Aluminum-plastic composite film and method for manufacturing the same

Abstract

The present application provides an aluminum-plastic composite film and a preparation method thereof. The aluminum-plastic composite film comprises an aluminum foil layer, a protective layer on one side of the aluminum foil layer, and a heat-seal layer on the other side of the aluminum foil layer. The heat-seal layer is made of a thermoplastic resin material, and the protective layer is made of a heat-resistant resin material. The protective layer comprises a nylon layer close to the aluminum foil layer and a polyethylene terephthalate layer away from the aluminum foil layer. The thickness ratio of the heat-seal layer to the protective layer is less than 2.5, and the thickness ratio of the nylon layer to the polyethylene terephthalate layer in the protective layer is 3-6. The aluminum-plastic composite film of the present application controls the thickness ratio of each layer made of a heat-resistant resin material and a thermoplastic resin material in a specific way, so that the stress on the side of the heat-resistant resin material can offset the stress on the side of the thermoplastic resin material, and the thickness ratio of the nylon layer to the polyethylene terephthalate layer is controlled to ensure the punching performance, thereby realizing an aluminum-plastic composite film with low curling.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum-plastic film for power battery, and particularly relates to an aluminum-plastic composite film and a preparation method thereof. BACKGROUND

[0002] The aluminum-plastic composite film generally comprises an aluminum foil and a protective layer and a heat-seal layer on both sides of the aluminum foil, the protective layer is generally a heat-resistant resin, such as nylon, and the heat-seal layer is generally a thermoplastic resin, such as a polypropylene film. The aluminum-plastic composite film is formed into an outer packaging shell of a power battery by stamping. Because there is a large difference in stress between the heat-resistant resin and the thermoplastic resin, after the shell is punched, it will be rolled up to one side, and even cause the difficulty of the battery cell into the shell. In addition, because of the serious curling, manual rework is required to fold it, which may cause local wrinkles or damage to the appearance. For this reason, many battery manufacturers require the aluminum-plastic composite film to have low curling after the shell is punched. SUMMARY

[0003] In view of the problem of serious curling of the aluminum-plastic composite film after the shell is punched, the purpose of the present application is to provide an aluminum-plastic composite film with low curling.

[0004] To achieve the above-mentioned purpose, the present application provides an aluminum-plastic composite film, comprising an aluminum foil layer, a protective layer on one side of the aluminum foil layer, and a heat-seal layer on the other side of the aluminum foil layer, the heat-seal layer is made of a thermoplastic resin material, the protective layer is made of a heat-resistant resin material, the protective layer comprises a nylon layer close to one side of the aluminum foil layer and a polyethylene terephthalate layer away from one side of the aluminum foil layer, the thickness ratio of the heat-seal layer to the protective layer is less than 2.5, and the thickness ratio of the nylon layer to the polyethylene terephthalate layer is 3-6.

[0005] Compared with the prior art, the aluminum-plastic composite film of the present application sets the heat-seal layer on one side of the aluminum foil layer, and sets the nylon layer and the polyethylene terephthalate layer (PET layer) in sequence on the other side. The nylon layer and the polyethylene terephthalate layer together form the protective layer. By controlling the thickness ratio of the heat-seal layer to the protective layer to be less than 2.5, and the thickness ratio of the nylon layer to the polyethylene terephthalate layer in the protective layer to be 3-6, the stress on the side of the heat-resistant resin material can offset the stress on the side of the thermoplastic resin material by controlling the thickness ratio of each layer made of the heat-resistant resin material and the thermoplastic resin material. At the same time, the thickness ratio of the nylon layer to the polyethylene terephthalate layer is controlled to ensure the punching performance, so as to realize the aluminum-plastic composite film with low curling.

[0006] In some embodiments, the thickness ratio of the heat-seal layer to the protective layer is less than 2.3. As an example, the thickness ratio of the heat-seal layer to the protective layer is 2.1 or 2.2, but is not limited thereto.

[0007] In some embodiments, the ratio of the thickness of the nylon layer to the thickness of the polyethylene terephthalate layer is 3-6, preferably 3-5, for example, the ratio of the thickness of the nylon layer to the thickness of the polyethylene terephthalate layer is 3, 4, 5, 6, but not limited thereto.

