Aluminum-plastic composite film and preparation method thereof

Abstract

The invention discloses an aluminum-plastic composite film and a preparation method thereof, and relates to the technical field of packaging materials. The aluminum-plastic composite film comprises an outer layer, a barrier layer and an inner layer which are sequentially stacked, the outer layer comprises a paper base layer and a first material layer which are stacked in sequence, the blocking layer comprises an aluminum foil layer and a second material layer, and the inner layer comprises a third material layer; wherein the first material layer is made of at least one of PET (Polyethylene Terephthalate) and nylon, the second material layer is made of at least one of PVDC (Polyvinyl Dichloride) and EVOH (Ethylene Vinyl Alcohol), and the third material layer is made of at least one of PE (Polyethylene) and PP (Polypropylene). The aluminum-plastic composite film prepared in the invention is specially used for packaging medical apparatuses and instruments, realizes optimal balance of performance and cost, has good water and gas resistance, high temperature resistance and high mechanical strength, and is lower in processing cost and processing difficulty compared with similar products.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, and in particular to an aluminum-plastic composite film and its preparation method. Background Technology

[0002] As an indispensable and crucial component of medical devices, the sterile barrier system's core material is a sterile barrier polymer, which is directly and closely related to maintaining the sterility of the medical device and its overall performance during actual use. In practical applications, packaging materials for medical devices need to possess excellent comprehensive properties across multiple dimensions, including excellent air permeability, heat resistance, chemical corrosion resistance, and mechanical strength, to adapt to diverse sterilization methods and packaging design specifications. However, in related technologies, packaging materials for medical devices suffer from problems such as poor extensibility, easy tearing, and easy breakage during folding, or insufficient water-blocking, gas-blocking, and light-blocking properties, coupled with high processing costs. Summary of the Invention

[0003] The main objective of this invention is to develop an aluminum-plastic composite film specifically designed for medical device packaging, which has excellent water and gas barrier properties, high temperature resistance, and high mechanical strength. At the same time, a low-cost and easy-to-process preparation method has been designed for this product.

[0004] To achieve the above objectives, the present invention proposes an aluminum-plastic composite film, comprising an outer layer, a barrier layer, and an inner layer stacked sequentially; the outer layer comprises a paper base layer and a first material layer stacked sequentially, the barrier layer comprises an aluminum foil layer and a second material layer, and the inner layer comprises a third material layer; the first material layer is bonded to the aluminum foil; wherein the material of the first material layer comprises at least one of PET and nylon, the material of the second material layer comprises at least one of PVDC and EVOH, and the material of the third material layer comprises at least one of PE and PP.

[0005] In one embodiment, the outer layer has a thickness of 12 μm to 50 μm; the barrier layer has a thickness of 5 μm to 15 μm; and the inner layer has a thickness of 20 μm to 100 μm.

[0006] In one embodiment, the outer layer has a PET layer with a thickness of 12 μm to 25 μm, a nylon layer with a thickness of 15 μm to 50 μm, and a paper base layer with a thickness of 40 μm to 50 μm.

[0007] In one embodiment, the thickness of the second material layer in the barrier layer is 5 μm to 10 μm, and the thickness of the aluminum foil layer is 6 μm to 9 μm.

[0008] In one embodiment, the aluminum-plastic composite film is further provided with a nano barrier coating; the nano barrier coating is disposed on one side of the first material layer, and the thickness of the nano barrier coating is 50nm to 100nm; or, the nano barrier coating is disposed on the side of the second material layer opposite to the aluminum foil, and the thickness of the nano barrier coating is 10nm to 50nm; or, the nano barrier coating is disposed on one side of the aluminum foil, and the thickness of the nano barrier coating is 10nm to 100nm.

[0009] In one embodiment, the nano-barrier coating is selected from either nano-silica or nano-alumina; and / or, the coating amount of the nano-barrier coating is 0.1 g / m³. 2 ~0.5g / m 2 .

[0010] In one embodiment, the aluminum-plastic composite film further includes an interface modifier, which acts on the interface between the nano barrier coating and the first material layer.

[0011] In one embodiment, the aluminum-plastic composite film further includes an interface modifier, which acts on the interface between the second material layer and the third material layer.

[0012] In one embodiment, the aluminum-plastic composite film further includes an interface modifier, which acts on the interface between the aluminum foil and the first material layer.

[0013] In one embodiment, the aluminum-plastic composite film further includes 0.1 wt% to 5 wt% of an interface modifier, wherein the interface modifier is selected from at least one of maleic anhydride graft polymer, silane coupling agent, titanate coupling agent, and epoxy acrylate.

