Hot melt adhesive film for bonding PET and metal, preparation method of hot melt adhesive film and composite board

Abstract

The invention relates to the technical field of hot melt adhesive films, in particular to a hot melt adhesive film for bonding PET and metal, a preparation method of the hot melt adhesive film and a composite board. The hot melt adhesive film comprises a first adhesive layer, a core layer and a second adhesive layer; the first adhesive layer comprises a maleic anhydride terpolymer and a maleic anhydride grafted polymer, and the maleic anhydride grafted polymer comprises at least one of a maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS; in the first adhesive layer, the total proportion of the maleic anhydride terpolymer and the maleic anhydride grafted polymer is greater than or equal to 80wt%; the second adhesive layer comprises maleic anhydride grafted polyethylene; the core layer comprises polyethylene; the mass ratio of the first adhesive layer to the core layer to the second adhesive layer is (2-4): (3-5): (2-4). The hot melt adhesive film disclosed by the invention can be used for bonding PET (Polyethylene Terephthalate) and a metal plate and has good water resistance, and the bonding performance still meets the requirements after the hot melt adhesive film is soaked in water for 48 hours.

Description

Technical Field

[0001] The present invention relates to the technical field of hot melt adhesive films, in particular to a hot melt adhesive film for bonding PET and metal, a preparation method thereof, and a composite board. Background Art

[0002] PET / metal composite panels are functional composite panels with metal plates as the base material and PET (polyethylene terephthalate) film composited on the surface. They combine the characteristics of PET and metal and have the advantages of being beautiful, corrosion-resistant, scratch-resistant, heat-insulating, and lightweight. They are widely used in building decoration materials, food packaging materials and other fields.

[0003] Currently, liquid adhesives are mostly used to bond the PET and metal sheets in PET / metal composite panels. Two-component polyurethane adhesives are the most widely used. However, polyurethane liquid adhesives lack water resistance, and their peel strength is significantly reduced after soaking in water, resulting in insufficient adhesion and shortening the service life. Furthermore, the small molecules in polyurethane liquid adhesives have a certain degree of permeability, which can easily damage the bonding interface and affect the bonding strength of the composite product. Furthermore, the production process of polyurethane liquid adhesives is relatively complex, and there are problems such as odor and flammability, which limit their large-scale application.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a hot melt adhesive film for bonding PET and metal, a preparation method thereof, and a composite board. The hot melt adhesive film of the present invention has excellent bonding performance to PET and metal, and can solve the problem of insufficient water resistance of liquid glue, while avoiding the problem of small molecules penetrating into the bonding interface.

[0006] To achieve the above-mentioned object of the present invention, the first aspect of the present invention provides a hot melt adhesive film for bonding PET and metal, comprising a first adhesive layer for bonding PET, a second adhesive layer for bonding metal, and a core layer disposed between the first adhesive layer and the second adhesive layer; The first adhesive layer comprises a maleic anhydride terpolymer and a maleic anhydride grafted polymer, wherein the maleic anhydride grafted polymer comprises at least one of a maleic anhydride grafted ethylene-acrylate copolymer and a maleic anhydride grafted SEBS; in the first adhesive layer, the maleic anhydride terpolymer and the maleic anhydride grafted polymer account for ≥80wt%; the second adhesive layer comprises maleic anhydride grafted polyethylene; and the core layer comprises polyethylene; The mass ratio of the first adhesive layer, the core layer and the second adhesive layer is (2-4): (3-5): (2-4).

[0007] In a specific embodiment of the present invention, the maleic anhydride terpolymer comprises an ethylene-acrylate-maleic anhydride copolymer. Further, in the maleic anhydride terpolymer, the maleic anhydride content is 0.3 wt% to 5 wt%, and the acrylate content is ≥10 wt%.

[0008] In a specific embodiment of the present invention, the maleic anhydride terpolymer has a melt index of 2 to 20 g / 10 min at 190° C. and 2.16 kg.

