example 1 of the present invention at a magnification of 10K.

[0026] Figure 4 This is a diameter analysis diagram of the CA membrane described in Comparative Example 1 of the present invention.

[0027] Figure 5 The CA-Cu described in Embodiment 4 of the present invention 2+ SEM image of the composite film at 5K magnification.

[0028] Figure 6 The CA-Cu described in Embodiment 4 of the present invention 2+ SEM image of the composite film at 10K magnification.

[0029] Figure 7 The CA-Cu described in Embodiment 4 of the present invention2+ Diameter analysis diagram of the composite membrane.

[0030] Figure 8 The CA-Cu described in Embodiment 4 of the present invention 2+ C element distribution spectrum of composite membrane EDS.

[0031] Figure 9 The CA-Cu described in Embodiment 4 of the present invention 2+ O element distribution spectrum of composite membrane EDS.

[0032] Figure 10 The CA-Cu described in Embodiment 4 of the present invention 2+ Cu elemental distribution spectrum of composite membrane EDS.

[0033] Figure 11 The CA-Cu described in Embodiment 4 of the present invention 2+ Surface potential diagram of the composite film.

[0034] Figure 12 The CA-Cu described in Embodiment 4 of the present invention 2+ Filtration performance and quality factor of composite membrane for PM 0.3. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0036] This invention discloses a high electrostatic cellulose acetate-based electret air filter material (i.e., cellulose acetate / Cu). 2+ Preparation methods of composite electret air filter materials, such as Figure 1 As shown, the specific steps are as follows:

[0037] Step 1: Weigh 1.7g of cellulose acetate powder (CA) and 0.017~0.068g of CuSO4 powder and dissolve them in 8.3g of a mixed solvent of N,N-dimethylacetamide (DMAc) and acetone (Ac) (solvent mass ratio of 1:1).

[0038] Step 2: Stir the solution in (1) at 5~45℃ for 6.5~7.5h to completely dissolve it, and obtain a spinning solution with a certain viscosity.

[0039] Step 3: Load the obtained spinning solution into an injection needle tube equipped with a metal needle, then fix the opening of the injection needle tube horizontally on the jetting device (injection pump), connect the positive electrode of the high voltage power supply of the electrospinning instrument to the metal needle, wrap the nonwoven fabric on the roller-shaped negative electrode, align the injection needle tube with the center of the roller, and keep the working chamber of the electrospinning instrument sealed.

[0040] Step 4: Set the working chamber temperature to 25-30°C during the electrospinning process. o C, the relative humidity of the environment is 30%~40%, the voltage of the high voltage power supply is 18~22 kV, the distance from the needle to the center of the roller is 16~18 cm, and the spinning flow rate is 0.015~0.018 ml / min.

[0041] Step 5: Place the composite nanofiber membrane obtained by electrospinning in a vacuum oven at 60°C for 3 hours to remove excess solvent.

[0042] Example 1:

[0043] Step 1: Weigh 1.7g of cellulose acetate powder (CA) and 0.017g of CuSO4 powder and dissolve them in 8.3g of a mixed solvent of N,N-dimethylacetamide (DMAc) and acetone (Ac) (solvent mass ratio of 1:1).

[0044] Step 2: Stir the solution in (1) at 25°C for 7 hours to completely dissolve it, and obtain a spinning solution with a certain viscosity.

[0045] Step 3: Load the obtained spinning solution into an injection needle tube equipped with a metal needle, then fix the injection needle tube horizontally on the spraying device, connect the positive electrode of the high voltage power supply of the electrospinning instrument to the metal needle, wrap the nonwoven fabric on the roller-shaped negative electrode, align the injection needle tube with the center of the roller, and keep the working chamber of the electrospinning instrument in a sealed state.

[0046] Step 4: Set the working chamber temperature to 27°C during the electrospinning process. o C, the relative humidity of the environment is 35%, the voltage of the high voltage power supply is 20 kV, the distance from the needle to the center of the roller is 18 cm, and the spinning flow rate is 0.017 ml / min.

