High-barrier packaging material based on PE and forming process thereof

Abstract

The invention discloses a PE-based high-barrier packaging material and a forming process thereof, and belongs to the technical field of packaging materials, the packaging material is formed by sequentially compounding a surface layer film, a middle layer film and an inner layer heat sealing layer film; wherein the surface-layer film comprises the following raw materials: metallocene polyethylene, high-density polyethylene, an antioxidant and a lubricant, and the surface of the surface-layer film is coated with a functional coating solution; the middle-layer film is prepared from the following raw materials: high-density polyethylene, a modification additive, a compatilizer, an antioxidant and a lubricant; the inner heat-sealing layer film is prepared from the following raw materials: metallocene polyethylene, low-density polyethylene, an antioxidant and a lubricant. The prepared single-material high-barrier packaging material can solve the problem that a traditional multi-layer composite packaging material is difficult to recycle, has excellent barrier performance and mechanical strength, and meanwhile meets the requirements of environmental protection and consumers.

Description

Technical Field

[0001] This invention belongs to the field of packaging materials technology, and in particular relates to a high-barrier packaging material based on PE and its molding process. Background Technology

[0002] With increasing global environmental awareness, consumers' demand for sustainable packaging is growing, and the packaging industry is accelerating its transformation towards environmental protection and sustainability. Traditional multi-layer composite packaging materials face numerous challenges in recycling and reuse, such as insufficient physical strength and processability, hindering effective resource recycling. This has made the development of high-barrier packaging using a single material one of the hottest research topics in the international packaging field. Internationally, many well-known companies and research institutions have been deeply involved in this area and have made significant progress. For example, Dow Chemical has launched a portfolio of high-barrier, recyclable polyethylene products suitable for flexible packaging. Its food flexible packaging operates on a high-speed packaging machine at 240 meters per minute, with barrier performance equivalent to an EVOH multi-layer structure. Swiss company Bobst has launched its "Generation 2.0" high-barrier flexible packaging solution, with samples including new ultra-high and high-barrier all-polypropylene (PP) composite bags. By combining digital inkjet printing with UV flexographic printing and solvent-free adhesives, it achieves recyclable high-barrier packaging bags using a single material. The deinkable, recyclable single-material polyethylene packaging bag, developed collaboratively by five companies including ExxonMobil, utilizes various high-performance polyethylene resins and advanced coating and printing technologies. It boasts excellent barrier properties, physical characteristics, and shelf appeal, and exhibits good recyclability. These examples demonstrate the technological advancement and innovation capabilities of foreign companies in this field.

[0003] Domestically, with the continuous tightening of national environmental protection policies, higher requirements have been placed on the recycling and utilization of packaging waste. After years of development, the domestic plastic packaging industry has gradually approached international advanced levels. In the field of single-material high-barrier packaging, domestic research institutions are actively exploring new materials and technologies, providing theoretical support and technological innovation for industry development. Some research teams have achieved certain research results in areas such as polyolefin material modification and high-performance additives, providing new ideas and methods for improving the performance of single-material packaging. Domestic enterprises are collaborating with universities and research institutions to conduct research and development on single-material high-barrier packaging products, launching products that meet market demands, while investing in equipment upgrades and technological transformation to improve production efficiency and product quality. However, the overall technological level in this field still lags behind that of foreign countries. Domestic enterprises still have considerable room for improvement in areas such as material stability, the refinement of production processes, and the consistency of product quality, requiring further increases in research and development investment to narrow the gap with foreign countries.

[0004] Driven by increased consumer environmental awareness and stricter policy requirements, the global packaging industry will focus on functionalization and high performance, intelligentization and informatization, and environmental friendliness in packaging. This includes improving the barrier properties and mechanical properties of packaging materials, adopting recyclable and biodegradable materials, and integrating smart elements to meet the needs of multiple sectors. Regarding functionalization and high performance, continuous improvement in the barrier properties, mechanical properties, and chemical resistance of materials is crucial to meet the high barrier and safety requirements of food, pharmaceuticals, and chemical products. In terms of intelligentization and informatization, future packaging will incorporate more intelligent and informational elements, such as adding sensors and chips to packaging bags to achieve real-time monitoring and traceability of information such as temperature and humidity inside the bag, thereby improving product quality and safety. In terms of environmental friendliness, the use of recyclable and biodegradable single-material packaging will become the mainstream trend in future packaging materials. This will not only reduce reliance on traditional petroleum-based plastics and reduce the pollution of packaging waste, but also improve the recycling rate of packaging materials, achieving resource recycling. Single-material packaging aligns with sustainable development requirements, and its market size continues to grow. According to data from the Market Study Report, the global market for single-material plastic packaging films was valued at US$38.78 billion in 2023 and is projected to reach US$70.9 billion by 2030, representing a CAGR of 8.7%. According to QYR statistics, the global market for single-material barrier packaging generated US$6.53 billion in sales in 2023 and is projected to reach US$8.82 billion by 2030, with a CAGR of 4.46% from 2024 to 2030.

