Matt car paint repairing method

Abstract

The invention relates to the technical field of car paint repairing, and particularly discloses a matte car paint repairing method which comprises the steps that S1, a grinding sand disc is adopted for grinding the defect position of matte car paint, and a grinding area is obtained; s2, the surface of the grinding area is coated with matte car paint polishing paste, and a paste coating area is obtained; and S3, the pasting area is polished through accurate grinding sand cotton, and the repaired matte car paint is obtained. The repairing method is simple in procedure and easy and convenient to operate, online repairing can be achieved, the glossiness of the repaired matte car paint surface is consistent with that of the original car paint surface, the repairing effect is good, and the success rate is high.

Description

Technical Field

[0001] The present invention relates to the field of vehicle paint repair, and more specifically, to a method for repairing matte vehicle paint. Background Art

[0002] Matt paint mainly relies on matting powder to reduce the gloss value of car paint. Matting powder 1 is dispersed in a solvent to make a coating, which is then sprayed onto the surface of the substrate 2. Figure 1 As shown in FIG. 1 , after the coating is formed, the matting powder 1 forms an up-and-down convection as the solvent evaporates, and is carried to the surface of the coating. Due to the high viscosity of the surface, the matting powder is retained on the surface, forming a fine rough surface, i.e., a dry film 3, as shown in FIG. Figure 2 As shown. When the incident light reaches this surface, it is scattered, resulting in a matte effect, making the paint surface appear matte. However, matte car paint is prone to defects such as inconsistent gloss, and the defective parts with gloss differences need to be repaired.

[0003] The existing matte car paint repair method is to grind the repaired position, re-spray varnish, solidify the varnish, and even need to spray multiple times. This repair method has many processes, complicated and cumbersome operation, high requirements on the craftsman's skills, difficult online repair, and different proportions of varnish need to be configured for car paints with different glossiness to match the glossiness value of the car paint. During online production, the glossiness value of the car body is affected by the fluctuation of spraying conditions and changes in paint film thickness, and the varnish needs to be configured in advance. It is difficult to control the glossiness of the matte car paint after repair to be consistent with the glossiness of the original car paint, and the success rate is low. Therefore, the existing matte car paint repair method has many processes, cumbersome operation, difficulty in online repair, and low success rate. Summary of the invention

[0004] In order to solve the problems of existing matte car paint repair methods, such as multiple processes, complicated operations, difficulty in online repair and low success rate, the present application provides a matte car paint repair method.

[0005] The present application provides a method for repairing matte car paint, comprising: S1. Grind the defective position of the matte car paint with a grinding disc to obtain a grinding area; S2, applying matte car paint polishing paste on the surface of the polishing area to obtain a paste-coated area; S3, polishing the paste-coated area with fine sanding cotton to obtain a repaired matte car paint.

[0006] Optionally, in step S2, the amount of matte car paint polishing paste applied is determined according to the size of the polishing area, and the amount of matte car paint polishing paste applied can be 0.3-0.5 g.

[0007] Optionally, in step S3, when the glossiness value of the matte car paint is lower than 30, 1500#-2000# fine frosting cotton is used; when the glossiness value of the matte car paint is 30-50, 2500#-3000# fine frosting cotton is used; The fine grinding cotton is firstly polished at a speed of 1000 rpm for 3-5 s, and then polished at a speed of 2000 rpm for 5-10 s.

[0008] It should be noted that the defective position of the car paint is polished with a grinding disc to make the defective car paint flat and easy to repair later; according to the gloss value of the car paint, select fine grinding cotton of appropriate particle size, and control the roughness and gloss of the matte car paint by controlling the coarseness of the fine grinding cotton. Stick the fine grinding cotton to the eccentric polishing machine to control the speed and polishing rate of the fine grinding cotton through the polishing machine. Turn on the polishing machine and polish at 1000rpm for 3-5s to spread the polishing paste evenly on the area to be polished, then adjust to 2000rpm for 5-10s to repair the gloss of the polished area to be consistent with the surrounding car paint.

[0009] Optionally, in step S3, the fine sanding cotton includes an abrasive layer, a cloth base layer, a sponge layer and a silk brushed layer stacked in sequence.

[0010] Optionally, the abrasive layer comprises the following components in parts by weight: 50-75 parts of abrasive, 3-10 parts of filler, 20-40 parts of phenolic resin, 5-15 parts of epoxy resin, 0.3-1 parts of wetting and dispersing agent, 0.1-0.5 parts of adhesion promoter and 20-40 parts of solvent.