[0047] Step 5: Place the composite nanofiber membrane obtained by electrospinning in a vacuum oven at 60°C for 3 hours to remove excess solvent.

[0048] Beneficial effects of the present invention: using CA-Cu 2+ The prepared electret filter membrane has a surface potential of 5.50 kV, a filtration efficiency of 96.16% for PM0.3, a filtration resistance of only 27.9 Pa, and a quality factor of ( ). ) reached 0.118 Pa -1 .

[0049] Example 2:

[0050] Step 1: Weigh 1.7g of cellulose acetate powder (CA) and 0.034g of CuSO4 powder and dissolve them in 8.3g of a mixed solvent of N,N-dimethylacetamide (DMAc) and acetone (Ac) (solvent mass ratio of 1:1).

[0051] Step 2: Stir the solution in (1) at 25°C for 7 hours to completely dissolve it, and obtain a spinning solution with a certain viscosity.

[0052] Step 3: Load the obtained spinning solution into an injection needle tube equipped with a metal needle, then fix the injection needle tube horizontally on the spraying device, connect the positive electrode of the high voltage power supply of the electrospinning instrument to the metal needle, wrap the nonwoven fabric on the roller-shaped negative electrode, align the injection needle tube with the center of the roller, and keep the working chamber of the electrospinning instrument in a sealed state.

[0053] Step 4: Set the working chamber temperature to 27°C during the electrospinning process. o C, the relative humidity of the environment is 35%, the voltage of the high voltage power supply is 20 kV, the distance from the needle to the center of the roller is 18 cm, and the spinning flow rate is 0.017 ml / min.

[0054] Step 5: Place the composite nanofiber membrane obtained by electrospinning in a vacuum oven at 60°C for 3 hours to remove excess solvent.

[0055] Beneficial effects of the present invention: using CA-Cu 2+ The prepared electret filter membrane has a surface potential of 6.09 kV, a filtration efficiency of 96.43% for PM0.3, a filtration resistance of only 28.5 Pa, and a quality factor of 0.118 Pa. -1 .

[0056] Example 3:

[0057] Step 1: Weigh 1.7g of cellulose acetate powder (CA) and 0.051g of CuSO4 powder and dissolve them in 8.3g of a mixed solvent of N,N-dimethylacetamide (DMAc) and acetone (Ac) (solvent mass ratio of 1:1).

[0058] Step 2: Stir the solution in (1) at 25°C for 7 hours to completely dissolve it, and obtain a spinning solution with a certain viscosity.

[0059] Step 3: Load the obtained spinning solution into an injection needle tube equipped with a metal needle, then fix the injection needle tube horizontally on the spraying device, connect the positive electrode of the high voltage power supply of the electrospinning instrument to the metal needle, wrap the nonwoven fabric on the roller-shaped negative electrode, align the injection needle tube with the center of the roller, and keep the working chamber of the electrospinning instrument in a sealed state.

[0060] Step 4: Set the working chamber temperature to 27°C during the electrospinning process. o C, the relative humidity of the environment is 35%, the voltage of the high voltage power supply is 20 kV, the distance from the needle to the center of the roller is 18 cm, and the spinning flow rate is 0.017 ml / min.

[0061] Step 5: Place the composite nanofiber membrane obtained by electrospinning in a vacuum oven at 60°C for 3 hours to remove excess solvent.

[0062] Beneficial effects of the present invention: using CA-Cu 2+ The prepared electret filter membrane has a surface potential of 6.27 kV, a filtration efficiency of 99.31% for PM0.3, a filtration resistance of only 40 Pa, and a quality factor of 0.128 Pa. -1 .

[0063] Example 4:

[0064] Step 1: Weigh 1.7g of cellulose acetate powder (CA) and 0.051g of CuSO4 powder and dissolve them in 8.3g of a mixed solvent of N,N-dimethylacetamide (DMAc) and acetone (Ac) (solvent mass ratio of 1:1).

