Filter material and use thereof

Abstract

The application discloses a filtering material and application thereof, which comprises, from top to bottom, a polytetrafluoroethylene film, a first polyphenylene sulfide fiber mixed resin layer, a second polyphenylene sulfide fiber layer and a third polyphenylene sulfide fiber mixed resin layer, wherein the thickness of the first polyphenylene sulfide fiber mixed resin layer and the third polyphenylene sulfide fiber mixed resin layer accounts for 1 / 6-1 / 3 of the thickness of the filtering material. The filtering material has the advantages of high rigidity and softness and high ventilation at high temperature, and can be applied to the filtering fields of steel, thermal power generation, cement and garbage incineration.

Description

Technical Field

[0001] This invention relates to a filter material and its uses. Background Technology

[0002] Pleated filter bags, as a new type of filter bag, have been widely used in power plant boiler dust removal and high-emission fields such as the steel industry. Currently, most pleated filter bags on the market are made with resin-processed filter media. The concentration and distribution of the resin affect the rigidity and air permeability of the filter media. When the resin concentration is high, the resin may be distributed throughout the entire thickness of the filter media, leading to decreased air permeability and increased pressure loss. When the resin concentration is low, the resin may be distributed only in localized areas of the filter media's thickness, resulting in low rigidity and inability to withstand the pressure generated during the cleaning process, thus affecting the dust removal effect, causing dust accumulation on the filter media, and increasing operating resistance.

[0003] For example, Chinese patent CN114452718A discloses a novel functional filter felt and its production method. This filter material is a nonwoven material with a porous structure formed by mechanically needle-punching and high-pressure hydroentangling fibers on the dust-facing and dust-repellent sides, causing them to interlock and entangle. After being impregnated with a circulating slurry, the slurry gradually penetrates into the filter felt. After heat setting, the slurry solidifies on the surface and inside of the filter felt. Therefore, the slurry is mainly distributed on the surface and middle layers of the filter felt, or on the surface, middle layers, and reverse side. Due to the high resin content, although the filter material has high rigidity and flexibility, the three-dimensional pores of the filter felt are filled by the slurry, resulting in smaller pores and thus reduced air permeability and increased pressure loss.

[0004] For example, Chinese patent CN115999253A discloses a method for preparing rigid membrane filter media for filter cartridges and its product. This filter media is prepared by uniformly coating the clean air surface of a fiber felt with a stiffening agent. However, most of the stiffening agent only adheres to the clean air surface of the fiber felt, with very little or no stiffening agent on the dust-facing surface. Therefore, the filter media has low rigidity and is prone to deformation during use, further reducing its filtration efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a filter material that maintains high rigidity and flexibility and high air permeability at high temperatures.

[0006] The technical solution of the present invention is as follows: The filter material of the present invention comprises, from top to bottom, a polytetrafluoroethylene membrane, a first polyphenylene sulfide fiber mixed resin layer, a second polyphenylene sulfide fiber layer, and a third polyphenylene sulfide fiber mixed resin layer, wherein the thickness of the first polyphenylene sulfide fiber mixed resin layer and the third polyphenylene sulfide fiber mixed resin layer accounts for 1 / 6 to 1 / 3 of the thickness of the filter material, respectively.

[0007] The average hair length on the surface of the first polyphenylene sulfide fiber-reinforced resin layer is preferably 0.10 to 0.20 mm.

[0008] The number of hairs on the surface of the first polyphenylene sulfide fiber-resin composite layer is preferably 2 to 20 hairs / cm.

[0009] The first polyphenylene sulfide fiber-reinforced layer contains solid blocks, and the average area of ​​90% of the solid blocks is preferably 10,000 to 30,000 μm. 2 .

[0010] The average pore size of the filter material of the present invention is preferably 0.50 to 1.50 μm.

[0011] The thickness of the filter material of the present invention is preferably 0.40 to 1.80 mm.

[0012] The stiffness of the filter material of this invention after being treated at 160°C for 30 minutes is preferably less than 45°.

[0013] The membrane adhesion of the filter material of the present invention is preferably grade 1.

[0014] The filter material of the present invention preferably has a capture efficiency of 99% or higher for particles with a diameter of 0.3 to 0.5 μm.

