A high-efficiency, low-resistance composite air filter material and its preparation method

Abstract

This application belongs to the field of air filtration, specifically disclosing a high-efficiency, low-resistance composite air filter material and its preparation method. The preparation method involves mixing polyethylene terephthalate (PET), 1,2-butanediol, vinyl acetate, polybutylene succinate (PEG), and diethylene glycol to obtain modified PET. Then, the modified PET is mixed with a first solvent to obtain a first spinning solution. Unmodified PET is mixed with a second solvent to obtain a second spinning solution. A substrate nonwoven fabric is alternately spun using the first and second spinning solutions to form a nanofiber membrane layer on the substrate nonwoven fabric. A protective layer is then superimposed on the nanofiber membrane layer and bonded and reinforced by heating to finally form the high-efficiency, low-resistance composite air filter material. This application does not alter the original structure of the nanofiber membrane layer, nor does it cause a decrease in porosity affecting air permeability, thus enabling the preparation of a high-efficiency, low-resistance composite air filter material.

Description

Technical Field

[0001] This application belongs to the field of air filtration, and more specifically, relates to a high-efficiency, low-resistance composite air filter material and its preparation method. Background Technology

[0002] High-efficiency air filters are essential components in various fields such as electronics, power, biomedicine, and beverage and food. They effectively improve air cleanliness, ensuring product quality and equipment operational stability. As the core of air filters, the filter material typically employs processes such as electrospinning and PTFE coating to reduce resistance and extend service life.

[0003] Electrospun membrane filter media achieves high-efficiency filtration by bonding a very thin nanofiber membrane onto a substrate using electrospinning technology. The thin membrane also results in very low resistance. However, a drawback of electrospun membrane filter media is its relatively low membrane strength. Processing and use can easily cause fiber breakage and holes, leading to reduced filtration efficiency. To protect the nanofiber membrane, a protective layer is typically added, and the composite process involves techniques such as hot rolling, ultrasonic bonding, or adhesive spraying. Hot rolling, due to its high pressure, can easily damage the original membrane structure, resulting in reduced filtration efficiency and increased resistance. Ultrasonic bonding creates a dense structure at the rolling points, leading to higher resistance and decreased overall permeability. Adhesive spraying can clog some pores, also resulting in higher resistance in the composite filter media. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a high-efficiency, low-resistance composite air filter material and its preparation method, aiming to solve the problem that the composite protective layer on the surface of nanofiber membranes in existing technologies leads to increased air filter material resistance.

[0005] According to one aspect of this application, a method for preparing a high-efficiency, low-resistance composite air filter material is provided, specifically as follows:

[0006] Polyethylene terephthalate, 1,2-butanediol, vinyl acetate polybutylene succinate and diethylene glycol are mixed to prepare modified polyethylene terephthalate, and then the modified polyethylene terephthalate is mixed with a first solvent to prepare a first spinning solution.

[0007] Unmodified polyethylene terephthalate is mixed with a second solvent to prepare a second spinning solution;

[0008] The substrate nonwoven fabric is alternately spun using the first spinning solution and the second spinning solution to form a nanofiber membrane layer on the substrate nonwoven fabric. Then, a protective layer is superimposed on the nanofiber membrane layer and bonded and reinforced by heating to finally form a high-efficiency, low-resistance composite air filter material.

[0009] Compared with the prior art, the technical solution conceived in this application, by preparing low-melting-point modified polyethylene terephthalate and using it to prepare spun fibers, can firmly bond the nanofiber membrane to the substrate nonwoven fabric and protective layer as a bonding medium during subsequent heating. This will not change the original structure of the nanofiber membrane, nor will it cause a decrease in porosity and affect air permeability, thus producing a high-efficiency, low-resistance composite air filter material.

[0010] As a further preferred embodiment, the specific preparation method of the modified polyethylene terephthalate is as follows: by mass, 50 to 70 parts of polyethylene terephthalate, 10 to 15 parts of 1,2-butanediol, 5 to 10 parts of vinyl acetate, 5 to 10 parts of polybutylene succinate and 10 to 15 parts of diethylene glycol are mixed, and then heated to 40°C to 50°C and stirred for 10 to 15 minutes to obtain the modified polyethylene terephthalate.

[0011] As a further preferred embodiment, the first solvent comprises, by mass parts, 40 to 50 parts of dimethylformamide, 25 to 30 parts of acetone and 25 to 30 parts of dioxane.

