Polishing powder for automobile paint surface and preparation method thereof

Abstract

The invention discloses polishing powder for an automobile paint surface and a preparation method of the polishing powder. The preparation method comprises the following steps: preparing a mixed solution; preparing a roasting material from the mixed solution and pseudo-boehmite, wherein the specific surface area of the roasting material is 30-60m < 2 > / g; grinding the roasted material to obtain aluminum oxide slurry; adding a coupling agent and a dispersing agent into the aluminum oxide slurry, and reacting under a stirring condition to prepare mixed slurry; and carrying out post-treatment on the mixed slurry to obtain the polishing powder of which the particle size distribution D50 is in a range of 0.6-0.9 mu m and the particle size distribution D100 is less than 10 mu m. According to the preparation method of the polishing powder, the prepared polishing powder has good polishing performance, the surface smoothness of a polished automobile paint surface is improved, the polishing powder is easy to store and transport, and the production cost can be effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of polishing technology, and more particularly to polishing automotive paint surfaces, specifically to an alumina polishing powder for automotive paint surfaces and its preparation method. Background Technology

[0002] With the development of the automotive industry and the improvement of people's living standards, the number of cars on the road is constantly increasing; high-end automotive paint polishing requires a high mirror finish, namely high gloss and low haze. Alpha-alumina, due to its high hardness (Mohs hardness 8.8), acid and alkali resistance, and good thermal stability, is widely used as a polishing abrasive. Currently, automotive paint polishing often employs initial polishing, intermediate polishing, and fine polishing processes depending on the degree of damage. Fine polishing requires the use of alumina powder with a particle size of 0.5-2μm to balance the cutting amount and surface finish.

[0003] In conventional processes, alumina powder is often transported and stored in slurry form, which has a low solid content (typically 30%), resulting in high transportation and storage costs. If a dry process is used, uneven particle distribution and sharp particle morphology may affect polishing performance. Therefore, developing a new type of alumina powder that can guarantee a high mirror finish while reducing costs is of great significance. Summary of the Invention

[0004] In view of this, in order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a polishing powder for automotive paint and a method for preparing the same, which can effectively improve polishing performance and reduce production costs.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing polishing powder, comprising the following steps: Preparation of mixed solutions; A calcined material was prepared from a mixed solution and pseudoboehmite, the specific surface area of ​​the calcined material being 30-60 m². 2 / g; The calcined material is ground to obtain an alumina slurry; A mixed slurry was prepared by adding a coupling agent and a dispersant to an alumina slurry and reacting them under stirring conditions. The mixed slurry is post-processed to obtain the polishing powder, the particle size distribution of which is: D50 in the range of 0.6-0.9μm and D100 less than 10μm.

[0006] According to some preferred embodiments of the present invention, the method for preparing the mixed solution is as follows: Zirconium salt and titanium salt are added to deionized water and stirred until the zirconium salt and titanium salt are completely dissolved to obtain the mixed solution; wherein the mass ratio of zirconium salt to titanium salt is 1-4:1; and the mass ratio of the total mass of zirconium salt and titanium salt to the mass of deionized water is 490-500:3.

[0007] According to some preferred embodiments of the present invention, a method for preparing calcined materials from a mixed solution and boehmite is as follows: An equal mass of boehmite is added to the mixed solution and dispersed uniformly. Nitric acid is then added to prepare an aluminum sol with a pH of 3-4, which is then spray-dried to obtain an aluminum-doped precursor. The aluminum-doped precursor is then calcined at 1110-1150°C to obtain the calcined material. In some embodiments of the present invention, spray drying the aluminum sol helps to ensure a uniform particle size distribution and regular particle morphology in the obtained aluminum-doped precursor.

[0008] According to some preferred embodiments of the present invention, before calcining the doped aluminum precursor at a temperature of 1110-1150°C, the doped aluminum precursor is first heated from room temperature to a first temperature over 1-3 hours and held at the first temperature for 1-3 hours to dehydrate, then heated to a second temperature over 4-6 hours and held at the second temperature for 1-3 hours to undergo crystal transformation, and finally heated to 1110-1150°C over 2-4 hours and held at 1110-1150°C for 0.5-1.5 hours to calcine, obtaining the calcined material. This calcination process allows for the orderly development of the crystal phase, avoiding the problem of sharp-edged particles caused by single high-temperature calcination. Furthermore, the calcination process is controlled based on the specific surface area to ensure that the specific surface area of ​​the calcined material obtained after calcination is controlled at 30-60 m². 2 Within a range of / g, this ensures that it maintains a certain level of hardness while also ensuring sufficient chemical activity.

[0009] According to some preferred embodiments of the present invention, the first temperature is 100-300°C and the second temperature is 850-950°C.

