Low-temperature-resistant high-efficiency air filtering material and preparation method thereof

Abstract

The invention belongs to the technical field of filtration and separation, and particularly discloses a low-temperature-resistant efficient air filtration material and a preparation method thereof.The preparation method comprises the steps that polyimide resin, polystyrene, a flexibilizer and a silane coupling agent are mixed, heated and stirred, and modified polyimide resin emulsion is obtained; the modified polyimide resin emulsion is diluted and then activated; adding glass fibers and polyester fibers in a preset ratio into the dispersion liquid for dispersion treatment to obtain a fiber suspension; dehydrating the fiber suspension to obtain a first wet filter material; adding the first wet filter material into the activated emulsion, and adding an auxiliary agent for dispersion treatment to obtain a fiber suspension; dehydrating the fiber suspension to obtain a second wet filter material; and irradiating the second wet filter material by using a plasma beam, and heating and drying the treated second wet filter material to obtain the low-temperature-resistant efficient air filter material. The air filter material prepared by the invention can still keep good filtering performance in a low-temperature environment.

Description

Technical Field

[0001] The present application belongs to the field of filtration and separation technology, and more specifically, relates to a low-temperature resistant and efficient air filtration material and a preparation method thereof. Background Art

[0002] The key components of gas turbines used in extremely cold environments (ambient temperature ≤ -60°C) have high requirements for low temperature resistance. In particular, the air filter element that provides clean air for its operation is required to maintain good filtering performance at low temperatures. However, the air filter materials used in traditional air filters generally have poor low temperature resistance. In low temperature environments, they are prone to embrittlement and rupture under wind pressure, causing the filter element to lose its filtering performance. Therefore, in order to ensure the normal operation of gas turbines in extremely cold environments, it is of great significance to develop low-temperature resistant and efficient air filter materials. Summary of the invention

[0003] In view of the defects of the prior art, the purpose of the present application is to provide a low-temperature resistant and efficient air filter material and a preparation method thereof, aiming to solve the problem of brittle failure of air filter materials in low-temperature environments.

[0004] To achieve the above objectives, in a first aspect, the present application provides a method for preparing a low temperature resistant and high efficiency air filter material, comprising: S1: 73% to 86% of polyimide resin, 5% to 10% of polystyrene, 4% to 7% of toughening agent and 5% to 10% of silane coupling agent are mixed by mass percentage, heated and stirred to obtain a modified polyimide resin emulsion; S2 dilutes the modified polyimide resin emulsion and then performs activation treatment to obtain an activated emulsion; S3: adding glass fiber and polyester fiber in a preset ratio into a dispersion liquid for dispersion treatment to obtain a fiber suspension; dehydrating the fiber suspension to obtain a first wet filter material; S4: adding the first wet filter material to the activated emulsion, and adding an auxiliary agent for dispersion treatment to obtain a fiber suspension; dehydrating the fiber suspension to obtain a second wet filter material; S5: treating the second wet filter material by plasma beam irradiation, and then heating and drying the treated second wet filter material to obtain a low temperature resistant and high efficiency air filter material.

[0005] Furthermore, in step S1, the molecular weight of the polyimide resin is 4×10 4 ~7×10 4 .

[0006] Furthermore, in step S1, the toughening agent is a silicone acrylic resin.

[0007] Furthermore, in step S1, the temperature of heating and stirring is 58°C to 62°C, and the heating and stirring time is 15min to 20min.

[0008] Furthermore, in step S2, the modified polyimide resin emulsion is diluted to obtain a diluted emulsion with a mass concentration of 3% to 6%; an accelerator is added to the diluted emulsion for activation treatment, and the mass ratio of the diluted emulsion to the accelerator is 100:3 to 100:6; the accelerator is a siloxane compound.

[0009] Furthermore, in step S3, the glass fiber has an average diameter of 0.3 μm ~1 μm flame-processed glass wool; and / or, the mass ratio of the glass fiber to the polyester fiber is 6:1 to 8:1; and / or, the fiber concentration in the fiber suspension is 0.5% to 0.8%; and / or, the dispersion treatment is carried out by stirring and ultrasonication, and the dispersion treatment time is 10 min to 20 min.

