High-barrier antibacterial biodegradable film and preparation method thereof

Abstract

The preparation method comprises the following steps: S1, preparation of epoxy quaternary ammonium salt modified montmorillonite: dispersing montmorillonite in deionized water, adding long-chain epoxy quaternary ammonium salt, reacting, and then filtering, washing and drying to obtain the epoxy quaternary ammonium salt modified montmorillonite; s2, preparation of the high-barrier antibacterial biodegradable master batch: uniformly mixing a composite biodegradable material and the epoxy quaternary ammonium salt modified montmorillonite prepared in the step S1 in a high-speed mixer, and then performing mixing, granulation, water cooling and grain-sized dicing through a double-screw extruder to obtain the high-barrier antibacterial biodegradable master batch, and S3, preparation of the high-barrier antibacterial biodegradable film: drying the master batch prepared in S2, and then performing blow molding through a single-screw extrusion film blowing machine to obtain the high-barrier antibacterial biodegradable film. The preparation method has the advantages of low input cost, high production efficiency, simple preparation process, good compatibility and the like.

Description

Technical Field

[0001] This invention belongs to the field of packaging film technology, specifically relating to a high-barrier antibacterial biodegradable film and its preparation method. Background Technology

[0002] High-barrier packaging films, with their core function of effectively blocking oxygen, moisture, carbon dioxide, and volatile substances, can significantly slow down the rate of product oxidation, deterioration, and mold growth due to moisture. This not only greatly extends the shelf life of food and pharmaceutical products but also perfectly preserves their original flavor, efficacy, and performance. Therefore, their application in demanding fields such as food processing, pharmaceutical packaging, protection of precision electronic instruments, and storage of fine chemicals is becoming increasingly widespread and indispensable. In the food industry, they can be used to preserve fresh meat, baked goods, and vacuum-packed snacks, reducing the use of preservatives. In the pharmaceutical field, they provide a stable storage environment for capsules, tablets, and biological agents, ensuring that their efficacy is not affected by the environment. In the fields of precision instruments and fine chemicals, they effectively isolate external moisture and corrosive gases, preventing damage to product performance.

[0003] Polyolefin materials, including polyethylene (PE) and polypropylene (PP), have long been the preferred basic materials for water-blocking functions in packaging films due to their excellent water vapor barrier properties, low production costs, good flexibility and processing adaptability, and outstanding comprehensive mechanical properties. They are widely used in various general packaging scenarios. However, traditional polyolefin plastics are difficult to degrade naturally, and the "white pollution" caused by their large-scale use has become a global environmental problem. Waste plastics take hundreds of years to decompose slowly in the soil, not only damaging soil structure and affecting plant growth, but also harming ecosystems and human health through the food chain. With the awakening of global environmental awareness, governments around the world have introduced strict environmental policies to restrict the use of non-degradable plastics and promote the transformation of packaging materials towards green and sustainable development. Against this backdrop, biodegradable materials such as polylactic acid (PLA), polybutylene adipate / terephthalate (PBAT), polyhydroxyalkanoates (PHA), and polypropylene carbonate (PPC) have rapidly become research hotspots in the packaging materials field due to their advantage of being decomposed into harmless substances by microorganisms in the natural environment after use.

[0004] Unfortunately, existing biodegradable films generally suffer from insufficient gas barrier properties. Their oxygen and water vapor permeability is much higher than that of traditional polyolefin films, making it difficult to meet the stringent environmental isolation requirements of high-barrier packaging and greatly limiting their application in high-end packaging. For example, while pure PLA film has good mechanical properties and biocompatibility, its water vapor barrier properties are poor; PBAT has excellent flexibility but also suffers from weak gas barrier capabilities. This makes it difficult for a single biodegradable material to directly replace traditional high-barrier packaging materials. Therefore, developing novel packaging films that combine high barrier performance, antibacterial function, and biodegradability can not only overcome the application bottlenecks of biodegradable materials but also meet environmental policies and market demands, possessing significant academic value and industrial significance.

[0005] In existing related technologies, patent application CN119639199A discloses "high-barrier biodegradable composite film and its preparation method". This technology uses PLA, PBAT and PPC as base materials and modifies them by adding functional additives such as montmorillonite and epoxy chain extenders in an attempt to improve the barrier performance of the film. However, as an inorganic nanofiller, the interfacial compatibility between montmorillonite and organic biodegradable base materials has not been well resolved, which easily leads to the agglomeration of fillers in the matrix. This not only fails to effectively improve the barrier effect, but may also reduce the mechanical properties and processing stability of the film. Patent application CN118027366A discloses "A five-layer co-extruded biodegradable barrier film and its preparation method and application," employing an ABCBA five-layer composite structure. The A layer is a modified biodegradable material, the C layer is high-oxygen-barrier PVA (polyvinyl alcohol), and the B layer is a self-synthesized biodegradable copolyester. While it achieves a certain barrier effect, the five-layer co-extrusion process requires extremely high precision in production equipment, and the self-synthesized copolyester is complex and expensive, resulting in high film production costs and hindering large-scale promotion. Patent application CN120118391A discloses "A biodegradable lightweight high-barrier packaging film and its preparation process." Its raw materials consist of modified montmorillonite, modified nanocellulose, polyvinyl alcohol, plasticizer, curcumin, and deionized water. The preparation process involves rapid gelation through quenching of the mixture. This process differs significantly from the mainstream large-scale production processes in the packaging film industry, such as casting, blown film, and biaxial stretching. It requires specially customized production equipment, resulting in high investment costs and low production efficiency, making it difficult to meet the needs of large-scale industrial production. Patent application CN110835417A discloses "a barrier-resistant biodegradable antibacterial food preservation film and its preparation method and application". The method involves directly mixing polylactic acid, antibacterial nanomaterials, plasticizers, antioxidants, chain extenders, etc., followed by extrusion granulation, casting, and then biaxial stretching to obtain a film. However, this method directly blends antibacterial agents, barrier functional substances and biodegradable masterbatches without specifically optimizing the compatibility of each component. This can easily lead to uneven dispersion and agglomeration of functional components, which not only affects the stability of the film's barrier performance and antibacterial effect, but may also reduce the mechanical uniformity of the film.

