Glass-fiber-based filter material and preparation method therefor

Abstract

The present invention belongs to the technical field of filter materials, and relates to a glass-fiber-based filter material and a preparation method therefor. The glass fiber-based filter material comprises a first paper web; the first paper web is glass-fiber-based filter paper with acidified carbon nanotubes loaded on fiber surfaces; the acidified carbon nanotubes account for 2-6% of the total mass of the glass-fiber-based filter material. The acidified carbon nanotubes in the glass-fiber-based filter material provided by the present invention are uniformly loaded on the surfaces of the fibers, have high bonding strength with the fibers, do not easily detach, and have a high dust-holding capacity, a high filter efficiency and good temperature resistance, thereby meeting the usage requirements for high-cleanliness places such as medicine production workshops and clean rooms, and enabling the low energy consumption and long service life of the filter material in a high-temperature usage environment.

Description

A glass fiber-based filter material and its preparation method Technical Field

[0001] This invention relates to the field of filter materials technology, and in particular to a glass fiber-based filter material and its preparation method. Background Technology

[0002] With increasing environmental pollution, the demand for efficient and sustainable air purification technologies is rising. Fiberglass paper-based filter materials are the core material for achieving high-efficiency air purification. Due to their high filtration efficiency, superior chemical and thermal resistance, and high dust holding capacity, they have a wider range of applications than other filter separation materials, occupying an important position in air filtration. In industries such as medical and pharmaceutical manufacturing, environments require cleanliness and sterility. Traditional filtration methods use a combination of high-efficiency filters and activated carbon adsorption to adsorb and filter out harmful pollutants such as fine particles, bacteria, viruses, and microorganisms from the air, dynamically maintaining indoor air cleanliness.

[0003] To meet the demands of high-cleanliness environments for both indoor air cleanliness and low energy consumption of equipment, nanofibers, represented by carbon nanotubes (CNTs), possess characteristics such as high specific surface area and small diameter. By loading carbon nanotubes onto the surface of glass fibers, the resistance of filter materials can be significantly reduced. Furthermore, carbon nanotubes have a nanoscale tubular structure, which can selectively filter out molecules of specific sizes. At the same time, carbon nanotubes adsorb many chemical groups on their surface, exhibiting excellent adsorption performance, and are considered ideal materials for preparing high-efficiency air filter materials.

[0004] However, in existing glass fiber paper-based filter materials loaded with carbon nanotubes, the carbon nanotubes are unevenly loaded and have low bonding strength with the glass fiber, making them prone to detachment. This fails to meet the requirements for use in high-cleanliness environments such as pharmaceutical production workshops and cleanrooms. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, the present invention provides a glass fiber-based filter material and its preparation method. In the glass fiber-based filter material provided by the present invention, acidified carbon nanotubes are uniformly loaded on the fiber surface and have a high bonding strength with the fiber, making them difficult to fall off. It has high dust holding capacity, high filtration efficiency, and good temperature resistance, which can meet the usage requirements of high-cleanliness places such as pharmaceutical production workshops and clean rooms, and achieve low energy consumption and long service life of filter materials in high-temperature application environments.

[0006] In a first aspect, the present invention provides a glass fiber-based filter material comprising a first paper web; the first paper web being a glass fiber filter paper with acidified carbon nanotubes loaded on the fiber surface; the acidified carbon nanotubes accounting for 2-6% of the total mass of the glass fiber-based filter material.

[0007] Preferably, the glass fiber-based filter material further includes a second paper web laminated with the first paper web; the second paper web is glass fiber filter paper; the pore size of the first paper web is larger than the pore size of the second paper web; preferably, the mass of glass fiber in the first paper web accounts for 30-50% of the total mass of glass fiber in the glass fiber-based filter material.

[0008] In a second aspect, the present invention provides a method for preparing the glass fiber-based filter material described in the first aspect, the method comprising:

[0009] S1. A first wet paper web is prepared using a first glass fiber pulp;

[0010] S2. Under the action of an electric field, acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then subjected to vacuum dehydration, reinforcement modification, drying and curing to obtain a glass fiber-based filter material.

[0011] Preferably, prior to vacuum dehydration, the process further includes: preparing a second wet paper web using a second glass fiber slurry, and placing a first wet paper web loaded with acidified carbon nanotubes onto the second wet paper web.

[0012] Preferably, loading acidified carbon nanotubes onto the fiber surface of the first wet paper web under the action of an electric field includes: placing the first wet paper web between a lower electrode plate connected to the positive terminal of a power source and an upper electrode plate connected to the negative terminal of a power source; overflowing the acidified carbon nanotube dispersion onto the surface of the first wet paper web; and loading the acidified carbon nanotubes onto the fiber surface of the first wet paper web under the action of an electric field.

[0013] Preferably, the mass fraction of acidified carbon nanotubes in the acidified carbon nanotube dispersion is 2-10%;

[0014] The electric field strength is 10–120 V·cm. -1 ; and / or

[0015] The load duration is 10–40 seconds.

[0016] Preferably, the glass fibers in the first glass fiber slurry and the second glass fiber slurry include microfiber glass wool and alkali-free chopped strands;

[0017] The concentrations of the first glass fiber slurry and the second glass fiber slurry are 0.7–1.2%.

[0018] The pH of the first glass fiber slurry is 2.5–3.0; and / or

[0019] The pH of the second glass fiber slurry is 3.0 to 3.5.

[0020] Preferably, the moisture content of the first wet paper web is 25-30%; and / or

[0021] The moisture content of the first wet paper web loaded with acidified carbon nanotubes is 40-60%; and / or

[0022] The moisture content of the second wet paper web is 40-60%; and / or

[0023] The moisture content of the paper web after vacuum dewatering is 25-35%.

