Polyethylene cover film for plastic container and preparation method of polyethylene cover film

Abstract

The invention relates to the technical field of polyethylene films, and particularly discloses a polyethylene cover film for a plastic container and a preparation method of the polyethylene cover film. The polyethylene cover film for the plastic container is mainly prepared from the following raw materials in parts by weight: 45 to 55 parts of low-density polyethylene, 45 to 55 parts of linear low-density polyethylene, 25 to 35 parts of metallocene low-density polyethylene, 15 to 25 parts of propylene-ethylene copolymer, 8 to 12 parts of modified graphene oxide, 0.1 to 0.5 part of lubricant and 0.2 to 0.8 part of antioxidant, the modified graphene oxide is obtained by treating graphene oxide by adopting 3-methacryloxy propyl trimethoxy silane, maleic anhydride, 2-acrylamide-2-methylpropanesulfonic acid and triallyl isocyanurate. The invention further discloses a preparation method of the modified graphene oxide. The polyethylene cover film has the advantages of high tensile strength, good barrier property and high heat sealing strength, and meets market requirements.

Description

Technical Field

[0001] This application relates to the field of polyethylene film technology, and more specifically, to a polyethylene capping film for plastic containers and a method for preparing the same. Background Technology

[0002] Plastic containers, due to their advantages such as light weight, impact resistance, low cost, and ease of processing, have been widely used in many fields, including food, daily chemicals, and pharmaceuticals. Polyethylene (PE) cap film is a film used to seal the opening of plastic containers. It typically involves first applying the PE cap film to the opening of the plastic container, followed by heat sealing to secure the PE cap film to the plastic container. Existing PE cap films generally use low-density polyethylene as raw material, obtained through melt extrusion, blown film production, and cooling. While this type of PE cap film can achieve heat sealing at the opening of plastic containers, its tensile strength and barrier properties are poor. It is easily damaged by external forces during processing and use, and it is also prone to oxygen permeation, causing oxidation and deterioration of the contents, making it difficult to meet market demands. Summary of the Invention

[0003] To improve the tensile strength and barrier properties of polyethylene capping film, this application provides a polyethylene capping film for plastic containers and a method for preparing the same.

[0004] In a first aspect, this application provides a polyethylene cap film for plastic containers, employing the following technical solution: A polyethylene cap film for plastic containers, the polyethylene cap film being mainly made from the following raw materials in parts by weight: 45-55 parts of low-density polyethylene, 45-55 parts of linear low-density polyethylene, 25-35 parts of metallocene low-density polyethylene, 15-25 parts of propylene-ethylene copolymer, 8-12 parts of modified graphene oxide, 0.1-0.5 parts of lubricant, and 0.2-0.8 parts of antioxidant; wherein the modified graphene oxide is obtained by treating graphene oxide with 3-methacryloyloxypropyltrimethoxysilane, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid, and triallyl isocyanurate.

[0005] The polyethylene capping film for plastic containers described in this application, through the interplay of raw materials, achieves a transverse tensile strength >35MPa, a longitudinal tensile strength >40MPa, and a water vapor permeability <1g / (m²). 2 •24h), oxygen permeability <1500cm 3 / (m 2With a tensile strength of 0.1 MPa (24h) and a heat seal strength >30 N / 15 mm, this film exhibits excellent overall performance, including high tensile strength, good barrier properties, and high heat seal strength. It effectively reduces damage during processing and use, increases stability, and effectively blocks the penetration of oxygen and water vapor, minimizing oxidation, deterioration, or moisture absorption of the contents, thus extending shelf life and meeting market demands. When used on plastic containers, this film can heat-seal both PE and PP plastic container openings, expanding its application range.

