Super-hydrophobic aramid fiber spunlace honeycomb porous filter material and preparation process thereof

Abstract

The invention discloses a super-hydrophobic aramid spunlaced honeycomb porous filter material and a preparation process thereof, and belongs to the technical field of porous filter materials, the super-hydrophobic aramid spunlaced honeycomb porous filter material is prepared from aramid fibers, super-hydrophobic nanoparticles are grafted on the surfaces of the aramid fibers, the filter material has a honeycomb porous structure, the side length of hexagonal cells of the honeycomb porous structure is 0.1-1mm, and the side length of the hexagonal cells of the honeycomb porous structure is 0.1-1mm. The preparation method comprises the following steps: cleaning aramid fibers, soaking the aramid fibers in a sodium hydroxide solution with the mass fraction of 5-15%, treating at the temperature of 50-70 DEG C for 30-60 minutes, then washing the aramid fibers with deionized water until the aramid fibers are neutral, and drying the aramid fibers, wherein the pore wall thickness is 0.01-0.1 mm, the porosity of the filter material is 60-90%, the water contact angle is greater than 150 degrees, and the rolling angle is less than 10 degrees; the pretreated aramid fibers are immersed in a solution containing 1-5% by mass of super-hydrophobic nanoparticles and 0.5-2% by mass of a coupling agent, stirring is conducted for 2-4 h at the room temperature, then washing and drying are conducted, the grafted aramid fibers are carded into a fiber net with the surface density being 50-200 g / m, and the fiber net is fed into a spunlace machine.

Description

Technical Field

[0001] The invention relates to a porous filter material, in particular to a super-hydrophobic aramid spunlace honeycomb porous filter material and a preparation process thereof, belonging to the technical field of porous filter materials. Background Art

[0002] Traditional aramid filter materials have the following technical bottlenecks in practical applications:

[0003] Polar groups on the surface of aramid fibers (such as amide groups) easily form hydrogen bonds with water molecules. This causes moisture to be adsorbed and accumulated on the fiber surface and in the pores when the filter media is handling humid gases or liquids. This can cause clogging of the filter media, increase air flow resistance, and significantly reduce filtration efficiency. For example, when using ordinary aramid spunlace filter media in an environment with humidity greater than 60%, filtration resistance can increase by 30%-50%, shortening its service life by over 50%.

[0004] Existing aramid filter media often utilize a random porous structure, making it difficult to achieve a balance between filtration accuracy, air and water permeability, and specific surface area. Filter media produced through traditional hydroentanglement typically have a porosity of less than 60% and an uneven pore size distribution. This results in insufficient filtration efficiency (<90%) for submicron particles (such as PM2.5 and oil mist particles), coupled with low air flow (<80 L / (m²・s)), making it unable to meet high-flow filtration requirements.

[0005] Existing methods for improving the hydrophobicity of aramid (such as fluorocarbon coating and plasma treatment) suffer from complex processes, high costs, and poor durability. For example, while fluorocarbon coating can increase the contact angle to approximately 120°, the coating easily wears off and clogs the filter media pores, resulting in a more than 20% decrease in air permeability. Therefore, a super-hydrophobic aramid spunlace honeycomb porous filter media and its preparation process were designed to address these issues. Summary of the Invention

[0006] The main purpose of the present invention is to provide a super-hydrophobic aramid spunlace honeycomb porous filter material and a preparation process thereof.

[0007] The purpose of the present invention can be achieved by adopting the following technical solutions:

[0008] A super-hydrophobic aramid spunlace honeycomb porous filter material is made from aramid fibers, with super-hydrophobic nanoparticles grafted onto the surface of the aramid fibers. The filter material has a honeycomb porous structure with a hexagonal cell side length of 0.1-1 mm and a cell wall thickness of 0.01-0.1 mm. The filter material has a porosity of 60-90%, a water contact angle greater than 150°, and a rolling angle less than 10°.

[0009] Preferably, the super-hydrophobic nanoparticles are silicon dioxide nanoparticles, carbon fluoride nanoparticles, or a mixture of the two, and the particle size of the nanoparticles is 10-100 nm.

