Nanometer antibacterial polyethylene composite material for paint bucket and preparation method thereof

Abstract

The present application relates to the technical field of composite materials, and particularly relates to a nano-antibacterial polyethylene composite material for paint buckets and a preparation method thereof; the nano-antibacterial polyethylene composite material for paint buckets is composed of the following components in mass percentage: 60-75% high-density polyethylene, 10-18% maleic anhydride grafted polyethylene, 6.8-9% hydroxypropyltrimethylammonium chloride chitosan, 6.25-7.25% nano-core-shell antibacterial microspheres, 1-3% gamma-aminopropyltriethoxysilane, 0.5-1.5% polyethylene wax, 0.1-0.3% antioxidant 1010, 0.1-0.3% antioxidant 168, 0.2-0.5% polycarbodiimide and 0.05-0.15% calcium stearate; the present application solves the problems of the polyethylene antibacterial material, such as difficult to balance the quick-acting and persistence, poor dispersibility and serious performance attenuation after recycling, and through the synergy of double-time-scale cooperative antibacterial, dynamic ionic anchoring and chain extension repair, realizes the quick-acting and long-acting antibacterial, environment-responsive release and mechanical property maintenance after multiple recycling of the composite material, and provides a composite material solution with high-efficient antibacterial and cyclic regeneration for the field of composite materials.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a nano-antibacterial polyethylene composite material for paint buckets and its preparation method. Background Technology

[0002] Polyethylene is widely used in the manufacture of paint packaging drums due to its light weight, chemical resistance, and ease of processing. However, during the storage of water-based paints in polyethylene drums, the humid microenvironment of prolonged contact between the drum wall and the paint can breed bacteria and mold, leading to paint odor, delamination, and spoilage, resulting in significant economic losses. Existing polyethylene antibacterial technologies employ the addition of silver-based antibacterial masterbatches or organic antibacterial agents. Silver-based antibacterial agents are expensive and tend to migrate and agglomerate during repeated heat processing and recycling. Organic antibacterial agents suffer from poor heat resistance and can migrate and precipitate, contaminating the paint inside the drum. Meanwhile, while chitosan, as a natural antibacterial polymer, has advantages such as abundant sources and good biocompatibility, its dispersibility in non-polar polyethylene matrices is extremely poor, and ordinary chitosan lacks sufficient thermal stability, beginning to degrade at polyethylene extrusion processing temperatures, severely limiting its application in antibacterial polyethylene materials for paint drums.

[0003] To achieve multiple processing and recycling, existing technologies rely on adding antioxidants to slow down the thermo-oxidative degradation of polyethylene molecular chains. However, antioxidants can only slow down the degradation rate and cannot repair broken molecular chains. After more than three recycling cycles, the mechanical properties will decrease by more than 20%, necessitating downgraded use. Therefore, the key to overcoming the technological barriers of antibacterial and recyclable coating buckets lies in how to construct a polyethylene composite material that balances rapid bactericidal action and long-term antibacterial activity while maintaining the thermal stability and dispersibility of chitosan, and also retains its mechanical properties after multiple thermal processing and recycling.

[0004] To address the above problems, the present invention provides a solution. Summary of the Invention

[0005] The purpose of this invention is to provide a nano-antibacterial polyethylene composite material for paint buckets and its preparation method, which can meet the contradictory requirements of rapid sterilization and long-term antibacterial effect, while maintaining the mechanical properties after multiple heat processing and recycling. To achieve the above objectives, the present invention adopts the following technical solution: A nano-antibacterial polyethylene composite material for paint buckets is composed of the following components by mass percentage: 60-75% high-density polyethylene, 10-18% maleic anhydride-grafted polyethylene, 6.8-9% hydroxypropyltrimethylammonium chloride chitosan, 6.25-7.25% nano-core-shell antibacterial microspheres, 1-3% γ-aminopropyltriethoxysilane, 0.5-1.5% polyethylene wax, 0.1-0.3% antioxidant 1010, 0.1-0.3% antioxidant 168, 0.2-0.5% polycarbodiimide, and 0.05-0.15% calcium stearate; Furthermore, the preparation method of the aforementioned core-shell antibacterial microspheres includes the following steps: A1: Add mesoporous silica to deionized water and ultrasonically disperse it at 25°C for 30-35 min with an ultrasonic power of 300-350W to obtain a mesoporous silica suspension, wherein the mass ratio of mesoporous silica to deionized water is 1:80. A2: Add zinc nitrate hexahydrate to deionized water, set the stirrer speed to 350-400 rpm, and stir for 5-6 minutes to prepare a zinc nitrate solution, wherein the mass ratio of zinc nitrate hexahydrate to deionized water is 1:8.5. Keep the speed constant, add the zinc nitrate solution dropwise to the mesoporous silica suspension at a rate of 0.2-0.3 kg / min using a constant flow pump, wherein the mass ratio of zinc nitrate solution to mesoporous silica suspension is 1:7. After the dropwise addition is completed, set the stirring speed to 400-450 rpm and continue stirring for 3 hours to obtain the loaded suspension. A3: Add a 2.5wt% dilute ammonia solution dropwise to the loaded suspension using a constant flow pump at a rate of 0.1-0.15 kg / min. Monitor the pH of the system in real time during the dropwise addition. Stop the dropwise addition when the pH reaches 7.8-8. Then set the stirring speed to 300-350 rpm and continue stirring and aging for 4-5 hours. Maintain the pH at 7.5-8 during the aging process to obtain the precursor suspension. A4: Vacuum filter the precursor suspension. After vacuum filtration, wash the filter cake repeatedly with deionized water 3-5 times. After washing, place the filter cake in a forced-air drying oven and set the temperature to 80-85℃ for 12-14 hours to obtain precursor powder. Place the precursor powder in a muffle furnace and set the heating rate to 2-3℃ / min. Calcinate at 450℃ for 3-4 hours. After calcination, cool to room temperature with the furnace, grind, and pass through a 300-mesh sieve to obtain nano-core-shell antibacterial microspheres.

