A fiber composite needled filter material and a method for producing the same

Abstract

This invention relates to the field of dust removal filter media technology, specifically to a fiber composite needle-punched filter media and its preparation method. To enhance the high-temperature performance of the needle-punched filter media, this invention adds modified carbon fiber material to polyethylene terephthalate (PET). This invention further enhances the compatibility and bonding strength between the carbon nanofibers and PET by oxidizing the surface and then carboxylating it, introducing fluorine elements onto the carbon fiber surface, and further preparing a PET-like structure. This significantly increases the compatibility and bonding strength between the carbon nanofibers and PET. Simultaneously, the fluorine introduced in this process significantly improves the stability of polyester fibers at high temperatures and enhances their resistance to chemical corrosion such as acids and alkalis, thereby improving the service life of the filter media in high-temperature flue gas.

Description

Technical Field

[0001] This invention relates to the field of dust removal filter material technology, specifically to a fiber composite needle-punched filter material and its preparation method. Background Technology

[0002] In recent years, with the development of my country's industry, the air pollution caused by industry has received increasing attention. At present, atmospheric dust pollution accounts for a large proportion of industrial pollution. Fine dust generated by various industries will remain suspended in the atmosphere for a long time, causing a decline in air quality and affecting human health. Therefore, composite fiber filter media are often used in the industrial field to treat exhaust gas.

[0003] Patent CN201611224888.2 discloses a manufacturing process for medium and low temperature filter media, which uses polyester as the main raw material. Polyester fiber has excellent mechanical properties, but its performance will be severely degraded in high temperature environments, especially in environments with temperatures exceeding 150°C, and it cannot meet the filtration treatment of high temperature gases. Therefore, it is necessary to study this defect in order to meet market demand. Summary of the Invention

[0004] The purpose of this invention is to provide a fiber composite needle-punched filter material and its preparation method to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a fiber composite needle-punched filter material, having the following technical features: by weight fraction, the fiber composite needle-punched filter material is composed of a base fabric and fiber layers covering the upper and lower surfaces of the base fabric;

[0006] The fiber layer contains 60-85% high-temperature resistant polyester fiber by weight, with the remainder being reinforcing fiber.

[0007] The reinforcing fiber is either polyphenylene sulfide fiber or PTFE fiber.

[0008] Furthermore, by weight, the high-temperature resistant polyester fiber is composed of 45-65 parts polyethylene terephthalate, 5-15 parts modified carbon nanofibers, 0.08-0.15 parts antioxidant, 0.3-0.45 parts antistatic agent, and 0.1-0.2 parts dispersant;

[0009] The antioxidant is either 2,5-di-tert-butylhydroquinone or N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine; the antistatic agent is potassium acetate; and the dispersant is stearic acid.

[0010] Furthermore, the base fabric is a PPS base fabric.

[0011] Furthermore, a method for preparing a fiber composite needle-punched filter material includes the following steps:

[0012] S1. Preparation of modified carbon nanofibers;

[0013] S11. Disperse carbon nanofibers in concentrated sulfuric acid, heat to 80±5℃, add potassium persulfate, stir and react for 5-8 hours, cool to 10±5℃, add sodium nitrate and potassium permanganate, heat to 40±5℃, stir and react for 4-6 hours, centrifuge to separate the precipitate, wash the precipitate 3-5 times with hydrogen peroxide and dilute hydrochloric acid respectively, disperse the carbon nanofibers again in deionized water, add monochloroacetic acid and sodium hydroxide, heat to 50±5℃, stir and react for 4-5 hours, centrifuge to separate the precipitate, and vacuum dry to constant weight to obtain carboxylated carbon nanofibers;

[0014] S12. Add 10-15% by volume of deionized water to glycerol, mix for 5-10 min, then add sodium hydroxide, continue stirring and mixing for 2-15 min, then under nitrogen atmosphere protection, add perfluoro2-methyl-3-oxahexanoic acid dropwise, stirring continuously during the dropwise addition. After the dropwise addition is completed, heat the mixture to 95±3℃, reflux for 2-8 h, remove excess solvent by rotary evaporation, wash the reaction product 1-3 times with deionized water at 3±2℃, and then evaporate under vacuum to constant weight to obtain the fluoroalcohol intermediate.

