A composite high-temperature resistant filter felt and its preparation method

Abstract

The present invention discloses a composite high-temperature resistant filter felt and a preparation method thereof, relating to the technical field of filter materials. The technical key points include the following structural layers: Base fabric layer: woven by blending basalt fibers and polyimide fibers, with a gram weight of 400 g / m² - 600 g / m²; Composite material layer: composed of ceramic fibers, silicon carbide nanowires and polytetrafluoroethylene modified fibers, which are compounded on both sides of the base fabric layer through a gradient needling process, and the total gram weight of the composite material layer is 200 g / m² - 350 g / m²; Surface functional layer: composed of a blend coating of polytetrafluoroethylene emulsion and silicon carbide nanoparticles. The technical effect is that through the composite system of ceramic fibers and SiC nanowires, the prepared filter felt has a high retention rate of strength at 300 °C, and is also significantly higher than that without using gradient needling composite, reflecting that through the cooperation of gradient needling composite, the high-temperature resistance performance is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of filter materials, and particularly to a composite high-temperature resistant filter felt and a preparation method thereof. Background Art

[0002] Filter felt, as an efficient filter material, plays a crucial role in the solid-liquid separation and gas purification processes in various industries. It is usually made of high-quality fiber materials carefully processed, and these fibers are intertwined with each other to form an extremely fine and uniform pore structure. This unique structure endows the filter felt with excellent filtering performance, enabling it to accurately intercept and separate various fine particles, from impurities in industrial wastewater to dust in the air, with a filtering accuracy up to the micron level.

[0003] In terms of materials, filter felt covers various types. For example, chemical fiber filter felt, with its good chemical corrosion resistance, can adapt to the filtering work in various harsh chemical environments such as strong acids and alkalis; while glass fiber filter felt has excellent high-temperature resistance and can operate stably in high-temperature working conditions to ensure that the filtering effect is not affected by temperature fluctuations. In terms of performance, it not only has high filtering efficiency but also has a strong dirt-holding capacity, and can work continuously for a long time without frequent replacement, greatly reducing the maintenance cost and the risk of production interruption.

[0004] In modern industrial production, industries such as iron and steel smelting, chemical industry, and electric power often generate high-temperature dusty gases. The temperature of these gases is often higher than 300 °C, and there may be a radiation environment at the same time. Under such an environment, traditional filter felt has insufficient high-temperature resistance, and fiber aging and fracture are likely to occur, resulting in a sharp decline in filtering efficiency. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a composite high-temperature resistant filter felt and a preparation method thereof, and this process can significantly improve the high-temperature resistance and radiation resistance of the filter felt.

[0006] To achieve the above object, the present invention provides the following technical solutions: A composite high-temperature resistant filter felt and a preparation method thereof, including the following structural layers:

[0007] Base cloth layer: It is woven by blending basalt fiber and polyimide (P84) fiber, and the gram weight is 400 g / m² - 600 g / m²;

[0008] Composite material layer: It is composed of ceramic fiber, silicon carbide nanowire and polytetrafluoroethylene (PTFE) modified fiber and is compounded on both sides of the base cloth layer through a gradient needling process. The total gram weight of the composite material layer is 200 g / m² - 350 g / m²;

[0009] Surface functional layer: It is composed of a blend coating of polytetrafluoroethylene emulsion and silicon carbide nanoparticles, with a thickness of 5μm - 15μm and a surface pore size of 0.5μm - 2μm.

[0010] Preferably, the weight ratio of basalt fiber to polyimide fiber in the base fabric layer is 3:1 - 5:1, and the fiber fineness is 1.5D - 3D (D is denier).

[0011] Preferably, the components of the composite material layer by weight include: 40 - 60 parts of ceramic fiber, 10 - 20 parts of silicon carbide nanowire, 20 - 30 parts of polytetrafluoroethylene modified fiber, 1 - 3 parts of silane coupling agent, and 0.5 - 1 part of dispersant.

[0012] Preferably, the polytetrafluoroethylene modified fiber is the product of PPS fiber impregnated with polytetrafluoroethylene emulsion, and the impregnation liquid carrying rate is 50% - 120%.

[0013] Preferably, the particle size of the silicon carbide nanoparticles in the surface functional layer is 50 - 200nm, and the solid content of the polytetrafluoroethylene emulsion is 55 - 65wt%.

