A spunlace filter material for filter cartridges and a method for producing the same

Abstract

The present application relates to the technical field of industrial filter material, and particularly relates to a spunlace filter material for filter cartridge and a preparation method thereof, comprising the following steps: S1, modifying polytetrafluoroethylene fibers and polyester fibers are respectively subjected to opening and mixing treatment to obtain mixed fibers, and the mixed fibers are subjected to carding, web laying, web combining and pre-needling to obtain a pre-needled felt; S2, the pre-needled felt is subjected to spunlace reinforcement and drying and setting to obtain a filter material base felt; S3, the surface of the filter material base felt is subjected to singeing treatment, then is immersed in a finishing liquid, and the filter material base felt after immersion is subjected to liquid rolling and drying to obtain the spunlace filter material for filter cartridge. Through the chemical cross-linking of the epoxy groups introduced on the surface of the modified polytetrafluoroethylene fibers and the amino groups on the surface of the modified silicon dioxide and the finishing liquid immersion technology, the comprehensive improvement of the flame-retardant performance, the corrosion-resistant performance and the filtration efficiency of the spunlace filter material for filter cartridge is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial filter materials, and particularly relates to a spunlace filter material for filter cartridges and a preparation method thereof. BACKGROUND

[0002] As an important component of industrial dust removal filter materials, filter cartridge filter materials are widely used in flue gas purification and dust collection systems in the steel, cement, chemical, and power industries. Filter cartridge filter materials have the advantages of large filtration area, low resistance, and good dust removal effect, and are the core filter elements of bag-type dust collectors and filter cartridge dust collectors. With the increasingly stringent national environmental protection standards and the complication of industrial production conditions, higher requirements are put forward for the filtration accuracy, service life, temperature resistance, and chemical stability of filter cartridge filter materials. In particular, under harsh conditions such as high temperature, strong acid and alkali, and organic solvents, the filter material needs to have excellent filtration efficiency and long-term stability.

[0003] The existing patent CN202310238590.0 discloses a production method of high-strength corrosion-resistant industrial filter material, aiming to provide a production method of industrial filter material with high comprehensive performance, high structural strength of the coating, high strength, and strong corrosion resistance. The technical scheme is that by using polyester fibers or polytetrafluoroethylene fibers or a mixture of the two fibers, the polyester fibers and the polytetrafluoroethylene fibers are light in quality and have strong high-temperature resistance. When they are used in filter materials, the base cloth layer of the filter material has strong high-temperature resistance. The fiber felt is first impregnated in an impregnation tank filled with polytetrafluoroethylene emulsion before the base cloth layer is prepared, greatly improving the corrosion resistance of the fiber felt. The base cloth layer formed has the best high-temperature resistance and corrosion resistance. However, the existing technology has the following disadvantages: first, the polytetrafluoroethylene emulsion impregnation treatment is only physical coating, and there is a lack of effective chemical bonding between polytetrafluoroethylene and the fiber substrate, which can easily cause the coating to fall off and the performance to decay during long-term use; second, pure polytetrafluoroethylene impregnation cannot simultaneously improve the surface wettability, antistatic property, and antibacterial property of the filter material, and the comprehensive functionalization effect is limited. SUMMARY

[0004] Therefore, the present application provides a spunlace filter material for filter cartridges and a preparation method thereof, aiming to solve the problems of coating falling off caused by a lack of effective chemical bonding in existing filter materials and the difficulty in realizing the synergistic optimization of multiple properties such as filtration performance and corrosion resistance through single functional modification.

[0005] The technical scheme of the present application is as follows: The present application provides a preparation method of a spunlace filter material for filter cartridges, including the following steps:

[0006] S1. Modified polytetrafluoroethylene fiber and polyester fiber are opened and mixed separately to obtain mixed fiber, wherein the mass ratio of modified polytetrafluoroethylene fiber and polyester fiber is 1:1. The mixed fiber is carded, laid, fused and pre-needled to obtain pre-needled felt.

