Composite antibacterial air filtering material as well as preparation method and application thereof

Abstract

The invention discloses a composite antibacterial air filtering material as well as a preparation method and application thereof. According to the preparation method, plant fibers, glass fibers and single-layer or double-layer silver-loaded nanocellulose (CNC / BC) are compounded, wet forming is adopted, and a liquid nitrogen freezing-freeze-drying process is combined, so that the composite antibacterial air filtering material is prepared. An axially ordered fiber network and a multi-stage pore structure are formed in the air filtering material, and the air filtering material has excellent mechanical property, filtering property and antibacterial property, is suitable for air purification in multiple scenes such as medical treatment and industry, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of functional paper-based materials technology, and in particular to a composite antibacterial air filter material, its preparation method, and its application. Background Technology

[0002] With accelerated industrialization and increased emphasis on a healthy breathing environment, the demand for antibacterial air filtration materials in the air purification field is becoming increasingly urgent. In public places, medical facilities, and homes, air filtration materials not only need to effectively intercept particulate matter but also must have the ability to inhibit the growth and spread of bacteria and viruses to ensure indoor air quality and reduce the risk of respiratory infections. Therefore, high-performance antibacterial air filtration materials have become a key research direction in the industry.

[0003] Currently, air filtration materials on the market struggle to simultaneously meet the demands for mechanical performance, antibacterial properties, and filtration efficiency. While traditional glass fiber filter materials offer good mechanical strength and particulate matter interception capabilities, they lack antibacterial properties, making them susceptible to microbial growth that can negatively impact both material strength and filtration effectiveness. Some antibacterial filter materials, while inhibiting bacterial growth, perform poorly in terms of mechanical properties and filtration efficiency, and their antibacterial and filtration performance rapidly declines with prolonged use. Furthermore, single-material air filtration materials, regardless of improvements, cannot achieve a synergistic enhancement of multiple performance characteristics, failing to meet the requirements of complex usage scenarios.

[0004] To overcome these technical bottlenecks, researchers have conducted extensive research. Regarding improving antibacterial performance, some studies have employed a method of coating the filter material with quaternary ammonium salt antibacterial coatings. While this can provide short-term antibacterial effects, the coating is prone to detachment under airflow friction and humid environments, leading to a rapid decline in antibacterial performance. Other studies have incorporated nano-silver particles into the filter material; however, the poor dispersion of nano-silver particles in the material and their tendency to aggregate not only affect the material's uniformity but may also cause excessive release of silver ions in certain areas, posing safety hazards. In terms of improving overall performance, attempts have been made to simply blend multiple materials. However, due to poor interfacial compatibility between different materials, this has actually reduced the material's mechanical properties and increased air resistance, thus lowering filtration efficiency. Furthermore, some studies using physical modifications, such as altering the material's pore structure, can optimize filtration to some extent, but their improvement in the material's antibacterial properties and mechanical stability is very limited.

[0005] Based on this, a new type of antibacterial air filter material was developed, which effectively solves the technical problem that existing materials cannot achieve the same performance, while also having good safety and environmental friendliness, and has good application prospects in the field of antibacterial air filter materials. Summary of the Invention

[0006] The primary objective of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a method for preparing a composite antibacterial air filter material.

[0007] Another object of the present invention is to provide a composite antibacterial air filter material prepared by the method described above.

[0008] Another object of the present invention is to provide the application of the composite antibacterial air filter material.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for preparing a composite antibacterial air filter material includes the following steps:

[0011] (1) Preparation of fiber paper: Plant fiber and glass fiber are mixed in a sulfuric acid solution with a pH of 2.5 to 3.0 (as a dispersion), and the mixture is disintegrated at a speed of 12,000 to 20,000 rpm to obtain a fiber suspension; then the fiber suspension is formed into a paper to obtain a fiber paper.

[0012] (2) Preparation of composite slurry: Silver-loaded cellulose nanocrystals (CNC) are mixed with starch and water to prepare silver-loaded CNC-starch slurry; Silver-loaded bacterial cellulose (BC) is mixed with starch and water to prepare silver-loaded BC-starch slurry;

[0013] (3) Coating with composite slurry:

[0014] ① Coat one side of the fiber paper sample evenly with silver-loaded CNC-starch paste or silver-loaded BC-starch paste (single-sided coating) to obtain composite paper sample A;

[0015] ② Coat one side of the fiber paper sample evenly with silver-loaded CNC-starch paste (single-sided coating) to form a silver-loaded CNC-starch composite layer; then, before it is completely dry, continue to coat the silver-loaded CNC-starch composite layer with silver-loaded BC-starch paste (to complete the secondary composite) to obtain composite paper sample B.

[0016] (4) Post-processing: The composite paper sample A or composite paper sample B is completely immersed in the acrylic resin emulsion. After immersion, the excess emulsion is removed by vacuum filtration. Then, it is placed in liquid nitrogen to freeze and freeze-dried at -60 to -30°C. Finally, it is hot-pressed to obtain the composite antibacterial air filter material.

[0017] The plant fiber mentioned in step (1) is preferably hardwood fiber; more preferably bleached sulfate hardwood pulp fiber.

[0018] The mass ratio of plant fiber to glass fiber in step (1) is 1:(3-7); preferably 1:5.

[0019] The preferred rotation speed for the scavenging process in step (1) is 12,000 to 18,000 rpm; more preferably 15,000 rpm.

[0020] The preferred method for papermaking in step (1) is to use a paper forming machine. The specific steps are as follows: the fiber suspension is transferred to the paper forming machine and the water is filtered and formed by vacuum filtration to obtain a fiber paper sample.

[0021] The concentration of the fiber suspension in step (1) is 1.0 to 2.0 wt%; preferably 1.0 wt%.

