Hot-melt adhesive film for bonding pet and metal and preparation method therefor, and composite panel

Abstract

The present application relates to the technical field of hot-melt adhesive films, and in particular to a hot-melt adhesive film for bonding PET and a metal and a preparation method therefor, and a composite panel. 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; the maleic anhydride-grafted polymer comprises at least one of a maleic anhydride-grafted ethylene-acrylic ester copolymer and maleic anhydride-grafted SEBS; and 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 80 wt%. The second adhesive layer comprises maleic anhydride-grafted polyethylene. 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). The hot-melt adhesive film of the present application can realize of the bonding of PET and a metal plate; and in addition, the hot-melt adhesive film exhibits good water resistance, and the bonding performance of the hot-melt adhesive film still meets the requirements after being immersed in water for 48 hours.

Description

Hot melt adhesive film for bonding PET and metal, its preparation method and composite board Technical Field

[0001] This application relates to the field of hot melt adhesive film technology, and in particular to a hot melt adhesive film for bonding PET and metal, a method for preparing the film, and a composite board thereof. Background Technology

[0002] PET / metal composite board is a type of functional composite board with metal sheet as the base material and PET (polyethylene terephthalate) film laminated on the surface. It combines the properties of PET and metal, and has advantages such as beauty, corrosion resistance, scratch resistance, heat insulation and lightweight. It is 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 boards, with two-component polyurethane adhesives being the most widely used. However, polyurethane liquid adhesives have insufficient water resistance; their peel strength decreases significantly after soaking in water, resulting in insufficient adhesion and affecting service life. Furthermore, the small molecules in polyurethane liquid adhesives have a certain degree of permeability, easily damaging the bonding interface and affecting the bond strength of the laminated product. In addition, the production process of polyurethane liquid adhesives is relatively complex, and they have issues such as odor and flammability, limiting their large-scale application.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0006] The purpose of this application is to provide a hot melt adhesive film for bonding PET and metal, a method for preparing the film, and a composite board thereof. The hot melt adhesive film of this application has excellent bonding performance to PET and metal, and can solve the problem of insufficient water resistance of liquid adhesives, while avoiding the problem of small molecules penetrating to the bonding interface.

[0007] To achieve the above objectives, the first aspect of this application 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;

[0008] 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 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 ≥80wt%; the second adhesive layer comprises maleic anhydride grafted polyethylene; the core layer comprises polyethylene.

[0009] The mass ratio of the first adhesive layer, the core layer and the second adhesive layer is (2-4):(3-5):(2-4).

[0010] In a specific embodiment of this application, the maleic anhydride terpolymer comprises an ethylene-acrylate-maleic anhydride copolymer. Further, in the maleic anhydride terpolymer, the content of maleic anhydride is 0.3 wt% to 5 wt%, and the content of acrylate is ≥10 wt%.

[0011] In a specific embodiment of this application, the melt index of the maleic anhydride terpolymer at 190°C and 2.16 kg is 2-20 g / 10 min.

[0012] In a specific embodiment of this application, the content of maleic anhydride in the maleic anhydride-grafted ethylene-acrylate copolymer is 0.2wt% to 0.6wt%, and the content of acrylate is ≥15wt%.

[0013] In a specific embodiment of this application, the melt index of the maleic anhydride-grafted ethylene-acrylate copolymer at 190°C and 2.16 kg is 2-20 g / 10 min.

[0014] In a specific embodiment of this application, the mass ratio of the maleic anhydride terpolymer to the maleic anhydride graft polymer is (0.4-0.6):1.

[0015] In a specific embodiment of this application, the mass ratio of the maleic anhydride-grafted ethylene-acrylate copolymer to the maleic anhydride-grafted SEBS in the maleic anhydride-grafted polymer is (2-3):1.

[0016] In a specific embodiment of this application, the polyethylene in the core layer includes at least one of LLDPE and LDPE. Further, the mass ratio of LLDPE to LDPE in the core layer is (3-6):1.

