A fire-resistant needle-punched filter material with high flame retardancy

Abstract

The present invention relates to the technical field of filter materials, specifically a fire-resistant needle-punched filter material with high flame retardancy. The filter material is composed of at least two types of fibers on the dust-facing surface, one of which is a modified polyacrylonitrile fiber. The modified polyacrylonitrile fiber molecular chain contains a molecular ring composed of carbon and nitrogen, and the molecular ring accounts for 50% to 80% of the molecular weight. The modified polyacrylonitrile fiber accounts for 30wt% to 80wt% of the weight of the filter material on the dust-facing surface; the other fiber is a polytetrafluoroethylene fiber, and the polytetrafluoroethylene fiber accounts for 20wt% to 70wt% of the weight of the filter material on the dust-facing surface. The present invention has excellent fire resistance and flame retardancy, outstanding wear and folding resistance, and can meet ultra-low emission requirements. It is suitable for all types of dust removal and collection conditions with sparks, flammable and explosive materials, and can solve the current problems in the new energy battery and photovoltaic fields where bags are prone to carbonization, burning, wear, and powder leakage during collection.

Description

Technical Field

[0001] The present invention relates to the technical field of filter materials, in particular to a fire-resistant needle-punched filter material with high flame retardancy. Background Art

[0002] In recent years, China has continuously strengthened its focus on the new energy sector, with booming development in the fields of ternary lithium batteries, lithium iron phosphate batteries, and photovoltaic monocrystalline silicon. Dust collector bags made of needle-punched filter materials are becoming increasingly widespread. Currently, in the battery sector, materials such as PPS, aramid, and PTFE are primarily used for dust collection in processes such as ferrophosphorus flash evaporation, ferrophosphorus calcination, and lithium iron phosphate atomization drying. These bags are prone to wear, surface carbonization and burning caused by high-temperature dust accumulation, and powder seepage due to insufficient filtration accuracy (ultrafine dust). Consequently, their service life is typically limited to 3-6 months.

[0003] In the photovoltaic field, PTFE is mainly used for dust filtration in single crystal silicon pulling furnaces. It is prone to filter bag folding and wear, surface carbonization and burning caused by high-temperature dust accumulation, and its service life ranges from 4 to 6 months.

[0004] Chinese patent CN201810689270.6 discloses a flame-retardant and high-temperature resistant dust bag material, which uses 9 substances in a high-speed mixer. "While blending, they must be heated to 300-350°C and can be taken out only after they are completely dried. They are granulated and cold-cut using a twin-screw extruder, and then melt-extruded through a twin-screw extruder and spun through a spinning box spinneret, cooled and shaped to obtain mesh; the mesh is woven to obtain a flame-retardant and high-temperature resistant dust bag material." It has complex ingredients, high production difficulty, low production efficiency, and the process route is not a needle punching process.

[0005] For example, China's patent CN202310656388.X discloses a high-temperature resistant, anti-corrosion and flame-retardant filter material and its preparation method and application. The alkali-free glass fiber accounts for 60% to 65% of the fiber ratio, and 300g / m 2 For high-weight glass fiber base cloth, this method is still mainly based on glass fiber and relies on the heat-resistant properties of glass fiber for research and development, but glass fiber has poor folding resistance, which is not conducive to long-term use in on-site working conditions, and its hydrolysis resistance is general and its lifespan is limited.

[0006] The fire-resistant and highly flame-retardant needle-punched filter material involved in the present invention aims to solve the pain points of use in the fields of new energy batteries and photovoltaics, solve the problems of carbonization, burning, wear and powder penetration on site, and extend the service life of dust removal filter bags. Summary of the Invention

[0007] The present invention aims to address the aforementioned technical problems by providing a fire-resistant needle-punched filter material with high flame retardancy. Another object of the present invention is to extend the service life of filter bags in dust removal equipment where sparks or high-temperature dust accumulation are prone to smoldering, and to maintain the integrity of the filter material after at least two years of use.

[0008] In order to achieve the above technical objectives and meet the above technical requirements, the technical solution adopted by the present invention is: a fire-resistant needle-punched filter material with high flame retardancy, wherein the filter material is composed of at least two kinds of fibers on the dust-facing surface, one of which is a fiber containing Figure 1 The modified polyacrylonitrile fiber has the molecular structure shown, and the modified polyacrylonitrile fiber molecular chain segment contains a molecular ring composed of carbon and nitrogen, and the proportion of the molecular ring in the molecular weight is 50% to 80%, and the weight proportion of the modified polyacrylonitrile fiber in the dust-facing surface of the filter material is 30wt% to 80wt%; the other fiber is polytetrafluoroethylene fiber, and the weight proportion of the polytetrafluoroethylene fiber in the dust-facing surface of the filter material is 20wt% to 70wt%.

