Spot paint for vehicle and spraying repair process thereof

Abstract

The application discloses a kind of point spray varnish for vehicle, including the following mass components: 10~30 parts carboxylated polycarbonate, 35~60 parts epoxy polyacrylate resin, 6~12 parts crosslinking agent, 0.1~8.0 parts auxiliary agent, 2~4 parts initiator, relate to the technical field of automobile varnish.The application utilizes carboxylated polycarbonate, epoxy polyacrylate resin to build varnish crosslinking network, and introduces polycarbonate structure, to improve the impact resistance, water resistance, chemical corrosion resistance and other properties of paint film;And the spraying repair process of point spray varnish is optimized, the original car paint is retained to a greater extent, and excessive maintenance is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile clear varnish, in particular to a vehicle point spraying clear varnish and a spraying repair process thereof. BACKGROUND

[0002] With the rapid development of China's economy, the automobile after market is further developed. In the field of vehicle paint repair, the quality and performance requirements of vehicle owners for the repaired paint film are also improved. This requires the performance balance between the repaired paint and the original factory high-temperature paint, so as to make them comparable in durability. However, the main component of the existing clear varnish is acrylic resin, which has poor water resistance, durability and poor tolerance to external environment. Excessive repair during repair also causes the devaluation of the vehicle value. Therefore, we propose a vehicle point spraying clear varnish and a spraying repair process thereof. SUMMARY

[0003] The purpose of the present application is to provide a vehicle point spraying clear varnish and a spraying repair process thereof to solve the problems raised in the background art.

[0004] In order to solve the above technical problems, the present application provides the following technical scheme: a vehicle point spraying clear varnish, comprising the following mass components: 10-30 parts of carboxylated polycarbonate, 35-60 parts of epoxy polyacrylate resin, 6-12 parts of crosslinking agent, 0.1-8.0 parts of additive, and 2-4 parts of initiator.

[0005] Further, the epoxy polyacrylate resin is prepared by the following process:

[0006] Mix ethyl acrylate, acrylic acid, N-carbazole dithioformic acid benzyl ester, and 25-35% of the mass of the remaining components azo initiator, and react at 50-55℃ for 18-24h under nitrogen atmosphere protection;

[0007] Mix with ethyl acetate, add isooctyl acrylate, 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, and the remaining component azo initiator, and react at 62-68℃ for 18-24h under nitrogen atmosphere protection to obtain polyacrylate;

[0008] Mix with epoxy compound and triethylamine, and react at 95-105℃ for 4-5h; cool to obtain epoxy polyacrylate resin.

[0009] Further, the epoxy compound is one or more of tetrahydrophthalic acid diglycidyl ester, bisphenol A epoxy diacrylate, and bisphenol F diglycidyl ether.

[0010] Further, the azo initiator is one or more of azobisisoheptane nitrile, azobisisobutane nitrile, 1,1-azobis(cyclohexane-1-carbonitrile).

[0011] Further, the epoxy-based polyacrylate resin comprises the following components by mass: 25-30 parts of ethyl acrylate, 9.8-20.5 parts of acrylic acid, 10-15 parts of 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1.2-1.5 parts of N-carbazole dithioformic acid benzyl ester, 42-80 parts of isooctyl acrylate, 50-70 parts of an epoxy compound, 0.6-1.0 parts of an azo initiator, 5-7 parts of triethylamine, and 50-70 parts of ethyl acetate.

[0012] In the above technical solution, the polyacrylate resin as a varnish component has good adhesion, light resistance, weather resistance, etc., but its water resistance, solvent resistance, etc. are poor. The epoxy resin has the characteristics of high stability, excellent chemical corrosion resistance, mechanical properties, and adhesion, but its weather resistance and decoration are poor. The combination of polyacrylate and epoxy resin can effectively improve the comprehensive performance of the varnish, such as adhesion, chemical corrosion resistance, water resistance, and weather resistance. The carboxyl group reacts with the epoxy group in this application, introducing an epoxy (ester) compound structure into the acrylate polymer molecular chain, thereby obtaining a varnish component, epoxy-based polyacrylate resin, which has excellent performance. It has an epoxy group that can react with active functional groups in other varnish components such as carboxylated polycarbonate, forming a cross-linked structure in the prepared paint film, which helps to improve the surface hardness, mechanical properties, water resistance, and chemical corrosion resistance of the paint film.

[0013] When the component of the epoxy compound is selected as tetrahydrophthalic acid diglycidyl ester, it contains an unsaturated double bond in its structure, which can participate in the reaction between the unsaturated bonds in the carboxylated polycarbonate emulsion under the action of the initiator, forming a more dense paint film, and synergistically improving its water resistance, chemical corrosion resistance, and mechanical properties.

[0014] Further, the carboxylated polycarbonate is prepared by the following process:

[0015] Mixing epoxy-terminated polydimethylsiloxane, propylene oxide, epoxy ethane-2-tert-butyl carboxylate, and a catalyst, passing in carbon dioxide, stirring for 24-36 h; cooling, dissolving with dichloromethane, precipitating with ethanol, and vacuum drying to obtain silicone-modified polycarbonate;

[0016] Mixing silicone-modified polycarbonate and a solvent, adding trifluoroacetic acid, stirring for 1-8 h; vacuum distillation, extraction, washing, and drying to obtain carboxylated polycarbonate.

[0017] Further, the catalyst is a mixture of Schiff base cobalt (SalenCoCl) and bis (triphenylphosphine) imine (PPNCl), and the mass ratio is 10:9.