[0010] According to some preferred embodiments of the present invention, the α-Al2O3 in the calcined material has a Mohs hardness of 9.2-9.3 and a grain size of 40-60 nm.

[0011] In this invention, a mixed solution of zirconium salt and titanium salt is prepared and used as a dopant to achieve uniform elemental distribution in the boehmite precursor stage. During calcination, Zr... 4+ With Ti 4+Entering the alumina lattice to form a solid solution can, on the one hand, increase the microhardness of α-Al2O3 (Mohs hardness can reach 9.2-9.3), enhancing its cutting ability; on the other hand, it can inhibit excessive grain growth, keeping the grain size within the range of 40-60nm, thus avoiding scratches on the car paint caused by coarse grains.

[0012] According to some preferred embodiments of the invention, the purity of the pseudoboehmite is greater than or equal to 99.99%.

[0013] According to some preferred embodiments of the present invention, a method for grinding calcined materials to obtain alumina slurry is as follows: The calcined material is first coarsely ground until a coarse grinding material with a particle size distribution of D50 in the range of 2-3 μm and D100 less than 15 μm is obtained. Then, a grinding aid is added to the coarse grinding material for fine grinding until a fine grinding material with a particle size distribution of D50 in the range of 0.6-0.9 μm and D100 less than 10 μm is obtained. The fine grinding material is an alumina slurry. The solid content of the slurry during coarse grinding and fine grinding is 30%-40%. The mass percentage of the added grinding aid to the mass of the calcined material added during coarse grinding is 0.3%-1%. The addition of the grinding aid helps to disperse the material, reduce friction between the grinding media, improve grinding efficiency, and help to uniformly disperse the material and prevent particle agglomeration.

[0014] According to some preferred embodiments of the present invention, the process of adding a coupling agent and a dispersant to an alumina slurry and reacting them under stirring conditions to prepare a mixed slurry is as follows: first, a coupling agent is added to the alumina slurry, and the mixture is stirred at a temperature of 50-60°C for 1-2 hours; then, a dispersant is added, and the mixture is stirred at a temperature of 50-60°C for another 2-3 hours to obtain the mixed slurry; wherein the mass percentage of the added coupling agent is 0.2%-0.5% of the mass of the calcined material added during coarse grinding, and the mass percentage of the added dispersant is 1%-3% of the mass of the calcined material added during coarse grinding. The dispersant is added to ensure the dispersibility and suspension of the alumina slurry in the system.

[0015] According to some preferred embodiments of the present invention, the post-processing includes the following steps: The prepared mixed slurry is first sieved and then freeze-dried, then pulverized and sieved a second time. Finally, after mixing, the polishing powder is obtained. The mesh size of the sieve used in the first sieve is 400-600 mesh, and the mesh size of the sieve used in the second sieve is 100-300 mesh. In this invention, through freeze-drying and pulverization, the dispersibility of the alumina dry powder is made close to that of the alumina slurry, making it easy to store and transport while also possessing good polishing performance.

[0016] According to some preferred embodiments of the present invention, the coupling agent is a silane coupling agent, and the dispersant is nano-silica. In this invention, the silane coupling agent may be γ-aminopropyltriethoxysilane, whose amino group can form a chemical bond with the hydroxyl group on the surface of alumina, and whose ethoxy group at the other end condenses with the hydrolysis products of nano-silica, thereby constructing a robust composite coating layer. This composite coating layer has a dual function: firstly, it buffers the impact between alumina particles and the paint surface through the low hardness of silica, reducing mechanical scratches; secondly, it improves the dispersibility of alumina particles through the steric hindrance effect of silane molecules.

[0017] Preferably, the method for preparing the polishing powder of the present invention specifically includes the following steps: Step 1: Prepare the mixed solution.

[0018] Zirconium salt and titanium salt were added to deionized water and stirred until the zirconium salt and titanium salt were completely dissolved to obtain a mixed solution.

[0019] The mass ratio of zirconium salt to titanium salt is 1-4:1, and the mass ratio of the total mass of zirconium salt and titanium salt to the mass of deionized water is 490-500:3.

[0020] Step 2: Prepare calcined material from the mixed solution and pseudoboehmite.

[0021] Take an appropriate amount of the mixed solution from step 1, add an equal mass of boehmite and disperse it evenly, then add nitric acid to prepare an aluminum sol with a pH of 3-4. Spray dry the sol to obtain an aluminum-doped precursor. First, heat the aluminum-doped precursor from room temperature to a first temperature over 1-3 hours and hold it at the first temperature for 1-3 hours to dehydrate it. Then, heat it to a second temperature over 4-6 hours and hold it at the second temperature for 1-3 hours to perform crystal transformation. Finally, heat it to 1110-1150℃ over 2-4 hours and hold it at 1110-1150℃ for 0.5-1.5 hours to calcine it, obtaining a calcined material with a specific surface area controlled to be 30-60 m². 2 / g; In addition, the Mohs hardness of α-Al2O3 of the calcined material is 9.2-9.3, and HSEM characterization is used to monitor the grain size of the calcined material to ensure that the grain size of the calcined material is 40-60nm.

