Low-gram-weight air filtering material and preparation method thereof

Abstract

The invention relates to the technical field of filtering materials, in particular to a low-gram-weight air filtering material and a preparation method thereof. The low-gram-weight air filtering material is developed by combining low-density polypropylene (PP) fibers and ultralow-gram-weight polyamide 6 (PA6) electrostatic spinning nanofibers, and the gram weight of the low-gram-weight air filtering material is reduced by 50% or above compared with that of a traditional melt-blown material; a plasma treatment technology is adopted, so that the binding force of the PP micron fibers and the PA6 nanofibers is improved by 50%, high binding strength is realized, and layering is avoided; corona electret treatment is adopted, so that the electrostatic adsorption stability is enhanced; one-step electrostatic spinning compounding is adopted, multi-layer bonding is not needed, and the production process is simplified.

Description

Technical Field

[0001] This invention relates to the field of filter material technology, and in particular to a low-weight air filter material and its preparation method. Background Technology

[0002] With the increasing demand for air pollution control and health protection, air filtration materials are being used more and more widely in both civilian and industrial fields. Traditional air filtration materials (such as meltblown fabric, glass fiber, or high-efficiency filter paper) usually improve filtration efficiency by increasing the material basis weight (mass per unit area), but high basis weight leads to increased material thickness, reduced air permeability, and increased pressure drop, thereby increasing energy consumption.

[0003] In recent years, electrospun nanofiber technology has attracted much attention because it can produce ultrafine fibers. Through the dual mechanism of small pore size and electrostatic adsorption, it can achieve high-efficiency filtration at low basis weight. However, its mechanical strength is insufficient when used alone, and it needs to be combined with a multi-layer structure.

[0004] In related technologies, the preparation methods of multilayer composite air filter materials mainly include the following categories: Mechanical lamination: Different fiber webs or nonwoven fabrics are directly stacked and bonded together through hot pressing, hot rolling, or needle punching processes. This method is simple, but the interlayer bonding strength is limited and delamination is prone to occur.

[0005] Impregnation or coating lamination: A functional layer is formed on a substrate by impregnating it with a polymer solution or emulsion and drying it into a film. This method is easy to implement, but it significantly reduces air permeability, which is not conducive to high-volume applications.

[0006] Adhesive lamination method: Hot melt adhesive web, sprayed adhesive, or dotted resin is introduced between the layers, followed by hot pressing. Although the bonding strength is strong, it increases the additional weight and cost, and may adversely affect air permeability.

[0007] Electret treatment: After multilayer composite, charges are introduced through corona discharge or electret processes to enhance electrostatic adsorption and improve filtration efficiency. However, this method cannot fundamentally solve the problem of insufficient interlayer bonding and has poor long-term stability.

[0008] In summary, existing multilayer composite air filter materials often suffer from problems such as complex processes, high production costs, insufficient interlayer bonding, and significant performance trade-offs, making it difficult to simultaneously meet the comprehensive requirements of low weight, high filtration performance, and ease of industrial production. Summary of the Invention

[0009] In view of this, the purpose of this invention is to provide a low-weight air filter material and its preparation method. The preparation process of this invention is simple, and the prepared air filter material has low weight, good filtration performance and air permeability, and strong interlayer bonding.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a low-weight air filter material, comprising the following steps: After being opened, PP microfibers are combed into PP thin fiber webs and then subjected to plasma treatment to obtain modified PP thin fiber webs; the basis weight of the PP thin fiber webs is 5~15 g / m. 2 ; PA6 is dissolved in a solvent to obtain a spinning solution; the solvent is a formic acid / chloroform mixed solvent, hexafluoroisopropanol, or a formic acid / acetic acid mixed solvent. Using the modified PP thin fiber web as the receiving substrate, electrospinning is performed using the spinning solution to form a PA6 nanofiber web on the modified PP thin fiber web, resulting in a single-layer composite fiber web. Several layers of the single-layer composite fiber web are stacked and then hot-pressed to obtain a multilayer composite material; the PA6 nanofiber web is spaced out in the multilayer composite material. The multilayer composite material is subjected to corona electret treatment to obtain the low-basis-weight air filter material; the basis weight of the low-basis-weight air filter material is 35~60 g / m³. 2 The low-weight air filter material contains 30-80% PP microfibers by mass, with the remainder being PA6 nanofibers.