[0006] Furthermore, the mesoporous silica has a pore size of 6 nm and a specific surface area of ​​750 m². 2 / g, with an average particle size of 150nm; Furthermore, a method for preparing a nano-antibacterial polyethylene composite material for paint buckets includes the following steps: S1: Add γ-aminopropyltriethoxysilane to anhydrous ethanol, set the stirrer speed to 300 rpm, and stir for 15 min to obtain a coupling agent solution, wherein the mass ratio of γ-aminopropyltriethoxysilane to anhydrous ethanol is 1:8. S2: Place the nano-core-shell antibacterial microspheres in a high-speed mixer, set the speed to 1000 rpm, and use an atomizing nozzle to evenly spray the coupling agent solution onto the surface of the nano-core-shell antibacterial microspheres while stirring. After spraying, increase the speed of the mixer to 1800 rpm, set the mixing temperature to 70℃, and mix for 20 minutes. After mixing, transfer the mixture to a vacuum drying oven, set the temperature to 90℃, the vacuum degree to -0.09 MPa, and dry for 3 hours. After drying, pass the mixture through a 200-mesh sieve to obtain modified core-shell antibacterial microspheres, and seal them for moisture protection before use. S3: High-density polyethylene, maleic anhydride-grafted polyethylene, hydroxypropyltrimethylammonium chloride chitosan, modified core-shell antibacterial microspheres, polyethylene wax, antioxidant 1010, antioxidant 168, polycarbodiimide and calcium stearate are added to a high-speed mixer, the speed is set to 600 rpm, the mixing temperature is 30℃, and the mixture is mixed for 12 minutes to obtain a premix. S4: The premixed material is fed into the twin-screw extruder through the main feed port for melt blending and extrusion. The temperature of the twin-screw extruder is set to 145℃ for the feeding section, 155℃ for the plasticizing section, 160℃ for the metering section, and 160℃ for the die head. The screw speed is 200 rpm. The molten material is extruded through the die head to form a continuous strip with a diameter of 3 mm. S5: Feed the continuous strip into the water-cooled strip pelletizer, set the cooling water tank temperature to 30℃, the traction speed to 15m / min, and the pelletizer speed to 750rpm. After pelletizing, cylindrical particles with a diameter of 2.5mm and a length of 3mm are obtained. The particles are then conveyed to a vibrating screen to remove debris with a diameter of less than 1mm and connected particles with a diameter of more than 4mm, thus obtaining qualified pellets. S6: Place the qualified pellets in a vacuum drying oven, set the temperature to 75℃ and the vacuum degree to -0.09MPa, and dry for 4 hours. After drying, fill the pellets into sealed packaging bags lined with aluminum foil through a packaging machine. During filling, the material temperature is controlled below 30℃. Heat seal the bags to obtain nano antibacterial polyethylene composite material for use in paint buckets.