[0024] Preferably, the vacuum pressure for vacuum dehydration is 35–65 kPa;

[0025] The enhancement and modification are performed using an atomized sizing method; and / or

[0026] The drying and curing process is achieved using a contact drying system.

[0027] Preferably, the reinforcing modifier used in the reinforcing modification includes a reinforcing agent and a water-repellent agent; the reinforcing agent includes one or more of phenolic resin, acrylic resin, and polyvinyl acetate resin; the water-repellent agent is a fluorine-free water-repellent agent; and / or

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] The glass fiber-based filter material provided by this invention has acidified carbon nanotubes uniformly loaded on the fiber surface, and the bonding strength with the fiber is high, making it difficult to fall off. It has high dust holding capacity, high filtration efficiency, and good temperature resistance, which can meet the usage requirements of high-cleanliness places such as pharmaceutical production workshops and clean rooms, and achieve low energy consumption and long service life of filter materials in high-temperature application environments.

[0030] This invention first prepares a first wet paper web using a first glass fiber slurry. Utilizing the negatively charged properties of acidified carbon nanotubes, under the influence of an external electric field, the acidified carbon nanotubes are uniformly loaded onto the fiber surface of the wet paper web, enhancing the adsorption effect of the filter material on pollutants and improving its filtration efficiency and dust holding capacity. Simultaneously, the loading method under the influence of an electric field strengthens the bonding between the carbon nanotubes and the fibers. Then, the moisture content of the paper web is controlled by vacuum dehydration, and the paper web is reinforced and modified. Because the acidified carbon nanotubes have hydrophilic carboxyl and hydroxyl groups on their surface, not only can the dispersion performance of the carbon nanotubes be improved, but also hydrogen bonds and other interactions can be formed with the reinforcing modifier during the reinforcement modification process, further enhancing the bonding between the carbon nanotubes and the paper web and improving the overall performance of the filter material. Furthermore, loading the acidified carbon nanotubes after forming the wet paper web avoids the contamination problem of the slurry supply system caused by directly mixing carbon nanotubes into the slurry, which is beneficial for the mass production of carbon nanotube / glass fiber paper-based filter materials. Detailed Implementation

[0031] 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.

[0032] In a first aspect, the present invention provides a glass fiber-based filter material comprising a first paper web; the first paper web being a glass fiber filter paper with acidified carbon nanotubes loaded on the fiber surface; the acidified carbon nanotubes accounting for 2-6% of the total mass of the glass fiber-based filter material.

[0033] The glass fiber-based filter material provided by this invention has acidified carbon nanotubes uniformly loaded on the fiber surface, and the bonding strength with the fiber is high, making it difficult to fall off. It has high dust holding capacity, high filtration efficiency, and good temperature resistance, which can meet the usage requirements of high-cleanliness places such as pharmaceutical production workshops and clean rooms, and achieve low energy consumption and long service life of filter materials in high-temperature application environments.

[0034] The inventors discovered that as the content of acidified carbon nanotubes increases, the dust holding capacity first increases and then decreases. The initial increase in dust holding capacity is due to the adsorption properties of acidified carbon nanotubes, while the subsequent decrease is due to the fact that excessive acidified carbon nanotubes will clog the pores. The negative effect of clogging the pores gradually outweighs the positive effect of the adsorption properties themselves. At the same time, excessive acidified carbon nanotubes clogging the pores will lead to increased filtration resistance and reduced filtration performance.

[0035] According to some preferred embodiments, the glass fiber-based filter material further includes a second paper web laminated with the first paper web; the second paper web is glass fiber filter paper; the pore size of the first paper web is larger than the pore size of the second paper web; preferably, the mass of glass fiber in the first paper web accounts for 30-50% of the total mass of glass fiber in the glass fiber-based filter material.

[0036] In a second aspect, the present invention provides a method for preparing the glass fiber-based filter material described in the first aspect, the method comprising:

[0037] S1. A first wet paper web is prepared using a first glass fiber pulp;

[0038] S2. Under the action of an electric field, acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then subjected to vacuum dehydration, reinforcement modification, drying and curing to obtain a glass fiber-based filter material.

[0039] This invention first prepares a first wet paper web using a first glass fiber slurry. Utilizing the negatively charged nature of acidified carbon nanotubes, under the influence of an external electric field, the acidified carbon nanotubes are uniformly loaded onto the fiber surface of the wet paper web, enhancing the adsorption effect of the filter material on pollutants and improving filtration efficiency and dust holding capacity. Simultaneously, the loading method under the influence of an electric field strengthens the bonding between the carbon nanotubes and the fibers. Then, the moisture content of the paper web is controlled by vacuum dehydration, and the paper web is reinforced and modified. Because the acidified carbon nanotubes have hydrophilic carboxyl and hydroxyl groups on their surface, not only is the dispersion performance of the carbon nanotubes improved, but hydrogen bonds and other interactions can also be formed with the reinforcing modifier during the reinforcement modification process, further enhancing the bonding between the carbon nanotubes and the paper web and improving the overall performance of the filter material. Furthermore, loading the acidified carbon nanotubes after forming the wet paper web avoids the contamination problems of the slurry supply system caused by directly mixing carbon nanotubes into the slurry, which is beneficial for the mass production of carbon nanotube / glass fiber paper-based filter materials.