[0015] S13. Disperse the carboxylated carbon nanofibers obtained in step S11 into perfluorooctane, sonicate for 25-60 min, then under nitrogen atmosphere protection, add the fluoroalcohol intermediate prepared in step S12, heat to 85±10℃, stir for 4-12 h, centrifuge to separate the precipitate, wash 2-3 times with pure perfluorooctane, heat to 110℃ and dry for 24 h, then disperse the dried product again in toluene, sonicate for 30-45 min, add p-toluenesulfonic acid, continue mixing for 3-5 min, add benzoic acid, heat to 110±5℃, react for 1.5-8 h, centrifuge to separate the precipitate, wash 2-3 times with toluene, and vacuum dry to constant weight to obtain modified carbon nanofibers;

[0016] S2. Preparation of high-temperature resistant polyester fibers;

[0017] S21. Polyethylene terephthalate chips are mixed with modified carbon nanofibers, premixed at 230±10℃ for 5-10 min, antioxidants, antistatic agents and dispersants are added, and mixing is continued for 3-5 min. The mixture is then extruded into chips to obtain high-temperature resistant polyester masterbatch.

[0018] S22. High-temperature resistant polyester masterbatch is melt-spun to obtain high-temperature resistant polyester fiber;

[0019] S3. Preparation of fiber composite needle-punched filter media;

[0020] After mixing high-temperature resistant polyester fibers and reinforcing fibers in a certain proportion, the fibers are carded and laid to form a fiber layer. The fiber layer is then applied to the upper and lower surfaces of the base fabric. After needle punching, the surface is coated with polytetrafluoroethylene emulsion and dried to form a fiber composite needle punched filter material.

[0021] Furthermore, in step S11, the mass ratio of the nanofibers, potassium persulfate, sodium nitrate and potassium permanganate is 1:(3-5):(1-5):(5-10) by weight.

[0022] The mass ratio of the nanofibers, monochloroacetic acid, and sodium hydroxide is 1:(3-5):(4-5).

[0023] Furthermore, in step S12, the mass ratio of glycerol, sodium hydroxide, and perfluoro2-methyl-3-oxahexanoic acid is 10:(0.2-0.6):(10-95) by weight.

[0024] Furthermore, in step S13, the mass ratio of the carboxylated carbon nanofibers to the fluoroethanol intermediate is 1:(0.5-4) by weight.

[0025] Furthermore, in step S13, the mass ratio of the carboxylated carbon nanofibers, p-toluenesulfonic acid, and benzoic acid is 1:(0.02-0.04):(0.5-5) by weight.

[0026] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0027] In order to enhance the high-temperature performance of needle-punched filter media, the present invention improves the raw materials of the filter media by adding modified carbon fiber material to polyethylene terephthalate.

[0028] In the process of preparing modified carbon fiber materials, the present invention first oxidizes the carbon nanofibers by using the strong oxidizing power of substances such as concentrated sulfuric acid and potassium permanganate to generate active groups such as epoxy groups on the surface of the carbon nanofibers. Then, carboxyl groups are further generated on the surface of the carbon nanofibers using raw materials such as monochloroacetic acid.

[0029] Based on this, the present invention uses glycerol as a raw material and reacts it with perfluoro2-methyl-3-oxahexanoic acid to obtain a fluoroalcohol intermediate containing a large amount of fluorine. Then, it is mixed with carboxylated carbon nanofibers with carboxyl groups on the surface, thereby introducing fluorine and alcohol hydroxyl groups into the surface of the carbon nanofibers. Subsequently, it reacts with benzoic acid to generate a terephthalate-like structure on the surface of the carbon nanofibers, which greatly increases the compatibility and bonding strength between the carbon nanofibers and polyethylene terephthalate. At the same time, the fluorine introduced in this process can greatly improve the stability of polyester fibers at high temperatures and enhance their resistance to chemical corrosion such as acids and alkalis, thereby improving their service life in high-temperature flue gas. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The base fabric used in this application is made of 1.5D*51mm textile with 150 warp yarns / 10cm and a weft yarn density of 60 warp yarns / 10cm.

