High-barrier antibacterial packaging material, preparation method thereof and packaging bag

Abstract

The invention discloses a high-barrier antibacterial packaging material, a preparation method thereof and a packaging bag, and belongs to the technical field of packaging, the packaging material comprises the following raw materials by weight: 75-85 parts of polylactic acid, 15-25 parts of poly (butylene succinate), 2-6 parts of epoxidized urushiol, and 1-3 parts of benzyl quaternary ammonium salt modified montmorillonite; the epoxidized urushiol is prepared by carrying out epoxidation reaction on urushiol and organic peroxy acid; the packaging material further comprises the following raw materials: 2-5 parts of sepiolite fiber loaded magnesium oxide; according to the invention, biodegradable polylactic acid and poly (butylene succinate) are taken as base materials, and epoxidized urushiol is taken as a reactive compatilizer, so that the compatibility between polylactic acid and poly (butylene succinate) is improved, and meanwhile, the binding property between a polymer matrix and benzyl quaternary ammonium salt modified montmorillonite and sepiolite loaded magnesium oxide is enhanced; the packaging material with good mechanical property, barrier property and antibacterial property is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of packaging, and in particular relates to a high-barrier antibacterial packaging material, a preparation method thereof, and a packaging bag. Background Art

[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 steady growth in the food industry, and demand is expected to continue to grow.

[0003] The barrier packaging materials on the market mainly include polyvinylidene chloride (PVDC) coating film, aluminized film, aluminum foil, nylon film, etc. These barrier packaging materials have many disadvantages: (1) PVDC coating film: requires special coating equipment, which increases the use process and cost of downstream customers, and has low efficiency. The coating process will produce 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 and has poor folding resistance, and needs to be printed or hot-dip printed. The use of sealing substrates by coating and laminating also has the problem of VOC pollution; (3) Nylon film: the raw material cost is relatively high, the product is easy to absorb moisture, and the barrier properties will be greatly reduced after moisture absorption; during the printing and laminating production process, due to the hygroscopicity of the film, a layer of fine water droplets will form on the surface, blocking the adhesion of ink and adhesive, and causing quality problems such as small bubbles or white spots; In addition, these packaging materials are not easy to biodegrade and pose a risk to environmental health. Based on this, R&D personnel will focus on the development of degradable high-barrier packaging materials.

[0004] Polylactic acid (PLA) is a biodegradable material. Its products can be completely degraded into carbon dioxide and water through composting, achieving a virtuous cycle in nature. Consequently, research on PLA-based packaging materials is increasing. However, compared with high-barrier nylon, polyvinylidene chloride, etc., PLA has poor oxygen and water vapor barrier properties, resulting in limited preservation effects on fruits and vegetables in practical applications. Specifically, when used for fruit and vegetable packaging, its excessively high oxygen permeability makes it impossible to effectively inhibit respiration, accelerating the metabolic spoilage process of the contents. At the same time, the material itself lacks antibacterial properties, making it difficult to block the growth and reproduction of microorganisms. These two technical bottlenecks further weaken the actual preservation effect of PLA packaging materials. Therefore, the development of PLA-based composite packaging materials with both high barrier properties and antibacterial functions is a key technical requirement to overcome the limitations of existing applications and expand the market prospects of biodegradable materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a high barrier and antibacterial packaging material, a preparation method thereof, and a packaging bag, so as to solve the problems of poor barrier properties 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, which comprises the following components in parts 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 and an organic peracid.

[0008] The epoxidized urushiol structural formula is as follows: ; R is or or or .

[0009] The raw materials for preparing the benzyl quaternary ammonium salt modified montmorillonite include benzyl quaternary ammonium salt and sodium montmorillonite, and the mass ratio of benzyl quaternary ammonium salt to sodium montmorillonite is 1:0.5-1.