[0007] S2. The pre-needle-punched felt is hydroentangled and dried to obtain plain filter felt;

[0008] S3. After singeing the surface of the filter media felt, it is immersed in the finishing solution. The immersed filter media felt is then rolled and dried to obtain hydroentangled filter media for the filter cartridge.

[0009] Specifically, the blending of modified PTFE fiber and polyester fiber ensures the excellent chemical resistance and high-temperature resistance of PTFE while fully utilizing the good mechanical strength and molding and processing properties of polyester fiber. The fiber felt structure formed by carding, web laying, web forming, and pre-needling processes is uniform and stable. Hydroentangling reinforcement treatment further enhances the mechanical bonding between fibers, effectively improving the tensile strength and dimensional stability of the filter media. Singeing removes surface fuzz, reduces filtration resistance, and improves surface smoothness. Finally, a functional coating is formed on the surface of the filter media through finishing liquid impregnation, rolling, and drying processes. This not only enhances the corrosion resistance and antistatic properties of the filter media but also ensures a strong bond between the coating and the substrate through chemical bonding. This results in a high-performance filter cartridge with hydroentangling filter media that integrates high filtration accuracy, strong corrosion resistance, excellent mechanical properties, and long service life, meeting the long-term stable dust removal requirements under complex flue gas conditions in industries such as steel, cement, and chemicals.

[0010] Based on the above technical solutions, the preferred method for preparing the modified polytetrafluoroethylene fiber is as follows:

[0011] Polytetrafluoroethylene (PTFE) fibers were fully impregnated in a reaction solution composed of glycidyl methacrylate and methanol. Nitrogen gas was introduced to remove oxygen, the solution was sealed, and the reaction was carried out by cobalt-60 gamma ray irradiation to obtain modified PTFE fibers.

[0012] Based on the above technical solutions, preferably, the mass ratio of polytetrafluoroethylene fiber to glycidyl methacrylate is 100:10~20.

[0013] Based on the above technical solutions, preferably, the irradiation reaction temperature is 25~30℃ and the irradiation dose is 30~40kGy.

[0014] Specifically, the strong penetrating power and ionizing ability of cobalt-60 gamma rays directly act on glycidyl methacrylate molecules and the surface of polytetrafluoroethylene (PTFE) fibers, initiating a free radical polymerization reaction. This results in the grafting of glycidyl methacrylate segments containing active epoxy groups onto the PTFE fiber surface. This not only overcomes the inherent defect of strong chemical inertness of PTFE fiber surface, but also significantly improves the surface wettability, compatibility with other fibers, and interfiber bonding force during hydroentangling reinforcement. At the same time, it introduces abundant epoxy group reaction sites to the fiber surface, laying the foundation for the chemical bonding of functional components such as modified silica in the subsequent finishing solution.

[0015] Based on the above technical solutions, preferably, the finishing solution comprises, by weight, 8-15 parts of triphenyl phosphate, 3-8 parts of modified silica, 8-10 parts of melamine polyphosphate, and 100-200 parts of deionized water.

[0016] Specifically, in the finishing solution, triphenyl phosphate, as a highly efficient organophosphorus flame retardant, decomposes at high temperatures to generate phosphoric acid and polyphosphoric acid, forming a dense carbonized protective layer on the filter media surface. This effectively blocks heat transfer and the diffusion of combustible gases. Melamine polyphosphate, as an intumescent flame retardant, undergoes a deamination reaction upon heating to generate melamine pyrophosphate, which further decomposes to form a porous carbon layer. This layer works synergistically with the carbonized layer formed by triphenyl phosphate to construct a dual flame-retardant barrier, significantly improving the flame-retardant performance and thermal stability of the filter media. Modified silica, as a functional inorganic filler, not only provides excellent high-temperature resistance and chemical stability, but more importantly, its abundant amino groups react chemically with the epoxy groups on the surface of modified polytetrafluoroethylene fibers to form a stable covalent network structure. This ensures a strong bond between the functional components in the finishing solution and the fiber substrate. Deionized water, as a carrier solvent, ensures the uniform dispersion and deep penetration of each component, allowing the finishing solution to fully wet the internal fibers of the filter media, achieving uniform distribution and effective fixation of the functional components within the filter media.