[0008] In some embodiments, the thickness of the aluminum-plastic composite film is 140-158 μm, about 140-150 μm, about 145-155 μm, about 150-158 μm, about 140-145 μm, about 143-155 μm, for example, the thickness of the aluminum-plastic composite film is 153 μm, 148 μm, 146 μm, etc., but not limited thereto.

[0009] In some embodiments, the thickness of the aluminum foil layer is 40-45 μm, about 40-50 μm, about 40-55 μm, about 45-50 μm, about 45-55 μm, about 50-55 μm, for example, the thickness of the aluminum foil layer is 40 μm, 45 μm, 50 μm, etc., but not limited thereto.

[0010] In some embodiments, the thickness of the heat-seal layer is 70-80 μm, about 70-75 μm, about 75-80 μm, for example, the thickness of the heat-seal layer is 70 μm, 75 μm, 80 μm, etc., but not limited thereto.

[0011] In some embodiments, the heat-seal layer is a polypropylene film, preferably a three-layer cast polypropylene film, but not limited thereto, and other thermoplastic resin materials can be used as the heat-seal layer.

[0012] Correspondingly, the present application also provides a preparation method of the above-mentioned aluminum-plastic composite film, comprising the following steps:

[0013] (1) performing double-side passivation treatment on the aluminum foil layer;

[0014] (2) compounding the nylon layer with one side of the aluminum foil layer;

[0015] (3) compounding the polyethylene terephthalate layer with the nylon layer;

[0016] (4) compounding the heat-seal layer with the other side of the aluminum foil layer.

[0017] Correspondingly, the present application also provides a preparation method of the above-mentioned aluminum-plastic composite film, comprising the following steps:

[0018] (1) performing double-side passivation treatment on the aluminum foil layer;

[0019] (2) co-extruding the nylon and the polyethylene terephthalate to obtain a co-extruded film; compounding one side of the nylon layer of the co-extruded film with one side of the aluminum foil layer;

[0020] (3) The heat-sealing layer is compounded with the other side of the aluminum foil layer.

[0021] That is, the protective layer is formed by co-extruding the nylon and polyethylene terephthalate to obtain a co-extruded film, or by laminating the nylon layer and the polyethylene terephthalate layer to form the protective layer.

[0022] In some embodiments, the heat-sealing layer and the aluminum foil layer are compounded by a thermal method.

[0023] In some embodiments, the nylon layer and the aluminum foil layer are compounded by a dry method. DETAILED DESCRIPTION

[0024] The following describes preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the embodiments of the present application, and these improvements and refinements are also considered within the scope of protection of the embodiments of the present application.

[0025] Example 1

[0026] A preparation method of an aluminum-plastic composite film, comprising the steps of:

[0027] (1) A 45 μm 8021 O-state aluminum foil is subjected to double-side passivation treatment, and then one side thereof is dry compounded with a 25 μm biaxially stretched nylon film, with a glue application amount of 4-5 g / m 2 , and a layer of 8 μm polyethylene terephthalate film is compounded on the surface of the nylon film, with a glue application amount of 2-3 g / m 2 , and is baked at 75°C for 3 days to obtain a semi-finished product;

[0028] (2) The semi-finished product is heat compounded with a 70 μm three-layer cast polypropylene film to obtain an aluminum-plastic composite film.

[0029] Example 2

[0030] A preparation method of an aluminum-plastic composite film, comprising the steps of:

[0031] (1) A 45 μm 8021 O-state aluminum foil is subjected to double-side passivation treatment;

[0032] (2) A co-extruded film is obtained by co-extruding nylon and polyethylene terephthalate, wherein the thickness of the nylon film and the thickness of the polyethylene terephthalate are 25 μm and 6 μm, respectively, and the nylon film side of the co-extruded film is dry compounded with an aluminum foil layer, with a glue application amount of 4-5 g / m 2 , to obtain a semi-finished product;

[0033] (3) The semi-finished product is heat compounded with a 70 μm three-layer cast polypropylene film to obtain an aluminum-plastic composite film.