[0011] Preferably, the mass ratio of formic acid to chloroform in the formic acid / chloroform mixed solvent is (7:3) to (9:1); the mass ratio of formic acid to acetic acid in the formic acid / acetic acid mixed solvent is (7:3) to (9:1).

[0012] Preferably, the concentration of PA6 in the spinning solution is 8~25 wt%.

[0013] Preferably, the conditions for plasma treatment include: a power of 50~200 W, a treatment time of 0.25~2.0 h, an atmosphere of any one or more of air, oxygen and argon, and a pressure of 10~100 Pa.

[0014] Preferably, the electrospinning conditions include: a spinning voltage of 12~20 kV and a feed rate of 0.2~1.0 mL·h. -1 The receiving distance is 16~20 cm, and the spinning time is 0.5~2.0 h.

[0015] Preferably, the diameter of the PP microfiber is 5~15μm.

[0016] Preferably, the diameter of the PA6 nanofibers in the PA6 nanofiber network is 100~300 nm.

[0017] Preferably, the hot pressing temperature is 90~110℃, the pressure is 0.05~0.1 MPa, and the time is 10~60 s.

[0018] Preferably, the conditions for the corona electret treatment include: electret voltage of 10~40 KV, electret velocity of 6~12 m / min, and electret height of 2~5 cm.

[0019] This invention provides a low-basis-weight air filter material prepared by the method described above, comprising alternating layers of modified PP thin fiber mesh and PA6 nanofiber mesh; the basis weight of the low-basis-weight air filter material is 35~60 g / m³. 2 The filtration efficiency for 0.2 µm particles is ≥98.5%, the pressure drop is ≤110 Pa, and the binding strength is >1.15 N / cm.

[0020] This invention combines low-density polypropylene (PP) fibers and ultra-low basis weight polyamide 6 (PA6) electrospun nanofibers to develop a low basis weight air filter material, reducing the basis weight by more than 50% compared to traditional meltblown materials. Plasma treatment technology is used to increase the bonding strength between PP microfibers and PA6 nanofibers by 50% (compared to simple hot pressing without plasma treatment), achieving high bonding strength and preventing delamination. Corona electret treatment is used to enhance electrostatic adsorption stability. A one-step electrospinning composite process eliminates the need for multi-layer bonding, simplifying the production process. Attached Figure Description

[0021] Figure 1 The image shows the microstructure of the low-weight air filter material prepared in Example 1. Detailed Implementation

[0022] This invention provides a method for preparing a low-weight air filter material, comprising the following steps: After being opened, PP microfibers are combed into PP thin fiber webs and then subjected to plasma treatment to obtain modified PP thin fiber webs; the basis weight of the PP thin fiber webs is 5~15 g / m. 2 ; PA6 is dissolved in a solvent to obtain a spinning solution; the solvent is a formic acid / chloroform mixed solvent, hexafluoroisopropanol, or a formic acid / acetic acid mixed solvent. Using the modified PP thin fiber web as the receiving substrate, electrospinning is performed using the spinning solution to form a PA6 nanofiber web on the modified PP thin fiber web, resulting in a single-layer composite fiber web. Several layers of the single-layer composite fiber web are stacked and then hot-pressed to obtain a multilayer composite material; the PA6 nanofiber web is spaced out in the multilayer composite material. The multilayer composite material is subjected to corona electret treatment to obtain the low-basis-weight air filter material; the basis weight of the low-basis-weight air filter material is 35~60 g / m³. 2 The low-weight air filter material contains 30-80% PP microfibers by mass, with the remainder being PA6 nanofibers.

[0023] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0024] This invention involves combing opened PP microfibers into a PP thin fiber web and then subjecting it to plasma treatment to obtain a modified PP thin fiber web.

[0025] In this invention, the diameter of the PP microfibers is preferably 5-15 μm. In specific embodiments of this invention, PP short fibers produced by Zhangjiagang Hongte Chemical Fiber Co., Ltd. are used. This invention does not have special requirements for the opening treatment; well-known opening treatment steps in the art are sufficient. Preferably, this invention involves carding the PP microfibers into a PP thin fiber web in a carding machine. In this invention, the basis weight of the PP thin fiber web is 5-15 g / m². 2 In specific embodiments, the concentration can be 5, 7, 10, 12, or 15 g / m³. 2 .

