A filter screen and a method of making and using the same

Abstract

The application relates to a filter screen and a preparation method and application thereof, and belongs to the technical field of filtering equipment. The filter screen comprises a hydrophobic reinforcing layer, a pre-filtering layer and a core filtering layer which are sequentially stacked; the hydrophobic reinforcing layer is composed of metal fibers; the pre-filtering layer is composed of basalt fibers; and the core filtering layer is composed of polytetrafluoroethylene fibers and polyether ether ketone fibers. The filter screen can stably work in a high-temperature environment, has excellent hydrophobic performance, high filtering efficiency and controllable manufacturing cost through the design of the structure of the filter screen.

Description

Technical Field

[0001] This invention relates to the field of filtration equipment technology, and in particular to a filter screen, its preparation method, and its application. Background Technology

[0002] Currently, dust generation and emission are prevalent problems in industrial production, construction projects, and numerous commercial venues. Effective fire-fighting dust suppression measures are crucial, and as one of the core components of a fire-fighting dust suppression system, the performance and design of the filter directly affect the safety and reliability of the entire system.

[0003] Currently, fire-fighting dust collector filters on the market are mainly divided into several types, including bag filters, cartridge filters, and oil mesh filters, each playing an important role in different application scenarios. These filters primarily utilize glass fiber filters, metal fiber filters, and organic material filters.

[0004] Glass fiber filters have the advantage of low manufacturing cost, but because the softening point of glass fiber is 500-550℃, it is prone to softening and bonding in high-temperature environments above 600℃, resulting in a decrease in porosity of more than 50% and a sharp drop in filtration efficiency. It also has the problem of insufficient temperature resistance. In addition, the surface of glass fiber has abundant hydroxyl groups, which are highly hydrophilic and have a contact angle with droplets of only 20-40°. In high water mist environments, it is easy to form a water film, which increases air resistance by 200-300%, seriously affecting its filtration effect and usage.

[0005] Metal fiber filters have advantages such as good high temperature resistance (up to 800℃), high mechanical strength, and long service life (3000-5000 h). However, due to the relatively large diameter of metal fibers, the filtration efficiency for fine particulate matter such as PM2.5 is only 60-75%, resulting in low filtration accuracy. Furthermore, the manufacturing cost is high, the manufacturing process is complex, and the metal itself has a high density, making the resulting filter heavier. Using metal filters increases the burden on the equipment.

[0006] In recent years, polytetrafluoroethylene (PTFE) membrane composite filters have been widely used in filtration equipment due to their high filtration accuracy (PM0.3 efficiency can reach 99.97%) and certain hydrophobicity (contact angle 110-130°). However, PTFE membranes have disadvantages such as easy decomposition above 350℃, easy damage under high pressure differential, short service life (500-800 h), and high cost.

[0007] In summary, most existing technologies suffer from drawbacks such as difficulty in balancing high temperature resistance and filtration efficiency, contradictions between hydrophobicity and mechanical strength, mismatch between manufacturing costs and performance requirements, and lack of systematic structural design.

[0008] Therefore, how to achieve a filter screen that combines high temperature resistance with filtration efficiency, hydrophobic properties with mechanical strength, and low manufacturing cost has become an urgent problem to be solved. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a filter screen, its preparation method, and its application. By designing the structure of the filter screen, a filter screen that can operate stably in high-temperature environments, possesses excellent hydrophobic properties and filtration efficiency, and has controllable manufacturing costs is obtained.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a filter screen comprising a hydrophobic enhancement layer, a pre-filtration layer and a core filtration layer stacked sequentially.

[0012] The hydrophobic reinforcement layer is composed of metal fibers;

[0013] The pre-filter layer is composed of basalt fibers;

[0014] The core filter layer is composed of polytetrafluoroethylene fibers and polyetheretherketone fibers.

[0015] This invention provides a filter with a three-layer composite structure through the design of the filter's structure. The hydrophobic reinforcing layer uses metal fibers as its material, enhancing the overall strength of the filter. The pre-filtration layer uses basalt fibers as its material; basalt fibers can withstand temperatures above 700℃ and possess excellent mechanical properties and chemical stability, effectively blocking large particles, providing structural stability, and protecting the inner structure. The core filtration layer uses a composite material of polytetrafluoroethylene (PTFE) fibers and polyetheretherketone (PEEK) fibers, achieving high-precision filtration. The composite structure of PTFE and PEEK fibers improves the core filtration layer's temperature resistance, chemical stability, and mechanical properties.

[0016] Preferably, the diameters of the metal fibers, basalt fibers, polytetrafluoroethylene fibers, and polyetheretherketone fibers are each independently selected from 8-15 μm, for example, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm, and the lengths are each independently selected from 25-40 mm, for example, 25 mm, 27 mm, 29 mm, 30 mm, 32 mm, 34 mm, 35 mm, 37 mm, 39 mm, or 40 mm.