[0012] As a further preferred embodiment, the mass fraction of modified polyethylene terephthalate in the first spinning solution is 7% to 9%, and the first spinning solution is prepared by stirring at 40°C to 50°C for 5 to 10 minutes.

[0013] As a further preferred embodiment, the second solvent comprises, by mass parts, 40 to 60 parts of dimethylacetamide and 40 to 60 parts of dimethyl carbonate.

[0014] As a further preferred embodiment, the mass fraction of unmodified polyethylene terephthalate in the second spinning solution is 10% to 12%, and the second spinning solution is prepared by stirring at room temperature for 5 to 10 minutes.

[0015] As a further preferred method, the specific method of alternating spinning is as follows: the first spinning solution is injected into the odd-numbered syringe, and the second spinning solution is injected into the even-numbered syringe. Alternating spinning is carried out by electrostatic traction, with an electrostatic traction voltage of 18kV to 25kV and an extrusion speed of 1.5mL / h to 3mL / h.

[0016] As a further preferred embodiment, the basis weight of the substrate nonwoven fabric is 50 g / m². 2 ~70g / m 2 The quantitative composition of the nanofiber membrane is 1.5 g / m³. 2 ~3.0g / m 2 The quantitative amount of the protective layer is 25 g / m³. 2 ~30g / m2 .

[0017] As a further preferred method, hot air at 100℃~130℃ is used for bonding and reinforcement, and the bonding time is 5s~10s.

[0018] According to another aspect of this application, a high-efficiency, low-resistance composite air filter material obtained by the above-described preparation method is provided.

[0019] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages:

[0020] 1. This application prepares low-melting-point modified polyethylene terephthalate and uses it to spin alternately with unmodified polyethylene terephthalate. On the one hand, it can avoid the filter efficiency being affected by the excessively large diameter of the spun fibers made from modified polyethylene terephthalate. On the other hand, it can use the spun fibers made from modified polyethylene terephthalate as a bonding medium during the subsequent heating process to firmly bond the nanofiber membrane layer to the substrate nonwoven fabric and the protective layer. Compared with existing processes such as hot rolling composite, ultrasonic composite, and spray adhesive composite, it does not change the original structure of the nanofiber membrane layer and does not cause a decrease in porosity that affects air permeability, thus producing a high-efficiency, low-resistance composite air filter material.

[0021] 2. In particular, by optimizing the preparation methods of the first and second spinning solutions, this application can ensure continuous spinning while avoiding needle clogging;

[0022] 3. In addition, this application optimizes the bonding temperature and bonding time, which can ensure the bonding effect while avoiding excessive softening that would increase resistance. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the preparation process of the high-efficiency, low-resistance composite air filter material provided in the embodiments of this application;

[0024] Figure 2 This is a SEM image of the high-efficiency, low-resistance composite air filter material prepared in Example 1 of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0026] like Figure 1 As shown, according to one aspect of this application, a method for preparing a high-efficiency, low-resistance composite air filter material is provided, specifically as follows:

[0027] A modified polyethylene terephthalate (PET) is prepared by mixing polyethylene terephthalate (PET), 1,2-butanediol, vinyl acetate, polybutylene succinate (PET), and diethylene glycol. This modified PET exhibits a lower melting point compared to unmodified PET. The modified PET is then mixed with a first solvent and stirred at 40°C–50°C for 5–10 minutes to prepare a first spinning solution. The first solvent comprises 40–50 parts by mass of dimethylformyl... The mixture consists of amine, 25-30 parts acetone, and 25-30 parts dioxane, where dioxane is the solvent. Dimethylformamide and acetone are used to adjust the solvent evaporation rate. If the proportion of dioxane is too high, it will make continuous spinning difficult; if the proportion is too low, it will reduce the solubility. If the proportion of dimethylformamide is too high, the evaporation rate will be too low, making it difficult to spin into fibers; if the proportion is too low, the evaporation rate will be too high, easily clogging the needle. Similarly, if the proportion of acetone is too high, the evaporation rate will be too high, easily clogging the needle; if the proportion is too low, the evaporation rate will be too low, making it difficult to spin into fibers.

