High-temperature-resistant filter cloth material and preparation method thereof

Abstract

The application discloses a high-temperature-resistant filter cloth material and a preparation method thereof, and belongs to the technical field of filter cloth materials. The filter cloth material is formed in a sandwich structure with PI superfine fiber web layers in the middle and glass fiber woven fabrics on both sides. The diameter of the PI superfine fiber web layers is in the nanometer level, and the PI superfine fiber web layers can efficiently intercept small-particle-size dust particles. The glass fiber woven fabrics serve as outer reinforcing materials and can provide a pre-filtering effect for the filter cloth. Large-particle-size dust particles are first intercepted, and the sandwich structure is used to improve the filtering effect. The PI superfine fiber web layers are treated in a special way, so that the interface of the layers can not be delaminated, debonded or fractured due to different thermal expansion and cold shrinkage coefficients of the layers, and the overall performance of the composite material is further damaged, especially the filtering performance and the mechanical strength are reduced. The application of the filter cloth material to industrial dust removal has good filtering effect, and the filter cloth material has excellent strength and toughness.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of filter cloth materials, and particularly relates to a high-temperature-resistant filter cloth material and a preparation method thereof. BACKGROUND

[0002] Industrial filter cloth is a filter medium woven from natural fibers and synthetic fibers, and is mainly used for solid-liquid separation, gas-solid separation and industrial dust removal; the existing synthetic fibers for industrial filter cloth mainly include polypropylene, polyester, nylon and vinylon, among which, polyester and polypropylene are most commonly used, and solid-liquid separation is mainly used, and the general industrial filter cloth also includes various metal material woven meshes such as stainless steel wire, nickel wire and brass wire. The weaving methods include plain weaving, twill weaving and satin weaving, and non-woven needle punching forming. The industrial filter cloth has the characteristics of high precision, high load, acid resistance, alkali resistance, temperature resistance, wear resistance and special filtering performance. However, the existing industrial filter cloth often works in a complex and harsh environment, and the mechanical strength of the industrial filter cloth is not high, so that the service life of the industrial filter cloth is greatly shortened if the strength of the industrial filter cloth is not high.

[0003] Glass fiber is an inorganic non-metallic material with excellent performance. It is made of glass balls or waste glass as raw materials through processes such as high-temperature melting, wire drawing, winding and weaving, and the diameter of the single fiber is several microns to twenty microns. Each bundle of fiber filaments is composed of hundreds or even thousands of single fibers. High strength is a prominent advantage of glass fiber, and the high strength characteristic makes glass fiber widely used. However, glass fiber also has obvious disadvantages, such as brittleness, poor folding resistance and poor wear resistance. In the process of use, frequent dust removal, easy wear and breakage affect the service life.

[0004] Therefore, there is an urgent need in the existing market to seek a filter cloth with high strength, wear resistance and long service life. At present, polytetrafluoroethylene (PTFE) fiber filter material, polyphenylene sulfide (PPS) fiber filter material, glass fiber filter material, ceramic fiber filter material and metal fiber filter material are used. However, the fiber diameter of these traditional filter materials is large, and the pore size of the fabric is also large, so there is almost no filtering effect on small particle size dust particles, and therefore the filter material cannot meet the current dust removal standard. SUMMARY

[0005] The purpose of the present application is to provide a high-temperature-resistant filter cloth material and a preparation method thereof. The PI ultra-fine fiber net layer in the middle and the glass fiber woven fabric on both sides form a sandwich structure, the diameter of the PI ultra-fine fiber net layer is in the nanometer level, and some small particle size dust particles can be efficiently intercepted. The glass fiber woven fabric not only serves as an outer reinforcing material, but also provides a pre-filtering effect for the filter cloth, so that large particle size dust particles are first intercepted, and the sandwich structure works together to improve the filtering effect.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] The application discloses a preparation method of a high-temperature-resistant filter cloth material.

[0008] Step one: anhydride-modified silsesquioxane is obtained by copolymerization of octaalkenyl silsesquioxane, alkenyl succinic anhydride and diethylene glycol divinyl ether under the action of benzoyl peroxide.