[0014] Preferably, it includes the following steps:

[0015] S1. Base fabric preparation: Blend and weave basalt fiber and polyimide fiber into a base fabric, and conduct heat setting treatment at a temperature of 200℃ - 250℃ for 5min - 10min;

[0016] S2. Pretreatment of composite material layer: After mixing ceramic fiber, silicon carbide nanowire and polytetrafluoroethylene modified fiber, conduct plasma surface activation treatment at a power of 200W - 400W for 3 - 5min;

[0017] S3. Gradient needle punching composite: Lay the pretreated composite material layer on both sides of the base fabric, and conduct pre-needle punching and main needle punching in sequence. The pre-needle punching density is 300 times / cm² - 500 times / cm², and the main needle punching density is 800 times / cm² - 1000 times / cm²;

[0018] S4. Coating of surface functional layer: Mix polytetrafluoroethylene emulsion and silicon carbide nanoparticles and spray them on the surface of the composite material layer. After drying at 100℃ - 120℃, conduct high-temperature sintering at 300℃ - 350℃ for 2min - 5min to obtain the filter felt.

[0019] Preferably, the gas for the plasma treatment is a mixed gas of argon and oxygen, and the volume ratio is 4:1.

[0020] Preferably, it further includes an impregnation strengthening treatment: impregnating the composite filter felt in a dispersion containing silica sol, with the silica sol concentration being 5% - 10%, the impregnation time being 10 min - 20 min, and then curing at a high temperature of 250°C - 280°C for 3 min - 5 min.

[0021] Compared with the prior art, the present invention provides a composite high-temperature resistant filter felt and its preparation method, having the following beneficial effects: Through the composite system of ceramic fibers and SiC nanowires, the strength retention rate of the prepared filter felt at 300°C is relatively high, and it is also significantly higher than that without gradient needle punching composite, reflecting that through the cooperation of gradient needle punching composite, the high-temperature resistance performance is further improved; the surface layer has a significant improvement in the plasma treatment process and the anti-radiation characteristics with SiC nanoparticles, and the plasma treatment process and SiC nanoparticles have a synergistic promoting effect on the radiation resistance performance. Description of the Drawings

[0022] Figure 1 It is a column chart of the strength retention rate of a composite high-temperature resistant filter felt at 300°C;

[0023] Figure 2 It is a broken line chart of the elongation at break loss of a composite high-temperature resistant filter felt after γ irradiation. Detailed Embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Basalt fiber: Derived from natural ore, it is made by high-temperature melting and drawing. It has high strength and high modulus, can withstand large external forces without being easily broken. Its outstanding high-temperature resistance makes its structure stable in high-temperature environments without softening or deformation. It has good chemical stability and can effectively resist the erosion of various chemical substances. In the preparation of the filter felt base fabric, it is blended with P84 fiber to build a solid strength foundation for the base fabric and ensure the structural integrity of the base fabric under high-temperature working conditions.

[0026] P84 fiber: Belonging to high-performance synthetic fibers, it has excellent high-temperature resistance characteristics and can be used in high-temperature environments for a long time. It has strong chemical tolerance and can resist the corrosion of common chemical substances. At the same time, it has flame retardant properties, reducing the fire risk. When blended with basalt fiber, it can effectively improve the flexibility of the base fabric, overcome the deficiency of the large rigidity of basalt fiber, make the base fabric have high strength while being easier to process and form, and have higher comfort in actual use.

[0027] Ceramic fiber: Renowned for its extremely excellent high-temperature resistance, it can withstand temperatures exceeding 1000°C. It has good heat insulation performance and can effectively prevent heat transfer. Chemically stable, it is not prone to chemical reactions in complex chemical environments. In the composite material layer of the filter felt, it is the core material to enhance the overall high-temperature resistance. It works synergistically with other materials to ensure that the filter felt can still maintain a relatively high strength after long-term use at 300°C.

[0028] SiC nanowires: Their size is at the nanoscale and the diameter is extremely fine. They have a high specific surface area, which can greatly increase the contact area with other materials and promote the interaction between them. They possess high strength and excellent thermal stability, and their performance is stable at high temperatures. In the filter felt, when compounded with ceramic fibers, they can optimize the mechanical properties and heat conduction properties of the composite material layer. In the surface functional layer, they participate in constructing a micro-nano hydrophobic structure, which contributes significantly to enhancing the self-cleaning function.

[0029] PTFE modified fiber (impregnated with PPS substrate): PTFE is polytetrafluoroethylene, which has extremely excellent chemical stability and hardly reacts with any chemical substances. It has extremely strong corrosion resistance and can resist harsh chemical environments such as strong acids and alkalis. Its low friction coefficient makes its surface smooth and not easy to adhere to impurities. After being impregnated with PPS as the substrate, the comprehensive performance of the fiber is further improved, and it has an important impact on the structural stability and overall performance in the composite material layer.

