An organic coating composition for oxidized surfaces of aluminum alloys and coatings, a production process, an aluminum alloy piece

Abstract

The application discloses an organic coating composition of an aluminum alloy part, a coating, a preparation process and the aluminum alloy part, and belongs to the technical field of aluminum alloy surface treatment. The organic coating composition contains the following components in mass fraction: methylsiloxane, 20-35 parts; acrylic modified silicone resin, 15-25 parts; silica sol, 5-10 parts; solvent, 27-58 parts; and leveling agent, 2-3 parts. The composition can form an alkali corrosion-resistant film layer and has hydrophobic and oleophobic properties, so that the aluminum alloy part is not corroded and has no discoloration defect after being treated by an alkaline cleaning agent.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy surface treatment technology, specifically relating to an organic coating composition, coating, preparation process, and aluminum alloy parts for aluminum alloy anodized surfaces. Background Technology

[0002] Anodizing of aluminum alloys is an electrochemical surface treatment process mainly used for aluminum and its alloys to improve their corrosion resistance, wear resistance, insulation, decorative properties, and other characteristics. The process involves placing aluminum or aluminum alloy as the anode in an acidic electrolyte (usually sulfuric acid), where electrolysis forms an aluminum oxide film on the aluminum surface.

[0003] However, in practical applications, although there is an aluminum oxide film on the surface-treated aluminum alloy, it is easily corroded by alkaline substances. This is because aluminum oxide reacts with hydroxide ions in an alkaline environment. Therefore, when aluminum alloy anodized workpieces used in kitchen appliances come into contact with alkaline cleaning agents (such as Green Umbrella, Mighty, etc.), the aluminum oxide film layer will be damaged, resulting in adverse effects such as discoloration. Summary of the Invention

[0004] To address the aforementioned technical problems, this application improves the formulation of the coating composition to obtain an aluminum alloy part resistant to alkali corrosion. One objective of this invention is to provide an organic coating composition for aluminum alloy parts; another objective is to provide a corresponding coating; a third objective is to provide a corresponding preparation process; and a fourth objective is to provide a corresponding aluminum alloy part.

[0005] The specific technical solution is explained below:

[0006] An organic coating composition for aluminum alloy parts, comprising the following components by mass fraction:

[0007] Methylsiloxane, 20-35 parts;

[0008] Acrylic-modified silicone resin, 15-25 parts;

[0009] Silica sol, 5-10 parts;

[0010] Solvent, 27-58 parts;

[0011] Leveling agent, 2-3 parts.

[0012] In the above technical solution:

[0013] The main component that resists alkali corrosion is silica sol;

[0014] Methylsiloxane and acrylic acid-modified silicone resin cross-link with each other to form a film during the preparation process;

[0015] Among them, methylsiloxane provides methyl branches, which form microscopic synaptic structures, giving the film a certain degree of hydrophobicity and oleophobicity.

[0016] Acrylic-modified silicone resin can improve the gloss and film-forming properties of the film.

[0017] Solvents provide a homogeneous environment;

[0018] Leveling agents can reduce the surface tension of the liquid phase, thereby forming a smoother and flatter film.

[0019] In a preferred embodiment, the methylsiloxane is polydimethylsiloxane and / or methylhydrosiloxane, the acrylic modified silicone resin is methyl silicone resin, the solvent is one or a combination of several of ethylene glycol butyl ether, ethyl acetate, and isopropanol, and the leveling agent is polyacrylate or propylene glycol methyl ether.

[0020] In a preferred embodiment, the mass ratio of the methylsiloxane to the acrylic modified silicone resin is in the range of 0.8 to 2.33. Relatively speaking, if this ratio is too low, the hydrophobicity and oleophobicity of the film will be significantly reduced; if this ratio is too high, the gloss of the film will be significantly reduced.

[0021] In a further preferred embodiment, the mass ratio of the methylsiloxane to the acrylic-modified silicone resin is in the range of 1.25 to 1.67. Within this range, the ratio of methylsiloxane to acrylic-modified silicone resin provides a relatively balanced hydrophobicity, oleophobicity, and gloss, as well as good film-forming properties.

[0022] In a further preferred embodiment, the ratio of the sum of the masses of the methylsiloxane and the acrylic-modified silicone resin to the mass of the silica sol is in the range of 4.3 to 12. If this ratio is too low, it will be difficult to form a continuous film layer, and if this ratio is too low, the coating will have insufficient resistance to alkali corrosion.

[0023] The coating is prepared from the organic coating composition described in any of the above technical solutions.

[0024] The coating preparation process of the organic coating composition described in any of the above technical solutions includes the following steps:

[0025] ① Degreasing: Wipe the anodized and sealed aluminum alloy parts with an organic solvent to remove oil and other impurities from the surface, and allow them to dry at room temperature for 10-20 minutes.