[0006] Therefore, existing technologies for preparing high-barrier biodegradable films suffer from drawbacks such as poor component compatibility, complex and costly processes, or difficulty in large-scale production, failing to adequately balance high barrier properties, antibacterial properties, biodegradability, and industrial feasibility. Thus, it is necessary to propose a simple, cost-controllable biodegradable film preparation process that ensures good component compatibility and simultaneously achieves high barrier and antibacterial functions. This would promote the widespread application of biodegradable packaging materials in high-end packaging and contribute to the sustainable development of the environmental protection and packaging industries. Summary of the Invention

[0007] To address the aforementioned shortcomings of the prior art, this invention provides a high-barrier antibacterial biodegradable film and its preparation method, solving the problems of poor compatibility, complex preparation process, low production efficiency, and high investment cost of existing high-barrier antibacterial biodegradable films.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing a high-barrier antibacterial biodegradable film includes the following steps: S1. Preparation of epoxy quaternary ammonium salt modified montmorillonite: Montmorillonite is dispersed in deionized water, long-chain epoxy quaternary ammonium salt is added, and after reaction, it is filtered, washed and dried to obtain the epoxy quaternary ammonium salt modified montmorillonite. S2. Preparation of high-barrier antibacterial biodegradable masterbatch: The composite biodegradable material and the epoxy quaternary ammonium salt modified montmorillonite obtained in S1 are mixed evenly in a high-speed mixer, and then the mixture is compounded, granulated, water-cooled and pelletized by a twin-screw extruder to obtain the high-barrier antibacterial biodegradable masterbatch. S3. Preparation of high-barrier antibacterial biodegradable film: The masterbatch obtained in S2 is dried and then blown into a film by a single-screw extrusion blown film machine to obtain the high-barrier antibacterial biodegradable film.

[0009] Preferably, the long-chain epoxy quaternary ammonium salt in S1 is prepared by the following method: Long-chain ammonium amide propyl dimethylamine was dissolved in ethanol, heated to 50-70°C, and epichlorohydrin was added dropwise. The reaction was carried out for 4-8 hours, and the product was then obtained by vacuum distillation and drying. The long-chain amamidopropyl dimethylamine is any one of lauramidopropyl dimethylamine, myristamidopropyl dimethylamine, palmitamidopropyl dimethylamine, and stearamidopropyl dimethylamine; the molar ratio of long-chain amamidopropyl dimethylamine to epichlorohydrin is 1:1.

[0010] Preferably, the montmorillonite in S1 is sodium-based montmorillonite, and the mass ratio of sodium-based montmorillonite to long-chain epoxy quaternary ammonium salt is 10:(2-5).

[0011] In the above scheme, montmorillonite is a natural layered silicate mineral composed of aluminum-oxygen octahedra and silicon-oxygen tetrahedra. It is abundant and widely available, has a large specific surface area, and excellent barrier properties, which can improve the water vapor and gas barrier performance of the material. However, montmorillonite has strong hydrophilicity and poor compatibility with the polymer matrix, making it difficult to achieve good dispersion. This not only hinders the improvement of the membrane material's barrier performance but also often damages the material's mechanical properties. The general chemical formula of montmorillonite is (M... y nH2O)(Al 4y Mg y Si8O 20(OH)4, where M refers to interlayer exchangeable cations such as Na+, Ca2+, and Mg2+, which have the ability to exchange with other organic cations, thereby achieving the organic modification of montmorillonite.

[0012] Preferably, the composite biodegradable material in S2 is a mixture of poly(dibutyl terephthalate), polylactic acid, and polypropylene carbonate in a mass ratio of (6-8):(1-2):(1-2).

[0013] Preferably, the mass ratio of the composite biodegradable material and the epoxy quaternary ammonium salt modified montmorillonite in S2 is 100:(2-5).

[0014] Preferably, the reaction temperature range in S1 is 50–80°C, and the reaction time range is 2–5 hours.

[0015] Preferably, the twin-screw extruder in S2 includes seven temperature control zones, namely zone 1, zone 2, zone 3, zone 4, zone 5, zone 6, and zone 7, wherein the temperatures of zone 1, zone 2, zone 3, zone 4, zone 5, zone 6, and zone 7 are 135°C, 145°C, 150°C, 155°C, 155°C, 160°C, and 160°C, respectively, and the rotational speed of the twin-screw extruder is 270 rpm.

[0016] Preferably, the single-screw extruder blown film extruder in S3 includes four temperature control zones, namely zone 1, zone 2, zone 3 and zone 4, wherein the temperatures of zone 1, zone 2, zone 3 and zone 4 are 145°C, 150°C, 150°C and 150°C respectively, and the rotation speed of the single-screw extruder blown film extruder is 270 rpm.