[0017] In a specific embodiment of this application, the first adhesive layer further includes at least one of ethylene-vinyl acetate copolymer and ethylene-acrylate copolymer. Further, the VA content in the ethylene-vinyl acetate copolymer is 10 wt% to 35 wt%.

[0018] The second aspect of this application provides a method for preparing a hot melt adhesive film for bonding PET and metal according to the first aspect of this application, comprising the following steps:

[0019] The first adhesive layer material, the core layer material, and the second adhesive layer material are co-extruded or co-extruded into a blown film.

[0020] A third aspect of this application provides a composite board comprising a PET layer, a metal plate, and at least one of a hot melt adhesive film of the first aspect of this application disposed between the PET layer and the metal plate; a first adhesive layer of the hot melt adhesive film is bonded to the PET layer, and a second adhesive layer of the hot melt adhesive film is bonded to the metal plate.

[0021] Compared with the prior art, the beneficial effects of this application are as follows:

[0022] (1) This application uses a hot melt adhesive film with a multi-layer structure, which can bond PET and metal plates. In addition, polyethylene is used as an intermediate layer in the first adhesive layer and the second adhesive layer to organically combine the first adhesive layer and the second adhesive layer and ensure the stability of the composite structure. The hot melt adhesive film of this application has good water resistance and its bonding performance still meets the requirements after soaking in water for 48 hours.

[0023] (2) The hot melt adhesive film of this application avoids the problem of small molecules penetrating to the bonding interface in existing polyurethane liquid adhesives, and the preparation method is simple to operate and environmentally friendly.

[0024] After reading and understanding the detailed description, other aspects can be understood. Detailed Implementation

[0025] The technical solution of this application will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this application, not all embodiments, and are only used to illustrate this application, and should not be regarded as limiting the scope of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0026] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] The first aspect of this application provides a hot melt adhesive film for bonding PET and metal, including 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;

[0028] 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 maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS; in the first adhesive layer, the total proportion of maleic anhydride terpolymer and maleic anhydride grafted polymer is ≥80wt%; the second adhesive layer comprises maleic anhydride grafted polyethylene; the core layer comprises polyethylene.

[0029] The mass ratio of the first adhesive layer, the core layer, and the second adhesive layer is (2-4):(3-5):(2-4).

[0030] This application uses a multi-layer hot melt adhesive film that can bond PET and metal sheets. Polyethylene is used as an intermediate layer between the first and second adhesive layers to organically combine the first and second adhesive layers and ensure the stability of the composite structure. The hot melt adhesive film of this application has good water resistance and its bonding performance still meets the requirements after soaking in water for 48 hours.

[0031] In the first adhesive layer of this application, the total proportion of maleic anhydride terpolymer and maleic anhydride graft polymer can be 80wt%, 82wt%, 85wt%, 88wt%, 90wt%, 92wt%, 95wt%, 98wt%, 100wt%, or any combination thereof. This application uses a blend of maleic anhydride terpolymer and maleic anhydride graft polymer as the first adhesive layer, which can simultaneously improve PET wettability, adhesion, and water resistance.

[0032] 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 any combination 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 any combination thereof. This helps to improve the compatibility of the first adhesive layer, the core layer, and the second adhesive layer while ensuring the adhesion performance to PET and metal, and further helps to improve the composite stability of the hot melt adhesive film.

[0033] In a specific embodiment of this application, the maleic anhydride terpolymer comprises an ethylene-acrylate-maleic anhydride copolymer. Further, in the maleic anhydride terpolymer, the content of maleic anhydride is 0.3wt% to 5wt%, for example, it can be 0.3wt%, 0.5wt%, 0.8wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, or any combination thereof, and the content of acrylate is ≥10wt%, for example, it can be 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, or any combination thereof. The maleic anhydride and acrylate content in the maleic anhydride terpolymer within the above ranges is more conducive to improving the adhesion performance of the first adhesive layer to PET, while ensuring the water resistance of the first adhesive layer.

[0034] In a specific embodiment of this application, 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.

