Moisture and heat resistant cold aluminum sheet and method of making same

Abstract

The application belongs to the technical field of cold aluminum sheet, and specifically provides a moisture and heat resistant cold aluminum sheet and a preparation method thereof. The moisture and heat resistant cold aluminum sheet comprises, from top to bottom, a polyamide layer, a bonding layer, an aluminum foil layer, a bonding layer and a polyvinyl chloride layer, wherein the bonding layer is formed by curing a polyurethane adhesive; and the aluminum foil layer is first cleaned and then sprayed with a phosphonic acid compound treatment solution. In the preparation of the moisture and heat resistant cold aluminum sheet, polyurethane adhesive is first coated on both sides of the treated aluminum foil, and then the polyurethane adhesive is cured to be combined with a polyamide film and a polyvinyl chloride film, and the moisture and heat resistant cold aluminum sheet is obtained after aging. The cold aluminum sheet has good temperature resistance and moisture and heat resistance, and does not delaminate and has a low bubble breaking rate when subjected to bubble cap deep drawing.

Description

Technical Field

[0001] This application belongs to the field of cold aluminum sheet technology, and in particular relates to a moisture- and heat-resistant cold aluminum sheet and its preparation method. Background Technology

[0002] Cold-pressed aluminum sheet is a multi-layer composite material widely used in high-end flexible packaging fields such as pharmaceutical blister packaging and food thermoforming trays. It is usually composed of polyamide (PA), aluminum foil (Al), and polyvinyl chloride (PVC) bonded together with adhesives. Polyamide provides high mechanical strength, puncture resistance, and grease resistance; PVC provides good heat-sealing and forming capabilities; the adhesive is generally a polyurethane adhesive to achieve interlayer bonding at the polyamide / aluminum foil interface and the aluminum foil / PVC interface; aluminum foil has excellent gas (oxygen, water vapor) barrier properties, complete light-blocking properties, excellent mechanical protection properties, and excellent deep-drawing forming properties. Therefore, cold-pressed aluminum sheet has become the preferred packaging material for products sensitive to moisture, heat, and oxygen.

[0003] However, with increasingly stringent market requirements for the shelf life of pharmaceuticals and food, and the challenges of global climate diversification, existing cold-pressed aluminum sheets still face the following key technical problems under long-term humid and hot environments: After deep processing, blister packs in prolonged humid and hot environments experience delamination between the composite layers, leading to blister breakage, packaging seal failure, and deterioration of the contents, ultimately causing significant economic losses and safety hazards. The delamination is mainly caused by the large number of urethane and urea groups in the polyurethane adhesive molecular backbone. In humid and hot environments, water molecules, acting as nucleophiles, attack the carbonyl groups in the molecular backbone, causing chemical bond breakage, significantly reducing interfacial bonding strength, and resulting in interfacial debonding. Furthermore, in humid and hot environments, the alumina film on the aluminum foil surface is also easily damaged by competitive adsorption of water molecules, further exacerbating interfacial debonding.

[0004] To address the issues of reduced interfacial bonding strength and interfacial debonding, a common approach is to improve the hydrolysis resistance of polyurethane adhesives. For example, aliphatic isocyanates can be used to prepare polyurethane. However, aliphatic polyurethanes have relatively low initial bond strength, and their mechanical properties and heat resistance are also reduced. Therefore, developing a cold aluminum sheet with high initial bond strength and good resistance to damp heat is of great significance. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a moisture- and heat-resistant aluminum sheet and its preparation method.

[0006] This application first provides a moisture- and heat-resistant aluminum sheet, which consists of a polyamide layer, an adhesive layer, an aluminum foil layer, an adhesive layer, and a polyvinyl chloride layer from top to bottom. The adhesive layer is formed by curing a polyurethane adhesive. The aluminum foil layer is processed using a method comprising the following steps: S1: The aluminum foil is sequentially subjected to alkaline washing, hot water washing, acid washing, water washing, and drying to obtain clean aluminum foil; S2: Dissolve alkylphosphonic acid compound and hydroxyethylidene diphosphonic acid in an alcohol-water medium, add an acid catalyst, and adjust the pH to 3-5 to prepare a treatment solution. Coat the treatment solution onto the surface of a clean aluminum foil and allow it to cure.

