Preparation method and application of super-oleophobic agent for filter material

Abstract

The invention relates to the technical field of polymer synthesis and filter materials, in particular to a preparation method and application of a super-oleophobic agent for a filter material. The preparation method comprises the following two steps: firstly, reacting dehydrated hydroxyl silicone oil with isocyanate under the protection of nitrogen, then adding a hydrophilic chain extender and perfluoropolyether alcohol for end capping, and carrying out triethylamine neutralization, water emulsification and desolvation treatment to obtain a perfluoropolyether polyurethane aqueous emulsion; and secondly, mixing the emulsion with a silane coupling agent, a cosolvent, a compound emulsifier and deionized water to form a pre-emulsion, dropwise adding a nano silicon dioxide aqueous dispersion, and stirring for reaction to obtain the stable super-oleophobic agent. According to the super-oleophobic agent, the perfluoropolyether is used for providing extremely low surface energy, the hydroxyl silicone oil is used for enhancing the flexibility of a chain segment, the silane coupling agent is in bridge connection with the organic polymer and the inorganic nanoparticles, a micro-nano double coarse structure is cooperatively constructed, and therefore the super-hydrophobic performance of low-surface-tension oil is achieved.

Description

Technical Field

[0001] This invention belongs to the fields of polymer synthesis technology and filter material technology, specifically relating to a method for preparing and applying a superoleophobic agent for filter materials. Background Technology

[0002] Natural gas is an important component of my country's energy industry structure. Natural gas typically refers to oilfield gas and gas field gas, which is primarily composed of hydrocarbons and contains non-hydrocarbon gases. Natural gas extracted from oil and gas fields usually contains impurities such as minerals, condensate, and free water. These impurities often cause corrosion and even damage to pipeline equipment and instruments during pipeline transportation, severely impacting and harming the pipeline transportation system. Therefore, removing impurities from natural gas pipelines and ensuring the cleanliness of natural gas energy is of great significance in industry.

[0003] Using filter materials to create gas-liquid coalescing filter elements is currently an effective method for separating impurities in natural gas pipeline transportation. However, traditional filter materials are prone to rapid "poisoning" when faced with impurities rich in condensate oil (a mixture of light hydrocarbons) due to oil wetting. Once the material is wetted by oil, its pores become blocked, leading to a sharp drop in separation efficiency and a surge in airflow resistance (pressure drop). This necessitates frequent shutdowns to replace the filter element, significantly increasing operating costs and safety hazards.

[0004] Wettability has been proven to be a crucial factor affecting the gas-liquid coalescence filtration performance of filter materials. Superoleophobic materials, due to their excellent oleophobicity and self-cleaning properties, show promising application prospects in gas-liquid coalescence filtration separation. Superoleophobic materials typically refer to materials that exhibit extremely high repulsion to oils with low surface tension (usually <30 mN / m), with both water and oil contact angles greater than 150° and a roll-off angle less than 10°. In natural gas gas-liquid coalescence filtration, they effectively prevent oil from clogging the filter media pores, significantly extending the filter element's lifespan, reducing maintenance frequency, and maintaining low flow resistance over a long period, thereby reducing the pumping energy consumption required for natural gas transportation and achieving industrial goals of energy conservation and emission reduction. Currently, the development of superoleophobic filter materials for natural gas gas-liquid separation faces the following challenges: 1) Currently, superoleophobic materials are mainly prepared using flat, rigid materials, with limited research on filtration materials. Porous filter fiber materials typically require altering their surface wettability while preserving their original unique pore structure, which presents a significant challenge.

[0005] 2) Currently, the synthesis and preparation process of superoleophobic coating agents is relatively complex, and it uses expensive fluorinated siloxanes and complicated synthesis processes, which is not conducive to industrial production.