[0032] The carbon nanofibers used have a diameter × length of 100nm × 20-200μm and a density of 1.9g / mL;

[0033] The polyethylene terephthalate chips used were type B2520 polyethylene terephthalate;

[0034] The polytetrafluoroethylene emulsion used has a solid content of 28%;

[0035] Example 1. A method for preparing a fiber composite needle-punched filter material, comprising the following steps:

[0036] S1. Preparation of modified carbon nanofibers;

[0037] S11. By weight, 1 part of carbon nanofibers was dispersed in 95 parts of concentrated sulfuric acid, heated to 80°C, 4 parts of potassium persulfate were added, and the mixture was stirred for 5 hours. The mixture was then cooled to 5°C, 3 parts of sodium nitrate and 10 parts of potassium permanganate were added, the mixture was heated to 40°C, and the mixture was stirred for 4 hours. The precipitate was separated by centrifugation, and the precipitate was washed three times with hydrogen peroxide and dilute hydrochloric acid, respectively. The carbon nanofibers were then dispersed again in 100 parts of deionized water, 3 parts of monochloroacetic acid and 4 parts of sodium hydroxide were added, the mixture was heated to 55°C, and the mixture was stirred for 4 hours. The precipitate was then separated by centrifugation and vacuum dried to constant weight to obtain carboxylated carbon nanofibers.

[0038] S12. According to the weight parts, add 10% of the volume of deionized water to 10 parts of glycerol, mix for 5 min, add 0.3 parts of sodium hydroxide, continue stirring and mixing for 10 min, under nitrogen atmosphere protection, add 10 parts of perfluoro2-methyl-3-oxahexanoic acid dropwise, stirring continuously during the dropwise addition. After the dropwise addition is completed, heat the mixture to 98°C, reflux for 6 h, remove excess solvent by rotary evaporation, wash the reaction product twice with deionized water at 3°C, and then evaporate under vacuum to constant weight to obtain the fluoroalcohol intermediate;

[0039] S13. By weight, 1 part of the carboxylated carbon nanofibers obtained in step S11 were dispersed in perfluorooctane. After ultrasonic dispersion for 45 min, under nitrogen atmosphere protection, 0.5 parts of the fluoroalcohol intermediate prepared in step S12 were added, the temperature was raised to 85℃, and the reaction was stirred for 8 h. After centrifugation to separate the precipitate, the product was washed twice with pure perfluorooctane, and then dried at 110℃ for 24 h. The dried product was dispersed again in toluene, ultrasonically treated for 30 min, and then 0.02 parts of p-toluenesulfonic acid were added. After mixing for 4 min, 0.5 parts of benzoic acid were added, the temperature was raised to 110℃, and the reaction was carried out for 4 h. After centrifugation to separate the precipitate, the product was washed twice with toluene, and then vacuum dried to constant weight to obtain modified carbon nanofibers.

[0040] S2. Preparation of high-temperature resistant polyester fibers;

[0041] S21. By weight, 50 parts of polyethylene terephthalate chips and 5 parts of modified carbon nanofibers were mixed. After premixing at 240℃ for 8 minutes, 0.15 parts of 2,5-di-tert-butylhydroquinone antioxidant, 0.3 parts of potassium acetate antistatic agent, and 0.2 parts of stearic acid dispersant were added. After mixing for 3 minutes, the mixture was extruded into chips to obtain high-temperature resistant polyester masterbatch.

[0042] S22. High-temperature resistant polyester masterbatch is melt-spun to obtain high-temperature resistant polyester fiber with a diameter of 0.9D*51mm;

[0043] S3. Preparation of fiber composite needle-punched filter media;

[0044] By weight, 8 parts of high-temperature resistant polyester fiber and 2 parts of 1.2D*51mm PPS reinforcing fiber are mixed in a certain proportion and then carded and laid to form a fiber layer. The fiber layer is then applied to the upper and lower surfaces of the base fabric. After needle punching, the surface is coated with polytetrafluoroethylene emulsion and dried to form a fiber composite needle punched filter material.

[0045] Example 2. A method for preparing a fiber composite needle-punched filter material, comprising the following steps:

[0046] Compared with Example 1, this example increases the amount of modified carbon fiber added in step S21;

[0047] S1. Preparation of modified carbon nanofibers;

[0048] S11. By weight, 1 part of carbon nanofibers was dispersed in 95 parts of concentrated sulfuric acid, heated to 80°C, 4 parts of potassium persulfate were added, and the mixture was stirred for 5 hours. The mixture was then cooled to 5°C, 3 parts of sodium nitrate and 10 parts of potassium permanganate were added, the mixture was heated to 40°C, and the mixture was stirred for 4 hours. The precipitate was separated by centrifugation, and the precipitate was washed three times with hydrogen peroxide and dilute hydrochloric acid, respectively. The carbon nanofibers were then dispersed again in 100 parts of deionized water, 3 parts of monochloroacetic acid and 4 parts of sodium hydroxide were added, the mixture was heated to 55°C, and the mixture was stirred for 4 hours. The precipitate was then separated by centrifugation and vacuum dried to constant weight to obtain carboxylated carbon nanofibers.