[0009] In a specific embodiment of the present invention, in the maleic anhydride grafted ethylene-acrylate copolymer, the content of maleic anhydride is 0.2 wt% to 0.6 wt%, and the content of acrylate is ≥15 wt%.

[0010] In a specific embodiment of the present invention, the maleic anhydride grafted ethylene-acrylate copolymer has a melt index of 2 to 20 g / 10 min at 190° C. and 2.16 kg.

[0011] In a specific embodiment of the present invention, the mass ratio of the maleic anhydride terpolymer to the maleic anhydride grafted polymer is (0.4-0.6):1.

[0012] In a specific embodiment of the present invention, in the maleic anhydride grafted polymer, the mass ratio of the maleic anhydride grafted ethylene-acrylate copolymer to the maleic anhydride grafted SEBS is (2-3):1.

[0013] In a specific embodiment of the present invention, the polyethylene in the core layer includes at least one of LLDPE and LDPE. Furthermore, in the core layer, the mass ratio of LLDPE to LDPE is (3-6):1.

[0014] In a specific embodiment of the present invention, the first adhesive layer further comprises at least one of ethylene-vinyl acetate copolymer and ethylene-acrylate copolymer. Furthermore, the VA content of the ethylene-vinyl acetate copolymer is 10 wt% to 35 wt%.

[0015] The second aspect of the present invention provides a method for preparing the hot melt adhesive film for bonding PET and metal according to the first aspect of the present invention, comprising the following steps: The first adhesive layer raw material, the core layer raw material and the second adhesive layer raw material are subjected to multi-layer co-extrusion casting or co-extrusion blown film.

[0016] The third aspect of the present invention provides a composite panel comprising a PET layer, a metal plate, and at least one of the hot melt adhesive films of the first aspect of the present invention arranged between the PET layer and the metal plate; the first adhesive layer of the hot melt adhesive film is adhered to the PET layer, and the second adhesive layer of the hot melt adhesive film is adhered to the metal plate.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a hot melt adhesive film with a multi-layer structure, which can achieve bonding to PET and metal plates, and uses polyethylene as an intermediate layer in the first adhesive layer and the second adhesive layer, organically combining the first adhesive layer and the second adhesive layer to ensure the stability of the composite structure; the hot melt adhesive film of the present invention has good water resistance, and the bonding performance still meets the requirements after being soaked in water for 48 hours; (2) The hot melt adhesive film of the present invention avoids the problem of small molecules in existing polyurethane liquid adhesives penetrating into the bonding interface, and the preparation method is simple to operate and environmentally friendly. DETAILED DESCRIPTION

[0018] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0019] In the description of the present invention, it should be noted that terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" to indicate positions or relationships are used solely to facilitate description and simplify the present invention. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific manner. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] A first aspect of the present invention provides a hot melt adhesive film for bonding PET and metal, comprising a first adhesive layer for bonding PET, a second adhesive layer for bonding metal, and a core layer disposed between the first adhesive layer and the second adhesive layer; The first adhesive layer comprises a maleic anhydride terpolymer and a maleic anhydride grafted polymer, wherein the maleic anhydride grafted polymer comprises at least one of a maleic anhydride grafted ethylene-acrylate copolymer and a maleic anhydride grafted SEBS; in the first adhesive layer, the maleic anhydride terpolymer and the maleic anhydride grafted polymer account for ≥80wt%; the second adhesive layer comprises maleic anhydride grafted polyethylene; and the core layer comprises polyethylene; The mass ratio of the first rubber layer, the core layer and the second rubber layer is (2~4) : (3~5) : (2~4).

[0021] The present invention adopts a hot-melt adhesive film with a multi-layer structure, which can achieve bonding to PET and metal plates, and uses polyethylene as an intermediate layer in the first adhesive layer and the second adhesive layer, organically combining the first adhesive layer and the second adhesive layer to ensure the stability of the composite structure; the hot-melt adhesive film of the present invention has good water resistance, and the bonding performance still meets the requirements after being soaked in water for 48 hours.