[0006] Current superoleophobic materials can generally achieve contact angles greater than 150° for liquids with high surface tension, but achieving superoleophobicity for liquids with low surface tension remains quite challenging. Achieving superoleophobicity for liquids with low surface tension often requires multi-layer coating processes, which is not conducive to industrialization. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing and applying a superoleophobic agent for filter materials, in order to solve the above-mentioned technical problems in the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a superoleophobic agent for filter materials, comprising the following steps: Step (1) Synthesis of perfluoropolyether polyurethane aqueous emulsion: Dehydrated hydroxyl silicone oil and catalyst are added to the reactor, and isocyanate is added under nitrogen protection. The reaction is carried out at 70°C until the theoretical residual -NCO value is reached. Then, hydrophilic chain extender is slowly added dropwise to continue the reaction. The solvent is added to adjust the viscosity of the system. After the theoretical residual -NCO value is reached again, perfluoropolyether alcohol is added, the temperature is raised to 75-85°C, and the reaction is carried out for 2-4 hours for end-capping. After end-capping, the temperature is lowered to 40-50°C, and triethylamine (TEA) is added to neutralize for 0.5-1.5 hours. Then, deionized water is added for high-speed dispersion and emulsification for 1 hour to discharge the material to obtain a crude emulsion. Finally, the residual solvent is removed by rotary evaporation to obtain a uniform and stable perfluoropolyether polyurethane aqueous emulsion. Step (2) Synthesis of superoleophobic agent for filter material: The perfluoropolyether polyurethane aqueous emulsion obtained in step (1), silane coupling agent, cosolvent, deionized water and composite emulsifier are mixed and dispersed at high speed for 25-35 min to obtain a pre-emulsion. Nano silica is dispersed in water and added dropwise to the pre-emulsion under stirring. The reaction is continued for 2-4 h to obtain superoleophobic agent for filter material.

[0009] Preferably, the hydroxyl silicone oil has the following structural formula (I) and a molecular weight of 200-2000, more preferably 500-1000: (I) .

[0010] Preferably, the isocyanate is selected from one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI).

[0011] Preferably, the hydrophilic chain extender is selected from dimethylolpropionic acid (DMPA) or dimethylolbutyric acid (DMBA).

[0012] Preferably, the perfluoropolyether alcohol has the following structural formula (II) and a molecular weight of 200-2000, more preferably 500-1000: (II) .

[0013] Preferably, the catalyst is an organobismuth catalyst.

[0014] Preferably, the perfluoropolyether polyurethane accounts for 30-80% of the total mass of the superoleophobic agent on a solid basis, more preferably 40-60%.

[0015] Preferably, in step (1), the solvent is selected from acetone, butanone or N-methylpyrrolidone.

[0016] Preferably, the silane coupling agent is selected from one or more of methyltrimethoxysilane, methyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane.

[0017] Preferably, the amount of the silane coupling agent accounts for 2-20% of the total mass of the superoleophobic agent, more preferably 5-10%.

[0018] Preferably, the co-solvent is selected from one or more of ethanol, isopropanol, dipropylene glycol, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, or tripropylene glycol monomethyl ether.

[0019] Preferably, the amount of the co-solvent accounts for 1-10% of the total mass of the superoleophobic agent, more preferably 3-6%.

[0020] Preferably, the particle size of the nano-silica is 1-500 nm, more preferably 50-200 nm.

[0021] Preferably, the amount of nano-silica accounts for 1-20% of the total mass of the superoleophobic agent, more preferably 5-10%.

[0022] Preferably, the composite emulsifier is selected from one or two of sodium dodecylbenzenesulfonate (SDS), alkylphenol polyoxyethylene ether (OP), and polyoxyethylene sorbitan monostearate (Tween).

[0023] Preferably, the amount of the composite emulsifier accounts for 0.1-0.5% of the total mass of the superoleophobic agent, more preferably 0.1-0.3%.

[0024] In a second aspect, the present invention provides a superoleophobic agent for filter materials prepared by a method for preparing a superoleophobic agent for filter materials.

[0025] Thirdly, the present invention provides the application of the superoleophobic agent in the preparation of superoleophobic filter materials.

[0026] Preferably, the application includes: mixing the superoleophobic agent provided by the present invention with a commercially available acrylic adhesive in a certain proportion, diluting with water to a suitable solid content, applying it to the surface of the filter material substrate by impregnation, roller coating or spraying, and then drying and curing it in a hot air oven at 100-180°C.

[0027] Preferably, the filter material substrate is selected from glass fiber nonwoven fabric, polyester nonwoven fabric, polypropylene nonwoven fabric, or composites thereof.

[0028] Preferably, the amount of adhesive applied to the treated filter material by the impregnation solution is 6-8% of the substrate mass.

