A multi-layer structure nanofiber composite filtration material

Abstract

The application discloses a kind of multilayer structure nanofiber composite filter materials, it is related to air filter material technical field, the filter material has four-layer structure, first layer structure is filter surface layer, and the weight ratio of proportion is less than 30% of the total weight of filter material, second layer structure is nanofiber composite layer, and more than 95% of the fiber diameter distribution of nanofiber composite layer is 0.1~10 μm, third layer structure is base cloth layer, fourth layer structure is the support layer of filter material, and the weight ratio of proportion is higher than 40% of the total weight of filter material, the total weight of the filter material is 350‑950g / m 2 The filter material has the characteristics of high-precision filtration and high wind speed resistance, and can maintain stable performance after long-term use, and is suitable for industrial flue gas treatment, waste gas treatment and other fields.

Description

Technical Field

[0001] This invention relates to the field of air filtration materials technology, and in particular to a multi-layered nanofiber composite filtration material. Background Technology

[0002] With the acceleration of industrial modernization and the comprehensive improvement of environmental protection awareness, filtration technology has become an indispensable core support link in energy, chemical, environmental protection, pharmaceutical, and electronics industries. The market's demands for core performance characteristics of filter materials, such as "high precision, low resistance, high dust holding capacity, and long lifespan," are becoming increasingly stringent. Traditional filter materials, mostly employing single structures or simple composite forms, suffer from significant performance bottlenecks and struggle to meet the diverse application scenarios under complex working conditions.

[0003] Breakthroughs in nanofiber technology offer a key direction for addressing the aforementioned pain points. On one hand, its ultra-fine diameter enables highly efficient interception of submicron and nanoscale dust, far exceeding traditional filter media. On the other hand, its high porosity structure reduces airflow resistance while maintaining high precision, resolving the core contradiction of "high precision and low resistance." However, single-layer nanofiber membranes suffer from low mechanical strength, high cost, and small dust holding capacity, making them difficult to apply directly to industrial-scale filtration. Therefore, there is an urgent need for a novel multilayer filter material that can achieve highly efficient nanoscale filtration while also possessing high strength, large dust holding capacity, and stable performance even after prolonged use, to meet the development needs of modern industry and environmental protection.

[0004] For example, patent CN202410680676.3 discloses a high-temperature flue gas filter needle-punched felt with an asymmetric gradient structure. The filter material's first layer is an electrospun, wrinkled, porous polyimide microfiber felt layer; the second layer is a fine mixed needle-punched felt layer; the third layer serves as the base fabric; and the outermost layer is a basalt fiber wear-resistant layer. This method improves the filtration accuracy and dust holding capacity of the filter material. However, electrospun microfiber felt suffers from unstable manufacturing structures and low strength. In contrast, the nanocomposite fiber layer in this case incorporates nanofibers into microfibers, using the microfibers to provide skeletal support. This not only achieves the same excellent filtration effect but also exhibits a more stable structure.

[0005] For example, patent CN201811205339.X discloses a composite high-efficiency air filter material and its preparation process. The filter material has a small-pore mesh protective layer on the surface, a polymer nanofiber layer on the second layer, a melt-blown layer on the third layer, and a substrate layer on the fourth layer. This method greatly extends the service life of the filter material. However, the small-pore mesh protective layer of the filter material has a low basis weight, which limits the protection of the nanolayer and has a low dust holding capacity. In contrast, the filter surface layer of this case can perform primary filtration and provide excellent wear resistance to ensure that the core nanocomposite layer is not damaged. At the same time, the nanofiber composite layer has a micron fiber skeleton, and the nano-microstructure is more stable. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned technical problems and provide a high-precision multilayer nanofiber composite filter material.

[0007] To achieve the above-mentioned technical objectives and requirements, the technical solution adopted by this invention is: a multi-layered nanofiber composite filter material, wherein the filter material has a four-layer structure. The first layer is a filter surface layer, the basis weight of which is less than 30% of the total basis weight of the filter material. The second layer is a nanofiber composite layer, wherein more than 95% of the fibers in the nanofiber composite layer have a diameter distribution of 0.1~10μm. The third layer is a base fabric layer. The fourth layer is a support layer of the filter material, the basis weight of which is more than 40% of the total basis weight of the filter material. The total basis weight of the filter material is 350-950 g / m³. 2 .

