Nano non-woven fabric with high air permeability and preparation method thereof

Abstract

The invention discloses a high-air-permeability nano non-woven fabric and a preparation method thereof, and relates to the technical field of nano non-woven fabrics, the high-air-permeability nano non-woven fabric comprises nano cloth, the nano cloth comprises three-dimensional meshes, nano fibers are interwoven in a three-dimensional space to form a porous structure similar to sponge, and the pore diameter between the fibers is 5-10 microns; according to the nano non-woven fabric, a three-dimensional mesh structure is formed through a melt spinning netting method or an electrostatic spinning method, pores of the three-dimensional mesh structure create a large number of circulation channels for air, gas molecules can be rapidly diffused and exchanged, the air permeability of the nano non-woven fabric is remarkably improved, more comfortable experience is brought to a user, stuffiness and discomfort are reduced, and the nano non-woven fabric is suitable for being used in a large scale. No matter in the field of sportswear, a sportsman can keep the body dry and comfortable during strenuous exercise, or in the application of a protective mask worn for a long time, the breathing burden of a user is relieved, and the performance is excellent.

Description

Technical Field

[0001] The invention relates to the technical field of nano nonwoven fabrics, in particular to a high-air-permeability nano nonwoven fabric and a preparation method thereof. Background Art

[0002] With the rapid development of science and technology and the continuous improvement of people's living standards, the demand for high-performance materials is growing. Non-woven fabrics, as a widely used material, play an important role in many fields.

[0003] However, traditional nonwoven fabrics have gradually exposed some limitations in practical applications.

[0004] In the field of medical protection, products such as masks and protective clothing have extremely high requirements for the filtering and breathability properties of materials.

[0005] Traditional non-woven fabrics often find it difficult to effectively filter harmful substances such as bacteria, viruses, and droplets while ensuring good breathability.

[0006] This makes medical staff and users prone to discomfort symptoms such as stuffiness and difficulty breathing when wearing the device for a long time, which not only affects work efficiency and user experience, but may even reduce the protective effect due to poor breathing and increase the risk of infection.

[0007] In the field of sportswear and outdoor equipment, people sweat a lot when exercising or doing outdoor activities, so the clothing materials need to have excellent breathability to discharge water vapor in time and keep the body dry and comfortable, while also having certain windproof, waterproof and protective functions.

[0008] The air permeability of traditional non-woven fabrics is limited and cannot meet the needs of high-intensity exercise or complex outdoor environments. It is easy for the clothing to become damp and stick to the body, affecting athletic performance and body comfort. It is also difficult to achieve an ideal balance between waterproof and protective functions.

[0009] In view of this, this application is hereby filed. Summary of the invention

[0010] The object of the present invention is to provide a high air permeability nano nonwoven fabric and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0011] In order to solve the above technical problems, the present invention provides a high-permeability nano non-woven fabric, including a nanocloth, wherein the nanocloth includes: a three-dimensional mesh, in which nanofibers are interwoven in a three-dimensional space to form a porous structure similar to a sponge, and the pore diameter between the fibers is 5-10 microns; gradient pores, in which the pores gradually become larger or smaller from one side of the nanocloth to the other side, wherein the outer layer pore diameter is 0.1-0.3 microns, and the inner layer pore diameter gradually increases from 0.3 microns to 1-2 microns.

[0012] Furthermore, the three-dimensional mesh is prepared by a melt spinning method, which includes: heating the polymer raw material to a molten state, and spraying the molten polymer into nano-scale fibers using a spinning nozzle by controlling parameters such as spinning speed, temperature and pressure; interweaving the nanofibers with each other to form a fiber web with a certain thickness and density by means of air flow or mechanical force; heat treating the fiber web, and controlling the temperature and time of the heat treatment so that the fibers are firmly bonded and the structure is stable, wherein the parameters such as the spinning speed, temperature and pressure are adjusted according to the target pore size and fiber diameter. When smaller diameter fibers are required to form smaller pores, the spinning pressure can be appropriately increased, the spinning temperature can be reduced, and the spinning speed can be accelerated.

