Environment-friendly antibacterial polyethylene inner film for packaging and preparation method thereof

Abstract

This invention discloses an environmentally friendly antibacterial polyethylene inner film material for packaging and its preparation method, belonging to the field of plastic inner film technology. This invention uses bio-based polyethylene made from sugarcane ethanol as the matrix, and mixes waste orange peel fiber, grain husks, and thermoplastic starch as natural fillers, with no organic solvents or harmful byproducts throughout the process. Plant extracts are used to replace metal ion antibacterial agents; they are first encapsulated with cyclodextrin to form an antibacterial masterbatch, which is then concentrated and added to the inner layer of the inner film through multi-layer co-extrusion. The outer thermal insulation layer protects the antibacterial activity and avoids the risk of metal migration. After composting and dispersion optimization, the inner film maintains the required mechanical properties at a high bio-based content; the high filler content makes the film material semi-transparent white or matte, with a light-blocking effect, which helps reduce the oxidation of photosensitive foods. This material can be processed using conventional equipment, with a process similar to ordinary polyethylene blown film, and the high-filler system exhibits good fluidity. The used film material can be industrially composted together with kitchen waste.

Description

Technical Field

[0001] This invention relates to the field of plastic inner film technology, specifically to an environmentally friendly antibacterial polyethylene inner film material for packaging and its preparation method. Background Technology

[0002] Most commercially available polyethylene inner films for food packaging are made from petroleum-based polyethylene. These materials consume large amounts of fossil fuels during production, resulting in heavy carbon emissions. Furthermore, they are difficult to degrade in the natural environment after use, relying primarily on incineration or landfill for disposal, thus placing continuous pressure on the ecosystem. To reduce the proportion of petroleum-based plastics, some studies have attempted to add biomass fillers such as starch and plant fibers to the polyethylene matrix. However, due to the significant difference in polarity between starch and polyethylene, their compatibility is very poor. When the filler content is high, the tensile strength and elongation at break of the film decrease significantly, making the material brittle and prone to breakage, failing to meet the basic requirements for flexibility and strength in food packaging. Simultaneously, unmodified plant fibers tend to agglomerate in the polyethylene melt, leading to particles or holes on the film surface, affecting processing stability and appearance quality. Therefore, current technologies struggle to maintain good mechanical properties in films with high biomass content.

[0003] Regarding antibacterial properties, ordinary polyethylene inner films themselves lack antibacterial capabilities, making it easy for microorganisms to grow inside food packaging, resulting in a short shelf life. To impart antibacterial properties to the inner film, some technologies employ antibacterial agents such as silver, copper, and zinc ions, which inhibit bacterial growth through the slow release of metal ions. However, these metal ions pose a risk of migration into food, especially when in contact with acidic or high-moisture foods, where migration increases significantly, and long-term ingestion may harm human health. Furthermore, metal ions are difficult to degrade in the environment, causing secondary pollution, and are also costly. In highly packed biomass systems, their dispersion is uneven, making it difficult to guarantee the stability and durability of the antibacterial effect. While natural plant extracts are safe and renewable, their thermal stability is poor. The melting processing temperature of polyethylene is typically over 100 degrees Celsius, and direct addition can lead to the volatilization or decomposition of antibacterial active ingredients, leaving very little effective residue after processing, which cannot exert a stable antibacterial effect in the film. In summary, existing technologies lack a polyethylene inner film solution that can utilize a high proportion of biomass raw materials, maintain good mechanical properties, and safely and efficiently achieve antibacterial functions. Summary of the Invention

[0004] The purpose of this invention is to provide an environmentally friendly antibacterial polyethylene inner film material for packaging and its preparation method, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an environmentally friendly antibacterial polyethylene inner film material for packaging, wherein the film material is obtained by washing, drying, crushing, and sieving waste orange peel fiber and grain husks, spraying them with a silane coupling agent solution for surface modification, and drying to obtain surface-modified biomass filler; drying starch and adding plasticizer to obtain thermoplastic starch paste, cooling and crushing to obtain thermoplastic starch powder; encapsulating plant extracts with cyclodextrin and then melt-blending and pelletizing with bio-based low-density polyethylene to obtain antibacterial masterbatch; mixing bio-based low-density polyethylene, bio-based high-density polyethylene, ethylene ethyl acrylate, maleic anhydride grafted polyethylene, and dispersant to obtain a polyethylene mixture; mixing thermoplastic starch, surface-modified biomass filler, antibacterial masterbatch, and plasticizer mixture to obtain a filler mixture; adding the filler mixture from the main feed port of a twin-screw extruder and the polyethylene mixture from the side feed port, melt-blending, extruding, cooling, pelletizing, drying, and then blowing film through a blown film machine to obtain an environmentally friendly antibacterial bio-based polyethylene inner film.

[0006] Furthermore, the biomass filler powder is obtained by drying waste orange peel fiber and grain husk at 90°C to constant weight, pulverizing and passing through a 200-mesh sieve.

[0007] Furthermore, the silane coupling agent used in the surface modification is γ-aminopropyltriethoxysilane, and the dosage is 2% of the filler mass. It is first diluted with anhydrous ethanol to a mass fraction of 15% before being sprayed in. The mixer temperature is 110℃, the stirring speed is 800rpm, and the modification treatment lasts for 20-40min.