[0015] The beneficial effects of this invention are: the first and third layers of the filter material are both polyphenylene sulfide fiber mixed resin layers, ensuring that the filter material retains its advantages of high rigidity and flexibility, and high air permeability even when used at high temperatures. The filter material of this invention can be applied to process filtration in industries such as steelmaking, thermal power generation, cement, and waste incineration. Detailed Implementation

[0016] The filter material of this invention comprises, from top to bottom, a polytetrafluoroethylene (PTFE) membrane, a first polyphenylene sulfide (PPS) fiber-resin blend layer, a second PPS fiber layer, and a third PPS fiber-resin blend layer. From a macroscopic perspective, the filter material of this invention includes a PTFE membrane and a single sheet of PPS nonwoven fabric; from a microscopic perspective, the filter material of this invention includes a PTFE membrane, a first PPS fiber-resin blend layer, a second PPS fiber layer, and a third PPS fiber-resin blend layer. The preparation method of the above four-layer structure is as follows: First, the prepared PPS spunlace nonwoven fabric is immersed in a resin tank, and then pressed by a rolling mill. After adjusting the appropriate roller pressure, the surface of the PPS spunlace nonwoven fabric contacts the upper roller, and the reverse side contacts the lower roller, so that resin adheres to both the surface and reverse side of the PPS spunlace nonwoven fabric, and no residual resin permeates the middle layer. Therefore, the surface is the first PPS fiber-resin blend layer, the middle layer is still the second PPS fiber layer, and the reverse side is the third PPS fiber-resin blend layer. Secondly, the polyphenylene sulfide spunlace nonwoven fabric undergoes a heat-setting process to dry the resin adhering to the surface and reverse sides. This heat-setting process eliminates the internal stress generated during the stretching process of the polyphenylene sulfide spunlace nonwoven fabric, causing a certain degree of relaxation in the macromolecules, thereby improving the dimensional stability of the polyphenylene sulfide spunlace nonwoven fabric. Finally, after the surface of the polyphenylene sulfide spunlace nonwoven fabric is singed, a polytetrafluoroethylene membrane is hot-pressed onto the surface of the first polyphenylene sulfide fiber-resin mixture layer to obtain the filter material of this invention.

[0017] The thickness of the first polyphenylene sulfide fiber mixed resin layer accounts for 1 / 6 to 1 / 3 of the filter material thickness, and the thickness of the third polyphenylene sulfide fiber mixed resin layer accounts for 1 / 6 to 1 / 3 of the filter material thickness. If the proportion is less than 1 / 6, it indicates that there is only a very small amount of resin on the surface and back of the polyphenylene sulfide spunlace felt, resulting in a decrease in the rigidity and flexibility of the filter material. On the one hand, when the low-rigidity filter material is folded into pleats, it is prone to poor shape stability, and deformation will occur due to repeated spraying during actual use. On the other hand, the low-rigidity filter material is more prone to wear or damage during use, which will shorten the service life of the filter material. Frequent replacement of filter media not only increases costs but also affects the stability and efficiency of the filtration system. If the resin content is greater than 1 / 3, it indicates that a large amount of resin has seeped into the surface and back of the polyphenylene sulfide spunlace felt, and there is also a large amount of resin inside the filter media. This resin adheres to the polyphenylene sulfide fibers or between the fibers, significantly reducing the pore size and air permeability of the filter media. Since dust easily penetrates deep into the filter media and is difficult to clean, the pores gradually become clogged over time, leading to a further decrease in air permeability and a significant increase in operating resistance. This not only increases energy consumption but also reduces the lifespan of the filter media. Considering the high rigidity and flexibility and high air permeability of the filter media, the thickness of the first polyphenylene sulfide fiber mixed resin layer and the third polyphenylene sulfide fiber mixed resin layer should preferably be 1 / 5 to 1 / 4 of the total filter media thickness.

[0018] The average hair length on the surface of the first polyphenylene sulfide fiber-resin blend layer is preferably 0.10–0.20 mm. The hair on the surface of this first polyphenylene sulfide fiber-resin blend layer is formed by the mechanical forces acting on the polyphenylene sulfide fibers during the hydroentangling process. Through hydroentangling, high-pressure, high-speed micro-flows of water impact the polyphenylene sulfide fiber web, causing the fibers in the web to intertwine and become fixed, forming a polyphenylene sulfide hydroentangled felt with a certain strength. If the average feather length is too short, it becomes more difficult to determine whether the feathers have been effectively removed during visual inspection of the singeing effect, making it impossible to accurately judge the singeing effect. If the singeing effect is poor, it is easy for the polytetrafluoroethylene membrane to be difficult to cover with polyphenylene sulfide spunlace felt during membrane coating, thus the filtration accuracy of the filter material tends to decrease. If the average feather length is too long, the flame will require a longer time and higher temperature to completely remove the feathers during the singeing process, causing the feathers on the filter material surface to melt into large clumps. These large clumps are prone to damaging the polytetrafluoroethylene membrane during membrane coating, resulting in a tendency for the outlet concentration of the filter material to increase. Considering the high filtration accuracy and low outlet concentration of the filter material, the average feather length on the surface of the first polyphenylene sulfide fiber mixed resin layer is more preferably 0.12-0.18 mm.