[0009] Step two: a silsesquioxane-modified polyamide acid solution is obtained by using octaalkenyl silsesquioxane, 4,4'-oxybisphthalic anhydride, 1,3-bis(4'-aminophenoxy) benzene and 3,5-diaminobenzoic acid as raw materials and N-methyl-2-pyrrolidone as a solvent.

[0010] Step three: PAA nanofiber membrane is obtained by electrospinning of the silsesquioxane-modified polyamide acid solution.

[0011] Step four: glass fiber woven fabric is used as the reinforcing layer of the upper layer and the lower layer respectively, and the PAA nanofiber membrane is used as the middle layer to be stitched, and then gradient temperature treatment is carried out, so that a "sandwich structure" composite filter material composed of the upper reinforcing layer, the middle PI ultrafine net filter layer and the lower reinforcing layer is formed, and the high-temperature-resistant filter cloth material is obtained.

[0012] Further, the preparation steps of the anhydride-modified silsesquioxane are as follows:

[0013] Octaalkenyl silsesquioxane and dichloromethane are poured into a four-necked flask provided with a rotating vane impeller, a reflux condenser, a thermometer and a nitrogen inlet, stirring is carried out under the protection of nitrogen at 20-25 DEG C and 500-600 r / min for 20-30 min, heating is carried out to 80-90 DEG C, then benzoyl peroxide, alkenyl succinic anhydride and diethylene glycol divinyl ether are added, and stirring is continuously carried out for 4-5 h, and the solvent is removed by rotary evaporation, so that the anhydride-modified silsesquioxane is obtained.

[0014] Further, the dosage ratio of octaalkenyl silsesquioxane, dichloromethane, benzoyl peroxide, alkenyl succinic anhydride and diethylene glycol divinyl ether is 20-30 g:90-100 g:1-2 g:20-25 g:3-5 g.

[0015] Further, the preparation steps of the silsesquioxane-modified polyamide acid solution are as follows:

[0016] 4,4'-O-diphthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene, 3,5-diaminobenzoic acid, and N-methyl-2-pyrrolidone were added to a reaction vessel and stirred for 20-30 min at 0-4℃ and 500-600 r / min under nitrogen protection. Then, the mixture was heated to 20-25℃ and stirred for 4-5 h. Then, anhydride-modified silsesquioxane was added and the mixture was stirred for 10-12 h to obtain a silsesquioxane-modified polyamic acid solution.

[0017] Furthermore, the ratio of 4,4'-oxophthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene, 3,5-diaminobenzoic acid, N-methyl-2-pyrrolidone and anhydride-modified silsesquioxane is 130-140g: 120-130g: 50-60g: 800-900mL: 80-90g.

[0018] Furthermore, the specific preparation steps of the PI ultrafine fiber network layer are as follows:

[0019] The silsesquioxane-modified polyamic acid solution was diluted to prepare silsesquioxane-modified polyamic acid diluents. The diluents were then magnetically stirred for 24-26 hours and ultrasonically dispersed for 1-2 hours. A suitable amount of the diluent was carefully drawn using a syringe needle, a 21G needle was attached, and the needle was fixed to the injection pump for spinning. Spinning was carried out under the following conditions: the injection pump extrusion rate was 0.2-0.4 mL / h, the output voltage of the high-voltage power supply was 11-13 kV, and the rotation speed of the collecting roller was 5-7 r / min. The positive terminal of the high-voltage power supply was applied to the needle, the collecting roller was grounded, the output voltage of the high-voltage power supply was adjusted, and spinning was started. A layer of milky white PAA nanofiber membrane was collected on the collecting device. The milky white PAA nanofiber membrane was dried at 80-90℃ for 6-7 hours to remove residual solvent, thus obtaining the PAA nanofiber membrane.

[0020] Furthermore, the mass concentration of the sesquioxane-modified polyamic acid diluent is 12wt%-14wt%.

[0021] Furthermore, the gradient temperature treatment involves heating to 100-110℃, 200-210℃, 300-310℃, and 350-360℃, holding each temperature for 30-50 minutes.

[0022] Furthermore, the specific preparation steps for the high-temperature resistant filter cloth material are as follows:

[0023] The receiving layer glass fiber woven fabric, PAA nanofiber membrane, and glass fiber woven fabric are sewn together in the direction perpendicular to the fabric surface using polyimide yarn, ultimately forming a "sandwich structure" composite filter material consisting of an upper reinforcing layer, a middle PI microfiber mesh filter layer, and a lower reinforcing layer. Then, a gradient heating treatment is performed to allow the PAA nanofiber mesh to undergo a gradient thermal cyclization reaction, resulting in a high-temperature resistant filter cloth material.

