A preparation method of antistatic pleated filter cartridge

Abstract

The present application relates to the technical field of high-temperature flue gas filtration, and specifically discloses a method for preparing an antistatic folded filter cartridge. The method comprises the following steps: opening and mixing synthetic fibers and metal fibers, using a cloth containing conductive fibers as a base fabric, combing, laying a mesh, combining meshes, and pre-needling to obtain a pre-needled felt; hydroentangling the pre-needled felt to obtain a filter material felt; singeing the filter material felt, immersing it in a finishing agent, squeezing the liquid, and drying it to obtain a stiff filter material felt; trimming and folding the stiff filter material felt, welding a fixing band, and welding the center seam of the stiff filter material felt to obtain a cylindrical filter material; installing a metal mesh inside the cylindrical filter material, welding the sealing of the fixing band to obtain the main body of the filter cartridge; installing galvanized metal end caps at both ends of the main body of the filter cartridge to obtain an antistatic folded filter cartridge. The present application can improve the antistatic performance of the filter cartridge, making the filter cartridge more suitable for the special working environments of the coal mining industry, chemical industry, and oil and gas extraction industry.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature flue gas filtration, and in particular to a method for preparing an antistatic folded filter cartridge. Background Art

[0002] Dust removal bags are widely used in the high-temperature flue gas filtration industry. In some special working environments, such as the coal mining industry, chemical industry, and oil and gas extraction industry, due to the presence of flammable substances such as coal ash powder and flammable gases, if the dust rubs against the surface fibers of the filter material and generates static electricity, it may cause serious accidents such as fire or explosion. Therefore, when using filter bags to filter dust, the filter bags must have anti-static properties.

[0003] In related art, Chinese patent CN109435375A discloses a dust removal bag. The filter bag is formed from filter material into a bag shape. The filter material comprises, from top to bottom, a first layer and a second layer. The first and second layers can be made of glass fiber. The glass fiber used in the first and second layers can be the same type, different types, or a mixed type. The mixed type refers to the glass fibers having different diameters.

[0004] Since glass fiber, PPS, aramid, polyester and other fibers are fiber materials with extremely low conductivity and are prone to accumulate static electricity, the dust removal bags disclosed in the above-mentioned related technologies have poor anti-static properties and it is difficult to avoid the risks of explosion and fire caused by static electricity in special environments. Summary of the Invention

[0005] In order to improve the antistatic performance of a filter cartridge, the present application provides a method for preparing an antistatic pleated filter cartridge.

[0006] The present application provides a method for preparing an antistatic folded filter cartridge, which adopts the following technical solution:

[0007] A method for preparing an antistatic folded filter cartridge comprises the following steps:

[0008] The synthetic fiber and the metal fiber are opened separately, and mixed in a weight ratio of 100:(5-10) of synthetic fiber to metal fiber to obtain a mixed fiber. The cloth containing conductive yarn is used as a base fabric, and the mixed fiber is combed, laid, combined and pre-needled to obtain a pre-needled felt.

[0009] The pre-needled felt is subjected to hydroentanglement to obtain filter material felt;

[0010] After the surface of the filter material felt is singed, it is immersed in a finishing agent, and the impregnated filter material felt is squeezed and dried to obtain a stiff filter material felt;

[0011] After trimming and folding the stiff filter material felt, a fixing band is welded to the outer side of the stiff filter material felt, and the center seam of the stiff filter material felt is welded to obtain a cylindrical filter material;

[0012] Install the metal mesh inside the cylindrical filter material and weld the sealing of the fixing band to obtain the main body of the filter cartridge;

[0013] Galvanized metal end caps are installed at both ends of the main body of the filter cartridge to obtain an antistatic pleated filter cartridge.

[0014] By adopting the above-mentioned technical solution, a mixture of synthetic fiber and metal fiber is used as the raw material, and a cloth containing conductive yarn is used as the base fabric. Since the electrical conductivity of metal fiber is higher than that of synthetic fiber, and the base fabric itself is also conductive, the volume resistance of the filter material can be effectively reduced. Moreover, the present application adopts the form of a filter cartridge to replace the traditional filter bag and skeleton separation matching, and sets a metal mesh in the filter cartridge and galvanized metal end caps at both ends. This can not only increase the filtration area, but also through structural improvements, the metal mesh and galvanized metal end caps can be matched to effectively reduce the charge accumulation of the folded filter cartridge and reduce the overall volume resistance of the folded filter cartridge. Therefore, the present application can improve the antistatic performance of the filter cartridge, making the filter cartridge more suitable for the special working environment of the coal mining industry, chemical industry and oil and gas extraction industry.

