Aluminum powder pigment with three-layer coating structure and preparation method of aluminum powder pigment

Abstract

The invention belongs to the technical field of fine powder materials, and particularly relates to an aluminum powder pigment with a three-layer coating structure and a preparation method of the aluminum powder pigment. The preparation method of the aluminum powder pigment comprises the following steps: adding pretreated aluminum powder into a solvent, carrying out ultrasonic treatment to form a suspension, dropwise adding tetraethoxysilane, adjusting the pH value, and carrying out a heating reaction to obtain inner-layer SiO2 coated aluminum powder; uniformly mixing epoxy resin and acetone, adding a silane coupling agent, the inner-layer SiO2 coated aluminum powder and a curing agent, and carrying out heating reaction to obtain silicon-resin double-layer coated aluminum powder; the silicon-resin double-layer coated aluminum powder is placed in an ALD reaction cavity, vacuumizing and heating are carried out, the constant temperature is maintained, SiCl4 is introduced firstly, then nitrogen is introduced for purging, water vapor is introduced, then nitrogen is introduced for purging again, the steps are repeated for 100-300 times, SiO2 is deposited layer by layer, cooling and drying are carried out, and the silicon-resin double-layer coated aluminum powder is obtained. And the defects of easy oxidation, interlayer stripping, single function and the like of the traditional aluminum powder pigment are overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of fine powder materials, and particularly relates to a three-layer coated aluminum powder pigment and a preparation method thereof. Background Art

[0002] With the global emphasis on environmental protection, countries have introduced stringent environmental regulations to strictly control the emission of volatile organic compounds. Driven by environmental policies, powder coatings, as pollution-free and highly efficient coatings, will see even greater development potential and a growing range of applications. Since the development of wet-process aluminum powder production technology in 1910, aluminum powder has been mass-produced and incorporated into production, making it the most versatile and diverse metallic pigment. Due to its metallic luster, angular color shift, and low price, it is primarily used in the production of coatings, printing inks, and plastics. It has found widespread application in a wide range of industries, including automotive, electronics, building materials, home appliances, printing inks, equipment, ships, aircraft, plastics, and textiles. Aluminum pigments used in coatings require strong acid and alkali resistance. However, aluminum flakes have a large surface area and are easily corroded by acidic and alkaline media when exposed to air, severely impacting their performance. Therefore, surface treatment is essential.

[0003] Coated aluminum powder pigment is a functional material that is modified by surface coating technology. Its core goal is to improve the corrosion resistance, chemical stability, dispersibility and optical properties of aluminum powder through the coating layer, thereby expanding its application in coatings, inks, plastics, cosmetics and other fields. At present, there are two main methods for silicon-coated aluminum powder pigments: one is silicon single-layer coating, and the other is silicon-resin double-layer coating. However, the existing aluminum powder pigments have the following problems: 1) Single-layer inorganic silicon (SiO2) coated aluminum powder pigments are highly brittle and easily cracked by external forces such as paint spraying and mechanical grinding; 2) Silicone-resin coated aluminum powder pigments are prone to interlayer delamination due to poor compatibility between the inorganic (SiO2) / organic (resin) interface, especially under thermal cycling or mechanical stress, resulting in performance degradation and other problems. 3) Microcracks or pinholes exist in the single inorganic layer coated with silicon-resin, and corrosive media (such as Cl - 4) Silicone-resin coated aluminum pigments: The outer resin layer can easily soften or decompose at high temperatures (>200°C), leading to coating failure. Summary of the Invention

[0004] To address the above technical issues, the present invention provides a three-layer aluminum pigment with a coating structure and a preparation method. This aluminum pigment features an inorganic-organic-inorganic three-layer composite structure. Through the physical isolation of the aluminum substrate by a dense inner layer of silica, the stress buffering and chemical bonding strengthening of a middle resin layer, and the surface protection provided by an outer layer of functionalized silica, a synergistic protective system is formed. This fundamentally addresses the inherent drawbacks of traditional aluminum pigments, such as susceptibility to oxidation, interlayer delamination, and a single function.

[0005] One of the purposes of the present invention is to provide a method for preparing a three-layer coated aluminum powder pigment.