[0010] Furthermore, in step S4, the auxiliary agent is polyoxypropylene-ethylene oxide copolyether or polyoxyolefin-polysiloxane copolymer, and is dispersed by injecting compressed air, and the dispersion treatment time is 5 minutes to 10 minutes; and / or, the mass ratio of the auxiliary agent to the activated emulsion is 1:100; and / or, the water content of the second wet filter material is 73% to 87%.

[0011] Furthermore, in step S5, the discharge power of the plasma beam is 100W to 300W, the voltage applied to the upper and lower positive and negative electrodes is 100 to 200V, the plasma beam irradiation time is 10s to 30s, and the frequency of the plasma beam excitation source is 40KHz to 60KHz.

[0012] Furthermore, in step S5, the temperature of heating and drying is 160°C to 180°C, and the drying time is 5min to 10min.

[0013] In the second aspect, the present application provides a low-temperature resistant and efficient air filter material, which is prepared using the preparation method as described above. The air filter material comprises mixed fibers composed of glass fibers and polyester fibers, and a modified polyimide resin is adhered to the surface of the mixed fibers.

[0014] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0015] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: (1) The preparation method of the low-temperature resistant and high-efficiency air filter material provided in the present application is to prepare a modified polyimide resin by mixing a polyimide resin, polystyrene, a toughening agent and a silane coupling agent, and then heating and stirring. The modified polyimide resin is used as a fiber adhesive to replace the acrylic resin, epoxy resin and other adhesives that are not resistant to low temperatures used in traditional air filter materials, thereby greatly improving the overall low-temperature resistance of the air filter material, so that it can still maintain good filtering performance in a low-temperature environment, and can be widely used in various low-temperature air filtration fields.

[0016] (2) The preparation method of the low-temperature resistant and high-efficiency air filter material provided in the present application enhances the adhesion of the modified polyimide resin emulsion on the fiber by adding a promoter; and by adding an auxiliary agent and treating the filter material surface with a plasma beam, the modified polyimide resin molecules are further evenly and firmly attached to the surface of the mixed fiber.

[0017] (3) The preparation method of the low-temperature resistant and high-efficiency air filter material provided in the present application forms a film at the intersection of fibers by drying and curing the wet filter material under specific conditions, which does not block the pore channels between the fibers. This allows the filter material of the present application to have good low-temperature resistance as a whole while not affecting the air permeability of the filter material.

[0018] (4) The present application controls the filtration efficiency of the filter material within an appropriate range by adjusting the ratio of submicron glass fiber to polyester fiber. Since the initial resistance of the filter material is related to the porosity and its pore uniformity, the greater the porosity of the filter material, the better the pore uniformity, and the lower the initial resistance of the filter material. The more adhesive is added, the higher the low-temperature resistance of the filter material can be. However, excessive addition will clog the pores and reduce the pore uniformity, resulting in an increase in initial resistance. The present application effectively disperses the fibers under ultrasonic and compressed air conditions, while adding additives and controlling the emulsion concentration in a lower range, so that the resin molecules are uniformly attached to the fibers in a smaller amount. This ensures the low-temperature resistance effect while obtaining a higher porosity and good uniformity, resulting in a lower initial resistance of the filter material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A flow chart of the preparation method of the low temperature resistant high efficiency air filter material provided in this application; Figure 2 This is a schematic diagram of a low temperature resistant and high efficiency air filter material prepared in an embodiment of the present application; Figure 3 This is a SEM image of the low-temperature resistant and high-efficiency air filter material prepared in the examples of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0022] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, a first response message and a second response message are used to distinguish different response messages rather than to describe a specific order of the response messages.

[0023] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0024] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more than two. For example, multiple processing units refer to two or more processing units, etc.; multiple elements refer to two or more elements, etc.