[0015] In a specific embodiment, the finishing agent comprises the following raw materials in weight percentage: 20-30% stiffening agent, 3-5% antistatic agent, 10-15% PTFE emulsion, 1-3% coupling agent, and the balance is water.

[0016] By adopting the above technical solution and using a finishing agent containing an antistatic agent, the antistatic agent can penetrate into the interior and surface of the filter material during the impregnation process, further reducing the volume resistance of the filter material, thereby improving the antistatic performance of the filter material itself.

[0017] In a specific embodiment, the antistatic agent includes potassium salt of fatty alcohol ether phosphate, sodium salt of octadecylbenzenesulfonic acid and conductive polyaniline microspheres in a weight ratio of 1:(0.6-1.2):(0.3-0.6).

[0018] By adopting the above technical solution, the potassium salt of fatty alcohol ether phosphate has excellent chemical stability, which can prevent corrosion of metal fibers and cause rust. It can also reduce the friction coefficient between fibers and the surface resistance of fibers, thereby effectively suppressing the generation of static charge. The sodium salt of octadecylbenzenesulfonic acid helps to increase the surface activity of the potassium salt of fatty alcohol ether phosphate and conductive polyaniline microspheres, promoting their penetration between fibers and into the base fabric. The conductive polyaniline microspheres can form a continuous conductive path between non-woven fibers, significantly reducing the overall volume resistance of the filter material and improving its overall conductivity, thereby effectively preventing the accumulation and discharge of static electricity.

[0019] In a specific embodiment, the weight of the stiff filter felt material is 330-370 g / m 2 .

[0020] By adopting the above technical solution, the grammage of the stiff filter felt is related to the amount of glue applied. If the amount of glue applied is too high, the stiff filter felt will be too brittle, which will be damaged during the subsequent folding operation, resulting in the final antistatic pleated filter cartridge being easily worn, pilling, or ruptured. If the amount of glue applied is too low, the stiff filter felt will easily deform, and its fiber structure may change, which can easily affect the adsorption and filtration performance of the antistatic pleated filter cartridge. Through experiments, the present applicant has found that by controlling the grammage of the stiff filter felt within the above range, the resulting antistatic pleated filter cartridge has good adsorption and filtration performance and is not easily worn, pilling, or ruptured.

[0021] In a specific embodiment, the weight of the filter material felt is 285-315 g / m 2 .

[0022] By adopting the above technical solution, the grammage of the filter material felt affects the thickness and the amount of glue applied to the stiff filter material felt in the subsequent steps. The thickness also affects the folding performance of the stiff filter material felt. This application pre-controls the grammage of the filter material felt within the above range, which helps to adjust the grammage of the stiff filter material felt to 330-370g / m in the subsequent steps. 2 , making the stiff filter felt easy to fold, and having good adsorption and filtration effects and good durability.

[0023] In a specific embodiment, the impregnated filter material felt is squeezed and dried at a pressure of 7-8 bar. After squeezing, the liquid content of the impregnated filter material felt is 50-70%; the drying temperature is 140℃-240℃.

[0024] By adopting the above technical solution, the present application has found through experiments that the liquid carrying rate of the impregnated filter material felt can be controlled at 50-70% by squeezing the liquid under the above pressure. At the above liquid carrying rate and drying temperature, it can be quickly dried and the weight of the filter material felt can be 330-370g / m 2 The stiff filter felt material helps improve the durability and production efficiency of this application. Moreover, this application found that the volume resistivity of the antistatic pleated filter cartridges obtained using the above process conditions is lower, which shows that the above process conditions also help to improve the finishing effect of the finishing liquid and improve the antistatic performance of the pleated filter cartridges.

[0025] In a specific embodiment, the pre-needling density is 60-100 needles / cm 2 The needle penetration depth is 11-15mm, and the water spunlace pressure of water spunlace reinforcement is 260-360bar.