[0022] In the first adhesive layer of the present invention, the total proportion of the maleic anhydride terpolymer and the maleic anhydride grafted polymer can be 80wt%, 82wt%, 85wt%, 88wt%, 90wt%, 92wt%, 95wt%, 98wt%, 100wt%, or a range consisting of any two thereof. The present invention utilizes a composite of the maleic anhydride terpolymer and the maleic anhydride grafted polymer as the first adhesive layer, thereby improving wettability, adhesion, and water resistance to PET.

[0023] For example, in different embodiments, the mass ratio of the first adhesive layer to the core layer can be 2:3, 2:4, 2:5, 3:3, 3:4, 3:5, 4:3, 4:5 or a range consisting of any two thereof; the mass ratio of the core layer to the second adhesive layer can be 3:2, 4:2, 5:2, 3:3, 4:3, 5:3, 3:4, 5:4 or a range consisting of any two thereof. This helps to improve the matching of the first adhesive layer, the core layer and the second adhesive layer while ensuring the bonding performance to PET and metal, and further helps to improve the composite stability of the hot melt adhesive film.

[0024] In a specific embodiment of the present invention, the maleic anhydride terpolymer comprises an ethylene-acrylate-maleic anhydride copolymer. Furthermore, the maleic anhydride content in the maleic anhydride terpolymer is 0.3 wt% to 5 wt%, for example, 0.3 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, or any two thereof, and the acrylate content is ≥ 10 wt%, for example, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, or any two thereof. When the maleic anhydride and acrylate contents in the maleic anhydride terpolymer are within the above ranges, it is more advantageous to improve the bonding performance of the first adhesive layer to PET while ensuring the water resistance of the first adhesive layer.

[0025] In a specific embodiment of the present invention, the maleic anhydride terpolymer includes at least one of ethylene-acrylate-maleic anhydride copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer, and ethylene-butyl acrylate-maleic anhydride copolymer.

[0026] In a specific embodiment of the present invention, the maleic anhydride terpolymer has a melt index of 2 to 20 g / 10 min at 190° C. and 2.16 kg, for example, 2 g / 10 min, 5 g / 10 min, 8 g / 10 min, 10 g / 10 min, 12 g / 10 min, 15 g / 10 min, 18 g / 10 min, 20 g / 10 min, or any combination thereof. The maleic anhydride terpolymer employed in the present invention has good fluidity, which helps improve the wettability of the first adhesive layer to PET, thereby improving the bonding performance.

[0027] In a specific embodiment of the present invention, the maleic anhydride grafted ethylene-acrylate copolymer has a maleic anhydride content of 0.2 wt% to 0.6 wt%, for example, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, or any two thereof, and an acrylate content of ≥ 15 wt%, for example, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, or any two thereof. The introduction of the maleic anhydride grafted ethylene-acrylate copolymer into the first adhesive layer helps improve the compatibility between the first adhesive layer and the core layer.

[0028] In a specific embodiment of the present invention, the melt index of the maleic anhydride grafted ethylene-acrylate copolymer at 190°C and 2.16 kg is 2 to 20 g / 10 min, for example, it can be 2 g / 10 min, 5 g / 10 min, 8 g / 10 min, 10 g / 10 min, 12 g / 10 min, 15 g / 10 min, 18 g / 10 min, 20 g / 10 min or a range consisting of any two of them.

[0029] In a specific embodiment of the present invention, the melt index of the maleic anhydride-grafted SEBS at 230°C and 2.16 kg is 1 to 10 g / 10 min, for example, 1 g / 10 min, 3 g / 10 min, 5 g / 10 min, 8 g / 10 min, 10 g / 10 min, or a range consisting of any two thereof. The introduction of the maleic anhydride-grafted SEBS into the first adhesive layer further improves the compatibility of the components in the first adhesive layer and with the core layer, further balances the rigidity and toughness of the hot-melt adhesive film, and contributes to improving the overall performance of the composite board.