[0017] Preferably, the mass ratio of the metal fiber, basalt fiber, polytetrafluoroethylene fiber and polyetheretherketone fiber is 1:(1.5-5):(4-10):(2.5-7).

[0018] Among them, 1.5-5 can be 1.5, 2, 3, 4 or 5, etc.; 2.5-7 can be 2.5, 3, 4, 5, 6 or 7, etc.; and 4-10 can be 4, 5, 6, 7, 8, 9 or 10, etc.

[0019] Preferably, the metal fiber comprises stainless steel fiber.

[0020] Preferably, the hydrophobic reinforcement layer has a mesh structure.

[0021] Preferably, the length of a single grid in the grid structure is 30-70 μm, for example, it can be 30 μm, 40 μm, 50 μm, 60 μm or 70 μm, and the width is 30-70 μm, for example, it can be 30 μm, 40 μm, 50 μm, 60 μm or 70 μm.

[0022] Preferably, the surface of the hydrophobic reinforcement layer has a nanofiber structure.

[0023] Preferably, the height of the nanofiber structure is 0.1-0.3 μm, for example, it can be 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm or 0.3 μm.

[0024] Preferably, the surface of the hydrophobic reinforcement layer has a micro / nanopapillary structure.

[0025] Preferably, the height of the micro / nanoplasty structure is 2-5 μm, for example, it can be 2 μm, 3 μm, 4 μm or 5 μm.

[0026] Preferably, the diameter of the micro / nanopapillary structure is 2-5 μm, for example, it can be 2 μm, 3 μm, 4 μm or 5 μm.

[0027] Preferably, the spacing between the micro / nanoplasty structures is 8-12 μm, for example, it can be 8 μm, 9 μm, 10 μm, 11 μm or 12 μm.

[0028] Preferably, the pre-filter layer is a non-woven fabric A containing basalt fibers.

[0029] Preferably, the nonwoven fabric A is prepared using a hydroentangling process.

[0030] Preferably, the weave density of the pre-filter layer is 120-150 mesh, for example, it can be 120 mesh, 130 mesh, 140 mesh or 150 mesh, etc.

[0031] Preferably, the pore size of the pre-filter layer is 100-150 μm, for example, it can be 100 μm, 110 μm, 120 μm, 130 μm, 140 μm or 150 μm.

[0032] Preferably, the core filter layer is a nonwoven fabric B containing polytetrafluoroethylene fibers and polyetheretherketone fibers.

[0033] Preferably, the nonwoven fabric B is prepared using a hydroentangling process.

[0034] Preferably, the core filter layer has a herringbone interwoven structure.

[0035] Preferably, the interlacing angle of the herringbone interlacing structure is ±(40-50)°, for example, it can be 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 49°, 50°, -40°, -41°, -42°, -43°, -44°, -45°, -46°, -47°, -48°, -49° or -50°, etc.

[0036] Preferably, the weave density of the core filter layer is 300-400 mesh, for example, it can be 300 mesh, 320 mesh, 340 mesh, 350 mesh, 360 mesh, 380 mesh or 400 mesh, etc.

[0037] Preferably, the pore size of the core filter layer is 15-25 μm, for example, it can be 15 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm or 25 μm.

[0038] The core filter layer of this invention uses a spiral interlacing weaving process to interweave polytetrafluoroethylene fibers and polyetheretherketone fibers in a herringbone cross structure. The herringbone cross structure can evenly distribute stress on the fibers, forming a stable three-dimensional structure and improving the structural stability of the core filter layer.

[0039] The pore sizes of the hydrophobic reinforcement layer, pre-filtration layer, and core filtration layer provided by this invention can be adjusted by adjusting the parameters of the weaving equipment to achieve a decrease in the gradient from micron-sized pores to nano-sized pores.

[0040] The filter screen provided by this invention further optimizes the filtration path structure. During the filtration operation, the material to be separated passes sequentially through the micron-scale mesh structure of the hydrophobic reinforcement layer, the high-density pre-filter layer, and the core filter layer. The gradient decrease in pore size from micron to nanometer in the pre-filter layer and the core filter layer achieves a highly efficient dust removal effect.

[0041] Preferably, the filter screen further includes a frame structure and an internal support mesh.

[0042] Preferably, the thickness of the frame structure is 3-5 mm, for example, it can be 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm.

[0043] Preferably, the frame structure includes a steel alloy frame.

[0044] Preferably, the internal support mesh is a hexagonal honeycomb support structure.

[0045] Preferably, the mesh spacing of the internal support mesh is 10-15 mm, for example, it can be 10 mm, 11 mm, 12 mm, 13 mm, 14 mm or 15 mm, etc.

[0046] Preferably, the internal support mesh comprises stainless steel wire mesh.

[0047] Preferably, the support mesh is disposed below the core filter layer.