[0006] The polyethylene capping film of this application is compounded with a specific ratio of low-density polyethylene, linear low-density polyethylene, metallocene low-density polyethylene, and propylene-ethylene copolymer to balance the flexibility, mechanical strength, and heat-sealing properties of the polyethylene capping film. Based on this, modified graphene oxide is added, and 3-methacryloyloxypropyltrimethoxysilane, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid, and triallyl isocyanurate are grafted onto the surface of the graphene oxide, introducing a large number of siloxy groups, ester groups, anhydride groups, amide groups, sulfonic acid groups, isocyanurate rings, etc., forming an interconnected and functionally complementary organic whole. It not only increases dispersion but also enhances interfacial bonding, strengthens network structure, increases density, reduces network structure defects, reduces slippage, increases network structure stability, improves tensile strength, and forms a continuous "labyrinthine" barrier network in the polyethylene matrix, extending the permeation path of water vapor and oxygen, improving barrier properties. It also reduces agglomeration at the heat-sealing interface, reduces heat-sealing interface defects, increases interfacial compatibility, and forms "nanorhines" at the heat-sealing interface to improve heat-sealing strength, enabling the polyethylene capping film to exhibit superior overall performance.

[0007] Optionally, the modified graphene oxide is prepared using the following method: S1. At a temperature of 60-70℃, water and graphene oxide are mixed, 3-(methacryloyloxy)propyltrimethoxysilane is added, the mixture is stirred for 2-4 hours, filtered, and silanized graphene oxide is obtained. S2. At a temperature of 60-70℃, organic solvent and silanized graphene oxide are mixed, maleic anhydride, 2-acrylamide-2-methylpropanesulfonic acid and triallyl isocyanurate are added and mixed, organic peroxide is added, and the mixture is stirred for 4-6 hours. After filtration, washing and drying, modified graphene oxide is obtained.

[0008] Optionally, the weight ratio of the graphene oxide, 3-methacryloyloxypropyltrimethoxysilane, maleic anhydride, 2-acrylamide-2-methylpropanesulfonic acid, and triallyl isocyanurate is 20:(2-4):(0.5-1.5):(0.5-1.5):(0.3-0.7).

[0009] By employing the above technical solution, 3-(methacryloyloxy)propyltrimethoxysilane is first grafted onto the surface of graphene oxide to obtain silanized graphene oxide containing carbon-carbon unsaturated bonds. Then, the silanized graphene oxide, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid, and triallyl isocyanurate are mixed and subjected to a free radical grafting polymerization reaction in the presence of an organic peroxide to achieve the grafting of maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid, and triallyl isocyanurate, thus obtaining modified graphene oxide. The step-by-step grafting method facilitates the preparation of modified graphene oxide and ensures the stability of the grafting.

[0010] Optionally, the weight ratio of the graphene oxide to the organic peroxide is 20:(0.2-0.5).

[0011] By adopting the above technical solution, the amount of organic peroxide added is limited to ensure that there are enough free radicals in the system to initiate grafting, thereby ensuring the efficiency and amount of free radical grafting polymerization reaction and ensuring the stability of modified graphene oxide.

[0012] Optionally, the organic peroxide is selected from one or more of benzoyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, and tert-butyl peroxide.

[0013] By adopting the above technical solution, the organic peroxides are limited, which facilitates the selection of organic peroxides.

[0014] Optionally, the weight ratio of the graphene oxide, water, and organic solvent is 20:(400-600):(400-600).

[0015] In several implementations, the weight ratio of graphene oxide, water, and organic solvent is 20:500:500. However, the weight ratio can also be set to 20:400:400, 20:400:500, 20:400:600, 20:500:400, 20:500:600, 20:600:400, 20:600:500, 20:600:600, etc., as needed. But it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0016] Optionally, the graphene oxide is multilayer graphene oxide, with a thickness of 1-10 nm, a sheet diameter of 1-20 μm, and an oxygen content of 20-40 wt%.

