Paper-based filtering material with hydrophobic and oleophobic properties as well as preparation method and application of paper-based filtering material

Abstract

The invention discloses a paper-based filtering material with hydrophobic and oleophobic properties as well as a preparation method and application of the paper-based filtering material. On the basis of a plasma enhanced chemical vapor deposition (PECVD) technology, the microporous structure of the filter material is kept, and meanwhile, a film layer with low surface energy is deposited on the surface of a base material fiber, so that the hydrophobic and oleophobic effects are achieved. The base material of the paper-based filter material is a cellulosic fiber, synthetic fiber, inorganic fiber and composite fiber filter material. A precursor used for deposition is fluorine-containing acrylate, and a uniform and compact fluorine-containing micro-nano film layer is formed on the surface and hole walls of the filter material through single-step PECVD (Plasma Enhanced Chemical Vapor Deposition). The hydrophobic grade of the inner layer and the outer layer of the paper-based filtering material reaches 12 grade, the oleophobic grade reaches 8 grade, the water contact angle is larger than or equal to 150 degrees, the oil contact angle is larger than or equal to 150 degrees, and the surface and the interior can be endowed with uniform and consistent hydrophobic and oleophobic performance. The method has the advantages of simple steps and mild reaction conditions, and can be used for air filtration, liquid filtration, oil-gas separation, oil-water separation and preparation of protective materials.

Description

A paper-based filter material with hydrophobic and oleophobic properties, its preparation method and application Technical Field

[0001] This invention belongs to the field of paper-based filter material preparation technology, specifically relating to a paper-based filter material with hydrophobic and oleophobic properties, its preparation method, and its application. Background Technology

[0002] With increasing demands for industrial production, environmental governance, and high-purity media control, the performance requirements for filter materials are constantly rising. While traditional paper-based filter materials possess some filtration capacity, they are prone to pore blockage and adsorption saturation under complex conditions such as high humidity, oily aerosols, or water vapor, leading to shortened service life and reduced filtration efficiency. Dual hydrophobic properties (possessing both hydrophobic and oleophobic properties) play a crucial role in paper-based filter materials, effectively reducing the wetting of pore structures by liquid contaminants, improving the filter material's antifouling properties, environmental adaptability, and service life, thereby maintaining high filtration efficiency.

[0003] Currently, commonly used methods for hydrophobic modification of filter materials include impregnation, spraying, graft polymerization, and sol-gel methods. For example, patent CN107020071B uses graft polymerization to modify the surface of a composite carbon aerogel doped with carbon nanotubes to achieve superhydrophobic properties. Patent CN110270161A uses a spraying method to apply a fluorocarbon modifier to the surface of polyvinyl alcohol formal foam and then forms a hydrophobic and oleophobic layer through vacuum heat treatment. Patent CN119327181A obtains a dual-functional hydrophobic filter material by spraying a superhydrophobic modification solution and an antibacterial modification solution onto a nonwoven fabric. Patents CN101601940A and CN108686628A use an impregnation modification method, immersing the material in a hydrophobic / oleophobic agent solution and then drying it to obtain a dual-hydrophobic surface. The sol-gel method typically involves constructing a rough layer of nanoparticles on the surface of the filter material, followed by modification with fluorosilane compounds, thereby forming an organic-inorganic hybrid hydrophobic coating.

[0004] However, existing dual-hydrophobic modification methods generally suffer from the following problems: low modification efficiency and cumbersome process steps; easy damage to the filter material fiber structure or pore blockage, thereby reducing filtration performance; insufficient coating adhesion and durability, resulting in a short service life; poor modification uniformity; and limited applicability to different substrates. Plasma-enhanced chemical vapor deposition (PECVD) is a technique that uses plasma to excite precursor gases to deposit functional films on the surface of a substrate. This method can achieve high-quality, dense, and uniform film deposition at relatively low temperatures, making it particularly suitable for the surface functionalization of fibrous materials. Therefore, applying PECVD technology to the dual-hydrophobic modification of paper-based filter materials can impart excellent hydrophobic and oleophobic properties while maintaining the original pore structure of the filter material. Summary of the Invention

[0005] To address the problems of filter material damage, membrane unevenness, and performance degradation in the existing dual-repellent modification process, the present invention aims to provide a dual-repellent surface modification process suitable for paper-based filter materials. By utilizing plasma-enhanced chemical vapor deposition (PECVD) technology and combining the synergistic effect of ultra-low pressure diffusion and low-power free radical reaction, the process achieves uniform dual-repellent properties of the inner and outer layers of the filter material while maintaining the microporous structure and air flux of the paper-based filter material.