[0022] The basis weight of the fiber paper sample mentioned in step (1) is approximately 50 g / m³. 2 .

[0023] The starch mentioned in step (2) is corn starch.

[0024] The mass ratio of silver-loaded cellulose nanocrystals (CNC) to starch in step (2) is (1-5):1; preferably 3:1.

[0025] The silver content in the silver-loaded cellulose nanocrystals (CNC) described in step (2) is 1.3 ± 0.1 wt%, and the particle size is 25–45 nm; preferably, it is prepared by the following method:

[0026] Softwood pulp was hydrolyzed with sulfuric acid, and CNC dispersion was obtained after dialysis and centrifugation purification. Then, the CNC dispersion was mixed with silver nitrate solution, stirred at room temperature, and reduced with sodium borohydride solution. Finally, silver-loaded cellulose nanocrystals (CNC) were obtained by freeze drying.

[0027] The dialysis is performed using a dialysis bag with a molecular weight cutoff of 1000-3500 Da; preferably, dialysis is performed for 12-24 hours using a dialysis bag with a molecular weight cutoff of 1000-3500 Da, with the dialysis solution being changed every 4-6 hours.

[0028] The dialysate used in the dialysis was deionized water.

[0029] The concentration of the sulfuric acid is 64 ± 4 wt%.

[0030] The hydrolysis conditions are: hydrolysis at 50±5℃ for 2±0.5h.

[0031] The solid-liquid ratio of the softwood pulp to sulfuric acid is 1g:15-30mL; preferably 1g:20mL.

[0032] The concentrations of the CNC dispersion, silver nitrate solution, and sodium borohydride solution can be adjusted according to actual needs. For example, the preferred concentration of the CNC dispersion is 1 wt%; the preferred concentration of the silver nitrate solution is 0.05 mol / L; the preferred concentration of the sodium borohydride solution is 0.02 mol / L; and the preferred concentration of Ag in the silver nitrate solution is... + With BH4 in sodium borohydride solution - Molar ratio 1:2.

[0033] The mass ratio of the CNC dispersion to the silver nitrate solution is 10:1.

[0034] The stirring time at room temperature is 2 to 4 hours; preferably 3 hours.

[0035] The solid content of the silver-loaded CNC-starch slurry mentioned in step (2) is 2% to 8%; preferably 5%.

[0036] The silver content in the silver-loaded bacterial cellulose (BC) described in step (2) is 0.9 ± 0.05 wt%, and the fiber diameter is 15–25 nm; preferably, it is prepared by the following method:

[0037] Acetobacter xylose was inoculated into a culture medium and allowed to stand to grow to obtain a BC membrane. The BC membrane was then immersed in silver nitrate solution, reduced with ascorbic acid solution, washed, and freeze-dried to obtain silver-loaded bacterial cellulose.

[0038] The preferred Acetobacter xylinum is CGMCC 1.1812.

[0039] The culture medium has the following formulation: glucose 20 g / L, peptone 5 g / L, yeast extract 5 g / L, pH 6.0.

[0040] The conditions for static culture are: static culture at 30±2℃ for 5 to 8 days; preferably: static culture at 30℃ for 7 days.

[0041] The concentrations of the silver nitrate solution and the ascorbic acid solution can be adjusted according to actual needs. For example, the concentration of the silver nitrate solution is preferably 0.15 mol / L, and the concentration of the ascorbic acid solution is preferably 0.08 mol / L.

[0042] The mass ratio of silver-loaded bacterial cellulose (BC) to starch in step (2) is (1-10):1; preferably (3-7):1; more preferably 5:1.

[0043] In step (2), the preparation of silver-loaded CNC-starch slurry is aided by magnetic stirring, which enables the silver-loaded cellulose nanocrystals (CNC) to be fully dispersed with starch, forming a slurry with uniform texture and good fluidity.

[0044] The stirring speed is 800-1000 rpm; preferably 850 rpm.

[0045] The stirring time is 80 to 100 minutes; preferably 90 minutes.

[0046] The solid content of the silver-loaded BC-starch slurry mentioned in step (2) is 2% to 8%; preferably 3%.

[0047] In step (2), the preparation of silver-loaded BC-starch slurry is aided by magnetic stirring, which allows the silver-loaded bacterial cellulose (BC) and starch to be fully dispersed, resulting in a uniform slurry.

[0048] The stirring speed is 800-1000 rpm; preferably 1000 rpm.

[0049] The stirring time is 20 to 40 minutes; preferably 30 minutes.

[0050] The coating process described in steps (3) ① and ② is preferably carried out using a doctor blade coating machine to achieve wet forming, allowing the slurry to be tightly bonded to the paper sample.

[0051] The coating conditions described in steps (3) ① and ② are: the spacing between the scrapers is maintained at 0.5 to 1.2 mm, and the scraper speed is 1 to 10 cm / min; preferably: the spacing between the scrapers is maintained at 0.8 mm, and the scraper speed is 10 cm / min.

[0052] In steps (3) ① and ②, the coating thickness of the silver-loaded CNC-starch paste or the silver-loaded BC-starch paste is 0.15 to 0.35 mm; preferably 0.3 mm.

[0053] The concentration of the acrylic resin emulsion in step (4) is 6% to 11% by mass; preferably 10% by mass.

[0054] The solid content of the acrylic resin emulsion mentioned in step (4) is 40±1wt%.

[0055] The soaking time in step (4) is 3 to 9 minutes; preferably 5 minutes.

[0056] In step (4), the freezing time in liquid nitrogen is 20 to 35 minutes; preferably 30 minutes.

[0057] The freeze-drying (freeze-drying) mentioned in step (4) refers to freeze-drying using a freeze dryer.

[0058] The vacuum degree of the freeze-drying in step (4) is 0.005 to 0.02 mbar; preferably 0.01 mbar.

