A coating suitable for spraying on the surface of automobile body and a preparation method thereof

Abstract

The invention belongs to the technical field of automotive coatings, and in particular to a method for preparing a coating suitable for automobile body surface spraying, comprising the following steps: modified acrylic resin, hydrophobic modified polyurethane, hydrophobic nano silica, dispersant, anti-settling agent, leveling agent, defoamer are mixed, and high pressure homogenization and grinding are performed to obtain; wherein, the method for preparing modified acrylic resin is: using 3 (N-allylamino) propyltrimethoxysilane and 2 benzyloxirane as raw materials to prepare intermediates, then using intermediates and trifluorobutyric acid as raw materials to prepare modifiers, and finally using hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, modifiers as raw materials, to prepare modified acrylic resin. The present invention, by adjusting the raw material ratio and optimizing the process conditions, the coating prepared has excellent hardness, adhesion, wear resistance, hydrophobicity, heat resistance, stain resistance, acid and alkali corrosion resistance and aging resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile coatings, and in particular relates to a coating suitable for spraying on the surface of an automobile body and a preparation method thereof. Background Art

[0002] Automotive coatings are specially manufactured coatings used to protect and beautify the surface of a car. They have the following properties: (1) Protective: Automotive coatings can protect the surface of a car from damage by factors such as oxidation, corrosion, and ultraviolet radiation, thus extending the service life of the car; (2) Decorative: Automotive coatings come in a variety of colors and effects to make the car look more attractive; (3) Durability: Automotive coatings need to have good resistance to abrasion, chemicals, and weathering to cope with common road and environmental conditions. The purpose of automotive coatings is mainly to decorate and protect the exterior surface of the car, while also enhancing the overall value of the car. Coatings are usually applied to the body, doors, hood, and other parts of the car.

[0003] The patent with application number CN201410235074.3 provides an automobile coating, including the following raw materials: europium trifluoroacetylacetonate, tetrahydrofuran, 3-chloropropyne, benzyltrimethylammonium tribromide, ferrocyanate, polyurethane resin, tetrabutylphosphine chloride, sodium thiocyanate, acrylic resin, butyl acetate. The automobile coating provided by the invention has good viscosity, fineness, hiding power, adhesion, pollution resistance, aging resistance and other properties. It is applied to the surface of the car to form a paint film. The paint film has a gorgeous and soft gloss and good image clarity. However, its raw material components are relatively complex, and the compatibility between the components is poor. The paint film is prone to cracking and bubbling. The patent with application number CN201911401816.4 provides an environmentally friendly high-flow dry powder coating for automobile wheels, including the following raw materials: epoxy resin, amino resin, Acrylic resin, saturated hydroxy polyester resin, polytetrafluoroethylene wax, leveling agent, curing agent, leveling aid, benzoin, pigment, barium sulfate, cosolvent. The coating provided by the invention has good impact resistance, corrosion resistance, adhesion and hardness, which is beneficial to improving the stability, reliability and durability of automobile wheel hubs. However, the coating composition has high viscosity, poor fluidity, high processing cost, and weather resistance needs to be further improved. In addition, acrylic resin is added to the coatings provided by the above two patents. Acrylic resin has good film-forming property, light and color retention, and dries quickly, with high coating gloss and low cost. Therefore, it is widely used in the field of coatings. However, the structural characteristics of acrylic resin itself determine that its water resistance is not ideal, and its heat resistance, UV aging resistance and stain resistance are poor, which limits its application to a certain extent. Summary of the invention

[0004] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a coating suitable for spraying on the surface of an automobile body, the coating product having excellent hardness, adhesion, wear resistance, hydrophobicity, heat resistance, and also having strong stain resistance, acid and alkali corrosion resistance and aging resistance; the present invention also provides a method for preparing the coating.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0006] A coating suitable for spraying on the surface of an automobile body comprises the following raw materials in parts by weight: 25-55 parts of a modified acrylic resin, 5-15 parts of a hydrophobic modified polyurethane, 1-4 parts of a hydrophobic nano-silicon dioxide, 0.1-0.4 parts of a dispersant, 0.5-2 parts of an anti-settling agent, 0.1-0.3 parts of a leveling agent, and 0.1-0.4 parts of a defoaming agent; the preparation method of the modified acrylic resin is as follows:

[0007] S1. Disperse 3-(N-allylamino)propyltrimethoxysilane in 2-methyltetrahydrofuran under stirring, heat to 60-80°C, add 2-benzylethylene oxide and N,N-dimethylbenzylamine in sequence, react for 5-8h, filter, take the filtrate, distill under reduced pressure, and dry to obtain an intermediate;

[0008] S2. Disperse the intermediate in 2-methyltetrahydrofuran under stirring, heat to 70-80°C, add p-toluenesulfonic acid and trifluorobutyric acid in sequence, react for 5-10 hours, filter, take the filtrate, distill under reduced pressure, extract, and dry to obtain a modifier;

[0009] S3, hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, part of diisopropylbenzene peroxide and modifier are mixed uniformly to obtain a mixed solution, xylene is heated to 135-145°C under nitrogen atmosphere and stirring, the mixed solution is added dropwise, the addition is completed within 2-4 hours, stirring is continued for 1-3 hours, the remaining diisopropylbenzene peroxide is added, stirring is continued for 0.5-1.5 hours, cooling, filtering and discharging to obtain;

[0010] Among them, the synthetic route of the modifier is as follows:

[0011] ;

[0012] .

[0013] Modifying acrylic resin is an effective means to expand its application field. The present invention first uses 3-(N-allylamino)propyltrimethoxysilane and 2-benzyloxirane as raw materials, and causes a ring-opening reaction of the epoxy compound under the action of N,N-dimethylbenzylamine to obtain an intermediate; then uses the intermediate and trifluorobutyric acid as raw materials, and causes an esterification reaction under the action of p-toluenesulfonic acid to obtain a modifier; finally, uses hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, and the modifier as raw materials, and causes a polymerization reaction under the action of diisopropylbenzene peroxide to obtain a modified acrylic resin.

[0014] In order to obtain the modified acrylic resin, the molar ratio of 3-(N-allylamino)propyltrimethoxysilane, 2-benzyloxirane and N,N-dimethylbenzylamine in step S1 is 0.8-1.0:1:0.02-0.05, the amount of 3-(N-allylamino)propyltrimethoxysilane added to 2-methyltetrahydrofuran is 0.2-0.5 g / mL; the molar ratio of the intermediate, p-toluenesulfonic acid and trifluorobutyric acid in step S2 is 0.7-1.0:1:0.02-0.05. 0.9:0.01-0.04:1, the amount of the intermediate added to the 2-methyltetrahydrofuran is 0.1-0.3 g / mL; the mass ratio of hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, xylene, dicumyl peroxide and modifier in step S3 is 1-5:20-28:4-8:35-55:0.8-1.6:2-5, and the partial dicumyl peroxide accounts for 40-60% of the total mass of dicumyl peroxide.

[0015] Preferably, the dispersant is one of polyvinyl pyrrolidone, fatty alcohol polyoxyethylene ether AEO-3, and fatty alcohol polyoxyethylene ether AEO-7; the anti-settling agent is polyamide wax or polyethylene wax; the leveling agent is BYK-333 or BYK-358N; and the defoaming agent is one of BYK1797, BYK052, and BYK381.

[0016] The present invention also provides a method for preparing a coating suitable for spraying on the surface of an automobile body, comprising the following steps: mixing modified acrylic resin, hydrophobic modified polyurethane, hydrophobic nano-silica, a dispersant, an anti-settling agent, a leveling agent, and a defoaming agent, and subjecting the mixture to high-pressure homogenization and grinding treatment to obtain the coating; wherein the homogenization pressure of the high-pressure homogenization is 30-50MPa, the homogenization time is 5-20s, and the grinding time is 20-40min.