[0006] The present invention adopts the following technical solution: a method for preparing a paper-based filter material with hydrophobic and oleophobic properties, comprising the following steps: (1) preparing paper-based filter material: wet papermaking of fiber raw material, pressing and dehydration, drying to constant weight, and sizing treatment to obtain a matrix paper-based filter material; (2) plasma pretreatment: placing the paper-based filter material obtained in step (1) in a low-temperature plasma reaction chamber, introducing gas for plasma treatment to remove impurities on the surface of the paper-based filter material and introduce active groups; (3) dual hydrophobic modification: using plasma-enhanced chemical vapor deposition for dual hydrophobic modification: placing the pretreated paper-based filter material in a vacuum reaction chamber, adding liquid fluorinated ester monomers in a storage tank, and after the monomers are heated and vaporized, entering the reaction chamber through a heat-insulated conveying pipe to excite the gaseous monomers with plasma, and depositing a uniform nanoscale hydrophobic and oleophobic thin film layer on the surface of the paper-based filter material in situ.

[0007] Preferably, in step (1), the fiber raw material is selected from at least one of glass fiber, aramid fiber, Tencel fiber, kapok fiber, nylon fiber, and PET fiber.

[0008] Preferably, in step (2), the plasma atmosphere is selected as oxygen or argon. The plasma treatment is performed at 100-500W for 1-10 minutes.

[0009] Preferably, in step (2), the paper-based filter material is laid flat in the reaction chamber to avoid overlapping or obstruction.

[0010] Preferably, in step (3), the fluorinated ester monomer is perfluorooctyl ethyl acrylate.

[0011] Preferably, in step (3), the monomer vaporization temperature is 160-190℃, and after vaporization, it is transported to the reaction chamber through a 170-200℃ insulated pipeline. The reaction chamber temperature is controlled to not exceed 80℃, the working vacuum degree is controlled at 1-10 Pa, the radio frequency power is controlled at 5-35 W, and the processing time is controlled at 10 s-15 min.

[0012] The paper-based filter material with hydrophobic and oleophobic properties obtained by the above preparation method has a hydrophobicity level of 12 and an oleophobicity level of 8 for both the inner and outer layers, with a water contact angle ≥150° and an oil contact angle ≥150°, which can impart uniform hydrophobic and oleophobic properties to the surface and interior.

[0013] The paper-based filter material with hydrophobic and oleophobic properties obtained by the above preparation method can be used to prepare air filtration, liquid filtration, oil-water separation, oil-gas separation and protective materials.

[0014] Compared with existing technologies, the advantages and beneficial effects of this invention are as follows: 1. The substrate of the paper-based filter material of this invention is cellulose fiber, synthetic fiber, inorganic fiber, and composite fiber filter material. The precursor used for deposition is fluorinated acrylate, and a uniform and dense fluorinated micro / nano film layer is formed on the surface and pore walls of the filter material through single-step PECVD. This addresses the characteristics of paper-based filter materials, such as low thermal stability and susceptibility to plasma damage.

[0015] 2. This invention performs free radical reaction deposition under low pressure (1–10 Pa) and power (5–35 W) conditions to maintain the integrity of the microporous structure of the filter material. In a very short processing time of 10 s, the hydrophobicity of the inner and outer layers reaches level 12 and the oleophobicity reaches level 8, with a water contact angle ≥150° and an oil contact angle ≥150°, which can impart uniform hydrophobic and oleophobic properties to the surface and interior.

[0016] 3. The method of the present invention is simple in steps and mild in reaction conditions, and can be used for air filtration, liquid filtration, oil-gas separation, oil-water separation and preparation of protective materials. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 is an infrared spectrum of the dual-hydrophobic modified paper-based filter material provided by the present invention.

[0019] Figure 2 shows the contact angle images of the PECVD dual-hydrophobic modified glass fiber filter media provided in Example 1; where a and b are the water contact angle image and oil contact angle image of the dual-hydrophobic glass fiber filter media, respectively, and c is the water contact angle image of the unmodified filter media.