[0059] The freeze-drying time in step (4) is 18 to 72 hours; preferably 24 hours.

[0060] The conditions for hot pressing in step (4) are: hot pressing temperature 120-220℃, hot pressing pressure 1-15MPa, and hot pressing time 15-90 minutes; preferably: hot pressing temperature 150℃, hot pressing pressure 5MPa, and hot pressing time 20 minutes.

[0061] A composite antibacterial air filter material is prepared by any of the methods described above.

[0062] The application of the aforementioned composite antibacterial air filter material in the preparation of air purification materials, medical masks, and / or industrial dust removal materials.

[0063] The air purification materials mentioned include those used in air purification filters, industrial or household air purifiers, medical air purification (such as air purification for medical operating rooms), air purification in automotive air conditioning, and protection of energy equipment (such as air purification materials for fuel cells).

[0064] This invention proposes a novel composite antibacterial air filter material. On the one hand, this material possesses excellent mechanical strength, ensuring structural stability under long-term use and complex environments. On the other hand, through a unique fiber structure design and distribution, the porosity and pore size distribution of the material are optimized, significantly improving the interception efficiency of fine particulate matter while maintaining low filtration resistance. Through a scientific composite process, the properties of each component of the material achieve synergistic complementarity, effectively solving the technical challenge of balancing the performance of existing materials. Simultaneously, it exhibits good safety and environmental friendliness, opening a new path for the development of antibacterial air filter materials.

[0065] The present invention has the following advantages and effects compared with the prior art:

[0066] (1) The composite antibacterial air filter material prepared in this invention combines an innovative composite structure with a freeze-drying process to synergistically enhance its comprehensive performance: By combining glass fiber, plant fiber, and double-layer silver-loaded nanocellulose (CNC / BC) and using a liquid nitrogen freeze-drying process, a multi-level porous structure with oriented fiber arrangement is constructed. Among them, glass fiber and plant fiber form a high-strength skeleton (tensile strength is increased by 34.7% compared with traditional materials), and the freeze-drying process promotes the orderly arrangement of fibers along the axial direction and enhances mechanical interlocking; the composite coating of silver-loaded CNC and BC, through a "rapid release-slow release" synergistic mechanism, enables the inhibition zone of Escherichia coli to reach 8.36 mm and the inhibition zone of Staphylococcus aureus to reach 9.00 mm, with an antibacterial rate of over 99%. At the same time, the multi-level porous structure reduces the filtration resistance to 78 Pa (57.7% lower than that of a single coating) and increases the filtration efficiency of 0.3 μm particles to 99.99%, breaking through the contradiction between the mechanical properties and filtration performance of traditional materials and meeting the needs of medical-grade air purification.

[0067] (2) The composite antibacterial air filter material prepared by this invention has environmental advantages in terms of green process and structural design: it adopts a wet molding process with water as the dispersion medium, avoiding organic solvent pollution; plant fiber and starch are used as coating matrices, replacing some synthetic materials, reducing energy consumption by more than 20%. Silver-loaded nanocellulose is prepared through green chemistry, with no risk of heavy metal release, and the material is biodegradable after disposal. Compared with traditional resin-containing filter materials, the process of this invention can reduce carbon emissions, and the freeze-drying process avoids high-temperature energy consumption, making it suitable for medical and industrial air purification, environmentally friendly air purification filter elements, medical masks, and other scenarios.

[0068] (3) The composite antibacterial air filter material prepared by this invention has precise performance control and industrial adaptability: by adjusting the mass ratio of glass fiber to plant fiber, the coating sequence of silver-loaded nanocellulose (CNC before BC), and the freeze-drying process parameters, precise performance optimization can be achieved. For example, the tensile strength of the double-layer coating is increased by 25%-30% compared with the single-layer coating, and the filtration resistance is reduced by 12%-27%. The hot-pressing process parameters (150℃, 5MPa, 20min) are suitable for continuous industrial production, with strong equipment compatibility, and the cost can be reduced through large-scale production. The adjustable performance range covers low-resistance civilian scenarios (filtration resistance ≤100Pa) and high antibacterial medical needs (antibacterial zone ≥8mm), and the application scenarios can be flexibly expanded.

[0069] (4) In this invention, by adjusting the mass ratio of glass fiber to plant fiber (1:5), and then using high speed of 15,000 revolutions to decompose, the high speed rotation can grind the plant fiber into fine hairs (microfibrillation), which are more tightly wrapped with the glass fiber, making the material stronger; then combined with liquid nitrogen freezing and hot pressing: the fine hairs ground by high speed decomposition will form a regular pore structure when frozen with liquid nitrogen, and become a stable "skeleton" after hot pressing. In addition, two layers of silver-loaded nanocellulose can filter fine particles, have antibacterial properties, and are not easy to break.

[0070] (5) The two layers of nanocellulose in this invention can produce a synergistic effect: The synergistic effect of the two layers of silver-loaded nanocellulose (silver-loaded CNC-starch layer and silver-loaded BC-starch layer) enhances the core performance of the filter material through "functional division of labor + structural complementarity": In terms of functional division of labor, the silver-loaded CNC has a small particle size (about 20-50nm) and can penetrate into the fine pores of the fiber skeleton, intercepting small particles such as PM2.5 like a "nanofilter"; its loaded silver ions are densely distributed and can quickly kill bacteria attached to the pores; while the silver-loaded BC is a nanofiber network (diameter 10-30nm) that covers the surface, enhancing the wear resistance of the material surface like a "protective net" and reducing the risk of the CNC layer falling off due to friction. At the same time, its fiber gaps can adsorb larger dust particles and share the filtration pressure. In terms of structural complementarity, the CNC layer fills the inner pores, and the BC layer strengthens the surface structure. The combination of the two allows the material to form a gradient structure of "surface wear resistance + inner fine filtration". Test results show that: using the CNC layer alone, although the filtration efficiency is high, silver ions are easily lost (the antibacterial zone is reduced); using the BC layer alone, the filtration accuracy is insufficient (PM 2.5 filtration efficiency is 15% lower); while after the two layers are combined, the filtration efficiency remains above 95%, and the antibacterial rate is still over 90% after 10 rubs. Attached Figure Description

