Acid corrosion resistant filter material and manufacturing process thereof

Abstract

The present invention relates to the technical field of filter materials, and specifically discloses an acid corrosion resistant filter material and a manufacturing process thereof. The preparation method of the filter material of the present invention comprises the following steps: step S1, adding p-toluenesulfonyl chloride to a tetrahydrofuran solution of 4,4',4"-triaminotriphenylmethane and triethylamine to synthesize an intermediate 1; step S2, adding the intermediate 1 and 3,3',4,4'-benzophenonetetracarboxylic dianhydride to N,N-dimethylacetamide to polymerize into polyamic acid; step S3, spinning the polyamic acid The polyamic acid nanofiber nonwoven membrane is spun and then thermally imidized to form a polyimide nanofiber nonwoven membrane; in step S4, the polyimide nanofiber nonwoven membrane is immersed in a magnesium-methanol suspension and subjected to suspension ultrasonication to obtain a modified polyimide fiber membrane; and in step S5, the modified polyimide fiber membrane and a modified polytetrafluoroethylene fiber membrane are hot-pressed to form a filter material. By combining the modified polyimide fiber membrane with the polytetrafluoroethylene membrane, the present invention improves the creep resistance and corrosion resistance of the filter material and the overlap strength between the membranes.

Description

Technical Field

[0001] The invention relates to the field of filter materials, and in particular to an acid corrosion resistant filter material and a manufacturing process thereof. Background Art

[0002] While resource-intensive heavy industries like electricity, metallurgy, and chemicals create enormous economic value, they also cause severe environmental pollution. Air pollution from heavy industry primarily consists of high-temperature flue gases, with major pollutants such as sulfur dioxide, nitrogen oxides, and dust particles. These pollutants not only severely pollute the environment but can also cause respiratory, cardiovascular, and cerebrovascular diseases when inhaled. To strengthen environmental protection efforts, national environmental protection standards are becoming increasingly stringent. Consequently, filter media with advantages such as high efficiency, high-temperature resistance, chemical corrosion resistance, water and oil repellency, and long service life are attracting increasing attention.

[0003] The commonly used raw materials for high-temperature resistant filter materials are glass fiber, aramid fiber, polyimide fiber, polyphenylene sulfide fiber, and polytetrafluoroethylene fiber. These fibers can usually withstand high-temperature flue gas of 200-300°C, but they also have their own defects and certain limitations in use: glass fiber is brittle and not resistant to folding, and is easily damaged during the high-temperature flue gas filtration process; aramid fiber is easily hydrolyzed and has a short service life; polyimide fiber has high breaking strength, low elongation, and good thermal stability, non-flammability and insulation properties. It is stable to dilute acid, but has the disadvantage of poor water resistance; polytetrafluoroethylene fiber is resistant to various chemical corrosion, is almost immune to erosion, has a smooth surface, is hydrophobic and resistant to condensation, but has poor compatibility with other substances and poor creep resistance, which affects its service life.

[0004] The invention improves the creep resistance of polytetrafluoroethylene, enhances the corrosion resistance of polyimide and improves the lap strength between filter material membranes by cross-linking and compounding modified polytetrafluoroethylene fiber membrane and modified polyimide fiber membrane. Summary of the Invention

[0005] In order to overcome the above technical problems, the purpose of the present invention is to provide an acid corrosion resistant filter material and a manufacturing process thereof, which can effectively filter particulate matter, is resistant to acid corrosion, and has a long service life.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The invention discloses an acid corrosion resistant filter material, which comprises a three-layer structure, wherein the core material is a modified polyimide fiber membrane and the outer layer is a modified polytetrafluoroethylene fiber membrane.