[0008] Preferably, the filter material has a filtration efficiency of ≥99.99% at the end of the benchmark test based on VDI 3926 "Standard Test Methods for Evaluating Cleanable Filter Media".

[0009] Preferably, the filter surface layer is made by mixing and needle punching or hydroentangling one or more of the following fibers: polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber, and the average linear density of the fiber is 0.5~10D.

[0010] Preferably, the basis weight of the filter surface layer is 30-200 g / m³. 2 .

[0011] Preferably, the nanofibers in the nanofiber composite layer are made of one or more of the following materials: polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber; the nanofibers with a diameter of 100-999 nm form a dense three-dimensional network structure, and the proportion of nanofibers is 50-80%; the microfibers with a diameter of 1-10 μm serve as the supporting framework of the nanofiber composite layer, and the proportion of microfibers is 20-50%; the basis weight of the nanofiber composite layer is 50-150 g / m³. 2 .

[0012] Preferably, the micron fibers of the nanofiber composite layer are uniformly distributed in a "well" shape in the three-dimensional network structure of nanofibers, and the average distribution angle of the micron fibers in the radial direction is 0~20 degrees, and the average distribution angle of the micron fibers in the latitudinal direction is 0~20 degrees.

[0013] Preferably, the base fabric layer is woven from one or more fibers selected from polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber, and the basis weight of the base fabric layer is 70~130 g / m². 2 .

[0014] Preferably, the support layer is made by mixing and needle punching or hydroentangling one or more of the following fibers: polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber, and the average linear density of the fiber is 0.5~10D.

[0015] Preferably, the basis weight of the support layer is 200~600g / m². 2 .

[0016] Preferably, the filter material can be applied to fields such as industrial flue gas treatment and waste gas treatment.

[0017] Compared with traditional structures, the beneficial effects of this invention are: the multilayer nanofiber composite filter material of this invention has excellent filtration effect, which can meet the requirements of 10mg / Nm³. 3 Even 5mg / Nm 3 The dust concentration emission is reduced, with a filtration efficiency exceeding 99.99%. Simultaneously, through a multi-layered structure design, it features high filtration accuracy and resistance to high wind speeds, maintaining stable performance even after prolonged use and meeting ultra-low emission requirements. The filter material of this invention, after being sewn into bags, can be applied in fields such as industrial flue gas treatment and waste gas treatment. Detailed Implementation

[0018] The present invention will be further described below.

[0019] A multi-layered nanofiber composite filter material has four layers. The first layer is a filter surface layer, with a basis weight of less than 30% of the total basis weight of the filter material. The second layer is a nanofiber composite layer, with more than 95% of the fibers having a diameter of 0.1~10μm. The third layer is a base fabric layer. The fourth layer is a support layer, with a basis weight of more than 40% of the total basis weight of the filter material. The total basis weight of the filter material is 350-950 g / m³. 2 .

[0020] The first filter layer is a non-woven fabric made of needle-punched or hydroentangled material. During dust filtration, it effectively intercepts large dust particles, providing a primary filtration effect. Simultaneously, it improves the overall wear resistance of the filter media and protects the core nano-filter layer. The basis weight of the filter layer should be less than 30% of the total basis weight of the filter material. If it is higher than or equal to 30%, the basis weight of the filter layer is too high, allowing small dust particles to continuously enter the filter layer. Excessive dust accumulation will clog the filter layer, significantly increasing the overall pressure drop of the filter media, failing to achieve a low-resistance effect, and making dust removal difficult. If the basis weight of the filter layer is less than 30% of the total basis weight of the filter material, even if small dust particles enter the filter layer and cause some clogging, the limited dust accumulation due to the low basis weight of the filter layer will not significantly increase the overall pressure drop of the filter media.

[0021] The second nanofiber composite layer is made of nanofibers and microfibers. The nanofibers provide efficient filtration, while the microfibers provide a skeletal support structure. The nanofibers and microfibers contain an adhesive, preferably with a content of 3-8%. The adhesive is preferably one or more of phenolic resin, acrylic resin, epoxy resin, or polyacetic acid resin. The adhesive bonds the nanofibers to each other, to each other, and to each other, forming a membrane structure. This not only further improves the filtration accuracy but also enhances the entanglement strength between the fibers, further increasing the strength of the nanocomposite layer. More than 95% of the fibers in the nanofiber composite layer have a diameter distribution of 0.1-10 μm. If the distribution of fibers with a diameter of 0.1-10 μm is less than 95%, it indicates that the proportion of fibers smaller than 0.1 and larger than 10 μm is too high, resulting in uneven fiber distribution in the overall nanolayer and affecting filtration performance.

