Corrosion-resistant filter bag and method of making same

Abstract

The application discloses a kind of corrosion-resistant filter bag and preparation method thereof, basalt fiber is mixed with fluorine-containing benzimidazole metal coordination type polyimide modified fiber to obtain base cloth by weaving, with the aid of doctor blade coating film machine, uniform coating foaming finishing agent is formed on the surface of base cloth;Subsequently, drying, sintering are sequentially completed by adopting two-stage continuous heating process, and then slowly cooling, so that the surface layer of the fabric forms a protective coating with micropores, and the finished product filter bag is obtained after cutting and sewing.The modified polyimide fiber used endows the fabric with basic heat resistance by virtue of its own rigid molecular skeleton, and the benzimidazole metal coordination structure in the fiber constructs a three-dimensional crosslinked network, greatly improving the overall thermal stability.The modified filler component in the foaming finishing agent builds a heat-resistant rigid skeleton with high-thermal-conductivity boron nitride, and relies on the barrier effect of the lamella to extend the penetration path of the corrosion medium, while introducing high-temperature stable cerium to synergistically enhance the comprehensive performance of the filter material in terms of corrosion resistance and high-temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of filter material technology, specifically to a corrosion-resistant filter bag and its preparation method. Background Technology

[0002] Filter bags are core consumables for industrial dust removal, waste gas purification, and fluid filtration, widely used in industries such as cement, steel, chemical, power, and pharmaceuticals. They are primarily used to trap dust and corrosive fluid impurities in flue gas, ensuring that industrial exhaust gases meet emission standards and that production fluids remain clean. Currently, conventional filter bags on the market have significant performance limitations under complex industrial conditions, making them unsuitable for extreme production environments. Regarding high-temperature resistance, traditional filter bag materials have a low heat resistance limit. Prolonged exposure to flue gas temperatures above 200°C can easily lead to fiber aging, embrittlement, and deformation. Sudden high-temperature impacts can also cause structural damage, significantly shortening their service life. In terms of corrosion resistance, industrial flue gas and fluids often contain acidic and alkaline media, sulfides, and organic solvents. Conventional filter bag fibers are prone to hydrolysis and oxidation, leading to a decrease in bag strength, pore deformation, filtration failure, and dust leakage. Existing filter bags lack sufficient temperature and corrosion resistance, which not only increases equipment maintenance and replacement costs but also reduces filtration accuracy and production stability, failing to meet the long-term use requirements of harsh working conditions in high-end industries. Therefore, it is urgent to optimize and improve the high temperature and corrosion resistance of filter bags. Summary of the Invention

[0003] The purpose of this invention is to provide a corrosion-resistant filter bag to solve the problems of insufficient temperature resistance and corrosion resistance of existing filter bags.

[0004] The objective of this invention can be achieved through the following technical solutions: A method for preparing a corrosion-resistant filter bag specifically includes the following steps: Basalt fiber and modified fiber are woven to obtain a base fabric. A foaming agent is evenly coated on the surface of the base fabric using a doctor blade coating machine to obtain a pre-treated fabric. The pre-treated fabric is placed in a hot air dryer and dried at 160°C for 5 minutes. Then it is transferred to an electric heating blast drying oven and sintered at 360°C for 10 minutes. After that, it is slowly cooled to room temperature. Finally, it is cut and sewn to obtain a corrosion-resistant filter bag.

[0005] Furthermore, the mass ratio of basalt fiber to modified fiber is 60-70:25-30. The basalt fiber and modified fiber are woven in a twill weave with a warp density of 240 threads / 10cm and a weft density of 200 threads / 10cm. The hot air drying heating rate is 8℃ / min, the hot air velocity is 2m / s, and nitrogen inert protection is used for sintering. The temperature is raised to 360℃ at a rate of 4℃ / min, and after sintering, it is lowered to 80℃ at a rate of 3℃ / min and then naturally cooled to room temperature. The sewing thread is made of PTFE corrosion-resistant thread with a stitch density of 4 stitches / cm.

[0006] Furthermore, the modified fiber is made by the following steps: Step A1: Mix oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine and ethylene glycol evenly, stir for 15-20 minutes at a speed of 300-400 r / min and a temperature of 20-30℃, then slowly add polyphosphoric acid, heat to 180-185℃ and reflux for 10-12 hours to obtain intermediate 1; Step A2: Mix intermediate 1, palladium on carbon catalyst and 1,4-dioxane evenly, stir for 10-20 min at a speed of 200-300 r / min and a temperature of 75-80℃, then slowly add hydrazine hydrate dropwise and react at a constant temperature for 8-10 h to obtain intermediate 2. Step A3: Mix pyromellitic dianhydride, intermediate 2 and N,N-dimethylacetamide evenly, stir for 20-24 hours at a speed of 200-300℃ and a temperature of 10℃ with nitrogen gas, add ferric nitrate nonahydrate and mix thoroughly for 6-8 hours to obtain the spinning solution. Step A4: Spinning solution under the conditions of 15KV high voltage power supply, 1000r / min receiver rotation speed and 15℃ ambient temperature to obtain pretreated fiber. Place the pretreated fiber in a vacuum oven and dry it at 60-80℃. Then put it into a high temperature tube furnace for thermal imidization to obtain modified fiber.

