Nanofiber coated fuel filter material and preparation method thereof

Abstract

The invention discloses a nanofiber membrane fuel filter material and a preparation method thereof, and relates to the technical field of filter materials, the nanofiber membrane fuel filter material comprises a base material, an adhesive layer, a middle layer and a nanofiber membrane layer, and each layer is composed of the following raw materials in parts by weight: the base material comprises 60-80 parts of bamboo fiber microfibers; 5 to 10 parts of nano lignin; 1-3 parts of a coupling agent; the adhesive layer comprises the following components in parts by weight: 10-20 parts of maleic anhydride grafted starch; 6 to 10 parts of carboxymethyl chitosan; 2-5 parts of a plasticizer; the middle layer comprises 40-60 parts of polylactic acid; 2-5 parts of a plasticizer; the nanofiber coating layer comprises 30 to 50 parts of cellulose nanofiber; 20 to 30 parts of chitosan; 3 to 6 parts of polydopamine; 3-6 parts of a cross-linking agent; and 1-4 parts of a surface modifier. According to the fuel filter material, the nano material is used for replacing glass fibers, gradient aperture design, interface strengthening and surface modification are combined, the filtering efficiency and corrosion resistance of the filter material are improved, the environment compatibility is achieved, and harm to the environment and organisms is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of filter materials, and particularly to a nanofiber-coated fuel filter material and a preparation method thereof. Background Art

[0002] As the core material of the internal combustion engine fuel filtration system, the performance of fuel filter materials affects engine efficiency, emission control and service life. Traditional fuel filter materials mainly use glass fiber filter materials. The invention publication number CN113931010B provides a fuel filter material, the composition of which includes non-alkali glass fiber filaments. Glass fiber filter materials are prone to release micron-sized glass fiber fragments during production, use and disposal, and long-term exposure may cause respiratory damage and skin irritation to the human body. Moreover, glass fiber materials are non-degradable, posing a threat to the ecological environment. Summary of the Invention

[0003] To solve the biological hazard and environmental unsustainability defects of traditional glass fiber fuel filter materials, the present invention provides a nanofiber-coated fuel filter material. Through the composite structure of a base material, an intermediate layer and a nanofiber coating layer, combined with the interfacial strengthening system of an adhesive layer, the present invention realizes multi-stage pore size collaborative filtration and constructs an oil-repellent surface, improving fuel corrosion resistance and filtration efficiency. Moreover, the present invention uses degradable materials, and there is no risk of glass fiber pollution during production and disposal, comprehensively solving the three major technical problems of traditional filter materials: harm to human health, insufficient filtration efficiency and poor environmental compatibility.

[0004] The technical solution adopted by the present invention to achieve the above object is as follows:

[0005] The present invention provides a nanofiber-coated fuel filter material, which includes a base material, an adhesive layer, an intermediate layer and a nanofiber coating layer. Each layer is composed of the following raw materials in parts by weight:

[0006] The base material includes: 60-80 parts of bamboo fiber microfibrils; 5-10 parts of nano-lignin; 1-3 parts of coupling agent;

[0007] The adhesive layer includes: 10-20 parts of maleic anhydride grafted starch; 6-10 parts of carboxymethyl chitosan; 2-5 parts of plasticizer;

[0008] The intermediate layer includes: 40-60 parts of polylactic acid; 2-5 parts of plasticizer;

[0009] The nanofiber coating layer includes: 30-50 parts of cellulose nanofibers; 20-30 parts of chitosan; 3-6 parts of polydopamine; 3-6 parts of crosslinking agent; 1-4 parts of surface modifier.

[0010] Preferably, the bamboo fiber microfiber has a diameter of 5-15 μm; the nano-lignin has a diameter of 50-200 nm; and the cellulose nanofiber has a diameter of 20-50 nm. Through the interfacial strengthening and synergistic effect of fibers with different diameters, the filter material has both high strength, high toughness and excellent environmental stability.

[0011] Preferably, the coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane. Through the chemical-physical synergistic effect of the silane coupling agent, the interfacial peeling and swelling deformation of the filter material are inhibited. At the same time, a highly permeable micro-nano structure with moderate oil repellency is constructed to balance the fuel penetration and interception efficiency, and the high-temperature stability is enhanced by thermal crosslinking.

[0012] Preferably, the plasticizer is one or more of glycerol, citrate or epoxidized soybean oil.

[0013] Preferably, the crosslinking agent is glutaraldehyde. A flexible crosslinked network is constructed to enhance the resilience of the material.

[0014] Preferably, the surface modifier is one or more of stearic acid or nano-silica.

[0015] The present invention also provides a preparation method of a nanofiber-coated fuel filter material, comprising the following steps:

[0016] (1) Mix the base material raw materials, perform wet lamination molding, and hot press and dry; dissolve the adhesive layer raw materials in deionized water and mix evenly; dissolve the intermediate layer raw materials in a chloroform / DMF solution and electrospin to form a film; mix the nanofiber coating layer raw materials and vacuum filter to form a film;

[0017] (2) Coat the adhesive layer on the base material, stack the base material, adhesive layer, intermediate layer and nanofiber coating layer in sequence, and form an integrated structure by gradient hot pressing;

[0018] (3) Immerse the composite filter material in a 1% ethanol solution of perfluorooctyltriethoxysilane, take it out and dry it at 80 °C, and perform ultraviolet irradiation crosslinking to obtain the nanofiber-coated fuel filter material;

[0019] Preferably, the hot press drying conditions of the base material raw materials in step (1) are: hot press temperature 120-150 °C, pressure 5-10 MPa, pressure holding time 5-10 minutes, and wet lamination is formed using an 80-120 mesh screen mold. Through the synergistic activation of temperature and pressure for directional binding of components, and the regulation of fiber arrangement and pore structure by gradient screen mold, interfacial strengthening, improvement of thermal stability and retention of degradable characteristics are synchronously achieved during low-temperature hot press curing. Finally, a filter material with fuel impact resistance, low flow resistance and long-term interception performance is obtained, which meets the requirements of complex working conditions.

[0020] Preferably, the electrospinning parameters of the intermediate layer raw material in step (1) are: voltage 18 - 25 kV, receiving distance 10 - 20 cm, and spinning solution flow rate 0.5 - 1.5 mL / h. By constructing a submicron - scale fiber network, the polylactic acid filter membrane has both a high specific surface area, controllable porosity, and flexibility, while ensuring high - efficiency fuel filtration performance and retaining the biodegradable characteristics.

[0021] Preferably, in the mixing process of the nanofiber coating layer in step (1), a high - speed disperser is used to stir at a speed of 2000 - 4000 rpm for 30 - 60 minutes, the vacuum filtration pressure is maintained at - 0.08 - - 0.1 MPa, and the filtration time is 30 - 90 minutes. By regulating the coating structure, the directional arrangement of nanofibers and the construction of a dense coating layer are realized. While obtaining high mechanical strength, uniform permeability, and precise retention performance, the biodegradable characteristics of bio - nanomaterials are maintained to meet the requirements of high - efficiency filtration and functional coatings.