[0020] Figure 3 is a scanning electron microscope (SEM) image of the PECVD-modified glass fiber filter material provided in Example 1; where a and b are SEM images of the glass fiber filter material before and after modification, respectively.

[0021] Figure 4 shows the oil-gas separation performance test diagram of the dual-hydrophobic modified glass fiber filter material provided in Example 1; where a and b are the oil-gas separation time-pressure drop curve and the oil-gas separation efficiency diagram, respectively.

[0022] Figure 5 shows the contact angle images of the PECVD dual-hydrophobic modified aramid filter material provided in Example 2; where a and b are the water contact angle and oil contact angle images of the dual-hydrophobic aramid filter material, respectively.

[0023] Figure 6 shows the contact angle images of the PECVD dual-hydrophobic modified glass fiber filter material provided in Example 3; where a and b are the water contact angle and oil contact angle images of the dual-hydrophobic glass fiber filter material, respectively.

[0024] Figure 7 shows the contact angle images of the PECVD dual-hydrophobic modified glass fiber filter material provided in Example 4; where a and b are the water contact angle images and oil contact angle images of the dual-hydrophobic glass fiber filter material, respectively. Figure 8 shows the contact angle images of the PECVD dual-hydrophobic modified glass fiber filter material provided in Comparative Example 1; where a and b are the water contact angle images and oil contact angle images of the dual-hydrophobic glass fiber filter material, respectively.

[0025] Figure 9 shows the contact angle of the glass fiber filter material obtained by the activation-impregnation method provided in Comparative Example 2.

[0026] Figure 10 shows the contact angle images of the PECVD-modified glass fiber filter media provided in Comparative Example 3; where a and b are the water contact angle and oil contact angle images of the modified glass fiber filter media, respectively. Detailed Implementation

[0027] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0028] Example 1: PECVD double-hydrophobic modification of glass fiber filter material. A preparation process of a double-hydrophobic glass fiber filter material includes the following steps: (1) Step 1: Preparation of glass fiber paper-based filter material. 20% chopped glass fiber, 15% 475-19 glass wool and 65% 475-29 glass wool are selected as fiber raw materials according to the ratio and mixed with deionized water at a mass ratio of 0.25:1000. Wet paper forming is adopted, and after pressing and dehydration, it is dried at 105°C to constant weight. Acrylic resin emulsion is used to sizing the obtained paper-based filter material, and the sizing amount is controlled at 5±0.5%. After drying at 105°C to constant weight, it is cured at 160°C to obtain the matrix paper-based filter material. The basis weight of the filter material is 80 g / m³. 2 The air permeability is 120 mm / s.

[0029] (2) Step Two: Plasma Pretreatment. The paper-based filter material obtained in Step One is placed in a low-temperature plasma reaction chamber. Argon is selected as the working gas, with a gas flow rate of 200 sccm. The material is treated for 10 min at a radio frequency power of 300 W to remove surface impurities. The pretreatment process is mild and can effectively improve the adhesion and uniformity of the subsequent deposition layer.

[0030] (3) Step 3: Dual-hydrophobic modification. Perfluorooctyl ethyl acrylate was used as the modifying agent to perform dual-hydrophobic modification on the paper-based filter material obtained in Step 2 using plasma-enhanced chemical vapor deposition (PECVD). During the modification process, the monomer was heated to 170°C and vaporized by a heating system, and then transported to the reaction chamber through a 185°C insulated pipeline. The reaction conditions were controlled at a vacuum of 10 Pa, a radio frequency plasma power of 15 W, and a processing time of 5 min.

[0031] Gas-phase perfluorooctyl ethyl acrylate dissociates under low-power radio frequency plasma excitation to generate active free radicals, which deposit on the surface of the filter material and diffuse into the internal pores, forming a uniform nanoscale hydrophobic and oleophobic fluorocarbon film on both the inner and outer layers of the filter material. After reaching the preset processing time, the monomer inlet and plasma power supply are sequentially turned off. After the system returns to normal pressure, the sample is removed without post-processing. The deposition rate of the dual-hydrophobic glass fiber filter material prepared in this embodiment is 2.93% according to weighing calculations.

