High-barrier polyethylene film and preparation method thereof

Abstract

The invention discloses a high-barrier polyethylene film and a preparation method thereof, and relates to the technical field of high polymer materials. The invention discloses a high-barrier polyethylene film. The high-density polyethylene composite material is prepared from the following raw materials in parts by weight: 25 to 40 parts of high-density polyethylene, 15 to 30 parts of linear low-density polyethylene, 8 to 16 parts of ethylene-vinyl alcohol copolymer, 3 to 8 parts of nano montmorillonite, 5 to 10 parts of modified layered double hydroxide, 2 to 6 parts of nano silicon dioxide aerogel, 0.2 to 0.6 part of antioxidant 1076, 0.1 to 0.4 part of light stabilizer UV-770, 3 to 7 parts of tributyl citrate and 1 to 3 parts of octadecanamide. 1-3 parts of polyethylene wax, 0.6-1.2 parts of a silane coupling agent KH560 and 7-12 parts of a functional additive. According to the high-barrier polyethylene film disclosed by the invention, by using the modified layered double hydroxide and the functional additive, the barrier property and the antibacterial property are enhanced, the mechanical property is improved, the comprehensive performance is excellent, and the application prospect is good.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a high-barrier polyethylene film and its preparation method. Background Technology

[0002] In the field of polymer materials, polyethylene film occupies an important position in many fields such as packaging, agriculture, and industry due to its good chemical stability, processing performance, and cost advantages. From everyday food packaging to agricultural greenhouse coverings and industrial product protection, it can be found everywhere.

[0003] However, with the development of various industries, the requirements for the performance of polyethylene film are becoming increasingly stringent. Ordinary polyethylene film has poor barrier properties and cannot effectively block oxygen and moisture. In food packaging, this can lead to oxidation, spoilage, and mold growth, significantly shortening the shelf life of food. When used in pharmaceutical packaging, the drug components may undergo chemical reactions upon contact with external gases and moisture, reducing efficacy and even posing safety hazards. Its low barrier properties are also a key factor restricting product preservation and transportation when packaging high-value electronic components and highly reactive chemical raw materials.

[0004] In terms of mechanical properties, existing polyethylene films lack sufficient tensile strength and tear resistance. During packaging and transportation, the film is easily torn by sharp objects, or it may break under pressure during handling and stacking, resulting in damage to the internal products and affecting their integrity and safety.

[0005] Meanwhile, polyethylene film has significant shortcomings in terms of chemical resistance, antibacterial properties, and weather resistance. When exposed to certain chemicals, the film corrodes, causing a rapid decline in performance; its lack of antibacterial properties makes it unsuitable for packaging in high-hygiene-standard fields such as food and medical applications; and under long-term exposure to ultraviolet light and heat, the film is prone to aging and becoming brittle, shortening its lifespan and increasing usage costs. Therefore, developing polyethylene films with high barrier properties, excellent mechanical properties, and good antibacterial, weather-resistant, and chemical-resistant properties has become an urgent problem for the industry and is of great significance for promoting the sustainable development of related industries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high-barrier polyethylene film and its preparation method, thus solving the aforementioned problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A high-barrier polyethylene film comprises the following raw materials in parts by weight: 25-40 parts high-density polyethylene, 15-30 parts linear low-density polyethylene, 8-16 parts ethylene-vinyl alcohol copolymer, 3-8 parts nano-montmorillonite, 5-10 parts modified layered double hydroxide, 2-6 parts nano-silica aerogel, 0.2-0.6 parts antioxidant 1076, 0.1-0.4 parts light stabilizer UV-770, 3-7 parts tributyl citrate, 1-3 parts stearamide, 1-3 parts polyethylene wax, 0.6-1.2 parts silane coupling agent KH560, and 7-12 parts functional additives.