[0022] Preferably, the coating amount of the adhesive layer in step (2) is 0.6 - 1 g / m 2 . By regulating the distribution density of the adhesive, the interfacial bonding strength and permeability are balanced.

[0023] Preferably, the gradient hot - pressing in step (2) is divided into three stages: the first stage has a temperature of 80 °C for 2 min; the second stage has a temperature of 145 °C, a pressure of 10 MPa for 10 min; the third stage has a temperature of 70 °C for 5 min. Through the precise matching of temperature, pressure, and time, the step - by - step regulation of the performance of bio - nanomaterials is achieved.

[0024] Preferably, the surface of the hot - pressing die in step (2) is provided with a micro - convex structure of 50 - 100 μm; nitrogen is introduced during the hot - pressing process, and the oxygen content range is 50 - 100 ppm. The temperature reduction rate during the cooling process is controlled at 5 - 8 °C / min. Through the synergistic effect of physical interface regulation and inert gas, the performance of bio - nanomaterials is optimized.

[0025] Preferably, the infiltration time in step (3) is 10 - 30 min.

[0026] Preferably, the ultraviolet irradiation parameters in step (3) are: irradiation wavelength 350 - 380 nm, radiation luminance 40 - 60 mW / cm 2 , and the irradiation duration is 10 - 20 minutes. Through the synergistic effect of photochemistry and energy input, the directional regulation of the performance of nanomaterials is achieved.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) A bio-nanomaterial system is used to replace the traditional glass fiber filter material, avoiding the risk of micron-sized glass fiber release from the source and solving the environmental pollution problems in the production, use and waste disposal links; (2) Through the collaborative design of the gradient pore sizes of the substrate, the intermediate layer and the film coating layer, multi-stage filtration efficiency is achieved, significantly improving the interception ability of submicron particles and meeting the high-precision fuel filtration requirements; (3) Based on the chemical bonding of the adhesive layer and the stepped hot pressing process, the interfacial bonding between layers is strengthened, effectively resisting the long-term erosion of fuel, and greatly improving the structural stability and service life of the filter material; (4) Combining the surface oleophobic modification process, the filter material is given the characteristics of long-term oil corrosion resistance, overcoming the problem of performance attenuation caused by fuel penetration of traditional materials. Detailed implementation manners

[0028] The present invention will be further described below in conjunction with embodiments:

[0029] General embodiment

[0030] The present invention provides a nanofiber-coated fuel filter material, specifically including a substrate, an adhesive layer, an intermediate layer and a nanofiber coating layer. Each layer is composed of the following raw materials in parts by weight:

[0031] The substrate includes: 60-80 parts of bamboo fiber microfibers; 5-10 parts of nano-lignin; 1-3 parts of coupling agent;

[0032] The adhesive layer includes: 10-20 parts of maleic anhydride grafted starch; 6-10 parts of carboxymethyl chitosan; 2-5 parts of plasticizer;

[0033] The intermediate layer includes: 40-60 parts of polylactic acid; 2-5 parts of plasticizer;

[0034] The nanofiber coating layer includes: 30-50 parts of cellulose nanofibers; 20-30 parts of chitosan; 3-6 parts of polydopamine; 3-6 parts of crosslinking agent; 1-4 parts of surface modifier.

[0035] In some preferred embodiments, the diameter of the bamboo fiber microfibers is 5-15 μm; the diameter of the nano-lignin is 50-200 nm; the diameter of the cellulose nanofibers is 20-50 nm. The technical effects are as follows: The bamboo fiber microfibers provide mechanical support, the cellulose nanofibers build a submicron network, and the nano-lignin enhances the interfacial bonding. Combining the gradient barrier design and the optimization of mechanical properties, while maintaining the characteristics of nanomaterials, high strength, high toughness and excellent environmental stability are achieved.

[0036] In some preferred embodiments, the coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or γ-methacryloxypropyltrimethoxysilane. Its technical effect lies in that: by introducing a specific silane coupling agent, its organic active end combines with the hydroxyl groups of nanocellulose / lignin to form a stable covalent interface layer; while the silanol groups generated after the hydrolysis of siloxane form a physical anchoring network with the surface of the substrate fibers through a condensation reaction. The chemical-physical synergistic effect effectively inhibits the interfacial peeling and swelling deformation of the filter material in the fuel environment. At the same time, by regulating the surface function, a micro-nano structure with moderate oil repellency but high permeability is formed on the surface of the filter membrane, balancing the rapid passage of the fuel fluid and the efficient interception of particulate pollutants.

[0037] In some preferred embodiments, the plasticizer is one or more of glycerol, citrate ester, or epoxidized soybean oil. Its technical effect lies in that: the polyhydroxyl groups of glycerol weaken the rigid connection between cellulose molecular chains through hydrogen bonding, improving the flexibility and processing fluidity of the material; the ester functional groups of citrate ester form a conjugate with the aromatic structure of lignin, enhancing the component compatibility and inhibiting the migration of the plasticizer; the epoxy groups of epoxidized soybean oil crosslink with cellulose hydroxyl groups through a ring-opening reaction to form a dynamic reversible network, improving the thermal stability while retaining the resilience of the material.

[0038] In some preferred embodiments, the crosslinking agent is glutaraldehyde. Its technical effect lies in that: the aldehyde groups of glutaraldehyde form dynamic imine bonds with cellulose hydroxyl groups to construct a flexible crosslinked network to enhance the resilience of the material.

[0039] In some preferred embodiments, the surface modifier is one or more of stearic acid or nano-silica. Its technical effect lies in that: the long-chain alkyl groups of stearic acid form a low-surface-energy monolayer on the cellulose surface through chemical grafting, generating hydrophobicity; nano-silica constructs a micro-nano rough structure through physical deposition, synergistically enhancing the surface oil-repellent effect and reducing the damage to the filter material caused by fuel penetration.

[0040] The present invention also provides a preparation method for a nanofiber-coated fuel filter material, which specifically includes the following steps:

[0041] (1) Mix the substrate raw materials, perform wet lamination molding, and hot press for drying; dissolve the adhesive layer raw materials in deionized water and mix evenly; dissolve the intermediate layer raw materials in a chloroform / DMF solution and electrospun into a film; mix the nanofiber coating layer raw materials and vacuum filter into a film;

[0042] (2) Coat the adhesive layer on the substrate, stack the substrate, adhesive layer, intermediate layer, and nanofiber coating layer in sequence, and form an integrated structure through gradient hot pressing;

[0043] The composite filter material was immersed in 1% perfluorooctyltriethoxysilane ethanol solution, taken out and dried at 80°C, and cross-linked by ultraviolet radiation to obtain a nanofiber coated fuel filter material.

