Aluminum-plated stretch film for food packaging and preparation method of aluminum-plated stretch film

Abstract

The invention discloses an aluminum-plated stretch film for food packaging and a preparation method thereof, and relates to the technical field of stretch films, the aluminum-plated stretch film comprises a stretch base film, an aluminum-plated film and a CPP printing film. The modified COC resin is used in the stretching base film, so that the tensile strength and the aluminum plating composite strength are improved; the barrier layer is used as a mechanical support to improve the barrier property; the metal luster is excellent. The aluminized film adopts a vacuum evaporation aluminized layer, so that the adhesive force is good, and the uniformity of the aluminized layer is high; the aluminum alloy instead of pure aluminum is selected, Cu in the aluminum alloy can adjust the metallic luster and prolong the color stability, the Al2O3 oxide layer delays the oxidation failure of the aluminum layer, and the shelf life is prolonged. The CPP printing film adopts a three-layer structural design, so that the heat sealing performance and the printing adaptability are improved, and the food contact standard is met. The aluminum-plated stretch film comprehensively improves barrier property, mechanical strength, production efficiency and functionality, and is suitable for the field of food packaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of stretch film, in particular to an aluminized stretch film for food packaging and a preparation method thereof. BACKGROUND

[0002] The current food packaging field has a high demand for high-barrier, high-transparency and functional films. Traditional aluminized films have technical bottlenecks, such as insufficient barrier property of single-layer base film, poor adhesion of aluminized layer due to insufficient polarity of surface layer, easy oxidation and cracking of pure aluminum coating, poor barrier durability, and the like. Therefore, there is an urgent need for food packaging.

[0003] Stretch film, also known as thermoforming film, for food sealed packaging uses high-barrier stretch film to ensure the freshness of fresh meat, and uses stretch film with metallic luster to significantly improve the packaging level, which is welcomed by the market. In order to solve the above problems, the present application provides an aluminized stretch film for food packaging and a preparation method thereof, which provides a packaging solution with high barrier property and good stretch for food with long shelf life. The aluminized film has excellent moisture resistance, light resistance and oxygen resistance, and excellent durability and crack resistance. Combined with the inherent characteristics of biaxially oriented film and the advantages of advanced aluminizing technology, the present application has a good prospect in the field of food packaging. SUMMARY

[0004] The present application aims to provide an aluminized stretch film for food packaging and a preparation method thereof to solve the problems in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: A preparation method of an aluminized stretch film for food packaging, characterized in that the steps of the preparation method are as follows: S1: co-extruding a heat-sealing layer, an adhesive layer, a barrier layer, an adhesive layer and a surface film, and performing stretch treatment to obtain a stretch base film; S2: performing vacuum aluminizing treatment on the stretch base film to form an aluminized layer on the surface film, thereby obtaining an aluminized base film; S3: solvent-free compounding a CPP printed film with the aluminized base film to obtain an aluminized stretch film for food packaging; More preferably, the stretch base film comprises, from top to bottom, a heat-sealing layer, an adhesive layer, a barrier layer, an adhesive layer and a surface film, and the thickness of the stretch base film is 50-300 μm; more preferably, the thickness of the stretch base film is 100-200 μm; the thickness ratio of the surface layer, the adhesive layer, the barrier layer, the adhesive layer and the heat-sealing layer in the stretch base film is (10-20):(5-8):(40-45):(5-8):(30-35); More preferably, the raw material of the surface layer film is a modified COC resin; the raw material of the adhesive layer is one of maleic anhydride grafted polypropylene and polyethylene; the raw material of the barrier layer is one of modified ethylene-vinyl alcohol copolymer resin and nylon; and the raw material of the heat-sealing layer is one of polyethylene and polypropylene.