[0071] Figure 1 This is a flowchart illustrating the preparation process of the composite air filter material in Example 1. Detailed Implementation

[0072] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the raw materials, reagents, methods, and equipment used in the present invention are conventional raw materials, reagents, methods, and equipment in this technical field. Test methods in the following embodiments that do not specify specific experimental conditions are generally performed according to conventional experimental conditions or experimental conditions recommended by the manufacturer. Unless otherwise specified, the reagents and raw materials used in the present invention are commercially available.

[0073] The raw material information involved in the embodiments and comparative examples of this invention is as follows:

[0074] 1. Broadleaf wood fiber, glass fiber

[0075] Hardwood fiber: Purchased from Shandong Sun Paper Industry Co., Ltd. The product is bleached sulfate hardwood pulp fiber with the following specifications: fiber length 0.9-1.1 mm, diameter 22-28 μm, brightness 86% ISO, and freeness 30-35°SR.

[0076] Glass fiber: Purchased from Jushi Group Co., Ltd., the product is alkali-free chopped glass fiber (model ECS13-4.5-534), specifications: length 4.5mm, diameter 7μm, tensile strength 3100MPa, density 2.54g / cm³. 3 Moisture content ≤ 0.1%.

[0077] 2. Silver-loaded CNC (silver-loaded cellulose nanocrystals), silver-loaded BC (silver-loaded bacterial cellulose)

[0078] Silver-loaded CNC machining, the specific fabrication process is as follows:

[0079] CNC was obtained by hydrolyzing softwood pulp (purchased from UPM, Finland, model Nordic White) with 64 wt% sulfuric acid at 50°C for 2 h (solid-liquid ratio 1:20, g / mL), followed by dialysis (molecular weight cutoff: 1000-3500 Da; dialysate: deionized water, changed every 4-6 hours; time: 12-24 hours, until the dialysate pH stabilizes at 6-7) and centrifugation (8000 r / min, 15 min). The CNC dispersion (1 wt%) was mixed with 0.05 mol / L silver nitrate solution at a mass ratio of 10:1, stirred at room temperature for 3 h, and then reduced with 0.02 mol / L sodium borohydride solution (Ag). + With BH4 - The silver-loaded CNCs were obtained by freeze-drying (molar ratio 1:2), with a silver content of 1.3 ± 0.1 wt% and a particle size of 25–45 nm.

[0080] The specific preparation process for silver-loaded BC is as follows:

[0081] Acetobacter xylinum (purchased from China General Microbiological Culture Collection Center, CGMCC 1.1812) was used as the strain. BC membranes were obtained by static culture at 30°C for 7 days in a medium containing 20 g / L glucose, 5 g / L peptone, and 5 g / L yeast extract (pH 6.0). The BC membranes were then immersed in 0.15 mol / L silver nitrate solution for 24 h, reduced with 0.08 mol / L ascorbic acid solution for 2 h, washed, and freeze-dried to obtain silver-loaded BCs with a silver content of 0.9 ± 0.05 wt% and a fiber diameter of 15–25 nm.

[0082] 3. Starch

[0083] The corn starch was purchased from COFCO Biochemical Energy (Zhaodong) Co., Ltd. The product model is food-grade corn starch, with the following specifications: amylose content 26±1%, water 13±0.5%, ash content ≤0.08%, and pH 6.5~7.0.

[0084] 4. Acrylic resin emulsion

[0085] Acrylic resin emulsion, purchased from BASF (China) Co., Ltd., product model Acronal S 760, specifications: solid content 40±1wt%, viscosity at 25℃ 600~800mPa·s, pH value 7.5±0.5, minimum film-forming temperature 23℃, glass transition temperature (T g At 32℃, the density is 1.05 g / cm³. 3 .

[0086] Example 1

[0087] (1) In preparing the novel composite antibacterial air filter material, a sulfuric acid solution with a pH of 2.5–3.0 was first prepared as a dispersion. Then, hardwood fibers and glass fibers were weighed at a mass ratio of 1:5 and added to the dispersion. A fiber disintegration machine was used to disintegrate the fibers at a high speed of 15,000 rpm for 15 minutes, resulting in a uniform fiber suspension (1.0 wt%). The fiber suspension was then poured into a paper forming machine, and a vacuum filtration device was started. The material was dehydrated for 30 seconds under a pressure of -0.08 MPa, resulting in a yield of approximately 50 g / m³. 2 Preliminary fiber paper pattern.

[0088] (2) When preparing the silver-loaded CNC-starch composite layer, weigh the silver-loaded CNC and starch at a mass ratio of 3:1, add deionized water to prepare a mixture with a solid content of 5% (silver-loaded CNC-starch slurry), place it on a magnetic stirrer, and stir at a speed of 850 rpm for 90 minutes. Then fix the preliminary fiber paper sample on the coating machine platform, set the doctor blade spacing to 0.8 mm, the coating speed to 10 cm / min, and uniformly coat the silver-loaded CNC-starch slurry (single-sided coating) to make the wet coating thickness about 0.3 mm.