[0028] Unmodified polyethylene terephthalate (PET) is mixed with a second solvent and stirred at room temperature for 5-10 minutes to prepare a second spinning solution. The second solvent comprises 40-60 parts by mass of dimethylacetamide and 40-60 parts by mass of dimethyl carbonate, where dimethyl carbonate is the solvent and dimethylacetamide regulates the solvent evaporation rate. If the proportion of dimethyl carbonate is too high, continuous spinning will be difficult; if the proportion is too low, the solubility will be reduced. If the proportion of dimethylacetamide is too high, the evaporation rate will be too fast, easily clogging the spinning needle; if the proportion is too low, the evaporation rate will be too low, making spinning difficult.

[0029] Considering the large diameter of the filaments formed by the first spinning solution, to avoid affecting the filtration efficiency, the substrate nonwoven fabric is spun alternately using the first and second spinning solutions to form a nanofiber membrane layer on the substrate nonwoven fabric. Then, a protective layer is superimposed on the nanofiber membrane layer and bonded and reinforced by heating to finally form a high-efficiency, low-resistance composite air filter material. The filaments formed by the first spinning solution melt during heating to act as a bonding medium to bond the nanofiber membrane layer, the protective layer, and the substrate nonwoven fabric. This method can achieve the composite protective layer on the surface of the nanofiber membrane without using processes such as hot rolling, ultrasonication, or spraying adhesive, without changing the original structure and porosity of the nanofiber membrane layer. Furthermore, the alternating spinning of the first and second spinning solutions ensures uniform distribution. After reinforcement, a strong fiber mesh and interlayer structure are formed, while ensuring the high efficiency and low resistance characteristics of the air filter material.

[0030] Furthermore, the specific preparation method of modified polyethylene terephthalate is as follows: by mass, 50-70 parts of polyethylene terephthalate, 10-15 parts of 1,2-butanediol, 5-10 parts of vinyl acetate, 5-10 parts of polybutylene succinate and 10-15 parts of diethylene glycol are mixed, and then heated to 40℃-50℃ and stirred for 10-15 minutes to obtain modified polyethylene terephthalate.

[0031] Furthermore, the modified polyethylene terephthalate in the first spinning solution has a mass fraction of 7% to 9%. Too low a mass fraction will make continuous spinning difficult, while too high a mass fraction will clog the spinning needles. The unmodified polyethylene terephthalate in the second spinning solution has a mass fraction of 10% to 12%. Too low a mass fraction will make continuous spinning difficult, while too high a mass fraction will clog the spinning needles.

[0032] Furthermore, the specific method of alternating spinning can be set while balancing adhesion stability and air permeability. In a preferred embodiment of this application, the specific method of alternating spinning is as follows: the first spinning solution is injected into odd-numbered syringes, and the second spinning solution is injected into even-numbered syringes. Alternating spinning is performed by electrostatic traction, with an electrostatic traction voltage of 18kV to 25kV and an extrusion speed of 1.5mL / h to 3mL / h.

[0033] Furthermore, the basis weight of the substrate nonwoven fabric is 50 g / m². 2 ~70g / m 2 Within this range, suitable initial resistance and filtration efficiency can be obtained. The preferred nonwoven substrate is polyethylene terephthalate nonwoven fabric, polypropylene nonwoven fabric, or nylon nonwoven fabric manufactured using a melt-blown process. The basis weight (weight of the nanofiber membrane layer per unit area) is 1.5 g / m². 2 ~3.0g / m 2 The protective layer is made of polyethylene terephthalate, polypropylene, or nylon, and its basis weight (weight of the protective layer per unit area) is 25 g / m². 2 ~30g / m 2 .

[0034] Furthermore, hot air at 100℃~130℃ is used for bonding and reinforcement, with a bonding time of 5s~10s. Too low a temperature or too short a bonding time will result in poor bonding effect, while too high a temperature or too long a bonding time will cause the resistance to increase.

[0035] According to another aspect of this application, a high-efficiency, low-resistance composite air filter material obtained by the above-described preparation method is provided.

[0036] The technical solutions provided in this application will be further described below with reference to specific embodiments.

[0037] Example 1

[0038] (1) Based on the mass fraction, 50 parts of polyethylene terephthalate, 10 parts of vinyl acetate, 15 parts of 1,2-butanediol, 10 parts of polybutylene succinate, and 15 parts of diethylene glycol are mixed and stirred at 40°C for 15 min to prepare modified polyethylene terephthalate.

[0039] (2) A certain amount of modified polyethylene terephthalate is placed in the first solvent and mixed and stirred at 40°C for 10 min to form a first spinning solution with a mass fraction of 7%. The first solvent includes 40 parts of dimethylformamide, 30 parts of acetone and 30 parts of dioxane by mass fraction.