[0007] Furthermore, the maleic anhydride-grafted polyethylene has a maleic anhydride grafting rate of 1% and a melt index of 3 g / 10 min under conditions of 190°C and 2.16 kg load; the high-density polyethylene has a melt index of 0.5 g / 10 min and a density of 0.954 g / cm³ under conditions of 190°C and 2.16 kg load.3 The hydroxypropyltrimethylammonium chloride chitosan has a degree of substitution of 92% and an initial thermal decomposition temperature ≥200℃ under a nitrogen atmosphere; the polycarbodiimide has a number-average molecular weight of 3000 and a carbodiimide group content of 13%. In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: 1: This invention creates a dual-timescale synergistic antibacterial system using hydroxypropyltrimethylammonium chloride chitosan as a fast-acting bactericidal component and nano-core-shell antibacterial microspheres as a slow-release antibacterial carrier. The quaternary ammonium salt cations of hydroxypropyltrimethylammonium chloride chitosan rapidly destroy bacterial cell membranes through electrostatic adsorption to achieve contact sterilization. The nano-core-shell antibacterial microspheres have mesoporous silica as the core and nano-zinc oxide as the shell. The mesoporous channel confinement effect allows zinc ions to be continuously and slowly dissolved, maintaining an effective antibacterial concentration on a 28-day timescale. This systematically solves the contradiction between the traditional single antibacterial mechanism and the inability to achieve both fast-acting bactericidal effect and long-term antibacterial effect. 2: This invention uses the dynamic ionic crosslinking formed between the carboxyl groups of maleic anhydride-grafted polyethylene and the quaternary ammonium salt cations of hydroxypropyltrimethylammonium chloride chitosan as the core anchoring mechanism, which realizes the nanoscale uniform dispersion and reversible anchoring of chitosan in the polyethylene matrix. During processing, high temperature and shearing cause the ionic bonds to dissociate and the chitosan to be uniformly dispersed. After cooling, the ionic bonds are rebuilt and the chitosan is anchored in the matrix. During use, the humid environment inside the container triggers the hydrolysis and breakage of the ionic bonds, releasing chitosan to exert a bactericidal effect. After drying, the ionic bonds are reformed and the anchoring is restored, giving the composite material an environmentally responsive intelligent antibacterial ability. 3: This invention achieves the retention of mechanical properties of composite materials after multiple thermal processing and recycling, providing a high-value polyethylene composite material solution for the coating packaging barrel industry that combines fast-acting and long-lasting synergistic antibacterial properties, intelligent release in response to environmental conditions, and the ability to retain mechanical properties after multiple recycling. Detailed Implementation

[0008] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0009] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. Example

[0010] 1: Add 100g of mesoporous silica to 8kg of deionized water and ultrasonically disperse at 25℃ for 30min with an ultrasonic power of 300W to obtain 8.099kg of mesoporous silica suspension; 2: Add 120g of zinc nitrate hexahydrate to 1.02kg of deionized water, set the stirrer speed to 350rpm, and stir for 5min to prepare 1.14kg of zinc nitrate solution. Keep the speed constant, add the 1.14kg of zinc nitrate solution dropwise to 7.98kg of mesoporous silica suspension at a rate of 0.2kg / min using a constant flow pump. After the addition is completed, set the stirring speed to 400rpm and continue stirring for 3h to obtain 9.236kg of loaded suspension. 3: A 2.5 wt% dilute ammonia solution was added dropwise to the loaded suspension at a rate of 0.1 kg / min using a constant flow pump. The pH of the system was monitored in real time during the addition. When the pH reached 7.8, the addition was stopped. Then, the stirring speed was set to 300 rpm, and stirring and aging continued for 4 hours. During the aging process, the pH was maintained at 7.5-8, and 9.416 kg of precursor suspension was obtained. 4. Vacuum filter the precursor suspension. After vacuum filtration, wash the filter cake three times with deionized water. After washing, place the filter cake in a forced-air drying oven at 80°C and dry for 12 hours to obtain 148g of precursor powder. Place the precursor powder in a muffle furnace and calcine at 450°C for 3 hours at a heating rate of 2°C / min. After calcination, cool the powder to room temperature with the furnace, grind it, and pass it through a 300-mesh sieve to obtain 135g of the nano-core-shell antibacterial microspheres prepared in Example 1. Example

[0011] 1: Add 100g of mesoporous silica to 8kg of deionized water and ultrasonically disperse at 25℃ for 35min with an ultrasonic power of 350W to obtain 8.098kg of mesoporous silica suspension; 2: Add 120g of zinc nitrate hexahydrate to 1.02kg of deionized water, set the stirrer speed to 400rpm, and stir for 6min to prepare a 1.14kg zinc nitrate solution. Keep the speed constant, add the 1.14kg zinc nitrate solution dropwise to 7.98kg of mesoporous silica suspension at a rate of 0.3kg / min using a constant flow pump. After the addition is complete, set the stirring speed to 450rpm and continue stirring for 3h to obtain a 9.233kg loaded suspension. 3: A 2.5 wt% dilute ammonia solution was added dropwise to the loaded suspension at a rate of 0.15 kg / min using a constant flow pump. The pH of the system was monitored in real time during the addition. When the pH reached 8, the addition was stopped. Then, the stirring speed was set to 350 rpm, and stirring and aging continued for 5 hours. During the aging process, the pH was maintained at 7.5-8, and 9.418 kg of precursor suspension was obtained. 4. Vacuum filter the precursor suspension. After vacuum filtration, wash the filter cake five times with deionized water. After washing, place the filter cake in a forced-air drying oven at 85°C and dry for 14 hours to obtain 150g of precursor powder. Place the precursor powder in a muffle furnace and calcine at 450°C for 4 hours at a heating rate of 3°C / min. After calcination, cool the powder to room temperature with the furnace, grind it, and pass it through a 300-mesh sieve to obtain 133g of the nano-core-shell antibacterial microspheres prepared in Example 2. Example