[0008] Furthermore, the thermoplastic starch powder is prepared by adding ordinary corn starch or potato starch to a reaction vessel, drying at 90°C for 60 minutes, adding a plasticizer (a mixture of white oil and tri-n-butyl acetyl citrate in a 1:1 mass ratio, with the amount of plasticizer being 20-25% of the starch mass), and mixing at 120°C and 800 rpm for 30 minutes to obtain a thermoplastic starch paste; after cooling to room temperature, it is pulverized and passed through a 100-mesh sieve.

[0009] Furthermore, the antibacterial masterbatch is prepared by mixing plant extracts and cyclodextrin at a mass ratio of 1:4-1:6, adding deionized water, and maintaining a solid-liquid ratio of 1:5-1:8. The mixture is stirred and infused at 50-70℃ for 1-3 hours. After infusion, it is vacuum dried at 60℃ for 24 hours and then pulverized through a 100-mesh sieve to obtain the infusion powder. The infusion powder is then mixed with bio-based low-density polyethylene at a mass ratio of 1:2-1:4 and mixed at room temperature for 15 minutes. The mixture is then melt-blended using a twin-screw extruder. The extruder temperature is set to 120℃ in zone 1, 125℃ in zone 2, 130℃ in zone 3, 135℃ in zone 4, and 140℃ in zone 5. The die temperature is 138℃, and the screw speed is 200 rpm. The material is then water-cooled, stretched, and pelletized after extrusion.

[0010] Furthermore, the membrane material raw materials are weighed according to the following components in parts by weight: 25-45 parts of bio-based low-density polyethylene, 5-25 parts of bio-based high-density polyethylene, 4-20 parts of ethylene acrylate, 1-8 parts of maleic anhydride grafted polyethylene, 30-65 parts of thermoplastic starch, 5-20 parts of surface-modified biomass filler, 5-15 parts of antibacterial masterbatch, 3-19 parts of plasticizer mixture, and 1-8 parts of dispersant.

[0011] Furthermore, the dispersant is a mixture of oxidized polyethylene wax and trihydroxy polyoxypropylene ether in a mass ratio of 1:1.

[0012] Furthermore, the modified blended granules are melt-blended using a twin-screw extruder. The filler mixture is added through the main feed port, and the polyethylene mixture is added through the side feed port. The twin-screw extruder has a length-to-diameter ratio of 36 and a screw diameter of 55 mm. The extruder temperatures are set as follows: Zone 1: 135°C, Zone 2: 145°C, Zone 3: 150°C, Zone 4: 155°C, Zone 5: 160°C, Zone 6: 165°C, Zone 7: 155°C, Zone 8: 150°C, and the die temperature is 155°C. The screw speed is 300 rpm. After melt blending, the material is extruded from the die, cooled in a water bath at a water temperature of 20-30°C, pelletized by a pelletizer, and dried at 70°C for 3 hours to obtain the modified blended granules.

[0013] Furthermore, the environmentally friendly antibacterial bio-based polyethylene inner film is formed by blown film forming using a blown film machine. The temperatures of each heating zone of the blown film machine are set as follows: zone 1 160℃, zone 2 165℃, zone 3 170℃, and the die head temperature 165℃; the screw speed is 60 rpm, the traction speed is 10 m / min, and the blow-up ratio is 3; thus, an environmentally friendly antibacterial bio-based polyethylene inner film with a thickness of 50 μm is obtained.

[0014] Furthermore, the plant extract is at least one of citrus extract, green tea polyphenols, or carvacrol.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. This invention uses bio-based low-density polyethylene and bio-based high-density polyethylene made from sugarcane ethanol as the matrix. Waste orange peel fiber and grain husks are washed, dried, and crushed, then mixed with thermoplastic starch as a natural filler. The starch is pre-treated with plasticizers and accelerators to convert it into melt-processable thermoplastic starch. The entire process does not use organic solvents and does not produce harmful byproducts.

[0016] 2. This invention utilizes plant extracts to replace metal ion antibacterial agents. First, the extract is encapsulated with cyclodextrin to form an antibacterial masterbatch. During melt blending, the antibacterial masterbatch is concentrated and added to the inner layer of the inner membrane using a multi-layer co-extrusion technique. The outer matrix layer provides thermal insulation for the internal antibacterial agent, reducing the residence time of the antibacterial agent in high-temperature zones and ensuring the effective retention of antibacterial active ingredients. The resulting membrane material has antibacterial capabilities in its inner layer, eliminates the risk of metal ion migration, and will not contaminate the food inside the packaging. It is suitable for packaging fresh food, ready-to-eat food, and other products with high hygiene requirements.

[0017] 3. After volume expansion and dispersion optimization, the inner membrane of this invention maintains the tensile strength and elongation at break required for packaging even with a high bio-based content, meeting the basic requirements for flexibility and strength of conventional food inner membranes. Due to the high filler content, the membrane material exhibits a semi-transparent white or matte appearance, which also provides a certain light-blocking effect, helping to reduce the oxidative deterioration of photosensitive foods.