[0010] Polybutylene succinate is a fully biodegradable aliphatic polyester. Compared with polylactic acid, it has better impact toughness, ductility and heat resistance, but lower strength and modulus. Blending polybutylene succinate and polylactic acid can not only achieve complementary advantages in the performance of the two polymer materials but also completely retain the biodegradability of the materials. However, the two are incompatible blending systems, the toughening modification effect is poor, and the strength of polylactic acid will be lost. Based on this, the present invention uses epoxidized urushiol as a reaction compatibilizer, and utilizes epoxy groups to undergo a ring-opening reaction with the terminal -OH / -COOH groups of polylactic acid and polybutylene succinate during the melt blending process to generate a graft copolymer distributed at the phase interface to enhance the interfacial adhesion between the two. Epoxy urushiol is a small molecule with a plasticizing effect, which can also enhance the toughness of polylactic acid. Epoxy urushiol carries catechol groups and has good antibacterial properties, which can give the packaging material good bactericidal properties. In addition, the present invention uses benzyl quaternary ammonium salt-modified montmorillonite as a filler. The benzyl quaternary ammonium salt modification treatment can improve the agglomeration problem of montmorillonite and utilize the π-π interaction between benzyl and epoxidized urushiol to enhance the interfacial adhesion between montmorillonite and the polymer matrix, thereby further enhancing the mechanical properties of the composite material. At the same time, the nano-layered structure of montmorillonite can also hinder the penetration of water molecules and oxygen, thereby enhancing the gas barrier properties of the material and expanding the application potential of the blended material in the fields of packaging, biomedicine, etc., thereby achieving biodegradable materials that meet more practical use needs while maintaining excellent comprehensive performance.

[0011] In a preferred embodiment, the benzyl quaternary ammonium salt is a C12-C18 benzyl quaternary ammonium salt, specifically at least one of octadecyldimethylbenzylammonium chloride, hexadecyldimethylbenzylammonium chloride, tetradecyldimethylbenzylammonium chloride and dodecyldimethylbenzylammonium chloride.

[0012] In a preferred embodiment, the method for preparing the epoxidized urushiol comprises the following steps: S1. Add urushiol, xylene, acetic anhydride and pyridine to a flask, stir evenly, and heat to 90°C for 1-2 hours. After the reaction is completed, add deionized water to adjust the pH to neutral, separate the liquid and take the oil phase, and evaporate under reduced pressure to remove pyridine and xylene to obtain acetylated urushiol; S2. Add acetylated urushiol and formic acid into a flask, add hydrogen peroxide solution dropwise in an ice-water bath, and react at room temperature for 24 hours. After the reaction is complete, add deionized water to adjust to neutrality, and evaporate under reduced pressure to remove water to obtain acetylated epoxy urushiol; S3. Add acetylated epoxy urushiol to anhydrous ethanol, stir evenly, then add sodium hydroxide, and react at 40-50° C. for 0.5-1 h. After the reaction is completed, 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.

[0013] First, acetic anhydride is used to protect the phenolic hydroxyl groups in the urushiol molecular structure. Then, in formic acid and hydrogen peroxide solution, the unsaturated groups in the urushiol molecular chain are converted into epoxy groups. After that, epoxidized urushiol is obtained through deprotection treatment.

[0014] 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.

[0015] 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%.

[0016] 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%.

[0017] In a preferred embodiment, the preparation method of the benzyl quaternary ammonium salt modified montmorillonite comprises the following steps: Sodium montmorillonite was ultrasonically dispersed in deionized water to obtain a suspension. Benzyl quaternary ammonium salt was added at 60-65°C and stirred for reaction for 6-8 hours. 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 0.1 mol / L silver nitrate). The mixture was then vacuum dried to obtain benzyl quaternary ammonium salt-modified montmorillonite.

[0018] Benzyl quaternary ammonium salt is used as a modifier and benzyl groups are introduced into montmorillonite by ion exchange reaction, which increases the interlayer distance of montmorillonite and enhances its affinity with the polymer matrix.

[0019] In a second aspect, the present invention provides a method for preparing the above-mentioned high barrier antibacterial packaging material, comprising the following steps: The raw materials were weighed according to the formula ratio. Polylactic acid and polybutylene succinate were first dried at 50-60°C for 4-8 hours respectively, then added to a mixer and mixed evenly with epoxidized urushiol and benzyl quaternary ammonium salt-modified montmorillonite. The mixture was transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier and antibacterial packaging material.

[0020] In a preferred embodiment, the raw materials of the high barrier and antibacterial packaging material further include 2-5 parts of sepiolite fiber loaded with magnesium oxide.