[0007] Furthermore, the ratio of oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine, ethylene glycol, and polyphosphoric acid used in step A1 is 3.6g:19g:320mL:20mL.

[0008] Furthermore, the ratio of intermediate 1, palladium catalyst on carbon, 1,4-dioxane and hydrazine hydrate in step A2 is 5g:0.6g:60mL:7.66g, and the palladium content in the palladium catalyst on carbon is 0.5%.

[0009] Furthermore, the ratio of the ethanol solution of pyromellitic dianhydride, intermediate 2, N,N-dimethylacetamide and ferric nitrate nonahydrate described in step A3 is 1 mol: 1 mol: 100 mL: 0.2 mol.

[0010] Furthermore, the distance from the fiber receiver to the needle tip in step A4 is 25cm. The thermal imidization procedure is as follows: the temperature is rapidly increased from room temperature to 150°C in 30 minutes, held at the temperature for 2 hours, then increased to 250°C, held at the temperature for 1 hour, and then increased to 380°C. The heating rate is 2°C / min, and the entire process is carried out under nitrogen protection.

[0011] Furthermore, the foaming finishing agent is prepared by the following steps: Step B1: Disperse boron nitride and 2-amino-5-mercapto-1,3,4-thiadiazole in deionized water, sonicate in liquid phase for 3-4 hours, centrifuge at 3000-3200 r / min for 30-35 minutes, collect the supernatant and filter under reduced pressure to obtain pretreated boron nitride nanosheets. Disperse the pretreated boron nitride nanosheets in Tris buffer at pH 8.5, sonicate at 30-40 kHz for 40-50 minutes, stir and add dopamine hydrochloride at 180-200 r / min and 20-30℃, and react for 10-12 hours to obtain the pretreated filler. Step B2: Add 3-aminopropyltrimethoxysilane to an ethanol / water mixture and hydrolyze it for 1-2 hours at a rotation speed of 200-300 r / min, a temperature of 40-50℃, and a pH of 4-5. Then, raise the temperature to 60-70℃ and slowly add an ethanol dispersion of cerium oxide. React for 2-4 hours to obtain pretreated cerium oxide. Disperse the pretreated filler in N,N-dimethylformamide and add the pretreated cerium oxide at a rotation speed of 300-400 r / min and a temperature of 20-30℃. Disperse the pretreated cerium oxide evenly for 1-2 hours and then raise the temperature to 60-80℃. React for 4-6 hours to obtain the modified filler. Step B3: Add polytetrafluoroethylene emulsion to deionized water, then add betaine, Tween 80, methylcellulose and modified filler in sequence. After mixing evenly, stir for 10-12 minutes at a speed of 2000-2500 r / min to obtain the foaming finishing agent.

[0012] Furthermore, in step B1, the ratio of boron nitride, 2-amino-5-mercapto-1,3,4-thiadiazole, and deionized water is 0.2 g: 0.2 g: 180 mL, and the ratio of pretreated boron nitride nanosheets, Tris buffer, and dopamine hydrochloride is 2 g: 400 mL: 0.8 g.

[0013] Furthermore, in step B2, the ratio of 3-aminopropyltrimethoxysilane, ethanol / water mixed solution, and cerium oxide ethanol dispersion is 0.05-0.1g:60mL:100mL, the mass ratio of ethanol to water in the ethanol / water mixed solution is 85:15, the cerium oxide ethanol dispersion is prepared by dispersing 1.2g of cerium oxide in 100mL of ethanol, and the ratio of pretreated filler, N,N-dimethylformamide, and pretreated cerium oxide is 0.3g:60mL:0.3g.

[0014] Furthermore, the ratio of deionized water, polytetrafluoroethylene emulsion, betaine, Tween 80, methylcellulose and modified filler in step B3 is 60g:20-24g:2g:0.5-1g:2g:0.4-0.8g, and the solid content of polytetrafluoroethylene emulsion is 54%.

[0015] The beneficial effects of this invention are as follows: A foaming agent is uniformly coated on a base fabric woven from basalt fiber and modified fiber to obtain a pre-treated fabric. The pre-treated fabric is then dried, sintered, and slowly cooled through a two-step heating process, resulting in a coating microporous structure on the surface of the pre-treated fabric. Finally, the fabric is cut and sewn to obtain a corrosion-resistant filter bag.

