Composite aluminum foil and preparation method thereof

Abstract

The invention provides a composite aluminum foil and a preparation method thereof, and belongs to the technical field of aluminum foil material preparation. The aluminum foil is cleaned and passivated, then the aluminum foil is bonded to the two sides of the plastic substrate through the environment-friendly adhesive, and the composite aluminum foil is obtained; and carrying out pre-baking, high-temperature pressing, post-baking and acidic reagent treatment on the composite aluminum foil to obtain a finished product of the composite aluminum foil. The aluminum foil is cleaned and passivated, so that the corrosion resistance of the aluminum foil and the adhesive force between the aluminum foil and an adhesive are improved, and then the processes of pre-baking, high-temperature pressing and post-baking are combined, so that the binding force between the layers of the prepared composite aluminum foil is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of aluminum foil material preparation technology, specifically relating to a composite aluminum foil and its preparation method. Background Technology

[0002] Aluminum foil possesses excellent ductility, barrier properties, thermal conductivity, and electrical conductivity. It is also easy to process and recycle, making it widely used in various industries, including packaging (such as linings for milk powder containers, pharmaceutical bags, and vacuum packaging bags), electronics (such as current collectors for lithium-ion batteries, cable shielding layers, and heat-conducting components for refrigeration equipment), construction (such as aluminum foil bubble wrap and aluminum foil composite rock wool boards), transportation (such as automotive heat and sound insulation mats), printing (such as hot stamping foil), and aerospace. However, traditional single aluminum foil is heavy, lacks flexibility, and has low strength, making it prone to tearing during processing or use. Repeated bending can cause cracks, affecting its lifespan. Therefore, aluminum foil is often combined with polymer plastics, paper, or other thin metal sheets to create composite materials.

[0003] In the preparation of composite aluminum foil, the surface treatment of the aluminum foil, the selection of adhesives, the coating process, and the curing of the adhesives all affect the flexibility and interlayer bonding strength of the composite aluminum foil, which in turn relates to the service life of the composite aluminum foil. For example, the surface of aluminum foil has a dense alumina film, which is a polar surface, while plastics are mostly non-polar polymers, resulting in a large difference in interfacial tension between the two. If the adhesive is not selected properly or the pretreatment process of the aluminum foil surface is inappropriate, it will lead to insufficient interfacial bonding strength, resulting in delamination and blistering during subsequent processing (such as stamping and heat sealing) or use (such as in high-temperature environments). Summary of the Invention

[0004] To address the problem of insufficient interlayer bonding strength in composite aluminum foil, which affects product service quality and lifespan, this invention provides a composite aluminum foil and its preparation method. The process involves pre-treating the aluminum foil, laminating it with a plastic substrate, followed by pre-baking, high-temperature pressing, post-baking, and surface treatment to obtain a composite aluminum foil with high interlayer bonding strength.

[0005] Specifically, in order to achieve the above objectives, the present invention adopts the following technical solution: A method for preparing composite aluminum foil includes the following steps: S1. Clean the aluminum foil and immerse the cleaned aluminum foil in a passivation solution for passivation treatment; the passivation solution is composed of chromate and phosphate. S2. Apply adhesive evenly to one side of the aluminum foil treated in step S1 to obtain a first adhesive layer; attach a plastic substrate to the surface of the first adhesive layer; apply adhesive evenly to the surface of the plastic substrate away from the first adhesive layer to obtain a second adhesive layer; attach another aluminum foil treated in step S1 to the exposed surface of the second adhesive layer. S3. Bake the composite aluminum foil obtained in step S2 to allow the adhesive to initially cure. S4. The composite aluminum foil obtained in step S3 is pressed at 120℃~180℃ and 0.5MPa~2MPa. S5. Bake the composite aluminum foil obtained in step S4 to completely cure the adhesive. S6. Use an acidic reagent to remove the oxides on the surface of the composite aluminum foil obtained in step S5 to obtain the finished composite aluminum foil.