[0012] 1: Add 100g of γ-aminopropyltriethoxysilane to 800g of anhydrous ethanol, set the stirrer speed to 300rpm, and stir for 15min to obtain 900g of coupling agent solution; 2: Place 625g of the nano-core-shell antibacterial microspheres prepared in Example 1 in a high-speed mixer, set the speed to 1000 rpm, and use an atomizing nozzle to evenly spray the coupling agent solution onto the surface of the nano-core-shell antibacterial microspheres while stirring. After spraying, increase the speed of the mixer to 1800 rpm, set the mixing temperature to 70℃, and mix for 20 min. After mixing, transfer to a vacuum drying oven, set the temperature to 90℃, the vacuum degree to -0.09 MPa, and dry for 3 h. After drying, pass through a 200-mesh sieve to obtain 721g of modified core-shell antibacterial microspheres, seal them to prevent moisture and set aside for later use. 3: Add 7.5 kg of high-density polyethylene, 1 kg of maleic anhydride-grafted polyethylene, 680 g of hydroxypropyltrimethylammonium chloride chitosan, modified core-shell antibacterial microspheres, 50 g of polyethylene wax, 10 g of antioxidant 1010, 10 g of antioxidant 168, 20 g of polycarbodiimide and 5 g of calcium stearate to a high-speed mixer. Set the speed to 600 rpm and the mixing temperature to 30°C. Mix for 12 minutes to obtain 9.988 kg of premix. 4: The premixed material is fed into the twin-screw extruder through the main feed port for melt blending and extrusion. The temperature of the twin-screw extruder is set to 145℃ for the feeding section, 155℃ for the plasticizing section, 160℃ for the metering section, and 160℃ for the die head. The screw speed is 200 rpm. The molten material is extruded through the die head to form a continuous strip with a diameter of 3 mm. 5: Feed the continuous strip into the water-cooled strip pelletizer, set the cooling water tank temperature to 30℃, the traction speed to 15m / min, and the pelletizer speed to 750rpm. After pelletizing, cylindrical particles with a diameter of 2.5mm and a length of 3mm are obtained. The particles are then conveyed to a vibrating screen to remove debris smaller than 1mm and connected particles larger than 4mm, resulting in 9.65kg of qualified pellets. 6: Place the qualified pellets in a vacuum drying oven, set the temperature to 75℃ and the vacuum degree to -0.09MPa, and dry for 4 hours. After drying, fill the pellets into sealed packaging bags lined with aluminum foil using a packaging machine. During filling, the material temperature is controlled below 30℃. Heat seal the bags to obtain 9.63kg of the nano-antibacterial polyethylene composite material for paint buckets prepared in Example 3. Example

[0013] 1: Add 300g of γ-aminopropyltriethoxysilane to 2.4kg of anhydrous ethanol, set the stirrer speed to 300rpm, and stir for 15min to obtain 2.7kg of coupling agent solution; 2: Place 725g of the nano-core-shell antibacterial microspheres prepared in Example 2 into a high-speed mixer, set the speed to 1000 rpm, and use an atomizing nozzle to evenly spray the coupling agent solution onto the surface of the nano-core-shell antibacterial microspheres while stirring. After spraying, increase the speed of the mixer to 1800 rpm, set the mixing temperature to 70℃, and mix for 20 min. After mixing, transfer to a vacuum drying oven, set the temperature to 90℃, the vacuum degree to -0.09 MPa, and dry for 3 h. After drying, pass through a 200-mesh sieve to obtain 834g of modified core-shell antibacterial microspheres, seal them for moisture protection and use later. 3: Add 6 kg of high-density polyethylene, 1.8 kg of maleic anhydride-grafted polyethylene, 900 g of hydroxypropyltrimethylammonium chloride chitosan, modified core-shell antibacterial microspheres, 150 g of polyethylene wax, 30 g of antioxidant 1010, 30 g of antioxidant 168, 50 g of polycarbodiimide and 15 g of calcium stearate to a high-speed mixer, set the speed to 600 rpm, the mixing temperature to 30℃, mix for 12 min, and obtain 9.975 kg of premix; 4: The premixed material is fed into the twin-screw extruder through the main feed port for melt blending and extrusion. The temperature of the twin-screw extruder is set to 145℃ for the feeding section, 155℃ for the plasticizing section, 160℃ for the metering section, and 160℃ for the die head. The screw speed is 200 rpm. The molten material is extruded through the die head to form a continuous strip with a diameter of 3 mm. 5: Feed the continuous strip into the water-cooled strip pelletizer, set the cooling water tank temperature to 30℃, the traction speed to 15m / min, and the pelletizer speed to 750rpm. After pelletizing, cylindrical particles with a diameter of 2.5mm and a length of 3mm are obtained. The particles are then conveyed to a vibrating screen to remove debris smaller than 1mm and connected particles larger than 4mm, resulting in 9.58kg of qualified pellets. 6: Place the qualified pellets in a vacuum drying oven, set the temperature to 75℃ and the vacuum degree to -0.09MPa, and dry for 4 hours. After drying, fill the pellets into sealed packaging bags lined with aluminum foil using a packaging machine. During filling, the material temperature is controlled below 30℃. Heat seal the bags to obtain 9.55kg of the nano-antibacterial polyethylene composite material for paint buckets prepared in Example 4.