[0025] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0026] Example 1 (1) By mass percentage, 73% of polyimide resin (polyimide resin molecular weight is 4×10 4 ), 10% polystyrene, 7% silicone acrylic resin toughening agent and 10% silane coupling agent are mixed in a reaction kettle, and then gradually heated to a temperature of 60±2°C and continuously stirred for 15 minutes to form a modified polyimide resin emulsion; (2) adding a dispersion liquid to the modified polyimide resin emulsion. In this embodiment, the dispersion liquid is deionized water, and stirring for 20 minutes to dilute the emulsion to a mass concentration of 3%; (3) adding octaaminopropylsiloxane to the diluted emulsion obtained in step (2) at a mass ratio of diluted emulsion to activator of 100:6 for activation treatment to obtain an activated emulsion; (4) Submicron glass fiber and polyester fiber were weighed in a mass ratio of 6:1. The average diameter of the submicron glass fiber was 0.6 μm, and the average diameter of the polyester fiber was 8 μm and the average length was 5 mm. The two weighed fibers were added into clean water to a fiber concentration of 0.5%. The fibers were first dispersed under stirring and ultrasonic conditions for 20 min, and then dispersed by passing compressed air for 5 min to form a fiber suspension. (5) dehydrating the dispersed fiber suspension to form a wet filter material (i.e., the first wet filter material); (6) adding the wet filter material to the activated emulsion obtained in step (3), and adding polyoxypropylene-ethylene oxide copolyether at a mass ratio of 1:100, and again introducing compressed air to disperse for 5 minutes to form a fiber suspension; (7) Dehydrating the dispersed fiber suspension to form a wet filter material (i.e., the second wet filter material), wherein the moisture content of the wet filter material is 75±2%; (8) The wet filter material is treated with a plasma beam. The discharge power of the plasma beam is 100 W, the voltage applied to the upper and lower positive and negative electrodes is 100 V, the time is 30 s, and the frequency of the excitation source is 40 kHz; (9) The treated wet filter material is heated in a drying oven with 180°C hot air for 5 minutes to form a quantitative 70g / m 2 , filter material with a filtration efficiency of 99.5% (0.3μm particle size test).

[0027] The photo and SEM image (scanning electron microscope) of the filter material prepared in Example 1 are shown in Figure 2 and Figure 3 It can be seen that the macroscopic appearance of the filter material is flake-shaped, and its microscopic structure is obtained by bonding glass fibers and polyester fibers of different lengths and diameters with the above-mentioned diluted emulsion as an adhesive.

[0028] Example 2 This embodiment provides a method for preparing a low temperature resistant high efficiency air filter material, which specifically comprises the following steps: (1) 80% of polyimide resin (polyimide resin molecular weight is 5×10 4 ), 7% polystyrene, 6% silicone acrylic resin toughening agent and 7% silane coupling agent were put into a reaction kettle and mixed, and heated and stirred at a temperature of 60±2°C for 18 minutes to form an emulsion; (2) Add deionized water to the emulsion and dilute it to a mass concentration of 5% with stirring for 25 minutes to form a diluted emulsion; (3) adding phenylaminopropyltrimethoxysilane to the diluted emulsion obtained in step (2) at a mass ratio of diluted emulsion to activator of 100:5 for activation treatment to obtain an activated emulsion; (4) Submicron glass fiber with an average diameter of 0.3 μm and polyester fiber with an average diameter of 10 μm and a length of 5.5 mm were weighed in a mass ratio of 7:1, and then the two weighed fibers were added to clean water to obtain a mixed solution with a fiber concentration of 0.7%; the fiber mixed solution was first dispersed under stirring and ultrasonic conditions for 15 minutes, and then compressed air was introduced for dispersion for 7 minutes to form a fiber suspension; (5) dehydrating the fiber suspension after dispersion treatment to form a wet filter material (i.e., the first wet filter material); (6) adding the wet filter material obtained in step (5) to the activated emulsion obtained in step (3), and adding polyoxyalkylene-polysiloxane at a mass ratio of 1:100, and passing compressed air again for dispersion treatment for 7 minutes to form a fiber suspension; (7) Dehydrating the dispersed fiber suspension to form a wet filter material, wherein the moisture content of the wet filter material is 80±2%; (8) The surface of the wet filter material is treated with a plasma beam. The plasma beam discharge power is 200 W, the voltage applied to the upper and lower positive and negative electrodes is 150 V, the time is 20 s, and the frequency of the excitation source is 50 KHz; (9) The treated wet filter material was heated in a drying oven with hot air at 170°C for 8 minutes to form a quantitative 73g / m 2 , filter material with a filtration efficiency of 99.9% (tested with 0.3μm particle size).