[0008] A process for manufacturing an acid corrosion resistant filter material comprises the following steps:

[0009] Step S1: Add anhydrous tetrahydrofuran, 4,4',4"-triaminotriphenylmethane, and triethylamine to reactor A, protect with nitrogen, stir, cool to 0°C, add dropwise a solution of p-toluenesulfonyl chloride in anhydrous tetrahydrofuran, keep the temperature for 1 hour, quench the reaction by adding saturated sodium chloride solution, precipitate a solid, filter, wash with water, and dry to obtain intermediate 1;

[0010] Step S2, adding N,N-dimethylacetamide, intermediate 1, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride to reaction kettle B, stirring at room temperature for 5 hours, adding N,N-dimethylacetamide, pouring the reaction solution into deionized water, filtering the precipitated solid, washing with water, and drying to obtain polyamic acid;

[0011] Step S3, dissolving polyamic acid in N,N-dimethylacetamide, stirring for 3 hours and aging for 12 hours, obtaining a polyamic acid nanofiber nonwoven membrane by electrospinning, and then pre-baking in a vacuum oven at 80° C. for 0.5 hours, and then subjecting the membrane to programmed temperature to obtain a polyimide nanofiber nonwoven membrane;

[0012] Step S4, soaking the polyimide nanofiber nonwoven membrane in a methanol suspension of magnesium powder, suspending and ultrasonicating for 1 hour, adding a 20% by mass ammonium chloride aqueous solution, and then suspending and ultrasonicating for 0.5 hour, taking out, washing, and drying to obtain a modified polyimide fiber membrane;

[0013] Step S5: placing the modified polyimide fiber membrane between two layers of modified polytetrafluoroethylene fiber membranes, vacuum hot pressing at 180-200° C., cooling, trimming, and rolling to obtain a filter material.

[0014] Furthermore, in step S1, the molar ratio of 4,4',4"-triaminotriphenylmethane, triethylamine, and p-toluenesulfonyl chloride is 1:1.05-1.2:1-1.1.

[0015] Furthermore, in step S2, the molar ratio of the intermediate 1 to 3,3',4,4'-benzophenonetetracarboxylic dianhydride is 1:1 to 1.1.

[0016] Furthermore, in step S3, the mass ratio of N,N-dimethylacetamide to polyamic acid is 8:1, the syringe used for electrospinning uses a No. 19 stainless steel needle, the distance from the needle to the collecting device is 15 cm, and the voltage is 20 kV; the programmed temperature includes a first stage heating rate of 10°C / min from 80°C to 150°C, a second stage heating rate of 5°C / min from 150°C to 220°C, and a third stage heating rate of 10°C / min from 220°C to 300°C, and keeping warm for 0.5 h.

[0017] Furthermore, in step S4, the mass ratio of magnesium powder, methanol, ammonium chloride and polyamide nanofiber non-woven fabric membrane is 0.3:3:1.5:1.

[0018] Furthermore, the vacuum hot pressing time in step S5 is 15 seconds.

[0019] Furthermore, the modified polytetrafluoroethylene fiber membrane used in step S5 is prepared by the following process:

[0020] The polytetrafluoroethylene fiber membrane was washed with acetone, dried and irradiated under vacuum; OP-10 emulsifier was added to an 80% by mass acrylic acid aqueous solution, vacuumed and ultrasonically deoxidized, and then coated on one side of the irradiated polytetrafluoroethylene fiber membrane, reacted at 90°C for 24 hours to obtain a polytetrafluoroethylene fiber membrane grafted with acrylic acid, which was then washed with water, washed with acetone and dried to obtain a modified polytetrafluoroethylene fiber membrane.

[0021] Furthermore, the polytetrafluoroethylene fiber membrane was irradiated in a vacuum state with a radiation voltage of 0.5 MV, a radiation beam current of 15 mA, and an irradiation time of 30 s; the mass ratio of acrylic acid, OP-10 emulsifier and polytetrafluoroethylene fiber membrane was 10:0.05:100.

[0022] An acid corrosion resistant filter material is prepared by any of the above-mentioned preparation processes.

[0023] Beneficial effects of the present invention:

[0024] The invention causes the exposed amino groups on the modified polyimide fiber membrane to react with the exposed carboxyl groups on the modified polytetrafluoroethylene fiber membrane during heat processing to generate crosslinking, thereby increasing the composite strength and improving the creep resistance of polytetrafluoroethylene and the corrosion resistance of polyimide.