[0014] Comparative Example 1 The difference between this comparative example and Example 4 is that no nano-core-shell antibacterial microspheres and the corresponding γ-aminopropyltriethoxysilane coupling agent are added. That is, it relies solely on the single antibacterial mechanism of hydroxypropyltrimethylammonium chloride chitosan and has no long-term antibacterial synergistic effect of slow-release zinc ions. The specific preparation method is as follows: 1: Add 6.691 kg of high-density polyethylene, 2.007 kg of maleic anhydride-grafted polyethylene, 900 g of hydroxypropyltrimethylammonium chloride chitosan, 150 g of polyethylene wax, 30 g of antioxidant 1010, 30 g of antioxidant 168, 50 g of polycarbodiimide, and 15 g of calcium stearate to a high-speed mixer. Set the speed to 600 rpm and the mixing temperature to 30°C. Mix for 12 minutes to obtain 9.976 kg of premix. 2: The premixed material is fed into the twin-screw extruder through the main feed port for melt blending and extrusion. The temperature of the twin-screw extruder is set to 145℃ in the feeding section, 155℃ in the plasticizing section, 160℃ in the metering section, and 160℃ in the die head. The screw speed is 200 rpm. The molten material is extruded through the die head to form a continuous strip with a diameter of 3mm. 3: Feed the continuous strip into the water-cooled strip pelletizer, set the cooling water tank temperature to 30℃, the traction speed to 15m / min, and the pelletizer speed to 750rpm. After pelletizing, cylindrical particles with a diameter of 2.5mm and a length of 3mm are obtained. The particles are then conveyed to a vibrating screen to remove debris smaller than 1mm and connected particles larger than 4mm, resulting in 9.585kg of qualified pellets. 4: Place the qualified pellets in a vacuum drying oven, set the temperature to 75℃ and the vacuum degree to -0.09MPa, and dry for 4 hours. After drying, fill the pellets into sealed packaging bags lined with aluminum foil using a packaging machine. During filling, the material temperature is controlled below 30℃. Heat seal the bags to obtain 9.560 kg of the nano-antibacterial polyethylene composite material for paint buckets prepared in Comparative Example 1.

[0015] Comparative Example 2 The difference between this comparative example and Example 3 is that ordinary chitosan is used instead of hydroxypropyltrimethylammonium chloride chitosan. The ordinary chitosan has a degree of deacetylation of 95%, a viscosity-average molecular weight of 100 kDa, and no quaternary ammonium salt substituents. The specific preparation method is as follows: 1: Add 100g of γ-aminopropyltriethoxysilane to 800g of anhydrous ethanol, set the stirrer speed to 300rpm, and stir for 15min to obtain 900g of coupling agent solution; 2: Place 625g of the nano-core-shell antibacterial microspheres prepared in Example 1 into a high-speed mixer, set the speed to 1000 rpm, and use an atomizing nozzle to uniformly spray the coupling agent solution obtained in step 1 onto the surface of the nano-core-shell antibacterial microspheres while stirring. After spraying, increase the speed of the mixer to 1800 rpm, set the mixing temperature to 70℃, and mix for 20 min. After mixing, transfer to a vacuum drying oven, set the temperature to 90℃, the vacuum degree to -0.09 MPa, and dry for 3 h. After drying, pass through a 200-mesh sieve to obtain 721g of modified core-shell antibacterial microspheres, seal them to prevent moisture and set aside for later use. 3: Add 7.5 kg of high-density polyethylene, 1 kg of maleic anhydride-grafted polyethylene, 680 g of ordinary chitosan, 721 g of modified core-shell antibacterial microspheres obtained in step 2, 50 g of polyethylene wax, 10 g of antioxidant 1010, 10 g of antioxidant 168, 20 g of polycarbodiimide and 5 g of calcium stearate to a high-speed mixer, set the speed to 600 rpm, the mixing temperature to 30℃, mix for 12 min, and obtain 9.988 kg of premix; 4: The premixed material is fed into the twin-screw extruder through the main feed port for melt blending and extrusion. The temperature of the twin-screw extruder is set to 145℃ for the feeding section, 155℃ for the plasticizing section, 160℃ for the metering section, and 160℃ for the die head. The screw speed is 200 rpm. The molten material is extruded through the die head to form a continuous strip with a diameter of 3 mm. 5: Feed the continuous strip into the water-cooled strip pelletizer, set the cooling water tank temperature to 30℃, the traction speed to 15m / min, and the pelletizer speed to 750rpm. After pelletizing, cylindrical particles with a diameter of 2.5mm and a length of 3mm are obtained. The particles are then conveyed to a vibrating screen to remove debris smaller than 1mm and connected particles larger than 4mm, resulting in 9.645kg of qualified pellets. 6: Place the qualified pellets in a vacuum drying oven, set the temperature to 75℃ and the vacuum degree to -0.09MPa, and dry for 4 hours. After drying, fill the pellets into sealed packaging bags lined with aluminum foil using a packaging machine. During filling, the material temperature is controlled below 30℃. Heat seal the bags to obtain 9.625 kg of the nano-antibacterial polyethylene composite material for paint buckets prepared in Comparative Example 2.