[0089] (3) Next, prepare the silver-loaded BC-starch composite layer. Weigh the silver-loaded BC and starch at a mass ratio of 5:1, add deionized water to prepare a mixture with a solid content of 3% (silver-loaded BC-starch slurry), and stir with an electric stirrer at a speed of 1000 rpm for 30 minutes. Before the silver-loaded CNC-starch layer is completely dry, immediately coat the silver-loaded BC-starch slurry on top of the silver-loaded CNC-starch layer with a doctor blade spacing of 0.8 mm and a coating speed of 10 cm / min, so that the wet coating thickness is about 0.3 mm.

[0090] (Note: Single-sided coating is used, on the same side as the CNC layer. That is, silver-loaded BC-starch slurry is coated on the surface of the already coated silver-loaded CNC-starch layer (not completely dry), and the same applies below. This process ensures that the two layers of nanocellulose form a gradient composite structure: the BC layer (protective mesh function) covers the surface of the CNC layer, which not only enhances wear resistance, but also works with the CNC layer to achieve the complementary functions of "surface wear resistance + inner fine filtration".)

[0091] (4) After completing the double-layer lamination, a post-processing step is performed. First, the double-layer lamination paper sample is completely immersed in an acrylic resin emulsion with a mass fraction of 10% and kept for 5 minutes. Then, excess adhesive is removed by vacuum filtration under a pressure of -0.05 MPa. Next, the paper sample is quickly placed in liquid nitrogen (tank) and frozen for 30 minutes. Then, it is transferred to a freeze dryer and freeze-dried at -50℃ and 0.01 mbar for 24 hours. Finally, the freeze-dried paper sample is placed in the mold of a hot press and hot-pressed at 150℃ and 5 MPa for 20 minutes to obtain the final air filter material.

[0092] (5) After the material is prepared, its performance needs to be tested. The mechanical properties are tested according to GB / T 12914-2018 standard, using a universal testing machine, with the tensile speed set to 100 mm / min. The filtration performance is tested by generating NaCl particles with a median diameter of 0.3 μm using an aerosol generator. The filtration efficiency and resistance are tested according to GB / T 6165-2008 under the condition of a wind speed of 5.3 cm / s. The antibacterial performance is tested according to GB / T 20944.3-2008 standard, inoculating Escherichia coli and Staphylococcus aureus, and calculating the antibacterial rate after 24 hours of incubation. The antibacterial performance test of each batch of products needs to be repeated 3 times in parallel. Among them, Escherichia coli ATCC 25922 (US Center for Type Culture Collection) is a conventional type strain and can be purchased through commercial channels (Beijing Beina Chuanglian Biotechnology Research Institute); Staphylococcus aureus ATCC 6538 (US Center for Type Culture Collection) is a standard test strain and can be purchased through commercial channels (China Industrial Microbial Culture Collection Center, CICC 10201).

[0093] Throughout the entire preparation process of this invention, the preparation of concentrated sulfuric acid must be carried out in a fume hood, and operators must wear acid and alkali resistant gloves and goggles. At the same time, the coating machine scraper must be calibrated regularly to ensure that the spacing error is <±0.05mm. During the freeze-drying process, the sample must be kept away from the air for a long time to prevent moisture absorption.

[0094] Example 2

[0095] (1) In preparing the novel composite antibacterial air filter material, a sulfuric acid solution with a pH of 2.5–3.0 was first prepared as a dispersion. Then, hardwood fibers and glass fibers were weighed at a mass ratio of 1:5 and added to the dispersion. A fiber disintegration machine was used to disintegrate the fibers at a high speed of 15,000 rpm for 15 minutes, resulting in a uniform fiber suspension (1.0 wt%). The fiber suspension was then poured into a paper forming machine, and a vacuum filtration device was started. The material was dehydrated for 30 seconds under a pressure of -0.08 MPa, resulting in a yield of approximately 50 g / m³. 2 Preliminary fiber paper pattern.

[0096] (2) First, prepare the silver-loaded BC-starch composite layer. Weigh the silver-loaded BC and starch at a mass ratio of 5:1, add deionized water to prepare a mixture with a solid content of 3%, and stir with an electric stirrer at a speed of 1000 rpm for 30 minutes. Apply the silver-loaded BC-starch slurry (single-sided coating) with a doctor blade spacing of 0.8 mm and a coating speed of 10 cm / min to make the wet coating thickness about 0.3 mm.

[0097] (3) After lamination, post-processing is performed. First, the composite paper sample is completely immersed in an acrylic resin emulsion with a mass fraction of 10% and kept for 5 minutes. Then, excess adhesive is removed by vacuum filtration under a pressure of -0.05 MPa. Next, the paper sample is quickly placed in liquid nitrogen and frozen for 30 minutes. Then, it is transferred to a freeze dryer and freeze-dried at -50℃ and 0.01 mbar for 24 hours. Finally, the freeze-dried paper sample is placed in the mold of a hot press and hot-pressed at 150℃ and 5 MPa for 20 minutes to obtain the final air filter material.

[0098] (4) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0099] Example 3

[0100] (1) In preparing the novel composite antibacterial air filter material, a sulfuric acid solution with a pH of 2.5–3.0 was first prepared as a dispersion. Then, hardwood fibers and glass fibers were weighed at a mass ratio of 1:5 and added to the dispersion. A fiber disintegration machine was used to disintegrate the fibers at a high speed of 15,000 rpm for 15 minutes, resulting in a uniform fiber suspension (1.0 wt%). The fiber suspension was then poured into a paper forming machine, and a vacuum filtration device was started. The material was dehydrated for 30 seconds under a pressure of -0.08 MPa, resulting in a yield of approximately 50 g / m³. 2 Preliminary fiber paper pattern.

[0101] (2) When preparing the silver-loaded CNC-starch composite layer, weigh the silver-loaded CNC and starch at a mass ratio of 3:1, add deionized water to prepare a mixture with a solid content of 5%, place it on a magnetic stirrer, and stir at a speed of 850 rpm for 90 minutes. Then fix the preliminary fiber paper sample on the coating machine platform, set the doctor blade spacing to 0.8 mm, the coating speed to 10 cm / min, and uniformly coat the silver-loaded CNC-starch slurry (single-sided coating) to make the wet coating thickness about 0.3 mm.