[0009] Preferably, the filter material is a three-layer space structure, including a surface dust-facing layer, a base fabric support layer, and a back layer. The base fabric support layer is made of one or more mixed fibers such as polytetrafluoroethylene, aromatic polyamide, polyphenylene sulfide, and polyaromatic oxadiazole. The back layer is made of one or more mixed needle-punched fibers such as polytetrafluoroethylene, aromatic polyamide, polyphenylene sulfide, polyaromatic oxadiazole, and annular trapezoidal structure modified polyacrylonitrile. The overall gram weight of the filter material is 500g / m 2 ~900g / m 2 .

[0010] Preferably, polyphenylene sulfide fibers may be added to the dust-facing side of the filter material, with an average linear density of 0.8-3.0 dtex and a weight proportion of 20 wt%-40 wt%.

[0011] Preferably, the average linear density of the modified polyacrylonitrile fiber is 1.0-3.0 dtex, and the average linear density of the polytetrafluoroethylene fiber is 2.5-7.0 dtex.

[0012] Preferably: the filter material is tested using the vertical combustion method of GB / T 5455-2014 "Fire performance of textiles - Determination of vertical direction damage length, smoldering and afterflaming time", with an afterflaming time of ≤1s, a damage length of ≤5mm, and a combustion characteristic of no droplets; and a surface flame heating test is performed on it, meeting the fire resistance shrinkage rate of ≤1%.

[0013] Preferably, the surface of the filter material can also be optimized by using an aqueous solution of an anionic or nonionic adhesive mixed with a silane coupling agent as a treating agent for surface treatment to improve its loose surface structure. The wear resistance is ≥ 100,000 revolutions when tested in accordance with GB / T21196.2-2007 "Textiles - Determination of the Abrasion Resistance of Fabrics by the Martindale Method - Part 2: Determination of Specimen Damage" using wool woven cloth as an abrasive.

[0014] Preferably: in the surface treatment agent of the filter material, the component of the adhesive is esters of acrylic acid and its homologues, the silane coupling agent is one or a mixture of vinyltriethoxysilane and vinyltrimethoxysilane, and the adhesive, coupling agent and water are mixed in a weight ratio of adhesive: coupling agent: water of 50wt%~80wt%:1wt%~5wt%:15wt%~49wt%.

[0015] Preferred: Based on the VDI3926 "Standard Test Method for Evaluating Cleanable Filter Media" standard test, the dynamic filtration efficiency of the filter material is ≥99.995%, and it can handle dust particle size ≥3 microns and outlet concentration ≤5mg / m 3 Ultra-low dust emissions below.

[0016] Preferably, based on the GB / T457-2008 “Determination of folding endurance of paper and paperboard” standard test, the folding endurance of the filter material is ≥ 200,000 times.

[0017] Preferably, the filter material can be operated continuously at a temperature of ≤220°C for a long period of time, and the thermal shrinkage in the longitudinal and latitudinal directions is <1%.

[0018] Compared with the traditional structure, the present invention has the following advantages:

[0019] 1. The fire-resistant needle-punched filter material with high flame retardancy of the present invention has excellent fire resistance and flame retardancy. Especially when encountering sparks or high-temperature dust accumulation that is easy to smolder on its surface, it can still maintain a very small surface shrinkage rate and the filter material structure is not destroyed. Moreover, because it has high wear resistance, high folding resistance and high-precision filtering capacity, it can ensure that it still maintains excellent performance after 2 years of use, can meet the requirements of ultra-low emissions, and is suitable for all kinds of dust removal and collection conditions with sparks, flammable and explosive materials.

[0020] 2. After the filter material of the present invention is sewn into a bag shape, it can be used for dust collection in fields such as ternary lithium batteries, lithium iron phosphate batteries, photovoltaic monocrystalline silicon, etc. where there are sparks or dust accumulation and easy combustion. It can greatly improve the service life and collection effect of the current filter bags in the industry, and solve the current problems in the new energy battery and photovoltaic fields where cloth bags are prone to carbonization, burning, wear and powder penetration during collection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a molecular structure diagram of the modified polyacrylonitrile fiber of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below.

