High-barrier food packaging material and preparation process thereof

Abstract

The application discloses a kind of high-barrier food packaging materials and preparation process thereof, belong to food packaging technical field.The barrier layer, core layer and secondary barrier layer, core layer is between barrier layer and secondary barrier layer;Barrier layer, core layer, secondary barrier layer are made into one by co-extrusion after two-way stretching, once extrusion molding, method is simple.Secondary barrier layer material is polyethylene, nylon and curcumin blend, wherein polyethylene and nylon complementary advantages, greatly enhance the barrier property and mechanical property of packaging material;Curcumin can not only improve the antibacterial property of packaging material, but also enhance the antioxidant property of packaging material.Barrier layer material is modified polyvinyl alcohol, has excellent barrier property to gas, is modified by grafting organic molecular chain, and the compatibility with polypropylene is better, can also greatly enhance the antibacterial property, mechanical property and antioxidant property of packaging material, and the performance is long and stable, has important application value in the field of food packaging technology.

Description

Technical Field

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

[0002] With the continuous development of science and technology, people's quality of life has greatly improved, and they are paying more and more attention to food quality and safety. Therefore, the field of food packaging materials related to food safety has also received considerable attention. One important property of food packaging materials is barrier properties. Barrier properties refer to the ability of a material to prevent substances from penetrating from one side to the other. These substances include common gases, liquids, water vapor, and organic matter. High-barrier food packaging materials can effectively prevent food oxidation, mold, and spoilage, and have significant application value in the field of food packaging technology.

[0003] To improve the barrier properties of food packaging materials, packaging films are often in the form of composite packaging films, such as biaxially oriented polypropylene (BOPP) film. BOPP film production involves first forming molten polypropylene into sheets or thick films through a narrow die head, then stretching it simultaneously or stepwise in two perpendicular directions (longitudinal and transverse) at a specific temperature and speed in a specialized stretching machine. The resulting film undergoes appropriate cooling or heat treatment, or special processing (such as corona treatment or coating). This type of film boasts high physical stability, mechanical strength, good airtightness, high transparency and gloss, and is tough and wear-resistant, earning it the nickname "Queen of Packaging." However, BOPP film has poor antibacterial properties. For foods stored for extended periods, bacteria and mold can proliferate, easily leading to food contamination by mold and microorganisms. Furthermore, prolonged storage of BOPP film causes aging, resulting in a decline in film performance. Therefore, there is an urgent need to invent a food packaging material that can solve these problems to meet the higher demands of the food packaging technology field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-barrier food packaging material and its preparation process.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A high-barrier food packaging material includes a barrier layer, a core layer, and a secondary barrier layer, with the core layer located between the barrier layer and the secondary barrier layer. The barrier layer, core layer, and secondary barrier layer are integrally formed by co-extrusion followed by biaxial stretching. The mass percentages of the barrier layer material, core layer material, and secondary barrier layer material are as follows: barrier layer 15-25%, core layer 50-70%, and secondary barrier layer 15-25%.

[0007] A process for preparing a high-barrier food packaging material includes the following steps:

[0008] A1. The barrier layer material, core layer material, and secondary barrier layer material are extruded into barrier layer sheets, core layer sheets, and secondary barrier layer sheets respectively by three extruders;

[0009] A2. The extruded barrier layer, core layer, and secondary barrier layer are extruded into a casting through a die head. The temperature at the die head is set to 245℃. The core layer is located between the barrier layer and the secondary barrier layer. After the casting is shaped by a chilling roller, it is stretched longitudinally and laterally into a film. The film is then corona treated, wound up, and slit to produce high-barrier food packaging material.

[0010] Furthermore, in step A1, the core material is polypropylene.

[0011] Furthermore, in step A1, the extrusion temperature of the extruder for extruding the barrier layer is 200-215℃, the extrusion temperature of the extruder for extruding the core layer is 200-220℃, and the extrusion temperature of the extruder for extruding the secondary barrier layer is 210-230℃.

[0012] Packaging material is produced by co-extruding three layers: a barrier layer, a core layer, and a secondary barrier layer. The core layer material is polypropylene, which has strong chemical resistance and good mechanical properties. Furthermore, it is produced by one-time extrusion molding, making the method simple.