[0102] (3) After lamination, post-processing is performed. First, the composite paper sample is completely immersed in an acrylic resin emulsion with a mass fraction of 10% and kept for 5 minutes. Then, excess adhesive is removed by vacuum filtration under a pressure of -0.05 MPa. Next, the paper sample is quickly placed in liquid nitrogen and frozen for 30 minutes. Then, it is transferred to a freeze dryer and freeze-dried at -50℃ and 0.01 mbar for 24 hours. Finally, the freeze-dried paper sample is placed in the mold of a hot press and hot-pressed at 150℃ and 5 MPa for 20 minutes to obtain the final air filter material.

[0103] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0104] Example 4

[0105] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the mass ratio of broadleaf wood fiber to glass fiber is 1:4, and the other steps are the same.

[0106] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0107] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0108] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0109] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0110] Example 5

[0111] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the mass ratio of broadleaf wood fiber to glass fiber is 1:6, and the other steps are the same.

[0112] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0113] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0114] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0115] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0116] Example 6

[0117] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the mass ratio of broadleaf wood fiber to glass fiber is 1:3, and the other steps are the same.

[0118] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0119] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0120] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0121] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0122] Example 7

[0123] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the mass ratio of broadleaf wood fiber to glass fiber is 1:7, and the other steps are the same.

[0124] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0125] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0126] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0127] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0128] Example 8

[0129] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0130] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1, except that the ratio of silver-loaded CNC to starch is 1:1.

[0131] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0132] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0133] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0134] Example 9

[0135] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0136] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1, except that the ratio of silver-loaded CNC to starch is 5:1.

[0137] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0138] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0139] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0140] Example 10

[0141] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0142] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0143] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1, except that the ratio of silver-loaded BC to starch is 3:1.

[0144] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0145] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0146] Example 11

[0147] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0148] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0149] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1, except that the ratio of silver-loaded BC to starch is 7:1.

[0150] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0151] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0152] Example 12

[0153] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the speed of the fiber desiccant is 12000 rpm.

[0154] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0155] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0156] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0157] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0158] Example 13

[0159] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the speed of the fiber desiccant is 18,000 rpm.

[0160] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0161] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0162] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0163] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0164] Example 14

[0165] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0166] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0167] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0168] (4) After completing the double-layer composite, the post-processing process is carried out: the method is the same as step (4) in Example 1, except that the freeze-drying temperature is -30℃ and the time is 72h.

[0169] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0170] Example 15

[0171] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0172] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0173] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0174] (4) After completing the double-layer composite, the post-processing process is carried out: the method is the same as step (4) in Example 1, except that the freeze-drying temperature is -60℃ and the time is 18h.

[0175] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0176] Example 16

[0177] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0178] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0179] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0180] (4) After completing the double-layer composite, perform the post-processing: the method is the same as step (4) in Example 1, except that the liquid nitrogen freezing time is 20 minutes.

[0181] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0182] Example 17

[0183] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0184] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0185] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0186] (4) After completing the double-layer composite, perform the post-processing: the method is the same as step (4) in Example 1, except that the liquid nitrogen freezing time is 35 minutes.

[0187] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0188] Example 18

[0189] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0190] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0191] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0192] (4) After completing the double-layer composite, perform the post-processing: the method is the same as step (4) in Example 1, except that the hot pressing temperature is 120℃ and the time is 90 minutes.

[0193] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0194] Example 19

[0195] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0196] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0197] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0198] (4) After completing the double-layer composite, perform the post-processing: the method is the same as step (4) in Example 1, except that the hot pressing temperature is 220℃ and the time is 15 minutes.

[0199] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0200] Comparative Example 1

[0201] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0202] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0203] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0204] (4) Post-processing after completing the double-layer composite: The method is the same as step (4) in Example 1, except that liquid nitrogen freezing and freeze-drying are not performed. That is, the double-layer composite paper sample is first immersed in an acrylic resin emulsion with a mass fraction of 10% and kept for 5 minutes. Then, excess adhesive is removed by vacuum filtration under a pressure of -0.05MPa. The composite paper sample is then placed in the mold of a hot press and hot-pressed at 150°C and 5MPa for 20 minutes to obtain the final air filter material.

[0205] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0206] Comparative Example 2

[0207] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0208] (2) First, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0209] (3) Post-processing after lamination: The method is the same as step (4) in Example 1, except that liquid nitrogen freezing and freeze-drying are not performed. Instead, the composite paper sample is first immersed in an acrylic resin emulsion with a mass fraction of 10% and kept for 5 minutes. Then, excess adhesive is removed by vacuum filtration under a pressure of -0.05 MPa. The composite paper sample is then placed in the mold of a hot press and hot-pressed at 150°C and 5 MPa for 20 minutes to obtain the final air filter material.

[0210] (4) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0211] Comparative Example 3

[0212] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1.

[0213] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0214] (3) Post-processing after lamination: The method is the same as step (4) in Example 1, except that liquid nitrogen freezing and freeze-drying are not performed. Instead, the composite paper sample is first immersed in an acrylic resin emulsion with a mass fraction of 10% and kept for 5 minutes. Then, excess adhesive is removed by vacuum filtration under a pressure of -0.05 MPa. The composite paper sample is then placed in the mold of a hot press and hot-pressed at 150°C and 5 MPa for 20 minutes to obtain the final air filter material.

[0215] (4) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0216] Comparative Example 4

[0217] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the mass ratio of broadleaf wood fiber to glass fiber is 1:3, and the other steps are the same.