[0029] Example 3 This embodiment provides a method for preparing a low temperature resistant high efficiency air filter material, which specifically comprises the following steps: (1) 86% of polyimide resin (polyimide resin molecular weight is 7×10 4 ), 5% polystyrene, 4% toughening agent and 5% silane coupling agent were put into a reaction kettle and mixed, and the mixture was heated and stirred at a temperature of 60±2℃ for 20min to form an emulsion; (2) Add deionized water to the emulsion and stir to dilute it to a liquid mass concentration of 6% for 30 minutes to form a diluted emulsion; (3) adding the diluted emulsion obtained in step (2) to octaaminopropyl siloxane at a mass ratio of the diluted emulsion to octaaminopropyl siloxane of 100:3 for activation treatment to obtain an activated emulsion; (4) Submicron glass fibers with an average diameter of 0.8 μm and polyester fibers with an average diameter of 6 μm and a length of 6 mm were weighed in a mass ratio of 8:1, and the two weighed fibers were added into clean water to obtain a fiber mixture with a fiber concentration of 0.8%; the fiber mixture was first dispersed under stirring and ultrasonic conditions for 10 minutes, and then dispersed by passing compressed air for 10 minutes to form a fiber suspension; (5) dehydrating the dispersed fiber suspension to form a wet filter material (i.e., the first wet filter material); (6) adding the wet filter material to the activated emulsion obtained in step (3), and adding polyoxypropylene-ethylene oxide copolyether to the activated emulsion at a mass ratio of 1:100, and passing compressed air again for dispersion treatment for 10 minutes to form a fiber suspension; (7) Dehydrating the dispersed fiber suspension to form a wet filter material, wherein the moisture content of the wet filter material is 85±2%; (8) The surface of the wet filter material is treated with a plasma beam. The discharge power of the plasma beam is 300 W, the voltage applied to the upper and lower positive and negative electrodes is 200 V, the time is 10 s, and the frequency of the excitation source is 60 KHz; (9) The treated wet filter material is heated in a drying oven at 160°C for 10 minutes to form a quantitative 75g / m 2 , filter material with an efficiency of 99% (tested with 0.3μm particle size).

[0030] Comparative Example 1 The main difference between this comparative example and Example 1 is that the mass concentration of the diluted emulsion in step (2) is 8%.

[0031] Comparative Example 2 The main difference between this comparative example and Example 1 is that the mass concentration of the diluted emulsion in step (2) is 1%.

[0032] Comparative Example 3 The main difference between this comparative example and Example 1 is that only polyimide resin and silane coupling agent are added in step (1).

[0033] Comparative Example 4 The main difference between this comparative example and Example 1 is that no polystyrene is added in step (1).

[0034] Comparative Example 5 The main difference between this comparative example and Example 1 is that no toughening agent is added in step (1).

[0035] Comparative Example 6 The main difference between this comparative example and Example 1 is that there is no dilution treatment step (2).

[0036] Comparative Example 7 The main difference between this comparative example and Example 1 is that there is no activation treatment step (3).

[0037] Comparative Example 8 The main difference between this comparative example and Example 1 is that in step (4), the fiber mixture is only dispersed under stirring and ultrasonic conditions without introducing compressed air.

[0038] Comparative Example 9 The main difference between this comparative example and Example 1 is that in step (4), only compressed air is introduced for dispersion treatment, and stirring and ultrasonic dispersion treatment are not performed.

[0039] Comparative Example 10 The main difference between this comparative example and Example 1 is that no auxiliary agent is added in step (6), and only compressed air is introduced for dispersion treatment.

[0040] Comparative Example 11 The main difference between this comparative example and Example 1 is that the moisture content of the wet filter material in step (7) is 70%.

[0041] Comparative Example 12 The main difference between this comparative example and Example 1 is that the water content of the wet filter material in step (7) is 90%.

[0042] Comparative Example 13 The main difference between this comparative example and Example 1 is that there is no step (8), that is, the wet filter material (the second wet filter material) is not treated with a plasma beam.

[0043] Measurement items and methods: The filter materials prepared in Examples 1 to 3 and Comparative Examples 1 to 13 were subjected to initial resistance and low temperature tests, i.e., kept at -60°C for 72 hours, and the filtration efficiency and tensile strength of various filter materials before and after the initial resistance and low temperature tests were tested and compared. The test conditions are as follows: (1) Initial resistance: in accordance with test standard EN143:2006; (2) Filtration efficiency: in accordance with test standard EN143:2006; (3) Tensile strength: in accordance with the test standard GB / T12914-2018; The performance test results are shown in Table 1 below.

