An antibacterial plastic lunch box material and its preparation method

Abstract

This invention discloses an antibacterial plastic lunchbox material and its preparation method, belonging to the field of plastic materials technology and patent classification number C08K3 / 08. The method first modifies and carboxylates mesoporous silica, then prepares a composite antibacterial precursor through zinc nitrate chelation and quaternary ammonium salt ion exchange, followed by a crosslinking reaction to obtain an antibacterial carrier. On the other hand, polylactic acid and polycaprolactone are blended to obtain a matrix, and a plastic matrix resin is prepared through graft copolymerization and ring-opening reaction. Finally, the plastic matrix resin, antibacterial carrier, polyethylene glycol 400, zinc stearate, antioxidant, and ultraviolet absorber are melt-extruded and injection-molded to obtain the antibacterial plastic lunchbox material. This method achieves a highly efficient and long-lasting antibacterial effect by synergistically anchoring zinc ions and quaternary ammonium salts to the functionalized mesoporous filler carrier and uniformly dispersing them in the graft-modified resin matrix, while the material also possesses good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of plastic materials technology, belonging to patent classification number C08K3 / 08, specifically to an antibacterial plastic lunch box material and its preparation method. Background Technology

[0002] With the increasing global awareness of environmental protection and the implementation of policies such as plastic restriction orders, biodegradable materials have become the core direction for replacing traditional petroleum-based plastics. Among them, polylactic acid (PLA) has received widespread attention in the food packaging field, especially in the production of lunch boxes, due to its advantages such as renewable raw materials (derived from biomass fermentation such as corn and potatoes), excellent biocompatibility, and stable processing performance. PLA lunch boxes can degrade into carbon dioxide and water in the natural environment, effectively solving the white pollution problem caused by traditional plastics. Moreover, its mechanical properties are similar to those of traditional plastics such as polypropylene (PP), which can meet the molding and usage requirements of lunch boxes.

[0003] However, the inherent defects of pure polylactic acid (PLA) materials limit its extensive application in the food contact field. The core problem lies in its poor antibacterial properties; it can only produce a weak antibacterial effect through a slightly acidic surface environment and cannot effectively inhibit the adhesion and reproduction of common pathogenic bacteria such as Escherichia coli and Staphylococcus aureus. During food storage, transportation, and use, PLA food containers easily become carriers of microbial growth, which not only leads to food spoilage and shortened shelf life, causing huge economic losses, but also may cause food safety problems and endanger consumer health. This shortcoming makes PLA food containers unsuitable for the packaging needs of perishable foods such as meat, seafood, and cooked food, severely restricting the expansion of its application scenarios. Summary of the Invention

[0004] The purpose of this invention is to provide an antibacterial plastic lunchbox material and its preparation method, thereby solving the technical problems mentioned in the background section. The plastic lunchbox material prepared by this invention has excellent antibacterial properties.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing an antibacterial plastic lunchbox material includes the following steps:

[0007] S1. Mesoporous silica is pretreated by calcination, then mixed with anhydrous ethanol and deionized water, and then 3-aminopropyltriethoxysilane is added to react and obtain amino-modified mesoporous silica. The amino-modified mesoporous silica is mixed with toluene and maleic anhydride is added in a nitrogen atmosphere to react and obtain carboxyl-functionalized mesoporous silica.

[0008] S2. Mix carboxyl-functionalized mesoporous silica with deionized water, then add zinc nitrate aqueous solution to carry out a chelation reaction to obtain zinc chelated functionalized mesoporous silica. Mix zinc chelated functionalized mesoporous silica with deionized water, then add hexadecyltrimethylammonium bromide and dodecyldimethylbenzylammonium chloride to carry out an ion exchange reaction to obtain a composite antibacterial precursor.

[0009] S3. Add adipate dihydrazide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to the composite antibacterial precursor to carry out a cross-linking reaction and obtain the antibacterial carrier.

[0010] S4. Polylactic acid and polycaprolactone are blended to obtain a blend matrix; N-vinylcaprolactam, glycidyl methacrylate and anhydrous ethanol are mixed to obtain an antibacterial monomer mixture; the blend matrix, antibacterial monomer mixture, benzoyl peroxide and dodecyl mercaptan are extruded to obtain a crude graft copolymer; the crude graft copolymer is subjected to a ring-opening reaction with ethanolamine to obtain a plastic matrix resin.

[0011] S5. Mix the plastic matrix resin, antibacterial carrier, polyethylene glycol 400, zinc stearate, antioxidant and ultraviolet absorber, and then melt extrusion and injection molding to obtain antibacterial plastic lunch box material.

[0012] In this invention, the antibacterial properties of polylactic acid (PLA) plastic lunch boxes are improved synergistically from two aspects. Firstly, an antibacterial functional filler carrier is prepared. The mesoporous structure of mesoporous silica provides a large specific surface area and abundant pores, enhancing the carrier for efficient loading of antibacterial components. Subsequently, amino groups are introduced through 3-aminopropyltriethoxysilane, and carboxyl groups are grafted onto maleic anhydride, gradually constructing specific binding sites. The carboxyl groups form stable coordination bonds with zinc ions through chelation, ensuring uniform dispersion and preventing detachment of zinc ions. Quaternary ammonium salts (hexadecyltrimethylammonium bromide and dodecyldimethylbenzylammonium chloride) are adsorbed onto the carrier surface through ion exchange. The two antibacterial components work synergistically: zinc ions can penetrate bacterial cell walls, disrupting the bacterial enzyme system and genetic material, inhibiting bacterial metabolism and reproduction; quaternary ammonium salts, with their cationic properties, bind to anionic groups on the bacterial cell membrane, disrupting cell membrane integrity and leading to bacterial lysis and death. The complementary mechanisms of action significantly broaden the antibacterial spectrum and improve bactericidal efficiency. In addition, the cross-linking effect of adipic acid dihydrazide forms a three-dimensional network structure on the carrier surface, which further locks in the antibacterial components and prevents them from migrating and being lost during use, thus achieving a long-lasting antibacterial effect.