[0017] Based on the above technical solutions, preferred methods for preparing modified silica include:

[0018] (1) Dissolve 1-methylbenzotriazole-5-carboxylic acid in DMF, add 3-(N-allylamino)propyltrimethoxysilane and N,N'-dicyclohexylcarbodiimide, and react at 80-100℃ for 6-8h to generate a modifier;

[0019] (2) Disperse silica in an aqueous ethanol solution, add a modifier, and react at 60-80°C for 2-4 hours to obtain silanized silica;

[0020] (3) Disperse silanized silica in toluene, add oleamide and azobisisobutyronitrile under a nitrogen atmosphere, and react at 60~80℃ for 3~5h to obtain modified silica.

[0021] Specifically, in step (1), an amidation reaction is carried out between 1-methylbenzotriazole-5-carboxylic acid and 3-(N-allylamino)propyltrimethoxysilane, and an organic group containing a benzotriazole structure is attached to the silane molecule via an amide bond to form a modifier. The benzotriazole group has excellent UV absorption and metal complexation capabilities, which can effectively resist the chemical corrosion of the filter material by high-temperature oxidizing flue gas. At the same time, its nitrogen heterocyclic structure has a complexation and capture effect on heavy metal ions in the flue gas, which not only protects the filter material from heavy metal corrosion, but also reduces the emission of heavy metal ions to a certain extent. In addition, the benzotriazole group exhibits good thermal stability at high temperatures, providing chemical protection for the long-term stable operation of the filter material in harsh flue gas environments; in step (2), the modifier is reacted with dimethylbenzotriazole-5-carboxylic acid and 3-(N-allylamino)propyltrimethoxysilane to form a modifier. Hydrolysis and condensation reactions occur on the hydroxyl groups of silica surface, successfully grafting organic segments containing allyl and benzotriazole functional groups onto the silica surface, thus achieving surface functionalization modification of silica. In step (3), the allyl double bonds on the silanized silica surface undergo free radical addition reactions with oleamide molecules to achieve a strong bond. The long-chain alkyl structure in the oleamide molecule endows the filter material surface with a certain degree of hydrophobicity, effectively preventing water vapor in the flue gas from condensing on the filter material surface to form a liquid film, which leads to a sharp increase in filtration resistance and dust adhesion. In addition, the oleamide molecule has a certain adsorption and blocking effect on organic pollutants and tar-like substances in the flue gas, preventing these substances from penetrating into the filter material and causing irreversible blockage, thereby significantly extending the service life of the filter material and maintaining stable filtration performance. Furthermore, the terminal amino groups of the oleamide molecule are exposed on the silica surface to form active reaction sites. During the drying process after impregnation with the finishing liquid, these surface amino groups can chemically bond with the epoxy groups on the surface of the modified polytetrafluoroethylene fiber, forming a chemical cross-linking network between the modified silica and the fiber substrate, ensuring the stable loading of the functional filler.

[0022] Based on the above technical solutions, preferably, in step (1), the molar ratio of 1-methylbenzotriazole-5-carboxylic acid, 3-(N-allylamino)propyltrimethoxysilane and N,N'-dicyclohexylcarbodiimide is 1:(1.0~1.2):(1.0~1.1).

[0023] Based on the above technical solutions, preferably, the mass ratio of silicon dioxide to modifier in step (2) is 100:(5~15).

[0024] Based on the above technical solutions, preferably, the mass ratio of silanized silica, oleamide and azobisisobutyronitrile in step (3) is 100:(20~40):(0.2~0.4).

[0025] The present invention also discloses a filter cartridge with hydroentangled filter media obtained by the preparation method described in any of the preceding claims.

