A filter material, its preparation and use

Abstract

The application provides a filtering material and a preparation method and application thereof, relates to the technical field of filtering materials, and the filtering material comprises a first filter paper layer and a second filter paper layer; the average pore diameter of the first filter paper layer is smaller than that of the second filter paper layer; the first filter paper layer comprises a first fiber component and a reinforcing agent; the fiber component comprises micro-fiber glass cotton, alkali-free short-cut filaments and kapok fiber mercerized pulp; the second filter paper layer comprises a second fiber component and a reinforcing modifier; the second fiber component comprises micro-fiber glass cotton, alkali-free short-cut filaments and chemical fibers; and the reinforcing modifier comprises the reinforcing agent and a waterproof and oil-proof agent. The filtering material has a large oil absorption capacity and a high oil-gas separation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of filter material technology, and specifically relates to a filter material, its preparation method, and its application. Background Technology

[0002] When a fuel engine is running, the high-pressure combustible mixture and burned gas in the cylinder combustion chamber leak into the crankcase through the gap between the piston assembly and the cylinder. The accumulation of the oil-gas mixture increases the crankcase pressure, causing more engine oil to enter the combustion chamber, which further increases oil consumption and exhaust emissions, seriously affecting the engine's service life and causing excessive exhaust emissions.

[0003] Currently, oil droplets and gas in the oil-gas mixture are typically separated by adding an oil-gas separator to the crankcase ventilation system. However, most of the filter materials used in existing oil-gas separators suffer from low oil absorption capacity and low oil-gas separation efficiency.

[0004] Therefore, there is an urgent need to provide a filter material with high oil absorption capacity and high oil-gas separation efficiency. Summary of the Invention

[0005] To address the problems of low oil absorption capacity and low oil-gas separation efficiency in existing filter materials, this invention provides a filter material, its preparation method, and its application. The filter material provided by this invention has a large oil absorption capacity and high oil-gas separation efficiency, which can meet the requirements of engine for oil-gas separation.

[0006] In a first aspect, the present invention provides a filter material comprising a first filter paper layer and a second filter paper layer; wherein the average pore size of the first filter paper layer is smaller than the average pore size of the second filter paper layer.

[0007] The first filter paper layer comprises a first fiber component and a reinforcing agent; the first fiber component comprises microfiber glass wool, alkali-free chopped strands, and kapok fiber photopolymerized pulp;

[0008] The second filter paper layer comprises a second fiber component and a reinforcing modifier; the second fiber component comprises microfiber glass wool, alkali-free chopped strands, and chemical fibers; the reinforcing modifier comprises a reinforcing agent and a waterproof and oil-repellent agent.

[0009] Preferably, the first filter paper layer comprises 90-96% by mass of a first fiber component and 4-10% by mass of a reinforcing agent; the first fiber component comprises 55-70% by mass of microfiber glass wool, 10-20% by mass of alkali-free chopped strands and 20-25% by mass of kapok fiber mercerized pulp.

[0010] Preferably, the second filter paper layer comprises 90-96% by mass of a second fiber component and 4-10% by mass of a reinforcing modifier; the second fiber component comprises 60-75% by mass of microfiber glass wool, 10-20% by mass of alkali-free chopped strands and 15-20% by mass of chemical fibers; and the mass ratio of the reinforcing modifier to the waterproof and oil-repellent agent in the reinforcing modifier is 40:(1-5).

[0011] Preferably, the mass ratio of the first filter paper layer to the second filter paper layer is (1-2):1;

[0012] The average pore size of the first filter paper layer is 4–6 μm, and the average pore size of the second filter paper layer is 8–12 μm.

[0013] Preferably, the microfiber glass wool has a tapping degree of 14–49°SR and a diameter of 0.5–5 μm.

[0014] The diameter of the alkali-free short shredded wire is 6-8 μm;

[0015] The degree of dissociation of the kapok fiber filament photochemical pulp is 15-25°SR;

[0016] The chemical fiber is a bicomponent fiber, preferably CO-PET / PET fiber.

[0017] Secondly, the present invention provides a method for preparing the filter material described in the first aspect, the method comprising the following steps:

[0018] S1. Disperse microfiber glass wool, alkali-free chopped filaments and kapok fiber photochemical pulp in an acidic solution to obtain a first pulp, and subject the first pulp to a first pulping and web-making process and a first vacuum dewatering and forming process to obtain a first wet paper web. Then, use a reinforcing agent to perform a first reinforcing modification treatment on the first wet paper web to obtain a first reinforced modified wet paper web.

[0019] S2. Microfiber glass wool, alkali-free chopped strands, and chemical fibers are dispersed in an acidic solution to obtain a second slurry. The second slurry is then subjected to a second slurry washing and web forming, followed by a second vacuum dewatering and forming process to obtain a second wet paper web. The second wet paper web is then subjected to a second reinforcement modification treatment using a reinforcement modifier to obtain a second reinforced modified wet paper web. The reinforcement modifier includes a reinforcement agent and a waterproof and oil-resistant agent.