[0017] By adopting the above technical solution, the thickness, sheet diameter, and oxygen content of the multilayer graphene oxide are limited, ensuring the stability of the multilayer graphene oxide source. In several embodiments, the thickness of the multilayer graphene oxide is 6nm, the sheet diameter is 15μm, and the oxygen content is 30wt%. The thickness can also be set to 1nm, 3nm, 5nm, 7nm, 10nm, etc., as needed; the sheet diameter can also be set to 1μm, 3μm, 5μm, 7μm, 10μm, 13μm, 17μm, 20μm, etc., as needed; and the oxygen content can also be set to 20wt%, 25wt%, 35wt%, 40wt%, etc., as needed. However, it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] Optionally, the organic solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, toluene, and xylene.

[0019] By employing the above technical solution, the organic solvent is limited, facilitating its selection. Furthermore, the organic solvent ensures sufficient contact between silanized graphene oxide, maleic anhydride, 2-acrylamide-2-methylpropanesulfonic acid, and triallyl isocyanurate, guaranteeing the smooth progress of the reaction and ensuring the quality, performance, and effectiveness of the modified graphene oxide.

[0020] Optionally, the organic solvent is selected from N,N-dimethylformamide and xylene, and the weight ratio of N,N-dimethylformamide and xylene is (1-3):(1-3).

[0021] In several implementations, the weight ratio of N,N-dimethylformamide to xylene is 1:1. However, the weight ratio can also be set to 1:2, 1:3, 2:1, 2:3, 3:1, 3:2, etc., as needed, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Optionally, the lubricant is selected from one or more of erucamide, oleamide, stearamide, and ethylene bis-stearamide; the antioxidant is selected from one or more of antioxidant 1076, antioxidant 1010, antioxidant 626, and antioxidant 168.

[0023] By adopting the above technical solution, the lubricant and antioxidant are limited, facilitating their selection. Furthermore, the lubricant improves the processing fluidity of the polyethylene capping film, while the antioxidant reduces oxidation during processing and use, extending its service life.

[0024] Optionally, the antioxidant is selected from antioxidant 1010 and antioxidant 168, and the weight ratio of antioxidant 1010 and antioxidant 168 is (1-3):(1-3).

[0025] In several implementations, the weight ratio of antioxidant 1010 and antioxidant 168 is 2:1. However, the weight ratio can also be set to 1:1, 1:2, 1:3, 2:3, 3:1, 3:2, etc., as needed, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Optionally, the thickness of the polyethylene cover film is 10-80 μm.

[0027] By adopting the above technical solution, the polyethylene cap film, with a thickness ranging from 10 to 80 μm, can maintain good tensile strength and barrier properties, meeting the requirements for heat sealing of plastic container openings. In several embodiments, the thickness of the polyethylene cap film is 50 μm, but it can also be set to 10 μm, 20 μm, 30 μm, 40 μm, 60 μm, 70 μm, 80 μm, etc., as needed, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] Secondly, this application provides a method for preparing the polyethylene cap film for plastic containers, which adopts the following technical solution: A method for preparing the polyethylene cap film for plastic containers includes the following steps: Low-density polyethylene, linear low-density polyethylene, metallocene low-density polyethylene, propylene-ethylene copolymer, modified graphene oxide, lubricant, and antioxidant are mixed, melt-extruded, blown into a film, and cooled to obtain a polyethylene capping film.

[0029] By adopting the above technical solution, the preparation of polyethylene cover film is facilitated.

[0030] Optionally, the melt extrusion temperature is 170-190℃.

[0031] In several implementations, the melt extrusion temperature is 180°C, but it can also be set to 170°C, 175°C, 185°C, 190°C, etc. as needed, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] In summary, this application has at least the following beneficial effects: 1. The polyethylene capping film for plastic containers of this application, through the interaction of raw materials, has the advantages of high tensile strength, good barrier properties, and high heat-sealing strength, and its tensile strength is >35MPa and water vapor transmission rate is <1g / (m²). 2 •24h), oxygen permeability <1500cm 3 / (m 2With a heat-sealing strength of >30N / 15mm and a pressure of 0.1MPa (24h), it exhibits excellent comprehensive performance and meets market demands.