[0017] In the above-mentioned scheme, the epoxy quaternary ammonium salt modified montmorillonite not only retains the layered structure of montmorillonite, but also inserts long-chain epoxy quaternary ammonium salts into the interlayer spaces of montmorillonite through cation exchange, increasing the interlayer spacing. This facilitates the "multi-path effect" and "permeable area reduction effect" in biodegradable films, thereby improving gas barrier performance. On the other hand, the long-chain epoxy quaternary ammonium salt structure contains hydrophobic long-chain alkyl carbon chains, which can improve the hydrophilicity of montmorillonite, thus enhancing the hydrophobicity of the biodegradable film. Simultaneously, the introduction of epoxy groups provides chemical bonding sites, enabling the modified montmorillonite to undergo an epoxy ring-opening reaction with the biodegradable material. Furthermore, the amide groups present in the long-chain alkyl carbon chains can form hydrogen bonds with the carbonyl groups in the biodegradable material molecular chains, improving the interfacial compatibility between the two through reaction compatibilization and hydrogen bonding, thereby enhancing the mechanical and gas barrier properties of the film. In addition, the quaternary ammonium salt in the modified montmorillonite structure has good bactericidal activity, endowing the biodegradable film with durable and stable antibacterial properties.

[0018] The present invention also discloses a high-barrier antibacterial biodegradable film, which is prepared by the above-described method for preparing a high-barrier antibacterial biodegradable film.

[0019] By adopting the above technical solution, the present invention has the following beneficial effects: In this invention, the epoxy quaternary ammonium salt-modified montmorillonite prepared via cation exchange retains the layered structure of montmorillonite while increasing the distance between the layers, thus exhibiting a "multi-path effect" and a "reduction in permeable area" to enhance the gas barrier properties of the biodegradable film. Secondly, the hydrophobic long-chain alkyl carbon chains introduced into the modified montmorillonite structure improve its hydrophilicity, facilitating good dispersion of montmorillonite in the biodegradable film and enhancing its hydrophobicity. Thirdly, the epoxy groups introduced into the modified montmorillonite structure can interact with biodegradable materials. The terminal carboxyl and hydroxyl groups in the resin undergo ring-opening reactions, while the amide groups can form hydrogen bonds with the carbonyl groups in the biodegradable resin molecular chain. Through multiple interactions such as chemical bonding and hydrogen bonding, the interfacial compatibility between the two is improved, further enhancing the mechanical and gas barrier properties of the film. In addition, the quaternary ammonium salts contained in the modified montmorillonite serve as antibacterial groups, endowing the biodegradable film with durable and stable antibacterial properties. Finally, the preparation process of the high-barrier antibacterial biodegradable film provided by this invention is simple and does not require changes to existing processes, making it suitable for large-scale promotion and application.

[0020] In summary, the present invention has the advantages of low input cost, high production efficiency, simple preparation process, and good compatibility. Attached Figure Description

[0021] Figure 1 This is the chemical reaction equation for the long-chain epoxy quaternary ammonium salt of the present invention. Detailed Implementation

[0022] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following detailed description is provided in conjunction with specific embodiments.

[0023] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0024] Those skilled in the art will recognize that the chemical reactions described in this invention can be suitably used to prepare many other compounds of this invention, and that other methods for preparing the compounds of this invention are considered to be within the scope of this invention. For example, the synthesis of those non-illustrative compounds according to this invention can be successfully accomplished by those skilled in the art through modification methods, such as by appropriately protecting interfering groups, by utilizing other known reagents besides those described in this invention, or by making some conventional modifications to the reaction conditions. Furthermore, the reactions disclosed in this invention or the known reaction conditions are also generally accepted to be applicable to the preparation of other compounds of this invention.

[0025] Unless otherwise specified, all raw materials used in this invention are derived from commercially available pharmaceuticals in this field. Specifically, PLA (brand name LX-175) is from TotalEnergies Ltd., Thailand; PBAT (brand name TH-801T) is from Xinjiang Lanshan Tunhe Chemical Co., Ltd.; and PPC (brand name HF901) is from Huafeng Group Co., Ltd.

[0026] The performance measurement methods involved in the following embodiments of the present invention are described below: Mechanical properties: Tested according to GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets"; Water vapor transmission rate: Tested according to GB / T1037-2021 "Determination of water vapor transmission performance of plastic films and sheets - cup method for weight gain and weight loss"; Oxygen permeability: Tested according to GB / T1038.1-2022 "Test methods for gas permeability of plastic films and sheets - Part 1: Differential pressure method"; Antibacterial properties: Tested according to GB / T31402-2015 "Test Method for Antibacterial Properties of Plastic Surfaces", with Escherichia coli strain number ATCC-8739 and Staphylococcus aureus strain number ATCC-6538P.