[0048] In a second aspect, the present invention provides a method for preparing a filter screen as described in the first aspect, the method comprising the following steps:

[0049] The filter screen is obtained by combining and shaping the hydrophobic reinforcement layer, the pre-filter layer and the core filter layer, and then performing surface modification hydrophobic treatment.

[0050] Preferably, the composite process is performed using a needle punching technique.

[0051] Preferably, the shaping is hot pressing.

[0052] Preferably, the hot pressing temperature is 280-320℃, for example, it can be 280℃, 290℃, 300℃, 310℃ or 320℃.

[0053] Preferably, the pressure for hot pressing is 2-5 MPa, for example, it can be 2 MPa, 3 MPa, 4 MPa or 5 MPa, etc.

[0054] Preferably, the hydrophobic reinforcement layer is subjected to surface-modified hydrophobic treatment.

[0055] Preferably, the surface modification hydrophobic treatment includes sequentially performing plasma fluorination treatment, nano-coating treatment, and laser etching treatment.

[0056] Preferably, the fluorinating agent for plasma fluorination treatment includes... .

[0057] Preferably, the power of the plasma fluorination treatment is 150-250 W, for example, it can be 150 W, 160 W, 180 W, 200 W, 220 W, 240 W or 250 W.

[0058] Preferably, the plasma fluorination treatment time is 3-5 min, for example, it can be 3 min, 3.5 min, 4 min, 4.5 min or 5 min, etc.

[0059] Preferably, the nanocoating treatment includes immersing the hydrophobic reinforcing layer in a coupling agent solution.

[0060] Preferably, the nanocoating treatment may also include spraying a coupling agent solution onto the hydrophobic reinforcement layer.

[0061] Preferably, the concentration of the coupling agent in the coupling agent solution is 0.5-1 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%, etc.

[0062] Preferably, the coupling agent comprises a fluorosilane coupling agent.

[0063] Preferably, the immersion time is 20-40 s, for example, 20 s, 25 s, 30 s, 35 s or 40 s.

[0064] Preferably, the impregnation process further includes a curing step.

[0065] Preferably, the curing temperature is 150-200℃, for example, 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃, and the curing time is 20-40 min, for example, 20 min, 25 min, 30 min, 35 min or 40 min.

[0066] Preferably, the nano-coating treatment forms a nanofiber structure on the surface of the hydrophobic reinforcement layer.

[0067] Preferably, after laser etching, a micro / nanopapillary structure is formed on the surface of the hydrophobic reinforcement layer.

[0068] This invention modifies the filter screen by performing a hydrophobic surface treatment. First, plasma fluorination introduces fluorine-containing groups onto the surface of the hydrophobic reinforcement layer, forming fluorocarbon chains with low surface energy. The fluorine-containing groups themselves have extremely low surface energy, significantly reducing the free energy of the hydrophobic reinforcement layer surface, thereby reducing the spread of water molecules on the surface and enhancing hydrophobicity. Further, a nano-coating treatment is applied to the surface of the hydrophobic reinforcement layer. A fluorinated silane coupling agent is used to modify the fibers, improving the hydrophobic properties of the reinforcement layer. The fluorinated silane coupling agent reacts with the fluorine-containing groups grafted onto the surface of the hydrophobic reinforcement layer after plasma fluorination to form a nanofiber structure. Then, a micro / nanopapular structure is formed on the surface using laser etching technology. This micro / nanopapular structure, combined with a nano-coating to form a nanofiber structure, creates a unique "lotus leaf-shaped" surface micro / nano structure on the hydrophobic reinforcement layer. When in contact with a droplet, the droplet only contacts the nanofibers at its tip. Furthermore, gaps exist between the micro / nanopapular structures, forming an air layer that prevents the droplet from completely adhering to the hydrophobic reinforcement layer surface, resulting in a semi-suspended state and reducing the actual contact area between the droplet and the hydrophobic reinforcement layer surface (contact area <5%). The filter provided by this invention, through surface modification and hydrophobic treatment, effectively adsorbs organic pollutants while maintaining hydrophobicity.

[0069] Thirdly, the present invention provides an application of the filter screen as described in the first aspect in a filtration device.

[0070] The filter provided by this invention can be used in the treatment of industrial high-temperature waste gas in the steel, cement and chemical industries, fire dust removal, extreme environment filtration in aerospace, and high-temperature dust removal equipment in the nuclear industry.

[0071] Compared with the prior art, the present invention has at least the following beneficial effects:

[0072] (1) By designing the structure of the filter screen, the present invention provides a filter screen with a three-layer composite structure, which integrates the triple properties of high temperature resistance, excellent filtration efficiency and superhydrophobicity, and solves the problem that the single-structure design of existing products cannot simultaneously achieve high temperature resistance, filtration performance and mechanical performance.