[0026] In this invention, the preferred conditions for plasma treatment include: a power of 50-200 W, a treatment time of 0.25-2.0 h, an atmosphere of any one or more of air, oxygen, and argon, and a pressure of 10-100 Pa. In embodiments of this invention, the power of the plasma treatment can be 50, 80, 100, 120, 150, 180, or 200 W; the treatment time can be 0.25, 0.5, 1.0, 1.5, or 2.0 h; and the pressure can be 10, 20, 30, 50, 60, 80, or 100 Pa. In this invention, the plasma treatment is preferably performed in a plasma surface treatment apparatus. This invention improves the bonding strength between PP microfibers and PA6 nanofibers through plasma treatment. Specifically, high-energy particles bombard the surface of PP fibers, which on the one hand micro-etches the fiber surface, increasing its specific surface area and surface roughness, and providing more physical attachment sites for PA6 nanofibers; on the other hand, it can introduce polar groups such as hydroxyl and carboxyl groups on the surface of PP fibers, improving the surface inertness of PP material itself. Since PA6 nanofibers have a certain degree of polarity, chemical and physical interactions such as hydrogen bonds and van der Waals forces can be formed between the polar groups of the two, which greatly enhances the interfacial bonding ability and ultimately improves the bonding force between PP microfibers and PA6 nanofibers.

[0027] In this invention, PA6 is dissolved in a solvent to obtain a spinning solution.

[0028] In this invention, the solvent is a formic acid / chloroform mixed solvent, hexafluoroisopropanol, or a formic acid / acetic acid mixed solvent; the mass ratio of formic acid to chloroform in the formic acid / chloroform mixed solvent is (7:3) to (9:1), and in specific embodiments it can be 7:3, 8:2, or 9:1; the mass ratio of formic acid to acetic acid in the formic acid / acetic acid mixed solvent is (7:3) to (9:1), and in specific embodiments it can be 7:3, 8:2, or 9:1. The use of the above solvents in this invention can ensure the fiber formation quality of PA6 nanofibers and guarantee good filtration and air permeability.

[0029] This invention does not have special requirements for the process of dissolving PA6 in the solvent, as long as PA6 can be completely dissolved. In the embodiments of this invention, PA6 is placed in the solvent and stirred at 50°C until a uniform and transparent solution is formed. In this invention, the concentration of PA6 in the spinning solution is preferably 8~25 wt%, and in specific embodiments it can be 8, 10, 13, 16, 18, 20 or 25 wt%.

[0030] After obtaining the modified PP thin fiber web and the spinning solution, the present invention uses the modified PP thin fiber web as the receiving substrate and performs electrospinning using the spinning solution to form a PA6 nanofiber web on the modified PP thin fiber web, thereby obtaining a single-layer composite fiber web.

[0031] In this invention, the preferred conditions for electrospinning include: a spinning voltage of 12~20 kV and a feed rate of 0.2~1.0 mL·h. -1 The receiving distance is 16-20 cm, and the spinning time is 0.5-2.0 h. In embodiments of the present invention, the spinning voltage can be 12, 14, 16, 18, or 20 kV; the feeding rate can be 0.2, 0.4, 0.5, 0.8, or 1.0 mL·h. -1 The receiving distance can be 16, 17, 18, 19 or 20 cm; the spinning time can be 0.5, 1.0, 1.5 or 2.0 h.

[0032] In this invention, the diameter of the PA6 nanofibers in the PA6 nanofiber network is preferably 100~300 nm, more preferably 120~200 nm.

[0033] This invention simplifies the production process by electrospinning PP microfibers and PA6 nanofibers, eliminating the need for multi-layer bonding. Using microfibers as the substrate skeleton, this invention can form a low-basis-weight thin fiber web through combing, providing good mechanical strength and structural support for the material. The microfiber pore size also ensures smooth airflow, preventing excessive degradation of the material's permeability. Nanofibers are directly composited onto the surface of the modified PP thin fiber web using electrospinning technology. Their ultra-fine size results in a high specific surface area, allowing for the capture of ultrafine particles through a combination of small-pore interception and electrostatic adsorption, achieving highly efficient filtration.