[0034] Example 3

[0035] Example 3 is substantially the same as Example 1, except that the thickness of the three-layer cast polypropylene film in Example 1 is 70 μm, while the thickness of the three-layer cast polypropylene film in Example 3 is 80 μm, and the rest is the same, which is not described here.

[0036] Comparative Example 1

[0037] Comparative Example 1 is substantially the same as Example 2, except that the thickness of the nylon film and the thickness of the polyethylene terephthalate in Example 2 are 25 μm and 6 μm, respectively, while the thickness of the nylon film and the thickness of the polyethylene terephthalate in Comparative Example 1 are 20 μm and 6 μm, respectively, and the rest is the same, which is not described here.

[0038] Comparative Example 2

[0039] Comparative Example 2 is substantially the same as Example 1, except that the thickness of the polyethylene terephthalate film in Example 1 is 8 μm, while the thickness of the polyethylene terephthalate film in Comparative Example 1 is 4 μm, and the rest is the same, which is not described here.

[0040] Comparative Example 3

[0041] Comparative Example 3 is substantially the same as Example 1, except that the thickness of the polyethylene terephthalate film in Example 1 is 8 μm, while the thickness of the polyethylene terephthalate film in Comparative Example 1 is 0 μm, i.e. no polyethylene terephthalate film, and the rest is the same, which is not described here.

[0042] Comparative Example 4

[0043] Comparative Example 4 is substantially the same as Example 1, and the total thickness of the protective layer is the same, but the thickness of the nylon layer and the polyethylene terephthalate film is different, specifically, the thickness of the polyethylene terephthalate film in Example 1 is 8 μm, and the thickness of the nylon film is 25 μm, while the thickness of the polyethylene terephthalate film in Comparative Example 4 is 3 μm, and the thickness of the nylon film is 30 μm, and the rest is the same, which is not described here.

[0044] Comparative Example 5

[0045] Comparative Example 5 is basically the same as Example 1, the total thickness of the protective layer is the same, but the thicknesses of the nylon layer and the polyethylene terephthalate film are different, specifically, the thickness of the polyethylene terephthalate film in Example 1 is 8 μm, the thickness of the nylon film is 25 μm, while the thickness of the polyethylene terephthalate film in Comparative Example 5 is 10 μm, the thickness of the nylon film is 23 μm, and the rest are the same, which will not be described here.

[0046] The aluminum-plastic composite films obtained in the examples and comparative examples are subjected to punching test, and the results are shown in Table 1.

[0047] The punching test method is as follows:

[0048] The aluminum-plastic film is cut into a sample piece with a size of 120*150 mm, and is subjected to punching by a shell punching machine, the pit size is 55*60 mm, the shell punching depth is set to X mm, 40 shells are continuously punched, and a strong flashlight is used to observe the pit in the dark box to determine whether it is damaged, if it is not damaged, the depth is increased by 0.2 mm based on X, if the probability of damage occurs at X mm, the depth is reduced by 0.2 mm based on X, and the punching and damage observation are continued according to the above method. The final punching depth H is the depth at which there is no damage and the probability of damage increases by 0.2 mm, and the non-damage value at this time is taken as the result of the punching depth.

[0049] The curling degree after shell punching is observed, as shown in Table 1, the more stars, the more serious the curling.

[0050] Table 1 Performance test results

[0051]

[0052] Note: The more stars, the more serious the curling, the fewer stars, the more flat. The more stars, the more difficult the production process, the more difficult the process.

[0053] From the data in Table 1, it can be seen that the aluminum-plastic composite films obtained in Examples 1-3 have a lower curling degree after shell punching, which is because the thickness ratio of each layer of the heat-resistant resin material and the thermoplastic resin material is controlled to offset the stress of the heat-resistant resin material side to the stress of the thermoplastic resin material side, and the thickness ratio of the nylon layer and the polyethylene terephthalate layer is controlled to ensure good punching performance, so as to realize the low-curling aluminum-plastic composite film.