[0032] Tests showed that the modified dual-hydrophobic glass fiber filter material provided in this embodiment has an air permeability of 118 mm / s, a hydrophobicity level of 12, and an oleophobicity level of 8. As shown in Figure 2, the water contact angle of the glass fiber filter material modified in Example 1 reaches 158° (as shown in Figure 2a) and the oil contact angle reaches 158° (as shown in Figure 2b), while the unmodified glass fiber filter material allows droplets to penetrate its surface instantly (as shown in Figure 2c).

[0033] Figure 1 shows a comparison of the infrared spectra of the dual-hydrophobic modified paper-based filter material provided by this invention. The carbonyl group (C=O) in the acrylate monomer structure is an important characteristic absorbing group. The modified filter material absorbs at 1750 cm⁻¹. -1 A distinct carbonyl stretching vibration peak appeared at [value missing], and its intensity was significantly enhanced compared to the unmodified sample. Furthermore, at 1199 cm⁻¹... -1 and 1146 cm -1 Absorption of stretching and bending vibration characteristics of C–F bonds can be observed at the locations. These changes indicate that the monomer structure is effectively excited and deposited on the fiber surface during PECVD, thereby forming a fluorinated modified layer with dual hydrophobic properties on the filter material.

[0034] Figure 3 is a scanning electron microscope (SEM) image of the dual-hydrophobic modified glass fiber filter material provided in this embodiment. Figure 3a shows the surface morphology of the glass fiber filter material before modification, and Figure 3b shows the surface morphology of the glass fiber filter material after PECVD modification. As can be observed in Figure 3a, after sizing, the fibers of the original glass fiber filter material are bonded together by the adhesive. In Figure 3b, a continuous and dense fluorocarbon film is uniformly covered on the surface of the modified filter material. This film adheres tightly to the substrate without localized particle aggregation or significant detachment, indicating that the PECVD process achieved uniform deposition of monomers, thus successfully modifying the surface of the glass fiber filter material.

[0035] Figure 4 shows the oil-gas separation performance test results of the dual-repellent modified glass fiber filter media provided in Example 1; where a and b represent the oil-gas separation time-pressure drop curve and the change in oil-gas separation efficiency, respectively. As can be seen from the figure, PECVD modification results in lower operating resistance of the filter media when entering the steady-state stage. The steady-state pressure drop of the unmodified filter media is approximately 7100 Pa, indicating significant obstruction of the airflow as it passes through the fiber network; while the steady-state pressure drop of the PECVD modified filter media is reduced to approximately 5500 Pa, a decrease of over 20%. Simultaneously, the steady-state separation efficiency of the unmodified filter media is 95.6%, while the modified steady-state efficiency increases to 99.4%. This achieves a synergistic optimization of low pressure drop and high efficiency.

[0036] Example 2: PECVD double-hydrophobic modification of aramid filter material. A preparation process of a double-hydrophobic aramid filter material includes the following steps: (1) Step 1: Preparation of glass fiber composite paper-based filter material. 100% fibrillated aramid fiber is selected as raw material and mixed with deionized water at a mass ratio of 0.25:1000. Wet paper forming is adopted, and after pressing and dehydration, it is dried at 105°C to constant weight. Acrylic resin emulsion is used to sizing the obtained paper-based filter material, and the sizing amount is controlled at 5±0.5%. After drying at 105°C to constant weight, it is cured at 160°C to obtain the matrix paper-based filter material. The basis weight of the filter material is 60 g / m³. 2The air permeability is 46 mm / s.

[0037] (2) Step Two: Plasma Pretreatment. The paper-based filter material obtained in Step One is placed in a low-temperature plasma reaction chamber. Oxygen is selected as the working gas, with a gas flow rate of 200 sccm. The material is treated for 5 min at a radio frequency power of 450 W to remove surface impurities and introduce hydroxyl active functional groups. The pretreatment process is mild and can effectively improve the adhesion and uniformity of the subsequent deposition layer.

[0038] (3) Step 3: Dual-hydrophobic modification. Perfluorooctyl ethyl acrylate was used as the modifying agent to perform dual-hydrophobic modification on the paper-based filter material obtained in Step 2 using plasma-enhanced chemical vapor deposition (PECVD). During the modification process, the monomer was heated to 175°C and vaporized by the heating system, and then transported to the reaction chamber through a 185°C insulated pipeline. The reaction conditions were controlled at a vacuum of 10 Pa, a radio frequency plasma power of 25 W, and a processing time of 5 min.