[0073] (2) The filter screen provided by the present invention adopts a three-layer composite one-time molding process, which greatly improves the production efficiency. Due to its excellent service life and hydrophobic properties, the filter screen does not need to be replaced and cleaned frequently, thereby reducing the downtime of its application equipment and saving a lot of filter screen material costs, manufacturing costs and maintenance costs, making it suitable for large-scale production applications.

[0074] (3) The filter screen provided by the present invention can be widely used in many fields due to its excellent temperature resistance and hydrophobic properties. It can be used in the treatment of industrial high temperature exhaust gas in the steel, cement and chemical industries, fire dust removal, extreme environment filtration in aerospace and nuclear industry, and high temperature dust removal equipment. In particular, in the field of fire protection, it can also play the role of ensuring fire safety, improving air quality and preventing secondary pollution, thus solving the problem of insufficient adaptability of the existing technology in extreme fire protection environment (high temperature, high humidity and high particulate matter concentration).

[0075] (4) Specifically, the filter screen provided by the present invention can withstand a maximum heat of 500-620℃, has excellent filtration efficiency, and can achieve a filtration efficiency of over 95% for PM0.3, PM2.5 and PM10. It has excellent hydrophobic properties, with a static contact angle >100° and a dynamic contact angle <50°. It can withstand water pressure ≥1500 Pa and has a service life ≥1000 h. It has excellent mechanical properties, with a tensile strength >150 kPa and a wind resistance increase rate of <50% in water mist environment. After working continuously for 1000 h in a constant temperature environment of 600℃, its structural integrity can reach over 90%, and its filtration performance retention rate after thermal cycling is ≥90%. Attached Figure Description

[0076] Figure 1 This is a diagram of the filter structure provided by the present invention;

[0077] Among them, 1-hydrophobic reinforcement layer, 2-pre-filtration layer, 3-core filtration layer. Detailed Implementation

[0078] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0079] The specific information of the materials used in the following specific embodiments of the present invention is as follows:

[0080] Stainless steel fiber, specifications: 316L material, diameter 8-12 μm, length 25-35 mm, tensile strength ≥4.0cN / dtex;

[0081] Basalt fiber, specifications: continuous fiber, diameter 9-13 μm, length 30-40 mm, temperature resistance above 700℃, SiO2 content ≥45%;

[0082] Polytetrafluoroethylene fiber, specifications: short fiber, diameter 8-15 μm, length 25-30 mm, melting point 327℃;

[0083] Polyetheretherketone fiber, specifications: short fiber, diameter 10-15 μm, length 30-35 mm, glass transition temperature 143℃, melting point 334℃;

[0084] Fluorinated silane coupling agent, specification: KH-570 modified fluorinated silane coupling agent, purity ≥98%, fluorine content 15-18%, molecular formula .

[0085] Example 1

[0086] This embodiment provides a filter screen and its preparation method, the cross-sectional structure of which is as follows: Figure 1 As shown, the filter screen includes a hydrophobic reinforcement layer 1, a pre-filtration layer 2, and a core filtration layer 3 stacked sequentially; the hydrophobic reinforcement layer includes 10 parts stainless steel fiber; the pre-filtration layer includes 15 parts basalt fiber; and the core filtration layer includes 40 parts polytetrafluoroethylene fiber and 35 parts polyetheretherketone fiber.

[0087] The length and width of a single mesh structure in the hydrophobic reinforcement layer are 50 μm; the weaving density of the pre-filter layer is 120 mesh and the pore size is 100 μm; the weaving density of the core filter layer is 300 mesh and the pore size of the core filter layer is 15 μm.

[0088] The preparation method includes:

[0089] (1) Preparation of hydrophobic reinforcement layer, pre-filtration layer and core filtration layer:

[0090] Metal fibers are made into a mesh structure to serve as a hydrophobic reinforcement layer;

[0091] Basalt fibers are opened, combed, and then hydroentangled to prepare nonwoven fabric A, which serves as a pre-filter layer.

[0092] Polytetrafluoroethylene fiber and polyetheretherketone fiber are mixed in a certain weight ratio, and after opening, carding, and hydroentangling, a nonwoven fabric B with a herringbone interlacing structure is prepared, which serves as the core filter layer.

[0093] (2) Preparation of composite structure:

[0094] The hydrophobic reinforcement layer, pre-filtration layer and core filtration layer were composited in order from top to bottom using a needle punching process, and then hot-pressed at 300℃ and 3 MPa for characterization.

[0095] (3) Perform surface hydrophobic modification treatment:

[0096] use The hydrophobic reinforcement layer was subjected to plasma treatment at a power of 200 W for 4 hours, resulting in a surface with... The hydrophobic reinforcement layer of the group is further immersed in a 0.8 wt% fluorinated silane coupling agent solution for 30 s, then cured at 180℃ for 30 min, and then laser etched to obtain the hydrophobically modified composite structure.