[0005] In the flexible packaging sector, packaging with a load-bearing capacity exceeding 5kg is generally defined as heavy-duty packaging. Heavy-duty packaging bags, due to their ability to withstand greater weight and volume, are widely used in the food and chemical industries. In the food industry, the global flexible food packaging market reached 58.006 billion yuan in 2023 and is projected to reach 74.755 billion yuan by 2029. As people's living standards improve, the requirements for the safety, environmental friendliness, and convenience of food packaging are increasing. The demand for heavy-duty packaging bags is rising because they effectively prevent food contamination and extend shelf life; convenient designs such as self-sealing bags and zipper bags are increasingly favored. In the chemical industry, because many chemical products are corrosive, volatile, or toxic, high requirements are placed on the barrier properties and chemical resistance of packaging. Heavy-duty packaging bags prevent products from contacting the outside environment, avoiding leakage and deterioration, and ensuring safe transportation and storage. With the development of the chemical industry and the increasing environmental protection requirements, the demand for heavy-duty packaging bags will also increase. However, heavy-duty packaging is typically a multi-layered composite structure, with nylon (polyamide) being widely used due to its extremely high puncture resistance. Common structures include NY / PE, NY / NY / PE, and PET / NY / PE. However, these packages, composed of multiple materials such as polyamide, polyethylene, and polyester, are often difficult to recycle and cannot be degraded, resulting in significant environmental impact after disposal. To address these issues, this invention aims to develop a high-barrier heavy-duty packaging material made from a single material. This material can overcome the recycling difficulties of traditional multi-layered composite heavy-duty packaging bags, meet environmental and consumer demands, and promote the sustainable development of the packaging industry. Summary of the Invention

[0006] The purpose of this invention is to provide a high-barrier packaging material based on PE. Using PE as a single material, a functional coating liquid is coated on the surface of the top layer film, and specific modifying agents are added to form an intermediate layer film. This not only overcomes the problem of difficult recycling of traditional multi-layer composite packaging materials, but also has excellent barrier properties and mechanical strength, while meeting the needs of environmental protection and consumers.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a high-barrier packaging material based on PE, which is composed of a top layer film, an intermediate layer film and an inner heat-sealing layer film in sequence, wherein the surface of the top layer film is coated with a functional coating liquid.

[0008] Preferably, the surface film comprises, by weight, the following raw materials: 50-90 parts metallocene polyethylene, 10-40 parts high-density polyethylene, 0.3-0.8 parts antioxidant, and 0.5-1.5 parts lubricant.

[0009] Preferably, the intermediate layer film comprises, by weight, the following raw materials: 80-120 parts high-density polyethylene, 2-5 parts modifying agent, 1-3 parts compatibilizer, 0.3-0.8 parts antioxidant, and 0.5-1.5 parts lubricant.

[0010] Preferably, the inner heat-sealing film comprises, by weight, the following raw materials: 60-100 parts metallocene polyethylene, 10-30 parts low-density polyethylene, 0.3-0.8 parts antioxidant, and 0.5-1.5 parts lubricant.

[0011] Preferably, the modifying agent is composed of hydrophobically modified nanocellulose and graphene oxide; the weight ratio of the hydrophobically modified nanocellulose to graphene oxide is 12-14:1-3.

[0012] Preferably, the hydrophobically modified nanocellulose is prepared by reacting nanocellulose with silane compounds (such as triethoxysilane) to introduce hydrophobic groups on the surface of nanocellulose.

[0013] Preferably, the hydrophobic modified nanocellulose has a fiber length of 500-1000 nm and a fiber diameter of 3-5 nm; the hydrophobic modified nanocellulose is model TL-017 (Nanjing Tianlu Nanotechnology Co., Ltd.).

[0014] Preferably, the graphene oxide has a thickness of 0.8-1.2 nm and a particle size of 1-10 μm; the graphene oxide is of type LN-GO (Shandong Lite Nanotechnology Co., Ltd.).

[0015] Among the aforementioned modifying agents, the hydrophobic modified nanocellulose, after undergoing hydrophobic treatment such as silanization, significantly reduces its hydrophilicity, avoiding the decrease in barrier performance caused by moisture absorption in the polymer matrix. Simultaneously, its high aspect ratio fibrous structure interweaves within the matrix, forming a dense three-dimensional network framework. This network effectively mechanically blocks and greatly extends the diffusion path of small molecules such as oxygen and water vapor, increasing their penetration difficulty. Meanwhile, graphene oxide, as a two-dimensional sheet nanomaterial, can spread parallel within the matrix after dispersion, forming a physical barrier similar to a brick wall structure. It possesses excellent shielding properties against gas molecules. When combined with nanocellulose, the two-dimensional graphene oxide sheets can effectively penetrate and cover the one-dimensional nanocellulose fiber network. On one hand, this fills in potential macroscopic defects between the fiber networks; on the other hand, it interlocks with the fibers, constructing a multi-scale, more tortuous and complex "maze-like" barrier channel from one-dimensional to two-dimensional, requiring penetrating molecules to take longer routes.

[0016] Preferably, the method for preparing the functional coating liquid includes the following steps: Sodium-based montmorillonite was mixed with an aqueous ethanol solution, stirred, and γ-aminopropyltriethoxysilane was added. The mixture was then sonicated, filtered, and dried to obtain pretreated montmorillonite. The pretreated montmorillonite was then mixed with anhydrous ethanol, sonicated, heated, and octadecyltrichlorosilane and isopropyltris(dioctylpyrophosphate)titanate were added. The mixture was stirred, filtered, and dried to obtain modified montmorillonite. Ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and an aqueous ethanol solution were mixed, heated, and stirred to obtain a base liquid. Modified montmorillonite was mixed with an aqueous ethanol solution and sonicated to obtain a modified montmorillonite dispersion. Under stirring conditions, the modified montmorillonite dispersion was added dropwise to the base liquid. After the addition was complete, stirring was continued, and then tetramethoxysilane was added and stirred. After cooling, a functional coating liquid was obtained.

