Composite aluminum foil-aluminum plastic film and preparation method thereof

Abstract

The application relates to the technical field of lithium battery aluminum plastic film, and discloses a composite aluminum foil aluminum plastic film and a preparation method thereof.The composite aluminum foil aluminum plastic film comprises, from top to bottom, an outer layer, a PP composite aluminum foil core layer and an inner layer; the outer layer comprises a heat-resistant resin film and an outer adhesive layer; the inner layer comprises a thermoplastic resin film and an inner adhesive layer; the PP composite aluminum foil core layer comprises a PP film and aluminum foils arranged on the two sides of the PP film; the aluminum foils are in contact with the outer adhesive layer and the inner adhesive layer.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium battery aluminum plastic film, and discloses a composite aluminum foil aluminum plastic film and a preparation method thereof. BACKGROUND

[0002] At present, the aluminum plastic film has the advantages of light weight, thin thickness, flexible design and the like as a soft package battery packaging film. As one of the five materials of the soft package battery, the aluminum plastic film plays an important role in protecting the inner core of the lithium battery. Therefore, the cost proportion of the aluminum plastic film is only second to that of the positive electrode material and the separator.

[0003] Based on the application of the soft package aluminum plastic film in the lithium battery and the importance of the aluminum plastic film to the whole battery package, the aluminum plastic film should have good barrier property and double-sided composite aluminum foil performance, good cold stamping forming performance, good deep drawing property and light weight. At present, the aluminum plastic film and the base layer on the market are generally 35-40 mu thick aluminum foil. When the aluminum plastic film is made into a soft package battery, the cold stamping forming performance is not good, leading to an increase in the soft package aluminum plastic film defective rate caused by leakage. After forming, the aluminum foil has poor plasticity and poor packaging performance, leading to a risk of thinning at the corner and corrosion of the aluminum foil by the electrolyte.

[0004] In summary, it is of great significance to prepare a composite aluminum foil aluminum plastic film. SUMMARY

[0005] The application aims to provide a composite aluminum foil aluminum plastic film and a preparation method thereof to solve the problems in the background.

[0006] In order to solve the above technical problems, the application provides the following technical scheme:

[0007] A composite aluminum foil aluminum plastic film comprises, from top to bottom, an outer layer, a PP composite aluminum foil core layer and an inner layer. The outer layer comprises a heat-resistant resin film and an outer adhesive layer. The inner layer comprises a thermoplastic resin film and an inner adhesive layer. The PP composite aluminum foil core layer comprises a PP film and aluminum foils arranged on both sides of the PP film. The aluminum foils are in contact with the outer adhesive layer and the inner adhesive layer.

[0008] More preferably, the heat-resistant resin film comprises a nylon film. The outer adhesive layer comprises at least one of an acrylic resin, a polyester resin and a derivative thereof. The thermoplastic resin film comprises a polypropylene film. The raw material of the inner adhesive layer comprises one or more of polypropylene resin and a derivative thereof. The aluminum foil is an O-state soft aluminum foil.

[0009] More preferably, the thickness of the heat-resistant resin film is 15-30 μm; the coating amount of the outer adhesive layer is 3-4 g / m2; the thickness of the thermoplastic resin film is 10-13 μm; and the coating amount of the inner adhesive is 2-3 g / m2.

[0010] More preferably, the thickness of the PP composite aluminum foil core layer is 30-40 μm; the thickness of the aluminum foil is 10-13 μm; and the thickness of the PP film is 10-14 μm.

[0011] More preferably, the method comprises the following steps:

[0012] Step 1: laminating two aluminum foils on both sides of a PP film, and compounding at 150-165℃ to obtain a PP composite aluminum foil core layer;

[0013] Step 2: coating an outer adhesive on one side of the PP composite aluminum foil core layer, laminating a heat-resistant resin film, and hot bonding at 85-110℃ to form an outer layer; coating an inner adhesive on the other side of the PP composite aluminum foil core layer, laminating a thermoplastic resin film, and hot bonding at 85-110℃ to form an inner layer; and obtaining a composite film;

[0014] Step 3: placing the composite film obtained in Step 2 at 55-60℃ for 5-7 days for curing to obtain a composite aluminum foil plastic film.