[0065] Step 2: Stir the solution in (1) at 35°C for 7 hours to completely dissolve it, and obtain a spinning solution with a certain viscosity.

[0066] Step 3: Load the obtained spinning solution into an injection needle tube equipped with a metal needle, then fix the injection needle tube horizontally on the spraying device, connect the positive electrode of the high voltage power supply of the electrospinning instrument to the metal needle, wrap the nonwoven fabric on the roller-shaped negative electrode, align the injection needle tube with the center of the roller, and keep the working chamber of the electrospinning instrument in a sealed state.

[0067] Step 4: Set the working chamber temperature to 27°C during the electrospinning process. o C, the relative humidity of the environment is 35%, the voltage of the high voltage power supply is 20 kV, the distance from the needle to the center of the roller is 18 cm, and the spinning flow rate is 0.017 ml / min.

[0068] Step 5: Place the composite nanofiber membrane obtained by electrospinning in a vacuum oven at 60°C for 3 hours to remove excess solvent.

[0069] Beneficial effects of the present invention: using CA-Cu 2+ The prepared electret filter membrane has a surface potential of 7.97 kV, a filtration efficiency of 99.15% for PM0.3, a filtration resistance of only 37.3 Pa, and a quality factor of 0.131 Pa. -1 .

[0070] Example 5:

[0071] Step 1: Weigh 1.7g of cellulose acetate powder (CA) and 0.068g of CuSO4 powder and dissolve them in 8.3g of a mixed solvent of N,N-dimethylacetamide (DMAc) and acetone (Ac) (solvent mass ratio of 1:1).

[0072] Step 2: Stir the solution in (1) at 45°C for 7 hours to completely dissolve it, and obtain a spinning solution with a certain viscosity.

[0073] Step 3: Load the obtained spinning solution into an injection needle tube equipped with a metal needle, then fix the injection needle tube horizontally on the spraying device, connect the positive electrode of the high voltage power supply of the electrospinning instrument to the metal needle, wrap the nonwoven fabric on the roller-shaped negative electrode, align the injection needle tube with the center of the roller, and keep the working chamber of the electrospinning instrument in a sealed state.

[0074] Step 4: Set the working chamber temperature to 28°C during the electrospinning process. o C, the relative humidity of the environment is 35%, the voltage of the high voltage power supply is 20 kV, the distance from the needle to the center of the roller is 18 cm, and the spinning flow rate is 0.017 ml / min.

[0075] Step 5: Place the composite nanofiber membrane obtained by electrospinning in a vacuum oven at 60°C for 3 hours to remove excess solvent.

[0076] Beneficial effects of the present invention: using CA-Cu 2+ The prepared electret filter membrane has a surface potential of 12.52 kV, a filtration efficiency of 93.79% for PM0.3, a filtration resistance of only 30.5 Pa, and a quality factor of 0.092 Pa. -1 .

[0077] Comparative Example 1:

[0078] Step 1: Weigh 1.7g of cellulose acetate powder (CA) and dissolve it in 8.3g of a mixed solvent of N,N-dimethylacetamide (DMAc) and acetone (Ac) (solvent mass ratio of 1:1).

[0079] Step 2: Stir the solution in (1) at 25°C for 7 hours to completely dissolve it, and obtain a spinning solution with a certain viscosity.

[0080] Step 3: Load the obtained spinning solution into an injection needle tube equipped with a metal needle, then fix the injection needle tube horizontally on the spraying device, connect the positive electrode of the high voltage power supply of the electrospinning instrument to the metal needle, wrap the nonwoven fabric on the roller-shaped negative electrode, align the injection needle tube with the center of the roller, and keep the working chamber of the electrospinning instrument in a sealed state.

