A high-barrier antibacterial packaging material, its preparation method, and packaging bag.

Abstract

This invention discloses a high-barrier antibacterial packaging material, its preparation method, and packaging bags, belonging to the field of packaging technology. The packaging material, by weight, comprises the following raw materials: 75-85 parts polylactic acid (PLA), 15-25 parts polybutylene succinate (PBS), 2-6 parts epoxidized urushiol, and 1-3 parts benzyl quaternary ammonium salt modified montmorillonite. The epoxidized urushiol is obtained by epoxidation of urushiol with organic peroxyacid. The raw materials also include 2-5 parts of sepiolite fiber-supported magnesium oxide. This invention uses biodegradable PLA and PBS as base materials and employs epoxidized urushiol as a reactive compatibilizer to improve the compatibility between PLA and PBS while strengthening the bonding between the polymer matrix and benzyl quaternary ammonium salt modified montmorillonite and sepiolite-supported magnesium oxide, thus obtaining a packaging material with good mechanical properties, barrier properties, and antibacterial properties.

Description

Technical Field

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

[0002] The development of the packaging industry has driven market demand for packaging materials, new technologies, and new processes, leading to the emergence of barrier packaging materials. Currently, barrier packaging materials are experiencing stable growth in the food industry, and demand is expected to continue to increase.

[0003] The main barrier packaging materials on the market include polyvinylidene chloride (PVDC) coated film, aluminized film, aluminum foil, nylon film, etc. These barrier packaging materials have many disadvantages: (1) PVDC coated film: requires special coating equipment, which increases the process and cost for downstream customers, and has low efficiency. The coating process generates a large amount of volatile organic compounds (VOCs). When the waste is burned, it will produce substances such as hydrogen chloride and dioxins that are toxic and harmful to the human body and the environment; (2) Aluminized film: the product is opaque, has poor folding resistance, and needs to be printed or heated. The use of adhesive coating composite for sealing substrate also presents VOC pollution problems; (3) Nylon film: The raw material cost is high, the product is easy to absorb moisture, and the barrier properties will be greatly reduced after absorbing moisture; During the printing and composite production process, due to the hygroscopicity of the film, a layer of fine water droplets forms on the surface, which blocks the adhesion of ink and adhesive, and will produce quality problems such as small bubbles or white spots; In addition, these packaging materials are not easy to biodegrade, which poses a problem of harming environmental health. Based on this, researchers focus on the development of biodegradable high barrier packaging materials.

[0004] Polylactic acid (PLA) is a biodegradable material whose products can be completely degraded into carbon dioxide and water through composting, achieving a virtuous cycle in nature. Therefore, research on PLA-based packaging materials is increasing. However, compared to high-barrier materials like nylon and polyvinylidene chloride, PLA has poor oxygen and water vapor barrier properties, limiting its effectiveness in preserving fruits and vegetables in practical applications. Specifically, when used for fruit and vegetable packaging, its excessively high oxygen permeation rate fails to effectively inhibit respiration, accelerating the metabolic spoilage process of the contents. Simultaneously, the material itself lacks antibacterial properties, making it difficult to inhibit microbial growth and reproduction. These dual technical bottlenecks further weaken the actual preservation effect of PLA packaging materials. Therefore, developing PLA-based composite packaging materials that combine high barrier properties with antibacterial functions is a key technological requirement for overcoming existing application limitations and expanding the market prospects of biodegradable materials. Summary of the Invention

[0005] The purpose of this invention is to provide a high-barrier antibacterial packaging material, its preparation method, and packaging bag, thereby solving the problems of poor barrier performance and lack of antibacterial properties of existing polylactic acid packaging materials.

[0006] In a first aspect, the present invention provides a high-barrier antibacterial packaging material, comprising the following raw materials by weight: 75-85 parts of polylactic acid, 15-25 parts of polybutylene succinate, 2-6 parts of epoxidized urushiol, and 1-3 parts of benzyl quaternary ammonium salt modified montmorillonite.

[0007] The epoxidized urushiol is prepared by epoxidation reaction of urushiol with organic peroxy acid.

[0008] The epoxidized urushiol has the following structural formula:

[0009] R is or or or .

[0010] The raw materials for preparing the benzyl quaternary ammonium salt modified montmorillonite include benzyl quaternary ammonium salt and sodium montmorillonite, with a mass ratio of benzyl quaternary ammonium salt to sodium montmorillonite of 1:0.5-1.