[0016] Modified Fiber: Using polyphosphoric acid as a catalyst and dehydrating agent, polyphosphoric acid can protonate the carboxyl group of oxalic acid, effectively enhancing the electrophilicity of the carbonyl group. Based on this, the o-phenylenediamine structure of 4-fluoro-5-nitrobenzene-1,2-diamine attacks the carbonyl group of oxalic acid, undergoing two intramolecular nucleophilic addition-elimination reactions accompanied by double dehydration and ring closure to construct a benzimidazole heterocyclic structure, yielding intermediate 1. Using hydrazine hydrate as a mild hydrogen donor and palladium on carbon as a hydrogenation reduction catalyst, the nitro group on intermediate 1 can be selectively reduced to an amino group, obtaining intermediate 2 containing an active amino functional group. Under a low-temperature nitrogen protective atmosphere, the anhydride group of pyromellitic dianhydride undergoes a ring-opening stepwise polymerization reaction with the amino group of intermediate 2 to generate a linear high-molecular-weight polyamic acid system. Ferric nitrate nonahydrate was added to a polyamic acid system. The lone pair electrons of the nitrogen atom on the five-membered ring of benzimidazole formed coordinate bonds with ferric ions, constructing a stable three-dimensional cross-linked network structure, ultimately yielding a uniform and stable modified spinning solution. The above spinning solution was electrospinned to obtain precursor fibers, which were then subjected to gradient thermal imidization to complete the molecular ring-closure reaction, finally preparing structurally stable modified fibers.

[0017] Foaming agent: 2-Amino-5-mercapto-1,3,4-thiadiazole was used as an intercalation anchoring corrosion inhibitor. The mercapto group of this molecule forms intermolecular hydrogen bonds with the hydroxyl groups on the surface of boron nitride. Its five-membered conjugated heterocycle and the six-membered ring of boron nitride form π-π stacking. Through the synergistic effect of hydrogen bonding and π-π stacking, the corrosion inhibitor is firmly anchored to the boron nitride sheets, thus preparing pretreated boron nitride nanosheets. In a weakly alkaline environment with a pH of 8.5, dopamine undergoes oxidative self-polymerization to form a polydopamine film on the surface of the pretreated boron nitride nanosheets, thus preparing the pretreated filler. The methoxy group on 3-aminopropyltrimethoxysilane is hydrolyzed to generate silanol groups, which undergo dehydration condensation with Ce-OH on cerium oxide to prepare pretreated cerium oxide. The pretreated filler and pretreated cerium oxide are uniformly dispersed and heated. The quinone groups on the surface of polydopamine react with the amino groups on the surface of pretreated cerium oxide to form covalent bonds, thus obtaining the modified filler. Finally, a basic aqueous emulsion was constructed using deionized water and PTFE emulsion. Betaine foaming agent, Tween 80 foam stabilizer, and methylcellulose thickener were added, and then modified filler was mixed thoroughly to obtain the foaming finishing agent.

[0018] The modified fiber used in this invention is a fluorinated benzimidazole metal-coordinated polyimide fiber. The intrinsic rigid skeleton of polyimide imparts basic heat resistance to the substrate, while the benzimidazole metal coordination within the fiber constructs a three-dimensional cross-linked network, further enhancing overall thermal stability. The introduction of fluorine into the fiber significantly improves its resistance to acids, alkalis, and organic solvents. The modified fiber, combined with chemically inert basalt fiber, works synergistically to effectively block the penetration of corrosive media, resulting in a fabric with excellent high-temperature resistance and chemical corrosion resistance. The modified filler uses high thermal conductivity boron nitride to construct a rigid heat-resistant skeleton, utilizing its lamellar structure to extend the diffusion path of corrosive media, forming a "maze barrier." Simultaneously, the intercalated 2-amino-5-mercapto-1,3,4-thiadiazole corrosion inhibitor synergistically isolates the corrosive media. The system is compounded with a high-temperature stable cerium oxide phase, which can inhibit the thermal decomposition of the filler, slow down high-temperature oxidation behavior, and significantly improve the overall thermal stability and resistance to thermal decomposition of the filler. Detailed Implementation

[0019] 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.

[0020] Example 1: A method for preparing a corrosion-resistant filter bag, specifically including the following steps: Basalt fiber and modified fiber are woven to obtain a base fabric. A foaming agent is evenly coated on the surface of the base fabric using a doctor blade coating machine to obtain a pre-treated fabric. The pre-treated fabric is placed in a hot air dryer and dried at 160°C for 5 minutes. Then it is transferred to an electric heating blast drying oven and sintered at 360°C for 10 minutes. After that, it is slowly cooled to room temperature. Finally, it is cut and sewn to obtain a corrosion-resistant filter bag.