[0040] According to some preferred embodiments, the preparation method of acidified carbon nanotubes includes: mixing carbon nanotubes with a nitric acid solution and reacting at 150°C for 60 min to obtain acidified carbon nanotubes; wherein the concentration of the nitric acid is 0.75–2 mol·L⁻¹. -1 Specifically: carbon nanotubes are placed in a hydrothermal reactor, and then a prepared solution of 0.75–2 mol·L⁻¹ is added. -1 Anionization of carbon nanotubes can be achieved by reacting with HNO3 solution at 150℃ for 60 min. After removing the reaction vessel and cooling to room temperature, the acidified carbon nanotubes are washed with deionized water until neutral, and then completely dried in an oven at 50±10℃ for later use.

[0041] It should be noted that the preparation method of acidified carbon nanotubes in this invention is not limited to the above method. As long as the carbon nanotubes can be negatively charged and have a large number of carboxyl and hydroxyl groups on the surface, it is acceptable.

[0042] According to some preferred embodiments, prior to vacuum dehydration, the process further includes: preparing a second wet paper web using a second glass fiber slurry, and placing a first wet paper web loaded with acidified carbon nanotubes onto the second wet paper web.

[0043] According to some preferred embodiments, loading acidified carbon nanotubes onto the fiber surface of a first wet paper web under the action of an electric field includes: placing the first wet paper web between a lower electrode plate connected to the positive terminal of a power source and an upper electrode plate connected to the negative terminal of a power source; overflowing an acidified carbon nanotube dispersion onto the surface of the first wet paper web; and loading the acidified carbon nanotubes onto the fiber surface of the first wet paper web under the action of an electric field. This invention controls the potential difference between the positive and negative electrodes, thereby controlling the electric field strength between the upper and lower electrodes. Preferably, the electric field in this invention is a uniform electric field to ensure that the acidified carbon nanotubes are more evenly distributed on the fiber surface, further improving the bonding strength between the acidified carbon nanotubes and the fibers.

[0044] According to some preferred embodiments, the mass fraction of acidified carbon nanotubes in the acidified carbon nanotube dispersion is 2-10%; the dispersant used in the acidified carbon nanotube dispersion is water. This invention disperses acidified carbon nanotubes in water to obtain an acidified carbon nanotube dispersion. Because the surface of acidified carbon nanotubes has hydrophilic carboxyl and hydroxyl groups, which can effectively improve the dispersion performance of carbon nanotubes, the content of acidified carbon nanotubes in this invention is controlled within the above-mentioned range to ensure that a uniformly dispersed acidified carbon nanotube dispersion is obtained.

[0045] According to some preferred embodiments, the electric field strength is 10–120 V·cm. -1 (For example, it can be 10V·cm) -1 20V·cm -1 30V·cm -1 40V·cm -1 50V·cm -1 60V·cm -1 70V·cm -1 80V·cm -1 90V·cm -1 100V·cm -1 110V·cm -1 Or 120V·cm -1 ).

[0046] According to some preferred embodiments, the load duration is 10 to 40 seconds (e.g., it can be 10 seconds, 10 seconds, 15 seconds, 20 seconds, 25 seconds, 30 seconds, 35 seconds or 40 seconds).

[0047] This invention allows for the control of the loading amount of acidified carbon nanotubes by adjusting the electric field strength and the loading time (determined by the paper web running speed; the faster the paper web runs, the shorter the loading time). Under otherwise constant conditions, the loading amount can be increased by increasing the electric field strength and extending the loading time. The electric field strength and loading time are not limited to the ranges described above; considering both efficiency and operability, the above ranges are preferred.

[0048] According to some preferred embodiments, the glass fibers in the first glass fiber slurry and the second glass fiber slurry include microfiber glass wool and alkali-free chopped strands.

[0049] According to some preferred embodiments, the concentrations of the first glass fiber slurry and the second glass fiber slurry are 0.7% to 1.2%.

[0050] According to some preferred embodiments, the pH of the first glass fiber slurry is 2.5 to 3.0.

[0051] According to some preferred embodiments, the pH of the second glass fiber slurry is 3.0 to 3.5.

[0052] The first glass fiber slurry contains microfiber glass wool with a beating degree of 14–49°SR (e.g., 14°SR, 17°SR, 19°SR, 34°SR, 44°SR, or 49°SR), fiber diameter of 0.5–5 μm, alkali-free chopped filaments with a diameter of 7 μm and a length of 6–12 mm (e.g., 6 mm, 9 mm, or 12 mm), and a pulping white water pH of 2.5–3.0. The preparation method of the first glass fiber slurry is as follows: first, alkali-free chopped filaments are fed into a pulper, the frequency of the pulper rotor is controlled at 20–30 Hz, and the dispersion time is 90–150 s. After dispersion, microfiber glass wool is added, the frequency of the pulper rotor is controlled at 37.5–45 Hz, and the pulping time is 300–420 s. Low-consistency pulping is controlled to obtain a first glass fiber slurry with a concentration of 0.7–1.2%.

[0053] The second glass fiber slurry contains microfiber glass wool with a beating degree of 34–59°SR (e.g., 34°SR, 44°SR, 49°SR, 54°SR, 59°SR), a fiber diameter of 0.3–3 μm, alkali-free chopped filaments with a diameter of 7 μm and a length of 6–12 mm (e.g., 6 mm, 9 mm, 12 mm), and a pulping white water pH of 3.0–3.5. The preparation method of the second glass fiber slurry is as follows: First, alkali-free chopped filaments are fed into a pulper, the frequency of the pulper rotor is controlled at 20–30 Hz, and the dispersion time is 90–150 s. After dispersion, microfiber glass wool is added, the frequency of the pulper rotor is controlled at 37.5–45 Hz, and the pulping time is 240–300 s. Low-consistency pulping is controlled to obtain a second glass fiber slurry with a concentration of 0.7–1.2%.

