Preparation method of ultra-thin and ultra-fine scaly zinc powder

Abstract

The invention discloses a preparation method of ultra-thin and ultra-fine scaly zinc powder, and belongs to the technical field of non-ferrous metal functional powder materials. Comprising the following steps that a zinc ingot is subjected to liquation and impurity removal in a refining furnace at the constant temperature, zinc liquid is made to form zinc steam at the set evaporation rate, when the zinc steam enters a condenser, the zinc steam is subjected to micron-level condensation spheroidization nucleation, airflow classification is conducted under inert gas protection, and 3-7-micron superfine ultra-pure high-activity zinc powder is obtained; the preparation method comprises the following steps: grinding zinc powder serving as a raw material, an organic solvent, a material-liquid ratio, a stearic acid composite grinding aid, spherical zinc powder and a grinding medium zirconium oxide serving as grinding media in a horizontal grinder to obtain slurry; and introducing into a sedimentation centrifuge, and carrying out vacuum drying, polishing and grading to obtain scaly zinc powder. The prepared flaky zinc powder is obvious in metallic luster, the performance reaches the international advanced level, the flaky zinc powder can be ultrathin and ultrafine, the purity and the particle size distribution range exceed the international similar product indexes, and the physical and chemical index requirements for preparing anti-corrosion materials are met.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal materials, in particular to a method for preparing ultra-thin and ultra-fine flaky zinc powder. Background Art

[0002] At present, there is only a single spherical zinc powder or a process for producing zinc powder from spherical zinc powder as raw material. There is no complete set of processes and equipment from zinc ingots to zinc powder, and there are no relevant preparation technical parameters and technical indicators of zinc powder, so the method and preparation device cannot be realized. The current status of domestic ultra-thin and ultra-fine flaky zinc powder indicators shows that the technical indicators and data of ultra-thin and ultra-fine flaky zinc powder given by enterprises are different due to different preparation processes, and there are large differences in indicator parameters and data. Some use production processes such as closed evaporation in electric furnaces, inert gas protection, micro-positive pressure operation, rapid condensation, and airflow classification to produce irregular flake or spherical zinc powder with an average particle size of 2-4μm; some use distilled zinc liquid as raw material and use efficient dust collection technology and equipment to produce high-activity micron zinc powder with an average particle size of 2-4μm, which belongs to spherical powder; some produce zinc powder in irregular flakes with a maximum flake diameter of 16-22um, some produce zinc powder with a maximum flake diameter of 10-15um, and some produce zinc powder with a maximum flake diameter of 10-22um by wet method. The particle size of zinc powder produced in China is above 5μm or 16-22um, 10-15um, 10-22um, and the chemical indicators such as metal zinc and trace elements are not up to standard. Although flake zinc powder can be produced abroad, the particle size distribution is narrow, and the average particle size is 10-14um. Therefore, it is necessary to produce a zinc powder with large particle size, wide particle size distribution, high purity, strong activity, and its comprehensive performance is better than various domestic and foreign products.

[0003] The applicant has developed a method for preparing ultra-thin and ultra-fine flaky zinc powder by further upgrading and integrating the technology based on the original invention patents: 1. Spherical zinc powder patent: ZL 2009 1 0181678.3, ZL 2014 10157239.X; 2. Zinc powder process patent: ZL03112749.5. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing ultra-thin and ultra-fine flaky zinc powder.

[0005] A method for preparing ultrathin and ultrafine flaky zinc powder comprises the following steps: (1) The zinc ingot is melted and removed at a constant temperature in a refining furnace. The flow rate of the zinc liquid is controlled to make it flow into a closed evaporation pool at a stable and constant speed. The evaporation temperature in the evaporation pool is controlled to make the zinc liquid form zinc vapor at a set evaporation rate. When the zinc vapor enters the condenser, the condensation temperature and the flow rate of the inert gas circulating in the condenser are controlled to make the zinc vapor condense and spheroidize into nuclei at the micron level. Then, airflow classification is carried out under the protection of inert gas to obtain 3-7um ultra-fine ultra-pure high-activity zinc powder; (2) Using 3-7um ultrafine ultrapure high-activity zinc powder as raw material, organic solvent, material-liquid ratio of 2:3, and then adding 1% of the total mass of stearic acid as a composite grinding aid, spherical zinc powder and grinding medium zirconium oxide as grinding medium, material-ball ratio of 3:5, grinding in a horizontal grinder, the spindle speed of the grinder is 500r / min, and the average particle size of the prepared slurry is 18-22um, and the thickness is 0.3um-0.15um; (3) passing the ground slurry into a sedimentation centrifuge to separate the liquid and solid by centrifugal force to obtain paste-like flaky zinc powder; (4) Placing the paste-like flaky zinc powder in a vacuum drying oven, maintaining the vacuum degree of the drying oven at ≤ -0.095 MPa, the internal temperature of the drying oven at 60-70°C, and operating the vacuum drying oven for 8 hours to obtain flaky zinc powder with a moisture content of ≤3%; (5) Put the dried flaky zinc powder into the polishing equipment according to the proportion, add 0.5% composite modifier to the total amount of the material, and polish; (6) The polished flaky zinc powder is put into a classifier for classification to obtain ultra-thin and ultra-fine flaky zinc powder with an average particle size of 18-22 μm; Furthermore, the diameters of the zirconia balls are 2 mm, 3 mm, and 10 mm, respectively, with a ratio of 3:4:1.