[0049] S12. According to the weight parts, add 10% of the volume of deionized water to 10 parts of glycerol, mix for 5 min, add 0.3 parts of sodium hydroxide, continue stirring and mixing for 10 min, under nitrogen atmosphere protection, add 10 parts of perfluoro2-methyl-3-oxahexanoic acid dropwise, stirring continuously during the dropwise addition. After the dropwise addition is completed, heat the mixture to 98°C, reflux for 6 h, remove excess solvent by rotary evaporation, wash the reaction product twice with deionized water at 3°C, and then evaporate under vacuum to constant weight to obtain the fluoroalcohol intermediate;

[0050] S13. By weight, 1 part of the carboxylated carbon nanofibers obtained in step S11 were dispersed in perfluorooctane. After ultrasonic dispersion for 45 min, under nitrogen atmosphere protection, 0.5 parts of the fluoroalcohol intermediate prepared in step S12 were added, the temperature was raised to 85℃, and the reaction was stirred for 8 h. After centrifugation to separate the precipitate, the product was washed twice with pure perfluorooctane, and then dried at 110℃ for 24 h. The dried product was dispersed again in toluene, ultrasonically treated for 30 min, and then 0.02 parts of p-toluenesulfonic acid were added. After mixing for 4 min, 0.5 parts of benzoic acid were added, the temperature was raised to 110℃, and the reaction was carried out for 4 h. After centrifugation to separate the precipitate, the product was washed twice with toluene, and then vacuum dried to constant weight to obtain modified carbon nanofibers.

[0051] S2. Preparation of high-temperature resistant polyester fibers;

[0052] S21. By weight, 50 parts of polyethylene terephthalate chips and 15 parts of modified carbon nanofibers were mixed. After premixing at 240℃ for 8 minutes, 0.15 parts of 2,5-di-tert-butylhydroquinone antioxidant, 0.3 parts of potassium acetate antistatic agent, and 0.2 parts of stearic acid dispersant were added. After mixing for 3 minutes, the mixture was extruded into chips to obtain high-temperature resistant polyester masterbatch.

[0053] S22. High-temperature resistant polyester masterbatch is melt-spun to obtain high-temperature resistant polyester fiber with a diameter of 0.9D*51mm;

[0054] S3. Preparation of fiber composite needle-punched filter media;

[0055] By weight, 8 parts of high-temperature resistant polyester fiber and 2 parts of 1.2D*51mm PPS reinforcing fiber are mixed in a certain proportion and then carded and laid to form a fiber layer. The fiber layer is then applied to the upper and lower surfaces of the base fabric. After needle punching, the surface is coated with polytetrafluoroethylene emulsion and dried to form a fiber composite needle punched filter material.

[0056] Example 3. A method for preparing a fiber composite needle-punched filter material, comprising the following steps:

[0057] Compared with Example 1, this example increases the amount of fluoro2-methyl-3-oxahexanoic acid added in step S12;

[0058] S1. Preparation of modified carbon nanofibers;

[0059] S11. By weight, 1 part of carbon nanofibers was dispersed in 95 parts of concentrated sulfuric acid, heated to 80°C, 4 parts of potassium persulfate were added, and the mixture was stirred for 5 hours. The mixture was then cooled to 5°C, 3 parts of sodium nitrate and 10 parts of potassium permanganate were added, the mixture was heated to 40°C, and the mixture was stirred for 4 hours. The precipitate was separated by centrifugation, and the precipitate was washed three times with hydrogen peroxide and dilute hydrochloric acid, respectively. The carbon nanofibers were then dispersed again in 100 parts of deionized water, 3 parts of monochloroacetic acid and 4 parts of sodium hydroxide were added, the mixture was heated to 55°C, and the mixture was stirred for 4 hours. The precipitate was then separated by centrifugation and vacuum dried to constant weight to obtain carboxylated carbon nanofibers.