[0013] On the other hand, polylactic acid and polycaprolactone are pretreated by high-temperature blending to form a matrix framework that is both degradable and flexible, providing a stable base for antibacterial functionalization. Then, N-vinylcaprolactam and glycidyl methacrylate are grafted onto the blend matrix backbone through reactive extrusion. The cyclic structure and amide groups of N-vinylcaprolactam can interact with bacterial cell membranes, changing cell membrane permeability and interfering with bacterial metabolic processes, enabling the matrix itself to have active antibacterial capabilities. This avoids the problem of uneven local concentrations that easily occurs when traditional antibacterial agents rely solely on external addition. Meanwhile, the epoxy groups of glycidyl methacrylate are introduced with hydroxyl groups after ring-opening with ethanolamine. The hydroxyl groups improve the surface activity of the matrix, making it easier to disperse plasticizers, antioxidants and other additives in subsequent composite preparation, improving the overall uniformity of the material, and avoiding the impact of additive agglomeration on the stability of antibacterial and mechanical properties. In addition, the antibacterial activity of the matrix resin can form an antibacterial barrier on the material surface, preventing bacterial adsorption and initial reproduction. Meanwhile, the antibacterial carrier dispersed inside the matrix continuously releases zinc ions and quaternary ammonium salts through long-term slow release, killing bacteria that penetrate the surface barrier. The two form a synergistic antibacterial mode of surface barrier and internal killing, which greatly improves the antibacterial coverage and bactericidal efficiency.

[0014] Preferably, in step S1, the mass ratio of mesoporous silica to 3-aminopropyltriethoxysilane is 25:(0.7-1.5).

[0015] Preferably, in step S1, the mass ratio of amino-modified mesoporous silica to maleic anhydride is 25:(6-10).

[0016] Preferably, in step S2, the mass ratio of hexadecyltrimethylammonium bromide to dodecyldimethylbenzylammonium chloride is 8:(1-3).

[0017] Preferably, in step S3, the mass ratio of the composite antibacterial precursor to adipic acid dihydrazide is 20:(3-6).

[0018] Preferably, in step S4, the mass ratio of polylactic acid to polycaprolactone is 70:(25-35).

[0019] Preferably, in step S5, the antibacterial carrier undergoes surface modification treatment with 3-methacryloyloxypropyltrimethoxysilane.

[0020] In the technical solution of this invention, the research team discovered through in-depth research that the polylactic acid / polycaprolactone matrix and the antibacterial carrier are prone to excessive hydrogen bonding during composite preparation. Both have high-density and complementary hydrogen bond donor and acceptor sites, and there is no steric hindrance. In addition, the process conditions further promote this process, ultimately leading to carrier aggregation. Specifically, the matrix introduces a large number of hydroxyl groups after glycidyl methacrylate epoxy ring-opening, and the high grafting rate results in a dense distribution of hydroxyl groups. The antibacterial carrier has a large specific surface area due to its mesoporous structure, and the residual carboxyl and amino groups on its surface are also polar groups with both donor and acceptor functions, with high loading density and no steric hindrance. When the two come into contact in a high-temperature, high-speed mixing process, the movement of the matrix molecular chains intensifies, and hydroxyl groups diffuse more easily to the surface of the carrier. Multiple carboxyl / amino groups of a carrier particle can form dozens or even hundreds of hydrogen bonds with hydroxyl groups of multiple matrix molecular chains. These matrix molecular chains then act as hydrogen bond bridges connecting other carrier particles. Since hydrogen bonds are thermodynamically stable and difficult to break after formation, the shearing force of subsequent processes cannot completely disperse them, ultimately leading to carrier aggregation, pore blockage, obstruction of the slow-release channels of zinc ions and quaternary ammonium salts, and difficulty in uniformly diffusing and contacting bacteria with antibacterial components, directly reducing the antibacterial efficiency of the antibacterial carrier. To further address this technical problem, this invention grafts 3-methacryloxypropyltrimethoxysilane onto an antibacterial carrier. The alkoxy group of 3-methacryloxypropyltrimethoxysilane hydrolyzes in anhydrous ethanol to generate an active silanol group, which undergoes dehydration condensation with the residual carboxyl and amino groups on the surface of the antibacterial carrier to form a stable covalent bond, thus firmly grafting it onto the carrier surface. The long-chain alkyl group at the other end forms a hydrophobic coating layer, which not only covers some polar sites to reduce hydrogen bond pairing, but also forms a physical barrier through steric hindrance, thereby inhibiting carrier aggregation and ensuring unobstructed pores and uniform and slow release of antibacterial components.

[0021] Preferably, the mass ratio of the antibacterial carrier to 3-methacryloyloxypropyltrimethoxysilane is 20:(1-3).

[0022] Preferably, the mass ratio of the plastic matrix resin to the antibacterial carrier is 100:(10-15).

[0023] An antibacterial plastic lunchbox material is prepared by the method described above.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. By simultaneously loading zinc ions and quaternary ammonium salts onto functionalized mesoporous silica, the different mechanisms by which they disrupt bacterial cell walls / membranes and internal metabolism are utilized to form a complementary relationship, significantly expanding the antibacterial spectrum and improving bactericidal efficiency.

[0026] 2. A three-dimensional network structure is formed on the surface of the antibacterial carrier through a cross-linking reaction, locking in the antibacterial components and preventing them from being lost too quickly; in addition, the matrix resin and the internal antibacterial carrier constitute a dual protection of surface barrier and internal slow-release killing, achieving a long-lasting antibacterial effect.

[0027] 3. By modifying the matrix resin, its compatibility with additives is improved; at the same time, the surface of the antibacterial carrier is hydrophobically modified to effectively prevent its agglomeration during processing, ensuring that the antibacterial components can be uniformly dispersed and stably released, thereby guaranteeing the stability of the final antibacterial and mechanical properties of the material. Attached Figure Description

[0028] Figure 1 This is a SEM image of the antibacterial carrier prepared in Example 1 of the present invention.