[0097] (4) The hydrophobically modified composite structure is placed on a stainless steel wire mesh (mesh spacing of 10 mm) and spot-welded and mechanically pressed together with a high-temperature resistant alloy steel (Inconel 625) frame with a thickness of 4 mm to obtain the filter screen.

[0098] Example 2

[0099] This embodiment provides a filter screen and its preparation method, the cross-sectional structure of which is as follows: Figure 1 As shown, the filter screen includes a hydrophobic reinforcement layer 1, a pre-filtration layer 2, and a core filtration layer 3 stacked sequentially; the hydrophobic reinforcement layer includes 5 parts stainless steel fiber; the pre-filtration layer includes 20 parts basalt fiber; and the core filtration layer includes 45 parts polytetrafluoroethylene fiber and 30 parts polyetheretherketone fiber.

[0100] The length and width of a single mesh structure in the hydrophobic reinforcement layer are 70 μm; the weaving density of the pre-filter layer is 140 mesh and the pore size is 120 μm; the weaving density of the core filter layer is 350 mesh and the pore size of the core filter layer is 20 μm.

[0101] The preparation method is the same as in Example 1.

[0102] Example 3

[0103] This embodiment provides a filter screen and its preparation method, the cross-sectional structure of which is as follows: Figure 1 As shown, the filter screen includes a hydrophobic reinforcement layer 1, a pre-filtration layer 2, and a core filtration layer 3 stacked sequentially; the hydrophobic reinforcement layer includes 10 parts stainless steel fiber; the pre-filtration layer includes 25 parts basalt fiber; and the core filtration layer includes 50 parts polytetrafluoroethylene fiber and 25 parts polyetheretherketone fiber.

[0104] The length and width of a single mesh structure in the hydrophobic reinforcement layer are 30 μm; the weaving density of the pre-filter layer is 150 mesh and the pore size is 150 μm; the weaving density of the core filter layer is 400 mesh and the pore size of the core filter layer is 25 μm.

[0105] The preparation method is the same as in Example 1.

[0106] Example 4

[0107] This embodiment provides a filter screen and its preparation method, the cross-sectional structure of which is as follows: Figure 1As shown, the filter screen includes a hydrophobic reinforcement layer 1, a pre-filtration layer 2, and a core filtration layer 3 stacked sequentially; the hydrophobic reinforcement layer includes 10 parts stainless steel fiber; the pre-filtration layer includes 15 parts basalt fiber; and the core filtration layer includes 65 parts polytetrafluoroethylene fiber and 10 parts polyetheretherketone fiber.

[0108] The length and width of a single mesh structure in the hydrophobic reinforcement layer are 50 μm; the weaving density of the pre-filter layer is 130 mesh and the pore size is 120 μm; the weaving density of the core filter layer is 300-400 mesh and the pore size of the core filter layer is 16 μm.

[0109] The preparation method is the same as in Example 1.

[0110] Example 5

[0111] This embodiment provides a filter screen and its preparation method, the cross-sectional structure of which is as follows: Figure 1 As shown, the filter screen includes a hydrophobic reinforcement layer 1, a pre-filtration layer 2, and a core filtration layer 3 stacked sequentially; the hydrophobic reinforcement layer includes 10 parts stainless steel fiber; the pre-filtration layer includes 15 parts basalt fiber; and the core filtration layer includes 15 parts polytetrafluoroethylene fiber and 60 parts polyetheretherketone fiber.

[0112] The length and width of a single mesh structure in the hydrophobic reinforcement layer are 50 μm; the weaving density of the pre-filter layer is 140 mesh and the pore size is 135 μm; the weaving density of the core filter layer is 320 mesh and the pore size of the core filter layer is 22 μm.

[0113] The preparation method is the same as in Example 1.

[0114] Example 6

[0115] This embodiment provides a filter screen and its preparation method, which differs from Embodiment 1 in that its preparation method does not include step (3).

[0116] Example 7

[0117] This embodiment provides a filter screen and its preparation method, which differs from Embodiment 1 in that the preparation method includes:

[0118] (1) Preparation of hydrophobic reinforcement layer, pre-filtration layer and core filtration layer:

[0119] Metal fibers are made into a mesh structure to serve as a hydrophobic reinforcement layer;

[0120] Basalt fibers are opened, combed, and then hydroentangled to prepare nonwoven fabric A, which serves as a pre-filter layer.

[0121] Polytetrafluoroethylene fiber and polyetheretherketone fiber are mixed in a certain weight ratio, and after opening, carding, and hydroentangling, a nonwoven fabric B with a herringbone interlacing structure is prepared, which serves as the core filter layer.

[0122] (2) Preparation of composite structure:

[0123] The hydrophobic reinforcement layer, pre-filtration layer and core filtration layer were composited in order from top to bottom using a needle punching process, and then hot-pressed at 300℃ and 3 MPa for characterization.