[0044] In some preferred implementation cases, the hot pressing and drying conditions of the substrate raw material in step (1) are: hot pressing temperature 120-150°C, pressure 5-10MPa, holding time 5-10 minutes, and wet lamination using a 80-120 mesh mold. Its technical effects are: activating components through the synergistic effect of temperature and pressure, promoting physical penetration and chemical bonding between the nano-coating and the substrate, and forming a dense and defect-free composite interface; the mesh number ladder of the mesh mold regulates the directional arrangement of fibers, and optimizes the pore distribution in combination with stress relaxation in the holding stage, balancing high flux and high retention performance. The temperature control range ensures that the crosslinking agent and the surface modifier are fully cured while avoiding thermal degradation of the material, and enhances thermal stability; the low energy consumption characteristics of the wet process and low-temperature hot pressing work together to reduce environmental load.

[0045] In some preferred implementation cases, the electrospinning parameters of the intermediate layer raw material in step (1) are: voltage 18-25 kV, receiving distance 10-20 cm, spinning solution flow rate 0.5-1.5 mL / h. Its technical effect is: the fiber forming process is regulated by the synergistic effect of electric field force and fluid dynamics: the voltage range ensures stable jet stretching to avoid droplet breakage or uneven fiber diameter; the receiving distance optimizes the balance between solvent volatilization and fiber solidification to form a continuous and uniform nano- to submicron-scale fiber network; flow rate control limits excessive solution injection to maintain fiber morphology consistency. This combination of parameters enables the polylactic acid fiber membrane to have high specific surface area, controllable porosity and flexible mechanical properties, which is suitable for efficient fuel filtration.

[0046] In some preferred implementation cases, the mixing process of the nanofiber coating layer in step (1) is stirred at a speed of 2000 to 4000 rpm by a high-speed disperser for 30 to 60 minutes, the vacuum filtration pressure is maintained at -0.08 to -0.1 MPa, and the filtration time is 30 to 90 minutes. The technical effect is: the coating structure is optimized through the synergistic effect of high shear force dispersion and directional desolventization: high-speed stirring breaks the agglomeration of nanofibers and promotes uniform dispersion of components to form a stable colloidal system; vacuum filtration accelerates the directional removal of solvent under negative pressure drive, inducing nanofibers to stack directional along the surface of the filter membrane to form a dense coating with controllable pore gradient. This process achieves efficient oriented arrangement of nanofibers and close integration with the interface through the coupling of physical shear and pressure field regulation, giving the coating layer high mechanical strength, uniform permeability and precise interception.

[0047] In some preferred implementation cases, the coating amount of the adhesive layer in step (2) is 0.6 to 1 g / m 2。Its technical effect is as follows: By precisely controlling the distribution density of the adhesive, a balance is achieved between the interfacial bonding strength and the material permeability. The adhesive fully wets the fiber surface to form a continuous interface, while retaining the natural porous structure and degradability of the nanomaterials, taking into account the mechanical durability and filtration efficiency of the filter medium, and meeting the dual requirements of the fuel filtration system for material function and sustainability.

[0048] In some preferred embodiments, the gradient hot pressing in step (2) is divided into three stages: The first stage has a temperature of 80 °C for 2 minutes; the second stage has a temperature of 145 °C, a pressure of 10 MPa for 10 minutes; the third stage has a temperature of 70 °C for 5 minutes; during the cooling process, the temperature reduction rate is controlled at 5 - 8 °C / min. Its technical effect is as follows: Through the precise matching of temperature, pressure, and time, a stepped regulation of the material properties is achieved: In the first stage, low-temperature preheating softens the constituent materials, promoting the uniform wetting of the fiber interface by the adhesive; in the second stage, high-temperature and high-pressure activate the cross-linking reaction and drive the dense bonding of the nano-coating and the substrate to form a stable composite structure resistant to fuel penetration; in the third stage, gentle cooling combined with controlled-rate cooling inhibits the generation of interfacial microcracks through molecular chain relaxation and stress release. This gradient process strengthens the interfacial bonding strength and thermo-mechanical stability while avoiding material thermal degradation, enabling the filter medium to have high oil pressure resistance, low thermal shrinkage rate, and long-term dimensional stability, meeting the long-term use requirements of the fuel system under high-temperature conditions.

[0049] In some preferred embodiments, the surface of the hot pressing mold in step (2) is provided with a micro-protrusion structure of 50 - 100 μm; nitrogen is introduced during the hot pressing process, and the oxygen content range is 50 - 100 ppm. Its technical effect is to optimize the properties of the nanomaterials through the synergistic effect of physical interface regulation and inert gas: The micro-protrusion structure enhances the interlock between fiber layers through the mechanical biting effect during hot pressing, forming a bionic interface with local stress dispersion, improving the delamination resistance and overall mechanical strength; the high-nitrogen condition inhibits the oxidative degradation and thermal cross-linking side reactions of the nanomaterials at high temperatures, maintaining the chemical stability of natural polymer chains such as cellulose and lignin. The two work together to form controllable micro-textures on the material surface to adapt to fluid dynamic requirements, while avoiding embrittlement or performance degradation caused by high-temperature oxidation, ultimately achieving a comprehensive improvement in the high interfacial bonding strength, heat aging resistance, and long-term working condition stability of the filter medium.

[0050] In some preferred embodiments, the infiltration time in step (3) is 10 - 30 minutes.

[0051] In some preferred embodiments, the ultraviolet irradiation parameters in step (3) are: irradiation wavelength 350 - 380 nm, radiation luminance 40 - 60 mW / cm 2, the irradiation duration is 10 to 20 minutes. Its technical effect lies in: achieving the directional regulation of the properties of nanomaterials through the synergistic effect of photochemistry and energy input: specific wavelengths match the light absorption characteristics of the material components, activating the photoinitiator in the adhesive to generate free radicals or cations, triggering the selective cross-linking of the cellulose and lignin networks; the radiation brightness and duration control the depth of the photoreaction and the cross-linking density, forming a dense protective layer on the surface while retaining the porous structure inside the material. This parameter combination can avoid the decomposition of polymer chains under ultraviolet irradiation, enhance the interfacial bonding strength of the coating layer and the chemical resistance to fuel oil, and at the same time maintain the degradability of the nanomaterials. Specific embodiments

[0053] Comparative example 1

[0054] Prepare fuel filters using the formula and preparation method disclosed in invention patent No. CN113931010B.

[0055] Comparative example 2

[0056] A fiber-coated fuel filter is made from the following raw materials in parts by weight:

[0057] Base material: 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin, 2 parts of γ-glycidoxypropyltrimethoxysilane;

[0058] Adhesive layer: 18 parts of maleic anhydride grafted starch; 8 parts of carboxymethyl chitosan; 3 parts of glycerol;

[0059] Intermediate layer: 55 parts of polylactic acid; 4 parts of epoxidized soybean oil;

[0060] Fiber coating layer: 45 parts of microcrystalline cellulose; 25 parts of chitosan; 5 parts of polydopamine; 5 parts of glutaraldehyde; 3 parts of nano-silica.