[0011] Optionally, the abrasive is silicon carbide, preferably, the abrasive is green silicon carbide with a particle size of 1500#-3000#; The filler is one or two of calcium carbonate whiskers and fumed silica; The phenolic resin is a water-soluble phenolic resin; The epoxy resin is a water-soluble bisphenol A epoxy ester, and its epoxy equivalent is 500-2000; The wetting and dispersing agent is sodium polyacrylate; The adhesion promoter is one of γ-aminopropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane; The solvent is a mixture of water and alcohol in a volume ratio of water:alcohol=3-1:1.

[0012] It should be noted that phenolic resin and epoxy resin can be diluted with water, which can effectively reduce the amount of organic solvents used; the wetting dispersant can effectively disperse the abrasive in the system to avoid agglomeration and other phenomena that affect the use of the abrasive; the cloth base is the carrier of the abrasive layer, a mesh cloth blended with nylon and polyester, with a thickness of 0.1-1mm and a gram weight of 200-300g / m2 The sponge layer is a porous polyether sponge with a hardness of 30-50. The porous structure of the sponge layer forms a multi-channel structure for accommodating grinding chips, temporarily storing the grinding chips during the grinding process. It also has a certain deformation ability, which can adapt to the grinding of arcs, corners and pits, and improve the fit between the abrasive layer and the polished part.

[0013] Optionally, the preparation method of fine frosted cotton includes: (a) bonding the cloth base layer, the sponge layer and the silk brushed layer in sequence through a flame lamination process to obtain a sand cotton base material; (b) mixing and stirring the phenolic resin and the epoxy resin to obtain a mixed resin; (c) adding a wetting and dispersing agent and an adhesion promoter to the mixed resin and stirring the mixture to obtain a first mixture; (d) adding abrasive and filler to the first mixture and dispersing at high speed for 30-50 minutes to obtain a second mixture; (e) adding a solvent to the second mixture, adjusting the viscosity and stirring uniformly to obtain a spray slurry; (f) pouring the spray slurry into a spray gun, spraying it on the sand wool substrate, and drying it to obtain the finely ground sand wool.

[0014] It should be noted that when fine sanding cotton is used for polishing, the abrasive layer of the fine sanding cotton is attached to the paste area to polish the paste area; the spray slurry is poured into the spray gun and sprayed on the sanding cotton substrate, and the spraying consumption is 150-250 / m 2 The sprayed sand cotton substrate is placed in a drying tunnel and dried for 30 minutes, then transferred to a 130°C oven and dried for 15 minutes, and then the fine sand cotton is cut into a specified shape to obtain the required fine sand cotton.

[0015] Optionally, in step S2, the matte car paint polishing paste includes the following components in percentage by mass: 25-35% alumina powder, 7-14% solvent oil, 1-3% lubricant, 3-6% antifreeze, 0.3-0.8% pH adjuster, 0.5-2% emulsifier, 0.1-0.3% defoamer, 0.1-0.2% bactericidal preservative, 0.5-1% dispersant, 0.5-0.8% thickener, and the rest is deionized water.

[0016] Optionally, the alumina powder includes a first alumina powder and a second alumina powder, the particle size of the first alumina powder is 3-6 microns, the particle size of the second alumina powder is 9-12 microns, and the mass ratio of the first alumina powder to the second alumina powder is 1-3:10. Figure 3 As shown in FIG. 1 , the microscopic morphology of the first alumina powder is agglomeration of multiple cubes, such as Figure 4 As shown, the second alumina powder is a block structure with micropores on the surface.

[0017] It should be noted that the alumina powder of the present application is compounded with a first alumina powder and a second alumina powder. The first alumina powder is agglomerated by multiple cubes, has a high hardness, and has a slow repair effect on car paint sand grains. The porous structure of the second alumina powder gives it a large specific surface area, and it can be continuously broken during the polishing process to expose new cutting edges, thereby improving the ability to repair large sand grains. The present application slows down the repair effect of abrasives on sand grains by using two types of alumina powders in combination, and solves the problem that conventional polishing pastes cannot polish matte car paint by using them in combination with fine sanding cotton.