[0124] (3) Perform surface hydrophobic modification treatment:

[0125] use The hydrophobic reinforcement layer was subjected to plasma treatment at a power of 200 W for 4 hours, resulting in a surface with... The hydrophobic reinforcement layer of the group is further immersed in a 0.8 wt% fluorinated silane coupling agent solution for 30 s, and then cured at 180℃ for 30 min to obtain the hydrophobically modified composite structure.

[0126] (4) The hydrophobically modified composite structure is placed on a stainless steel wire mesh (mesh spacing of 10 mm) and spot-welded and mechanically pressed together with a high-temperature resistant alloy steel (Inconel 625) frame with a thickness of 4 mm to obtain the filter screen.

[0127] Example 8

[0128] This embodiment provides a filter screen and its preparation method, which differs from Embodiment 1 in that the preparation method includes:

[0129] (1) Preparation of hydrophobic reinforcement layer, pre-filtration layer and core filtration layer:

[0130] Metal fibers are made into a mesh structure to serve as a hydrophobic reinforcement layer;

[0131] Basalt fibers are opened, combed, and then hydroentangled to prepare nonwoven fabric A, which serves as a pre-filter layer.

[0132] Polytetrafluoroethylene fiber and polyetheretherketone fiber are mixed in a certain weight ratio, and after opening, carding, and hydroentangling, a nonwoven fabric B with a herringbone interlacing structure is prepared, which serves as the core filter layer.

[0133] (2) Preparation of composite structure:

[0134] The hydrophobic reinforcement layer, pre-filtration layer and core filtration layer were composited in order from top to bottom using a needle punching process, and then hot-pressed at 300℃ and 3 MPa for characterization.

[0135] (3) Perform surface hydrophobic modification treatment:

[0136] The hydrophobic reinforcement layer was laser etched to obtain a hydrophobically modified composite structure.

[0137] (4) The hydrophobically modified composite structure is placed on a stainless steel wire mesh (mesh spacing of 10 mm) and spot-welded and mechanically pressed together with a high-temperature resistant alloy steel (Inconel 625) frame with a thickness of 4 mm to obtain the filter screen.

[0138] Figure 1 The filter structure diagram provided by the present invention includes, from top to bottom, a hydrophobic reinforcement layer 1, a pre-filtration layer 2, and a core filtration layer 3. The present invention optimizes the fibers and filtration path of each layer to make the filter with excellent filtration efficiency and high temperature resistance.

[0139] Comparative Example 1

[0140] This comparative example provides a polytetrafluoroethylene-glass fiber filter (model FG-2500), purchased from Freudenberg, Germany.

[0141] Comparative Example 2

[0142] This comparative example provides a metal fiber filter (model 1000SS) purchased from the Versapor series of sintered metal fiber filters of 3M Company, USA.

[0143] Comparative Example 3

[0144] This comparative example provides a polytetrafluoroethylene membrane filter (model TF200), purchased from Toray Industries, Inc., Japan.

[0145] Comparative Example 4

[0146] This comparative example provides a HEPA membrane filter (model Megalam H14) purchased from Camfil, Sweden.

[0147] Test methods

[0148] The following performance tests were performed on the filters provided in Examples 1-8 and Comparative Examples 1-4:

[0149] (1) Temperature resistance (°C): The test was conducted using a muffle furnace (model SX2-4-10, Shanghai Yiheng) in accordance with GB / T 17219-1998 standard. The filter screen was cut into 10 cm × 10 cm samples and subjected to gradient heating (temperature rise of 50°C). After each heating, the temperature was kept constant for 2 h. The highest heat resistance temperature was defined as the temperature at which the filter screen showed obvious shrinkage, cracking, melting, or fiber breakage.

[0150] (2) Filtration efficiency (%): The particle counting method was used to test the filtration efficiency of 0.3 μm, 2.5 μm and 10 μm particles. The test conditions were: wind speed 5.33 cm / s, test area 100 cm², NaCl aerosol particles were used, and the filtration efficiency of 0.3 μm, 2.5 μm and 10 μm particles were tested respectively.

[0151] Calculation formula: Filtration efficiency (%) = (upstream concentration - downstream concentration) / upstream concentration × 100%.

[0152] (3) Contact angle (°): The contact angle was measured using an OCA20 contact angle meter (DataPhysics, Germany) and the pendant drop method. Test conditions: room temperature 25°C, relative humidity 45%, deionized water was used as the test liquid, droplet volume was 2 μL, and 5 points were tested for each sample and the average value was taken.

[0153] (4) Service life (h): The filter screen is placed in a high temperature aging test chamber (model DHG-9420A) and continuously operated in a constant temperature environment of 600℃±5℃. The filtration efficiency is tested every 100 h. When the filtration efficiency drops to below 70% of the initial value, the corresponding time is recorded as the service life.