[0006] A second object of the present invention is to provide an aluminum powder pigment with a three-layer coating structure.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A method for preparing a three-layer coated aluminum powder pigment comprises the following steps: (1) Add the pretreated aluminum powder to a solvent, ultrasonically treat it to form a suspension, add ethyl orthosilicate dropwise, adjust the pH, and heat the solution to react. After the reaction is completed, centrifuge, wash, and dry the solution to obtain an inner layer of SiO2-coated aluminum powder; (2) Evenly mix epoxy resin and acetone, add silane coupling agent, inner layer SiO2 coated aluminum powder, and curing agent, heat to react, centrifuge, wash, and dry the solution after the reaction to obtain silicon-resin double-layer coated aluminum powder; (3) Place the silicon-resin double-layer coated aluminum powder in the ALD reaction chamber, evacuate, heat and maintain constant temperature, first introduce SiCl4, then introduce nitrogen purge, then introduce water vapor, and then introduce nitrogen purge again, and repeat this cycle 100-300 times to deposit SiO2 layer by layer. After cooling and drying, the product is obtained.

[0008] Furthermore, the pretreated aluminum powder in step (1) is prepared by the following method: The method comprises adding aluminum powder into a hydrochloric acid solution, performing ultrasonic treatment, and then centrifuging, washing and drying the treated solution to obtain the product.

[0009] Furthermore, the average particle size of the aluminum powder is 10-20 μm, the mass ratio of the aluminum powder to the hydrochloric acid solution is (10-25): (100-300), the concentration of the hydrochloric acid solution is 1 mol / L; the power of the ultrasound is 200-300 W, the frequency is 40 kHz, and the time is 15-30 min.

[0010] This method pre-treats aluminum powder using acid activation to thoroughly remove the surface oxide layer (Al2O3) and impurities. Nitrogen protection prevents secondary oxidation of the pre-treated aluminum powder. This pre-treated aluminum powder improves the adhesion of the coating and reduces the risk of subsequent coating shedding.

[0011] The present invention utilizes gradient pH control: a higher pH (10-11) in the inner layer for rapid film formation, and a slightly lower pH (9-10) in the outer layer to ensure uniform film formation. The resulting inner SiO2-coated aluminum powder forms a dense inorganic barrier, preventing oxidation and corrosion of the aluminum substrate.

[0012] Furthermore, the ratio of the pretreated aluminum powder, tetraethyl orthosilicate, and solvent in step (1) is 10-20 g: 5-10 mL: 200-400 mL, and the solvent is ethanol or n-propanol.

[0013] Furthermore, in step (1), the time for adding ethyl orthosilicate is 10-20 minutes; the pH is adjusted to 10-11; the temperature of the reaction is 50-60°C, and the time is 6-8 hours; the temperature of the drying is 50-70°C, and the time is 4-6 hours.

[0014] Furthermore, in step (2), the mass ratio of the epoxy resin, silane coupling agent, inner layer SiO2 coated aluminum powder, and curing agent is (5-10): (0.1-0.2): (8-20): (2.5-5); the epoxy resin is epoxy resin E-44; the silane coupling agent is KH-550; the curing agent is polyamide 650; and the amount ratio of the epoxy resin to acetone is 5-10 g: 50-100 mL.

[0015] Furthermore, in step (2), the heating reaction temperature is 70-90°C and the time is 3-5 hours; the drying temperature is 50-60°C and the time is 5-8 hours.

[0016] Furthermore, after step (3), the vacuum degree is ≤5×10 -4 Pa; the heating temperature is 150 ℃; the SiCl4 pulse time is 0.2-2s, the nitrogen purge time is 20-30s, the water vapor pulse time is 0.3-2s, and the nitrogen purge time is again 20-30s.

[0017] Furthermore, the deposition thickness of each cycle in step (3) is 0.1 nm.

[0018] The three-layer coated aluminum powder pigment of the present invention is prepared by adopting the above-mentioned preparation method.

[0019] The silicone-resin double-layered aluminum powder of this invention features a flexible buffer layer, enhancing impact resistance and improving interlayer bonding. Firstly, the epoxy groups (-O-) form a chemical bond (Si-OC) with the silane coupling agent (KH-550), enhancing interfacial bonding. Secondly, the in-situ polymerization process, directly on the aluminum powder surface, avoids compatibility issues between the resin prepolymer and the SiO2 layer.