[0019] The preferred number of hairs on the surface of the first polyphenylene sulfide (PPS) fiber-resin blend layer is 2 to 20 hairs / cm. If the number of hairs is too low, the surface of the PPS spunlace felt is too smooth, lacking roughness. This prevents the PTFE membrane from adhering evenly to the surface of the first PPS fiber-resin blend layer, reducing adhesion to the substrate and potentially leading to blistering and peeling. This results in increased outlet concentration and reduced circulation time for the filter material. Conversely, if the number of hairs is too high, the surface of the PPS spunlace felt is rough. After singeing, most hairs melt and form large clumps. These clumps can damage the PTFE membrane during lamination. Once the PTFE membrane is damaged, dust can more easily penetrate from the PTFE membrane surface to the third PPS fiber-resin blend layer, causing dust penetration and blockage, thus reducing the filter material's lifespan. Furthermore, an excessive number of hairs may require higher temperatures to ensure uniform and firm lamination, placing greater thermal stress on the lamination equipment and resulting in poor stability in filter material mass production. Considering the coating strength and the service life of the filter material, the number of hairs in the first polyphenylene sulfide fiber-resin composite layer is more preferably 8 to 15 hairs / cm.

[0020] The first polyphenylene sulfide fiber-reinforced layer contains solid blocks, and the average area of ​​90% of the solid blocks is preferably 10,000 to 30,000 μm. 2 The solid lumps here refer to clumps formed when the surface fiber hairs of the first polyphenylene sulfide fiber-resin composite layer melt upon heating and then cool. Specifically, the surface of the first polyphenylene sulfide fiber-resin composite layer is singed, with a flame burning the surface fiber hairs, causing them to melt and form solid lumps. The average area of ​​the solid lumps refers to the average area of ​​the dark yellow lumps formed after the flame burned the surface fiber hairs of the first polyphenylene sulfide fiber-resin composite layer during singing and then cooled. If the average area of ​​the 90% solid blocks in the first polyphenylene sulfide fiber-resin composite layer is too small, it indicates that the surface fiber hairs were not sufficiently burned during the singeing process, resulting in a smaller number of solid blocks. This leads to more voids between the solid blocks, resulting in poor adhesion between the first polyphenylene sulfide fiber-resin composite layer and the polytetrafluoroethylene (PTFE) membrane during hot-pressing and lamination on the rolls, causing air bubbles. The PTFE membrane may then tend to detach during repeated blowing, reducing the lifespan of the filter material. Conversely, if the average area is too large, excessive clumps will clog the three-dimensional pores of the first polyphenylene sulfide fiber-resin composite layer, leading to high pressure loss and low air permeability. Considering the bonding strength between the PTFE membrane and the first polyphenylene sulfide fiber-resin composite layer, as well as the pressure loss and air permeability of the filter material, the average area of ​​the 90% solid blocks is more preferably 20,000–25,000 μm. 2 .

[0021] The average pore size of the filter material of this invention is preferably 0.50–1.50 μm. If it is too small, although the filtration accuracy of the filter material will be improved, the air permeability will be low, resulting in a large initial pressure loss and a rapid increase in pressure loss. This leads to short blowing intervals, and after repeated high-frequency blowing over a short period, the strength of the filter material decreases. If it is too large, although the initial operating pressure loss of the filter material is very low, the dust collection efficiency is reduced. Dust penetrates into the interior of the filter material, making it difficult to form a powder cake layer only on the surface, thus failing to achieve a good filtration effect and failing to meet the current domestic requirement of emissions below 10 mg. Considering the balance between the collection efficiency and pressure loss of the filter material, the average pore size of the filter material is more preferably 0.80–1.20 μm.

[0022] The thickness of the filter material in this invention is preferably 0.40–1.80 mm. If the thickness is too small, the shape retention will be poor, reducing the effective filtration area and causing a decline in the filtration performance of the filter material. It will also make the material more susceptible to mechanical damage, deformation, and even breakage during use, significantly shortening its service life. If the thickness is too large, on the one hand, during pulse cleaning, the excessively thick filter material will result in incomplete cleaning, affecting the stable operation of the dust collector. On the other hand, the excessively thick filter material will increase the resistance of the fluid passing through the filter cartridge, leading to an increase in overall pressure loss. Considering the filtration effect and pressure loss of the filter material, the thickness of the filter material is more preferably 0.80–1.50 mm.

[0023] The stiffness-softness ratio of the filter material of this invention after high-temperature treatment at 160℃ for 30 minutes is preferably less than 45°. If it is too high, the structure of the filter material is more susceptible to external impact and wear, and it may also lead to a decrease in both warp and weft tensile strength and elongation at break, thereby reducing the filtration efficiency and shortening the service life of the filter material. Considering the strength and filtration performance of the filter material, the stiffness-softness ratio of the filter material after high-temperature treatment at 160℃ for 30 minutes is more preferably less than 30°.

