PE inner film of aluminum cover film

Abstract

The invention relates to the technical field of PE films, and particularly discloses a PE inner film of an aluminum cover film. The PE inner film of the aluminum cover film is prepared from the following raw materials: LDPE, LLDPE, MLLDPE, HDPE, nano boron nitride, nano aluminum oxide, ethylene-vinyl acetate copolymer, maleic anhydride grafted polyethylene, an antioxidant and calcium stearate. The heat sealing strength of the PE inner film at 110 DEG C, 113 DEG C and 116 DEG C is 1.00-1.79 N, 6.50-7.80 N and 9.60-11.18 N respectively, the change rate of tensile strength after curing is lower than 4.8%, the change rate of elongation at break is lower than 6.9%, the heat sealing strength and high temperature resistance of the PE inner film are improved, and the requirements for high heat sealing strength and high temperature resistance of the PE inner film under a high-frequency large-current sealing process can be met at the same time.

Description

Technical Field

[0001] This application relates to the field of PE film, and more specifically, to an aluminum-capped PE inner film. Background Technology

[0002] Aluminum cap film is a composite packaging material that achieves a seal with the bottle neck through heating and pressurization. It prevents the contents from directly contacting the aluminum foil and reacting. It is mainly used for sealing the necks of various bottles, cans, cups, and other containers. Aluminum cap film is typically composed of multiple layers, including a protective or printed layer, an aluminum foil layer, and a heat-sealing layer. Currently, three-layer aluminum cap film (PET / aluminum foil / PE) is widely used in pharmaceutical and food packaging, employing a PE inner film as the heat-sealing layer. Therefore, the performance of the PE inner film directly affects the sealing quality and the safety of the product's shelf life.

[0003] As the packaging industry continues to demand higher sealing efficiency and reliability, PE inner film is unable to meet the extreme conditions required by high-frequency, high-current sealing processes, and it is also difficult to balance multiple properties such as thermal conductivity, heat sealing strength, and temperature resistance.

[0004] In related technologies, a general-purpose PE inner film is used to achieve sealing by increasing the sealing time and current intensity. Although the cost is low and the process is mature, the heat conduction efficiency is low, the sealing is uneven, and it is easy to cause heat damage to the bottle mouth. While the temperature resistance of the PE inner film modified with added fillers is improved, the heat sealing strength is insufficient, and it is easy to delaminate or delaminate during the sterilization process. Summary of the Invention

[0005] In order to simultaneously meet the requirements of high heat sealing strength and high temperature resistance of PE inner film under high frequency and high current sealing process, this application provides an aluminum cap PE inner film.

[0006] In a first aspect, this application provides an aluminum-coated PE inner film, which adopts the following technical solution: An aluminum-coated PE inner film comprises the following raw materials in parts by weight: 20-30 parts LDPE, 40-70 parts LLDPE, 10-30 parts MLLDPE, 10-30 parts HDPE, 2-5 parts nano boron nitride, 1-3 parts nano alumina, 5-10 parts ethylene-vinyl acetate copolymer, 2-5 parts maleic anhydride-grafted polyethylene, 0.3-0.5 parts antioxidant, and 0.5-1 parts calcium stearate.

[0007] By adopting the above scheme, using LDPE and LLDPE as the main raw materials, LDPE has a large proportion of amorphous regions, and its molecular chains undergo intense thermal motion under a high-frequency electric field, enabling rapid transfer of Joule heat to the entire heat-sealing layer. However, pure LDPE has low crystallinity and low thermal conductivity. LLDPE has a much higher thermal conductivity than LDPE, and the crystalline lamellar crystals of LLDPE can act as a "bridge" for heat conduction, accelerating heat transfer within the film. Simultaneously, its melting temperature is close to that of LDPE, ensuring synchronous melting. Using MLLDPE and HDPE as secondary raw materials, MLLDPE has large spherulites and high thermal conductivity. Adding MLLDPE to the PE inner film can significantly improve the overall thermal conductivity, allowing the heat-sealing layer to quickly reach the melting temperature under high-frequency, high-current conditions. At the same time, the high crystallinity of HDPE improves its temperature resistance.