[0010] A process for preparing a super-hydrophobic aramid spunlace honeycomb porous filter material comprises the following steps:

[0011] Aramid fiber pretreatment: After cleaning, immerse the aramid fiber in a 5-15% sodium hydroxide solution at 50-70°C for 30-60 minutes, then rinse with deionized water until neutral and dry;

[0012] Superhydrophobic nanoparticle grafting: The pretreated aramid fiber was immersed in a solution containing 1-5% by mass of superhydrophobic nanoparticles and 0.5-2% by mass of a coupling agent, stirred at room temperature for 2-4 hours, then rinsed and dried;

[0013] Fiber web formation: The grafted aramid fibers are combed into a fiber web with a surface density of 50-200g / m²;

[0014] Spunlace forming: The fiber web is fed into the spunlace machine and a multi-stage spunlace process is adopted. The first stage spunlace pressure is 10-20 bar, the second stage spunlace pressure is 20-30 bar, and the third stage spunlace pressure is 30-40 bar. At the same time, a honeycomb spunlace mold is used to form the filter material blank.

[0015] Hot pressing: hot press the filter material blank at 180-220℃ and 5-10MPa pressure for 3-5min.

[0016] Preferably, the coupling agent is a silane coupling agent or a titanate coupling agent.

[0017] Preferably, the hexagonal pore structure on the honeycomb spunlace mold matches the honeycomb porous structure of the filter material.

[0018] Preferably, in the aramid fiber pretreatment step, the drying temperature is 80-100°C.

[0019] Preferably, in the super-hydrophobic nanoparticle grafting step, the drying temperature is 80-100°C.

[0020] Preferably, the multi-stage spunlace process is a three-stage spunlace process.

[0021] Preferably, in the hot pressing step, the hot pressing temperature is 200° C., the pressure is 8 MPa, and the time is 4 minutes.

[0022] Preferably, the super-hydrophobic nanoparticles are a mixture of silicon dioxide nanoparticles and carbon fluoride nanoparticles, with a mass ratio of 1:1.

[0023] Beneficial technical effects of the present invention:

[0024] The present invention provides a super-hydrophobic aramid spunlace honeycomb porous filter material and its preparation process. By grafting silica or carbon fluoride nanoparticles (particle size 10-100 nm) onto the surface of aramid fibers, a micro-nano composite roughened structure is formed on the filter material surface. Combined with a low-surface-energy material, this material achieves a water contact angle exceeding 150° (158° in Example 2) and a rolling angle less than 10° (6° in Example 5), achieving super-hydrophobicity. In comparison, honeycomb filter material without the nanoparticles grafted onto it (Comparative Example 2) exhibits a water contact angle of only 110°, while conventional aramid filter material (Comparative Example 1) exhibits a contact angle of only 90°. This filter material effectively prevents water adsorption and clogging in humid environments.

[0025] Experimental data show that after continuous use for 100 hours under conditions of 80% humidity, the air permeability attenuation rate of the filter materials of Examples 1-7 is less than 5%, while the air permeability attenuation rate of the ordinary filter material of Comparative Example 1 reaches 40%, proving that the filter material of the present invention has a longer service life in a humid environment.

[0026] The filter media's porosity can reach 60-90% (90% in Example 4), a 40-80% improvement over conventional aramid filter media (50%). The honeycomb-shaped hexagonal cells have a side length of 0.1-1mm, a wall thickness of 0.01-0.1mm, and a uniform pore size distribution. This structure increases the filter media's specific surface area to 15-20m² / g (compared to <10m² / g for conventional filter media), significantly increasing adsorption sites and achieving a filtration efficiency of over 99% for particles 0.25-0.35μm (0.25μm in Example 3 and 0.35μm in Example 4), representing a 40% improvement in accuracy over Comparative Example 1 (0.5μm).

[0027] Thanks to the optimized fluid dynamics of the honeycomb structure, the filter media achieves an air permeability of 100-150 L / (m²・s) (150 L / (m²・s) in Example 4), a 25-87.5% increase compared to conventional filter media (80 L / (m²・s)), while simultaneously reducing filtration resistance by over 30%. For example, at a porosity of 80%, Example 2 achieves an air permeability of 130 L / (m²・s) and a filtration efficiency of 0.3 μm, achieving the synergistic optimization of "high flow, low resistance, and high precision."