[0023] A fire-resistant needle-punched filter material with high flame retardancy, wherein the filter material is composed of at least two types of fibers on the dust-facing surface, one of which contains Figure 1 The modified polyacrylonitrile fiber has the molecular structure shown, and the modified polyacrylonitrile fiber molecular chain segment contains a molecular ring composed of carbon and nitrogen, and the proportion of the molecular ring in the molecular weight is 50% to 80%, and the weight proportion of the modified polyacrylonitrile fiber in the dust-facing surface of the filter material is 30wt% to 80wt%; the other fiber is polytetrafluoroethylene fiber, and the weight proportion of the polytetrafluoroethylene fiber in the dust-facing surface of the filter material is 20wt% to 70wt%.

[0024] In the molecular chain segments of the modified polyacrylonitrile fiber, the proportion of molecular rings composed of carbon and nitrogen needs to be controlled within a certain range, because the molecular rings play a key role in fire resistance. Therefore, if the proportion of the carbon-nitrogen molecular rings in the molecular weight is less than 50%, its fire resistance will be affected and the requirements of fire resistance shrinkage rate will not be met. If the proportion of the carbon-nitrogen molecular rings in the molecular weight is greater than 80%, although the fire resistance is excellent, the strength loss of the modified polyacrylonitrile fiber will be greater as the proportion of carbon-nitrogen molecular rings increases. Therefore, the filter material prepared has poor strength, a short lifespan in actual working conditions, and cannot meet the actual service life requirements, posing a greater risk of use. Taking all factors into consideration, the proportion of carbon-nitrogen molecular rings in the molecular weight is preferably 60% to 70%.

[0025] The weight proportion of the modified polyacrylonitrile fiber in the dust-facing surface of the filter material is 30wt% to 80wt%; the weight proportion of another fiber, polytetrafluoroethylene fiber, in the dust-facing surface of the filter material is 20wt% to 70wt%.

[0026] If the weight proportion of modified polyacrylonitrile fiber on the dust-facing side is less than 30% and the weight proportion of polytetrafluoroethylene fiber is greater than 70%, its fire resistance will be affected and it will not be able to meet the fire resistance shrinkage requirement. In addition, after the polytetrafluoroethylene fiber on the dust-facing side is increased, the polytetrafluoroethylene fiber itself is uneven in thickness, with more coarse fibers and an irregular flat shape, resulting in large gaps between fibers and poor filtration efficiency, which cannot meet the requirement of ≤5mg / m 3The following ultra-low dust emissions. If the weight proportion of modified polyacrylonitrile fiber is greater than 80% and the weight proportion of polytetrafluoroethylene fiber is less than 20%, the entanglement effect of the production process will be worse, and the strength of modified polyacrylonitrile fiber is worse than that of polytetrafluoroethylene fiber. Therefore, the filter material made from it has poor strength, wear resistance and folding resistance, and has a short lifespan in actual working conditions, and has a greater risk of use. Taking into account fire resistance, filtration and service life, the preferred ratio is that the weight proportion of modified polyacrylonitrile fiber in the dust-facing side of the filter material is 50wt%~70wt%, and the weight proportion of polytetrafluoroethylene fiber in the dust-facing side of the filter material is 30wt%~50wt%.

[0027] During the production process of the fire-resistant needle-punched filter material with high flame retardancy of the present invention, the modified polyacrylonitrile fiber and the polytetrafluoroethylene fiber are fully mixed in proportion and then opened, carded and laid to form the surface structure of the needle-punched filter material. One or more fibers such as polytetrafluoroethylene, aromatic polyamide, polyphenylene sulfide, polyaromatic oxadiazole, and the above-mentioned modified polyacrylonitrile are simultaneously used, fully mixed and then opened, carded and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are mixed with one or more fibers such as polytetrafluoroethylene, aromatic polyamide, polyphenylene sulfide, polyaromatic oxadiazole to form a base cloth support layer, which is then pre-needled and needle-punched to form a three-layer space needle-punched filter material. The overall gram weight is preferably 500g / m 2 ~900g / m 2 If the weight of the filter material is too low, the strength of the filter material will be insufficient; if the weight of the filter material is too high, although the performance will be improved, the cost will increase. The weight is more preferably 600g / m 2 ~800g / m 2 .