[0040] (3) A certain amount of unmodified polyethylene terephthalate is placed in the second solvent and stirred at room temperature for 10 min to dissolve it and form a second spinning solution with a mass fraction of 10%. The second solvent includes 40 parts of dimethylacetamide and 60 parts of dimethyl carbonate by mass fraction.

[0041] (4) Inject the first spinning solution from step (2) into the odd-numbered syringe and inject the second spinning solution from step (3) into the even-numbered syringe.

[0042] (5) The first and second spinning solutions are electrostatically tractioned to form a nonwoven fabric substrate with a basis weight of 1.5 g / m². 2 Nanofiber membrane;

[0043] (6) A layer with a quantitative concentration of 25 g / m² is superimposed on the nanofiber membrane. 2 Polyethylene terephthalate spunbond nonwoven fabric is used as a protective layer;

[0044] (7) The material obtained in step (6) is further reinforced by hot air bonding to form a high-efficiency, low-resistance composite air filter material, the SEM image of which is shown below. Figure 2 As shown.

[0045] In this embodiment, the unmodified polyethylene terephthalate has a melting point of 230°C and a melt index of 50 g / 10 min, and the substrate nonwoven fabric has a basis weight of 70 g / m³. 2 The polyethylene terephthalate meltblown nonwoven fabric has an electrostatic traction voltage of 18kV, a receiving distance of 20cm, an extrusion speed of 1.5ml / h, a hot air bonding time of 10s, and a hot air temperature of 100℃.

[0046] Example 2

[0047] (1) By mass, 60 parts of polyethylene terephthalate, 8 parts of vinyl acetate, 12 parts of 1,2-butanediol, 8 parts of polybutylene succinate, and 12 parts of diethylene glycol are mixed and stirred at 45°C for 12 min to prepare modified polyethylene terephthalate.

[0048] (2) A certain amount of modified polyethylene terephthalate is placed in the first solvent and mixed and stirred at 45°C for 7 min to form a first spinning solution with a mass fraction of 8%. The first solvent includes 40 parts of dimethylformamide, 30 parts of acetone and 25 parts of dioxane by mass fraction.

[0049] (3) A certain amount of unmodified polyethylene terephthalate is placed in the second solvent and stirred at room temperature for 7 minutes to dissolve it and form a second spinning solution with a mass fraction of 11%. The second solvent includes 50 parts of dimethylacetamide and 50 parts of dimethyl carbonate by mass fraction.

[0050] (4) Inject the first spinning solution from step (2) into the odd-numbered syringe and inject the second spinning solution from step (3) into the even-numbered syringe.

[0051] (5) The first and second spinning solutions are electrostatically tractioned to form a nonwoven fabric substrate with a basis weight of 2 g / m². 2 Nanofiber membrane;

[0052] (6) A layer with a quantitative concentration of 27 g / m² is superimposed on the nanofiber membrane. 2 Polyethylene terephthalate spunbond nonwoven fabric is used as a protective layer;

[0053] (7) The material obtained in step (6) is further reinforced by hot air bonding to form a high-efficiency, low-resistance composite air filter material.

[0054] In this embodiment, the unmodified polyethylene terephthalate has a melting point of 245°C and a melt index of 40 g / 10 min, and the substrate nonwoven fabric has a basis weight of 60 g / m³. 2 The polyethylene terephthalate meltblown nonwoven fabric has an electrostatic traction voltage of 20kV, a receiving distance of 22cm, an extrusion speed of 2ml / h, a hot air bonding time of 8s, and a hot air temperature of 120℃.

[0055] Example 3

[0056] (1) According to the mass fraction, 70 parts of polyethylene terephthalate, 5 parts of vinyl acetate, 10 parts of 1,2-butanediol, 5 parts of polybutylene succinate, and 10 parts of diethylene glycol are mixed and stirred at 50°C for 10 min to prepare modified polyethylene terephthalate.

[0057] (2) A certain amount of modified polyethylene terephthalate is placed in the first solvent and mixed and stirred at 50°C for 5 min to form a first spinning solution with a mass fraction of 9%. The first solvent includes 50 parts of dimethylformamide, 25 parts of acetone and 25 parts of dioxane by mass fraction.