[0029] Figure 2 This is a TEM image of the antibacterial carrier prepared in Example 1 of the present invention. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for preparing an antibacterial plastic lunchbox material includes the following steps:

[0033] Step 1: Weigh 25g of mesoporous silica and place it in a muffle furnace. Set the temperature to 580℃ and calcine for 3.5 hours. After naturally cooling to room temperature, collect and set aside.

[0034] The calcined mesoporous silica was added to a mixed solution of 140 mL anhydrous ethanol and 25 mL deionized water and ultrasonically dispersed at 450 W and 48 kHz for 35 min. The pH of the system was adjusted to 4.0 with 0.8 mol / L hydrochloric acid, and then 1.3 g KH550 was added. The mixture was refluxed in a water bath at 75 °C and 350 rpm for 7 h. After the reaction was completed, the precipitate was collected by centrifugation at 8000 rpm, washed 4 times with anhydrous ethanol, and dried in a vacuum drying oven at 105 °C for 9 h to obtain amino-modified mesoporous silica.

[0035] 25g of amino-modified mesoporous silica was added to 120mL of toluene, and nitrogen gas was introduced (flow rate 50mL / min). The system was heated to 110℃ and 9g of maleic anhydride was added. The reaction was carried out at a stirring rate of 400rpm for 5h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the precipitate was collected by centrifugation at 8000rpm. The precipitate was washed twice with toluene and twice with acetone. The precipitate was then dried in a vacuum drying oven at 95℃ for 7h to obtain carboxyl-functionalized mesoporous silica.

[0036] Step 2: Add 25g of carboxyl-functionalized mesoporous silica to 180mL of deionized water, and disperse it ultrasonically at 450W for 25min. Adjust the pH of the system to 6.5 with 0.1mol / L sodium hydroxide, and slowly add 80mL of 0.8mol / L zinc nitrate aqueous solution. Stir and chelate for 3.5h at 45℃ and 280rpm. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm, and wash it repeatedly with deionized water to obtain zinc-chelated functionalized mesoporous silica.

[0037] 25g of zinc-chelated functionalized mesoporous silica was added to 140mL of deionized water and ultrasonically dispersed at 450W for 18min. Then, 8g of hexadecyltrimethylammonium bromide and 2.5g of dodecyldimethylbenzylammonium chloride were added, and the mixture was stirred at 55℃ and 320rpm for 6h for ion exchange reaction. After the reaction was completed, the precipitate was collected by centrifugation at 8000rpm and washed three times with deionized water to obtain the zinc-quaternary ammonium salt composite antibacterial precursor.

[0038] Step 3: Add 5g of adipic acid dihydrazide and 0.5g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to 20g of zinc-quaternary ammonium salt composite antibacterial precursor. Adjust the pH of the system to 8.5 with 0.1mol / L sodium hydroxide. Stir and crosslink the reaction at 75℃ and 420rpm for 2.5h. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm and dry it in a vacuum drying oven at 85℃ for 13h. Grind the dried product and pass it through a 350-mesh sieve to obtain the antibacterial carrier.

[0039] Step 4: Weigh 70g of polylactic acid and 32g of polycaprolactone, dry them in an 80℃ vacuum drying oven for 4 hours, then add them to a high-speed mixer, set the temperature to 175℃ and the speed to 550rpm, mix for 18 minutes and then discharge to obtain a uniform PLA / PCL blend matrix.

[0040] Weigh 8g of N-vinylcaprolactam, 5g of glycidyl methacrylate and 15mL of anhydrous ethanol and add them to a beaker. Place the beaker in a 35℃ constant temperature water bath and simultaneously turn on a 350W ultrasonic disperser to disperse for 12 minutes to completely dissolve the monomers and form a homogeneous antibacterial monomer mixture.

[0041] 120 parts by weight of PLA / PCL blend matrix were added to a twin-screw extruder. The extruder temperature was set to 165°C in zone 1, 175°C in zone 2, 185°C in zone 3, and 180°C at the die head, with a screw speed of 220 rpm. 10 parts by weight of antibacterial monomer mixture were continuously fed in via a side feeder, along with 0.52 parts by weight of benzoyl peroxide and 0.4 parts by weight of dodecyl mercaptan. After extrusion, the material was water-cooled and pelletized to obtain crude graft copolymer. The crude graft copolymer was added to 220 mL of deionized water, along with 2.4 parts by weight of ethanolamine. The mixture was stirred at 90°C and 320 rpm for 3.5 h to initiate a ring-opening reaction. After the reaction, the mixture was cooled to room temperature, filtered to collect the precipitate, washed three times with deionized water, and then dried in a 75°C vacuum drying oven for 11 h to obtain the plastic matrix resin.

[0042] Step 5: Weigh 20g of antibacterial carrier and add it to 50mL of anhydrous ethanol. Then add 2.5g of 3-methacryloyloxypropyltrimethoxysilane. Set the temperature to 80℃ and the stirring speed to 300rpm, and react at a constant temperature for 1.5h. After the reaction is complete, centrifuge at 8000rpm to collect the precipitate. Place the precipitate in a vacuum drying oven at 85℃ and dry it for 5h to obtain the surface-modified antibacterial carrier.

[0043] Weigh out 100 parts by weight of plastic matrix resin, 14 parts by weight of surface-modified antibacterial carrier, 6.5 parts by weight of polyethylene glycol 400, 0.6 parts by weight of zinc stearate, 0.8 parts by weight of antioxidant 1010, and 0.4 parts by weight of UV absorber 531. Add all raw materials to a high-speed mixer, set the temperature to 120℃ and the speed to 650 rpm, mix for 25 minutes, and then discharge to obtain a homogeneous mixture. Place the mixture in an 85℃ vacuum drying oven for 6 hours, and then add it to a twin-screw extruder. Set the extruder temperature to 175℃ in zone 1, 185℃ in zone 2, 195℃ in zone 3, and 190℃ at the die head, with a screw speed of 280 rpm. After melting, mixing, extruding, and pelletizing, the material is obtained as antibacterial plastic lunch box material.