[0028] During the production process of the fire-resistant needle-punched filter material with high flame retardancy of the present invention, polyphenylene sulfide fiber can also be added to the dust-facing surface. Since polyphenylene sulfide fiber is a thermoplastic fiber, it will melt in the flame, form a film after leaving the fire, and adhere to the surface of the filter material. It can better ensure the integrity of the filter material after being burned by the flame when combined with modified polyacrylonitrile fiber. In addition, polyphenylene sulfide fiber has a heat-insulating effect. After forming a film, it can isolate most of the heat so that the material no longer continues to burn. Therefore, polyphenylene sulfide fiber can be selected as a preferred addition, and the addition ratio is preferably 20wt%~40wt%. If the addition ratio is too small, the complete film-forming effect cannot be achieved, and the thermal insulation is insufficient. If the addition ratio is too large, droplets will be generated and the fire-resistant performance cannot be guaranteed. The average fiber linear density is preferably 0.8~3.0dtex. If the fiber linear density is too fine, the cost will increase and combing will become difficult. If the strong fiber linear density is too coarse, the micropores formed between the fibers will also become larger, and the filtration accuracy is difficult to guarantee, and it is difficult to cope with 5mg / m 3 emission requirements.

[0029] The fire-resistant needle-punched filter material with high flame retardancy of the present invention preferably has an average linear density of 1.0-3.0 dtex for modified polyacrylonitrile fibers and an average linear density of 2.5-7.0 dtex for polytetrafluoroethylene fibers. If the linear density of the fibers is too fine, the cost will increase and combing will become difficult. If the linear density of the strong fibers is too coarse, the micropores formed between the fibers will also become larger, making it difficult to ensure the filtration accuracy and to cope with 5mg / m 3 emission requirements.

[0030] The fire-resistant needle-punched filter material of the present invention, which has high flame retardancy, is tested using the vertical combustion method according to GB / T 5455-2014 "Determination of vertical direction damage length, smoldering and afterflaming time of textiles". The afterflaming time is preferably ≤1s, the damage length is ≤5mm, and the combustion characteristics do not produce droplets. Furthermore, the surface flame heating test is conducted on the material, and the fire-resistant shrinkage rate is ≤1%. Since the fire-resistant needle-punched filter material with high flame retardancy needs to be used in working conditions with sparks or high-temperature dust accumulation, if the afterflaming time is too long and the damage length is large, the filter material will fail and dust will penetrate. If droplets are produced during combustion, the melted material will fall into the dust collection working condition, causing dust pollution. If the fire-resistant shrinkage rate is too high, the surface will shrink significantly during combustion, and there will be obvious wrinkles on the surface, which will cause dust to accumulate in the wrinkles, making it difficult to clean and collect dust, and also increasing the risk of spontaneous combustion.

[0031] The fire-resistant needle-punched filter material with high flame retardancy of the present invention can be surface-treated with an aqueous solution of an anionic or nonionic binder mixed with a silane coupling agent to improve its loose surface structure. According to GB / T 21196.2-2007, "Textiles - Determination of the Abrasion Resistance of Fabrics by the Martindale Method - Part 2: Determination of Specimen Breakage," using wool woven cloth as an abrasive, the abrasion resistance is ≥ 100,000 revolutions. After surface treatment, the abrasion resistance is increased by more than 10 times compared to untreated materials, making them more resistant to on-site dust erosion.

[0032] The fire-resistant needle-punched filter material with high flame retardancy of the present invention is composed of an adhesive component that is an ester of acrylic acid and its homologues, and a silane coupling agent that can be one of vinyltriethoxysilane, vinyltrimethoxysilane, or a mixture of the two. The surface treatment agent ratio is preferably 50wt%~80wt% of adhesive: 1wt%~5wt% of silane coupling agent: water: 15wt%~49wt%. The main function of the adhesive is to bond the fibers together and improve the inter-fiber porosity. If the adhesive ratio is less than 50%, the bonding effect is poor and the wear resistance cannot reach more than 100,000 revolutions. If the ratio is too large, the viscosity is too high and it cannot be evenly and effectively attached to the surface of the filter material during production, resulting in production difficulties. A certain proportion of silane coupling agent can also be added to react chemically with the groups in the acrylic adhesive to increase the bonding strength and form a silicon oxide layer, so that the acrylic adhesive has better weather resistance and chemical resistance, thereby increasing its service life on site. If the silane coupling agent ratio is less than 1%, it will not fully react with the adhesive, resulting in poor improvement. If the silane coupling agent ratio is greater than 5%, the excess silane coupling agent will accumulate on the surface after hydrolysis, forming an isolated area, affecting the coupling agent already bonded to the surface and preventing it from coupling with the adhesive, thereby reducing the performance of the material. A more preferred ratio of surface treatment agent is 65wt%-75wt%: 1wt%-3wt%: 22wt%-34wt%.