[0008] Furthermore, the modified layered double hydroxide is prepared using the following specific steps: A1. Disperse the layered double hydroxide in deionized water, sonicate for 30 min, add sodium dodecyl sulfate, stir and react at 55 °C for 8 h. After the reaction is complete, filter, wash until neutral, and dry at 80 °C for 12 h to obtain the organic intercalation modified layered double hydroxide. A2. Disperse the organic intercalation-modified layered double hydroxide in deionized water, add cerium nitrate and zinc nitrate, adjust the pH to 9 with ammonia, stir the reaction at 60℃ for 6h, after the reaction is completed, centrifuge, collect the precipitate, wash, dry at 70℃ for 10h to obtain metal ion doped modified layered double hydroxide. A3. Add the metal ion-doped modified layered double hydroxide to toluene, ultrasonically disperse for 20 min, add maleic anhydride-grafted polypropylene and benzoyl peroxide, reflux at 110℃ for 5 h, filter, collect the precipitate, wash, and vacuum dry at 60℃ for 8 h to obtain polymer-grafted modified layered double hydroxide. A4. The polymer-grafted modified layered double hydroxide was dispersed in anhydrous ethanol, and the nano-silver-chitosan complex was added. The mixture was ultrasonically dispersed for 30 min, stirred at room temperature for 10 h, centrifuged, the precipitate was collected, washed, and dried at 50 °C for 8 h to obtain the modified layered double hydroxide.

[0009] Furthermore, in step A1, the ratio of layered double hydroxide, deionized water, and sodium dodecyl sulfate is 10g:250mL:10g; the stirring speed is 300r / min, and the precipitate is washed with deionized water; in step A2, the ratio of organically intercalated modified layered double hydroxide, deionized water, cerium nitrate, and zinc nitrate is 10g:200mL:0.5g:0.3g; the stirring speed is 300r / min, the centrifugation speed is 6000r / min, and each centrifugation lasts for 10min. The precipitate is first washed with deionized water until no metal ions are detected, and then washed with ethanol.

[0010] Furthermore, in step A3, the ratio of metal ion-doped modified layered double hydroxide, toluene, maleic anhydride-grafted polypropylene, and benzoyl peroxide is 8g:150mL:6g:0.5g; the precipitate is washed with ethanol; in step A4, the ratio of polymer-grafted modified layered double hydroxide, anhydrous ethanol, and nano-silver-chitosan complex is 6g:120mL:2g; the stirring speed is 300r / min, the centrifugation speed is 5000r / min, and each centrifugation is 10min; the precipitate is washed with anhydrous ethanol.

[0011] During organic intercalation modification, sodium dodecyl sulfate is inserted between the layers of layered double hydroxides to expand the interlayer spacing and increase its compatibility with the polymer; metal ion doping introduces cerium and zinc ions, changing the crystal structure and enhancing the absorption and stability of ultraviolet light; polymer grafting modification involves grafting maleic anhydride onto polypropylene and onto the surface of layered double hydroxides, further improving the interfacial bonding with polyethylene; and antibacterial agent loading utilizes the antibacterial properties of the nano-silver-chitosan composite to endow the film with antibacterial function.

[0012] Furthermore, the specific preparation steps for the functional additive are as follows: B1. Add adipic acid, ethylene glycol and tetrabutyl titanate to the reaction vessel, start stirring, introduce nitrogen gas, heat to 170℃ and stir for 5 hours. After the reaction is completed, stop heating and wait for the temperature to drop to 100℃. While hot, transfer the product to a separatory funnel, let it stand to separate into layers, remove the lower aqueous phase, and obtain crude polyester polyol. B2. Add the crude polyester polyol to the reactor, start stirring, and add hydroxyethyl methacrylate and hydroquinone in sequence. Stir for 15 minutes, then heat to 190°C and stir for 3 hours. After the reaction is complete, stop heating, add toluene to the reaction system, and stir until the product is fully dissolved. Transfer the solution to a separatory funnel, wash three times with saturated sodium bicarbonate solution, and allow it to stand for separation after each wash. Remove the lower aqueous phase, wash with deionized water until neutral, and finally dry with anhydrous magnesium sulfate. Filter to remove the desiccant to obtain the intermediate product solution. B3. Add benzoyl peroxide to the above intermediate product solution, stir for 30 min, then heat to 140℃ and stir for 6 h. After the reaction is complete, pour the product solution into petroleum ether to precipitate, stir evenly, filter, collect the filter cake, wash the filter cake with petroleum ether, place the filter cake in a vacuum drying oven, and dry at 50℃ for 12 h to obtain a functional additive with a three-dimensional network structure.

[0013] Furthermore, in step B1, the ratio of adipic acid, ethylene glycol, and tetrabutyl titanate is 15g:12g:0.4g; the nitrogen flow rate is 50mL / min, and the inlet time is 15min; the temperature is increased at a rate of 5℃ / min; and the stirring speed is 150r / min. In step B2, the ratio of crude polyester polyol, hydroxyethyl methacrylate, and hydroquinone is 25g:5g:0.3g; the temperature is increased at a rate of 8℃ / min; and the stirring speed is 180r / min. In step B3, the ratio of intermediate product solution and benzoyl peroxide is 30g:0.6g; and the stirring speed is 200r / min.

