Preparation method of surface-coated flaky zinc powder and zinc powder

Abstract

The invention relates to the technical field of preparation of metal powder materials, and discloses a preparation method of surface-coated scaly zinc powder and the zinc powder.The preparation method comprises the five steps of zinc powder pretreatment, coating liquid preparation, surface coating, drying and curing and screening treatment.The high-purity zinc powder is subjected to ball milling to be of a scaly structure; the method comprises the following steps: adding zinc particles into a coating solution, then adding a coating solution formed by fully mixing a silane coupling agent, an organosilicon compound, an antioxidant, a performance enhancer and a water-containing alcohol ether solvent, filtering and separating zinc powder and the coating solution after a compact coating layer is formed on the surfaces of the zinc particles, drying and curing, and finally screening the cured and cooled zinc powder. The method has the effect of improving the oxidation resistance of the zinc powder.

Description

Technical Field

[0001] The present application relates to the technical field of metal powder material preparation, and in particular to a preparation method of surface-coated flaky zinc powder and the zinc powder. Background Art

[0002] Zinc powder is widely used in anti-corrosion coatings due to its excellent electrochemical protection properties. Primers containing zinc powder are generally referred to as zinc-rich primers. Zinc-rich primers primarily protect steel from corrosion through two methods: shielding and cathodic protection. Shielding isolates the corrosive medium from the steel substrate through the dense coating. Cathodic protection relies on contact between zinc particles and the steel substrate within the zinc-rich primer coating, forming a smooth conductive network and achieving electrochemical protection. Therefore, zinc powder is one of the most important fillers influencing the performance of zinc-rich primers.

[0003] Compared to spherical zinc powder, flake zinc powder offers superior hiding power, floatation, and shielding capabilities. It can form a layered shielding layer within the coating, effectively improving the coating's corrosion resistance, making it a key raw material for high-performance anti-corrosion coatings. However, zinc powder is chemically reactive and easily reacts with oxygen and moisture in the air during storage and use, leading to surface oxidation and reducing its corrosion resistance and service life. Currently, the main methods for improving the oxidation resistance of zinc powder include physical coating and chemical modification. Physical coating typically involves coating the zinc powder with materials such as polymers. While this method can isolate the zinc powder from oxygen and moisture to a certain extent, it suffers from weak bonding between the coating and the zinc powder, making it susceptible to detachment during processing and use. Chemical modification involves a chemical reaction on the zinc powder surface to form a protective film. However, this process is complex and costly, and the zinc powder's oxidation resistance often fails to meet practical requirements. Therefore, the development of a zinc powder with a simple preparation process and high oxidation resistance is urgent. Summary of the Invention

[0004] In order to form a uniform, dense and firmly bonded coating layer on the surface of zinc powder and effectively improve the antioxidant ability of zinc powder, the present application provides a preparation method of surface-coated flaky zinc powder and zinc powder.

[0005] In the first aspect, the present application provides a method for preparing a surface-coated flaky zinc powder using the following technical solution: A method for preparing surface-coated flaky zinc powder comprises the following steps: S1. Zinc powder pretreatment: Add high-purity zinc powder and environmentally friendly dispersing solvent into a ball mill for ball milling. The zinc powder is processed into a flaky structure by ball milling, and then washed and dried for later use; S2. Preparation of coating solution: fully mix the silane coupling agent, organosilicon compound, antioxidant, performance enhancer and aqueous alcohol ether solvent for later use; S3, surface coating: adding the pre-treated flaky zinc powder to the prepared coating solution and stirring thoroughly; S4, drying and solidifying: filtering and separating the flaky zinc powder coated with the coating liquid from the coating liquid, and drying and solidifying the flaky zinc powder coated with the coating liquid; S5. Screening treatment: Cool the solidified zinc powder to room temperature and screen it through a sieve to obtain surface-coated flaky zinc powder.

[0006] By adopting the above technical solution, the zinc powder is mechanically pressed into a flaky structure to increase the specific surface area. When applied to the coating, the shielding performance and electrochemical protection efficiency of the coating are improved. The addition of an environmentally friendly dispersing solvent can prevent the zinc powder from agglomerating and ensure that the flaky structure is evenly dispersed. The organic silicon compound has good film-forming properties and flexibility, and can form a continuous and dense coating on the surface of the zinc powder. It can also improve the hydrophobicity and antioxidant properties of the zinc powder. The silane coupling agent is easily hydrolyzed into silanol in the presence of water. The silanol can react with the organic silicon compound and the hydroxyl group on the surface of the zinc powder to synergistically It plays a role in connection and anchoring, improving the adhesion of the coating layer; adding antioxidants can capture free radicals in the system, preventing or delaying the oxidation reaction of zinc powder; adding performance enhancers can form a three-dimensional network structure in the coating layer of zinc powder, so that sufficient points are evenly distributed on the surface of the flake zinc powder for the antioxidant to arrange, which is beneficial to enhancing the bonding strength and anti-oxidation of the coating layer, and ensuring uniform mixing and full contact between the zinc powder and the coating liquid; screening treatment can remove agglomerated particles and unqualified products, so that the prepared zinc powder meets environmental protection requirements while ensuring product quality and stability.