[0061] The target fiber-coated fuel filter is prepared according to the following steps:

[0062] (1) Material preparation:

[0063] Base material preparation: Add 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin and 2 parts of γ-glycidoxypropyltrimethoxysilane to deionized water, stir to form a uniform suspension; inject the suspension into an 80-mesh stainless steel mesh mold, preliminarily filter to remove 40% of the water, and then transfer it to a hot press; preheat at 145°C for 3 minutes, apply a pressure of 10 MPa and hold for 10 minutes, and cool to room temperature at a rate of 5°C / min during the cooling stage to form a 0.8-mm-thick base material.

[0064] Intermediate layer preparation: 55 parts of polylactic acid are dissolved in a mixed solvent of chloroform / DMF (volume ratio 7:3), 4 parts of epoxidized soybean oil are added, and magnetic stirring is carried out until completely dissolved. The solution is loaded into a syringe pump, a 25 kV high-voltage power supply is used, the receiving distance is 15 cm, the flow rate is 1.0 mL / h, and a fiber membrane with a thickness of 50 μm is formed on an aluminum foil receiver.

[0065] Fiber coating layer preparation: 45 parts of micron-scale cellulose and 25 parts of chitosan are added to deionized water, and then 5 parts of polydopamine, 5 parts of glutaraldehyde and 3 parts of nano-silica are added. A high-speed disperser is used at 3500 rpm / min and stirred for 45 minutes to form a stable colloid. The mixed solution is poured into a Buchner funnel and vacuum filtered at -0.1 MPa for 60 minutes. After film formation, it is cured with hot air at 60 °C for 2 hours, and the film thickness is 130 μm.

[0066] (2) Hot pressing and compounding:

[0067] 18 parts of maleic anhydride starch, 8 parts of carboxymethyl chitosan, and 3 parts of glycerol are mixed evenly and uniformly coated on the surface of the substrate by spraying, and the coating amount is 0.8 g / m 2 , pre-dried at 50 °C for 10 minutes; stacked in the order of substrate, adhesive layer, intermediate layer and fiber coating layer, and the layer alignment accuracy is ±0.5 mm; gradient hot pressing is carried out. The first stage: preheat at 80 °C for 2 minutes; the second stage: hold the pressure at 145 °C and 10 MPa for 10 minutes to trigger chemical crosslinking; the third stage: slowly cool at 70 °C for 5 minutes, and control the cooling speed (5 °C / min) to 40 °C and then release the pressure.

[0068] (3) Post-treatment:

[0069] The composite filter material is immersed in a 1 wt% ethanol solution of perfluorooctyltriethoxysilane for 20 minutes; dried with circulating hot air at 80 °C for 60 minutes; irradiated with a 365 nm ultraviolet lamp with a radiation brightness of 50 mW / cm 2 , irradiated for 15 minutes to obtain a nanofiber-coated fuel filter material.

[0070] Comparative Example 3 A nanofiber-coated fuel filter material is made from the following raw materials in parts by weight:

[0071] Substrate: 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin, 2 parts of γ-glycidyletheroxypropyltrimethoxysilane;

[0072] Adhesive layer: 18 parts of maleic anhydride grafted starch; 8 parts of carboxymethyl chitosan; 3 parts of glycerol;

[0073] Intermediate layer: 55 parts of polylactic acid; 4 parts of epoxidized soybean oil;

[0074] Nanofiber coating layer: 80 parts of cellulose nanofibers; 25 parts of chitosan; 5 parts of polydopamine; 5 parts of glutaraldehyde; 3 parts of nano-silica.

[0075] The target nanofiber-coated fuel filter media is prepared according to the following steps:

[0076] (1) Material preparation:

[0077] Substrate preparation: Add 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin, and 2 parts of γ-glycidoxypropyltrimethoxysilane to deionized water, stir to form a uniform suspension; inject the suspension into an 80-mesh stainless steel mesh mold, preliminarily press-filter to remove 40% of the water, and then transfer it to a hot press; preheat at 145 °C for 3 minutes, apply a pressure of 10 MPa and hold for 10 minutes, and cool to room temperature at a rate of 5 °C / min during the cooling stage to form a substrate with a thickness of 0.8 mm.

[0078] Intermediate layer preparation: Dissolve 55 parts of polylactic acid in a mixed solvent of chloroform / DMF (volume ratio 7:3), add 4 parts of epoxidized soybean oil, and stir magnetically until completely dissolved: load the solution into an injection pump, use a 25 kV high-voltage power supply, the receiving distance is 15 cm, the flow rate is 1.0 mL / h, and a fiber membrane with a thickness of 50 μm is formed on an aluminum foil receiver.

[0079] Nanofiber coating layer preparation: Add 80 parts of cellulose nanofibers and 25 parts of chitosan to deionized water, then add 5 parts of polydopamine, 5 parts of glutaraldehyde, and 3 parts of nano-silica, use a high-speed disperser at 3500 rpm / min, stir for 45 minutes to form a stable colloid; pour the mixture into a Buchner funnel, filter under a negative pressure of -0.1 MPa for 60 minutes, and cure with hot air at 60 °C for 2 hours after film formation, with a film thickness of 90 μm.

[0080] (2) Hot pressing and compounding:

[0081] Mix 18 parts of maleic anhydride starch, 8 parts of carboxymethyl chitosan, and 3 parts of glycerol evenly, and coat the surface of the substrate evenly by spraying, with a coating amount of 0.8 g / m 2 , pre-dry at 50 °C for 10 minutes; stack the substrate, adhesive layer, intermediate layer, and nanofiber coating layer in sequence, with the alignment accuracy between layers being ±0.5 mm; perform gradient hot pressing, the first stage: preheat at 80 °C for 2 minutes; the second stage: hold at 145 °C and 10 MPa pressure for 10 minutes to trigger chemical crosslinking; the third stage: cool slowly at 70 °C for 5 minutes, and control the cooling rate (5 °C / min) to 40 °C and then release the pressure.

[0082] (3) Post-treatment:

[0083] Immerse the composite filter media in a 1 wt% ethanol solution of perfluorooctyltriethoxysilane for 20 minutes; dry in a circulating hot air at 80 °C for 60 minutes; use a 365 nm ultraviolet lamp with a radiation brightness of 50 mW / cm2 , irradiate for 15 minutes to obtain a nanofiber-coated fuel filter medium.

[0084] Comparative Example 4

[0085] A nanofiber-coated fuel filter medium is made from the following raw materials in parts by weight:

[0086] Base material: 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin, 2 parts of γ-glycidyl ether oxypropyltrimethoxysilane;

[0087] Adhesive layer: 18 parts of maleic anhydride grafted starch; 8 parts of carboxymethyl chitosan; 3 parts of glycerol;

[0088] Intermediate layer: 55 parts of polylactic acid, 4 parts of epoxidized soybean oil;

[0089] Nanofiber coating layer: 20 parts of cellulose nanofibers, 25 parts of chitosan, 5 parts of polydopamine, 5 parts of glutaraldehyde, 3 parts of nano-silica.