[0011] Polybutylene succinate (PBS) is an aliphatic polyester with full biodegradability. Compared with polylactic acid (PLA), it has better impact toughness, ductility, and heat resistance, but lower strength and modulus. Blending PBS and PLA can not only achieve complementary advantages in the properties of the two polymer materials but also fully retain the biodegradability of the material. However, the two are incompatible blending systems, resulting in poor toughening and modification effects and loss of PLA strength. Based on this, this invention uses epoxy urushiol as a reaction compatibilizer. During the melt blending process, the epoxy groups react with the terminal -OH / -COOH groups of PLA and PBS to generate graft copolymers distributed at the phase interface to improve the interfacial adhesion between the two. Epoxy urushiol is a small molecule with plasticizing effect, which can also improve the toughness of PLA. Epoxy urushiol carries catechol groups, which have good antibacterial properties and can give the packaging material good bactericidal properties.

[0012] Furthermore, this invention uses benzyl quaternary ammonium salt modified montmorillonite as a filler. The benzyl quaternary ammonium salt modification treatment firstly improves the agglomeration problem of montmorillonite, and secondly, utilizes the π-π interaction between benzyl and epoxidized urushiol to enhance the interfacial adhesion between montmorillonite and the polymer matrix, further strengthening the mechanical properties of the composite material. At the same time, the nanolayered structure of montmorillonite can also hinder the penetration of water molecules and oxygen, improving the gas barrier properties of the material, expanding the application potential of blended materials in packaging, biomedicine and other fields, and realizing that biodegradable materials can meet more practical needs while maintaining excellent comprehensive performance.

[0013] In a preferred embodiment, the benzyl quaternary ammonium salt is a C12 to C18 benzyl quaternary ammonium salt, specifically at least one of octadecyl dimethyl benzyl ammonium chloride, hexadecyl dimethyl benzyl ammonium chloride, tetradecyl dimethyl benzyl ammonium chloride, and dodecyl dimethyl benzyl ammonium chloride.

[0014] In a preferred embodiment, the method for preparing the epoxidized urushiol includes the following steps:

[0015] S1. Add urushiol, xylene, acetic anhydride and pyridine to the flask, stir well, heat to 90℃ and react for 1-2 hours. After the reaction is completed, add deionized water to adjust the pH to neutral, separate the oil phase, and evaporate under reduced pressure to remove pyridine and xylene to obtain acetylated urushiol.

[0016] S2. Add acetylated urushiol and formic acid to a flask, add hydrogen peroxide solution dropwise under an ice-water bath, and react at room temperature for 24 hours. After the reaction is complete, add deionized water to adjust to neutral, evaporate under reduced pressure to remove water, and obtain acetylated epoxy urushiol.

[0017] S3. Add acetylated epoxy urushiol to anhydrous ethanol, stir well, then add sodium hydroxide, and react at 40-50℃ for 0.5-1h. After the reaction is complete, add dilute hydrochloric acid to adjust the pH to 7, filter, and distill the filtrate under reduced pressure to remove ethanol and water, thus obtaining epoxy urushiol.

[0018] First, acetic anhydride is used to protect the phenolic hydroxyl groups in the urushiol molecule. Then, in a solution of formic acid and hydrogen peroxide, the unsaturated groups in the urushiol molecule chain are converted into epoxy groups. After deprotection treatment, epoxidized urushiol is obtained.

[0019] In a preferred embodiment, the mass ratio of urushiol, xylene, acetic anhydride and pyridine in S1 is 100:50 to 100:65.5:56.4 to 75.6.

[0020] In a preferred embodiment, the mass ratio of acetylated urushiol, formic acid and hydrogen peroxide solution in S2 is 10:28-29:39-41, and the mass fraction of hydrogen peroxide solution is 30%.

[0021] In a preferred embodiment, the mass ratio of acetylated epoxy urushiol, anhydrous ethanol and sodium hydroxide in S3 is 10:100:5.5-6.5, and the mass fraction of dilute hydrochloric acid is 5-15%.

[0022] In a preferred embodiment, the method for preparing the benzyl quaternary ammonium salt modified montmorillonite includes the following steps:

[0023] Sodium-based montmorillonite was ultrasonically dispersed in deionized water to obtain a suspension. Benzyl quaternary ammonium salt was added at 60–65 °C, and the mixture was stirred for 6–8 h. After the reaction was complete, the mixture was filtered, and the filter cake was washed with anhydrous ethanol until no chloride ions were detected (tested with 0.1 mol / L silver nitrate). The mixture was then vacuum dried to obtain benzyl quaternary ammonium salt modified montmorillonite.

[0024] Using benzyl quaternary ammonium salt as a modifier, benzyl groups are introduced into montmorillonite through ion exchange reaction, which increases the interlayer spacing of montmorillonite and enhances its affinity with the polymer matrix.