[0007] In a specific embodiment, the environmentally friendly dispersing solvent in S1 is one or more of anhydrous ethanol and propylene glycol methyl ether.

[0008] By adopting the above technical solution, anhydrous ethanol plays a key role as a dispersion medium in zinc powder pretreatment. On the one hand, it reduces the surface energy between zinc powder particles, effectively preventing agglomeration due to mutual attraction during ball milling, ensuring that the zinc powder is evenly affected by the grinding media, thus forming an ideal flaky structure. On the other hand, anhydrous ethanol has good fluidity, which can drive the zinc powder movement within the ball mill, ensuring full contact between the zinc powder and the grinding media, improving ball milling efficiency, and achieving a more uniform zinc powder particle size.

[0009] The molecular structure of propylene glycol methyl ether combines the properties of both alcohol and ether, offering excellent solubility and dispersion capabilities, as well as a moderate volatilization rate that effectively reduces the surface tension between zinc powder particles, preventing particle agglomeration. During the ball milling process, it interacts with the zinc powder surface through intermolecular forces, maintaining a uniform dispersion of the zinc powder within the mill and ensuring smooth flaking. Furthermore, alcohol-ether solvents are less toxic and pose minimal health risks to operators. Residual solvents are also easier to remove during subsequent washing and drying steps, minimizing the impact on subsequent zinc powder coating and performance, thus meeting the requirements of modern green chemical processes. Both solvents are recyclable, ensuring uniform dispersion of flaky zinc powder, controllable particle size, and environmental compliance.

[0010] In a specific embodiment, the mass ratio of the silane coupling agent, the organosilicon compound, the antioxidant and the performance enhancer in S2 is 1:4:0.35:0.2.

[0011] The inventors discovered that controlling the mass ratio of the silane coupling agent, organosilicon compound, antioxidant, and performance enhancer within the aforementioned range allows for the formation of a dense coating with a more optimal ratio on the surface of the zinc particles, enhancing the bonding between the coating and the zinc powder, and improving the zinc powder's antioxidant capacity and dispersion stability. The silane coupling agent provides sufficient chemical bonding sites, ensuring a strong bond between the coating and the zinc powder; the organosilicon compound content ensures the formation of a continuous film; the appropriate amount of antioxidant inhibits oxidation, while an excessive amount may affect the stability of the coating; and the performance enhancer regulates the system viscosity, assisting in the effective distribution of the antioxidant on the zinc powder surface; an excessive amount can lead to excessive system viscosity, affecting workability.

[0012] In a specific embodiment, the silane coupling agent is KH-550.

[0013] By adopting the above technical solution, KH-550 (γ-aminopropyltriethoxysilane) is hydrolyzed to generate silanol (Si-OH), which reacts with the hydroxyl groups on the surface of the zinc powder and can also react and couple with the organic silicon compound to form a continuous and dense coating film on the surface of the zinc powder, thereby improving the bonding strength between the coating layer and the zinc powder, enhancing the water resistance and chemical corrosion resistance, increasing the crosslinking density of the coating layer, and improving the density of the coating layer wrapped around the zinc powder.

[0014] In a specific embodiment, the organosilicon compound is hydroxy silicone oil.

[0015] By adopting this technical solution, the hydroxy silicone oil forms a coating on the zinc powder surface, reducing the van der Waals forces between zinc powder particles, inhibiting agglomeration, and improving dispersion stability through steric hindrance. The silanol (-Si-OH) groups generated by the hydrolysis of the ethoxy groups (-OC2H5) in the KH-550 coating solution further condense with the -OH groups in the hydroxy silicone oil. The resulting siloxane network chemically anchors and encapsulates the zinc powder particles, forming a continuous, dense organosilicon coating that isolates the zinc powder from direct contact with the external environment and enhances corrosion resistance.

[0016] In a specific embodiment, the antioxidant is one or more of a phenolic antioxidant, a phosphite antioxidant, and a thioester antioxidant.