[0090] The target nanofiber-coated fuel filter medium is prepared according to the following steps:

[0091] (1) Material preparation:

[0092] Base material preparation: Add 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin and 2 parts of γ-glycidyl ether oxypropyltrimethoxysilane to deionized water, stir to form a uniform suspension; inject the suspension into an 80-mesh stainless steel mesh mold, initially filter under pressure to remove 40% of the water, and then transfer it to a hot press; preheat at 145°C for 3 minutes, apply a pressure of 10 MPa and hold the pressure for 10 minutes, and cool to room temperature at a rate of 5°C / min during the cooling stage to form a base material with a thickness of 0.8 mm.

[0093] Intermediate layer preparation: Dissolve 55 parts of polylactic acid in a mixed solvent of chloroform / DMF (volume ratio 7:3), add 4 parts of epoxidized soybean oil, and stir magnetically until completely dissolved: load the solution into an injection pump, use a 25 kV high-voltage power supply, with a receiving distance of 15 cm and a flow rate of 1.0 mL / h to form a fiber film with a thickness of 50 μm on an aluminum foil receiver.

[0094] Nanofiber coating layer preparation: Add 20 parts of cellulose nanofibers and 25 parts of chitosan to deionized water, then add 5 parts of polydopamine, 5 parts of glutaraldehyde and 3 parts of nano-silica, use a high-speed disperser at 3500 rpm / min and stir for 45 minutes to form a stable colloid; pour the mixture into a Buchner funnel and filter under a negative pressure of -0.1 MPa for 60 minutes, and cure with hot air at 60°C for 2 hours after forming the film, with a film thickness of 80 μm.

[0095] (2) Hot pressing and compounding:

[0096] Mix 18 parts of maleic anhydride starch, 8 parts of carboxymethyl chitosan, and 3 parts of glycerol evenly, and coat the surface of the substrate evenly by spraying method, with a coating amount of 0.8 g / m 2 , pre-dry at 50 °C for 10 minutes; stack in the order of substrate, adhesive layer, intermediate layer, and nanofiber coating layer, with the interlayer alignment accuracy of ±0.5 mm; perform gradient hot pressing. The first stage: preheat at 80 °C for 2 minutes; the second stage: hold the pressure at 145 °C and 10 MPa for 10 minutes to trigger chemical cross-linking; the third stage: slowly cool at 70 °C for 5 minutes, and control the cooling rate (5 °C / min) to 40 °C and then release the pressure.

[0097] (3) Post-treatment:

[0098] Immerse the composite filter material in a 1 wt% ethanol solution of perfluorooctyltriethoxysilane for 20 minutes; dry in circulating hot air at 80 °C for 60 minutes; use a 365 nm ultraviolet lamp with a radiation brightness of 50 mW / cm 2 , irradiate for 15 minutes to obtain a nanofiber-coated fuel filter material.

[0099] Comparative Example 5

[0100] Substrate: 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin, 2 parts of γ-glycidyletheroxypropyltrimethoxysilane;

[0101] Adhesive layer: 18 parts of maleic anhydride grafted starch; 8 parts of carboxymethyl chitosan; 3 parts of glycerol;

[0102] Intermediate layer: 55 parts of polylactic acid; 4 parts of epoxidized soybean oil;

[0103] Nanofiber coating layer: 45 parts of cellulose nanofibers; 10 parts of chitosan; 5 parts of polydopamine; 5 parts of glutaraldehyde; 3 parts of nano-silica.

[0104] The target nanofiber-coated fuel filter material is prepared according to the following steps:

[0105] (1) Material preparation:

[0106] Substrate preparation: Add 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin, and 2 parts of γ-glycidyletheroxypropyltrimethoxysilane to deionized water, stir to form a uniform suspension; inject the suspension into an 80-mesh stainless steel mesh mold, preliminarily filter to remove 40% of the moisture, and then transfer it to a hot press; preheat at 145 °C for 3 minutes, apply a pressure of 10 MPa and hold for 10 minutes, and cool to room temperature at a rate of 5 °C / min during the cooling stage to form a substrate with a thickness of 0.8 mm.

[0107] Intermediate layer preparation: 55 parts of polylactic acid are dissolved in a mixed solvent of chloroform / DMF (7:3 volume ratio), 4 parts of epoxidized soybean oil are added, and magnetic stirring is carried out until completely dissolved. The solution is loaded into a syringe pump, a 25 kV high-voltage power supply is used, the receiving distance is 15 cm, the flow rate is 1.0 mL / h, and a fiber membrane with a thickness of 50 μm is formed on an aluminum foil receiver.

[0108] Preparation of nanofiber coating layer: 45 parts of cellulose nanofibers and 10 parts of chitosan are added to deionized water, then 5 parts of polydopamine, 5 parts of glutaraldehyde and 3 parts of nano-silica are added, and a high-speed disperser is used at 3500 rpm for 45 minutes to form a stable colloid. The mixture is poured into a Buchner funnel and filtered under a negative pressure of -0.1 MPa for 60 minutes. After film formation, it is cured with hot air at 60 °C for 2 hours, and the film thickness is 75 μm.

[0109] (2) Hot pressing and compounding:

[0110] 18 parts of maleic anhydride starch, 8 parts of carboxymethyl chitosan and 3 parts of glycerol are mixed evenly and uniformly coated on the surface of the substrate by spraying, and the coating amount is 0.8 g / m 2 , and pre-dried at 50 °C for 10 minutes; stack the substrate, adhesive layer, intermediate layer and nanofiber coating layer in sequence, and the layer alignment accuracy is ±0.5 mm; perform gradient hot pressing. The first stage: preheat at 80 °C for 2 minutes; the second stage: keep the pressure at 145 °C and 10 MPa for 10 minutes to trigger chemical cross-linking; the third stage: slow cooling at 70 °C for 5 minutes, and cool at a controlled speed (5 °C / min) to 40 °C and then release the pressure.

[0111] (3) Post-treatment:

[0112] The composite filter material is immersed in a 1 wt% ethanol solution of perfluorooctyltriethoxysilane for 20 minutes; dried with circulating hot air at 80 °C for 60 minutes; irradiated with a 365 nm ultraviolet lamp with a radiation brightness of 50 mW / cm 2 , and irradiated for 15 minutes to obtain a nanofiber-coated fuel filter material.

[0113] Comparative Example 6

[0114] Substrate: 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin, 2 parts of γ-glycidoxypropyltrimethoxysilane;

[0115] Adhesive layer: 18 parts of maleic anhydride grafted starch; 8 parts of carboxymethyl chitosan; 3 parts of glycerol;

[0116] Intermediate layer: 55 parts of polylactic acid; 4 parts of epoxidized soybean oil;

[0117] Nanofiber coating layer: 45 parts of cellulose nanofibers; 40 parts of chitosan; 5 parts of polydopamine; 5 parts of glutaraldehyde; 3 parts of nano-silica.