[0024] The preferred coating adhesion of the filter material of this invention is grade 1. Grade 1 coating adhesion means that the area of ​​the polytetrafluoroethylene membrane adhered to the tape accounts for 4 cm² of the area of ​​the test sample. 2 The preferred ratio is below 30%. The percentage of the torn area is determined by comparing the area of ​​the white PTFE film adhered to the tape with the area of ​​the test sample. If the film adhesion of the filter material is less than grade 1, meaning the area of ​​the PTFE film adhered to the tape accounts for a certain percentage of the test sample area (4cm²), then the film adhesion is considered acceptable. 2 The proportion of PTFE membrane exceeding 30% indicates weak interfacial bonding between the PTFE membrane and the first polyphenylene sulfide fiber-reinforced resin layer. Low membrane adhesion leads to quality problems such as wrinkles, bubbles, and curling during use. These issues not only affect the product's appearance but also reduce its filtration efficiency and durability.

[0025] The preferred collection efficiency of the filter material for particles with a diameter of 0.3–0.5 μm is 99% or higher. If the efficiency is too low, it indicates that dust can easily penetrate from the polytetrafluoroethylene membrane layer to the third polyphenylene sulfide fiber-reinforced resin layer, making it difficult to remove during cleaning. Over time, the pressure loss of the filter material will significantly increase, resulting in a large overall pressure drop. Simultaneously, because dust easily penetrates the interior of the filter material, it is difficult to form a powder cake layer on its surface, failing to achieve a good filtration effect, thus leading to an increase in the outlet concentration of the filter material. Considering the pressure drop and outlet concentration of the filter material, the collection efficiency of the filter material for particles with a diameter of 0.3–0.5 μm is more preferably 99.5% or higher.

[0026] The method for manufacturing the filter material of the present invention includes the following steps:

[0027] (1) Preparation of polyphenylene sulfide hydroentangled nonwoven fabric: polyphenylene sulfide fiber raw material is fed in, opened, carded, laid into a web, hydroentangled, dried and wound into a fabric to obtain polyphenylene sulfide hydroentangled nonwoven fabric;

[0028] (2) Preparation of hardened polyphenylene sulfide spunlace nonwoven fabric: Acrylic resin and deionized water are mixed in a ratio of 10:90 to 90:10 and stirred evenly to prepare a hardener solution. The polyphenylene sulfide spunlace nonwoven fabric obtained in step (1) is then immersed in the hardener solution. After being rolled by a rolling mill and the appropriate rolling pressure is adjusted, the surface of the polyphenylene sulfide spunlace nonwoven fabric is brought into contact with the upper rolling mill and the reverse side is brought into contact with the lower rolling mill, so that the surface and reverse side of the polyphenylene sulfide spunlace nonwoven fabric are both covered with the hardener solution and no residual hardener solution penetrates the middle layer. After being dried, it is heat-set to obtain the hardened polyphenylene sulfide spunlace nonwoven fabric.

[0029] (3) Preparation of polyphenylene sulfide spunlace nonwoven fabric singeing: The hardened polyphenylene sulfide spunlace nonwoven fabric obtained in step (2) is singeed to obtain polyphenylene sulfide spunlace nonwoven fabric singeing.

[0030] (4) Preparation of filter material: Polyphenylene sulfide spunlace nonwoven fabric is coated with polytetrafluoroethylene membrane to obtain the filter material of the present invention.

[0031] The present invention will be further illustrated by the following embodiments, but the scope of protection of the present invention is not limited to the embodiments. The physical properties in the embodiments are determined by the following methods.

[0032] The thicknesses of the first and third polyphenylene sulfide fiber mixed resin layers represent the respective proportions of the filter material's total thickness.

[0033] Cross-sections of the filter material were photographed using a scanning electron microscope (SEM). Ten random points on the filter material were selected for sample testing, with each point magnified 200 times. The distance from the upper surface of the first polyphenylene sulfide (PPS) fiber-resin composite layer to the upper surface of the second PPS fiber layer beneath the PTFE membrane was randomly measured; this distance represents the thickness of the first PPS fiber-resin composite layer. At least five thickness values ​​were recorded at each point, for a total of at least 50 thickness values. The average thickness of the first PPS fiber-resin composite layer was calculated. Following this method, the average thickness of the third PPS fiber-resin composite layer and the average thickness of the filter material were then recorded. Specifically, the percentage of the first PPS fiber-resin composite layer thickness to the filter material thickness (%) = (thickness of the first PPS fiber-resin composite layer (mm) / thickness of the filter material (mm)) × 100%; the percentage of the third PPS fiber-resin composite layer thickness to the filter material thickness (%) = (thickness of the third PPS fiber-resin composite layer (mm) / thickness of the filter material (mm)) × 100%.