[0033] 2. The polyethylene cap film of this application is compounded with a specific ratio of low-density polyethylene, linear low-density polyethylene, metallocene low-density polyethylene, and propylene-ethylene copolymer to balance the flexibility, mechanical strength and heat-sealing properties of the polyethylene cap film. It can achieve heat sealing at the opening of PE plastic containers as well as heat sealing at the opening of PP plastic containers, thus expanding the application range.

[0034] 3. The polyethylene cover film of this application incorporates modified graphene oxide in the raw materials. The modified graphene oxide contains a large number of siloxy groups, ester groups, acid anhydride groups, amide groups, sulfonic acid groups, isocyanurate rings, and other groups, forming an interconnected and functionally complementary organic whole, which improves tensile strength, barrier properties, and heat-sealing strength, thus enabling the polyethylene cover film to exhibit superior overall performance. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the embodiments.

[0036] Preparation Example Preparation Example 1 A modified graphene oxide is prepared by the following method: S1. At a rotation speed of 400 r / min and a temperature of 65℃, 20 kg of graphene oxide was added to 500 kg of water and stirred for 10 min. Then, 3 kg of 3-(methacryloyloxy)propyltrimethoxysilane was added and stirred for 3 h. Finally, the mixture was filtered to obtain silanized graphene oxide.

[0037] The multilayer graphene oxide has a thickness of 6 nm, a sheet diameter of 15 μm, and an oxygen content of 30 wt%.

[0038] S2. At a rotation speed of 400 r / min and a temperature of 65℃, the silanized graphene oxide obtained in step S1 was added to 500 kg of organic solvent and stirred for 10 min. Then, 1 kg of maleic anhydride, 1 kg of 2-acrylamido-2-methylpropanesulfonic acid, and 0.5 kg of triallyl isocyanurate were added and stirred for 10 min. Finally, 0.3 kg of organic peroxide was added and stirred for 5 h. The mixture was then filtered, washed once with 200 kg of xylene, once with 200 kg of ethanol, once with 200 kg of 50% ethanol aqueous solution, and once with 200 kg of water. The mixture was then dried at 90℃ to obtain modified graphene oxide.

[0039] The organic solvent is selected from N,N-dimethylformamide and xylene, and the weight ratio of N,N-dimethylformamide and xylene is 1:1; the organic peroxide is selected from benzoyl peroxide.

[0040] Preparation Example 2 A modified graphene oxide differs from that in Preparation Example 1 in that the amount of 3-methacryloxypropyltrimethoxysilane added in step S1 is different, and the amount of 3-methacryloxypropyltrimethoxysilane added is 2 kg. Meanwhile, in step S2, the amounts of maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid, triallyl isocyanurate, and organic peroxide added are different, with maleic anhydride added at 0.5 kg, 2-acrylamido-2-methylpropanesulfonic acid at 1.5 kg, triallyl isocyanurate at 0.3 kg, and organic peroxide at 0.2 kg.

[0041] Preparation Example 3 A modified graphene oxide differs from that in Preparation Example 1 in that the amount of 3-methacryloxypropyltrimethoxysilane added in step S1 is different, and the amount of 3-methacryloxypropyltrimethoxysilane added is 4 kg. Meanwhile, in step S2, the amounts of maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid, triallyl isocyanurate, and organic peroxide added are different, with maleic anhydride added at 1.5 kg, 2-acrylamido-2-methylpropanesulfonic acid at 0.5 kg, triallyl isocyanurate at 0.7 kg, and organic peroxide at 0.5 kg. Example

[0042] Table 1. Raw material consumption of polyethylene cover film (unit: kg) Example Example 1 Example 2 Example 3 Low-density polyethylene 50 45 55 Linear low-density polyethylene 50 55 45 Metallocene low-density polyethylene 30 25 35 propylene-ethylene copolymer 20 15 25 Modified graphene oxide 10 12 8 lubricant 0.3 0.1 0.5 antioxidants 0.5 0.8 0.2 Example 1 A polyethylene cap film for plastic containers, the polyethylene cap film having a thickness of 50 μm. The raw materials and their proportions for the polyethylene cap film are shown in Table 1.