[0026] The filter cartridge of the present invention, using spunlace filter media and its preparation method, has the following advantages over the prior art:

[0027] (1) This invention achieves a comprehensive improvement in the flame retardant performance, corrosion resistance and filtration efficiency of hydroentangled filter media by introducing epoxy groups on the surface of modified polytetrafluoroethylene fibers and chemical crosslinking with amino groups on the surface of modified silica, as well as by using finishing liquid impregnation technology. The composite structure of modified polytetrafluoroethylene fibers and polyester fibers maintains the excellent chemical stability and high temperature resistance of polytetrafluoroethylene fibers, and improves the compatibility between fibers and the hydroentanglement reinforcement effect through modification treatment. The synergistic effect of flame retardant components in finishing liquid and modified silica forms a functional protective layer on the surface of filter media, which significantly enhances the service life and filtration stability of filter media in high temperature and corrosive industrial flue gas environment.

[0028] (2) The finishing solution significantly enhances the flame retardant performance by compounding triphenyl phosphate, melamine polyphosphate and modified silica. Triphenyl phosphate decomposes at high temperature to form a carbonized layer of phosphoric acid and polyphosphate, which forms a porous carbon layer with the deammoniation reaction of melamine polyphosphate to form a double flame retardant barrier, effectively blocking heat transfer and the diffusion of combustible gases. Modified silica not only has anti-corrosion effect, but the chemical bonding between its surface amino groups and fiber epoxy groups also ensures the long-term fixation of flame retardant components, avoiding the technical defects of easy detachment of functional components in traditional physical impregnation methods, so that the filter material can maintain stable flame retardant and corrosion resistance during repeated cleaning and long-term use.

[0029] (3) The modified silica is provided with excellent antioxidant and heavy metal complexing ability by loading 1-methylbenzotriazole-5-carboxylic acid. Its nitrogen heterocyclic structure can effectively resist the chemical corrosion of strong oxidizing gases in industrial flue gas, and at the same time, it has a complexing and capturing effect on heavy metal ions in flue gas, preventing heavy metal corrosion and reducing heavy metal emissions to a certain extent. The good thermal stability of the benzotriazole group at high temperature provides chemical protection for the long-term stable operation of the filter material in harsh flue gas environment. The grafting of oleamide introduces active amino groups, and its long-chain fatty acid amide structure gives the filter material surface hydrophobic properties, effectively preventing water vapor in flue gas from condensing to form a corrosive liquid film, and has an adsorption and barrier effect on organic pollutants and tar substances in flue gas, preventing these corrosive substances from penetrating into the filter material and causing irreversible damage. The chemical cross-linking of surface amino groups with modified polytetrafluoroethylene fiber epoxy groups ensures the stable loading of these corrosion-resistant functional components, forming a durable and effective chemical protection system. 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 a part of the embodiments of the present invention, and not all of the 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] It should be noted that the polytetrafluoroethylene fiber was purchased from Xiamen Bairun Fluorine Materials Technology Co., Ltd., and the polyester fiber was purchased from Taian Hongtong New Materials Co., Ltd.

[0032] Example 1

[0033] This embodiment provides a method for preparing hydroentangled filter media for filter cartridges, including the following steps:

[0034] S1. 50 kg of modified polytetrafluoroethylene fiber and 50 kg of polyester fiber are opened and mixed to obtain mixed fiber. The mixed fiber is then carded, laid into a web, connected and pre-needled to obtain pre-needled felt.

[0035] S2. The pre-needled felt is hydroentangled and dried to obtain the filter material felt. The hydroentanglement is carried out with a water pressure of 20MPa, a needle density of 250 needles / cm², and a drying temperature of 130℃ for 13min.

[0036] S3. After singeing the surface of the filter media felt, it is immersed in the finishing solution. The immersed filter media felt is then rolled and dried. The immersion time is 8 minutes, the rolling pressure is 0.3 MPa, the drying temperature is 165℃, and the drying time is 18 minutes to obtain the hydroentangling filter media for the filter cartridge.