[0007] Furthermore, the polyamide layer has a thickness of 15-30 μm, the aluminum foil layer has a thickness of 20-60 μm, and the polyvinyl chloride layer has a thickness of 40-60 μm.

[0008] Furthermore, in step S2, the alkylphosphonic acid compound includes, but is not limited to, one or more of 1-dodecylphosphonic acid, 1-tetradecylphosphonic acid, 1-hexadecylphosphonic acid, and 1-octadecylphosphonic acid; and / or, the molar ratio of the alkylphosphonic acid compound to hydroxyethylidene diphosphonic acid is (5-9.5):(0.5-5).

[0009] Furthermore, in step S2, the curing temperature is 80-140℃.

[0010] Furthermore, the polyurethane adhesive is prepared by reacting polycarbonate diol and diisocyanate under the action of a catalyst.

[0011] Furthermore, the diisocyanate includes, but is not limited to, one or more of isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and toluene diisocyanate; the molar ratio of polycarbonate diol to diisocyanate is 1:(1.05-1.2).

[0012] Furthermore, the polycarbonate diol is prepared by reacting organic carbonates with long-chain alkyl diols under the action of a catalyst.

[0013] Furthermore, the organic carbonate includes, but is not limited to, dimethyl carbonate or diphenyl carbonate; and / or, the long-chain alkyl diol includes, but is not limited to, one or more of 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecyldiol, and 1,16-hexadecanediol; and / or, the molar ratio of the organic carbonate to the long-chain alkyl diol is 1:(1-1.1).

[0014] This application also provides a method for preparing a moisture- and heat-resistant aluminum sheet, comprising the following steps: The polyurethane adhesive is coated on both sides of the treated aluminum foil, cured and dried, and then laminated with a corona-treated polyamide film and a polyvinyl chloride film. After further curing, the product is ready.

[0015] Furthermore, the dry coating amount on both sides is 2-4 g / ㎡, the curing temperature is 80-100℃, and the curing conditions are: temperature 40-60℃, time 48-72h.

[0016] Compared with the prior art, this application has the following beneficial effects: 1. This application utilizes the reaction between the phosphonic acid group of long-chain alkyl phosphonic acid and the hydroxyl group on the surface of aluminum foil to form a hydrophobic layer, reducing the adsorption and penetration of water molecules. The hydroxyl group in hydroxyethylidene diphosphonic acid reacts with the isocyanate group in the polyurethane adhesive, thereby enhancing the interfacial bonding strength between the aluminum foil and the adhesive. This reduces the damage of water molecules to the interfacial layer, making it less likely for the aluminum foil layer to be peeled off from the polyamide layer and the polyvinyl chloride layer.

[0017] 2. The polycarbonate-based polyurethane of this application exhibits excellent water resistance. Furthermore, the introduction of long carbon chains into the polycarbonate diol enhances hydrophobicity, further reducing the water absorption rate of the polyurethane adhesive and effectively slowing down the diffusion rate of water molecules within the adhesive layer. In addition, the polycarbonate-based polyurethane also possesses excellent mechanical properties, heat resistance, and flexibility. During deep drawing, the adhesive layer can stretch synergistically with the aluminum foil without generating microcracks, thereby protecting the aluminum foil from stress concentration and tearing. Detailed Implementation

[0018] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments, clearly and completely describing the technical solutions in the embodiments of this application. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] Based on extensive experimental research, this application provides a moisture- and heat-resistant aluminum sheet, which consists of, from top to bottom, a polyamide layer, an adhesive layer, an aluminum foil layer, an adhesive layer, and a polyvinyl chloride layer, wherein the adhesive layer is formed by curing a polyurethane adhesive. The aluminum foil layer is processed using a method comprising the following steps: S1: The aluminum foil is sequentially subjected to alkaline washing, hot water washing, acid washing, water washing, and drying to obtain clean aluminum foil; S2: Dissolve alkylphosphonic acid compound and hydroxyethylidene diphosphonic acid in an alcohol-water medium, add an acid catalyst, and adjust the pH to 3-5 to prepare a treatment solution. Coat the treatment solution onto the surface of a clean aluminum foil and allow it to cure.