[0020] The present invention adopts ALD ultra-thin deposition technology to deposit atomic-level thickness SiO2 layer by layer through alternating pulse precursors (SiCl4 and H2O). The thickness of single-cycle deposition is about 0.1 nm.

[0021] The present invention adopts atomic layer deposition (ALD) technology to form nano-scale SiO2 on the surface of silicon-resin double-layer coated aluminum powder, sealing the defects of the resin layer, and enhancing the scratch resistance, high temperature resistance and chemical stability.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) The core advantage of this invention stems from its innovative inorganic-organic-inorganic three-layer composite structure. Through the physical isolation of the aluminum substrate by the dense inner silica layer, the stress buffering and chemical bonding strengthening by the middle resin layer, and the surface protection by the functionalized outer silica layer, a synergistic protection system is formed, which fundamentally solves the inherent defects of traditional aluminum powder pigments such as easy oxidation, interlayer delamination, and single function. In response to extreme environmental challenges, the coordinated design of high-temperature resistant resin and gradient thermal expansion coefficient gives the coating excellent thermal stability, which can withstand drastic temperature changes and chemical erosion.

[0023] (2) In terms of production process, the present invention adopts the composite application of ALD technology and sol-gel technology to take into account both coating accuracy and cost control. DETAILED DESCRIPTION

[0024] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are for describing specific embodiments rather than for limiting the scope of protection of the present invention.

[0026] When numerical ranges are given in the examples, it should be understood that, unless otherwise specified herein, 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 herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs.

[0027] Example 1 A method for preparing a three-layer coated aluminum powder pigment comprises the following steps: Step 1: Add 15g of aluminum powder (>99.5% purity) with an average particle size of 20μm to 200mL of 1M hydrochloric acid solution and sonicate (40kHz, 300W) for 20 minutes. After sonication, centrifuge the mixture at 8000rpm for 5 minutes, and discard the supernatant. Add deionized water and repeat the centrifugation until the supernatant reaches a pH of 7. The centrifuged aluminum powder is then dried in a vacuum oven at 60°C for 6 hours to obtain the pretreated aluminum powder.

[0028] Step 2: Add 10g of pretreated aluminum powder to 200mL of ethanol and ultrasonically disperse for 30 minutes (200W power, pulse mode) to form a stable suspension. The suspension was transferred to a reaction vessel, and a magnetic stirrer was started at 500rpm. While stirring, 5mL of tetraethyl orthosilicate (TEOS) was added dropwise, and stirring was continued for 10 minutes. After the addition was complete, ammonia was added dropwise until the solution pH reached 10.0. The temperature was raised to 50°C, the stirring rate was increased to 800 rpm, and the reaction was continued for 6 hours. After the reaction was completed and cooled to room temperature, the coated aluminum powder was collected by centrifugation, washed three times with ethanol, and vacuum dried (60°C, 4 hours) to obtain aluminum powder coated with an inner SiO2 layer.

[0029] Step 3: Mix 5g of epoxy resin E-44 with 50mL of acetone, add 0.1g of KH-550, and ultrasonically disperse for 10 minutes (ultrasonic power 150W). Add 8g of inner-layer SiO2-coated aluminum powder to this solution and ultrasonicate for 20 minutes to form a stable suspension. Transfer the suspension to a reaction vessel, start a magnetic stirrer at 600rpm, and slowly add 2.5g of polyamide 650 dropwise while stirring. Raise the temperature to 70°C and continue the reaction for 4 hours. After the reaction is complete and cooled to room temperature, collect the coated product by centrifugation, wash twice with acetone, and vacuum dry (50°C, 6 hours) to obtain the silicon-resin double-layer coated aluminum powder.

[0030] Step 4: Spread the coated aluminum powder obtained in step 3 evenly on the ALD sample tray and load it into the reaction chamber. Reduce the pressure of the reaction chamber to a basic vacuum of 5×10 -4 Pa, and the heated susceptor was maintained at 150°C. A SiCl₄ pulse was introduced for 0.2 s, followed by a 20 s N₂ purge, followed by a 0.3 s H₂O pulse, and finally a 20 s N₂ purge. This cycle was repeated 300 times, resulting in a deposited thickness of approximately 0.1 nm per cycle. After deposition, the sample was cooled to below 80°C under nitrogen protection, removed, and stored in a dry nitrogen cabinet. This resulted in an aluminum pigment with a SiO₂-resin-SiO₂ triple-layer structure.