[0034] [Average hair length on the surface of the first polyphenylene sulfide fiber-reinforced layer]

[0035] The polytetrafluoroethylene (PTFE) film was peeled off from the first polyphenylene sulfide (PPS) fiber-resin composite layer. The surface of the first PPS fiber-resin composite layer was then tested using a VHX ultra-depth-of-field 3D microscope at 50x magnification. The distance from the bottom to the top of the hairs was measured, i.e., the hair length. A total of 20 hair lengths were randomly photographed, and the average of these 20 hair lengths was taken as the average hair length on the surface of the first PPS fiber-resin composite layer.

[0036] [Number of hairs on the surface of the first polyphenylene sulfide fiber-reinforced layer]

[0037] The polytetrafluoroethylene (PTFE) film was peeled off from the first polyphenylene sulfide (PPS) fiber-resin composite layer. The surface of the first PPS fiber-resin composite layer was then tested using a VHX ultra-depth-of-field 3D microscope at 50x magnification. The total number of hairs with a length exceeding 0.10 mm within 10 cm was recorded. The formula for calculating the number of hairs (hair / cm) is as follows: Total number of hairs with a length exceeding 0.10 mm / 10 cm.

[0038] Average area of ​​solid blocks

[0039] The polytetrafluoroethylene (PTFE) film was peeled off from the first polyphenylene sulfide (PPS) fiber-reinforced resin layer. The area was then automatically measured using a VHX ultra-depth-of-field 3D microscope at 30x magnification. The surface morphology of the first PPS fiber-reinforced resin layer was photographed under the same light beam. Non-solid blocky areas appeared brightly colored, while solid blocky areas appeared dark yellow. The captured morphology images were processed by computer pixel analysis to extract the brightly colored non-solid blocky areas, yielding their area. The total area of ​​the entire region at 30x magnification was 107,188,793 μm. 2 The formula for calculating the area of ​​a solid block is as follows: Area of ​​solid block (μm²) 2 = Total area of ​​the entire region (107188793μm) 2 - Area of ​​non-solid blocks (μm) 2 The area of ​​a total of 5 solid blocks was calculated, and the final result was the average of the 5 solid blocks. The average area (μm) of 90% of the solid blocks is shown. 2 = 90% × average value of 5 solid blocks (μm) 2 ).

[0040] Average pore size

[0041] Cut the filter material into 1.5cm diameter circles, soak them in surfactant for 30 minutes, then place the filter material upwards into the test tank of the capillary flow porosity tester. After tightening the cap of the tank, conduct the test. The test results directly calculate the distribution of the proportion (%) of each pore size (μm) of the filter material in the whole material (including average pore size, maximum pore size μm, minimum pore size μm, pore size distribution, etc.). Take three measurements on average, and the final result is the average of the three measurements.

[0042] Average thickness

[0043] Based on the JIS L 1913 standard, the test material size was 200mm×200mm, with 5 test points, and the average value was taken.

[0044] [Stiffness and softness after high-temperature treatment]

[0045] Based on GB / T24218.3 standard, three samples were taken parallel to the warp and weft directions of the filter material, with an effective sample size of (200±1)mm × (50±1)mm. Each sample was at least 100mm from the edge of the fabric. The filter material stiffness tester was placed at a position where the horizontal platform and test line could be comfortably observed. The sample was horizontally clamped onto the fixed fixture of the filter material stiffness tester with the dust-facing side facing upwards, ensuring that the length of the filter material was perpendicular to the fixture and the distance between the protruding direction of the filter material and the clamping point was 200mm±1mm. The fixture was then tightened. The stiffness tester with the clamped filter material was horizontally placed in a constant temperature oven at 160℃. After drying the sample in the oven for 30 minutes, it was removed and cooled at room temperature for at least 5 minutes. The angle between the lowest point of the sample's droop and the parallel clamping point and the horizontal line was observed, and the stiffness value C of the angle was recorded. 11 C 12 C 13 C1 is the average value of the stiffness of the filter media's angle after high-temperature treatment. A smaller C1 value indicates better stiffness of the filter media at high temperatures; conversely, a larger C1 value indicates poorer stiffness. The formula for calculating C1 is as follows:

[0046] Ventilation

[0047] According to the Fraser type fabric air permeability test method specified in JISL 1096, the air permeability of the filter material was determined, and 10 points were randomly selected for measurement.