[0020] S3. After bonding the first reinforced modified wet paper web and the second reinforced modified wet paper web together, a third vacuum dehydration molding process is performed to obtain a composite wet paper web;

[0021] S4. The composite wet paper web is dried and cured to obtain the filter material.

[0022] Preferably, the pH of the acidic solution is 2 to 3.5;

[0023] The sum of the mass of the microfiber glass wool, alkali-free chopped filaments, and kapok fiber photochemical pulp accounts for 0.5 to 1.5% of the total mass of the first pulp.

[0024] The sum of the mass of the microfiber glass wool, alkali-free chopped strands, and chemical fibers accounts for 0.5 to 1.5% of the total mass of the second slurry.

[0025] Preferably, the online concentration of the first slurry is 0.05-0.15%;

[0026] The online concentration of the second slurry is 0.1–0.2%; and / or

[0027] The vacuum degree of the first vacuum dehydration molding is greater than that of the second vacuum dehydration molding; preferably, the vacuum degree of the first vacuum dehydration molding is 0.025-0.03 MPa; and the vacuum degree of the second vacuum dehydration molding is 0.02-0.025 MPa.

[0028] Preferably, the vacuum degree of the third vacuum dehydration molding is greater than that of the first vacuum dehydration molding; more preferably, the vacuum degree of the third vacuum dehydration molding is 0.04–0.048 MPa; and / or

[0029] The drying and curing process includes a first stage drying and curing process, a second stage drying and curing process, and a third stage drying and curing process; the temperature of the first stage drying and curing process is 40-60℃, the temperature of the second stage drying and curing process is 130-140℃, and the temperature of the third stage drying and curing process is 150-160℃.

[0030] Thirdly, the present invention provides the application of the filter material described in the first aspect in engine oil-gas separation.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] This invention improves the oil absorption capacity of the filter material by introducing mercerized kapok fiber pulp (kapok fiber after mercerization treatment), which has a hollow structure, smooth fiber surface, and strong oil adsorption, into the first filter paper layer. A water- and oil-repellent agent is introduced into the second filter paper layer to enhance the water- and oil-repellent properties of the filter material, effectively preventing secondary entrainment of oil droplets. The average pore size of the first filter paper layer is smaller than that of the second filter paper layer. When the oil-gas mixture enters the filter material through the pores of the first filter paper layer, it aggregates and enlarges, thus better adsorbing oil droplets within the filter material. Simultaneously, the gradient structure with increased pore size increases the air permeability of the filter material, reduces filtration resistance, and facilitates gas permeation. The filter material of this invention has a large oil absorption capacity and high oil-gas separation efficiency, meeting the requirements of engine oil-gas separation. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] In a first aspect, the present invention provides a filter material comprising a first filter paper layer and a second filter paper layer; wherein the average pore size of the first filter paper layer is smaller than the average pore size of the second filter paper layer.

[0035] The first filter paper layer comprises a first fiber component and a reinforcing agent; the first fiber component comprises microfiber glass wool, alkali-free chopped strands, and kapok fiber photopolymerized pulp;

[0036] The second filter paper layer comprises a second fiber component and a reinforcing modifier; the second fiber component comprises microfiber glass wool, alkali-free chopped strands, and chemical fibers; the reinforcing modifier comprises a reinforcing agent and a waterproof and oil-repellent agent.

[0037] It should be noted that, during use, one side of the first filter paper layer of the filter material of this invention is the inflow surface, and one side of the second filter paper layer is the outflow surface. The kapok fiber mercerized pulp of this invention can be purchased directly or prepared in-house; specifically, the in-house kapok fiber mercerized pulp is obtained by mercerizing kapok fibers; this is achieved by soaking kapok fibers in a 1 mol / L NaOH solution at 50°C for 60 minutes, followed by washing and dehydration.

[0038] This invention improves the oil absorption capacity of the filter material by introducing mercerized kapok fiber pulp (kapok fiber after mercerization treatment), which has a hollow structure, smooth fiber surface, and strong oil adsorption, into the first filter paper layer. A water- and oil-repellent agent is introduced into the second filter paper layer to enhance the water- and oil-repellent properties of the filter material, effectively preventing secondary entrainment of oil droplets. The average pore size of the first filter paper layer is smaller than that of the second filter paper layer. When the oil-gas mixture enters the filter material through the pores of the first filter paper layer, it aggregates and enlarges, thus better adsorbing oil droplets within the filter material. Simultaneously, the gradient structure with increased pore size increases the air permeability of the filter material, reduces filtration resistance, and facilitates gas permeation. The filter material of this invention has a large oil absorption capacity and high oil-gas separation efficiency, meeting the requirements of engine oil-gas separation.

[0039] In addition, the surface of the mercerized pulp of kapok fiber is smooth and has good air permeability, which will not affect the filtration performance of the filter material.

