An antibacterial aluminum foil packaging box for food and a method for manufacturing the same

Abstract

This application relates to the field of food packaging technology, specifically to an antibacterial aluminum foil packaging box for food and its preparation method. The packaging box includes an outer support box and an inner liner box disposed inside it, the two being fixedly connected at the opening edge. The inner liner box is formed by stamping an antibacterial aluminum foil composite sheet. The composite sheet, from the outside to the inside, includes an outer protective layer, an aluminum foil substrate, a coordination transition layer, and an antibacterial heat-sealing layer. The antibacterial heat-sealing layer is formed by segmented drying of a coating liquid containing ethylene-acrylic acid copolymer, polylactic acid, chitosan lactate, nisin, glyceryl monolaurate, choline ferulic acid, and a crosslinking aid. The packaging box obtained by this application has stable interfacial bonding, good stamping adaptability, long-lasting antibacterial properties, and excellent oil and acid resistance, making it suitable for food packaging.

Description

Technical Field

[0001] This application relates to the field of food packaging technology, specifically to an antibacterial aluminum foil packaging box for food and its preparation method. Background Technology

[0002] Aluminum foil packaging boxes are widely used in airline meal boxes, takeaway cooked food boxes, pre-cooked food boxes, baking food boxes, and cold chain food packaging due to their advantages such as good barrier properties, wide range of high and low temperature resistance, stamping and molding capabilities, and easy recycling. With the rapid development of the ready-to-eat food, takeaway delivery, and pre-cooked food industries, food is more susceptible to microbial contamination and spoilage during packaging, transportation, short-term heating, and storage before and after opening. Therefore, food packaging not only needs to meet basic barrier, protection, and molding requirements, but also needs to consider food contact safety, antibacterial preservation, oil and acid resistance, and processing compatibility.

[0003] From a technological development perspective, food-grade aluminum foil packaging boxes have generally gone through stages such as single-layer aluminum foil stamped boxes, surface-coated aluminum foil boxes, and aluminum foil and plastic composite heat-sealing boxes. Early products primarily relied on the barrier properties and formability of the aluminum foil itself to meet usage requirements. However, these products were prone to problems in practical applications, including insufficient box stiffness, easy deformation after stamping, and limited folding resistance and corrosion resistance. To improve these shortcomings, existing technologies typically involve applying a coating to the aluminum foil surface or using composite materials to enhance heat-sealing performance, oil resistance, and appearance quality.

[0004] For example, patent application CN114011877A discloses a manufacturing process for aluminum foil lunch boxes. This process involves steps such as smelting, casting, annealing, cold rolling, foil rolling, and coating the aluminum foil surface with antibacterial and protective agents, attempting to simultaneously address the issues of insufficient strength and weak antibacterial ability in aluminum foil lunch boxes. This solution imparts antibacterial properties to the lunch box by coating the aluminum foil surface with silver ion antibacterial agents and protective agents. However, the antibacterial layer is mainly formed on the surface of the metallic aluminum foil, lacking an effective interface transition between the aluminum foil and the organic coating. After stamping, micro-cracks or poor adhesion of the coating easily occur at corners, the stretching area at the bottom of the box, and other areas. Furthermore, silver ion antibacterial agents raise concerns about migration and dispersion stability in food contact environments, making it difficult to simultaneously achieve antibacterial durability, heat-sealing properties, and oil and acid resistance.

[0005] Furthermore, patent application CN121470022A discloses an antibacterial food composite bag and its preparation method. It employs a three-layer structure: a PET outer layer, an aluminum foil middle layer, and an antibacterial PE inner layer. The antibacterial inner layer is constructed by using modified halloysite loaded with oregano essential oil as an antibacterial agent, a silver-carbon dot composite antibacterial agent, and a compatibilizer to improve the antibacterial spectrum and duration. While this solution enhances the antibacterial and barrier properties of the composite packaging by incorporating an antibacterial polyethylene inner layer, it primarily targets flexible composite bag structures. The antibacterial layer relies on polyethylene blown film and interlayer lamination, neglecting the deep-drawing, folding, and bottom stretching processes required for aluminum foil food boxes. Therefore, it struggles to address issues such as easy cracking of the food contact layer after stamping, insufficient interfacial bonding, inadequate heat-sealing stability at the rim, and insufficient oil and acid resistance continuity in aluminum foil packaging boxes.

[0006] Existing antibacterial aluminum foil packaging technologies for food generally suffer from the following problems: First, the interfacial bonding between the aluminum foil substrate and the functional coating is insufficient, and the coating is prone to cracking, peeling, or local failure during stamping, bending, and heat sealing. Second, if inorganic silver-based or copper-based materials are used for antibacterial components, they may face problems such as uneven dispersion, migration risk, and insufficient food contact stability. Third, if natural antibacterial components such as chitosan, nisin, and essential oils are used, they are prone to defects such as poor compatibility with heat-sealing resins, rapid loss of activity during drying and processing, and significant initial release followed by significant decline. Fourth, simply pursuing antibacterial performance often sacrifices the heat-sealing properties, oil and acid resistance, and stamping formability of the aluminum foil box, making it difficult to form a comprehensive solution suitable for industrial mass production.

[0007] Therefore, there is an urgent need for a new type of antibacterial aluminum foil packaging box for food to solve the problems existing in the current technology, such as poor interfacial bonding, easy migration of antibacterial components, easy deactivation of heat-sensitive antibacterial components, easy cracking of coating after stamping, and difficulty in achieving comprehensive performance. Summary of the Invention

[0008] This application aims to overcome at least one of the defects of the prior art and provide an antibacterial aluminum foil packaging box for food and its preparation method. By setting a coordination transition layer on the surface of the aluminum foil substrate and further constructing an antibacterial heat-sealing layer, and at the same time combining the outer support box body and the inner liner box body, the packaging box has better interface bonding stability, antibacterial durability and molding and processing adaptability.

[0009] In a first aspect, embodiments of this application provide an antibacterial aluminum foil packaging box for food, achieved through the following technical solution: An antibacterial aluminum foil packaging box for food includes an outer support box and an inner liner box disposed inside the outer support box, wherein the outer support box and the inner liner box are fixedly connected at the opening edge area. The inner liner box is formed by stamping antibacterial aluminum foil composite sheet, which includes an outer protective layer, an aluminum foil substrate, a coordination transition layer and an antibacterial heat-sealing layer from the outside to the inside. The preparation of the antibacterial heat-sealing layer includes the following steps: applying an antibacterial heat-sealing coating liquid onto the surface of the coordination transition layer, and drying it in stages to form the antibacterial heat-sealing layer; The raw materials for preparing the antibacterial heat-sealing coating liquid, by solid weight, include: 55-78 parts of ethylene-acrylic acid copolymer, 8-22 parts of polylactic acid, 2-8 parts of chitosan lactate, 0.3-2.5 parts of nisin, 1-6 parts of glyceryl monolaurate, 0.5-5 parts of choline ferulic acid, and 0.2-2 parts of crosslinking aid.

[0010] The antibacterial aluminum foil packaging box for food according to the embodiments of this application has at least the following beneficial effects: This application combines an outer support box and an inner liner box, allowing the load-bearing support function and food contact function of the packaging box to be configured relatively independently. The outer support box provides overall rigidity, compressive strength, and aesthetic support, while the inner liner box provides food contact barrier, antibacterial properties, and temperature resistance. This ensures the box is lightweight while improving stability during transportation, resistance to deformation, and protective performance in actual use. It is suitable for scenarios with high requirements for comprehensive packaging performance, such as takeaway cooked food, pre-prepared dishes, and baked goods.