[0006] Furthermore, the organic solvent is 200# solvent oil.

[0007] Furthermore, the grinding time is 2-4 hours.

[0008] Furthermore, the rotation speed of the sedimentation centrifuge is 1000r / min.

[0009] Furthermore, the polishing time is 2 hours.

[0010] Furthermore, the composite modifier is a composite modifier composed of a silane coupling agent and a rare earth metal in the polishing process, the ratio of the silane coupling agent to the rare earth metal is 5:1, which mainly improves the corrosion resistance and oxidation resistance of the flaky zinc powder, and can also improve the adaptability of the flaky zinc powder in the application. Experiments have shown that the best effect is achieved when the composite modifier accounts for 2.8% of the total amount of zinc powder.

[0011] Compared with the prior art: (1) The flaky zinc powder prepared by the method of the present invention has obvious metallic luster, and the product performance reaches the international advanced level. The product can be ultra-thin and ultra-fine, and the purity and particle size distribution range exceed the indicators of similar international products, and meet the physical and chemical index requirements for the preparation of anti-corrosion materials. The new process technology can produce ultra-thin and ultra-fine flaky zinc powder with total zinc ≥96%, metallic zinc ≥92%, Fe≤0.015, Pb≤0.005, Cd≤0.005, hydrochloric acid insoluble matter ≤0.20, oil content ≤3, average particle size above 18-22μm, and flake thickness of 0.1-0.3μm. The zinc powder produced by this technology has large particle size, wide particle size distribution, high purity, strong activity, and its comprehensive performance is better than various domestic and foreign products. (2) For the first time, a system process and device for preparing spherical zinc powder from zinc ingots by melt distillation and condensation, and then realizing the preparation of ultra-thin and ultra-fine flaky zinc powder for terminal projects through sheet forming is realized. (3) The ultra-thin and ultra-fine flaky zinc powder produced can significantly reduce the consumption of zinc powder by about 30%-40% without changing the performance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is further explained below in conjunction with the accompanying drawings.

[0014] The preparation method of the present invention is as follows Figure 1 As shown, the ultra-thin and ultra-fine flaky zinc powder is produced by combining physical principles with mechanical technology, using spherical zinc powder preparation devices such as melting, evaporation, and condensation, and ultra-thin and ultra-fine flaky zinc powder equipment such as ball milling, polishing, and drying.

[0015] 1. Technical solution for preparation of spherical zinc powder The zinc ingot raw material is melted and removed from the impurities at a constant temperature in a melting furnace, and the flow rate of the zinc liquid is controlled to make it flow into a closed evaporation pool at a stable and constant speed. The evaporation temperature in the evaporation pool is controlled to make the zinc liquid form zinc vapor at a set evaporation rate. When the zinc vapor enters the condenser, the condensation temperature and the flow rate of the inert gas circulating in the condenser are controlled so that the zinc vapor can condense and spheroidize into nuclei at the micron level, and then air flow classification is carried out under the protection of the inert gas to obtain ultra-fine, ultra-pure and highly active zinc powder, which is the raw material for preparing ultra-thin, ultra-fine flaky zinc powder.