[0013] Furthermore, the material of the secondary barrier layer is prepared through the following steps:

[0014] After the polyethylene resin, curcumin and PA6 are mixed evenly, they are added to a twin-screw extruder, melt-blended and extruded to obtain the secondary barrier layer material.

[0015] Furthermore, the raw materials are as follows by weight: 80-100 parts polyethylene resin, 3-5 parts curcumin, and 10-20 parts PA6.

[0016] Polyethylene has good impact resistance and good water vapor barrier properties, while nylon has high strength and good oxygen barrier properties. The two complement each other, giving the secondary barrier layer material excellent barrier properties and mechanical strength. The added curcumin has significant antibacterial activity against foodborne pathogens, which can not only improve the antibacterial properties of the secondary barrier layer material, but also enhance the material's antioxidant properties.

[0017] Furthermore, the material of the barrier layer is prepared through the following steps:

[0018] S1. In a three-necked flask equipped with a stirrer, 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine (condensing agent), and toluene were mixed, heated to 40°C, and stirred until the solid was completely dissolved. 3,4-Diaminopyridine was added, and the reaction was maintained at this temperature for 4 hours. After the reaction was completed, the mixture was allowed to cool naturally and then distilled under reduced pressure to obtain intermediate 1. The ratio of the amounts of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine, toluene, and 3,4-diaminopyridine was 23.4 g: 15 mL: 100 mL: 11.4 g.

[0019] Under the action of a condensing agent, the amino group on 3,4-diaminopyridine condenses with the aldehyde group on 3,5-di-tert-butyl-4-hydroxybenzaldehyde to form an imine group (C=N Schiff base structure). By controlling the molar ratio of the two to be close to 1:1 and with a slight excess of 3,4-diaminopyridine, only one amino group on 3,4-diaminopyridine participates in the reaction, yielding intermediate 1. The specific reaction process is shown below:

[0020]

[0021] S2. Add intermediate 1, stearic acid, dicyclohexylcarbodiimide (DCC, dehydrating agent) and toluene to a three-necked flask equipped with a stirrer. After stirring and mixing evenly, place the flask in a water bath at 55°C and heat for 6 hours. After the reaction is complete, filter the mixture, remove the solvent by vacuum distillation, and then purify it by column chromatography (using a mixed solvent of benzene and ethyl acetate as the eluent, with a volume ratio of 4:3). Remove the eluent by rotary evaporation to obtain intermediate 2. The ratio of intermediate 1, stearic acid, dicyclohexylcarbodiimide and toluene is 32.5 g: 28.4 g: 20.6 g: 150 mL.

[0022] Under the action of dicyclohexylcarbodiimide, intermediate 1 undergoes an amidation reaction with stearic acid to give intermediate 2; the specific reaction process is shown below:

[0023]

[0024] S3. In a three-necked flask equipped with a stirrer, add intermediate 2 and toluene and stir until homogeneous. Then add epoxybromopropane and control the reaction temperature at 75℃. React for 12 hours until the reaction is complete. Remove some of the solvent under vacuum and then purify by column chromatography (using a mixed solvent of benzene and ethyl acetate as the eluent, with a volume ratio of 4:3). Remove the eluent by rotary evaporation to obtain the modifier. The ratio of intermediate 2, toluene, and epoxybromopropane is 59.1g:150mL:14.1g.

[0025] Intermediate 2 undergoes a quaternization reaction with epichlorohydrin to yield a modifier; the specific reaction process is shown below:

[0026]

[0027] S4. Add dimethyl sulfoxide and polyvinyl alcohol to a three-necked flask equipped with a stirrer. Under magnetic stirring, heat the oil bath to 95°C until the polyvinyl alcohol is completely dissolved. Cool to 65°C and keep the temperature constant. Add the modifier and stir for 10 minutes. Then add sodium hydroxide solution (12% by mass) dropwise to adjust the pH of the reaction system to 9-10. React at 65°C for 6 hours. After the reaction is complete, cool to room temperature and add to acetone. Stir at room temperature until a gel-like precipitate forms. Filter and vacuum dry to obtain the barrier layer material. The ratio of dimethyl sulfoxide, polyvinyl alcohol, and modifier is 50 mL: 10 g: 8 g.