[0017] By adopting the above technical solution, in the preparation method of surface-coated flaky zinc powder, adding phenol, phosphite, and thioester antioxidants (one or more) can inhibit the surface oxidation of zinc powder, stabilize its activity, and improve the durability of the coating layer, thereby improving the corrosion resistance of zinc powder in the coating.

[0018] In a specific embodiment, the antioxidant includes a phenolic antioxidant, a phosphite antioxidant and a thioester antioxidant, and the mass ratio of the phenolic antioxidant, the phosphite antioxidant and the thioester antioxidant is 4:2:1.

[0019] The inventors discovered that combining phenolic, phosphite, and thioester antioxidants in a mass ratio of 4:2:1 unexpectedly improved antioxidant efficacy compared to conventional antioxidant combinations. This combination achieves enhanced antioxidant efficacy through a triple synergistic mechanism: free radical capture, peroxide decomposition, and antioxidant regeneration. Phenolic antioxidants primarily terminate oxidative chain reactions by capturing free radicals; phosphite antioxidants focus on decomposing hydroperoxides (ROOH), converting them into stable non-radical products; and thioester antioxidants inhibit the oxidation process by consuming oxygen molecules and reacting with free radicals. When these three antioxidants are combined, the phenolic antioxidants rapidly capture initially generated free radicals, the phosphite antioxidants promptly decompose the hydroperoxides (ROOH), preventing them from initiating further free radical reactions, and the thioester antioxidants continuously consume oxygen molecules, inhibiting free radicals. Together, these three antioxidants form a multi-stage, multi-pathway antioxidant system.

[0020] If the proportion of phenolic antioxidants is too high, even if the initial free radical scavenging ability is strong, the accumulation of ROOH produced after the consumption of phenolic antioxidants in the middle and late stages may lead to weakening of antioxidant properties; if the ratio of phosphite antioxidants / thioester antioxidants is too high, it may lead to insufficient initial free radical scavenging, resulting in aggravated early oxidation and decreased ability to digest oxygen molecules.

[0021] The antioxidant compound ratio of 4:2:1 has been verified by experiments to achieve a dynamic balance between free radical scavenging (phenolic antioxidants) and ROOH decomposition (phosphite antioxidants + thioester antioxidants) and the elimination of nutrient molecules, thereby achieving long-term antioxidant effects.

[0022] In a specific embodiment, the phenolic antioxidant is hindered phenolic antioxidant 1010, the phosphite antioxidant is triphenyl phosphite, and the thioester antioxidant is dilauryl thiodipropionate.

[0023] By adopting this technical solution, hindered phenol antioxidant 1010, which features four hindered phenol units, offers significant steric hindrance and high antioxidant efficiency. It effectively captures free radicals generated by zinc powder surface oxidation. Furthermore, it exhibits excellent compatibility with coating materials such as organosilicon compounds, without affecting the stability of the coating solution or the zinc powder coating effect. When used alone, it significantly slows zinc powder oxidation under standard storage and usage conditions.

[0024] Hindered phenol antioxidant 1010 first captures free radicals, and triphenyl phosphite then decomposes COOH. The two work synergistically to effectively protect zinc powder in high-temperature environments. For example, in zinc powder coating for powder metallurgy, it can prevent zinc powder from oxidizing during high-temperature pressing and sintering.

[0025] Dilauryl thiodipropionate reacts with ROOH via its sulfur atom, reducing it to an alcohol and thus preventing further oxidation. When combined with Hindered Phenolic Antioxidant 1010, Hindered Phenolic Antioxidant 1010 provides initial antioxidant protection, while Dilauryl thiodipropionate takes effect later, extending the antioxidant life of the zinc powder. During storage, the zinc powder's antioxidant properties are maintained for extended periods, ensuring the long-term effectiveness of the coating.

[0026] In a specific embodiment, the performance enhancer is HOOC(CH2) 17 NH3 + Modified organic montmorillonite.

[0027] The inventors found that adding HOOC(CH2) to the coating solution containing the above antioxidants in the present application 17 NH3 + The modified organic montmorillonite unexpectedly greatly improved the antioxidant properties of the coated zinc powder. After analysis, this may be due to the fact that the montmorillonite is 17 NH3 +Modification replaces the inorganic cations between montmorillonite layers with organic ammonium ions, increasing the interlayer spacing. When zinc powder is immersed in the coating solution, it acts as a "core," bonding between surface hydroxyl groups (Zn-OH) and the COOH / NH2 groups of the organic montmorillonite to anchor the flakes to the particle surface, forming a three-dimensional "zinc powder-montmorillonite" composite network. This network also provides ample sites for antioxidants to align, enhancing the antioxidant properties of the zinc flakes after coating.

