Composite processing method of PTFE folding cylinder filter material

Abstract

The invention relates to the related field of filter materials, in particular to a composite processing method of a PTFE folding cylinder filter material, which realizes good combination of a PTFE fiber filter material and a metal wire mesh through composite processing of needling and spunlace, and realizes processing of a stiff and foldable PTFE filter material. The PTFE and the stainless steel fiber have high temperature resistance and corrosion resistance, and are suitable for filtering high-temperature smoke dust in a severe working condition environment; the PTFE folding cylinder filter material prepared by the invention has good conductive and explosion-proof functions, and the surface resistance is about 105 power.

Description

Technical Field

[0001] The present invention relates to the field of filter materials, and specifically to a composite processing method for PTFE folded cartridge filter materials. Background Art

[0002] In recent years, with the development and progress of environmental protection science and technology, the high-temperature air filtration market has been developing towards efficient energy-saving production and green environmental protection. Especially for the tail gas filtration in the waste incineration industry, the filter material is required to have acid and alkali resistance, corrosion resistance, and high-temperature resistance at about 200 degrees Celsius. At the same time, high-efficiency filters require small volume, high wind speed, and large air volume. The folded cartridge filter bag adapts to the development direction of filter materials and realizes the folding process through its own hardening treatment. Currently, traditional high-temperature filter bags are gradually being replaced by folded filter cartridges. The folded cartridge filter bag effectively increases the filtration area of the material through the folding treatment, improving the efficiency by more than 50% compared to traditional filter bags. PTFE filter material is a filter material with very excellent chemical resistance and high-temperature resistance. However, due to the difficulty of performing conventional hardening treatment on PTFE filter material, it is usually used as a filter bag with needle punching reinforcement. Therefore, in order to expand the use of PTFE filter material, the problem of folding PTFE filter material needs to be solved urgently.

[0003] PTFE, also known as polytetrafluoroethylene, commonly known as the king of plastics, is a material with excellent acid and alkali resistance and high and low temperature resistance. The fibers and filter materials made from it have excellent corrosion resistance, acid and alkali resistance, and high-efficiency filtration performance. PTFE needle punched felt can be obtained by needle punching PTFE and is widely used for the tail gas dust filtration in harsh working conditions such as waste incineration and cement kilns. The performance of PTFE fiber is soft, and it is difficult to use it as a folded cartridge filter material. Due to the water and oil repellent characteristics of PTFE, it is generally very difficult to perform stiffening treatment with chemical reagents. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite processing method for PTFE folded cartridge filter materials to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A composite processing method for PTFE folded cartridge filter materials, comprising the following steps:

[0006] Step S1: Select appropriate PTFE fibers for standby, and then open, card, and lay the PTFE fibers. Through single-sided and double-sided needle punching processing, a pre-reinforced needle punched filter material is obtained;

[0007] Step S2: Single-sided reinforce the pre-reinforced needle punched filter material and the metal wire mesh through a high-pressure water jet process. The number of water jet reinforcement passes is 2 - 3 times, and the water jet pressure range is 120 MPa to 250 MPa to realize the composite of the pre-reinforced needle punched filter material and the metal wire mesh, obtaining a composite needle punched filter material;

[0008] Step S3: Impregnate the composite needle-punched filter media with PTFE emulsion to achieve a PTFE emulsion concentration of 20% for saturated impregnation treatment. After soaking, the needle-punched filter media is pressed and dried to cure the filter media.

[0009] Step S4: Conduct heat setting treatment on the cured needle-punched filter media at a setting temperature of 250 - 270 °C.

[0010] Step S5: Carry out film covering processing of PTFE film on the surface of the set needle-punched filter media, and then carry out processing of folded cartridge filter bags to obtain PTFE folded cartridge filter media.

[0011] Preferably, in step S1, the gram weight range of PTFE fibers is 50 - 70 gsm, the number of laying layers is 4 layers, and during the needling process, the pre-needling density is 50 needles per square centimeter, and the main needling density is 120 needles per square centimeter.

[0012] Preferably, the specific steps for obtaining the pre-reinforced needle-punched filter media by opening, carding, and laying PTFE fibers and through single-sided and double-sided needling processing in step S1 are as follows:

[0013] Step S1.1: First, carry out an opening process on PTFE fibers to remove impurities, short fibers, and sliver in the fibers.

[0014] Step S1.2: Then, card the PTFE fibers after opening, where the PTFE fibers are straightened and arranged to ensure uniformity during laying.

[0015] Step S1.3: Uniformly spread the carded PTFE fibers to a predetermined width and thickness to form a continuous fiber layer.

[0016] Step S1.4: Use a needling machine to puncture and fix the fiber layer in step S1.3 through a row of small needles arranged vertically to achieve the directional arrangement of PTFE fibers and the preliminary consolidation of the structure. Subsequently, carry out needling processing on the reverse side of the fiber layer to further improve the structural strength and stability of the filter media.