[0048]

Lamination adhesion

[0049] The coating adhesion was determined according to the ASTM D3359-02 tape method. The tape model was fixed as TERAOKA / Termaoka Industrial Curing Tape NO4140. Three to five 2cm × 2cm samples were taken from an intact area of ​​the sample. Three to five strips of tape, each 2.5cm long and 5cm wide, were torn off. The sample was gently placed on the tape, and pressure was applied to the tape for 60 seconds using a 550g weight. After applying pressure, the tape was slightly separated from the edge of the test sample, and then torn off within 1 second. The proportion of the torn area indicates the ratio of the area of ​​the white PTFE film adhered to the tape to the area of ​​the test sample; this ratio reflects the coating adhesion.

[0050] [Capture Efficiency]

[0051] Five 20cm x 20cm samples were taken from the filter material across its width. The collection efficiency of the filter material was tested using a UTF003 testing device. The aerosol particles were sodium chloride. The measured wind speed was 3.2 m / min, and the measurement area was 100 cm². 2 The final result is the average of these 5 trials.

[0052] [VDI3926 Filtration Performance, Outlet Concentration, Pressure Loss, and Circulation Time]

[0053] The performance of the filter material was determined based on the VDI 3926 standard. The experimental sample was a circle with a diameter of 150 mm. The feed dust concentration was 5.0 ± 0.5 g / m³. 3 This corresponds to a VDI filtration velocity of 1.0 m / min in actual use, which is 2 m / min (air volume 1.85 m³ / min). 3 / h), corresponding to a VDI filtration velocity of 1.2 m / min in actual use, which is 2.4 m / min. The experimental sequence was: initial 30 cycles + stabilization 5000 cycles + final 30 cycles. The method for the initial 30 cycles and the final 30 cycles was as follows: as the running time increased, the pressure difference between the two sides of the filter material gradually increased. When the pressure difference reached 1000 Pa, pulsed air was used to clean the dust on the surface of the filter material, and then the next process was carried out. This process was repeated 30 times. During the experiment, the experimental time (t / s) and pressure changes were recorded, and the weight M (g) of dust passing through the filter material was weighed. The stabilization process refers to cleaning the filter material at 5-second intervals during operation, with a cleaning pressure of 5 bar, and 5000 cleaning cycles.

[0054] The outlet dust concentration C = weight of dust passing through the filter material M / (1.85 × time t / 3600), and the unit of outlet dust concentration C is mg / Nm³. 3 When the VDI outlet concentration is less than 0.12 mg / Nm³ 3 At that time, on-site use can correspond to 5mg / Nm 3 Emission requirements.

[0055] Collection efficiency = (1 - outlet dust concentration C / 5) × 100%.

[0056] Pressure loss is the pressure loss automatically recorded by the equipment after the last injection in the last 30 cycles.

[0057] The loop time is the total time spent on the last 30 iterations.

[0058]

Durability (Resistance to Spraying)

[0059] The evaluation method for durability (blow-off resistance) is as follows: ◎: No damage after more than 40,000 blow-offs, ○: No damage after more than 30,000 blow-offs, △: No damage after more than 10,000 blow-offs, ×: Damage before 10,000 blow-offs.

[0060] Example 1

[0061] (1) Preparation of polyphenylene sulfide hydroentangled nonwoven fabric: polyphenylene sulfide fiber raw material is fed in, opened, carded, laid into a web, hydroentangled, dried and wound into a fabric to obtain polyphenylene sulfide hydroentangled nonwoven fabric;

[0062] (2) Preparation of hardened polyphenylene sulfide spunlace nonwoven fabric: Acrylic resin and deionized water are mixed in a ratio of 15:85 and stirred evenly to prepare a hardener solution. The polyphenylene sulfide spunlace nonwoven fabric obtained in step (1) is then immersed in the hardener solution. After being rolled by a rolling mill and the appropriate rolling pressure is adjusted, the surface of the polyphenylene sulfide spunlace nonwoven fabric is brought into contact with the upper rolling mill and the reverse side is brought into contact with the lower rolling mill, so that the surface and reverse side of the polyphenylene sulfide spunlace nonwoven fabric are both covered with the hardener solution and no residual hardener solution penetrates the middle layer. After being dried, it is heat-set to obtain the hardened polyphenylene sulfide spunlace nonwoven fabric.

[0063] (3) Preparation of polyphenylene sulfide spunlace nonwoven fabric singeing: The hardened polyphenylene sulfide spunlace nonwoven fabric obtained in step (2) is singeed to obtain polyphenylene sulfide spunlace nonwoven fabric singeing.

[0064] (4) Preparation of filter material: Polyphenylene sulfide spunlace nonwoven fabric was coated with polytetrafluoroethylene membrane to obtain the filter material of the present invention. The physical properties of the filter material are shown in Table 1.

[0065] Example 2

[0066] In the preparation of the cured polyphenylene sulfide spunlace nonwoven fabric, acrylate resin and deionized water are mixed at a ratio of 10:90. The preparation methods for the remaining polyphenylene sulfide spunlace nonwoven fabric, cured product, singed product, and filter material are the same as in Example 1. The physical properties of the filter material of this invention are shown in Table 1.