[0029] Preferably, the filter material is one of non-woven fabric, glass fiber and synthetic fiber blend.

[0030] Fourthly, the present invention provides a superoleophobic filter material, characterized in that a functional coating formed by the superoleophobic agent is attached to the surface of the filter material substrate.

[0031] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention abandons traditional long-chain (C8) perfluoroalkyl compounds and selects perfluoropolyether alcohol (PFPE) as the fluorine source. The ether bond (-O-) in the perfluoropolyether molecular chain provides excellent internal rotational freedom, making the molecular chain more flexible. This flexibility allows the fluorinated segments to migrate and align more freely at the coating or air interface during film formation, thereby exposing the -CF3 groups with the lowest surface energy more densely and effectively on the outermost layer of the coating, providing a molecular structural basis for obtaining ultra-low surface energy and superoleophobic properties.

[0032] 2. This invention creatively employs a two-step synthesis method. First, a polyurethane with hydroxyl silicone oil as the soft segment, containing hydrophilic groups, and capped with perfluoropolyether is synthesized. This polymer combines the flexibility of silicone oil, the strong adhesion and toughness of polyurethane, and the extremely low surface energy of perfluoropolyether. In the second step, a portion of the introduced silane coupling agent reacts with the active groups (such as silanol groups) on the polyurethane chain, while the other portion hydrolyzes and condenses with the silanol groups on the surface of nano-silica, forming a bond between the inorganic nanoparticles and the organic polymer. This achieves stable dispersion of nano-silica in the emulsion system and strong chemical bonding with the resin matrix after film formation, solving the problems of easy agglomeration and detachment of nanoparticles.

[0033] 3. The present invention uses nano-silica fixed in the resin through the above-mentioned chemical bonding method. During the coating drying and curing process, it can synergistically promote the self-assembly of long-chain alkyl groups of the silane coupling agent to construct a durable and stable micro-nano-scale dual roughness structure on the coating surface. This, combined with the low surface energy of the perfluoropolyether segments, enables the coating to exhibit superoleophobic properties against various oily liquids (including low surface energy oils). The static contact angle of water droplets can be greater than 150°, and the roll-off angle less than 10°.

[0034] 4. The filter material treated with the superoleophobic agent of this invention has a fiber surface with extremely strong repulsive force against oil droplets. Oil mist is difficult to spread and remain on the fiber surface during the filtration process, reducing the pressure difference rise caused by droplets clogging the filter channels, improving the service life of the filter material, providing more stable filtration efficiency and lower operating energy consumption, and has significant economic benefits and application value.

[0035] 5. The preparation process of this invention is an aqueous system, which is safe and environmentally friendly; the resulting product is a stable nanocomposite emulsion with good storage stability, and is fully compatible with existing filter material processing technology (impregnation, spraying), making it easy to achieve large-scale industrial production and application. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a process flow diagram of the preparation process of the superoleophobic agent for the filter material of the present invention; Figure 2 The contact angle of water droplets from the filter material of this invention on the surface of the superoleophobic composite coating; Figure 3 It is the contact angle of oil droplets from the filter material of this invention on the surface of the superoleophobic composite coating. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0039] This embodiment discloses a method for preparing a superoleophobic agent for filter materials, comprising the following steps: Step (1) In a 500 mL four-necked flask, add 50 g of hydroxyl-terminated polydimethylsiloxane with a Mw of 500 that has been dehydrated under reduced pressure at 120 °C for 1 h and 0.05 g of organic bismuth catalyst (TIB KAT 716). Purge the air in the reactor three times with dry nitrogen. Under continuous nitrogen purging, slowly add 23 g of the catalyst dropwise using a constant pressure dropping funnel. IPDI was added at a controlled rate to maintain the reaction temperature at 70°C. After the addition was complete, the reaction was continued at 70°C. Samples were taken every 30 minutes to determine the -NCO content using di-n-butylamine titration. When the -NCO content reached the theoretical value, 13.4g of DMPA, pre-dissolved in 10g of acetone, was slowly added dropwise, maintaining the system temperature throughout the addition. After the addition was complete, the reaction was continued at 70°C for approximately 1.5 hours. During this period, due to increased viscosity, 15g of acetone was added to facilitate stirring. When the -NCO content again reached the theoretical value, 52g of perfluoropolyether alcohol with a molecular weight of approximately 500 was added in one go. The temperature was raised to 80°C and maintained for 3 hours. After end-capping, the system was cooled to 45°C, and 1g of... TEA was neutralized for 1 hour. Under high-speed stirring at 1200 rpm, 150 g of deionized water was slowly added to the neutralized prepolymer. The mixture was continuously dispersed and emulsified at high speed for 1 hour to obtain a white emulsion. Finally, the acetone solvent in the system was removed by vacuum distillation in a rotary evaporator at 45 °C to obtain a perfluoropolyether polyurethane aqueous emulsion, denoted as A1.