[0154] (5) Water pressure resistance: Refer to GB / T 4744-2013 standard and use a hydrostatic pressure tester (model YG461E) for testing. Test conditions: pressure increase rate 10±2 kPa / min, test area 20 cm², and the average pressure value when water seepage occurs at three different locations on the filter screen is taken as the water pressure resistance value.

[0155] (6) Tensile strength (kPa): The test was conducted using a universal testing machine (model CMT4104) in accordance with GB / T 3923.1-2013 standard. Filter screen sample size: 200 mm × 25 mm, clamping length: 50 mm, tensile speed: 100 mm / min, test temperature: 23±2℃, relative humidity: 65±2%.

[0156] (7) Increase rate of wind resistance in high water mist environment (%): A high humidity environment (relative humidity 95%±3%, temperature 25±2℃) was created using a constant temperature and humidity test chamber (model BPHJ-120A, Shanghai Yiheng). A digital micro differential pressure gauge (model testo 512, German Testo) was used to measure the pressure difference of the filter screen in dry and high humidity environments. A constant wind speed of 5 m / s was generated by a blower.

[0157] Calculation formula: Wind resistance increase rate (%) = (pressure difference in high humidity environment - pressure difference in dry environment) / pressure difference in dry environment × 100%.

[0158] (8) Structural integrity: After continuous operation at a constant temperature of 600℃ for 1000 h, the structure was evaluated by visual inspection combined with microscopic observation (model XSP-8CA, Shanghai Optics). Visual inspection criteria: ① No obvious cracks or enlarged holes; ② No obvious fiber breakage or shedding; ③ No deformation or shrinkage of the overall structure; ④ No cracks at the seams. The integrity of the fiber structure was observed under a microscope (100x) and the percentage of damaged area was recorded.

[0159] (9) Thermal cycling test: The temperature cycle of 25-600℃ was carried out using a programmable temperature control test chamber (model BPH-9052A), with a heating rate of 5℃ / min, a constant temperature time of 30 min, a cooling rate of 5℃ / min, and after 500 cycles, the PM2.5 filtration efficiency was retested using a TSI-8130A automatic filter media tester.

[0160] Retention rate calculation formula: Retention rate (%) = Filtration efficiency after circulation / Filtration efficiency before circulation × 100%.

[0161] Test environment conditions: Unless otherwise specified, all tests were conducted at a temperature of 23±2℃, relative humidity of 45±5%, and atmospheric pressure of 86-106 kPa. Each test was repeated 3 times, and the average value was taken as the final result.

[0162] Test Results

[0163] The performance test results of the filters provided in Examples 1-8 and Comparative Examples 1-4 are shown in Tables 1 and 2:

[0164] Table 1

[0165]

[0166] Table 2

[0167]

[0168] The test results show that:

[0169] (1) As can be seen from Examples 1 to 8, the filter screen provided by the present invention has a maximum heat resistance of 500-620℃, a filtration efficiency of over 95% for PM0.3, PM2.5, and PM10, excellent hydrophobic properties, a static contact angle >100°, a dynamic contact angle <50°, water pressure resistance ≥1500 Pa, a service life ≥1000 h, excellent mechanical properties, tensile strength >150 kPa, wind resistance increase rate in water mist environment <50%, and after continuous operation at a constant temperature of 600℃ for 1000 h, the structural integrity can reach over 90%, the filtration performance retention rate after thermal cycling is ≥90%, and the manufacturing cost is controllable. Compared with the prior art, the filter screen provided by the present invention has improved the performance by 30-70% and reduced the manufacturing cost by 60-70%, achieving the integration of high temperature resistance, excellent filtration efficiency, and superhydrophobicity.

[0170] (2) As can be seen from Examples 1 and 4-5, by further limiting the mass ratio of polytetrafluoroethylene fiber and polyetheretherketone fiber in the core filter layer, the present invention can achieve the technical effect of better balancing the temperature resistance, filtration performance and extending the service life of the filter.

[0171] (3) As can be seen from Examples 1 and 6-8, the present invention can obtain a better hydrophobic effect by performing surface hydrophobic modification treatment on the hydrophobic reinforcement layer.

[0172] (4) As can be seen from Example 1 and Comparative Examples 1-4, the polytetrafluoroethylene-glass fiber filter provided in Comparative Example 1 has a maximum heat resistance temperature of only 350°C due to the high-temperature decomposition problem of polytetrafluoroethylene. However, the present invention uses a composite system of basalt fiber, polytetrafluoroethylene fiber and polyether ether ketone fiber to solve the high-temperature decomposition problem of polytetrafluoroethylene. Moreover, the filter provided in Comparative Example 1 has a thickness of only 20-30 μm, which is more prone to damage during use and has an actual service life of only 500-800h. In contrast, the filter provided in Example 1 of the present invention adopts a three-layer composite structure with an overall thickness of 2-3 mm and a service life of ≥2000h.