[0013] Furthermore, the three-dimensional mesh structure is prepared by an electrospinning method, which includes: dissolving a polymer in an appropriate solvent, adding an appropriate amount of additives and stirring evenly to form a spinning solution with a certain concentration and viscosity; loading the spinning solution into a syringe with a nozzle or a spinning device, applying a high-voltage electrostatic field, and adjusting parameters such as the electric field strength, the solution flow rate, and the distance between the nozzle and the collecting device, so that the solution forms nanoscale fibers under the action of the electric field force and is sprayed onto the collecting device to interweave with each other to form a nano non-woven fabric, wherein increasing the electric field strength can make the fibers thinner and thus affect the pore size.

[0014] Furthermore, the gradient pores are constructed by adding a porogen, which includes adding an appropriate amount of a porogen when preparing the nano non-woven fabric, removing the porogen by high-temperature treatment or the like after the non-woven fabric is formed to leave the pores, and forming a gradient pore structure by controlling the amount of porogen added, the particle size distribution, and the distribution in the material, that is, adding more porogen with larger particle size on one side of the non-woven fabric and adding less porogen with smaller particle size on the other side to obtain a gradient pore structure in which the pores gradually change from one side to the other.

[0015] Furthermore, the gradient pores are constructed using a multi-layer composite structure method, which includes compositely bonding nano non-woven fabrics with different porosities or pore sizes in multiple layers so that the pores between the layers cooperate with each other to form a gradient pore. Specifically, the nano non-woven fabric with smaller pores is used as the outer layer, and the nano non-woven fabric with larger pores is used as the inner layer, and a transition layer is set in the middle to gradually increase the pores from the outside to the inside.

[0016] Furthermore, it also includes a multi-layer composite micro-perforated structure, which is composed of multiple layers of nano cloth, and each layer is provided with tiny perforations. The multi-layer nano non-woven fabric includes an outer layer of waterproof cloth, a middle layer of filter cloth and an inner layer of breathable cloth.

[0017] Furthermore, the physical puncture method in its multi-layer composite micro-perforated structure includes using a special microneedle array or laser micro-machining equipment to puncture each layer of nano non-woven fabric according to a predetermined perforation pattern and density to form tiny perforations, wherein the perforation diameter is controlled at 10-50 microns, and the perforation spacing is adjusted between 0.5-2 mm according to the air permeability and strength requirements of the material.

[0018] Furthermore, the chemical etching method in its multi-layer composite micro-perforated structure includes selecting a suitable etchant, immersing the multi-layer nano non-woven fabric in the etchant for a certain period of time, and partially dissolving the fiber surface to form tiny perforations by controlling parameters such as the etchant concentration, temperature and immersion time. After etching, the non-woven fabric is fully cleaned and dried to remove residual etchant.

[0019] A preparation method, applied to any of the above-mentioned high-permeability nano nonwoven fabrics, specifically comprising the following steps: S1. Raw material preparation: Select appropriate polymer raw materials, such as polypropylene, polyester, etc., and perform pretreatment such as drying and screening to ensure the purity and particle size uniformity of the raw materials; S2, three-dimensional mesh: formed by melt spinning or electrostatic spinning; S3, gradient pores: constructed by adding porogens or multi-layer composite structure; S4. Preparation of multi-layer composite micro-perforated structure: prepared by physical puncture method or chemical etching method; S5. Post-processing and performance optimization: Post-process the prepared high air permeability nano non-woven fabric, such as surface coating to improve water vapor permeability or antibacterial properties.

[0020] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, the three-dimensional mesh structure formed by melt spinning or electrostatic spinning has pores that create a large number of circulation channels for air, allowing gas molecules to diffuse and exchange quickly, significantly improving the air permeability of the nano non-woven fabric, bringing a more comfortable experience to users, and reducing the feeling of stuffiness and discomfort. Whether in the field of sportswear, it allows athletes to keep their bodies dry and comfortable during strenuous exercise, or in the application of protective masks worn for a long time, it reduces the user's breathing burden, and performs well.