[0025] Secondly, the present invention provides a method for preparing the above-mentioned high-barrier antibacterial packaging material, comprising the following steps:

[0026] Weigh the raw materials according to the formula ratio, first dry polylactic acid and polybutylene succinate at 50-60℃ for 4-8 hours, then add them to the mixer and mix them evenly with epoxidized urushiol and benzyl quaternary ammonium salt modified montmorillonite. The mixture is then transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier antibacterial packaging material.

[0027] In a preferred embodiment, the raw materials of the high-barrier antibacterial packaging material further include 2-5 parts of sepiolite fiber-loaded magnesium oxide.

[0028] High-barrier packaging materials, due to their low gas permeability, prevent the timely release of moisture produced by respiration in fruits and vegetables during preservation. Excessive humidity in this environment promotes bacterial growth and accelerates spoilage. To address this, this invention introduces sepiolite fibers loaded with magnesium oxide into the high-barrier packaging material. Sepiolite fibers possess a rich porous structure and excellent adsorption properties, effectively absorbing water vapor and oxygen. This slows down the respiration of fruits and vegetables while reducing humidity. Magnesium oxide reacts with water vapor to form magnesium hydroxide, consuming water vapor and creating a "tunneling effect" to further enhance the material's barrier properties. Additionally, magnesium oxide can also react with oxygen... Peroxidation-reduction reactions produce peroxide ions, which can disrupt the peptide chains of bacterial cell membrane proteins, leading to microbial lysis and apoptosis, thereby exerting an antibacterial effect. This invention improves the aggregation of magnesium oxide particles in the polymer matrix through loading treatment, allowing magnesium oxide to fully exert its hygroscopic and antibacterial effects. In addition, magnesium oxide and epoxidized urushiol can undergo chelation (magnesium oxide and catechol groups), improving the interfacial adhesion between sepiolite fiber-loaded magnesium oxide and the polymer matrix. This allows sepiolite fiber-loaded magnesium oxide and benzyl quaternary ammonium salt-modified montmorillonite to form a network structure of different dimensions in the polymer groups, further enhancing the mechanical properties of the composite material.

[0029] In a preferred embodiment, the method for preparing the sepiolite fiber-supported magnesium oxide includes the following steps:

[0030] Sepiol fibers were added to hydrochloric acid solution, stirred evenly for 48 hours, filtered, and the filter cake was washed with deionized water until the washing liquid was neutral and dried to obtain acidified sepiolite fibers.

[0031] Magnesium nitrate hexahydrate was added to deionized water and stirred until homogeneous. Then, acidified sepiolite fibers were added. Under nitrogen protection, sodium hydroxide solution was added dropwise to adjust the pH to 11. After stirring for 3-5 hours, the mixture was filtered. The filter cake was washed with deionized water until the washing liquid was neutral. After drying, it was calcined at 350-450℃ for 2 hours and then ground through a 100-mesh sieve to obtain magnesium oxide supported on sepiolite fibers.

[0032] Using sepiolite fibers with a large specific surface area and porous structure as a carrier, magnesium hydroxide was anchored and loaded onto the surface of the sepiolite fibers by precipitation, and then calcined to obtain magnesium oxide loaded onto sepiolite fibers.

[0033] In a preferred embodiment, the ratio of sepiolite fiber to hydrochloric acid solution is 1g:15-20mL, and the concentration of hydrochloric acid solution is 0.5-0.7mol / L.

[0034] In a preferred embodiment, the mass ratio of magnesium nitrate hexahydrate to acidified sepiolite fiber is 0.4–0.8:1, and the sodium hydroxide solution concentration is 1 mol / L.

[0035] Secondly, the present invention provides a method for preparing the above-mentioned high-barrier antibacterial packaging material, which further includes the following steps:

[0036] Weigh the raw materials according to the formula ratio. First, dry polylactic acid and polybutylene succinate at 50-60℃ for 4-8 hours. Then, add them to the mixer and mix them evenly with epoxidized urushiol, benzyl quaternary ammonium salt modified montmorillonite, and sepiolite fiber loaded magnesium oxide. Transfer the mixture to a twin-screw extruder for shearing and granulation to obtain a high-barrier antibacterial packaging material.

[0037] In a preferred embodiment, the temperatures of zones one through seven of the twin-screw extruder are 135–140°C, 150–160°C, 160–165°C, 170°C, 165–170°C, 150–160°C, and 150–155°C, respectively, and the rotation speed is 30–50 r / min.

[0038] In a preferred embodiment, the raw materials of the high-barrier antibacterial packaging material further include 0.5-1 part antioxidant.