[0017] Step S1.5: After the fiber layer undergoes single-sided and double-sided needling processing, a layer of pre-reinforced needle-punched filter media is obtained as the base material for bonding with the metal wire mesh.

[0018] Preferably, in step S2, the metal wire mesh uses 304 stainless steel wire, with a smooth surface, the wire diameter is between 0.18 - 0.21 mm, and the mesh number is 20 meshes.

[0019] Preferably, in step S2, the gram weight of the composite needle-punched filter media is between 650 - 850 gsm, and the composite needle-punched filter media has electrical conductivity, and the surface resistance of the composite needle-punched filter media is 10^5 Ω.

[0020] Preferably, the solid content of PTFE in the PTFE emulsion in step S3 is 50%.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1) Through the combined processing of needling and hydroentangling, the present invention realizes the good combination of PTFE fiber filter material and metal wire mesh, and realizes the processing of a stiff and foldable PTFE filter material;

[0023] 2) Both PTFE and stainless steel fibers in the present invention have the properties of high temperature resistance and corrosion resistance, and are suitable for filtering high temperature soot under harsh working conditions.

[0024] 3) The PTFE folded cartridge filter material made by the present invention has good conductivity and explosion-proof functions, and the surface resistance is about 10^5. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic flow chart of the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Please refer to Figure 1 , the present invention provides a technical solution: a composite processing method for a PTFE folded cartridge filter material, comprising the following steps:

[0028] Step S1: Select suitable PTFE fibers for standby, and then open, card, and lay the PTFE fibers, and obtain a pre-reinforced needle-punched filter material through single-sided and double-sided needling processes;

[0029] Step S2: Unidirectionally reinforce the pre-reinforced needle-punched filter material and the metal wire mesh through a high-pressure hydroentangling process. The number of hydroentangling passes is 2-3 times, and the hydroentangling pressure range is 120 MPa to 250 MPa, so as to realize the composite of the pre-reinforced needle-punched filter material and the metal wire mesh, and obtain a composite needle-punched filter material;

[0030] Step S3: Immerse the composite needle-punched filter material in PTFE emulsion to make the concentration of PTFE emulsion reach 20% for saturated impregnation treatment, and the immersed needle-punched filter material is pressed and dried to cure the filter material;

[0031] Step S4. Perform heat setting on the solidified needle-punched filter material, with the setting temperature being 250 - 270°C;

[0032] Step S5. Perform PTFE membrane coating on the surface of the needle-punched filter material after setting, and then perform the processing of folded cartridge filter bags to obtain PTFE folded cartridge filter material.

[0033] Further, in step S1, the grammage range of PTFE fibers is 50 - 70 gsm, the number of laying layers is 4 layers, and during the needling process, the pre-needling density is 50 needles per square centimeter, and the main-needling density is 120 needles per square centimeter.

[0034] Further, the specific steps of opening, carding, and laying the PTFE fibers in step S1 and obtaining the pre-reinforced needle-punched filter material through single-sided and double-sided needling processing are as follows:

[0035] Step S1.1. First, perform the opening process on the PTFE fibers to remove impurities, short fibers, and sliver in the fibers;

[0036] Step S1.2. Then, card the PTFE fibers after opening, where the PTFE fibers are straightened and arranged to ensure uniformity during laying;

[0037] Step S1.3. Uniformly spread the carded PTFE fibers to a predetermined width and thickness to form a continuous fiber layer;

[0038] Step S1.4. Use a needling machine to puncture and fix the fiber layer in step S1.3 through a row of small needles arranged vertically to achieve the directional arrangement of PTFE fibers and the preliminary consolidation of the structure. Subsequently, perform needling processing on the reverse side of the fiber layer to further improve the structural strength and stability of the filter material;

[0039] Step S1.5. After the fiber layer undergoes single-sided and double-sided needling processing, a layer of pre-reinforced needle-punched filter material is obtained as the base material for combination with the metal wire mesh.

[0040] Further, in step S2, the metal wire mesh uses 304 stainless steel wire, with a smooth surface, the wire diameter being between 0.18 - 0.21 mm, and the mesh number being 20 meshes.

[0041] Further, in step S2, the grammage of the combined needle-punched filter material is between 650 - 850 gsm, and the combined needle-punched filter material has electrical conductivity, and the surface resistance of the combined needle-punched filter material is approximately 10^5 Ω.

[0042] Further, in step S3, the solid content of PTFE in the PTFE emulsion is 50%.

[0043] Specifically, the present invention will be further elaborated in detail below in combination with the processing embodiment of producing 750 gsm high-temperature PTFE folded cartridge filter media:

[0044] 1) Open and clean the prepared PTFE fibers, card them to a grammage of 50 - 70 gsm, lay 4 layers of webs, and perform needling. The pre-needling density is 50 needles per square centimeter, and the main needling one is 120 needles per square centimeter to obtain a pre-consolidated needle-punched filter media. Among them, the weight of PTFE fibers is 120 gsm. The PTFE fibers are needled through two passes of web laying to obtain a 720 - 750 gsm needle-punched filter media, and the production speed is 3.5 meters per minute.