[0030] In a specific embodiment of the present invention, the mass ratio of the maleic anhydride terpolymer to the maleic anhydride grafted polymer is (0.4-0.6):1, for example, it can be 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1 or a range consisting of any two thereof, thereby helping to take into account the wettability, adhesion, water resistance of the first adhesive layer to PET and compatibility with the core layer.

[0031] In a specific embodiment of the present invention, in the maleic anhydride grafted polymer, the mass ratio of the maleic anhydride grafted ethylene-acrylate copolymer to the maleic anhydride grafted SEBS is (2-3):1, for example, it can be 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1 or a range consisting of any two thereof, thereby helping to further improve the bonding performance and toughness of the hot melt adhesive film.

[0032] In a specific embodiment of the present invention, the polyethylene in the core layer includes at least one of LLDPE and LDPE. Furthermore, the mass ratio of LLDPE to LDPE in the core layer is (3-6) : 1, for example, 3:1, 4:1, 5:1, 6:1, or any combination thereof. This helps improve the bonding performance and performance matching between the first and second adhesive layers.

[0033] In a specific embodiment of the present invention, in the core layer, the melt index of polyethylene at 190°C and 2.16 kg is 0.5 to 5 g / 10 min, for example, it can be 0.5 g / 10 min, 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min or a range consisting of any two of them.

[0034] In a specific embodiment of the present invention, the melt index of the maleic anhydride grafted polyethylene at 190°C and 2.16 kg is 1 to 15 g / 10 min, for example, it can be 1 g / 10 min, 3 g / 10 min, 5 g / 10 min, 8 g / 10 min, 10 g / 10 min, 12 g / 10 min, 15 g / 10 min or a range consisting of any two of them.

[0035] In a specific embodiment of the present invention, the first adhesive layer further comprises at least one of ethylene-vinyl acetate copolymer and ethylene-acrylate copolymer. Furthermore, the ethylene-vinyl acetate copolymer may have an EVA content of 10 wt% to 35 wt%, for example, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or any combination thereof. The introduction of EVA can appropriately improve the toughness of the hot-melt adhesive film, but excessive EVA may reduce the water resistance of the hot-melt adhesive film.

[0036] The second aspect of the present invention provides a method for preparing the hot melt adhesive film for bonding PET and metal according to the first aspect of the present invention, comprising the following steps: The first adhesive layer raw material, the core layer raw material and the second adhesive layer raw material are subjected to multi-layer co-extrusion casting or co-extrusion blown film.

[0037] In a specific embodiment of the present invention, in a multi-layer co-extrusion cast or co-extrusion blown film, the extrusion section temperature of the first adhesive layer and the core layer is 150-180°C, the extrusion section temperature of the second adhesive layer is 140-170°C; and the die head temperature is 160-200°C.

[0038] The third aspect of the present invention provides a composite board comprising a PET layer, a metal plate, and at least one of the hot melt adhesive films of the first aspect of the present invention arranged between the PET layer and the metal plate; the first adhesive layer of the hot melt adhesive film is adhered to the PET layer, and the second adhesive layer of the hot melt adhesive film is adhered to the metal plate.

[0039] Example 1 This embodiment provides a hot-melt adhesive film for bonding PET and metal. The film comprises a first adhesive layer for bonding PET, a second adhesive layer for bonding metal, and a core layer disposed between the first and second adhesive layers. The mass ratio of the first adhesive layer, the core layer, and the second adhesive layer is 3:4:3, and the total thickness of the hot-melt adhesive film is 40 μm.

[0040] The raw materials of the first adhesive layer include maleic anhydride terpolymer and maleic anhydride grafted polymer in a mass ratio of 3:7; the maleic anhydride grafted polymer includes maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS in a mass ratio of 2.5:1.