[0035] In a specific embodiment of this application, the melt index of the maleic anhydride terpolymer at 190°C and 2.16 kg is 2–20 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 any combination thereof. The maleic anhydride terpolymer used in this application has good flowability, which helps to improve the wettability of the first adhesive layer to PET, thereby improving the adhesive performance.

[0036] In a specific embodiment of this application, the maleic anhydride-grafted ethylene-acrylate copolymer contains maleic anhydride at a 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 combination thereof, and the acrylate content is ≥15 wt%, for example, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, or any combination 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.

[0037] In a specific embodiment of this application, 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 any combination thereof.

[0038] In a specific embodiment of this application, the melt index of maleic anhydride-grafted SEBS at 230°C and 2.16 kg is 1–10 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, or any combination thereof. The introduction of maleic anhydride-grafted SEBS into the first adhesive layer can further improve the compatibility of each component in the first adhesive layer with the core layer, and can further balance and improve the rigidity and toughness of the hot melt adhesive film, thus contributing to the improvement of the overall performance of the composite board.

[0039] In a specific embodiment of this application, the mass ratio of maleic anhydride terpolymer to maleic anhydride graft polymer is (0.4 to 0.6):1, for example, it can be a range of 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1 or any combination thereof, thereby helping to balance the wettability, adhesion, water resistance of the first adhesive layer to PET and its compatibility with the core layer.

[0040] In a specific embodiment of this application, the mass ratio of maleic anhydride-grafted ethylene-acrylate copolymer to maleic anhydride-grafted SEBS in the maleic anhydride-grafted polymer is (2-3):1, for example, it can be a range of 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1 or any two of these, thereby helping to further improve the adhesive properties and rigidity / toughness of the hot melt adhesive film.

[0041] In a specific embodiment of this application, the polyethylene in the core layer includes at least one of LLDPE and LDPE. Further, the mass ratio of LLDPE to LDPE in the core layer is (3-6):1, for example, it can be a range of 3:1, 4:1, 5:1, 6:1, or any combination thereof, thereby contributing to improved adhesion and performance matching between the first and second adhesive layers.

[0042] In a specific embodiment of this application, the melt index of polyethylene in the core layer 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 any combination thereof.

[0043] In a specific embodiment of this application, the melt index of 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 any combination thereof.

[0044] In a specific embodiment of this application, the first adhesive layer further includes at least one of ethylene-vinyl acetate copolymer and ethylene-acrylate copolymer. Further, in the ethylene-vinyl acetate copolymer, the VA content is 10wt% to 35wt%, for example, it can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, or any combination thereof. The introduction of EVA can appropriately improve the toughness of the hot melt adhesive film, but excessive EVA will lead to a decrease in the water resistance of the hot melt adhesive film.

[0045] The second aspect of this application provides a method for preparing a hot melt adhesive film for bonding PET and metal according to the first aspect of this application, comprising the following steps:

[0046] The first adhesive layer material, the core layer material, and the second adhesive layer material are co-extruded or co-extruded into a blown film.

[0047] In a specific embodiment of this application, in the multilayer co-extrusion casting 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.

[0048] A third aspect of this application provides a composite board, including a PET layer, a metal plate, and at least one of the hot melt adhesive film of the first aspect of this application disposed between the PET layer and the metal plate; a first adhesive layer of the hot melt adhesive film is bonded to the PET layer, and a second adhesive layer of the hot melt adhesive film is bonded to the metal plate.

[0049] Example 1

[0050] This embodiment provides a hot melt adhesive film for bonding PET and metal, including 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.

[0051] The raw materials for 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.

[0052] Among them, the maleic anhydride terpolymer is an ethylene-acrylate-maleic anhydride copolymer with a maleic anhydride content of 0.3wt% and 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% and an acrylate content of 30wt%, and a melt index of 5g / 10min at 190℃ / 2.16kg; the maleic anhydride-grafted SEBS copolymer has a melt index of 8g / 10min at 230℃ / 2.16kg.

[0053] The core layer consists of LLDPE 7042 and LDPE 2420H in a mass ratio of 4:1.

[0054] The raw material for the second adhesive layer includes VB550SD (Guangzhou Lushan New Materials Co., Ltd.).