[0011] The inner liner of this application is made of antibacterial aluminum foil composite sheet through stamping, which can balance the barrier properties, heat resistance, and molding adaptability of aluminum foil material. Compared with packaging structures that rely solely on the aluminum foil itself, this solution improves the applicability of the food contact surface under heating, refrigeration, and short-term storage and transportation conditions without significantly increasing the material thickness. At the same time, it reduces box deformation, wrinkles, or springback problems caused by insufficient rigidity of single-layer aluminum foil, which is conducive to improving the stability and consistency of industrial box manufacturing.

[0012] This application incorporates a coordination transition layer between the aluminum foil substrate and the antibacterial heat-sealing layer. This provides a better bonding foundation between the coating system and the aluminum foil surface, thereby improving the continuity and integrity of the edges, folds, and stretched areas during subsequent stamping processes, and reducing the risk of coating cracking, peeling, or localized failure. Simultaneously, this transition layer enhances the aluminum foil substrate's resistance to acidic or highly saline food environments, reducing corrosion and performance degradation caused by contact with the medium during use.

[0013] The antibacterial heat-sealing layer of this application is formed by compounding ethylene-acrylic acid copolymer, polylactic acid, chitosan lactate, nisin, glyceryl monolaurate, choline ferulic acid, and crosslinking aids, which can provide continuous antibacterial effect while meeting the requirements of heat-sealing processing. Among them, ethylene-acrylic acid copolymer and polylactic acid are beneficial to improving the film-forming properties, oil resistance, and heat-sealing compatibility of the coating, while chitosan lactate, nisin, and glyceryl monolaurate together enhance the inhibitory effect on common food spoilage microorganisms, thereby improving the freshness preservation ability of the packaging box during storage and distribution.

[0014] This application introduces choline ferulic acid salt as a synergistic component, which helps improve the dispersion stability of the antibacterial heat-sealing coating solution in an aqueous system and provides a certain degree of sustained release for chitosan lactate and nisin, thereby improving the persistence of the antibacterial effect. Combined with a segmented drying process, it can reduce the loss of heat-sensitive components during processing, reduce coating surface adhesion and performance fluctuations, and enable the packaging box to possess good processing adaptability, durable antibacterial properties, and food contact safety.

[0015] According to some embodiments of this application, the choline ferulic acid salt is prepared by reacting choline bicarbonate or choline hydroxide with ferulic acid in water and / or ethanol, wherein the molar ratio of choline bicarbonate or choline hydroxide to ferulic acid, calculated as choline, is 0.95 to 1.1:1, the reaction temperature is 45 to 60°C, and the solvent is removed after the system pH reaches 6.2 to 7.4.

[0016] This method can complete the salt formation under milder conditions, reducing the degradation and side reactions of ferulic acid caused by high temperature or strong alkali, reducing the generation of impurities and improving the purity of the product; the resulting choline ferulic acid salt is easy to disperse in the aqueous coating system, which is beneficial to improving the stability and processing adaptability of the antibacterial heat-sealing coating, while enhancing the antioxidant and antibacterial synergistic effects of the ferulic acid component.

[0017] According to some embodiments of this application, the antibacterial heat-sealing coating liquid further contains 0.1 to 1.5 parts by weight of silica or montmorillonite. Silica or montmorillonite can be dispersed as an inorganic regulating component in the antibacterial heat-sealing coating, which can improve the surface smoothness and anti-blocking properties of the coating, reduce the risk of coating stickiness, roughening, and local accumulation during winding, stacking, and stamping, and at the same time help improve the heat resistance, oil resistance, and processing stability of the coating, thereby enhancing the overall performance of the packaging box during subsequent molding and use.

[0018] According to some embodiments of this application, the crosslinking aid is at least one of polycarbodiimide, aziridine crosslinking agent, or food contact epoxysilane.

[0019] Crosslinking aids can crosslink or couple with active groups such as carboxyl, hydroxyl, or amino groups in the antibacterial heat-sealing layer, improving the cohesive strength of the coating and the bonding stability with the coordination transition layer, reducing cracking, sticking, or delamination during stamping, folding, and heat sealing. At the same time, they can improve the water resistance, oil resistance, and acid resistance of the antibacterial heat-sealing layer, reduce the excessive migration of antibacterial components during food contact, and enable the coating to maintain relatively stable antibacterial and heat-sealing properties under storage, transportation, heating, and sealing conditions.

[0020] According to some embodiments of this application, the coating amount of the antibacterial heat-sealing coating liquid is 2-8 g / m² on a dry basis. 2 .

[0021] This coating amount ensures the formation of a continuous antibacterial heat-sealing layer on the food contact surface, while avoiding insufficient antibacterial component load, unstable heat-sealing strength, and local aluminum exposure due to an excessively thin coating. It also avoids accumulation, cracking, sticking to the mold, or blistering during stamping due to an excessively thick coating, thus balancing antibacterial durability, heat-sealing reliability, and adaptability to aluminum foil box forming and processing.

[0022] According to some embodiments of this application, the preparation method of the antibacterial heat-sealing coating liquid includes: preparing an aqueous dispersion of ethylene-acrylic acid copolymer, adding polylactic acid emulsion, chitosan lactate aqueous solution, glyceryl monolaurate emulsion and choline ferulic acid solution, stirring evenly at 25-45°C, then adding nisin and crosslinking aid, adjusting the pH to 5.8-6.8 to obtain the antibacterial heat-sealing coating liquid.

[0023] This scheme first constructs an ethylene-acrylic acid copolymer aqueous dispersion system, then sequentially introduces polylactic acid, chitosan lactate, glyceryl monolaurate, and choline ferulic acid, and adds nisin and crosslinking aids at a lower temperature. This improves the dispersion uniformity and system stability of each component, and avoids the heat-sensitive antibacterial components from being deactivated by heat during preparation. At the same time, adjusting the pH to 5.8–6.8 helps to balance the solubility stability of chitosan lactate and the activity retention of nisin, and improves the film-forming properties, heat-sealing properties of the coating solution, and the water and oil resistance of the subsequent coating, thereby enhancing the persistence of the antibacterial effect and the processing adaptability.

[0024] According to some embodiments of this application, the segmented drying in the preparation of the antibacterial heat seal layer involves first drying at 55–75°C for 20–90 seconds, and then drying at 85–115°C for 10–60 seconds.

[0025] The segmented drying method, which involves first drying at low temperatures and then at high temperatures, allows moisture and low-boiling-point components in the coating to escape slowly. This avoids rapid surface film formation, residual solvents inside, and blistering, pinholes, and cracking caused by one-time high-temperature drying. Subsequently, curing is completed at a higher temperature, improving the density, adhesion, and heat-sealing stability of the antibacterial heat-sealing layer. At the same time, this process helps reduce the deactivation of heat-sensitive antibacterial components such as nisin during processing, maintaining the antibacterial activity and long-term performance of the coating.

[0026] According to some embodiments of this application, the preparation of the coordination transition layer includes the following steps: coating a zinc phytate treatment solution onto one side of an aluminum foil substrate and drying it to form a coordination transition layer.

[0027] By coating the aluminum foil substrate with zinc phytate solution and drying it to form a coordination transition layer, the polyphosphate groups and zinc ions in phytic acid can coordinate or complex with the active sites on the aluminum foil surface, thereby improving the adhesion stability between the subsequent antibacterial heat-sealing layer and the aluminum foil substrate, and reducing coating cracking, peeling or aluminum exposure during stamping, bending and heat sealing. At the same time, this coordination transition layer can improve the corrosion resistance and coating uniformity of the aluminum foil surface, which is beneficial to improving the reliability of the packaging box in acidic and salty food contact environments.