[0008] In addition, the long branched structure of LDPE gives it a strong ability to entangle its molecular chains. After melting, it quickly intertwines with the molecular chains of the opposite film layer to form initial adhesion. After cooling, it has few physical cross-linking points and its heat-sealing strength is easily weakened. The short branched molecular chains of LLDPE have better regularity than LDPE. After melting, they diffuse quickly and entangle with the molecular chains of LDPE. At the same time, its crystalline lamellae form "physical anchor points" at the interface, which improves the stability of the adhesion.

[0009] The fine crystalline grains of MLLDPE form a dense crystalline layer at the heat-sealing interface, further enhancing heat-sealing strength and maintaining adhesion even at higher temperatures after heat sealing. HDPE significantly improves the heat-sealing strength of the inner layer of PE. Furthermore, LDPE has poor temperature resistance, while LLDPE has a higher melting point and higher crystallinity, which improves the heat deformation resistance of the heat-sealing layer.

[0010] Using LDPE and LLDPE as the main raw materials and MLLDPE and HDPE as secondary raw materials, it can achieve rapid and uniform sealing even under the instantaneous action of high current. This reduces the continuous heat conduction time to the bottle opening, lowers the risk of heat damage, and ensures that even if the sealing width is slightly narrowed due to process fluctuations, the remaining sealing area can still provide sufficient high heat sealing strength, guaranteeing high-temperature performance and avoiding the risk of later leakage or detachment due to heat decay.

[0011] The addition of nano-boron nitride to PE inner film raw materials creates a graphite-like layered structure with high in-plane thermal conductivity, forming continuous in-plane thermal conductive pathways within the PE inner film. Nano-alumina, also with high thermal conductivity, fills the gaps between the nano-boron nitride layers, forming a three-dimensional thermally conductive network that comprehensively improves the thermal conductivity of the PE inner film. Furthermore, nano-alumina reduces the viscosity of molten PE, increasing its fluidity during heat sealing and allowing PE molecular chains to more easily penetrate the surface of the substrate being bonded, increasing the contact area. The sheet-like structure of nano-boron nitride forms a "physical skeleton" within the molten PE, preventing material loss during heat sealing due to excessive fluidity and ensuring uniform adhesive layer thickness. The combined addition of nano-alumina and nano-boron nitride avoids insufficient adhesion due to insufficient fluidity and prevents a decrease in heat-sealing strength due to excessively low viscosity, thus improving the overall heat-sealing strength of the PE inner film. Furthermore, the sheet-like structure of nano-boron nitride has excellent thermal insulation properties, which can form a "sheet-like thermal insulation layer" in the PE matrix, hindering the transfer and diffusion of heat and slowing down the thermal motion of PE molecular chains. Nano-alumina can inhibit the thermal expansion of the matrix when PE is heated and reduce thermal deformation. The three-dimensional network structure formed by the combination of the two can form a continuous thermal barrier on the surface and inside of PE, which can prevent the rapid transfer of external heat and inhibit the accumulation of internal heat, thereby improving the temperature resistance of the PE inner film.

[0012] Ethylene-vinyl acetate copolymer and maleic anhydride-grafted polyethylene are added to the PE inner film raw material. The maleic anhydride groups in the maleic anhydride-grafted polyethylene have strong polarity and can form hydrogen bonds and dipole interactions with the PE molecular chains, inducing a more regular arrangement of PE molecular chains, reducing the disorder of amorphous regions, and improving the thermal conductivity of the PE matrix itself. The vinyl acetate units in the ethylene-vinyl acetate copolymer are flexible segments that can be embedded in the gaps between PE molecular chains, reducing "voids" between molecular chains and lowering phonon transmission scattering losses. The combination of these two materials, with maleic anhydride-grafted polyethylene acting as a "nucleating agent," promotes the formation of finer spherulites in PE, while the ethylene-vinyl acetate copolymer inhibits grain boundary defects caused by excessive spherulite growth, resulting in a continuous distribution of crystalline regions and forming a smoother heat transfer path, thereby improving thermal conductivity. In addition, the ethylene-vinyl acetate copolymer reduces the crystallinity of the polymer, lowering the melting temperature of the compound system and improving melt fluidity, making it easier to wet the surface of the substrate being bonded during heat sealing and increasing the actual contact area. Maleic anhydride-grafted polyethylene (MPPE) enhances molecular chain entanglement, ensuring cohesive strength in the molten state and preventing the heat-sealing layer from losing structural support due to excessive fluidity, thus improving the heat-sealing strength of the PE inner film. Furthermore, MPPE increases the entanglement density of molecular chains, raising the system's glass transition temperature and heat distortion temperature. The ethylene-vinyl acetate copolymer hinders the slippage and cold flow of PE molecular chains at high temperatures, reducing heat distortion. MPPE provides rigid crosslinking nodes, while the ethylene-vinyl acetate copolymer provides flexible segmental connections, preventing brittle fracture at high temperatures and inhibiting plastic deformation, thereby improving the temperature resistance of the PE inner film.