[0022] The first temperature is 100-300℃, and the second temperature is 850-950℃.

[0023] Step 3: Grind the roasted material to prepare alumina slurry.

[0024] Take an appropriate amount of the roasted material from step 2 and coarsely grind it until a coarse grinding material with a particle size distribution of D50 in the range of 2-3 μm and D100 less than 15 μm is obtained. Then add a grinding aid to the coarse grinding material and finely grind it until a fine grinding material with a particle size distribution of D50 in the range of 0.6-0.9 μm and D100 less than 10 μm is obtained. The fine grinding material is the alumina slurry.

[0025] The solid content of the slurry during coarse grinding and fine grinding is 30%-40%; the mass of the added grinding aid accounts for 0.3%-1% of the mass of the roasted material added during coarse grinding.

[0026] Preferably, both coarse grinding and fine grinding can be done by ball milling. For coarse grinding, a stirred ball mill can be used, and for fine grinding, a sand mill can be used. The speed of the sand mill is controlled at 1000-1100 rpm, and the diameter of the grinding beads is 0.8-1.2 mm.

[0027] Step 4: Add coupling agent and dispersant to alumina slurry and react under stirring conditions to prepare a mixed slurry.

[0028] Take an appropriate amount of the alumina slurry from step 3, add a coupling agent to it, and stir at 50-60℃ for 1-2 hours. Then add a dispersant and continue stirring at 50-60℃ for 2-3 hours to obtain a mixed slurry.

[0029] The mass percentage of the added coupling agent is 0.2%-0.5% of the mass of the roasted material added during coarse grinding in step 3, and the mass percentage of the added dispersant is 1%-3% of the mass of the roasted material added during coarse grinding in step 3.

[0030] Step 5: Post-process the mixed slurry to obtain polishing powder.

[0031] The prepared mixed slurry is first sieved and then freeze-dried, then pulverized and sieved a second time, and finally mixed to obtain polishing powder.

[0032] The first sieve uses a screen with a mesh size of 400-600, and the second sieve uses a screen with a mesh size of 100-300.

[0033] Another object of the present invention is to provide a polishing powder for automotive paint surfaces prepared by the preparation method described above. Compared with traditional alumina polishing powder, the polishing powder of the present invention not only improves polishing performance, but is also easy to transport and store, and can effectively reduce transportation and storage costs.