[0021] The mass ratio of basalt fiber to modified fiber is 70:25. The basalt fiber and modified fiber are woven in a twill weave with a warp density of 240 threads / 10cm and a weft density of 200 threads / 10cm. The hot air drying heating rate is 8℃ / min, the hot air velocity is 2m / s, and nitrogen inert protection is used for sintering. The temperature is raised to 360℃ at a rate of 4℃ / min, and after sintering, it is lowered to 80℃ at a rate of 3℃ / min and then naturally cooled to room temperature. The sewing thread is made of PTFE corrosion-resistant sewing thread with a stitch density of 4 stitches / cm.

[0022] The modified fiber is made by the following steps: Step A1: Oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine and ethylene glycol are mixed evenly and stirred for 15 minutes at a speed of 300 r / min and a temperature of 20℃. Then, polyphosphoric acid is slowly added dropwise, the temperature is raised to 180℃, and the reaction is refluxed for 10 hours to obtain intermediate 1. Step A2: Mix intermediate 1, palladium on carbon catalyst and 1,4-dioxane evenly, stir for 10 min at a speed of 200 r / min and a temperature of 75℃, then slowly add hydrazine hydrate dropwise and react at a constant temperature for 8 h to obtain intermediate 2. Step A3: Mix pyromellitic dianhydride, intermediate 2 and N,N-dimethylacetamide evenly, stir for 20 h at a speed of 200 °C and a temperature of 10 °C with nitrogen gas, add ferric nitrate nonahydrate and mix thoroughly for 6 h to obtain the spinning solution. Step A4: Spinning solution under the conditions of 15KV high voltage power supply, 1000r / min receiver rotation speed and 15℃ ambient temperature to obtain pretreated fiber. Place the pretreated fiber in a vacuum oven and dry it at 60℃. Then put it into a high temperature tube furnace for thermal imidization to obtain modified fiber.

[0023] The ratio of oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine, ethylene glycol, and polyphosphoric acid used in step A1 is 3.6g:19g:320mL:20mL.

[0024] The ratio of intermediate 1, palladium catalyst on carbon, 1,4-dioxane and hydrazine hydrate in step A2 is 5g:0.6g:60mL:7.66g, and the palladium content in the palladium catalyst on carbon is 0.5%.

[0025] The ratio of the amount of pyromellitic dianhydride, intermediate 2, N,N-dimethylacetamide and ferric nitrate nonahydrate in the ethanol solution described in step A3 is 1 mol: 1 mol: 100 mL: 0.2 mol.

[0026] The distance from the fiber receiver to the needle tip in step A4 is 25cm. The thermal imidization procedure is as follows: the temperature is rapidly increased from room temperature to 150℃ in 30min, held at the temperature for 2h, then increased to 250℃, held at the temperature for 1h, and then increased to 380℃. The heating rate is 2℃ / min. The entire process is carried out under nitrogen protection.

[0027] The foaming finishing agent is prepared by the following steps: Step B1: Boron nitride and 2-amino-5-mercapto-1,3,4-thiadiazole were dispersed in deionized water and sonicated in liquid phase for 3 hours. After centrifugation at 3000 r / min for 30 minutes, the supernatant was collected and filtered under reduced pressure to obtain pretreated boron nitride nanosheets. The pretreated boron nitride nanosheets were dispersed in Tris buffer solution at pH 8.5 and sonicated at 30 kHz for 40 minutes. Dopamine hydrochloride was added and stirred at 180 r / min and 20 °C for 10 hours to obtain the pretreated filler. Step B2: 3-Aminopropyltrimethoxysilane was added to an ethanol / water mixture and hydrolyzed for 1 hour at a speed of 200 r / min, a temperature of 40 °C, and a pH of 4. The temperature was then raised to 60 °C, and an ethanol dispersion of cerium oxide was slowly added dropwise. The reaction was carried out for 2 hours to obtain pretreated cerium oxide. The pretreated filler was dispersed in N,N-dimethylformamide and pretreated cerium oxide was added at a speed of 300 r / min and a temperature of 20 °C. The mixture was uniformly dispersed for 1 hour, and then the temperature was raised to 60 °C and the reaction was carried out for 4 hours to obtain the modified filler. Step B3: Add polytetrafluoroethylene emulsion to deionized water, then add betaine, Tween 80, methylcellulose and modified filler in sequence. After mixing evenly, stir for 10 minutes at a speed of 2000 r / min to obtain the foaming finishing agent.

[0028] In step B1, the ratio of boron nitride, 2-amino-5-mercapto-1,3,4-thiadiazole, and deionized water is 0.2 g: 0.2 g: 180 mL, and the ratio of pretreated boron nitride nanosheets, Tris buffer, and dopamine hydrochloride is 2 g: 400 mL: 0.8 g.

[0029] The ratio of 3-aminopropyltrimethoxysilane, ethanol / water mixed solution, and cerium oxide ethanol dispersion in step B2 is 0.05 g: 60 mL: 100 mL. The mass ratio of ethanol to water in the ethanol / water mixed solution is 85:15. The cerium oxide ethanol dispersion is prepared by dispersing 1.2 g of cerium oxide in 100 mL of ethanol. The ratio of pretreated filler, N,N-dimethylformamide, and pretreated cerium oxide is 0.3 g: 60 mL: 0.3 g.