[0006] In weight parts, the raw material of the stretched base film is: 10-20 parts of modified COC resin, 5-8 parts of maleic anhydride grafted polypropylene, 40-45 parts of modified ethylene-vinyl alcohol copolymer resin, 5-8 parts of maleic anhydride grafted polypropylene, and 30-35 parts of metallocene polyethylene. More preferably, the modified ethylene-vinyl alcohol copolymer resin is prepared by the following process: mixing mica powder, calcined kaolin and aminosilane coupling agent, spraying 0.5% polyethyleneimine aqueous solution, and drying to obtain mixed particles; mixing nano-SiO2, 3-glycidoxypropyltrimethoxysilane coupling agent, ethanol and deionized water, and stirring to obtain epoxidized SiO2; premixing the epoxidized SiO2 and ethylene-vinyl alcohol copolymer resin, and then adding the mixed particles, double-screw extruding, water cooling and granulating to obtain the modified ethylene-vinyl alcohol copolymer resin. More preferably, the modified COC resin is prepared by the following process: double-screw extruding COC resin and aminosilica, water cooling and granulating to obtain the modified COC resin. The COC resin is a high-performance transparent copolymer. The aminosilica is prepared by the following process: mixing γ-aminopropyltriethoxysilane coupling agent, deionized water and ethanol solvent, adjusting pH to 4.5 with acetic acid, stirring at 40℃ for 30 min, adding nano-SiO2, stirring at 60℃ for 4 h, centrifuging and drying to obtain the aminosilica. More preferably, in S1, the stretching treatment is longitudinal and transverse stretching, and the longitudinal and transverse stretching ratios are 3.2:3.8. More preferably, S2 is: plasma cleaning pretreatment of the surface layer of the stretched base film, vacuumizing in a vacuum aluminum plating machine, temperature control, configuring aluminum alloy as the evaporation source, co-evaporating on the surface layer to form an aluminum plating layer, introducing high-purity oxygen, generating a dense oxide layer on the surface of the aluminum plating layer, and obtaining an aluminum-plated base film; the aluminum alloy is compounded by aluminum, copper and magnesium in a mass ratio of 95: (3-5): (1-2); and the thickness of the aluminum plating layer is 50-100 μm. More preferably, the preparation process of the CPP printed film in S3 is: drying and dehumidifying the raw materials of the corona layer, the intermediate layer and the heat-sealing layer respectively, co-extrusion flow casting, printing irreversible temperature change ink on the corona layer after corona treatment, and obtaining the CPP printed film. The raw material of the corona layer is a propylene-ethylene-butylene terpolymer and a homopolymer polypropylene compounded in a weight ratio of (7-8):(2-3), the raw material of the intermediate layer is a modified homopolymer polypropylene, and the raw material of the heat-sealing layer is a propylene-ethylene copolymer; the thickness of the CPP printing film S3 is 30-100 mu m; and the thickness ratio of the corona layer, the intermediate layer and the heat-sealing layer of the CPP printing film is 1:4:1. By printing different colors of inks on the surface of the CPP printing film, the stretched film with different metal luster can be prepared after being combined with the aluminized stretched film, such as the stretched film with one side of gold color and one side of silver color can be obtained by printing transparent yellow ink.

[0007] Compared with the prior art, the present application has the following advantages: The aluminized stretched film for food packaging of the present application comprises three parts of a stretched base film, an aluminized film and a CPP printing film. The stretched base film comprises, from inside to outside, a surface layer, an adhesive layer, a barrier layer, an adhesive layer and a heat-sealing layer. The surface layer film is a premix of COC resin and modified nano-SiO2, which improves the tensile strength. The modified nano-SiO2 prolongs the gas diffusion path and blocks the water vapor permeation. The grafted chain of the adhesive layer polypropylene and maleic anhydride reduces the melt viscosity and improves the sealing permeability. At the same time, the maleic anhydride group forms a chemical bond with the aluminum layer to improve the peeling strength. The barrier layer modified ethylene-vinyl alcohol copolymer resin improves the rigidity, barrier property and heat resistance of the base film. The bis-aminosilane simultaneously bonds the hydroxyl groups on the surface of mica and kaolin through hydrolysis and condensation reaction to form a covalent bond, which significantly improves the dispersibility. The primary amine group of the polyethylene imine is combined with the amino group at the end of the silane layer through hydrogen bond and ionic bond to form a three-dimensional network structure, which enhances the interfacial bonding force of the filler and the resin. At the same time, the polyethylene imine can form hydrogen bonds with the ethylene-vinyl alcohol copolymer resin to improve the aluminizing peeling strength and fill the gap between the molecular chains of the ethylene-vinyl alcohol copolymer resin. The epoxidized SiO2 improves the compatibility and blocks the oxygen permeation path. The metallocene polyethylene has the characteristics of high transparency and high toughness. The synchronous bidirectional stretching during the preparation not only improves the efficiency and reduces the energy consumption, but also improves the tensile strength, so that the product has excellent mechanical properties.