[0014] In one embodiment, the third material layer is made of low-density polyethylene; or, the third material layer is made of 30wt% to 70wt% low-density polyethylene and 30wt% to 70wt% metallocene polyethylene.

[0015] In one embodiment, the third material layer further includes 1 wt% to 3 wt% of a long-chain branching agent and / or 1 wt% to 3 wt% of a nanofiller, wherein the long-chain branching agent is selected from at least one of maleic anhydride grafted polymers and acrylate branching agents, and the nanofiller is selected from at least one of nano-calcium carbonate, montmorillonite, nano-silica, talc, graphene, and carbon nanofibers.

[0016] The present invention also proposes a method for preparing the aluminum-plastic composite film, comprising the following steps:

[0017] S10. The material used to prepare the first material layer is melted, extruded, biaxially stretched, coated on one surface of the paper base layer, and heat-set to obtain the outer layer.

[0018] S20. The material used to prepare the second material layer is co-extruded in five layers, cast, biaxially stretched, and heat-set to form the second material layer. Then, the second material layer is bonded to the aluminum foil with an adhesive and cured to obtain a barrier layer.

[0019] S30. The material used to prepare the third material layer is melted, extruded, biaxially stretched, and heat-set to obtain the inner layer.

[0020] S40. The inner layer and the second material layer of the barrier layer are hot-pressed together until the inner layer and the barrier layer are completely bonded. The aluminum foil of the barrier layer and the second material layer of the outer layer are then bonded together with an adhesive and cured to obtain an aluminum-plastic composite film.

[0021] In one embodiment, in step S20, the second material layer and the aluminum foil layer need to be surface treated before being laminated; and / or, in step S40, the second material layer of the barrier layer and the inner layer need to be surface treated before being laminated; and / or, in step S40, the aluminum foil of the barrier layer and the inner layer need to be surface treated before being laminated.

[0022] The surface treatment includes plasma treatment and / or corona treatment;

[0023] The parameters of the plasma treatment include: the plasma gas is selected from any one of Ar / O2 mixture, O2, and N2; the treatment power is 50W to 300W; the treatment time is 0.5min to 5min; and the vacuum degree is 10Pa to 100Pa.

[0024] The parameters for the corona treatment include: electrode spacing of 1mm to 3mm, treatment voltage of 10kV to 20kV, treatment speed of 5m / min to 20m / min, and ambient humidity of less than 60%.

[0025] The aluminum-plastic composite membrane designed in this invention further reduces the permeation of oxygen and water vapor through the synergistic effect of high-barrier polymers and aluminum foil. By coating the aluminum foil or polymer surface with an ultra-thin, high-strength nano-coating, the mechanical and protective properties of the composite membrane are further improved while maintaining its air permeability. The addition of nanofillers, long-chain branching agents, and the use of high-performance metallocene polyethylene as the inner layer substrate further enhances the overall temperature resistance and uniform stability of the aluminum-plastic composite membrane. The use of interface modifiers and surface treatment further improves the interfacial bonding between different material layers, thereby reducing micro-defects within the barrier layer and minimizing the formation of permeation channels. In summary, the aluminum-plastic composite membrane prepared in this invention is specifically designed for medical device packaging and achieves an optimized balance between performance and cost. It possesses excellent water and gas barrier properties, high-temperature resistance, and high mechanical strength, while its processing cost and difficulty are lower than similar products. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0028] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0029] The technical problem solved by this application is that composite packaging films are mostly composed of a protective layer, an aluminum foil layer, and a barrier layer. In the past, the barrier layer was made of polyvinylidene chloride, which has unsatisfactory transparency, gloss, mechanical strength, elasticity, abrasion resistance, cold resistance, and surface strength. Furthermore, the aluminum foil layer is the only metal foil among composite packaging film packaging materials, and it has been used in packaging materials for a long time. Its water-blocking, gas-blocking, and light-blocking properties are unmatched by other metal packaging materials. However, aluminum foil generally has poor ductility, very low thickness, is easily torn, easily breaks when folded, has a relatively high weight per unit area, and is prone to producing pinholes and other inherent performance defects, resulting in unsatisfactory protection. At the same time, composite packaging films also suffer from low processing efficiency.

[0030] In related technologies, packaging materials used for medical devices have problems such as poor extensibility, easy tearing, and easy breakage when folded, or insufficient barrier properties such as water resistance, gas resistance, and light blocking, as well as high processing costs.

[0031] To address the aforementioned technical challenges, a new aluminum-plastic composite film has been developed specifically for medical device packaging, exhibiting excellent water and gas barrier properties and high mechanical strength.