[0017] The present invention has the following beneficial effects:

[0018] The present invention sequentially introduces siloxane, aromatic ring and fluorine element into the modified acrylic resin structure through epoxy ring-opening reaction, esterification reaction and polymerization reaction; the introduction of siloxane can improve the hydrophobicity and anti-ultraviolet aging performance of the modified acrylic resin; the synergistic effect of siloxane and fluorine element can not only further improve the hydrophobicity of the modified acrylic resin, but also significantly improve its adhesion and stain resistance; the aromatic ring structure has high stability and rigidity, can effectively resist external friction and wear, and the introduction of the aromatic ring structure into the modified acrylic resin can significantly improve its mechanical properties and wear resistance; in addition, the introduction of siloxane, aromatic ring and fluorine element can synergistically enhance the thermal stability and chemical stability of the modified acrylic resin, thereby improving the heat resistance and acid and alkali corrosion resistance of the coating. The modified acrylic resin provided by the present invention has good compatibility, and the various components of the raw materials synergize. By adjusting the ratio and optimizing the process, the prepared coating has excellent hardness, adhesion, wear resistance, hydrophobicity, heat resistance, stain resistance, acid and alkali corrosion resistance and aging resistance. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application. The raw materials used in the following embodiments are all common commercially available products.

[0020] Example 1

[0021] A method for preparing a modified acrylic resin comprises the following steps:

[0022] S1. Under stirring at 200 r / min, 3-(N-allylamino)propyltrimethoxysilane was dispersed in 2-methyltetrahydrofuran, and 2-benzyloxirane and N,N-dimethylbenzylamine were added in sequence after heating to 70°C, and the mixture was reacted for 6 hours. The mixture was filtered, and the filtrate was taken. 2-methyltetrahydrofuran was removed by vacuum distillation under reduced pressure, and the mixture was dried under vacuum at 55°C for 12 hours to obtain an intermediate, wherein the molar ratio of 3-(N-allylamino)propyltrimethoxysilane, 2-benzyloxirane and N,N-dimethylbenzylamine was 0.9:1:0.04, and the amount of 3-(N-allylamino)propyltrimethoxysilane added to 2-methyltetrahydrofuran was 0.35 g / mL.

[0023] S2. Under stirring at 200 r / min, the intermediate was dispersed in 2-methyltetrahydrofuran, and p-toluenesulfonic acid and trifluorobutyric acid were added in sequence after the temperature was raised to 75°C. The reaction was continued for 8 hours, and the mixture was filtered. The filtrate was taken and the 2-methyltetrahydrofuran was removed by distillation under reduced pressure. Ethyl acetate and deionized water were added for extraction. The organic phase was concentrated and dried under vacuum at 60°C for 24 hours to obtain a modifier, wherein the molar ratio of the intermediate, p-toluenesulfonic acid and trifluorobutyric acid was 0.8:0.03:1, the amount of the intermediate added to 2-methyltetrahydrofuran was 0.2 g / mL, and the volume ratio of ethyl acetate to deionized water was 1:1;

[0024] S3. Mix hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, part of diisopropylbenzene peroxide and modifier to obtain a mixed solution. Heat xylene to 138°C under nitrogen atmosphere and stirring at 200r / min, add the mixed solution dropwise, complete the addition in 3h, continue stirring for 2h, add the remaining diisopropylbenzene peroxide, stir for another 1h, cool to 65-75°C, filter, take the filtrate, and discharge to obtain a modified acrylic resin; wherein the mass ratio of hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, xylene, diisopropylbenzene peroxide and modifier is 3:24:6:45:1.2:3, part of diisopropylbenzene peroxide accounts for 50% of the total mass of diisopropylbenzene peroxide, the solid content of the modified acrylic resin is (46±1)%, the kinematic viscosity at 25°C is 1000mPa·S, and the average molecular weight is>18w;

[0025] Among them, the NMR results of the modifier are: 1 H NMR (300MHz, DMSO-d6) δ 7.19-7.23 (d, 5H), 5.80-5.84 (m, 1H), 5.16-5.20 (m, 2H), 4.98 (t, 1H), 3.55 (s, 9H), 3.05 (d, 2H), 2.88-2.92 ( m, 1H), 2.73-2.75 (m, 1H), 2.63-2.66 (m, 1H), 2.36-2.42 (m, 5H), 2.20 (t, 2H), 1.32-1.35 (m, 2H), 0.56 (t, 2H).