[0037] The preparation method of modified polytetrafluoroethylene fiber is as follows:

[0038] 100g of polytetrafluoroethylene fiber was fully impregnated in a reaction solution consisting of 15g of glycidyl methacrylate and 1000ml of methanol. Nitrogen gas was introduced to remove oxygen, the mixture was sealed, and the reaction was carried out at 27°C with cobalt-60 gamma rays at a dose of 35kGy. After the reaction was completed, the mixture was filtered, washed with methanol, and dried under vacuum to obtain modified polytetrafluoroethylene fiber.

[0039] The finishing solution, by weight, comprises 11 parts of triphenyl phosphate, 5.5 parts of modified silica, 9 parts of melamine polyphosphate, and 150 parts of deionized water. The finishing solution is obtained by weighing and mixing the ingredients according to the above weight proportions.

[0040] Methods for preparing modified silica include:

[0041] (1) Dissolve 177.16g of 1-methylbenzotriazole-5-carboxylic acid in DMF, add 241.28g of 3-(N-allylamino)propyltrimethoxysilane and 216.65g of N,N'-dicyclohexylcarbodiimide, react at 90℃ for 7h, cool to room temperature after the reaction is completed, extract with n-hexane, combine the organic phases, remove the solvent by rotary evaporation, and generate the modifier;

[0042] (2) Disperse 100g of silica in an ethanol aqueous solution, add 10g of modifier, react at 70℃ for 3h, centrifuge after the reaction is completed, wash and dry to obtain silanized silica;

[0043] (3) 100g of silanized silica was dispersed in toluene. Under a nitrogen atmosphere, 30g of oleamide and 0.3g of azobisisobutyronitrile were added and reacted at 70°C for 4h. After the reaction was completed, the silica was separated by centrifugation, washed and dried to obtain modified silica.

[0044] Example 2

[0045] This embodiment provides a method for preparing hydroentangled filter media for filter cartridges, including the following steps:

[0046] S1. 50 kg of modified polytetrafluoroethylene fiber and 50 kg of polyester fiber are opened and mixed to obtain mixed fiber. The mixed fiber is then carded, laid into a web, connected and pre-needled to obtain pre-needled felt.

[0047] S2. The pre-needled felt is hydroentangled and dried to obtain the filter material felt. The hydroentanglement is carried out with a water pressure of 15MPa, a needle density of 200 needles / cm², a drying temperature of 120℃, and a time of 10min.

[0048] S3. After singeing the surface of the filter media felt, immerse it in the finishing solution, then roll and dry the impregnated filter media felt. The impregnation time is 5 minutes, the rolling pressure is 0.2 MPa, the drying temperature is 150℃, and the time is 20 minutes to obtain the hydroentangling filter media for the filter cartridge.

[0049] The preparation method of modified polytetrafluoroethylene fiber is as follows:

[0050] 100g of polytetrafluoroethylene fiber was fully impregnated in a reaction solution consisting of 10g of glycidyl methacrylate and 1000ml of methanol. Nitrogen gas was introduced to remove oxygen, the solution was sealed, and the reaction was carried out at 25°C with cobalt-60 gamma rays at a dose of 40kGy. After the reaction was completed, the solution was filtered, washed with methanol, and dried under vacuum to obtain modified polytetrafluoroethylene fiber.

[0051] The finishing solution, by weight, comprises 8 parts of triphenyl phosphate, 3 parts of modified silica, 8 parts of melamine polyphosphate, and 100 parts of deionized water. The finishing solution is obtained by weighing and mixing the ingredients according to the above weight proportions.

[0052] Methods for preparing modified silica include:

[0053] (1) Dissolve 177.16g of 1-methylbenzotriazole-5-carboxylic acid in DMF, add 219.35g of 3-(N-allylamino)propyltrimethoxysilane and 206.33g of N,N'-dicyclohexylcarbodiimide, react at 80℃ for 8h, cool to room temperature after the reaction is completed, extract with n-hexane, combine the organic phases, remove the solvent by rotary evaporation, and generate the modifier;

[0054] (2) Disperse 100g of silica in an ethanol aqueous solution, add 5g of modifier, react at 60℃ for 4h, centrifuge after the reaction is completed, wash and dry to obtain silanized silica;

[0055] (3) Disperse 100g of silanized silica in toluene, add 20g of oleamide and 0.2g of azobisisobutyronitrile under a nitrogen atmosphere, react at 60°C for 5h, centrifuge after the reaction is completed, wash and dry to obtain modified silica.