[0040] According to some preferred embodiments, the first filter paper layer comprises 90-96% (e.g., 90%, 91%, 92%, 93%, 94%, 95%, or 96%) of a first fiber component by mass fraction and 4-10% (e.g., 90%, 91%, 92%, 93%, 94%, 95%, or 96%) of a reinforcing agent; the first fiber component comprises 55-70% (e.g., 55%, 56%, 58%, 60%, 62%, 65%, 66%, 68%, or 70%) of microfiber glass wool by mass fraction, 10-20% (e.g., 10%, 12%, 14%, 16%, 18%, or 20%) of alkali-free chopped strands, and 20-25% (e.g., 20%, 21%, 22%, 23%, 24%, or 25%) of kapok fiber mercerized pulp by mass fraction. The inventors discovered that within the above-mentioned range, the styrochemical pulp of kapok fiber is beneficial for the adsorption of oil. However, if the amount of styrochemical pulp of kapok fiber is too large, it will reduce the air permeability of the filter material, increase the filtration resistance of the filter material, and hinder the permeation of gas.

[0041] According to some preferred embodiments, the second filter paper layer comprises 90-96% (e.g., 90%, 91%, 92%, 93%, 94%, 95%, or 96%) of a second fiber component by mass fraction and 4-10% (e.g., 4%, 5%, 6%, 7%, 8%, 9%, or 10%) of a reinforcing modifier; the second fiber component comprises 60-75% (e.g., 60%, 62%, 64%, 65%, 66%, 68%, 70%) of microfiber glass wool by mass fraction. 72%, 74%, or 75%); 10-20% alkali-free chopped filaments (e.g., 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%); 15-20% chemical fibers (e.g., 15%, 16%, 17%, 18%, 19%, or 20%); the mass ratio of reinforcing agent to waterproof and oil-repellent agent in the reinforcing modifier is 40:(1-5) (e.g., 40:1, 40:2, 40:3, 40:4, or 40:5).

[0042] In some preferred embodiments of the present invention, the reinforcing agent is one or more of phenolic resin, acrylic resin, and polyvinyl acetate resin; the waterproofing and oil-repellent agent is a fluorinated waterproofing and oil-repellent agent. It should be noted that the reinforcing agent and waterproofing and oil-repellent agent of the present invention are not limited to the types mentioned above.

[0043] In some preferred embodiments of the present invention, the microfiber glass wool comprises microfiber glass wool with low and high beating degrees; preferably, the microfiber glass wool comprises 475# microfiber glass wool with a beating degree of 14°SR and 475# microfiber glass wool with a beating degree of 49°SR; increasing the content of low beating degree microfiber glass wool is beneficial to obtaining a filter paper layer with a larger average pore size; therefore, the present invention preferably has a lower content of low beating degree microfiber glass wool in the first filter paper layer than in the second filter paper layer.

[0044] According to some preferred embodiments, the mass ratio of the first filter paper layer and the second filter paper layer is (1-2):1 (for example, it can be 1:1, 1.2:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1);

[0045] The average pore size of the first filter paper layer is 4 to 6 μm (e.g., it can be 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, 5 μm, 5.2 μm, 5.4 μm, 5.6 μm, 5.8 μm or 6 μm), and the average pore size of the second filter paper layer is 8 to 12 μm (e.g., it can be 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm or 12 μm).

[0046] According to some preferred embodiments, the percussion degree of the microfiber glass wool is 14-49°SR (e.g., it can be 14°SR, 16°SR, 17°SR, 18°SR, 19°SR, 20°SR, 22°SR, 24°SR, 34°SR or 49°SR), and the diameter of the microfiber glass wool is 0.5-5μm (e.g., it can be 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm).

[0047] The diameter of the alkali-free short chopped filaments is 6 to 8 μm (for example, it can be 6 μm, 6.2 μm, 6.4 μm, 6.5 μm, 6.6 μm, 7 μm, 7.2 μm, 7.4 μm, 7.5 μm, 7.6 μm, 7.8 μm or 8 μm).

[0048] The degree of dissociation of the kapok fiber filament pulp is 15-25°SR (for example, it can be 14°SR, 16°SR, 17°SR, 19°SR, 20°SR, 22°SR, 24°SR or 25°SR);

[0049] The chemical fiber is a bicomponent fiber, preferably CO-PET / PET fiber. It should be noted that the sheath structure of the CO-PET / PET fiber is CO-PET with a melting point of 100–110°C, and the core structure is PET with a melting point of 250–280°C. The sheath melting point of this fiber is lower than the curing temperature of the reinforcing agent and reinforcing modifier. During the drying and curing process, the sheath melts, acting as a binder to better bond the microfiber glass wool and alkali-free chopped filaments together, thus improving the strength of the filter material. Simultaneously, the core layer has a higher melting point, which also enhances the strength of the filter material. The chemical fiber of this invention is not limited to the aforementioned bicomponent fiber; it can also be other chemical fibers, such as polyester fiber, aramid fiber, polytetrafluoroethylene fiber, and polyvinyl alcohol fiber.