[0044] Table 1 Performance test results

[0045] As can be seen from Table 1, the air filter materials prepared by the methods of Examples 1 to 3 are compared before and after the low-temperature test, and the filtration efficiency and tensile strength remain unchanged, both of which are 1.2 kN / m, indicating that the low-temperature resistant air filter materials prepared by the preparation method of the present application maintain the same filtration performance after low-temperature freezing. At the same time, it can be seen from Examples 1 to 3 that the smaller the average diameter of the submicron glass fiber, the greater the original filtration efficiency and initial resistance.

[0046] By comparing Example 1 with Comparative Example 1 and Comparative Example 2, it can be seen that the higher the concentration of the diluted emulsion, the higher the tensile strength of the filter material before and after the test, but its initial resistance also increases. On the contrary, as the concentration of the diluted emulsion decreases, although the initial resistance of the filter material before and after the low-temperature test decreases, the tensile strength also decreases. Therefore, the concentration of the diluted emulsion must be controlled within the range of 3% to 6%. Too much or too little will affect the performance of the filter material.

[0047] By comparing Example 1 and Comparative Example 3, it can be seen that the tensile strength (1.2 kN / m) and filtration efficiency (99.5%) of Example 1 before and after the low-temperature test are higher than those of Comparative Example 3 before and after the low-temperature test (1.0 kN / m before the test and 0.8 kN / m after the test) and filtration efficiency (99.5% before the test and 96.3% after the test), indicating that the addition of polystyrene and toughening agent in the present application can effectively improve the low-temperature resistance and strength properties of the filter material.

[0048] Comparison of Example 1 and Comparative Example 4 can further illustrate that the addition of polystyrene in the present application can effectively improve the low temperature resistance of the filter material.

[0049] Comparison of Example 1 and Comparative Example 5 can further illustrate that adding a toughening agent can effectively improve the strength performance of the filter material.

[0050] By comparing Example 1 and Comparative Example 6, it can be seen that when the modified polyimide resin emulsion is not diluted, although the filtration efficiency and tensile strength are improved, the initial resistance will also increase significantly, so the dilution step is essential.

[0051] By comparing Example 1 and Comparative Example 7, it can be seen that the initial resistance of the filter material after molding can be reduced from 254 Pa to 216 Pa by activating the diluted emulsion, which fully demonstrates that it is very necessary to activate the diluted emulsion.

[0052] By comparing Example 1, Comparative Example 8 and Comparative Example 9, it can be seen that the initial resistance of the filter material is higher when the dispersion is carried out only under the conditions of stirring and ultrasonic waves or when the dispersion is carried out only by passing compressed air than when the dispersion is carried out under both conditions. This fully demonstrates that the present invention first disperses under the conditions of stirring and ultrasonic waves and then disperses by passing compressed air, which can fully disperse the fibers and thus reduce the initial resistance of the filter material.

[0053] Comparing Example 1 and Comparative Example 10, it can be seen that the initial resistance of the filter material in Example 1 is less than that in Comparative Example 10. This indicates that the addition of an auxiliary agent during the preparation of Example 1 is beneficial to reducing the probability of the modified polyimide resin blocking the pores of the filter material, thereby reducing the initial resistance of the filter material. This fully demonstrates that it is very necessary to add an auxiliary agent during the preparation of low-temperature resistant air filter material.

[0054] By comparing Example 1 with Comparative Example 11 and Comparative Example 12 respectively, it can be seen that the initial resistance of Example 1 (216Pa) is smaller than that of Comparative Example 11 (242Pa) and Comparative Example 12 (247Pa). The moisture content of the wet filter material (i.e., the second wet filter material) before plasma beam treatment must be within an appropriate range. Too high or too low a moisture content will affect the plasma beam treatment effect, thereby affecting the adhesion effect of the modified polyimide resin on the fiber surface, causing the initial resistance of the molded air filter material to increase.

[0055] Comparing Example 1 and Comparative Example 13, the initial resistance of Example 1 (216Pa) is smaller than that of Comparative Example 13 (246Pa), which fully demonstrates that plasma beam treatment of wet filter materials can reduce the initial resistance of the air filter materials after molding, proving that plasma beam treatment of wet filter materials is very necessary.