[0067] Example 3

[0068] In the preparation of the cured polyphenylene sulfide spunlace nonwoven fabric, acrylate resin and deionized water are mixed in a ratio of 25:75. The preparation methods for the remaining polyphenylene sulfide spunlace nonwoven fabric, cured product, singed product, and filter material are the same as in Example 1. The physical properties of the filter material of this invention are shown in Table 1.

[0069] Examples 4-11

[0070] The preparation process is the same as in Example 1. For specific formulations and properties, please refer to Table 1.

[0071] Example 12

[0072] In the preparation of the cured polyphenylene sulfide spunlace nonwoven fabric, acrylate resin and deionized water are mixed in a ratio of 60:40. The preparation methods for the remaining polyphenylene sulfide spunlace nonwoven fabric, cured product, singed product, and filter material are the same as in Example 1. The physical properties of the filter material of this invention are shown in Table 1.

[0073] The filter materials prepared in Examples 1-12 can be applied in the fields of steel, thermal power generation, cement, and waste incineration.

[0074] Comparative Example 1

[0075] (1) Preparation of polyphenylene sulfide hydroentangled nonwoven fabric: polyphenylene sulfide fiber raw material is fed in, opened, carded, laid into a web, hydroentangled, dried and wound into a fabric to obtain polyphenylene sulfide hydroentangled nonwoven fabric;

[0076] (2) Preparation of hardened polyphenylene sulfide spunlace nonwoven fabric: Acrylic resin and deionized water are mixed in a ratio of 15:85 and stirred evenly to prepare a hardener solution. The polyphenylene sulfide spunlace nonwoven fabric obtained in step (1) is then immersed in the hardener solution. After being rolled by a rolling mill and the appropriate rolling pressure is adjusted, the surface of the polyphenylene sulfide spunlace nonwoven fabric is brought into contact with the upper rolling mill and the reverse side is brought into contact with the lower rolling mill, so that the surface and reverse side of the polyphenylene sulfide spunlace nonwoven fabric are both covered with the hardener solution and no residual hardener solution penetrates the middle layer. After being dried, it is heat-set to obtain the hardened polyphenylene sulfide spunlace nonwoven fabric.

[0077] (3) Preparation of polyphenylene sulfide spunlace nonwoven fabric singeing: The hardened polyphenylene sulfide spunlace nonwoven fabric obtained in step (2) is singeed to obtain polyphenylene sulfide spunlace nonwoven fabric singeing.

[0078] (4) Preparation of filter material: Polyphenylene sulfide spunlace nonwoven fabric was coated with polytetrafluoroethylene membrane to obtain filter material. The physical properties of the filter material are shown in Table 2.

[0079] Comparative Example 2

[0080] In the preparation of the cured polyphenylene sulfide spunlace nonwoven fabric, acrylate resin and deionized water were mixed at a ratio of 90:10. The preparation methods for the remaining polyphenylene sulfide spunlace nonwoven fabric, cured product, singed product, and filter material were the same as in Comparative Example 1. The physical properties of this filter material are shown in Table 2.

[0081] Comparative Example 3

[0082] The preparation process is the same as that of Comparative Example 1, and the specific formulation and physical properties are shown in Table 2.

[0083] Table 1

[0084]

[0085] Table 2

[0086]

[0087] According to the table above,

[0088] (1) As can be seen from Examples 1, 2 and 3, under the same conditions, the thickness of the first polyphenylene sulfide fiber mixed resin layer in Example 1 is within the preferred range to the thickness of the filter material. The filter material obtained in Example 1 has low stiffness and softness after high temperature treatment, indicating that the filter material can maintain high stiffness and softness, long cycle time and low pressure loss.

[0089] (2) As can be seen from Examples 1 and 4, under the same conditions, the average hair length of the surface of the first polyphenylene sulfide fiber mixed resin layer in the former is in a better range. Compared with the latter, the filter material obtained by the former has low stiffness and softness after high temperature treatment, indicating that the filter material can maintain high stiffness and softness, long cycle time and low pressure loss.

[0090] (3) As can be seen from Examples 4 and 10, under the same conditions, the average hair length of the surface of the first polyphenylene sulfide fiber mixed resin layer in the latter is shorter. Compared with the former, the filter material obtained by the latter has a tendency to decrease in rigidity and softness after high temperature treatment, and the air permeability is slightly lower.

[0091] (4) As can be seen from Examples 1 and 5, under the same conditions, the number of hairs on the surface of the first polyphenylene sulfide fiber mixed resin layer in the former is within a better range. Compared with the latter, the filter material obtained by the former has low stiffness and softness after high temperature treatment, indicating that the filter material can maintain high stiffness and softness, long circulation time and low outlet dust concentration.