[0030] The ratio of deionized water, polytetrafluoroethylene emulsion, betaine, Tween 80, methylcellulose and modified filler in step B3 is 60g:20g:2g:0.5g:2g:0.4g, and the solid content of polytetrafluoroethylene emulsion is 54%.

[0031] Example 2, a method for preparing a corrosion-resistant filter bag, specifically includes the following steps: Basalt fiber and modified fiber are woven to obtain a base fabric. A foaming agent is evenly coated on the surface of the base fabric using a doctor blade coating machine to obtain a pre-treated fabric. The pre-treated fabric is placed in a hot air dryer and dried at 160°C for 5 minutes. Then it is transferred to an electric heating blast drying oven and sintered at 360°C for 10 minutes. After that, it is slowly cooled to room temperature. Finally, it is cut and sewn to obtain a corrosion-resistant filter bag.

[0032] The mass ratio of basalt fiber to modified fiber is 70:28. The basalt fiber and modified fiber are woven in a twill weave with a warp density of 240 threads / 10cm and a weft density of 200 threads / 10cm. The hot air drying heating rate is 8℃ / min, the hot air velocity is 2m / s, and nitrogen inert protection is used for sintering. The temperature is raised to 360℃ at a rate of 4℃ / min, and after sintering, it is lowered to 80℃ at a rate of 3℃ / min and then naturally cooled to room temperature. The sewing thread is made of PTFE corrosion-resistant thread with a stitch density of 4 stitches / cm.

[0033] The modified fiber is made by the following steps: Step A1: Oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine and ethylene glycol are mixed evenly and stirred for 18 minutes at a speed of 350 r / min and a temperature of 25°C. Then, polyphosphoric acid is slowly added dropwise, the temperature is raised to 180°C, and the mixture is refluxed for 11 hours to obtain intermediate 1. Step A2: Mix intermediate 1, palladium on carbon catalyst and 1,4-dioxane evenly, stir for 15 min at a speed of 250 r / min and a temperature of 76℃, then slowly add hydrazine hydrate dropwise and react at a constant temperature for 9 h to obtain intermediate 2. Step A3: Mix pyromellitic dianhydride, intermediate 2 and N,N-dimethylacetamide evenly, stir for 22 hours at a speed of 250°C and a temperature of 10°C with nitrogen gas, add ferric nitrate nonahydrate and mix thoroughly for 7 hours to obtain the spinning solution. Step A4: Spinning solution under the conditions of 15KV high voltage power supply, 1000r / min receiver rotation speed and 15℃ ambient temperature to obtain pretreated fiber. Place the pretreated fiber in a vacuum oven and dry it at 70℃. Then put it into a high temperature tube furnace for thermal imidization to obtain modified fiber.

[0034] The ratio of oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine, ethylene glycol, and polyphosphoric acid used in step A1 is 3.6g:19g:320mL:20mL.

[0035] The ratio of intermediate 1, palladium catalyst on carbon, 1,4-dioxane and hydrazine hydrate in step A2 is 5g:0.6g:60mL:7.66g, and the palladium content in the palladium catalyst on carbon is 0.5%.

[0036] The ratio of the amount of pyromellitic dianhydride, intermediate 2, N,N-dimethylacetamide and ferric nitrate nonahydrate in the ethanol solution described in step A3 is 1 mol: 1 mol: 100 mL: 0.2 mol.

[0037] The distance from the fiber receiver to the needle tip in step A4 is 25cm. The thermal imidization procedure is as follows: the temperature is rapidly increased from room temperature to 150℃ in 30min, held at the temperature for 2h, then increased to 250℃, held at the temperature for 1h, and then increased to 380℃. The heating rate is 2℃ / min. The entire process is carried out under nitrogen protection.

[0038] The foaming finishing agent is prepared by the following steps: Step B1: Boron nitride and 2-amino-5-mercapto-1,3,4-thiadiazole were dispersed in deionized water and sonicated in liquid phase for 3 hours. After centrifugation at 3000 r / min for 33 minutes, the supernatant was collected and filtered under reduced pressure to obtain pretreated boron nitride nanosheets. The pretreated boron nitride nanosheets were dispersed in Tris buffer solution at pH 8.5 and sonicated at 35 kHz for 45 minutes. Dopamine hydrochloride was added and stirred at 190 r / min and 25 °C for 11 hours to obtain the pretreated filler. Step B2: 3-Aminopropyltrimethoxysilane was added to an ethanol / water mixture and hydrolyzed for 1 hour at a speed of 250 r / min, a temperature of 45 °C, and a pH of 4. The temperature was then raised to 65 °C, and an ethanol dispersion of cerium oxide was slowly added dropwise. The reaction was carried out for 3 hours to obtain pretreated cerium oxide. The pretreated filler was dispersed in N,N-dimethylformamide and pretreated cerium oxide was added at a speed of 350 r / min and a temperature of 25 °C. The mixture was uniformly dispersed for 1 hour, and then the temperature was raised to 70 °C and the reaction was carried out for 5 hours to obtain the modified filler. Step B3: Add polytetrafluoroethylene emulsion to deionized water, then add betaine, Tween 80, methylcellulose and modified filler in sequence. After mixing evenly, stir for 11 minutes at a speed of 2200 r / min to obtain the foaming finishing agent.