[0008] The aluminized layer is vacuum evaporated by the gas phase deposition method, so that the film surface has metal luster, the film surface tension is durable, the adhesion is good, the aluminum layer uniformity is high, the cost is low and the efficiency is high. The plasma cleaning can improve the aluminizing adhesion, and the vacuum extraction can prevent oxidation. The aluminum alloy instead of pure aluminum is selected. The Cu in the aluminum alloy can adjust the metal luster, the Mg can inhibit the oxidation of copper, prolong the color stability, and at the same time, the trace CuO and MgO after oxidation can improve the corrosion resistance, the Al2O3 oxide layer can delay the oxidation failure of the aluminum layer, and the shelf life is prolonged.

[0009] The CPP printing film adopts a three-layer structure design, and the heat sealing performance and printing adaptability are improved; the corona layer is used for printing and extrusion, the heat sealing layer uses pure binary copolymerized polypropylene, has good high temperature resistance, and uses irreversible temperature change ink, so that whether the food storage is abnormal can be directly observed; the middle layer uses modified homopolymerized polypropylene, so that the composite packaging film has high tensile property and good transparency, and the performance of the composite packaging film is greatly improved.

[0010] The application improves the barrier property, mechanical strength, production efficiency and functionality by material compounding, synchronous stretching, co-evaporation aluminum plating, five-layer base film and three-layer CPP structure design, and more than 70% COC resin content in the stretched base film. DETAILED DESCRIPTION

[0011] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0012] Embodiment 1: A preparation method of an aluminum-plated stretched film for food packaging, and the steps of the preparation method are as follows: S1: Dry the raw materials of the surface layer, the adhesive layer, the barrier layer, the adhesive layer and the heat sealing layer, add them to a co-extrusion system, co-extrude, use a synchronous double-direction stretching machine, stretch longitudinally at a ratio of 3.2 times, and stretch transversely at a ratio of 3.8 times, to obtain a stretched base film with a total thickness of 150 μm; S2: Plasma clean the stretched base film, put it into a vacuum aluminum plating machine, vacuumize to 4*10 -4 Pa, configure an aluminum alloy as an evaporation source, co-evaporate to form an aluminum-plated layer on the surface layer film, pass in high-purity oxygen (0.1 Pa, 5 s) to generate a 3 nm dense oxide layer, and obtain an aluminum-plated base film; S3: 1) Dry and dehumidify the raw materials of the corona layer, the middle layer and the heat sealing layer respectively, co-extrude and form, control the thickness of the CPP printing film to be 50 μm, print irreversible temperature change ink on the surface of the corona layer, and prepare a CPP printing film; 2) Compound the CPP printing film with the aluminum-plated base film without solvent, and prepare an aluminum-plated stretched film for food packaging; In S1, the raw material of the surface layer film is modified COC resin; the raw material of the adhesive layer is maleic anhydride grafted polypropylene; the raw material of the barrier layer is modified ethylene-vinyl alcohol copolymer resin; and the raw material of the heat sealing layer is polyethylene; The raw materials of the stretch base film are, in parts by weight, 15 parts of modified COC resin, 6 parts of maleic anhydride grafted polypropylene, 43 parts of modified ethylene-vinyl alcohol copolymer resin, 6 parts of maleic anhydride grafted polypropylene, and 30 parts of polyethylene; the surface layer is 22.5 μm thick, the adhesive layer is 9 μm thick, the barrier layer is 64.5 μm thick, the adhesive layer is 9 μm thick, and the heat seal layer is 45 μm thick. The modified COC resin is prepared by mixing 3 g of methyltrimethoxysilane coupling agent, 10 mL of deionized water, and 90 mL of ethanol solvent, adjusting the pH to 4.5 with acetic acid, stirring at 40° C. for 60 minutes, adding 100 g of nano-SiO2, stirring at 60° C. for 4 hours, centrifuging, washing with ethanol, and drying to obtain amino-SiO2; and double-screw extruding 140 g of COC resin and 6 g of amino-SiO2, water-cooling and pelletizing to obtain the modified COC resin. The preparation process of the modified ethylene-vinyl alcohol copolymer resin is as follows: 8g of mica powder, 3g of calcined kaolin, and 0.4g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane coupling agent are mixed, 20mL of a 1% polyethyleneimine aqueous solution is sprayed, and the mixture is dried at 80°C for 60min to obtain mixed particles; 100g of nano-SiO2, 5g of 3-glycidyloxypropyltrimethoxysilane coupling agent, 95g of ethanol, and 400mL of deionized water are mixed, stirred at 60°C for 2h, and centrifuged to obtain epoxidized SiO2; 1g of epoxidized SiO2 and 100g of ethylene-vinyl alcohol copolymer resin are premixed and added to the mixed particles, twin-screw extruded, and water-cooled and pelletized to obtain the modified ethylene-vinyl alcohol copolymer resin; In S2, the aluminum alloy is compounded by aluminum, copper, and magnesium in a mass ratio of 95:4:1; the thickness of the aluminum plating layer is 90 μm; In S3, the raw material of the corona layer is a compound of propylene-ethylene-butene terpolymer and homopolypropylene, the raw material of the intermediate layer is modified homopolypropylene, and the raw material of the heat sealing layer is propylene-ethylene binary copolymer; The raw materials of the CPP printing film are, in parts by weight, 12 parts of propylene-ethylene-butene terpolymer, 4 parts of homopolypropylene, 66 parts of modified homopolypropylene, and 16 parts of propylene-ethylene binary copolymer; the thickness of the CPP printing film is 50 μm; the thickness of the corona layer is 8 μm, the thickness of the intermediate layer is 34 μm, and the thickness of the heat sealing layer is 8 μm.