[0006] In the preferred embodiment, the aluminum foil is cleaned by ultrasonic treatment in step S1, and the ultrasonic conditions are as follows: power of 300W~500W, frequency of 20kHz~80kHz, and time of 10~30 seconds.

[0007] In a further preferred embodiment, when cleaning the aluminum foil using ultrasonic treatment in step S1, a neutral cleaning agent is added.

[0008] In a further preferred embodiment, the neutral cleaning agent mainly comprises at least two components selected from fatty alcohol polyoxyethylene ether, alkyl glycoside, fatty acid methyl ester ethoxylate, and low-foaming polyether.

[0009] In a preferred embodiment, the passivation solution in step S1 is composed of sodium chromate and sodium dihydrogen phosphate, wherein the concentration of sodium chromate in the passivation solution is 0.05 mol / L to 0.2 mol / L, and the concentration of sodium dihydrogen phosphate is 0.1 mol / L to 0.3 mol / L.

[0010] In a preferred embodiment, the thickness of the aluminum foil obtained after processing in step S1 is 1~8 μm.

[0011] In a preferred embodiment, the adhesive used in step S2 is either a polyurethane adhesive or an acrylic adhesive.

[0012] In a preferred embodiment, the plastic substrate in step S2 is a polypropylene film, a polyethylene terephthalate film, or a polyimide film.

[0013] In a preferred embodiment, the thickness of the plastic substrate in step S2 is 10~50μm.

[0014] In a preferred embodiment, when preparing the first adhesive layer in step S2, the coating amount of the adhesive is 3~10 g / m². 2 .

[0015] In a preferred embodiment, when preparing the second adhesive layer in step S2, the adhesive coating amount is 3~10 g / m². 2 .

[0016] In the preferred embodiment, the baking temperature in step S3 is 80℃~100℃, and the baking time is 2~5 minutes.

[0017] In the preferred embodiment, the baking temperature in step S5 is 140℃~160℃, and the baking time is 1~2 hours.

[0018] In a preferred embodiment, the acidic reagent in step S6 is any one of citric acid aqueous solution, sulfuric acid aqueous solution, and hydrochloric acid, and the percentage content of solute in the acidic reagent is 2wt%~4wt%.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: In this invention, after cleaning the aluminum foil, it is passivated using a passivation solution composed of chromate and phosphate to improve the corrosion resistance of the aluminum foil and its adhesion to the adhesive. After laminating the aluminum foil and plastic substrate with an adhesive, the adhesive is first pre-baked to allow it to initially cure, then pressed under high temperature and pressure, followed by baking to fully cure the adhesive. Finally, an acidic reagent is used to remove the oxides from the surface of the composite aluminum foil, resulting in a composite aluminum foil with an interlayer bonding strength ≥8N / 15mm. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the composite aluminum foil prepared according to the present invention.

[0021] In the figure: 1. First aluminum foil; 2. First adhesive layer; 3. Plastic substrate; 4. Second adhesive layer; 5. Second aluminum foil. Detailed Implementation

[0022] The following description, in conjunction with embodiments, clearly and completely describes the technical solutions of this application, so that those skilled in the art can fully understand this application. Obviously, the described embodiments are merely some preferred embodiments of this application, and not all embodiments. Any equivalent modifications or substitutions made by those skilled in the art to the following embodiments without creative effort are within the protection scope of this application.