[0018] 4. The material prepared by this invention can be processed using conventional twin-screw extruders and blown film equipment, with process parameters similar to those of ordinary polyethylene blown film. The combined action of plasticizers and dispersants maintains good fluidity in the highly filled system, ensuring a stable blown film process and a smooth film surface.

[0019] 5. The used membrane material can be composted in the industrial process together with kitchen waste. The starch and plant filler can be decomposed by microorganisms, providing multiple ways to treat packaging waste. Detailed Implementation

[0020] 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.

[0021] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The testing methods for various indicators of an environmentally friendly antibacterial polyethylene inner film material for packaging are as follows: Mechanical properties: According to GB 1040-79 "Tension Test Method for Plastics", the tensile strength and elongation at break of the specimens were determined at room temperature using a WD-5 electronic universal testing machine. The specimen size was φ3×10mm. Each sample was measured 10 times, and the average value of the 10 data was taken. Before measurement, the specimens were placed in an environment with a relative humidity of 50% for 48 hours, and the tensile rate was 100mm / min.

[0022] Antibacterial performance test: The sample was cut into round pieces with a diameter of 6 mm, sterilized by ultraviolet light, and placed in a sterile container. The purified Escherichia coli and Staphylococcus aureus were inoculated into nutrient broth and cultured at 37°C for 12 h. The bacterial solution was diluted according to the ratio, and the diluted bacterial solution was evenly spread on agar-coated petri dishes and cultured in an incubator at 37°C for 24 h. After the culture was completed, the diameter of the inhibition zone was measured.

[0023] Example 1 (1) The waste orange peel fiber and grain husk were washed to remove soil and impurities, dried at 90°C to constant weight, crushed by a pulverizer and passed through a 200-mesh sieve to obtain biomass filler powder; the powder was added to a high-speed mixer and a silane coupling agent solution was sprayed in. The silane coupling agent was γ-aminopropyltriethoxysilane, and the amount was 2% of the filler mass; the silane coupling agent was first diluted with anhydrous ethanol to a mass fraction of 15% before being sprayed in; the mixer temperature was set to 110°C and the stirring speed was 800 rpm, and the modification treatment was carried out for 20 min; after the modification was completed, the surface-modified biomass filler was vacuum dried at 80°C for 2 h to remove residual ethanol. (2) Add ordinary corn starch or potato starch to the reaction vessel, start stirring, dry at 90°C for 60 min, add plasticizer, which is a mixture of white oil and tri-n-butyl acetyl citrate in a mass ratio of 1:1, and the amount of plasticizer is 20% of the starch mass. Mix at 120°C and 800 rpm for 30 min to obtain thermoplastic starch paste; take out the paste, cool it to room temperature, pulverize it, and pass it through a 100-mesh sieve to obtain thermoplastic starch powder; (3) The plant extract and cyclodextrin were mixed at a mass ratio of 1:4, and deionized water was added. The solid-liquid ratio was 1:5. The mixture was stirred and encapsulated at 50°C for 1 hour. After encapsulation, it was vacuum dried at 60°C for 24 hours and pulverized through a 100-mesh sieve to obtain the encapsulation powder. The plant extract was citrus extract. The encapsulation powder was mixed with bio-based low-density polyethylene at a mass ratio of 1:2 and added to a high-speed mixer and mixed at room temperature for 15 minutes. Then, a twin-screw extruder was used for melt blending. The extruder temperature was set as follows: Zone 1 120°C, Zone 2 125°C, Zone 3 130°C, Zone 4 135°C, Zone 5 140°C, and the die temperature was 138°C. The screw speed was 200 rpm. After extrusion, the material was water-cooled, stretched, and pelletized to obtain antibacterial masterbatch. (4) Weigh each component according to the following weight proportions: 25 parts of bio-based low-density polyethylene, 5 parts of bio-based high-density polyethylene, 4 parts of ethylene ethyl acrylate, 1 part of maleic anhydride grafted polyethylene, 30 parts of thermoplastic starch, 5 parts of surface-modified biomass filler, 5 parts of antibacterial masterbatch, 3 parts of plasticizer mixture, and 1 part of dispersant; the dispersant is a mixture of oxidized polyethylene wax and trihydroxy polyoxypropylene ether in a mass ratio of 1:1; add bio-based low-density polyethylene, bio-based high-density polyethylene, ethylene ethyl acrylate, maleic anhydride grafted polyethylene, and dispersant to a high-speed mixer and mix at room temperature for 5 minutes to obtain a polyethylene mixture; add thermoplastic starch, surface-modified biomass filler, antibacterial masterbatch, and plasticizer mixture to another mixer and mix at room temperature for 15 minutes to obtain a filler mixture; use a twin-screw extruder for melt blending, and add the filler mixture from the main feeder. The polyethylene mixture is fed into the side feed port; the twin-screw extruder has a length-to-diameter ratio of 36 and a screw diameter of 55mm; the extruder temperature settings are as follows: Zone 1 135℃, Zone 2 145℃, Zone 3 150℃, Zone 4 155℃, Zone 5 160℃, Zone 6 165℃, Zone 7 155℃, Zone 8 150℃, and die temperature 155℃; the screw speed is 300rpm; the material is melt-blended and extruded from the die, passing through... The mixture was cooled in a water tank at 20°C, then pelletized by a pelletizer and dried at 70°C for 3 hours to obtain blended modified pellets. These pellets were then blown into a film using a blown film machine. The temperatures of each heating zone of the blown film machine were set as follows: Zone 1 160°C, Zone 2 165°C, Zone 3 170°C, and the die head temperature 165°C. The screw speed was 60 rpm, the traction speed was 10 m / min, and the blow-up ratio was 3. This resulted in an environmentally friendly, antibacterial, bio-based polyethylene inner film with a thickness of 50 μm.