[0028] The use of a multi-stage hydroentanglement process (10-40 bar) and a honeycomb hydroentanglement mold can precisely control the cell size and wall thickness, with a cell side length error of less than ±5% (for example, the cell side length in Example 1 is 0.5 mm, but the actual measured value is 0.48-0.52 mm), meeting the customized pore size requirements for different filtration scenarios.

[0029] The fiber surface etching (NaOH solution treatment) and coupling agent (silane or titanate) grafting process increased the bonding strength between the nanoparticles and the aramid fiber to 20-30N / cm (untreated fiber <5N / cm). After 50 water washes, the water contact angle decay rate was <3% (the contact angle of comparative example 2 decayed by 20% after water washing), proving that the modified layer has excellent durability.

[0030] The process route is compatible with existing spunlace production lines. It only requires the addition of honeycomb molds and nanoparticle grafting equipment. The equipment modification cost is low, and the amount of nanoparticles used is only 1-5%, which is more than 40% lower than the cost of traditional fluorocarbon coating processes and is suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an exploded view of the overall three-dimensional structure of a device according to a preferred embodiment of a super-hydrophobic aramid spunlace honeycomb porous filter material and its preparation process of the present invention. DETAILED DESCRIPTION

[0032] In order to make the technical solution of the present invention more clear and specific to those skilled in the art, the present invention is further described in detail below with reference to embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0033] The super-hydrophobic aramid spunlace honeycomb porous filter material of the present invention is prepared from aramid fibers as the main raw material, super-hydrophobic nanoparticles are grafted onto the surface of the aramid fibers, and the filter material has a honeycomb porous structure. The hexagonal cells of the honeycomb porous structure have a side length of 0.1-1 mm, a cell wall thickness of 0.01-0.1 mm, a porosity of 60-90%, a water contact angle greater than 150°, and a rolling angle less than 10°.

[0034] The super-hydrophobic nanoparticles are either silica nanoparticles or carbon fluoride nanoparticles, or a mixture thereof, with a particle size of 10-100 nm. By grafting the super-hydrophobic nanoparticles onto the surface of aramid fibers, the fibers are endowed with super-hydrophobic properties, making it difficult for water to penetrate the fiber surface when the filter media comes into contact with water, thereby preventing filter media clogging due to water adsorption.

[0035] The honeycomb-shaped porous structure can provide a larger specific surface area, which is beneficial to improving the adsorption and filtration capabilities of the filter material. At the same time, the hexagonal pore structure has good mechanical stability, ensuring that the filter material is not easily deformed during use.

[0036] Preparation process of super-hydrophobic aramid spunlace honeycomb porous filter material;

[0037] The aramid fibers are cleaned to remove surface impurities and oil. The cleaned fibers are then immersed in a 5-15% sodium hydroxide solution at 50-70°C for 30-60 minutes to etch the fiber surface, increasing its roughness and improving the binding force between the fiber and the superhydrophobic nanoparticles. The etched fibers are then rinsed with deionized water until neutral and dried at 80-100°C for later use.

[0038] The pretreated aramid fiber is immersed in a solution containing 1-5% superhydrophobic nanoparticles by mass and 0.5-2% by mass of a coupling agent, such as a silane or titanate coupling agent. The solution is stirred at room temperature for 2-4 hours to allow the nanoparticles to fully graft onto the aramid fiber surface. The grafted aramid fiber is then rinsed with deionized water to remove ungrafted nanoparticles and coupling agent, and then dried at 80-100°C.

[0039] The aramid fibers grafted with super-hydrophobic nanoparticles are combed through a carding machine to form a uniform fiber web. During the carding process, the surface density of the fiber web is controlled to be 50-200g / m².

[0040] The fiber web is fed into a hydroentanglement machine for hydroentanglement. A multi-stage hydroentanglement process is employed, with the first stage at a pressure of 10-20 bar, the second at 20-30 bar, and the third at 30-40 bar. During the hydroentanglement process, a specially designed honeycomb-shaped spunlace die is used. The die's hexagonal pore structure matches the porous honeycomb structure of the target filter media. High-pressure water jets through the die's pores, entangle the fibers, and form a filter media blank with a porous honeycomb structure.