[0016] Antibacterial performance test The nano-antibacterial polyethylene composite materials prepared in Examples 3, 4, Comparative Example 1, and Comparative Example 2 were injection molded into circular samples with a diameter of 100 mm and a thickness of 2 mm at 190 °C. The samples were tested according to GB / T 31402-2015 "Test Method for Antibacterial Properties of Plastic Surfaces". The test bacteria were Escherichia coli and Staphylococcus aureus. The contact time was 24 h, and the antibacterial rate was calculated. The long-term antibacterial performance was determined using the inhibition zone method. Sample discs were placed on the surface of agar plates coated with bacteria and incubated in a 37°C incubator for 28 days. The width of the inhibition zone was measured every 7 days. Each group of samples was tested in parallel three times, and the average value was recorded. Table 1. Results of antibacterial performance test 24-hour E. coli antibacterial rate / % 99.6 99.8 96.2 88.5 24-hour Staphylococcus aureus antibacterial rate / % 99.4 99.7 95.8 86.3 7-day antibacterial zone width / mm 2.5 2.8 1.2 1.8 14-day antibacterial zone width / mm 2.3 2.6 0.5 1.3 28-day antibacterial zone width / mm 2.1 2.4 0 0.8 Analysis of Table 1 shows that the antibacterial rate of Examples 3 and 4 reached over 99% in 24 hours, and the inhibition zone remained above 2 mm in 28 days. This proves that the quaternary ammonium salt cation of hydroxypropyltrimethylammonium chloride chitosan provides rapid contact bactericidal ability. At the same time, the nano-core-shell antibacterial microspheres continuously release zinc ions through mesoporous channels, maintaining an effective antibacterial concentration for 28 days, thus achieving a balance between rapid bactericidal effect and long-term antibacterial effect. The antibacterial zone width in Example 4 is greater than that in Example 3. The reason for this is that the amount of nano-core-shell antibacterial microspheres used in Example 4 is higher, resulting in a greater total release of zinc ions. The antibacterial rate of Comparative Example 1 was still over 95% after 24 hours, indicating that chitosan alone can provide rapid bactericidal effect. However, the inhibition zone decreased to 1.2 mm after 7 days, only 0.5 mm after 14 days, and completely disappeared after 28 days. This proves that after removing the nano-core-shell antibacterial microspheres, the zinc ion slow-release mechanism was lost, and the long-term antibacterial requirement could not be met by relying solely on the chitosan single antibacterial mechanism. The 24-hour antibacterial rate of Comparative Example 2 was only 88.5% and 86.3%, significantly lower than that of Example 3. The inhibition zone after 28 days was only 0.8 mm. The reason for this is that ordinary chitosan does not have quaternary ammonium salt cationic groups, and its ability to electrostatically adsorb bacterial cell membranes is weak. At the same time, the amino and carboxyl groups only form weak hydrogen bonds rather than strong ionic crosslinks, resulting in poor dispersibility of chitosan in the matrix, reduced effective antibacterial surface area, and a significant decrease in antibacterial activity.

[0017] Thermal stability and dispersibility test The nano-antibacterial polyethylene composite materials prepared in Examples 3, 4, Comparative Example 1, and Comparative Example 2 were heated from room temperature to 600°C at a rate of 10°C / min using a thermogravimetric analyzer under a nitrogen atmosphere, and the initial thermal decomposition temperature (at the thermometer when the mass loss was 5%) was recorded. The dispersibility was determined by observing the microstructure of the liquid nitrogen brittle fracture surface of the sample using a scanning electron microscope. The accelerating voltage was 15 kV and the magnification was 5000x. Ten fields of view were randomly selected, and the average particle size of the dispersed phase was statistically analyzed using image analysis software. Each group of samples was tested in parallel three times, and the average value was recorded. Table 2. Results of thermal stability and dispersibility tests Initial thermal decomposition temperature / °C 215 212 218 182 Average particle size of dispersed phase / nm 85 92 78 1850 As can be seen from the analysis of Table 2, the average particle size of the chitosan dispersed phase in Examples 3 and 4 is 85nm and 92nm respectively, both less than 100nm. This proves that a highly efficient dynamic ionic crosslinking is formed between the carboxyl group of maleic anhydride grafted polyethylene and the quaternary ammonium salt cation of hydroxypropyltrimethylammonium chloride chitosan, realizing the nanoscale uniform anchoring of chitosan in the polyethylene matrix. The dispersed phase particle size in Example 4 is slightly larger than that in Example 3. The reason for this is that the amount of chitosan used in Example 4 is higher, and the increased density of the dispersed phase leads to the merging of a small number of adjacent micro-regions, resulting in a slight increase in particle size. The average particle size of the dispersed phase in Comparative Example 1 was 78 nm, which is the same as that in Examples 3 and 4, indicating that the removal of the core-shell antibacterial microspheres does not affect the dynamic ion anchoring dispersion effect of chitosan.