[0041] Among them, the maleic anhydride terpolymer is an ethylene-acrylate-maleic anhydride copolymer, with a maleic anhydride content of 0.3wt%, an acrylate content of 20wt%, and a melt index of 8g / 10min at 190℃ / 2.16kg; the maleic anhydride grafted ethylene-acrylate copolymer has a maleic anhydride content of 0.35wt%, an acrylate content of 30wt%, and a melt index of 5g / 10min at 190℃ / 2.16kg; the melt index of maleic anhydride grafted SEBS at 230℃ / 2.16kg is 8g / 10min.

[0042] The raw materials of the core layer include LLDPE 7042 and LDPE 2420H in a mass ratio of 4:1.

[0043] The raw materials for the second adhesive layer include VB550SD (Guangzhou Lushan New Materials Co., Ltd.).

[0044] The method for preparing the hot-melt adhesive film of this embodiment includes the following steps: weighing the raw material components of the first adhesive layer, the core layer, and the second adhesive layer in appropriate proportions, performing multi-layer co-extrusion casting, cooling, and winding to obtain the hot-melt adhesive film. The extrusion section temperature of the first adhesive layer and the core layer is 150-180°C, the extrusion section temperature of the second adhesive layer is 140-170°C, and the die head temperature is 160-200°C.

[0045] Example 2 This embodiment refers to the hot melt adhesive film and preparation method of Example 1, with the only difference being that the raw material composition of the first adhesive layer is different.

[0046] The raw materials of the first adhesive layer of this embodiment include maleic anhydride terpolymer and maleic anhydride grafted polymer in a mass ratio of 3:7; the maleic anhydride grafted polymer includes maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS in a mass ratio of 1:1.

[0047] Example 3 This embodiment refers to the hot melt adhesive film and preparation method of Example 1, with the only difference being that the raw material composition of the first adhesive layer is different.

[0048] The raw materials of the first adhesive layer of this embodiment include maleic anhydride terpolymer and maleic anhydride grafted polymer in a mass ratio of 3:7; the maleic anhydride grafted polymer includes maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS in a mass ratio of 4:1.

[0049] Example 4 This embodiment refers to the hot melt adhesive film and preparation method of Example 1, with the only difference being that the raw material composition of the first adhesive layer is different.

[0050] The raw materials of the first adhesive layer of this embodiment include a maleic anhydride terpolymer and a maleic anhydride grafted polymer in a mass ratio of 3:7; the maleic anhydride grafted polymer is a maleic anhydride grafted ethylene-acrylate copolymer.

[0051] Example 5 This embodiment refers to the hot melt adhesive film and preparation method of Example 1, with the only difference being that the raw material composition of the first adhesive layer is different.

[0052] The raw materials of the first adhesive layer of this embodiment include a maleic anhydride terpolymer and a maleic anhydride grafted polymer in a mass ratio of 3:7; the maleic anhydride grafted polymer is maleic anhydride grafted SEBS.

[0053] Example 6 This embodiment refers to the hot melt adhesive film and preparation method of Example 1, with the only difference being that the raw material composition of the first adhesive layer is different.

[0054] The raw materials of the first adhesive layer of this embodiment include maleic anhydride terpolymer and maleic anhydride grafted polymer in a mass ratio of 2:8; the maleic anhydride grafted polymer includes maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS in a mass ratio of 2.5:1.

[0055] Example 7 This embodiment refers to the hot melt adhesive film and preparation method of Example 1, with the only difference being that the raw material composition of the first adhesive layer is different.

[0056] The raw materials of the first adhesive layer of this embodiment include maleic anhydride terpolymer and maleic anhydride grafted polymer in a mass ratio of 4:6; the maleic anhydride grafted polymer includes maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS in a mass ratio of 2.5:1.

[0057] Example 8 This embodiment refers to the hot melt adhesive film and preparation method of Example 1, with the only difference being that the raw material composition of the first adhesive layer is different.