[0032] This invention proposes an aluminum-plastic composite film, comprising an outer layer, a barrier layer, and an inner layer stacked sequentially; the outer layer comprises a paper base layer and a first material layer stacked sequentially, the barrier layer comprises an aluminum foil layer and a second material layer, and the inner layer comprises a third material layer; the first material layer is bonded to the aluminum foil; wherein the material of the first material layer comprises at least one of PET and nylon, the material of the second material layer comprises at least one of PVDC and EVOH, and the material of the third material layer comprises at least one of PE and PP.

[0033] It should be noted that the outer layer is composed of a paper base layer and a first material layer. The interwoven fiber structure of the paper base layer provides tear resistance, while the first material layer is a polyester layer and / or polyamide film prepared by a biaxial stretching process, whose molecular chain orientation enhances puncture resistance. The composite design of the paper base layer and polyester layer maintains the rigidity of the outer layer while improving the material's air permeability through the porous structure of the paper base. The barrier layer utilizes a high-barrier material containing polar groups, stably bonded to the aluminum foil, significantly increasing the effective barrier area. During hot pressing, the polyolefin material layer in the inner layer undergoes molecular chain entanglement, forming an interpenetrating network structure with the polar polymer layer of the barrier layer. On one hand, its creep characteristics absorb deformation energy, improving the film's bending resistance; on the other hand, the polyolefin material, through modification, exhibits high temperature resistance, allowing it to withstand multiple high-temperature and high-pressure sterilization cycles.

[0034] It should also be noted that this application effectively solves the problems of barrier failure and mechanical damage in medical device packaging materials. The modulus gradient distribution of the three-layer structure ensures that the composite film maintains its structural integrity after repeated bending, and the synergistic effect of the polar polymer layer and aluminum foil reduces water vapor permeability to an extremely low level. The inner layer material has high thermal bonding strength, thereby ensuring the sealing reliability of the sterilization packaging. This composite film can withstand multiple high-temperature and high-pressure sterilization cycles without delamination while maintaining processing economy.

[0035] In one embodiment, the outer layer has a thickness of 12 μm to 50 μm; the barrier layer has a thickness of 5 μm to 15 μm; and the inner layer has a thickness of 20 μm to 100 μm.

[0036] In a preferred embodiment, in the outer layer, the thickness of the PET layer is 12μm to 25μm, the thickness of the nylon layer is 15μm to 50μm, the thickness of the paper base layer is 40μm to 50μm, the thickness of the aluminum foil layer is 5μm to 10μm, and the thickness of the aluminum foil layer is 6μm to 9μm.

[0037] It should be noted that for the aluminum-plastic composite film of this invention, an outer layer thickness exceeding 50 μm leads to a significant increase in material brittleness, an inner layer thickness below 20 μm is prone to heat-sealing failure, and a barrier layer thickness below 5 μm easily results in substandard barrier performance. Furthermore, an excessively thin paper base layer easily leads to interlayer delamination or insufficient mechanical support; an excessively thick layer easily leads to brittle fracture. An excessively thick aluminum foil layer easily leads to interlayer delamination or hot-pressing failure. Through the above technical solutions, this application solves the problems of insufficient ductility, folding breakage, and substandard barrier performance in aluminum-plastic composite films caused by unreasonable layer thicknesses, achieving synergistic optimization of material mechanical properties, barrier performance, and processing efficiency.

[0038] In one embodiment, the aluminum-plastic composite film is further provided with a nano barrier coating; the nano barrier coating is disposed on one side of the first material layer, and the thickness of the nano barrier coating is 50nm to 100nm; or, the nano barrier coating is disposed on the side of the second material layer opposite to the aluminum foil, and the thickness of the nano barrier coating is 10nm to 50nm; or, the nano barrier coating is disposed on one side of the aluminum foil, and the thickness of the nano barrier coating is 10nm to 100nm.

[0039] It should be noted that this invention forms a dense oxide coating on the surface of aluminum foil or polymer using magnetron sputtering. This coating fills the microscopic pores on the substrate surface, forming a continuous barrier and thus improving barrier performance. The nano-barrier coating can compensate for gas barrier defects in the first material layer itself; or enhance the barrier performance of the aluminum foil layer; or serve as an additional barrier layer to improve overall barrier integrity. When the coating is located on the first material layer, it can compensate for gas permeation defects in PET or nylon materials; when located on the back of the second material layer, the thin coating assists in barrier function while avoiding interfacial interference with the inner layer material; when directly coated on the aluminum foil, it repairs surface defects while avoiding increased processing costs due to excessive thickness. The three coating positions can be selected and combined to achieve a balance between barrier performance and cost.