[0023] The ordinal numbers used in this application, such as “first” and “second”, are used only for descriptive purposes to distinguish identical or similar objects, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0024] Specific embodiments of the present invention are provided as follows: Figure 1 The method for preparing a composite aluminum foil includes the following steps: S1. Aluminum Foil Pretreatment: The aluminum foil is treated using a combination of ultrasonic cleaning and chemical passivation. The aluminum foil is placed in an ultrasonic cleaning device with a neutral cleaning agent added, and ultrasonically cleaned for 10-30 seconds at a power of 300W-500W and a frequency of 20kHz-80kHz to remove oil and dust from the surface. The cleaned aluminum foil is then immersed in a passivation solution for 10-30 seconds to form a dense passivation film on the surface, improving its corrosion resistance and adhesion to adhesives. The passivation solution consists of sodium chromate and sodium dihydrogen phosphate, with the sodium chromate concentration being 0.05mol / L-0.2mol / L and the sodium dihydrogen phosphate concentration being 0.1mol / L-0.3mol / L. The thickness of the pretreated aluminum foil is 1-8μm.

[0025] S2. Adhesive Coating and Lamination: The adhesive is evenly coated onto one side surface of the first aluminum foil 1 after step S1 by roller coating, with a coating amount of 3g / m². 2 ~10g / m 2 A first adhesive layer 2 is obtained. The plastic substrate 3 is then smoothly bonded to the exposed surface of the first adhesive layer 2, ensuring no bubbles or wrinkles. The same adhesive is then evenly coated onto the side of the plastic substrate 3 facing away from the first adhesive layer 2 using a roller coating method, with a coating amount of 3 g / m². 2 ~10g / m 2 A second adhesive layer 4 is obtained; a second aluminum foil 5, which has undergone the pretreatment in step S1, is then bonded to the exposed surface of the second adhesive layer 4.

[0026] S3. Pre-baking: Bake the composite aluminum foil obtained in step S2 at 80℃~100℃ for 2~5 minutes to prevent the adhesive from overflowing.

[0027] S4. High-temperature pressing: Place the pre-baked composite aluminum foil from step S3 into a pressing machine, set the pressing temperature to 120℃~180℃, the pressure to 0.5MPa~2MPa, and press for 30 minutes to ensure that the layers of the composite aluminum foil are fully bonded and that the interlayer bonding force is guaranteed.

[0028] S5. Post-baking: Place the composite aluminum foil obtained in step S4 into an oven, set the baking temperature to 140-160℃, and bake for 1-2 hours to allow the adhesive to fully cure and further enhance the interlayer bonding force.

[0029] S6. Surface Treatment: The composite aluminum foil obtained in step S5 is treated with an acidic reagent to remove surface oxides, resulting in the following: Figure 1 The composite aluminum foil shown. The acidic reagent is one of 2wt%~4wt% citric acid, 2wt%~4wt% sulfuric acid, or 2wt%~4wt% hydrochloric acid.

[0030] As an example, the neutral cleaning agent in step S1 is at least one of LEO-116, JC-018, and SELRNA D2202.

[0031] As an example, in step S2, the plastic substrate is at least one of PP (polypropylene) film, PET (polyethylene terephthalate) film, and PI (polyimide) film.

[0032] As an example, the adhesive used in step S2 is a polyurethane adhesive, specifically Henkel Loctite 3542.

[0033] Example 1 A method for preparing composite aluminum foil includes the following steps: S1. Aluminum Foil Pretreatment: The aluminum foil is treated using a combination of ultrasonic cleaning and chemical passivation. The aluminum foil is placed in an ultrasonic cleaning device with a neutral cleaning agent, LEO-116, and ultrasonically cleaned for 20 seconds at 400W power and 60kHz frequency to remove oil and dust from the surface. The cleaned aluminum foil is then immersed in a passivation solution for 30 seconds to form a dense passivation film on the surface, improving its corrosion resistance and adhesion to adhesives. The passivation solution consists of an aqueous solution of sodium chromate and sodium dihydrogen phosphate, with a sodium chromate concentration of 0.1 mol / L and a sodium dihydrogen phosphate concentration of 0.2 mol / L. The thickness of the pretreated aluminum foil is 5 μm.