[0018] Further, the mass ratio of propylene oxide, ethylene oxide-2-tert-butyl carboxylic acid, epoxy-terminated polydimethylsiloxane and catalyst is (50-90):(10-50):(1-10):(0.1-0.3).

[0019] Further, the reaction is carried out in a high-pressure reaction kettle, and after the carbon dioxide is introduced, the pressure of the high-pressure reaction kettle is 3.0-4.0 MPa.

[0020] Further, the solvent is a mixture of benzene and tetrahydrofuran, and the volume ratio is 1:1.

[0021] Further, the ratio of silicone-modified polycarbonate, trifluoroacetic acid and solvent is 3.5 g:(0.03-0.05) g:100 mL.

[0022] In the above technical solution, the polycarbonate has the advantages of high strength, high temperature stability, weather resistance, chemical corrosion resistance, wear resistance, etc., and has good transparency and gloss; when used as a varnish component, it has good decorative properties and can effectively improve the overall performance. Under the action of the catalyst, propylene oxide and ethylene oxide-2-tert-butyl carboxylic acid undergo ring-opening polymerization to form carbon dioxide-based polycarbonate, which is grafted with epoxy-terminated polydimethylsiloxane block, thereby forming silicone-modified polycarbonate; then the tert-butyl group in the structure of ethylene oxide-2-tert-butyl carboxylic acid is removed to obtain carboxylated polycarbonate, which introduces carboxyl groups into the structure, which helps the reaction and crosslinking between the subsequent varnish component system and improves the performance of the paint film. The introduction of the silicone segment helps to improve the flexibility of the carboxylated polycarbonate molecular segment, which can improve the processing flowability of the varnish, and the toughness, weather resistance, water resistance and chemical corrosion resistance of the prepared paint film are improved.

[0023] Further, the varnish is water-based, and the carboxylated polycarbonate and the epoxy-based polyacrylate resin are added in the form of an emulsion.

[0024] Further, the carboxylated polycarbonate emulsion is prepared by the following process:

[0025] Mix polypropylene glycol and isophorone diisocyanate, heat to 65-80℃, add dimethylolpropionic acid and hydroxyl-terminated polybutadiene and react for 2-4h, add catalyst and continue to react for 2-3h; cool to 30-40℃, add carboxylated polycarbonate, add deionized water, and disperse at a speed of 2700-3000 rpm for 10-20 min to obtain a carboxylated polycarbonate emulsion with a solid content of 30%-60%.

[0026] Further, the carboxylated polycarbonate emulsion comprises the following mass components: 100 parts of carboxylated polycarbonate, 16-20 parts of polypropylene glycol, 5-12 parts of isophorone diisocyanate, 0.2-1.0 parts of dimethylol propionic acid, 0.5-1.0 parts of hydroxyl-terminated polybutadiene, and 0.005-0.020 parts of a catalyst dibutyltin dilaurate.

[0027] Further, the epoxy-based polyacrylate resin emulsion is prepared by the following process:

[0028] The epoxy-based polyacrylate resin and the emulsifier are mixed, and the temperature is raised to 50-70°C. The pH of the system is adjusted to 7-8. Deionized water is slowly added at a speed of 1200-2000 rpm, and the addition is completed within 60-90 minutes. Then the temperature is maintained at 2700-3000 rpm for 30-60 minutes. Water is added to adjust the solid content to 30%-60%, and the epoxy-based polyacrylate resin emulsion is obtained.

[0029] Further, the mass ratio of the epoxy-based polyacrylate resin to the emulsifier is 100:(5-10).

[0030] Further, the crosslinking agent is a water-based amine crosslinking agent.

[0031] Further, the auxiliary agent includes one or more of defoamers, cosolvents, wetting agents, leveling agents, thickening agents, light stabilizers, adhesion promoters, ultraviolet absorbers, light stabilizers, and antioxidants.

[0032] The initiator is one or more of ammonium persulfate, potassium persulfate, photoinitiator 1173, and photoinitiator 522.

[0033] A spraying repair process for a point-spraying clear varnish for vehicles includes pretreatment, corrosion prevention treatment, middle coating primer spraying, surface micro-filling, topcoat spraying, clear varnish spraying, and post-treatment.

[0034] Further, the pretreatment includes part cleaning, part oil removal, damage assessment, sheet metal deformation recovery, detection of the flatness of the shaped part, and re-cleaning and oil removal.

[0035] Part cleaning includes vehicle cleaning and damaged part cleaning.

[0036] Part oil removal is cleaning of the entire damaged part.

[0037] Damage assessment is to determine the damage range to develop a repair plan.

[0038] Sheet metal deformation recovery: if the damaged part has sheet metal deformation, it must be repaired by shaping equipment tools and concave repair methods; then detect the flatness of the shaped part, use a laser caliper to detect the flatness of the shaped part, and the positive and negative flatness cannot be greater than 0.2 mm, after inspection, it is qualified and enters the next process; after cleaning and degreasing again, it is prepared for corrosion protection treatment.

[0039] Further, corrosion protection treatment: use corrosion protection paint to perform corrosion protection treatment on the sheet metal repair site after pretreatment; then dry at 60°C for 30 minutes;

[0040] The thickness of the corrosion protection paint film formed by the corrosion protection treatment should be 18-20 microns, and the film thickness detected by the film thickness meter should meet the requirements before preparing for primer spraying.