[0028] The hydroxyl groups on the polyvinyl alcohol molecule react with the epoxy groups on the modifier, grafting the modifier onto the polyvinyl alcohol macromolecular chain to obtain a barrier layer material.

[0029] The resulting barrier layer material is modified polyvinyl alcohol (PVA). PVA exhibits excellent barrier properties against oxygen, nitrogen, hydrogen, and carbon dioxide, thus improving the barrier performance of packaging materials. Modifying PVA by grafting organic molecular chains reduces its polarity and improves its compatibility with polypropylene. Furthermore, the grafted organic molecular chains contain pyridine quaternary ammonium salts, Schiff bases, long carbon chains, benzene rings, and hindered phenolic structures. Among these, pyridine quaternary ammonium salts are a novel type of quaternary ammonium salt with a more concentrated positive charge, resulting in stronger bactericidal activity. This avoids the bacterial resistance problems caused by the long-term, large-scale use of quaternary ammonium salt antibacterial agents, significantly enhancing the antibacterial properties of the material. Additionally, C=N Schiff bases... The structure can interact with bacterial proteins and enzymes, inhibiting the synthesis of bacterial nucleotides and amino acids. It also works synergistically with pyridine quaternary ammonium salts to further improve the antibacterial properties of the material. The introduced long carbon chain, with its methylene segment being a flexible segment, not only enhances the mechanical properties of the material to a certain extent but also, like the benzene ring, belongs to hydrophobic groups, improving the material's water resistance. The hindered phenolic structure has excellent antioxidant properties, not only improving the material's antioxidant performance but also acting as an antioxidant during the production process, avoiding the need for additional antioxidants that could affect the material's homogeneity. Finally, the polyvinyl alcohol graft modifier prevents the migration and shedding of small-molecule modifiers, ensuring the long-term stability of the material's properties.

[0030] The beneficial effects of this invention are:

[0031] 1. The packaging material obtained by the present invention is a three-layer co-extrusion of a barrier layer, a core layer and a secondary barrier layer. The core layer material is polypropylene, which has strong chemical resistance and good mechanical properties. Furthermore, it is produced by one-time extrusion molding, which is a simple method.

[0032] 2. The secondary barrier layer material is made of polyethylene, nylon and curcumin. Polyethylene and nylon complement each other, greatly enhancing the barrier and mechanical properties of the packaging material. Curcumin can not only improve the antibacterial properties of the packaging material, but also enhance its antioxidant properties.

[0033] 3. The barrier layer material is modified polyvinyl alcohol, which has excellent gas barrier properties. It is modified by grafting organic molecular chains. Compared with ordinary polyvinyl alcohol, it has better compatibility with polypropylene and can also significantly enhance the antibacterial, mechanical and antioxidant properties of the packaging material, and its performance is stable over a long period of time.

[0034] Therefore, the packaging material obtained by this invention has stable and efficient barrier, antibacterial, mechanical and antioxidant properties, and has important application value in the field of food packaging technology. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] Preparation of barrier layer materials:

[0038] S1. In a three-necked flask equipped with a stirrer, 23.4 g of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 15 mL of piperidine and 100 mL of toluene were mixed, heated to 40 °C and stirred until the solid was completely dissolved. 11.4 g of 3,4-diaminopyridine was added and the reaction was maintained at this temperature for 4 h. After the reaction was completed, the mixture was allowed to cool naturally and then distilled under reduced pressure to obtain intermediate 1.

[0039] S2. Add 32.5g of intermediate 1, 28.4g of stearic acid, 20.6g of dicyclohexylcarbodiimide and 150mL of toluene to a three-necked flask equipped with a stirrer. After stirring and mixing evenly, place the flask in a water bath at 55℃ and heat for 6 hours. After the reaction is complete, filter the flask, remove the solvent by vacuum distillation, and then purify the flask by column chromatography (using a mixed solvent of benzene and ethyl acetate as the eluent, with a volume ratio of 4:3). Remove the eluent by rotary evaporation to obtain intermediate 2.