[0021] In the present invention, through the special gradient pore design, the air flow path is further optimized, the air flow blockage caused by pore mutation is avoided, and the air permeability resistance is reduced, which has obvious advantages in two-way ventilation scenarios such as exhalation and inhalation of masks and air exchange inside and outside clothing.

[0022] In the present invention, the tiny perforations in the multi-layer composite micro-perforated structure provide a direct and fast channel for air and water vapor, which cooperate with the three-dimensional mesh and gradient pore structure to form an all-round breathable network, so that the nano non-woven fabric can meet the application fields with extremely high requirements for breathability, such as high-performance sportswear and protective masks worn for a long time, ensuring that users can maintain good breathing experience and comfort in various complex environments and usage conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the cross-sectional structure of a nano nonwoven fabric with high air permeability; Figure 2 for Figure 1 The enlarged view of point A in the middle; Figure 3 A schematic diagram of the microstructure of a high air permeability nano nonwoven fabric; Figure 4 The present invention is a flow chart of a method for preparing a high air permeability nano nonwoven fabric.

[0024] In the figure: 1. Nanofabric; 101. Waterproof cloth; 102. Filter cloth; 103. Breathable cloth; 2. Three-dimensional mesh; 3. Gradient pores. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0026] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0027] See also Figure 1-4 , the present invention provides a technical solution: A high-air-permeability nano nonwoven, comprising a nano cloth 1, wherein the nano cloth 1 comprises: Three-dimensional mesh 2, nanofibers interweave in three-dimensional space to form a sponge-like porous structure, with the pore diameter between the fibers being 5-10 microns; The rich porous network formed by the three-dimensional mesh 2, whether prepared by melt spinning or electrospinning, has a pore diameter of 5-10 microns, which provides sufficient circulation space for air, allowing gas molecules to diffuse and exchange quickly, significantly improving the air permeability of the nano non-woven fabric, and can effectively solve the problem of poor air permeability of traditional non-woven fabrics due to their dense structure, allowing users to feel more comfortable when wearing or wearing products containing this material, reducing the feeling of stuffiness and discomfort.

[0028] Although the three-dimensional mesh 2 has high air permeability, by reasonably adjusting the parameters such as fiber thickness and interweaving density, it can effectively intercept common allergens and pollutants such as dust and pollen at the nanoscale.

[0029] The tiny gaps between the nanofibers can form a physical barrier to block the passage of tiny particles, ensuring that the device can filter out harmful substances in the air while ensuring breathability, thus protecting the health and safety of users.

[0030] The gradient pores 3 gradually become larger or smaller from one side of the nanocloth 1 to the other side, wherein the outer pore diameter is 0.1-0.3 microns, and the inner pore diameter gradually increases from 0.3 microns to 1-2 microns.

[0031] Gradient pore 3 further optimizes the air flow path and reduces air permeability resistance through a special pore gradient design.

[0032] When air passes through non-woven fabrics, it can flow more smoothly according to the gradient changes of the pores, avoiding airflow blockage caused by sudden changes in the pores, and further enhancing the overall breathability. This is especially true in application scenarios that require two-way breathability, such as exhalation and inhalation of masks, and air exchange inside and outside clothing.

[0033] In the gradient pores 3, the small pores of 0.1-0.3 microns in the outer layer can first intercept and filter larger droplets, dust and other particles, playing a preliminary protective role.

[0034] As the air flows to the inner layer with gradually larger pores, the 0.3-1-2 micron pores in the inner layer can not only ensure the smooth discharge of exhaled gas, but also further capture and filter some smaller particles, realizing multi-level fine filtration, greatly improving the filtration efficiency and protective effect, and is particularly suitable for medical protective products such as masks and other products that have strict requirements on filtration performance.

[0035] It also includes a multi-layer composite micro-perforated structure, which is composed of multiple layers of nano cloth 1, with tiny perforations between each layer. The multi-layer nano non-woven fabric includes an outer waterproof cloth 101, a middle layer filter cloth 102 and an inner layer breathable cloth 103.