[0024] Example 2 (1) The waste orange peel fiber and grain husk were washed to remove soil and impurities, dried at 90°C to constant weight, crushed by a pulverizer and passed through a 200-mesh sieve to obtain biomass filler powder; the powder was added to a high-speed mixer and a silane coupling agent solution was sprayed in. The silane coupling agent was γ-aminopropyltriethoxysilane, and the amount was 2% of the filler mass; the silane coupling agent was first diluted with anhydrous ethanol to a mass fraction of 15% before being sprayed in; the mixer temperature was set to 110°C and the stirring speed was 800 rpm, and the modification treatment was carried out for 25 min; after the modification was completed, the surface-modified biomass filler was vacuum dried at 80°C for 2 h to remove residual ethanol. (2) Add ordinary corn starch or potato starch to the reaction vessel, start stirring, dry at 90°C for 60 min, add plasticizer, which is a mixture of white oil and tri-n-butyl acetyl citrate in a mass ratio of 1:1, and the amount of plasticizer is 22.5% of the starch mass. Mix at 120°C and 800 rpm for 30 min to obtain thermoplastic starch paste; take out the paste, cool it to room temperature, pulverize it, and pass it through a 100-mesh sieve to obtain thermoplastic starch powder; (3) The plant extract and cyclodextrin were mixed at a mass ratio of 1:4.5, and deionized water was added. The solid-liquid ratio was 1:5.5. The mixture was stirred and encapsulated at 55°C for 1.5 h. After encapsulation, it was vacuum dried at 60°C for 24 h and pulverized through a 100-mesh sieve to obtain the encapsulation powder. The plant extract was citrus extract. The encapsulation powder was mixed with bio-based low-density polyethylene at a mass ratio of 1:2.5 and added to a high-speed mixer and mixed at room temperature for 15 min. Then, a twin-screw extruder was used for melt blending. The extruder temperature was set as follows: Zone 1 120°C, Zone 2 125°C, Zone 3 130°C, Zone 4 135°C, Zone 5 140°C, and the die temperature was 138°C. The screw speed was 200 rpm. After extrusion, the material was water-cooled, stretched, and pelletized to obtain antibacterial masterbatch. (4) Weigh each component according to the following weight proportions: 30 parts of bio-based low-density polyethylene, 10 parts of bio-based high-density polyethylene, 8 parts of ethylene ethyl acrylate, 2.5 parts of maleic anhydride grafted polyethylene, 38.5 parts of thermoplastic starch, 8.5 parts of surface-modified biomass filler, 7.5 parts of antibacterial masterbatch, 7 parts of plasticizer mixture, and 2.5 parts of dispersant; the dispersant is a mixture of oxidized polyethylene wax and trihydroxy polyoxypropylene ether in a mass ratio of 1:1; add bio-based low-density polyethylene, bio-based high-density polyethylene, ethylene ethyl acrylate, maleic anhydride grafted polyethylene, and dispersant to a high-speed mixer and mix at room temperature for 6 minutes to obtain a polyethylene mixture; add thermoplastic starch, surface-modified biomass filler, antibacterial masterbatch, and plasticizer mixture to another mixer and mix at room temperature for 15 minutes to obtain a filler mixture; use a twin-screw extruder for melt blending to mix the filler mixture. The material is fed through the main feed port, and the polyethylene mixture is fed through the side feed port; the twin-screw extruder has a length-to-diameter ratio of 36 and a screw diameter of 55mm; the extruder temperature settings are as follows: Zone 1 135℃, Zone 2 145℃, Zone 3 150℃, Zone 4 155℃, Zone 5 160℃, Zone 6 165℃, Zone 7 155℃, Zone 8 150℃, and the die temperature is 155℃; the screw speed is 300rpm; the material is melt-blended and extruded from the die, passing through... The mixture was cooled in a water bath at 22.5℃, then pelletized by a pelletizer and dried at 70℃ for 3 hours to obtain blended modified pellets. These pellets were then blown into a film using a blown film machine. The temperatures of each heating zone of the blown film machine were set as follows: Zone 1 160℃, Zone 2 165℃, Zone 3 170℃, and the die head temperature 165℃. The screw speed was 60 rpm, the traction speed was 10 m / min, and the blow-up ratio was 3. This process yielded an environmentally friendly, antibacterial, bio-based polyethylene inner film with a thickness of 50 μm.