[0033] The fire-resistant needle-punched filter material with high flame retardancy of the present invention preferably has a dynamic filtration efficiency of ≥99.995%, can handle dust particles with a diameter of ≥3 microns and an outlet concentration of ≤5 mg / m 3 The following ultra-low dust emissions: If the filtration efficiency is too low, dust can easily penetrate and cannot meet the ultra-low emission requirements; if the filtration efficiency is too high, the filter material is too compact and air cannot pass through, resulting in a high initial pressure loss during use, which is not conducive to actual on-site use.

[0034] The fire-resistant needle-punched filter material of the present invention, which has high flame retardancy, preferably has a folding endurance of 200,000 or more, as tested according to the GB / T457-2008 "Paper and board - Determination of folding endurance" standard. If the folding endurance is too low, repeated on-site cleaning may cause creases on the filter material's surface, leading to dust accumulation and shortening its service life.

[0035] The fire-resistant needle-punched filter material with high flame retardancy of the present invention can operate continuously at a temperature of ≤220°C for a long time, and the thermal shrinkage in the warp and weft directions is preferably less than 1%. Since the filter material is used in a high-temperature environment, if the thermal shrinkage rate is too high, it will shrink significantly again under the influence of the high-temperature environment. The shrunken filter material is prone to deformation or locking of the frame, thereby affecting the dust cleaning effect of the filter material.

[0036] The test methods for the various properties of the fire-resistant, high flame retardant needle-punched filter material of the present invention are as follows:

[0037] Determination of molecular ring ratio

[0038] Use mass spectrometry NMR analysis to analyze the chemical structure of fiber molecules. Specific operation method:

[0039] 1) Ionization: Sample molecules are ionized into charged ions in the ion source.

[0040] 2) Mass Analysis: Ions undergo velocity dispersion under the influence of electric and magnetic fields. A mass analyzer is used to obtain a mass spectrum and determine the mass of the ions.

[0041] 3) NMR analysis: The obtained ions are subjected to NMR analysis, and the position and intensity of the nuclear magnetic resonance signal are recorded to obtain environmental information about the atomic nuclei within the molecule.

[0042]

Determination of fiber weight ratio

[0043] Before blending, use an electronic scale to weigh the fiber weight, and then mix them according to the required proportions.

[0044]

Measurement of gram weight of filter material

[0045] The gram weight of the filter material is determined in accordance with GB / T 24218.1-2009 Determination of mass per unit area.

[0046]

Fiber linear density determination

[0047] The fiber linear density was determined in accordance with GB / T14335-2008 Test method for linear density of chemical staple fibers.

[0048]

Determination of afterburning time and damage length

[0049] The afterflame time and damage length were measured in accordance with GB / T 5455-2014 Textiles Burning Performance - Determination of Damage Length, Smoldering and Afterflame Time in Vertical Direction.

[0050]

Fire resistance shrinkage test

[0051] Cut a 100mm x 100mm (measured with a steel ruler) sample of the filter material, mark its center, and place it on a metal stand. Use a standard alcohol burner, ignite it, and heat it with the outer flame focused on the center for 10 seconds.

[0052] Extinguish the alcohol lamp, remove the material block, and measure the side length of the filter material again, which is L1mm in length and L2mm in width.

[0053] Fire resistance shrinkage = MAX ( , ).

[0054]

Abrasion resistance test

[0055] The abrasion resistance test was carried out in accordance with GB / T 21196.2-2007 Textiles - Determination of the abrasion resistance of fabrics by the Martindale method - Part 2. The filter material was worn until it leaked through the base fabric, and the number of revolutions was recorded.

[0056]

Surface treatment agent ratio determination

[0057] Use an electronic scale to weigh each ingredient and then mix them according to the required proportions.