[0022] The third base layer is a woven fabric. The woven fabric forms a stable fabric structure through the interweaving of warp and weft yarns, providing the necessary strength and structural stability for the filter material.

[0023] The fourth support layer is a non-woven fabric produced by needle punching. It provides excellent load-bearing capacity to the outer high-efficiency filter layer while ensuring structural stability and good air permeability. The support layer's basis weight should be higher than 40% of the total basis weight of the filter material. If it is lower than or equal to 40%, the support layer is too small and cannot provide adequate structural support. The total basis weight of the filter material is 350-950 g / m³. 2 If the total weight of the filter material is less than 350g / m³ 2 The overall strength will decrease significantly, the dust holding capacity will be reduced, and the service life of the filter material will be affected. If the total weight of the filter material exceeds 950g / m³, 2 The overall air permeability of the filter material will decrease, the pressure loss will increase, leading to increased energy consumption of the dust removal equipment and a significant increase in cost.

[0024] The filter material of this invention, based on the VDI 3926 standard test method for evaluating cleanable filter media, has a filtration efficiency of ≥99.99% at the end of the benchmark test. If it is lower than 99.99%, its filtration effect will be affected.

[0025] The filter surface layer is made by mixing and needle punching or hydroentangling one or more of the following: polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber. The average linear density of the fiber is 0.5~10D. If the fiber linear density is less than 0.5D, it is difficult to comb the fiber into a web, making mass production difficult. If the fiber linear density is greater than 10D, the entanglement between fibers is reduced, the overall strength of the nonwoven fabric will decrease significantly, and the average pore size will increase, reducing the ability to intercept large dust particles and failing to achieve the effect of primary filtration.

[0026] The weight of the filter surface layer is 30-200 g / m³. 2 If the filter surface layer weight is less than 30g / m² 2 The carding machine struggles to card the material into a web, making preparation difficult and reducing the surface's abrasion resistance. Furthermore, if the basis weight of the filter layer exceeds 200 g / m², this will negatively impact the filter's performance. 2 Dust will continue to accumulate on the filter surface, leading to higher pressure loss and affecting the overall service life of the filter material.

[0027] The nanofibers are made of one or more of the following materials: polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber. The nanofibers, with a diameter of 100-999 nm, form a dense three-dimensional network structure. If the fiber diameter is less than 100 nm, the nanostructure will be too dense, leading to a sharp increase in pressure loss and making it difficult to achieve a low-resistance effect. If the fiber diameter is greater than 999 nm, the overall density will decrease, the average pore size will increase, and the filtration accuracy will decrease. The proportion of nanofibers is 50-80%. If the proportion of nanofibers is less than 50%, it is difficult for the nanofibers and microfibers to cover each other evenly to form a uniform three-dimensional network structure and achieve a good filtration effect. If the proportion of nanofibers is greater than 80%, the nanolayers and microfibers will not be able to form a uniform three-dimensional network structure. An overly dense structure leads to increased pressure loss and insufficient microfiber content, resulting in reduced overall strength of the composite layer. Microfibers with diameters of 1-10 μm serve as the supporting framework for the nanofiber composite layer. If the diameter of the microfibers is less than 1 μm, the entanglement and cohesion between fibers decrease, making it difficult to form a strong supporting framework, which will cause difficulties in mass production. If the diameter of the microfibers is greater than 10 μm, the pore size of the formed microfiber supporting framework becomes larger, making it more difficult for the nanofibers to form a three-dimensional network structure or causing uneven coverage of the three-dimensional network structure, affecting the filtration effect. The proportion of microfibers should be 20-50%. If the proportion is less than 20%, there are too few microfibers, making it difficult to form a strong nanofiber composite layer, affecting subsequent production. If the proportion is greater than 50%, there are too many microfibers, increasing the average pore size and leading to a decrease in overall filtration accuracy. The basis weight of the nanofiber composite layer is 50-150 g / m³. 2 If the basis weight of the nanofiber composite layer is less than 50 g / m 2 This can lead to excessively low strength in the nanofiber layer, making lamination difficult and affecting subsequent mass production. Furthermore, it can reduce filtration accuracy and dust holding capacity if the basis weight exceeds 150 g / m³. 2 Excessive basis weight of nanofiber composite layers can lead to a sharp increase in pressure loss, resulting in increased energy consumption during production operations in practical applications.