[0041] The hydroentangled filter media is then fed into a hot press for hot pressing at a temperature of 180-220°C, a pressure of 5-10 MPa, and a time of 3-5 minutes. This hot pressing further enhances the strength and stability of the filter media, while also making its honeycomb porous structure more regular.

[0042] Example 1;

[0043] After washing the aramid fiber with deionized water, the fiber was immersed in a sodium hydroxide solution with a mass fraction of 8%, treated at 60°C for 45 minutes, then rinsed with deionized water until neutral, and dried at 90°C for later use.

[0044] The pretreated aramid fiber was immersed in a solution containing 2% by mass of silica nanoparticles and 1% by mass of a silane coupling agent, stirred at room temperature for 3 h, then rinsed with deionized water and dried at 90°C.

[0045] The grafted aramid fibers were combed by a carding machine to control the fiber web density to 100 g / m².

[0046] The fiber web is fed into the hydroentanglement machine and a three-stage hydroentanglement process is adopted. The first-stage hydroentanglement pressure is 15 bar, the second-stage hydroentanglement pressure is 25 bar, and the third-stage hydroentanglement pressure is 35 bar. A honeycomb hydroentanglement mold is used for hydroentanglement to form a filter material blank.

[0047] The filter media blank was placed in a hot press and hot-pressed at 200°C and 8 MPa for 4 minutes to produce a super-hydrophobic aramid spunlace honeycomb porous filter media. Testing revealed that the honeycomb porous structure had hexagonal cells with a side length of 0.5 mm, a cell wall thickness of 0.05 mm, a porosity of 75%, a water contact angle of 155°, and a rolling angle of 8°, demonstrating excellent filtration performance.

[0048] Example 2;

[0049] After cleaning, the aramid fibers were immersed in a 12% sodium hydroxide solution at 65°C for 50 minutes, rinsed until neutral, and then dried at 95°C. Superhydrophobic nanoparticle grafting: The pretreated aramid fibers were immersed in a solution containing 3% by mass of carbon fluoride nanoparticles and 1.5% by mass of a titanate coupling agent. The solution was stirred at room temperature for 3.5 hours, then rinsed and dried.

[0050] The grafted aramid fibers are combed to achieve a fiber web density of 150g / m².

[0051] The spunlace process parameters were the same as in Example 1, and a honeycomb spunlace mold was used for spunlace molding;

[0052] Hot pressing at 210°C and 9 MPa for 4.5 minutes yielded a filter material with hexagonal cells of 0.6 mm side length, 0.06 mm cell wall thickness, 80% porosity, 158° water contact angle, and 7° rolling angle, demonstrating excellent filtration performance.

[0053] Example 3;

[0054] After cleaning, the aramid fiber was immersed in a 5% by mass sodium hydroxide solution at 50°C for 60 min, rinsed with deionized water until neutral, and dried at 80°C.

[0055] Superhydrophobic nanoparticle grafting: The pretreated fibers were immersed in a solution containing 1% silica nanoparticles and 0.5% silane coupling agent, stirred at room temperature for 4 h, rinsed, and dried at 80 °C.

[0056] Comb the grafted fibers and control the fiber web density to 50g / m².

[0057] It adopts three-stage hydroentanglement, the first stage is 10bar, the second stage is 20bar, and the third stage is 30bar, and the hydroentanglement is formed using a honeycomb mold.

[0058] After hot pressing at 180°C and 5 MPa for 5 minutes, the filter material obtained had a pore side length of 0.1 mm, a wall thickness of 0.01 mm, a porosity of 60%, a water contact angle of 152°, and a rolling angle of 9°.

[0059] Example 4;

[0060] The cleaned aramid fiber was immersed in a 15% by mass sodium hydroxide solution, treated at 70°C for 30 min, and then washed and dried.

[0061] The fiber was immersed in a solution containing 5% carbon fluoride nanoparticles and 2% titanate coupling agent, stirred at room temperature for 2 h, and then rinsed and dried.

[0062] The fibers are carded to a web density of 200g / m².

[0063] The water spunlace pressure is 20 bar, 30 bar, and 40 bar respectively, and the honeycomb mold is used for molding.