[0060] S12. According to the weight parts, add 10% of the volume of deionized water to 10 parts of glycerol, mix for 5 min, add 0.3 parts of sodium hydroxide, continue stirring and mixing for 10 min, under nitrogen atmosphere protection, add 95 parts of perfluoro2-methyl-3-oxahexanoic acid dropwise, stirring continuously during the dropwise addition. After the dropwise addition is completed, heat the mixture to 98°C, reflux for 6 h, remove excess solvent by rotary evaporation, wash the reaction product twice with deionized water at 3°C, and then evaporate under vacuum to constant weight to obtain the fluoroalcohol intermediate;

[0061] S13. By weight, 1 part of the carboxylated carbon nanofibers obtained in step S11 were dispersed in perfluorooctane. After ultrasonic dispersion for 45 min, under nitrogen atmosphere protection, 0.5 parts of the fluoroalcohol intermediate prepared in step S12 were added, the temperature was raised to 85℃, and the reaction was stirred for 8 h. After centrifugation to separate the precipitate, the product was washed twice with pure perfluorooctane, and then dried at 110℃ for 24 h. The dried product was dispersed again in toluene, ultrasonically treated for 30 min, and then 0.02 parts of p-toluenesulfonic acid were added. After mixing for 4 min, 0.5 parts of benzoic acid were added, the temperature was raised to 110℃, and the reaction was carried out for 4 h. After centrifugation to separate the precipitate, the product was washed twice with toluene, and then vacuum dried to constant weight to obtain modified carbon nanofibers.

[0062] S2. Preparation of high-temperature resistant polyester fibers;

[0063] S21. By weight, 50 parts of polyethylene terephthalate chips and 5 parts of modified carbon nanofibers were mixed. After premixing at 240℃ for 8 minutes, 0.15 parts of 2,5-di-tert-butylhydroquinone antioxidant, 0.3 parts of potassium acetate antistatic agent, and 0.2 parts of stearic acid dispersant were added. After mixing for 3 minutes, the mixture was extruded into chips to obtain high-temperature resistant polyester masterbatch.

[0064] S22. High-temperature resistant polyester masterbatch is melt-spun to obtain high-temperature resistant polyester fiber with a diameter of 0.9D*51mm;

[0065] S3. Preparation of fiber composite needle-punched filter media;

[0066] By weight, 8 parts of high-temperature resistant polyester fiber and 2 parts of 1.2D*51mm PPS reinforcing fiber are mixed in a certain proportion and then carded and laid to form a fiber layer. The fiber layer is then applied to the upper and lower surfaces of the base fabric. After needle punching, the surface is coated with polytetrafluoroethylene emulsion and dried to form a fiber composite needle punched filter material.

[0067] Example 4. A method for preparing a fiber composite needle-punched filter material, comprising the following steps:

[0068] Compared with Example 1, this example increases the amount of fluoroalcohol intermediate added in step S13;

[0069] S1. Preparation of modified carbon nanofibers;

[0070] S11. By weight, 1 part of carbon nanofibers was dispersed in 95 parts of concentrated sulfuric acid, heated to 80°C, 4 parts of potassium persulfate were added, and the mixture was stirred for 5 hours. The mixture was then cooled to 5°C, 3 parts of sodium nitrate and 10 parts of potassium permanganate were added, the mixture was heated to 40°C, and the mixture was stirred for 4 hours. The precipitate was separated by centrifugation, and the precipitate was washed three times with hydrogen peroxide and dilute hydrochloric acid, respectively. The carbon nanofibers were then dispersed again in 100 parts of deionized water, 3 parts of monochloroacetic acid and 4 parts of sodium hydroxide were added, the mixture was heated to 55°C, and the mixture was stirred for 4 hours. The precipitate was then separated by centrifugation and vacuum dried to constant weight to obtain carboxylated carbon nanofibers.