[0034] S2. Coating and Lamination: Henkel Loctite 3542 is uniformly coated onto one side of the first aluminum foil treated in step S1 using a roller coating method, with a coating amount of 6 g / m². 2 A first adhesive layer is obtained. A 30 μm thick polypropylene (PP) film is smoothly bonded to the exposed surface of the first adhesive layer, ensuring no bubbles or wrinkles. The same adhesive is then uniformly coated onto the side of the PP film opposite to the first adhesive layer using a roller coating method, with a coating amount of 6 g / m². 2 A second adhesive layer is obtained; a second aluminum foil pretreated in step S1 is then bonded to the exposed surface of the second adhesive layer.

[0035] S3. Pre-baking: Bake the composite aluminum foil obtained in step S2 at 90°C for 3 minutes to prevent adhesive from overflowing.

[0036] S4. High-temperature pressing: Place the pre-baked composite aluminum foil from step S3 into a pressing machine, set the pressing temperature to 150℃ and the pressure to 1.5MPa, and press for 30 minutes to ensure that the layers of the composite aluminum foil are fully bonded together and that the interlayer bonding force is guaranteed.

[0037] S5. Post-baking: Place the composite aluminum foil obtained in step S4 into an oven, set the baking temperature to 150℃, and the baking time to 1.5 hours to allow the adhesive to fully cure and further enhance the interlayer bonding force.

[0038] S6. Surface treatment: The composite aluminum foil obtained in step S5 is treated with a 3% citric acid aqueous solution to remove surface oxides.

[0039] Example 2 A method for preparing composite aluminum foil includes the following steps: S1. Aluminum Foil Pretreatment: The aluminum foil is treated using a combination of ultrasonic cleaning and chemical passivation. The aluminum foil is placed in an ultrasonic cleaning device with a neutral cleaning agent, LEO-116, and ultrasonically cleaned for 10 seconds at 300W power and 80kHz frequency to remove oil and dust from the surface. The cleaned aluminum foil is then immersed in a passivation solution for 20 seconds to form a dense passivation film on the surface, improving its corrosion resistance and adhesion to adhesives. The passivation solution consists of an aqueous solution of sodium chromate and an aqueous solution of sodium dihydrogen phosphate, with a sodium chromate concentration of 0.05mol / L and a sodium dihydrogen phosphate concentration of 0.3mol / L. The thickness of the pretreated aluminum foil is 1μm.

[0040] S2. Coating and Lamination: Henkel Loctite 3542 is uniformly coated onto one side of the first aluminum foil treated in step S1 using a roller coating method, with a coating amount of 5 g / m². 2 A first adhesive layer is obtained. A PET film (10 μm thick) is smoothly laminated onto the exposed surface of the first adhesive layer, ensuring no bubbles or wrinkles. The same adhesive is then uniformly coated onto the side of the PET film opposite the first adhesive layer using a roller coating method, with a coating amount of 5 g / m². 2 A second adhesive layer is obtained; a second aluminum foil pretreated in step S1 is then bonded to the exposed surface of the second adhesive layer.

[0041] S3. Pre-baking: Bake the composite aluminum foil obtained in step S2 at 80°C for 5 minutes to prevent adhesive from overflowing.

[0042] S4. High-temperature pressing: Place the pre-baked composite aluminum foil from step S3 into a pressing machine, set the pressing temperature to 120℃ and the pressure to 2MPa, and press for 30 minutes to ensure that the layers of the composite aluminum foil are fully bonded and that the interlayer bonding force is guaranteed.

[0043] S5. Post-baking: Place the composite aluminum foil obtained in step S4 into an oven, set the baking temperature to 160℃, and bake for 1 hour to allow the adhesive to fully cure and further enhance the interlayer bonding force.

[0044] S6. Surface treatment: The composite aluminum foil obtained in step S5 is treated with 2wt% sulfuric acid to remove surface oxides.