[0039] In a preferred embodiment, the raw materials of the high-barrier antibacterial packaging material further include 0.5-1.5 parts of lubricant.

[0040] In a preferred embodiment, the antioxidant is at least one of antioxidant 245, antioxidant 300, antioxidant 330, antioxidant 1010, antioxidant 168, antioxidant 264 and antioxidant 1098.

[0041] In a preferred embodiment, the lubricant is at least one of stearic acid, paraffin wax, and polyethylene wax.

[0042] Thirdly, the present invention provides a packaging bag, which is made from the above-mentioned packaging material through extrusion, blown film, and bag making processes.

[0043] In a preferred embodiment, the extrusion and blown film process uses a single-screw blown film machine. The heating temperatures of each section of the blown film machine from the feed inlet to the die are 130-135℃, 160℃, 165℃ and 140℃, respectively, and the screw speed is 30-45 r / min.

[0044] The beneficial effects of this invention are:

[0045] This invention provides a high-barrier antibacterial packaging material, its preparation method, and packaging bags. Using biodegradable polylactic acid (PLA) and polybutylene succinate (PBS) as base materials, and employing epoxidized urushiol as a reactive compatibilizer, the compatibility between PLA and PBS is improved. Simultaneously, the bonding between the polymer matrix and benzyl quaternary ammonium salt-modified montmorillonite (or sepiolite-loaded magnesium oxide) is strengthened, resulting in a packaging material with excellent mechanical properties, barrier properties, and antibacterial properties. The sepiolite-loaded magnesium oxide also exhibits good hygroscopic and antibacterial properties, absorbing and binding moisture to reduce environmental humidity, preventing condensation and helping to reduce microbial growth. Even if microorganisms do grow, they can be killed through redox reactions, thus extending the shelf life of the packaged goods. Detailed Implementation

[0046] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0047] It should be understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0048] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0049] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0050] In this application, the polylactic acid (PLA) is designated Ingeo2003D, with a weight-average molecular weight (Mw) of 1.8 × 10⁻⁶. 5 g / mol, melt flow rate (MFR) of 6 g / 10 min (210 °C, 2.16 kg), polybutylene succinate (PBS): brand name Bionalle 1020MD, MFR of 4.5 g / 10 min (190 °C, 2.16 kg), sodium montmorillonite (Na-MMT): brand name PGN, ion exchange capacity (CEC) of 100 meq / 100 g. Unless otherwise specified, other raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0051] The technical solution of this application will be illustrated below through specific embodiments and comparative examples.

[0052] Preparation Example 1

[0053] The preparation steps of epoxidized urushiol are as follows:

[0054] S1. Add 100g urushiol, 50g xylene, 65.5g acetic anhydride and 56.4g pyridine to a flask, stir for 15min, heat to 90℃ and react for 1h. After the reaction is complete, add deionized water to adjust the pH to neutral, separate the oil phase, evaporate under reduced pressure to remove pyridine, and obtain acetylated urushiol.

[0055] S2. Add 10g of acetylated urushiol and 28g of formic acid to a flask, add 39g of 30% hydrogen peroxide solution dropwise under an ice-water bath, react at room temperature for 24h, after the reaction is complete, add deionized water to adjust to neutral, evaporate under reduced pressure to remove water, and obtain acetylated epoxy urushiol.

[0056] S3. Add 10g of acetylated epoxy urushiol to 100g of anhydrous ethanol, stir well, then add 5.5g of sodium hydroxide, react at 40℃ for 0.5h. After the reaction is complete, add 5% by mass dilute hydrochloric acid to adjust the pH to 7, filter, and distill the filtrate under reduced pressure to remove ethanol and water, to obtain epoxy urushiol.

[0057] Preparation Example 2

[0058] The preparation steps of epoxidized urushiol are as follows:

[0059] S1. Add 100g urushiol, 80g xylene, 65.5g acetic anhydride and 65.6g pyridine to a flask, stir for 18min, heat to 90℃ and react for 1.5h. After the reaction is complete, add deionized water to adjust the pH to neutral, separate the oil phase, evaporate under reduced pressure to remove pyridine, and obtain acetylated urushiol.

[0060] S2. Add 10g of acetylated urushiol and 28.5g of formic acid to a flask, add 40g of 30% hydrogen peroxide solution dropwise under an ice-water bath, react at room temperature for 24h, after the reaction is complete, add deionized water to adjust to neutral, evaporate under reduced pressure to remove water, and obtain acetylated epoxy urushiol.