[0056] In another embodiment, a low-temperature resistant and efficient air filter material is provided. The low-temperature resistant and efficient air filter material is prepared using the preparation method described in any of the previous embodiments. The prepared air filter material contains mixed fibers composed of glass fibers and polyester fibers, and the mixed fibers are bonded together by modified polyimide resin.

[0057] It should be understood that expressions such as "including" and "may include" that may be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0058] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0059] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the relative position relationship after connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0060] In addition, in the embodiments of the present application, the mathematical concepts mentioned are symmetry, equality, parallelism, verticality, etc. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense, and allow a small amount of deviation, approximation to symmetry, approximation to equality, approximation to parallelism, approximation to verticality, etc. are all possible. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0061] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a low temperature resistant high efficiency air filter material, characterized in that: include: S1: 73% to 86% of polyimide resin, 5% to 10% of polystyrene, 4% to 7% of toughening agent and 5% to 10% of silane coupling agent are mixed by mass percentage, heated and stirred to obtain a modified polyimide resin emulsion; S2 dilutes the modified polyimide resin emulsion and then performs activation treatment to obtain an activated emulsion; S3: adding glass fiber and polyester fiber in a preset ratio into the dispersion liquid for dispersion treatment to obtain a fiber suspension; Dehydrating the fiber suspension to obtain a first wet filter material; S4: adding the first wet filter material to the activated emulsion, and adding an auxiliary agent for dispersion treatment to obtain a fiber suspension; Dehydrating the fiber suspension to obtain a second wet filter material; S5: treating the second wet filter material by plasma beam irradiation, and then heating and drying the treated second wet filter material to obtain a low temperature resistant and high efficiency air filter material.

2. The preparation method according to claim 1, characterized in that In step S1, the molecular weight of the polyimide resin is 4×10 4 ~7×10 4 .

3. The preparation method according to claim 1, characterized in that: In step S1, the toughening agent is a silicone acrylic resin.

4. The preparation method according to claim 1, characterized in that: In step S1, the temperature of heating and stirring is 58°C to 62°C, and the heating and stirring time is 15min to 20min.

5. The preparation method according to claim 1, characterized in that: In step S2, the modified polyimide resin emulsion is diluted to obtain a diluted emulsion with a mass concentration of 3% to 6%; an accelerator is added to the diluted emulsion for activation treatment, and the mass ratio of the diluted emulsion to the accelerator is 100:3 to 100:6; the accelerator is a siloxane compound.

6. The preparation method according to claim 1, characterized in that: In step S3, the glass fiber has an average diameter of 0.3 μm ~1 μm flame-processed glass wool; and / or, the mass ratio of the glass fiber to the polyester fiber is 6:1 to 8:1; and / or, the fiber concentration in the fiber suspension is 0.5% to 0.8%; and / or, the dispersion treatment is carried out by stirring and ultrasonication, and the dispersion treatment time is 10 min to 20 min.

7. The preparation method according to claim 1, characterized in that: In step S4, the auxiliary agent is polyoxypropylene-ethylene oxide copolyether or polyoxyolefin-polysiloxane copolymer, and is dispersed by injecting compressed air, and the dispersion treatment time is 5min to 10min; and / or the mass ratio of the auxiliary agent to the activated emulsion is 1:100; and / or the water content of the second wet filter material is 73% to 87%.

8. The preparation method according to claim 1, characterized in that: In step S5, the discharge power of the plasma beam is 100W-300W, the voltage applied to the upper and lower positive and negative electrodes is 100-200V, the plasma beam irradiation time is 10s-30s, and the frequency of the plasma beam excitation source is 40KHz-60KHz.

9. The preparation method according to claim 1, characterized in that: In step S5, the heating and drying temperature is 160°C to 180°C, and the drying time is 5min to 10min.

10. A low temperature resistant high efficiency air filter material, characterized in that: The low-temperature resistant and high-efficiency air filter material is prepared by the preparation method described in any one of claims 1 to 9. The air filter material comprises mixed fibers consisting of glass fibers and polyester fibers, and a modified polyimide resin is adhered to the surface of the mixed fibers.

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