[0015] More preferably, in Step 1, the aluminum foil is pretreated; the specific process is as follows: degreasing the aluminum foil in acetone, then immersing in a molybdate solution at 40-50℃ for 60-120 seconds, washing with water, and drying to obtain a pretreated aluminum foil; laminating the pretreated aluminum foil on both sides of a PP film, and compounding at 150-165℃ to obtain a PP composite aluminum foil core layer.

[0016] The raw materials of the molybdate solution include the following components: 55-60 g / L phosphoric acid, 5-7 g / L ammonium molybdate, 2-3 g / L sodium fluoride, 4-5 g / L tartaric acid, and 2-3 g / L additive.

[0017] More preferably, the additive is prepared by the following method: adding phosphorus oxychloride into a reaction kettle, adding a polyethylene glycol-tetrahydrofuran mixed solution dropwise at 5-10℃, and constant-temperature reacting for 5-6 hours; adding a mercaptotetraethylene glycol-tetrahydrofuran mixed solution dropwise, increasing the temperature to 25-30℃, and reacting for 4-4.5 hours; increasing the temperature to 60-65℃, adding deionized water, stirring for 1.5-2 hours, removing tetrahydrofuran by reduced-pressure distillation, and neutralizing with a sodium hydroxide solution; diluting with water, vacuum drying, and obtaining the additive.

[0018] More preferably, the raw material of the additive comprises the following materials: 3-3.2 parts by weight of phosphorus oxychloride, 3.8-4.2 parts by weight of polyethylene glycol, and 4.1-4.3 parts by weight of mercaptotetraethylene glycol.

[0019] More preferably, in step 1, the PP film is subjected to surface modification; specifically, after irradiation, the PP film is quickly placed in a glycidyl methacrylate-methanol solution, the pressure is set to 0.15-0.25 MPa, the temperature is set to 35-45 DEG C, and the film is immersed for 60-90 minutes, then washed and dried to obtain a modified PP film; the pretreated aluminum foil is arranged on both sides of the modified PP film, and the composite is obtained by compounding at 150-165 DEG C to obtain a PP composite aluminum foil core layer.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] (1) In the scheme, the lightweight of the aluminum foil and the plastic film is further improved, the density of the aluminum foil is 2.71 g / cm 2 , and the density of the PP film is 0.091 g / cm 2 . The PP film is replaced with a lighter PP film, which reduces the weight of the aluminum foil matrix by 1 / 3, thereby reducing the weight of the aluminum-plastic film under the same area, and thereby reducing the weight of the entire battery shell. In addition, the aluminum foil is a soft aluminum foil in O state, which has good rust prevention, water resistance, and heat preservation effects, and has good plasticity.

[0022] (2) In the scheme, in order to improve the cold stamping performance of the aluminum-plastic film, a PP composite aluminum foil core layer is introduced into the aluminum-plastic film. Because the PP film has good toughness and softness, the deep drawing performance is improved, the rupture of the aluminum-plastic film during the forming process is avoided, the generation of defective products is reduced, and the production efficiency is improved. It is particularly noted that if the thickness of the PP composite aluminum foil core layer is released to the requirement, the cost and the deep drawing performance will be affected.

[0023] (3) In the scheme, the PP composite aluminum foil core layer has a sandwich structure, which has good electrical insulation and effectively blocks the conductive medium in the external environment.

[0024] (4) In the scheme, in order to increase the interfacial action between the PP film and the aluminum foil in the PP composite aluminum foil core layer and improve the performance, the aluminum foil and the PP film are further pretreated and modified.