[0026] ② Spraying: The organic coating composition is mixed and then sprayed onto the aluminum alloy parts, with a coating thickness of 3-10 μm;

[0027] ③ Curing: Curing is carried out at a temperature of 120℃~150℃, and then aluminum alloy parts with organic coating are obtained.

[0028] The aluminum alloy parts are prepared using the coating process described above.

[0029] In summary, the technical solution described in this invention has the following main beneficial effects:

[0030] Compared with the prior art, the technical solution of the present invention can form a film layer resistant to alkali corrosion and has hydrophobic and oleophobic properties;

[0031] Furthermore, the invented technical solution can also form a smooth and glossy film.

[0032] Further or more detailed beneficial effects will be described in conjunction with specific embodiments in the detailed implementation. Attached Figure Description

[0033] Figure 1 This is a diagram illustrating the assessment of the appearance of the aluminum alloy parts described in the embodiments; Detailed Implementation

[0034] The present invention will be further explained in conjunction with the embodiments:

[0035] The core technical problem faced by the technical solution of this application embodiment stems from the inventor's accurate understanding of the prior art. Therefore, how to obtain an aluminum alloy part resistant to alkali corrosion is a technical problem that the inventor urgently needs to solve.

[0036] At the same time, how to make the coating hydrophobic, oleophobic, smooth, and glossy is also a technical problem that the inventors are trying to solve simultaneously.

[0037] It should be noted that the embodiments do not constitute a limitation on the scope of protection of the claims of this invention. All technical solutions that can be reasonably expected by those skilled in the art based on the technical concepts provided / proved by the embodiments should be covered within the scope of protection of the claims of this invention.

[0038] The specific implementation examples are detailed below:

[0039] The manufacturing process for aluminum alloy parts with organic coatings is as follows:

[0040] (S1): Degreasing: Wipe the anodized and sealed aluminum alloy parts with an alcohol solution of ≥50% concentration to remove oil and other impurities from the surface, and allow them to dry at room temperature of 20-40℃ for 10-20 minutes.

[0041] (S2): The organic coating composition is mixed and then sprayed onto the aluminum alloy part using an electrostatic rotary cup to achieve a coating thickness of 5 μm.

[0042] (S3): The aluminum alloy parts with organic coating are obtained by curing in a high-temperature tunnel furnace at a temperature of 120℃~150℃ for 15 minutes.

[0043] in:

[0044] The organic coating composition in (S2) consists of the following components by mass fraction:

[0045] At least one of polydimethylsiloxane and methylhydrosiloxane, 20-35 parts;

[0046] 15-25 parts of methyl silicone resin;

[0047] Silica sol, 5-10 parts;

[0048] A composition of one or more of ethylene glycol butyl ether, ethyl acetate, and isopropanol, in 27 to 58 parts;

[0049] Polyacrylate or propylene glycol methyl ether, 2 to 3 parts.

[0050] The alkali resistance test method in the examples is as follows:

[0051] 1. Prepare a sodium hydroxide aqueous solution with pH=8, and immerse the aluminum alloy parts in it for 24 hours at room temperature;

[0052] 2. Spray kitchen stain remover (Green Umbrella) onto the aluminum alloy parts and wipe with a cloth with a force of 10N for 30 seconds;

[0053] The test results of methods 1 and 2 above show no cracking or peeling of the coating, which is considered qualified; otherwise, they are considered unqualified.

[0054] The test methods for hydrophobicity and oleophobicity are as follows:

[0055] A water contact angle ≥90° is acceptable; otherwise, it is unacceptable.

[0056] When the water contact angle is ≥90°, it means that the surface energy is very low, and therefore it has both hydrophobic and oleophobic properties.

[0057] The method for judging the appearance effect is attached to the instruction manual. Figure 1 :

[0058] Appendix Figure 1 In the image, the left side shows a good appearance, the middle side shows a slightly discolored appearance, and the right side shows a low gloss appearance.

[0059] The test method for thermal shock is as follows:

[0060] The aluminum alloy part is kept in an environment of 150℃±3℃ for 30 minutes, then removed and kept at room temperature for 10 minutes. The sample is then kept in an environment of -30℃±3℃ for 30 minutes. This is one cycle. The process is repeated for 15 cycles. If the coating does not crack or peel off, it is considered qualified. If the coating does not crack or peel off after 18 cycles, it is considered excellent.

[0061] The formulations in Examples 1-5 and Comparative Examples 1-2 consist of the following: polydimethylsiloxane, methyl silicone resin, silica sol, ethyl acetate, and polyacrylate.

[0062] The formulations of the organic coating compositions described in Examples 1-5 and Comparative Examples 1-2 are shown in Table 1 below:

[0063] Table 1. Formulations and curing temperatures of the organic coating compositions described in Examples 1-5 and Comparative Examples 1-2.

[0064]

[0065] The performance test results of the coatings involved in Examples 1-5 and Comparative Examples 1-2 are shown in Table 2 below:

[0066] Table 2. Performance test results of the organic coatings described in Examples 1-5 and Comparative Examples 1-2.