[0018] Optionally, the solvent oil is one or both of isoparaffin solvent oil and intermediate aliphatic solvent naphtha; The antifreeze agent is one or more of ethylene glycol, propylene glycol and glycerol; The pH regulator is one of sodium hydroxide, ammonia water, triethanolamine, and 2-amino-2-methyl-1-propanol. Preferably, the pH regulator is triethanolamine or 2-amino-2-methyl-1-propanol. The emulsifier is one or both of a nonionic emulsifier and an anionic emulsifier. Preferably, the emulsifier is polysorbate-20, sorbitan monolaurate, and fatty alcohol polyoxyethylene ether in a mass ratio of 1:1:2. The defoamer is a non-silicone defoamer, preferably, the defoamer is a polymer composite mineral oil or a fatty alcohol polyether; The thickener is one of lithium magnesium silicate, acrylate polymer dispersion, fumed silica, and alkali-swellable acrylic emulsion. Preferably, the thickener is alkali-swellable acrylic emulsion.

[0019] It should be noted that the solvent oil is a petroleum distillate, and the solvent oil can be a commercially available environmentally friendly solvent oil. Preferably, environmentally friendly solvent oils D40, D60, and D80 are mixed and used in a mass ratio of 1:1.5-2:1.5-2. The lubricant is one or more of 10# white oil, 15# white oil, and 26# white oil. The purpose of using a defoamer is mainly to eliminate the bubbles generated when the automotive grinding paste is prepared in the water-in-oil emulsion. The alkali-swellable acrylic emulsion is supplied in liquid form and will not thicken the system in a neutral environment. Only when the automotive grinding paste is alkaline will a thickening response occur. At the same time, the alkali-swellable acrylic emulsion can be hydrophobically modified, and can simultaneously adsorb the water phase and the oil phase to increase the stability of the automotive grinding paste system.

[0020] Optionally, the preparation method of the matte car paint polishing paste includes: A. Evenly mix solvent oil and lubricant to obtain oil phase; B. Take another clean container, add bactericidal preservative, emulsifier and defoaming agent to deionized water in sequence at a stirring speed of 300-500 rpm, and stir for 5-10 minutes to obtain an aqueous phase; C. Slowly add the oil phase into the water phase, while increasing the speed to 600-800 rpm. After the mixed oil phase and water phase become milky white liquid, increase the speed to 900-1100 rpm and disperse at high speed for 30 minutes to obtain a primary mixture; D. adding antifreeze agent, dispersant and pH regulator to the primary mixture and stirring for 5 min to obtain a prefabricated paste; E. Add alumina powder to the prefabricated paste and stir for 10 minutes to obtain a paste; F. Slowly add thickener to the paste. After the viscosity increases, increase the speed to 1300-1500rpm and disperse at high speed for 40-60min. If the amount of the paste is large, the dispersion time can be appropriately extended to obtain the matte car paint polishing paste.

[0021] In summary, this application has the following beneficial effects: 1. Compared with the prior art repair method of re-spraying varnish, curing varnish, or even spraying multiple times, there are many processes, cumbersome operation, difficulty in online repair, low success rate and other problems. The repair method of the present application only needs to squeeze matte car paint polishing paste on the polished area to be repaired, and then polish with fine sanding cotton for more than ten seconds to complete the repair of matte car paint. The process is simple, the operation is easy, and online repair can be achieved. The glossiness of the matte car paint surface after repair is consistent with that of the original car paint surface, the repair effect is good, and the success rate is high; 2. Compared with the prior art solution of using wool balls or sponge balls with high-gloss car paint polishing paste, there is a large difference in gloss between the repaired matte car paint and the original matte car paint surface, and the repair effect is not good. The present application uses a combination of fine abrasive cotton and matte car paint polishing paste. During polishing, the fine abrasive cotton continuously polishes the car paint, causing the surface of the car paint to continuously produce fine sand grains to form a matte effect; while the matte car paint polishing paste will continuously repair the fine sand grains, causing the gloss to slowly increase, and by controlling the polishing time, the gloss of the polished area is made close to or even consistent with the gloss of the surrounding area, thereby achieving the repair effect, solving the problem that matte paint products are difficult to repair, difficult to directly rework or cannot be fully qualified, improving the product qualification rate, and effectively avoiding the cost waste caused by paint gloss defects in the preparation process of matte parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the principle of matte car paint in the prior art; Figure 2 yes Figure 1 Schematic diagram of the dry film of matte car paint after the solvent evaporates; Figure 3 This is a microscopic morphology diagram of the first alumina powder of the present application; Figure 4 This is a microscopic morphology diagram of the second alumina powder of the present application.