[0013] Preferably, the aluminum cap film PE inner film comprises the following raw materials in parts by weight: LDPE 24-28 parts, LLDPE 45-65 parts, MLLDPE 15-25 parts, HDPE 15-25 parts, nano boron nitride 3-4 parts, nano alumina 1.5-2.5 parts, ethylene-vinyl acetate copolymer 7-9 parts, maleic anhydride grafted polyethylene 3-4 parts, antioxidant 0.35-0.45 parts, and calcium stearate 0.7-0.9 parts.

[0014] In this application, the raw materials for the aluminum cap film PE inner membrane can be selected from any range of LDPE 24-28 parts, LLDPE 45-65 parts, MLLDPE 15-25 parts, HDPE 15-25 parts, nano boron nitride 3-4 parts, nano alumina 1.5-2.5 parts, ethylene-vinyl acetate copolymer 7-9 parts, maleic anhydride grafted polyethylene 3-4 parts, antioxidant 0.35-0.45 parts, and calcium stearate 0.7-0.9 parts, which can simultaneously meet the requirements of high heat sealing strength and high temperature resistance of the aluminum cap film PE inner membrane under high frequency and high current sealing process.

[0015] Preferably, the weight ratio of the nano-alumina to the nano-boron nitride is 1:(2-4).

[0016] By adopting the above scheme and adjusting the weight ratio of nano-alumina to nano-boron nitride, the heat-sealing strength and high-temperature resistance of PE inner film can be further improved.

[0017] Preferably, the weight ratio of the maleic anhydride-grafted polyethylene to the ethylene-vinyl acetate copolymer is 1:(2-4).

[0018] By adopting the above scheme and adjusting the weight ratio of maleic anhydride-grafted polyethylene to ethylene-vinyl acetate copolymer, the heat-sealing strength and high-temperature resistance of PE inner film can be further improved.

[0019] Preferably, the nano-boron nitride and nano-alumina are obtained through modification treatment, specifically: S1. Vacuum dry the nano-alumina at 100-120℃ for 2-4 hours, and set aside for later use; S2. Place the nano-boron nitride in a muffle furnace and heat it to 400-500℃ at a rate of 5℃ / min in an air atmosphere. Calcinate at a constant temperature for 2-3 hours. After naturally cooling to room temperature, add the oxidized BN to deionized water and stir for 1 hour. Filter, dry, and set aside. S3. Mix the dried nano-alumina from step S1 with the pre-treated nano-boron nitride and MAH-g-PP wax, add an antioxidant, mix at 80-100℃ and 1500-2000 r / min for 5-10 min, extrude using a twin-screw extruder, control the screw temperature, speed at 200-300 r / min, residence time at 3-5 min, water cooling, pelletizing, vacuum drying, and pulverizing to obtain the modified nano-boron nitride and nano-alumina.

[0020] The amount of antioxidant used is 0.1%-0.5% of the total mass of nano-alumina and nano-boron nitride.

[0021] By adopting the above method, vacuum drying of nano-alumina removes water molecules and hydroxyl aggregates adsorbed on the surface of nano-alumina, avoiding the decrease in grafting efficiency due to the presence of moisture during subsequent reaction with maleic anhydride-grafted polyethylene wax, and at the same time reducing the interfacial voids of the filler in the matrix.

[0022] Nano-boron nitride is calcined at low temperature in a muffle furnace to prevent excessive oxidation. Washing with deionized water removes soluble borate impurities generated during calcination, preventing impurities from forming defects on the filler surface and ensuring the mechanical properties of nano-boron nitride.

[0023] Subsequently, MAH-g-PP wax grafting modification of nano-alumina and nano-boron nitride was used to improve the dispersibility of nano-alumina and nano-boron nitride in the PE inner layer raw material, thereby improving the heat sealing strength and high temperature resistance of the PE inner film.