[0058] The raw materials for the first adhesive layer of this embodiment include a maleic anhydride terpolymer, a maleic anhydride grafted polymer, and an ethylene-vinyl acetate copolymer in a mass ratio of 2.4:5.6:2. The maleic anhydride grafted polymer includes a maleic anhydride-grafted ethylene-acrylate copolymer and a maleic anhydride-grafted SEBS in a mass ratio of 2.5:1. The ethylene-vinyl acetate copolymer has a VA content of 18 wt% and a melt index of 3 g / 10 min at 190°C / 2.16 kg.

[0059] Comparative Example 1 Comparative Example 1 refers to the hot melt adhesive film and preparation method thereof of Example 1, except that the raw material composition of the first adhesive layer is different.

[0060] The raw material of the first adhesive layer of Comparative Example 1 includes a maleic anhydride terpolymer (the maleic anhydride terpolymer is the same as that of Example 1).

[0061] Comparative Example 2 Comparative Example 2 refers to the hot melt adhesive film and preparation method thereof of Example 1, except that the raw material composition of the first adhesive layer is different.

[0062] The raw material of the first subbing layer in Comparative Example 2 includes a maleic anhydride grafted polymer (the maleic anhydride grafted polymer is the same as that in Example 1).

[0063] Comparative Example 3 Comparative Example 3 refers to the hot melt adhesive film and preparation method of Example 8, except that the raw material composition of the first adhesive layer is different.

[0064] The raw materials of the first adhesive layer of Comparative Example 3 include maleic anhydride terpolymer, maleic anhydride grafted polymer and ethylene-vinyl acetate copolymer in a mass ratio of 2.1:4.9:3.

[0065] Comparative Example 4 Comparative Example 4 refers to the hot melt adhesive film and preparation method thereof of Example 1, except that the raw material composition of the first adhesive layer is different.

[0066] The raw material of the first adhesive layer of Comparative Example 4 includes ethylene-vinyl acetate copolymer (ethylene-vinyl acetate copolymer, the same as Example 8).

[0067] Experimental example The hot melt adhesive films of different embodiments and comparative examples were made into test specimens, and peel strength tests were performed under different conditions. The test results are shown in Table 1.

[0068] Preparation of test specimens: PET (corona treated), hot melt adhesive film, and galvanized sheet are stacked in order (the first adhesive layer of the hot melt adhesive film is attached to the PET, and the second adhesive layer is attached to the galvanized sheet). Hot press on a flat vulcanizer at 170°C and 0.2 MPa for 15 seconds, then cool and test.

[0069] Test method: Test the peel strength of the test sample after cooling to room temperature for 30 minutes after hot pressing; After soaking the test sample in water at room temperature for 48 hours, test the peel strength and observe whether there is any glue remaining on the PET surface after peeling. The presence of residual glue indicates that the corresponding hot melt adhesive film has better bonding performance after soaking in water.

[0070] The above peel strength test refers to the 180° peel strength test method in GB / T 2792.

[0071] Table 1 Test results of different hot melt adhesive films

[0072] A composite PET hot-melt adhesive film (made by bonding corona-treated PET and a single-sided polymer film with a commercially available two-component polyurethane adhesive, with a 4μm adhesive layer and a 40μm single-sided polymer film made of PE and VB550SD in a 7:3 mass ratio) was hot-pressed onto a galvanized sheet on a flatbed vulcanizer at 170°C and 0.2 MPa for 15 seconds, followed by cooling. The single-sided polymer film was bonded to the galvanized sheet. The corresponding peel strength was tested using the aforementioned method and was less than 20N / 25mm, with no adhesive residue on the PET surface.