[0064] Hot pressing at 220℃ and 10MPa for 3min, the filter material has a pore side length of 1mm, a wall thickness of 0.1mm, a porosity of 90%, a water contact angle of 156°, and a rolling angle of 7°.

[0065] Example 5;

[0066] After cleaning, the aramid fiber was treated in a 10% by mass sodium hydroxide solution at 65°C for 40 min, and then rinsed and dried.

[0067] The fiber was immersed in a solution containing 3% silica and carbon fluoride mixed nanoparticles (mass ratio 1:1) and 1% silane coupling agent, stirred for 3 hours, rinsed and dried.

[0068] Carded into a 120g / m² fiber web.

[0069] The three-level water spunlace pressure is 12bar, 22bar and 32bar respectively, and the mold is formed.

[0070] Hot pressing at 200℃ and 7MPa for 4min, the filter material has a pore side length of 0.4mm, a wall thickness of 0.04mm, a porosity of 72%, a water contact angle of 157°, and a rolling angle of 6°.

[0071] Example 6;

[0072] After cleaning the aramid fiber, place it in an 8% by mass sodium hydroxide solution at 60°C for 45 minutes, then wash and dry it.

[0073] The fibers were immersed in a solution containing 2% silica nanoparticles and 1% titanate coupling agent, stirred for 3.5 h, and then rinsed and dried.

[0074] Carded fiber web density 130g / m².

[0075] The hydroentanglement pressure is 15bar, 25bar, 35bar, and the mold is formed.

[0076] Hot pressing at 210℃ and 8MPa for 4min, the filter material has a pore side length of 0.6mm, a wall thickness of 0.06mm, a porosity of 78%, a water contact angle of 154°, and a rolling angle of 8°.

[0077] Example 7;

[0078] After cleaning, the aramid fiber was treated in a 12% by mass sodium hydroxide solution at 65°C for 50 min, and then rinsed and dried.

[0079] The fiber was immersed in a solution containing 3% carbon fluoride nanoparticles and 1.5% silane coupling agent, stirred for 3 h, and then rinsed and dried.

[0080] Carded fiber web density 180g / m².

[0081] The hydroentanglement pressure is 20bar, 30bar, 40bar, and the mold is formed.

[0082] Hot pressing at 220℃ and 9MPa for 3.5min, the filter material has a pore side length of 0.8mm, a wall thickness of 0.08mm, a porosity of 85%, a water contact angle of 153°, and a rolling angle of 7°.

[0083] Comparative Example 1 (ordinary aramid spunlace filter material);

[0084] Aramid fiber pretreatment: After cleaning, the aramid fiber was treated in 8% by mass sodium hydroxide solution at 60°C for 45 minutes, then washed and dried.

[0085] Fiber web forming: carding fibers to form a 100g / m² fiber web.

[0086] Hydroentanglement: Three-stage hydroentanglement is used, with pressures of 15 bar, 25 bar, and 35 bar respectively. No honeycomb mold is used, and ordinary hydroentanglement is used.

[0087] Hot pressing: hot pressing at 200℃ and 8MPa for 4min. The obtained filter material has no honeycomb structure, a porosity of 50%, a water contact angle of 90°, and a rolling angle of 45°.

[0088] Comparative Example 2 (honeycomb porous aramid filter material without grafting superhydrophobic nanoparticles);

[0089] Aramid fiber pretreatment: After cleaning, the aramid fiber was treated in 8% by mass sodium hydroxide solution at 60°C for 45 minutes, then washed and dried.

[0090] Fiber web formation: Carded fibers form a 100g / m² fiber web.

[0091] Hydroentanglement: Three-stage hydroentanglement is used with pressures of 15 bar, 25 bar, and 35 bar respectively, and honeycomb molds are used for molding.

[0092] Hot pressing: 200℃, 8MPa hot pressing for 4min. Although the filter material has a honeycomb structure, the water contact angle is 110° and the rolling angle is 30°.