[0050] Secondly, the present invention provides a method for preparing the filter material described in the first aspect, the method comprising the following steps:

[0051] S1. Disperse microfiber glass wool, alkali-free chopped filaments and kapok fiber photochemical pulp in an acidic solution to obtain a first pulp, and subject the first pulp to a first pulping and web-making process and a first vacuum dewatering and forming process to obtain a first wet paper web. Then, use a reinforcing agent to perform a first reinforcing modification treatment on the first wet paper web to obtain a first reinforced modified wet paper web.

[0052] S2. Microfiber glass wool, alkali-free chopped strands, and chemical fibers are dispersed in an acidic solution to obtain a second slurry. The second slurry is then subjected to a second slurry washing and web forming, followed by a second vacuum dewatering and forming process to obtain a second wet paper web. The second wet paper web is then subjected to a second reinforcement modification treatment using a reinforcement modifier to obtain a second reinforced modified wet paper web. The reinforcement modifier includes a reinforcement agent and a waterproof and oil-resistant agent.

[0053] S3. After bonding the first reinforced modified wet paper web and the second reinforced modified wet paper web together, a third vacuum dehydration molding process is performed to obtain a composite wet paper web;

[0054] S4. The composite wet paper web is dried and cured to obtain the filter material.

[0055] It should be noted that the first and second slurries of this invention include a slag removal step before slurry washing and wire bonding; specifically, the first and second slurries are diluted respectively, and the slag removal concentration is controlled to be 0.4-0.6%. ， The pulp is then conveyed to a deslagging device for deslagging. The first pulp deslagging concentration refers to the mass fraction of microfiber glass wool, alkali-free chopped strands, and kapok fiber photopolymerized pulp in the diluted pulp. The second pulp deslagging concentration refers to the mass fraction of microfiber glass wool, alkali-free chopped strands, and chemical fibers in the diluted pulp. The reinforcing agent is added in the form of a reinforcing agent solution; preferably, the mass ratio of reinforcing agent to water in the reinforcing agent solution is 4:96. The waterproof and oil-repellent agent is added in the form of a waterproof and oil-repellent agent solution; preferably, the mass ratio of waterproof and oil-repellent agent to water in the waterproof and oil-repellent agent solution is 3:97. The moisture content of the composite wet paper web is 65-70%.

[0056] This invention involves dispersing microfiber glass wool, alkali-free chopped strands, and kapok fiber mercerized pulp in an acidic solution to obtain a first pulp. The first pulp undergoes a first sizing and web-making process followed by a first vacuum dewatering to obtain a first wet paper web. Then, a reinforcing agent is used to perform a first reinforcement modification treatment on the first wet paper web to obtain a first reinforced modified wet paper web. Next, microfiber glass wool, alkali-free chopped strands, and chemical fibers are dispersed in an acidic solution to obtain a second pulp. This second pulp undergoes a second sizing and web-making process followed by a second vacuum dewatering to obtain a second wet paper web. Then, a reinforcing agent and a waterproofing and oil-repellent agent are used to perform a second reinforcement modification treatment on the second wet paper web to obtain a second reinforced modified wet paper web. The first and second reinforced modified wet paper webs are then bonded together and subjected to a third vacuum dewatering to obtain a composite wet paper web. Finally, the composite wet paper web is dried and cured to obtain a filter material comprising a first filter paper layer and a second filter paper layer.

[0057] This invention prepares a first reinforced modified wet paper web and a second reinforced modified wet paper web separately, then laminates the two together and performs a third vacuum dehydration molding process to tightly interweave them, resulting in a composite wet paper web. No additional binder is required, and the filter material can be obtained after drying and curing.

[0058] This invention prepares a filter material with an increased pore size gradient (the average pore size of the first filter paper layer is smaller than that of the second filter paper layer) by controlling and designing the microstructure of the filter material. It introduces mercerized kapok fiber pulp with a smooth fiber surface and strong oil adsorption into the first filter paper layer to enhance the filter material's oil adsorption capacity. The first filter paper layer (inflow surface) is reinforced and modified, while the second filter paper layer (outflow surface) is reinforced and modified for water and oil resistance. The water and oil resistance of the second filter paper layer (outflow surface) can effectively prevent secondary entrainment of oil droplets.

[0059] The filter material of this invention has good air permeability (greater than 75 L / (m³)). 2 It has a large oil absorption capacity (greater than 2.8 g / g) and a high oil-gas separation efficiency (greater than 99.5%).

[0060] According to some preferred embodiments, the pH of the acidic solution is 2 to 3.5 (for example, it can be 2, 2.2, 2.4, 2.5, 2.6, 2.8, 3, 3.2 or 3.5);

[0061] The sum of the mass of the microfiber glass wool, alkali-free chopped filaments and kapok fiber photochemical pulp accounts for 0.5% to 1.5% of the total mass of the first pulp (for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%).

[0062] The sum of the mass of the microfiber glass wool, alkali-free chopped strands, and chemical fibers accounts for 0.5% to 1.5% of the total mass of the second slurry (for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%).