[0041] Further, middle coating primer spraying: use middle coating primer to spray 2 times; then dry at 60°C for 30 minutes

[0042] The thickness of the primer film formed by the middle coating primer spraying should be 35-40 microns, and the thickness of the corrosion protection paint film should be 53-60 microns, and the film thickness detected by the film thickness meter should meet the requirements before performing surface micro-filling.

[0043] Further, surface micro-filling; use polyurethane resin to micro-fill surface pinholes and other defects, and after filling, dry, polish, and then perform surface flatness modification, cleaning, dust removal, and oil removal;

[0044] Surface flatness modification: use dry grinding process and 500-600 mesh dry sandpaper to polish the surface of the middle coating primer area to have no spraying texture and show flatness. Expand and polish the original paint surface outside the middle coating primer, use 1500 mesh dry sandpaper or 2000 mesh water ink sandpaper to polish the area, and the polishing range should be controlled outside the varnish spraying range;

[0045] Cleaning, dust removal, and oil removal; use compressed air and dust blowing gun to blow dust and clean the polished area, blow out dust from gaps and paint surface pinholes, and use oil removal agent to clean and remove oil from the entire construction area.

[0046] After the process is completed, the overall film thickness should be not less than 50 microns; if it is less than 50 microns, 1-2 coats of primer should be continuously sprayed.

[0047] Further, topcoat spraying includes:

[0048] Preparation before topcoat spraying: clean and degrease the sprayed parts; except for the sprayed area, all other parts are shielded to avoid spraying paint mist from splashing onto other parts of the vehicle; clean and degrease the sprayed area again to ensure the cleanliness of the sprayed parts.

[0049] Topcoat matching: The topcoat color is matched by computer or manually. When the colors are similar by visual inspection, the color plate is sprayed. When there is a color difference by visual inspection, a color matching instrument is used to analyze the color hue, and the result is adjusted manually. When the colors are consistent by visual inspection, the color plate is sprayed again. When the color difference is less than 1 by color matching instrument analysis, it is considered qualified and can be sprayed.

[0050] Topcoat spraying: Before topcoat spraying, a layer of topcoat primer stabilizer is sprayed. The spraying range is larger than the topcoat spraying range and smaller than the varnish spraying range. After drying, the surface is prepared for topcoat spraying. The first pass of topcoat spraying uses a 0.5mm small-bore spray gun with a pressure gauge pressure of 1.5-2kg. The spraying is thin and the gun is collected inward. The topcoat spraying area should not exceed the edge of the mid-coat primer by 2-3cm. Before the second pass of topcoat spraying, the surface is cleaned. The same pressure and method are used for spraying. The gun is collected outward for transition spraying. The new sprayed color and the original vehicle color are gradually changed to reduce color unevenness and repair marks. The spraying range should not exceed the edge of the first pass by 2-3cm. The color of the sprayed area and the original color of the part are observed with a color contrast lamp. If the color has covered the base color and the color edge transition is uniform and consistent, the next varnish spraying process can be performed. If the colors are not consistent, the second process can be repeated until the color and edge are consistent.

[0051] After the process is completed, the overall film thickness should be controlled at 80-88 microns.

[0052] Further, the varnish spraying includes:

[0053] Varnish spraying: The entire spraying area is cleaned. A 0.8-1.0 bore spray gun is used to spray varnish. The spraying environment temperature should be controlled at 25-30℃. The first pass of varnish spraying should control the varnish range to be equivalent to the topcoat spraying range. After flash drying for 5-10 minutes, the second pass of varnish spraying is performed. The second pass of varnish spraying range should be larger than the first pass. The varnish spraying edge should be controlled as much as possible to avoid paint mist splashing in the non-sprayed area. This process will affect the varnish joint process. After the second pass of varnish spraying, the varnish joint is prepared.

[0054] Varnish joint: The varnish and joint water are mixed at a volume ratio of 1:1. The varnish edge is sprayed to promote the fusion of the new and old paint films. The varnish edge is sprayed with joint water for the second time to promote the fusion of the new and old paint films. The varnish edge is smooth and flat by visual inspection. The fusion is good and the next process can be performed. The spraying speed and thickness should be controlled during the process to avoid improper spraying.

[0055] Varnish drying process: After the varnish is sprayed and flash dried for 10 minutes, it is baked at 60℃ for 30 minutes until the paint film is completely dry. The paint film gloss and surface condition should be observed during the baking process to avoid uncontrollable defects caused by excessive baking temperature or time.

[0056] Further, the post-processing includes:

[0057] Polishing treatment; after drying, the paint film is tested for film thickness at different positions using a film thickness gauge, and the overall film thickness should be between 120-140 microns. If some positions are greater than the above reference thickness, polishing treatment is required;

[0058] After adjusting the paint film thickness by polishing and removing surface dust points, orange peel and other defects, use medium-coarse polishing wax with medium-coarse polishing disc or wool disc to polish and grind the polishing marks until it is glossy, and the interface should be lightly polished during this period. Use a gloss meter to test the gloss to above 90, and replace the polishing wax and polishing disc. Use mirror polishing wax with fine polishing disc to restore the brightness of the paint surface to above 100 gloss, and use a light lamp to observe whether there are fine polishing marks and light ring marks on the paint surface, if so, continue to use mirror wax to grind until there are no marks and light rings;

[0059] Interface processing; after polishing the sprayed part, carefully polish the interface, check whether the paint surface is smooth and flat, and whether there are serious paint misting phenomena; if so, use 2000-3000 mesh cosmetic sandpaper to polish the defect area until it is smooth and flat, and pay attention to not over-polish the edge of the interface. Use medium-coarse wax with medium-coarse polishing disc to polish along the edge of the varnish interface, until the new and old paint film cannot be seen, and use mirror wax to polish in the same way until there are no polishing marks and light rings;

[0060] Interface testing; use a cleaning cloth with oil remover to clean the polishing wax residue on the interface, and carefully observe whether the interface is perfect, if there are interface marks, repeat the above polishing process to continue polishing.