[0028] Furthermore, the drying temperature in the preparation of the coordination transition layer is 70–130°C, and the drying time is 8–60 seconds. This method can complete the dehydration and film formation of the zinc phytate treatment solution in a short time, allowing the coordination transition layer to quickly solidify and stably adhere to the aluminum foil surface. This avoids weak interlayer bonding due to insufficient drying or coating embrittlement, crystallization, and thermal damage to the aluminum foil due to prolonged high temperature, thereby improving the folding resistance, adhesion stability, and corrosion resistance during subsequent stamping.

[0029] Furthermore, the zinc phytate treatment solution comprises phytic acid, zinc salt, film-forming regulator and water, wherein the concentration of phytic acid in the zinc phytate treatment solution is 0.3-3 g / L, the concentration of zinc salt (calculated as zinc ion concentration) is 0.05-1.2 g / L, and the concentration of film-forming regulator is 0.5-5 g / L.

[0030] In the zinc phytate treatment solution, phytic acid and zinc ions can form a stable coordination bond layer on the aluminum foil surface, enhancing the adhesion between the aluminum foil substrate and the subsequent antibacterial heat-sealing layer. The film-forming regulator helps improve the spreadability and film continuity of the treatment solution, reducing pinholes, shrinkage cavities, and localized crystallization defects. By limiting the concentration ranges of phytic acid, zinc ions, and the film-forming regulator, the coating interface stability, resistance to damp heat, and resistance to acid corrosion can be improved without affecting the stamping formability of the aluminum foil.

[0031] Furthermore, the zinc salt is at least one of zinc acetate, zinc lactate, and zinc gluconate. This approach improves the compatibility of phytic acid with zinc ions and the stability of the treatment solution, making it easier to form a uniform and continuous coating in the coordination transition layer. Simultaneously, the zinc salt has good solubility, facilitating control of the treatment solution composition and coating uniformity, thereby improving the bonding strength between the aluminum foil substrate and subsequent functional layers, and contributing to improved corrosion resistance and coating integrity after stamping.

[0032] Furthermore, the film-forming regulator is at least one of polyvinyl alcohol, hydroxypropyl methylcellulose, or aqueous polyurethane. This solution can improve the film-forming uniformity and coating stability of the zinc phytate treatment solution, reduce the occurrence of salt crystallization, pinholes, and localized cracking during the drying process, and enable the coordination transition layer to form a continuous and dense thin layer, thereby enhancing its adhesion to the aluminum foil substrate and subsequent coatings, and further improving the corrosion resistance and stamping adaptability of the packaging box.

[0033] Furthermore, the pH of the zinc phytate treatment solution is 3.0–5.2. This approach helps maintain a stable coordination state between phytic acid and zinc ions, avoiding excessively high pH levels that could lead to zinc salt hydrolysis and precipitation, or excessively low pH levels that could result in insufficient coordination. This improves the storage stability and coating uniformity of the treatment solution. Simultaneously, it allows the solution to form a continuous and dense coordination transition layer on the aluminum foil surface, enhancing the adhesion to subsequent coatings and improving the corrosion resistance of the aluminum foil substrate.

[0034] Furthermore, the coating amount of the zinc phytate treatment solution is 15–120 mg / m³ on a dry basis. 2 This coating amount can form a continuous and stable coordination transition layer on the aluminum foil surface, while avoiding excessive coating thickness that could lead to brittleness, uneven adhesion, or affect subsequent stamping and forming. At the same time, it is beneficial to improve the interfacial bonding strength, corrosion resistance, and film formation consistency of the antibacterial heat-sealing layer, thus taking into account both processing adaptability and service stability.

[0035] According to some embodiments of this application, the fixed connection method includes at least one of folding and covering, hot pressing and bonding, edge curling and clamping, snap-fitting, or adhesive fixing. This can be flexibly selected according to different box types and production processes, enabling a stable connection between the inner liner box and the outer support box in the opening area. This facilitates assembly and mass production, while also improving the structural strength, sealing stability, and resistance to loosening during use at the opening, thereby enhancing the overall forming quality and reliability of the packaging box.

[0036] According to some embodiments of this application, the outer protective layer is one of a polyester coating, an acrylic coating, or a polyurethane coating; the coating weight of the outer protective layer is 0.6–3.5 g / m² on a dry basis. 2 .

[0037] The outer protective layer is made of polyester, acrylic, or polyurethane coating, and the coating amount is controlled between 0.6 and 3.5 g / m². 2 Within this range, a continuous protective film can be formed on the outer surface of the aluminum foil, improving the wear resistance, scratch resistance, moisture and heat resistance, and pollution resistance of the outer side of the packaging box. This reduces the impact of oxidation, scratches, or dirt on the aluminum foil surface during stamping, stacking, transportation, and use on the appearance and protective performance. At the same time, this coating amount range can ensure that the outer protective layer has sufficient coverage and adhesion stability, while avoiding excessive coating thickness that could lead to stamping cracks, increased springback, or increased material costs. This is beneficial for maintaining the forming adaptability, appearance stability, and industrial continuous processing performance of the aluminum foil composite sheet.

[0038] According to some embodiments of this application, the outer support box is one of a paper-based support box, a biodegradable plastic support box, or a paper-plastic composite support box. It can be flexibly selected according to different application scenarios, providing necessary external support and protection for the inner liner box, facilitating compatibility with environmental recycling systems, reducing overall packaging material costs, and enhancing the carbon reduction properties and market applicability of the packaging box.

[0039] According to some embodiments of this application, the aluminum foil substrate is one of 8011 aluminum foil, 3003 aluminum foil, or 8079 aluminum foil. This solution can balance the material's ductility, stamping formability, and barrier properties; among them, 8011 aluminum foil and 8079 aluminum foil are beneficial for improving the adaptability of the box body to deep drawing and the surface integrity after forming, while 3003 aluminum foil is beneficial for improving the box body's stiffness and dimensional stability, thereby enabling the inner liner box body to meet food contact requirements while having good box-making processability and reliability in use.

[0040] According to some embodiments of this application, the thickness of the aluminum foil substrate is 35–120 μm. This thickness ensures that the aluminum foil composite sheet has good barrier properties, heat resistance, and formability, while also taking into account the requirements for box stamping depth, edge stability, and overall stiffness. Too thin a thickness can easily lead to tearing, exposed aluminum, and insufficient puncture resistance, while too thick a thickness is detrimental to deep drawing and increases material costs. Limiting the thickness to this range helps to achieve a balance between processing adaptability and performance.

[0041] Secondly, the embodiments of this application provide a method for preparing the above-mentioned antibacterial aluminum foil packaging box for food, which is achieved through the following technical solution: A method for preparing an antibacterial aluminum foil packaging box for food includes the following steps: S1. Degrease, clean and surface activate the aluminum foil substrate; form a coordination transition layer on one side of the aluminum foil substrate, form an antibacterial heat-sealing layer on the surface of the coordination transition layer; form an outer protective layer on the other side of the aluminum foil substrate to obtain an antibacterial aluminum foil composite sheet; S2. The antibacterial aluminum foil composite sheet is stamped into an inner liner box, and then the inner liner box is combined and fixed with the outer support box to obtain an antibacterial aluminum foil packaging box for food.