[0025] The aluminum foil is pretreated with molybdate, which can improve the corrosion resistance of the aluminum foil and increase the surface roughness of the aluminum foil, thereby increasing the interfacial action with the PP film, increasing the glass strength, and thereby improving the packaging strength of the aluminum foil and the aluminum-plastic film. However, due to the high reactivity of aluminum and water, the surface modification of the aluminum foil will promote the absorption of hydrogen, which will cause hydrogen embrittlement. Therefore, an additive is introduced into the scheme (the reaction equation is as follows Figure 2The ether bond and hydrophilic group in the polyethylene glycol form hydrogen bonds with water molecules, and a mesh-like adsorption film is formed on the metal surface, which effectively avoids the hydrogen embrittlement phenomenon. On the other hand, due to the presence of the mercapto group in the additive, the modified PP film (surface grafted with epoxy group by using glycidyl methacrylate GMA) can react and crosslink at a lower temperature. By using the sequence before and after crosslinking, the concentrated stress of crosslinking of the hydroxyl group and the epoxy group at high temperature is reduced, and the performance is enhanced. At the same time, the two crosslinking processes effectively improve the chemical interaction between the layers and improve the bonding strength. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings are included to provide a further understanding of the application, and constitute a part of the specification, which together with the embodiments of the application, serve to explain the application, and do not constitute a limitation on the application. In the drawings:

[0027] Figure 1 It is a structural schematic diagram of a composite aluminum foil and aluminum plastic film;

[0028] Figure 2 It is a reaction equation of the additive;

[0029] Figure: 1-heat-resistant resin film; 2-outer adhesive layer; 3-PP composite aluminum foil core layer; 4-thermoplastic resin film; 5-inner adhesive layer. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0031] It should be noted that there is no special limitation on the purchase manufacturers of all raw materials involved in the application, which exemplarily include: in the following embodiments, the CAS number of phosphorus oxychloride is 10025-87-3; polyethylene glycol is polyethylene glycol-400, which is provided by Jinan Jinhuo Chemical Industry; the CAS number of mercapto tetraethylene glycol is 90952-27-5, and the model number is BK03481, which is provided by Wuhan Bolun Kaiyun Pharmaceutical Industry; the model numbers of the outer adhesive and the inner adhesive are both PVDF-5140, which are provided by Shujia Plastic; the model number of the heat-resistant resin film is CM1011G45, which is provided by Japan Toray; and the model number of the thermoplastic resin film is TORAYCON1164G-30, which is provided by Japan Toray.

[0032] The preparation method of the additive is: 3.1 g of phosphorus oxychloride is added to a reaction kettle, and a polyethylene glycol-tetrahydrofuran mixed solution (4 g of polyethylene glycol, 20 g of tetrahydrofuran) is added dropwise at 5°C, and the reaction is kept constant for 6 hours; a mercaptotetraethylene glycol-tetrahydrofuran mixed solution (4.2 g of mercaptotetraethylene glycol, 20 g of tetrahydrofuran) is added dropwise, and the temperature is raised to 30°C, and the reaction is carried out for 4 hours; the temperature is raised to 60°C, deionized water is added, stirred for 2 hours, and the tetrahydrofuran is removed by vacuum distillation, and then a 30 wt% sodium hydroxide solution is added to neutralize to pH = 7.2; dilute with water to a solid content of 40%, vacuum dry, and obtain the additive.

[0033] Example 1: A preparation method of a composite aluminum foil-aluminum plastic film:

[0034] Step 1: Two 10 μm thick aluminum foils (O-state soft aluminum foil of type 8079 provided by Japan Toyo Aluminum) are arranged on both sides of a 10 μm thick PP film (provided by Japan Toray Tek), and are compounded at 160°C to obtain a PP composite aluminum foil core layer;

[0035] Step 2: The outer adhesive of the PP composite aluminum foil core layer is coated by gravure coating, and the coating amount is 3 g / m 2 , dried at 85°C for 2 minutes; a 15 μm thick heat-resistant resin film is arranged on the outer adhesive side of the PP composite aluminum foil core layer, and is hot laminated at 95°C; the inner adhesive of the PP composite aluminum foil core layer is coated by gravure coating, and the coating amount is 2 g / m 2 , dried at 85°C for 2 minutes, and then a 20 μm thick thermoplastic resin film is arranged on the inner adhesive side of the PP composite aluminum foil core layer, and is hot laminated at 95°C; to obtain a composite film;

[0036] Step 3: The composite film is aged at 55°C for 6 days to obtain a composite aluminum foil-aluminum plastic film.