[0020] In some embodiments of this application, the aluminum foil is cleaned by alkaline washing, water washing, and acid washing to remove rolling oil and natural oxide layer contaminants from the surface of the aluminum foil, exposing a surface rich in active sites. This is beneficial for improving the adhesion of the coating and reducing interfacial separation. After cleaning, the aluminum foil surface exposes active hydroxyl groups, which undergo condensation reactions with the phosphonic acid groups at one end of the phosphonic acid compound to form stable covalent bonds, hindering water molecules from entering the interfacial layer and causing damage to the interface. Specifically, the alkyl groups of the alkylphosphonic acid compound form a hydrophobic layer on the aluminum foil surface, reducing the adsorption and penetration of water molecules and hindering water molecules from entering the interfacial layer, thereby inhibiting wet peeling. The hydroxyl groups in hydroxyethylidene diphosphonic acid can react with the isocyanate groups in the polyurethane adhesive, increasing the bonding strength with the polyurethane adhesive and further reducing interfacial separation.

[0021] In some embodiments of this application, the thickness of the polyamide layer is 15-30 μm, for example, it can be 15 μm, 18 μm, 20 μm, 25 μm, 28 μm, or 30 μm; the thickness of the aluminum foil layer is 20-60 μm, for example, it can be 20 μm, 25 μm, 28 μm, 30 μm, 35 μm, 38 μm, 40 μm, 45 μm, 48 μm, 50 μm, 55 μm, or 60 μm; and the thickness of the polyvinyl chloride layer is 40-60 μm, for example, it can be 40 μm, 45 μm, 50 μm, 55 μm, or 60 μm.

[0022] In some embodiments of this application, in step S2, the alkylphosphonic acid compound includes, but is not limited to, one or more of 1-dodecylphosphonic acid, 1-tetradecylphosphonic acid, 1-hexadecylphosphonic acid, and 1-octadecylphosphonic acid; long-chain alkyl groups can provide strong hydrophobicity, reduce the adsorption and permeation of water molecules, and reduce the influence of water molecules on the interface.

[0023] In some embodiments of this application, the molar ratio of the alkylphosphonic acid compound to hydroxyethylidene diphosphonic acid is (5-9.5):(0.5-5), for example, it can be 5:5, 5.5:4.5, 6:4, 6.5:3.5, 7:3, 7.5:2.5, 8:2, 8.5:1.5, 9:1, 9.5:0.5.

[0024] In some embodiments of this application, the curing temperature in step S2 is 80-140℃, for example, it can be 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, or 140℃. In some embodiments of this application, the polyurethane adhesive is prepared by reacting polycarbonate diol and diisocyanate under the action of a catalyst.

[0025] In some embodiments of this application, the polyurethane adhesive exhibits excellent weather resistance and bonding performance, achieving good adhesion to various substrates. Because polycarbonate diol molecules contain carbonate groups, possessing both polarity and a degree of flexibility, the adhesive layer can stretch synergistically with the aluminum foil during deep drawing, preventing microcracks and thus protecting the aluminum foil from stress concentration and tearing. The polyurethane synthesized from polycarbonate diol combines the excellent mechanical properties and heat resistance of polyester-type polyurethane with the excellent water resistance of polyether-type polyurethane.

[0026] In some embodiments of this application, the diisocyanate includes, but is not limited to, one or more of isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and toluene diisocyanate.

[0027] In some embodiments of this application, the molar ratio of polycarbonate diol to diisocyanate is 1:(1.05-1.2), for example, it can be 1:1.05, 1:1.07, 1:1.1, 1:1.15, 1:1.17, or 1:1.2.

[0028] In some embodiments of this application, the polycarbonate diol is prepared by reacting organic carbonates with long-chain alkyl diols under the action of a catalyst.

[0029] In some embodiments of this application, the organic carbonate includes, but is not limited to, dimethyl carbonate or diphenyl carbonate.

[0030] In some embodiments of this application, the long-chain alkyl diols include, but are not limited to, one or more of 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecyldiol, and 1,16-hexadecanediol; the introduction of long-chain alkyl groups enhances the hydrophobicity of polyurethane, further reducing the water absorption rate of the polyurethane adhesive, thereby effectively slowing down the diffusion rate of water molecules inside the adhesive layer.