[0039] In step B1, the ratio of boron nitride, 2-amino-5-mercapto-1,3,4-thiadiazole, and deionized water is 0.2 g: 0.2 g: 180 mL, and the ratio of pretreated boron nitride nanosheets, Tris buffer, and dopamine hydrochloride is 2 g: 400 mL: 0.8 g.

[0040] The ratio of 3-aminopropyltrimethoxysilane, ethanol / water mixed solution, and cerium oxide ethanol dispersion in step B2 is 0.05 g: 60 mL: 100 mL. The mass ratio of ethanol to water in the ethanol / water mixed solution is 85:15. The cerium oxide ethanol dispersion is prepared by dispersing 1.2 g of cerium oxide in 100 mL of ethanol. The ratio of pretreated filler, N,N-dimethylformamide, and pretreated cerium oxide is 0.3 g: 60 mL: 0.3 g.

[0041] The ratio of deionized water, polytetrafluoroethylene emulsion, betaine, Tween 80, methylcellulose and modified filler in step B3 is 60g:20g:2g:0.5g:2g:0.6g, and the solid content of polytetrafluoroethylene emulsion is 54%.

[0042] Example 3, a method for preparing a corrosion-resistant filter bag, specifically includes the following steps: Basalt fiber and modified fiber are woven to obtain a base fabric. A foaming agent is evenly coated on the surface of the base fabric using a doctor blade coating machine to obtain a pre-treated fabric. The pre-treated fabric is placed in a hot air dryer and dried at 160°C for 5 minutes. Then it is transferred to an electric heating blast drying oven and sintered at 360°C for 10 minutes. After that, it is slowly cooled to room temperature. Finally, it is cut and sewn to obtain a corrosion-resistant filter bag.

[0043] The mass ratio of basalt fiber to modified fiber is 70:30. The basalt fiber and modified fiber are woven in a twill weave with a warp density of 240 threads / 10cm and a weft density of 200 threads / 10cm. The hot air drying heating rate is 8℃ / min, the hot air velocity is 2m / s, and nitrogen inert protection is used for sintering. The temperature is raised to 360℃ at a rate of 4℃ / min, and after sintering, it is lowered to 80℃ at a rate of 3℃ / min and then naturally cooled to room temperature. The sewing thread is made of PTFE corrosion-resistant thread with a stitch density of 4 stitches / cm.

[0044] The modified fiber is made by the following steps: Step A1: Oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine and ethylene glycol are mixed evenly and stirred for 20 min at a speed of 400 r / min and a temperature of 30℃. Then, polyphosphoric acid is slowly added dropwise, the temperature is raised to 185℃, and the reaction is refluxed for 12 h to obtain intermediate 1. Step A2: Mix intermediate 1, palladium on carbon catalyst and 1,4-dioxane evenly, stir for 20 min at 300 r / min and 80 °C, then slowly add hydrazine hydrate dropwise and react at a constant temperature for 10 h to obtain intermediate 2. Step A3: Mix pyromellitic dianhydride, intermediate 2 and N,N-dimethylacetamide evenly, stir for 24 hours at a speed of 300℃ and a temperature of 10℃ with nitrogen gas, add ferric nitrate nonahydrate and mix thoroughly for 8 hours to obtain the spinning solution. Step A4: Spinning solution under the conditions of 15KV high voltage power supply, 1000r / min receiver rotation speed and 15℃ ambient temperature to obtain pretreated fiber. Place the pretreated fiber in a vacuum oven and dry it at 80℃. Then put it into a high temperature tube furnace for thermal imidization to obtain modified fiber.

[0045] The ratio of oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine, ethylene glycol, and polyphosphoric acid used in step A1 is 3.6g:19g:320mL:20mL.

[0046] The ratio of intermediate 1, palladium catalyst on carbon, 1,4-dioxane and hydrazine hydrate in step A2 is 5g:0.6g:60mL:7.66g, and the palladium content in the palladium catalyst on carbon is 0.5%.

[0047] The ratio of the amount of pyromellitic dianhydride, intermediate 2, N,N-dimethylacetamide and ferric nitrate nonahydrate in the ethanol solution described in step A3 is 1 mol: 1 mol: 100 mL: 0.2 mol.