[0017] This invention first utilizes γ-aminopropyltriethoxysilane to pre-treat montmorillonite with an amination compound. This not only introduces active amino groups onto the surface of the montmorillonite layers through silane hydrolysis and condensation, effectively improving reactivity, but more importantly, provides molecular anchoring sites for subsequent hydrophobic modification. Secondly, the long-chain alkyl group of octadecyltrichlorosilane is used to hydrophobically graft the amination compound onto the montmorillonite, transforming the montmorillonite surface into a strongly hydrophobic layer, significantly enhancing its ability to impede water vapor molecules. Simultaneously, the insertion of the long-chain alkyl group helps to widen the interlayer spacing of the montmorillonite, facilitating its exfoliation and dispersion in the matrix. The introduction of isopropyltris(dioctylpyrophosphate)titanate further enhances its hydrophobicity. The key synergistic modification and interface optimization effects are that the pyrophosphate oxy group in the molecule can interact with the filler surface to further enhance the hydrophobic effect and effectively reduce the surface energy of the nanoparticles, preventing them from agglomerating during subsequent processing and ensuring uniform dispersion in the final coating. This maximizes the "maze effect," forcing oxygen and water vapor molecules to bypass the long paths set by these nanosheets during permeation, significantly reducing the permeation rate. This invention preferably uses a blend of ethylene-vinyl alcohol copolymer and polyvinyl alcohol as the film-forming substrate. The hydrogen bond network formed between their molecular chains constitutes a dense physical barrier, and together they form the continuous phase of the coating, providing high barrier strength. Furthermore, the aforementioned functional coating liquid significantly improves the thermal stability of the coating, allowing it to maintain its intact structure and excellent barrier function at higher temperatures, and preventing softening or deformation.

[0018] Preferably, the weight ratio of sodium montmorillonite to γ-aminopropyltriethoxysilane is 0.1-0.5:0.1-0.2.

[0019] Preferably, the weight ratio of the pretreated montmorillonite, octadecyltrichlorosilane, and isopropyltris(dioctylpyrophosphoryloxy)titanate is 0.1-0.3:0.06-0.12:0.03-0.07.

[0020] Preferably, the weight ratio of the ethylene-vinyl alcohol copolymer, polyvinyl alcohol and ethanol aqueous solution is 0.5-1.5:0.3-0.6:10-20.

[0021] Preferably, the weight ratio of the modified montmorillonite to the ethanol aqueous solution is 0.1-0.2:20-40.

[0022] Preferably, the weight ratio of the modified montmorillonite dispersion, the base liquid, and the tetramethoxysilane is 2-4:12-18:0.2-0.4.

[0023] Preferably, the method for preparing the functional coating liquid includes the following steps: By weight, 0.1-0.5 parts of sodium montmorillonite are mixed with 50-200 parts of 20-30 wt% ethanol aqueous solution, stirred at 300-500 r / min for 10-15 h, 0.1-0.2 parts of γ-aminopropyltriethoxysilane are added, and the mixture is ultrasonically treated for 20-50 min, filtered, and dried to obtain pretreated montmorillonite; 0.1-0.3 parts of pretreated montmorillonite are mixed with 50-150 parts of anhydrous ethanol, ultrasonically treated for 10-20 min, heated to 65-80℃, 0.06-0.12 parts of octadecyltrichlorosilane and 0.03-0.07 parts of isopropyltris(dioctylpyrophosphate)titanate are added, and the mixture is stirred at 100-200 r / min for 3-8 h, filtered, and dried to obtain modified montmorillonite; Mix 0.5-1.5 parts of ethylene-vinyl alcohol copolymer, 0.3-0.6 parts of polyvinyl alcohol, and 10-20 parts of 50-60 wt% ethanol aqueous solution, and stir at 70-85℃ and 100-300 r / min for 2-4 h to obtain a base liquid; mix 0.1-0.2 parts of modified montmorillonite with 20-40 parts of 50-60 wt% ethanol aqueous solution, and sonicate for 20-40 min to obtain a modified montmorillonite dispersion; under stirring conditions of 45-60℃ and 300-500 r / min, add 2-4 parts of the modified montmorillonite dispersion dropwise to 12-18 parts of the base liquid, and continue stirring for 1-3 h after the addition is complete, then add 0.2-0.4 parts of tetramethoxysilane and stir for 1-2 h, and cool to room temperature to obtain a functional coating liquid.

[0024] Preferably, the frequency of the ultrasound is 30-50kHz and the power is 200-300W.

[0025] Preferably, the dripping time is controlled within 10-20 minutes.

[0026] Preferably, the antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 626, antioxidant 1098, and antioxidant DSTDP.

[0027] Preferably, the lubricant is at least one of oleamide, erucamide, stearamide, ethylene bis-stearamide, and ethylene bis-oleamide.

[0028] Preferably, the compatibilizer is at least one of maleic anhydride-grafted polyethylene, glycidyl methacrylate-grafted polyethylene, and maleic anhydride-grafted polypropylene.

[0029] Preferably, the thickness of the surface layer film is 25-32 μm, the thickness of the intermediate layer film is 35-42 μm, and the thickness of the inner heat-sealing layer film is 50-56 μm.

[0030] This invention provides a molding process for a high-barrier packaging material based on PE, comprising the following steps: Step 1: After mixing the raw materials for the surface film, the mixture is melt-extruded and cast into sheets, followed by biaxial stretching in both the longitudinal and transverse directions to obtain the surface film; the surface film is subjected to corona treatment, and a functional coating is uniformly coated on the corona-treated side of the surface film and cured into a film; patterns and text are printed on the outer surface of the coating of the surface film. Step 2: After mixing the intermediate layer film raw materials, the mixture is melt-extruded, cast into sheets, and then biaxially stretched in both the longitudinal and transverse directions to obtain the intermediate layer film. Step 3: After mixing the raw materials of the inner heat-sealing layer film, the mixture is melt-extruded and cast into sheets, and then bidirectionally stretched in both the longitudinal and transverse directions to obtain the inner heat-sealing layer film. Step 4: Apply adhesive evenly to the surface of the intermediate layer film, then laminate the unprinted side of the top layer film with the adhesive-coated intermediate layer film, and cure to obtain composite film I. Step 5: Apply adhesive evenly to the other side of composite film I, then laminate the inner heat-sealing layer film with the adhesive-coated composite film I, and cure it to obtain a high-barrier packaging material based on PE. Step Six: Slitting: Slitting the packaging material into small rolls according to the requirements of various bag types; Step 7: Bag making: The slit roll film is made into packaging bags as needed.