[0042] The method for preparing antibacterial aluminum foil packaging boxes for food according to the embodiments of this application has at least the following beneficial effects: This preparation method first degreases, cleans, and surface-activates the aluminum foil substrate to remove surface oil and impurities, improving the wettability and adhesion of subsequent coatings and providing a foundation for the stable formation of each functional layer. A coordination transition layer is first formed on one side of the aluminum foil substrate, followed by an antibacterial heat-sealing layer. This enhances the interfacial bonding between the coating and the aluminum foil, reducing the risk of cracking, delamination, or exposed aluminum during subsequent stamping, folding, and heat sealing, while also improving the corrosion resistance after molding. An outer protective layer is formed on the other side of the aluminum foil substrate, enhancing the abrasion resistance, stain resistance, and printability of the composite sheet's outer surface. This reduces surface scratches, adhesion, or performance degradation during transportation and use, improving the overall stability of the packaging box. The antibacterial aluminum foil composite sheet is stamped into an inner liner box, which is then combined and fixed with the outer support box. This allows the antibacterial barrier function of the inner liner layer to work synergistically with the support function of the outer layer, ensuring both the box's molding precision and strength, while also improving the overall performance of the packaging box during filling, transportation, and storage.

[0043] According to some embodiments of this application, the fillet radius of the die used for stamping in step S2 is 1–4 mm, and the stamping depth is 15–65 mm. This design allows the antibacterial aluminum foil composite sheet to be subjected to more uniform stress during stretching and bending, reducing coating cracking, wrinkling, and aluminum exposure in the fillet, sidewall, and bottom transition areas. Simultaneously, it ensures the box body has good forming depth, volumetric stability, and edge flatness, which is beneficial for subsequent assembly and fixation with the outer support box body and heat sealing of the cover film.

[0044] In this article, the numerical ranges mentioned all include the endpoint values ​​and cover any subranges within that range, such as the ranges obtained by arbitrarily combining the specifically listed numerical values.

[0045] Unless otherwise specified, the weight parts of raw materials mentioned herein shall be understood as the weight ratio between the raw materials. For example, 55 to 78 parts of ethylene-acrylic acid copolymer indicates the relative amount of ethylene-acrylic acid copolymer in the raw materials for preparing the antibacterial heat-sealing coating liquid. Based on 8 to 22 parts of polylactic acid, it can be understood that the weight ratio of ethylene-acrylic acid copolymer to polylactic acid is 55 to 78: 8 to 22. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a comparison chart showing the minimum antibacterial rate and heat seal strength of the rounded corner areas of the antibacterial aluminum foil packaging boxes for food prepared in Examples 1-4 and Comparative Examples 1-4 of this application; Figure 2 This is a comparison chart showing the Escherichia coli and Staphylococcus aureus antibacterial rates of the antibacterial aluminum foil packaging boxes for food prepared in Examples 1-4 and Comparative Examples 1-4 of this application. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this application clearer, a further detailed description will be provided below in conjunction with specific embodiments. The embodiments described herein are merely some examples of this application and should not be construed as limiting the scope of protection of this application. Unless otherwise specified, the raw materials used in the embodiments are all commercially available, and the equipment and testing methods used are conventional equipment and methods in the art.

[0049] Example 1 Preparation of antibacterial aluminum foil packaging boxes for food: (1) 70μm thick 8011 aluminum foil is selected as aluminum foil substrate, and the aluminum foil substrate is subjected to alkaline degreasing, water washing, deionized water washing and corona treatment. (2) Coat the side of the aluminum foil substrate closest to the food with a zinc phytate treatment solution, with a coating amount of 55 mg / m² on a dry basis. 2 The composition of the zinc phytate treatment solution is: 1.5 g / L phytic acid, 0.6 g / L zinc acetate (calculated as zinc ions), and 3 g / L polyvinyl alcohol. The pH of the zinc phytate treatment solution is 4.1. It is dried at 100℃ for 40 seconds to form a coordination transition layer. (3) Apply an antibacterial heat-sealing coating liquid to the surface of the coordination transition layer. The coating amount is 5 g / m² on a dry basis. 2 First, dry at 65℃ for 55 seconds, then dry at 100℃ for 40 seconds to form an antibacterial heat-sealing layer; The preparation method of the antibacterial heat-sealing coating liquid is as follows: 67 parts by weight of ethylene-acrylic acid copolymer are prepared into an ethylene-acrylic acid copolymer aqueous dispersion with a solid content of 30%. A polylactic acid emulsion with a solid content of 20% prepared from 15 parts of polylactic acid and a chitosan lactate aqueous solution with a mass fraction of 10% prepared from 5 parts of chitosan lactate are added and mixed. The mixture is stirred at 35°C for 20 min. A monolaurate emulsion with a solid content of 10% prepared from 3 parts of monolaurate and a choline ferulic acid solution with a solid content of 40% prepared from 3 parts of choline ferulic acid are added and the mixture is stirred for another 15 min. Then, 1.5 parts of nisin, a silica dispersion with a solid content of 20% prepared from 0.5 parts of silica and 1 part of polycarbodiimide are added and the pH is adjusted to 6.3 to obtain the antibacterial heat-sealing coating liquid. Preparation of choline ferulic acid salt: 10 kg of ferulic acid was added to 60 kg of 50% ethanol aqueous solution, and the mixture was heated to 55 °C and stirred to disperse. According to the molar ratio of choline to ferulic acid of 1.05:1, 45% choline bicarbonate aqueous solution was slowly added, and the addition rate was controlled to keep the system temperature at 55 °C. After the ferulic acid was completely dissolved, the mixture was stirred for 1 hour until the pH reached 6.8. Ethanol and some water were removed under reduced pressure to obtain an aqueous solution of choline ferulic acid salt with a solid content of 40%. (4) Coat the aluminum foil substrate on the side away from the food with a dry basis of 1.8 g / m 2 A polyester coating is applied to form an outer protective layer, resulting in an antibacterial aluminum foil composite sheet. The polyester coating is prepared using VYLON 200 polyester resin from Toyobo Co., Ltd. as the main film-forming substance, combined with isocyanate crosslinking agents, leveling agents, defoamers, and a mixed organic solvent of ethyl acetate-butanone. (5) After the antibacterial aluminum foil composite sheet is cured for 24 hours, it is stamped into an inner liner box with a stamping depth of 40 mm and a mold corner radius of 2 mm. The outer support box is made of PE coated white cardboard. The edge of the inner liner box is folded over and hot-pressed to be fixed to the upper edge of the outer support box, thus obtaining a food antibacterial aluminum foil packaging box.