[0063] According to some preferred embodiments, the online concentration of the first slurry is 0.05-0.15% (for example, it can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14% or 0.15%).

[0064] The online concentration of the second slurry is 0.1-0.2% (e.g., it can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%); and / or

[0065] The vacuum degree of the first vacuum dehydration molding is greater than that of the second vacuum dehydration molding; preferably, the vacuum degree of the first vacuum dehydration molding is 0.025 to 0.03 MPa (for example, it can be 0.025 MPa, 0.026 MPa, 0.027 MPa, 0.028 MPa, 0.029 MPa or 0.03 MPa); and the vacuum degree of the second vacuum dehydration molding is 0.02 to 0.025 MPa (for example, it can be 0.02 MPa, 0.021 MPa, 0.022 MPa, 0.023 MPa, 0.024 MPa or 0.025 MPa).

[0066] The vacuum degree of the first vacuum dehydration molding of the present invention is greater than that of the second vacuum dehydration molding, which can ensure that the average pore size of the first filter paper layer is smaller than that of the second filter paper layer.

[0067] According to some preferred embodiments, the vacuum degree of the third vacuum dehydration forming is greater than that of the first vacuum dehydration forming; preferably, the vacuum degree of the third vacuum dehydration forming is 0.04 to 0.048 MPa (for example, it can be 0.04 MPa, 0.042 MPa, 0.044 MPa, 0.046 MPa or 0.048 MPa); the fact that the vacuum degree of the third vacuum dehydration forming of the present invention is greater than that of the first vacuum dehydration forming can ensure that the first reinforced modified wet paper web and the second reinforced modified wet paper web are tightly interwoven during the vacuum dehydration forming process.

[0068] The drying and curing process includes a first-stage drying and curing process, a second-stage drying and curing process, and a third-stage drying and curing process; the temperature of the first-stage drying and curing process is 40-60℃ (for example, it can be 40℃, 42℃, 44℃, 45℃, 46℃, 48℃, 50℃, 52℃, 54℃, 56℃, 58℃ or 60℃), the temperature of the second-stage drying and curing process is 130-140℃ (for example, it can be 130℃, 132℃, 134℃, 136℃, 138℃ or 140℃), and the temperature of the third-stage drying and curing process is 150-160℃ (for example, it can be 150℃, 151℃, 152℃, 153℃, 154℃, 155℃, 156℃, 157℃, 158℃, 159℃ or 160℃). To ensure the overall performance of the filter material, a three-stage contact drying and curing process is adopted. Preferably, the first stage of drying and curing is carried out in a low-temperature drying cylinder at 40-60℃, the second stage is carried out in a drying cylinder at 130-140℃, and the third stage is carried out in a drying cylinder at 150-160℃, with each stage lasting 40-60 seconds. The lower temperature in the first stage effectively prevents deformation of the reinforced composite wet paper web caused by excessive temperature. The second and third stages ensure that the composite wet paper web is fully dried and that the reinforcing agent and reinforcing modifier are fully cured, thereby enhancing the performance of the filter material.

[0069] Thirdly, the present invention provides the application of the filter material described in the first aspect in engine oil-gas separation.

[0070] The filter material provided by this invention comprises a first filter paper layer and a second filter paper layer with progressively increasing pore size. In use, the first filter paper layer is the inflow surface. Introducing mercerized kapok fiber pulp (kapok fiber after mercerization treatment), which has a hollow structure, smooth fiber surface, and strong oil adsorption, into the first filter paper layer increases the oil absorption capacity of the filter material. The second filter paper layer contains a water- and oil-repellent agent, improving the water- and oil-repellent properties of the filter material and effectively preventing secondary entrainment of oil droplets. When the oil-gas mixture enters the filter material through the pores of the first filter paper layer, it aggregates and enlarges. The average pore size of the first filter paper layer is smaller than that of the second filter paper layer, allowing for better adsorption of oil droplets within the filter material. Simultaneously, the gradient structure with increasing pore size increases the air permeability of the filter material, reduces filtration resistance, and facilitates gas permeation. Thus, oil-gas separation can be achieved more effectively, improving the oil-gas separation efficiency of the filter material. The filter material of this invention has a large oil absorption capacity and high oil-gas separation efficiency, meeting the requirements of engines for oil-gas separation.

[0071] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below in conjunction with embodiments.

[0072] It should be noted that the materials and reagents used in this invention can be purchased commercially or prepared in-house, and there are no restrictions on specific models. Softwood mercerized pulp can be purchased directly or prepared in-house. In-house prepared softwood mercerized pulp is obtained by mercerizing softwood; specifically, it is obtained by soaking softwood fibers in a 1 mol / L NaOH solution at 50°C for 60 minutes, followed by washing and dehydration. The parts in the examples and comparative examples refer to parts by mass.