[0025] Example 3 (1) The waste orange peel fiber and grain husk were washed to remove soil and impurities, dried at 90°C to constant weight, crushed by a pulverizer and passed through a 200-mesh sieve to obtain biomass filler powder; the powder was added to a high-speed mixer and a silane coupling agent solution was sprayed in. The silane coupling agent was γ-aminopropyltriethoxysilane, and the amount was 2% of the filler mass; the silane coupling agent was first diluted with anhydrous ethanol to a mass fraction of 15% before being sprayed in; the mixer temperature was set to 110°C and the stirring speed was 800 rpm, and the modification treatment was carried out for 30 min; after the modification was completed, the surface-modified biomass filler was vacuum dried at 80°C for 2 h to remove residual ethanol. (2) Add ordinary corn starch or potato starch to the reaction vessel, start stirring, dry at 90°C for 60 min, add plasticizer, which is a mixture of white oil and tri-n-butyl acetyl citrate in a mass ratio of 1:1, and the amount of plasticizer is 25% of the starch mass. Mix at 120°C and 800 rpm for 30 min to obtain thermoplastic starch paste; take out the paste, cool it to room temperature, pulverize it, and pass it through a 100-mesh sieve to obtain thermoplastic starch powder; (3) The plant extract and cyclodextrin were mixed at a mass ratio of 1:5, and deionized water was added. The solid-liquid ratio was 1:6. The mixture was stirred and encapsulated at 60°C for 2 hours. After encapsulation, the mixture was vacuum dried at 60°C for 24 hours and pulverized through a 100-mesh sieve to obtain the encapsulation powder. The plant extract was green tea polyphenol. The encapsulation powder was mixed with bio-based low-density polyethylene at a mass ratio of 1:3 and added to a high-speed mixer and mixed at room temperature for 15 minutes. Then, a twin-screw extruder was used for melt blending. The extruder temperature was set as follows: Zone 1 120°C, Zone 2 125°C, Zone 3 130°C, Zone 4 135°C, Zone 5 140°C, and the die temperature was 138°C. The screw speed was 200 rpm. After extrusion, the material was water-cooled, stretched, and pelletized to obtain antibacterial masterbatch. (4) Weigh each component according to the following weight proportions: 35 parts of bio-based low-density polyethylene, 15 parts of bio-based high-density polyethylene, 12 parts of ethylene ethyl acrylate, 4 parts of maleic anhydride grafted polyethylene, 47 parts of thermoplastic starch, 12 parts of surface-modified biomass filler, 10 parts of antibacterial masterbatch, 11 parts of plasticizer mixture, and 4 parts of dispersant; the dispersant is a mixture of oxidized polyethylene wax and trihydroxy polyoxypropylene ether in a mass ratio of 1:1; add bio-based low-density polyethylene, bio-based high-density polyethylene, ethylene ethyl acrylate, maleic anhydride grafted polyethylene, and dispersant to a high-speed mixer and mix at room temperature for 7 minutes to obtain a polyethylene mixture; add thermoplastic starch, surface-modified biomass filler, antibacterial masterbatch, and plasticizer mixture to another mixer and mix at room temperature for 15 minutes to obtain a filler mixture; use a twin-screw extruder for melt blending, and transfer the filler mixture from... The main feed port is used to add the polyethylene mixture, while the side feed port is used. The twin-screw extruder has a length-to-diameter ratio of 36 and a screw diameter of 55mm. The extruder temperature settings are as follows: Zone 1 135℃, Zone 2 145℃, Zone 3 150℃, Zone 4 155℃, Zone 5 160℃, Zone 6 165℃, Zone 7 155℃, Zone 8 150℃, and die temperature 155℃. The screw speed is 300rpm. After melt blending, the material is extruded from the die. The mixture was cooled in a water bath at 25°C, then pelletized by a pelletizer and dried at 70°C for 3 hours to obtain blended modified pellets. These pellets were then blown into a film using a blown film machine. The temperatures of each heating zone of the blown film machine were set as follows: Zone 1 160°C, Zone 2 165°C, Zone 3 170°C, and the die head temperature 165°C. The screw speed was 60 rpm, the traction speed was 10 m / min, and the blow-up ratio was 3. This process yielded an environmentally friendly, antibacterial, bio-based polyethylene inner film with a thickness of 50 μm.