[0036] The tiny perforations in the multi-layer composite micro-perforated structure provide a direct and fast channel for air and water vapor, accelerating the transmission of gas between multi-layer materials.

[0037] Whether it is the perforations formed by physical puncture or chemical etching, they effectively supplement the breathability pathway without affecting the overall structural integrity of the material, and cooperate with the three-dimensional mesh 2 and the gradient pores 3 to comprehensively improve the breathability of the nano non-woven fabric, enabling it to meet the application fields with extremely high requirements for breathability, such as high-performance sportswear and protective masks worn for a long time.

[0038] The middle layer filter cloth 102 in the multi-layer composite micro-perforated structure plays a core filtering function in the multi-layer composite system.

[0039] Its own fiber composition and pore structure can effectively filter impurities in the air and work together with the outer waterproof cloth 101 and the inner breathable cloth 103.

[0040] The outer waterproof fabric 101 can prevent the penetration of impurities carried by external liquids, while the inner breathable fabric 103 helps to maintain the comfort of the internal environment and promote the discharge of water vapor. The functions of each layer cooperate with each other, so that the entire multi-layer composite structure has high air permeability and reliable filtering performance at the same time, and can cope with complex usage environments and filtering needs.

[0041] The outer waterproof fabric 101 in the multi-layer composite micro-perforated structure gives the material waterproof properties, allowing it to be used in outdoor clothing and other products that need to resist rain; the inner breathable fabric 103 focuses on water vapor dissipation and comfort, meeting the physiological needs of the human body during exercise or long-term use; the middle layer filter fabric 102 ensures the filtration of air impurities and is suitable for protective products.

[0042] This multifunctional integrated feature enables the nano nonwoven fabric to adapt to a variety of different application scenarios, from medical protection to sports and leisure, from industrial filtration to daily necessities, and has broad market application potential.

[0043] The personalized needs of different user groups and specific application environments can be met by adjusting the parameters and material composition of each structural layer, such as changing the fiber material of the three-dimensional mesh 2, the type of porogen of the gradient pore 3, or the performance characteristics of each layer of non-woven fabric in the multi-layer composite micro-perforated structure.

[0044] For example, for users who are severely allergic to pollen, the filtration accuracy of the outer layer of the gradient pores 3 can be further optimized; for people working in extremely humid environments, the waterproof performance of the outer waterproof cloth 101 and the moisture resistance of the middle layer filter cloth 102 can be enhanced, etc., which reflects the good adaptability and customizability of the material.

[0045] Furthermore, the three-dimensional mesh 2 is prepared by a melt spinning method, which comprises: The polymer raw material is heated to a molten state, and the molten polymer is sprayed into nano-scale fibers using a spinning nozzle by controlling parameters such as spinning speed, temperature and pressure; The nanofibers are interwoven with each other by air flow or mechanical force to form a fiber web with a certain thickness and density; The fiber web is heat-treated, and the temperature and time of the heat treatment are controlled to ensure that the fibers are firmly bonded and the structure is stable. Parameters such as spinning speed, temperature and pressure are adjusted according to the target pore size and fiber diameter. When smaller diameter fibers are required to form smaller pores, the spinning pressure can be appropriately increased, the spinning temperature can be lowered and the spinning speed can be accelerated.

[0046] Melt spinning web forming method: First, the polymer raw material is heated to a molten state, and by precisely controlling key parameters such as spinning speed, temperature and pressure, the molten polymer is extruded from the spinning nozzle to form nano-scale fibers.

[0047] For example, increasing the spinning pressure can increase the extrusion rate and stretching force of the polymer melt, making the fibers thinner; lowering the spinning temperature can increase the melt viscosity, which also helps to thin the fibers; and increasing the spinning speed gives the fibers greater stretching force, making their diameter smaller.

[0048] Subsequently, these nanofibers are interwoven into a network in three-dimensional space with the help of air flow or mechanical force, and heat treatment is performed to make the bonds between the fibers tight and stable.