[0040] In one embodiment, the nano-barrier coating is selected from either nano-silica or nano-alumina; and / or, the coating amount of the nano-barrier coating is 0.1 g / m³. 2 ~0.5g / m 2 .

[0041] It should be noted that, under the premise of the process parameters corresponding to existing equipment, the present invention selects specific nano-oxide particles as the coating material to construct a chemically stable nano-barrier layer, which can effectively block the penetration path of water molecules and oxygen molecules, while avoiding the material embrittlement problem caused by excessive coating.

[0042] In one specific embodiment, the aluminum-plastic composite film further includes an interface modifier, which acts on the interface between the nano barrier coating and the first material layer.

[0043] In one specific embodiment, the aluminum-plastic composite film further includes an interface modifier, which acts on the interface between the second material layer and the third material layer.

[0044] In one specific embodiment, the aluminum-plastic composite film further includes an interface modifier, which acts on the interface between the aluminum foil and the first material layer.

[0045] It should be noted that the interface between the nano-barrier coating and the first material layer refers to the contact surface between the inorganic nano-coating and the organic polymer layer. This interface is prone to stress concentration due to the difference in the thermal expansion coefficients of the materials. The interface between the second and third material layers refers to the contact surface between the barrier polymer layer and the heat-sealing polymer layer. This interface is prone to weak adhesion due to the difference in polarity. The interface between the aluminum foil and the first material layer refers to the contact surface between the metal layer and the plastic layer. This interface is prone to insufficient adhesion due to the difference in surface energy. Through the above technical solutions, this application effectively suppresses interfacial delamination between aluminum-plastic composite film layers caused by material differences, avoids the reduction in barrier performance due to delamination, and improves the structural integrity of the composite film under mechanical stresses such as folding and stretching, thus extending the material's lifespan in complex usage environments.

[0046] In one embodiment, the aluminum-plastic composite film further includes 0.1 wt% to 5 wt% of an interface modifier, wherein the interface modifier is selected from at least one of maleic anhydride graft polymer, silane coupling agent, titanate coupling agent, and epoxy acrylate.

[0047] In one specific embodiment, the anhydride groups in the maleic anhydride-grafted polymer react chemically with the alumina layer on the aluminum foil surface to form a stable chemically bonded layer. The silane coupling agent, after hydrolysis, generates silanol groups, which form hydrogen bonds with the hydroxyl groups on the aluminum foil surface, while the organic groups at the other end entangle with the polymer molecular chains. The titanate coupling agent coordinates with inorganic substances at the interface through monoalkoxy groups and is compatible with organic substances through long-chain alkyl groups, achieving molecular bridging of the inorganic-organic interface. During hot pressing, the epoxy groups of the epoxy acrylate undergo ring-opening reactions with the terminal amino groups of materials such as nylon and PET, forming a three-dimensional cross-linked network. The synergistic effect of the four modifiers covers various interface types, including metal-polymer, polar-nonpolar, and crystalline-amorphous interfaces, enhancing interfacial bonding strength through multiple mechanisms such as chemical bonds, hydrogen bonds, and molecular chain entanglement.

[0048] In one embodiment, the third material layer is made of low-density polyethylene; or, the third material layer is made of 30wt% to 70wt% low-density polyethylene and 30wt% to 70wt% metallocene polyethylene.

[0049] It should be noted that the narrow molecular weight distribution of metallocene polyethylene can improve the material's mechanical strength and heat-sealing performance; long-chain branching agents are additives that can introduce branched structures into the polymer backbone, specifically using maleic anhydride-grafted polypropylene or acrylate copolymers, which enhance molecular chain entanglement and improve ductility. Through the above technical solutions, this application forms a composite structure with both flexibility and strength in the inner layer of medical device packaging materials, and also exhibits good temperature resistance, solving the tearing problem caused by insufficient ductility and reducing the risk of breakage during folding.

[0050] The present invention also proposes a method for preparing the aluminum-plastic composite film, comprising the following steps:

[0051] S10. The material used to prepare the first material layer is melted, extruded, biaxially stretched, coated on one surface of the paper base layer, and heat-set to obtain the outer layer.

[0052] S20. The material used to prepare the second material layer is co-extruded in five layers, cast, biaxially stretched, and heat-set to form the second material layer. Then, the second material layer is bonded to the aluminum foil with an adhesive and cured to obtain a barrier layer.

[0053] S30. The material used to prepare the third material layer is melted, extruded, biaxially stretched, and heat-set to obtain the inner layer.

[0054] S40. The inner layer and the second material layer of the barrier layer are hot-pressed together until the inner layer and the barrier layer are completely bonded. The aluminum foil of the barrier layer and the second material layer of the outer layer are then bonded together with an adhesive and cured to obtain an aluminum-plastic composite film.