[0030] PTFE emulsion: Formed by dispersing PTFE in water, it has good fluidity and film-forming properties, and can be evenly coated on the surface of the filter felt. After forming a film, it has waterproof and oil-proof properties and can effectively prevent liquids and oil stains from adhering. In the coating of the surface functional layer, when paired with SiC particles of different particle sizes, they jointly construct a micro-nano hydrophobic structure, significantly reducing the adhesion of dust on the surface of the filter felt and reducing the difficulty of dust cleaning.

[0031] Silica sol: It is a colloidal solution of silicic acid and has good permeability. In the impregnation and strengthening treatment, it can penetrate into the internal pores of the filter felt and fill the tiny voids. After curing, it can enhance the bonding force between the layers of materials, significantly improve the overall strength of the filter felt, and at the same time enhance its corrosion resistance and extend the service life of the filter felt.

[0032] Example 1, a composite high-temperature resistant filter felt and its preparation method, including the following steps:

[0033] S1. Base fabric preparation: Basalt fiber and P84 fiber are blended in a ratio of 3:1 (fineness 1.5D), woven into a 400 g / m² base fabric, and subjected to heat setting treatment at 200°C for 10 minutes;

[0034] S2. Pretreatment of composite material layer: It contains 40 parts of ceramic fibers (diameter 5 μm), 10 parts of SiC nanowires (diameter 30 nm), and 20 parts of PTFE-modified fibers (liquid impregnation rate of PPS substrate is 50%), and is treated with 200W argon-oxygen mixed gas plasma for 3 minutes;

[0035] S3. Gradient needle punching composite: The pre-needling density is 300 times / cm², and the main needling density is 800 times / cm² to form a composite layer with a total weight of 200 g / m²;

[0036] S4. Coating of surface functional layer: A mixture of 55% solid content PTFE emulsion and 50 nm SiC particles (10:1) is sprayed, pre-dried at 120 °C and then sintered at 300 °C for 2 minutes to form a 5 μm functional layer;

[0037] S5. Impregnation reinforcement treatment: Impregnated with 5% silica sol for 15 minutes and then cured at 280 °C for 3 minutes.

[0038] Example 2 includes the following steps:

[0039] S1. Base fabric preparation: Basalt / P84 is made into a 500 g / m² base fabric according to a ratio of 4:1 (2D fineness) and shaped at 225 °C for 8 minutes;

[0040] S2. Pretreatment of composite material layer: 50 parts of ceramic fibers + 15 parts of SiC nanowires + 25 parts of PTFE fibers (liquid impregnation rate 85%), treated with 300W plasma for 4 minutes;

[0041] S3. Gradient needle punching composite: 400 times / cm² pre-needling + 900 times / cm² main needling to form a 275 g / m² composite layer;

[0042] S4. Coating of surface functional layer: 60% PTFE emulsion and 100 nm SiC (12.5:1) are sprayed, pre-dried at 110 °C + sintered at 325 °C for 3 minutes to obtain a 10 μm functional layer;

[0043] S5. Impregnation reinforcement treatment: Impregnated with 7.5% silica sol for 15 minutes + cured at 265 °C for 4 minutes.

[0044] Example 3 includes the following steps:

[0045] S1. Base fabric preparation: Basalt / P84 with a ratio of 5:1 (3D fineness) is made into a 600 g / m² base fabric and shaped at 250 °C for 5 minutes;

[0046] S2. Pretreatment of composite material layer: 60 parts of ceramic fibers + 20 parts of SiC nanowires + 30 parts of PTFE fibers (liquid impregnation rate 120%), treated with 400W plasma for 5 minutes;

[0047] S3. Gradient needle punching composite: Pre-punching at 500 times / cm² + main punching at 1000 times / cm² to form a 350 g / m² composite layer;

[0048] S4. Surface functional layer coating: Spraying 65% PTFE emulsion and 200 nm SiC (15:1), pre-drying at 120 °C + sintering at 350 °C for 5 min to obtain a 15 μm functional layer;

[0049] S5. Impregnation strengthening treatment: Impregnating with 10% silica sol for 20 min + curing at 250 °C for 5 min.

[0050] In Comparative Example 1, the base fabric layer uses pure basalt fiber, and other steps are the same as in Example 1.

[0051] In Comparative Example 2, the plasma treatment process is omitted, and other steps are the same as in Example 1.

[0052] In Comparative Example 3, there are no SiC nanoparticles in the surface layer, and other steps are the same as in Example 1.