[0073] Example 1

[0074] S1. Weigh the first fiber component: 56 parts of 475# microfiber glass wool with a beating degree of 14°SR, 15 parts of 475# microfiber glass wool with a beating degree of 49°SR, 14 parts of alkali-free chopped strands with a diameter of 7μm, and 15 parts of kapok fiber pulp with a beating degree of 25°SR. First, put the alkali-free chopped strands and kapok fiber pulp into the pulper, and control the pH of the pulping white water to 3. The stirring and dispersion time is 600s. Then, add the 475# microfiber glass wool. During pulping... The pulping process is carried out for 300 seconds with low-concentration beating to obtain a first pulp with a concentration of 1.2%. The first pulp is then fed onto the wire with a wire concentration of 0.15%, and vacuum dewatered and formed at 0.028 MPa to obtain a first wet paper web. Then, a reinforcing agent (acrylic resin emulsion) is applied to the first wet paper web through an overflow sizing method to perform a first reinforcement modification treatment. The reinforcing agent is added in the form of a reinforcing agent solution (the mass ratio of reinforcing agent to water is 4:96) to obtain a first reinforced modified wet paper web.

[0075] S2. Weigh the second fiber component: 60 parts of 475# microfiber glass wool with a beating degree of 14°SR, 12 parts of 475# microfiber glass wool with a beating degree of 49°SR, 13 parts of alkali-free chopped strands with a diameter of 7μm, and 15 parts of chemical fibers (CO-PET / PET fibers); first, put the alkali-free chopped strands and chemical fibers into a pulper, control the pH of the pulping water to 3, and the stirring and dispersion time to 420s. Then, add the 475# microfiber glass wool, and pulp for 300s, controlling the low-consistency pulping to obtain a second pulp with a concentration of 1.2%; then, flush the second pulp. The first wet paper web, with a web concentration of 0.2%, is vacuum dehydrated and formed at 0.023 MPa to obtain a second wet paper web. Then, a first reinforcement modification treatment is performed on the first wet paper web by overflow sizing using a reinforcing agent (acrylic resin emulsion) and a waterproof and oil-repellent agent (C6 waterproof and oil-repellent agent). The reinforcing agent is added in the form of a reinforcing agent solution (the mass ratio of reinforcing agent to water is 4:96), and the waterproof and oil-repellent agent is added in the form of a waterproof and oil-repellent agent solution (the mass ratio of waterproof and oil-repellent agent to water is 3:97). The mass ratio of the reinforcing agent solution to the waterproof and oil-repellent agent solution is 10:1 to obtain the second reinforced and modified wet paper web.

[0076] S3. The first reinforced modified wet paper web and the second reinforced modified wet paper web are bonded together and subjected to a third vacuum dehydration molding at 0.045 MPa to obtain a composite wet paper web with a moisture content of 65-70%.

[0077] S4. The composite wet paper web is subjected to a first-stage drying and curing treatment (a low-temperature drying cylinder at 40°C for 1 min), a second-stage drying and curing treatment (a drying cylinder at 140°C for 1 min), and a third-stage drying and curing treatment (a drying cylinder at 160°C for 1 min) to obtain a filter material comprising a first filter paper layer (average pore size of 4-6 μm) and a second filter paper layer (average pore size of 8-12 μm).

[0078] Example 2

[0079] Example 2 is basically the same as Example 1, except that in step S1, the first fiber component consists of 53 parts of 475# microfiber glass wool with a beating degree of 14°SR and 14 parts of 475# microfiber glass wool with a beating degree of 49°SR, 13 parts of alkali-free chopped filaments with a diameter of 7μm and 20 parts of kapok fiber photopolymerized pulp with a beating degree of 25°SR.

[0080] Example 3

[0081] Example 3 is basically the same as Example 1, except that in step S1, the first fiber component consists of 50 parts of 475# microfiber glass wool with a beating degree of 14°SR and 13 parts of 475# microfiber glass wool with a beating degree of 49°SR, 12 parts of alkali-free chopped filaments with a diameter of 7μm and 25 parts of kapok fiber vitrified pulp with a beating degree of 25°SR.

[0082] Example 4

[0083] Example 4 is basically the same as Example 1, except that: in step S1, the first fiber component is: 53 parts of 475# microfiber glass wool with a beating degree of 14°SR and 14 parts of 475# microfiber glass wool with a beating degree of 49°SR, 13 parts of alkali-free short chopped filaments with a diameter of 7μm and 20 parts of kapok fiber photopolymerized pulp with a beating degree of 25°SR;

[0084] In step S2, the mass ratio of the waterproof and oil-repellent agent to water in the waterproof and oil-repellent solution is 5:97.

[0085] Comparative Example 1

[0086] Comparative Example 1 is basically the same as Example 1, except that in step S1, the first fiber component consists of 66 parts of 475# microfiber glass wool with a beating degree of 14°SR, 18 parts of 475# microfiber glass wool with a beating degree of 49°SR, and 16 parts of alkali-free short chopped filaments with a diameter of 7μm.