[0028] The tert-butyl structure of HPA 1010 is embedded in the hydrophobic environment of the long-chain alkyl groups of montmorillonite, enhancing its stability through van der Waals forces and anchoring it to the polar regions of the network. The three-dimensional network utilizes steric hindrance to restrict the migration of HPA 1010, achieving its effective and stable distribution.

[0029] The P=O bond of triphenyl phosphite and Zn on the surface of zinc powder 2+ Or the metal ions between montmorillonite layers form coordination bonds (P=O→Zn 2+ ), anchored in the three-dimensional network nodes, its benzene ring structure and the long chain of the organic modifier between the montmorillonite layers undergo π-π stacking, which enhances the anchoring adsorption force, and the triphenyl phosphite molecules are trapped between the montmorillonite layers, slowly releasing and decomposing ROOH, which is beneficial to improving the antioxidant property.

[0030] The long chain alkyl group of dilauryl thiodipropionate (C 12 H 25 -) easily reacts with the long-chain alkyl (CH2) of montmorillonite 17 The molecules are entangled and concentrated in the non-polar region of the three-dimensional network. Therefore, HOOC(CH2) 17 NH3 + The addition of modified organic montmorillonite enables the three specific antioxidants of the present application to form a more stable and reasonable distribution in the coating layer, forming a gradient protection in which the polar region is enriched with hindered phenol antioxidant 1010 (capturing free radicals), the non-polar region is enriched with dilauryl thiodipropionate, and triphenyl phosphite is distributed at the interface between the two (decomposing ROOH), which is more conducive to achieving the synergistic effect of the three antioxidants on the zinc surface, greatly improving the binding force and antioxidant performance of the coating layer.

[0031] In a second aspect, the present application provides a zinc powder prepared by the above-mentioned preparation method of surface-coated flaky zinc powder.

[0032] By employing this technical solution, an environmentally friendly, flaky zinc powder with a dense coating can be produced. This flaky structure allows the zinc powder to align itself during subsequent coating applications, creating a "maze effect" that significantly enhances the coating's shielding properties. Furthermore, the dense coating and the composite antioxidant system work synergistically to enhance the zinc powder's antioxidant capacity, extending its salt spray resistance in subsequent coating applications. This approach also avoids the challenges of traditional coating methods, such as weak adhesion and easy shedding, the introduction of harmful substances, and the complex and costly process, offering the advantages of environmental friendliness and a long lifespan.

[0033] In summary, this application includes at least one of the following beneficial technical effects: 1. Use pretreatment to make zinc powder form a flaky structure to enhance its shielding ability, use a specific coating liquid to form a dense coating layer on the surface of zinc particles, and after drying, solidification and screening treatment, it can effectively improve the antioxidant ability of zinc powder and extend its service life. In this specific coating liquid, the silane coupling agent is hydrolyzed in an aqueous alcohol ether solvent to form silanol, which bonds with zinc powder and organosilicon compounds. The organosilicon compound has good film-forming properties and flexibility, and can form a continuous and dense coating film on the surface of zinc powder. The silanol reacts with the organosilicon compound and the hydroxyl group on the surface of zinc powder to synergistically play a connecting and anchoring role, thereby improving the hydrophobicity and antioxidant properties of zinc powder; the antioxidant can capture the free radicals in the system, further preventing or delaying the oxidation reaction of zinc powder; the performance enhancer can form a three-dimensional network structure in the coating liquid, so that the surface of the flaky zinc powder is evenly distributed with enough points for the antioxidant to arrange, so that different antioxidants are reasonably distributed in the coating layer on the surface of the zinc powder, better exerting their synergistic effects, and greatly improving the antioxidant properties through the performance enhancer. The entire process is environmentally friendly and no harmful substances are introduced, while ensuring product quality; 2. Phenolic antioxidants mainly terminate the oxidation chain reaction by capturing free radicals; phosphite antioxidants focus on decomposing ROOH and converting it into stable non-free radical products; thioester antioxidants react with ROOH to reduce it to alcohols, inhibiting the oxidation process. The three are combined: phenolic antioxidants first quickly capture the free radicals generated in the early stage, phosphite antioxidants promptly decompose the generated ROOH to prevent it from further initiating free radical reactions, and thioester antioxidants play a role in the middle and late stages of oxidation, continuously consuming ROOH. The three cooperate with each other to form a multi-stage, multi-pathway antioxidant system; 3. Add HOOC (CH2) to the coating solution 17 NH3 +Modified montmorillonite: Zinc powder coordinates with the COOH / NH2 groups of the montmorillonite via surface hydroxyl groups (Zn-OH), anchoring the sheet to the particle surface and forming a "zinc powder-montmorillonite" composite three-dimensional network. This three-dimensional network provides ample sites for the antioxidants to assemble, ultimately creating a gradient protection structure with polar regions enriched with hindered phenolic antioxidant 1010 (to capture free radicals), non-polar regions enriched with dilauryl thiodipropionate, and triphenyl phosphite distributed at the interface between the two (to decompose ROOH). Triphenyl phosphite (decomposing ROOH) significantly enhances the coating's bonding strength and antioxidant properties. DETAILED DESCRIPTION

