A coated modified zinc powder and its preparation method

Abstract

This invention discloses a coated modified zinc powder and its preparation method, belonging to the field of metal powder surface modification technology. The coated modified zinc powder uses zinc powder as its core, with a water-soluble polyacrylic acid (PAA) micelle layer formed by aqueous dissolution and ethanol-induced precipitation. This micelle layer is insoluble in ethanol but soluble in water. The preparation method includes zinc powder pretreatment, PAA aqueous dissolution, micelle coating, and post-treatment steps. The key step is to inhibit micelle agglomeration by intermittently replenishing deionized water, achieving uniform coating. This invention solves the contradictions of existing zinc powder oxidation, agglomeration, and storage and use. The modified zinc powder exhibits significantly improved storage stability, rapid removal of the micelle layer in the aqueous phase during use to restore its intrinsic activity, and excellent dispersion performance. The process is simple and easily scalable, making it suitable for anti-corrosion coatings, chemical catalysis, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of metal powder surface modification technology, specifically relating to a coated modified zinc powder and its preparation method. Background Technology

[0002] Zinc powder, as a key type of functional metallic powder, is widely used in anti-corrosion coatings, chemical catalysis, and electronic materials due to its sacrificial anodic protection properties, high specific surface area, and excellent reactivity. In anti-corrosion coatings, zinc powder can form a dense protective layer to isolate corrosive media, significantly extending the service life of steel components. In catalytic reactions, zinc powder acts as a catalyst or carrier, efficiently promoting the target reaction. In electronic pastes, the conductivity of zinc powder meets the connection and conduction requirements of electronic components.

[0003] However, existing zinc powders face three major technical challenges in practical applications: First, poor chemical stability. The surface of zinc powder is prone to oxidation reactions with oxygen and moisture in the air, forming a dense zinc oxide film that covers its active sites, severely weakening its core properties such as corrosion resistance and catalysis. Second, poor dispersibility. Zinc powder particles are prone to agglomeration due to van der Waals forces and electrostatic interactions, making it difficult to disperse evenly in coatings, slurries, and other systems, resulting in fluctuations in product performance. Third, the contradiction between storage and use. Existing modification technologies mostly improve stability through permanent coating, but the coating layer hinders the effective contact between zinc powder and the matrix or reaction system in practical applications, leading to activity decay. Temporary protection strategies are mostly physical adsorption, which has poor protection effects and cannot meet the requirements of long-term storage.

[0004] To address these issues, the industry has developed various surface modification technologies, such as silane coupling agent coating, resin coating, and inorganic oxide coating. However, all of these technologies have significant drawbacks: while permanent coatings can improve storage stability, they sacrifice the usability of zinc powder; temporary protection strategies, such as physically adsorbed antioxidants, are prone to detachment and failure, failing to provide long-term protection. Therefore, developing a modification technology that can achieve long-term stable storage of zinc powder, rapidly restore its intrinsic activity during use, and simultaneously possess good dispersibility has become a critical issue that the industry urgently needs to solve. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a coated modified zinc powder and its preparation method. By optimizing the micelle coating process and adopting the method of "aqueous dissolution-ethanol-induced precipitation", water-soluble polyacrylic acid (PAA) forms a tightly coated micelle layer on the surface of zinc powder. This not only solves the problems of oxidation and agglomeration during zinc powder storage, but also allows for rapid removal of the micelle layer in aqueous phase, restoring the intrinsic activity of zinc powder and achieving a synergistic unity of "storage stability" and "high efficiency in use".

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing coated modified zinc powder includes the following steps:

[0008] S1. Zinc powder pretreatment: Remove the oxide film on the surface of the original zinc powder, wash with deionized water, disperse the washed zinc powder in a 3-5% hydrogen peroxide solution, stir at room temperature for 8-12 minutes, and form hydroxyl (-OH) active sites on the surface of the zinc powder through mild oxidation, which enhances the interaction with the carboxyl (-COOH) group of PAA molecules. Then centrifuge and vacuum dry for later use.

[0009] S2. PAA aqueous phase dissolution: Add 1.0~1.5g of polyacrylic acid (PAA) to 50~60mL of deionized water and stir to dissolve to form a homogeneous PAA aqueous solution;

[0010] S3. Zinc powder dispersion and micelle coating: Add 1~1.5g of pretreated zinc powder to the PAA aqueous solution, stir to suspend the zinc powder, control the temperature to 5℃ and slowly add 20~24mL of anhydrous ethanol. After the ethanol is added, add 6mL of deionized water every 20min, and then continue stirring for 60~80min to complete the micelle coating.