[0087] Comparative Example 2

[0088] Comparative Example 2 is basically the same as Example 1, except that in step S1, the first fiber component is: 66 parts of 475# microfiber glass wool with a beating degree of 14°SR, 18 parts of 475# microfiber glass wool with a beating degree of 49°SR, and 16 parts of alkali-free short chopped filaments with a diameter of 7μm.

[0089] In step S2, the second fiber component consists of 66 parts of 475# microfiber glass wool with a beating degree of 14°SR, 18 parts of 475# microfiber glass wool with a beating degree of 49°SR, and 16 parts of alkali-free chopped filaments with a diameter of 7μm.

[0090] Comparative Example 3

[0091] Comparative Example 3 is basically the same as Example 2, except that no waterproof and oil-repellent solution was added in step S2.

[0092] Comparative Example 4

[0093] Comparative Example 4 is basically the same as Example 2, except that in step S2, the second fiber component consists of 53 parts of 475# microfiber glass wool with a beating degree of 14°SR, 14 parts of 475# microfiber glass wool with a beating degree of 49°SR, 13 parts of alkali-free chopped filaments with a diameter of 7μm, and 20 parts of kapok fiber vitrified pulp with a beating degree of 25°SR.

[0094] Comparative Example 5

[0095] Comparative Example 5 is basically the same as Example 2, except that in step S1, the first fiber component consists of 60 parts of 475# microfiber glass wool with a beating degree of 14°SR, 12 parts of 475# microfiber glass wool with a beating degree of 49°SR, 13 parts of alkali-free short chopped filaments with a diameter of 7μm and 15 parts of chemical fibers.

[0096] In step S2, the second fiber component consists of: 53 parts of 475# microfiber glass wool with a beating degree of 14°SR, 14 parts of 475# microfiber glass wool with a beating degree of 49°SR, 13 parts of alkali-free chopped filaments with a diameter of 7μm, and 20 parts of kapok fiber vitrified pulp with a beating degree of 25°SR.

[0097] Comparative Example 6

[0098] Comparative Example 6 is basically the same as Example 2, except that in step S1, the first fiber component consists of 53 parts of 475# microfiber glass wool with a beating degree of 14°SR and 14 parts of 475# microfiber glass wool with a beating degree of 49°SR, 13 parts of alkali-free short chopped filaments with a diameter of 7μm and 20 parts of kapok fiber (without mercerization treatment).

[0099] Comparative Example 7

[0100] Comparative Example 7 is basically the same as Example 2, except that: the first fiber component consists of 53 parts of 475# microfiber glass wool with a beating degree of 14°SR and 14 parts of 475# microfiber glass wool with a beating degree of 49°SR, 13 parts of alkali-free chopped filaments with a diameter of 7μm and 20 parts of softwood photochemical pulp with a beating degree of 25°SR.

[0101] Comparative Example 8

[0102] Comparative Example 8 is basically the same as Example 2, except that: the first fiber component consists of 46 parts of 475# microfiber glass wool with a beating degree of 14°SR and 12.5 parts of 475# microfiber glass wool with a beating degree of 49°SR, 11.5 parts of alkali-free chopped filaments with a diameter of 7μm and 30 parts of kapok fiber photopolymerized pulp with a beating degree of 25°SR.

[0103] Table 1. Performance data of filter materials prepared in the examples and comparative examples

[0104]

[0105] It should be noted that in Table 1, the test standard for air permeability refers to GB / T5453; the test standard for oil-water separation efficiency refers to ISO12500-1:2007; and the liquid absorption (g / g) = oil mass (g) / filter paper mass (g).