[0016] 2. Technical solution for the preparation of zinc powder for flaking The dry flake conversion process is achieved through ball milling, pulping, degreasing, and drying, and then dispersion, polishing, and grading technology are used to prepare ultra-thin and ultra-fine flaky zinc powder. Grinding and flaking are carried out in a horizontal grinder. Before grinding, a mixer is required to pre-disperse and wet the material. The pre-processed material is a mixture of solid and liquid. The dispersed material is input into the horizontal grinder through an electric diaphragm pump. After the material enters the cylinder, the material and the grinding medium in the cylinder will rotate at a high speed due to the stirring action of the disperser. This causes a very strong collision between the solid and some particles in the material and the grinding medium, and friction and shearing between them, so that the material can be flaked. During the grinding process, the movement speed of the grinding medium, the mutual movement mode between the balls, and the collision impulse determine the energy level or efficiency of the grinder. The energy required for the deformation and tearing of spherical powder is mainly obtained by the collision of the balls. If the ball movement speed is low, the mutual movement is mainly friction, and the probability of collision is low, the grinding efficiency is low. Increasing the speed of the ball will increase the probability of collision and reduce the probability of friction. The kinetic energy of the grinding ball Ekin = 1 / 2mv 2 , where Ekin is the kinetic energy of the ball, m is the mass of the ball, and v is the speed of the ball. From this formula, it can be seen that the most effective way to increase the kinetic energy of the ball is to increase its speed, because the kinetic energy is in a square relationship with the speed. By adjusting the speed of the horizontal grinder and controlling the collision speed of the grinding medium during high-energy grinding, ultra-thin and ultra-fine flaky zinc powder with different particle size distributions can be achieved.

[0017] 3. Process parameters of the zinc powder preparation technology for flaking According to product requirements, the optimal process parameters were determined.

[0018] 3.1 Grinding process: 3-7um high-purity low-impurity spherical zinc powder is used as raw material, 200# solvent oil is used as solvent (material-liquid ratio is 2:3), and 1% stearic acid of the total material is added as a composite grinding aid, and 2mm, 3mm, and 10mm diameter zirconium oxide balls are added (zirconia parameter ratio is 3:4:1), spherical zinc powder and grinding medium zirconium oxide are used as grinding media (material-ball ratio is 3:5), and the slices are made by grinding in a horizontal grinder for about 3 hours, the spindle speed of the grinder is 500r / min, and samples are taken for testing after stopping. At this time, the average particle size of the slurry is 18-22um, and the particle thickness is 0.3um-0.15um. Note: During the grinding process, the ratio is appropriately adjusted according to the viscosity of the slurry.

[0019] 3.2 Deliquidation process: The qualified slurry is passed into the sedimentation centrifuge (flat plate) at a speed of 1000r / min. The liquid and solid are separated by centrifugal force to obtain paste-like flaky zinc powder. Note: During the deliquidation process, the speed of the sedimentation centrifuge can be adjusted to obtain paste-like flaky zinc powder with different solid contents. Ensure that there are no impurities or debris in the process.

[0020] 3.3 Drying process: Place the paste-like flaky zinc powder in a vacuum drying oven, maintain the vacuum degree of the drying oven ≤-0.095MPa, and the internal temperature of the drying oven at 60-70℃. The vacuum drying oven works for 8 hours to obtain flaky zinc powder with a moisture content of ≤3%, which meets the technical requirements of GB / T 26035-2010. Note: Considering the safety of the equipment and the purity of the product, the vacuum degree of the vacuum drying oven must meet the requirements of this process.

[0021] 3.4 Polishing process: Put the dried flaky zinc powder into the homemade polishing equipment in proportion, add 0.5% composite modifier to the total material, and polish for 2 hours. The composite modifier is a composite modifier composed of silane coupling agent and rare earth metal in the polishing process, and the ratio of silane coupling agent to rare earth metal is 5:1, which mainly improves the corrosion resistance and oxidation resistance of flaky zinc powder, and at the same time can improve the adaptability of flaky zinc powder in application. Experiments have shown that the best effect is achieved when the composite modifier accounts for 2.8% of the total zinc powder.

[0022] 3.5 Classification process: This process plays a vital role. The polished flaky zinc powder is put into a classifier with a fixed frequency for classification to obtain flaky zinc powder with an average particle size of about 18-22um.

[0023] 3.6 Packaging: The qualified flaky zinc powder shall be packaged according to the packaging requirements of GB / T 26035-2010. The packaging barrel and packaging bag must be sealed in place.

[0024] The influence of raw materials on the preparation of ultra-thin ultra-fine flaky zinc powder under the conditions of raw material average particle size of 3-7um and metal zinc at 97%-98%: raw material spherical zinc powder with different particle size distribution and metal activity directly affects the performance of ultra-thin ultra-fine flaky zinc powder. When the average particle size of raw material spherical zinc powder is less than 3um, its fluidity is worse, and the oxidation rate is high during grinding, resulting in insufficient extension during grinding. When the average particle size of raw material is greater than 7um, the oxidation rate becomes smaller during grinding, but the grinding force is uneven, and the average particle size of the obtained product does not meet the technical requirements of GB / T 26035-2010 (national standard for flaky zinc powder). The average particle size of the raw materials is between 3-7um, the metal zinc is between 97%-98%, and the average particle size of the ultra-thin and ultra-fine flaky zinc powder produced meets the technical requirements of GB / T 26035-2010 (national standard for flaky zinc powder) and enterprise standard Q / 321202HKC001-2019, and the metallic luster is obvious. The technology and product performance of this project have reached the international advanced level, among which the product can achieve ultra-thin and ultra-fine, and the purity and particle size distribution range exceed the indicators of similar international products, and meet the physical and chemical index requirements for the preparation of anti-corrosion materials.