[0118] The target nanofiber-coated fuel filter media is prepared according to the following steps:

[0119] (1) Material preparation:

[0120] Substrate preparation: Add 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin, and 2 parts of γ-glycidyl ether oxypropyltrimethoxysilane to deionized water, stir to form a homogeneous suspension; inject the suspension into an 80-mesh stainless steel mesh mold, preliminarily press-filter to remove 40% of the moisture, and then transfer it to a hot press; preheat at 145 °C for 3 minutes, apply a pressure of 10 MPa and hold for 10 minutes, and cool to room temperature at a rate of 5 °C / min during the cooling stage to form a substrate with a thickness of 0.8 mm.

[0121] Intermediate layer preparation: Dissolve 55 parts of polylactic acid in a mixed solvent of chloroform / DMF (volume ratio of 7:3), add 4 parts of epoxidized soybean oil, and stir magnetically until completely dissolved: load the solution into an injection pump, use a 25 kV high-voltage power supply, a receiving distance of 15 cm, and a flow rate of 1.0 mL / h to form a fiber membrane with a thickness of 50 μm on an aluminum foil receiver.

[0122] Nanofiber coating layer preparation: Add 45 parts of cellulose nanofibers and 40 parts of chitosan to deionized water, then add 5 parts of polydopamine, 5 parts of glutaraldehyde, and 3 parts of nano-silica, and use a high-speed disperser at 3500 rpm / min to stir for 45 minutes to form a stable colloid; pour the mixture into a Buchner funnel and perform negative pressure filtration at -0.1 MPa for 60 minutes, and cure with hot air at 60 °C for 2 hours after forming the film, with a film thickness of 100 μm.

[0123] (2) Hot pressing and compounding:

[0124] Mix 18 parts of maleic anhydride starch, 8 parts of carboxymethyl chitosan, and 3 parts of glycerol evenly, and coat the surface of the substrate evenly by spraying, with a coating amount of 0.8 g / m 2 , and pre-dry at 50 °C for 10 minutes; stack the substrate, adhesive layer, intermediate layer, and nanofiber coating layer in sequence, with the layer alignment accuracy of ±0.5 mm; perform gradient hot pressing, the first stage: preheat at 80 °C for 2 minutes; the second stage: hold at 145 °C and 10 MPa for 10 minutes to trigger chemical cross-linking; the third stage: slowly cool at 70 °C for 5 minutes, and cool at a controlled rate (5 °C / min) to 40 °C and then release the pressure.

[0125] (3) Post-treatment:

[0126] Immerse the composite filter media in a 1 wt% ethanol solution of perfluorooctyltriethoxysilane for 20 minutes; dry with circulating hot air at 80 °C for 60 minutes; irradiate with a 365 nm ultraviolet lamp with a radiation brightness of 50 mW / cm 2 , and irradiate for 15 minutes to obtain the nanofiber-coated fuel filter media.

[0127] Example 1

[0128] A nanofiber-coated fuel filter material is made from the following raw materials by weight:

[0129] Base material: 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin, 2 parts of γ-glycidyl ether oxypropyltrimethoxysilane;

[0130] Adhesive layer: 18 parts of maleic anhydride grafted starch; 8 parts of carboxymethyl chitosan; 3 parts of glycerol;

[0131] Intermediate layer: 55 parts of polylactic acid; 4 parts of epoxidized soybean oil;

[0132] Nanofiber coating layer: 45 parts of cellulose nanofibers; 25 parts of chitosan; 5 parts of polydopamine; 5 parts of glutaraldehyde; 3 parts of nano-silica.

[0133] The target nanofiber-coated fuel filter material is prepared according to the following steps:

[0134] (1) Material preparation:

[0135] Base material preparation: Add 75 parts of bamboo fiber microfibrils, 8 parts of nano-lignin and 2 parts of γ-glycidyl ether oxypropyltrimethoxysilane into deionized water, stir to form a uniform suspension; inject the suspension into an 80-mesh stainless steel mesh mold, preliminarily filter to remove 40% of the water, and then transfer it to a hot press; preheat at 145°C for 3 minutes, apply a pressure of 10 MPa and hold for 10 minutes, and cool to room temperature at a rate of 5°C / min during the cooling stage to form a base material with a thickness of 0.8 mm.

[0136] Intermediate layer preparation: Dissolve 55 parts of polylactic acid in a mixed solvent of chloroform / DMF (volume ratio of 7:3), add 4 parts of epoxidized soybean oil, and stir magnetically until completely dissolved: load the solution into a syringe pump, use a 25 kV high-voltage power supply, with a receiving distance of 15 cm and a flow rate of 1.0 mL / h to form a fiber membrane with a thickness of 50 μm on an aluminum foil receiver.

[0137] Nanofiber coating layer preparation: Add 45 parts of cellulose nanofibers and 25 parts of chitosan into deionized water, then add 5 parts of polydopamine, 5 parts of glutaraldehyde and 3 parts of nano-silica, use a high-speed disperser at 3500 rpm / min and stir for 45 minutes to form a stable colloid; pour the mixed liquid into a Buchner funnel and filter under a negative pressure of -0.1 MPa for 60 minutes, and cure with hot air at 60°C for 2 hours after forming the film, with a film thickness of 80 μm.

[0138] (2) Hot press lamination:

[0139] Mix 18 parts of maleic anhydride starch, 8 parts of carboxymethyl chitosan and 3 parts of glycerol evenly, and coat the surface of the base material evenly by spraying, with a coating amount of 0.8 g / m 2, pre-dry at 50°C for 10 minutes; stack in the order of substrate, adhesive layer, intermediate layer, and nanofiber coating layer, with the layer alignment accuracy of ±0.5 mm; perform gradient hot pressing. The first stage: preheat at 80°C for 2 minutes; the second stage: hold the pressure at 145°C and 10 MPa for 10 minutes to trigger chemical crosslinking; the third stage: cool slowly at 70°C for 5 minutes, and cool at a controlled rate (5°C / min) to 40°C and then release the pressure.

[0140] (3) Post-treatment:

[0141] Immerse the composite filter medium in a 1 wt% ethanol solution of perfluorooctyltriethoxysilane for 20 minutes; dry in circulating hot air at 80°C for 60 minutes; use a 365 nm ultraviolet lamp with a radiation brightness of 50 mW / cm 2 , irradiate for 15 minutes to obtain the nanofiber-coated fuel filter medium.

[0142] Example 2

[0143] A nanofiber-coated fuel filter medium is made from the following raw materials by weight:

[0144] Substrate: 70 parts of bamboo fiber microfibrils, 6 parts of nano-lignin, 3 parts of γ-methacryloxypropyltrimethoxysilane;

[0145] Adhesive layer: 15 parts of maleic anhydride grafted starch; 9 parts of carboxymethyl chitosan; 4 parts of citrate ester;

[0146] Intermediate layer: 50 parts of polylactic acid; 3 parts of glycerol;

[0147] Nanofiber coating layer: 40 parts of cellulose nanofibers; 28 parts of chitosan; 4 parts of polydopamine; 6 parts of glutaraldehyde; 2 parts of nano-silica.