[0026] A coating suitable for spraying on the surface of an automobile body, comprising the following raw materials in parts by weight: 40 parts of modified acrylic resin, 10 parts of hydrophobic modified polyurethane (model RM-8W, solid content 21.5%, purchased from Jining Tangyi Chemical Co., Ltd.), 2 parts of hydrophobic nano-silicon dioxide (model HN-SQ20S-C, particle size 20nm, purchased from Hangzhou Hengna New Materials Co., Ltd.), 0.2 parts of dispersant, 1 part of anti-settling agent, 0.2 parts of leveling agent, and 0.2 parts of defoaming agent; wherein the dispersant is fatty alcohol polyoxyethylene ether AEO-3 (effective ingredient content 99%, Purchased from Shandong Hanyue Chemical Co., Ltd.), the anti-settling agent is polyamide wax (brand Fenghong / Huate, model PA-8600, density 1.1kg / m³, purchased from Zhejiang Huate New Materials Co., Ltd.), the leveling agent is BYK-333 (brand German BYK, density 1.04kg / m³, effective ingredient content 90%, the main ingredient is polyether modified polydimethylsiloxane, purchased from Hunan Jiaxinzhi New Materials Technology Co., Ltd.), and the defoaming agent is BYK052 (brand German BYK, purity 90%, the main ingredient is polyether, purchased from Shenzhen Huixin Plastic Chemical Co., Ltd.).

[0027] A method for preparing a coating suitable for spraying on the surface of an automobile body comprises the following steps: mixing modified acrylic resin, hydrophobic modified polyurethane, hydrophobic nano-silica, dispersant, anti-settling agent, leveling agent and defoaming agent, subjecting the mixture to high-pressure homogenization, and grinding the mixture with a sand mill for 30 minutes to obtain the coating; wherein the homogenization pressure is 40 MPa and the homogenization time is 10 seconds. When used, the coating is evenly applied on a substrate, and cured at a temperature of (28±2)°C for 24 hours to form a coating film for the surface of an automobile body.

[0028] Example 2

[0029] A method for preparing a modified acrylic resin is prepared according to the process described in Example 1, except that in step S3, the mass ratio of hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, xylene, dicumyl peroxide and modifier is 3:24:6:45:1.2:2.

[0030] A coating suitable for spraying on the surface of an automobile body, comprising the following raw materials in parts by weight: 40 parts of modified acrylic resin, 10 parts of hydrophobic modified polyurethane (model RM-8W, solid content 21.5%, purchased from Jining Tangyi Chemical Co., Ltd.), 2 parts of hydrophobic nano-silicon dioxide (model HN-SQ20S-C, particle size 20nm, purchased from Hangzhou Hengna New Materials Co., Ltd.), 0.2 parts of dispersant, 1 part of anti-settling agent, 0.2 parts of leveling agent, and 0.2 parts of defoaming agent; wherein the dispersant is fatty alcohol polyoxyethylene ether AEO-3 (effective ingredient content 99%, Purchased from Shandong Hanyue Chemical Co., Ltd.), the anti-settling agent is polyamide wax (brand Fenghong / Huate, model PA-8600, density 1.1kg / m³, purchased from Zhejiang Huate New Materials Co., Ltd.), the leveling agent is BYK-333 (brand German BYK, density 1.04kg / m³, effective ingredient content 90%, the main ingredient is polyether modified polydimethylsiloxane, purchased from Hunan Jiaxinzhi New Materials Technology Co., Ltd.), and the defoaming agent is BYK052 (brand German BYK, purity 90%, the main ingredient is polyether, purchased from Shenzhen Huixin Plastic Chemical Co., Ltd.).

[0031] Example 3

[0032] A method for preparing a modified acrylic resin is prepared according to the process described in Example 1, except that in step S3, the mass ratio of hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, xylene, dicumyl peroxide and modifier is 3:24:6:45:1.2:5.