[0013] Example 2: A method for preparing an aluminized stretch film for food packaging, the steps of the preparation method are as follows: S1: Dry the raw materials of the surface layer, the adhesive layer, the barrier layer, the adhesive layer and the heat-seal layer, add them into a co-extrusion system, co-extrude them, use a synchronous double stretching machine to stretch the co-extruded film in the longitudinal direction by a ratio of 3.2 times and in the transverse direction by a ratio of 3.8 times, and obtain a stretched base film with a total thickness of 150 μm; S2: Clean the stretched base film by plasma, put it into a vacuum aluminum plating machine, vacuumize it to 4*10 -4 Pa, configure an aluminum alloy as an evaporation source, co-evaporate on the surface layer film to form an aluminum plating layer, pass high-purity oxygen (0.1 Pa, 5 s) to generate a 3 nm dense oxide layer, and obtain an aluminum-plated base film; S3: 1) Dry and dehumidify the raw materials of the corona layer, the intermediate layer and the heat-seal layer respectively, co-extrude and form them, control the thickness of the CPP printed film to be 50 μm, print irreversible temperature change ink on the surface of the corona layer, and obtain a CPP printed film; 2) Solvent-free compound the CPP printed film with the aluminum-plated base film, and obtain an aluminum-plated stretched film for food packaging; In S1, the raw material of the surface layer film is a modified COC resin; the raw material of the adhesive layer is maleic anhydride grafted polypropylene; the raw material of the barrier layer is a modified ethylene-vinyl alcohol copolymer resin; and the raw material of the heat-seal layer is polyethylene; The raw materials of the stretched base film are 10 parts of modified COC resin, 7 parts of maleic anhydride grafted polypropylene, 45 parts of modified ethylene-vinyl alcohol copolymer resin, 7 parts of maleic anhydride grafted polypropylene and 31 parts of polyethylene, by weight; the thickness of the surface layer is 22.5 μm; the thickness of the adhesive layer is 9 μm; the thickness of the barrier layer is 64.5 μm; the thickness of the adhesive layer is 9 μm; and the thickness of the heat-seal layer is 45 μm; The preparation process of the modified COC resin is as follows: mix 3 g of methyltrimethoxysilane coupling agent, 10 mL of deionized water and 90 mL of ethanol solvent, adjust the pH to 4.5 with acetic acid, stir at 40℃ for 60 min, add 100 g of nano-SiO2, stir at 60℃ for 4 h, centrifuge, wash with ethanol and dry to obtain amino-SiO2; double-screw extrude 140 g of COC resin and 6 g of amino-SiO2, water-cool and cut into particles to obtain the modified COC resin; The preparation process of the modified ethylene-vinyl alcohol copolymer resin is as follows: 8 g of mica powder, 3 g of calcined kaolin, and 0.4 g of N-(2-aminoethyl)-3-aminopropyl trimethoxysilane coupling agent are mixed, 20 mL of 1% polyethyleneimine aqueous solution is sprayed, dried at 80℃ for 60 min, and mixed particles are obtained; 100 g of nano-SiO2, 5 g of 3-glycidyloxypropyl trimethoxysilane coupling agent, 95 g of ethanol, and 400 mL of deionized water are mixed, stirred at 60℃ for 2 h, and centrifuged and dried to obtain epoxidized SiO2; 1 g of epoxidized SiO2 and 100 g of ethylene-vinyl alcohol copolymer resin are premixed and added to the mixed particles, and a double-screw extruder is used for water cooling and pelletizing to obtain the modified ethylene-vinyl alcohol copolymer resin; In S2, the aluminum alloy is composed of aluminum, copper, and magnesium with a mass ratio of 95:3:2; and the thickness of the aluminum plating layer is 90 μm. In S3, the raw material of the corona layer is a propylene-ethylene-butene terpolymer and a homopolymer polypropylene, the raw material of the intermediate layer is a modified homopolymer polypropylene, and the raw material of the heat-sealing layer is a propylene-ethylene binary copolymer. In terms of weight parts, the raw material of the CPP printing film is 12 parts of a propylene-ethylene-butene terpolymer, 4 parts of a homopolymer polypropylene, 66 parts of a modified homopolymer polypropylene, and 16 parts of a propylene-ethylene binary copolymer; the thickness of the CPP printing film is 50 μm; the thickness of the corona layer is 8 μm, the thickness of the intermediate layer is 34 μm, and the thickness of the heat-sealing layer is 8 μm.