[0028] The microfibers in the nanofiber composite layer are uniformly dispersed in a three-dimensional network structure of nanofibers in a "well" shape, serving as a supporting framework. The "well" shaped supporting framework is a thin felt made by cross-laying short-cut microfibers combed from the radial and latitudinal directions, and then nanofibers are obtained by electrospinning or wet spinning. The nanofibers are then composited onto the microfiber thin felt and cross-linked and cured to form the nanofiber composite layer. This structure has better stability and support compared to disordered or unidirectional network laying. The average radial distribution angle of the microfibers is 0~20 degrees, and the average latitudinal distribution angle of the microfibers is also 0~20 degrees. If the average radial and latitudinal distribution angles of the microfibers are greater than 20 degrees, there will be problems such as uneven and scattered distribution of microfibers, which will not only affect the three-dimensional network distribution of nanofibers, but also lead to a decrease in the warp and latitudinal strength of the nanofiber layer, thus affecting the overall filtration performance.

[0029] The base fabric layer is woven from one or more of the following: polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber. The basis weight of the base fabric layer is 70~130 g / m². 2 If the base weight is less than 70 g / m 2 This will lead to a decrease in mechanical strength, making it unable to effectively support the entire filter material. If the Kibbuc weight is greater than 130 g / m³, 2 This will lead to performance redundancy and increased costs.

[0030] The support layer is made by mixing and needle-punching or hydroentangling one or more of the following: polypropylene fibers, homopolymer polyacrylonitrile fibers, polyester fibers, polyamide fibers, polyphenylene sulfide fibers, aromatic polyamide fibers, polytetrafluoroethylene fibers, polyimide fibers, polyaryldiazole fibers, glass fibers, and ceramic fibers. The average linear density of the fibers is 0.5~10D. If the fiber linear density is less than 0.5D, it is difficult to comb the fibers into a web, making mass production difficult. If the fiber linear density is greater than 10D, the entanglement between fibers decreases, and the overall strength of the nonwoven fabric will drop significantly, failing to provide strong structural support for the filter material.

[0031] The weight of the support layer is 200~600 g / m³. 2 If the weight is less than 200g / m 2 The support layer is not strong enough to effectively support the upper filter material. If the basis weight is greater than 600 g / m³, 2 This will significantly increase air resistance, affect the dust removal effect, and increase material costs.

[0032] The testing methods for various properties of the filter material of the present invention are as follows:

[0033] Fiber composition: Refer to FZ / T01144-2018 "Quantitative Analysis of Textile Fibers - Near Infrared Spectroscopy". Use a sample crushing device or tool to crush the sample fibers into fragments smaller than 1.5 mm, mix them evenly, fill them into a sample pressing device, and compact them as tightly as possible into a fiber cake with a thickness greater than 3 mm and a diameter greater than the detector window. Ensure that the optical path of the test is consistent with the optical path when establishing the calibration model. Use a spectrometer to test the spectral data of no less than 2 points of the sample.

[0034] Fiber diameter: The surface of the filter material was tested using a scanning electron microscope (SEM). Ten points were randomly selected for sample preparation and testing. The magnification of each point was 100 to 1000 times. The diameter of the structural fibers in the sample was randomly marked. The diameter of at least 10 fibers was marked at each point, and the average value was taken.

[0035] Linear density of fibers: Based on GB / T 14335-2008 "Test Method for Linear Density of Short Chemical Fibers", approximately 10g of sample was randomly selected from the specimens as the linear density test sample, and pre-mixed and conditioned according to regulations. The sample was brought to hygroscopic equilibrium (the mass change during continuous weighing every 30 minutes should not exceed 0.1%). For tow samples, after obtaining representative samples from the batch, 10 test samples of suitable length were cut, and approximately 10g of sample was randomly selected as the linear density test sample. Under standard atmospheric conditions, a certain length of fiber bundle was cut from the straightened fiber bundle, and the mass and number of fibers in this middle section of the fiber bundle were measured. The average linear density was calculated.