[0061] S3. Add 10g of acetylated epoxy urushiol to 100g of anhydrous ethanol, stir well, then add 6g of sodium hydroxide, react at 45℃ for 0.8h. After the reaction is complete, add 10% dilute hydrochloric acid to adjust the pH to 7, filter, and distill the filtrate under reduced pressure to remove ethanol and water, to obtain epoxy urushiol.

[0062] Preparation Example 3

[0063] The preparation of magnesium oxide supported on sepiolite fibers is as follows:

[0064] 20g of sepiolite fiber was added to 350mL of 0.6mol / L hydrochloric acid solution, stirred evenly for 48h, then filtered, the filter cake was washed with deionized water until the washing liquid was neutral, and dried to obtain acidified sepiolite fiber.

[0065] Add 4g of magnesium nitrate hexahydrate to 100mL of deionized water, stir well, then add 10g of acidified sepiolite fiber. Under nitrogen protection, add 1mol / L sodium hydroxide solution to adjust the pH to 11. After stirring for 3h, filter, wash the filter cake with deionized water until the washing liquid is neutral, dry, then calcine at 350℃ for 2h, grind through a 100-mesh sieve to obtain magnesium oxide supported on sepiolite fiber.

[0066] Preparation Example 4

[0067] The preparation of magnesium oxide supported on sepiolite fibers is as follows:

[0068] 20g of sepiolite fiber was added to 350mL of 0.6mol / L hydrochloric acid solution, stirred evenly for 48h, then filtered, the filter cake was washed with deionized water until the washing liquid was neutral, and dried to obtain acidified sepiolite fiber.

[0069] Add 6g of magnesium nitrate hexahydrate to 100mL of deionized water, stir well, then add 10g of acidified sepiolite fiber. Under nitrogen protection, add 1mol / L sodium hydroxide solution to adjust the pH to 11. After stirring for 4h, filter the mixture. Wash the filter cake with deionized water until the washing liquid is neutral, dry it, and then calcine it at 400℃ for 2h. Grind it through a 100-mesh sieve to obtain magnesium oxide supported on sepiolite fiber.

[0070] Preparation Example 5

[0071] The preparation of magnesium oxide supported on sepiolite fibers is as follows:

[0072] 20g of sepiolite fiber was added to 400mL of 0.7mol / L hydrochloric acid solution, stirred evenly for 48h, then filtered, the filter cake was washed with deionized water until the washing liquid was neutral, and dried to obtain acidified sepiolite fiber.

[0073] Add 8g of magnesium nitrate hexahydrate to 100mL of deionized water, stir well, then add 10g of acidified sepiolite fiber. Under nitrogen protection, add 1mol / L sodium hydroxide solution to adjust the pH to 11. After stirring for 5h, filter, wash the filter cake with deionized water until the washing liquid is neutral, dry, then calcine at 450℃ for 2h, grind through a 100-mesh sieve to obtain magnesium oxide supported on sepiolite fiber.

[0074] Example 1

[0075] A high-barrier antibacterial packaging material, by weight, comprises the following raw materials: 75 parts polylactic acid, 25 parts polybutylene succinate, 2 parts epoxidized urushiol of Preparation Example 1, 1 part benzyl quaternary ammonium salt modified montmorillonite, 0.5 parts antioxidant 245, and 0.5 parts stearic acid.

[0076] The preparation method of the benzyl quaternary ammonium salt modified montmorillonite includes the following steps:

[0077] 5g of sodium montmorillonite was ultrasonically dispersed in 100mL of deionized water to obtain a suspension. 2.5g of dodecyl dimethyl benzyl ammonium chloride was added at 65℃ and the mixture was stirred for 6h. After the reaction was completed, the mixture was filtered and the filter cake was washed with anhydrous ethanol until no chloride ions were detected (tested with 0.1mol / L silver nitrate). The mixture was then vacuum dried to obtain benzyl quaternary ammonium salt modified montmorillonite.

[0078] The preparation method of the above-mentioned high-barrier antibacterial packaging material includes the following steps:

[0079] Weigh the raw materials according to the formula ratio, first dry polylactic acid and polybutylene succinate at 50℃ for 8 hours, then add them to the mixer and mix them evenly with epoxidized urushiol, benzyl quaternary ammonium salt modified montmorillonite, antioxidant 245 and stearic acid. The mixture is then transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier antibacterial packaging material.

[0080] The temperatures of zones one through seven of the twin-screw extruder are 135℃, 150℃, 160℃, 170℃, 165℃, 150℃, and 150℃, respectively, and the rotation speed is 30 r / min.