[0045] Example 3 A method for preparing composite aluminum foil includes the following steps: S1. Aluminum Foil Pretreatment: The aluminum foil is treated using a combination of ultrasonic cleaning and chemical passivation. The aluminum foil is placed in an ultrasonic cleaning device with a neutral cleaning agent, LEO-116, and ultrasonically cleaned for 30 seconds at 500W power and 20kHz frequency to remove oil and dust from the surface. The cleaned aluminum foil is then immersed in a passivation solution for 10 seconds to form a dense passivation film on the surface, improving its corrosion resistance and adhesion to adhesives. The passivation solution consists of an aqueous solution of sodium chromate and sodium dihydrogen phosphate, with a sodium chromate concentration of 0.2 mol / L and a sodium dihydrogen phosphate concentration of 0.1 mol / L. The thickness of the pretreated aluminum foil is 8 μm.

[0046] S2. Coating and Lamination: Henkel Loctite 3542 is uniformly coated onto one side of the first aluminum foil treated in step S1 using a roller coating method, with a coating amount of 8 g / m². 2 A first adhesive layer is obtained. A PI film (50 μm thick) is smoothly bonded to the exposed surface of the first adhesive layer, ensuring no bubbles or wrinkles. The same adhesive is then uniformly coated onto the side of the PI film facing away from the first adhesive layer using a roller coating method, with a coating amount of 8 g / m². 2 A second adhesive layer is obtained; a second aluminum foil pretreated in step S1 is then bonded to the exposed surface of the second adhesive layer.

[0047] S3. Pre-baking: Bake the composite aluminum foil obtained in step S2 at 100°C for 2 minutes to prevent adhesive from overflowing.

[0048] S4. High-temperature pressing: Place the pre-baked composite aluminum foil from step S3 into a pressing machine, set the pressing temperature to 180℃ and the pressure to 0.5MPa, and press for 30 minutes to ensure that the layers of the composite aluminum foil are fully bonded and that the interlayer bonding force is guaranteed.

[0049] S5. Post-baking: Place the composite aluminum foil obtained in step S4 into an oven, set the baking temperature to 140℃, and bake for 2 hours to allow the adhesive to fully cure and further enhance the interlayer bonding force.

[0050] S6. Surface treatment: The composite aluminum foil obtained in step S5 is treated with 4wt% hydrochloric acid to remove surface oxides.

[0051] Example 4 The method for preparing the composite aluminum foil in this embodiment is basically the same as that in Example 1, except that: when preparing the first adhesive layer in step S2, the coating amount of the adhesive is 3g / m². 2 When preparing the second adhesive layer, the adhesive coating amount is 10 g / m². 2 .

[0052] Example 5 The method for preparing the composite aluminum foil in this embodiment is basically the same as that in Example 1, except that: when preparing the first adhesive layer in step S2, the coating amount of the adhesive is 10 g / m². 2 When preparing the second adhesive layer, the adhesive coating amount is 3 g / m². 2 .

[0053] Comparative Example 1 The difference between the preparation method of the composite aluminum foil in this comparative example and that in Example 1 is: S1. Aluminum Foil Pretreatment: The aluminum foil is treated using a combination of ultrasonic cleaning and chemical passivation. The aluminum foil is placed in an ultrasonic cleaning device, and a neutral cleaning agent, LEO-116, is added. The foil is ultrasonically cleaned for 20 seconds at a power of 400W and a frequency of 60kHz to remove oil and dust from its surface. That is, in this comparative example, step S1 does not involve passivation of the aluminum foil.

[0054] Comparative Example 2 The difference between the preparation method of the composite aluminum foil in this comparative example and that in Example 1 is that step S3 is omitted. That is, in this comparative example, step S4 is performed directly after step S2.

[0055] Comparative Example 3 The difference between the preparation method of the composite aluminum foil in this comparative example and that in Example 1 is that the adhesive used in step S2 is Loctite EA 9492 (purchased from Henkel Loctite (China) Co., Ltd.).