[0031] In some embodiments of this application, the molar ratio of the organic carbonate to the long-chain alkyl diol is 1:(1-1.1), for example, it can be 1:1, 1:1.03, 1:1.05, 1:1.07, or 1:1.1.

[0032] This application also provides a method for preparing a moisture- and heat-resistant aluminum sheet, comprising the following steps: The polyurethane adhesive is coated on both sides of the treated aluminum foil, cured and dried, and then laminated with a corona-treated polyamide film and a polyvinyl chloride film. After further curing, the product is ready.

[0033] In some embodiments of this application, the dry coating amount on both sides is 2-4 g / m², for example, 2 g / m², 2.5 g / m², 3 g / m², 3.5 g / m², or 4 g / m²; the curing temperature is 80-100℃, for example, 80℃, 85℃, 90℃, 95℃, or 100℃; the curing conditions are: temperature 40-60℃, for example, 40℃, 45℃, 50℃, 55℃, or 60℃; and time 48-72h, for example, 48h, 60h, or 72h.

[0034] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0035] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0036] Example 1 The moisture- and heat-resistant aluminum sheet of this embodiment includes the following structure: from top to bottom, it consists of a PA layer, an adhesive layer, an aluminum foil layer, an adhesive layer, and a PVC layer; the adhesive layer is formed by curing polyurethane adhesive. The method for preparing the moisture- and heat-resistant cold aluminum sheet in this embodiment includes the following steps: (1) Take an aluminum foil with a thickness of 35μm and clean it by online spraying at a speed of 15m / min: First, spray with 2wt% sodium hydroxide solution for 15s, then spray with 60℃ deionized water for 20s, then spray with 5wt% nitric acid solution for 10s, and finally spray with deionized water for 15s. After blowing with 100℃ air for 20s, clean aluminum foil is obtained. (2) Mix octadecylphosphonic acid and hydroxyethylidene diphosphonic acid in a molar ratio of 6:4, add an alcohol-water mixed solvent (anhydrous ethanol and deionized water in a volume ratio of 90:10) to prepare a solution with a concentration of 5 mmol / L, add 0.5% p-toluenesulfonic acid equal to the sum of the mass of octadecylphosphonic acid and hydroxyethylidene diphosphonic acid, and adjust the pH to 4 to obtain a pretreatment solution; (3) Spray the pretreatment liquid onto the surface of the clean aluminum foil. The running speed of the aluminum foil is 15m / min and the wet film thickness is controlled at 15μm. After spraying, it enters a three-stage oven. The first stage: 80℃, stay for 10s; the second stage: 130℃, stay for 20s; the third stage: 100℃, stay for 20s. After exiting the oven, it is naturally cooled to obtain the pretreated aluminum foil. (4) Coat the pretreated aluminum foil with polyurethane adhesive on both sides, with a dry coating amount of 3g / ㎡ on each side. After coating, dry at 100℃. Then, combine the aluminum foil with a polyamide film (thickness of 25μm) and a polyvinyl chloride film (thickness of 50μm) that have been corona treated. Place the composite film in a constant temperature oven at 45℃ for 60h to cure.

[0037] Example 2 The moisture- and heat-resistant aluminum sheet of this embodiment includes the following structure: from top to bottom, it consists of a PA layer, an adhesive layer, an aluminum foil layer, an adhesive layer, and a PVC layer; the adhesive layer is formed by curing polyurethane adhesive. The method for preparing the polyurethane adhesive in this embodiment includes the following steps: Weigh 20g of polycarbonate diol and place it in a round-bottom flask. Add 100ml of tetrahydrofuran and stir to dissolve. Then add 4.50g of isophorone diisocyanate. After evacuating the entire apparatus and circulating nitrogen three times, heat it to 60℃. Under nitrogen protection, add 10g of ethyl acetate containing 6mg of dibutyltin dilaurate and stir to react for 2h. After the reaction is complete, cool it to 40℃ and add 0.6g of 1,6-hexanediol and an appropriate amount of ethyl acetate to adjust the solid content. The method for preparing polycarbonate diol in this embodiment includes the following steps: Weigh out 9g of diphenyl carbonate and place it in a flask. Add 7.6g of 1,8-octanediol and 10.5g of 1,12-dodecyl diol. Under nitrogen protection, heat to 170℃ and stir until melted. Add 4mg of dibutyltin dilaurate and react for 2h. Perform vacuum distillation. After cooling to room temperature, add 200mL of tetrahydrofuran and stir for 30min. Precipitate with methanol, filter and dry to obtain the product. The preparation method of the moisture- and heat-resistant aluminum sheet in this embodiment is the same as that in Example 1.