[0173] The metal fiber filter screen provided in Comparative Example 2 can only perform coarse filtration, with poor filtration effect. It also has high product density, heavy weight, heavy equipment burden, and the pure metal material is expensive and the manufacturing process is complicated. In contrast, the filter screen provided in Example 1 of this invention can perform filtration with higher precision. The multi-fiber composite design results in a lower filter screen density, which can reduce the weight by more than 50% compared to the pure metal filter screen without affecting the mechanical strength of the filter screen. It is also low in cost and has a simple manufacturing process.

[0174] The polytetrafluoroethylene membrane filter provided in Comparative Example 3 has a maximum heat resistance temperature of only 260°C, and its high wind resistance increase rate in high humidity environments cannot meet fire protection requirements. In contrast, the filter provided in Example 1 of this invention has a maximum heat resistance temperature of over 600°C, and its wind resistance increase rate in high humidity environments is only 8.2%. It combines ultra-high temperature stability and harsh environment stability, and its PM2.5 filtration efficiency is basically the same, while its PM0.3 and PM10 filtration efficiency is even better.

[0175] Although the HEPA membrane filter provided in Comparative Example 4 has excellent maximum heat resistance temperature, its poor hydrophobicity requires frequent replacement and cleaning, which increases maintenance costs.

[0176] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A filter screen, characterized in that, The filter screen comprises a hydrophobic enhancement layer, a pre-filtration layer, and a core filtration layer stacked sequentially. The hydrophobic reinforcement layer is composed of metal fibers; The pre-filter layer is composed of basalt fibers; The core filter layer is composed of polytetrafluoroethylene fiber and polyetheretherketone fiber. The surface of the hydrophobic reinforcement layer has a nanofiber structure; The surface of the hydrophobic reinforcement layer has a micro / nanoplasty structure; The height of the nanofiber structure is 0.1-0.3 μm; The height of the micro / nanoplasty structure is 2-5 μm; The diameter of the micro / nanoplasty structure is 2-5 μm; The spacing between the micro / nanoplastic structures is 8-12 μm; The core filter layer is a nonwoven fabric B containing polytetrafluoroethylene fiber and polyetheretherketone fiber; The core filter layer has a herringbone interwoven structure; The core filter layer has a weave density of 300-400 mesh; The core filter layer has a pore size of 15-25 μm.

2. The filter screen according to claim 1, characterized in that, The diameter of each of the metal fibers, basalt fibers, polytetrafluoroethylene fibers and polyetheretherketone fibers is independently selected from 8-15 μm, and the length of each is independently selected from 25-40 mm. The mass ratio of the metal fiber, basalt fiber, polytetrafluoroethylene fiber and polyetheretherketone fiber is 1:(1.5-5):(4-10):(2.5-7).

3. The filter screen according to claim 1 or 2, characterized in that, The metal fibers include stainless steel fibers; The hydrophobic reinforcement layer has a mesh structure; The length and width of a single grid in the grid structure are 30-70 μm.

4. The filter screen according to claim 1, characterized in that, The pre-filter layer is a non-woven fabric A containing basalt fibers; The pre-filter layer has a weave density of 120-150 mesh; The pore size of the pre-filter layer is 100-150 μm.

5. The filter screen according to claim 1, characterized in that, The filter screen also includes a frame structure and an internal support mesh; The thickness of the frame structure is 3-5 mm; The frame structure includes a steel alloy frame; The internal support network is a hexagonal honeycomb support structure; The mesh spacing of the internal support mesh is 10-15 mm; The internal support mesh includes stainless steel wire mesh; The internal support network is located below the core filter layer.

6. A method for preparing a filter screen as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: The filter screen is obtained by combining and shaping the hydrophobic reinforcement layer, the pre-filter layer and the core filter layer, and then performing surface modification hydrophobic treatment.

7. The method for preparing a filter screen according to claim 6, characterized in that, The composite process is performed using a needle punching technique. The shaping process is hot pressing. The hot pressing temperature is 280-320℃; The pressure for hot pressing is 2-5 MPa; The surface modification hydrophobic treatment includes sequential plasma fluorination treatment, nano-coating treatment, and laser etching treatment; The fluorinating agent used in the plasma fluorination treatment includes CF4; The power of the plasma fluorination treatment is 150-250 W; The plasma fluorination treatment time is 3-5 min; The nano-coating treatment includes immersing the hydrophobic reinforcing layer in a coupling agent solution; The concentration of the coupling agent in the coupling agent solution is 0.5-1 wt%; The coupling agent includes a fluorinated silane coupling agent; The immersion time is 20-40 seconds; The impregnation process also includes a curing step; The curing temperature is 150-200℃, and the curing time is 20-40 min; After the nano-coating treatment, a nanofiber structure was formed on the surface of the hydrophobic reinforcement layer. After laser etching, a micro / nanopapillary structure was formed on the surface of the hydrophobic reinforcement layer.

8. The use of a filter screen as described in any one of claims 1-5 in a filtration device.

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