[0053] In Comparative Example 4, the gradient needle punching is changed to uniform needle punching with a needle punching density of 800 times / cm², and other steps are the same as in Example 1.

[0054] In Comparative Example 5, the silica sol impregnation treatment is not carried out, and other steps are the same as in Example 1.

[0055] In Comparative Example 6, a commercially available needle punched filter felt (model HTF-3000) is purchased, and the specific components are shown in Table 1.

[0056] Table 1 is the relevant component table of Comparative Example 6

[0057]

[0058] The nine groups of filter felts in Example 1, 2, 3 and Comparative Example 1, 2, 3, 4, 5, 6 are grouped and numbered in sequence as FH-GLZ1001, FH-GLZ1002, FH-GLZ1003, FH-GLZ1004, FH-GLZ1005, FH-GLZ1006, FH-GLZ1007, FH-GLZ1008, FH-GLZ1009, and the grouped filter felts are tested for high temperature resistance (strength retention rate at 300 °C) and radiation resistance (elongation at break loss after γ irradiation), and the specific test results are shown in Table 2.

[0059] Table 2 is the test results of high temperature resistance and radiation resistance of Examples and Comparative Examples

[0060]

[0061] Table 3 Test results of dust stripping rate, dust cleaning resistance and corrosion grade performance of Examples and Comparative Examples

[0062]

[0063] As can be seen from Table 2, in terms of high temperature resistance, the strength retention rate of the ceramic fiber and SiC nanowire composite system (Example 2) reaches 93.5% at 300 °C, which is significantly higher than that of Comparative Example 4 (84.9%) without the gradient structure; in terms of anti-radiation characteristics, after 1000 h of γ irradiation, the elongation at break losses of the Example group are 4.8%, 3.2%, and 5.1% in sequence, while the radiation resistance of Comparative Example 2 without plasma treatment and the radiation resistance of the group without SiC nanoparticles both decrease to varying degrees, indicating that the plasma treatment process and SiC nanoparticles have a synergistic promoting effect on radiation resistance; in terms of the self-cleaning effect, the dust stripping rate of the Example group containing SiC nanoparticles is better, and the dust cleaning resistance is significantly reduced compared with that of Comparative Example 3, verifying the synergistic effect of the micro-nano structure; in terms of process innovation, the acid corrosion resistance is significantly improved by silica sol impregnation.

[0064] High temperature resistance evaluation standard: The high temperature resistance is evaluated by the strength retention rate at 300 °C and is divided into three grades. The excellent grade requires a strength retention rate ≥ 90%, meeting the long-term use requirements under high temperature conditions; the qualified grade has a strength retention rate between 80% - 89%, and it needs to be replaced regularly or used at a lower level; the unqualified grade has a strength retention rate < 80% and cannot pass the high temperature durability test;

[0065] Test method and data basis: The test method is based on "GB / T3923.1 - 2013 Textiles - Tensile Properties - Part 1: Determination of Strip Specimens", and after treating the specimen in a 300 °C constant temperature oven for 500 h, the breaking strength retention rate is measured.

[0066] Anti-radiation performance evaluation standard: The anti-radiation performance is evaluated by the elongation at break loss rate after γ irradiation and is divided into three grades. The excellent grade requires an elongation at break loss rate ≤ 5%, having excellent anti-irradiation embrittlement ability; the qualified grade has an elongation at break loss rate between 6% - 10%, and the irradiation dose needs to be restricted during use; the unqualified grade has an elongation at break loss rate > 10%, and the material will embrittle and fail after irradiation;

[0067] Test method and data basis: The test method refers to "ASTM D1876 - 08 Standard Test Method for Evaluating the Performance of Plastics Exposed to a Radiation Environment", irradiating with a 60Co γ-ray source for 1000 h (dose rate 1 kGy / h), and measuring the change in elongation at break.

[0068] Self-cleaning performance evaluation criteria: The self-cleaning performance is evaluated based on the dust stripping rate and the dust cleaning resistance, and is divided into three grades. The excellent grade requires a dust stripping rate ≥ 98% and a dust cleaning resistance ≤ 2.5 kPa, indicating that the micro-nano hydrophobic structure can significantly reduce dust accumulation; the qualified grade has a dust stripping rate between 90% - 97% and a dust cleaning resistance between 2.6 - 3.5 kPa, and the dust cleaning frequency needs to be increased during use; the unqualified grade has a dust stripping rate < 90% and a dust cleaning resistance > 3.5 kPa, and there will be a situation where dust caking causes filter material blockage.