[0025] The present invention introduces an amino protecting group into the amino group of 4,4',4"-triaminotriphenylmethane, controls the feeding method to form protection only on one amino group, and allows two amino groups to participate in the reaction to avoid the formation of a network structure and agglomeration during the synthesis of polyamic acid. After thermal imidization, the amino groups on the surface of the polyimide fiber membrane are exposed by deprotection, which facilitates the participation in the cross-linking reaction. At the same time, large side groups, twisted and non-coplanar structures are introduced into the monomer molecular structure to prevent the close stacking of polymer molecular chains, thereby reducing the intermolecular force and improving the air permeability of the membrane.

[0026] The present invention grafts acrylic acid onto the single-side surface of a polytetrafluoroethylene fiber membrane by electron beam irradiation, thereby improving the surface wettability of the polytetrafluoroethylene, increasing the compatibility of the modified surface of the polytetrafluoroethylene fiber membrane with other substances, and facilitating adhesion; the exposed carboxyl groups in the acrylic acid continue to undergo a dehydration reaction with the amino groups during hot pressing, causing the polyimide fiber membrane to be cross-linked with the surface of the polytetrafluoroethylene fiber membrane, thereby increasing the connection stability; at the same time, the water removed at high temperature is released in the form of gas, reducing the blockage of pores on the surface of the fiber membrane during the hot pressing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings.

[0028] Figure 1 is a reaction formula of the synthetic intermediate of the present invention;

[0029] Figure 2 is the reaction equation for synthesizing polyamic acid of the present invention;

[0030] Figure 3 The reaction equation for synthesizing the polyimide nanofiber nonwoven membrane of the present invention is:

[0031] Figure 4 is the reaction equation for synthesizing the modified polyimide fiber membrane of the present invention;

[0032] Figure 5 is the reaction equation for synthesizing the modified polytetrafluoroethylene fiber membrane of the present invention;

[0033] Figure 6 It is the reaction equation for synthesizing filter material of the present invention.

[0034] Figure 7 This is the reaction equation for synthesizing the polyimide non-woven membrane in Comparative Example 1. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] Example 1

[0037] See also Figure 1-4 , a modified polyimide fiber membrane, comprising the following steps:

[0038] Step S1. Add 72 mL of anhydrous tetrahydrofuran, 14.5 g of 4,4',4"-triaminotriphenylmethane, and 5.3 g of triethylamine to reactor A under nitrogen protection, stir, and cool to 0°C; dissolve 9.6 g of toluenesulfonyl chloride in 43 mL of anhydrous tetrahydrofuran and inject the mixture into reactor A with a syringe pump. Control the dropwise addition rate of p-toluenesulfonyl chloride and keep the addition time at least 4 hours to reduce the reaction between the p-toluenesulfonyl group and the multiple amino groups on 4,4',4"-triaminotriphenylmethane; after keeping the reaction warm for 1 hour, add 115 mL of saturated sodium chloride solution to quench the reaction, precipitate the solid, filter it, wash it with deionized water, and dry it in a vacuum oven at 60°C for 12 hours to obtain intermediate 1.

[0039] Step S2: Add 177 mL of N,N-dimethylacetamide, 16.1 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 22.2 g of intermediate 1 to reactor B, stir at room temperature for 5 hours, and add 133 mL of N,N-dimethylacetamide to dilute the reaction solution; pour the reaction solution into 250 mL of deionized water, stir to precipitate a solid, filter, wash with deionized water, and place in a vacuum oven at 60°C for 12 hours to obtain polyamic acid.

[0040] Step S3, add 306mL of N,N-dimethylacetamide and 38.3g of polyamic acid to a beaker, stir for 3h and age for 12h, and charge the aged polyamic acid solution into a syringe with a No. 19 stainless steel needle. The syringe is connected to the positive electrode of the high-voltage electrostatic power supply of the electrospinning device, and the distance from the needle to the collecting device is 15cm. Spinning is carried out at a voltage of 20kV, and the drum is rotated to collect to obtain a polyamic acid nanofiber non-woven fabric membrane, which is then placed in a vacuum oven at 80°C for pre-baking for 0.5h, and then subjected to programmed temperature heating for thermal imidization. The programmed temperature heating includes a first stage heating rate of 10°C / min from 80°C to 150°C, a second stage heating rate of 5°C / min from 150°C to 220°C, and a third stage heating rate of 10°C / min from 220°C to 300°C, and is kept warm for 0.5h. After cooling, a polyimide nanofiber non-woven fabric membrane is obtained.