[0026] Example 4 (1) The waste orange peel fiber and grain husk were washed to remove soil and impurities, dried at 90°C to constant weight, crushed by a pulverizer and passed through a 200-mesh sieve to obtain biomass filler powder; the powder was added to a high-speed mixer and a silane coupling agent solution was sprayed in. The silane coupling agent was γ-aminopropyltriethoxysilane, and the amount was 2% of the filler mass; the silane coupling agent was first diluted with anhydrous ethanol to a mass fraction of 15% before being sprayed in; the mixer temperature was set to 110°C and the stirring speed was 800 rpm, and the modification treatment was carried out for 35 min; after the modification was completed, the surface-modified biomass filler was vacuum dried at 80°C for 2 h to remove residual ethanol. (2) Add ordinary corn starch or potato starch to the reactor, start stirring, dry at 90°C for 60 min, add plasticizer, which is a mixture of white oil and tri-n-butyl acetyl citrate in a mass ratio of 1:1, and the amount of plasticizer is 27.5% of the starch mass. Mix at 120°C and 800 rpm for 30 min to obtain thermoplastic starch paste; take out the paste, cool it to room temperature, pulverize it, and pass it through a 100-mesh sieve to obtain thermoplastic starch powder; (3) The plant extract and cyclodextrin were mixed at a mass ratio of 1:5.5, and deionized water was added. The solid-liquid ratio was 1:7. The mixture was stirred and encapsulated at 65°C for 2.5 h. After encapsulation, it was vacuum dried at 60°C for 24 h and pulverized through a 100-mesh sieve to obtain the encapsulation powder. The plant extract was carvacrol. The encapsulation powder was mixed with bio-based low-density polyethylene at a mass ratio of 1:3.5 and added to a high-speed mixer and mixed at room temperature for 15 min. Then, a twin-screw extruder was used for melt blending. The extruder temperature was set as follows: Zone 1 120°C, Zone 2 125°C, Zone 3 130°C, Zone 4 135°C, Zone 5 140°C, and the die temperature was 138°C. The screw speed was 200 rpm. After extrusion, the material was water-cooled, stretched, and pelletized to obtain antibacterial masterbatch. (4) Weigh each component according to the following weight proportions: 40 parts of bio-based low-density polyethylene, 20 parts of bio-based high-density polyethylene, 16 parts of ethylene ethyl acrylate, 6 parts of maleic anhydride grafted polyethylene, 56 parts of thermoplastic starch, 16 parts of surface-modified biomass filler, 12.5 parts of antibacterial masterbatch, 15.4 parts of plasticizer mixture, and 6 parts of dispersant; the dispersant is a mixture of oxidized polyethylene wax and trihydroxy polyoxypropylene ether in a mass ratio of 1:1; add bio-based low-density polyethylene, bio-based high-density polyethylene, ethylene ethyl acrylate, maleic anhydride grafted polyethylene, and dispersant to a high-speed mixer and mix at room temperature for 8.5 min to obtain a polyethylene mixture; add thermoplastic starch, surface-modified biomass filler, antibacterial masterbatch, and plasticizer mixture to another mixer and mix at room temperature for 15 min to obtain a filler mixture; use a twin-screw extruder for melt blending to mix the filler mixture. The material is fed through the main feed port, and the polyethylene mixture is fed through the side feed port; the twin-screw extruder has a length-to-diameter ratio of 36 and a screw diameter of 55mm; the extruder temperature settings are as follows: Zone 1 135℃, Zone 2 145℃, Zone 3 150℃, Zone 4 155℃, Zone 5 160℃, Zone 6 165℃, Zone 7 155℃, Zone 8 150℃, and the die temperature is 155℃; the screw speed is 300rpm; the material is melt-blended and extruded from the die, passing through... The mixture was cooled in a water bath at 27.5℃, then pelletized by a pelletizer and dried at 70℃ for 3 hours to obtain blended modified pellets. These pellets were then blown into a film using a blown film machine. The temperatures of each heating zone of the blown film machine were set as follows: Zone 1 160℃, Zone 2 165℃, Zone 3 170℃, and the die head temperature 165℃. The screw speed was 60 rpm, the traction speed was 10 m / min, and the blow-up ratio was 3. This process yielded an environmentally friendly, antibacterial, bio-based polyethylene inner film with a thickness of 50 μm.