[0054] According to some preferred embodiments, the moisture content of the first wet paper web is 25-30% (e.g., 25%, 26%, 27%, 28%, 29%, or 30%). The present invention prepares a first wet paper web with low moisture content to better load acidified carbon nanotubes onto the fiber surface of the first wet paper web.

[0055] According to some preferred embodiments, the moisture content of the wet paper web loaded with acidified carbon nanotubes is 40-60% (e.g., 40%, 45%, 50%, 55% or 60%).

[0056] According to some specific implementation methods, after loading acidified carbon nanotubes onto the fiber surface of the first wet paper web, the water content of the paper web is controlled to be 40-60% by vacuum dehydration.

[0057] According to some preferred embodiments, the moisture content of the second wet paper web is 40-60% (e.g., 40%, 45%, 50%, 55% or 60%).

[0058] By controlling the moisture content of the wet paper web loaded with acidified carbon nanotubes and the second wet paper web within the above-mentioned range, this invention can ensure fiber interweaving at the junction of the two layers during vacuum dehydration.

[0059] According to some specific implementation methods, the preparation method of the first wet paper web includes: subjecting the first glass fiber slurry to three-stage deslagging treatment, then sequentially conveying it to the headbox via a slurry pump to achieve uniform distribution of the slurry on the web, and then subjecting it to gravity dewatering and vacuum dewatering to form the first wet paper web. The vacuum pressure of the vacuum dewatering is 15-40 kPa, and the moisture content of the first wet paper web is controlled to be 25-30%.

[0060] According to some specific implementation methods, the preparation method of the second wet paper web includes: the second glass fiber slurry is subjected to three-stage deslagging treatment, and then sequentially transported to the headbox by a slurry pump to achieve uniform distribution of the slurry on the web, and then subjected to gravity dewatering and vacuum dewatering to form the second wet paper web. The vacuum pressure of vacuum dewatering is 15-50 kPa, and the moisture content of the second wet paper web is controlled to be 40-60%.

[0061] According to some preferred embodiments, the moisture content of the paper web after vacuum dewatering is 25% to 35% (for example, it can be 25%, 26%, 28%, 30%, 32% or 35%).

[0062] According to some preferred embodiments, the vacuum pressure for vacuum dehydration is 35 to 65 kPa (for example, it can be 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa or 65 kPa).

[0063] According to some specific implementation methods, a wet paper web loaded with acidified carbon nanotubes is drawn onto a second wet paper web via a wire roller. Vacuum dehydration is performed under a controlled vacuum pressure of 35–65 kPa, achieving fiber interlacing at the junction of the two layers. The moisture content of the interlaced wet paper web is controlled to be 25–35%. Because the fiber porosity of the second wet paper web is smaller, carbon nanotubes can be effectively prevented from permeating through the second wet paper web during vacuum dehydration.

[0064] According to some preferred embodiments, the reinforcement modification is performed using atomized sizing. The mass ratio of reinforcing agent to water-resistant agent is accurately controlled by an electromagnetic flowmeter, and after mixing, the mixture is pressurized by a sizing pump and delivered to the atomized sizing device to treat the wet paper web.

[0065] According to some preferred embodiments, the drying and curing is achieved using a contact drying system. The reinforced and modified wet paper web is introduced into an 80°C low-temperature drying cylinder, then dried and initially cured in a drying cylinder group at 130–150°C, and finally cured in a drying cylinder group at 150–170°C, so as to achieve the purpose of complete reaction and curing of the reinforcing agent and water-resistant agent.

[0066] According to some preferred embodiments, the reinforcing modifier used in the reinforcing modification includes a reinforcing agent and a water-resistant agent; the reinforcing agent includes one or more of phenolic resin, acrylic resin and polyvinyl acetate resin; the water-resistant agent is a fluorine-free waterproofing agent.

[0067] According to some specific embodiments, the reinforcing modifier includes a first reinforcing agent solution, a second reinforcing agent solution, and a water-resistant agent solution in a mass ratio of 3:6:1; the first reinforcing agent solution contains 20 wt% of the first reinforcing agent and 80 wt% of water; the second reinforcing agent solution contains 20 wt% of the second reinforcing agent and 80 wt% of water; and the water-resistant agent solution contains 10 wt% of the water-resistant agent and 90 wt% of water.

[0068] In some preferred embodiments of the present invention, the first reinforcing agent and the second reinforcing agent are two acrylic resins with different glass transition temperatures (Tg). The acrylic resin with the higher glass transition temperature (Tg) is harder after curing, while the acrylic resin with the lower glass transition temperature (Tg) is softer after curing.

[0069] The specific sizing process is as follows: the mass ratio of the first reinforcing agent solution, the second reinforcing agent solution, and the water-resistant agent solution is accurately controlled at 3:6:1 using an electromagnetic flowmeter. After mixing, the mixture is pressurized by a sizing pump and delivered to an atomizing sizing device to treat the wet paper web. The reinforced wet paper web is then vacuum dehydrated and tightly interwoven to form a filter material. When the paper web treated in the sizing process includes two layers of wet paper web, the two layers of wet paper web are vacuum dehydrated and tightly interwoven to form a filter material with a gradient structure.

[0070] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below with reference to embodiments. The present invention does not specifically limit the source of the reagents used in the embodiments and comparative examples; they can be directly purchased or synthesized in-house.