[0031] This embodiment also provides a three-layer coated aluminum powder pigment, which is prepared by the above preparation method.

[0032] Example 2 A method for preparing a three-layer coated aluminum powder pigment comprises the following steps: Step 1: 22 g of aluminum powder (>99.5% purity) with an average particle size of 10 μm was added to 300 mL of 1 M hydrochloric acid solution and sonicated (40 kHz, 300 W) for 20 minutes. After sonication, the mixture was centrifuged at 8000 rpm for 5 minutes, and the supernatant was discarded. Deionized water was added, and the centrifugation was repeated until the supernatant pH reached 7. The centrifuged aluminum powder was then dried in a vacuum oven at 60°C for 6 hours to obtain the pretreated aluminum powder.

[0033] Step 2: Add 20g of pretreated aluminum powder to 350mL of ethanol and ultrasonically disperse for 30 minutes (200W power, pulse mode) to form a stable suspension. Transfer the suspension to a reaction vessel, start a magnetic stirrer at 500rpm, and add 10mL of TEOS dropwise while stirring for 20 minutes. After the addition is complete, add aqueous ammonia dropwise until the solution reaches a pH of 10.2. Raise the temperature to 55°C, increase the stirring rate to 800rpm, and allow the reaction to proceed for 8 hours. After the reaction is complete and the mixture is cooled to room temperature, the coated aluminum powder is collected by centrifugation, washed three times with ethanol, and vacuum dried (60°C, 4 hours) to obtain aluminum powder coated with an inner SiO2 layer.

[0034] Step 3: Mix 10g of epoxy resin E-44 with 80mL of acetone, add 0.2g of KH-550, and ultrasonically disperse for 10 minutes (power 150W). Add 18g of aluminum powder coated with an inner layer of SiO2 to the solution and ultrasonicate for 20 minutes to form a stable suspension. Transfer the suspension to a reaction vessel, start a magnetic stirrer at 600rpm, and slowly add 4g of polyamide 650 dropwise while stirring. Raise the temperature to 70°C and continue the reaction for 4 hours. After the reaction is complete and cooled to room temperature, collect the coated product by centrifugation, wash twice with acetone, and vacuum dry (50°C, 6 hours) to obtain the silicon-resin double-layer coated aluminum powder.

[0035] Step 4: Spread the coated aluminum powder obtained in step 3 evenly on the ALD sample tray and load it into the reaction chamber. Reduce the pressure of the reaction chamber to a basic vacuum of 5×10 -4 Pa, and the heated susceptor was maintained at 150°C. A SiCl₄ pulse was introduced for 0.2 s, followed by a N₂ purge for 20 s, followed by a H₂O pulse for 0.3 s, and finally a N₂ purge for 20 s. This cycle was repeated 200 times, resulting in a deposited thickness of approximately 0.1 nm per cycle. After deposition, the sample was cooled to below 80°C under nitrogen protection, removed, and stored in a dry nitrogen cabinet. This resulted in an aluminum pigment with a SiO₂-resin-SiO₂ triple-layer structure.

[0036] This embodiment also provides a three-layer coated aluminum powder pigment, which is prepared by the above preparation method.

[0037] Example 3 A method for preparing a three-layer coated aluminum powder pigment comprises the following steps: Step 1: 13g of aluminum powder (>99.5% purity) with an average particle size of 20μm was added to 150mL of 1M hydrochloric acid solution and sonicated (40kHz, 300W) for 20 minutes. After the reaction, the mixture was centrifuged at 8000rpm for 5 minutes, and the supernatant was discarded. Deionized water was added, and the centrifugation was repeated until the supernatant pH reached 7. The centrifuged aluminum powder was dried in a vacuum oven at 60°C for 6 hours to obtain the pretreated aluminum powder.