[0043] Among them, the low-density polyethylene was selected from Daqing Petrochemical 2426H LDPE; the linear low-density polyethylene was selected from Daqing Petrochemical DFDA-7042 LLDPE; the metallocene low-density polyethylene was selected from Dow 5401G LLDPE; and the propylene-ethylene copolymer was selected from Dow's propylene-ethylene copolymer VERSIFY. TM2300; the lubricant is selected from ethylene bis-stearamide; the antioxidant is selected from antioxidant 1010 and antioxidant 168, and the weight ratio of antioxidant 1010 and antioxidant 168 is 2:1; the modified graphene oxide is obtained by treating graphene oxide with 3-methacryloyloxypropyltrimethoxysilane, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid, and triallyl isocyanurate, and the modified graphene oxide is prepared by the method of Preparation Example 1.

[0044] A method for preparing a polyethylene cap film for plastic containers includes the following steps: Linear low-density polyethylene, metallocene low-density polyethylene, and propylene-ethylene copolymer were added to low-density polyethylene and stirred for 5 minutes. Modified graphene oxide, lubricant, and antioxidant were added and stirred for 5 minutes. Then, using a blown film extruder, the mixture was melt-extruded at 180°C, blown into a film, and cooled to obtain a polyethylene capping film.

[0045] Example 2 A polyethylene capping film for plastic containers differs from Example 1 in that the raw material ratio of the polyethylene capping film is different, and the raw material ratio of the polyethylene capping film is shown in Table 1.

[0046] Example 3 A polyethylene capping film for plastic containers differs from Example 1 in that the raw material ratio of the polyethylene capping film is different, and the raw material ratio of the polyethylene capping film is shown in Table 1.

[0047] Example 4 A polyethylene capping film for plastic containers differs from Example 1 in that the modified graphene oxide in the polyethylene capping film is from a different source, and the modified graphene oxide is prepared using the method of Preparation Example 2.

[0048] Example 5 A polyethylene capping film for plastic containers differs from Example 1 in that the modified graphene oxide in the polyethylene capping film is from a different source, and the modified graphene oxide is prepared using the method of Preparation Example 3.

[0049] Comparative Example Comparative Example 1 A polyethylene capping film for plastic containers differs from Example 1 in that, in the raw materials of the polyethylene capping film, an equal amount of graphene oxide replaces the modified graphene oxide.

[0050] Comparative Example 2 A polyethylene capping film for plastic containers differs from Example 1 in that, in the preparation method of modified graphene oxide in the raw materials of the polyethylene capping film, an equal amount of 3-aminopropyltriethoxysilane is used to replace 3-methacryloyloxypropyltrimethoxysilane, maleic anhydride, 2-acrylamide-2-methylpropanesulfonic acid, and triallyl isocyanurate.

[0051] Comparative Example 3 A polyethylene capping film for plastic containers differs from Example 1 in that, in the preparation method of modified graphene oxide in the raw materials of the polyethylene capping film, maleic anhydride, 2-acrylamide-2-methylpropanesulfonic acid, and triallyl isocyanurate are replaced with an equal amount of 3-methacryloyloxypropyltrimethoxysilane.

[0052] Comparative Example 4 A polyethylene capping film for plastic containers differs from Example 1 in that, in the preparation method of modified graphene oxide in the raw materials of the polyethylene capping film, maleic anhydride is used to replace 2-acrylamide-2-methylpropanesulfonic acid and triallyl isocyanurate.

[0053] Comparative Example 5 A polyethylene capping film for plastic containers differs from Example 1 in that, in the preparation method of modified graphene oxide in the raw materials of the polyethylene capping film, an equal amount of 2-acrylamide-2-methylpropanesulfonic acid is used to replace triallyl isocyanurate.