[0018] The average particle size of the dispersed phase in Comparative Example 2 was as high as 1850 nm, which is 21.8 times that of Example 3. This proves that ordinary chitosan cannot form an effective ionic crosslinking anchor by relying solely on the weak hydrogen bonding between amino and carboxyl groups. Chitosan severely aggregated in the polyethylene matrix, and its dispersibility was significantly deteriorated.

[0019] Multiple processing and recycling performance tests The nano-antibacterial polyethylene composite materials prepared in Examples 3, 4, Comparative Example 1, and Comparative Example 2 were pulverized using a pulverizer and then granulated three times under the same extrusion conditions. After each granulation, the samples were injection molded into dumbbell-shaped tensile specimens according to ISO 527-2 standard type 1A. The tensile strength was tested at a tensile rate of 10 mm / min, and the tensile strength retention rate after each recycling was calculated based on the initial tensile strength. Each group of samples was tested in parallel three times, and the average value was recorded. Table 3. Results of multiple processing and recycling performance tests Initial tensile strength / MPa 24.5 23.2 25.8 21.6 Initial fracture elongation / % 380 320 420 240 Tensile strength retention rate after one recycling / % 96.8 95.5 94.2 90.3 Tensile strength retention rate after two recycling cycles / % 93.5 91.8 88.6 82.5 Tensile strength retention rate after 3 recyclings / % 89.2 87.0 82.1 73.8 As shown in Table 3, after three recycling cycles, the tensile strength retention rates of Examples 3 and 4 reached 89.2% and 87.0%, respectively. This demonstrates that the carbodiimide groups of polycarbodiimide undergo a chain extension reaction with the terminal carboxyl groups generated during repeated heat processing, effectively repairing the degraded polyethylene molecular chains and inhibiting the decline in the mechanical properties of the recycled material. The retention rate of Example 3 was slightly higher than that of Example 4. The reason for this is that the content of polar components in Example 4 was higher, and the thermal shearing during multiple processing caused greater damage to the molecular chains. The initial tensile strength and elongation of Comparative Example 1 were higher than those of Example 4. The reason for this is that Comparative Example 1 did not contain rigid inorganic antibacterial microspheres, and the composite material had better flexibility. However, after three recycling cycles, the retention rate dropped to 82.1%, which was lower than 87.0% of Example 4. This indicates that although the antibacterial microsphere-free system had better initial mechanical properties, its recycling stability was slightly worse. The initial tensile strength of Comparative Example 2 was only 21.6 MPa, and the elongation at break was only 240%, which was significantly lower than that of Example 3. Moreover, the retention rate after three recycling cycles was only 73.8%. The reason for this was that ordinary chitosan has poor thermal stability, and some degradation during extrusion produces defect points. At the same time, the formation of stress concentration points by micron-sized chitosan aggregates led to a comprehensive decline in mechanical properties, and the degradation was further aggravated during recycling and reprocessing.

[0020] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A nano-antibacterial polyethylene composite material for paint buckets, characterized in that, It is composed of the following components by weight percentage: 60-75% high-density polyethylene, 10-18% maleic anhydride-grafted polyethylene, 6.8-9% hydroxypropyltrimethylammonium chloride chitosan, 6.25-7.25% nano-core-shell antibacterial microspheres, 1-3% γ-aminopropyltriethoxysilane, 0.5-1.5% polyethylene wax, 0.1-0.3% antioxidant 1010, 0.1-0.3% antioxidant 168, 0.2-0.5% polycarbodiimide, and 0.05-0.15% calcium stearate.

2. The nano-antibacterial polyethylene composite material for paint buckets according to claim 1, characterized in that, The maleic anhydride-grafted polyethylene has a maleic anhydride grafting rate of 1% and a melt index of 3 g / 10 min under conditions of 190°C and 2.16 kg load.

3. The nano-antibacterial polyethylene composite material for paint buckets according to claim 1, characterized in that, The high-density polyethylene described above has a melt flow index of 0.5 g / 10 min and a density of 0.954 g / cm³ under conditions of 190°C and 2.16 kg load. 3 .

4. The nano-antibacterial polyethylene composite material for paint buckets according to claim 1, characterized in that, The degree of substitution of the hydroxypropyltrimethylammonium chloride chitosan is 92%, and the initial thermal decomposition temperature under nitrogen atmosphere is ≥200℃.

5. The nano-antibacterial polyethylene composite material for paint buckets according to claim 1, characterized in that, The polycarbodiimide has a number average molecular weight of 3000 and a carbodiimide group content of 13%.