[0024] Preferably, the amount of MAH-g-PP wax used is 20-40% of the total mass of nano-alumina and nano-boron nitride.

[0025] By adopting the above scheme, the amount of MAH-g-PP wax is controlled at 20-40% of the total mass of nano-alumina and nano-boron nitride, ensuring the grafting effect of nano-alumina and nano-boron nitride, and further improving the heat sealing strength and high temperature resistance of PE inner film.

[0026] Preferably, the MAH-g-PP wax is pulverized to 100 mesh.

[0027] By adopting the above scheme, MAH-g-PP wax is pulverized to 100 mesh, which optimizes its mixing uniformity with nanofillers, improves grafting modification efficiency, ensures smooth mixing and extrusion, and enhances the modification effect, thereby further improving the heat sealing strength and high temperature resistance of PE inner film.

[0028] Secondly, this application provides a method for preparing the aluminum cap film PE inner film according to any one of claims 1-7, which is specifically achieved through the following technical solution: A method for preparing an aluminum-capped PE inner film according to any one of claims 1-7, comprising the following steps: drying LDPE, LLDPE, MLLDPE, and HDPE at 80°C for 2 hours for later use; subsequently, vacuum drying ethylene-vinyl acetate copolymer and maleic anhydride-grafted polyethylene at 90°C for 4 hours for later use; mixing the dried LDPE, LLDPE, MLLDPE, HDPE, ethylene-vinyl acetate copolymer, and maleic anhydride-grafted polyethylene at 80°C and a rotation speed of 2000 r / min for 15 minutes, melt blending, extruding at 160-190°C, cooling and drying, pelletizing, melt plasticizing, casting and cooling, traction and winding, and curing at 40°C for 24 hours to obtain an aluminum-capped PE inner film.

[0029] In summary, this application includes at least one of the following beneficial technical effects: 1. This application improves the heat-sealing strength and high-temperature resistance of the PE inner film by controlling the types and amounts of raw materials and dosages of each raw material in the aluminum-capped PE inner film. The heat-sealing strength of the aluminum-capped PE inner film at 110℃, 113℃ and 116℃ is 1.60-1.64N, 7.25-7.32N and 10.25-10.76N respectively. The change rate of tensile strength and the change rate of elongation at break after curing are 3.9-4.1% and 6.3-6.5% respectively.

[0030] 2. This application further modifies nano-boron nitride and nano-alumina, and controls the raw material dosage and MAH-g-PP wax particle size, so that the heat-sealing strength of the aluminum cap film PE inner film at 110℃, 113℃ and 116℃ is 1.79N, 7.80N and 11.18N respectively, and the change rate of tensile strength and elongation at break after curing is 3.0% and 5.0% respectively, which further improves the heat-sealing strength and high temperature resistance of the PE inner film. Detailed Implementation

[0031] The following detailed description, in conjunction with specific embodiments, further illustrates this application. All the raw materials used in this application are commercially available products and are intended to fully disclose the raw materials used in this application; they should not be construed as limiting the source of the raw materials. Specifically: LDPE, brand Qatar Petrochemical, grade MG70; LLDPE, brand Daqing Petrochemical, grade 8320; MLLDPE, brand Daelim (Korea), grade XP9200; HDPE, grade 9455F; nano boron nitride, particle size 50nm; nano alumina, particle size 30nm; ethylene-vinyl acetate copolymer, brand Elvax, grade 670; maleic anhydride grafted polyethylene, brand Shenghao Plastics, grade PE-14L; antioxidant, antioxidant 1035 selected; calcium stearate, effective substance content 99%; MAH-g-PP wax, brand Clariant, model 4351.

[0032] The following are examples of the preparation of modified nano boron nitride and nano alumina. Preparation Example 1 The modified boron nitride nanoparticles and alumina nanoparticles prepared in Example 1 are specifically as follows: S1. Dry 1 kg of nano-alumina under vacuum at 110℃ for 3 hours, and set aside for later use; S2. Place 3 kg of nano boron nitride in a muffle furnace and heat it to 450°C at a rate of 5°C / min in air atmosphere. Calcinate at a constant temperature for 2.5 h. After naturally cooling to 25±2°C, add the oxidized nano boron nitride to deionized water and stir for 1 h. Filter, dry, and set aside. S3. The dried nano-alumina and pre-treated nano-boron nitride from step S1 are mixed with 400g of MAH-g-PP wax, and 1.2g of antioxidant is added. The mixture is stirred at 90℃ and 1800r / min for 7min, then extruded by twin screws. The screw temperature is controlled at 250r / min and the residence time is 4min. The mixture is then water-cooled, pelletized, vacuum-dried, and pulverized to obtain the modified nano-boron nitride and nano-alumina.