[0067]

[0068] As shown in Tables 1 and 2, the curing temperature has a significant impact on the appearance. The curing temperature of Comparative Example 1 is too high, at 160℃, which results in a slight discoloration of its appearance. The curing temperature of Comparative Example 2 is too low, at 110℃, which results in low gloss and failure to pass the alkali resistance test.

[0069] In Examples 1, 2, and 5, the ratio of methylsiloxane to acrylic-modified silicone resin falls between 1.25 and 1.67, exhibiting excellent resistance to thermal shock. In Examples 3 and 5, the ratios of methylsiloxane to acrylic-modified silicone resin are 2 and 0.8, respectively, falling outside the 1.25-1.67 range, yet still possessing acceptable thermal shock resistance. In kitchen appliances, sudden temperature changes are frequently encountered; therefore, the coatings corresponding to Examples 1, 2, and 5 are more suitable for the working environment of kitchens with drastic temperature changes.

[0070] The only difference between Comparative Examples 1 and 2 and Example 1 is the curing temperature. However, their thermal shock performance is not excellent, which shows that choosing a suitable curing temperature has an appropriate impact on the thermal shock performance of the film.

[0071] Comparative Example 3:

[0072] The only difference from Example 3 is that the ratio of polydimethylsiloxane to methyl silicone resin is approximately 2.46.

[0073] Comparative Example 4:

[0074] The only difference from Example 4 is the presence of polydimethylsiloxane, with the proportion of methyl silicone resin being approximately 0.7%.

[0075] Comparative Example 5:

[0076] The only difference from Example 3 is that the mass ratio of polydimethylsiloxane to methyl silicone resin and the mass ratio of polydimethylsiloxane to silica sol is 4.

[0077] Comparative Example 6:

[0078] The only difference from Example 5 is that the mass ratio of polydimethylsiloxane to methyl silicone resin and to silica sol is approximately 13.

[0079] The formulations of the organic coating compositions described in Comparative Examples 3-6 are shown in Table 3 below:

[0080] Table 3 shows the formulations of the organic coating compositions described in Comparative Examples 3-6.

[0081]

[0082] The performance test results of the coatings involved in Comparative Examples 3 to 6 are shown in Table 4 below:

[0083] Table 4 shows the performance test results of the organic coatings described in Comparative Examples 3-6.

[0084]

[0085] As can be seen from Tables 3 and 4:

[0086] Comparative Example 3 has lower gloss compared to Example 3;

[0087] Compared with Example 4, Comparative Example 4 failed in terms of hydrophobicity and oleophobicity.

[0088] Compared to Example 3, Comparative Example 5 had difficulty forming a complete film layer;

[0089] Compared with Example 5, Comparative Example 6 failed the alkali resistance test.

[0090] In the description of this specification, the references to terms such as "embodiment," "basic embodiment," "preferred embodiment," "other embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0091] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0092] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An organic coating composition for aluminum alloy parts, characterized in that, Based on mass fraction, it consists of the following components: Methylsiloxane, 20-35 parts; Acrylic-modified silicone resin, 15-25 parts; Silica sol, 5-10 parts; Solvent, 27-58 parts; Leveling agent, 2-3 parts; The methylsiloxane is polydimethylsiloxane and / or methylhydrosiloxane; The acrylic-modified silicone resin is a methyl silicone resin; The mass ratio of the methylsiloxane to the acrylic acid-modified silicone resin is in the range of 0.8 to 2.

33. The ratio of the sum of the masses of the methylsiloxane and the acrylic acid-modified silicone resin to the mass of the silica sol is in the range of 4.3 to 12.

2. The organic coating composition according to claim 1, characterized in that: The solvent is one or a combination of several of ethylene glycol butyl ether, ethyl acetate, and isopropanol.

3. The organic coating composition according to claim 1 or 2, characterized in that: The leveling agent is polyacrylate or propylene glycol methyl ether.

4. The organic coating composition according to claim 1, characterized in that: The mass ratio of the methylsiloxane to the acrylic acid-modified silicone resin is in the range of 1.25 to 1.

67.

5. A coating, characterized in that: It is prepared from the organic coating composition according to any one of claims 1 to 3.

6. The coating preparation process of the organic coating composition according to any one of claims 1 to 3, characterized in that, Includes the following steps: ① Degreasing: Wipe the anodized and sealed aluminum alloy parts with a cleaning agent to remove surface oil and allow them to dry at room temperature; ② Spraying: The organic coating composition is mixed and then sprayed onto the aluminum alloy parts, with a coating thickness of 3~10μm; ③ Curing: Curing is carried out at a temperature of 120℃~150℃, and then aluminum alloy parts with organic coating are obtained.

7. An aluminum alloy part, characterized in that: It is prepared by the coating preparation process described in claim 5.

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