[0034] Due to the adoption of the above technical solutions, the advantages of this invention compared to existing technologies are as follows: The preparation method of the polishing powder for automotive paint surfaces of this invention uses high-purity boehmite as raw material, and involves doping with Zr in a mixed solution. 4+ With Ti 4+ To enhance the cutting ability of α-Al2O3 while controlling grain size, and through the interaction of alumina with coupling agents and dispersants, a strong composite coating layer is constructed for alumina, thereby improving the dispersibility of alumina particles and reducing mechanical scratches on automotive paint surfaces, thus improving surface smoothness. The polishing powder for automotive paint surfaces of this invention is easy to store and transport, and has good polishing performance. Its particle size distribution is narrow and its microstructure is uniform, which enables the polished automotive paint surface to have high gloss and low haze. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a scanning electron microscope image of the aluminum-doped precursor obtained after step 2 in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the calcined material obtained after step 2 in Example 1 of the present invention; Figure 3 This is a particle size distribution diagram of the alumina slurry obtained after step 3 in Example 1 of the present invention; Figure 4 This is a particle size distribution diagram of the material obtained after freeze-drying in step 5 of Example 1 of the present invention. Figure 5 This is a particle size distribution diagram of the polishing powder prepared in Example 1 of the present invention; Figure 6 This is a scanning electron microscope image of the polishing powder prepared in Example 1 of the present invention; Figure 7 This is a scanning electron microscope image of the aluminum-doped precursor obtained after step 2 in Example 2 of the present invention; Figure 8 This is a scanning electron microscope image of the calcined material obtained after step 2 in Example 2 of the present invention; Figure 9 This is a particle size distribution diagram of the alumina slurry obtained after step 3 in Example 2 of the present invention; Figure 10This is a particle size distribution diagram of the material obtained after freeze-drying in step 5 of Example 2 of the present invention. Figure 11 This is a particle size distribution diagram of the polishing powder prepared in Example 2 of the present invention; Figure 12 This is a scanning electron microscope image of the polishing powder prepared in Example 2 of the present invention; Figure 13 This is a scanning electron microscope image of the aluminum precursor prepared in Comparative Example 1 of the present invention; Figure 14 This is a scanning electron microscope image of the calcined material obtained after calcination in Comparative Example 1 of the present invention. Figure 15 This is a particle size distribution diagram of the alumina slurry in Comparative Example 1 of the present invention; Figure 16 This is a particle size distribution diagram of the material obtained after freeze-drying in Comparative Example 1 of the present invention. Figure 17 This is a particle size distribution diagram of the polishing powder prepared in Comparative Example 1 of the present invention; Figure 18 This is a scanning electron microscope image of the polishing powder prepared in Comparative Example 1 of the present invention; Figure 19 This is a particle size distribution diagram of the material obtained after freeze-drying in Comparative Example 2 of the present invention. Figure 20 This is a particle size distribution diagram of the polishing powder prepared in Comparative Example 2 of the present invention; Figure 21 This is a scanning electron microscope image of the polishing powder prepared in Comparative Example 2 of the present invention; Figure 22 This is a scanning electron microscope image of the calcined material obtained after calcination in Comparative Example 3 of the present invention. Figure 23 This is a particle size distribution diagram of the alumina slurry in Comparative Example 3 of the present invention; Figure 24 This is a particle size distribution diagram of the material obtained after freeze-drying in Comparative Example 3 of the present invention. Figure 25 This is a particle size distribution diagram of the polishing powder prepared in Comparative Example 3 of the present invention; Figure 26 This is a scanning electron microscope image of the polishing powder prepared in Comparative Example 3 of the present invention; Figure 27 This is a scanning electron microscope image of aluminum hydroxide in Comparative Example 4 of the present invention; Figure 28 This is a scanning electron microscope image of the calcined material obtained after calcination in Comparative Example 4 of the present invention. Figure 29This is a particle size distribution diagram of the alumina slurry in Comparative Example 4 of the present invention; Figure 30 This is a particle size distribution diagram of the material obtained after freeze-drying in Comparative Example 4 of the present invention. Figure 31 This is a particle size distribution diagram of the polishing powder prepared in Comparative Example 4 of the present invention; Figure 32 This is a scanning electron microscope image of the polishing powder prepared in Comparative Example 4 of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0038] Unless otherwise specified in the following examples and comparative examples, all raw materials were commercially available or prepared using conventional methods in the art. Specifically, the boehmite in Examples 1 and 2, and Comparative Examples 1 to 3, was purchased from Yangzhou Zhongtianli, grade ZTL-CAH-4, with a purity of ≥99.99%. The aluminum hydroxide in Comparative Example 4 was purchased from Yangzhou Zhongtianli, grade ZTL-WTCAH-30, with a purity of ≥99%.

[0039] Example 1 This embodiment provides a method for preparing polishing powder for automotive paint surfaces and the polishing powder produced therefrom. The preparation method of the polishing powder specifically includes the following steps: Step 1: Prepare the mixed solution.

[0040] By weight, 0.4 parts of zirconium oxychloride and 0.2 parts of titanium tetrachloride were added to 99.4 parts of deionized water, and the mixture was stirred until the zirconium oxychloride and titanium tetrachloride were completely dissolved to obtain a mixed solution.

[0041] Step 2: Prepare calcined material from the mixed solution and pseudoboehmite.

[0042] Take an appropriate amount of the mixed solution from step 1, add an equal mass of boehmite and disperse it evenly, then add analytical grade nitric acid to prepare an aluminum sol with a pH of 3-4, and spray dry to obtain the aluminum-doped precursor. See the scanning electron microscope image of the aluminum-doped precursor for details. Figure 1The aluminum-doped precursor was placed in a muffle furnace and heated from room temperature to 150°C over 2 hours, then held at 150°C for 1 hour for dehydration. The temperature was then increased to 900°C over 5 hours and held at 900°C for 2 hours for crystal transformation. Finally, the temperature was increased to 1135°C over 3 hours and held at 1135°C for 1 hour for calcination, yielding the calcined material. The specific surface area of ​​the calcined material was monitored using a specific surface area analyzer, and the specific surface area was found to be 43 m². 2 / g; and the grain size of the calcined material was monitored by HSEM characterization, and the grain size of the calcined material was found to be 56nm. See the SEM image of the calcined material for details. Figure 2 .

[0043] Step 3: Grind the roasted material to prepare alumina slurry.