[0011] S4. Post-processing: Centrifuge to collect the precipitate, wash, dry, pulverize and sieve to obtain coated modified zinc powder.

[0012] As a further preferred option for this technical solution.

[0013] Preferably, in step S1, the method for removing the oxide film on the surface of the original zinc powder is as follows: add the original zinc powder to a hydrochloric acid solution with a mass fraction of 1~2% and ultrasonically soak it at room temperature for 3~5 minutes.

[0014] Preferably, in step S1, the drying conditions are: drying in a vacuum oven at 80~100℃.

[0015] Preferably, in step S2, the molecular weight of the PAA is 5000.

[0016] Preferably, in step S2, the stirring speed is 300~400 r / min.

[0017] Preferably, in step S3, the stirring speed for suspending the zinc powder is 600~800 r / min, and the stirring time is 5~10 min.

[0018] Preferably, in step S4, the cleaning method is anhydrous ethanol cleaning, the drying conditions are drying in a vacuum oven at 70~90℃ for 2~3 hours, and the sieve mesh is 200 mesh.

[0019] A coated modified zinc powder was obtained according to the above preparation method.

[0020] The innovation lies in dissolving PAA in water and then adding a specific amount of anhydrous ethanol to form micelles, which are then deposited on the surface of zinc powder. To prevent micelles from colliding and agglomerating during stirring, deionized water is added at intervals, thereby making the micelles deposited more evenly on the surface of zinc powder.

[0021] Beneficial effects of the present invention

[0022] (1) Significantly improved storage stability: The composite structure physically coated by PAA micelles forms an isolation barrier, effectively blocking oxygen and moisture from contacting the zinc powder core and slowing down its oxidation;

[0023] (2) Rapid recovery of activity: PAA micelles are insoluble in ethanol but soluble in water. When using them, simply add the modified zinc powder to the aqueous system and the micelle layer will be rapidly dissolved and removed within 5 to 10 minutes. The intrinsic activity of the zinc powder surface will be restored without any additional complicated treatment. The operation is simple and efficient.

[0024] (3) Excellent dispersion performance: During the coating process, deionized water is added intermittently, which can inhibit the agglomeration of micelles after collision during stirring, promote the uniform deposition of micelles on the surface of zinc powder, reduce the van der Waals forces and electrostatic effects between particles, reduce the agglomeration of zinc powder, improve its dispersion uniformity in coatings, slurries and other systems, and reduce product performance fluctuations.

[0025] (4) Tightly bonded coating: The "water phase dissolution-ethanol induced precipitation" process is adopted, and the micelle layer is firmly bonded to the zinc powder surface. It is not easy to fall off during storage and transportation, ensuring the protective effect. At the same time, the subsequent removal is thorough, and no residual impurities affect the performance of zinc powder. Attached Figure Description

[0026] Figure 1 The image shows an electron microscope (SEM) image of the coated modified zinc powder prepared in Example 1.

[0027] Figure 2 Fourier transform infrared spectra of the coated modified zinc powder and pure zinc powder prepared in Example 1;

[0028] Figure 3 The X-ray diffraction (XRD) patterns of the coated modified zinc powder and pure zinc powder prepared in Example 1 after heating at 100 degrees Celsius for 72 hours are shown.

[0029] Figure 4 The Fourier transform infrared spectrum of the modified zinc powder coated in Example 1 after washing with deionized water;

[0030] Figure 5 (a)-(b) are photographs of the micelle solutions in Example 1 and Comparative Example 1, respectively, and (c) is a SEM image of the coated modified zinc powder prepared in Comparative Example 1.

[0031] Figure 6 (a)-(c) are photographs of the micelle solutions in Comparative Example 2, Comparative Example 3 and Comparative Example 4, respectively;

[0032] Figure 7 The Fourier transform infrared spectrum is shown for the sample prepared in Comparative Example 5. Detailed Implementation

[0033] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to examples. The following content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the concept of the invention, they should all fall within the protection scope of the present invention.

[0034] The preparation method of the present invention will be described below through specific embodiments and comparative examples.

[0035] Example 1

[0036] A method for preparing coated modified zinc powder includes the following steps:

[0037] S1. Zinc powder pretreatment: Add the raw zinc powder to a 1% hydrochloric acid solution, ultrasonically soak for 5 minutes at room temperature to remove the surface oxide film, wash with deionized water, disperse the washed zinc powder in a 5% hydrogen peroxide solution, stir at room temperature for 8 minutes, then centrifuge, and then dry in an 80℃ vacuum oven for later use.