[0014] The functional additive is first synthesized into a polyester polyol, and then hydroxyethyl methacrylate is introduced to give it polymerizable double bonds and functional groups such as hydroxyl groups. During the cross-linking polymerization stage, benzoyl peroxide initiator decomposes to generate free radicals, which promote cross-linking of the double bonds in the molecule, forming a three-dimensional network structure. This structure enhances the interaction between the additive and the polyethylene matrix, resulting in reinforcement, toughening, and other effects, thus improving the overall performance of the film.

[0015] A method for preparing a high-barrier polyethylene film specifically includes the following steps: S1. Dry the nano-montmorillonite, high-density polyethylene, linear low-density polyethylene, and ethylene-vinyl alcohol copolymer; first, add the dried high-density polyethylene and linear low-density polyethylene to a high-speed mixer and mix for 10 minutes; then add the dried ethylene-vinyl alcohol copolymer to the high-speed mixer and speed up the mixing for 15 minutes. S2. Add the dried nano-montmorillonite and modified layered double hydroxide to the mixer and stir for 5 minutes. Then add the nano-silica aerogel and continue stirring for 5 minutes. Subsequently, add antioxidant 1076, light stabilizer UV-770, tributyl citrate, stearamide, polyethylene wax and silane coupling agent KH560 in sequence, stirring for 3 minutes after each addition. Finally, add the functional additive and speed up the stirring for 15 minutes. S3. Preheat the blow molding machine. After the temperature of each section stabilizes, slowly add the blended and modified material into the feeding hopper. The material is heated and melted in the extruder. After being filtered through two layers of 100-mesh filters, it is extruded from the die head to form a film preform. The film preform is pulled forward by the casting roller and cooling roller while being inflated by air and stretched longitudinally to obtain a polyethylene film. The temperature of the cooling roller is 10℃, and a 10℃ cooling air ring is used to cool the polyethylene film, so that the film gradually cools down and solidifies. After passing through the traction roller, it is wound into a bundle.

[0016] Furthermore, in step S1, the initial mixing speed is 1100 r / min, and the speed is increased to 1200 r / min.

[0017] Furthermore, in step S2, the stirring speed is 1200 r / min, and after adding the functional additive, the stirring speed is 1300 r / min.

[0018] Furthermore, in step S3, the temperatures of the feeding section, melting section, and homogenization section of the blow molding machine are set to 150℃, 180℃, and 200℃, respectively; the extrusion temperature is 150℃; and the die head temperature is 180℃. The blow-up ratio is controlled to be 2.5-3.5, and the traction speed is 18-25m / s.

[0019] This invention provides a high-barrier polyethylene film and its preparation method, which has the following beneficial effects: 1. Superior Barrier Performance: The ethylene-vinyl alcohol copolymer possesses excellent gas barrier properties, which is a crucial foundation for enhancing the barrier performance of the film. Nano-montmorillonite and modified layered double hydroxides are uniformly distributed in a lamellar pattern within the film, constructing complex and tortuous permeation pathways, acting as barriers that prevent small molecules such as oxygen and water vapor from easily passing through. The unique porous structure of nano-silica aerogel not only increases the difficulty of gas diffusion but also adsorbs some gas molecules, further strengthening the barrier effect. This allows the film to meet the packaging requirements of products with extremely high barrier performance requirements, such as food, pharmaceuticals, and high-end electronic products, effectively extending product shelf life and ensuring product quality.

[0020] 2. Excellent Mechanical Properties: High-density polyethylene (HDPE) possesses high rigidity, providing a solid foundation for strength; linear low-density polyethylene (LLDPE) imparts good flexibility to the film. The combination of these two materials complements each other, allowing the film to maintain good flexibility while possessing sufficient strength, making it less prone to brittleness. The self-made functional additives, with their three-dimensional network structure, are tightly interwoven with the polyethylene matrix, acting as a stable supporting framework within the film, enhancing overall structural strength. The silane coupling agent acts like a bridge, improving the interfacial bonding between the inorganic filler and the polymer, thus strengthening the synergistic effect between the components. These factors work together to significantly improve the film's tensile strength, tear resistance, and other mechanical properties, making it more resistant to wear and tear during packaging and transportation, effectively protecting the product inside.