[0056] Product performance testing The properties of the composite aluminum foils prepared in Examples 1-5 and Comparative Examples 1-3 were tested according to the methods of GB / T 22638.11-2023 "Test Methods for Aluminum Foil - Part 11: Tests for Mechanical Properties" and GB / T2792-2014 "Test Method for Peel Strength of Adhesive Tapes". The test results are shown in Table 1.

[0057] Table 1 Performance test results of composite aluminum foils prepared by different methods

[0058] In Table 1, peel strength I represents the peel strength between the first aluminum foil and the plastic substrate, and peel strength II represents the peel strength between the second aluminum foil and the plastic substrate. As can be seen from the data in Table 1, the interlayer bonding strength of the composite aluminum foil prepared by this invention is all >8 N / 15 mm.

[0059] The embodiments described above are merely preferred embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by anyone skilled in the art. Any simple equivalent changes and modifications made based on the scope of protection claimed in this application and the content of the specification should be included within the scope of protection of this application.

Claims

1. A method for preparing composite aluminum foil, characterized in that, Includes the following steps: S1. Clean the aluminum foil and immerse the cleaned aluminum foil in a passivation solution for passivation treatment; the passivation solution is composed of chromate and phosphate. S2. Apply the adhesive evenly to one side of the aluminum foil treated in step S1 to obtain the first adhesive layer. The plastic substrate is bonded to the surface of the first adhesive layer; A second adhesive layer is obtained by uniformly applying adhesive to the surface of the plastic substrate on the side opposite to the first adhesive layer; another aluminum foil processed in step S1 is then bonded to the exposed surface of the second adhesive layer. S3. Bake the composite aluminum foil obtained in step S2 to allow the adhesive to initially cure. S4. The composite aluminum foil obtained in step S3 is pressed at 120℃~180℃ and 0.5MPa~2MPa. S5. Bake the composite aluminum foil obtained in step S4 to completely cure the adhesive. S6. Use an acidic reagent to remove the oxides on the surface of the composite aluminum foil obtained in step S5 to obtain the finished composite aluminum foil.

2. The preparation method according to claim 1, characterized in that, In step S1, the aluminum foil is cleaned by ultrasonic treatment. The ultrasonic conditions are as follows: power of 300W~500W, frequency of 20kHz~80kHz, and time of 10~30 seconds.

3. The preparation method according to claim 1, characterized in that, The passivation solution in step S1 is composed of sodium chromate and sodium dihydrogen phosphate. The concentration of sodium chromate in the passivation solution is 0.05 mol / L to 0.2 mol / L, and the concentration of sodium dihydrogen phosphate is 0.1 mol / L to 0.3 mol / L.

4. The preparation method according to claim 1, characterized in that, The adhesive mentioned in step S2 is either a polyurethane adhesive or an acrylic adhesive.

5. The preparation method according to claim 1, characterized in that, The plastic substrate mentioned in step S2 is a polypropylene film, a polyethylene terephthalate film, or a polyimide film.

6. The preparation method according to claim 1, characterized in that, In step S2, the amount of adhesive applied when preparing the first adhesive layer is 3~10 g / m². 2 ; or / and, when preparing the second adhesive layer, the adhesive coating amount is 3~10 g / m 2 .

7. The preparation method according to claim 1, characterized in that, In step S3, the baking temperature is 80℃~100℃ and the baking time is 2~5 minutes.

8. The preparation method according to claim 1, characterized in that, In step S5, the baking temperature is 140℃~160℃ and the baking time is 1~2 hours.

9. The preparation method according to claim 1, characterized in that, The acidic reagent mentioned in step S6 is any one of citric acid aqueous solution, sulfuric acid aqueous solution, and hydrochloric acid, and the percentage content of solute in the acidic reagent is 2wt%~4wt%.

10. The composite aluminum foil prepared by the preparation method according to any one of claims 1 to 9.

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