[0033] A coating suitable for spraying on the surface of an automobile body, comprising the following raw materials in parts by weight: 40 parts of modified acrylic resin, 10 parts of hydrophobic modified polyurethane (model RM-8W, solid content 21.5%, purchased from Jining Tangyi Chemical Co., Ltd.), 2 parts of hydrophobic nano-silicon dioxide (model HN-SQ20S-C, particle size 20nm, purchased from Hangzhou Hengna New Materials Co., Ltd.), 0.2 parts of dispersant, 1 part of anti-settling agent, 0.2 parts of leveling agent, and 0.2 parts of defoaming agent; wherein the dispersant is fatty alcohol polyoxyethylene ether AEO-3 (effective ingredient content 99%, Purchased from Shandong Hanyue Chemical Co., Ltd.), the anti-settling agent is polyamide wax (brand Fenghong / Huate, model PA-8600, density 1.1kg / m³, purchased from Zhejiang Huate New Materials Co., Ltd.), the leveling agent is BYK-333 (brand German BYK, density 1.04kg / m³, effective ingredient content 90%, the main ingredient is polyether modified polydimethylsiloxane, purchased from Hunan Jiaxinzhi New Materials Technology Co., Ltd.), and the defoaming agent is BYK052 (brand German BYK, purity 90%, the main ingredient is polyether, purchased from Shenzhen Huixin Plastic Chemical Co., Ltd.).

[0034] Example 4

[0035] A coating suitable for spraying on the surface of an automobile body, comprising the following raw materials in parts by weight: 25 parts of the modified acrylic resin prepared in Example 1, 15 parts of hydrophobic modified polyurethane (model RM-8W, solid content 21.5%, purchased from Jining Tangyi Chemical Co., Ltd.), 1 part of hydrophobic nano-silicon dioxide (model HN-SQ20S-C, particle size 20 nm, purchased from Hangzhou Hengna New Materials Co., Ltd.), 0.1 parts of a dispersant, 0.5 parts of an anti-settling agent, 0.3 parts of a leveling agent, and 0.4 parts of a defoaming agent; wherein the dispersant is fatty alcohol polyoxyethylene ether AEO-3 (the active ingredient contains The content of active ingredients is 99%, purchased from Shandong Hanyue Chemical Co., Ltd.), the anti-settling agent is polyamide wax (brand Fenghong / Huate, model PA-8600, density 1.1kg / m³, purchased from Zhejiang Huate New Materials Co., Ltd.), the leveling agent is BYK-333 (brand German BYK, density 1.04kg / m³, active ingredient content 90%, main component polyether modified polydimethylsiloxane, purchased from Hunan Jiaxinzhi New Materials Technology Co., Ltd.), and the defoaming agent is BYK052 (brand German BYK, purity 90%, main component polyether, purchased from Shenzhen Huixin Plastic Chemical Co., Ltd.).

[0036] Example 5

[0037] A coating suitable for spraying on the surface of an automobile body, comprising the following raw materials in parts by weight: 55 parts of the modified acrylic resin prepared in Example 1, 5 parts of hydrophobic modified polyurethane (model RM-8W, solid content 21.5%, purchased from Jining Tangyi Chemical Co., Ltd.), 4 parts of hydrophobic nano-silicon dioxide (model HN-SQ20S-C, particle size 20 nm, purchased from Hangzhou Hengna New Materials Co., Ltd.), 0.4 parts of dispersant, 2 parts of anti-settling agent, 0.1 parts of leveling agent, and 0.1 parts of defoaming agent; wherein the dispersant is fatty alcohol polyoxyethylene ether AEO-3 (effective ingredient content 9 9%, purchased from Shandong Hanyue Chemical Co., Ltd.), the anti-settling agent is polyamide wax (brand Fenghong / Huate, model PA-8600, density 1.1kg / m³, purchased from Zhejiang Huate New Materials Co., Ltd.), the leveling agent is BYK-333 (brand German BYK, density 1.04kg / m³, effective ingredient content 90%, main ingredient polyether modified polydimethylsiloxane, purchased from Hunan Jiaxinzhi New Materials Technology Co., Ltd.), and the defoaming agent is BYK052 (brand German BYK, purity 90%, main ingredient polyether, purchased from Shenzhen Huixin Plastic Chemical Co., Ltd.).