[0034] The present application is further described in detail below with reference to the following examples and comparative examples: Some of the raw materials used in the examples and comparative examples: Zinc powder (CAS No.: 7440-66-6); KH-550 (CAS No.: 919-30-2); hydroxy silicone oil with the product brand MY1203, purchased from Anhui Mingyi Silicon Industry Co., Ltd.; antioxidant 1010 (CAS No.: 6683-19-8); triphenyl phosphite (CAS No.: 101-02-0); dilauryl thiodipropionate (CAS No.: 123-28-4); inorganic montmorillonite (CAS No.: 1318-93-0); sodium montmorillonite with the brand Y16776, purchased from Beijing Biolab Technology Co., Ltd.

[0035] The raw materials used in the examples and comparative examples that are not otherwise specified are all conventional products that can be purchased from the market.

[0036] Preparation Example Preparation Example 1 HOOC(CH2) 17 NH3 + Preparation steps of modified organic montmorillonite: 1. Raw material pretreatment: Purification of montmorillonite: Weigh 50 g of sodium montmorillonite and add 1000 mL of deionized water to prepare a 5% suspension; stir at 200 r / min for 30 min, let it stand for 2 h, then pour out the supernatant, repeat washing twice, and finally collect the precipitate and drain the water (residual water content is about 10 g).

[0037] Modifier preparation: Add 8.9g oleic acid (HOOC(CH2) 17 CH=CH2, 0.03mol), introduce ammonia (NH3) until the solution pH = 9.0 (monitored by precision pH test paper), continue stirring for 2h, and generate HOOC (CH2) 17 NH3 + Modifier (ammonium oleate), actual yield is about 92% (about 8.2g).

[0038] 2. Ion exchange modification Activation of montmorillonite suspension: Transfer the purified montmorillonite suspension (total mass approximately 110 g) into a 250 mL beaker and heat to 80°C (using a water bath). Add 5 g of NaCl and stir at 200 rpm for 1 hour to complete sodium activation.

[0039] Modification reaction: 10g HOOC(CH2) 17 NH3 + The modifier was added to the activated suspension, and the pH was adjusted to 6.5 with 1 mol / L HCl. The suspension was transferred to a 1 L three-necked flask and stirred in an 80 °C oil bath at 300 r / min for 4 h. Deionized water (about 50 mL) was added during the reaction to prevent the suspension from drying up.

[0040] 3. Washing and Dehydration Centrifugal washing: After the reaction solution has cooled to room temperature, transfer it to a 50 mL centrifuge tube and centrifuge at 4000 rpm for 15 min. Discard the supernatant. Resuspend the precipitate in 50 mL of deionized water and repeat the centrifugation washing three times until the conductivity of the washing solution is <100 μS / cm (measured with a conductivity meter).

[0041] Vacuum drying: Spread the washed filter cake on a petri dish and place it in a vacuum drying oven at 60°C and -0.08 MPa for 12 hours until constant weight (weight loss ≤ 0.5 g) is obtained to obtain HOOC (CH2) 17 NH3 + The modified organic montmorillonite is about 58g.

[0042] 4. Crushing and screening Mechanical crushing: The dried product is crushed with a micro airflow crusher (such as AS-200 model), controlling the air inlet pressure to 0.6 MPa, the crushing time to 5 min, and the cavity temperature to <40°C.

[0043] Sieving and grading: Pass through a 200-mesh standard sieve (sieve size 74 μm), collect the undersize material, and the yield is about 90% (52 g). Example

[0044] Example 1 A preparation method for surface-coated flaky zinc powder comprises the following steps: S1. Zinc powder pretreatment: 1000 g of electrolytic zinc powder with a purity of not less than 95% and 150 g of anhydrous ethanol were added to a ball mill and ball-milled at 400 r / min for 3 hours. After the ball milling, the zinc powder and ethanol were separated by filtration, and the zinc powder was washed with deionized water several times to remove residual impurities and ethanol on the surface. Finally, the zinc powder was placed in a vacuum drying oven and dried at 70°C to constant weight.