[0049] This three-dimensional interwoven structure forms a rich sponge-like porous network with pore diameters of 5-10 microns, providing a large number of circulation channels for air and achieving high air permeability.

[0050] Furthermore, the three-dimensional mesh 2 structure is prepared by an electrospinning method, which comprises: The polymer is dissolved in a suitable solvent, and a suitable amount of additives is added and stirred evenly to prepare a spinning solution with a certain concentration and viscosity; The spinning solution is loaded into a syringe or spinning device with a nozzle, and a high-voltage electrostatic field is applied. By adjusting parameters such as the electric field strength, solution flow rate, and the distance between the nozzle and the collecting device, the solution is formed into nano-scale fibers under the action of the electric field force and sprayed onto the collecting device to interweave and form a nano non-woven fabric. Increasing the electric field strength can make the fibers thinner and thus affect the pore size.

[0051] The spinning solution is prepared by dissolving the polymer in a suitable solvent and adding additives.

[0052] Under the action of high-voltage electrostatic field, the solution overcomes the surface tension due to the electric field force to form nano-scale fibers that are sprayed onto the collecting device and interwoven into a web.

[0053] The electric field strength is a key factor, and its magnitude directly affects the degree of fiber stretching and thinning.

[0054] A stronger electric field will cause the solution jet to be subjected to greater stretching force, thereby forming finer fibers, which in turn changes the pore size and constructs a three-dimensional mesh 2. Air can freely shuttle between the pores of the interwoven fibers, ensuring breathability.

[0055] Furthermore, the gradient pores 3 are constructed by adding a porogen, which includes adding an appropriate amount of a porogen when preparing the nano non-woven fabric, removing the porogen by high-temperature treatment or the like after the non-woven fabric is formed to leave the pores, and forming the gradient pores 3 by controlling the amount of the porogen added, the particle size distribution, and the distribution in the material, that is, adding more porogens with larger particle sizes on one side of the non-woven fabric and adding less porogens with smaller particle sizes on the other side to obtain a gradient pore 3 structure in which the pores gradually change from one side to the other.

[0056] In the process of preparing nano nonwoven fabrics, porogens of different amounts and particle sizes are added to different parts of the material according to the design.

[0057] The porogen is evenly dispersed in the polymer system. After the non-woven fabric is formed, the porogen is removed by high-temperature treatment and other means, and pores are formed in the space originally occupied by the porogen.

[0058] By adding more porogen with larger particle size on one side of the non-woven fabric and less porogen with smaller particle size on the other side, a gradient structure with gradually changing pores from one side to the other is naturally formed.

[0059] When air enters from the side with small pores, the small pores first perform preliminary filtration on the tiny particles in the air. As the air flows to the side with large pores, the resistance gradually decreases, achieving coordinated optimization of ventilation and filtration.

[0060] Furthermore, the gradient pore 3 is constructed using a multi-layer composite structure method, which includes compositely combining nano non-woven fabrics with different porosities or pore sizes in multiple layers so that the pores between the layers cooperate with each other to form the gradient pore 3. Specifically, the nano non-woven fabric with smaller pores is used as the outer layer, and the nano non-woven fabric with larger pores is used as the inner layer, and a transition layer is set in the middle to gradually increase the pores from the outside to the inside.

[0061] The nano nonwoven fabrics with different porosities or pore sizes are multi-layered.

[0062] The nano nonwoven fabric with smaller pores is used as the outer layer, the nano nonwoven fabric with larger pores is used as the inner layer, and a transition layer is provided to gradually increase the pore size.

[0063] This structural design ensures that when air passes through the non-woven fabric, it is first filtered through the finer pores in the outer layer, then gradually adapts to the larger pores in the middle transition layer, and finally is discharged more smoothly from the large pores in the inner layer, effectively guiding the flow path of air molecules, improving air permeability efficiency and ensuring filtering effect.