[0027] Example 1 In this embodiment, a method for preparing a high-barrier antibacterial biodegradable film is provided, comprising the following steps: S1. Preparation of epoxy quaternary ammonium salt modified montmorillonite: Montmorillonite is dispersed in deionized water, a long-chain epoxy quaternary ammonium salt is added, and after reaction, it is filtered, washed, and dried to obtain the epoxy quaternary ammonium salt modified montmorillonite. The preparation method of the long-chain epoxy quaternary ammonium salt is as follows: Long-chain ammonium amide propyl dimethylamine was dissolved in ethanol, heated to 50-70°C, and epichlorohydrin was added dropwise. The reaction was carried out for 4-8 hours, and the product was then obtained by vacuum distillation and drying. The long-chain amamidopropyl dimethylamine is any one of lauramidopropyl dimethylamine, myristamidopropyl dimethylamine, palmitamidopropyl dimethylamine, and stearamidopropyl dimethylamine; the molar ratio of long-chain amamidopropyl dimethylamine to epichlorohydrin is 1:1; Specifically, the montmorillonite in S1 is sodium-based montmorillonite, and the mass ratio of sodium-based montmorillonite to long-chain epoxy quaternary ammonium salt is 10:(2-5). The reaction temperature range in S1 is 50-80℃, and the reaction time range is 2-5h. S2. Preparation of high-barrier antibacterial biodegradable masterbatch: The composite biodegradable material and the epoxy quaternary ammonium salt modified montmorillonite obtained in S1 are mixed evenly in a high-speed mixer, and then the mixture is compounded, granulated, water-cooled and pelletized by a twin-screw extruder to obtain the high-barrier antibacterial biodegradable masterbatch. Specifically, the composite biodegradable material in S2 is a mixture of poly(dibutyl terephthalate), polylactic acid, and polypropylene carbonate in a mass ratio of (6-8):(1-2):(1-2). The mass ratio of the composite biodegradable material in S2 to the epoxy quaternary ammonium salt modified montmorillonite is 100:(2-5). Furthermore, the twin-screw extruder in S2 includes seven temperature control zones, namely zone 1, zone 2, zone 3, zone 4, zone 5, zone 6, and zone 7. The temperatures of zones 1, 2, 3, 4, 5, 6, and 7 are 135°C, 145°C, 150°C, 155°C, 155°C, 160°C, and 160°C, respectively. The rotation speed of the twin-screw extruder is 270 rpm. S3. Preparation of high-barrier antibacterial biodegradable film: The masterbatch obtained in S2 is dried and then blown into a film by a single-screw extrusion blown film machine to obtain the high-barrier antibacterial biodegradable film. The single-screw extrusion blown film machine in S3 includes 4 temperature control zones, namely zone 1, zone 2, zone 3 and zone 4. The temperatures of zone 1, zone 2, zone 3 and zone 4 are 145℃, 150℃, 150℃ and 150℃, respectively. The rotation speed of the single-screw extrusion blown film machine is 270 rpm.

[0028] The present invention also discloses a high-barrier antibacterial biodegradable film, which is prepared by the above-described method for preparing a high-barrier antibacterial biodegradable film.

[0029] More specifically, the above describes the preparation method of the high-barrier antibacterial biodegradable film of the present invention and the description of the preparation of the high-barrier antibacterial biodegradable film by the method. The following is a more detailed process of preparation using specific parameters in this application: S1. Preparation of epoxy quaternary ammonium salt modified montmorillonite: 0.1 mol myristamidopropyl dimethylamine was dissolved in ethanol, heated to 60°C, and 0.1 mol epichlorohydrin was added dropwise. The reaction was carried out for 6 hours, and the product was obtained by vacuum distillation and drying to obtain long-chain epoxy quaternary ammonium salt. 100 g of montmorillonite was dispersed in deionized water, and 30 g of long-chain epoxy quaternary ammonium salt was added. The product was reacted at 60°C for 3 hours, and the product was obtained by filtration, washing, and drying to obtain the epoxy quaternary ammonium salt modified montmorillonite. S2. Preparation of high-barrier antibacterial biodegradable masterbatch: 60 parts of poly(butylene adipate / terephthalate), 20 parts of polylactic acid, 20 parts of polypropylene carbonate were used as composite biodegradable materials, and 3 parts of epoxy quaternary ammonium salt modified montmorillonite obtained in step (1) were mixed evenly in a high-speed mixer. Then, the mixture was compounded, granulated, water-cooled, and pelletized by a twin-screw extruder to obtain the high-barrier antibacterial biodegradable masterbatch. The operating parameters of the twin-screw extruder were as follows: the temperatures of zones 1 to 7 were 135℃, 145℃, 150℃, 155℃, 155℃, 160℃, and 160℃, respectively, and the rotation speed was 270 rpm. S3. Preparation of high-barrier antibacterial biodegradable film: The masterbatch obtained in step (2) is dried and then blown into a film by a single-screw extrusion blown film machine to obtain the high-barrier antibacterial biodegradable film; The working parameters of the single-screw extrusion blown film machine are: the temperatures of zones 1 to 4 are 145℃, 150℃, 150℃, and 150℃, respectively, and the rotation speed is 50rpm.

[0030] Example 2 This embodiment proposes another method for preparing a barrier antibacterial biodegradable film. The specific steps required for its preparation are basically the same as those in Example 1, but the specific raw materials and related parameters used are different.

[0031] Specifically, the preparation steps are as follows: S1. Preparation of epoxy quaternary ammonium salt modified montmorillonite: 0.1 mol palmitamide propyl dimethylamine was dissolved in ethanol, heated to 50°C, and 0.1 mol epichlorohydrin was added dropwise. The reaction was carried out for 8 hours, and the product was obtained by vacuum distillation and drying to obtain long-chain epoxy quaternary ammonium salt. 100 g of montmorillonite was dispersed in deionized water, and 20 g of long-chain epoxy quaternary ammonium salt was added. The product was reacted at 50°C for 5 hours, and the product was obtained by filtration, washing, and drying to obtain the epoxy quaternary ammonium salt modified montmorillonite. S2. Preparation of high-barrier antibacterial biodegradable masterbatch: 70 parts of poly(butylene adipate / terephthalate), 20 parts of polylactic acid, 10 parts of polypropylene carbonate were used as composite biodegradable materials, and 4 parts of epoxy quaternary ammonium salt modified montmorillonite obtained in step (1) were mixed evenly in a high-speed mixer. Then, the mixture was compounded, granulated, water-cooled, and pelletized by a twin-screw extruder to obtain the high-barrier antibacterial biodegradable masterbatch. The operating parameters of the twin-screw extruder were as follows: the temperatures of zones 1 to 7 were 135℃, 145℃, 150℃, 155℃, 155℃, 160℃, and 160℃, respectively, and the rotation speed was 270 rpm. S3. Preparation of high-barrier antibacterial biodegradable film: The masterbatch obtained in step (2) is dried and then blown into a film by a single-screw extrusion blown film machine to obtain the high-barrier antibacterial biodegradable film; The working parameters of the single-screw extrusion blown film machine are: the temperatures of zones 1 to 4 are 145℃, 150℃, 150℃, and 150℃, respectively, and the rotation speed is 50rpm.