[0033] Preparation Examples 2-5 The modified boron nitride nano and alumina nano in Preparation Examples 2-5 were exactly the same as those in Preparation Example 1 in terms of raw material types and preparation methods. The difference was that the amount of MAH-g-PP wax was different, specifically 800g, 1200g, 1600g and 2000g. The other steps were the same as those in Preparation Example 1.

[0034] Preparation Example 6 The modified boron nitride nano and alumina nano in Preparation Example 6 were made from the same raw materials and prepared by the same method as those in Preparation Example 3. The only difference was that the MAH-g-PP wax was pulverized to 100 mesh. The remaining steps were the same as those in Preparation Example 3.

[0035] Example 1 Example 1: The aluminum cap film PE inner film was prepared through the following steps: According to the dosage in Table 1, LDPE, LLDPE, MLLDPE, and HDPE were dried at 80℃ for 2 hours and set aside. Then, ethylene-vinyl acetate copolymer and maleic anhydride grafted polyethylene were vacuum dried at 90℃ for 4 hours and set aside. The dried LDPE, LLDPE, MLLDPE, HDPE, ethylene-vinyl acetate copolymer, and maleic anhydride grafted polyethylene were mixed at 80℃ and 2000 r / min for 15 minutes, melt-blended, extruded at 160-190℃, cooled and dried, pelletized, melt-plasticized, cast and cooled, drawn and wound, and cured at 40℃ for 24 hours to obtain aluminum cap PE inner film.

[0036] Examples 2-5 The preparation methods and raw material types of the aluminum cap film PE inner film in Examples 2-5 are exactly the same as those in Example 1, except that the dosage of each raw material is different, as detailed in Table 1.

[0037] Table 1. Raw material dosage for aluminum cap film and PE inner film in Examples 1-5 (unit: kg) Examples 6-9 The preparation methods and raw material types of the aluminum cap film PE inner film in Examples 6-9 are exactly the same as those in Example 3, except that the dosage of each raw material is different, as detailed in Table 2.

[0038] Table 2. Raw material dosage for aluminum cap film and PE inner film in Examples 6-9 (unit: kg) Examples 10-15 The preparation methods of the aluminum cap film PE inner film in Examples 10-15 are the same as those in Example 7, except that the nano boron nitride and nano alumina in the PE inner film raw materials are modified nano boron nitride and nano alumina prepared in Examples 1-6, and the types and amounts of other raw materials are the same as those in Example 7.

[0039] Comparative Example 1 The preparation method of the aluminum cap film PE inner film in Comparative Example 1 is exactly the same as that in Example 1, except that LLDPE is replaced with LDPE in equal amounts, and the other raw materials and dosages are the same as in Example 1.

[0040] Comparative Example 2 The preparation method of the aluminum cap film PE inner film in Comparative Example 2 is exactly the same as that in Example 1, except that LDPE is replaced with LLDPE in equal amounts, and the remaining raw materials and dosages are the same as in Example 1.

[0041] Comparative Example 3 The preparation method of the aluminum cap film PE inner film in Comparative Example 3 is exactly the same as that in Example 1, except that MLLDPE is replaced with HDPE in equal amounts, and the remaining raw materials and dosages are the same as in Example 1.

[0042] Comparative Example 4 The preparation method of the aluminum cap film PE inner film in Comparative Example 4 is exactly the same as that in Example 1, except that HDPE is replaced with MLLDPE in equal amounts, and the other raw materials and dosages are the same as in Example 1.

[0043] Comparative Example 5 The preparation method of the aluminum cap film PE inner film in Comparative Example 5 is exactly the same as that in Example 1, except that nano boron nitride is replaced with nano aluminum oxide in equal amounts, and the other raw materials and dosages are the same as in Example 1.

[0044] Comparative Example 6 The preparation method of the aluminum cap film PE inner film in Comparative Example 6 is exactly the same as that in Example 1, except that nano alumina is replaced with nano boron nitride in equal amounts, and the other raw materials and dosages are the same as in Example 1.