[0061] Overall acceptance; park the vehicle in the sunlight and observe the color and gloss at 90° angle from the front and 45° angle from the side to see if there are any defects; park the vehicle in the shade and observe the color and gloss at 90° angle from the front and 45° angle from the side to see if there are any defects.

[0062] In the above technical solution, based on the traditional automobile paint spraying process, the construction process is continuously optimized and technically innovated, the damaged part of the paint is repaired as much as possible, the original paint is preserved to the greatest extent, and the value of the vehicle is not devalued due to excessive maintenance.

[0063] The traditional spraying process is not mature in realizing local point spraying for small-scale damage, and can only implement whole spraying for the damaged part, which will cause the paint film of the whole panel to be too thick. The overall paint film thickness of the part can be detected by a paint film gauge, which can determine whether the part is the original paint, and the damage to the vehicle can be determined by the spraying area.

[0064] Further, before the varnish is sprayed, a diluent (deionized water) is added to adjust the viscosity to 15-17 seconds flow rate (25℃ environment);

[0065] When the initiator is a photo initiator, during the varnish flash drying process, UV light is irradiated for 10-120s. DETAILED DESCRIPTION

[0066] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0067] In the following detailed description, the "parts" are all mass parts;

[0068] The catalyst is a mixture of Schiff base cobalt (SalenCoCl) and bis(triphenylphosphine) imine (PPNCl) with a mass ratio of 10:9;

[0069] Carboxyl acrylic resin: DVK-FS-2061, from Chengdu Huidi High Chemical Product Co., Ltd.;

[0070] Bisphenol A type epoxy acrylate: RJ313, from Guangdong Gaoliang Technology Co., Ltd.;

[0071] Hydroxyl acrylic resin: SK6305, from Jining Zhongjian Chemical Co., Ltd.;

[0072] Polyethylene glycol: Mn = 4000, polypropylene glycol: Mn = 1000, from Dow Chemical;

[0073] Emulsifier: Tween 80, from Tianjin Fenshen Chemical Reagent Technology Co., Ltd.;

[0074] Crosslinking agent: CYMEL 385, from Zhanxin;

[0075] When the initiator is a photo initiator, during the varnish flash drying process, UV light is irradiated for 20s;

[0076] The auxiliary agent includes defoamer BYK141, leveling agent BYK358N, ultraviolet absorber 328, and light stabilizer 292 with a mass ratio of 1:4:10:5.

[0077] A spraying repair process for a point-spraying varnish for vehicles, comprising pretreatment, corrosion prevention treatment, middle coating primer spraying, surface micro-filling, topcoat spraying, varnish spraying, and post-treatment;

[0078] The pre-treatment includes component cleaning, component degreasing, damage assessment, sheet metal deformation recovery, detection of the flatness of the shaped component, and re-cleaning and degreasing;

[0079] Anti-corrosion treatment: the anti-corrosion paint is used for anti-corrosion treatment of the sheet metal repair part after pre-treatment; and then dried at 60°C for 30 minutes; the anti-corrosion paint film formed by the anti-corrosion treatment has a thickness of 19 microns;

[0080] Mid-coat primer spraying: the mid-coat primer is sprayed for 2 times; and then dried at 60°C for 30 minutes; the primer film formed by the mid-coat primer spraying has a thickness of 38 microns;

[0081] Surface micro-filling: the polyurethane resin is used for micro-filling of the surface pinhole and other defects; after filling, the surface flatness modification, cleaning, dust removal and degreasing are performed after drying and polishing; and then the surface flatness modification, cleaning, dust removal and degreasing are performed; the overall film thickness is 54 microns after the process is completed;

[0082] Topcoat spraying: the sprayed component is cleaned and degreased; the non-sprayed area is shielded, and the sprayed area is cleaned and degreased again; the topcoat is color matched; the topcoat primer stabilizer is sprayed, the first pass of topcoat is sprayed (spray gun caliber 0.5 mm, air pressure 1.8 kg pressure), dust removal is performed, and the second pass of topcoat is sprayed; the overall film thickness is 85 microns after the process is completed;

[0083] Clearcoat spraying: dust removal; the spray gun caliber is 0.8 mm, the ambient temperature should be controlled at 27°C, the first pass of clearcoat is sprayed, the second pass of clearcoat is sprayed after flash drying for 8 minutes; the clearcoat and the interface water are mixed at a volume ratio of 1:1, and the clearcoat edge is sprayed; the clearcoat edge is sprayed again with the interface water; flash drying is performed for 10 minutes, and then 60°C baking is performed for 30 minutes;

[0084] Post-treatment includes polishing treatment, polishing and trimming, interface treatment, interface testing, and overall acceptance; the overall film thickness is 130 microns.