[0040] Step (2) In a high-speed disperser with a speed of 2000 rpm, 50 g of the above emulsion A1 (based on solid content), 10 g of hexadecyltrimethoxysilane, 3 g of propylene glycol methyl ether, 0.1 g of sodium dodecylbenzenesulfonate (SDS), 0.1 g of OP-10, and 28.8 g of deionized water were added sequentially and dispersed at high speed for 30 min to form a uniform and stable pre-emulsion. 8 g of hydrophilic fumed silica nanoparticles with a particle size of about 100 nm were taken and dispersed in 20 g of deionized water under ultrasonic assistance to prepare a uniform silica aqueous dispersion. Under mechanical stirring at a speed of 500 rpm, the above silica aqueous dispersion was slowly added dropwise to the pre-emulsion over 30 min. After the addition was completed, the temperature of the reaction system was maintained at room temperature and the reaction was continued to be stirred for 3 h. After the reaction was completed, superoleophobic agent S1 for filter materials was obtained.

[0041] The contact angle of water droplets on the surface of the superoleophobic composite coating of the filter material prepared in Example 1 is as follows: Figure 2 As shown; the contact angle of oil droplets from the filter material provided in Example 1 on the surface of the superoleophobic composite coating is as follows. Figure 3 As shown. Example 2

[0042] This embodiment discloses a method for preparing a superoleophobic agent for filter materials, comprising the following steps: Step (1) Synthesis of perfluoropolyether polyurethane emulsion (A2): The steps are similar to those in Example 1, except for the raw materials: 50g of hydroxyl silicone oil with a molecular weight of 500, 23g of IPDI, 13.4g of DMPA, 105g of perfluoropolyether alcohol with a molecular weight of approximately 1000, 0.05g of organic bismuth catalyst, 20g of acetone added during the reaction to adjust the viscosity, 1g of TEA used for neutralization, and 210g of emulsifying water are added to finally obtain perfluoropolyether polyurethane aqueous emulsion A2.

[0043] Step (2) Synthesis of superoleophobic agent S2 for filter materials: In a high-speed disperser, add 60g of emulsion A2 (based on solid content), 7g of hexadecyltrimethoxysilane, 5g of tripropylene glycol monomethyl ether, 0.1g of SDS, 0.1g of polyethylene oxide sorbitol monostearate (Tween-80), and 21.8g of deionized water, and disperse at high speed for 30 minutes to obtain a pre-emulsion.

[0044] 6g of nano-silica with a particle size of about 200nm was ultrasonically dispersed in 15g of deionized water, and pre-emulsion was added dropwise under stirring. The mixture was stirred at room temperature for 3h to obtain superoleophobic agent S2 for filter materials. Example 3

[0045] This embodiment discloses a method for preparing a superoleophobic agent for filter materials, comprising the following steps: Step (1) Synthesis of perfluoropolyether polyurethane emulsion (A3): The steps are similar to those in Example 1, except for the raw materials: 50g of hydroxyl silicone oil with a molecular weight of 1000, 8.7g of toluene diisocyanate (TDI-80 / 20), 7.4g of DMBA, 26g of perfluoropolyether alcohol with a molecular weight of 500, 0.05g of organic bismuth catalyst, 10g of acetone added during the reaction, 0.5g of TEA used for neutralization, and 100g of emulsifying water. The final product is perfluoropolyether polyurethane aqueous emulsion A3.