[0071] Example 1

[0072] A method for preparing a glass fiber-based filter material includes:

[0073] Preparation of the first wet paper web: 475# microfiber glass wool with a freeness of 19°SR and 49°SR were weighed in a mass ratio of 60:25:15, along with alkali-free chopped strands with a diameter of 7μm. The pH of the pulping water was 3.0. First, the alkali-free chopped strands were fed into a pulper at a rotor frequency of 25Hz for a dispersion time of 120s. After dispersion, the 475# microfiber glass wool was added, with a pulper rotor frequency of 42.5Hz and a pulping time of 300s. Low-consistency beating was controlled to obtain a first glass fiber pulp with a concentration of 1.0%. The first glass fiber pulp underwent three stages of deslagging treatment, and then was sequentially pumped to the headbox to achieve uniform distribution of the pulp on the web, with a web concentration of 0.15%. It was then subjected to gravity dewatering and vacuum dewatering (vacuum pressure 35kPa) to form the first wet paper web (moisture content 30%).

[0074] Loading acidified carbon nanotubes: A first wet paper web is placed between a lower electrode plate connected to the positive terminal of a power supply and an upper electrode plate connected to the negative terminal of a power supply. A 5% (by mass) dispersion of acidified carbon nanotubes is overflowed onto the surface of the first wet paper web. An electric field (field intensity up to 60 V·cm) is applied. -1 Under the action of ), the paper web running speed is controlled and the loading of acidified carbon nanotubes is adjusted. The acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then vacuum dehydration is performed (vacuum pressure is 40 kPa). The moisture content of the dehydrated wet paper web is 50%, and the acidified carbon nanotubes account for 4% of the total mass of the glass fiber-based filter material, thus obtaining the modified wet paper web.

[0075] Reinforcement Modification: The dehydrated modified wet paper web is reinforced and modified using atomized sizing agents. The reinforcement modifiers include a first reinforcement solution, a second reinforcement solution, and a water-resistant agent solution in a mass ratio of 3:6:1. In the first reinforcement solution, the first reinforcement (first acrylic resin) accounts for 20 wt% and water accounts for 80 wt%; in the second reinforcement solution, the second reinforcement (second acrylic resin) accounts for 20 wt% and water accounts for 80 wt%. The glass transition temperatures of the first and second acrylic resins are different. In the water-resistant agent solution, the water-resistant agent (fluorine-free water-resistant agent) accounts for 10 wt% and water accounts for 90 wt%. After sizing, the reinforcement modifier accounts for 4% of the filter paper mass. Then, after vacuum dehydration (vacuum pressure of 55 kPa), the two layers of wet paper web are further tightly interwoven, at which point the moisture content is 30%.

[0076] Drying and curing: The reinforced and modified wet paper web is introduced into an 80℃ low-temperature drying cylinder, then dried and initially cured in a 150℃ drying cylinder group, and finally cured in a 170℃ drying cylinder group, so that the reinforcing agent and water-resistant agent can fully react and cure to obtain glass fiber-based filter material.

[0077] Example 2

[0078] The process is basically the same as in Example 1, except that in the preparation of the first wet paper web, the mass ratio of 475# microfiber glass wool with a freeness of 19°SR and 475# microfiber glass wool with a freeness of 49°SR to alkali-free short chopped filaments with a diameter of 7μm is 30:55:15.

[0079] Loading acidified carbon nanotubes: A first wet paper web is placed between a lower electrode plate connected to the positive terminal of a power supply and an upper electrode plate connected to the negative terminal of a power supply. A 2% (by mass) dispersion of acidified carbon nanotubes is overflowed onto the surface of the first wet paper web. An electric field (field intensity up to 60 V·cm) is applied. -1 Under the action of ), the paper web running speed is controlled and the loading of acidified carbon nanotubes is adjusted. The acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then vacuum dehydration is performed (vacuum pressure is 55 kPa). The moisture content of the dehydrated wet paper web is 30%, and the acidified carbon nanotubes account for 2% of the total mass of the glass fiber-based filter material, thus obtaining the modified wet paper web.

[0080] Example 3

[0081] The process is essentially the same as in Example 2, except that acidified carbon nanotubes are loaded: a first wet paper web is placed between a lower electrode plate connected to the positive terminal of a power source and an upper electrode plate connected to the negative terminal of a power source. A 5% (by mass) dispersion of acidified carbon nanotubes is overflowed onto the surface of the first wet paper web, and an electric field (field intensity up to 60 V·cm) is applied. -1Under the action of ), the paper web running speed is controlled and the loading of acidified carbon nanotubes is adjusted. The acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then vacuum dehydration is performed (vacuum pressure is 40 kPa). The moisture content of the dehydrated wet paper web is 50%, and the acidified carbon nanotubes account for 4% of the total mass of the glass fiber-based filter material, thus obtaining the modified wet paper web.

[0082] Example 4

[0083] The process is essentially the same as in Example 2, except that acidified carbon nanotubes are loaded: a first wet paper web is placed between a lower electrode plate connected to the positive terminal of a power source and an upper electrode plate connected to the negative terminal of a power source. A 10% (by mass) dispersion of acidified carbon nanotubes is overflowed onto the surface of the first wet paper web, and an electric field (field intensity up to 120 V·cm) is applied. -1 Under the action of ), the paper web running speed is controlled and the loading of acidified carbon nanotubes is adjusted. The acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then vacuum dehydration is performed (vacuum pressure is 40 kPa). The moisture content of the dehydrated wet paper web is 40%, and the acidified carbon nanotubes account for 6% of the total mass of the glass fiber-based filter material, thus obtaining the modified wet paper web.

[0084] Comparative Example 1

[0085] The process is basically the same as in Example 3, except that acidified carbon nanotubes are loaded: a dispersion of acidified carbon nanotubes with a mass fraction of 5% is overflowed onto the surface of the first wet paper web, and then vacuum dehydration is performed (vacuum pressure is 40 kPa). The moisture content of the wet paper web after dehydration is 50%, and the acidified carbon nanotubes account for 4% of the total mass of the glass fiber-based filter material, thus obtaining the modified wet paper web.