[0032] Example 3 This embodiment proposes another method for preparing a barrier antibacterial biodegradable film. The specific steps required for its preparation are basically the same as those in Example 1, but the specific raw materials and related parameters used are different.

[0033] Specifically, the preparation steps are as follows: S1. Preparation of epoxy quaternary ammonium salt modified montmorillonite: 0.1 mol lauramidopropyl dimethylamine was dissolved in ethanol, heated to 70°C, and 0.1 mol epichlorohydrin was added dropwise. The reaction was carried out for 4 hours, and the product was obtained by vacuum distillation and drying to obtain long-chain epoxy quaternary ammonium salt. 100 g of montmorillonite was dispersed in deionized water, and 40 g of long-chain epoxy quaternary ammonium salt was added. The product was reacted at 70°C for 3 hours, and the product was obtained by filtration, washing, and drying to obtain the epoxy quaternary ammonium salt modified montmorillonite. S2. Preparation of high-barrier antibacterial biodegradable masterbatch: 80 parts of poly(butylene adipate / terephthalate), 10 parts of polylactic acid, 10 parts of polypropylene carbonate as composite biodegradable materials, and 5 parts of epoxy quaternary ammonium salt modified montmorillonite obtained in step (1) are mixed evenly in a high-speed mixer, and then the mixture is compounded, granulated, water-cooled and pelletized by a twin-screw extruder to obtain the high-barrier antibacterial biodegradable masterbatch; the working parameters of the twin-screw extruder are: the temperatures of zones 1 to 7 are 135℃, 145℃, 150℃, 155℃, 155℃, 160℃ and 160℃ respectively, and the rotation speed is 270 rpm; S3. Preparation of high-barrier antibacterial biodegradable film: The masterbatch obtained in step (2) is dried and then blown into a film by a single-screw extrusion blown film machine to obtain the high-barrier antibacterial biodegradable film; The working parameters of the single-screw extrusion blown film machine are: the temperatures of zones 1 to 4 are 145℃, 150℃, 150℃, and 150℃, respectively, and the rotation speed is 50rpm.

[0034] Example 4 This embodiment proposes another method for preparing a barrier antibacterial biodegradable film. The specific steps required for its preparation are basically the same as those in Example 1, but the specific raw materials and related parameters used are different.

[0035] Specifically, the preparation steps are as follows: S1. Preparation of epoxy quaternary ammonium salt modified montmorillonite: 0.1 mol lauramidopropyl dimethylamine was dissolved in ethanol, heated to 60℃, and 0.1 mol epichlorohydrin was added dropwise. The reaction was carried out for 5 h, and the product was obtained by vacuum distillation and drying to obtain long-chain epoxy quaternary ammonium salt. 100 g of montmorillonite was dispersed in deionized water, and 50 g of long-chain epoxy quaternary ammonium salt was added. The product was reacted at 65℃ for 4 h, and the product was obtained by filtration, washing, and drying to obtain the epoxy quaternary ammonium salt modified montmorillonite. S2. Preparation of high-barrier antibacterial biodegradable masterbatch: 70 parts of poly(butylene adipate / terephthalate), 15 parts of polylactic acid, 15 parts of polypropylene carbonate were used as composite biodegradable materials, and 2 parts of epoxy quaternary ammonium salt modified montmorillonite obtained in step (1) were mixed evenly in a high-speed mixer. Then, the mixture was compounded, granulated, water-cooled, and pelletized by a twin-screw extruder to obtain the high-barrier antibacterial biodegradable masterbatch. The operating parameters of the twin-screw extruder were as follows: the temperatures of zones 1 to 7 were 135℃, 145℃, 150℃, 155℃, 155℃, 160℃, and 160℃, respectively, and the rotation speed was 270 rpm. S3. Preparation of high-barrier antibacterial biodegradable film: The masterbatch obtained in step (2) is dried and then blown into a film by a single-screw extrusion blown film machine to obtain the high-barrier antibacterial biodegradable film; The working parameters of the single-screw extrusion blown film machine are: the temperatures of zones 1 to 4 are 145℃, 150℃, 150℃, and 150℃, respectively, and the rotation speed is 50rpm.

[0036] For comparison purposes, this invention also provides five comparative examples for specific comparison.

[0037] Comparative Example 1 This comparative example provides a method for preparing a barrier biodegradable film. S1. Preparation of the barrier biodegradable masterbatch: 60 parts of poly(butylene adipate / terephthalate), 20 parts of polylactic acid, and 20 parts of polypropylene carbonate were used as composite biodegradable materials, and 3 parts of montmorillonite were mixed evenly in a high-speed mixer. Then, the mixture was compounded, granulated, water-cooled, and pelletized through a twin-screw extruder to obtain the barrier biodegradable masterbatch. The operating parameters of the twin-screw extruder were as follows: the temperatures of zones 1 to 7 were 135℃, 145℃, 150℃, 155℃, 155℃, 160℃, and 160℃, respectively, and the rotation speed was 270 rpm. S2. Preparation of the barrier biodegradable film: The masterbatch obtained in step (1) is dried and then blown into a film by a single screw extrusion blown film machine to obtain the barrier biodegradable film; The working parameters of the single screw extrusion blown film machine are: the temperatures of zones 1 to 4 are 145℃, 150℃, 150℃ and 150℃ respectively, and the rotation speed is 50rpm.