[0031] Preferably, in step one, the melt extrusion temperature is 240-260℃; the longitudinal stretching temperature is 95-105℃ and the stretching ratio is 4.0-5.0; and the transverse stretching temperature is 125-135℃ and the stretching ratio is 6-10.

[0032] Preferably, in step two, the melt extrusion temperature is 240-260℃; the longitudinal stretching temperature is 100-110℃ and the stretching ratio is 3.5-4.5; and the transverse stretching temperature is 130-140℃ and the stretching ratio is 6-10.

[0033] Preferably, in step three, the melt extrusion temperature is 240-260℃; the longitudinal stretching temperature is 95-105℃ and the stretching ratio is 3.0-4.0; the transverse stretching temperature is 120-130℃ and the stretching ratio is 5-8.

[0034] Preferably, the surface corona discharge of the thin film after the corona treatment in step one reaches 30-40 dynes / cm.

[0035] Preferably, the curing temperature in step one is 50-60℃, the time is 12-20h, and the coating thickness is 1-3μm.

[0036] Preferably, in step four, the composite pressure is 0.2-0.4 MPa, the curing temperature is 50-60℃, and the time is 20-30 h.

[0037] Preferably, in step five, the composite pressure is 0.2-0.4 MPa, the curing temperature is 50-60℃, and the time is 20-30 h.

[0038] Preferably, the adhesive used in step four is a solvent-free polyurethane adhesive, with a coating amount of 1-4 g / m². 2 .

[0039] Preferably, the adhesive used in step five is a solvent-free polyurethane adhesive, with a coating amount of 1-4 g / m². 2 .

[0040] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention provides a high-performance, environmentally friendly, and recyclable packaging material that reduces packaging waste, lowers the consumption of natural resources, alleviates environmental pressure, and contributes to the sustainable development of society as a whole. This single-material high-barrier packaging material can be used in a variety of fields and has broad market prospects.

[0041] 2. This invention involves biaxial stretching of polyethylene material after casting to achieve directional arrangement of molecules, significantly improving intermolecular cohesion and mechanical strength; single polyethylene material can achieve good barrier performance; by designing the inner and outer layer material structures, better temperature difference effect is obtained, and the flatness of the sealed edge is improved after packaging.

[0042] 3. This invention modifies polyolefin materials by adding modifying agents and combining this with surface treatment to improve key performance indicators such as barrier properties, mechanical strength, and temperature resistance. It optimizes processes such as biaxial stretching, coating, and lamination, achieving full orientation and crystallization of polyolefin molecular chains through precise control of stretching temperature and stretching ratio, thereby enhancing the material's mechanical and barrier properties. By selecting suitable adhesives and controlling lamination temperature and pressure, it improves the composite strength between polyolefin materials. Furthermore, by adjusting the thickness ratio, material properties, and interfacial bonding of each layer, it further optimizes the overall performance of the packaging material, achieving a balance and synergy in barrier properties, mechanical strength, and processing performance. Detailed Implementation

[0043] 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.

[0044] The raw materials used in the embodiments and comparative examples of this invention are described below: Metallocene polyethylene, grade: HPR1018HA, manufacturer: PetroChina Dushanzi Petrochemical Company.

[0045] High-density polyethylene, grade: 3300F, manufacturer: Sinopec Yangzi Petrochemical Company.

[0046] Low-density polyethylene, grade: LD605, manufacturer: Sinopec Yanshan Petrochemical Company.

[0047] Hydrophobically modified nanocellulose, model: TL-017, manufacturer: Nanjing Tianlu Nanotechnology Co., Ltd.

[0048] Graphene oxide, model: LN-GO, manufacturer: Shandong Lite Nanotechnology Co., Ltd.

[0049] Maleic anhydride-grafted polyethylene, grade: FT900E, manufacturer: Nanjing Feiteng New Material Technology Co., Ltd.

[0050] Nano silica, model: M600, particle size: 10-20nm, manufacturer: Jiaozuo Yukun Mining Co., Ltd.

[0051] Sodium-based montmorillonite, model: PGW, manufacturer: Beijing Yiwei Special Chemical Technology Development Co., Ltd.

[0052] Ethylene-vinyl alcohol copolymer, model: EVAL G156B, manufacturer: Dongguan Jinjirui Plastic Raw Materials Co., Ltd.

[0053] Polyvinyl alcohol, model: PVA17-88, manufacturer: Inner Mongolia Shuangxin Environmental Protection Materials Co., Ltd.

[0054] Solvent-free polyurethane adhesive, model: WP8057, manufacturer: Meibang (Huangshan) Adhesive Co., Ltd.

[0055] Example 1 This embodiment provides a high-barrier packaging material based on PE, which is composed of a top layer film, a middle layer film and an inner heat-sealing layer film in sequence, wherein the surface of the top layer film is coated with a functional coating liquid; The surface film, by weight, comprises the following raw materials: 70 parts metallocene polyethylene, 30 parts high-density polyethylene, 0.5 parts antioxidant 1010, and 1 part oleamide.