[0041] Step S4, adding 11.0g of magnesium powder to 90mL of methanol to form a suspension, adding 36.5g of polyimide nanofiber non-woven fabric membrane to the suspension, suspending and ultrasonicating for 1h to remove the p-methylbenzenesulfonyl protecting group on the surface of the polyimide nanofiber non-woven fabric membrane, exposing part of the amino group; then adding 240mL of a 20% by mass aqueous solution of ammonium chloride, and suspending and ultrasonicating for 0.5h to dissolve and remove the magnesium powder; after the magnesium powder solid disappears, taking out the polyimide membrane, washing with deionized water, and placing it in a vacuum oven at 60°C to dry for 12h to obtain a modified polyimide fiber membrane.

[0042] Example 2

[0043] See also Figure 1-4 , a modified polyimide fiber membrane, comprising the following steps:

[0044] Step S1. Add 72 mL of anhydrous tetrahydrofuran, 14.5 g of 4,4',4"-triaminotriphenylmethane, and 5.6 g of triethylamine to reactor A under nitrogen protection, stir, and cool to 0°C; dissolve 10 g of toluenesulfonyl chloride in 43 mL of anhydrous tetrahydrofuran and inject the mixture into reactor A with a syringe pump. Control the dropwise addition rate of p-toluenesulfonyl chloride and keep the addition time at least 4 hours to reduce the reaction between the p-toluenesulfonyl group and the multiple amino groups on 4,4',4"-triaminotriphenylmethane; after keeping the reaction warm for 1 hour, add 115 mL of saturated sodium chloride solution to quench the reaction, precipitate the solid, filter it, wash with deionized water, and dry it in a vacuum oven at 60°C for 12 hours to obtain intermediate 1.

[0045] Step S2: Add 177 mL of N,N-dimethylacetamide, 16.9 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 22.2 g of intermediate 1 to reactor B, stir at room temperature for 5 hours, and add 133 mL of N,N-dimethylacetamide to dilute the reaction solution; pour the reaction solution into 250 mL of deionized water, stir to precipitate a solid, filter, wash with deionized water, and place in a vacuum oven at 60°C for 12 hours to obtain polyamic acid.

[0046] Step S3, add 306mL of N,N-dimethylacetamide and 38.3g of polyamic acid to a beaker, stir for 3h and age for 12h, and charge the aged polyamic acid solution into a syringe with a No. 19 stainless steel needle. The syringe is connected to the positive electrode of the high-voltage electrostatic power supply of the electrospinning device, and the distance from the needle to the collecting device is 15cm. Spinning is carried out at a voltage of 20kV, and the drum is rotated to collect to obtain a polyamic acid nanofiber non-woven fabric membrane, which is then placed in a vacuum oven at 80°C for pre-baking for 0.5h, and then subjected to programmed temperature heating for thermal imidization. The programmed temperature heating includes a first stage heating rate of 10°C / min from 80°C to 150°C, a second stage heating rate of 5°C / min from 150°C to 220°C, and a third stage heating rate of 10°C / min from 220°C to 300°C, and is kept warm for 0.5h. After cooling, a polyimide nanofiber non-woven fabric membrane is obtained.

[0047] Step S4, adding 11.0g of magnesium powder to 90mL of methanol to form a suspension, adding 36.5g of polyimide nanofiber non-woven fabric membrane to the suspension, suspending and ultrasonicating for 1h to remove the p-methylbenzenesulfonyl protecting group on the surface of the polyimide nanofiber non-woven fabric membrane, exposing part of the amino group; then adding 240mL of a 20% by mass aqueous solution of ammonium chloride, and suspending and ultrasonicating for 0.5h to dissolve and remove the magnesium powder; after the magnesium powder solid disappears, taking out the polyimide membrane, washing with deionized water, and placing it in a vacuum oven at 60°C to dry for 12h to obtain a modified polyimide fiber membrane.