[0045] Comparative Example 7 The preparation method of the aluminum cap film PE inner film in Comparative Example 7 is exactly the same as that in Example 1, except that the ethylene-vinyl acetate copolymer is replaced with maleic anhydride-grafted polyethylene in equal amounts, and the remaining raw materials and dosages are the same as in Example 1.

[0046] Comparative Example 8 The preparation method of the aluminum cap film PE inner film in Comparative Example 8 is exactly the same as that in Example 1, except that maleic anhydride grafted polyethylene is replaced with an equal amount of ethylene-vinyl acetate copolymer, and the remaining raw materials and dosages are the same as in Example 1.

[0047] Performance testing The performance of the aluminum cap PE inner film obtained in different Examples 1-15 and Comparative Examples 1-8 was tested using the following testing standards or methods. The test results are shown in Table 3.

[0048] Heat seal strength: With the hot knife fixed at 100℃, the heat seal strength was tested at different temperatures of 110℃, 113℃ and 116℃.

[0049] High temperature resistance: The PE inner film was cured at 60℃ for 48 hours, and the change rate of tensile strength and the change rate of elongation at break were detected before and after curing.

[0050] Table 3 Performance test results of different aluminum cap films and PE inner films The test results in Table 3 show that the heat-sealing strength of the aluminum cap PE inner film obtained in this application is 1.00-1.79N, 6.50-7.80N, and 9.60-11.18N at 110℃, 113℃, and 116℃, respectively. The change rate of tensile strength after curing is less than 4.8%, and the change rate of elongation at break is less than 6.9%, which improves the heat-sealing strength and high-temperature resistance of the PE inner film and can simultaneously meet the requirements of high heat-sealing strength and high temperature resistance under high-frequency high-current sealing process.

[0051] Based on the performance test data of the aluminum-capped PE inner film in Examples 1-5, it was found that the heat-sealing strength of the aluminum-capped PE inner film in Examples 2-4 at 110℃, 113℃, and 116℃ was 1.35-1.56N, 6.74-7.01N, and 9.81-10.13N, respectively, which were all higher than those in Examples 1 and 5. The change rate of tensile strength and the change rate of elongation at break after curing were 4.3-4.6% and 6.6-6.8%, respectively, which were lower than those in Examples 1 and 5. This indicates that the optimal weight ratio of nano-alumina to nano-boron nitride in the raw material of the aluminum-capped PE inner film is 1:(2-4), which improves the heat-sealing strength and high-temperature resistance of the PE inner film.

[0052] Combining the performance test data of the aluminum-capped PE inner film of Examples 6-9 and Example 3, it was found that the heat-sealing strength of the aluminum-capped PE inner film of Examples 6-8 at 110℃, 113℃ and 116℃ were 1.60-1.64N, 7.25-7.32N and 10.25-10.76N respectively, which were all higher than those of Examples 3 and 9. The change rate of tensile strength and the change rate of elongation at break after curing were 3.9-4.1% and 6.3-6.5% respectively, which were both lower than those of Examples 3 and 9. This indicates that the optimal weight ratio of maleic anhydride grafted polyethylene to ethylene-vinyl acetate copolymer in the raw material of the aluminum-capped PE inner film is 1:(2-4), which improves the heat-sealing strength and high-temperature resistance of the PE inner film.

[0053] Based on the performance test data of the aluminum-capped PE inner film in Examples 10-14, it was found that the heat-sealing strength of the aluminum-capped PE inner film in Examples 11-13 at 110℃, 113℃, and 116℃ was 1.00-1.70-1.75N, 7.51-7.58N, and 10.91-11.05N, respectively, all higher than that in Examples 10 and 14. The change rate of tensile strength and the change rate of elongation at break after curing were 3.1-3.5% and 5.2-5.7%, respectively, both lower than those in Examples 10 and 14. This indicates that when modifying with nano-boron nitride and nano-alumina, it is more appropriate for MAH-g-PP wax to be 20-40% of the total amount of nano-alumina and nano-boron nitride, which improves the heat-sealing strength and high-temperature resistance of the PE inner film.