[0038] Step 2: Add 10g of pretreated aluminum powder to 200mL of ethanol and ultrasonically disperse for 30 minutes (200W power, pulse mode) to form a stable suspension. Transfer the suspension to a reaction vessel, start a magnetic stirrer at 500rpm, and add 10mL of TEOS dropwise while stirring for 20 minutes. After the addition is complete, add ammonia dropwise until the solution reaches a pH of 11.2. Raise the temperature to 50°C, increase the stirring rate to 800rpm, and allow the reaction to proceed for 8 hours. After the reaction is complete and the mixture is cooled to room temperature, the coated aluminum powder is collected by centrifugation, washed three times with ethanol, and vacuum dried (60°C, 4 hours). This results in aluminum powder coated with an inner SiO2 layer.

[0039] Step 3: Mix 6g of epoxy resin E-44 with 80mL of acetone, add 0.2g of KH-550, and ultrasonically disperse for 10 minutes (power 150W). Add 8g of aluminum powder coated with an inner layer of SiO2 to this solution and ultrasonicate for 20 minutes to form a stable suspension. Transfer the suspension to a reaction vessel, start a magnetic stirrer at 600rpm, and slowly add 3g of polyamide 650 dropwise while stirring. Raise the temperature to 90°C and continue the reaction for 4 hours. After the reaction is complete and cooled to room temperature, collect the coated product by centrifugation, wash twice with acetone, and vacuum dry (50°C, 6 hours) to obtain the silicon-resin double-layer coated aluminum powder.

[0040] Step 4: Spread the coated aluminum powder obtained in step 3 evenly on the ALD sample tray and load it into the reaction chamber. Reduce the pressure of the reaction chamber to a basic vacuum of 5×10 -4 Pa, and the heated susceptor was maintained at 150°C. A SiCl₄ pulse was introduced for 0.2 s, followed by a N₂ purge for 20 s, followed by a H₂O pulse for 0.3 s, and finally a N₂ purge for 20 s. This cycle was repeated 300 times, resulting in a deposited thickness of approximately 0.1 nm per cycle. After deposition, the sample was cooled to below 80°C under nitrogen protection, removed, and stored in a dry nitrogen cabinet. This resulted in an aluminum pigment with a SiO₂-resin-SiO₂ triple-layer structure.

[0041] This embodiment also provides a three-layer coated aluminum powder pigment, which is prepared by the above preparation method.

[0042] Example 4 A method for preparing a three-layer coated aluminum powder pigment comprises the following steps: Step 1: Add 20 g of aluminum powder (>99.5% purity) with an average particle size of 20 μm to 400 mL of 1 M hydrochloric acid solution and ultrasonicate (40 kHz, 300 W) for 20 minutes. After the reaction, centrifuge the mixture at 8000 rpm for 5 minutes, and discard the supernatant. Add deionized water and repeat the centrifugation until the supernatant reaches a pH of 7. The centrifuged aluminum powder is then dried in a vacuum oven at 60°C for 6 hours to obtain the pretreated aluminum powder.

[0043] Step 2: 10g of pretreated aluminum powder was added to 280mL of n-propanol and ultrasonically dispersed for 20 minutes (200W power, pulse mode) to form a stable suspension. The suspension was transferred to a reaction vessel, and a magnetic stirrer was started at 500rpm. While stirring, 10mL of TEOS was added dropwise over 20 minutes. After the addition was complete, aqueous ammonia was added dropwise until the solution reached a pH of 11.0. The temperature was raised to 60°C, the stirring rate was increased to 800 rpm, and the reaction was continued for 6 hours. After the reaction was completed and cooled to room temperature, the coated aluminum powder was collected by centrifugation, washed three times with n-propanol, and vacuum dried (60°C, 4 hours) to obtain aluminum powder coated with an inner SiO2 layer.

[0044] Step 3: Mix 5g of epoxy resin E-44 with 50mL of acetone, add 0.1g of KH-550, and ultrasonically disperse for 10 minutes (power 150W). Add 8g of aluminum powder coated with an inner layer of SiO2 to the solution and ultrasonicate for 20 minutes to form a stable suspension. Transfer the suspension to a reaction vessel, start a magnetic stirrer at 600rpm, and slowly add 2.5g of polyamide 650 dropwise while stirring. Raise the temperature to 70°C and continue the reaction for 4 hours. After the reaction is complete and cooled to room temperature, collect the coated product by centrifugation, wash twice with acetone, and vacuum dry (50°C, 6 hours) to obtain the silicon-resin double-layer coated aluminum powder.