[0071] S12. According to the weight parts, add 10% of the volume of deionized water to 10 parts of glycerol, mix for 5 min, add 0.3 parts of sodium hydroxide, continue stirring and mixing for 10 min, under nitrogen atmosphere protection, add 10 parts of perfluoro2-methyl-3-oxahexanoic acid dropwise, stirring continuously during the dropwise addition. After the dropwise addition is completed, heat the mixture to 98°C, reflux for 6 h, remove excess solvent by rotary evaporation, wash the reaction product twice with deionized water at 3°C, and then evaporate under vacuum to constant weight to obtain the fluoroalcohol intermediate;

[0072] S13. By weight, 1 part of the carboxylated carbon nanofibers obtained in step S11 were dispersed in perfluorooctane. After ultrasonic dispersion for 45 min, under nitrogen atmosphere protection, 4 parts of the fluoroalcohol intermediate prepared in step S12 were added, the temperature was raised to 85℃, and the reaction was stirred for 8 h. After centrifugation to separate the precipitate, the product was washed twice with pure perfluorooctane, and then dried at 110℃ for 24 h. The dried product was dispersed again in toluene, ultrasonically treated for 30 min, and then 0.02 parts of p-toluenesulfonic acid were added. After mixing for 4 min, 0.5 parts of benzoic acid were added, the temperature was raised to 110℃, and the reaction was carried out for 4 h. After centrifugation to separate the precipitate, the product was washed twice with toluene, and then vacuum dried to constant weight to obtain modified carbon nanofibers.

[0073] S2. Preparation of high-temperature resistant polyester fibers;

[0074] S21. By weight, 50 parts of polyethylene terephthalate chips and 5 parts of modified carbon nanofibers were mixed. After premixing at 240℃ for 8 minutes, 0.15 parts of 2,5-di-tert-butylhydroquinone antioxidant, 0.3 parts of potassium acetate antistatic agent, and 0.2 parts of stearic acid dispersant were added. After mixing for 3 minutes, the mixture was extruded into chips to obtain high-temperature resistant polyester masterbatch.

[0075] S22. High-temperature resistant polyester masterbatch is melt-spun to obtain high-temperature resistant polyester fiber with a diameter of 0.9D*51mm;

[0076] S3. Preparation of fiber composite needle-punched filter media;

[0077] By weight, 8 parts of high-temperature resistant polyester fiber and 2 parts of 1.2D*51mm PPS reinforcing fiber are mixed in a certain proportion and then carded and laid to form a fiber layer. The fiber layer is then applied to the upper and lower surfaces of the base fabric. After needle punching, the surface is coated with polytetrafluoroethylene emulsion and dried to form a fiber composite needle punched filter material.

[0078] Example 5. A method for preparing a fiber composite needle-punched filter material, comprising the following steps:

[0079] Compared with Example 1, this example increases the amount of benzoic acid added in step S12;

[0080] S1. Preparation of modified carbon nanofibers;

[0081] S11. By weight, 1 part of carbon nanofibers was dispersed in 95 parts of concentrated sulfuric acid, heated to 80°C, 4 parts of potassium persulfate were added, and the mixture was stirred for 5 hours. The mixture was then cooled to 5°C, 3 parts of sodium nitrate and 10 parts of potassium permanganate were added, the mixture was heated to 40°C, and the mixture was stirred for 4 hours. The precipitate was separated by centrifugation, and the precipitate was washed three times with hydrogen peroxide and dilute hydrochloric acid, respectively. The carbon nanofibers were then dispersed again in 100 parts of deionized water, 3 parts of monochloroacetic acid and 4 parts of sodium hydroxide were added, the mixture was heated to 55°C, and the mixture was stirred for 4 hours. The precipitate was then separated by centrifugation and vacuum dried to constant weight to obtain carboxylated carbon nanofibers.

[0082] S12. According to the weight parts, add 10% of the volume of deionized water to 10 parts of glycerol, mix for 5 min, add 0.3 parts of sodium hydroxide, continue stirring and mixing for 10 min, under nitrogen atmosphere protection, add 10 parts of perfluoro2-methyl-3-oxahexanoic acid dropwise, stirring continuously during the dropwise addition. After the dropwise addition is completed, heat the mixture to 98°C, reflux for 6 h, remove excess solvent by rotary evaporation, wash the reaction product twice with deionized water at 3°C, and then evaporate under vacuum to constant weight to obtain the fluoroalcohol intermediate;

[0083] S13. By weight, 1 part of the carboxylated carbon nanofibers obtained in step S11 were dispersed in perfluorooctane. After ultrasonic dispersion for 45 min, under nitrogen atmosphere protection, 0.5 parts of the fluoroalcohol intermediate prepared in step S12 were added, the temperature was raised to 85℃, and the reaction was stirred for 8 h. After centrifugation to separate the precipitate, the product was washed twice with pure perfluorooctane, and then dried at 110℃ for 24 h. The dried product was dispersed again in toluene, ultrasonically treated for 30 min, and then 0.02 parts of p-toluenesulfonic acid were added. After mixing for 4 min, 5 parts of benzoic acid were added, the temperature was raised to 110℃, and the reaction was carried out for 4 h. After centrifugation to separate the precipitate, the product was washed twice with toluene, and then vacuum dried to constant weight to obtain modified carbon nanofibers.

