A paint for an aluminum alloy sheet subjected to an anodizing treatment

Abstract

This invention belongs to the field of coating technology and discloses a coating for anodized aluminum alloy sheets, comprising a clear varnish and a curing agent. The clear varnish is mainly composed of acrylic resin, amino resin, and coating additives. This coating overcomes the technical problems of poor adhesion, poor water resistance, poor impact resistance in thick films, and poor hardness of the pendulum rod at high thicknesses in existing technologies for anodized aluminum alloy sheets. Furthermore, the artificial aging of this coating reaches over 4000 hours.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a coating suitable for anodized aluminum alloy sheets, serving as a protective layer and also for decorative purposes. Background Technology

[0002] With the rapid development of my country's industrialization and automobile industry, coupled with national encouragement for the low-altitude economy, investment in this sector is increasing. Anodized aluminum alloy sheets, possessing a superior metallic texture, high-end appearance, and a gleaming shine, are increasingly being used as decorative components by many automakers. Therefore, coating anodized aluminum alloy sheets has become a new research topic in the coatings industry. Currently, the main challenges in coating anodized aluminum alloy sheets on the market are as follows: 1. The surface tension of anodized aluminum alloy sheets is low, making it difficult for general coatings to wet them effectively, resulting in poor adhesion; 2. The water resistance, hardness, and impact resistance of coatings on anodized aluminum alloy sheets are relatively poor; 3. The artificial aging and weathering resistance of clear coats cannot reach 4000 hours. Summary of the Invention

[0003] The purpose of this invention is to provide a coating suitable for anodized aluminum alloy plates. This coating overcomes the poor adhesion and impact resistance of existing varnishes to anodized aluminum alloy plates. This varnish formulation overcomes the technical problem of poor impact resistance in thick films. It also overcomes the technical problem of poor hardness in existing coatings.

[0004] To achieve the objectives of this invention, the following implementation scheme is provided.

[0005] In one embodiment, a coating of the present invention suitable for anodized aluminum alloy plates comprises a varnish and a curing agent, wherein the varnish is composed of the following components in weight percentage: 64.6% acrylic resin, 10.0% amino resin A15-75, 0.2% leveling agent BYK-390, 0.2% leveling agent BYK-333, 2-5% light stabilizer UV-1130, 1-2.5% light stabilizer UV-292, 10% butyl acetate, 2% adherant ADP, 5% tricresylbenzene, and the balance being amyl acetate as a diluent.

[0006] In some embodiments, the acrylic resin in the coating of the present invention is SETALUX® 1766 VB-64 (abbreviated as "1766 VB-64").

[0007] In some embodiments, the curing agent in the coating of the present invention is an isocyanate.

[0008] In one specific embodiment, the present invention provides a coating suitable for anodized aluminum alloy plates, wherein the varnish is composed of the following weight percentages: Acrylic resin 1766 VB-64 accounts for 64.6%. Amino resin A15-75 accounts for 10.0%. The coating additive BYK-390 accounts for 0.2%. The coating additive BYK-333 accounts for 0.2%. The light stabilizer UV-1130 accounts for 2.0%. The light stabilizer UV-292 accounts for 1.0%. Butyl acetate accounts for 10.0%. Adherent ADP accounted for 2.0%. Trimethylbenzene accounted for 5.0%. The diluent, amyl acetate, accounts for 5.0%.

[0009] In the clear varnish components, coating additives BYK-390 and BYK-333 are leveling agents, UV-1130 and UV-292 are light stabilizers, and Adherant ADP is an adhesion improver that increases toughness.

[0010] Technical effects: The coating of this invention is mainly applicable to the coating of anodized aluminum alloy plates for automobiles. It is a high-gloss, high-transparency coating that can clearly show the brilliant colors of the anodized aluminum alloy plate. It has high fullness and high gloss, good paint surface effect, and orange peel texture. For flat surfaces: LW≦4, SW≦17; for vertical surfaces: LW≦8, SW≦17. It has high adhesion, strong hardness, and weather resistance of over 4000h.