[0056] Example 3

[0057] This embodiment provides a method for preparing hydroentangled filter media for filter cartridges, including the following steps:

[0058] S1. 50 kg of modified polytetrafluoroethylene fiber and 50 kg of polyester fiber are opened and mixed to obtain mixed fiber. The mixed fiber is then carded, laid into a web, connected and pre-needled to obtain pre-needled felt.

[0059] S2. The pre-needled felt is hydroentangled and dried to obtain the filter material felt. The hydroentanglement is carried out with a water pressure of 25MPa, a needle density of 300 needles / cm², and a drying temperature of 140℃ for 15min.

[0060] S3. After singeing the surface of the filter media felt, immerse it in the finishing solution, then roll and dry the impregnated filter media felt. The impregnation time is 10 minutes, the rolling pressure is 0.4 MPa, the drying temperature is 180℃, and the time is 15 minutes to obtain the hydroentangling filter media for the filter cartridge.

[0061] The preparation method of modified polytetrafluoroethylene fiber is as follows:

[0062] 100g of polytetrafluoroethylene fiber was fully impregnated in a reaction solution consisting of 20g of glycidyl methacrylate and 1000ml of methanol. Nitrogen gas was introduced to remove oxygen, the solution was sealed, and the reaction was carried out at 30°C with cobalt-60 gamma rays at a dose of 30kGy. After the reaction was completed, the solution was filtered, washed with methanol, and dried under vacuum to obtain modified polytetrafluoroethylene fiber.

[0063] The finishing solution, by weight, includes 15 parts of triphenyl phosphate, 8 parts of modified silica, 10 parts of melamine polyphosphate and 200 parts of deionized water. The finishing solution is obtained by weighing and mixing the ingredients according to the above weight proportions.

[0064] Methods for preparing modified silica include:

[0065] (1) Dissolve 177.16g of 1-methylbenzotriazole-5-carboxylic acid in DMF, add 263.22g of 3-(N-allylamino)propyltrimethoxysilane and 226.96g of N,N'-dicyclohexylcarbodiimide, react at 100℃ for 6h, cool to room temperature after the reaction is completed, extract with n-hexane, combine the organic phases, remove the solvent by rotary evaporation, and generate the modifier;

[0066] (2) Disperse 100g of silica in an ethanol aqueous solution, add 15g of modifier, react at 80℃ for 2h, centrifuge after the reaction is completed, wash and dry to obtain silanized silica;

[0067] (3) 100g of silanized silica was dispersed in toluene, and 40g of oleamide and 0.4g of azobisisobutyronitrile were added under a nitrogen atmosphere. The mixture was reacted at 80°C for 3 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain modified silica.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing hydroentangled filter media for filter cartridges. The preparation method is the same as in Example 1, except that the polytetrafluoroethylene fibers are not modified, i.e.:

[0070] S1. 50 kg of polytetrafluoroethylene fiber and 50 kg of polyester fiber are opened and mixed separately to obtain mixed fibers. The mixed fibers are then carded, laid into a web, fused together, and pre-needled to obtain pre-needled felt. The remaining steps are the same as in Example 1.

[0071] Comparative Example 2

[0072] This comparative example provides a method for preparing hydroentangled filter media for filter cartridges. The preparation method is the same as in Example 1, except that: the modified silica is not grafted with 1-methylbenzotriazole-5-carboxylic acid, that is:

[0073] The preparation method of modified silica is as follows:

[0074] (1) Disperse 100g of silica in an ethanol aqueous solution, add 10g of 3~(N~allylamino)propyltrimethoxysilane, react at 70℃ for 3h, centrifuge after the reaction is completed, wash and dry to obtain silanized silica;

[0075] (2) 100g of silanized silica was dispersed in toluene. Under a nitrogen atmosphere, 30g of oleamide and 0.3g of azobisisobutyronitrile were added and reacted at 70°C for 4h. After the reaction was completed, the silica was separated by centrifugation, washed and dried to obtain modified silica.