[0034] After obtaining a single-layer composite fiber web, the present invention stacks several layers of the single-layer composite fiber web and then hot-presses them to obtain a multi-layer composite material.

[0035] This invention does not impose a specific limitation on the number of layers in the single-layer composite fiber web, as long as it meets the weight requirement of low-weight air filter materials. In an embodiment of this invention, two layers of single-layer composite fiber webs are stacked and hot-pressed. In this invention, the stacking is performed in the order of the PA6 nanofiber web spacing.

[0036] In this invention, the hot-pressing temperature is preferably 90~110℃, and in specific embodiments it can be 90, 95, 100, 105 or 110℃; the hot-pressing pressure is preferably 0.05~0.1 MPa; the hot-pressing time is preferably 10~60s, and in specific embodiments it can be 10, 20, 30, 40, 50 or 60s. This invention achieves the bonding of composite fiber webs through hot pressing.

[0037] After obtaining the multilayer composite material, the present invention performs corona electret treatment on the multilayer composite material to obtain the low basis weight air filter material.

[0038] In this invention, the preferred conditions for the corona electret treatment include: an electret voltage of 10-40 kV, an electret velocity of 6-12 m / min, and an electret height of 2-5 cm. In specific embodiments, the electret voltage can be 10, 20, 30, or 40 kV, the electret velocity can be 6, 8, 10, or 12 m / min, and the electret height can be 2, 3, 4, or 5 cm. This invention enhances the stability of electrostatic adsorption through corona electret treatment.

[0039] In this invention, the basis weight of the low-weight air filter material is 35~60 g / m³. 2 In specific embodiments, the concentration can be 35, 40, 45, 50, 55, or 60 g / m³. 2The mass percentage of PP microfiber in the low-weight air filter material is 30-80%, and in specific embodiments it can be 30, 40, 50, 55, 60, 70 or 80%, with the remainder being PA6 nanofiber.

[0040] In this invention, the PP thin fiber web undergoes plasma treatment before lamination, significantly enhancing its surface activity and improving the bonding force between PP microfibers and PA6 nanofibers, thus fundamentally improving the interlayer bonding. Secondly, the single-layer composite fiber web itself is an integrated structure formed by direct lamination of PP microfibers and PA6 nanofibers through a one-step electrospinning process. The hot pressing after multi-layer lamination is not a simple mechanical lamination of fiber webs in traditional technology, but a synergistic bonding of "modified PP fibers + PA6 nanofibers," resulting in stronger overall interlayer bonding. Finally, the hot pressing parameters are precisely matched to effectively achieve interlayer bonding of the multi-layer composite fiber web without damaging the original pore structure and properties of the fibers, ultimately making the bonding strength of the material far exceed that of existing filter materials.

[0041] This invention provides a low-basis-weight air filter material prepared by the method described above, comprising alternating layers of modified PP thin fiber mesh and PA6 nanofiber mesh; the basis weight of the low-basis-weight air filter material is 35~60 g / m³. 2 The filtration efficiency for 0.2 µm particles is ≥98.5%, the pressure drop is ≤110 Pa, and the binding strength is >1.15 N / cm.

[0042] This invention uses micron-sized PP fibers as the substrate skeleton, which can form a low-weight thin fiber web through combing, providing good mechanical strength and structural support for the material. The micron-sized pores also ensure smooth airflow and prevent excessive reduction in the material's air permeability. Nano-sized PA6 fibers are directly composited onto the surface of the modified PP thin fiber web using electrospinning technology. Their ultra-fine size results in a high specific surface area, which can capture ultrafine particles through a combination of small-pore interception and electrostatic adsorption, achieving high-efficiency filtration.

[0043] The following detailed description of the low-weight air filter material and its preparation method provided by the present invention, with reference to specific embodiments, should not be construed as limiting the scope of protection of the present invention.