[0081] Example 2

[0082] A high-barrier antibacterial packaging material, by weight, comprises the following raw materials: 80 parts polylactic acid, 20 parts polybutylene succinate, 4 parts epoxidized urushiol of Preparation Example 2, 2 parts benzyl quaternary ammonium salt modified montmorillonite, 0.8 parts antioxidant 245, and 1.0 part stearic acid.

[0083] The preparation method of the benzyl quaternary ammonium salt modified montmorillonite includes the following steps:

[0084] 5g of sodium montmorillonite was ultrasonically dispersed in 300mL of deionized water to obtain a suspension. 3.5g of tetradecyl dimethyl benzyl ammonium chloride was added at 65℃ and the mixture was stirred for 7h. After the reaction was completed, the mixture was filtered and the filter cake was washed with anhydrous ethanol until no chloride ions were detected (tested with 0.1mol / L silver nitrate). The mixture was then vacuum dried to obtain benzyl quaternary ammonium salt modified montmorillonite.

[0085] The preparation method of the above-mentioned high-barrier antibacterial packaging material is the same as that in Example 1.

[0086] Example 3

[0087] A high-barrier antibacterial packaging material, by weight, comprises the following raw materials: 85 parts polylactic acid, 15 parts polybutylene succinate, 6 parts of epoxidized urushiol from Preparation Example 2, 3 parts benzyl quaternary ammonium salt modified montmorillonite, 1 part antioxidant 330, and 1.5 parts polyethylene wax.

[0088] The preparation method of the benzyl quaternary ammonium salt modified montmorillonite includes the following steps:

[0089] 5g of sodium montmorillonite was ultrasonically dispersed in 500mL of deionized water to obtain a suspension. 5g of hexadecyl dimethyl benzyl ammonium chloride was added at 65℃ and the mixture was stirred for 8h. After the reaction was completed, the mixture was filtered, and the filter cake was washed with anhydrous ethanol until no chloride ions were detected (tested with 0.1mol / L silver nitrate). The mixture was then vacuum dried to obtain benzyl quaternary ammonium salt modified montmorillonite.

[0090] The preparation method of the above-mentioned high-barrier antibacterial packaging material includes the following steps:

[0091] Weigh the raw materials according to the formula ratio, first dry polylactic acid and polybutylene succinate at 60℃ for 8 hours, then add them to the mixer and mix them evenly with epoxidized urushiol, benzyl quaternary ammonium salt modified montmorillonite, antioxidant 330 and polyethylene wax. The mixture is then transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier antibacterial packaging material.

[0092] The temperatures of zones one through seven of the twin-screw extruder are 140℃, 160℃, 165℃, 170℃, 170℃, 160℃, and 155℃, respectively, and the rotation speed is 50 r / min.

[0093] Example 4

[0094] A high-barrier antibacterial packaging material, compared with Example 3, differs only in that the raw materials of the high-barrier antibacterial packaging material in this example also include 2 parts by weight of the sepiolite fiber-loaded magnesium oxide prepared in Example 3.

[0095] The method for preparing the high-barrier antibacterial packaging material in this embodiment includes the following steps:

[0096] The raw materials were weighed according to the formula ratio. Polylactic acid and polybutylene succinate were dried at 60°C for 4 hours. Then they were added to a mixer and mixed evenly with epoxidized urushiol, benzyl quaternary ammonium salt modified montmorillonite, sepiolite fiber loaded magnesium oxide, antioxidant 330 and polyethylene wax. The mixture was transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier antibacterial packaging material.

[0097] The temperatures of zones one through seven of the twin-screw extruder are 140℃, 160℃, 165℃, 170℃, 170℃, 160℃, and 155℃, respectively, and the rotation speed is 50 r / min.

[0098] Example 5

[0099] A high-barrier antibacterial packaging material, compared with Example 4, differs only in that the sepiolite fiber loaded with magnesium oxide has a weight ratio of 3.5.

[0100] Example 6

[0101] A high-barrier antibacterial packaging material, compared with Example 4, differs only in that the sepiolite fiber loaded with magnesium oxide has a weight of 5 parts.

[0102] Example 7

[0103] A high-barrier antibacterial packaging material, compared with Example 5, differs only in that the sepiolite fiber-loaded magnesium oxide in Example 5 is replaced with an equal weight of the product obtained in Preparation Example 4.

[0104] Example 8

[0105] A high-barrier antibacterial packaging material, which differs from Example 5 only in that the sepiolite fiber-loaded magnesium oxide in Example 5 is replaced with an equal weight of the product obtained in Preparation Example 5.