[0050] Example 2 Preparation of antibacterial aluminum foil packaging boxes for food: (1) 3003 aluminum foil with a thickness of 120μm was selected as the aluminum foil substrate, and the aluminum foil substrate was subjected to alkaline degreasing, water washing, deionized water washing and corona treatment. (2) Apply zinc phytate treatment solution to the side of the aluminum foil substrate closest to the food, with a coating amount of 15 mg / m² on a dry basis. 2 The composition of the zinc phytate treatment solution is: 3 g / L phytic acid, 0.05 g / L zinc lactate (calculated as zinc ions), and 5 g / L hydroxypropyl methylcellulose. The pH of the zinc phytate treatment solution is 3.0. It is dried at 130℃ for 8 seconds to form a coordination transition layer. (3) Apply an antibacterial heat-sealing coating liquid to the surface of the coordination transition layer. The coating amount is 8 g / m² on a dry basis. 2 First, dry at 55℃ for 90 seconds, then dry at 85℃ for 60 seconds to form an antibacterial heat-sealing layer; The preparation method of the antibacterial heat-sealing coating liquid is as follows: 55 parts of ethylene-acrylic acid copolymer are prepared into an ethylene-acrylic acid copolymer aqueous dispersion with a solid content of 30% by weight. A polylactic acid emulsion with a solid content of 20% prepared from 22 parts of polylactic acid and a chitosan lactate aqueous solution with a mass fraction of 10% prepared from 2 parts of chitosan lactate are added and mixed. The mixture is stirred at 45°C for 20 min. A monolaurate emulsion with a solid content of 10% prepared from 1 part of monolaurate and a choline ferulic acid solution with a solid content of 40% prepared from 5 parts of choline ferulic acid are added and the mixture is stirred for another 15 min. Then, 0.3 parts of nisin, a montmorillonite dispersion with a solid content of 20% prepared from 1.5 parts of montmorillonite and 0.2 parts of aziridine crosslinking agent are added and the pH is adjusted to 6.8 to obtain the antibacterial heat-sealing coating liquid. Preparation of choline ferulic acid salt: 10 kg of ferulic acid was added to 60 kg of 50% ethanol aqueous solution, and the mixture was heated to 45°C and stirred to disperse. According to the molar ratio of choline to ferulic acid of 1.1:1, 45% choline hydroxide aqueous solution was slowly added, and the addition rate was controlled to keep the system temperature at 45°C. After the ferulic acid was completely dissolved, the mixture was stirred for 1 hour until the pH reached 7.4. The ethanol and some water were removed under reduced pressure to obtain an aqueous solution of choline ferulic acid salt with a solid content of 40%. (4) Coat the aluminum foil substrate on the side away from the food with a dry basis of 0.6 g / m 2 An acrylic coating is applied to form an outer protective layer, resulting in an antibacterial aluminum foil composite sheet. The acrylic coating is prepared using Joncryl 678 acrylic resin produced by BASF as the main film-forming substance, combined with an amino resin crosslinking agent, leveling agent, defoamer, and deionized water-isopropanol mixed dispersion medium. (5) After the antibacterial aluminum foil composite sheet is cured for 24 hours, it is stamped into an inner liner box with a stamping depth of 65 mm and a mold radius of 1 mm. The outer support box is made of pulp molded support box. The edge of the inner liner box is folded over and hot-pressed to be fixed to the upper edge of the outer support box to obtain a food antibacterial aluminum foil packaging box.

[0051] Example 3 Preparation of antibacterial aluminum foil packaging boxes for food: (1) 35μm thick 8079 aluminum foil was selected as the aluminum foil substrate, and the aluminum foil substrate was subjected to alkaline degreasing, water washing, deionized water washing and corona treatment. (2) Coat the side of the aluminum foil substrate closest to the food with a zinc phytate treatment solution, with a coating amount of 120 mg / m² on a dry basis. 2 The composition of the zinc phytate treatment solution is: 0.3 g / L phytic acid, 1.2 g / L zinc acetate (calculated as zinc ions), and 0.5 g / L polyvinyl alcohol. The pH of the zinc phytate treatment solution is 5.2. It is dried at 70℃ for 60 seconds to form a coordination transition layer. (3) Apply an antibacterial heat-sealing coating liquid to the surface of the coordination transition layer. The coating amount is 2 g / m² on a dry basis. 2 First, dry at 75℃ for 20 seconds, then dry at 115℃ for 10 seconds to form an antibacterial heat-sealing layer; The preparation method of the antibacterial heat-sealing coating liquid is as follows: 78 parts of ethylene-acrylic acid copolymer are prepared into an ethylene-acrylic acid copolymer aqueous dispersion with a solid content of 30% by weight. Polylactic acid emulsion with a solid content of 20% prepared from 8 parts of polylactic acid and chitosan lactate aqueous solution with a mass fraction of 10% prepared from 8 parts of chitosan lactate are added and mixed. The mixture is stirred at 25°C for 20 min. Glyceryl monolaurate emulsion with a solid content of 10% prepared from 6 parts of glyceryl monolaurate and choline ferulic acid solution with a solid content of 40% prepared from 0.5 parts of choline ferulic acid are added and the mixture is stirred for 15 min. Then, 2.5 parts of nisin, silica dispersion with a solid content of 20% prepared from 0.1 parts of silica and 2 parts of A-171 silane coupling agent are added and the pH is adjusted to 5.8 to obtain the antibacterial heat-sealing coating liquid. Preparation of choline ferulic acid salt: 10 kg of ferulic acid was added to 60 kg of 50% ethanol aqueous solution, and the mixture was heated to 60 °C and stirred to disperse. According to the molar ratio of choline to ferulic acid of 0.95:1, 45% choline bicarbonate aqueous solution was slowly added, and the addition rate was controlled to keep the system temperature at 60 °C. After the ferulic acid was completely dissolved, the mixture was stirred for 1 hour until the pH reached 6.2. Ethanol and some water were removed under reduced pressure to obtain an aqueous solution of choline ferulic acid salt with a solid content of 40%. (4) Coat the aluminum foil substrate on the side away from the food with a dry basis of 3.5 g / m 2 A polyurethane coating is applied to form an outer protective layer, resulting in an antibacterial aluminum foil composite sheet. The polyurethane coating is prepared using Covestro's Bayhydrol UH 2558 waterborne polyurethane dispersion as the main film-forming substance, combined with a waterborne crosslinking agent, leveling agent, defoamer, and deionized water. (5) After the antibacterial aluminum foil composite sheet is cured for 24 hours, it is stamped into an inner liner box with a stamping depth of 15 mm and a mold radius of 4 mm. The outer support box is made of PLA support box. The edge of the inner liner box is folded over and hot-pressed to be fixed to the upper edge of the outer support box to obtain a food antibacterial aluminum foil packaging box.

[0052] Example 4 Preparation of antibacterial aluminum foil packaging boxes for food: (1) 8011 aluminum foil with a thickness of 60μm was selected as the aluminum foil substrate, and the aluminum foil substrate was subjected to alkaline degreasing, water washing, deionized water washing and corona treatment. (2) Coat the side of the aluminum foil substrate closest to the food with a zinc phytate treatment solution, with a coating amount of 70 mg / m² on a dry basis. 2 The composition of the zinc phytate treatment solution is: 2 g / L phytic acid, 0.9 g / L zinc gluconate (calculated as zinc ions), and 2.5 g / L waterborne polyurethane. The pH of the zinc phytate treatment solution is 4.8. It is dried at 90℃ for 40 seconds to form a coordination transition layer. (3) Apply an antibacterial heat-sealing coating liquid to the surface of the coordination transition layer. The coating amount is 6 g / m² on a dry basis. 2 First, dry at 70℃ for 40 seconds, then dry at 100℃ for 35 seconds to form an antibacterial heat-sealing layer; The preparation method of the antibacterial heat-sealing coating liquid is as follows: 62 parts by weight of ethylene-acrylic acid copolymer are made into an ethylene-acrylic acid copolymer aqueous dispersion with a solid content of 30%. A polylactic acid emulsion with a solid content of 20% made from 15 parts of polylactic acid and a chitosan lactate aqueous solution with a mass fraction of 10% made from 4 parts of chitosan lactate are added and mixed. The mixture is stirred at 35°C for 20 minutes. A monolaurate emulsion with a solid content of 10% made from 4 parts of monolaurate and a choline ferulic acid solution with a solid content of 40% made from 2 parts of choline ferulic acid are added and the mixture is stirred for another 15 minutes. Then, 1 part of nisin, a montmorillonite dispersion with a solid content of 20% made from 1 part of montmorillonite and 1.5 parts of polycarbodiimide are added and the pH is adjusted to 6.1 to obtain the antibacterial heat-sealing coating liquid. Preparation of choline ferulic acid salt: 10 kg of ferulic acid was added to 60 kg of 50% ethanol aqueous solution, and the mixture was heated to 55 °C and stirred to disperse. According to the molar ratio of choline to ferulic acid of 1:1, 45% choline bicarbonate aqueous solution was slowly added, and the addition rate was controlled to keep the system temperature at 55 °C. After the ferulic acid was completely dissolved, the mixture was stirred for 1 hour and reacted until the pH reached 7.0. Ethanol and some water were removed under reduced pressure to obtain an aqueous solution of choline ferulic acid salt with a solid content of 40%. (4) Coat the aluminum foil substrate on the side away from the food with a dry basis of 2.2 g / m 2 A polyester coating is applied to form an outer protective layer, resulting in an antibacterial aluminum foil composite sheet. The polyester coating is prepared using VYLON 200 polyester resin from Toyobo Co., Ltd. as the main film-forming substance, combined with isocyanate crosslinking agents, leveling agents, defoamers, and a mixed organic solvent of ethyl acetate-butanone. (5) After the antibacterial aluminum foil composite sheet is cured for 24 hours, it is stamped into an inner liner box with a stamping depth of 45 mm and a mold corner radius of 3 mm. The outer support box is made of paper / PBAT composite support box. The edge of the inner liner box is folded over and hot-pressed to be fixed to the upper edge of the outer support box to obtain a food antibacterial aluminum foil packaging box.