[0058]

Dynamic filtration efficiency and outlet concentration measurement

[0059] According to VDI3926 Standard Test Method for Evaluating Cleanable Filter Media, the size of the test sample is 150mm in diameter. The dust concentration is 5.0±0.5g / m 3 , the filtration wind speed is 2m / min (air volume 1.85m 3 The test sequence is 30 cycles in the initial stage, 5,000 cycles for stabilization, and 30 cycles in the final stage. Dynamic filtration efficiency and outlet concentration can be calculated after testing.

[0060]

Folding endurance test

[0061] In accordance with the provisions of GB / T 457, the filter material is tested under a tension of 14.72N, with a full swing of 175±10 times per minute and an angle of 135°±2° from the vertical.

[0062]

Determination of thermal shrinkage in warp and weft directions

[0063] In accordance with the test requirements of Appendix C of "T / CAEPI21-2019 Technical Requirements for Filter Materials for Bag Dust Collection", the test was carried out in an oven at a temperature of 220°C for 24 hours.

[0064] Example 1: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 3:7, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0065] Example 2: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0066] Example 3: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 8:2, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0067] Example 4: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 50% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0068] Example 5: Modified polyacrylonitrile fiber with an average linear density of 2.2dtex and a carbon-nitrogen molecular ring ratio of 80% is mixed with polytetrafluoroethylene fiber with an average linear density of 3.5dtex in a weight ratio of 6:4, and then the surface structure of the needle-punched filter material is formed through opening, carding, and laying. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 68%:2%:30%) to obtain a final weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0069] Example 6: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 1.0 dtex and polytetrafluoroethylene fiber with an average linear density of 3.5 dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0070] Example 7: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 3.0 dtex and polytetrafluoroethylene fiber with an average linear density of 3.5 dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0071] Example 8: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 2.5dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0072] Example 9: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 7.0dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0073] Example 10: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex, polytetrafluoroethylene fiber with an average linear density of 3.5dtex and polyphenylene sulfide fiber with an average linear density of 2.2dtex are mixed in a weight ratio of 3:5:2, and then opened, carded and laid to form the surface structure of the needle-punched filter material. The back layer fibers are mixed with the surface layer, and then opened, carded and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent and water in a ratio of 68%:2%:30%) to finally obtain a material with a gram weight of 750g / m 2This example demonstrates that the addition of 20% polyphenylene sulfide fiber significantly improves weft strength. When measuring the afterburning time and damage length, surface observation reveals a significant film-forming effect, which better ensures the integrity of the filter material after flame ignition. The physical properties of the fire-resistant, highly flame-retardant needle-punched filter material of this invention are shown in Table 1.

[0074] Example 11: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex, polytetrafluoroethylene fiber with an average linear density of 3.5dtex and polyphenylene sulfide fiber with an average linear density of 2.2dtex are mixed in a weight ratio of 3:3:4, and then opened, carded and laid to form the surface structure of the needle-punched filter material. The back layer fibers are mixed with the surface layer, and then opened, carded and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent and water in a ratio of 68%:2%:30%) to finally obtain a material with a gram weight of 750g / m 2 This example demonstrates that the addition of 40% polyphenylene sulfide fiber further improves the weft strength compared to Example 10. During the afterflame time and damage length measurement, it was observed that droplets were generated. Therefore, the flame retardancy is not as good as that of Example 10, but it is still usable. The physical properties of the fire-resistant, highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0075] Example 12: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are mixed with the surface layer, and then opened, carded, and laid to form the back layer structure. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive and coupling agent and water in a ratio of 68%:2%:30%) to finally obtain a weight of 500g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0076] Example 13: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive and coupling agent and water in a ratio of 68%:2%:30%) to finally obtain a material with a gram weight of 900g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0077] Example 14: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex is mixed with polytetrafluoroethylene fiber with an average linear density of 3.5dtex in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fiber is fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material without surface treatment, and finally a weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0078] Example 15: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive, coupling agent, and water in a ratio of 50%:2%:50%) to finally obtain a material with a gram weight of 750g / m 2 The physical properties of the fire-resistant and highly flame-retardant needle-punched filter material of the present invention are shown in Table 1.

[0079] Comparative Example 1: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 40% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive and coupling agent to water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The filter material, the physical properties of the filter material are shown in Table 2.

[0080] Comparative Example 2: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 90% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 6:4, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are fully mixed with the surface layer and then opened, carded, and laid to form the back layer structure of the needle-punched filter material. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive and coupling agent to water in a ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The filter material, the physical properties of the filter material are shown in Table 2.