[0148] The target nanofiber-coated fuel filter medium is prepared according to the following steps:

[0149] (1) Material preparation:

[0150] Substrate preparation: Add 70 parts of bamboo fiber microfibrils, 6 parts of nano-lignin, and 3 parts of γ-methacryloxypropyltrimethoxysilane to deionized water, stir to form a uniform suspension; inject the suspension into a 100-mesh stainless steel mesh mold, preliminarily filter to remove 40% of the water, and then transfer it to a hot press; preheat at 145°C for 3 minutes, apply a pressure of 10 MPa and hold for 10 minutes, and cool to room temperature at a rate of 5°C / min during the cooling stage to form a substrate with a thickness of 0.7 mm.

[0151] Intermediate layer preparation: 50 parts of polylactic acid were dissolved in a mixed solvent of chloroform / DMF (volume ratio 7:3), 3 parts of glycerol were added, and magnetic stirring was carried out until completely dissolved. The solution was loaded into a syringe pump, a 25 kV high-voltage power supply was used, the receiving distance was 18 cm, the flow rate was 0.8 mL / h, and a fiber membrane with a thickness of 40 μm was formed on an aluminum foil receiver.

[0152] Preparation of nanofiber coating layer: 40 parts of cellulose nanofibers and 28 parts of chitosan were added to deionized water, and then 4 parts of polydopamine, 6 parts of glutaraldehyde and 2 parts of nano-silica were added. Stirring was carried out with a high-speed disperser (3500 rpm) for 45 minutes to form a stable colloid; the mixed solution was poured into a Buchner funnel and vacuum filtered at -0.09 MPa for 75 minutes. After film formation, it was cured with hot air at 60 °C for 2 hours, and the film thickness was 80 μm.

[0153] (2) Hot pressing and compounding:

[0154] A mold with 80 μm micro-protrusions on the surface was used, and the substrate was placed on it; 15 parts of maleic anhydride grafted starch, 9 parts of carboxymethyl chitosan, and 4 parts of citric acid ester were mixed evenly and uniformly coated on the surface of the substrate by spraying, and the coating amount was 0.8 g / m 2 , pre-dried at 50 °C for 10 minutes; stacked in the order of substrate, adhesive layer, intermediate layer and nanofiber coating layer, and the layer alignment accuracy was ±0.5 mm; gradient hot pressing was carried out. The first stage: preheated at 80 °C for 2 minutes; the second stage: held at 145 °C and 10 MPa for 12 minutes; the third stage: slowly cooled at 70 °C for 5 minutes, and cooled at a controlled speed (5 °C / min) to 40 °C and then depressurized.

[0155] (3) Post-treatment:

[0156] The composite filter material was immersed in a 1 wt% ethanol solution of perfluorooctyltriethoxysilane for 20 minutes; dried with circulating hot air at 80 °C for 60 minutes; irradiated with a 370 nm ultraviolet lamp, the radiation brightness was 60 mW / cm 2 , and the irradiation time was 20 minutes to obtain a nanofiber-coated fuel filter material.

[0157] Example 3

[0158] A nanofiber-coated fuel filter material is made from the following raw materials in parts by weight:

[0159] Substrate: 65 parts of bamboo fiber microfibrils, 9 parts of nano-lignin, 2.5 parts of γ-aminopropyltriethoxysilane;

[0160] Adhesive layer: 12 parts of maleic anhydride grafted starch; 10 parts of carboxymethyl chitosan; 5 parts of epoxy soybean oil;

[0161] Intermediate layer: 60 parts of polylactic acid; 2 parts of glycerol;

[0162] Nanofiber coating layer: 50 parts of cellulose nanofibers; 20 parts of chitosan; 6 parts of polydopamine; 4 parts of glutaraldehyde; 2 parts of nano-silica; 2 parts of stearic acid.

[0163] The target nanofiber-coated fuel filter media is prepared according to the following steps:

[0164] (1) Material preparation:

[0165] Substrate preparation: Add 65 parts of bamboo fiber microfibrils, 9 parts of nano-lignin and 2.5 parts of γ-methacryloxypropyltrimethoxysilane into deionized water, stir to form a uniform suspension; inject the suspension into a 100-mesh stainless steel mesh mold, preliminarily press-filter to remove 40% of the water, and then transfer it to a hot press; preheat at 145 °C for 3 minutes, apply a pressure of 10 MPa and hold for 10 minutes, and cool to room temperature at a rate of 5 °C / min during the cooling stage to form a substrate with a thickness of 0.7 mm.

[0166] Intermediate layer preparation: Dissolve 60 parts of polylactic acid in a mixed solvent of chloroform / DMF (volume ratio 7:3), add 2 parts of glycerol, and stir magnetically until completely dissolved; load the solution into an injection pump, use a 25 kV high-voltage power supply, a receiving distance of 18 cm, and a flow rate of 0.8 mL / h to form a fiber membrane with a thickness of 40 μm on an aluminum foil receiver.

[0167] Nanofiber coating layer preparation: Add 50 parts of cellulose nanofibers and 20 parts of chitosan into deionized water, then add 6 parts of polydopamine, 4 parts of glutaraldehyde, 2 parts of nano-silica and 2 parts of stearic acid, use a high-speed disperser at 3500 rpm / min and stir for 45 minutes to form a stable colloid; pour the mixture into a Buchner funnel, carry out negative pressure filtration at -0.09 MPa for 75 minutes, and cure with hot air at 60 °C for 2 hours after forming the film, with a film thickness of 80 μm.

[0168] (2) Hot pressing and lamination:

[0169] Use a mold with 80-μm micro-protrusions on the surface, and place the substrate on it; mix 12 parts of maleic anhydride grafted starch, 10 parts of carboxymethyl chitosan and 5 parts of epoxy soybean oil evenly, and coat the surface of the substrate evenly by spraying, with a coating amount of 0.8 g / m 2 , pre-dry at 50 °C for 10 minutes; stack the substrate, adhesive layer, intermediate layer and nanofiber coating layer in sequence, with an alignment accuracy of ±0.5 mm between layers; carry out gradient hot pressing, the first stage: preheat at 80 °C for 2 minutes; the second stage: hold at 145 °C and 10 MPa pressure for 12 minutes; the third stage: slowly cool at 70 °C for 5 minutes, and control the cooling rate (5 °C / min) to 40 °C and then release the pressure.

[0170] (3) Post-treatment:

[0171] The composite filter medium was immersed in a 1 wt% ethanol solution of perfluorooctyltriethoxysilane for 20 minutes; dried in circulating hot air at 80 °C for 60 minutes; irradiated with a 370 nm ultraviolet lamp with a radiant luminance of 60 mW / cm 2 , and irradiated for 20 minutes to obtain a nanofiber-coated fuel filter medium.

[0172] The performance of the oil filter media prepared in Comparative Example and Examples 1-3 was tested, and the test results are shown in Table 1.

[0173] Table 1

[0174] According to the content of Table 1, it can be concluded that the nanofiber-coated fuel filter medium prepared by the present invention exhibits significant technical advantages.