[0056] The intermediate layer film, by weight, comprises the following raw materials: 100 parts high-density polyethylene, 3 parts modifying agents, 2 parts maleic anhydride-grafted polyethylene, 0.5 parts antioxidant 1010, and 1 part oleamide. The modifying agents are composed of hydrophobically modified nanocellulose and graphene oxide in a weight ratio of 13:2.

[0057] The inner heat-sealing film comprises, by weight, the following raw materials: 80 parts metallocene polyethylene, 20 parts low-density polyethylene, 0.5 parts antioxidant 1010, and 1 part oleamide.

[0058] The preparation method of the functional coating liquid includes the following steps: By weight, 0.3 parts of sodium montmorillonite were mixed with 100 parts of 25wt% aqueous ethanol solution and stirred at 450 r / min for 12 h. Then, 0.15 parts of γ-aminopropyltriethoxysilane were added, and the mixture was ultrasonically treated at 40 kHz and 250 W for 30 min. After filtration and drying, pretreated montmorillonite was obtained. 0.2 parts of pretreated montmorillonite were mixed with 100 parts of anhydrous ethanol and ultrasonically treated at 40 kHz and 250 W for 15 min. The mixture was heated to 70 °C, and 0.1 parts of octadecyltrichlorosilane and 0.05 parts of isopropyltris(dioctylpyrophosphate)titanate were added. The mixture was stirred at 150 r / min for 5 h, filtered, and dried to obtain modified montmorillonite. One part of ethylene-vinyl alcohol copolymer, 0.5 parts of polyvinyl alcohol, and 15 parts of 55wt% ethanol aqueous solution were mixed and stirred at 80℃ and 200r / min for 3h to obtain a base liquid. 0.15 parts of modified montmorillonite and 30 parts of 55wt% ethanol aqueous solution were mixed and ultrasonically treated at 40kHz and 250W for 30min to obtain a modified montmorillonite dispersion. Under stirring conditions of 50℃ and 400r / min, 3 parts of the modified montmorillonite dispersion were added dropwise to 15 parts of the base liquid, with the addition time controlled at 15min. After the addition was completed, stirring was continued for 2h, and then 0.3 parts of tetramethoxysilane were added and stirred for 1.5h. The mixture was then cooled to room temperature to obtain a functional coating liquid.

[0059] This embodiment provides a molding process for a high-barrier packaging material based on PE, including the following steps: Step 1: After mixing the surface film raw materials, the mixture is melt-extruded and cast into sheets, followed by biaxial stretching in both the longitudinal and transverse directions to obtain a surface film (thickness 30 μm). The surface film is then subjected to corona treatment, achieving a surface corona discharge of 36 dynes / cm. A functional coating is uniformly coated on the corona-treated side of the surface film and cured at 55°C for 16 hours to form a film with a coating thickness of 2 μm. Patterns and text are printed on the outer surface of the coating on the surface film. The melt extrusion temperature is 250°C; the longitudinal stretching temperature is 100°C with a stretch ratio of 4.5; and the transverse stretching temperature is 130°C with a stretch ratio of 8. Step 2: After mixing the interlayer film raw materials, the mixture is melt-extruded and cast into sheets, followed by biaxial stretching in both the longitudinal and transverse directions to obtain an interlayer film (thickness of 40 μm); wherein the melt extrusion temperature is 250℃; the longitudinal stretching temperature is 105℃ with a stretching ratio of 4.0; and the transverse stretching temperature is 135℃ with a stretching ratio of 8. Step 3: After mixing the raw materials for the inner heat-sealing layer film, the mixture is melt-extruded and cast into sheets, followed by biaxial stretching in both the longitudinal and transverse directions to obtain the inner heat-sealing layer film (thickness of 55μm); wherein the melt extrusion temperature is 250℃; the longitudinal stretching temperature is 100℃ with a stretching ratio of 3.5; and the transverse stretching temperature is 125℃ with a stretching ratio of 6. Step 4: Uniformly coat the surface of the intermediate layer film with adhesive. Laminate the unprinted side of the top layer film with the adhesive-coated intermediate layer film. The lamination pressure is 0.3 MPa. After lamination, cure at 50°C for 24 hours to obtain composite film I. The adhesive is a solvent-free polyurethane adhesive with a coating amount of 2.5 g / m³. 2 ; Step 5: Apply adhesive evenly to the other side of composite film I. Then, laminate the inner heat-sealing layer film to composite film I coated with adhesive. The lamination pressure is 0.3 MPa. After lamination, cure at 50°C for 24 hours to obtain a high-barrier packaging material based on PE. The adhesive is a solvent-free polyurethane adhesive with a coating amount of 2.5 g / m³. 2 ; Step Six: Slitting: Slitting the packaging material into small rolls according to the requirements of various bag types; Step 7: Bag making: The slit roll film is made into packaging bags as needed.

[0060] Example 2 This embodiment provides a high-barrier packaging material based on PE, which is composed of a top layer film, a middle layer film and an inner heat-sealing layer film in sequence, wherein the surface of the top layer film is coated with a functional coating liquid; The surface film, by weight, comprises the following raw materials: 50 parts metallocene polyethylene, 10 parts high-density polyethylene, 0.3 parts antioxidant 1010, and 0.5 parts oleamide.

[0061] The intermediate layer film, by weight, comprises the following raw materials: 80 parts high-density polyethylene, 2 parts modifying agent, 1 part maleic anhydride-grafted polyethylene, 0.3 parts antioxidant 1010, and 0.5 parts oleamide. The modifying agent is composed of hydrophobically modified nanocellulose and graphene oxide in a weight ratio of 12:3.