[0021] Due to the low gas permeability of high-barrier packaging materials, during the preservation process of fruits and vegetables, the moisture generated by the respiration of fruits and vegetables cannot be discharged in time. The environmental humidity is too high, which easily breeds bacteria and aggravates the spoilage process of fruits and vegetables. To this end, the present invention introduces sepiolite fiber loaded with magnesium oxide into the high-barrier packaging material. The sepiolite fiber has a rich void structure and good adsorption properties. It can absorb water vapor and oxygen, slowing down the respiration of fruits and vegetables while reducing the environmental humidity. Magnesium oxide can react with water vapor to form magnesium hydroxide, consuming water vapor while forming a "tunnel effect" with the help of magnesium hydroxide, further improving the barrier properties of the material. In addition, magnesium oxide can also pass through oxygen The peroxidation-reduction reaction produces peroxide ions, which can destroy the protein peptide chains of the bacterial cell membrane wall, causing the microorganisms to lyse and apoptosis, thereby exerting an antibacterial effect. The present invention improves the agglomeration phenomenon of magnesium oxide particles in the polymer matrix through loading treatment, so that magnesium oxide can 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 the sepiolite fiber-loaded magnesium oxide and the polymer matrix, so that the sepiolite fiber-loaded magnesium oxide and the benzyl quaternary ammonium salt-modified montmorillonite form network structures of different dimensions in the polymer group, further enhancing the mechanical properties of the composite material.

[0022] In a preferred embodiment, the method for preparing the sepiolite fiber loaded with magnesium oxide comprises the following steps: Adding sepiolite fiber to hydrochloric acid solution, stirring evenly for 48 hours, filtering, washing the filter cake with deionized water until the washing liquid is neutral, and drying to obtain acidified sepiolite fiber; Magnesium nitrate hexahydrate is added to deionized water, stirred evenly, and then acidified sepiolite fiber is added. Under nitrogen protection, sodium hydroxide solution is added dropwise to adjust the pH value to 11. After stirring for 3 to 5 hours, the mixture is filtered and the filter cake is washed with deionized water until the washing liquid is neutral. The filter cake is dried and then calcined at 350 to 450° C. for 2 hours. The filter cake is ground through a 100-mesh sieve to obtain sepiolite fiber-loaded magnesium oxide.

[0023] Taking sepiolite fiber with large specific surface area and porous structure as carrier, magnesium hydroxide is anchored and loaded on the surface of sepiolite fiber by precipitation method, and then calcined to obtain sepiolite fiber loaded magnesium oxide.

[0024] In a preferred embodiment, the usage ratio of sepiolite fiber to hydrochloric acid solution is 1 g: 15-20 mL, and the concentration of hydrochloric acid solution is 0.5-0.7 mol / L.

[0025] In a preferred embodiment, the mass ratio of magnesium nitrate hexahydrate to acidified sepiolite fiber is 0.4-0.8:1, and the concentration of the sodium hydroxide solution is 1 mol / L.

[0026] In a second aspect, the present invention provides a method for preparing the above-mentioned high barrier antibacterial packaging material, further comprising the following steps: The raw materials are weighed according to the formula ratio. Polylactic acid and polybutylene succinate are first dried at 50-60°C for 4-8 hours, then added to a mixer and evenly mixed with epoxidized urushiol, benzyl quaternary ammonium salt-modified montmorillonite, and sepiolite fiber-loaded magnesium oxide. The mixture is transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier and antibacterial packaging material.

[0027] In a preferred embodiment, the temperatures of zones 1 to 7 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 30-50r / min.

[0028] In a preferred embodiment, the raw materials of the high barrier and antibacterial packaging material further include 0.5-1 parts of antioxidant.

[0029] In a preferred embodiment, the raw materials of the high barrier and antibacterial packaging material further include 0.5-1.5 parts of a lubricant.

[0030] 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.

[0031] In a preferred embodiment, the lubricant is at least one of stearic acid, paraffin wax and polyethylene wax.

[0032] In a third aspect, the present invention provides a packaging bag, which is made from the above packaging material through extrusion, film blowing and bag making processes.