[0175] Comparative Example 1 is a prior art, with a retention efficiency of only 89%, a maximum pore size of up to 80 μm, and a dry burst strength of 366 kPa, indicating that traditional filter media cannot achieve high-precision filtration due to the lack of a nanoscale structure; in Comparative Example 2, after replacing cellulose nanofibers with micron-sized cellulose, the film layer thickness increased sharply to 1020 μm, and the air permeability reached 105 L / m 2 ·s, but the retention efficiency was only 91%, proving that micron-sized fibers are difficult to form a dense network, resulting in a decline in filtration performance; in Comparative Example 3, due to an excessive amount of cellulose nanofibers, the air permeability dropped sharply to 60 L / m 2 ·s, and the retention efficiency was only 92.2%, indicating that the excessive fiber accumulation hinders effective crosslinking instead; in Comparative Example 4, due to insufficient cellulose content, the maximum pore size increased to 54 μm, and the filtration accuracy decreased to 10 μm, verifying the key role of fiber content in pore size control; in Comparative Example 5, an excessive amount of chitosan led to a sharp reduction in air permeability to 70 L / m 2 ·s, and the retention efficiency was only 90.1%, reflecting that excessive chitosan will damage the pore structure of the coated film layer; in Comparative Example 6, due to insufficient chitosan, although the air permeability reached 110 L / m 2 ·s, but the retention efficiency was only 91.5%, indicating that chitosan is indispensable for adhering nanofibers and improving the retention efficiency.

[0176] In the examples of the present invention, through precise control of the synergistic ratio, combined with the gradient hot pressing and ultraviolet curing processes, the retention efficiency was successfully increased to over 99%, the maximum pore size was reduced to 41 μm, and the dry burst strength reached over 510 kPa. The nanofiber-coated film layer forms a dense network structure under the action of negative pressure filtration and polydopamine crosslinking, which not only ensures a filtration accuracy of <5 μm, but also, through the composite strengthening of the bamboo fiber substrate and epoxidized soybean oil, stabilizes the air permeability at 87 ± 2 L / m 2 ·s.

[0177] In summary, through the multi-scale structure design of the nanofiber coating layer, the present invention realizes the fine regulation of pore size, greatly improves the filtration accuracy and interception efficiency while maintaining high air permeability; due to the synergistic strengthening effect of the bamboo fiber substrate and the adhesive layer, the bursting strength of the material is significantly improved compared with the comparative example; compared with the glass fiber-based fuel filter material, the present invention adopts a biological nano raw material system, avoiding the potential hazards of glass dust to human health and the ecological environment.

[0178] Unless otherwise specified, the raw materials and equipment used in the present invention are all common raw materials and equipment in the art; unless otherwise specified, the methods used in the present invention are all conventional methods in the art. The above description is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change and equivalent transformation made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A nanofiber-coated fuel filter medium, characterized in that It includes a substrate, an adhesive layer, an intermediate layer, and a nanofiber coating layer. Each layer is composed of the following raw materials in parts by weight: The substrate includes: 60 - 80 parts of bamboo fiber microfibrils; 5 - 10 parts of nano-lignin; 1 - 3 parts of coupling agent; The adhesive layer includes: 10 - 20 parts of maleic anhydride grafted starch; 6 - 10 parts of carboxymethyl chitosan; 2 - 5 parts of plasticizer; The intermediate layer includes: 40 - 60 parts of polylactic acid; 2 - 5 parts of plasticizer; The nanofiber coating layer includes: 30 - 50 parts of cellulose nanofibers; 20 - 30 parts of chitosan; 3 - 6 parts of polydopamine; 3 - 6 parts of crosslinking agent; 1 - 4 parts of surface modifier.

2. The nanofiber-coated fuel filter medium according to claim 1, characterized in that, The diameter of the bamboo fiber microfibrils is 5 - 15μm; the diameter of the nano-lignin is 50 - 200nm; the diameter of the cellulose nanofibers is 20 - 50nm.

3. The nanofiber-coated fuel filter medium according to claim 1, wherein The coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidyletheroxypropyltrimethoxysilane, or γ-methacryloxypropyltrimethoxysilane.

4. The nanofiber-coated fuel filter medium according to claim 1, wherein The plasticizer is one or more of glycerol, citrate ester, or epoxidized soybean oil.

5. The nanofiber-coated fuel filter medium according to claim 1, wherein The crosslinking agent is glutaraldehyde.

6. The nanofiber-coated fuel filter medium according to claim 1, wherein The surface modifier is one or more of stearic acid or nano-silica.

7. A method for preparing the nanofiber-coated fuel filter medium according to any one of claims 1 to 6, characterized in that, It includes the following steps: (1) Mix the substrate raw materials, form by wet lamination, and hot press and dry; dissolve the adhesive layer raw materials in deionized water and mix evenly; dissolve the intermediate layer raw materials in a chloroform / DMF solution and electrospin to form a film; mix the nanofiber coating layer raw materials and vacuum filter to form a film; (2) Coat the adhesive layer on the substrate, stack the substrate, adhesive layer, intermediate layer, and nanofiber coating layer in sequence, and form an integrated structure by gradient hot pressing; (3) Immerse the composite filter material in a 1wt% ethanol solution of perfluorooctyltriethoxysilane, take it out and dry it, and crosslink by ultraviolet irradiation to obtain a nanofiber-coated fuel filter material.

8. The preparation method according to claim 7, characterized in that, The hot press drying conditions of the substrate raw materials in step (1): hot press temperature 120 - 150°C, pressure 5 - 10MPa, pressure holding time 5 - 10 minutes, and wet lamination is formed using an 80 - 120 mesh screen mold; the electrospinning parameters of the intermediate layer raw materials: voltage 18 - 25kV, receiving distance 10 - 20cm, spinning solution flow rate 0.5 - 1.5mL / h; the mixing process of the nanofiber coating layer is stirred at a speed of 2000 - 4000rpm for 30 - 60 minutes using a high-speed disperser, the vacuum filtration pressure is maintained at -0.08 - -0.1MPa, and the filtration time is 30 - 90 minutes.

9. The preparation method according to claim 7, characterized in that, The coating amount of the adhesive layer in step (2) is 0.6 to 1 g / m 2 ; The gradient hot pressing is divided into three stages: the first stage is at a temperature of 80°C for a duration of 2 minutes; The temperature in the second stage is 145°C, the pressure is 10MPa for 10min; in the third stage, the temperature is 70°C for 5min; the surface of the hot press mold is provided with a micro-protrusion structure of 50 - 100μm; nitrogen is introduced during the hot pressing process, the oxygen content range is 50 - 100ppm, and the temperature reduction rate during the cooling process is 5 - 8°C / min.

10. The preparation method according to any one of claims 7 to 9, characterized in that, The infiltration time in step (3) is 10 to 30 minutes; the drying temperature is 70 to 90 °C, and the drying time is 30 to 90 minutes; the ultraviolet irradiation parameters are: irradiation wavelength 350 to 380 nm, radiant luminance 40 to 60 mW / cm 2 , and the irradiation duration is 10 to 20 minutes.

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