[0048] The distance from the fiber receiver to the needle tip in step A4 is 25cm. The thermal imidization procedure is as follows: the temperature is rapidly increased from room temperature to 150℃ in 30min, held at the temperature for 2h, then increased to 250℃, held at the temperature for 1h, and then increased to 380℃. The heating rate is 2℃ / min. The entire process is carried out under nitrogen protection.

[0049] The foaming finishing agent is prepared by the following steps: Step B1: Boron nitride and 2-amino-5-mercapto-1,3,4-thiadiazole were dispersed in deionized water and sonicated in liquid phase for 4 hours. After centrifugation at 3200 r / min for 35 min, the supernatant was collected and filtered under reduced pressure to obtain pretreated boron nitride nanosheets. The pretreated boron nitride nanosheets were dispersed in Tris buffer solution at pH 8.5 and sonicated at 40 kHz for 50 min. Dopamine hydrochloride was added and stirred at 200 r / min and 30 °C for 12 h to obtain the pretreated filler. Step B2: 3-Aminopropyltrimethoxysilane was added to an ethanol / water mixture and hydrolyzed for 2 hours at a speed of 300 r / min, a temperature of 50 °C, and a pH of 5. The temperature was then raised to 70 °C, and an ethanol dispersion of cerium oxide was slowly added dropwise. The reaction was carried out for 4 hours to obtain pretreated cerium oxide. The pretreated filler was dispersed in N,N-dimethylformamide and pretreated cerium oxide was added at a speed of 400 r / min and a temperature of 30 °C. The mixture was uniformly dispersed for 2 hours, and then the temperature was raised to 80 °C and the reaction was carried out for 6 hours to obtain the modified filler. Step B3: Add polytetrafluoroethylene emulsion to deionized water, then add betaine, Tween 80, methylcellulose and modified filler in sequence. After mixing evenly, stir for 12 minutes at a speed of 2500 r / min to obtain the foaming finishing agent.

[0050] In step B1, the ratio of boron nitride, 2-amino-5-mercapto-1,3,4-thiadiazole, and deionized water is 0.2 g: 0.2 g: 180 mL, and the ratio of pretreated boron nitride nanosheets, Tris buffer, and dopamine hydrochloride is 2 g: 400 mL: 0.8 g.

[0051] The ratio of 3-aminopropyltrimethoxysilane, ethanol / water mixed solution, and cerium oxide ethanol dispersion in step B2 is 0.05 g: 60 mL: 100 mL. The mass ratio of ethanol to water in the ethanol / water mixed solution is 85:15. The cerium oxide ethanol dispersion is prepared by dispersing 1.2 g of cerium oxide in 100 mL of ethanol. The ratio of pretreated filler, N,N-dimethylformamide, and pretreated cerium oxide is 0.3 g: 60 mL: 0.3 g.

[0052] The ratio of deionized water, polytetrafluoroethylene emulsion, betaine, Tween 80, methylcellulose and modified filler in step B3 is 60g:20g:2g:0.5g:2g:0.8g, and the solid content of polytetrafluoroethylene emulsion is 54%.

[0053] Comparative Example 1: In this comparative example, 4-nitro-1,2-phenylenediamine was used instead of 4-fluoro-5-nitrobenzene-1,2-diamine, while the other steps were the same.

[0054] Comparative Example 2: Compared with Example 1, this comparative example did not add ferric nitrate nonahydrate in step A3, but the other steps were the same.

[0055] Comparative Example 3: This comparative example uses pretreatment filler instead of modified filler, but the other steps are the same as in Example 1.

[0056] The corrosion-resistant filter bags prepared in Examples 1-3 and Comparative Examples 1-3 were tested for tensile strength according to GB / T3923.1-2013 "Textiles - Tensile Properties of Fabrics - Part 1: Determination of Breaking Strength and Elongation at Break (Strip Method)". The test results are shown in Table 1. The sample size was 200mm × 50mm and the tensile speed was 100mm / min.

[0057] (1) The sample was aged in a constant temperature oven at 230℃ for 1000h and its fracture strength retention rate was tested.

[0058] (2) The sample was completely immersed in the corrosive agent. The corrosive agent was selected as 5% sulfuric acid aqueous solution / 5% sodium hydroxide aqueous solution. The soaking time was 72h. After soaking, the sample was taken out and rinsed repeatedly with deionized water until the pH was neutral. Then it was dried in a 40℃ forced-air oven and its fracture strength retention rate was tested.

[0059] Table 1

[0060] As shown in Table 1, the corrosion-resistant filter bags prepared in Examples 1-3 retained 88.4%-92.2% of their tensile strength after aging in a 230℃ constant temperature oven for 1000 hours, indicating that the present invention has excellent high-temperature resistance. The samples treated with corrosion reagents also retained more than 80% of their tensile strength, indicating that the present invention has good corrosion resistance.