[0054] Comparative Example 6 A polyethylene capping film for plastic containers differs from Example 1 in that, in the preparation method of modified graphene oxide in the raw materials of the polyethylene capping film, an equal amount of triallyl isocyanurate is used to replace 2-acrylamide-2-methylpropanesulfonic acid.

[0055] For performance testing, the polyethylene cap films obtained in Examples 1-5 and Comparative Examples 1-6 were used as samples, and the following performance tests were performed on the polyethylene cap films. The test results are shown in Table 2.

[0056] In accordance with GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", the transverse tensile strength and longitudinal tensile strength of polyethylene cover film were tested.

[0057] The water vapor transmission rate of the polyethylene cover film was tested according to YBB00092003-2015 "Method for Determination of Water Vapor Transmission".

[0058] The oxygen permeability of the polyethylene cover film was tested according to YBB00082003-2015 "Determination of Gas Transmission Rate".

[0059] According to GB / T34445-2017 "Determination of heat-sealing properties of thermoplastic plastics and their composites", the heat-sealing strength of polyethylene cover film was tested.

[0060] Table 2 Detection Results As shown in Table 2, the polyethylene cover film of this application exhibits high tensile strength, with a transverse tensile strength of 35.62-38.33 MPa and a longitudinal tensile strength of 40.88-43.56 MPa, demonstrating its high tensile strength characteristics. Furthermore, it also exhibits low water vapor transmission and oxygen transmission rates, with a water vapor transmission rate of 0.81-0.93 g / (m²). 2 • 24h), oxygen permeability is 985-1345 cm⁻¹ 3 / (m 2 It exhibits good barrier properties (with a tensile strength of 0.1 MPa over 24 hours). Simultaneously, it also possesses high heat-sealing strength, ranging from 30.74 to 32.65 N / 15 mm, demonstrating high heat-sealing strength. In other words, the polyethylene cover film of this application, through the synergistic effect of the raw materials, possesses advantages such as high tensile strength, good barrier properties, and high heat-sealing strength, exhibiting excellent comprehensive performance and meeting market demands.

[0061] Comparative Example 1 and Example 1 were compared. Graphene oxide was added to the raw material of the polyethylene cap film in Comparative Example 1; modified graphene oxide was added to the raw material of the polyethylene cap film in Example 1. It can be seen that modifying graphene oxide can improve the performance and increase the overall performance of the polyethylene cap film.

[0062] Comparative Examples 2 and 3 were compared. The modified graphene oxide in Comparative Example 2 was obtained by treating graphene oxide with 3-aminopropyltriethoxysilane; the modified graphene oxide in Comparative Example 3 was obtained by treating graphene oxide with 3-methacryloxypropyltrimethoxysilane. This shows that grafting 3-aminopropyltriethoxysilane or 3-methacryloxypropyltrimethoxysilane onto the surface of graphene oxide is beneficial for improving the performance of the polyethylene cap film. Furthermore, Comparative Example 4, which was obtained by treating graphene oxide with 3-methacryloxypropyltrimethoxysilane and maleic anhydride, shows that grafting 3-methacryloxypropyltrimethoxysilane onto the surface of graphene oxide has limited effect on improving the performance of the polyethylene cap film. Moreover, grafting maleic anhydride onto the surface of 3-methacryloxypropyltrimethoxysilane can further improve the tensile strength, barrier properties, and heat-sealing strength of the polyethylene cap film.