[0033] In a preferred embodiment, the extrusion and film blowing process uses a single-screw film blowing machine, and the temperatures of the heating sections from the feed port to the die are 130-135°C, 160°C, 165°C and 140°C respectively, and the screw speed is 30-45r / min.

[0034] Beneficial effects of the present invention: The present invention provides a high-barrier and antibacterial packaging material, a preparation method thereof, and a packaging bag. The material uses biodegradable polylactic acid and polybutylene succinate as base materials, and adopts epoxidized urushiol as a reactive compatibilizer to improve the compatibility between polylactic acid and polybutylene succinate while strengthening the binding between the polymer matrix and benzyl quaternary ammonium salt-modified montmorillonite (or sepiolite-loaded magnesium oxide), thereby obtaining a packaging material having excellent mechanical properties, barrier properties, and antibacterial properties. The sepiolite-loaded magnesium oxide also has excellent hygroscopic and antibacterial properties, can absorb and bind moisture to reduce environmental humidity, avoid the generation of condensation, and help reduce the growth of microorganisms. Even if microorganisms are generated, they can be killed through redox reactions, which helps extend the shelf life of the packaged items. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0036] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution. Some or all steps can 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.

[0037] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0038] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0039] In this application, polylactic acid (PLA): brand Ingeo2003D, weight average molecular weight (Mw) is 1.8×10 5 g / mol, melt flow rate (MFR) is 6 g / 10 min (210°C, 2.16 kg), polybutylene succinate (PBS): brand Bionalle1020MD, MFR is 4.5 g / 10 min (190°C, 2.16 kg), sodium montmorillonite (Na-MMT): brand PGN, ion exchange capacity (CEC) is 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.

[0040] The technical solution of the present application is illustrated below through specific embodiments and comparative examples.

[0041] Preparation Example 1 Preparation of epoxidized urushiol, the steps are as follows: S1. Add 100 g of urushiol, 50 g of xylene, 65.5 g of acetic anhydride, and 56.4 g of pyridine to a flask, stir for 15 min, heat to 90°C, and react for 1 h. After the reaction, add deionized water to adjust the pH to neutral, separate the liquid and take the oil phase, and evaporate under reduced pressure to remove pyridine to obtain acetylated urushiol; S2. Add 10 g of acetylated urushiol and 28 g of formic acid into a flask, add dropwise 39 g of 30% by mass hydrogen peroxide solution under an ice-water bath, and react at room temperature for 24 h. After the reaction is complete, add deionized water to adjust to neutrality, and evaporate under reduced pressure to remove water to obtain acetylated epoxy urushiol; S3. Add 10 g of acetylated epoxy urushiol to 100 g of anhydrous ethanol, stir evenly, add 5.5 g of sodium hydroxide, and react at 40°C for 0.5 h. After the reaction is completed, 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.

[0042] Preparation Example 2 Preparation of epoxidized urushiol, the steps are as follows: S1. Add 100 g of urushiol, 80 g of xylene, 65.5 g of acetic anhydride, and 65.6 g of pyridine to a flask, stir for 18 min, heat to 90°C, and react for 1.5 h. After the reaction is complete, add deionized water to adjust the pH to neutral, separate the liquid and take the oil phase, and evaporate under reduced pressure to remove pyridine to obtain acetylated urushiol; S2. Add 10 g of acetylated urushiol and 28.5 g of formic acid into a flask, add dropwise 40 g of 30% by mass hydrogen peroxide solution under an ice-water bath, and react at room temperature for 24 h. After the reaction is complete, add deionized water to adjust to neutrality, and evaporate under reduced pressure to remove water to obtain acetylated epoxy urushiol; S3. Add 10 g of acetylated epoxy urushiol to 100 g of anhydrous ethanol, stir evenly, add 6 g of sodium hydroxide, and react at 45°C for 0.8 h. After the reaction is completed, add 10% 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.