[0014] In example 3, a preparation method of an aluminum-plated stretch film for food packaging is provided, and the steps of the preparation method are as follows: S1: The raw materials of the surface layer, the adhesive layer, the barrier layer, the adhesive layer, and the heat-sealing layer are dried and added to a co-extrusion system for multi-layer co-extrusion; a synchronous double-direction stretching machine is used for stretching in the longitudinal direction with a ratio of 3.2 times and in the transverse direction with a ratio of 3.8 times to obtain a stretched base film with a total thickness of 150 μm; S2: The stretched base film is cleaned by plasma and placed in a vacuum aluminum plating machine; vacuum is drawn to 4×10 -4 Pa, and an aluminum alloy is used as an evaporation source to form an aluminum plating layer on the surface layer film by co-evaporation; high-purity oxygen is introduced (0.1 Pa, 5 s) to form a 3 nm dense oxide layer, and an aluminum-plated base film is obtained; S3: 1) The raw materials of the corona layer, the intermediate layer, and the heat-sealing layer are dried and dehumidified, co-extrusion casting is performed, the thickness of the CPP printing film is controlled to be 50 μm, and irreversible temperature change ink is printed on the surface of the corona layer to obtain a CPP printing film; 2) The CPP printing film is solvent-free compounded with the aluminum-plated base film to obtain an aluminum-plated stretch film for food packaging. In S1, the raw material of the surface layer film is a modified COC resin; the raw material of the adhesive layer is maleic anhydride grafted polypropylene; the raw material of the barrier layer is a modified ethylene-vinyl alcohol copolymer resin; and the raw material of the heat-seal layer is polyethylene; In weight parts, the raw material of the stretched base film is 10 parts of a modified COC resin, 8 parts of maleic anhydride grafted polypropylene, 40 parts of a modified ethylene-vinyl alcohol copolymer resin, 8 parts of maleic anhydride grafted polypropylene, and 34 parts of polyethylene; the thickness of the surface layer is 22.5 μm; the thickness of the adhesive layer is 9 μm; the thickness of the barrier layer is 64.5 μm; the thickness of the adhesive layer is 9 μm; and the thickness of the heat-seal layer is 45 μm. The preparation process of the modified COC resin is as follows: 3 g of methyltrimethoxysilane coupling agent, 10 mL of deionized water, and 90 mL of ethanol solvent are mixed, acetic acid is used to adjust the pH to 4.5, stirring is performed at 40°C for 60 min, 100 g of nano-SiO2 is added, stirring is performed at 60°C for 4 h, centrifugation is performed, ethanol washing and drying are performed, and thus amino-SiO2 is obtained; 140 g of COC resin and 6 g of amino-SiO2 are double-screw extruded, water cooling and pelletizing are performed, and thus the modified COC resin is obtained. The preparation process of the modified ethylene-vinyl alcohol copolymer resin is as follows: 8 g of mica powder, 3 g of calcined kaolin, and 0.4 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane coupling agent are mixed, 20 mL of a polyethyleneimine aqueous solution with a mass concentration of 1% is sprayed, drying is performed at 80°C for 60 min, and thus mixed particles are obtained; 100 g of nano-SiO2, 5 g of 3-glycidyloxypropyltrimethoxysilane coupling agent, 95 g of ethanol, and 400 mL of deionized water are mixed, stirring is performed at 60°C for 2 h, centrifugation and drying are performed, and thus epoxy-SiO2 is obtained; 1 g of epoxy-SiO2 and 100 g of ethylene-vinyl alcohol copolymer resin are premixed and then added to the mixed particles, double-screw extrusion is performed, water cooling and pelletizing are performed, and thus the modified ethylene-vinyl alcohol copolymer resin is obtained. In S2, the aluminum alloy is composed of aluminum, copper, and magnesium at a mass ratio of 95:3:2; and the thickness of the aluminum plating layer is 90 μm. In S3, the raw material of the corona layer is a propylene-ethylene-butene terpolymer and a homopolymer polypropylene; the raw material of the intermediate layer is a modified homopolymer polypropylene; and the raw material of the heat-seal layer is a propylene-ethylene binary copolymer. In weight parts, the raw material of the CPP printing film is 12 parts of a propylene-ethylene-butene terpolymer, 4 parts of a homopolymer polypropylene, 66 parts of a modified homopolymer polypropylene, and 16 parts of a propylene-ethylene binary copolymer; the thickness of the CPP printing film is 50 μm; the thickness of the corona layer is 8 μm; the thickness of the intermediate layer is 34 μm; and the thickness of the heat-seal layer is 8 μm.