[0045] S2. Preparation of coating liquid: Based on 100 g of coating liquid, weigh 4 g of silane coupling agent (KH-550), 16 g of hydroxy silicone oil, 1.4 g of hindered phenol antioxidant 1010, 0.8 g of inorganic montmorillonite, and the rest is 95% by mass of propylene glycol dimethyl ether aqueous solution.

[0046] First, slowly add the silane coupling agent into the aqueous alcohol ether solvent and hydrolyze it for 30 minutes at a stirring speed of 200 / min to generate silanol; then add hydroxy silicone oil and continue stirring for 60 minutes to fully mix it with the silanol; then add the antioxidant and stir for 30 minutes to evenly disperse it; finally, add the inorganic montmorillonite and continue stirring for 20 minutes.

[0047] S3. Surface coating: 50 g of pre-treated flaky zinc powder was slowly added to the prepared coating solution, and stirred at a stirring speed of 200 / min and a temperature of 60°C for 90 minutes using a double planetary mixer; S4, drying and curing: filtering and separating the zinc powder and the coating liquid, placing the zinc powder in a forced air drying oven, and drying at 100°C for 90 minutes; then transferring the dried zinc powder to a high-temperature curing furnace, and curing at 200°C for 0.5 hours; S5. Screening treatment: Cool the solidified zinc powder to room temperature and screen it through a sieve to obtain surface-coated flaky zinc powder.

[0048] Example 2 The difference between this embodiment and embodiment 1 is that the antioxidant is replaced by triphenyl phosphite in equal amounts.

[0049] That is, S2, coating liquid preparation: based on 100g of coating liquid, weigh 4g of silane coupling agent (KH-550), 16g of hydroxy silicone oil, 1.4g of triphenyl phosphite, 0.8g of inorganic montmorillonite, and the rest is 95% by mass of propylene glycol dimethyl ether aqueous solution.

[0050] Example 3 The difference between this embodiment and embodiment 1 is that the antioxidant is replaced by dilauryl thiodipropionate in an equal amount.

[0051] That is, S2, coating liquid preparation: based on 100g of coating liquid, weigh 4g of silane coupling agent (KH-550), 16g of hydroxy silicone oil, 1.4g of dilauryl thiodipropionate, 0.8g of inorganic montmorillonite, and the rest is 95% by mass of propylene glycol dimethyl ether aqueous solution.

[0052] Example 4 The difference between this embodiment and embodiment 1 is that the single-component antioxidant is replaced by a composite antioxidant (the mass ratio of hindered phenol antioxidant 1010, triphenyl phosphite and dilauryl thiodipropionate is 1:1:1) That is, S2, coating liquid preparation: based on 100g of coating liquid, weigh 4g of silane coupling agent (KH-550), 16g of hydroxy silicone oil, 0.46g of hindered phenol antioxidant 1010, 0.46g of triphenyl phosphite, 0.46g of dilauryl thiodipropionate, 0.8g of inorganic montmorillonite, and the rest with 95% by mass of propylene glycol dimethyl ether aqueous solution.

[0053] Example 5 The difference between this embodiment and embodiment 1 is that the single-component antioxidant is replaced by a composite antioxidant (the mass ratio of hindered phenol antioxidant 1010, triphenyl phosphite and dilauryl thiodipropionate is 1:2:4) That is, S2, coating liquid preparation: based on 100g of coating liquid, weigh 4g of silane coupling agent (KH-550), 16g of hydroxy silicone oil, 0.2g of hindered phenol antioxidant 1010, 0.4g of triphenyl phosphite, 0.8g of dilauryl thiodipropionate, 0.8g of inorganic montmorillonite, and the rest with 95% by mass of propylene glycol dimethyl ether aqueous solution.

[0054] Example 6 The difference between this embodiment and embodiment 1 is that the single-component antioxidant is replaced by a composite antioxidant (the mass ratio of hindered phenol antioxidant 1010, triphenyl phosphite and dilauryl thiodipropionate is 4:2:1) That is, S2, coating liquid preparation: based on 100g of coating liquid, weigh 4g of silane coupling agent (KH-550), 16g of hydroxy silicone oil, 0.8g of hindered phenol antioxidant 1010, 0.4g of triphenyl phosphite, 0.2g of dilauryl thiodipropionate, 0.8g of inorganic montmorillonite, and the rest with 95% by mass of propylene glycol dimethyl ether aqueous solution.