[0043] Preparation Example 3 Preparation of sepiolite fiber loaded with magnesium oxide, the steps are as follows: 20 g of sepiolite fiber was added to 350 mL of 0.6 mol / L hydrochloric acid solution, stirred evenly and treated for 48 h, then filtered, the filter cake was washed with deionized water until the washing liquid was neutral, and dried to obtain acidified sepiolite fiber; 4 g of magnesium nitrate hexahydrate was added to 100 mL of deionized water, stirred evenly, and then 10 g of acidified sepiolite fiber was added. Under nitrogen protection, 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH value to 11. After stirring for 3 hours, the mixture was filtered and the filter cake was washed with deionized water until the washing liquid was neutral. The filter cake was then dried and calcined at 350°C for 2 hours. The mixture was ground through a 100-mesh sieve to obtain sepiolite fiber-loaded magnesium oxide.

[0044] Preparation Example 4 Preparation of sepiolite fiber loaded with magnesium oxide, the steps are as follows: 20 g of sepiolite fiber was added to 350 mL of 0.6 mol / L hydrochloric acid solution, stirred evenly and treated for 48 h, then filtered, the filter cake was washed with deionized water until the washing liquid was neutral, and dried to obtain acidified sepiolite fiber; 6 g of magnesium nitrate hexahydrate was added to 100 mL of deionized water, stirred evenly, and then 10 g of acidified sepiolite fiber was added. Under nitrogen protection, 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH value to 11. After stirring for 4 hours, the mixture was filtered and the filter cake was washed with deionized water until the washing liquid was neutral. The filter cake was then dried and calcined at 400 ° C for 2 hours. The mixture was ground through a 100 mesh sieve to obtain sepiolite fiber-loaded magnesium oxide.

[0045] Preparation Example 5 Preparation of sepiolite fiber loaded with magnesium oxide, the steps are as follows: 20 g of sepiolite fiber was added to 400 mL of 0.7 mol / L hydrochloric acid solution, stirred evenly and treated for 48 h, then filtered, the filter cake was washed with deionized water until the washing liquid was neutral, and dried to obtain acidified sepiolite fiber; 8 g of magnesium nitrate hexahydrate was added to 100 mL of deionized water, stirred evenly, and then 10 g of acidified sepiolite fiber was added. Under nitrogen protection, 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH value to 11. After stirring for 5 hours, the mixture was filtered and the filter cake was washed with deionized water until the washing liquid was neutral. The filter cake was then dried and calcined at 450°C for 2 hours. The mixture was ground through a 100-mesh sieve to obtain sepiolite fiber-loaded magnesium oxide.

[0046] Example 1 A high-barrier antibacterial packaging material comprises the following components in parts by weight: 75 parts of polylactic acid, 25 parts of polybutylene succinate, 2 parts of epoxidized urushiol of Preparation Example 1, 1 part of benzyl quaternary ammonium salt-modified montmorillonite, 0.5 parts of antioxidant 245, and 0.5 parts of stearic acid.

[0047] The preparation method of the benzyl quaternary ammonium salt modified montmorillonite comprises the following steps: 5 g of sodium montmorillonite was ultrasonically dispersed in 100 mL of deionized water to obtain a suspension. 2.5 g of dodecyldimethylbenzyl ammonium chloride was added at 65 °C and stirred for 6 h. 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 0.1 mol / L silver nitrate). The mixture was then vacuum dried to obtain benzyl quaternary ammonium salt-modified montmorillonite.

[0048] The method for preparing the above-mentioned high barrier antibacterial packaging material comprises the following steps: The raw materials were weighed according to the formula ratio. Polylactic acid and polybutylene succinate were first dried at 50°C for 8 hours, then added to a mixer and evenly mixed with epoxidized urushiol, benzyl quaternary ammonium salt-modified montmorillonite, antioxidant 245 and stearic acid. The mixture was transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier and antibacterial packaging material.

[0049] The temperatures of zones 1 to 7 of the twin-screw extruder are 135°C, 150°C, 160°C, 170°C, 165°C, 150°C, and 150°C, respectively, and the rotation speed is 30 r / min.

[0050] Example 2 A high-barrier antibacterial packaging material comprises the following components in parts by weight: 80 parts of polylactic acid, 20 parts of polybutylene succinate, 4 parts of epoxidized urushiol of Preparation Example 2, 2 parts of benzyl quaternary ammonium salt-modified montmorillonite, 0.8 parts of antioxidant 245, and 1.0 parts of stearic acid.