[0055] The preparation method of the hot melt adhesive film in this embodiment includes the following steps: weighing the raw material components of the first adhesive layer, the core layer, and the second adhesive layer according to the proportion, 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.

[0056] Example 2

[0057] This embodiment refers to the hot melt adhesive film and its preparation method in Embodiment 1, 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 in 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.

[0059] Example 3

[0060] This embodiment refers to the hot melt adhesive film and its preparation method in Embodiment 1, the only difference being that the raw material composition of the first adhesive layer is different.

[0061] The raw materials for the first adhesive layer in this embodiment include maleic anhydride terpolymer and maleic anhydride graft polymer in a mass ratio of 3:7; the maleic anhydride graft polymer includes maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS in a mass ratio of 4:1.

[0062] Example 4

[0063] This embodiment refers to the hot melt adhesive film and its preparation method in Embodiment 1, the only difference being that the raw material composition of the first adhesive layer is different.

[0064] The raw materials for the first adhesive layer in this embodiment include maleic anhydride terpolymer and maleic anhydride graft polymer in a mass ratio of 3:7; the maleic anhydride graft polymer is maleic anhydride grafted ethylene-acrylate copolymer.

[0065] Example 5

[0066] This embodiment refers to the hot melt adhesive film and its preparation method in Embodiment 1, the only difference being that the raw material composition of the first adhesive layer is different.

[0067] The raw materials for the first adhesive layer in this embodiment include maleic anhydride terpolymer and maleic anhydride graft polymer in a mass ratio of 3:7; the maleic anhydride graft polymer is maleic anhydride grafted SEBS.

[0068] Example 6

[0069] This embodiment refers to the hot melt adhesive film and its preparation method in Embodiment 1, the only difference being that the raw material composition of the first adhesive layer is different.

[0070] The raw materials for the first adhesive layer in this embodiment include maleic anhydride terpolymer and maleic anhydride graft polymer in a mass ratio of 2:8; the maleic anhydride graft polymer includes maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS in a mass ratio of 2.5:1.

[0071] Example 7

[0072] This embodiment refers to the hot melt adhesive film and its preparation method in Embodiment 1, the only difference being that the raw material composition of the first adhesive layer is different.

[0073] The raw materials for the first adhesive layer in this embodiment include maleic anhydride terpolymer and maleic anhydride graft polymer in a mass ratio of 4:6; the maleic anhydride graft polymer includes maleic anhydride grafted ethylene-acrylate copolymer and maleic anhydride grafted SEBS in a mass ratio of 2.5:1.

[0074] Example 8

[0075] This embodiment refers to the hot melt adhesive film and its preparation method in Embodiment 1, the only difference being that the raw material composition of the first adhesive layer is different.

[0076] The raw materials for the first adhesive layer in this embodiment include a maleic anhydride terpolymer, a maleic anhydride graft polymer, and an ethylene-vinyl acetate copolymer in a mass ratio of 2.4:5.6:2. The maleic anhydride graft polymer includes a maleic anhydride grafted ethylene-acrylate copolymer and a maleic anhydride grafted SEBS copolymer in a mass ratio of 2.5:1. The ethylene-vinyl acetate copolymer contains 18 wt% VA and has a melt index of 3 g / 10 min at 190°C / 2.16 kg.

[0077] Comparative Example 1

[0078] Comparative Example 1 refers to the hot melt adhesive film and its preparation method in Example 1, the difference being that the raw material composition of the first adhesive layer is different.

[0079] The raw material for the first adhesive layer of Comparative Example 1 includes maleic anhydride terpolymer (the same maleic anhydride terpolymer as in Example 1).

[0080] Comparative Example 2

[0081] Comparative Example 2 refers to the hot melt adhesive film and its preparation method in Example 1, the difference being that the raw material composition of the first adhesive layer is different.

[0082] The raw material for the first adhesive layer of Comparative Example 2 includes maleic anhydride grafted polymer (the same maleic anhydride grafted polymer as in Example 1).