[0040] S3. Add 59.1g of intermediate 2 and 150mL of toluene to a three-necked flask equipped with a stirrer and stir until well mixed. Then add 14.1g of epoxybromopropane and control the reaction temperature at 75℃. React for 12h until the reaction is complete. Remove part of the solvent under vacuum and then purify by column chromatography (using a mixed solvent of benzene and ethyl acetate as the eluent, with a volume ratio of 4:3). Remove the eluent by rotary evaporation to obtain the modifier.

[0041] S4. Add 50 mL of dimethyl sulfoxide and 10 g of polyvinyl alcohol to a three-necked flask equipped with a stirrer. Under magnetic stirring, heat the oil bath to 95 °C until the polyvinyl alcohol is completely dissolved. Cool to 65 °C and keep the temperature constant. Add 8 g of modifier and stir for 10 min. Then add sodium hydroxide solution (12% by mass) dropwise to adjust the pH of the reaction system to 9. React at 65 °C for 6 h. After the reaction is complete, cool to room temperature and add to acetone. Stir at room temperature until a gel-like precipitate forms. Filter and vacuum dry to obtain the barrier layer material.

[0042] Example 2

[0043] Preparation of barrier layer materials:

[0044] S1. In a three-necked flask equipped with a stirrer, 46.8 g of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 30 mL of piperidine and 200 mL of toluene were mixed, heated to 40 °C and stirred until the solid was completely dissolved. 22.8 g of 3,4-diaminopyridine was added, and the reaction was maintained at this temperature for 4 h. After the reaction was completed, the mixture was allowed to cool naturally and then distilled under reduced pressure to obtain intermediate 1.

[0045] S2. Add 65g of intermediate 1, 56.8g of stearic acid, 41.2g of dicyclohexylcarbodiimide and 300mL of toluene to a three-necked flask equipped with a stirrer. After stirring and mixing evenly, place the flask in a water bath at 55℃ and heat for 6 hours. After the reaction is complete, filter the flask, remove the solvent by vacuum distillation, and then purify the flask by column chromatography (using a mixed solvent of benzene and ethyl acetate as the eluent, with a volume ratio of 4:3). Remove the eluent by rotary evaporation to obtain intermediate 2.

[0046] S3. Add 118.2g of intermediate 2 and 300mL of toluene to a three-necked flask equipped with a stirrer and stir until well mixed. Then add 28.2g of epoxybromopropane and control the reaction temperature at 75℃. React for 12 hours until the reaction is complete. Remove part of the solvent under vacuum and then purify by column chromatography (using a mixed solvent of benzene and ethyl acetate as the eluent, with a volume ratio of 4:3). Remove the eluent by rotary evaporation to obtain the modifier.

[0047] S4. Add 100 mL of dimethyl sulfoxide and 20 g of polyvinyl alcohol to a three-necked flask equipped with a stirrer. Under magnetic stirring, heat the oil bath to 95 °C until the polyvinyl alcohol is completely dissolved. Cool to 65 °C and keep the temperature constant. Add 16 g of modifier and stir for 10 min. Then add sodium hydroxide solution (12% by mass) dropwise to adjust the pH of the reaction system to 10. React at 65 °C for 6 h. After the reaction is complete, cool to room temperature and add to acetone. Stir at room temperature until a gel-like precipitate forms. Filter and vacuum dry to obtain the barrier layer material.

[0048] Example 3

[0049] Preparation of secondary barrier layer materials:

[0050] After mixing 80g of polyethylene resin, 3g of curcumin and 10g of PA6 evenly, the mixture was added to a twin-screw extruder, melt-blended and extruded to obtain the secondary barrier layer material.

[0051] Example 4

[0052] Preparation of secondary barrier layer materials:

[0053] After mixing 100g of polyethylene resin, 5g of curcumin and 20g of PA6 evenly, the mixture was added to a twin-screw extruder, melt-blended and extruded to obtain the secondary barrier layer material.