[0021] 3. Antibacterial and Weather Resistance: The modified layered double hydroxide-supported nano-silver-chitosan composite exhibits strong antibacterial capabilities. Nano-silver can disrupt bacterial cell membranes and respiratory enzyme systems, inhibiting bacterial growth and reproduction; chitosan can alter the permeability of bacterial cell membranes, synergistically enhancing the antibacterial effect of nano-silver. This makes the film highly effective in packaging applications with extremely high hygiene requirements, such as food and medical packaging, effectively preventing microbial contamination and ensuring product safety. Simultaneously, antioxidants and light stabilizers work synergistically. Antioxidants capture free radicals generated during oxidation, preventing the chain reaction of oxidation; light stabilizers absorb or quench ultraviolet energy, preventing film degradation due to light exposure. Together, they effectively inhibit the aging and degradation of the film under light and oxidative conditions, extending its service life in harsh environments such as outdoor and chemical settings, and reducing usage costs.

[0022] 4. Wide Applicability: A major advantage of this invention lies in its high flexibility. By cleverly adjusting the raw material formulation and precisely controlling the preparation process parameters, the film's performance can be precisely controlled. For food preservation packaging, the barrier and antibacterial properties can be optimized to ensure food freshness; for pharmaceutical moisture-proof and oxidation-proof packaging, barrier properties and stability are enhanced; and for antistatic packaging of electronic products, its insulating and antistatic properties are emphasized. This wide applicability allows the film to fully leverage its advantages in different fields, greatly expanding the application boundaries of polyethylene film and providing related industries with more high-performance packaging material options. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: Preparation of high-barrier polyethylene film. The specific preparation steps are as follows: S1. Dry nano-montmorillonite, high-density polyethylene, linear low-density polyethylene, and ethylene-vinyl alcohol copolymer; first, add 25 parts of dried high-density polyethylene and 15 parts of linear low-density polyethylene to a high-speed mixer and stir at 1100 r / min for 10 min; then add 8 parts of dried ethylene-vinyl alcohol copolymer to the high-speed mixer and stir at 1200 r / min for 15 min. S2. Add 3 parts of dried nano-montmorillonite and 5 parts of modified layered double hydroxide to a mixer and stir at 1200 r / min for 5 min. Then add 2 parts of nano-silica aerogel and continue stirring for 5 min. Subsequently, add 0.2 parts of antioxidant 1076, 0.1 parts of light stabilizer UV-770, 3 parts of tributyl citrate, 1 part of stearamide, 1 part of polyethylene wax and 0.6 parts of silane coupling agent KH560 in sequence, stirring for 3 min after each addition. Finally, add 7 parts of functional additives and stir at 1300 r / min for 15 min. S3. Preheat the feeding section, melting section, and homogenization section of the blow molding machine to 150℃, 180℃, and 200℃ respectively. After the temperature of each section stabilizes, slowly add the blended and modified material into the feeding hopper. The material is heated and melted in the extruder, filtered through two layers of 100-mesh filters, and extruded from the 180℃ die head to form a film preform. The film preform is pulled forward by the casting roller and cooling roller while being air-blown and longitudinally stretched to obtain a polyethylene film. The blow-blowing ratio is controlled at 2.5, the traction speed is 18m / s, the temperature of the cooling roller is 10℃, and a 10℃ cooling air ring is used to cool the polyethylene film, so that the film gradually cools down and solidifies. After passing through the traction roller, it is wound into a bundle.

[0025] Example 2: Preparation of high-barrier polyethylene film. The specific preparation steps are as follows: S1. Dry nano-montmorillonite, high-density polyethylene, linear low-density polyethylene, and ethylene-vinyl alcohol copolymer; first, add 40 parts of dried high-density polyethylene and 30 parts of linear low-density polyethylene to a high-speed mixer and stir at 1100 r / min for 10 min; then add 16 parts of dried ethylene-vinyl alcohol copolymer to the high-speed mixer and stir at 1200 r / min for 15 min. S2. Add 8 parts of dried nano-montmorillonite and 10 parts of modified layered double hydroxide to a mixer and stir at 1200 r / min for 5 min. Then add 6 parts of nano-silica aerogel and continue stirring for 5 min. Subsequently, add 0.6 parts of antioxidant 1076, 0.4 parts of light stabilizer UV-770, 7 parts of tributyl citrate, 3 parts of stearamide, 3 parts of polyethylene wax and 1.2 parts of silane coupling agent KH560 in sequence, stirring for 3 min after each addition. Finally, add 12 parts of functional additives and stir at 1300 r / min for 15 min. S3. Preheat the feeding section, melting section, and homogenization section of the blow molding machine to 150℃, 180℃, and 200℃ respectively. After the temperature of each section stabilizes, slowly add the blended and modified material into the feeding hopper. The material is heated and melted in the extruder, filtered through two layers of 100-mesh filters, and extruded from the 180℃ die head to form a film preform. The film preform is pulled forward by the casting roller and cooling roller while being air-blown and longitudinally stretched to obtain a polyethylene film. The blow-blowing ratio is controlled at 3.5, the traction speed is 25m / s, the temperature of the cooling roller is 10℃, and a 10℃ cooling air ring is used to cool the polyethylene film, so that the film gradually cools down and solidifies. After passing through the traction roller, it is wound into a bundle.