[0081] Comparative Example 3: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 2:8, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are mixed with the surface layer, and then opened, carded, and laid to form the back layer structure. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive and coupling agent and water ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The filter material, the physical properties of the filter material are shown in Table 2.

[0082] Comparative Example 4: Modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 65% and an average linear density of 2.2dtex and polytetrafluoroethylene fiber with an average linear density of 3.5dtex are mixed in a weight ratio of 9:1, and then opened, carded, and laid to form the surface structure of the needle-punched filter material. The back layer fibers are mixed with the surface layer, and then opened, carded, and laid to form the back layer structure. The surface structure and the back layer structure are pre-needled and needle-punched with a 100g polytetrafluoroethylene cloth support layer to form a three-layer space needle-punched filter material, and then impregnated with a surface treatment agent (adhesive and coupling agent and water ratio of 68%:2%:30%) to finally obtain a weight of 750g / m 2 The filter material, the physical properties of the filter material are shown in Table 2.

[0083] Table 1 Physical properties of needle-punched filter materials of Example 1 to Example 15

[0084]

[0085]

[0086] Table 2 Physical properties of filter materials of Comparative Examples 1 to 4

[0087] According to the above Table 1: (1) It can be seen from Examples 1, 2, and 3 that, under the same conditions, the weight ratio of modified polyacrylonitrile fiber and polytetrafluoroethylene fiber in Example 2 is within the preferred range, and the resulting filter material has better flame retardant properties than that of Example 1, higher dynamic filtration efficiency, and lower outlet concentration. Compared with Example 3, it has better strength, and has better wear resistance and folding resistance.

[0088] It can be seen from Examples 2, 4, and 5 that, under the same conditions, the proportion of carbon-nitrogen molecular rings in the modified polyacrylonitrile fiber in Example 2, which accounts for 65% of the molecular weight, is within the preferred range. The resulting filter material has better flame retardant properties than that of Example 4, and better strength than that of Example 5, and has better wear resistance and folding resistance.

[0089] (3) It can be seen from Examples 2, 6, and 7 that, under the same conditions, the average linear density of the modified polyacrylonitrile fiber in Example 2 is 2.2 dtex, which is better than the thinner 1.0 dtex in Example 6, and has better spinnability and lower production cost in the actual production process. Compared with the coarser 3.0 dtex in Example 7, it has higher dynamic filtration efficiency and lower outlet concentration.

[0090] (4) It can be seen from Examples 2, 8, and 9 that, under the same conditions, the average linear density of the polytetrafluoroethylene fiber in Example 2 is 3.5 dtex, which is better than the relatively fine 2.5 dtex in Example 8, and has better spinnability and lower production cost in the actual production process. Compared with the relatively coarse 7.0 dtex in Example 9, it has higher dynamic filtration efficiency and lower outlet concentration.

[0091] (5) It can be seen from Examples 2, 10, and 11 that under the same conditions, Examples 10 and 11 added polyphenylene sulfide fibers, which reduced the flame retardant properties and heat shrinkage rate compared to Example 2, but improved the strength, and had higher dynamic filtration efficiency and lower outlet concentration.

[0092] (6) From Examples 2, 12, and 13, it can be seen that under the same conditions, the weight of Example 2 is 750 g / m 2 In a more preferred range, the obtained filter material is 500 g / m2 heavier than that of Example 12. 2， It has better strength, better wear resistance, higher dynamic filtration efficiency and lower outlet concentration. Compared with the 900g / m 2， The cost will also be lower.

[0093] (7) It can be seen from Examples 2, 14, and 15 that, under the same conditions, the ratio of the surface treatment agent used in Example 2 is within a more preferred range, and the resulting filter material has significantly improved wear resistance compared to Example 14 without the addition of the surface treatment agent and Example 15 with a smaller amount of adhesive.

[0094] According to Table 2 above: It can be seen from Example 2 and Comparative Example 1 that under the same conditions, the modified polyacrylonitrile fiber with a carbon-nitrogen molecular ring ratio of 40% used in Comparative Example 1 has poor flame retardant properties and fire-resistant shrinkage rate.

[0095] It can be seen from Example 2 and Comparative Example 2 that, under the same conditions, the modified polyacrylonitrile fiber in which the carbon-nitrogen molecular ring accounts for 90% used in Comparative Example 2 produces a filter material with poor strength, insufficient wear resistance and insufficient folding resistance.