[0045] Step 4: Spread the coated aluminum powder obtained in step 3 evenly on the ALD sample tray and load it into the reaction chamber. Reduce the pressure of the reaction chamber to a basic vacuum of 5×10 -4 Pa, and the heated susceptor was maintained at 150°C. A SiCl₄ pulse was introduced for 0.2 s, followed by a N₂ purge for 20 s, followed by a H₂O pulse for 0.3 s, and finally a N₂ purge for 20 s. This cycle was repeated 300 times, resulting in a deposited thickness of approximately 0.1 nm per cycle. After deposition, the sample was cooled to below 80°C under nitrogen protection, removed, and stored in a dry nitrogen cabinet. This resulted in an aluminum pigment with a SiO₂-resin-SiO₂ triple-layer structure.

[0046] This embodiment also provides a three-layer coated aluminum powder pigment, which is prepared by the above preparation method.

[0047] Comparative Example 1 This comparative example provides a method for preparing a silicon-resin double-layer coated aluminum powder pigment, comprising the following steps: Step 1: Add 10g of aluminum powder (>99.5% purity) with an average particle size of 20μm to 200mL of ethanol and ultrasonically disperse for 30 minutes (200W power, pulse mode) to form a stable suspension. Transfer the suspension to a reaction vessel, start a magnetic stirrer at 500rpm, and add 5mL of tetraethyl orthosilicate (TEOS) dropwise while stirring for 10 minutes. After the addition is complete, add ammonia dropwise until the solution pH reaches 10.0. Raise the temperature to 50°C, increase the stirring rate to 800rpm, and react for 6 hours. After the reaction is complete and cool to room temperature, collect the coated aluminum powder by centrifugation, wash three times with ethanol, and vacuum dry (60°C, 4 hours) to obtain aluminum powder coated with an inner SiO2 layer.

[0048] Step 2: Add 5g of epoxy resin E-44 to 0.1g of KH-550 and ultrasonically disperse for 10 minutes (ultrasonic power 150W). Add 8g of aluminum powder coated with an inner layer of SiO2 to the solution and ultrasonicate for 20 minutes to form a stable suspension. Centrifuge the suspension, collect the coated product, and vacuum dry it (50°C, 6 hours) to obtain the silicon-resin double-layer coated aluminum powder.

[0049] Comparative Example 2 This comparative example provides a method for preparing a double-layer coated aluminum powder pigment. The difference from Example 1 is that the fourth step is omitted to obtain a silicone-resin double-layer coated aluminum powder.

[0050] Comparative Example 3 This comparative example provides a method for preparing a three-layer coated aluminum powder pigment, which differs from Example 1 in that the fourth step of deposition is repeated 100 times.

[0051] Test Case The properties of the products obtained from Examples 1-4 of the present invention and Comparative Examples 1-3 were tested, as follows: The test samples of Examples 1-4 and Comparative Examples 1-3 were mixed with a primer (AENOO20A model purchased from Guangdong Aiyue Powder Coating Co., Ltd.) at a 2 wt% addition amount and attached to a stainless steel substrate by electrostatic spraying (except for the short-term high temperature resistance test, the detailed test process is as follows): 1. Corrosion resistance: Use the acetic acid accelerated salt spray test (AASS) specified in GB / T 10125 for 1000 hours to observe the corrosion of the coating surface.

[0052] 2. Impact resistance test: A 4 mm diameter steel ball is dropped from a height of 50 cm to impact the coating and the peeling area is evaluated.

[0053] 3. High temperature resistance: (1) Short-term heat resistance: Spread the test sample evenly on the sample tray and place it in an oven at 300℃ for 2 hours to observe the color change.

[0054] (2) Long-term heat resistance: Place the electrostatically sprayed sample in an oven and bake it at 150°C for 300 hours to observe the integrity of the coating.

[0055] 4. Interface compatibility: The test sample was placed at -40°C for 30 minutes, then at 150°C for 30 minutes, and subjected to 100 hot and cold cycles to observe the cracking of the coating.

[0056] The above test results are shown in Table 1.