[0024] Furthermore, the fiberglass woven fabric is a double twill weave with a weight of 780 g / m². 2 .

[0025] Furthermore, the present invention also provides a high-temperature resistant filter cloth material, which is obtained by the above-mentioned method for preparing the high-temperature resistant filter cloth material.

[0026] The beneficial effects of this invention are:

[0027] 1. The high-temperature resistant filter cloth material of the present invention forms a sandwich structure, with a PI microfiber mesh layer in the middle and glass fiber woven fabric on both sides. Under high temperature environment, the PI microfiber mesh layer is specially treated to avoid the possibility of delamination, debonding or interface fracture caused by the different thermal expansion and contraction coefficients of the materials in each layer, which would further damage the overall performance of the composite material, especially the filtration performance and mechanical strength. It has a good filtration effect when applied to industrial dust removal, and at the same time has excellent strength, toughness and high temperature resistance.

[0028] 2. The PI ultrafine fiber mesh layer of the present invention is modified by polysilsesquioxane (POSS) modification of polyamic acid, grafting PSS onto the polyamic acid main chain, and then cyclizing it through a stepwise heating process. The PSS structure itself has extremely high thermal stability. When PSS is successfully doped or grafted onto the PI main chain or side chain, it can significantly increase the decomposition temperature and carbon residue of the PI material, which helps the material to serve for a long time in high-temperature environments. After the rigid cage structure of PSS is added, it restricts the movement of PI chain segments and reduces the flexibility of the molecular chain, thereby reducing the linear coefficient of thermal expansion (CTE) of the polyimide material. This is especially important for precision fields such as electronic device packaging. The inorganic cage structure of PSS enhances the overall rigidity of the material, but excessive addition will increase the brittleness of the material itself, reduce the elongation and fracture toughness. Therefore, by graft copolymerization, a performance balance can be achieved. Appropriate introduction of PSS can increase the modulus and strength of polyimide, avoiding the compatibility problems and self-aggregation caused by traditional direct addition, uneven dispersion, or excessive doping ratio, which leads to a decrease in mechanical properties.

[0029] 3. The diameter of the PI microfiber mesh layer is in the nanometer range, which can efficiently intercept some small-diameter dust particles. This avoids the poor filtration efficiency caused by the large fiber diameter and large pore size of traditional filter materials. Furthermore, by forming a sandwich structure, the glass fiber woven fabric, as the outer reinforcing material, can isolate some heat radiation and protect the PI microfiber mesh layer from direct thermal shock in high-temperature flue gas. The PI microfiber mesh layer maintains the shape of the filter layer through the rigid structure of the molecular chain, preventing the propagation of microcracks caused by the brittleness of the glass fiber. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] In a specific embodiment of the present invention, the glass fiber woven fabric is a double twill fabric with a weight of 780 g / m². 2 .

[0032] Example 1: A method for preparing a high-temperature resistant filter cloth material, comprising the following steps:

[0033] S1: Pour 20g of octaenyl silsesquioxane and 90g of dichloromethane into a four-necked flask equipped with a rotating blade impeller, a reflux condenser, a thermometer, and a nitrogen inlet. Under nitrogen protection, stir for 20min at 20℃ and 500r / min, heat to 80℃, then add 1g of benzoyl peroxide, 20g of alkenyl succinic anhydride, and 3g of diethylene glycol divinyl ether. Continue stirring and react for 4h. Remove the solvent by rotary evaporation to obtain anhydride-modified silsesquioxane.

[0034] S2: 130g of 4,4'-oxophthalic anhydride, 120g of 1,3-bis(4'-aminophenoxy)benzene, 50g of 3,5-diaminobenzoic acid and 800mL of N-methyl-2-pyrrolidone were added to a reaction vessel. Under nitrogen protection, the mixture was stirred at 0℃ and 500r / min for 20min. Then, it was heated to 20℃ and stirred for 4h. Then, 80g of anhydride-modified silsesquioxane was added and the mixture was stirred for 10h to obtain a silsesquioxane-modified polyamic acid solution.