[0039] After deposition, the monomer inlet and plasma power supply were turned off sequentially. Once the system returned to normal pressure, the sample was removed without further post-processing. Weighing and calculation showed that the deposition rate of the dual-hydrophobic glass fiber filter material prepared in this embodiment was 3.01%.

[0040] Testing showed that the modified dual-hydrophobic fiberglass filter material provided in this embodiment has an air permeability of 44 mm / s, a hydrophobicity rating of 12, and an oleophobicity rating of 8. As shown in Figure 5, the dual-hydrophobic fiberglass filter material prepared in this embodiment has a water contact angle of 150° (as shown in Figure 5a) and an oil contact angle of 150° (as shown in Figure 5b).

[0041] Example 3: PECVD double-hydrophobic modification of glass fiber filter material. A preparation process of a double-hydrophobic glass fiber filter material includes the following steps: (1) Step 1: Preparation of glass fiber paper-based filter material. 20% chopped glass fiber, 15% 475-19 glass wool and 65% 475-29 glass wool are selected as fiber raw materials according to the ratio and mixed with deionized water at a mass ratio of 0.25:1000. Wet paper forming is adopted, and after pressing and dehydration, it is dried at 105°C to constant weight. Acrylic resin emulsion is used to sizing the obtained paper-based filter material, and the sizing amount is controlled at 5±0.5%. After drying at 105°C to constant weight, it is cured at 160°C to obtain the matrix paper-based filter material. The basis weight of the filter material is 80 g / m³. 2 The air permeability is 119 mm / s.

[0042] (2) Step Two: Plasma Pretreatment. The paper-based filter material obtained in Step One is placed in a low-temperature plasma reaction chamber. Argon is selected as the working gas, with a gas flow rate of 200 sccm. The treatment is carried out for 5 minutes at a radio frequency power of 450 W to remove surface impurities. The pretreatment process is mild and can effectively improve the adhesion and uniformity of the subsequent deposition layer.

[0043] (3) Step 3: Dual-hydrophobic modification. Perfluorooctyl ethyl acrylate was used as the modifying agent to perform dual-hydrophobic modification on the paper-based filter material obtained in Step 2 by plasma-enhanced chemical vapor deposition (PECVD). During the modification process, the monomer was heated to 170°C and vaporized by the heating system, and then transported to the reaction chamber through a 185°C insulated pipeline. The reaction conditions were controlled at a vacuum of 10 Pa, a radio frequency plasma power of 5 W, and a processing time of 15 min.

[0044] Gas-phase perfluorooctyl ethyl acrylate dissociates under low-power radio frequency plasma excitation to generate active free radicals, which deposit on the surface of the filter material and diffuse into the internal pores, forming a uniform nanoscale hydrophobic and oleophobic fluorocarbon film on both the inner and outer layers of the filter material. After reaching the preset processing time, the monomer inlet and plasma power supply are sequentially turned off. After the system returns to normal pressure, the sample is removed without post-processing. The deposition rate of the dual-hydrophobic glass fiber filter material prepared in this embodiment is 4.05% based on weighing and calculation.

[0045] Tests showed that the modified dual-hydrophobic glass fiber filter material provided in this embodiment has an air permeability of 118 mm / s, a hydrophobicity grade of 12, and an oleophobicity grade of 8. As shown in Figure 6, the modified dual-hydrophobic glass fiber filter material prepared in this embodiment has a water contact angle of 151° (as shown in Figure 6a) and an oil contact angle of 152° (as shown in Figure 6b).

[0046] Example 4: PECVD double-hydrophobic modification of glass fiber filter material. A preparation process of a double-hydrophobic glass fiber filter material includes the following steps: (1) Step 1: Preparation of glass fiber paper-based filter material. 20% chopped glass fiber, 15% 475-19 glass wool and 65% 475-29 glass wool are selected as fiber raw materials according to the ratio and mixed with deionized water at a mass ratio of 0.25:1000. Wet paper forming is adopted, and after pressing and dehydration, it is dried at 105°C to constant weight. Acrylic resin emulsion is used to sizing the obtained paper-based filter material, and the sizing amount is controlled at 5±0.5%. After drying at 105°C to constant weight, it is cured at 160°C to obtain the matrix paper-based filter material. The basis weight of the filter material is 81 g / m³. 2 The air permeability is 119 mm / s.