[0015] Comparative Example 1: As a control group of Example 1, 60 g of polypropylene was used to replace part of the COC resin, so that the COC resin content was 59%, and the other procedures were normal.

[0016] Comparative Example 2: As a control group of Example 1, pure aluminum was used to replace aluminum alloy, and the other procedures were normal.

[0017] Comparative Example 3: As a control group of Example 1, ethylene-vinyl alcohol copolymer resin was used to replace modified ethylene-vinyl alcohol copolymer resin, and the other procedures were normal.

[0018] The sources of the raw materials used (only as an example) are as follows: The raw materials in the technical solution are all products currently sold on the market. COC resin (brand TOPAS-8007F): Dongguan Yilai Plastic Co., Ltd.; Nano-SiO2 (20 nm, 7631-86-9, 90%): Xi'an Qiyue Biological Technology Co., Ltd.; Maleic anhydride grafted polypropylene (PO-1015, PO-1015): Shenzhen Wanplasource Rubber and Plastic Co., Ltd.; Calcined kaolin (1332-58-7, 99%): Hubei Chengfeng Chemical Co., Ltd.; Mica powder (12001-26-2, 99.5%): Luquan Anliada Powder Material Factory; Polyethyleneimine (9002-98-6, 99%): Hubei Shixing Chemical Co., Ltd.; N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (1760-24-3, 98%): Tianmen Hengchang Chemical (Hubei) Co., Ltd.; Gamma-aminopropyltriethoxysilane (919-30-2, 98%): Hubei Xinkang Pharmaceutical Chemical Co., Ltd.; Ethylene-vinyl alcohol copolymer resin (EV3201F, EVOH EV3201F): Ningbo Qihuida Material Technology Co., Ltd.; Propylene-ethylene-butene terpolymer (9003-07-0, F800E): Shanghai Petrochemical Co., Ltd.; Polyethylene (9002-88-4, ELITE™ 5400G): Dow Chemical Company; Homopolymer polypropylene (9003-07-0, F800EDF): Sinopec Shanghai Petrochemical Co., Ltd.; Modified homopolymer polypropylene (9003-07-0, HD915): Sinopec Shanghai Petrochemical Co., Ltd.; Propylene-ethylene copolymer (9003-07-0, F800E): Sinopec Shanghai Petrochemical Co., Ltd.; Irreversible ink (36431-22-8, viscosity 1000S): Guangzhou Chongyu Industrial Material Technology Co., Ltd.; 3-glycidyloxypropyltrimethoxysilane (2530-83-8, 99.8%): Comdis Chemical (Hubei) Co., Ltd.; Polypropylene (9003-07-0, 99%): Hubei Yongkuo Technology Co., Ltd.; Al (98%): Shanghai Yuanye Biological Technology Co., Ltd.; Cu (99.9%): Tim (Beijing) New Material Technology Co., Ltd.; Mg (99%): HeFei Kexing Material Co., Ltd.; Ethanol and acetic acid were commercially available.