[0218] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0219] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0220] (4) After completing the double-layer lamination, a post-processing process is performed, referring to the same method as step (4) in Example 1, except that hot pressing is not performed. Instead, the double-layer lamination paper sample is first completely immersed in an acrylic resin emulsion with a mass fraction of 10% and kept for 5 minutes. Then, excess adhesive is removed by vacuum filtration under a pressure of -0.05 MPa. The paper sample is then quickly placed in liquid nitrogen and frozen for 30 minutes, and then transferred to a freeze dryer for freeze drying at -50°C and 0.01 mbar for 24 hours to obtain the final air filter material.

[0221] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0222] Comparative Example 5

[0223] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the speed of the fiber desiccant is 1500 rpm, and the rest of the steps are the same.

[0224] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0225] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0226] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0227] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0228] Comparative Example 6

[0229] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the speed of the fiber desiccant is 5000 rpm, and the rest of the steps are the same.

[0230] (2) Preparation of silver-loaded CNC-starch composite layer: The method is the same as step (2) in Example 1.

[0231] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0232] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0233] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0234] Comparative Example 7

[0235] (1) Preparation of preliminary fiber paper sample: The method is the same as step (1) in Example 1, except that the speed of the fiber desiccant is 10,000 rpm, and the other steps are the same.

[0236] (2) When preparing the silver-loaded CNC-starch composite layer: the method is the same as step (2) in Example 1.

[0237] (3) Next, prepare the silver-loaded BC-starch composite layer: the method is the same as step (3) in Example 1.

[0238] (4) After completing the double-layer composite, perform post-processing: the method is the same as step (4) in Example 1.

[0239] (5) After the material is obtained, its performance needs to be tested. The specific testing method is the same as step (5) in Example 1.

[0240] Effect Example

[0241] 1. The mechanical properties, filtration properties and antibacterial properties of the composite antibacterial air filter materials obtained in Examples 1 to 19 and Comparative Examples 1 to 7 were compared, and the results are shown in Table 1.

[0242] Table 1. Analysis of the performance of the composite antibacterial air filter materials prepared in the examples and comparative examples.

[0243]

[0244]

[0245] (1) After liquid nitrogen freezing and freeze-drying, the tensile strength (56-66 MPa) of Examples 1-3 was significantly higher than that of Comparative Examples 1-3 (39-49 MPa) without this process. This may be because liquid nitrogen freezing can form uniform ice crystals inside the material, and the sublimation of the ice crystals during freeze-drying leaves directional pores, which promotes the fibers to arrange into an ordered network structure along the axial direction, enhances the hydrogen bonding and mechanical interlocking between fibers, and thus improves the axial tensile strength. For example, the tensile strength of Example 1 was 34.7% higher than that of Comparative Example 1, which fully demonstrates the optimization effect of this process on mechanical properties.

[0246] (2) In Example 1, when silver-loaded CNC and BC were combined, the filtration resistance (78 Pa) was lower than that of Examples 2-3 (89-105 Pa) containing only single nanocellulose, while the filtration efficiency (99.99%) was higher. This may be because the combination of CNC and BC forms a multi-level pore or multi-level nanostructure: the nanofibers of CNC fill the micropores, and the three-dimensional network structure of BC increases pore connectivity, which reduces airflow resistance and improves the capture efficiency of 0.3 μm particles through Brownian motion and interception effect. Compared with the high resistance (182-227 Pa) of the single coating in Comparative Examples 1-3, the synergistic filtration advantage of the composite coating is further highlighted.

[0247] (3) Comparing Example 1 and Comparative Example 1, it can be seen that the inhibition zone of *Escherichia coli* (8.36 mm) and *Staphylococcus aureus* (9.00 mm) in Example 1 are both larger than those in Comparative Examples 1-3 (7.22–8.45 mm). The mechanism of action may be that the double-layer coating of silver-loaded CNC and BC constructs a denser silver ion release network—the high specific surface area of ​​CNC allows for rapid release of silver ions, while the porous structure of BC provides a slow release of silver ions; the two work synergistically to prolong the antibacterial effect. Furthermore, the double-layer structure increases the contact area with bacteria, enhancing the destructive effect of silver ions on bacterial cell membranes, thus improving the antibacterial effect by approximately 10%–20%.

[0248] (4) Example 1 fully employs the "liquid nitrogen freezing + freeze-drying + hot-pressing" process, achieving optimal tensile strength, filtration efficiency, and antibacterial zone. In contrast, Comparative Examples 1-3, by omitting the freeze-drying step, exhibit disordered pores within the material, resulting in a 25%–40% decrease in tensile strength and a 133%–191% increase in filtration resistance. This indicates that the freeze-drying process is crucial for the formation of unidirectional fiber arrangement. The absence of this step leads to disordered fiber stacking, reducing mechanical strength, increasing airflow resistance due to pore blockage, and weakening the uniformity of nanocellulose dispersion, thus affecting the antibacterial properties.

[0249] (5) Comparing Example 1 with Comparative Examples 5-7 (de-fibrillation speeds of 1500 rpm, 5000 rpm, and 10000 rpm), it is evident that high-speed de-fibrillation at 15000 rpm is a guarantee of performance: Example 1 (15000 rpm) has a tensile strength of 66 MPa and a filtration efficiency of 99.99%, which is significantly higher than Comparative Example 7 (1500 rpm, tensile strength 22 MPa, filtration efficiency 92.15%) and Comparative Example 8 (5000 rpm, tensile strength 29 MPa, filtration efficiency 96.23%). The reason may be that the strong shear force at 15000 rpm can cause microfibrillation of the plant fiber surface, forming a tight entanglement with the glass fiber; while when the speed is insufficient, the fibers cannot be fully dispersed and entangled, resulting in a significant decrease in mechanical strength and filtration efficiency.