[0044] The raw materials used in the following examples and comparative examples are as follows: PP short fiber, Zhangjiagang Hongte Chemical Fiber Co., Ltd., diameter 5~15μm; formic acid, analytical grade, Sinopharm Chemical Reagent Co., Ltd.; chloroform, analytical grade, Sinopharm Chemical Reagent Co., Ltd.; acetic acid, analytical grade, Sinopharm Chemical Reagent Co., Ltd.; hexafluoroisopropanol, purity ≥99.5%, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0045] Example 1 Preparation of PP thin fiber web: Opened PP fibers are fed into a carding machine and carded to a density of 5 g / m. 2 Thin fiber mesh was placed in a plasma surface treatment instrument for further surface modification. The power was set to medium (100 W), the gas was air with a flow rate of 100 mL / min, the gas pressure was 50 Pa, and the treatment time was 0.5 h. The modified PP thin fiber mesh obtained after treatment was used as the receiving substrate for electrospun nanofibers.

[0046] Preparation of PA6 electrospinning solution: Take 1.17 g of PA6 powder and place it in a mixture of 9.39 g formic acid and 4.03 g chloroform (the mass ratio of formic acid to chloroform is 7:3). Stir at 50℃ for 2.5 h until a uniform and transparent viscous solution is formed, which is used as the spinning solution. The concentration of PA6 in the spinning solution is 8 wt%.

[0047] Preparation of low-gram-weight composite filter material: Modified PP thin fiber mesh was placed on the roller of an electrospinning device, and the spinning solution was injected into a syringe to prepare a single-layer composite fiber mesh (1 layer of PA6 nanofiber mesh + 1 layer of PP microfiber mesh). The spinning voltage was 18 kV and the feed rate was 0.5 mL·h. -1 The distance between the syringe needle tip and the collector was 20 cm, and the spinning time was 0.5 h. Two single-layer composite fiber webs were stacked to form a multi-layer composite fiber web, hot-pressed at 105℃ and 0.1 MPa for 30 s, followed by room-temperature corona electret treatment with an electret voltage of 20 kV, an electret velocity of 10 m / min, and an electret height of 5 cm, resulting in a low-basis-weight air filter material with a basis weight of 39.2 g / m³. 2 The composition includes 30 wt% PP fiber and 70 wt% PA6 nanofiber layer. The microstructure of the resulting low-weight air filter material is as follows: Figure 1 As shown. Figure 1 The composite structure of micron-sized PP fibers and nano-sized PA6 electrospun fibers is clearly visible. The PP micron-sized fibers form a mesh-like framework as the substrate, while the PA6 nanofibers are uniformly covered on its surface and in the pores, without any gaps or delamination. The macroscopic pores constructed by the PP micron-sized fibers are retained, while the nanofiber layer forms a large number of microscopic pores. The pore structure is interconnected and uniformly distributed, providing a dual channel for air circulation and particle capture.

[0048] Example 2 The difference from Example 1 is that the mass ratio of formic acid to chloroform in the formic acid / chloroform mixed solvent is 8:2; the concentration of PA6 in the spinning solution is 16 wt%, and other parameters and preparation methods are the same as in Example 1. The final low-weight air filter material contains 55 wt% PP fiber and 45 wt% PA6 nanofiber layer.

[0049] Example 3 The difference from Example 1 is that the mass ratio of formic acid to chloroform in the formic acid / chloroform mixed solvent is 9:1; the concentration of PA6 in the spinning solution is 25 wt%, and other parameters and preparation methods are the same as in Example 1. The final low-weight air filter material consists of 80 wt% PP fiber and 20 wt% PA6 nanofiber layer.

[0050] Examples 1-3 tested the basis weight, filtration efficiency and pressure drop for different 0.2 μm particles, and bonding strength of the low-basis-weight air filter materials. The filtration efficiency test method was performed according to GB / T 12625.1-2001 "Air Filters - Part 1: Test Methods for Filtration Efficiency". For the 0.2 µm particle test, the relevant test methods in this standard were used, employing a particle counter and atomization testing methods to evaluate the filtration efficiency. The pressure drop test was performed according to GB / T 14295-2008 "Air Filter Performance Test Methods", using a pressure drop gauge or differential pressure gauge to measure the pressure difference across the filter. The bonding strength test was performed according to ASTM D1876 (T-Peel), with a loading rate of 254 mm / min; the sample width was 25 mm, and the effective bond length was ≥100 mm. Conditions: 23℃ / 50%RH conditioning for 24 h. The results are listed in Table 1.

[0051] Table 1 Performance data of Examples 1-3

[0052] Comparative Example 1 To compare the effect of the "plasma treatment" step on interlayer bonding, Comparative Example 1 was set up. The plasma treatment step of Example 1 was removed, while other parameters and preparation methods were the same as in Example 1.