[0038] S2. PAA aqueous phase dissolution: Add 1.0 g PAA (molecular weight 5000) to 50 mL of deionized water, stir at room temperature at a stirring speed of 300 r / min to dissolve and form a homogeneous PAA aqueous solution;

[0039] S3. Zinc powder dispersion and micelle coating: Add 1g of zinc powder pretreated in step S1 to the PAA aqueous solution in step S2, stir at 600r / min for 5min to suspend the zinc powder in the PAA aqueous solution, then place it in a magnetic water bath, add ice to the water bath to lower the temperature to 5℃, slowly add 20ml of anhydrous ethanol, after the ethanol is completely added, add 1mL of deionized water every 20min, for a total of 6mL, after the addition is complete, continue stirring for 60min;

[0040] S4. Post-processing: After the reaction is completed, the precipitate is obtained by centrifugation, then washed with anhydrous ethanol, and then dried in a vacuum oven at 70°C for 2 hours. The precipitate is then pulverized and passed through a 200-mesh sieve to obtain coated modified zinc powder.

[0041] Example 2

[0042] A method for preparing coated modified zinc powder includes the following steps:

[0043] S1. Zinc powder pretreatment: Add the raw zinc powder to a 1.5% hydrochloric acid solution and ultrasonically soak for 4 minutes at room temperature to remove the surface oxide film; wash with deionized water, disperse the washed zinc powder in a 4% hydrogen peroxide solution, stir at room temperature for 10 minutes, then centrifuge, and then dry in a vacuum oven at 90℃ for later use;

[0044] S2. PAA aqueous phase dissolution: Add 1.2g PAA (molecular weight 5000) to 55mL of deionized water, stir at room temperature at a stirring speed of 350r / min to dissolve and form a homogeneous PAA aqueous solution;

[0045] S3. Zinc powder dispersion and micelle coating: Add 1.2g of zinc powder pretreated in step S1 to the PAA aqueous solution in step S2, stir at 700r / min for 7min to suspend the zinc powder in the PAA aqueous solution, then place it in a magnetic water bath, add ice to the water bath to lower the temperature to 5℃, slowly add 22ml of anhydrous ethanol, after the ethanol is completely added, add 1mL of deionized water every 20min, for a total of 6mL, after the addition is complete, continue stirring for 70min;

[0046] S4. Post-processing: After the reaction is completed, the precipitate is obtained by centrifugation, then washed with anhydrous ethanol, and then dried in a vacuum oven at 80℃ for 2.5h. The precipitate is then pulverized and passed through a 200-mesh sieve to obtain coated modified zinc powder.

[0047] Example 3

[0048] A method for preparing coated modified zinc powder includes the following steps:

[0049] S1. Zinc powder pretreatment: Add the raw zinc powder to a 2% hydrochloric acid solution and ultrasonically soak for 3 minutes at room temperature to remove the surface oxide film; wash with deionized water, disperse the washed zinc powder in a 5% hydrogen peroxide solution, stir for 8 minutes at room temperature, then centrifuge, and then dry in a vacuum oven at 100℃ for later use.

[0050] S2. PAA aqueous phase dissolution: Add 1.5g PAA (molecular weight 5000) to 60mL of deionized water, stir at room temperature at a stirring speed of 400r / min to dissolve and form a homogeneous PAA aqueous solution;

[0051] S3. Zinc powder dispersion and micelle coating: Add 1.5g of zinc powder pretreated in step S1 to the PAA aqueous solution in step S2, stir at 800r / min for 10min to suspend the zinc powder in the PAA aqueous solution, then place it in a magnetic water bath, add ice to the water bath to lower the temperature to 5℃, slowly add 24ml of anhydrous ethanol, after the ethanol is completely added, add 1mL of deionized water every 20min, for a total of 6mL, after the addition is complete, continue stirring for 80min;

[0052] S4. Post-processing: After the reaction is completed, the precipitate is obtained by centrifugation, then washed with anhydrous ethanol, and then dried in a vacuum oven at 90℃ for 3 hours. The precipitate is then pulverized and passed through a 200-mesh sieve to obtain coated modified zinc powder.

[0053] Comparative Example 1 (Comparison of the Effects of Temperature)

[0054] The difference from Example 1 is that ice was not added to the magnetic water bath in step S3 to control the temperature, and ethanol was added and stirred at room temperature (25°C). The remaining steps, raw material amounts and parameters are the same as in Example 1.

[0055] Result: The sol system became turbid within 10 minutes after the addition of ethanol.