[0061] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a corrosion-resistant filter bag, characterized in that: Specifically, the steps include the following: Basalt fiber and modified fiber are woven to obtain a base fabric. A foaming agent is evenly coated on the surface of the base fabric using a doctor blade coating machine to obtain a pre-treated fabric. The pre-treated fabric is placed in a hot air dryer for drying, and then transferred to an electric heating drying oven for sintering. After sintering, it is slowly cooled to room temperature. Finally, it is cut and sewn to obtain a corrosion-resistant filter bag. The mass ratio of basalt fiber to modified fiber is 60-70:25-30.

2. The method for preparing a corrosion-resistant filter bag according to claim 1, characterized in that: The modified fiber is made by the following steps: Step A1: Oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine and ethylene glycol are mixed evenly and stirred. Then, polyphosphoric acid is slowly added dropwise, the mixture is heated and refluxed to obtain intermediate 1. Step A2: Mix intermediate 1, palladium on carbon catalyst and 1,4-dioxane evenly, stir, then slowly add hydrazine hydrate dropwise, and react at a constant temperature to obtain intermediate 2; Step A3: Mix pyromellitic dianhydride, intermediate 2 and N,N-dimethylacetamide evenly and stir. Add ferric nitrate nonahydrate and mix thoroughly to obtain the spinning solution. Step A4: Spin the spinning solution to obtain pretreated fibers. Place the pretreated fibers in a vacuum oven for drying, and then place them in a high-temperature tube furnace for thermal imidization to obtain modified fibers.

3. The method for preparing a corrosion-resistant filter bag according to claim 1, characterized in that: The ratio of oxalic acid, 4-fluoro-5-nitrobenzene-1,2-diamine, ethylene glycol, and polyphosphoric acid used in step A1 is 3.6g:19g:320mL:20mL.

4. The method for preparing a corrosion-resistant filter bag according to claim 1, characterized in that: The ratio of intermediate 1, palladium on carbon catalyst, 1,4-dioxane and hydrazine hydrate used in step A2 is 5g:0.6g:60mL:7.66g.

5. The method for preparing a corrosion-resistant filter bag according to claim 1, characterized in that: The ratio of the amount of pyromellitic dianhydride, intermediate 2, N,N-dimethylacetamide and ferric nitrate nonahydrate in the ethanol solution described in step A3 is 1 mol: 1 mol: 100 mL: 0.2 mol.

6. The method for preparing a corrosion-resistant filter bag according to claim 1, characterized in that: The foaming finishing agent is prepared by the following steps: Step B1: Boron nitride and 2-amino-5-mercapto-1,3,4-thiadiazole were dispersed in deionized water, subjected to liquid-phase assisted sonication, centrifuged, and the supernatant was collected and filtered under reduced pressure to obtain pretreated boron nitride nanosheets. The pretreated boron nitride nanosheets were dispersed in Tris buffer, sonicated, stirred, and dopamine hydrochloride was added to react and obtain the pretreated filler. Step B2: Add 3-aminopropyltrimethoxysilane to an ethanol / water mixture for hydrolysis and heating. Slowly add cerium oxide in ethanol to carry out the reaction and obtain pretreated cerium oxide. Disperse the pretreated filler in N,N-dimethylformamide, add the pretreated cerium oxide, disperse it evenly, and then heat it to carry out the reaction to obtain the modified filler. Step B3: Add polytetrafluoroethylene emulsion to deionized water, then add betaine, Tween 80, methylcellulose and modified filler in sequence, mix evenly and stir to obtain foaming finishing agent.

7. The method for preparing a corrosion-resistant filter bag according to claim 6, characterized in that: In step B1, the ratio of boron nitride, 2-amino-5-mercapto-1,3,4-thiadiazole, and deionized water is 0.2 g: 0.2 g: 180 mL, and the ratio of pretreated boron nitride nanosheets, Tris buffer, and dopamine hydrochloride is 2 g: 400 mL: 0.8 g.

8. The method for preparing a corrosion-resistant filter bag according to claim 6, characterized in that: The ratio of 3-aminopropyltrimethoxysilane, ethanol / water mixed solution and cerium oxide ethanol dispersion in step B2 is 0.05-0.1g:60mL:100mL, and the ratio of pretreatment filler, N,N-dimethylformamide and pretreatment cerium oxide is 0.3g:60mL:0.3g.

9. The method for preparing a corrosion-resistant filter bag according to claim 6, characterized in that: The ratio of deionized water, polytetrafluoroethylene emulsion, betaine, Tween 80, methylcellulose and modified filler in step B3 is 60g:20-24g:2g:0.5-1g:2g:0.4-0.8g.

10. A corrosion-resistant filter bag, characterized in that: Prepared according to any one of the preparation methods described in claims 1-9.

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