[0019] Performance test: the aluminum-plated stretch film for food packaging prepared by the examples and comparative examples was tested: The aluminum-plated stretch film was cured in a mold and used as a sample.

[0020] (1) Oxygen barrier test (OTR): the sample was cut into a circular size of 100 mm in diameter, sealed in a test chamber, and a differential pressure method gas permeation instrument was used, with a temperature of 23°C, a humidity of 50% RH, high-purity oxygen (99.999%) as the test gas, a pressure difference of 0.1 MPa, and the stable penetration amount was recorded for 24 hours, and the oxygen transmission rate (OTR, unit: cc / m²·day) was calculated.

[0021] (2) Tensile property test (MD / TD direction): an electronic universal testing machine (ASTM D882 standard) was used, with a 500N load sensor, a gauge length of 100 mm, and a sample strip of 15 mm wide and 150 mm long was cut along the longitudinal direction (MD) and the transverse direction (TD), respectively, with a clamping distance of 50 mm, and the tensile strength (MPa) was recorded at a speed of 500 mm / min, with 5 groups of tests in each direction, and the average value was taken after removing abnormal values.

[0022] (3) Peel strength test: according to the requirements of GB / T 8808 standard, the sample was cut into a standard size film strip of 15 mm wide and 200 mm long, a universal material testing machine was selected, a 50 mm starting end was manually peeled off, the clamp was clamped, the universal material testing machine was peeled off at a speed of 300 mm / min, and the average peel force in the range of 100-150 mm was recorded, the peel strength = average peel force (N) x 15 / sample width (mm) (unit: N / 15 mm), and the arithmetic mean value of 5 groups of samples was taken.

[0023] (4) Heat seal strength: a heat seal tester was used with a universal tensile machine, with a heat seal pressure of 0.2 MPa, a time of 1.0 s, a temperature of 110°C, a 15 mm wide sample was cut after heat sealing, and the heat seal strength (unit: N / 15 mm) was recorded at a speed of 200 mm / min.

[0024] The test results are as follows: Table 1

[0025] The analysis results are as follows: The prepared aluminum-plated stretch film is subjected to performance test analysis, and the oxygen barrier property OTR is less than 0.5 cc / m2·day, and the barrier property is excellent; the tensile property test shows that the synchronous biaxial stretching improves the efficiency and reduces the energy consumption, the MD / TD strength difference is less than 5%, and the biaxial stretching process is balanced; the elongation at break is greater than 90%, indicating that the deep drawing formability is excellent, and the peel strength is greater than 4.0 N / 15 mm, and the Al2O3 oxide layer effectively inhibits delamination; the hot sealing test machine is combined with the universal tensile testing machine, and effective sealing can be realized at 110 DEG C, and the hot sealing strength is greater than 18 N / 15 mm, which is suitable for packaging of heat-sensitive contents, and the results meet the needs of food packaging.

[0026] It can be seen from the combination of Example 1 and Comparative Examples 1, 2 and 3 and the data in Table 1 that the content of the surface layer COC resin is less than 70%, which will result in insufficient polarity of the surface layer, the combination of aluminum atoms and the -OH bond of COC will be weakened, the aluminum-plated layer cannot be effectively adsorbed, and even the aluminum-plated layer falls off; if pure aluminum is used for the aluminum-plated layer, the barrier and durability performance will be reduced, the ductility of pure aluminum is poor, the brittleness of the aluminum-plated layer is increased, which will result in a substantial decrease in peel strength and easy cracking when bending, and the oxygen barrier property is deteriorated, and a dense oxide layer cannot be formed; the polarity of ordinary EVOH is weak, and the bonding force with the aluminum-plated layer is poor, while the polyethylene imine and silane coupling agent in the modified EVOH can enhance the interfacial bonding force, so the peel strength is obviously decreased; since the epoxidized SiO2 and mineral fillers in the modified EVOH can prolong the gas permeation path, the OTR will increase significantly; the mineral fillers can provide reinforcement effect and improve the tensile strength but reduce the elongation at break; after being replaced by ordinary EVOH, the tensile strength will decrease.