[0069] Test methods and data basis: In terms of test methods, the dust stripping rate is calculated according to "ISO11057 Test for Dust Cleaning Performance of Air Filter Media". After simulating a dust load (5 g / m²), pulse dust cleaning is carried out, and the proportion of the residual dust mass is calculated; the dust cleaning resistance is measured by a differential pressure gauge to determine the difference in the filter media resistance before and after dust cleaning.

[0070] Corrosion resistance evaluation criteria: During the test, no peeling and no color change indicate excellent interface bonding and sealing, then it is grade excellent (A); if there is local slight peeling during the test and auxiliary anti-corrosion treatment is required, then it is grade qualified (B); if obvious cracking and powdering occur and it cannot pass the industrial corrosion environment test, then it is grade unqualified (C).

[0071] Test methods and data basis: The corrosion resistance is based on the extended method of "ISO9227 Salt Spray Test". After soaking in a 10% HCl solution for 72 h, the surface state is observed.

[0072] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements, or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all covered by the protection scope of the present invention.

Claims

1. A preparation method of a composite high-temperature resistant filter felt, characterized in that, It includes the following steps: S1. Base fabric preparation: Blend and weave basalt fibers and polyimide fibers into a base fabric, and conduct heat setting treatment at a treatment temperature of 200°C - 250°C for 5 min - 10 min; S2. Pretreatment of composite material layer: After mixing ceramic fibers, silicon carbide nanowires and polytetrafluoroethylene modified fibers, conduct plasma surface activation treatment with a treatment power of 200 W - 400 W for 3 - 5 min; S3. Gradient needle punching composite: Lay the pretreated composite material layer on both sides of the base fabric, and conduct pre-needle punching and main needle punching in sequence. The pre-needle punching density is 300 times / cm² - 500 times / cm², and the main needle punching density is 800 times / cm² - 1000 times / cm²; The gas for the plasma treatment is a mixed gas of argon and oxygen with a volume ratio of 4:1; S4. Coating of surface functional layer: Mix polytetrafluoroethylene emulsion and silicon carbide nanoparticles and spray them on the surface of the composite material layer. After drying at 100°C - 120°C, conduct high-temperature sintering at 300°C - 350°C for 2 min - 5 min to obtain a filter felt.

2. The preparation method according to claim 1, wherein, The weight ratio of the polytetrafluoroethylene emulsion to the silicon carbide nanoparticles is 10:1 - 15:1, and the spraying pressure is 0.3 MPa - 0.5 MPa.

3. The preparation method according to claim 1, wherein During the needle punching forming, it also includes impregnation strengthening treatment: Immerse the composite filter felt in a dispersion liquid containing silica sol with a silica sol concentration of 5% - 10% for 10 min - 20 min, and then conduct high-temperature curing at 250°C - 280°C for 3 min - 5 min.

4. A composite high-temperature resistant filter felt, characterized in that, Made by the method described in claim 1, it includes the following structural layers: Base fabric layer: Blended and woven from basalt fibers and polyimide fibers, with a gram weight of 400 g / m² - 600 g / m²; Composite material layer: Composed of ceramic fibers, silicon carbide nanowires and polytetrafluoroethylene modified fibers, which are compounded on both sides of the base fabric layer through a gradient needle punching process. The total gram weight of the composite material layer is 200 g / m² - 350 g / m²; Surface functional layer: Composed of a blend coating of polytetrafluoroethylene emulsion and silicon carbide nanoparticles, with a thickness of 5 μm - 15 μm and a surface pore diameter of 0.5 μm - 2 μm.

5. The composite high-temperature resistant filter felt according to claim 4, wherein, In the base fabric layer, the weight ratio of basalt fibers to polyimide fibers is 3:1 - 5:1, and the fiber fineness is 1.5 D - 3 D.

6. The composite high-temperature resistant filter felt according to claim 4, wherein, The components of the composite material layer include, by weight: 40 - 60 parts of ceramic fibers, 10 - 20 parts of silicon carbide nanowires, 20 - 30 parts of polytetrafluoroethylene modified fibers, 1 - 3 parts of silane coupling agent, and 0.5 - 1 part of dispersant.

7. The composite high-temperature resistant filter felt according to claim 4, characterized in that, The polytetrafluoroethylene modified fiber is a product obtained by impregnating PPS fiber with polytetrafluoroethylene emulsion, and the impregnation liquid holding rate is 50% - 120%.

8. The composite high-temperature resistant filter felt according to claim 4, wherein The particle size of the silicon carbide nanoparticles in the surface functional layer is 50 - 200 nm, and the solid content of the polytetrafluoroethylene emulsion is 55 - 65 wt%.

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