[0035] S3: Dilute the silsesquioxane-modified polyamic acid solution to a 12wt% silsesquioxane-modified polyamic acid dilution. Then, magnetically stir the dilution for 24 hours and ultrasonically disperse it for 1 hour. Carefully draw an appropriate amount of the dilution with a syringe needle, attach a needle (21G) and fix it on the injection pump for spinning. Spinning is carried out under the conditions of an injection pump extrusion rate of 0.2mL / h, an output voltage of 11kV from the high voltage power supply, and a collection roller rotation speed of 5r / min. The positive terminal of the high voltage power supply is applied to the needle, the collection roller is grounded, the output voltage of the high voltage power supply is adjusted and spinning begins. A layer of milky white PAA nanofiber membrane will be collected on the collection device. The milky white PAA nanofiber membrane is dried at 80℃ for 6 hours to remove residual solvent, thus obtaining the PAA nanofiber membrane.

[0036] S4: Using polyimide yarn, the receiving layer glass fiber woven fabric, PAA nanofiber membrane, and glass fiber woven fabric are sewn together in the direction perpendicular to the fabric surface to form a "sandwich structure" composite filter material consisting of an upper reinforcing layer, a middle PI microfiber mesh filter layer, and a lower reinforcing layer. Then, it is heated to 110℃, 210℃, 310℃, and 360℃, with each temperature held for 40 minutes. This gradient heating treatment causes the PAA nanofiber mesh to undergo a gradient thermal cyclization reaction, resulting in a high-temperature resistant filter cloth material.

[0037] Example 2: A method for preparing a high-temperature resistant filter cloth material, comprising the following steps:

[0038] S1: 25g of octaenylsilsesquioxane and 95g of dichloromethane were poured into a four-necked flask equipped with a rotating blade impeller, a reflux condenser, a thermometer, and a nitrogen inlet. Under nitrogen protection, the mixture was stirred for 25min at 22.5℃ and 550r / min, heated to 85℃, and then 1.5g of benzoyl peroxide, 22g of alkenyl succinic anhydride, and 4g of diethylene glycol divinyl ether were added. The mixture was stirred and reacted for another 4.5h. The solvent was removed by rotary evaporation to obtain anhydride-modified silsesquioxane.

[0039] S2: 135g of 4,4'-oxophthalic anhydride, 125g of 1,3-bis(4'-aminophenoxy)benzene, 55g of 3,5-diaminobenzoic acid, and 850mL of N-methyl-2-pyrrolidone were added to a reaction vessel. Under nitrogen protection, the mixture was stirred at 2℃ and 550r / min for 25min. Then, the mixture was heated to 22.5℃ and stirred for 4.5h. Then, 85g of anhydride-modified silsesquioxane was added, and the mixture was stirred for 11h to obtain a silsesquioxane-modified polyamic acid solution.

[0040] S3: The silsesquioxane-modified polyamic acid solution was diluted to a mass concentration of 13wt% to obtain a silsesquioxane-modified polyamic acid diluent. The diluent was then magnetically stirred for 25 hours and ultrasonically dispersed for 1.5 hours. An appropriate amount of the diluent was carefully drawn with a syringe needle, a needle (21G) was attached and fixed to the injection pump for spinning. Spinning was carried out under the conditions of an injection pump extrusion rate of 0.3mL / h, a high voltage power supply output voltage of 12kV and a collecting roller rotation speed of 6r / min. The positive terminal of the high voltage power supply was applied to the needle, the collecting roller was grounded, the output voltage of the high voltage power supply was adjusted and spinning was started. A layer of milky white PAA nanofiber membrane was collected on the collecting device. The milky white PAA nanofiber membrane was dried at 85℃ for 6.5 hours to remove residual solvent, and the PAA nanofiber membrane was obtained.

[0041] S4: Using polyimide yarn, the receiving layer glass fiber woven fabric, PAA nanofiber membrane, and glass fiber woven fabric are sewn together in the direction perpendicular to the fabric surface to form a "sandwich structure" composite filter material consisting of an upper reinforcing layer, a middle PI microfiber mesh filter layer, and a lower reinforcing layer. Then, it is heated to 110℃, 210℃, 310℃, and 360℃, with each temperature held for 40 minutes. This gradient heating treatment causes the PAA nanofiber mesh to undergo a gradient thermal cyclization reaction, resulting in a high-temperature resistant filter cloth material.