[0062] The inner heat-sealing film comprises, by weight, the following raw materials: 60 parts metallocene polyethylene, 10 parts low-density polyethylene, 0.3 parts antioxidant 1010, and 0.5 parts oleamide.

[0063] The preparation method of the functional coating liquid is the same as that in Example 1.

[0064] The molding process of the PE-based high-barrier packaging material is the same as that in Example 1.

[0065] Example 3 This embodiment provides a high-barrier packaging material based on PE, which is composed of a top layer film, a middle layer film and an inner heat-sealing layer film in sequence, wherein the surface of the top layer film is coated with a functional coating liquid; The surface film, by weight, comprises the following raw materials: 90 parts metallocene polyethylene, 40 parts high-density polyethylene, 0.8 parts antioxidant 1010, and 1.5 parts oleamide.

[0066] The intermediate layer film, by weight, comprises the following raw materials: 120 parts high-density polyethylene, 5 parts modifying agents, 3 parts maleic anhydride-grafted polyethylene, 0.8 parts antioxidant 1010, and 1.5 parts oleamide. The modifying agents are composed of hydrophobically modified nanocellulose and graphene oxide in a weight ratio of 14:1.

[0067] The inner heat-sealing film comprises, by weight, the following raw materials: 100 parts metallocene polyethylene, 30 parts low-density polyethylene, 0.8 parts antioxidant 1010, and 1.5 parts oleamide.

[0068] The preparation method of the functional coating liquid is the same as that in Example 1.

[0069] The molding process of the PE-based high-barrier packaging material is the same as that in Example 1.

[0070] Comparative Example 1 The difference between this comparative example and Example 1 is that the composition of the modifying agent in the raw material formulation of the intermediate layer film is different, as follows: the modifying agent is composed of hydrophobic modified nanocellulose and graphene oxide in a weight ratio of 10.5:4.5.

[0071] Comparative Example 2 The difference between this comparative example and Example 1 is that the composition of the modifying agent in the raw material formulation of the intermediate layer film is different, as follows: the modifying agent is composed of hydrophobic modified nanocellulose and graphene oxide in a weight ratio of 14.5:0.5.

[0072] Comparative Example 3 The difference between this comparative example and Example 1 is that the preparation method of the functional coating liquid is different, as follows: The preparation method of the functional coating liquid includes the following steps: By weight, 0.3 parts of sodium montmorillonite were mixed with 100 parts of 25wt% ethanol aqueous solution and stirred at 450 r / min for 12 h. Then, 0.15 parts of γ-glycidoxypropyltrimethoxysilane were added, and the mixture was ultrasonically treated at a frequency of 40 kHz and a power of 250 W for 30 min. The mixture was then filtered and dried to obtain pretreated montmorillonite. 0.2 parts of pretreated montmorillonite were mixed with 100 parts of anhydrous ethanol and ultrasonically treated at a frequency of 40 kHz and a power of 250 W for 15 min. The mixture was heated to 70 °C, and 0.1 parts of octadecyltrichlorosilane and 0.05 parts of isopropyltris(dioctylpyrophosphate)titanate were added. The mixture was stirred at 150 r / min for 5 h, filtered, and dried to obtain modified montmorillonite. One part of ethylene-vinyl alcohol copolymer, 0.5 parts of polyvinyl alcohol, and 15 parts of 55wt% ethanol aqueous solution were mixed and stirred at 80℃ and 200r / min for 3h to obtain a base liquid. 0.15 parts of modified montmorillonite and 30 parts of 55wt% ethanol aqueous solution were mixed and ultrasonically treated at 40kHz and 250W for 30min to obtain a modified montmorillonite dispersion. Under stirring conditions of 50℃ and 400r / min, 3 parts of the modified montmorillonite dispersion were added dropwise to 15 parts of the base liquid, with the addition time controlled at 15min. After the addition was completed, stirring was continued for 2h, and then 0.3 parts of tetramethoxysilane were added and stirred for 1.5h. The mixture was then cooled to room temperature to obtain a functional coating liquid.

[0073] Comparative Example 4 The difference between this comparative example and Example 1 is that the preparation method of the functional coating liquid is different, as follows: The preparation method of the functional coating liquid includes the following steps: By weight, 0.3 parts of sodium-based montmorillonite were mixed with 100 parts of 25wt% aqueous ethanol solution and stirred at 450 r / min for 12 h. 0.15 parts of γ-aminopropyltriethoxysilane were added, and the mixture was ultrasonically treated at 40 kHz and 250 W for 30 min. After filtration and drying, pretreated montmorillonite was obtained. 0.2 parts of pretreated montmorillonite were mixed with 100 parts of anhydrous ethanol and ultrasonically treated at 40 kHz and 250 W for 15 min. The mixture was heated to 70 °C, and 0.1 parts of di-n-octyldichlorosilane and 0.05 parts of isopropyltris(dioctylpyrophosphate)titanate were added. The mixture was stirred at 150 r / min for 5 h, filtered, and dried to obtain modified montmorillonite. One part of ethylene-vinyl alcohol copolymer, 0.5 parts of polyvinyl alcohol, and 15 parts of 55wt% ethanol aqueous solution were mixed and stirred at 80℃ and 200r / min for 3h to obtain a base liquid. 0.15 parts of modified montmorillonite and 30 parts of 55wt% ethanol aqueous solution were mixed and ultrasonically treated at 40kHz and 250W for 30min to obtain a modified montmorillonite dispersion. Under stirring conditions of 50℃ and 400r / min, 3 parts of the modified montmorillonite dispersion were added dropwise to 15 parts of the base liquid, with the addition time controlled at 15min. After the addition was completed, stirring was continued for 2h, and then 0.3 parts of tetramethoxysilane were added and stirred for 1.5h. The mixture was then cooled to room temperature to obtain a functional coating liquid.