[0026] Example 3: Preparation of high-barrier polyethylene film. The specific preparation steps are as follows: S1. Dry nano-montmorillonite, high-density polyethylene, linear low-density polyethylene, and ethylene-vinyl alcohol copolymer; first, add 32 parts of dried high-density polyethylene and 22 parts of linear low-density polyethylene to a high-speed mixer and stir at 1100 r / min for 10 min; then add 12 parts of dried ethylene-vinyl alcohol copolymer to the high-speed mixer and stir at 1200 r / min for 15 min. S2. Add 5 parts of dried nano-montmorillonite and 7 parts of modified layered double hydroxide to a mixer and stir at 1200 r / min for 5 min. Then add 4 parts of nano-silica aerogel and continue stirring for 5 min. Subsequently, add 0.4 parts of antioxidant 1076, 0.3 parts of light stabilizer UV-770, 5 parts of tributyl citrate, 2 parts of stearamide, 2 parts of polyethylene wax and 0.9 parts of silane coupling agent KH560 in sequence, stirring for 3 min after each addition. Finally, add 9 parts of functional additives and stir at 1300 r / min for 15 min. S3. Preheat the feeding section, melting section, and homogenization section of the blow molding machine to 150℃, 180℃, and 200℃ respectively. After the temperature of each section stabilizes, slowly add the blended and modified material into the feeding hopper. The material is heated and melted in the extruder, filtered through two layers of 100-mesh filters, and extruded from the 180℃ die head to form a film preform. The film preform is pulled forward by the casting roller and cooling roller while being air-blown and longitudinally stretched to obtain a polyethylene film. The blow-blowing ratio is controlled at 3, the traction speed is 21m / s, the temperature of the cooling roller is 10℃, and a 10℃ cooling air ring is used to cool the polyethylene film, so that the film gradually cools down and solidifies. After passing through the traction roller, it is wound into a bundle.

[0027] Example 4: Preparation of modified layered double hydroxides. The specific preparation steps are as follows: A1. Disperse 10g of layered double hydroxide in 250mL of deionized water, sonicate for 30min, add 10g of sodium dodecyl sulfate, stir at 300r / min at 55℃ for 8h, filter after the reaction, wash the precipitate with deionized water until neutral, and dry at 80℃ for 12h to obtain organic intercalation modified layered double hydroxide. A2. Disperse 10g of organically intercalated modified layered double hydroxide in 200mL of deionized water, add 0.5g of cerium nitrate and 0.3g of zinc nitrate, adjust the pH to 9 with ammonia, and stir at 300r / min at 60℃ for 6h. After the reaction is completed, centrifuge at 6000r / min for 10min each time, collect the precipitate, wash with deionized water until no metal ions are detected, wash with ethanol, and dry the precipitate at 70℃ for 10h to obtain metal ion doped modified layered double hydroxide. A3. Add 8g of metal ion-doped modified layered double hydroxide to 150mL of toluene, sonicate for 20min, add 6g of maleic anhydride-grafted polypropylene and 0.5g of benzoyl peroxide, reflux at 110℃ for 5h, filter, collect the precipitate, wash the precipitate with ethanol, and vacuum dry at 60℃ for 8h to obtain polymer-grafted modified layered double hydroxide. A4. Disperse 6g of polymer-grafted modified layered double hydroxide in 120mL of anhydrous ethanol, add 2g of nano-silver-chitosan complex, sonicate for 30min, stir at 300r / min at room temperature for 10h, centrifuge at 5000r / min for 10min each time, collect the precipitate, wash with anhydrous ethanol, and dry the precipitate at 50℃ for 8h to obtain modified layered double hydroxide.