[0036] Weight per unit length: Based on GB / T 4669-2008 "Textiles - Determination of Mass per Unit Length and Mass per Unit Area of ​​Woven Fabrics", 100cm of fabric was cut using a cutter. 2 A circular sample was tested at 5 points, and the average value was taken.

[0037] The ratio of the filter layer to the support layer:

[0038] Weigh the pre-punched filter surface layer, the support layer, and the total weight of the main punched filter material. The calculation formula is as follows:

[0039] The proportion of the filter surface layer = (weight of the filter surface layer / total weight of the filter material) × 100%;

[0040] The proportion of the support layer = weight of the support layer / total weight of the filter material × 100%.

[0041] VDI3926 (2004) trapping efficiency, outlet concentration, pressure drop, and cycle time:

[0042] The performance of filter materials was determined based on the standard test method for evaluating cleanable filter media (VDI 3926). The experimental sample size was 150 mm in diameter. The feed dust concentration was 5.0 ± 0.5 g / m³. 3 The filtration velocity is 2 m / min (air volume 1.85 m³ / min). 3 / h). The experimental sequence was: initial 30 cycles + stabilization 5000 cycles + final 30 cycles. The initial 30 cycles and final 30 cycles were performed as follows: as the running time increased, the pressure difference across the filter material gradually increased. When the pressure difference reached 1000 Pa, pulsed air was used to clean the dust on the surface of the filter material, and then the next process was performed. This process was repeated 30 times. During the experiment, the experimental time (t / s) and pressure changes were recorded, and the weight M (g) of dust passing through the filter material was measured. The stabilization process involved cleaning the filter material at 5-second intervals during operation, with a cleaning pressure of 5 bar, for 5000 cleaning cycles. The formulas for calculating the outlet dust concentration and collection efficiency are as follows:

[0043] The outlet dust concentration C = weight of dust passing through the filter material M / (1.85 × time t / 3600), and the unit of outlet dust concentration C is g / m³. 3 ;

[0044] Collection efficiency = (1 - outlet dust concentration C / 5) × 100%;

[0045] Pressure loss is the pressure loss automatically recorded by the equipment after the last pulse injection in the last 30 cycles;

[0046] The loop time is the total time spent on the last 30 iterations.

[0047] The present invention will be described in more detail through the following embodiments and comparative examples, but the present invention is not limited to these embodiments.

[0048] Example 1: Polyphenylene sulfide chopped fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 30g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is made of polytetrafluoroethylene fiber woven in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then integrated by needle punching to finally obtain the filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 1.

[0049] Example 2: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 50g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is made of polytetrafluoroethylene fiber woven in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then integrated by needle punching to finally obtain the filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 1.

[0050] Example 3: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is made of polytetrafluoroethylene fiber woven in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then integrated by needle punching to finally obtain the filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 1.

[0051] Example 4: Polyphenylene sulfide chopped fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 200g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is made of polytetrafluoroethylene fiber woven in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then integrated by needle punching to finally obtain the filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 1.

[0052] Example 5: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create a 50 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is made of polytetrafluoroethylene fiber woven in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then integrated by needle punching to finally obtain the filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 1.

[0053] Example 6: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create a 100g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form an integrated filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 2.

[0054] Example 7: Polyphenylene sulfide chopped fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create a 150 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form an integrated filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 2.

[0055] Example 8: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2The nanofiber composite felt contains 50% polypropylene nanofibers and 50% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form an integrated filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 2.

[0056] Example 9: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 80% polypropylene nanofibers and 20% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form an integrated filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 2.

[0057] Example 10: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 70 g / m². 2 The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form an integrated filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 2.

[0058] Example 11: Polyphenylene sulfide chopped fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 130 g / m². 2The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form an integrated filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 3.

[0059] Example 12: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface and 200g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form an integrated filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 3.

[0060] Example 13: Polyphenylene sulfide fibers with a linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface and 600g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form an integrated filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 3.

[0061] Example 14: Polytetrafluoroethylene fibers with a linear density of 3-5D were mixed, opened, carded, laid into a web, and pre-needled to obtain 100g / m² fibers. 2 Filter surface and 600g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form an integrated filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 3.