[0044] Take an appropriate amount of the roasted material from step 2 and first coarsely grind it using a stirred ball mill to obtain coarse abrasive with a particle size distribution of D50 of 2.52 μm and D100 of 13.25 μm. Then transfer the coarse abrasive to a sand mill (pin type) and add polyethylene glycol 200 to it for fine grinding to obtain fine abrasive with a particle size distribution of D50 of 0.7383 μm and D100 of 7.5948 μm. See the particle size distribution diagram below. Figure 3 Fine abrasive is alumina slurry.

[0045] The solid content of the slurry during coarse grinding and fine grinding was 32.5%; the mass of the added grinding aid polyethylene glycol 200 accounted for 0.5% of the mass of the calcined material added during coarse grinding; and the ball milling speed was 1000 rpm and the grinding ball diameter was 1 mm.

[0046] Step 4: Add coupling agent and dispersant to alumina slurry and react under stirring conditions to prepare a mixed slurry.

[0047] Take an appropriate amount of the alumina slurry from step 3, first add γ-aminopropyltriethoxysilane to it, and stir at 55°C for 1 hour. Then add nano-silica with a particle size of 15nm, and continue stirring at 55°C for 2.5 hours to obtain a mixed slurry.

[0048] The mass percentage of the added γ-aminopropyltriethoxysilane is 0.3% of the mass of the calcined material added during coarse grinding in step 3, and the mass percentage of the added nano-silica is 2% of the mass of the calcined material added during coarse grinding in step 3.

[0049] Step 5: Post-process the mixed slurry to obtain polishing powder.

[0050] The prepared mixed slurry was first passed through a 500-mesh vibrating screen and then freeze-dried. The particle size distribution of the material after freeze-drying is shown in the figure below. Figure 4 As shown, according to Figure 4 It can be seen that the particle size distribution of the freeze-dried material is: D50 is 2.51 μm and D100 is 26.11 μm. After being pulverized by a pulverizer and passed through a 100-mesh vibrating screen, the polishing powder is obtained by mixing it in a V-type mixer. The particle size distribution diagram and scanning electron microscope image of the polishing powder are shown in [reference 1]. Figure 5 and Figure 6 The particle size distribution of the polishing powder is: D50 is 0.712μm and D100 is 8.816μm.

[0051] Example 2 This embodiment provides a method for preparing polishing powder for automotive paint surfaces and the polishing powder produced therefrom. The preparation method of the polishing powder specifically includes the following steps: Step 1: Prepare the mixed solution.

[0052] By weight, 0.4 parts of zirconium oxychloride and 0.2 parts of titanium tetrachloride were added to 99.4 parts of deionized water, and the mixture was stirred until the zirconium oxychloride and titanium tetrachloride were completely dissolved to obtain a mixed solution.

[0053] Step 2: Prepare calcined material from the mixed solution and pseudoboehmite.

[0054] Take an appropriate amount of the mixed solution from step 1, add an equal mass of boehmite and disperse it evenly, then add analytical grade nitric acid to prepare an aluminum sol with a pH of 3-4, and spray dry to obtain the aluminum-doped precursor. See the scanning electron microscope image of the aluminum-doped precursor for details. Figure 7 The aluminum-doped precursor was placed in a muffle furnace and heated from room temperature to 150°C over 2 hours, then held at 150°C for 1 hour for dehydration. The temperature was then increased to 900°C over 5 hours and held at 900°C for 2 hours for crystal transformation. Finally, the temperature was increased to 1118°C over 3 hours and held at 1118°C for 1 hour for calcination, yielding the calcined material. The specific surface area of ​​the calcined material was monitored using a specific surface area analyzer, and the specific surface area was found to be 46 m². 2 / g; and the grain size of the calcined material was monitored by HSEM characterization, and the grain size of the calcined material was found to be 49nm. See the SEM image of the calcined material for details. Figure 8 .

[0055] Step 3: Grind the roasted material to prepare alumina slurry.

[0056] Take an appropriate amount of the roasted material from step 2 and first coarsely grind it using a stirred ball mill to obtain coarse abrasive with a particle size distribution of D50 of 2.58 μm and D100 of 13.25 μm. Then transfer the coarse abrasive to a sand mill (pin type) and add polyethylene glycol 200 to it for fine grinding to obtain fine abrasive with a particle size distribution of D50 in the range of 0.66 μm and D100 of 5.87 μm. See the particle size distribution diagram below. Figure 9 Fine abrasive is alumina slurry.

[0057] The solid content of the slurry during coarse grinding and fine grinding was 32.5%; the mass of the added grinding aid polyethylene glycol 200 accounted for 0.5% of the mass of the calcined material added during coarse grinding; and the ball milling speed was 1000 rpm and the grinding ball diameter was 1 mm.

[0058] Step 4: Add coupling agent and dispersant to alumina slurry and react under stirring conditions to prepare a mixed slurry.