[0028] Example 5: Preparation of functional additives. The specific preparation steps are as follows: B1. Add 15g adipic acid, 12g ethylene glycol and 0.4g tetrabutyl titanate to the reaction vessel, stir at 150r / min, introduce nitrogen gas at a flow rate of 50mL / min for 15min, heat to 170℃ at a rate of 5℃ / min and stir for 5h. After the reaction is completed, stop heating and wait for the temperature to drop to 100℃. While hot, transfer the product to a separatory funnel, let it stand to separate into layers, remove the lower aqueous phase, and obtain crude polyester polyol. B2. Add 25g of crude polyester polyol to the reactor and start stirring. Add 5g of hydroxyethyl methacrylate and 0.3g of hydroquinone in sequence. Stir at 180r / min for 15min, then heat to 190℃ at a rate of 8℃ / min and stir for 3h. After the reaction is complete, stop heating and add toluene to the reaction system. Stir until the product is fully dissolved. Transfer the solution to a separatory funnel and wash three times with saturated sodium bicarbonate solution. After each wash, allow the layers to separate. Remove the lower aqueous phase and wash with deionized water until neutral. Finally, dry with anhydrous magnesium sulfate and filter to remove the desiccant to obtain the intermediate product solution. B3. Add 0.6 g of benzoyl peroxide to the above intermediate product solution, stir at 200 r / min for 30 min, then heat to 140℃ and stir for 6 h. After the reaction is complete, pour the product solution into petroleum ether to precipitate, stir evenly, filter, collect the filter cake, wash the filter cake with petroleum ether, place the filter cake in a vacuum drying oven and dry at 50℃ for 12 h to obtain a functional additive with a three-dimensional network structure.

[0029] Comparative Example 1: A high-barrier polyethylene film was prepared. The specific preparation steps are as follows: The remaining steps remain the same, except that the modified layered double hydroxide in Example 2 is replaced with an untreated layered double hydroxide to prepare a high-barrier polyethylene film.

[0030] Comparative Example 2: A high-barrier polyethylene film was prepared. The specific steps are as follows: The remaining steps remain the same, except that the functional additives of Example 2 are replaced with untreated polyester polyols to prepare high-barrier polyethylene films.

[0031] Performance testing Test Project Test methods Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Oxygen permeability (cm³ / (m²·24h·0.1MPa)) The oxygen permeability of plastic films and sheets was tested according to GB / T1038-2000 "Gas Permeability Test Method - Differential Pressure Method" at 23℃ and 50% relative humidity. 5 3 4 15 12 Water vapor transmission rate (g / (m²·24h)) According to GB / T1037-1988 "Test Method for Water Vapor Permeability of Plastic Films and Sheets - Cup Method", the test was conducted at 38℃ and 90% relative humidity. 8 6 7 20 18 Tensile strength (MPa) According to GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", a universal testing machine was used with a tensile speed of 50 mm / min. 35 40 38 25 28 Elongation at break (%) Simultaneously with the tensile strength test, the elongation at the point of film fracture was recorded. 400 450 430 300 320 Right-angle tear strength (N / mm) The test was conducted according to GB / T16578.1-2008 "Determination of tear resistance of plastic films and sheets - Part 1: Pants tear test". 60 70 65 40 45 Antibacterial properties The plate count method was used, with Escherichia coli and Staphylococcus aureus as test bacteria. After the membrane sample was contacted with the bacterial solution for a certain period of time, the number of viable bacteria remaining on the membrane surface was detected, and the antibacterial rate was calculated. It has an antibacterial rate of 98% against Escherichia coli and 97% against Staphylococcus aureus. It has an antibacterial rate of 99% against Escherichia coli and 98% against Staphylococcus aureus. The antibacterial rate against Escherichia coli was 98.5%, and the antibacterial rate against Staphylococcus aureus was 97.5%. The antibacterial rate against Escherichia coli was 10%, and the antibacterial rate against Staphylococcus aureus was 12%. The antibacterial rate against Escherichia coli was 8%, and the antibacterial rate against Staphylococcus aureus was 10%. Aging resistance Accelerated aging tests were conducted using a xenon lamp aging chamber, where the film was treated for 1000 hours under specific light intensity, temperature, and humidity conditions. The changes in the film's appearance were observed, and its tensile strength retention was tested. The film showed no obvious discoloration or embrittlement, and retained 85% of its tensile strength. The film showed slight discoloration, no embrittlement, and retained 88% of its tensile strength. The film showed slight discoloration, but retained 86% of its tensile strength. The film was severely discolored and brittle, with only 50% of its tensile strength retained. The film showed obvious discoloration, but retained 60% of its tensile strength. Comparing the performance test results of the examples and comparative examples, it can be seen that the high-barrier polyethylene film prepared by the present invention has excellent performance. The films of Examples 1-3 have low oxygen and water vapor permeability, exhibiting excellent barrier properties; high tensile strength, elongation at break, and right-angle tear strength, demonstrating good mechanical properties; and an antibacterial rate exceeding 97% against Escherichia coli and Staphylococcus aureus, indicating strong antibacterial activity; after aging tests, the tensile strength retention rate is over 85%, demonstrating excellent aging resistance. Comparative Example 1 (unmodified layered double hydroxide) and Comparative Example 2 (untreated polyester polyol) resulted in films that were far inferior to the examples in terms of barrier, antibacterial, mechanical, and aging resistance properties, highlighting the importance of key raw material modification and additive use in improving film performance.