[0085] Example 1: a point-sprayed clearcoat for vehicles, comprising the following mass components: 10 parts of carboxylated polycarbonate, 35 parts of epoxy-based polyacrylate resin, 6 parts of crosslinking agent, 0.1 part of auxiliary agent, and 2 parts of initiator; the initiator is ammonium persulfate;

[0086] (1) The epoxy-based polyacrylate resin is prepared by the following process:

[0087] Ethyl acrylate, acrylic acid, N-carbazole dithioformic acid benzyl ester, and 25% of the mass of the component azo initiator are mixed, and reacted at 50°C for 18 hours under the protection of nitrogen atmosphere;

[0088] Add ethyl acetate, mix, add isooctyl acrylate, 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, the rest of the component mass azo initiator, under the protection of nitrogen atmosphere, heat to 62℃, react for 18h, to obtain polyacrylate;

[0089] Add epoxy compound, triethylamine, mix, heat to 95℃, react for 4h; cool to obtain epoxy polyacrylate resin; epoxy compound is tetrahydrophthalic acid diglycidyl ester; azo initiator is azobis diisopropyl cyanide; epoxy polyacrylate resin includes the following mass components: 25 parts of ethyl acrylate, 9.8 parts of acrylic acid, 10 parts of 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1.2 parts of N-carbazole dithioformic acid benzyl ester, 80 parts of isooctyl acrylate, 50 parts of epoxy compound, 0.6 parts of azo initiator, 5 parts of triethylamine, 50 parts of ethyl acetate;

[0090] (2) Carboxylated polycarbonate is prepared by the following process:

[0091] In a high-pressure reaction kettle, mix epoxy-terminated polydimethylsiloxane, propylene oxide, epoxy ethane-2-carboxylic acid tert-butyl ester, catalyst, introduce carbon dioxide, the pressure of the high-pressure reaction kettle is 3.0MPa, stir for 24h; cool, dissolve with dichloromethane, precipitate with ethanol, vacuum dry to obtain silicone-modified polycarbonate; the mass ratio of propylene oxide, epoxy ethane-2-carboxylic acid tert-butyl ester, epoxy-terminated polydimethylsiloxane, catalyst is 90:10:1:0.1;

[0092] Mix silicone-modified polycarbonate, solvent (benzene and tetrahydrofuran mixed liquid with a volume ratio of 1:1), add trifluoroacetic acid, stir for 1h; distill under reduced pressure, extract, wash, dry to obtain carboxylated polycarbonate; the ratio of silicone-modified polycarbonate, trifluoroacetic acid, solvent is 3.5g:0.03g:100mL;

[0093] The varnish is water-based, and the carboxylated polycarbonate and the epoxy polyacrylate resin are added in the form of an emulsion;

[0094] The carboxylated polycarbonate emulsion is prepared by the following process: mixing polypropylene glycol and isophorone diisocyanate, heating to 65°C, adding dimethylol propionic acid, and reacting for 2 hours, adding a catalyst and continuing to react for 2 hours; cooling to 30°C, adding carboxylated polycarbonate, adding deionized water, and dispersing for 10 minutes at a speed of 2700 rpm to obtain a carboxylated polycarbonate emulsion with a solid content of 40%; the carboxylated polycarbonate emulsion comprises the following mass components: 100 parts of carboxylated polycarbonate, 16 parts of polypropylene glycol, 5 parts of isophorone diisocyanate, 0.2 parts of dimethylol propionic acid, 0.5 parts of hydroxyl-terminated polybutadiene, and 0.005 parts of a catalyst dibutyltin dilaurate;

[0095] The epoxy-based polyacrylate resin emulsion is prepared by the following process: mixing epoxy-based polyacrylate resin and emulsifier, heating to 50°C, adjusting the pH of the system to 7, slowly adding deionized water at a speed of 1200 rpm, and adding all the deionized water within 60 minutes, and then dispersing for 30 minutes at a speed of 2700 rpm, and adjusting the solid content to 40% by adding water to obtain an epoxy-based polyacrylate resin emulsion; the mass ratio of epoxy-based polyacrylate resin to emulsifier is 100:5;

[0096] Before the varnish is sprayed, the viscosity is adjusted to 15 seconds flow rate (25°C environment) using a diluent.

[0097] Example 2: A point-spraying varnish for vehicles, comprising the following mass components: 20 parts of carboxylated polycarbonate, 45 parts of epoxy-based polyacrylate resin, 9 parts of crosslinking agent, 1.0 parts of auxiliary agent, and 3 parts of initiator; the initiator is a photoinitiator 1173;

[0098] (1) The epoxy-based polyacrylate resin is prepared by the following process:

[0099] Mixing ethyl acrylate, acrylic acid, N-carbazole dithioformic acid benzyl ester, and 30% of the mass of the remaining components azo initiator, under the protection of nitrogen atmosphere, at a temperature of 52°C, and reacting for 21 hours;

[0100] Mixing with the addition of ethyl acetate, adding isooctyl acrylate, 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, and the remaining components azo initiator, heating to 65°C under the protection of nitrogen atmosphere, and reacting for 21 hours to obtain a polyacrylate;

[0101] adding an epoxy compound, mixing with triethylamine, warming to 100°C, and reacting for 4.5 h; cooling to obtain an epoxy polyacrylate resin; the epoxy compound is tetrahydrophthalic acid diglycidyl ester; the azo initiator is azobisisobutyronitrile; the epoxy polyacrylate resin comprises the following mass components: 27 parts of ethyl acrylate, 15 parts of acrylic acid, 12 parts of 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1.3 parts of N-carbazole dithioformic acid benzyl ester, 60 parts of isooctyl acrylate, 60 parts of the epoxy compound, 0.8 parts of the azo initiator, 6 parts of triethylamine, 60 parts of ethyl acetate;

[0102] (2) The carboxylated polycarbonate is prepared by the following process:

[0103] In a high-pressure reaction kettle, epoxy-terminated polydimethylsiloxane, propylene oxide, epoxy ethane-2-tert-butyl carboxylate, and a catalyst are mixed, carbon dioxide is introduced, the pressure of the high-pressure reaction kettle is 3.5 MPa, and stirring is performed for 30 h; cooling, dissolving with dichloromethane, precipitating with ethanol, and vacuum drying to obtain a silicone-modified polycarbonate; the mass ratio of propylene oxide, epoxy ethane-2-tert-butyl carboxylate, epoxy-terminated polydimethylsiloxane, and catalyst is 70:30:5:0.2;

[0104] The silicone-modified polycarbonate, a solvent (a mixture of benzene and tetrahydrofuran in a volume ratio of 1:1), and trifluoroacetic acid are mixed, stirring is performed for 5 h; vacuum distillation, extraction, washing, and drying to obtain a carboxylated polycarbonate; the ratio of silicone-modified polycarbonate, trifluoroacetic acid, and solvent is 3.5 g:0.04 g:100 mL;

[0105] The varnish is water-based, and the carboxylated polycarbonate and the epoxy polyacrylate resin are added in the form of an emulsion;

[0106] The carboxylated polycarbonate emulsion is prepared by the following process: polypropylene glycol and isophorone diisocyanate are mixed, warmed to 72°C, dimethylolpropionic acid and hydroxyl-terminated polybutadiene are added, and reacted for 3 h, a catalyst is added and the reaction is continued for 2.5 h; cooled to 35°C, carboxylated polycarbonate is added, deionized water is added, and dispersed at a speed of 2900 rpm for 15 min to obtain a carboxylated polycarbonate emulsion with a solid content of 40%; the carboxylated polycarbonate emulsion comprises the following mass components: 100 parts of carboxylated polycarbonate, 18 parts of polypropylene glycol, 8 parts of isophorone diisocyanate, 0.5 parts of dimethylolpropionic acid, 0.8 parts of hydroxyl-terminated polybutadiene, and 0.010 parts of catalyst dibutyltin dilaurate;

[0107] The epoxy-based polyacrylate resin emulsion is prepared by the following process: mixing the epoxy-based polyacrylate resin and the emulsifier, heating to 60°C, adjusting the pH of the system to 7.5, slowly adding deionized water at a speed of 1600 rpm, adding completely within 75 min, and then dispersing at 2800 rpm for 45 min, adjusting the solid content to 40% by adding water, to obtain the epoxy-based polyacrylate resin emulsion; the mass ratio of the epoxy-based polyacrylate resin to the emulsifier is 100:8;

[0108] The viscosity of the varnish is adjusted to 16 seconds flow rate (at 25°C in the environment) using a diluent before spraying.

[0109] Example 3: A point-spraying varnish for vehicles, comprising the following mass components: 30 parts of carboxylated polycarbonate, 60 parts of epoxy-based polyacrylate resin, 12 parts of crosslinking agent, 2.6 parts of auxiliary agent, and 4 parts of initiator; the initiator is a mixture of photoinitiator 1173 and photoinitiator 522, with a mass ratio of 2:1;

[0110] (1) The epoxy-based polyacrylate resin is prepared by the following process:

[0111] Mixing ethyl acrylate, acrylic acid, benzyl N-carbazolyl dithioformate, and 35% of the mass of the azo initiator, and reacting at 55°C for 24 h under nitrogen atmosphere protection;

[0112] Mixing with ethyl acetate, adding isooctyl acrylate, 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, and the remaining mass of the azo initiator, heating to 68°C, and reacting for 24 h under nitrogen atmosphere protection to obtain the polyacrylate;

[0113] Mixing with the epoxy compound and triethylamine, heating to 105°C, and reacting for 5 h; cooling to obtain the epoxy-based polyacrylate resin; the epoxy compound is tetrahydrophthalic acid diglycidyl ester; the azo initiator is 1,1-azobis(cyclohexane-1-carbonitrile); the epoxy-based polyacrylate resin comprises the following mass components: 30 parts of ethyl acrylate, 20.5 parts of acrylic acid, 15 parts of 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1.5 parts of benzyl N-carbazolyl dithioformate, 42 parts of isooctyl acrylate, 70 parts of the epoxy compound, 1.0 part of the azo initiator, 7 parts of triethylamine, and 70 parts of ethyl acetate;

[0114] (2) The carboxylated polycarbonate is prepared by the following process:

[0115] In a high-pressure reactor, epoxy-terminated polydimethylsiloxane, propylene oxide, epoxy ethane-2-tert-butyl carboxylate, catalyst were mixed, carbon dioxide was introduced, the pressure of the high-pressure reactor was 4.0 MPa, and the stirring reaction was carried out for 36 h; cooling, dissolving with dichloromethane, precipitating with ethanol, and vacuum drying to obtain silicone-modified polycarbonate; the mass ratio of propylene oxide, epoxy ethane-2-tert-butyl carboxylate, epoxy-terminated polydimethylsiloxane, and catalyst was 50:50:10:0.3;

[0116] The silicone-modified polycarbonate, solvent (benzene and tetrahydrofuran mixed liquid in a volume ratio of 1:1), and trifluoroacetic acid were mixed, and stirred for 8 h; vacuum distillation, extraction, washing, and drying to obtain carboxylated polycarbonate; the ratio of silicone-modified polycarbonate, trifluoroacetic acid, and solvent was 3.5 g:0.05 g:100 mL;

[0117] The varnish is water-based, and the carboxylated polycarbonate and epoxy-based polyacrylate resin are added in the form of emulsion;