[0074] Comparative Example 5 The difference between this comparative example and Example 1 is that the preparation method of the functional coating liquid is different, as follows: The preparation method of the functional coating liquid includes the following steps: By weight, 0.3 parts of sodium-based montmorillonite were mixed with 100 parts of 25wt% aqueous ethanol solution and stirred at 450 r / min for 12 h. Then, 0.15 parts of γ-aminopropyltriethoxysilane were added, and the mixture was ultrasonically treated at 40 kHz and 250 W for 30 min. The mixture was then filtered and dried to obtain pretreated montmorillonite. 0.2 parts of pretreated montmorillonite were mixed with 100 parts of anhydrous ethanol and ultrasonically treated at 40 kHz and 250 W for 15 min. The mixture was heated to 70 °C, and 0.1 parts of octadecyltrichlorosilane and 0.05 parts of tetraisopropyl titanate were added. The mixture was stirred at 150 r / min for 5 h, filtered, and dried to obtain modified montmorillonite. One part of ethylene-vinyl alcohol copolymer, 0.5 parts of polyvinyl alcohol, and 15 parts of 55wt% ethanol aqueous solution were mixed and stirred at 80℃ and 200r / min for 3h to obtain a base liquid. 0.15 parts of modified montmorillonite and 30 parts of 55wt% ethanol aqueous solution were mixed and ultrasonically treated at 40kHz and 250W for 30min to obtain a modified montmorillonite dispersion. Under stirring conditions of 50℃ and 400r / min, 3 parts of the modified montmorillonite dispersion were added dropwise to 15 parts of the base liquid, with the addition time controlled at 15min. After the addition was completed, stirring was continued for 2h, and then 0.3 parts of tetramethoxysilane were added and stirred for 1.5h. The mixture was then cooled to room temperature to obtain a functional coating liquid.

[0075] Comparative Example 6 The difference between this comparative example and Example 1 is that the preparation method of the functional coating liquid is different, as follows: The preparation method of the functional coating liquid includes the following steps: By weight, 0.3 parts of sodium montmorillonite were mixed with 100 parts of 25wt% aqueous ethanol solution and stirred at 450 r / min for 12 h. Then, 0.15 parts of γ-aminopropyltriethoxysilane were added, and the mixture was ultrasonically treated at 40 kHz and 250 W for 30 min. After filtration and drying, pretreated montmorillonite was obtained. 0.2 parts of pretreated montmorillonite were mixed with 100 parts of anhydrous ethanol and ultrasonically treated at 40 kHz and 250 W for 15 min. The mixture was heated to 70 °C, and 0.1 parts of octadecyltrichlorosilane and 0.05 parts of isopropyltris(dioctylpyrophosphate)titanate were added. The mixture was stirred at 150 r / min for 5 h, filtered, and dried to obtain modified montmorillonite. 1.5 parts of polyvinyl alcohol were mixed with 15 parts of 55wt% aqueous ethanol solution and stirred at 80℃ and 200r / min for 3h to obtain a base solution. 0.15 parts of modified montmorillonite were mixed with 30 parts of 55wt% aqueous ethanol solution and ultrasonically treated at 40kHz and 250W for 30min to obtain a modified montmorillonite dispersion. Under stirring conditions of 50℃ and 400r / min, 3 parts of the modified montmorillonite dispersion were added dropwise to 15 parts of the base solution, with the addition time controlled at 15min. After the addition was completed, stirring was continued for 2h, and then 0.3 parts of tetramethoxysilane were added and stirred for 1.5h. The mixture was then cooled to room temperature to obtain a functional coating solution.

[0076] Performance Test 1 The following basic performance tests were conducted on the PE-based high-barrier packaging material prepared in Example 1 above, including: appearance quality, dimensional tolerance, peel strength, coefficient of friction, heat seal strength, tensile properties, oxygen permeability, water vapor permeability, and solvent residue. Specifically, peel strength was tested according to standard GB 8808-1988; coefficient of friction was tested according to standard GB / T 10006-2021; tensile properties were tested according to standard ASTM D882-18; oxygen permeability was tested according to standard GB / T 19789-2021; and water vapor permeability was tested according to standard GB / T 21529-2008. The results are shown in Table 1.

[0077] Table 1: Test Results of Basic Performance of Packaging Materials Performance Test 2 The barrier properties and thermal stability of the PE-based high-barrier packaging materials prepared in Examples 1-3 and Comparative Examples 1-6 were tested. Oxygen permeability was tested according to standard GB / T 19789-2021; water vapor permeability was tested according to standard GB / T 21529-2008. The thermal stability test method was as follows: the packaging materials in each example were cut to obtain 10mg test samples, which were then heated from room temperature to 300℃ (heating rate 10℃ / min) under a nitrogen atmosphere for thermogravimetric analysis, and the weight retention rate was calculated. The results are shown in Table 2.

[0078] Table 2: Comparison Results of Barrier Properties and Thermal Stability of Packaging Materials The performance test results above show that the PE-based high-barrier packaging materials prepared in Examples 1-3 have excellent barrier properties, heat resistance, and mechanical strength. In particular, the high-barrier packaging material prepared in Example 1 exhibits the most outstanding comprehensive performance. This is because the present invention uses PE as a single material as raw material, and by coating the surface of the top layer film with a functional coating liquid and adding specific modifying agents to form the intermediate layer film, the barrier and heat resistance properties of the packaging material are significantly improved, and the problem of difficult recycling of traditional multi-layer composite packaging materials is overcome. In contrast, Comparative Examples 1-6 did not employ the necessary technical solutions of the present invention. Specifically, the intermediate layer film in Comparative Examples 1-2 did not use modifying agents with a specific ratio, and Comparative Examples 4-6 did not use a functional coating liquid prepared by a specific method. This resulted in their barrier properties against oxygen and water vapor and their thermal stability being significantly inferior to Examples 1-3. The test results further demonstrate that the technical solutions defined in the present invention are crucial for achieving the above-mentioned technical effects.