[0055] In a specific embodiment, in step S10, the material used to prepare the first material layer is melted, extruded, and stretched longitudinally by 3 to 5 times at 100°C to 150°C, and then stretched transversely by 3 to 4 times at 160°C to 180°C. The material is then coated on one surface of the paper base layer and heat-set to obtain the outer layer.

[0056] In a specific embodiment, in step S20, the material used to prepare the second material layer is subjected to five-layer co-extrusion and casting. The extrusion temperature of EVOH is controlled at 190℃~230℃, the extrusion temperature of PVDC is controlled at 160℃~180℃, the die temperature is 200℃~220℃, and the cooling roller temperature is 20℃~40℃. A polyurethane adhesive, epoxy resin adhesive, or acrylate adhesive is used at a coating amount of 2 g / m². 2 ~4g / m 2 The coating, lamination, and curing process was carried out for 48 hours to complete the preparation.

[0057] In one embodiment, in step S20, the second material layer and the aluminum foil layer need to be surface treated before being laminated; and / or, in step S40, the second material layer of the barrier layer and the inner layer need to be surface treated before being laminated; and / or, in step S40, the aluminum foil of the barrier layer and the inner layer need to be surface treated before being laminated.

[0058] In one specific embodiment, the surface treatment includes plasma treatment and / or corona treatment; the parameters of the plasma treatment include: the plasma gas is selected from any one of Ar / O2 mixture, O2, and N2; the treatment power is 50W to 300W; the treatment time is 0.5min to 5min; and the vacuum degree is 10Pa to 100Pa; the parameters of the corona treatment include: the electrode spacing is set to 1mm to 3mm; the treatment voltage is set to 10kV to 20kV; the treatment speed is set to 5m / min to 20m / min; and the ambient humidity is less than 60%.

[0059] Through the above technical solution, this application solves the problem of reduced barrier performance caused by insufficient interlayer bonding of aluminum-plastic composite films, while avoiding material damage caused by improper parameters in traditional processing methods. The combination of parameters for plasma treatment and corona treatment enhances surface activity while maintaining the integrity of the barrier layer, and the control of environmental humidity and vacuum level further ensures the stability of the processing, making it suitable for high-speed continuous production lines.

[0060] The present invention will be further described below through specific embodiments:

[0061] Example 1

[0062] The aluminum-plastic composite film in Example 1 comprises an outer layer, a barrier layer, and an inner layer stacked sequentially. The outer layer comprises a paper base layer, a PET layer, and a nylon layer stacked sequentially, with the paper base layer having a thickness of approximately 40 μm, the PET layer approximately 25 μm, and the nylon layer approximately 15 μm. The barrier layer comprises an aluminum foil layer and an EVOH layer stacked sequentially, with the aluminum foil layer approximately 7 μm thick and the EVOH layer approximately 8 μm thick. The inner layer is a PE layer with a thickness of approximately 30 μm. Furthermore, the nylon layer is bonded to the aluminum foil layer, and the EVOH layer is bonded to the PE layer.

[0063] In the aluminum-plastic composite film of Example 1, the EVOH layer near the PE layer is also coated with a layer of nano-silicon oxide, approximately 60 nm thick, with a coating amount of approximately 0.2 g / m. 2 In the aluminum-plastic composite film of Example 1, the interfaces between the EVOH layer and the PE layer, as well as the interfaces between the aluminum foil layer and the nylon layer, are coated with a polyurethane adhesive containing 0.2 wt% of maleic anhydride-grafted polypropylene copolymer of the total mass of the aluminum-plastic composite film.

[0064] In the aluminum-plastic composite film of Example 1, the PE layer specifically includes low-density polyethylene and metallocene polyethylene in a mass ratio of 1:1, and also includes 1 wt% acrylate branching agent and 3 wt% nano-calcium carbonate (D50 about 50 nm) by mass of the PE layer.

[0065] The preparation process of the aluminum-plastic composite film in Example 1 includes the following steps:

[0066] S10. PET and nylon used to prepare the first material layer are melted and extruded respectively, and stretched longitudinally by 3 to 5 times at 100℃ to 150℃, and then stretched transversely by 3 to 4 times at 160℃ to 180℃. Then, the molten PET is coated on one surface of the paper base layer and heat-set. Then, the molten nylon is coated on the surface of the PET layer and heat-set to obtain the outer layer.