[0054] Combining the performance test data of the aluminum-capped PE inner film from Examples 12 and 15, it was found that the heat-sealing strength of the aluminum-capped PE inner film from Example 15 at 110℃, 113℃, and 116℃ was 1.79N, 7.80N, and 11.18N, respectively, all higher than that of Example 12. The change rates of tensile strength and elongation at break after curing were 3.0% and 5.0%, respectively, both lower than those of Example 12. This indicates that when modifying with nano-boron nitride and nano-alumina, pulverizing MAH-g-PP wax to 100 mesh is more suitable, improving the heat-sealing strength and high-temperature resistance of the PE inner film.

[0055] Based on the performance test data of the aluminum cap film PE inner film in Example 1 and Comparative Examples 1-8, it was found that adding LDPE, LLDPE, MLLDPE, HDPE, nano boron nitride, nano alumina, ethylene-vinyl acetate copolymer, and maleic anhydride grafted polyethylene to the PE inner film raw materials can improve the thermal conductivity, heat sealing strength and high temperature resistance of the PE inner film to varying degrees.

[0056] 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 type of aluminum-coated PE inner film, characterized in that, It comprises the following raw materials in parts by weight: 20-30 parts LDPE, 40-70 parts LLDPE, 10-30 parts MLLDPE, 10-30 parts HDPE, 2-5 parts nano boron nitride, 1-3 parts nano alumina, 5-10 parts ethylene-vinyl acetate copolymer, 2-5 parts maleic anhydride grafted polyethylene, 0.3-0.5 parts antioxidant, and 0.5-1 parts calcium stearate.

2. The aluminum cap film PE inner film according to claim 1, characterized in that, The aluminum cap film PE inner film comprises the following raw materials in parts by weight: LDPE 24-28 parts, LLDPE 45-65 parts, MLLDPE 15-25 parts, HDPE 15-25 parts, nano boron nitride 3-4 parts, nano alumina 1.5-2.5 parts, ethylene-vinyl acetate copolymer 7-9 parts, maleic anhydride grafted polyethylene 3-4 parts, antioxidant 0.35-0.45 parts, and calcium stearate 0.7-0.9 parts.

3. The aluminum cap film PE inner film according to claim 1, characterized in that, The weight ratio of the nano-alumina to the nano-boron nitride is 1:(2-4).

4. The aluminum cap film PE inner film according to claim 1, characterized in that, The weight ratio of the maleic anhydride-grafted polyethylene to the ethylene-vinyl acetate copolymer is 1:(2-4).

5. The aluminum cap film PE inner film according to claim 1, characterized in that, The nano-boron nitride and nano-alumina are obtained through modification treatment, specifically: S1. Vacuum dry the nano-alumina at 100-120℃ for 2-4 hours, and set aside for later use; S2. Place the nano boron nitride in a muffle furnace and heat it to 400-500℃ at a rate of 5℃ / min in an air atmosphere. Calcinate at a constant temperature for 2-3 hours. After naturally cooling to 25±2℃, add the oxidized nano boron nitride to deionized water and stir for 1 hour. Filter, dry, and set aside. S3. Mix the dried nano-alumina from step S1 with the pre-treated nano-boron nitride and MAH-g-PP wax, add an antioxidant, mix at 80-100℃ and 1500-2000 r / min for 5-10 min, extrude using a twin-screw extruder, control the screw temperature, speed at 200-300 r / min, residence time at 3-5 min, water cooling, pelletizing, vacuum drying, and pulverizing to obtain the modified nano-boron nitride and nano-alumina.

6. The aluminum cap film PE inner film according to claim 5, characterized in that, The MAH-g-PP wax comprises 20-40% of the total amount of nano-alumina and nano-boron nitride.

7. The aluminum cap film PE inner film according to claim 5, characterized in that, The MAH-g-PP wax was pulverized to 100 mesh.

8. A method for preparing the aluminum cap film PE inner film according to any one of claims 1-7, characterized in that, The process includes the following steps: LDPE, LLDPE, MLLDPE, and HDPE are dried at 80℃ for 2 hours and set aside; then, ethylene-vinyl acetate copolymer and maleic anhydride-grafted polyethylene are vacuum dried at 90℃ for 4 hours and set aside; the dried LDPE, LLDPE, MLLDPE, HDPE, ethylene-vinyl acetate copolymer, and maleic anhydride-grafted polyethylene are mixed at 80℃ and 2000 r / min for 15 minutes, melt-blended, extruded at 160-190℃, cooled and dried, pelletized, melt-plasticized, cast and cooled, drawn and wound, and cured at 40℃ for 24 hours to obtain the aluminum-capped PE inner film.

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