[0054] Comparative Example 1 has a thinner nylon film layer compared to Example 2, which has a significant impact on the punching depth, and because the overall thickness of the protective layer is reduced, it cannot offset the stress of the heat-sealing layer, which also has a certain impact on curling.

[0055] Comparative Example 2 and Comparative Example 3 are compared with the examples, mainly the thickness of the PET layer is reduced, because the PET layer is rigid and insufficiently tough, reducing the PET layer helps to the depth of the punch, but because the thickness of the PET film of the protective layer is reduced, the stress is reduced, and the curling is affected. At the same time, Comparative Example 2 reduces the thickness of the PET layer to 4 μm, which has a certain impact on the production of composite, the thinner the thickness, the higher the requirement for tension and the stability of the whole process control, because the thickness of the PET layer is reduced, the curling is also deteriorated.

[0056] Example 1 is compared with Comparative Examples 4-5, although the ratio between the total thickness of the protective layer and the heat-seal layer is unchanged, but because the thickness ratio of the nylon layer and the polyethylene terephthalate layer in the protective layer is changed. In Comparative Example 4, the thickness of the nylon film is increased, which has a significant improvement on the depth of the punch, but because the thickness of the PET layer is reduced to 3 μm, it has a certain impact on the production of composite, the thinner the thickness, the higher the requirement for tension and the stability of the whole process control, and the process control is more difficult than Comparative Example 2. In Comparative Example 5, the thickness of the nylon layer is reduced and the thickness of the PET layer is increased, and the curling is not deteriorated, but the reduction of the thickness of the nylon layer causes the decrease of the punch depth, which is not worth the loss.

[0057] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limited to the scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, it is not limited to the examples listed in the embodiments, and those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the present application.

Claims

1. An aluminum-plastic composite film, characterized in that, The device includes an aluminum foil layer, a protective layer located on one side of the aluminum foil layer, and a heat-sealing layer located on the other side of the aluminum foil layer. The heat-sealing layer is made of a thermoplastic resin material, and the protective layer is made of a heat-resistant resin material. The protective layer includes a nylon layer on the side closer to the aluminum foil layer and a polyethylene terephthalate layer on the side farther from the aluminum foil layer. The thickness ratio of the heat-sealing layer to the protective layer is less than 2.5, and the thickness ratio of the nylon layer to the polyethylene terephthalate layer is 3-6.

2. The aluminum-plastic composite film according to claim 1, characterized in that, The thickness ratio of the heat-sealing layer to the protective layer is less than 2.

3.

3. The aluminum-plastic composite film according to claim 1, characterized in that, The thickness ratio of the nylon layer to the polyethylene terephthalate layer is 3-5.

4. The aluminum-plastic composite film according to claim 1, characterized in that, The thickness of the aluminum-plastic composite film is 140–158 μm.

5. The aluminum-plastic composite film according to claim 1, characterized in that, The thickness of the aluminum foil layer is 40–55 μm.

6. The aluminum-plastic composite film according to claim 1, characterized in that, The thickness of the heat-sealing layer is 70–80 μm.

7. The aluminum-plastic composite film according to claim 1, characterized in that, The heat-sealing layer is a three-layer cast polypropylene film.

8. A method for preparing the aluminum-plastic composite film according to any one of claims 1-7, characterized in that, Including the following steps: (1) Passivate the aluminum foil layer on both sides; (2) Composite the nylon layer with one side of the aluminum foil layer; (3) Composite the polyethylene terephthalate layer with the nylon layer; (4) Composite the heat-sealing layer with the other side of the aluminum foil layer.

9. A method for preparing the aluminum-plastic composite film according to any one of claims 1-7, characterized in that, Including the following steps: (1) Passivate the aluminum foil layer on both sides; (2) Nylon and polyethylene terephthalate are co-extruded to obtain a co-extruded film; the nylon layer side of the co-extruded film is laminated with the aluminum foil layer side; (3) Composite the heat-sealing layer with the other side of the aluminum foil layer.

10. The method for preparing the aluminum-plastic composite film according to claim 9, characterized in that, The heat-sealing layer and the aluminum foil layer are bonded together using a thermal method; The nylon layer and the aluminum foil layer are bonded together using a dry lamination process.

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