[0051] The preparation method of the benzyl quaternary ammonium salt modified montmorillonite comprises the following steps: 5 g of sodium montmorillonite was ultrasonically dispersed in 300 mL of deionized water to obtain a suspension. 3.5 g of tetradecyldimethylbenzyl ammonium chloride was added at 65 °C and stirred for 7 h. 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 0.1 mol / L silver nitrate) and vacuum dried to obtain benzyl quaternary ammonium salt modified montmorillonite.

[0052] The preparation method of the above-mentioned high barrier antibacterial packaging material is the same as that in Example 1.

[0053] Example 3 A high-barrier antibacterial packaging material comprises the following components in parts by weight: 85 parts of polylactic acid, 15 parts of polybutylene succinate, 6 parts of the epoxidized urushiol of Preparation Example 2, 3 parts of benzyl quaternary ammonium salt-modified montmorillonite, 1 part of antioxidant 330, and 1.5 parts of polyethylene wax.

[0054] The preparation method of the benzyl quaternary ammonium salt modified montmorillonite comprises the following steps: 5 g of sodium montmorillonite was ultrasonically dispersed in 500 mL of deionized water to obtain a suspension. 5 g of hexadecyldimethylbenzyl ammonium chloride was added at 65 °C and stirred for 8 h. 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 0.1 mol / L silver nitrate). The mixture was then vacuum dried to obtain benzyl quaternary ammonium salt-modified montmorillonite.

[0055] The method for preparing the above-mentioned high barrier antibacterial packaging material comprises the following steps: The raw materials were weighed according to the formula ratio. Polylactic acid and polybutylene succinate were first dried at 60°C for 8 hours, then added to a mixer and evenly mixed with epoxidized urushiol, benzyl quaternary ammonium salt-modified montmorillonite, antioxidant 330 and polyethylene wax. The mixture was transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier and antibacterial packaging material.

[0056] The temperatures of zones 1 to 7 of the twin-screw extruder are 140°C, 160°C, 165°C, 170°C, 170°C, 160°C, and 155°C, respectively, and the rotation speed is 50 r / min.

[0057] Example 4 A high barrier and antibacterial packaging material is different from Example 3 in that the raw materials of the high barrier and antibacterial packaging material in this embodiment further include 2 parts by weight of the sepiolite fiber-loaded magnesium oxide of Preparation Example 3.

[0058] The method for preparing the high barrier and antibacterial packaging material in this embodiment includes the following steps: The raw materials were weighed according to the formula ratio. Polylactic acid and polybutylene succinate were first dried at 60°C for 4 hours, then added to a mixer and evenly mixed 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 and antibacterial packaging material.

[0059] The temperatures of zones 1 to 7 of the twin-screw extruder are 140°C, 160°C, 165°C, 170°C, 170°C, 160°C, and 155°C, respectively, and the rotation speed is 50 r / min.

[0060] Example 5 A high barrier and antibacterial packaging material, compared with Example 4, the only difference is that the weight portion of magnesium oxide loaded on the sepiolite fiber in this example is 3.5.

[0061] Example 6 A high barrier and antibacterial packaging material, compared with Example 4, the only difference is that the sepiolite fiber in this embodiment is loaded with 5 parts by weight of magnesium oxide.

[0062] Example 7 A high barrier and antibacterial packaging material, compared with Example 5, the only difference is that the sepiolite fiber loaded with magnesium oxide in Example 5 is replaced by an equal weight portion of the product obtained in Preparation Example 4.

[0063] Example 8 A high barrier and antibacterial packaging material, compared with Example 5, the only difference is that the sepiolite fiber loaded with magnesium oxide in Example 5 is replaced by an equal weight portion of the product obtained in Preparation Example 5.

[0064] Comparative Example 1 A high barrier and antibacterial packaging material, compared with Example 1, the only difference is that the dodecyldimethylbenzylammonium chloride in Example 1 is replaced with dodecyltrimethylammonium chloride of equal mass.

[0065] Comparative Example 2 A high barrier and antibacterial packaging material is provided. Compared with Example 1, the only difference is that the epoxidized urushiol in Example 1 is replaced by an equal weight portion of chain extender ADR-4370F.