[0025] The new process technology developed in this project can produce ultra-thin and ultra-fine flaky zinc powder with total zinc ≥ 96%, metallic zinc ≥ 92%, Fe ≤ 0.015, Pb ≤ 0.005, Cd ≤ 0.005, hydrochloric acid insoluble matter ≤ 0.20, oil content ≤ 3, average particle size above 18-22μm, and flake thickness of 0.1-0. 3μm. The particle size of zinc powder produced domestically is above 5μm or 16-22um, 10-15um, 10-22um, and chemical indicators such as metallic zinc and trace elements are not up to standard. Although flake zinc powder can be produced abroad, the particle size distribution is narrow, and the average particle size is 10-14um. Therefore, the zinc powder produced by this technology has a large particle size, a wide particle size distribution, high purity, strong activity, and its comprehensive performance is better than various domestic and foreign products.

Claims

1. A method for preparing ultrathin and ultrafine flaky zinc powder, characterized in that: The following steps are included: (1) The zinc ingot is melted and removed at a constant temperature in a refining furnace. The flow rate of the zinc liquid is controlled to make it flow into a closed evaporation pool at a stable and constant speed. The evaporation temperature in the evaporation pool is controlled to make the zinc liquid form zinc vapor at a set evaporation rate. When the zinc vapor enters the condenser, the condensation temperature and the flow rate of the inert gas circulating in the condenser are controlled to make the zinc vapor condense and spheroidize into nuclei at the micron level. Then, airflow classification is carried out under the protection of inert gas to obtain 3-7um ultra-fine ultra-pure high-activity zinc powder; (2) Using 3-7um ultrafine ultrapure high-activity zinc powder as raw material, organic solvent, material-liquid ratio of 2:3, and then adding 1% of the total mass of stearic acid as a composite grinding aid, spherical zinc powder and grinding medium zirconium oxide as grinding medium, material-ball ratio of 3:5, grinding in a horizontal grinder, the spindle speed of the grinder is 500r / min, and the average particle size of the prepared slurry is 18-22um, and the thickness is 0.3um-0.15um; (3) passing the ground slurry into a sedimentation centrifuge to separate the liquid and solid by centrifugal force to obtain paste-like flaky zinc powder; (4) Placing the paste-like flaky zinc powder in a vacuum drying oven, maintaining the vacuum degree of the drying oven at ≤ -0.095 MPa, the internal temperature of the drying oven at 60-70°C, and operating the vacuum drying oven for 8 hours to obtain flaky zinc powder with a moisture content of ≤3%; (5) Put the dried flaky zinc powder into the polishing equipment according to the proportion, add 0.5% composite modifier to the total amount of the material, and polish; (6) The polished flaky zinc powder is put into a classifier for classification to obtain ultra-thin and ultra-fine flaky zinc powder with an average particle size of 18-22 um.

2. The method for preparing ultrathin and ultrafine flaky zinc powder according to claim 1, characterized in that: The diameters of the zirconia balls are 2 mm, 3 mm, and 10 mm, respectively, with a ratio of 3:4:

1.

3. The method for preparing ultrathin and ultrafine flaky zinc powder according to claim 1, characterized in that: The organic solvent is 200# solvent oil.

4. The method for preparing ultrathin and ultrafine flaky zinc powder according to claim 1, characterized in that: The grinding time is 2-4 hours.

5. The method for preparing ultrathin and ultrafine flaky zinc powder according to claim 1, characterized in that: The rotation speed of the sedimentation centrifuge is 1000r / min.

6. The method for preparing ultrathin and ultrafine flaky zinc powder according to claim 1, characterized in that: The polishing time is 2 hours.

7. The method for preparing ultrathin and ultrafine flaky zinc powder according to claim 1, characterized in that: The composite modifier is a composite modifier composed of a silane coupling agent and a rare earth metal, and the ratio of the silane coupling agent to the rare earth metal is 5:

1.

8. The method for preparing ultrathin and ultrafine flaky zinc powder according to claim 7, characterized in that: The composite modifier accounts for 2.8% of the total amount of zinc powder.

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