[0073] The test results above indicate that the present invention utilizes a multi-layer hot-melt adhesive film capable of bonding PET and metal plates, and utilizes polyethylene as an intermediate layer between the first and second adhesive layers to organically combine the first and second adhesive layers, thereby ensuring the stability of the composite structure. The hot-melt adhesive film of the present invention exhibits excellent water resistance, and its bonding performance still meets the requirements after being soaked in water for 48 hours.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Hot melt adhesive film for bonding PET and metal, characterized in that: It includes a first adhesive layer for bonding PET, a second adhesive layer for bonding metal, and a core layer arranged between the first adhesive layer and the second adhesive layer; The first adhesive layer comprises a maleic anhydride terpolymer and a maleic anhydride grafted polymer, wherein the maleic anhydride grafted polymer comprises at least one of a maleic anhydride grafted ethylene-acrylate copolymer and a maleic anhydride grafted SEBS; in the first adhesive layer, the total proportion of the maleic anhydride terpolymer and the maleic anhydride grafted polymer is ≥80wt%; the second adhesive layer comprises maleic anhydride grafted polyethylene; and the core layer comprises polyethylene; The mass ratio of the first adhesive layer, the core layer and the second adhesive layer is (2-4): (3-5): (2-4).

2. The hot melt adhesive film for bonding PET and metal according to claim 1, characterized in that: The maleic anhydride terpolymer comprises an ethylene-acrylate-maleic anhydride copolymer; the maleic anhydride terpolymer has at least one of the following characteristics: (1) In the maleic anhydride terpolymer, the content of maleic anhydride is 0.3wt% to 5wt%, and the content of acrylate is ≥10wt%; (2) The maleic anhydride terpolymer has a melt index of 2 to 20 g / 10 min at 190° C. and 2.16 kg.

3. The hot melt adhesive film for bonding PET and metal according to claim 1, characterized in that: The maleic anhydride grafted ethylene-acrylate copolymer has at least one of the following characteristics: (1) In the maleic anhydride grafted ethylene-acrylate copolymer, the content of maleic anhydride is 0.2wt% to 0.6wt%, and the content of acrylate is ≥15wt%; (2) The maleic anhydride grafted ethylene-acrylate copolymer has a melt index of 2 to 20 g / 10 min at 190° C. and 2.16 kg.

4. The hot melt adhesive film for bonding PET and metal according to claim 1, characterized in that: The mass ratio of the maleic anhydride terpolymer to the maleic anhydride grafted polymer is (0.4-0.6):

1.

5. The hot melt adhesive film for bonding PET and metal according to claim 1, characterized in that: In the maleic anhydride grafted polymer, the mass ratio of the maleic anhydride grafted ethylene-acrylate copolymer to the maleic anhydride grafted SEBS is (2-3):

1.

6. The hot melt adhesive film for bonding PET and metal according to claim 1, characterized in that: In the core layer, the polyethylene includes at least one of LLDPE and LDPE.

7. The hot melt adhesive film for bonding PET and metal according to claim 6, characterized in that: In the core layer, the mass ratio of LLDPE to LDPE is (3-6):

1.

8. The hot melt adhesive film for bonding PET and metal according to claim 1, characterized in that: The first adhesive layer further comprises at least one of ethylene-vinyl acetate copolymer and ethylene-acrylate copolymer; In the ethylene-vinyl acetate copolymer, the VA content is 10wt% to 35wt%.

9. The method for preparing a hot melt adhesive film for bonding PET and metal according to any one of claims 1 to 8, characterized in that: The steps include: The first adhesive layer raw material, the core layer raw material and the second adhesive layer raw material are subjected to multi-layer co-extrusion casting or co-extrusion blown film.

10. A composite board, characterized in that: It comprises a PET layer, a metal plate and a hot-melt adhesive film arranged between the PET layer and the metal plate; the hot-melt adhesive film comprises the hot-melt adhesive film for bonding PET and metal as described in any one of claims 1 to 8; the first adhesive layer of the hot-melt adhesive film is adhered to the PET layer, and the second adhesive layer of the hot-melt adhesive film is adhered to the metal plate.

Images