[0054] Example 5

[0055] A1. 15g of the barrier layer material prepared in Example 1, 50g of the core layer material (polypropylene), and 15g of the secondary barrier layer material prepared in Example 3 were extruded into barrier layer sheets, core layer sheets, and secondary barrier layer sheets with the same cross-sectional area using three extruders respectively; wherein the extrusion temperature of the extruder for extruding the barrier layer sheet was 200°C, the extrusion temperature of the extruder for extruding the core layer sheet was 200°C, and the extrusion temperature of the extruder for extruding the secondary barrier layer sheet was 210°C.

[0056] A2. The extruded barrier layer, core layer, and secondary barrier layer are extruded into a casting through a die head. The temperature at the die head is set to 245℃. The core layer is located between the barrier layer and the secondary barrier layer. After the casting is shaped by a chilling roller, it is stretched longitudinally and laterally into a film with a thickness of 80μm. The film is corona treated, wound up, and slit to produce high-barrier food packaging material.

[0057] Example 6

[0058] A1. 20g of the barrier layer material prepared in Example 1, 60g of the core layer material (polypropylene), and 20g of the secondary barrier layer material prepared in Example 3 were extruded into barrier layer sheets, core layer sheets, and secondary barrier layer sheets with the same cross-sectional area using three extruders respectively; wherein the extrusion temperature of the extruder for extruding the barrier layer sheet was 210°C, the extrusion temperature of the extruder for extruding the core layer sheet was 210°C, and the extrusion temperature of the extruder for extruding the secondary barrier layer sheet was 220°C.

[0059] A2. The extruded barrier layer, core layer, and secondary barrier layer are extruded into a casting through a die head. The temperature at the die head is set to 245℃. The core layer is located between the barrier layer and the secondary barrier layer. After the casting is shaped by a chilling roller, it is stretched longitudinally and laterally into a film with a thickness of 80μm. The film is corona treated, wound up, and slit to produce high-barrier food packaging material.

[0060] Example 7

[0061] A1. 25g of the barrier layer material prepared in Example 1, 50g of the core layer material (polypropylene), and 25g of the secondary barrier layer material prepared in Example 3 were extruded into barrier layer sheets, core layer sheets, and secondary barrier layer sheets with the same cross-sectional area using three extruders respectively; wherein the extrusion temperature of the extruder for extruding the barrier layer sheet was 215°C, the extrusion temperature of the extruder for extruding the core layer sheet was 220°C, and the extrusion temperature of the extruder for extruding the secondary barrier layer sheet was 230°C.

[0062] A2. The extruded barrier layer, core layer, and secondary barrier layer are extruded into a casting through a die head. The temperature at the die head is set to 245℃. The core layer is located between the barrier layer and the secondary barrier layer. After the casting is shaped by a chilling roller, it is stretched longitudinally and laterally into a film with a thickness of 80μm. The film is corona treated, wound up, and slit to produce high-barrier food packaging material.

[0063] Comparative Example 1

[0064] Unlike Example 7, the barrier layer material uses the same mass fraction of ordinary polyvinyl alcohol to produce the food packaging material.

[0065] Comparative Example 2

[0066] Unlike Example 7, the barrier layer material uses an equal mass fraction of ordinary polyvinyl alcohol, and the secondary barrier layer material uses an equal mass fraction of ordinary polyethylene to obtain food packaging material.

[0067] Comparative Example 3

[0068] Commercially available high-barrier BOPP film with a thickness of 80μm is used.

[0069] Examples 5-7 and Comparative Examples 1-3 were manufactured into corresponding shapes according to different testing standards, and the following performance tests were conducted:

[0070] Tensile strength was determined according to the national standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets";

[0071] The oxygen permeability was determined using the national standard GB / T 1038-2022 "Test Method for Gas Permeability of Plastic Films and Sheets - Differential Pressure Method";

[0072] The moisture permeability was determined using the national standard GB / T 1037-2010 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Method for Weight Gain and Weight Loss".

[0073] The antibacterial properties of plastic surfaces were tested using the national standard GB / T 31402-2015 "Test Method for Antibacterial Properties of Plastic Surfaces" and the film coating method. The method is as follows: Escherichia coli or Staphylococcus aureus bacteria were inoculated onto agar plates, covered and preserved for 24 hours, and then viable bacteria were cultured. The results of parallel experiments with empty samples were compared to obtain the antibacterial rate of the samples.