[0037] Example 2: A preparation method of a composite aluminum foil-aluminum plastic film, the difference is that the thickness of the PP film used is 13 μm; the rest of the process is the same as example 1.

[0038] Example 3: A preparation method of a composite aluminum foil-aluminum plastic film: the difference is that the thickness of the PP film used is 13 μm, and the thickness of the aluminum foil used is 12 μm; the rest of the process is the same as example 1.

[0039] Example 4: A preparation method of a composite aluminum foil-aluminum plastic film: the difference is that the thickness of the PP film used is 14 μm, and the thickness of the aluminum foil used is 13 μm; the rest of the process is the same as example 1.

[0040] Example 5: A preparation method of a composite aluminum foil-aluminum plastic film:

[0041] Step 1: Two 13 μm thick aluminum foils (O-temper soft aluminum foil of type 8079 provided by Japan Toyo Aluminum) were laminated on both sides of a 14 μm thick PP film (provided by Japan Toray), and the PP film was melted to be compounded with the inner and outer aluminum foils at 160°C to obtain a PP compounded aluminum foil core layer;

[0042] Step 2: The outer adhesive was coated on one side of the PP compounded aluminum foil core layer by gravure coating, the coating amount was 4 g / m 2 , and dried at 90°C for 2 minutes; a 20 μm thick heat-resistant resin film was laminated on the side of the PP compounded aluminum foil core layer with the outer adhesive, and hot bonded at 100°C; the inner adhesive was coated on the other side of the PP compounded aluminum foil core layer by gravure coating, the coating amount was 3 g / m 2 , and dried at 90°C for 2 minutes, and then a 70 μm thick thermoplastic resin film was laminated on the side of the PP compounded aluminum foil core layer with the inner adhesive, and hot bonded at 100°C; to obtain a compounded film;

[0043] Step 3: The compounded film was aged at 55°C for 6 days to obtain a compounded aluminum foil-aluminum plastic film.

[0044] Example 6: A method for preparing a compounded aluminum foil-aluminum plastic film:

[0045] Step 1: (1) 10 μm thick aluminum foil (O-temper soft aluminum foil of type 8079 provided by Japan Toyo Aluminum) was placed in acetone, degreased at 40°C for 10 minutes, and then immersed in a molybdate solution at 45°C for 90 seconds, washed with water and dried to obtain a pretreated aluminum foil; the raw materials of the molybdate solution include the following components: 60 g / L phosphoric acid, 6 g / L ammonium molybdate, 2 g / L sodium fluoride, 4 g / L tartaric acid, and 2.5 g / L additive.

[0046] (2) The 10 μm thick PP film (provided by Japan Toray) was subjected to electron irradiation at 240 kV, the electron beam current was 4.0 mA, and the irradiation energy was 101 kGy; after irradiation, the modified PP film was quickly placed in a 40 wt% glycidyl methacrylate-methanol solution, set to a pressure of 0.2 Mpa and a temperature of 40°C, and immersed for 90 minutes, washed and dried to obtain a modified PP film;

[0047] (3) Two modified aluminum foils were laminated on both sides of the modified PP film, dried at 120°C for 2 minutes, and the PP film was melted to be compounded with the inner and outer aluminum foils at 160°C to obtain a PP compounded aluminum foil core layer;