[0053] Comparative Example 1 (The difference from Example 1 is that no coordination transition layer is provided, and the antibacterial heat-sealing layer is directly coated on the surface of the corona-treated aluminum foil) Preparation of antibacterial aluminum foil packaging boxes for food: (1) 70μm thick 8011 aluminum foil is selected as aluminum foil substrate, and the aluminum foil substrate is subjected to alkaline degreasing, water washing, deionized water washing and corona treatment. (2) Apply an antibacterial heat-sealing coating liquid to the side of the aluminum foil substrate closest to the food, with a coating amount of 5 g / m² on a dry basis. 2 First, dry at 65℃ for 55 seconds, then dry at 100℃ for 40 seconds to form an antibacterial heat-sealing layer; The preparation method of the antibacterial heat-sealing coating liquid is as follows: 67 parts by weight of ethylene-acrylic acid copolymer are prepared into an ethylene-acrylic acid copolymer aqueous dispersion with a solid content of 30%. A polylactic acid emulsion with a solid content of 20% prepared from 15 parts of polylactic acid and a chitosan lactate aqueous solution with a mass fraction of 10% prepared from 5 parts of chitosan lactate are added and mixed. The mixture is stirred at 35°C for 20 min. A monolaurate emulsion with a solid content of 10% prepared from 3 parts of monolaurate and a choline ferulic acid solution with a solid content of 40% prepared from 3 parts of choline ferulic acid are added and the mixture is stirred for another 15 min. Then, 1.5 parts of nisin, a silica dispersion with a solid content of 20% prepared from 0.5 parts of silica and 1 part of polycarbodiimide are added and the pH is adjusted to 6.3 to obtain the antibacterial heat-sealing coating liquid. Preparation of choline ferulic acid salt: 10 kg of ferulic acid was added to 60 kg of 50% ethanol aqueous solution, and the mixture was heated to 55 °C and stirred to disperse. According to the molar ratio of choline to ferulic acid of 1.05:1, 45% choline bicarbonate aqueous solution was slowly added, and the addition rate was controlled to keep the system temperature at 55 °C. After the ferulic acid was completely dissolved, the mixture was stirred for 1 hour until the pH reached 6.8. Ethanol and some water were removed under reduced pressure to obtain an aqueous solution of choline ferulic acid salt with a solid content of 40%. (3) Coating the aluminum foil substrate on the side away from the food with a dry basis of 1.8 g / m 2 A polyester coating is applied to form an outer protective layer, resulting in an antibacterial aluminum foil composite sheet. The polyester coating is prepared using VYLON 200 polyester resin from Toyobo Co., Ltd. as the main film-forming substance, combined with isocyanate crosslinking agents, leveling agents, defoamers, and a mixed organic solvent of ethyl acetate-butanone. (4) After the antibacterial aluminum foil composite sheet is cured for 24 hours, it is stamped into an inner liner box with a stamping depth of 40 mm and a mold radius of 2 mm. The outer support box is made of PE coated white cardboard. The edge of the inner liner box is folded over and hot-pressed to be fixed to the upper edge of the outer support box, thus obtaining a food antibacterial aluminum foil packaging box.

[0054] Comparative Example 2 (different from Example 1 in that choline ferulic acid salt is not added to the antibacterial heat-sealing coating solution) Preparation of antibacterial aluminum foil packaging boxes for food: (1) 70μm thick 8011 aluminum foil is selected as aluminum foil substrate, and the aluminum foil substrate is subjected to alkaline degreasing, water washing, deionized water washing and corona treatment. (2) Coat the side of the aluminum foil substrate closest to the food with a zinc phytate treatment solution, with a coating amount of 55 mg / m² on a dry basis. 2 The composition of the zinc phytate treatment solution is: 1.5 g / L phytic acid, 0.6 g / L zinc acetate (calculated as zinc ions), and 3 g / L polyvinyl alcohol. The pH of the zinc phytate treatment solution is 4.1. It is dried at 100℃ for 40 seconds to form a coordination transition layer. (3) Apply an antibacterial heat-sealing coating liquid to the surface of the coordination transition layer. The coating amount is 5 g / m² on a dry basis. 2 First, dry at 65℃ for 55 seconds, then dry at 100℃ for 40 seconds to form an antibacterial heat-sealing layer; The preparation method of the antibacterial heat-sealing coating liquid is as follows: 67 parts by weight of ethylene-acrylic acid copolymer are made into an ethylene-acrylic acid copolymer aqueous dispersion with a solid content of 30%. 15 parts of polylactic acid are added to a polylactic acid emulsion with a solid content of 20% and 5 parts of chitosan lactate aqueous solution with a mass fraction of 10%. The mixture is stirred at 35°C for 20 min. 3 parts of glyceryl monolaurate emulsion with a solid content of 10% is added and stirred for another 15 min. 1.5 parts of nisin, 0.5 parts of silica dispersion with a solid content of 20% and 1 part of polycarbodiimide are then added. The pH is adjusted to 6.3 to obtain the antibacterial heat-sealing coating liquid. (4) Coat the aluminum foil substrate on the side away from the food with a dry basis of 1.8 g / m 2 A polyester coating is applied to form an outer protective layer, resulting in an antibacterial aluminum foil composite sheet. The polyester coating is prepared using VYLON 200 polyester resin from Toyobo Co., Ltd. as the main film-forming substance, combined with isocyanate crosslinking agents, leveling agents, defoamers, and a mixed organic solvent of ethyl acetate-butanone. (5) After the antibacterial aluminum foil composite sheet is cured for 24 hours, it is stamped into an inner liner box with a stamping depth of 40 mm and a mold corner radius of 2 mm. The outer support box is made of PE coated white cardboard. The edge of the inner liner box is folded over and hot-pressed to be fixed to the upper edge of the outer support box, thus obtaining a food antibacterial aluminum foil packaging box.