[0026] By adopting the above technical solution, since the pre-needling density affects the stiffness of the needled felt, and the needling depth affects the thickness of the pre-needling felt, the higher the hydroentanglement pressure, the greater the hydroentanglement energy generated, the greater the entanglement degree of the filter material felt, the lower the thickness, and the higher the strength. Therefore, only by rationally regulating the pre-needling density and needling depth, as well as the hydroentanglement pressure of the hydroentanglement reinforcement, can the thickness and stiffness be achieved. Through experiments, the present applicant found that the filter material prepared using the above-mentioned pre-needling and hydroentanglement reinforcement process conditions is not only easy to fold, but also has an appropriate stiffness, is not easy to wear and fuzz, and has good durability.

[0027] In a specific embodiment, the synthetic fiber includes at least one of polyester fiber, aramid fiber or PPS fiber, and the conductive yarn-containing fabric is any one of polyester fabric, aramid fabric or PPS fabric containing conductive yarn in both the warp and weft directions.

[0028] By adopting the above technical solutions, polyester exhibits excellent wrinkle resistance, is not prone to wrinkling, has high strength and elastic recovery, and is durable and wear-resistant. Aramid exhibits high strength, excellent high-temperature resistance, chemical corrosion resistance, and self-extinguishing properties. PPS exhibits excellent heat resistance, chemical resistance, and flame retardancy. Fibers and fabrics made from all three materials can be used to manufacture the filter cartridges of this application. Furthermore, the resulting filter cartridges are adaptable to high-temperature flue gas filtration environments and exhibit excellent durability.

[0029] In summary, this application has the following beneficial effects:

[0030] 1. This application can effectively reduce the charge accumulation of the pleated filter cartridge, reduce the overall volume resistance of the pleated filter cartridge, and improve the antistatic performance of the filter cartridge, making the filter cartridge more suitable for the special working environment of the coal mining industry, chemical industry and oil and gas extraction industry.

[0031] 2. In this application, a mixture of fatty alcohol ether phosphate potassium salt, octadecylbenzenesulfonic acid sodium salt and conductive polyaniline is preferably used as an antistatic agent, which can significantly reduce the overall volume resistance of the filter material and improve the overall conductivity of the filter material, thereby effectively preventing the accumulation and discharge of static electricity. DETAILED DESCRIPTION

[0032] The present application is further described in detail below with reference to the following examples and comparative examples.

[0033] Example

[0034] Example 1

[0035] This embodiment provides a method for preparing an antistatic pleated filter cartridge, which comprises the following steps:

[0036] The polyester fiber and the stainless steel fiber were opened separately and mixed in a weight ratio of 100:8 to obtain a mixed fiber. The polyester fabric containing conductive yarns in both the warp and weft directions was used as the base fabric. The mixed fiber was combed and then laid, combined and pre-needled. The needle punching density was 80 needles / cm 2 , the needling depth is 13 mm, and a pre-needled felt is obtained.

[0037] The pre-needled felt was subjected to hydroentanglement reinforcement, wherein 5 hydroentanglement heads were used, the hydroentanglement pressure was 310 bar, and the vehicle speed was 5.5 m / min to obtain filter material felt.

[0038] The surface of the filter felt was singed at a speed of 26 m / min. After singeing, it was immersed in a finishing agent and squeezed at a pressure of 7.5 bar. After squeezing, the impregnated filter felt had a liquid retention rate of 62%. The material was then oven-dried at 190°C and a speed of 5 m / min to form a stiffened filter felt. The finishing agent consisted of the following raw materials in weight percentage: 25% stiffening agent (Xinyi Synthetic LB814), 4% antistatic agent, 10% PTFE emulsion (AMP-95), 1% KH550 coupling agent, and the balance was water. The antistatic agent was a mixture of fatty alcohol ether phosphate potassium salt (MOA-3PK), sodium octadecylbenzenesulfonate, and conductive polyaniline microspheres (Xinyuhong XYH001) in a weight ratio of 1:1:0.5.

[0039] After trimming the stiff filter felt, it is sent to a folding machine for folding with a folding depth of 25 mm. A fixing strap made of the same material as the stiff filter felt is welded to the outer side of the stiff filter felt. An ultrasonic welding machine is used to weld the center seam of the stiff filter felt to obtain a cylindrical filter material.