[0044] Example 2

[0045] A method for preparing an antibacterial plastic lunchbox material includes the following steps:

[0046] Step 1: Weigh 25g of mesoporous silica and place it in a muffle furnace. Set the temperature to 580℃ and calcine for 3.5 hours. After naturally cooling to room temperature, collect and set aside.

[0047] The calcined mesoporous silica was added to a mixed solution of 140 mL anhydrous ethanol and 25 mL deionized water and ultrasonically dispersed at 450 W and 48 kHz for 35 min. The pH of the system was adjusted to 4.0 with 0.8 mol / L hydrochloric acid, and then 0.8 g KH550 was added. The mixture was refluxed in a water bath at 75 °C and 350 rpm for 7 h. After the reaction was completed, the precipitate was collected by centrifugation at 8000 rpm, washed 4 times with anhydrous ethanol, and dried in a vacuum drying oven at 105 °C for 9 h to obtain amino-modified mesoporous silica.

[0048] 25g of amino-modified mesoporous silica was added to 120mL of toluene, and nitrogen gas was introduced (flow rate 50mL / min). The system was heated to 110℃ and 7g of maleic anhydride was added. The reaction was carried out at a stirring rate of 400rpm for 5h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the precipitate was collected by centrifugation at 8000rpm. The precipitate was washed twice with toluene and twice with acetone. The precipitate was then dried in a vacuum drying oven at 95℃ for 7h to obtain carboxyl-functionalized mesoporous silica.

[0049] Step 2: Add 25g of carboxyl-functionalized mesoporous silica to 180mL of deionized water, and disperse it ultrasonically at 450W for 25min. Adjust the pH of the system to 6.5 with 0.1mol / L sodium hydroxide, and slowly add 80mL of 0.8mol / L zinc nitrate aqueous solution. Stir and chelate for 3.5h at 45℃ and 280rpm. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm, and wash it repeatedly with deionized water to obtain zinc-chelated functionalized mesoporous silica.

[0050] 25g of zinc-chelated functionalized mesoporous silica was added to 140mL of deionized water and ultrasonically dispersed at 450W for 18min. Then, 8g of hexadecyltrimethylammonium bromide and 1.5g of dodecyldimethylbenzylammonium chloride were added, and the mixture was stirred at 55℃ and 320rpm for 6h for ion exchange reaction. After the reaction was completed, the precipitate was collected by centrifugation at 8000rpm and washed three times with deionized water to obtain the zinc-quaternary ammonium salt composite antibacterial precursor.

[0051] Step 3: Add 4g of adipic acid dihydrazide and 0.5g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to 20g of zinc-quaternary ammonium salt composite antibacterial precursor. Adjust the pH of the system to 8.5 with 0.1mol / L sodium hydroxide. Stir and crosslink the reaction at 75℃ and 420rpm for 2.5h. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm and dry it in a vacuum drying oven at 85℃ for 13h. Grind the dried product and pass it through a 350-mesh sieve to obtain the antibacterial carrier.

[0052] Step 4: Weigh 70g of polylactic acid and 28g of polycaprolactone, dry them in an 80℃ vacuum drying oven for 4 hours, then add them to a high-speed mixer, set the temperature to 175℃ and the speed to 550rpm, mix for 18 minutes and then discharge to obtain a uniform PLA / PCL blend matrix.

[0053] Weigh 8g of N-vinylcaprolactam, 5g of glycidyl methacrylate and 15mL of anhydrous ethanol and add them to a beaker. Place the beaker in a 35℃ constant temperature water bath and simultaneously turn on a 350W ultrasonic disperser to disperse for 12 minutes to completely dissolve the monomers and form a homogeneous antibacterial monomer mixture.

[0054] 120 parts by weight of PLA / PCL blend matrix were added to a twin-screw extruder. The extruder temperature was set to 165°C in zone 1, 175°C in zone 2, 185°C in zone 3, and 180°C at the die head, with a screw speed of 220 rpm. 10 parts by weight of antibacterial monomer mixture were continuously fed in via a side feeder, along with 0.52 parts by weight of benzoyl peroxide and 0.4 parts by weight of dodecyl mercaptan. After extrusion, the material was water-cooled and pelletized to obtain crude graft copolymer. The crude graft copolymer was added to 220 mL of deionized water, along with 2.4 parts by weight of ethanolamine. The mixture was stirred at 90°C and 320 rpm for 3.5 h to initiate a ring-opening reaction. After the reaction, the mixture was cooled to room temperature, filtered to collect the precipitate, washed three times with deionized water, and then dried in a 75°C vacuum drying oven for 11 h to obtain the plastic matrix resin.

[0055] Step 5: Weigh 20g of antibacterial carrier and add it to 50mL of anhydrous ethanol. Then add 2.5g of 3-methacryloyloxypropyltrimethoxysilane. Set the temperature to 80℃ and the stirring speed to 300rpm, and react at a constant temperature for 1.5h. After the reaction is complete, centrifuge at 8000rpm to collect the precipitate. Place the precipitate in a vacuum drying oven at 85℃ and dry it for 5h to obtain the surface-modified antibacterial carrier.

[0056] Weigh out 100 parts by weight of plastic matrix resin, 12 parts by weight of surface-modified antibacterial carrier, 6.5 parts by weight of polyethylene glycol 400, 0.6 parts by weight of zinc stearate, 0.8 parts by weight of antioxidant 1010, and 0.4 parts by weight of UV absorber 531. Add all raw materials to a high-speed mixer, set the temperature to 120℃ and the speed to 650 rpm, mix for 25 minutes, and then discharge to obtain a homogeneous mixture. Place the mixture in an 85℃ vacuum drying oven for 6 hours, and then add it to a twin-screw extruder. Set the extruder temperature to 175℃ in zone 1, 185℃ in zone 2, 195℃ in zone 3, and 190℃ at the die head, with a screw speed of 280 rpm. After melting, mixing, extruding, and pelletizing, the material is obtained as antibacterial plastic lunch box material.