[0084] S2. Preparation of high-temperature resistant polyester fibers;

[0085] S21. By weight, 50 parts of polyethylene terephthalate chips and 5 parts of modified carbon nanofibers were mixed. After premixing at 240℃ for 8 minutes, 0.15 parts of 2,5-di-tert-butylhydroquinone antioxidant, 0.3 parts of potassium acetate antistatic agent, and 0.2 parts of stearic acid dispersant were added. After mixing for 3 minutes, the mixture was extruded into chips to obtain high-temperature resistant polyester masterbatch.

[0086] S22. High-temperature resistant polyester masterbatch is melt-spun to obtain high-temperature resistant polyester fiber with a diameter of 0.9D*51mm;

[0087] S3. Preparation of fiber composite needle-punched filter media;

[0088] By weight, 8 parts of high-temperature resistant polyester fiber and 2 parts of 1.2D*51mm PPS reinforcing fiber are mixed in a certain proportion and then carded and laid to form a fiber layer. The fiber layer is then applied to the upper and lower surfaces of the base fabric. After needle punching, the surface is coated with polytetrafluoroethylene emulsion and dried to form a fiber composite needle punched filter material.

[0089] Comparative Example 1. A method for preparing a fiber composite needle-punched filter material, comprising the following steps:

[0090] Compared to Example 1, this comparative example only used ordinary carbon nanofibers;

[0091] S1. Preparation of high-temperature resistant polyester fibers;

[0092] S11. By weight, 50 parts of polyethylene terephthalate chips and 5 parts of modified carbon nanofibers were mixed. After premixing at 240℃ for 8 minutes, 0.15 parts of 2,5-di-tert-butylhydroquinone antioxidant, 0.3 parts of potassium acetate antistatic agent, and 0.2 parts of stearic acid dispersant were added. After mixing for 3 minutes, the mixture was extruded into chips to obtain high-temperature resistant polyester masterbatch.

[0093] S12. High-temperature resistant polyester masterbatch is melt-spun to obtain high-temperature resistant polyester fiber with a diameter of 0.9D*51mm;

[0094] S2. Preparation of fiber composite needle-punched filter media;

[0095] By weight, 8 parts of high-temperature resistant polyester fiber and 2 parts of 1.2D*51mm PPS reinforcing fiber are mixed in a certain proportion and then carded and laid to form a fiber layer. The fiber layer is then applied to the upper and lower surfaces of the base fabric. After needle punching, the surface is coated with polytetrafluoroethylene emulsion and dried to form a fiber composite needle punched filter material.

[0096] Detection:

[0097] The fiber composite needle-punched filter media prepared in Examples 1-5 and Comparative Example 1 were prepared into samples with a thickness of 1.5 ± 0.5 mm.

[0098] The basis weight of the samples prepared in Examples 1-5 and Comparative Example 1 was tested according to GB / T 24218.1-2009; the air permeability of the samples prepared in Examples 1-5 and Comparative Example 1 was tested according to GB / T 5453-1997; and the breaking strength and elongation of the samples prepared in Examples 1-5 and Comparative Example 1 were tested according to GB / T 24218.3-2010.

[0099] After placing the samples prepared in Examples 1-5 and Comparative Example 1 in an environment at 160°C for 30 days, the fracture strength was tested again. The test results are shown in the table below.

[0100]