[0038] Comparative Example 1 The moisture- and heat-resistant aluminum sheet of this comparative example comprises the following structure from top to bottom: PA layer, adhesive layer, aluminum foil layer, adhesive layer, and PVC layer; the adhesive layer is formed by curing polyurethane adhesive. The preparation method of the moisture- and heat-resistant aluminum sheet in this comparative example includes the following steps: (1) Take an aluminum foil with a thickness of 35μm and clean it by online spraying at a speed of 15m / min: First, spray with 2wt% sodium hydroxide solution for 15s, then spray with 60℃ deionized water for 20s, then spray with 5wt% nitric acid solution for 10s, and finally spray with deionized water for 15s. After blowing with 100℃ air for 20s, clean aluminum foil is obtained. (2) Apply polyurethane adhesive to both sides of clean aluminum foil, with a dry coating amount of 3g / ㎡ on each side. After coating, dry at 100℃. Then, combine the aluminum foil with a polyamide film (thickness of 25μm) and a polyvinyl chloride film (thickness of 50μm) that have been corona treated. Place the composite film in a constant temperature oven at 45℃ for 60h to cure.

[0039] Comparative Example 2 The moisture- and heat-resistant aluminum sheet of this comparative example comprises the following structure: from top to bottom, a PA layer, an adhesive layer, an aluminum foil layer, an adhesive layer, and a PVC layer; the adhesive layer is formed by curing polyurethane adhesive. The preparation method of the polyurethane adhesive in this comparative example is the same as that in Example 2; The preparation method of the moisture- and heat-resistant cold aluminum sheet in this comparative example includes the following steps: (1) Take an aluminum foil with a thickness of 35μm and clean it by online spraying at a speed of 15m / min: First, spray with 2wt% sodium hydroxide solution for 15s, then spray with 60℃ deionized water for 20s, then spray with 5wt% nitric acid solution for 10s, and finally spray with deionized water for 15s. After blowing with 100℃ air for 20s, clean aluminum foil is obtained. (2) Apply polyurethane adhesive to both sides of clean aluminum foil, with a dry coating amount of 3g / ㎡ on each side. After coating, dry at 100℃. Then, combine the aluminum foil with a polyamide film (thickness of 25μm) and a polyvinyl chloride film (thickness of 50μm) that have been corona treated. Place the composite film in a constant temperature oven at 45℃ for 60h to cure.

[0040] Performance testing 1. Peel strength test The initial peel strength (23℃×50RH%), high temperature peel strength (120℃), and peel strength after 7 days of damp heat aging (85℃×85RH%) of the damp heat resistant cold aluminum sheets of Examples 1-2 and Comparative Examples 1-2 were tested according to YBB00102003-2015 "Peel Strength Test Method". The strip width was 15mm, the peeling speed was 300mm / min, and 5 parallel samples were tested for each group of samples. The average value was taken. The test results are shown in Table 1.

[0041] 2. Deep-water bubbling rate test A flat blister forming machine was used. The mold was round, the blister depth was 10mm, the diameter was 12mm, the stamping speed was 60 times / min, and 1000 blister were stamped continuously. The vacuum leak detection method was used to detect whether there was leakage. The blister breakage rate = number of leaking blister / 1000 × 100%. The test results are shown in Table 1.

[0042] 3. Deep drawing layering test After 7 days of damp heat aging (85℃×85RH%), the blister samples were cut along the central axis of the blister. The interface was then probed with the tip of a utility knife, and the PA / Al / PVC layer interface was observed under a microscope to determine whether it was delaminated. The criteria for judgment were: no delamination (the interface was completely bonded and there was no separation when probed), slight delamination (local delamination but not continuous separation), and severe delamination (the interface was completely separated). The results are shown in Table 1.