[0042] Example 3: A method for preparing a high-temperature resistant filter cloth material, comprising the following steps:

[0043] S1: Pour 30g of octaenylsilsesquioxane and 100g of dichloromethane into a four-necked flask equipped with a rotating blade impeller, a reflux condenser, a thermometer, and a nitrogen inlet. Under nitrogen protection, stir for 30min at 25℃ and 600r / min, heat to 90℃, then add 2g of benzoyl peroxide, 25g of alkenyl succinic anhydride, and 5g of diethylene glycol divinyl ether. Continue stirring and react for 5h. Remove the solvent by rotary evaporation to obtain anhydride-modified silsesquioxane.

[0044] S2: 140g of 4,4'-oxophthalic anhydride, 130g of 1,3-bis(4'-aminophenoxy)benzene, 60g of 3,5-diaminobenzoic acid, and 900mL of N-methyl-2-pyrrolidone were added to a reaction vessel. Under nitrogen protection, the mixture was stirred at 4℃ and 600r / min for 30min. Then, the mixture was heated to 25℃ and stirred for 5h. Then, 90g of anhydride-modified silsesquioxane was added and the mixture was stirred for 12h to obtain a silsesquioxane-modified polyamic acid solution.

[0045] S3: The silsesquioxane-modified polyamic acid solution was diluted to a mass concentration of 14wt% to obtain a silsesquioxane-modified polyamic acid diluent. The diluent was then magnetically stirred for 26 hours and ultrasonically dispersed for 2 hours. An appropriate amount of the diluent was carefully drawn with a syringe needle, a needle (21G) was attached and fixed to the injection pump for spinning. Spinning was carried out under the conditions of an injection pump extrusion rate of 0.4mL / h, a high voltage power supply output voltage of 13kV and a collection roller rotation speed of 7r / min. The positive terminal of the high voltage power supply was applied to the needle, the collection roller was grounded, the output voltage of the high voltage power supply was adjusted and spinning was started. A layer of milky white PAA nanofiber membrane was collected on the collection device. The milky white PAA nanofiber membrane was dried at 90℃ for 7 hours to remove residual solvent, and the PAA nanofiber membrane was obtained.

[0046] S4: Using polyimide yarn, the receiving layer glass fiber woven fabric, PAA nanofiber membrane, and glass fiber woven fabric are sewn together in the direction perpendicular to the fabric surface to form a "sandwich structure" composite filter material consisting of an upper reinforcing layer, a middle PI microfiber mesh filter layer, and a lower reinforcing layer. Then, it is heated to 110℃, 210℃, 310℃, and 360℃, with each temperature held for 40 minutes. This gradient heating treatment causes the PAA nanofiber mesh to undergo a gradient thermal cyclization reaction, resulting in a high-temperature resistant filter cloth material.

[0047] Comparative Example 1: Based on Example 3, the octaenyl silsesquioxane in step S1 was omitted.

[0048] Comparative Example 2: Based on Example 3, the anhydride-modified silsesquioxane in step S2 was replaced with the octaenyl silsesquioxane in step S1.

[0049] Comparative Example 3: Based on Example 3, the diethylene glycol divinyl ether in step S1 was removed, and silsesquioxane was directly attached to the polyimide backbone only through the anhydride group.

[0050] The performance of the high-temperature resistant filter cloth materials obtained in Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in Table 1:

[0051] 1. Filtration efficiency test: Refer to the test standard GB / T 6165-2021 "Performance Test Method for High-Efficiency Air Filters - Efficiency and Resistance", which specifies the use of 0.3μm standard dust (NaCl aerosol), and the concentration difference before and after filtration is measured by a particle counter to calculate the efficiency.

[0052] 2. Strength test: Refer to the test standard GB / T 7689.5-2013 "Test method for tensile strength of reinforced woven fabrics", use 250mm×25mm specimens, tensile rate of 10mm / min, and record the warp breaking strength.

[0053] 3. Elongation at break test: Refer to the test standard GB / T 7689.5-2013, conduct the test simultaneously with the strength test, and record the elongation at break.