[0032] 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 polyethylene film, characterized in that: It contains the following raw materials by weight: 25-40 parts high-density polyethylene, 15-30 parts linear low-density polyethylene, 8-16 parts ethylene-vinyl alcohol copolymer, 3-8 parts nano montmorillonite, 5-10 parts modified layered double hydroxide, 2-6 parts nano silica aerogel, 0.2-0.6 parts antioxidant 1076, 0.1-0.4 parts light stabilizer UV-770, 3-7 parts tributyl citrate, 1-3 parts stearamide, 1-3 parts polyethylene wax, 0.6-1.2 parts silane coupling agent KH560, and 7-12 parts functional additives.

2. The high-barrier polyethylene film according to claim 1, characterized in that: The modified layered double hydroxide is prepared by the following steps: A1. Disperse the layered double hydroxide in deionized water, sonicate for 30 min, add sodium dodecyl sulfate, stir and react at 55 °C for 8 h. After the reaction is complete, filter, wash until neutral, and dry at 80 °C for 12 h to obtain the organic intercalation modified layered double hydroxide. A2. Disperse the organic intercalation-modified layered double hydroxide in deionized water, add cerium nitrate and zinc nitrate, adjust the pH to 9 with ammonia, stir the reaction at 60℃ for 6h, after the reaction is completed, centrifuge, collect the precipitate, wash, dry at 70℃ for 10h to obtain metal ion doped modified layered double hydroxide. A3. Add the metal ion-doped modified layered double hydroxide to toluene, ultrasonically disperse for 20 min, add maleic anhydride-grafted polypropylene and benzoyl peroxide, reflux at 110℃ for 5 h, filter, collect the precipitate, wash, and vacuum dry at 60℃ for 8 h to obtain polymer-grafted modified layered double hydroxide. A4. The polymer-grafted modified layered double hydroxide was dispersed in anhydrous ethanol, and the nano-silver-chitosan complex was added. The mixture was ultrasonically dispersed for 30 min, stirred at room temperature for 10 h, centrifuged, the precipitate was collected, washed, and dried at 50 °C for 8 h to obtain the modified layered double hydroxide.

3. The high-barrier polyethylene film according to claim 2, characterized in that: In step A1, the ratio of layered double hydroxide, deionized water, and sodium dodecyl sulfate is 10g:250mL:10g; the stirring speed is 300r / min, and the precipitate is washed with deionized water. In step A2, the ratio of organically intercalated modified layered double hydroxide, deionized water, cerium nitrate, and zinc nitrate is 10g:200mL:0.5g:0.3g; the stirring speed is 300r / min, the centrifugation speed is 6000r / min, and each centrifugation lasts for 10min. The precipitate is first washed with deionized water until no metal ions are detected, and then washed with ethanol.

4. A high-barrier polyethylene film according to claim 2, characterized in that: In step A3, the ratio of metal ion-doped modified layered double hydroxide, toluene, maleic anhydride-grafted polypropylene, and benzoyl peroxide is 8g:150mL:6g:0.5g; the precipitate is washed with ethanol. In step A4, the ratio of polymer-grafted modified layered double hydroxide, anhydrous ethanol, and nano-silver-chitosan complex is 6g:120mL:2g; the stirring speed is 300r / min, the centrifugation speed is 5000r / min, and each centrifugation is 10min; the precipitate is washed with anhydrous ethanol.