[0048] Example 3

[0049] See also Figure 1-4The modified polyimide fiber membrane prepared by the present invention comprises the following steps:

[0050] Step S1. Add 72 mL of anhydrous tetrahydrofuran, 14.5 g of 4,4',4"-triaminotriphenylmethane, and 6.1 g of triethylamine to reactor A under nitrogen protection, stir, and cool to 0°C; dissolve 10.5 g of toluenesulfonyl chloride in 43 mL of anhydrous tetrahydrofuran and inject the mixture into reactor A with a syringe pump. Control the dropwise addition rate of p-toluenesulfonyl chloride and keep the addition time at least 4 hours to reduce the reaction between the p-toluenesulfonyl group and the multiple amino groups on 4,4',4"-triaminotriphenylmethane; after keeping the reaction warm for 1 hour, add 115 mL of saturated sodium chloride solution to quench the reaction, precipitate a solid, filter, wash with deionized water, and dry in a vacuum oven at 60°C for 12 hours to obtain intermediate 1.

[0051] Step S2: Add 177 mL of N,N-dimethylacetamide, 17.7 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 22.2 g of intermediate 1 to reactor B, stir at room temperature for 5 hours, and add 133 mL of N,N-dimethylacetamide to dilute the reaction solution; pour the reaction solution into 250 mL of deionized water, stir to precipitate a solid, filter, wash with deionized water, and place in a vacuum oven at 60°C for 12 hours to obtain polyamic acid.

[0052] Step S3, add 306mL of N,N-dimethylacetamide and 38.3g of polyamic acid to a beaker, stir for 3h and age for 12h, and charge the aged polyamic acid solution into a syringe with a No. 19 stainless steel needle. The syringe is connected to the positive electrode of the high-voltage electrostatic power supply of the electrospinning device, and the distance from the needle to the collecting device is 15cm. Spinning is carried out at a voltage of 20kV, and the drum is rotated to collect to obtain a polyamic acid nanofiber non-woven fabric membrane, which is then placed in a vacuum oven at 80°C for pre-baking for 0.5h, and then subjected to programmed temperature heating for thermal imidization. The programmed temperature heating includes a first stage heating rate of 10°C / min from 80°C to 150°C, a second stage heating rate of 5°C / min from 150°C to 220°C, and a third stage heating rate of 10°C / min from 220°C to 300°C, and is kept warm for 0.5h. After cooling, a polyimide nanofiber non-woven fabric membrane is obtained.

[0053] Step S4, adding 11.0g of magnesium powder to 90mL of methanol to form a suspension, adding 36.5g of polyimide nanofiber non-woven fabric membrane to the suspension, suspending and ultrasonicating for 1h to remove the p-methylbenzenesulfonyl protecting group on the surface of the polyimide nanofiber non-woven fabric membrane, exposing part of the amino group; then adding 240mL of a 20% by mass aqueous solution of ammonium chloride, and suspending and ultrasonicating for 0.5h to dissolve and remove the magnesium powder; after the magnesium powder solid disappears, taking out the polyimide membrane, washing with deionized water, and placing it in a vacuum oven at 60°C to dry for 12h to obtain a modified polyimide fiber membrane.

[0054] Example 4

[0055] See also Figure 5 , a modified polytetrafluoroethylene fiber membrane, comprising the following steps:

[0056] 30 g of polytetrafluoroethylene fiber membrane (purchased from Suzhou Youkefa New Material Technology Co., Ltd.) was washed with acetone to remove surface dust and grease, placed in a vacuum oven at 60°C for 12 h, and then placed in the beam area of ​​a high-frequency, high-pressure self-shielded electron accelerator for irradiation under vacuum, with a radiation voltage of 0.5 MV, a radiation beam current of 15 mA, and an irradiation time of 30 s; 0.015 g of OP-10 emulsifier was added to 3.8 g of an 80% by mass acrylic acid aqueous solution, and after vacuum ultrasonic deoxidation, the solution was coated on one side of the irradiated polytetrafluoroethylene fiber membrane, placed in an oven, and reacted at 90°C for 24 h under nitrogen protection to obtain a polytetrafluoroethylene fiber membrane grafted with acrylic acid, which was then washed with deionized water and acetone to remove unreacted monomers and homopolymers on the surface, and placed in a vacuum oven at 60°C for 12 h to obtain a modified polytetrafluoroethylene fiber membrane.