[0063] Comparative Examples 5-6 and Example 1 were compared. The modified graphene oxide of Comparative Example 5 was obtained by treating graphene oxide with 3-methacryloxypropyltrimethoxysilane, maleic anhydride, and 2-acrylamido-2-methylpropanesulfonic acid; the modified graphene oxide of Comparative Example 6 was obtained by treating graphene oxide with 3-methacryloxypropyltrimethoxysilane, maleic anhydride, and triallyl isocyanurate; the modified graphene oxide of Example 1 was obtained by treating graphene oxide with 3-methacryloxypropyltrimethoxysilane, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid, and triallyl isocyanurate. This demonstrates that by grafting 3-methacryloxypropyltrimethoxysilane and maleic anhydride onto the surface of graphene oxide, and simultaneously grafting 2-acrylamido-2-methylpropanesulfonic acid and triallyl isocyanurate, the surface contains a large number of siloxy groups, ester groups, acid anhydride groups, amide groups, sulfonic acid groups, isocyanurate rings, and other groups, forming an interconnected and functionally complementary organic whole. This further improves tensile strength, barrier properties, and heat-sealing strength, giving the polyethylene cover film superior overall performance.

[0064] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A polyethylene lidding film for a plastic container, characterized by: The polyethylene cover film is mainly made of the following raw materials by weight: low density polyethylene 45-55 parts, linear low density polyethylene 45-55 parts, metallocene low density polyethylene 25-35 parts, propylene-ethylene copolymer 15-25 parts, modified graphene oxide 8-12 parts, lubricant 0.1-0.5 parts, antioxidant 0.2-0.8 parts; the modified graphene oxide is obtained by treating graphene oxide with 3-methacryloyloxypropyltrimethoxysilane, maleic anhydride, 2-acrylamide-2-methylpropane sulfonic acid, triallyl isocyanurate.

2. A polyethylene lidding film for a plastic container according to claim 1, characterised in that: The modified graphene oxide is prepared by the following method: S1, mix water and graphene oxide at a temperature of 60-70℃, add 3-(methacryloyloxy) propyltrimethoxysilane, stir for 2-4h, filter, and obtain silanized graphene oxide; S2, mix organic solvent and silanized graphene oxide at a temperature of 60-70℃, add maleic anhydride, 2-acrylamide-2-methylpropane sulfonic acid, triallyl isocyanurate mixture, add organic peroxide, stir for 4-6h, filter, wash, dry, and obtain modified graphene oxide.

3. A polyethylene lidding film for a plastic container according to claim 2, characterised in that: The weight ratio of the graphene oxide, 3-methacryloyloxypropyltrimethoxysilane, maleic anhydride, 2-acrylamide-2-methylpropane sulfonic acid, and triallyl isocyanurate is 20:(2-4):(0.5-1.5):(0.5-1.5):(0.3-0.7).

4. A polyethylene lidding film for a plastic container according to claim 2, wherein: The weight ratio of the graphene oxide and organic peroxide is 20:(0.2-0.5).

5. A polyethylene lidding film for a plastic container according to claim 2, wherein: The organic peroxide is selected from one or more of dibenzoyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, and tert-butyl peroxybenzoate.

6. A polyethylene lidding film for a plastic container according to claim 2, wherein: The graphene oxide is multilayer graphene oxide, the thickness of the multilayer graphene oxide is 1-10nm, the flake diameter is 1-20μm, and the oxygen content is 20-40wt%.

7. A polyethylene lidding film for a plastic container according to claim 2, wherein: The organic solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, toluene, and xylene.

8. A polyethylene lidding film for a plastic container according to claim 1, characterized in that: The lubricant is selected from one or more of erucamide, oleamide, stearamide, and ethylene bis-stearamide; the antioxidant is selected from one or more of antioxidant 1076, antioxidant 1010, antioxidant 626, and antioxidant 168.

9. A polyethylene lidding film for a plastic container according to claim 1, characterized in that: The thickness of the polyethylene cover film is 10-80μm.

10. A method of producing a polyethylene lidding film for plastic containers according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: Mix low density polyethylene, linear low density polyethylene, metallocene low density polyethylene, propylene-ethylene copolymer, modified graphene oxide, lubricant, and antioxidant, melt extrude, film blowing, cool, and obtain polyethylene cover film.

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