[0040] A stainless steel mesh roll is installed inside the cylindrical filter material, and the sealing of the fixing band is welded by a welding machine to obtain the main body of the filter cartridge.

[0041] The two ends of the main body of the filter cartridge are placed in galvanized metal end caps that match the size of the filter cartridge, and fixed with glue to obtain an antistatic pleated filter cartridge.

[0042] Example 2

[0043] The only difference between this embodiment and embodiment 1 is that the polyester fiber and the stainless steel fiber are mixed in a weight ratio of 100:5 to obtain the mixed fiber.

[0044] Example 3

[0045] The only difference between this embodiment and embodiment 1 is that the polyester fiber and the stainless steel fiber are mixed in a weight ratio of 100:10 to obtain the mixed fiber.

[0046] Example 4

[0047] The only difference between this embodiment and embodiment 1 is that the finishing agent includes the following raw materials in weight percentage: 20% stiffening agent, 3% antistatic agent, 15% PTFE emulsion, 3% KH550 coupling agent, and the balance is water.

[0048] Example 5

[0049] The only difference between this embodiment and embodiment 1 is that the finishing agent includes the following raw materials in weight percentage: 30% stiffening agent, 5% antistatic agent, 13% PTFE emulsion, 2% KH550 coupling agent, and the balance is water.

[0050] Example 6

[0051] The only difference between this embodiment and embodiment 1 is that the antistatic agent is a mixture of potassium salt of fatty alcohol ether phosphate, sodium salt of octadecylbenzenesulfonate and conductive polyaniline microspheres in a weight ratio of 1:0.5:0.2.

[0052] Example 7

[0053] The only difference between this embodiment and embodiment 1 is that the antistatic agent is a mixture of potassium salt of fatty alcohol ether phosphate, sodium salt of octadecylbenzenesulfonate and conductive polyaniline microspheres in a weight ratio of 1:0.6:0.3.

[0054] Example 8

[0055] The only difference between this embodiment and embodiment 1 is that the antistatic agent is a mixture of potassium salt of fatty alcohol ether phosphate, sodium salt of octadecylbenzenesulfonate and conductive polyaniline microspheres in a weight ratio of 1:1.2:0.6.

[0056] Example 9

[0057] The only difference between this embodiment and embodiment 1 is that the antistatic agent is a mixture of potassium salt of fatty alcohol ether phosphate, sodium salt of octadecylbenzenesulfonate and conductive polyaniline microspheres in a weight ratio of 1:1.4:0.7.

[0058] Example 10

[0059] The only difference between this embodiment and embodiment 1 is that the acupuncture density is 50 needles / cm 2 , the needling depth is 10 mm and the water puncture pressure is 250 bar.

[0060] Example 11

[0061] The only difference between this embodiment and embodiment 1 is that the acupuncture density is 60 needles / cm 2 , the needling depth is 11 mm and the water puncture pressure is 260 bar.

[0062] Example 12

[0063] The only difference between this embodiment and embodiment 1 is that the acupuncture density is 100 punctures / cm 2 , the needling depth is 15 mm and the water puncture pressure is 360 bar.

[0064] Example 13

[0065] The only difference between this embodiment and embodiment 1 is that the acupuncture density is 110 needles / cm 2 , the needling depth is 16 mm and the water puncture pressure is 380 bar.

[0066] Example 14

[0067] The only difference between this embodiment and embodiment 1 is that the impregnated filter material felt is squeezed with liquid at a pressure of 6.5 bar. After squeezing, the impregnated filter material felt has a liquid content of 78%. The filter material felt is then dried and shaped in an oven at a temperature of 250°C and an oven speed of 6 m / min to obtain a stiff filter material felt.

[0068] Example 15

[0069] The only difference between this embodiment and embodiment 1 is that the impregnated filter material felt is squeezed with liquid at a pressure of 7 bar. After squeezing, the impregnated filter material felt has a liquid rate of 70%. It is then dried and shaped in an oven at a temperature of 240°C and an oven speed of 6 m / min to obtain a stiff filter material felt.