[0045] 2) Unroll the pre-consolidated needle-punched filter media and unroll the metal wire mesh, and perform pre-wetting. The specific parameters for pre-wetting are a pressure of 50 Mpa, main hydro-needling one, main hydro-needling two, and the hydro-needling pressure is 120 Mpa - 250 Mpa;

[0046] 3) Immerse the above-treated needle-punched filter media in PTFE emulsion. The solid content of the PTFE emulsion is 50%, and the formulation concentration is 20%. Subsequently, the needle-punched filter media impregnated with PTFE emulsion is pressed and dried at high temperature;

[0047] 4) Perform heat setting on the above-dried needle-punched filter media, and the setting temperature is 250 - 270 °C;

[0048] 5) After the needle-punched filter media is completed with heat setting, perform surface coating, use the coating process of PTFE film, and then process the needle-punched filter media into a folded cartridge filter bag to obtain a PTFE folded cartridge filter media.

[0049] Through the combined processing of needling and hydro-needling, the present invention realizes the good combination of PTFE fiber filter media and metal wire mesh, and realizes the processing of a stiff and foldable PTFE filter media; in the present invention, both PTFE and stainless steel fibers have the properties of high temperature resistance and corrosion resistance, and are suitable for filtering high-temperature soot under harsh working conditions; the PTFE folded cartridge filter media made by the present invention has good conductivity and explosion-proof functions, and the surface resistance is about 10^5.

[0050] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A composite processing method for PTFE folded cylinder filter media, characterized in that, It includes the following steps: Step S1: Select appropriate PTFE fibers for standby, and then open, card, and lay the PTFE fibers. Through single-sided and double-sided needling processes, a pre-consolidated needle-punched filter medium is obtained; Step S2: Unidirectionally consolidate the pre-consolidated needle-punched filter medium and the wire mesh through a high-pressure hydroentangling process. The number of hydroentangling passes is 2 - 3, and the hydroentangling pressure ranges from 120 MPa to 250 MPa to achieve the composite of the pre-consolidated needle-punched filter medium and the wire mesh, obtaining a composite needle-punched filter medium; Step S3: Immerse the composite needle-punched filter medium in PTFE emulsion to make the PTFE emulsion concentration reach 20% for saturated impregnation treatment. The immersed needle-punched filter medium is pressed and dried to cure the filter medium; Step S4: Perform heat setting on the cured needle-punched filter medium, and the setting temperature is 250 - 270 °C; Step S5: Perform film laminating of PTFE membrane on the surface of the set needle-punched filter medium, and then perform the processing of folded cartridge filter bags to obtain PTFE folded cartridge filter medium.

2. The composite processing method of a PTFE folded cylinder filter medium according to claim 1, characterized in that: In the step S1, the gram weight range of the PTFE fibers is 50 - 70 gsm, the number of laying layers is 4 layers, and during the needling process, the pre-needling density is 50 needles / cm², and the main needling density is 120 needles / cm².

3. A composite processing method of a PTFE folded cylinder filter material according to claim 1, characterized in that: The specific steps of obtaining the pre-consolidated needle-punched filter medium by opening, carding, laying the PTFE fibers, and through single-sided and double-sided needling processes in the step S1 are as follows: Step S1.1: First, perform an opening process on the PTFE fibers to remove impurities, short fibers, and sliver in the fibers; Step S1.2: Then card the PTFE fibers after the opening process, where the PTFE fibers are straightened and arranged to ensure uniformity during laying; Step S1.3: Uniformly spread the carded PTFE fibers to a predetermined width and thickness to form a continuous fiber layer; Step S1.4: Use a needling machine to puncture and fix the fiber layer in step S1.3 through a row of small needles arranged vertically to achieve the directional arrangement of the PTFE fibers and the preliminary consolidation of the structure. Subsequently, perform needling on the reverse side of the fiber layer to further improve the structural strength and stability of the filter medium; Step S1.5: After the fiber layer undergoes single-sided and double-sided needling processes, a layer of pre-consolidated needle-punched filter medium is obtained as the base material for bonding with the wire mesh.

4. A composite processing method of a PTFE folded cylinder filter medium according to claim 1, characterized in that: In the step S2, the wire mesh uses 304 stainless steel wire, with a smooth surface, the wire diameter is between 0.18 - 0.21 mm, and the mesh number is 20 meshes.

5. A composite processing method of a PTFE folded cylinder filter material according to claim 1, characterized in that: In the step S2, the gram weight of the composite needle-punched filter medium is between 650 - 850 gsm, and the composite needle-punched filter medium has electrical conductivity, and the surface resistance of the composite needle-punched filter medium is about 10^5 Ω.

6. A composite processing method of a PTFE folded cartridge filter material according to claim 1, characterized in that: In the step S3, the solid content of PTFE in the PTFE emulsion is 50%.

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