[0106] Comparative Example 1

[0107] A high-barrier antibacterial packaging material, compared with Example 1, differs only in that dodecyl dimethyl benzyl ammonium chloride is replaced with an equal mass of dodecyl trimethyl ammonium chloride in Example 1.

[0108] Comparative Example 2

[0109] A high-barrier antibacterial packaging material, compared with Example 1, differs only in that the epoxy urushiol in Example 1 is replaced with an equal part by weight of chain extender ADR-4370F.

[0110] Comparative Example 3

[0111] A high-barrier antibacterial packaging material, compared with Example 6, differs only in that the magnesium oxide loaded with sepiolite fiber in Example 6 is replaced with an equal mass of the product obtained by physically mixing acidified sepiolite fiber and magnesium oxide at a mass ratio of 10:1.26, and the mixture is stirred in a mixer at 100 r / min for 20 min. The preparation process of acidified sepiolite fiber is the same as that of Preparation Example 5.

[0112] The high-barrier antibacterial packaging materials of Examples 1-8 and Comparative Examples 1-3 were prepared into dumbbell-shaped specimens. According to GB / T1040.1-2018, the tensile properties of the dumbbell-shaped specimens of each group of packaging materials were determined by a universal testing machine at 25°C and 55% relative humidity. The tensile speed was 200 mm / s. Each test was performed 5 times and the average value was taken.

[0113] The high-barrier antibacterial packaging materials from Examples 1-8 and Comparative Examples 1-3 were subjected to a blow molding-stretching process using a single-screw blown film extrusion machine. The heating temperatures of each section of the blown film extrusion machine from the feed inlet to the die were 135°C, 160°C, 165°C, and 140°C, respectively. The screw speed was 30 r / min, and the traction speed was 7 m / min. The resulting film materials were then tested for water vapor barrier properties, antibacterial properties, and freshness preservation properties.

[0114] (1) Water vapor barrier performance test:

[0115] According to GB / T1037-2021, the water vapor barrier properties of thin films were determined by the evaporation method. The thickness of the thin film was controlled at (10±1) μm, the test temperature was 23℃±0.5℃, and the relative humidity was 90%±2%.

[0116] (2) Antibacterial performance analysis: The method for detecting the antibacterial rate is in accordance with QB / T2591-2003 "Antibacterial Plastics - Test Methods for Antibacterial Performance and Antibacterial Effect". Each sample is tested 10 times and the average value is taken.

[0117] (3) Preservation performance analysis: Fresh cherries were purchased from the supermarket, divided into equal portions, and placed in the preservation film prepared by each group of packaging materials. After sealing, the cherries were stored in a refrigerator at 4°C. After 15 days, the good fruit rate was calculated and the preservation effect was evaluated.

[0118] The test results are shown in Table 1:

[0119]

[0120] Analysis of the data recorded in Table 1 shows that the tensile strength of the packaging material in Example 3 is slightly lower than that in Example 2, but the water vapor transmission rate is significantly lower than that in Example 2, and the antibacterial effect is also significantly higher than that in Example 2. Therefore, among the packaging materials obtained in Examples 1-3, Example 3 has the best overall effect.

[0121] Analysis of the test results of Examples 3, 4, 5, and 6 shows that, based on the formulation of Example 3, the introduction of sepiolite fiber loaded with magnesium oxide can enhance the mechanical properties, barrier properties, and antibacterial properties of the packaging material. Among them, Example 5 has the best effect because an appropriate amount of sepiolite fiber loaded with magnesium oxide can adsorb water vapor and oxygen, and at the same time, it can form a "tunneling effect" with the help of magnesium hydroxide, thereby improving the barrier properties of the material. In addition, magnesium oxide can also produce peroxide ions through redox reaction with oxygen. Peroxide ions can destroy the protein peptide chains of bacterial cell membrane walls, leading to microbial lysis and apoptosis, thereby exerting an antibacterial effect.

[0122] Analysis of the test results of Examples 5, 7, and 8 shows that the packaging materials prepared using the sepiolite fibers loaded with magnesium oxide obtained in Preparation Examples 3, 4, and 5 have very little difference in performance.

[0123] Analysis of the test results of Example 1 and Comparative Example 1 shows that when modified montmorillonite is prepared by replacing benzyl quaternary ammonium salt with conventional quaternary ammonium salt, due to the lack of benzene ring, the modified montmorillonite and epoxidized urushiol cannot form π-π interaction, resulting in a significant deterioration in the mechanical properties and barrier properties of the packaging material. The antibacterial properties do not change significantly, but the final preservation effect is worse.

[0124] Analysis of the test results of Example 1 and Comparative Example 2 shows that when commercially available chain extenders are used to replace epoxidized urushiol in Example 1, the antibacterial properties of the resulting packaging material are significantly reduced due to the lack of antibacterial agents.