6. The nano-antibacterial polyethylene composite material for paint buckets according to claim 1, characterized in that, The preparation method of the aforementioned core-shell antibacterial microspheres includes the following steps: A1: Add mesoporous silica to deionized water and ultrasonically disperse it at 25°C for 30-35 min with an ultrasonic power of 300-350W to obtain a mesoporous silica suspension, wherein the mass ratio of mesoporous silica to deionized water is 1:

80. A2: Add zinc nitrate hexahydrate to deionized water, set the stirrer speed to 350-400 rpm, and stir for 5-6 minutes to prepare a zinc nitrate solution, wherein the mass ratio of zinc nitrate hexahydrate to deionized water is 1:8.

5. Keep the speed constant, add the zinc nitrate solution dropwise to the mesoporous silica suspension at a rate of 0.2-0.3 kg / min using a constant flow pump, wherein the mass ratio of zinc nitrate solution to mesoporous silica suspension is 1:

7. After the dropwise addition is completed, set the stirring speed to 400-450 rpm and continue stirring for 3 hours to obtain the loaded suspension. A3: Add a 2.5wt% dilute ammonia solution dropwise to the loaded suspension using a constant flow pump at a rate of 0.1-0.15 kg / min. Monitor the pH of the system in real time during the dropwise addition. Stop the dropwise addition when the pH reaches 7.8-8. Then set the stirring speed to 300-350 rpm and continue stirring and aging for 4-5 hours. Maintain the pH at 7.5-8 during the aging process to obtain the precursor suspension. A4: Vacuum filter the precursor suspension. After vacuum filtration, wash the filter cake repeatedly with deionized water 3-5 times. After washing, place the filter cake in a forced-air drying oven and set the temperature to 80-85℃ for 12-14 hours to obtain precursor powder. Place the precursor powder in a muffle furnace and set the heating rate to 2-3℃ / min. Calcinate at 450℃ for 3-4 hours. After calcination, cool to room temperature with the furnace, grind, and pass through a 300-mesh sieve to obtain nano-core-shell antibacterial microspheres.

7. The method for preparing a nano-antibacterial polyethylene composite material for paint buckets according to claim 1, characterized in that, Includes the following steps: S1: Add γ-aminopropyltriethoxysilane to anhydrous ethanol, set the stirrer speed to 300 rpm, and stir for 15 min to obtain a coupling agent solution, wherein the mass ratio of γ-aminopropyltriethoxysilane to anhydrous ethanol is 1:

8. S2: Place the nano-core-shell antibacterial microspheres in a high-speed mixer, set the speed to 1000 rpm, and use an atomizing nozzle to evenly spray the coupling agent solution onto the surface of the nano-core-shell antibacterial microspheres while stirring. After spraying, increase the speed of the mixer to 1800 rpm, set the mixing temperature to 70℃, and mix for 20 minutes. After mixing, transfer the mixture to a vacuum drying oven, set the temperature to 90℃, the vacuum degree to -0.09 MPa, and dry for 3 hours. After drying, pass the mixture through a 200-mesh sieve to obtain modified core-shell antibacterial microspheres, and seal them for moisture protection before use. S3: High-density polyethylene, maleic anhydride-grafted polyethylene, hydroxypropyltrimethylammonium chloride chitosan, modified core-shell antibacterial microspheres, polyethylene wax, antioxidant 1010, antioxidant 168, polycarbodiimide and calcium stearate are added to a high-speed mixer, the speed is set to 600 rpm, the mixing temperature is 30℃, and the mixture is mixed for 12 minutes to obtain a premix. S4: The premixed material is fed into the twin-screw extruder through the main feed port for melt blending and extrusion. The temperature of the twin-screw extruder is set to 145℃ for the feeding section, 155℃ for the plasticizing section, 160℃ for the metering section, and 160℃ for the die head. The screw speed is 200 rpm. The molten material is extruded through the die head to form a continuous strip with a diameter of 3 mm. S5: Feed the continuous strip into the water-cooled strip pelletizer, set the cooling water tank temperature to 30℃, the traction speed to 15m / min, and the pelletizer speed to 750rpm. After pelletizing, cylindrical particles with a diameter of 2.5mm and a length of 3mm are obtained. The particles are then conveyed to a vibrating screen to remove debris with a diameter of less than 1mm and connected particles with a diameter of more than 4mm, thus obtaining qualified pellets. S6: Place the qualified pellets in a vacuum drying oven, set the temperature to 75℃ and the vacuum degree to -0.09MPa, and dry for 4 hours. After drying, fill the pellets into sealed packaging bags lined with aluminum foil through a packaging machine. During filling, the material temperature is controlled below 30℃. Heat seal the bags to obtain nano antibacterial polyethylene composite material for use in paint buckets.

8. The nano-antibacterial polyethylene composite material for paint buckets according to claim 6, characterized in that, The mesoporous silica has a pore size of 6 nm and a specific surface area of ​​750 m². 2 / g, with an average particle size of 150nm.