[0054] 4. Temperature Resistance Test: Referring to the test standard HJ / T 324-2006, the test temperature is 200℃. The filter material sample is continuously heated at the set high temperature, and the breaking strength after heating for 100 hours is measured and compared with the breaking strength of the original unheated sample to calculate the strength retention rate.

[0055] Table 1. Performance Test Table of High Temperature Resistant Filter Cloth Materials

[0056] Item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Filtering efficiency (%) 99.3 99.5 99.8 81.2 82.9 71.3 Strength (CN) 473 482 493 401 416 379 Elongation at break (%) 44.8 46.5 48.2 32.6 33.8 27.5 Temperature resistance (%) 91.6 92.5 93.5 78.3 76.5 65.3

[0057] As can be seen from Table 1, the filtration efficiency, strength and elongation at break of the high-temperature resistant filter cloth materials obtained in Examples 1-3 are significantly better than those in the comparative examples. This indicates that the high-temperature resistant filter cloth materials prepared by the present invention have a good filtration effect when applied to industrial dust removal, and at the same time have excellent strength, toughness and high-temperature resistance.

[0058] In Comparative Example 1, the octaenyl silsesquioxane was discarded, and in step S1, the octaenyl POSS was directly discarded. Only alkenyl succinic anhydride and diethylene glycol divinyl ether were used for the reaction. The cage-like siloxane structure of POSS can improve the high temperature resistance of polyimide. After discarding it, the molecular chain of the PI microfiber mesh layer may break at temperatures above 300°C, causing the filter cloth to soften and deform easily in high-temperature flue gas, resulting in loss of filtration efficiency. The rigid cage-like structure of POSS can inhibit the thermal motion of PI chain segments and reduce CTE. After its absence, the difference in thermal expansion between the PI layer and the glass fiber layer increases, and the interface is prone to delamination. The filter cloth fails prematurely under alternating hot and cold conditions. POSS enhances the intermolecular forces of PI through grafting and improves the breaking strength. After its absence, the nanofiber membrane becomes more brittle, and the scouring of the cleaning airflow may cause the fiber web to break.

[0059] In Comparative Example 2, the anhydride-modified silsesquioxane was replaced with octaenyl silsesquioxane. The active groups of the anhydride-modified POSS can react with the amino groups of polyamic acid to form chemical bonds, ensuring uniform dispersion. The alkenyl groups of the unmodified POSS cannot react with polyamic acid, causing POSS to agglomerate in the solution. The inert surface of the unmodified POSS cannot participate in the imidization reaction. When the temperature is increased by gradient, micropores are generated between POSS and the polyimide matrix, reducing the fiber density. The agglomerated POSS becomes a stress concentration point, resulting in a decrease in the breaking strength of the PI microfiber web.

[0060] In Comparative Example 3, diethylene glycol divinyl ether was omitted. The unmodified POSS surface has a rigid cage structure. When it is directly bonded to the polyimide chain, stress concentration points are formed at the interface due to the large difference in modulus. Under external force, microcracks are easily induced. Diethylene glycol divinyl ether can give the rigid cage structure flexible properties. Without the buffer of flexible chain, POSS acts as a rigid point to hinder dislocation slip, and the elongation at break of the material decreases significantly.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a high-temperature resistant filter cloth material, characterized in that, Includes the following steps: Step 1: Anhydride-modified silsesquioxane is obtained by copolymerizing octaenyl silsesquioxane, alkenyl succinic anhydride and diethylene glycol divinyl ether under the action of benzoyl peroxide. Step 2: A silsesquioxane-modified polyamic acid solution is obtained by using anhydride-modified silsesquioxane, 4,4'-oxobisphthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene and 3,5-diaminobenzoic acid as raw materials and N-methyl-2-pyrrolidone as solvent. Step 3: The silsesquioxane-modified polyamic acid solution is electrospun to obtain PAA nanofiber membranes; Step 4: Use glass fiber woven fabric as the outer and bottom reinforcing layers respectively, and PAA nanofiber membrane as the middle layer for sewing. Then, after gradient heating treatment, high temperature resistant filter cloth material is obtained.