[0076] Comparative Example 3

[0077] This comparative example provides a method for preparing hydroentangled filter media for filter cartridges. The preparation method is the same as in Example 1, except that: the modified silica is not grafted with oleamide, that is:

[0078] The preparation method of modified silica is as follows:

[0079] (1) Dissolve 177.16g of 1-methylbenzotriazole-5-carboxylic acid in DMF, add 241.28g of 3-(N-allylamino)propyltrimethoxysilane and 216.65g of N,N'-dicyclohexylcarbodiimide, react at 90℃ for 7h, cool to room temperature after the reaction is completed, extract with n-hexane, combine the organic phases, remove the solvent by rotary evaporation, and generate the modifier;

[0080] (2) Disperse 100g of silica in an ethanol aqueous solution, add 10g of modifier, react at 70℃ for 3h, centrifuge after the reaction is completed, wash and dry to obtain silanized silica.

[0081] Comparative Example 4

[0082] This comparative example provides a method for preparing hydroentangled filter media for filter cartridges. The preparation method is the same as in Example 1, except that the modified silica is prepared as follows:

[0083] 100g of silica, 10g of 1-methylbenzotriazole-5-carboxylic acid and 30g of oleamide were added to 500ml of anhydrous ethanol and mechanically stirred at room temperature for 2h to ensure that the components were fully mixed and dispersed. Then, the mixture was stirred and dried at 80℃ to remove the ethanol and obtain modified silica.

[0084] Comparative Example 5

[0085] This comparative example provides a method for preparing hydroentangled filter media for filter cartridges. The preparation method is the same as in Example 1, except that: the finishing liquid, by weight, includes 5.5 parts of modified silica, 20 parts of melamine polyphosphate and 150 parts of deionized water. The finishing liquid is obtained by weighing and mixing the above-mentioned weight parts evenly.

[0086] Performance testing

[0087] The filter cartridges prepared in Examples 1 and Comparative Example 1 were subjected to performance testing using spunlace filter media samples. The test indicators included flame retardancy, corrosion resistance, high-temperature resistance, and filtration performance. For flame retardancy, the limiting oxygen index (LOI) was tested according to standard GB / T2406.2~2009. For corrosion resistance, the samples were immersed in a 10% sulfuric acid aqueous solution at 90℃ for 24 hours, and the tensile strength before and after immersion was tested according to QB / T4876-2015. Corrosion resistance was expressed as the tensile strength retention rate, i.e., tensile strength after immersion / tensile strength before immersion. For high-temperature resistance, the thermal shrinkage rate of the filter media after heat treatment was expressed according to GB / T6719-2009 "Technical Requirements for Bag Filters". Air permeability was tested according to GBT5453-1997 "Determination of Air Permeability of Textile Fabrics". For filtration performance, the VDI test was conducted according to GBT6719-2009 "Technical Requirements for Bag Filters". The test indicators are shown in Tables 1 and 2.

[0088] Table 1 Corrosion resistance and high temperature resistance

[0089]

[0090] Table 2 Flame retardant properties and filtration properties

[0091]