[0067] S20. The EVOH used to prepare the second material layer is co-extruded in five layers and cast. The extrusion temperature is controlled at 190℃~230℃, the die temperature is 200℃~220℃, and the cooling roller temperature is 20℃~40℃. The material is stretched longitudinally by 3~5 times at 100℃~150℃, and then stretched transversely by 3~4 times at 160℃~180℃. The material is then heat-set to form the second material layer. The second material layer is then laminated with aluminum foil using polyurethane adhesive, wherein the polyurethane adhesive contains 0.2wt% of silane coupling agent by the total mass of the aluminum-plastic composite film. The material is then cured for 48 hours to obtain the barrier layer.

[0068] S21. The surface of the second material layer of the barrier layer obtained in step S20 is subjected to low-pressure plasma treatment. The treatment parameters are: plasma gas is O2, treatment power is 100W, treatment time is 3min, and vacuum degree is 50Pa. Then, the surface of the second material layer after low-pressure plasma treatment is subjected to magnetron sputtering under the same vacuum degree to deposit a nano-silicon oxide layer with a thickness of about 50nm.

[0069] S30. Low-density polyethylene, metallocene polyethylene, acrylate branching agent and nano-calcium carbonate used to prepare the third material layer are mixed, melted and extruded. The extrusion temperature is controlled at 180℃~220℃. The material is stretched longitudinally by 3~5 times at 100℃~150℃, and then stretched transversely by 3~4 times at 160℃~180℃. The material is then heat-set to obtain the inner layer.

[0070] S40. The surface of the nano-silica layer of the barrier layer and the surface of the outer nylon layer are subjected to low-pressure plasma treatment. The treatment parameters are: plasma gas selected from O2, treatment power of 100W, treatment time of 5min, and vacuum degree of 60Pa. The surface of the aluminum foil layer of the barrier layer is subjected to corona treatment. The treatment parameters are: electrode spacing of 2mm, treatment voltage of 10kV, treatment speed of 5m / min, and ambient humidity of about 45%RH. Then, the inner layer and the nano-silica layer of the barrier layer are hot-pressed together using polyurethane adhesive. Then, the surface of the aluminum foil layer of the barrier layer is bonded to the surface of the first material layer of the outer layer using polyurethane adhesive. After curing, an aluminum-plastic composite film is obtained.

[0071] Example 2

[0072] Example 2 is based on Example 1, except that the second material layer (EVOH layer) of the barrier layer in the aluminum-plastic composite film of Example 2 is not coated with a nano-silicon oxide coating on the side of the barrier layer near the PE layer.

[0073] The aluminum-plastic composite film of Example 2 comprises an outer layer, a barrier layer, and an inner layer stacked sequentially. The outer layer comprises a paper base layer, a PET layer, and a nylon layer stacked sequentially, with the paper base layer having a thickness of approximately 40 μm, the PET layer approximately 25 μm, and the nylon layer approximately 15 μm. The barrier layer comprises an aluminum foil layer and an EVOH layer stacked sequentially, with the aluminum foil layer approximately 7 μm thick and the EVOH layer approximately 8 μm thick. The inner layer is a PE layer with a thickness of approximately 30 μm. Furthermore, the nylon layer is bonded to the aluminum foil layer, and the EVOH layer is bonded to the PE layer.

[0074] In the aluminum-plastic composite film of Example 2, the interfaces between the EVOH layer and the PE layer, as well as the interfaces between the aluminum foil layer and the nylon layer, are coated with a polyurethane adhesive containing 0.2 wt% of maleic anhydride-grafted polypropylene copolymer of the total mass of the aluminum-plastic composite film.

[0075] The preparation process of the aluminum-plastic composite film in Example 2 is the same as that in Example 1. The difference is that the preparation process in Example 2 does not include step S21, and in step S40, the second material layer of the barrier layer is directly bonded to the inner layer using the corresponding adhesive.

[0076] Example 3

[0077] Example 3 is based on Example 1, except that the inner PE layer of the aluminum-plastic composite film in Example 3 contains only pure low-density polyethylene and has a thickness of about 30 μm.

[0078] The aluminum-plastic composite film in Example 3 comprises an outer layer, a barrier layer, and an inner layer stacked sequentially. The outer layer comprises a paper base layer, a PET layer, and a nylon layer stacked sequentially, with the paper base layer having a thickness of approximately 40 μm, the PET layer approximately 25 μm, and the nylon layer approximately 15 μm. The barrier layer comprises an aluminum foil layer and an EVOH layer stacked sequentially, with the aluminum foil layer approximately 7 μm thick and the EVOH layer approximately 8 μm thick. The inner layer is a PE layer with a thickness of approximately 30 μm. Furthermore, the nylon layer is bonded to the aluminum foil layer, and the EVOH layer is bonded to the PE layer.