[0048] Step 2: The outer adhesive was coated on one side of the PP compounded aluminum foil core layer by gravure coating, the coating amount was 3 g / m 2, 85℃ drying for 2 minutes; 15 μm thick heat-resistant resin film was laminated on the side of the PP composite aluminum foil core layer with the adhesive, and hot bonding was performed at 95℃; the inner adhesive of the PP composite aluminum foil core layer was coated using a gravure coater, and the coating amount was 2 g / m 2 , 85℃ drying for 2 minutes, and then 20 μm thick thermoplastic resin film was laminated on the side of the PP composite aluminum foil core layer with the adhesive, and hot bonding was performed at 95℃; a composite film was obtained;

[0049] Step 3: The composite film was aged at 55℃ for 6 days to obtain a composite aluminum foil-aluminum plastic film.

[0050] Comparative Example 1: A method for preparing a composite aluminum foil-aluminum plastic film: the difference lies in that the PP composite aluminum foil core layer is a single-layer aluminum foil core layer; the rest of the process is the same as that of Example 1.

[0051] Comparative Example 2: A method for preparing a composite aluminum foil-aluminum plastic film: the difference lies in that the additive used is directly polyethylene glycol-400; the rest of the process is the same as that of Example 6.

[0052] Comparative Example 3: A method for preparing a composite aluminum foil-aluminum plastic film: the difference lies in that the aluminum foil is treated with an alkaline solution, specifically: 10 μm thick aluminum foil (O-state soft aluminum foil of type 8079 provided by Japan Toyo Aluminum) is placed in acetone, degreased at 40℃ for 10 minutes, then immersed in an alkaline solution at 45℃ for 90 seconds, washed with water and dried to obtain a pretreated aluminum foil; the raw materials of the alkaline solution include the following components: 10 g / L sodium silicate, 20 g / L sodium phosphate, 10 g / L sodium fluoride, 10 g / L sodium carbonate; the rest is the same as that of Example 6.

[0053] Performance test of the examples and comparative examples: (1) Package peeling strength test: draw a 60 mm x 40 mm rectangular sample, fold it in half, and seal both sides with a 185℃ sealing knife, with a sealing time of 3 seconds and a sealing head width of 2 mm; pour in 5 g of electrolyte, and place in an 80℃ oven for 2 days; use a tensile testing machine to test the package peeling strength, with a peeling rate of 300 mm / min. (2) Limit forming depth test: use a shell punching machine, test 10 samples at each depth of 4.5 mm, 5.0 mm, 5.5 mm, 6.0 mm, and 6.5 mm, from small to large, to determine whether the aluminum plastic film is damaged or has pinholes after forming, and the maximum depth reached is the limit forming depth. The data obtained are shown in the following table:

[0054]

[0055] Conclusion: From the data in the above table, it can be seen that the data in Examples 1-5 show that as the thickness of the PP film and the aluminum foil increases, the forming depth and the package strength limit increase; and the data in Example 6 show that the pretreatment of the aluminum foil can effectively improve the forming depth and the package strength. The data in Example 1 and Comparative Example 1 show that in the scheme, on the basis of effectively ensuring the package strength limit and the forming depth, lightweight is effectively achieved. The data in Comparative Examples 2-3 show that the additive is polyethylene glycol-400, which reduces the interfacial action and reduces the inhibition of hydrogen embrittlement, thereby reducing the performance; and in Comparative Example 3, although the alkali treatment can increase the surface roughness, the alkali treatment increases the surface defects, thereby reducing the performance.