[0047] (2) Step Two: Plasma Pretreatment. The paper-based filter material obtained in Step One is placed in a low-temperature plasma reaction chamber. Oxygen is selected as the working gas, and the gas flow rate is 200 sccm. The material is treated for 10 min under a radio frequency power of 300 W to remove surface impurities. The pretreatment process is mild and can effectively improve the adhesion and uniformity of the subsequent deposition layer.

[0048] (3) Step 3: Dual-hydrophobic modification. Perfluorooctyl ethyl acrylate was used as the modifying agent to perform dual-hydrophobic modification on the paper-based filter material obtained in Step 2 using plasma-enhanced chemical vapor deposition (PECVD). During the modification process, the monomer was heated to 170°C and vaporized by the heating system, and then transported to the reaction chamber through a 185°C insulated pipeline. The reaction conditions were controlled at a vacuum of 10 Pa, a radio frequency plasma power of 15 W, and a processing time of 1 min.

[0049] Gas-phase perfluorooctyl ethyl acrylate dissociates under low-power radio frequency plasma excitation to generate active free radicals, which deposit on the surface of the filter material and diffuse into the internal pores, forming a uniform nanoscale hydrophobic and oleophobic fluorocarbon film on both the inner and outer layers of the filter material. After reaching the preset processing time, the monomer inlet and plasma power supply are sequentially turned off. After the system returns to normal pressure, the sample is removed without post-processing. The deposition rate of the dual-hydrophobic glass fiber filter material prepared in this embodiment is 0.21% according to weighing calculations.

[0050] Tests showed that the modified dual-hydrophobic glass fiber filter material provided in this embodiment has an air permeability of 118 mm / s, a hydrophobicity grade of 12, and an oleophobicity grade of 8. As shown in Figure 7, the modified dual-hydrophobic glass fiber filter material prepared in this embodiment has a water contact angle of 154° (as shown in Figure 7a) and an oil contact angle of 151° (as shown in Figure 7b).

[0051] Comparative Example 1: PECVD Dual-Repellent Modification of Glass Fiber Filter Material with Different Monomer Reagents A preparation process of a dual-repellent glass fiber filter material includes the following steps: (1) Step 1: Preparation of Glass Fiber Paper-Based Filter Material 20% chopped glass fiber, 15% 475-19 glass wool, and 65% 475-29 glass wool were selected as fiber raw materials according to the following ratio and mixed with deionized water at a mass ratio of 0.25:1000. Wet paper forming was adopted, and after pressing and dehydration, it was dried at 105℃ to constant weight. Acrylic resin emulsion was used to sizing the obtained paper-based filter material, and the sizing amount was controlled at 5±0.5%. After drying at 105℃ to constant weight, it was cured at 160℃ to obtain the matrix paper-based filter material. The basis weight of this filter material is 80 g / m³. 2 The air permeability is 120 mm / s.

[0052] (2) Step Two: Plasma Pretreatment. The paper-based filter material obtained in Step One is placed in a low-temperature plasma reaction chamber, with argon as the working gas and a gas flow rate of 200 sccm. It is treated for 10 min at a radio frequency power of 300 W to remove surface impurities. The pretreatment process is mild and can effectively improve the adhesion and uniformity of the subsequent deposition layer.

[0053] (3) Step 3: Dual-repellent modification. Hexafluorobutyl acrylate was used as the modifying agent to perform dual-repellent modification on the paper-based filter material obtained in Step 2 using plasma-enhanced chemical vapor deposition (PECVD). During the modification process, the monomer was heated to 165°C and vaporized by the heating system, and then transported to the reaction chamber through a 185°C insulated pipeline. The reaction conditions were controlled at a vacuum of 10 Pa, a radio frequency plasma power of 15 W, and a processing time of 5 min.

[0054] After the preset processing time is reached, the monomer inlet and plasma power supply are turned off sequentially. Once the system returns to normal pressure, the sample is removed without further processing. Weighing and calculation show that the deposition rate of the dual-hydrophobic glass fiber filter material prepared in this embodiment is 5.87%.