[0038] Comparative Example 2 This comparative example provides a method for preparing a barrier biodegradable film. S1. Preparation of the barrier biodegradable masterbatch: 70 parts of poly(butylene adipate / terephthalate), 20 parts of polylactic acid, 10 parts of polypropylene carbonate as composite biodegradable materials, and 4 parts of montmorillonite were mixed evenly in a high-speed mixer, and then the mixture was compounded, granulated, water-cooled, and pelletized through a twin-screw extruder to obtain the barrier biodegradable masterbatch; the operating parameters of the twin-screw extruder were: temperatures of zones 1 to 7 were 135℃, 145℃, 150℃, 155℃, 155℃, 160℃, and 160℃, respectively, and the rotation speed was 270 rpm; S2. Preparation of the barrier biodegradable film: The masterbatch obtained in step (1) is dried and then blown into a film by a single screw extrusion blown film machine to obtain the barrier biodegradable film; The working parameters of the single screw extrusion blown film machine are: the temperatures of zones 1 to 4 are 145℃, 150℃, 150℃ and 150℃ respectively, and the rotation speed is 50rpm.

[0039] Comparative Example 3 This comparative example provides a method for preparing a barrier biodegradable film. S1. Preparation of the barrier biodegradable masterbatch: 80 parts of poly(butylene adipate / terephthalate), 10 parts of polylactic acid, and 10 parts of polypropylene carbonate were used as composite biodegradable materials, and 5 parts of montmorillonite were mixed evenly in a high-speed mixer. Then, the mixture was compounded, granulated, water-cooled, and pelletized through a twin-screw extruder to obtain the barrier biodegradable masterbatch. The operating parameters of the twin-screw extruder were as follows: the temperatures of zones 1 to 7 were 135℃, 145℃, 150℃, 155℃, 155℃, 160℃, and 160℃, respectively, and the rotation speed was 270 rpm. S2. Preparation of the barrier biodegradable film: The masterbatch obtained in step (1) is dried and then blown into a film by a single screw extrusion blown film machine to obtain the barrier biodegradable film; The working parameters of the single screw extrusion blown film machine are: the temperatures of zones 1 to 4 are 145℃, 150℃, 150℃ and 150℃ respectively, and the rotation speed is 50rpm.

[0040] Comparative Example 4 This comparative example provides a method for preparing a barrier biodegradable film. S1. Preparation of the barrier biodegradable masterbatch: 70 parts of poly(butylene adipate / terephthalate), 15 parts of polylactic acid, 15 parts of polypropylene carbonate as composite biodegradable materials, and 2 parts of montmorillonite were mixed evenly in a high-speed mixer. Then, the mixture was compounded, granulated, water-cooled, and pelletized through a twin-screw extruder to obtain the barrier biodegradable masterbatch. The operating parameters of the twin-screw extruder were: temperatures of zones 1 to 7 were 135℃, 145℃, 150℃, 155℃, 155℃, 160℃, and 160℃, respectively, and the rotation speed was 270 rpm. S2. Preparation of the barrier biodegradable film: The masterbatch obtained in step (1) is dried and then blown into a film by a single screw extrusion blown film machine to obtain the barrier biodegradable film; The working parameters of the single screw extrusion blown film machine are: the temperatures of zones 1 to 4 are 145℃, 150℃, 150℃ and 150℃ respectively, and the rotation speed is 50rpm.

[0041] Comparative Example 5 This comparative example provides a method for preparing a biodegradable thin film. S1. Preparation of biodegradable masterbatch: 60 parts of poly(butylene adipate / terephthalate), 20 parts of polylactic acid, and 20 parts of polypropylene carbonate were used as composite biodegradable materials and mixed evenly in a high-speed mixer. Then, the mixture was compounded, granulated, water-cooled, and pelletized through a twin-screw extruder to obtain the biodegradable masterbatch. The operating parameters of the twin-screw extruder were as follows: the temperatures of zones 1 to 7 were 135℃, 145℃, 150℃, 155℃, 155℃, 160℃, and 160℃, respectively, and the rotation speed was 270 rpm. S2. Preparation of biodegradable film: The masterbatch obtained in step (1) is dried and then blown into a film by a single screw extrusion blown film machine to obtain the biodegradable film; The working parameters of the single screw extrusion blown film machine are: the temperatures of zones 1 to 4 are 145℃, 150℃, 150℃ and 150℃ respectively, and the rotation speed is 50rpm.

[0042] The biodegradable films of Examples 1-4 and Comparative Examples 1-5 were tested for gas barrier properties, antibacterial properties, and mechanical properties, respectively. The results are shown in Table 1. Table 1. Performance of the biodegradable films prepared in Examples 1-4 and Comparative Examples 1-5