[0027] It is apparent for those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and the present application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the present application being defined by the appended claims rather than the foregoing description, and it is intended to embrace all changes and modifications that fall within the meaning and scope of equivalents of the claims.

Claims

1. A method for preparing an aluminized stretch film for food packaging, characterized in that: The steps of the preparation method are as follows: S1: Co-extruding a heat-sealing layer, an adhesive layer, a barrier layer, an adhesive layer, and a surface film, and stretching the film to obtain a stretched base film; S2: vacuum-plating the stretched base film to form an aluminum-plated layer on the surface film to obtain an aluminum-plated base film; S3: The CPP printed film is compounded with the aluminized base film without solvent to produce an aluminized stretch film for food packaging.

2. The method for preparing an aluminized stretch film for food packaging according to claim 1, wherein: The raw material of the surface film is modified COC resin; the raw material of the adhesive layer is one of maleic anhydride grafted polypropylene and polyethylene; the raw material of the barrier layer is one of modified ethylene-vinyl alcohol copolymer resin and nylon; the raw material of the heat sealing layer is one of polyethylene and polypropylene.

3. The method for preparing an aluminized stretch film for food packaging according to claim 1, wherein: The thickness of the stretched base film is 50-300 μm; the thickness of the aluminum plating layer is 50-100 μm; and the thickness of the CPP printing film is 30-150 μm.

4. The method for preparing an aluminized stretch film for food packaging according to claim 2, wherein: The preparation process of the modified ethylene-vinyl alcohol copolymer resin is as follows: mica powder, calcined kaolin, and a bisaminosilane coupling agent are mixed, a polyethyleneimine aqueous solution is sprayed, and the mixed particles are dried; nano-SiO2, 3-glycidoxypropyltrimethoxysilane coupling agent, ethanol, and deionized water are mixed, and stirred to obtain epoxidized SiO2; epoxidized SiO2 and ethylene-vinyl alcohol copolymer resin are premixed and added to the mixed particles, twin-screw extruded, and water-cooled and pelletized to obtain the modified ethylene-vinyl alcohol copolymer resin.

5. The method for preparing an aluminized stretch film for food packaging according to claim 2, wherein: The preparation process of the modified COC resin is as follows: extruding the COC resin and amino SiO2, and water-cooling and pelletizing to obtain the modified COC resin.

6. The method for preparing an aluminized stretch film for food packaging according to claim 5, wherein: The preparation process of the amination SiO2 is as follows: gamma-aminopropyltriethoxysilane coupling agent, deionized water and ethanol solvent are mixed, pH is adjusted, stirring is performed, nano-SiO2 is added, stirring is performed, and centrifugal drying is performed to obtain the amination SiO2.

7. The method for preparing an aluminized stretch film for food packaging according to claim 1, wherein: The S2 comprises: plasma cleaning the stretched base film, placing it in a vacuum aluminum coating machine, evacuating the film, controlling the temperature, configuring an aluminum alloy as an evaporation source, co-evaporating to form an aluminum coating layer on the surface film, introducing high-purity oxygen, and generating a dense oxide layer on the surface of the aluminum coating layer to obtain an aluminum-coated base film; the aluminum alloy is compounded by aluminum, copper, and magnesium in a mass ratio of 95:(3-5):(1-2).

8. The method for preparing an aluminized stretch film for food packaging according to claim 1, wherein: The preparation process of the CPP printed film described in S3 is: drying and dehumidifying the raw materials of the corona layer, the middle layer, and the heat sealing layer respectively, forming them by co-extrusion casting, corona treating the corona layer, and then printing irreversible temperature-changing ink to obtain the CPP printed film.

9. The method for preparing an aluminized stretch film for food packaging according to claim 8, wherein: The raw material of the corona layer is a propylene-ethylene-butene terpolymer and a homopolymer polypropylene in a weight ratio of (7-8): (2-3), the raw material of the intermediate layer is a modified homopolymer polypropylene, and the raw material of the heat sealing layer is a propylene-ethylene binary copolymer.

10. An aluminized stretch film for food packaging, characterized by: Prepared according to the preparation method according to any one of claims 1 to 9.

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