[0059] Take an appropriate amount of the alumina slurry from step 3, first add γ-aminopropyltriethoxysilane to it, and stir at 55°C for 1 hour. Then add nano-silica with a particle size of 15nm, and continue stirring at 55°C for 2.5 hours to obtain a mixed slurry.

[0060] The mass percentage of the added γ-aminopropyltriethoxysilane is 0.3% of the mass of the calcined material added during coarse grinding in step 3, and the mass percentage of the added nano-silica is 2% of the mass of the calcined material added during coarse grinding in step 3.

[0061] Step 5: Post-process the mixed slurry to obtain polishing powder.

[0062] The prepared mixed slurry was first passed through a 500-mesh vibrating screen and then freeze-dried. The particle size distribution of the material after freeze-drying is shown in the figure below. Figure 10 As shown, according to Figure 10 It can be seen that the particle size distribution of the freeze-dried material is: D50 is 2.19 μm and D100 is 17.377 μm. After being pulverized by a pulverizer and passed through a 100-mesh vibrating screen, the polishing powder is obtained by mixing it in a V-type mixer. The particle size distribution diagram and scanning electron microscope image of the polishing powder are shown in [reference 1]. Figure 11 and Figure 12 The particle size distribution of the polishing powder is: D50 is 0.699μm and D100 is 6.72μm.

[0063] Comparative Example 1 The basic structure is the same as in Example 1, except that: Comparative Example 1 does not prepare a mixed solution, that is, it does not have step 1 in Example 1. In step 2, aluminum sol is prepared from boehmite and spray-dried to obtain an aluminum precursor, which is then calcined to obtain a roasted material.

[0064] In this comparative example, the aluminum precursor obtained by preparing aluminum sol from boehmite (high purity, above 99.99%) and spray drying is shown in the scanning electron microscope image. Figure 13 The scanning electron microscope image of the calcined material obtained after calcination is shown in [reference]. Figure 14 See the particle size distribution diagram of the alumina slurry. Figure 15 The particle size distribution diagram of the material obtained after freeze-drying is shown in the figure. Figure 16 The particle size distribution diagram and scanning electron microscope image of the final polishing powder are shown in the following figures. Figure 17 and Figure 18 The particle size distribution of the polishing powder in this comparative example is: D50 is 0.758 μm and D100 is 10.10 μm.

[0065] Comparative Example 2 The preparation process of Comparative Example 2 is basically the same as that of Example 1, except that the preparation process of Comparative Example 2 does not include step 4 of Example 1. After the alumina slurry is prepared in step 3, it is directly post-processed to obtain polishing powder.

[0066] In this comparative example, the particle size distribution diagram of the material obtained after freeze-drying during the preparation process is shown in the figure. Figure 19 The particle size distribution diagram and scanning electron microscope image of the final polishing powder are shown in the following figures. Figure 20 and Figure 21 The particle size distribution of the polishing powder in this comparative example is: D50 is 0.787 μm and D100 is 17.377 μm.

[0067] Comparative Example 3 The process is basically the same as in Example 1, except that in step 2 of Comparative Example 3, the temperature is directly and uniformly increased from room temperature to 1135°C during calcination to obtain the calcined material.

[0068] In this comparative example, the scanning electron microscope image of the calcined material obtained by calcination after a uniform temperature rise from room temperature to 1135℃ is shown below. Figure 22 See the particle size distribution diagram of the alumina slurry. Figure 23 The particle size distribution diagram of the material obtained after freeze-drying is shown in the figure. Figure 24 The particle size distribution diagram and scanning electron microscope image of the final polishing powder are shown in the following figures. Figure 25 and Figure 26 The particle size distribution of the polishing powder in this comparative example is: D50 is 0.801 μm and D100 is 11.565 μm.

[0069] Comparative Example 4 The process is basically the same as in Example 1, except that in Comparative Example 4, aluminum hydroxide is directly calcined as described in step 2 of Example 1 to obtain the calcined material.

[0070] In this comparative example, the scanning electron microscope image of aluminum hydroxide is shown below. Figure 27 The scanning electron microscope image of the calcined material obtained after calcination is shown in [reference]. Figure 28 See the particle size distribution diagram of the alumina slurry. Figure 29 The particle size distribution diagram of the material obtained after freeze-drying is shown in the figure. Figure 30 The particle size distribution diagram and scanning electron microscope image of the final polishing powder are shown in the following figures. Figure 31 and Figure 32 The particle size distribution of the polishing powder in this comparative example is: D50 is 0.84 μm and D100 is 22.70 μm.