[0057] Example 5

[0058] See also Figure 6 , a filter material, comprising the following steps:

[0059] The modified polyimide fiber membrane in Example 1 is placed between two layers of modified polytetrafluoroethylene fiber membrane in Example 4, with the modified surface of the modified polytetrafluoroethylene fiber membrane facing the modified polyimide fiber membrane. The three-layer membrane is placed in a vacuum hot press and hot-pressed at 180-200°C for 15s, so that the exposed amino groups on the surface of the modified polyimide fiber membrane and the carboxyl groups on the acrylic acid grafted on one side of the surface of the modified polytetrafluoroethylene fiber membrane are thermally dehydrated, cross-linked and composited into a whole, and then cooled, trimmed and rolled up to obtain the filter material.

[0060] Example 6

[0061] See also Figure 6 , a filter material, comprising the following steps:

[0062] The modified polyimide fiber membrane in Example 2 is placed between two layers of modified polytetrafluoroethylene fiber membrane in Example 4, with the modified surface of the modified polytetrafluoroethylene fiber membrane facing the modified polyimide fiber membrane. The three-layer membrane is placed in a vacuum hot press and hot-pressed at 180-200°C for 15s, so that the exposed amino groups on the surface of the modified polyimide fiber membrane and the carboxyl groups on the acrylic acid grafted on one side of the surface of the modified polytetrafluoroethylene fiber membrane are thermally dehydrated, cross-linked and composited into a whole, and then cooled, trimmed and rolled up to obtain the filter material.

[0063] Example 7

[0064] See also Figure 6, a filter material, comprising the following steps:

[0065] The modified polyimide fiber membrane in Example 3 is placed between two layers of modified polytetrafluoroethylene fiber membrane in Example 4, with the modified surface of the modified polytetrafluoroethylene fiber membrane facing the modified polyimide fiber membrane. The three-layer membrane is placed in a vacuum hot press and hot-pressed at 180-200°C for 15s, so that the exposed amino groups on the surface of the modified polyimide fiber membrane and the carboxyl groups on the acrylic acid grafted on one side of the surface of the modified polytetrafluoroethylene fiber membrane are thermally dehydrated, cross-linked and composited into a whole, and then cooled, trimmed and rolled up to obtain the filter material.

[0066] Comparative Example 1

[0067] See also Figure 7 , a preparation method of a polyimide nonwoven membrane comprises the following steps:

[0068] At room temperature, 160 mL of N, N-dimethylacetamide and 20 g of 4, 4'-diaminodiphenyl ether were added to the reactor C and stirred continuously until the 4, 4'-diaminodiphenyl ether was completely dissolved to form a colorless and transparent solution. 31 g of 3, 3', 4, 4'-diphenyl ether tetracarboxylic dianhydride was added to the solution in batches. When the equivalent point was almost reached, the viscosity of the polyimide increased rapidly. Stirring was continued for 2 h to stabilize the viscosity. 300 mL of N, N-dimethylacetamide was added, stirred for 3 h and aged for 12 h. The aged polyamic acid solution was placed in a syringe with a No. 19 stainless steel needle. The syringe was The positive electrode of the high-voltage electrostatic power supply of the electrospinning device was connected, the distance between the needle and the collecting device was 15 cm, spinning was carried out at a voltage of 20 kV, and the drum was rotated for collection to obtain a polyamic acid non-woven fabric membrane, which was then placed in a vacuum oven for pre-baking at 80°C for 0.5 h, and then subjected to programmed temperature rise for thermal imidization. The programmed temperature rise included a first stage heating rate from 80°C to 150°C at a heating rate of 10°C / min, a second stage heating rate from 150°C to 220°C at a heating rate of 5°C / min, and a third stage heating rate from 220°C to 300°C at a heating rate of 10°C / min. The membrane was kept warm for 0.5 h and cooled to obtain a polyimide non-woven fabric membrane.