[0023] Explanation of reference numerals: 1. matting powder; 2. base material; 3. dry film. DETAILED DESCRIPTION

[0024] The present application is further described in detail with reference to the following examples. It should be noted that if no specific conditions are specified in the following examples, the conventional conditions or the conditions recommended by the manufacturer are followed, and the raw materials used in the following examples can be obtained from common commercial sources unless otherwise specified.

[0025] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0026] In this application, "first aspect", "second aspect", "third aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0027] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0028] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0029] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0030] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field of this application. The terms used in this application and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more related listed items. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise clearly and specifically limited.

[0031] In addition, it is explained that the raw materials used in this application are all commercially available raw materials.

[0032] Example Example 1 The abrasive layer comprises the following components in parts by weight: 50 parts of 3000# green silicon carbide, 3 parts of fumed silica, 20 parts of phenolic resin, 15 parts of epoxy resin, 1 part of wetting and dispersing agent, 0.1 parts of adhesion promoter, and 40 parts of solvent.

[0033] The preparation method of fine frosted cotton comprises the following steps: (a) bonding the cloth base layer, the sponge layer and the silk brushed layer in sequence through a flame lamination process to obtain a sand cotton base material; (b) mixing and stirring the phenolic resin and the epoxy resin to obtain a mixed resin; (c) adding a wetting and dispersing agent and an adhesion promoter to the mixed resin and stirring the mixture to obtain a first mixture; (d) adding abrasive and filler to the first mixture and dispersing at high speed for 45 minutes to obtain a second mixture; (e) adding a solvent to the second mixture, adjusting the viscosity and stirring uniformly to obtain a spray slurry; (f) Pour the spray slurry into a spray gun and spray it on the sand wool substrate. The spray consumption is 150g / m 2 The sprayed sand cotton substrate is placed in a drying tunnel and dried for 30 minutes, then transferred to a 130° C. oven and dried for 15 minutes, and cut into a specified shape to obtain the finely ground sand cotton.

[0034] Example 2 The abrasive layer comprises the following components in parts by weight: 58 parts of 2500# green silicon carbide, 7 parts of fumed silica, 25 parts of phenolic resin, 5 parts of epoxy resin, 1 part of wetting and dispersing agent, 0.5 parts of adhesion promoter, and 35 parts of solvent.

[0035] In the preparation method of fine frosted cotton, the spraying consumption is 180g / m 2 , the rest is the same as Example 1.

[0036] Example 3 The abrasive layer comprises the following components in parts by weight: 65 parts of 2000# green silicon carbide, 5 parts of calcium carbonate whiskers, 35 parts of phenolic resin, 10 parts of epoxy resin, 0.7 parts of wetting dispersant, 0.3 parts of adhesion promoter, and 30 parts of solvent.

[0037] In the preparation method of fine frosted cotton, the spraying consumption is 210g / m 2 , the rest is the same as Example 1.

[0038] Example 4 The abrasive layer comprises the following components in parts by weight: 75 parts of 1500# green silicon carbide, 10 parts of calcium carbonate whiskers, 40 parts of phenolic resin, 13 parts of epoxy resin, 0.3 parts of wetting dispersant, 0.5 parts of adhesion promoter, and 20 parts of solvent.

[0039] In the preparation method of fine frosted cotton, the spraying consumption is 250g / m 2 , the rest is the same as Example 1.

[0040] Example 5 The matte car paint polishing paste includes the following components in percentage by mass: 25% alumina micropowder, 7% solvent oil, 3% lubricant, 6% antifreeze agent, 0.8% pH adjuster, 0.5% emulsifier, 0.1% defoamer, 0.1% bactericidal preservative, 0.5% dispersant, 0.5% thickener, and the balance is deionized water.

[0041] The preparation method of matte car paint polishing paste comprises: A. Evenly mix solvent oil and lubricant to obtain oil phase; B. Take another clean container, add bactericide, preservative, emulsifier and defoamer to deionized water in sequence at a stirring speed of 500 rpm, and stir for 10 minutes to obtain an aqueous phase; C. Slowly add the oil phase into the water phase, while increasing the speed to 700 rpm. After it becomes a milky white liquid, increase the speed to 1100 rpm and disperse at high speed for 30 minutes to obtain a primary mixture; D. adding antifreeze agent, dispersant and pH regulator to the primary mixture and stirring for 5 min to obtain a prefabricated paste; E. Add alumina powder to the prefabricated paste and stir for 10 minutes while making sure that the powder does not adhere to the inner wall of the container to obtain a paste; F. Slowly add thickener to the paste. After the viscosity increases, increase the speed to 1300 rpm and disperse at high speed for 50 min. If the amount of the paste is large, the dispersion time can be appropriately extended to obtain the matte car paint polishing paste.