[0125] Analysis of the test results of Example 6 and Comparative Example 3 shows that, compared with the physical mixture of magnesium oxide and sepiolite fiber, the packaging material obtained by loading magnesium oxide with sepiolite fiber has better mechanical properties, barrier properties and antibacterial properties.

[0126] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0127] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-barrier antibacterial packaging material, characterized in that, By weight, it includes the following raw materials: 75-85 parts polylactic acid, 15-25 parts polybutylene succinate, 2-6 parts epoxidized urushiol, and 1-3 parts benzyl quaternary ammonium salt modified montmorillonite. The epoxidized urushiol is prepared by epoxidation reaction of urushiol and organic peroxy acid; The method for preparing the epoxidized urushiol includes the following steps: S1. Add urushiol, xylene, acetic anhydride and pyridine to the flask, stir well, heat to 90℃ and react for 1-2 hours. After the reaction is completed, add deionized water to adjust the pH to neutral, separate the oil phase, and evaporate under reduced pressure to remove pyridine and xylene to obtain acetylated urushiol. S2. Add acetylated urushiol and formic acid to a flask, add hydrogen peroxide solution dropwise under an ice-water bath, and react at room temperature for 24 hours. After the reaction is complete, add deionized water to adjust to neutral, evaporate under reduced pressure to remove water, and obtain acetylated epoxy urushiol. S3. Add acetylated epoxy urushiol to anhydrous ethanol, stir well, then add sodium hydroxide, and react at 40-50℃ for 0.5-1h. After the reaction is complete, add dilute hydrochloric acid to adjust the pH to 7, filter, and distill the filtrate under reduced pressure to remove ethanol and water to obtain epoxy urushiol. The raw materials for the high-barrier antibacterial packaging material also include 2-5 parts of sepiolite fiber-loaded magnesium oxide.

2. The high-barrier antibacterial packaging material according to claim 1, characterized in that, The raw materials for preparing the benzyl quaternary ammonium salt modified montmorillonite include benzyl quaternary ammonium salt and sodium montmorillonite, with a mass ratio of benzyl quaternary ammonium salt to sodium montmorillonite of 1:0.5-1.

3. The high-barrier antibacterial packaging material according to claim 2, characterized in that, The benzyl quaternary ammonium salt is at least one of octadecyl dimethyl benzyl ammonium chloride, hexadecyl dimethyl benzyl ammonium chloride, tetradecyl dimethyl benzyl ammonium chloride, and dodecyl dimethyl benzyl ammonium chloride.

4. The high-barrier antibacterial packaging material according to claim 1, characterized in that, The method for preparing the sepiolite fiber-supported magnesium oxide includes the following steps: Sepiol fibers were added to hydrochloric acid solution, stirred evenly for 48 hours, filtered, and the filter cake was washed with deionized water until the washing liquid was neutral and dried to obtain acidified sepiolite fibers. Magnesium nitrate hexahydrate was added to deionized water and stirred until homogeneous. Then, acidified sepiolite fibers were added. Under nitrogen protection, sodium hydroxide solution was added dropwise to adjust the pH to 11. After stirring for 3-5 hours, the mixture was filtered. The filter cake was washed with deionized water until the washing liquid was neutral. After drying, the cake was calcined at 350-450℃ for 2 hours and then ground through a 100-mesh sieve to obtain magnesium oxide supported on sepiolite fibers.

5. The high-barrier antibacterial packaging material according to claim 4, characterized in that, The ratio of sepiolite fiber to hydrochloric acid solution is 1g:15-20mL, and the concentration of hydrochloric acid solution is 0.5-0.7mol / L.

6. The high-barrier antibacterial packaging material according to claim 4, characterized in that, The mass ratio of magnesium nitrate hexahydrate to acidified sepiolite fiber is 0.4–0.8:

1.

7. A method for preparing a high-barrier antibacterial packaging material, characterized in that, The preparation of the high-barrier antibacterial packaging material according to any one of claims 1-6 includes the following steps: Weigh the raw materials according to the formula ratio. First, dry polylactic acid and polybutylene succinate at 50-60℃ for 4-8 hours. Then, add them to the mixer and mix them evenly with epoxidized urushiol, benzyl quaternary ammonium salt modified montmorillonite, and sepiolite fiber loaded magnesium oxide. Transfer the mixture to a twin-screw extruder for shearing and granulation to obtain a high-barrier antibacterial packaging material.

8. A packaging bag, characterized in that, It is prepared from the packaging material described in any one of claims 1-6.

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