[0027] Example 5 (1) The waste orange peel fiber and grain husk were washed to remove soil and impurities, dried at 90°C to constant weight, crushed by a pulverizer and passed through a 200-mesh sieve to obtain biomass filler powder; the powder was added to a high-speed mixer and a silane coupling agent solution was sprayed in. The silane coupling agent was γ-aminopropyltriethoxysilane, and the amount was 2% of the filler mass; the silane coupling agent was first diluted with anhydrous ethanol to a mass fraction of 15% before being sprayed in; the mixer temperature was set to 110°C and the stirring speed was 800 rpm, and the modification treatment was carried out for 40 min; after the modification was completed, the surface-modified biomass filler was dried under vacuum at 80°C for 2 h to remove residual ethanol. (2) Add ordinary corn starch or potato starch to the reaction vessel, start stirring, dry at 90°C for 60 min, add plasticizer, which is a mixture of white oil and tri-n-butyl acetyl citrate in a mass ratio of 1:1, and the amount of plasticizer is 30% of the starch mass. Mix at 120°C and 800 rpm for 30 min to obtain thermoplastic starch paste; take out the paste, cool it to room temperature, pulverize it, and pass it through a 100-mesh sieve to obtain thermoplastic starch powder; (3) The plant extract and cyclodextrin were mixed at a mass ratio of 1:6, and deionized water was added. The solid-liquid ratio was 1:8. The mixture was stirred and encapsulated at 70°C for 3 hours. After encapsulation, the mixture was vacuum dried at 60°C for 24 hours and pulverized through a 100-mesh sieve to obtain the encapsulation powder. The plant extract was carvacrol. The encapsulation powder was mixed with bio-based low-density polyethylene at a mass ratio of 1:4 and added to a high-speed mixer and mixed at room temperature for 15 minutes. Then, a twin-screw extruder was used for melt blending. The extruder temperature was set as follows: Zone 1 120°C, Zone 2 125°C, Zone 3 130°C, Zone 4 135°C, Zone 5 140°C, and the die temperature was 138°C. The screw speed was 200 rpm. After extrusion, the material was water-cooled, stretched, and pelletized to obtain antibacterial masterbatch. (4) Weigh each component according to the following weight proportions: 45 parts of bio-based low-density polyethylene, 25 parts of bio-based high-density polyethylene, 20 parts of ethylene ethyl acrylate, 8 parts of maleic anhydride grafted polyethylene, 65 parts of thermoplastic starch, 20 parts of surface-modified biomass filler, 15 parts of antibacterial masterbatch, 19 parts of plasticizer mixture, and 8 parts of dispersant; the dispersant is a mixture of oxidized polyethylene wax and trihydroxy polyoxypropylene ether in a mass ratio of 1:1; add bio-based low-density polyethylene, bio-based high-density polyethylene, ethylene ethyl acrylate, maleic anhydride grafted polyethylene, and dispersant to a high-speed mixer and mix at room temperature for 10 min to obtain a polyethylene mixture; add thermoplastic starch, surface-modified biomass filler, antibacterial masterbatch, and plasticizer mixture to another mixer and mix at room temperature for 15 min to obtain a filler mixture; use a twin-screw extruder for melt blending to obtain the filler mixture. The polyethylene mixture is fed through the main feed port and then through the side feed port; the twin-screw extruder has a length-to-diameter ratio of 36 and a screw diameter of 55mm; the extruder temperature settings are as follows: Zone 1 135℃, Zone 2 145℃, Zone 3 150℃, Zone 4 155℃, Zone 5 160℃, Zone 6 165℃, Zone 7 155℃, Zone 8 150℃, and the die temperature is 155℃; the screw speed is 300rpm; the material is melt-blended and then extruded through the die. The mixture was cooled in a water tank at 30°C, then pelletized by a pelletizer and dried at 70°C for 3 hours to obtain blended modified granules. These granules were then blown into a film using a blown film machine. The temperatures of each heating zone of the blown film machine were set as follows: Zone 1 160°C, Zone 2 165°C, Zone 3 170°C, and the die head temperature 165°C. The screw speed was 60 rpm, the traction speed was 10 m / min, and the blow-up ratio was 3. This resulted in an environmentally friendly, antibacterial, bio-based polyethylene inner film with a thickness of 50 μm.

[0028] Comparative Example 1 The difference between Comparative Example 1 and Example 3 lies in the different step (1). Step (1) is changed to: washing the waste orange peel fiber and grain husk to remove soil and impurities, drying them at 90°C to constant weight, crushing them in a pulverizer and passing them through a 200-mesh sieve to obtain biomass filler powder; the powder is used directly without surface modification treatment; the remaining steps are the same as in Example 3.

[0029] Comparative Example 2 The difference between Comparative Example 2 and Example 3 lies in step (3). Step (3) is changed to: instead of preparing plant extract antibacterial masterbatch, silver ion antibacterial agent is used: silver ion-loaded zirconium phosphate and bio-based low-density polyethylene are mixed at a mass ratio of 1:20 and melt-blended using a twin-screw extruder. The extruder temperature is set to 120°C in zone 1, 125°C in zone 2, 130°C in zone 3, 135°C in zone 4, and 140°C in zone 5. The die temperature is 138°C and the screw speed is 200 rpm. After extrusion, the material is water-cooled, stretched, and pelletized to obtain metal antibacterial masterbatch. The remaining steps are the same as in Example 3.

[0030] Comparative Example 3 The difference between Comparative Example 3 and Example 3 lies in step (4). The components in step (4) are changed to: maleic anhydride-grafted polyethylene is not added; the remaining steps are the same as in Example 3.

[0031] Comparative Example 4 The difference between Comparative Example 4 and Example 3 lies in the difference between steps (3) and (4). In step (3), the bio-based low-density polyethylene is replaced with petroleum-based low-density polyethylene, and in step (4), the bio-based low-density polyethylene and bio-based high-density polyethylene are replaced with equal amounts of petroleum-based low-density polyethylene and petroleum-based high-density polyethylene; the remaining steps are the same as in Example 3.

[0032] Example of effect Table 1 below shows the performance analysis results of an environmentally friendly antibacterial polyethylene inner film material for packaging, using Examples 1 to 5 and Comparative Examples 1 to 4 of the present invention.

[0033] Table 1 It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. An environmentally friendly antibacterial polyethylene inner film material for packaging, characterized in that, The membrane material is prepared by washing, drying, crushing, and sieving waste orange peel fiber and grain husks, then spraying them with a silane coupling agent solution for surface modification, followed by drying to obtain a surface-modified biomass filler; drying starch and adding a plasticizer to obtain a thermoplastic starch paste, followed by cooling and crushing to obtain thermoplastic starch powder; encapsulating plant extracts with cyclodextrin and then melt-blending and pelletizing them with bio-based low-density polyethylene to obtain an antibacterial masterbatch; mixing bio-based low-density polyethylene, bio-based high-density polyethylene, ethylene ethyl acrylate, maleic anhydride-grafted polyethylene, and a dispersant to obtain a polyethylene mixture; mixing thermoplastic starch, surface-modified biomass filler, antibacterial masterbatch, and a plasticizer mixture to obtain a filler mixture; adding the filler mixture through the main feed port of a twin-screw extruder and the polyethylene mixture through the side feed port, melt-blending, extruding, cooling, pelletizing, drying, and then blowing the mixture into a film using a blown film extruder to obtain an environmentally friendly antibacterial bio-based polyethylene inner membrane.