[0056] Finally, it should be noted that the above is only the preferred examples of the present application and is not intended to limit the present application, although the present application has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a composite aluminum foil aluminum-plastic film, characterized in that: The following steps are involved: Pre-preparation: (1) Degrease the aluminum foil in acetone, then place it in a molybdate solution, soak it at 40-50°C for 60-120 seconds, wash it with water, and dry it to obtain a pretreated aluminum foil; (2) After irradiating the PP film, quickly place it in a methacrylate glycidyl ether-methanol solution, set the pressure to 0.15-0.25 MPa, the temperature to 35-45°C, soak it for 60-90 minutes, wash it, and dry it to obtain a modified PP film; Step 1: Lay the pretreated aluminum foil on both sides of the modified PP film and laminate at 150-165°C to obtain a PP composite aluminum foil core layer; Step 2: coating one side of the PP composite aluminum foil core layer with an external adhesive, laminating with a heat-resistant resin film, and thermally laminating at 85-110° C. to form an outer layer; coating the other side of the PP composite aluminum foil core layer with an internal adhesive, laminating with a thermoplastic resin film, and thermally laminating at 85-110° C. to form an inner layer; obtaining a composite film; Step 3: placing the composite film obtained in step 2 at 55-60° C. for aging for 5-7 days to obtain a composite aluminum foil and aluminum-plastic film; The raw materials of the molybdate solution include the following components: 55-60 g / L phosphoric acid, 5-7 g / L ammonium molybdate, 2-3 g / L sodium fluoride, 4-5 g / L tartaric acid, and 2-3 g / L additives; The preparation method of the additive comprises the following steps: adding phosphorus oxychloride into a reaction kettle, dropwise adding a polyethylene glycol-tetrahydrofuran mixed solution at 5-10° C., and reacting at a constant temperature for 5-6 hours; dropwise adding a mercaptotetraethylene glycol-tetrahydrofuran mixed solution, heating to 25-30° C., and reacting for 4-4.5 hours; heating to 60-65° C., adding deionized water, stirring for 1.5-2 hours, removing tetrahydrofuran by vacuum distillation, and neutralizing by adding a sodium hydroxide solution; diluting with water, and vacuum drying to obtain the additive.

2. The method for preparing a composite aluminum foil aluminum-plastic film according to claim 1, wherein: The raw materials of the additive include the following materials: 3 to 3.2 parts of phosphorus oxychloride, 3.8 to 4.2 parts of polyethylene glycol, and 4.1 to 4.3 parts of mercapto tetraethylene glycol, by weight.

3. A composite aluminum foil and aluminum-plastic film, characterized by: The composite aluminum foil and aluminum-plastic film is prepared according to the preparation method of any one of claims 1 to 2; the composite aluminum foil and aluminum-plastic film comprises, from top to bottom, an outer layer, a PP composite aluminum foil core layer (3), and an inner layer; the outer layer comprises a heat-resistant resin film (1) and an outer adhesive layer (2); the inner layer comprises a thermoplastic resin film (5) and an inner adhesive layer (4); the PP composite aluminum foil core layer (3) comprises, in sequence, a PP film and aluminum foils arranged on both sides of the PP film; the aluminum foil is in contact with the outer adhesive layer (2) and the inner adhesive layer (4).

4. The composite aluminum foil and aluminum-plastic film according to claim 3, characterized in that: The heat-resistant resin film (1) comprises a nylon film; the outer adhesive layer (2) comprises at least one of acrylic resin, polyester resin and derivatives thereof; the thermoplastic resin film (5) comprises a polypropylene film; the raw material of the inner adhesive layer (4) comprises one or more of polypropylene resin and derivatives thereof; and the aluminum foil is an O-state soft aluminum foil.

5. The composite aluminum foil and aluminum-plastic film according to claim 3, characterized in that: The thickness of the heat-resistant resin film (1) is 15 to 30 μm; the coating amount of the external adhesive layer (2) is 3 to 4 g / m 2 The thickness of the thermoplastic resin film (5) is 10 to 13 μm; the coating amount of the inner adhesive layer (4) is 2 to 3 g / m 2 .

6. The composite aluminum foil and aluminum-plastic film according to claim 3, characterized in that: The thickness of the PP composite aluminum foil core layer (3) is 30 to 40 μm; wherein the thickness of the aluminum foil is 10 to 13 μm; and the thickness of the PP film is 10 to 14 μm.

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