[0053] Comparative Example 2 To compare the effect of the "mixed solvent" on fiber morphology and bonding, Comparative Example 2 was set up. Chloroform was removed from the formic acid / chloroform mixed solvent in Example 1, while other parameters and preparation methods were the same as in Example 1.

[0054] The basis weight and filtration efficiency and pressure drop of the low basis weight air filter materials in Examples 1-2 were tested and compared. The results are listed in Table 2.

[0055] Table 2 Performance data for Comparative Examples 1-2

[0056] Compared to Example 1, Comparative Example 1 showed a significant decrease in interlayer bonding strength and filtration efficiency after plasma treatment removal, indicating that plasma treatment is crucial for interfacial bonding. In Comparative Example 2, although bonding strength was somewhat guaranteed after chloroform removal due to plasma retention, the deterioration of fiber morphology led to a suboptimal pressure drop, demonstrating the key role of the formic acid / chloroform mixed solvent in fiber quality and overall filtration performance. In conclusion, the synergistic effect of plasma treatment combined with the formic acid / chloroform mixed solvent is essential for achieving high efficiency, low pressure drop, and high bonding strength.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-grammage air filter material, characterized in that, Includes the following steps: After the opened PP microfibers are combed into PP thin fiber webs, they are subjected to plasma treatment to obtain modified PP thin fiber webs. The basis weight of the PP thin fiber web is 5~15 g / m. 2 ; PA6 is dissolved in a solvent to obtain a spinning solution; the solvent is a formic acid / chloroform mixed solvent, hexafluoroisopropanol, or a formic acid / acetic acid mixed solvent. Using the modified PP thin fiber web as the receiving substrate, electrospinning is performed using the spinning solution to form a PA6 nanofiber web on the modified PP thin fiber web, resulting in a single-layer composite fiber web. Several layers of the single-layer composite fiber web are stacked and then hot-pressed to obtain a multilayer composite material; the PA6 nanofiber web is spaced out in the multilayer composite material. The multilayer composite material is subjected to corona electret treatment to obtain the low-basis-weight air filter material; the basis weight of the low-basis-weight air filter material is 35~60 g / m³. 2 The low-weight air filter material contains 30-80% PP microfibers by mass, with the remainder being PA6 nanofibers.

2. The preparation method according to claim 1, characterized in that, The mass ratio of formic acid to chloroform in the formic acid / chloroform mixed solvent is (7:3) to (9:1); the mass ratio of formic acid to acetic acid in the formic acid / acetic acid mixed solvent is (7:3) to (9:1).

3. The preparation method according to claim 1 or 2, characterized in that, The concentration of PA6 in the spinning solution is 8~25wt%.

4. The preparation method according to claim 1, characterized in that, The conditions for plasma treatment include: power of 50~200 W, treatment time of 0.25~2.0 h, atmosphere of any one or more of air, oxygen and argon, and pressure of 10~100 Pa.

5. The preparation method according to claim 1, characterized in that, The electrospinning conditions include: a spinning voltage of 12~20 kV and a feed rate of 0.2~1.0 mL·h. -1 The receiving distance is 16~20 cm, and the spinning time is 0.5~2.0 h.

6. The preparation method according to claim 1, characterized in that, The diameter of the PP microfiber is 5~15μm.

7. The preparation method according to claim 1, characterized in that, The diameter of the PA6 nanofibers in the PA6 nanofiber network is 100~300 nm.

8. The preparation method according to claim 1, characterized in that, The hot pressing temperature is 90~110℃, the pressure is 0.05~0.1 MPa, and the time is 10~60 s.

9. The preparation method according to claim 1, characterized in that, The conditions for the corona electret treatment include: electret voltage of 10~40 KV, electret velocity of 6~12 m / min, and electret height of 2~5 cm.

10. The low-basis-weight air filter material prepared by the preparation method according to any one of claims 1 to 9, comprising alternating layers of modified PP thin fiber mesh and PA6 nanofiber mesh; the basis weight of the low-basis-weight air filter material is 35-60 g / m³. 2 The filtration efficiency for 0.2 µm particles is ≥98.5%, the pressure drop is ≤110 Pa, and the binding strength is >1.15 N / cm.

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