[0106] As shown in Table 1, the filter materials prepared in Examples 1-4 of this invention have good air permeability (greater than 75 L / (m³)). 2The filter material exhibits high oil absorption (greater than 2.8 g / g) and high oil-gas separation efficiency (greater than 99.5%), effectively preventing secondary entrainment of oil droplets in the gas. Comparative Example 1 shows that without the addition of kapok fiber sizing to the first filter paper layer, the liquid absorption of the resulting filter material is significantly reduced. Comparative Example 2 shows that when neither the first filter paper layer (inlet surface) nor the second filter paper layer (outlet surface) contains kapok fiber sizing and has no gradient microstructure (both layers have the same composition), the liquid absorption of the filter material is significantly reduced compared to Comparative Example 1 with a gradient microstructure. Comparative Example 3, without the addition of any water-repellent or oil-repellent agent, shows increased liquid absorption compared to Example 2, but significantly reduced oil-gas separation efficiency, resulting in secondary entrainment of oil droplets and potential pollution of the engine operating environment. In Comparative Example 4, both the first and second filter paper layers contained mercerized kapok fiber pulp and had no gradient microstructure (both layers had the same composition). Compared to Examples 2 and 4, the filter material prepared in Comparative Example 4 had increased liquid absorption, but significantly reduced oil-gas separation efficiency. Comparative Example 5 differed from Example 2 only in that the fiber components of the first and second filter paper layers were interchanged. The resulting filter material had significantly lower liquid absorption, air permeability, and oil-gas separation efficiency compared to Example 2. Compared to Example 2, Comparative Example 6, using untreated kapok fiber, resulted in a significantly reduced air permeability, liquid absorption, and oil-gas separation efficiency. Compared to Example 2, Comparative Example 7, using coniferous wood mercerized pulp, lacked a hollow structure, resulting in significantly reduced air permeability, liquid absorption, and oil-gas separation efficiency. Compared to Example 2, in Comparative Example 8, the mass fraction of kapok fiber mercerized pulp in the first fiber component was too high, significantly reducing the air permeability of the filter material and hindering gas permeation.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A filter material, characterized in that, The filter material comprises a first filter paper layer with an average pore size of 4-6 μm and a second filter paper layer with an average pore size of 8-12 μm; the average pore size of the first filter paper layer is smaller than the average pore size of the second filter paper layer. The first filter paper layer contains 90-94% by mass of a first fiber component and 6-10% by mass of a reinforcing agent; the first fiber component contains 55-70% by mass of microfiber glass wool, 10-20% by mass of alkali-free chopped strands and 20-25% by mass of kapok fiber photochemical pulp; the kapok fiber photochemical pulp has a beating degree of 15-25°SR. The second filter paper layer comprises 90-94% by mass of a second fiber component and 6-10% by mass of a reinforcing modifier; the second fiber component comprises 60-75% by mass of microfiber glass wool, 10-20% by mass of alkali-free chopped strands, and 15-20% by mass of chemical fibers; the mass ratio of reinforcing agent to waterproof and oil-repellent agent in the reinforcing modifier is 40:(1-5); wherein the degree of beating of the microfiber glass wool is 14-49°SR, and the diameter of the microfiber glass wool is 0.5-5μm; the filter material is obtained by three vacuum dehydration molding processes.

2. The filter material according to claim 1, characterized in that, The mass ratio of the first filter paper layer to the second filter paper layer is (1~2):

1.

3. The filter material according to claim 1, characterized in that, The diameter of the alkali-free short shredded wire is 6~8μm; The chemical fiber is a bicomponent fiber.

4. The filter material according to claim 3, characterized in that, The bicomponent fiber is CO-PET / PET fiber.

5. A method for preparing the filter material according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: S1. Disperse microfiber glass wool, alkali-free chopped filaments and kapok fiber photochemical pulp in an acidic solution to obtain a first pulp, and subject the first pulp to a first pulping and web-making process and a first vacuum dewatering and forming process to obtain a first wet paper web. Then, use a reinforcing agent to perform a first reinforcing modification treatment on the first wet paper web to obtain a first reinforced modified wet paper web. S2. Disperse microfiber glass wool, alkali-free chopped filaments and chemical fibers in an acidic solution to obtain a second slurry. Then, subject the second slurry to a second pulping and web-making process and a second vacuum dewatering and forming process to obtain a second wet paper web. Finally, use a reinforcing modifier to perform a second reinforcing modification treatment on the second wet paper web to obtain a second reinforced modified wet paper web. The reinforcing modifier comprises a reinforcing agent and a waterproof and oil-repellent agent; S3. After bonding the first reinforced modified wet paper web and the second reinforced modified wet paper web together, a third vacuum dehydration molding process is performed to obtain a composite wet paper web; S4. The composite wet paper web is dried and cured to obtain the filter material.

6. The preparation method according to claim 5, characterized in that, The pH of the acidic solution is 2-3.5; The sum of the mass of the microfiber glass wool, alkali-free chopped filaments, and kapok fiber mercerized pulp accounts for 0.5% to 1.5% of the total mass of the first pulp. The total mass of the microfiber glass wool, alkali-free chopped filaments, and chemical fibers accounts for 0.5 to 1.5% of the total mass of the second slurry.

7. The preparation method according to claim 5, characterized in that, The online concentration of the first slurry is 0.05~0.15%; The online concentration of the second slurry is 0.1~0.2%.

8. The preparation method according to claim 5, characterized in that, The vacuum degree of the first vacuum dehydration molding is greater than that of the second vacuum dehydration molding.

9. The preparation method according to claim 8, characterized in that, The vacuum degree of the first vacuum dehydration molding is 0.025~0.03MPa; the vacuum degree of the second vacuum dehydration molding is 0.02~0.025MPa.

10. The preparation method according to claim 5, characterized in that, The vacuum degree of the third vacuum dehydration molding is greater than that of the first vacuum dehydration molding.

11. The preparation method according to claim 10, characterized in that, The vacuum degree of the third vacuum dehydration molding is 0.04~0.048MPa.

12. The preparation method according to claim 5, characterized in that, The drying and curing process includes a first stage drying and curing process, a second stage drying and curing process, and a third stage drying and curing process; the temperature of the first stage drying and curing process is 40~60℃, the temperature of the second stage drying and curing process is 130~140℃, and the temperature of the third stage drying and curing process is 150~160℃.

13. The application of the filter material according to any one of claims 1-4 in engine oil-gas separation.

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