[0083] Comparative Example 3

[0084] Comparative Example 3 refers to the hot melt adhesive film and its preparation method in Example 8, the difference being that the raw material composition of the first adhesive layer is different.

[0085] The raw materials for the first adhesive layer of Comparative Example 3 include maleic anhydride terpolymer, maleic anhydride graft polymer and ethylene-vinyl acetate copolymer in a mass ratio of 2.1:4.9:3.

[0086] Comparative Example 4

[0087] Comparative Example 4 refers to the hot melt adhesive film and its preparation method in Example 1, the difference being that the raw material composition of the first adhesive layer is different.

[0088] The raw material for the first adhesive layer of Comparative Example 4 includes ethylene-vinyl acetate copolymer (ethylene-vinyl acetate copolymer, same as in Example 8).

[0089] Experimental Example

[0090] Test specimens were prepared from hot melt adhesive films of different embodiments and comparative examples, and peel strength tests were conducted under different conditions. The test results are shown in Table 1.

[0091] Preparation of test specimens: PET (corona-treated), hot melt adhesive film, and galvanized sheet are stacked in sequence (the first adhesive layer of the hot melt adhesive film is bonded to PET, and the second adhesive layer is bonded to the galvanized sheet), and hot-pressed for 15s on a flat vulcanizing machine at 170℃ and 0.2MPa, and then cooled for testing.

[0092] Test method: The peel strength of the test specimen after hot pressing and cooling to room temperature for 30 minutes is tested.

[0093] After soaking the test sample in water at room temperature for 48 hours, the peel strength was tested, and it was observed whether there was any adhesive residue on the PET surface after peeling. The presence of adhesive residue indicates that the corresponding hot melt adhesive film has better bonding performance after soaking in water.

[0094] The above peel strength test refers to the 180° peel strength test method in GB / T 2792.

[0095] Table 1 Test results of different hot melt adhesive films

[0096] A composite PET hot melt adhesive film (made by bonding corona-treated PET and a single-sided polymer film together with commercially available two-component polyurethane adhesive, with an adhesive layer thickness of 4μm and a single-sided polymer film thickness of 40μm, the single-sided polymer film being made of PE and VB550SD in a mass ratio of 7:3) was hot-pressed with a galvanized sheet at 170℃ and 0.2MPa on a flat vulcanizing machine for 15s, followed by cooling and testing; the single-sided polymer film was bonded to the galvanized sheet. The corresponding peel strength II, tested according to the above method, was less than 20N / 25mm, and no adhesive residue was found on the PET surface.

[0097] The test results above show that the hot melt adhesive film with a multi-layer structure used in this application can bond PET and metal plates. In addition, polyethylene is used as an intermediate layer between the first adhesive layer and the second adhesive layer to organically combine the first adhesive layer and the second adhesive layer and ensure the stability of the composite structure. The hot melt adhesive film of this application has good water resistance and its bonding performance still meets the requirements after soaking in water for 48 hours.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. 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 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 ≥80wt%; the second adhesive layer comprises maleic anhydride grafted polyethylene; 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, wherein, 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 melt index of the maleic anhydride terpolymer at 190℃ and 2.16kg is 2 to 20 g / 10 min.

3. The hot melt adhesive film for bonding PET and metal according to claim 1, wherein, 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 melt index of the maleic anhydride-grafted ethylene-acrylate copolymer at 190°C and 2.16 kg is 2 to 20 g / 10 min.

4. The hot melt adhesive film for bonding PET and metal according to claim 1, wherein, The mass ratio of the maleic anhydride terpolymer to the maleic anhydride graft polymer is (0.4–0.6):

1.

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

9. A method for preparing a hot melt adhesive film for bonding PET and metal according to any one of claims 1 to 8, comprising the following steps: The first adhesive layer material, the core layer material, and the second adhesive layer material are co-extruded or co-extruded into a blown film.

10. A composite board comprising a PET layer, a metal plate, and a hot melt adhesive film disposed between the PET layer and the metal plate, wherein, The hot melt adhesive film includes 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 bonded to the PET layer, and the second adhesive layer of the hot melt adhesive film is bonded to the metal plate.

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