[0250] 2. The antibacterial properties of the composite antibacterial air filter materials prepared in Examples 1-3 were subjected to friction treatment and tested. The specific steps are as follows:

[0251] (1) Antibacterial rate test: Referring to QB / T 2591-2003 "Test method for antibacterial properties of antibacterial plastics", Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 6538) were used as test bacteria, and the antibacterial rate was determined by shaking flask method after 24 hours.

[0252] (2) Friction treatment: A wear tester was used to simulate the wear of the material during use by applying a 500g load and 10 reciprocating friction cycles (the friction medium was cotton cloth, and the speed was 30 cycles / min).

[0253] (3) Antibacterial rate test after friction: Repeat the above antibacterial rate test steps on the sample after friction.

[0254] The results are shown in Table 2: the antibacterial rate of the material prepared in Example 1 still exceeded 90% after 10 rubs.

[0255] Table 2

[0256]

[0257] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite antibacterial air filter material, characterized in that, Includes the following steps: (1) Preparation of fiber paper sample: Plant fiber and glass fiber are mixed in sulfuric acid solution with pH value of 2.5 to 3.0 and disintegrated at a speed of 12,000 to 20,000 rpm to obtain fiber suspension; The fiber suspension is then formed into a paper pattern to obtain a fiber paper sample. (2) Preparation of composite slurry: Silver-loaded cellulose nanocrystals were mixed with starch and water were added to prepare silver-loaded CNC-starch slurry; silver-loaded bacterial cellulose was mixed with starch and water were added to prepare silver-loaded BC-starch slurry; (3) Coating with composite slurry: ① Apply silver-loaded CNC-starch paste or silver-loaded BC-starch paste evenly to one side of the fiber paper sample to obtain composite paper sample A; ② Coat one side of the fiber paper sample evenly with silver-loaded CNC-starch paste to form a silver-loaded CNC-starch composite layer; then, before it is completely dry, continue to coat the silver-loaded CNC-starch composite layer with silver-loaded BC-starch paste to obtain composite paper sample B; (4) Post-processing: The composite paper sample A or composite paper sample B is completely immersed in the acrylic resin emulsion. After immersion, the excess emulsion is removed by vacuum filtration. Then, it is placed in liquid nitrogen to freeze and freeze-dried at -60℃ to -30℃. Finally, it is hot-pressed to obtain the composite antibacterial air filter material.

2. The method according to claim 1, characterized in that: The silver content in the silver-loaded cellulose nanocrystals described in step (2) is 1.3 ± 0.1 wt%, and the particle size is 25–45 nm. The silver content in the silver-loaded bacterial cellulose described in step (2) is 0.9±0.05wt%, and the fiber diameter is 15-25nm.

3. The method according to claim 1, characterized in that: The mass ratio of plant fiber to glass fiber in step (1) is 1:3 to 7; The concentration of the fiber suspension mentioned in step (1) is 1.0 to 2.0 wt%. The rotation speed for the scavenging process described in step (1) is 12,000 to 18,000 revolutions per minute; The mass ratio of silver-loaded cellulose nanocrystals to starch in step (2) is 1 to 5:1; The solid content of the silver-loaded CNC-starch slurry mentioned in step (2) is 2% to 8%; The mass ratio of silver-loaded bacterial cellulose to starch in step (2) is 1 to 10:1; The solid content of the silver-loaded BC-starch slurry mentioned in step (2) is 2% to 8%; The concentration of the acrylic resin emulsion mentioned in step (4) is 6% to 11% by mass.

4. The method according to claim 3, characterized in that: The mass ratio of plant fiber to glass fiber in step (1) is 1:5; The concentration of the fiber suspension mentioned in step (1) is 1.0 wt%. The rotation speed for the scavenging process described in step (1) is 15,000 revolutions per minute; The mass ratio of silver-loaded cellulose nanocrystals to starch in step (2) is 3:1; The solid content of the silver-loaded CNC-starch slurry mentioned in step (2) is 5%; The mass ratio of silver-loaded bacterial cellulose to starch in step (2) is 3 to 7:1; The solid content of the silver-loaded BC-starch slurry mentioned in step (2) is 3%; The concentration of the acrylic resin emulsion mentioned in step (4) is 10% by mass.

5. The method according to claim 1, characterized in that: The soaking time described in step (4) is 3 to 9 minutes; In step (4), the freezing time in liquid nitrogen is 20–35 minutes; The vacuum degree of the freeze-drying process described in step (4) is 0.005 to 0.02 mbar; The freeze-drying time described in step (4) is 18 to 72 hours.

6. The method according to claim 1, characterized in that: The coating conditions described in steps (3) ① and ② are: the spacing between the scrapers is maintained at 0.5 to 1.2 mm, and the scraper speed is 1 to 10 cm / min; In steps (3) ① and ②, the coating thickness of the silver-loaded CNC-starch paste or the silver-loaded BC-starch paste is 0.15 to 0.35 mm. The conditions for hot pressing in step (4) are: hot pressing temperature 120-220℃, hot pressing pressure 1-15MPa, and hot pressing time 15-90 minutes.

7. The method according to claim 1, characterized in that: The plant fiber mentioned in step (1) is broadleaf wood fiber; The starch mentioned in step (2) is corn starch.

8. A composite antibacterial air filter material, characterized in that: It is prepared by the method described in any one of claims 1 to 7.

9. The application of the composite antibacterial air filter material according to claim 8 in the preparation of air purification materials, medical masks and / or industrial dust removal materials.

10. The application according to claim 9, characterized in that: The air purification materials mentioned include those used in air purification filters, industrial or household air purifiers, medical air purification, air purification in automotive air conditioning, and air purification materials for the protection of energy equipment.

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