[0057] Example 3

[0058] A method for preparing an antibacterial plastic lunchbox material includes the following steps:

[0059] Step 1: Weigh 25g of mesoporous silica and place it in a muffle furnace. Set the temperature to 580℃ and calcine for 3.5 hours. After naturally cooling to room temperature, collect and set aside.

[0060] The calcined mesoporous silica was added to a mixed solution of 140 mL anhydrous ethanol and 25 mL deionized water and ultrasonically dispersed at 450 W and 48 kHz for 35 min. The pH of the system was adjusted to 4.0 with 0.8 mol / L hydrochloric acid, and then 1.0 g KH550 was added. The mixture was refluxed in a water bath at 75 °C and 350 rpm for 7 h. After the reaction was completed, the precipitate was collected by centrifugation at 8000 rpm, washed 4 times with anhydrous ethanol, and dried in a vacuum drying oven at 105 °C for 9 h to obtain amino-modified mesoporous silica.

[0061] 25g of amino-modified mesoporous silica was added to 120mL of toluene, and nitrogen gas was introduced (flow rate 50mL / min). The system was heated to 110℃ and 8g of maleic anhydride was added. The reaction was carried out at a stirring rate of 400rpm for 5h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the precipitate was collected by centrifugation at 8000rpm. The precipitate was washed twice with toluene and twice with acetone. The precipitate was then dried in a vacuum drying oven at 95℃ for 7h to obtain carboxyl-functionalized mesoporous silica.

[0062] Step 2: Add 25g of carboxyl-functionalized mesoporous silica to 180mL of deionized water, and disperse it ultrasonically at 450W for 25min. Adjust the pH of the system to 6.5 with 0.1mol / L sodium hydroxide, and slowly add 80mL of 0.8mol / L zinc nitrate aqueous solution. Stir and chelate for 3.5h at 45℃ and 280rpm. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm, and wash it repeatedly with deionized water to obtain zinc-chelated functionalized mesoporous silica.

[0063] 25g of zinc-chelated functionalized mesoporous silica was added to 140mL of deionized water and ultrasonically dispersed at 450W for 18min. Then, 8g of hexadecyltrimethylammonium bromide and 2g of dodecyldimethylbenzylammonium chloride were added, and the mixture was stirred at 55℃ and 320rpm for 6h for ion exchange reaction. After the reaction was completed, the precipitate was collected by centrifugation at 8000rpm and washed three times with deionized water to obtain the zinc-quaternary ammonium salt composite antibacterial precursor.

[0064] Step 3: Add 4.5g of adipic acid dihydrazide and 0.5g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to 20g of zinc-quaternary ammonium salt composite antibacterial precursor. Adjust the pH of the system to 8.5 with 0.1mol / L sodium hydroxide. Stir and crosslink the reaction at 75℃ and 420rpm for 2.5h. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm and dry it in a vacuum drying oven at 85℃ for 13h. Grind the dried product and pass it through a 350-mesh sieve to obtain the antibacterial carrier.

[0065] Step 4: Weigh 70g of polylactic acid and 30g of polycaprolactone, dry them in an 80℃ vacuum drying oven for 4 hours, then add them to a high-speed mixer, set the temperature to 175℃ and the speed to 550rpm, mix for 18 minutes and then discharge to obtain a uniform PLA / PCL blend matrix.

[0066] Weigh 8g of N-vinylcaprolactam, 5g of glycidyl methacrylate and 15mL of anhydrous ethanol and add them to a beaker. Place the beaker in a 35℃ constant temperature water bath and simultaneously turn on a 350W ultrasonic disperser to disperse for 12 minutes to completely dissolve the monomers and form a homogeneous antibacterial monomer mixture.

[0067] 120 parts by weight of PLA / PCL blend matrix were added to a twin-screw extruder. The extruder temperature was set to 165°C in zone 1, 175°C in zone 2, 185°C in zone 3, and 180°C at the die head, with a screw speed of 220 rpm. 10 parts by weight of antibacterial monomer mixture were continuously fed in via a side feeder, along with 0.52 parts by weight of benzoyl peroxide and 0.4 parts by weight of dodecyl mercaptan. After extrusion, the material was water-cooled and pelletized to obtain crude graft copolymer. The crude graft copolymer was added to 220 mL of deionized water, along with 2.4 parts by weight of ethanolamine. The mixture was stirred at 90°C and 320 rpm for 3.5 h to initiate a ring-opening reaction. After the reaction, the mixture was cooled to room temperature, filtered to collect the precipitate, washed three times with deionized water, and then dried in a 75°C vacuum drying oven for 11 h to obtain the plastic matrix resin.

[0068] Step 5: Weigh 20g of antibacterial carrier, add it to 50mL of anhydrous ethanol, then add 2g of 3-methacryloyloxypropyltrimethoxysilane. Set the temperature to 80℃ and the stirring speed to 300rpm, and react at a constant temperature for 1.5h. After the reaction is complete, centrifuge at 8000rpm to collect the precipitate, and place the precipitate in a vacuum drying oven at 85℃ for 5h to obtain the surface-modified antibacterial carrier.

[0069] Weigh out 100 parts by weight of plastic matrix resin, 13 parts by weight of surface-modified antibacterial carrier, 6.5 parts by weight of polyethylene glycol 400, 0.6 parts by weight of zinc stearate, 0.8 parts by weight of antioxidant 1010, and 0.4 parts by weight of UV absorber 531. Add all raw materials to a high-speed mixer, set the temperature to 120℃ and the speed to 650 rpm, mix for 25 minutes, and then discharge to obtain a homogeneous mixture. Place the mixture in an 85℃ vacuum drying oven for 6 hours, and then add it to a twin-screw extruder. Set the extruder temperature to 175℃ in zone 1, 185℃ in zone 2, 195℃ in zone 3, and 190℃ at the die head, with a screw speed of 280 rpm. After melting, mixing, extruding, and pelletizing, the material is obtained as antibacterial plastic lunch box material.