[0055] Comparative Example 3 (different from Example 1 in that the antibacterial heat-sealing layer does not contain chitosan lactate, nisin, glyceryl monolaurate and choline ferulic acid, but is composed only of ethylene-acrylic acid copolymer, polylactic acid, polycarbodiimide and silica as a conventional heat-sealing layer) Preparation of antibacterial aluminum foil packaging boxes for food: (1) 70μm thick 8011 aluminum foil is selected as aluminum foil substrate, and the aluminum foil substrate is subjected to alkaline degreasing, water washing, deionized water washing and corona treatment. (2) Coat the side of the aluminum foil substrate closest to the food with a zinc phytate treatment solution, with a coating amount of 55 mg / m² on a dry basis. 2 The composition of the zinc phytate treatment solution is: 1.5 g / L phytic acid, 0.6 g / L zinc acetate (calculated as zinc ions), and 3 g / L polyvinyl alcohol. The pH of the zinc phytate treatment solution is 4.1. It is dried at 100℃ for 40 seconds to form a coordination transition layer. (3) Apply an antibacterial heat-sealing coating liquid to the surface of the coordination transition layer. The coating amount is 5 g / m² on a dry basis. 2 First, dry at 65℃ for 55 seconds, then dry at 100℃ for 40 seconds to form an antibacterial heat-sealing layer; The preparation method of the antibacterial heat-sealing coating liquid is as follows: 67 parts of ethylene-acrylic acid copolymer are made into an ethylene-acrylic acid copolymer aqueous dispersion with a solid content of 30% by weight, and 15 parts of polylactic acid emulsion with a solid content of 20% are added and mixed. The mixture is stirred at 35°C for 20 minutes, and then 0.5 parts of silica dispersion with a solid content of 20% and 1 part of polycarbodiimide are added. The pH is adjusted to 6.3 to obtain the antibacterial heat-sealing coating liquid. (4) Coat the aluminum foil substrate on the side away from the food with a dry basis of 1.8 g / m 2 A polyester coating is applied to form an outer protective layer, resulting in an antibacterial aluminum foil composite sheet. The polyester coating is prepared using VYLON 200 polyester resin from Toyobo Co., Ltd. as the main film-forming substance, combined with isocyanate crosslinking agents, leveling agents, defoamers, and a mixed organic solvent of ethyl acetate-butanone. (5) After the antibacterial aluminum foil composite sheet is cured for 24 hours, it is stamped into an inner liner box with a stamping depth of 40 mm and a mold corner radius of 2 mm. The outer support box is made of PE coated white cardboard. The edge of the inner liner box is folded over and hot-pressed to be fixed to the upper edge of the outer support box, thus obtaining a food antibacterial aluminum foil packaging box.

[0056] Comparative Example 4 (different from Example 1 in that ferulic acid of equal solid mass is used instead of choline ferulic acid salt) Preparation of antibacterial aluminum foil packaging boxes for food: (1) 70μm thick 8011 aluminum foil is selected as aluminum foil substrate, and the aluminum foil substrate is subjected to alkaline degreasing, water washing, deionized water washing and corona treatment. (2) Coat the side of the aluminum foil substrate closest to the food with a zinc phytate treatment solution, with a coating amount of 55 mg / m² on a dry basis. 2 The composition of the zinc phytate treatment solution is: 1.5 g / L phytic acid, 0.6 g / L zinc acetate (calculated as zinc ions), and 3 g / L polyvinyl alcohol. The pH of the zinc phytate treatment solution is 4.1. It is dried at 100℃ for 40 seconds to form a coordination transition layer. (3) Apply an antibacterial heat-sealing coating liquid to the surface of the coordination transition layer. The coating amount is 5 g / m² on a dry basis. 2 First, dry at 65℃ for 55 seconds, then dry at 100℃ for 40 seconds to form an antibacterial heat-sealing layer; The preparation method of the antibacterial heat-sealing coating liquid is as follows: 67 parts by weight of ethylene-acrylic acid copolymer are prepared into an ethylene-acrylic acid copolymer aqueous dispersion with a solid content of 30%. A polylactic acid emulsion with a solid content of 20% prepared from 15 parts of polylactic acid and a chitosan lactate aqueous solution with a mass fraction of 10% prepared from 5 parts of chitosan lactate are added and mixed. The mixture is stirred at 35°C for 20 min. A monolaurate emulsion with a solid content of 10% prepared from 3 parts of monolaurate glycerol and a ferulic acid ethanol aqueous solution with a mass fraction of 10% prepared from 3 parts of ferulic acid are added and the mixture is stirred for another 15 min. Then, 1.5 parts of nisin, a silica dispersion with a solid content of 20% prepared from 0.5 parts of silica and 1 part of polycarbodiimide are added and the pH is adjusted to 6.3 to obtain the antibacterial heat-sealing coating liquid. (4) Coat the aluminum foil substrate on the side away from the food with a dry basis of 1.8 g / m 2 A polyester coating is applied to form an outer protective layer, resulting in an antibacterial aluminum foil composite sheet. The polyester coating is prepared using VYLON 200 polyester resin from Toyobo Co., Ltd. as the main film-forming substance, combined with isocyanate crosslinking agents, leveling agents, defoamers, and a mixed organic solvent of ethyl acetate-butanone. (5) After the antibacterial aluminum foil composite sheet is cured for 24 hours, it is stamped into an inner liner box with a stamping depth of 40 mm and a mold corner radius of 2 mm. The outer support box is made of PE coated white cardboard. The edge of the inner liner box is folded over and hot-pressed to be fixed to the upper edge of the outer support box, thus obtaining a food antibacterial aluminum foil packaging box.

[0057] Experimental Example The antibacterial aluminum foil packaging boxes for food prepared in Examples 1-4 and Comparative Examples 1-4 were tested for their main properties.

[0058] The testing items and methods are as follows: The antibacterial properties were tested according to GB / T 31402-2023 "Determination of antibacterial activity of plastics and other non-porous materials". The test strains were Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538. Considering the actual state of the packaging box after stamping and short-term heat sealing, the test samples were all taken from the bottom plane area and the rounded corner stretching area of ​​the box after molding. Before testing, the samples were treated in hot air at 80℃ for 10 minutes.

[0059] The heat seal strength was tested according to QB / T 2358-1998 "Test Method for Heat Seal Strength of Plastic Film Packaging Bags". The heat seal was performed using the easy-open lid film commonly used in food packaging, with a heat seal temperature of 160℃, a pressure of 0.25MPa, and a time of 1.0s.

[0060] The coating adhesion was tested according to GB / T 9286-2021 "Cross-cut test for paints and varnishes".

[0061] The acid corrosion resistance test used a mixed aqueous solution of 3% acetic acid and 2% sodium chloride. After contacting the food at 40°C for 72 hours, the surface of the food contact was observed to see if it turned black, blistered, or exposed aluminum, and the change in coating adhesion was measured.

[0062] Total migration was determined according to GB 31604.8-2021, "National Food Safety Standard - Determination of Total Migration in Food Contact Materials and Articles". Food simulants used were 4% acetic acid, 10% ethanol, and olive oil. The test conditions were 40℃ for 10 days. The suitability of the food contact materials was evaluated according to the relevant requirements of GB 4806.7-2023 and GB 4806.9-2023.

[0063] The antioxidant retention performance was evaluated using DPPH free radical scavenging rate as an auxiliary indicator. The extract of the antibacterial heat seal layer in food contact was used to determine the effective retention of ferulic acid salt components after processing.

[0064] The test data is shown in Table 1 below: Table 1 Performance test results of antibacterial aluminum foil packaging boxes for food Reference Figures 1-2 As can be seen from Table 1, the antibacterial aluminum foil packaging boxes for food prepared in Examples 1 to 4 of this application all have high antibacterial rates, especially with stable inhibitory effects against Staphylococcus aureus; the stamped rounded corner areas still maintain a high antibacterial rate, indicating that the antibacterial components are well dispersed and maintained in the coating.

[0065] Comparative Example 1 did not have a coordination transition layer. The antibacterial heat-sealing layer was formed directly on the surface of the corona-treated aluminum foil. Everything else was the same as in Example 1. The planar area of ​​the antibacterial aluminum foil packaging box prepared in Comparative Example 1 still had a certain antibacterial effect, but the antibacterial rate in the rounded corner area dropped to a minimum of 81.6%. The heat-sealing strength and cross-cut adhesion were also significantly worse than in Example 1. This indicates that during the stamping, stretching and edge hot pressing process, the lack of a zinc phytate coordination transition layer will lead to insufficient interfacial bonding between the aluminum foil and the organic antibacterial heat-sealing layer. Micro-cracks, local delamination, or discontinuous coatings are prone to occur in areas with concentrated stress, such as rounded corners and folded edges, thereby weakening the effective retention of antibacterial components and reducing acid corrosion resistance.