[0086] Comparative Example 2

[0087] This is essentially the same as Example 3, except that acidified carbon nanotubes were not loaded onto the fiber surface of the first wet paper web.

[0088] Comparative Example 3

[0089] The process is basically the same as in Example 3, except that the surface of the first wet paper web is loaded with acidified carbon nanotubes, which account for 8% of the total mass of the glass fiber-based filter material.

[0090] Example 5

[0091] A method for preparing a glass fiber-based filter material includes:

[0092] Preparation of the first wet paper web: 475# microfiber glass wool with a freeness of 19°SR and 49°SR were weighed in a mass ratio of 60:25:15, along with alkali-free chopped strands with a diameter of 7μm. The pH of the pulping water was 3.0. First, the alkali-free chopped strands were fed into a pulper at a rotor frequency of 25Hz for a dispersion time of 120s. After dispersion, the 475# microfiber glass wool was added, with a pulper rotor frequency of 42.5Hz and a pulping time of 300s. Low-consistency beating was controlled to obtain a first glass fiber pulp with a concentration of 1.0%. The first glass fiber pulp underwent three stages of deslagging treatment, and then was sequentially pumped to the headbox to achieve uniform distribution of the pulp on the web, with a web concentration of 0.15%. It was then subjected to gravity dewatering and vacuum dewatering (vacuum pressure 35kPa) to form the first wet paper web (moisture content 25%).

[0093] Loading acidified carbon nanotubes: A first wet paper web is placed between a lower electrode plate connected to the positive terminal of a power supply and an upper electrode plate connected to the negative terminal of a power supply. A 2% (by mass) dispersion of acidified carbon nanotubes is overflowed onto the surface of the first wet paper web. An electric field (field intensity up to 60 V·cm) is applied. -1 Under the action of ), the paper web running speed is controlled and the loading of acidified carbon nanotubes is adjusted. The acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then vacuum dehydration is performed (vacuum pressure is 40 kPa). The moisture content of the dehydrated wet paper web is 60%, and the acidified carbon nanotubes account for 2% of the total mass of the glass fiber-based filter material, thus obtaining the modified wet paper web.

[0094] Preparation of the second wet paper web: Weigh 475# microfiber glass wool with a freeness of 34°SR and 475# microfiber glass wool with a freeness of 49°SR, along with 7μm alkali-free chopped filaments, at a mass ratio of 25:60:15. The pH of the pulping water is 3.5. First, the alkali-free chopped filaments are fed into the pulper. The pulper rotor frequency is 25Hz and the dispersion time is 120s. After dispersion, 475# microfiber glass wool is added. The pulper rotor frequency is 42.5Hz and the pulping time is 360s. Low-consistency beating is controlled, resulting in a second glass fiber pulp with a concentration of 1.0%. The ratio of the total mass of glass fibers in the second glass fiber pulp to the total mass of glass fibers in the first glass fiber pulp is 1:1. The second glass fiber slurry is subjected to three stages of slag removal treatment, and then sequentially transported to the headbox by a slurry pump to achieve uniform distribution of the slurry on the web with a web concentration of 0.15%. It is then subjected to gravity dewatering and vacuum dewatering (vacuum pressure of 50 kPa) to form the second wet paper web (moisture content of 60%).

[0095] Double-layer composite: The modified wet paper web is guided to the second wet paper web by the guide roller, and then dewatered under vacuum (vacuum pressure is 55 kPa). The moisture content of the wet paper web after vacuum dewatering is controlled to be 25%, thus obtaining the composite wet paper web.

[0096] Reinforcement and Modification: The composite wet paper web is reinforced and modified using atomized sizing agents. The reinforcement and modification agents include a first reinforcement solution, a second reinforcement solution, and a water-resistant agent solution in a mass ratio of 3:6:1. In the first reinforcement solution, the first reinforcement (first acrylic resin) accounts for 20 wt% and water accounts for 80 wt%; in the second reinforcement solution, the second reinforcement (second acrylic resin) accounts for 20 wt% and water accounts for 80 wt%. The glass transition temperatures of the first and second acrylic resins are different. In the water-resistant agent solution, the water-resistant agent (fluorine-free water-resistant agent) accounts for 10 wt% and water accounts for 90 wt%. After sizing, the reinforcement and modification agents account for 4% of the filter paper mass. Then, after vacuum dehydration (vacuum pressure of 55 kPa), the two layers of wet paper web are further tightly interwoven, at which point the moisture content is 25%.

[0097] Drying and curing: The reinforced modified wet paper web is introduced into an 80℃ low-temperature drying cylinder, then dried and initially cured in a 140℃ drying cylinder group, and finally cured in a 160℃ drying cylinder group, so that the reinforcing agent and water-resistant agent can fully react and cure to obtain glass fiber-based filter material.

[0098] Example 6

[0099] It is basically the same as Example 5, except that:

[0100] Loading acidified carbon nanotubes: A first wet paper web is placed between a lower electrode plate connected to the positive terminal of a power supply and an upper electrode plate connected to the negative terminal of a power supply. A 5% (by mass) dispersion of acidified carbon nanotubes is overflowed onto the surface of the first wet paper web. An electric field (field intensity up to 60 V·cm) is applied. -1 Under the action of ), the paper web running speed is controlled and the loading of acidified carbon nanotubes is adjusted. The acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then vacuum dehydration is performed (vacuum pressure is 40 kPa). The moisture content of the dehydrated wet paper web is 50%, and the acidified carbon nanotubes account for 4% of the total mass of the glass fiber-based filter material, thus obtaining the modified wet paper web.