[0038] Comparative Example 1

[0039] A coating suitable for spraying on the surface of an automobile body comprises the following raw materials in parts by weight: 10 parts of modified acrylic resin prepared in Example 1, 10 parts of hydrophobic modified polyurethane, 2 parts of hydrophobic nano-silica, 0.2 parts of a dispersant, 1 part of an anti-settling agent, 0.2 parts of a leveling agent, and 0.2 parts of a defoaming agent; wherein the dispersant is fatty alcohol polyoxyethylene ether AEO-3, the anti-settling agent is polyamide wax, the leveling agent is BYK-333, and the defoaming agent is BYK052.

[0040] Comparative Example 2

[0041] A coating suitable for spraying on the surface of an automobile body comprises the following raw materials in parts by weight: 30 parts of common commercially available acrylic resin (viscosity 700-1500 mPa·s at 25°C, solid content 32-34%, active ingredient content 34%), 10 parts of hydrophobically modified polyurethane, 2 parts of hydrophobic nano-silica, 0.2 parts of a dispersant, 1 part of an anti-settling agent, 0.2 parts of a leveling agent, and 0.2 parts of a defoaming agent; wherein the dispersant is fatty alcohol polyoxyethylene ether AEO-3, the anti-settling agent is polyamide wax, the leveling agent is BYK-333, and the defoaming agent is BYK052.

[0042] The coatings suitable for spraying on the surface of automobile bodies described in Examples 2-5 and Comparative Examples 1-2 were prepared according to the method described in Example 1.

[0043] The coatings suitable for automobile body surface spraying prepared in Examples 1-5 and Comparative Examples 1-2 were uniformly coated on the upper glass plate with a coating thickness of 0.1 mm, cured at (28±2)°C for 24 hours, and then placed for 168 hours before relevant performance tests. The hardness (pencil scratch) test is carried out in accordance with GB / T6793-2006 "Determination of film hardness by pencil method for paints and varnishes"; the adhesion test is carried out in accordance with GB / T9286-2021 "Scratch test for paints and varnishes"; the wear resistance test is carried out in accordance with GB / T1768-2006 "Determination of abrasion resistance of paints and varnishes by rotating rubber grinding wheel method", test conditions: 750g, 1000r, calculate the mass loss; the stain resistance test is carried out in accordance with GB / T9780-2013 "Test method for stain resistance of architectural coatings"; the contact angle test is carried out using the K100 fully automatic surface tension meter produced by Kruss Company of Germany; the acid and alkali corrosion resistance test is carried out in accordance with GB / T9274-1988 "Determination of resistance of paints and varnishes to liquid media", acid resistance test conditions: 0.05mol / L H2SO4, (23±2)℃, 48h, alkali resistance test conditions: 0.1mol / L NaOH, (23 ± 2) ° C, 48h, the paint film has no obvious blistering, swelling, and shedding; the artificial accelerated aging test adopts ultraviolet light aging, the test time is 3000h, the paint film powdering, discoloration, and gloss loss are all ≤1 level, no cracking, no blistering; the heat resistance test is carried out in accordance with GB / T1740-2007 "Determination of Moisture and Heat Resistance of Paint Film"; the test results are shown in Table 1. It can be seen from the table that the hardness, adhesion, wear resistance, stain resistance, hydrophobicity, heat resistance, acid and alkali corrosion resistance, and aging resistance of the coatings for automobile body surface spraying prepared in Examples 1-5 are significantly better than those in Comparative Examples 1-2; it can be seen from the data of Comparative Examples 1 and 2 that chemical modification of acrylic resin and compounding it with raw materials such as hydrophobic modified polyurethane and hydrophobic nano-silica can significantly improve the comprehensive performance of the coating; it can be seen from the data of Example 1 and Comparative Example 1 that the addition amount of modified acrylic resin in the coating composition will have a greater impact on the performance of the coating.