[0046] Step (2) Synthesis of superoleophobic agent S3 for filter materials: In a high-speed disperser, 45g of emulsion A3 (based on solid content), 10g of octadecyltrimethoxysilane, 6g of propylene glycol methyl ether, 0.1g of SDS, 0.1g of OP-10, and 28.8g of deionized water were added and dispersed at high speed for 30min to obtain a pre-emulsion. 10g of nano-silica with a particle size of about 100nm was ultrasonically dispersed in 25g of deionized water and added dropwise to the pre-emulsion under stirring. The mixture was stirred at room temperature for 4h to obtain superoleophobic agent S3 for filter materials. Example 4

[0047] This embodiment discloses a method for preparing a superoleophobic agent for filter materials, comprising the following steps: Step (1) Synthesis of perfluoropolyether polyurethane emulsion (A4): The steps are similar to those in Example 1, except for the raw materials: 50g of hydroxyl silicone oil with a molecular weight of 500, 17.4g of toluene diisocyanate (TDI-80 / 20), 13.4g of DMPA, 52g of perfluoropolyether alcohol with a molecular weight of approximately 500, 0.05g of organic bismuth catalyst, and 15g of acetone added during the reaction. 1g of TEA was used for neutralization, and 145g of water was used for emulsification. The final product is perfluoropolyether polyurethane aqueous emulsion A4.

[0048] Step (2) Synthesis of superoleophobic agent S4 for filter materials: In a high-speed disperser, 55g of emulsion A4 (based on solid content), 8g of octadecyltrimethoxysilane, 5g of tripropylene glycol monomethyl ether, 0.1g of SDS, 0.1g of Tween-80, and 23.8g of deionized water were added and dispersed at high speed for 30 minutes to obtain a pre-emulsion. 8g of nano-silica with a particle size of about 200nm was ultrasonically dispersed in 20g of deionized water and added dropwise to the pre-emulsion while stirring. The mixture was stirred at room temperature for 2 hours to obtain superoleophobic agent S4 for filter materials.

[0049] Comparative Example 1 Step (1) Comparison of the synthesis of polyurethane emulsion (B1): The steps are basically the same as step (1) in Example 1, except that 50g of hydroxyl silicone oil is replaced with an equal mass of polyethylene adipate diol (polyester polyol) with a molecular weight of about 1000, and finally the comparative polyurethane emulsion B1 is obtained.

[0050] Step (2) Comparison of the synthesis of superoleophobic agent D1: The steps are exactly the same as step (2) in Example 1, except that 50g of emulsion B1 is used to replace emulsion A1, and the types and amounts of other raw materials remain unchanged, so as to prepare the comparative superoleophobic agent D1.

[0051] Comparative Example 2 Step (1) Synthesis of perfluoropolyether polyurethane emulsion (A1) is the same as step (1) in Example 1. Step (2) Compare the synthesis of superoleophobic agent D2: The steps are basically the same as step (2) in Example 1, except that hexadecyltrimethoxysilane is not added. 50g of emulsion A1, 3g of propylene glycol methyl ether, 0.1g of SDS, 0.1g of OP-10 and 38.8g of deionized water are dispersed at high speed to obtain a pre-emulsion. The subsequent addition of nano-silica and the reaction process remain unchanged, and the comparative superoleophobic agent D2 is prepared.

[0052] Comparative Example 3 Step (1) Synthesis of perfluoropolyether polyurethane emulsion (A1) is the same as step (1) in Example 1.

[0053] Step (2) Comparison of the synthesis of superoleophobic agent D3: The steps are basically the same as step (2) of Example 1, except that no nano-silica is added. 60g of emulsion A1 (based on solid content), 12g of hexadecyltrimethoxysilane, 3g of propylene glycol methyl ether, 0.1g of SDS, 0.1g of OP-10, and 24.8g of deionized water are dispersed at high speed and stirred directly for 3h without adding nano-silica to prepare the comparative superoleophobic agent D3.

[0054] Comparative Example 4 Step (1) Comparison of the synthesis of fluorinated emulsion (C1): In the reactor, 52g of polyether polyol with a molecular weight of about 500 and 0.05g of organic bismuth catalyst were added. Nitrogen gas was purged and 23g of IPDI was added. The reaction was carried out at 70°C until the theoretical value of -NCO was reached. 13.4g of DMPA dissolved in 10g of acetone was added and the reaction was continued. Finally, 52g of perfluorinated polyether alcohol with a molecular weight of 500 was added for end capping. The subsequent neutralization, emulsification and desolvation processes were the same as step (1) in Example 1, and the comparative fluorinated polyurethane emulsion C1 was obtained.