[0066] Comparative Example 3 A high-barrier antibacterial packaging material, compared with Example 6, the only difference is that the sepiolite fiber-loaded magnesium oxide in Example 6 is replaced by a product obtained by physically mixing equal parts by weight of acidified sepiolite fiber and magnesium oxide in a mass ratio of 10:1.26, and the mixture is stirred in a mixer at 100 r / min for 20 minutes. The preparation process of the acidified sepiolite fiber is the same as that of Preparation Example 5.

[0067] The high-barrier and antibacterial packaging materials of Examples 1 to 8 and Comparative Examples 1 to 3 were prepared into dumbbell-shaped specimens. The tensile properties of the dumbbell-shaped specimens of each group of packaging materials were measured using a universal mechanical testing machine at 25°C and a relative humidity of 55% in accordance with GB / T1040.1-2018. The tensile speed was 200 mm / s. Each test was performed five times, and the average value was taken. The high barrier and antibacterial packaging materials of Examples 1 to 8 and Comparative Examples 1 to 3 were subjected to a blow molding-stretching process using a single-screw film blowing machine. The temperatures of the heating sections from the feed port to the die of the film blowing machine were 135° C., 160° C., 165° C., and 140° C., respectively. The screw speed was 30 r / min, and the pulling speed was 7 m / min to obtain film materials. The film samples prepared from each group of packaging materials were tested for water vapor barrier properties, antibacterial properties, and freshness preservation properties: (1) Water vapor barrier performance test: According to GB / T1037-2021, the water vapor barrier properties of the film are determined using the evaporation method. The film thickness is controlled at (10±1)μm, the test temperature is 23℃±0.5℃, and the relative humidity is 90%±2%. (2) Antibacterial performance analysis: The antibacterial rate detection method refers to QB / T2591-2003 "Antibacterial Plastics - Antibacterial Performance Test Method and Antibacterial Effect". Each sample is tested 10 times and the results are averaged. (3) Analysis of fresh-keeping performance: Fresh cherries were purchased from the supermarket, divided equally into small pieces and placed in plastic wrap prepared from each group of packaging materials. The cherries were sealed and stored in a refrigerator at 4°C. After 15 days, the good fruit rate was calculated and the fresh-keeping effect was evaluated. The test results are shown in Table 1:

[0068] Analysis of the data recorded in Table 1 shows that the tensile strength of the packaging material of Example 3 is slightly lower than that of Example 2, but the water vapor transmission rate is significantly lower than that of Example 2, and the antibacterial effect is also significantly higher than that of Example 2. Therefore, among the packaging materials obtained from Examples 1 to 3, Example 3 has the best overall effect; Analysis of the test results of Examples 3, 4, 5, and 6 shows that, based on the formula of Example 3, the introduction of sepiolite fiber-loaded magnesium oxide can enhance the mechanical properties, barrier properties, and antibacterial properties of the packaging material. Example 5 has a better effect because an appropriate amount of sepiolite fiber-loaded magnesium oxide can adsorb water vapor and oxygen, and at the same time, form a "tunnel effect" with the help of magnesium hydroxide, thereby improving the barrier properties of the material. In addition, magnesium oxide can also react with oxygen through an oxidation-reduction reaction to produce peroxide ions. The peroxide ions can destroy the protein peptide chains of bacterial cell membrane walls, causing microbial lysis and apoptosis, thereby exerting an antibacterial effect. Analysis of the test results of Example 5, Example 7 and Example 8 shows that the performance of the packaging materials prepared using the sepiolite fibers loaded with magnesium oxide obtained in Preparation Examples 3, 4 and 5 is very different; Analysis of the test results of Example 1 and Comparative Example 1 shows that when conventional quaternary ammonium salt is used instead of benzyl quaternary ammonium salt to prepare modified montmorillonite, due to the lack of benzene ring, the modified montmorillonite and epoxidized urushiol cannot form a π-π interaction, the mechanical properties and barrier properties of the packaging material are significantly deteriorated, the antibacterial properties do not change significantly, but the final preservation effect is deteriorated; Analysis of the test results of Example 1 and Comparative Example 2 shows that the use of a commercially available chain extender to replace the epoxidized urushiol in Example 1 significantly reduces the antibacterial properties of the resulting packaging material due to the lack of an antibacterial agent; Analysis of the test results of Example 6 and Comparative Example 3 shows that compared with the physical mixture product of magnesium oxide and sepiolite fiber, the mechanical properties, barrier properties and antibacterial properties of the packaging material obtained by loading treatment with sepiolite fiber loaded with magnesium oxide as filler are better.