[0056] Comparative Example 2 (Comparison of the Effect of Solvent Ratio on Example 1)

[0057] The difference from Example 1 is that the amount of anhydrous ethanol added in step S3 is 16 mL (the volume ratio of deionized water to anhydrous ethanol is 50:16≈3.125:1, which exceeds 2:1). The remaining steps, raw material amounts and parameters are the same as in Example 1.

[0058] Result: The system immediately became turbid and precipitated during the addition of anhydrous ethanol.

[0059] Comparative Example 3 (Comparison of the Effect of Solvent Ratio 2)

[0060] The difference from Example 1 is that the amount of anhydrous ethanol added in step S3 is 12.5 mL (the volume ratio of deionized water to anhydrous ethanol is 50:12.5 = 4:1, which exceeds 3:1). The remaining steps, raw material amounts and parameters are the same as in Example 1.

[0061] Results: The system remained a homogeneous solution throughout, and no micelle structures were formed.

[0062] Comparative Example 4 (Comparison of the impact of water replenishment methods)

[0063] A zinc powder coating process differs from Example 1 in that: after the anhydrous ethanol is completely added in step S3, deionized water is not added; the remaining steps, raw material amounts, and parameters are the same as in Example 1.

[0064] Result: After stirring for 60 minutes, the system became turbid and produced a large amount of aggregated precipitate.

[0065] Comparative Example 5

[0066] A zinc powder coating process differs from Example 1 in that: in step S1: zinc powder pretreatment: the original zinc powder is added to a 1% hydrochloric acid solution, ultrasonically soaked at room temperature for 5 minutes to remove the surface oxide film, washed with deionized water, and then dried in a vacuum oven at 80°C for later use; the remaining steps, raw material amounts and parameters are the same as in Example 1.

[0067] Figure 1 The image shows a SEM image of the coated modified zinc powder prepared in Example 1. The SEM image clearly shows that the coated modified zinc powder particles are nearly spherical, with no obvious agglomeration between particles. This demonstrates the effectiveness of the interval-based water replenishment process: by adding 1 mL of deionized water every 20 minutes, micelle collision and agglomeration are effectively suppressed, allowing PAA micelles to be uniformly deposited on the zinc powder surface, forming a continuous and dense coating layer. This avoids agglomeration between zinc powder particles caused by van der Waals forces and electrostatic interactions, directly proving the beneficial effect of "excellent dispersion performance".

[0068] Figure 2 Fourier transform infrared (FT-IR) spectra of the coated modified zinc powder and pure zinc powder prepared in Example 1; comparing the FT-IR curves of pure zinc powder and coated modified zinc powder: pure zinc powder in the 1000-1800 cm⁻¹ range... -1 There are no characteristic absorption peaks in the range; while the coated modified zinc powder shows a peak at 1720 cm⁻¹. -1 A distinct C=O stretching vibration absorption peak appears at 1410 cm⁻¹. -1 The presence of a CH bending vibration absorption peak indicates that these characteristic peaks are typical infrared signals of PAA molecules. This demonstrates that the aqueous dissolution-ethanol-induced precipitation process of this invention successfully formed a PAA micelle coating layer on the surface of zinc powder.

[0069] Figure 3 The XRD diffraction patterns are those of the coated modified zinc powder and pure zinc powder prepared in Example 1 after heating at 100°C for 72 hours.

[0070] Explanation of the attached figure: In the XRD pattern, the intensity of the characteristic diffraction peaks of Zn (2θ=36.3°, 42.3°, 61.4°) reflects the degree of oxidation of zinc powder (after oxidation, ZnO is formed, and the intensity of the Zn characteristic peaks weakens). The comparison shows that after heating pure zinc powder at 100℃ for 72 hours, the intensity of the Zn characteristic peaks significantly decreased, and obvious ZnO characteristic peaks (2θ=31.7°, 34.4°) appeared; while the intensity of the Zn characteristic peaks in the coated modified zinc powder showed almost no decrease, and no obvious ZnO diffraction peaks were detected. This demonstrates the effect of the PAA micelle barrier: the micelle layer effectively blocks oxygen from contacting the zinc powder core, significantly slowing down the oxidation rate, directly proving the beneficial effect of "significantly improved storage stability," and solving the technical pain point of "poor chemical stability" in existing zinc powders.

[0071] Figure 4 The Fourier transform infrared spectrum of the modified zinc powder coated in Example 1 after washing with deionized water shows that the original PAA characteristic absorption peaks of the modified zinc powder after washing with deionized water have completely disappeared, and are basically consistent with the infrared spectrum of pure zinc powder, proving that the PAA micelle layer can be quickly dissolved and removed by aqueous phase.