[0055] The prepared filter material was tested and found to have an air permeability of 117 mm / s, a hydrophobicity rating of 4, and an oleophobicity rating of 2. Contact angle data are shown in Figure 8: the water contact angle is 142.5° (Figure 8a), and the oil contact angle shows rapid penetration (Figure 8b).

[0056] Hexafluorobutyl acrylate contains only a four-carbon fluorine chain, limiting the availability of fluorine-rich structures. This makes it difficult to form a dense, low-surface-energy layer in the deposited film, resulting in insufficient repellency against low-surface-tension oils. In contrast, the monomer used in this invention is perfluorooctyl ethyl acrylate, which has an eight-carbon perfluorine chain and a high fluorine content. During plasma deposition, it more easily retains and enriches fluorine-containing structures, forming a well-oriented and dense fluorocarbon layer, significantly reducing surface energy and thus achieving stable oleophobic properties and superior oil and heat resistance. Comparative Example 1, which did not use the monomer reagent of this invention, resulted in filter media with insufficient hydrophobicity and oleophobicity. This demonstrates that the monomer used in this invention has a significant effect on improving functionality.

[0057] Comparative Example 2: Low-temperature plasma activation-impregnation modification of glass fiber filter material with different monomer reagents. Filter substrate: Glass fiber filter material (formulation: 90% glass wool 253-39 + 10% glass wool 253-19) Monomer reagents: Hexafluorobutyl acrylate, perfluorohexyl propylene oxide, nonafluorohexyl acrylate, perfluorooctyl ethyl acrylate (1) Step 1: Low-temperature plasma activation of glass fiber filter material. The glass fiber filter material is treated by low-temperature plasma modification, and the surface of the material is bombarded to improve the surface energy of the material. The plasma reaction gas is oxygen, the gas flow rate is 200 sccm, the activation time is 1 / 5 / 10 min, the working vacuum degree is 10Pa, and the activation power is 450 W.

[0058] (2) Step 2: Prepare the modified grafting solution. The solute is selected from one of the following four: hexafluorobutyl acrylate, perfluorohexyl propylene oxide, nonafluorohexyl acrylate, and perfluorooctyl acrylate. The solvent is N,N-dimethylformamide (DMF). The dilution ratio of reagent to solvent is set to 5%.

[0059] (3) Step 3: Preparation of impregnated modified glass fiber filter material. Take out the glass fiber filter material obtained in step 1, soak it in the modification reagent for 24 h, then wash it with acetone for 5 min, and then soak it in acetone again for 0.5 h. Finally, dry it at 80℃ for 40 min to obtain each modified sample.

[0060] As shown in Table 1, the substrates immersed in the four liquid monomers were not successfully modified to be hydrophobic or oleophobic, with all four having a hydrophobic or oleophobic rating of 0. Figure 9 shows that penetration occurred the instant the droplets came into contact with the filter material.

[0061] Comparative Example 2 did not employ the plasma-enhanced chemical vapor deposition modification method used in this invention, and the resulting filter material did not possess hydrophobic and oleophobic properties. This demonstrates that the modification method used in this invention has a significant effect on improving functionality.

[0062] Table 1. Hydrophobic and oleophobic grades of modified liquid-impregnated glass fiber filter materials prepared with different monomers.

[0063] Comparative Example 3: 50W High-Power PECVD Double-Repellent Modification of Glass Fiber Filter Material A preparation process for a double-repellent glass fiber filter material includes the following steps: (1) Step 1: Preparation of Glass Fiber Paper-Based Filter Material 20% chopped glass fiber, 15% 475-19 glass wool, and 65% 475-29 glass wool were selected as fiber raw materials according to the following ratio, and mixed with deionized water at a mass ratio of 0.25:1000. Wet paper forming was adopted, and after pressing and dehydration, it was dried at 105℃ to constant weight. Acrylic resin emulsion was used to sizing the obtained paper-based filter material, and the sizing amount was controlled at 5±0.5%. After drying at 105℃ to constant weight, it was cured at 160℃ to obtain the matrix paper-based filter material. The basis weight of this filter material is 80 g / m³.2 The air permeability is 120 mm / s.