[0055] Example 7 The difference between this embodiment and embodiment 1 is that the inorganic montmorillonite is replaced by HOOC (CH2) in equal amounts. 17 NH3 + Modified organic montmorillonite.

[0056] That is, S2, coating liquid preparation: based on 100g coating liquid, weigh 4g silane coupling agent (KH-550), 16g hydroxy silicone oil, 1.4g hindered phenol antioxidant 1010, 0.8g HOOC (CH2) 17 NH3 + The modified organic montmorillonite is used, and the rest is a 95% by mass aqueous solution of propylene glycol dimethyl ether.

[0057] Example 8 The difference between this embodiment and embodiment 2 is that the inorganic montmorillonite is replaced by HOOC (CH2) in equal amounts. 17 NH3 + Modified organic montmorillonite.

[0058] That is, S2, coating liquid preparation: based on 100g coating liquid, weigh 4g silane coupling agent (KH-550), 16g hydroxy silicone oil, 1.4g triphenyl phosphite, 0.8g HOOC (CH2) 17 NH3 + The modified organic montmorillonite is used, and the rest is a 95% by mass aqueous solution of propylene glycol dimethyl ether.

[0059] Example 9 The difference between this embodiment and embodiment 3 is that the inorganic montmorillonite is replaced by HOOC (CH2) in equal amounts. 17 NH3 + Modified organic montmorillonite.

[0060] That is, S2, coating liquid preparation: based on 100g coating liquid, weigh 4g silane coupling agent (KH-550), 16g hydroxy silicone oil, 1.4g dilauryl thiodipropionate, 0.8g HOOC (CH2) 17 NH3 + The modified organic montmorillonite is used, and the rest is a 95% by mass aqueous solution of propylene glycol dimethyl ether.

[0061] Example 10 The difference between this embodiment and embodiment 6 is that the inorganic montmorillonite is replaced by HOOC (CH2) in equal amounts. 17 NH3 + Modified organic montmorillonite.

[0062] That is, S2, coating liquid preparation: based on 100g coating liquid, weigh 4g silane coupling agent (KH-550), 16g hydroxy silicone oil, 0.8g hindered phenol antioxidant 1010, 0.4g triphenyl phosphite, 0.2g dilauryl thiodipropionate, 0.8g HOOC(CH2) 17 NH3 + The modified organic montmorillonite is used, and the rest is a 95% by mass aqueous solution of propylene glycol dimethyl ether.

[0063] Comparative Example Comparative Example 1 The only difference between this comparative example and Example 6 is that in S2, the inorganic montmorillonite is removed and an equal amount of hydroxy silicone oil is added.

[0064] That is, S2, coating liquid preparation: based on 100g of coating liquid, weigh 4g of silane coupling agent (KH-550), 16.8g of hydroxy silicone oil, 0.8g of hindered phenol antioxidant 1010, 0.4g of triphenyl phosphite and 0.2g of dilauryl thiodipropionate, and the rest is 95% by mass of propylene glycol dimethyl ether aqueous solution.

[0065] Performance test The flaky zinc powder prepared in Examples 1-10 and Comparative Example 1 was used to prepare a coating by the following conventional zinc-rich coating preparation method: the raw materials are expressed in parts by weight: 20 parts of epoxy resin (E-44) and 10 parts of ethyl acetate (solvent) were mixed in a high-speed shearing machine, and 65 parts of flaky zinc powder, 5 parts of anti-settling agent, 3 parts of dispersant, 2 parts of defoaming agent and 10 parts of polyamide curing agent (650#) were added in batches and mixed to obtain a coating.

[0066] The coatings prepared in Examples 1-10 and Comparative Example 1 were applied by roller coating on a sample steel plate of 60 mm × 120 mm and a thickness not exceeding 3 mm at a rate of -4 cups / 25 seconds (25°C), and cured at 60°C for 1 hour. The coating thickness was 0.1 mm, forming a coating on the sample steel plate.

[0067] 1. Ultraviolet (UV) aging test: The UV aging resistance of the corresponding coating was tested according to the standard GB / T 16422.3-2014. The test conditions were: irradiation with a fluorescent UV lamp (UVA-340, wavelength 340 nm) for 1000 h, temperature 60°C, and humidity 65%. The evaluation index was: measurement of the integrity (%) of the coating after UV aging.

[0068] 2. Salt spray aging test Refer to standard GB / T 10125-2021, test conditions: 5% NaCl solution, 35°C, for 240 hours; evaluation index: measure the rust area (%) after salt spray test.

[0069] 3. High temperature oxidation test According to the standard GB / T 13303-1991, the test conditions are: 300°C for 100 hours in an air atmosphere; the evaluation index is to measure the oxidation weight gain (%).