[0101] Preparation of the second wet paper web: A second wet paper web with a moisture content of 50% was prepared using the preparation method of Example 5.

[0102] Double-layer composite: A composite wet paper web with a moisture content of 30% was prepared using the preparation method of Example 5.

[0103] Reinforcement modification: The method of Example 5 was used for reinforcement modification to obtain a reinforced and modified wet paper web with a moisture content of 30%.

[0104] Drying and curing: The reinforced modified wet paper web is introduced into an 80℃ low-temperature drying cylinder, then dried and initially cured in a 140℃ drying cylinder group, and finally cured in a 160℃ drying cylinder group, so that the reinforcing agent and water-resistant agent can fully react and cure to obtain glass fiber-based filter material.

[0105] Example 7

[0106] It is basically the same as Example 5, except that:

[0107] Loading acidified carbon nanotubes: A first wet paper web is placed between a lower electrode plate connected to the positive terminal of a power supply and an upper electrode plate connected to the negative terminal of a power supply. A 10% (by mass) dispersion of acidified carbon nanotubes is overflowed onto the surface of the first wet paper web. An electric field (field intensity up to 120 V·cm) is applied. -1 Under the action of ), the paper web running speed is controlled and the loading of acidified carbon nanotubes is adjusted. The acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then vacuum dehydration is performed (vacuum pressure is 40 kPa). The moisture content of the dehydrated wet paper web is 40%, and the acidified carbon nanotubes account for 6% of the total mass of the glass fiber-based filter material, thus obtaining the modified wet paper web.

[0108] Preparation of the second wet paper web: A second wet paper web with a moisture content of 40% was prepared using the preparation method of Example 5.

[0109] Double-layer composite: A composite wet paper web with a moisture content of 35% was prepared using the preparation method of Example 5.

[0110] Reinforcement modification: The method of Example 5 was used for reinforcement modification to obtain a reinforced modified wet paper web with a moisture content of 35%;

[0111] Drying and curing: The reinforced and modified wet paper web is introduced into an 80℃ low-temperature drying cylinder, then dried and initially cured in a 150℃ drying cylinder group, and finally cured in a 170℃ drying cylinder group, so that the reinforcing agent and water-resistant agent can fully react and cure to obtain glass fiber-based filter material.

[0112] Example 8

[0113] It is basically the same as Example 6, except that the ratio of the total mass of glass fibers in the first glass fiber slurry to the total mass of glass fibers in the second glass fiber slurry is 1:2.

[0114] Example 9

[0115] It is basically the same as Example 6, except that the ratio of the total mass of glass fibers in the first glass fiber slurry to the total mass of glass fibers in the second glass fiber slurry is 3:7.

[0116] Comparative Example 4

[0117] The process is basically the same as in Example 6, except that acidified carbon nanotubes are loaded: a dispersion of 5% by mass of acidified carbon nanotubes is overflowed onto the surface of the first wet paper web, and then vacuum dehydration is performed (vacuum pressure is 40 kPa). The moisture content of the dehydrated wet paper web is 50%, and the acidified carbon nanotubes account for 4% of the total mass of the glass fiber-based filter material, thus obtaining the modified wet paper web.

[0118] Comparative Example 5

[0119] This is essentially the same as Example 6, except that acidified carbon nanotubes were not loaded onto the fiber surface of the first wet paper web.

[0120] Comparative Example 6

[0121] This is basically the same as Example 6, except that the surface of the first wet paper web is loaded with acidified carbon nanotubes, which account for 8% of the total mass of the glass fiber-based filter material.

[0122] The performance of the glass fiber-based filter materials provided in the embodiments and comparative examples of the present invention was tested, and the specific test methods are as follows:

[0123] Dust holding capacity test of air filter paper: The test was conducted in accordance with the national standard JG / T22-1999 "Test Method for Performance of Air Filters for General Ventilation".

[0124] Air filter paper filtration efficiency and filtration resistance tests: conducted in accordance with the national standard GB / T 6165-2021 "Performance Test Methods for High-Efficiency Air Filters: Efficiency and Resistance".

[0125] Table 1. Performance data of glass fiber-based filter materials prepared in various embodiments and comparative examples of the present invention. Note: ① The fiber mass ratio of the first paper web and the fiber mass ratio of the second paper web refer to the mass ratio of 475# microfiber glass wool with a freeness of 19°SR, 475# microfiber glass wool with a freeness of 49°SR, and alkali-free chopped strands in the paper web. ② The fiber mass ratio of the two paper webs refers to the ratio of the total mass of glass fibers in the first paper web to the total mass of glass fibers in the second paper web. ③ CNT content refers to the mass fraction of acidified carbon nanotubes in the glass fiber-based filter material. ④ Quality factor η = -100*Log(1-E) / (P / 10), where E is the filtration efficiency and P is the filtration resistance. ⑤ The above performance data were obtained by testing the glass fiber-based filter material after treating it at 350℃.

[0126] As shown in Table 1, both the single-layer glass fiber-based filter material and the double-layer gradient glass fiber-based filter material prepared in the embodiments of the present invention have excellent filtration performance and high dust holding capacity.

[0127] As shown in Examples 1 and 3, under the same quantitative conditions, the adsorption performance and dust holding capacity of a single-layer glass fiber-based filter material can be controlled by adjusting the proportion of each fiber in the first paper web. As shown in Examples 1 and 6, under the same carbon nanotube loading and similar quantitative conditions, after loading acidified carbon nanotubes onto the first paper web (inflow surface) and then compounding it with a second paper web to obtain a double-layer gradient glass fiber-based filter material, the dust holding capacity of the filter material can be further improved without affecting its filtration performance. This invention can meet different application requirements by adjusting the content and structure (single-layer or double-layer) of each fiber component in the glass fiber-based filter material.