[0011] The coating of this invention contains 10% amino resin A15-75 in the clear varnish, which has a curing effect and works synergistically with the curing agent isocyanate to form a dual curing combination channel. The coating route is the same as that of 2K clear varnish used in automobiles, so that when the film thickness is 300 micrometers, the hardness can reach the pendulum hardness of 210s.

[0012] The coating of this invention only requires a clear varnish to meet the mechanical performance and appearance requirements of coating.

[0013] By combining clear varnish with amino resin and then isocyanate to form a dual curing channel, the pendulum hardness of the topcoat reaches 210s, and the artificial aging level is increased to over 4000h. Detailed Implementation

[0014] The following examples are merely representative and are used to further understand the spirit of the present invention, but do not limit the scope of the present invention in any way.

[0015] Example 1: Varnish of Coating Varnish formula: Acrylic resin 1766 VB-64 accounts for 64.6%. Amino resin A15-75 accounts for 10.0%. The coating additive BYK-390 accounts for 0.2%. The coating additive BYK-333 accounts for 0.2%. The light stabilizer UV-1130 accounts for 2.0%. The light stabilizer UV-292 accounts for 1.0%. Butyl acetate accounts for 10.0%. Adherent ADP accounted for 2.0%. Trimethylbenzene accounted for 5.0%. The diluent, amyl acetate, accounts for 5.0%.

[0016] Preparation method of varnish: Add the ingredients in the formula one by one and mix. Stir at 300 rpm for 8-10 minutes after each addition. After all the ingredients are added, stir and mix evenly to obtain the varnish.

[0017] The coating's fineness, viscosity, and other conventional physicochemical properties were tested and found to meet the requirements of GB 30981.2-2025.

[0018] Paint application process: 1) Wipe the surface of the anodized aluminum alloy plate; 2) Mix the varnish with the curing agent isocyanate (Desmodur ultra N 3390) at a weight ratio of 3:1, and stir well; 3) Spray clear varnish and allow it to dry at room temperature (25℃) for 10 minutes; 4) Place at 120℃ and bake for 40 minutes to complete the paint spraying.

[0019] Example 2 investigated the effects of different types and contents of materials on the performance of varnish. 1. The effect of different types of leveling agents Based on the varnish formulation of Example 1, the effect of different types of leveling agents on the leveling effect of the varnish was investigated. The resins and contents of different types of leveling agents are shown in Table 1 (sample 1 in Table 1 is the control varnish, which is GP41006A high-performance varnish supplied by BASF to Seres, and the same applies below). The varnish was prepared and applied according to the coating process of Example 1. The leveling properties of the varnish were tested, and the results are shown in Table 2.

[0020] Table 1. Different types of leveling agents and their contents (Sample No. 1 is the marketed reference standard)

[0021] "-" indicates an unknown amount.

[0022] Table 2. Leveling property test results of varnish samples with different types of leveling agents

[0023] The results in Table 2 show that the surface leveling properties of sample No. 3 (3) varnish are superior to those of the marketed control varnish. The surface leveling properties of samples No. 5-13 are significantly inferior to those of the marketed product and sample No. 3 (3), indicating that the type of leveling agent has a significant impact on the surface leveling properties of the varnish. Therefore, the preferred leveling agent combination is a 0.2% BYK-333 and a 0.2% BYK-390.

[0024] 2. Investigate the effect of different combinations of light stabilizers on weather resistance. Based on the varnish formulation of Example 1, the effects of different types of light stabilizers (UV light additives) and their different combinations on the weather resistance of the varnish were investigated. Different combinations and contents of light stabilizers are shown in Table 3. The varnish was then prepared. Referring to the varnish coating of Example 1, the weather resistance of the varnish was tested, and the results are shown in Table 4.