[0118] The carboxylated polycarbonate emulsion was prepared by the following process: polypropylene glycol and isophorone diisocyanate were mixed, heated to 80°C, dimethylol propionic acid and hydroxyl-terminated polybutadiene were added and reacted for 4 h, and a catalyst was added and continued to react for 3 h; cooled to 40°C, added carboxylated polycarbonate, added deionized water, and dispersed at a speed of 3000 rpm for 20 min to obtain a carboxylated polycarbonate emulsion with a solid content of 40%; the carboxylated polycarbonate emulsion includes the following mass components: 100 parts of carboxylated polycarbonate, 20 parts of polypropylene glycol, 12 parts of isophorone diisocyanate, 1.0 part of dimethylol propionic acid, 1.0 part of hydroxyl-terminated polybutadiene, and 0.020 parts of catalyst dibutyltin dilaurate;

[0119] The epoxy-based polyacrylate resin emulsion was prepared by the following process: epoxy-based polyacrylate resin and emulsifier were mixed, heated to 70°C, the pH of the system was adjusted to 8, deionized water was slowly added at a speed of 2000 rpm, and the addition was completed within 90 min, and then dispersed at a speed of 3000 rpm for 60 min, and the solid content was adjusted to 40% by adding water to obtain an epoxy-based polyacrylate resin emulsion; the mass ratio of epoxy-based polyacrylate resin to emulsifier was 100:10;

[0120] Before spraying the varnish, the viscosity was adjusted to 17 seconds flow rate (25°C environment) using a diluent.

[0121] Comparative Example 1: a point spraying varnish for vehicles, including the following mass components: 10 parts of carboxylated polycarbonate, 35 parts of bisphenol A type epoxy acrylate, 6 parts of crosslinking agent, and 0.1 part of auxiliary agent;

[0122] The carboxylated polycarbonate emulsion is prepared by the following process: mixing polypropylene glycol and isophorone diisocyanate, heating to 65℃, adding dimethylol propionic acid, and reacting for 2h, adding a catalyst and continuing to react for 2h; cooling to 30℃, adding carboxylated polycarbonate, adding deionized water, and dispersing at a speed of 2700rpm for 10min to obtain a carboxylated polycarbonate emulsion with a solid content of 40%; the carboxylated polycarbonate emulsion comprises the following mass components: 100 parts of carboxylated polycarbonate, 16 parts of polypropylene glycol, 5 parts of isophorone diisocyanate, 0.2 parts of dimethylol propionic acid, and 0.005 parts of a catalyst dibutyltin dilaurate

[0123] Other processes are the same as in Example 1 to obtain a varnish.

[0124] Comparative Example 2: a car point spraying varnish, comprising the following mass components: 10 parts of carboxylated acrylic resin, 35 parts of bisphenol A type epoxy acrylate, 6 parts of crosslinking agent, and 0.1 parts of auxiliary agent, other processes are the same as in Example 1 to obtain a varnish.

[0125] Comparative Example 3: a car point spraying varnish, comprising the following mass components: 10 parts of hydroxyl acrylic resin, 35 parts of bisphenol A type epoxy acrylate, 6 parts of crosslinking agent, and 0.1 parts of auxiliary agent, other processes are the same as in Example 1 to obtain a varnish.

[0126] Experiment: take the varnish obtained in Examples 1-3 and Comparative Examples 1-4, spray it on the surface of tinplate, flash dry for 10min, and bake at 60℃ for 30min to obtain a test sample, and detect the performance of the test sample and record the detection results:

[0127] Hardness test: take GB / T 6739 as a reference standard to detect the pencil hardness of the test sample;

[0128] Adhesion test: take GB / T 9286 as a reference standard, use grid method, paste 3M tape on the surface of the test sample, and then quickly tear off the tape to observe the appearance of the varnish;

[0129] Water resistance test: take GB / T 1733 as a reference standard, soak in 40℃ water for 240h, take out and dry, and then detect the adhesion grade of the test sample again;

[0130] Butanone resistance test: take ASTM D 5402 as a reference standard, repeatedly wipe with butanone,

[0131] Weather resistance test: take exposure period 7 in GB / T 14522 as a reference standard, test for 1 000h, and take GB / T 1766 as the evaluation method;

[0132] Mechanical property test: according to GB / T 1732 as a reference standard, the impact resistance of the sample was tested, the multiple of 5cm was used for each drop height, and the sample surface was observed by 4 times lens to see if there were cracks, wrinkles, peeling phenomenon.

[0133] Pencil hardness Adhesion rating Post-water adhesion rating Ketone rub resistance (cycles) Weathering rating Impact resistance (cm) Example 1 H-2H 0-1 rating 1 rating 62 1 rating 70 Example 2 2H 0 rating 0 rating 65 0 rating 75 Example 3 2H 0 rating 0 rating 69 0 rating 80 Comparative Example 1 H 1 rating 1-2 rating 57 1 rating 65 Comparative Example 2 H 1-2 rating 3 rating 51 2 rating 55 Comparative Example 3 HB 2 rating 4 rating 46 3 rating 45

[0134] According to the data in the above table, the following conclusions can be clearly obtained:

[0135] The varnish obtained in examples 1-3 is compared with the varnish obtained in comparative examples 1-3, and the test results show that,

[0136] Compared with the comparative examples, the varnish obtained in examples 1-3 has higher pencil hardness, weather resistance grade, butanone wiping resistance, impact resistance, and better adhesion grade data before and after water resistance. This fully shows that the present application improves the surface hardness, impact resistance, adhesion, water resistance, chemical corrosion resistance and weather resistance of the prepared varnish.