[0064] Furthermore, the physical puncture method in its multi-layer composite micro-perforated structure includes using a special microneedle array or laser micro-machining equipment to puncture each layer of nano non-woven fabric according to a predetermined perforation pattern and density to form tiny perforations, wherein the perforation diameter is controlled at 10-50 microns, and the perforation spacing is adjusted between 0.5-2 mm according to the air permeability and strength requirements of the material.

[0065] Using a specially made microneedle array or laser micromachining equipment, puncture operations are performed on each layer of nano nonwoven fabric according to a pre-set perforation pattern and density.

[0066] By precisely controlling the perforation diameter of 10-50 microns and the perforation spacing of 0.5-2 mm, a direct circulation channel is created for air and water vapor without destroying the overall structural strength of the non-woven fabric.

[0067] For example, in a multi-layer structure, air can enter the middle layer from the outer layer through the perforations, and then enter the inner layer through the perforations after being filtered or functionally treated by the middle layer, thus achieving the synergistic effect of the functions of different layers and efficient ventilation function.

[0068] Furthermore, the chemical etching method in its multi-layer composite micro-perforated structure includes selecting a suitable etchant, immersing the multi-layer nano non-woven fabric in the etchant for a certain period of time, and partially dissolving the fiber surface to form tiny perforations by controlling parameters such as the etchant concentration, temperature and immersion time. After etching, the non-woven fabric is fully cleaned and dried to remove residual etchant.

[0069] Select a suitable etchant and soak the multilayer nano nonwoven fabric in it for a certain period of time.

[0070] The etchant will react chemically with the fiber surface. By controlling parameters such as etchant concentration, temperature and immersion time, the fiber surface will be partially dissolved to form tiny perforations.

[0071] This method can precisely control the formation of perforations at the nanoscale, so that microscopic connecting channels are formed between the layers of nano non-woven fabrics. Water vapor and air molecules can flow orderly along these channels between the multiple layers. While achieving the breathable function, it also meets a variety of application needs by leveraging the characteristics of different layers, such as waterproof outer layer, filtering middle layer, and breathable and skin-friendly inner layer.

[0072] A preparation method is applied to any of the above high air permeability nano nonwoven fabrics, and the specific steps include: S1. Raw material preparation: Select appropriate polymer raw materials, such as polypropylene, polyester, etc., and perform pretreatment such as drying and screening to ensure the purity and particle size uniformity of the raw materials; S2, three-dimensional mesh 2: formed by melt spinning or electrostatic spinning; S3, gradient pore 3: constructed by adding porogen or multilayer composite structure method; S4. Preparation of multi-layer composite micro-perforated structure: prepared by physical puncture method or chemical etching method; S5. Post-processing and performance optimization: Post-process the prepared high air permeability nano non-woven fabric, such as surface coating to improve water vapor permeability or antibacterial properties.

Claims

1. A high air permeability nano nonwoven fabric, comprising a nano fabric (1), characterized in that: The nanocloth (1) comprises: The three-dimensional mesh (2) is formed by nanofibers interweaving with each other in three-dimensional space to form a porous structure similar to a sponge, and the diameter of the pores between the fibers is 5-10 microns; The gradient pores (3) gradually increase or decrease in size from one side to the other side of the nanocloth (1), wherein the outer pore diameter is 0.1-0.3 microns, and the inner pore diameter gradually increases from 0.3 microns to 1-2 microns.

2. The high air permeability nano nonwoven fabric according to claim 1, characterized in that: The three-dimensional mesh (2) is prepared by a melt spinning method, which comprises: The polymer raw material is heated to a molten state, and the molten polymer is sprayed into nano-scale fibers using a spinning nozzle by controlling parameters such as spinning speed, temperature and pressure; The nanofibers are interwoven with each other by air flow or mechanical force to form a fiber web with a certain thickness and density; The fiber web is heat-treated, and the temperature and time of the heat treatment are controlled to ensure that the fibers are firmly bonded and the structure is stable. The parameters such as the spinning speed, temperature and pressure are adjusted according to the target pore size and fiber diameter. When smaller diameter fibers are required to form smaller pores, the spinning pressure can be appropriately increased, the spinning temperature can be lowered and the spinning speed can be accelerated.