[0079] In the aluminum-plastic composite film of Example 3, the EVOH layer near the PE layer is also coated with a layer of nano-silicon oxide, approximately 60 nm thick, with a coating amount of approximately 0.2 g / m. 2 In Example 3, the interface between the EVOH layer and the PE layer, as well as the interface between the aluminum foil layer and the nylon layer, are coated with a polyurethane adhesive containing 0.2 wt% of maleic anhydride-grafted polypropylene copolymer of the total mass of the aluminum-plastic composite film.

[0080] The preparation process of the aluminum-plastic composite film in Example 3 is the same as that in Example 1.

[0081] Comparative Example 1

[0082] Comparative Example 1 is based on Example 1, except that: in the preparation process of the aluminum-plastic composite film in Comparative Example 1, the first material layer, the second material layer and the third material layer are not biaxially stretched, but are only normally cast into a film.

[0083] Comparative Example 2

[0084] Comparative Example 2 is based on Example 1, except that: the barrier layer of the aluminum-plastic composite film in Comparative Example 4 only includes an aluminum foil layer, that is, the aluminum-plastic composite film in Comparative Example 2 does not have a second material layer and a nano-silicon oxide layer deposited on the surface of the second material layer; wherein, the thickness of the aluminum foil layer is changed to 15 μm.

[0085] The aluminum-plastic composite film in Comparative Example 2 comprises an outer layer, a barrier layer, and an inner layer stacked sequentially. The outer layer consists of a paper base layer, a PET layer, and a nylon layer stacked sequentially. The paper base layer is approximately 40 μm thick, the PET layer is approximately 25 μm thick, and the nylon layer is approximately 15 μm thick. The barrier layer consists only of an aluminum foil layer, which is approximately 15 μm thick. The inner layer is a PE layer with a thickness of approximately 30 μm. Furthermore, the nylon layer is bonded to the aluminum foil layer, and the EVOH layer is bonded to the PE layer.

[0086] Performance testing

[0087] (1) The oxygen barrier properties of the aluminum-plastic composite films prepared in the examples and comparative examples were determined in accordance with the standard ASTM D3985-17, "Standard Test Method for Measuring the Oxygen Transmission Rate Through Plastic Films and Sheets by Coulometric Sensor".

[0088] (2) The water vapor barrier properties of the aluminum-plastic composite films prepared in the examples and comparative examples were determined in accordance with the standard ASTM F1249-13, "Standard Test Method for Determining the Permeability of Water Vapor to Plastic Films and Sheets Using Modulated Infrared Sensors".

[0089] (3) The tear strength of the aluminum-plastic composite films prepared in the examples and comparative examples was determined in accordance with the standard ASTM D 1004-13 "Standard Test Method for Tear Resistance of Plastic Films and Sheets";

[0090] (4) The puncture resistance of the aluminum-plastic composite films prepared in the examples and comparative examples was determined with reference to the standard GB / T37841-2019 "Test method for puncture resistance of plastic films and sheets".

[0091] The measurement results are shown in Table 1.

[0092] Table 1

[0093]

[0094] Analysis of the data in Table 1 shows that, by comparing the performance data in Examples 1, 2, and 3, the synergistic effect of the nano-coating and the second material layer significantly improves the oxygen barrier capacity of the aluminum-plastic composite film, while also further enhancing its puncture resistance. Secondly, the incorporation of metallocene polyethylene and nanofillers into the third material layer significantly improves the mechanical strength, stiffness, and barrier properties of the aluminum-plastic composite film. Comparing the examples with Comparative Example 1 reveals that the biaxial stretching process is beneficial for adjusting the molecular orientation of the polymers in the first, second, and third material layers; otherwise, even if the aluminum-plastic composite film of this application adopts a multilayer structure, is coated, or doped with fillers, its mechanical strength and puncture resistance remain at a low level. Comparing the examples with Comparative Example 2 shows that the synergistic arrangement of the aluminum foil layer and the second material layer in the barrier layer enables the aluminum-plastic composite film to maintain strong oxygen and water barrier properties even in high humidity environments; otherwise, these properties would be significantly reduced.

[0095] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An aluminum-plastic composite film, characterized in that, The aluminum-plastic composite film comprises an outer layer, a barrier layer, and an inner layer stacked sequentially. The outer layer includes a paper base layer and a first material layer stacked sequentially, the barrier layer includes an aluminum foil layer and a second material layer, and the inner layer includes a third material layer; the first material layer is attached to the aluminum foil. The first material layer is made of at least one of PET and nylon, the second material layer is made of at least one of PVDC and EVOH, and the third material layer is made of at least one of PE and PP.