[0072] Figure 5 (a)-(b) are photographs of the micelle solutions in Example 1 and Comparative Example 1, respectively; Figure 5 (a) In Example 1, at a low temperature of 5°C, the micelle solution was in a uniform and transparent state, and no precipitation was generated within 30 minutes, which proved that the micelle structure was stable at low temperature and could be uniformly dispersed and deposited on the surface of zinc powder. Figure 5 (b) (Comparative Example 1, room temperature 25°C) Within 10 minutes after the addition of ethanol, the micelles became turbid and precipitated, and the system became unstable. Figure 5 (c) is a SEM image of the modified zinc powder obtained in Comparative Example 1, showing obvious agglomeration. This indicates that low-temperature temperature control is a necessary condition for stable micelle formation: at room temperature, PAA molecules move violently, micelles are prone to collision and agglomeration, and uniform coating cannot be achieved, while a low-temperature environment can inhibit micelle instability and ensure the effectiveness of the coating process.

[0073] Figure 6 (a)-(c) are photographs of the micelle solutions in Comparative Example 2, Comparative Example 3 and Comparative Example 4, respectively; Figure 6 In (a) (Comparative Example 2, water:ethanol ≈ 3.125:1), the solution immediately precipitates, proving that when the solvent ratio exceeds a certain proportion, the ethanol concentration is too high, causing PAA to precipitate instantaneously and unable to form stable micelles. Figure 6 (b) In (Comparative Example 3, water:ethanol = 4:1), the solution was always uniform and transparent, with no micelles produced, proving that when the ethanol concentration is too low, it cannot induce PAA to form a micelle structure. Figure 6(c) (Comparative Example 4, without replenishment of deionized water) A large amount of agglomerated precipitate appeared after 60 min, proving that without replenishment of deionized water, micelle collision and agglomeration cannot be suppressed, resulting in uneven deposition.

[0074] Figure 7 The Fourier transform infrared spectrum of the sample prepared in Comparative Example 5 shows that there is no strong PAA characteristic absorption peak in the curve. This indicates that the amount of PAA absorbed by the untreated zinc powder surface is relatively small. This is because the formation of hydroxyl (-OH) active sites on the zinc powder surface through mild oxidation enhances the interaction with the carboxyl (-COOH) group of the PAA molecule, thereby causing PAA to be deposited on the zinc powder surface.

Claims

1. A method for producing a coated modified zinc powder, characterized by, Comprising the following steps: S1. Zinc powder pretreatment: removing the original zinc powder surface oxide film, washing with deionized water, dispersing the washed zinc powder in a 3-5% hydrogen peroxide solution by mass fraction, stirring at room temperature for 8-12 min, then centrifuging and vacuum drying for standby; S2. PAA aqueous solution dissolution: 1.0-1.5 g of polyacrylic acid (PAA) is added to 50-60 mL of deionized water, and stirred to form a uniform PAA aqueous solution; S3. Zinc powder dispersion and micelle coating: 1-1.5 g of pretreated zinc powder is added to the PAA aqueous solution, stirred to suspend the zinc powder, controlled to 5°C, then slowly added 20-24 mL of anhydrous ethanol, after the ethanol is added, every 20 min, add 6 mL of deionized water in total, then continue to stir for 60-80 min to complete the micelle coating; S4. Post-processing: collect the precipitate by centrifugation, wash, dry, crush and sieve to obtain coated modified zinc powder.

2. The production method according to claim 1, characterized by, In step S1, the method for removing the original zinc powder surface oxide film is: adding the original zinc powder to a 1-2% hydrochloric acid solution, ultrasonic immersion at room temperature for 3-5 min.

3. The preparation method according to claim 1, characterized in that, In step S1, the drying conditions are: drying in a 80-100°C vacuum oven.

4. The method of claim 1, wherein, In step S2, the molecular weight of the PAA is 5000.

5. The preparation method according to claim 1, characterized in that, In step S2, the stirring speed is 300-400 r / min.

6. The method of claim 1, wherein, In step S3, the stirring speed for suspending the zinc powder is 600-800 r / min, and the stirring time is 5-10 min.

7. The preparation method according to claim 1, characterized in that, In step S4, the washing method is anhydrous ethanol washing, the drying conditions are 70-90°C vacuum oven drying for 2-3 h, and the sieving mesh size is 200 mesh.

8. A coated modified zinc powder characterized in that, Prepared by the method of any one of claims 1-7.

Images