3. The high air permeability nano nonwoven fabric according to claim 1, characterized in that: The three-dimensional mesh (2) structure is prepared by an electrospinning method, which comprises: The polymer is dissolved in a suitable solvent, and a suitable amount of additives is added and stirred evenly to prepare a spinning solution with a certain concentration and viscosity; The spinning solution is loaded into a syringe or spinning device with a nozzle, and a high-voltage electrostatic field is applied. By adjusting parameters such as the electric field strength, solution flow rate, and the distance between the nozzle and the collecting device, the solution is formed into nano-scale fibers under the action of the electric field force and sprayed onto the collecting device to interweave and form a nano non-woven fabric. Increasing the electric field strength can make the fibers thinner and thus affect the pore size.

4. The high air permeability nano nonwoven fabric according to claim 1, characterized in that: The gradient pores (3) are constructed by adding a porogen, which comprises adding an appropriate amount of a porogen when preparing a nano non-woven fabric, removing the porogen by high temperature treatment or the like after the non-woven fabric is formed to leave pores, and forming the gradient pores (3) by controlling the amount of porogen added, the particle size distribution, and the distribution of the porogen in the material, that is, adding more porogen with a larger particle size on one side of the non-woven fabric and adding less porogen with a smaller particle size on the other side to obtain a gradient pore (3) structure in which the pores gradually change from one side to the other side.

5. The high air permeability nano nonwoven fabric according to claim 1, characterized in that: The gradient pores (3) are constructed by a multi-layer composite structure method, which includes composite nano non-woven fabrics with different porosities or pore sizes in multiple layers, so that the pores between the layers cooperate with each other to form the gradient pores (3). Specifically, the nano non-woven fabric with smaller pores is used as the outer layer, the nano non-woven fabric with larger pores is used as the inner layer, and a transition layer is arranged in the middle so that the pores gradually increase from the outside to the inside.

6. The high air permeability nano nonwoven fabric according to claim 1, characterized in that: It also comprises a multi-layer composite micro-perforated structure, which is composited by multiple layers of nano-cloth (1), with micro-perforations provided between each layer, and the multi-layer nano-nonwoven fabric comprises an outer layer of waterproof cloth (101), a middle layer of filter cloth (102), and an inner layer of breathable cloth (103).

7. The high air permeability nano nonwoven fabric according to claim 6, characterized in that: The physical puncture method in its multi-layer composite micro-perforated structure includes the use of a special microneedle array or laser micro-machining equipment to puncture each layer of nano non-woven fabric according to a predetermined perforation pattern and density to form tiny perforations, where the perforation diameter is controlled at 10-50 microns, and the perforation spacing is adjusted between 0.5-2 mm according to the material's air permeability and strength requirements.

8. The high air permeability nano nonwoven fabric according to claim 6, characterized in that: The chemical etching method in its multi-layer composite micro-perforated structure includes selecting a suitable etchant, immersing the multi-layer nano non-woven fabric in the etchant for a certain period of time, and partially dissolving the fiber surface to form tiny perforations by controlling parameters such as the etchant concentration, temperature and immersion time. After etching, the non-woven fabric is fully cleaned and dried to remove residual etchant.

9. A preparation method, characterized in that: A nano nonwoven fabric with high air permeability as described in any one of claims 1 to 8, wherein the specific steps include: S1. Raw material preparation: Select appropriate polymer raw materials, such as polypropylene, polyester, etc., and perform pretreatment such as drying and screening to ensure the purity and particle size uniformity of the raw materials; S2, three-dimensional mesh (2): formed by melt spinning or electrospinning; S3, gradient pore (3): constructed by adding porogen or multilayer composite structure; S4. Preparation of multi-layer composite micro-perforated structure: prepared by physical puncture method or chemical etching method; S5. Post-processing and performance optimization: Post-process the prepared high air permeability nano non-woven fabric, such as surface coating to improve water vapor permeability or antibacterial properties.

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