2. The aluminum-plastic composite film as described in claim 1, characterized in that, The outer layer has a thickness of 12μm to 50μm; the barrier layer has a thickness of 5μm to 15μm; and the inner layer has a thickness of 20μm to 100μm.

3. The aluminum-plastic composite film as described in claim 2, characterized in that, In the outer layer, the thickness of the PET layer is 12μm to 25μm, the thickness of the nylon layer is 15μm to 50μm, and the thickness of the paper base layer is 40μm to 50μm; And / or, in the barrier layer, the thickness of the second material layer is 5μm to 10μm, and the thickness of the aluminum foil layer is 6μm to 9μm.

4. The aluminum-plastic composite film as described in claim 1, characterized in that, The aluminum-plastic composite film is also provided with a nano barrier coating. The nano barrier coating is disposed on one side of the first material layer, and the thickness of the nano barrier coating is 50nm to 100nm; or, the nano barrier coating is disposed on the side of the second material layer opposite to the aluminum foil, and the thickness of the nano barrier coating is 10nm to 50nm; or, the nano barrier coating is disposed on one side of the aluminum foil, and the thickness of the nano barrier coating is 10nm to 100nm.

5. The aluminum-plastic composite film as described in claim 4, characterized in that, The nano barrier coating is selected from either nano silicon dioxide or nano aluminum oxide. And / or, the coating amount of the nano-barrier coating is 0.1 g / m 2 ~0.5g / m 2 .

6. The aluminum-plastic composite film as described in claim 4, characterized in that, The aluminum-plastic composite film also includes an interface modifier, which acts on the interface between the nano barrier coating and the first material layer. And / or, the aluminum-plastic composite film further includes an interface modifier, which acts on the interface between the second material layer and the third material layer; And / or, the aluminum-plastic composite film further includes an interface modifier, which acts on the interface between the aluminum foil and the first material layer.

7. The aluminum-plastic composite film as described in claim 6, characterized in that, The aluminum-plastic composite film also includes 0.1 wt% to 5 wt% of an interface modifier, which is selected from at least one of maleic anhydride graft polymer, silane coupling agent, titanate coupling agent, and epoxy acrylate.

8. The aluminum-plastic composite film as described in claim 1, characterized in that, The third material layer is made of low-density polyethylene; Alternatively, the material of the third material layer may include 30wt% to 70wt% of low-density polyethylene and 30wt% to 70wt% of metallocene polyethylene; And / or, the third material layer further includes 1 wt to 3 wt% of a long-chain branching agent and / or 1 wt to 3 wt% of a nanofiller, wherein the long-chain branching agent is selected from at least one of maleic anhydride grafted polymers and acrylate branching agents, and the nanofiller is selected from at least one of nano-calcium carbonate, montmorillonite, nano-silica, talc, graphene, and nano-carbon fiber.

9. A method for preparing an aluminum-plastic composite film as described in any one of claims 1 to 8, characterized in that, The method for preparing the aluminum-plastic composite film includes the following steps: S10. The material used to prepare the first material layer is melted, extruded, biaxially stretched, coated on one surface of the paper base layer, and heat-set to obtain the outer layer. S20. The material used to prepare the second material layer is co-extruded in five layers, cast, biaxially stretched, and heat-set to form the second material layer. Then, the second material layer is bonded to the aluminum foil with an adhesive and cured to obtain a barrier layer. S30. The material used to prepare the third material layer is melted, extruded, biaxially stretched, and heat-set to obtain the inner layer. S40. The inner layer and the second material layer of the barrier layer are hot-pressed together until the inner layer and the barrier layer are completely bonded. The aluminum foil of the barrier layer and the second material layer of the outer layer are then bonded together with an adhesive and cured to obtain an aluminum-plastic composite film.

10. The method for preparing the aluminum-plastic composite film as described in claim 9, characterized in that, In step S20, the second material layer and the aluminum foil layer need to be surface treated before being laminated; and / or, in step S40, the second material layer of the barrier layer and the inner layer need to be surface treated before being laminated. And / or, in step S40, the aluminum foil of the barrier layer and the inner layer need to undergo surface treatment before being laminated; The surface treatment includes plasma treatment and / or corona treatment; The parameters of the plasma treatment include: the plasma gas is selected from any one of Ar / O2 mixture, O2, and N2; the treatment power is 50W to 300W; the treatment time is 0.5min to 5min; and the vacuum degree is 10Pa to 100Pa. The parameters for the corona treatment include: electrode spacing of 1mm to 3mm, treatment voltage of 10kV to 20kV, treatment speed of 5m / min to 20m / min, and ambient humidity of less than 60%.

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