2. The method for preparing a high-temperature resistant filter cloth material according to claim 1, characterized in that, The specific preparation steps for the anhydride-modified silsesquioxane are as follows: Octadenyl silsesquioxane and dichloromethane were poured into a four-necked flask equipped with a rotating blade impeller, a reflux condenser, a thermometer, and a nitrogen inlet. Under nitrogen protection, the mixture was stirred for 20-30 minutes at 20-25°C and 500-600 r / min. The mixture was then heated to 80-90°C, and benzoyl peroxide, alkenyl succinic anhydride, and diethylene glycol divinyl ether were added. The mixture was stirred and reacted for another 4-5 hours. The solvent was removed by rotary evaporation to obtain anhydride-modified silsesquioxane.

3. The method for preparing a high-temperature resistant filter cloth material according to claim 2, characterized in that, The ratio of the amounts of octaenyl silsesquioxane, dichloromethane, benzoyl peroxide, alkenyl succinic anhydride, and diethylene glycol divinyl ether is 20-30g: 90-100g: 1-2g: 20-25g: 3-5g.

4. The method for preparing a high-temperature resistant filter cloth material according to claim 1, characterized in that, The specific preparation steps of the silsesquioxane-modified polyamic acid solution are as follows: 4,4'-O-diphthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene, 3,5-diaminobenzoic acid, and N-methyl-2-pyrrolidone were added to a reaction vessel and stirred for 20-30 min at 0-4℃ and 500-600 r / min under nitrogen protection. Then the mixture was heated to 20-25℃ and stirred for 4-5 h. Then anhydride-modified silsesquioxane was added and the mixture was stirred for 10-12 h to obtain a silsesquioxane-modified polyamic acid solution.

5. The method for preparing a high-temperature resistant filter cloth material according to claim 4, characterized in that, The ratio of the amounts of 4,4'-oxophthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene, 3,5-diaminobenzoic acid, N-methyl-2-pyrrolidone, and anhydride-modified silsesquioxane is 130-140g: 120-130g: 50-60g: 800-900mL: 80-90g.

6. The method for preparing a high-temperature resistant filter cloth material according to claim 1, characterized in that, The specific preparation steps of the PAA nanofiber membrane are as follows: The silsesquioxane-modified polyamic acid solution was diluted to prepare silsesquioxane-modified polyamic acid diluents. The diluents were then magnetically stirred for 24-26 hours and ultrasonically dispersed for 1-2 hours. A suitable amount of the diluent was carefully drawn using a syringe needle, which was then attached to the syringe pump for spinning. Spinning was carried out under the following conditions: the syringe pump extrusion rate was 0.2-0.4 mL / h, the output voltage of the high-voltage power supply was 11-13 kV, and the rotation speed of the collecting roller was 5-7 r / min. The positive terminal of the high-voltage power supply was applied to the needle, the collecting roller was grounded, the output voltage of the high-voltage power supply was adjusted, and spinning was started. A layer of milky white PAA nanofiber membrane was collected on the collecting device. The milky white PAA nanofiber membrane was dried at 80-90℃ for 6-7 hours to remove residual solvent, thus obtaining the PAA nanofiber membrane.

7. The method for preparing a high-temperature resistant filter cloth material according to claim 6, characterized in that, The mass concentration of the sesquioxane-modified polyamic acid diluent is 12wt%-14wt%.

8. The method for preparing a high-temperature resistant filter cloth material according to claim 6, characterized in that, The gradient heating process involves heating to 100-110℃, 200-210℃, 300-310℃, and 350-360℃, with each temperature held for 30-50 minutes.

9. The method for preparing a high-temperature resistant filter cloth material according to claim 1, characterized in that, The specific preparation steps for the high-temperature resistant filter cloth material are as follows: The receiving layer glass fiber woven fabric, PAA nanofiber membrane, and glass fiber woven fabric are sewn together in the direction perpendicular to the fabric surface using polyimide yarn, and finally a "sandwich structure" composite filter material consisting of an upper reinforcing layer, a middle PAA nanofiber membrane filter layer, and a lower reinforcing layer is formed. Gradient heating treatment is used to make the PAA nanofiber membrane undergo a gradient thermal cyclization reaction to obtain a high-temperature resistant filter cloth material.

10. A high-temperature resistant filter cloth material, characterized in that, It is obtained by the method for preparing the high-temperature resistant filter cloth material according to any one of claims 1-9.