[0137] Compared with example 1, comparative example 1 replaces the epoxy-based polyacrylate resin with bisphenol A type epoxy acrylate; comparative example 2 replaces the carboxylated polycarbonate with carboxyl acrylate resin, and the epoxy-based polyacrylate resin with bisphenol A type epoxy acrylate; comparative example 3 replaces the carboxylated polycarbonate with hydroxyl acrylate resin, and the epoxy-based polyacrylate resin with bisphenol A type epoxy acrylate. The varnish obtained in comparative examples 1-3 has poorer pencil hardness, weather resistance grade, butanone wiping resistance, impact resistance, and adhesion grade data before and after water resistance. It can be seen that the present application can improve the comprehensive improvement of the surface hardness, impact resistance, adhesion, water resistance, chemical corrosion resistance and weather resistance of the varnish components and process.

[0138] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the examples should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application.

Claims

1. A type of automotive spot spray clear coat, characterized in that: It includes the following components by weight: 10-30 parts carboxylated polycarbonate, 35-60 parts epoxy-based polyacrylate resin, 6-12 parts crosslinking agent, 0.1-8.0 parts additives, and 2-4 parts initiator; The epoxy-based polyacrylate resin is prepared by the following process: Ethyl acrylate, acrylic acid, benzyl N-carbazole dithiocarbamate, and 25%–35% of the component mass of azo initiator were mixed and reacted at 50–55°C for 18–24 h under a nitrogen atmosphere. Ethyl acetate was added and mixed, followed by isooctyl acrylate, 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, and the remaining component mass of azo initiator. The mixture was then heated to 62–68°C and reacted for 18–24 h under a nitrogen atmosphere to obtain polyacrylate. Add an epoxy compound and triethylamine, heat to 95–105°C, and react for 4–5 hours; cool to obtain an epoxy-based polyacrylate resin. The epoxy compound is one or a mixture of tetrahydrophthalic acid diglycidyl ester and bisphenol A epoxy diacrylate; The carboxylated polycarbonate is prepared by the following process: Epoxy-terminated polydimethylsiloxane, propylene oxide, ethylene oxide-2-carboxylic acid tert-butyl ester, and catalyst were mixed, carbon dioxide was introduced, and the mixture was stirred for 24–36 h to obtain organosilicon-modified polycarbonate. Organosilicon-modified polycarbonate and solvent were mixed, trifluoroacetic acid was added, and the mixture was stirred for 1 to 8 hours to obtain carboxylated polycarbonate. The varnish is water-based, and carboxylated polycarbonate and epoxy-based polyacrylate resin are added in the form of an emulsion. The carboxylated polycarbonate emulsion is prepared by the following process: Polypropylene glycol and isophorone diisocyanate are mixed and heated to 65-80°C. Dimethylolpropionic acid and hydroxyl-terminated polybutadiene are added and reacted for 2-4 hours. A catalyst is added and the reaction continues for 2-3 hours. The temperature is then lowered to 30-40°C, carboxylated polycarbonate is added, and deionized water is added. The mixture is dispersed at 2700-3000 rpm for 10-20 minutes to obtain a carboxylated polycarbonate emulsion with a solid content of 30%-60%.

2. The automotive spot spray clear coat according to claim 1, characterized in that: The epoxy-based polyacrylate resin comprises the following components by weight: 25-30 parts ethyl acrylate, 9.8-20.5 parts acrylic acid, 10-15 parts 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1.2-1.5 parts benzyl N-carbazole dithiocarbamate, 42-80 parts isooctyl acrylate, 50-70 parts epoxy compound, 0.6-1.0 parts azo initiator, 5-7 parts triethylamine, and 50-70 parts ethyl acetate.

3. The automotive spot spray clear coat according to claim 1, characterized in that: The mass ratio of propylene oxide, ethylene oxide-2-carboxylic acid tert-butyl ester, epoxy-terminated polydimethylsiloxane, and catalyst is (50-90):(10-50):(1-10):(0.1-0.3).

4. The spraying repair process for automotive spot spray clear coat according to any one of claims 1-3, characterized in that: It includes pretreatment, anti-corrosion treatment, intermediate primer spraying, surface micro-filling, topcoat spraying, clear coat spraying, and post-treatment.

5. The spraying repair process for automotive spot spray clear coat according to claim 4, characterized in that: The thickness of the anti-corrosion paint film formed by the anti-corrosion treatment should be 18 to 20 micrometers.

6. The spraying repair process for automotive spot spray clear coat according to claim 4, characterized in that: The intermediate primer is applied as follows: two coats of intermediate primer are applied; then dried at 60°C for 30 minutes. The thickness of the primer film formed by the intermediate primer spraying is 35-40 micrometers, and the thickness of the superimposed anti-corrosion paint film is 53-60 micrometers; after the topcoat is sprayed, the overall film thickness should be 80-88 micrometers.

7. The spraying repair process for automotive spot spray clear coat according to claim 4, characterized in that: The clear varnish spraying process includes clear varnish spraying and clear varnish interface. The clear varnish spraying process uses a 0.8-1.0 caliber spray gun to spray two coats of clear varnish. The clear varnish interface process is as follows: mix clear varnish and interface water at a volume ratio of 1:1 and spray it onto the edge of the clear varnish film; use interface water to spray a second coat onto the edge of the clear varnish; then flash dry for 10 minutes and bake at 60℃ for 30 minutes.