[0070] Example 4

[0071] A method for preparing an antibacterial plastic lunchbox material includes the following steps:

[0072] Step 1: Weigh 25g of mesoporous silica and place it in a muffle furnace. Set the temperature to 580℃ and calcine for 3.5 hours. After naturally cooling to room temperature, collect and set aside.

[0073] The calcined mesoporous silica was added to a mixed solution of 140 mL anhydrous ethanol and 25 mL deionized water and ultrasonically dispersed at 450 W and 48 kHz for 35 min. The pH of the system was adjusted to 4.0 with 0.8 mol / L hydrochloric acid, and then 1.5 g KH550 was added. The mixture was refluxed in a water bath at 75 °C and 350 rpm for 7 h. After the reaction was completed, the precipitate was collected by centrifugation at 8000 rpm, washed 4 times with anhydrous ethanol, and dried in a vacuum drying oven at 105 °C for 9 h to obtain amino-modified mesoporous silica.

[0074] 25g of amino-modified mesoporous silica was added to 120mL of toluene, and nitrogen gas was introduced (flow rate 50mL / min). The system was heated to 110℃ and 10g of maleic anhydride was added. The reaction was carried out at a stirring rate of 400rpm for 5h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the precipitate was collected by centrifugation at 8000rpm. The precipitate was washed twice with toluene and twice with acetone. The precipitate was then dried in a vacuum drying oven at 95℃ for 7h to obtain carboxyl-functionalized mesoporous silica.

[0075] Step 2: Add 25g of carboxyl-functionalized mesoporous silica to 180mL of deionized water, and disperse it ultrasonically at 450W for 25min. Adjust the pH of the system to 6.5 with 0.1mol / L sodium hydroxide, and slowly add 80mL of 0.8mol / L zinc nitrate aqueous solution. Stir and chelate for 3.5h at 45℃ and 280rpm. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm, and wash it repeatedly with deionized water to obtain zinc-chelated functionalized mesoporous silica.

[0076] 25g of zinc-chelated functionalized mesoporous silica was added to 140mL of deionized water and ultrasonically dispersed at 450W for 18min. Then, 8g of hexadecyltrimethylammonium bromide and 3g of dodecyldimethylbenzylammonium chloride were added, and the mixture was stirred at 55℃ and 320rpm for 6h for ion exchange reaction. After the reaction, the precipitate was collected by centrifugation at 8000rpm and washed three times with deionized water to obtain the zinc-quaternary ammonium salt composite antibacterial precursor.

[0077] Step 3: Add 6g of adipic acid dihydrazide and 0.5g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to 20g of zinc-quaternary ammonium salt composite antibacterial precursor. Adjust the pH of the system to 8.5 with 0.1mol / L sodium hydroxide. Stir and crosslink the reaction at 75℃ and 420rpm for 2.5h. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm and dry it in a vacuum drying oven at 85℃ for 13h. Grind the dried product and pass it through a 350-mesh sieve to obtain the antibacterial carrier.

[0078] Step 4: Weigh 70g of polylactic acid and 35g of polycaprolactone, dry them in an 80℃ vacuum drying oven for 4 hours, then add them to a high-speed mixer, set the temperature to 175℃ and the speed to 550rpm, mix for 18 minutes and then discharge to obtain a uniform PLA / PCL blend matrix.

[0079] Weigh 8g of N-vinylcaprolactam, 5g of glycidyl methacrylate and 15mL of anhydrous ethanol and add them to a beaker. Place the beaker in a 35℃ constant temperature water bath and simultaneously turn on a 350W ultrasonic disperser to disperse for 12 minutes to completely dissolve the monomers and form a homogeneous antibacterial monomer mixture.

[0080] 120 parts by weight of PLA / PCL blend matrix were added to a twin-screw extruder. The extruder temperature was set to 165°C in zone 1, 175°C in zone 2, 185°C in zone 3, and 180°C at the die head, with a screw speed of 220 rpm. 10 parts by weight of antibacterial monomer mixture were continuously fed in via a side feeder, along with 0.52 parts by weight of benzoyl peroxide and 0.4 parts by weight of dodecyl mercaptan. After extrusion, the material was water-cooled and pelletized to obtain crude graft copolymer. The crude graft copolymer was added to 220 mL of deionized water, along with 2.4 parts by weight of ethanolamine. The mixture was stirred at 90°C and 320 rpm for 3.5 h to initiate a ring-opening reaction. After the reaction, the mixture was cooled to room temperature, filtered to collect the precipitate, washed three times with deionized water, and then dried in a 75°C vacuum drying oven for 11 h to obtain the plastic matrix resin.

[0081] Step 5: Weigh 20g of antibacterial carrier, add it to 50mL of anhydrous ethanol, then add 3g of 3-methacryloyloxypropyltrimethoxysilane. Set the temperature to 80℃ and the stirring speed to 300rpm, and react at a constant temperature for 1.5h. After the reaction is complete, centrifuge at 8000rpm to collect the precipitate, and place the precipitate in a vacuum drying oven at 85℃ for 5h to obtain the surface-modified antibacterial carrier.

[0082] Weigh out 100 parts by weight of plastic matrix resin, 15 parts by weight of surface-modified antibacterial carrier, 6.5 parts by weight of polyethylene glycol 400, 0.6 parts by weight of zinc stearate, 0.8 parts by weight of antioxidant 1010, and 0.4 parts by weight of UV absorber 531. Add all raw materials to a high-speed mixer, set the temperature to 120℃ and the speed to 650 rpm, mix for 25 minutes, and then discharge to obtain a homogeneous mixture. Place the mixture in an 85℃ vacuum drying oven for 6 hours, and then add it to a twin-screw extruder. Set the extruder temperature to 175℃ in zone 1, 185℃ in zone 2, 195℃ in zone 3, and 190℃ at the die head, with a screw speed of 280 rpm. After melting, mixing, extruding, and pelletizing, the material is obtained as antibacterial plastic lunch box material.