[0025] Table 3. Light stabilizers and their content (No. 1 is the marketed reference varnish)

[0026] "-" indicates an unknown amount.

[0027] Table 4. Test results of aging time index for each sample varnish

[0028] The results in Table 1-10 indicate that the weather resistance of sample No. 3 is comparable to that of the marketed reference product. The results also show that different combinations of light stabilizers UV-1130 and UV-292 have no significant impact on weather resistance; both exhibit good anti-aging properties, and their weather resistance is essentially equivalent to that of the marketed reference product (No. 1). Based on the principle of cost-saving, the optimal light stabilizer combination for sample No. 3 is the combination of 2% UV-1130 and 1% UV-292.

[0029] 3. Investigate the effect of different types of adhesion promoters on the adhesion of clear varnish. Based on the varnish formulation of Example 1, the effects of different types and models of adhesion promoters on the adhesion of aluminum alloy plates after anodizing were investigated. The different types and contents of adhesion promoters are shown in Table 5. The varnish was then prepared. Referring to the varnish coating of Example 1, the weather resistance of the varnish was tested, and the results are shown in Table 6.

[0030] Table 5. Samples with different types and contents of adhesion promoters

[0031] "-" indicates an unknown amount.

[0032] Table 6. Test results of various adhesion indicators

[0033] The results in Table 6 show that sample 5 exhibits significantly better adhesion than other additives and dosages. Therefore, 2% Adherant ADP is the optimal concentration.

[0034] Example 3: Performance testing of clear varnish on anodized aluminum alloy plates The adhesion, impact resistance, pendulum hardness (210s), mechanical properties, appearance leveling, and weather resistance (with artificial aging levels increased to over 4000 hours) of the coating (varnish + hardener) used in Example 1 on an anodized aluminum alloy plate were tested using conventional testing methods in the art. These results were compared with a commercially available control coating (the commercially available control in the table is BASF's GP41006A high-performance varnish supplied to Seres). The results are shown in Table 7.

[0035] Table 7. Test results of various indicators of the coating in Example 1

[0036] The results show that the coating of the present invention meets the requirements of national standards in all test indicators and is superior to the marketed reference product in many aspects, such as adhesion, appearance, hardness and impact resistance.

[0037] The focus of this invention is to explore novel coatings for anodized aluminum alloy sheets. A coating is provided that meets the coating requirements of anodized aluminum alloy sheets for automobiles and low-altitude aircraft, offering greater savings in coating time and cost compared to existing coatings on the market. Example 1 above is merely representative; any simple modifications or variations made within the spirit and essence of this invention fall within its scope.

Claims

1. A coating suitable for anodized aluminum alloy sheets, comprising a varnish and a curing agent, said varnish being composed of the following components by weight percentage: Acrylic resin accounts for 64.6%, amino resin A15-75 accounts for 10.0%, leveling agent BYK-390 accounts for 0.2%, leveling agent BYK-333 accounts for 0.2%, light stabilizer UV-1130 accounts for 2-5%, light stabilizer UV-292 accounts for 1-2.5%, butyl acetate accounts for 10%, adherant ADP accounts for 2%, thiol accounts for 5%, and amyl acetate accounts for the balance.

2. The coating as claimed in claim 1, wherein the acrylic resin in the varnish is 1766 VB-64.

3. The coating as described in claim 1, wherein the curing agent is an isocyanate.

4. The coating as described in claim 1, wherein the components of the varnish are (by weight percentage): Acrylic resin 1766 VB-64 accounts for 64.6%. Amino resin A15-75 accounts for 10.0%. The leveling agent BYK-390 accounts for 0.2%. The leveling agent BYK-333 accounts for 0.2%. The light stabilizer UV-1130 accounts for 2.0%. The light stabilizer UV-292 accounts for 1.0%. Butyl acetate accounts for 10.0%. Adherent ADP accounted for 2.0%. Trimethylbenzene accounted for 5.0%. The diluent, amyl acetate, accounts for 5.0%.

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