[0070] Example 16

[0071] The only difference between this embodiment and embodiment 1 is that the impregnated filter material felt is squeezed with liquid at a pressure of 8 bar. After squeezing, the impregnated filter material felt has a liquid rate of 50%. It is then dried and shaped in an oven at a temperature of 140°C and an oven speed of 4 m / min to obtain a stiff filter material felt.

[0072] Example 17

[0073] The only difference between this embodiment and embodiment 1 is that the impregnated filter material felt is squeezed with liquid at a pressure of 8.5 bar. After squeezing, the impregnated filter material felt has a liquid content of 41%. The filter material felt is then dried and shaped in an oven at a temperature of 120°C and an oven speed of 4 m / min to obtain a stiff filter material felt.

[0074] Example 18

[0075] The only difference between this embodiment and embodiment 1 is that the polyester fiber is replaced by an equal amount of aramid fiber, and the polyester fabric is replaced by an aramid fabric of equal thickness containing conductive yarns in both the warp and weft directions.

[0076] Example 19

[0077] The only difference between this embodiment and embodiment 1 is that the polyester fiber is replaced by an equal amount of PPS fiber, and the polyester fabric is replaced by a PPS fabric of equal thickness containing conductive yarns in both the warp and weft directions.

[0078] Comparative Example

[0079] Comparative Example 1

[0080] The only difference between this comparative example and Example 1 is that the stainless steel fiber is replaced by an equal amount of polyester fiber.

[0081] Comparative Example 2

[0082] The only difference between this comparative example and Example 1 is that the polyester fiber and the stainless steel fiber are mixed in a weight ratio of 100:4 to obtain the mixed fiber.

[0083] Comparative Example 3

[0084] The only difference between this comparative example and Example 1 is that the polyester fiber and the stainless steel fiber are mixed in a weight ratio of 100:11 to obtain the mixed fiber.

[0085] Comparative Example 4

[0086] The only difference between this comparative example and Example 1 is that no stainless steel mesh roll is installed inside the cylindrical filter material.

[0087] Comparative Example 5

[0088] The only difference between this comparative example and Example 1 is that no galvanized metal end caps are installed at both ends of the filter cartridge body, and the filter cartridge body is directly used as an antistatic folded filter cartridge.

[0089] Performance testing

[0090] The following performance tests were performed on the antistatic pleated filter cartridges prepared in Examples 1-19 and Comparative Examples 1-5:

[0091] The filter material felt and stiff filter material felt in each embodiment and comparative example were weighed respectively, and the gram weight was calculated according to the following formula: gram weight = weight ÷ area.

[0092] According to GB / T 12703.4-2010, the volume resistivity of stiff filter felt and antistatic pleated filter cartridges is tested.

[0093] According to GB / T12625-1990, the dust removal rate of the antistatic pleated filter cartridge is tested.

[0094] The test results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] Combining Example 1 and Comparative Examples 1-5 and Table 1, it can be seen that compared with Example 1, the volume resistance of the antistatic folded filter cartridges of Comparative Examples 1, 4 and 5 is significantly increased, the volume resistance of the stiff filter material felt of Comparative Examples 1 and 2 is significantly increased, and the volume resistance of the stiff filter material felt of Comparative Example 3 is reduced, but the dust removal rate of the antistatic folded filter cartridge of Comparative Example 3 is reduced. This shows that the volume resistance of the stiff filter material felt is reduced due to the addition of stainless steel fiber, and the volume resistance of the antistatic folded filter cartridge is reduced by using stainless steel mesh and galvanized metal end caps. However, adding too much stainless steel fiber may result in a decrease in the dust removal rate of the filter cartridge. Therefore, the raw material ratio and process conditions of Example 1 are used to help improve the antistatic performance of the stiff filter material felt and the antistatic folded filter cartridge, and enable the stiff filter material felt and the antistatic folded filter cartridge to maintain a good dust removal rate.

[0099] Combining Examples 1-5 and 18-19 and Table 1, it can be seen that the stiff filter felt material and antistatic pleated filter cartridge of Examples 1-5 have a relatively small volume resistivity, and the dust removal rate of the antistatic pleated filter cartridge is greater than 99.99%. Therefore, the antistatic performance of the antistatic pleated filter cartridge can be improved by using the raw material ratio within the range of Examples 1-5.