[0079] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A PE-based high-barrier packaging material, characterized by, The surface of the surface layer film is coated with a functional coating liquid; The intermediate layer film comprises the following raw materials in parts by weight: 80-120 parts of high-density polyethylene, 2-5 parts of a modification aid, 1-3 parts of a compatibilizer, 0.3-0.8 parts of an antioxidant, and 0.5-1.5 parts of a lubricant.

2. The PE-based high-barrier packaging material according to claim 1, characterized in that, The surface layer film comprises the following raw materials in parts by weight: 50-90 parts of metallocene polyethylene, 10-40 parts of high-density polyethylene, 0.3-0.8 parts of an antioxidant, and 0.5-1.5 parts of a lubricant; and the inner heat-seal layer film comprises the following raw materials in parts by weight: 60-100 parts of metallocene polyethylene, 10-30 parts of low-density polyethylene, 0.3-0.8 parts of an antioxidant, and 0.5-1.5 parts of a lubricant.

3. The PE-based high-barrier packaging material according to claim 1, characterized in that, The modification aid is composed of hydrophobically modified nanocellulose and graphene oxide; and the weight ratio of the hydrophobically modified nanocellulose to the graphene oxide is 12-14:1-3.

4. The PE-based high-barrier packaging material according to claim 1, characterized in that, The preparation method of the functional coating liquid comprises the following steps: The sodium-based montmorillonite is mixed with an ethanol aqueous solution, stirred, and then γ-aminopropyl triethoxysilane is added thereto, followed by ultrasonic treatment, filtration, and drying to obtain pretreated montmorillonite; the pretreated montmorillonite is mixed with anhydrous ethanol, ultrasonically treated, and then heated, and octadecyltrichlorosilane and isopropyl tri(dioctyl pyrophosphoryloxy) titanate are added thereto, followed by stirring and reaction, filtration, and drying to obtain modified montmorillonite; The ethylene-vinyl alcohol copolymer and polyvinyl alcohol are mixed with an ethanol aqueous solution, and heated and stirred to obtain a base liquid; the modified montmorillonite is mixed with an ethanol aqueous solution, and ultrasonically treated to obtain a modified montmorillonite dispersion liquid; the modified montmorillonite dispersion liquid is added dropwise to the base liquid under stirring, and after the dropwise addition is completed, the stirring is continued, and then tetramethoxysilane is added and stirred, and then cooled to obtain the functional coating liquid.

5. The PE-based high-barrier packaging material according to claim 4, characterized in that, The weight ratio of the sodium-based montmorillonite to the γ-aminopropyl triethoxysilane is 0.1-0.5:0.1-0.2; the weight ratio of the pretreated montmorillonite to the octadecyltrichlorosilane to the isopropyl tri(dioctyl pyrophosphoryloxy) titanate is 0.1-0.3:0.06-0.12:0.03-0.07; and the weight ratio of the modified montmorillonite dispersion liquid to the base liquid to the tetramethoxysilane is 2-4:12-18:0.2-0.

4.

6. The PE-based high-barrier packaging material according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 626, antioxidant 1098, and antioxidant DSTDP.

7. The PE-based high-barrier packaging material according to claim 1, characterized in that, The lubricant is at least one of oleic acid amide, erucic acid amide, stearyl amide, ethylene bis-stearyl amide, and ethylene bis-oleic acid amide.

8. The PE-based high-barrier packaging material according to claim 1, characterized in that, The compatibilizer is at least one of maleic anhydride grafted polyethylene, glycidyl methacrylate grafted polyethylene, and maleic anhydride grafted polypropylene.

9. The PE-based high-barrier packaging material according to claim 1, characterized in that, The thickness of the surface layer film is 25-32 μm, the thickness of the intermediate layer film is 35-42 μm, and the thickness of the inner heat-seal layer film is 50-56 μm.

10. A forming process of a PE-based high-barrier packaging material according to any one of claims 1-9, characterized in that, The method comprises the following steps: Step one, after mixing the raw materials of the surface layer film, melt extrusion, casting sheet, followed by longitudinal and transverse two-way stretching, the surface layer film is prepared; the surface layer film is treated by corona discharge, and a functional coating is uniformly coated on one side of the surface layer film treated by corona discharge, and then solidified into a film; patterns and characters are printed on the outer surface of the coating of the surface layer film; Step two, after mixing the raw materials of the intermediate layer film, melt extrusion, casting sheet, followed by longitudinal and transverse two-way stretching, the intermediate layer film is prepared; Step three, after mixing the raw materials of the inner layer heat seal layer film, melt extrusion, casting sheet, followed by longitudinal and transverse two-way stretching, the inner layer heat seal layer film is prepared; Step four, uniformly coat adhesive on the surface of the intermediate layer film, and then composite the unprinted side of the surface layer film with the intermediate layer film coated with adhesive, and then mature, to obtain a composite film I; Step five, uniformly coat adhesive on the other side of the composite film I, and then composite the inner layer heat seal layer film with the composite film I coated with adhesive, and then mature, to obtain a PE-based high-barrier packaging material; Step six, slitting; Step seven, bag making.

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