[0055] Step (2) Comparison of the preparation of superoleophobic agent D4: In a high-speed disperser, 30g of emulsion C1, 12g of hexadecyltrimethoxysilane, 3g of propylene glycol methyl ether, 0.1g of SDS, 0.1g of OP-10, 15g of nano-silica with a particle size of approximately 100nm, and 39.8g of deionized water were mixed and dispersed at high speed for 30min, followed by stirring for 1h. This process did not involve pre-emulsification or dropwise reaction steps; the components were directly mixed and dispersed at high speed without forming a chemically bonded network, resulting in the comparative superoleophobic agent D4.

[0056] The raw material composition of the superoleophobic agents in Examples 1-4 and Comparative Examples 1-4 is shown in Table 1:

[0057] Application example: Preparation and performance testing of superoleophobic filter materials 1. Preparation of superoleophobic filter materials: Take 1g each of the products from Examples 1-4 (S1-S4) and Comparative Examples 1-4 (D1-D4) prepared above, add 2g of thermosetting acrylic resin (Dow Chemical, Model 05A), 1g of thermoplastic acrylic resin (Dow Chemical, Model 32N), and 96g of deionized water. Stir at 500rpm for 30min to prepare a uniform impregnation working solution. Lay the molded glass fiber paper flat and immerse it in the diluted solution for 30s. Remove it, aspirate, and cure at 150℃ for 15min to obtain the superoleophobic filter material. Control the final adhesive content of the sample to be between 6-8% by weighing.

[0058] 2. Performance testing methods and results: (1) Hydrophobic and oleophobic properties: The oleophobic properties of the material are characterized by measuring the static and dynamic contact angles of water and oil using a contact angle meter.

[0059] (2) Thickness: The thickness shall be measured in accordance with the test standard GB / T451.3-2002 "Determination of thickness of paper and paperboard".

[0060] (3) Air permeability: The air permeability was tested using an FX3300-IV air permeability meter at a pressure of 200 Pa and a test area of ​​20 cm². 2 .

[0061] (4) Aperture: The average and maximum pore diameter of the material were measured using a PMI capillary flow pore diameter tester.

[0062] The performance data is shown in Table 2: Table 2: Performance Data of Superoleophobic Filter Materials

[0063] The results in the table show that the filter materials prepared in Examples 1-4 all exhibit excellent superhydrophobic and superoleophobic properties. The static water contact angle is greater than 152°, and the water roll-off angle is less than 6.3°; the DEHS static contact angle is greater than 150°, and the oil roll-off angle is less than 8.0°, demonstrating superhydrophobic and superoleophobic characteristics. Furthermore, the treated filter materials are essentially the same as the blank samples in terms of thickness and average pore size, with only a slight increase in air permeability (<6.5%). This indicates that the treatment process of this invention, while imparting superoleophobic functionality, maximizes the preservation of the original three-dimensional porous structure of the filter material, without negatively impacting its core filtration performance, such as pressure differential and dust holding capacity.

[0064] Compared to Examples 1-4, Comparative Example 1 shows that the hydrophobic segments provided by hydroxyl silicone oil are crucial for achieving ultra-low surface energy in synergy with perfluoropolyethers. Using polyester polyol significantly reduces oleophobicity, and the roll-off angles are all greater than 10°, failing to achieve a superoleophobic state. Compared to Examples 1-4, Comparative Example 2 shows that the absence of a silane coupling agent, which connects nano-silica to the resin matrix and constructs a stable rough structure, reduces hydrophobicity, and oil droplets penetrate within 5 seconds, completely losing oleophobicity. Compared to Examples 1-4, Comparative Example 3 shows that the micro-nano rough structure constructed by nano-silica... The low surface energy obtained by chemical modification without the addition of any additives resulted in hydrophobic and oleophobic contact angles not reaching 150° and roll-off angles greater than 10°, making it impossible to achieve a superhydrophobic state. Compared with Examples 1-4, Comparative Example 4 showed that the polyether polyol-perfluoropolyether system was less oleophobic than the hydroxyl silicone oil-perfluoropolyether system, and the simple physical mixing process could not achieve stable bonding and uniform dispersion of nanoparticles, resulting in uneven coating, nanoparticle agglomeration and blockage or enlarged pores. As a result, the oil contact angle was only 124.66°, and the oil roll-off angle was >10°, with a significant increase in air permeability and a slight increase in pore size.