[0043] 4. Water absorption rate test of polyurethane adhesive Take the polyurethane adhesive from Examples 1-2, cure it into a 2mm thick test piece, weigh it W0, and then place it in a humid heat aging chamber (85℃×85RH%) for 7 days. Take it out, wipe off the surface moisture, weigh it W1, and calculate the water absorption rate according to the formula (W1-W0) / W0×100%.

[0044] Table 1 Performance Test Results As can be seen from the interfacial peel strength data in Table 1, the initial peel strength, high-temperature peel strength, and peel strength after damp heat aging of the cold aluminum sheet in the examples are all high, and no interfacial debonding phenomenon is observed, indicating that the cold aluminum sheet has good high-temperature resistance and damp heat resistance. From the damp heat deep drawing delamination data, it can be seen that the cold aluminum sheet in the examples does not exhibit delamination, while the cold aluminum sheet in the comparative example shows slight delamination. From the bubble breaking rate data, it can be seen that the bubble breaking rate of the cold aluminum sheet in the examples is relatively low, and even the bubble breaking rate of the cold aluminum sheet in Example 2 is almost zero. From the water absorption rate data, it can be seen that the polycarbonate-type polyurethane adhesive prepared in Example 2 and Comparative Example 2 has a low water absorption rate, while the commercially available polyurethane adhesive has a relatively high water absorption rate.

[0045] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A moisture- and heat-resistant aluminum sheet, characterized in that: From top to bottom, the layers are: a polyamide layer, an adhesive layer, an aluminum foil layer, another adhesive layer, and a polyvinyl chloride layer. The adhesive layer is formed by curing a polyurethane adhesive. The polyurethane adhesive is prepared by reacting polycarbonate diol and diisocyanate under the action of a catalyst. The polycarbonate diol is prepared by reacting organic carbonate and long-chain alkyl diol under the action of a catalyst. The aluminum foil layer is processed using a method comprising the following steps: S1: The aluminum foil is sequentially subjected to alkaline washing, hot water washing, acid washing, water washing, and drying to obtain clean aluminum foil; S2: Dissolve alkylphosphonic acid compound and hydroxyethylidene diphosphonic acid in an alcohol-water medium, add an acid catalyst, and adjust the pH to 3-5 to prepare a treatment solution. Coat the treatment solution onto the surface of a clean aluminum foil and allow it to cure.

2. The moisture- and heat-resistant aluminum sheet according to claim 1, characterized in that: The polyamide layer has a thickness of 15-30 μm, the aluminum foil layer has a thickness of 20-60 μm, and the polyvinyl chloride layer has a thickness of 40-60 μm.

3. The moisture- and heat-resistant aluminum sheet according to claim 1, characterized in that: In step S2, the alkylphosphonic acid compound is one or more of 1-dodecylphosphonic acid, 1-tetradecylphosphonic acid, 1-hexadecylphosphonic acid, and 1-octadecylphosphonic acid; and / or, the molar ratio of the alkylphosphonic acid compound to hydroxyethylidene diphosphonic acid is (5-9.5):(0.5-5).

4. The moisture- and heat-resistant aluminum sheet according to claim 1, characterized in that: In step S2, the curing temperature is 80-140℃.

5. The moisture- and heat-resistant aluminum sheet according to claim 1, characterized in that: The diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and toluene diisocyanate; the molar ratio of polycarbonate diol to diisocyanate is 1:(1.05-1.2).

6. The moisture- and heat-resistant aluminum sheet according to claim 1, characterized in that: The organic carbonate is dimethyl carbonate or diphenyl carbonate; and / or the long-chain alkyl diol is one or more of 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecyldiol, and 1,16-hexadecanediol; and / or the molar ratio of the organic carbonate to the long-chain alkyl diol is 1:(1-1.1).

7. A method for preparing a moisture- and heat-resistant aluminum sheet according to any one of claims 1-6, characterized in that: Includes the following steps: The polyurethane adhesive is coated on both sides of the treated aluminum foil, cured and dried, and then laminated with a corona-treated polyamide film and a polyvinyl chloride film. After further curing, the product is ready.

8. The method for preparing a moisture- and heat-resistant aluminum sheet according to claim 7, characterized in that: The dry coating amount on both sides is 2-4 g / ㎡, the curing temperature is 80-100℃, and the curing conditions are: temperature 40-60℃, time 48-72h.

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