[0058] (3) A certain amount of unmodified polyethylene terephthalate is placed in the second solvent and stirred at room temperature for 5 minutes to dissolve it and form a second spinning solution with a mass fraction of 12%. The second solvent includes 60 parts of dimethylacetamide and 40 parts of dimethyl carbonate by mass fraction.

[0059] (4) Inject the first spinning solution from step (2) into the odd-numbered syringe and inject the second spinning solution from step (3) into the even-numbered syringe.

[0060] (5) The first and second spinning solutions are electrostatically tractioned to form a nonwoven fabric substrate with a basis weight of 3g / m². 2 Nanofiber membrane;

[0061] (6) A layer with a quantitative concentration of 30 g / m² is superimposed on the nanofiber membrane. 2 Polyethylene terephthalate spunbond nonwoven fabric is used as a protective layer;

[0062] (7) The material obtained in step (6) is further reinforced by hot air bonding to form a high-efficiency, low-resistance composite air filter material.

[0063] In this embodiment, the unmodified polyethylene terephthalate has a melting point of 260°C and a melt index of 30 g / 10 min, and the substrate nonwoven fabric has a basis weight of 50 g / m³. 2 The polyethylene terephthalate meltblown nonwoven fabric has an electrostatic traction voltage of 25kV, a receiving distance of 25cm, an extrusion speed of 3ml / h, a hot air bonding time of 5s, and a hot air temperature of 130℃.

[0064] Control group 1

[0065] Other conditions are the same as in Example 1, except that step (1) does not involve vinyl acetate.

[0066] Control group 2

[0067] Other conditions are the same as in Example 1, except that step (1) does not include polybutylene succinate.

[0068] Control group 3

[0069] Other conditions are the same as in Example 1, except that in step (6), a layer with a quantitative concentration of 40 g / m is superimposed on the nanofiber membrane. 2 Polyethylene terephthalate spunbond nonwoven fabric.

[0070] Control group 4

[0071] Other conditions are the same as in Example 1, except that steps (1) and (2) are omitted, and step (7) is performed by hot rolling.

[0072] Control group 5

[0073] Other conditions are the same as in Example 1, except that steps (1) and (2) are omitted, and step (7) is performed by ultrasonic process.

[0074] Control group 6

[0075] Other conditions are the same as in Example 1, except that steps (1) and (2) are omitted, and step (7) is performed by spraying adhesive.

[0076] Control group 7

[0077] Other conditions are the same as in Example 1, except that step (3) is omitted and all spinning solutions in the syringes are obtained in step (2).

[0078] control group 8

[0079] Other conditions are the same as in Example 1, except that the substrate has a basis weight of 40 g / m³. 2 Polyethylene terephthalate meltblown nonwoven fabric.

[0080] Control group 9

[0081] Other conditions are the same as in Example 1, except that the substrate has a basis weight of 80 g / m³. 2 Polyethylene terephthalate meltblown nonwoven fabric.

[0082] The composite filter materials of Examples 1-3 and Control Groups 1-9 were tested for filtration efficiency, initial resistance, and peel strength under the following conditions:

[0083] (1) Filtration efficiency: According to the test standard: EN143:2006;

[0084] (2) Initial resistance: According to the test standard: EN143:2006;

[0085] (3) Peel strength: According to the test standard: GB / T 34444−2017

[0086] The softening point of the modified polyethylene terephthalate (PET) from Examples 1-3 and Control Groups 1-9 was tested under the following conditions:

[0087] Softening point: According to test standard: ASTM E793-2001

[0088] The performance test results are shown in Table 1.

[0089] Table 1 Performance Test Results

[0090]

[0091] Comparing Examples 1, 2, and 3, the filtration efficiency of the composite filter material increased with the quantitative increase of the electrospun nanofiber membrane, but the initial resistance also increased. It can also be seen that as the total proportion of vinyl acetate and polybutylene succinate decreased, the softening point of modified polyethylene terephthalate increased, indicating that to reduce the softening point, it is necessary to control the content of vinyl acetate and polybutylene succinate.

[0092] Comparing Example 1 and Control Group 1, it can be seen that the softening point of Control Group 1 is higher than that of Example 1, which fully demonstrates that the addition of vinyl acetate in this invention is beneficial to reducing the softening point of modified polyethylene terephthalate. Similarly, comparing Example 1 and Control Group 2, it can be seen that the addition of polybutylene succinate in this invention is beneficial to reducing the softening point of modified polyethylene terephthalate.