[0074] After the samples were placed at room temperature for 180 days, the tensile strength, oxygen permeability and moisture permeability of the samples were determined using the same standard.

[0075] The measurement results are shown in the table below:

[0076]

[0077]

[0078] As can be seen from the table above, the packaging material prepared by the embodiments of the present invention has higher barrier properties, antibacterial properties, and mechanical properties than the comparative example, and its performance is stable over a long period of time, which has important application value in the field of food packaging technology.

[0079] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0080] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A high-barrier food packaging material, comprising a barrier layer, a core layer, and a secondary barrier layer, characterized in that, The material of the barrier layer is prepared by the following steps: S1. Mix 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine and toluene, heat to 40°C, stir until the solid is completely dissolved, add 3,4-diaminopyridine, keep the reaction at the temperature for 4 hours, the reaction is complete, cool naturally, and distill under reduced pressure to obtain intermediate 1; S2. Add intermediate 1, stearic acid, dicyclohexylcarbodiimide and toluene to a three-necked flask, stir and mix well, heat at 55°C for 6 hours, filter, distill under reduced pressure, purify by column chromatography, and rotary evaporate to obtain intermediate 2. S3. Add intermediate 2 and toluene to a three-necked flask and stir until well mixed. Then add epoxybromopropane and react at 75°C for 12 hours. After the reaction is complete, remove part of the solvent under vacuum, purify by column chromatography, and obtain the modifier by rotary evaporation. S4. Add dimethyl sulfoxide and polyvinyl alcohol to a three-necked flask. Under magnetic stirring, heat to 95°C until the polyvinyl alcohol is completely dissolved. Cool to 65°C and keep the temperature constant. Add the modifier and stir for 10 minutes. Then add sodium hydroxide solution dropwise to adjust the pH of the reaction system to 9-10. React at 65°C for 6 hours. After the reaction is complete, cool and add to acetone. Stir at room temperature until a precipitate forms. Filter and vacuum dry to obtain the barrier layer material.

2. The high-barrier food packaging material according to claim 1, characterized in that, In step S1, the ratio of the amounts of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine, toluene, and 3,4-diaminopyridine is 23.4 g: 15 mL: 100 mL: 11.4 g.

3. The high-barrier food packaging material according to claim 1, characterized in that, In step S2, the ratio of intermediate 1, stearic acid, dicyclohexylcarbodiimide, and toluene is 32.5g:28.4g:20.6g:150mL.

4. The high-barrier food packaging material according to claim 1, characterized in that, In step S3, the ratio of intermediate 2, toluene, and epichlorohydrin is 59.1 g: 150 mL: 14.1 g.

5. The high-barrier food packaging material according to claim 1, characterized in that, In step S4, the ratio of dimethyl sulfoxide, polyvinyl alcohol, and modifier is 50 mL: 10 g: 8 g.

6. The high-barrier food packaging material according to claim 1, characterized in that, The material for the secondary barrier layer is prepared through the following steps: After the polyethylene resin, curcumin and PA6 are mixed evenly, they are added to a twin-screw extruder, melt-blended and extruded to obtain the secondary barrier layer material.

7. A high-barrier food packaging material according to claim 6, characterized in that, The raw materials are as follows by weight: 80-100 parts polyethylene resin, 3-5 parts curcumin, and 10-20 parts PA6.

8. The preparation process of a high-barrier food packaging material according to claim 1, characterized in that, Includes the following steps: A1. The barrier layer material, core layer material, and secondary barrier layer material are extruded into barrier layer sheets, core layer sheets, and secondary barrier layer sheets respectively by three extruders; A2. The extruded barrier layer, core layer, and secondary barrier layer are extruded into a casting through a die head. The temperature at the die head is set to 245℃. The core layer is located between the barrier layer and the secondary barrier layer. After the casting is shaped by a chilling roller, it is stretched longitudinally and laterally into a film. The film is then corona treated, wound up, and slit to produce high-barrier food packaging material.

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