[0062] Example 15: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polyimide nanofibers and polyimide chopped fibers together with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polyimide nanofibers and 30% polyimide chopped strands, with a density of 100 g / m². 2 The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then integrated by needle punching to finally obtain the filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 4.

[0063] Example 16: Polyphenylene sulfide short-cut fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding glass nanofibers and chopped polyester fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% glass nanofibers and 30% chopped polyester fibers, with a density of 100g / m². 2 The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then integrated by needle punching to finally obtain the filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 4.

[0064] Example 17: Polyphenylene sulfide chopped fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding ceramic nanofibers and chopped glass fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% ceramic nanofibers and 30% chopped glass fibers, with a density of 100 g / m². 2The base fabric layer is woven from polytetrafluoroethylene fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then integrated by needle punching to finally obtain the filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 4.

[0065] Example 18: Polyphenylene sulfide chopped fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is woven from polyphenylene sulfide fibers in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then integrated by needle punching to finally obtain the filter material of the present invention. The physical properties of the filter material of the present invention are shown in Table 4.

[0066] Comparative Example 1: Polyphenylene sulfide chopped fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2 Filter surface layer and 300g / m 2 The supporting layer is then made of polytetrafluoroethylene fibers woven in a warp and weft pattern to a density of 100g / m². 2 The base fabric layer is then layered with the filter surface layer, nanofiber composite layer, base fabric layer and support layer in sequence, and then reinforced by needle punching to obtain the filter material. The physical properties of the filter material are shown in Table 5.

[0067] Comparative Example 2: Polyphenylene sulfide chopped fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain fibers with a density of 200 g / m². 2 Filter surface and 200g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 70% polypropylene nanofibers and 30% polyester chopped strand fibers, with a density of 100 g / m². 2 The base fabric layer is made of polytetrafluoroethylene fiber woven in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form a whole, and finally the filter material is obtained. The physical properties of the filter material are shown in Table 5.

[0068] Comparative Example 3: Polyphenylene sulfide chopped fibers with a fiber linear density of 2D were mixed, opened, carded, laid up, and pre-needled to obtain 100g / m² fibers. 2Filter surface layer and 300g / m 2 A support layer is then formed by bonding polypropylene nanofibers and polyester chopped fibers with an adhesive to create an 80 g / m² structure. 2 The nanofiber composite felt contains 30% polypropylene nanofibers and 70% polyester chopped strand fibers, with a density of 100g / m². 2 The base fabric layer is made of polytetrafluoroethylene fiber woven in a warp and weft pattern. Finally, the filter surface layer, nanofiber composite layer, base fabric layer and support layer are stacked in sequence and then reinforced by needle punching to form a whole, and finally the filter material is obtained. The physical properties of the filter material are shown in Table 5.

[0069] Table 1. Properties of Filter Materials from Examples 1-5

[0070]

[0071] Table 2. Properties of Filter Materials from Examples 6 to 10

[0072]

[0073] Table 3. Properties of Filter Materials from Examples 11-14

[0074]

[0075] Table 4. Properties of Filter Materials from Examples 15 to 18

[0076]

[0077] Table 5. Properties of Filter Materials for Comparative Examples 1-3

[0078]

[0079] Based on Tables 1-5 above, the following conclusions can be drawn:

[0080] (1) As can be seen from Examples 1, 2, 3 and 4, under the same conditions, when the weight ratio of the filter surface layer is within the preferred range, the resulting filter material has high capture efficiency, low outlet concentration and long circulation time.

[0081] (2) As can be seen from Examples 3, 5, 6 and 7, under the same conditions, when the basis weight ratio of the nanofiber layer is within the preferred range, the resulting filter material has high capture efficiency, low outlet concentration, long circulation time and good wear resistance.

[0082] (3) As can be seen from Examples 3, 8 and 9, under the same conditions, when the proportion of nanofibers and microfibers in the nanolayer is within the preferred range, the resulting filter material has high capture efficiency, low outlet concentration and long circulation time.

[0083] (4) As can be seen from Examples 3, 10 and 11, under the same conditions, when the basis weight of the base fabric layer is within the preferred range, the resulting filter material has high capture efficiency, low outlet concentration and long circulation time.

[0084] (5) As can be seen from Examples 3, 12 and 13, under the same conditions, when the weight of the support layer is within the preferred range, the resulting filter material has high capture efficiency, low outlet concentration and long circulation time.