[0066] Comparative Example 2 did not contain choline ferulic acid salts, but all other aspects were the same as in Example 1. The antibacterial rate, antibacterial retention rate of the rounded corner area, and DPPH scavenging rate of the antibacterial aluminum foil packaging box prepared in Comparative Example 2 were significantly reduced, while the total migration amount increased to 5.1 mg / dm³. 2 These results indicate that choline ferulic acid salt not only functions as an antioxidant but also improves the dispersion stability of chitosan lactate, nisin, and glyceryl monolaurate in aqueous heat-sealing systems and plays a regulatory role in the release of antimicrobial components during food contact. The absence of this component leads to a decrease in the distribution and retention of active components in the antimicrobial heat-sealing layer, resulting in a simultaneous decline in antimicrobial durability, antioxidant retention, and migration control.

[0067] Comparative Example 3 did not include chitosan lactate, nisin, glyceryl monolaurate, or choline ferulic acid; it only retained the ordinary heat-sealing resin system, and everything else was the same as in Example 1. The antibacterial aluminum foil packaging box prepared in Comparative Example 3 had higher heat-sealing strength, indicating that the ethylene-acrylic acid copolymer, polylactic acid, and crosslinking aid could form a relatively complete heat-sealing coating. However, its antibacterial rates against Escherichia coli and Staphylococcus aureus were only 19.6% and 24.3%, respectively, and its DPPH scavenging rate was only 3.4%. This indicates that the ordinary heat-sealing layer itself does not have effective antibacterial and antioxidant functions. The antibacterial effect of this application mainly comes from the synergistic effect of the natural antibacterial components and choline ferulic acid, rather than simply relying on the barrier effect of the resin coating or aluminum foil.

[0068] Comparative Example 4 used ferulic acid in place of choline ferulate at an equal solid mass, with all other aspects remaining the same as in Example 1. The antibacterial aluminum foil packaging box prepared in Comparative Example 4 exhibited inferior antibacterial rate, heat-sealing strength, adhesion, and total migration compared to Example 1, and also showed localized haze and slight wrinkling at the rounded corners. These results indicate that free ferulic acid lacks compatibility and dispersion stability in aqueous antibacterial heat-sealing systems, making it prone to precipitation, localized enrichment, or phase separation during coating liquid storage or drying, thus affecting coating continuity and heat-sealing performance. Converting ferulic acid into choline ferulate significantly improves its dispersibility and processing compatibility in aqueous systems, resulting in a more stable antibacterial, antioxidant, and shape-retention effect in the antibacterial heat-sealing layer.

[0069] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions or alterations can be made to these embodiments without departing from the principles and spirit of this application, and the technical solutions resulting from such changes, modifications, substitutions or alterations will all fall within the protection scope of this application.

Claims

1. A food-grade antibacterial aluminum foil packaging box, characterized in that, It includes an outer support box and an inner liner box disposed inside the outer support box, wherein the outer support box and the inner liner box are fixedly connected in the rim area. The inner liner box is formed by stamping antibacterial aluminum foil composite sheet, which includes an outer protective layer, an aluminum foil substrate, a coordination transition layer and an antibacterial heat-sealing layer from the outside to the inside. The preparation of the antibacterial heat-sealing layer includes the following steps: An antibacterial heat-sealing coating liquid is applied to the surface of the coordination transition layer and dried in stages to form an antibacterial heat-sealing layer. The raw materials for preparing the antibacterial heat-sealing coating liquid, by solid weight, include: 55-78 parts of ethylene-acrylic acid copolymer, 8-22 parts of polylactic acid, 2-8 parts of chitosan lactate, 0.3-2.5 parts of nisin, 1-6 parts of glyceryl monolaurate, 0.5-5 parts of choline ferulic acid, and 0.2-2 parts of crosslinking aid.

2. The antibacterial aluminum foil packaging box for food according to claim 1, characterized in that, The choline ferulic acid salt is prepared by reacting choline bicarbonate or choline hydroxide with ferulic acid in water and / or ethanol, wherein the molar ratio of choline bicarbonate or choline hydroxide to ferulic acid, calculated as choline, is 0.95–1.1:1, the reaction temperature is 45–60 °C, and the solvent is removed after the system pH reaches 6.2–7.

4.

3. The antibacterial aluminum foil packaging box for food according to claim 1, characterized in that, The antibacterial heat-sealing coating liquid also contains 0.1 to 1.5 parts by weight of silica or montmorillonite; And / or, the crosslinking aid is at least one of polycarbodiimide, aziridine crosslinking agent, or food contact epoxysilane; And / or, the coating amount of the antibacterial heat-seal coating solution is 2 to 8 g / m 2 .

4. The antibacterial aluminum foil packaging box for food according to claim 1, characterized in that, The method for preparing the antibacterial heat-sealing coating solution includes: preparing an aqueous dispersion of ethylene-acrylic acid copolymer, adding polylactic acid emulsion, chitosan lactate aqueous solution, glyceryl monolaurate emulsion and choline ferulic acid solution, stirring evenly at 25-45°C, then adding nisin and crosslinking aid, adjusting the pH to 5.8-6.8 to obtain the antibacterial heat-sealing coating solution.

5. The antibacterial aluminum foil packaging box for food according to claim 1, characterized in that, In the preparation of the antibacterial heat-sealing layer, the segmented drying process involves first drying at 55–75°C for 20–90 seconds, and then drying at 85–115°C for 10–60 seconds.

6. The antibacterial aluminum foil packaging box for food according to claim 1, characterized in that, The preparation of the coordination transition layer includes the following steps: A zinc phytate treatment solution is coated on one side of an aluminum foil substrate and dried to form a coordination transition layer. The zinc phytate treatment solution includes phytic acid, zinc salt, film-forming regulator and water, wherein the concentration of phytic acid in the zinc phytate treatment solution is 0.3-3 g / L, the concentration of zinc salt (calculated as zinc ion concentration) is 0.05-1.2 g / L, and the concentration of film-forming regulator is 0.5-5 g / L.

7. The antibacterial aluminum foil packaging box for food according to claim 6, characterized in that, The zinc salt is at least one of zinc acetate, zinc lactate, and zinc gluconate; And / or, the film-forming regulator is at least one of polyvinyl alcohol, hydroxypropyl methylcellulose or waterborne polyurethane; and / or the coating amount of the zinc phytate treatment liquid is 15 to 120 mg / m 2 .

8. The antibacterial aluminum foil packaging box for food according to claim 1, characterized in that, The outer protective layer is one of a polyester coating, an acrylic coating or a polyurethane coating; the coating amount of the outer protective layer is 0.6-3.5 g / m 2 .

9. A food-grade antibacterial aluminum foil packaging box according to claim 1, characterized in that, The outer support box is one of a paper-based support box, a biodegradable plastic support box, or a paper-plastic composite support box; And / or, the aluminum foil substrate is one of 8011 aluminum foil, 3003 aluminum foil or 8079 aluminum foil, and the thickness of the aluminum foil substrate is 35 to 120 μm.

10. A method for preparing an antibacterial aluminum foil packaging box for food as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Degrease, clean and surface activate the aluminum foil substrate; form a coordination transition layer on one side of the aluminum foil substrate, form an antibacterial heat-sealing layer on the surface of the coordination transition layer; form an outer protective layer on the other side of the aluminum foil substrate to obtain an antibacterial aluminum foil composite sheet; S2. The antibacterial aluminum foil composite sheet is stamped into an inner liner box, and then the inner liner box is combined and fixed with the outer support box to obtain an antibacterial aluminum foil packaging box for food.

Images