[0042] Example 6 The matte car paint polishing paste includes the following components in percentage by mass: 28% alumina micropowder, 9% solvent oil, 1% lubricant, 5% antifreeze agent, 0.3% pH adjuster, 1.3% emulsifier, 0.3% defoamer, 0.2% bactericidal preservative, 0.6% dispersant, 0.6% thickener, and the balance is deionized water.

[0043] The preparation method of matte car paint polishing paste is the same as that of Example 5.

[0044] Example 7 The matte car paint polishing paste includes the following components in percentage by mass: 32% alumina micropowder, 12% solvent oil, 1% lubricant, 4% antifreeze agent, 0.5% pH adjuster, 1.6% emulsifier, 0.2% defoamer, 0.1% bactericidal preservative, 0.8% dispersant, 0.7% thickener, and the balance is deionized water.

[0045] The preparation method of matte car paint polishing paste is the same as that of Example 5.

[0046] Example 8 The matte car paint polishing paste includes the following components in percentage by mass: 35% alumina micropowder, 14% solvent oil, 2% lubricant, 3% antifreeze agent, 0.4% pH adjuster, 2% emulsifier, 0.2% defoamer, 0.2% bactericidal preservative, 1% dispersant, 0.8% thickener, and the balance is deionized water.

[0047] The preparation method of matte car paint polishing paste is the same as that of Example 5.

[0048] Comparative Example Comparative Example 1 The matte car paint polishing paste of Example 5 is applied to the surface of the polishing area, and polishing is performed using a wool ball.

[0049] Comparative Example 2 The matte car paint polishing paste of Example 8 was applied to the surface of the polishing area, and polishing was performed using a sponge ball.

[0050] Comparative Example 3 Apply G3 wax block to the surface of the polishing area and polish with a sponge ball.

[0051] Effect Example The glossiness of the original matte car paint was tested using a gloss tester, and the fine-ground frosted cotton of Examples 1-4 of the present application was used in combination with the matte car paint polishing paste of Examples 5-8 to test the glossiness of the repaired matte car paint; the glossiness of the original matte car paint was tested using a gloss tester, and the scheme of Comparative Examples 1-3 was used to test the glossiness of the repaired matte car paint.

[0052] Table 1 Gloss comparison of matte car paint before and after the test

[0053] The test results are shown in Table 1. When the fine-grit frosted cotton of Examples 1-4 of the present application is used in combination with the matte car paint polishing paste of Examples 5-8, the glossiness of the repaired matte car paint is basically consistent with the glossiness of the original car paint, and the naked eye cannot see the obvious difference; however, when the method of Comparative Examples 1-3 is used, the glossiness of the matte car paint after repair is significantly different from the glossiness of the original car paint, and the matte car paint cannot be repaired. Comparative Examples 1-3 cannot achieve the glossiness repair effect of the combination of the fine frosted cotton and the matte car paint polishing paste of the present application.

[0054] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for repairing matte car paint, characterized in that: include: S1. Grind the defective position of the matte car paint with a grinding disc to obtain a grinding area; S2, applying matte car paint polishing paste on the surface of the polishing area to obtain a paste-coated area; S3, polishing the paste-coated area with fine sanding cotton to obtain a repaired matte car paint.

2. The method for repairing matte vehicle paint according to claim 1, characterized in that: In step S3, when the glossiness value of the matte paint is lower than 30, 1500#-2000# fine frosting cotton is used; when the glossiness value of the matte paint is 30-50, 2500#-3000# fine frosting cotton is used; The fine grinding cotton is firstly polished at a speed of 1000 rpm for 3-5 s, and then polished at a speed of 2000 rpm for 5-10 s.

3. The method for repairing matte vehicle paint according to claim 1, characterized in that: In step S3, the fine sanding cotton includes an abrasive layer, a cloth base layer, a sponge layer and a silk brushed layer stacked in sequence.