[0069] Comparative Example 2

[0070] The polyimide non-woven fabric membrane in Comparative Example 1 was placed between two layers of polytetrafluoroethylene fiber membrane (purchased from Suzhou Youkefa New Material Technology Co., Ltd.), placed in a vacuum hot press at 180-200°C for 15s, cooled, trimmed, and rolled to obtain a filter material.

[0071] Comparative Example 3

[0072] The polyimide nonwoven fabric membrane in Comparative Example 1 was placed between two layers of modified polytetrafluoroethylene fiber membranes prepared in Example 4, with the modified surface of the modified polytetrafluoroethylene fiber membrane facing the modified polyimide fiber membrane. The three-layer membrane was placed in a vacuum hot press at 180-200°C for 15s, cooled, trimmed, and rolled up to obtain a filter material.

[0073] Comparative Example 4

[0074] The modified polyimide fiber membrane in Example 1 was placed between two layers of polytetrafluoroethylene fiber membrane (purchased from Suzhou Youkefa New Material Technology Co., Ltd.), and placed in a vacuum hot press at 180-200°C for 15s, cooled, trimmed, and rolled to obtain a filter material.

[0075] Creep resistance test

[0076] The high-temperature creep test was carried out in an oven. The upper end of a 10 mm × 150 mm specimen was fixed on the oven rack, and a 3 kg weight was loaded on the lower end. The specimen was suspended horizontally at 200 °C for 4 h. The strain of the specimen was recorded, and the residual strength of the specimen was measured using an electronic fabric strength tester (purchased from Nantong Hongda Experimental Instrument Co., Ltd.). The test results are shown in Table 1.

[0077] Table 1: Creep resistance test

[0078]

[0079] It can be seen from Table 1 that the acid corrosion resistant filter material prepared by the present invention has good creep resistance.

[0080] Filtration performance test

[0081] With reference to GB / T14295-2008, the filtration efficiency and resistance of the sample were tested using an air filtration test bench. The test parameters were set as follows: sample diameter 15 cm, temperature 25°C, relative humidity 65%, and gas flow rate 10 m 3 / h, dust concentration 1mg / m 3 The aerosol type used was dioctyl sebacate, and the diameter of the aerosol particles was set to 0.2-0.3 μm. The test results are shown in Table 2.

[0082] Table 2: Filtration performance test

[0083]

[0084]

[0085] It can be seen from Table 2 that the acid corrosion resistant filter material prepared by the present invention has good filtration efficiency and small filtration resistance.

[0086] Acid resistance test

[0087] The sample was immersed in a 10% sulfuric acid aqueous solution at 90°C for 24 hours, and the change in tensile strength was measured according to QB / T4876-2015. The test results are shown in Table 3.

[0088] Table 3: Acid resistance test

[0089]

[0090] It can be seen from Table 3 that after acid corrosion, the acid corrosion-resistant filter material prepared by the present invention has a smaller decrease in tensile strength and has strong acid corrosion resistance.

[0091] Water contact angle and lap strength test

[0092] The contact angle of a water droplet on the sample surface was measured using a contact angle tester. The droplet volume was 2.0 μL, and the test conditions were 25°C and 60% relative humidity.

[0093] The filter material sample was tested for the overlap strength between membranes using an electronic tensile testing machine with a tensile speed of 50 mm / min and a test area of ​​10 cm 2 , the test results are shown in Table 4.

[0094] Table 4: Water contact angle and lap strength test

[0095]

[0096] As can be seen from Table 4, the water contact angle of the modified surface of the modified polytetrafluoroethylene prepared by the present invention is greatly reduced, the wettability is greatly improved, the overlap strength is slightly improved after being compounded with the ordinary polyimide membrane, and the overlap strength between membranes is significantly improved after being compounded with the modified polyimide prepared by the present invention, that is, the acid corrosion-resistant filter material prepared by the present invention.