2. The environmentally friendly antibacterial polyethylene inner film material for packaging according to claim 1, characterized in that, The biomass filler powder is obtained by drying waste orange peel fiber and grain husk at 90°C to constant weight, pulverizing and passing through a 200-mesh sieve.

3. The environmentally friendly antibacterial polyethylene inner film material for packaging according to claim 1, characterized in that, The silane coupling agent used in the surface modification is γ-aminopropyltriethoxysilane, and the amount used is 2% of the filler mass. It is first diluted with anhydrous ethanol to a mass fraction of 15% before being sprayed in. The temperature of the mixer is 110℃, the stirring speed is 800rpm, and the modification treatment is 20-40min.

4. The environmentally friendly antibacterial polyethylene inner film material for packaging according to claim 1, characterized in that, The thermoplastic starch powder is obtained by adding ordinary corn starch or potato starch to a reaction vessel, drying at 90°C for 60 minutes, adding a plasticizer (a mixture of white oil and tri-n-butyl acetyl citrate in a 1:1 mass ratio, with the amount of plasticizer being 20-25% of the starch mass), mixing at 120°C and 800 rpm for 30 minutes to obtain a thermoplastic starch paste; after cooling to room temperature, pulverizing and passing through a 100-mesh sieve.

5. The environmentally friendly antibacterial polyethylene inner film material for packaging according to claim 1, characterized in that, The antibacterial masterbatch is prepared by mixing plant extracts and cyclodextrin at a mass ratio of 1:4-1:6, adding deionized water, and stirring at 50-70℃ for 1-3 hours for inclusion. After inclusion, the mixture is vacuum dried at 60℃ for 24 hours and then pulverized through a 100-mesh sieve to obtain inclusion powder. The inclusion powder is then mixed with bio-based low-density polyethylene at a mass ratio of 1:2-1:4 and mixed at room temperature for 15 minutes. The mixture is then melt-blended using a twin-screw extruder with the following temperatures set: zone 1 120℃, zone 2 125℃, zone 3 130℃, zone 4 135℃, zone 5 140℃, die temperature 138℃, and screw speed 200 rpm. The material is then water-cooled, stretched, and pelletized after extrusion.

6. The environmentally friendly antibacterial polyethylene inner film material for packaging according to claim 1, characterized in that, The membrane material raw materials are weighed according to the following parts by weight: 25-45 parts of bio-based low-density polyethylene, 5-25 parts of bio-based high-density polyethylene, 4-20 parts of ethylene ethyl acrylate, 1-8 parts of maleic anhydride grafted polyethylene, 30-65 parts of thermoplastic starch, 5-20 parts of surface-modified biomass filler, 5-15 parts of antibacterial masterbatch, 3-19 parts of plasticizer mixture, and 1-8 parts of dispersant.

7. The environmentally friendly antibacterial polyethylene inner film material for packaging according to claim 6, characterized in that, The dispersant is a mixture of oxidized polyethylene wax and trihydroxy polyoxypropylene ether in a mass ratio of 1:

1.

8. The environmentally friendly antibacterial polyethylene inner film material for packaging according to claim 1, characterized in that, The modified blended granules are produced by melt blending using a twin-screw extruder. The filler mixture is added through the main feed port, and the polyethylene mixture is added through the side feed port. The twin-screw extruder has a length-to-diameter ratio of 36 and a screw diameter of 55 mm. The extruder temperatures are set as follows: Zone 1: 135℃, Zone 2: 145℃, Zone 3: 150℃, Zone 4: 155℃, Zone 5: 160℃, Zone 6: 165℃, Zone 7: 155℃, Zone 8: 150℃, and the die temperature is 155℃. The screw speed is 300 rpm. After melt blending, the material is extruded from the die, cooled in a water bath at 20-30℃, pelletized by a pelletizer, and dried at 70℃ for 3 hours to obtain the modified blended granules.

9. The environmentally friendly antibacterial polyethylene inner film material for packaging according to claim 1, characterized in that, The environmentally friendly antibacterial bio-based polyethylene inner film is formed by blown film forming using a blown film machine. The temperatures of each heating zone of the blown film machine are set as follows: zone 1 160℃, zone 2 165℃, zone 3 170℃, and the die head temperature 165℃; the screw speed is 60 rpm, the traction speed is 10 m / min, and the blow-up ratio is 3; thus, an environmentally friendly antibacterial bio-based polyethylene inner film with a thickness of 50 μm is obtained.

10. The environmentally friendly antibacterial polyethylene inner film material for packaging according to claim 1, characterized in that, The plant extract is at least one of citrus extract, green tea polyphenols, or carvacrol.

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