[0083] Example 5

[0084] A method for preparing an antibacterial plastic lunchbox material includes the following steps:

[0085] Step 1: Weigh 25g of mesoporous silica and place it in a muffle furnace. Set the temperature to 580℃ and calcine for 3.5 hours. After naturally cooling to room temperature, collect and set aside.

[0086] The calcined mesoporous silica was added to a mixed solution of 140 mL anhydrous ethanol and 25 mL deionized water and ultrasonically dispersed at 450 W and 48 kHz for 35 min. The pH of the system was adjusted to 4.0 with 0.8 mol / L hydrochloric acid, and then 0.7 g KH550 was added. The mixture was refluxed in a water bath at 75 °C and 350 rpm for 7 h. After the reaction was completed, the precipitate was collected by centrifugation at 8000 rpm, washed four times with anhydrous ethanol, and dried in a vacuum drying oven at 105 °C for 9 h to obtain amino-modified mesoporous silica.

[0087] 25g of amino-modified mesoporous silica was added to 120mL of toluene, and nitrogen gas was introduced (flow rate 50mL / min). The system was heated to 110℃ and 6g of maleic anhydride was added. The reaction was carried out at a stirring rate of 400rpm for 5h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the precipitate was collected by centrifugation at 8000rpm. The precipitate was washed twice with toluene and twice with acetone. The precipitate was then dried in a vacuum drying oven at 95℃ for 7h to obtain carboxyl-functionalized mesoporous silica.

[0088] Step 2: Add 25g of carboxyl-functionalized mesoporous silica to 180mL of deionized water, and disperse it ultrasonically at 450W for 25min. Adjust the pH of the system to 6.5 with 0.1mol / L sodium hydroxide, and slowly add 80mL of 0.8mol / L zinc nitrate aqueous solution. Stir and chelate for 3.5h at 45℃ and 280rpm. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm, and wash it repeatedly with deionized water to obtain zinc-chelated functionalized mesoporous silica.

[0089] 25g of zinc-chelated functionalized mesoporous silica was added to 140mL of deionized water and ultrasonically dispersed at 450W for 18min. Then, 8g of hexadecyltrimethylammonium bromide and 1g of dodecyldimethylbenzylammonium chloride were added, and the mixture was stirred at 55℃ and 320rpm for 6h for ion exchange reaction. After the reaction, the precipitate was collected by centrifugation at 8000rpm and washed three times with deionized water to obtain the zinc-quaternary ammonium salt composite antibacterial precursor.

[0090] Step 3: Add 3g of adipic acid dihydrazide and 0.5g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to 20g of zinc-quaternary ammonium salt composite antibacterial precursor. Adjust the pH of the system to 8.5 with 0.1mol / L sodium hydroxide. Stir and crosslink the reaction at 75℃ and 420rpm for 2.5h. After the reaction is completed, collect the precipitate by centrifugation at 8000rpm and dry it in a vacuum drying oven at 85℃ for 13h. Grind the dried product and pass it through a 350-mesh sieve to obtain the antibacterial carrier.

[0091] Step 4: Weigh 70g of polylactic acid and 25g of polycaprolactone, dry them in an 80℃ vacuum drying oven for 4 hours, then add them to a high-speed mixer, set the temperature to 175℃ and the speed to 550rpm, mix for 18 minutes and then discharge to obtain a uniform PLA / PCL blend matrix.

[0092] Weigh 8g of N-vinylcaprolactam, 5g of glycidyl methacrylate and 15mL of anhydrous ethanol and add them to a beaker. Place the beaker in a 35℃ constant temperature water bath and simultaneously turn on a 350W ultrasonic disperser to disperse for 12 minutes to completely dissolve the monomers and form a homogeneous antibacterial monomer mixture.

[0093] 120 parts by weight of PLA / PCL blend matrix were added to a twin-screw extruder. The extruder temperature was set to 165°C in zone 1, 175°C in zone 2, 185°C in zone 3, and 180°C at the die head, with a screw speed of 220 rpm. 10 parts by weight of antibacterial monomer mixture were continuously fed in via a side feeder, along with 0.52 parts by weight of benzoyl peroxide and 0.4 parts by weight of dodecyl mercaptan. After extrusion, the material was water-cooled and pelletized to obtain crude graft copolymer. The crude graft copolymer was added to 220 mL of deionized water, along with 2.4 parts by weight of ethanolamine. The mixture was stirred at 90°C and 320 rpm for 3.5 h to initiate a ring-opening reaction. After the reaction, the mixture was cooled to room temperature, filtered to collect the precipitate, washed three times with deionized water, and then dried in a 75°C vacuum drying oven for 11 h to obtain the plastic matrix resin.

[0094] Step 5: Weigh 20g of antibacterial carrier, add it to 50mL of anhydrous ethanol, then add 1g of 3-methacryloyloxypropyltrimethoxysilane. Set the temperature to 80℃ and the stirring speed to 300rpm, and react at a constant temperature for 1.5h. After the reaction is completed, centrifuge at 8000rpm to collect the precipitate, and place the precipitate in a vacuum drying oven at 85℃ for 5h to obtain the surface-modified antibacterial carrier.

[0095] Weigh out 100 parts by weight of plastic matrix resin, 10 parts by weight of surface-modified antibacterial carrier, 6.5 parts by weight of polyethylene glycol 400, 0.6 parts by weight of zinc stearate, 0.8 parts by weight of antioxidant 1010, and 0.4 parts by weight of UV absorber 531. Add all raw materials to a high-speed mixer, set the temperature to 120℃ and the speed to 650 rpm, mix for 25 minutes, and then discharge to obtain a homogeneous mixture. Place the mixture in an 85℃ vacuum drying oven for 6 hours, and then add it to a twin-screw extruder. Set the extruder temperature to 175℃ in zone 1, 185℃ in zone 2, 195℃ in zone 3, and 190℃ at the die head, with a screw speed of 280 rpm. After melting, mixing, extruding, and pelletizing, the material is obtained as antibacterial plastic lunch box material.

[0096] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that steps 1-3 are omitted, and the surface-modified antibacterial carrier in step 5 is replaced with an equal mass of mesoporous silica.