[0071] Results and Discussion To further verify the polishing performance of the polishing powder prepared in this invention, all polishing powders from Examples 1 to 2, Comparative Examples 1 to 4, and an imported polishing powder (Ferro, brand name 796, with a particle size distribution of D50 of 2.55 μm and D100 of 13.25 μm) were formulated into polishing pastes. The polishing pastes, by weight, comprised the following components: 1.2 parts glycerol, 5.8 parts siloxane, 1.9 parts liquid paraffin, 9.7 parts Isopar H (solvent), 4.9 parts Exxsol D80 (solvent), 0.4 parts triethanolamine, 0.2 parts bactericide, 5 parts Tween 80 (emulsifier), 0.2 parts defoamer, 15 parts polishing powder, 4.5 parts TT615 (thickener), and 51.2 parts deionized water. All polishing compounds underwent the following polishing tests. The instruments used in the polishing tests included: a painted aluminum plate, a polishing machine (a modified 3M-28769), a polishing pad (3M-02648), and a gloss and haze meter (Rhopoint-1Q 20 / 60 / 85 GlossHaze DOI Meter). The painted aluminum plate was a 200mm*200mm*2mm aluminum plate that had been sequentially sprayed with primer (Parrot epoxy primer 801-72), color paint (Parrot 1K original pure black paint 55-1250), and clear coat (Parrot 923-447 clear coat). The polishing test results are shown in Table 1.

[0072] Polishing tests include cutting amount test, gloss and haze test, and sandpaper scratch removal effect test, as detailed below: Cutting amount test: The painted board was first polished with 2500 grit sandpaper and weighed. Then, equal amounts of polishing paste were applied to a new polishing sponge pad. The sponge pad was placed upside down on the fixed painted board, and the sponge pad was attached to the polishing machine. Polishing was carried out at a speed of 2100 rpm for 5 minutes, and the polishing air pressure was 0.1 MPa (a 2 kg iron block was placed on the polishing pad). The polishing was repeated 10 times and the average value was calculated to obtain the cutting amount of the sample. The higher the cutting amount, the stronger the cutting force of the sample.

[0073] Gloss and Haze Tests: Gloss and haze tests were conducted at the 3rd, 6th, and 9th cuts. The painted surface was fixed and cleaned with an organic solvent (degreasing agent or a 1:1 IPA aqueous solution) and 3M lint-free wipes. After wiping with the organic solvent, the surface was quickly dried with dry 3M lint-free wipes. The painted surface was divided into 9 equal parts, and each part was tested twice using a gloss and haze meter. The gloss and Log Haze (where Haze is a logarithmic transformation index used to quantify the degree of haze or blurring in optical materials or imaging systems) were read at 20°. Higher gloss and lower haze indicate better polishing results.

[0074] Sandpaper scratch removal effect comparison test: Take a new painted board, wipe it clean, and polish the painted surface with 3M 2500 grit sandpaper until the painted surface is smooth. Weigh an equal amount of polishing wax and polish for a time (without moving the painted board, only polish the 3-inch part of the polishing pad) until all scratches on the painted surface are removed. Compare the polishing time used by each polishing compound in the sandpaper scratch removal test. The shorter the time, the better the effect.

[0075] Table 1. Summary of polishing test results using polishing pastes prepared from Examples 1 to 2, Comparative Examples 1 to 4, and an imported polishing powder. The test results in Table 1 show that the overall performance of the polishing powders prepared in Examples 1 and 2 is significantly better than that of the polishing powders prepared in Comparative Examples 1 to 4. The specific analysis is as follows: In Comparative Example 1, because a mixed solution of zirconium and titanium salts was not added as a dopant, the polishing paste prepared from the polishing powder of Comparative Example 1 had a lower cutting depth compared to Example 1. In Comparative Example 2, the lack of composite coating resulted in more severe agglomeration after drying compared to coated examples. Even after dispersing, there were more agglomerates than with coating, and these agglomerates persisted after dissolving in water, leading to significantly worse gloss and haze. In Comparative Example 3, the lack of gradient calcination resulted in insufficient uniformity of calcination, leading to over-calcination in some areas and under-calcination in others. This resulted in a decrease in cutting depth after mixing, and a corresponding decrease in gloss and haze. In Comparative Example 4, aluminum hydroxide was used. The morphology of the calcined material was lamellar and irregular, with a relatively wide particle size distribution, which significantly reduced the cutting depth and resulted in a corresponding decrease in gloss and haze.