[0044] Table 1 Coating related performance test results

[0045]

[0046] Although the embodiments of the present application have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A coating suitable for spraying on the surface of an automobile body, characterized in that: The invention comprises the following raw materials in parts by weight: 25-55 parts of modified acrylic resin, 5-15 parts of hydrophobic modified polyurethane, 1-4 parts of hydrophobic nano-silicon dioxide, 0.1-0.4 parts of dispersant, 0.5-2 parts of anti-settling agent, 0.1-0.3 parts of leveling agent, and 0.1-0.4 parts of defoaming agent; the preparation method of the modified acrylic resin is as follows: S1. Disperse 3-(N-allylamino)propyltrimethoxysilane in 2-methyltetrahydrofuran under stirring, heat to 60-80°C, add 2-benzyloxirane and N,N-dimethylbenzylamine in sequence, react for 5-8h, filter, take the filtrate, distill under reduced pressure, and dry to obtain an intermediate. The structural formula of the intermediate is: ； S2. Under stirring conditions, disperse the intermediate in 2-methyltetrahydrofuran, heat to 70-80°C, add p-toluenesulfonic acid and trifluorobutyric acid in sequence, react for 5-10 hours, filter, take the filtrate, distill under reduced pressure, extract, and dry to obtain a modifier, the structural formula of the modifier is: ； S3. Evenly mix hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, part of diisopropylbenzene peroxide and modifier to obtain a mixed solution. Heat xylene to 135-145°C under nitrogen atmosphere and stirring, add the mixed solution dropwise, complete the addition within 2-4 hours, continue stirring for 1-3 hours, add the remaining diisopropylbenzene peroxide, stir for another 0.5-1.5 hours, cool, filter and discharge to obtain the product.

2. A coating suitable for spraying on the surface of an automobile body according to claim 1, characterized in that: The molar ratio of 3-(N-allylamino)propyltrimethoxysilane, 2-benzylethylene oxide and N,N-dimethylbenzylamine in step S1 is 0.8-1.0:1:0.02-0.05, and the amount of 3-(N-allylamino)propyltrimethoxysilane added to the 2-methyltetrahydrofuran is 0.2-0.5 g / mL.

3. The coating suitable for spraying on the surface of an automobile body according to claim 1, characterized in that: The molar ratio of the intermediate, p-toluenesulfonic acid and trifluorobutyric acid in step S2 is 0.7-0.9:0.01-0.04:1, and the amount of the intermediate added to the 2-methyltetrahydrofuran is 0.1-0.3 g / mL.

4. The coating suitable for spraying on the surface of an automobile body according to claim 1, characterized in that: In step S3, the mass ratio of hydroxyethyl methacrylate, methyl methacrylate, butyl acrylate, xylene, dicumyl peroxide and modifier is 1-5:20-28:4-8:35-55:0.8-1.6:2-5, and the partial dicumyl peroxide accounts for 40-60% of the total mass of dicumyl peroxide.

5. The coating suitable for spraying on the surface of an automobile body according to claim 1, characterized in that: The dispersant is one of polyvinyl pyrrolidone, fatty alcohol polyoxyethylene ether AEO-3 and fatty alcohol polyoxyethylene ether AEO-7.

6. The coating suitable for spraying on the surface of an automobile body according to claim 1, characterized in that: The anti-settling agent is polyamide wax or polyethylene wax.

7. The coating suitable for spraying on the surface of an automobile body according to claim 1, characterized in that: The leveling agent is BYK-333 or BYK-358N.

8. The coating suitable for spraying on the surface of an automobile body according to claim 1, characterized in that: The defoamer is one of BYK1797, BYK052 and BYK381.

9. A method for preparing a coating suitable for spraying on the surface of an automobile body according to any one of claims 1 to 8, characterized in that: The following steps are involved: The modified acrylic resin, hydrophobic modified polyurethane, hydrophobic nano-silica, dispersant, anti-settling agent, leveling agent and defoaming agent are mixed, and the mixture is subjected to high-pressure homogenization and grinding to obtain the product.

10. A method for preparing a coating suitable for spraying on the surface of an automobile body according to claim 9, characterized in that: The homogenization pressure of the high-pressure homogenization is 30-50 MPa, the homogenization time is 5-20 s, and the grinding time is 20-40 min.

Images