[0097] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that step 4 is omitted and the plastic matrix resin in step 5 is replaced with an equal mass of polylactic acid.

[0098] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the antibacterial carrier in step 5 was not modified with 3-methacryloyloxypropyltrimethoxysilane.

[0099] Performance testing:

[0100] 1. Initial antibacterial performance test: Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 6538) were selected as test strains. The lunch box materials prepared in the examples and comparative examples were processed into samples of 50mm×50mm×2mm. After ultraviolet disinfection, 100μL of a 1×10⁻⁶ concentration was added. 6 CFU / mL bacterial suspension was uniformly inoculated onto the sample surface and incubated at 37℃ and 90% relative humidity for 24 h. After incubation, the sample surface was rinsed with sterile physiological saline, and the rinsing solution was collected for serial dilution. The number of colonies was counted using the plate count method, and the antibacterial rate was calculated as follows: Antibacterial rate (%) = (Number of colonies in blank control group - Number of colonies in sample group) / Number of colonies in blank control group × 100%. Each sample was tested in parallel for 5 times, and the average value was taken. The test results are shown in Table 1.

[0101] 2. Antibacterial durability test: The sample was placed in distilled water (40℃) and shaken at 100 rpm for 30 minutes as one water washing cycle. This was repeated 50 times. After that, the sample was removed and dried in a 60℃ oven for 2 hours. Then, following the "Initial Antibacterial Performance Test" method described above, the antibacterial rate of the washed sample against Escherichia coli and Staphylococcus aureus was determined to evaluate the antibacterial durability. The test results are shown in Table 1.

[0102] Table 1:

[0103]

[0104] 3. Mechanical property testing: The samples were processed into type 1A dumbbell-shaped specimens (4 mm thick) and pretreated for 24 hours in an environment of 23℃ and 50% relative humidity. Using an electronic universal testing machine, the tensile strength (maximum stress at fracture) and elongation at break (ratio of elongation at fracture to initial gauge length) were recorded. Five specimens were tested in each group, and the average value was taken. The test results are shown in Table 2.

[0105] 4. Biodegradability Test: The sample was crushed into particles with a diameter of less than 2 mm. 5 g of the sample was weighed and mixed with 100 g of compost inoculum (taken from the composting workshop of a municipal wastewater treatment plant). The mixture was placed in a composting container, and the composting temperature was controlled at 58℃ and the humidity at 55%. The released carbon dioxide was collected periodically, and its content was detected using an infrared gas analyzer. The biodegradation rate after 6 months was calculated as follows: Biodegradation rate (%) = Actual carbon dioxide released by the sample / Theoretical maximum carbon dioxide released × 100%. The test results are shown in Table 2.

[0106] Table 2:

[0107]

[0108] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an antibacterial plastic lunchbox material, characterized in that, Includes the following steps: S1. Mesoporous silica is pretreated by calcination, then mixed with anhydrous ethanol and deionized water, and then 3-aminopropyltriethoxysilane is added to react and obtain amino-modified mesoporous silica. The amino-modified mesoporous silica is mixed with toluene and maleic anhydride is added in a nitrogen atmosphere to react and obtain carboxyl-functionalized mesoporous silica. S2. Mix carboxyl-functionalized mesoporous silica with deionized water, then add zinc nitrate aqueous solution to carry out a chelation reaction to obtain zinc chelated functionalized mesoporous silica. Mix zinc chelated functionalized mesoporous silica with deionized water, then add hexadecyltrimethylammonium bromide and dodecyldimethylbenzylammonium chloride to carry out an ion exchange reaction to obtain a composite antibacterial precursor. S3. Add adipate dihydrazide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to the composite antibacterial precursor to carry out a cross-linking reaction and obtain the antibacterial carrier. S4. Polylactic acid and polycaprolactone are blended to obtain a blend matrix; N-vinylcaprolactam, glycidyl methacrylate and anhydrous ethanol are mixed to obtain an antibacterial monomer mixture; the blend matrix, antibacterial monomer mixture, benzoyl peroxide and dodecyl mercaptan are extruded to obtain a crude graft copolymer; the crude graft copolymer is subjected to a ring-opening reaction with ethanolamine to obtain a plastic matrix resin. S5. The antibacterial carrier is modified by surface modification with 3-methacryloyloxypropyltrimethoxysilane. The antibacterial plastic lunch box material is obtained by mixing a plastic matrix resin, a surface-modified antibacterial carrier, polyethylene glycol 400, zinc stearate, antioxidants, and ultraviolet absorbers, followed by melt extrusion and injection molding.

2. The method for preparing an antibacterial plastic lunchbox material according to claim 1, characterized in that, In step S1, the mass ratio of mesoporous silica to 3-aminopropyltriethoxysilane is 25:(0.7-1.5).

3. The method for preparing an antibacterial plastic lunchbox material according to claim 1, characterized in that, In step S1, the mass ratio of amino-modified mesoporous silica to maleic anhydride is 25:(6-10).

4. The method for preparing an antibacterial plastic lunchbox material according to claim 1, characterized in that, In step S2, the mass ratio of hexadecyltrimethylammonium bromide to dodecyldimethylbenzylammonium chloride is 8:(1-3).

5. The method for preparing an antibacterial plastic lunchbox material according to claim 1, characterized in that, In step S3, the mass ratio of the composite antibacterial precursor to adipic acid dihydrazide is 20:(3-6).

6. The method for preparing an antibacterial plastic lunchbox material according to claim 1, characterized in that, In step S4, the mass ratio of polylactic acid to polycaprolactone is 70:(25-35).

7. The method for preparing an antibacterial plastic lunchbox material according to claim 1, characterized in that, The mass ratio of the antibacterial carrier to 3-methacryloyloxypropyltrimethoxysilane is 20:(1-3).

8. The method for preparing an antibacterial plastic lunchbox material according to claim 1, characterized in that, The mass ratio of the plastic matrix resin to the surface-modified antibacterial carrier is 100:(10-15).

9. An antibacterial plastic lunchbox material, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

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