[0043] As shown in Table 1, the water vapor transmission rate and oxygen transmission rate of the high-barrier antibacterial biodegradable films prepared in Examples 1-4 of this invention are significantly lower than those in Comparative Examples 1-5, indicating that the introduction of epoxy quaternary ammonium salt modified montmorillonite effectively improves the water vapor and oxygen barrier properties of the biodegradable films. Meanwhile, thanks to the antibacterial effect of the quaternary ammonium salt in the epoxy quaternary ammonium salt modified montmorillonite structure, the biodegradable films prepared in Examples 1-4 of this invention exhibit excellent antibacterial properties against both *Escherichia coli* and *Staphylococcus aureus*. Furthermore, unlike the decrease in mechanical properties of biodegradable films caused by the direct addition of montmorillonite, the epoxy groups in the epoxy quaternary ammonium salt modified montmorillonite structure of Examples 1-4 of this invention can undergo ring-opening reactions with the terminal carboxyl and hydroxyl groups in the biodegradable resin. Simultaneously, the amide groups form hydrogen bonds with the carbonyl groups in the molecular chain of the biodegradable material. These multiple forces, including reaction compatibilization and hydrogen bonding, effectively improve the interfacial compatibility between montmorillonite and the resin. Therefore, the mechanical properties of the high-barrier antibacterial biodegradable films prepared in Examples 1-5 are significantly better than those in Comparative Examples 1-5. It is evident that the high-barrier antibacterial biodegradable film provided by this invention has broad market application prospects and deserves vigorous promotion.

[0044] Specifically, existing technologies have consistently failed to simultaneously solve three core challenges: first, the compatibility issue between inorganic barrier fillers and biodegradable matrices, resulting in limited improvement in barrier performance and easy damage to mechanical properties; second, the synergistic achievement of antibacterial function with barrier and degradation performance, with existing solutions either lacking antibacterial properties or exhibiting unstable and short-lasting antibacterial effects; and third, the contradiction between process complexity and large-scale production, leading to either cumbersome and costly processes or incompatibility with existing industrial production systems. These technological bottlenecks prevent existing products from meeting the multiple demands of the high-end packaging sector for high barrier properties, long-lasting antibacterial effects, full biodegradability, and industrial feasibility. This invention can overcome these problems.

[0045] One of the core innovations of this invention lies in the modification design of montmorillonite. Sodium-based montmorillonite is organically modified by long-chain epoxy quaternary ammonium salts, achieving a three-in-one effect of "barrier enhancement, compatibility improvement, and antibacterial function conferment". This is a creative design that has not been achieved in the prior art. Specifically, long-chain epoxy quaternary ammonium salts are inserted into the interlayer of montmorillonite through cation exchange. On the one hand, this disrupts the hydrogen bonds between the montmorillonite layers, significantly increasing the interlayer spacing and making it easier for montmorillonite to be exfoliated and uniformly dispersed in a biodegradable matrix. This fully leverages the "multi-path effect" and "reduction of permeable area" of the layered structure, greatly improving its gas and water vapor barrier properties. On the other hand, the hydrophobic long-chain alkyl carbon chains in the long-chain epoxy quaternary ammonium salt molecules can replace the original hydrophilic cations in montmorillonite, thoroughly improving its hydrophilicity and significantly enhancing its interfacial compatibility with the hydrophobic biodegradable matrix material, thus avoiding the decline in mechanical properties caused by filler agglomeration. At the same time, the quaternary ammonium salt groups in the long-chain epoxy quaternary ammonium salt molecules are natural antibacterial active centers that can exert bactericidal effects by disrupting the bacterial cell membrane structure. Furthermore, because the quaternary ammonium salt groups are chemically bonded to the montmorillonite layers, they will not detach or migrate during use, giving the film durable and stable antibacterial properties. Furthermore, the epoxy groups in long-chain epoxy quaternary ammonium salt molecules are key reactive functional groups that can undergo ring-opening reactions with the terminal carboxyl and hydroxyl groups in the molecular chain of biodegradable materials during subsequent processing, forming stable chemical bonds. At the same time, the amide groups in the molecule can also form hydrogen bonds with the carbonyl groups in the molecular chain of biodegradable materials. Through the dual synergy of chemical bonding and hydrogen bonding, the interfacial bonding force between montmorillonite and the matrix material is further strengthened, thereby simultaneously improving the mechanical properties of the film.

[0046] Another inventive design of this invention lies in the optimized formulation of the composite biodegradable materials. Through the synergistic blending of three biodegradable materials, complementary and synergistic performance enhancements are achieved. Polybutylene adipate / terephthalate (PBAT) possesses excellent flexibility, processing fluidity, and biodegradability, providing the film with good molding and processing performance and flexibility. Polylactic acid (PLA) has high rigidity and mechanical strength, enhancing the structural stability and load-bearing capacity of the film. Polypropylene carbonate (PPC) exhibits relatively good gas barrier properties and transparency, further optimizing the barrier effect of the film. The specific ratio of these three materials not only compensates for the shortcomings of individual biodegradable materials, forming a balanced performance system of "flexibility-rigidity-barrier properties," but more importantly, the polarity and melting characteristics of this composite system are highly compatible with the structure of epoxy quaternary ammonium salt modified montmorillonite. This provides a favorable matrix environment for the uniform dispersion of modified montmorillonite, promoting interfacial interactions between modified montmorillonite and the matrix material, and achieving synergistic optimization of barrier properties, mechanical properties, and processing performance. This precise matching design of the composite matrix and the modified filler is an important guarantee for the simultaneous improvement of multiple properties in this invention.

[0047] This invention also demonstrates significant innovation in its process design, employing a two-step process of "twin-screw extrusion granulation - single-screw extrusion blown film," with precise optimization of equipment parameters. This approach is compatible with existing industrial production systems while fully leveraging the material's performance potential. The multi-segment gradient temperature control design of the twin-screw extruder enables gradual melting and full plasticization of the composite biodegradable material, preventing degradation caused by localized overheating. Simultaneously, the strong shearing action of the screw promotes further exfoliation and uniform dispersion of the epoxy quaternary ammonium salt modified montmorillonite, providing sufficient reaction conditions for the ring-opening reaction between the epoxy groups and the biodegradable material. The specific screw speed design balances the mixing effect and production efficiency, ensuring the compositional uniformity and performance stability of the masterbatch. The optimized temperature and speed parameters of the single-screw extrusion blown film machine precisely control the viscosity and flowability of the melt, ensuring a stable film forming process and preventing defects such as uneven film thickness, bubbles, and crystal points. It also ensures that the modified montmorillonite maintains a good orientation distribution in the film, further enhancing its barrier properties. The entire process is simple and efficient, requiring no additional special equipment, and is fully compatible with existing packaging film production lines, enabling direct large-scale production and solving the problems of complex processes, high costs, or difficulty in industrialization in existing technologies.