[0085] (6) As can be seen from Examples 13 and 14, under the same conditions, when the fiber materials of the filter layer and the support layer are within the preferred range, the resulting filter material has high capture efficiency, low outlet concentration and long circulation time.

[0086] (7) As can be seen from Examples 3, 15, 16 and 17, under the same conditions, the nanofiber material has a high capture efficiency, low outlet concentration and long circulation time in the obtained filter material within the preferred range.

[0087] (8) As can be seen from Examples 3 and 18, under the same conditions, when the base fabric material is within the preferred range, the resulting filter material has high capture efficiency, low outlet concentration and long circulation time.

[0088] (9) As can be seen from Example 3 and Comparative Example 1, under the same conditions, the former has a composite layer of nanofibers, and the resulting filter material has high capture efficiency, low outlet concentration and long circulation time.

[0089] (10) As can be seen from Example 3 and Comparative Example 2, under the same conditions, the former has a filter surface weight ratio within the preferred range, and the resulting filter material has high capture efficiency, low outlet concentration and long circulation time.

[0090] (11) As can be seen from Example 2 and Comparative Example 3, under the same conditions, the proportion of nanofibers and microfibers in the former is within the preferred range, and the resulting filter material has high capture efficiency, low outlet concentration and long circulation time.

[0091] The above embodiments of the present invention are merely examples to clearly illustrate the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent technical solutions also fall within the scope of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A multilayer nanofiber composite filter material, characterized in that: The filter material has a four-layer structure. The first layer is a filter surface layer, which accounts for less than 30% of the total weight of the filter material. The second layer is a nanofiber composite layer, in which more than 95% of the fibers have a diameter of 0.1-10 μm, and nanofibers with a diameter of 100-999 nm form a dense three-dimensional network structure, accounting for 50-80% of the total weight. Microfibers with a diameter of 1-10 μm serve as the supporting framework of the nanofiber composite layer, accounting for 20-50% of the total weight. The third layer is a base fabric layer. The fourth layer is a support layer of the filter material, which accounts for more than 40% of the total weight of the filter material. The total weight of the filter material is 350-950 g / m³. 2 .

2. The multilayer nanofiber composite filter material according to claim 1, characterized in that: The filter material achieved a filtration efficiency of ≥99.99% at the end of the VDI3926 benchmark test.

3. The multilayer nanofiber composite filter material according to claim 1, characterized in that: The filter surface layer is made by mixing and needle punching or hydroentangling one or more of the following fibers: polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber. The average linear density of the fibers is 0.5~10D.

4. The multilayer nanofiber composite filter material according to claim 1, characterized in that: The weight of the filter surface layer is 30-200 g / m³. 2 .

5. The multilayer nanofiber composite filter material according to claim 1, characterized in that: The nanofibers in the nanofiber composite layer are made of one or more of the following fibers: polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber; the basis weight of the nanofiber composite layer is 50-150 g / m³. 2 .

6. The multilayer nanofiber composite filter material according to claim 1, characterized in that: The micron-fibers in the nanofiber composite layer are evenly distributed in a "well" shape in the three-dimensional network structure of nanofibers. The average distribution angle of the micron-fibers in the radial direction is 0~20 degrees, and the average distribution angle of the micron-fibers in the latitudinal direction is 0~20 degrees.

7. The multilayer nanofiber composite filter material according to claim 1, characterized in that: The base fabric layer is woven from one or more fibers selected from polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryldiazole fiber, glass fiber, and ceramic fiber, and the basis weight of the base fabric layer is 70~130 g / m². 2 .

8. The multilayer nanofiber composite filter material according to claim 1, characterized in that: The support layer is made by mixing and needle punching or hydroentangling one or more of the following fibers: polypropylene fiber, homopolymer polyacrylonitrile fiber, polyester fiber, polyamide fiber, polyphenylene sulfide fiber, aromatic polyamide fiber, polytetrafluoroethylene fiber, polyimide fiber, polyaryloxadiazole fiber, glass fiber, and ceramic fiber. The average linear density of the fibers is 0.5~10D.

9. The multilayer nanofiber composite filter material according to claim 1, characterized in that: The weight of the support layer is 200~600 g / m³. 2 .

10. The multilayer nanofiber composite filter material according to any one of claims 1-9, characterized in that: The filter material is used in industrial flue gas treatment and waste gas treatment.

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