[0065] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0066] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a superoleophobic agent for filter materials, characterized in that, Includes the following steps: Step (1) Under nitrogen protection, the dehydrated hydroxyl silicone oil and catalyst are mixed, isocyanate is added to react, and then hydrophilic chain extender is added to continue the reaction. According to the viscosity of the reaction system, solvent is added to adjust the viscosity. Then perfluoropolyether alcohol is added for end capping. After neutralization with TEA, water is added for emulsification and solvent is removed to obtain perfluoropolyether polyurethane emulsion. Step (2) Mix the perfluoropolyether polyurethane aqueous emulsion, silane coupling agent, cosolvent, deionized water and composite emulsifier, disperse at high speed to form a pre-emulsion, and then add the aqueous dispersion of nano-silica to the pre-emulsion and stir to react to obtain the superoleophobic agent.

2. The method for preparing the superoleophobic agent for filter materials according to claim 1, characterized in that, In step (1), the hydroxyl silicone oil has the following structural formula (I): (I)； ； Among them, the molecular weight (Mw) of hydroxyl silicone oil is 200-2000.

3. The method for preparing the superoleophobic agent for filter materials according to claim 1, characterized in that, In step (1), the perfluoropolyether alcohol has the following structural formula (II): (II); ； The molecular weight (Mw) of the perfluoropolyether alcohol is 200-2000.

4. The method for preparing the superoleophobic agent for filter materials according to claim 1, characterized in that, In step (1), the isocyanate is selected from one of TDI, MDI, HDI or IPDI; the hydrophilic chain extender is DMPA or DMBA.

5. The method for preparing the superoleophobic agent for filter materials according to claim 1, characterized in that, In step (1), the reaction temperature is 70℃; the end-capping conditions are: end-capping temperature of 75-85℃ and end-capping time of 2-4h; the neutralization conditions are: neutralization temperature of 40-50℃ and neutralization time of 0.5-1.5h; the emulsification time is 1h; the catalyst is an organic bismuth catalyst; the solvent is selected from acetone, butanone or N-methylpyrrolidone; the solvent is removed by rotary evaporation.

6. The method for preparing the superoleophobic agent for filter materials according to claim 1, characterized in that, The perfluoropolyether polyurethane accounts for 30-80% of the total mass of the superoleophobic agent on a solid basis; the silane coupling agent is selected from one or more of methyltrimethoxysilane, methyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane, and is used in an amount of 2-20% of the total mass of the superoleophobic agent.

7. The method for preparing the superoleophobic agent for filter materials according to claim 1, characterized in that, The co-solvent is selected from one or more of ethanol, isopropanol, dipropylene glycol, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, or tripropylene glycol monomethyl ether, and its amount accounts for 1-10% of the total mass of the superoleophobic agent; the nano silica has a particle size of 1-500 nm and its amount accounts for 1-20% of the total mass of the superoleophobic agent.

8. The method for preparing the superoleophobic agent for filter materials according to claim 1, characterized in that, The composite emulsifier is selected from one or two of sodium dodecylbenzenesulfonate (SDS), alkylphenol polyoxyethylene ether (OP), and polyethylene oxide sorbitol monostearate (Tween), and the total amount used accounts for 0.1-0.5% of the total mass of the superoleophobic agent.

9. The application of a superoleophobic agent prepared by the method according to any one of claims 1-8 in the preparation of superoleophobic filter materials, characterized in that, The superoleophobic agent is mixed with an acrylic binder, diluted with water, and applied to the surface of a glass fiber, polyester, or polypropylene nonwoven fabric substrate. After heat curing at 100-180℃, a superoleophobic filter material is obtained.

10. The application according to claim 9, characterized in that, The mass ratio of the superoleophobic agent to the binder is 1:(1-3), and the amount of adhesive applied to the treated filter material is 6-8% of the mass of the substrate.

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