[0048] The inventiveness of this invention is also reflected in the synergistic achievement of multiple properties. Through the structural design of modified montmorillonite, the optimization of the composite biodegradable matrix ratio, and the precise matching of process parameters, multiple objectives of high barrier properties, long-lasting antibacterial effect, excellent mechanical properties, and full biodegradability are simultaneously achieved, solving the problem of mutual constraints and difficulty in achieving all properties in existing technologies. Specifically, the addition of modified montmorillonite not only improves barrier and antibacterial properties but also enhances mechanical properties through strengthened interfacial interactions; the synergistic effect of the composite biodegradable matrix ensures the full biodegradability of the material and provides a foundation for processing and performance; the process design ensures the full realization of the material's performance potential, achieving integrated innovation of "material design-process optimization-performance synergy". Compared with existing technologies, the film of this invention has significant improvements in gas barrier properties, antibacterial durability, and mechanical stability, and the process is simple, cost-controllable, and scalable, truly meeting the multiple needs of the high-end packaging field, and possessing outstanding technical advantages and market competitiveness.

[0049] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection for this invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of this invention, or any equivalent structural or procedural transformations made using the specifications of this invention, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection for this invention.

Claims

1. A method for preparing a high-barrier antibacterial biodegradable film, characterized in that, Includes the following steps: S1. Preparation of epoxy quaternary ammonium salt modified montmorillonite: Montmorillonite is dispersed in deionized water, long-chain epoxy quaternary ammonium salt is added, and after reaction, it is filtered, washed and dried to obtain the epoxy quaternary ammonium salt modified montmorillonite. S2. Preparation of high-barrier antibacterial biodegradable masterbatch: The composite biodegradable material and the epoxy quaternary ammonium salt modified montmorillonite obtained in S1 are mixed evenly in a high-speed mixer, and then the mixture is compounded, granulated, water-cooled and pelletized by a twin-screw extruder to obtain the high-barrier antibacterial biodegradable masterbatch. S3. Preparation of high-barrier antibacterial biodegradable film: The masterbatch obtained in S2 is dried and then blown into a film by a single-screw extrusion blown film machine to obtain the high-barrier antibacterial biodegradable film.

2. The method for preparing the high-barrier antibacterial biodegradable film according to claim 1, characterized in that: The preparation method of the long-chain epoxy quaternary ammonium salt in S1 is as follows: Long-chain ammonium amide propyl dimethylamine was dissolved in ethanol, heated to 50-70°C, and epichlorohydrin was added dropwise. The reaction was carried out for 4-8 hours, and the product was then obtained by vacuum distillation and drying. The long-chain amamidopropyl dimethylamine is any one of lauramidopropyl dimethylamine, myristamidopropyl dimethylamine, palmitamidopropyl dimethylamine, and stearamidopropyl dimethylamine; the molar ratio of long-chain amamidopropyl dimethylamine to epichlorohydrin is 1:

1.

3. The method for preparing the high-barrier antibacterial biodegradable film according to claim 1, characterized in that: The montmorillonite in S1 is sodium-based montmorillonite, and the mass ratio of sodium-based montmorillonite to long-chain epoxy quaternary ammonium salt is 10:(2-5).

4. The method for preparing the high-barrier antibacterial biodegradable film according to claim 1, characterized in that: The composite biodegradable material in S2 is a mixture of poly(dibutyl terephthalate), polylactic acid, and polypropylene carbonate in a mass ratio of (6-8):(1-2):(1-2).

5. The method for preparing the high-barrier antibacterial biodegradable film according to claim 1, characterized in that: The mass ratio of the composite biodegradable material and the epoxy quaternary ammonium salt modified montmorillonite in S2 is 100:(2-5).

6. The method for preparing the high-barrier antibacterial biodegradable film according to claim 1, characterized in that: The reaction temperature range in S1 is 50–80°C, and the reaction time range is 2–5 hours.

7. The method for preparing the high-barrier antibacterial biodegradable film according to claim 1, characterized in that: The twin-screw extruder in S2 includes seven temperature control zones, namely zone 1, zone 2, zone 3, zone 4, zone 5, zone 6, and zone 7. The temperatures of zones 1, 2, 3, 4, 5, 6, and 7 are 135°C, 145°C, 150°C, 155°C, 155°C, 160°C, and 160°C, respectively. The rotational speed of the twin-screw extruder is 270 rpm.

8. The method for preparing the high-barrier antibacterial biodegradable film according to claim 1, characterized in that: The single-screw extrusion blown film machine in S3 includes four temperature control zones, namely zone 1, zone 2, zone 3, and zone 4. The temperatures of zone 1, zone 2, zone 3, and zone 4 are 145°C, 150°C, 150°C, and 150°C, respectively. The rotation speed of the single-screw extrusion blown film machine is 270 rpm.

9. A high-barrier antibacterial biodegradable film, characterized in that: It is prepared by the method of any one of claims 1 to 8 for preparing a high-barrier antibacterial biodegradable film.

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