[0092] (5) As can be seen from Examples 1 and 11, the surface of the first polyphenylene sulfide fiber mixed resin layer in the latter has a larger number of hair roots. Compared with the former, the air permeability of the filter material obtained in the latter tends to decrease.

[0093] (6) As can be seen from Examples 1 and 6, under the same conditions, the average area of ​​90% of the solid blocks in the first polyphenylene sulfide fiber mixed resin layer in the former is within a more preferred range. Compared with the latter, the filter material obtained by the former has low stiffness and softness after high temperature treatment, indicating that the filter material can maintain high stiffness and softness, long circulation time and low outlet dust concentration.

[0094] (7) As can be seen from Examples 1 and 12, under the same conditions, the average area of ​​90% solid blocks in the first polyphenylene sulfide fiber mixed resin layer in the latter is smaller. Compared with the former, the stiffness and softness of the filter material obtained by the latter tend to decrease after high temperature treatment.

[0095] (8) As can be seen from Examples 1 and 7, under the same conditions, the thickness of the third polyphenylene sulfide fiber mixed resin layer in the former is within the preferred range of the thickness of the filter material. Compared with the latter, the filter material obtained by the former has higher rigidity and softness and higher air permeability after high temperature treatment.

[0096] (9) As can be seen from Examples 1 and 8, under the same conditions, the average pore size of the filter material in the former is in a more preferred range. Compared with the latter, the filter material obtained in the former has a longer circulation time and a lower outlet concentration.

[0097] (10) As can be seen from Examples 1 and 9, under the same conditions, the average thickness of the filter material in the former is in a better range. Compared with the latter, the filter material obtained in the former has a longer circulation time and a lower outlet concentration.

[0098] (11) As can be seen from Example 1 and Comparative Example 1, under the same conditions, the thickness of the first polyphenylene sulfide fiber mixed resin layer in the former is too small as a proportion of the thickness of the filter material. Compared with the former, the filter material obtained by the latter has a large stiffness and softness after high temperature treatment, indicating that the filter material has a poor stiffness and softness retention rate, short circulation time and high outlet dust concentration.

[0099] (12) As can be seen from Example 1 and Comparative Example 2, under the same conditions, the thickness of the first polyphenylene sulfide fiber mixed resin layer in Comparative Example 2 is too large as a proportion of the thickness of the filter material, that is, most of the filter material is filled with resin. Compared with the former, the filter material obtained by the latter has poor air permeability and poor durability.

[0100] (13) As can be seen from Example 1 and Comparative Example 3, under the same conditions, the thickness of the third polyphenylene sulfide fiber mixed resin layer in Comparative Example 3 is too small as a proportion of the thickness of the filter material. Compared with the former, the filter material obtained by the latter has a large stiffness and softness after high temperature treatment, indicating that the filter material has a poor stiffness and softness retention rate, short circulation time and high outlet dust concentration.

Claims

1. A filter material, characterized in that: The filter material comprises, from top to bottom, a polytetrafluoroethylene membrane, a first polyphenylene sulfide fiber mixed resin layer, a second polyphenylene sulfide fiber layer, and a third polyphenylene sulfide fiber mixed resin layer. The thickness of the first polyphenylene sulfide fiber mixed resin layer and the third polyphenylene sulfide fiber mixed resin layer are respectively 1 / 6 to 1 / 3 of the thickness of the filter material.

2. The filter material according to claim 1, characterized in that: The average hair length on the surface of the first polyphenylene sulfide fiber-resin blend layer is 0.10–0.20 mm.

3. The filter material according to claim 1 or 2, characterized in that: The number of hairs on the surface of the first polyphenylene sulfide fiber-resin composite layer is 2 to 20 hairs / cm.

4. The filter material according to claim 1, characterized in that: The first polyphenylene sulfide fiber-resin composite layer contains solid blocks, and 90% of the solid blocks have an average area of ​​10,000–30,000 μm. 2 .

5. The filter material according to claim 1, characterized in that: The average pore size of the filter material is 0.50–1.50 μm.

6. The filter material according to claim 1, characterized in that: The average thickness of the filter material is 0.40–1.80 mm.

7. The filter material according to claim 1, characterized in that: The stiffness of the filter material after being treated at 160°C for 30 minutes is less than 45°.

8. The filter material according to claim 1, characterized in that: The membrane strength of the filter material is grade 1.

9. The filter material according to claim 1, characterized in that: The filter material has a capture efficiency of over 99% for particles with a diameter of 0.3–0.5 μm.

10. The application of the filter material according to claim 1 in the fields of steel, thermal power generation, cement, and waste incineration.

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