[0076] In summary, the preparation method of the polishing powder for automotive paint surfaces of the present invention uses high-purity boehmite as raw material, and involves doping with Zr in a mixed solution. 4+ With Ti 4+ Therefore, it can effectively improve the cutting ability of α-Al2O3 while controlling the grain size; through the interaction between alumina and coupling agent and dispersant, a strong composite coating layer is constructed for alumina, which is beneficial to improve the dispersibility of alumina particles and reduce mechanical scratches on the car paint surface, thereby improving the surface smoothness; the polishing powder prepared in this invention has a narrow particle size distribution and uniform microstructure, which can make the polished car paint surface have high gloss and low haze.

[0077] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing polishing powder, characterized in that, Includes the following steps: Preparation of mixed solutions; A calcined material was prepared from a mixed solution and pseudoboehmite, the specific surface area of ​​the calcined material being 30-60 m². 2 / g; The calcined material is ground to obtain an alumina slurry; A mixed slurry was prepared by adding a coupling agent and a dispersant to an alumina slurry and reacting it under stirring conditions. The mixed slurry is post-processed to obtain the polishing powder, the particle size distribution of which is: D50 in the range of 0.6-0.9μm and D100 less than 10μm.

2. The preparation method according to claim 1, characterized in that, The method for preparing the mixed solution is as follows: Zirconium salt and titanium salt are added to deionized water and stirred until the zirconium salt and titanium salt are completely dissolved to obtain the mixed solution; wherein the mass ratio of zirconium salt to titanium salt is 1-4:1; and the mass ratio of the total mass of zirconium salt and titanium salt to the mass of deionized water is 490-500:

3.

3. The preparation method according to claim 2, characterized in that, The method for preparing calcined materials from a mixed solution and pseudoboehmite is as follows: An equal mass of boehmite is added to the mixed solution and dispersed evenly. Nitric acid is then added to prepare an aluminum sol with a pH of 3-4. The sol is then spray-dried to obtain an aluminum-doped precursor. The aluminum-doped precursor is then calcined at a temperature of 1110-1150℃ to obtain the calcined material.

4. The preparation method according to claim 3, characterized in that, Before calcining the doped aluminum precursor at 1110-1150℃, the doped aluminum precursor is first heated from room temperature to a first temperature over 1-3 hours and held at the first temperature for 1-3 hours to dehydrate. Then, it is heated to a second temperature over 4-6 hours and held at the second temperature for 1-3 hours to perform crystal transformation. Finally, it is heated to 1110-1150℃ over 2-4 hours and held at 1110-1150℃ for 0.5-1.5 hours to calcine, thereby obtaining the calcined material.

5. The preparation method according to claim 4, characterized in that, The first temperature is 100-300℃, and the second temperature is 850-950℃.

6. The preparation method according to claim 4, characterized in that, The α-Al2O3 in the calcined material has a Mohs hardness of 9.2-9.3 and a grain size of 40-60 nm.

7. The preparation method according to claim 3, characterized in that, The purity of the pseudoboehmite is greater than or equal to 99.99%.

8. The preparation method according to claim 3, characterized in that, The method for grinding calcined materials to obtain alumina slurry is as follows: First, the calcined material is coarsely ground until a coarse grinding material with a particle size distribution of D50 in the range of 2-3 μm and D100 less than 15 μm is obtained. Then, a grinding aid is added to the coarse grinding material for fine grinding until a fine grinding material with a particle size distribution of D50 in the range of 0.6-0.9 μm and D100 less than 10 μm is obtained. The fine grinding material is an alumina slurry. The solid content of the slurry during coarse grinding and the solid content of the slurry during fine grinding are both 30%-40%. The mass percentage of the added grinding aid is 0.3%-1% of the mass of the calcined material added during coarse grinding.

9. The preparation method according to claim 8, characterized in that, The process of adding a coupling agent and a dispersant to an alumina slurry and reacting them under stirring conditions to prepare a mixed slurry is as follows: First, a coupling agent is added to the alumina slurry, and the mixture is stirred at 50-60℃ for 1-2 hours. Then, a dispersant is added, and the mixture is stirred at 50-60℃ for 2-3 hours to obtain the mixed slurry. The mass percentage of the added coupling agent is 0.2%-0.5% of the mass of the calcined material added during coarse grinding, and the mass percentage of the added dispersant is 1%-3% of the mass of the calcined material added during coarse grinding.

10. The preparation method according to claim 9, characterized in that, The post-processing includes the following steps: The prepared mixed slurry is first sieved and then freeze-dried, then pulverized and sieved a second time, and finally mixed to obtain the polishing powder; wherein the mesh size of the sieve during the first sieve is 400-600 mesh, and the mesh size of the sieve during the second sieve is 100-300 mesh.

11. The preparation method according to claim 9, characterized in that, The coupling agent is a silane coupling agent, and the dispersant is nano-silica.

12. A polishing powder for automotive paint surfaces, characterized in that, It is prepared by the preparation method according to any one of claims 1-11.

Images