[0093] Comparing Example 1 and Control Group 3, it can be seen that increasing the basis weight of polyethylene terephthalate spunbond nonwoven fabric increases the resistance of the composite filter material, indicating that the basis weight of polyethylene terephthalate spunbond nonwoven fabric needs to be controlled within an appropriate range.

[0094] Comparing Example 1, Control Group 4, Control Group 5, and Control Group 6, it can be seen that the present invention uses modified polyethylene terephthalate combined with hot air bonding process, which reduces the resistance of composite filter material compared with traditional hot rolling process, ultrasonic process and spray adhesive process.

[0095] Comparing Example 1 and Control Group 7, it can be seen that if the nanofiber membrane of the present invention is entirely made of modified polyethylene terephthalate, although the peel strength is improved and the initial resistance is reduced, the filtration efficiency will be reduced. This indicates that the nanofibers made of modified polyethylene terephthalate have a larger diameter than those made of unmodified polyethylene terephthalate, and both modified and unmodified polyethylene terephthalate are needed to ensure both high filtration efficiency and low initial resistance.

[0096] Comparing Example 1, Control Group 8, and Control Group 9, it can be seen that when the substrate quantity is too low, although the initial resistance is reduced, the filtration efficiency also decreases. Conversely, when the substrate quantity is too high, both the initial resistance and the filtration efficiency increase. Therefore, the substrate quantity needs to be within an appropriate range.

[0097] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0098] Furthermore, throughout this specification, references to "an embodiment"; "an embodiment," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. Therefore, the appearance of the phrase "in one embodiment;" throughout this specification, and similar language, may, but not necessarily, refer to the same embodiment.

[0099] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a high-efficiency, low-resistance composite air filter material, characterized in that, The specific preparation method is as follows: A modified polyethylene terephthalate (PET) is prepared by mixing polyethylene terephthalate (PET), 1,2-butanediol, vinyl acetate, polybutylene succinate (PBS), and diethylene glycol. The modified PET is then mixed with a first solvent to prepare a first spinning solution. The first solvent comprises 40-50 parts dimethylformamide, 25-30 parts acetone, and 25-30 parts dioxane. The mass fraction of the modified PET in the first spinning solution is 7%-9%, and the solution is prepared by stirring at 40-50°C for 5-10 minutes. Unmodified polyethylene terephthalate is mixed with a second solvent to prepare a second spinning solution. The second solvent includes 40 to 60 parts of dimethylacetamide and 40 to 60 parts of dimethyl carbonate. The mass fraction of unmodified polyethylene terephthalate in the second spinning solution is 10% to 12%. The second spinning solution is prepared by stirring at room temperature for 5 to 10 minutes. The substrate nonwoven fabric is alternately spun using the first spinning solution and the second spinning solution to form a nanofiber membrane layer on the substrate nonwoven fabric. Then, a protective layer is superimposed on the nanofiber membrane layer and bonded and reinforced by heating to finally form a high-efficiency, low-resistance composite air filter material. The specific method of alternating spinning is as follows: the first spinning solution is injected into odd-numbered syringes, and the second spinning solution is injected into even-numbered syringes. Alternating spinning is carried out by electrostatic traction. The electrostatic traction voltage is 18kV~25kV, and the extrusion speed is 1.5mL / h~3mL / h.

2. The preparation method according to claim 1, characterized in that, The specific preparation method of the modified polyethylene terephthalate is as follows: by mass, 50 to 70 parts of polyethylene terephthalate, 10 to 15 parts of 1,2-butanediol, 5 to 10 parts of vinyl acetate, 5 to 10 parts of polybutylene succinate and 10 to 15 parts of diethylene glycol are mixed, and then heated to 40°C to 50°C and stirred for 10 to 15 minutes to obtain the modified polyethylene terephthalate.

3. The preparation method according to claim 1, characterized in that, The basis weight of the nonwoven fabric is 50 g / m². 2 ~70g / m 2 The quantitative composition of the nanofiber membrane is 1.5 g / m³. 2 ~3.0g / m 2 The quantitative amount of the protective layer is 25 g / m³. 2 ~30g / m 2 .

4. The preparation method according to any one of claims 1 to 3, characterized in that, Hot air at 100℃~130℃ is used for bonding and reinforcement, and the bonding time is 5s~10s.

5. A high-efficiency, low-resistance composite air filter material obtained by the preparation method according to any one of claims 1 to 4.

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