[0092] As shown in Tables 1 and 2, the filter cartridge prepared by the technical solution of this invention, using spunlace filter media, maintains filtration efficiency while also exhibiting good flame retardancy, corrosion resistance, and high-temperature resistance. In Comparative Example 1, the polytetrafluoroethylene fiber surface lacks epoxy groups, preventing the formation of chemical cross-linking bonds with the amino groups on the modified silica surface. This results in insufficient bonding between the functional components in the finishing solution and the fiber substrate, making it prone to detachment in acidic corrosive environments, significantly reducing flame retardancy and corrosion resistance. In Comparative Example 2, the lack of benzotriazole groups weakens the modified silica's ability to resist strong oxidizing gas erosion in acidic flue gas environments, significantly reducing corrosion resistance. In Comparative Example 3, the absence of terminal amino groups introduced by oleamide prevents the modified silica from forming a β-hydroxyamine cross-linking structure with the epoxy groups of the polytetrafluoroethylene fiber, and also lacks the protection of long-chain hydrophobic structures. The lack of protection leads to insufficient bonding between the functional filler and the fiber, making it susceptible to corrosion by water vapor and organic pollutants, resulting in a double decline in corrosion resistance and filtration performance. In Comparative Example 4, the modified silica prepared by physical compounding lacks the stability of chemical bonding, and the functional components are prone to detachment and failure under high-temperature corrosive environments, leading to a comprehensive decline in overall performance. Comparative Example 5 lacks triphenyl phosphate, a key organophosphorus flame retardant, and cannot decompose at high temperatures to form a dense carbonized protective layer of phosphoric acid and polyphosphoric acid. It only relies on the intumescent flame retardant mechanism of melamine polyphosphate to form a porous carbon layer, lacking the synergistic effect of dual flame retardant barriers, resulting in a significant decline in flame retardant performance.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 method for preparing a filter cartridge using spunlace filter media, characterized in that, Includes the following steps: S1. Modified polytetrafluoroethylene fiber and polyester fiber are opened and mixed to obtain mixed fiber. The mixed fiber is then carded, laid, combined and pre-needled to obtain pre-needled felt. S2. The pre-needle-punched felt is hydroentangled and dried to obtain plain filter felt; S3. After singeing the surface of the filter media felt, it is immersed in the finishing solution. The impregnated filter media felt is then rolled and dried to obtain the hydroentangled filter media for the filter cartridge. The finishing solution, by weight, comprises 8-15 parts of triphenyl phosphate, 3-8 parts of modified silica, 8-10 parts of melamine polyphosphate, and 100-200 parts of deionized water. The preparation method of modified silica includes the following steps: (1) Dissolve 1-methylbenzotriazole-5-carboxylic acid in DMF, add 3-(N-allylamino)propyltrimethoxysilane and N,N'-dicyclohexylcarbodiimide, and react at 80~100℃ for 6~8h to generate a modifier; (2) Disperse silica in an aqueous ethanol solution, add a modifier, and react at 60-80°C for 2-4 hours to obtain silanized silica; (3) Disperse silanized silica in toluene, add oleamide and azobisisobutyronitrile under a nitrogen atmosphere, and react at 60~80℃ for 3~5h to obtain modified silica; The modified polytetrafluoroethylene fiber is prepared as follows: Polytetrafluoroethylene (PTFE) fibers were thoroughly impregnated into a reaction solution composed of glycidyl methacrylate and methanol. Nitrogen gas was introduced to remove oxygen, and the mixture was sealed. 60 Modified polytetrafluoroethylene fibers were obtained by irradiation reaction with Co source gamma rays.

2. The method for preparing a filter cartridge using spunlace filter media as described in claim 1, characterized in that: The mass ratio of polytetrafluoroethylene fiber to glycidyl methacrylate is 100:10~20.

3. The method for preparing a filter cartridge with spunlace filter media as described in claim 1, characterized in that: The irradiation reaction temperature is 25~30℃, and the irradiation dose is 30~40kGy.

4. The method for preparing a filter cartridge with spunlace filter media as described in claim 1, characterized in that: In step (1), the molar ratio of 1-methylbenzotriazole-5-carboxylic acid, 3-(N-allylamino)propyltrimethoxysilane and N,N'-dicyclohexylcarbodiimide is 1:1.0~1.2:1.0~1.

1.

5. The method for preparing a filter cartridge with spunlace filter media as described in claim 1, characterized in that: In step (2), the mass ratio of silicon dioxide to modifier is 100:5~15.

6. The method for preparing a filter cartridge with spunlace filter media as described in claim 1, characterized in that: In step (3), the mass ratio of silanized silica, oleamide and azobisisobutyronitrile is 100:20~40:0.2~0.

4.

7. A filter cartridge with hydroentangled filter media obtained by the preparation method according to any one of claims 1 to 6.

Images