[0081] Step 4: Set the working chamber temperature to 27°C during the electrospinning process. o C, the relative humidity of the environment is 35%, the voltage of the high voltage power supply is 20 kV, the distance from the needle to the center of the roller is 18 cm, and the spinning flow rate is 0.017 ml / min.

[0082] Step 5: Place the composite nanofiber membrane obtained by electrospinning in a vacuum oven at 60°C for 3 hours to remove excess solvent.

[0083] Beneficial effects of the present invention: using CA-Cu 2+ The prepared electret filter membrane has a surface potential of 1.17 kV, a filtration efficiency of 70.83% for PM0.3, a filtration resistance of 36 Pa, and a quality factor of 0.0342 Pa. -1 .

[0084] Figure 2 , Figure 3 and Figure 5 , Figure 6 Comparative analysis of CA film and CA-Cu using SEM images 2+ The change in fiber diameter of the composite membrane Figure 4 and Figure 7 A comparative analysis of CA film and CA-Cu was conducted using bar charts. 2+ The change in fiber diameter of the composite membrane reveals that the addition of copper sulfate increases the conductivity of the spinning solution, thus reducing the fiber diameter.

[0085] Figure 8 The distribution of C element in the composite membrane is shown. Figure 9 The distribution of O element in the composite membrane is shown. Figure 10 The distribution of Cu in the composite membrane is shown; the Cu elements are uniformly distributed without agglomeration.

[0086] from Figure 11 It can be seen that the surface potential increases with the increase of CuSO4 content. The surface potential is the largest when the CuSO4 content is 0.068g and the reaction temperature is 45℃.

[0087] from Figure 12 It can be seen that the composite membrane exhibits the best filtration performance when the CuSO4 content is 0.051 g and the reaction temperature is 35℃, with a filtration efficiency of 99.15%, a filtration resistance of 37.3 Pa, and a quality factor of 0.131 Pa. -1 This indicates that Cu 2+ Coordination does indeed enhance the electrostatic adsorption of the composite membrane.

Claims

1. A method for producing a high-electrostatic-cellulose acetate-based electret air filter material, characterized by, Comprising the following steps: S1, adding cellulose acetate and CuSO4 powder into N,N-dimethylacetamide and acetone, the mass ratio of N,N-dimethylacetamide and acetone is 1:1, the mass ratio of the total mass of N,N-dimethylacetamide and acetone to the mass of cellulose acetate powder is 83:17, then stirring at 5-45℃ until the cellulose acetate powder and CuSO4 powder are completely dissolved to obtain a mixed solution, the mixed solution is loaded into a syringe needle with a metal needle, the nozzle of the syringe needle is fixed horizontally on a spraying device, the positive electrode of the high-voltage power supply of the electrospinning instrument is connected to the metal needle, the non-woven fabric is wrapped on the drum-shaped negative electrode, the syringe needle is aligned with the center of the negative electrode, the working chamber of the electrospinning instrument is kept sealed, and electrospinning is carried out at a voltage of 18-22 kV, the mass ratio of cellulose acetate and CuSO4 is 1:(0.01-0.04), the distance from the metal needle of the syringe needle to the center of the negative electrode is 16-18 cm, the flow rate is 0.015-0.018 ml / min, and a composite nanofiber membrane is obtained; S2, removing the excess solvent in the composite nanofiber membrane to obtain a high-electrostatic cellulose acetate-based electret air filtration material.

2. The process for preparing a high electrostatic cellulose acetate-based electret air filter material according to claim 1, characterized by, The electrospinning described in S1 was performed at 25-30 o C and 30-40% relative humidity of the environment.

3. The preparation method of the high electrostatic cellulose acetate-based electret air filter material according to claim 1, characterized by, S2, removing the excess solvent in the composite nanofiber membrane by vacuum drying, the vacuum drying is carried out at 60℃ for 3h.

4. A high-electrostatic cellulose acetate-based electret air filtration material prepared by the method of any one of claims 1-3.

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