[0057] Table 1 From the above test results, it can be seen that the products obtained in Examples 1-4 of the present invention have good corrosion resistance, impact resistance, short-term and long-term high temperature resistance, and interface compatibility.

[0058] Compared with Example 1, the comprehensive performance of Comparative Examples 1-3 is poor, among which the corrosion resistance, impact resistance and interface compatibility of Comparative Examples 1 and 2 are worse, and the comprehensive performance of Comparative Example 3 is slightly better.

[0059] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for preparing a three-layer coated aluminum powder pigment, characterized in that: The steps include: (1) Add the pretreated aluminum powder to a solvent, ultrasonically treat to form a suspension, add ethyl orthosilicate dropwise, adjust the pH, and heat to react. After the reaction is completed, centrifuge, wash, and dry the solution to obtain an inner layer of SiO2-coated aluminum powder; (2) Evenly mix epoxy resin and acetone, add silane coupling agent, inner layer SiO2 coated aluminum powder, and curing agent, heat to react, centrifuge, wash, and dry the solution after the reaction to obtain silicon-resin double-layer coated aluminum powder; (3) Place the silicon-resin double-layer coated aluminum powder in the ALD reaction chamber, evacuate, heat and maintain constant temperature, first introduce SiCl4, then introduce nitrogen purge, then introduce water vapor, and then introduce nitrogen purge again, and repeat this cycle 100-300 times to deposit SiO2 layer by layer. After cooling and drying, the product is obtained.

2. The method for preparing the three-layer coated aluminum powder pigment according to claim 1, characterized in that: The pretreated aluminum powder in step (1) is prepared by the following method: The method comprises adding aluminum powder into a hydrochloric acid solution, performing ultrasonic treatment, and then centrifuging, washing and drying the treated solution to obtain the product.

3. The method for preparing the three-layer coated aluminum powder pigment according to claim 2, characterized in that: The average particle size of the aluminum powder is 10-20 μm, the mass ratio of the aluminum powder to the hydrochloric acid solution is (10-25): (100-300), and the concentration of the hydrochloric acid solution is 1 mol / L; the power of the ultrasound is 200-300 W, the frequency is 40 kHz, and the time is 15-30 min.

4. The method for preparing the three-layer coated aluminum powder pigment according to claim 1, characterized in that: The amount ratio of the pretreated aluminum powder, ethyl orthosilicate, and solvent in step (1) is 10-20 g: 5-10 mL: 200-400 mL, and the solvent is ethanol or n-propanol.

5. The method for preparing the three-layer coated aluminum powder pigment according to claim 1, characterized in that: In step (1), the time for adding ethyl orthosilicate is 10-20 minutes; the pH is adjusted to 10-11; the temperature of the reaction is 50-60°C and the time is 6-8 hours; the temperature of the drying is 50-70°C and the time is 4-6 hours.

6. The method for preparing the three-layer coated aluminum powder pigment according to claim 1, characterized in that: In step (2), the mass ratio of the epoxy resin, silane coupling agent, inner layer SiO2 coated aluminum powder, and curing agent is (5-10): (0.1-0.2): (8-20): (2.5-5); the epoxy resin is epoxy resin E-44; the silane coupling agent is KH-550; the curing agent is polyamide 650; and the amount ratio of the epoxy resin to acetone is 5-10 g: 50-100 mL.

7. The method for preparing the three-layer coated aluminum powder pigment according to claim 1, characterized in that: In step (2), the heating reaction temperature is 70-90°C and the time is 3-5 hours; the drying temperature is 50-60°C and the time is 5-8 hours.

8. The method for preparing a three-layer coated aluminum powder pigment according to claim 1, characterized in that: Step (3) Vacuum degree after vacuuming ≤5×10 -4 Pa; the heating temperature is 150 ℃; the SiCl4 pulse time is 0.2-2s, the nitrogen purge time is 20-30s, the water vapor pulse time is 0.3-2s, and the nitrogen purge time is again 20-30s.

9. The method for preparing a three-layer coated aluminum powder pigment according to claim 1, characterized in that: The deposition thickness of each cycle in step (3) is 0.1 nm.

10. The three-layer coated aluminum powder pigment according to any one of claims 1 to 9, characterized in that: The product is prepared by the above-mentioned preparation method.

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