[0097] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A process for preparing an acid corrosion resistant filter material, characterized in that: The steps include: Step S1: Add anhydrous tetrahydrofuran, 4,4',4"-triaminotriphenylmethane, and triethylamine to reactor A, protect with nitrogen, stir, cool to 0°C, add dropwise a solution of p-toluenesulfonyl chloride in anhydrous tetrahydrofuran, keep the temperature for 1 hour, quench the reaction by adding saturated sodium chloride solution, precipitate a solid, filter, wash with water, and dry to obtain intermediate 1; Step S2, adding N,N-dimethylacetamide, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and intermediate 1 into reactor B, stirring at room temperature for 5 hours, adding N,N-dimethylacetamide, pouring the reaction solution into deionized water, filtering, washing, and drying the precipitated solid to obtain polyamic acid; Step S3, dissolving polyamic acid in N,N-dimethylacetamide, stirring for 3 hours and aging for 12 hours, obtaining a polyamic acid nanofiber nonwoven membrane by electrospinning, and then pre-baking in a vacuum oven at 80° C. for 0.5 hours, and then subjecting the membrane to programmed temperature to obtain a polyimide nanofiber nonwoven membrane; Step S4, soaking the polyimide nanofiber nonwoven membrane in a methanol suspension of magnesium powder, suspending and ultrasonicating for 1 hour, adding a 20% by mass ammonium chloride aqueous solution, and then suspending and ultrasonicating for another 0.5 hour, taking out, washing, and drying to obtain a modified polyimide fiber membrane; Step S5, placing the modified polyimide fiber membrane between two layers of modified polytetrafluoroethylene fiber membranes, vacuum hot pressing at 180-200° C., cooling, trimming, and rolling to obtain a filter material; The modified polytetrafluoroethylene fiber membrane used in step S5 is prepared by the following process: The polytetrafluoroethylene fiber membrane was washed with acetone, dried, and irradiated under vacuum; OP-10 emulsifier was added to an 80% by mass acrylic acid aqueous solution, and after vacuum ultrasonic deoxygenation, it was coated on one side of the irradiated polytetrafluoroethylene fiber membrane and reacted at 90°C for 24 hours to obtain a polytetrafluoroethylene fiber membrane grafted with acrylic acid, which was then washed with water, washed with acetone, and dried to obtain a modified polytetrafluoroethylene fiber membrane.

2. The process for preparing an acid corrosion resistant filter material according to claim 1, characterized in that: In step S1, the molar ratio of 4,4',4"-triaminotriphenylmethane, triethylamine, and p-toluenesulfonyl chloride is 1:1.05-1.2:1-1.

1.

3. The process for preparing an acid corrosion resistant filter material according to claim 1, characterized in that: In step S2, the molar ratio of the intermediate 1 to 3,3',4,4'-benzophenonetetracarboxylic dianhydride is 1:1-1.

1.

4. The process for preparing an acid corrosion resistant filter material according to claim 1, characterized in that: In step S3, the mass ratio of N,N-dimethylacetamide to polyamic acid is 8:1, the syringe used for electrospinning uses a 19-gauge stainless steel needle, the distance from the needle to the collection device is 15 cm, and the voltage is 20 kV; The programmed temperature rise included a first stage of heating from 80°C to 150°C at a rate of 10°C / min, a second stage of heating from 150°C to 220°C at a rate of 5°C / min, and a third stage of heating from 220°C to 300°C at a rate of 10°C / min, with retention for 0.5 h.

5. The process for preparing an acid corrosion resistant filter material according to claim 1, characterized in that: In step S4, the mass ratio of magnesium powder, methanol, ammonium chloride and polyimide nanofiber non-woven fabric membrane is 0.3:3:1.5:

1.

6. The process for preparing an acid corrosion resistant filter material according to claim 1, characterized in that: The vacuum hot pressing time in step S5 is 15 seconds.

7. The process for preparing an acid corrosion resistant filter material according to claim 1, characterized in that: The polytetrafluoroethylene fiber membrane was placed in a vacuum state and irradiated with a radiation voltage of 0.5 MV, a radiation beam current of 15 mA, and an irradiation time of 30 s; the mass ratio of acrylic acid, OP-10 emulsifier and polytetrafluoroethylene fiber membrane was 10:0.05:

100.

8. An acid corrosion resistant filter material, characterized in that: The invention is prepared by the preparation process described in any one of claims 1 to 7.

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