[0128] As can be seen from Examples 3 and 1, and Examples 6 and 4, when the carbon nanotube loading is the same and the quantitative difference is similar, compared with the method of uniformly loading acidified carbon nanotubes onto the fiber surface under the action of an electric field, the method of directly loading acidified carbon nanotubes by overflowing the dispersion onto the first wet paper surface results in the acidified carbon nanotubes only adsorbing onto the paper surface and failing to be uniformly distributed on the fiber surface. This covers the voids in the paper, increases the filtration resistance, and reduces the adsorption and filtration performance and dust holding capacity of the filter paper. Furthermore, the method of directly loading acidified carbon nanotubes by overflowing the dispersion onto the first wet paper surface results in low bonding strength between the acidified carbon nanotubes and the fibers, making them prone to detachment.

[0129] As can be seen from Examples 2-4 and Comparative Example 2, Examples 5-7 and Comparative Example 5, when the fiber composition is the same and the quantitative difference is similar, loading carbon nanotubes on the fiber surface helps to improve the adsorption effect of the filter material on pollutants, and improve the filtration performance and dust holding capacity of the filter material.

[0130] As can be seen from Examples 2-4 and Comparative Examples 3, Examples 5-7 and Comparative Examples 6, under similar quantitative conditions, if the content of acidified carbon nanotubes loaded on the fiber surface is too high, it will block the pores between the fibers, increase the filtration resistance, reduce the filtration performance of the filter material, and at the same time, it will not be conducive to improving the dust holding capacity of the filter material.

[0131] The glass fiber-based filter material prepared in Example 6 was treated at 25°C and 350°C respectively, and its performance was tested. The results showed that the filter material treated at 25°C had a filtration efficiency of 99.9952%, a filtration resistance of 328 Pa, a quality factor of 13.2, and a dust holding capacity of 72 g / m³. 2 The filter material treated at 350℃ has a filtration efficiency of 99.9956%, a filtration resistance of 328 Pa, a quality factor of 13.3, and a dust holding capacity of 74 g / m³. 2 This indicates that different processing temperatures have little impact on the performance of the filter material, and the prepared glass fiber-based filter material has high temperature resistance.

[0132] 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 modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to 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 glass fiber-based filter material, characterized in that, The glass fiber-based filter material includes a first paper web; the first paper web is glass fiber filter paper with acidified carbon nanotubes loaded on the fiber surface; the acidified carbon nanotubes account for 2-6% of the total mass of the glass fiber-based filter material.

2. The glass fiber-based filter material according to claim 1, characterized in that, The glass fiber-based filter material further includes a second paper web laminated with the first paper web; the second paper web is glass fiber filter paper; the pore size of the first paper web is larger than the pore size of the second paper web; Preferably, the mass of glass fiber in the first paper web accounts for 30-50% of the total mass of glass fiber in the glass fiber-based filter material.

3. A method for preparing the glass fiber-based filter material according to any one of claims 1-2, characterized in that, The preparation method includes: S1. A first wet paper web is prepared using a first glass fiber pulp; S2. Under the action of an electric field, acidified carbon nanotubes are loaded onto the fiber surface of the first wet paper web, and then subjected to vacuum dehydration, reinforcement modification, drying and curing to obtain a glass fiber-based filter material.

4. The preparation method according to claim 3, characterized in that, Prior to the vacuum dehydration, the process further includes: preparing a second wet paper web using a second glass fiber slurry, and placing a first wet paper web loaded with acidified carbon nanotubes onto the second wet paper web.

5. The preparation method according to claim 3, characterized in that, Under the action of an electric field, acidified carbon nanotubes are loaded onto the fiber surface of a first wet paper web, comprising: placing the first wet paper web between a lower electrode plate connected to the positive terminal of a power source and an upper electrode plate connected to the negative terminal of a power source; overflowing an acidified carbon nanotube dispersion onto the surface of the first wet paper web; and loading the acidified carbon nanotubes onto the fiber surface of the first wet paper web under the action of an electric field.

6. The preparation method according to claim 5, characterized in that, The mass fraction of acidified carbon nanotubes in the acidified carbon nanotube dispersion is 2-10%. The electric field strength is 10–120 V·cm. -1 ; and / or The load duration is 10–40 seconds.

7. The preparation method according to claim 4, characterized in that, The glass fibers in the first glass fiber slurry and the second glass fiber slurry include microfiber glass wool and alkali-free chopped strands; The concentrations of the first glass fiber slurry and the second glass fiber slurry are 0.7% to 1.2%. The pH of the first glass fiber slurry is 2.5–3.0; and / or The pH of the second glass fiber slurry is 3.0 to 3.

5.

8. The preparation method according to claim 4, characterized in that, The moisture content of the first wet paper web is 25-30%; and / or The moisture content of the first wet paper web loaded with acidified carbon nanotubes is 40-60%; and / or The moisture content of the second wet paper web is 40-60%; and / or The moisture content of the paper web after vacuum dewatering is 25-35%.

9. The preparation method according to claim 3, characterized in that, The vacuum pressure for vacuum dehydration is 35–65 kPa; The enhancement and modification are performed using an atomized sizing method; and / or The drying and curing process is achieved using a contact drying system.

10. The preparation method according to claim 3, characterized in that, The reinforcing modifier used in the reinforcement modification includes a reinforcing agent and a water-resistant agent; the reinforcing agent includes one or more of phenolic resin, acrylic resin and polyvinyl acetate resin; the water-resistant agent is a fluorine-free waterproofing agent.

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