[0100] Combining Examples 1, 6-9, and Table 1, it can be seen that the volume resistivity of the stiff filter felt materials of Examples 1, 6-9 is ranked from smallest to largest: Example 8 < Example 9 < Example 1 < Example 7 < Example 6. However, the weight ratio of the conductive polyaniline microspheres in the antistatic agent is ranked from smallest to largest: Example 6 < Example 7 < Example 1 < Example 8 < Example 9. This indicates that within a weight ratio of fatty alcohol ether phosphate potassium salt, octadecylbenzenesulfonic acid sodium salt, and conductive polyaniline microspheres of 1:(0.6-1.2):(0.3-0.6), the volume resistivity of the stiff filter felt material is lower, helping to further improve the antistatic performance of the antistatic pleated filter cartridge.

[0101] Combining Examples 1, 10-13 and Table 1, it can be seen that as the needling density, needling depth and spunlace pressure increase, the weight of the filter material felt gradually increases. However, when the needling density is 60-100 punctures / cm 2 Under the process conditions of acupuncture depth of 11-15mm and water entanglement pressure of 260-360bar, the volume resistance of the stiff filter felt material is smaller and the dust removal rate is high.

[0102] Combining Examples 1, 14-17 and Table 1, it can be seen that when the pressure of the squeeze liquid is less than 7 bar, the liquid carrying rate of the impregnated filter material felt is greater than 70%. Even if it is dried at a temperature higher than 240°C at the same speed, the stiffness of the filter material felt is still greater than 370g / m 2 , the dust removal rate is low. When the pressure of the squeeze liquid is greater than 8 bar, the liquid rate of the impregnated filter material felt is less than 50%. Even if it is dried at a temperature below 140℃ at the same speed, the stiffness of the filter material felt is still less than 330g / m 2 , and the volume resistivity of the stiff filter felt material increased significantly. This indicates that when the liquid is squeezed out at a pressure of 7-8 bar, the liquid content of the impregnated filter felt is 50-70% after the squeeze is completed. A drying temperature of 140°C-240°C is conducive to obtaining a stiff filter felt material with low volume resistivity and high dust removal efficiency.

[0103] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing an antistatic folded filter cartridge, characterized in that: The steps include: The synthetic fiber and the metal fiber are opened separately, and mixed in a weight ratio of 100:(5-10) of synthetic fiber to metal fiber to obtain a mixed fiber. The cloth containing conductive yarn is used as a base fabric, and the mixed fiber is combed, laid, combined and pre-needled to obtain a pre-needled felt. The pre-needled felt is subjected to hydroentanglement to obtain filter material felt; After the surface of the filter material felt is singed, it is immersed in a finishing agent, and the impregnated filter material felt is squeezed and dried to obtain a stiff filter material felt; After trimming and folding the stiff filter material felt, a fixing band is welded to the outer side of the stiff filter material felt, and the center seam of the stiff filter material felt is welded to obtain a cylindrical filter material; Install the metal mesh inside the cylindrical filter material and weld the sealing of the fixing band to obtain the main body of the filter cartridge; Galvanized metal end caps are installed at both ends of the filter cartridge body to obtain an antistatic pleated filter cartridge; The finishing agent comprises the following raw materials in weight percentage: 20-30% stiffening agent, 3-5% antistatic agent, 10-15% PTFE emulsion, 1-3% coupling agent, and the balance is water; the antistatic agent comprises potassium salt of fatty alcohol ether phosphate, sodium salt of octadecylbenzenesulfonic acid, and conductive polyaniline microspheres in a weight ratio of 1: (0.6-1.2): (0.3-0.6); The weight of the stiff filter felt is 330-370g / m 2 ; The weight of the filter material felt is 285-315g / m 2 ; When the impregnated filter material felt is squeezed and dried, the squeeze is carried out at a pressure of 7-8 bar. After the squeeze is completed, the liquid content of the impregnated filter material felt is 50-70%; the drying temperature is 140℃-240℃; The density of pre-needling is 60-100 needles / cm 2 , the needling depth is 11-15mm, and the spunlace pressure for spunlace reinforcement is 260-360bar; The synthetic fiber includes at least one of polyester fiber, aramid fiber or PPS fiber, and the cloth containing conductive yarn is any one of polyester cloth, aramid cloth or PPS cloth containing conductive yarn in both warp and weft directions.

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