[0096] It can be seen from Example 2 and Comparative Example 3 that, under the same conditions, the weight proportion of the modified polyacrylonitrile fiber used in Comparative Example 3 is insufficient, and the fire-resistant shrinkage rate and outlet concentration are high.

[0097] It can be seen from Example 2 and Comparative Example 4 that, under the same conditions, the modified polyacrylonitrile fiber used in Comparative Example 4 has a high weight proportion, and the resulting filter material has poor strength, and insufficient wear resistance and folding resistance.

[0098] The above embodiments of the present invention are merely examples to clearly illustrate the present invention, but are not intended to limit the scope of protection of the present invention. All equivalent technical solutions also fall within the scope of the present invention. The scope of patent protection of the present invention should be defined by the claims.

Claims

1. A fire-resistant needle-punched filter material with high flame retardancy, characterized by: The filter material is composed of at least two types of fibers on the dust-facing surface, one of which is modified polyacrylonitrile fiber, and the modified polyacrylonitrile fiber molecular chain segment contains a molecular ring composed of carbon and nitrogen, and the proportion of the molecular ring in the molecular weight is 50% to 80%, and the weight of the modified polyacrylonitrile fiber in the dust-facing surface of the filter material is 30wt% to 80wt%; the other fiber is polytetrafluoroethylene fiber, and the weight of the polytetrafluoroethylene fiber in the dust-facing surface of the filter material is 20wt% to 70wt%.

2. The fire-resistant needle-punched filter material with high flame retardancy according to claim 1, characterized in that: The filter material is a three-layer space structure, including a dust-facing surface layer, a base fabric support layer, and a back layer. The base fabric support layer is made of one or more mixed fibers of polytetrafluoroethylene, aromatic polyamide, polyphenylene sulfide, and polyaromatic oxadiazole. The back layer is made of one or more mixed fibers of polytetrafluoroethylene, aromatic polyamide, polyphenylene sulfide, polyaromatic oxadiazole, and modified polyacrylonitrile. The overall gram weight of the filter material is 500g / m 2 ~900g / m 2 .

3. The fire-resistant needle-punched filter material with high flame retardancy according to claim 1, characterized in that: The filter material has polyphenylene sulfide fibers added to the dust-facing side, with an average linear density of 0.8-3.0 dtex and a weight proportion of 20 wt%-40 wt%.

4. The fire-resistant needle-punched filter material with high flame retardancy according to claim 1, characterized in that: The average linear density of the modified polyacrylonitrile fiber is 1.0-3.0 dtex, and the average linear density of the polytetrafluoroethylene fiber is 2.5-7.0 dtex.

5. The fire-resistant needle-punched filter material with high flame retardancy according to claim 1, characterized in that: The filter material is tested using a vertical combustion method, and its after-flame time is ≤1s, its damaged length is ≤5mm, and its combustion characteristics do not produce molten droplets; and its surface flame heating test satisfies the fire-resistant shrinkage rate of ≤1%.

6. The fire-resistant needle-punched filter material with high flame retardancy according to claim 1, characterized in that: The surface of the filter material is treated with an aqueous solution of an anionic or nonionic adhesive mixed with a silane coupling agent as a treating agent to improve its loose surface structure. Wool woven cloth is used as an abrasive for testing, and the wear resistance is ≥100,000 revolutions.

7. The fire-resistant needle-punched filter material with high flame retardancy according to claim 6, characterized in that: The adhesive comprises esters of acrylic acid and its homologues, the silane coupling agent comprises one or a mixture of vinyltriethoxysilane and vinyltrimethoxysilane, and the adhesive, coupling agent and water are mixed in a weight ratio of adhesive: coupling agent: water of 50wt%~80wt%:1wt%~5wt%:15wt%~49wt%.

8. The fire-resistant needle-punched filter material with high flame retardancy according to claim 1, characterized in that: The dynamic filtration efficiency of the filter material is ≥99.995%, and it can handle dust particles with a diameter of ≥3 microns and an outlet concentration of ≤5 mg / m 3 Ultra-low dust emissions below.

9. The fire-resistant needle-punched filter material with high flame retardancy according to claim 1, characterized in that: The folding resistance of the filter material is ≥200,000 times.

10. The fire-resistant needle-punched filter material with high flame retardancy according to claim 1, characterized in that: The filter material can be operated continuously at a temperature of ≤220° C. for a long period of time, and the thermal shrinkage in the longitudinal and latitudinal directions is both less than 1%.

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