5. A high-barrier polyethylene film according to claim 1, characterized in that: The specific preparation steps for the functional additive are as follows: B1. Add adipic acid, ethylene glycol and tetrabutyl titanate to the reaction vessel, start stirring, introduce nitrogen gas, heat to 170℃ and stir for 5 hours. After the reaction is completed, stop heating and wait for the temperature to drop to 100℃. While hot, transfer the product to a separatory funnel, let it stand to separate into layers, remove the lower aqueous phase, and obtain crude polyester polyol. B2. Add the crude polyester polyol to the reactor, start stirring, and add hydroxyethyl methacrylate and hydroquinone in sequence. Stir for 15 minutes, then heat to 190°C and stir for 3 hours. After the reaction is complete, stop heating, add toluene to the reaction system, and stir until the product is fully dissolved. Transfer the solution to a separatory funnel, wash three times with saturated sodium bicarbonate solution, and allow it to stand for separation after each wash. Remove the lower aqueous phase, wash with deionized water until neutral, and finally dry with anhydrous magnesium sulfate. Filter to remove the desiccant to obtain the intermediate product solution. B3. Add benzoyl peroxide to the above intermediate product solution, stir for 30 min, then heat to 140℃ and stir for 6 h. After the reaction is complete, pour the product solution into petroleum ether to precipitate, stir evenly, filter, collect the filter cake, wash the filter cake with petroleum ether, place the filter cake in a vacuum drying oven, and dry at 50℃ for 12 h to obtain a functional additive with a three-dimensional network structure.

6. A high-barrier polyethylene film according to claim 5, characterized in that: In step B1, the ratio of adipic acid, ethylene glycol, and tetrabutyl titanate is 15g:12g:0.4g; nitrogen gas is introduced at a flow rate of 50mL / min for 15min; the temperature is increased at a rate of 5℃ / min; and the stirring speed is 150r / min. In step B2, the ratio of crude polyester polyol, hydroxyethyl methacrylate, and hydroquinone is 25g:5g:0.3g; the temperature is increased at a rate of 8℃ / min; and the stirring speed is 180r / min. In step B3, the ratio of intermediate product solution and benzoyl peroxide is 30g:0.6g; and the stirring speed is 200r / min.

7. A method for preparing a high-barrier polyethylene film, characterized in that: Specifically, it includes the following steps: S1. Dry nano-montmorillonite, high-density polyethylene, linear low-density polyethylene, and ethylene-vinyl alcohol copolymer; first, add the dried high-density polyethylene and linear low-density polyethylene to a high-speed mixer and mix for 10 minutes; then add the dried ethylene-vinyl alcohol copolymer to the high-speed mixer and speed up the mixing for 15 minutes. S2. Add the dried nano-montmorillonite and modified layered double hydroxide to the mixer and stir for 5 minutes. Then add the nano-silica aerogel and continue stirring for 5 minutes. Subsequently, add antioxidant 1076, light stabilizer UV-770, tributyl citrate, stearamide, polyethylene wax and silane coupling agent KH560 in sequence, stirring for 3 minutes after each addition. Finally, add the functional additive and speed up the stirring for 15 minutes. S3. Preheat the blow molding machine. After the temperature of each section stabilizes, slowly add the blended and modified material into the feeding hopper. The material is heated and melted in the extruder. After being filtered through two layers of 100-mesh filters, it is extruded from the die head to form a film preform. The film preform is pulled forward by the casting roller and cooling roller while being inflated by air and stretched longitudinally to obtain a polyethylene film. The temperature of the cooling roller is 10℃, and a 10℃ cooling air ring is used to cool the polyethylene film, so that the film gradually cools down and solidifies. After passing through the traction roller, it is wound into a bundle.

8. The method for preparing a high-barrier polyethylene film according to claim 7, characterized in that: In step S1, the initial mixing speed is 1100 r / min, and the speed is increased to 1200 r / min.

9. The method for preparing a high-barrier polyethylene film according to claim 7, characterized in that: In step S2, the stirring speed is 1200 r / min, and after adding the functional additive, the stirring speed is 1300 r / min.

10. The method for preparing a high-barrier polyethylene film according to claim 7, characterized in that: In step S3, the temperatures of the feeding section, melting section, and homogenization section of the blow molding machine are set to 150℃, 180℃, and 200℃, respectively; the extrusion temperature is 150℃; and the die head temperature is 180℃. The blow-up ratio is controlled at 2.5-3.5, and the traction speed is 18-25m / s.