[0069] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0070] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high barrier antibacterial packaging material, characterized in that: The composition comprises the following raw materials in parts 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; The epoxidized urushiol is prepared by epoxidation reaction of urushiol with an organic peracid; The preparation method of the epoxidized urushiol comprises the following steps: S1. Add urushiol, xylene, acetic anhydride and pyridine to a flask, stir evenly, and heat to 90°C for 1-2 hours. After the reaction is completed, add deionized water to adjust the pH to neutral, separate the liquid and take the oil phase, and evaporate under reduced pressure to remove pyridine and xylene to obtain acetylated urushiol; S2. Add acetylated urushiol and formic acid into a flask, add hydrogen peroxide solution dropwise in an ice-water bath, and react at room temperature for 24 hours. After the reaction is complete, add deionized water to adjust to neutrality, and evaporate under reduced pressure to remove water to obtain acetylated epoxy urushiol; S3. Add acetylated epoxy urushiol to anhydrous ethanol, stir evenly, then add sodium hydroxide, and react at 40-50° C. for 0.5-1 h. After the reaction is completed, 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.

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, and the mass ratio of the benzyl quaternary ammonium salt to the sodium montmorillonite is 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 octadecyldimethylbenzyl ammonium chloride, hexadecyldimethylbenzyl ammonium chloride, tetradecyldimethylbenzyl ammonium chloride and dodecyldimethylbenzyl ammonium chloride.

4. The high barrier antibacterial packaging material according to claim 1, characterized in that: The raw materials of the high barrier and antibacterial packaging material also include 2-5 parts of sepiolite fiber loaded with magnesium oxide.

5. The high barrier antibacterial packaging material according to claim 4, characterized in that: The preparation method of the sepiolite fiber loaded with magnesium oxide comprises the following steps: Adding sepiolite fiber to hydrochloric acid solution, stirring evenly for 48 hours, filtering, washing the filter cake with deionized water until the washing liquid is neutral, and drying to obtain acidified sepiolite fiber; Magnesium nitrate hexahydrate is added to deionized water, stirred evenly, and then acidified sepiolite fiber is added. Under nitrogen protection, sodium hydroxide solution is added dropwise to adjust the pH value to 11. After stirring for 3 to 5 hours, the mixture is filtered. The filter cake is washed with deionized water until the washing liquid is neutral, dried, calcined at 350 to 450°C for 2 hours, and ground through a 100-mesh sieve to obtain sepiolite fiber-loaded magnesium oxide.

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

7. The high barrier antibacterial packaging material according to claim 5, characterized in that: The mass ratio of magnesium nitrate hexahydrate to acidified sepiolite fiber is 0.4-0.8:

1.

8. A method for preparing a high barrier antibacterial packaging material, characterized in that: The method for preparing the high barrier and antibacterial packaging material according to any one of claims 1 to 3 comprises the following steps: The raw materials were weighed according to the formula ratio. Polylactic acid and polybutylene succinate were first dried at 50-60°C for 4-8 hours respectively, then added to a mixer and mixed evenly with epoxidized urushiol and benzyl quaternary ammonium salt-modified montmorillonite. The mixture was transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier and antibacterial packaging material.

9. A method for preparing a high barrier antibacterial packaging material, characterized in that: The method for preparing the high barrier and antibacterial packaging material according to any one of claims 4 to 7 comprises the following steps: The raw materials are weighed according to the formula ratio. Polylactic acid and polybutylene succinate are first dried at 50-60°C for 4-8 hours, then added to a mixer and evenly mixed with epoxidized urushiol, benzyl quaternary ammonium salt-modified montmorillonite, and sepiolite fiber-loaded magnesium oxide. The mixture is transferred to a twin-screw extruder for shearing and granulation to obtain a high-barrier and antibacterial packaging material.

10. A packaging bag, characterized in that: Prepared from the packaging material according to any one of claims 1 to 7.

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