[0101] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fiber composite needle-punched filter material, characterized in that: By weight fraction, the fiber composite needle-punched filter material consists of a base fabric and fiber layers covering the upper and lower surfaces of the base fabric; The fiber layer contains 60-85% high-temperature resistant polyester fiber by weight, with the remainder being reinforcing fiber; the reinforcing fiber is either polyphenylene sulfide fiber or PTFE fiber. By weight, the high-temperature resistant polyester fiber is composed of 45-65 parts polyethylene terephthalate, 5-15 parts modified carbon nanofibers, 0.08-0.15 parts antioxidant, 0.3-0.45 parts antistatic agent, and 0.1-0.2 parts dispersant; The method for preparing the modified carbon nanofibers includes the following steps: S11. Disperse carbon nanofibers in concentrated sulfuric acid, heat to 80±5℃, add potassium persulfate, stir and react for 5-8 hours, cool to 10±5℃, add sodium nitrate and potassium permanganate, heat to 40±5℃, stir and react for 4-6 hours, centrifuge to separate the precipitate, wash the precipitate 3-5 times with hydrogen peroxide and dilute hydrochloric acid respectively, disperse the carbon nanofibers again in deionized water, add monochloroacetic acid and sodium hydroxide, heat to 50±5℃, stir and react for 4-5 hours, centrifuge to separate the precipitate, and vacuum dry to constant weight to obtain carboxylated carbon nanofibers; S12. Add 10-15% by volume of deionized water to glycerol, mix for 5-10 min, then add sodium hydroxide, continue stirring and mixing for 2-15 min, then under nitrogen atmosphere protection, add perfluoro2-methyl-3-oxahexanoic acid dropwise, stirring continuously during the dropwise addition. After the dropwise addition is completed, heat the mixture to 95±3℃, reflux for 2-8 h, remove excess solvent by rotary evaporation, wash the reaction product 1-3 times with deionized water at 3±2℃, and then evaporate under vacuum to constant weight to obtain the fluoroalcohol intermediate. S13. Disperse the carboxylated carbon nanofibers obtained in step S11 into perfluorooctane, sonicate for 25-60 min, then under nitrogen atmosphere protection, add the fluoroalcohol intermediate prepared in step S12, heat to 85±10℃, stir for 4-12 h, centrifuge to separate the precipitate, wash 2-3 times with pure perfluorooctane, heat to 110℃ and dry for 24 h, then disperse the dried product again in toluene, sonicate for 30-45 min, add p-toluenesulfonic acid, continue mixing for 3-5 min, add benzoic acid, heat to 110±5℃, react for 1.5-8 h, centrifuge to separate the precipitate, wash 2-3 times with toluene, and vacuum dry to constant weight to obtain modified carbon nanofibers; The antioxidant is either 2,5-di-tert-butylhydroquinone or N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine; the antistatic agent is potassium acetate; and the dispersant is stearic acid.

2. The fiber composite needle-punched filter material according to claim 1, characterized in that: The base fabric is PPS base fabric.

3. A method for preparing fiber composite needle-punched filter material as described in any one of claims 1-2, characterized in that, Includes the following steps: S2. Preparation of high-temperature resistant polyester fibers; S21. Polyethylene terephthalate chips are mixed with modified carbon nanofibers, premixed at 230±10℃ for 5-10 min, antioxidants, antistatic agents and dispersants are added, and mixing is continued for 3-5 min. The mixture is then extruded into chips to obtain high-temperature resistant polyester masterbatch. S22. High-temperature resistant polyester masterbatch is melt-spun to obtain high-temperature resistant polyester fiber; S3. Preparation of fiber composite needle-punched filter material: After mixing high-temperature resistant polyester fiber and reinforcing fiber in a certain proportion, the fiber layer is formed by carding and web laying. The fiber layer is then covered on the upper and lower surfaces of the base fabric. After needle punching, the surface is coated with polytetrafluoroethylene emulsion and dried to form fiber composite needle-punched filter material.

4. The method for preparing a fiber composite needle-punched filter material according to claim 3, characterized in that: In step S11, the mass ratio of the nanofibers, potassium persulfate, sodium nitrate and potassium permanganate is 1:(3-5):(1-5):(5-10) by weight; the mass ratio of the nanofibers, monochloroacetic acid and sodium hydroxide is 1:(3-5):(4-5).

5. The method for preparing a fiber composite needle-punched filter material according to claim 3, characterized in that: In step S12, the mass ratio of glycerol, sodium hydroxide, and perfluoro2-methyl-3-oxahexanoic acid is 10:(0.2-0.6):(10-95) by weight.

6. The method for preparing a fiber composite needle-punched filter material according to claim 3, characterized in that: In step S13, the mass ratio of the carboxylated carbon nanofibers to the fluoroethanol intermediate is 1:(0.5-4) by weight.

7. The method for preparing a fiber composite needle-punched filter material according to claim 3, characterized in that: In step S13, the mass ratio of the carboxylated carbon nanofibers, p-toluenesulfonic acid, and benzoic acid is 1:(0.02-0.04):(0.5-5) by weight.

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