[0070] The above test results are recorded in Table 1.

[0071] Table 1 Combining the test results of Examples 1-3 and Examples 4-6, the compound antioxidant (Examples 4-6) significantly improves the performance, especially when the mass ratio of hindered phenol antioxidant 1010, triphenyl phosphite and dilauryl thiodipropionate is 4:2:1 (Example 6), the oxidation weight gain rate is reduced to 1.8%, because hindered phenol, phosphite and thioester form a synergistic antioxidant system, covering multiple mechanisms such as free radical capture and peroxide decomposition.

[0072] 2. Specifically, based on the test results of Examples 1-3 and 7-10, the inorganic montmorillonite is replaced by HOOC (CH2) 17 NH3 + After the modification of organic montmorillonite, all properties are significantly improved, and the salt spray corrosion area (%) is further reduced by 26.1%, and the oxidation weight gain rate (%) is further reduced by 21.4%. Compared with Examples 1-3 and 7-9, Example 10 has the most obvious performance improvement compared with Example 6, indicating that the present application, after HOOC (CH2) 17 NH3 + The modified organic montmorillonite increases the interlayer spacing and forms a composite three-dimensional network with the zinc flake powder, so that sufficient antioxidant sites are evenly distributed on the surface of the zinc flake powder, providing a sequential distribution of the three compounded antioxidants. Ultimately, in the coating solution, the three-dimensional network forms a gradient protection with the polar region enriched with hindered phenolic antioxidant 1010 (capturing free radicals), the non-polar region enriched with dilauryl thiodipropionate, and triphenyl phosphite distributed at the interface between the two (decomposing ROOH). It can be seen that through HOOC(CH2) 17 NH3 + The addition of modified organic montmorillonite greatly improves the bonding strength and antioxidant properties of the coating layer.

[0073] This specific embodiment is merely an explanation of the present application and does not limit the present application. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical scope of the present application. The technical scope of the present application is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for preparing surface-coated flaky zinc powder, characterized in that: The steps include: S1. Zinc powder pretreatment: Add high-purity zinc powder and environmentally friendly dispersing solvent into a ball mill for ball milling. The zinc powder is processed into a flaky structure by ball milling, and then washed and dried for later use; S2. Preparation of coating solution: fully mix the silane coupling agent, organosilicon compound, antioxidant, performance enhancer and aqueous alcohol ether solvent for later use; S3, surface coating: adding the pre-treated flaky zinc powder to the prepared coating solution and stirring thoroughly; S4, drying and solidifying: filtering and separating the flaky zinc powder coated with the coating liquid from the coating liquid, and drying and solidifying the flaky zinc powder coated with the coating liquid; S5. Screening treatment: Cool the solidified zinc powder to room temperature and screen it through a sieve to obtain surface-coated flaky zinc powder.

2. The method for preparing the surface-coated flaky zinc powder according to claim 1, wherein The environmentally friendly dispersing solvent in S1 is one or more of anhydrous ethanol and propylene glycol methyl ether.

3. The method for preparing the surface-coated flaky zinc powder according to claim 1, wherein: The mass ratio of the silane coupling agent, the organosilicon compound, the antioxidant and the performance enhancer in S2 is 1:4:0.35:0.

2.

4. The method for preparing the surface-coated flaky zinc powder according to claim 1, wherein: The silane coupling agent is KH-550.

5. The method for preparing the surface-coated flaky zinc powder according to claim 1, wherein: The organic silicon compound is hydroxy silicone oil.

6. The method for preparing surface-coated flaky zinc powder according to claim 1, wherein: The antioxidant is one or more of phenolic antioxidants, phosphite antioxidants and thioester antioxidants.

7. The method for preparing surface-coated flaky zinc powder according to claim 1, wherein: The antioxidants include phenolic antioxidants, phosphite antioxidants and thioester antioxidants, and the mass ratio of the phenolic antioxidants, phosphite antioxidants and thioester antioxidants is 4:2:

1.

8. The method for preparing surface-coated flaky zinc powder according to claim 7, wherein: The phenolic antioxidant is hindered phenolic antioxidant 1010, the phosphite antioxidant is triphenyl phosphite, and the thioester antioxidant is dilauryl thiodipropionate.

9. The method for preparing surface-coated flaky zinc powder according to claim 1, wherein: The performance enhancer is HOOC(CH2) 17 NH3 + Modified organic montmorillonite.

10. A zinc powder, characterized in that: The zinc powder is prepared by the method according to any one of claims 1 to 9.

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