[0093] Experimental results comparison table:

[0094] Example Hole side length (mm) Cell wall thickness (mm) Porosity (%) Water contact angle (°) Roll angle (°) Air permeability (L / (m²・s)) Filtration efficiency (μm, 99%) Example 1 0.5 0.05 75 155 8 120 0.3 Example 2 0.6 0.06 80 158 7 130 0.3 Example 3 0.1 0.01 60 152 9 100 0.25 Example 4 1 0.1 90 156 7 150 0.35 Example 5 0.4 0.04 72 157 6 115 0.28 Example 6 0.6 0.06 78 154 8 125 0.3 Example 7 0.8 0.08 85 153 7 140 0.32 Comparative Example 1 - - 50 90 45 80 0.5 Comparative Example 2 0.5 0.05 75 110 30 105 0.4

[0095] The above is only a further embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and concepts of the present invention within the scope disclosed by the present invention, which fall within the scope of protection of the present invention.

Claims

1. A super-hydrophobic aramid spunlace honeycomb porous filter material, characterized by: It is made of aramid fiber, the surface of which is grafted with super-hydrophobic nanoparticles. The filter material has a honeycomb porous structure with a hexagonal cell side length of 0.1-1mm and a cell wall thickness of 0.01-0.1mm. The porosity of the filter material is 60-90%, the water contact angle is greater than 150°, and the rolling angle is less than 10°.

2. The super-hydrophobic aramid spunlace honeycomb porous filter material according to claim 1, characterized in that: The super-hydrophobic nanoparticles are silicon dioxide nanoparticles, carbon fluoride nanoparticles, or a mixture of the two. The particle size of the nanoparticles is 10-100 nm.

3. A process for preparing a super-hydrophobic aramid spunlace honeycomb porous filter material, based on the super-hydrophobic aramid spunlace honeycomb porous filter material according to claims 1-2, characterized in that: The steps include: After cleaning, the aramid fiber is immersed in a sodium hydroxide solution with a mass fraction of 5-15%, treated at 50-70°C for 30-60 minutes, then rinsed with deionized water until neutral and dried; The pretreated aramid fiber was immersed in a solution containing 1-5% by mass of superhydrophobic nanoparticles and 0.5-2% by mass of a coupling agent, stirred at room temperature for 2-4 hours, and then rinsed and dried; Combing the grafted aramid fibers into a fiber web with an area density of 50-200 g / m²; The fiber web is fed into the hydroentanglement machine, which adopts a multi-stage hydroentanglement process. The first stage hydroentanglement pressure is 10-20 bar, the second stage hydroentanglement pressure is 20-30 bar, and the third stage hydroentanglement pressure is 30-40 bar. At the same time, a honeycomb hydroentanglement mold is used to form the filter material blank; The filter material blank is hot pressed at 180-220°C and 5-10 MPa pressure for 3-5 minutes.

4. The process for preparing a super-hydrophobic aramid spunlace honeycomb porous filter material according to claim 3, characterized in that: The coupling agent is a silane coupling agent or a titanate coupling agent.

5. The process for preparing a super-hydrophobic aramid spunlace honeycomb porous filter material according to claim 3, characterized in that: The hexagonal pore structure on the honeycomb spunlace mold matches the honeycomb porous structure of the filter material.

6. The process for preparing a super-hydrophobic aramid spunlace honeycomb porous filter material according to claim 3, characterized in that: In the aramid fiber pretreatment step, the drying temperature is 80-100°C.

7. The process for preparing a super-hydrophobic aramid spunlace honeycomb porous filter material according to claim 3, characterized in that: In the super-hydrophobic nanoparticle grafting step, the drying temperature is 80-100°C.

8. The process for preparing a super-hydrophobic aramid spunlace honeycomb porous filter material according to claim 3, characterized in that: The multi-stage spunlace process is a three-stage spunlace process.

9. The process for preparing a super-hydrophobic aramid spunlace honeycomb porous filter material according to claim 3, characterized in that: In the hot pressing shaping step, the hot pressing temperature is 200° C., the pressure is 8 MPa, and the time is 4 minutes.

10. The process for preparing a super-hydrophobic aramid spunlace honeycomb porous filter material according to claim 3, characterized in that: The super-hydrophobic nanoparticles are a mixture of silicon dioxide nanoparticles and carbon fluoride nanoparticles, with a mass ratio of 1:1.

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