[0064] (2) Step Two: Plasma Pretreatment. The paper-based filter material obtained in Step One is placed in a low-temperature plasma reaction chamber, with argon as the working gas and a gas flow rate of 200 sccm. It is treated for 10 min at a radio frequency power of 300 W to remove surface impurities. The pretreatment process is mild and can effectively improve the adhesion and uniformity of the subsequent deposition layer.

[0065] (3) Step 3: Dual-hydrophobic modification. Perfluorooctyl ethyl acrylate was used as the modifying agent, and the paper-based filter material obtained in Step 2 was subjected to dual-hydrophobic modification by plasma-enhanced chemical vapor deposition (PECVD). During the modification process, the monomer was heated to 165°C and vaporized by the heating system, and then transported to the reaction chamber through a 185°C insulated pipeline. The reaction conditions were controlled at a vacuum of 10 Pa, a radio frequency plasma power of 50 W, and a processing time of 20 min.

[0066] After the preset processing time was reached, the monomer inlet and plasma power supply were turned off sequentially. The sample was removed after the system returned to normal pressure; no post-processing was required. The deposition rate of the bis-hydrophobic glass fiber filter material prepared in this comparative example was calculated to be 5.11%.

[0067] Testing showed that the modified dual-hydrophobic glass fiber filter material provided in this comparative example had an air permeability of 117 mm / s, a hydrophobicity rating of 9, and an oleophobicity rating of 6. Contact angle data are shown in Figure 10. Comparative Example 3 did not use the parameter range of this invention; the water contact angle was 132° (as shown in Figure 10a) and the oil contact angle was 101° (as shown in Figure 10b), resulting in a decrease in both hydrophobicity and oleophobicity of the obtained filter material. This demonstrates that the parameters defined in this invention have a significant effect on improving the hydrophobic functionality.

[0068] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a paper-based filter material with hydrophobic and oleophobic properties, characterized in that, The process includes the following steps: (1) Preparation of paper-based filter material: the fiber raw material is wet-processed into shape, pressed and dehydrated, dried to constant weight, and sizing is performed to obtain the matrix paper-based filter material; (2) Plasma pretreatment: the paper-based filter material obtained in step (1) is placed in a low-temperature plasma reaction chamber, and gas is introduced for plasma treatment to remove impurities on the surface of the paper-based filter material and introduce active groups. (3) Dual hydrophobic modification: The plasma-enhanced chemical vapor deposition method is used for dual hydrophobic modification: the pretreated paper-based filter material is placed in a vacuum reaction chamber, and liquid fluorinated ester monomers are added to the storage tank. After the monomers are heated and vaporized, they enter the reaction chamber through a heat-insulated conveying pipe. The vaporized monomers are excited by plasma and deposited in situ on the surface of the paper-based filter material to form a uniform nanoscale hydrophobic and oleophobic film layer.

2. The preparation method according to claim 1, characterized in that, In step (1), the fiber raw material is selected from at least one of glass fiber, aramid fiber, Tencel fiber, kapok fiber, nylon fiber, and PET fiber.

3. The preparation method according to claim 1, characterized in that, In step (2), the plasma atmosphere is selected as oxygen or argon.

4. The preparation method according to claim 1, characterized in that, In step (2), the plasma treatment is performed at 100-500 W for 1-10 min.

5. The preparation method according to claim 1, characterized in that, In step (2), the paper-based filter material is laid flat in the reaction chamber to avoid overlapping or obstruction.

6. The preparation method according to claim 1, characterized in that, In step (3), the fluorinated ester monomer is perfluorooctyl ethyl acrylate.

7. The preparation method according to claim 1, characterized in that, In step (3), the monomer vaporization temperature is 160-190℃, and after vaporization, it is transported to the reaction chamber through a 170-200℃ heat-insulated pipeline.

8. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the reaction chamber is controlled to not exceed 80°C, the working vacuum is controlled to 1-10 Pa, the radio frequency power is controlled to 5-35 W, and the processing time is controlled to 10 s-15 min.

9. A paper-based filter material with hydrophobic and oleophobic properties obtained by the preparation method according to any one of claims 1-8.

10. The application of the paper-based filter material with hydrophobic and oleophobic properties as described in claim 9 in air filtration, liquid filtration, oil-water separation, oil-gas separation, and protective materials.

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