4. The method for repairing matte vehicle paint according to claim 3, characterized in that: The abrasive layer comprises the following components in parts by weight: 50-75 parts of abrasive, 3-10 parts of filler, 20-40 parts of phenolic resin, 5-15 parts of epoxy resin, 0.3-1 parts of wetting dispersant, 0.1-0.5 parts of adhesion promoter and 20-40 parts of solvent.

5. The method for repairing matte vehicle paint according to claim 4, characterized in that: The abrasive is green silicon carbide with a particle size of 1500#-3000#; The filler is one or two of calcium carbonate whiskers and fumed silica; The phenolic resin is a water-soluble phenolic resin; The epoxy resin is a water-soluble bisphenol A epoxy ester with an epoxy equivalent of 500-2000; The wetting and dispersing agent is sodium polyacrylate; The adhesion promoter is one of γ-aminopropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane; The solvent is a mixture of water and alcohol, with water:alcohol=3-1:

1.

6. The method for repairing matte vehicle paint according to claim 4, characterized in that: The preparation method of the fine frosted cotton comprises: (a) bonding the cloth base layer, the sponge layer and the silk brushed layer in sequence through a flame lamination process to obtain a sand cotton base material; (b) mixing and stirring the phenolic resin and the epoxy resin to obtain a mixed resin; (c) adding a wetting and dispersing agent and an adhesion promoter to the mixed resin and stirring the mixture to obtain a first mixture; (d) adding abrasive and filler to the first mixture and dispersing at high speed for 30-50 minutes to obtain a second mixture; (e) adding a solvent to the second mixture, adjusting the viscosity and stirring uniformly to obtain a spray slurry; (f) pouring the spray slurry into a spray gun, spraying it on the sand wool substrate, and drying it to obtain the finely ground sand wool.

7. The method for repairing matte vehicle paint according to any one of claims 1-2, characterized in that: In step S2, the matte car paint polishing paste includes the following components in mass percentage: 25-35% alumina powder, 7-14% solvent oil, 1-3% lubricant, 3-6% antifreeze, 0.3-0.8% pH adjuster, 0.5-2% emulsifier, 0.1-0.3% defoamer, 0.1-0.2% bactericidal preservative, 0.5-1% dispersant, 0.5-0.8% thickener, and the rest is deionized water.

8. The method for repairing matte vehicle paint according to claim 7, characterized in that: The alumina micropowder includes a first alumina micropowder and a second alumina micropowder, the particle size of the first alumina micropowder is 3-6 microns, the particle size of the second alumina micropowder is 9-12 microns, the mass ratio of the first alumina micropowder to the second alumina micropowder is 1-3:10, the microscopic morphology of the first alumina micropowder is an agglomeration of multiple cubes, and the second alumina micropowder is a block structure with micropores on the surface.

9. The method for repairing matte vehicle paint according to claim 7, characterized in that: The solvent oil is one or two of isoparaffin solvent oil and intermediate aliphatic solvent naphtha; The antifreeze agent is one or more of ethylene glycol, propylene glycol and glycerol; The pH regulator is one of sodium hydroxide, ammonia water, triethanolamine, and 2-amino-2-methyl-1-propanol; The emulsifier is one or both of a nonionic emulsifier and an anionic emulsifier; The defoamer is a polymer composite mineral oil or a fatty alcohol polyether; The thickener is one of lithium magnesium silicate, acrylate polymer dispersion, fumed silica, and alkali-swollen acrylic emulsion.

10. The method for repairing matte vehicle paint according to claim 8, characterized in that: The preparation method of the matte car paint polishing paste comprises: A. Evenly mix solvent oil and lubricant to obtain oil phase; B. Add bactericidal preservative, emulsifier and defoaming agent to deionized water in sequence at a stirring speed of 300-500 rpm, and stir for 5-10 minutes to obtain an aqueous phase; C. Slowly add the oil phase into the water phase, while increasing the speed to 600-800 rpm. After the mixed water phase and oil phase become a milky white liquid, increase the speed to 900-1100 rpm and disperse at high speed for 30 minutes to obtain a primary mixture; D. adding antifreeze agent, dispersant and pH regulator to the primary mixture and stirring for 5 min to obtain a prefabricated paste; E. Add alumina powder to the prefabricated paste and stir for 10 minutes to obtain a paste; F. Slowly add a thickener to the paste, and after the viscosity increases, increase the speed to 1300-1500 rpm, and disperse at high speed for 40-60 min to obtain the matte car paint polishing paste.

Images